BLOOD
FLOW
CAPILLARIES
VELOCITY
IN CEREBRAL
CORTEX
(MICROCINEPHOTOGRAPHIC
STUDY)
M. K. Kalinina, Yu. I. Levkovich, K. P. Ivanov and V. K. Trusova
UDC 612.135
The b r a i n p o s s e s s e s v e r y few r e s e r v e c a p i l l a r i e s as c o m p a r e d with the m u s c l e s [1-4], and the oxygen supply to the n e r v e c e l l s is r e g u l a t e d m a i n l y b y changes in the blood flow velocity in fimctioning c a p i l l a r i e s . Studies on m a t h e m a t i c a l m o d e l s of diffusion and utilization of oxygen In b r a i n t i s s u e [5] have shown tMs type of r e g u l a t i o n to b e highly effective, although t h e r e is v i r t u a l l y no d i r e c t e x p e r i m e n t a l evidence of this b e c a u s e of the g r e a t technical difficulties involved. The only r e p o r t in the w o r l d l i t e r a t u r e [6], so f a r as we a r e a w a r e , c o n e e r n i n g t h e d i r e c t m e a s u r e m e n t of blood flow velocity in c e r e b r a l c a p i l l a r i e s was c a r r i e d out on c a p i l l a r i e s and l a r g e r v e s s e l s of the s u b a r a c h n o i d s p a c e in a n e s t h e t i z e d a n i m a l s . Naturally, the d i r e c t m e a s u r e m e n t of blood flow v e l o c i t y in c e r e b r a l c o r t i c a l c a p i l l a r i e s and the l i m i t s of its physiologic v a r i a t i o n s a r e o f exceptional i n t e r e s t . In the study that we m a d e on the blood flow v e l o c i t y in individual c a p i l l a r i e s of the c e r e b r a l c o r t e x having a lumen d i a m e t e r of 3-6 # in conscious a n i m a l s we developed a technic of m i c r o c i n e p h o t o g r a p h y followed b y i n t e r p r e t a t i o n of the individual p h o t o g r a p h s . T h i s involved the c o n s t r u c t i o n of a s p e c i a l l y d e v i s e d a r r a n g e m e n t f o r o b s e r v i n g and filming c e r e b r a l c o r t i c a l v e s s e l s l o c a t e d both on the s u r f a c e and at a depth of 10-30 ~ with an effective magnification of 300 • New to motion p i c t u r e filming was a 20 • 0.60 contact objective designed in the m i c r o s c o p y l a b o r a t o r y of the S. I. Vavilov State Optical Institute. This s y s t e m has a n u m b e r of a d v a n t a g e s o v e r the conventional technic of filming opaque biologic objects by m e a n s of contact o b j e c t i v e s in p o l a r i z e d light [7]. It has a high r e s o l v i n g power enabling investigations
tz
Fig. 1
Fig. 2
Fig. 1. Schematic r e p r e s e n t a t i o n o f a p p a r a t u s f o r i n t r a v i t a l m i c r o cinefilming of c e r e b r a l c o r t i c a l c a p i l l a r i e s . F o r 1-9, 11, s e e text; 10) motion p i c t u r e c a m e r a ; 12) b r a i n s u r f a c e . Fig. 2. Showing a l i g n m e n t of e r y t h r o c y t e s while p a s s i n g through tiniest v e s s e l s , a) in v e s s e l with i n t e r n a l d i a m e t e r of 5-6! b) 3-4. A r r o w s denote p l a s m a - f i l l e d lumen.
I. P. Pavlov Institute of Physiology, A c a d e m y of Sciences of the USSR, L e n i n g r a d . ( P r e s e n t e d by A c a d e m i c i a n V. N. Chernigovskii, August 27, 1975.) T r a n s l a t e d f r o m Doklady Akademii Nauk SSSR, Vol. 226, No. 1, pp. 230-233, J a n u a r y , 1976. Original a r t i c l e s u b m i t t e d June 27, 1975.
0097-0549/78/0902-0185507.50
9 1979 Plenum Publishing Corporation
185
Fig. 3. Microcinephotograph of c a p i l l a r i e s of s u r face l a y e r of c e r e b r a l c o r t e x . I n t e r v a l between f r a m e s is 0.05 s e c . One s e e s shifting of the ' p l a s m a s p a c e ' (1-4) along the v e s s e l (arrows). D i a g r a m shows route taken by ' c l e a r s p a c e ' during this t i m e i n t e r v a l . to be performed on the smallest vessels, and a good lighting performance in close-up illumination enabling one to make a serial film of movingblood in reflected light at a rate of 40 fraxnes per see. Fig. 1 presents the theoretical optical design of the apparatus. The light beam from lamp 1 is directed by condenser 2 to the diaphragm with ring aperture 3. The elliptic mirror 4 deflects the circular light beam to the peripheral part of the objective I I . This ensures that theobjecttobe examined is illuminated only at the site of contact of the frontal lens of the objective with the surface of the preparation. The lower layer of the specimen remains unilluminated. This system gives a dark field effect, which greatly enhances image contrast. The light divider 5 in the sight tube 6 enables one to monitor the preparation during filming. The ocular 7, prism 8,and correcting objective 9 direct and focus the image in the plane of the light-sensitive layer. The optic system is mounted on a NBB-1Amicroscope which has a fixed optic system and a solid plate on which the condenser is rigidly mounted. The light source used was a mercury quartz lamp having a bright-line spectrum with an emission peak in the region of maximal absorption of hemoglobin. A certain inconstancy of the actinic light beam was compensatedby altering the opening of the diaphragm of the motion picture through 40-100~. Correctionwas applied during filming using a mirror diaphragm. To increase the contrast and the light sensitivity the negative was developed in a photographic developer for the maximal time; the positive was treated under standard conditions. This method of chemical photographic treatment provided a good image quality on film KN-3 with lighting from a mercury quartz lamp. Experiments were carried out on conscious white rats weighing about 300 g. The operative intervention was described in our preceding report [7]. The skull was trephined in the temporal region (6 • 8 ram) and dura mater was removed under ether anesthesia. The brain surface was irrigated with physiologic solution at 37~ Under local anesthesia a catheter was inserted into the femoral artery to monitor the arterial pressure. By means of controllable heating the brain surface temperature was maintained constant at 35 -~0.5~and the rectal temperature at 37.5:~0.5~ About 30-40 rain after stopping the anesthesia the prepared animal was firmly fixed to a special bench and placed on the all-purpose examination table of a device whereby the brain surface was brought into contact with the frontal lens of the objective. In this way the i m a g e of the s u r f a c e s t r u c t u r e s of the b r a i n was located in the focal plane. Choice of v i s u a l field w a s m a d e b y d i s p l a c i n g t h e a n i m a l on the examination table in a s t r i c t l y h o r i z o n t a l plane [8]. F o c u s ing at the r e q u i s i t e depth f o r inspection w a s done by a l t e r i n g the effective length of the m i c r o s c o p e tube,
186
b y displacing the ocular 7 upward or downward b y m e a n s of a special a d j u s t e r . It should be mentioned that with this m o d e of focusing t h e r e is no change in the distance between objective and object, and consequently the frontal lens of the objective m e r e l y touches the s u r f a c e to b e examined throughout the e x p e r i m e n t without exerting p r e s s u r e on it. To d e t e r m i n e the blood flow v e l o c i t y d i s t i n c t l y , v i s i b l e v e s s e l s having a d i a m e t e r of 3-6/~ and a length of 60-250/~ w e r e s e l e c t e d . In t h e s e v e s s e l s one could c l e a r l y distinguish the s e p a r a t e e r y t h r o c y t e s moving along in r a n k one a f t e r the o t h e r . In v e s s e l s having a d i a m e t e r of 5-6 # the e r y t h r o c y t e s w e r e as a rule packed like columns of coins, differing f r o m the a r r a n g e m e n t found in v e s s e l s of s m a l l e r d i a m e t e r (3-4 p) as shown in Fig. 2. In a continuous s t r e a m of e r y t h r o c y t e s one could f r o m t i m e to t i m e s e e s p a c e s between e r y t h r o c y t e s occupied solely by p l a s m a . On t h e p o s i t i v e motion picture t h e s e s p a c e s showed up as c l e a r spots against the d a r k background of the v e s s e l filled with e r y t h r o c y t e s (Fig. 3). The blood flow velocity in the c a p i l l a r i e s was d e t e r m i n e d f r o m the velocity of m o v e m e n t of these " p l a s m a s p a c e s . " The two b o u n d a r i e s (along the v e s s e l axis) of the ' c l e a r s p a c e ' w e r e used as r e f e r e n c e points for m e a s u r i n g the blood flow velocity. The s e l e c t e d field of vision was photographed on motion p i c t u r e film with a fixed f r e q u e n c y of 40 f r a m e s p e r sec f o r 20-30 s e c . Filming was r e p e a t e d t h r e e to four t i m e s during the e x p e r i m e n t at i n t e r v a l s of 2-5 rain. This enabled f a i r l y a c c u r a t e m e a s u r e m e n t within the studied range of blood flow v e l o c i t i e s . Readings w e r e done on the positive i m a g e of individual f r a m e s p r o j e c t e d onto a special (5PO-1) s c r e e n . The v e s s e l contours w e r e t r a c e d with a pencil on a sheet of p a p e r placed in the plane of the s c r e e n . Then, on a s u c c e s s i v e s e r i e s of s e v e r a l f r a m e s in which the ' p l a s m a s p a c e ' was moving along the s e g m e n t of v e s s e l included in the film, the boundaries of the s p a c e w e r e m a r k e d on these contours (Fig. 3). The d i s p l a c e m e n t of the r e f e r e n c e points In one or s e v e r a l f r a m e s was m e a s u r e d with a r u l e r c a l i b r a t e d in m i c r o n s and a c c u r a t e to within 1/~. The t i m e gap between two f r a m e s when the filmIng was done at a r a t e of 40 f r a m e s p e r sec was 0.025 s e c . The blood flow velocity was calculated f r o m the a n t e r i o r and p o s t e r i o r l i m i t s of the ' s p o t ' and the m e a n value was then d e t e r m i n e d . The m e a s u r e m e n t data w e r e subjected to s t a t i s t i c a l a n a l y s i s . In 28 e x p e r i m e n t s on 28 r a t s a total of 110 f i l m s w e r e taken to investigate the blood flow r a t e in 80 c a p i l l a r i e s having a d i a m e t e r of 3-6 p . T a b l e 1 gives the main r e s u l t s of the investigations; it shows that the l i n e a r velocity of blood flow in c a p i l l a r i e s of the s u p e r f i c i a l l a y e r s of c e r e b r a l c o r t e x is v i r t u a l l y u n i f o r m (about 0.8 m m / s e c ) for c a p i l l a r i e s having a d i a m e t e r of 3-4 and 5-6/~ (P< 0.25), this value being s i m i l a r to that r e p o r t e d in [6]. The m e a n values of v e l o c i t y calculated according to the onward m o v e m e n t of the a n t e r i o r and the p o s t e r i o r l i m i t s of the ' c l e a r s p a c e ' coincide. Thus, the changes in contour frequently noted in the ' c l e a r s p a c e ' as it m o v e d onward, which might be the r e s u l t of v a r i a b i l i t y ' o f v e s s e l d i a m e t e r and of m i n o r bends in the v e r t i c a l plane of s m a l l e r magnitude than the s h a r p n e s s of the image, have little influences on the m e a n value of blood flow velocity. However, it w a s noted at the s a m e t i m e that in a given c a p i l l a r y the blood flow velocity o v e r the c o u r s e of 0.5-15 rain frequently v a r i e d between m a x i m u m , w h i c h a v e r a g e d 1.01-~ 0.04 r a m / s e e , a n d a m i n i m u m which a v e r a g e d 0.58 • 0.03 m m / s e c (n = 110). All m e a s u r e m e n t s of the c a p i l l a r y blood flow velocity w e r e c a r r i e d out on conscious a n i m a l s with an a r t e r i a l p r e s s u r e in the r a n g e of 80-120 m m Hg. Within this r a n g e the magnitude of the c a p i l l a r y blood flow velocity was not dependent on the height of the a r t e r i a l blood p r e s s u r e , as was e s t a b l i s h e d by m e a n s of a special s t a t i s t i c a l study.
TABLE
1
Vessel diameter ( p ) No. of vessels No. of films N1o. of 'clear spaces' 0on zlow vezoeiZy (2:~$~; m m / s e c ) at a~tezior limit of 'clear space' at posterior limit of 'clear space' Mean velocity
3-4 67 92 i039 0,77•
5-6 t3 t8 231
3-6 80 li0 i270
0,84-+0,08 0,78-+0,03
0,73-+0,08 0,79-+0,07 0,74+-0,03 0.75-+0,04
0,82-+0108 0,76--:-0.03
187
T h e m e a n l i n e a r velocity of c a p i l l a r y blood flow and the r a n g e of its v a r i a t i o n , obtained by a fairly a c c u r a t e method, a r e of t h e o r e t i c a l i m p o r t a n c e for elucidating the m e c h a n i s m s of the t r a n s p o r t of oxygen and of its regulation in the c e r e b r a l t i s s u e s . According to r e c e n t m a t h e m a t i c a l studies of p r o c e s s e s of diffusion and utilization of oxygen in c e r e b r a l n e r v e c e l l s [5], for c a p i l l a r i e s having a d i a m e t e r of about 6 # the optimal l i n e a r blood flow v e l o c i t y is between 0.75 and 1.0 r a m / s e e . A velocity exceeding 1 m m / s e c hardly i m p r o v e s the oxygen supply to the t i s s u e s due to the s p e c i a l conditions of diffusion, while a fall to below 0.75 m m / s e c leads to a r a p i d fall of t i s s u e oxygen tension f o r the s a m e r e a s o n s . Hence the m a i n tenance of the m e a n c a p i l l a r y blood flow velocity at around 0.8 r a m / s e e is close to optimality and is p h y s iologically v e r y i m p o r t a n t . The periodic v a r i a t i o n s in c a p i l l a r y blood flow velocity within the m e a n l i m i t s of 0.58-1.00 r a m / s e e m a y be r e g a r d e d as a m e c h a n i s m for regulating the oxygen supply to the t i s s u e s , depending on changes in t h e i r c u r r e n t energy needs. This a s s u m p t i o n is supported by the finding that within this velocity r a n g e the r a t e of diffusion of oxygen f r o m the c a p i l l a r i e s c o r r e l a t e s a l m o s t l i n e a r l y with the blood flow v e l o c i t y [5]. LITERATURE
Y. Fulton, A Textbook of Physiology, Philadelphia a n d - L o n d o n (1955). E. Optiz and M. Schneider, Pflffgers A r c h . Ges. Physiol., Vol. 251 (1949), 369. M.Scheneider, Zs. Nervenheilkunde, 162,113 (1950). K. P. Ivanov, Usp. Fiziol. Nauk, 5, No. 2, 128 (1974). Yu. Ya. K i s l y a k o v and K. P. Ivanov, Fiziol. Zh. SSSR, 60, No. 8, 1216 (1974). Y. P. Maa, A. Koo, et al., Mierov. R e s . , 8, No. 1, 1 (1974). M. K. Kalinina, Yu. I. Levkovich and K. P. Ivanov, Dokl. Akad. Nauk SSSR, 215, No. 1, 226 (1974). Yu. I. Levkovieh, Motion P i c t u r e and T e l e v i s i o n Technique [in Russian], (1971), No. 2.
la 2. 3. 4. 5. 6. 7. 8.
NUCLEAR IN
CITED
HISTONE
CERTAIN
DURING
PARTS PROLONGED
LEVEL OF
IN THE
NEURONS
NEUROGLIA
HYPOTHALAMUS
COOLING
A. A. Krichevskaya, and L. Z. Pevzner
AND
L. V.
OF
ANIMALS
Mogil'nitskaya,
UDC 612.8.015
The hypothalamus p l a y s a principal role in maintaining t e m p e r a t u r e h o m e o s t a s i s in h o m o i o t h e r m a l a n i m a l s by coordinating the many r e g u l a t o r y p r o c e s s e s which e n s u r e constant body t e m p e r a t u r e [1-5]. As shown in [6], changes in the functional activity of hypothalamic s t r u c t u r e s during adaptation to cold are a c c o m p a n i e d by m e t a b o l i c r e a r r a n g e m e n t s of m a c r o m o l e c u l e s (RNA in p a r t i c u l a r ) in the neurons and neuroglia cells of the hypothalamus. In cell nuclei, RNA m o l e c u l e s g e n e r a l l y f o r m c o m p l e x e s with nuclear p r o t e i n s , p r i m a r i l y histones and other b a s i c p r o t e i n s [7]. We chose n u c l e a r histones as our objects for study, since they a r e the p r i n cipal m a c r o m o l e c u l e s r e s p o n s i b l e for assigning specific r o l e s to the s t r u c t u r a l components in cell nuclei, and also take p a r t in the regulation of genome activity [7, 8]. T e s t s w e r e c a r r i e d out on pubescent m a l e r a t s weighing 110-130 g by placing t h e m in a cold c h a m b e r ( t e m p e r a t u r e 2-4~ The animals showed little activity and s o m e weight loss during the f i r s t few days. A f t e r two weeks in the c h a m b e r t h e i r b e h a v i o r b e c a m e i n c r e a s i n g l y stable and the a n i m a l s began to gain weight. The r e c t a l t e m p e r a t u r e of the r a t s r e m a i n e d unchanged throughout the duration of the e x p e r i m e n t . The control group was made up of r a t s of the s a m e sex, age, and weight exposed to standard v i v a r i u m conditions at 19-21~ I. P. Pavlov Institute of Physiology, A c a d e m y of Sciences of the USSR, Leningrad. Rostov State University. ( P r e s e n t e d by A c a d e m i c i a n V. N. Chernigovskii, S e p t e m b e r 8, 1975.) T r a n s l a t e d f r o m Doklady Akademii Nauk SSSR, Vol. 226, No. 4, pp. 982-984, F e b r u a r y , 1976. Original a r t i c l e submitted S e p t e m b e r 8, 1975.
188
0097-0549/78/0902-0188507.50 9 1979 Plenum Publishing Corporation
FLOW
CAPILLARIES
VELOCITY
IN CEREBRAL
CORTEX
(MICROCINEPHOTOGRAPHIC
STUDY)
M. K. Kalinina, Yu. I. Levkovich, K. P. Ivanov and V. K. Trusova
UDC 612.135
The b r a i n p o s s e s s e s v e r y few r e s e r v e c a p i l l a r i e s as c o m p a r e d with the m u s c l e s [1-4], and the oxygen supply to the n e r v e c e l l s is r e g u l a t e d m a i n l y b y changes in the blood flow velocity in fimctioning c a p i l l a r i e s . Studies on m a t h e m a t i c a l m o d e l s of diffusion and utilization of oxygen In b r a i n t i s s u e [5] have shown tMs type of r e g u l a t i o n to b e highly effective, although t h e r e is v i r t u a l l y no d i r e c t e x p e r i m e n t a l evidence of this b e c a u s e of the g r e a t technical difficulties involved. The only r e p o r t in the w o r l d l i t e r a t u r e [6], so f a r as we a r e a w a r e , c o n e e r n i n g t h e d i r e c t m e a s u r e m e n t of blood flow velocity in c e r e b r a l c a p i l l a r i e s was c a r r i e d out on c a p i l l a r i e s and l a r g e r v e s s e l s of the s u b a r a c h n o i d s p a c e in a n e s t h e t i z e d a n i m a l s . Naturally, the d i r e c t m e a s u r e m e n t of blood flow v e l o c i t y in c e r e b r a l c o r t i c a l c a p i l l a r i e s and the l i m i t s of its physiologic v a r i a t i o n s a r e o f exceptional i n t e r e s t . In the study that we m a d e on the blood flow v e l o c i t y in individual c a p i l l a r i e s of the c e r e b r a l c o r t e x having a lumen d i a m e t e r of 3-6 # in conscious a n i m a l s we developed a technic of m i c r o c i n e p h o t o g r a p h y followed b y i n t e r p r e t a t i o n of the individual p h o t o g r a p h s . T h i s involved the c o n s t r u c t i o n of a s p e c i a l l y d e v i s e d a r r a n g e m e n t f o r o b s e r v i n g and filming c e r e b r a l c o r t i c a l v e s s e l s l o c a t e d both on the s u r f a c e and at a depth of 10-30 ~ with an effective magnification of 300 • New to motion p i c t u r e filming was a 20 • 0.60 contact objective designed in the m i c r o s c o p y l a b o r a t o r y of the S. I. Vavilov State Optical Institute. This s y s t e m has a n u m b e r of a d v a n t a g e s o v e r the conventional technic of filming opaque biologic objects by m e a n s of contact o b j e c t i v e s in p o l a r i z e d light [7]. It has a high r e s o l v i n g power enabling investigations
tz
Fig. 1
Fig. 2
Fig. 1. Schematic r e p r e s e n t a t i o n o f a p p a r a t u s f o r i n t r a v i t a l m i c r o cinefilming of c e r e b r a l c o r t i c a l c a p i l l a r i e s . F o r 1-9, 11, s e e text; 10) motion p i c t u r e c a m e r a ; 12) b r a i n s u r f a c e . Fig. 2. Showing a l i g n m e n t of e r y t h r o c y t e s while p a s s i n g through tiniest v e s s e l s , a) in v e s s e l with i n t e r n a l d i a m e t e r of 5-6! b) 3-4. A r r o w s denote p l a s m a - f i l l e d lumen.
I. P. Pavlov Institute of Physiology, A c a d e m y of Sciences of the USSR, L e n i n g r a d . ( P r e s e n t e d by A c a d e m i c i a n V. N. Chernigovskii, August 27, 1975.) T r a n s l a t e d f r o m Doklady Akademii Nauk SSSR, Vol. 226, No. 1, pp. 230-233, J a n u a r y , 1976. Original a r t i c l e s u b m i t t e d June 27, 1975.
0097-0549/78/0902-0185507.50
9 1979 Plenum Publishing Corporation
185
Fig. 3. Microcinephotograph of c a p i l l a r i e s of s u r face l a y e r of c e r e b r a l c o r t e x . I n t e r v a l between f r a m e s is 0.05 s e c . One s e e s shifting of the ' p l a s m a s p a c e ' (1-4) along the v e s s e l (arrows). D i a g r a m shows route taken by ' c l e a r s p a c e ' during this t i m e i n t e r v a l . to be performed on the smallest vessels, and a good lighting performance in close-up illumination enabling one to make a serial film of movingblood in reflected light at a rate of 40 fraxnes per see. Fig. 1 presents the theoretical optical design of the apparatus. The light beam from lamp 1 is directed by condenser 2 to the diaphragm with ring aperture 3. The elliptic mirror 4 deflects the circular light beam to the peripheral part of the objective I I . This ensures that theobjecttobe examined is illuminated only at the site of contact of the frontal lens of the objective with the surface of the preparation. The lower layer of the specimen remains unilluminated. This system gives a dark field effect, which greatly enhances image contrast. The light divider 5 in the sight tube 6 enables one to monitor the preparation during filming. The ocular 7, prism 8,and correcting objective 9 direct and focus the image in the plane of the light-sensitive layer. The optic system is mounted on a NBB-1Amicroscope which has a fixed optic system and a solid plate on which the condenser is rigidly mounted. The light source used was a mercury quartz lamp having a bright-line spectrum with an emission peak in the region of maximal absorption of hemoglobin. A certain inconstancy of the actinic light beam was compensatedby altering the opening of the diaphragm of the motion picture through 40-100~. Correctionwas applied during filming using a mirror diaphragm. To increase the contrast and the light sensitivity the negative was developed in a photographic developer for the maximal time; the positive was treated under standard conditions. This method of chemical photographic treatment provided a good image quality on film KN-3 with lighting from a mercury quartz lamp. Experiments were carried out on conscious white rats weighing about 300 g. The operative intervention was described in our preceding report [7]. The skull was trephined in the temporal region (6 • 8 ram) and dura mater was removed under ether anesthesia. The brain surface was irrigated with physiologic solution at 37~ Under local anesthesia a catheter was inserted into the femoral artery to monitor the arterial pressure. By means of controllable heating the brain surface temperature was maintained constant at 35 -~0.5~and the rectal temperature at 37.5:~0.5~ About 30-40 rain after stopping the anesthesia the prepared animal was firmly fixed to a special bench and placed on the all-purpose examination table of a device whereby the brain surface was brought into contact with the frontal lens of the objective. In this way the i m a g e of the s u r f a c e s t r u c t u r e s of the b r a i n was located in the focal plane. Choice of v i s u a l field w a s m a d e b y d i s p l a c i n g t h e a n i m a l on the examination table in a s t r i c t l y h o r i z o n t a l plane [8]. F o c u s ing at the r e q u i s i t e depth f o r inspection w a s done by a l t e r i n g the effective length of the m i c r o s c o p e tube,
186
b y displacing the ocular 7 upward or downward b y m e a n s of a special a d j u s t e r . It should be mentioned that with this m o d e of focusing t h e r e is no change in the distance between objective and object, and consequently the frontal lens of the objective m e r e l y touches the s u r f a c e to b e examined throughout the e x p e r i m e n t without exerting p r e s s u r e on it. To d e t e r m i n e the blood flow v e l o c i t y d i s t i n c t l y , v i s i b l e v e s s e l s having a d i a m e t e r of 3-6/~ and a length of 60-250/~ w e r e s e l e c t e d . In t h e s e v e s s e l s one could c l e a r l y distinguish the s e p a r a t e e r y t h r o c y t e s moving along in r a n k one a f t e r the o t h e r . In v e s s e l s having a d i a m e t e r of 5-6 # the e r y t h r o c y t e s w e r e as a rule packed like columns of coins, differing f r o m the a r r a n g e m e n t found in v e s s e l s of s m a l l e r d i a m e t e r (3-4 p) as shown in Fig. 2. In a continuous s t r e a m of e r y t h r o c y t e s one could f r o m t i m e to t i m e s e e s p a c e s between e r y t h r o c y t e s occupied solely by p l a s m a . On t h e p o s i t i v e motion picture t h e s e s p a c e s showed up as c l e a r spots against the d a r k background of the v e s s e l filled with e r y t h r o c y t e s (Fig. 3). The blood flow velocity in the c a p i l l a r i e s was d e t e r m i n e d f r o m the velocity of m o v e m e n t of these " p l a s m a s p a c e s . " The two b o u n d a r i e s (along the v e s s e l axis) of the ' c l e a r s p a c e ' w e r e used as r e f e r e n c e points for m e a s u r i n g the blood flow velocity. The s e l e c t e d field of vision was photographed on motion p i c t u r e film with a fixed f r e q u e n c y of 40 f r a m e s p e r sec f o r 20-30 s e c . Filming was r e p e a t e d t h r e e to four t i m e s during the e x p e r i m e n t at i n t e r v a l s of 2-5 rain. This enabled f a i r l y a c c u r a t e m e a s u r e m e n t within the studied range of blood flow v e l o c i t i e s . Readings w e r e done on the positive i m a g e of individual f r a m e s p r o j e c t e d onto a special (5PO-1) s c r e e n . The v e s s e l contours w e r e t r a c e d with a pencil on a sheet of p a p e r placed in the plane of the s c r e e n . Then, on a s u c c e s s i v e s e r i e s of s e v e r a l f r a m e s in which the ' p l a s m a s p a c e ' was moving along the s e g m e n t of v e s s e l included in the film, the boundaries of the s p a c e w e r e m a r k e d on these contours (Fig. 3). The d i s p l a c e m e n t of the r e f e r e n c e points In one or s e v e r a l f r a m e s was m e a s u r e d with a r u l e r c a l i b r a t e d in m i c r o n s and a c c u r a t e to within 1/~. The t i m e gap between two f r a m e s when the filmIng was done at a r a t e of 40 f r a m e s p e r sec was 0.025 s e c . The blood flow velocity was calculated f r o m the a n t e r i o r and p o s t e r i o r l i m i t s of the ' s p o t ' and the m e a n value was then d e t e r m i n e d . The m e a s u r e m e n t data w e r e subjected to s t a t i s t i c a l a n a l y s i s . In 28 e x p e r i m e n t s on 28 r a t s a total of 110 f i l m s w e r e taken to investigate the blood flow r a t e in 80 c a p i l l a r i e s having a d i a m e t e r of 3-6 p . T a b l e 1 gives the main r e s u l t s of the investigations; it shows that the l i n e a r velocity of blood flow in c a p i l l a r i e s of the s u p e r f i c i a l l a y e r s of c e r e b r a l c o r t e x is v i r t u a l l y u n i f o r m (about 0.8 m m / s e c ) for c a p i l l a r i e s having a d i a m e t e r of 3-4 and 5-6/~ (P< 0.25), this value being s i m i l a r to that r e p o r t e d in [6]. The m e a n values of v e l o c i t y calculated according to the onward m o v e m e n t of the a n t e r i o r and the p o s t e r i o r l i m i t s of the ' c l e a r s p a c e ' coincide. Thus, the changes in contour frequently noted in the ' c l e a r s p a c e ' as it m o v e d onward, which might be the r e s u l t of v a r i a b i l i t y ' o f v e s s e l d i a m e t e r and of m i n o r bends in the v e r t i c a l plane of s m a l l e r magnitude than the s h a r p n e s s of the image, have little influences on the m e a n value of blood flow velocity. However, it w a s noted at the s a m e t i m e that in a given c a p i l l a r y the blood flow velocity o v e r the c o u r s e of 0.5-15 rain frequently v a r i e d between m a x i m u m , w h i c h a v e r a g e d 1.01-~ 0.04 r a m / s e e , a n d a m i n i m u m which a v e r a g e d 0.58 • 0.03 m m / s e c (n = 110). All m e a s u r e m e n t s of the c a p i l l a r y blood flow velocity w e r e c a r r i e d out on conscious a n i m a l s with an a r t e r i a l p r e s s u r e in the r a n g e of 80-120 m m Hg. Within this r a n g e the magnitude of the c a p i l l a r y blood flow velocity was not dependent on the height of the a r t e r i a l blood p r e s s u r e , as was e s t a b l i s h e d by m e a n s of a special s t a t i s t i c a l study.
TABLE
1
Vessel diameter ( p ) No. of vessels No. of films N1o. of 'clear spaces' 0on zlow vezoeiZy (2:~$~; m m / s e c ) at a~tezior limit of 'clear space' at posterior limit of 'clear space' Mean velocity
3-4 67 92 i039 0,77•
5-6 t3 t8 231
3-6 80 li0 i270
0,84-+0,08 0,78-+0,03
0,73-+0,08 0,79-+0,07 0,74+-0,03 0.75-+0,04
0,82-+0108 0,76--:-0.03
187
T h e m e a n l i n e a r velocity of c a p i l l a r y blood flow and the r a n g e of its v a r i a t i o n , obtained by a fairly a c c u r a t e method, a r e of t h e o r e t i c a l i m p o r t a n c e for elucidating the m e c h a n i s m s of the t r a n s p o r t of oxygen and of its regulation in the c e r e b r a l t i s s u e s . According to r e c e n t m a t h e m a t i c a l studies of p r o c e s s e s of diffusion and utilization of oxygen in c e r e b r a l n e r v e c e l l s [5], for c a p i l l a r i e s having a d i a m e t e r of about 6 # the optimal l i n e a r blood flow v e l o c i t y is between 0.75 and 1.0 r a m / s e e . A velocity exceeding 1 m m / s e c hardly i m p r o v e s the oxygen supply to the t i s s u e s due to the s p e c i a l conditions of diffusion, while a fall to below 0.75 m m / s e c leads to a r a p i d fall of t i s s u e oxygen tension f o r the s a m e r e a s o n s . Hence the m a i n tenance of the m e a n c a p i l l a r y blood flow velocity at around 0.8 r a m / s e e is close to optimality and is p h y s iologically v e r y i m p o r t a n t . The periodic v a r i a t i o n s in c a p i l l a r y blood flow velocity within the m e a n l i m i t s of 0.58-1.00 r a m / s e e m a y be r e g a r d e d as a m e c h a n i s m for regulating the oxygen supply to the t i s s u e s , depending on changes in t h e i r c u r r e n t energy needs. This a s s u m p t i o n is supported by the finding that within this velocity r a n g e the r a t e of diffusion of oxygen f r o m the c a p i l l a r i e s c o r r e l a t e s a l m o s t l i n e a r l y with the blood flow v e l o c i t y [5]. LITERATURE
Y. Fulton, A Textbook of Physiology, Philadelphia a n d - L o n d o n (1955). E. Optiz and M. Schneider, Pflffgers A r c h . Ges. Physiol., Vol. 251 (1949), 369. M.Scheneider, Zs. Nervenheilkunde, 162,113 (1950). K. P. Ivanov, Usp. Fiziol. Nauk, 5, No. 2, 128 (1974). Yu. Ya. K i s l y a k o v and K. P. Ivanov, Fiziol. Zh. SSSR, 60, No. 8, 1216 (1974). Y. P. Maa, A. Koo, et al., Mierov. R e s . , 8, No. 1, 1 (1974). M. K. Kalinina, Yu. I. Levkovich and K. P. Ivanov, Dokl. Akad. Nauk SSSR, 215, No. 1, 226 (1974). Yu. I. Levkovieh, Motion P i c t u r e and T e l e v i s i o n Technique [in Russian], (1971), No. 2.
la 2. 3. 4. 5. 6. 7. 8.
NUCLEAR IN
CITED
HISTONE
CERTAIN
DURING
PARTS PROLONGED
LEVEL OF
IN THE
NEURONS
NEUROGLIA
HYPOTHALAMUS
COOLING
A. A. Krichevskaya, and L. Z. Pevzner
AND
L. V.
OF
ANIMALS
Mogil'nitskaya,
UDC 612.8.015
The hypothalamus p l a y s a principal role in maintaining t e m p e r a t u r e h o m e o s t a s i s in h o m o i o t h e r m a l a n i m a l s by coordinating the many r e g u l a t o r y p r o c e s s e s which e n s u r e constant body t e m p e r a t u r e [1-5]. As shown in [6], changes in the functional activity of hypothalamic s t r u c t u r e s during adaptation to cold are a c c o m p a n i e d by m e t a b o l i c r e a r r a n g e m e n t s of m a c r o m o l e c u l e s (RNA in p a r t i c u l a r ) in the neurons and neuroglia cells of the hypothalamus. In cell nuclei, RNA m o l e c u l e s g e n e r a l l y f o r m c o m p l e x e s with nuclear p r o t e i n s , p r i m a r i l y histones and other b a s i c p r o t e i n s [7]. We chose n u c l e a r histones as our objects for study, since they a r e the p r i n cipal m a c r o m o l e c u l e s r e s p o n s i b l e for assigning specific r o l e s to the s t r u c t u r a l components in cell nuclei, and also take p a r t in the regulation of genome activity [7, 8]. T e s t s w e r e c a r r i e d out on pubescent m a l e r a t s weighing 110-130 g by placing t h e m in a cold c h a m b e r ( t e m p e r a t u r e 2-4~ The animals showed little activity and s o m e weight loss during the f i r s t few days. A f t e r two weeks in the c h a m b e r t h e i r b e h a v i o r b e c a m e i n c r e a s i n g l y stable and the a n i m a l s began to gain weight. The r e c t a l t e m p e r a t u r e of the r a t s r e m a i n e d unchanged throughout the duration of the e x p e r i m e n t . The control group was made up of r a t s of the s a m e sex, age, and weight exposed to standard v i v a r i u m conditions at 19-21~ I. P. Pavlov Institute of Physiology, A c a d e m y of Sciences of the USSR, Leningrad. Rostov State University. ( P r e s e n t e d by A c a d e m i c i a n V. N. Chernigovskii, S e p t e m b e r 8, 1975.) T r a n s l a t e d f r o m Doklady Akademii Nauk SSSR, Vol. 226, No. 4, pp. 982-984, F e b r u a r y , 1976. Original a r t i c l e submitted S e p t e m b e r 8, 1975.
188
0097-0549/78/0902-0188507.50 9 1979 Plenum Publishing Corporation
