Regional cerebral blood flow of the rat in acute carbon monoxide intoxication.

The effect of carbon monoxide (CO) on the regional cerebral blood flow was studied by exposing lightly anesthetized rats for 30 min to 0.5, 1.0, 1.5, and 2.0% CO gas mixtures. Cortical cerebral blood flow (CBF) increases of near 200%, 300%, and 400% control were observed at 0.5, 1.0, and 1.5% CO, respectively; whereas at 2.0% CO a reversal of the CBF increase was observed with values declining to near 300% control. The CBF response of subcortical, cerebellar, and brain stem areas was quantitatively similar to that of cortex, indicating that the CBF changes in CO intoxication are general. The decrease in CBF at 2.0% CO was related to significant decreases in arterial CO2 tension. Comparison of the CBF data to previous metabolic results in CO poisoning suggests that the CBF increases are a principal factor in the maintenance of an intact energy state in CO poisoning.     

Intravascular and extracellular volumes in the diabetic rat

Simultaneously measured intravascular (IVV) and extracellular (ECV) volumes in diabetic rats have not been reported. We evaluated IVV and ECV in alloxan induced diabetic rats which were either untreated (DU) or received supplemental daily insulin (DI) for three months. Two separate groups of control rats were comparably weight matched to each experimental group. Radio-iodinated (125-I) human serum albumin (RISA) and 35-S sulfate were used to determine IVV and ECV respectively. In DU rats, values for IVV and ECV expressed as a percentage of body weight were 9.3±0.5% and 35±2% respectively; both are significantly larger than the volumes measured in control rats (IVV=6.6±0.2%, p^<0.001 and ECV=28±1%, p<0.01). DI rats had volumes (IVV=6.0±0.3% and ECV=24±3%) which were not significantly different than those of control rats (IVV=5.7±0.1% and ECV=22±1%). Thus, untreated diabetic rats had increased IVV and ECV while diabetic rats that received insulin were normovolemic despite the presence of hyperglycemia.     

Fluorescent microsphere technique to measure cerebral blood flow in the rat

The present protocol describes a method for parallel measurement of cerebral blood flow (CBF) using fluorescent microspheres and structural assessment of the same material. The method is based on the standard microsphere technique, embolizing capillaries proportional to the blood flow, but requires dissolution of the tissue to retrieve the microspheres. To link the blood flow to the tissue morphology we modified the technique to fluorescent microspheres, which are quantified in cryo- or vibratome sections, allowing structural analysis by, for example, immunohistochemistry or standard histology. The protocol takes 8 h 50 min, without pauses, to complete, but additional flow measurements or specific protocols can increase the time needed.     

Migration and geographic variations in blood pressure in Britain.

OBJECTIVE--To evaluate the relative contributions of factors acting at different stages in life to regional differences in adult blood pressure. DESIGN--Prospective cohort study (British regional heart study). SETTING--One general practice in each of 24 towns in Britain. SUBJECTS--7735 Men aged 40-59 years when screened in 1978-80 whose geographic zone of birth and zone of examination were classified as south of England, midlands and Wales, north of England, and Scotland. Non-migrants (n = 3144) were born in the town where they were examined; internal migrants (n = 4147) were born in Great Britain but not in the town where they were examined; and international migrants (n = 422) were born outside Great Britain. MAIN OUTCOME MEASURES--Systolic and diastolic blood pressures and height. RESULTS--Regardless of where they were born, men living in the south of England had lower mean blood pressures than men living in Scotland (142.5/80.1 v 148.1/85.2 mm Hg). The effects of the place of birth and place of examination on adult blood pressure were examined in a multiple regression model. For internal migrants the modelled increase in mean systolic blood pressure across adjacent zones of examination was 2.1 mm Hg (95% confidence interval 1.3 to 2.9); for adjacent zones of birth the corresponding increase was 0.1 mm Hg (-0.7 to 0.7). The place of examination seemed to be a far more important determinant of mean adult blood pressure than the place of birth. Height is an accepted marker of genetic and early life influences. Regional differences in height were therefore analysed to test whether the multiple regression model could correctly distinguish between the influence of place of birth and place of examination. As expected, men born in Scotland were shorter on average than men born in the south of England irrespective of where they lived in Britain (172.6 cm v 175.1 cm for internal migrants). CONCLUSION--Regional variations in blood pressure were strongly influenced by where the men had lived for most of their adult lives rather than by where they were born and brought up. Among middle aged men, factors acting in adult life seemed to be more important determinants of regional differences in blood pressure than those acting early in life such as genetic inheritance, intrauterine environment, and childhood experience.     

Red cell and total blood volumes during sexual excitement and copulation in the boar.

Measurements of hematocrit, total plasma protein and red cell volume were made during sexual excitement and copulation in boars. Red cell volume (RCV) was determined by isotope dilution technique using endogenous 51Cr-tagged red cells. Basing on these data changes in the total blood volume (TBV) and plasma volume (PV) were calculated by 2 indirect methods. RCV increased by 12% to 16% in the intial phase of ejaculation and remained increased during ejaculation and 40 minutes after copulation. TBV and PV decreased during copulation, greatest drop being found in the final phase of ejaculation. After ejaculation the TBV was increasing, first to the resting value before copulation (about 20 minutes after copulation), thereafter it became markedly higher than during the resting period. Depending on the method used for calculation significant differences were found in the quantity of TBV and PV drop during ejaculation.     

Effect of L-fucose on proliferation and myo-inositol metabolism in cultured cerebral microvessel and aortic endothelial cells.

Decreased myo-inositol metabolism possibly contributes to the development of diabetic complications including micro and macrovascular disease. Previous studies have shown that hyperglycemia may be partially responsible for this defect. We have found that L-fucose, a monosaccharide present in low concentrations in normal circulation and found to be elevated in diabetes, causes defects in cultured endothelial cells, including alterations in myo-inositol metabolism and proliferation. Murine cerebral microvessel and bovine aortic endothelial cells take up L-fucose from the medium in a time and concentration-dependent manner. Both acute and chronic exposure of these cultured endothelial cells to media containing L-fucose at concentrations that may exist in diabetic sera cause a significant decrease in the accumulation of myo-inositol and its incorporation into inositol phospholipids. There is a concomitant decrease in the intracellular levels of myo-inositol. Kinetic analysis of the effect of L-fucose on myo-inositol uptake suggests that L-fucose competitively inhibits the transport of myo-inositol, exhibiting a Ki in the range of 1.6-4.1 mM for both cell types. Endothelial cells exposed to L-fucose concentrations of 0.5-20 mM exhibit depressed rates of proliferation in a concentration-dependent fashion. Furthermore, L-fucose causes a concentration-dependent decrease in synthesis of proteoglycan by cultured cerebral microvessel endothelial cells as measured by incorporation of 35S; however, this effect is not observed in the aortic endothelia. These data suggest that L-fucose at concentrations that may exist in diabetic sera may impair myo-inositol metabolism and proliferation of the vascular endothelium.     

Diurnal and seasonal variations of glycogen content in the rat brain.

The effect of seasonal and diurnal variations on glycogen content in the brain was investigated in 3-month old Wistar rats. In the first experimental series, the glycogen content in the brain was determined every 2-months, throughout a whole year. In each experiment, the material was taken at the same time of a day. The results indicated that the brain glycogen content did not change significantly, during the periods of a year examined. In the second series of experiments, the glycogen content in the rat brain was assayed every 3 hours, during a 24-hour-period. A low content of glycogen in the rat brain was found during the night, with a pronounced decrease of this value between 9.00 p.m. and midnight. A possible relationship between the diurnal changes in the brain glycogen content and catecholamine metabolism in the central nervous system is discussed.     

Age-related characteristics of cerebral blood vessels in the rat (morphometric study)

Age changes in the vascular network density and transversal section of the vessels have been studied in the cerebral hemisphere cortex, corpus callosum, septum and nucleus caudatus of Wistar rats. Angiography has been performed by means of intracardiac injection of Indian ink, frontal colloidin slices of the brain 15 mcm thick have been prepared. Amount of vessels and section area of each vessel have been measured, using the automatic analysis. Each brain area studied has homogeneous vascularization density, however, they differ from each other by the amount of vessels. The vascular size in the areas does not differ. At the age of 2-20 months the average number of vessels in all the cerebral areas investigated does not change, while the vascular diameters demonstrate certain tendency to increase after 17 months of life.     

Acetylcholinesterase in neurons of the rat cerebral cortex.

AChE-containing neurons have been demonstrated by electron-microscopical histochemistry in the neocortex of the rat. These cells are mainly located in layer VI. AChE activity is seen in the cisternae of the RER, in subsurface cisternae and in the dendritic membranes.     

Quantitative analysis of albumin uptake and transport in the rat microvessel endothelial monolayer

We determined the concentration dependence of albumin binding, uptake, and transport in confluent monolayers of cultured rat lung microvascular endothelial cells (RLMVEC). Transport of (125)I-albumin in RLMVEC monolayers occurred at a rate of 7.2 fmol. min(-1). 10(6) cells(-1). Albumin transport was inhibited by cell surface depletion of the 60-kDa albumin-binding glycoprotein gp60 and by disruption of caveolae using methyl-beta-cyclodextrin. By contrast, gp60 activation (by means of gp60 cross-linking using primary and secondary antibodies) increased (125)I-albumin uptake 2.3-fold. At 37 degrees C, (125)I-albumin uptake had a half time of 10 min and was competitively inhibited by unlabeled albumin (IC(50) = 1 microM). Using a two-site model, we estimated by Scatchard analysis the affinity (K(D)) and maximal capacity (B(max)) of albumin uptake to be 0.87 microM (K(D1)) and 0.47 pmol/10(6) cells (B(max1)) and 93.3 microM (K(D2)) and 20.2 pmol/10(6) cells (B(max2)). At 4 degrees C, we also observed two populations of specific binding sites, with high (K(D1) = 13.5 nM, 1% of the total) and low (K(D2) = 1.6 microM) affinity. On the basis of these data, we propose a model in which the two binding affinities represent the clustered and unclustered gp60 forms. The model predicts that fluid phase albumin in caveolae accounts for the bulk of albumin internalized and transported in the endothelial monolayer.     

Regional cerebral blood flow thresholds during cerebral ischemia.

The development of methods of determining regional cerebral blood flow (rCBF) has made possible the determination of thresholds for the appearance of cerebral ischemia. These thresholds vary depending on the method used for assessing cerebral ischemia. The following thresholds have been determined in man and nonhuman primates: 20 cc/100 g per min, electroencephalogram (EEG) and evoked cortical potential abnormalities appear, paralysis seen in waking monkeys; 15 cc/100 g per min. EEG and evoked cortical potential are lost; 12 cc/100 g per min, flows at this level in excess of 120 min produce infarction in waking animals; and 6 cc/100 g per min, massive loss of intracellular [K+]. The residual rCBF and the duration of ischemia determine the appearance of infarction in waking Macaca irus monkeys.     

Origins of blood acetate in the rat.

1. Fluorimetric techniques were used to characterize the environment of tryptophan residues in thermolysin and apo-thermolysin. The apo-thermolysin was obtained by dissolving the enzyme in the presence of 10mm-EDTA, which removed the functional Zn(2+) ion and the four Ca(2+) ions/molecule from the enzyme. 2. At 25 degrees C in aqueous solution the fluorescence-emission spectrum of the native holoenzyme, on excitation at 290nm, was essentially characteristic of tryptophan, with an emission maximum at 333nm. The emission maximum of the apoenzyme is red-shifted to 338nm and the relative intensity of fluorescence is decreased by 10%, both effects indicating some unfolding of the protein molecule, with the indole groups being transferred to a more hydrophilic environment. 3. Fluorescence quenching studies using KI, N'-methylnicotinamide hydrochloride and acrylamide indicated a more open structure in the apoenzyme, with the tryptophan residues located in a negatively charged environment. 4. The thermal properties of the apoenzyme, as monitored by fluorescence-emission measurements, are dramatically changed with respect to the native holoenzyme. In fact, whereas the native enzyme is heat-stable up to about 80 degrees C, for the apoenzyme a thermal transition is observed near 48 degrees C. The apoenzyme is also unstable to the action of unfolding agents such as urea and guanidinium chloride, much as for other globular proteins from mesophilic organisms. 5. The functional Zn(2+) ion does not contribute noticeably to the stability of thermolysin. 6. It is concluded that a major role in the structural stability of thermolysin is played by the Ca(2+) ions, which have a bridging function within this disulphide-free protein molecule.     

Circadian and seasonal variations in pineal gland intercellular canaliculi in the white rat.

Seventy Wistar rats are used to study the changes in pineal intercellular canaliculi over a 21-hour period and for two different photoperiods (pre-autumn, first week of September, and winter, first week of February). The study considers these changes at pineal body, cortical and medullar level separately, and compares the values obtained. The results show variations in canalicular surface at different point times (10:00, 14:00, 18:00) and for both photoperiods. The variations are found to favour the cortical layer, and are also observed between nocturnal and diurnal hours. Canalicular surface to greater during the diurnal hours of both photoperiods. Interesting histological findings are described that suggest an important function of the intercellular canaliculi in pineal gland metabolic exchange.