Postnatal vascular growth in the neocortex of normal and protein-deprived rats. Morphometric studies

A low-protein isocaloric diet during gestation affects brain development and alters permanently cerebral cortex blood vessels in rat offspring

In humans, low birth weight is associated with nonfatal stroke, cardiovascular disease and diabetes at adulthood. The aim of this study was to investigate in rats the effect of early protein restriction, inducing low birth weight, on brain and endocrine pancreas vascularization at birth and to study if such alterations lasted until adulthood. Pregnant rats were fed either 20 or 8% protein isocaloric diets. Control newborns were nursed by their dams fed the 20% protein diet and low protein (LP) pups by dams fed either the 8 or 20% protein diet. The diets given during lactation were maintained until adulthood. The blood vessel density of cerebral cortex analyzed by morphometry in 3-d-old pups from dams fed the 8% protein diet was lower than in control (C). It remained lower at adulthood whether a LP or a C diet was given postnatally. Reduction of vascularization at adulthood induced by the LP diet limited to fetal life seems characteristic for the brain since vascularization of islets of Langerhans was reduced in neonates but normalized at adulthood by a C diet postnatally. Body and brain weights were lower in LP pups and adults. DNA concentration was lower in forebrain and higher in cerebellum in LP pups. In brain of LP adults, DNA, protein, cholesterol and phospholipid concentrations were lower and were restored at adulthood by a normal diet after birth. In conclusion, cerebral cortex of offspring exposed to a LP isocaloric diet during fetal development showed reduced vascularization which remained throughout life.

Successful prediction of immediate effects of undernutrition throughout the brain growth spurt on capillarity and synapse-to-neuron ratio of cerebral cortex in rats

Based on the hypothesis that undernutrition depresses the growth rate of all processes in brain contemporaneous with it to the same extent (Peeling & Smart, 1994), specific predictions were made regarding the effect of undernutrition on two quite different facets of anatomical development within visual cortex. It was predicted that severe undernutrition during the suckling period would leave capillarity unaffected, but would result in a deficit in synapse-to-neuron ratio of similar magnitude to that in brain weight. At birth rat pups were fostered and either well fed to 30 days or undernourished to the same age by underfeeding their foster mothers. Rats were killed at 30 days by perfusion with glutaraldehyde. Visual cortex was dissected out for quantitative histological study. The number of capillary profiles per unit area of section and the area of each profile were assessed with an image analysis system. Quantitative characteristics of the neuron and synapse populations were estimated by light and electron microscopy respectively. Undernutrition resulted in a 21% deficit in brain weight, and a 22% deficit in the number of synapses per neuron. Capillarity, expressed as the fraction of section area occupied by capillary lumen, appeared completely indifferent to nutrition. However, fewer capillary profiles were found per unit area of section in growth-restricted samples, and the profiles which were present were, on average, larger. Neuron density was elevated by 19% in the undernourished group. These findings are in good agreement with the hypothesis.

Neonatal enucleation induces correlated modification in sensory responsive areas and pial angioarchitecture of the parietal and occipital cortex of albino rats

This study was carried out to investigate whether correlations existing in normal adult rats (Ambach et al., '86) between functional characteristics of neocortical areas and their pial angioarchitecture can be correspondingly modified under pathological conditions. The right eyes of albino rats were enucleated on the 1st, 8th, 15th and 30th day after birth, respectively. At the age of 3 to 4 months, the responsiveness of the parieto-occipital cortex to sensory stimuli was studied in enucleated animals and age matched controls. After the mapping of visually and somatosensorily evoked potentials, the vascular system was filled with dye. Monocular enucleation at birth induced bilateral modifications in sensory responsiveness and corresponding changes in pial angioarchitecture, especially in the venous drainage fields. In comparison with the controls, a considerable expansion was observed in the overlapping zone between visually and somatosensorily responsive areas. In contrast, borders of the visual cortex toward the auditory and retrosplenial areas were essentially stable. Corresponding changes were found in the pial distribution patterns of cerebral veins but not of arteries. The major effect of neonatal enucleation on angioarchitecture was a change in the subdivision of the parieto-occipital veins drainage fields. This was due to a significant enlargement of the anterior accessory occipital (O3) vein, which compressed the drainage fields of the parietal and occipital veins and completely separated them from one another. The results suggest that during ontogenesis: (1) alterations in the formation of sensory input may interfere with neocortical angiogenesis, especially the structuring of veins, (2) after monocular enucleation this influence is prominent in parietal and occipital cerebral veins, and (3) these angiogenetic processes are vulnerable only during the perinatal and early postnatal period.

Changes in brain microvasculature resulting from early postnatal alcohol exposure

The microvasculature in selected brain regions in rats was examined on postnatal day 10 following exposure to alcohol on postnatal days 4 to 10. The alcohol-exposed rats were artificially reared and given 6.6 g/kg of ethanol condensed into 8 hr of each 24-hr period. A gastrostomy-control group was reared in the same manner but maltose-dextrin was substituted for ethanol in the formula. A suckle-control group was reared normally by dams. Measurements were taken from midsagittal sections of the cerebellum and sections of the hippocampal formation at a midtemporal level. Although the overall area of the vermal cerebellum was decreased as a consequence of the alcohol exposure, the capillary density was unchanged. However, cerebellar capillary diameters were increased in some lobules in the alcohol-exposed rats. In the dentate gyrus, there was a trend toward a decrease in capillary numerical density but no change in regional area or capillary diameter in the alcohol-exposed rats. In the hippocampus proper, there was a decrease in regional area, no change in capillary density, and an increase in capillary diameter due to alcohol. These results indicate that alcohol exposure during the early postnatal period affects the microvasculature differentially in the cerebellum, hippocampus proper and dentate gyrus.

Functional development of the visual system in normal and protein-deprived rats. VIII. Post-natal development of optic nerve axons

Protein deprivation results in a persistent impairment of transmission of impulses from the specific cortical projection within the visual cortex. In order to evaluate changes in subcortical structures during pre-weaning development, a study was made on number, calibre and myelination of optic nerve axons in control (C) and protein-deprived (PD) rats 5, 12, 20 and 30 days of age. Protein deprivation was induced by giving rat mothers a diet containing 7% protein by weight (control diet 14%, during gestation and lactation. The cross-sectional area of the nerve was measured on a digitizer. Between 3000 and 4000 axons collected from 7-13 field areas sampled by a random, systematic procedure from a cross-shaped area of the nerve were counted and measured. Between 5 and 12 days after birth, the number of axons was reduced by 50% in C rats. The total number of optic nerve axons was not significantly different in PD compared to C rats, indicating that protein deprivation does not affect the formation or naturally occurring nerve cell death of retinal ganglion cells. At all ages examined there were significant reductions in the number of axons larger than 0.52 micron as well as the number of myelinated axons. The rates of growth/maturation and myelination of axons in C rats and PD rats suggested that the reductions seen in PD rats up to 20 days of age may represent a developmental delay of approximately 4 days. At 30 days, a delay or a distortion of development may present. The retarded development of optic nerve axons is discussed in relation to delays, distortions and deficits during visual system maturation in protein-deprived rats.

Functional development of the visual system in normal and protein-deprived rats. VII. Lamination of oxidative enzyme activity in the visual cortex during post-natal development

Lamination of activity of two mitochondrial enzymes-succinate dehydrogenase (SDH) and menadione-dependent alpha-glycerophosphate dehydrogenase (M-GPDH) - was examined in the visual cortex of control (C) and protein-deprived (PD) rats from 10 days old to adult. In C rats, lamination of enzyme activity was evident from 10 days by a band of higher activity in lamina IV. A band of higher SDH activity was seen in superficial lamina VI from 15 days. Lamination of M-GPDH activity became less pronounced with increasing age, whereas distinct bands of high SDH activity in lamina IV and VI remained also in adult rats. PD rats showed a developmental delay of approximately 5 days with regard to the general increase in neuropile activity. A band of higher enzyme activity in lamina IV was present from 10 days, but it was markedly less distinct in the PD rats compared to the C rats between 15 and 25 days. A band of higher SDH activity in superficial lamina VI was not seen until 25 days in PD rats. No apparent differences were seen between adult C and PD rats. The observed developmental alterations are discussed in relation to other delays, distortions and deficits found in the visual system of PD rats.

Functional development of the visual system in normal and protein-deprived rats. IX. Visual evoked response in young rats

Changes in latencies of the visual evoked response (VER) during early post-natal development were examined in protein-deprived (PD) rats. The evoked response to light-flash stimulation was recorded in the dorsal lateral geniculate nucleus (dLGN) and on the surface of the visual cortex. In control rats, latencies of the cortical VER decreased rapidly up to 20 days and slowly thereafter. In PD rats, the latencies of the cortical VER were increased by 10-15 ms at 17 days; the developmental decrease was delayed by approximately 3 days. After 20 days, PD rats also went into a phase with slow decrease of the latencies, and the onset latency of the cortical VER was still increased by some 10 ms at 26/27 days. At this age, PD rats showed an increase in the latencies of the VER in the dLGN which was of similar magnitude to that in the cortical VER, indicating that alterations were more marked in the peripheral parts of the visual system at this stage of development. The findings are in agreement with previous studies indicating that there is a delay of visual system development in PD rats before 20 days. A maturational event which turns rapid into slow development at approximately 20 days in both C and PD rats turns this delay into a distortion of development. The delays and distortions of visual system development may be one causative factor for the functional deficit present in the visual cortex of adult PD rats.

The vascular response to tumor infiltration in malignant gliomas. Morphometric and reconstruction study

Neo-vascularization and endothelial hyperplasia have been shown to be very active in malignant gliomas. In this contribution the vascularization of the cortex infiltrated by malignant gliomas is morphometrically studied and the endothelial proliferations are immunohistochemically investigated and reconstructed by a three-dimensional computer-assisted procedure. Vessel density increases after tumor infiltration in some cases only. The diameter of vessels increases and so does the number of nuclei/vessel after the complete invasion of the cortex when vascular glomeruli develop. In completely infiltrated cortex with development of glomeruli and circumscribed necroses, vessel density is very low. No neoformation of vessels takes place before the complete infiltration of the cortex by the tumor. The hyperplastic formations, usually arranged parallel to the deep or outer cortical layers, take origin from the radially penetrating vessels from the meninges and their lateral branching. The hyperplasia deforms the vascular network, making it often inadequate to supply tumor cells. Immunohistochemically, the cells composing the hyperplastic structures are variably positive for factor VIII/RAg and, at a lesser extent, for alpha-smooth muscle actin. The poorness of the vascular network in many instances of completely infiltrated cortex is responsible for the development of circumscribed necroses.

Changes in brain temperature and free amino acids in normal and protein deprived suckling rats exposed to room temperature

Previous reports on early-induced protein-calorie malnutrition (PCM) in rats have indicated alterations in the concentration of free amino acids and of protein synthesis in the brain. Recently it was shown that early-induced protein deprivation (PD) retards the development of thermoregulation. This resulted in a failure to maintain a normal rectal temperature after short exposure to room temperature (+22 degrees C) still at the age of 20-25 days corresponding to changes seen in normal rats at an age of 10-15 days. In the present study, 20-day old PD and normal rats where examined with regard to the effect of exposure to room temperature on brain temperature and on brain free amino acids. The results show a similar reduction in brain and rectal temperature of the PD rats occurring within 30 minutes after exposure to room temperature. The reduction was in the range of 5 degrees C. PD rats kept in room temperature for 5 hours and then allowed to recover at 32.5 degrees C showed a slow increase in brain and rectal temperature but normal temperatures were not reached even after 1 hour. The concentration of free amino acids in the brain was examined in rats kept for 1 hour at room temperature or at 32.5 degrees C. In the PD rats kept at 32.5 degrees C, free aspartate and glutamate were reduced whereas taurine, GABA and glycine were increased as compared to their corresponding control rats. As a result of the reduced brain temperature in PD rats exposed to room temperature there was a reduction in free asparagine.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional development of the visual system in normal and protein-deprived rats. V. Specific cortical response and repetitive stimulation in adult rats

Recent studies on the specific visual system have indicated that early induced protein deprivation results in an impaired transmission from cell to cell in the cortex. To further investigate cortical mechanisms the response to repetitive light flashes and to electrical stimulation of the optic tract (OT) and the dorsal lateral geniculate nucleus (dLGN) were examined. The first potential of the surface visual evoked response (VER) and the monosynaptic response to OT and dLGN stimulation showed similar sensitivity to repetitive stimulation in C and PD rats. In PD rats later activity was significantly more sensitive to repetitive stimulation than in controls. By using paired stimuli with a short inter-stimulus interval, similar inhibitory mechanisms in PD and C rats were demonstrated. The results support the view that protein deprivation results in impaired cortical synaptic activation. The results are discussed in relation to previously described impairment at the cortical level in malnourished animals.

Functional development of the visual system in normal and protein-deprived rats. IV. Latencies in the specific visual pathway of adult rats

It was recently shown that an increase in latency of the cortical visual evoked response (VER) seen in young malnourished animals persists in adult rats given a low protein diet. In the present paper the VER latencies of the specific visual pathway were measured in order to establish the level at which the latency increase occurs in protein-deprived rats. The VER in the dorsal lateral geniculate nucleus (dLGN) showed no significant differences to onset or peak latencies between control (C) and the protein-deprived (PD) rats. The dLGN activity was higher in C rats than in PD rats. Late components differed in median values between the two groups, but the individual variations were large. Generally, the VER of the dLGN in PD rats was more stereotype compared with the C rats. Intracortical VER at a depth of 0.4-0.5 mm showed a small negative component of short onset latency in both C and PD rats. This component preceded the onset of the initial positivity recorded from the cortical surface by 1-2 ms in C rats and by 3-6 ms in PD rats. Following electrical stimulation of the dLGN, no differences in onset latency of the first cortical activity (monosynaptic response) were recorded between C and PD rats, whereas later activity was significantly delayed in PD compared with C rats. The laminar potential pattern was less distinct in PD compared with C rats, and the late components of the evoked response from deep cortical layers were markedly attenuated or lacking.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional development of the visual system in normal and protein-deprived rats. VI. Evoked responses in adult rats, protein deprived in early life and nutritionally rehabilitated from weaning

Previous studies have shown an increase in latency of the visual evoked response (VER) recorded from the cortical surface of adult rats subjected to protein deprivation (PD) during pre- and postnatal development. This alteration has been shown to originate mainly from the cortex itself. In the present study the possibility of normalizing such VER alterations by nutritional rehabilitation after early protein deprivation (R-PD) was investigated. Male rats were subjected to pre- and early postnatal protein deprivation through their mothers. Nutritional rehabilitation was started from weaning. The rats gained weight rapidly compared with rats subjected to protein deprivation throughout postnatal development but never reached the weight of controls (C) of the same age. Food consumption in relation to body weight was similar to that of controls. Rehabilitation continued until adult age when neurophysiological experiments were performed. The VER recordings from the dorsal lateral geniculate nucleus (dLGN) showed latencies similar to those reported previously for adult C and PD rats. The latencies of onset and first peaks of the cortical response recorded from the surface were increased by 5-6 ms in R-PD compared with C rats and hence similar to the latencies of adult PD rats. Intracortical responses to electrical stimulation in the dLGN were also similar to those of adult PD rats showing an normal onset latency but an increased latency of the peaks of the monosynaptic and late responses compared with C rats. The present results imply that the increased VER latencies noted in adult PD and R-PD rats are due to changes installed by protein deprivation during early development since they can not be reversed by nutritional rehabilitation starting at weaning.

Changes in specific gravity as a sign of disturbed brain maturation in protein-deprived rats

The specific gravity of the cerebral cortex of normal and protein-deprived rats aged 15, 21 and 25 days was determined. The increase in specific gravity seen in control rats in the course of their development was reduced in protein-deprived rats in the course of the period between 15 and 21 days of age. The results are in agreement with previous reports on delayed maturation of the brain in protein-deprived rats and indicate that determination of brain specific gravity may serve as a suitable screening method in situations when a disturbed brain maturation is suspected.

Functional development of the visual system in normal and protein deprived rats. III: Recordings from adult optic nerve in vitro

A persistent increase in the latencies of the visual evoked response recorded from the cortical surface of protein deprived adult rats was described recently (Sjöström et al. 1984). The morphological correlate to this alteration is unknown. Previous studies on malnourished rats have shown a reduction of axonal diameters and in the number of myelin lamellae in relation to axonal circumference, and hence the possibility of a decrease in fibre conduction velocity must be considered. In parallel study, we have established that changes in diameters and myelination of optic nerve fibres similar to those previously reported in malnourished rats are present in adult protein deprived (PD) rats (Conradi et al. 1985). In the present paper, recordings of optic nerves in vitro from adult normal (C) and protein deprived (PD) rats are described. The compound action potentials were very similar in the two groups. Three positive peaks were easily defined, probably corresponding to three functional groups of optic nerve fibers. No significant differences in amplitudes or conduction velocities for the three peaks were found between the C and PD rats. It is concluded that the increased latencies of the evoked response are not caused by a decrease in conduction velocity.

A morphometric study of the microvasculature of a rat glioma

Intracerebral tumours were produced in BD IX rats by the inoculation of neoplastic astrocytes. Following perfusion-fixation, 1.0 micron sections were stained with toluidine-blue and photographed so as to construct photomontages embracing deep tumour, tumour edge and surrounding brain. Thirteen montages from 9 tumours were studied. Successive 200 micron samples were analysed with a digitizing tablet and, for each sample the following were measured: the number of vascular profiles per unit area, the mean vessel circumference and diameter and the approximate fractions of the sample occupied by tumour and necrosis. Towards the tumour centre, vascular density dropped to 20% of that for normal cortex but vessel size more than doubled. The surface area fraction of the vessels reached a maximum at the tumour edge. These results provide not only an anatomical framework for both a variety of physiological studies and for the investigation of angiogenesis in this system but also have pharmacokinetic implications for the treatment of brain tumours.

Functional development of the visual system in normal and protein deprived rats. II. Morphometric and biochemical studies on adult optic nerve

The optic nerve of normal (C) and protein deprived (PD) adult rats was examined by morphometry and biochemistry. The mean cross-sectional area of the optic nerve was reduced by 15% and the number of axons per unit area increased by 17% in the PD rats. Calibre spectrum analysis of axons revealed a reduction in median diameter from 0.49 micron in controls to 0.45 micron in PD rats. The number of axons with a diameter larger than 1 micron was reduced by 35% in PD rats. These reductions were probably due to a general reduction in size, since the calculated total number of axons in the optic nerve was almost identical in C and PD rats (126 X 10(3) and 124 X 10(3), respectively). The increased packing density of axons in the nerve was not only due to thinner axons. The biochemical measurements showed a marked reduction in myelin basic protein in the optic nerves of PD rats, without an alteration in the composition of the total protein. This confirms the persistent hypomyelination which has been reported previously in other malnutrition models. The possible relations between the structural and biochemical changes affecting optic nerve fibres and physiological findings on cortical visual evoked response and on optic nerve in vitro in PD rats are discussed.

The angiogenesis of micrencephalic rat brains caused by methylazoxymethanol acetate. I. Superficial venous system. A quantitative analysis

The angiogenesis of the rat cerebrum was studied under pathologic conditions caused by the administration of the neurotoxin methylazoxymethanol acetate (MAMAc) in the time (E14) of neuroblast migration. The sinovenous junction of the main superficial cerebral veins and the morphological changes of the veins were examined by a quantitative analytic method. The hypoplastic areas of the brains showed extremely malformed venous systems with pathologic changes of the sinovenous junctions depending on the degree of disturbance of the neuroblast migration. These findings suggest the primary role of the neuronal maturation in the angioarchitectonic development and the direct dependency of the vascular differentiation on the neuroblast migration of the drained territory.

Effect of ambient temperature on rectal temperature in normal and malnourished rats during early postnatal development

Information on body temperature is frequently lacking in metabolic studies on normal and malnourished suckling rats although differences in their thermoregulatory efficiency may be expected. The aim of the present study was to evaluate the effect of different ambient temperatures on the rectal temperature of litters of normal and protein deprived rats to establish the ambient temperatures at which a normal rectal temperature can be expected at various postnatal ages. The offspring of normal rats and rats subjected to a dietary reduction of 50% of the protein intake were examined 10 days to 30 days postnatally. The pups were transferred from the nest cage to an incubator: the rectal temperature was measured immediately after transfer to the incubator and 30 and 60 min later at ambient temperatures of 35, 30 and 25 degrees C. Up to 15 days of age control pups showed a fall in rectal temperature after the short exposure to room temperature (22 degrees C) needed for transfer. A similar fall of rectal temperature was recorded in the malnourished pups up to 25 days age. The effects of the ambient temperatures on the malnourished pups indicated a delay in the control of body temperature of some 10 days. This is in agreement with a previous report on semi-starved rats (Heim & Szelenyi 1965). The conditions for the maintenance of a normal rectal temperature in litters of normal and malnourished suckling rats separated from their mother are out-lined.

Functional development of the visual system in normal and protein deprived rats. I. Persistent changes in light-induced cortical evoked response

During an investigation focused on development of visual evoked responses (VER) in normal and protein deprived rats indications of persisting latency differences were found. Since such differences are in variance with previous reports special attention was paid to compare control and protein deprived adult rats. Protein deprivation was induced by feeding rats a diet with 50% reduction in protein content compared with control rat diet from two weeks before onset of gestation until examination. Dependence on experimental variables of latencies and complexity of the VER illustrated the need of a well defined experimental situation. Adult protein deprived rats showed significantly longer latencies to onset and to the first three peaks of the VER and an altered complexity of the response. It is suggested that the observed alterations result from effects of the protein deprivation on early brain development since this and previous studies have shown similar alterations in developing young rats. The divergence in findings between the present and previous reports may be explained by differences in degree of malnutrition and in other experimental conditions.

Vulnerability to lead in protein-deprived suckling rats

Most studies on lead toxicity in the suckling rat have been performed with doses leading to growth retardation. In a previous paper ( Sundstr öm et al. 1983), the effects of different lead doses on normal suckling rats were described. The dose of 10 mg/kg body weight daily given on days 1-15 pp produced minute hemorrhagic lesions on day 15 in the cerebellum, whereas rats given 5 mg/kg body weight daily lacked microscopically discernible pathologic changes in the brain. None of these groups exhibited growth retardation. To further elucidate the association between lead encephalopathy and malnutrition, lead was administered to protein-deprived suckling rats. Protein deprivation was achieved by a diet with 50% reduction of protein content. The mothers of the pups were fed this diet from 2 weeks before conception throughout the experiment. Experimental animals were injected i.p. with 5 mg or 10 mg lead nitrate/kg b.wt. daily. Littermates, injected with vehicle without lead nitrate served as controls. Protein-deprived rats without either treatment were "external" controls. Animals were killed at 10, 15, and 20 days age for determination of lead content in blood and brain and for light-microscopic examination. The protein-deprived rats given 10 mg/kg b.wt. daily were growth-retarded as compared to unexposed protein-deprived rats. The mortality was almost 100% at 15-20 days pp. At 15 days, the cerebellum of these rats showed abundant hemorrhages, and the cerebrum was also hemorrhagically discolored. Protein-deprived rats given 5 mg/kg b.wt. daily did not differ significantly from unexposed protein-deprived rats with regard to body weight gain.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellular enzymatic differentiation in brain vessels of normal and protein-deprived rats. Biochemical studies

Brain capillary development was studied in normal and protein-deprived rats using the specific activity of alkaline phosphatase (EC 3.1.3.1) and gamma-glutamyl transpeptidase (EC 2.3.2.1) in whole brain homogenates and microvessels obtained by gradient centrifugation according to Orlowski et al. (1974). Pre- and postnatal protein deprivation was induced by a 50% reduction in the dietary protein content. The density of microvessel fragments changed during development. Most of the early developmental increase in the specific activity of both enzymes in whole brain homogenates of normal rats can probably be explained by a rapid formation of new capillary segments. The increase in specific activity of gamma-glutamyl transpeptidase in microvessels was interpreted as a sign of cellular differentiation. Protein deprivation resulted in reduced specific activity of both enzymes in whole brain homogenates of 30-day-old rats, probably as a result of the decreased length per volume of the cerebral capillary network at this age (Conradi et al. 1979a). Signs of impaired endothelial growth were also present in the protein-deprived rats since the distribution of microvessel fragments in the 30-day-old protein-deprived rats was similar to that in 3-week-old normal rats. The specific activity of alkaline phosphatase was decreased in the microvessel fractions of 30- and 96-day-old protein-deprived rats, apparently signifying an effect of the protein deprivation on the endothelial cells. These effects of protein deprivation on the brain capillary endothelial transport system may have negative consequences for growth and function in the brain.

The influence of protein deprivation during development on amino acid incorporation into cerebral proteins

The incorporation of 3H-valine into protein of cerebrum, liver, and muscle was studied in rats fed a low protein diet. Animals, 15-50 days old, were used to cover the period during and after the most rapid phase of cerebral protein synthesis. The precursor was administered in doses resulting in brain concentrations of free valine in the 0.1-0.3 mM range. Two series of experiments were run and the injected dose varied for comparison of protein synthesis at different concentrations of precursor valine. By concomitant amino-acid analysis it was shown that the concentration of other amino-acids in the brain was not changed by the injected valine. The changes in the amino-acid pool with age in control rats were in agreement with previous findings. Only small alterations were seen in the amino acid pool as an effect of protein deprivation, the results being consistent with those of some previous reports. Uptake of valine into the brain appeared to be decreased only in 15-17-day-old protein-deprived rats. Valine incorporation into cerebral protein was decreased in the youngest age group but no effect was seen in older animals. Liver protein incorporation was slightly decreased by low protein diet but a marked reduction was observed for muscle protein. The changes in brain protein synthesis during normal development were in agreement with previous studies and differed qualitatively from those in liver and muscle.

The effects of chlorpromazine and phenobarbital on vasculogenesis in the cerebellar cortex

The morphological effects of two chemically different neuroactive drugs (chlorpromazine and phenobarbital) on vasculogenesis in rat cerebellum were examined to determine the presence of vascular alterations. Therapeutic dosages of both drugs were chronically administered to separate groups of maternal rats beginning on days 10, 13, 15, 18, and 21. In chlorpromazine-treated animals the specific length of blood vessels was most severely reduced in the Purkinje cell layer. Animals treated with phenobarbital demonstrated an initial reduction in specific length in the Purkinje cell layer but returned to control values by day 21 postnatal (p.n.). Blood vessels in the molecular and granular layers showed little change. The observed changes have been discussed in relation to possible mechanisms and their relationship to neurogenesis.

Morphometric comparison of hippocampal microvasculature in ageing and demented people: diameters and densities

The diameters and densities of capillaries and arterioles in the hippocampal cortex of normal subjects and patients with Alzheimer's dementia were measured in thick celloidin sections stained for alkaline phosphatase. Microvascular diameters in general are affected more by age than by the presence of dementia of the Alzheimer type. The diameter of both capillaries and arterioles increases significantly with age. The density of capillaries decreases whereas that of the arterioles increases significantly. The capillary changes suggest that a reduced exchange potential accompanies ageing. In brains of people with Alzheimer's disease the overall capillary diameters and densities do not differ from those of age-matched controls. Regional changes may, however, be important: those hippocampal zones showing the greatest severity of or increment in nerve cell lesions do correspond to those having the highest levels of or increase in capillary density and the greatest decrease in diameter, suggesting a direct association between neuronal susceptibility to Alzheimer changes and degree of regional blood supply. Capillary surface areas, volumes and area/capillary volume ratios support the possibility of this relationship. Neurofibrillary tangles and granulovacuolar degeneration do not correlate equally with the degree of capillary "irrigation"; tangles are more closely related to these morphological vascular parameters.

Motor nerve conduction velocity and nerve fibre diameter in experimental protein deprivation. Studies on rat peripheral nerve during development

Motor nerve conduction velocity (MCV) and nerve fibre calibre spectra of peripheral nerves were determined at different ages, during development in normal and protein-deprived rats. The protein deprivation was achieved by feeding female rats a protein deficient diet. Compared to control rats which were given a balanced diet, given ad lib from 2 weeks before conception and onwards. After weaning, the offspring were fed the same protein-deficient diet, the protein-deprived rats showed considerably reduced body weights but moderately reduced values of albumin and total protein in serum at 6 and 15 weeks of age. Although essentially the same, the mean nerve fibre diameter of the studied dorsal tail nerve was slightly larger in the protein-deprived rats at 6 weeks of age than in controls, while the inverse relationship was found at 15 weeks of age. The increase of MCV in normal and protein-deprived rats followed essentially the same curve during the period from 5-30 weeks of age. The results indicate that the MCV and nerve fibre diameter during development are correlated to chronological age and not to body size, although protein deprivation may, to a minor extent, influence nerve fibre calibre growth.

Postnatal vascular growth in the cerebellar cortex of normal and protein-deprived rats. Morphometric studies

The postnatal vascular growth in the cortex of vermis cerebelli folium IX of normal and pre- and postnatally protein-deprived rats was examined. The rate of increase in specific length of vessels seem to parallel the functional maturation of neurons in all cortical layers. From the first postnatal week there is a higher specific length of vessels in the Purkinje cell layer than in the adjoining parts of the molecular and granular layers. The results indicate that such differences are present also after the period of rapid vascular growth. Protein deprivation appears to affect the postnatal increase in specific length of vessels less in the Purkinje cell layer than in the granular and molecular layer where a significant reduction compared to controls was seen for the interval 7--20 days of age. At 90 days of age no significant differences were seen between control and protein-deprived rats.