The behavioral and neuromorphological characteristics of rats with spontaneous hypertension

Rats with spontaneous hypertension (strain SHR) reveal retarded somatic growth at early stages of ontogenesis. However, in further postnatal life, after transition to self-feeding, these animals exhibit larger body mass. Significant correlation was found between the arterial pressure and body mass. Some peculiarities in the behaviour of rats from the strain SHR were found already at early stages of ontogenesis. In 2-month animals, the brain exhibits some unusual features: lateral ventricles are enlarged, the corpus callosum is thinner, the volume of the pyramids in the dorsal hippocamp (field CA3) is less than in normal rats, the structure of the lateral hypothalamus being also different. It is suggested that unusual behaviour of hypertensive strain is due to the observed structural differences, as well as to changes in noradrenergic system of the brain.     

Morphometric analysis of the development of the cortical layers and extension of the forceps major of the corpus callosum in the mouse

The reduction of the forceps major of the corpus callosum was estimated quantitatively in relation to the lesions to the neocortex in animals to which methylazoxymethanol-acetate (MAM) had been administered on the 13 th, 15 th or 17 th day of embryonic development. The specimens which received a prenatal injection of MAM the 13 th or 15 the day of gestation show noticeable reductions in both the extension of the occipital neocortex and the forceps major of the corpus callosum. Parallelly in MAM 13 there is a significant reduction in cell density both in the deeper layers and the more superficial ones, whereas in MAM 15 only the supragranular layers seem to be altered. Such a quantitative analysis shows a close correlation among the decreases in the area of the forceps major of the corpus callosum, in the area of the occipital neocortex and in cell density of the infragranular and supragranular layers.     

Magnetic Resonance Findings of the Corpus Callosum in Canine and Feline Lysosomal Storage Diseases

Several reports have described magnetic resonance (MR) findings in canine and feline lysosomal storage diseases such as gangliosidoses and neuronal ceroid lipofuscinosis. Although most of those studies described the signal intensities of white matter in the cerebrum, findings of the corpus callosum were not described in detail. A retrospective study was conducted on MR findings of the corpus callosum as well as the rostral commissure and the fornix in 18 cases of canine and feline lysosomal storage diseases. This included 6 Shiba Inu dogs and 2 domestic shorthair cats with GM1 gangliosidosis; 2 domestic shorthair cats, 2 familial toy poodles, and a golden retriever with GM2 gangliosidosis; and 2 border collies and 3 chihuahuas with neuronal ceroid lipofuscinoses, to determine whether changes of the corpus callosum is an imaging indicator of those diseases. The corpus callosum and the rostral commissure were difficult to recognize in all cases of juvenile-onset gangliosidoses (GM1 gangliosidosis in Shiba Inu dogs and domestic shorthair cats and GM2 gangliosidosis in domestic shorthair cats) and GM2 gangliosidosis in toy poodles with late juvenile-onset. In contrast, the corpus callosum and the rostral commissure were confirmed in cases of GM2 gangliosidosis in a golden retriever and canine neuronal ceroid lipofuscinoses with late juvenile- to early adult-onset, but were extremely thin. Abnormal findings of the corpus callosum on midline sagittal images may be a useful imaging indicator for suspecting lysosomal storage diseases, especially hypoplasia (underdevelopment) of the corpus callosum in juvenile-onset gangliosidoses.     

The degenerative process during development of the corpus callosum

The ontogenesis of the corpus callosum is inextricably linked with the various processes controlling prosencephalic development. Our study is based on series of frontal and sagittal sections through the prosencephalon of 16 and 17 day mouse embryos and on ultrathin sections of the septum, particularly of the zone where the callosal fibres cross. The septum, which contains the first callosal fibres, does not undergo the fusional process described by other authors. The passage of pioneer fibres from one hemisphere to the other is preceded by the degeneration and death of the atrocytes of the cortical plate in the fundus of the interhemispheric issure, and by proliferation of the subependymal cells. The proliferation and migration of the subependymal cells from the medial angles of the lateral ventricles may well assist the passage of pioneering callosal fibres.     

Developmental Changes in the Corpus Callosum from Infancy to Early Adulthood: A Structural Magnetic Resonance Imaging Study

Previous research has reported on the development trajectory of the corpus callosum morphology. However, there have been only a few studies that have included data on infants. The goal of the present study was to examine the morphology of the corpus callosum in healthy participants of both sexes, from infancy to early adulthood. We sought to characterize normal development of the corpus callosum and possible sex differences in development. We performed a morphometric magnetic resonance imaging (MRI) study of 114 healthy individuals, aged 1 month to 25 years old, measuring the size of the corpus callosum. The corpus callosum was segmented into seven subareas of the rostrum, genu, rostral body, anterior midbody, posterior midbody, isthmus and splenium. Locally weighted regression analysis (LOESS) indicated significant non-linear age-related changes regardless of sex, particularly during the first few years of life. After this increase, curve slopes gradually became flat during adolescence and adulthood in both sexes. Age of local maximum for each subarea of the corpus callosum differed across the sexes. Ratios of total corpus callosum and genu, posterior midbody, as well as splenium to the whole brain were significantly higher in females compared with males. The present results demonstrate that the developmental trajectory of the corpus callosum during early life in healthy individuals is non-linear and dynamic. This pattern resembles that found for the cerebral cortex, further suggesting that this period plays a very important role in neural and functional development. In addition, developmental trajectories and changes in growth do show some sex differences.     

Morphology of the human corpus callosum: the shape of its mediosagittal section

The shape of the corpus callosum was studied on mediosagittal sections of 50 human brains. The terms "facies corticalis" and "facies profunda" are proposed for the sides of corpus callosum. Each of 50 brains had a different shape of callosal mediosagittal section and any available classification was not possible. In 94% of cases, the contour of callosal cortical surface exhibited a posterior depression and in 46% also an anterior one. Other details of callosal morphology influencing its shape on mediosagittal section (transverse folds, circumscribed depressions) were described. The junction of fornix and corpus callosum in 78% was in 3rd and in 14% in 4th quarter of callosal length. The possible significance of these findings for further studies of human brain morphology is discussed.     

Earliest renin containing cell differentiation during ontogenesis in the rat

Summary The differentiation of renin containing cells was studied by immunocytochemistry in normal rat fetuses by the use of highly specific renin, angiotensin I and II antisera.Renin synthesizing cells were detectable as early as the 15th day of gestation outside the nephrogen territories within the walls of mesonephrotic-gonadic and renal arteries. Intrarenal differentiation began at the 17th day and progressed along the intrarenal arterial tree. AII immunostaining appeared concomitantly in the renin containing cells and developed considerably during ontogenesis, suggesting intracellular biosynthesis.It can be suggested that in the fetus newly synthesized AH may contribute to the early systemic and renal blood pressure regulation.     

Earliest renin containing cell differentiation during ontogenesis in the rat. An immunocytochemical study

The differentiation of renin containing cells was studied by immunocytochemistry in normal rat fetuses by the use of highly specific renin, angiotensin I and II antisera. Renin synthesizing cells were detectable as early as the 15th day of gestation outside the nephrogen territories within the walls of mesonephrotic-gonadic and renal arteries. Intrarenal differentiation began at the 17th day and progressed along the intrarenal arterial tree. AII immunostaining appeared concomitantly in the renin containing cells and developed considerably during ontogenesis, suggesting intracellular biosynthesis. It can be suggested that in the fetus newly synthesized AII may contribute to the early systemic and renal blood pressure regulation.     

Corpus callosum morphology in capuchin monkeys is influenced by sex and handedness

Sex differences have been reported in both overall corpus callosum area and its regional subdivisions in humans. Some have suggested this reflects a unique adaptation in humans, as similar sex differences in corpus callosum morphology have not been reported in any other species of primate examined to date. Furthermore, an association between various measurements of corpus callosum morphology and handedness has been found in humans and chimpanzees. In the current study, we report measurements of corpus callosum cross-sectional area from midsagittal MR images collected in vivo from 14 adult capuchin monkeys, 9 of which were also characterized for hand preference on a coordinated bimanual task. Adult females were found to have a significantly larger corpus callosum: brain volume ratio, rostral body, posterior midbody, isthmus, and splenium than adult males. Left-handed individuals had a larger relative overall corpus callosum area than did right-handed individuals. Additionally, a significant sex and handedness interaction was found for anterior midbody, with right-handed males having a significantly smaller area than right-handed females. These results suggest that sex and handedness influences on corpus callosum morphology are not restricted to Homo sapiens.     

Effects of environmental conditions in the period of early ontogenesis on the formation of defensive behavior in juvenile roach Rutilus rutilus (Cyprinidae)

The feeding and defensive behavior of juvenile roach Rutilus rutilus (offspring of one pair of spawners) that were held at early stages of ontogenesis under conditions of differently enriched environments was studied. After the beginning of active swimming (the 12th day upon hatching), roach were reared for 95 days under different environmental conditions (feeding on active or immobilized organisms, the presence or absence of constant water flow, and the presence or absence of a predator), after which comparison of the efficiency of feeding behavior in the presence of a predator in juveniles of different groups was performed. It was established that the degree of environmental richness at early stages of ontogenesis exerts a determining effect on the formation of habits of defensive and feeding behavior. The most efficient behavior was observed in individuals that were held together with the predator during rearing.     

The characteristics of the programming action of androgens on the formation of sexual dimorphism in the level of corticosteroid-binding globulin in rats

The role of sex steroids in the programming of the level of serum corticosteroid binding globulin (CBG) of male and female rats has been studied at different stages of ontogenesis. It was shown that castration of adult males lead to the increase of the level of CBG, but not to the elimination of sex differences. Gonadectomy of males up to 28th day of postnatal life results in complete feminization of the CBG content in these animals at the age of 10-12 weeks. The castration after 35th day of life does not prevent the formation of the male phenotype of CBG content. The results of administration of testosterone-propionate (TP) to castrated males at different periods of ontogenesis suggests that the sensitivity to irreversible negative action of androgens appears after 28th day of life and disappears after the puberty. It was concluded that short period of ontogenesis from 29th to 35th days of life is critical for the realization of the irreversible masculinization of CBG level upon the influence of androgens in the physiological conditions. It was found that injections of both synthetic estrogens diethylstilbestrol or TP in the sensitive period of ontogenesis lead to the expression of male phenotype of CBG level in a similar fashion.     

Anatomy of corpus callosum in prenatally malnourished rats

The effect of prenatal malnutrition on the anatomy of the corpus callosum was assessed in adult rats (45-52 days old). In the prenatally malnourished animals we observed a significant reduction of the corpus callosum total area, partial areas, and perimeter, as compared with normal animals. In addition, the splenium of corpus callosum (posterior fifth) showed a significant decrease of fiber diameters in the myelinated fibers without changing density. There was also a significant decrease in diameter and a significant increase in density of unmyelinated fibers. Measurements of perimeter's fractal dimensions from sagittal sections of the brain and corpus callosum did not show significant differences between malnourished and control animals. These findings indicate that cortico-cortical connections are vulnerable to the prenatal malnutrition, and suggest this may affect interhemispheric conduction velocity, particularly in visual connections (splenium).     

Morphometric Changes of the Corpus Callosum in Congenital Blindness

We examined the effects of visual deprivation at birth on the development of the corpus callosum in a large group of congenitally blind individuals. We acquired high-resolution T1-weighted MRI scans in 28 congenitally blind and 28 normal sighted subjects matched for age and gender. There was no overall group effect of visual deprivation on the total surface area of the corpus callosum. However, subdividing the corpus callosum into five subdivisions revealed significant regional changes in its three most posterior parts. Compared to the sighted controls, congenitally blind individuals showed a 12% reduction in the splenium, and a 20% increase in the isthmus and the posterior part of the body. A shape analysis further revealed that the bending angle of the corpus callosum was more convex in congenitally blind compared to the sighted control subjects. The observed morphometric changes in the corpus callosum are in line with the well-described cross-modal functional and structural neuroplastic changes in congenital blindness.     

Age-related Changes of Elements in Human Corpus Callosum and Relationships Among These Elements

To elucidate compositional changes of the corpus callosum with aging, the authors investigated age-related changes of elements and relationships with their element contents in the corpus callosum. After ordinary dissection by medical students at Nara Medical University was finished, the genu, trunk, and splenium of the corpus callosum were resected from the subjects ranging in age from 58 to 94 years. The element contents of the corpus callosum were determined by inductively coupled plasma-atomic emission spectrometry. The contents of Ca, P, S, Mg, Zn, Fe, and Na did not change significantly in the genu, trunk, and splenium of the corpus callosum with aging. Regarding the relationships among the element contents, significant correlations were found among the contents of Ca, P, S, Mg, and Fe in all of the genu, trunk, and splenium of the corpus callosum with some exceptions.     

Early components of transcallosal responses in acute ischaemia of the corpus callosum

In 8 baboons maintained under propofol anaesthesia, transcallosal evoked responses were recorded from the primary motor cortex following electrical stimulation of the contralateral homotopic cortical surface. The corpus callosum was made ischaemic by transorbital occlusion of the common anterior cerebral artery; blood flow (measured by the hydrogen clearance method) in the stimulating and recording regions was not significantly affected by this procedure. The transcallosal responses from the normally perfused brain contained early positive (P1) and negative (N1) components. As stepwise ischaemia was produced in the corpus callosum, the amplitude of P1 initially increased up to 150% of control and the peak latency of P1 was significantly prolonged. At flows below 8 ml/100/g/min the amplitude rapidly decreased. Wave form changes and flow threshold of N1 were similar to those of P1. These results suggest that measurement of early transcallosal responses could be useful clinically as monitors of the ischaemic level in anterior cerebral artery territory.     

Immunolocalization of type IV collagen and laminin during rat gonadal morphogenesis and postnatal development of the testis and epididymis

Summary The distribution of type IV collagen and laminin was studied by immunocytochemistry during rat gonadal morphogenesis and postnatal development of the testis and epididymis. Immunostaining appeared as early as the 12th day of gestation along the basement membranes of the mesonephric-gonadal complex. The connection between some mesonephric tubules and coelomic epithelium was seen between the 12th and 13th day of gestation. Discontinuous immunostained basement membranes delineated the differentiating sexual cords in 13-day-old fetuses; this process probably began in the inner part of the gonadal ridge. The seminiferous cords surrounded by a continuous immunoreactive basement membrane are separated from the coelomic epithelium by the differentiating tunica albuginea in 14-day-old fetuses. During the postnatal maturation of epididymis and testis, the differentiation of peritubular cells is accompanied by a progressive organisation of the extracellular matrix into a continuous basement membrane. This change is associated with a gradual condensation of peritubular cells inducing an increase of immunostaining. In adult animals, the tubular wall of epididymis is thicker than the lamina propria of seminiferous tubules. Both type IV collagen and laminin immunostaining paralleled during ontogenesis at the light-microscope level.     

Immunolocalization of type IV collagen and laminin during rat gonadal morphogenesis and postnatal development of the testis and epididymis

The distribution of type IV collagen and laminin was studied by immunocytochemistry during rat gonadal morphogenesis and postnatal development of the testis and epididymis. Immunostaining appeared as early as the 12th day of gestation along the basement membranes of the mesonephric-gonadal complex. The connection between some mesonephric tubules and coelomic epithelium was seen between the 12th and 13th day of gestation. Discontinuous immunostained basement membranes delineated the differentiating sexual cords in 13-day-old fetuses; this process probably began in the inner part of the gonadal ridge. The seminiferous cords surrounded by a continuous immunoreactive basement membrane are separated from the coelomic epithelium by the differentiating tunica albuginea in 14-day-old fetuses. During the postnatal maturation of epididymis and testis, the differentiation of peritubular cells is accompanied by a progressive organisation of the extracellular matrix into a continuous basement membrane. This change is associated with a gradual condensation of peritubular cells inducing an increase of immunostaining. In adult animals, the tubular wall of epididymis is thicker than the lamina propria of seminiferous tubules. Both type IV collagen and laminin immunostaining paralleled during ontogenesis at the light-microscope level.     

Effect of gangliosides on adenylyl cyclase activity in the cortex and striatum of rats

By studying the effects of gangliosides (G) on learning and memory we have found that i.p. administration of G led to a decrease in AC activity in the cortex (Cx) and striatum (Str) as well as in the threshold of the sensitivity of striatal neurons to the effect of cholinergic agonists. G also modified the sensitivity of AC from the Cx and Str to such agents as Gpp[NH]p and forskolin. The aim of this work was to analyze the correlation between the changes in the activity of AC in the Cx and Str, concentration of G in these brain structures as well as formation of motor reactions of newborn rats during the first month of postnatal ontogenesis. It was found that new born rats develop normal body rotation by sixth day, locomotion by fifteenth day and stabilization of locomotor activity and supporting body balance by 20–22nd day. As shown previously, the concentration of gangliosides in the Cx and Str is gradually increasing during the first month of animal development. The activity of AC (pmol cAMP/min/mg of protein) in the Cx was found to decrease from 34.75 to 4.09 and in the Str from 46.00 to 11.67 during the first week after birth. However in the periods of formation of general behavioural reactions we observed a statistically significant increase in AC activity: in the Str on 10th and 26th days (p < 0.01) and in the Cx from 10th to 19th days (p < 0.05) compared to the AC activity on 5th and 30th days. Thus, formation of locomotor activity and posture‐tonic reactions during development of rats in early postnatal ontogenesis correlates with increasing concentration of G and basal activity of AC. Supported by RFBR (99‐04‐49751) and RAS (99‐06‐287).