Development of human lateral geniculate nucleus: an electron microscopic study

A qualitative and quantitative ultrastructural study has been carried out on lateral geniculate nuclei (LGN) of 21 human fetuses ranging in gestational age from 13-14 to 34-35 weeks. At the early age period of 13-15 weeks, LGN is characterized by immature cells with indented nuclei possessing multiple nucleoli and by a sparse neuropil. During the subsequent age periods studied progressive maturational changes lead to neurons having round nuclei with a single nucleolus and well-developed cytoplasmic organelles as well as to an elaborate neuropil. Synaptic contacts which are seen for the first time at the age of 13-14 weeks are of retinogeniculate type. They show features of immature synapses and are located mainly on the juxtasomatic parts of dendrites. With increasing gestational age, the synapses increase in size, maturity, types and complexity; an acquisition of complex synaptic arrangement (triad) occurs by 20-21 weeks. Excitatory synapses appear earlier than do the inhibitory ones. Formation of retinogeniculate contacts precedes that of the corticogeniculate type. The synaptic density and total synapse number show a progressive increase with increasing gestational age. The age period of 15-20 weeks of gestation is marked by presence of organelles suggestive of a high rate of metabolic activity, significant increase in synaptogenesis, presence of transient contacts on soma and large number of free postsynaptic membrane densities (PSD). The period thereby represents a critical period in the development of synapses in LGN. The numerical values obtained by by the age of 34-35 weeks are still low as compared to the values reported for other areas of brain.

Human retinal ganglion cell development in early prenatal period using carbocyanine dye DiI

Early development of retinal ganglion cell morphology has been studied in human fetuses of gestational age ranging from 7-8 weeks to 19-20 weeks by retrograde labelling with a lipophilic fluorescent dye, DiI. The retinal ganglion cells with simple and relatively uniform appearance having few dendritic processes between 7 to 11 weeks of gestation show progressive growth and elaboration of dendrites at 17-18 weeks revealing some morphological variation in shapes. It is by 19-20 weeks of gestation that the three major ganglion cell types resembling the alpha, beta and gamma classes of cat ganglion cells are identifiable in the developing human retina. The dendrites of some ganglion cells exhibit varicosities, filiform processes and spines even as early as 10-11 weeks indicating a possibility of involvement in synaptic connectivity.

An immunohistochemical study of neurotransmitter profiles in developing human visual cortex

The temporal pattern of development and distribution of gamma aminobutyric acid, serotonin, substance P and neuropeptide Y immunoreactive profiles was studied in the human visual cortex from 16 to 26 weeks of gestation, using an immunohistochemical technique. The immunoreactive profiles showed an increase in number and a change in their morphology and distribution pattern over the time period studied. A large number of neurons, fibers and terminals were stained with GABA antibody at 17-18 weeks and were distributed throughout the five zones of the developing visual cortex. GABA neurons were non-pyramidal and bipolar in form at 17-18 weeks while at 18-19 and 20-21 weeks the cells of subplate and intermediate zones were multipolar. Substance P and serotonin immunopositive fibers were present mainly in the intermediate zone at 16 and 17-18 weeks, where they were oriented in a horizontal manner. At subsequent ages they invaded the other zones also. Substance P positive neurons could be visualized only at 26 weeks of gestation in the intermediate, subventricular and ventricular zones; no cell bodies, however, stained with serotonin antibody. Neuropeptide Y immunoreactive cells and fibers were first seen in the intermediate zone but later were found to be distributed in other zones too. The observations indicate that the intermediate zone of the visual cortex in which the transmitters and peptides appear earlier assumes importance in the normal development as also noted in other mammals.

Expression of substance P in dentate nucleus of human cerebellum

The expression of substance P (SP) was examined in dentate nucleus (DN) of human cerebellum. A spatial and temporal sequence was observed in the innervation of the DN. SP appeared at 9-10 weeks and was dense in the dorsomedial region of DN. The SP immunoreactivity continued to increase until 19-21 weeks and showed a decline in the dorsomedial region by 24 weeks. By now, however, the ventrolateral region had a denser innervation. There is thus seemingly a relation between SP innervation and gyri formation in DN. SP-positive fibers were also localized in the neuroepithelium of the IV ventricle at all the ages studied. SP-positive fibers, however, reached the cerebellar cortex only by 24 weeks.

Prenatal human lateral geniculate nucleus: a quantitative light microscopic study

Using morphometric methods, a quantitative study has been carried out on the lateral geniculate nucleus (LGN) of human fetuses ranging in gestational age from 13 to 38 weeks. The volume of the nucleus as well as the neuronal, glial and dead cell populations have been studied in Nissl preparations. While the volume of the LGN shows a progressive increase throughout the period of study, the age period of 15-20 weeks is identified as a period of spurt in volumetric growth. Neuronal density and total neuronal number fall continuously while glial density and total glial population show a steady increase with advancing gestational age. Pyknotic dead cells are seen throughout the period of study with a peak die off between 14 and 18 weeks. The study, for the first time, outlines the critical period for volumetric spurt and neuronal death in the developing human LGN.

Developing dentate nucleus in man: a qualitative and quantitative study

Histological and quantitative studies were carried out in dentate nucleus (DN) of 14 human fetuses of gestational ages ranging from 10 weeks to 28 weeks in Nissl stained sections. The dentate nucleus was already well delineated at 11 weeks, but the adult profile was attained only by 27-28 weeks. The magnocellular dorsomedial region and the parvocellular ventrolateral region became apparent at 17-18 weeks. The numerical density of neurons showed a steady decline with advancing gestational age. However, the absolute neuronal count until 19-20 weeks was 367.1 x 10(3) followed by a count of 249.5 x 10(3) at 22-23 weeks. The reduction in the count between the two periods was significant and coincided with cell death which was striking between 19 and 23 weeks. The glial cell population continued to increase with advancing gestational age. The occurrence of significant neuronal cell death and its probable role in the developing human DN is reported for the first time.

Polyacrylamide as an infiltrating and embedding medium for vibratome sectioning of human fetal cerebellum containing DiI-filled axons

Polyacrylamide is widely used for the separation of proteins by electrophoresis. Here the usage of polyacrylamide as an infiltrating and embedding medium for vibratome sectioning of human fetal cerebellum containing DiI-filled axons is reported. The procedure is simple to implement and has several advantages: it does not require prior dehydration and clearing of tissue; it can be carried out at a low temperature of 4 degrees C; and the polyacrylamide neither dissolves the DiI nor does it interfere with the visualizing of DiI-filled profiles under fluorescence microscope.

Cytoarchitectural development of the human dentate nucleus: a Golgi study

Golgi-stained sections of the human cerebellar dentate nucleus (DN) at various gestational ages were examined to study the dendritic proliferation and maturation of the DN neurons. Bipolar cells were seen at 14-15 weeks. By 19-20 weeks, three cell types were identifiable: bipolar, hemispheric and pyriform. The cells of the dorsomedial region matured earlier than those of the ventrolateral region. In addition to the above cell types, multipolar and nuclear boundary cells were observable at 24-25 weeks. The five cell types persisted during subsequent development. At no stage of development was any neuronal organizational pattern apparent. A remarkable dendritic proliferation occurred at 27-28 weeks. Spines and filiform processes were seen at 34 weeks of intrauterine life.

Configurational and volumetric changes of the early prenatal human cerebellar dentate nucleus

The three-dimensional configurational and volumetric changes of the human dentate nucleus (DN) during intrauterine life were examined in 11 fetuses (11 to 27-28 weeks of gestation). During intrauterine life, the dentate nuclear profile successively passes through the pongid, cercopithecus and prosimian phases of configuration. The smooth, elongated, crescent-shaped DN of 11 weeks lies along a dorsal-ventral axis. A 45 degrees clockwise shift in the position of the nucleus changes the axis to dorsomedial-ventrolateral at 14-15 weeks, which is maintained in subsequent ages. The formation of gyri is preceded by a thinning of the substantia grisea. This begins at 17-18 weeks in the dorso-medial region of the DN. Gyri first make their appearance at 24-25 weeks. The DN of 27-28 weeks resembles the adult human DN. Two regions are discernible at this stage--a microgyric, magnocellular region and a macrogyric, parvocellular region. The DN volume increases with increasing gestational age. Between 14-15, 19-20 and 24-25 weeks the volumetric increase is statistically significant. This is simultaneously accompanied by a modification of the configuration of the DN.

Development of substance P, Leu-enkephalin and serotonin profiles in the lateral geniculate nuclear complex of albino rat

Immunohistochemical studies for analysing the development of the profile of two peptides--substance P (SP) and Leu-enkephalin (Leu-ENK), and serotonin (SER)--have been conducted on the lateral geniculate nuclear (LGN) complex of albino rats at gestation day 18 and various postnatal age periods. SP immunoreactivity is found to increase from 1 day postnatal (DPN) up to 20 DPN and decrease thereafter, whereas the SER and Leu-ENK-immunoreactive fibres and terminals seen as occasional fibres at 1, 5, and 10 DPN are better visualized from 20 DPN and gradually increase up to 40 DPN. The possible role and significance of the changes seen in these putative neurotransmitters/neuromodulators with development are discussed.

Early development of visual cortex in human fetuses

Prenatal development of visual cortex (area 17) was studied in human fetuses of 8-9, 13-15 and 16-18 weeks of gestation, with a view to analyse the early critical events. Under light microscope, five zones of development were seen in all the age groups. The total thickness of cortex of area 17 as well as that of its cortical plate was measured with the help of camera lucida. It was observed that the total thickness of the cortex increased with increase in age. Diversity in the shape, size, staining intensity and arrangement of neurons was noted in the different zones. Most of the cells were found to have a thin rim of cytoplasm and a prominent nucleus with multiple nucleoli. The cells in subventricular zone and cortical plate were regularly arranged in vertical rows while in other zones, they were irregularly scattered. Several mitotic figures were seen in the ventricular zone at 8-9 weeks but later they were also noticed in subventricular and intermediate zones. In the later ages the mitotic figures were observed to be fewer in the ventricular zone. No mitosis was seen in cortical plate at any age period.

Substance P-immunoreactivity in the developing human retinogeniculate pathway

Substance P has been immunohistochemically localized in the human optic nerves and lateral geniculate nuclei during the prenatal period from 13-14 to 37 weeks of gestation. Substance P-immunoreactive fibres were present in the optic nerves and lateral geniculate nuclei in all these ages thereby providing direct evidence of this undecapeptide being associated with the retinogeniculate pathway. At 16-17 weeks, greater numbers of fibres were observed than in the later ages. It is likely that the reduction in number of optic nerve fibres seen quantitatively during prenatal life may partly be due to the loss of substance P fibres.

Imbalances in T cell subpopulations in human gliomas

The quantitation of cells bearing CD3, CD4, CD8, and B cell phenotypic markers, as well as an estimation of serum immunoglobulin (Ig)G, IgA, and IgM, was carried out in a group of 39 glioma patients with different grades of malignancy. The findings were compared with those obtained from 21 normal healthy control subjects. The analysis revealed a significant decrease both in the absolute numbers and in the percentages of circulating CD3+ (p less than 0.001) and CD4+ (p less than 0.001) cells, while the CD8+ and Pan B+ cells remained within the normal range irrespective of the type and grade of tumor. The CD4+:CD8+ ratio was significantly decreased in all categories of patients. The CD4 lymphopenia was also evident in 10 patients who had no history of previous immunosuppressive drug therapy (steroids and anticonvulsants) until the commencement of the study. The Ig levels were within the normal range in patients with malignant astrocytoma and glioblastoma multiforme, whereas a three- and fourfold increase in the IgM level was observed in patients with astrocytoma. It is suggested that T cell lymphopenia in glioma patients could mainly be due to a selective depletion of CD4+ cells and that it occurs principally as a reaction to the tumor.

Cytodifferentiation and developing neuronal circuitry in the human lateral geniculate nucleus

The developing neural substrate in dorsal lateral geniculate nucleus of human fetuses and premature, full-term and postnatal infants, has been analysed using rapid Golgi impregnation, computerized image analysis, electronmicroscopy, and immunocytochemical method for localization of gamma-aminobutyric acid. Nuclear and cytoplasmic neuronal maturation is observed to extend over the entire period studied. Axodendritic synapses, presumably of retinal origin, are occasionally seen at 13-14 fetal weeks. They become increasingly apparent at 18-19 weeks. Dendrodendritic contacts are visualized at 15 weeks. Cortical terminals and occasional triadic contacts are evident around 21 weeks. The inhibitory interneurons containing gamma-aminobutyric acid are present in small numbers at 15-16 weeks; their numerical density increases considerably at 17 weeks but decreases thereafter. The presence of gamma-aminobutyric acid containing nerve cells and synaptic triads is indicative of the formation of inhibitory circuitry. At 15-16 weeks neurons are mostly bipolar although different forms of multipolar cells may be seen. By 24 weeks the radiated and bitufted multipolar neurons, neurons with beaded dendrites and neurons with axon-like dendritic processes are identifiable. There are no apparent differences in differentiation of neurons between the cranial and caudal parts of dorsal lateral geniculate nucleus. At 15-16 weeks, however, the cells of prospective magnocellular zone appear to be more mature than do the cells in the parvocellular zone. The neuronal soma increases continuously in size. Dendrite development starts at 15-16 weeks of gestation, thereafter the increase in number of their branches and their length is observed. Between 15-16 and 24 weeks, spines and filiform processes appear first on the proximal shafts of the dendrites and subsequently on their distal portion. There is increase in the number of filiform processes and hair-like appendages on geniculate neurons of premature infants born at 32 and 37 weeks of gestation and of a 4-day postnatal infant. Computerized quantitative data substantiate the progressive increase in growth parameters. The significance of comparative and functional aspect of the data is discussed.

Ultrastructure of marginal zone during prenatal development of human spinal cord

Electron microscopic studies were conducted in the marginal zone (lamina I) in human fetuses ranging from 8-25 weeks of gestational age. At 8 weeks the neurons have indented nuclei and sparse organelles in the cytoplasm. The neuropil shows contacts between the axons and dendritic profiles. Some of them are well defined synapses with post synaptic thickening and agranular spherical vesicles in the presynaptic terminal. At 18 weeks compactly packed organelles with long cisternae of rough endoplasmic reticulum could be visualized in the neuronal cytoplasm. At 25 weeks the neurons have heterochromatin patches in the nuclei. Axosomatic, dendrodendritic, axoaxonic, symmetrical, asymmetrical and multisynaptic contacts with agranular and dense core vesicles are seen at different sequential age periods.

Immunohistochemical localization of GABAergic cells in the developing human dorsal lateral geniculate nucleus

GABAergic neurons were demonstrated in the dorsal lateral geniculate nucleus (dLGN) of human foetuses of 21 weeks gestation using unlabelled antibodies against gamma-aminobutyric acid (GABA). These inhibitory neurons are thus cytochemically identifiable prior to appearance of lamination, at a period when there is reportedly segregation of retinal afferents from both eyes and formation of morphologically defined synapses. Their presence in the prenatal period indicates that the morphological substrate responsible, in part, for the orientation sensitivity of the dLGN neurons exists before birth in man.

DNA loss in the developing cerebellum of nervous mouse: a flow cytometric study

Flow-cytometry of cerebellar EGL cells of nervous (nr) mouse revealed a reduction in DNA quantity per cell accompanied by an increase in the DNA dispersion during 6-8 days of postnatal life. This loss of DNA is due to a partial degeneration of the cells of EGL during the first week of postnatal life. The surviving cells later on achieve a DNA content equivalent to their bone marrow cells. The flow-cytometric technique also facilitates an early detection of the homozygous nervous mutant, almost 2 weeks before the clinical manifestation of the disease, which to date was not possible.

Contact areas in human elbow joints

The paper describes the results of in-vitro experiments to determine the contact areas in the elbow joint during different anatomical positions. The casting technique, using wax as a casting material, was used in this study. The shape and size of the contact areas change, in different elbow positions ranging from full extension to full flexion. The joint stability was preserved during the experiments. In full extension the area of contact was observed on the lower-medial aspect of the ulna while in other postures the pressure areas were found as a strip extending from posterolateral to anteromedial. The radio-capitulum joint also revealed contact during flexion under no externally applied loads.

The intermediolateral gray columns in the spinal cord of Macaca mulatta

The mean length of spinal segments in Macaca mulatta varied from 0.55 to 1.4 cm. Upper thoracic and lumbar segments were shorter; middle and distal thoracic segments are longer. The intermediolateral gray column extended from the middle of the eighth cervical to the fourth lumbar spinal segments. This column as observed in the serially cut cross-sections varied in shape and in position in different regions of the spinal cord. The mean counts of intermediolateral neurons in the males were significantly higher than females (P less than 0.001) and varied from segment to segment. Their number was slightly higher on the right side and funicular cells were more numerous in male spinal cords than in females. The neurons were of varied shapes from fusiform to multipolar and measured from 7.5 to 25 micrometers in size.

Birth weight and development of cerebellar cortex

Postnatal development of the cerebellar cortex in the mouse is characterised by proliferation of cells of the external granular cell layer, migration of the granule cells across the molecular layer and simultaneous maturation of the Purkinje cells. At the same time, there is elaboration of the folia and fissures of the cerebellum. These features were studied postnatally in relation to the age and weight of the animal in the inbred strain of C3HeB/FeJ mice fed on standard diet. In every litter there was a difference in body weight of the various pups, and for the present study, the lowest and highest weighing animals from each litter were used. The observations presented here are on animals at the 1st, 7th, 13th and 24th days postnatum. It appears that the size of the cerebellum and the degree of the development of the cerebellar cortex are directly proportional to the weight of the animal for that age period.

"Physiological" and cytotoxic cell death in protein deficiency. A study in developing cerebellum in rats

Effects of undernutrition on natural ("physiological") and cytotoxic cell death due to X-irradiation was studied in developing cerebellum in rats. Undernutrition was induced right from birth by doubling the litter size. Animals reared in a litter of 8 served as controls. In order to get an idea of the relationship of cell death to phases of the cell cycle, the number of labelled dead cells, in the EGL of the fissure prima, was estimated, at time intervals following administration of 3HTdR in a group of 9-day-old rats. No differences were observed in the quantum of "physiological" cell death as well as in the rate of nuclear autolysis in the two groups. Undernutrition, however, prolonged the G2-M junction in animals X-irradiated with 200 rads. The kinetics of appearance of labelled dead cells suggested that irrespective of the diet the cells die immediately following mitosis, although the "decision to die" was taken at the end of S-phase. It is concluded that the reduction in cell number in the brain in undernutrition is not due to increased cell death.

Undernutrition and the developing cerebellar cortex in the rat

Undernutrition of the newborn rats, produced during the first 3 weeks by increasing the litter size and restricting the mother's diet, resulted in reduction of the body and brain weights of the experimental animals. One group of undernourished animals showed especially severe reduction of body and cerebellar weights. These animals, on the 10th postnatal day, had an immature cerebellar cortex corresponding to that of the 7th day postnatal control animals. The external granular layer persisted in the cerebellar cortex of the underweight animals until the 23rd day, while it disappeared by 20th day in the control animals. Mitotic activity was evident until the 21st postnatal day in these animals while it stopped in the normal animal by 16th postnatal day. There was no marked difference in the fine structure of the various cell types in the control and undernourished animals. Midsagittal tracings of the cerebellar cortex showed a reduced surface area in the undernourished animals, while the thickness of the external granular layer and molecular layer did not show any significant difference when compared to that of the control animals, thus showing a reduction in total cell number, but not per unit area. The normal morphological appearance of the cerebellar cortex in the underfed animals of higher weight probably indicates that these animals are adequately nourished in spite of the reduction in weight when compared to the control animals, which probably are overfed.