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Biomedical subjects

V Bijlani

Publications and source records attributed to V Bijlani.

At least 19 recordsLinked to original sources
PubMed1994

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.

Adult↗
PubMed1993

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.

Animals↗
PubMed1993

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.

Cerebellar Nuclei↗
PubMed1993

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.

Female↗
PubMed1993

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.

Cell Death↗
PubMed1992

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.

Cell Count↗
PubMed1992

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.

Acrylamides↗
PubMed1992

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.

Cerebellar Nuclei↗
PubMed1991

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.

Cell Differentiation↗
PubMed1990

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.

Aging↗
PubMed1988

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.

Embryonic and Fetal Development↗
PubMed1988

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.

Cell Differentiation↗
PubMed1988

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.

Adult↗
PubMed1988

Numerical estimates of GABA immunoreactive neurons in the human lateral geniculate nucleus in the prenatal period.

Quantitative analysis has been performed on Nissl stained and gamma-aminobutyric acid (GABA) immunoreactive neurons in the lateral geniculate nucleus (LGN) of human fetuses ranging from 8 to 37 weeks of gestation. Total cell density in the LGN increases from 8 to 12 weeks of gestation with a subsequent decline continuously up to 37 weeks. No GABA immunoreactive neurons are visualized in the LGN of 8 and 12 weeks fetuses. At 15-16 weeks of gestation 1% of neurons are immunostained. A peak rise is seen to occur at 17 weeks when 16% cells are GABA immunopositive. However, at 19 weeks there is an equally sharp decline in the percentage of GABA neurons to 4%. Subsequently, with the continued reduction in overall numerical density the percentage of GABA neurons remains relatively constant but rises again to 5% at 26 weeks. On making quantitative estimations of numerical density and percentage of GABA neurons separately for the prospective magno- and parvocellular regions in the early age periods from 15-16 to 21 weeks as well as at 22-23 weeks, when magnocellular laminae begin to segregate, and at 26 weeks when distinct laminae are present, it is observed that the magnocellular regions have a higher density and percentage of GABA neurons at all the gestational ages in comparison to the parvocellular region. With increasing gestational age, non-GABA neurons gradually increase in size with marked growth of magnocellular neurons at 26 weeks. The GABA neurons, on the other hand, have an almost constant size up to 19 weeks and start growing from 21 weeks onwards. The GABA neurons tend to be larger in the magno- than in parvocellular regions at all gestational ages studied.

Cell Count↗
PubMed1986

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.

Axons↗