Biomedical subjects

A Hayaran

Publications and source records attributed to A Hayaran.

5 recordsLinked to original sources

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↗

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↗