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Biomedical subjects

B H Choi

Publications and source records attributed to B H Choi.

At least 109 records · Page 6Linked to original sources
PubMed1984

Expression of glial fibrillary acidic protein in immature oligodendroglia.

In the human fetal spinal cord at 15 to 16 weeks, glial fibrillary acidic protein (GFAP) was demonstrated within the cytoplasm and processes of cells having the cytological, ultrastructural, and immunocytochemical features of oligodendrocytes--including processes that extend into and contribute to the formation of myelin sheaths. By 17 to 18 weeks, however, GFAP immunoreactivity was no longer evident within such cells. Thus GFAP is expressed by myelin-forming oligodendroglia early in their development.

Cytoplasm↗
PubMed1984

Nonhemorrhagic venous infarction of the spinal cord.

A 71-year-old man experienced gradually progressive leg weakness, urinary retention, and mild loss of sensation in dermatomes T8 through T12 bilaterally. After 5 to 6 weeks of illness, he developed flaccid paraplegia and sensory loss below T8. He died 16 weeks after onset of neurological symptoms. Neuropathologically, there was widespread, subtotal necrosis of the spinal cord, largely of nonhemorrhagic character, from T8 downward. Dorsal and anterior median spinal veins were occluded by a partially organized thrombus. Comparison of this case with 19 previously recorded examples of venous infarction of the spinal cord (8 hemorrhagic, 7 nonhemorrhagic, and 4 embolic) suggests major differences in clinical presentation, rate of progression, and length of survival among the three groups.

Aged↗
PubMed1984

The comparative effects of methylmercuric chloride and mercuric chloride upon DNA synthesis in mouse fetal astrocytes in vitro.

The relative effects of direct exposure to methylmercuric chloride (MMC) and mercuric chloride (MC) upon [3H]thymidine incorporation were determined using cultured mouse fetal astrocytes. The labeling indices of cells exposed to MMC were significantly lower than those of cells exposed to equimolar concentrations of MC. These results indicate that on a mole-for-mole basis, MMC is much more deleterious upon DNA synthesis of mouse fetal astrocytes than those of MC.

Animals↗
PubMed1984

Cellular and subcellular demonstration of mercury in situ by modified sulfide-silver technique and photoemulsion histochemistry.

Young adult C57BL/6J mice were injected with 4.0 mg/kg body wt of methylmercuric chloride (MMC) for 3 consecutive days for a total of 12.0 mg/kg. Control animals received physiological saline in place of MMC. One week following the last injection, the animals were sacrificed. Representative tissue blocks and sections from the brain, kidney, and liver were subjected to a modified sulfide-silver technique (SST) and the photoemulsion histochemical method. The results show that both of these techniques demonstrate consistent and distinct localization of mercury (Hg) gains in cells and subcellular organelles. These methods are based on the principle that Hg compounds react strongly with sulfhydryl groups in tissues and cells to form Hg-sulfides and also on the affinity of Hg and silver to form an amalgam when placed in a physical developer or photographic emulsion. Thus Hg in cells is demonstrable without prior treatment of sulfide solution. The methods are simple and reliable when used with proper controls. Specific localization of Hg in cells in situ without the use of radioactive material and without disruption of anatomical relationships provided by these methods offers distinct advantages over other methods of Hg determination. Thus it would be possible to conduct a retrospective or prospective study of human autopsy materials and also would allow direct correlation of Hg deposition with pathological changes in cells and subcellular organelles.

Animals↗
PubMed1981

Hematogenous cells in the central nervous system of developing human embryos and fetuses.

Examination of large blocks of Epon-embedded, 1.0-micrometer sections of human embryos and fetuses reveal the presence of hematogenous cells in various stages of differentiation in neural tissue. In every embryo and fetus of 10 weeks ovulation age and younger, hematogenous cells are found randomly scattered in the cerebrum, cerebellum, and spinal cord. Many of these cells appear to undergo spontaneous degeneration in neural tissue and become rarer in older fetuses. Also identified in the neuropil of normal embryos and fetuses are cells with the typical morphological appearance of macrophage containing numerous inclusions of various kinds, both inside and outside the blood vessels. In addition, scattered in the subpial, perivascular, and perineuronal regions of the neural parenchyma are small cells with fusiform nuclei and a small amount of cytoplasm as well as cells with a moderate amount of elongated cytoplasm containing various inclusions and oblong nuclei. All of these cells have clumped heterochromatin along the nuclear membrane which differs from other neuroectodermal cells of the developing human CNS. Although there is no direct evidence to indicate transformation of macrophages to "microglia" or vice versa, the presence of cells having similar nuclear morphology and chromatin pattern while appearing to be transitional forms of macrophage, varying from undifferentiated to fully developed, suggest a common lineage of these latter types. It is concluded that migration of hematogenous cells into neural tissue is a ubiquitous developmental phenomenon in young human embryos and fetuses.

Brain↗
PubMed1981

A Golgi and electron-microscopic study of cerebellum in methylmercury-poisoned neonatal mice.

Neonatal C57BL/6J mice were injected with 5 mg/kg body weight of 203Hg-labeled methylmercuric chloride on postnatal days 3, 4, and 5, totaling 15 mg/kg body weight per animal. The experimental and control animals were sacrificed on postnatal by 15. Whole body radioactivity of 203Hg progressively increased during the 3-day injection period and reached the peak level and remained at peak levels until the time of sacrifice. This indicates a lack of clearance of 203Hg by neonatal mice during the period examined in this study. Golgi preparations of cerebella of MeHg-treated animals revealed significant reduction in dendritic arborization of Purkinje cells. Ultrastructurally, the vascular endothelium showed attenuation with increased electron density and frequent vacuolization of cytoplasm. Marked swelling of perivascular glia was noted in most of the capillaries throughout the cerebella of MeHg-treated animals.

Animals↗
PubMed1981

Abnormal neuronal migration and gliomatosis cerebri in epidermal nevus syndrome.

A detailed neuropathologic examination of the brain of a child with the typical epidermal nevus syndrome revealed a primary disturbance of development of the brain. The developmental disturbance consisted of an abnormal or incomplete migration of neurons to form the cerebral and cerebellar cortices. The normal architectonic pattern of the cortical layer formation of the cerebrum and cerebellum was also disturbed. In addition, there was an abnormality in the proliferative activity of astroglial cells resulting in gliomatosis cerebri. It is suggested that the basic abnormality underlying various neurologic derangements in epidermal nevus syndrome is the result of a defect in specific developmental events, such as neuronal migration and cortical differentiation.

Brain↗
PubMed1981

Radial glia of developing human fetal spinal cord: Golgi, immunohistochemical and electron microscopic study.

Radial glia of the developing spinal cord were examined by Golgi, electron microscopic and immunohistochemical methods in 40 human embryos and fetuses of ovulation age 6-20 weeks. As in developing cerebrum and cerebellum, gliogenesis in the spinal cord occurs much earlier than traditionally believed. The presence of transitional forms suggests that subependymal glia originate from detached radial glia that divide and differentiate in their new location. Well-differentiated astroglia evolve from radial glia as fetal age advances.

Astrocytes↗
PubMed1981

Distribution and biotransformation of methyl mercuric chloride in different tissues of mice.

The distribution of 203Hg radioactivity has been studied in various organs of adult male and female mice from one hour to 21 days after treating with 203 Hg-labeled methyl mercuric chloride (MMC). The amount of methyl mercury (MeHg) and inorganic mercury (Hg) has also been determined by injecting single doses of non-radioactive MMC, and subsequently measuring total, organic and inorganic Hg content by atomic absorption technique. In addition, photoemulsion histochemical method (PEHM) was used to demonstrate localization of Hg grains in various cellular compartments of organs and tissues. The highest levels of radioactivity were attained at 7 hours post-treatment in all organs except for brain and testis. The testis showed the highest radioactivity at one day and the brain at two days post-treatment. MeHg persisted in brain over a longer period though the level was not as high. The content of MeHg and inorganic Hg was maximum in kidneys as compared to other organs. The brain and the reproductive organs contained the least amount of inorganic Hg. By PEHM, Hg grains were most prominently observed in the sinusoids, Kupfer cells, hepatic cells and bile duct epithelium of liver; in the lumen of blood vessels, convoluted and collecting tubules of kidneys; and in the gastrointestinal epithelium. The pattern of uptake and distribution of MeHg correlated well with the morphological demonstration of Hg grains in tissue sections.

Animals↗
PubMed1980

Evolution of Bergmann glia in developing human fetal cerebellum: a Golgi, electron microscopic and immunofluorescent study.

Astrogliogenesis in the human fetal cerebellum was examined in 46 cerebella obtained from hysterotomy specimens ranging between 9 and 20 weeks of ovulation age. By correlating the results obtained by rapid Golgi and Golgi-Cox methods, the indirect immunofluorescence technique for glial fibrillary acidic protein, and electron microscopy, it was possible to ensure identification of cells and obtain a comprehensive view of the ontogenesis of cerebellar astroglia, in particular Bergmann fibers. Radial fibers were present at 9 weeks of ovulation age, with features of astroglial differentiation. In the cerebellar hemisphere radial fibers arising near the ventricular zone did not reach all the way to the pial surface but terminated in vascular walls of the intermediate zone. A second set of glial cells located in the intermediate zone gave rise to long, tapering processes oriented radially to the pia, some reaching to the pial surface and terminating there in conical swellings. Radial glia with these features were observed in cerebella at all fetal ages examined, indicating their availability for guidance of external granular cells as they migrate inward. With advancing fetal age, the segment of those radial glia traversing the molecular layer demonstrated an increasing resemblance to Bergmann fibers, though the cell bodies giving rise to these processes were still located below the Purkinje cells. Transitional forms between radial glial processes and fibers beginning to resemble Bergmann fibers were observed in numerous specimens impregnated with the Golgi methods. Astrogliogenesis in human fetal cerebellum occurs earlier than formerly believed, and Bergmann fibers are a final stage in the development of a defined group of radial glia in the cerebellum.

Astrocytes↗
PubMed1978

Radial glia in the human fetal cerebrum: a combined Golgi, immunofluorescent and electron microscopic study.

Golgi techniques, immunofluorescence for glial fibrillary acidic (GFA) protein, and electron microscopy (EM) were used to determine the nature of radial glia in the cerebrum of human fetuses ranging from 7 to 20 weeks of ovulation age. Successful Golgi impregnation of radial fibers was achieved in fetuses 12 weeks of age and older. These fibers spanned the entire thickness of the hemisphere. At the pial surface many of them branched and terminated in pyramidal end feet expansions. Indirect immunofluorescent preparations utilizing antiserum to GFA protein, a protein specific for astrocytes, demonstrated numerous radially oriented nearly parallel fluorescent fibres between the ventricular zone and pia mater. GFA protein-positive fibers were demonstrated in all fetal specimens examined with this technique (10 weeks of age and older). Along the outer border of the marginal zone they formed a horizontal GFA protein-containing subpial membrane. By EM there were numerous linear electron lucent astrocytic processes containing 8-9 nm filaments and occasional glycogen granules at all levels of the cerebrum. They were interspersed among smaller and darker neuronal processes containing 20-25 nm neurotubules, and were demonstrable at all fetal ages between 7 and 18 weeks. They formed pericapillary investments and subpial terminal expansions closely abutting basal lamina of pia mater in every specimen examined. On the basis of these combined analyses, we conclude that radial glial fibers in early human fetal cerebrum represent processes of immature astrocytes. Although subsequently undergoing further maturation, radial glia already possess fundamental immunocytochemical and morphological characteristics indicative of astrocytic differentiation. A significant implication of our findings is that the development of astrocytes in the human fetal brain occurs much earlier than formerly believed.

Astrocytes↗