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Biomedical subjects

S Koh

Publications and source records attributed to S Koh.

At least 73 records · Page 4Linked to original sources
PubMed1989

NGF induction of NGF receptor gene expression and cholinergic neuronal hypertrophy within the basal forebrain of the adult rat.

Chronic infusion of nerve growth factor (NGF) into the forebrain of the adult rat produced increases in NGF receptor (NGF-R) mRNA hybridization, NGF-R immunoreactivity, choline acetyltransferase (ChAT) mRNA hybridization, and neuronal hypertrophy, when compared with vehicle infusion or noninfused rat brain. In situ hybridization showed NGF induction of NGF-R gene expression, documented by increases in the number of NGF-R mRNA-positive cells within the medial septum, diagonal band, and nucleus basalis magnocellularis. NGF also produced hypertrophy of ChAT mRNA-positive neurons. These results suggest that NGF produces cholinergic neuronal hypertrophy through induction of NGF-R gene expression within the basal forebrain.

Animals↗
PubMed1989

NGF receptor reexpression and NGF-mediated cholinergic neuronal hypertrophy in the damaged adult neostriatum.

Adult cholinergic interneurons of the neostriatum are not immunoreactive for monoclonal antibody to NGF receptor, whereas the developing neostriatum is immunoreactive for this same antibody. Chronic NGF infusion into the adult neostriatum resulted in reexpression of the NGF receptor such that many cholinergic interneurons became immunoreactive for NGF receptor. NGF infusion dramatically increased the size and choline acetyltransferase immunoreactivity of these same cholinergic neurons. Additionally, in situ hybridization demonstrated an increase in the number of cells expressing NGF receptor mRNA in the NGF-infused striatum. These findings indicate that central cholinergic neurons which lose their NGF receptors during postnatal development will resume their NGF responsiveness when the tissue is damaged. Such a damage-induced mechanism may act to enhance the action of trophic factors, including NGF, released at the site of injury and enhance the responsiveness of damaged CNS neurons to exogenously administered trophic factors.

Aging↗
PubMed1989

Two-year follow-up of changes in clinical chemistry in Singaporean Norplant acceptors: haemostatic changes.

A longitudinal study of coagulation parameters was carried out on 100 Singaporean acceptors using Norplant for contraceptive purposes. At the end of 2 years of use, results from this ongoing study indicate that these acceptors continue to have an increased predisposition to thrombosis as evidenced by significant increases in platelet count and aggregability. The shortened but stable prothrombin time and activated partial thromboplastin time and increase in certain coagulation factors indicate that Norplant acceptors still have a possible potential for hypercoagulation at the end of two years of use.

Blood Coagulation↗
PubMed1989

Two-year follow-up of changes in clinical chemistry in Singaporean Norplant-2 rod acceptors: haemostatic changes.

A longitudinal study of coagulation parameters was carried out on 100 Singaporean acceptors using Norplant-2 rods for contraceptive purposes. At the end of 2 years of use, results from this study show a return of platelet count to preinsertion level while platelet aggregation remained significantly enhanced. Thus the net effect of these two changes on an increased tendency for thrombosis needs further evaluation. The PT and APTT continued to remain persistently shortened during the period of use. There was also a general fall in fibrinogen and most other coagulation factors during the two years of use. Thus, again, the net effect of these two changes on the exposed potential for hypercoagulation at the end of the first year needs further evaluation throughout the five years of Norplant-2 use.

Blood Coagulation↗
PubMed1989

Localization and development of nerve growth factor-sensitive rat basal forebrain neurons and their afferent projections to hippocampus and neocortex.

In order to understand further the role of NGF in the development of NGF-sensitive basal forebrain neurons and their afferent connections to the hippocampus and neocortex, we have used monoclonal antibody 192 IgG to detect and localize NGF receptors immunocytochemically in the developing rat brain. NGF receptor immunoreactivity (NGF-RI) is first visible at embryonic day 13 (E 13) in the ventrolateral telencephalic wall and follows a caudal-to-rostral gradient in its initial appearance. NGF-RI neuronal number and neuropil staining undergo substantial increases before birth, and extensive dendritic growth and increases in perikaryal size continue during the first 3 weeks of postnatal life. This growth and cellular differentiation, however, is followed in the fourth postnatal week and later by an apparent decrease in dendritic arborization and 50% shrinkage in the size of perikarya. Initial NGF-RI fiber outgrowth from immature basal forebrain neurons directed toward appropriate target fields is observed as early as E 15. The formation of a laminar pattern by septal axons in the hippocampal terminal fields and invasion of NB afferents into the cortex occur postnatally over a protracted time. In the hippocampus, NGF-RI is initially diffusely distributed, and wide bands of immature granule and pyramidal cells are almost devoid of immunoreactive fibers; however, with maturity, septal axon terminals become concentrated in narrow zones closely associated with the cellular layers. In the neocortex, early-arriving basal forebrain afferents accumulate in the intermediate zone underneath the darkly immunoreactive subplate before they enter The cortex. Dense subplate and transiently present, radially aligned fiber staining completely disappear in later postnatal week and are gradually replaced by specific axonal and terminal staining associated with NB afferents. The expression of NGF receptor in the subplate zone at the time afferents arrive and its subsequent disappearance with the specific terminal formation suggest that NGF receptor and concomitant accumulation of NGF in the subplate may act as a temporary target for the early-arriving basal forebrain afferents; ingrowing afferents may then be guided by radially oriented NGF-RI fibers to proper synaptic sites.

Afferent Pathways↗
PubMed1989

[A study on clinical findings and surgical treatment of pulmonary mycosis].

Between 1974 and 1987, 14 patients (10 male and 4 female) underwent thoracotomy for treatment of pulmonary mycosis. They were studied on their clinical findings and surgical treatment. The median age was 48 years (range 19 to 71 years). Fourteen cases consisted of 9 aspergillosis and 5 cryptococcosis. None of them was either debilitated or immunosuppressed before falling ill. Five of the 14 patients had other pulmonary disease and 11 had symptoms; i.e. hemoptysis or bloody sputum in 4 cases, chest pain in 3, fever in 3, cough and sputum in 2. Nine aspergillosis consisted of 4 aspergilloma, 3 aspergillus pneumonia and 2 aspergillus empyema. Three cases of aspergillosis occurred in preexisting cavity. Five cryptococcosis consisted of 3 pseudotumorous, 1 disseminated small nodular, and 1 infiltrative types. Preoperative diagnosis was as follows; pulmonary mycosis 5, pulmonary tuberculosis 4, lung cancer 3, empyema 1 and hydropneumothorax 1. Four patients underwent partial resection, 8 lobectomy, 1 pneumonectomy, 1 muscle prombage and thoracoplasty. The prognosis is satisfactory. All patients are alive and has no recurrence. On histopathological examination, in aspergilloma cases, invasion of aspergillus to surrounding lung tissue was not seen. In addition to well-known fact that blood-borne dissemination hardly occurred in aspergilloma in contrast to cryptococcosis. These findings suggest that aspergilloma and solitary lesion of cryptococcosis should be resected, and adjuvant chemotherapy should be accompanied for cryptococcosis.

Adult↗
PubMed1988

Age-related loss of nerve growth factor sensitivity in rat basal forebrain neurons.

Nerve growth factor (NGF) has recently been implicated as a trophic agent in the survival and maintenance of basal forebrain cholinergic neurons. To test the hypothesis that NGF may play a role in the age-related degeneration of basal forebrain neurons and decline of cerebral cholinergic function, we have used a monoclonal antibody to the NGF receptor, 192 IgG, to immunocytochemically visualize and compare rat basal forebrain neurons responsive to NGF in aged (30 months) and young adult (10 months) rats. In a subpopulation of aged rats, NGF receptor-immunoreactive cells in the basal forebrain appear vacuolated and shrunken, and the neuropil staining is markedly reduced. While no substantial decline in cell density is apparent in Nissl-stained sections, the number of NGF receptor-positive cell profiles within the vertical limb of diagonal band nuclei is reduced by an average of 32% in aged rats. Marked reduction in the expression of NGF receptors in aged rats may signify loss of capacity of the basal forebrain neurons to bind and transport NGF from their terminals in the hippocampus and cortex, subsequent decrease in NGF delivered to the cell bodies, and eventual cellular dysfunction and death of neurons in aging.

Aging↗
PubMed1988

The effects of Norplant-2 rods on clinical chemistry in Singaporean acceptors after 1 year of use: haemostatic changes.

A longitudinal study of coagulation parameters was carried out on 100 Singapore acceptors using the levonorgestrel subdermal implants Norplant-2 rods for contraceptive purposes. At the end of 1 year of use, results from this on-going study indicates that these acceptors have an enhanced potential for hypercoagulation with a significant shortening of their prothrombin time and activated partial thromboplastin time. They also have an increased predisposition to thrombosis as evidenced by significant increases in platelet count and aggregability. A number of other parameters achieved statistically significant differences by the end of one year but since the results were within the normal accepted range, they were therefore unlikely to be of much clinical importance.

Adult↗
PubMed1988

The effects of Norplant on clinical chemistry in Singaporean acceptors after 1 year of use: I. Haemostatic changes.

A longitudinal study of coagulation parameters was carried out on 100 Singaporean acceptors using the levonorgestrel subdermal implants NORPLANT for contraceptive purposes. At the end of 1 year of use, results from this on-going study indicate that these subjects may have an increased predisposition to thrombosis as evidenced by significant increase in platelet count and aggregability. The results also show that NORPLANT acceptors may have an enhanced potential for hypercoagulation - with a significant shortening of their Prothrombin Time and Activated Partial Thromboplastin Time and increases in Factors V and X. As previously documented, mean values for haemoglobin and haematocrit were significantly elevated by the end of 1 year. A number of other parameters achieved statistically significant differences by the end of 1 year but these were probably due to the large sample size involved and were therefore not likely to be of much clinical importance.

Adult↗
PubMed1988

Pathological changes in the cartilaginous plates in relation to intervertebral disc lesions.

Three hundred sixty-eight intervertebral discs (T11/12-L5/S1) were obtained at autopsy from 61 individuals (36 male, 25 female) ranging from 25 to 85 years of age, and subsequently examined histopathologically as sagittal-sectioned specimens with special reference to the cartilaginous plates. The numbers of cartilaginous foci found in fissured and ruptured regions of the plates were found to increase with age, and were considered to represent a restoration mechanism. Measurement of the cartilaginous plate/intervertebral disc antero-posterior length ratio showed a decrease with age in intervertebral discs from the same spinal level. Therefore, cartilage cell proliferation in the vertebral body rim was found following rupture of the outer layer of the annulus fibrosus and was thought to be one of the causes of spur formation in spondylosis deformans. When the changes in a cartilaginous plate with aging were accompanied by destructive processes of the vertebrae such as osteoporosis or metastatic cancer, an increase in the height of the disc, or ballooning, developed. On the other hand, when degeneration of the intervertebral disc increased and the nucleus pulposus collapsed, the height of the disc decreased. Thus, although the cartilaginous plate exhibits a restoration mechanism, degeneration with age progresses, resulting in various disc lesions.

Adult↗
PubMed1987

Basal forebrain magnocellular neurons stain for nerve growth factor receptor: correlation with cholinergic cell bodies and effects of axotomy.

Recent evidence has demonstrated the presence of nerve growth factor (NGF) in areas of the central nervous system characterized by cholinergic innervation. We report that a unique population of rat basal forebrain magnocellular neurons that project to the cortex and hippocampus are immunoreactive to a monoclonal antibody to the NGF receptor. Removal of target contact results in a time-dependent loss or shrinkage of cells in the basal forebrain that stain for NGF receptor and acetylcholinesterase, suggesting that under normal conditions, basal forebrain cholinergic neurons utilize NGF for trophic support.

Animals↗
PubMed1987

Demonstration of the retrograde transport of nerve growth factor receptor in the peripheral and central nervous system.

NGF acts on responsive neurons by binding to specific NGF receptors on axonal termini, after which a critical biochemical signal is retrogradely transported to the cell body. The identity of the signal(s) is unknown; candidates include NGF itself or some other "second messenger." A possible second messenger is the NGF receptor. As a first step in assessing the possible role of NGF receptor in the generation of the NGF-dependent signal, and in understanding the economy of NGF receptor synthesis and utilization, we determined whether the NGF receptor is retrogradely transported. Using immunohistochemical staining with a monoclonal antibody (192-IgG) against rat NGF receptor, we looked for accumulation of NGF receptor molecules distal (retrograde transport), as well as proximal (anterograde transport), to sites of axonal ligation or transection. By 10-12 hr in both the ligated sciatic nerve and the lesioned fimbria-fornix, accumulated NGF receptor was detected proximal and distal to the ligation/lesion site. The transported receptor presumably was located in sympathetic and sensory neurons in the sciatic nerve and in forebrain cholinergic neurons projecting from the medial septum to the hippocampus. In both anatomical sites, accumulation of NGF receptor on the proximal (anterograde) side occurred in streams of fine axonal processes, whereas staining on the distal (retrograde) side occurred in varicose or granular configurations. These results raise the possibility that the NGF receptor has a role in the mechanism of NGF beyond the initial binding event at the plasma membrane of the axonal terminus.

Animals↗
PubMed1986

Differences in coagulation and haemostatic parameters in normal women of childbearing age from different ethnic groups and geographical locations. Task Force on Oral Contraceptives--WHO Special Programme of Research, Development and Research Training in Human Reproduction.

A comparative study of coagulation and fibrinolytic laboratory parameters was undertaken in four countries (Salvador, Brazil; Singapore; Santiago, Chile and Dublin, Ireland) among apparently healthy women of reproductive age. A continuous external quality control scheme of the laboratory measurements was employed to permit comparison among centres. Significant and consistent differences were found between the four centres. In Dublin, the prothrombin time and activated partial thromboplastin time (APTT) were accelerated, and the specific factor assays showed more activity, whereas the antiprotease levels were higher than in the other centres. In Salvador, a contrasting tendency was found with longer prothrombin times and APTT and lower Factor VII and antiprotease levels. The results from the other two centres were approximately midway between these two extremes. The study has revealed important differences in the coagulation and haemostatic tests between women from widely diverse geographical areas. It is not certain whether these are due to ethnic, nutritional or economic factors but they may be related to the apparent varying incidence of thrombosis in these ethnic groups.

Adolescent↗
PubMed1984

[An arachnoid cyst in the left lateral ventricle].

Generally arachnoid cysts are congenital in origin and found over the cerebral convexity, in the major fissures, and in the folded portions of the brain wherever the arachnoid membrane extends. Including other central nervous system (CNS) cysts, the location of these cysts has implications as to their origin, for examples, intracerebral cysts generally are ependymal cysts, while extracerebral cysts are mostly arachnoid cysts. An 8-month-old boy was admitted to our department because of enlarged head and developmental retardation. Computerized tomographic scan (CT) revealed remarkable hydrocephalus and a relatively high-dense, round lesion between the lateral ventricles. During surgery the cyst was found to arise from the left ventricular floor. Histologically the cyst wall was arachnoid membrane.

Arachnoid↗