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Biomedical subjects

M Hsu

Publications and source records attributed to M Hsu.

At least 55 records · Page 3Linked to original sources
PubMed1995

Effect of cerebral ischemia on calcium/calmodulin-dependent protein kinase II activity and phosphorylation.

The effects of cerebral ischemia on calcium/calmodulin-dependent kinase II (CaM kinase II) were investigated using the rat four-vessel occlusion model. In agreement with previous results using rat or gerbil models of cerebral ischemia or a rabbit model of spinal cord ischemia, this report demonstrates that transient forebrain ischemia leads to a reduction in CaM kinase II activity within 5 min of occlusion onset. Loss of activity from the cytosol fractions of homogenates from the neocortex, striatum, and hippocampus correlated with a decrease in the amount of CaM kinase alpha and beta isoforms detected by immunoblotting. In contrast, there was an apparent increase in the amount of CaM kinase alpha and beta in the particulate fractions. The decrease in the amount of CaM kinase isoforms from the cytosol but not the particulate fractions was confirmed by autophosphorylation of CaM kinase II after denaturation and renaturation in situ of the blotted proteins. These results indicate that ischemia causes a rapid inhibition of CaM kinase II activity and a change in the partitioning of the enzyme between the cytosol and particulate fractions. CaM kinase II is a multifunctional protein kinase, and the loss of activity may play a critical role in initiating the changes leading to ischemia-induced cell death. To identify a structural basis for the decrease in enzyme activity, tryptic peptide maps of CaM kinase II phosphorylated in vitro were compared. Phosphopeptide maps of CaM kinase alpha from particulate fractions of control and ischemic samples revealed not only reduced incorporation of phosphate into the protein but also the absence of a limited number of peptides in the ischemic samples. This suggested that certain sites are inaccessible, possibly due to a conformational change, a covalent modification of CaM kinase II, or steric hindrance by an associated molecule. Verifying one of these possibilities should help to elucidate the mechanism of ischemia-induced modulation of CaM kinase II.

Animals↗
PubMed1994

Short-term and long-term changes in the postischemic hippocampus.

We have demonstrated a far more widespread and selective ischemic cell damage than previously thought. In area CA3, a distinct subpopulation of interneurons, characterized by their spiny dendrites and their calretinin content, was selectively vulnerable in the absence of any other CA3 involvement. In the dentate hilus, four different types of spiny cells were consistently damaged. The common denominator in these two cell groups is the presence of spines on their dendrites and hence the greater density of mossy fiber innervation they receive. A common mechanism of cell death may be the presence of non-NMDA receptor subtypes that are highly permeable to calcium. We speculate that they may constitute an important control mechanism in the CA3 region and the hilus, and impairment of this mechanism may be causal to delayed neuronal death in CA1. We have also shown that neuronal degeneration does not end after delayed cell death of CA1 pyramidal cells. Our results suggest that there is progressive degeneration throughout the life of the animal and degeneration of additional cell populations (e.g. CA1 interneurons and CA3 pyramidal cells) may also occur secondary to the insult.

Animals↗
PubMed1993

The growth of Chinese minority populations.

This is a review of recent demographic trends among the 55 recognized minority ethnic groups in China, which have a total population of 91.2 million. Reasons for the rapid growth among many of these populations since the 1960s are analyzed. They include "the significant improvement of public health in the 1950s and 1960s, the leniency in the implementation of the birth control policies in minority communities, the relatively high birth and fertility rates in these communities, and the reaffirmation of racial identity in the 1980s."

Asia↗
PubMed1993

Four modified silver methods for thick sections of formaldehyde-fixed mammalian central nervous tissue: 'dark' neurons, perikarya of all neurons, microglial cells and capillaries.

Four reliable silver methods for the visualization of acute or advanced phases of neuronal damage have been modified so that they can be performed with good results on materials freshly fixed with transcardial perfusion of buffered formaldehyde for other silver methods and immunocytochemical techniques. The four modified methods respectively stain: (1) the somata and dendrites of 'dark' (impaired) neurons, (2) the perikarya of all neurons, (3) microglial cells, and (4) capillaries. Without the present modifications the 'dark' neuron method is only effective with glutaraldehyde fixation while the other three methods predominantly stain myelin in freshly fixed mammalian nervous tissue.

Animals↗
PubMed1993

Sex differences in minor psychiatric morbidity among three aboriginal groups in Taiwan: the effects of lineage.

Sex differences in minor psychiatric morbidity (MPM) have been investigated among three aboriginal groups in Taiwan. The study included both ethnographic observation and a sample survey (N = 733) using a modified Clinical Interview Schedule. The findings lend support to the hypothesis that although a female excess of MPM will be found among the patrilineal group (the Bunun), the reverse will be observed in the matrilineal group (the Ami); no such difference will be found in the bilateral group (the Atayal). Further analysis revealed sex differences in the mean duration of MPM and similar incidence ratios between two sexes in these three groups. Possible sociocultural explanations are proposed.

Adult↗
PubMed1993

Maternal-fetal histocompatibility in intrauterine growth retarded and normal weight babies.

PROBLEM: To determine whether risk for intrauterine growth retardation (IUGR) is increased in HLA-DQA1 compatible pregnancies. METHOD: Paired maternal and cord blood samples were obtained from 30 IUGR and 31 non-IUGR pregnancies delivered at a university hospital. Samples were typed for eight HLA-DQA1 alleles using 10 sequence-specific oligonucleotides probes. Associations between IUGR and HLA-DQ compatibility status, and other risk factors were examined using logistic regression analysis. RESULTS: HLA-DQ compatibility and history of spontaneous abortion were not individually significant risk factors for IUGR; however, there was an interactive effect between these two factors and IUGR (P = 0.085) that improved the overall fit of the logistic model (P < 0.001). No individual allele was more common in IUGR pregnancies. CONCLUSIONS: HLA compatibility per se is not associated with sufficient inhibition of fetal growth to result in IUGR as defined. However, in women with a history of spontaneous abortion, HLA compatibility may have an effect.

Abortion, Spontaneous↗
PubMed1993

Vulnerability of mossy fiber targets in the rat hippocampus to forebrain ischemia.

Much of the work on forebrain ischemia in the hippocampus has focused on the phenomenon of delayed neuronal death in CA1. It is established that dentate granule cells and CA3 pyramidal cells are resistant to ischemia. However, much less is known about interneuronal involvement in CA3 or ischemic injury in the dentate hilus other than the fact that somatostatin neurons in the latter lose their immunoreactivity. We combined two sensitive methods--heat-shock protein (HSP72) immunocytochemistry and a newly developed Gallyas silver stain for demonstrating impaired cytoskeletal elements--to investigate the extent of ischemic damage to CA3 and the dentate hilus using the four-vessel-occlusion model for inducing forebrain ischemia. HSP72-like immunoreactivity was induced in neuronal populations previously shown to be vulnerable to ischemia. In addition, a distinct subset of interneurons in CA3 was also extremely sensitive to ischemia, even more so than the CA1 pyramidal cells. These neurons are located in the stratum lucidum of CA3 and possess a very high density of dendritic spines. In silver preparations, they were among the first to be impregnated as "dark" neurons, before CA1 pyramidal cells; microglial reaction was also initiated first in the stratum lucidum of CA3. Whereas CA1 damage was most prominent in the septal half of the hippocampus, hilar and CA3 interneuronal damage had a more extensive dorsoventral distribution. Our results also show a far greater extent of damage in hilar neurons than previously reported. At least four hilar cell types were consistently compromised: mossy cells, spiny fusiform cells, sparsely spiny fusiform cells, and long-spined multipolar cells. A common denominator of the injured neurons in CA3 and the hilus was the presence of spines on their dendrites, which in large part accounted for the far greater number of mossy fiber terminals they receive than their non-spiny neighbors. We suggest that the differential vulnerability of neuronal subtypes in these two regions may be attributed to their extremely dense innervation by the mossy fibers and/or the presence of non-NMDA receptor subtypes that are highly permeable to calcium. In addition, early impairment of these spiny CA3 cells and hilar neurons after ischemia may be causal to delayed neuronal death in the CA1 pyramidal cells.

Animals↗
PubMed1992

Delayed degeneration of the optic tract and neurons in the superior colliculus after forebrain ischemia.

Neuronal damage induced by 15-min forebrain ischemia was investigated in adult rats 1-5 days (short-term group) and 1-5 months (long-term group) after the initial ischemic attack. In addition to the vulnerable areas reported previously, we observed that the optic tract was also very susceptible. Degeneration of the optic tract and subsequent transsynaptic cell death in the superior colliculus developed slowly and was observed only in the long-term group. The delayed, progressive neuronal damage in this sensory system may serve as a suitable model to investigate the mechanisms of long-term changes in the injured brain.

Animals↗
PubMed1992

An experimental study of the osteogenicity of free periosteal allografts with cyclosporine A administration.

Free tibial periosteum was grafted onto the dorsum (m. cutaneous trunci) of Sprague-Dawley rats to examine its osteogenic potential. The animals were divided into 3 groups based on type of: A. autogenous periosteum, B. allogeneic periosteum and C. allogeneic periosteum, and treated with cyclosporine A immunosuppression. The osteogenic response was evaluated radiologically and histologically. This study indicates that in this model periosteal allografts with immunosuppression of the recipient result in osteogenesis. Clinical application of the technique will only be possible if immunosuppressive methods with minimal morbidity are developed so that they can be used for prolonged periods.

Animals↗
PubMed1992

A community study of mental disorders among four aboriginal groups in Taiwan.

In this paper background, objectives, methodology and a few preliminary findings of a comparative epidemiological study of mental disorders among four aboriginal groups in Taiwan are presented. The study includes both a cross-sectional sample survey (N = 993) and prospective cohort studies involving psychoses, minor psychiatric morbidity, alcoholism, suicide, and accidental death. The total response rate to the sample survey was 98.3%; respondents were found to be representative. A preliminary analysis found very high rates of death from suicide, accidents and chronic liver and lung disease with a previous history of alcoholism in many of these deaths. Implications of these findings and studies of risk factors of all these health problems and their relationships are discussed.

Acculturation↗
PubMed1991

Absence of magnetic resonance imaging evidence of pontine abnormality in infantile autism.

In vivo studies involving magnetic resonance imaging and studies of neuropathologic specimens have shown that autism is most consistently associated with developmental hypoplasia of the neocerebellum. We investigated whether the cerebellar hypoplasia was accompanied by gross structural abnormalities in the major input (cerebrocerebellar) and output (cerebrorubral) pathways to the cerebellum by measuring the area of the ventral pons (including the pontine nuclei and the transverse fibers) and the midbrain on midsagittal magnetic resonance images in 34 autistic and 44 subjects. The area of the entire pons and several regions of interest within the midbrain (including the superior and inferior colliculi) were also determined with midsagittal magnetic resonance images. We found no significant difference between measurements of the pons and midbrain in autistic and control subjects. Our data show no evidence of gross anatomic abnormalities in the input and output pathways to the cerebellum in autism, a finding that is consistent with previous studies of neuropathologic specimens; rather, the reduced size of the neocerebellum in autism appears to be the result of maldevelopment within the cerebellum itself.

Adolescent↗
PubMed1991

Emergence and propagation of interictal spikes in the subcortically denervated hippocampus.

Spontaneous and evoked field potentials and cellular discharges of the subcortically denervated dorsal hippocampus were studied by multisite recordings in the freely behaving rat. Characteristic short-duration (< 100 ms), large-amplitude (up to 10 mV) transients, termed interictal spikes (IIS), were seen after fimbria-fornix (FF) lesion. Both pyramidal cells and putative interneurons fired maximally during IIS, with some interneurons sustaining long bursts (up to 400 ms) of high-frequency discharges (400-600 Hz) after the IIS. The speed of propagation of IIS along the longitudinal axis of the hippocampus varied from 0.2 m/s to > 3 m/s. The majority of IIS (type 1) could be accounted for by an enhanced activity of the intrahippocampal associational systems; a second class of IIS (type 2) had positive polarities in the stratum radiatum of CA1 and CA3 and propagated very rapidly (> 1.5 m/s). The authors propose that type 2 IIS reflect somatic depolarization and discharge of pyramidal neurons due to nonsynaptic (probably ephaptic) effects. Ephaptic interactions may also explain the longitudinal propagation of IIS at speeds higher than the conduction velocities (0.5 m/s) of hippocampal fiber systems. IIS emerged during the first 3 weeks after fimbria-fornix lesion, their incidence reaching a plateau of 2/min thereafter. During the same time period, paired-pulse suppression increased in the dentate gyrus. The amplitude of test responses to angular bundle stimulation was potentiated by small-amplitude IIS but suppressed by large-amplitude IIS. The incidence of IIS was significantly suppressed during walking relative to standing still. Tetanic stimulation of the angular bundle or handling-induced stress resulted in a 10- to 20-fold increase in the incidence of IIS that lasted for about 30 minutes. There was a negative correlation between evoked field PSP slope and population spike amplitude in the dentate gyrus of FF-lesioned rats; this correlation was positive in intact rats. The authors attribute the above pathophysiological changes to sprouting of both excitatory and inhibitory GABAergic pathways as a result of denervation of the intrahippocampal circuitry. They hypothesize that the majority of the observed physiological alterations can be traced to a weakening of feedforward inhibition coupled with an enhancement of feedback inhibition and excitation.

Animals↗
PubMed1991

Analysis of DNA restriction fragments greater than 5.7 Mb in size from the centromeric region of human chromosomes.

Pulsed electrophoresis was used to study the organization of the human centromeric region. Genomic DNA was digested with rare-cutting enzymes. DNA fragments from 0.2 to greater than 5.7 Mb were separated by electrophoresis and hybridized with alphoid and simple DNA repeats. Rare-cutting enzymes (Mlu I, Nar I, Not I, Nru I, Sal I, Sfi I, Sst II) demonstrated fewer restriction sites at centromeric regions than elsewhere in the genome. The enzyme Not I had the fewest restriction sites at centromeric regions. As much as 70% of these sequences from the centromeric region are present in Not I DNA fragments greater than 5.7 and estimated to be as large as 10 Mb in size. Other repetitive sequences such as short interspersed repeated segments (SINEs), long interspersed repeated segments (LINEs), ribosomal DNA, and mini-satellite DNA that are not enriched at the centromeric region, are not enriched in Not I fragments of greater than 5.7 Mb in size.

Centromere↗
PubMed1991

Alkaline reflux gastritis.

Alkaline reflux gastritis and the symptoms associated with alkaline reflux gastritis have been reported in the medical literature since shortly after Billroth successfully performed his first gastrectomy in the 1880s. The disease process is produced by, or at least is associated with, the reflux of alkaline secretions into the gastric remnant. Although it occurs after any procedure that ablates the pylorus including pyloroplasty, it would appear to be most common after a Billroth II gastrojejunostomy. How the alkaline secretions cause the gastritis is still controversial. Clearly, the most effective therapy is to reroute the secretions from the biliary tract, pancreas, and duodenum so that they will not reflux into the gastric remnant. This is most effectively accomplished by a Roux-en-Y gastrojejunostomy with the afferent limb measuring at least 18 inches (40 cm). The surgeon and the patient should be aware that the construction of such a gastric outlet channel is associated with delayed gastric emptying. The etiology of this impaired emptying is also controversial. If the patient has symptoms of dumping (either early or late), these symptoms may also be abated using the Roux limb. At least 40% of patients will have gastric outlet obstruction. Supportive therapy is appropriate in the majority of these patients.

Duodenogastric Reflux↗
PubMed1990

Cancerous colonic polyps. "Hands on" or "hands off?".

Management of the malignant colonic polyp remains a subject for debate even after almost two decades of experience. Some researchers believe all patients should have a colonic resection; others argue that only certain cases call for laparotomy, while still others hold for a selective approach but with varying criteria. Therefore, a survey has been made of current practice and opinion from the time colonoscopic polypectomy was introduced in 1969 to the present. The authors have reviewed a sizable segment of their experience, dividing cases of malignant polyps into two broad categories: those in which complete polypectomy was followed by bowel resection; and those undergoing polypectomy alone. The determinants leading to one course or the other were analyzed, as were the results.

Colectomy↗
PubMed1988

Seasonal energetics of opossums (Didelphis virginiana) in Ohio.

1. Female opossums acclimatized to each of the four seasons were not significantly different (P greater than 0.05) in oxygen consumption at a Ta of 0 degrees C; the overall average was 0.66 +/- 0.1 ml O2/g-hr. 2. Body weight decreased by 27% from autumn to spring; pelage density increased in winter, but thermal conductance changed very little between seasons. 3. Respirometry revealed no evidence of thermoregulatory adjustments in opossums acclimatized to winter in Ohio.

Adaptation, Physiological↗