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Biomedical subjects

L Hsu

Publications and source records attributed to L Hsu.

At least 163 records · Page 9Linked to original sources
PubMed1982

An autoradiographic study of the role of satellite cells and myonuclei during myogenesis in vitro.

Satellite cells and myonuclei of neonatal rat muscles were differentially labeled with 3H-thymidine according to the procedure of Moss and Leblond (1971). Minced muscles fragments containing either labeled satellite cells or labeled myonuclei were cultured until multinucleated myotubes grew out from the explants. Reutilzation of isotope released from degenerating nuclei was competitively inhibited by using a culture medium containing excess (0.32-0.41 mM) cold thymidine. after an 8-10 day growth period, the explants were fixed and prepared for autoradiographic (ARG) examination to determine whether labeled satellite cells or myonuclei had contributed to the myonuclear population of the developing myotubes. Counts were made of the number of labeled myotubes in the explants and compared with the number of labeled satellite cells and myonuclei in samples of the original muscle tissues fixed at the time of explantation. The original muscles showed a mean satellite cell labeling index of 51.7% and gave rise to myotubes with a mean labeling incidence of 40%. In contrast, myonuclear labeling in the original muscle tissues showed no correlation with subsequent myotube labeling. Only 3.4% myotube labeling was found in explants in which over 30% of the original tissue myonuclei had been labeled. Under conditions controlled for isotope reutilization, these observations confirm results of in vivo ARG studies indicating that satellite cells are the only significant source of regenerating myoblasts in injured muscle tissue.

Animals↗
PubMed1981

CTL helper factor(s) produced by peritoneal cells of mice immunized to Listeria monocytogenes: relationship to interferon.

We have studied the relationship of interferons (IFN) to soluble helper factor(s) produced in vitro by activated peritoneal exudate cells of mice immunized to Listeria monocytogenes. This helper factor(s) can assist the generation of cytotoxic lymphocytes (CTLs) in response to allogeneic thymocytes that have been heat-treated to remove functional antigens that would normally stimulate CTLs in the absence of added exogenous help. In addition to IFN and CTL helper activity, a thymocyte proliferative activity also was detected. There appeared to be collaboration between activated nonadherent T cells and macrophages (MO) in the production of all three activities. The IFN produced appeared to be primarily IFN-gamma, however, some IFN-alpha/beta probably was present as well. Although CTL helper activity and IFN were both contained in fractions comprising the major peak of thymocyte proliferative activity when supernatant fluids containing all three were chromatographed, functional IFN could be deleted with pH-2 and anti-IFN treatment without appreciably altering the other two activities. Furthermore, when fluids containing helper activity, but depleted of functional IFN, were added to cultures of responder lymphocytes and heat-treated thymocytes, IFN was produced during the course of the five day culture as were CTLs. In parallel cultures to which fluids containing helper factor(s) were not added, no IFN was produced, and no CTLs were generated. Thus, although fluids having activities required for the generation of CTLs may be depleted of IFN at the time they are added to cultures, a role for IFN in some phase of CTL development cannot be excluded.

Animals↗
PubMed1980

A murine leukemia virus yield-reduction semi-microassay for interferon.

Interferon (IF) treatment of murine cells chronically producing infectious leukemia virus results in a decreased yield of extracellular virus. We have utilized this principle to develop a useful semi-microassay for IF. The assay incorporates the desirable features of both virus yield-reduction and plaque-reduction assays, yet has few of the undesirable features associated with many IF assays. Being a semi-micro assay, it is amenable to the screening of multiple samples for IF and is economical with respect to cell culture materials, reagents and amount of sample required for testing.

Animals↗
PubMed1980

Age-related alterations in the rodent brain cholinergic system and behavior.

Pre- and postsynaptic cholinergic markers were studied in various brain regions of mice and rats aged 6 to 30 months in an attempt to determine whether alterations in this transmitter system occur during the normal aging process. Reliable decreases in cholinergic receptor binding and choline acetyltransferase (CAT) activity were found in the cerebral cortex and corpus striatum. These alterations in the cholinergic system were typically more consistent and robust than changes involving glutamic acid decarboxylase, and enzyme marker for GABA neurons. No statistically significant changes in any markers were found in the hippocampus of either species. Significant age-related changes in retention of passive avoidance learning and locomotor activity were also observed in these same animals. These findings demonstrate that changes in the cholinergic system occur naturally in aged mice and rats and that both the loss of cholinergic receptors and decrease in cat activity may contribute to the motor and mental impairments that often accompany old age.

Aging↗
PubMed1980

Membranous bodies in the myelin sheath of Schwann cells.

Electron microscopy of muscle biopsies of patients with paralytic scoliosis and tuberculosis of spines reveals membranous bodies in the myelin sheath of Schwann cells. On the basis of this morphological pattern and indirect biochemical evidence, it is suggested that these bodies were formed by abnormal myelin metabolism.

Humans↗
PubMed1979

An electronmicroscopic analysis of the optic nerve in the golden hamster.

The electronmicroscopic examination of sections taken from the hamster's optic nerve 5 mm behind the globe indicated that the nerve contains 110,165 +/- 4,177 (p less than 0.05) fibres of which 96.4% are myelinated. The fibre diameter distribution is unimodal with a peak at 1.2 micrometer and axon diameters ranging from 0.20 micrometer to 3.93 micrometer. Fibres of all sizes are distributed uniformly throughout the cross section of the nerve. The thickness of the myelin sheath surrounding a given axon is highly (0.80) correlated with axonal diameter and the degree of myelination for a fibre of a given size is nearly constant throughout the nerve's cross section. In nerve sections taken just posterior to the globe most (64%) of the fibres counted are unmyelinated and the percentage of unmyelinated axons is highest near the peripheral boundary of the nerve. The process of myelination is essentially complete in sections taken 3.5 mm behind the eye. These differences in the myelination of the proximal and distal nerve most probably account for the discrepancy between the results reported here and those provided by a previous study (Tiao and Blakemore, '76) concerned with the structure of the optic nerve in this species.

Animals↗
PubMed1979

Age related changes in auto-erythrocyte rosettes in the C57BL/6J and NZB/BINJ mice.

The changes in the auto-erythrocyte rosetting thymic and splenic lymphocytes and the induction of autoimmunity was followed with age in C57BL/6J and NZB/BINJ mice. The auto-erythrocyte rosetting cells (auto-RFC) showed shifts in their pattern in both thymus and spleen in C57BL/6J and NZB/BINJ mice. Both strains had approximately the same percentage (approximately 3%) of thymic auto-RFC at 1 month of age. In C57BL/6J mice the rosette population increased to 6.6% by 2 months, declined after 3 months and subsequently increased gradually with age. In contrast, the NZB/BINJ thymic auto-rosettes peaked at 4 months and gradually declined thereafter. Both the NZB/BINJ and C57BL/6J strains were tested for the presence of anti-erythrocyte antibodies by the direct Coombs' agglutination test. The results showed that at 6 and 10 months 50% and 90% of the NZB/BINJ mice were positive for antibodies, respectively, and the thymic and splenic auto-RFC dramatically decreased in numbers. In the C57BL/6J mice during this same period, very low incidence of auto-antibodies was detected by the Coombs' test and auto-RFC increased in numbers.

Aging↗
PubMed1978

Myosin: immunofluorescent localization in neuronal and glial cultures.

The distribution of intracellular myosin was studied by the double antibody immunofluorescence method in primary organotypic neuronal cultures and two established neuronal and glial cell lines. An array of parallel filaments aligned with the major cellular axis and a three-dimensional subsurface network were shown to react with two different myosin antibodies. The presence of myosin-rich filaments in regions known to contain actin filaments suggests that these proteins interact to generate the motive force in nonmuscle contractile systems.

Cell Line↗
PubMed1978

The in vivo differentiation of murine neuroblastoma.

C1300 neuroblastoma was implanted with regenerating skeletal muscle to study the role of tissue interactions during tumor cell differentiation. Combined tumor-muscle implants, placed subcutaneously or within diffusion chambers were compared with control tumors implanted without muscle. Neuroblastoma implanted with injured muscle undergoes a partial neuronal differentiation. The tumor cells lose their normal round cell configuration and develop numerous cytoplasmic processes. Accompanying these outward changes are an increased content of microtubules in the neuritic processes; the appearance of glial-like processes containing abundant microfilaments; and the occurrence of growth vesicles identical to those of the growth cones of normal neurites. Although the implants usually contain large numbers of regenerated myofibers, tumor cell differentiation is not dependent upon the presence of these newly formed fibers. Tumor differentiation occurs equally well on the surfaces of degenerating muscle fragments, fibrin deposits and on the membrane surfaces of the diffusion chambers. These observations suggest that non-specific cell surface phenomena, rather than neuromuscular interactions were primarily responsible for the tumor cell differentiation in vivo.

Animals↗
PubMed1977

Physiologic and pharmacologic influences on adrenergic regulation of renin release.

Changes in hemodynamic variables and plasma renin activity (PRA) induced by short-term alteration of blood pressure and sympathetic nervous system activity were studied in normotensive and hypertensive men on high-sodium and low-sodium intake. Blood pressure and heart rate alterations caused by standard cold pressor tests, amyl nitrite inhalation, phentolamine infusion, and phenylephrine infusion were recorded. PRA was measured at time 0, 5, 15, and 30 min. No change in PRA occurred in either group following cold pressore test and amyl nitrite inhalation. Phenylephrine suppressed PRA in normal but not hypertensive subjects, and phentolamine elevated PRA in normotensive and hypertensive subjects regardless of diet. Short-term stimulation of the sympathetic nervous system does not appear to elevate PRA in man. Suppression of PRA by an alpha agonist was not observed in hypertensives and may reflect barorecptor insensitivity in this group of subjects.

Adult↗