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Biomedical subjects

M H Snow

Publications and source records attributed to M H Snow.

At least 19 recordsLinked to original sources
PubMed1990

Satellite cell response in rat soleus muscle undergoing hypertrophy due to surgical ablation of synergists.

Although the role of satellite cells has been confirmed during skeletal muscle growth and regeneration, their involvement during work-induced muscle growth remains uncertain. In this study, chronically overloaded rat soleus muscles were ultrastructurally monitored following surgical ablation of synergists to examine cytological adaptations of satellite cells and myofibers. The left soleus muscle of 20 female Sprague-Dawley rats (7 weeks of age) was induced to hypertrophy by excising the contralateral plantaris and gastrocnemius muscles under pentobarbital anesthesia. Right limbs were sham-operated and served as controls. On days 3, 7, 14, 21, and 30 after surgery, the soleus muscles were removed and processed for electron microscopy. Two morphologically distinct phases were noted in the surgically overloaded muscles. The first stage (week 1) was characterized by a significant increase in the number of satellite cells, and by more than half of the experimental muscle fibers displaying myofibrillar disruptions, mitochondrial alterations and glycogen pooling. The second phase (weeks 2-4) featured mostly normal, although larger appearing muscle fibers, with the satellite cell frequency remaining slightly elevated. These findings suggest that muscle fiber structural abnormalities, rather than an increase in muscle activity, may play a more significant role in the early activation of satellite cells during compensatory hypertrophy, whereas activation of satellite cells during the later stages may be in response to increased levels of muscle activity.

Animals↗
PubMed1990

Primordial germ cells in the mouse embryo during gastrulation.

With the aid of a whole-mount technique, we have detected a small cluster of alkaline phosphatase (ALP)-positive cells in whole mounts of mid-primitive-streak-stage embryos, 7-7 1/4 days post coitum (dpc). Within the cluster, about 8 cells contain a small cytoplasmic spot, intensely stained for ALP activity and possibly associated with an active Golgi complex. The cluster lies just posterior to the definitive primitive streak in the extraembryonic mesoderm, separated from the embryo by the amniotic fold. Towards the end of gastrulation, the number of cells containing the ALP-positive spot rises to between 50 and 80. Thereafter the number of cells in the extraembryonic cluster declines, and similar cells start to be seen in the mesoderm of the primitive streak and then in the endoderm. At 8 dpc, about 125 ALP-stained cells are found, mainly in the hindgut endoderm and also at the base of the allantois, their appearance and location at this stage agreeing closely with previous reports on primordial germ cells (PGCs). Embryos from which the cluster area has been removed at the 7-day stage are devoid of PGCs after culture for 48 h, whereas the excised tissue is rich in PGCs. We argue that the cells in the cluster are indeed primordial germ cells, at a stage significantly earlier than any reported previously. This would indicate that the PGC lineage in the mouse is set aside at least as early as 7 dpc, possibly as one of the first 'mesodermal' cell types to emerge, and that its differentiation, as expressed by ALP activity, is gradual.

Alkaline Phosphatase↗
PubMed1989

Hypercalcaemia in association with enteric fever.

We report 2 cases of hypercalcaemia and hypercalciuria, with detectable levels of parathyroid hormone, which appeared to be precipitated by enteric fever. Extensive investigation of one case, including ultrasound, isotope scanning, angiography, computed tomographic scanning and surgical exploration, failed to detect a parathyroid adenoma. In both cases biochemical and hormonal abnormalities resolved several months after recovery of enteric fever. The mechanism of the proposed association is unexplained but it should be considered in any patient with hypercalcaemia and detectable parathyroid hormone levels, who is suffering from or has recently recovered from enteric fever. If such a patient is well, a period of several month's observation is recommended. We believe these two cases to be the first such reports of hypercalcaemia in association with enteric fever.

Adolescent↗
PubMed1989

Yersinia pseudotuberculosis infection as a cause of reactive arthritis as seen in a genitourinary clinic: case report.

Patients are often referred to the genitourinary clinic for screening for urethral infections after a clinical diagnosis of Reiter's syndrome or reactive arthritis. We report a case of reactive polyarthritis in which serological evidence of Yersinia pseudotuberculosis infection was found in the absence of the other common precipitating organisms, such as Chlamydia spp, Klebsiella spp, Shigella spp, Campylobacter spp, or Yersinia enterocolitica.

Adult↗
PubMed1987

Frequency of bifurcated muscle fibers in hypertrophic rat soleus muscle.

The total number of bifurcated and nonbifurcated fibers were counted in rat soleus muscles induced to hypertrophy by surgical ablation of the gastrocnemius and plantaris muscles. Sham-operated and normal soleus muscles served as controls. Every muscle fiber within the entire muscle was individually examined and counted with the aid of a dissecting microscope following a 10-12 hour nitric acid digestion of the connective tissue. The results show that the total number of muscle fibers in the hypertrophic soleus did not differ significantly from the control. The frequency of bifurcated fibers observed in the control muscles was significantly greater than has been previously reported, and their frequency in the hypertrophic muscles, although slightly increased, was not significantly different from control values. These data confirm that fiber hypertrophy is not accompanied by hyperplasia, and they further suggest that bifurcated fibers probably play an insignificant role during muscle adaptation to hypertrophy due to their very low frequency.

Animals↗
PubMed1986

Cinemicrographic study of the cell movement in the primitive-streak-stage mouse embryo.

Migration of the mesoderm cells in the primitive-streak-stage mouse embryo was directly studied by cinemicrography using whole embryo culture and Nomarski differential interference contrast optics. Relative transparency and small size of the early mouse embryos enabled direct observation of the individual cells and their cell processes. Seven-day-old mouse embryos were isolated and cultured in a small chamber in a medium consisting of 50% rat serum and 50% Dulbecco's modified minimum essential medium. The mesoderm cells move away from the primitive streak in both anterior and antimesometrial (distal) directions at a mean velocity of 46 micron h-1. They extend cell processes and constantly change cell shape. They do not translocate extensively as isolated single cells, but usually maintain attachment to other mesoderm cells. They show frequent cell division preceded by rounding up of the cell bodies, and accompanied by vigorous blebbing before and after cytokinesis. This study shows that it is possible to examine the motility of embryonic cells inside the mammalian embryo by direct observation if the embryo is small and transparent enough for the use of the Nomarski optics.

Animals↗
PubMed1985

Sarcoidosis of the tongue--a case report.

A case of sarcoidosis, unusual in that it was confined to the tongue, is reported in a 50 year-old female. The condition resolved after 1 year of steroid therapy and excision of fibrous tethering bands. Intra-oral sarcoidosis should be considered in the differential diagnosis of lingual swelling and induration.

Female↗
PubMed1979

The pituitary-gonadal response to the gonadotrophin releasing hormone analogue D-Ser (TBU)6-Des Gly10-LHRH-ethylamide in normal men.

We have studied the dose-response characteristics of the LHRH analogue D-Ser (TBU)6-Des Gly10-LHRH-ethylamide administered subcutaneously to five normal male volunteers. The relative potency of the analogue is about sixty times (FSH) and forty times (LH) that of the parent peptide and the increased potency and duration of action of the analogue lead to enhanced biological effect in terms of testosterone release. The prolonged duration of action of the analogue suggests that a single daily dosage regime could be used although further chronic studies with this potent analogue should be undertaken in normal volunteers to determine optimum dosage schedules.

Adult↗
PubMed1979

Thyroid stimulating antibodies and metastatic thyroid carcinoma.

A patient with previously treated follicular carcinoma of the thyroid developed Graves' disease with a high titre of thyroid-stimulating antibodies (TSAb). He developed functioning pulmonary metastases leading to hyperthyroidism. Levels of TSAb paralleled the functional status of the metastases suggesting that hyperfunction of the neoplastic tissues was caused by TSAb.

Adenocarcinoma↗
PubMed1979

Dopamine is a physiological regulator of thyrotrophin (TSH) secretion in normal man.

Using a sensitive and precise radioimmunoassay for human TSH we have demonstrated significant elevations in serum TSH levels in euthyroid volunteers following administration of the dopamine receptor blocking drug metoclopramide when compared with placebo. The degree of TSH response is significantly greater in females than in males and is sustained over a 3-hour period after a single oral 10 mg dose of metoclopramide. The degree of TSH release after metoclopramide is inversely related to the basal TSH level suggesting that dopamine is a determinant of low daytime TSH levels and is thus implicated in the circadian rhythm of TSH secretion. Pretreatment with 10 mg of metoclopramide orally, one hour before TRH administration leads to significant enhancement of the TSH response to TRH. Our findings provide further evidence for the physiological inhibitory role of dopamine in the contol of TSH secretion in normal man. The possible mode of action of dopamine and the clinical implications of this neuroregulatory pathway are discussed.

Adult↗
PubMed1978

An autoradiographic study of satellite cell differentiation into regenerating myotubes following transplantation of muscles in young rats.

Satellite cells were traced autoradiographically during the regeneration of skeletal muscle in young Sprague-Dawley rats. Approximately 31% of the satellite cells in uninjured muscles appeared labelled after three injections of tritiated thymidine; none of the myonuclei were labelled in the same muscles. Four to six days after transplanting the radioactive muscles to non-radioactive littermates, regenerating myotube nuclei in the host appeared labelled. Thus, this study confirms that satellite cells in young rats can differentiate into multinucleated myotubes following muscle injury.

Animals↗
PubMed1978

Plasma renin activity following renal transplantation.

Plasma renin activity (PRA) was studied serially for up to 21 days following transplantation in thirteen patients receiving renal allografts. PRA was measured during fasting and recumvency and its relationship to renal function, diuretic administration, plasma sodium, allograft rejection and blood pressure was examined. PRA fell steadily as renal function improved and plasma sodium rose following transplantation and when rejection episodes were excluded an inverse relationship between PRA and renal function could be seen. It is not possible to say whether the changes in PRA and function are causally related or whether changes in plasma sodium alone account for the observed changes in PRA. Some rejection episodes were accompanied by an increase in PRA, but this was not sufficiently consistent to be of value in the diagnosis of rejection. PRA also increased in relation to frusemide-induced fluid loss. There was no relationship in these patients between PRA and blood pressure.

Creatinine↗