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Biomedical subjects

M McLean

Publications and source records attributed to M McLean.

At least 109 records · Page 6Linked to original sources
PubMed1986

Total hip replacement and sciatic nerve trauma.

Intraoperative injury to the sciatic nerve is a known risk during total hip replacement. Postoperative injury by an implant is rare. A case of sciatic nerve laceration possibly caused by a protrusio ring is presented. The presentation of the patient, the mechanism of injury, and the means to avoid it are discussed.

Aged↗
PubMed1986

Morphometric analysis of in vivo development of porcine ovarian granulosa cells in preovulatory antral follicles.

Granulosa cells (GC) from immature (1-2 mm), developing (3-5 mm), and preovulatory (6-12 mm) antral porcine follicles were examined by stereological, ultrastructural techniques. Partial cell volumes occupied by nuclei or mitochondria did not differ significantly as follicles enlarged. Whorled smooth endoplasmic reticulum (ER) increased significantly in large follicles compared to either small or medium sized follicles. Whorled rough ER elements were present in similar amounts in small and medium sized follicles and absent in large follicles. The GC of large follicles contained significantly more lipid and Golgi complexes than that of small follicles, but the lipid and Golgi complex content of GC from medium follicles was not significantly different from that of either small or large follicles. Proportions of total cell volumes occupied by lysosomes and multivesicular bodies increased as follicular size increased. This confirms earlier qualitative studies, and provides a quantitative in situ basis for future in vitro studies.

Animals↗
PubMed1982

Sympathetic and parasympathetic cardiac control in athletes and nonathletes at rest.

A simple model to characterize sympathetic and parasympathetic effects on heart rate (R) was tested during rest in 10 nonathletes and 8 world-class oarsmen. The model states that R = mnR0, where R0 is the intrinsic cardiac rate, and m and n depend only on sympathetic and parasympathetic activity, respectively. The multipliers, m and n, were determined by dual pharmacological blockade in two sessions under similar conditions, but in one session propranolol and in the other atropine was given first. In agreement with the model, when corrections were made for atropine-induced blood pressure changes, m and n did not depend on which blocking agent was administered first. In athletes the control heart rate [55 +/- 3.3 (SD) beats/min] and R0 (81 +/- 8.3 beats/min) were lower than in nonathletes (62 +/- 6.0, P less than 0.01 and 102 +/- 11, P less than 0.001, respectively). The sympathetic multiplier, m, was similar (1.18 +/- 0.06 vs. 1.20 +/- 0.05, P greater than 0.4) in the two groups, but n, the parasympathetic multiplier, was closer to 1 in the athletes (0.57 +/- 0.03 vs. 0.51 +/- 0.05, P less than 0.01). We conclude that the model is suitable for the quantitative study of sympathetic/parasympathetic heart rate control in humans, and that the lower resting heart rate in oarsmen is solely due to a reduction in intrinsic cardiac rate, and not to an increase in parasympathetic tone.

Adult↗
PubMed1977

Structural changes in light- and dark-adapted compound eyes of the Australian earwig Labidura riparia truncata (Dermaptera).

The apposition acone eye of Labidura is relatively small--550-600 facets--with a thick corneal lens and shallow retina. The retina cell columns are each formed of six peripheral cells plus two central cells, a partially fused rhabdom, and dense pigment in two or three cell types. Upon adaptation from light to dark, the most striking photomechanical response is a proximal broadening of the cone cells, which results in a 38-fold increase in cross-sectional area of the aperture. While longitudinal rhabdom movement is small, microvillar diameters swell in response to light and contract in the dark. Irregularities of facet pattern and shape, and in ommatidial alignment were found, particularly towards eye margins. Three types of interommatidial sense organs on the eye surface are described, one of which has not been previously reported. An argument is presented to explain how the field of view and sensitivity are both apparently decreased in the acone eye by exposure to light.

Animals↗
PubMed1976

Target discrimination in regenerating insect sensory nerve.

The paired abdominal cerci of the cricket Acheta domesticus are mechanosensory appendages which regenerate readily when amputated during larval life. Their peripherally-located sense cells form axons which project centrally as a purely sensory nerve to the terminal abdominal ganglion. In an attempt to analyze some of the factors which guide a regenerating sensory nerve to correct central terminations, implants of homologous, supernumerary terminal ganglia were made in cricket larvae and the host cerci amputated. The possibility that implants with multiple nerve stumps might release an attracting substance was considered. Surgical procedures used were (1) implant in posterior abdomen; (2) implant in posterior abdomen, ipsilateral to chronic cercal deprivation; (3) implant in mesothoracic leg socket, adjacent to heterotopically-transplanted regenerated cercus; (4) implant in posterior abdomen, ipsilateral host cercal motor nerve sectioned; (5) implant in posterior abdomen, ipsilateral margin of host terminal ganglion wounded. Results were determined after the adult molt, by conventional histology or by cobalt chloride filling of regenerated cercal nerves. In all procedures except (3) and (4), the regenerated afferent nerve bypassed the implant and terminated in the host terminal ganglion. In (3), the regenerated fibers from cercal grafts bypassed the implant; terminations were not found. In (4), some regenerated cercal axons connected with the implant and the majority terminated in the host ganglion. It is suggested that regenerating cercal afferents may depend in a facultative way on the cercal motor nerve as a pathway guide but there is as yet no clear evidence for a trophic influence from the central nervous system.

Animals↗
PubMed1975

Nursing in the sky.

Explore the source record for details and available documents.

Aerospace Medicine↗
PubMed1975

Sodium iodoacetate as an antiglycolytic agent in blood samples.

We evaluated the effect of sodium iodoacetate on glycolysis in a series of randomly selected blood samples from patients. Glucose values for serum and for serum with added sodium fluoride (2.5 g/liter) or sodium iodoacetate (2 g and 0.5 g/liter) were compared at room temperature. Respective declines in glucose values averaged 170, 40, 30, and 30 mg/liter after 24 h. Iodoacetate-preserved (0.5 g/liter) samples showed no visible hemolysis. Results of determinations of urea with urease and of other tests on SMA 12/60 (Technicon) panels were unaffected.

Autoanalysis↗
PubMedDate not supplied

Transcervico-mandibulo-palatal approach for surgical salvage of recurrent nasopharyngeal cancer.

BACKGROUND: Local relapse of nasopharyngeal carcinoma is a difficult problem of management that is usually treated by re-irradiation. Surgical salvage is rarely offered, judging by the paucity of reports in the literature. METHODS: This article reviews the six previously described methods of performing nasopharyngectomy and recounts experience with a series of seven patients using a transcervico-mandibulo-palatal approach, which is described. RESULTS: The results of this small series show survivorship and morbidity which seem to compare favorably with other published surgical treatment options. CONCLUSIONS: If retreatment with radiotherapy is not favored, the transcervico-mandibulo-palatal approach may be a suitable method of surgical salvage for small, locally recurrent, nasopharyngeal cancer.

Adult↗
PubMedDate not supplied

Aflatoxin B1--its effects on an in vitro plant system.

The phytotoxic effects of aflatoxin B1 (AFB1) on in vitro cultures of differentiating calli and regenerating plantlets of Nicotiana tabacum were assessed. Callus appeared more sensitive to the effects of AFB1, with fresh mass accumulation and callus chlorophyll levels affected at low (approximately 0.5 micrograms/ml) aflatoxin concentrations. Transmission electron microscopy revealed early deteriorative alterations in chloroplast morphology. Inhibitory effects of the toxin (up to and including 10 micrograms/ml) on callus fresh mass accumulation were reversed following a 3 week toxin-free recovery period. In tobacco plantlets, root and leaf development, and root and leaf mass were significantly inhibited in a dose-dependent fashion with increasing AFB1 concentration above 0.5 micrograms/ml. Inhibitory effects on plantlet root development were more pronounced that on leaf development.

Aflatoxin B1↗