Biomedical subjects

C Leigh

Publications and source records attributed to C Leigh.

8 recordsLinked to original sources

PubMed2005

Comparative study of sperm chromatin condensation in the excurrent ducts of the laboratory mouse Mus musculus and spinifex hopping mouse Notomys alexis.

In most mammals, post-testicular sperm maturation is completed in the caput and corpus epididymides, with storage occurring in the cauda epididymides. However, in the spinifex hopping mouse, Notomys alexis, epididymal sperm transit is rapid and some sperm storage occurs in the distal region of the vas deferens. The aim of the present study was to determine whether the rapid progression of sperm into the vas deferens in the hopping mouse results in late sperm maturation. To determine this, sperm nuclei from the epididymides and vasa deferentia of laboratory and hopping mice were compared for: (1) thiol content after staining with monobromobimane (mBBr); (2) chromatin resistance to acid denaturation following incubation with acetic alcohol and staining with acridine orange; and (3) chromatin resistance to in vitro decondensation after incubation with 1% sodium dodecyl sulfate (SDS). It was found that, whereas laboratory mouse sperm completed chromatin condensation by the time they reached the cauda epididymidis, hopping mouse sperm nuclei from the vas deferens showed significantly less mBBr fluorescence and a greater proportion of sperm were resistant to decondensation with SDS than those in the cauda epididymidis. Therefore, the results of the present study indicate that, unlike in the laboratory mouse, hopping mouse chromatin condensation of spermatozoa continues in the vas deferens and this may be due, at least in part, to rapid epididymal transit.

Acridine Orange↗

PubMed2004

Dietary aluminium and renal failure in the koala (Phascolarctos cinereus).

The study investigated the link between the potentially nephrotoxic levels of aluminium ingested in the natural diet of eucalypt leaves by koalas in the Adelaide Hills, South Australia, and the high incidence of renal failure in koalas within this habitat. Routine histology of kidney specimens revealed no pathologies at the light microscopic level and contrasted sharply with the clinical signs of renal failure. However staining with solochrome azurine and Perl's Prussian blue showed aluminium was present in some proximal convoluted tubules in all specimens. Aluminium was also found in bone samples. The presence of aluminium in bone and kidney tissues was confirmed using electron dispersive x-ray analysis with transmission and scanning electron microscopy. Ultrastructural changes, including a decrease in lysosomal numbers, were seen in proximal convoluted tubules and these changes were shown to coincide with the presence of aluminium. No aluminium was found in koalas that died from causes other than renal failure. It was concluded that renal failure in the koalas of the Adelaide Hills is characterised by the presence of aluminium in the kidneys and bone and it is probably related to the high levels of aluminium in their restricted diet of eucalypt leaves. However, it is not known if the presence of aluminium is the cause or effect of the renal failure. The study is the first account where aluminium ingested as part of the natural diet of mammals has been shown to accumulate in the animal and be implicated with nephrotoxicity.

Aluminum↗

PubMed1999

Substance P-induced enhanced permeability of dura mater microvessels is accompanied by pronounced ultrastructural changes, but is not dependent on the density of endothelial cell anionic sites.

Experimental data point to a determinant role for endothelial cell (EC) anionic sites in the regulation of vascular permeability. Previous studies have shown that EC anionic sites density is reduced in conditions of enhanced permeability. The pathophysiology of migraine and vascular headache encompasses dilatation of dural vessels and extravasation of plasma proteins. The current study was carried out to determine if the density of EC anionic sites is reduced in enhanced permeability of dural vessels. Enhanced permeability was chemically induced in rats by intravenous injection of substance P and was tested by assessing leakage of horseradish peroxidase (HRP). Anionic sites were labelled with cationic colloidal gold and their density was quantified from electron microscopy negatives. Experimental animals showed increased leakage of HRP from dural vessels. However, anionic sites in EC membranes (luminal and abluminal) showed no statistical differences when their mean densities in experimental and control animals were compared. The results indicate that in this model, factors other than the density of anionic sites may be important determinants in the permeability of dural vessels. Such factors may include structural alteration of ECs consistent with an increased permeability. In this study pronounced ultrastructural changes in ECs were noted in experimental animals including widening of intercellular junctions and an increase in the number of EC gaps and vesicles.

Animals↗

PubMed1996

Evaluation of non-invasive techniques to assess vasoconstriction in healthy volunteers using methoxamine as a probe drug.

Non-invasive methods for assessment of the vascular effects of antimigraine drugs were evaluated with respect to their utility, variability and sensitivity in a double-blind, placebo-controlled, three-period crossover study in six healthy volunteers using an intravenous vasoconstrictor, methoxamine, as a probe drug. Changes in the internal diameter of the brachial and radial arteries were measured using ultrasound which had low between-day and within-day coefficients of variation. Peak systolic velocity (PSV), time-averaged velocity (TAV), total flow, resistance (RI) and pulsatility indices (PI) were measured by Doppler from one arterial wave form. Whilst PSV and TAV increased with methoxamine, because of bradycardia, changes in PI and RI were difficult to interpret. An automatic oscillometric cuff, a mercury-in-silastic strain gauge method and the "Finapres", finger arterial blood pressure monitor were used to follow changes in systolic blood pressure (SBP). The strain gauge technique underestimated arm SBP compared to the oscillometric method but clearly showed drug-related increases whilst the Finapres did not reflect changes in blood pressure detected by the other methods.

Adult↗

PubMed1994

Staged diabetes management. Toward an integrated model of diabetes care.

This paper introduces a new and innovative approach to diabetes management in the primary-care setting. Staged diabetes management (SDM) represents a four-year effort to develop and test a data-based approach to diabetes management that could be easily adapted to a variety of health-care settings in which diabetes management is principally under the direction of primary-care physicians was limited access to specialists. After testing under controlled circumstances at the International Diabetes Center (Minneapolis, MN), SDM was subjected to substantial field trials under conditions that represent the scope and variety of primary-care practices in diabetes. The following represents the work of several investigators who independently undertook a review of SDM.

Databases, Factual↗

PubMed1993

Collagenous colitis associated with chronic constipation.

We present a case in which the classical histopathologic features associated with collagenous colitis were present throughout the colectomy specimen of a 69-year-old woman operated on for life-long intractable idiopathic constipation. This patient had never suffered from episodes of watery diarrhea. The reasons for this paradox are unclear, but suggest that a thickened collagen table and damaged surface epithelium may not be entirely specific pathologic findings marking the clinicopathological syndrome of collagenous colitis.

Aged↗

PubMed1993

Occurrence of melanin in pheochromocytoma.

Melanin or a melanin-like pigment was observed in six of 19 pheochromocytomas. The intracellular pigment was Fontana-positive, bleach-labile dark brown to black material and distinct from coincidental hemosiderin and lipochrome. Ultrastructural components of the pigmented tumors include melanosomes and premelanosomes. Two patients with pigmented tumors had associated von Hippel-Lindau syndrome, and one had neurofibromatosis. The occurrence of melanin and melanosomes in pheochromocytoma has not been previously reported in the English literature. It is probably a reflection of the neural crest origin of this neoplasm.

Adrenal Gland Neoplasms↗

PubMed1987

Properties of the extract and spicules of the dermatitis inducing sponge Neofibularia mordens Hartman.

Skeletal components and the exudate of the sponge Neofibularia mordens, as well as four fractions of the extract were investigated. Possible causes, and management, of the contact dermatitis resulting from application of extract fractions were studied. Antimicrobial activity of the sponge extract fractions, together with their effect on small crustaceans, was determined. Two fractions exhibited strong neuroactivity on guinea-pig isolated intestine, octopus-arm nerve-muscle and crustacean cheliped nerve-muscle preparations.

Animals↗