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Biomedical subjects

J C Robertson

Publications and source records attributed to J C Robertson.

At least 19 recordsLinked to original sources
PubMed1996

Thyroid hormone controls the onset of androgen sensitivity in the developing larynx of Xenopus laevis.

Gonadal differentiation, the onset of androgen-stimulated laryngeal growth and the genesis of a sex difference in laryngeal innervation, all temporally coincide with thyroid hormone (TH)-induced metamorphosis in Xenopus laevis. To explore the role TH plays in the ontogeny of the Xenopus androgen-sensitive vocal neuromuscular system, we examined gonadal and laryngeal development in tadpoles in which metamorphosis had been blocked by treatment with the thyroxine synthesis inhibitor propylthiouracil (PTU). PTU treatment did not arrest gonadal differentiation. Testes from PTU-treated male tadpoles had seminiferous tubules and advanced stage male germ cells, while in females stage 1 oocytes were present. In contrast to the gonads, PTU did block morphological development of the larynx. Tadpoles treated with PTU for 50 or 100 days had larynges which structurally resembled those of stage 54 control tadpoles. PTU-treated animals did not exhibit the extensive development of the laryngeal cartilage seen in untreated animals. Laryngeal cartilages of hypothyroid tadpoles exhibited low density and minimal patterning of chondrocytes; the complex lumen and marked expansion of the dilator muscles characteristic of 50- and 100-day untreated animals were absent. Laryngeal growth evoked by exposure to exogenous androgen (dihydrotestosterone) was entirely prevented by PTU treatment. Hypothyroid tadpoles did not exhibit the decline in laryngeal nerve axon number characteristic of age-matched controls, nor were laryngeal nerve axon numbers sexually dimorphic. PTU treatment also interfered with the myelination of laryngeal axons. We conclude that while gonadal differentiation is independent of TH, androgen sensitive laryngeal development and sexually dimorphic laryngeal innervation require exposure to secreted TH.

Animals↗
PubMed1995

Cholesterol content of trout plasma membranes varies with acclimation temperature.

Involvement of cholesterol in thermally induced restructuring of biological membranes was investigated in several tissues of rainbow trout (Oncorhynchus mykiss). Cholesterol-rich plasma membranes (PM) were isolated from erythrocytes, liver, kidney, and gill of fish acclimated to 5 and 20 degrees C. Mean PM cholesterol-to-phospholipid molar ratios (C/P) from warm-acclimated animals were significantly higher than those of cold-acclimated fish in liver (0.26 vs. 0.18; P < 0.01), kidney (0.49 vs. 0.40; P < 0.02), and gill (0.66 vs. 0.60; P < 0.05); erythrocyte C/P did not differ significantly with acclimation temperature (0.28 vs. 0.25; P = 0.25). In light of the ordering effects of cholesterol on fluid-phase membranes, these results are consistent with a role for cholesterol in the homeoviscous response of some poikilotherm PMs. Tissue differences in both PM cholesterol levels and the magnitude of thermally evoked cholesterol changes may reflect tissue-specific membrane functions. Lower PM C/P of trout tissues relative to corresponding data available for homeotherms also support a possible evolutionary relationship between cholesterol content and thermal adaptation of the PM.

Acclimatization↗
PubMed1994

Androgen directs sexual differentiation of laryngeal innervation in developing Xenopus laevis.

In adult Xenopus laevis, innervation of the vocal organ is more robust in males than in females. This sex difference originates during tadpole development; at stage 56, when the gonads first differentiate, the number of axons entering the larynx is the same in the sexes, but by stage 62, innervation is greater in males. To determine if androgen secretion establishes sex differences in axon number, we treated tadpoles with antiandrogen or androgen beginning at stage 48 or 54 and counted laryngeal nerve axons at stage 62 using electron microscopy. When male tadpoles were treated with the antiandrogen hydroxyflutamide, axon numbers were reduced to female-typical values; axon numbers in females were unaffected by antiandrogen treatment. When female tadpoles were treated with the androgen DHT (dihydrotestosterone), axon numbers were increased to male-like values. These findings suggest that endogenous androgen secretion during late tadpole stages in males is required for the sexual differentiation of laryngeal innervation observed from stage 62 on. Because androgen treatment and laryngeal innervation affect myogenesis in postmetamorphic frogs, numbers of laryngeal dilator muscle fibers were determined for hormonally manipulated tadpoles. At stage 62, vehicle-treated males had more laryngeal axons than females; laryngeal muscle fiber numbers did not, however, differ in the sexes. Both male and female tadpoles, treated from stage 54 with DHT, had more muscle fibers at stage 62 than vehicle-treated controls. Thus, while endogenous androgen secretion during late tadpole stages is subthreshold for the establishment of masculinized muscle fiber numbers, laryngeal myogenesis is androgen sensitive at this time and can be increased by suprathreshold provision of exogenous DHT. A subgroup of tadpoles, DHT treated from stage 54 to 62, was allowed to survive, untreated, until postmetamorphic stage 2 (PM2: 5 months after metamorphosis is complete). Androgen treatment between tadpole stages 54 and 62 does not prevent the ontogenetic decrease in axon numbers characteristic of laryngeal development. In addition, the elevation in stage 62 axon numbers produced by DHT-treatment at late tadpole stages was not associated with elevated numbers of laryngeal muscle fibers at PM2. Juvenile males normally maintain elevated axon numbers (relative to final adult values) through PM2 and the presence of these additional axons may result from--rather than contribute directly to--laryngeal muscle fiber addition.

Animals↗
PubMed1987

Indices of disease activity in psoriatic arthritis.

Psoriatic arthritis (PA) may respond to disease-modifying antirheumatic therapy. The value of assessing disease activity with indices devised for rheumatoid arthritis (RA) was investigated in 72 patients with seronegative PA. Thirty patients had a peripheral polyarthritis including the distal interphalangeal joints (DIPJs) and 15 a symmetrical arthritis sparing DIPJs (RA-like). Significant correlations (Spearman rank test) were seen between the clinical variables (pain score, grip strength, Ritchie articular index and a summated index of disease activity) in these two groups. Ten patients with a markedly asymmetrical arthritis showed a poor correlation between clinical variables. Although the objective indices - erythrocyte sedimentation rate (ESR) and C-reactive protein - correlated together in the first two groups, the ESR correlated solely with clinical indices, and then only in RA-like patients. These results cast some doubt on the value of assessment methods based on RA when evaluating subgroups of PA other than RA-like disease.

Arthritis↗
PubMed1985

Spontaneous fusion of atlanto-axial dislocation in psoriatic spondylitis.

A 36-year-old man, suffering from psoriatic arthritis from the age of 17 years, was found to have developed atlanto-axial dislocation at the age of 30. Spontaneous fusion took place over the next two years. An explanation for this finding is based upon a review of the literature regarding the nature of spinal involvement in psoriatic arthritis.

Adult↗
PubMed1984

Polymyalgia rheumatica and antimitochondrial antibodies.

Antimitochondrial antibodies (AMA) were detected in the sera of 11 of 36 patients with a clinical diagnosis of polymyalgia rheumatica (PMR) in whom comprehensive autoantibody screening had been performed. AMA did not correlate with biochemical changes of hepatic dysfunction, which are common in PMR, nor with parameters of musculoskeletal inflammation. Possible explanations are discussed.

Aged↗
PubMed1984

Nutritional status in patients with rheumatoid arthritis.

A nutritional assessment of 50 patients with rheumatoid arthritis (RA) showed evidence of malnutrition in 13 (26%), while all 50 control subjects had normal nutritional status. Of the anthropometric measurements the body-mass index and triceps skinfold thickness values in men and women were significantly reduced in RA patients compared with controls. Upper arm muscle circumference was significantly less in male but not female rheumatoid patients. In addition all six biochemical determinants of nutrition assayed-serum albumin, transferrin, retinol-binding protein, thyroxine-binding prealbumin, zinc, and folic acid-were significantly lower in the RA group of patients. Malnourished patients had more active disease than the remaining RA patients, with significantly higher ESR, C-reactive protein, and alpha 1 antichymotrypsin measurements. Significant inverse correlations were found between some biochemical measurements of nutrition and indices of disease activity. Our results suggest that in RA the severity of disease adversely affects the nutritional status.

Adult↗
PubMed1982

Grip "strength' in the healthy.

The grip pressures of a normal population were determined using a 900 mmHg column. Men were stronger than women. The dominant hand was the stronger and the difference between the dominant and nondominant hand pressures was less than 10% in both sexes. One determination of grip pressure is adequate for clinical purposes. Much information is lost if the standard 300 mm mercury or aneroid sphygmomanometers are used.

Adult↗
PubMed1980

Seating the disabled.

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Persons with Disabilities↗
PubMed1980

Pressure therapy for hypertrophic scarring: preliminary communication.

A six-point programme for the prevention and pressure therapy of hypertrophic scarring started in 1975 at Odstock Hospital. The work reported here includes a pressure calibration of batches of the material chosen for pressure bandaging; a pressure study of the bandages on volunteers' limbs; and the formation of a pressure therapy clinic. The clinic results were similar to those reported by Thomson (1974) and were considered sufficiently favourable to justify continuing the clinic and instituting a policy of close review and early therapy for all burns patients. The programme proved the accuracy of the pressure sensor and attempted to develop an objective method of recording progress. Arguments for pressure versus occlusion as the therapeutic agent are discussed and supported by a case report. It is suggested that a controlled trial of pressure therapy should be carried out.

Bandages↗