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Biomedical subjects

S Travis

Publications and source records attributed to S Travis.

At least 19 recordsLinked to original sources

Doctor on a mountaineering expedition.

Doctors are welcome members on mountaineering expeditions to remote areas, but practical advice on how to prepare and what kit to take can be difficult to find. This article is a ragbag of useful advice on diverse topics. It explains the necessary preparation, provides tips for a healthy expedition, and summarises the common disorders encountered at high altitude. The comprehensive drug and equipment lists and first aid kit for climbers were used for the 1992 Everest in winter expedition. They are there to be sacrificed to personal preference and the experience and size of individual expeditions.

Altitude Sickness

Acute colorectal ischaemia after anaphylactoid shock.

A 29 year old woman is reported with bloody diarrhoea three hours after developing anaphylactoid shock. Sigmoidoscopy, barium enema, and histology showed rectal and colonic ischaemia to the splenic flexure. Recovery was complete. There was no history of vascular disease but the patient was taking an oral contraceptive. Thirty one other cases of spontaneous ischaemic proctitis are reviewed.

Acute Disease

Micromethod for demonstrating increased platelet surface immunoglobulin G: findings in acute, chronic, and human immunodeficiency virus-1-related immunologic thrombocytopenias.

A method has been developed for the demonstration of increased platelet surface IgG that uses 1 ml of blood regardless of the platelet count. Platelets are gel filtered to remove plasma and contaminating lymphocytes. They are then reacted with fluorescein-conjugated antihuman IgG and analysed by flow cytometry. Percent positive staining cells vary from 10% to 80% of total cells examined. A platelet antibody index is derived from the product of percent positive staining cells X mean fluorescence intensity of positive staining cells. All patients studied with chronic idiopathic thrombocytopenia purpura (ITP) or human immunodeficiency virus-1 (HIV-1)-related thrombocytopenia had increased platelet surface IgG. Twelve acute children and 11 chronic children had indices averaging 3.5- and 8.9-fold greater than 12 normal children, respectively. Five of 12 children with acute ITP had normal platelet IgG. There was no linear correlation between the platelet antibody index and platelet count. Platelets of patients with acute, chronic, or HIV-1-related ITP displayed autofluorescence. In chronic ITP, the percentage of platelets displaying autofluorescence had a significant negative correlation with the platelet count. This technique will be a valuable diagnostic tool in the pediatric population.

Acute Disease

Heat illness.

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Heat Exhaustion

Toe temperatures during arctic training.

The surface toe temperature of 10 subjects was monitored in the field in Arctic Norway (minimum air temperature -27 degrees C). The lowest skin temperature recorded was 1.9 degrees C. The mean estimated time for the toe temperature to cool from 25 degrees C to 5 degrees C was 109 minutes (SD, 10.2) at an ambient temperature of -21 degrees C. One subject experienced a toe temperature below 5 degrees C for 2.9 hours during a 27-hour period. Surprisingly none of the subjects demonstrated clinical signs of cold injury, but this does not mean that this exposure was without risk. Cold sensitization could have occurred.

Adult

Morphogenesis and pathogenicity of Histoplasma capsulatum.

The sulfhydryl blocking agent p-chloromercuriphenylsulfonic acid (PCMS) irreversibly inhibited the mycelium-to-yeast transitions of two virulent strains of Histoplasma capsulatum, G184A and G222B, when the temperature of incubation was raised to 37 degrees C, and the block persisted even after the cultures were washed free of PCMS. Instead of transforming to yeast cells, PCMS-treated mycelia continued to grow as mycelia at the elevated temperatures. A less virulent strain (Downs) was more temperature sensitive, but it showed a similar irreversible effect at 34 degrees C. Therefore, the mycelium-to-yeast transition of H. capsulatum is not required for the adaptation of mycelia to elevated temperatures but probably results from the temperature-dependent activation of yeast-specific genes. The transition to yeast is inferred to be obligate for pathogenicity in mice because PCMS-treated mycelia failed to cause infection, and no fungi were seen in tissues after PCMS-treated mycelia were injected into mice.

4-Chloromercuribenzenesulfonate

Comparison of the in vitro and in vivo activity of the bis-triazole derivative UK 49,858 with that of amphotericin B against Histoplasma capsulatum.

The antifungal activity of UK 49,858, a difluorophenyl bis-triazole derivative, was evaluated in vitro against seven strains of Histoplasma capsulatum and in vivo in AKR and C57BL/6 murine models of histoplasmosis. UK 49,858 had a lower toxicity for AKR and C57BL/6 mice than amphotericin B did. The therapeutic index of UK 49,858 was 4.3 for AKR mice and 7.1 for C57BL/6; with amphotericin B it was 2 for both mouse strains. Given orally, UK 49,858 compared favorably with amphotericin B given intraperitoneally in either AKR or C57BL/6 mice infected with H. capsulatum.

Amphotericin B