Embryos at the Edge of Tolerance: Effects of Environment and Structure of Egg Masses on Supply of Oxygen to Embryos.

Oxygen concentrations in gelatinous egg masses of two species of opisthobranch gastropods were examined with microelectrodes. Embryos in central positions are near the limit of the oxygen supply required for development. This limit is approached despite a diffusion constant for oxygen in masses that is close to that in water. Closed-chamber respirometry shows that oxygen is consumed by masses in the dark but generated in the light. Internal oxygen concentrations were greater in bright than in dim light. Thus photosynthesis and respiration of microorganisms associated with the masses affects the supply of oxygen to embryos within the mass. This effect of light was confirmed for egg masses of a polychaete. These observations, together with other published observations on the effects of hypoxia on development, indicate that the developmental rates of embryos in egg masses may depend on algal photosynthesis and metabolism. Flow around the masses also affects delivery of oxygen to embryos, but masses in dim light are at the limit of adequate supply even in a strong flow with a very thin boundary layer. Because the central embryos are near the limit for adequate supply of oxygen by diffusion, their development rate thus depends on light, abundance of photosynthetic and heterotrophic microorganisms, flow, and oxygen concentration in the surrounding water.

Chest radiographic and CT findings after laser-assisted thoracic surgery.

OBJECTIVE: Laser-assisted thoracic surgery (performed through a thoracotomy or as an endoscopic procedure with thoracoscopy [pleural endoscopy]) is being used increasingly for lung-sparing resections of neoplasms, biopsies, and ablation of bullae. The technique is useful in treating patients who have limited pulmonary reserve and may avoid the problem of distortion of surrounding pulmonary tissue. Because laser energy causes injury to lung tissue, postoperative radiographs may show findings unique to the laser-assisted technique. The objective of this study was to determine postoperative radiographic findings common to laser-assisted surgery. MATERIALS AND METHODS: Pre- and postoperative and all follow-up chest radiographs were reviewed for 52 consecutive patients who had 60 laser-assisted thoracic surgical procedures (35 with an open thoracotomy, 25 with thoracoscopy) for resection of peripheral nodules (40), biopsy of focal (five) or diffuse (four) lung disease, or ablation of bullae (three). Postoperative chest CT studies available for 20 patients also were reviewed. All postoperative radiographic studies were evaluated for the presence and duration of pneumothoraces, pleural effusions, areas of parenchymal opacification or cavitation, and complications requiring surgical or radiologic intervention. RESULTS: Pneumothoraces and pleural effusions were seen in 88% and 83% of cases, respectively, and were typically small, uncomplicated, and of limited duration. Nonspecific parenchymal opacification of various degrees was observed at the operative site in all cases and usually regressed within days or weeks to areas of parenchymal scarring. Parenchymal cavitation at the operative site occurred in 15 patients (29%). Eight patients (15%) had complications that required intervention, primarily prolonged air leaks and pleural space complications. CONCLUSION: Radiographic findings after laser-assisted thoracic surgery are often nonspecific and of limited duration. In an asymptomatic patient, cavitation at the operative site is a normal finding related to the surgical technique and should not be misdiagnosed as infection or tumor. Radiographic findings normally resolve to stable cavitary or linear scars.

An update on HIV-testing at a London sexually transmitted diseases clinic: long-term impact of the AIDS media campaigns.

Trends in the number of tests for HIV-1 antibody at a London sexually transmitted diseases clinic showed substantial changes between September 1985 and June 1988. From an average of 100 tests per month between September 1985 and August 1986, the average increased to 365 tests per month for September 1986 to August 1987. This levelled off at 243 tests per month between September 1987 and June 1988. The average number of positive tests per month between September 1985 and June 1988 remained constant, though the number of seropositive tests in females increased. Male and female populations displayed similar temporal patterns. The greatest increase was seen in the tests generated by heterosexual males and females with no other risk factors. This group generated 42% of the 8012 tests performed during the study period. The Clinic's catchment area predominantly included London and surrounding areas and temporal patterns were similar for residents from each of the Thames Regions. The temporal patterns observed coincided with periods of increased media attention on HIV infection/AIDS and involved campaigns by the popular press, television, Department of Health Education Authority. The increase in tests during the time of maximum media exposure, the subsequent plateau at a level substantially higher compared with the period preceding the media campaigns and the large increase in heterosexual males and females tested, all suggest that the campaigns have contributed to increasing awareness of HIV infection/AIDS as a major contemporary public health problem.

Risk factors for HIV-1 infection in a British population: lessons from a London sexually transmitted diseases clinic.

Between September 1985 and June 1988, 6923 people (4550 men and 2373 women) were tested for HIV-1 antibodies at a sexually transmitted disease clinic, London, UK. Of the 6923 individuals tested, 558 (8%) were seropositive, of whom 523 (94%) were men and 35 (6%) women. Of the seropositives, 84% were homosexual or bisexual men, 5% were intravenous drug users, 4% were heterosexual contacts of HIV seropositives, 4% had multiple risk factors, 2% were heterosexual contacts of central African partners and 1% were heterosexuals with no other risk factors. This prevalence pattern conforms to that observed in other industrialized nations. For the women, heterosexual intercourse with an HIV-infected partner, intravenous drug use and heterosexual contact with a partner from central Africa were the main risk factors for infection. The important risk factors among the men were heterosexual contact with an HIV-seropositive partner, being homosexual or bisexual, intravenous drug use and heterosexual contact with a resident from central Africa. heterosexual and homosexual transmission were implicated as the main routes for viral spread in this British population.

Alpha-locus hexosaminidase genetic compound with juvenile gangliosidosis phenotype: clinical, genetic, and biochemical studies.

A 3-year-old boy developed progressive neurological deterioration in his third year, characterized by dementia, ataxia, myoclonic jerks, and bilateral macular cherry-red spots. Hexosaminidase A (HEX A) was partially decreased in the patient's serum, leukocytes, and cultured skin fibroblasts. Hexosaminidase was studied in serum and leukocytes from family members. Four members of the paternal branch appeared to be carriers of classical infantile Tay-Sachs allele, HEX alpha 2, probably receiving the gene from one great-grandparent of Ashkenazi origin. In the maternal branch, no one was a carrier of classical infantile Tay-Sachs disease, but five individuals were carriers of a milder alpha-locus defect. The patient, therefore, was a genetic compound of two different alpha-locus hexosaminidase mutations. At least 21 families with late-infantile or juvenile GM2 gangliosidosis have been reported, 18 of them with alpha-locus mutations, and three with beta-locus mutations. Genetic compounds of hexosaminidase have been reported in at least seven families, five with alpha-locus mutations and two with beta-locus mutations. The compound had the phenotype of infantile Tay-Sachs disease in one family, infantile Sandhoff disease in another, and the normal phenotype in the rest.