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Biomedical subjects

A Oren

Publications and source records attributed to A Oren.

100 records · Page 6Linked to original sources
PubMed1978

Induction of anaerobic, photoautotrophic growth in the cyanobacterium Oscillatoria limnetica.

Anaerobic photoautotrophic growth of the cyanobacterium Oscillatoria limnetica was demonstrated under nitrogen in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (5micron), a constant concentration of Na2S (2.5 mM), and constant pH (7.3). The photoanaerobic growth rate (2 days doubling time) was similar to that obtained under oxygenic photoautotrophic growth conditions. The potential of oxygenic photosynthesis is constitutive in the cells; that of anoxygenic photosynthesis is rapidly (2 h) induced in the presence of Na2S in the light in a process requiring protein synthesis. The facultative anaerobic phototrophic growth physiology exhibited by O. limnetica would seem to represent an intermediate physiological pattern between the obligate anaerobic one of photosynthetic bacteria and the oxygenic one of eucaryotic algae.

Aerobiosis↗
PubMed1977

Quantum yields for oxygenic and anoxygenic photosynthesis in the cyanobacterium Oscillatoria limnetica.

A comparison of the quantum yield spectra of the oxygenic (H(2)O as the electron donor) with the anoxygenic (H(2)S as the electron donor) photosynthesis of the cyanobacterium, Oscillatoria limnetica reveals that anoxygenic photosynthesis is driven by photosystem I only. The highest quantum yields of the latter (maximum; 0.059 CO(2) molecules/quantum of absorbed light) were obtained with wavelengths which preferentially excite photosystem I (<550, >650) in which chlorophyll a and carotenoids are the major pigments. The addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea had no effect on anoxygenic photosynthesis, and no enhancement in quantum efficiency was observed by a superimposition of light preferentially exciting photosystem II.Oxygenic photosynthesis efficiently utilizes only a narrow range of the absorption spectrum (550-650 nm) where light is provided in excess to photosystem II via phycocyanin. The quantum yield (0.033 CO(2) molecules/quantum of absorbed light) is lower than the theoretical yield by a factor of 3, possibly due to inefficient light transfer from photosystem II to I. Thus, 3-fold enhancement of oxygenic photosynthesis by superimposition of photosystem I light, and low quantum yields for anoxygenic photosynthesis, were obtained in this region. These results are consonant with the suggestion that such a cyanobacterium represents an intermediate stage in phototrophic evolution.

Journal Article↗
PubMed1977

Occurrence of facultative anoxygenic photosynthesis among filamentous and unicellular cyanobacteria.

Eleven of 21 cyanobacteria strains examined are capable of facultative anoxygenic photosynthesis, as shown by their ability to photoassimilate CO2 in the presence of Na2S, 3-(3,4-dichlorophenyl)-1,1-dimethylurea and 703-nm light. These include different cyanobacterial types (filamentous and unicellular) of different growth histories (aerobic, anaerobic, and marine and freshwater). Oscillatoria limnetica, Aphanothece halophytica (7418), and Lyngbya (7104) have different optimal concentrations of Na2S permitting CO2 photoassimilation, above which the rate decreases: 3.5, 0.7, and 0.1 mM, respectively. In A. halophytica, for each CO2 molecule photoassimilated two sulfide molecules are oxidized to elemental sulfur, which is excreted from the cells. The ecological and evolutionary significance of anoxygenic photosynthesis in the cyanobacteria is discussed.

Aerobiosis↗
PubMed1976

Acute coronary occlusion following blunt injury to the chest in the absence of coronary atherosclerosis.

A 35-year-old man suffered transmural diaphragmatic wall infarction immediately after receiving a nonpenetrating trauma to his chest. During subsequent months crippling angina pectoris developed and coronary arteriography was performed. A complete obstruction of the left circumflex coronary artery was demonstrated 2 cm. distal to its origin. In contrast to most cases previously published, in this case no signs of atherosclerosis were observed in the other coronary arteries. It must be assumed, therefore, that blunt trauma can induce complete coronary occlusion with infarction, even in subjects with normal coronary arteries.

Acute Disease↗
PubMed1976

Short duration-high area regular dialysis using two UF 2 coils in series.

To increase the number of regular dialysis patients without increasing apparatus, staff or buildings, short time-high area dialysis was undertaken for 3.5 h twice a week or 3 h three times a week with two UF 2 coils in series (2 m2) with dialysis fluid flow of 300 ml/min/kidney in parallel. The biochemical and clinical results were compared with those obtained in a period immediately prior to this using conventional 7-hours dialysis twice a week or 6 h three times a week on UF 145. Urea, creatinine and vitamin B12 clearances, predialysis blood urea and creatinine levels and the clinical state of the patients were satisfactory on short double UF 2 coil in series dialysis. Addition of 1-1.5 liters of saline during dialysis permitted an average net fall in body weight of 1 kg without cramps or hypotension. The merits of rapid dialysis with a large area dialyzer are discussed.

Blood Urea Nitrogen↗
PubMed1976

Dialysis in renal failure casued by amyloidosis of familial Mediterranean fever. A report of ten cases.

Ten unselected patients with renal failure casued by amyloidosis associated with FMF were treated by regular hemodialysis therapy from 1969 to 1974. They were compared to age-matched control patients treated by hemodialysis in the same unit during the same period, who were suffering from renal failure caused by other disease. Mortality in FMF and control patients was 30% with no significant difference in mean survival, shunt life, serum albumin or hemoglobin levels between the two groups. There was no significant difference in blood pressure measured predialysis or postdialysis in patients with FMF or in controls. The synthetic ACTH stimulation test showed adequate or elevated adrenocortical function. It is concluded that life can be prolonged up to 3 1/2 years by hemodialysis in renal failure caused by amyloidosis complicating FMF, and that renal failure casued by FMF is not a contraindication to regular hemodialysis therapy.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

A dose-titration trial of guanadrel as step-two therapy in essential hypertension.

The efficacy and safety of low-dose guanadrel sulfate were evaluated in 20 patients with essential hypertension based on seated diastolic blood pressures (SDBP) ranging from 95 to 115 mm Hg despite a trial dosage of hydrochlorothiazide 50 mg/d for up to five weeks. These patients had been resistant to, or intolerant of, one or more step-two antihypertensive drugs in the past (i.e., methyldopa, beta-adrenergic blocking agents, clonidine, or prazosin). The majority of patients demonstrated a satisfactory response (SDBP 95 mm Hg or reduction in SDBP of 10 mm Hg) to guanadrel. Nine patients responded at a low dosage, 10 to 20 mg/d and remained free from adverse effects throughout the study (up to 12 weeks of treatment). Of the remaining 11 patients titrated to higher dosages of guanadrel (30 to 60 mg/d), three had no discernible response while six developed adverse effects. The results of the study suggest that guanadrel has an acceptable benefit-to-risk ratio only when used in low dosages (10 to 30 mg/d) and may be successfully employed as step-two antihypertensive therapy in patients resistant to, or intolerant of, other step-two agents.

Adult↗
PubMedDate not supplied

Serum granulocyte-macrophage colony-stimulating factor and interleukin-1 levels in patients with repeated and non-repeated pulmonary infections.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has a stimulating effect on erythroid, megakaryocytic and granulocyte-macrophage progenitors. Activated T lymphocytes, monocytes, fibroblasts and endothelial cells release GM-CSF after stimulation by endotoxin and cytokines such as interleukin-1 (IL-1) and tumor necrosis factor. IL-1 is also released in response to bacterial infections and inflammation by phagocytic mononuclear cells. GM-CSF and IL-1 levels were examined in 10 patients with recurrent pulmonary infection (repeaters) and in 10 patients with acute pulmonary infection (non-repeaters) in the acute and recovery periods of infection. The mean serum GM-CSF and IL-1 levels of non-repeaters were significantly higher than those of repeaters in the acute period of infection (p < 0.002), but the same parameters of both groups were not different in the recovery period (p > 0.05). In addition, both the serum GM-CSF and IL-1 levels of repeaters and non-repeaters in the acute period of infection were higher than those in the recovery period (p < 0.05). There was a positive correlation between serum IL-1 and GM-CSF levels in non-repeaters (r = 0.746, p = 0.013), but no significant correlation between the same parameters in repeaters (r = 0.395, p = 0.259). In this study, we could not explain why the serum GM-CSF and IL-1 levels in repeaters did not increase as they did in non-repeaters; moreover, there was no significant correlation between serum IL-1 and GM-CSF levels in repeaters during the acute period of infection. These findings may be due to microenvironmental factors in bone marrow and/or other factors.

Acute Disease↗