A comparison of the detection sensitivity of lymphocyte membrane antigens using fluorescein and phosphor immunoconjugates

In Escherichia coli, UV and many chemicals appear to cause mutagenesis by a process of translesion synthesis that requires some form of DNA polymerase III and the SOS-regulated proteins UmuD, UmuC and RecA. An analysis of SOS mutagenesis offers insights into the molecular basis of induced mutagenesis and into mechanisms of DNA damage tolerance.     

Effects of temperature and volatile anesthetics on GABA(A) receptors

BACKGROUND: Potentiation of the activity of the gamma-aminobutyric acid type A (GABA(A)) receptor channel by volatile anesthetic agents is usually studied in vitro at room temperature. Systematic variation of temperature can be used to assess the relevance of this receptor to general anesthesia and to characterize the modulation of its behavior by volatile agents at normal body temperature. METHODS: Potentiation of the GABA(A) receptor by halothane, sevoflurane, isoflurane, and methoxyflurane was studied at six temperatures in the range 10-37 degrees C using the whole-cell patch-clamp technique and mouse fibroblast cells stably transfected with defined GABA(A) receptor subunits. RESULTS: Control GABA concentration-response plots showed small and physically reasonable changes in the GABA concentration required for a half-maximal effect, the Hill coefficient, and maximal response over the range 10-30 degrees C. Potentiations of GABA (1 microM) responses by aqueous minimum alveolar concentrations of the volatile anesthetic agents decreased with increasing temperature from 10-37 degrees C in an agent-specific manner (methoxyflurane > isoflurane > sevoflurane > halothane) but tended to equalize at normal body temperature (37 degrees C). These findings are in line with published results on the temperature dependence of anesthetic potencies in animals. CONCLUSIONS: These results are consistent with direct binding of volatile anesthetic agents to the GABA(A) receptor channel playing an important role in general anesthesia. The finding that the degree of anesthetic potentiation was agent-specific at low temperatures but not at 37 degrees C emphasizes the importance of doing in vitro experiments at normal body temperature.     

The material basis for reduced mechanical properties in oim mice bones

Osteogenesis imperfecta (OI), a heritable disease caused by molecular defects in type I collagen, is characterized by skeletal deformities and brittle bones. The heterozygous and homozygous oim mice (oim/+ and oim/oim) exhibit mild and severe OI phenotypes, respectively, serving as controlled animal models of this disease. In the current study, bone geometry, mechanics, and material properties of 1-year-old mice were evaluated to determine factors that influence the severity of phenotype in OI. The oim/oim mice exhibited significantly smaller body size, femur length, and moment of area compared with oim/+ and wild-type (+/+) controls. The oim/oim femur mechanical properties of failure torque and stiffness were 40% and 30%, respectively, of the +/+ values, and 53% and 36% of the oim/+ values. Collagen content was reduced by 20% in the oim/oim compared with +/+ bone and tended to be intermediate to these values for the oim/+. Mineral content was not significantly different between the oim/oim and +/+ bones. However, the oim/oim ash content was significantly reduced compared with that of the oim/+. Mineral carbonate content was reduced by 23% in the oim/oim bone compared with controls. Mineral crystallinity was reduced in the oim/oim and oim/+ bone compared with controls. Overall, for the majority of parameters examined (geometrical, mechanical, and material), the oim/+ values were intermediate to those of the oim/oim and +/+, a finding that parallels the phenotypes of the mice. This provides evidence that specific material properties, such as mineral crystallinity and collagen content, are indicative and possibly predictive of bone fragility in this mouse model, and by analogy in human OI.     

The influence of burnishing on the properties of electrospark coatings

Translated from Fiziko-khimicheskaya Mekhanika Materialov, Vol. 26, No. 5, pp. 119–120, September–October, 1990.     

Immunizing patients with metastatic melanoma using recombinant adenoviruses encoding MART-1 or gp100 melanoma antigens

BACKGROUND: The characterization of the genes encoding melanoma-associated antigens MART-1 or gp100, recognized by T cells, has opened new possibilities for the development of immunization strategies for patients with metastatic melanoma. With the use of recombinant adenoviruses expressing either MART-1 or gp100 to immunize patients with metastatic melanoma, we evaluated the safety, immunologic, and potential therapeutic aspects of these immunizations. METHODS: In phase I studies, 54 patients received escalating doses (between 10(7) and 10(11) plaque-forming units) of recombinant adenovirus encoding either MART-1 or gp100 melanoma antigen administered either alone or followed by the administration of interleukin 2 (IL-2). The immunologic impact of these immunizations on the development of cellular and antibody reactivity was assayed. RESULTS: Recombinant adenoviruses expressing MART-1 or gp100 were safely administered. One of 16 patients with metastatic melanoma receiving the recombinant adenovirus MART-1 alone experienced a complete response. Other patients achieved objective responses, but they had received IL-2 along with an adenovirus, and their responses could be attributed to the cytokine. Immunologic assays showed no consistent immunization to the MART-1 or gp100 transgenes expressed by the recombinant adenoviruses. High levels of neutralizing antibody were found in the pretreatment sera of the patients. CONCLUSIONS: High doses of recombinant adenoviruses could be safely administered to cancer patients. High levels of neutralizing antibody present in patients' sera prior to treatment may have impaired the ability of these viruses to immunize patients against melanoma antigens.     

Exercise responses in patients with IDDM

OBJECTIVE: The hemodynamic, respiratory, and metabolic responses to exercise were studied in IDDM patients and control subjects to detect diabetic cardiomyopathy. RESEARCH DESIGN AND METHODS: Eight subjects aged 25-40 years with diabetes of at least 10 years' duration were compared with eight control subjects aged 21-46 years. All subjects underwent a progressive incremental bicycle exercise test with measurement of gas exchange, blood glucose, lactate, fat metabolite, and catecholamine levels and two steady-state exercise tests with measurement of cardiac output by a CO2 rebreathing method. A new first-pass radionuclide method was used to measure cardiac ejection fractions (EFs) at rest, peak exercise, and steady-state exercise. RESULTS: The peak achieved oxygen consumption was similar in the diabetic and control subjects (29.9 [25.1-34.6] and 31.4 [26.9-35.9] ml.min-1.kg-1, respectively; mean [95% CI]). There were no significant differences in heart rate, double product, ventilation, respiratory exchange ratio, or ventilatory equivalents for oxygen and CO2 during the incremental test. Glucose levels were higher in the diabetic subjects, but there were no significant differences in levels of lactate, catecholamines, free fatty acids, glycerol, or beta-hydroxybutyrate. Left ventricular EF fell from rest to peak exercise within the diabetic group (66.0% [59.6-72.4] at rest; 53.6% [45.6-61.6] at peak; P < 0.05) but this did not differ significantly from the control group (58.7% [52.3-65.1] at rest; 60.3% [48.9-71.7] at peak). Right ventricular EFs were similar in each group, and there was no reduction in peak filling rate to suggest diastolic dysfunction. The cardiac output responses to exercise were also similar in the two groups. CONCLUSIONS: There is no evidence of impairment of the exercise response in subjects with long-standing diabetes, and the apparent fall in left ventricular EF at peak exercise could be related to hemodynamic adaptation.     

Interaction of a thrombin inhibitor and a platelet GP IIb/IIIa antagonist in vivo: evidence that thrombin mediates platelet aggregation and subsequent thromboxane A2 formation during coronary thrombolysis

We examined the effect of a specific thrombin inhibitor, Ro 46-6240, alone and combined with an antagonist of the platelet GP IIb/IIIa, Ro44-9883, on the response to tissue-type plasminogen activator in a canine model of thrombolysis. Platelet activity was determined by measuring the excretion of 2,3-dinorthromboxane (TX)B2, an enzymatic metabolite of TXA2. Ro 46-6240 administered before tissue-type plasminogen activator induced a dose-dependent prolongation of the activated partial thromboplastin time and prothrombin time. The time to reperfusion decreased dose-dependently (P < .01) to 10 +/- 6 min vs. 52 +/- 5 min in controls. Ro 46-6240 also prevented reocclusion, which occurred in every case in control experiments. Urinary excretion of 2,3-dinor-TXB2 increased from 3 +/- 1 to 37 +/- 9 ng/mg creatinine in controls after reperfusion. This increase was reduced in a dose-dependent fashion by Ro 46-6240, such that at the highest dose, urinary 2,3-dinor-TXB2 after reperfusion was 5.6 +/- 1 ng/mg creatinine. Similar functional and biochemical effects were seen when a subthreshold dose of Ro 46-6240 was combined with Ro 44-9883. At the dose used, Ro 44-9883 alone abolished platelet aggregation ex vivo but failed to modify the response to tissue-type plasminogen activator or the excretion of 2,3-dinor-TXB2 after reperfusion (51 +/- 6 ng/mg creatinine, n = 3). However, the combination of Ro 44-9883 and Ro 46-6240 reduced the time to reperfusion (40 +/- 8 vs. 68 +/- 15 min; n = 7, P < .05), prevented reocclusion and abolished the rise in urinary 2,3-dinor-TXB2 (5 +/- 1 ng/mg creatinine, n = 4). These findings suggest that thrombin mediates platelet activation during coronary thrombolysis. The increased platelet activity results in platelet aggregation and a subsequent increase in TXA2 formation.