The interaction of Cibacron Blue F3GA with troponin and its subunits

Binding of troponin to Cibacron Blue F3GA-agarose column and its selective release from the gel in the presence of 0.5 M KCl provides the basis for a new purification method. The two-step procedure consists of isoelectric precipitation of tropomyosin and chromatography of the resultant crude troponin supernatant on Affi-Gel Blue column. Adsorption of troponin to the immobilized dye appears to occur through the troponin-T subunit. Troponin-I and troponin-C do not bind to the blue agarose column, whereas troponin-T binds to it very tightly. Binding of the dye to troponin-T prevents formation of troponin-T-troponin-C complex, but does not interfere with direct interaction of troponin-T with troponin-I. The activity of troponin in conferring calcium sensitivity on actomyosin ATPase is not affected by Cibacron Blue. Circular dichroism and difference absorption measurements of complexes of the blue dye with troponin and its subunits reveal the presence of a tight binding site on whole troponin and on troponin-T (KA greater than or equal to 10(6) M). The existence of weak binding sites for the dye on troponin and all of its subunits is deduced from difference absorption studies. Cibacron Blue appears to be a sensitive probe for subunit interactions in troponin.

Dissimilar effects of ultraviolet light on HLA-D and HLA-DR antigens

Since HLA-DR antigens are closely related to HLA-D antigens, we studied the effect of low-dose ultraviolet irradiation on the ability of human lymphocytes to induce a proliferative response in mixed lymphocyte culture (HLA-D) and on the serologic reactivity of B lymphocyte HLA-DR antigens. We found (1) no alteration in the serologic definition of DR antigens despite the abrogation of the induction of proliferative responses in mixed lymphocyte culture, (2) no evidence that ultraviolet light (UVL) stimulated suppressor cells contributed to the loss of allostimulation, and (3) no evidence that the abrogation of the induction of proliferative responses could be modified by increasing the number of UVL exposed lymphocytes in mixed lymphocyte culture. These findings suggest that HLA-D and HLA-DR antigens are different molecularly, but are also consistent with the concept that certain active metabolic processes are required of stimulator cells for allostimulation and that these processes are UVL sensitive.

The frequency of suicides around major public holidays: some surprising findings

This paper analyzes the recorded number of U.S. daily suicides, 1972-1976. The paper shows that: there is a dip in suicides on and just before major public holidays; there is a peak in suicides just after these holidays; and, the dip in suicides is somewhat larger than the peak--hence, there is a net decrease in suicides around the holidays. On balance, the holidays appear to reduce the number of suicides, not increase them, as previously believed. In addition, previous research has focussed on the negative psychological impact of holidays. Our findings indicate that holidays have a positive component, which should be taken into account in future research.

Radiation exposure to medical personnel during iodine-125 seed implantation of the prostate

Radiation exposure to operating room personnel was measured by thermoluminescent dosimeters and an ionization chamber during a simulated iodine-125 seed implantation of the prostate gland. The exposure rates at points around the implanted phantom were measured and compared with the calculated values. The data suggested that even with a schedule of 25 prostate implants per year, exposure levels would not exceed 5% of the recommended maximum limits for occupationally exposed personnel.

Accommodation dynamics I. Range nonlinearity

We show the presence of a new nonlinearity in accommodation dynamics. Positive accommodation is slower when the eye is operating in the near range; conversely, relaxation of accommodation is apparently slower during work in the far range. Latency of accommodation is unaffected by working range. This new dynamic range nonlinearity has been defined in connection with a continuing research study of accommodation responses in normal subjects and in clinic patients. Instrumentation and analysis procedures are described.

Effect of hyperoxia, hypoxia, and maturation on superoxide dismutase activity in isolated alveolar macrophages

The influence of ambient O2 tensions and of cell maturation on superoxide dismutase activity were studied in tissue culture--maintained mouse alveolar macrophages. Cultivation under hyperoxic conditions (PO2 about 640 mmHg) for 24 hours was associated with a significant increase in superoxide dismutase activity as compared with normoxic conditions (PO2 approximately 150 mmHg). (Hyperoxia: superoxide dismutase = 7.9 +/- 4.0 (SD); normoxia: superoxide dismutase = 4.4 +/- 1.7 units X mg cell protein-1 P less than 0.05). Hypoxic exposure (PO2 approximately 15 mmHg) was associated with a significant decrease in superoxide dismutase compared to normoxic controls (hypoxia: 2.2 +/- 0.6; normoxic: 3.8 +/- 0.6 units X mg protein-1 P less than 0.01). This decrease was found only after 168 hours of in vitro hypoxia. The in vitro maturation of alveolar macrophages cultivated in air was associated with a progressive increase in superoxide dismutase activity per 10(6) cells, although superoxide dismutase activity per unit protein remained constant. Molecular O2 may modify cell superoxide dismutase activity by altering intrinsic enzyme regulation. The increase in superoxide dismutase activity with hyperoxia and the decrease with hypoxia are consistent with but not unequivocally establish an important role for superoxide dismutase in protecting against cellular O2 toxicity.

Superoxide dismutase (SOD) activity in hypoxic mammalian systems

Superoxide Dismutase (SOD) activity was compared in rabbit peritoneal macrophages (ambient PO2 approximately 15 Torr) and alveolar macrophages (ambient PO2 approximately 100 Torr) and in brain, lung, cardiac muscle, and skeletal muscle of chromically hypoxic mice(ambient PO2 approximately 50 Torr) and normoxic mice (ambient PO2 approximately 150 Torr). Peritoneal macrophages (PM) have significantly less SOD activity than alveolar macrophages (AM) (PM: 2.94 +/- 0.49 (mean +/- SD); AM:6.03 +/- 1.60 units-mg protein -1 (P less than 0.01)). SOD activity of lung and brain homogenates from the hypoxic mice was significantly less than from the normoxic controls. Heart and skeletal muscle SOD activities were not significantly different. These studies show that limitations of O2 supply are associated with reductions in SOD and are consistent with the thesis that SOD plays an important role in protection against oxygen toxicity in mammalian systems.

Some comparative aspects of the organ distribution of superoxide dismutase activity in the freshwater turtle, Pseudemys scripta elegans

1. Superoxide dismutase activities in five tissues of the relatively anaerobic freshwater turtle were compared with SOD activities in the same tissues of two mammalian species (mouse and rabbit) with a more usual pattern of dependence on O2 availability. 2. SOD activities in brain, lung and skeletal muscle, but not liver or cardiac muscle, are significantly lower in the turtle. The turtle also shows differences in the pattern of relative SOD activities in various tissues as compared to the two mammalian species. 3. The data indicate that a relationship does exist between SOD activities and O2 exposure in intact vertebrate systems, and is consistent with a physiological role for SOD in tissue O2 metabolism.