Spectral and photochemical properties of borohydride-treated D1-D2-cytochrome b-559 complex of photosystem II

The D1-D2-cytochrome b-559 reaction center complex of photosystem II with an altered pigment composition was prepared from the original complex by treatment with sodium borohydride (BH4-). The absorption spectra of the modified and original complexes were compared to each other and to the spectra of purified chlorophyll a and pheophytin a (Pheo a) treated with BH4- in methanolic solution. The results of these comparisons are consistent with the presence in the modified complex of an irreversibly reduced Pheo a molecule, most likely 13(1)-deoxo-13(1)-hydroxy-Pheo a, replacing one of the two native Pheo a molecules present in the original complex. Similar to the original preparation, the modified complex was capable of a steady-state photoaccumulation of Pheo- and P680+. It is concluded that the pheophytin a molecule which undergoes borohydride reduction is not involved in the primary charge separation and seems to represent a previously postulated photochemically inactive Pheo a molecule. The Qy and Qx transitions of this molecule were determined to be located at 5 degrees C at 679.5-680 nm and 542 nm, respectively.     

Evaluation of a population with occupational exposure to airborne ammonium perchlorate for possible acute or chronic effects on thyroid function

Employees at an ammonium perchlorate production facility in Nevada and a larger control population from the same chemical complex without direct AP exposure were monitored extensively for airborne perchlorate exposure. Single-shift and working-lifetime cumulative dose estimates were made using standard breathing-rate estimates and assuming rapid absorption, based upon solubility. Calculated single-shift doses ranged from 0.2 to 436 micrograms/kg, with an average of 36 micrograms/kg. Working-lifetime cumulative doses in the higher exposure group ranged from 8,000 to 88,000 micrograms/kg, with an average of 38,000 micrograms/kg. Thyroid profiles, including free thyroxine index and thyroid-stimulating hormone level, were obtained both before shift and after shift to assess thyroid-axis perturbation due to single working-shift perchlorate exposure. Thyroid-function data were also analyzed with respect to estimates of cumulative exposure to assess any measurable chronic effects on thyroid gland function. Additionally, standard clinical blood test parameters of liver, kidney, and bone marrow function were evaluated to assess any measurable chronic effects of perchlorate exposure on those organs. Multiple regression was used to assess the effects of exposure variables and demographic variables on organ function parameters. No perchlorate-attributable effects on thyroid, bone marrow, kidney, or liver function were detected.     

Distinct roles for B7 costimulation in contact hypersensitivity and humoral immune responses to epicutaneous antigen

Productive interactions between B7-1 and B7-2 costimulatory molecules on dendritic cells (DC) and CD28 on T cells are thought to be critical for successful antigen presentation. Epicutaneous application of haptens induces both contact hypersensitivity (CHS), an inflammatory cutaneous response mediated by CD8+ T cells, and an anti-hapten antibody response mediated by CD4+ helper T cells. The role of B7 costimulation in the immune response to oxazolone (Ox) was analyzed using mice lacking either B7-1 (B7-1-/-), B7-2 (B7-2-/-), or both (Db-/-) of these costimulatory molecules. The absence of both B7-1 and B7-2 results in diminished CHS. This inhibition is largely overcome at higher hapten sensitizing doses indicating the presence of compensatory pathways. In contrast, anti-Ox IgG1 and IgG2a responses were not detected in the absence of both B7-1 and B7-2, even at high sensitizing doses, indicating an obligatory role of B7 costimulation in IgG class switching. B7-1 and B7-2 have overlapping functions in both CHS responses and anti-hapten response. B7-2-/- mice demonstrated a modestly reduced CHS response only at very low doses of Ox (0.05%), but responded normally at higher Ox doses, and B7-1-/- mice had CHS responses indistinguishable from those of wild-type mice. Similarly, anti-Ox IgG responses were comparable in wild-type, B7-1-/- and B7-2-/- mice. Taken together, these studies reveal distinct roles for B7 costimulation in response to epicutaneous antigens with an obligatory role for IgG class switching and an important, but nonessential role for CHS responses.     

Efficacy of phytase in improving the bioavailability of phosphorus in soybean meal and corn-soybean meal diets for pigs

Four experiments involving 225 pigs were conducted to assess the efficacy of a microbial phytase (FINASE, Alko Ltd. Biotechnology, Rajam?ki, Finland) produced by Aspergillus niger in corn-soybean meal or dextrose-cornstarch-soybean meal-based diets. In two experiments with growing-finishing pigs, fortified corn-soybean meal diets were formulated to be adequate (.50%) or inadequate (.40 or .30%) in P during the growing phase followed by adequate (.40%) or inadequate (.30%) P in the finishing phase. Mono-dicalcium phosphate was the source of supplemental P. Half the diets were supplemented with phytase (500 phytase units/g). Rate and efficiency of gain and bone breaking strength were decreased when P-deficient diets were fed. Phytase supplementation of the low-P diets restored growth rate and feed:gain to levels that approached those of pigs fed the adequate-P control diet. Bone strength was partially restored to that of the controls. In two additional experiments, pigs were fed low-P basal diets in which all the dietary P came from soybean meal or a corn-soybean meal blend. Both diets contained .05% available P. Graded levels of monosodium phosphate were added to these diets, up to .15% added P, to establish a standard curve. Phytase was added to the basal diet at 250, 500, or 1,000 units/g. Growth rate and bone strength improved linearly (P < .01) with added monosodium phosphate and with increasing levels of supplemental phytase. Based on estimates of total and available P intakes, the highest level of phytase (1,000 units/g) increased the bioavailability of the P from 25% in the soybean meal diet to 57% in the phytase-supplemented diet, and from 15% in the corn-soybean diet to 43% in the phytase-supplemented diet. Expressed on the basis of the improvement in phytate P availability, this level of phytase converted approximately one-third of the unavailable P to an available form. The results indicate that the phytase was efficacious in improving the bioavailability of phytate P for pigs.     

Initial results of a new access device for hemodialysis technical note

A new subcutaneous device (Dialock; Biolink Corp., Middleboro, MA) provides vascular access to patients who currently require hemodialysis (HD). The device consists of a port-like valve, implanted subcutaneously below the clavicle, which provides a linear flow passage to two catheters placed in the right atrium via the jugular vein. The valve is accessed percutaneously with needle-cannulas that functionally convert the device to twin catheters for connecting the patient to the HD lines. Interdialytic patency is maintained using a standard heparin lock. The device has been implanted in 10 outpatients under local anesthesia, with almost immediate use for HD (median, 3 days) and has functioned successfully for more than 6 months (mean +/- SD, 4.0 +/- 1.7; > 400 dialysis sessions). Blood flows over 300 ml/min were consistently achieved (average, 320 +/- 50) with venous and arterial pressures of 197 +/- 42 mmHg and -241 +/- 31 mmHg, respectively. After 40 patient-months, condition of the needle puncture sites remains satisfactory. Four systemic infections have occurred in three patients; all have resolved without the need for device removal. There have been no infections at the puncture sites. One patient whose heparin lock was not changed for 23 days (for reasons unrelated to the device) required fibrin sheath stripping of his catheters. Patient and nurse acceptance has been excellent. The device may offer substantial improvement over conventional devices for HD access.     

Dog-bite induced sepsis: a report of four cases

Occasionally, a dog-bite is complicated by a systemic overwhelming infection. We report four consecutive patients who were admitted to our intensive care unit because of sepsis syndrome following dog-bites. The history of these patients did not reveal any immunocompromising conditions. Capnocytophaga canimorsus (C. canimorsus) was cultured from the blood culture of 2 patients. Our data illustrate that in patients with lack of immune-deficiency severe sepsis may develop.     

Development of hydroxyapatite derived from Indian coral

A simple method of converting the calcium carbonate skeleton of the corals available in the Indian coast into hydroxyapatite granules has been developed. By heating the coral to 900 degrees C, the organic materials were eliminated. Powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were employed to characterize the coral and to optimize the processing parameters as well as to confirm the hydroxyapatite formation. The coral used exhibits the presence of both aragonite and calcite phases (dimorphism). At a temperature of 900 degrees C the coral was found to decompose all the carbonate phases. The pre-heated coral is converted into hydroxyapatite by a chemical exchange reaction with di-ammonium phosphate under hydrothermal conditions. The hydroxyapatite obtained was in powder form and does not contain any impurities. The in vitro solubility test of the apatite granules performed in Gomoris, Michalelis, Sorensens, Ringer's and phosphate buffer of pH 7.2 and de-ionized water indicated the stability of the coralline hydroxyapatite.     

Striated muscle calcium-stimulated cysteine protease (calpain-like) activity promotes myeloperoxidase activity with exercise

An inflammatory response triggered by neutrophil accumulation into muscle tissue is thought to occur with exercise-induced muscle damage. To investigate the relationship between Ca2+-stimulated proteolysis (calpain-like activity) and neutrophil accumulation [myeloperoxidase (MPO) activity], cardiac and plantaris muscles from rats (n = 10) completing 1 h exercise (25 m/min) were investigated. Exercise promoted increases (P<0.05) in both calpain-like and MPO activities; ranging from 2.79 to 58.9 U/g wet weight (ww) and 0.03 to 4.88 U/g ww respectively. Pearson's correlational analysis (r) on calpain-like and MPO activities for cardiac and plantaris muscle data were 0.97 (P<0.001) and 0.68 (P<0.05) respectively, with a combined r of 0.83 (P<0.001) for both muscles across all conditions. To investigate further the extent to which calpain-like activity may promote neutrophil accumulation, another exercise group (n = 5) was pre-injected with the cysteine protease inhibitor, E64c, 1 h before exercise. Administration of E64c lowered calpain-like and MPO activities by 66% and 56% respectively (average from both muscles). From these results it is concluded that a relationship exists between Ca2+-stimulated proteolysis and neutrophil accumulation into striated muscle with exercise, and that the calpain system is involved in localizing the neutrophilic response with exercise.