The effect of low exposure-rate gamma irradiation on T and B lymphocyte function in the mouse

The effect of chronic irradiation on T and B cell numbers and function was studied in mice. Cobalt 60 gamma radiation at 6 R/hour reduced the numbers of anti-SRBC PFC in the spleen, with minimal levels recorded after total exposures of 1000-2000 R. Recovery was incomplete after 1000 R, reaching only 40-50 per cent of normal in four months and remaining at that level for the animal's lifetime. The long-term deficiency in PFC formation was not due to a quantitative lack of T or B cells since normal cell numbers were observed in the spleen 60-144 days after 1000 R. Adoptive transfer studies with combinations of bone marrow and thymus cells, or of splenic T and B cells, from normal and irradiated mice, revealed functional defects in both cell compartments during the first two months. Normal and near normal function of T and B cells occurred 100 days postirradiation, a time when the splenic in vivo response was still only 50 per cent of the controls. The latter observation suggests that the microenvironment of the chronically irradiated spleen alters factors regulating T and B cell interactions in response to a T-dependent antigen.     

The role of cytochrome P-450 in the synthesis of polar metabolites of aldosterone by microsomes of male rat liver

Among the tissues of the male rat studied, the largest quantities of the neutral polar metabolites of aldosterone were synthesized by the hepatic microsomal fraction. The polar metabolites of aldosterone were separated by HPLC into six peaks. Three peaks of non-polar (reduced) metabolites were also synthesized. Synthesis of at least four of the neutral polar metabolites was induced by phenobarbital and inhibited by both CO and SKF-525A. The rates of synthesis of these metabolites, which were linear up to 5 minutes, correlated well with the concentration of cytochrome P-450 in the liver microsomes. Addition of aldosterone to the microsomal fraction caused a pronounced type 1 change in the cytochrome P-450 spectrum. The half maximal spectral change (K_s) for aldosterone was calculated to be 8 μM. These experiments indicate that the neutral polar metabolites of aldosterone are produced by cytochrome P-450 dependent hydroxy lations.     

Isolation and characterization of an hydroxykynureninase from homogenates of adult mouse liver

A kynureninase-type enzyme was isolated from adult mouse liver. With kynurenine as the substrate, this enzyme has a K_m of 300 μ$\text{M}$; when the substrate is hydroxykynurenine, the K_m is 6 μ$\text{M}$. We conclude that this enzyme is an hydroxykynureninase. No enzyme which we could characterize as a kynureninase was found in this preparation. This suggests that tryptophan metabolism in the mouse occurs primarily through pathways that use hydroxykynurenine rather than kynurenine. Preliminary studies indicate that the enzyme is inhibited by its reaction product, hydroxyanthranilate, which is an intermediate in the synthesis of NAD. Such control of the hydroxykynureninase reaction may be of physiological importance in regulating the synthesis of NAD and/or in preventing the accumulation of hydroxyanthranilate, a putative carcinogen.     

Effect of immunizing prepuberal lambs of low and high ovulation rate genotypes with inhibin partially purified from bovine follicular fluid

Active immunization of prepuberal lambs with a partially purified inhibin preparation, isolated from bovine follicular fluid, increased the ovulation rate. In ewe lambs of a low fecundity breed (Suffolk x Galway), the ovulation rate rose from 1.15 to 1.95 (P<0.05) compared with that of the controls. An ovulation rate of 3.38 was recorded for immunized ewe lambs of a high fecundity breed (Finn x Dorset Horn), while the rate for mature ewes from the same flock was 2.29. Immunization did not affect the time of onset of puberty or estrous cycle length. Following immunization, antibodies were produced that bound to a pure preparation of 68kDa bovine inhibin. This report demonstrates the production of antibody to a 68kDa preparation of inhibin following active immunization of sheep using a partially purified preparation. It was concluded that the increased ovulation rate was due to the production of antibodies to inhibin, which may have reduced its negative feedback effect of FSH secretion.     

The effect of culture and membrane potential on Goα expression in neonatal rat cardiac myocytes

The effects of culture and membrane potential on G_o39 expression were examined in neonatal rat cardiac myocytes. During six days of culture, the amount of G_o39 in myocytes increased six-fold. The increase in G_o39 appeared to be programmed, since G_o39 of rat hearts also increased in vivo within three days after birth before declining by six days after birth. Furthermore, the age of the rat from which cardiac myocytes were isolated determined the amount of G_o39 that accumulated in cultured cells with myocytes from two day-old rats producing more G_o39 than myocytes from six day-old rats. In addition, agents which alter membrane potential (KCl and bupivacaine) inhibited the accumulation of G_o39 in cultured myocytes. In an attempt to identify the signaling pathway in which cardiac G_o39 is involved, muscarinic receptor-stimulated inositol phosphate production was examined, but was found to be comparable in myocytes that had six-fold differences in G_o39 content. Thus G_o39 does not appear to couple muscarinic receptors to phospholipase C in rat cardiac myocytes.     

Professional burnout and its relation to job characteristics, satisfaction, and control

Burnout scores for 104 professionals in the fields of college student personnel, health and mental health, administration and miscellaneous other professionals were correlated with ratings on 13 job characteristics, and ratings of satisfaction with, and control over, these characteristics. Results indicate significant positive correlations between the burnout scores and 10 of the 13 job characteristics. Significant positive correlations were found for burnout and all 13 items of job satisfaction. Significant negative correlations were found for 6 of the items where control was rated. Demographic variables of age, sex, marital status, employment status of spouse, dependents, number of hours worked, and being on call showed no significant correlations with burnout. Recommendations are made for continued research and theory building which take into account the concept of control over one's work environment.     

Viability of Bradyrhizobium japonicum bacteriods

Homogenates from soybean nodules, formed by 12 strains of Bradyrhizobium japonicum, were plated into yeast-extract mannitol agar containing 3 or 37 g mannitol 1^-1. Viable counts ranged from 8.298 to 11.265 log₁₀ cells-gram nodule^-1. When monitored over the life cycle of the symbiosis, the viability of strains USDA 110 and USDA 123 increased with days after planting (DAP), and at 70 DAP was 95% and 81%, respectively. By contrast, the viability of USDA 38 bacteroids decreased with time, and at 70 DAP was only 1.9%. At 49 DAP, nodules induced by USDA 38 had significantly fewer bacteroids per peribacteroid membrane than those formed by USDA 110 or USDA 123, and at 70 DAP, 27% of the USDA 38 bacteroids showed some degree of degeneration. Viable counts of USDA 123 and USDA 110 bacteroids, isolated from the nodules of 12 different cultivars, ranged from 10.963 to 11.463 and from 10.683 to 11.117 log₁₀ viable cells-gram nodule^-1, respectively. Varying the osmolarity of the medium had no predictable effect on bacteroid viability. When surface-sterilized nodules of IPAGO 587 (high bacteroid viability) and USDA 38 (low bacteroid viability) were inoculated into a nonsterile silt loam soil, at rates equivalent to 5.0×10⁸ and 5.0×10⁶ viable bacteroids g^-1 soil, respectively, and then incubated at 28° C for 60 days, 4.3×10⁴ and 1.5×10⁴ surviving cells g^-1 soil, respectively, were recovered. Thus, despite differences due to host and strain variation, bacteroid viability appears to be unrelated to persistence of individual strains following an annual legume crop cycle.Journal paper No. 14930, Agricultural Experiment Station University of Minnesota, St. Paul, MN 55108, USA     

Removal of Arg1 and Phe22 from CLIP (ACTH18-39) by rodent pituitary and blood peptidases

The major product on incubation of CLIP (ACTH18-39) with rat and mouse serum, rat plasma and whole blood, and soluble extracts of rat pituitary is [des-Arg1]-CLIP (ACTH19-39) while [des-Phe22]-CLIP (ACTH18-38) is the major product with pituitary particulate fraction. In both cases, p-chloromercuribenzoate-sensitive, metal-dependent peptidase activity appears to be responsible for the cleavage. The serum enzyme may be related to proline aminopeptidase. Material coeluting with [des-Arg]-CLIP on two HPLC solvent gradients is present in the superfusion media from neurointermediate lobes of genetically obese (ob/ob) mice but is not present in acid extracts of the lobe. This suggests that postsecretory processing of CLIP may involve removal of the N-terminal Arg residue.     

Structure of the manganese complex of photosystem II upon removal of the 33-kilodalton extrinsic protein: an X-ray absorption spectroscopy study

The structure of the Mn complex of photosystem II (PSII) was studied by X-ray absorption spectroscopy. Oxygen-evolving spinach PSII membranes containing 4-5 Mn/PSII were treated with 0.8 M CaCl2 to extract the 33-, 24-, and 16-kilodalton (kDa) extrinsic membrane proteins. Mn was not released by this treatment, but subsequent incubation at low Cl- concentration generated preparations containing 2 Mn/PSII. The Mn X-ray absorption K-edge spectrum of the CaCl2-washed preparation containing 4 Mn/PSII is very similar to spectrum of native PSII, indicating that the oxidation states and ligand symmetry of the Mn complex in these preparations are not significantly different. The Mn extended X-ray absorption fine structure (EXAFS) of CaCl2-washed PSII fits to a Mn neighbor at approximately 2.75 A and two shells of N or O at approximately 1.78 and approximately 1.92 A. These distances are similar to those we have previously reported for native PSII preparations [Yachandra, V. K., Guiles, R. D., McDermott, A. E., Cole, J. L., Britt, R. D., Dexheimer, S. L., Sauer, K., & Klein, M. P. (1987) Biochemistry (following paper in this issue)] and are indicative of an oxo-bridged Mn complex. Our results demonstrate that the structure of the Mn complex is largely unaffected by removal of 33-, 24-, and 16-kDa extrinsic proteins, do not provide ligands to Mn. The Mn K-edge spectrum of the CaCl2-washed sample containing 2 Mn/PSII has a dramatically altered shape, and the edge inflection point is shifted to lower energy. The position of the edge is consistent with a Mn oxidation state of +3.(ABSTRACT TRUNCATED AT 250 WORDS)     

Food and feeding behavior of the hoplonemertean Oerstedia dorsalis

The monostiliferous nemertean Oerstedia dorsalis was collected from eelgrass (Zostera marina) beds located along the coast of New Jersey, and feeding responses to amphipods and isopods were observed in the laboratory. Tests with 46 worms showed that they fed suctorially on Ampelisca vadorum, Ampithoe longimana, Corophium acherusicum and C. tuberculata. Corophiids were preferred. Upon contact with an amphipod, the proboscis is everted and strikes the prey on the ventral side, immobilizing it in a few minutes. The worm probes the sternal region with its head and everts its proboscis one or more times during the process. The exoskeleton is eventually penetrated by the head, and the stomach is everted into the hemocoel as a flattened funnel-like structure. Peristaltic undulations of the body signify the suctorial action that removes the living contents from the exoskeleton. The actual feeding process (from head penetration to removal of the head) takes about 7 min. O. dorsalis is only the third species within the Prosorhochmidae for which the feeding behavior has been documented. The other two are terrestrial species, and are also suctorial.