Asymmetry of the phospholipid bilayer of rat liver endoplasmic reticulum

The phospholipids of intact microsomal membranes were hydrolysed 50% by phospholipase C of Clostridium welchii, without loss of the secretory protein contents of the vesicle, which are therefore not permeable to the phospholipase. Phospholipids extracted from microsomes and dispersed by sonication were hydrolysed rapidly by phospholipase C-Cl. welchii with the exception of phosphatidylinositol. Assuming that only the phospholipids of the outside of the bilayer of the microsomal membrane are hydrolysed in intact vesicles, the composition of this leaflet was calculated as 84% phosphatidylcholine, 8% phosphatidylethanolamine, 9% sphingomyelin and 4% phosphatidylserine, and that of the inner leaflet 28% phosphatidylcholine, 37% phosphatidylethanolamine, 6% phosphatidylserine and 5% sphingomyelin. Microsomal vesicles were opened and their contents released in part by incubation with deoxycholate (0.098%) lysophosphatidylcholine (0.005%) or treatment with the French pressure cell. Under these conditions, hydrolysis of the phospholipids by phospholipase C-Cl. welchii was increased and this was mainly due to increased hydrolysis of those phospholipids assigned to the inner leaflet of the bilayer, phosphatidylethanolamine and phosphatidylserine. Phospholipase A₂ of bee venom and phospholipase C of Bacillus cereus caused rapid loss of vesicle contents and complete hydrolysis of the membrane phospholipids, with the exception of sphingomyelin which is not hydrolysed by the former enzyme.     

Polymorphisms of DQ β genes in HLA-DR4 haplotypes from healthy and diabetic individuals

The restriction fragment length polymorphism (RFLP) of DQ was assessed in a panel of control and insulin-dependent diabetes (IDD) patients who were serologically typed as HLA-DR4 homozygotes or HLA-DR3, DR4 heterozygotes. Digestions of genomic DNA with Barn HI, Bg1 II, Pst I, Xba I, and Hind III revealed a total of 15 RFLPs in the panel of 71 HLA-DR4 chromosomes. These RFLPs were organized into six allelic groups on the basis of segregation analysis in families. Complete RFLP haplotypes for the 5 restriction enzymes could be constructed for 42 of the HLA-DR4 chromosomes. This analysis revealed 18 RFLP haplotypes of DQ associated with the DR4 chromosomes tested. Two of these haplotypes, designated DQ3.DR4.a and DQ3.DR4.b, accounted for over 50 % of the DR4 chromosomes analyzed. These two haplotypes were antithetical for the RFLPs detected by all five enzymes, indicating that they represent very distinct forms of DQ . The remaining 16 haplotypes were infrequent or unique and were closely related to either a DQ3.DR4.a or DQ3.DR4.b. Two of the RFLPs detected, a 5.8 kb Bg1 II fragment and a 10.5 kb Barn HI fragment, had increased frequencies in disease-associated chromosomes. However, none of the RFLPs we detected exhibited a statistically significant increase in IDD or control populations. In contrast, the DQ3.DR4.b DQ haplotype was significantly decreased in IDD-associated DR4 chromosomes. (P=0.04). These results suggest that the DQ3.DR4.b DQ allele may be protective for the development of IDD.     

Zinc,copper, selenium,and glutathione peroxidase in blood of 11-yr-old dunedin,New Zealand children

Blood was obtained from 564 11-yr-old children who had participated since birth in a multidisciplinary health and development study. Serum zinc concentration did not differ between the boys and the girls (mean±SD: 91=17 μg/100 mL,n=453). Five-6% of serum zinc values were low; although there was a weak correlation with height, none of the boys with low values were below the 10th percentile for height for this group. Serum copper concentration (112±24 μg/100 mL,n=454) was unrelated to sex, height, weight, body mass index, socioeconomic status (SES), or iron status. Blood selenium concentration (49±10 ng/mL,n=564) was lower than previously reported for Dunedin children; it was higher in children in the lower SES categories. The data represent normal values for healthy, 11-yr-old NZ children.     

Age at maturity in landlocked and anadromous Atlantic salmon parr from two Québec rivers

Synopsis Age at maturity in male Atlantic salmon parr from landlocked populations in the Watshishou and Musquaro Rivers is significantly greater than in anadromous populations from the same rivers. We conclude that high post-smolt mortality in anadromous stocks is conducive to male parr maturity at an early age. We also suggest that the lower proportion of maturing male parr in landlocked stocks may be related to competition among males for mates and the smaller ultimate size of spawning adult landlocked salmon.     

A miniaturised parallel-plate shearing apparatus for the measurement of cell adhesion

The design and construction of a miniaturised shearing apparatus is described. Cultures (24 h) of an established epithelial cell line (BEB) were exposed to flow conditions in the shearing chamber at 37 degrees C, and subsequently glass coverslip cultures were prepared for photography. The critical shear radius (CSR) was determined by densitometry from a negative film and the minimum distraction force (MDF) at the CSR calculated using predetermined viscosity values of the flow medium. The mean calculated MDF of BEB cells ranged from 1.04-1.36 Nm-2, and was independent of the culture inoculation density (9 to 37 X 10(4) cells cm-2) and the time (5-20 min) of exposure to shearing conditions. The MDF was increased to 3.3 Nm-2 by a 30 min exposure of cultures to concanavalin A (50 micrograms ml-1), and this effect was abolished by treating with mannose (0.05 M). The results demonstrated that the radial flow chamber principle is applicable to the measurement of cell to substratum adhesion of cultured mammalian cells.     

Recovery of murine lens epithelial cells from single and fractionated doses of X rays and neutrons

Subpopulations of mouse lens epithelial cells, differing in proliferative status, were irradiated with either X rays or fission spectrum neutrons given singly or in four weekly fractions. After various times, epithelia were mitogenically stimulated by wounding and DNA synthesis responses were determined by incorporation of [3H]thymidine. At 1 h following both X and neutron irradiations, significant suppression of the wound response after single doses and a sparing effect of fractionation were evident in both the mitotically quiescent and the slowly proliferating subpopulations. At 1 week following single or fractionated doses of both radiations, recovery was evident in both subpopulations. By 4 weeks, the quiescent subpopulation showed significant recovery after both single and fractionated doses of X rays or neutrons. In contrast, a marked decreased ability to respond after neutron irradiation and, in addition, a significant enhancement effect of neutron fractionation were observed for the slowly proliferating subpopulation. Per gray, neutrons were about 7.5 times more effective than X rays as a single dose and 25 times more effective in four equal fractions. The shift from an initial sparing to a final enhancing effect of neutron fractionation for the slowly proliferating subpopulation has importance for understanding divergent early and late radiation responses following dose fractionation.     

Fine structural aspects of secretory processes in a pentastomid arthropod parasite in its mouse and rattlesnake hosts

The histology and development of three extensive glands in the porocephalid pentastomid Porocephalus crotali is described by light and electron microscopy, during growth of the parasite to an infective stage in the tissues of mouse; the infective stage in rattlesnake definitive hosts is also included. These glands elaborate excretory/secretory components which are channelled, via chitin-lined efferent ductules, on to the parasite cuticle. Hook and frontal glands are relatively compact, and within each gland ductules serving individual secretory lobules collect into common ducts which discharge over each of the four hooks, or at the anterior margin of the cephalothorax respectively. Subparietal gland cell lobules, composed of two large and two small secretory cells, are distributed under the cuticle and each is served by a single efferent ductule; these erupt over the entire cuticle. The large cells in subparietal glands secrete lamellate droplets which coat the cuticle with thin layers. Identical cells are found in hook and frontal glands, in addition to to three morphologically distinct types of protein secretory cell. Preliminary data on the composition and immunological properties of the various secretory products are presented.     

Development of captive bongos (Tragelaphus eurycerus): Activity budgets and developmental milestones

The development of changes in visual orientation, posture, activity budgets, and behavioral milestones was examined in five bongo calves which were observed from birth to 4 or 6 months of age. The only significant change in the calves' visual orientation was an increase in orientation to food. Reclining declined significantly over weeks, while standing increased and moving did not change. Overall, stationary behaviors dominated the activity budget, but decreased significantly over the study. The category that included locomotion, object exploration, and auto-play did not change, while forage and rumination increased significantly. Contrary to expectation, the decline in suckling was not significant. Affiliative interactions with the dam decreased significantly during the study, but increases in affiliation with other bongos were not significant. Levels of agonistic behavior between the calves and their dams and other herd members were low throughout the study, and did not change significantly. One female calf achieved several developmental milestones later than the others. It is suggested that these differences may have been influenced by the dominance status of her dam. The results conform to the general developmental pattern of “hider” bovids. Bongos, however, show somewhat different patterns of social development than eland, which are reported to be more precocial in expression of aggressive and sexual behaviors. © 1992 Wiley-Liss, Inc.     

Recruiting physicians to rural practice. Suggestions for success.

Medical school graduates from 1986 to 1988 and current residents in 12 family practice residency programs in the Northwest (N = 302) were surveyed to identify important factors in the recruitment process for their first postresidency placement. The study sought to compare the recruitment practices of rural communities and urban sites. Specific questions addressed in the study concerned sources of information about practice opportunities, stage in training when job search was initiated, factors related to unsuccessful site visits, and activities scheduled in the visit. Results indicated that referrals from faculty were the most valued source of information. Most job searches were initiated in the first 6 months of the third year in training. An unreceptive physician community and a reluctant spouse or partner were substantial problems for residents making site visits to rural communities. Rural sites tended to provide a broader mix of professional and personal activities during the visit.     

Water and solute regulation in Procephalothrix spiralis Coe and Clitellio arenarius (Müller) III. Long-term acclimation to diluted seawaters and effect of putative neuroendocrine structures

When acutely transferred to diluted seawater (SW), Procephalothrix spiralis and Clitellio arenarius regulate water content (g H₂O/g solute free dry wt = s.f.d.w.) via loss of Na and Cl (µmoles/g.s.f.d.w.). The present study extends these observations to a greater range of salinities and determines the effects of long-term, stepwise acclimation to diluted seawaters. Final exposure to a given experimental seawater (70, 50, 30, 15%) was 48 hours. Osmolality (mOsm/kg H₂O) and Na, K, and Cl ion concentrations (mEq/l) were determined in total tissue water and in the extracellular fluid of C. arenarius. Extracellular volume was determined as the ¹⁴C-polyethylene glycol space. Both species behaved as hyperosmotic conformers in diluted seawaters. However, reduction of the osmotic gradient between worm and medium occurred in P. spiralis, but not C. arenarius, in 30 and 15% SW. In both species, osmolality and Na, Cl, and K concentrations in total tissue water decreased with increased dilution of the SW. Water content increased with dilution of the medium but was lower than that which would be predicted based on approximation of the van't Hoff relation. This indicated the occurrence of regulatory volume decrease (RVD). In P. spiralis, in 70 or 50% SW, RVD was accompanied by loss of Na and Cl contents. However, in 30 or 15% SW, Na and Cl contents increased and in worms in 15% SW K content decreased. The latter movements of Na, Cl and K are indicative of cellular hysteresis and were associated with decreased viability, indicating the lower limits of regulatory ability in this species. In comparison, RVD in C. arenarius occurred in all diluted seawaters and was accompanied by loss of Na and Cl contents. In C. arenarius, evidence for reduced viability was absent. Removal of the supra- and subesophageal ganglia of C. arenarius resulted in retention of water, Na and Cl (g H₂O or µmoles/g s.f.d.w.) in worms acclimated to 70% SW. Removal of the cerebral ganglia and cephalic glands of P. spiralis did not significantly influence regulation of water content.