Rotavirus-associated diarrhea in a commercial rabbitry

An epizootic of diarrheal disease occurred in a commercial specific-pathogen-free rabbitry, and was characterized by sudden onset, rapid spread, and high morbidity and mortality among sucklings. Affected rabbits rapidly became dehydrated and most died within two days of the onset of diarrhea. Eight of these rabbits were necropsied. Five had blunted and fused small intestinal villi with attenuated villous enterocytes. A rotavirus was isolated from four rabbits, and five survivors of affected litters had strong antibody responses to rotavirus.     

Defect in expression of heat-shock proteins at high temperature in xthA mutants.

Escherichia coli mutants lacking exonuclease III (xthA) are defective in the induction of heat-shock proteins upon severe heat-shock treatment (upshift from 30 to 50 degrees C) but not mild heat-shock treatment (upshift from 30 to 42 degrees C). We show that this defect is due to the xthA mutation by complementation. Furthermore, increasing the gene dosage of xthA+ prolongs the synthesis of heat shock proteins seen after a shift to 42 degrees C. Increasing the gene dosage of htpR+ partially suppresses the defect of xthA mutants in the synthesis of heat-shock proteins at 50 degrees C. When an xthA strain was incubated at 42 degrees C before a shift to 50 degrees C, it was then able to carry out the synthesis of heat-shock proteins at 50 degrees C.     

Histamine releases PGI2 from human pulmonary artery

Histamine caused a triphasic response of human pulmonary artery strips in vitro, consisting of a small initial contraction followed by pronounced relaxation preceding a second contractile response. These characteristics were not seen with other contractile stimuli including 5-hdyroxytryptamine, leukotriene D₄, and KC1. The relaxant component of this response was ablated by removal of endothelium from the vascular strips or by pretreatment of the tissues with 1μM indomethacin. Measurement of the PGI₂ degradation product 6-keto-PGF_1α in supernatants from histamine-challenged tissues confirmed the synthesis of PGI₂. Supernatants from unstimulated or leukotriene-challenged tissues contained no detectable amounts of 6-keto-PGF_1α. The histamine H₁ antagonist diphenhydramine inhibited both the contractile and relaxant responses to histamine whereas the H₂ antagonist cimetidine affected neither component. The released PGI₂ significantly altered the dose-respons curve to histamine without inhibiting the maximal contractile responses. We conclude that histamine induces PGI₂ formation from pulmonary arterial endothelium via an H₁ receptor.     

Thermoregulation, metabolism, and stages of sleep in cold-exposed men

Four naked men, selected for their ability to sleep in the cold, were exposed to an ambient temperature (Ta) of 21 degrees C for five consecutive nights. Electrophysiological stages of sleep, O2 consumption (VO2), and skin (Tsk), rectal (Tre), and tympanic (Tty) temperatures were recorded. Compared with five nights at a thermoneutral Ta of 29 degrees C, cold induced increased wakefulness and decreased stage 2 sleep, without significantly affecting other stages. Tre and Tty declined during each condition. The decrease in Tre was greater at 21 degrees C than at 29 degrees C, whereas Tty did not differ significantly between conditions. Increases in Tty following REM sleep onset at 21 degrees C were negatively correlated with absolute Tty. VO2 and forehead Tsk also increased during REM sleep at both TaS, whereas Tsk of the limb extremities declined at 21 degrees C. Unsuppressed REM sleep in association with peripheral vasoconstriction and increased Tty and VO2 in cold-exposed humans, do not signify an inhibition of thermoregulation during this sleep stage as has been observed in other mammals.     

The role of encapsulation in the pathogenesis of anaerobic gram-positive cocci

The pathogenicity of 22 anaerobic and facultative Gram-positive cocci (AFGPC) was investigated by inoculating them into mice and determining their ability to cause subcutaneous abscesses. Only 11 heavily encapsulated isolates (greater than 50% of the cells were encapsulated) induced abscesses. However, when the other 11 isolates were injected with Bacteroides sp. or facultative and aerobic bacteria, abscesses were formed in 8 of the 11 combinations. The AFGPC recovered from the mixed infections contained many encapsulated cells. Encapsulation also occurred in cocci injected with capsular material or with Formalin-killed cells of Klebsiella pneumoniae or capsule-positive Bacteroides sp. After acquisition of capsules, these strains could induce abscesses on reinoculation in mice.     

Yolk polypeptide gene expression in Minute Drosophila females

Minutes have been considered for some time to be mutant at the sites of synthesis of some components of the protein synthetic apparatus. To study the hypothetical relationship between Minutes and suboptimal translation, a group of abundant proteins, the yolk polypeptides, was assayed in outcrossed females bearing M(3)w, M(3)h ^y , or M(1)n mutations. Recently emerged Minute females contained a lower amount of yolk polypeptides, in both ovarian and nonovarian tissues, than their non-Minute sisters. This low level correlated with the lower abundance of cytoplasmic RNA in Minutes compared to control females. By 1 week of age, both M(3)w and their non-Minute sibs contained the same amount of yolk polypeptides and the corresponding mRNA. The double heterozygote, ap ⁴/+;M(3)w/+, did not differ in yolk polypeptide content from control flies. M(3)w females demonstrated reduced fecundity during the period of low yolk polypeptide content but gradually increased egg deposition as yolk polypeptide levels rose. These results suggest that the low protein levels are due to the slower maturation of M(3)w, and not to less efficient translation machinery.This work was supported by the NSERC (Canada) and a Queen's University ARC grant.     

Comparison of glucokinase in C3H/He and C58 mice that differ in their hepatic activity

Partially purified preparations of the hepatic glucokinase from C3H/He and C58 inbred mice have been used to explore the molecular basis for the observed twofold difference in activity between the strains. The single codominant gene that appears to regulate activity, the alleles of which are designated Gk^a and Gk^b, respectively, for the two strains, could represent a structural gene change. This now seems unlikely because the mouse enzyme, although showing small differences from rat glucokinase, appeared to be identical in the two strains with respect to thermal stability, electrophoretic mobility in agarose gels, and kinetic properties such as the apparent K _m values for MgATP^2– and glucose and the unique cooperative interaction with the latter substrate. The enzymes also reacted identically in a range of immunological tests (double-diffusion, immunoelectrophoresis, immune precipitation and immune inhibition assays) and ELISA immune inhibition assays indicated that the twofold difference in activity was due to a similar difference in antigenically active enzyme. Genetic control over the physiologically significant regulation of enzyme amount is therefore probable.This work has been supported in part by a grant from the British Diabetic Association and a Training Studentship to PAJ from the Medical Research Council (U.K.).     

The skeleton of early Eocene Cantius, oldest lemuriform primate

A recently discovered partial skeleton of the adapid Cantius trigonodus from the early Eocene Willwood Formation of the Bighorn Basin, Wyoming, documents substantial new information about the anatomy of the oldest lemuriform primates. It is very similar in all features to its descendant, middle Eocene Notharctus, and both exhibit numerous resemblances to certain extant Malagasy lemurs, particularly Lepilemur, Propithecus, Lemur, and Hapalemur griseus. Like these forms, Cantius had relatively long hind limbs and short forelimbs. Forelimb traits (prominent brachialis flange of the humerus, well-developed olecranon process of the ulna, and strong shafts of the ulna and radius) suggest active use of the forelimbs in progression. Specializations in the hind limb (e.g., expanded articular surface of the femoral head, narrow and elevated patellar trochlea and prominent lateral trochlear ridge, posteriorly oriented femoral and tibial condyles, narrow and elongate talus, and hallucal metatarsal with prominent peroneal tubercle) indicate capabilities for leaping and for powerful grasping with an opposable hallux. Cantius was presumably primitive in having a relatively long ischium and much more distal inferior tibial tuberosity than most extant lemurs--traits suggesting that powerful extension of the thigh and flexion at the knee were important in its locomotion and posture. We interpret Cantius as an active arboreal quadruped with a propensity for leaping. The existence of this skeletal structure in one of the oldest primates of modern aspect suggests that it represents the primitive lemuriform morphology.     

The thermodynamics of bovine and porcine insulin and proinsulin association determined by concentration difference spectroscopy

Difference spectroscopy was used to determine the equilibrium constants and thermodynamic parameters for the monomer-dimer association of bovine and porcine insulin and bovine proinsulin at pH 2.0 and 7.0. At pH 2 delta G degree 25, delta S degree, and delta H degree for dimerization of bovine insulin were found to be -6.6 kcal/mol, -18 cal/mol-deg, and -12 kcal/mol, respectively. Porcine insulin behaved similarly to bovine insulin in its dimerization properties in that delta G degree 25, delta S degree, and delta H degree were found to be -6.8 kcal/mol, -14 cal/mol-deg, and -11 kcal/mol, respectively. At pH 7 delta G degree 25, delta S degree, and delta H degree for dimerization of bovine insulin were found to be -7.2 kcal/mol, -16 cal/mol/deg, and -12 kcal/mol, respectively. At pH 7.0 delta G degree 25, delta S degree, and delta H degree for dimerization of porcine insulin were -6.7 kcal/mol, -11.6 cal/mol-deg, and -10 kcal/mol, respectively. The similarity in the thermodynamic parameters of both insulin species at the different pH's suggests that there are minimal structural changes at the monomer-monomer contact site over this pH range. The dimerization of both insulin species is under enthalpic control. This may suggest that the formation of the insulin dimer is not driven by hydrophobic bonding but, rather, is driven by the formation between subunits of four hydrogen bonds in an apolar environment. At pH 2 delta G degree 25, delta S degree, and delta H degree for dimerization of bovine proinsulin were found to be -5.3 kcal/mol, -26 cal/mol-deg, and -13 kcal/mol, respectively. At pH 7 delta G degree 25, delta S degree, and delta H degree for dimerization of proinsulin were -5.9 kcal/mol, -4.2 cal/mol-deg, and -7.2 kcal/mol, respectively. Although the presence of the C-peptide on proinsulin does not drastically affect the overall free energy change of dimer formation (as compared to insulin), the other thermodynamic parameters are rather drastically altered. This may be because of electrostatic interactions of groups on the C-peptide with groups on the B-chain which are near the subunit contact site in the insulin dimer.     

Hormonal modulation of responses to thymus-independent and thymus-dependent antigens in autoimmune NZB/W mice

Previous work suggested that gonadal steroids influence immunity through the thymus, but the mechanisms were unclear. To investigate the effects of these hormones on immune responses to T1 and TD antigens in autoimmune mice, we studied hybrid NZB/W mice and the nonautoimmune DBA/2 strain. Mice castrated at 14 days of age were implanted with Silastic capsules releasing, in adults, physiologic levels of E2 in males or Te in females. Sham-operated controls received empty capsules. Splenic PFC were quantified 4 to 5 days after challenge with the TI2 antigen TNP-Ficoll, the TI1 antigen TNP-LPS, or the TD antigen SRBC. Young castrated NZB/W males implanted with E2 had striking enhancement of IgM responses to TNP-Ficoll when compared to castrated Te-treated females and comparable sham-operated controls of both sexes. E2 also stimulated responses to TNP-LPS. In response to challenge with SRBC, young E2-treated NZB/W males had a consistent trend to increased IgM PFC, and the stimulatory effect of E2 on IgG plaques was variable. Physiologic doses of Te had no consistent effect on responses in young mice. In old female NZB/W mice, Te caused PFC response after immunization with TNP-Ficoll to resemble age-matched NZB/W males. As sham-operated NZB/W females grew older, PFC responses to SRBC fell. This age-related phenomenon was delayed, however, in female castrates implanted with Te. In contrast, Te clearly suppressed responses to TNP-LPS. Implantation of E2 did not alter responses to TNP-Ficoll, TNP-LPS, or SRBC in nonautoimmune DBA/2 males. This finding suggested that exogenous E2 given in physiologic doses did not influence immunologic responsiveness in a normal strain to the degree seen in hormone-sensitive NZB/W mice. It was concluded that E2 enhanced responses to a variety of exogenous antigens in autoimmune NZB/W mice. The most consistent E2-induced increase in PFC response was observed with TI antigens, suggesting that E2 exerted its effects on B cells or Ts.