Cold shock and heat shock: a comparison of the protection generated by brief pretreatment at less severe temperatures

Abstract Brief exposure to low (0^oC) or high (40^oC) temperature elicits a protective response that prevents injury when the flesh fly, Sarcophaga crassipalpis Macquart, is subjected to more severe cold (-10^oC) or heat (45^oC). Both the low and high temperature responses were found in all developmental stages of the fly, but were most pronounced in the pupal and pharate adult stages. The protective responses generated by brief exposure to 0 or 40^oC appear similar in that both result in a rapid acquisition of cold or heat tolerance and a loss of protection after the flies are returned to 25^oC. The protection generated by chilling is obvious within 10 min of exposure to 0^oC while a 30 min exposure to 40^oC is required to induce the high temperature protection. High temperature protects against cold shock injury within a narrow range (around 36^oC) but we have no evidence that low temperature can protect against heat injury. We previously demonstrated that the rapid increase in cold tolerance correlates with concomitant increases in glycerol concentration, but in this study we found no significant elevation in glycerol in heat-shocked flies. Thus the physiological and biochemical bases for the rapid responses to cold and heat appear to be different.     

Chronic Giardia muris infection in anti-IgM-treated mice. I. Analysis of immunoglobulin and parasite-specific antibody in normal and immunoglobulin-deficient animals

To investigate the role of B cells and antibody in the immune response of mice to the murine intestinal parasite Giardia muris, we used mice treated from birth with rabbit anti-IgM antisera (aIgM). Such mice developed in serum and in gut secretions extreme Ig deficiency (IgM, IgA, and IgG) relative to control animals. The aIgM-treated mice showed no anti-G. muris antibody in serum or in gut wash material. Infections of G. muris in these mice were chronic, with a high load of parasite present in the small bowel, as reflected by prolonged cyst excretion (greater than 11 wk) and high trophozoite counts. In contrast, normal, untreated mice or NRS-treated animals developed anti-parasite IgA and IgG antibody in serum, demonstrated IgA antibody against the parasite in gut washings, and expelled the parasite within 9 wk. These effects of aIgM treatment on the murine response to primary infection with G. muris were demonstrated in two strains of mice: BALB/c and (C57BL/6 X C3H/He) F1. It was also observed that the response to G. muris infection in untreated animals was characterized by higher than normal total secretion of IgA into the gut and a concomitant increase in the serum polymeric IgA level. Mice treated with aIgM had a marked decrease of both monomeric and polymeric IgA in serum, and little detectable IgA in the intestinal lumen. These experiments provide the first demonstration that anti-IgM treatment suppresses a specific intestinal antibody response to antigen, and provide evidence that B cells and antibody play a role in the development of an effective response to a primary infection with G. muris in mice.     

Biomass: Is it a useful tool in paleocommunity reconstruction?

In general, more of the biomass of the community is preserved than is its numerical abundance. Thus, the paleontologist, on the average, works with more of the community when biomass is used. Community characteristics such as taxon dominance and habitat proportions are at least as accurately derived from biomass as numerical abundance. The use of biomass is clearly more appropriate in describing energy flow and trophic proportions. Whenever possible, biomass should be used as a complement to numerical abundance in future paleoecologic reconstructions.     

Purification and characterization of two Cl- -activated aminopeptidases hydrolysing basic termini from human skeletal muscle

Two aminopeptidases (I and II), hydrolysing basic termini, were purified to homogeneity (as judged by polyacrylamide gel electrophoresis) from human quadriceps muscle by anion-exchange chromatography and preparative electrophoresis. The electrophoretic migration rate of II was approximately 80% of that of I. Both enzymes had the following properties: optimum activity was at pH 6.5; addition of 0.15 M Cl- or Br- anions resulted in a 20-fold or 10-fold increase in activity respectively. There was little or no increase in activity on the addition of other anions, or divalent cations (0.05-5mM). Approximately 50% inhibition of activity was obtained in the presence of bestatin (0.1 microM), rho-hydroxymercuriphenylsulphonic acid (0.1 microM), EDTA (10 mM), 1,10-phenanthroline (100 microM), N-ethylmaleimide (1 mM) and But-Thr-Phe-Pro (0.5 mM). The molecular mass was 72 000 Da (gel filtration). Only the arginyl and lysyl 7-amino-4-methylcoumarin (Amc) derivatives were appreciably hydrolysed; approximate Km values for the reaction of I and II with these substrates (10-250 microM) were estimated as follows: Arg-Amc, KmI = 70 microM, KmII = 270 microM; Lys-Amc KmI = 280 microM, KmII = 400 microM. Both enzymes hydrolysed dipeptides with Arg or Lys as the NH2-terminal amino acid, however this was not an absolute requirement for dipeptide hydrolysis. The action of I and II on physiologically active oligopeptides was very restricted, with only bradykinin, proangiotensin and neurotensin being appreciably degraded. The breakdown of these peptides did not occur by classical aminopeptidase action (i.e. hydrolysis of the NH2-terminal residues), but via cleavage of internal peptide bonds. These results suggest that I and II may be isoenzymes of a Cl- -requiring, thiol-type aminopeptidase, which hydrolyses basic termini. These enzymes may act primarily as dipeptidases, with a very restricted mode of action in the degradation of naturally occurring oligopeptides.     

On the Trail of Atmospheric Mutagens and Carcinogens: A Combined Chemical/Microbiological Approach

Major ecological problems of our polluted troposphere includeairborne toxic chemicals, acid rain and photochemical smog,all three of which are now recognized as being closely relatedchemical phenomena. We also recognize that inorder to developcost-effective strategies for their control, which protect publichealth and the environment, there must be close scientific interactionsbetween chemists and biological scientists. For example, ofrapidly emerging importance is the development of risk assessmentevaluations for specific aspects of each of these problem areas.In preparing such assessments, chemists must define the "exposure,"and biological scientists the "effects." In this paper, I discuss an example of how such close interactionsproved indispensible in our search for atmospheric mutagensand carcinogens. Thus, an integrated chemical/ microbiologicalprocedure for the isolation and identificationof particulatechemical mutagens in respirable diesel soot and ambient particlesis described. Emphasis is placed on our use of the short-term,Ames Salmonella typhimurium bacterial mutagenicity test as arapid, and relatively inexpensive, means of following the biologicalactivities of these environmental mutagens through the chemicalsteps of their separation, isolation and identification fromhighly complex environmental samples. Possible mechanisms offormation of these particulate mutagens are discussed. Theyinclude the reactions of polycyclic aromatic hydrocarbons presenton the surfaces of combustion-generated particles with gaseousco-pollutants such as nitrogen dioxide plus nitric acid, andozone. In discussing this research on a societally "relevant" problem,we illustrate the importance of "Science as a Way of Knowing."We further suggest that this integrated approach to scientificproblem solving by chemical and biological scientists mightserve as an example of a discussion topic on human ecology forundergraduate courses in the natural sciences.     

Influence of testosterone on ventilation and chemosensitivity in male subjects

There is increasing evidence that men have higher ventilatory responses to chemical stimuli than age-matched women and that certain disorders of respiratory rhythmicity, particularly sleep apnea, occur more commonly in men. Accordingly, we studied the influence of the male hormone, testosterone, on the control of breathing. Twelve hypogonadal males were studied at least 30 (mean +/- SE: 69.7 +/- 8.9) days after discontinuing testosterone replacement and again following hormone administration. In each subject plasma testosterone concentration, metabolic rate [O2 consumption (VO2) and CO2 production (VCO2)], minute ventilation (VE), and chemosensitivity [hypoxic (HVR) and hypercapnic (HCVR) ventilatory responses] were determined on and off hormone replacement. With testosterone administration VO2 increased from 248 +/- 15 to 276 +/- 18 ml/min (P less than 0.05), with VCO2 showing a similar but nonsignificant trend. This was associated with an increase in VE from 8.41 +/- 0.78 to 9.91 +/- 0.75 l/min (P less than 0.05) but no change in PCO2. The HVR, expressed as A, increased 44% with hormone replacement from a value of 122 +/- 23 to 176 +/- 28 (P less than 0.01), whereas the HCVR was minimally affected by testosterone administration. These findings may in part explain the previously described differences between male and female subjects in hypoxic sensitivity.     

ESTIMATES OF CARRY-OVER EFFECTS IN TWO-PRODUCT HOME USAGE CONSUMER TESTS

In-house use consumer test data from four studies dealing with three pairs of household products and a pair of antiperspirant products were examined for significant carry-over (product usage order) effects, which would confound the analysis of treatment (product) effects. In each study, two products were compared using a two-period crossover design. One hundred twenty panelists participated in each study. A forced choice preference scale or a 9-point hedonic scale was used to obtain responses from various sensory attributes. In all studies, the estimates of carry-over effects were not significant at the 5% level. Transformation of hedonic scale data into preference dichotomy also gave estimates of carry-over effects which were not significant at the 5% level, but led to a loss of test sensitivity for detecting treatment differences. The authors recommend that all comparative crossover design studies in sensory evaluation be monitored for carry-over effects and that statistically determined sample size should be used to reduce the possibility of obtaining significant carry-over effects.     

The effects of adrenal and gonadal steroids and K+-canrenoate on the metabolism of aldosterone by rat liver microsomes

The synthesis of polar aldosterone metabolites by rat liver microsomes at physiological concentrations of aldosterone (21.5 nM), was markedly inhibited by progesterone, testosterone, corticosterone, K+-canrenoate and estradiol-17 beta. In contrast, corticosterone and estradiol-17 beta significantly increased the synthesis of reduced aldosterone metabolites by 8- and 15-fold respectively, the majority of which were 5 alpha-reduced products of aldosterone. In experiments at higher substrate (aldosterone) concentrations (20-200 microM) the synthesis of ring A-reduced aldosterone metabolites by liver microsomes followed Michaelis-Menten kinetics with a Km[app] for aldosterone of 160 microM and Vmax[app] of 12.2 nmoles/mg protein/5 min. In these experiments progesterone, testosterone and K+-canrenoate all competitively inhibited the synthesis of reduced metabolites with inhibition constants (Ki [app]) of 70, 85 and 55 microM respectively; however, corticosterone did not. In contrast, estradiol-17 beta increased the rate of synthesis of reduced products by 40%, lowering the Km[app] to 83 microM.     

Ontogeny of the Behavior of Strombus maculatus (Gastropoda: Strombidae)

The ontogeny of strombid behavior was studied by observing thebehavior of Strombus maculatus veligers collected from the planktonand reared past metamorphosis to adults, and by observing juvenilestrombids collected in the field. Complete adult modal actionpatterns (MAP's) associated with locomotion, feeding, and rightingof overturned shells are performed by S. maculatus juvenilesimmediately after metamorphosis. There are changes in the frequencyof the use of certain MAP's which are associated with variationsin shell shape and size. The unique strombid escape response to molluscivorous gastropods(Conns spp.) is not released until juvenile S. maculatus arethree weeks past metamorphosis and two millimeters in shelllength. At that stage, the complete response is released uponthe first encounter with a predator. Experience with a predatordoes not seem to lower the age or size criteria. During ontogeny there is a trend toward an increasing complexityof behavior which is paralleled by an increasing complexityof neural structure and general morphology. There are majorsteps in the ontogeny of strombid behavior which probably coincidewith neural and morphological stages.