Capsaicin-evoked bradycardia in anesthetized guinea pigs is mediated by endogenous tachykinins

The present study was done to characterize the effects of endogenous tachykinins on heart rate in urethane-anesthetized guinea pigs. Intravenous injection of capsaicin (32 nmol/kg) was used to evoke release of tachykinins and calcitonin gene-related peptide (CGRP) from cardiac sensory nerve fibers. Such injections caused a brief decrease in heart rate (− 37 ± 7 beats/min, n = 6) that was followed by a more prolonged increase (+ 44 ± 10 beats/min). Blood pressure was lowered by − 11 ± 2 mmHg. Bilateral vagotomy did not affect the chronotropic or depressor responses to capsaicin, but atropine (1 µmol/kg) nearly abolished the bradycardic response (− 8 ± 3 beats/min, n = 7). Combined blockade of NK₂ and NK₃ receptors, with SR48968 and SR14801 respectively, also caused a significant reduction of capsaicin-evoked bradycardia (− 14 ± 3 beats/min, n = 4) but did not affect bradycardia evoked by vagal nerve stimulation. Blockade of CGRP receptors eliminated capsaicin-evoked tachycardia and prolonged the capsaicin-evoked bradycardia. These findings suggest that capsaicin-evoked bradycardia in the anesthetized guinea pig is mediated by tachykinins that stimulate cardiac cholinergic neurons. This effect appears to be truncated by the positive chronotropic action of CGRP that is also released from cardiac afferents by capsaicin.     

Multiple effects of brood parasitism reduce the reproductive success of prothonotary warblers, Protonotaria citrea

Avian brood parasitism often has multiple negative effects on the reproductive success of the host. Most studies have focused on one or two of these effects, but rarely have they all been studied simultaneously for one species. I studied prothonotary warblers to quantify the effects of different intensities of (i.e. multiple) brood parasitism by brown-headed cowbirds, Molothrus ater, on the production of host and cowbird young and on the between-year returns of adult warblers. Host clutch size decreased with an increase in the number of cowbird eggs laid in nests. The hatching success of warbler and cowbird eggs decreased with increased cowbird eggs in nests, but was always higher for cowbird eggs than warbler eggs. The survival of warbler nestlings, but not cowbird nestlings, decreased with increased cowbird nestlings in the brood. An increase in the number of cowbird nestlings in broods resulted in a reduction in the average mass of warbler nestlings but not cowbird nestlings. The number of cowbird eggs or nestlings present did not affect nest predation, and the fledging of cowbirds did not influence the renesting interval of female warblers. In addition, the between-year returns of adult warblers were not negatively affected by brood parasitism. Decreased hatching success and nestling survival reduced the reproductive output of the warblers the most. These effects were substantial and appear to favour the evolution of behavioural responses that reduce the effects of brood parasitism on prothonotary warblers. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour      

Effect of heat–moisture treatment on the structure and physicochemical properties of tuber and root starches

Starch from tubers potato (Solanum tuberosum), taro (Alocassia indica), new cocoyam (Xanthosoma sagitifolium), true yam (Dioscorea alata), and root cassava, (Manihot esculenta) crops was isolated and its morphology, composition and physicochemical properties were investigated before and after heat–moisture treatment (HMT) (100 °C, for 10 h at a moisture content of 30%). Native starch granules were round to oval to polygonal with smooth surfaces. The granule size (diameter) ranged from 3.0 to 110 μm.The total amylose content ranged from 22.4 to 29.3%, of which 10.1–15.5% was complexed by native lipid. The phosphorus content ranged from 0.01 to 0.1%. The X-ray pattern of potato and true yam was of the ‘B’-type. Whereas, that of new cocoyam and taro was of the ‘A’-type. Cassava exhibited a mixed ‘A+B’-type X-ray pattern. The relative crystallinity, swelling factor (SF), amylose leaching (AML), gelatinization temperature range and the enthalpy of gelatinization of the native starches ranged from 30 to 46, 22 to 54, 5 to 23%, 13 to 19 °C and 12 to 18 J/g, respectively. Susceptibility of native starches towards hydrolysis by 2.2N HCl and porcine pancreatic -amylase were 60–86% (after 12 days), and 4–62% (after 72 h), respectively. Retrogradation was most pronounced in the B-type starches. Granule morphology remained unchanged after HMT. The X-ray pattern of the B-type starches was altered (B→A+B) on HMT. However, that of the other starches remained unchanged. HMT decreased SF, AML, gelatinization enthalpy and susceptibility towards acid hydrolysis, but increased gelatinization temperatures and enzyme susceptibility. Extent of retrogradation and relative crystallinity decreased on HMT of true yam and potato starches, but remained unchanged in the other starches. The foregoing data showed that changes in physicochemical properties on HMT are influenced by the interplay of crystallite disruption, starch chain associations and disruption of double helices in the amorphous regions.     

Glutamate transprot in rat kidney mitochondria

The quantitative characteristics of [U-14C]glutamate transport were determined in rotenone-inhibited energized rat kidney mitochondria at pH 7.0 and 28 degrees C. Glutamate efflux was observed to be first order with respect to matrix glutamate with a rate constant of 0.457 min-1. Uptake kinetic studies indicated that the Km of external glutamate was 1.4 mM and the Vmax 3.2 nmol/mg X min. These kinetic values were found to be unchanged at pH 6.6 or in mitochondria obtained from kidneys of chronically acidotic rats. Parallel studies of glutamate deamination were performed in which mitochondria were incubated in state 3, state 4, and with carbonyl cyanide p-trifluoromethoxyphenylhydrazone, in the presence of malonate. The oxidative deamination of glutamate determined with 1 and 10 mM glutamate never exceeded the simultaneously measured rate of glutamate transport. No glutamate was detectable within the mitochondrial matrix under the conditions of these metabolic experiments. The studies indicate that the glutamate hydroxyl transporter is quite slow and rate limiting for the oxidative deamination of external glutamate in rat kidney mitochondria.     

Decrease in adhesion of cells cultured in polyunsaturated fatty acids

The addition of long chain unsaturated fatty acids (linoleic, linolenic and arachidonic acids) to BHK cells reduces the cell to substrate adhesion, causes morphological changes and alters the cellular growth properties. The new characteristics are similar to those of transformed cells. The data indicate that the effects are probably due to actual changes in the surface membrane lipids and not due to prostaglandin synthesis.     

Simultaneous Comparisons of Multiple Treatments to Two (or More) Control

DUNNETT (1955) developed a procedure simultaneously comparing k treatments to one control with an exact overall type I error of α when all sampling distributions are normal. Sometimes it is desirable to compare k treatments to m≧2 controls, in particular to two controls. For instance, several new therapies (e.g., pain relievers) could be compared to two standard therapies (e.g., Aspirin and Tylenol). Alternatively, a standard therapy could be very expensive, difficult to apply and/or have bad side effects, making it useful to compare each new therapy to both standard therapy and no therapy (Placebo). Dunnett's method is expanded here to give comparisons of mean values for k treatments to mean values for m≧2 controls at an exact overall type I error of α when all sampling distributions are normal. Tabled values needed to make exact simultaneous comparisons at α = .05 are given for m = 2. An application is made to an example from the literature.