Repellent response functions of the Trg and Tap chemoreceptors of Escherichia coli.

The chemoreceptors responsible for the repellent response of Escherichia coli to phenol were investigated. In the absence of all four known methyl-accepting chemoreceptors (Tar, Tsr, Trg, and Tap), cells showed no response to phenol. However, when Trg, which mediates the attractant response to ribose and galactose, was introduced via a plasmid, the cells acquired a repellent response to phenol. About 1 mM phenol induced a clear repellent response; this response was suppressed by 1 mM ribose. Thus, Trg mediates the repellent response to phenol. Mutant Trg proteins with altered sensing for ribose and galactose showed a normal response to phenol, indicating that the interaction site for phenol differs from that for the ribose- and galactose-binding proteins. Tap, which mediates the attractant response to dipeptides, mediated a weaker repellent response to phenol. Tsr, which mediates the attractant response to serine, mediated an even weaker response to phenol. Trg and Tap were also found to function as intracellular pH sensors. Upon a pH decrease, Trg mediated an attractant response, whereas Tap mediated a repellent response. These results indicate that all the receptors in E. coli have dual functions, mediating both attractant and repellent responses.     

Physicochemical studies of taste reception. V. Suppressive effect of salts on sugar response of the frog

The model membrane composed of a Millipore filter paper and the total lipids from bovine tongue epithelium or phosphatidylcholine from egg yolk simulated well the water response of a living taste cell. The water response observed with the model membrane adapted to various salt solutions was interpreted in terms of changes in electric potential at the membrane-solution interface, i.e. the water response was attributed to the e.m.f. change produced by diffusion of the electrolytes dissolved in (or adsorbed on) the membrane surface into the bulk solution.The water response of the frog tongue was also investigated by measuring the neural response of the glossopharyngeal nerve. The results obtained were consistent with the mechanism proposed in the present paper. The response of the frog to Ca²⁺ was examined under the condition where the water response was suppressed, and it was concluded that the water response of the frog is different from the response to Ca²⁺.     

The analysis of response similarity in single neurons of the goldfish olfactory bulb using amino-acids as odor stimuli

The response of goldfish olfactory bulb neurons to a range ofamino acid olfactory stimuli was recorded. The results showthat comparisons of response patterns at a single concentrationare inadequate to describe the similarity of response of thesystem to pairs of substances because response patterns changedwith concentration. For some pairs of stimuli, the similaritybetween response patterns was consistent at different concentrationsdespite the changes seen in the responses themselves. In thesecases the similarity of response appeared to reflect the degreeof similarity in chemical structure of the stimuli. Preliminaryevidence is presented that differences in response to differentamino acids are not simply due to differences in stimulatoryeffectiveness for a single receptor process.     

Immune response in dog 2 effect of dose of antigen on antibody production.

The primary antibody response of dogs and rabbits to both 'H' and 'O' antigens of Salmonella typhosa following intravenous injection with a formalin killed vaccine from 2.4 x 10(6) to 2.4 x 10(10) organisms/kg body weight was analysed. The animals were restimulated 80 days later with various vaccine concentrations. The lgM anti-'O' and lgG anti-'H' and 'O' antigens in the dogs, were significantly weaker in both primary and secondary response than the comparable rabbit group. Primary lgM anti-'H' response in the dog was found to be greater, equal, or less than that observed in the rabbit. A closer analysis of the primary response indicated that both animal species show the same latent period and doubling time in respect of anti-'H', and the differences observed are probably the result of the number of progenitor cells stimulated by the antigen. On the other hand the suppressed response of the dog to 'O'-antigen is the result of an overall weaker response of this animal to the antigen. The secondary anti-'H' lgM response was found to be greater than, equal to, or less than the primary response in the same animal. The significant inhibition of this response was observed in those animals which received a high primary dose of antigen.     

Seasonal peculiarities of female hormonal response of females to conspecific chemical signals of the male in two species of the genus Phodopus

Changes in diestrous female blood plasma progesterone, estradiol, and cortisol in response to odors of urine and midventral gland secretion (MVGS) of conspecific males during different seasons have been studied in the desert hamster (Phodopus roborowskii and Djungarian hamster (P. sungorus). In desert hamster females, a statistically significant (p ?? 0.05) increase in the plasma hormonal level was observed: for progesterone in response to conspecific male MGVS in all seasons except winter, and to conspecific male urine in spring and summer; for cortisol in response to male MVGS and urine in all seasons except spring; and for estradiol in response to male MGVS in autumn. Djungarian hamster females demonstrated a statistically significant increase in the plasma progesterone level in response to conspecific male MVGS and urine in winter and summer, and no response to the estradiol and cortisol level for both odors in all seasons. The results showed important differences in the physiological response to odors of conspecific males between females of two species of dwarf hamsters.     

Temporal dynamics of a T-cell mediated immune response in desert rodents

Immunocompetence, the general capacity of an individual host to mount an immune response against pathogens, is commonly assessed by the response to a challenge of the immune system by injection of phytohaemagglutinin (PHA). The response to PHA is commonly considered a reliable estimate of the T-cell mediated immune response. We investigated the temporal pattern of the PHA response in 10 rodent species from the Negev desert, Israel. We hypothesized that the temporal dynamics of the PHA response would differ among species with different natural patterns of flea parasitism. We injected PHA subcutaneously in the footpad of each rodent and measured its PHA response 6, 24 and 48 h after injection. Rodent species showed two types of PHA response. One type was rapid and characteristic of rodents that had either species-poor flea assemblages, or that are rarely attacked by fleas. This response peaked approximately 6 h after PHA injection. The second type of response was delayed and was typical of rodents that have either species-rich flea assemblages or high abundance and prevalence of fleas or both. Their response to PHA peaked 24 h after injection. Furthermore, rodents that responded promptly had a lower maximum response than rodents with a delayed response. Our results suggest the occurrence of a trade-off between intensity and latency of the PHA response and, therefore, the necessity to account for the relationship between maximum PHA response and time after injection when making interspecific comparisons of immunocompetence.     

Neurotransmission of autonomic components of aortic baroreceptor afferents in the NTS of awake rats

The effect of sequential blockade of N-methyl-D-aspartic acid (NMDA) receptors with DL-2-amino-5-phosphonopentanoic acid (AP-5) and non-NMDA receptors with 6,7-dinitroquinoxaline-2,3 dione (DNQX) in the nucleus tractus solitarii (NTS) on the cardiovascular responses to electrical stimulation (ES) of the aortic depressor nerve (ADN) was evaluated in awake rats. Two protocols were used. In protocol 1, bilateral microinjection of AP-5 into the NTS (n = 7) reduced the hypotensive response to ES of the ADN; subsequent microinjection of DNQX produced additional reduction in this response. AP-5 reduced the bradycardic response, and DNQX almost abolished this response. In protocol 2, bilateral microinjection of DNQX into the NTS (n = 6) reduced the hypotensive response, and subsequent microinjection of AP-5 significantly reduced this response. DNQX produced a significant reduction in bradycardic response, and AP-5 abolished this response. The data indicate that processing of the parasympathetic component of the NTS aortic baroreceptor afferents is mediated by both NMDA and non-NMDA receptors, whereas processing of the sympathoinhibitory component seems to be only partially mediated by ionotropic receptors.     

Mechanism of rapid-phase insulin response to elevation of portal glucose concentration

The hepatoportal region is important for glucose sensing; however, the relationship between the hepatoportal glucose-sensing system and the postprandial rapid phase of the insulin response has been unclear. We examined whether a rapid-phase insulin response to low amounts of intraportal glucose infusion would occur, compared that with the response to intrajugular glucose infusion in conscious rats, and assessed whether this sensing system was associated with autonomic nerve activity. The increases in plasma glucose concentration did not differ between the two infusions at 3 min, but the rapid-phase insulin response was detected only in the intraportal infusion. A sharp and rapid insulin response was observed at 3 min after intraportal infusion of a small amount of glucose but not after intrajugular infusion. Furthermore, this insulin response was also induced by intraportal fructose infusion but not by nonmetabolizable sugars. The rapid-phase insulin response at 3 min during intraportal infusion did not differ between rats that had undergone hepatic vagotomy or chemical sympathectomy with 6-hydroxydopamine compared with control rats, but this response disappeared in rats that had undergone chemical vagotomy with atropine. We conclude that the elevation of glucose concentration in the hepatoportal region induced afferent signals from undetectable sensors and that these signals stimulate pancreas to induce the rapid-phase insulin response via cholinergic nerve action.     

Physicochemical studies of taste reception. III. Interpretation of the water response in taste reception

The model membrane composed of a Millipore filter paper and the total lipids from bovine tongue epithelium or phosphatidylcholine from egg yolk simulated well the water response of a living taste cell. The water response observed with the model membrane adapted to various salt solutions was interpreted in terms of changes in electric potential at the membrane-solution interface, i.e. the water response was attributed to the e.m.f. change produced by diffusion of the electrolytes dissolved in (or adsorbed on) the membrane surface into the bulk solution.The water response of the frog tongue was also investigated by measuring the neural response of the glossopharyngeal nerve. The results obtained were consistent with the mechanism proposed in the present paper. The response of the frog to Ca²⁺ was examined under the condition where the water response was suppressed, and it was concluded that the water response of the frog is different from the response to Ca²⁺.     

Immunology of Dermatophytosis

The immune response to infection by dermatophytes ranges from a non-specific host mechanism to a humoral and cell-mediated immune response. The currently accepted view is that a cell-mediated immune response is responsible for the control of dermatophytosis. Indeed, some individuals develop a chronic or recurrent infection mediated by the suppression of a cell-mediated immune response. The immune response to Trichophyton is unusual in that this fungus can elicit both immediate hypersensitivity (IH) and delayed-type hypersensitivity (DTH) in different individuals when they are submitted to a skin test reaction. Understanding the nature and function of the immune response to dermatophytes is an exciting challenge that might lead to novel approaches in the treatment and immunological prophylaxis of dermatophytosis.     

植物根向水性反应研究进展

根的向水性生长是指植物通过根尖感知土壤中的水分梯度, 向着水势较高区域生长的一种生物学特性, 这一特性对植物从土壤中有效获取水分极为重要。植物向水性研究已成为当前植物学研究的热点领域, 但对于调控这一生理反应的分子机制仍知之甚少。目前的研究表明, MIZ1和GNOM作为植物向水性反应的重要调节因子, 正向调控植物根的向水性生长。此外, 植物激素、光、ROS及钙离子也参与调节植物的向水性反应。该文将从向水性的研究历史、调控基因以及内外因素等方面进行阐述, 便于读者全面了解植物向水性研究进展, 以期为向水性研究提供新思路。     

Kinetics of activation of a PKC-regulated epithelial calcium channel

The kinetics of calcium entry through regulated calcium channels in cultured renal proximal tubule cells was studied with Fura-2 fluorescence ratio imaging in single cells. The calcium entry was activated by 1-oleoyl-2-acetyl-sn-glycerol (OAG) and phorbol-12-myristat-13-acetate (PMA), similar to that observed for activation by osmo-mechanical stress. OAG (2.5 microM) or PMA (0.5 microM) activated calcium entry is characterized by a significant latency between agonist application and the response, whereas the effect of osmo-mechanical stress was immediate. This pre-response latency was 260 +/- 70s with OAG stimulation and 79.2 +/- 17.3s with PMA stimulation. Once a cell responds, the intracellular calcium level reaches a peak value within seconds. The cell response to agonist is independent of the response of neighboring cells. The response kinetics resembles those of the calcium sparks in excitable cells, except the response is much slower. In all cases, the response appears to be an all-or-none event, that is characteristics of an elementary binary switch. It is suggested that the binary response and the lack of coordinated response of calcium entry in single cells results from limited availability of the calcium channels and/or PKC that activates the channel. The experimental data could be fit to a single binary response mathematical model assuming each response reflected an elementary event of a single channel opening or a co-ordinated opening of a cluster of several channels.     

Experimental Predictions of The Functional Response of A Freshwater Fish

The functional response is the relationship between the feeding rate of an animal and its food density. It is reliant on two basic parameters; the volume searched for prey per unit time (searching rate) and the time taken to consume each prey item (handling time). As fish functional responses can be difficult to determine directly, it may be more feasible to measure their underlying behavioural parameters in controlled conditions and use these to predict the functional response. Here, we tested how accurately a Type II functional response model predicted the observed functional response of roach Rutilus rutilus, a visually foraging fish, and compared it with Type I functional response. Foraging experiments were performed by exposing fish in tank aquaria to a range of food densities, with their response captured using a two‐camera videography system. This system was validated and was able to accurately measure fish behaviour in the aquaria, and enabled estimates of fish reaction distance, swimming speed (from which searching rate was calculated) and handling time to be measured. The parameterised Type II functional response model accurately predicted the observed functional response and was superior to the Type I model. These outputs suggest it will be possible to accurately measure behavioural parameters in other animal species and use these to predict the functional response in situations where it cannot be observed directly.     

Effect of experimental information and emotional stress on the primary immune response of different strains of mice

Experimentally induced information and emotional stress in mice, resulting from the congestion of the animals, has been shown to cause the suppression of primary immune response to sheep red blood cells (SRBC) in males. The comparative analysis of the character of changes in immune response to SRBC in mice of various strains differing in the intensity of immune response to this antigen is presented. The analysis shows that only prolonged and strong emotional stress produces a considerable immunological defect in CBA mice with highly pronounced response to SRBC. In C57BL mice, normally showing weak response to SRBC, considerable immunodeficiency is observed in cases of both prolonged and comparatively short-term stress.     

A meta-analysis of community response predictability to anthropogenic disturbances

Abstract Disturbances often lead to changes in average values of community properties; however, disturbances can also affect the predictability of a community's response. We performed a meta-analysis to determine how response predictability, defined as among-replicate variance in diversity and community abundance, is affected by species removals, species invasions, nutrient addition, temperature increase, and habitat loss/fragmentation, and we further determined whether response predictability differed according to habitat and trophic role. Species removals and nutrient addition decreased response predictability, while species invasions increased response predictability. In aquatic habitats, disturbances generally led to a decrease in response predictability, whereas terrestrial habitats showed no overall change in response predictability, suggesting that differences in food web and ecosystem structure affect how communities respond to disturbance. Producers were also more likely to show decreases in response predictability, particularly following species removals, highlighting widespread destabilizing effects of species loss at the producer level. Overall, our results show that whether disturbances cause changes in response predictability is highly contingent on disturbance type, habitat, and trophic role. The nature of changes in response predictability-for example, strong decreases following species invasions and increases following species removals-will likely play a major role in how communities recover from disturbance.     

Effects of morphine on hexamethonium-sensitive and -resistant excitatory responses of stomach to stimulation of vagal trunk in cats

Electrical stimulation of the vagal trunk with 10 Hz in frequency, 3 ms in duration and 15 volt in intensity for 10 s in cats produced an excitatory response of the stomach and the response was composed of two phases, an initial rapid excitation during stimulation period and the late multi-peak response after stimulation period. The initial response was inhibited by the administrations of hexamethonium (10 mg/kg, i.v.) and atropine (100 micrograms/kg, i.v.). The late response was not inhibited by hexamethonium but was inhibited by atropine (100 micrograms/kg, i.v.). The hexamethonium-sensitive initial excitation was not affected by the administration of morphine and gamma-aminobutyric acid (GABA). On the other hand, the hexamethonium-resistant late response was attenuated by the treatment with morphine (1 to 10 mg/kg, i.v.) and GABA (100 to 500 micrograms/kg, i.v.). Such inhibitory actions of morphine and GABA on the late response were antagonized by picrotoxin. From these results, it was concluded that morphine might inhibit specifically the hexamethonium-resistant late excitatory response of the stomach without affecting the hexamethonium-sensitive initial excitatory response and the inhibitory effect of morphine on the late response of stomach might be due to action of GABA released from the intramural neurons of gastric walls in cats.     

Effects of bile acids on expression of the human apical sodium dependent bile acid transporter gene

Using a luciferase reporter assay in both LMH cells and Caco2 cells we found that certain bile acids including unconjugated deoxycholic and others transactivated the ileal apical sodium-dependent bile acid transporter (ASBT) at concentrations ranging from 20 to 300 microM. Confirming this effect, addition of deoxycholic acid to fresh human ileal biopsies caused an approximate 40% increase in endogenous ASBT mRNA production. Promoter deletion analysis indicated the effect of bile acids was mediated by a response element located in the downstream half of the 5'-UTR, a region known to contain a retinoic acid (RXR/RAR) response element and an activated protein-1 (AP-1) response element. Site-directed mutagenesis of the RAR/RXR response element actually enhanced response to deoxycholic acid. Site-directed mutagenesis of the downstream AP-1 response element reduced activation by deoxycholic acid while deletion of this response element completely eliminated this response. The epidermal growth factor (EGF) receptor inhibitor, AG1478, completely eliminated the response to bile acid while the mitogen-activated protein extracellular signal-regulated kinase cascade (MEK) inhibitor, U0126, partially inhibited the response to bile acid. These studies demonstrate that certain bile acids stimulate ASBT gene expression acting on the down-stream AP-1 response element via the EGF receptor and MEK cascade.