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61.
Valic Zoran; Vidruk Edward H.; Ruble Stephen B.; Buckwalter John B.; Clifford Philip S. 《Journal of applied physiology》2001,90(1):23-28
To investigate whether efferent parasympathetic fibers to the trachealsmooth muscle course through the pararecurrent nerve rather than therecurrent or the superior laryngeal nerve, we stimulated all threenerves in anesthetized dogs. We also recorded the pararecurrentnerve activity response to bronchoconstrictor stimuli and compared itwith pressure changes inside a saline-filled cuff of an endotrachealtube. Electrical stimulation (30 s, 100 Hz, 0.1 ms, 10 mA) increasedtracheal cuff pressure by 21.0 ± 3.2 and 1.3 ± 0.7 cmH2O for the pararecurrent and the recurrent laryngealnerve, respectively. Stimulation of the superior laryngeal nerveincreased tracheal cuff pressure before, but not after, sectioning ofthe ramus anastomoticus, which connects it to the pararecurrent nerve.Intravenous administration of sodium cyanide increased pararecurrentnerve activity by 208 ± 51% and tracheal cuff pressure by14.4 ± 3.5 cmH2O. Elevation of end-tidalPCO2 to 50 Torr increased pararecurrent nerveactivity by 49 ± 19% and tracheal cuff pressure by 8.4 ± 3.6 cmH2O. Further elevation to 60 Torr increasedpararecurrent nerve activity by 101 ± 33% and tracheal cuffpressure by 11.3 ± 2.9 cmH2O. These results lead usto the conclusion that parasympathetic efferent fibers reach the smoothmuscle of the canine trachea via the pararecurrent nerve. 相似文献
62.
Stephen G Bennett James A Comer Heather M Smith James P Webb 《Journal of vector ecology》2007,32(2):198-201
We detected antibodies reactive with Rickettsia akari, the etiologic agent of rickettsialpox in humans and in 83 of 359 (23%) rodents belonging to several species, collected in Orange County, CA. Reciprocal antibody titers >1:16 to R. akari were detected in native mice and rats (Peromyscus maniculatus, P. eremicus, and Neotoma fuscipes) and in Old World mice and rats (Mus musculus, Rattus rattus, and R. norvegicus), representing the first time that antibodies reactive with this agent have been detected in four of these species and the first report of these antibodies in rodents and humans west of the Mississippi River. We then tested serum samples from individuals who used a free clinic in downtown Los Angeles and found that 25 of 299 (8%) of these individuals had antibody titers >1:64 to R. akari. Serologic evidence suggested that R. akari or a closely related rickettsia is prevalent among several rodent species at these localities and that infection spills over into certain segments of the human population. Isolation or molecular confirmation of the agent is needed to conclusively state that R. akari is the etiologic agent infecting these rodents. 相似文献
63.
Ectopic Expression of the Tetratricopeptide Repeat Domain of SPINDLY Causes Defects in Gibberellin Response 下载免费PDF全文
The SPINDLY (SPY) protein of Arabidopsis is a negative regulator of gibberellin (GA) response. The SPY protein has 10 copies of the tetratricopeptide repeat (TPR) at the N terminus. TPR motifs function as protein-protein interaction domains. Several spy alleles are affected only in the TPR region suggesting that protein-protein interactions mediated by this domain are important for proper GA signaling. We have used a reverse genetics approach to further investigate the role of the TPR domain. The TPR domain of SPY was overexpressed in wild-type, gai, and spy plants. Expression of the TPR domain alone is not sufficient to rescue spy mutants. Expression of the TPR domain in a wild-type background produces phenotypes similar to those caused by loss-of-function spy mutants including resistance to GA biosynthesis inhibitors, short hypocotyl length, and early flowering. The dwarfing of the floral shoot internodes caused by the gai mutation was suppressed by expression of the TRP domain. Expression of the TPR domain had no effect on the abundance of endogenous SPY mRNA. The TPR domain was found to interact with SPY both in vitro and in yeast two-hybrid assays. These data indicate that the TPR domain of SPY can participate in protein-protein interactions and that these interactions are important for the proper functioning of SPY. 相似文献
64.
65.
Species-specific algal responses to zooplankton: experimental and field observations in three nutrient-limited lakes 总被引:3,自引:0,他引:3
Elser James J.; Goff Nancy C.; MacKay Neil A.; Amand Ann L.St.; Elser Monica M.; Carpenter Stephen R. 《Journal of plankton research》1987,9(4):699-717
A series of 4-day manipulations of zooplankton biomass and nutrientavailability was performed in enclosures in three lakes to determinespecies-specific algal responses to herbivory and nutrient enrichment.Algal performance in enclosures was compared to the relationshipsbetween weekly algal growth rates and the zooplankton in situ.When in situ growth rates were significant functions of zooplanktonbiomass, the responses were generally consistent with responsesin the enclosure experiments. The importance of both nutrientsand zooplankton in mediating algal growth was demonstrated bynumerous observations: strong algal community response to enrichment,unimodal or positive responses of certain algal taxa to zooplanktonbiomass, differences in degree of nutrient limitation amongthe algal response types, lack of nutrient limitation of non-grazedalgal taxa and a preponderance of taxa with no net responseto increasing zooplankton biomass. Variation in the zooplanktoncommunity may be the largest source of variability in nutrientsupply rate during summer in stratified lakes, and causes substationalvariability in the algae. Algae responded more strongly to changesin zooplankton composition than to changes in zooplankton biomass.We conclude that, due to the close coupling of phytoplanktonand zooplankton communities in these nutrient-limited lakes,major compositional changes in the zooplankton have greatereffects on the algae than do changes in biomass of grazers alreadypresent.
1Present address: Division of Environmental Studies, Universityof California, Davis, CA 95616, USA
2Present address: Division of Biological Sciences, Universityof California, Davis, CA 95616, USA 相似文献
66.
Nigel J. Fuller Dorothy M. Stirling Stephen Dunnett Gavin P. Reynolds Margaret Ashwell 《Bioscience reports》1987,7(2):121-127
The effects of reducing brain serotonin (5-HT) levels by means of intracerebral-ventricular injections of the tryptophan antagonist p-chlorophenylalanine (PCPA) were investigated in male rats. Six days after the operation, PCPA-treated rats, either fedad libitum or pair-fed to the food intake of control rats, showed decreased thermogenic activity and capacity in their interscapular brown adipose tissue (BAT) and also increased fat storage in their white adipose tissue (WAT). These results indicate that serotonergic synapses might play a regulatory role in the sympathetic control of BAT thermogenesis and in the rate of WAT deposition (by an as yet unidentified mechanism), in addition to their well established role in controlling food intake. 相似文献
67.
Stephen Chan James Orenberg Noam Lahav 《Origins of life and evolution of the biosphere》1987,17(2):121-134
The adsorption of 5-AMP and 5-CMP was studied in saturated solutions of several soluble mineral salts (NaCl, Na2SO4, MgCl2·6H2O, MgSO4·7H2O, CaCl2·2H2O, CaSO4·2H2O, SrCl2·6H2O, SrSO4, and ZnSO4·7H2O) as a function of pH, ionic strength, and surface area of the solid salt. The adsorption shows a pH dependence; this can be correlated with the charge on the nucleotide molecule which is determined by the state of protonation of the N-1 nitrogen of 5-AMP or N-3 nitrogen of 5-CMP and the phosphate oxygens. The adsorption which results from the binding between the nucleotide molecule and the salt surface is proposed as being due to electrostatic forces. It was concluded that the adsorption was reversible in nature. The adsorption shows a strong dependence upon ionic strength and decreases with increasing ionic strength. Surface area is shown to be an important factor in evaluating and comparing the magnitude of adsorption of nucleotides onto various mineral salts. The implications of the results of the study are discussed in terms of the importance of soluble mineral salts as adsorption sites in the characterization of the adsorption reactions of an adsorbed template in biogeochemical cycles. 相似文献
68.
Calcium-Dependent Release of Tyrosine in Brain Elicited by Stimulation of Neuropeptide Receptors 总被引:1,自引:1,他引:0
We sought to establish whether the endogenous opiate-receptor agonist Met-enkephalin (m-ENK) selectively modulates the release of endogenous tyrosine (Tyr) from brain slices prepared from the corpus striatum (CS). Amino acids (AAs) released from slices of CS and, for comparison, cerebral cortex (Cx) were measured by HPLC. Incubation of slices with m-ENK (1-10 microM) increased the basal release of Tyr (up to 293% of control) from CS, but not Cx, whereas other nonneurotransmitter AAs, phenylalanine (Phe) and valine (Val), were unchanged. The release of the putative neurotransmitter AAs glutamate (Glu), taurine (Tau), and glycine (Gly) were similarly increased by 50-150% with m-ENK in slices of CS, but not Cx. The enhanced release of AAs by m-ENK was prevented by removal of extracellular Ca2+ or by preincubation with the opiate receptor antagonist naloxone. Neuronal depolarization by potassium (5-55 mM) in the presence of Ca2+ did not affect the release of Tyr, whereas release of neurotransmitter AAs such as gamma-aminobutyric acid (GABA) were markedly increased. The increase in basal Tyr release by m-ENK was not the result of a decreased uptake of Tyr. Relative to slices, the basal release of Tyr, Phe, and Val from a synaptosomal (P2) preparation of CS was small (8-51%) compared to that of GABA, Gly, Glu, and Tau (49-123%). Nonetheless, m-ENK (10 microM) markedly increased the release of Tyr (to 833%), but not Glu, Gly, and Tau from the P2 fraction.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
69.
To study the effects of volume overload and renal failure on plasma levels of immunoreactive atrial natriuretic hormone (IR-ANH), we measured levels of this hormone in normal subjects, in patients with advanced chronic renal failure (CRF) with and without clinically evident volume overload, and in patients with end-stage renal disease (ESRD) treated with chronic hemodialysis. The levels were 13 +/- 2 pmol/l in normal volunteers, 77 +/- 24 pmol/l in patients with CRF without volume overload, and 219 +/- 50 pmol/l in patients with CRF and clinically evident volume overload (analysis of variance, p less than 0.001, alpha = 0.05 compared to normals). In patients with ESRD, the levels of IR-ANH were 145 +/- 46 pmol/l before dialysis and decreased to 87 +/- 31 after dialysis (p less than 0.025). No correlation was found between the decrease in IR-ANH levels and the decrease in weight during dialysis. A significant positive correlation was found between the IR-ANH levels and blood urea nitrogen in patients with CRF (r = 0.658, p less than 0.01). Volume overload appears to be the most important stimulatory factor for ANH secretion in renal failure patients but other mechanisms, especially a decrease in metabolic clearance, may also contribute to elevated plasma levels. The increased secretion of ANH in patients with renal failure may be an important adaptive response to volume overload and hypertension. 相似文献
70.
Summary Mutations or herbicides which inhibit the accumulation of carotenoid pigments in higher plants also result in the arrest of chloroplast development at a very early stage. The cause is extensive photooxidative damage within the chloroplast in the absence of protective carotenoids. Because the extent of photooxidation is dependent upon light intensity, normal chloroplast development can occur when carotenoid-deficient seedlings are grown in very dim light. Normal accumulation of chloroplastic and cytosolic mRNAs encoding chloroplast proteins proceeds only under permissive dim light conditions. Illumination with higher intensity light causes rapid chlorophyll photooxidation and the loss of two cytosolic mRNAs coding for proteins destined for the chloroplast, but does not affect another light-regulated cytosolic mRNA encoding a cytosolic protein. This experimental system may have uncovered a mechanism which coordinates the expression of genes in different cellular compartments.Abbreviations LHCP
light-harvesting chlorophyll a/b protein
- SSu
small subunit
- RuBP
fibulose 1,5-bisphoshate
- PEP
phosphoenolpyruvate 相似文献