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81.
82.
Detached leaves of Bryophyllum fedtschenkoi Hamet et Perrier kept in normal air show a single period of net CO2 fixation on transfer to constant darkness at temperatures in the range 0–25 °C. The duration of this initial fixation period is largely independent of temperature in the range 5–20 °C, but lengthens very markedly at temperatures below 4 °C, and is reduced at temperatures above 25 °C. The onset of net fixation of CO2 on transfer of leaves to constant darkness is immediate at low temperatures, but is delayed as the temperature is increased. The ambient temperature also determines whether or not a circadian rhythm of CO2 exchange occurs. The rhythm begins to appear at about 20 °C, is most evident at 30 °C and becomes less distinct at 35 °C. The occurrence of a distinct circadian rhythm in CO2 output at 30° C in the absence of a detectable rhythm in PEPCase kinase activity shows that the kinase rhythm is not a mandatory requirement for the rhythm of PEPCase activity. However, when it occurs, the kinase rhythm undoubtedly amplifies the PEPCase rhythm.Abbreviation PEPCase
phosphoenolpyruvate carboxylase
We thank the Agricultural and Food Research Council for financial support for this work. 相似文献
83.
Zfy1 is a mouse Y chromosomal gene encoding a zincfinger protein which is thought to have some function during spermatogenesis. Here we show that, when introduced into tissue culture cells, Zfy1 is targeted to the nucleus. Two independent signals are present within the protein for nuclear localization. This nuclear Zfy1 protein is able to bind strongly to DNA-cellulose and, using site-selection assays, we have identified specific Zfy1 DNA binding sites. Taken together these results suggest that Zfy1 is a nuclear-located sequence-specific DNA binding protein which functions during spermatogenesis. 相似文献
84.
Joan E. Kuster Mary H. Guarnieri Jeffrey G. Ault Lorraine Flaherty Pamela J. Swiatek 《Mammalian genome》1997,8(9):673-681
The laminin-5 molecule functions in the attachment of various epithelia to basement membranes. Mutations in the laminin-5-coding
genes have been associated with Herlitz junctional epidermolysis bullosa (HJEB), a severe and often lethal blistering disease
of humans. Here we report the characterization of a spontaneous mouse mutant with an autosomal recessive blistering disease.
These mice exhibit sub-epithelial blisters of the skin and mucosal surfaces and abnormal hemidesmosomes lacking sub-basal
dense plates. By linkage analysis the genetic defect was localized to a 2-cM region on distal Chromosome (Chr) 1 where a laminin-5
subunit gene, LamB3, was previously localized. LamB3 mRNA and laminin-5 protein were undetectable by Northern blot analysis and immunohistochemical methods, respectively. DNA
sequence analysis indicated that the LamB3 genetic defect resulted from disruption of the coding sequence by insertion of an intracisternal-A particle (IAP) at an exon/intron
junction. These findings suggest a role for laminin-5 in hemidesmosome formation and indicate that the LamB3
IAP
mutant is a useful mouse model for HJEB.
Received: 27 March 1997 / Accepted: 14 May 1997 相似文献
85.
Roemmich James N.; Clark Pamela A.; Weltman Arthur; Rogol Alan D. 《Journal of applied physiology》1997,83(3):927-935
Roemmich, James N., Pamela A. Clark, Arthur Weltman, andAlan D. Rogol. Alterations in growth and body composition duringpuberty. I. Comparing multicompartment body composition models.J. Appl. Physiol. 83(3): 927-935, 1997.A four-compartment (4C) model of body composition was used as acriterion to determine the accuracy of three-compartment (3C) andtwo-compartment (2C) models to estimate percent body fat (%BF) inprepubertal and pubertal boys (genital I & II,n = 17; genital III & IV,n = 7) and girls (breast I & II, n = 8; breast III & IV,n = 15). The 3C water-density (3C-H2O) and 3C mineral-densitymodels, dual-energy X-ray absorptiometry, the Lohman age-adjustedequations, the Slaughter et al. skinfold equations, and the Houtkooperet al. and Boileau bioelectrical impedance equations wereevaluated. Agreement with the 4C model increased with thenumber of compartments (i.e., body water, bone mineral) measured.Except for the 3C-H2O model, thelimits of agreement were large and did not perform well forindividuals. The mean %BF by dual-energy X-ray absorptiometry (23.6%)was greater than that of the criterion 4C method (21.7%).For the field methods, the Slaughter et al. skinfold equationsperformed better than did the Houtkooper et al. and Boileaubioimpedance equations. The hydration of the fat-free mass decreased(genital I & II = 75.7%, genital III & IV = 74.8%, breast I & II = 75.5%, breast III & IV = 74.4%) and the mineral content increased(genital I & II = 4.9%, genital III & IV = 5.0%, breast I & II = 5.1%, breast III & IV = 5.7%) with maturation. The densityof the fat-free mass also increased (genital I & II = 1.084 g/ml,genital III & IV = 1.087 g/ml, breast I & II = 1.086 g/ml, breast III & IV = 1.091 g/ml) with maturation. All of the models reduced the %BF overprediction of the Siri 2C model, but only the 4C and3C-H2O models should be used ascriterion methods for body composition validation in children andadolescents. 相似文献
86.
Ventilation and metabolism among rat strains 总被引:3,自引:0,他引:3
Strohl Kingman P.; Thomas Agnes J.; St. Jean Pamela; Schlenker Evelyn H.; Koletsky Richard J.; Schork Nicholas J. 《Journal of applied physiology》1997,82(1):317-323
Strohl, Kingman P., Agnes J. Thomas, Pamela St. Jean, EvelynH. Schlenker, Richard J. Koletsky, and Nicholas J. Schork. Ventilation and metabolism among rat strains. J. Appl. Physiol. 82(1): 317-323, 1997.We examinedventilation and metabolism in four rat strains with variation in traitsfor body weight and/or blood pressure regulation.Sprague-Dawley [SD; 8 males (M), 8 females (F)], BrownNorway (BN; 10 M, 11 F), and Zucker (Z; 11 M, 12 F) rats were comparedwith Koletsky (K; 11 M, 11 F) rats. With the use of noninvasiveplethysmography, frequency, tidal volume, minute ventilation(E),O2 consumption, andCO2 production were derived atrest during normoxia (room air) and during the 5th minute of exposureto each of the following: hyperoxia (100% O2), hypoxia (10%O2-balanceN2), and hypercapnia (7%CO2-balance O2). Statistical methods probedfor strain and sex effects, with covariant analysis by body weight,length, and body mass. During resting breathing, strain effects werefound with respect to both frequency (BN, Z > K, SD) and tidal volume(SD > BN, Z) but not to E. Sexinfluenced frequency (F > M) alone. Z rats had higher values forO2 consumption,CO2 production, and respiratoryquotient than the other three strains, with no independent effect bysex. During hyperoxia, frequency was greater in BN and Z than in SD orK rats; SD rats had a larger tidal volume than BN or Z rats; Z rats hada greater E than K rats; and M had alarger tidal volume than F. Strain differences persisted duringhypercapnia, with Z rats exhibiting the highest frequency andE values. During hypoxic exposure,strain effects were found to influenceE (SD > K, Z), frequency (BN > K), and tidal volume (SD > BN, K, Z). Body mass was only amodest predictor of E during normoxia, of both E and tidal volume withhypoxia, hypercapnia, or hyperoxia, and of frequency duringhypercapnia. We conclude that strain of rats, more than their body massor sex, has major and different influences on metabolism, the patternand level of ventilation during air breathing, and ventilation duringacute exposure to hypercapnia or hypoxia. 相似文献
87.
Pamela S. Soltis Gregory M. Plunkett Stephen J. Novak Douglas E. Soltis 《American journal of botany》1995,82(10):1329-1341
Genetic diversity in the introduced diploids Tragopogon dubius, T. porrifolius, and T. pratensis and their neoallotetraploid derivatives T. mirus and T. miscellus was estimated to assess the numbers of recurrent, independent origins of the two tetraploid species in the Palouse region of eastern Washington and adjacent Idaho. These tetraploid species arose in this region, probably within the past 50–60 yr, and provide one of the best models for the study of polyploidy in plants. The parental species of both T. mirus and T. miscellus have been well documented, and each tetraploid species has apparently formed multiple times. However, a recent survey of the distributions of these allotetraploids revealed that both tetraploid species have expanded their ranges considerably during the past 50 yr, and several new populations of each species were discovered. Therefore, to evaluate the possibility that these recently discovered populations are of recent independent origin, a broad analysis of genetic diversity in T. mirus, T. miscellus, and their diploid progenitors was conducted. Analyses of allozymic and DNA restriction site variation in all known populations of T. mirus and T. miscellus in the Palouse and several populations of each parental diploid species revealed several distinct genotypes in each tetraploid species. Four isozymic multilocus genotypes were observed in T. mirus, and seven were detected in T. miscellus. Tragopogon mirus possesses a single chloroplast genome, that of T. porrifolius, and two distinct repeat types of the 18S-26S ribosomal RNA genes. Populations of T. miscellus from Pullman, Washington, have the chloroplast genome of T. dubius; all other populations of T. miscellus have the chloroplast DNA of T. pratensis. All populations of T. miscellus combine the ribosomal RNA repeat types of T. dubius and T. pratensis, as demonstrated previously. When all current and previously published data are considered, both T. mirus and T. miscellus appear to have formed numerous times even within the small geographic confines of the Palouse, with estimates of five to nine and two to 21 independent origins, respectively. Such recurrent polyploidization appears to characterize most polyploid plant species investigated to date (although this number is small) and may contribute to the genetic diversity and ultimate success of polyploid species. 相似文献
88.
We demonstrated previously that an α1—β2—γ2 gene cluster of the γ-aminobutyric acid (GABAA) receptor is located on human chromosome 5q34–q35 and that an ancestral α—β—γ gene cluster probably spawned clusters on chromosomes 4, 5, and 15. Here, we report that the α4 gene (GABRA4) maps to human chromosome 4p14–q12, defining a cluster comprising the α2, α4, β1, and γ1 genes. The existence of an α2—α4—β1—γ1 cluster on chromosome 4 and an α1—α6—β2—γ2 cluster on chromosome 5 provides further evidence that the number of ancestral GABAA receptor subunit genes has been expanded by duplication within an ancestral gene cluster. Moreover, if duplication of the α gene occurred before duplication of the ancestral gene cluster, then a heretofore undiscovered subtype of α subunit should be located on human chromosome 15q11–q13 within an α5—αx—β3—γ3 gene cluster at the locus for Angelman and Prader—Willi syndromes. 相似文献
89.
Pamela J. Weathers 《Applied microbiology》1984,48(6):1251-1253
Evidence is presented here that axenic cultures of Chlorella, Scenedesmus, Coelastrum, and Chlorococcum spp. evolve N2O when grown on NO2−, showing that the Chlorophyceae are a source of N2O in aquatic systems. 相似文献
90.
Ammonia oxidation, as measured by nitrite production, was inhibited by 2-chloro-6-trichloromethyl-pyridine (nitrapyrin, N-serve) in the methane-oxidizing bacterium,Methylosinus trichosporium OB3b, and the autotrophic nitrifying organisms,Nitrosococcus oceanus andNitrosomonas marina. 6-Chloropicolinic acid, a hydrolysis product of nitrapyrin, was ineffective as an inhibitor of ammonia oxidation by either the methanotroph or the autotrophs. Picolinic acid (2-carboxy-pyridine), in contrast, inhibited nitrification by the methane-oxidizing bacterium but not by the autotrophic cultures. Picolinic acid may provide a means for differentiating ammonia oxidation attributable to methanotrophs from that resulting from autotrophs in environmental studies. 相似文献