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61.
R Burstein Y Epstein Y Shapiro I Charuzi E Karnieli 《Journal of applied physiology》1990,69(1):299-304
The effect of acute exercise on insulin action has been studied in six obese (150-250% ideal body weight) non-insulin-dependent diabetics (OD), seven obese normoglycemics (ON), and six lean healthy controls (LC). Using a three-stage euglycemic clamp, the metabolic clearance rate (MCR) of glucose under increasing insulin concentrations was measured. The insulin dose-response curve was assessed on two separate occasions: 1) a base-line test and 2) 1 h after aerobic treadmill exercise at a steady-state heart rate of 150-160 beats/min. In the base-line test, under all insulin levels, glucose MCR was significantly lower in obese compared with lean individuals (P less than 0.01). Exercise increased glucose MCR at the highest hormonal concentrations applied to 124 and 134% of base line in OD and in ON, respectively (P less than 0.05); the insulin concentration required for one-half of the maximal clearance rate of glucose achieved in this study decreased from 200 to 130 and from 160 to 95 microU/ml in OD and ON, respectively (P less than 0.05). The changes in these parameters were insignificant in LC. It is suggested that acute exercise affected the insulin dose-response curve in OD and in ON but not in LC; although enhanced by exercise, glucose MCR remained significantly lower in both obese groups compared with control subjects. We concluded that insulin resistance, which accompanies extreme obesity, could be markedly decreased but not completely reversed by one bout of exercise. 相似文献
62.
Hagit Shapira Meir Mouallem Menachem S. Shapiro Yosef Weisman Zvi Farfel 《Human genetics》1996,97(1):73-75
Pseudohypoparathyroidism type Ia (PHP-Ia) is a hereditary disease characterized by resistance to PTH and other hormones that act via cAMP. Patients have deficient activity of Gs, the subunit of the G protein, which couples hormone receptors to stimulation of adenylate cyclase. We describe two new mutations discovered in two sporadic patients with PHP-Ia. Using genomic DNA, we have amplified exons 2–13 of the Gs gene (GNAS1) by PCR, and sequenced the resulting products. Both patients had Albright's hereditary osteodystrophy, resistance to multiple hormones, and deficient Gs activity. In the first patient, a deletion of a C in exon 5 at codon 115 was found. In the second patient, an insertion of a C in exon 10 at codon 267 was detected. Both these heterozygous mutations cause frameshift, and predict decreased production of Gs. This report adds two new Gs mutations to the known ten mutations recently described. 相似文献
63.
Simon C. Allen K. Ravi Acharya Kathleen A. Palmer Robert Shapiro Bert L. Vallee Harold A. Scheraga 《Journal of Protein Chemistry》1994,13(7):649-658
The three-dimensional structure of human angiogenin has been determined by X-ray crystallography and is compared here with an earlier model which predicted its structure, based on the homology of angiogenin with bovine pancreatic ribonuclease A. Comparison of the predicted model and crystal structure shows that the active-site histidine residues and the core of the angiogenin molecule, including most of the-strands and-helices, were predicted reasonably well. However, the structure of the surface loop regions and residues near the truncated C-terminus differs significantly. The C-terminal segment includes the active-site residues Asp-116, Gln-117, and Ser-118; Gln-117 in particular has been shown to be important in affecting the ribonucleolytic activity of angiogenin. Also, the orientation of one helix in the model differed from the orientation observed experimentally by about 20°, resulting in a large displacement of this chain segment. The difficulty encountered in predicting the surface loop regions has led to a new algorithm [Palmer and Scheraga (1991),J. Comput. Chem.,12, 505–526; (1992),J. Comput. Chem.,13, 329–350] for predicting the conformations of surface loops. 相似文献
64.
Despite the extensive electromyographic research that has addressed limb muscle function during primate quadrupedalism, the role of the back muscles in this locomotor behavior has remained undocumented. We report here the results of an electromyographic (EMG) analysis of three intrinsic back muscles (multifidus, longissimus, and iliocostalis) in the baboon (Papio anubis), chimpanzee (Pan troglodytes), and orangutan (Pongo pygmaeus) during quadrupedal walking. The recruitment patterns of these three back muscles are compared to those reported for the same muscles during nonprimate quadrupedalism. In addition, the function of the back muscles during quadrupedalism and bipedalism in the two hominoids is compared. Results indicate that the back muscles restrict trunk movements during quadrupedalism by contracting with the touchdown of one or both feet, with more consistent activity associated with touchdown of the contralateral foot. Moreover, despite reported differences in their gait preferences and forelimb muscle EMG patterns, primates and nonprimate mammals recruit their back muscles in an essentially similar fashion during quadrupedal walking. These quadrupedal EMG patterns also resemble those reported for chimpanzees, gibbons and humans (but not orangutans) walking bipedally. The fundamental similarity in back muscle function across species and locomotor behaviors is consistent with other data pointing to conservatism in the evolution of the neural control of tetrapod limb movement, but does not preclude the suggestion (based on forelimb muscle EMG and spinal lesion studies) that some aspects of primate neural circuitry are unique. © 1994 Wiley-Liss, Inc. 相似文献
65.
Desmond R. Jimenez Jeffrey P. Shapiro Raymond K. Yokomi 《Entomologia Experimentalis et Applicata》1994,70(2):143-152
This study was conducted to evaluate the effect of two different biotypes of the sweetpotato whitefly,Bemisia tabaci (Gennadius), on the induction of squash silverleaf (SSL), and to determine if double-stranded RNA (dsRNA) occurs in geographically
remote populations of the two biotypes. Recently collected B-biotype whiteflies from Florida, Arizona, Mississippi, and Texas
(SPW-B) all contained a 7.0 kb dsRNA molecule. Kb dsRNA molecule. Laboratory colonies of A-biotype whiteflies that were originally
collected in 1981 from cotton in Arizona and California did not contain the 7.0 Kb dsRNA. When the two biotypes were compared
only the SPW-B induced rapid onset, grade 5, SSL. DsRNA similar to that found in adult SPW-B was concentrated in whitefly
nymphs, but host plant leaf tissue did not contain any consistent dsRNA molecules. SPW-A only induced low-grade SSL and progeny
of SPW-A that were fed on pumpkin plants displaying SSL did not acquire the ability to express dsRNA or induce SSL. Our data
suggest that dsRNA is not directly involved in the induction of SSL and that SSL is a host-specific response, to a feeding
injury induced by B-biotype whiteflies. The origin and source of the 7.0 Kb dsRNA molecule remains enigmatic but its expression
is constant in the whitefly biotype that is responsible for the induction of SSL and several other plant disorders in the
U.S. 相似文献
66.
The roles of starvation and selective substrates in the emergence of araB-lacZ fusion clones. 总被引:2,自引:0,他引:2
The araB-lacZ fusion system has been a key case in the 'directed mutation' controversy. Fusions did not occur detectably during normal growth but formed readily after prolonged incubation on selective Ara-Lac medium. To distinguish the roles of starvation stress and selective substrates in coding sequence fusions, we applied sib selection and PCR technologies. Sib selection of the prefusion strain, MCS2, starved under aerobic conditions permitted us to isolate active fusion clones which had never been in contact with arabinose or lactose. Hence, a directive role for selective substrates is not essential. Aerobiosis was necessary for fusions to appear in glucose-starved cultures. The difference in fusion formation between normal and starved conditions is best explained by the response of a signal transduction network to physiological stimuli to activate Mu prophage joining of araB and lacZ sequences. PCR analysis revealed that direct plating on selective Ara-Lac agar yielded mostly a single class of 'standard' fusions, while sib selection yielded a broader spectrum of fusion structures. Standard fusions were found to occur within a narrow 9 bp window in lacZ. The high frequency of standard fusions in glucose-starved cultures suggested efficient and/or specific Mu action. 相似文献
67.
G. A. Belitsky T. A. Lytcheva I. A. Khitrovo R. D. Safaev V. S. Zhurkov I. F. Vyskubenko L. P. Sytshova O. G. Salamatova E. G. Feldt V. V. Khudoley I. V. Mizgirev E. M. Khovanova E. G. Ugnivenko T. B. Tanirbergenov K. I. Malinovskaya Yu. A. Revazova F. I. Ingel V. A. Bratslavsky A. B. Terentyev A. A. Shapiro G. M. Williams 《Cell biology and toxicology》1994,10(4):265-279
The activities of 1,2-dibromopropane (DBP) and 1,1,3-tribromopropane (TBP) were studied in seven genotoxicity assays, (i) SOS-induction inE. coli, (ii) DNA repair in primary rat hepatocyte culture, (iii) theSalmonella/microsome assay, (iv) a host-mediated assay usingSalmonella, (v) the somatic mutation and recombination assay inDrosophila melanogaster, (vi) HGPRT-mutagenesis assay in ARL 18 cells, and (vii) micronucleus formation assay in mouse polychromatophylic erythrocytes (PCE), forestomach (FS), glandular stomach (GS), duodenum (D), jejunum (J), cecum (C) and liver (L). The halopropanes were also tested for tumor formation in the fishDanio rerio. DBP was active in assays (ii), (v), (vii FS) and (vii L). TBP was positive in assays (ii) and (iii), strongly positive in (vii L) and borderline positive in (iv). However, neither DBP nor TBP induced tumors in fish, in contrast to the carcinogenic 1,2-dibromo-3-chloropropane. The genotoxicity and potential carcinogenicity of DBP and TBP in mammals is discussed.Abbreviations 2-AA
2-aminoanthracene
- DBCP
1,2-dibromo-3-chloropropane
- DBP
1,2-dibromopropane
- HGPRT
hypoxanthine-guanine phosphoribosyl transferase
- i.p.
intraperitoneal(ly)
- NQO
4-nitro-quinoline-1-oxide
- PCE
polychromatic erythrocytes
- TBP
1,1,3-tribromopropane
- WME
Williams' medium E 相似文献
68.
The recognition of polar bacterial organization is just emerging. The examples of polar localization given here are from a variety of bacterial species and concern a disparate array of cellular functions. A number of well-characterized instances of polar localization of bacterial proteins, including the chemoreceptor complex in both C. crescentus and E. coli, the maltose-binding protein in E. coli, the B. japonicum surface attachment proteins, and the actin tail of L. monocytogenes within a mammalian cell, involve proteins or protein complexes that facilitate bacterial interaction with the environment, either the extracellular milieux or that within a plant or mammalian host. The significance of this observation remains unclear. Polarity in bacteria poses many problems, including the necessity for a mechanism for asymmetrically distributing proteins as well as a mechanism by which polar localization is maintained. Large structures, such as a flagellum, are anchored at the pole by means of the basal body that traverses the peptidoglycan wall. But for proteins and small complexes, whether in the periplasm or the membrane, one must invoke a mechanism that prevents the diffusion of these proteins away from the cell pole. Perhaps the periplasmic proteins are retained at the pole by the presence of the periseptal annulus (35). The constraining features for membrane components are not known. For large aggregates, such as the clusters of MCP, CheA, and CheW complexes, perhaps the size of the aggregate alone prevents displacement. In most cases of cellular asymmetry, bacteria are able to discriminate between the new pole and the old pole and to utilize this information for localization specificity. The maturation of new pole to old pole appears to be a common theme as well. Given numerous examples reported thus far, we propose that bacterial polarity displays specific rules and is a more general phenomenon than has been previously recognized. 相似文献
69.
The challenge-phage assay reveals differences in the binding equilibria of mutant Escherichia coli Trp super-repressors in vivo.
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The phenotypes of four mutant Escherichia coli Trp repressor proteins with increased activities have been examined in vivo using the challenge-phage assay, an assay based on a positive genetic selection for DNA binding. These proteins, which differ by single amino acid changes from the wild type (Glu13-->Lys, Glu18-->Lys, Glu49-->Lys and Ala77-->Val), require less L-tryptophan than wild-type repressor for activation in vivo, and are super-aporepressors. However, none of the four mutant repressors binds DNA in a corepressor-independent manner. Three of the four mutant repressors (with Glu-->Lys changes) are more active when complexed with tryptophan, and are superholorepressors. Challenge-phage assays with excess tryptophan rank the mutant holorepressors in the same order as determined by binding studies in vitro. Challenge-phage assays with limiting tryptophan reveal additional phenotypic differences among the mutant proteins. These results show that the challenge-phage assay is a robust assay for measuring the relative affinities of specific protein-DNA interactions in vivo. 相似文献
70.