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1.
Byron S. Tepper 《Journal of bacteriology》1968,95(5):1713-1717
A basic difference was found in the kinetics of uptake and utilization of glucose and glycerol by washed suspensions of Mycobacterium phlei. With glucose, the rates of uptake, respiration, and assimilation were saturated at low external substrate concentration. With glycerol, these rates were found to increase with increasing substrate concentration and did not show saturation at any concentration tested. Qualitatively similar patterns were observed for cells grown on either glycerol or glucose. Above a saturation concentration, ratios of cell (14)C to CO(2) (14)C for uniformly labeled (14)C-glucose were constant at a value of 0.96. Glycerol-U-(14)C, on the other hand, yielded cell-(14)C/CO(2)-(14)C ratios which were highest at the lowest glycerol concentration tested, and decreased with increasing substrate concentration. The distribution of the glucose and glycerol carbons assimilated into M. phlei were qualitatively similar. Quantitatively, however, the uptake and assimilation of glycerol was far more rapid than that of glucose for all substrate concentrations employed. These quantitative differences in the utilization of glycerol and glucose could account for the increased content of nonessential lipid and polysaccharide found in glycerol-grown M. phlei. 相似文献
2.
Serum form of the rat insulin-like growth factor II/mannose 6-phosphate receptor is truncated in the carboxyl-terminal domain 总被引:6,自引:0,他引:6
R G MacDonald M A Tepper K B Clairmont S B Perregaux M P Czech 《The Journal of biological chemistry》1989,264(6):3256-3261
The insulin-like growth factor (IGF)-II/mannose 6-phosphate (Man-6-P) receptor present in mammalian tissues as an apparent molecular mass = 250 kDa glycoprotein has recently been detected in fetal rat serum in a lower molecular mass form (240 kDa). In the present studies the serum receptor was affinity labeled with 125I-IGF-II after its adsorption onto pentamannosyl 6-phosphate-Sepharose, demonstrating that it can also bind both ligands simultaneously. The receptors in both serum and fresh plasma exhibited the lower molecular mass compared to tissue receptors, indicating this form circulates in vivo. In order to probe the structural basis of the serum receptor's lower mass, we raised antipeptide antibodies against cytoplasmic and extracellular domains of the tissue form of the rat receptor deduced from complementary DNA clones (MacDonald, R. G., Pfeffer, S. R., Coussens, L., Tepper, M. A., Brocklebank, C. M., Mole, J. E., Anderson, J. K., Chen, E., Czech, M. P., and Ullrich, A. (1988) Science 239, 1134-1137). Peptide 22C, Glu-Glu-Glu-Thr-Asp-Glu-Asn-Glu-Thr-Glu-Trp-Leu-Met-Glu-Glu-Ile-Gln-Val- Pro-Ala - Pro-Arg, located in the cytoplasmic domain 32 residues carboxyl-terminal to the transmembrane region, and peptide 13D, Tyr-Tyr-Leu-Asn-Val-Cys-Arg-Pro-Leu-Asn-Pro-Val-Pro-Gly-Cys-Asp, located 1476 residues amino-terminal to the transmembrane domain were synthesized and used as immunogens in rabbits. IGF-II/Man-6-P receptors were first immunoprecipitated from either rat serum or a Triton X-100 extract of rat placental plasma membranes using a polyclonal antireceptor antibody. The immunoadsorbed receptors were then reduced, alkylated, electrophoresed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, blotted onto nitrocellulose, and probed with antipeptide antibodies. Anti-13D revealed the major receptor band in all the membrane and serum samples tested as well as several minor species of lower apparent mass in serum. Fetal and neonatal rat sera contained 3-4 times as much of the receptor as adult serum. In contrast, anti-22C recognized the membrane IGF-II/Man-6-P receptor but failed to recognize any of the serum receptor species. These results indicate that the serum IGF-II/Man-6-P receptor is truncated or altered in its cytoplasmic domain, consistent with the hypothesis that it is derived from cells by proteolytic cleavage. 相似文献
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We assessed pulmonary mechanics in six open-chest rabbits (3 young and 3 adult) by the forced oscillation technique between 0.16 and 10.64 Hz. Under control conditions, pulmonary resistance (RL) decreased markedly between 0.16 and 4 Hz, after which it became reasonably constant. Measurements of alveolar pressure from two alveolar capsules in each rabbit showed that the large decrease of RL with increasing frequency below 4 Hz was due to lung tissue rheology and that tissue resistance was close to zero above 4 Hz. Estimates of resistance and elastance, also obtained by fitting tidal ventilation data at 1 Hz to the equation of the linear single-compartment model, gave values for RL motion that were slightly higher than those obtained by forced oscillations at the same frequency, presumably because of the flow dependence of airways resistance. After treatment with increasing doses of aerosolized methacholine, RL and pulmonary elastance between 0.16 and 1.34 Hz progressively increased, as did the point at which the pulmonary reactance crossed zero (the resonant frequency). The alveolar pressure measurements showed the lung to become increasingly inhomogeneously ventilated in all six animals, whereas in the three younger rabbits lobar atelectasis developed at high methacholine concentrations and the alveolar capsules ceased to communicate with the central airways. We conclude that the low-frequency pulmonary impedance of rabbits exhibits the same qualitative features observed in other species and that it is a sensitive indicator of the changes in pulmonary mechanics occurring during bronchoconstriction. 相似文献
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Alien invasive species have detrimental effects on invaded communities. Aliens do not invade a vacuum, but rather a community consisting of native and often other alien species. Our current understanding of the pathways and network of interactions among multiple invasive species within whole communities is limited. Eradication efforts often focus on a single target species, potentially leading to unexpected outcomes on interacting non-target species. We aimed to examine the interaction network in a cavity-nesting community consisting of native and invasive birds. We studied the nesting cavities in the largest urban park in Israel over two breeding seasons. We found evidence for a complex interaction network that includes negative, neutral and positive interactions, but no synergistic positive interactions among aliens. Three major factors shaped the interaction network: breeding timing, nesting preferences and the ability to excavate or widen the cavities, which were found to be a limited resource. Cavity enlargement by the early-breeding invasive rose-ringed parakeet may enhance breeding of the invasive common myna in previously unavailable holes. The myna excludes the smaller invasive vinous-breasted starling, a direct competitor of the primary nest excavator, the native Syrian woodpecker. Therefore, management and eradication efforts directed towards the common myna alone may actually release the vinous-breasted starling from competitive exclusion by the common myna, increasing the negative impact of the vinous-breasted starling on the native community. As found here, interactions among multiple alien species can be crucial in shaping invasion success and should be carefully considered when aiming to effectively manage biological invasions. 相似文献
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Marcus H. Jones Andréa L. Corso Robert S. Tepper Maria I. A. Edelweiss Luciana Friedrich Paulo M. C. Pitrez Renato T. Stein 《PloS one》2013,8(12)
Objective
To explore the relationship between prematurity, gender and chorioamnionitis as determinants of early life lung function in premature infants.Methods
Placenta and membranes were collected from preterm deliveries (<37 weeks gestational age) and evaluated for histological chorioamnionitis (HCA). Patients were followed and lung function was performed in the first year of life by Raised Volume-Rapid Thoracic Compression Technique.Results
Ninety-five infants (43 males) born prematurely (median gestational age 34.2 weeks) were recruited. HCA was detected in 66 (69%) of the placentas, and of these 55(58%) were scored HCA Grade 1, and 11(12%) HCA Grade 2. Infants exposed to HCA Grade 1 and Grade 2, when compared to those not exposed, presented significantly lower gestational ages, higher prevalence of RDS, clinical early-onset sepsis, and the use of supplemental oxygen more than 28 days. Infants exposed to HCA also had significantly lower maximal flows. There was a significant negative trend for z-scores of lung function in relation to levels of HCA; infants had lower maximal expiratory flows with increasing level of HCA. (p = 0.012 for FEF50, p = 0.014 for FEF25–75 and p = 0.32 for FEV0.5). Two-way ANOVA adjusted for length and gestational age indicated a significant interaction between sex and HCA in determining expiratory flows (p<0.01 for FEF50, FEF25–75 and p<0.05 for FEV0.5). Post-hoc comparisons revealed that female preterm infants exposed to HCA Grade 1 and Grade 2 had significant lower lung function than those not exposed, and this effect was not observed among males.Conclusions
Our findings show a sex-specific negative effect of prenatal inflammation on lung function of female preterm infants. This study confirms and expands knowledge upon the known association between chorioamnionitis and early life chronic lung disease. 相似文献9.
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