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51.
Sharon L. Crowell-Davis 《Applied animal behaviour science》1994,40(3-4):197-210
Upright and recumbent rest of 15 Welsh pony foals and their mothers was studied over a 2 year period. During their first week of life, the foals spent 32% of the time in recumbent rest. Subsequently, the percentage of time spent in recumbent rest decreased, but was still greater than for the foal's mother by Week 21, when the foals spent 6.5% of their time in recumbent rest. Adults spent little time in recumbent rest. Foals rested upright only 3.5% of the time during their first week of life. Mares rested upright more than foals did to Week 13, at which time peak values for time spent in upright rest occurred for both mares (32.5%) and foals (23%). Subsequently, mares and foals spent equal, but decreasing, amounts of time resting upright. The total time spent resting by the foals decreased gradually, and was characterized by a transition from recumbent rest to upright rest. Foals were more likely to be resting, either recumbent or upright, if their mother was resting upright. During the late spring, summer, and early autumn, mares and foals were most likely to be resting upright between 09:00 and 17:00 h. 相似文献
52.
Souvik Sen Harold Goldman Marilyn Morehead Sharon Murphy John W. Phillis 《Free radical biology & medicine》1994,16(6)
Traumatic brain injury (TBI) is one of the important causes of mortality and morbidity. The pathogenesis of the underlying brain dysfunction is poorly understood. Recent data have suggested that oxygen free radicals play a key role in the primary and secondary processes of acute TBI. We report direct electron spin resonance (ESR) evidence of hydroxyl (·OH) radical generation in closed-head injury of rats. Moderate brain concussion was produced by controlled and reproducible mechanical, fixed, closed-head injury. A cortical cup was placed over one cerebral hemisphere within 20 min of the concussion, perfused with artificial cerebrospinal fluid (aCSF) containing the spin trap agent pyridyl-N-oxide-tert-butyl nitrone (POBN, 100 mM), and superfusate samples collected at 10 min intervals for a duration up to 130 min post brain trauma. In addition, POBN was administered systematically (50 mg/kg body wt.) 10 min pretrauma and 20 min posttrauma to improve our ability to detect free radicals. ESR analysis of the superfusate samples revealed six line spectra (αN = 15.4 and αβH = 2.5 G) characteristic of POBN-OH radical adducts, the intensity of which peaked 40 min posttrauma. The signal was undetectable after 120 min. Administration of α-phenyl-tert-butyl-nitrone (PBN), a spin adduct forming agent systemically (100 mg/kg body wt. IP 10 min prior to concussion) alone or along with topical PBN (100 mM PBN in aCSF),6significantly (P< 0.001) attenuated the ESR signal, suggesting its possible role in the treatment of TBI. 相似文献
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54.
Familial mediterranean fever (FMF) in Moroccan Jews: Demonstration of a founder effect by extended haplotype analysis 总被引:12,自引:9,他引:3
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Ivona Aksentijevich Elon Pras Luis Gruberg Yang Shen Katherine Holman Sharon Helling Leandrea Prosen Grant R. Sutherland Robert I. Richards Michael Dean Mordechai Pras Daniel L. Kastner 《American journal of human genetics》1993,53(3):644-651
Familial Mediterranean fever (FMF) is an autosomal recessive disease causing attacks of fever and serositis. The FMF gene (designated “MEF”) is on 16p, with the gene order 16cen–D16S80–MEF–D16S94–D16S283–D16S291–16pter. Here we report the association of FMF susceptibility with alleles at D16S94, D16S283, and D16S291 among 31 non-Ashkenazi Jewish families (14 Moroccan, 17 non-Moroccan). We observed highly significant associations at D16S283 and D16S291 among the Moroccan families. For the non-Moroccans, only the allelic association at D16S94 approached statistical significance. Haplotype analysis showed that 18/25 Moroccan FMF chromosomes, versus 0/21 noncarrier chromosomes, bore a specific haplotype for D16S94–D16S283–D16S291. Among non-Moroccans this haplotype was present in 6/26 FMF chromosomes versus 1/28 controls. Both groups of families are largely descended from Jews who fled the Spanish Inquisition. The strong haplotype association seen among the Moroccans is most likely a founder effect, given the recent origin and genetic isolation of the Moroccan Jewish community. The lower haplotype frequency among non-Moroccan carriers may reflect differences both in history and in population genetics. 相似文献
55.
Sharon X. Chen Charles C. Hardin Harold E. Swaisgood 《Journal of Protein Chemistry》1993,12(5):613-625
Incubation of -lactoglobulin with immobilized trypsin at 5–10°C results in a time-dependent release of several fragments of the core domain in yields approaching 15%. Digests were fractionated by ion-exchange chromatography with a Mono Q HR5/5 column and analyzed after disulfide reduction by polyacrylamide gel electrophoresis in sodium dodecylsulfate. Three fragments with approximate molecular weights of 13.8, 9.6, and 6.7 kD were identified. The fraction from ion-exchange chromatography yielding the 6.7 kD fraction after disulfide reduction was further characterized because it was most homogeneous and gave the highest yield. The C-terminal cleavage site of the 6.7 kD core fragment appeared to be Lys100 or Lys101 as determined by C-terminal amino acid analysis. The exact masses, after reduction with dithiothreitol, are 6195 and 6926 as determined by laser desorption mass spectrometry, corresponding to residues 48–101 and 41–100. Prior to reduction, -lactoglobulin C-terminal residues 149–162 are connected to these core domain fragments as shown by C-terminal analysis and mass spectrometry. Structural studies indicate that these 7.9 and 8.6 kD core domain fragments released by immobilized trypsin retain much of their native structure. CD spectra indicate the presence of antiparallel -sheet structure similar to the native protein but the -helix is lost. Spectra in the aromatic region indicate the existence of tertiary structure. Moreover, structural transitions in urea are completely reversible as measured by CD spectra, although the extrapolated G
D
H20
and the urea concentration at the transition midpoint are lower than for the native protein. The core domain fragments also display apH-dependent binding to immobilizedtrans-retinal as does intact protein. A single endotherm is obtained for both core domain fragments and native protein upon differential scanning calorimetry, but again, the domain is less stable as indicated by a transition peak maxima of 56.9°C as compared with 81.1°C for native protein.Abbreviations used: CD, circular dichroism; CPG, controlled pore glass; DSC, differential scanning calorimetry; DTT, dithiothreitol; FPLC, fast flow liquid chromatography; HPLC, high-performance liquid chromatography; PITC, phenylisothiocyanate; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; TEA, triethylamine; UV, ultraviolet. 相似文献
56.
Logan J. Pallin Nick M. Kellar Debbie Steel Natalia Botero-Acosta C. Scott Baker Jack A. Conroy Daniel P. Costa Chris M. Johnson David W. Johnston Ross C. Nichols Doug P. Nowacek Andrew J. Read Oksana Savenko Oscar M. Schofield Sharon E. Stammerjohn Deborah K. Steinberg Ari S. Friedlaender 《Global Change Biology》2023,29(8):2108-2121
The krill surplus hypothesis of unlimited prey resources available for Antarctic predators due to commercial whaling in the 20th century has remained largely untested since the 1970s. Rapid warming of the Western Antarctic Peninsula (WAP) over the past 50 years has resulted in decreased seasonal ice cover and a reduction of krill. The latter is being exacerbated by a commercial krill fishery in the region. Despite this, humpback whale populations have increased but may be at a threshold for growth based on these human-induced changes. Understanding how climate-mediated variation in prey availability influences humpback whale population dynamics is critical for focused management and conservation actions. Using an 8-year dataset (2013–2020), we show that inter-annual humpback whale pregnancy rates, as determined from skin-blubber biopsy samples (n = 616), are positively correlated with krill availability and fluctuations in ice cover in the previous year. Pregnancy rates showed significant inter-annual variability, between 29% and 86%. Our results indicate that krill availability is in fact limiting and affecting reproductive rates, in contrast to the krill surplus hypothesis. This suggests that this population of humpback whales may be at a threshold for population growth due to prey limitations. As a result, continued warming and increased fishing along the WAP, which continue to reduce krill stocks, will likely impact this humpback whale population and other krill predators in the region. Humpback whales are sentinel species of ecosystem health, and changes in pregnancy rates can provide quantifiable signals of the impact of environmental change at the population level. Our findings must be considered paramount in developing new and more restrictive conservation and management plans for the Antarctic marine ecosystem and minimizing the negative impacts of human activities in the region. 相似文献
57.
Sharon A. Robinson Catherine E. Lovelock C. B. Osmond 《Plant biology (Stuttgart, Germany)》1993,106(4):307-312
The leaves of the Crassulacean acid metabolism plant Cotyledon orbiculata have a waxy coating which is highly reflective but can be easily removed by brushing. This provided an ideal system in which to investigate the role of epidermal wax as a possible photoprotectant. Removal of the wax, prior to exposure to natural sunlight, resulted in substantial decreases in Fv/Fm and in severe cases evidence of photoinhibitory damage, as indicated by a rise in Fo. Leaves from which wax had been removed also showed higher conversion of violaxanthin to zeaxanthin than waxed leaves. Recovery of brushed leaves over a 12 day period was correlated with an increase in the total pool of xanthophyll cycle components. This study suggests that the presence of highly reflective wax on the epidermis may confer significant photoprotection to plants exposed to high solar radiation environments. 相似文献
58.
Mutants in dolichol synthesis: conversion of polyprenol to dolichol appears to be a rate-limiting step in dolichol synthesis 总被引:3,自引:1,他引:2
Rosenwald Anne G.; Stanley Pamela; McLachlan Karen R.; Krag Sharon S. 《Glycobiology》1993,3(5):481-488
Chinese hamster ovary (CHO) cells of the Lec9 recessive complementationgroup display a distinctive profile of resistance to a varietyof toxic lectins. In addition, they accumulate cis--unsaturatedpolyprenol and use mainly polyprenol rather than dolichol tosynthesize the glycosylated lipids used in asparagine-linkedglycosylation of proteins. The primary defect in these cellsis thought to result from a deficiency in polyprenol reductaseactivity. Three new mutants were isolated and determined tohave qualitatively, although not quantitatively, similar lectinresistance profiles to Lec9 cells. Two of these mutants (AbrRand RicR) also contained polyprenol rather than dolichol. Thelectin resistance profile of an independent mutant which accumulatespolyprenol, F2A8, was also found to be qualitatively similarto the Lec9 pattern. The relationship among these mutants wasanalysed in more detail by construction of cellcell hybrids.Lectin resistance profiles of the hybrids demonstrated thatAbrR, RicR and F2A8 fell into the Lec9 complementation group.Analysis of prenols in the hybrids also showed that F2A8 wasa member of the Lec9 group. Surprisingly, a significant fractionof the prenols found in Lec9 Parent hybrids was polyprenol(up to 30% of the neutral fraction), whereas the prenols foundin Parent Parent hybrids were nearly exclusively dolichol(97% of the neutral lipid fraction). Therefore, reduction ofpolyprenol to dolichol appears to be a rate-limiting step inthe synthesis of dolichol since hybrids with differing numbersof wild-type alleles can be biochemically distinguished. CHO cells dolichol lectins mutants polyprenol reductase 相似文献
59.
60.
Barindra Sana Ke Ding Jia Wei Siau Rupali Reddy Pasula Sharon Chee Sharad Kharel Jean-Baptise Henri Lena Eunice Goh Lakshminarayanan Rajamani Yeng Ming Lam Sierin Lim John F. Ghadessy 《Biotechnology and bioengineering》2023,120(11):3200-3209
Polyethylene terephthalate (PET) hydrolase enzymes show promise for enzymatic PET degradation and green recycling of single-use PET vessels representing a major source of global pollution. Their full potential can be unlocked with enzyme engineering to render activities on recalcitrant PET substrates commensurate with cost-effective recycling at scale. Thermostability is a highly desirable property in industrial enzymes, often imparting increased robustness and significantly reducing quantities required. To date, most engineered PET hydrolases show improved thermostability over their parental enzymes. Here, we report engineered thermostable variants of Ideonella sakaiensis PET hydrolase enzyme (IsPETase) developed using two scaffolding strategies. The first employed SpyCatcher-SpyTag technology to covalently cyclize IsPETase, resulting in increased thermostability that was concomitant with reduced turnover of PET substrates compared to native IsPETase. The second approach using a GFP-nanobody fusion protein (vGFP) as a scaffold yielded a construct with a melting temperature of 80°C. This was further increased to 85°C when a thermostable PETase variant (FAST PETase) was scaffolded into vGFP, the highest reported so far for an engineered PET hydrolase derived from IsPETase. Thermostability enhancement using the vGFP scaffold did not compromise activity on PET compared to IsPETase. These contrasting results highlight potential topological and dynamic constraints imposed by scaffold choice as determinants of enzyme activity. 相似文献