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排序方式: 共有526条查询结果,搜索用时 15 毫秒
101.
GM Howard TV Nguyen M Harris PJ Kelly JA Eisman 《Canadian Metallurgical Quarterly》1998,13(8):1318-1327
This study was designed to assess the relative contributions of genetic and environmental factors to the variation and covariation of quantitative ultrasound (QUS) measurements and their relationships to bone mineral density (BMD). Forty-nine monozygotic (MZ) and 44 dizygotic (DZ) female twins between 20 and 83 years of age (53 +/- 13 years, mean +/- SD) were studied. Digital (phalangeal) QUS (speed of sound [SOS]) and calcaneal QUS (broadband ultrasound attenuation [BUA] and velocity of sound [VOS]) were measured using a DBM Sonic 1200 ultrasound densitometer and a CUBA ultrasound densitometer, respectively. Femoral neck (FN), lumbar spine (LS), and total body (TB) BMD were measured using dual-energy X-ray absorptiometry. Familial resemblance and hence heritability (proportion of variance of a trait attributable to genetic factors) were assessed by analysis of variance, univariate, and multivariate model-fitting genetic analyses. In both QUS and BMD parameters, MZ twins were more alike than DZ pairs. Estimates of heritability for age- and weight-adjusted BUA, VOS, and SOS were 0.74, 0.55, and 0.82, respectively. Corresponding indices of heritability for LS, FN, and TB BMD were 0.79, 0.77, and 0.82, respectively. In cross-sectional analysis, both BUA and SOS, but not VOS, were independently associated with BMD measurements. However, analysis based on intrapair differences suggested that only BUA was related to BMD. Bivariate genetic analysis indicated that the genetic correlations between BUA and BMD ranged between 0.43 and 0.51 (p < 0.001), whereas the environmental correlations ranged between 0.20 and 0.28 (p < 0.01). While the genetic correlations within QUS and BMD measurements were significant, factor analysis indicates that common genes affect BMD at different sites. Also, individual QUS measurements appear to be influenced by some common sets of genes rather than by environmental factors. Significant environmental correlations were only found for BMD measurements and ranged between 0.50 and 0.65 (p < 0.001). These data suggest that QUS and BMD measurements are highly heritable traits. While it appears that there is a common set of genes influencing both QUS and BMD measurements, specific genes yet to be identified appear to have greater effects than that of shared genes in each trait. 相似文献
102.
NI Perrone-Bizzozero TV Isaacson GM Keidan C Eriqat KF Meiri DD Savage AM Allan 《Canadian Metallurgical Quarterly》1998,71(5):2104-2111
Consumption of moderate quantities of ethanol during pregnancy produces deficits in long-term potentiation in the hippocampal formation of adult offspring. Protein kinase C (PKC)-mediated phosphorylation of the presynaptic protein GAP-43 is critical for the induction of long-term potentiation. We tested the hypothesis that this system is affected in fetal alcohol-exposed (FAE) rats by measuring GAP-43 phosphorylation and PKC activity in the hippocampus of adult offspring of rat dams that had consumed one of three diets throughout gestation: (a) a 5% ethanol liquid diet, which produced a maternal blood ethanol concentration of 83 mg/dl (FAE); (b) an isocalorically equivalent 0% ethanol diet (pair-fed); or (c) lab chow ad libitum. Western blot analysis using specific antibodies to PKC-phosphorylated GAP-43 revealed that FAE rats had an approximately 50% reduction in the proportion of phosphorylated GAP-43. Similarly, we found that PKC-mediated incorporation of 32P into GAP-43 was reduced by 85% in hippocampal slices from FAE rats compared with both control groups. FAE animals also showed a 50% reduction in total hippocampal PKC activity, whereas the levels of six major PKC isozymes did not change in any of the diet groups. These results suggest that GAP-43 phosphorylation deficits in rats prenatally exposed to moderate levels of ethanol are not due to alterations in the expression of either the enzyme or substrate protein, but rather to a defect in kinase activation. 相似文献
103.
D Gautrin C Infante-Rivard TV Dao M Magnan-Larose D Desjardins JL Malo 《Canadian Metallurgical Quarterly》1997,155(6):1841-1847
Atopy, specific IgE sensitization, and bronchial hyperresponsiveness (BHR) were examined in a cohort of 769 apprentices starting career programs in animal health or veterinary medicine (Group 1), pastry making (Group 2), and dental hygiene (Group 3). The hypothesis were that: (1) a proportion of subjects can be "sensitized" although no significant specific occupational exposure has occurred; and (2) there is a relationship between baseline specific sensitization to work-related antigens and host characteristics. Skin tests were administered using 11 common inhalants and specific allergens, including six laboratory animal extracts, three cereal antigens, alpha-amylase, and latex. Methacholine challenge tests were performed. The prevalence of atopy was 54.4% in Group 1, 58.1% in Group 2, and 52.5% in Group 3. Skin reactivity to work-specific proteins was as follows: laboratory animal proteins, 13.8% in Group 1, 14.0% in Group 2, and 15.6% in Group 3. No subject was sensitized to alpha-amylase, whereas 1.2% in Group 1, 5% in Group 2, and 4.1% in Group 3 were sensitized to flour. Five subjects reacted to latex. BHR (PC20 < or = 8 mg/ml) was present in 17.6%, 21.2%, and 14.8% of subjects in Groups 1, 2, and 3, respectively. Specific sensitization was associated with positive skin reactions to common allergens, work-related symptoms, and BHR. These results suggest that students starting career programs with exposure to high-molecular-weight allergens have a low but substantial frequency of specific sensitization to work-related allergens that is related to atopy and BHR. 相似文献
104.
Individual somatotype parameters and peculiarities of constitution in 7-12 years boys were evaluated in the present investigation. The age range studied was shown to be divided on 3 stages. Regular growth processes with the prevalence of "infantal" proportions occur at the age of 7-9. Signs of definite constitutional type are expressed yet insufficiently. The age of 10-11 is transitional which shows in delay of muscle growth. At the age of 11-12 prepubescent sets in, during which features of constitution types and appropriate somatotype parameters are distinctly manifested. 相似文献
105.
MA Gorbunov LI Pavlova IA Titov TA Bektimirov VP Selezneva OIu Shitikova TV Mamontova IN Indikova 《Canadian Metallurgical Quarterly》1997,(6):55-58
The results of field clinical trials of Russian and American yeast vaccines against hepatitis B are presented. The study revealed that both vaccines were faintly reactogenic, safe and exhibited high immunological activity. After the full course of immunization following the schedule 0-1-2 months 92.5% and 97.5% of patients receiving, respectively. Russian vaccine "Combiotech" and American vaccine "H-B-Vax II" were found to have specific antibodies. The maximum effect was registered when the vaccines were introduced according to the schedule 0-1-6 months. Seroconversions were observed in 97.5% and 100% of the vaccinees receiving the Russian and American vaccines respectively, in the latter case the highest antibody level being observed. The use of the vaccines within the prophylactic immunization schedule showed that antibodies to hepatitis B appeared in immunized children in 93-100% of cases. Seroconversion indices and the levels of antibodies to diphtheria, tetanus, poliomyelitis and measles were statistically significant and were the same in children receiving only the vaccines according to the immunization schedule and in children immunized, in addition to these vaccines, against hepatitis B. 相似文献
106.
Burova TV; Choiset Y; Tran V; Haertle T 《Protein engineering, design & selection : PEDS》1998,11(11):1065-1073
Mixed disulfide derivatives of bovine beta-lactoglobulin (BLG) were studied
by circular dichroism (CD), gel-permeation HPLC and high- sensitivity
differential scanning calorimetry (HS-DSC). It was shown that modification
of Cys121 with mercaptopropionic acid and mercaptoethanol does not affect
the secondary structure of BLG, but results instead in tertiary and
quaternary structure changes. At neutral pH, the equilibrium
dimer<==>monomer of modified beta- lactoglobulin is shifted towards
monomeric form. In contrast to native BLG, thermal denaturation of modified
beta-lactoglobulin is fully reversible in neutral and acidic pH as
demonstrated by CD and HS-DSC measurements. Modification of Cys121 results
in a significant decrease of transition temperature (-6 degrees C) and
enthalpy (-106 kJ/mol) at pH 2.05 while unfolding heat capacity increment
remains unchanged. Thermal unfolding transitions of native and modified
beta-lactoglobulin at pH 2.05 are well approximated by a two-state model
suggesting that no intermediate states appear after modification. The
difference in Gibbs energy of denaturation between native and modified
beta- lactoglobulin, 8.5 kJ/mol at 37 degrees C and pH 2.05, does not
depend on the nature of the introduced group (charged or neutral). Computer
analysis of possible interactions involving Cys121 in a three- dimensional
structure of beta-lactoglobulin revealed that the thiol group is too far
away from neighboring residues to form side-chain hydrogen bonds. This
suggests that the sulfhydryl group of Cys121 may contribute to the
maintenance of BLG tertiary structure via water mediated H-bonding.
相似文献
107.
108.
JA Asensio D Demetriades JD Berne A Falabella H Gomez J Murray EE Cornwell G Velmahos H Belzberg W Shoemaker TV Berne 《Canadian Metallurgical Quarterly》1997,174(1):54-60
OBJECTIVE: It is necessary to have thorough knowledge of the survival of extreme low birth weight infants (ELBWI) in order to make it easier for obstetricians, neonatologists and the family to make a decision. PATIENTS AND METHODS: A revision of the 100 ELBWI in our service between 1988 and 1995, considering live births, those deceased in the same birthing room and those followed until their discharge from the hospital, was performed. The differences between the periods before and after the introduction of pulmonary surfactant in 1992 were analyzed. RESULTS: The total survival was 37% for those with a birth weight superior to 750 g or 26 weeks gestation. There were 44.2% males and 28.9% females. The total survival improved from 26.1% during 1988-1991 to 46.3% during the period of 1992-1995. During this period (1992-1995), the newborns weighing more than 750 g had a survival rate of 72.4% and for those of 26 weeks gestation it was 73.3%. Those born at 28 weeks gestation and those with 25 weeks of gestation and weighing more than 750 g, the total survival was 63% and the survival rate in the last four years was 75.9%. CONCLUSIONS: The mortality of the ELBWI descends in similar proportion to the remainder fo the ELBWI. In order to predict the prognosis, it would be necessary to carry out a correct ultrasound estimation of the gestational age and weight. It is necessary to offer a mother in the process of childbirth with a fetus of 28 weeks gestation or with 25 weeks gestation and a fetus with an ultrasound weight greater than 750 g, intrapartum fetal monitoring and to finish by Cesarean section in case of acute fetal distress, as well as intense and immediate neonatal attention as indicated by the index of survival reached in the group mentioned during the later years. 相似文献
109.
The regulation of plasma lecithin:cholesterol acyltransferase (LCAT) expression is not well understood. Although oleic acid increases both the secretion of triglycerides and LCAT by primary rat hepatocytes, the effect of other fatty acids (FA) on LCAT secretion is not known. This study was designed to examine the effect of FA on the hepatic secretion of LCAT, triglyceride and apolipoprotein A-1 (apoA-1). Primary rat hepatocytes were incubated with serum-free medium, supplemented with individual FA (0-1 mmol/L) for 22-24 h. Preliminary studies indicated a linear secretion of LCAT up to 24 h in both control and FA-treated cells. When hepatocytes were incubated with 1 mmol/L FA, the LCAT secretion increased 50-100% (P < 0.01) in the presence of the 18-carbon FA (stearic, oleic, elaidic and linoleic acids), whereas the presence of butyric, lauric and palmitic acids had no significant effect. LCAT secretion decreased (P < 0.01) in the presence of docosahexaenoic acid (DHA). All FA (except DHA) significantly enhanced triglyceride secretion; however, only the 18 carbon FA significantly stimulated the synthesis and secretion of apoA-1 and secretion of LCAT. The secretion of LCAT correlated with apoA-1 secretion (r = 0.88, P = 0.004) but not with triglyceride secretion (r = 0.55, P = 0.12). Treatment with oleic acid resulted in a 1.5-fold increase in hepatocyte LCAT mRNA accumulation, whereas butyrate and palmitate had no effect. These data indicate that FA that promote the apparent synthesis and secretion of apoA-1 also stimulate the secretion of LCAT in vitro, suggesting a coordinate regulatory mechanism for apoA-1 and LCAT expression. 相似文献
110.
Conformational properties of the molecules of angiotensin II and some of its analogs are analysed with regard to the quantitative characteristics of their biological activities. Connections between low-energy conformations of angiotensin II and its biological functions are established. The hormone's spatial structures plausible in terms of interactions with the specific receptors located in smooth muscles and adrenal cortex tissues have been identified. 相似文献