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1.
Emily Graves Allen Sallie B. Freeman Charlotte Druschel Charlotte A. Hobbs Leslie A. O’Leary Paul A. Romitti Marjorie H. Royle Claudine P. Torfs Stephanie L. Sherman 《Human genetics》2009,125(1):41-52
We examined the association between maternal age and chromosome 21 nondisjunction by origin of the meiotic error. We analyzed
data from two population-based, case–control studies: Atlanta Down Syndrome Project (1989–1999) and National Down Syndrome
Project (2001–2004). Cases were live born infants with trisomy 21 and controls were infants without trisomy 21 delivered in
the same geographical regions. We enrolled 1,215 of 1,881 eligible case families and 1,375 of 2,293 controls. We report four
primary findings. First, the significant association between advanced maternal age and chromosome 21 nondisjunction was restricted
to meiotic errors in the egg; the association was not observed in sperm or in post-zygotic mitotic errors. Second, advanced
maternal age was significantly associated with both meiosis I (MI) and meiosis II (MII). For example, compared to mothers
of controls, mothers of infants with trisomy 21 due to MI nondisjunction were 8.5 times more likely to be ≥40 years old than
20–24 years old at the birth of the index case (95% CI = 5.6–12.9). Where nondisjunction occurred in MII, mothers were 15.1
times more likely to be ≥40 years (95% CI = 8.4–27.3). Third, the ratio of MI to MII errors differed by maternal age. The
ratio was lower among women <19 years of age and those ≥40 years (2.1, 2.3, respectively) and higher in the middle age group
(3.6). Lastly, we found no effect of grand-maternal age on the risk for maternal nondisjunction. This study emphasizes the
complex association between advanced maternal age and nondisjunction of chromosome 21 during oogenesis.
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position
of the Centers for Disease Control and Prevention. 相似文献
2.
Telomeric length and telomerase activity vary with age in peripheral blood cells obtained from normal individuals 总被引:21,自引:0,他引:21
Hiroshi Iwama K. Ohyashiki Junko H. Ohyashiki Shigifumi Hayashi Naoyuki Yahata Keiko Ando Keisuke Toyama Akinori Hoshika Masaru Takasaki Mayumi Mori Jerry W. Shay 《Human genetics》1998,102(4):397-402
The telomerase activity and length of telomeres of peripheral blood mononuclear cells obtained from 124 healthy individuals
aged 4–95years was measured. Telomerase activity level was semiquantitatively assessed by a fluorescent-telomeric repeat amplification
protocol (fluorescent-TRAP) using an internal telomerase assay standard, fluorescent primers and an automated laser fluorescent
DNA sequencer. Telomeric length, measured by assay of terminal restriction fragments (TRFs), was determined in HinfI-digested DNA by Southern blot analysis using a (TTAGGG)4 probe. TRF length was determined in 80 individuals and age-related progressive reduction of size was observed. TRF length
in peripheral blood mononuclear cells obtained from normal individuals (aged 4–39years) decreased by approximately 84bp per
year, while in individuals aged ≥40years it decreased by 41bp per year. In contrast, telomerase activity showed an apparent biphasic pattern with aging. Individuals
aged 4–39years showed a progressive decrease in telomerase activity, whereas 65% of those aged ≥40years showed relatively stable but very low telomerase activity, and the remaining individuals aged ≥40years had no detectable telomerase activity. These data obtained from normal individuals might in the future be of value
to help risk stratify and manage the care of patients with leukemia.
Received: 18 August 1997 / Accepted: 10 December 1997 相似文献
3.
Galbiatti AL Ruiz MT Rodrigues JO Raposo LS Maníglia JV Pavarino ÉC Goloni-Bertollo EM 《Molecular biology reports》2012,39(1):635-643
Functional polymorphisms in genes encoding enzymes involved in folate metabolism might modulate head and neck carcinoma risk
because folate participates in DNA methylation and synthesis. We therefore conducted a case–control study of 853 individuals
(322 head and neck cancer cases and 531 non-cancer controls) to investigate associations among MTHFR C677T and MTHFR A1298C polymorphisms and head and neck squamous cell carcinoma risk. Interactions between these two polymorphisms and risk
factors and clinical histopathological parameters were also evaluated. The polymerase chain reaction-restriction fragment
length polymorphism (PCR-RFLP) technique was used to genotype the polymorphisms and Chi-square test and multiple logistic
regression were used for statistical analyses. The variables age ≥49 years, male gender, tobacco habits and alcohol consumption,
MTHFR 1298 AC or CC genotypes, combined genotypes with two or more polymorphic alleles and 677T and 1298C polymorphic alleles were
associated with increased risk for this disease (P < 0.05). Furthermore, we found that 1298 AC or CC genotypes were associated with age ≥49 years, tobacco and alcohol habits
(P < 0.05). Regarding clinical histopathological parameters, the A1298C polymorphism was more frequent in patients with oral
cavity as primary site (P < 0.05). MTHFR polymorphisms may contribute for increase risk for head and neck carcinoma and the variables age ≥49 years, male gender,
tobacco and alcohol habits were associated with MTHFR 1298AC or CC genotypes, confirming that individuals with these variables and MTHFR A1298C polymorphism has higher risk for
this disease. 相似文献
4.
Kaufman BD Auerbach S Reddy S Manlhiot C Deng L Prakash A Printz BF Gruber D Papavassiliou DP Hsu DT Sehnert AJ Chung WK Mital S 《Human genetics》2007,122(5):515-523
Hypertrophic Cardiomyopathy (HCM) is a disease with variable rate of progression. Young age is an independent risk factor
for poor outcome in HCM. The influence of renin–angiotensin–aldosterone (RAAS) genotype on the progression of HCM in children
is unknown. Children with HCM (n = 65) were enrolled prospectively across two centers (2001–2005). All subjects were genotyped for five RAAS gene polymorphisms
previously associated with LV hypertrophy (pro-LVH): AGT M235T, ACE DD, CMA-1903 A/G, AGTR1 1666 A/C and CYP11B2-344 C/T. Linear regression models, based on maximum likelihood estimates, were created to assess the independent effect of RAAS genotype
on LV hypertrophy (LVH). Forty-six subjects were homozygous for <2 and 19 were homozygous for ≥2 pro-LVH RAAS polymorphisms.
Mean age at presentation was 9.6 ± 6 years. Forty children had follow-up echocardiograms after a median of 1.5 years. Indexed
LV mass (LVMI) and LV mass z-scores were higher at presentation and follow-up in subjects with ≥2 pro-LVH genotypes compared to those with <2 (P < 0.05). Subjects with ≥2 pro-LVH genotypes also demonstrated a greater increase in septal thickness (IVST) and in LV outflow
tract (LVOT) obstruction on follow-up (P < 0.05). On multivariate analysis, a higher number of pro-LVH genotypes was associated with a larger effect size (P < 0.05). Pro-LVH RAAS gene polymorphisms are associated with progressive septal hypertrophy and LVOT obstruction in children
with HCM. Identification of RAAS modifier genes may help to risk-stratify patients with HCM.
This work was presented in part at the Annual Scientific Sessions of the American Heart Association, New Orleans, November
2004. 相似文献
5.
Ahmed W Malik M Saeed I Khan AA Sadeque A Kaleem U Ahmed N Ajmal M Azam M Qamar R 《Molecular biology reports》2011,38(4):2541-2548
A case–control association study on 229 Myocardial Infarction (MI) patients and 217 healthy controls was carried out to determine
the role of tissue-plasminogen activator (t-PA) (Alu-repeat insertion (I)/deletion (D)) and plasminogen activator inhibitor
(PAI-1) (4G/5G insertion/deletion) polymorphisms with MI in the Pakistani population. In MI patients the genotype distribution
of the PAI-1 gene was not found to be different when compared with the unaffected controls (P > 0.05, χ2 = 1.03). The risk allele 4G was also not associated with MI (P > 0.05, χ2 = 0.46, odds ratio (OR) = 1.1 (95% confidence interval (CI) = 0.84–1.43), P > 0.05). Similarly, the genotype frequencies of t-PA I/I, I/D and D/D were not different from the unaffected controls (P > 0.05, χ2 = 1.60), and the risk allele “I” was not found to be associated with MI (P > 0.05, χ2 = 1.35, OR = 0.86 (95% CI = 0.66–1.11), P > 0.05). However, when the data were distributed along the lines of gender a significant association of the 4G/4G PAI-1 genotype
was observed with only the female MI patients (P < 0.05, z-test = 2.21). When the combined genotypes of both the polymorphisms were analyzed, a significant association of
MI was observed with the homozygous DD/4G4G genotype (P < 0.01, z-test = 2.61), which was specifically because of the female samples (P = 0.01, z-test = 2.53). In addition smoking (P < 0.001, χ2 = 13.52, OR = 3.45 (95% CI = 1.77–6.94)), diabetes (P < 0.001, χ2 = 22.45, OR = 8.89 (95% CI = 2.96–29.95)), hypertension (OR = 7.76 (95% CI = 2.88–22.68), P < 0.001) family history (P < 0.001, χ2 = 13.72, OR = 3.7 (95% CI = 1.71–8.18)) and lower HDL levels (P < 0.05) were found to be significantly associated with the disease. In conclusion the PAI-1 gene polymorphism was found to
have a gender specific role in the female MI patients. 相似文献
6.
Chemokines regulates the trafficking of leukocytes to the site of inflammation hence may be implicated in cardiac events.
Currently no consistent effects have been revealed their role in acute myocardial infarction (MI). The aim of current study
was to investigate the impact of human chemokine receptor genetic variants, CCR5-Δ32 insertion/deletion, CCR5-59029-A/G, CX3CR1-V249I
and CX3CR1-T280 M on acute MI. 230 acute MI and 300 controls were examined. Patients carrying CCR5-Δ32 genotype were at three
times higher risk of developing MI odds ratio (OR, 3.24, CI 1.127–9.356, P = 0.04). Significant association was found with risk of acute MI in recipients who possessed homozygous 59029-A allele (OR
1.47, CI 1.03–2.09, P = 0.03). While CX3CR1-I249 and M280 were found to be protective in MI patients with OR 0.46, CI 0.32–0.66, P < 0.0001 and OR 0.36, CI 0.24–0.55, P < 0.0001, respectively. It might be possible that risk of acute MI is associated with genetic variation in chemokine receptors,
i.e., CCR5 and CX3CR1. 相似文献
7.
Short-term cultured cumulus cell lines (1-5BCC) derived from 5 individual cows were used in nuclear transfer (NT) and 1188 enucleated bovine oocytes matured in vitro were used as nuclear recipients. A total of 931 (78.4%) cloned embryos were reconstructed, of which 763 (82%) cleaved, 627 (67.3%) developed to 8-cell stage, and 275 (29.5%) reached blastocyst stage. The average cell number of blastocysts was 124±24.5 (n=20). In this study, the effects of donor cell sources, serum starvation of donor cells, time interval from fusion to activation (IFA) were also tested on cloning efficiency. These results showed that blastocyst rates of embryos reconstructed from 5 different individuals cells were significantly different among them (14.1%, 45.2%, 27.3%, 34.3%, vs 1.5%, P<0.05); that serum starvation of donor cells had no effect on blastocyst development rate of NT embryos (47.1% vs 44.4%, P>0.05); and that blastocyst rate (20.3%) of the group with fusion/activation interval of 2–3 h, was significantly lower than that of the 3–6 h groups (31.0%), while not significantly different among 3–4 h (P < 0.05), 4–5 h, and 5–6 h groups (P≥0.05). Sixty-three thawed NT blastocysts were transferred to 31 recipient cows, of which 4 pregnancies were established and two cloned calves were given birth. These results indicate that serum starvation of cumulus cells is not a key factor for successful bovine cloning, while IFA treatment and sources of donor cells have effects on cloning efficiency. 相似文献
8.
The association between the polymorphic CAG repeat in androgen receptor gene (AR) and prostate cancer susceptibility has been studied extensively. However, the results are contradictory. The purpose of
our meta-analysis was to investigate whether CAG repeat related to prostate cancer risk and had genetic heterogeneity across
different geographic regions and study designs. Random-effects model was performed irrespective of between-study heterogeneity.
Data and study quality were assessed in duplicate. Publication bias was assessed by the fail-safe number and Egger’s test.
There were 16 (patients/controls: 2972/3792), 19 (3835/4908) and 12 (3372/2631) study groups for comparisons of ≥20, 22 and
23 repeats of CAG sequence, respectively. Compared with CAG repeat <20, 22 or 23, carriers of ≥20, 22 or 23 repeats had 21%
(95% CI: 0.61–1.02; P = 0.076), 5% (95% CI: 0.81–1.11; P = 0.508) and 5% (95% CI: 0.76–1.20; P = 0.681) decreased risk of prostate cancer. After classifying studies by geographic areas, carriers of ≥20 repeats had 11%
decreased risk in populations from USA, 53% from Europe, and 20% from Asia (P > 0.05), whereas comparison of ≥23 repeats with others generated a significant prediction in European populations (OR = 1.17;
P = 0.039). Stratification by study designs revealed no material changes in risk estimation. Meta-regression analysis found
no significant sources of between-study heterogeneity for age, study design and geographic region for all comparisons. There
was no identified publication bias. Taken together, our results demonstrated that AR CAG repeat polymorphism with ≥20 repeats might confer a protective effect among the prostate cancer patients with 45 years
older but not all the prostate cancer patients. 相似文献
9.
B. Mercier P. Granier J. Mercier L. Foucat G. Bielicki J. Pradere J. P. Renou C. Prefaut 《European journal of applied physiology and occupational physiology》1998,78(1):20-27
We investigated whether localized 1H nuclear magnetic resonance spectroscopy (NMRS) using stimulated echoes (STEAM) with a long mixing time (t
m) allowed the suppression of the fat signal and detection of lactate in skeletal muscle. The 1H NMRS sequence was first validated in three isolated and perfused rabbit biceps brachii muscles. Spectra were obtained on a wide-bore spectrometer using a dual-tuned probe (1H and 31P). Death was simulated by ceasing the muscle perfusion, which allowed post-mortem changes to be followed. During and after the simulated death, changes in levels of pH and in content of energy-rich compounds
were observed with 31P NMRS. Our results showed an inverse linear relationship between pH and lactate in each of the three rabbits (r = 0.93, P < 0.001; r = 0.92, P < 0.01; r = 0.89, P < 0.01) and a decrease in phosphocreatine and concomitant increase in lactate. We then investigated whether this sequence
allowed repeated detection of lactate in human soleus muscle during the recovery between periods of intense exercise (force-velocity
test, F-v test). Seven subjects mean age 25.1 (SEM 0.8) years participated in this study. Soleus muscle lactate was detected at rest
and for 3 min 30 s of the 5-min recovery between periods using a 2.35-T 40-cm bore magnet spectrometer. Arm venous plasma
lactate concentration was measured at rest, during the F-v test when the subject stopped pedalling (S1), and at the end of each 5-min recovery between periods (S2). Results showed that the venous plasma lactate concentration at S1 and S2 increased significantly from the beginning of the F-v test to peak anaerobic power (W
an,peak) (P < 0.001). The spectra showed that muscle lactate resonance intensity rose markedly when W
an,peak was achieved. The muscle lactate resonance intensity plotted as a percentage of the resting value increased significantly
at W
an,peak compared with submaximal braking forces (P < 0.05). We concluded from these results that localized 1H NMRS using STEAM with a long t
m allows suppression of the fat signal and repeated detection of lactate on isolated perfused skeletal muscle in animals and
between periods of intense exercise in humans.
Accepted: 19 January 1998 相似文献
10.
Ole Rintek Madsen Ulrik Birk Lauridsen Andreas Hartkopp Ole Helmer S?rensen 《European journal of applied physiology and occupational physiology》1997,75(3):239-245
Dual energy x-ray absorptiometry (DEXA) offers the possibility of assessing regional soft tissue composition, i.e. lean mass (LM) and fat
mass : LM may be considered a measure of muscle mass. We examined age-related differences in LM, percentage fat (%fat) and
muscle strength in 100 healthy non-athletic women aged 18–87 years. Relationships between muscle strength and leg LM in 20
elite female weight lifters and in 18 inactive women with previous hip fractures were also studied. The LM and %fat of the
whole body, trunk, arms and legs were derived from a whole body DEXA scan. Isokinetic knee extensor strength (KES) and flexor
strength (KFS) at 30° · s–1 were assessed using an isokinetic dynamometer. The women aged 71–87 years had 35% lower KES and KFS than the women aged 18–40
years (P < 0.0001). Differences in LM were less pronounced. The LM of the legs, for instance, was 15% lower in the old than in the
young women (P < 0.0001). In a multiple regression analysis with age, body mass, height and leg LM or KES as independent variables and KES
or leg LM as the dependent variable, age was the most important predictor of KES (r
partial = −0.74, P < 0.0001). The same applied to KFS. Body mass, not age, was the most important predictor of leg LM (r
partial = 0.65, P < 0.0001) and of LM at all other measurement sites. The LM measured at different regions decreased equally with increasing
age. The KES:leg LM ratio was negatively correlated with age (r = −0.70, P < 0.0001). The weight lifters had significantly higher KES:leg LM ratios than age-matched controls (+12%, P < 0.0001) and vice versa for the women with previous hip fractures (–36%, P < 0.0001). In conclusion, from our study it would seem that in healthy nonathletic women, age is a more important determinant
of muscle strength than is LM as measured by DEXA. Muscle strengthening exercises and inactivity seem to have a considerably
stronger influence on muscle strength than on LM.
Accepted: 27 August 1996 相似文献
11.
X-chromosomal short tandem repeats (X-STR) loci are used for forensic practice in recent years in some complex kinship cases.
The commercially available kit of Investigator Argus X-12 (Qiagen, Hilden, Germany) makes it possible to examine the markers
of DXS10148–DXS10135–DXS8378, DXS7132–DXS10079–DXS10074, DXS10103–HPRTB–DXS10101 and DXS10146–DXS10134–DXS7423, which belong
to four linkage groups of X-chromosome. In this study, a total of 309 unrelated individuals (200 males and 109 females) from
Shanghai Han population were successfully analyzed with this kit. Hardy–Weinberg equilibrium tests demonstrated no significant
deviation from expected values (P > 0.05) for all of the 12 X-STR loci in the Shanghai Han population. Linkage disequilibrium tests were performed for all
pairs of loci by the Arlequin v3.1 software and only DXS10103–DXS10101 remained significant after adjustment for multiple
testing (P < 0.05/66). The combined power of discrimination in males (CDPM) was 0.999999996 while in females (CDPF) was 0.999999999999995, and the combined mean exclusion chance in duo cases (CMECD) was 0.999998 while in trio cases (CMECT) was 0.999999986. The results suggest that the twelve X-STR loci may provide high polymorphic information for paternity testing
and forensic identification in Chinese Han population from Shanghai. 相似文献
12.
Exercise- and methylcholine-induced sweating responses in older and younger men: effect of heat acclimation and aerobic fitness 总被引:2,自引:0,他引:2
Inoue Y Havenith G Kenney WL Loomis JL Buskirk ER 《International journal of biometeorology》1999,42(4):210-216
The purpose of this investigation was to examine the effects of aging and aerobic fitness on exercise- and methylcholine-induced
sweating responses during heat acclimation. Five younger [Y group – age: 23±1 (SEM) years; maximal oxygen consumption (V.O2max): 47±3 ml·kg–1·min–1], four highly fit older (HO group – 63±3 years; 48±4 ml·kg–1·min–1) and five normally fit older men (NO group – 67±3 years; 30±1 ml·kg–1·min–1) who were matched for height, body mass and percentage fat, were heat acclimated by daily cycle exercise (≈35% V.O2max for 90 min) in a hot (43°C, 30% RH) environment for 8 days. The heat acclimation regimen increased performance time, lowered
final rectal temperature (T
re) and percentage maximal heart rate (%HRmax), improved thermal comfort and decreased sweat sodium concentration similarly in all groups. Although total body sweating
rates (M.sw) during acclimation were significantly greater in the Y and HO groups than in the NO group (P<0.01) (because of the lower absolute workload in the NO group), the M.sw did not change in all groups with the acclimation sessions. Neither were local sweating rates (m.
sw) on chest, back, forearm and thigh changed in all groups by the acclimation. The HO group presented greater forearm m.
sw (30–90 min) values and the Y group had greater back and thigh m.
sw (early in exercise) values, compared to the other groups (P<0.001). In a methylcholine injection test on days immediately before and after the acclimation, the order of sweat output
per gland (SGO) on chest, back and thigh was Y>HO>NO, and on the forearm Y=HO>NO. No group differences were observed for activated
sweat gland density at any site. The SGO at the respective sites increased in the post-acclimation test regardless of group
(P<0.01), but on the thigh the magnitude of the increase was lower in the NO (P<0.02) and HO (P=0.07) groups than in the Y group. These findings suggest that heat tolerance and the improvement with acclimation are little
impaired not only in highly fit older but also normally fit older men, when the subjects exercised at the same relative exercise
intensity. Furthermore, the changes induced by acclimation appear associated with an age-related decrease in V.O2max. However methylcholine-activated SGO and the magnitude of improvement of SGO with acclimation are related not only to V.O2max but also to aging, suggesting that sensitivity to cholinergic stimulation decreases with aging.
Received: 8 May 1998/Accepted: 5 October 1998 相似文献
13.
This study analyzes the population structure and dynamics of an invasive population of Procambarus clarkii (Girard, 1852) in a Mediterranean wetland using the Bhattacharya’s and Von Bertallanfy’s analytical methods. The main purpose
was to collect biological data necessary for the management of this nuisance species. A maximum of five age classes were identified
for both sexes, three of which being composed of a few or zero individuals. Age classes were classified into two subgroups––spring
(SpL) and summer (SuL) lines––on the basis of the different hatching periods. Individuals of SpL showed a faster growth rate
and reached a larger body size than those belonging to SuL, probably because they were able to grow for a longer time. No
between-sex differences were found in growth patterns except for the asymptotic length (L∞), which was reached faster by the females. Other population properties were analyzed, such as a high mortality rate, a maximum
longevity of 4 years, and a low mean life-time (<12 months). Finally, a relatively small fraction of individuals seemed to
survive after the first reproductive peak in spring. Consequently, the structure and dynamics of the study population seem
to reveal its stability and spreading potential, as a confirmation of the invasiveness of P. clarkii in Mediterranean wetlands.
Handling editor: P. Viaroli 相似文献
14.
A. Nemetz M. Pilar Nosti-Escanilla Tamás Molnár Adorján Köpe Ágota Kovács János Fehér Zsolt Tulassay Ferenc Nagy M. Asunción García-González A. S. Peña 《Immunogenetics》1999,49(6):527-531
There is evidence of a disbalance in the inflammatory regulation of patients with inflammatory bowel diseases (IBD). Interleukin-1β
plays an important role in the pro-inflammatory response. Our aim was to study the influence which IL1B gene polymorphisms may have on the severity and course of these diseases. Ninety-six patients with ulcerative colitis (UC),
98 patients with Crohn's disease (CD), and 132 ethnically matched healthy individuals (HC) were typed for the polymorphic
sites in the promoter region (position –511) and in exon 5 (position +3953) of the IL1B gene, using polymerase chain reaction (PCR)-based methods. In the CD group a significant association (P=0.009) was found in this pair of genes. Homozygotes for allele 1 at position +3953 were more often present (69% vs 31%) in
the subgroup of patients carrying at least one copy of allele 2 at position –511. This association was significant in patients
with non-perforating disease (P=0.002), but was not present in patients with perforating-fistulizing disease. The distribution of both allelic pairs in the
non-fistulizing group proved to be significantly different from HC (P<0.05), UC (P<0.03), and the fistulizing group (P<0.05). There was a similar association in non-operated patients (P=0.024), whereas no such association was found in surgically treated patients. Among carriers of allele 2 at position –511,
UC patients with more severe bleeding symptoms (P=0.006) were less frequently found. These results suggest that IL1B gene polymorphisms participate in determining the course and severity of inflammatory bowel disease and contribute to explain
the heterogeneity of these diseases.
Received: 16 July 1998 / Revised: 3 November 1998 相似文献
15.
Transpiration and whole-tree conductance in ponderosa pine trees of different heights 总被引:17,自引:0,他引:17
M. G. Ryan B. J. Bond B. E. Law R. M. Hubbard D. Woodruff E. Cienciala J. Kucera 《Oecologia》2000,124(4):553-560
Changes in leaf physiology with tree age and size could alter forest growth, water yield, and carbon fluxes. We measured tree
water flux (Q) for 14 ponderosa pine trees in two size classes (12 m tall and ∼40 years old, and 36 m tall and ∼ 290 years old) to determine
if transpiration (E) and whole-tree conductance (g
t) differed between the two sizes of trees. For both size classes, E was approximately equal to Q measured 2 m above the ground: Q was most highly correlated with current, not lagged, water vapor pressure deficit, and night Q was <12% of total daily flux. E for days 165–195 and 240–260 averaged 0.97 mmol m–2 (leaf area, projected) s–1 for the 12-m trees and 0.57 mmol m–2 (leaf area) s–1 for the 36-m trees. When photosynthetically active radiation (I
P) exceeded the light saturation for photosynthesis in ponderosa pine (900 μmol m–2 (ground) s–1), differences in E were more pronounced: 2.4 mmol m–2 (leaf area) s–1 for the 12-m trees and 1.2 mmol m–2 s–1 for the 36-m trees, yielding g
t of 140 mmol m–2 (leaf area) s–1 for the 12-m trees and 72 mmol m–2 s–1 for the 36-m trees. Extrapolated to forests with leaf area index =1, the 36-m trees would transpire 117 mm between 1 June
and 31 August compared to 170 mm for the 12-m trees, a difference of 15% of average annual precipitation. Lower g
t in the taller trees also likely lowers photosynthesis during the growing season.
Received: 19 April 1999 / Accepted: 23 March 2000 相似文献
16.
Mechanosensitive channels have been determined to work as transducers of mechanoelectric feedback in the heart, which is associated
with the generation of arrhythmias. Recent studies have investigated the role of the cytoskeleton in ion channels control.
This study explored the ability of taxol to inhibit stretch-induced electrophysiological alterations in the ischemic myocardium.
Thirty-two Wistar rats were randomly divided into four groups: normal control group (n=9), taxol group (n=7), myocardial infarction (MI) group (n=9), and MI+taxol group (n=7). After Langendorff perfusion, the isolated hearts were stretched for 5 s by balloon inflation to 0.2 or 0.3 mL. The effects
of stretching on 90% monophasic action potential duration (MAPD90), premature ventricular beats (PVB), and ventricular tachycardia (VT) were observed for 30 s. Stretching increased MAPD90 in both the normal control and MI groups, but MAPD90 increased more in the MI group for the same degree of stretch. Taxol (5 μmol L−1) had no effect on MAPD90 under baseline, unstretched conditions, but MAPD90 in the taxol group was slightly increased after stretching compared with the normal control group (P>0.05). However, taxol reduced MAPD90 in infarcted myocardium (P<0.05 at ΔV=0.3 mL). The incidences of PVB and VT in the MI group were higher than in the normal control group (both P<0.01). Taxol had no effect on the occurrence of arrhythmias in normal myocardium, but it inhibited PVB and VT in infarcted
hearts (both P<0.01). Thus changes in MAPD and the occurrence of arrhythmias caused by mechanical stretching of the myocardium could be
inhibited by taxol in isolated rat hearts during AMI, indicating the involvement of tubulin in mechanoelectric feedback in
AMI. 相似文献
17.
Liu SY Lin MH Hsu YR Shih YY Chiang WF Lee CH Chou TH Liu YC 《Journal of biomedical science》2008,15(6):823-831
Areca nut (AN) is recognized as a human carcinogen; however, few studies of the cytotoxic effects of AN ingredients on cells
have been reported. In Taiwan, AN, lime and inflorescence of Piper betle are the common components of betel quid (BQ). We recently noticed that extract of AN (ANE), but not those of lime and inflorescence
of Piper betle, induces rounding cell morphology and nuclear shrinkage in different types of carcinoma cells. In this study, the rounding
cell activity was first traced to the partially purified ≥10 kDa fraction (ANE ≥ 10 K) and subsequently to the 30–100 kDa
fraction (ANE 30–100 K). ANE and ANE ≥10 K stimulated nuclear shrinkage (P < 0.001 in both cases) and the clearance of the cytoplasm. ANE, ANE ≥ 10 K, and ANE 30–100 K induced the cleavage of LC3-I
(P < 0.05, 0.01, and 0.05, respectively) and the emergence of autophagic vacuoles (AVs) and acidic vesicles. On the other hand,
arecoline (Are, the major alkaloid of AN) triggered caspase-3 activation, peri-nuclear chromatin condensation, and micronucleation.
Meanwhile, ANE 30–100 K, but not Are, inhibited the phosphorylation of the mammalian target of rapamycin (mTOR)-Ser2448. In conclusion, this study demonstrates that different AN ingredients exerting differential impact on mTOR-Ser2448 phosphorylation are capable of triggering apoptosis and autophagy.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Shyun-Yeu Liu, Mei-Huei Lin, Yu-Rung Hsu and Ya-Yun Shih contributed equally to this work. 相似文献
18.
Shi D Guo S Liao S Su R Guo M Liu N Li P Tang Z 《Biological trace element research》2012,145(3):312-317
To investigate the protection of selenium on hepatic mitochondrial functions, 90 7-day-old ducklings were randomly divided
into three groups (groups I–III). Group I was used as a blank control. Group II was administered with aflatoxin B1 (0.1 mg/kg body weight). Group III was administered with aflatoxin B1 (0.1 mg/kg body weight) plus selenium (sodium selenite, 1 mg/kg body weight). All treatments were given once daily for 21 days.
The results showed that the activities of hepatic mitochondrial complexes I–IV in group II ducklings significantly decreased
when compared with group I (P < 0.01). Furthermore, the activities of hepatic mitochondrial complexes I–IV in group III significantly increased when compared
with group II (P < 0.05). The hepatic mitochondrial respiratory control ratio (RCR) in group II ducklings significantly decreased when compared
with group I (P < 0.01). In addition, the hepatic mitochondrial RCR in group III significantly increased when compared with group II (P < 0.05). These results revealed that the aflatoxin B1 significantly induced hepatic mitochondrial dysfunction in the activities of hepatic mitochondrial respiratory chain complexes
I–IV and the RCR in ducklings. However, sodium selenite could significantly ameliorate the negative effect induced by aflatoxin
B1. 相似文献
19.
Patrick Mucci Jacques Prioux Maurice Hayot Michèle Ramonatxo Christian Préfaut 《European journal of applied physiology and occupational physiology》1998,77(4):343-351
Exercise-induced hypoxaemia (EIH) in master athletes may be related to a diminished exercise hyper- pnoea. The aim of this
study was to determine whether EIH is associated with a change in the sensitivity of the ventilation response to activation
of the central chemoreceptors. The ventilation response to CO2 was measured in nine elderly untrained men (UT) [mean age 66.3 (SEM 3.1) years] and nine master athletes (MA) [mean age 62.7
(SEM 0.8) years] at rest, during moderate exercise (40% maximal oxygen uptake, V˙O2max), and during strenuous exercise (70% V˙O2max) using the rebreathing method. Our results showed that the ventilation response to CO2 did not differ with endurance training and/or exercise, that the threshold of the CO2 response (Th) increased with exercise (P < 0.001), that the increase in Th in MA was higher than in UT between rest and moderate exercise [ΔTh0–40: 8.55 (SEM 1.8) vs 3.06 (SEM 1.72) mmHg, P < 0.05], and that ΔTh0–40 and Th during moderate exercise were negatively correlated with arterial O2 saturation during maximal exercise (r = 0.50, P<0.05). We concluded therefore that exercise-induced hypoxaemia in master athletes may not be due to a lower ventilation response
to CO2, but may be partly related to a greater increase in Th during moderate exercise.
Accepted: 18 August 1997 相似文献
20.
In previous studies, we have shown that cerebral hypoxia results in increased activity of caspase-9, the initiator caspase,
and caspase-3, the executioner of programmed cell death. We have also shown that cerebral hypoxia results in high affinity
Ca2+–ATPase-dependent increase in nuclear Ca2+-influx in the cerebral cortex of newborn piglets. The present study tests the hypothesis that inhibiting nuclear Ca2+-influx by pretreatment with clonidine, an inhibitor of high affinity Ca2+–ATPase, will prevent the hypoxia-induced increase in caspase-9 and caspase-3 activity in the cerebral cortex of newborn piglets.
Thirteen newborn piglets were divided into three groups, normoxic (Nx, n = 4), hypoxic (Hx, n = 4), and hypoxic treated with clonidine (100 mg/kg) (Hx–Cl, n = 5). Anesthetized, ventilated animals were exposed to an FiO2 of 0.21 (Nx) or 0.07 (Hx) for 60 min. Cerebral tissue hypoxia was documented biochemically by determining levels of ATP and
phosphocreatine (PCr). Caspase-9 and -3 activity were determined spectrofluoro-metrically using specific fluorogenic synthetic
substrates. ATP (μmoles/g brain) was 4.6 ± 0.3 in Nx, 1.7±0.4 in Hx (P < 0.05 vs. Nx), and 1.5 ± 0.2 in Hx–Cl (P < 0.05 vs. Nx). PCr (μmoles/g brain) was 3.6 ± 0.4 in Nx, 1.1 ± 0.3 in Hx (P < 0.05 vs. Nx), and 1.0 ± 0.2 in Hx–Cl (P < 0.05 vs. Nx). Caspase-9 activity (nmoles/mg protein/h) was 0.548 ± 0.0642 in Nx and increased to 0.808 ± 0.080 (P < 0.05 vs. Nx and Hx–Cl) in the Hx and 0.562 ± 0.050 in the Hx–Cl group (p = NS vs. Nx). Caspase-3 activity (nmoles/mg protein/h)
was 22.0 ± 1.3 in Nx and 32 ± 6.3 in Hx (P < 0.05 vs. Nx) and 18.8 ± 3.2 in the Hx–Cl group (P < 0.05 vs. Hx). The data demonstrate that clonidine administration prior to hypoxia prevents the hypoxia-induced increase
in the activity of caspase-9 and caspase-3. We conclude that the high afinity Ca2+–ATPase-dependent increased nuclear Ca2+ during hypoxia results in increased caspase-9 and caspase-3 activity. 相似文献