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Biomedical subjects

F Xu

Publications and source records attributed to F Xu.

At least 253 records · Page 14Linked to original sources
PubMed1995

Meiosis-specific double-strand DNA breaks at the HIS4 recombination hot spot in the yeast Saccharomyces cerevisiae: control in cis and trans.

The region of Saccharomyces cerevisiae chromosome III located between the 5' end of the HIS4 gene and the 3' end of the adjacent BIK1 gene has a very high level of meiotic recombination. In wild-type strains, a meiosis-specific double-strand DNA break occurs in the hot spot region. This break is absent in strains in which the transcription factors Rap1p, Bas1p, and Bas2p cannot bind to the region upstream of HIS4. In strains with levels of recombination that are higher than those of the wild type, the break is found at elevated levels. The linear relationship between hot spot activity and the frequency of double-strand DNA breaks suggests that these lesions are responsible for initiating recombination at the HIS4 recombination hot spot.

Chromosome Aberrations↗
PubMed1995

Hypoxic respiratory responses attenuated by ablation of the cerebellum or fastigial nuclei.

The general contribution of the cerebellum to hypoxic respiratory responses and the special role of the fastigial nucleus (FN) in the hypoxic respiratory reflex mediated via peripheral chemoreceptors were investigated in anesthetized and spontaneously breathing cats. Seven cats were exposed to isocapnic progressive hypoxia before and after cerebellectomy by decreasing the fractional concentration of end-tidal O2 (FETO2) from 15 +/- 0.3% to 7% while maintaining the pressure of end-tidal CO2 at a constant level of approximately 30 mmHg. Five additional cats inhaled five breaths of pure N2 (transient hypoxia) and received sodium cyanide (50 micrograms iv) before and after thermal lesions of the bilateral FN. The results showed that cerebellectomy or FN lesions failed to alter the respiratory variables (minute ventilation, tidal volume, respiratory frequency, and the peak of integrated diaphragm activity) during eupneic breathing. However, cerebellectomy significantly attenuated minute ventilation (FETO2 < or = 13%) and the peak of integrated diaphragm activity (FETO2 < or = 10%) compared with control. During progressive hypoxia, changes in respiratory frequency were noted earlier (FETO2 < or = 13%) than changes in tidal volume (FETO2 < or = 10%). Similarly, bilateral lesions of the FN resulted in a profound reduction in these respiratory responses to transient hypoxia and sodium cyanide. We conclude that the cerebellum can facilitate the respiratory response to hypoxia and that the FN is an important region in the modulation of the hypoxic respiratory responses, presumably via its effects on inputs from peripheral chemoreceptors.

Animals↗
PubMed1995

Longitudinal studies of blood pressure in children.

A longitudinal study of six years was conducted to find out the pattern of longitudinal changes of blood pressure and to affirm the "tracking phenomenon" of blood pressure in children in China. We initially measured blood pressure and related parameters of 2,946 children (aged 4-14 years) in 1981 at Fanshan county, Beijing, and then two follow-up remeasurements were conducted in 1985 and 1987, respectively. The results indicated that: the average level of blood pressure increases with age even after adjusting for height and weight; tracking coefficients of systolic blood pressure range from weak to moderate levels, increasing with age. Only 30% of the children whose systolic blood pressure was beyond the 90th percentile of the systolic pressure distribution at the first examination remained at the same region after four years. Multiple stepwise regression was used to determine factors correlated with blood pressure. Our results indicate that systolic blood pressure in children is correlated with body weight, pulse rate, serum glucose and HDL-C, while diastolic blood pressure is correlated only with pulse rate and serum glucose.

Adolescent↗
PubMed1995

Phenotypic analysis of early hematopoietic progenitors in cord blood and determination of their correlation with clonogenic progenitors: relevance to cord blood stem cell transplantation.

Human cord blood (CB) can be utilized as a source of transplantable stem cells. In the clinical setting, the numbers of clonogenic progenitors and nucleated cells are used as indirect measures of the stem cell content of CB samples. In an attempt to define other parameters of engraftment potential, we have determined the numbers of CD34+ cells, and of CD34+ cells co-expressing CD38 and/or HLA-DR in 17 CB samples. At the same time, clonogenic progenitors were assayed in the presence of erythropoietin and different combinations of rhIL-3, rhG-CSF, rhGM-CSF, rh-Steel Factor and medium conditioned by the PU34 primate cell line. Unseparated CB contained a mean of 14.8 x 10(4) CD34+ cells/mL. CD34+CD38-, CD34+DR+ and CD34+DR+ CD38- cells represented 12.2%, 91% and 10% of all CD34+ cells, respectively. Linear regression analysis demonstrated that the total number of CD34+ cells, as well as the different subsets, correlated positively with the numbers of total colonies and day 14 CFU-GM. Furthermore, the proportion of CD34+CD38- cells was significantly higher than has been reported for adult marrow. Cord blood CD34+CD38- and CD34+DR+ cells have a high proliferative potential and are enriched for primitive hematopoietic progenitors. Thus, we conclude that a single collection of CB could be sufficient to engraft an adult recipient, and that quantitation of CD34+ cells and their subsets may be useful in determining the engraftment potential of CB samples.

ADP-ribosyl Cyclase↗
PubMed1995

[The detection and significance of HBV-DNA in serum of pulmonary tuberculous patients].

Hepatitis B virus deoxyribonucleic acid (HBV-DNA) in the serum and the liver function from 268 patients with pulmonary tuberculosis were investigated. The patients have been followed up for 3.5 years. In the course of antituberculous chemotherapy, the abnormal liver function rate turned to be 95% in the positive HBV-DNA group but only 10% and 5.1% in the negatives, HBV-DNA group and pulmonary tuberculosis group respectively (P < 0.01, P < 0.01, P > 0.05). The abnormal liver function rate turned to be 49% in the positive HBV-M group but only 5.1% and 10% in the negative control group and pulmonary tuberculosis group (P < 0.01, P < 0.01, P > 0.05) respectively. The presence of HBV-DNA in patients with pulmonary tuberculosis was associated with high mortality rate and the cause of death was related to hepatic failure. The results suggest that to detect serum HBV-DNA is important in pulmonary tuberculous patients. Antiviral therapy for patients with pulmonary tuberculosis who had detectable HBV-DNA may improve prognosis.

Adult↗
PubMed1995

[Changes in surface microcirculation of extensor digitorum longus tendon after ischemia-reperfusion of rabbit hindlimbs].

The circulation was stopped by tourniquet in one rabbit hindlimb. After 2 or 5 hr of ischemia, the hindlimb was reperfused. During the first 1 hr of reperfusion, dynamic changes in surface microcirculation of extensor digitorum longus tendon were observed by using intravital microscopy. Particular attention was paid to leukocyte-endothelium adhesion and microvascular perfusion condition. It was found that 1) the number of leukocytes adherent to the venular endothelium of ischemic tissue significantly increased following reperfusion and the degree of increases appeared to be directly related to the duration of ischemic period; 2) reperfusion after 5 hr of ischemia could result in the formation of "no reflow phenomenon" in the ischemic tissues, including "primary no reflow" and "secondary capillary perfusion failure". These results suggest that 1) leukocyte-endothelium adhesion may contribute to the development of ischemia reperfusion injury; 2) in the limbs undergone 5 hr of ischemia, not all injuries that occur after ischemi-reperfusion can be attributed to ischemia reperfusion injury. The injury seen some in areas may be produced by ischemia alone, and in others ischemia-reperfusion-secondary ischemia injury may be responsible.

Animals↗
PubMed1995

[Status and strategy of parasitosis control in preventive health care in China].

According to the result of nationwide human parasitic disease distribution survey, the public significance of parasitosis control was set forth in terms of preventive health care and economic impact as well as parasitosis control and primary health care. A suggestion was made on the control strategy aiming at the parasitosis of priorities listed in the above survey.

China↗
PubMed1994

Sodium-coupled transport of glucose by plasma membranes of type II pneumocytes.

Sodium-dependent absorption of alveolar fluid promotes efficient gas exchange. In animal models, alveolar glucose stimulates phlorizin-sensitive, Na(+)-dependent fluid absorption. It is hypothesized that Na+/glucose cotransporters are localized to apical membranes of type II pneumocytes. Enriched apical and basolateral plasma membrane vesicles were isolated from adult bovine type II pneumocytes. Uptakes of 22Na+ and [3H]glucose by enriched apical and basolateral vesicles were monitored over time. Following addition of external glucose (75 mM), 22Na+ uptake by mannitol-loaded, apically-enriched vesicles was significantly increased over controls. Substitution of interior-negative charge gradients for internally directed Na+ gradients increased glucose-dependent Na+ uptakes even greater. By contrast, external glucose did not significantly promote 22Na+ uptake by enriched basolateral vesicles. External Na+ (75 mM) significantly increased [3H]glucose uptakes by enriched apical vesicles with evidence of overshoot. Phlorizin (100 microM) inhibited both glucose-coupled 22Na+ uptakes and Na(+)-coupled [3H]glucose uptakes. These observations support localization of electrogenic, Na+/glucose cotransporters to enriched apical membranes of mature type II pneumocytes.

Animals↗
PubMed1994

Sodium chloride cotransport at the basolateral membrane of type II pneumocytes.

Current evidence indirectly supports the hypothesis that Na+/Cl- cotransport occurs at basolateral membranes of type II pneumocytes. To test this hypothesis, enriched apical and basolateral plasma membrane vesicles were prepared from adult bovine type II pneumocytes. Uptake of 22Na+ or 36Cl- by these vesicle populations was monitored over time. Using enriched basolateral vesicles, substitution of formate- for Cl- nearly eliminated 22Na+ uptake, and substitution of Tris+ for Na+ significantly reduced 36Cl- uptake. These observations of Cl(-)-dependent 22Na+ uptake and Na(+)-dependent 36Cl- uptake demonstrated coupling between Na+ and Cl- absorption at the basolateral membrane. Na+/Cl- cotransport inhibitors, furosemide (1 mM) and bumetanide (0.1 mM), also reduced 22Na+ and 36Cl- uptakes by enriched basolateral vesicles. By contrast, furosemide and bumetanide did not affect 22Na+ and 36Cl- uptakes by enriched apical vesicles. Collectively, these observations support localization of Na+/Cl- cotransport to the basolateral membranes of mature type II pneumocytes.

Animals↗