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Y L Tang

Publications and source records attributed to Y L Tang.

10 recordsLinked to original sources
PubMed2005

A hypoxia-inducible vigilant vector system for activating therapeutic genes in ischemia.

Hypoxia represents an endogenous pathophysiological signal underlying cell growth, adaptation and death in a variety of diseases, including ischemic heart diseases, stroke and solid tumors. A vigilant vector system depends on a gene switch which can sense the hypoxia signal occurring in ischemic events and turn on/off protective gene expressions when necessary. This system uses the oxygen-dependent degradation domain derived from hypoxia-inducible factor 1alpha as the hypoxia sensor and a double-vector system as signal amplifier. For treating ischemic heart diseases, a cardiac-specific MLC-2v promoter is used to deliver transgenes specifically to the heart. When tested in cardiomyocyte cultures, it produced a rapid and robust gene induction upon exposure to low oxygen. In a mouse model for myocardial infarction, the vigilant vectors turned on therapeutic genes such as heme oxygenase-1 in response to ischemia, significantly reduced apoptosis in the infarct area and improved cardiac functions. The hypoxia-regulated gene transfer afforded by the vigilant vectors may provide a powerful tool for delivering therapeutic proteins specifically to ischemic tissues with optimal physiological control.

Animals↗
PubMed2001

Sequence-dependent interactions of two forms of UvrC with DNA helix-stabilizing CC-1065-N3-adenine adducts.

The uvrA, uvrB, and uvrC genes of Escherichia coli control the initial steps of nucleotide excision repair. The uvrC gene product is involved in at least one of the dual incisions produced by the UvrABC complex. Using single-stranded (ss) DNA affinity chromatography, we have separated two forms of UvrC from both wild-type E. coli cells and overproducing cells. UvrCI elutes at 0.4 M KCl, and UvrCII elutes at 0.6 M KCl. In general, both forms, in the presence of UvrA and UvrB, actively incise UV-irradiated and CC-1065-modified DNA in the same fashion; i.e., they incise six to eight nucleotides 5' to and three to five nucleotides 3' to a photoproduct or a CC-1065-N3-adenine adduct. They produce different incisions, however, at a CC-1065-N3-adenine adduct in the sequence 5'-GATTACG- present in the MspI-BstNI 117 bp fragment of M13mp1. UvrABCI incises at both the 5' and 3' sides of the adduct (UvrABCI cut), while UvrABCII incises only at the 5' side (UvrABCII cut). Mixing UvrCI and UvrCII results in both UvrABCI and UvrABCII cuts, and the levels of these two types of cutting are proportional to the amount of UvrCI and UvrCII. DNase I footprints of the MspI-BstNI 117 bp DNA fragment containing a site-directed CC-1065-adenine adduct at the 5'-GATTACG- site show that UvrCII, but not UvrCI, binds to the adduct site. Furthermore, the pattern of DNase I footprints induced by UvrCII binding differs from the pattern of the footprints induced by UvrA, UvrAB, and UvrABCI binding. Interestingly, while the presence of unirradiated DNA enhances the efficiency of UvrABCII in incising UV-irradiated DNA, it does not enhance UvrABCII incision of the CC-1065-N3-adenine adduct formed at 5'-GATTACG-. These results show that two different forms of UvrC differ in DNA binding properties as well as incision modes at some kinds of DNA damage.

Adenine↗
PubMed2000

The bioavailability of beta-carotene in stir- or deep-fried vegetables in men determined by measuring the serum response to a single ingestion.

To evaluate the bioavailability of beta-carotene from plant foods, the serum beta-carotene response to a single ingestion of various beta-carotene sources was determined in 10 healthy men. Tested beta-carotene sources included stir-fried shredded carrot, stir-fried water convolvulus leaves, deep-fried sweet potato ball, purified beta-carotene in a capsule (beadlets) and beadlets with beta-carotene free oriental radish (beadlets + radish). The maximal change in serum beta-carotene concentration occurred at 24 or 32 h post ingestion. This response to beadlets was significantly higher than that to the other four tested beta-carotene sources (P < 0.05). The maximal serum response to beadlets + radish was also significantly higher than that to the three food beta-carotene sources (P < 0.05). The maximal serum response to sweet potato was significantly higher than that to water convolvulus leaves (P < 0. 05). The bioavailability relative to beta-carotene beadlets was calculated by dividing the maximal change in serum concentration to each test meal of each subject by his own serum maximal change in response to beadlets. Accordingly, the bioavailability was 65% for beadlets + radish, 33% for carrots, 26% for water convolvulus leaves and 37% for sweet potatoes. Concurrent ingestion of oriental radish reduced the bioavailability of beadlets to two-thirds of its original value, which partially accounted for the difference between the bioavailability of beadlets and natural foods. The relative bioavailability of beta-carotene from stir-fried and deep-fried vegetables was about one-third to one-fourth that of the purified beta-carotene beadlets. These bioavailabilities are higher than previously reported values.

Adult↗
PubMed1998

Susceptibility to vaccine-preventable diseases in a sexually transmitted disease clinic population.

BACKGROUND AND OBJECTIVE: Sexually transmitted disease (STD) clinics often serve a population that has low medical care utilization. The objective of this study was to determine the susceptibility of an STD clinic population to vaccine-preventable diseases. STUDY DESIGN: A cross-sectional study of immunization practices and susceptibility to vaccine-preventable diseases was undertaken by enrolling consecutive patients attending an STD clinic. Demographic information and a history of disease or immunization was assessed by interview. Immunity to measles and rubella was determined by measuring IgG antibodies by ELISA assays. RESULTS: Of the 288 patients evaluated, the mean age was 28 years and 70.5% were male. Serologically, 16.3% were susceptible to rubella and 8% to measles. Only 8% reported hepatitis B immunization. Although measles protection was high, nearly one in six was susceptible to rubella. Hepatitis B immunization was severely underused. CONCLUSION: Baltimore STD clinic patients may benefit from an enhanced rubella and hepatitis B prevention strategy.

Adult↗
PubMed1989

Hypercapnia and response of cerebral blood flow to hypoxia in newborn lambs.

Individual effects of hypoxic hypoxia and hypercapnia on the cerebral circulation are well described, but data on their combined effects are conflicting. We measured the effect of hypoxic hypoxia on cerebral blood flow (CBF) and cerebral O2 consumption during normocapnia (arterial PCO2 = 33 +/- 2 Torr) and during hypercapnia (60 +/- 2 Torr) in seven pentobarbital-anesthetized lambs. Analysis of variance showed that neither the magnitude of the hypoxic CBF response nor cerebral O2 consumption was significantly related to the level of arterial PCO2. To determine whether hypoxic cerebral vasodilation during hypercapnia was restricted by reflex sympathetic stimulation we studied an additional six hypercapnic anesthetized lambs before and after bilateral removal of the superior cervical ganglion. Sympathectomy had no effect on base-line CBF during hypercapnia or on the CBF response to hypoxic hypoxia. We conclude that the effects of hypoxic hypoxia on CBF and cerebral O2 consumption are not significantly altered by moderate hypercapnia in the anesthetized lamb. Furthermore, we found no evidence that hypercapnia results in a reflex increase in sympathetic tone that interferes with the ability of cerebral vessels to dilate during hypoxic hypoxia.

Animals↗
PubMed1988

Base-line O2 extraction influences cerebral blood flow response to hematocrit.

We have shown that the fall in cerebral blood flow (CBF) as hematocrit (Hct) rises is due to the independent effects of increasing red blood cell (RBC) concentration and arterial O2 content (CaO2). In the present study, we tested the hypothesis that the magnitude of the effect of RBC concentration depends on the base-line cerebral fractional oxygen extraction (E). E is the ratio of O2 demand (cerebral O2 consumption, CMRO2) to supply (cerebral O2 transport: OT = CBF x CaO2) and is assumed to be inversely related to tissue O2 availability. Pentobarbital-anesthetized 1- to 7-day-old sheep were first exchange transfused with plasma to lower Hct to 20%. Base-line E was set to either high or low levels by induction of hypocarbia [arterial CO2 partial pressure (PaCO2) = 15.3 +/- 0.7 mmHg, means +/- SE; n = 7] or hypercarbia (PaCO2 = 62.7 +/- 1.1 mmHg; n = 5), respectively. A second isovolemic exchange transfusion with pure methemoglobin-containing adult sheep red cells then raised Hct (to 38.5 +/- 0.5%) with no significant increase in CaO2. PaCO2 was maintained and other variables (oxyhemoglobin affinity, pH, mean arterial blood pressure) with potential effect on CBF did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1987

Effect of hematocrit on cerebral blood flow with induced polycythemia.

Cerebral blood flow (CBF) is lowered during polycythemia. Whether this fall is due to an increase in red blood cell concentration (Hct) or to an increase in arterial O2 content (Cao2) is controversial. We examined the independent effects of Hct and Cao2 on CBF as Hct was raised from 30 to 55% in anesthetized 1- to 7-day-old sheep. CBF was measured by the radiolabeled microsphere technique before and after isovolemic exchange transfusion with either oxyhemoglobin-containing erythrocytes (in 5 control animals) or with methemoglobin-containing erythrocytes (in 9 experimental animals). Following exchange transfusion in the control animals, Hct rose (30 +/- 1 vs. 55 +/- 1%, mean +/- SE), Cao2 increased (15.1 +/- 0.8 vs. 26.7 +/- 0.9 vol%), and CBF fell (66 +/- 9 vs. 35 +/- 5 ml X min-1 X 100 g-1). Because the fall in CBF was proportionate to the rise in Cao2, cerebral O2 transport (CBF X Cao2) was unchanged. Following exchange transfusion in the experimental animals, Hct rose (32 +/- 1 vs. 55 +/- 1%) but Cao2 did not change. Nevertheless, CBF still fell (73 +/- 4 vs. 48 +/- 2 ml X min-1 X 100 g-1) and, as a result, cerebral O2 transport also fell. The latter cannot be attributed to a fall in cerebral O2 uptake, as cerebral O2 uptake was unaffected during each of these conditions. Comparison of the two groups of animals showed that approximately 60% of the fall in CBF may be attributed to the increase in red cell concentration alone. It is probable that this effect is due largely to changes in blood viscosity.

Animals↗