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Biomedical subjects

X Y Ma

Publications and source records attributed to X Y Ma.

49 records · Page 3Linked to original sources
PubMed1990

Interaction of a noncytopathic human immunodeficiency virus type 1 (HIV-1) with target cells: efficient virus entry followed by delayed expression of its RNA and protein.

Recently described noncytopathic human immunodeficiency viruses type-1 (HIV-1) form a new category within the HIV-1 family due to their unique biological properties and predominant occurrence in symptom-free individuals. To study the mechanism of noncytopathic HIV-1 infection, we compared the infectivity and life cycles of two closely related HIV-1 clones with noncytopathic (N1T-E) or cytopathic (N1T-A) properties. N1T-E virus exhibited slow kinetics of infection in T cells and monocytes. Slow infection was not due to defective virus entry, because N1T-E and N1T-A exhibited equally efficient virus-cell fusion activity and nucleocapsid internalization. Kinetic studies of N1T-E genome expression revealed low levels of viral RNA, structural proteins, and Tat protein during the first 7 days after virus entry. In contrast, cells infected with the same dose of cytopathic N1T-A virus began to express high levels of genomic RNA, structural proteins, and Tat protein within 48 hr of infection; the expression peaked on Day 5, followed by complete cell lysis. No delay in N1T-E replication, as compared to N1T-A, was observed after transfection of cloned N1T-E proviral DNA. N1T-E virus had intact Tat, Rev, and fusion functions and replicated well in chronically infected cells. These results suggest that delayed processing or expression of HIV-1 genome during the early phase of the virus replicative cycle is an important determinant in noncytopathic infection.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Effect of medial arterial calcification on O2 supply to exercising diabetic feet.

We investigated whether medial arterial calcification (MAC) impairs O2 supply to the exercising foot in diabetic patients with foot lesions. Transcutaneous O2 tension (tcPO2) was monitored at the dorsum of the foot before and after bicycle exercise in 11 diabetic patients with peripheral ischemic vascular disease (PIVD) with or without concomitant existence of MAC, 10 patients with MAC but without PIVD, 10 diabetic control subjects, and 6 nondiabetic control subjects. The mean preexercise tcPO2 level was comparable in these four groups. However, tcPO2 decreased significantly with exercise in feet with PIVD (mean +/- SE -17.9 +/- 2.7%, P less than 0.01, n = 11), regardless of presence or absence of vascular calcification. On the other hand, the value increased significantly with exercise in feet with MAC but without PIVD (21.2 +/- 3.5%, P less than 0.01, n = 10) and in those of diabetic control subjects (14.9 +/- 3.6%, P less than 0.01), respectively. The tcPO2 remained unchanged in the feet of nondiabetic control subjects (1.7 +/- 1.1%). The results suggest that MAC is not associated with reduced O2 supply to the exercising foot in diabetic patients.

Adult↗
PubMed1989

[The synthesis and pharmacological activities of analogs of erycibe alkaloid II].

The C2 deoxy and C6 electron isosteric analogs of a new antiglaucoma agent, erycibe alkaloid II, were designed and synthesized. The main pharmacological results were as follows: 1. The C2-OH in erycibe alkaloid II was one of the key groups for its myotic activity; 2. It was worth noting that compounds 2 and 4 showed cholinergic and anticholinergic activities, respectively. This phenomenon in tropane alkaloids was not reported before; 3. The C6 electron isosteric compounds 16 and 17 showed neither anticholinergic nor cholinergic activities.

Animals↗
PubMed1988

Role of oxygen during horseradish peroxidase turnover and inactivation.

Horseradish peroxidase catalyzed oxidation of phenol has been reinvestigated to determine the requirements of facile enzyme autoinactivation. Turnover of this peroxidase was monitored spectrophotometrically at 400 nm and found dependent on the concentration of phenol and hydrogen peroxide. The inactivation of the peroxidase required both substrates, phenol and H2O2, but surprisingly was also potentiated by molecular oxygen. Exclusion of diffusible superoxide or hydroxyl radicals had slight effect on product formation or loss of catalytic activity. A mechanism is proposed to explain the unanticipated role of oxygen during enzyme inactivation.

Free Radicals↗
PubMed1988

Low-cytopathic infectious clone of human immunodeficiency virus type I (HIV-I).

Single genotypic variants of HIV-I, contained in a parental cytopathic HIV-I isolate, were isolated by molecular cloning and propagated in susceptible cells. Two such HIV-I clones, designated N1T-E and N1T-A, exhibited similar restriction endonuclease maps but strikingly different biological activities. Infection of T lymphocytes or monocytes by clone N1T-E was characterized by slow kinetics and lack of significant cytopathic effects, but high reverse transcriptase activity levels in culture supernatants of chronically-infected cells. Clone N1T-A, like the parental HIV-I isolate, exhibited fast kinetics of infection in T cells and monocytes and strong cytopathicity in these cells. Full characterization of the low-cytopathic virus in comparison to the structurally similar cytopathic clone may facilitate the elucidation of the molecular basis of HIV cytopathogenicity.

Cloning, Molecular↗
PubMed1988

Differences in cytopathogenicity and host cell range among infectious molecular clones of human immunodeficiency virus type 1 simultaneously isolated from an individual.

A cytopathic human immunodeficiency virus type 1 (HIV-1) isolate containing multiple virus genotypes was molecularly cloned, and the biological activity of six randomly selected clones was assessed by transfection into human lymphoid or glial cell lines. Five infectious clones of HIV-1, termed N1T-A through -E, were isolated in this manner. Clones N1T-A, -B, -C, and -E could be distinguished by restriction endonuclease mapping whereas clones N1T-B and -D had identical maps with the enzymes used. Each clone exhibited a distinct host cell range as well as markedly different infection kinetics and cytopathogenic properties when tested in human cell lines of T-lymphocytic, monocytic, and astrocytic origin. In particular, infection with HIV-1 clone N1T-E was characterized by slow kinetics and lack of significant cytopathic effects in acutely and chronically infected cells. Clone N1T-A, similar to the parental isolate N1T, exhibited a wide host cell range, fast kinetics of infection, and high cytopathogenicity. These data indicate that HIV-infected individuals may carry multiple HIV-1 genotypes with distinct cytopathogenic potential and cell tropism. Analysis of virus isolates must take into account the contribution, or masking, of individual virus clones.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Results of air pressure enema reduction of intussusception: 6,396 cases in 13 years.

Intussusception is the most common surgical emergency of childhood in China. Over the past 10 years, the incidence of intussusception has steadily increased world-wide, as well as in China. For example, 279 cases were treated in the Shanghai Children's Hospital in 1974, while 615 were treated in 1984. Twelve cases were treated in a course of a single night during 1985. Over the past 13 years, for which we have good records, 6,396 cases of intussusception were treated at the Shanghai Children's Hospital. Males outnumber females by a ratio of 2 to 1. In 3,872 cases seen over the past 6 years, 35.1% were under 6 months of age, 65.9% less than 1 year of age, and 88.4% less than 2 years of age.

Age Factors↗