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Biomedical subjects

G Peng

Publications and source records attributed to G Peng.

66 records · Page 4Linked to original sources
PubMed1993

Soft x-ray magnetic circular dichroism: a probe for studying paramagnetic bioinorganic systems.

Soft x-ray magnetic circular dichroism was used to study a paramagnetic bioinogranic system. We measured the Fe L edges of Pyrococcus furiosus rubredoxin, using circularly polarized synchrotron radiation, a split-coil super-conducting magnet, low sample temperatures, and fluorescence detection. The observed dichroism effect is strong (30%) and in general agreement with the calculation. The method is element- and oxidation state-specific, and the data can be interpreted by established theoretical procedures. Soft x-ray magnetic circular dichroism demonstrates enormous potential as a probe for studying paramagnetic systems in biology, chemistry, and material science.

Bacteria↗
PubMed1992

Increased mitochondrial activities in pigmented (melanized) fish cells and nucleotide sequence of mitochondrial large rRNA.

Using the subtracted probe approach, we had previously isolated eight cDNAs whose corresponding RNAs are more abundant in pigmented (melanized) than in closely related unpigmented goldfish cell lines. We report here that two of these are of mitochondrial origin, suggesting that pigmentation is accompanied by higher content (activity) of mitochondria. We also present the complete nucleotide sequence of the full length cDNA for the large mitochondrial rRNA, showing the presence of a polyA tail, two polyadenylation signals and a long open reading frame potentially encoding for a polypeptide of 166 amino acids and with no known protein homologue. It is however unknown whether such a polypeptide is actually produced.

Animals↗
PubMed1988

Regulation of the distribution of carotenoid droplets in goldfish xanthophores and possible implication to secretory processes.

In goldfish xanthophores, the formation of pigment aggregate requires: 1) that a pigment organelle (carotenoid droplet) protein p57 be in the unphosphorylated state; 2) that self-association of pigment organelles occur in a microtubule-independent manner; and 3) that pigment organelles via p57 associate with microtubules. In the fully aggregated state, the pigment organelles are completely stationary. Pigment dispersion is initiated by activation of a cAMP-dependent protein kinase, which phosphorylates p57 and allows pigment dispersion via an active process dependent on F-actin and a cytosolic factor. This factor is not an ATPase, and its function is unknown. However, its abundance in different tissues parallels secretory activity of the tissues, suggesting a similarity between secretion and pigment dispersion in xanthophores. The identity of the motor for pigment dispersion is unclear. Experimental results show that pigment organelles isolated from cells with dispersed pigment have associated actin and ATPase activity comparable to myosin ATPase. This ATPase is probably an organelle protein of relative molecular mass approximately 72,000, and unlikely to be an ion pump. Isolated pigment organelles without associated actin have 5x lower ATPase activity. Whether this organelle ATPase is the motor for pigment dispersion is under investigation. The process of pigment aggregation is poorly understood, with conflicting results for and against the involvement of intermediate filaments.

Actin Cytoskeleton↗
PubMed1984

Cardiac actions of bovine parathyroid hormone fragment (1-34) in some lower vertebrates.

Only recently have the cardiac actions of parathyroid hormone and its N-terminal (1-34) fragment (bPTH(1-34] been examined. Parathyroid hormone was found to exert a positive chronotropic effect on the heart tissue of several mammals and one amphibian in vivo and/or in vitro. The purpose of the present study was to examine in vitro the heart tissue of several lower vertebrates, particularly aquatic vertebrates, for responsiveness to bPTH(1-34) and, for comparative purposes, isoproterenol. Heart tissue (atrium or the entire heart) from all the animals studied (trout, mudpuppy, bullfrog tadpole, and adult bullfrog) responded to isoproterenol in a dose-dependent fashion with increased heart rate and contractile force. Only the atria from the adult bullfrog, however, responded in a similar manner to the administration of bPTH(1-34). In all cases propranalol (10(-6) M) was able to block both chronotropic and inotropic effects of isoproterenol but had no effect on the cardiac stimulation induced by bPTH(1-34) in the adult bullfrog atrium. The data suggests that cardiac responsiveness to bPTH(1-34) is associated with a terrestrial as opposed to an aquatic existence.

Animals↗
PubMed1978

Potential CNS antitumor agents-phenothiazines II: fluphenazine analogs.

Fluphenazine was found to possess moderate reproducible activity against the intraperitoneal L-1210 and P-388 leukemia murine tumor models. Seven ether derivatives of fluphenazine and eight compounds in which the terminal side-chain hydroxyl group was replaced by an amine function were prepared and evaluated in the intraperitoneal L-1210, P-388, and B16 melanoma systems as well as the intracerebral L-1210 and ependymoblastoma brain tumor models. While no substantial intracerebral activity was observed, seven derivatives possessed reproducible activity in the intraperitoneal L-1210 or P-388 system. Several gave T/C values of 150%. No B16 melanoma activity was observed. These compounds were also tested for their cytotoxic properties in culture against L-1210, P-388, and KB cells. The amine isosteres, while possessing little in vivo activity, were the most cytotoxic of the compounds prepared, with several having ED50 values less than 1 microgram/ml.

Animals↗
PubMed1977

Opium and heroin addicts in Laos. I. A comparative study.

Students of narcotic addiction have believed that heroin addiction is more debilitating than the "traditional" opium addiction. Access to both opium and heroin addicts in a Laotian treatment facility provided an opportunity to test this hypothesis. All subjects were volunteer narcotic addicts seeking treatment at an inpatient detoxification facility over a 12-month period. The research format consisted of five demographic characteristics, four aspects of past narcotic usage, and three aspects of current narcotic usage. Fifty-one heroin addicts were compared to 438 opium addicts. Many of the demographic differences in the two groups reflected the urban residence of most heroin addicts and the mixed urban-rural residence of opium addicts. Heroin addicts had more frequent daily doses of drug, spent considerably more money for their drug, and required higher initial methadone doses for detoxification. It also appeared that heroin addicts might have "deteriorated" faster and thus sought treatment earlier than opium addicts. Since the heroin and opium addicts in this study differed significantly on most demographic characteristics, it was difficult to know whether these observed differences were due to drug factors or demographic factors. Thus, a study of pairs matched for age, sex, and ethnicity was subsequently undertaken to test the hypotheses generated by this study.

Adolescent↗
PubMed1977

Opium and heroin addicts in Laos. II. A study of matched pairs.

Fifty-one Asian heroin addicts in Laos were matched for sex, ethnicity, and age with 51 opium addicts. All subjects were voluntary patients at a treatment facility for addicts. The two groups were compared for demographic characteristics, past narcotic history, current narcotic use, and readmission within 1 year following discharge from treatment. Heroin addicts took more doses of drug per day, spent more money per day on narcotic drugs, required higher detoxification doses of methadone, and sought treatment much sooner than did opium addicts. The two groups did not differ for duration of narcotic use prior to becoming addicted, or for rate of readmission following treatment. Demographic differences in occupation and employment reflected the urban distribution of heroin addicts, and the mixed urban-rural residence of opium addicts. These data suggest that heroin is not per se more or less apt to produce addiction (i.e., is not more "addictogenic") as compared to opium. The type of narcotic drug also does not appear to be an important factor in determining treatment outcome. However, heroin does appear to be more "pathogenic" than opium, since heroin addicts sought treatment much sooner than did opium addicts. This may have been due to economic factors (i. e., heroin addicts took more doses per day, spent more time in phases of intoxication and withdrawal, and spent less time in the middle phase with work and other coping behaviors). Opium addiction is not a "benign" or "social" form of addiction. In comparison to heroin, however, opium does cost less, requires fewer doses per day, and has a less toxic withdrawal (at least in the initial phase). Moreover, opium apparently takes longer to produce life crises that motivate the addict to seek treatment.

Adolescent↗
PubMedDate not supplied

Efficacy and safety of abacavir plus lamivudine versus didanosine plus stavudine when combined with a protease inhibitor, a nonnucleoside reverse transcriptase inhibitor, or both in HIV-1 positive antiretroviral-naive persons.

PURPOSE: The combination of abacavir + lamivudine (ABC+3TC) versus didanosine + stavudine (ddI+d4T), each combined with other classes of antiretrovirals (ARVs) in ARV-naive patients, was compared for the combined endpoint of time to plasma HIV RNA >50 copies/mL (at or after the 8-month visit) or death (primary endpoint) in a nested substudy of an ongoing multicenter randomized trial. METHOD: The substudy enrolled 182 patients; mean HIV RNA and CD4+ cell counts at baseline were 5.1 log10 copies/mL and 212 cells/mm3, respectively. RESULTS: After a median follow-up of 28 months, rates of primary endpoint were 57.2 and 67.8 per 100 person-years for the ABC+3TC and ddI+d4T groups (hazard ratio [HR]=0.81, 95% confidence interval [CI] 0.58-1.14, p=.23). CONCLUSION: There was a trend for treatments containing ABC+3TC to be better than treatments containing ddI+d4T with respect to HIV RNA decreases, CD4+ cell count increases, and tolerability.

Anti-HIV Agents↗
PubMedDate not supplied

Human T cells transduced by a retroviral vector to express Herpesvirus saimiri proteins TIP and STPC.

Herpesvirus saimiri is a virus capable of inducing oncogenic transformation of T lymphocytes of New World primates and immortalizing human T cells in vitro. T lymphocytes immortalized by H. saimiri demonstrate functional biological responses to their antigens. Therefore, H. saimiri-induced transformation of T cells emerges as a very powerful tool of T-cell biology. Although the mechanism of this transformation remains to be understood, it is thought that H. saimiri proteins Tip and StpC play important roles. To facilitate functional studies of Tip and StpC, we retrovirally transduced human MOLT4, Jurkat and JCaM1 T-cell lines to express these H. saimiri proteins, using a three-plasmid system allowing for rapid and efficient production of high-titer retroviral stocks. Several cell lines expressing Tip and/or StpC in a stable fashion were obtained and characterized.

3T3 Cells↗