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Biomedical subjects

C Peng

Publications and source records attributed to C Peng.

83 records · Page 5Linked to original sources
PubMed1991

Metabolism of gonadotropin-releasing hormone in goldfish: serum clearance and tissue uptake studies.

The metabolic clearance rate (MCR) and initial half-disappearance time (T(1/2)i) of salmon gonadotropin-releasing hormone (sGnRH) and its agonist analog [D-Arg6,Pro9-NEt]-sGnRH (sGnRH-A) were investigated in goldfish, following a single intraarterial injection of radioiodinated sGnRH and sGnRH-A. The tissue uptake of radioiodinated sGnRH-A was also investigated. 125I-sGnRH had a MCR of 0.01173 ml min-1 35 g-1 and a (T(1/2)i) of 32.38 min; 125I-sGnRH-A had a MCR of 0.0192 ml min-1 35 g-1 and a (T(1/2)i) of 72.95 min. In the tissue uptake experiments, high levels of accumulated labeled sGnRH-A were generally found in the gills, kidney, liver, and pituitary compared to air bladder, brain, gonad, eyes, and muscle. Coinjection of excess amount of cold sGnRH-A caused decreased uptake of labeled sGnRH-A only in pituitary, but increased accumulation of labeled sGnRH-A in some other tissues. Our results show a correlation between the T(1/2)i and the affinity of the peptides for a serum GnRH binding protein present in the goldfish, suggesting that the formation of a hormone-binding protein complex may decrease the MCR of GnRH in the circulation in goldfish. Our data also indicate specific uptake of 125I-sGnRH-A by the pituitaries of both male and female goldfish, confirming the pituitary as a major target organ of GnRH in goldfish.

Air Sacs↗
PubMed1991

A blind mobility aid modeled after echolocation of bats.

A new model of a mobility aid for the blind was designed using microprocessor and ultrasonic devices. This mobility aid was evaluated based on psychophysical experiments. In this model, a downswept FM ultrasound signal is emitted from a transmitting array with broad directional characteristics in order to detect obstacles. The ultrasound reflections from the obstacles are picked up by a two-channel receiver. The frequency of the emitted ultrasound is swept from 70 to 40 kHz within 1 ms, so it has almost the same characteristics as the ultrasound a bat produces for echolocation. The frequency of the reflected ultrasound wave is down converted by about 50:1 by using a microcomputer with A/D and D/A converters. These audible waves are then presented binaurally through earphones. In this method obstacles may be perceived as localized sound images corresponding to the direction and the size of the obstacles. From the results of psychophysical experiments, it was found that downswept FM ultrasound was superior for the recognition of small obstacles compared to other ultrasonic schemes. With it a blind person can recognize a 1-mm-diameter wire. It was also proved that the blind could discriminate between several obstacles at the same time without any virtual images. This mobility aid, modeled after the bat's echolocation system, is very effective at detecting small obstacles placed in front of the head.

Animals↗
PubMed1991

Identification and characterization of human immunodeficiency virus type 1 gag-pol fusion protein in transfected mammalian cells.

Three human immunodeficiency virus type 1 (HIV-1) mutants were constructed with mutations in their protease genes: AH2-pSVL, with an in-phase deletion; BH27-pSVL, with an out-of-phase deletion creating a stop codon immediately after the deletion site; and CA-pSVL, with a point mutation creating an Asp-to-Ala substitution at the putative protease active site. The wild-type, HXB2-pSVL, and the mutated viral genomes were used to transfect COS-M6 cells and to produce virions. Immunoblotting assays with a monoclonal antibody (MAb) specific for p24 showed that all three mutant contained a gag precursor, Pr56gag, with AH2 and CA expressing an extra band of about 160 kDa. Similar assays with a MAb specific for HIV-1 reverse transcriptase (RT) also revealed a 160-kDa protein from AH2 and CA virions and two mature p66 and p51 RT subunits from HXB2 virions. In addition, HXB2, AH2, and CA but not BH27 virions exhibited RT activity. The same protein in the 160-kDa band seemed to possess both p24 and RT components, since the MAb against p24 was able to immunoadsorb RT antigen and enzymatic activity. These results indicate that the HIV-1 gag-pol fusion protein produced in mammalian cells expressed significant RT activity.

Amino Acid Sequence↗
PubMed1990

Two isoforms of human membrane-bound alpha Ig resulting from alternative mRNA splicing in the membrane segment.

Antibodies specific for membrane-bound Ig (mIg) but not for their secreted forms would be useful not only for studying the function of mIg but also for modulating B cell activities in vivo. We have proposed that the extracellular portions of the membrane anchor peptides of mIg can be used as antigenic sites for isotype-specific targeting of B cells. Clones containing the genes of human Ig alpha 1 or alpha 2 subclasses were isolated from a genomic DNA library. The gene segments encoding the membrane peptides and their flanking regions were amplified by polymerase chain reaction, subcloned into plasmid pUC19, and the DNA sequences were determined. Human alpha 1 and alpha 2 genes, like murine alpha gene, each has only one membrane exon. The sequences of the human alpha 1 and alpha 2 genes are almost identical in the membrane peptide-coding region. The mRNA from a human mIgA-expressing B cell line, DAKIKI, was isolated, its cDNA prepared, and the segments spanning the membrane peptide-coding region and a part of the constant domain 3 amplified by polymerase chain reaction. DNA sequences revealed that there are two isoforms of alpha 1-chain, resulting from the alternative splicing of the third constant domain of H chain to two acceptor sites in the membrane exon. One isoform has a segment of 32 and the other 26 amino acid residues in the extracellular portion of the membrane peptide. These segments may serve as isotype-specific antigenic epitopes for antibody targeting of mIgA-bearing B cells.

Base Sequence↗
PubMed1990

Neuropeptide Y stimulates growth hormone and gonadotropin release from the goldfish pituitary in vitro.

The effects of neuropeptide Y (NPY) on release of growth hormone (GH) and gonadotropin (GTH) from the goldfish pituitary in vitro were investigated. Exposure of perifused pituitary fragments, taken from female goldfish at late stages of gonadal recrudescence, to 5-min pulses of human NPY resulted in a rapid dose-dependent stimulation of GH and GTH release, with half-maximal effective dosages of 0.51 +/- 0.24 and 2.37 +/- 1.05 nM for GH and GTH, respectively. Repeated treatments with pulses of NPY (10 nM for GH, 5 nM for GTH) at 55-min intervals did not significantly alter the responsiveness of pituitary fragments to NPY; however, prior exposure of pituitary fragments to pulses of higher doses of NPY (50 nM GH, 10 nM for GTH) significantly reduced the subsequent hormone responses. When given at 85-min intervals repeated treatment with NPY did not blunt hormone responses to the second and third stimulations at these higher dosages. These results indicate that NPY acts at the pituitary level to stimulate GH and GTH secretion in female goldfish. The GTH response and, to a lesser extent, the GH response become desensitized to further stimulation by NPY in dose- and time-dependent manners. NPY should be considered as one element in the multifactorial systems regulating the GH and GTH secretion in goldfish.

Animals↗
PubMed1990

[A comparative study of the clinical features of neurosis in urban and rural areas].

A clinical comparison of neurotic patients in urban area (Nanjing) and rural area (Huaiyin) is reported. There were 100 out-patients in each of these two groups. Both groups were similar in gender distribution, but the average age of onset was older in the urban area. Neurasthenic patients were more than 50% in each group. Depressive neurotic patients were more in the urban area; and hysterical patients were more in the rural area. In the urban group, there were more excited symptoms and sleep disturbance in the neurasthenic patients, but emotional disturbances were more in the rural group. For hysteric patients, there were more "possession" syndrome in the rural area. There were some other differences on the clinical symptoms in both groups. We have made some discussions about this respect.

Adolescent↗
PubMed1989

Role of human immunodeficiency virus type 1-specific protease in core protein maturation and viral infectivity.

It is generally believed that the gag gene product of human immunodeficiency virus type 1 (HIV-1) is processed into several core proteins by a virus-specific protease. We used deletion mutation analysis to study the role of HIV-specific protease in the processing of core proteins and its requirement for viral infectivity. Several mutant genomes with deletions in the protease gene were constructed. A mammalian cell line, COS-M6, transfected with the wild-type viral genome was shown to produce virions containing processed core proteins, while COS-M6 cells transfected with two mutated genomes could express only the core protein precursor, Pr56gag. The wild-type transfectant produced infectious virus; both transfectants expressing the mutated genomes also produced virions, and one of them still retained reverse transcriptase activity. However, the mutant viral particles were devoid of infectivity. Virions with a distinct central core and an electron-dense nucleoid budded out from the plasma membrane of COS-M6 cells transfected with the wild-type genome. In contrast, noninfectious virions that budded either into cytoplasmic vacuoles or out from the plasma membrane of COS-M6 cells transfected with mutant genomes contained ring-shaped nucleoids. These results indicate that the HIV-1 protease plays a role not only in the maturation of the core proteins but also in the assembly of the virus and thus is required for viral infectivity.

Amino Acid Sequence↗
PubMed1986

Effects of [D-Ala6, Pro9-NEt]-LHRH and catecholaminergic drugs on gonadotropin secretion and ovulation in the Chinese loach (Paramisgurnus dabryanus).

The effects of [D-Ala6,Pro9-NEt]-LHRH (LHRH-A) alone and in combination with drugs which influence the actions of dopamine or the synthesis of catecholamines on gonadotropin (GtH) secretion and ovulation in the loach (Paramisgurnus dabryanus) were investigated. LHRH-A alone stimulated an increase in serum GtH levels in the loach, but was a relatively ineffective treatment for the induction of ovulation. Injection of the dopamine receptor antagonist pimozide caused a marked potentiation of the GtH-release response to LHRH-A, and combined injections of pimozide and LHRH-A were an effective treatment for the induction of ovulation. Reserpine, a drug which causes depletion of catecholamines from presynaptic terminals, also caused a marked potentiation of the GtH-release response to LHRH-A and combined treatment induced ovulation. Similarly, administration of alpha-methyl-para-tyrosine to block conversion of tyrosine to L-dopa, or carbidopa to block conversion of L-dopa to dopamine, potentiated the GtH-release response to LHRH-A and induced ovulation. In contrast, the use of diethyldithiocarbamate, to block conversion of dopamine to norepinephrine, failed to augment the action of LHRH-A on GtH release and ovulation. The present results provide further evidence to suggest that dopamine functions as a gonadotropin release-inhibitory factor in teleosts, and demonstrate that the use of drugs which block either the synthesis or the actions of dopamine potentiates the action of LHRH-A in teleosts.

Animals↗
PubMedDate not supplied

Gonadotropin-releasing hormone receptor: gene structure, expression and regulation.

Gonadotropin-releasing hormone (GnRH) plays a major role in the endocrine control of reproduction. GnRH, released from the hypothalamus, acts upon the pituitary to stimulate LH and FSH secretion. In addition, GnRH also functions as a local regulator in a number of tissues and cell lines. GnRH interacts with a membrane receptor which belongs to the G-protein-coupled receptor family. The GnRH-R is encoded by a single-copy gene consisting of three exons and two introns. Consistent with the sites of its action, GnRH-R mRNA has been found in the brain, pituitary, gonads, placenta, as well as a number of carcinoma tissues and cells. GnRH-R mRNA level in the pituitary and gonads is controlled by a number of physiological regulators, such as GnRH, gonadotropin, estradiol and progesterone.

Animals↗
PubMedDate not supplied

Activin and follistatin as local regulators in the human ovary.

There is increasing evidence that activin may act as an autocrine/paracrine regulator of ovarian functions. Activin subunit mRNAs as well as activin immunoreactivities have been detected in the human ovary. Activin alters granulosa cell proliferation and steroidogenesis. The effect of activin is most likely mediated through specific receptors as mRNAs encoding several forms of activin receptors, namely ActR-I, ActR-IB, ActR-II and ActR-IIB are found in the preovulatory follicles as well as in cultured granulosa-luteal cells. Activin-binding protein, follistatin (FS), is also produced in the human ovary. In addition to neutralizing the effect of activin on steroid production, FS on its own also enhances estradiol production, an effect similar to that seen after activin treatment. These findings strongly suggest that activin and FS are important local regulators of steroidogenesis in the human ovary.

Activin Receptors↗