Modification of the rabbit carotid body type I cell mitochondria by high altitude exposure and the effects of dracocephalum heterophyllum.
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Altitude↗
Biomedical subjects
F Yang
Publications and source records attributed to F Yang.
A proper transmembrane Ca2+ gradient is essential for the stimulation of adenylate cyclase activity by stimulatory GTP-binding protein.
Stimulatory GTP-binding Protein (Gs) and adenylate cyclase prepared from bovine brain cortices were co-reconstituted into asolectin vesicles with or without 1000-fold transmembrane Ca2+ gradient. The results showed that both basal activity and Gs-stimulated activity of adenylate cyclase were highest in proteoliposomes with a transmembrane Ca2+ gradient similar to physiological condition (1 microM Ca2+ outside and 1 mM Ca2+ inside) and lowest when the transmembrane Ca2+ gradient was in the inverse direction. Such a difference could be diminished following dissipation of the transmembrane Ca2+ gradient by A23187. Comparable conformational changes of Gs in proteoliposomes were also observed when Gs was labeled with the fluorescence probe, acrylodan. These results may indicate that a proper transmembrane Ca2+ gradient is essential not only for higher adenylate cyclase activity but also for its stimulation by Gs.
Adenosine Monophosphate↗
Human 17 beta-hydroxysteroid dehydrogenase: overproduction using a baculovirus expression system and characterization.
Estrogenic 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) plays a pivotal role in the synthesis of estrogens. We overproduced human placental estrogenic 17 beta-HSD using a baculovirus expression system for the study of the enzyme mechanism. A cDNA encoding the entire open reading frame of human 17 beta-HSD was inserted into the genome of Autographa californica nuclear polyhedrosis virus and expressed in Spodoptera frugiperda (Sf9) insect cells. Metabolic labeling and Western blot analysis using polyclonal antibodies raised against native human 17 beta-HSD indicated that a molecule with an apparent mass of 35 kDa was maximally expressed 60 h after infection. At that time interval, intracellular 17 beta-HSD activity reached 0.26 U/mg of protein in crude homogenate, about 70 times the level measured in human placenta. Purification of recombinant 17 beta-HSD was achieved by a single affinity fast liquid protein chromatography step yielding 24 mg of purified 17 beta-HSD protein per liter of suspension culture, with a specific activity of about 8 mumol/min/mg of protein for conversion of estradiol into estrone, at pH 9.2. In addition, the recombinant protein purified from infected Sf9 cells was assembled as a dimer with molecular mass and specific activity identical to those of the enzyme purified directly from placenta. The present data show that the baculovirus expression system can provide active 17 beta-HSD that is functionally identical to its natural counter-part and easy to purify in quantities suitable for its physico-chemical studies.
17-Hydroxysteroid Dehydrogenases↗
Terminal differentiation and senescence in the human melanocyte: repression of tyrosine-phosphorylation of the extracellular signal-regulated kinase 2 selectively defines the two phenotypes.
Melanocytes are pigmented cells distributed in humans in several organs like the epidermis, the leptomeninges, the eye, and the inner ear. Epidermal melanocytes, whether derived from adult or neonatal skin, proliferate well in a medium supplemented with phorbol esters and other mitogens before they undergo senescence. Potent cAMP inducers like cholera toxin are also growth promoters for neonatal melanocytes but only transient growth stimulators for cells derived from adults. We used this cellular system to delineate biochemical pathways involved in proliferation and in terminal differentiation. Here we show that after a period of 4-8 wk of sustained proliferation in the presence of cholera toxin, the adult melanocytes became round, flat, and enlarged. These changes were associated with terminal growth and preceded by a five- to sixfold increase in cAMP levels and an 8- to 10-fold increase in melanin content. The simultaneous addition of phorbol esters and cholera toxin did not prevent cells from reaching terminal differentiation. Identified targets for phorbol esters are protein kinase C (PKC) and the mitogen-activated kinases (MAPKs), also called extracellular signal-regulated kinases (ERKs). PKC was found to be similarly regulated in proliferating and in terminally differentiated melanocytes. Proliferating melanocytes in early or late passage showed identical activation of the kinase ERK2. This kinase was rapidly phosphorylated upon phorbol 12-myristate 13-acetate (PMA) addition and specifically accumulated in the nucleus of the cells, whereas in unstimulated cells it had a perinuclear distribution. In contrast, senescent and terminally differentiated cells were unable to phosphorylate tyrosine residues of the ERK2 gene product in spite of presenting normal amounts of ERK2 protein. In addition, ERK2 did not show the nuclear accumulation observed in proliferating melanocytes after PMA activation and remained localized in the perinuclear area. These results demonstrate that senescent and terminally differentiated melanocytes share a common block in a critical pathway thought to integrate multiple intracellular signals transmitted by various second messengers and specifically prevent the continuation of the signal transduction cascade initiated by PMA activation of PKC.
Adult↗
Electron-impact-ionization cross section for the hydrogen atom.
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Journal Article↗
Optical confirmation of the extended mean-field theory for a smectic-C*-smectic-A transition.
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Journal Article↗
Isolation of ribonucleotide reductase from Mycobacterium tuberculosis and cloning, expression, and purification of the large subunit.
Ribonucleotide reductase, an allosterically regulated, cell cycle-dependent enzyme catalyzing a unique step in the synthesis of DNA, the reduction of 2'-ribonucleotides to 2'-deoxyribonucleotides, was purified 500-fold from Mycobacterium tuberculosis Erdman strain through cell disruption, ammonium sulfate fractionation, and dATP-Sepharose affinity column chromatography. As in eucaryotes and certain bacteria and viruses, the M. tuberculosis enzyme consists of two nonidentical subunits, R1 and R2, both of which are required for activity. R1 has a molecular mass of 84 kDa, as identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and photoaffinity labeling with dATP. The amino acid sequences of the N-terminal peptide and two internal peptides were determined, and a partial R1 gene was isolated by PCR with primers designed from these amino acid sequences. Additional coding sequences were isolated by screening size-selected libraries, and a full-length form of M. tuberculosis R1 was generated by PCR amplification of high-molecular-weight M. tuberculosis DNA and expressed in Eschericnia coli. This coding sequence is 2,169 nucleotides long and contains no introns. The predicted molecular mass of R1 from the DNA sequence is 82,244 Da. Recombinant M. tuberculosis R1, purified to homogeneity, was biochemically active when assayed with extracts of M. tuberculosis enriched for R2.
Adenosine Triphosphate↗
Peroneal muscular atrophy with pyramidal tract features (hereditary motor and sensory neuropathy type V): a clinical, neurophysiological, and pathological study of a large kindred.
A large family with autosomal dominant inheritance of peroneal muscular atrophy, associated with extensor plantar responses in some cases, has been studied. Onset was usually in the first two decades and spasticity was not a feature. Nerve conduction studies in 21 cases and light and electron microscope findings on six sural nerve biopsies were similar to those in hereditary motor and sensory neuropathy type II.
Adolescent↗
Ventilatory response to randomly modulated hypercapnia and hypoxia in humans.
We have developed a new method for characterizing the ventilatory response to combined hypercapnia and hypoxia (HCVR-HVR) based on the results of a single test procedure. The method is designed to evoke both hypercapnic and hypoxic responses simultaneously and to enable quantification of their static and dynamic features using an estimation algorithm based on the prediction error method. In six healthy subjects, we measured HCVR-HVR by modulating the CO2 and O2 content of the inhaled mixture in the form of two statistically independent random sequences. A two-component dynamic model was found to provide an adequate description of the stimulation-response data sets. The model consisted of a CO2 subsystem and a CO2-O2 subsystem in which a multiplicative interaction between hypercapnia and hypoxia was assumed. The steady-state gains were 2.08 +/- 0.68 (SD) 1.min-1.Torr-1 for the CO2 subsystem and 0.10 +/- 0.05 l.min-1.Torr-1 for the CO2-O2 subsystem, and the corresponding time constants were 116.7 +/- 32.3 and 19.0 +/- 4.4 s, respectively. Our results suggest that the hypercapnic component of HCVR-HVR is mediated primarily by the central chemoreceptors, whereas the interaction component is mediated largely by the peripheral chemoreceptors.
Adult↗
Further study on the spontaneous partial folding of chicken heart apocytochrome c.
It has been previously reported (Biochem. Mol. Biol. Int., 30(5), 867-876, 1993) that chicken heart apocytochrome c has stronger tendency to fold spontaneously in aqueous solution than those from other species, and the relevance of its folding state with its ability to penetrate across the lipid bilayers has also been studied. In the present paper, the spontaneous folding characteristics of chicken heart apocytochrome c was further examined by the studies of Fourier-transform infrared spectra, the properties of intrinsic tryptophan fluorescence, and the measurements of hydrophobicity. In addition, it was also demonstrated that the partially-folded apocytochrome c is easily to be aggregated and hence relatively incompetent for translocation across the phospholipid bilayers.
Animals↗
[Epidemiology and control of hookworm infection in Fujian province].
Fujian province has been known to be endemic for mixed hookworm infection with Ancylostoma duodenale as the predominant species. The infection rate was 50% before 1980. As a result of mass treatment starting from 1980, the infection rate was decreased in most areas. And, infection foci were changed from sweet potato fields to the banana, sweatcane and asparagus fields where the infection rate tended to increase. It is stressed that the current endemic characteristics of hookworm infection should be paid more attention in implementing the control programme of hookworm infection.
Adolescent↗
[Effect of anti-fibronectin-serum on fertilization capacity of human spermatozoa].
Using the in vitro penetration test, we initially studied effects of anti-fibronectin (FN)-serum on fertilization capacity of human spermatozoa. Owing to the coincubation of anti-FN-serum in a heterologous system (human spermatozoa and zona-free gold hamster oocyte), a certain increase was found in the penetration rate at a low concentration of anti-FN-serum. The penetration rate in the treated group was 20% higher than that in the control group at an anti-FN-serum concentration of 10 microliters/ml (P < 0.05), but at a higher concentration of anti-FN-serum, the penetration rate was not affected. The results suggest that anti-FN-serum can improve the fertilization capacity of human spermatozoa, help to treat the unexplained infertility, and increase the repregnancy rate of vasovasotomy.
Animals↗
[Effects of fibronectin on cytodifferentiation (T56) of human squamous cell carcinoma of tongue].
Fibronectin (FN) are large glycoproteins that have been implicated in a wide variety of cellular properties, including cell adhesion, morphology, cytoskeletal organization, migration, differentiation, and oncogenic transformation. T56 cells were treated with 20, 50, and 100 micrograms/ml of FN for 48 h, and the changes in cells were analysed qualitatively and quantitatively with the methods of transmission electron microscopy, enzyme cytochemistry, and cell electrophoresis, etc. The studies were made to test the effects of FN on T56 cells in biological behaviour in terms of cell growth, multiplication, cell metabolism, cell electrophoresis and surface morphology. The results indicated that FN could partially restore T56 cell normal epidermic cell's phenotype, inhibit cell mitosis, increase contact of cells, decrease the number of microvilli and ruffles, and promote cell oxybiotic metabolism. These results suggest that FN might relate in many aspects to the biological behaviour of T56 cell and could affect changes in the behaviour.
Carcinoma, Squamous Cell↗
[Infantile indirect inguinal hernia treated with laparoscopy high ligation of hernial sac].
22 cases of infantile indirect inguinal hernia were treated with laparoscopy high ligation of hernial sac. They were followed up for 9-18 months, the primary results were satisfactory and quite encouraging. The merits of this newly developed method are: The technique is relatively simple and less of postoperative complications. The technique and key point of the method were described in detail.
Child↗
[Effects of fibronectin on cell attachment and migration of human tongue squamous cancer line Tca8113].
By using the cell culture technique in vitro, quantitative studies were carried out to test the effects of fibronectin (FN) on cell biological behaviour of human tongue squamous cancer line Tca8113 in terms of cell attachment to rat-tail collagen substrata supplemented with different concentration of FN or/and anti-FN serum as well as cell migrating distance from the agarose drop cultured with different media containing FN or/and anti-FN serum. The results displayed that FN could increase the density of cells attached to collagen substrata; the cell attachment was dose-dependent on FN. In addition, cell migration from the agarose drop might be induced and cell motility might be promoted by FN. Anti-FN serum could abolish or weaken the above-mentioned FN effects.
Carcinoma, Squamous Cell↗
[Studies of the miotic chromosomes, meiosis and spermatogenesis of a macaque hybrid].
The mitotic and meiotic chromosomes, as well as the spermatogenesis of a male hybrid between Macaca fascicularis and M. assamensis have been studied using chromosome banding, microspreading, and tissue sectioning techniques. The band patterns of the parental chromosome complements are found highly homologous. The observation on meiosis and testis histology indicates that the hybrid should be fertile. It is suggested that the reproductive barrier between M. fascicularis and M. assamensis is not complete and may resulted from ecological isolation. The taxonomic status of M. fascicularis and M. assamensis is discussed also.
Animals↗
[Changes in cell spreading area and cell surface morphology of Tca8113 line affected by fibronectin].
Morphometric changes in cell spreading area and morphological alternation in cell surface of human tongue squamous cancer line Tca8113 on rat-tail collagen substrata supplemented with different concentration of FN and/or anti-FN serum were quantified and observed with cell culture technique as well as light and scanning electron microscopes. It was found that FN could increase the cell spreading area and also area of lamellar cytoplasm of Tca8113 cells on collagen substrata, and that cells grown on FN-collagen substrata tended to flatten out, stretch out more filopodia, and sink more deeply into the substrata with the FN concentration. The results indicated that FN might relate closely to certain stages in the process of tumor invasion.
Carcinoma, Squamous Cell↗
[Value of CA125 (carbon hydrate tumor-associated antigen) and endometrial antibodies for the detections of endometriosis].
Levels of CA125 and endometrial antibodies (EMAb) in serum and peritoneal fluid were determined in 42 cases, including 28 cases of endometriosis as trial group and 14 infertile patients without endometriosis as controls. Results showed that the levels of CA125 and EMAb in peritoneal fluid were higher significantly than in serum, but no difference were found between two groups. Serum EMAb levels were significantly higher in the trial group than in the controls. There was no significant difference in the levels of serum CA125 between two groups. The positive rate of serum CA125 and EMAb were 71.43% and 82.14% respectively. The sensitivity of CA125 and EMAb measurements in the diagnosis of endometriosis were 71.43% and 82.14%, and the specificity were 57.21% and 57.14% respectively.
Adult↗