Biomedical subjects

L C Wang

Publications and source records attributed to L C Wang.

At least 145 records · Page 8Linked to original sources

PubMed1990

Effect of intracerebroventricular injection of neokyotorphin on the thermoregulatory responses in rats.

Intracerebroventricular injection of neokyotorphin (NKT) (0.5-2.0 micrograms) caused a dose-related increase in body temperature (Tb) of rats maintained at 28 degrees C. The change in Tb of the rat induced by the optimal dose of NKT (1 microgram) was attenuated when the rat was exposed to 18 degrees C. At both ambient temperatures, heat production was not affected but heat loss was significantly reduced at 28 degrees C in rats receiving 1 microgram NKT. Pretreatment with naloxone (5 mg/kg, IP) significantly reduced the hyperthermic effect induced by NKT (1 microgram). These results suggest that NKT can affect the prevailing thermoregulatory heat loss activities and this effect may be mediated through stimulated release of endogenous opioids.

Amino Acid Sequence↗

PubMed1990

Smooth muscle contractility and calcium channel density in hibernating and nonhibernating animals.

Hibernating animals consistently survive prolonged periods of cold with body temperatures near the freezing point. Previous studies have suggested that regulation of calcium influx may be a fundamental cellular mechanism for cold tolerance in hibernating species. The present study was undertaken to compare (i) the calcium dependence of contractility and (ii) [3H]nitrendipine binding in homogenates of ileal longitudinal smooth muscle from the nonhibernating guinea pig (Cavia porcellus) and a hibernator, the ground squirrel (Spermophilus richardsonii). The contractility studies indicate that both the activation threshold for calcium and the concentration-response curve were shifted to the right in ground squirrel when compared with guinea pig. The binding site density in ground squirrel muscle was about an order of magnitude less than in guinea pig (Bmax = 10 +/- 2 (n = 12) and 86 +/- 6 fmol/mg protein (n = 5), respectively). These results indicate that ground squirrel tissues are less sensitive to external calcium and clearly have fewer calcium channels than the smooth muscle of the non-hibernator. The results continue to support the hypothesis that cold tolerance in hibernating species involves calcium homeostatic control mechanisms.

Animals↗

PubMed1990

Enhancement of maximal thermogenesis by reducing endogenous adenosine activity in the rat.

Adenosine has been shown in vitro to be a potent antilipolytic agent and an inhibitor of insulin-stimulated glucose utilization in skeletal muscle. To test whether endogenously produced adenosine (e.g., from ATP hydrolysis) shares these deleterious effects on substrate mobilization and utilization and thus limits maximum thermogenesis in vivo, adenosine deaminase (converts adenosine to inosine) was given to rats 15 min before cold exposure. Significant (P less than 0.05) increases in thermogenesis were observed under both well-fed (100 units/kg ip) and food-rationed (200 units/kg ip) states. Significant (P less than 0.05) increases in thermogenesis and cold resistance were also observed after pretreatment with selective adenosine receptor antagonists [8-cyclopentyltheophylline (1 microgram/kg ip) greater than 1,3-dipropyl-8-p-sulfophenylxanthine (1.25 mg/kg ip) greater than aminophylline (18.7 mg/kg ip)], indicating an A1-receptor-mediated effect. These results indicate that endogenously released adenosine can indeed attenuate the thermogenic capacity in severe cold and that adenosine antagonists, especially those selective for A1-receptor, are useful in improving cold resistance under varying nutritional states.

Adenosine↗

PubMed1989

Acquired immunity in rats against Angiostrongylus cantonensis infection.

Acquired immunity against Angiostrongylus cantonensis was induced by immunizing rats with somatic antigens from fifth-stage larvae and adult worms and live third-stage larvae. Rats immunized twice had significantly fewer worms than rats immunized three times. Fewer worms were recovered from rats immunized with 200 live third-stage larvae than from any other groups. Rats immunized with somatic antigens had higher enzyme-linked immunosorbent assay (ELISA) antibody levels than rats immunized with live larvae. Rats immunized with live third-stage larvae of Angiostrongylus cantonensis were more strongly protected against challenge infections (62-92%) than rats immunized with antigens extracted from fifth-stage larvae (0-30%) and adult worms (11-24%).

Angiostrongylus↗

PubMed1989

Mechanisms underlying the supra-maximal thermogenesis elicited by aminophylline in rats.

Previous studies showed that acute treatment with aminophylline (AMPY) significantly elevated maximum thermogenesis and improved cold tolerance in rats and man in severe cold. However, the exact mechanism by which AMPY enhances thermogenesis was unknown. Rats receiving enprofylline (ENPRO) (1.5 and 15 mg/kg, i.p.), a selective phosphodiesterase inhibitor, failed to show enhanced thermogenesis. In contrast, treatment with a selective adenosine receptor antagonist, 8-phenyltheophylline(8-PT; 2.5 to 10 mg/kg, i.p.), significantly increased (p less than 0.05) thermogenesis and cold tolerance. However, the maximal thermogenic effect by optimal dose of 8-PT (5 mg/kg) was significantly lower than that with optimal dose of AMPY (18.7 mg/kg, i.p.); the deficit could be eradicated by combining optimal 8-PT dose with a low dose of AMPY (1.25 mg/kg), but not with ENPRO. These results indicate that the thermogenic effect of AMPY is not by inhibition of phosphodiesterase but at least partially by antagonism of adenosine receptors. It is also apparent that older mechanisms in addition to adenosine antagonism are also involved in AMPY's thermogenic action.

Adenosine↗

PubMed1989

Soybean metal-binding proteins: calmodulin purification by hydrophobic interaction with polymer 3520.

Polymer 3520, a non-polar styrene divinylbenzene polymer, provides a simple way to purify calmodulin (CAM) from soybeans. This polymer, which selectively adsorbs CAM by hydrophobic interaction within the polymer matrix, contains no exchangeable groups; thus, interaction with CAM requires no Ca++ ions, and elution is achieved with 50% ethanol. Purification by this form of reversed-phase liquid chromatography is a substantial improvement over the conventional method, which requires high salt in elution buffers. CAM in soybean meal is first extracted with 80% ethanol in the presence of EGTA at room temperature and then chromatographed directly on a polymer 3520 column to yield pure CAM. Addition of non-ionic detergent (Nonidet P-40) to the ethanolic extract helps to separate extraneous proteins, lipids, sugars, and isoflavones. Such isolated CAM migrates as a single band during polyacrylamide gel electrophoresis and reversed-phase HPLC, and it retains activity stimulatory to phosphodiesterase.

Adsorption↗

PubMed1989

Brown fat thermogenesis during hibernation and arousal in Richardson's ground squirrel.

The thermogenic activity [mitochondrial guanosine 5'-diphosphate (GDP) binding] and capacity (uncoupling protein concentration, cytochrome oxidase activity) of brown adipose tissue have been investigated at different phases of the seasonally linked hibernation cycle in Richardson's ground squirrel. The amount of axillary brown adipose tissue and the total mitochondrial content of the tissue were substantially greater in hibernating squirrels than in squirrels caught posthibernation in April or May; cold acclimation induced qualitatively similar differences. The specific mitochondrial concentration of uncoupling protein was high under all conditions (compared with other species), differing little between hibernating, posthibernating, and cold-acclimated squirrels. The thermogenic capacity of brown adipose tissue in Richardson's ground squirrels is therefore modulated almost exclusively by changes in the mitochondrial content of the tissue. Mitochondrial GDP binding was increased on cold acclimation, but similar binding levels were observed in hibernating and posthibernation (May) animals. GDP binding and the GDP-sensitive component of acetate-induced mitochondrial swelling were increased during the early stages of arousal from hibernation. These changes, which indicate an activation of the thermogenic proton conductance pathway in arousal, occurred without an alteration in the specific mitochondrial concentration of uncoupling protein. Increased GDP binding during arousal is clearly due to the unmasking of binding sites, reflecting an acute activation of preexisting uncoupling protein.

Acetates↗

PubMed1989

Responses of Beijing black hogs to porcine somatotropin.

Somatotropin treatment of U.S-breed finishing hogs improves feed efficiency, growth rate and carcass lean-to-fat ratio. Because Chinese-bred hogs have poorer feed efficiency, growth rate and lean-to-fat ratio than U.S. bred hogs, the characteristics affected by porcine somatotropin (PST) may respond differently to treatment. In the present experiment, Beijing Black finishing hogs (a composite of a local Chinese, Berkshire and Yorkshire breeds) were treated with PST for 28 d from average initial to final weights of 67.8 to 96.6 kg. In hogs individually fed as much as they would eat four times a day (n = 12/treatment group, six gilts and six barrows), feed efficiency was improved by 22.4 and 29.9% by 2 and 4 mg/d PST, respectively (P less than .01), primarily due to increased growth rate (22.1 and 32.6% greater than control, respectively, P less than .01); feed intake was not affected. Performance of group-housed and group-fed hogs (six/pen, four pens/treatment) administered 2 mg/d PST for 28 d (average initial and final weights of 66.5 +/- 1.7 and 94.0 +/- 2.4 kg, respectively) was similar (22.7% improved feed efficiency, P less than .01; 25% increased growth rate, P less than .01). At slaughter, last rib backfat thickness was decreased an average of 19.2% for hogs treated with 2 and 4 mg/d PST (P less than .01). Percentage of total muscle, obtained by physical separation of the half-carcass, was increased an average of 13.5% (P less than .01), whereas percentage of total fat was decreased 21.8% (P less than .01) in PST-treated hogs. The pH, water-holding capacity and meat color scores of longissimus muscle from PST-treated hogs did not differ from those of control hogs. Growth rate, feed efficiency and muscle weight responses to PST treatment were at least as large as those for U.S. breeds.

Animal Nutritional Physiological Phenomena↗

PubMed1989

[Development of endoplasmic reticulum and its enzymic marker in cultured mouse spinal neurons].

In an attempt to elucidate the relationship between synapse formation and cell development, the morphology and cytochemistry of the endoplasmic reticulum and its enzymic marker, glucose-6-phosphatase (G-6-Pase), in cultured mouse spinal neurons were investigated ultrastructurally. It was found that in the early period of the development, neurons were characterized by scarceness of organelles; only a few of granular or agranular endoplasmic reticulum and mitochondria were seen. The endoplasmic reticulum and nuclear envelope were packed specifically with G-6-Pase resection product but the product was weak. After a period of culture, most of the neurons had well-developed endoplasmic reticulum, Golgi apparatus, mitochondria and microtubules, etc. The Golgi apparatus was relatively large, having some cisternae associated with vesicles. Either concave of convex face of the saccules was labeled by thiamine pyrophosphatase (TPPase) specifically. GERL, labeled by cytidine monophosphatase (CMPase), was also seen close to the inner or outer face of some Golgi apparatus. The endoplasmic reticulum at this stage was distributed throughout the cytoplasm, including that in dendrites; its enzyme marker (G-6-Pase) localized consistently within the lumen of all endoplasmic reticulum, nuclear space and subsurface cisternae, and frequently in the concave saccules of the Golgi apparatus. After a long-term culture, some neurons became "aged". The endoplasmic reticulum cisternae enlarged and G-6-Pase reaction reduced. Along with the neuronal development, especially maturation of the endoplasmic reticulum and its enzymic marker, synapse formation was begun at the neuropile area. The axo-dendritic synapses always occurred between the axonal terminals and dendrites where the endoplasmic reticulum had showed positive G-6-Pase reactions. Considering the fact, it suggests that the appearance and change of these specific enzymes may be related to the maturation of the neurons in vitro, and also related to the synapse formation between neurons.

Animals↗

PubMed1989

[Morphological study on the role of coated vesicle in the specialization of synaptic membrane in synaptogenesis].

Our object was to characterize the morphological changes of coated vesicles and synaptic membranes during synaptogenesis. Neurons from spinal cords of fetal mice were established as isolated cells in primary culture. After a few days in vitro, the neurons extended their neurites and started their interaction. At timed intervals thereafter, cultures were fixed for electron microscopic observation. Coated vesicles were prominent in the neuronal cytoplasm at the time of synaptogenesis (about 7-10 days in vitro). Similar vesicles were seen in continuity with some cisternae in the Golgi regions and there was an increase in number during the synaptogenic period. Indeed it is not established whether the coated vesicles were exocytotic or pinocytotic in nature, but the cisternae which were in continuity with coated vesicles could be labelled by glucose-6-phosphatase (G6Pase) but not by thiamine pyrophosphatase (TPPase). Such vesicles were also seen in continuity with the neuronal plasmalemma near the closest contact site and contributed their undercoating to pre- and postsynaptic densities. The formation of bilateral membrane specialization was described as being structurally similar to synaptic active zones and appeared to be the first definitive sign of synapseformation. It has been suggested that the synaptic dense material may derive wholly or in part from the exocytic coated vesicles which apparently budding off from endoplasmic reticulum cisternae. This incorporation could provide the mechanism for confining specific characteristics of neuronal membrane to the synaptic region.

Animals↗

PubMed1988

Calorimetric and spectroscopic studies of lipid thermotropic phase behavior in liver inner mitochondrial membranes from a mammalian hibernator.

Arrhenius plots of various enzyme and transport systems associated with the liver mitochondrial inner membranes of ground squirrels exhibit changes in slope at temperatures of 20-25 degrees C in nonhibernating but not in hibernating animals. It has been proposed that the Arrhenius breaks observed in nonhibernating animals are the result of a gel to liquid-crystalline phase transition of the mitochondrial membrane lipids, which also occurs at 20-25 degrees C, and that the absence of such breaks in hibernating animals is due to a major depression of this lipid phase transition to temperatures below 4 degrees C. In order to test this hypothesis, we have examined the thermotropic phase behavior of liver inner mitochondrial membranes from hibernating and nonhibernating Richardson's ground squirrels, Spermophilus richardsonii, by differential scanning calorimetry and by 19F nuclear magnetic resonance and fluorescence polarization spectroscopy. Each of these techniques indicates that no lipid phase transition occurs in the membranes of either hibernating or nonhibernating ground squirrels within the physiological temperature range of this animal (4-37 degrees C). Moreover, differential scanning calorimetric measurements indicate that only a small depression of the lipid gel to liquid-crystalline phase transition, which is centered at about -5 degrees C in nonhibernating animals and at about -9 degrees C in hibernators, occurs. We thus conclude that the Arrhenius plot breaks observed in some membrane-associated enzymatic and transport activities of nonhibernating animals are not the result of a lipid phase transition and that a major shift in the gel to liquid-crystalline lipid phase transition temperature is not responsible for seasonal changes in the thermal behavior of these inner mitochondrial membrane proteins.

Acclimatization↗

PubMed1988

Variants of amphotropic type-C retrovirus isolated from cultures of Moloney- and Rauscher-MuLV-induced tumors.

We isolated and characterized 2 strains of type-C retrovirus, R5NX and YACNX, from established lymphoid cell cultures derived from Rauscher-MuLV-induced lymphoma (RBL-5) in a C57BL/6 mouse, and Moloney-MuLV-induced lymphoma (YAC) in an A-strain mouse, respectively. The R5NX and YACNX viruses were compared with the prototype 4070A strain of amphotropic virus isolated from feral mice in California, and were found to belong to the same amphotropic virus class on the basis of viral interference, neutralization tests, and other biological properties. However, they were not quite identical with respect to viral neutralization antigens and restriction enzyme cleavage patterns of the proviral DNA. The possibility that these viruses may have been present in the original tumor together with the R-MuLV or M-MuLV as "exogenous" viruses rather than as contaminants of cell cultures by the 4070A virus is discussed. Although these 2 isolates were not pathogenic when inoculated into newborn C3H/HE mice, they could establish persistent infections in these mice.

Animals↗

PubMed1988

Concomitant infection of HTLV-I and HIV-1: prevalence of IgG and IgM antibodies in Washington, D.C. area.

Serum samples collected from four groups of individuals in the Washington, D.C. area were examined for the presence of IgG and IgM classes of antibody reacting against HTLV-I and HIV-1. These four groups were: (1) healthy adults with negative premarital VDRL test for syphilis (n = 113), (2) miscellaneous common disease patients (n = 155), (3) drug abusers (n = 130), and (4) homosexual men (n = 187). The former two groups are considered to be low-risk groups, and the latter two, high-risk groups. The prevalence of IgG antibody on ELISA/Western blot tests for these groups were respectively: (1) 5.3%/1.8%, (2) 5.2%/1.9%, (3) 13.9%/4.6%, and (4) 4.3%/1.6% for HTLV-I, and (1) 2.7%/0.9%, (2) 4.5%/0%, (3) 12.3%/5.4%, and (4) 8.0%/5.9% for HIV-1. Instances of possible concomitant infection as shown by the presence of antibodies against both HTLV-I and HIV-1 were found only in the latter two high-risk groups, i.e. two (1.5%) in group (3), and three (1.6%) in group (4) as confirmed by both Western blot and immunofluorescence tests. Out of 97 sera collected from drug abusers in 1985-86 which had IgG antibody by Western blot test against HIV-1, 23 (23.7%) were HTLV-I antibody positive by ELISA test (Group 5), and 8 of these were confirmed by Western blot test. Among these 8 persons, IgM antibody against HTLV-I was found in 2, while that against HIV-1 was positive in 7 persons.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗

PubMed1988

The "hibernation induction trigger": specificity and validity of bioassay using the 13-lined ground squirrel.

Even though the existence of the blood-borne "hibernation induction trigger" has been reported in the 13-lined ground squirrel, transfusion of plasma from hibernating rodents with other hibernating species as the recipients failed to induce the occurrence of summer hibernation. In order to verify whether the response to the "trigger" substance is species specific, the present study was carried out to compare the effect of plasma from hibernating Richardson's ground squirrels on the incidence of summer hibernation in both juvenile Richardson's and adult 13-lined ground squirrels. In two series of experiments, 13-lined ground squirrels entered hibernation quite readily independent of the treatment. The rate of occurrence of hibernation ranged from 78% after sham injection to 86% after warm saline, fresh summer active plasma, and fresh hibernating plasma, respectively. There were no differences in the number of hibernation bouts and the number of days in hibernation after each treatment. In contrast, none of the juvenile Richardson's ground squirrels entered hibernation after any of the treatments up to the end of the 8-week observation period. These results not only argue against the existence of blood-borne "trigger" substance, at least in the Richardson's ground squirrel, but also caution against the use of the 13-lined ground squirrel as a standard test animal for the bioassay of the "trigger" substance.

Animals↗

PubMed1988

Insulin secretion and substrate homeostasis in prolonged hypothermia in rats.

In hypothermia, impairment of metabolic substrate mobilization and utilization may be a factor limiting survival. By use of a newly developed technique, substrate profiles and their regulation by insulin were examined in hypothermic rats (body temperature 19 degrees C) over 24 h. Plasma glucose concentrations increased to approximately 300 mg/dl during cooling and remained high throughout the period of hypothermia. Free fatty acid (FFA) concentration was not altered during cooling or during the first 10 h of hypothermia (approximately 700 mu eq/l) but progressively decreased thereafter, reaching 420 mu eq/l by 20 h. Plasma insulin decreased dramatically during cooling and remained very low (9 +/- 2 microU/ml) during the whole period of hypothermia, reflecting the suppression of insulin secretion by isolated islets at low temperatures. To test he hypothesis that suppression of endogenous insulin secretion may hamper glucose utilization and thus limit survival in hypothermia, exogenous insulin was administered. At doses of 0.1, 0.5, and 1 U/kg intravenously, insulin slowly decreased plasma glucose and FFA. However, at 0.1 and 1 U/kg intraperitoneally, insulin resulted in a dose-dependent decrease in survival time in the hypothermic rat. It is possible that the antilipolytic effect of insulin may have outweighed any beneficial effect of improving glucose utilization in hypothermia.

Animals↗

PubMed1988

The role of v-mos in transformation, oncogenicity, and metastatic potential of mink lung cells.

A cloned line of S + L- mink lung cells (A clone), which exhibited a flat morphology, was superinfected with a novel dual-tropic virus (E1BX-MuLV) showing a broad host range and a B-tropism. These cells gave rise to transformed cells with two phenotypes: those which were still anchorage-dependent (AD), and those which readily detached spontaneously from the substratum and grew in suspension. A clone of these AD cells (B clone) was isolated and compared with a clone of the anchorage-independent suspension-cultured (AISC) cells (C clone). While the C clone exhibited a high oncogenicity and ability to metastasize in nude mice, the A and B clones were not tumorigenic. The integrated v-mos was greatly amplified in the C clone, and moderately increased in the B clone as compared with the A clone. The amounts of v-mos mRNA expressed by B and C clones paralleled those of v-mos sequence in their chromosomal DNA, whereas there was no detectable v-mos mRNA in the A clone. Thus, conversion of S + L- mink cells from an AD growth to an AISC phenotype accompanied by manifestation of oncogenicity and metastatic potential in nude mice is associated with amplification of integrated v-mos gene and its enhanced expression. Furthermore, a revertant (D clone) showing AD phenotype was derived from the C clone by selective growth in ouabain. This revertant exhibited a markedly decreased oncogenicity in nude mice, although the copy numbers of integrated v-mos gene and its mRNA did not differ from those of the parent C clone. While more p37mos protein was found in the C than in the D clone, it was not detectable in the A and B clone. The amounts of helper virus-related mRNA and infectious E1BX-MuLV were markedly higher in the B than in the C and D clones. It is concluded that v-mos gene amplification and overexpression is necessary for these cells to exhibit oncogenicity, but other factors associated with ouabain-resistance can modify or suppress its oncogenicity despite the v-mos amplification and mRNA overexpression.

Animals↗

PubMed1987

Amplification and enhanced expression of the c-Ki-ras2 protooncogene in human embryonal carcinomas.

Two cell lines of human embryonal carcinoma, Tera-1 and Tera-2, have been found to exhibit a 4- to 6-fold amplification of protooncogene c-Ki-ras2. The polyadenylic acid selected RNA also showed 8-fold or greater enhancement, showing marked elevation in the level of two major mRNAs, 5.7 and 4.0 kilobases, and two additional minor mRNAs, 2.3 and 1.2 kilobases, as compared with those of a normal human embryonic fibroblast cell line, MRC-5. More than one-half of the number of tumor samples obtained from metastatic human embryonal carcinomas also showed c-Ki-ras2 gene amplification and enhanced mRNA expression. However, the c-Ki-ras2 gene amplification did not always lead to enhanced mRNA expression, and some embryonal carcinomas showed mRNA overexpression without apparent c-Ki-ras2 gene amplification. These results suggest that human embryonal carcinomas may have c-Ki-ras2 amplification and/or overexpression before in vitro culture. Among various chromosomal changes observed in Tera-1 and Tera-2 cells, there were anomalies in chromosome 12 in which c-Ki-ras2 is located although these karyological changes alone could not account for the amplification observed. It is suggested that the genomic instability and active DNA replication during the early developmental period may give rise to changes involving c-Ki-ras2 which may contribute to oncogenic processes.

Aneuploidy↗

PubMed1987

First report of an epidemic of diarrhoea in human neonates involving the new rotavirus and biological characteristics of the epidemic virus strain (KMB/R85).

An outbreak of diarrhoea in neonates occurred at the nurseries of the Department of Obstetrics of Zhao Tong Regional Hospital, Yunnan Province, from the middle of August to the end of November, 1985. Fifty-one percent of children were affected 2-8 days after birth. The clinical symptoms were mild; patients mainly had diarrhoea and did not vomit. Rotaviruses were detected in 66.7% by RNA PAGE and in 72.7% by EM. The virus strain designated as KMB/R85 had a typical morphology, which was indistinguishable from that of infantile rotaviruses by EM. The viral RNA genome was composed of 11 segments. The buoyant density in CsCl was 1.377 g/cm3. The KMB/R85 strain possessed a hemagglutinin for rhesus monkey erythrocytes. By ELISA, IEM, and HAI, it was found that KMB/R85 strain did not possess the common group antigen shared by group A rotaviruses and was antigenically similar to the Chinese adult diarrhoea rotavirus (serogroup B).

Centrifugation, Isopycnic↗