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Biomedical subjects

Y Gu

Publications and source records attributed to Y Gu.

At least 361 records · Page 20Linked to original sources
PubMed1991

Gossypol pharmacokinetics in mid-lactation Brown Swiss dairy cows.

A bolus equivalent to 450 ppm (dosage based on average feed intake for lactating dairy cows of similar mass) of gossypol was administered orally to three Brown Swiss dairy cows in mid lactation daily for a 7-day treatment period. Blood samples were taken during a 2-day pretreatment period, the 7-day treatment period and a 6-day recovery period. The serum recovered from the cows was stored at -20 degrees C until analysis for extractable gossypol content. The highest concentration of gossypol (a mean of 0.53 microgram/ml serum) was attained in all the cows on day 6 of the treatment period, indicating that a steady-state condition had been reached before the end of the treatment period. The gossypol concentrations then gradually declined during the 6-day recovery period but never fell to the zero baseline. The cows exhibited terminal elimination half-lives of 67, 67.5 and 40 h. Gossypol elimination was best described by a bi-exponential decay curve in two cows and a mono-exponential decay curve in the remaining cow.

Absorption↗
PubMed1991

Identification of two amino acid residues in the epsilon subunit that promote mammalian muscle acetylcholine receptor assembly in COS cells.

We have used a species difference in epsilon subunits of the acetylcholine receptor (AChR) to investigate regions of the subunit protein that are important in receptor assembly. Upon transient transfection of COS cells, mouse epsilon subunit cDNA is approximately 10 times more effective than that of the rat in supporting expression of surface AChRs when the other subunits are from either mouse or rat. In cells transfected with only alpha and epsilon subunit cDNAs, the formation of an alpha epsilon heterodimer, a presumed assembly intermediate, is also less efficient with rat than with mouse epsilon subunit. By site-directed mutagenesis, we have found that these differences can be accounted for by 2 amino acid differences in the N-terminal domain at positions 106 and 115 of the rat and mouse epsilon subunits, suggesting that the region near these 2 amino acid residues is important for AChR assembly.

Amino Acid Sequence↗
PubMed1991

Gossypolone suppresses progesterone synthesis in bovine luteal cells.

Gossypolone, a proposed major metabolite of gossypol, was synthesized and investigated for its effect on progesterone synthesis in cultured bovine luteal cells. Gossypolone inhibited human chorionic gonadotropin(hCG)-stimulated progesterone secretion, reduced substrate-enhanced conversions of 25-hydroxycholesterol to pregnenolone and of pregnenolone to progesterone in a dose-dependent fashion. These findings indicate that gossypolone inhibits not only 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity, as gossypol does, but also side-chain cleavage enzyme complex (cytochrome P450scc) activity. However, the two compounds appear to have a similar potency in inhibiting progesterone secretion. Both gossypolone and gossypol (8.5 microM) induced morphological changes in cellular organelles.

3-Hydroxysteroid Dehydrogenases↗
PubMed1991

Assembly of the mammalian muscle acetylcholine receptor in transfected COS cells.

We have investigated the mechanisms of assembly and transport to the cell surface of the mouse muscle nicotinic acetylcholine receptor (AChR) in transiently transfected COS cells. In cells transfected with all four subunit cDNAs, AChR was expressed on the surface with properties resembling those seen in mouse muscle cells (Gu, Y., A. F. Franco, Jr., P.D. Gardner, J. B. Lansman, J. R. Forsayeth, and Z. W. Hall. 1990. Neuron. 5:147-157). When incomplete combinations of AChR subunits were expressed, surface binding of 125I-alpha-bungarotoxin was not detected except in the case of alpha beta gamma which expressed less than 15% of that seen with all four subunits. Immunoprecipitation and sucrose gradient sedimentation experiments showed that in cells expressing pairs of subunits, alpha delta and alpha gamma heterodimers were formed, but alpha beta was not. When three subunits were expressed, alpha delta beta and alpha gamma beta complexes were formed. Variation of the ratios of the four subunit cDNAs used in the transfection mixture showed that surface AChR expression was decreased by high concentrations of delta or gamma cDNAs in a mutually competitive manner. High expression of delta or gamma subunits also each inhibited formation of a heterodimer with alpha and the other subunit. These results are consistent with a defined pathway for AChR assembly in which alpha delta and alpha gamma heterodimers are formed first, followed by association with the beta subunit and with each other to form the complete AChR.

Animals↗
PubMed1991

Gossypol effects on monoamine oxidase (MAO) activity in several organs of term rats.

In order to study the effect of gossypol on the monoamine oxidase (MAO) activity in pregnant rat organs, 20 day pregnant rats were sacrificed, and MAO activity/0.02 g tissue of several organs and total MAO activity/organ, were determined. The control group (n = 5) were injected with vehicle intramuscularly on the 17th, 18th and 19th day of pregnancy, and the gossypol treated group (n = 4) were injected with gossypol acetic acid (GAA) (25 mg/kg of body weight) intramuscularly on the 17th, 18th and 19th day and were decapitated on the 20th day of pregnancy. Maternal liver, uterus, placenta, and fetal liver were collected and examined. In placenta, total MAO activity/organ was significantly (p less than 0.05) lower in the GAA treated group than that in the control group. However, in maternal liver, uterus and fetal liver, there was no significant difference in total MAO activity/organ between the two groups. There was no significant difference in MAO activity/0.02 g tissue (specific activity), weight of organ, protein weight/organ and protein/g tissue between the two groups in maternal liver, uterus, placenta and fetal liver. These results suggest that, after intramuscular injection of GAA, total MAO activity/organ in the placenta of pregnant rats might decrease significantly.

Animals↗
PubMed1991

Effects of ractopamine, genotype, and growth phase on finishing performance and carcass value in swine: I. Growth performance and carcass merit.

A replicated factorial experiment using 183 individually fed crossbred barrows was conducted. Pigs were fed an 18.5% CP (.95% lysine) diet with 3,594 kcal of ME/kg. The effects of five genotypes (GT): 1) Hampshire (H) x (H x Duroc [D]), 2) synthetic terminal sire line, 3) (H x D) x (Landrace [L] x [Yorkshire (Y) x D]), 4) L x (Y x D), and 5) Y x L; two levels of ractopamine (RAC) treatment: 0 and 20 ppm; and three treatment weight periods (WT): 1) 59 to 100, 2) 73 to 114, and 3) 86 to 127 kg live weight on growth performance and carcass traits were evaluated. Ractopamine increased (P less than .0001) amount (FSL) and percentage (PFSL) of carcass lean standardized to 10% fat content, loin eye area (LEA), and dressing percentage (PDRES) and reduced (P less than .01) amount (DF) and percentage (PDF) of dissected fat. Magnitudes of RAC effects were smaller than those reported by other researchers. Effects of GT and WT on all growth and carcass traits were highly significant (P less than .001) except for those of WT on ADG (P less than .05) and GT on average feed intake (AFI) and backfat thickness at the last rib (BFLR; P less than .05). Genotype 3 performed better for most economically important traits than did GT 1 and 4, suggesting that heterosis existed in GT 3, which essentially was obtained by crossing GT 1 and 4. Among the three treatment periods, WT 2 had the highest ADG. As BW increased from WT 1 to 3, AFI and AFI/ADG ratio (FCR) increased and lean percentage decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1991

Effects of ractopamine, genotype, and growth phase on finishing performance and carcass value in swine: II. Estimation of lean growth rate and lean feed efficiency.

A replicated factorial experiment using 183 individually fed crossbred barrows was conducted. The pigs were fed an 18.5% CP (.95% lysine) diet with 3.594 kcal of ME/kg. The effects of five genotypes (GT): 1) Hampshire (H) X (H X Duroc [D]), 2) synthetic terminal sire line, 3) (H X D) X (Landrace [L] X [Yorkshire (Y) X D]), 4) L X (Y X D), and 5) Y X L; two levels of ractopamine (RAC) treatment: 0 and 20 ppm; and three treatment weight periods (WT): 1) 59 to 100, 2) 73 to 114, and 3) 86 to 127 kg live weight on ADG of dissected lean (ADLG) and fat standardized lean adjusted to 10% fat content (ADSLG) and feed efficiency of ADLG (LFE) and ADSLG (SLFE) were evaluated. Initial carcass lean quantity of each individual animal was determined by a regression equation (R2 = .95) generated from 30 additional barrows (six per GT) slaughtered at 59 kg and 30 (six per GT) untreated pigs slaughtered at 100 kg average live weight. Logarithmic and reciprocal transformations of dependent variables were used to stabilize heterogeneous variances and to improve normality of the residuals. Ractopamine increased (P less than .0001) ADLG, ADSLG, LFE, and SLFE, respectively, by 19.5, 25.0, 19.6, and 25.5%. Differences (P less than .001) were observed among genotypes for all traits, showing that considerable variation existed in the data and indicating that genetic improvement can be realized through the identification and selection of superior genotypes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Suppression of adrenocorticotropic hormone (ACTH)-induced corticosterone secretion in cultured rat adrenocortical cells by gossypol and gossypolone.

We have reported that gossypol, an antifertility agent, and gossypolone, a major metabolite of gossypol, inhibited steroidogenesis in bovine luteal cells in vitro. In the current study, the effects of these two compounds on steroidogenesis were examined in adrenocortical cells of young rats. ACTH-induced corticosterone secretion and intracellular adenosine monophosphate (cAMP) formation were significantly inhibited by gossypol at concentrations of 8.6 and 4.3 microM, respectively, and by gossypolone at concentrations of 8.6 and 4.3 microns, respectively. The present study demonstrated that both compounds inhibit ACTH-induced corticosterone synthesis and secretion in rat adrenocortical cell and this inhibition is, at least partially, attributed to the reduction of intracellular cAMP formation. Our data suggest that gossypol and its metabolite(s) probably affect steroidogenesis not only in gonads but also in adrenal glands by a common mean-reduction of intracellular cAMP.

Adrenal Cortex↗
PubMed1991

[Studies on the thermostable L-lactate dehydrogenase from thermophilic bacteria].

About 200 strains of extreme thermophilic bacteria were isolated from hot springs in Guandong province. A strain, HG25, was found to produce thermostable intracellular L-lactate dehydrogenase (EC. 1.1.1.27). It has the characteristic of Thermus sp. The cells were gram-negative, non-sporulating, nonmotile, aerobic rods containing yellow pigment. The optimum temperature for growth was between 65 degrees C to 75 degrees C, the maximum 85 degrees C, and minimum 40 degrees C. The generation time at the optimum was about 80 min. Starch was not hydrolyzed. Acid was not produced from glucose. The G+C content in DNA was 62-65 mol% (Tm). As the properties of strain HG25 is similar to those of Thermus aquaticus and T. thermophilus HB 8 belonging to the genus Thermus. The thermostable L-lactate dehydrogenase was partially purified by ammonium sulfate fractionation and DEAE-cellulose column chromatography. For pyruvate reduction, the optimum temperature of the enzyme was 60 degrees C and pH 8.0. After incubation in 0.1 mol/L phosphate buffer pH 7.4 at 70 degrees C for 10 min, the enzyme retained about 85% of its original activity. The half-live time (t1/2) at 85 degrees C was 10 min.

L-Lactate Dehydrogenase↗
PubMed1990

Inhibitory effect of gossypol on steroidogenic pathways in cultured bovine luteal cells.

Gossypol inhibits the reproductive system and steroidogenesis in both sexes. The present study investigated some possible sites subsequent to cAMP formation at which gossypol may inhibit progesterone biosynthesis. Bovine luteal cells were cultured with dibutyryl cAMP (dbcAMP), 25-OH cholesterol, or pregnenolone in the presence or absence of gossypol. Gossypol, at 17-34 microM, inhibited dbcAMP-induced progesterone secretion. Gossypol significantly inhibited the conversions of exogenous 25-OH cholesterol and pregnenolone to progesterone. However, the conversion of 25-OH cholesterol to pregnenolone was not significantly inhibited by gossypol at low doses (less than or equal to 34 microM). These results suggest that gossypol inhibits progesterone synthesis in bovine luteal cells by suppressing steroidogenic enzyme activity.

Animals↗
PubMed1990

Taenia taeniaeformis: inactivation of metacestodes by gossypol in vitro.

Gossypol, a natural biphenyl compound inhibits Taenia taeniaeformis metacestode development in vivo. In this paper, the direct effect of gossypol on metacestodes was examined. Within 24 hr of incubation at 37 degrees C in greater than or equal to 10(-5) M gossypol, shedding of the tegument from the surface of the metacestodes was observed. There was a significant decrease in [3H]thymidine uptake by T. taeniaeformis in greater than or equal to 10(-5)M gossypol. In addition, NADH lactate dehydrogenase activity of metacestodes was significantly inhibited in greater than or equal to 10(-5) M gossypol. Thus, gossypol has a direct inhibitory effect on T. taeniaeformis metacestodes in vitro.

Animals↗
PubMed1990

Effects of larval tapeworm (Taenia taeniaeformis) infection on reproductive functions in male and female host rats.

This report examined the effects of larval tapeworm infection on the reproductive functions in both male and female host rats. Female rats were matched by age, then randomly assigned to control and treatment groups (infected with larval tapeworms). Estrous cycles were determined by vaginal smear with 95% of the control group exhibiting 4-day normal cyclicity and only 55% of the treated group exhibiting normal cycles. Female fertility was then evaluated for the normally cycling rats based on the percentage of successful matings on the evening of proestrus, number of implantation sites on Day 8 of pregnancy, and number of pups born at term. The normally cycling rats exhibited 96% successful mating, 12.95 +/- 1.80 implantation sites, and 11.20 +/- 1.80 pups born. Five months after larval tapeworm infection, the fertility parameters were decreased to 79%, 9.10 +/- 1.20, and 7.50 +/- 1.50, respectively. The control females were then used in a study of male fertility after larval tapeworm infection employing the same parameters used to test female fertility. At the onset of the study, control groups exhibited 95% successful mating, 12.50 +/- 1.50 implantation sites, and 11.60 +/- 1.60 pups born at full term. After the 5-month infection period, the parameters were substantially reduced to 29%, 6.20 +/- 0.80 implantation sites, and 5.10 +/- 0.80 pups, respectively. Average testosterone concentrations in serum and testis from control male rats were 8.80 +/- 0.95 ng/ml and 3.88 +/- 0.25 ng/mg protein, respectively. After the 5-month infection period, these levels were reduced to 2.47 +/- 0.31 ng/ml and 1.28 +/- 0.12 ng/mg protein, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Inhibitory effect of gossypol on human chorionic gonadotropin (hCG)-induced progesterone secretion in cultured bovine luteal cells.

Inhibitory effects of gossypol on the female reproductive system have been recently reported. This study investigated a possible site of gossypol action on progesterone synthesis. Bovine luteal cells were cultured with hCG and forskolin in the presence or absence of gossypol. At 10 micrograms/ml, gossypol significantly inhibited hCG- and forskolin-stimulated progesterone secretion and intracellular cAMP formation; at 20 micrograms/ml, gossypol completely abolished the stimulative effect of hCG and forskolin. The results suggest that adenylate cyclase may be a site of gossypol action on steroidogenesis of bovine luteal cells.

Animals↗
PubMed1990

Effects of ractopamine on adipose tissue metabolism and insulin binding in finishing hogs. Interaction with genotype and slaughter weight.

Twenty-four barrows were divided among eight treatments in a 2 x 2 x 2 design to quantify the influence of ractopamine (0 or 20 mg/kg diet) over the final 40 kg of gain on metabolic activity in adipose tissue. Interactions with genotype (Hampshire cross or Landrace cross) and slaughter weight (100 or 127 kg) were investigated also. Backfat was removed at slaughter and rates of lipolysis and fatty acid synthesis (FS), activities of malic enzyme (ME) and fatty acid synthetase (FAS), and insulin binding to adipocytes were assessed. Adipocytes from ractopamine-fed pigs were less sensitive (EC50 increased 90%) and had a lower maximum lipolytic response (40%) to ractopamine stimulation. Rates of basal and insulin-stimulated FS were decreased 40% in ractopamine-fed pigs and were reflected in lower activities of ME (50%) and FAS (15%). Breed and slaughter weight had no consistent influence on the ractopamine response. Landrace-cross pigs had greater insulin binding capacity (30-60%) whether data were expressed on a cell or surface area basis. Ractopamine feeding did not consistently affect insulin binding capacity. Results suggest that ractopamine interacts in vivo with the beta-adrenergic receptor of swine adipocytes, decreasing lipogenic capacity and diminishing responsiveness to beta-adrenergic stimulation.

Adipose Tissue↗
PubMed1990

Properties of embryonic and adult muscle acetylcholine receptors transiently expressed in COS cells.

We used transient transfection in COS cells to compare the properties of mouse muscle acetylcholine receptors (AChRs) containing alpha, beta, delta, and either gamma or epsilon subunits. gamma- and epsilon-AChRs had identical association rates for binding 125I-alpha-bungarotoxin, and identical curves for inhibition of toxin binding by d-tubocurarine, but epsilon-AChRs had a significantly longer half-time of turnover in the membrane than gamma-AChRs. A myasthenic serum specific for the embryonic form of the AChR reduced toxin binding to gamma-, but not epsilon-AChRs. The gamma-AChRs had channel characteristics of embryonic AChRs, whereas the major class of epsilon-AChR channels had the characteristics of adult AChRs. Two minor channel classes with smaller conductances were also seen with epsilon-AChR. Thus, some, but not all, of the differences between AChRs at adult endplates and those in the extrasynaptic membrane can be explained by the difference in subunit composition of gamma- and epsilon-AChRs.

Animals↗
PubMed1990

[Studies on antigens of human lung adenocarcinoma with McAb LC-1].

The soluble antigens extracted from both human lung adenocarcinoma cell line SPC-A-1, and normal adult lung tissue with non-idet P-40 were subjected to 10% SDS-PAGE. The number of bands distinguishable by naked eyes of lung adenocarcinoma are 57, in which 4 bands are more significant. The bands of normal human lung tissue are 52, in which 2 bands are more significant. The molecular weights of these bands mainly are within 30 to 94 KD The thin layer chromatographs of these two antigenic extracts have shown that there is difference in their sugar content, but both of them shown little sialic acid. The Immunoblot pattern of McAb LC-1 reacted with the extracts of SPC-A-1 cells shows that all of 3 bands detected can be stained by alcian blue, indicating that they are glycoproteins. However, of them two bands, M. W. of 70 KD and 51 KD can also be stained by Sudan Black B, indicating that these two bands are glycolipoproteins. The ganglioside and neutral glycolipid can inhibit the binding of LC-1 with the extract of SPC-A-1 cells. The results indicate that the epitopes of SPC-A-1 cell extract reacted with McAb LC-1 are probably located in the polysaccharide.

Adenocarcinoma↗
PubMed1990

[Vascular anastomosis using CO2 laser: an experimental study].

This experiment was done on 50 left side carotid communal arteries of rats. The arteries were cut and then anastomosed by welding using CO2 laser which produced by a self design laser microsurgical machine which was designed by us, while the right side arteries as control were anastomosed by conventional suturing with 11/0 nylon thread. The results showed that the patency rate was 100% in both groups either immediately or 1 hour, 3 days, and 10 days and 2 months after operation. The operative time of the laser group is about 5-6 min shorter than the sutured group which took 10-15 min. The anastomotic quality was examined by scanning electronmicroscopy. The results showed: On the third day the endothelium growth rate was 18% and on the 10th day was 98% in the laser group which was very close to the sutured group.

Anastomosis, Surgical↗