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Biomedical subjects

S R Liu

Publications and source records attributed to S R Liu.

At least 19 recordsLinked to original sources
PubMed1997

Interaction between triiodothyronine and ovarian steroid hormones on the regulation of the release of thyrotropin and thyrotropin-releasing hormone in vitro.

In vivo and in vitro experiments were designed to examine [1] the effect of triiodothyronine (T3) and/or ovarian steroids on the spontaneous and thyrotropin-releasing hormone (TRH)-stimulated release of thyrotropin (TSH) by the anterior pituitary gland (AP) in vitro; and [2] the in vivo effects of T3 and ovarian steroids on TRH-release in vitro. In the experiment 1, ovariectomized-thyroidectomized (Ovx-Tx) rats were injected with triiodothyronine (T3, 2 micrograms/kg), estradiol benzoate (EB, 25 micrograms/kg), progesterone (P, 10 mg/kg), T3 plus EB, T3 plus P, EB plus P, or T3 plus EB and P for 6 days before decapitation. The AP was incubated with Locke's medium, challenged with TRH (30 nM), recovered and then with T3 (10 nM) only or with T3+TRH, 30 min for each interval. Mediobasal hypothalami (MBHs) were challenged with high potassium (60 mM) for 30 min. In the experiment 2, the APs of Ovx-Tx rats were enzymatically dispersed and the AP cells were pretreated with or without EB (0-6 nM) for 72 h, and further with T3 (10 nM) for 24 h, followed by an incubation for 30 min with TRH (0-100 nM). The spontaneous and TRH-induced release of TSH in vitro from rat APs, and pituitary TSH content were increased by T3, or T3 plus P as compared with the animals injected with vehicle, or P alone. EB inhibits the effect of T3 on TSH release in vitro. Application of T3 in vitro prevented the release of TSH in response to TRH. EB dose-dependently relieved the inhibitory effect of T3 on TRH-induced TSH release in vitro. TRH release from MBH was increased by EB and inhibited by T3 or P. EB prevented the inhibitory effect of T3 on TRH release. P plus T3 potentiated the stimulatory effects of EB on TRH release. These results suggest that [1] the reduction of the concentration of plasma TSH by T3 is at least in part due to the inhibitory effects of T3 on TRH release from mediobasal hypothalamus, and TSH release in response to TRH, [2] the increased content and release of TSH from rat AP tissue by T3 via an in vivo effect may be involved in a short feedback loop of TSH on TRH release, and [3] ovarian steroid hormones play an inhibitory role in regulating T3 effects on the release of TSH and TRH.

Animals↗
PubMed1995

Gastric inhibitory polypeptide and gastric acid secretion in pregnant rats.

The effects of pregnancy on the basal and pentagastrin-stimulated gastric acid secretion and the level of plasma gastric inhibitory polypeptide (GIP) in rats were studied on pentobarbital-anaesthetized non-pregnant rats and rats in the 1st, 2nd, or 3rd week of gestation. Acid output was determined by titration of the gastric perfusate. Basal secretion was collected for 45 min before a 30 min infusion of pentagastrin (8 micrograms/ml/300 g body weight). Concentration of plasma GIP was measured by a radioimmunoassay (RIA). The immunoreactivity of GIP-like substance in the extract of the rat placenta collected from the rat at day 21 of gestation was examined by RIA. The biological activity of GIP-like substance in the rat placenta extract was tested by the reduction of pentagastrin-stimulated gastric acid secretion in male rats. The basal level of gastric secretion was higher in late pregnancy as compared with the non-pregnant rats. Pentagastrin induced a greater increase of gastric acid secretion in early but not late pregnant rats as compared with the non-pregnant animals. The basal and post-pentagastrin level of plasma GIP was higher in rats in late pregnancy. Both immunoreactivity and biological activity of GIP exist in the rat placenta extract. These results suggest that the normalization of gastric acid secretion in late pregnant rats is at least in part due to the production of GIP-like substance from placenta.

Animals↗
PubMed1994

Calcitonin inhibits testosterone and luteinizing hormone secretion through a mechanism involving an increase in cAMP production in rats.

Effects of calcitonin peptides, including human calcitonin (hCT), salmon calcitonin (sCT), and calcitonin gene-related peptide (CGRP), on the secretion of testosterone and luteinizing hormone (LH) in male rats were studied. Male rats were injected intravenously with human chorionic gonadotropin (hCG), calcitonin peptides, or hCG plus calcitonin peptides. Blood samples were collected at several intervals following hormone challenge. In an in vitro experiment, testis blocks were incubated with hCG (0, 0.05, 0.5, or 5 IU/ml) or hCG (0.5 IU/ml) plus calcitonin peptides (0-10(-9) or 10(-6) M) at 34 degrees C for 30 minutes. Both medium and plasma samples were extracted by ether and analyzed for testosterone by radioimmunoassay (RIA). The concentration of calcium in each plasma sample was measured by an automatic calcium analyzer. The anterior pituitary gland (AP) was incubated with or without calcitonin peptides (0-10 nM) at 37 degrees C for 30 minutes. They were then incubated with gonadotropin releasing hormone (GnRH, 10 nM) for a further 30 minutes. The concentration of LH in AP medium was measured by RIA. The accumulation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in both testicular tissues and APs were measured by RIA. A single intravenous injection of calcitonin peptides decreased the basal and hCG-stimulated levels of plasma testosterone gradually from 60 to 180 or 360 minutes after challenge. The plasma calcium was not altered by the injection of calcitonin peptides and/or hCG. Administration of calcitonin peptides in vitro resulted in a dose-dependent inhibition of both basal and hCG-stimulated release of testosterone.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1994

[The association of Epstein-Barr virus with Hodgkin's lymphoma in childhood].

Specimens from 82 children with Hodgkin's lymphoma were studied by immunohistochemical technique for Epstein-Barr virus encoded latent membrane protein (LMP). LMP was demonstrated in 67 cases 81.7%, the positive rate for the mixed cellular subtype was 90.9%. The positive rate for the 3-5 year old group of patients was 100%, 75% for the 6-10 year old group and only 62.5% for the 11-14 year old group. These findings suggest that Epstein-Barr virus is strongly associated with Hodgkin's lymphoma, the younger the age, the stronger the association. Mixed cellular subtype of Hodgkin's lymphoma had the strongest association with Epstein-Barr virus among all subtypes.

Adolescent↗
PubMed1994

[The effect of calmodulin antagonist on the anticancer effect of vinblastine].

Calmodulin exists in all eukaryotic cells. It functions as the intracellular receptor of Ca, regulates various cellular physiological processes. We studied the effect of calmodulin antagonist W-7 on the anti-cancer effects of vinblastine. With the method that calmodulin can activate cyclic nucleotide PDE, we found that W-7 can significantly reduce the calmodulin level of MGC803 cell (P < 0.05). W-7 could not only increase the uptaking and accumulating of -3H-Vinblastine in MGC803 cells (P < 0.05), but also decrease the IC50 of Vinblastine (from 12.0 +/- 0.03 nmol to 5.27 +/- 0.02 nmol) in MGC803 cells. It is indicated that calmodulin antagonist W-7 can enhance the anticancer effect of vinblastine.

Adenocarcinoma↗
PubMed1994

[Biological characteristics of Ligusticum chuanxiong Hort].

Observational studies were conducted on the biological characteristics of Ligusticum chuanxiong, such as suitable growth environment, growing period, growth of stems, leaves and rhizomes, yield structure, etc. The specific regularities of each growth period were also studied.

Plants, Medicinal↗
PubMed1992

The screening diagnosis of tetrahydrobiopterin deficient phenylketonuria.

Since 1990, 20 diagnostically confirmed phenylketonuria (PKU) patients have been screened with a tetrahydrobiopterin (BH4) loading test, in which plasma phenylalanine and urinary pterin metabolites were investigated, ind activity of dihydropteridine reductase (DHPR) was determined as well. The results showed that there was no statistical difference between the concentrations of plasma phenylalanine before and after BH4 (20mg/kg) administration in all patients, and values of urinary neopterin and biopterin were within the range of classic PKU. All patients but one had normal activity of DHPR in red cells. This suggests that incidence of BH4 deficiency in PKU patients amounts to five percent (1/20) which is almost the same as reported abroad.

Biopterins↗
PubMed1992

Identification of three novel missense PKU mutations among Chinese.

Three novel missense mutations have been identified in the phenylalanine hydroxylase (PAH) genes of Chinese individuals afflicted with various degrees of phenylketonuria (PKU). A T-to-C transition was observed in exon 5 of the gene, resulting in the substitution of Phe161 by Ser161. Two substitutions, G-to-T and T-to-G, were observed in exon 7, resulting in the substitution of Gly247 by Val247 and Leu255 by Val255, respectively. Expression analysis demonstrated that these mutant proteins produced between 0 and 15% of normal PAH enzyme activity. Population screening of a Chinese sample population indicates that these mutations are quite rare, together accounting for only about 4% of all PKU alleles among the Chinese. The P161S and G247V mutations were each present on a single PAH RFLP haplotype 4 chromosome in patients form Northern China, while the L255V mutation was present on chromosomes of both haplotypes 18 and 21 in patients from Southern China. These results suggest that the remaining 30% of uncharacterized PKU alleles in the Chinese population may bear a large number of relatively rare PAH mutations.

Alleles↗
PubMed1992

Identification of three novel PKU mutations among Chinese: evidence for recombination or recurrent mutation at the PAH locus.

Three novel mutations have been identified in the phenylalanine hydroxylase (PAH) genes of Chinese classical phenylketonuria (PKU) patients. Two of these substitutions (W326X and Y356X) result in the generation of a premature stop codon, while the third (IVS-7nt2) alters an invariant dinucleotide splicing signal. These mutations together account for about 10% of all PKU alleles in the Chinese population. The W326X mutation is associated with PAH RFLP haplotype 4, the most common haplotype in Orientals, while the IVS-7nt2 mutation occurs once on a haplotype 7 chromosome. The Y356X mutation is associated with multiple haplotypes, possibly due to crossover, gene conversion, or recurrent mutation.

Asian People↗
PubMed1992

[Analysis of 10,686 cataract operations in Guangdong Province].

Among 10,686 cataract operations performed in Guangdong province from 1988 to 1989, 80.16% of the patients were over 55 years of age, the ratio of female to male was 1.37:1, and 53.76% were peasants, mostly little educated. Blindness was unilateral in 55.46%, bilateral in 38.83%, and low vision in 5.71%. The mode of operation was intracapsular in 68.83%, extracapsular in 25.77%, and couching in 0.52%. After operation, 50.20% of the patients were restored useful vision, and 45.25% saved from disablement, the total success rate being 95.45%. 2.13% were ineffective and 2.14% had complications. The curative effects were up to the standards stipulated by the National Federation of Disabled Persons.

Aged↗
PubMed1991

Missense mutations prevalent in Orientals with phenylketonuria: molecular characterization and clinical implications.

Two missense mutations in the phenylalanine hydroxylase (PAH) genes of Orientals with phenylketonuria (PKU) have been identified. A G-to-A transition in exon 7 of the gene results in the substitution of Gln243 for Arg243 (R243Q) and accounts for 18% of all PKU chromosomes among Chinese. An A-to-G transition in exon 6 of the gene results in the substitution of Cys204 for Tyr204 (Y204C) and identifies about 13 and 5% of all PKU chromosomes in the Chinese and Japanese populations, respectively. The R243Q construct produced less than 10% of normal PAH activity in in vitro expression analysis in a eukaryotic cell system, and patients homozygous for this substitution exhibit a severe clinical phenotype. These results are consistent with previous findings in this expression system. The Y204C construct, however, produced near normal levels of PAH enzyme activity and immunoreactivity in this in vitro expression system. Because this substitution is present only on PKU chromosomes, it is a valuable marker for identifying the corresponding mutant allele for carrier screening of PKU. With the characterization of these two substitutions, about 60% of PKU alleles in China can now be identified. The continuing search for additional PKU mutations will permit effective carrier screening and prenatal gene diagnosis of PKU in East Asia.

Alleles↗
PubMed1990

[Changing prevalence of blindness in 30 years in Guangdong Province].

After 30 years of efforts for the prevention and treatment of blindness, the prevalence of blindness in Guangdong Province decreased from 0.64% of the 60's, 0.62% of the 70's, to 0.35% of the 80's. The prevalence of blindness was found to rise with age, i.e. 38.60% in people over 50 years and 34.40% in people under 20 years in the 60's. The figures became 78.02% and 12.74% respectively in the 80's, and always higher in women than in men. The leading cause of blindness was cataract, representing 36.00% of the blind in the 60's, 41.18% in the 70's, and 63.05% in the 80's. The authors that treatment of cataract was important for reducing the prevalence of blindness, while glaucoma, infectious diseases and trachoma should also not be overlooked.

Adult↗
PubMed1989

[Dammarane-type saponins in leaves of Panax collected in Sichuan].

Three saponins have been isolated from the leaves of Panax japonicus ssp. elegantior var. major (Burkill) Wu et Feng collected in Sichuan, China. They were identified as ginsenoside-Rd (0.5%), ginsenoside-Rg2 (0.025%) and ginsenoside-Rg1 (0.016%), respectively, based on the chemical and spectral analytical data obtained.

Ginsenosides↗