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Biomedical subjects

X D Wang

Publications and source records attributed to X D Wang.

At least 109 records · Page 6Linked to original sources
PubMed1993

Intestinal perfusion of beta-carotene in the ferret raises retinoic acid level in portal blood.

To determine whether beta-carotene (beta-C) can serve as a source of intestinally-derived retinoic acid (RA), either 15,15'-[14C]beta-C or unlabeled beta-C was perfused through 30 cm jejunal segments of ferrets in vivo. Portal vein blood was sampled periodically via an indwelling catheter. RA was identified in portal blood by comparing retention times in HPLC, by UV absorption, and by derivatization (methylation) and subsequent GC-MS analysis. The RA concentration in the portal blood increased 3-fold with perfusion of beta-C (P < 0.05), and remained at 18 nmol/L during the perfusion of beta-C. The single peak of RA in HPLC was shown to consist of four separate peaks by GC-MS, which may be cis-trans isomers of RA. The concentration of RA in portal blood returned to the initial level (5 nmol/L) after a 2 h period of intestinal perfusion with 5% dextrose. Retinyl ester concentration in portal blood did not change before or after the perfusion, whereas retinol decreased significantly during the perfusion of beta-C. This study clearly indicates that a considerable quantity and number of polar metabolites, including RA, are formed from beta-C in the ferret intestine which are transported via the portal vein to the liver.

Animals↗
PubMed1993

Bacterial translocation in acute liver failure induced by 90 per cent hepatectomy in the rat.

Bacterial infection and bacteraemia have been observed in patients with acute liver failure. The exact source of bacteria and nature of pathophysiological mechanisms explaining the development of infection remain unclear. In the present study, acute liver failure was induced by 90 per cent hepatectomy in the rat. The mesenteric lymph nodes and organs were harvested aseptically for bacteriological culture after sham operation or 90 per cent hepatectomy. Function of the liver and reticuloendothelial system (RES) was assayed; gut oxygen extraction was also measured. Translocation of enteric bacteria occurred 2 h after operation and increased with time following hepatectomy. Overgrowth of Escherichia coli in the distal small intestine started 2 h after operation. RES function decreased immediately after 90 per cent hepatectomy; uptake rates per gram tissue in other organs increased significantly. These results indicate that bacterial translocation occurred early after 90 per cent hepatectomy, associated with a decrease in RES function and gut oxygen extraction, and overgrowth of intestinal bacteria.

Animals↗
PubMed1993

Retinoic acid regulates retinol metabolism via feedback inhibition of retinol oxidation and stimulation of retinol esterification in ferret liver.

When the plasma concentration of retinoic acid is increased, there is an accompanying reduction of circulating levels of retinol, suggesting that retinoic acid may have a regulatory effect on retinol metabolism in vivo. To determine which specific step(s) of retinol metabolism might be regulated by retinoic acid, retinol was incubated with ferret liver microsomes or cytosol with retinoic acid in vitro. Incubating the microsomal fraction with retinoic acid resulted in a dose-dependent (up to 0.5 mumol/L) decrease in the formation of retinal. On the contrary, no retinoic acid inhibitory effect was observed on retinal synthesis in the cytosol incubation, or in the cytosol plus microsome incubation. However, when retinoic acid was added to the cytosolic incubation mixture in the presence of the retinal oxidative inhibitor, citral, a dose-dependent inhibition of retinal synthesis was observed. Furthermore, the effect of retinoic acid on retinyl ester metabolism in ferret liver was studied by using endogenous retinyl esters of ferret liver as the substrate. When retinoic acid was added to the incubation mixture of microsomes plus cytosol, small, nonsignificant increases in retinol and retinyl esters were observed. When retinoic acid was added in the presence of citral, both the inhibition of retinol oxidation and the stimulation of retinol esterification were dose dependent up to approximately 0.3 mumol/L and then remained the same up to 1.0 mumol/L. These data strongly suggest that retinoic acid has a regulatory effect on retinol metabolism in ferret liver, which may occur via feedback inhibition of retinol oxidation and stimulation of retinol esterification.

Animals↗
PubMed1993

Identification of a nonsense mutation at amino acid 584-arginine of platelet glycoprotein IIb in patients with type I Glanzmann thrombasthenia.

Using Southern blot, the restriction digests of genomic DNAs in 11 patients with Glanzmann thrombasthenia from 10 unrelated kindreds were probed with a full-length GPIIb cDNA. An additional 2.3 kb Taq I fragment and two 1.65 kb and 0.65 kb fragments with reduced band intensity were found in the genes of two affected siblings from a family originating from the city of Huang Yan in the Zhejiang province. The Taq I digest of the abnormal gene was further probed with three portions of GPIIb cDNA, revealing that the heterozygous mutation was present in the region around exons 15-17 of the GPIIb gene. Two primers for polymerase chain reaction (PCR) were then designed, and a 394 bp PCR product was generated and sequenced, indicating that a stop codon (TGA) was substituted for an Arg codon (CGA) at amino acid position 584 of GPIIb, and resulted in a premature termination of translation and production of a shortened protein. The Western blot analysis showed that GPIIIa at the platelet surface was apparently deficient, it may be ascribed to the rapid turn-over of GPIIIa uncomplexed with the truncated GPIIb. The abnormal 2.3 kb Taq I fragment was used as a specific genetic marker to detect the carrier status of the patient family. The abnormal allele was proved to be derived from the mother, the two affected siblings are double heterozygotes, and one clinically unaffected daughter has also inherited this defective allele, while the father carries another recessive abnormal allele unidentified.

Amino Acid Sequence↗
PubMed1993

Reverse cholesterol transport in the rat: influence of short-term D-myo-inositol-1,2,6 trisphosphate (PP56) infusion.

D-myo-inositol-1,2,6 trisphosphate (PP56) was infused in rats for 3 hr at a rate of 30.28 microM/hr/kg body weight. The cholesterol content in plasma, erythrocytes, the aorta, and the liver was monitored before and at the end of the infusion and at 1 and 21 hr after the infusion. We found that the aortic total and free cholesterol content was reduced after the infusion and continuously until the end of the experiment (by 27% each after 21 hr P < 0.05, P < 0.01, respectively). Erythrocyte cholesterol was increased by 6.6% (P < 0.05) at the end of the infusion and 9.5% (P < 0.01) at the end of the experiment, while plasma and high-density lipoprotein cholesterol did not change significantly. Free cholesterol in the liver after infusion was decreased by 27% (P < 0.001) and cholesterol ester increased by 97% (P < 0.05) and did not return to the preinfusion level. Short-term PP56 infusion in the rat apparently influences cholesterol transport in a way which would suggest a promoted reverse cholesterol transport. Since the lipid values did not return to the preinfusion level, a long-term study is needed to elucidate in more detail the influence of PP56 on cholesterol metabolism in vivo.

Animals↗
PubMed1993

The influence of surgically induced acute liver failure on the intestine in the rat.

The influence of acute liver failure induced by 90% hepatectomy on the intestine was evaluated in the rat. Small-intestinal mucosal mass decreased 2 h after hepatectomy. Microvillous height decreased significantly from 1 h and on, and villous height and area in the distal small intestine from 2 h after operation. Ninety per cent hepatectomy resulted in a decrease in systemic arterial blood pressure and an increase in portal venous pressure. Subserosal microcirculation and small-arterial circulation in the proximal and distal small intestine and colon decreased significantly after 90% hepatectomy. Overgrowth and colonization of Escherichia coli occurred in the distal small intestine from 1 h and on after hepatectomy. Protein content in enterocytes and bile secretion from the liver remnant were markedly reduced in hepatectomized rats. Thus, the present study shows evidence of alterations in intestinal morphology and function that can contribute to explain the enteric bacterial translocation after surgically induced acute liver failure.

Animals↗
PubMed1993

Enteric bacterial translocation after intraperitoneal implantation of rubber drain pieces.

To study the kinetics and mechanisms of bacterial translocation from the gut after intraperitoneal (IP) implantation of prosthetic materials, different sizes of rubber drain pieces were intraperitoneally implanted in the rat, followed by evaluation of ileal mucosal permeability after 2 days and of the occurrence of bacterial translocation and gut oxygen extraction at various time points. Enteric bacteria translocated to mesenteric lymph nodes and disseminated to systemic organs (liver, spleen, lungs, and kidneys), the portal vein, and inferior vena cava 2, 4, and 6 h after IP implantation of rubber drain pieces with 10-, 7-, and 3-cm2 areas, respectively, and subsequently to the IP rubber drain piece and the peritoneal cavity on the 2nd postoperative day. The incidence of translocation correlated with the size of the implanted material and time after implantation. The gut oxygen extraction increased significantly after IP implantation of 7- and 10-cm2 rubber drain pieces. The ileal mucosal permeability was enhanced in the groups implanted with 7- and 10-cm2 drain pieces. Thus, bacterial translocation occurs already in the early period after IP implantation of rubber drain and increased with time. The increased gut oxygen extraction implies that the gut is susceptible to IP inflammatory stimulation, and the enhanced ileal permeability suggests that the integrity of the gastrointestinal tract is compromised, which might facilitate bacterial translocation.

Animals↗
PubMed1993

[Effect of sodium prasterone on termination of mid-trimester pregnancy].

Sodium prasterone sulfate was used before termination of mid-trimester pregnancy in 50 cases, and another 50 cases taking no drug as the control group. Both groups were given intraamniotic rivanol. In the treatment group, the results indicated that the Bishop score was elevated by 1 to 8. There were an effective rate of 86% and satisfactory rate of 98%. In comparison, the control group showed 40% (P < 0.001) and 76% (P < 0.01) respectively, and there was significant difference between the 2 groups. The average induction-abortion time interval was 13.2 hours shorter in treatment group (P < 0.01). Adverse effects such as nausea or fatigue was only seen occasionally.

Adult↗
PubMed1993

[Intragenic variable number tandom repeats in coagulation factor VIII gene of Chinese origin].

Using polymerase chain reaction, we analysed the variable number tandom repeats (VNTR) in intron 13 of coagulation factor VIII gene in the Chinese. Study of 115 X chromosomes from 77 normal Chinese revealed that the VNTR is composed of at least 4 different alleles in the Chinese, i.e. 19, 20, 21, and 23 repeats 53% of the females analysed were heterozygous of this VNTR. The discovery and application of this new molecular genetic marker is of significance in genetic consultation and prenatal diagnosis of hemophilia A.

Alleles↗
PubMed1992

Retinoic acid can be produced from excentric cleavage of beta-carotene in human intestinal mucosa.

The hypothesis that retinoic acid (RA) is produced from the excentric cleavage of beta-carotene was tested in human intestinal homogenates in vitro. Significant amounts of RA were identified by HPLC and derivatization after incubation of intestinal mucosal homogenates with retinal, beta-carotene, or beta-apocarotenals at 37 degrees C for 60 min. RA formation was inhibited, in a dose-dependent fashion, when retinal was incubated in the presence of 0.1-3.0 mM citral (3,7-dimethyl-2,6-octadienal) under identical experimental conditions. The formation of RA from both beta-carotene and beta-apocarotenals was dose and time dependent and RA was the major metabolite of both beta-apo-8'-carotenal and beta-apo-12'-carotenal after the incubation. However, citral (0.1 to 4 mM) did not inhibit the formation of beta-apocarotenals and RA from 2 microM beta-carotene (P greater than 0.05), which proves the existence of an excentric cleavage mechanism for beta-carotene conversion into retinoids. Furthermore, RA formation from both beta-apo-8'-carotenal and beta-apo-12'-carotenal in human intestinal homogenate occurred in the presence of citral, which demonstrates that RA can be produced from excentric cleavage of beta-carotene via a series of beta-apocarotenals as intermediates.

Acyclic Monoterpenes↗
PubMed1992

Intestinal uptake and lymphatic absorption of beta-carotene in ferrets: a model for human beta-carotene metabolism.

To determine the appropriateness of the ferret as a model for human beta-carotene (beta-C) metabolism, we have perfused both 15,15'-beta-[14C]C and unlabeled beta-C through the upper 30-cm portion of the small intestine of ferrets in vivo. The effluents of a mesenteric lymph duct cannulation and a common bile duct cannulation, as well as portal vein blood periodically sampled via an indwelling catheter, were collected. Ten percent (9.5 +/- 0.06%) of the total administered beta-C was taken up by the intestine after a 4-h perfusion. Of the radioactivity taken up, 68.6 +/- 6.5% remained in the intestinal mucosa, 3.2 +/- 0.2% was recovered in the lymph, and 28.2 +/- 6.5% (calculated) was absorbed via the portal system. The total uptake/absorption of beta-C was 12.9 +/- 6.8 nmol.h-1.30 cm intestine-1. Large amounts of unchanged beta-C and relatively small amounts of both beta-apo-12'-carotenal and beta-apo-10'-carotenal were isolated in the intestinal mucosa after a 4-h perfusion with beta-C. Considerable amounts of metabolites more polar than retinol were formed and comprised 35% of the total radioactivity recovered in the intestinal mucosa. Polar metabolites were absorbed mostly into the portal venous system, whereas retinol and retinyl esters were absorbed mainly into the mesenteric lymph. Of the total absorbed radioactivity in lymph, 10 +/- 1.0% appeared as unchanged beta-C, with peak absorption occurring at 3 h after beginning the perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1992

National epidemiological survey of blindness and low vision in China.

According to the National Sample Survey of Blindness and Low Vision, the prevalence of blindness in China was 0.43%, resulting chiefly from cataract (41.06%), corneal diseases (15.38%), trachoma (10.87%), and glaucoma (8.80%); and the prevalence of low vision in China was 0.58%, of which the main causes were cataract (49.83%), ametropia/amblyopia (14.98%), trachoma (9.55%), corneal diseases (8.48%), chorioretinal diseases (6.27%), etc. Among children under 14 years of age, the leading cause of blindness and low vision was heredity (48.46%). Among elderly of 60 years and over, the leading cause of blindness and low vision was cataract (73.13%).

Aged↗
PubMed1992

Mirror writing of Chinese characters in children and neurologic patients.

Mirror writing was done in 72 preschool children, 40 school children, 60 mentally retarded school children, 40 normal adults, 37 patients suffering from cerebrovascular diseases with or without aphasia and 13 patients with Parkinson's disease. The results showed that total mirror writing was demonstrated in only 2 cases and partial mirror writing with the left hand in 72 cases and with the right hand in 16 cases. The incidence of mirror writing in writing with left hand was higher (45.8%) in preschool children. It gradually decreased to 43.3% in mentally retarded school children, 24.3% in cerebrovascular disease (CVD) patients, 10.0% in school children, 7.7% in Parkinson's disease (PD) patients and 2.5% in normal adults. The relationships between mirror writing and left/right disorientation, between mirror writing and development of Chinese writing language and between mirror writing and higher cerebral function were observed.

Adult↗
PubMed1991

Molecular evolution of the urate oxidase-encoding gene in hominoid primates: nonsense mutations.

Nucleotide sequences of portions of second and fifth exons of urate oxidase encoding gene (UOX) of chimpanzee, gorilla, orangutan, rhesus monkey and squirrel monkey obtained following amplification by polymerase chain reaction have been compared with corresponding sequences of human, baboon and rat UOX. Two or more nonsense mutations are found in the coding regions of this UOX gene thus far analyzed in human, chimpanzee, gorilla and orangutan, but not in the baboon, rhesus monkey and squirrel monkey. Of these nonsense mutations, the stop codon at amino acid position 33 is constant in the human and the three great apes suggesting that this may be the original mutation responsible for the inactivation of the UOX gene during hominoid evolution.

Amino Acid Sequence↗
PubMed1991

Characterization of beta-apo-13-carotenone and beta-apo-14'-carotenal as enzymatic products of the excentric cleavage of beta-carotene.

Two new products from the incubation of beta-carotene with intestinal mucosa homogenates of human, monkey, ferret, and rat were isolated using high-performance liquid chromatography (HPLC). Identification by comparing retention times in HPLC, by monitoring ultraviolet/visible spectra, by reduction to corresponding alcohol, by oxime formation, and by mass spectrometry demonstrated that they are beta-apo-13-carotenone and beta-apo-14'-carotenal. These compounds were not found in incubations done without intestinal homogenates or with disulfiram as an inhibitor. Under standard incubation conditions, these products increased linearly for 60 min and up to a protein concentration of 1.5 mg/mL and increased along with increasing concentrations of beta-carotene. Therefore, they are enzymatic cleavage products from beta-carotene. The formation of the beta-apo-13-carotenone and beta-apo-14'-carotenal provides direct evidence for an enzymatic excentric cleavage mechanism.

Animals↗
PubMed1991

Enzymatic conversion of beta-carotene into beta-apo-carotenals and retinoids by human, monkey, ferret, and rat tissues.

Whether the conversion of beta-carotene into retinoids involves an enzymatic excentric cleavage mechanism was examined in vitro with homogenates prepared from human, monkey, ferret, and rat tissue. Using high-performance liquid chromatography, significant amounts of beta-apo-12'-, -10'-, and -8'-carotenals, retinal, and retinoic acid were found after incubation of intestinal homogenates of the four different species with beta-carotene in the presence of NAD+ and dithiothreitol. No beta-apo-carotenals or retinoids were detected in control incubations done without tissue homogenates. The production of beta-apo-carotenals was linear for 30 min and up to tissue protein concentrations of 1.5 mg/ml. The rate of formation of beta-apo-carotenals from 2 microM beta-carotene was about 7- to 14-fold higher than the rate of retinoid formation in intestinal homogenates, and the rate of beta-apo-carotenal production was fivefold greater in primate intestine vs rat or ferret intestine (P less than 0.05). The amounts of beta-apo-carotenals and retinoids formed were markedly reduced when NAD+ was replaced by NADH, or when dithiothreitol and cofactors were deleted from the incubation mixture. Both beta-apo-carotenal and retinoid production from beta-carotene were inhibited completely by adding disulfiram, an inhibitor of sulfhydryl-containing enzymes. Incubation of beta-carotene with liver, kidney, lung, and fat homogenates from each species also resulted in the appearance of beta-apo-carotenals and retinoids. The identification of three unknown compounds which might be excentric cleavage products is ongoing. These data support the existence of an excentric cleavage mechanism for beta-carotene conversion.

Animals↗
PubMed1991

Rat urate oxidase: cloning and structural analysis of the gene and 5'-flanking region.

The structural gene (UOX) encoding rat urate oxidase (UOX) spans at least 23 kb and is composed of eight exons and seven introns. All of the exon-intron splice junction sequences conformed to the GT/AG consensus established for eukaryotic genes. The transcription start point (tsp) was determined using S1-type nuclease protection riboprobe, and assigned to an adenine 54 nucleotides (nt) upstream of the ATG start codon. A 456-bp 5'-terminal fragment, starting at the ATG codon, carries a putative TATA (ATAAAA) sequence at -32, and two putative 'CAAT box' sequences at -62 and -71 bp upstream from the tsp. No sequence resembling 'GC' box hexanucleotides (GGGCGG or CCGCCC) was found. The structural features of the 5'-flanking region of the UOX gene are distinct from the 5'-flanking sequences of peroxisomal beta-oxidation system genes which contain one or more 'GC' box elements but lack TATA- and CAAT-like features [Osumi et al., J. Biol. Chem. 262 (1987) 8138-8143; Ishii et al., J. Biol. Chem. 262 (1987) 8144-8150]. The 5'-flanking region of the UOX gene reveals a sequence, TTAGTAATT at nt -276 from the tsp, which appears to be complementary to the underlined part of the liver-specific LF-B1/HNF-1 consensus sequence, GTTAATNATTAAC (where N = A, C, T, G or no nt).

Amino Acid Sequence↗