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Biomedical subjects

S Yu

Publications and source records attributed to S Yu.

At least 379 records · Page 21Linked to original sources
PubMed1994

Comparison between time-dependent changes in iron metabolism of rats as induced by marginal deficiency of either vitamin A or iron.

To compare the changes in Fe metabolism during the development of vitamin A and Fe deficiencies, rats were given either a control diet with sufficient Fe (35 mg added Fe/kg feed) and retinol (1200 retinol equivalents/kg feed), a diet without added vitamin A or a diet with sufficient vitamin A but only 3.5 mg added Fe/kg feed. During a period of 10 weeks, indicators of vitamin A and Fe status were monitored. Neither vitamin A nor Fe deficiency produced clinical signs. Fe deficiency induced an immediate fall in blood haemoglobin concentration. Vitamin A deficiency produced a mild anaemia as the first change in Fe metabolism, pointing to impaired erythropoiesis. This effect was followed by a rise in Fe absorption and an increased amount of Fe in the spleen. By the end of the study, blood haemoglobin, packed cell volume, plasma Fe and Fe content in kidney and femur had increased above control levels, while total Fe-binding capacity had decreased. We speculate that the initial anaemia was masked later by haemoconcentration. The decrease in Fe mobilization, shown by lower total Fe-binding capacity, and the increase in Fe absorption may have caused the observed continuous rise in tissue Fe concentration in rats with vitamin A deficiency. In the rats with Fe deficiency, low tissue Fe levels coincided with high Fe absorption and high total Fe-binding capacity. Thus, changes in Fe metabolism with vitamin A deficiency differed from those with Fe deficiency.

Anemia, Hypochromic↗
PubMed1994

Dietary ascorbic acid lowers the concentration of soluble copper in the small intestinal lumen of rats.

We tested the hypothesis that ascorbic acid in the diet of rats lowers the concentration of soluble Cu in the small intestine, causing a decrease in apparent Cu absorption. Male rats were fed on diets adequate in Cu (5 mg Cu/kg) without or with 10 g ascorbic acid/kg. The diet with ascorbic acid was fed for either 6 or 42 d. Ascorbic acid depressed tissue Cu concentrations after a feeding period of 42, but not after 6 d. Dietary ascorbic acid lowered apparent Cu absorption after 6, but not after 42 d. The lowering of tissue Cu concentrations after long-term ascorbic acid feeding may have increased the efficiency of Cu absorption, and thus counteracted the inhibitory effect of ascorbic acid. Dietary ascorbic acid caused a significant decrease in the Cu concentrations in the liquid phase of both the proximal and distal parts of the small intestinal lumen. This effect was due to both a decrease in the amount of Cu in the liquid digesta and an increase in the volume of the liquid phase; only the latter effect for the distal intestine was statistically significant. We conclude that ascorbic acid supplementation lowers Cu absorption by decreasing the concentration of soluble Cu in the small intestine.

Animals↗
PubMed1994

Increasing intakes of iron reduce status, absorption and biliary excretion of copper in rats.

High intakes of Fe may impair Cu status, but the underlying mechanism is not known. Male rats, aged 7 weeks, were given purified diets adequate in Cu (8 mg Cu/kg) and containing either 7, 40 or 389 mg Fe/kg. After 6 weeks the concentrations of Fe in liver and spleen were positively related with dietary Fe level and those of Cu were negatively related with dietary Fe level. Increasing Fe intakes reduced apparent absorption and biliary excretion of Cu in a dose-dependent fashion. In individual rats, biliary Cu excretion showed a significant, positive correlation with liver Cu concentration. It is concluded that increased Fe intakes depress Cu absorption which produces a decrease in plasma and organ Cu concentrations. As a result, biliary Cu excretion is lowered which contributes to achieving Cu balance at high Fe intakes. Because the concentrations of Cu in plasma and bile, and also plasma ceruloplasmin (EC 1.16.3.1) activities, showed much greater percentage reductions with increasing Fe intake than did the concentrations of Cu in organs, it is possible that increased Fe status interferes with the mobilization of Cu stores.

Animals↗
PubMed1994

Identification of genes involved in the sequestration of iron in mycobacteria: the ferric exochelin biosynthetic and uptake pathways.

Mycobacteria produce two siderophores, mycobactin and exochelin. Mycobacterium smegmatis mutants defective in the production of exochelin were isolated using agar medium containing chrome azural S for the sensitive detection of siderophores. Cosmids of genomic libraries from M. smegmatis and Mycobacterium bovis BCG were screened for complementation of the mutation. Subcloning of the complementing M. smegmatis cosmid identified a 4.3 kb fragment required for restoring exochelin biosynthesis. Sequencing of the DNA revealed four open reading frames whose genes were named fxuA, fxuB, fxuC, and fxbA. FxuA, FxuB, and FxuC share amino acid sequence homology with the iron permeases FepG, FepC, and FepD from Escherichia coli, respectively. Deletion analysis identified fxbA as the gene required to restore exochelin biosynthesis in our mutant. Although fxbA does not share amino acid sequence homology with any of the published sequences for siderophore biosynthetic genes, it does show limited homology with the phosphoribosylglycineamide formyltransferases (GAR enzymes) and methionyl-tRNA formyltransferase over a limited region of the sequence, suggesting that fxbA may code for an enzyme which adds a formyl group in the synthesis of exochelin. A fusion of fxbA with the E. coli lacZ gene demonstrated regulation of gene expression by iron. The ability of M. smegmatis mutants to produce mycobactin in the absence of exochelin supports the hypothesis that exochelin is not a precursor of mycobactin and suggests that the siderophores have independent biosynthetic pathways. In addition, complementation of the M. smegmatis mutant with the BCG cosmid restored the synthesis of the M. smegmatis exochelin, demonstrating the use of M. smegmatis as a surrogate host for analysis of exochelins from slow-growing mycobacteria.

Amino Acid Sequence↗
PubMed1994

[Report on the first nationwide survey of the distribution of human parasites in China. 1. Regional distribution of parasite species].

A nationwide (Taiwan Province not included) survey of the distribution of human parasites in China during 1988-1992 was conducted under the auspices of the Ministry of Public Health, with stratified masses randomly sampling. A total of 2,848 pilot sites in 726 counties with a population of 1,477,742 were surveyed, according to unified standard, unified diagnostic method and control quality. The overall infection rate of parasites was 62. 632%. Among them, the infection rate was over 50% in 17 provinces/autonomous regions/municipalities (P/A/M), over 80% in Hainan, Guangxi, Sichuan, Fujian, Zhejiang and Guizhou, being highest in Hainan (94. 735%). Altogether 56 species were detected. Centrocestus formosanus is reported for the first time at home, Echinochasmus liliputanus and Echinostoma angustitestis are reported for the first time at home and abroad. Echinochasmus fujianensis is a new species. E. histolytica, G. lamblia, A. lumbricoides, whipworm and pinworm were distributed nationwide, while Cysticercus (27 P/A/M), Taenia (27), hookworm (26), Balantidium coli (22), Clonorchis sinensis (22), Paragonimus westermani (21), H. diminuta (21), Echinococcus (18), H. nana (17), Fasciolopsis buski (16), T. spiralis (12) were distributed non-nationwide. A preliminary suggestion on intervention of the common and/or most detrimental parasitic diseases was submitted, including hydatidosis, taeniasis, cysticercosis, clonorchiasis, paragonimiasis, trichinellosis, hookworm disease, ascariasis, trichuriasis and enterobiasis.

Animals↗
PubMed1994

[Epidemiological study on risk factors of cervical cancer].

The relationship between cervical cancer and risk factors including virus infection of cervix was studied with methods of molecular and serological epidemiology. DNA extracted from cervical biopsies taken from 57 cases and 51 controls were tested for HPV6/11, HPV16/18 by Dot-blot hybridization and for HSV-2 by PCR. Sera were detected for HCMV-IgM by ELISA. The results and risk factors were analyzed by logistic regression model. The multiple logistic regression model results showed that HPV16/18 infection was an important risk factor, the infection rate was significantly higher in the group of cervical cancer, the OR was 31.96. Other risk factors were the educational level and the number of birth, the OR were 0.57 and 1.85, respectively. The difference of HSV-2 infection of cervix and HCMV-IgM in serum was not significant between the two groups.

Case-Control Studies↗
PubMed1994

[Interaction among the relative risk factors of primary liver cancer in a case-control study].

This paper evaluates the combined effect of HBsAg, drinking water and aflatoxin B1 (AFB1) on the primary hepatocellular carcinoma (PHC) in a case-control study which was carried out in Fusui, Guangxi. We used relative risk model (from subadditive to supermultiplicative) to fit the relationship. The results showed that the combined effect of HBsAg infection and drinking pond-ditch water is nearly multiplicative, and the combined effect of HBsAg infection and AFB1 intake as well as drinking pond-ditch water and AFB1 intake were nearly additive.

Aflatoxin B1↗
PubMed1994

Portal vein administration of donor cells promotes peripheral allospecific hyporesponsiveness and graft tolerance.

BACKGROUND: Major histocompatibility complex-mismatched Lewis rate cardiac grafts (inferior vena cava drained) are promptly rejected by Buffalo recipients (mean survival time, 7 days). Ultraviolet-B (UVB) irradiation modulates donor immunogenicity and down-regulates in vitro immune responses. We found that Buffalo recipients (BUF; RT1b) preimmunized with 2.5 x 10(7) nontreated Lewis spleen cells (LEW; RT1(1)) by portal venous (PV) injection 7 days before a portal vein-drained heterotopic graft of LEW heart resulted in only 20% surviving long-term (n = 10) (naive rats rejected a cardiac allograft drained into the portal vein in mean survival time of 13.5 days [n = 5]). In contrast, BUF recipients receiving PV injection of UVB-treated LEW spleen cells permitted 70.6% indefinite allograft survival (n = 34) with a mean survival time of greater than 150 days. METHODS: These studies examined the effect of untreated or UVB-irradiated donor spleen cells administered intraportally on the recipient's cell-mediated responsiveness as serially measured by the mixed lymphocyte culture and limiting dilution analysis of T-helper precursors (pTH) and cytotoxic precursors (pCTL). Survival of heterotopic cardiac allografts transplanted with PV drainage at various intervals after PV alloantigen administration were correlated with changes in these in vitro studies. RESULTS: The precursor frequencies in the spleens of BUF recipients given nontreated LEW spleen cells intraportally 7 days previously were 1/16,170 (pTH) and 1/11,929 (pCTL), whereas those in the spleen of BUF recipients receiving UVB-treated LEW spleen cells decreased to 1/152,409 pTH and < 1/5 X 10(5) pCTL. These hyporesponsive BUF spleen cells responded normally to the third-party alloantigen, irradiated ACI spleen cells (RT1 alpha), with mixed lymphocyte culture tritiated incorporation of 133,220 cpm (control, 123,276 cpm), 1/13,364 pTH (control, 1/13,541), and 1/71,156 pCTL (control, 1/73,985), indicating that the hyporesponsiveness induced by UVB-treated donor spleen cells is antigen specific. The recovery of in vitro responsiveness correlates with decreasing cardiac graft survival to normal rejection times by 200 days after portal vein antigen administration. When 100 units/ml exogenous recombinant interleukin-2 (rIL-2), but not rIL-1 or rIL-4, was added to cultures, the hyporesponsiveness of spleen cells recovered to normal levels with tritiated incorporation of 201,227 cpm and pTH frequency of 1/32,227, suggesting that the hyporesponsiveness to donor antigen is due to anergized T-helper lymphocytes and not to clonal deletion. CONCLUSIONS: By administering properly modified alloantigen into the hepatic environment by portal vein inoculation, prolonged T-cell anergy can be induced, which allows the indefinite acceptance of donor-specific heterotopic cardiac allografts.

Animals↗
PubMed1994

The in vitro pharmacology of SC-51146: a potent antagonist of leukotriene B4 receptors.

Previously, we reported that SC-41930 is a potent leukotriene B4 (LTB4) receptor antagonist. An analog of SC-41930, SC-51146, was evaluated as an antagonist of LTB4 receptors. SC-51146 was shown to bind to LTB4 high affinity binding sites on human neutrophils (PMN) with a dissociation constant (KD) value of 1.5 +/- 0.1 nM, compared to 19 +/- 1.3 nM for SC-41930. PMN chemotaxis studies and Scatchard analyses of [3H]LTB4 binding in PMN membranes indicated that SC-51146 acted as a competitive antagonist. The IC50 value of SC-51146 for the inhibition of PMN chemotaxis induced by 30 nM LTB4 was 38 +/- 12 nM. SC-51146 inhibited PMN degranulation induced by 50 nM LTB4 with an IC50 value of 29 +/- 7 nM. The antagonism by SC-51146 of LTB4-induced PMN degranulation appeared to be noncompetitive. The specificity of SC-51146 for LTB4 receptors vs. fMLP receptors was improved approximately 29 and 44 times over SC-41930. SC-51146 showed relatively weak inhibitory activity on the production of superoxide, LTB4 and/or prostaglandin E2 by human PMN or HL-60 cells. SC-51146 had little activity on ram seminal vesicle cyclooxygenase, and no activity on porcine pancreatic phospholipase A2. SC-51146 is a racemate comprised of the (+) enantiomer, SC-53228, and the (-) enantiomer, SC-53229. Both stereoisomers exhibited pharmacological profiles similar to SC-51146 in these aforementioned in vitro systems. The highly potent and specific antagonistic action of SC-51146 on LTB4 receptors should be particularly useful in elucidating the role of LTB4 in the pathogenesis of inflammatory diseases where excessive levels of LTB4 have been reported.

Benzamides↗
PubMed1994

[Chronic empyema associated with large cell carcinoma of lung: case report with review of the literature].

A 71-year-old female was seen with a complaint of chest pain and cough, and a history of tuberculous pleurisy and artificial pneumothorax 40 years ago. The diagnosis of empyema with carcinoma was made by chest X-ray and CT scans. The examination of lung function showed a restrictive disorder. The value of the predicted postoperative FEV1 0.75 l encouraged to perform operation. A left pleuropneumonectomy and combined resections of the invasive portion of the pericardium and left atrium was performed. Histological examination revealed large cell carcinoma of lung (pT 4 N 1 M 0). The literatures are reviewed concerning the thoracic malignant tumor arising in chronic empyema cavity on Japanese cases.

Aged↗
PubMed1993

Alpha-1,4-glucan lyase, a new class of starch/glycogen degrading enzyme. I. Efficient purification and characterization from red seaweeds.

This study presents the first purification and characterization of an alpha-1,4-glucan lyase. The enzyme degraded alpha-1,4-glucan to produce 1,5-anhydrofructose. A simple and efficient purification procedure has been developed and the enzyme has been purified to homogeneity from two red seaweeds Gracilariopsis lemaneiformis and Gracilaria verrucosa. alpha-1,4-Glucan lyase was apparently a single polypeptide as a molecular weight of 111,000 was observed in SDS-gel electrophoresis, and 98,000 by gel filtration chromatography on Sephacryl S-200. Amino acid composition analysis of the enzyme showed high amounts of Asp/Asn, Gly and Glu/Gln. The isoelectric point of the enzyme was 3.9, as revealed by isoelectrofocusing. The concentrations of maltotriose, maltose and amylopectin that yield half of the maximum activity were 798 micrograms ml-1 (1.58 mM), 1,418 micrograms ml-1 (4.14 mM) and 1,600 micrograms ml-1, respectively. alpha-1,4-Glucan lyase exhibited a wide pH optimum range from pH 2.5 to 7.0 for maltose and from pH 3.5 to 7.5 for amylopectin. The optimal temperature for activity of the algal lyase was 50 degrees C when maltose or amylopectin was used as a substrate under the assay conditions. The Arrhenius activation energies were 45.8 and 44.0 kJ mol-1 for maltose and amylopectin as substrate, respectively. Only one form of alpha-1,4-glucan lyase was found in cell-free extracts of the two red seaweeds.

Amino Acids↗
PubMed1993

Alpha-1,4-glucan lyase, a new class of starch/glycogen-degrading enzyme. II. Subcellular localization and partial amino-acid sequence.

Antibodies have been raised against an alpha-1,4-glucan lyase purified from the red alga Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Foldvik. Localization of alpha-1,4-glucan lyase in ultra-thin sections of the red alga was performed using immunogold/transmission electron microscopy. The enzyme was found exclusively in the stroma of the chloroplasts of the algal cells, not in the cell wall, cytosol or around the cytosolic starch granules. Partial amino-acid sequences of the algal lyase, with a total length of 100 amino-acid residues, were obtained. No sequence homology was found with proteins and peptides of known sequences.

Amino Acid Sequence↗
PubMed1993

Leukotriene B4-induced granulocyte trafficking in guinea pig dermis. Effect of second-generation leukotriene B4 receptor antagonists, SC-50605 and SC-51146.

Leukotriene B4 (LTB4) is a proinflammatory product of arachidonic acid metabolism that has been implicated as a mediator in a number of inflammatory diseases. When injected intradermally into the guinea pig, LTB4 elicits a dose-dependent migration (chemotaxis) of neutrophils (PMNs) into the injection sites as assessed by the presence of a neutrophil marker enzyme myeloperoxidase. SC-41930 (7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)propoxy]-3,4-dihydro-8-p ropyl-2H-1-benzopyran-2-carboxylic acid), a first-generation LTB4 receptor antagonist inhibited the chemotactic actions of LTB4 when coadministered into the dermal site and when given orally with ED50 values of 340 ng and 1.7 mg/kg, respectively. The second-generation LTB4 receptor antagonists SC-50605 (7-[3-[2(cyclopropylmethyl)-3-methoxy-4-(4-thiazolyl)phenoxy]propoxy]- 3,4-dihydro-8-propyl-2H-1-benzopyran-2-carboxylic acid) and SC-51146 (7-[3-[2(cyclopropylmethyl)-3-methoxy-4-[(methylamino)carbonyl] phenoxy]propoxy]-3,4-dihydro-8-propyl-2H-1-benzopyran-2-propanoic acid) inhibited LTB4-induced chemotaxis when coadministered with ED50 values of 70 ng and 32 ng, respectively, and when given intragastrically with ED50 values of 0.10 and 0.09 mg/kg, respectively. SC-41930, SC-50605, and SC-51146 had oral durations of action of 5.5, 15, and 21 h, respectively. These potent, LTB4 receptor antagonists may well have application in the medical management of disease states such as asthma, rheumatoid arthritis, inflammatory bowel disease, contact dermatitis, and psoriasis, where LTB4 is implicated as an inflammatory mediator.

Administration, Oral↗
PubMed1993

Dietary fructose vs glucose lowers copper solubility in the digesta in the small intestine of rats.

The hypothesis was tested that dietary fructose vs glucose lowers copper solubility in the digesta in the small intestine of rats, which in turn causes a decreased copper absorption. Male rats were fed adequate-copper (5 mg Cu/kg) diets containing either fructose or glucose (709.4 g monosaccharide/kg) for a period of 5 wk. Fructose vs glucose significantly lowered copper concentrations in plasma and the liver, but did not alter hepatic copper mass. Fructose feeding resulted in a significantly lesser intestinal solubility of copper as based on either a smaller soluble fraction of copper in the liquid phase of small intestinal contents or a lower copper concentration in the liquid phase. The latter fructose effect can be explained by the observed fructose-induced increase in volume of liquid phase of intestinal digesta. After administration of a restricted amount of diet extrinsically labeled with 64Cu, rats fed fructose also had significantly lower soluble 64Cu fraction in the digesta of the small intestine. Although this study shows that fructose lowered intestinal copper solubility, only a slight reduction of apparent copper absorption was observed. It is suggested that the fructose-induced lowering of copper status in part counteracted the fructose effect on copper absorption at the level of the intestinal lumen.

Animals↗
PubMed1993

Fragile X syndrome unstable element, p(CCG)n, and other simple tandem repeat sequences are binding sites for specific nuclear proteins.

The trinucleotide repeat sequences which become unstable in fragile X syndrome and myotonic dystrophy are located in the untranslated regions of their respective genes, FMR1 and DM1. This implies that a functional constraint other than coding capacity maintains the presence of the repeats. In the case of fragile X syndrome, sequences adjacent to the repeat are methylated in affected individuals and the FMR1 gene is transcriptionally inactive. We demonstrate that the fragile X p(CCG)n repeat itself is methylated in vivo and that methylation of this repeat is able to inhibit in vitro binding of a novel, specific nuclear p(CCG)n binding protein (CCG-BP1)--one of at least 10 distinct simple tandem repeat sequence binding proteins (STR-BPs). We describe additional, apparently distinct, binding activities both for the methylated form of the p(CCG)n repeat and for each of the single strands of the repeat.

Base Sequence↗
PubMed1993

Intrathymic injection of donor alloantigens induces specific tolerance to cardiac allografts.

The induction of donor-specific tolerance would eliminate the risk of long-term immunosuppression while ensuring allograft function and survival. Male Buffalo (RT1b) rats were exposed to donor alloantigen by an intrathymic, intrasplenic, s.c., or i.v. injection of 25 x 10(6) syngeneic Buffalo (RT1b) or MHC fully mismatched Lewis (RT1l), ACI (RT1a), or UV-B irradiated Lewis (RT1l) splenocytes. The Buffalo recipients were given 1 cc of rabbit antirat antilymphocyte serum (ALS) i.p. at the time of the donor antigen injection, and 21 days later received a heterotopic Lewis or ACI heart transplant. Only intrathymic alloantigen injection induced a donor-specific tolerance which allowed the cardiac allograft to survive indefinitely (mean survival time [MST] > 176.8 days) in > 86% of the recipients without the need for further immunosuppression, whereas groups receiving antigen injections at other sites rejected cardiac allografts in control time (MST approximately 7.0 days). Histologic examination of long-term tolerated Lewis cardiac allografts revealed the presence of healthy cardiac myocytes without mononuclear infiltration. Buffalo rats with a long-term surviving Lewis cardiac allograft did not reject a second Lewis cardiac allograft (MST > 100.0 days), but rejected a heterotopic ACI cardiac allograft in normal time (MST approximately 7.0 days). By limiting dilution analysis (LDA), maturation of donor-specific CTLs (pCTL) from long-term recipient splenocytes was markedly diminished, whereas third party pCTL was not altered, and T helper-precursors were moderately decreased without alteration in the peripheral CD4+ and CD8+ phenotype frequencies. MLC responses of recipients with long-term surviving cardiac allografts to donor-specific and third party stimulation were not significantly different from naive controls. Microchimerism is unlikely because Lewis allograft survival was also prolonged (MST > 96.0 days) in rats receiving UV-B irradiated Lewis splenocytes which cannot proliferate. The absence of increased allograft survival after transfer of long-term recipient splenocytes into naive animals suggests that donor-specific suppressor cells are not present. Additionally, in vitro lymphocyte proliferative responses to mitogenic or allogeneic stimulation in MLC was not diminished by the addition of these long-term recipient splenocytes. This model emphasizes the importance of exposure of T cell precursors to foreign donor alloantigen in the thymic environment for the development of unresponsiveness to a donor-specific vascularized allograft.

Animals↗