PubMed Health⌕ Search

Biomedical subjects

S M Wu

Publications and source records attributed to S M Wu.

At least 127 records · Page 7Linked to original sources
PubMed1991

Identification and purification to near homogeneity of the vitamin K-dependent carboxylase.

Vitamin K-dependent carboxylase catalyzes the modification of specific glutamic acids to gamma-carboxyglutamic acid in several blood-coagulation proteins. This modification is required for the blood-clotting activity of these proteins and has thus been the subject of intense investigation. We have now identified the bovine vitamin K-dependent carboxylase and purified it to near homogeneity by an affinity procedure that uses the 59-amino acid peptide FIXQ/S (residues -18 to 41 of factor IX with mutations Arg----Gln at residue -4 and Arg----Ser at residue -1). The carboxylase as purified has a molecular weight of 94,000. It is also the major protein that can be cross-linked to iodinated FIXQ/S and is the only protein whose cross-linking is prevented by a synthetic factor IX propeptide. The degree of purification is about 7000-fold with reference to ammonium sulfate-fractionated microsomal protein from liver.

Amino Acid Sequence↗
PubMed1991

Coexistence and function of glutamate receptor subtypes in the horizontal cells of the tiger salamander retina.

Effects of the major glutamate receptor agonists, kainate (KA), alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), quisqualate (QA), N-methyl-D-aspartate (NMDA), L-alpha-amino-4-phosphonobutyrate (L-AP4), and trans-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) on horizontal cells (HCs) were studied in superfused larval tiger salamander retina. 20 microM of KA, AMPA, and QA mimicked the action of 3 mM glutamate in the absence and presence of 1 mM Co2+. 20 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) blocked the actions of KA and AMPA, but not those of QA and glutamate, indicative of the existence of CNQX-resistant QA receptors in the tiger salamander HCs. Prolonged application of ACPD hyperpolarized the HCs and enhanced the light responses, probably by shifting the resting HC voltage (Er) to a more hyperpolarized position. It is possible that the KA, AMPA, and CNQX-resistant QA receptors are involved in mediating the postsynaptic light responses in HCs, and ACPD receptors are involved in sensitivity adjustment of the HC responses.

Animals↗
PubMed1991

Impact of menstrual periodicity on serum lipid levels and estimates of dietary intakes.

Nine eumenorrheic women were studied at five separate times each month for a minimum of 2 months. Fasting bloods and 1-day food records were obtained from all women at these times to describe the pattern and magnitude of within-person variation in selected nutrient and lipid indicators attributable to menstrual cyclicity. Serum cholesterol, beta-carotene, 17 beta-estradiol (E2), and dietary selenium intakes exhibited significant periodic regressions against time. For the group as a whole, however, only serum cholesterol and E2 measures exhibited significantly strong consistent periodicities. Future studies with a larger sample of women are warranted to confirm these findings. Unless strict blood sampling protocols are followed, variation attributable to menstrual cyclicity may mitigate the reliability of the serum cholesterol screenings advocated in the past few years.

Adult↗
PubMed1991

Chronic disease risk factors in vitamin/mineral supplement users and nonusers in a farm population.

Dietary, anthropometric, and chronic disease risk factors (CDRF) in vitamin/mineral supplement users (U) and non-users (NU) were measured in a farm population consisting of 162 subjects (46% females and 54% males; 20-79 years of age, mean age: 52 years). Subjects were white, except for two black males. Supplements were used by 62 subjects (38%); 47% of females and 31% of males used supplements; 43% of subjects over 50 years of age and 32% of subjects age 50 or under used supplements. Both dietary intake and energy expenditure were measured using 4-day records. Indices of adiposity included body weight, BMI, and estimated body fat. Total cholesterol (TC), high-density-lipoprotein cholesterol (HDL-C), serum ferritin, hemoglobin, hematocrit, zinc, copper, and vitamin C were based on 12-hr fasting blood samples. Dietary intake (excluding supplements) for vitamin/mineral U was greater than NU for vitamin C (p = 0.006), thiamin (p = 0.01), riboflavin (p = 0.03), niacin (p = 0.02), folic acid (p = 0.001), vitamin B6 (p = 0.01), and magnesium (p = 0.019). Vitamin C levels were significantly higher and the sum of four skinfolds was significantly lower among U than NU. In this population, 24% of males and 18% of females had TC levels over 240 mg%; 8% of both males and females had blood pressures (BP) greater than 140/90 mm Hg, while 49% of males and 46% of females had BP between 120/80 and 140/90; and 71% of males were more than 25% fat, and 56% of females were more than 35% fat. Despite the high prevalence of CDRF, there were no significant differences between supplement U and NU.

Adult↗
PubMed1991

Input-output relations of the feedback synapse between horizontal cells and cones in the tiger salamander retina.

1. The input-output relation of the feedback synapse between horizontal cells (HCs) and cones was studied by simultaneously recording the light responses of the HCs and of cones the outer segments of which were truncated off. 2. The postsynaptic light response of the truncated cone was depolarizing and free of direct influence of photocurrents. These postsynaptic light responses were graded and sustained; their waveform resembled that of the HC light responses. 3. Input-output relation of the HC-cone feedback synapse was obtained by plotting the simultaneous voltage points of the HC and truncated cone light responses. At the resting potential of the cone (-40 mV), the voltage gain of the feedback synapse was about -0.33 when VHC = -20 mV and it was about -0.03 when VHC = -60 mV. 4. At more hyperpolarized cone voltages, the feedback signals in cones became smaller, and they reversed at about -67 mV. The voltage gain of the feedback synapse at VHC = -20 mV was about -0.23, -0.18, -0.07, and +0.2 when Vcone = -44.5, -52.5, -65, and -77.5 mV, respectively. 5. Light hyperpolarized the HC, which resulted in a conductance change (delta Gs) in cones. The cone conductance decreased progressively as the HCs were increasingly hyperpolarized, and delta Gs reached a maximum value of 0.93 nS when the HCs were hyperpolarized from -20 to -52 mV. 6. The peak light responses of intact cones were plotted against the peak HC light responses. This gives the relationship between the pre- and postsynaptic voltages of the cone-HC (forward) and HC-cone (feedback) synapses at any given light intensity. Combining this relationship with the input-output relations obtained at various voltages of the truncated cones allows the input-output relation of the feedback synapse for light-evoked signals to be obtained. 7. The input-output relation of the feedback synapse for light-evoked signals was bell-shaped, because the feedback light responses were controlled by two opposing factors: as the light became brighter, the postsynaptic conductance change increased, but the driving force decreased. 8. For light-evoked signals, the slope gain (slope of the input-output relation) of the HC-cone feedback synapse was negative (varied from -0.33 to 0) when VHC lay between -20 and -52 mV; and it was positive (0 to +0.8) when VHC lay between -52 and -72 mV. 9.(ABSTRACT TRUNCATED AT 400 WORDS)

Ambystoma↗
PubMed1991

Thin-layer chromatographic detection of glucocorticoids.

An adsorption thin-layer chromatography (TLC) is described for the detection of glucocorticoids including triamcinolone, prednisolone, 6 alpha-methylprednisolone, betamethasone, dexamethasone, hydrocortisone, prednisone and cortisone. Separation of the glucocorticoids was performed on a silica stationary phase with chloroform-dioxane-methanol (15:4:1, v/v) as a mobile phase. The complete resolution of the epimers of betamethasone and dexamethasone was attained by derivatization of them with (1S)-(-)-camphanic chloride using triethylamine as a catalyst. The application of the method to the analysis of glucocorticoids in various samples is being smoothly developed.

Betamethasone↗
PubMed1990

In vitro gamma-carboxylation of a 59-residue recombinant peptide including the propeptide and the gamma-carboxyglutamic acid domain of coagulation factor IX. Effect of mutations near the propeptide cleavage site.

We report the expression in Escherichia coli of a fusion protein that contains the propeptide sequence and gamma-carboxyglutamic acid domain (residues -18 to 41) of human factor IX (FIXGla). CNBr was used to release FIXGla from the fusion protein. The 59-amino acid peptide is an efficient substrate for in vitro gamma-carboxylation. Its Km,app (0.55 microM) is several thousand-fold lower than that of the commonly used substrate FLEEL and about 5 times lower than proPT28 or proFIX28, (Hubbard, B. R., Jacobs, M., Ulrich, M. M. W., Walsh, C., Furie, B., and Furie, B. C. (1989) J. Biol. Chem. 264, 14145-14150). In addition, FIXGla is the first peptide substrate that is carboxylated in vitro to more than one gamma-carboxyglutamic acid/molecule (6-11 gamma-carboxyglutamic acids/molecule). We created peptides with mutations identical to FIXSan Dimas or FIXCambridge as well as a peptide with both mutations in the propeptide sequence and examined the effect of the mutations on in vitro carboxylation. Enzyme kinetic studies revealed no significant difference in Vmax/Km values between normal and mutant substrates. Maximum carbon dioxide incorporation was achieved with the double mutant. From these data we conclude the following. 1) FIXGla and its mutants are excellent substrates for studying the mechanism of gamma-carboxylase. 2) Although arginines at positions -4 and -1 are highly conserved in the propeptide sequence of all the vitamin K-dependent proteins, neither is critical for gamma-carboxylation.

1-Carboxyglutamic Acid↗
PubMed1990

Deduced amino acid sequence of mouse blood-coagulation factor IX.

A mouse fetal liver cDNA library was screened with a cDNA clone encoding human blood coagulation factor IX protein (hBCFIX). A bacteriophage lambda clone was isolated and the nucleotide sequence of a 2710-bp insert was determined. An open reading frame of 459 amino acids (aa) was identified within the sequence that has an 80% sequence similarity with hBCFIX. The cDNA contains a long 3'-untranslated sequence similar to that of BcfIX gene from human and canine sources. However, instead of a sequence that might form two hair-pins such as those found in hBcfIX, a (GA)16 repeat that has been reported to form H-DNA [Htun and Dahlberg, Science 241 (1988) 1791-1796; Johnston, Science 241 (1988) 1800-1804] was found in the 3'-untranslated region. The predicted aa sequence of mouse BCFIX serves as a comparative sequence for identifying key residues within hBCFIX where epitopes recognized by monoclonal antibodies produced from an immunized mouse are compared with respect to the human and mouse primary BCFIX sequence.

Amino Acid Sequence↗
PubMed1990

Study on the relation of Se, Mn, Fe, Sr, Pb, Zn, Cu, and Ca to liver cancer mortality from analysis of scalp hair.

This project made use of Chongming Island, a high prevalence area for liver cancer, with an uneven geographical distribution, to study the relation between trace elements and high liver cancer incidence. A comparative study of Se, Mn, Fe, Sr, Pb, Zn, Cu and Ca contents of scalp hair of normal persons living in areas with different incidences of liver cancer, and a case-control investigation matched with sex and age were made. The selenium level is relatively low compared with other locations in China, which might indicate Se deficiency on the island. Iron and Mn show an obvious difference, indicating that the availability of these elements was less in the high cancer incidence part of the island than in the low incidence part. The hair iron content of patients with liver cancer is clearly lower than that of normal controls. Selenium, Mn and Fe should be taken into consideration in liver cancer prevention research.

Adult↗
PubMed1990

Independent influences of rod adaptation on cone-mediated responses to light onset and offset in distal retinal neurons.

1. The influence of rod adaptation on cone-mediated intracellular responses of distal retinal neurons was examined in the larval tiger salamander. Rods were selectively stimulated by the use of 450-520 nm adapting stimuli too dim to appreciably influence cones. Cones were primarily stimulated with the use of deep-red stimuli (maximally sensitive to wavelengths greater than 650 nm). The qualitative properties of rod-cone interaction were assessed with the use of several different photic-stimulus paradigms. 2. Confirming results of prior studies, we showed that rod adaptation changed the time course of cone-mediated responses to the onset of square-wave light flashes in horizontal cells (HCs); rod adaptation had no similar influence in other distal retinal neurons. Rod adaptation also enhanced cone-mediated responses to rapid flicker in cones, hyperpolarizing (HPBCs) and depolarizing (DPBCs) bipolar cells, as well as HCs. 3. We also examined the influence of rod-stimulating background fields on cone-mediated responses to slow (approximately 1-Hz) flicker composed of sawteeth with a rapid onset (ramp offset) or with a rapid offset (ramp onset). Such stimulation maintained a constant state of long-term adaptation while providing cones with transient-ON or transient-OFF stimulation. 4. Rod adaptation speeds up the response of HCs to rapid onset and increases response amplitude. Rod adaptation had no reliable influence on response to rapid onset in cones or bipolar cells. 5. Rod adaptation enhanced the amplitude of responses of HCs to rapid offset without altering response time course. 6. Rod adaptation greatly enhanced the amplitude of DPBC responses to rapid offset having no reliable influence on the time course of the response. 7. Rod adaptation caused responses of HPBCs to rapid offset to become much more transient. Rod backgrounds had a similar but smaller and less reliable influence on the response of cones to rapid offset. 8. The foregoing results indicate that rod adaptation exerts a minimum of two separate influences on cone-mediated responses in distal amphibian retina. Changes at light onset must reflect the operation of a mechanism that alters response kinetics of the HC membrane. Changes at light offset reflect the operation of a separate mechanism or set of mechanisms that must act in part presynaptically to the HCs.

Adaptation, Physiological↗
PubMed1990

Localization of classical neurotransmitters in interneurons of the larval tiger salamander retina.

Autoradiography was used to visualize the neurons in the tiger salamander retina that exhibit high-affinity uptake of 3H-dopamine, [3H]-serotonin, [3H]-glycine, and [3H]-GABA. Both [3H]-dopamine and [3H]-serotonin were accumulated by amacrine cells and by displaced amacrine cells. [3H]-glycine was taken up by amacrine cells, displaced amacrine cells, bipolar cells, and displaced bipolar cells. [3H]-GABA was accumulated by amacrine cells and by cells in the ganglion cell layer that may be displaced amacrine or ganglion cells. [3H]-GABA was also taken up by horizontal cells, bipolar cells, and displaced bipolar cells.

Animals↗
PubMed1990

[An application of oligonucleotide-directed mutagenesis on making deletion mutation].

By the method of oligonucleotide-directed mutagenesis, we made 27bp and 18bp deletion at junction region between alpha-factor signal sequence and alpha-hANP gene, alpha-factor signal sequence and alpha-IFN gene, respectively. Since the deleted region contains one HindIII site, the mutants without this site were selected. The result of DNA sequence analysis showed that the sequences of the mutants were the same as designed.

Atrial Natriuretic Factor↗
PubMed1990

Synaptic inputs from rods and cones to horizontal cells in the tiger salamander retina.

Synaptic inputs from rods and cones to horizontal cells (HCs) were studied in the flatmounted isolated retinas of the tiger salamander. Voltage-intensity relations, spectral sensitivities and response waveforms of the rod, the cone, and the HC under dark- and light-adapted conditions were examined. HCs receive mixed inputs from rods and cones in both dark- and light-adapted retinas. The relative rod/cone input in HCs depends on the intensity of stimulus and background illumination, and it varies from HC to HC.

Ambystoma↗
PubMed1989

Chloroplast biogenesis: quantitative determination of monovinyl and divinyl chlorophyll(ide) a and b by spectrofluorometry.

Simultaneous equations for the determination of monovinyl (MV) and divinyl (DV) Chl a and b by spectrofluorometry in unsegregated mixtures of these tetrapyrroles were derived. The same equations can also be used for the quantitative determination of MV and DV chlorophyllide (Chlide) a and b in unpurified mixtures, after extraction of the Chls in hexane. The equations used differences in the Soret excitation maxima of these tetrapyrroles in ether at 77 degrees K, in order to correct the Soret excitation overlap between MV and DV Chl(ide) a and between MV and DV Chl(ide) b.

Chlorophyll↗
PubMed1989

Modulation of rod-cone coupling by light.

Although electrical coupling between rods and cones in the retina has been assumed to be static, it has now been shown that rod-cone coupling can be strengthened by light. Increment threshold measurements reveal that cone input to rods increases progressively as background light becomes brighter. Current injection into cones produces larger responses in adjacent rods in the presence of background light than in darkness. Weak coupling under dark-adapted conditions facilitates synaptic transmission of small rod signals, and strong coupling under light-adapted conditions enhances transmission of large cone signals.

Ambystoma↗
PubMed1989

Selected indices of micronutrient status in adult patients with sickle cell anemia (SCA).

In 24 adults with hemoglobin SS followed at the Duke University Comprehensive Sickle Cell Center, we have studied the following nutritional parameters: reduced ascorbic acid; dehydroascorbic acid; alpha and beta carotenes; cryptoxanthin; and alpha and gamma tocopherols in whole blood, washed red blood cells, plasma, or serum. In the same population we also examined reduced glutathione (GSH) and oxidized glutathione (GSSG). Fifteen of these 24 patients also were interviewed for usual dietary intakes using a 28-day dietary history. Data obtained from patients with hemoglobin SS, sickle cell anemia (SCA) were compared to those found for seven healthy normal black adults of similar age. Plasma alpha tocopherol levels were significantly lower in SCA individuals than those of the controls (P less than 0.004). Alpha and gamma tocopherol levels in sickle RBCs were significantly higher than those from RBC suspensions of control subjects (P less than 0.007, and P less than 0.001, respectively). All serum values for carotenoids examined, specifically, beta carotene, alpha carotene, and cryptoxanthin were also markedly depressed when compared to those of healthy controls (P less than 0.001, P less than 0.002, and P less than 0.001, respectively). No other statistically significant differences were found between the two groups for any of the remaining variables, including dietary estimates. Dietary analyses suggest that dietary intakes of SCA individuals exceeded the recommended daily allowances (RDA) of all macro- and micronutrients measured, and intakes of most nutrients exceeded those of black controls interviewed. These results suggest that in individuals with SCA, several micronutrients vital to maintaining reducing capacity are present in diminished quantities in plasma/serum. These anomalies exist in SCA patients even though their intake of these micronutrients are similar to those of healthy black men and women.

Adult↗
PubMed1989

Effects of CNQX, APB, PDA, and kynurenate on horizontal cells of the tiger salamander retina.

Effects of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), 2-amino-4-phosphonobutyrate (APB), cis-2,3-piperidine dicarboxylic acid (PDA), and kynurenate (KYN) on the depolarizing actions of glutamate and kainate on horizontal cells (HCs) were studied in the larval tiger salamander retina. APB, PDA, and KYN hyperpolarized the HCs, but they failed to block either the actions of glutamate and kainate, or the HC light responses. APB and PDA did not cause membrane polarizations in either rods or cones, suggesting that the HC hyperpolarizations were not mediated by presynaptic actions of these compounds. CNQX, the newly synthesized non-NMDA (N-Methyl-D-Aspartate) receptor antagonist, blocked the HC light responses and the action of kainate, but not that of glutamate. These results suggest that the synaptic receptors in the tiger salamander HCs are probably non-NMDA although extra-synaptic NMDA receptors may exist in these cells.

6-Cyano-7-nitroquinoxaline-2,3-dione↗