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Biomedical subjects

Z Wu

Publications and source records attributed to Z Wu.

At least 667 records · Page 37Linked to original sources
PubMed1994

In vitro assembly of coiled bodies in Xenopus egg extract.

When demembranated sperm nuclei are placed in a Xenopus egg extract, they become surrounded by a nuclear envelope and then swell to form morphologically typical pronuclei. Granules ranging from < 1.0 to approximately 3.0 microns in diameter appear within such nuclei. Bell et al. identified four nucleolar proteins in these "prenucleolar bodies" by immunofluorescent staining (fibrillarin, nucleolin, B23/NO38, 180-kDa nucleolar protein). By in situ hybridization we show that these bodies also contain U3 and U8 small nuclear RNAs (snRNAs), known to be involved in pre-rRNA processing. Moreover, they contain all the snRNAs involved in pre-mRNA splicing (U1, U2, U4, U5, and U6), as well as U7, which is required for histone pre-mRNA 3' end formation. In addition to the nucleolar antigens previously identified, we demonstrated staining with antibodies against the Sm epitope, trimethylguanosine, and coilin. Because the composition of these prenucleolar bodies is closer to that of coiled bodies than to nucleoli, we propose that they be referred to as coiled bodies. The existence of large coiled bodies in transcriptionally inactive pronuclei suggests that they may play a role in the import, assembly, and storage of RNA processing components but are not themselves sites of processing. In transcriptionally active nuclei coiled bodies could serve as sites for initial preassembly and distribution of snRNP complexes for the three major RNA processing pathways: pre-mRNA splicing, pre-rRNA processing, and histone pre-mRNA 3' end formation.

Amino Acid Sequence↗
PubMed1994

Coiled-coil molecular recognition: directed solution assembly of receptor ectodomains.

The high affinity interleukin-2 (IL-2) receptor is composed of at least three cell surface proteins (alpha, beta and gamma subunits), each of which is independently capable of ligand binding. Physiologically, these subunits cooperate to form dimeric and trimeric complexes that efficiently capture IL-2 and transmit the signal across the membrane. The knowledge of how each subunit functions with respect to ligand capture, signal transmission and internalization is essential for the development of ligand-based IL-2 agonists and antagonists, as well as receptor-related therapeutic and diagnostic reagents. Only one of the subunits (p55 or alpha chain) is capable of interacting with ligand in solution in a manner that resembles cell surface binding. To generate soluble multimeric complexes of the IL-2 receptor subunits that may bind ligand in solution in a fashion that mimics the same receptor complexes on the cell surface, we have added recognition sequences (coiled-coil heptad repeats) to the ectodomains of the individual receptors. Here we describe the expression and characterization of a prototype IL-2 beta receptor ectodomain-coiled-coil fusion protein and demonstrate that this is a feasible approach to the preparation of cytokine receptor solution complexes.

Amino Acid Sequence↗
PubMed1994

Perforin expression by thyroid-infiltrating T cells in autoimmune thyroid disease.

Infiltration of the thyroid gland by lymphocytes is a hall-mark of autoimmune thyroid disease; it is particularly evident in Hashimoto's thyroiditis but is also seen in most patients with Graves' disease. Infiltrating cells are comprised primarily of T lymphocytes, of which only a minority appears to be activated. Their precise pathogenic role is largely unknown. Since perforin has been a marker for functionally activated cytotoxic T cells in situ we elected to assess the presence of perforin-containing cells in thyroid-infiltrating lymphocytes and establish their phenotype. Cells were isolated from seven subtotal thyroidectomy specimens, five from patients with Graves' disease and two with Hashimoto's thyroiditis. The novel findings were as follows: CD4+ perforin-containing T cells occurred only in Hashimoto's glands, suggesting a class II-restricted component of cytotoxicity; in Graves' disease, and to a lesser extent in Hashimoto's, perforin-expressing cells were primarily T cell receptor alpha beta- CD4-CD8- (double negative); double negative perforin-containing cells in peripheral blood of normal individuals were largely gamma delta + T cells. In Hashimoto's samples, the predominant population of T cells expressing perforin was CD8+. By comparison, in studies of the synovial fluid of knee joints from patients with rheumatoid arthritis only a minor population of the perforin-containing cells was double-negative. The data suggest significant differences in cytotoxic autoimmune mechanisms between the two autoimmune thyroid diseases. Functional characterization of double-negative T cells is necessary to define their role in autoimmunity.

Arthritis, Rheumatoid↗
PubMed1994

Effect of perfusion flow rate on the tissue uptake of solutes after dermal application using the rat isolated perfused hindlimb preparation.

The rat perfused hindlimb preparation was investigated as a model to study the dermal clearance and tissue distribution of three solutes with differing physicochemical properties ([3H]water, [3H]diazepam, and [14C]lignocaine). The dermal clearance of each solute increased and the depth of tissue preparation decreased with increasing perfusion flow rate. The half-life for solute efflux from tissues into perfusate, and the peak times for amount of solute in tissue were in the order water > lignocaine > diazepam. Topical iontophoresis, which has previously been shown to achieve similar clearances from topical sites to those seen following passive dermal application, resulted in a clearance of lignocaine in the perfused hindlimb comparable with that obtained in the preparation following passive absorption through exposed dermis. The distribution of capillary blood flow in the perfused hindlimb was quantified using 51Cr-labelled 15-microns microspheres, with greater increases in flow found in deeper muscle tissues with increasing perfusion flow rate compared with superficial layers. Microsphere studies in anaesthetized rats also demonstrate slight differences in the distribution of flow within the hindlimb compared with the perfused preparation. We conclude that the rat perfused hindlimb preparation successfully combines many of the advantages of in-vitro and in-vivo methods and has potential for routine use in the study of solute dermal absorption kinetics.

Animals↗
PubMed1994

Presentation of native epitopes in the V1/V2 and V3 regions of human immunodeficiency virus type 1 gp120 by fusion glycoproteins containing isolated gp120 domains.

The immune response to viral glycoproteins is often directed against conformation- and/or glycosylation-dependent structures; synthetic peptides and bacterially expressed proteins are inadequate probes for the mapping of such epitopes. This report describes a retroviral vector system that presents such native epitopes on chimeric glycoproteins in which protein fragments of interest are fused to the C terminus of the N-terminal domain of the murine leukemia virus surface protein, gp70. The system was used to express two disulfide-bonded domains from gp120, the surface protein of human immunodeficiency virus type 1 (HIV-1), that include potent neutralization epitopes. The resulting fusion glycoproteins were synthesized at high levels and were efficiently transported and secreted. A fusion protein containing the HXB2 V1/V2 domain was recognized by an HIVIIIB-infected patient serum as well as by 17 of 36 HIV-1 seropositive hemophiliac, homosexual male and intravenous drug user patient sera. Many of these HIV+ human sera reacted with V1/V2 domains from several HIV-1 clones expressed in fusion glycoproteins, indicating the presence of cross-reactive antibodies against epitopes in the V1/V2 domain. Recognition of gp(1-263):V1/V2HXB2 by the HIVIIIB-infected human patient serum was largely blocked by synthetic peptides matching V1 but not V2 sequences, while recognition of this construct by a broadly cross-reactive hemophiliac patient serum was not blocked by individual V1 or V2 peptides or by mixtures of these peptides. A construct containing the V3 domain of the IIIB strain of HIV-1, gp(1-263):V3HXB2, was recognized by sera from a human and a chimpanzee that had been infected by HIVIIIB but not by sera from hemophiliac patients who had been infected with HIV-1 of MN-like V3 serotype. The reactive sera had significantly higher titers when assayed against gp(1-263):V3HXB2 than when assayed against matching V3 peptides. Immunoprecipitation of this fusion glycoprotein by the human serum was only partially blocked by V3 peptide, indicating that this infected individual produced antibodies against epitopes in V3 that were expressed on the fusion glycoprotein but not by synthetic peptides. These data demonstrated that the chimeric glycoproteins described here effectively present native epitopes present in the V1/V2 and V3 domains of gp120 and provide efficient methods for detection of antibodies directed against native epitopes in these regions and for characterization of such epitopes.

3T3 Cells↗
PubMed1994

Type I adenylyl cyclase functions as a coincidence detector for control of cyclic AMP response element-mediated transcription: synergistic regulation of transcription by Ca2+ and isoproterenol.

Studies carried out with mammals and invertebrates suggest that Ca(2+)-sensitive adenylyl cyclases may be important for neuroplasticity. Long-term potentiation in the hippocampus requires increases in intracellular Ca2+ which are accompanied by elevated cyclic AMP (cAMP). Furthermore, activation of cAMP-dependent protein kinase is required for the late stage of long-term potentiation in the CA1 region of the hippocampus, which is also sensitive to inhibitors of transcription. Therefore, some forms of synaptic plasticity may require coordinate regulation of transcription by Ca2+ and cAMP. In this study, we demonstrate that the expression of type I adenylyl cyclase in HEK-293 cells allows Ca2+ to stimulate reporter gene activity mediated through the cAMP response element. Furthermore, simultaneous activation by Ca2+ and isoproterenol caused synergistic stimulation of transcription in HEK-293 cells and cultured neurons. We propose that Ca2+ and neurotransmitter stimulation of type I adenylyl cyclase may play a role in synaptic plasticity by generating optimal cAMP signals for regulation of transcription.

Adenylyl Cyclases↗
PubMed1994

Indirect validation of a retrospective method of exposure assessment used in a nested case-control study of lung cancer and silica exposure.

Validations of retrospective methods of assessment used in occupational epidemiological studies have rarely been published. This study is an indirect validation of a quantitative retrospective assessment of exposure to silica used in a nested case-control study of lung cancer among workers at 29 metal mines and pottery factories in China. Indices of cumulative total dust and cumulative respirable dust were calculated by merging work histories with the historical exposure profile for each subject. To validate indirectly the methods of exposure assessment used in the study of lung cancer, trends for exposure response relation between the two indices of exposure to silica and risk of silicosis were evaluated with 376 patients with silicosis from the study population as the cases, and 1262 controls without silicosis for comparison. Age adjusted odds ratios (ORs) as a measure of risk of silicosis showed striking trends with both indices of exposure to silica. For cumulative respirable dust, the OR (95% confidence interval) rose from 7.6 (5.1-11.4) for low exposure to 20.0 (13.2-30.6) for medium exposure, and to 51.7 (31.0-86.8) for high exposure. The strength of the association between exposure to silica and risk of silicosis suggests that the retrospective assessment of exposure used in the case-control study of lung cancer would accurately reflect an exposure response relation between silica and lung cancer, if it existed.

Case-Control Studies↗
PubMed1994

Urinary angiotensin II: a marker of renal tissue activity?

The methodology for the collection, extraction, separation and measurement of urinary angiotensin II [the octapeptide, ANG(1-8)] is described. To determine the origin of urinary ANG(1-8), mean arterial pressure, renal hemodynamics and the arterial, renal venous and urinary concentrations of ANG(1-8) were examined prior to and following the constant intra-arterial infusion of tritiated angiotensin II [3H-ANG(1-8)] in graded doses of 0.5, 2.0 and 2.5 ng/kg/min in 5 uninephrectomized, anesthetized female dogs. The infusion of 3H-ANG-(1-8) had no significant effect on mean arterial pressure, glomerular filtration rate, renal blood flow or urine flow rate. The mean concentration of ANG(1-8) in the urine was 3.7 fmol/ml. None or only trace amounts of 3H-ANG(1-8) were detected in the urine in spite of marked increases in renal arterial 3H-ANG(1-8) concentrations. These observations suggest that urinary ANG(1-8) was derived de novo from the intrarenal generation of angiotensin II. In addition, plasma and urinary concentrations of ANG(1-8) were assessed in patients with essential hypertension undergoing treatment with either a diuretic (n = 14) or an angiotensin-converting enzyme inhibitor (n = 14). Although the concentrations of plasma ANG(1-8) responded appropriately to the respective therapies, the urinary excretion of ANG(1-8) was not different following either therapy. These data suggest that ANG(1-8) collected from the urinary bladder may not occur in adequate concentrations to accurately assess the activity of the intrarenal renin-angiotensin system.

Angiotensin II↗
PubMed1994

Site of mineral absorption in lactating cows fed high-fat diets.

Five lactating Holstein cows with ruminal and duodenal cannulas were used in a 5 x 5 Latin square to determine the site of mineral absorption and effects of sources and amount of dietary fat on apparent absorption. Cows were fed (DM, 17.4 +/- .8 kg/d) chopped alfalfa hay, alfalfa haylage, corn silage, and concentrate at 1:1:1:2 (DM) at 12-h intervals. Calcium salts of palm fatty acid distillate (CS) or animal-vegetable (AV) fat were 0% (control), 2.5% (low, L), or 5.0% (high, H) of the diet DM. After 2 wk of adaptation, duodenal and fecal grab samples were collected at 7-h intervals for 5 d and composited by animal. Calcium intake increased (P < .05) with high-fat diets (195 vs 170 g/d), whereas Mg intake remained unchanged (54.3 +/- 9.0 g/d). Apparent absorption, estimated by Cr2O3, was regressed on Ca or Mg intake (grams/day) and fatty acid (FA) intake (grams/day). Total absorption of Ca (grams/day) = -37.4 + .264 Ca (P = .07, R2 = .14). Ruminal absorption of Mg was independent of FA intake, and magnesium was secreted posterior to the duodenum. Total tract Mg absorption (grams/day) was described by -7.685 + .464 Mg -.0044 FA (P < .0005, R2 = .46). Fat intake decreased (P < .05) total tract Mg absorption, and Ca absorption was decreased by high fat compared with low fat intake (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1994

Influence of yucca extract on ruminal metabolism in cows.

Two trials were conducted to determine the influence of yucca extract on ruminal digestion, fermentation, and ammonia patterns using ruminally and duodenally cannulated dairy cows. In Trial 1, urea at 0 or 1% of the diet and yucca extract at 0 or 4 g/d formed four dietary treatments in a 2 x 2 factorial arrangement. The experimental design was a 4 x 4 Latin square with 15-d periods. Duodenal digesta were sampled every 6 h during the last 4 d of each period to determine OM and ADF digestibilities and bacterial protein synthesis in the rumen using Cr2O3 and 15N markers. Ruminal digestibilities were (percentage): OM 46.3 vs 43.0%, and ADF 35.9 vs 41.4%, with or without Deodorase. Microbial protein entering the duodenum averaged 2.7 vs 3.1 kg/d for the respective treatments. Ruminal measurements were not affected by treatment (P > .10). In Trial 2, five cows were used in a 5 x 5 Latin square with 7-d periods. Treatments were 0, 2, 4, 6, and 8 g/d of yucca extract administered via ruminal cannulas. Ruminal fluid was sampled 0, 1, 2, 4, 7, 11, 16, and 22 h after feeding during the last 2 d of each period. Average ruminal NH3 N ranged from 31.4 to 35.4 mg/dL, pH 5.99 to 6.18, and total VFA from 120 to 129 mM, and all did not differ among treatments (P > .10). Yucca extract administered at 4 g/d did not significantly affect ruminal digestibilities of OM and ADF, and up to 8 g/d did not affect ruminal NH3, pH, or VFA.

Ammonia↗
PubMed1994

Effect of steam flaking of corn and sorghum grains on performance of lactating cows.

The objective of this study was to compare the relative feeding value of sorghum versus corn grain in rolled or steam-flaked forms in diets for lactating dairy cows. Twenty-four Holstein cows (averaging 110 DIM) were divided into four groups and fed diets of 40% grain as dry-rolled sorghum, steam-rolled corn, steam-flaked sorghum, or steam-flaked corn for 70 d. Compared with rolling, flaking of both grains increased yields of milk, milk protein and fat, and protein percentage of milk, but differences tended to be greater for sorghum than for corn. Efficiency of feed utilization was higher for steam-flaked than for dry-rolled sorghum but was unaffected by corn processing. Flaking of both grains increased total tract digestibilities of DM, OM, CP, starch, ADF, and NDF. Estimates for NEL were 21% higher for flaked than for rolled sorghum and 6% higher for flaked than for rolled corn. No differences in performance of cows existed between corn and sorghum grains. Cows fed 40% of their diet as steam-flaked sorghum or corn yielded more milk and milk protein than those fed the rolled form of the grains, and no differences existed between types of grain fed.

Animal Feed↗
PubMed1994

Effect of isocaloric infusion of glucose in the rumen or propionate in the duodenum.

This study was undertaken to understand better the mechanisms causing increased milk protein. Cows fed steam-flaked sorghum have increased milk protein compared with that of cows fed dry-rolled sorghum because of a large shift of starch digestion from the intestine to the rumen. Five cannulated lactating cows were infused with glucose in the rumen or with propionate in the duodenum in two trials. The experimental design was a 2 x 2 Latin square with 7 d of adjustment and 7 d of infusion. During the experiment, cows received a TMR containing 19.3% CP and 1.56 Mcal/kg of NEL (on a DM basis); alfalfa hay and dry-rolled sorghum grain were the principal ingredients. Similar concentrations in feces of cows among propionate treatments suggested complete absorption of infused propionate. Milk yield did not differ, but protein percentage of milk was higher (2.88 versus 2.72%) for cows infused ruminally with glucose than for those infused in the duodenum with propionate. For the respective treatments, duodenal flows were 2.11 and 1.76 kg/d for microbial protein and 3.44 and 2.73 kg/d for total CP (or 85 and 74% of CP intake). These data demonstrate that increased propionate availability for gluconeogenesis and a possible sparing of essential AA did not result in increased milk protein content, but ruminal infusion of glucose, which tended to increase microbial protein synthesis, did increase the protein percentage of milk.

Adenosine Triphosphate↗
PubMed1994

Effect of source and amount of supplemental fat on lactation and digestion in cows.

Thirty Holstein cows averaging 50 DIM were assigned to five dietary treatments for 75 d to determine the effects of source and amount of supplemental fat on milk yield, milk composition, and nutrient digestibilities. Diets were 1) control, 2) diet 1 plus 12% whole cotton-seed, 3) diet 2 plus 2.2% safflower oil, 4) diet 2 plus 2.2% prilled tallow fatty acids, and 5) diet 2 plus 4.4% prilled tallow fatty acids. Milk yield was increased an average of 2.1 kg/d by addition of 2.2% prilled tallow fatty acids or safflower oil to the diet (7% fatty acids) containing 12% whole cottonseed. However, when fatty acids were increased to 9.1% with additional prilled tallow fatty acids, milk yield, DMI, and fatty acid digestibility decreased. Whole cottonseed alone and in combination with all fat additions decreased milk protein concentrations. Safflower oil increased C18:0, C18:1, and C18:2 fatty acids in milk. Digestibilities of OM, NDF, and ADF were not affected by diet. Supplementation of a saturated or unsaturated fat source to increase fatty acid content to 7.0% of dietary DM increased milk yield, but a further increase in fat to 9.1% with the saturated source appeared excessive for cows yielding 30 to 35 kg/d of milk.

Animals↗
PubMed1994

Heat stress interactions with protein, supplemental fat, and fungal cultures.

Cows that were subjected to hot environmental temperatures yielded less milk (3.1 kg/d) on a diet high in CP (18.4%) and of medium degradability (65%) than on diets high in CP of low degradability (59%) or medium in CP (16.1%). The high CP diets were associated with decreased DMI and higher water intake, ruminal NH4, and blood urea. Negative effects on yield from the high CP, medium degradability diet were not observed at moderate temperatures. Evaporative cooling of cows in hot weather resulted in a greater milk yield response to low versus medium rumen-undegradabale protein diets than for uncooled cows. Evaporative cooling of cows also affected response to protein quality. For cooled cows, high Lys diet (soybean, fish, and blood meals) increased milk yield 14% over that with low Lys diet (corn gluten meal), but, for uncooled cows, a high Lys diet only increased yield by 9%. Percentage of CP, degradability, and protein quality had no effect on body temperatures or respiration rates of lactating cows. Some, but not other, reports showed that supplementation of 2 to 2.5% fat to diets fed under hot summer conditions resulted in less yield response than when fat was added at moderate temperatures. In several studies, fungal cultures (3 to 5 g/d) in the diet decreased body temperatures and respiration rates in hot, but not cool, weather. Increased milk yields and cellulose digestibility also resulted from dietary fungal cultures in some, but not all, trials. The mechanism of action exerted by fungal cultures on body temperature and respiration rate is unclear.

Animal Feed↗
PubMed1994

Mechanism and etiology of primary chronic angle closure glaucoma.

The ocular anatomic features, pupil-blocking force, status of angle synechiae closure and positivity of provocative tests were compared between the primary chronic angle closure glaucoma (PCACG) and primary acute angle closure glaucoma (PAACG) by using ultrasonic biometry, computerized anterior ocular segment image processing technique, gonioscopy and provocative tests. The studies showed that the anterior chamber depth of PAACG were shallower than that of PCACG; the pupil-blocking force of PAACG was stronger than that of PCACG; the status of angle synechiae closure of PCACG were mainly creeping synechiac closure; the positivity of mydriasis test was much higher (46.01%) in PCACG than that (6.8%) in PAACG after iridectomy. These facts suggest approximately half of the PCACG cases may be mult-mechanism to contribute to the angle closure besides the mechanism of pupillary block. Therefore, the authors emphasis that the pupillary block must be eliminated as well as the other mechanism for the treatment of PCACG and finally, a criteria of diagnosis and principles of management of PCACG were proposed.

Adult↗
PubMed1994

[Effect of hypoxia at 5% oxygen on global electrophysiological responses from normal awake guinea pigs].

All experiments were conducted on awake guinea pigs warranting a normal physiological function of the circulatory system. Global electrophysiological responses from the round window of cochlea were monitored: cochlear microphonic (CM), summating potential (SP) and auditory compound action potential (AP). The results showed that hypoxia induced a threshold elevation at all frequencies thus affecting the whole cochlea, and also very large diminutions of AP at high intensity level exclusively in response to a high frequency, and very large increases of SP at 2 kHz and 8 kHz. After hypoxia, which lasted thirty minutes, a considerable recovery occurred, and at the end of the session recovery reached around eighty percent. Alterations of cochlea action potential in response to high intensity stimuli were dissociated from threshold changes. We speculate that threshold elevation could be associated with over-all energetic (ATP) decrease leading to diminution of endolymphatic resting potential. Action potential changes at high intensity and at cochlear base could reflect neurotransmission (afferent, efferent or sympathetic) disturbance.

Action Potentials↗
PubMed1994

Reinfection with Schistosoma japonicum after treatment with praziquantel in Poyang lake region, China.

The study on reinfection with Schistosoma japonicum after treatment was carried out in a cohort of subjects in a heavy endemic village of Poyang lake region, China. After mass treatment with praziquantel in non-transmission time, detailed observations of water contact were estimated using the mean area of skin exposed daily. One year after treatment, the prevalence of infection in study subjects was 54.48%, returning to 83% of initial prevalence. The peak prevalence occurred the 11-15 year age class, but intensity of exposure also varies with age and that age group supporting the higher prevalence of reinfection had high levels of exposure. Among groups of subjects with a similar exposure stratum, young subjects under the age of 21 years were more heavily reinfected, while no heavy reinfection was observed in adults (> or = 25 years). These observations suggest that subjects in this area slowly acquire an increasing degree of immunity to lighten the intensity of infection with S. japonicum.

Adolescent↗