Biomedical subjects

Z Wu

Publications and source records attributed to Z Wu.

At least 469 records · Page 26Linked to original sources

PubMed1997

Regulation of the ecdysone receptor, USP, E75 and MHR3 mRNAs by 20-hydroxyecdysone in the GV1 cell line of the tobacco hornworm, Manduca sexta.

The responsiveness of several nuclear transcription factor genes to 20-hydroxyecdysone (20E) was characterized in an embryonic cell line, GV1, from Manduca sexta. The mRNA for the Manduca ecdysone receptor (MsEcR) was present in the GV1 cells and transiently increased 2.3-fold by 5 h after the addition of 2 micrograms/ml (4 x 10(-6) M) 20-hydroxyecdysone (20E). In contrast, Manduca ultraspiracle (MsUSP) mRNA level in the GV1 cells decreased slowly to half of its initial level by 12 h when exposed to the same concentration of 20E. The mRNAs for two putative transcription factors, MsE75 and MHR3, were induced in the GV1 cells by 20E, with that for E75 appearing within 1 h whereas that for MHR3 within 2 h. The ED50S for induction of MsE75 and MHR3 gene expression in GV1 cells were 1.2 x 10(-6) and 2.5 x 10(-6) M 20E, respectively.

Animals↗

PubMed1997

Mechanisms of inhibition of calmodulin-stimulated cyclic nucleotide phosphodiesterase by dihydropyridine calcium antagonists.

Calmodulin-dependent cyclic nucleotide phosphodiesterase (CaMPDE) is one of the key enzymes involved in the complex interaction between the cyclic nucleotide and Ca2+ second-messenger systems. CaMPDE exists as tissue-specific isozymes, and initially these isozymes were designated according to their respective subunit molecular mass. A variety of pharmacological agents have been used to inhibit CaMPDE, and this inhibition occurs mostly via Ca2+-dependent association with the proteins. We have examined the effect of dihydropyridine Ca2+-channel blockers felodipine and nicardipine on CaMPDE. The results suggest that the 63-kDa (PDE 1B1) and 60-kDa (PDE 1A2) CaMPDE isozymes are inhibited by felodipine and nicardipine by partial competitive inhibition and that these two Ca2+ antagonists appear to counteract each other. This study further demonstrates the existence of a specific site, distinct from the active site on CaMPDE, that exhibits high-affinity binding of these drugs. Felodipine and nicardipine have similar affinities for 60-kDa CaMPDE isozymes but bring about different levels of enzyme inhibition, suggesting the possibility of designing specific drugs that can protect the enzyme from inhibition by dihydropyridine Ca2+-channel blockers.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1997

Isolated limb perfusion with melphalan for human melanoma xenografts in the hindlimb of nude rats: a surviving animal model.

We have established a surviving model of isolated limb perfusion using xenografts of the human melanoma cell line MM 96L injected subcutaneously into the hindlimb of a nude rat. The femoral artery and vein were cannulated via the left renal artery and vein and the hind limb was isolated using tourniquets. The limb was perfused with Krebs Heinseleit buffer at 37 degrees C containing 4.7% bovine serum albumin at a constant flow rate of 4 ml per min for 30-60 min with 100% survival of the animals. Tumour vascularization and blood flow were demonstrated using vascular casts and [51Cr]-microspheres. Following the addition of melphalan (15 or 100 micrograms/ml), drug concentrations in the perfusate, tissues and systemic circulation were determined using high pressure liquid chromatography (HPLC). Systemic leakage, assessed using [125I]albumin and melphalan and detected by a gamma-counter and HPLC respectively, was < 0.5%. The melphalan concentration and tissue flow rate in the tumour deposits were 40 and 30% respectively, when compared with the surrounding subcutaneous tissue. At a dose of 15 micrograms/ml, melphalan caused a reduction in tumour growth after 60 min perfusion, and a significant reduction in tumour size was seen when the melphalan dose was 100 micrograms/ml. The surviving nude rat model of isolated limb perfusion for recurrent melanoma will allow examination of optimal perfusion conditions, along with the pharmacokinetics, pharmacodynamics and efficacy of melphalan and other drugs.

Animals↗

PubMed1997

A time domain binaural model based on spatial feature extraction for the head-related transfer function.

A complex-valued head-related transfer function (HRTF) can be represented as a real-valued head-related impulse response (HRIR). The interaural time and level cues of HRIRs are extracted to derive the binaural model and also to normalize each measured HRIR. Using the Karhunen-Loeve expansion, normalized HRIRs are modeled as a weighted combination of a set of basis functions in a low-dimensional subspace. The basis functions and the space samples of the weights are obtained from the measured HRIR. A simple linear interpolation algorithm is employed to obtain the modeled binaural HRIRs. The modeled HRIRs are nearly identical to the measured HRIRs from an anesthetized live cat. Typical mean-square errors and cross-correlation coefficients between the 1816 measured and modeled HRIRs are 1% and 0.99, respectively. The real-valued operations and linear interpolating in the model are very effective for speeding up the model computation in real-time implementation. This approach has made it possible to simulate real free-field signals at the two eardrums of a cat via earphones and to study the neuronal responses to such a virtual acoustic space (VAR).

Acoustic Stimulation↗

PubMed1997

Genetic analysis of second-site revertants of bacteriophage lambda integrase mutants.

Bacteriophage lambda site-specific recombination is catalyzed by the phage-encoded integrase (Int) protein. Using a collection of 21 recombination-defective Int mutants, we performed a second-site reversion analysis. One of the primary mutants contained a valine-to-glutamic acid change at position 175 (V175E), and a pseudorevertant with a lysine change at this site (V175K) was also isolated. Relative to the wild-type protein, the V175E protein was defective in its ability to form the attL complex and to catalyze excision in vivo and in vitro. A mutant containing an alanine substitution (V175A) was made by site-directed mutagenesis, and it was more efficient than the V175K protein in forming the attL complex and promoting excision. These results indicate that a nonpolar side chain at residue 175 is required for function. The second primary mutant contained a proline-to-leucine change at position 243 (P243L). A true second-site revertant was isolated that contained a glutamic acid-to-lysine change (E218K). The P243L-E218K protein promoted recombination and bound arm-type sites more efficiently than the original P243L protein but not as efficiently as the protein containing the E218K substitution alone. The E218K substitution also restored activity to a mutant with a threonine-to-isoleucine substitution at position 270 (T270I). This result showed that suppression by the E218K change is not allele specific and suggests that the substitution improves an inherent activity of Int rather than directly compensating for the defect caused by the primary substitutions. Results with challenge phages carrying attL sites with altered core sites indicate that the E218K change may improve binding to the core site.

Bacteriophage lambda↗

PubMed1997

Molecular cloning and characterization of human JNKK2, a novel Jun NH2-terminal kinase-specific kinase.

At least three mitogen-activated protein kinase (MAPK) cascades were identified in mammals, each consisting of a well-defined three-kinase module composed of a MAPK, a MAPK kinase (MAPKK), and a MAPKK kinase (MAPKKK). These cascades play key roles in relaying various physiological, environmental, or pathological signals from the environment to the transcriptional machinery in the nucleus. One of these MAPKs, c-Jun N-terminal kinase (JNK), stimulates the transcriptional activity of c-Jun in response to growth factors, proinflammatory cytokines, and certain environmental stresses, such as short wavelength UV light or osmotic shock. The JNKs are directly activated by the MAPKK JNKK1/SEK1/MKK4. However, inactivation of the gene encoding this MAPKK by homologous recombination suggested the existence of at least one more JNK-activating kinase. Recently, the JNK cascade was found to be structurally and functionally conserved in Drosophila, where DJNK is activated by the MAPKK DJNKK (hep). By a database search, we identified an expressed sequence tag (EST) encoding a portion of human MAPKK that is highly related to DJNKK (hep). We used this EST to isolate a full-length cDNA clone encoding a human JNKK2. We show that JNKK2 is a highly specific JNK kinase. Unlike JNKK1, it does not activate the related MAPK, p38. Although the regulation of JNKK1 activities and that of JNKK2 activities could be very similar, the two kinases may play somewhat different regulatory roles in a cell-type-dependent manner.

Amino Acid Sequence↗

PubMed1997

The human Myt1 kinase preferentially phosphorylates Cdc2 on threonine 14 and localizes to the endoplasmic reticulum and Golgi complex.

Entry into mitosis requires the activity of the Cdc2 kinase. Cdc2 associates with the B-type cyclins, and the Cdc2-cyclin B heterodimer is in turn regulated by phosphorylation. Phosphorylation of threonine 161 is required for the Cdc2-cyclin B complex to be catalytically active, whereas phosphorylation of threonine 14 and tyrosine 15 is inhibitory. Human kinases that catalyze the phosphorylation of threonine 161 and tyrosine 15 have been identified. Here we report the isolation of a novel human cDNA encoding a dual-specificity protein kinase (designated Myt1Hu) that preferentially phosphorylates Cdc2 on threonine 14 in a cyclin-dependent manner. Myt1Hu is 46% identical to Myt1Xe, a kinase recently characterized from Xenopus laevis. Myt1Hu localizes to the endoplasmic reticulum and Golgi complex in HeLa cells. A stretch of hydrophobic and uncharged amino acids located outside the catalytic domain of Myt1Hu is the likely membrane-targeting domain, as its deletion results in the localization of Myt1Hu primarily to the nucleus.

Amino Acid Sequence↗

PubMed1997

Marital instability after midlife.

"Divorce in later life has been shown to produce dramatic declines in the economic, psychological, and physical well-being of marital partners. This study examines the prevalence and determinants of marital disruption after midlife using Becker's theory of marital instability. Using recent Canadian national data, the marital outcomes of women and men who were married as of age 40 are tracked across the remaining years of the marriage. Cox proportional hazard regression models indicate stabilizing effects of the duration of the marriage, the age at first marriage, the presence of young children, as well as of remarriage for middle-aged and older persons. Other significant risk factors include education, heterogamous marital status, premarital cohabitation, number of siblings, and region."

Adolescent↗

PubMed1997

Effects of supplemental fat and protein source on ruminal fermentation and nutrient flow to the duodenum in dairy cows.

Four lactating Holstein cows, fitted with ruminal and T-type duodenal cannulas, were used in a 4 x 4 Latin square design for four periods (14 d each). Treatments were 1) medium fat and low quality protein, 2) medium fat and high quality protein, 3) high fat and low quality protein, and 4) high fat and high quality protein. Fat was supplemented by addition of 2.5% prilled fatty acids to high fat diets. The low quality diets contained corn gluten meal and 0.47% Lys, and the high quality diets contained a mixture of fish, blood, and soybean meals and 0.77% Lys. The percentage of Met was similar for all diets (mean, 0.28%). Diets contained 35 to 38% steam-flaked sorghum and 32% chopped alfalfa hay. Dietary CP averaged 18%, and all diets were high in RUP (44% of CP). Yields of milk, milk protein, and SNF were increased by added fat and by high quality protein. Ruminal NH3 and butyrate were increased by supplemental fat. Cows fed high quality protein had increased ruminal VFA, propionate, butyrate, and valerate, but decreased ratios of acetate to propionate. Essential AA concentrations in coccygeal plasma and arteriovenous differences across the mammary gland were higher for Lys and lower for Leu in cows fed high quality protein than in those fed low quality protein.

Animal Feed↗

PubMed1997

Lactational performance of cows fed low or high ruminally undegradable protein prepartum and supplemental methionine and lysine postpartum.

Multiparous Holstein cows (n = 24) were fed diets containing 34 or 41% ruminally undegradable protein (RUP) for 30 d before parturition; then each group was fed a basal diet supplemented with or without ruminally stable Met (10.6 g/d) and Lys (15.2 g/d) for 75 d in the subsequent lactation. Supplementation of Met and Lys increased the milk yield of cows previously fed the low RUP diet, but milk yields before and after amino acid (AA) supplementation were similar for cows previously fed the high RUP diet. Milk protein content (percentage) increased from 2.83 to 2.96 for cows previously fed the high RUP diet. Milk protein yield increased from 1.13 to 1.21 kg/d when Met and Lys were fed. Data on AA concentration in plasma and AA extraction by the mammary gland suggest that the supplementation of Met and Lys corrected a Met limitation. According to the Cornell Net Carbohydrate and Protein System, the lactation diet was limiting for Met for maximum milk yield and was corrected by AA supplementation. Based on limiting AA, allowable milk yield was 42.5 kg/d, and the observed yield was 40.9 kg/d averaged across treatments. The group with the greatest allowable milk yield (45.2 kg/d) had the greatest actual milk yield (43.0 kg/d). The regression equation of observed milk yield on allowable milk yield was Y = 3.4 + 0.8805X.

Animals↗

PubMed1997

Effects of ruminally inert fat and evaporative cooling on dairy cows in hot environmental temperatures.

Under hot summer conditions of Tucson, Arizona, 24 Holstein cows (mean = 80 d of lactation) were assigned for 56 d to four treatments in a randomized block design with a 2 x 2 factorial arrangement of treatments. Factors were 1) medium [4.6% of dry matter (DM)] versus high (7.4% of DM) amounts of dietary fat and 2) corral shade only versus shade equipped with evaporative cooling. The high fat diet contained 3% prilled fatty acids. The efficiency of the conversion of feed to milk tended to be better for cows fed prilled fat than for cows fed medium dietary fat, but other lactation measurements were unaffected. Cows with access to evaporative cooling had greater milk yields than did cows with access to shade only. Prilled fatty acids did not depress the percentage of milk protein, but reduced short- and medium-chain fatty acids (C6:0 to C14:0) in milk fat and increased palmitic acid. Digestibilities of DM, organic matter, crude protein, acid detergent fiber, neutral detergent fiber, and starch were unaffected by amount of fat or by cooling method, but prilled fatty acids tended to decrease apparent digestibility of fatty acids. No differences were observed among treatments in respiration rates or rectal temperatures. When rectal temperatures were determined, cows were crowded, which probably negated detection of an effect of evaporative cooling. Evaporative cooling increased milk yield of cows in hot weather, but the addition of 3% fatty acids did not increase yield, and no interactions were observed.

Animals↗

PubMed1997

Adequacy of amino acids in diets fed to lactating dairy cows.

The Cornell Net Carbohydrate and Protein System was used to evaluate absorbable limiting amino acids (AA) for milk yield. The system was utilized to characterize whether diets in five previous experiments met AA requirements for milk protein synthesis. Twenty-nine treatment means for milk yield from 367 cows constituted the database for the evaluation. Using the mechanistic relationships of nutrient metabolism described in the Cornell system, absorbed amounts were predicted of each essential AA from a diet and milk yields allowed by the most limiting AA. Regression of observed milk yield (Y) on predicted milk yield (X) using all treatment means (n = 29) was Y = 2.3 + 0.799X (r2 = 0.72). The linear relationship was stronger using 6 treatment means (n = 18) when protein supplements were fed rather than when ruminally protected AA were fed or when AA were postruminally infused (Y = -1.8 + 0.983X; r2 = 0.93). The Cornell system predicted that, for diets based on corn, Met or Lys was limiting when soybean meal was the protein source, but Lys was limiting when corn gluten meal or brewers grains were the source of protein. By AA limitation, the Cornell system explained differences in milk yield for diets that differed in supplemental protein sources in some of the experiments. As determined from milk protein yields in these studies, requirements for individual essential AA were expressed as a percentage of dietary dry matter or total essential AA, and values were relatively constant among dietary treatments and experiments.

Amino Acids↗

PubMed1997

Comparison of barley and sorghum grain processed at different densities for lactating dairy cows.

To vary ruminally degradable starch, sorghum grain was dry-rolled or steam-flaked to different densities and compared with dry-rolled barley in total mixed diets fed to 40 lactating cows (111 d of lactation) assigned to five dietary treatments. Diets contained (percentage of dry matter) 35% alfalfa hay, 4.1% cottonseed hulls, 10% whole cottonseed, 2% fish meal, 4% soybean meal, and 4.9% of a molasses, mineral, and vitamin supplement. Treatments were 40% sorghum grain either dry-rolled or steam-processed at flake densities of 437, 360, and 283 g/L. A fifth diet containing 42% dry-rolled barley was fed. Cows were blocked according to pretreatment (14 d) milk yield and received experimental diets for 56 d. Increasing ruminal starch degradability by including steam-flaked sorghum grain or barley in the diet did not increase milk yield or milk protein percentage and yield, as was shown in eight previous studies. Steam-flaked sorghum or dry-rolled barley in the diet decreased dry matter intake, resulting in a 10 to 19% higher efficiency of conversion of feed dry matter to milk than that for dry-rolled sorghum. Milk urea N was decreased, and milk casein yield tended to be increased, by steam-flaking sorghum at the moderate density compared with dry-rolling or fine flaking. Dietary protein was more efficiently converted to milk protein and casein from flaked sorghum and dry-rolled barley than from dry-rolled sorghum. In this study, increasing ruminal starch degradability resulted in higher feed efficiency and lower feed intakes, bu optimal flake densities for steam-processed sorghum gain to maximize milk and milk protein yield were not clarified.

Animal Feed↗

PubMed1997

Administration of recombinant bovine somatotropin to dairy cows for four consecutive lactations.

Effects of long-term administration of recombinant bovine somatotropin (bST) to dairy cows on complete lactational performance [60 (+/- 3) to 284 (+/- 3) d in milk (DIM)] were studied for four consecutive lactations. Beginning on d 60 (+/- 3) postpartum, Holstein cows received biweekly injections (500 mg) of bST (n = 39) or a placebo (control; n = 39) during the first lactation of the study. Cows either continued on the same treatment (n = 26) or were switched to the opposite treatment (n = 29) during the second lactation. Cows that changed treatments were injected for only 16 wk during the second lactation. Six cows per treatment completed four consecutive lactations. Treatment with bST during the first lactation did not have a residual effect on milk yields during the second lactation. Injections of bST during the second lactation increased milk yield 6.5 kg/d from 60 (+/- 3) to 172 DIM. For the four lactations, cows receiving bST yielded 3.7 kg/d (14%) more milk and gained 52 kg (37%) more body weight than did controls. Pretreatment (from 0 to 56 DIM) milk yields in yr 2, 3, and 4 were not affected by previous bST treatment. Milk yield, efficiency of feed utilization, and body weights were enhanced in cows injected with bST for four consecutive lactations. Previous bST treatment did not diminish milk yields in subsequent lactations.

Animals↗

PubMed1997

Influence of fat source and sorghum grain treatment on performance and digestibilities of high yielding dairy cows.

Forty-eight lactating Holstein cows averaging 81 d in milk were allotted to eight blocks based on milk yield during the 14-d pretreatment period and randomly assigned to six treatment groups in a 2 x 3 factorial arrangement of treatments for 64 d. Factors were type of sorghum grain processing [dry-rolled vs. steam-flaked; fed at 34% of dry matter (DM) in a total mixed ration (TMR) based on alfalfa] and type of supplemental fat (2.5% of DM as cottonseed oil, tallow, or prilled fatty acids). Compared with dry-rolled sorghum, steam-flaked sorghum did not affect milk yield, fat percentage, or fat yield but did increase milk protein percentage, body weight gains, and estimated net energy for lactation (22%). Fat source did not affect lactational response, but, compared with tallow, prilled fatty acids tended to decrease DM intake. Steam-flaked sorghum, compared with dry-rolled sorghum, increased digestibilities of DM, organic matter, crude protein, and starch, regardless of fat source. The TMR containing prilled fat had lower digestibilities of DM and organic matter than did TMR containing cottonseed oil or tallow; and TMR containing prilled fat had lower digestibilities of crude protein and total fatty acids than did TMR containing tallow. This study showed that steam-flaking of sorghum grain increased milk protein content, body weight gains, and estimated net energy for lactation, regardless of dietary fat source.

Animal Feed↗

PubMed1997

Response of Brazilian crossbred cows to varying doses of bovine somatotropin.

The effect of n-methionyl bovine somatotropin (bST) on milk yield was evaluated in crossbred cows (40 1/2 Bos indicus x 1/2 Bos taurus and 18 1/4 B. indicus x 3/4 B. taurus) in Brazil. Cows were randomly assigned to treatments within stage of lactation [stage 1 = 56 to 100 d in milk (DIM); stage 2 = 101 to 199 DIM] and breed groups (1/2 vs. 1/4 B. indicus blood). Treatments were 250 or 500 mg of bST administered every 14 d. Cows in the control group did not receive bST or a placebo. Treated cows received bST injected subcutaneously in the postscapular region, alternating between the left and right sides. The 26-wk experiment consisted of 2 wk of pretreatment and 24 wk of treatment. Cows were housed in an open lot with regulated access to pasture. Cows were milked twice daily and scored for body condition at 2-wk intervals. Compared with controls, milk yield increased equally (22%) for cows receiving 250 or 500 mg of bST. Milk yield response to bST was higher and persisted longer during stage 1 of lactation than during stage 2 of lactation. No difference in response to bST was noted between cows with 1/2 or 1/4 B. indicus blood. Cows treated with 500 mg of bST tended to have more mastitis, but no other adverse health effects were observed. The potential use of 250-mg doses of bST at 14-d intervals in crossbred cattle in Brazil and other subtropical regions throughout the world is suggested, particularly before about 220 DIM.

Animals↗

PubMed1997

Effect of steam-flaked or steam-rolled corn with or without Aspergillus oryzae in the diet on performance of dairy cows fed during hot weather.

The objective of this study was to determine the effects of steam-rolled versus steam-flaked corn in the diet with or without the addition of a culture of Aspergillus oryzae on the performance of high producing dairy cows during hot summer weather. Thirty-two Holstein cows averaging 92 (+/- 60) d in milk were fed a pretreatment diet for 21 d followed by a 70-d experimental period in a completely randomized block design with a 2 x 2 factorial arrangement of treatments. Diets were 1) steam-flaked corn plus 3 g/d of A. oryzae, 2) steam-flaked corn, 3) steam-rolled corn plus 3 g/d of A. oryzae, and 4) steam-rolled corn. Intake was not affected significantly by grain processing or addition of A. oryzae. Compared with effects from steam-rolled corn in the diet, steam-flaked corn increased milk production; percentage of milk protein; yields of milk protein, lactose, and SNF; and the efficiency of conversion of dry matter to fat-corrected milk. Addition of A. oryzae tended to increase protein percentage and increased the percentage of SNF. Changes in body weight and body condition score tended to be higher, and somatic cell count tended to be lower, for cows fed the flaked corn than for cows fed the rolled corn. No interactions were significant. Treatments did not affect rectal temperatures or respiration rates; however, high mean values measured at 1400 h once weekly indicated thermal stress. These data show improved milk production from cows fed steam-flaked corn but not from those fed diets supplemented with A. oryzae.

Animal Feed↗

PubMed1997

[One-year-result of excimer laser for photorefractive keratectomy in very high myopia].

We corrected 53 cases (84 eyes) of very high myopia using photorefractive keratectomy (PRK) with VISX 20/20 excimer laser, and followed up the cases more than one year. The rates of visual acuity more than or equal to 0.5 or 1.0 were 81.0% and 23.9%, 75.0% eyes were within +/- 2.00 diopter of the desired emmetropia. Grade 2 or more severe corneal haze were presented in 13.1% eyes. PRK with VISX 20/20 excimer laser may be an effective method to correct very high myopia from -10.00 to -16.00 diopters.

Adolescent↗