Biomedical subjects

W Z Yang

Publications and source records attributed to W Z Yang.

At least 37 records · Page 2Linked to original sources

PubMed2000

Effects of barley grain processing on extent of digestion and milk production of lactating cows.

Effects of barley processing on site and extent of digestion and milk production in dairy cows were evaluated in a 4 x 4 Latin square design with four lactating cows with ruminal and duodenal cannulas. Barley grain was steam-rolled to four thicknesses: coarse, medium, medium-flat, and flat. The processing index (PI), measured as volume weight of barley after processing expressed as a percentage of its volume weight before processing, was 81.0, 72.5, 64.0, and 55.5% for the four treatments, respectively. Diets consisted of 53% concentrate (dry matter basis) containing one of the four processed barleys. Cows were offered ad libitum access to a total mixed ration three times daily. Dry matter intake was quadratically increased with decreasing PI, with maximum intake for cows fed medium-flat barley. Although ruminal digestibilities of organic matter, starch, and crude protein were not affected by grain processing, intestinal and total tract digestibilities were linearly increased as PI of barley was reduced. Milk yield was quadratically increased (25.6, 28.1, 30.8, and 29.0 kg/d) with decreasing PI, and maximum milk yield was for cows fed medium-flat barley. Milk fat and lactose contents were similar, but milk protein content was increased with decreasing PI. These results indicate that the optimal extent of barley processing for dairy cows fed diets supplying adequate fiber was medium-flat, corresponding to a processing index of about 64%. Coarsely or flatly rolled barley is not recommended, because extensive processing did not further improve intake of digestible nutrients, and coarsely processed barley resulted in the lowest intake of digestible organic matter; hence, lowest milk production. Processing index is a reliable and practical method to quantitatively measure extent of steam rolling.

Animal Nutritional Physiological Phenomena↗

PubMed2000

Synergy between ruminal fibrolytic enzymes and enzymes from Trichoderma longibrachiatum.

The mechanism by which enzyme additives improve feed digestion in ruminants is not fully understood. Direct hydrolysis of feed in the rumen is a potential mode of action, but the importance of this mode needs to be quantified because of the relatively low exogenous hydrolase activity added compared with the total activity present in the rumen. We examined the interactions between ruminal and exogenous enzymes on fiber degradation using a completely randomized experimental design, with an 11 (enzyme preparations and their combinations) x 5 (assay pH) arrangement of treatments. Ruminal enzymes were extracted from cattle receiving high fiber or high concentrate diets and exogenous enzymes were Trichoderma longibrachiatum preparations containing different proportions of xylanase and cellulase activities. Ruminal and exogenous enzyme preparations and their combinations were tested for the ability to degrade soluble cellulose, xylan, and corn silage over a range of pH from 4.5 to 6.5 at 39 degrees C. T. longibrachiatum enzymes acted synergistically with enzymes from mixed rumen microorganisms in degrading soluble cellulose, xylan, and corn silage. Hydrolysis increased by up to 35, 100, and 40% for soluble cellulose, xylan, and corn silage, respectively, and was most evident at a pH range between 5.0 and 6.0. The synergistic effect between ruminal and exogenous enzymes increases the hydrolytic potential within the rumen environment and is likely a significant mechanism by which enzyme additives improve feed digestion.

Animal Feed↗

PubMed2000

A comparison of methods of adding fibrolytic enzymes to lactating cow diets.

Holstein cows (n = 43) in early lactation were used to investigate effects of method of adding fibrolytic enzymes to diets on feed intake, milk production, and digestibility. Cows were blocked according to parity and calving date and randomly assigned to three treatments: control, enzymes applied to the total mixed ration (E-TMR), or enzymes added to the barley-based concentrate (E-Conc). The enzyme product used was a proprietary blend that contained relatively high xylanase and low cellulase activities (Biovance Technol. Inc., Omaha, NE). An enzyme solution (50 mg of enzyme powder dissolved into 20 ml of water) was sprayed onto each kilogram of total mixed ration (dry matter basis) before feeding. Alternatively, 73 g of enzyme powder, dissolved in 20 L of water, was added per ton of concentrate (50 mg of enzyme/kg of diet dry matter). The total mixed rations contained 24% corn silage, 14% alfalfa hay, and 62% concentrate (dry matter basis) and were offered ad libitum. In vitro gas production assays and two experiments using sheep were conducted to measure the effects of enzyme treatment on digestibility. Dry matter intake (mean: 19.8 kg/d) was not affected by enzyme supplementation. Milk yield (kg/d) was higher for cows fed E-Conc (37.4) than for cows fed control (35.3) or E-TMR (35.2) with no effects on milk composition. Total tract digestibility (%) of dry matter was higher for E-Conc (66.6%) than for the control diet (63.9%) and intermediate for E-TMR (65.7%) when measured in dairy cows. However, the digestibility of the diets was substantially higher when measured in sheep than in dairy cows, with no effects of enzyme supplementation. The results indicate that fibrolytic enzymes have the potential to increase digestibility and milk production in dairy cows because digestion is low relative to potential digestibility. When digestion is higher, as was observed in lambs or in vitro, no improvement in digestibility occurs. Method of enzyme delivery must also be considered to maximize the benefits of using fibrolytic enzymes in dairy cow diets.

Animal Feed↗

PubMed1999

Crystallization and preliminary crystallographic analysis of the Escherichia coli tyrosine aminotransferase.

Tyrosine aminotransferase catalyzes transamination for both dicarboxylic and aromatic amino-acid substrates. The substrate-free Escherichia coli tyrosine aminotransferase (eTAT) bound with the cofactor pyridoxal 5'-phosphate (PLP) was crystallized in the trigonal space group P3(2). A low-resolution crystal structure of eTAT was determined by molecular-replacement methods. The overall folding of eTAT resembles that of the aspartate aminotransferases, with the two identical subunits forming a dimer in which each monomer binds a PLP molecule via a covalent bond linked to the epsilon-NH(2) group of Lys258. Comparison of the structure of eTAT with those of the open, half-open or closed form of chicken or E. coli aspartate aminotransferases shows the eTAT structure to be in the open conformation.

Animals↗

PubMed1999

Effects of grain source and enzyme additive on site and extent of nutrient digestion in dairy cows.

Four lactating, cannulated Holstein cows were used in a 4 x 4 Latin square design to investigate the effects of grain source and fibrolytic enzyme supplementation on ruminal fermentation, nutrient digestion in the rumen and in the intestine, and milk production. A 2 x 2 factorial arrangement was used; two grains (barley and hull-less barley) were combined with and without enzyme. The enzyme supplement (Pro-Mote; Biovance Technologies Inc., Omaha, NE) contained primarily cellulase and xylanase activities and was applied daily to the total mixed diet. Dry matter intake was not affected by diet, but starch intake was greatest when hull-less barley was fed. Starch from hull-less barley was more digestible in the rumen and in the total tract than was starch from barley, but opposite results occurred for fiber digestion, indicating that hull-less barley depressed fiber digestion. As a result, cows fed the hull-less barley diets tended to produce more milk with a higher milk lactose content than did cows fed the barley diets. Enzyme supplementation had minimal effects on ruminal digestion but increased nutrient digestibility in the total tract and the proportion of microbial N in nonammonia N. Consequently, cows fed diets supplemented with enzyme had a higher milk protein content and tended to produce more 4% fat-corrected milk than did control cows. These results indicate that the use of hull-less barley rather than barley increased the digestible energy intake of dairy cows, resulting in higher milk production. The use of a fibrolytic enzyme mixture enhanced feed digestibility and milk production.

Animals↗

PubMed1999

Effects of an enzyme feed additive on extent of digestion and milk production of lactating dairy cows.

A study was conducted using lactating Holstein cows with ruminal and duodenal cannulas in a 4 x 4 Latin square design to investigate fibrolytic enzyme supplementation on site and extent of nutrient digestion. The four diets consisted of 45% concentrate, 10% barley silage, and 45% cubed alfalfa hay (dry matter basis) and differed in enzyme supplementation: 1) control cubes, 2) cubes treated with 1 g of enzyme mixture/kg of cubes, 3) cubes treated with 2 g of enzyme mixture/kg of cubes, and 4) both concentrate and cubes treated with 1 g of enzyme mixture/kg of dry matter. The enzyme supplement contained primarily cellulase and xylanase activities. Digestion of organic matter and neutral detergent fiber in the total tract was higher for cows fed the high dosage of enzyme than for cows fed the control cubes. Ruminal digestibility of crude protein was higher, but that of organic matter and neutral detergent fiber was only numerically higher, for cows fed the high dosage of enzyme compared with that of cows fed the control cubes. Higher ruminal digestibility associated with the high dosage of enzyme resulted in more microbial protein synthesis. Milk production increased for cows fed the high dosage of enzyme compared with cows fed the control cubes and effects of the addition of enzyme on milk composition were minimal. The results demonstrated the benefits of using a fibrolytic enzyme additive to enhance feed digestion and milk production by dairy cows. The response to enzyme supplementation was affected more by amount of enzyme than by whether the enzyme was added to forage or concentrate.

Animal Feed↗

PubMed1999

Fibrolytic enzyme supplements for dairy cows in early lactation.

Twenty multiparous lactating Holstein cows in early lactation were used to investigate effects of exogenous fibrolytic enzyme supplementation on dry matter intake, milk production, and digestibility. Cows were blocked according to parity, expected calving date, and milk yield in the previous lactation, and then randomly assigned after calving to two treatments: control or enzyme. The enzyme mixture, which contained mainly xylanase and cellulase activities (Pro-Mote, Biovance Technol. Inc., Omaha, NE), was added to the concentrate to supply 1.3 g/kg of total mixed ration (dry matter basis). The total mixed rations contained 24% corn silage, 15% alfalfa hay, and 61% barley concentrate (dry matter basis) and were offered for ad libitum intake. Enzyme addition did not affect dry matter intake. However, total digestibility of nutrients, determined using Cr2O3, was dramatically increased by enzyme treatment (dry matter, 61.7 vs. 69.1%; neutral detergent fiber, 42.5 vs. 51.0%; acid detergent fiber, 31.7 vs. 41.9%; crude protein, 61.7 vs. 69.8%). Consequently, milk yield tended to increase (35.9 vs. 39.5 kg/d). Percentage of milk fat was lower, and percentages of milk protein tended to be lower for cows fed a diet supplemented with enzymes, such that component yields were similar for cows fed either diet. Energy deficiency was numerically lower for cows fed a diet supplemented with enzymes than for cows fed the control diet (-3.62 vs. -3.33 Mcal/d). Supplementing dairy cow diets with a fibrolytic enzyme mixture has the potential to enhance milk yield and nutrient digestibility of cows in early lactation without changing feed intake.

Animals↗

PubMed1998

Conversion of a beta-strand to an alpha-helix induced by a single-site mutation observed in the crystal structure of Fis mutant Pro26Ala.

The conversion from an alpha-helix to a beta-strand has received extensive attention since this structural change may induce many amyloidogenic proteins to self-assemble into fibrils and cause fatal diseases. Here we report the conversion of a peptide segment from a beta-strand to an alpha-helix by a single-site mutation as observed in the crystal structure of Fis mutant Pro26Ala determined at 2.0 A resolution. Pro26 in Fis occurs at the point where a flexible extended beta-hairpin arm leaves the core structure. Thus it can be classified as a "hinge proline" located at the C-terminal end of the beta2-strand and the N-terminal cap of the A alpha-helix. The replacement of Pro26 to alanine extends the A alpha-helix for two additional turns in one of the dimeric subunits; therefore, the structure of the peptide from residues 22 to 26 is converted from a beta-strand to an alpha-helix. This result confirms the structural importance of the proline residue located at the hinge region and may explain the mutant's reduced ability to activate Hin-catalyzed DNA inversion. The peptide (residues 20 to 26) in the second monomer subunit presumably retains its beta-strand conformation in the crystal; therefore, this peptide shows a "chameleon-like" character since it can adopt either an alpha-helix or a beta-strand structure in different environments. The structure of Pro26Ala provides an additional example where not only the protein sequence, but also non-local interactions determine the secondary structure of proteins.

Amino Acid Sequence↗

PubMed1997

The transactivation region of the fis protein that controls site-specific DNA inversion contains extended mobile beta-hairpin arms.

The Fis protein regulates site-specific DNA inversion catalyzed by a family of DNA invertases when bound to a cis-acting recombinational enhancer. As is often found for transactivation domains, previous crystal structures have failed to resolve the conformation of the N-terminal inversion activation region within the Fis dimer. A new crystal form of a mutant Fis protein now reveals that the activation region contains two beta-hairpin arms that protrude over 20 A from the protein core. Saturation mutagenesis identified the regulatory and structurally important amino acids. The most critical activating residues are located near the tips of the beta-arms. Disulfide cross-linking between the beta-arms demonstrated that they are highly flexible in solution and that efficient inversion activation can occur when the beta-arms are covalently linked together. The emerging picture for this regulatory motif is that contacts with the recombinase at the tip of the mobile beta-arms activate the DNA invertase in the context of an invertasome complex.

Amino Acid Sequence↗

PubMed1997

Effects of nonstructural carbohydrates and source of cereal grain in high concentrate diets of dairy cows.

Five primiparous and 5 multiparous Holstein cows were used in an experiment with a double 5 x 5 Latin square design to evaluate the effects of lowering the concentration of nonstructural carbohydrates in high grain diets on intake, chewing activities, digestibility, and yield and composition of milk. Cows received diets consisting of 30% barley silage (dry matter basis) and one of five isocaloric concentrates containing corn, hull-less barley, or barley, ranging in the percentage of nonstructural carbohydrates from 24 to 42%. Diet did not affect the dry matter intake (DMI) of primiparous cows. However, for multiparous cows, as the concentration of nonstructural carbohydrates in the corn diets was lowered from 34 to 30%, DMI increased from 16.3 to 18.9 kg/d (2.66 to 3.07% of body weight), and, as the concentration of nonstructural carbohydrates in the barley diets was lowered from 29 to 22%, DMI increased from 19.6 to 21.0 kg/d (3.09 to 3.19% of body weight). For both groups of cows, a reduction in the nonstructural carbohydrates in either the corn or barley diets had minimal effects on milk yield, fat-corrected milk yield, fat content, and protein content, except that the fat content of milk from younger cows fed barley diets was lowered (2.70% vs. 2.30%). For diets formulated at similar concentrations of nonstructural carbohydrates, grain source had no effect on DMI or digestible DMI, but milk yield was lower for cows fed the diet containing hull-less barley (25.2 kg/d) than for cows fed the diets containing corn (26.8 kg/d) or barley (28.1 kg/d). When the concentrations of nonstructural carbohydrates in high grain diets were reduced, feed intake was enhanced, but the relationship between the concentration of nonstructural carbohydrates and performance was not consistent. Differences in ruminal availability of carbohydrates need to be accounted for when diets are formulated on the basis of nonstructural carbohydrates using a range of cereal grains.

Animal Feed↗

PubMed1997

Comparison of hull-less barley, barley, or corn for lactating cows: effects on extent of digestion and milk production.

Six lactating, cannulated Holstein cows were used in a double 3 x 3 Latin square design to compare the effects of hull-less barley with barley and corn on ruminal fermentation, rate of passage, flow of nutrients to the duodenum, and milk production. Diets consisted of 60% concentrate, 30% barley silage, and 10% alfalfa hay (dry matter basis). Concentrates contained steam-rolled grains: hull-less barley, barley, or corn. Dry matter intake was unaffected by grain source, but starch intake tended to be greatest when hull-less barley or corn was fed. The barley diet was more degradable in the rumen than was the hull-less barley or corn diet, and, therefore, flow of microbial organic matter to the duodenum was greatest for cows fed the barley diet. Flow of microbial N to the duodenum was greater (50 g/d) for cows fed the barley diet than for cows fed the other diets, and the flow of ruminally undegradable N was greater (43 and 28 g/d) for cows fed the hull-less barley and corn diets, respectively, than for cows fed the barley diet. As a result, flow of nonammonia N to the duodenum was unaffected by grain source. Total tract apparent digestibility was highest for cows fed the barley and corn diets. Despite its low digestibility, cows fed the hull-less barley diet produced a similar amount of milk as did cows fed the barley and corn diets. Further studies are needed to evaluate the effects of processing hull-less barley on its utilization by dairy cows.

Animal Feed↗

PubMed1997

Comparison of barley, hull-less barley, and corn in the concentrate of dairy cows.

Twelve multiparous and 12 primiparous lactating Holstein cows were used to compare the effects of hull-less barley with barley and corn on dry matter intake (DMI), digestibility, and milk production. Three concentrates were formulated using steam-rolled grains: barley, hull-less barley, or corn. During three 21-d periods, cows received a total mixed diet consisting of 60% concentrate, 30% barley silage, and 10% cubed alfalfa hay [dry matter (DM) basis]. Milk production and DMI were higher for cows fed the corn diet than for cows fed the barley or hull-less barley diets; no interaction with parity was detected. The DMI of cows fed the hull-less barley and barley diets were similar. Despite the higher estimated energy density of the hull-less barley diet, milk production was similar for cows fed the hull-less barley and barley diets because of the lower digestibility of the hull-less barley. Results of an in situ study showed that, for steam-rolled grains, DM and starch from hull-less barley were less degradable than were DM and starch from barley, although the opposite result was observed for ground grains. For steam-rolled hull-less barley, low ruminal degradabilities of DM and starch were apparently not compensated by high intestinal digestibility because total tract digestibility and milk production were lower than expected. Although the net energy for lactation value of hull-less barley is higher than that for barley, milk production by cows might be limited unless hull-less barley is adequately processed to ensure high ruminal and total tract digestibilities.

Animal Feed↗

PubMed1996

Metabolite and hormonal responses to glucose or propionate infusions in periparturient dairy cows supplemented with chromium.

Two studies were conducted to evaluate the effects of Cr supplementation on blood metabolite and hormonal responses of Holstein cows to glucose challenges during late pregnancy and early lactation and to propionate challenges during early lactation. Eight multiparous and 4 primiparous cows (Experiment 1) and 12 primiparous cows (Experiment 2) were assigned to one of two treatments: control and 0.5 ppm of supplemental Cr. The glucose challenges were performed at 2 wk prepartum and at 2 wk postpartum, and the propionate challenges were conducted at wk 2 and 6 postpartum. During glucose tolerance tests, Cr supplementation reduced the ratio of insulin to glucose and reduced plasma concentrations of insulin and triglycerides of primiparous cows during the prepartum period. Chromium supplementation decreased plasma Cr of primiparous cows following glucose challenge. With supplemental Cr, insulin sensitivity was reduced postpartum, particularly for primiparous cows, but insulin sensitivity was increased prepartum. Results of this study suggested that primiparous cows experienced Cr deficiency during late pregnancy and possibly during early lactation. Following propionate infusion, Cr supplementation increased the serum glucose peak, increased the area under the response curve for serum glucose, and tended to increase IGF-I concentrations. Chromium supplementation tended to reduce the ratio of insulin to glucagon. Supplementation might have enhanced gluconeogenesis or glycogenolysis. Supplemental Cr also resulted in reduced variability of most parameters during both experiments.

Animals↗

PubMed1995

Immunomodulatory activity of blood serum from chromium-supplemented periparturient dairy cows.

Our previous research showed enhanced immune responses, including mitogen-induced blastogenesis of peripheral blood mononuclear cells from feedlot calves and periparturient dairy cows supplemented with dietary chromium (Cr). The objective of the present study were to test whether blood sera from Cr-supplemented periparturient cows contained immunomodulatory activity for mitogen-stimulated peripheral blood mononuclear cells and, if so, to determine if this activity was explicable by differences in blood profiles of some glucose-regulating hormones (insulin, cortisol, growth hormone, insulin-like growth factor I, and tumor necrosis factor-alpha) between Cr-supplemented and unsupplemented (control) animals. Blood sera from ten unsupplemented cows and nine Cr-supplemented cows (0.5 ppm day-1) were collected weekly from 2 weeks before to 6 weeks after parturition, and were used to supplement (1, 10, and 20% vol/vol) culture medium supporting concanavalin A (Con A) stimulated mononuclear cells enriched from blood of four nulliparous donor cows. Hormone concentrations were determined using radioimmunoassays. Con A-induced blastogenesis was enhanced when 1, 10, and 20% sera from Cr-supplemented cows was added to the mononuclear cell cultures, and this was particularly evident around parturition. Conversely, peripartum sera from unsupplemented cows depressed Con A-induced blastogenesis. Except for a marginal rise in blood cortisol 2-4 weeks after parturition, no significant effects of Cr supplementation on other hormones (insulin, growth hormone, insulin-like growth factor I, tumor necrosis factor-alpha) were observed. These observations suggest that factors in peripheral blood serum from Cr-supplemented cows, other than absolute concentrations of the glucose-regulating hormones studied, modulate Con A-induced blastogenesis of mononuclear leukocytes.

Adjuvants, Immunologic↗

PubMed1995

[Transdermal iontophoresis of insulin: effect of penetration enhancers on blood glucose level in diabetic rats].

The effects of many usual penetration enhancers such as azone (AZ), oleic acid (OA), poloxamer 188 (POL 188) and propylene glycol (PG) on the blood glucose level in diabetic rats after transdermal iontophoresis of insulin were studied. The change of blood glucose level (D%), defined as the percent ratio of the concentration of blood glucose in rats after the iontophoretic application of insulin to that before administration of insulin, was used to present the data. The results showed that following iontophoretic application of insulin for 3 h, the D% in diabetic rats treated with 100% AZ and 5% AZ/PG was 38.58% and 25.28% respectively, and the D% in diabetic rats untreated with enhancers was 45.48%. The D% in diabetic rats treated with 100% OA, 10%-OA/PG, 10% POL 188/PG and 100% PG was 66.28%, 60.47%, 76.75% and 57.93% respectively. So, AZ showed a synergistic effect on the ability of iontophoresis to promote skin permeation of insulin, and PG further increased this effect. The combination of AZ, PG and iontophoresis increased the permeation of insulin significantly. OA, POL 188 and PG did not display synergistic effect on iontophoresis enhancement. The combination of iontophoresis and some enhancers provided a novel idea and possibility for the administration of polypeptide drugs.

Administration, Cutaneous↗

PubMed1994

The structure of Fis mutant Pro61Ala illustrates that the kink within the long alpha-helix is not due to the presence of the proline residue.

The influence of proline on bending of the alpha-helix was investigated by replacement of the proline residue located in the middle of the long alpha-helix of the Fis protein with alanine, serine, or leucine. Each of the three substitutions folded into a stable protein with the same or higher melting points than the wild-type, but only Pro61Ala was functionally active in stimulating Hin-mediated DNA inversion. Pro61Ala formed crystals that were isomorphous with the wild-type protein allowing the structure to be determined at 1.9-A resolution by x-ray diffraction methods. The structure of the Pro61Ala mutant is almost identical to the wild-type protein, consistent with its near wild-type activity. One of the alpha-helices, the B-helix, is kinked in the wild-type Fis protein by 20 degrees which was previously assumed to be caused solely by the presence of proline 61 in the center of the helix. However, the B-helix is still kinked by 16 degrees when proline 61 is replaced by alanine. Local peptide backbone movement around residue 57 adjusts the geometry of the helix to accommodate the new main chain hydrogen bond between the -CO group in Glu57 and the -NH group in Ala61. Thus, the kink of the alpha-helix in Pro61Ala does not require the presence of proline.

Alanine↗

PubMed1994

[Inorganic element analysis on different compatibility of sini decoction].

Thirteen kinds of inorganic elements in Sini decoction with different compatibility were analysed by atomic absorption spectrophotometry. The change in quantity and kind of medicines has no obvious effect on each element. But the extraction rate is reduced according to the increase in quantity and herb medicines in the prescription.

Calcium↗

PubMed1994

[Retinoblastoma: cell origin and differentiation].

50 retinoblastoma paraffin blocks were studied immunohistochemically (NSE, GFAP) and histochemically (colloidal-iron, RNA), and 13 cases by EM. The Rb cells demonstrated varying degrees of positive or negative reaction to NSE, most F-W and H-W rosettes being positive and the fleuretes weakly positive or negative. The GFAP positive cells were mainly found in the periphery of the tumor mass and around the blood vessels, and sparsely among the NSE positive cells. Fleuretes were clearly shown by RNA-Brachet staining. F-W rosettes and fleuretes showed similar ultrastructures as the photoreceptor of normal retina. The results confirmed that retinoblastoma originates from the retinoblast with potential of differentiation into photoreceptors and neurons. The glial components pertained to reactive gliosis, however, the rare possibility of forming a small portion of the tumor could not be ruled out.

Eye Neoplasms↗