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Biomedical subjects

Y Han

Publications and source records attributed to Y Han.

At least 289 records · Page 16Linked to original sources
PubMed1994

Potential use of BacT/Alert automated blood culture system for antifungal susceptibility testing.

A simple, rapid susceptibility test is needed to determine the possible resistance of yeasts to commonly used antifungal agents. The BacT/Alert automated blood culture system was evaluated as one technology for development of such a test. Yeast nitrogen base was used as the growth medium, and amphotericin B was the test antifungal agent. Isolates of various Candida species, Torulopsis glabrata, Saccharomyces cerevisiae, and Cryptococcus neoformans were evaluated. The results suggest that detection of amphotericin B resistance of yeast isolates within 12 to 14 h after inoculation of test medium is possible.

Amphotericin B↗
PubMed1994

Ideal amino acid profile for chicks during the first three weeks posthatching.

Two chick bioassays with chemically defined amino acid (AA) diets were conducted to compare three different AA profiles: the NRC 1984 and NRC 1994 requirement profile and the Illinois Ideal Chick Protein (IICP) AA profile. The two battery studies involved chicks during the 2nd and 3rd wk after hatching. In Assay 1, indispensable AA (including glycine and proline) were ratioed to lysine according to requirement ratios present in NRC 1984 and NRC 1994, with digestible lysine set at either deficient (.80% of diet) or superadequate (1.12% of diet) levels for the purified diet in question. All diets were kept isonitrogenous (2.83% N) by varying the level of L-glutamic acid. At .80% lysine, chicks fed the NRC 1994 AA profile gained 60% faster (P < .01) than those fed the NRC 1984 AA profile. With excess digestible lysine (1.12%) and all other indispensable AA increased proportionately, chicks fed NRC 1994 still out-gained those fed NRC 1984 by 13% (P < .05). Ratios of AA (with respect to lysine) in NRC 1994 were equal to or higher than those in IICP, except for histidine. This was due to a lower estimated lysine requirement in NRC 1994 than that used for IICP. When NRC 1994 was compared with IICP in a chick bioassay involving isonitrogenous diets (2.36% N) and digestible lysine set at a deficient level of .90%, weight gain and feed efficiency were similar between diets. This result suggested that most of the indispensable AA in the NRC 1994 AA profile were too high relative to lysine, probably because lysine, the reference AA, was too low relative to the other AA.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1994

Digestible lysine requirement of male and female broiler chicks during the period three to six weeks posthatching.

Experiments were conducted to determine the dietary digestible lysine requirement of male and female broilers (Ross x Ross) during the period 22 to 43 d posthatching. An amino acid-fortified basal diet containing corn, feather meal, and soybean meal as intact protein sources provided .63% total lysine, 20% CP, and 3,200 kcal MEn/kg. The basal diet contained .51% true digestible lysine as determined with a precision-fed cecectomized adult cockerel assay. Growth rate and feed efficiency of birds fed the basal diet fortified with a surfeit level of L-lysine were equal to those of birds fed a methionine-supplemented corn-soybean meal positive control diet (20% CP; 3,200 kcal MEn/kg). Graded levels of synthetic L-lysine (0, .1, .2, .3, .4, .5, .6%) were added to the basal diet to produce growth response curves. Subjecting the growth data to broken-line analysis indicated that the digestible lysine requirement for maximum body weight gain was .85% for males and .78% for females. The requirement for optimum feed efficiency was higher: .89% for males and .85% for female broilers. Breast meat (Pectoralis major) yield increased quadratically in response to lysine addition, and the responses suggested that the lysine requirement for maximal breast yield was not greatly different from that predicted from the feed efficiency data. Abdominal fat (percentage of live body weight) increased from the first to the second increment of lysine, but it then declined as lysine level was increased further.

Adipose Tissue↗
PubMed1994

Limiting order of amino acids in corn and soybean meal for growth of the chick.

Several experiments were conducted with crossbred chicks during the period 8 to 22 d posthatching to establish the limiting order of amino acids (AA) in corn and dehulled soybean meal (SBM) and in a corn-SBM mixture. Cecectomized adult cockerels were used to determine true AA digestibilities in both corn and SBM, and AA fortification levels were based upon bringing digestible AA levels to their ideal levels (expressed as a percentage of CP). Ideal ratios (percentage of lysine) used were Lys, 100; sulfur AA (SAA), 72; Arg, 105; Val, 77; Thr, 67; Trp, 16; Ile, 67; His, 37; Phe+Tyr, 105; and Leu, 111. Diets were fed at 10% CP, but they contained corn or SBM in amounts that would just meet the ideal concentration of the AA in greatest excess (Leu for corn; Phe for SBM). Thus, the corn diets contained only 5.6% CP from corn whereas the SBM diets contained only 8.0% CP from SBM. Diets were adjusted to 10% CP from AA additions, with glutamate varying as necessary. The limiting order of AA in corn was 1) Lys, 2) Thr, 3) Trp, 4) Arg, Ile, and Val, 5) Met+cystine, 6) Phe+Tyr, and 7) His. In SBM, the limiting order was 1)Met+cystine, 2) Thr, 3) Lys and Val, 4) nonspecific amino nitrogen, and 5) His. The order of limiting AA in the corn-SBM mixture was 1) Met, 2) Thr, 3) Lys, 4) Val, 5) Arg, and 6) Trp.

Amino Acids↗
PubMed1994

[The effect of Tripterygium wilfordii monomers T4,T7,T15 and Triptolide on rat nuclear protein].

Rat epididymal sperms were collected after 7 weeks of treatment with Tripterygium wilfordii monomers T4,T7,T15 and triptolide. Total nuclear basic protein (TNBP) were extracted from sperm nuclei isolated by sonication. The relative proportions of histones and protamine were determined by scanning microdensitometry following electrophoresis of TNBP in polyacrylamide gels. It was found that the content of TNBP was reduced while the total histone/protamine ratios were increased following treatment, indicating a marked decrease of protamine levels as compared with the control group. These results suggest that the interruption of nuclear protein transition of spermatids induced by T4,T7,T15 and triptolide might lead to infertility.

Animals↗
PubMed1993

C. elegans lin-45 raf gene participates in let-60 ras-stimulated vulval differentiation.

Vulval differentiation in Caenorhabditis elegans is controlled by intercellular signalling mediated by a receptor tyrosine kinase and a ras gene product. The lin-45 gene encodes a homologue of the raf family of serine/threonine kinases and is necessary for vulval differentiation. The lin-45 raf gene product appears to act downstream of the ras protein in this pathway. A proto-oncogene-mediated signalling pathway may be a common feature of metazoan development.

Amino Acid Sequence↗
PubMed1993

Left ventricular pressure transmission to myocardial lymph vessels is different during systole and diastole.

In six open-thorax-anaesthetized dogs with paced hearts and a retrogradely cannulated epicardial lymph vessel, the sensitivity of myocardial lymph pressure to left ventricular pressure during systole and during diastole was determined. The lymph vessels were cannulated using PE-90 tubing, and lymph pressure was measured by connecting the cannula to a microtip pressure transducer. To obtain the systolic sensitivity, left ventricular pressure was changed by clamping the descending aorta, which caused left ventricular pressure to increase. The diastolic sensitivity was obtained from natural variation to left ventricular pressure caused by atrial contractions during induced long diastoles. The mean ratio of the pulse in lymph pressure to the pulse in left ventricular pressure was determined: systole: 0.069 +/- 0.013, n = 213, diastole: 0.76 +/- 0.16, n = 249 and, if possible, linear regression analysis between lymph and left ventricular pressure was performed. The systolic regression coefficients could be determined in six dogs and the diastolic coefficients in three dogs. During long diastoles lymph pressure variations are on average 76 per cent of those in the left ventricle. However, during systole, the sensitivity of lymph pressure to left ventricular pressure is more than ten times lower. It is not unlikely that the structural embedment of lymph vessels within the myocardium is such that volume variations by cardiac contraction are limited.

Animals↗
PubMed1993

Risk profile for Chlamydia infection in women from public health clinics in New York State.

The prevalence of chlamydial infection and associated risk factors were studied in 1531 women from ten clinics in New York State excluding New York City. Overall Chlamydia infection rates were 13.6%; 17.6% in eight high risk family planning and STD clinics, and 5.7% in two low risk college and private clinics. Risk factors for Chlamydia infection included: age < 20 years (odds ratio 1.6), use of oral contraceptives (odds ratio 2.0), a history of having more than one sexual partner (odds ratio 1.7) and, in one clinic where data was available, inflammation on Papanicolaou smears (odds ratio 2.1). These data helped secure funding for Chlamydia preventive services and permitted development of a risk profile (score card) of Chlamydia for each age group. Use of such a score card can be most helpful in assigning which patients could benefit most from Chlamydia cultures, especially in those areas where testing is unavailable or too costly to screen all patients.

Adolescent↗
PubMed1993

Point-neuron model for binaural interaction in MSO.

A point-neuron model for the activity of individual cells in the medial superior olive (MSO) is described and shown to generate discharge patterns consistent with the activity of real neurons as reported in response to low-frequency sinusoidal stimulation. Inputs to the model cell are specified as primarylike firing patterns, and the cell membrane characteristics are specified in terms of constant-potential sources and time-varying conductances. Some conductances are determined in response to the input firings and some in response to output firing times, which are generated when the membrane potential of the model cell crosses threshold. Output firing patterns generated by the model cells are consistent with those reported from neurons in dog and cat MSO. These patterns are also compatible with those of the functionally specified coincidence model described in Colburn et al. (1990). Given these observations, the following questions are addressed: What parameter values in the point-neuron model are required to generate output patterns like those observed? How do these values compare to those expected or estimated from intracellular measurements in brainstem neurons? How might one reconcile the fact that inhibitory inputs are not necessary in the model for the generation of the observed firing patterns with the fact that MSO cells receive numerous inhibitory inputs?

Acoustic Stimulation↗
PubMed1993

Novel peroxisome clustering mutants and peroxisome biogenesis mutants of Saccharomyces cerevisiae.

The goal of this research is to identify and characterize the protein machinery that functions in the intracellular translocation and assembly of peroxisomal proteins in Saccharomyces cerevisiae. Several genes encoding proteins that are essential for this process have been identified previously by Kunau and collaborators, but the mutant collection was incomplete. We have devised a positive selection procedure that identifies new mutants lacking peroxisomes or peroxisomal function. Immunofluorescence procedures for yeast were simplified so that these mutants could be rapidly and efficiently screened for those in which peroxisome biogenesis is impaired. With these tools, we have identified four complementation groups of peroxisome biogenesis mutants, and one group that appears to express reduced amounts of peroxisomal proteins. Two of our mutants lack recognizable peroxisomes, although they might contain peroxisomal membrane ghosts like those found in Zellweger syndrome. Two are selectively defective in packaging peroxisomal proteins and moreover show striking intracellular clustering of the peroxisomes. The distribution of mutants among complementation groups implies that the collection of peroxisome biogenesis mutants is still incomplete. With the procedures described, it should prove straightforward to isolate mutants from additional complementation groups.

Acetyl-CoA C-Acetyltransferase↗
PubMed1993

Bioavailable level and source of cysteine determine protein quality of a commercial enteral product: adequacy of tryptophan but deficiency of cysteine for rats fed an enteral product prepared fresh or stored beyond shelf life.

Young rats were used in bioassays designed to assess the protein quality and tryptophan as well as cystine adequacy of the enteral product TwoCal-HN that was either freshly prepared or had been stored (nonrefrigerated) in a warehouse for 10 mo (i.e., beyond shelf life). Based upon supplementation studies, cystine was observed to be the first-limiting amino acid in both fresh and expired TwoCal-HN, and tryptophan was not second limiting. Protein efficiency ratio (PER) of expired, but not fresh, TwoCal-HN was lower than that of the casein control diet, but with cystine supplementation, PER of the TwoCal-HN products was equal to or greater than the PER of the casein control. With a diet containing 10 g protein/100 g that also contained energy-furnishing ingredients simulating TwoCal-HN, maximal growth enhancement occurred with a supplement of 1 g cystine/kg diet. Both glutathione and N-acetyl-L-cysteine were observed to be equivalent to an isomolar level of L-cystine in stimulating growth. Using a chemically defined amino acid diet that was singly deficient in tryptophan, bioavailability of tryptophan was determined for casein, fresh TwoCal-HN, expired TwoCal-HN and D-tryptophan. Slope-ratio bioefficacy values relative to L-tryptophan (weight gain regressed on supplemental tryptophan intake) indicated that none of the experimental sources of tryptophan had bioavailabilities different from 100%. The results indicated that tryptophan did not deteriorate, as measured analytically or biologically, as a result of storing TwoCal-HN beyond shelf life.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Evidence that mannans of Candida albicans are responsible for adherence of yeast forms to spleen and lymph node tissue.

We have described a unique binding system between Candida albicans yeast-form cells and the marginal zone of mouse spleen (16). The chemical nature of the fungal adhesin(s) involved in this binding phenomenon was examined. A fraction obtained by 2-mercaptoethanol extraction (2-ME extract) of fungal cells caused a dose-response inhibition of yeast cell adherence to splenic marginal zone sites and also to subcapsular and medullary sinuses of mouse popliteal lymph nodes. Latex beads coated with the 2-ME extract showed a pattern of spleen and lymph node tissue binding identical to that observed with yeast cells. The extracted adhesins retained their binding activity in vivo. When 0.5 mg of the 2-ME extract was given intravenously to mice, spleen tissue removed up to 3 h later showed over 80% inhibition of yeast cell binding to the spleen marginal zone, and over 50% inhibition was retained for at least 24 h. The adhesins bound to a concanavalin A affinity column and were eluted by 0.5 M alpha-methyl-D-mannopyranoside, and the eluted adhesins were designated Fr.II. Fr.II was further fractioned by DEAE-Sephacel ion-exchange column chromatography, and one especially active and abundant fraction was designated Fr.IIa. The adhesin moiety appeared to be carbohydrate, because the activity of Fr.IIa was destroyed by 20 mM sodium periodate or by 5 U of alpha-mannosidase, but boiling (30 min) or proteinase K (100 micrograms/ml) treatments had no effect. Chemically, whereas the 2-ME extract contained significant amounts of protein and mannose, Fr.IIa consisted of over 98% mannose and less than 0.5% protein. These data strongly suggest that the mannan portion within a mannoprotein is responsible for the binding of yeast cells to splenic marginal zone and to subcapsular and medullary sinuses of mouse lymph node tissue.

Animals↗
PubMed1993

Binding of Candida albicans yeast cells to mouse popliteal lymph node tissue is mediated by macrophages.

We previously reported that Candida albicans yeast cells adhere to the macrophage-rich medullary and subcapsular sinus areas of mouse lymph node tissue. To determine whether the yeast cell-lymph node interaction is mediated by macrophages, the effect of specific elimination of macrophages on yeast cell binding was studied, and yeast cell adherence was correlated with the ingestion of India ink by lymph node cells. Macrophage elimination was done by use of liposome-containing dichloromethylene diphosphonate (L-Cl2MDP). Mice were injected in the hind footpads with the L-Cl2MDP preparation, popliteal lymph nodes were removed 5 days later, and yeast cell adherence was determined by an ex vivo binding assay. As controls, lymph nodes from mice that received footpad injections of either phosphate-buffered saline (PBS) alone or liposome-containing PBS were used. Use of macrophage- and neutrophil-specific monoclonal antibodies in tissue immunostaining showed that the L-Cl2MDP treatment eliminated macrophages but not neutrophils from the medullary and subcapsular sinus areas of the popliteal lymph nodes. A striking reduction of yeast cell adherence occurred with lymph nodes from L-Cl2MDP-treated mice compared with lymph nodes from control animals. The lymph node-yeast cell binding patterns of L-Cl2MDP-treated and control mice were the same regardless of mouse strain, sex, or T-cell competency. Results of India ink experiments, in which India ink was injected into footpads of mice and was rapidly taken up by popliteal lymph node macrophages, showed a strong correlation between yeast adherence and India ink staining of cells. In addition, the interaction of yeast cells with lymph node tissue from normal mice was not significantly affected by the addition of two extracellular matrix proteins, fibronectin and laminin, during the ex vivo adherence assay. These data indicate that medullary and subcapsular sinus lymph node macrophages express an adhesion system similar to that described for mouse splenic marginal zone macrophages.

Animals↗
PubMed1993

Stopped-flow epicardial lymph pressure is affected by left ventricular pressure in anesthetized goats.

We measured epicardial lymph pressure (Plymph) in the anesthetized goat (n = 5 goats). To study the transmission of systolic left ventricular pressure (PLV) to Plymph, the effect of an increase in PLV caused by clamping of the descending aorta on Plymph was evaluated. Peak systolic PLV was 131 +/- 4 (+/- SE) mmHg during control (43 beats) and 188 +/- 4 mmHg when elevated due to aortic clamping (157 beats). Peak systolic Plymph was 24.8 +/- 1.0 and 34.8 +/- 1.1 mmHg during control and elevated PLV, respectively. In the first beat of elevated PLV, peak Plymph did not change, although the pressure waveform did. In the subsequent beats, Plymph increased proportionally with increased PLV. When PLV was decreased back to control, Plymph also decreased but did not reach control level until after three beats. The relationship between normalized Plymph and normalized PLV is given by Plymph = 0.70 x PLV + 0.09. The results show that PLV does affect Plymph in a normal beating heart.

Animals↗
PubMed1993

Fructose-1,6-bisphosphate reduces infarct volume after reversible middle cerebral artery occlusion in rats.

BACKGROUND AND PURPOSE: We tested the hypothesis that fructose-1,6-bisphosphate, when administered 10 minutes before the end of 2 hours of reversible middle cerebral artery occlusion, reduces ischemia-reperfusion injury and infarct volume measured after a 3-day survival period in rats. METHODS: After 1 hour and 50 minutes of middle cerebral artery occlusion by the intraluminal suture method, fructose-1,6-bisphosphate, 500 mg/kg in group 1 and 350 mg/kg in group 2 (or an equivalent volume of 1.8% saline as placebo in each group), was given intravenously for a period of 15 minutes to fasted adult Sprague-Dawley rats. After 2 hours of ischemia, the suture was withdrawn and the rats allowed to survive for 3 days. The areas of infarction in 10 hematoxylin-eosin-stained coronal sections of the brain were measured and used to calculate infarct volume. RESULTS: In group 1, fructose-1,6-bisphosphate decreased total cerebral hemispheric infarct volume by 43% (from 199.6 +/- 11.2 to 114.2 +/- 35.8 mm3, P < .04; mean +/- SEM). Cerebral cortical and subcortical infarct volumes were decreased by 46% (from 137.3 +/- 7.5 to 74.1 +/- 28.6 mm3, P < .04) and 36% (from 62.3 +/- 5.1 to 40.0 +/- 8.3 mm3, P < .04), respectively. In group 2, fructose-1,6-bisphosphate had no effect on infarct volume in rats that developed mild intraischemic hyperthermia, but in rats kept normothermic during ischemia, fructose-1,6-bisphosphate reduced subcortical infarct volume from 53.7 +/- 8.1 to 18.4 +/- 8.0 mm3 (P < .03). CONCLUSIONS: Fructose-1,6-bisphosphate improves functional neurological outcome and reduces infarct volume after reversible middle cerebral artery occlusion in rats.

Animals↗
PubMed1993

Bioavailability of zinc in ground beef.

Based on zinc uptake in chick tibia, Zn bioavailability in cooked ground beef was equal to that of Zn in an inorganic standard (ZnSO4), whether Zn supplements were added to a soy-concentrate diet containing phytate or to a phytate-free egg-white diet. With both diet types, total tibia Zn was a linear (P < .01) function of supplemental Zn intake from ZnSO4, but the slope of the linear regression line was twice as great for the egg-white diet as for the soy-concentrate diet that contained phytate. At 10 mg/kg of supplemental Zn, freeze-dried ground beef produced the same tibia Zn concentration (and total Zn content) as that obtained with ZnSO4. The results suggest that the relative bioavailability of Zn in cooked ground beef is as great as that in ZnSO4, whether consumed in diets with or in those without phytate.

Animals↗
PubMed1993

Tryptophan requirement of pigs in the weight category 10 to 20 kilograms.

Experiments were conducted to determine the tryptophan (Trp) requirement of 10- to 20-kg pigs. A Trp-deficient experimental diet (.11% total Trp, 18% CP, 3,320 kcal of ME/kg) was composed of corn, feather meal, corn gluten meal, soybean meal, and dried whey. True digestibility of Trp in the experimental diet was 70% (.077% digestible Trp) as established in a digestibility assay that involved cecectomized, adult cockerels (Exp. 1). An initial pig study (Exp. 2) verified that the experimental basal diet, when fortified with sufficient L-Trp, was capable of producing growth rate and feed efficiency similar to that of pigs fed a conventional corn-soybean meal-dried whey diet (18% CP, 3,320 kcal of ME/kg). In Exp. 3, crossbred pigs with an average BW of 10.9 kg were fed the Trp-deficient basal diet supplemented with 0, .015, .030, .045, .060, and .075% L-Trp. In Exp. 4, crossbred pigs that averaged 9.5 kg were fed the basal diet fortified with .030, .045, .060, and .075% L-Trp. By examining the data from Exp. 3 and 4 together, the digestible Trp requirement for maximum daily weight gain was estimated to be .14% of the diet. Assuming an 88% true digestibility of Trp in commercial diets based on corn and soybean meal (calculated from published data), the total Trp required in practice would be .16% (.89% of the dietary protein).

Animal Feed↗