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Biomedical subjects

B Park

Publications and source records attributed to B Park.

At least 37 records · Page 2Linked to original sources
PubMed1998

Diabetes-induced impairment of macrophage cytokine release in a rat model: potential role of serum lipids.

Diabetes (type I and type II) affects approximately 13 million people in the United States. Delayed and incomplete healing of wounds can be a major problem for diabetic patients. Macrophages are an important cell in the complex process of wound repair representing the major source of cytokines throughout the wound healing process. Cytokines mediate many of the cellular responses critical to timely wound repair. It has been suggested that diabetes impairs wound healing through disruption of local cytokine production. We previously demonstrated that platelet-derived growth factor B chain (PDGF-B) levels are deficient at the wound site of diabetic rats. In the present study, we measured the levels of several marker cytokines released from cultured peritoneal macrophages of diabetic, nondiabetic hyperlipidemic, and normal rats. The diabetic condition was associated with a generalized reduction of macrophage cytokine release. Nondiabetic hyperlipidemic animals demonstrated similar cytokine reduction supporting the hypothesis that elevated serum lipids are the primary determinants of diabetes-induced reductions in macrophage cytokine release. Thus, manipulation of serum lipids may be a therapeutically useful modality for controlling macrophage cytokine release in the inflammatory and/or wound environment.

Animals↗
PubMed1998

Near-infrared reflectance analysis for predicting beef longissimus tenderness.

Near-infrared reflectance spectra (1,100 to 2,498 nm) were collected on beef longissimus thoracis steaks for the purpose of establishing the feasibility of predicting meat tenderness by spectroscopy. Partial least squares (PLS) analysis (up to 20 factors) and multiple linear regression (MLR) were used to predict cooked longissimus Warner-Bratzler shear (WBS) force values from spectra of steaks from 119 beef carcasses. Modeling used the combination of log(1/R) and its second derivative. Overall, absorption was higher for extremely tough steaks than for tender steaks. This was particularly true at wavelengths between 1,100 and 1,350 nm. For PLS regression, optimal model conditions (R2 = .67; SEC = 1.2 kg) occurred with six PLS factors. When the PLS model was tested against the validation subset, similar performance was obtained (R2 = .63; SEP = 1.3 kg) and bias was small (<.3 kg). Among the 39 samples in the validation data set, 48.7, 87.7, and 97.4% of the samples were predicted within 1.0, 2.0, and 3.0 kg, respectively, of the observed Warner-Bratzler shear force value. The optimal PLS model was able to predict whether a steak would have a Warner-Bratzler shear force value < 6 kg with 75% accuracy. The R2 of MLR model was .67, and 89% of samples were correctly classified (< 6 vs > 6 kg) for Warner-Bratzler shear force. These data indicate that NIR is capable of predicting Warner-Bratzler shear force values of longissimus steaks. Refinement of this technique may allow nondestructive measurement of beef longissimus at the processing plant level.

Animals↗
PubMed1997

Intensive care for people with serious mental illness.

This article describes the development of a psychiatric 'intensive care' service for men and women with serious or enduring forms of psychotic disorder. The authors suggest that such a residential therapeutic service may be an essential part of the development of community care for the most vulnerable people served by mental health services.

Critical Care↗
PubMed1997

Evidence for racial prejudice at the implicit level and its relationship with questionnaire measures.

The content of spontaneously activated racial stereotypes among White Americans and the relation of this to more explicit measures of stereotyping and prejudice were investigated. Using a semantic priming paradigm, a prime was presented outside of conscious awareness (BLACK or WHITE), followed by a target stimulus requiring a word-nonword decision. The target stimuli included attributes that varied in valence and stereotypicality for Whites and African Americans. Results showed reliable stereotyping and prejudice effects: Black primes resulted in substantially stronger facilitation to negative than positive stereotypic attributes, whereas White primes facilitated positive more than negative stereotypic traits. The magnitude of this implicit prejudice effect correlated reliably with participants' scores on explicit racial attitude measures, indicating that people's spontaneous stereotypic associations are consistent with their more controlled responses.

Adult↗
PubMed1997

Longitudinal changes in consensus as a function of acquaintance and agreement in liking.

By using a round-robin design, groups of freshmen reported their impressions of dormmates at 4 different times during the year. Consensus on W. T. Norman's Big Five (1963) did not increase over the year, even though reported acquaintance did increase. Agreement in liking predicted agreement in the trait ratings, such that groups that agreed in their evaluations of one another were more likely to agree in their trait impressions of one another, and vice versa. These patterns, obtained by using trait ratings, were replicated with open-ended descriptions of the targets. Correlations with self-judgments did not increase with acquaintance. The data suggest that increased acquaintance does not produce increased consensus. Instead, the role of agreement in evaluations is explored as a determining factor in the level of obtained consensus.

Cross-Sectional Studies↗
PubMed1996

Energy functions that discriminate X-ray and near native folds from well-constructed decoys.

This study generates ensembles of decoy or test structures for eight small proteins with a variety of different folds. Between 35,000 and 200,000 decoys were generated for each protein using our four-state off-lattice model together with a novel relaxation method. These give compact self-avoiding conformations each constrained to have native secondary structure. Ensembles of these decoy conformations were used to test the ability of several types of empirical contact, surface area and distance-dependent energy functions to distinguish between correct and incorrect conformations. These tests have shown that none of the functions is able to distinguish consistently either the X-ray conformation or the near-native conformations from others which are incorrect. Certain combinations of two of these energy functions were able, however, consistently to identify X-ray structures from amongst the decoy conformations. These same combinations are better also at identifying near-native conformations, consistently finding them with a hundred-fold higher frequency than chance. The fact that these combination energy functions perform better than generally accepted energy functions suggests their future use in folding simulations and perhaps threading predictions.

Crystallography, X-Ray↗
PubMed1996

Enhanced surface hardness by boron implantation in Nitinol alloy.

Boron implantation into Nitinol alloy has a potential for developing improved Nitinol root canal instruments with excellent cutting properties, without affecting their superelastic bulk-mechanical properties. The surface hardness of nickel-titanium (NiTi) alloy, also known as "Nitinol" (50 atm% nickel+50 atm% titanium), has been improved by ion-beam surface modification. With an implantation dose of 4.8 x 10(17) boron/cm2, a high concentration of boron (30 atm%) is incorporated into NiTi alloy by 110 keV boron ions at room temperature (25 degrees C). Boron-implanted and unimplanted (pure) Nitinol alloys show surface hardness of 7.6 +/- 0.2 and 3.2 +/- 0.2 GPa, respectively, at the nanoindentation depth of 0.05 micron. The ion-beam-modified NiTi alloy exceeds the surface hardness of stainless steel.

Boron↗
PubMed1996

Cyclosporine A upregulates platelet-derived growth factor B chain in hyperplastic human gingiva.

Cyclosporine A (CSA) is a widely used immunosuppressant for transplant patients and is also used for the treatment of a wide variety of systemic diseases with immunologic components. A prominent side effect of CSA administration is gingival overgrowth (hyperplasia). It has been postulated that CSA alters fibroblast activity through effects on various growth factors/cytokines. However, as yet, data concerning the molecular mechanisms involved in pathologic connective tissue proliferation are preliminary in nature. Our previous investigations concerning phenytoin-induced effects on platelet-derived growth factor B (PDGF-B) gene expression have demonstrated that other drugs which cause gingival overgrowth can upregulate macrophage PDGF-B gene expression in vitro and in vivo. The purpose of the present study was to evaluate PDGF-B gene expression in gingival tissues of patients receiving CSA therapy and exhibiting gingival overgrowth to determine if similar PDGF-B upregulation occurs in response to CSA and to identify PDGF-B producing cells in these tissues. Quantitative competitive reverse transcription polymerase chain reaction (QC-RTPCR) techniques were utilized to measure PDGF-B mRNA levels in CSA overgrowth patients and normal controls (N = 6/group). Results were expressed as mean +/- mRNA copy number and tested for significance using unpaired t-tests. Gingival samples were harvested (standardized for local inflammation at the sample site), total RNA was extracted, and QC-RTPCR was performed using specific PDGF-B primers and a corresponding competitive internal standard. CSA-treated patients exhibiting gingival overgrowth demonstrated approximately 48-fold increase in PDGF-B mRNA (7667.1 +/- 477.4 copies for CSA patients vs. 158.2 +/- 37.1 copies for controls; P < 0.001). Additionally, dual fluorescence immunohistochemistry for mature macrophage marker antigen (CD51) and intracellular PDGF-B was utilized to identify and localize PDGF-B producing cells were demonstrated to be macrophages distributed in a non-uniform manner throughout the papillary connective tissue. These results further support the hypothesis that the molecular mechanisms responsible for drug-induced gingival overgrowth may involve upregulation of PDGF-B macrophage gene expression. We continue to investigated specific CSA-induced alterations of macrophage PDGF-B gene expression in vitro and in vivo.

Adult↗
PubMed1995

Stereotypes and ethnocentrism: diverging interethnic perceptions of African American and white American youth.

Much recent work on stereotyping has dealt with groups that are either artificially created or that do not have an extensive history of conflict. The authors attempted to overcome this limitation by examining issues of perceived variability and ethnocentrism among samples of White American and African American youth. The goals were both to examine theoretical issues in stereotyping and to describe the current state of ethnic interrelations among young people. Four studies are reported. Throughout, the samples of African Americans demonstrate interethnic judgments that are consistent with existing work on stereotyping and ethnocentrism. White American students, however, reported judgements that replicate neither the out-group homogeneity effect nor ethnocentrism. Alternative explanations for this difference are considered, and the discussion focuses on differing views concerning the role of ethnic identity and diversity in our society.

Adolescent↗
PubMed1995

Subtyping versus subgrouping processes in stereotype representation.

Participants were instructed to organize information about group members either by distinguishing stereotype-consistent from stereotype-inconsistent individuals (subtyping instructions), by dividing the individuals into multiple groups on the basis of similarities and differences (subgrouping instructions), or with no explicit organizing instructions. Participants given the subtyping instructions showed greater perceived stereotypicality and homogeneity and perceived a greater difference in how typical the confirming versus disconfirming group members were, relative to subgroup participants. Study 2 demonstrated natural variation among participants in the perceived atypicality of the disconfirming relative to confirming individuals when learning about a gay activist group. Atypicality predicted perceptions of this group, even when prejudice and strength of stereotyping toward gays as a whole were statistically controlled.

Female↗
PubMed1995

Evaluation of in vitro cytotoxicity of nonsteroidal anti-inflammatory drugs against canine tumor cells.

Piroxicam and other nonsteroidal anti-inflammatory drugs (NSAID) have antitumor activity against naturally acquired cancer in dogs and human beings, and against experimentally induced tumors in rodents. We are investigating potential mechanisms of NSAID antitumor activity. The direct cytotoxicity of piroxicam indomethacin, and aspirin against 4 canine tumor cell lines (transitional cell carcinoma, squamous cell carcinoma, melanoma, and soft tissue sarcoma) was determined in short-term growth rate assays and in clonogenic assays. Piroxicam was evaluated alone and in combination with the lipoxygenase inhibitor zileuton, and in combination with the chemotherapeutic agents cisplatin and carboplatin. The 50% inhibitory concentrations (IC50) against melanoma cells in short-term growth rate assays were: 530 microM piroxicam, 180 microM indomethacin, and greater than 1 mM aspirin. These IC50 values were over 10 times greater than serum concentrations of these drugs that could safely be achieved in vivo. The IC50 of zileuton combined with piroxicam (280 microM) was not different from the IC50 of zileuton alone (230 microM; ANOVA P = 0.47) in melanoma cells. Similarly, addition of piroxicam did not alter the IC50 of either cisplatin (1.6 microM) or carboplatin (6.1 microM). These results suggest that NSAID, at serum concentrations achievable in vivo, do not have direct cytotoxicity against canine tumor cells tested. It is unlikely that the in vivo antitumor activity of NSAID is attributable to a direct cytotoxic effect.

Animals↗
PubMed1994

Aggregating social behavior into person models: perceiver-induced consistency.

Two experiments explored the role of perceivers (judges) in aggregating social behavior into impressions. In Experiment 1, it was predicted and found that judges influence impressions (i.e., eye-of-the-beholder effects) not only because they disagree on how to interpret single acts but because they aggregate multiple acts in unique ways to arrive at idiosyncratic impressions. Using D. A. Kenny's (1991) general model of accuracy and consensus, it was found that judges perceived much greater consistency in the behavior of targets across situations when they were asked to aggregate the behavior than when they were not. Differential interpretation of single acts did not change as a function of aggregating behavior. This aggregation process was characterized as the construction of models of persons. In Experiment 2, the concept of person models was explored further, and it was argued that perceivers develop these models on the basis of what is viewed as the central concept of a target. For any given target, a limited number of models can be identified, and different perceivers develop different models. The particular model formed has implications for the perceiver's underlying memory representation and the perceived personality profile of the target.

Adult↗
PubMed1994

Low-density lipoprotein receptors in rat adipocytes: regulation with fasting.

Adipose tissue metabolism is exquisitely sensitive to caloric intake. With increasing adiposity more triglyceride and cholesterol are stored within increasingly large adipocytes, whereas less triglyceride and cholesterol are stored as the size of the fat cell decreases. A portion of the uptake of cholesterol by adipocytes is mediated by low-density lipoprotein (LDL) receptors. The present studies addressed whether LDL receptors are differentially regulated in adipose tissue and the liver during fasting in the rat. Two days of fasting caused a reduction in body weight with an approximately 40% decrease in the epididymal fat depot and fat cell size. No changes in serum cholesterol were noted, but serum triglycerides fell approximately 55% with fasting. LDL receptors detected by immunoblotting decreased progressively with fasting to levels that were 95% below controls in adipocytes isolated from epididymal fat pads by 2-3 days. In contrast, hepatic LDL receptor expression was unaltered by fasting. After 2 days of fasting, the rate of synthesis of LDL receptors in isolated adipose cells was decreased approximately 35%, whereas levels of LDL receptor mRNA were diminished approximately 55%. It is concluded that the expression of LDL receptors in rat adipocytes is markedly downregulated during fasting through transcriptional and posttranscriptional mechanisms. Furthermore, LDL receptor expression is differentially regulated in adipose tissue and liver during fasting in the rat.

Adipocytes↗
PubMed1994

Predicting intramuscular fat in beef longissimus muscle from speed of sound.

The ultrasonic A-mode method was investigated for intramuscular fat measurement of beef. Cubes of meat samples that had different marbling scores were used as specimens. Ultrasonic speed decreased with increasing fat concentration. The correlation coefficient was -.82 (P < .05). Conversely, the correlation coefficient between visual marbling score and fat concentration was .70 (P < .05). Quantitatively, from the first derivative of a nonlinear function, it was concluded that the speed decreased at a rate of 2.69 m/(s-% fat) as a function of intramuscular fat. A nonlinear regression model to predict intramuscular fat content in beef was developed as follows: percentage of fat concentration = 7132.1574-9.1222 x (speed) + 2.91803 x 10(-3) x (speed)2 (R2 = .81). The nonlinear model was capable of predicting intramuscular fat concentration with 90% accuracy (> 8% fat) and 76.4% accuracy (< 8% fat), respectively (P < .001).

Adipose Tissue↗
PubMed1994

Measuring intramuscular fat in beef with ultrasonic frequency analysis.

Frequency analysis of Fourier spectra from ultrasonic signals was used for predicting intramuscular fat content of beef tissue. The most significant parameter in the frequency domain for predicting intramuscular fat concentration in beef was the number of local maxima. It represents the discontinuity of the Fourier spectrum caused by inhomogeneous fat concentrations in the longissimus muscle, which had the correlation coefficient .89 (P < .05) when a 2.25-MHz shear probe was used. The optimum frequency for predicting the amount of intramuscular fat content in the longissimus muscle was found to be 1.92 MHz. A multivariate regression model was developed using parameters in the frequency domain as follows: percentage of fat concentration = 1.790 - 2.373x (lower frequency) + .049x (bandwidth) + 1.178x (local maxima) (R2 = .82). Validation demonstrated that the multivariate model in the frequency domain was capable of predicting intramuscular fat concentration with an average of 1.17 percentage of fat error (P < .05). The multivariate model was most appropriate for predicting intramuscular fat below 4%. The mean accuracy of the model in the frequency domain was approximately 79%.

Adipose Tissue↗