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T J Richards

Publications and source records attributed to T J Richards.

13 recordsLinked to original sources
PubMed2001

Measurement of NK activity by the microcytotoxicity assay (MCA): a new application for an old assay.

Natural killer (NK) cells are spontaneously cytotoxic immune effector cells with the ability to selectively destroy tumor cells without harming normal cells. To perform this function, NK cells utilize two main cytotoxicity pathways, the well known perforin/granzyme-mediated secretory/necrotic killing and the recently defined TNF family ligand-mediated non-secretory/apoptotic killing. The former mechanism is manifested mainly against a few cultured leukemia cell targets, while the latter mediates killing against a large variety of tumor cell targets. Therefore, the biological role and significance of these mechanisms might be different. The NK cell-mediated necrotic killing has been reliably and selectively measured in humans by the standard 4-h 51Cr release assay (CRA) against K562 myeloid leukemia cell targets. However, no standardized high throughput assay is available for testing the NK cell-mediated apoptotic killing. Here, we introduce the modified MCA as a convenient method for measuring perforin/granzyme-independent NK cell-mediated apoptotic killing. The assay is performed in microwells of Terasaki tissue culture microtest plates, using adherent tumor cell targets, which are selectively susceptible to non-secretory/apoptotic killing and resistant to secretory/necrotic killing mediated by NK cells. Target cells are plated in microwells and incubated overnight to adhere to the plastic surface and to regenerate cell surface-bound TNF family receptors. Following this adherence, target cells are co-incubated with freshly isolated human peripheral blood mononuclear leukocytes (PBMNL) or purified subpopulations of immune cells for 24 h in various effector/target (E/T) ratios. During this incubation, dead target cells become non-adherent and are removed by washing the wells. Remaining adherent (viable) target cells are fixed, stained and optically counted. A notable dose-dependent (peak at 200:1 E/T ratio), time-dependent (peak at 24 h of incubation) and donor-dependent killing of tumor cells was consistently and reproducibly induced by PBMNL of normal donors. Using purified subpopulations of immune cells, it was demonstrated that among PBMNL, CD3(-)CD56(+)CD16(+) mature NK cells are the only mediators of tumor cell killing in MCA, as well as in CRA. Comparative studies of NK activity detected by MCA and CRA, performed with PBMNL from normal individuals and breast cancer patients, showed no significant correlation between the cytotoxicities measured in the two assays. In addition, while NK activity measured in CRA was normal in most breast cancer patients, NK activity assessed in MCA was decreased in a large majority of the patients. Thus, MCA is a sensitive NK assay, which is biologically different from CRA, and may be clinically relevant. MCA has also a higher throughput, and is more practical and economical than CRA.

Apoptosis↗
PubMed1996

Progression from a smoking lapse to relapse: prediction from abstinence violation effects, nicotine dependence, and lapse characteristics.

Determinants of progression from an initial smoking lapse to relapse, using prospective data from 133 participants were examined. Participants used palm-top computers to record their first lapse, and their reaction to it, within minutes of the event, and were followed for 3 months to assess subsequent smoking. Indicators of the Abstinence Violation Effect--self-efficacy, attributions, and affective reactions to the lapse--generally failed to predict progression to relapse, but participants who felt like giving up after the first lapse progressed more rapidly to a second lapse. Participants who attempted restorative coping were less likely to progress to another lapse on the same day. Those whose lapses were triggered by stress progressed more quickly, whereas those triggered by eating and drinking or accompanied by alcohol consumption progressed more slowly. More nicotine-dependent participants progressed more rapidly toward relapse, but neither the amount smoked in the first lapse nor its subjective reinforcement predicted progression.

Adult↗
PubMed1996

Temptations to smoke after quitting: a comparison of lapsers and maintainers.

This study addresses whether characteristics of temptations to smoke differ for participants who quit smoking and maintain abstinence compared to those who quit and then lapse. Participants used hand-held computers to record temptations and were beeped at random for base-rate assessments. We used generalized estimating equations to compare 1,851 temptation episodes and 5,192 random assessments recorded by 151 participants (116 lapsers, 35 maintainers) over 1-23 days of abstinence. Compared to randomly sampled occasions, temptations were marked by greater negative affect, restlessness, attention disturbance, and exposure to smoking cues; participants were also more likely to be eating or drinking during temptations. Temptations reported by lapsers and maintainers did not differ in any respect, including their reported coping. The results highlight situational variance over individual differences.

Adaptation, Psychological↗
PubMed1996

Molecular analysis of melanoma precursor lesions.

Atypical (dysplastic) nevi are melanocytic lesions, which are precursors of melanoma as well as markers of increased melanoma risk. Although these lesions exhibit distinct clinical and histological features, their molecular features are largely unknown. To determine whether atypical, compared to benign nevi, from patients with a clinical history of malignant melanoma reveal molecular changes, we analyzed these lesions for the expression of two growth factors (basic fibroblast growth factor and transforming growth factor alpha), their receptors (fibroblast growth factor receptor-1 and epidermal growth factor receptor), and two cell adhesion molecules (MUC18 and alpha v beta 3 integrin), all of which are expressed in primary and metastatic melanomas. The results demonstrated a statistically significant correlation (P = 0.02) between increasing degrees of histological atypia and expression of epidermal growth factor receptor in the epidermal keratinocytes of atypical melanocytic lesions. Furthermore, both atypical and benign nevi revealed considerably high levels of overall gene activity in their dermal melanocytic and epidermal keratinocytic compartments. In contrast, the epidermal-dermal junction wherein melanoma evolves showed little gene activity, suggesting that molecular events occurring adjacent to this junction may be important for melanocytic transformation.

Antigens, CD↗
PubMed1994

Accuracy of end-tidal and transcutaneous PCO2 monitoring during sleep.

STUDY OBJECTIVE: Although it is intuitively desirable, the measurement of arterial carbon dioxide tension (PaCO2) during diagnostic polysomnography and nocturnal trials of positive pressure therapy is invasive and potentially expensive. The accuracy of end-tidal carbon dioxide tension (PETCO2) and transcutaneous carbon dioxide (tcPCO2) monitoring in these contexts has not been systematically evaluated. This investigation was undertaken to evaluate the accuracy of PETCO2 and tcPCO2 in patients undergoing polysomnography. METHODS AND PROCEDURES: Values of PETCO2 were compared with PaCO2 in 19 patients spontaneously breathing room air (condition 1), in 13 patients receiving supplemental oxygen via nasal cannula (condition 2), and in 22 patients receiving nocturnal positive pressure ventilatory assistance (all but one with continuous positive airway pressure or bilevel positive airway pressure) (condition 3). The accuracy of tcPCO2 monitoring during sleep was also examined by comparing tcPCO2 values with simultaneously recorded PaCO2 values obtained during sleep in patients undergoing nocturnal polysomnography. Data were collected using three commercially available brands of tcPCO2 monitors (capnograph R, n = 17 patients; capnograph S, n = 17; and capnograph N, n = 15). RESULTS: Accuracy of PETCO2--There was significant scatter in the PaCO2 vs PETCO2 relationship such that only 23 percent of the variability in PaCO2 was explained by variation of PETCO2 during condition 1 and only 15 percent and 20 percent of the variability in PaCO2 was explained by variation of PETCO2 during conditions 2 and 3, respectively. 21.3 percent of patients had average PETCO2 values in error by > 10 mm Hg during condition 1, while during conditions 2 and 3, 46.2 and 63.7 percent of patients had average values in error by > 10 mm Hg, respectively. Accuracy of tcPCO2--While capnographs S and N generally overestimated PaCO2 with a wide scatter, capnograph R tended to have offsetting overestimations and underestimations of PaCO2 with a wide scatter. With each capnograph, a relatively small portion of the variability of the PaCO2 was explained by variability of the tcPCO2 (r2 = 0.2, 0.45 and 0.64 for capnographs S, N, and R, respectively). Across the three capnographs, 43.1 to 66.7 percent of measurements were in error by > 10 mm Hg, and 5 to 20 percent of measurements reflected errors > 20 mm Hg. There was no consistent relationship between the tcPCO2 error and the level of PaCO2, nor was the tcPCO2 error consistent in individual patients. There was no relationship between tcPCO2 accuracy and body mass index. CONCLUSION: Neither PETCO2, measured within a face mask, nor tcPCO2 is a consistently accurate reflection of PaCO2. This limits the utility of these variables in monitoring patients during diagnostic and therapeutic sleep studies, and in particular, during trials of nocturnal ventilatory assistance where adequate levels of support are to be established and unacceptable hyperventilation and respiratory alkalosis must be recognized.

Adult↗
PubMed1992

Lactation curve estimation for use in economic optimization models in the dairy industry.

Monthly data on completed lactations were employed to estimate a three-stage least squares lactation curve model for milk production, milk fat content, milk protein content, and body weight change in lactating Holstein cattle. In comparison with previous work on the lactation curve, our study employed an augmented incomplete gamma model of the lactation curve, a simultaneous rather than single equation estimation technique, monthly rather than daily or weekly observations, and a pragmatic treatment of the genetic background of individual cows using sire proof data. In addition to considering genetic and dietary effects on the lactation curve, the model isolates the seasonal effect of calving date and current production month as well as the age of the cow. By allowing for the simultaneous explanation of various measures of cow performance, the model accommodates formulation of diets tailored for individual cows or groups of cows and can be used in profit-maximizing mathematical programming models. Diet, production, and body weight changes are determined simultaneously and are not independent of one another.

Aging↗
PubMed1991

Preparation and characterization of monoclonal antibodies against soybean seed lipoxygenase isoenzymes.

Sets of monoclonal antibodies have been prepared using two soybean seed lipoxygenase isoenzymes as the antigens. The antibodies were characterized by ELISA, Western blot analysis, immunoprecipitation, and in kinetic assays. Several antibodies displaying selectivity for the two closely related polypeptides were obtained, while the majority of the antibodies generated were crossreactive. Antibodies specific to the native and denatured forms of the two proteins were also obtained. Two of the monospecific antibodies were shown to immunoprecipitate the appropriate isoenzyme selectively from a mixture. When these antibodies were immobilized on agarose, they were successful in the immunoaffinity purification of the individual isoenzymes. In kinetic experiments certain antibodies were found to influence catalysis upon incubation with lipoxygenase. Antibodies which both inhibited and stimulated catalysis were identified.

Animals↗
PubMed1991

Quinolinic acid lesion of nucleus accumbens reduces D1 but not D2 dopamine receptors: an autoradiographic study.

Information concerning the cellular localization of dopamine receptor subtypes in the nucleus accumbens (NAcc) was obtained using receptor autoradiographic analysis. Unilateral, stereotaxic injection of the axon-sparing neurotoxin, quinolinic acid, into the NAcc resulted in a prominent loss of dopamine D1 receptors (as labeled by [3H]SCH 23390). Contrarily, no appreciable decrement in D2 receptors (labeled by [3H]raclopride) could be identified within the same region of the NAcc. The findings support the view that accumbens D1 receptors are located postsynaptically on neurons or their processes, while D2 receptors within this nucleus are primarily located on afferent terminals.

Animals↗