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Biomedical subjects

P A Patel

Publications and source records attributed to P A Patel.

5 recordsLinked to original sources
PubMed2005

Evidence for an intrinsic mechanism of antinociceptive tolerance within the ventrolateral periaqueductal gray of rats.

Repeated microinjections of morphine into the ventrolateral periaqueductal gray produce antinociceptive tolerance. This tolerance may be a direct effect of morphine on cells within the ventrolateral periaqueductal gray or may require activation of downstream structures such as the rostral ventromedial medulla or spinal cord. Experiment 1 examined whether tolerance develops when opioid receptors in the ventrolateral periaqueductal gray are blocked prior to repeated systemic morphine administration. Microinjections of naltrexone hydrochloride (1microg/0.4microl) into the ventrolateral periaqueductal gray blocked antinociception and significantly attenuated the development of antinociceptive tolerance produced from systemic morphine administration. Experiment 2 examined whether tolerance develops when the effects of morphine are isolated to the ventrolateral periaqueductal gray. This was accomplished by microinjecting morphine (5microg/0.4microl) into the ventrolateral periaqueductal gray while simultaneously blocking the descending output through the rostral ventromedial medulla. Inhibition of neurons within the rostral ventromedial medulla by microinjecting the GABA(A) agonist muscimol (10ng/0.5microl) blocked the antinociception produced by microinjection of morphine into the ventrolateral periaqueductal gray but did not block the development of tolerance. These data demonstrate that the ventrolateral periaqueductal gray is both necessary and sufficient to produce tolerance to the antinociceptive effect of morphine. The ventrolateral periaqueductal gray is necessary in that tolerance does not develop if opiate action within the ventrolateral periaqueductal gray is blocked (experiment 1). The ventrolateral periaqueductal gray is sufficient in that tolerance occurs even when morphine's effects are restricted to the ventrolateral periaqueductal gray (experiment 2).

Analgesics↗
PubMed1999

Application of mortality prediction systems to individual intensive care units.

OBJECTIVE: To evaluate the predictive accuracy of the severity of illness scoring systems in a single institution. DESIGN: A prospective study conducted by collecting data on consecutive patients admitted to the medical intensive care unit over 20 months. Surgical and coronary care admissions were excluded. SETTING: Veterans Affairs Medical Center at Buffalo, New York. PATIENTS AND PARTICIPANTS: Data collected on 302 unique, consecutive patients admitted to the medical intensive care unit. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Data required to calculate the patients' predicted mortality by the Mortality Probability Model (MPM) II, Acute Physiology and Chronic Health Evaluation (APACHE) II and Simplified Acute Physiology Score (SAPS) II scoring systems were collected. The probability of mortality for the cohort of patients was analyzed using confidence interval analyses, receiver operator characteristic (ROC) curves, two by two contingency tables and the Lemeshow-Hosmer chi-square statistic. Predicted mortality for all three scoring systems lay within the 95 % confidence interval for actual mortality. For the MPM II, SAPS II and APACHE II, the c-index (equivalent to the area under the ROC curve) was 0.695 +/- 0.0307 SE, 0.702 +/- 0.063 SE and 0.672 +/- 0.0306 SE, respectively, which were not statistically different from each other but were lower than values obtained in previous studies. CONCLUSION: Although the overall mortality was consistent with the predicted mortality, the poor fit of the data to the model impairs the validity of the result. The observed outcome could be due to erratic quality of care, or differences between the study population and the patient population in the original studies. The data cannot be used to distinguish between these possibilities. To increase predictive accuracy when studying individual intensive care units and enhance quality of care assessments it may be necessary to adapt the model to the patient population.

APACHE↗
PubMed1987

A self-heated thermistor technique to measure effective thermal properties from the tissue surface.

A microcomputer based instrument to measure effective thermal conductivity and diffusivity at the surface of a tissue has been developed. Self-heated spherical thermistors, partially embedded in an insulator, are used to simultaneously heat tissue and measure the resulting temperature rise. The temperature increase of the thermistor for a given applied power is a function of the combined thermal properties of the insulator, the thermistor, and the tissue. Once the probe is calibrated, the instrument accurately measures the thermal properties of tissue. Conductivity measurements are accurate to 2 percent and diffusivity measurements are accurate to 4 percent. A simplified bioheat equation is used which assumes the effective tissue thermal conductivity is a linear function of perfusion. Since tissue blood flow strongly affects heat transfer, the surface thermistor probe is quite sensitive to perfusion.

Animals↗
PubMed1979

Cell-mediated immunity to varicella-zoster virus infection in subjects with lymphoma or leukemia.

Normal subjects and patients with lymphoma or leukemia were tested for the levels of lymphocytes, E-rosette--forming T-cells, serum and vesicle fluid interferon, and specific in vitro proliferative response to varicella-zoster antigen after clinical varicella or herpes zoster illness. The effect of polyinosinic acid/polycytidilic acid on the immune response was also evaluated. The development of VZ specific cell-mediated response in normal subjects was characterized by intense proliferative activity eight to ten days after the onset of illness, with significant decline 70 to 80 days later. The responses in subjects with lymphoma or leukemia were much lower. Few subjects with chickenpox or zoster with lymphoma or leukemia died during the infection. Death was associated with significant depletion of E-rosette--forming T-cells, and grossly deficient specific cellular response to VZ antigen. Treatment with Poly IC frequently induced elevations in serum as well as vesicle fluid interferon levels, and increased the proliferative activity of lymphocytes against VZ antigen.

Adolescent↗