Biomedical subjects

K Feingold

Publications and source records attributed to K Feingold.

7 recordsLinked to original sources

PubMed1998

Acute barrier perturbation abolishes the Ca2+ and K+ gradients in murine epidermis: quantitative measurement using PIXE.

Epidermal permeability barrier homeostasis requires the delivery of lipids and hydrolytic enzymes by lamellar body exocytosis from the uppermost granular cells, a process that is upregulated following barrier disruption. As lamellar body secretion is controlled by ionic concentrations, especially Ca2+ and K+, we used a quantitative technique, microbeam proton-induced X-ray emission, to measure Ca2+, K+, Cl-, and P concentrations before and after acute barrier perturbation by acetone applications. We found a steep gradient of Ca2+ in normal tissue, peaking in the outer stratum granulosum, which disappeared after barrier disruption, and partially reformed as the barrier recovered. A similar gradient, peaking somewhat lower in the epidermis (i.e., at the stratum granulosum-stratum corneum interface), was found for K+. Epidermal concentrations of K+ also decreased after barrier abrogation, although to a lesser extent than Ca2+. In contrast, P and Cl- demonstrated distribution gradients at baseline, which remained unchanged after barrier disruption. These studies quantitate the levels of Ca2+, K+, Cl-, and P within specific epidermal cell layers at baseline, and in relation to changes in permeability barrier integrity. Ca2+ and K+, but not Cl- or P, decrease after barrier disruption, consistent with these two ion's role in barrier repair.

Animals↗

PubMed1996

Endotoxin and cytokines decrease serum levels and extra hepatic protein and mRNA levels of cholesteryl ester transfer protein in syrian hamsters.

Endotoxin alters the metabolism of lipoproteins, including that of high density lipoprotein (HDL). Cholesteryl ester transfer protein (CETP) facilitates exchange of HDL cholesterol for very low density lipoprotein (VLDL) triglyceride, leading to catabolism of HDL. We investigated the effects of endotoxin and cytokines on CETP in Syrian hamsters. Endotoxin induced a rapid and progressive decrease in serum CETP levels, by 48 h CETP had decreased to < 20% of control levels. Endotoxin also decreased CETP mRNA and protein levels in adipose tissue, heart, and muscle, the tissues with highest levels of CETP mRNA, providing a plausible mechanism for the endotoxin-induced decrease in circulating CETP. Dexamethasone did not mimic the effects of endotoxin on CETP, but the combination of tumor necrosis factor and interleukin-1 did, indicating that these cytokines may in part mediate the effects of endotoxin on CETP. The endotoxin-induced decrease in CETP may help maintain HDL cholesterol levels during infection and inflammation when increased triglyceride levels could drive the exchange of HDL cholesteryl ester for VLDL triglyceride. Maintaining circulating HDL may be important because HDL protects against the toxic effects of endotoxin and provides cholesterol for peripheral cells involved in the immune response and tissue repair.

Adipose Tissue↗

PubMed1995

Source estimation of auditory brainstem evoked potentials: comparison of 3CLT and dipole localization.

The generators of auditory brainstem evoked potentials (ABEPs) are generally agreed to be located between the auditory nerve and upper pons. Thus, they are all located within a few cm from the center of the head. Three-channel Lissajous' trajectory (3CLT) provides the amplitude and orientation of a centrally located equivalent dipole of surface recorded activity. Volume conductor theory predicts decreased spatial resolution of source estimation the deeper the source. In this study we compared source estimates obtained with 3CLT, using three orthogonal differential channels, with those obtained with two other source estimation methods: i) setting the generators at their known anatomical coordinates and calculating orientation and magnitude of the source (dipole localization method--DLM); ii) estimation of all source parameters, including the number of sources by wavelet-type decomposition, without assumptions on the location of the sources (multiple source estimate--MSE). 3CLT, DLM and MSE all converged on magnitudes and orientations that were not significantly different from each other, and locations that were within a few cm of each other. In conclusion, although 3CLT can only estimate a single, centrally located equivalent dipole, in the specific case of ABEPs, it provides the same information available from the more demanding source estimate methods. In addition to the considerable saving in recording channels, 3CLT is reference-independent and thus avoids ambiguities resulting from the choice of reference.

Electrodes↗

PubMed1994

Methicillin-resistant Staphylococcus aureus colonization in a new nursing home.

Methicillin-resistant Staphylococcus aureus (MRSA) has been detected in nursing homes and long-term care facilities. Studies disagree about the risk of infection with MRSA in colonized patients. MRSA colonization and infection were tracked for one year in all admissions to a 60-bed ward at the Philadelphia VA Nursing Home Care Unit (NHCU) from the time of its opening in June, 1990. Patients and staff were blinded to culture results, and the NHCU followed universal precautions for all patients. Of the first 72 patients, 7 were found to be colonized with MRSA; only one of them was known to have had MRSA prior to NHCU transfer. Three patients died (2 had negative cultures prior to death), and 1 was discharged home. Three patients spontaneously cleared MRSA colonization and lived to the end of the study. Three patients appeared to be colonized by MRSA after admission; subsequent cultures were negative. No patients were infected by MRSA in the NHCU. At the close of the study, one year after the nursing home opened, no patient in the nursing home had a culture positive for MRSA. In conclusion, colonization with MRSA at the time of admission to the nursing home is not uncommon, but patients can spontaneously clear it. Besides, nursing homes that pre-screen only those patients with classic risk factors may be admitting many MRSA-colonized patients. Nonetheless, universal precautions appear to be effective in limiting transmission of MRSA in the nursing home; in this study, MRSA acquisition was sporadic and brief.

Aged↗

PubMed1990

Three-channel Lissajous' trajectories of auditory brainstem evoked potentials: contribution of fast and slow components to planar segment formation.

Three-Channel Lissajous' Trajectories (3CLT) of Auditory Brainstem Evoked Potentials (ABEP) to clicks were obtained after finite impulse response filtering in three frequency bands. These bands were chosen to replicate the widely used passband (100-3000 Hz) and to selectively enhance the definition of the 'pedestal' (10-240 Hz) or the first, third and fifth components (240-483 Hz). Quantitative measures of 3CLT were calculated to describe apex latencies, planar segment orientations, durations, trajectory amplitude peaks and their latencies. In addition, dipole moments at the latencies of apical points along 3-CLT were calculated. The planarity of ABEP 3-CLT segments persisted after selective enhancement of the 'pedestal' or the first, third and fifth components. These results rule out the suggestion that planarity of ABEP segments results from the interaction of the 'pedestal' with the superimposed faster components. These results demonstrate summation of 3-CLT planar segments ('a' 'c' and 'e' with the 'pedestal') to form new segments (wide-band 'a', 'c' and 'e'). With the exception of 'c', planar segments and the equivalent dipole moments associated with apexes did not change orientations across passbands. The effects of passband on the orientation of planar segment 'c' and the dipole moment of its apex are explained by its superimposition on the 'pedestal' in the wide-band records. A similar analysis of ABEP to clicks as compared to low-frequency stimuli (high-pass masked clicks) revealed no change in planarity nor in plane parameters. These results are compatible with the suggestion that the generators of the first, third and fifth ABEP components are curved fiber tracts. The planarity of the slow 'pedestal' may be due to the summation of slow synaptic potentials in auditory brainstem nuclei. These findings indicate that the generators of ABEP are composites that may be separated by selective lesion studies.

Acoustic Stimulation↗

PubMed1984

Regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase and cholesterol synthesis and esterification during the first cell cycle of liver regeneration.

The regenerating rat liver provides a unique in vivo synchronized system for study of the interrelationships between mevalonate and sterol metabolism during the cell cycle. The regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, cholesterol synthesis and acyl coenzyme A: cholesterol acyltransferase during the first cell cycle was investigated. At 8 h postoperative and prior to onset of DNA synthesis or S phase, cholesterol synthesis was depressed in the regenerating liver relative to that in sham-operated controls. This suppression was observed whether assayed in vitro with liver homogenates utilizing radiolabeled acetate, mevalonate or water or in vivo with tritium water. In contrast, at this time point, 3-hydroxy-3-methylglutaryl-CoA reductase activity was increased in microsomes prepared both in the presence and absence of NaF. By 24 h, well into S phase and approaching mitosis, reductase activity and cholesterol synthesis both approached levels observed in the sham-operated control animals. There were no detectable changes in acyl-CoA: cholesterol acyltransferase activity at any time point. Thus, at the 8 h time point, the regulation of the three processes appeared uncoupled. The increased levels of in vitro expressed 3-hydroxy-3-methylglutaryl-CoA reductase activity compared with the decrease in the rate of both cholesterol and squalene biosynthesis suggested diversion of mevalonate into products other than squalene or sterols. We propose that this may reflect the needs of the cell for a nonsterol metabolite of mevalonate necessary for entry of cells into S phase.

Animals↗

PubMed1980

Studies on the pathophysiological role of thyroidal prostaglandin E (PGE) in Graves' disease.

A potential role for prostaglandin E (PGE) of thyroid origin in the pathogenesis of the hyperthyroidism of Graves' disease was investigated in vivo. The venous-arterio prostaglandin E (PGE) concentration gradient across the thyroid was measured in 5 patients undergoing subtotal thyroidectomy for Graves' disease. This gradient (161 +/- 14 pg/ml; mean /+- SE) was significantly greater than that found in 11 patients undergoing surgery for hyperparathyroidism and thyroid nodules (64 +/- 20 pg/ml; P < 0.01). This suggests that there is a net increase in PGE output by the thyroid gland in Graves' disease, but the thyroid cell-type responsible for this increased PGE output is unknown. In contrast to previous reports, thyrotropin (TSH) did not stimulate thyroid cell PGE generation in vitro, providing evidence against a role for TSH in this phenomenon. Administration of maximal doses of indomethacin to two thyrotoxic patients did not significantly alter peripheral thyroid hormone concentrations. These data suggest that thyroidal PGE has a function other than to stimulate thyroid hormone secretion in Graves' disease.

Adult↗