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Biomedical subjects

M H Welch

Publications and source records attributed to M H Welch.

16 recordsLinked to original sources
PubMed1992

Choline levels in human peritoneal dialysate.

The average free choline level was determined to be 14 M in peritoneal dialysates and 22 M in plasma of thirty patients on continuous ambulatory peritoneal dialysis (CAPD). Daily choline loss via dialysate averaged 129 moles with 32 moles choline lost per dwell. Daily choline loss via the dialysate was positively correlated with plasma choline concentrations. Choline levels in dialysate during CAPD exceed plasma levels of choline (9 M) in healthy individuals.

Choline↗
PubMed1991

Structure and function of non-enzymatically dissociated lacrimal gland acini.

Lacrimal gland acini were isolated utilizing a non-enzymatic dissociation procedure. This method resulted in the rapid isolation of an enriched population of acini from rat lacrimal gland with a complete absence of interlobular and rare occurrence of intralobular duct epithelium. The isolated acini had high viability and retained good histological organization. Alkaline phosphatase activity was present in the myoepithelial cells and capillaries associated with the periphery of the acini, indicating a relatively undisturbed basal surface. Secretion of peroxidase by the isolated acini in response to cholinergic and alpha-adrenergic stimulation indicated that the cell surface receptors in this preparation were retained and were physiologically functional. Thus, we report a dissociation protocol that eliminates enzymatic digestion, but results in a relatively enriched acinar preparation that is appropriate for the assessment of cellular biochemistry and physiology of lacrimal exocrine function of the acini.

Alkaline Phosphatase↗
PubMed1991

Lectins as probes of membrane carbohydrates in mesothelial cells in vitro.

Carbohydrates present on the surface of cells have been implicated in such processes as bacterial adherence, surfactant secretion and reutilization, and cell-cell recognition. In this study, fluorescein isothiocyanate (FITC) conjugated lectins were used to probe for such carbohydrates on the surface and interior regions of rabbit peritoneal mesothelial cells propagated in vitro. A cell permeabilization technique employing treatment with formalin and saponin provided the greatest presentation of surface membrane structure and lectin binding. FITC-lectins derived from C. ensiformis (Concanavalin A; mannose specific), T. vulgaris, A. hypogaea, E. cristagalli, B. simplicifolia, and M. pomifera bound to the cell surface. When two strains of Edwarsiella tarda were exposed to the mesothelial cells, only the mannose-specific strain (ET-4) demonstrated substantial adherence to the cell surface.

Animals↗
PubMed1989

Peroxidase secretion by lacrimal glands from juvenile F344 rats.

Secretion of peroxidase by rat lacrimal glands is generally acknowledged to be greater in juvenile rats than in adults. However, this phenomenon has not been so well documented in lacrimal glands as other age-related changes have been. Therefore, we studied lacrimal protein and peroxidase secretion in response to muscarinic cholinergic and alpha-adrenergic stimulation of glands from 35- to 90-day-old male F344 rats. Lacrimal tissue fragments were incubated in perifusion chambers, and secretion of protein and peroxidase was measured in response to stimulation by carbachol or phenylephrine. There was a negative first-order correlation between total protein secretion and age. Dose-response curves showed that at the highest doses there was a small but significant change in protein secretion. Secretion of lacrimal peroxidase in response to carbachol and phenylephrine changed significantly with increasing age. The tissue content of peroxidase was diminished by about 25% during this period, but that decrease alone was not sufficient to explain the changes in secretory responsiveness. The decrease of peroxidase secretion elicited by phenylephrine had both first- and second-order components in its correlation with age between 35 and 90 days. Dose-response curves for 5-week (35-41-day)- and 12-week (84-90-day)-old tissue showed that the maximum secretion of peroxidase was reduced by about 50%, but with no apparent shift in the dose-response curve.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Adrenocorticotropic hormone stimulation of lacrimal peroxidase secretion.

The effect of adrenocorticotropic hormone (ACTH) on secretion of lacrimal gland peroxidase was studied using an in vitro perifusion technique. The peptide stimulated a dose-dependent (1 nM to 100 nM) release of peroxidase, with the maximum level of secretion induced by 20 nM ACTH. Secretion in the presence of submaximal ACTH was potentiated with either 100 microM iso-butylmethylxanthine or 0.3 microM carbachol. In contrast, the combination of ACTH and phenylephrine was additive. Time-dependence studies demonstrated that the stimulation of peroxidase release by ACTH, as with other cyclic adenosine monophosphate mediated secretagogues, showed a latency in reaching the maximum rate which was not evident with either cholinergic or alpha-adrenergic stimulation. Furthermore, where potentiation of the response to ACTH occurred, the time course was distinctly altered from that obtained with either ACTH or the potentiating agonist alone. The data suggest that lacrimal gland function is regulated by a multiple system of neurotransmitters and (or) neuromodulators that involves the activation of peptidergic as well as cholinergic and alpha-adrenergic receptors.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Sympathomimetic protein secretion by young and aged lacrimal gland.

The diminished basal tear flow in aged individuals is associated with lymphocytic infiltrations and atrophy of the lacrimal ducts and acini. We have investigated the age-related physiological changes to sympathomimetic stimulation of lacrimal tissue from F344 rats to determine if the responses are uniformly diminished as would be expected by glandular atrophy. The quantitative and temporal pattern of protein and peroxidase secretion by lacrimal gland fragments from young (4 month) and aged (24 month) F344 male rats was examined in a perifusion system. Upon stimulation of tissue from young animals with 0.01 mM phenylephrine for 40 min, secretion above baseline levels of protein was 570.8 micrograms/g tissue and of peroxidase was 45.2 delta A X min-1/g tissue. The response of the aged tissue to phenylephrine was not significantly different from that of the young tissue. beta-adrenergic stimulation by isoproterenol (0.01 mM) evoked only a modest secretion of protein and no consistently measurable peroxidase from young tissue. IBMX alone and in combination with isoproterenol (0.1 mM and 0.01 mM respectively) evoked a large secretion of protein, 1345.7 micrograms/g tissue, and a modest secretion of peroxidase, 9.5 delta A X min-1/g tissue by young tissue. The aged tissue, upon stimulation with the combination of IBMX and isoproterenol, secreted significantly less protein and peroxidase than the young tissue. In separate experiments, the production of cAMP was measured. In young tissue, isoproterenol did not cause a measurable increase of intracellular cAMP. IBMX caused a 2-3 fold increase in cellular cAMP which was not increased further by addition of isoproterenol.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed1985

Lacrimal protein secretion: comparison of young and old rats.

The in vitro protein secretory response of lacrimal glands from healthy 4- and 24-month-old F344 rats was measured. Tissue fragments were incubated in a 0.2 ml perifusion chamber and stimulated to secrete protein by a 4-min bolus of 0.01 mM carbachol. Fractions of the perifusate were collected and assayed for protein concentration and peroxidase activity. The response to carbachol was a well-defined peak of secreted protein that included peroxidase. The response was inhibited by 1.0 microM atropine. No differences were found between the responses of male and female glands. The peak of protein secretion by the young glands contained 263.9 +/- 71.8 micrograms g tissue-1 compared to 175.4 +/- 56.5 micrograms g tissue-1 for the old glands (P less than 0.005). While the mean activity of the secreted peroxidase was similar in the two age groups, the aged glands were significantly more variable in their response. The F344 rat may provide a useful model for studying the normal age-dependent changes that occur in lacrimal gland.

Aging↗
PubMed1978

Oxygen toxicity.

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Animals↗
PubMed1977

The effect of tumor size and location on diagnosis by fiberoptic bronchoscopy.

Evaluation of data from fiberoptic bronchoscopic procedures revealed that for peripheral bronchogenic carcinomas, the diagnostic yield was influenced by the size of the lesion and its distance from the hilum. Failure to diagnose visible carcinomas was related to inability to obtain deep specimens for biopsy. Biopsy, brushing, and washing were complementary procedures in diagnosing bronchogenic carcinomas.

Biopsy↗
PubMed1975

Evidence for essential lysyl residues in ribulosebisphosphate carboxylase by use of the affinity label 3-bromo-1,4-dihydroxy-2-butanone 1,4-bisphosphate.

A previous study from our laboratory suggested that 3-bromo-1,4-dihydroxy-2-butanone 1,4-bisphosphate is an affinity label for spinach ribulosebisphosphate carboxylase. To identify the essential residues that react with the reagent we have isolated and characterized the labeled peptides that are present in tryptic digests of inactivated enzyme but lacking in digests of the substrate-protected enzyme. Peptides representing two sites of modification have been obtained from the inactivated carboxylase. Both sites of reaction have been identified as lysyl residues based on the conversion of the derivatives to free lysine by oxidation with sodium metaperiodate. Sodium dodecyl sulfate-gel electrophoretic experiments show that both essential lysyl residues are contained within the large subunit of ribulosebisphosphate carboxylase. In addition to lysyl residues, sulfhydryl groups of the carboxylase are also modified, but their modification seems to play little role in the inactivation process. The carboxylase modified in the presence of substrate contains sulfhydryl derivatives but is essentially lacking in lysyl derivatives. By comparing the profiles from ion exchange chromatography of labeled peptides in digests of inactivated and substrate-protected enzyme, we conclude that the same sulfhydryl groups are modified in the absence and presence of substrate.

Affinity Labels↗
PubMed1975

Hospital-acquired salicylate intoxication. report of a case with psychosis, acidosis, and coma.

A case of salicylate intoxication from repeated therapeutic doses of aspirin is reported in an adult with impairment of salicylate elimination. Evolution of acid-base disturbance from respiratory alkalosis to metablic acidosis is documented. Serum salicylate levels during several years of therapy demonstrate the acquisition of impaired elimination of the drug. This case illustrates the practical importance of special features of salicylate accumulation kinetics emphasized in a recent review.

Acidosis↗