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Biomedical subjects

J Welton

Publications and source records attributed to J Welton.

10 recordsLinked to original sources
PubMed2000

Removal of hydrogen peroxide by a 1-cysteine peroxiredoxin enzyme of the filarial parasite Dirofilaria immitis.

Prior studies have shown that filarial nematodes can effectively metabolize hydrogen peroxide in excess of that generated by activated host cells. However, the mechanisms of H2O2 removal by the filarial parasites are unclear. Herein we report the results of studies carried out on the biochemical activity and on immunolocalization of a recombinant peroxiredoxin (Prx) enzyme from the dog filarial parasite Dirofilaria immitis. A full-length cDNA encoding a 1-Cys Prx enzyme from the dog heartworm D. immitis was expressed in Escherichia coli as a recombinant polyhistidine fusion protein (rDiPrx-1). rDiPrx-1 was capable of reducing H2O2 in the presence of dithiothreitol. The apparent kinetic constants determined for DiPrx-1 using H2O2 as a substrate were a Michaelis constant (Km) of 16.28 mM and a maximal velocity (Vmax) of 16 micromol/min(-1). Consistent with the enzyme activity, D. immitis adult worms could detoxify exogenously added H2O2 in vitro. Antibodies to rDiPrx-1 identified a 27-kDa native antigen in parasite extracts and larval and adult excretory-secretory products. The antibodies were used to localize the native antigen to the lateral hypodermal chords of both male and female worms by immunohistochemistry. In addition, labeling was seen in the afibrillar muscle cells in male worms and in some areas of the uterine wall in female worms. Thus, DiPrx-1 is the first parasite Prx to be shown to detoxify exogenously added H2O2 in an in vitro system.

Animals↗
PubMed1999

Differential expression of the muscarinic m2 acetylcholine receptor by small and large motoneurons of the rat spinal cord.

The purpose of this study was to determine if motoneurons in the spinal ventral horn express the muscarinic m2 acetylcholine receptor. Motoneurons were retrogradely labelled in adult rats by intramuscular injection of Fluorogold and examined with confocal microscopy for evidence of immunoreactivity for the receptor. The cells were also double-labelled for choline acetyltransferase to determine if they were contacted by cholinergic axons. Almost all large motoneurons (diameters greater than 35 microm) displayed intense immunoreactivity for the receptor which was evenly distributed along the plasma membrane. Small cells were immunonegative for the receptor or weakly labelled. As large cells probably correspond to alpha-motoneurons and receive many cholinergic contacts, it is concluded that acetylcholine can influence this type of motoneuron by acting through the m2 receptor.

Animals↗
PubMed1998

Uptake and release of neurotransmitter candidates, [3H]serotonin, [3H]glutamate, and [3H]gamma-aminobutyric acid, in taste buds of the mudpuppy, Necturus maculosus.

Neurotransmitters in vertebrate taste buds have not yet been identified with confidence. Serotonin, glutamate, and gamma-aminobutyric acid (GABA) have been postulated, but the evidence is incomplete. We undertook an autoradiographic study of [3H]serotonin, [3H]glutamate, and [3H]GABA uptake in lingual epithelium from the amphibian, Necturus maculosus, to determine whether taste bud cells would accumulate and release these substances. Lingual epithelium containing taste buds was incubated in low concentrations (0.4-6 microM) of these tritiated transmitter candidates and the tissue was processed for light microscopic autoradiography. Merkel-like basal taste cells accumulated [3H]serotonin. When the tissue was treated with 40 mM K+ after incubating the tissue in [3H]serotonin, cells released the radiolabelled transmitter. Furthermore, depolarization (KCl)-induced release of [3H]serotonin was Ca-dependent: if Ca2+ was reduced to 0.4 mM and 20 mM Mg2+ added to the high K+ bathing solution, Merkel-like basal cells did not release [3H]serotonin. In contrast, [3H]glutamate was taken up by several cell types, including non-sensory epithelial cells, Schwann cells, and some taste bud cells. [3H]glutamate was not released by depolarizing the tissue with 40 mM K+. [3H]GABA uptake was also widespread, but did not occur in taste bud cells. [3H]GABA accumulated in non-sensory epithelial cells and Schwann cells. These data support the hypothesis that serotonin is a neurotransmitter or neuromodulator released by Merkel-like basal cells in Necturus taste buds. The data do not support (nor rule out) a neurotransmitter role for glutamate or GABA in taste buds.

Animals↗
PubMed1998

Fund raising mentors: wisdom for winning.

This article shares some of the most important lessons I have learned in 31 years of marketing and fund-raising activities from five mentors. It also points out the critical role that mentors play in one's career.

Fund Raising↗
PubMed1992

Immunocytochemical survey of putative neurotransmitters in taste buds from Necturus maculosus.

To investigate synaptic mechanisms in taste buds and collect information about synaptic transmission in these sensory organs, we have examined taste buds of the mudpuppy, Necturus maculosus for the presence of neurotransmitters and neuromodulators. Immunocytochemical staining at the light microscopic level revealed the presence of serotonin-like and cholecystokinin-like (CCK) immunoreactivity in basal cells in the taste bud. Nerve fibers innervating taste buds were immunoreactive for vasoactive intestinal peptide-like (VIP), substance P-like, and calcitonin gene-related peptide-like (CGRP) or compounds closely related to these substances. Immunoreactivity for tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) in the taste cells and nerve fibers was absent. These data suggest that serotonin, CCK, VIP, substance P, and CGRP are involved in synaptic transmission or neuromodulation in the peripheral organs of taste. No evidence was found for cholinergic or adrenergic mechanisms on the basis of the absence of immunocytochemical staining for key enzymes involved in these two transmitter systems.

Animals↗
PubMed1983

Will the Act work.

Explore the source record for details and available documents.

Education, Special↗
PubMedDate not supplied

Schools in the welfare network.

This paper examines the place of schools within the welfare network for children and young people, and notes potentially disfunctional elements of the social division of welfare. The stratification between welfare professions and the relationship between normal and crisis care is discussed. Three levels of school based welfare systems are identified, working alongside school attached and community based professions, each with its own characteristics. Trends are identified which reflect the development of more effective multi-professional cooperative care.

Communication↗