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J L Ellis

Publications and source records attributed to J L Ellis.

45 records · Page 3Linked to original sources
PubMed1989

Angiotensin neuromodulation of adrenergic and purinergic co-transmission in the guinea-pig vas deferens.

1. The effects of angiotensin II (AII) and angiotensin III (AIII) on the isolated vas deferens of the guinea-pig were studied via three parameters: the overflow of adenosine 5'-triphosphate (ATP) and tritiated noradrenaline (NA), the mechanical response to field stimulation and the mechanical response to exogenous NA and alpha, beta-methylene ATP (alpha, beta-mATP). 2. At 2 Hz, AII enhanced the overflow of ATP and NA, whereas at 20 Hz, AII enhanced the overflow of NA but was without significant effect on ATP overflow. AIII, at 2 Hz, inhibited the overflow of ATP, but enhanced NA overflow, whereas at 20 Hz ATP overflow was unaffected, but NA overflow was still enhanced. 3. At 2 Hz, AII enhanced both phases of the response to field stimulation and at 20 Hz the overall response. AIII at 2 Hz enhanced the adrenergic response, but was without effect on the purinergic response to field stimulation. At 20 Hz, AIII was without effect on the overall response. 4. AII enhanced responses to exogenous NA and alpha, beta-mATP, whereas AIII was without effect. 5. These results provide evidence that both ATP and NA release are capable of being modulated by angiotensins. Furthermore, modulation of ATP release is frequency-dependent, whereas [3H]-NA release is not. These results raise questions about the mechanisms of storage and release of the sympathetic co-transmitters NA and ATP; they also show that angiotensin receptors in the guinea-pig vas deferens are not a homogeneous population.

Adenosine Triphosphate↗
PubMed1989

Modulation of neurotransmission in the guinea-pig vas deferens by capsaicin: involvement of calcitonin gene-related peptide and substance P.

1. The effects of capsaicin, calcitonin gene-related peptide and substance P were studied via three parameters in the guinea-pig vas deferens: the overflow of ATP and of tritiated noradrenaline, the mechanical responses to field stimulation and the mechanical responses to exogenous noradrenaline and alpha, beta-methylene ATP. 2. At 2 Hz, capsaicin inhibited the stimulus-evoked release of ATP, whereas it was without effect on the release of noradrenaline. At 20 Hz capsaicin did not affect the release of either of the cotransmitters. Capsaicin enhanced responses to alpha, beta-methylene ATP, but not to exogenous noradrenaline. 3. Calcitonin gene-related peptide, like capsaicin, inhibited the release of ATP, but not noradrenaline at 2 Hz and was without effect on release at 20 Hz. However, calcitonin gene related peptide inhibited responses to alpha, beta-methylene ATP and was without effect on responses to exogenous noradrenaline. 4. Substance P had no effect on the release of either noradrenaline or ATP at either frequency. However, like capsaicin it enhanced responses to alpha, beta-methylene ATP and was without effect on exogenous noradrenaline. 5. These results suggest that the actions of capsaicin on the guinea-pig isolated vas deferens are mediated via the release of both calcitonin gene-related peptide and substance P. Furthermore, as capsaicin and calcitonin gene-related peptide prejunctionally modulate purinergic, but not noradrenergic transmission, this suggests that the mechanisms for the storage and release of the sympathetic co-transmitters noradrenaline and ATP may not be the same.

Animals↗
PubMedDate not supplied

Neurophysiology of mast cell-nerve interactions in the airways.

The sensitized guinea pig was employed as a model to study the effect of immunological activation of resident mast cells on neuronal activity in the airways. The trachea was isolated with the vagus nerves and vagal sensory ganglia intact. Using conventional electrophysiological recording techniques, we noted that antigenic stimulation led to an increase in the sensitivity of sensory nerve endings located in the airway wall. Moreover, previous work has revealed that antigen challenge potentiates action-potential-driven tachykinin release from afferent fibers in the guinea pig isolated airway. Anatomical and electrophysiological studies indicate that tachykinin-containing sensory fibers directly innervate the local parasympathetic ganglion neurons in the airway. Therefore, antigen-induced increases in the excitability of sensory fibers in the airways can increase parasympathetic tone in the airway by increasing central and peripheral reflex arcs. In addition, we have found that antigen stimulation has direct effects on the excitability of the parasympathetic ganglion neurons. Considered together, the data demonstrate that increased vagal sensory and parasympathetic activity may be a consequence of the allergic reaction in the airways.

Action Potentials↗
PubMedDate not supplied

Cardiovascular disease risk factors in native Americans: a literature review.

Cardiovascular disease (CVD) has become the leading cause of death for Native Americans and Alaska Natives. CVD risk factors (diabetes, hypertension, obesity, hypercholesterolemia, smoking, and sedentary lifestyle) have been studied in a number of Native American tribes, and such studies are increasing as the CVD mortality rate rises. This article reviews the literature between 1980 and 1991 concerning the prevalence of CVD risk factors in this population. In addition to summarizing the data, we describe limitations inherent in comparison and address the need for standardization of methodology in future studies.

Adult↗