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Biomedical subjects

M C Chen

Publications and source records attributed to M C Chen.

At least 145 records · Page 8Linked to original sources
PubMed1986

Prostanoid inhibition of canine parietal cells.

Cellular mechanisms underlying the anti-secretory actions of the prostaglandin E2 analogue enprostil were studied using enzyme-dispersed, elutriator-enriched canine parietal cells and the accumulation of the weak base 14C-labeled aminopyrine as a functional index. Enprostil inhibited the accumulation of aminopyrine stimulated by histamine and the phosphodiesterase inhibitor isobutylmethyl, but not by carbachol, gastrin, or dibutyryl cyclic adenosine monophosphate. Inhibition by enprostil was dose-dependent (0.1 nM to 1 microM), with maximal inhibition ranging from 65 to 95 percent. Over the same concentration range, enprostil inhibited the histamine-stimulated generation of cyclic adenosine monophosphate. This selective inhibition of histamine activation of parietal cell function was comparable to that found for prostaglandin E2. Forskolin, a diterpene that directly activates the catalytic subunit of adenylate cyclase, was also markedly inhibited by nanomolar concentrations of prostaglandin E2 and enprostil. We conclude that at least a component of the secretory inhibition by enprostil reflects direct interference with histamine stimulation of parietal cell adenylate cyclase.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Postulated cancer prevention diets. A guide to food selections.

We believe that sufficient circumstantial and epidemiologic data exist linking diets and nutrients to cancer to warrant modification of eating habits. The proposed menus and diets are examples of the types of foods that might be beneficial in reducing the risk factors of cancer and also consistent with good nutritional habits.

Diet↗
PubMed1984

Computer based instruments for laboratory environments.

The personal computer is viewed as an all-purpose laboratory instrument and work station. Popular architectures are examined with regard to advantages and limitations, and applications discussed in terms of "stand alone" environments, situations requiring passive interfaces, and those employing intelligent configurations. A new hardware/software architecture is presented which is highly modular, and which supports rapid instrumental reconfiguration, high throughput (information capacity), and ease of use.

Computers↗
PubMed1983

Uptake of [3H]serotonin in the abdominal ganglion of Aplysia californica. Further studies on the morphological and biochemical basis of presynaptic facilitation.

Sensitization of the gill-withdrawal reflex in Aplysia california is mediated, in part, by a group of identified neurons, the L29 cells, which produce presynaptic facilitation of transmitter release from siphon sensory neurons. Physiological and pharmacological studies have provided indirect evidence that the L29 cells are serotonergic. In the present study we have used the specific uptake [3H]serotonin ([3H]5-HT) and electron-microscopic autoradiography in combination with horseradish peroxidase-labeling of identified neurons to characterize the fine structure of Aplysia serotonergic terminals and to examine more directly the transmitter biochemistry of the L29 neurons. Abdominal ganglia were incubated for 2 h in 10(-6) M [3H]5-HT and thick and thin plastic sections examined with the light and electron microscope. L29 varicosities, identified by labeling with HRP, were found to accumulate [3H]5-HT. In addition, [3H]-5-HT was localized to unidentified varicosities within the neuropil as well as to vesicle-filled terminals that formed axosomatic contacts in the cortical regions of the ganglion. The processes that accumulated [3H]5-HT contained conspicuous dense core vesicles identical in morphology to those previously described for L29. Some processes were found to make contact with HRP-labeled varicosities of sensory neurons. Comparison with results obtained from ganglia exposed to [3H]5-HT in the presence of either non-radioactive 5-HT or non-radioactive dopamine indicate that the uptake process is transmitter-specific. These studies provide additional evidence that the L29 cells are serotonergic and are consistent with the notion that aminergic neurons may be preferentially involved in modulatory synaptic actions.

Animals↗
PubMed1982

Ultrastructure of a histaminergic synapses in Aplysia.

The ultrastructure of histaminergic synaptic terminals was studied by the means of intrasomatic injection of horseradish peroxidase into the identified histaminergic neuron C2 of Aplysia. The axonal tree of C2 was found to consist, in part, of varicosities that display putative release sites similar in morphology to those described in other neurons in Aplysia. The varicosities contain at least two populations of vesicles: a conspicuous class of of large vesicles with an electron-dense core that almost fills the entire vesicle and a heterogeneous class of large and small electron-lucent vesicles. The small lucent vesicles preferentially cluster near active zones.

Animals↗
PubMed1982

Effects of electromagnetic stimuli on bone and bone cells in vitro: inhibition of responses to parathyroid hormone by low-energy low-frequency fields.

Low-energy electromagnetic fields pulsed at frequencies of 10-90 Hz significantly increase healing of chronic fracture nonunions in man. These fields are effective at tissue current levels several orders of magnitude lower than those required for transmembrane depolarization of normal cells. We have examined the effects of two clinically used pulsed electromagnetic fields on cultures of the osteoblast-like mouse bone cell line MMB-1. Both fields significantly reduced cellular production of cAMP in response to parathyroid hormone and osteoclast activating factor. Neither basal nor fluoride-activated levels of adenylate cyclase were altered in membranes from cells cultured in the fields; however, the same membrane preparations exhibited markedly inhibited responses to parathyroid hormone. The fields blocked the inhibitory effects of the hormone on collagen synthesis by MMB-1 cells. However, there was no effect on the inhibition of collagen synthesis by 1,25-dihydroxyvitamin D(3), which is believed to act primarily by a nuclear, rather than by a membrane-dependent, mechanism. No significant differences were noted between effects of the two fields, one generating continuous pulse trains (72 Hz) and the other generating recurrent bursts (15 Hz) of shorter pulses. We hypothesize that these field effects are mediated primarily at the plasma membrane of osteoblasts, either by interference with hormone-receptor interactions or by blocking of receptor-cyclase coupling in the membrane. These responses occurred with induced extracellular fields of 1 mV/cm or less, even though transmembrane potential gradients are typically 10(5) V/cm.

Animals↗
PubMed1981

Colorectal cancer and schistosomiasis.

The risk of colorectal cancer is known to be increased in patients with long-standing schistosomal colitis. A retrospective review of clinical data and surgical specimens from 60 patients with schistosomal granulomatous disease of the large intestine but without carcinoma demonstrated that 36 of them had mild to severe grades of colonic epithelial dysplasia. This was either focal or diffuse in distribution and occurred in flat mucosa, in pseudopolyps, or in regenerating epithelium at the edges of ulcers. These dysplastic changes are regarded as the pathological basis for the malignant potential of schistosomal colitis, and they resemble the changes found in long-standing chronic ulcerative colitis.

Adolescent↗
PubMed1980

[A case report of variant form of multiple myeloma].

Multiple myeloma is usually manifested with multiple destructive bone lesion, plasmacytosis and monoclonal protein. Here in we report a case of IgA (lambda) multiple myeloma with hepatomegaly and anemia but without bone lesions. Differential diagnostic points among lymphoma, amyloidosis, cancer and heavy chain disease are discussed.

Anemia↗