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Biomedical subjects

J Coombs

Publications and source records attributed to J Coombs.

At least 37 records · Page 2Linked to original sources
PubMed1988

Spatial distribution of Ca currents in molluscan neuron cell bodies and regional differences in the strength of inactivation.

The spatial distribution of Ca current in molluscan neuron cell bodies was studied using a large patch method in combination with 2-microelectrode voltage clamp. The method has a spatial resolution equal to about 0.1% of the cell body area. Ca current is not uniformly distributed. The current density varies between patches, changing by as much as a factor of 2.5 over a distance of 20 micron, and there is evidence that Ca current occurs in "hot spots" involving a few hundred channels. The current density increases in a moderately steep gradient from the soma cap, opposite the axon, toward the axon hillock. Ca currents in patches from different regions of the soma are qualitatively different. Currents near the soma cap do not inactivate or inactivate weakly during depolarization, while currents of equal density nearer the axon hillock exhibit pronounced inactivation. The strength of inactivation increases in parallel with the gradient in current density, but local differences in current density, or in the number of active Ca channels, do not explain the variability in inactivation. Inactivating and noninactivating Ca currents could not be distinguished on the basis of activation or deactivation kinetics, voltage dependence of activation, or sensitivity to hyperpolarizing conditioning pulses. Also, the amplitude of noninactivating current near the soma cap is reduced by intracellular Ca injection showing that, like the whole-cell current, Ca current in this region is subject to Ca-dependent inactivation. The data favor the hypothesis that these cells express only one type of Ca channel. Differences in the strength of inactivation may result from local differences in cytoplasmic Ca buffering, local modification of Ca channels in a way that changes their sensitivity to Ca-dependent inactivation, or local differences in the availability of cytoplasmic factors or enzymes that are necessary for inactivation.

Animals↗
PubMed1987

Pediatricians' immunization consent practices in Washington state.

A survey of Washington state pediatricians and allied health professionals showed that two thirds provide written information to parents on diphtheria-tetanus-pertussis; measles-mumps-rubella; and oral polio vaccines. Twenty-two percent of pediatricians provide written information on inactivated polio vaccine. Sixty-two percent of pediatricians who give immunizations require a parent's signature as evidence of having provided information or obtained consent.

Immunization↗
PubMed1987

Forskolin's effect on transient K current in nudibranch neurons is not reproduced by cAMP.

Forskolin, a diterpene extracted from Coleus forskolii, stimulates the production of cAMP in a variety of cells and is potentially an important tool for studying the role of cAMP in the modulation of neuronal excitability. We studied the effects of forskolin on neurons of nudibranch molluscs and found that it caused characteristic, reversible changes in the amplitude and waveform of the transient K current, IA, and also activated an inward current similar to the cAMP-dependent inward current previously described in molluscan neurons. Forskolin altered the time course of IA activation and inactivation but did not affect the voltage dependence or the reversal potential of the current. IA normally inactivates exponentially, but in forskolin the time course of inactivation can be fit by the sum of 2 exponentials with an initial rate that is faster than the control and a final rate that is much slower. On depolarization in forskolin, IA begins to activate at the normal rate, but a slower component of activation is also seen. The changes in IA in the nudibranch cells were qualitatively different than the changes caused by forskolin in Aplysia bag cell neurons (Strong, 1984). Experiments were performed to determine whether these effects of forskolin require cAMP. Intracellular injection of cAMP, application of membrane-permeable analogs of cAMP, application of phosphodiesterase inhibitors, and intracellular injection of the active catalytic subunit of cAMP-dependent protein kinase did not affect the amplitude or waveform of IA. Also, the changes in IA that are caused by forskolin were not prevented or reversed by intracellular injection of an inhibitor of cAMP-dependent protein kinase. Cyclic AMP did, however, activate inward current at voltages near the resting potential. We conclude that the changes in IA and the activation of inward current represent separate affects of forskolin. The inward current appears to depend on an increase in intracellular cAMP, while the changes in IA do not. These experiments show that, in addition to activating adenylate cyclase, forskolin may have a separate direct affect on the transient K current.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1983

A comparison of cisplatin and the combination of cisplatin and cyclophosphamide in advanced urothelial cancer. A National Bladder Cancer Collaborative Group A Study.

A prospective multi-institutional randomized trial compared the use of cisplatin (DDP) alone to the combination of DDP and cyclophosphamide in patients with advanced urothelial cancer. Patients were stratified according to measurable or evaluable tumor and performance status. The dose of DDP was 70 mg/m2 and the initial dose of cyclophosphamide was 750 mg/m2. There were ten objective responders (20%), including five complete responders, among the 50 evaluable patients who received DDP alone, and seven responders (11.9%), three complete, among the 59 receiving the combination therapy. Approximately one third of the patients in each treatment arm were stable at the nine-week evaluation. There was no statistical significance between the response rates in the two treatment arms.

Cisplatin↗
PubMed1981

Phytochrome Control of Maize Coleoptile Section Elongation : A RAPID LOSS OF PHOTOREVERSIBILITY.

A rapid loss of far red light (FR) reversibility of red-light (R) stimulated elongation of maize coleoptile sections was observed. Reversal was not possible when the interval between R and FR treatment was greater than 45 seconds. Most of the R-stimulated elongation occurred during the first 15 hours after irradiation.Exogenous gibberellic acid did not alter the time course of R/FR reversibility loss. These results are interpreted as indicating independence of R- and gibberellic acid-stimulated elongation in this system.

Journal Article↗
PubMed1980

Unexplained hepatitis following halothane: case report.

A 50-year-old woman suffered severe jaundice following a second anaesthetic, two weeks after an anesthetic which had been followed by fever and malaise. An initial diagnosis of "probable halothane hepatitis" was made. This diagnosis is discussed, together with some implications.

Anesthetics↗
PubMed1980

Relationship of dietary regimens to success, efficiency, and cost of weight loss.

One hundred twenty-five subjects in a behaviorally oriented, weight loss program that used several dietary patterns were retrospectively grouped according to the percentage of time they followed one of four dietary regimens: (a) Group 1--partial fasting, 400 kcal; (b) group 2--600 kcal; (c) group 3--1,200 to 1,500 kcal; and (d) group 4--failure to diet. The groups were described and compared regarding program completion, i.e., success and cost of weight loss. Groups 1 and 2 did significantly better than the other two in nearly all respects. Group 1 did better than Group 2 on program completion; the reverse was true when success of those completing 75 and 100 per cent of the program was compared. Groups 1 and 2 did not differ significantly on success variables.

Adult↗
PubMed1979

Marriage matters.

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Education, Medical, Graduate↗
PubMed1976

Early onset of oral cancer among women who drink and smoke.

Potentially, one of the most useful warning signals for the detection of environmental hazards is an unusually early age at onset of disease. Animal studies have shown age effects of this type with co-carcinogens. A clearcut example of a downward age shift in humans is provided by a study of the consumption of alcoholic beverages and cigarettes in women with oral concer. Using data on 145 white females with intraoral cancer, and 1973 non-neoplastic controls from patients seen at Roswell Park Memorial Institute between 1957 and 1966, it can be shown that exposure to both alcohol and tobacco can lead to onset of oral cancer 15 or more years earlier than would occur in women who do not use either alcohol or tobacco. Exposure to smoking only produces a smaller age shift, but exposure to alcohol only does not produce any clear shift in age of onset. Implications for co-carcinogenesis and for early detection of co-carcinogens in the environment are suggested.

Adult↗
PubMed1975

Marital and reproductive experience in a community-wide epidemiological study of breast cancer.

The relationship of marital and reproductive experience to human breast cancer was studied using data collected during 1956-1962 by the Department of Biostatistics and Epidemiology at the Roswell Park Memorial Institute in Buffalo, New York. Information of epidemiological interest was obtained from all women with cancers of the reporductive organs in Buffalo, New York, and the adjoining township of Kenmore. For comparison, a probability sample of the same population was selected. During 1965-1967, an International Collaborative Study with similar objectives found a striking positive relationship between age at first birth and breast cancer risk. This finding can be interpreted as either indicating that an event associated with first birth at an early age protects against the development of breast cancer or that the hormonal status of a women both produces a delay in a woman becoming pregnant and increases the risk of developing breast cancer. The analysis of marital and reproductive histories in the Buffalo population study confirms previous reports of an increasing risk of breast cancer with increasing age at first birth. Attempts to distinguish the two interpretations mentioned by analyzing the interval between first marriage and time of birth in addition to age at first birth were not conclusive. This necessitated a similar analysis of data available in a larger series of 1164 breast cancer patients and 1200 non-neoplastic controls hospitalized at the Roswell Park Memorial Institute during 1957-1965. The results do not show an influence of interval between first marriage and first birth but do show an increased risk of breast cancer with increasing age at first birth. The results are thus consistent with a protective effect of an earyl age at first birth. These findings also have a bearing on recent suggestions that ovulatory failure predisposes to development of breast cancer.

Adult↗