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Biomedical subjects

J A Saunders

Publications and source records attributed to J A Saunders.

At least 37 records · Page 2Linked to original sources
PubMed1986

A versatile low-cost apparatus for cell electrofusion and other electrophysiological treatments.

Instrumentation is described which will generate AC fields and DC square pulses for cell electrofusion, electroporation and other electrophysiological experiments. The equipment can generate a constant or intermittent AC field and a single square pulse, either alone or in combination. It can also generate a train of intermittent square pulses. The components for the instrumentation are commercially available and can be assembled by persons with little or no training in electronics. A design is given for a mass treatment chamber that can be easily constructed and viewed with a microscope.

Cell Physiological Phenomena↗
PubMed1986

Behavior and viability of tobacco protoplasts in response to electrofusion parameters.

This investigation examines responses of protoplasts in a systematic and quantitative way to the various electrical treatments used to achieve electrofusion and their individual and cumulative effect on protoplast viability. Mesophyll and cell suspension protoplasts from two species of the same genera, Nicotiana tabacum and N. rustica var brasilia were used in these experiments. Optimal frequencies for alignment of tobacco protoplasts were between 500 kilohertz and 2 megahertz at 100 volts per centimeter. Variations in frequency and voltage of the alternating current (AC) field caused predictable movements of protoplasts within an electrofusion chamber. AC frequencies below 10 hertz or above 5 megahertz significantly decreased the viability of protoplasts in the fusion chamber as estimated by fluorescein diacetate staining 1 hour after treatment. Although the direct current (DC) pulse appeared to have a slight detrimental effect on protoplast viability, this effect was not significantly different from untreated control preparations.Protoplasts from both leaf mesophyll cells and suspension cells were induced to fuse with one or more 10 to 30 microseconds DC square wave pulses of approximately 1 kilovolt per centimeter after the protoplasts had been closely appressed with an AC field.

Journal Article↗
PubMed1985

9-1-1 implementation: implications for poison center access.

House Bill 3178, passed by the 1981 Oregon Legislature, requires state-wide participation in a 9-1-1 emergency telephone system by 1991. It further requires deletion of all emergency telephone numbers other than 9-1-1 from the front cover of all telephone directories. The gradual implementation of 9-1-1 provided a unique opportunity to study telephone access to the poison center. The impact of 9-1-1 implementation was assessed, in a two-month survey of calls from the general public, to determine awareness of 9-1-1 availability and the source used to gain access to the poison center. Results showed that most callers (72%) had access to and were aware of 9-1-1. Callers obtained the poison center number from the telephone directories (28%), health care providers (19%), poison symbols supplied by the poison center (15%), directory assistance (9%), or other sources. Only 3% of the callers were referred from 9-1-1. State-wide implementation of 9-1-1 will have a major impact on the public's access to the poison center. The results of this study will be used to develop strategies for cooperation with 9-1-1 agencies.

Information Services↗
PubMed1984

Localization and Substrate Specificity of Glycosidases in Vacuoles of Nicotiana rustica.

Vacuoles isolated from Nicotiana rustica var brasilia have been shown to contain significant levels of glycosidase activity when assayed using p-nitrophenyl-glycosides as substrates. The substrate specificity for the glycosidases in the vacuolar fraction closely paralleled that found in the protoplasts, and the leaf tissue from which the vacuoles were isolated. The substrate specificity of the vacuolar enzyme(s) was different from glycosidic activity found in the commercial digestive enzyme preparations used to isolate the protoplasts from leaf tissue. It was demonstrated that 70 to 90% of the glycosidases that were found in the protoplasts appeared to be localized within the vacuole, when the p-nitrophenyl substrates alpha- and beta-;d-galactose, beta-d-glucose, and alpha-d-mannose were used. Neither the vacuolar nor the protoplast enzymes were active towards the naturally occurring phenolic glycoside, rutin. alpha-Mannosidase appears to be a valuable marker enzyme for vacuoles isolated from mesophyll leaf cells of tobacco.

Journal Article↗
PubMed1979

Investigations of vacuoles isolated from tobacco: I. Quantitation of nicotine.

Nicotine was shown to be associated with mature vacuoles isolated from protoplasts of Nicotiana rustica. The vacuolar preparations also contained high levels of acid phosphatase, ATPase, and approximately 30% of the soluble protoplastic protein. The contamination of the vacuolar isolate by chlorophyll, succinate dehydrogenase, and NADPH cytochrome c reductase (markers for chloroplasts, mitochondria, and endoplasmic reticulum) was low. The enzymic activity associated with the vacuoles was not due to the exogenously supplied digestive enzymes used in the preparation of the protoplast. The relatively easy isolation of tobacco vacuoles makes this an excellent system for biochemical investigations of the vacuole.

Journal Article↗
PubMed1978

Presence of the cyanogenic glucoside dhurrin in isolated vacuoles from sorghum.

Large numbers of vacuoles (10(6)-10(7)) have been isolated from Sorghum bicolor protoplasts and analyzed for the cyanogenic glucoside dhurrin. Leaves from light-grown seedlings were incubated for 4 hours in 1.5% cellulysin and 0.5% macerase to yield mesophyll protoplasts which then were recovered by centrifugation, quantitated by a hemocytometer, and assayed for cyanogenic glucosides. Mature vacuoles, released from the protoplasts by osmotic shock, were purified on a discontinuous Ficoll gradient and monitored for intactness by their ability to maintain a slightly acid interior while suspended in an alkaline buffer as indicated by neutral red stain. Cyanide analysis of the protoplasts and the vacuoles obtained there from yielded equivalent values of 11 mumoles of cyanogenic glucoside dhurrin per 10(7) protoplasts or 10(7) vacuoles. This work supports an earlier study from this laboratory which demonstrated that the vacuole is the site of accumulation of the cyanogenic glucoside in Sorghum.

Journal Article↗
PubMed1977

Rickets in children receiving anticonvulsant drugs. Biochemical and hormonal markers.

Forty-one epileptic children, aged 2 to 16 years, receiving combinations of phenobarbital, phenytoin, and primidone, and 39 control children were studied. The epileptics demonstrated slight but significant reductions in serum calcium, phosphorus, and 25-hydroxyvitamin D concentrations, and a significant increase in serum alkaline phosphatase values. No significant difference in serum immunoreactive parathyroid hormone levels was noted. Further analysis of the data revealed that patients whose drug therapy included primidone had the lowest serum levels of calcium and 25-hydroxyvitamin D. They had also received the largest number of drugs for the longest duration, and had serum phenobarbital levels that were significantly higher than those of other patients. The minimal degree of vitamin D deficiency in our epileptic children contrasts with the results of other investigations and warrants emphasis. The reasons for this difference are not apparent.

Adolescent↗
PubMed1977

Subcellular localization of the cyanogenic glucoside of sorghum by autoradiography.

The use of microautoradiography at the electron microscopic level indicates that the vacuole is the site of accumulation of the cyanogenic glucoside of Sorghum bicolor. When a specific biosynthetic precursor of dhurrin, p-hydroxy[3,5-(3)H]phenylacetaldoxime, was used, 90% of the tritium label was recovered in the vacuoles of tissue prepared for microautoradiography. l-[3,5-(3)H]Tyrosine and d-[1-(3)H(N)]glucose, nonspecific precursors of dhurrin, of differing solubilities and biosynthetic capacity, were also fed to the shoots. The data obtained from these controls indicated that the high recovery of label in the vacuole of aldoxime-fed shoots was not indicative simply of the size of the vacuole, nor was it a result of movement of labeled compounds during preparation of the tissue for electron microscopy. The problem of movement of these labeled compounds during dehydration of tissue was dramatically reduced by chemical dehydration in 2,2-dimethoxypropane in less than 30 minutes rather than with routine dehydration in acetone or alcohol series for 24 hours.

Journal Article↗
PubMed1977

Localization of Cinnamic Acid 4-Monooxygenase and the Membrane-bound Enzyme System for Dhurrin Biosynthesis in Sorghum Seedlings.

The localization of three monooxygenase (hydroxylase) enzyme systems which occur in dark-grown seedlings of Sorghum bicolor has been studied. Cinnamic acid 4-hydroxylase (CAH) (trans-cinnamate 4-monooxygenase, EC 1.14.13.11), which has been increasingly utilized in plants as a marker for the endoplasmic reticulum, migrated with that fraction in continuous and discontinuous sucrose gradients. When 10 mm MgCl(2) was used to shift the density banding of the marker enzyme, NADPH cytochrome c reductase, from 1.12 to 1.17 g/cm(3), the CAH activity was displaced as well.The membrane-bound enzyme system involved in the biosynthesis of the cyanogenic glucoside dhurrin was also shown to be closely associated with the endoplasmic reticulum. This system contains hydroxylases capable of hydroxylating tyrosine to form N-hydroxytyrosine and hydroxylating p-hydroxyphenylacetonitrile to form p-hydroxy-(S)-mandelonitrile.

Journal Article↗
PubMed1974

The Suitability of a Quantitative Spectrophotometric Assay for Phenylalanine Ammonia-lyase Activity in Barley, Buckwheat, and Pea Seedlings.

It has been suggested by others that the spectrophotometric assay of phenylalanine ammonia-lyase based on changes in absorbance at 290 nm may be complicated by a side reaction involving transamination from phenylalanine onto alpha-keto acids. This would lead to the production of phenylpyruvate which would spontaneously tautomerize and form an enol borate complex absorbing at this wavelength. We find that the inclusion of 1 ml of either 60 mum alpha-ketoglutarate or 500 mum phenylpyruvate in our 3-ml reaction mixtures has no significant effect on the spectrophotometric assay of phenylalanine ammonia-lyase in shoots from young seedlings of barley (Hordeum vulgare), buckwheat (Fagopyrum esculentum), or pea (Pisum sativum). Although these side reactions may be involved in preparations with very low enzyme activity, the spectrophotometric determination of phenylalanine ammonia-lyase based on changes in absorbance at 290 nm appears to be a reliable and sensitive technique in these seedlings.

Journal Article↗