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Biomedical subjects

I K Smith

Publications and source records attributed to I K Smith.

At least 73 records · Page 4Linked to original sources
PubMed1983

Partial Purification and Characterization of Cystine Lyase from Cabbage (Brassica oleracea var capitata).

Cabbage (Brassica oleracea var capitata) leaves were used as a source of cystine lyase. Diethylaminoethyl-cellulose chromatography resolved two peaks of activity, designated I and II.Cystine lyase I (molecular weight 145,000) and O-acetylserine sulfhydrylase (molecular weight 70,000) were resolved by Bio-Gel A-0.5M chromatography. This isozyme catalyzed an alpha,beta-elimination reaction with cystine, cysteine, O-acetylserine, and several S-substituted cysteines. The substrate specificity was similar to previously reported S-alkylcysteine lyases. The elution profiles during purification, and heat inactivation studies indicated that the above reactions were catalyzed by a single protein. The pH optimun with cystine and cysteine as substrate was 8.5 to 9.0, and the K(m) values were: cystine (0.3 mm), cysteine (0.3 mm), O-acetylserine (6 mm), and S-methylcysteine sulfoxide (1.8 mm).Cystine lyase II was resolved into three peaks (molecular weight greater than 500,000, 240,000, and 145,000) using Bio-Gel A-0.5M chromatography. This enzyme degraded l-cystine, l-cysteine, O-acetylserine, S-methylcysteine sulfoxide, and djenkolic acid. The pH optimum with cystine and cysteine was 8.5 to 9.0, and the K(m) values were: cystine (0.3 mm), cysteine (0.3 mm), O-acetylserine (12.5 mm), and S-methylcysteine sulfoxide (3.7 mm).

Journal Article↗
PubMed1983

Guidelines for planning faculty development workshops.

This article presents guidelines for developing workshops based on practical experience and a review of the literature. Health science faculty tend to prefer workshops as a method of learning. However, the success of a workshop depends on thoughtful planning. The needs and expectations of participants should be thoroughly assessed. Workshop leaders must be competent, enthusiastic, and flexible; they must create a successful adult learning environment, especially for professionals with teaching experience. Evaluation of workshops should include both formative and summative methods.

Curriculum↗
PubMed1981

Sulfate Transport in Cultured Tobacco Cells : EFFECTS OF CALCIUM AND SULFATE CONCENTRATION.

Sulfate transport by tobacco cells (var. Xanthi) cultured in liquid medium was investigated. Monophasic uptake was observed over a sulfate concentration range from 0.01 to 10 millimolar, and the K(m) was 20 micromolar. A time-dependent stimulation of transport was observed when cells were incubated in medium containing 0.5 millimolar Ca(2+). Calcium stimulation was dependent on the culture cycle and was maximal during the early exponential phase. It was not observed in sulfur-deficient cells with high transport rates and was relatively small in sulfate-loaded cells with low transport rates. A kinetic analysis showed that Ca(2+) increased the maximum rate of transport without affecting the K(m).

Journal Article↗
PubMed1981

Compartmentation of Sulfur Metabolites in Tobacco Cells : USE OF EFFLUX ANALYSIS.

The distribution of sulfur-containing metabolites in cultured tobacco cells was determined by analyzing efflux kinetics. Transported sulfate rapidly labeled the cytoplasmic pools of sulfate (1 hour) and sulfur amino acids (6 hours). Excess sulfate and amino acids were transported into the vacuole. The size and distribution of the amino acid pool was not affected by increasing the sulfate content of the cells.Transported cysteine was rapidly degraded to sulfate. The cytoplasmic pools of sulfate and amino acids were completely labeled within 6 hours, whereas the vacuolar pools were labeled more slowly. The intracellular cysteine pool was elevated by decreasing the pH of the transport medium. In all experiments, between 60 and 90% of the label was present in the vacuole.

Journal Article↗
PubMed1981

Factors relating to aldosterone secretion rate, the excretions of aldosterone 18-glucuronide, and the plasma aldosterone concentration in cirrhosis.

In a group of eight patients with cirrhosis the rate of renal excretion of the 18-glucuronide metabolite of aldosterone (U Aldo V) was found to be closely related to the aldosterone secretion rate (ASR). U Aldo V was therefore used as an index of ASR in a further group of fifty patients in order to evaluate the possible importance of factors known to regulate aldosterone secretion. U Aldo V showed statistically significant relationships to both plasma renin activity (PRA) and the plasma sodium concentration (P Na), but not to the plasma potassium concentration (PK) or the renal excretion of cortisol (U Cort V), the latter sued as an index of adrencorticotrophic hormone activity. The plasma aldosterone concentration (P Aldo) was determined in fifty-eight patients and also found to show statistically significant relationships to PRA and P Na. P Aldo showed a weak, though statistically significant, relationship to PK, but not to U Cort V. These findings are in keeping with a role for the renin-angiotensin system in the control of aldosterone secretion in cirrhosis although evidence from other studies suggest other factors to be involved also. Whether P Na was another determinant of ASR, or whether aldosterone was a determinant of P Na through regulating sodium reabsorption by the proximal tubule of the nephron, is uncertain.

Adult↗
PubMed1981

Continuing education needs assessment in dentistry: the SNAP system.

Needs assessment has become an integral step in planning for continuing education. This article describes a computer-based needs assessment system that has been used successfully in planning continuing dental education in South Carolina. The Statewide Needs Assessment Program (SNAP) provides a general purpose system for collecting and analyzing continuing education needs data for large populations. Needs assessment data from 489 practicing dentists in South Carolina are presented and analyzed.

Computers↗
PubMed1980

Cysteine metabolism in cultured tobacco cells.

Transported l-[(35)S]cysteine was rapidly metabolized by cultured tobacco cells when supplied to the cells at 0.02 millimolar or 0.5 millimolar. The internal cysteine pool was expandable to approximately 2400 nmoles per gram fresh weight.The (35)S label derived from cysteine was found in several metabolites. The amount of label in glutathione and sulfate was directly proportional to the internal l-[(35)S]cysteine, while the levels of labeled methionine and protein were apparently independent of internal labeled cysteine. Cysteine was more rapidly metabolized when the external cysteine concentration was low (0.02 millimolar) with up to 90% of the (35)S label present as compounds other than cysteine.The initial step in cysteine degradation yielded pyruvate, sulfide, and presumably NH(4) (+). Stoichiometry studies using extracts prepared from acetone powders of tobacco cells indicated that pyruvate and sulfide were produced in a 1:1 ratio. The catabolic reaction was linear with respect to time and amount of protein and had a pH optimum of 8 in crude extracts. Preliminary kinetic data indicated the K(m) to be approximately 0.2 millimolar. The extractable degradative activity was enhanced 15- to 20-fold by preincubating the cells for 24 hours in 0.5 millimolar cysteine. The extractable specific enzyme activity roughly reflected the growth curve of the cells in culture. Maximal cysteine degradation was observed in extracts prepared from late log phase cultures that were preincubated in cysteine, while little activity was found in similar extracts from stationary phase cultures. These results are consistent with an inducible catabolic enzyme similar to the cysteine desulfhydrase from bacteria.

Journal Article↗
PubMed1980

Regulation of Sulfate Assimilation in Tobacco Cells: EFFECT OF NITROGEN AND SULFUR NUTRITION ON SULFATE PERMEASE AND O-ACETYLSERINE SULFHYDRYLASE.

The effect of nitrogen and sulfur nutrition on sulfate permease and O-acetylserine sulfhydrylase was studied in tobacco cells.Sulfate transport rates increased 10-fold in cells transferred to sulfur-deficient B-5 medium. The addition of either sulfate or l-cysteine reduced transport 95 and 80%, respectively. The pools of sulfate, cysteine, glutathione, and methionine declined in sulfur-starved cells. The addition of either sulfate or l-cysteine increased the pools of sulfur-containing compounds, but major quantitative differences were measured. Nitrogen-starved cells had low transport rates which were not increased by addition of nitrate/ammonia. The pools of sulfate, cysteine, and methionine were high in nitrogen-starved cells and remained high upon addition of a nitrogen source. The results show that sulfate transport is regulated by the intracellular sulfate pool.O-Acetylserine sulfhydrylase was not affected by sulfur nutrition. The extractable activity was high in B-5-grown cells, sulfur-deficient cells, and cells to which either sulfate or l-cysteine had been added. In contrast, the enzyme declined in cells transferred to nitrogen-deficient medium and the amount of enzyme/g fresh weight increased 10-fold when nitrate/ammonia was added. The addition of nitrate/ammonia had no effect on the cysteine or methionine pools but increased the total amino acid pool. The amount of O-acetylserine was positively correlated with extractable enzyme activity. This enzyme is positively regulated by an effector (possibly O-acetylserine) which is high under conditions of net nitrate assimilation.

Journal Article↗
PubMed1979

Studies on mineralocorticoid 'escape' in cirrhosis.

1. The mineralocorticoid 9 alpha-fluorohydrocortisone was given to 12 patients with cirrhosis without ascites. In seven an 'escape' from its sodium-retaining effects was observed, the other five continuing to retain sodium. 2. Changes in plasma renin activity (PRA) and inulin clearance (Cinulin) were used in the assessment of possible changes in the 'effective' extracellular fluid volume. PRA fell and Cinulin increased to a similar extent in each of the two groups of patients. The findings do not support the concept that the failure to show the mineralocorticoid escape in some patients with cirrhosis is due to a failure of expansion of the effective extracellular fluid volume. 3. Sodium reabsorption in the different segments of the nephron as estimated by clearance techniques under conditions of maximal water diuresis showed that the greatest changes to account for both mineralocorticoid escape and sodium retention were in the part of the nephron beyond the diluting segment.

Adult↗
PubMed1979

A comparison of the effects of labetalol, bendrofluazide and their combination in hypertension.

1 Bendrofluazide (10 mg/day) or labetalol (300 mg and 600 mg/day) produced significant reductions in lying, standing, and post-exercise blood pressure in ten hypertensives. 2 Active treatments were approximately equivalent in anti-hypertensive effect. However, comparing lying and standing determinations, labetalol (600 mg/day) produced significantly greater additional postural falls in systolic blood pressure than during placebo or bendrofluazide treatment. 3 Systolic blood pressure rose after exercise during placebo or bendrofluazide treatment. However, on labetalol, mean changes in systolic blood pressure after exercise were negative and significantly different from those seen on placebo. 4 Greater reductions in lying and post-exercise systolic blood pressure were produced by combination treatment than by either individual drug. Additional postural and exercise-related falls in systolic blood pressure tended to be smaller with combination treatment than during treatment with labetalol alone. 5 Labetalol significantly reduced lying, standing, or post-exercise heart rate by comparison with placebo or bendrofluazide. 6 Labetalol significantly reduced lying, standing, or post-exercise heart rate by comparison with placebo or bendrofluazide. 6 Labetalol moderately reduced plasma renin activity, whereas bendrofluazide caused marked elevation. The effect of bendrofluazide predominated during combination treatment.

Adult↗
PubMed1979

Diuretic-induced renal impairment without volume depletion in cirrhosis: changes in the renin-angiotensin system and the effect of beta-adrenergic blockade.

In 4 patients with cirrhosis and ascites, diuretic therapy resulted in an impairment of renal function that was associated with a rise in plasma renin activity (PRA). In 3, this occurred in the absence of volume depletion. When diuretics were discontinued, renal function returned to normal. beta-adrenergic blocking drugs were then given to suppress renin secretion and diuretics restarted. On this occasion, impairment of renal function did not occur. In 2 further patients, administration of beta-adrenergic blockers during a period of diuretic-induced renal impairment resulted in an improvement in renal function. Although these findings may indicate that diuretic-induced renal impairment in cirrhosis is at least partly due to activation of the renin-angiotensin system, in another group of patients a diuretic-induced rise in PRA was not associated with a deterioration in renal function.

Adrenergic beta-Antagonists↗
PubMed1978

Abnormalities of renal transport of sodium o-[131I]iodohippurate (Hippuran) in essential hypertension.

1. Renal function has been studied in 312 hypertensive patients by quantitative renography with sodium o-[131I]iodohippurate (131I-labelled Hippuran) and estimation of overall effective renal plasma flow. In 59% of the patients the results were normal. 2. Severe hypertension was associated not only with reduced effective renal plasma flow but also a characteristic abnormality of Hippuran transport in 10% of the patients in which there was a wider than normal variation in transit times of Hippuran through the kidney, which may reflect non-uniformity of reabsorption of filtrate by different groups of nephrons. 3. Plasma renin activity was higher in a group of 14 patients with multimodal transit time spectra than in a matched hypertensive control group, with very substantial overlap between the two groups. 4. The renographic abnormality was usually reversed by treatment.

Blood Flow Velocity↗
PubMed1978

Role of calcium in serine transport into tobacco cells.

The transport of serine into tobacco (Nicotiana tabacum L. var. Xanthi) cells grown in liquid medium was studied. Serine transport was maximal below pH 4.0. A time-dependent stimulation of transport was observed when cells were incubated in medium containing 0.5 mm Ca(2+). Maximum transport rates were achieved after 6 hours preincubation in Ca(2+). The following three distinct roles of Ca(2+) in serine transport were demonstrated: time-dependent stimulation of transport rate, maintenance of high transport rates, and retention of transported material. Stimulation occurred in the presence of either Ca(2+) or Mg(2+) and was inhibited by either La(3+) or K(+). Removal of Ca(2+) from the transport medium caused a rapid decline in the rate of serine uptake. This decline was prevented by addition of La(3+) after Ca(2+) removal. Cells transferred to medium lacking Ca(2+) lost substantial amounts of transported serine, this loss was significantly reduced by either La(3+) or K(+).Cells placed in (45)Ca(2+) rapidly bound more than 3 micromoles of Ca(2+)/gram fresh weight, which was exchangeable within 10 minutes with medium Ca(2+). Seventy-five per cent of the (45)Ca(2+) transported into the cells in 4 hours could be exchanged with medium Ca(2+) in the same period. The amount of net Ca(2+) transport into tobacco cells is insignificant relative to the total exchangeable Ca(2+).It is proposed that serine transport into tobacco cells involves H(+) cotransport and that the stimulation by Ca(2+) is due to an increase in the proton-motive force.

Journal Article↗