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Biomedical subjects

K Summers

Publications and source records attributed to K Summers.

32 records · Page 2Linked to original sources
PubMed1988

A comparison of two ranitidine intravenous infusion regimens in critically ill patients.

The effect of two ranitidine intravenous infusion regimens on intragastric pH was studied in 134 critically ill patients admitted to 15 intensive care units. Intragastric pH was determined hourly for 30 hours. Those patients whose intragastric acidity fell below pH 4.0 for 3 or more of the first 6 hours were considered 'at risk' of developing stress-related gastric lesions and randomized to receive a 50 mg bolus of ranitidine together with a continuous intravenous infusion of either 0.125 or 0.25 mg kg-1 h-1 ranitidine for 24 hours. The maximal elevation in intragastric pH was achieved within 12 hours. The median intragastric pH for the last 20 hours of the infusion period was 5.9 for the higher dose group and 5.6 for the lower dose group. The increase in intragastric pH achieved by the two dosage regimens did not differ significantly throughout the 24 hour period. Patients having two or more of five major risk factors (head injury, major trauma, sepsis, respiratory failure/insufficiency and major surgery) had better overall control of intragastric pH on the higher dose of ranitidine than those receiving the lower dose. The majority of intensive care patients are likely to receive satisfactory treatment with the lower dosage regimen that was tested (0.125 mg kg-1 h-1). Those with multiple risk factors may, however, require treatment with higher doses of ranitidine (0.25 mg kg-1 h-1).

Adolescent↗
PubMed1987

Ranitidine and cimetidine in the healing of duodenal ulcer: meta-analysis of comparative clinical trials.

All available ranitidine and cimetidine comparative trials in acute duodenal ulcer disease were examined: of the 44 trials, 36 favoured ranitidine, and there was an overall difference in ulcer healing of 7%. Further stratification enabled examination of trials with common attributes: the most frequent endoscopic assessment was at 4 weeks to compare ranitidine 150 mg twice daily with cimetidine 1 g day-1 or 400 mg b.d. Twenty of these trials had sufficient data to permit pooling. Ranitidine was favoured in 18/20 trials and in three the differences achieved statistical significance. Results of the trials were combined using meta-analysis to calculate differences in ulcer healing. Most studies had sample sizes that were insufficient to detect clinically-important differences; the power to detect a 20% difference was less than 80% in 15/20 trials, and for a 10% difference was less than 80% in all but one trial. Fifteen trials compared ranitidine 150 mg b.d. with cimetidine 1 g day-1: healing after 4 weeks therapy was overall 6% greater for ranitidine. This was statistically significant (P less than 0.05) and the combined total number of patients had a power of 83% to detect this difference. In five trials the dose of cimetidine used was 400 mg b.d.: the 12% difference in healing in favour of ranitidine 150 mg b.d. was statistically significant, and the combined trials had a power of 95% to detect this difference. Ranitidine 150 mg twice daily heals significantly more duodenal ulcers after 4 weeks of therapy than either cimetidine 400 mg b.d. or cimetidine 1 g day-1.

Cimetidine↗
PubMed1986

A single nighttime dose of ranitidine 300 mg versus ranitidine 150 mg twice daily in the acute treatment of duodenal ulcer: a European multicenter trial.

Six hundred and five patients with endoscopically diagnosed duodenal ulcer were randomly allocated to treatment with ranitidine 300 mg at night or ranitidine 150 mg twice daily in a prospective double-blind multicenter trial conducted in nine European countries. Endoscopy at 4 weeks showed complete ulcer healing in 246 of 301 patients (82%) treated with ranitidine 150 mg b.i.d. and 230 of 304 patients (76%) treated with ranitidine 300 mg at night. Cumulative healing rates at 8 weeks were 95 and 94% respectively. Both treatment regimens were equally effective at rapidly reducing the incidence of ulcer-related symptoms. Adverse events were few and consistent with those reported in previous studies with ranitidine 150 mg twice daily. The results of this trial indicate that a single nighttime dose of ranitidine is an effective and safe alternative to the twice daily regimen in the acute treatment of duodenal ulcer.

Adult↗
PubMed1986

A single night time dose of ranitidine in the acute treatment of gastric ulcer: a European multicentre trial.

Four hundred and twenty eight patients with endoscopically diagnosed gastric ulcers, randomly allocated to treatment with ranitidine 300 mg at night or ranitidine 150 mg twice daily, were evaluated in a double blind multicentre trial conducted in 10 European countries. After four weeks, complete ulcer healing was observed in 138 of 211 patients (65%) treated with ranitidine 300 mg nocte and in 155 of 217 patients (71%) receiving 150 mg bd. Cumulative healing rates at eight weeks were 90% and 93%, respectively. There was no statistically significant difference between the healing rates at either four or eight weeks. The treatment regimens were equally effective at rapidly reducing the incidence of ulcer related symptoms. Adverse events reported were minor and equally distributed between the two groups. The results of this trial show that 300 mg of ranitidine administered at night is an effective and safe alternative to the current twice daily regimen for the short term treatment of gastric ulcer.

Administration, Oral↗
PubMed1984

The influence of enterogastric reflux on gastric juice bacterial growth, nitrite, and N-nitroso compound concentrations following gastric surgery.

Detailed analyses were carried out in 207 fasting gastric juice samples obtained at endoscopy or with a nasogastric tube from 50 patients with partial gastrectomy, 43 with vagotomy, 20 with gastric carcinoma and 50 controls. Significantly higher mean pH, nitrite and N-nitroso compound (N-NO) concentrations and nitrate-reducing bacterial cultures were noted following partial gastrectomy compared with normal controls and comparable to findings in gastric cancer. A highly significant relationship (p less than 10(-6)) was also demonstrated between pH and N-NO concentrations, highest levels of which were seen following Billroth II gastrectomy, significantly higher (p = 0.02) than Billroth I, whereas the only change observed following proximal gastric vagotomy was a nearly threefold rise in N-NO compared with normal controls. However, vagotomy and pyloroplasty produced gastric juice changes comparable to those seen with gastrectomy and gastric carcinoma. Thus, the most marked changes were observed following surgical procedures involving increased enterogastric reflux and these findings lend further support to the possible involvement of N-nitroso compounds in the development of gastric cancer following both Billroth I and II gastrectomy and vagotomy with pyloroplasty.

Carcinoma↗
PubMed1979

Characteristics of the polar assembly and disassembly of microtubules observed in vitro by darkfield light microscopy.

We describe here the continuous observations of the polymerization of individual microtubules in vitro by darkfield microscopy. In homogeneous preparations we verify that polymerization can occur onto both ends of microtubules. The assembly of microtubules is polar, with one end growing at three times the rate of the other. The differential rate of elongation can be used to determine the polarity of growth off cellular nucleating centers. We show that the microtubules grow off the proximal end of ciliary axonemes at a growth rate equal to that of the slow growing end of free microtubules, while growth off the distal end proceeds at the same rate as the fast growing end. Applying this technique to microtubule growth from metaphase chromosomes isolated from HeLa and CHO cells, we demonstrate that chromosomes initiate polymerization with the fast growing end facing away from the chromosome nucleation site. The opposite ends of free microtubules show different sensitivities to microtubule depolymerizing agents such as low temperature, Ca++ or colchicine as measured directly by darkfield microscopy. The differing rates of assembly and disassembly of each end of a microtubule suggest that a difference in polarity of growth off nucleating sites could serve as one basis for regulating the polymerization of different groups of microtubules in the same cell.

Animals↗
PubMed1974

A functional mitotic spindle prepared from mammalian cells in culture.

MITOTIC CELLS LYSED INTO SOLUTIONS OF POLYMERIZABLE MICROTUBULE PROTEIN CONTAIN A SPINDLE WHICH IS SIMILAR TO THE LIVING SPINDLE IN TWO RESPECTS: it will lose and gain birefringence when cooled and warmed, and it will move anaphase chromosomes to the opposite ends of the cell. Early anaphase cells lysed into buffers containing high molecular weight polyethylene glycol and nucleotide triphosphates will continue chromosome motion and spindle elongation in the absence of exogenous spindle subunits. These results suggest that while spindle growth requires microtubule polymerization, anaphase motions do not.

Animals↗
PubMedDate not supplied

Cost-effectiveness of initial therapy with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors to treat hypercholesterolemia in a primary care setting of a managed-care organization.

From January 1994 through May 1995, Prudential HealthCare-North Texas prospectively studied 299 member patients diagnosed with hypercholesterolemia for whom pharmacotherapy with one of four 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, also known as statins, was prescribed. The purpose of this study was to measure the relative cost-effectiveness (CE) of these drugs in a real-world setting. This study provides information to assist decision makers in managed-care organizations (MCO) in making formulary selections. The study used a prospective, randomized, balanced cohort design, examining patients who had been prescribed initial therapy with a statin drug as monotherapy. Costs (direct medical and indirect costs) and effectiveness (percent reduction in low-density lipoprotein cholesterol levels) were based on approximately the first 6 months of initial therapy. Both the MCO and patient perspectives were considered. In the base case, mean CE ratios were significantly lower for fluvastatin compared with lovastatin, pravastatin, and simvastatin from both the managed-care perspective and the patient perspective. Sensitivity analysis did not alter the CE conclusions, even under conditions of varying cost structures. Although differences were found in the effectiveness of lovastatin, pravastatin, and simvastatin measured in this study versus efficacy measured for these drugs in controlled clinical trials, sensitivity analysis suggests that these differences alone do not determine the superior CE of fluvastatin. Finally, this study supports the idea that well-designed formularies should consider drug CE (based on safety, effectiveness, and cost) and that integration of the pharmacy benefit management with other medical management is essential. These results provide evidence that fluvastatin may represent a more cost-effective formulary choice among statin products used for initial monotherapy of hypercholesterolemia.

Adult↗
PubMedDate not supplied

Phenotypic and genetic divergence in three species of dart-poison frogs with contrasting parental behavior.

Why some species exhibit remarkable variation among populations while closely related species are relatively uniform remains unclear. The strawberry dart-poison frog (Dendrobates pumillo) exhibits spectacular color and pattern polmorphism among populations in the Bocas del Toro archipelago of Panama. In contrast, two other sympatric species of dart-poison frog, Phyllobates lugubris and Minyobates sp., show little color or pattern variation among island populations. Here we demonstrate that the color and pattern variation among populations of D. pumilio is not matched by higher levels of mitochondrial DNA sequence divergence relative to P. lugubris or Minyobates sp. Thus, neutral divergence in allopatry is unlikely to have caused the geographical differences observed in D. pumilio. We suggest that strong sexual selection associated with female parental care in D. pumilio, which contrasts the male parental care of P. lugubris and Minyobates sp., may have driven divergence in coloration and pattern in D. pumilio.

Animals↗
PubMedDate not supplied

Communicating an evolutionary diagnosis of disability to parents.

Communicating a diagnosis of disability to parents, when the diagnosis and prognosis are unclear, is problematic. This is discussed in the light of information received from mothers of such children who attended a counselling and support group. It is concluded that dissatisfaction with diagnosis is not inevitable, if similar guidelines to those suggested for children with Down's syndrome are used. It is essential that parents are involved in management and feel they have something practical to do to help their children. Clinics must organize themselves to avoid swamping parents with information and to provide regular ongoing support.

Adult↗