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Biomedical subjects

J T Smith

Publications and source records attributed to J T Smith.

At least 91 records · Page 5Linked to original sources
PubMed1991

Twenty-four hour intragastric acidity and plasma gastrin concentration profiles in female and male subjects.

1. Simultaneous 24 h intragastric acidity and plasma gastrin concentration profiles were determined in 35 healthy young women and 96 healthy young men. 2. The females had a consistently lower median hourly intragastric acidity, and a higher median hourly plasma gastrin concentration, throughout the 24 h. 3. The 24 h integrated intragastric acidity was significantly lower in the female group (females, 485 mmol.h.l-1; males, 842 mmol.h.l-1. P less than 0.001). The 24 h integrated plasma gastrin concentration was significantly higher in the female group (females, 407 pmol.h.l-1; males, 185 pmol.h.l-1; P less than 0.001).

Adult↗
PubMed1991

Long-term scintigraphic appearance of extremities following bone tumor resection and allograft reconstruction.

The authors retrospectively reviewed the Tc-99m medronate scan findings in six patients who had no evidence of metastatic disease following en bloc resection of a primary osteosarcoma and subsequent limb reconstruction using allograft bone. Persistently increased radionuclide uptake was noted at the junction between the host bone and the graft, while the graft cortical bone showed persistently decreased activity. Radionuclide uptake at the periphery of the graft varied. Over time the youngest patient in the series had increasingly normal scan findings.

Adolescent↗
PubMed1991

Protein- and RNA-synthesis independent bactericidal activity of ciprofloxacin that involves the A subunit of DNA gyrase.

Ciprofloxacin, unlike nalidixic acid, can kill Escherichia coli cells in the absence of synthesis of protein or RNA. Hence, chloramphenicol or rifampicin do not abolish the bactericidal activity of ciprofloxacin against wild-type E. coli. Protein and RNA synthesis were not required for the bactericidal activity of ciprofloxacin against nalB, nalC and nalD mutants of E. coli. However, the addition of chloramphenicol or rifampicin abolished the bactericidal activity of ciprofloxacin against a nalA mutant in nutrient broth. It is concluded that the ability of ciprofloxacin to kill E. coli in the absence of protein or RNA synthesis involves the A subunit of DNA gyrase.

Cell Membrane Permeability↗
PubMed1991

4-Quinolone interactions with gyrase subunit B inhibitors.

In studies which have involved determination of fractional inhibitory concentrations, synergy has been described between the 4-quinolones, which inhibit the A subunit of DNA gyrase, and either coumermycin or novobiocin, which inhibit the B subunit of the same enzyme. In this study, fixed concentrations of ciprofloxacin or ofloxacin were combined with varying concentrations of coumermycin or novobiocin and vice versa in nutrient broth. The bactericidal activities of the different mixtures against either Staphylococcus aureus E3T or S. warneri were determined and found to be less than those of equivalent concentrations of either 4-quinolone alone. The observation that gyrase B subunit inhibitors antagonised the bactericidal activity of 4-quinolones is in accordance with the report previously made by others that ciprofloxacin combined with coumermycin was less effective than ciprofloxacin alone in treating staphylococcal endocarditis in rats. Our results indicate that both inhibitory and bactericidal activity should be taken into account when assessing possible interactions in vivo between 4-quinolones and other antimicrobial agents.

Aminocoumarins↗
PubMed1991

Eradication of Helicobacter pylori abolishes 24-hour hypergastrinaemia: a prospective study in healthy subjects.

In a prospective study, eight young healthy subjects (five with an active H. pylori infection in the antral mucosa) were treated with a course of tripotassium dicitrato bismuthate, amoxycillin and metronidazole. The triple therapy eradicated infection when assessed 20-24 weeks later by antral biopsy (urease, histology, and 13C urea breath test [4 out of 5 subjects]). Twenty-four hour intragastric acidity and plasma gastrin concentration were measured before treatment, and 4-6 weeks and 20-24 weeks post-treatment. Treatment did not affect acidity in either the H. pylori-positive or H. pylori-negative groups, nor did it affect the plasma gastrin profile in the H. pylori-negative group. Eradication of H. pylori infection in five subjects caused a drop of the median integrated 24-hour plasma gastrin concentration from 558 pmol.h/L before treatment to 307 and 289 pmol.h/L at 4-6 and 20-24 weeks post-treatment, respectively. It is concluded that H. pylori infection is associated with 24-hour hypergastrinaemia, and that in apparently healthy subjects normal gastric physiology can be restored by eradication of the infection.

Adult↗
PubMed1991

The fluoroquinolones exert a reduced rate of kill against Enterococcus faecalis.

The bactericidal activities of ciprofloxacin, ofloxacin and DR-3355 have been investigated against Enterococcus faecalis, Staphylococcus aureus and Staphylococcus epidermidis over 24 h. The three fluoroquinolones were found to be rapidly bactericidal against the staphylococci, killing over 99% of the bacteria during the first 3 h of exposure with a further reduction in viability of approximately one logarithm occurring over the next 21 h. In contrast, the fluoroquinolones displayed a much slower rate of kill against E. faecalis, as little or no bactericidal activity was detected over the first 3 h for both E. faecalis ATCC19433 and a clinical isolate. At 6 h all three of the drugs were bactericidal against the enterococci although the amount of kill was not as great as against the staphylococci. However, at 24 h the amount of kill obtained with all three drugs was similar to that obtained for staphylococci exposed to these drugs. Ciprofloxacin, ofloxacin and DR-3355 were not active against E. faecalis ATCC19433 in phosphate buffered saline and therefore require cell division for their bactericidal activity against this species.

Anti-Infective Agents↗
PubMed1991

Rebound intragastric hyperacidity after abrupt withdrawal of histamine H2 receptor blockade.

In a series of 24 hour studies, intragastric acidity and plasma gastrin concentration were measured simultaneously in 46 healthy subjects before, during, and 24 to 48 hours after abrupt withdrawal of a histamine H2 receptor antagonist regimen. For 34 days subjects were given either cimetidine 800 mg at night (n = 8), ranitidine 150 mg twice daily (n = 10), ranitidine 300 mg at night (n = 12), nizatidine 300 mg at night (n = 8), or famotidine 40 mg at night (n = 8). All subjects responded to H2 blockade by a decrease in 24 hour intragastric acidity. Withdrawal of H2 blockade resulted in a significant rise in median nocturnal integrated intragastric acidity in 42 of 46 subjects (+36%; 95% CI +19, +55%) compared with prestudy values, but this rise was not associated with a significant change in the median integrated plasma gastrin concentration (+1%; 95% CI -12, +13%). A statistically significant rise in nocturnal acidity was observed after all regimens, except after dosing with famotidine. After stopping, median daytime integrated acidity and plasma gastrin concentrations in the whole group were raised, but not significantly: values were +15% (95% CI +4, +34%) and +5% (95% CI -2, +12%), respectively. A statistically significant increase in daytime acidity was observed only after dosing with ranitidine. In conclusion, intragastric hyperacidity occurs in most subjects after abrupt withdrawal of a histamine H2 receptor blocker, but this phenomenon is not associated with hypergastrinaemia.

Adult↗
PubMed1991

Ofloxacin, a bactericidal antibacterial.

Ofloxacin, like other 4-quinolones, is unusual among front line drugs available to treat bacterial infections since it affects bacterial DNA synthesis, rather than cell wall or protein synthesis. The 4-quinolones are also unusual because even for serious infections they can be given orally. Most unusually transferable resistance mediated by plasmids does not affect the 4-quinolone antibacterials. Thus the only way that bacteria can resist these drugs is by chromosomal mutation. However, when mutants gain resistance, they can also lose pathogenicity, and even should mutants remain pathogenic then their resistance cannot transfer to other bacteria by conjugation.

Anti-Infective Agents↗
PubMed1991

Decision points in the integrative research review process: a flow-chart approach.

With the ever increasing volume of research information appearing in the literature, research syntheses are becoming more popular among researchers in various disciplines. This phenomenon demands application of rigorous and systematic review methodologies. Using Cooper's five-stage process for conducting an integrative research review, the authors have constructed a flow chart for health sciences librarians and others using this approach to identify decision points in this process. The accompanying narrative details the information that must be considered and analyzed. Included in the flow chart and text is an elaboration of meta-analysis and an integrative review to accommodate both quantitative and qualitative research results. A case is made for a collaborative relationship between the researcher and the librarian.

Data Collection↗
PubMed1991

Treatment of comminuted femoral subtrochanteric fractures using the Russell-Taylor reconstruction intramedullary nail.

Seven patients with comminuted subtrochanteric fractures of the femur were treated with Russell-Taylor reconstruction intramedullary nails. Six of the seven fractures were AO/ASIF Type C and had resulted from high-energy trauma. The average time to clinical union was 10.5 weeks--a considerable improvement over what has been achieved with other methods. There were no delayed unions, nonunions, infections, or implant failures, either postoperatively or during follow up, which averaged 20.8 months (range: 16 to 28). The Russell-Taylor device offers mechanical and biologic advantages, and extends the indications for locked intramedullary nailing to include fractures at the level of or including the lesser trochanter.

Adult↗
PubMed1991

Blood pressure and heart rate of the preterm newborn following delivery.

Thirty-five preterm newborns were studied to determine the mean blood pressure and heart rate of preterm newborns less than 1500 gm and greater than or equal to 1500 gm at birth. Systemic blood pressure increased and heart rate decreased with increasing maturity at birth. Both systemic blood pressure and heart rate increased during the four days following delivery. The 95% prediction limits of stable preterm newborns less than 1500 gm and greater than or equal to 1500 gm at birth are useful criteria to define hypertension and hypotension, as well as tachycardia and bradycardia.

Aging↗
PubMed1990

Inhibition of mitochondrial palmitate oxidation by calmodulin antagonists.

1. The effect of calmodulin antagonists on the rate of palmitate oxidation by isolated rat liver mitochondria was studied. 2. In the presence of 100 microM amitriptyline, chlorpromazine, prenylamine, N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide or N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, palmitate oxidation was inhibited by 17, 34, 49, 31 and 37%, respectively. 3. The degree of inhibition of palmitate oxidation exerted by these chemical compounds did not appear to correlate appreciably with changes in mitochondrial membrane fluidity.

Animals↗
PubMed1990

A relationship between vitamin B12, folic acid, ascorbic acid, and mercury uptake and methylation.

Ingestion of megadoses of certain vitamins appears to influence the in vivo methylation of mercuric chloride in guinea pigs. The addition of megadoses of vitamin B12 fed either singularly or in combination with folic acid resulted in increased methylmercury concentrations in the liver. Moreover, percent methylmercury levels were significantly increased with B12 treatment in the liver (B12 only and B12/folic acid) and brain (B12/vitamin C). Incorporation of high levels of folic acid into the dietary regime also increased the methylmercury concentration particularly in the liver and hair tissues. The addition of vitamin C in the diet, particularly in combination with B12 (brain) or folic acid (muscle) resulted in increased methylmercury levels in these tissues and percent methylmercury values with B12 in the muscle and brain tissue.

Animal Nutritional Physiological Phenomena↗
PubMed1990

DNA breakdown by the 4-quinolones and its significance.

DNA breakdown occurred in Escherichia coli KL16 exposed to nalidixic acid, ciprofloxacin or norfloxacin. However DNA breakdown does not seem to be the cause of the lethality of the 4-quinolones because it still occurred under conditions which abolished the lethality of nalidixic acid. Furthermore, no correlation was found between the amount of DNA breakdown and the rate of death of bacteria caused by the three 4-quinolones. Similarly, DNA breakdown did not occur when recB or recC mutants were treated with nalidixic acid despite both mutants being killed by the drug, again suggesting that DNA breakdown is not the cause of bacterial death. Since recB and recC mutants lack exonuclease V, this enzyme may be responsible for the DNA breakdown observed in bacteria treated with 4-quinolones.

Ciprofloxacin↗
PubMed1990

Conditions required for the bactericidal activity of 4-quinolones against Serratia marcescens.

The conditions required to kill Serratia marcescens with nalidixic acid, ciprofloxacin, norfloxacin or ofloxacin were determined in nutrient broth and in phosphate-buffered saline. They were found to be similar to the conditions required for these 4-quinolones to kill Escherichia coli. Bacterial RNA synthesis and bacterial cell division were essential for the bactericidal activity of nalidixic acid but all three fluoroquinolones were bactericidal against non-dividing S. marcescens. However, as with E. coli, bacterial RNA synthesis was essential for the bactericidal activity of norfloxacin though this was not required to kill S. marcescens with ciprofloxacin or ofloxacin.

Anti-Bacterial Agents↗
PubMed1990

Clofibrate raises human 24 h intragastric acidity but does not affect plasma gastrin concentration.

1. We studied the effects of acute oral dosing with clofibrate (500 mg four times daily) on 24 h intragastric acidity and plasma gastrin concentration in 12 healthy female subjects. 2. The 24 h integrated intragastric acidity rose from 429 mmol l-1 h (95% CI 296-479) before dosing to 527 mmol l-1 h (95% CI 385-664) on the day of dosing (+23%; P = 0.041), but no change was observed in the 24 h integrated plasma gastrin concentration: 420 pmol l-1 h (95% CI 282-499) before and 389 pmol l-1 h (95% CI 249-489) during dosing (P = 0.182). 3. We conclude that clofibrate has no acute antisecretory effect on the human stomach, and that human gastrin-induced enterochromaffin-like cell proliferation is unlikely with this drug.

Adult↗