Search PubMed⌕ Search

Biomedical subjects

C Martin

Publications and source records attributed to C Martin.

At least 667 records · Page 37Linked to original sources
PubMed1993

Genetic characterization of a cryptic genospecies of Haemophilus causing urogenital and neonatal infections.

In recent years, reports originating from several areas of the world have identified biotype IV strains of Haemophilus influenzae as a cause of serious urogenital, neonatal, and mother-infant infections. Preliminary analysis of a sample of biotype IV isolates found evidence for a cryptic genospecies of Haemophilus (R. Quentin, A. Goudeau, R. J. Wallace, Jr., A. L. Smith, R. K. Selander, and J. M. Musser. J. Gen. Microbiol. 136:1203-1209, 1990). Eighteen biotype IV strains assigned to the cryptic genospecies were further characterized by their rDNA restriction fragment length polymorphism patterns and genomic DNA-DNA hybridization. Isolates of the cryptic genospecies have distinctive rDNA restriction fragment length polymorphisms that differ from those of Haemophilus haemolyticus and H. influenzae. Genomic hybridization studies show that these organisms are allied with H. influenzae and H. haemolyticus and suggest a distant trifurcation of H. influenzae, H. haemolyticus, and the cryptic genospecies.

Adult↗
PubMed1993

Heart rate variability and circulating catecholamine concentrations during steady state exercise in healthy volunteers.

OBJECTIVES: To assess whether exercise induced suppression of heart rate variability in the low frequency domain (0.06-0.15 Hz) is related to the increase in circulating catecholamine concentrations. DESIGN: Randomised crossover trial of three exercise tests characterised by different workloads. Pharmacological simulation of exercise-induced changes in vagal and sympathetic activity. PARTICIPANTS: Six healthy men with a mean age of 31.2 (SD 3.0) years. INTERVENTIONS: Three different workloads of steady state cycling ergometry: control state without cycling, cycling at a target heart rate of 100 beats/min, and cycling at a target heart rate of 150 beats/min. Intravenous infusion of atropine (target heart rate 100 beats/min) followed by the additional infusion of adrenaline and noradrenaline. MAIN OUTCOME MEASURES: Fast Fourier analysis of heart rate variability; blood pressure; and venous plasma concentrations of lactate, adrenaline, and noradrenaline. RESULTS: During the control exercise period there were no changes in the assessed variables compared with the preceding resting period. During exercise at a heart rate of 100 beats/min systolic blood pressure increased and heart rate variability decreased. During exercise at a heart rate of 150 beats/min systolic blood pressure and lactate, adrenaline, and noradrenaline concentrations increased. In addition, low frequency (LF) was lower than during exercise at 100 beats/min, high frequency (HF 0.15-0.80 Hz) resembled that during exercise at 100 beats/min, and diastolic blood pressure was reduced. Infusion of atropine caused no changes in blood pressure or plasma concentrations of lactate, adrenaline, and noradrenaline and decreased heart rate variability. The additional infusion of adrenaline and noradrenaline completely suppressed heart rate variability and increased blood pressure. CONCLUSIONS: The reduction in LF and HF during exercise at a heart rate of 100 beats/min, which is not characterised by increased plasma catecholamine concentrations, and during atropine infusion suggests that heart rate variability in the supine state is largely influenced by vagal activity. The additional reduction in LF during exercise at 150 beats/min and during catecholamine infusion may reflect a negative feedback of circulating catecholamines on the sympathetic control of heart rate.

Adult↗
PubMed1993

Development of short-term myocardial hibernation. Its limitation by the severity of ischemia and inotropic stimulation.

BACKGROUND: Short-term hibernating myocardium is characterized by a decrease in contractile function in proportion to the reduced myocardial blood flow. Myocardial creatine phosphate content, initially decreased during the first minutes of ischemia, returns to near-control values, the ischemia-induced net lactate production is attenuated, and the myocardium remains viable despite ongoing hypoperfusion and contractile dysfunction. Hibernating myocardium after 85 minutes of ischemia maintains an inotropic reserve and responds to short-term intracoronary dobutamine infusion with increased work; however, this inotropic response is at the expense of metabolic recovery. We therefore hypothesized that the development of myocardial hibernation is a delicate process that is easily disturbed by unfavorable alterations in the oxygen-supply demand balance. METHODS AND RESULTS: To study the impact of prolonged inotropic stimulation on the development of myocardial hibernation, the left anterior descending coronary artery was cannulated and hypoperfused at constant flow in 12 enflurane-anesthetized swine. The reduction of coronary inflow was followed by a reduction of regional myocardial work (sonomicrometry) from 248 +/- 59 mm Hg.mm to 73 +/- 35 mm Hg.mm (P < .05) at 5 minutes of ischemia. Dobutamine (2.5 +/- 1 micrograms/min) was then infused for an additional 85 minutes. Work was increased at 5 minutes of dobutamine to 139 +/- 34 mm Hg.mm (P < .05 versus 5 minutes of ischemia). However, this increase was only transient, and after 85 minutes of dobutamine, work was decreased below the initial ischemic value (42 +/- 34 mm Hg.mm). At 5 minutes of ischemia, creatine phosphate content was reduced from 8.80 +/- 1.97 to 6.21 +/- 3.87 mumol/g wet wt, and myocardial ATP content was decreased slightly from 4.75 +/- 0.92 to 4.12 +/- 1.29 mumol/g wet wt (both, P = NS). After 5 minutes of dobutamine, further reductions in creatine phosphate content to 3.11 +/- 0.76 mumol/g wet wt and in ATP to 3.14 +/- 0.81 mumol/g wet wt were observed (both, P < .05 versus control). During the remainder of the continuous dobutamine infusion, creatine phosphate content remained unchanged, whereas ATP further decreased significantly to 1.68 +/- 0.96 mumol/g wet wt. The beta-adrenoceptor density of the left anterior descending coronary artery-perfused myocardium was 36.5 +/- 5.8 fmol (-)-[125I]iodocyanopindolol/mg protein under control conditions, and this was unchanged during ischemia and the subsequent dobutamine infusion. Following 90 minutes of ischemia with 85 minutes of dobutamine and 2 hours of reperfusion, infarct size (triphenyl tetrazolium chloride staining) was 26.3 +/- 7.5% of the area at risk. With constant hypoperfusion, dobutamine redistributed blood flow away from the subendocardium (0.20 +/- 0.08 versus 0.11 +/- 0.04 mL.min-1.g-1) toward the subepicardium (0.45 +/- 0.13 versus 0.51 +/- 0.21 mL.min-1.g-1) as well as to the right ventricle (0.26 +/- 0.08 versus 0.32 +/- 0.09 mL.min-1.g-1). Therefore, in two other groups of six and five swine, the severity of ischemia was increased to achieve an 80% or a 90% reduction in regional function, respectively, and the importance of the severity of blood flow reduction per se for the development of myocardial infarction was studied. The infarct size in the animals undergoing 85 minutes of dobutamine (26.3 +/- 7.5%) was increased above the level expected from the blood flow reduction alone (6.3 +/- 6.4%, P < .01). CONCLUSIONS: Both the increased severity of ischemia and the enhanced energy expenditure induced by dobutamine impair the development of myocardial short-term hibernation and precipitate myocardial infarction.

Animals↗
PubMed1993

An isoelastic prosthesis using a new composite material.

A new particulate composite material has been assessed with regard to the design of an 'isoelastic' or 'modulus matched' hip prosthesis. Three different prototype designs were assessed, each of which consisted of a femoral component made from the composite material, attached to a metal ball via a metal 'spike' insert. The prototypes varied in terms of the detailed shape of the spike, which was modified in the light of photoelastic stress analysis, so as to produce a more acceptable stress distribution to the composite material in the proximal region. Prototypes were made by hand moulding and by transfer moulding; both methods produced defects of various kinds. Simulation tests were conducted using a model of the proximal femur constructed from glass fibre composite, cyclically loaded in a servo-hydraulic testing machine. Though some difficulties were experienced with defective mouldings, especially for the transfer moulding process, a clear improvement was demonstrated for the final (Mark III) design. The fatigue endurance of this prototype was similar to that of conventional metal prostheses tested under similar conditions. Fatigue crack propagation tests were carried out on samples of the composite material to establish its propagation threshold. These results were combined with a finite element stress analysis and fracture mechanics theory to estimate the critical crack length for fatigue in this prosthesis. It was thus possible to specify the maximum safe size of defect that could be tolerated in use.

Biocompatible Materials↗
PubMed1993

A reappraisal of blind bronchial sampling in the microbiologic diagnosis of nosocomial bronchopneumonia. A comparative study in ventilated patients.

STUDY OBJECTIVE: To assess the usefulness of fiberscopy for microbiologic diagnosis of nosocomial bronchopneumonia (NBP) in ventilated patients. DESIGN: Data were collected prospectively. We compared the results of semiquantitative cultures obtained by protected specimen brush (PSB), bronchoalveolar lavage (BAL) and blind bronchial sampling (BBS). Positive thresholds were 10(3) CFU ml-1 for PSB and BAL and 10(4) CFU ml-1 for BBS. We also evaluated the diagnostic performance of direct examination of samples obtained by BAL and BBS. PATIENTS: We carried out this study in 64 ventilated patients admitted to a medico-surgical ICU. RESULTS: During the study, 85 sets of samplings were obtained. The concordance between the results of specimen cultures obtained with the three techniques was 87 percent. The concordance between BBS and PSB or between BBS and BAL was 91.8 percent. In two of seven patients with discordant results between BBS and PSB, the microorganisms isolated from blood cultures were found on BBS, but not on PSB samples. As for direct examination, the thresholds for the diagnosis of NBP using BBS were as follows: > or = 10 polymorphonuclear neutrophils (PMN)/high-power field (HPF), > or = 1 bacteria/oil immersion field (OIF), presence of intracellular bacterial inclusions. Using BAL, the thresholds were as follows: > or = 1 PMN/HPF, presence of bacteria/OIF, presence of intracellular bacterial inclusions. The specificity of the presence of bacterial inclusions was excellent regardless of the sampling technique, but the sensitivity of this criteria was mediocre (30.8 percent with BBS and 19.2 percent with BAL). Except for the number of PMN on BBS, all the other diagnostic criteria (PMN count on BAL, bacterial count, count of cells exhibiting inclusions) provide a similar prediction of NBP (correctly classified: 61.2 to 81.2 percent). No combination of criteria enabled significantly better classification regardless of the sampling technique. CONCLUSIONS: In view of these findings and the high cost and morbidity of fiberscopy, it is arguably better to use a simple, repeatable, and risk-free technique for obtaining culture specimens from mechanically ventilated patients. Obviously, protected brushing techniques remain the most effective for nonintubated patients.

Bacteria↗
PubMed1993

Norepinephrine or dopamine for the treatment of hyperdynamic septic shock?

STUDY OBJECTIVE: To compare the ability of dopamine and norepinephrine to reverse hemodynamic and metabolic abnormalities of human hyperdynamic septic shock. DESIGN: Prospective, double-blind, randomized trial. SETTING: An ICU in a university hospital. PATIENTS: Adult patients with hyperdynamic septic shock after fluid resuscitation. INTERVENTIONS: Patients were assigned to receive either dopamine (2.5 to 25 micrograms/kg/min) or norepinephrine (0.5 to 5.0 micrograms/kg/min). If hemodynamic and metabolic abnormalities were not corrected with the maximum dose of one drug, the other was added. MEASUREMENTS AND RESULTS: The aim of therapy was to achieve and maintain for at least 6 h all of the following: (1) systemic vascular resistance index > 1,100 dynes.s/cm5.m2 and/or mean systemic blood pressure > or = 80 mm Hg; (2) cardiac index > or = 4.0 L/min/m2; (3) oxygen delivery > 550 ml/min/m2; and (4) oxygen uptake > 150 ml/min/m2. With the use of dopamine 10 to 25 micrograms/kg/min, 5 of 16 patients (31 percent) were successfully treated, as compared with 15 of 16 patients (93 percent) by norepinephrine at a dose of 1.5 +/- 1.2 micrograms/kg/min (p < 0.001). Ten of 11 patients who did not respond to dopamine and remained hypotensive and oliguric were successfully treated with the addition of norepinephrine. CONCLUSIONS: At the doses tested, norepinephrine was found, in the present study, to be more effective and reliable than dopamine to reverse the abnormalities of hyperdynamic septic shock. In the great majority of the study patients, norepinephrine was able to increase mean perfusing pressure without apparent adverse effect on peripheral blood flow or on renal blood flow (since urine flow was reestablished). At the same time, oxygen uptake was increased.

Dopamine↗
PubMed1993

Effects of consecutive protected specimen brushing and bronchoalveolar lavage on gas exchange and hemodynamics in ventilated patients.

OBJECTIVE: To assess cardiovascular effects and the oxygenation status of mechanically ventilated patients undergoing protected specimen brushing (PSB) and bronchoalveolar lavage (BAL) under fiberoptic bronchoscopy (FOB). DESIGN: A prospective study. SETTING: Polyvalent intensive care unit in a university hospital. PATIENTS: Twelve consecutive, critically ill, intubated, and mechanically ventilated patients with hemodynamic failure requiring invasive monitoring with an indwelling radial artery catheter and indwelling Swan-Ganz catheter were included in the study. INTERVENTIONS: Hemodynamic measurements, arterial and mixed-venous blood gas analyses, and arterial blood lactate analysis were performed before and at the end of a 10-min period of mechanical ventilation with a fractional concentration of oxygen in the inspired gas (FIO2) of 1.0. The same measurements and blood samplings were repeated at the end of the PSB procedure, at the end of the BAL procedure, and 1 h after the end of the BAL. During the study period the ECG, arterial oxygen saturation (SaO2), and mixed-venous oxygen saturation (SvO2) were continuously monitored. MAIN RESULTS: A moderate increase in both mean arterial pressure and mean pulmonary arterial pressure was observed during the FOB procedure (p < 0.05). One hour after the end of BAL, the PaO2 decreased when compared with values recorded at the beginning of the procedure with the same FIO2 (p < 0.05). An increase in intrapulmonary shunt was observed at the end of BAL (p < 0.01). A moderate increase in PaCO2 was also observed after PSB (p < 0.05) and after BAL (p < 0.01). Monitoring of SaO2 permitted us to observe a significant and sustained decrease after the end of the FOB procedure from 10 to 60 min. The decrease in SvO2 was less pronounced but reached statistical significance. CONCLUSIONS: We conclude that PSB and BAL under FOB are well tolerated in critically ill, mechanically ventilated patients with hemodynamic disturbances requiring inotropic or vasopressor agents (or both); however, a modest impairment in arterial oxygenation was observed after the end of the FOB procedure.

Adult↗
PubMed1993

Metabolic and endocrine changes associated with undernutrition in the peripubertal gilt.

The effect of feed restriction on circulating metabolites and metabolic and gonadotropic hormones was determined in Large White gilts. From 25 kg BW and 80 d of age, control gilts (CTRL, n = 10) were fed close to ad libitum intake, whereas restricted-fed gilts (REST, n = 10) were offered approximately 50% of the CTRL diet. Estrus was detected with a mature boar. Serial blood samples were collected at approximately 160 and 210 d of age from 0800 to 2000. A meal was supplied at 0900, and an i.v. injection of GnRH (80 ng/kg BW) was given at 1600. The gilts were slaughtered at 220 d of age. No REST and four CTRL gilts exhibited their first estrus between the two series of blood samplings. Feed intake, daily gain, and fat content of the carcass were reduced by 50% in REST gilts (P < .001). Preprandial concentrations of free fatty acids were significantly lower in CTRL gilts at 210 d of age than at 160 d and than in REST gilts at both ages. Within the CTRL group, concentrations were lower (P < .05) at both ages in gilts pubertal before 210 d than in others. After the meal, plasma insulin and urea increased in all gilts, whereas glucose increased and free fatty acids decreased in all except the 210-d CTRL gilts. The afternoon concentration of cortisol was slightly higher (P = .09) in REST than in CTRL gilts. The number of pulses and mean and interpulse concentrations of growth hormone did not show any clear variation with feed level and age.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of cyclosporin A and its metabolites and analogs on lipid peroxidation in rabbit renal microsomes.

Rabbit renal microsomes were used to investigate the effect on lipid peroxidation (LPO) of cyclosporin A (CsA) and its first generation metabolites M1, M17 and M21, and of two natural CsA analogs: cyclosporins C and D (CsC & CsD respectively), at concentrations of 1 to 10 micrograms/ml. No induction of lipid peroxidation was observed with these substances except CsA at a high level (10 microgram/ml); but at a concentration of CsA that would be reached in vivo, no inductive effect on LPO was noted. A moderate inhibitory effect upon LPO was observed with CsC and M21, but its biological significance is questionable.

Animals↗
PubMed1993

Cyanopeptolins, new depsipeptides from the cyanobacterium Microcystis sp. PCC 7806.

Four depsipeptides (peptide lactones), called cyanopeptolins A, B, C and D, have been isolated from the cyanobacterium Microcystis sp. PCC 7806. They possess identical structures consisting of cyclic L-glutamic acid-gamma-aldehyde, L-leucine, N-methyl-phenylalanine, L-valine, L-threonine, L-aspartic acid, hexanoic acid and a variable basic amino acid. This variable amino acid can be L-arginine (cyanopeptolin A), L-lysine (cyanopeptolin B), N epsilon-methyl-L-lysine (cyanopeptolin C) and N epsilon,N epsilon-dimethyl-L-lysine (cyanopeptolin D), respectively. The L-glutamic acid-gamma-aldehyde and the amino group of L-leucine form an unusual 3-amino-6-hydroxy-2-oxo-1-piperidine system. L-Threonine is connected to L-valine via its hydroxy-group forming an ester bonding. The hexanoic acid residue is attached to the N-terminal aspartic acid residue which is not a part of the ring structure. The isolation procedure of the four cyanopeptolins as well as structure elucidation are described. Amino acid analysis, GC/MS analysis, FAB-MS and several NMR techniques were used to reveal the structures.

Amino Acid Sequence↗
PubMed1993

[Early effects of neutron-gamma or gamma irradiation on the group toxicity induced by (+) amphetamine in mice].

To better understand the mechanism of action of gamma and neutron radiation on the dopaminergic system, the influence of the two irradiation modalities on the group toxicity of (+) amphetamine was studied in mice. Neutron-gamma irradiation (3.6-4.95 Gy) leads to an early toxicity reduction, while gamma-exposure (7-12 Gy) induces an increase in toxicity. This suggests that these two types of radiation induce different early effects on central dopaminergic system. Possible mechanisms are discussed.

Actuarial Analysis↗
PubMed1993

[Tissue diffusion of amoxicillin-clavulanic acid for antibiotic prophylaxis in colorectal surgery].

Tissue penetration of amoxicillin and clavulanic acid given for antibiotic prophylaxis was studied in 15 patients. On induction of anesthesia patients were given 2 g amoxicillin and 200 mg clavulanic acid. The same dose was given two hours later. At time of surgical incision amoxicillin and clavulanate levels were 15.9 +/- 7.7 micrograms/g and 2.23 +/- 2.69 micrograms/g in abdominal wall fat and 16.6 +/- 10.5 and 1.72 +/- 1.35 micrograms/g in epiploic fat, respectively. Similar levels were measured at time of closure of the abdomen. In colonic wall, amoxicillin et clavulanate levels were 22.7 +/- 13.4 micrograms/g and 2.65 +/- 2.35 micrograms/g. By comparison with blood levels, tissue penetration of both drugs was 20 to 30 p. cent into fatty tissues and 60 to 70 p. cent into colonic wall.

Adipose Tissue↗
PubMed1993

[Work and sterility. State of epidemiological research].

Among the factors of man or woman sterility some of them may be due to occupation. The identification of these factors may be performed through epidemiological studies; the fertility indices taken into account and the epidemiological strategies used are briefly described. As examples the results of studies on man hypofertility induced by dibromochloropropane and ionising radiations are presented.

Case-Control Studies↗
PubMed1993

[Laser: otology, oto-neurosurgery].

The use of lasers in otology is rather recent and their use in otoneurosurgery is even more so, as shown by the limited number of publications dealing with this subject in the literature. After a review of the main bibliographical data on these subjects, the authors present their experience and analyze their results. Two types of lasers were used successively, an Argon laser and then a laser with a double KTP 532 and Nd: YAG 1320 nm beam. The Argon laser and the KTP 532 laser were exclusively used in otology whereas in otoneurosurgery, both KTP 532 and Nd: YAG 1320 nm beams were used depending on the indications. The KTP 532 beam appears to be preferable for treating vascular and small-sized lesions; the Nd: YAG 1320 nm beam proves to be very advantageous for vaporizing the slightly vascular, larger lesions such as stage III and IV neurinomas of the VIIth.

Chronic Disease↗
PubMed1993

Pseudomonas aeruginosa and cystic fibrosis: intrastrain variability in relation to intensity of immune response and clinical outcome.

Over periods exceeding two years, 63 Pseudomonas aeruginosa strains isolated from three children with cystic fibrosis were characterized using a 154 character auxanogram. Numerical analysis was carried out to establish intrastrain variability in relation to intensity of immune response and clinical outcome. For two patients, strains segregated in two distinct phenons. For the last patient, strains did not cluster. The degree of intrastrain variability during the infection was correlated with an increasing number of precipitins and with an unfavorable clinical outcome. This would suggest that strains which have a singular potential for antigenic variability are more likely to promote a host-bacteria conflict.

Bacterial Typing Techniques↗
PubMed1992

Nucleotide sequence of the nfaA gene encoding the antigen 8786 adhesive factor of enterotoxigenic Escherichia coli.

The nucleotide sequence of a 714-bp DNA fragment containing the enterotoxic Escherichia coli (ETEC) adhesive factor 8786 structural gene, designated nfaA, revealed an open reading frame of 498 bp encoding a polypeptide of 166 amino acids. Primer-extension experiments showed that the nfaA gene is within a single transcription unit. No homology was found with the ETEC adhesive factors already sequenced. In contrast, a homology with Salmonella enteritidis fimbrin SEF 14 was observed.

Adhesins, Escherichia coli↗
PubMed1992

Nitric oxide from endothelium and smooth muscle modulates responses to sympathetic nerve stimulation: implications for endotoxin shock.

The influence of nitric oxide (NO) on vascular responses to transmural stimulation (TNS) of noradrenergic nerves was studied in isolated rings of rat iliac arteries. TNS produced frequency-dependent contractions in all vessels. The NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) significantly enhanced TNS responses in intact vessels, but not in those in which the endothelium had been removed. However, in endothelium-denuded rings incubated for 8 hours, L-NMMA increased the contractions induced by nerve stimulation, an effect which was prevented by treatment with dexamethasone or cycloheximide, and enhanced by incubation with lipopolysaccharide and gamma-interferon. Addition of L-arginine reversed the effect of L-NMMA in intact rings; however, it significantly decreased below control values TNS-induced contractions in vessels without endothelium. The results indicate that a) the arterial response to noradrenergic nerve stimulation is modulated by NO originating either in endothelial cells or in smooth muscle cells after induction of NO synthase activity, and b) once NO synthase is induced, the limiting step in NO production is the availability of the substrate L-arginine. An overproduction of vascular NO in the presence of endotoxin or other inflammatory stimuli may prevent the vascular response to sympathetic stimuli and contribute to the vasodilation observed in inflammation or endotoxic shock.

Acetylcholine↗