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Biomedical subjects

B Larsen

Publications and source records attributed to B Larsen.

At least 91 records · Page 5Linked to original sources
PubMed1994

Supercritical fluid extraction of polychlorinated biphenyls from lyophilized fish tissue.

A method for the rapid interference free analysis of polychlorinated biphenyl congeners (chlorinated biphenyls, CBs) in lyophilized fish tissue is presented. The method was developed on a lyophilized tuna muscle tissue that contained 2.8% lipid (dry mass based), and native CB concentrations in the range of 3-84 ng/g. Sample preparation was made by supercritical fluid extraction using pure CO2 as extraction fluid. Analysis by high-resolution gas chromatography-electron-capture detection analysis was carried out with on-column injection on two parallel coupled columns, a 60 m DB-17 column and a series combination of a 25 m SIL-8 column and a 25 m HT-5 column. Supercritical fluid extraction was compared with Soxhlet extraction and found to give quantitative recoveries, detection limits of 0.5-2 ng/g and standard deviations of less than 5% on average. The developed method was confirmed on nine different lyophilized fish samples which contained 6.1-26.5% lipid (dry mass based), and native CB concentrations in the range 0.8-134 ng/g.

Animals↗
PubMed1994

Skeletal muscle vascular responses in human limbs to isometric handgrip.

Studies of whole limb blood flow have shown that static handgrip elicits a vasodilatation in the resting forearm and vasoconstriction in the resting leg. We asked if these responses occur in the skeletal muscle vascular bed, and if so, what is the relative contribution of local metabolic versus other mechanisms to these vascular responses. Blood flow recordings were made simultaneously in the skeletal muscle of the resting arm and leg using the Xenon-washout method in ten subjects during 3 min of isometric handgrip at 30% of maximal voluntary contraction. In the arm, skeletal muscle vascular resistance (SMVR) decreased transiently at the onset of exercise followed by a return to baseline levels at the end of exercise. In the leg SMVR remained unchanged during the 1st min of handgrip, but had increased to exceed baseline levels by the end of exercise. During exercise electromyography (EMG) recordings from nonexercising limbs demonstrated a progressive 20-fold increase in activity in the arm, but remained at baseline in the leg. During EMG-signal modelled exercise performed to mimic the inadvertent muscle activity, decreases in forearm SMVR amounted to 57% of the decrease seen with controlateral handgrip. The present study would seem to indicate that vascular tone in nonexercising skeletal muscle in the arm and leg are controlled differently during the early stages of static handgrip. Metabolic vasodilation due to involuntary contraction could significantly modulate forearm skeletal muscle vascular responses, but other factors, most likely neural vasodilator mechanisms, must make major contributions. During the later stages of contralateral sustained handgrip, vascular adjustments in resting forearm skeletal muscle would seem to be the final result of reflex sympathetic vasoconstrictor drive, local metabolic vasodilator forces and possibly neurogenic vasodilator mechanisms.

Adult↗
PubMed1994

[Effects of propofol and fentanyl on the baroreceptor reflex in geriatric patients].

OBJECTIVE: Increasing age and anaesthetics diminish the baroreflex response to acute changes in blood pressure. This study was designed to investigate the effects of propofol and the combination of propofol with fentanyl on the baroreflex activity in geriatric patients. METHODS: Baroreflex sensitivity was studied by the method of Smyth et al. in 10 elderly (72 +/- 6 yrs) and in 10 younger (48 +/- 6 yrs) patients. Nitroprusside (depressor test) and phenylephrine (pressor test) were used to induce changes in blood pressure of 20 mmHg each to alter the stimulation of the baroreceptor sites. Anaesthesia was induced with propofol, 2 mg x kg-1 b.w.m, and maintained by a continuous infusion of 12 mg x kg-1 x h-1 for 10 min and thereafter with 6 mg x kg-1 x h-1. Then a bolus of fentanyl, 7 micrograms x kg-1 b.w. was injected. Haemodynamic parameters and baroreflex activity were measured in the awake state, 10 min after induction of anaesthesia and 10 min after the administration of fentanyl. Plasma propofol concentrations were determined by HPLC 10 min after induction of anaesthesia with propofol and 10 min after injection of fentanyl. The slope of the linear regression changes in RR-interval [ms] per changes in systolic pressure [mmHg] was used as an index of the baroreflex sensitivity. RESULTS: In the awake state the depressor slopes were significantly reduced by 60% in the elderly patients when compared to the younger patients. In both groups propofol decreased reflex sensitivity by 38% and 41% respectively; this effect was enhanced by the addition of fentanyl in the younger patients, while there was no further effect in the elderly. The pressor slopes did not change significantly in both groups neither with propofol nor with the combination of fentanyl, but again reflex response was significantly less in the elderly patients. CONCLUSION: Our data demonstrate that in geriatric patients the baroreflex control of heart rate already is attenuated in the awake state. Propofol produces a further reduction in reflex sensitivity to an acute decrease in blood pressure; this effect is more pronounced in elderly patients as compared to younger individuals. Acute changes in posture or circulating blood volume during propofol anaesthesia may result in greater cardiovascular instability in older patients due to the greater impairment of circulatory control mechanisms.

Adult↗
PubMed1994

The humoral immune response to Chlamydia trachomatis in patients with acute reactive arthritis.

Sera from 25 patients with clinical signs of reactive arthritis were analysed for antibodies against Chlamydia trachomatis by immunoblotting. Purified elementary bodies, purified Chlamydia outer membrane complexes, and purified recombinant subcomponents were used as antigens. Antibodies against C. trachomatis cysteine rich outer membrane protein 2 (Omp2) and lipopolysaccharide (LPS) were detected in 10 patients. Thus 40% of the patients presented antibodies specific for C. trachomatis. There was no correlation between acute reactive arthritis and antibodies to heat-shock proteins GroEL, GroES and DnaK.

Acute Disease↗
PubMed1994

Characterization of a linear epitope on Chlamydia trachomatis serovar L2 DnaK-like protein.

A cytoplasmic 75-kDa immunogen from Chlamydia trachomatis serovar L2 has previously been characterized as being similar to the Escherichia coli heat shock protein DnaK. We have localized a linear epitope for one monoclonal antibody specific for C. trachomatis DnaK. By use of a recombinant DNA technique, the epitope was limited to 14 amino acids. With synthetic peptides, the epitope was further limited to eight amino acids. Six of these amino acids are conserved in bovine HSP70, which has a known three-dimensional structure. The amino acid sequence homologous to the epitope is located in a linear part of the HSP70 molecule known as connect II.

Amino Acid Sequence↗
PubMed1994

Cloning and expression of an Azotobacter vinelandii mannuronan C-5-epimerase gene.

An Azotobacter vinelandii mannuronan C-5-epimerase gene was cloned in Escherichia coli. This enzyme catalyzes the Ca(2+)-dependent epimerization of D-mannuronic acid residues in alginate to the corresponding epimer L-guluronic acid. The epimerase gene was identified by screening a bacteriophage EMBL3 gene library of A. vinelandii DNA with a synthetic oligonucleotide probe. The sequence of this probe was deduced after determination of the N-terminal amino acid sequence of a previously reported extracellular mannuronan C-5-epimerase from A. vinelandii. A DNA fragment hybridizing against the probe was subcloned in a plasmid vector in E. coli, and the corresponding recombinant plasmid expressed intracellular mannuronan C-5-epimerase in this host. The nucleotide sequence of the gene encoding the epimerase was determined, and the sequence data showed that the molecular mass of the deduced protein is 103 kDa. A module consisting of about 150 amino acids was repeated tandemly four times in the C-terminal part of the deduced protein. Each of the four repeats contained four to six tandemly oriented nonameric repeats. The sequences in these motifs are similar to the Ca(2+)-binding domains of functionally unrelated secreted proteins reported previously in other bacteria. The reaction product of the recombinant epimerase was analyzed by nuclear magnetic resonance spectroscopy, and the results showed that the guluronic acid residues were distributed in blocks along the polysaccharide chain. Such a nonrandom distribution pattern, which is important for the commercial use of alginate, has previously also been identified in the reaction product of the corresponding enzyme isolated from A. vinelandii.

Alginates↗
PubMed1994

rRNA-mRNA base pairing stimulates a programmed -1 ribosomal frameshift.

Base pairing between the 3' end of 16S rRNA and mRNA is shown to be important for the programmed -1 frameshifting utilized in decoding the Escherichia coli dnaX gene. This pairing is the same as the Shine-Dalgarno pairing used by prokaryotic ribosomes in selection of translation initiators, but for frameshifting the interaction occurs within elongating ribosomes. For dnaX -1 frameshifting, the 3' base of the Shine-Dalgarno sequence is 10 nucleotides 5' of the shift site. Previously, Shine-Dalgarno rRNA-mRNA pairing was shown to stimulate the +1 frameshifting necessary for decoding the release factor 2 gene. However, in the release factor 2 gene, the Shine-Dalgarno sequence is located 3 nucleotides 5' of the shift site. When the Shine-Dalgarno sequence is moved to the same position relative to the dnaX shift site, it is inhibitory rather than stimulatory. Shine-Dalgarno interactions by elongating ribosomes are likely to be used in stimulating -1 frameshifting in the decoding of a variety of genes.

Base Composition↗
PubMed1994

Benign colonic ulcers associated with nonsteroidal antiinflammatory drug ingestion.

Nonsteroidal antiinflammatory drugs can be associated with benign colonic ulcers. The ulcers are easily diagnosed by colonoscopy, and, if uncomplicated, they are best treated by cessation of the nonsteroidal antiinflammatory drugs. Benign colonic ulcers should be included in the differential diagnosis of any patient who presents with gastrointestinal complaints and is taking nonsteroidal antiinflammatory drugs.

Aged↗
PubMed1993

[Radioiodine therapy of thyrotoxicosis in a central hospital].

The aim of this study was to assess the results of 131-I therapy on hyperthyroidism. 131-I doses were individually calculated on the basis of thyroid gland classification, size and iodine-uptake. All patients were pretreated with propylthiouracil or methimazole. Seventy-nine patients treated with radio-iodine during the period 1.3.81-1.6.88 were followed up. The period of observation was 12-100 months (median 57). After eight years and four months the cumulative incidence of hypothyroidism was 45%, being 69% for diffuse goitre, 31% for multinodular goitre and 24% for solitary adenoma. A Cox-analysis showed a significantly greater cumulative incidence of hypothyroidism in patients with diffuse goitre as opposed to non-diffuse. From our data we conclude that radio-iodine therapy of hyperthyroidism with individually calculated doses of 131-I is a satisfactory method, assuming that patients are subjected to lifelong follow-up.

Adult↗
PubMed1993

Studies on the carbohydrate-binding characteristics of human pulmonary surfactant-associated protein A and comparison with two other collectins: mannan-binding protein and conglutinin.

The surfactant-associated protein A (SP-A) belongs to the collectin family, a group of C-type lectins encompassing also surfactant-associated protein D, mannan-binding protein (MBP) and conglutinin. These proteins all have carbohydrate-recognition domains joined to collagen stalks. It seems likely that SP-A, like MBP and conglutinin, may mediate anti-microbial activity through binding to carbohydrates on the microorganisms and collectin receptors on phagocytic cells. We have studied the influence of carbohydrates on the binding of SP-A, MBP and conglutinin to mannan in an enzyme-linked lectin-binding assay. All sugars were of D-configuration, except fucose of which both L- and D-configurations were tested. The order of inhibiting potency on the binding of SP-A was: N-acetylmannosamine > L-fucose, maltose > glucose > mannose. The following sugars were non-inhibitory: galactose, D-fucose, glucosamine, mannosamine, galactosamine, N-acetylglucosamine, and N-acetylgalactosamine. The best inhibitor of MBP was N-acetylglucosamine. Otherwise MBP showed a selectivity similar to that of SP-A. Conglutinin binding was inhibited by all the sugars examined except N-acetylgalactosamine. For conglutinin, as for MBP, the best inhibitor was N-acetylglucosamine. Normal human SP-A, alveolar-proteinosis SP-A purified by ion-exchange chromatography, and alveolar-proteinosis SP-A purified by n-butanol extraction showed no difference in sugar selectivity. The influence of pH and of the calcium concentration was also examined. Organic solvent-extracted SP-A from patients suffering from alveolar proteinosis and normal SP-A showed different sensitivity profiles.

Antibody Specificity↗
PubMed1993

[Pulmonary edema during terbutaline infusion against threatened premature labor].

A case of pulmonary oedema during tocolytic therapy with terbutaline infusion is reported. Although a cardiogenic cause for this type of pulmonary oedema has never been proven, it is believed that physiologic changes in pregnancy aggravated by beta-2 stimulation together with fluid overload constitute the pathophysiologic background to this serious complication.

Adult↗
PubMed1993

[Upper gastrointestinal endoscopy. Assessment of activity during a 3-month period: clinical problems, diagnostic and therapeutic consequences].

All patients referred to upper gastrointestinal endoscopy, during a period of three months, were recorded prospectively. In connection with the endoscopy, the investigator completed a questionnaire, related to demographic data, results of endoscopy and therapeutic suggestions. Six weeks later the general practitioner received a second questionnaire concerning diagnostic and therapeutic consequences. At the same time the patient received a third questionnaire, concerning therapeutic and psychological consequences. In all, 200 endoscopies were performed; 147 diagnostic and 53 controls. Of the former, 65 were open access and 82 were admitted to a medical department. We found that the endoscopies were well founded. There was a great diagnostic yield and the patients, in general, followed the therapeutic aim. Furthermore we found a noticeable psychologic effect, independent of endoscopic findings.

Adult↗
PubMed1993

Pharmacokinetics of ampicillin and sulbactam in pregnancy.

OBJECTIVE: This study evaluated the effects pregnancy had on pharmacokinetic parameters of ampicillin and sulbactam. STUDY DESIGN: Twenty-two women undergoing cesarean section for obstetric indications were randomly assigned to receive a single intraoperative dose of either 1 gm of ampicillin intravenously or 1 gm of ampicillin plus 0.5 gm of sulbactam intravenously after umbilical cord clamping. Blood was drawn from an indwelling intravenous catheter at 15, 30, 45, 60, 120, 240, and 360 minutes after infusion of the antibiotic for determination of serum ampicillin and/or sulbactam levels. Pharmacokinetic parameters were determined by fitting data (serum concentrations versus time) to a single-compartment model that provided elimination rate constants, beta-intercept (calculated concentration at 0 minutes), area under the time-versus-concentration curve, half-life of the drug, total body clearance, and volume of distribution. After the examination 6 weeks post partum, each subject was given an additional dose of the drug she had received during cesarean section, and a second pharmacokinetic study was performed and compared with the previous results. RESULTS: Pregnancy significantly increased the elimination rate constant, decreased the area under the drug-versus-time curve, shortened the serum half-life, and increased the total body clearance in comparison with these parameters in the nonpregnant state for ampicillin. Sulbactam kinetics were similarly affected, although these changes failed to attain statistical significance. CONCLUSION: Because pregnancy is associated with more rapid elimination of beta-lactam drugs, physicians treating infections in pregnant or newly parturient women should consider using shorter intervals between antibiotic doses when a range of dosage intervals is under consideration.

Ampicillin↗
PubMed1993

[The hemodynamic effects of atracurium in geriatric patients during intravenous anesthesia using propofol].

OBJECTIVE: Neuromuscular blocking drugs may produce cardiovascular effects by virtue of drug-induced release of histamine or other vasoactive substances from circulating mast cells, effects at cardiac muscarinic receptors or effects at nicotinic receptors at autonomic ganglia. These haemodynamic reactions may be more pronounced in elderly patients, since cardiovascular compensating mechanisms are attenuated with advancing age. The present study was designed to investigate the cardiovascular effects of atracurium with special regard to the reactions in younger adults and in elderly patients. METHODS: 20 patients, ASA class I-II, who underwent a neurosurgical operation (posterior fossa surgery) were studied. The patients were divided into two groups including patients below (group A) and above (group B) 65 years of age. Anaesthesia was induced with propofol (2.5 mg/kg) and maintained with a Propofol/O2/N2O sequence. Under steady state conditions with propofol every patient received 0.5 mg/kg atracurium besylate. Haemodynamic parameters were recorded and plasma concentrations of epinephrine and norepinephrine were determined before (control) and 2, 5 and 10 minutes after the injection of the neuromuscular blocking agent. All measurements were performed before surgical stimulation in supine position. RESULTS: In the younger adults diastolic blood pressure and systemic vascular resistance decreased significantly 2 minutes after injection of atracurium and reached control level 5 minutes after application of the muscle relaxant. In the elderly patients peripheral vascular resistance decreased significantly after 5 minutes and returned to control 10 minutes after the application of atracurium. In both groups cardiac index, systolic and mean arterial pressure, central venous pressure and the parameters related to the pulmonary circulation were not affected. Plasma concentrations of epinephrine and norepinephrine remained essentially unchanged. Side effects due to a release of histamine such as facial or body blush or bronchial spasms were not noted. CONCLUSION: Since the results of the present study suggest that haemodynamic reactions in younger adults and in the elderly are rare, atracurium can be recommended for neuromuscular blockade in elderly patients under propofol anaesthesia.

Adult↗
PubMed1993

Vaginal flora in health and disease.

This chapter has portrayed the normal vaginal flora as a range of microbial species that associates in a stable way with human vaginal epithelium. The human vagina provides these microorganisms with the physical and chemical environment that allows them to use this tissue as a normal habitat. Because the relationship of the normal flora to the underlying tissue is that of an ecosystem, the components of this system are in dynamic equilibrium. Consequently, a change in the environmental conditions provided by the vaginal epithelium will result in changes in the population density or the species composition of the normal flora. Although the microbial flora appears to provide a benefit to the host by reducing the probability of colonization by exogenous microorganisms, it may participate in various undesirable symptoms, including various types of vaginitis or postoperative, postabortion, and post-Caesarean section infections, and upper tract invasion after lower tract infection. All future attempts to understand vaginitis in all its manifestations necessarily must include recognition of the importance of the normal flora because all types of vaginitis are superimposed on an existing endogenous microbial flora.

Animals↗