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Biomedical subjects

M Forsman

Publications and source records attributed to M Forsman.

At least 37 records · Page 2Linked to original sources
PubMed1998

Gastric emptying of solids measured by means of magnetised iron oxide powder.

The aim of this study was to develop a radiation-free method to measure gastric emptying. Such a method would be useful e.g. for patients who need repeated measurements and in pregnancy. Ferrimagnetic particles (gamma-Fe2O3), ingested within a solid test meal (pancakes), were magnetised by an applied magnetic field. After magnetisation, the remanent magnetic field was measured with fluxgate magnetometers outside the stomach (anterior and posterior). The intragastric contents was estimated from the strength of the remanent field. The procedure was repeated 18 times over a period of up to 2 h postprandially. The test meal was chosen to correspond to a radiolabelled test meal that had previously been used in a scintigraphic study with (other) healthy persons. In vivo measurements were carried out on 16 healthy male volunteers. The estimated retained magnetic tracer in the stomach after the 2 h measurement time was 31 +/- 12% (mean +/- SD) and the lag phase time was 31 +/- 11 min. The corresponding scintigraphic curve (from the previous study) from 16 males showed 40 +/- 14% retained isotope after 2 h. The early part of the mean emptying curve decreased slightly faster than the corresponding scintigraphic one, but the similarity of the two seems promising enough for further development of the present method.

Adult↗
PubMed1998

Comparison of multipole and mean value methods to quantify dust in human lungs: simulating the magnetopneumography procedure.

Magnetopneumography (MPG) can quantify the retention of magnetisable particles in the lung acquired, for instance, in welding work. MPG is non-invasive and is used in occupational health, industrial hygiene and lung physiology. Following a brief magnetisation, the remanent magnetic field is mapped with magnetometers outside the thorax. There is no unique analytical inverse solution to this class of magnetostatic problem, and various inverse methods have been proposed. In the present study, the influence of variations in size and shape of the lungs and chest, magnetic measurement noise, positional noise and spatial dust distribution are investigated in five inverse methods. The mean value of the field map, calibrated against a lung phantom, is the commonly used method. Lung and chest size influence the mean value method solutions strongly. Correction for chest size reduces these errors, but bias errors and sensitivity to the deposition pattern remains a problem. A multipolar expansion, including dipolar, quadrupolar and octopolar moments, yields best results overall, provided the single-to-noise ratio is sufficient. This inverse solution is unbiased, requires no calibration with phantom lung models and serves to minimise errors due to inter-individual differences in anatomy and to inhomogeneous retention of inhaled dust.

Dust↗
PubMed1997

The two beta-lactamase genes of Streptomyces cacaoi, blaL and blaU, are under the control of the same regulatory system.

The production of beta-lactamase in Streptomyces cacaoi, which contains two beta-lactamase-encoding genes, blaL and blaU, is inducible by beta-lactam compounds. The two genes have been cloned independently in S. lividans TK24, a beta-lactamase-negative species. The blaU clone did not respond to the presence of beta-lactams, whereas the blaL clone appeared to be inducible in S. lividans. The latter clone contains two open reading frames, blaA and blaB, located just upstream of but transcribed divergently from blaL, which were shown to be required for the production as well as the induction of BlaL. The deduced BlaA protein belongs to the LysR family of transcription regulators. In order to examine the role of BlaA in regulation, we here report on over-expression of a GST-BlaA fusion protein in Escherichia coli and its use for antibody preparation. The GST-BlaA fusion protein was partially purified and bandshift assays showed that it bound the 197-bp blaL-blaA intergenic region. The BlaA DNA binding-site was further restricted to a 30-bp sequence containing a T-N11-A motif, a characteristic of LysR-type promoters. Another T-N11-A motif upstream of the blaU gene was also shown to bind BlaA. The affinities of these two T-N11-A motifs in BlaA binding were comparable. A plasmid bearing the blaU structural gene and the blaA-blaB regulatory region was constructed and shown to confer on an S. lividans host the capacity to produce inducible beta-lactamase. It can thus be concluded that the S. cacaoi blaL and blaU genes are controlled by the same regulatory system.

Bacterial Proteins↗
PubMed1996

DNA recovery and PCR quantification of catechol 2,3-dioxygenase genes from different soil types.

With the objective of monitoring xenobiotic degrading bacteria in soil, a method for rapid extraction of DNA from soil, amenable to amplification by PCR, was developed. The method was based on lysis by freeze-thawing and subsequent addition of sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide and proteinase K. The extraction method required 2 h and was tested on six different soils differing in organic content, water holding capacity and pH, including ones from which DNA extraction is difficult. DNA yields from the soils ranged from 6.1 to 54.0 micrograms of DNA per g soil. The efficiency and reproducibility of the DNA extraction method were evaluated by competitive PCR. The organic content in the soils was a major factor affecting the amount of obtained DNA amenable for amplification by PCR. A PCR primer-pair was designed on the basis of the known nucleotide sequences of several catechol 2,3-dioxygenase genes. The specificity of the primer-pair was demonstrated on different sequenced catechol 2,3-dioxygenase genes and on site-specific bacterial isolates from polycyclic aromatic hydrocarbon (PAH)-contaminated soil. The concentration of catechol 2,3-dioxygenase DNA in PAH-contaminated sediment undergoing an ex situ compost process was quantified by competitive PCR over a period of 16 weeks. The concentration of PAHs and catechol 2,3-dioxygenase DNA in the soil samples, was found to correlate.

Catechol 2,3-Dioxygenase↗
PubMed1996

Adverse effects of hyperoxemia during cardiopulmonary bypass.

OBJECTIVE: Aiming at elucidating the effects on capillary blood flow and tissue oxygenation of hyperoxemia during cardiopulmonary bypass, we studied skeletal muscle surface oxygen tensions in 10 patients undergoing elective cardiac operations. METHODS: In a prospective investigation each patient was exposed to normoxemia (arterial oxygen tension 75 to 115 mm Hg) and hyperoxemia (arterial oxygen tension > 185 mm Hg, inspired oxygen fraction = 1.00) during normal anesthetized conditions before and after cardiopulmonary bypass, as well as during normothermic and hypothermic continuous-flow bypass. In each state hemodynamic variables and arterial and mixed venous blood gas and acid base values were measured. From these data oxygen transport variables were calculated. Tissue oxygenation was studied with the use of a multiple-point polarographic oxygen microelectrode, known to provide measures of oxygen tensions at the capillary level. The oxygen distribution profile of such a sample is also indicative of capillary blood flow distribution changes. RESULTS: In all patients and at each occasion of the investigation markedly low mean surface oxygen tensions in skeletal muscle were registered. When hyperoxemia was instituted, a significant decrease in these surface oxygen tensions together with an increase in distribution heterogeneity was seen during all stages. Contrary to prebypass, postbypass, and hypothermic bypass, where vascular resistance, oxygen delivery, and oxygen consumption remained similar during hyperoxemia and normoxemia, a significant (p < 0.05) increase in vascular resistance together with a decline in oxygen consumption was seen during hyperoxemic normothermic (35 degrees to 36 degrees C) cardiopulmonary bypass. CONCLUSION: These findings show that the microcirculatory response to hyperoxemia, seen under other circumstances, persists during continuous-flow cardiopulmonary bypass, normothermic as well as hypothermic. If these adverse effects on tissue oxygenation by hyperoxemia can be further verified and shown to be valid for other organs than skeletal muscle, we would suggest that hyperoxemia should be avoided, especially during normothermic cardiopulmonary bypass.

Acid-Base Equilibrium↗
PubMed1995

Nitrendipine and mefruside in elderly hypertensives: effects on blood pressure, cardiac output, cerebral blood flow and metabolic parameters.

In this multicentre, randomised, double-blind, cross-over study, we evaluated and compared the effects of nitrendipine (a calcium entry blocker of the dihydropyridine group) and mefruside (a diuretic) on BP, cardiac output, cerebral blood flow and metabolic parameters in 22 elderly hypertensives. Eight weeks of treatment with nitrendipine (27.3 mg daily) and mefruside (30.7 mg daily) significantly reduced BP values to almost the same extent. Heart rate, cardiac output (n = 14), cerebral blood flow (n = 20), renin activity and aldosterone remained unchanged during nitrendipine and mefruside treatment. Nitrendipine did not alter any metabolic parameter (electrolytes, lipid values and blood glucose); in patients treated with mefruside serum potassium fell by 0.4 mmol/l (P < 0.001). Minor adverse events were reported in both treatment groups, mostly due to vasodilation. We conclude that both drugs possess potent and comparable haemodynamic and anti-hypertensive properties. They reduce BP by reducing total peripheral vascular resistance with maintained autoregulation of cerebral blood flow. The metabolic disturbances induced by mefruside seem to be less pronounced than that observed with other thiazide diuretics.

Aged↗
PubMed1994

General intelligence and cognitive profile in women with congenital adrenal hyperplasia (CAH).

To investigate possible effects of prenatal androgen exposure on cognitive functions, general intelligence and cognitive profile were studied in 22 women, 17-34 years old, with prenatal virilization due to congenital adrenal hyperplasia (CAH) (21-hydroxylase deficiency) and 22 healthy controls matched for region and date of birth. The tests were selected to measure abilities where gender differences repeatedly had been observed or that had earlier shown differences between CAH subjects and controls. The following cognitive functions were tested: Verbal, Visuo-Spatial, Visuo-Motor, Arithmetical, Logical Inductive abilities, and Field Dependence. Contrary to earlier reports, the mean general intelligence level of the CAH (22) group was significantly lower than the controls' and the earlier observed inferiority for calculation abilities in female CAH subjects was not supported by the results of the present study. A possible verbal disadvantage with significantly inferior results was noted for the two verbal tests for the CAH (22) group. For the 13 CAH/control pairs with equal general intelligence levels, the discrepancy between the inferior verbal vs. visual, arithmetic, and logical category scores was significantly larger for the CAH group than the controls. These results may suggest that CAH women develop a more masculine cognitive pattern under the influence of increased prenatal androgen exposure.

Adolescent↗
PubMed1994

Analysis of 16S ribosomal DNA sequences of Francisella strains and utilization for determination of the phylogeny of the genus and for identification of strains by PCR.

The 16S ribosomal DNAs (rDNAs) of two strains of Francisella tularensis and one strain of Francisella philomiragia were sequenced. On the basis of phylogenetic analysis data, the genus Francisella was placed in the gamma subclass of the Proteobacteria. The most closely related organism was the intracellular bacterium Wolbachia persica. The sequenced 16S rDNA molecules of the Francisella species exhibited very high levels of similarity (98.5 to 99.9%). Two variable regions, comprising 390 to 450 nucleotides of the 16S rDNA molecules of 17 additional Francisella strains, including members of the species F. tularensis and F. philomiragia, were also sequenced. At most, six nucleotide differences were observed among the sequences of the F. tularensis strains. The sequence of Francisella novicida was virtually identical to the sequences of the F. tularensis strains, thereby supporting the hypothesis that these organisms are members of the same species. On the basis of the observed differences, primer pairs were designed to distinguish strains by using the PCR at the genus, species, and subspecies levels. This permitted sensitive identification of strains belonging to the genus Francisella and discrimination of the species F. tularensis and F. philomiragia.

Base Sequence↗
PubMed1994

An aromatic effector specificity mutant of the transcriptional regulator DmpR overcomes the growth constraints of Pseudomonas sp. strain CF600 on para-substituted methylphenols.

The pVI150 catabolic plasmid of Pseudomonas sp. strain CF600 carries the dmp system, which comprises the divergently transcribed dmpR gene and the dmp operon coding for the catabolic enzymes required for growth on (methyl)phenols. The constitutively expressed DmpR transcriptional activator positively controls the expression of the RpoN-dependent dmp operon promoter in the presence of the aromatic effector in the growth medium. However, the magnitude of the transcriptional response differs depending on the position of the methyl substituent on the aromatic ring. Experiments involving an elevated copy number of the dmp system demonstrate that growth on para-substituted methylphenols is limited by the level of the catabolic enzymes. An effector specificity mutant of DmpR, DmpR-E135K, that responded to the presence of 4-ethylphenol, a noneffector of the wild-type protein, was isolated by genetic selection. The single point mutation in DmpR-E135K, which results in a Glu-to-Lys change in residue 135, also results in a regulator with enhanced recognition of para-substituted methylphenols. The DmpR-E135K mutation, when introduced into the wild-type strain, confers enhanced utilization of the para-substituted methylphenols. These experiments demonstrate that the aromatic effector activation of wild-type DmpR by the para-substituted methylphenols is a major factor limiting the catabolism of these compounds.

Bacterial Proteins↗
PubMed1993

Identification and classification of different isolates of Francisella tularensis.

The causative agent of tularemia, Francisella tularensis, occurs in two main biovars, the highly virulent F. t. biovar tularensis, found in North America; and the less virulent biovar palaearctica, found all over the northern hemisphere. Two other biovars have been proposed, F. t. biovar mediaasiatica and F. t. biovar palaearctica var. japonica. In Sweden tularemia is most frequently observed in man and varying hares (Lepus timidus), and occasionally in other species. Tularemia in hares is normally an acute fatal disease, although less fatal infections have been reported. The diagnosis of tularemia is routinely based on immunological reactions. We studied 10 different isolates of F. tularensis from varying hares, one isolate from an Ural owl (Strix uralensis), one vaccine strain, one strain of F. t. biovar japonica, and six isolates from a virulence study of F. tularensis, by biochemical tests and by hybridization experiments with probes complementary to 16S rRNA. All isolates, except the isolate F. t. biovar japonica, were characterized as F. t. biovar palaearctica by biochemical tests. In the 16S rRNA analysis all isolates were positive to the probe for Francisella tularensis and the probe for F. t. biovar palaearctica with the exception that F. t. biovar japonica reacted with the probe specific to F. t. biovar tularensis. To further confirm that the strains used belonged to F. t. biovar palaearctica virulence tests in rabbits were performed which disclosed this phenotype. The results presented in this work show that the isolated strains from the western part of Europe were F. t. biovar palaearctica, irrespective of animal origin or virulence.

Animals↗
PubMed1993

Azepexole, a potent alpha 2-agonist with anaesthetic effects, does not affect cerebral energy consumption in dogs given isoflurane.

The effects of the alpha 2-agonist azepexole on the cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) were studied by a sagittal sinus outflow technique in dogs. Azepexole, 1 mg kg-1 (reported to decrease the anaesthetic requirement for isoflurane by almost 90%), caused no change in CMRO2 when given during 1.4% isoflurane anaesthesia. CBF was reduced by 26%. When the concentration of isoflurane was reduced to 0.2%, CMRO2 increased by 26% as would have been expected for the change in isoflurane concentration alone. Concomitantly CBF increased to a level not significantly different from control. Azepexole might be a useful adjunct to inhalational anaesthetics, and combined with a low dose of isoflurane it should be an excellent background anaesthetic when studying the effect of other drugs on CMRO2 in dogs as the combination seems to have little effect on the CMRO2.

Adrenergic alpha-Agonists↗
PubMed1992

Two different beta-lactamase genes are present in Streptomyces cacaoi.

Two beta-lactamase genes called blaL and blaU have been cloned independently in Liège and in Umeå, from Streptomyces cacaoi. Genes blaL and blaU were found to differ largely in their nucleotide sequences, although the encoded proteins both belonged to the class A of beta-lactamases (active-site serine penicillinases). DNA-hybridization and polymerase chain reaction assays have now demonstrated that both blaL and blaU genes were present in the S. cacaoi strains used in Liège and in Umeå.

Amino Acid Sequence↗
PubMed1992

Mutagenic analysis of the promoter of the Streptomyces fradiae beta-lactamase-encoding gene.

The Streptomyces fradiae beta-lactamase promoter (PblaF) was sequenced and characterized by promoter probing, primer extension, and exonuclease III-mediated deletions. The transcription start point (tsp) was the same in both S. lividans and S. fradiae. Oligodeoxyribonucleotide-directed random mutations and site-specific mutations were introduced in the promoter region. The effects of these mutations on transcription were assayed by an RNA colony hybridization method. This analysis identified cis-acting sequence determinants located similarly to the -10 and -35 regions of a typical Escherichia coli promoter. Also, a change in the distance between these regions from 19 to 17 bp drastically reduced promoter activity. PblaF was shown not to be recognized by sigma-whiG or by sigma-hrdA, hrdC, or hrdD. Sequence alignment of PblaF to sigma factor-classified Streptomyces promoters revealed little homology. Thus, PblaF is probably recognized by an as yet unidentified sigma factor.

Amino Acid Sequence↗
PubMed1992

Characterization and classification of strains of Francisella tularensis isolated in the central Asian focus of the Soviet Union and in Japan.

The two subspecies of Francisella tularensis, F. tularensis subsp. tularensis (type A) and F. tularensis subsp. palaearctica (type B), differ from each other in biochemistry and virulence. Strains of F. tularensis subsp. tularensis are believed to be confined to North America, whereas strains of F. tularensis subsp. palaearctica occur in Europe, in Asia, and in North America. Moreover, the existence of two other subspecies, designated F. tularensis subsp. mediaasiatica and F. tularensis subsp. palaearcitica japonica, has been suggested for strains of F. tularensis isolated in the central Asian focus of the Soviet Union and in Japan, respectively. In the present study, strains biochemically classified as F. tularensis subsp. mediaasiatica or F. tularensis subsp. palaearctica japonica have been investigated by hybridization with probes specific to 16S rRNAs of the two main subspecies. Furthermore, the virulence and biochemical characteristics of the strains were compared with those of strains belonging to F. tularensis subsp. palaearctica and F. tularensis subsp. tularensis. It was found that 16S rRNAs of F. tularensis subsp. mediaasiatica and F. tularensis subsp. palaearctica japonica hybridize with the probe specific to a genotype proposed herein, genotype A (F. tularensis subsp. tularensis), which shows that strains genetically related to this subspecies are found outside North America. However, the central Asian strains differed from F. tularensis subsp. palaearctica and F. tularensis subsp. tularensis strains when investigated by fermentation of glucose. The results of the biochemical tests could not be unambiguously used for differentiation of strains into F. tularensis subsp. palaearctica or F. tularensis subsp. tularensis. These drawbacks suggest that classification of strains of Francisella on the basis of 16S rRNA analysis may be preferable to classification on the basis of biochemical analysis.

Animals↗
PubMed1991

Cerebral effects of nitrous oxide when added to low and high concentrations of isoflurane in the dog.

The purpose of this canine study was to examine the cerebral vascular and metabolic effects of adding nitrous oxide to isoflurane from 1.4% expired (1 MAC) up to a concentration giving an isoelectric electroencephalogram (EEG). Cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) were determined using a sagittal sinus outflow technique. At 1.4% expired isoflurane, 70% nitrous oxide increased CBF but had no effect on CMRO2. At 3.1% expired isoflurane, 70% nitrous oxide had no effect on either CBF or CMRO2. The latter concentration of isoflurane rendered the EEG isoelectric, but when nitrous oxide was added, EEG activity reappeared. To again produce an isoelectric EEG required an increase in the isoflurane concentration to 3.5% +/- 0.2% (with no further effect on CMRO2). The authors also found that at 1.4% isoflurane, 0.9 micrograms.kg-1.min-1 of angiotensin significantly decreased CMRO2 without any effect on CBF. It is concluded that nitrous oxide, when added to isoflurane concentrations ranging from 1.4% to 3.5% in the dog, increases CBF at the low but not the high isoflurane concentrations although it has no effect on CMRO2.

Animals↗
PubMed1990

Effects of nimodipine on cerebral blood flow and neuropsychological outcome after cardiac surgery.

Thirty-five patients undergoing cardiac surgery requiring cardiopulmonary bypass (CPB) were allocated randomly in a prospective double-blind study to receive either nimodipine 0.5 micrograms kg-1 min-1 or placebo. Cerebral blood flow (CBF) was measured during and immediately after CPB. Neuropsychological tests were performed 6 months after surgery to determine any relationship between ischaemic damage and CBF and administration of nimodipine. There were no differences in CBF between the nimodipine (n = 18) and placebo groups (n = 17). Significant changes in neuropsychological tests were found in six patients tested 6 months after surgery but there were no conclusive signs of ischaemic damage. The nimodipine-treated group performed better in tests of verbal fluency and visual retention, suggesting that some memory functions were preserved better in this group.

Brain↗