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Biomedical subjects

M Knutsson

Publications and source records attributed to M Knutsson.

9 recordsLinked to original sources
PubMed2001

Vasoactive intestinal peptide has a direct positive inotropic effect on isolated human myocardial trabeculae.

The aim of the present study was to assess the inotropic effects of vasoactive intestinal peptide (VIP) on isolated myocardial trabeculae from the right atrium and the left ventricle of human hearts. Furthermore, using reverse transcriptase-PCR, we wanted to determine the presence of mRNAs encoding the three cloned human VIP receptors, VPAC(1), VPAC(2) and PAC(1). The trabeculae were paced at 1.0 Hz in tissue baths, and changes in isometric contractile force upon exposure to agonist were studied. VIP had a potent positive inotropic effect in some of the atrial and ventricular trabeculae tested. This effect was almost completely blocked by the VIP-receptor antagonist VIP-(6-28). mRNAs encoding the human VPAC(1), VPAC(2) and PAC(1) receptors were detected in human myocardial trabeculae from both the right atrium and the left ventricle. In conclusion, VIP has a direct positive inotropic effect in both the atria and the ventricles of the human heart. The presence of mRNAs for the VPAC(1), VPAC(2) and PAC(1) receptors suggest that VIP may mediate its effect via these receptors.

Adolescent↗
PubMed2000

Urine from chronic hepatitis B virus carriers: implications for infectivity.

Horizontal transmission of hepatitis B virus (HBV) without apparent sexual or parenteral exposure is common in hyperendemic areas. In most cases, the route of transmission is unknown. To investigate urine as a potential source of infection, serum and urine from 56 chronic hepatitis B surface antigen (HBsAg) carriers were examined for the presence of HBV DNA using the polymerase chain reaction (PCR). Thirty-four of the patients were anti-hepatitis B e antigen (anti-HBe) positive and 22 were hepatitis B e antigen (HBeAg) positive. HBV DNA was detected in serum from 46 patients (82%) and in urine from 28 patients (50%). Most HBeAg-positive patients had HBV DNA detectable in urine (91%), whereas urine samples from anti-HBe-positive patients were found to contain HBV DNA to a lesser extent (24%). When comparing HBV DNA from serum and urine by an end-point titration PCR, a titration difference averaging 10(3) was found between serum and urine. A significant female predominance was also noted among the positive urine samples (P < 0.05), which was not correlated to the presence of haematuria. Detection of HBV DNA may indicate active viral replication, and thereby infectivity. Because a high proportion of chronic HBV carriers were found to have HBV DNA in urine, it is suggested that irrespective of HBeAg/anti-HBe status, urine should be regarded as a potential route of transmission and therefore be investigated further as a means of horizontal and nosocomial transmission of HBV.

Adult↗
PubMed2000

Recent high incidence of fulminant hepatitis in Samara, Russia: molecular analysis of prevailing hepatitis B and D virus strains.

Until 1991, the Russian city of Samara was largely isolated from other parts of Russia and the rest of the world. Very recently, Samara has seen an alarming increase in the incidence of hepatitis. The proportion of fulminant cases is unusually high. We wanted to assess the roles of hepatitis B virus (HBV) and hepatitis D virus (HDV) in acute viral hepatitis in this region by analyzing the prevailing strains of both and by determining their genotypes and possible origin. Serum samples were screened for different serological markers and by PCR followed by direct sequencing. Of the 94 HBV-positive samples (80% of which were acute infections), 37 (39%) were also HDV positive. Sixty-seven percent of the patients had anti-HCV antibodies. Twenty-five percent of all patients in the study had fulminant hepatitis. Statistically significant sex differences were found among fulminant cases. For HBV, the core promoter sequences of 62 strains were determined and all but one were found to be of genotype D. None of these had any deletions. Only one strain, from a patient with fulminant fatal hepatitis, showed multiple mutations. The pre-S2 region sequences of 31 HBV strains were also compared. Phylogenetically, these fell into two distinct groups within genotype D, suggesting different origins. For HDV, part of the region encoding the delta-antigen was sequenced from four strains. All proved to be of genotype I and were similar to Far Eastern and Eastern European strains. The contribution of intravenous drug use to the sharp increase in viral hepatitis in this unique setting is discussed.

Acute Disease↗
PubMed1998

Novel chiral recognition elements for molecularly imprinted polymer preparation.

The use of a novel chiral functional monomer system in molecular imprinting protocols is described. The monomer, dibenzyl (2R,3R)-O-monoacryloyl tartrate, possesses a hydroxyl moiety which can be used to direct template-functional monomer interactions during molecular imprinting polymerization. This system simultaneously positions benzyl ester-protected carboxyl groups in close proximity to the template, which upon deprotection yield recognition sites with stronger ligand-binding capacities. Furthermore, the inherent chirality of the monomer engenders the polymer with an inbuilt preference for a given stereoisomer. Application of the system to the molecular imprinting of the cinchonidine alkaloids (+)-cinchonine and (-)-cinchonidine yielded stereoselective polymers. The effect of imprinting (+)-cinchonine produced a polymer which more than reversed the inherent chiral selectivity of the chiral monomer residues present in the matrix.

Binding Sites↗
PubMed1997

On-line supported liquid membrane-liquid chromatography with a phenol oxidase-based biosensor as a selective detection unit for the determination of phenols in blood plasma.

The potential of on-line combination of supported liquid membrane extraction and column liquid chromatography with a phenol oxidase-based biosensor as a selective detection unit has been investigated for the determination of phenols in human plasma. The phenols are selectively extracted into a porous PTFE (polytetraflouroethene) membrane impregnated with a water-immiscible organic solvent and further into an alkaline acceptor phase. Via an ion-exchange interface, the analytes are transferred to a reversed-phase column where they are separated and detected using the biosensor. No sample pretreatment before the extraction, except centrifugation, is made. Due to the high selectivity both in the extraction and in the detection steps and to the fact that the demands on the chromatographic separation are low, a quick separation using an eluent with a low concentration of organic modifier can be made, without affecting the biosensor response. Detection limits below the 50 microg/l level in blood plasma were obtained for the three model compounds, phenol, p-cresol and 4-chlorophenol.

Biosensing Techniques↗
PubMed1995

Temporary increase of FSH levels in healthy, nulliparous, young women after cessation of low-dose oral contraceptive use.

The effect of modern low-dose oral contraceptives (OCs) on the levels of follicle stimulating hormone (FSH) and luteinizing hormone (LH) in young, health, nulligravid women was studied in two independent samples. Elevated FSH levels were seen in former OC users compared with never users regardless of menstrual cycle phase. The increase in FSH levels seemed to peak one year after cessation of OC use. This relationship was still significant after exclusion of women with low progesterone levels. LH levels were significantly higher in former users compared with never users in the first sample, but not in the second sample. The difference in FSH concentrations was very small. Single blood samples were obtained from the subjects at each time point even though it is recognized that gonadotropin secretion is pulsatile. These results must be regarded as preliminary and unconfirmed due to small sample size.

Adult↗
PubMed1992

Plasma prolactin in relation to menstrual cycle phase, oral contraceptive use, arousal time and smoking habits.

The study was designed to investigate if modern low dosage combined oral contraceptives were associated with changes in plasma prolactin levels in healthy nulliparous women aged 19-25. Plasma prolactin was not significantly correlated to oral contraceptive use, nor to smoking habits. Plasma prolactin was, however, significantly negatively correlated to time since awakening. A significant two-way interaction on prolactin was also seen between smoking and present oral contraceptive use. In our material the mean values of plasma prolactin were higher in the follicular phase than in the luteal phase, although not significantly.

Adult↗