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Biomedical subjects

S Hansen

Publications and source records attributed to S Hansen.

At least 163 records · Page 9Linked to original sources
PubMed1994

Reducing work-related back injuries.

A centralized educational program: 1) increases awareness of prevention of back injury, 2) decreases the cost of workers' compensation claims resulting from work-related back injury/pain, 3) decreases the amount of employee sick time taken because of back pain, 4) increases work productivity through proper ergonomics, and 5) teaches staff members to take care of their backs at home and at work. A descriptive study, and tracking of reported back-injury cases and the cost per claim, evaluates the program's efficacy and cost-effectiveness.

Academic Medical Centers↗
PubMed1993

Hodgkin's disease: the protective effect of childbearing.

Register and census data for complete cohorts of Norwegian men and women born between 1935 and 1974 were used to examine the relationship between reproductive factors and the incidence of Hodgkin's disease (HD). Among 1.3 million men and 1.3 million women under observation, 695 male and 441 female cases of HD were diagnosed during the period of follow-up. Our hazard model estimates showed that women, at a given age and in a given birth cohort, have an HD incidence inversely related to current parity. A clear relationship was found only for the nodular sclerosis subtype. In men, the risk of HD development was higher than that in childless women, and there was no parity effect. The lower HD incidence among high-parity women could not be ascribed to their lower social status. Presumably, there is a still unidentified protective factor associated with the biology of childbearing, the effect of which possibly wears off with increasing length of time since childbirth. In addition, there are indications of a net effect of age at entry into motherhood, which may explain part of the estimated parity effect.

Adolescent↗
PubMed1993

Crystal structure of phospholipase C from Bacillus cereus complexed with a substrate analog.

We report the first crystal structure of a complex between PLC from Bacillus cereus (PLCBc) and a competitive inhibitor that is an analog of the natural phospholipid substrate. The structure has been determined at 1.9 A resolution and refined to a final R-factor of 15.7%. The inhibitor binds with its phosphonyl group to the three Zn ions in the active site of the enzyme and is also involved in a hydrogen bonded network including several water molecules and amino acid side-chains which appear to help orient the substrate for productive binding. The interactions within this complex provide some important information regarding the mechanism of PLC-catalyzed hydrolysis of membrane phospholipids. A water molecule, located approximately apical to the diacylglycerol leaving group, seems to be the most likely candidate for the attacking nucleophile which initiates the reaction.

Bacillus cereus↗
PubMed1993

The crystal structure of tris-inhibited phospholipase C from Bacillus cereus at 1.9 A resolution. The nature of the metal ion in site 2.

We report here the crystal structure of the complex formed between phospholipase C (PLC) from Bacillus cereus and the widely used biochemical buffer tris (hydroxymethyl)-methylamine (Tris). The structure has been determined at 1.9 A resolution and refined to R = 20.3%. Tris has metal-binding properties, especially to Zn2+, and has been reported to reduce the activity of PLC. The amine nitrogen atom in Tris is co-ordinated to one of the three Zn2+ ions in the active site of the enzyme, thus confirming its chelating properties and the involvement of the metal ions in the catalytic process. The occupancy of the Zn2+ ion in site 2 in native PLC is 0.6 which could imply the presence of Ca2+ rather than Zn2+. The fact that Tris binds to this metal ion, the nature of the site 2 co-ordination shell and comparison with several homologous Zn-metalloenzymes indicate that PLC is a 3-Zn metalloenzyme. This study is one of a series which explores the active site of PLC by complexing the enzyme with inhibitors and substrate analogues.

Bacillus cereus↗
PubMed1993

English yew poisoning in 43 cattle.

Thirty-five privately owned 1- to 2-year-old mixed-breed steers and heifers, weighing 340 to 454 kg, died from accidental ingestion of English yew (Taxus baccata). Estimated dosages ranged from 0.36 to 0.70 g of fresh plant/kg of body weight. Clinical signs of poisoning and death began 2 to 3 hours after first exposure, and cattle continued to have clinical signs, which ended in death 6 to 8 hours later. Most cattle had died by 4 hours after first ingestion. Necropsy of 4 cattle revealed substantial amounts of English yew leaves and small stems in the rumen contents. Grossly, there were areas of hyperemia in the abomasum and small intestine. Histologically, lesions were limited to the lungs and included moderate congestion and interlobular edema. Chemical analysis by thin-layer chromatography of suspected yew plant material from the rumen contents of the 4 necropsied cattle was compared to authentic taxol, and confirmed the presence of taxol in rumen samples.

Animals↗
PubMed1993

Effect of clonidine on the responsiveness of infant rats to maternal stimuli.

Clonidine (0.1 mg/kg), an alpha 2-adrenoceptor agonist, stimulated ultrasonic callings in 10-day-old rats. Unlike normal isolated rat pups, the vocalizations of clonidine-treated rats appeared resilient to maternal cues. Thus, clonidine-induced vocalizations did not decrease during intraoral infusions with 10% sucrose, exposure to home cage bedding or tactile stimulation of the skin. Clonidine (0.05; 0.1; 0.2 mg/kg) also disrupted the attraction normally shown by infant rats to home cage odours in an olfactory place preference test. This effect by clonidine was not shared by raclopride (1-4 mg/kg), naltrexone (0.5-2.0 mg/kg) or propranolol (2.5-10.0 mg/kg). Clonidine-treated infants (0.05; 0.1; 0.2 mg/kg) also failed to apprehend and attach to the anaesthetized mother's nipple. The results raise the possibility that alpha 2-adrenoceptor activation blunts the infant's receptivity to maternal olfactory incentives and intensifies separation-induced responses.

Animals↗
PubMed1993

Interaction with pups enhances dopamine release in the ventral striatum of maternal rats: a microdialysis study.

A growing body of evidence suggests that an interference with dopamine (DA) transmission disrupts maternal behavior in the rat. The present brain microdialysis study was therefore conducted to investigate whether infants can modulate ventral striatal DA release in mother rats. There was a significant rise in the extracellular concentrations DA, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) in the ventral striatum when mothers were reunited with their litters following separation overnight. Nursing was the predominant behavior during this phase of the experiment. More active behaviors were elicited by soiling pups with flowerpot earth, and this was accompanied by further increases in DA, DOPAC, HVA, and 5-HIAA. It is suggested that pup-induced stimulation of ventral striatal DA release facilitates parental responses such as pup retrieval.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

[Early amniocentesis between the 12th-14th week of pregnancy. Clinical experiences with 1,100 cases].

Information is presented on 1100 early amniocenteses between the 12th and 14th week of gestation, performed at the Evangelisches Krankenhaus Oberhausen over a two year period. In all cases, a sufficient amount of amniotic fluid was obtained. In 99.7%, the cytogenetic diagnosis was successful. In 2.6% (29 patients), an aberrant karyotype was found. The time of cultivation was in the same range as can be observed in standard amniocentesis. The AFP-median measurements correlate with other studies. The spontaneous abortion rate was 0.3%. We conclude, that early amniocentesis can be performed safely and successfully by an experienced surgeon between the 12th to 14th week of gestation.

Abortion, Spontaneous↗
PubMed1993

[HIV-patients self-evaluated health and functional status. Basis for individually-adapted nursing care planning].

The first case with HIV-infection in Sweden was recognized in the beginning of the nineteen eighties. Since then 2972 cases have been identified. The purpose of this study was to investigate HIV-infected patients' perception of their everyday life situation. Two questionnaires were used: Sickness Impact Profile (SIP) and one developed for the purpose of this study. Twenty patients, mean age 44 years with T4 cells, crucial for the immunological status, ranging from 0.15-0.2 x 109/l at a research unit participated in the study. The HIV patients investigated had high SIP-scores as compared to healthy controls. Thus the patients perceived their everyday health related behavior as impaired. The functions related to work, recreation-pasttime and sleep-rest were most impaired. Those who still were working and had had no physical impairments also evaluated their general health as being better as compared to non workers. The study, even when a small one, showed that the health related behaviors of these patients have a large individual variation. Therefore it is important to develop individual nursing care for this group of patients.

Activities of Daily Living↗
PubMed1993

A new proliferation-associated nuclear antigen detectable in paraffin-embedded tissues by the monoclonal antibody Ki-S1.

A monoclonal antibody (Ki-S1) has been raised that reacts with the nuclei of proliferating cells. The antigen recognized is resistant to formalin fixation and can be detected in frozen tissues as well as in routinely processed specimens. In immunohistochemistry, nuclear staining can be seen in those tissues and cellular compartments known to be actively proliferating. Peripheral blood lymphocytes are negative but show a strong increase in antigen expression after mitogen stimulation. Flow cytometric determination of DNA content and antigen expression revealed negativity of G0 cells and positivity of G1 to G2/M cells. A cytoplasmic co-reactivity, not associated with proliferation, was confined to Langerhans islands of the pancreas. The nuclear localized antigen has a molecular mass of 160 kd and therefore seems to be different from all other known immunohistochemical markers of proliferating cells. We conclude that the monoclonal antibody Ki-S1 might provide a useful tool for studying cell proliferation in situ under normal and pathological circumstances.

Animals↗
PubMed1992

Partial protective effect of MK-801 on MPTP-induced reduction of striatal dopamine in mice.

The protective effect of MK-801, an N-methyl-D-aspartate (NMDA) receptor antagonist on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced reduction of striatal dopamine (DA) was examined in C57 BL/6 mice. Striatal DA levels were significantly higher in animals receiving parenteral MK-801 before and for 48 h following MPTP administration after 28 days than in animals receiving MPTP alone. The effect was not due to inhibition of monoamine oxidase-B (MAO-B) by MK-801. These data suggest that NMDA receptors may be involved in some of the neurotoxicity produced by MPTP.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1992

Crystal structures of phosphate, iodide and iodate-inhibited phospholipase C from Bacillus cereus and structural investigations of the binding of reaction products and a substrate analogue.

The crystal structure of the complex formed between phospholipase C (PLC) from Bacillus cereus and inorganic phosphate (Pi), which is an inhibitor, has been determined and refined to 2.1 A resolution. The final R-factor is 19.7%. We have also studied the binding of two other inhibitors, iodide and iodate, to PLC. X-ray data for these two complexes were collected to 2.8 A resolution during the search for heavy-atom derivatives. A series of screening experiments where PLC crystals have been treated with several reaction products and a substrate analogue were carried out to clarify the question of substrate binding. The results have so far been ambiguous but are discussed briefly. Phosphate and iodate are both found to bind to the three metal ions in the protein molecule, suggesting that these ions are involved directly in the catalytic process and thereby identifying the active site. PLC also binds nine iodide ions, eight of which are on the surface of the molecule and of lower occupancy. The ninth blocks the entrance to the active site cleft and is of higher occupancy. Altogether, these results suggest that the substrate, a phospholipid, is associated directly with the metal ions during catalysis.

Bacillus cereus↗
PubMed1992

Prenatal diagnosis of monosomy 18 and ring chromosome 18 mosaicism.

The case of monosomy 18/ring chromosome 18 mosaicism which was detected prenatally by amniocentesis is presented. The pregnancy was terminated in week 18. Autopsy showed complex malformation of the fetus consisting of cebocephaly, hypotelorism, microphthalmia, severe defects of brain development, and arrest of placental maturation.

Adult↗
PubMed1992

Substrate-enzyme interactions and catalytic mechanism in phospholipase C: a molecular modeling study using the GRID program.

Based on the high-resolution X-ray crystallographic structure of phospholipase C from Bacillus cereus, the orientation of the phosphatidylcholine substrate in the active site of the enzyme is proposed. The proposal is based on extensive calculations using the GRID program and molecular mechanics geometry relaxations. The substrate model has been constructed by successively placing phosphate, choline and diacylglycerol moieties in the positions indicated from GRID calculations. On the basis of the resulting orientation of a complete phosphatidylcholine molecule, we propose a mechanism for the hydrolysis of the substrate.

Binding Sites↗
PubMed1992

Contrast variation studies of clathrin coated vesicles by small-angle neutron scattering.

Structural information on clathrin coated vesicles has been obtained by small angle neutron scattering using contrast variation. A characteristic peak in the neutron scattering profile, which is apparent in 75% D2O, as well as in H2O, disappears when contrast matching the protein component of the coated vesicles in 42% D2O. Neutron, as well as dynamic, light scattering give a coated vesicle size of about 900 A in H2O and D2O, but for neutron scattering the diameter decreases when matching out the protein coat of the clathrin coated vesicles. From the match point for the clathrin coated vesicles it is demonstrated that the clathrin cages do contain internal membrane. The mass of 34 MD and composition of 75% protein and 25% lipid found from the analysis of the small-angle scattering data are both in good agreement with the values reported in the literature. Electron microscopy gives an average outer diameter of 880 A for the coated vesicles and an average diameter of 460 A for the vesicle itself.

Biophysical Phenomena↗