Biomedical subjects

A Thelin

Publications and source records attributed to A Thelin.

At least 19 recordsLinked to original sources

PubMed2001

Monitoring of the subtraction process in solid-phase representational difference analysis: characterization of a candidate drug.

In this study, we have applied and evaluated a modified cDNA representational difference analysis (RDA) protocol based on magnetic bead technology to study the molecular effects of a candidate drug (N,N'-diacetyl-L-cystine, DiNAC) in a model for atherosclerosis. Alterations in a gene expression profile induced by DiNAC were investigated in a human monocytic cell line (THP-1) differentiated into macrophage-like cells by lipopolysaccharide and further exposed to DiNAC. Three rounds of subtraction have been performed and the difference products from the second and third rounds have been characterized in detail by analysis of over 1000 gene sequences. Two protocols for analysis of the subtraction products have been evaluated, a shotgun approach and size selection of both distinct fragments and band-patterned smear. We demonstrate that in order to obtain a representative view of the most abundant gene fragments, the shotgun procedure is preferred. The obtained sequences were analyzed against the UniGene and Expressed Gene Anatomy Database (EGAD) databases and the results were visualized and analyzed with the ExProView software enabling rapid pair-wise comparison and identification of individual genes or functional groups of genes with altered expression levels. The identified differentially expressed gene sequences were comprised of both genes with known involvement in atherosclerosis or cholesterol biosynthesis and genes previously not implicated in these processes. The applicability of a solid-phase shotgun RDA protocol, combined with virtual chip monitoring, results in new starting points for characterization of novel candidate drugs.

Arteriosclerosis↗

PubMed2001

Molecular analysis of commensal host-microbial relationships in the intestine.

Human beings contain complex societies of indigenous microbes, yet little is known about how resident bacteria shape our physiology. We colonized germ-free mice with Bacteroides thetaiotaomicron, a prominent component of the normal mouse and human intestinal microflora. Global intestinal transcriptional responses to colonization were observed with DNA microarrays, and the cellular origins of selected responses were established by laser-capture microdissection. The results reveal that this commensal bacterium modulates expression of genes involved in several important intestinal functions, including nutrient absorption, mucosal barrier fortification, xenobiotic metabolism, angiogenesis, and postnatal intestinal maturation. These findings provide perspectives about the essential nature of the interactions between resident microorganisms and their hosts.

Animals↗

PubMed2001

Nasal symptoms and pathophysiology in farmers.

OBJECTIVES: Increased morbidity and mortality in lower airway diseases have been reported among farmers. The aim of this study was to assess upper airway problems in farmers. SUBJECTS AND METHODS: Twenty-five dairy farmers, 20 pig farmers, 21 grain farmers and 19 control subjects were studied, by use of questionnaire, skin-prick test, dynamic spirometry, nasal inspection, acoustic rhinometry (before and after a decongestant) as well as by determinations of the olfactory threshold and nasal lavage (NAL) concentrations of eosinophil cationic protein (ECP), myeloperoxidase (MPO) and albumin. RESULTS: Compared with the control group, farmers had more complaints of work-related symptoms from the lower airways, and symptoms of smell impairment, and more often had nasal polyps and hyperaemia of the nasal mucosa. They also had higher levels of MPO in NAL (especially dairy farmers and pig farmers), and a tendency to more swollen nasal mucosa and lower olfactory threshold (especially grain farmers). CONCLUSIONS: The farmers had more pathological findings in their nasal mucosa, possibly indicating effects of allergens and irritants in their work environment. More studies are needed to evaluate work environment factors causing these pathological findings in farmers.

Adult↗

PubMed2001

A prospective study of morbidity and mortality rates among farmers and rural and urban nonfarmers.

Farmers are known to have lower morbidity and mortality rates than the mean for other occupational groups in the general population. Whether this is due to the urban-rural health gradient or to occupational factors related to farming is not clear. To explore this issue, we conducted a prospective study of farmers and matched rural and urban referents. Official hospital admission and mortality data for the years 1989-1996 were obtained. The relative risk of being admitted to hospital were 10% higher among rural and urban referents than among the farmers. The biggest differences were seen for mental and cardiovascular disorders. The odds of dying during follow-up did not differ between the two rural groups but were doubled among urban referents. In conclusion, the lower morbidity and mortality rates among farmers are partly due to the urban-rural health gradient but in addition salutogenic factors linked to farming seem to be active.

Adolescent↗

PubMed2001

Blood lipid levels in a rural male population.

OBJECTIVES: Farmers have a low risk for cardiovascular disease, which may be related to a favourable blood lipid profile. In order to study the blood lipid levels and evaluate the effect of other cardiovascular risk factors on the blood lipid profile, this cross-sectional study was made. MATERIAL AND METHODS: A total of 1013 farmers and 769 non-farming rural men in nine different Swedish counties were examined, interviewed, and replied to questionnaires. The inter-relationships between different risk factors were analysed using a multivariate linear regression model. RESULTS: The farmers had a significantly more favourable blood lipid profile than the non-farmers although the total cholesterol levels were almost the same for the two groups. In the total study population there were significant positive relationships between total cholesterol level and body mass index (BMI), diastolic blood pressure and smoking. The high-density lipoprotein (HDL) level was positively related to physical workload and alcohol consumption, and negatively related to BMI, waist/hip ratio and smoking. Triglyceride levels showed a positive relationship to BMI, waist/hip ratio and blood pressure. Differences between farmers and other rural males were seen, especially with respect to the effect of physical activity and psychosocial factors. Among the farmers, a negative correlation between the Karasek-Theorell authority over work index and total cholesterol, the low-density lipoprotein (LDL)/HDL ratio and triglyceride levels was observed. CONCLUSIONS: This study indicated that diet is of minor significance for the blood lipid profile, whereas factors such as physical activity, body weight and the waist/hip ratio, smoking, alcohol consumption, and perhaps psychosocial working conditions are major independent factors affecting the blood lipid profile most prominently among farmers, but also among non-farming rural men.

Age Factors↗

PubMed1998

Reported health status among farmers and nonfarmers in nine rural districts.

Farmers appear to have a lower morbidity and mortality rate than other occupational groups. Whether this better health is due to exposure to farming or to the well-known fact that rural populations have better health than urban ones, irrespective of occupation, is not clear. To explore this problem, all male farmers in nine administrative areas and age-matched nonfarmers from the same rural areas were sampled and invited to participate in a survey. 1782 (76%) men responded. We found that farmers had somewhat lower rates of outpatient health care utilization for causes other than trauma and fewer hospital admissions. These differences were independent of the urban-rural factor and could not be explained by traditional determinants of health and health care utilization. Other factors, linked to farming or to farmers' lifestyles, are probably involved.

Adult↗

PubMed1998

Prevalence of antibodies specific to Puumala virus among farmers in Sweden.

OBJECTIVES: The Puumala virus is the causative agent of nephropathia epidemica, a European form of hemorrhagic fever with a renal syndrome. From its reservoir in bank voles, the virus is spread by airborne transmission to humans. Occupational risks for the acquisition of nephropathia epidemica are not well defined. The prevalence of serum antibodies to Puumala virus was determined for Swedish farmers. From a comparison of the prevalence among farmers from various parts of the country, the assumption that Puumala virus occurs endemically only in the northern and central parts of Sweden was also tested. METHODS: Serum samples from 910 farmers and 663 referents living in various rural parts of Sweden were tested with an enzyme-linked immunosorbent assay, using a recombinant nucleocapsid protein of Puumala virus as the antigen. RESULTS: North of a latitude of 59 degrees N, the prevalence of Puumala virus antibodies was significantly higher among farmers (12.9%) than among referents (6.8%). In the southern areas, antibodies to Puumala virus were rare, and altogether only 2 of 459 persons had antibodies. Seropositive persons did not differ from seronegative ones with regard to blood pressure, and they did not comprise cases of chronic renal disease. CONCLUSIONS: Serological evidence confirmed that the exposure of humans to Puumala virus is firmly restricted to the northern and central parts of Sweden. In addition the evidence indicated that, in this region, farming is associated with an increased risk of contracting hantavirus infection.

Adult↗

PubMed1997

Coxarthrosis and farm work: a case-referent study.

The purpose of this case-referent study was to analyze the association between coxarthrosis and occupation. The study was performed in a Swedish agricultural county and comprised 269 cases of radiologically verified arthrosis of osteoarthritis (< 3 mm joint space) that were compared to 538 randomly selected controls in the same region, matched for age, sex, and place of residence. Farmers and agricultural workers showed an increased risk of coxarthrosis and the observed risk increased with increasing number of years of farming. Tractor driving and milking were associated with coxarthrosis, whereas no association with other types of machine work could be demonstrated. An association between coxarthrosis and heavy physical work before the age of 16 years was also observed. The results give only limited information on the external causes of coxarthrosis, however. More detailed studies of groups of individuals with coxarthrosis in order to obtain more information about contributing and underlying factors would therefore be valuable.

Adult↗

PubMed1995

Distribution of branch point prenyltransferases in regions of bovine brain.

Bovine brains contain large amounts of isoprenoid compounds and the enzymes involved in their biosynthesis were investigated. Ten different regions were dissected from fresh bovine brains and, in addition, fractions from cerebellum, spinal cord, and hypophysis were obtained. The cholesterol concentration was found to be approximately 8 mg/g in the cortex regions and three times higher in the pons, medulla oblongata, and white matter. Dolichol concentration varied between 8 and 40 micrograms/g in the different tissues, and ubiquinone was found at a lower level, which varied between 3 and 25 micrograms/g. Farnesylpyrophosphate synthase activity in cytosolic fractions from various regions exhibited only a twofold variation, whereas geranylgeranyl pyrophosphate synthase displayed larger differences, being particularly rich in the pons, medulla oblongata, white matter, and spinal cord. Squalene synthase activity was lowest in the thalamus and threefold higher in the pons. Determination of specific activity based on cholesterol content revealed that enzyme activities in various regions are not related to the actual lipid amount present. Both cis- and trans-prenyltransferases exhibited similarities in their regional distribution showing up to 20-fold differences in activity. Thus, it appears that the mevalonate pathway lipids and the various branch point enzymes involved in their syntheses vary greatly in different brain regions and are subjected to separate regulation.

Animals↗

PubMed1994

Effect of squalestatin 1 on the biosynthesis of the mevalonate pathway lipids.

The effects of squalestatin 1 on rat brain and liver homogenates and on Chinese hamster ovary tissue culture cells have been investigated. This compound effectively inhibits squalene biosynthesis in a highly selective manner. Cytoplasmic farnesyl pyrophosphate and geranylgeranyl pyrophosphate synthases are not affected, which is also the case for microsomal cis-prenyltransferase. In tissue culture cells, squalestatin 1 inhibits cholesterol biosynthesis completely, but does not alter dolichol synthesis or protein isoprenylation to a great extent. Incorporation of [3H]mevalonate into ubiquinone-9 and -10 increases 3-4-fold, probably as a result of increased synthesis of this lipid. Squalestatin 1 appears not only to be an effective inhibitor of cholesterol biosynthesis, but also to be more specific than other inhibitors used earlier in various in vitro and in vivo systems.

Animals↗

PubMed1994

Age-dependent changes in rat liver prenyltransferases.

Mevalonate pathway lipids including cholesterol, ubiquinone and dolichol, are of great importance for cellular function. Many of the enzymes of this pathway are thus strictly regulated. During development of the rat, the cellular levels of certain of these lipids vary. Prenyltransferases have been investigated and it is reported here that farnesyl pyrophosphate synthase activity in rat liver cytosol decreases after birth to a lower, steady level. This decrease is not paralleled by the level of synthase protein, which shows two maxima, one immediately after birth and the other 30 days later. cis-Prenyltransferase activity is low after birth, increases continuously up to day-54 and then decreases to a low level which was maintained throughout the remainder of the study (365 days). Squalene synthase exhibits high activity after birth, but decreases during the first 100 days thereafter, and subsequently remains at the low level thus reached. In contrast to these changes in the activities of the prenyltransferases, the level of cholesterol is constant and the dolichol concentration increases continuously throughout the entire period studied.

Aging↗

PubMed1994

Isoprenoid biosynthesis in rat liver mitochondria. Studies on farnesyl pyrophosphate synthase and trans-prenyltransferase.

Mevalonate pathway enzyme activities in rat liver mitochondria were investigated, and it was found that isopentenyl pyrophosphate can be utilized for the synthesis of all-trans-polyprenyl pyrophosphates in vitro. In this reaction sequence intermediate formation of farnesyl pyrophosphate (FPP) predominates, and the FPP synthase activity was studied in more detail. The mitochondrial activity constitutes 13% of the total hepatic capacity for FPP synthesis, exceeding the corresponding microsomal, nuclear, and peroxisomal activities by 10-fold. Mitochondrial FPP synthase exhibits trypsin sensitivity only after sonication of intact mitochondria and upon subfractionation the activity is found localized in the matrix. FPP synthase activities at different locations responded distinctly when rats were treated with a diet enriched in cholesterol or containing mevinolin or cholestyramine. With the high cholesterol diet, mitochondrial FPP synthase activity increased 2-fold, while the cytosolic activity was slightly decreased. Both mevinolin and cholestyramine treatment resulted in 3-fold increases in cytosolic FPP synthase activities, without altering the mitochondrial activity. FPP was utilized as substrate for trans-prenyltransferase activity in the inner mitochondrial membrane. The products formed in this reaction were identified as nona- and decaprenyl-PP, and the reaction was influenced by changes in both substrate and Mg2+ concentration, giving more decaprenyl-PP when the concentrations of these substances were increased. These results demonstrate that mitochondria utilize endogenously produced FPP for isoprenoid biosynthesis and that the biosynthetic steps in mitochondria are regulated independently from those occurring in other subcellular compartments.

Animals↗

PubMed1994

Change of occupation and retirement among Swedish farmers and farm workers in relation to those in other occupations. A study of "elimination" from farming during the period 1970-1988.

A number of studies carried out in different countries have shown that farmers have a low morbidity and mortality in comparison to those in other occupations. However, this has been questioned on the basis that some type of selective process may be operating, in that persons having health problems will avoid farming, or are forced to leave farming for other occupations. To determine the occurrence of a so-called 'healthy worker effect', this postal survey of 'elimination' from farming and farming-associated occupations has been carried out. A total of 1283 male farmers and 334 male farm workers born in 1935 and active in Sweden in 1970 were taken as the study group. As controls, a similar number of occupationally active men of the same age and living in the same municipalities were randomly chosen. The results showed that farmers changed occupation or retired early less often than those in other occupations did, whereas more farm workers changed occupation and retired than did other workers of the same age. Among the different reasons given for work change/retirement, low income/poor earning capacity was more common among the farmers and farm workers than among the controls. Illness was less common among farmers but tended to be more common among farm workers as cause of work change. Few farmers changed their occupation because they were offered other work, in comparison to those in other occupations. Allergic disease more often led to an occupation change among farmers, while they less often gave cardiac disease and locomotor problems as a reason for change of occupation, this was probably also true for the farm workers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Occurrence of prenylated proteins in plant cells.

In this paper evidence is presented for the occurrence of prenylated proteins in plants. When spinach leaves were incubated in the presence of [3H]mevalonate non-extractable lipids were found in the protein fraction after extraction with organic solvents. Alkaline hydrolysis liberated phytol, polyprenyl phosphates-11-15 and also, in contrast to animal cells, polyprenols-11-15. Complete removal of farnesol and geranylgeraniol required the cleavage of thioether linkages by iodomethane. The results indicate that several polyisoprenoid lipids in plant cells are covalently bound to proteins. So far a protein fraction dominated by one or more proteins in the 23 kDa region has been identified.

Chromatography, High Pressure Liquid↗

PubMed1993

Distribution of prenyltransferases in rat tissues. Evidence for a cytosolic all-trans-geranylgeranyl diphosphate synthase.

The present study describes the presence of two different geranylgeranyl diphosphate (GGPP) synthase activities, one cytosolic and one membrane-associated, in a number of rat tissues. Both enzymes utilize farnesyl diphosphate (FPP) and isopentenyl diphosphate (IPP) as substrates, but they give rise to different products. The membrane-associated activity produces trans,trans,cis-(E,E,Z)-GGPP, involved in the biosynthesis of long-chain polyprenols. The cytosolic activity produces only the all-trans-(E,E,E) isomer of GGPP, which is utilized as substrate in cytosolic protein prenylation reactions. All-trans-GGPP synthase activity was recovered in the cytosolic fraction from all tissues investigated, but the specific activities varied. The highest specific activities were found in brain, spleen, and testis, followed by kidney and liver. The enzyme activity in rat brain cytosol was further characterized and found to exhibit a narrow pH optimum around 5.0-6.0 and to be highly stimulated by Zn2+. Maximal stimulation was attained with 1 mM Zn2+, whereas Mg2+ had no effect on the enzyme activity. The all-trans-GGPP synthase activity exhibited high affinities for its substrates, i.e. the apparent Km values for FPP and IPP were found to be 0.6 and 3.5 microM, respectively. When rats were fed mevinolin (lovastatin), FPP and all-trans-GGPP synthase activities were affected differently in certain tissues. Mevinolin treatment resulted in an increase in FPP but a decrease in all-trans-GGPP synthase activity in rat liver and kidney. In spleen mevinolin treatment caused a greater than 70% decrease in all-trans-GGPP synthase activity, while FPP synthase was almost unaffected. The presence of two different GGPP synthase activities in the cell, together with the fact that FPP and all-trans-GGPP synthesis in the cytosol are regulated independently, may be of significance in the regulation of isoprenoid biosynthesis, as well as of protein isoprenylation.

Alkyl and Aryl Transferases↗

PubMed1992

Half-life of ubiquinone-9 in rat tissues.

The half-life of ubiquinone-9 in various rat tissues was determined. Rats were injected intraperitoneally with [3H]mevalonate and the decay of radioactivity incorporated into ubiquinone-9 was followed using reverse-phase HPLC. The half-life varied between 49 h (testis) and 125 h (kidney).

Animals↗

PubMed1992

Substrate specificity of cis-prenyltransferase in rat liver microsomes.

Long chain cis-prenyltransferase in rat liver microsomes was studied using various allylic isoprenoid substrates. Microsomes could utilize trans-geranyl pyrophosphate, but not cis-geranyl pyrophosphate for polyprenyl pyrophosphate synthesis. Both trans, trans-farnesyl pyrophosphate and trans,cis-farnesyl pyrophosphate were used as substrates with Km values of 24 and 5 microM, respectively. trans,trans,cis-Geranylgeranyl pyrophosphate could be used as substrate with an apparent Km of 36 microM. trans,trans,trans-Geranylgeranyl pyrophosphate was also utilized as substrate, but with a very low affinity. After pulse labeling for 4 min, using [3H]isopentenyl pyrophosphate and trans,trans-farnesyl pyrophosphate, the only product formed was trans,trans,cis-geranylgeranyl pyrophosphate, which, upon chasing, yielded polyprenyl pyrophosphate. Independent of the nature of the substrate used, even in the case of polyprenyl 12-pyrophosphate and all-trans-nonaprenyl pyrophosphate, the chain lengths of the products were identical, i.e. polyprenyl pyrophosphates with 15-18 isoprene residues. Microsomes were able to synthesize trans,trans-farnesyl pyrophosphate using trans-geranyl pyrophosphate as substrate. The results indicate that rat liver microsomes contain a farnesyl pyrophosphate synthase activity and that the reaction catalyzed by cis-prenyltransferase may consist of two individual steps, i.e. synthesis of trans,trans,cis-geranylgeranyl pyrophosphate and elongation of this product to long chain polyprenyl pyrophosphates.

Animals↗

PubMed1992

Isoprenoid biosynthesis in rat liver peroxisomes. Characterization of cis-prenyltransferase and squalene synthetase.

Isolated peroxisomes were able to utilize [3H]isopentenyl diphosphate to synthesize farnesyl diphosphate, which then was utilized as substrate by both the peroxisomal squalene synthetase and cis-prenyltransferase. The specific activity of squalene synthetase in peroxisomes was as high as in microsomes, i.e. 160 pmol/mg of protein/min. If NADPH was omitted from the assay medium, presqualene diphosphate accumulated, which indicates that the reaction occurs in two steps, as in microsomes. In the presence of NADPH, incorporation from [3H]farnesyl diphosphate was stimulated 3-fold, and the major products were squalene and cholesterol. The specific activity of cis-prenyl-transferase in peroxisomes was 4-fold higher than in microsomes, i.e. 456 pmol of isopentenyl diphosphate incorporated/mg of protein/h. There were two major products formed from farnesyl diphosphate and [3H] isopentenyl diphosphate, i.e. trans,trans,cis-geranylgeranyl diphosphate and long chain polyprenyl diphosphates. The polyprenyl diphosphates had the same chain length distribution as that of dolichol derivatives in rat liver, with the dominating polyisoprenes being C90 and C95. In contrast to the microsomal enzyme, peroxisomal cis-prenyltransferase did not require detergents for optimal activity. The enzyme was associated primarily with the peroxisomal membrane after sonication of the peroxisomes.

Animals↗