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Biomedical subjects

G Johansson

Publications and source records attributed to G Johansson.

At least 181 records · Page 10Linked to original sources
PubMed1992

The effect of a shift from a mixed diet to a lacto-vegetarian diet on human urinary and fecal mutagenic activity.

This is an investigation of the effects of a shift from a well-balanced mixed diet to a lacto-vegetarian diet on the mutagenic activity in urine and feces. The participants were 20 normal-weight, non-smoking subjects (4 men and 16 women, mean age 44 years, range 27-61 years). The fecal samples were assayed for direct-acting mutagens with the fluctuation test for weak mutagens and the urinary samples were assayed with the same assay but with a metabolic activation system, a so-called S9 fraction. The switch from a mixed diet to a lacto-vegetarian diet was not a shift from a so-called high to a low risk diet for colon cancer but rather from a 'medium high risk diet' to a 'low risk diet', even though there were significant changes in nutrients and food components between the two diets. There was a decrease in fat (P = 0.009) and protein intake (P = 0.04) and an increase in total carbohydrate (P = 0.001), fiber (P = 0.001), calcium (P = 0.006) and vitamin C intake (P = 0.019). Among the food preparation methods the use of frying decreased (P = 0.02) and the habit of eating a new vegetable meal increased (P = 0.05). Three months after the dietary shift the concentration of fecal direct-acting mutagens decreased significantly (P less than 0.05), though the total mutagenic activity excreted in feces per 24 h was not different between the two diet periods. Both the concentration and the total amount of promutagens in the urine were decreased after 3 months on the lacto-vegetarian diet. The decrease in fecal mutagenic activity might be explained by a higher fiber intake, which leads to higher water content in feces and thereby a dilution of fecal mutagenic compounds.

Adult↗
PubMed1992

Effects of reperfusion and superoxide dismutase on myocardial infarct size in a closed chest pig model.

OBJECTIVE: The aim was to study the effects on myocardial infarct size of reperfusion alone or of CuZn superoxide dismutase (SOD) as an adjunct to reperfusion. METHODS: Occlusion was induced in closed chest, pentobarbitone anaesthetised, mechanically ventilated pigs by injection of a 2 mm ball into a preselected coronary artery. Reperfusion was achieved by retraction of the ball via an attached filament. Twenty nine placebo treated and 25 SOD treated animals were subjected to 30 (n = 21), 60 (n = 21), and 90 (n = 12) min of coronary occlusion followed by reperfusion to 24 h; a control group of 24 pigs was subjected to a sustained occlusion for 24 h. Infarct size was assessed by tetrazolium staining and plasma creatine kinase (CK), aspartate aminotransferase (ASAT), and lactate dehydrogenase (LD). In the CuZn SOD group, 200 mg bovine CuZn SOD was given as a bolus intravenously immediately before reperfusion followed by a continuous infusion (100 mg) for 60 min. The size of the ischaemic myocardium at risk was measured from post mortem autoradiograms. RESULTS: Infarct size as percent of myocardium at risk was 46.0(SD 15.5)%, 80.1(9.9)%, and 88.9(5.0)% respectively in placebo animals with 30, 60, and 90 min occlusion, and 94.2(5.1)% in pigs with 24 h sustained occlusion. Compared to 24 h sustained occlusion, limitation of infarct size by reperfusion was only demonstrated in the 30 (p less than 0.001) and 60 min groups (p less than 0.001). Plasma values of CK, ASAT, and LD at 90 min post-reperfusion correlated closely with infarct size as assessed by tetrazolium staining and were related to occlusion duration. No myocardial salvage, as assessed by plasma ASAT, CK, or LD, was shown in the SOD treated groups. CONCLUSIONS: Early reperfusion resulted in myocardial salvage as assessed by tetrazolium staining and peak ASAT, CK, and LD at 90 min after the reperfusion. No limitation of infarct size by SOD could be demonstrated from analyses of plasma CK, ASAT, or LD.

Animals↗
PubMed1992

A closed-chest myocardial occlusion-reperfusion model in the pig: techniques, morbidity and mortality.

Extensive preparative surgery and lengthy experimentation may lead to high rate of complications and mortality in myocardial ischaemia studies. These problems are particularly common when pigs are used as the subject as they are prone to develop lethal ventricular arrhythmias. Here, a closed-chest model is presented, in which the trauma of major preparative surgery is avoided. One-hundred and twelve pentobarbital-anaesthetized, mechanically ventilated pigs were used. Coronary occlusion was produced by injection of a 2 mm diameter ball via a modified coronary angiography catheter. Reperfusion was induced by retraction of the ball via a thin filament attached to the ball. The amount of the myocardium at risk (MAR) was 8.23 +/- 2.41% (mean +/- SD) of the left plus right ventricular weight. It was possible to carry out scheduled 24 h experiments in 87 out of 93 animals (93.5%). Preparative mortality was 1.8% and 24 h mortality 6.5%. Ventricular fibrillation (VF) occurred during preparation in 3.6%, during coronary occlusion in 7.3% and during reperfusion in 5.0% of the animals. VF was significantly related to a large zone of MAR and insufficient premedication. Catheter- or ball-induced complications were found in 10.7%. Mortality and incidence of VF are considerably lower in this closed-chest model than in a previously reported open-chest pig preparation.

Animals↗
PubMed1992

Increase in testosterone sensitivity induced by constant light in relation to melatonin injections in rats.

In this experiment we investigated whether the lack of the nocturnal melatonin peak under constant light would cause an increase in testosterone sensitivity. Castrated rats were kept under periodic or constant light for one week. They received a daily injection of vehicle, testosterone propionate (125 micrograms), melatonin (50 micrograms) or testosterone plus melatonin (125 micrograms + 50 micrograms). Serum and pituitary gonadotrophins and pineal melatonin were measured at the end of the experiment. Under constant light, testosterone injections reduced the serum luteinizing hormone concentration in castrated rats to that in intact rats, but, under periodic light, the decrease was smaller. Melatonin did not reverse the stronger effect of testosterone under constant light. The serum melatonin peak produced by the exogenous melatonin injection had a higher amplitude, shorter duration and earlier appearance than the physiological melatonin peak. Exogenous melatonin did not modify the physiological melatonin secretion, measured either as serum melatonin concentration or pineal melatonin content on the consecutive day. We conclude that the increase in testosterone negative feedback sensitivity of castrated rats under constant light was not due to the absence of the nocturnal melatonin pulse.

Animals↗
PubMed1992

Validity of repeated dietary measurements in a dietary intervention study.

The aim of the study was to evaluate the compliance in a dietary intervention study. When drawing conclusions about the relationship between dietary intake and disease occurrence/disease-related variables it is important to obtain valid dietary data. 20 healthy, non-smoking normal-weight omnivores changed from a mixed to a lactovegetarian diet. Dietary surveys (four 24 h recalls per person and time-period), urinary and faecal sample collections were performed before and 3, 6 and 12 months after the dietary shift. The validation of energy, protein, sodium and potassium yielded approximately the same ratio of dietary intake to biological marker at 0 and 3 months. This ratio decreased towards 6 months and continued to decrease towards 12 months. The fibre intake was compared to the total faecal weight directly and indirectly by calculating the fibre intake from the stool weight, the water content in faeces and the excretion of short-chain fatty acids (SCFAs). These four methods of fibre validation showed that the ratio of dietary intake to biological marker was always highest at 12 months, indicating an overestimation of the fibre intake at the end of the study. This is the first time these methods of validating fibre intake have been used in an epidemiological study. The ratio of dietary calcium intake to urinary and faecal calcium excretion did not show any statistical difference between the period before and 3 months after the dietary shift. To conclude, almost all investigated dietary data show approximately the same validity before and 3 months after the dietary shift, and show the least validity 12 months after the dietary shift. Thus, this study demonstrates that it is difficult to obtain valid dietary data 1 year after a drastic dietary change, indicating a decreased compliance to the new dietary regimen at the end of the 1 year study period. This represents important information when attempting to relate biological effects to dietary intake, and illustrates the importance of using biological markers for food intake in dietary surveys.

Adult↗
PubMed1992

Changing from a mixed diet to a Scandinavian vegetarian diet: effects on nutrient intake, food choice, meal pattern and cooking methods.

Twenty healthy, non-smoking, normal-weight omnivores volunteered for a nutrition counselling programme and changed from a mixed to a Scandinavian lactovegetarian diet. Dietary surveys were performed before and 3, 6 and 12 months after the dietary shift. The major trends when changing from a mixed diet to a lactovegetarian diet included an increase in the consumption of fruits, berries, vegetables, herbal tea and dairy products, and a decrease in the intake of biscuits and buns, sweets, alcoholic beverages, coffee and tea. There was a total absence of fish, eggs and meat products at 3 and 6 months after the dietary shift. At 12 months after the dietary shift two subjects ate small amounts of these animal products. The energy intake decreased throughout the study. The nutrient intake showed the greatest change between the period before and 3 months after the dietary shift. Between 3, 6 and 12 months after the dietary shift there were only minor changes. The observed change in meal pattern is associated with the change in consumption of various food items, the change in nutrient intake and the change in food preparation methods. Further studies should try to clarify the relationship between meal pattern and food intake, nutrient intake and food preparation methods, because counselling on meal pattern most certainly is more rapid and more easily understood than counselling on food and nutrient intake.

Adult↗
PubMed1991

Subfractions of membranes from calf brain synaptosomes obtained and studied by liquid-liquid partitioning.

Synaptosomes isolated from calf brain cortex were lysed and fragmented by Yeda press treatment. The obtained membranes have previously been fractionated in a counter-current distribution process using a liquid-liquid two-phase system consisting of water, dextran, Ficoll and poly(ethylene glycol) [J. Chromatogr., 358 (1986) 147]. Using the fact that there are discrete membrane populations, a rapid preparative method for isolation of the two main fractions is presented in the present work, as well as a subfractionation of one of them using liquid-liquid extraction with dextran-bound Procion yellow HE-3G. The content of several membrane constituents, i.e. protein, acetylcholinesterase, succinate dehydrogenase and ATPase, as well as opiate binding, were determined for the three fractions. Counter-current distribution of the fractions elucidates their heterogeneity and the effectiveness of the purification.

Acetylcholinesterase↗
PubMed1991

Cellobiose oxidase from Phanerochaete chrysosporium can be cleaved by papain into two domains.

Cellobiose oxidase from the white rot fungus Phanerochaete chrysosporium has been purified to homogeneity by a new method. The enzyme has been cleaved by papain into two fragments: one containing the heme group and one containing the flavin group. The flavin fragment can oxidize cellobiose and is reoxidized by oxygen. Cellobiose oxidase binds to cellulose to approximately the same extent as cellobiohydrolase I. The cellulose-binding site is located on the flavin domain. The enzyme cannot be totally displaced from cellulose by cellobiose, and it is still active when adsorbed to cellulose. The possible role of the enzyme in lignocellulose degradation is discussed.

Amino Acids↗
PubMed1991

Heterogeneity of synaptosomal membrane preparations from different regions of calf brain studied by partitioning and counter-current distribution.

1. Membranes obtained by lysis and Yeda-press treatment of synaptosomes (nerve endings) from cortex, caudateus nucleus, and hippocampal region of calf brain have been studied by partitioning within a liquid-liquid aqueous two-phase system consisting of water, dextran, Ficoll, and poly(ethylene glycol). 2. The partitioning of membranes was sensitive to the presence of a dextran-bound dye, Procion yellow HE-3G, in the lower phase. 3. The two-phase system was used for counter-current distribution to study the heterogeneity of the synaptic membranes from the three regions of the brain and to separate the membranes into fractions. 4. The obtained counter-current distribution profiles strongly depended on the region of the brain from which the membranes were isolated. 5. The membrane fractions obtained showed marked differences in their SDS electrophoresis pattern.

Animals↗
PubMed1991

The 1,4-beta-D-glucan cellobiohydrolases from Phanerochaete chrysosporium. I. A system of synergistically acting enzymes homologous to Trichoderma reesei.

A physico-chemical and structural characterization of three 1,4-beta-D-glucan cellobiohydrolases (EC. 3.2.1.91), isolated from a culture filtrate of the white-rot fungus Phanerochaete chrysosporium, reveals that the cellulolytic enzyme secretion pattern and thus the general degradation strategy for P. chrysosporium is similar to that of Trichoderma reesei. Partial sequence data show that two of the isolated enzymes, i.e., CBHI, pI 3.82 and CBH62, pI 4.85, are homologous with CBHI and EGI from T. reesei; while, the third, i.e., CBH50, pI 4.87, is homologous to T. reesei CBHII. Limited proteolysis with papain cleaved each of the three enzymes into two domains: a core protein which retained full catalytic activity against low molecular weight substrates and a peptide fragment corresponding to the cellulose binding domain, in striking similarity to the structural organization of T. reesei. CBHI and CBH62 have their binding domain located at the C-terminus, whereas in CBH50 it is located at the N-terminus. It is evident that synergistically acting cellobiohydrolases is a general requirement for efficient hydrolysis of crystalline cellulose by cellulolytic fungi.

Amino Acid Sequence↗
PubMed1991

The 1,4-beta-D-glucan glucanohydrolases from Phanerochaete chrysosporium. Re-assessment of their significance in cellulose degradation mechanisms.

A physico-chemical, functional and structural characterization, including partial sequence data, of three major 1,4-beta-D-glucan glucanohydrolases (EC. 3.2.1.4) isolated from the culture filtrate of the white-rot fungus Phanerochaete chrysosporium, shows that all three enzymes belong to a single family of cellulases. EG44, pI 4.3, (named after its apparent molecular mass in kDa), shows a clear homology with Schizopyllum commune Endoglucanase I (EGI); whereas EG38, pI 4.9, (named in the same manner) is related more closely to Trichoderma reesei (Trichoderma longibrachiatum) Endoglucanase III (EGIII). EG36, pI 5.6-5.7, is probably an EG38 protein lacking its cellulose binding domain. Strong synergistic action is induced by the enzymes acting in concert with cellobiohydrolases (CBHI and CBHII) from the same organism, indicating a highly effective enzymatic system for cellulose degradation. Controlled proteolysis with papain has allowed a so far unique cleavage of endoglucanases EG44 and EG38 into two domains: a core protein, which virtually lacks the capacity to absorb onto microcrystal-line cellulose but retains full catalytic activity against carboxymethyl cellulose and low molecular weight soluble substrates; and a peptide fragment corresponding to the cellulose binding domain. The latter appears to be of paramount significance in the mechanisms involved in the hydrolysis of microcrystalline cellulose.

Amino Acid Sequence↗
PubMed1991

Smoking and sedentary behavior as related to work organization.

There is little research which has investigated whether working life may affect health behaviors. However, there is data suggesting that smoking as well as leisure activities are affected during times of stress. Both theoretical work and research suggests that work may socialize people such that the use of leisure time for active pursuits, including exercise, may be contingent upon jobs which promote interaction, learning, and activity on the job. In investigating whether the psychosocial structure of work might affect smoking and sedentary behavior, a subsample (n = 7.201) of a representative sample of the Swedish population aged 16-65 years was selected for study. Reports on job characteristics and health behaviors were obtained in personal or telephone interviews and a logistic regression analysis was performed. In general, job demands like shift work, piece work, hazardous exposure, and physical load tended to be associated with smoking and sedentary behavior, whereas job resources, including personal autonomy, were predictive of regular exercise, but unrelated to smoking behavior. Correlational patterns varied somewhat between sexes. The implications of these findings with respect to work organization, considerations in epidemiological research, and the conduct of health promotion programs are discussed.

Health Behavior↗
PubMed1991

Second generation biosensors.

Enzyme-membrane electrodes using glucose oxidase in combination with peroxide detection dominate in the field of laboratory analyzers for diluted samples. Using the same indication principle, extremely fast responding glucose sensors have been fabricated by covering thin metal electrodes with a porous enzyme layer. In the second generation auxiliary enzymes and/or co-reactants are coimmobilized with the analyte converting enzyme in order to improve the analytical quality and to simplify the performance. Following this line oxidizable interferences are suppressed by using a glucose oxidase/peroxidase complex which communicates with the electrode at a low working potential. Furthermore, fluctuations of pH or buffer capacity are ineffective when using a glucose oxidase/peroxidase layer covered fluoride FET in the potentiometric glucose determination. Enzymatic recycling of the analyte and/or accumulation of intermediates increase the sensitivity by several orders of magnitude. Inclusion of NAD bound to PEG in the glucose dehydrogenase layer allows a reagentless glucose measurement.

Biosensing Techniques↗
PubMed1991

Internal supply of coenzyme to an amperometric glucose biosensor based on a chemically modified electrode.

A biosensor for glucose using glucose dehydrogenase immobilized on a chemically modified graphite electrode was supplied with coenzyme, nicotinamide adenine dinucleotide (NAD+), through pores in the material. A graphite rod was hollowed out, leaving 0.3 mm at the end contacting the solution, filled with 10 mM NAD+ and pressurized. The response factor was 40% of that obtained when 2 mM NAD+ was mixed with the sample solution in a flow system. The coenzyme consumption was 11 microliters h-1 representing a 500-fold saving compared to supply through the bulk solution. The biosensor had a linear calibration curve from the detection limit, 1 microM, to 2 mM glucose and a repeatability of 0.3%. The graphite electrode was modified by adsorption of a bis-(benzophenoxazinyl)-terephthaloyl derivative in order to be able to oxidize NADH at 0 mV versus Ag/AgCl, 0.1 M KCl.

Biosensing Techniques↗
PubMed1991

Purification and characterization of pea chloroplastic phosphoriboisomerase.

Pea (Pisum sativum L.) chloroplastic phosphoriboisomerase (EC 5.3.1.6) can be purified to apparent homogeneity in less than 2 days time with a 53% yield. Important steps in the purification include heat treatment and pseudoaffinity chromatography on Red H-3BN Sepharose. The purified isomerase has a subunit molecular mass of 26.4 kD. The N-terminal sequence has been determined through 34 residues. pH optima are 7.8 (ribose-5-phosphate) and 7.7 (ribulose-5-phosphate); K(m) values are 0.9 millimolar (ribose-5-phosphate) and 0.6 millimolar (ribulose-5-phosphate). The enzyme is inhibited by erythrose-4-phosphate, sedoheptulosebisphosphate, glyceraldehyde-3-phosphate, and 3-phosphoglycerate at concentrations close to those found in photosynthesizing chloroplasts. Countercurrent phase partitioning experiments indicate that the pea chloroplastic phosphoriboisomerase interacts physically with phosphoribulokinase.

Journal Article↗