The disposition of citric acid cycle intermediates by isolated rat heart mitochondria

The mechanism of depletion of tricarboxylic acid cycle intermediates by isolated rat heart mitochondria was studied using hydroxymalonate (an inhibitor of malic enzymes) and mercaptopicolinate (an inhibitor of phosphoenolpyruvate carboxykinase) as tools. Hydroxymalonate inhibited the respiration rate of isolated mitochondria in state 3 by 40% when 2 mM malate was the only external substrate, but no inhibition was found with 2 mM malate plus 0.5 mM pyruvate as substrates. In the prescence od bicarbonate, arsenite and ATP, propionate was converted to pyruvate and malate at the rates of 14.0 ± 2.9 and 2.8 ± 1.8 nmol/mg protein in 5 min, respectively. Under these conditions, 0.1 mM mercaptopicolinate did not affect this conversion, but 2 mM hydroxymalonate inhibited pyruvate formation completely and resulted in an accumulation of malate up to 13.2 ± 2.9 nmol/mg protein. No accumulation of phosphoenolpyruvate was found under any condition tested. It is concluded that malic enzymes but not phosphoenolpyruvate carboxykinase, are involved in conversion of propionate to pyruvate in isolated rat heart mitochondria.     

Relationship between the seed rain and the establishment of vegetation in two areas abandoned after peat harvesting

In this study the number and species composition of diaspores dispersing into two newly abandoned peat harvesting areas in Finland were investigated. In an area abandoned six years earlier a total of 2978 living seeds m⁻², representing 18 species, was captured by using water-filled traps during two summers. In a one-year-old succession area the total number of living seeds m⁻² was 2241, representing 16 plant species. The soil seed banks were found to be empty of viable seeds. In neither area there appeared to be any relation between number of dispersing seeds and of plant individuals of the same species in the pioneer vegetation. It is suggested that unfavourable conditions on the soil surface for seed germination and seedling growth of most dispersed species are majors factor in determining the structure of the established vegetation.     

Variation in the carbon content of two Asplanchna species

The rotifers of the genus Asplanchna were sampled four times during the summer from eight lakes of different types. The mean individual carbon content in the population varied between 0.15–0.66 µg C ind.^-1 (n = 21) for A. priodonta and 1.0–1.6 µg C ind.^-1 (n = 3) for A. herricki. The carbon content and the size of A. priodonta varied considerably between the populations of both different lakes and dates.The carbon level of both Asplanchna species (sample mean 0.2–1% of wet weight) was considerably lower than is generally found for rotifers. Much of the variation of carbon level could be explained by an inverse relationship with wet weight. The high variation in the carbon content of individuals suggests that Asplanch population may adapt their mean body size to fit prevailing environmental conditions.     

The importance of bacterial utilization of released phytoplankton photosynthate in two humic forest lakes in southern Finland

Bacterial utilization of photosynthetically fixed dissolved organic carbon (PDOC) released from natural phytoplankton assemblages was studied in two small, extremely humic, forest lakes in southern Finland. Bacterial activity (measured as uptake of ¹⁴C-glucose) and phytoplankton photosynthesis (measured as light uptake of ¹⁴CO₂) could be most effectively separated using Nuclepore filters of pore size 1–2 μm. Released PDOC was 10–67% of total phytoplankton carbon fixation during in situ experiments, and represented about 0.1% of total DOC. Net uptake of PDOC by bacteria was found to be about 20% during 24 hour laboratory incubations, although about 40% of PDOC present at the start of an experiment could be utilized by bacteria during a 24 hour period. PDOC does not provide a quantitatively important substrate supply for bacterial respiration in humic forest lakes.     

Cold and hyperosmolar fluids in canine trachea: vascular and smooth muscle tone and albumin flux

We have studied the effects of liquids of various osmolalities and temperatures on the tracheal vasculature, smooth muscle tone, and transepithelial albumin flux. In 10 anesthetized dogs a 10- to 13-cm length of cervical trachea was cannulated to allow instillation of fluids into its lumen. The cranial tracheal arteries were perfused at constant flow, with monitoring of the perfusion pressures (Ptr) and the external tracheal diameter (Dtr). Control fluid was Krebs-Henseleit solution (KH) with NaCl added to result in a 325-mosM solution (isotonic). Hypertonic solutions were KH with NaCl (warm hypertonic) or glucose (hypertonic glucose) added to result in a 800-mosM solution. All solutions were at 38 degrees C, with isotonic and the hypertonic NaCl solutions also given at 18 degrees C (cold isotonic and cold hypertonic). Fluorescent labeled albumin was given intravenously, and the change in fluorescence in the fluid was measured during each 15-min period. Changing from warm isotonic to cold isotonic decreased Dtr and Ptr. Changing from warm isotonic to warm hypertonic or hypertonic glucose decreased Ptr with no change in Dtr. The cold hypertonic responses were not different from cold isotonic responses. Warm hypertonic solution increased albumin flux into the tracheal lumen over a 15-min period to three times that of the control period, persisting for 15 min after replacement with warm isotonic solution. Cooling induces a vasodilation and smooth muscle contraction of the trachea, whereas hypertonic solutions result in vasodilation and, if osmolality is increased with NaCl, an increase in albumin flux into the tracheal lumen.     

Interaction of workplace demands and cardiovascular reactivity in progression of carotid atherosclerosis: population based study.

OBJECTIVE: To examine the combined influence of workplace demands and changes in blood pressure induced by stress on the progression of carotid atherosclerosis. DESIGN: Population based follow up study of unestablished as well as traditional risk factors for carotid atherosclerosis, ischaemic heart disease, and other outcomes. SETTING: Eastern Finland. SUBJECTS: 591 men aged 42-60 who were fully employed at baseline and had complete data on the measures of carotid atherosclerosis, job demands, blood pressure reactivity, and covariates. MAIN OUTCOME MEASURES: Change in ultrasonographically assessed intima-media thickness of the right and left common carotid arteries from baseline to 4 year follow up. RESULTS: Significant interactions between workplace demands and stress induced reactivity were observed for all measures of progression (P < 0.04). Men with large changes in systolic blood pressure (20 mm Hg or greater) in anticipation of a maximal exercise test and with high job demands had 10-40% greater progression of mean (0.138 v 0.123 mm) and maximum (0.320 v 0.261 mm) intima-media thickness and plaque height (0.347 v 0.264) than men who were less reactive and had fewer job demands. Similar results were obtained after excluding men with prevalent ischaemic heart disease at baseline. Findings were strongest among men with at least 20% stenosis or non-stenotic plaque at baseline. In this subgroup reactive men with high job demands had more than 46% greater atherosclerotic progression than the others. Adjustment for atherosclerotic risk factors did not alter the results. CONCLUSIONS: Men who showed stress induced blood pressure reactivity and who reported high job demands experienced the greatest atherosclerotic progression, showing the association between dispositional risk characteristics and contextual determinants of disease and suggesting that behaviourally evoked cardiovascular reactivity may have a role in atherogenesis.     

Immunochemical characterization of human plasma fibronectin.

Human plasma fibronectin has been purified by a non-denaturing affinity chromatography procedure [Vuento & Vaheri, (1979) Biochem.J. 183, 331--337], and antisera have been raised by immunizing rabbits with the native protein. The antisera reacted strongly with native fibronectin, but only weakly with reduced and alkylated fibronectin or with heat-denaturated fibronectin. Denaturation also affected the haemagglutinating and gelatin-binding activities of fibronectin and increased its susceptibility to proteolytic degradation. The antisera reacted with fragments of fibronectin obtained by proteolysis with plasmin. Large fragments (mol.wt. 180000--200000), lacking the region harbouring the interchain disulphide bridges but containing the sites responsible for gelatin-binding and haemagglutinating activity, showed as intense a reaction with the antisera as intact fibronectin. Smaller peptides showed a weaker reaction. All fragments tested showed sensitivity to denaturation in their reaction with the antisera. The results were interpreted as showing that: (1) native fibronectin has an ordered conformation that is easily perturbed by denaturation; (2) most of the antigenic determinants of the protein are dependent on conformation; (3) the region of the fibronectin molecule containing the interchain disulphide bridges has only few antigenic determinants; and (4) covalent interaction of the two subunits does not contribute to the antigenic structure recognized by rabbit antisera. The observed correlation between the antigenic activity and a structural and functional intactness of fibronectin suggests that the antibodies to native fibronectin could be used as a conformational probe in studies on this protein.     

Effect of prolonged ethanol ingestion on hepatic lipogenesis and related enzyme activities

1. Hepatic lipogenesis in vivo and the activities of enzymes associated with fatty acid synthesis in the liver were studied in rats fed for 21 days on liquid diets containing ethanol. 2. The ethanol-fed rats developed a moderate hepatic triacylglycerol accumulation during this period. When carbohydrate was replaced by ethanol in the diet, the rate of fatty acid synthesis was slower in the ethanol-fed rats on low-, medium- and high-fat diets than in the appropriate controls. However, when the fat/carbohydrate ratio was kept the same in the ethanol-fed and control rats, ethanol had no influence on the rate of fatty acid synthesis. 3. Glucose 6-phosphate dehydrogenase activity was lower in the ethanol-fed group. ;Malic' enzyme activity did not change during the ethanol treatment when the fat/carbohydrate ratio was kept unchanged. 4. The ATP citrate lyase activity was lower in the ethanol-fed rats on all diets, whereas acetyl-CoA synthetase activity was independent of the composition of the control diet, but was lower in the ethanol-fed rats, in which the concentration of the active form of pyruvate dehydrogenase was also lower. 5. It is concluded that hepatic fatty acid synthesis does not play any major role in ethanol-induced triacylglycerol accumulation. Careful design of the diets is necessary to reveal the specific effects of ethanol on the enzymes associated with lipogenesis.     

Essential charged amino acids in the binding of fibronectin to gelatin.

The binding of fibronectin to gelatin-agarose was strictly dependent on pH, having a pH optimum of 7-9. The binding was strongly inhibited by increasing ionic strength. A chemical modification of lysyl and arginyl groups of fibronectin abolished the binding activity. The anionic detergents sodium dodecyl sulphate and sodium deoxycholate in concentrations of 10-100mM had the same effect. The binding was not affected by the non-ionic detergents Triton X-100, Tween 20 or Lubrol WX. The results demonstrate an important role of ionic interactions in the binding of fibronectin to gelatin. Absence of inhibition by non-ionic detergents suggests that hydrophobic interactions contribute relatively little to the binding of fibronectin to gelatin.     

Changes in coronary risk factors during comprehensive five-year community programme to control cardiovascular diseases (North Karelia project).

A comprehensive community programme to control cardiovascular diseases (CVD) in North Karelia, Finland, was carried out during 1972-7. The central intermediate objective of the programme was to reduce the prevalence of smoking, the serum cholesterol concentration, and raised blood-pressure values among the population of the area. The effect was evaluated by examining independent representative population samples in 1972 and 1977 in both the county of North Karelia and a matched control county. Over 10 000 subjects were studied each time, the participation rate being around 90%. The decrease that occurred in the risk factors, especially in men, was in general greater in North Karelia compared with the control county. When a multiple logistic function was used for the three risk factors an overall mean net reduction of 17% among men and 12% among women was observed in the estimated risk for coronary heart disease in North Karelia. This community programme effectively reduced the levels of the three main risk factors for CVD in the population, and thus mortality and morbidity from CVD should fall. This is assessed in further studies.