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Biomedical subjects

G Carta

Publications and source records attributed to G Carta.

At least 91 records · Page 5Linked to original sources
PubMed1986

[Left ventricular diastolic function in type I diabetes. A longitudinal echocardiographic study].

The present study was performed to assess the extent of left ventricular diastolic abnormalities and their possible progression with time in patients with type I (insulin dependent) diabetes. Two echocardiographic examinations were performed at an interval of 5 years in 18 study patients. Left ventricular diastolic function was assessed by computer digitized analysis of the M-mode echocardiographic tracings. During the study period all patients remained in satisfactory metabolic control and without retinopathy. Twelve normal subjects, matched for age and sex, were used as control group. Peak rate of left ventricular posterior wall excursion and the peak rate of increase in left ventricular internal dimensions were significantly reduced in patients with diabetes (14.12 +/- 2.5; 16.48 +/- 3.9 cm/sec) compared with controls (17.25 +/- 2.8; 20.41 +/- 3.6 cm/sec) (p less than .005; p less than .01). In addition time to peak rate of increase in left ventricular internal dimensions, isovolumic relaxation index and isovolumic relaxation time were significantly prolonged in patients with diabetes (63.66 +/- 16.5; 23.9 +/- 9; 72.7 +/- 14 msec) compared to controls (46.83 +/- 9.8; 13.4 +/- 4; 61.1 +/- 12 msec) (p less than .005; p less than .001; p less than .05). In the study patients, no relation was found between the extent of diastolic abnormalities and age, duration of the disease and insulin dosage. The extent of left ventricular diastolic dysfunction did not show significant changes during follow-up. Our results indicate that diastolic abnormalities are common in patients with type I diabetes and are not related to the duration of the disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetes Mellitus, Type 1↗
PubMed1984

Effect of nicotinic acid associated with retinol and tocopherols on plasma lipids in hyperlipoproteinaemic patients.

Twelve hypercholesterolaemic patients, with or without hypertriglyceridaemia, were treated sequentially with 600 mg nicotinic acid alone per day and 300 mg nicotinic acid plus 60,000 U retinol and 140 mg tocopherols per day, each treatment being given for 30 days in random order sequence. Plasma concentrations of lipid fractions were determined before the start of the study and at the end of each treatment period. Both treatments resulted in a significant decrease in total cholesterol and LDL-cholesterol; HDL-cholesterol showed a small but significant increase and plasma triglycerides presented a variable behaviour pattern of change. The difference between the hypolipidaemic effects of nicotinic acid alone and the lower dose given with Vitamins A and E was small but the combination seemed to be more effective. No side-effects were reported with either treatment.

Cholesterol, HDL↗
PubMedDate not supplied

Effect of aeration during cell growth on ketone reactions by immobilized yeast.

The effect of aeration during cell growth on the subsequent reduction of 2-hexanone and 2-octanone by yeast cells entrapped in calcium alginate beads was studied. The reactions were conducted using 2-propanol as a sacrificial substrate to regenerate the cofactor NAD(H), and a mixture of (S)- and (R)-alcohols was produced. The use of strictly aerobic conditions when growing the cells resulted in the highest initial reaction rates, as well as the production of only a single product (i.e., the enantiomeric excess of the (S)-alcohols was 1.0). However, initial reaction rates decreased proportionally with fermentation time regardless of whether the yeast were grown aerobically or under both aerobic and anaerobic conditions. The data also suggest that it is the aerobic (or anaerobic) condition, rather than the cell growth phase, which is responsible for the results seen.

2-Propanol↗
PubMedDate not supplied

Regioselective enzymatic diol esterification in batch and fixed-Bed adsorptive reactors: experiments and modeling.

The dynamic behavior of batch and fixed-bed adsorptive reactors is studied for the enzyme-catalyzed regioselective esterification of propionic acid and 2-ethyl-1,3-hexanediol in hexane. The reaction is equilibrium-limited with an apparent equilibrium constant of 0.6 +/- 0.1 at 22 degrees C. Moreover, accumulation of water produced in the reaction onto the biocatalyst causes a decrease in the catalytic activity. As a result, improvements in both reaction rate and final conversion can be achieved by operating in an adsorptive-reactor mode. Control of water in the reactor is achieved with a catalytically inert ion-exchange resin in Na-form. The resin prevents an excessive accumulation of water on the biocatalyst and reduces equilibrium limitations. The thermodynamic activity of water is identified as a key parameter for the design of such reactors. A mathematical model capable of predicting the water activity as a function of the varying concentrations of reactants and products is thus developed and found to successfully predict the experimental behavior observed in laboratory reactors. Substantial improvements in performance predicted by the model are seen experimentally in batch reactions and during the transient operation of continuous-flow fixed-bed reactors combining adsorptive and catalytic functions.

Adsorption↗
PubMedDate not supplied

Asymmetric ketone reduction with immobilized yeast in hexane: biocatalyst deactivation and regeneration.

There is a need to develop methods for producing enantiomerically pure pharmaceuticals because the racemic mixtures made today will probably not be allowed in the future. Synthetic chiral catalysts are being developed for this purpose, as well as new product separation techniques. Another possible option is to use biocatalysts, such as purified enzymes or whole microbial cells, since these can result in the production of mostly a single enantiomer. This study emphasizes the use of alginate-entrapped yeast cells to catalyze the reduction of ketones as a model system. The emphasis is on the factors that might limit the reactivity of such cells, such as equilibrium conditions, substrate or product inhibition, solvent toxicity, loss of cell viability, or the degradation of intracellular levels of enzymes or cofactors. It was found that there was a progressive loss of catalytic activity of the immobilized yeast cells, which appeared to be mainly associated with a loss of cell viability and a decline of intracellular NAD(H) levels during the reaction. The other factors investigated did not have a large effect. A regeneration scheme was developed in order to replenish the intracellular NAD(H) lost during the reaction, which involved removing the biocatalyst from the reaction and supplying the cells with a nutrient source. This resulted in an increase in the NAD(H) to initial levels and also resulted in a maintenance of the ketone reduction rate over time.

Alcohol Dehydrogenase↗