Biomedical subjects

D Juretić

Publications and source records attributed to D Juretić.

At least 19 recordsLinked to original sources

PubMed2004

Serum paraoxonase activity in dairy cows during pregnancy.

Preparturient dairy cows are at high risk of metabolic and reproductive disorders and oxidative stress is considered to be involved in these events. We investigated the serum paraoxonase activity in dairy cows during pregnancy and alterations in lipid and lipoprotein patterns in this period. The relation between paraoxonase activity and HDL-cholesterol concentration was also compared. The study was carried out on 76 pregnant lactating and 26 pregnant dry Holstein dairy cows. The serum paraoxonase activity was determined by the method of hydrolysing of paraoxon, while triglyceride, cholesterol and HDL-cholesterol concentrations were measured by the enzymatic kit methods. A significantly higher serum triglyceride concentration (P<0.001) was observed in dry cows compared to lactating cows. The total cholesterol and HDL-cholesterol concentrations were significantly lower (P<0.001) in dry cows than in lactating ones. In dry cows, paraoxonase activity was significantly lower than in those lactating (P<0.001). There was no significant difference in paraoxonase/HDL-cholesterol ratio between the investigated groups. It seems that the lower HDL concentration could be one of the causes of reduced paraoxonase activity considering the role of HDL as a carrier of most paraoxonase molecules in the blood. A decreased serum paraoxonase activity could diminish the effectiveness and total capacity of the whole antioxidative system during prepartum period in dairy cattle.

Animals↗

PubMed2003

Glutathione S-transferases and malondialdehyde in the liver of NOD mice on short-term treatment with plant mixture extract P-9801091.

Changes in the concentration of glutathione S-transferases (GSTs) and malondialdehyde (MDA) were assessed in the liver of normal and diabetic NOD mice with and without treatment with the plant extract P-9801091. The plant extract P-9801091 is an antihyperglycaemic preparation containing Myrtilli folium (Vaccinium myrtillus L.), Taraxaci radix (Taraxacum of fi cinale Web.), Cichorii radix (Cichorium intybus L.), Juniperi fructus (Juniperus communis L.), Centaurii herba (Centaurium umbellatum Gilib.), Phaseoli pericarpium (Phaseolus vulgaris L.), Millefoliiherba (Achillea millefolium L.), Mori folium (Morus nigra L.), Valerianae radix (Valeriana of ficinalis L.) and Urticae herba et radix (Urtica dioica L). Hyperglycaemia in diabetes mellitus is responsible for the development of oxidative stress (via glucose auto-oxidation and protein glycation), which is characterized by increased lipid peroxide production (MDA is a lipid peroxidation end product) and/or decreased antioxidative defence (GST in the liver is predominantly an alpha enzyme, which has antioxidative activity). The catalytic concentration of GSTs in the liver was significantly reduced in diabetic NOD mice compared with normal NOD mice (p < 0.01), while the concentration of MDA showed a rising tendency (not significant). The results showed that statistically significant changes in antioxidative defence occurred in the experimental model of short-term diabetes mellitus. A 7-day treatment with P-9801091 plant extract at a dose of 20 mg/kg body mass led to a significant increase in the catalytic concentration of GSTs in the liver of diabetic NOD mice (p < 0.01) and a decrease in MDA concentration (not significant), which could be explained by its antihyperglycaemic effect.

Animals↗

PubMed2003

Short-term effect of acarbose on specific intestinal disaccharidase activities and hyperglycaemia in CBA diabetic mice.

The purpose of this study was to examine the short-term effects of 75, 100 and 150 mg of acarbose mixed in 100 g standard laboratory chow on specific intestinal disaccharidase activities and on hyperglycaemia in diabetic CBA strain mice on standard diet. The small intestine was excised and divided into three segments, from pylorus to duodenum, and two equal lengths of the jejunum and ileum of control and diabetic mice with or without added acarbose. Specific maltase and sucrase activities were determined using maltose and sucrose as substrates respectively. Increased specific activities of maltase and sucrase were detected in the intestines of CBA mice on standard laboratory diet seven days after alloxan-induced diabetes. Feeding for 7 days with 75, 100 or 150 mg acarbose uniformly mixed in 100 g standard laboratory chow, induced a decrease in the specific maltase and sucrase activities, compared with diabetic mice on standard laboratory diet. Feeding with 75 mg acarbose mixed in 100 g standard laboratory chow caused a statistically significant decrease of maltase in the duodenum and of sucrase in duodenum and jejunum, without a antihyperglycaemic effect. Feeding with 100 or 150 mg caused statistically significant decreases in specific maltase and sucrase activities in duodenum, jejunum and ileum. An antihyperglycaemic effect was observed only in the group of diabetic mice fed with 100 mg acarbose. This indicates that the antihyperglycaemic effect of acarbose involves factors other than these, related only to its inhibitory effect on disaccharidase activities.

Acarbose↗

PubMed2002

Altered distribution of urinary glycosaminoglycans in diabetic subjects.

We studied the influence of type 1 and type 2 diabetes mellitus with similar duration on the urinary excretion of total glycosaminoglycans and alteration of urinary glycosaminoglycan distribution pattern. Investigations were performed in the 24-hour urine samples of 31 children with type 1 diabetes mellitus, 36 adults with type 2 diabetes mellitus and in 30 age-matched controls for each group. We found that type 2 diabetes mellitus also induced an increased urinary excretion of total glycosaminoglycans and that both type 1 and type 2 diabetes alter the urinary distribution of heparan sulphate and dermatan sulphate. Observed changes correlate with duration of the disease. Microalbuminuria was detected in 9 of 36 type 2 adult diabetics (25%). The microalbuminic group had a significantly higher heparan sulphate and/or dermatan sulphate excretion rate. To clarify whether an altered urinary distribution of heparan sulphate and dermatan sulphate may precede the development of microalbuminuria, it is necessary to performed a prospective study in which urinary glycosaminoglycans and microalbuminuria are measured year by year starting from the diagnosis of diabetes.

Adolescent↗

PubMed2001

Educational letter.

Explore the source record for details and available documents.

Chemistry, Clinical↗

PubMed2001

Serum paraoxonase activities in hemodialyzed uremic patients: cohort study.

AIM: To determine whether paraoxonase activity, paraoxonase phenotypes, and lipid status are altered in uremic patients on long-term hemodialysis treatment as compared to healthy population. METHODS: Patients (n = 69) and control subjects (n = 145) were from the area of Slavonski Brod, Croatia. Paraoxon was used as a substrate for measuring basal or sodium chloride-stimulated (NaCl-stimulated) paraoxonase activity, and phenylacetate for measuring arylesterase activity. The double substrate method was used to assign phenotypes. Cholesterol, triglycerides, and high-density lipoprotein cholesterol (HDL-cholesterol) were determined by methods routinely used in medical-biochemical laboratories. Enzyme activities are expressed as international units per liter of serum or per mmol of HDL-cholesterol (HDL-standardized activities). RESULTS: Basal and NaCl-stimulated paraoxonase activity, as well as arylesterase activity expressed per serum volume, were significantly lower in the hemodialyzed uremic patients compared to the controls; 69% (p < 0.001), 73% (p < 0.001) and 49%, (p < 0.001), respectively. However, basal and NaCl-stimulated paraoxonase activity standardized for HDL-cholesterol concentrations were not significantly reduced in the hemodialyzed uremic patients as compared to controls (86%, p = 0.614 and 87%, p = 0.720, respectively), contrary to arylesterase activity, which remained significantly lower (72%, p < 0.001). The distribution of paraoxonase phenotypes in hemodialyzed uremic patients and controls was as follows: AA 45% and 39%, AB 37% and 48%, BB 18%, and 13%, respectively. CONCLUSION: Patients on long-term hemodialysis have decreased paraoxonase/arylesterase activity, which might indicate a greater risk of premature atherogenesis.

Adolescent↗

PubMed1999

Current system of undergraduate and postgraduate education in clinical chemistry in Croatia.

We present here a specific model of education and practice in clinical chemistry that is almost exclusively based on the medical biochemists academically educated at the Faculty of Pharmacy and Biochemistry. This model has been successfully used for 35 years in Croatian Health Care System. Undergraduate education in clinical chemistry consists of four years of specific university education which provides for all requirements to maintain the high quality of our profession. Postgraduate education leading to more specific scientific and professional expertise is further regulated by the laws issued by The Ministry of Health and The Ministry of Science and Technology. At present there is a compulsory programme of lifelong continuing education recognised by Croatian Chamber of Medical Biochemists.

Chemistry, Clinical↗

PubMed1999

External quality assessment in clinical chemistry: review of the situation in Croatia with particular reference to equipment.

The effect of the use of new flame photometers (Ciba Corning 480, Chiron, Salzburg, Austria) and multichannel analyzers (BM Hitachi 904 or BM Hitachi 911, both Boehringer GmbH, Mannheim, Germany) on analytical quality was assessed in a number of medical biochemical laboratories (n=58) at health centers and general hospitals that provide primary health care services for the respective catchment areas. The laboratories were supplied during 1996 and 1997 with new equipment, as part of the First Croatian Health Project, Primary Health Care Subproject, carried out by the Croatian Ministry of Health and Croatian Institute of Health Insurance. We evaluated analytical performance of these laboratories for 19 analytes, according to the results reported in the Croatian External Quality Assessment Program for medical biochemical laboratories, performed four times per year. Changes of percentages of particular methods used by the participating laboratories were observed for inorganic phosphate, total bilirubin, urea and creatinine. Such changes were even more pronounced for enzymes, where changes in the measurement procedure such as incubation temperature and buffers were observed in the methods used. Evaluation of method performance revealed that after the introduction of new equipment interlaboratory variation decreased, so that an increasing proportion of laboratories included in the Project produced results within the target limits.

Chemistry, Clinical↗

PubMed1998

Preference functions for prediction of membrane-buried helices in integral membrane proteins.

The preference functions method is described for prediction of membrane-buried helices in membrane proteins. Preference for the alpha-helix conformation of amino acid residue in a sequence is a non-linear function of average hydrophobicity of its sequence neighbors. Kyte-Doolittle hydropathy values are used to extract preference functions from a training data set of integral membrane proteins of partially known secondary structure. Preference functions for beta-sheet, turn and undefined conformation are also extracted by including beta-class soluble proteins of known structure in the training data set. Conformational preferences are compared in tested sequence for each residue and predicted secondary structure is associated with the highest preference. This procedure is incorporated in an algorithm that performs accurate prediction of transmembrane helical segments. Correct sequence location and secondary structure of transmembrane segments is predicted for 20 of 21 reference membrane polypeptides with known crystal structure that were not included in the training data set. Comparison with hydrophobicity plots revealed that our preference profiles are more accurate and exhibit higher resolution and less noise. Shorter unstable or movable membrane-buried alpha-helices are also predicted to exist in different membrane proteins with transport function. For instance, in the sequence of voltage-gated ion channels and glutamate receptors, N-terminal parts of known P-segments can be located as characteristic alpha-helix preference peaks. Our e-mail server: predict@drava.etfos.hr, returns a preference profile and secondary structure prediction for a suspected or known membrane protein when its sequence is submitted.

Algorithms↗

PubMed1996

Influence of ochratoxin A treatment on the activity of membrane bound enzymes in rat brain regions.

Ochratoxin A is a mycotoxin produced by Aspergillus ochraceus and is a natural contaminant of mouldy food. We examined the neuroactive potential of ochratoxin A by measuring the changes in the activities of several membrane bound, cytoplasmic and lysosomal enzymes in the brain of adult female rats, following subchronic application of ochratoxin A. The activities of both soluble and membrane bound fractions of ecto-5'nucleotidase, ecto-Ca2+/Mg2+ATPase, alanine aminopeptidase, gamma-glutamyl transferase, as well as activities of lactate dehydrogenase and of N-acetyl-beta-D-glucosaminidase were followed. Biochemical effects were examined in cerebral cortex, cerebellum and hippocampus. The results obtained showed physiologically significant alterations in the activity of enzymes tested. The changes were found to be time-dependent and regionally selective. Compared to controls, statistically significant increases in gamma-glutamyl transferase were observed in all three brain regions, while in the case of alanine aminopeptidase activities differed with regard to region, the highest increase being observed in hippocampus. Ecto-Ca2+/Mg2+ATPase and ecto-5'nucleotidase showed distinct changes lasting for 20 days of treatment, while increase in the activities of N-acetyl-beta-D-glucosaminidase and lactate dehydrogenase were visible only at the beginning of the treatment. By the end of the trial the activities of almost all enzymes returned back to normal values.

Animals↗

PubMed1995

Functional synergism of the magainins PGLa and magainin-2 in Escherichia coli, tumor cells and liposomes.

Xenopus laevis skin secretion contains a mixture of magainins, which are small positively charged oligopeptides with antimicrobial activity. In this study, we show that two of these peptides, i.e. magainin-2 and PGLa, are much more active in biological functions when added together than when added alone. This synergy applies for the antimicrobial activity of these peptides, and for the toxic effects on tumor cells. We show that this peptide combination is also synergistic when permeabilizing protein-free liposomes for glucose, when dissipating the membrane potential in cytochrome oxidase liposomes and Escherichia coli, and, reversibly, when stimulating respiration in the liposomes. The occurrence of synergy in these diverse systems (complex and simple) suggests that the biological synergy results from synergy in the primary activity of the magainin peptides, namely the permeabilization of free-energy transducing membranes, possibly by forming a multimeric transmembrane pore of mixed peptide composition. The antimicrobial activity of X. laevis skin secretions may be greatly enhanced by the application of this binary weapon.

Amino Acid Sequence↗

PubMed1995

Effect of sodium valproate on renal cell brush-border enzymes in rats.

The effect of sodium valproate (200 mg/kg body weight) on renal cells was investigated during a 10-day trial, by determining the catalytic activities of alanine aminopeptidase, gamma-glutamyltransferase and alkaline phosphatase in the membrane cell brush-border of the renal proximal tubules. Four days after the administration of sodium valproate, a significant increase was observed in the volume of urine (9.2 +/- 4.2 ml/18-h volume; control group, 3.06 +/- 1.8 ml/18-h volume), and in the catalytic activities of gamma-glutamyltransferase (2.69 times that measured in the control group) and alkaline phosphatase (3.02 times that measured in the control group) in urine. After prolonged treatment the urine became alkaline (pH = 10.5 on day 10), thereby excluding alanine aminopeptidase as a useful indicator of renal cell changes following the administration of sodium valproate. The activities of alkaline phosphatase and gamma-glutamyltransferase in isolated vesicles of renal brush-border membrane cells were significantly increased (p < 0.05) and decreased, respectively. On the basis of the results obtained, we believe that the determination of the catalytic activities of gamma-glutamyltransferase and alkaline phosphatase in urine might prove useful for the follow-up of the renal cell state during therapy with sodium valproate.

Alkaline Phosphatase↗

PubMed1994

Magainin oligomers reversibly dissipate delta microH+ in cytochrome oxidase liposomes.

Magainin peptides present in the skin of Xenopus laevis and identified as antimicrobial agents are shown to decrease the membrane potential in cytochrome oxidase liposomes. They also released respiratory control with a third or higher order concentration dependence. Respiratory control was restored by proteolytic digestion of the added magainin. The amount of magainin required for half-maximal stimulation of respiration was proportional to lipid concentration. At appreciably higher concentrations magainins inhibited uncoupled respiration. The results are discussed in terms of a model in which most of the added magainin adsorbs as a monomer to the membranes but equilibrates with a multimeric pore that causes rather general permeability of membranes. The ensuing ion permeation dissipates membrane potential and stimulates respiration.

Animals↗

PubMed1993

Conformational preference functions for predicting helices in membrane proteins.

A suite of FORTRAN programs, PREF, is described for calculating preference functions from the data base of known protein structures and for comparing smoothed profiles of sequence-dependent preferences in proteins of unknown structure. Amino acid preferences for a secondary structure are considered as functions of a sequence environment. Sequence environment of amino acid residue in a protein is defined as an average over some physical, chemical, or statistical property of its primary structure neighbors. The frequency distribution of sequence environments in the data base of soluble protein structures is approximately normal for each amino acid type of known secondary conformation. An analytical expression for the dependence of preferences on sequence environment is obtained after each frequency distribution is replaced by corresponding Gaussian function. The preference for the alpha-helical conformation increases for each amino acid type with the increase of sequence environment of buried solvent-accessible surface areas. We show that a set of preference functions based on buried surface area is useful for predicting folding motifs in alpha-class proteins and in integral membrane proteins. The prediction accuracy for helical residues is 79% for 5 integral membrane proteins and 74% for 11 alpha-class soluble proteins. Most residues found in transmembrane segments of membrane proteins with known alpha-helical structure are predicted to be indeed in the helical conformation because of very high middle helix preferences. Both extramembrane and transmembrane helices in the photosynthetic reaction center M and L subunits are correctly predicted. We point out in the discussion that our method of conformational preference functions can identify what physical properties of the amino acids are important in the formation of particular secondary structure elements.

Animals↗

PubMed1993

Urinary glycosaminoglycans in different phases of Balkan endemic nephropathy.

The relationship between glycosaminoglycans and beta 2-microglobulin, glycosaminoglycans and N-acetyl-beta-D-glucosaminidase as well as the relationship between the chondroitin sulfate/heparan sulfate ratio and SDS electrophoresis in the urine of subjects from the endemic area of Balkan nephropathy was studied in order to establish a method for early detection of this disease. The results show an unquestionable increase in urinary excretion of total glycosaminoglycans in subjects with or suspected of having Balkan endemic nephropathy while the chondroitin sulfate/heparan sulfate ratio was not statistically different between the groups studied. Thus, the chondroitin sulfate/heparan sulfate ratio cannot be used as a cheap and quick semiquantitative method for the diagnosis of early tubular damage in Balkan endemic nephropathy. However, the determination of total glycosaminoglycans in the urine of subjects from endemic areas proved to be valuable additional information helping with the diagnosis of Balkan endemic nephropathy.

Acetylglucosaminidase↗

PubMed1992

Rapid and simple method for the determination of copper, manganese and zinc in rat liver by direct flame atomic absorption spectrometry.

An acidic homogenate method, which includes simple homogenization pre-treatment of tissue material and direct nebulization flame atomic absorption spectrometry (FAAS), is successfully applied to the simultaneous determination of copper, manganese and zinc in rat liver. The proposed method involves only a few steps for sample pre-treatment at room temperature, making the risk of systematic errors very small. Because recoveries of 101% for copper, 98% for manganese and 100% for zinc could be achieved using aqueous standards, matrix-matched standards were redundant. Favourable results obtained in biological media, including limits of detection of 0.04, 0.03 and 0.04 mg l-1 for Cu, Mn and Zn, respectively, together with accuracies of 0-3%, and relative standard deviations ranging from 2 to 10% are further evidence of the suitability of the method.

Animals↗

PubMed1991

Effect of ochratoxin A on brush border enzymes of rat kidney.

Ochratoxin A was given orally at 60 microgram/kg body weight in neutral olive oil to Fischer rats for 30 days, at which time they were killed. Clinical state, weights of animals and of their organs and urea and creatinine concentrations were not affected during the exposure period. Significant increases in the activity of enzymes in urine were found: 60% increase in alanine aminopeptidase, 45% increase in gamma-glutamyl-transferase and 90% increase in alkaline phosphatase. These changes indicate early pathological changes in the kidney. Relatively small amounts of the toxin thus affect kidney membrane cells.

Alkaline Phosphatase↗

PubMed1991

Application of the monodimensional electrophoresis for the separation of glycosaminoglycans on Cellogel cellulose acetate strip.

A monodimensional electrophoretic method for the separation of glycosaminoglycans on Titan III Zip Zone cellulose acetate plate based on their different electrophoretic mobilities in barium acetate and different solubilities in ethanol was applied to the Chemetron electrophoretic equipment. Improved timing of individual steps of electrophoretic run, additional cooling and pressure must be introduced for optimal separation of glycosaminoglycans mixture (dermatan sulphate, heparan sulphate, hyaluronic acid, chondroitin-4-sulphate, chondroitin-6-sulphate and keratan sulphate) resulting in five well separated sharp bands. By all these changes in the original procedure of Hopwood and Harrison, the separation of chondroitin-4-sulphate and chondroitin-6-sulphate was not achieved. The modified procedure on Cellogel strip is suitable for the screening of mucopolysaccharidoses.

Electrophoresis, Cellulose Acetate↗