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Biomedical subjects

M Horvat

Publications and source records attributed to M Horvat.

At least 55 records · Page 3Linked to original sources
PubMed1997

Influence of hemodynamic changes on neuroendocrine response in acute heart failure.

We studied 15 patients with acute deterioration of chronic left ventricular heart failure. We compared the influence of reduction of ventricular filling pressures with glyceryl trinitrate versus reduction of ventricular filling pressures with diuretics on plasma concentration of epinephrine, norepinephrine, aldosterone and renin activity. Reduction of ventricular filling pressures with glyceryl trinitrate had no influence on plasma concentrations of epinephrine, norepinephrine, aldosterone and renin activity. After reduction of ventricular filling pressures with diuretics plasma concentrations of epinephrine, norepinephrine and aldosterone decreased, while plasma renin activity did not change. We conclude that there is a difference in the influence of reduction of ventricular filling pressures with glyceryl trinitrate versus reduction of ventricular filling pressures with diuretics, on neuroendocrine response in patients with acute deterioration of left ventricular heart failure. Thus some of the neuroendocrine effects of glyceryl trinitrate are likely to be different from those of diuretics, though that they both produce a reduction in left ventricular filling pressure.

Acute Disease↗
PubMed1997

Heart conduction disturbances and cardiovascular collapse after disopyramide and low-dose metoprolol in a patient with hypertrophic obstructive cardiomyopathy.

Disopyramide as an antiarrhythmic can be prescribed to patients with atrial fibrillation and, owing to its negative inotropic effect, to patients with hypertrophic obstructive cardiomyopathy. It is known that in patients with cardiac conduction disturbances and heart failure, disopyramide can adversely affect heart rhythm and conduction and induce cardiovascular collapse. A patient with hypertrophic obstructive cardiomyopathy and paroxysms of atrial fibrillation is described who was treated with disopyramide and also, during the 5 days before admission, with metoprolol. In spite of normal cardiac conduction and function before disopyramide, this treatment was followed by hypotension, bradycardia, and cardiac conduction disturbances. Our case shows the potential for disopyramide, especially when combined with metoprolol, to induce grave adverse effects even in patients with normal cardiac conduction and ventricular function.

Anti-Arrhythmia Agents↗
PubMed1997

Isokinetic torque, average power, and flexion/extension ratios in nondisabled adults and adults with mental retardation.

For successful placement of individuals with mental retardation into community environments, a minimal amount of functional strength is required to promote self-independence. Since muscular strength and power are commonly deficient in these groups, the purpose of this study was to compare isokinetic elbow flexion and extension peak torque (Nm), average power (W), and corresponding flexion/extension ratios of adults males with Down syndrome, with mental retardation without Down syndrome, and sedentary adult males without mental retardation. Subjects with Down syndrome (N = 9), mental retardation without Down syndrome (N = 13), and without mental retardation (N = 13) were tested for elbow flexion and extension peak torque and average power at 60 and 90 degrees/sec on a Cybex 340 isokinetic dynamometer. Results indicated: 1) subjects without mental retardation displayed significantly greater ( p < 0.01) peak torque and average power elbow flexion and extension than subjects with Down syndrome and subjects with mental retardation without Down syndrome at speeds of 60 and 90 degrees/sec, and 2) there were no significant differences between groups in peak torque and average power elbow flexion/extension ratios at both angular velocities. The results of the data analysis support the premise that adults with mental retardation are in need of exercise programs to improve muscular strength.

Adult↗
PubMed1996

Peak torque, average power, and hamstrings/quadriceps ratios in nondisabled adults and adults with mental retardation.

OBJECTIVE: To compare isokinetic hamstring and quadriceps peak torque (Nm), average power (watts), and corresponding hamstring/quadriceps (HQ) ratios (as percentages) of adult men with Down syndrome(DS), with mental retardation without Down syndrome (NDS), and nondisabled sedentary controls (SC). DESIGN: Repeated measures analysis of variance. SETTING: Subjects were tested at a university exercise science laboratory. SUBJECTS: Volunteer sample of 35 subjects: SC(n=13), DS(n=9), and NDS (n=13). INTERVENTION: Subjects performed isokinetic strength tests at 60 degrees /sec and 90 degrees/sec using gravity effected torque procedures. Subjects with DS and NDS performed the test on two separate days with best results selected for statistical comparisons. Sedentary controls performed the test once. MAIN OUTCOME MEASURES: Isokinetic hamstring and quadriceps peak torque and average power, and corresponding HQ ratios on a Cybex 340 isokinetic dynamometer. RESULTS: In all isokinetic parameters measured, sedentary controls demonstrated significantly higher scores than subjects with DS and NDS. There was no significant difference between subjects with DS and NDS, although mean peak torque and average power scores were greater in subjects with NDS. Finally, there were no significant differences in peak torque and average power HQ ratios across groups (p> .01), although group mean peak torque HQ ratios were greatest for sedentary controls (range=61% to 63%) and approximated accepted HQ ratio norms, and lowest for subjects with DS(range=40% to 46%). CONCLUSIONS: Individuals with mental retardation are in need of progressive resistance exercise programs to improve hamstring and quadriceps strength and normalize HQ strength and power ratios.

Adult↗
PubMed1996

Preclinical trial of a bioartificial liver support system in a porcine fulminant hepatic failure model.

BACKGROUND: This study describes the pre-clinical trials of an extracorporeal bioartificial liver support system (BALSS). It includes the biochemical changes which occur in the plasma and blood of pigs with devascularized livers when the plasma is treated in a BALSS, and the testing of the system for presence or absence of infective agents, pyrogens and for toxicity. METHODS: Hepatic cells were prepared from littermate juvenile white landrace pigs with a double-step collagenase digest technique. The cell preparations were incubated with collagen-coated dextran microspheres (CDM) for 3 h and the medium was tested to determine cellular metabolic activity. Incubation continued for a further 20 h during which the hepatic cells attach to the CDM. The CDM-attached cells were inoculated into a hollow fibre bioreactor which was part of an extracorporeal liver support system. RESULTS: Hepatic cell content of the bioreactor was 6 x 10(9) +/- 3 x 10(8) cells, equivalent to those present in half a pig's liver. The system was tested in a controlled trial with the plasma of pigs with fulminant hepatic failure (FHF) due to devascularized livers. When plasma from FHF pigs was circulated through the device there was significantly less of an increase in the accumulation of ammonia, lactate and most amino acids when hepatic cells were included in the circuit compared with those in control experiments when they were excluded. Similar changes occurred in procine blood. There were few infections diagnosed and an absence of pyrogens, endotoxins and toxicity in the bioreactor contents or in the terminating reservoir or animal blood samples. CONCLUSIONS: We believe that the results, demonstrating function of the porcine hepatic cells in the circuit, together with low risks, justify a clinical trial of use of the BALSS in Australia.

Amino Acids↗
PubMed1996

Subacute rupture of the left ventricular free wall after acute myocardial infarction. Three cases of long-term survival without emergency surgical repair.

Rupture of the left ventricular free wall after acute myocardial infarction (AMI) has been regarded as uniformly fatal unless emergency surgical repair is performed. Among 2,862 patients admitted with AMI to our ICU during the last 8 years, 107 patients developed rupture of the left ventricular free wall. Twenty-nine patients had a subacute course and three of them survived for prolonged periods without having to have emergency surgical repair. At the onset of rupture on day 1 through 7 after AMI, the three survivors developed sudden hypotension accompanied by a new pericardial effusion. They were initially managed with hemodynamic support. Two patients had elective open-heart surgery 2 to 3 months after AMI, whereas one patient did nt require surgery. All three survived 1 1/2 to 8 1/2 years after AMI. This report indicates that a small subset of patients with subacute ventricular free wall rupture has a benign course that may allow for prolonged survival without having to have emergency surgical repair.

Aged↗
PubMed1996

Augmented feedback for enhanced skill acquisition in individuals with traumatic brain injury.

Coincident timing by individuals who exhibit traumatic brain injury was measured under conditions of no knowledge of results (no KR; n = 12), KR on every trial (n = 14), summary KR (n = 13), and average KR (n = 12). Following acquisition trials, groups performed immediate and longer retention trials without KR. Absolute constant error and variable error, analyzed in separate repeated-measures analyses of variance, indicated that during acquisition trials subjects receiving KR on every trial were the most accurate and the most consistent in their responses; however, subjects in groups receiving summary and average KR were the most accurate during immediate retention, with the group receiving summary KR being the most accurate during longer retention.

Adolescent↗
PubMed1995

Dietary mercury intake and human exposure in an Adriatic population.

A study was conducted to examine human exposure to mercury through dietary mercury intake in a population living in an industrially non-polluted area of the Adriatic Sea. The results have shown that approximately 20% of the subjects had a weekly dietary mercury intake above the provisional tolerable weekly intake (PTWI), primarily those consuming fish and other seafood > 6 times/week. The estimated seafood consumption corresponding to a mean intake of PTWI of 300 micrograms total mercury was 1559 g, and 1365 g for a PTWI of 200 micrograms methylmercury. However, the total mercury content in hair in individuals consuming total mercury above the PTWI was in the range of 1.3-12.9 micrograms/g, whereas the methylmercury content in hair in subjects consuming methylmercury above the PTWI was between 1.1-10.8 micrograms. Thus, the mercury content in hair did not reach the critical level at which toxic effects of mercury could be expected. The results, particularly those related to methylmercury exposure, did not differ significantly from data reported earlier from an industrially polluted area, thus indicating that the mercury content of fish and consequent human exposure to mercury reflects primarily the general ecological characteristics of the Adriatic, rather than the impact upon a specific local pollution.

Adolescent↗
PubMed1995

Coincident timing by nondisabled, mentally retarded, and traumatic brain-injured individuals under varying target-exposure conditions.

Coincident timing by 15 nondisabled individuals, 15 mentally retarded and 15 traumatically brain injured was measured under varying target-exposure conditions. Absolute constant error, constant error, and variable error were analyzed in separate repeated-measures analyses of variance for early performance (first block of practice), late performance (last block of practice), and retention (last block of retention). Subjects with mental retardation displayed the least accurate and most variable coincident-timing responses. Nondisabled subjects were most influenced by target-exposure time; subjects with traumatic brain injury were most influenced by target-viewing distance; and subjects with mental retardation were most influenced by a combination of target velocity and target-viewing distance. Subjects with mental retardation displayed a too-early response bias, while nondisabled subjects tended to have a too-late response bias. Individuals with traumatic brain injury had a variable response bias.

Acceleration↗
PubMed1994

No indication of in vivo methylation of inorganic mercury in chloralkali workers.

It has been shown in vitro that human oral and intestinal bacteria are able to methylate inorganic mercury (Hg) to methylmercury (MeHg). In vivo methylation has been reported for guinea pigs, and several studies have found higher levels of organic Hg in blood of workers exposed to inorganic Hg. In search for indications of in vivo methylation of Hg, we determined total Hg in urine (U), plasma (P), and erythrocytes (Ery), and MeHg in erythrocytes, in 22 chloralkali workers exposed to inorganic Hg, and in 22 age-matched referents. The subjects in both groups ate fish not more than once a week. MeHg was determined using ion exchange separation and cold vapor atomic absorption spectrometry. The mean concentrations of total mercury in chloralkali workers and referents were 26 vs 2.3 micrograms/g creatinine (U-Hg), 9.7 vs 1.8 ng/g (P-Hg), and 11.4 vs 5.6 ng/g (Ery-Hg). The mean Ery-MeHg concentrations were 3.0 vs 3.7 ng/g, and there were no correlations between Ery-MeHg on the one hand and U-Hg or P-Hg on the other. Our results indicate no significant in vivo methylation of inorganic Hg in man. Contradictory results from previous studies may be due either to bias owing to fish consumption or to analytical shortcomings.

Alkalies↗
PubMed1994

Intratester reliability of the Nicholas Manual Muscle Tester on individuals with intellectual disabilities by a tester having minimal experience.

The purpose of this investigation was to determine the intratester reliability of measurements obtained with the Nicholas Manual Muscle Tester (NMMT) by a tester having minimal experience on individuals with intellectual disabilities. Seventeen individuals classified as moderately mentally retarded between the ages of 14 and 24 (mean = 18.65) were evaluated with the NMMT using a test-retest reliability procedure after a familiarization session. Test-retest strength score relationships for dominant and nondominant elbow flexors and extensors revealed intraclass correlation coefficients from .83 to .86 (p < .001); whereas a series of paired t-tests revealed no significant differences between test and retest values. Finally, intraclass correlation coefficients ranging from .98 to .99 were evident in comparing the first trial to mean of three trials from the first testing session. It was concluded that testers with minimal experience with the NMMT could obtain reliable measurements with the NMMT for determining isometric force of elbow flexors and extensors in individuals with intellectual disabilities.

Adolescent↗
PubMed1994

Simultaneous determination of mercury speciation in biological materials by GC/CVAFS after ethylation and room-temperature precollection.

We developed a method for the simultaneous determination of monomethyl mercury (MMHg), inorganic mercury [Hg(II)], and total mercury (THg) in biological materials. A variety of biological materials can be digested in methanolic KOH solution. The MMHg and Hg(II) present are converted to volatile ethyl derivatives, methylethyl mercury and diethyl mercury, by an aqueous-phase ethylation reaction with sodium tetraethylborate. The ethyl derivatives are precollected onto a trapping column at room temperature, in case of disconnection with the separation/detection system, and then thermally desorbed into a packed isothermal gas chromatography (GC) column. Eluted organo-Hg compounds from the GC column are decomposed into Hg0, and detection is completed by cold vapor atomic fluorescence spectrometry (CVAFS). Pure standard solutions can be used for calibration. The sum of MMHg and Hg(II) obtained by this method equals the THg value obtained by digestion with HNO3 and H2SO4, reduction with SnCl2, and single-stage amalgamation/CVAFS for all biological materials studied. Absolute detection limits are 0.6 pg and 1.3 pg of Hg as MMHg and Hg(II), respectively, corresponding to 0.3 ng and 0.6 ng/g (wet) of sample.

Animals↗
PubMed1993

Magnitude and reliability of measurements of muscle strength across trials for individuals with mental retardation.

The purpose of this investigation was to examine the magnitude and reliability of strength measures on the Nicholas Manual Muscle Tester for individuals with mental retardation. 17 subjects were given six trials with the dominant and nondominant flexor and extensor muscle groups. No significant differences were found between dominant and nondominant muscle groups by side or by muscle group. Interclass correlations ranged from .96 to .98 for six and three trials, respectively. It was concluded that the test was appropriate for reliably assessing strength in this population and that these individuals can achieve a sufficient magnitude on three trials for a reliable measure of strength.

Adolescent↗
PubMed1992

Preliminary study of the effects of some physical parameters on the stability of methylmercury in biological samples.

The effects of storage conditions (long-term storage of wet samples in a deep-freeze or thermal cycling), freeze-drying and gamma-irradiation at 1 and 5 Mrad on the stability of methylmercury in some biological samples were investigated. Methylmercury was determined by volatilization separation followed by gas chromatography and by ion-exchange separation of inorganic and organic species followed by measurement by cold vapour atomic absorption spectrometry (CVAAS). Total mercury was determined by CVAAS. Biological samples studied included fish and shellfish tissues, human hair and blood samples and appropriate reference materials. From the preliminary results obtained it can be concluded that fresh and dried fish muscle and fish certified reference materials show good stability with time and against temperature cycling. Shellfish and blood should not be repeatedly frozen and unfrozen otherwise possible losses of methylmercury can occur. Losses of methylmercury of up to 30% from wet mussels occurred on prolonged storage in a deep-freeze. Gamma-irradiation reduced the methylmercury content of the fish and shellfish only for hake (Merluccius merluccius). Further experiments should be carried out to confirm this and to investigate if this effect is species dependent. Apparent losses of methylmercury on freeze-drying of blood need to be reconfirmed on further samples.

Animals↗
PubMed1992

Investigation of mercury speciation in lichens.

Epiphytic lichens have long been considered to be reliable bioindicators of air pollution. In the present study only one lichen species, Hypogymnia physodes (L.) Nyl., was chosen; this species is very often used for biomonitoring in Europe. Total mercury and methylmercury were determined in lichens taken from various polluted and unpolluted locations in Slovenia, including a mercury mining area around Idrija. Additionally, total gaseous mercury in air was also determined at several sampling points.

Air Pollutants↗