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Biomedical subjects

R Scharf

Publications and source records attributed to R Scharf.

At least 19 recordsLinked to original sources
PubMed2000

ESWL in hemophiliac patients.

OBJECTIVE: To assess ESWL treatment of urolithiasis in patients with hemophilia, the frequency of hemorrhagic complications, and to determine the treatment outline. PATIENTS AND METHODS: From 1991 to 1997, eleven patients with hemophilia were treated by ESWL for urolithiasis. Substitution of deficient coagulation factors was started on the day of treatment. Ultrasound examination was performed in all cases on the 1st day after the procedure in order to discover any potential hemorrhagic complications. Substitution withdrawal depended on the patients' general status, lack of hematuria and the absence of signs of hemorrhage. Preliminary results were evaluated after 7-10 days on the basis of plain abdominal X-ray of the kidney, ureter and bladder and ultrasonography. RESULTS: In total, 25 ESWL sessions were performed, 1-6/patient. Nine patients (81.8%) discharged stones, and 2 patients are being followed up. No hemorrhagic complications were observed. CONCLUSIONS: Substitution of deficient coagulation factors makes ESWL a safe method of urinary stone management in hemophiliacs. No hemorrhagic complications were seen in our patients. Substitution withdrawal may be based on the patients' good general status, lack of hematuria and absence of signs of hemorrhage.

Adult↗
PubMed2000

Influence of mycophenolic acid and FK-506 on human platelet activation in vitro.

BACKGROUND/AIM: FK-506 (FK) and mycophenolic acid (MPA) are immunosuppressive agents used in kidney transplant recipients. Their effect on posttransplant thromboembolic complications is either controversial (FK) or has not been described (MPA). Thromboembolic events are among the consequences of platelet hyperaggregability which can be identified by measuring platelet aggregation. The aim of this study was to evaluate the in vitro effects of MPA and FK upon platelet activation in healthy subjects. METHODS: Platelet-rich plasma from healthy volunteers (n = 18) was incubated with FK (70 ng/ml), FK vehicle, and MPA (30 microg/ml) before platelet aggregation was induced by the platelet agonists adenosine diphosphate (2 and 5 microM) and collagen 0.5 and 1.0 microg/ml). Aggregation was measured by recording the optical density. RESULTS: MPA resulted in a significant decrease in the platelet response to collagen (1.0 microg/ml) in platelet-rich plasma, whereas FK significantly increased platelet aggregation in response to collagen (0.5 microg/ml). The vehicle of FK had no influence on platelet aggregation with either agonist. CONCLUSIONS: The decreased platelet-activating response following preincubation with MPA may favor its use in kidney transplant recipients to reduce thromboembolic events. The FK-induced enhancement of platelet aggregation shown in vitro may lead to thromboembolic complications in transplant recipients.

Adenosine Diphosphate↗
PubMed1997

[Factor VIII inhibitor appearing in women during delivery].

Factor VIII inhibitor is rare, but very serious postpartum complication. Bleeding diathesis caused by this inhibitor is called acquired haemophilia. Three women with postpartum inhibitor to factor VIII and life threatening bleeding were described. In two patients bleeding was controlled by treatment with high doses of human and porcine factor VIII concentrates. One patient died presenting uncontrolled haemorrhagic diathesis. This work presents the problems of the diagnosis, treatment and also the elimination of the factor VIII inhibitor.

Adult↗
PubMed1995

General relation between variance-time curve and power spectral density for point processes exhibiting 1/f beta-fluctuations, with special reference to heart rate variability.

Counting statistics in the form of the variance-time curve provides an alternative to spectral analysis for point processes exhibiting 1/f beta-fluctuations, such as the heart beat. However, this is true only for beta < 1. Here, the case of general beta is considered. To that end, the mathematical relation between the variance-time curve and power spectral density in the presence of 1/f beta-noise is worked out in detail. A modified version of the variance-time curve is presented, which allows us to deal also with the case beta > or = 1. Some applications to the analysis of heart rate variability are given.

Animals↗
PubMed1995

Analog-digital recording of current and voltage during high voltage DC shocks.

UNLABELLED: Efficient on-line digitization is the prerequisite for computerized analysis of the electrical phenomena occurring during defibrillation. Conventional hardware presently provides only limited time resolution. The performance of various digitization rates for recording of voltage, current, and calculation of derived quantities like impedance, energy, and defibrillator capacitance was investigated. It was assessed both experimentally and by computer simulation of a trapezoidal discharge (of 9 msec duration into a constant resistive load of 50 omega with a defibrillator capacitance of 132 microF). The accuracy achieved with different digitization rates is given. For example, an accuracy of 1% for analog-digital conversion for impedance calculation during this kind of DC shock requires a sampling rate of 8 kHz without, and a rate of 1 kHz with linear interpolation to correct for the hardware dependent error due to sequential sampling. CONCLUSION: Highly efficient analog-digital conversion of delivered voltage and current during DC shocks is available within the limits of conventional inexpensive hardware.

Algorithms↗
PubMed1994

Evidence for the interference of aluminum with bacterial porphyrin biosynthesis.

Aluminum (0.74 mM) was found to retard bacterial growth, and enhance porphyrin formation and excretion in Arthrobacter aurescens RS-2. Coproporphyrin III was shown to be the main porphyrin excreted by aluminum-exposed A. aurescens RS-2 cultures and by RS-2 cultures grown under anoxic conditions. Synthesis and excretion of porphyrins in A. aurescens RS-2 increased in a dose-dependent manner when the bacteria were exposed to increasing aluminum concentrations. Incubation of A. aurescens RS-2 with delta-aminolevulinic acid (delta-ALA, 1.2 mM) brought about the intense formation and excretion of porphyrins by the cells, in the presence or absence of aluminum. delta-ALA slightly enhanced the toxicity of aluminum towards RS-2 bacteria. Furthermore, the intracellular concentration of heme was reduced by 63.9 +/- 8.67% in aluminum-exposed RS-2 bacteria when compared with control cultures. The results are discussed in light of the recent finding concerning aluminum toxicity and porphyrin biosynthesis in microorganisms.

Aluminum↗
PubMed1994

Transmyocardial impedance during single and multiple internal ventricular defibrillation shocks.

Little is known about the transmyocardial impedance during internal ventricular defibrillation. In a canine model, using high rate on-line digitization, random shock delivery, and titanium electrodes, we determined the relationship among voltage, current, and impedance, delivered energy, and defibrillation success within the individual and within successive defibrillation shocks. Impedance decreased with repeated defibrillation in 10 of 11 dogs. Impedance always increased during trapezoidal discharges, whereas voltage decreased. Impedance was lower with high energy-voltage shocks in all dogs. Visually, voltage and current waveform did not show a phase shift. There was no difference in the total energy delivered and the energy converted into heat by the resistive part of the impedance. With a formula valid only for resistive loads, the capacitance of the defibrillator was calculated to be within the measurement accuracy and tolerance of the factory-provided value of 132 microF. Polarization voltage was consistently observed. Thus the transmyocardial impedance during defibrillation is primarily resistive, nonlinear voltage dependent, and declines with successive shocks. Defibrillation success was not influenced by these phenomena.

Animals↗
PubMed1994

[Splenectomy in adult patients with idiopathic thrombocytopenic purpura after intravenous immunoglobulin treatment].

Eight patients with idiopathic thrombocytopenic purpura (ITP) and no response to steroids therapy were prepared for splenectomy, for 5 consecutive days, with intravenous immunoglobulin (IVIG, 0.4 g/kg body weight). Increase of platelet counts and/or remission of haemorrhagic diathesis were observed in 7 patients, in one case IVIG proved ineffective. Splenectomy was performed in 7 cases and the postoperative course was uneventful. IVIG treatment has proved efficient in preparing ITP patients for splenectomy.

Adolescent↗
PubMed1992

Aziridine-2-carboxylic acid. A reactive amino acid unit for a new class of cysteine proteinase inhibitors.

The three-membered ring of aziridine-2-carboxylic acid, which is susceptible to opening by nucleophiles, has been analyzed as a potential useful handle for the design of specific irreversible inhibitors of cysteine proteinases. For this thiol-reactive amino acid, an imino analogue of proline, a second-order rate constant of 17.07 M-1.s-1 for inactivation of papain was determined. Thus, the aziridine moiety proved to be remarkably more reactive than activated double bonds, e.g. N-ethylmaleimide, or halides such as alpha-iodopropionic acid or chloroacetic acid. Since it does not alkylate histidine under conditions in which quantitative alkylation occurs with N-ethyl-maleimide, it could represent an interesting reactive amino acid unit for the synthesis of a new class of irreversible inhibitors, at least in terms of specificity of the chemical reaction involved in the inactivation process.

Aziridines↗