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Biomedical subjects

M Kraft

Publications and source records attributed to M Kraft.

At least 73 records · Page 4Linked to original sources
PubMed1998

[Evaluation of the test strip Reflotron ALP (alkaline phosphatase) for blood samples of dogs and cats].

The test strip Reflotron ALP (alcaline phosphatase) was evaluated for use in canine and feline heparinized blood samples. The within-run and the day-to-day precision of blood and plasma samples was excellent. A haematocrit up to 60% of canine blood and up to 50% of feline blood had no influence on the measurements. Reflotron ALP was compared with ALP on Hitachi 717 (Boehringer Mannheim, Mannheim, Germany). The correlation of both methods was good for canine and feline blood samples. Reflotron ALP was higher than Hitachi ALP in both species. Despite an enormous deviation between Reflotron ALP and the reference method of canine and feline blood samples within the reference range, Reflotron ALP is a suited test for the detection of elevated ALP activity in canine and feline blood samples. Differences of the ALP activity might be caused by ALP isoenzymes. The activity of ALP isoenzymes depends on the method. The buffer systems of Reflotron ALP and Hitachi ALP are different. Significant exceeding of the reference range was reliably detected. In this investigation the study results for heparinized whole blood, heparinized plasma and serum are approximately the same.

Alkaline Phosphatase↗
PubMed1997

The N-terminal structure of HIV-1 Tat is required for suppression of CD26-dependent T cell growth.

Evidence exists that the human immunodeficiency virus-1 (HIV-1) transactivator Tat occurs extracellularly and is involved in the immunosuppression of non-HIV-1-infected T cells of acquired immunodeficiency syndrome (AIDS) patients. The mechanism of this immunosuppressive activity of Tat has been controversially discussed. Interestingly, Tat binds to the T cell activation marker CD26, which has been shown to play a key role in the regulation of growth of lymphocytes and to inhibit its dipeptidyl peptidase IV (DP IV) activity. Here we show that the N-terminal nonapeptide MDPVDPNIE of Tat is a competitive inhibitor of DP IV and suppresses DNA synthesis of tetanus toxoid-stimulated peripheral blood mononuclear cells. Amino acid exchanges at positions 5 and 6 strongly weaken these effects. 1H nuclear magnetic resonance and molecular dynamics simulations of Tat(1-9), I5-Tat(1-9), and L6-Tat(1-9) suggest a similar backbone conformation for Tat(1-9) and L6-Tat(1-9). The solution conformation of I5-Tat(1-9) considerably differs from the other two. However, Tat(1-9) fits into our previously proposed active site model of DP IV in contrast to I5-Tat(1-9) and L6-Tat(1-9). Conformational alterations with regard to the parent peptide and spatial hindrances between these both compounds and DP IV can explain the loss of inhibitory activity. Our data suggest that the N-terminal residues of HIV-1 Tat do interact directly with the active site of DP IV and that DP IV does mediate Tat's immunosuppressive effects.

Amino Acid Substitution↗
PubMed1997

Concurrent elevation of the levels of expression of striatal preproenkephalin and preprodynorphin mRNA in the rat brain by chronic treatment with caffeine.

Caffeine is a widely consumed substance that elicits psychomotor stimulant effects and also displays addictive properties. In order to assess the effect of caffeine on striatal neuropeptide mRNA expression, male rats were injected (i.p.) with caffeine at 20, 40 or 80 mg/kg of body weight twice daily for 9 consecutive days. Preproenkephalin (PPE), preprotachykinin A (PPT-A) and preprodynorphin (PPD) mRNA levels were determined in coronal sections of brain tissue by in situ hybridization histochemistry. PPE mRNA levels were increased by chronic caffeine in all subdivisions of the striatum at 80 mg/kg (dorsolateral caudate-putamen (dlCPu), +139%; dorsomedial CPu (dmCPu), +42%; ventrolateral CPu (vlCPu), +102%; ventromedial CPu (vmCPu), +20%; and anterior CPu (aCPu), +75% relative to vehicle-injected controls that were normalized to 0% change). Similarly, PPD mRNA expression was increased in all aspects of the striatum at 80 mg/kg (dlCPu, dmCPu, vlCPu, vmCPu and aCPu, +98%, +25%, +104%, +9% and +85%, respectively). In contrast to PPE mRNA, PPD mRNA was increased +117% above control in the nucleus accumbens (NAc) at 20 mg/kg of caffeine. PPT-A mRNA expression was not significantly affected by caffeine treatment in the CPu or NAc. The data demonstrate that repeated exposure to caffeine selectively increases opioid neuropeptide mRNA expression in the striatum and the NAc of the rat brain by a dopamine-independent mechanism.

Animals↗
PubMed1997

Spectroscopic investigations of HIV-1 trans-activator and related peptides in aqueous solutions.

The 86 amino acid trans-activator (Tat) protein of human immunodeficiency virus type 1 (HIV-1) is an RNA-binding transcriptional regulator. HIV-1 Tat proteins (wild type and Thr40Lys mutant) and the HIV-1 Tat peptide fragments Tat(32-48) and Tat(32-72) were chemically synthesized. One- and two-dimensional nuclear magnetic resonance spectroscopy experiments were performed to elucidate the structural features of these proteins. In fluorescence quenching studies of the full-length Tat protein (Thr40Lys), Trp11 was found to be only partially protected against solvent accessibility. Circular dichroism melting studies monitored a slight cooperative change in the conformation of the Tat with increasing temperature. Backbone NH protons of amino acids located in the main core element of the protein are partially protected against exchange.

Amino Acid Sequence↗
PubMed1997

A copia-like retrotransposon Tgmr closely linked to the Rps1-k allele that confers race-specific resistance of soybean to Phytophthora sojae.

We have isolated and characterized Tgmr, a copia-like retrotransposon, linked tightly to the Rps1-k allele that confers race-specific resistance of soybean to the the fungal pathogen Phytophthora sojae. Southern analysis followed by PCR and sequence analyses, using primers based on sequences flanking the insertion site confirmed that the element was inserted in the neighboring region of Rps1-k but not in that of the other four Rps1 alleles. This implies that Tgmr was transposed into the Rps1-k flanking site after the divergence of Rps1 alleles. Southern analysis of a series of diverse soybean cultivars revealed a high level of polymorphism of Tgmr-related sequences. These results indicate that this low copy retroelement family could have been active in the soybean genome in the recent past. Tgmr contains long terminal repeats (LTR) and four non-overlapping open reading frames (ORF), presumably originating from mutations leading to stop codons of a single ORF. The conserved domains for gag, protease, integrase, reverse transcriptase and RNaseH are present in the internal portion of the element. However, the protease, reverse transcriptase and RNaseH of this element are non-functional due to the presence of several stop codons. Possible transactivation of Tgmr and application of this element in insertional mutagenesis for soybean are discussed.

Alleles↗
PubMed1997

Intragastric pH after oral administration of single doses of ranitidine effervescent tablets, omeprazole capsules and famotidine fast-dissolving tablets to fasting healthy volunteers.

BACKGROUND: The therapeutic effect of drugs inhibiting acid production on acid-related discomforts is related to both the onset and duration of action of the drug. The effects on gastric pH by single oral doses of some acid-inhibiting drugs were investigated by measuring daytime (morning to lunch) intragastric pH in healthy volunteers. METHODS: This randomized, single-dose, 4-way crossover study included 15 healthy fasting subjects. Effervescent ranitidine tablets 150 and 300 mg, fast-dissolving famotidine tablets 20 mg and capsules of omeprazole 20 mg were administered. Measurements of intragastric pH were performed every 4 s for 10 min prior to drug administration and during the following 4 h. RESULTS: The effervescent ranitidine tablets (150 or 300 mg) produced similar changes in intragastric pH: following an immediate increase to about pH 5, intragastric pH decreased slightly over the next 10-20 min. Thereafter pH increased steadily, reaching pH 4 after 20-40 min and pH 6 after about 70 min. After famotidine, pH 4 was reached after 80 min, significantly slower than ranitidine. After omeprazole, pH 3 was never reached. Ranitidine 150 and 300 mg showed significantly larger integrated pH responses over the 4-h observation period, compared to famotidine (P = 0.0288 and 0.0074) or omeprazole (P < 0.001). CONCLUSIONS: After single-dose administration to healthy fasting volunteers), ranitidine effervescent tablets showed a significantly more rapid onset of action and a significantly larger integrated pH response compared to either famotidine 20 mg fast-dissolving tablets or omeprazole 20 mg capsules.

Administration, Oral↗
PubMed1997

Effects of ageing and X-irradiation on the diurnal rhythm of mouse urinary bladder capacity.

The effect of single-dose irradiation (19 Gy) or sham treatment on circadian variations in urinary bladder storage capacity was assessed during a 250-day period following treatment using transurethral cystometry under anesthesia. Changes in bladder function were quantified as the deviation from individual pretreatment values of bladder volume at defined intravesical pressures. A marked diurnal rhythm with a peak at 19.00 h and an extended nadir between 1.00 h and 12.00 h was found in 11- to 12-week-old untreated mice. No systematic changes in bladder function with age could be observed in repeated cystometries after sham treatment. X-Irradiation resulted in a triphasic response. After an early reversible decrease in bladder capacity (acute phase) complete recovery was observed within 30 days after irradiation. Following a symptom-free latent period of about 15 weeks, chronic progressive impairment of bladder storage function developed (chronic phase). During the acute and latent period, no changes in the diurnal pattern were observed. In the late phase, not only a decrease in the absolute capacity values but also in the amplitude of diurnal fluctuations was seen. The daily minimum values, however, were still found between 1.00 and 12.00 h. The data indicate that cystometry values obtained between 8.00 and 12.00 h provide suitable parameters for the quantification of radiation effects in the urinary bladder in longitudinal studies.

Aging↗
PubMed1997

The effect of salmeterol on nocturnal symptoms, airway function, and inflammation in asthma.

STUDY OBJECTIVE: To determine the efficacy of salmeterol alone in a group of patients with moderate asthma with nocturnal worsening of symptoms. DESIGN: Double-blind, randomized, placebo-controlled crossover study. SETTING: Tertiary care hospital specializing in respiratory diseases. PARTICIPANTS: Ten patients with nocturnal asthma. INTERVENTIONS: Subjects were randomized to salmeterol, 100 micrograms twice daily, or placebo for 6 weeks with a 1-week washout between treatment periods. Symptoms, nocturnal awakenings, and beta 2-agonist use were recorded daily. Spirometry was performed at weeks 1 and 6 of each period at bedtime and at 4 AM, and methacholine challenge was performed at 4 AM followed by bronchoscopy with BAL. BAL fluid analysis included cell count and differential count, eosinophil cationic protein, Charcot-Leyden crystal protein, leukotriene B4, and thromboxane B2. RESULTS: The percentage of nights with awakenings decreased significantly with salmeterol (69.8 +/- 8.7% vs 30.6 +/- 10.8% for placebo and salmeterol, respectively; p = 0.02). The percentage of 24-h days with supplemental inhaled beta 2-agonist use significantly decreased with salmeterol (85.9 +/- 9.4% vs 70.4 +/- 10.1% for placebo and salmeterol, respectively; p = 0.04). There were no significant differences in bronchial reactivity, 4 AM FEV1, overnight percentage change in FEV1, or indexes of airway inflammation. CONCLUSIONS: Salmeterol alone improves the number of nocturnal awakenings and supplemental 24-h beta 2-agonist use in nocturnal asthma without significantly altering lung function and airway inflammation.

Adrenergic beta-Agonists↗
PubMed1997

[Evaluation of possible measuring errors from overlaying pressure components in invasive blood pressure recording with external transducers].

Invasive arterial blood pressure measurement using external transducers is a routine measure in intensive care medicine and anaesthesiology. Despite the frequency of its use, measuring errors may occur that can strongly affect the significance of the results. The error with the greatest influence on blood pressure measurement arises from an inadequate dynamic behaviour of the measuring chain, and has been investigated in numerous publications. Measuring errors due to hydrostatic and dynamic pressure have not been considered to date. The present investigation describes an analysis of such measuring errors and possible ways of avoiding them. A side-hole catheter permits pressure measurements to be made without the measuring error caused by dynamic pressure behaviour. However, both analytical and experimental studies revealed that, since the velocities involved are small, this error is negligible in blood pressure measurements, and the increased cost of such catheters is therefore not justified. Measuring error due to hydrostatic pressure can be eliminated by using a zero point compensator. Such a compensator that permits vertical changes in the position of the patient without the need for manual resetting of the zero point has now been developed. However, the clinical test showed that the advantages offered by the zero point compensator again do not justify the increased cost. Furthermore, lateral changes in the patient's position during its use can lead to erroneous measurements.

Artifacts↗