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Biomedical subjects

G Merkel

Publications and source records attributed to G Merkel.

26 records · Page 2Linked to original sources
PubMed1993

Histamine release from basophils in childhood: age dependency and inhibition by pertussis infection and pertussis toxin.

The influence of childhood pertussis infection and of purified pertussis toxin on histamine release from human basophil leucocytes was investigated. Three different stimuli, the peptide N-formyl-Met-Phe (NFMP), anti-IgE, and the calciumionophore A23187 were used to challenge the cells. When NFMP was the stimulus, histamine release in the control group (age 0.5-17 years) increased in an age-dependent fashion, whereas anti-IgE and A23187 stimulated release did not vary with age. During the convulsive state of pertussis infection there was a significant reduction of histamine release in response to 10 microM NFMP (from 9.5 +/- 1.4 [n = 21] to 6.7 +/- 1.5 [n = 19], P < 0.05) and in response to 800 and 80 U/ml anti-IgE (from 28.5 +/- 5 [n = 19] to 16.3 +/- 5 [n = 13], P < 0.05, and from 6.9 +/- 1.7 [n = 16] to 2 +/- 0.8 [n = 13], P < 0.01), whereas histamine release stimulated by A23187 was unchanged compared to release in control children. In vitro pretreatment of basophils from healthy children and adults with pertussis toxin also inhibited histamine release. When NFMP was the stimulus, release was completely blocked by pertussis toxin with an IC50 of about 11 ng/ml, whereas anti-IgE stimulated release was only inhibited by 20%-30% and release induced by A23187 was reduced to 40%-50% by toxin treatment. In conclusion we have demonstrated a functional impairment of histamine release during the convulsive state of pertussis and that this inhibition is likely to be mediated by pertussis toxin.

Adolescent↗
PubMed1993

[Isolated proximal fibula fracture in Marfan syndrome].

An isolated fracture of the proximal fibular shaft without associated tibial or ankle injury and without resulting from direct violence is extremely rare. This report presents a case of an unusual isolated proximal fibular fracture (stress-fracture) in a female tennis-player with Marfan-syndrome. The literature is reviewed and diagnosis, treatment and etiology are discussed.

Adult↗
PubMed1992

Requirement for a conserved serine in both processing and joining activities of retroviral integrase.

Retroviruses encode a protein, the integrase (IN), that is required for insertion of the viral DNA into the host cell chromosome. IN alone can carry out the integration reaction in vitro. The reaction involves endonucleolytic cleavage near the 3' ends of both viral DNA strands (the processing step), followed by joining of these new viral DNA ends to host DNA (the joining step). Based on their evolutionary conservation, we have previously identified at least 11 amino acid residues of IN that may be essential for the reaction. Here we report that even conservative replacements of one of these residues, an invariant serine, produce severe reductions in both the processing and joining activities of Rous sarcoma virus IN in vitro. Replacement of the analogous serine of the type 1 human immunodeficiency virus IN had similar effects on processing activity. These results suggest that this single conserved serine is a component of the active site and that one active site is used for both processing and joining. Replacement of this serine with certain amino acids resulted in a loss or reduction in DNA binding activities, while other replacements at this position appeared to affect later steps in catalysis. All of the defective Rous sarcoma virus INs were able to compete with the wild-type protein, which supports a model in which IN functions in a multimeric complex.

Avian Sarcoma Viruses↗
PubMed1990

The avian retroviral IN protein is both necessary and sufficient for integrative recombination in vitro.

The integration of viral DNA into the host cell chromosome is an essential feature of the retroviral life cycle. The integration reaction requires cis-acting sequences at the ends of linear viral DNA and a trans-acting product of the pol gene, the integration protein (IN). Previously, we demonstrated that avian sarcoma-leukosis virus (ASLV) IN is able to carry out the first step in the integration process in vitro: nicking of the ends of linear viral DNA. In this paper, using two independent assays, we demonstrate that IN, alone, is sufficient to carry out the second step: cleavage and joining to the target DNA. These results demonstrate that the retroviral IN protein is an integrase.

Alpharetrovirus↗
PubMed1984

[Psychological aspects of spinal anesthesia. Vasovagal syncope and anxiolytic medication].

In 61 male and female patients, the influence of the preoperative emotional state on vasovagal syncopes and anxiolytic medication during spinal anaesthesia for elective orthopaedic surgery was investigated. Male patients pretended to feel emotionally better than female patients, but had higher rates of anxiolytic medication and vasovagal syncopes. Patients in a bad (n = 8) and in a good emotional state (n = 3) received more anxiolytic medication than those with a mean emotional state. Vasovagal syncopes were registered in patients who pretended to feel good (n = 6), in those who felt bad (n = 4) and only in one patient of the mean group. The factors anxiety and depression were the most responsible for this result. The importance of coping-mechanisms for the development of psychological and psychophysiological reactions is discussed. Vasovagal syncope is interpreted as a psychophysiological reaction. In consequence it needs psychoprophylaxis.

Adolescent↗