[Effect of botulinum toxin a and B on vegetative cardiac innervation]. / Die Wirkung von Botulinumtoxin A und B auf die vegetative kardiale Innervation.

The objective of this study was to examine whether vegetative cardiac innervation is affected by local application of botulinum toxin A and B. For that purpose, heart rate variability (HRV) was measured in 29 patients treated with botulinum toxin A and 26 patients treated with botulinum toxin B both prior to and three weeks following injection. Among the 14 parameters studied, 9 and 10 had significantly changed in terms of decreased HRV following treatment with botulinum toxin A and B, respectively. Obviously, either type of botulinum toxin exerts a systemic effect, although a clear-cut difference between the two preparations was undetectable. By and large, the changes observed tend to be low compared to, for instance, cardiac effects known to occur with tricyclic agents. However, the results might be of relevance for the use of botulinum toxins in patients with a history of cardiac disease since a reduction in HRV correlates with an increased incidence of cardiovascular events. Therefore, an ECG study is advised prior to onset of therapy with botulinum toxin. In addition, nonjudicious use of botulinum toxin outside a defined range of medical indications should be reassessed.

An isoform of microtubule-associated protein 2 (MAP2) containing four repeats of the tubulin-binding motif.

Microtubule-associated protein 2 (MAP2) exists in both high- and low-molecular mass isoforms, each of which has a tubulin-binding domain consisting of 3 imperfect tandem repeats of 31 amino acids containing a more highly conserved 18 amino acid 'core' sequence. We describe here a novel form of low molecular mass MAP2 (MAP2c) that contains an additional 4th repeat of this tubulin-binding motif. Like the 3 previously known repeat sequences, this 4th copy is highly conserved between MAP2 and the two other known members of the same gene family, tau and MAP4. In each of these three genes the additional 4th repeat is inserted between the 1st and 2nd repeats of the 3-repeat form of the molecule. Experiments with brain cell cultures, in which the relative proportions of neurons and glia had been manipulated by drug treatment, showed that 4-repeat MAP2c is associated with glial cells whereas 3-repeat MAP2c is expressed in neurons. Whereas 3-repeat MAP2c is expressed early in development and then declines, the level of 4-repeat MAP2c increases later in development, corresponding to the relatively late differentiation of glial cells compared to neurons. When transfected into non-neuronal cells, the 4-repeat version of MAP2c behaved indistinguishably from the 3-repeat form in stabilising and rearranging cellular microtubules. The presence of an additional 4th repeat of the tubulin-binding motif in all three members of the MAP2 gene family suggests that this variant arose prior to their differentiation from an ancestral gene.

The low molecular weight form of microtubule-associated protein 2 is transported into both axons and dendrites.

In the developing brain microtubule-associated protein MAP2 occurs as both a high molecular weight form, MAP2b, which is present only in dendrites, and a low molecular weight form, MAP2c, which is also present in axons. Because the MAP2c amino acid sequence is entirely contained within that of MAP2b it is not possible to raise a MAP2c-specific antibody, so that it has been impossible to determine whether MAP2c is present in dendrites along with MAP2b. To answer this question we have generated a MAP2c cDNA clone tagged with a 10 amino acid epitope from human c-myc. This additional sequence does not alter either the binding of MAP2c to microtubules or its effects on microtubules in non-neuronal cells. When expressed in cultured primary neurons by transfection, the myc tag allowed the distribution of MAP2c to be determined independently of endogenous MAP2 protein by immunostaining with an anti-myc antibody. This showed that MAP2c is present in all processes, indicating that it can enter all kinds of processes and is stable in their cytoplasm. The results further suggest that the selective association of high molecular weight MAP2 with dendrites depends on a mechanism that prevents either its entrance or survival in the axonal compartment.

HPV DNA detection in tumours of the head and neck: a comparative light microscopy and DNA hybridization study.

A series of 22 squamous cell carcinomas (4 cases grade 1; 11 cases grade 2; 7 cases grade 3) of the oral cavity (13 cases), (naso-)pharynx (5 cases) and larynx (4 cases) were studied by conventional light microscopy and filter (dot blot) hybridization for the detection of human papillomavirus (HPV) DNA. In 4 carcinomas, tumour-free tissue from the resection margins of the surgical sample was examined in addition to the tumour specimen. The same kind of investigation was carried out on 4 oral leukoplakias without dysplasia. All cases were thoroughly examined for HPV-associated cytopathic effects (koilocytosis). In all cases, material was obtained for DNA extraction followed by dot blot hybridization. DNA hybridization was carried out under stringent conditions with mixed probes of HPV 6/11 as well as HPV 16/18. Koilocytosis was observed in 10/22 carcinomas (45%, 4/4 G1 tumours, 6/11 G2 tumours, none out of 7 G3 tumours) and 3/4 leukoplakias. Koilocytosis always occurred at the tumour surface or the surface epithelium immediately adjacent to the tumour. HPV DNA was found in 8/22 carcinomas (36%, 2/4 G1 tumours, 5/11 G2 tumours, 1/7 G3 tumours). We observed HPV 16/18 infections in 3 cases and HPV 6/11 infection in 1 case. The other 4 cases were positive under relaxed conditions and, thus, could not be grouped into one of the examined types of HPV infections. In 4 carcinoma cases, tumour tissues and resection margins were examined. 3/4 cases showed concordant findings, i.e. in 2 cases tumour tissue and tumour-free mucosa (1-2 cm distant to the tumour) were positive for HPV, 1 case was negative in both samples. In 6/8 cases positive for HPV, HPV DNA detection corresponded to the observation of intensive koilocytosis. The leukoplakias were seen to harbour HPV DNA in 3 cases (1 case: HPV 6/11; 1 case: HPV 16/18; 1 case: positive under relaxed conditions). We did not observe HPV DNA in normal mucosal tissues. Our findings provide further evidence for the presence of HPV infections in tumours of the upper respiratory and digestive tract. Prospective studies now have to clarify the biological importance of HPV infections in this group of human cancer.