[On the relation of the microtubule length and dynamics: boundary effect and properties of an extended radial array].

In interphase cells, microtubules (MT) are long and form extended radial array. The length of individual MTs in living cells exhibits substantial stochastic fluctuations while the average length distribution in a cell remains nearly constant. We present a quantitative model that describes relation of the MT length and dynamics in the steady state in the cell using the minimal set of parameters (cell radius, tubulin concentration, critical concentration for plus end elongation, and the number of nucleation sites). The MT array is approximated as a radial system, where MT minus ends are associated with the nucleation sites on the centrosome, while plus ends grow and shorten. Dynamic instability of MT plus ends is approximated as a random walk process with boundary conditions and the behavior of MT array is quantified using diffusion and drift coefficients (Vorobjev et al., 1997, 1999). We show that establishment of the extended steady-state array could be accomplished solely by the limitation of the MT growth by the cell margin. We determined for the cell radius, tubulin concentration, critical concentration for plus end elongation, and number of nucleation sites the reference point in the parameter space where plus ends of individual MT on average neither elongate nor shorten. In this case average length of MT is equal to the half of cell radius. When any parameter is shifted from its reference value MTs become longer or shorter and consequently acquire positive or negative drift of their ends. In the vicinity of reference point, change in any parameter has major effect on the MT length and rather small effect on the drift. When mean length of the MTs is close to the cell radius the drift of the free plus ends becomes substantial, resulting in processive growth of individual MTs in the internal cytoplasm accompanied by apparent stabilization of the plus ends at the cell margin. Under these conditions small changes in parameters have significant impact on the magnitude of drift. Experimental analysis of the MT plus ends dynamics in different cultured cells shows that in most cases plus ends display positive drift, which, in the framework of the presented model, is in agreement with the simultaneous presence of long MTs.

[Laser therapy of malignant stricture of the gastric stump]. / A gyomorcsonk malignus szükületének lézer terápiája.

56 years old patient was operated (Billroth II) with gastric carcinoma. Two and half years after was diagnosed an inoperable recidive local tumor. Because of stomal outlet disturbances a tantalum endoprosthesis was implanted. The tumor grew through the Strecker-net. For desobliteration of stent we applied laser therapy, the gastric passage was free.

[First experiences with ultrasonic diagnosis using gastroenterologic endoscopy in Hungary]. / Elsö hazai tapasztalatok gastroenterologiai endoszkópos ultrahangvizsgálattal.

The authors were the first to gain experiences with gastroenterological endoscopic ultrasonography (EUS) in Hungary. Their examinations included the study of the esophageal wall and its environment as well as that of the stomach wall and the neighbouring organs. The construction of the instrument, the technique of the method and the indication for EUS are described on the basis of the authors' experiences and the literary data. They were the first to demonstrate perigastric effusion with EUS. On the basis of the observations it is stated that EUS is more reliable than other methods for the determination of the patency of varices following sclerotherapy. Thus this technique may improve the control of the efficacy of sclerotherapy in patients with portal hypertension. The authors wish to support their observation with prospective examination series carried out with high number of patients.

Ultrasonography in the preoperative diagnosis of chronic pancreatitis causing severe obstruction, and in indication for surgery.

It is pointed out that some cases of chronic pancreatitis causing severe obstruction may clinically simulate tumour. This can occasionally be confirmed by other examinations (e.g. ERCP) or by macroscopic inspection at surgery, and palpation. With the passive symptomatological treatment applied in these cases, the patients' condition keeps on deteriorating, reinforcing the suspicion of tumour. Sonography performed by a high-resolution equipment may raise, as an alternative to the tumour, the prevalence of chronic pancreatitis. Of 169 documented cases 7 were found to be of this condition. The strict criteria of establishing diagnosis are reviewed, supported by figures and case reports.