Factors affecting the yield and properties of bacterial cellulose.

Acetobacter xylinum E(25) has been applied in our studies in order to find optimal culture conditions for effective bacterial cellulose (BC) production. The strain displays significantly higher stability in BC production under stationary culture conditions. In contrast, intensive agitation and aeration appear to drastically reduce cellulose synthesis since such conditions induced formation of spontaneous cellulose nonproducing mutants (Cel-), which dominated in the culture. Mutation frequency strictly depends on the medium composition in agitated cultures. Enrichment of the standard SH and Yamanaka media with 1% ethanol significantly enhanced BC production in stationary cultures. Horizontal fermentors equipped with rotating discs or rollers were successfully applied in order to improve culture conditions. Relatively slow rotation velocity (4 rpm) and large surface area enabling effective cell attachment are optimal parameters for cellulose production. Physical properties of BC samples synthesized either in stationary cultures or in a horizontal fermentor revealed that cellulose from stationary cultures demonstrated a much higher value of Young's modulus, but a much lower value of water-holding capacity.

[Comparative studies of the administration of relanium and fenactil as sedatives in sheep]. / Badania porównawcze nad stosowaniem Relanium i Fenactilu do uspokajania owiec.

The objective of the studies was to examine the influence of sedatives drugs: Relanium and Fenactil on clinical parameters, blood pressure, blood composition, acid-base balance, arterial blood oxygenation, electrolytes, bilirubin and activity of enzymes in sera of sheep. Basing on these data the more effective drug for sedation in sheep has been chosen. It was found that intravenous injection of Relanium at a dose of 1 mg/kg b.w. enables an appropriate sedation with immobilisation lasting for 20 minutes, whereas Fenactil at a dose of 3 mg/kg b.w. injected intravenously caused a sedation of a various intensity lasting for about 20 minutes. Moreover, Fenactil revealed a depressive action in the respiratory center which was manifested by decrease in oxygenation of arterial blood and disturbances in acid-base balance. Relanium affected these parameters only slightly. The disturbances developing after Fenactil were more intense and long lasting. On the basis of the above data--Relanium (diazepam) appeared to be more convenient that Fenactil to sedation in sheep.

[Comparative studies of electro-analgesia and barbiturate general anesthesia in cattle]. / Badania porównawcze nad ogólnym znieczuleniem elektrycznym i barbituranowym u cielat.

The studies were carried out on 24 healthy young bulls divided into 2 groups. 12 calves, in group I were injected intravenously with 10% solution of gwajamar, dissolved in 10% glucose. Then the electric current of 700 Hz, 90-100 mA and 20 V was switched on. In group II, the mixture of 10% gwajamar, 0.6% thiopental dissolved in 10% glucose was administered intravenously. The studies performed showed that sinusoidal current of 90-110 mA, 700 Hz and about 20 V applied in calves, using needle electrodes on both temples after the administration of gvajamar causes general electric anesthesia during the time of current flow. The narcosis lasted 15 min. when the mixture of 10% gwajamar and 0.6% thiopental was used. During electric anesthesia the reduction in the number of breaths and pulse rate was statistically significant. The content of hemoglobin and lymphocytes in leukograph was decreased as well while metameric neutrophils were raised. In thiopental anesthesia, the pulse rate and the number of breaths were increased (statistically significant) but the number of erythrocytes decreased. The changes in leukograph were observed which were similar to those in the electric anesthesia group. In both kinds of anesthesia hypocalcemia, hypomagnesemia and hypophosphatemia were revealed. More advanced changes (hypocalcemia and hypophosphatemia) were found in electronarcosis. In the above mentioned kinds of anesthesia, the changes and shifts in spite of their statistical significance were temporary and with an exception of hypomagnesemia they reached the values close to the standard by the end of 7th day.