The pharmacokinetics of cytarabine administered subcutaneously, combined with prednisone, in dogs with meningoencephalomyelitis of unknown etiology.

The objective of this study was to describe the pharmacokinetics (PK) of cytarabine (CA) after subcutaneous (SC) administration to dogs with meningoencephalomyelitis of unknown etiology (MUE). Twelve dogs received a single SC dose of CA at 50 mg/m2 as part of treatment of MUE. A sparse sampling technique was used to collect four blood samples from each dog from 0 to 360 min after administration. All dogs were concurrently receiving prednisone (0.5-2 mg kg-1 day-1 ). Plasma CA concentrations were measured by HPLC, and pharmacokinetic parameters were estimated using nonlinear mixed-effects modeling (NLME). Plasma drug concentrations ranged from 0.05 to 2.8 µg/ml. The population estimate (CV%) for elimination half-life and Tmax of cytarabine in dogs was 1.09 (21.93) hr and 0.55 (51.03) hr, respectively. The volume of distribution per fraction absorbed was 976.31 (10.85%) ml/kg. Mean plasma concentration of CA for all dogs was above 1.0 µg/ml at the 30-, 60-, 90-, and 120-min time points. In this study, the pharmacokinetics of CA in dogs with MUE after a single 50 mg/m2 SC injection in dogs was similar to what has been previously reported in healthy beagles; there was moderate variability in the population estimates in this clinical population of dogs.

Effect of physiological age of mother tuber and number of subcultures on in vitro tuberisation of potato (Solanum tuberosum L.).

The physiological age of mother tubers (Solanum tuberosum L. cv. Kennebec) used as a source of material influenced kinetin-induced in vitro tuberisation. Tuberisation significantly increased with physiological age. Kinetin- or ancymidol-induced tuberisation, plantlet and microtuber dry weight decreased with increasing number of subcultures. Single-node segments obtained from tubers stored for more than 9.5 months at 4 °C showed increased kinetin-induced tuberisation rates and earlier tuberisation than those obtained from younger tubers. For any physiological age, material may be safely multiplied using node propagation until the third subculture and bioassayed for tuberisation without variation in the response.

Jasmonic Acid induces tuberization of potato stolons cultured in vitro.

The aim of the study was to assess the potential in vitro effects of jasmonic acid and kinetin on tuberization of potato (Solanum tuberosum). Of the two, the former was by far the stronger in vitro promoter of stolon tuberization. Number of tubers induced per stolon, tuberization rate, and final tuber weight were higher by factors of 2.8, 2.3, and 6.4, respectively. Bioassay sensitivity of jasmonic acid, measured in terms of the point at which the concentration for inducing tuberization was saturating, was more than 20 times greater than that of kinetin. Tuberization in both cases was associated with a decrease in rooting ability. Jasmonic acid also triggered a general state of induction throughout the stolon.

Studies on the carbon dioxide promotion and ethylene inhibition of tuberization in potato explants cultured in vitro.

Ethylene inhibited the tuberization of etiolated potato (Solanum tuberosum L. var. Red La Soda) sprout sections cultured in vitro. Carbon dioxide did not overcome the C(2)H(4) inhibition but it was required for normal tuberization. Ethylene totally prevented root formation and development. It inhibited stolon elongation, and caused thickening and diageotropical growth of the stolon. In addition, C(2)H(4) prevented the accumulation of both starch and red anthocyanin which are always present in a tuber. Ethylene also inhibited the kinetin-increased tuberization of sprout sections.Three to five days of exposure to CO(2) were required to obtain promotion of tuberization of stolons cultured in vitro. Bicarbonate ion did not affect starch synthetase activity isolated from potato tubers in vitro. The evidence presented suggests that CO(2) gas rather than HCO(-) (3) or CO(2-) (3) ions in equilibrium with dissolved CO(2) was probably responsible for the stimulation. Morphological changes elicited by CO(2) and C(2)H(4) are described and the mechanism of action of both on tuberization is discussed.

Effect of carbon dioxide and ethylene on tuberization of isolated potato stolons cultured in vitro.

Carbon dioxide stimulates tuberization of isolated potato (Solanum tuberosum L.) stolons cultured in vitro. The stimulatory effect is inhibited by C(2)H(4) which is by itself also inhibitory of tuberization. Furthermore, C(2)H(4) inhibits kinetin-induced tuber initiation. Both the formation and elongation of roots are inhibited by C(2)H(4). The antagonistic actions of CO(2) and C(2)H(4) on tuberization are discussed.