Production of adventitious shoots and plantlets from the hypocotyl explants of Sesbania rostrata (Bremek & obrem)

Summary Adventitious shoots were induced from the hypocotyl explants derived from 12–15-d-old seedlings of Sesbania rostrata on Nitsch's medium (Nitsch, 1969) supplemented with 1 mgl⁻¹ (4.4 μM), of N⁶-benzylademine (BA). A maximum of 5.9±3.4 shoots per explant in 100% of cultures were obtained. The BA treatment for different time durations (1, 3, 5, 7, 10, 17, 21, or 30 d) exhibited significant variation in the caulogenic potential of the explants. BA treatment for 10–17 d proved optimum for the response. Although at all concentrations of kinetin the explants developed multiple shoots, they were malformed. Sucrose at 3% exhibited the development of the maximum of 3.5±0.9 shoots per explant with an average shoot length of 4.7±3.9 cm. Among the different carbon sources, i.e., fructose, galactose, maltose, mannose, and sucrose at 3% (w/v), sucrose supported the best caulogenic response. The role of various other factors (viz. size, orientation of explant, and seedling age) on the caulogenic response of the hypocotyl explants of S. rostrata were also studied. The shoot development in all cases was accompanied by the development of moderate to profuse callus at the basal cut end of the explant. The in vitro-regenerated shoots produced roots when transferred to half-strength MS medium (Murashige and Skoog, 1962) supplemented with 3% sucrose and 1 mgl⁻¹ (4.9 μM) indole-3-butyric acid (IBA). The developed plantlets were transferred to the field after an initial acclimatization period of 3–4 mo. Such transferred plants produced flowers and fruits in the field and exhibited the development of prominent and organized stem nodules.     

Prompt Protein Glycosylation during Acute Heat Stress

Constitutive patterns of protein synthesis and protein glycosylation are severely disrupted by acute heat stress. Stressed cells respond by preferential synthesis of specific proteins, e.g., the well-known family of heat shock proteins. We observed another response that rapidly occurs during heating periods as short as 10 min at 45°C. During that period, CHO cells began to glycosylate specific proteins, designated as "prompt" stress glycoproteins (P-SG), while constitutive protein glycosylation ceased. Labeling of P-SGs showed a dose response with time and with temperature and appeared regardless of the label used (D-[³H]mannose or D-[³H]-glucose). On SDS-PAGE, the major P-SG was characterized by M_r ≈ 67 kDa (P-SG67) and pI = 5.1. Other less prominent P-SGs appeared at M_r 160, 100, 64, 60, and 47 kDa; incorporated label showed little turnover during 24 h at 37°C. Prompt glycosylation was inhibited by tunicamycin, and label incorporated into P-SGs was sensitive to N -glycosidase F, but not to O-glycosidase. Analysis of enzymatically digested P-SG67 indicated that label had been incorporated into both high-mannose (Man₉G1cNAc) and complex-type oligosaccharides. Brefeldin A did not eliminate P-SG67 labeling, but caused the further appearance of novel, Brefeldin-associated P-SGs. Labeling of P-SG67 oligosaccharides occurred without significant concomitant protein synthesis, suggesting that addition of labeled oligosaccharides largely occurred on mature, rather than nascent proteins. The functional significance of prompt glycosylation remains to be defined, but we propose that this novel phenomenon is an integral part of the cellular heat stress response.     

Changes in the activities of some enzymes of carbohydrate metabolism in Amaryllis vittata pollen suspension cultures

Amaryllis vittata pollen grown in suspension cultures utilizeexogenous carbohydrates for starch synthesis and pollen tubegrowth; tube growth is influenced by both monosaccharides andoligosaccharides in the culture medium but not by ribose andxylose. The level of starch in germinating pollen was influencedby the availability of exogenous carbohydrates. Specific activitiesof some enzymes of glycolysis and pentose phosphate pathwaysvaried during pollen germination. The activities of all theenzymes, except glucose-6-phosphate dehydrogenase, showed moreor less pronounced increase initially, followed by a generaldecrease in later stages. The increase in the enzyme activitieswas affected by the presence of cycloheximide in the incubationmedium. (Received October 20, 1977; )     

Purification and Characterization of Phosphoglucomutase from Heterotrophic Tissues of Brassica campestris L

Two isoforms of phosphoglucomutase (PGM, EC 2.7.5.1) designated as PGM-I and PGM-II were purified from developing seeds of Brassica campestris L to their electrophoretic homogeneity. Both the forms had molecular mass of 59 kD each and were monomeric. PGM-I exhibited maximum activity at pH 7.5, while PGM-II evinced pH optima at 8.25. Both the forms exhibited hyperbolic response towards increasing concentrations of the substrate with K_m values of 0.10 mM for PGM-I and 0.12 mM for PGM-II and had absolute requirement for glucose-1,6-P₂. Fructose-1,6-P₂ and 2,3-diphosphoglyceric acid inhibited the two forms non-competitively, whereas, ribulose-1,5-P₂ inhibited only PGM-II, with K_i value of 0.8 mM. ATP inhibited the enzyme uncompetitively with K_i values for 0.26 mM (PGM-I) and 0.12 mM (PGM-11). Use of group specific protease inhibitors indicated Ser, His and Cys to play significant role in catalysis. On the basis of their differential behaviour and kinetic properties, PGM-I and PGM-II may be the forms present in cytosol and leucoplasts, respectively.     

Biokinetics of lead in various organs of rats using radiotracer technique

Uptake, distribution, and elimination of lead in various organs of rats have been studied using a radiotracer technique. The elimination data for various organs, except whole blood, is fitted to a double-exponential function using a computer program. The biological half-lives along with the percent elimination of lead by two different decay modes in testis, epididymis, prostate, and seminal vesicles are being reported together with that in liver, kidney, blood, and whole body. It is evident from this study that the elimination of lead is limited for all the organs and permits lead accumulation in the bone, where it is stored and becomes almost unavailable for elimination. Lead levels in blood, testis, and femur of lead acetate-fed rats measured using atomic absorption spectroscopy have been correlated to the uptake of²¹⁰Pb in various organs.