In vitro propagation of green-foliaged Dracaena fragrans Ker.

Callus tissue was induced in young stem segments cultured on MS based media supplemented with 0.25–0.5 mg l^-1 2, 4-D. Shoots were differentiated on media containing 0.5–1.0 mg l^-1 BA and 0.5–2.0 mg l^-1 IBA or 0.1–0.2 mg l^-1 NAA. The same media were suitable for shoot multiplication. Shoot elongation and rooting were strongly inhibited by BA and stimulated by auxins IBA and NAA. Medium containing 0.5 mg l^-1 IBA was optimal for rooting. Root elongation was stimulated by light and inhibited in darkness. Transfer of rooted plantlets to outdoor conditions was feasible and special hardening procedures were not required. Among more than 5000 plants produced by this procedure only 9 off-type plants with variegated leaves were found.     

Hepatic glycogen metabolism in the db/db mouse

Summary Knowledge of the metabolic changes that occur in insulin-resistant type 2 diabetes is relatively lacking compared to insulin-deficient type 1 diabetes. This paper summarizes the importance of the C57BL/KsJ-db/db mouse as a model of type 2 diabetes, and illustrates the effects that insulin-deficient and insulin-resistant states have on hepatic glycogen metabolism. A longitudinal study of db/db mice of ages 2–15 weeks revealed that significant changes in certain parameters of hepatic glycogen metabolism occur during this period. The liver glycogen levels were similar between diabetic and control mice. However, glycogen particles from db/db mice were on average smaller in mass and had shorter exterior and interior chain lengths. Total phosphorylase and phosphorylase a activities were elevated in the genetically diabetic mice. This was primarily due to an increase in the amount of enzymic protein apparently the result of a decreased rate of degradation. It was not possible to find a consistent alteration in glycogen synthase activity in the db/db mice. Glycogen synthase and phosphorylase from diabetic liver revealed some changes in kinetic properties in the form of a decrease in V_max, and altered sensitivity to inhibitors like ATP. The altered glycogen structure in db/db mice may have contributed to changes in the activities and properties of glycogen synthase and phosphorylase. The exact role played by hormones (insulin and glucagon) in these changes is not clear but further studies should reveal their contributions. The db/db mouse provides a good model for type 2 diabetes and for fluctuating insulin and glucagon ratios. Its use should clarify the regulation of hepatic glycogen metabolism and other metabolic processes known to be controlled by these hormones. The other animal models of type 2 diabetes, ob/ob mouse and fatty Zucker (fa/fa) rat, show similar impairment of hepatic glycogen metabolism. The concentrations of glycogen metabolizing enzymes are high and in vitro studies indicate enhanced rate of glycogen synthesis and breakdown. However, streptozotocin-induced diabetic animals and BB rats which resemble insulin-deficient type 1 diabetes are characterized by decreased glycogen turnover as a result of reduction in the levels of glycogen metabolizing enzymes.     

Hypoxia-induced fibre type transformation in rat hindlimb muscles Histochemical and electro-mechanical changes

Twelve male Sprague-Dawley rats (21 days old) were randomly assigned into two experimental groups: sea level control (CONT) and hypobaric hypoxia (HYPO). The HYPO rats were kept in an hypobaric chamber maintaining a simulated altitude of 4000 m (61.1 kPa). After 10 weeks of treatment, the rat hindlimb muscles [soleus (SOL) and extensor digitorum longus (EDL)] were subjected to histochemical and electro-mechanical analyses. Results indicated that compared to CONT the HYPO SOL muscle had a significantly greater relative distribution of fast-twitch-oxidative-glycolytic (FOG) fibres (28.9% SEM 2.0 vs 18.3% SEM 1.8, P less than 0.01) with a significant decrease in slow twitch oxidative fibre distribution (69.5% SEM 2.4 vs 82.9% SEM 3.1, P less than 0.01). Compared to CONT the HYPO EDL muscle also manifested a significant increase in FOG fibre distribution (51.6% SEM 0.8 vs 46.6% SEM 1.1, P less than 0.01), but this was accompanied by a significant decrease in fast twitch glucolytic fibres (44.3% SEM 0.9 vs 49.2% SEM 1.7, P less than 0.05). These histochemical fibre type transformations accompanied significant and expected changes in the electro-mechanical parameters tested in situ, e.g. maximal twitch force, maximal rate of force development, contraction time, half relaxation time, force: frequency curve, and fatigability. It was concluded that chronic hypobaric hypoxia could have a potent influence upon the phenotype expression of muscle fibres.     

Muscle hypertrophy and fast fiber type conversions in heavy resistance-trained women

Twenty-four women completed a 20-week heavy-resistance weight training program for the lower extremity. Workouts were twice a week and consisted of warm-up exercises followed by three sets each of full squats, vertical leg presses, leg extensions, and leg curls. All exercises were performed to failure using 6-8 RM (repetition maximum). Weight training caused a significant increase in maximal isotonic strength (1 RM) for each exercise. After training, there was a decrease in body fat percentage (p less than 0.05), and an increase in lean body mass (p less than 0.05) with no overall change in thigh girth. Biopsies were obtained before and after training from the superficial portion of the vastus lateralis muscle. Sections were prepared for histological and histochemical examination. Six fiber types (I, IC, IIC, IIA, IIAB, and IIB) were distinguished following routine myofibrillar adenosine triphosphatase histochemistry. Areas were determined for fiber types I, IIA, and IIAB + IIB. The heavy-resistance training resulted in significant hypertrophy of all three groups: I (15%), IIA (45%), and IIAB + IIB (57%). These data are similar to those in men and suggest considerable hypertrophy of all major fiber types is also possible in women if exercise intensity and duration are sufficient. In addition, the training resulted in a significant decrease in the percentage of IIB with a concomitant increase in IIA fibers, suggesting that strength training may lead to fiber conversions.     

Production of novel pullulanases at high concentrations by two newly isolated thermophilic clostridia

Two thermophilic bacteria, which are capable of growing on starch at 60-70 degrees C under anaerobic conditions, were isolated from a sugar refinery in Uelzen and from Solar lake in Israel. On the basis of their physiological characteristics they were identified as Clostridium thermohydrosulfuricum Uel 1 and C. thermohydrosulfuricum Sol 1, respectively. The product pattern of glucose polymer hydrolysis showed that both strains secreted enzymes that possess amylolytic and pullulytic activities. The major product formed was maltose. In addition, alpha-glucosidase activity could be detected in the supernatants of Uel 1 strain. Compared to most anaerobes investigated these isolates secreted extremely high concentrations of pullulanases in batch culture. Up to 85% of the total enzyme synthesized was detected in the culture fluid. Unlike the pullulanases of type I, which can only attack the alpha-1,6-glycosidic linkages, the pullulanases of both clostridial strains were also capable of hydrolyzing alpha-1,4-linkages. The enzyme system of both bacteria was found to be highly thermoactive; optimal activity was detected at pH 5.0 and 85 degrees C. Even at 95 degrees C and without the addition of metal ions still 15% to 25% of enzymatic activity was detectable.     

Plant regeneration in vitro of South Pacific taro (Colocasia esculenta var. esculenta cv. Akalomamale,Aracea)

Summary Axillary bud expiants from South Pacific (Solomon Islands) taro, Colocasia esculenta var. esculenta cv. Akalomamale (Araceae) cultured on a modified Murashige-Skoog medium containing 1 mg NAA 1^–1 and TE formed callus and produced multiple plantlets. Explants died if NAA was present at levels lower than 0.1 mg 1^–1. BA was not required and may have been inhibitory. Plantlets developed faster and became larger following transfer to a hormone-free medium two weeks after the start of culture. Fully grown plants were established in a potting mix and are growing well in a greenhouse.Abbreviations BA benzyladenine - BM basal medium - Ca Colocasia esculenta var. antiquorum - Ce Colocasia esculenta var. esculenta - Ck cytokinin(s) - CW coconut water - HSMSM half strength Murashige Skoog macroelements - HSMS half strength Murashige and Skoog medium - IM initial medium(ia) - MS Murashige and Skoog medium - NAA naphthaleneacetic acid - SM second medium - TE taro corm extract - UCI University of California, Irvine     

Plant regeneration from callus and protoplasts of Brassica nigra (IC 257) through somatic embryogenesis

A method to obtain plants from embryogenic callus of Brassica nigra and protoplasts of hypocotyl expiants is described. Callus was initiated on Murashige and Skoog medium containing kinetin (kn) and 2,4-dichlorophenoxy acetic acid (2,4-D). Lowering of auxin induced embryo formation. Supplementation with gibberellic acid (GA₃) enhanced embryogenic response tenfold. Passage through liquid medium devoid of growth regulators was essential for the growth of embryos. Secondary embryos were produced on transfer to solid basal medium. Embryogenic callus retained its morphogenic ability even after 12 subcultures. Both primary and secondary embryos produced fertile plants. Hypocotyl-derived protoplasts were also regenerated to plants following the same protocol. The survival of plants on transfer to soil was about 80%. The seeds from plants derived from callus and protoplasts were viable.Abbreviations 2,4-D 2,4-dichlorophenoxy acetic acid - NAA naphthalene acetic acid - IAA indole acetic acid - kn kinetin - GA₃ gibberellic acid     

Synthesis of functional bovine opsin in insect cells under control of the baculovirus polyhedrin promoter

In vitro expression of cDNA encoding bovine opsin is accomplished using the baculovirus expression vector system. Full-length opsin was synthesized which was recognized by poly- and monoclonal antisera raised against bovine rhodopsin. Upon infection with a recombinant virus, 1×10⁶ insect cells produced up to 3 g opsin. Incubation of the in vitro synthesized opsin with 11-cis retinal produced a hydroxylamine-stable, photosensitive pigment.Abbreviations dpi days post infection - pfu plaque forming units - AcNPV Autographa californica nuclear polyhedrosis virus     

Regeneration of the cell wall in protoplasts of Candida albicans

To assess the dynamics of synthesis of the wall by regenerating Candida albicans protoplasts deposition of chitin and mannoproteins were investigated ultrastructurally using wheat germ agglutinin conjugated with either horseradish peroxidase or colloidal gold, and Concanavalin A coupled to ferritin respectively.Freshly prepared protoplasts lacked wheat germ agglutinin receptor sites but after 1–2 h of regeneration, they were detected. After 4–5 h of regeneration, the cell wall showed a discrete structure which was only labelled with wheat germ agglutinin in thin sections. At this stage of regeneration the outermost layer of the wall was labelled with clusters of Concanavalin A-ferritin particles.After 8 h regeneration, the cell wall appeared compact, and homogenously marked with wheat germ agglutinin whereas only the surface layers appeared consistently labelled with Concanavalin A-ferritin.From these observations we conclude that C. albicans protoplasts are able to regenerate in liquid medium a cell wall consisting of a network of chitin fibrils and mannoproteins at least (glucan polymers were not determined in the present cytological study). The former are the fundamental component of the inner layers at early stages of regeneration, whereas the latter molecules are predominant in the outer layers of the wall.Abbreviations WGA-HRP wheat germ agglutinin conjugated with horseradish peroxidase - WGA-Au wheat germ agglutinin conjugated with colloidal gold - Con A-ferritin Concanavalin A coupled to ferritin     

Increased totipotency of protoplasts from Brassica oleracea plants previously regenerated in tissue culture

Factors affecting the division of cells derived from leaf and cotyledon protoplasts from Brassica oleracea L. var. italica (Green Comet hybrid broccoli) were examined to optimize conditions for plant regeneration and to determine whether there was a genetic basis for improved regeneration from protoplasts derived from plants previously regenerated from tissue cultures [15]. When leaf protoplasts from different plants grown from hybrid seed were isolated and cultured simultaneously, division efficiencies of 1–95% were obtained. Cells from some plants showed high division efficiencies in consecutive experiments while cells from other plants had consistently low division rates. More plants from hybrid seed gave high division efficiencies when cotyledon protoplasts were used. However, cotyledon or leaf protoplasts from selfed progeny of regenerated plants produced more vigorous calli and more shoots than protoplasts from hybrid seed. These results suggest that there may be a genetic component to the increased totipotency of Brassica oleracea protoplasts.