Stable transformation of cultured tobacco cells by DNA-coated gold particles accelerated by gas-pressure-driven particle gun

Summary Stable transformation of suspension-cultured cells of tobacco with plasmid DNA (pCaMV-NEO) harbouring the neomycin phosphotransferase II (npt-II) gene was achieved using a previously described gas-pressure-driven particle acceleration device. The cells were bombarded with DNA-coated gold particles accelerated by the device, and callus containing the introduced gene was selected in the presence of geneticin disulphate. The geneticin-resistant callus exhibited npt-II enzyme activity, and Southern analysis confirmed the stable integration of the foreign gene into the tobacco genome. Transformants were obtained at a rate of more than 1.9 × 10^–4. Offprint requests to: H. Morikawa     

Isolation of plasma membrane vesicles,derived from transverse tubules,by selective homogenization of subcellular fractions of frog skeletal muscle in isotonic media

A new technique for isolating fragmented plasma membranes from skeletal muscle has been developed that is based on gentle mechanical disruption of selected homogenate fractions. $\text{(Na}{}^{\mathrm{+}}\text{+ K}{}^{\mathrm{+}}\text{)-stimulated}$, Mg²⁺-dependent ATPase was used as an enzymatic marker for the plasma membrane, Ca²⁺-stimulated, Mg²⁺-dependent ATPase as a marker for sarcoplasmic reticulum, and succinate dehydrogenase for mitochondria. Cell Cell segments in an amber low-speed ($\text{800 × g}$) pellet of a frog muscle homogenate were disrupted by repeated gentle shearing with a Polytron homogenizer. Sarcoplasmic reticulum was released into the low-speed supernatant, whereas most of the plasma membrane marker remained in a white, fluffy layer of the sediment, which contained sarcolemma and myofibrils. Additional gentle shearing of the white low-speed sediment extracted plasma membranes in a form that required centrifugation at $\text{100 000 × g}$ for pelleting. This pellet, the fragmented plasma membrane fraction, had a relatively high specific activity of $\text{(Na}{}^{\mathrm{+}}\text{+ K}{}^{\mathrm{+}}\text{)-stimulated}$ ATPase compared with the other fractions, but it had essentially no Ca²⁺-stimulated ATPase activity and only a small percentage of the succinate dehydrogenase activity of the homogenate.Experimental evidence suggests that the fragmented plasma membrane fraction is derived from delicate transverse tubules rather than from the thicker, basement membrane-coated sarcolemmal sheath of muscle cells. Electron microscopy showed small vesicles lined by a single thin membrane. Hydroxyproline, a characteristic constituent of collagen and basement membrane, could not be detected in this fraction.     

Mycobacterium malmoense Isolated from Soil

Mycobacterium malmoense was isolated from a soil sample, and biological, biochemical, antigenic, and genetic characteristics of the isolate were described. This is the first report of isolation of this organism in Japan.     

Novel Mouse Microsatellites: Primer Sequences and Chromosomal Location

Sixty-nine sequences containing microsatellites were determinedby analysis of clones from a pUC118 library of total genomicmouse DNA. These sequences were examined for size variationusing polymerase chain reaction and gel electrophoresis. Fifty-oneof them showed allelic variations between C57BL/6 and MSM, thetwo strains used for genetic mapping. Hence, their chromosomallocation was determined using a panel consisting of 131 backcrossmice that had been typed with 85 anchor loci. The microsatelliteswere distributed to most chromosomes except for chromosomes16 and 19. These novel markers with defined locations are usefulin linkage and genome mapping studies.     

Drug Resistance of Staphylococci

Induction of chloramphenicol (CM) resistance in Staphylococcus aureus was investigated by using several CM derivatives. It was found that dl-threo-1-p-nitrophenyl-2-dichloroacetamino-1,3-dichloropropane has high antibacterial activity but low activity of induction for CM resistance. In spite of low antibacterial activity, induction of CM resistance occurred after prior treatment with dl-threo-1-p-nitrophenyl-2-dichloroacetamino-3-chloropropane-1-ol. It was found that dl-chloramphenicol di-acetate, dl-threo-1-p-nitrophenyl-2-dichloroacetamino-3-bromopropane-1-ol and dl-threo-1-phenyl-2-dichloroacetamino-1,3-propanediol have induction ability in spite of the absence of antibacterial activity. Other derivatives were classified into two groups; (1) low antibacterial activity and induction of CM resistance and (2) loss of both activities.     

Investigation of vessel occlusion during cell seeding process

Biomechanics and Modeling in Mechanobiology - The seeding of cells into an organ is an important step in cell therapy because the final functional properties of the organ are related to...     

Mode of degradation of myofibrillar proteins by rabbit muscle cathepsin D

The mode of degradation of myofibrillar proteins by the action of highly purified rabbit muscle cathepsin D (EC 3.4.23.5) was studied using SDS-polyacrylamide gel electrophoresis. Cathepsin D optimally degraded myosin heavy chain, α-actinin, tropomyosin, troponin T and troponin I at around pH 3. It did not degrade actin or troponin C. Degradation of myosin heavy chain produced four major fragments of 155 000, 130 000, 110 000 and 90 000 daltons. Troponin T was hydrolyzed to 33 000-, and 20 000- and 11 000-dalton fragments. Troponin I was degraded into fragments of 13 000 and 11 000 daltons. Degradation of α-actinin and tropomyosin was not as rapid as that of mysoin and troponins T and I. Tropomyosin gave a fragment of 30 000 daltons, but α-actinin showed no distinct band of this fragment on gels.     

Racemization of Amino Acid Residues in Casein Roasted with Glucose and/or Methyl Linoleate

As model systems of foods, casein mixed with glucose and/or methyl linoleate were heated in an electric roaster at 120~230°C for 20 min under air or nitrogen and racemization of amino acid residues in these roasted materials was investigated by capillary column gas chromatography. On roasting the food model systems as well as in the case of pure protein, racemization in the amino acid residues occurred, and aspartic acid, glutamic acid and alanine residues were remarkably racemized. Correlation between the remaining ratio and the degree of racemization of amino acids is observed. It has been found that some components of food model systems, such as reducing sugar and lipid, promote the decomposition and racemization of amino acid residues.     

Histochemical localization of adenylate cyclase and phosphodiesterase activities in the foliate papillae of the rabbit. II. Electron microscopic observations

Adenylate cyclase and cyclic AMP phosphodiesterase activitiesin the foliate papillae of rabbit were studied by means of electronmicroscopic histochemistry using slightly modified proceduresof Howell and Whitfield (1972) and Florendo et al. (1971), respectively.The reaction products of both the enzyme activities were localizedon the surface membrane of the microvilli of the type I tastebud cells (dark cells). The results suggest that a cyclic nucleotidesystem is involved in the transduction process of taste organs.