Efficiency of particle-bombardment-mediated transformation is influenced by cell cycle stage in synchronized cultured cells of tobacco

Plasmid DNA pB1221 harboring β-glucuronidase gene was delivered to synchronized cultured tobacco (Nicotiana tabacum L. cv Bright Yellow-2) cells of different cell cycle stages by a pneumatic particle gun. The cells bombarded at M and G₂ phases gave 4 to 6 times higher transformation efficiency than those bombarded at the S and G₁ phases.     

Developmental regulation for collagen II gene expression in transgenic mice

In order to evaluate the involvement of the type II collagen regulatory sequences in development, we have injected a construct containing a toxin gene under the control of the rat type II collagen promoter and enhancer. The construct, pDAS10-DTA, contained the diphtheria toxin A chain gene under the control of type II collagen sequences which had been used previously to target cartilagenous tissues in transgenics. Inspection of developing fetuses at various stages of gestation revealed a high number of aborted implants as well as abnormally developing fetuses. These abnormal fetuses were of small size, had shortened and underdeveloped limbs, cleft palates, and generally resembled a phenotype similar to chondrodystrophic mice. Histological comparisons of normal and abnormal fetuses indicated a reduced amount of extracellular matrix surrounding chondrocytes, and a disorganized appearance of the tissue. These results suggest that the expression of the toxin has occurred in chondrocytes and altered the survival and development of the transgenic mice. These results also indicate that the promoter and enhancer sequences contained in the transgene controlled the developmental expression of the type II collagen gene expression.     

Functional domains of cell adhesion molecules.

A number of molecules involved in cell adhesion (e.g. fibronectin, laminin, collagens I and IV, thrombospondin, entactin) have now been identified and the consequent roles that they play in the processes of growth, migration, differentiation and tumor spread have been described. Active sequences of the molecules have been identified using synthetic peptides derived from specific domains. Several adhesive molecules contain multiple active domains with different biological activities.     

Preferential localisation of elastase in cytosol of human myeloid leukemia HL-60 cells.

The subcellular distribution of the elastase in human myeloid leukemia HL-60 cells was studied in comparison with that in normal leukocytes. On differential centrifugation, most of the elastase activity of HL-60 cell lysates was recovered in the 105,000 x g supernatant, while that of human peripheral blood leukocyte lysates was recovered in the 500 x g precipitate (azurophil granule-rich fraction). Moreover, on Percoll density gradient centrifugation, the elastase activity in HL-60 cell extracts was recovered in the lightest fraction with none in the azurophil granule-rich fractions, whereas most of the activity in leukocyte extracts was recovered in the azurophil granule-rich fractions. This subcellular localization of elastase did not change when HL-60 cells differentiated into monocytes and granulocytes by induction with 12-O-tetradecanoyl phorbol-13-acetate and retinoic acid, respectively. Furthermore, on Sephadex G-75 gel filtration, the elastase activity in HL-60 cell extracts was eluted earlier than that in leukocyte extracts. The size estimation indicated that the elastase of HL-60 cells was 36-30 kDa, corresponding to the size of an elastase precursor reported. The relevance of a large form of the elastase in HL-60 cells to its subcellular localization is discussed.     

A repeating unit of the DYZ1 family on the human Y chromosome consists of segments with partial male-specificity

An average-sized human Y chromosome contains about 3,000 copies of the repeating DNA family DYZ1. A major repeating unit of the family, pHY10, has been cloned and an entire 3,564-bp sequence has already been determined by Nakahori et al. (1986). In the present study, pHY10 was divided into six consecutive segments, A to F, which were independently amplified by the PCR technique to see if they were strictly male-specific. pHY10 appears to consist of segments of various male-specificity. The B segment was apparently male-specific; however, the use of additional techniques (Southern-blot analysis or second PCR amplification in combination with the standard PCR) revealed homologous sequences in some females. None of the six segments of pHY10 may be male-specific in a strict sense. Different segments appear to be conserved during evolution to different extents. The 323-bp E segment appears to be the least conserved and to be responsible for the generation of most variations within the DYZ1 family.     

Electrophoretic karyotyping and chromosomal gene mapping of Chlorella

Molecular karyotypes for six strains of four Chlorella species were obtained by using an alternating-field gel electrophoresis system which employs contour-clamped homogenous electric fields (CHEF). The number and migration pattern of the chromosomal DNA molecules varied greatly from strain to strain: for example, nine separated chromosomes of C. ellipsoidea C87 ranged from 2.5 to 6.5 megabase pairs (mbp) in size, whereas 16 chromosomes of C. vulgaris C169 were from 980 kilobase pairs (kbp) to 4.0 mbp. Depending on the chromosome migration patterns, the six strains were classified into two major chromosome-length polymorphism groups. Using hybridization techniques, the genes for alpha-tublin, chlorophyll-a, b-binding proteins, ribosomal RNAs, and the small subunit of ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBisCO) were mapped on the separated chromosomes of C. vulgaris C169. Since Chlorella chromosomes are small enough to separate and isolate individually by CHEF gel electrophoresis under ordinary conditions, they should serve as excellent materials to study the fundamental molecular structure of plant-type chromosomes.     

Neural coding of speech sound in the telencephalic auditory area of the mynah bird

Summary The responses of neurons in field L in the auditory neostriatum of the mynah bird, Gracula religiosa, were recorded during presentation of intact or manipulated mimic voices. A typical mimic voice konnichiwa elicited responses in most of the neurons. Neurons in the input layer (L2) of field L showed many peaks on peristimulus time histograms while those in other layers (L1 and L3) exhibited only one or two peaks. Several neurons in L1 and L3 responded only to the affricative consonant /t/ in the intact mimic voices. They did not respond to the affricative consonant in the isolated segment or to the one in the playbacked voice in reverse. Forty-five percent of the neurons (33/ 73) decreased in firing rates at the affricative consonant in the isolated segment compared with in the intact voice. Some of these neurons, in which neither the affricative consonant in the isolated segment nor bursts of noise alone elicited responses, exhibited clear phasic responses to /t/ in the case when bursts of noise with particular central frequencies preceded the affricative consonant. The responsiveness of these neurons appears to receive temporal facilitation. These results suggest that these neurons code the temporal relationship of speech sound.Abbreviations HVc hyperstriatum ventrale, pars caudale - TFN temporally facilitated neuron - TSN temporally suppressed neuron