Chain-length dependence of lipid bilayer properties near the liquid crystal to gel phase transition.

The temperature dependence of the mean orientational order parameter in the vicinity of the liquid crystal to gel phase transition is obtained from the first moment M1 of deuterium nuclear magnetic resonance spectra for bilayers of chain perdeuterated phosphatidylcholines with acyl chains of 12, 14, 16, and 18 carbons. The data clearly show an increasing temperature dependence of the orientational order parameter in the vicinity of the transition, with the effect becoming more pronounced with decreasing chain length. Assuming a linear relationship between the mean orientational order parameter and the extension of the acyl chain, estimates of the change in area of the membrane at the transition are shown to be consistent with those obtained from other measurements. It is shown that the transition may be modeled in terms of a Landau expansion of the free energy involving a small number of phenomenological parameters. From this it is shown that the behavior of these systems in the temperature range of interest is, in large part, controlled by the close proximity of a spinodal to the transition temperature.     

Direct shoot organogenesis and plant regeneration from leaves of grape (Vitis spp.)

Adventitious shoots developed from in vitro-grown leaves of Vitis vinifera cultivars Cabernet Sauvignon, French Colombard, Grenache, Thompson Seedless (syn. Sultana) and White Riesling, V. rupestris cv. St. George (syn. du Lot) and V. vinifera × rupestris cv. Ganzin 1. Leaf explants less than 15 mm long were excised from nodal cultures and cultured on Murashige and Skoog or Nitsch and Nitsch-based regeneration media with 0, 1, 2 or 4 mgl^-1 6-benzylaminopurine (BAP). Adventitious shoots developed within 4 weeks at the petiolar stub and occasionally from wounded lamina tissues. Shoot organogenesis occurred only on media containing BAP and at a higher frequency with 2 mgl^-1 than with 1 or 4 mgl^-1. On media containing 2 mgl^-1 BAP, 47, 67, 60, and 42%, respectively, of leaf explants of Cabernet Sauvignon, French Colombard, Thompson Seedless, and White Riesling produced adventitious shoots compared to 14, 14, and 29%, respectively, for Grenache, St. George, and Ganzin 1. Solid culture medium was superior to liquid medium and transfer frequency on solid medium did not affect the regeneration frequency. Further shoot growth was promoted by the transfer of regenerating tissues to fresh regeneration medium. More than 80% of explants initially producing adventitious buds exhibited further shoot growth, developing an average of more than 6 shoots each. Shoots rooted easily and the resulting plants appeared morphologically identical to parent vines.     

Dominant Pollen Types Recovered From commercial Louisiana honeys

Microscopical pollen analyses of 54 commercial honey samples collected from the major beekeeping areas of Louisiana during 1967–68 showed six dominant pollen types (a dominant type considered as one contributing over 45% of the total grains counted per sample and denoting a unifloral honey). The dominant pollen types and the “ bee plant ” species associated with each pollen type are identified and described. The pollen types are illustrated with light photomicrographs. The pollen types are in order of importance:Trifolium repens, white clover;Rubus spp., blackberry and/or dewberry;Berchemia scandens, rattan vine;Salix spp., willow; Asteraceae, Sunflower family; and Sapiumsebiferum,Chinese tallow tree. White clover and willow were the largest unifloral honey producers in a region including the floodplain and delta of the Mississippi River, and the floodplain of the Red River (the most productive beekeeping area of Louisiana); blackberry and/or dewberry were most significant in the longleaf pine flat woods and mixed hardwoods in the uplands section on the east side of the Mississippi River; rattan vine was most important in west-central Louisiana in an area consisting originally of pine-oak-hickory uplands and longleaf pine flat woods; white clover appeared most important in the prairie region of southwest Louisiana.     

Age-related changes, including synergy and suppression, in the mixed lymphocyte reaction in long-lived mice.

The mixed lymphocyte culture reaction represents the in vitro counterpart of the recognition phase of the graft-versus-host reaction, and of allograft rejection. The mixed lymphocyte culture reactivities of lymph node and spleen cells from all strains show a striking decline with advanced age. Furthermore, studies of "synergy" between subpopulations of T cells in the mixed lymphocyte culture reaction suggest that the cells of the recirculating lymphoid pool (T2 cells) in particular display a functional decline. Finally, spleen cells from old mice of appropriate strains inhibit or suppress the mixed lymphocyte culture reactivity of lymph node or spleen cells from young mice.     

The timing of RNA synthesis for spermiogenesis in organ cultures ofDrosophila melanogaster testes

Summary A method for the organ culture ofDrosophila testes is described which supports the differentiation of primary spermatocytes through the meiotic divisions to elongating spermatids. Autoradiographic and inhibitor studies reveal no evidence for RNA synthesis by developing spermatids ofDrosophila melanogaster; most, if not all, of the RNA required for the differentiation and elongation of sperm is synthesized earlier in the primary spermatocytes. Primary spermatocytes will differentiate into elongating spermatids in organ culture, despite severe (96–98%) inhibition of³H-uridine incorporation into RNA effected by 50 g/ml 3-deoxyadenosine. Protein synthesis in spermatids continues to be active in the presence of 3-deoxyadenosine, but that in growing spermatocytes is severely inhibited.Supported by grant number AEC PA 150-6 from the Atomic Energy Commission, and by grant number HD 03015 from the National Institutes of Health.     

A preparative column electrophoresis apparatus using Sephadex G-25

A preparative column electrophoresis apparatus using Sephadex G-25 as a support medium is described. The apparatus has been successfully employed in the separation of closely related horesradish peroxidase isoenzymes. Rechromatography of the isoenzymes on carboxymethyl- or diethylaminoethyl-cellulose columns was time consuming and often resulted in the irreversible adsorption of some of the protein. The apparatus described here offers both a convenient and an inexpensive method of purification and one in which the entire sample can be recovered. Quantities as large as 120 mg of protein can be applied to each of several columns with excellent resolution. The column may be reused repeatedly and under a variety of conditions by merely equilibrating the column with a different buffer.     

Effect of age on response to T- and B-cell mitogens in mice congenic at theH-2 locus

TheH-2 gene region is shown to display a considerable influence upon the age-specific response to T- and B-cell mitogens in congenic mice. Three sets of three strains each were studied, including mice congenic on A, C3H, and C57BL backgrounds. The sometimes rather striking differences in mitogenic responsiveness upon any one background were generally much less apparent in young mice than in mice examined at later stages in their lifespans, up to 28 to 30 months in the present investigation. Prior studies which failed to detect an effect ofH-2 upon mitogenic responsiveness have been limited to relatively young mice. We suggest thatH-2-linked genes may influence the maturation rates of various types of immune response, or perhaps the status of differentiation receptor sites. Different types of response may mature, peak, and decline at different ages and underH-2 contributory influence. The age-specific incidence of or susceptibility to certain diseases may in part reflect such diverse rates of change or balance among immune functions. The known associations of theH-2 andHLA systems with various malignancies and autoimmune diseases are not inconsistent with this possibility.     

Finding from Asia, Australia, Europe, and North Amercia on secular change in mean height of children, youths, and young adults.

Studies conducted during the past century in Australia, Canada, Japan, Norway and the United States indicate that the magnitude of secular increase in mean height rose with advancing age from childhood to mid-adolescence. Comparisons for a period approximating two-thirds of a century yield average increases in mean height of 12.2 cm for female youths age 12 years, and 12.5 cm for male youths age 14 years; for the same calendar span, the amount of secular increase in mean height declines from mid-adolescence to early adulthood. Comparisons of Belgian females, spanning a period approximating 130 years, yield increases in mean height of 18.1 cm at age 12 years, 11.9 cm at age 16 years, and 3.7 cm in early adulthood. For a period of 90 years, increases obtained on United States White males are 14.8 cm at age 14 years, 8.8 cm at age 17 years, and 5.3 cm in early adulthood. These and other displayed findings show clearly that the search for causes of secular change should take particular account of a phenomenon widespread among human populations, i.e., the phenomenon of childhood and early adolescent growth in body height proceeding at a faster pace in recent decades than about a century ago.