Duration of the calcium signal in the mitogenic stimulation of thymocytes.

An increase in the free cytoplasmic Ca2+ concentration in thymocytes can be detected by the fluorescent indicator quin 2 within a few seconds of the addition of concanavalin A and the response is quantified from the increased proportion of quin 2 in the cells chelated by Ca2+ ('% Ca-quin 2'). The % Ca-quin 2 in untreated cells is 53 +/- 6%, increases to 64 +/- 7% immediately after the addition of concanavalin A and declines spontaneously over 24 h back to the level in untreated cells (53 +/- 6%). The increase in % Ca-quin 2 in response to concanavalin A is completely blocked when 50 mM-alpha-methyl D-mannoside is added before concanavalin A and completely reversed when the competing sugar is added immediately after the mitogen. Addition of alpha-methyl D-mannoside at increasing intervals after concanavalin A addition causes a progressively smaller decrease in % Ca-quin 2 and has a negligible effect after 24 h, when the % Ca-quin 2 is the same as that in untreated cells. The decline in the calcium signal defined by these experiments has a similar time course to cap formation by concanavalin A on the cells. It is concluded that the calcium signal lasts only while concanavalin A is bound to the cell surface and is terminated either by capping or by the addition of alpha-methyl D-mannoside.     

A bibliography on howler monkeys (Alouatta sp.)

Reports dealing with howler monkeys since1900 have been assembled in the present bibliography. The references marked with(R) have been taken verbatim from Ruch's Bibliographia Primatologica. Papers identified by^* deal more extensively withAlouatta.     

Social and reproductive behavior ofChaetodontoplus mesoleucus (Pomacanthidae) at Bantayan island,Philippines, with notes on pomacanthid relationships

Chaetodontoplus mesoleucus occurs at Bantayan Island in a habitat of small patches of mixed scleractinian and alcyonacean corals of low diversity and simple structure. Male-female pairs were predominant, and the sex-ratio showed only a slight skew towards females. However, the presence of single male, two-female social groups demonstrates that the species is polygamous. Small size of social groups is attributed to a preference for a habitat lacking structural complexity. The species did not occur on complex coral reefs. Social and spawning behavior are nearly identical to that of most pomacanthids for which data are available, and although sex-change was not demonstrated, size-related dominance hierarchies and close phylogenetic relationships to sex-changing pomacanthids suggest protogynous hermaphroditism in this species. Behaviorally,C. mesoleucus appears quite similar to a large group of species proposed herein to represent a generalized pomacanthid behavioral type. Divergences from this generalized type by members ofGenicanthus, eastern PacificHolacanthus, and western AtlanticPomacanthus are discussed. Evidence is given to suggest the phylogenetic derivation of the subgenusCentropyge (genusCentropyge) from an ancestor of the subgenusXiphipops type. Color dimorphism and “rendezvous sites” are briefly discussed.     

The rare occurrence of plant tissue culture contamination by Methylobacterium mesophilicum

A pink-pigmented, facultative methylotrophic (PPFM) bacterium, Methylobacterium mesophilicum, which is found on the leaf surface of most plants, has been reported to be a covert contaminant of tissue cultures initiated from Glycine max (soybean) leaves and seeds by Holland and Polacco (1992). The bacteria can be detected as pink colonies when leaves are pressed or tissue culture homogenates are plated on a medium with methanol as the sole carbon source. Since the presence of contaminating bacteria can confound any biochemical results obtained with such cultures (Holland and Polacco 1992), we wanted to determine the extent of the contamination of our tissue cultures of soybean and other species. No PPFMs were detected in any soybean culture we have, and previous results describing the biochemical characteristics of ureide utilization by one of our soybean suspension cultures (27C) also indicates that PPFM bacteria were not present. Analysis of about 200 other strains of 11 different species maintained in this lab showed that only three of about 160 callus cultures, recently initiated from Datura innoxia leaves, contained PPFMs. The D. innoxia leaves did have PPFMs on their surface but in most cases they did not survive the surface disinfestation and culture regimes. Thus PPFM bacterial contamination should not be a serious problem in most plant tissue cultures.Abbreviations AMS ammonium mineral salts medium - PPFM pink-pigmented facultative methylotrophic bacteria     

Optimal door fitting with systematic fixture adjustment

A systematic approach is presented to obtain the best door gap quality through optimal door fitting in automobile body manufacturing. First, three indexes of gap quality are defined; they are: (1) door gap width deviation relative to design nominal; (2) door gap parallelism; and (3) car-to-car gap consistency. Then the door-fitting problem is formulated into a general constrained optimization problem. The effects of optimal door fitting on the three quality indexes are evaluated through computer simulation. These results provide a lower bound on the design of nominal door gap by considering process capability. Finally, a computer-aided fixture adjustment scheme is developed to orient a door in a body side opening to achieve the optimal fitting. The amount of adjustment, with the desired orientation obtained from optimization, is calculated based on parametrically modeled local surface features of the fixture and the door. The adequacy of door feature modeling is verified through a door-fitting experiment.     

Kinetics of growth and sugar consumption in yeasts

An overview is presented of the steady- and transient state kinetics of growth and formation of metabolic byproducts in yeasts.Saccharomyces cerevisiae is strongly inclined to perform alcoholic fermentation. Even under fully aerobic conditions, ethanol is produced by this yeast when sugars are present in excess. This so-called Crabtree effect probably results from a multiplicity of factors, including the mode of sugar transport and the regulation of enzyme activities involved in respiration and alcoholic fermentation. The Crabtree effect inS. cerevisiae is not caused by an intrinsic inability to adjust its respiratory activity to high glycolytic fluxes. Under certain cultivation conditions, for example during growth in the presence of weak organic acids, very high respiration rates can be achieved by this yeast.S. cerevisiae is an exceptional yeast since, in contrast to most other species that are able to perform alcoholic fermentation, it can grow under strictly anaerobic conditions.Non-Saccharomyces yeasts require a growth-limiting supply of oxygen (i.e. oxygen-limited growth conditions) to trigger alcoholic fermentation. However, complete absence of oxygen results in cessation of growth and therefore, ultimately, of alcoholic fermentation. Since it is very difficult to reproducibly achieve the right oxygen dosage in large-scale fermentations, non-Saccharomyces yeasts are therefore not suitable for large-scale alcoholic fermentation of sugar-containing waste streams. In these yeasts, alcoholic fermentation is also dependent on the type of sugar. For example, the facultatively fermentative yeastCandida utilis does not ferment maltose, not even under oxygen-limited growth conditions, although this disaccharide supports rapid oxidative growth.     

Design and applications of a self-aligning liquid junction-electrospray interface for capillary electrophoresis-mass spectrometry

A simple self-aligning liquid junction-electrospray interface for coupling a capillary electrophoresis (CE) system to an atmospheric pressure ionization (API) mass spectrometer (CE-MS) was developed. In contrast to previous liquid junction interfaces, the self-aligning liquid junction interface simplifies the precise alignment of the CE capillary and the sprayer needle and uses a positive make-up flow. Several capillary CE-MS applications were run using both the self-aligning liquid junction interface and the widely used sheath flow interface for comparison purposes. The electrospray stability of the self-aligning liquid junction interface is consistently better even when non-volatile electrolyte solutions are used. At first, some band broadening was obtained with the self-aligning liquid junction interface. Experiments with different CE buffer systems suggested that this band broadening was caused by the materials used in constructing the interface. By using a more inert material for the sprayer needle, the self-aligning liquid junction exhibits excellent electrophoretic resolution, comparable sensitivity, and higher signal-to-noise ratios when run under the same conditions as the sheath flow interface.     

Structure and Regulation of a Complex Locus: The Cut Gene of Drosophila

The cut locus encodes a homeobox protein that is localized in the nuclei of a variety of tissues and is required for proper morphogenesis of those tissues. Cut protein is required in embryonic and adult external sensory organs, where its absence results in conversion of the organs to chordotonal organs. Expression of cut also occurs in the Malpighian tubules, spiracles, central nervous system, and a number of other tissues. Gypsy transposon insertions upstream of the cut promoter block expression in subsets of these tissues. The effect of the gypsy insertions is polar, with those farthest from the promoter affecting the fewest tissues. The hypothesis that gypsy insertions block a series of tissue-specific enhancer elements that are distributed over a region of 80 kb upstream of the promoter predicts the location of the enhancers for cut expression in each of the tissues in which it is active in embryos. DNA fragments from this region drive expression of a reporter gene in each of the embryonic tissues in which endogenous cut gene is expressed. Each tissue has its own enhancer, and none of the enhancers require the activity of the endogenous cut gene to function.