Bacteria and heterotrophic microflagellate production in the Santa Rosa Sound, Florida

Bacterial and microflagellate biomass and production and grazing onbacteria were compared weekly at a fixed station in Santa Rosa Sound,Florida, starting in February and ending in October. For bothpopulations the weekly variation in biomass and production was aslarge as the seasonal variation. Cycles for biomass and production ofthese organisms were generally out of phase, rendering it difficultto estimate the net grazing of bacteria by microflagellates atindividual time points. For evaluation of factors that control thefate of carbon cycled by bacterial, experiments were conducted toexamine bacterial growth rates in the absence of predators. Thisexamination resulted in low bacterial growth rates when biomass washigh, and rapid growth rates typically occurred near minimumpopulations. Further analysis suggested that microflagellatepredation was greater than bacterial production during minimumbacterial growth rates. With integration of production and grazingrates over the study period, factors controlling bacterial growthwere examined. Using this approach, 71% of the bacterial productionwas grazed by < 8.0µm predators. The microflagellate biomassproduction was 41% of the grazing rate on bacteria. The total amountof bacterial production assimilated into microflagellate biomass was29%. However, based on the variations in biomass and activity of themicrobial assemblages, it appears that substrate and predation exertalternating control on bacterial abundance and production.     

A unique tubulin antiserum attenuates the rate of poleward chromosome movement in anaphase.

An antiserum against tubulin, NS20, was previously shown to specifically attenuate both fast axonal transport in vivo (Johnston, K. M. et al., Brain Res. 385, 38-45 (1986)) and in vitro (Johnston, K. M. et al., Cell Motil. Cytoskel. 7, 110-115 (1987)) and flagellar motility (Goldsmith, M. et al., Cell Motil. Cytoskel. 20, 249-262 (1991)). We hypothesized that NS20 blocked motility by binding to a multifunctional motor binding domain on the microtubules (MTs), or axonemes. Here we have examined the effect of microinjecting NS20, at metaphase, into dividing PtK2 cells. Plotting chromosome separation (CS) as a function of time, we report here that CS rates for anaphase A (chromosome-to-pole movement) were reduced by approximately 50% relative to uninjected controls. CS rates for anaphase B (spindle pole elongation) were unaffected by the NS20 antiserum. The inhibition of CS rate during anaphase A by NS20 was significantly greater than the inhibition caused by a control antitubulin serum (PC5). Two possible mechanisms underlying NS20's inhibition of CS during anaphase A were considered. NS20 could block the binding of a kinetochore-associated motor to kinetochore MTs (kMTs) or, alternatively, NS20 could stabilize kMTs against depolymerization. Our results favor the first alternative. In a cold-induced depolymerization assay, NS20 had no selective stabilizing effect on MTs. Moreover, we show that NS20 can selectively block the binding of a well characterized MT-associated motor (kinesin) to MTs, in vitro. These results suggest that NS20 may be defining a unique tubulin binding domain common to the motors underlying vesicle transport, flagellar motility, and chromosome movements during anaphase A.     

THE MANAGEMENT OF CHYLOTHORAX

Chylothorax is readily diagnosed from the characteristic qualities of the effusion. Treatment should initially be conservative, consisting of multiple aspirations followed, if necessary, by suction drainage.Approximately half of the patients will not respond to these measures, and direct ligation and division of the duct is necessary for cure. This operation is most readily carried out through the right chest, the thoracic duct being ligated just above the diaphragm. In cases in which the duct is surrounded by tumor, radiotherapy to the mediastinum is often successful in controlling the reaccumulation of chyle, but irradiation is generally not recommended until after a tissue diagnosis has been made by thoracotomy.Nutritional problems are often concomitants of chylothorax.