Adherence of Agrobacterium tumefaciens to the cells of immature wheat embryos

Agrobacterium attached to wheat embryos in vitro. This attachment was plasmid independent, and occurred on both wounded and unwounded cell surfaces. The pattern of attachment clearly demonstrated that bacterial attachment to cereal cells follows the same trends observed for dicotyledonous plants. During the inoculation period the bacterial cells attach to the plant cell walls either with lateral or polar orientation. Wounding (mechanical or enzymatic) preferentially promoted adherence of the bacteria at the wound site, however, attachment was not wound dependent.     

Loss of urease activity in Helicobacter mustelae

Urease-negative variants of Helicobacter mustelae were isolated after spontaneous loss of activity during sub-culture. The whole-cell protein patterns showed that the loss of urease activity was linked to the absence of two polypeptides of 29·1 and 65·4 kDa. Restriction endonuclease analysis of chromosomal DNA indicated no substantial differences between the urease negative and positive variants. It is likely that a change in the expression of the gene for urease was responsible for these observations.     

Control of regeneration and morphogenesis by divalent cations in Acetabularia mediterranea

A study of the effects of altered calcium and magnesium levels on the capacities of Acetabularia plants to elongate and to form whorls or caps revealed sharp transitions of regenerative state over small concentration changes of external calcium at both reduced and elevated levels. Cobalt and lanthanum, which interfere with calcium fluxes across membranes, also affect regeneration and morphogenesis with sharply defined transition ranges. It is shown that these effects are localized at the growing tip. The nature of the mechanisms involved in the transitions from one morphogenetic state to another in the regenerative process is considered.     

SPHINGOLIPIDS AND PHOSPHOLIPIDS IN MICROSOMES AND MYELIN FROM NORMAL AND PATHOLOGICAL BRAINS

—Myelin and microsomes were separated from human cerebral white matter and cortex respectively using the technique of 15% caesium chloride and their sphingolipid and phospholipid contents estimated. Normal brains as well as cerebral material from cases of metachromatic leucodystrophy, Krabbe's disease and Tay-Sachs’disease were studied. Gangliosides were not present in normal myelin but were found in microsomes and in myelin from the pathological material. The ratio of cerebroside to sulphatide in myelin was 4 to 1 in normal, 1 to 20 in metachromatic and 7 to 1 in Krabbe's disease. The results in the human material are briefly discussed.     

Radio Telemetry of the Electrocardiogram,Fitness Tests,and Oxygen Uptake of Water-Polo Players

During competitive water polo, heart rate in six subjects was monitored by cupped plastic and silver electrodes glued to the skin. Minimum rates during the game averaged 156 beats/min.; maximum rates averaged 186 beats/min. Mean maximum rate with bicycle exercise was 188 beats/min. Maximum oxygen (VO₂ max.) with bicycle exercise of 14 water-polo players was 53.3 ml./kg. Physical working capacity (PWC 170) was 1310 kilopond metres per square metre (k.p.m./sq.m.). PWC 170 correlated well with VO₂ max. in this small group (r = 0.77).Oxygen uptake was measured at three speeds of swimming and four levels of work on a bicycle ergometer. VO₂ max. of swimming was 88% of that obtained on bicycle exercise. The slope of the oxygen uptake vs. pulse rate curves was less for the swimming than for cycling, so that for a given oxygen uptake below the maximal, pulse rate was less in the swimmers. At near-maximal swimming, respiratory quotient was 0.95 compared with 1.27 for cycling, suggesting that the swimmers were underbreathing.     

Purification and characterization of methylmalonate-semialdehyde dehydrogenase from rat liver. Identity to malonate-semialdehyde dehydrogenase

Methylmalonate semialdehyde dehydrogenase was purified from rat liver in order to define the distal portion of valine catabolism and related pathways in mammals. The purified enzyme is active with malonate semialdehyde and consumes both stereoisomers of methylmalonate semialdehyde, implicating a single semialdehyde dehydrogenase in the catabolism of valine, thymine, and compounds catabolized by way of beta-alanine. The oxidation of malonate and methylmalonate semialdehydes by this enzyme is CoA-dependent, the products being acetyl-CoA and propionyl-CoA, respectively. Expected activity with ethylmalonate semialdehyde as substrate was not found. Methylmalonate semialdehyde dehydrogenase was separated on DEAE-Sephacel into two isoforms which differ in mobility during nondenaturing polyacrylamide gel electrophoresis. The two forms are immunologically cross-reactive and exhibit the same N-terminal sequence, suggesting that one form is the product of the other. The monomer molecular mass, determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, was 58 kDa. The native molecular mass, estimated by gel filtration, was 250 kDa, suggesting a tetrameric structure.     

Lipoxygenase inhibitors enhance the proliferation of human B cells

The addition of drugs which inhibit the lipoxygenase pathways of arachidonic acid metabolism to 5 day cultures of mitogen-stimulated human B cells enhanced the proliferative response more than 10-fold. Several chemically dissimilar lipoxygenase inhibitors increased proliferation in this system, whereas the specific cyclooxygenase inhibitor indomethacin had no effect. A lipoxygenase inhibitor could be added as late as 48 to 72 h after the initiation of culture and still cause a significant increase in B cell proliferation. These drugs increased the proliferation of both peripheral blood B cells and tonsillar B cells activated by Staphylococcus aureus Cowan I or anti-Ig M antibodies, in combination with a crude T cell supernate, a commercial B cell growth factor preparation, or recombinant lymphotoxin. A similar effect was observed in tonsillar B cells purified by counterflow centrifugal elutriation to remove esterase positive accessory cells, suggesting this is a direct effect on the B cell. Lipoxygenase blockade also caused a greater than twofold increase in polyclonal Ig production. The enhanced proliferation caused by lipoxygenase blockade could not be reversed by adding back exogenous leukotrienes or hydroxyeicosatetraenoic acids to the cultures. Furthermore, B cells prelabeled with [3H]arachidonic acid did not produce radiolabeled lipoxygenase metabolites of arachidonic acid under the same culture conditions in which the addition of lipoxygenase inhibitors had a profound effect on proliferation. Thus, lipoxygenase inhibitors markedly stimulate B cell proliferation under a variety of experimental conditions, although the mechanism responsible for this action has not yet been elucidated.