Incorporation of isotope from specifically labeled glucose into alginates of Pseudomonas aeruginosa and Azotobacter vinelandii.

The incorporation of isotope from [6-14C]glucose into alginate by both Pseudomonas aeruginosa and Azotobacter vinelandii was 10-fold greater than that from either [1-14C]- or [2-14C]glucose, indicating preferential utilization of the bottom half of the glucose molecule for alginate synthesis. These data strongly suggest that the Entner - Doudoroff pathway plays a major role in alginate synthesis in both P. aeruginosa and A. vinelandii.     

Identification of a tumor inhibitory factor in rat ascites fluid

A polypeptide which inhibits the growth of human carcinoma cells has been characterized from Novikoff rat ascites fluid. This tumor inhibitory factor co-purified with transforming growth factor activity through acid/ethanol extraction and Bio-Gel chromatography. The two activities were completely separated by reverse phase HPLC. The tumor inhibitory factor is heat stable and requires disulfide bonds for bioactivity. This factor inhibited the anchorage independent growth of the more differentiated human colon carcinoma cell lines but did not affect the less differentiated carcinoma cells. The presence of stimulatory and inhibitory activities in the same extracts suggests that the relative concentrations of these factors may be important in the control of cell growth.     

An intramolecular linkage involving isodityrosine in extensin

We isolated isodityrosine, a diphenyl ether linked amino acid, from cell wall hydrolysates and from two tryptic peptides of extensin. Determination of the molecular weights, net charges and composition of the peptides indicated that isodityrosine (IDT) can form a short intramolecular linkage in sequences consisting of:

     

Factors influencing algal species assemblages on reef and cobble substrata off Ghana

Subtidal algal assemblages were studied on two substrata, rocky reefs and calcareous cobbles. Although the two occur together at comparable depths, their vegetation differs in species composition and richness, and in patterns of plant size, life form, and longevity. The reef bears a species-rich, patchy cover of small filamentous and crustose forms, with occasional clumps of more robust species. The cobbles support a sparse cover of large leafy and dendritic species in addition to many of the smaller species found on the reef. The floristic separation arises from differential establishment and survival of species under conditions of (1) grazing by fish and urchins (on the reef only), and (2) seasonal physical disturbance during storms leading to the removal of most algae (on the cobbles only). Both substrata show a seasonal floristic cycle, but the trend is more pronounced on cobbles. Species do not depart from randomness in their patterns of co-occurrence on individual cobbles or reef fragments. Interspecific competition appears comparatively unimportant in determining species composition on either substratum.     

Evidence for Membrane-Associated Choline Kinase Activity in Rat Striatum

The distribution of choline kinase (EC 2.7.1.32) activity was investigated in subcellular fractions of rat striatum. Enzyme activity in the crude mitochondrial fraction, determined after dissolution in Triton X-100, was 5.90 mumol/g initial wet weight/h. When a crude mitochondrial preparation was hypoosmotically shocked and fractionated, followed by the addition of Triton X-100, choline kinase activity in the soluble and particulate fractions was 4.58 and 1.40 mumol/g initial wet weight/h, respectively. Enzyme activity in the particulate fraction was not detected in the absence of Triton X-100 or in the presence of NaCl (up to 1.5 M). Subcellular enzyme markers indicated that the membrane-associated activity was not attributable to mitochondrial or microsomal contamination. Kinetic analysis of the activity of soluble and membrane-solubilized choline kinase indicated Km values of 0.74 mM and 0.68 mM, respectively. Results indicate that choline kinase activity may be measured in both the soluble and the particulate fractions of rat striatum, the latter most likely involving enzyme associated with membrane through hydrophobic or covalent interactions. The specific function of the membrane-associated enzyme has not yet been determined.     

Rapid,gregarious settlement of the larvae of the marine echiuran Urechis caupo Fisher & MacGinitie 1928

Larvae of Urechis caupo Fisher & MacGinitie, reared in the laboratory, were exposed to potential settlement stimuli, including natural sediment from adult burrows, and “scent” obtained from the skin of adult animals. Competent larvae settled rapidly and specifically in response to adult burrow sediment when compared with their responses to other natural and abiotic sediments. Larvae also responded specifically to chemical “scent” from adult animals when the “scent” of another echiuran worm, Listriolobus pelodes Fisher served as a control. Larval responses to chemical “scent” were as great as their responses to natural burrow sediment. Hence, it is likely that larvae settle gregariously in nature in response to “scent” on sediment grains of adult burrows. The chemical “scent” had a molecular weight between ≈3500 and 14000 daltons, as determined by dialysis. It quickly lost its effectiveness in promoting settlement after it was heated to 80 °C, but was relatively stable at ambient ocean temperatures, retaining its effectiveness for several days. It was soluble in sea water. However, larvae did not respond to the chemical “scent”, unless it was adsorbed onto a surface. Purely tactile stimuli, such as the shape, texture, and size-distribution of particles, were not important settlement cues during these experiments.     

The establishment of cell lines from imaginal wing discs of Spodoptera frugiperda and Plodia interpunctella

Continuous cell cultures were established from imaginal wing discs of 2 Lepidoptera, Spodoptera frugiperda and Plodia interpunctella. The S. frugiperda line (IAL-SFD1) grows as multicellular vesicles and responds morphologically and biochemically to the insect hormone, 20-hydroxyecdysone. In contrast, the P. interpunctella cells (IAL-PID2) grow as attached monolayers of small spindle-shaped cells and do not appear to have specific responses to 20-hydroxyecdysone, although growth rates are slowed in these cells upon exposure to the hormone.     

Action of two juvenile hormone antagonists on lepidopteran epidermis

The juvenile hormone antagonist ETB (ethyl-4-2(t-butylcarbonyloxy)-butoxybenzoate) caused formation of precocious larval-pupal intermediates after the 4th (penultimate)-larval instar of the tobacco hornworm, Manduca sexta, when 50 μg were applied to any 3rd stage larvae or to 4th stage larvae within 12 hr after ecdysis. This dose was most effective within 12 hr after ecdysis to the 3rd stage. In the black mutant larval assay for juvenile hormone, ETB had activity, 0.75 μg per larva giving half-maximal score. In vitro ETB acted as a juvenile hormone to prevent the ecdysteroid-induced change in commitment at concentrations above 0.1 μg/ml with an ED₅₀ at 2.8 μg/ml and as a partial juvenile hormone antagonist to 0.1 μg/ml juvenile hormone I at concentrations between 10^?3 and 10^?2 μg/ml. By contrast, EMD (ethyl-E-3-methyl-2-dodecenoate) had little juvenile hormone-like activity in vitro up to its limits of solubility (100 μg/ml) and exhibited sporadic partial juvenile hormone antagonistic activity in vitro at concentrations between 1 and 100 μg/ml. Since these concentrations were 10–1000 times that of juvenile hormone I in the medium, EMD apparently is not an efficient competitor.