Morphology of nascent ziegler-natta polymers.

In the polymerization of alpha-olefins with heterogeneous Ziegler-Natta catalysts, the polymer is formed directly as long fibrillar units with folder chains. It is proposed that the fibrils are formed by the crystallization of polymer chains growing from the active sites on the catalyst surface, a process which is likened to root growth in whiskers.

Cellulose synthesis by Acetobacter xylinum. I. Low molecular weight compounds present in the region of synthesis.

An analysis has been made of the low molecular weight fraction present in the region of cellulose synthesis in Acetobacter xylinum suspensions. A number of nucleic acid bases, nucleosides and nucleotides, together with alpha-glucose 1-phosphate and UDPG, were detected in various extracts of washed cells supplied with glucose. Since glucose-6-P could be detected in extracts of ultrasonically disrupted cells, but not in extracts of whole cells, it was concluded that separate pools of hexose phosphate exist in A. xylinum. Preferential release of alpha-glucose-1-P, UDPG and nucleotides was observed during ethanol and EDTA treatment of bacteria. Electron microscopic examination of treated and untreated cells revealed that extensive modification of the cell wall region occurred during such treatments. The results support the proposal that alpha-glucose-1-P, UDPG and nucleotide pools are localised in the cell envelope region, possibly in the periplasm, and that A. xylinum possesses a second permeability barrier outside the cytoplasmic membrane. Nucleic acid bases and nucleosides were observed to diffuse freely through the cell wall and accumulate in the medium, probably as the result of nucleic acid breakdown. The results imply that the effects of cell damage caused by the isolation of the bacteria from the surface pellicle of the culture medium, together with nutrient deprivation, should be considered in work using the non-proliferating system. A stydy of the variation in concentration with time of alpha-glucose-1-P and UDPG, during cellulose synthesis, indicated that both components may play an immediate role in cellulose synthesis. Glycosylated lipid compounds were detected in both cell wall extracts and supernatant fluid, but it is not certain whether these compounds are constituents of the supernatant fluid in vivo.

Cellulose synthesis by Acetobacter xylinum. II. Investigation into the relation between cellulose synthesis and cell envelope components.

Cell envelope fractions, capable of cellulose synthesis from uridine diphosphate glucose, alpha-glucose-1-phosphate, glucose-6-phosphate and glucose, have been isolated from Acetobacter xylinum suspensions and various enzymatic properties examined. Essential enzymes were found to be distributed throughout the cell envelope region, with both inner (cytoplasmic) and outer (cell wall) membranes contributing to cellulose synthesis. The central role of UDPG in cellulose synthesis was confirmed and the results indicated that the nucleoside diphosphate sugar functions solely in the cell envelope region of whole cells. A comparison of properties of the cell envelope system with those of different preparations used by other workers, suggested that the method of cell disruption may influence substrate specificity.

Cellulose synthesis by Acetobacter xylinum. III. Matrix, primer and lipid requirements and heat stability of the cellulose-forming enzymes.

The addition of soluble cellodextrins of increasing size to a cell envelope preparation of Acetobacter xylinum stimulated cellulose synthesis from UDPG. This stimulation was attributed to both acceptor and activator effects. Enzymes required for cellulose synthesis were found to be heat-unstable and those required for synthesis of glycosylated lipid components from UDPG, heat-stable. Both heat-inactivated envelope fragments and supernatant fluid from whole cells were necessary for cellulose synthesis from UDPG. Cellulose was not formed from UDPG in the presence of either supernatant fluid alone or heat-inactivated envelopes alone. The combined results of this and previous studies suggest that either the cell envelope is necessary for synthesis of a more immediate precursor to cellulose than UDPG, or that the synthesis from UDPG requires a matrix. The former suggestion and its possible link with lipid intermediate involvement was strengthened by the observation of inefficient glycosylated lipid formation by a celluloseless mutant strain of A. xylinum. The possible locations of various enzyme activities required for the synthesis of the cellulose precursor are indicated and a possible microfibril nucleation process is discussed.

Side-effects and weight gain following a smoking cessation program.

Few prospective studies on possible side-effects of smoking cessation have been reported. In the current study, a variety of side-effects and weight gain were assessed throughout and following a smoking cessation program with 94 subjects. Subjects in a cognitive urge control maintenance condition were found to have gained significantly more weight than other conditions. This group also tended to have the highest abstinence rate and lowest percent baseline smoking at follow-up. Abstainers tended to have gained more weight than relapsers , and had rated themselves as higher on "eating more" and had placed themselves as farthest from "optimal" on a measure of general appetite and overeating. On all other side-effects, however, relapsers appeared to be reporting more negative attributes. These results were discussed within the context of incorporating side-effect control strategies as part of smoking cessation programs.

A method for the assessment of body image disturbance in patients with eating disorders.

This paper describes a new method for assessing body image disturbances in eating disordered patients. Fifteen bulimic, 25 anorexic, and 24 normal controls served as subjects. All subjects were matched for age and height, and bulimics and controls were matched for weight as well. All subjects completed the Perceived Body Image Scale (PBIS), which required subjects to report on how they see themselves when they look in the mirror, how they think they look, and how they feel themselves to be, reflecting the perceptual, cognitive, and affective aspects of body image, respectively. Subjects also selected their ideal. An objective rating was made. Objective ratings had a high correlation with the subject's weight. Results showed that both eating disorder groups demonstrated more apparent body image disturbance than controls, and that the bulimics showed significantly greater body image dissatisfaction than anorexics or controls. The potential use of the PBIS as a research and clinical instrument is discussed.