The enzymatic conversion of L-histidine to urocanic acid by whole cells of Micrococcus luteus immobilized on carbodiimide activated carboxymethylcellulose.

Whole cells of Micrococcus luteus (formerly Sarcina lutea ATCC 9341) have been covalently linked to a carboxymethylcellulose support system, with the retention of histidine ammonia-lyase activity. The dependence of the rate of urocanic acid formation on pH, temperature, and added surfactant concentration was similar for the free and the immobilized cells. The immobilization procedure used is based on the carbodiimide activation of carboxymethylcellulose and has been optimized for the histidine ammonia-lyase activity of the immobilized cells on a given weight of cellulose. In a column reactor at 23 degrees C and superficial velocity of 0.044 cm/min, 5 g of cellulose with bound cells gave a 35% conversion of an L-histidine solution (0.25M, pH 9.0) to urocanic acid for 16 days of continuous operation. The scope of this carbodiimide assisted immobilization procedure has been investigated for a series of microorganisms and a variety of carboxylate functionalized supports.     

Relationship of chin spot size to dominance in the black-chinned mouthbrooding cichlid fish (Sarotherodon melanotheron)

Aggressive interactions of male Sarotherodon melanotheron were studied to determine the communicative value of chin spot size in relation to dominance. In addition, the effects of residency and size on the aggressiveness of this fish were determined. Two-factor analysis of variance was used for frequencies of each modal action pattern for residency and size. Results show that residency played a major role in the outcome of an aggressive interaction, whereas size had little effect. Dominance of each experimental fish was calculated using Barlow & Ballin's (1976) dominance index. A chin spot ratio was obtained by dividing the chin spot area by the total surface area of the individual fish. Simple linear regression was conducted to determine if dominance and chin spot size were correlated and a positive linear relationship was found to exist between the two variables.     

Cloning of the aspartate-β-semialdehyde dehydrogenase structural gene fromEscherichia coli K12

Transformation ofEscherichia coli strains with the recombinant plasmid, prepared by shot gun cloning with pBR322 and containing the geneasd, the structural gene of aspartate--semialdehyde dehydrogenase, results in an increase in specific activity of 65-fold of the enzyme in crude extracts. Approximately 60 mg of pure enzyme may be obtained from 10 g of transformed cells (wet weight) in a simplified purification procedure. The molecular weight, amino acid composition, and kinetic properties of the enzyme appear to be the same as previously reported, and the first 36 amino acids of the N-terminal sequence have been determined.     

Electromyography of the gluteal muscles in Hylobates,Pongo, and pan: Implications for the evolution of hominid bipedality

The gluteal musculature of primates has been a focus of great research interest among those who study human evolution. Most current theorists agree that gluteus superficialis (= maximus) need not have changed its action in the step from pongid to hominid, but dispute has arisen over a purported change in action and role of the gluteus medius. To clarify the functions of gluteus medius, gluteus superficialis, and tensor fasciae femoris during ape locomotion, we conducted a telemetered electromyographic study of these muscles in two gibbons, one orangutan, and four chimpanzees as they walked bipedally on the ground and on a horizontal tree trunk, walked quadrupedally on the same substrates, and climbed a vertical tree trunk. The results indicate that the gluteus medius of apes is not, as has been previously suggested, primarily an extensor of the thigh; its action is chiefly that of medial rotation. The role of the gluteus medius during bipedality is the same in apes and humans–to provide side-to-side balance of the trunk at the hip. The change in the hominid lateral balance mechanism can be viewed as primarily osteological, allowing preservation of the same muscle function with an extended thigh. As a result, the stride length is increased and there occurs a diminution of the demands placed on other muscles to maintain anteroposterior balance at the hip and knee. Our data also support the view that vertical climbing may be specifically preadaptive to bipedalism. One may picture the earliest hominid as part biped, when on the ground traveling between scattered food trees, and part climber, when moving from the ground to food.     

Human colorectal tumours in short-term organ culture A stathmokinetic study

Abstract. Short-term organ culture, using a technique to preserve epithelial/stromal interaction and metabolism, is a useful technique for carrying out kinetic studies on human colorectal carcinoma and adjacent normal mucosa, providing initial perturbations of proliferative indices are allowed to settle. Tumours require 3.0 μg/ml vincristine for complete metaphase arrest compared with mucosa, which needs 0.5 μg/ml, a 6-fold difference. Using a stathmokinetic technique, the birth rate of tumour cells is 10.21 cells/1000 cells per hr, compared with 7.73 cells/1000 cells per hr for mucosa, a statistically significant difference ( P < 0.01).