The influence of diet on the growth of Stenonema vicarium (Walker) (Ephemeroptera: Heptageniidae)

Laboratory studies compared the growth rate of Stenonema vicarium (Walker) nymphs on diets of detritus and natural stream periphyton. In three consecutive runs of the experiment, growth rates were consistently higher on periphyton (mean growth rate = 2.1% wet wt. d⁻¹) than detritus (mean = 1.8% wet wt. d⁻¹). The starting date of each run also significantly influenced growth rates. In each treatment growth rates generally decreased over the course of the 3 runs, and ca. one-half of the nymphs in the last run did not molt or grow. It appeared that growth of S. vicarium may be partially controlled by seasonal factors.     

Salicyloylaspartate as an endogenous component in the leaves of Phaseolus vulgaris

An amide conjugate of o-methoxybenzoic acid and aspartic acid has been isolated from bean leaves. After extraction and methylation of plant material, this compound was isolated as two isomeric monoethyl monomethyl esters. The ethylation of the aspartyl carboxyl groups was shown to be a likely result of an extraction procedure utilising acidified ethanol, the methylation of the aromatic hydroxy of the methoxy group to be due to the derivatisation procedure. Studies with pentafluorobenzylation confirmed that the endogenous compound is o-hydroxybenzoylaspartate.     

Application of Deuterated A-Tocopherols to the Biokinetics and Bioavailability of Vitamin E

-Tocopherol, a superior chain-breaking, peroxyl radical-trapping antioxidant and the most active component of vitamin E, is elevated in liver tumor cells, contributing to their greater resistance towards lipid peroxidation compared to cells from normal tissues. Also, in regenerating rat liver the level of vitamin E has been found to fluctuate in phase with the rate of cell division. In order to study the biokinetcis and mechanisms of the distribution of vitamin E in organs and within tissues of animals, deuterated forms of -tocopherol have been synthesized and their uptake into blood and tissues has been measured by gas chromatography-mass spectrometry. Measurement of the competitive uptake from a mixture of the RRR-and SRR--tocopherol stereoisomers labelled with different amounts of deuterium shows that the liver exerts a strong preference for secretion of the natural (RRR) stereoisomer into the plasma. It is suggested that a tocopherol-binding protein plays a key role in this process.     

Characterisation of the anti-bladder-cancer monoclonal antibody BLCA-8: Identification of its antigen as a neutral glycolipid

A monoclonal antibody, BLCA-8, was raised against the human bladder cancer cell line, UCRU-BL-17CL. By flow cytometry and immunoperoxidase staining, this antibody was found to possess high specificity for bladder tumours, some reactivity with fetal tissues, and no reactivity with normal bladder, or any normal or malignant tissue. This high specificity and the stability of the antigen to the urinary environment suggest that BLCA-8 may have potential for use as an anti-bladder-cancer therapeutic agent. By thin-layer chromatography and autoradiography, BLCA-8 was found to bind four components within the neutral lipid fraction of a bladder cancer cell line, UCRU-BL-17/23. These components hadR _F values of 0.22, 0.16/0.15 (doublet), 0.12 and 0.08, and migrated below globoside, indicating the presence of more than four sugars. By enzyme-linked immunosorbant assay and thin-layer chromatography it was found that the binding of BLCA-8 to the lipid extract was increased by both mild alkaline hydrolysis and enzymatic treatments, indicating that adjacent phospholipids and glycolipids interfere with the accessibility of the antibody-binding site. Full biochemical characterisation of the BLCA-8 antigen is currently underway.     

Measures of geographic range size: the effects of sample size

A number of methods have been used for quantifying the sizes of the geographic ranges of species. The consequences of different levels of sampling (the proportion of actual spatial occurrences) are explored for eight of these, using data on the occurrences of butterfly species on a 10 × 10 km grid across Britain. For all methods, the percentage error of estimation (PEE) decreases with the number of 10 × 10 km squares which a species occupies, most rapidly for extent measures, and more rapidly for area measures than for measures of numbers of units occupied. The rate of decline in PEE itself falls as sampling effort increases. At a given sampling level, rank correlations between range sizes measured by different methods are generally high, but there is no consistent change in the magnitude of these correlations as the level of sampling increases. The composition of the set of species with the smallest range sizes changes with the level of sampling.     

ExbB acts as a chaperone-like protein to stabilize TonB in the cytoplasm

The TonB protein is required to transduce energy from the cytoplasmic membrane to outer membrane transport proteins of Gram-negative bacteria. Two accessory proteins, ExbB and ExbD, are required for TonB function and it has been suggested that TonB and ExbBD form a complex in the membrane. In this paper we demonstrate that there are two spatially distinct, functional interactions between ExbBD and TonB. First, there is an interaction between ExbBD and the N-terminal signal-like peptide of TonB, probabiy the formation of a stable complex in the membrane. Second, ExbB interacts with TonB in the cytoplasm. This interaction involves the domain of TonB that is normally periplasmic. Thus, this is a transient interaction which occurs during the synthesis and/or localization of TonB, implying a chaperone-like role for ExbB. The transmembrane topology of ExbB was shown to be consistent with this role.     

Parthenogenesis in an elasmobranch in the presence of conspecific males

Parthenogenesis has been observed in several elasmobranch species, primarily in public aquaria. The majority of cases of parthenogenesis have occurred either when females were held without males or once a male was removed from a female's habitat. Here we report a second instance of parthenogenesis in a zebra shark female that was housed with conspecific mature males. This study calls into question the conditions under which elasmobranch females undergo parthenogenesis.