The reduction of anti-tumour diaziridinyl benzoquinones

The properties of the semiquinone radicals produced for 2,5-bis(carboethoxyamino)-3,6-diaziridinyl-1,4-benzoquinone (AZQ) and 2,5-bis(2-hydroxyethylamino)-3,6-diaziridinyl-1,4-benzoquinone (BZQ), have been investigated. AZQ semiquinone radicals can be produced from the reduction of AZQ by superoxide radicals, whereas BZQ semiquinone radicals are unstable in the presence of oxygen. The one-electron reduction potentials of the couples Q/Q-. at pH 7.0 were determined as -70 +/- 10 mV for AZQ and -376 +/- 15 mV for BZQ. The difference in these potentials is explained. As a consequence of ESR studies on the enzymatically produced radicals, we have considered the factors which determine the detection of ESR signals for reduced quinones produced in a biological system.     

The spliceosomal snRNAs of Caenorhabditis elegans.

Nematodes are the only group of organisms in which both cis- and trans-splicing of nuclear mRNAs are known to occur. Most Caenorhabditis elegans introns are exceptionally short, often only 50 bases long. The consensus donor and acceptor splice site sequences found in other animals are used for both cis- and trans-splicing. In order to identify the machinery required for these splicing events, we have characterized the C. elegans snRNAs. They are similar in sequence and structure to those characterized in other organisms, and several sequence variations discovered in the nematode snRNAs provide support for previously proposed structure models. The C. elegans snRNAs are encoded by gene families. We report here the sequences of many of these genes. We find a highly conserved sequence, the proximal sequence element (PSE), about 65 bp upstream of all 21 snRNA genes thus far sequenced, including the SL RNA genes, which specify the snRNAs that provide the 5' exons in trans-splicing. The sequence of the C. elegans PSE is distinct from PSE's from other organisms.     

Control of follicular epithelium development and vitelline envelope formation in the mosquito; role of juvenile hormone and 20-hydroxyecdysone

Using microsurgical manipulations, hormone applications, and transmission electron microscopy we have investigated the regulation of differentiation of the follicular epithelium and formation of the vitelline envelope (VE) in primary follicles in the ovary of the mosquito, Aedes aegypti. During the first 3 days after eclosion, the primary follicle grows, and cells of the follicular epithelium differentiate, their content of mitochondria, rough endoplasmic reticulum, and Golgi complexes increases significantly. Growth and differentiation of the follicular epithelium appear to be under the control of juvenile hormone (JH), because they are blocked by removal of corpora allata in newly closed adult females and can be restored by either implantation of corpora allata or application of JH III. In insects, including mosquitoes, VE is the first layer of the eggshell to be deposited. It is formed from the secretory products of the follicle cells and its deposition coincides with yolk accumulation by developing oocytes. Only follicle cells adjacent to the oocyte deposit VE. In decapitated females, given a blood meal by enema and injected with picogram doses of 20-hydroxyecdysone (20-HE), follicle cells synthesize the VE precursors and deposit morphologically normal VE, in contrast to saline injected controls which deposit no VE. We conclude that 20-HE, as well as factors originating from the blood meal and the oocyte, are required for the normal formation of VE in the mosquito follicles.     

Confirmation of the chromosomal localization of human lamp genes and their exclusion as candidate genes for Salla disease

Summary Salla disease is an inherited lysosomal storage disorder caused by accumulation of free sialic acid in the lysosomes. Lamp genes, lamp A and lamp B (lysosome associated membrane proteins), are the first known genes encoding for human lysosomal membrane proteins. Absence of linkage in a large group of families shows that lamp genes are not involved in Salla disease. The lamp genes were localized, using Southern hybridization in hamster — human hybrid cell panels, to chromosomes 13 (lamp A) and X (lamp B).     

Individual variation in maximum aerobic capacity: cardiovascular and enzymatic correlates in Rana catesbeiana

We quantified natural variation in maximum aerobic capacity (V02max) exhibited by a free-living population of bullfrogs (Rana catesbeiana) and examined the degree to which such variation is associated with key parameters of the systemic oxygen transport apparatus and oxidative enzyme (citrate synthase) activity at the tissue level. Regression analysis of these data revealed that only ventricle mass and hemoglobin concentration accounted for significant fractions of the variation in V02max. Neither variation in maximum heart rate nor in citrate synthase activity were significantly correlated with individual variation in maximum aerobic capacity. These results support the contention that, in at least some taxa, maximum aerobic capacity is limited by the ability of the cardiovascular system to deliver oxygen to the tissues.     

Occurrence of type-1C fimbriae on Escherichia coli strains isolated from human extraintestinal infections

Two monoclonal antibodies specific for type-1C fimbriae of Escherichia coli were produced. In enzyme-linked immunosorbent assay and immunoblotting the antibodies, which were of the IgG1 isotype, reacted with type-1C, but not with P or type-1 fimbriae of E. coli strain KS71. Immunoblotting and immunoprecipitation of crude fimbrial extracts from 25 strains invariably gave an apparent molecular weight of 17 000 for the type-1C fimbrillin. A total of 313 E. coli strains, isolated from patients with extraintestinal infection or from faeces of healthy children, were screened for the presence of type-1C fimbriae using both the monoclonal and polyclonal antibodies. Of these, 45 (14%) strains had type-1C fimbriae, with the highest frequency (27%) on strains isolated from patients with pyelonephritis. No faecal strain had type-1C fimbriae, and the frequency on the other diagnostic groups ranged from 11 to 15%. Thus, no direct correlation between type-1C fimbriae and bacterial virulence in human extraintestinal infections was found. Type-1C fimbriae were detected on only a few E. coli serotypes, notably on all O6:K2:H1 and O22:K13:H1 strains tested.     

Relationships between unconjugated and sulphated steroids in porcine primary Leydig cell culture

Steroidogenesis in immature porcine Leydig cells was investigated in primary culture at 48-84 h under basal conditions and in the presence of hCG. The basal accumulation of unconjugated steroids was close to linear only during the first 4 h of study, whereas the sulphate-conjugated steroids accumulated essentially linearly over the 36 h experimental period. At the last time point, 95% of the steroids measured were sulphated. Stimulation with hCG (1 ng/ml) led to a still more pronounced sulphate conjugation, and approx 99% of the steroids measured were sulphated at 36 h. Under maximal stimulation with hCG (100 ng/ml) the sulphates accounted for 74% of the total steroids measured at 36 h. Testosterone, androstenedione, dehydroepiandrosterone, 5-androstene-3 beta, 17 beta-diol and estrone were usually quantitatively the most important unconjugated steroids, and sulphated dehydroepiandrosterone, estrone, testosterone and 5-androstene-3 beta, 17 beta-diol were the most important steroid sulphates, especially following maximal stimulation of the cultures. These data emphasize the importance of steroid sulphates in porcine testicular steroid metabolism. Under stimulation with hCG, there was a rapid response in testicular steroidogenesis, initially seen as a rapid increase in the secretion of unconjugated and sulphated steroids. At approx 4-12 h, the rate of sulphate conjugation appeared to reach or even to exceed that of steroid biosynthesis, which lead to stabilisation or a decrease in the concentrations of unconjugated steroids. Only high doses of hCG, 10-100 ng/ml, were then able to lead to a net accumulation of unconjugated steroids, at 24-36 h of incubation with hCG.