APC mutation in the alternatively spliced region of exon 9 associated with late onset familial adenomatous polyposis

Germ-line mutations in the adenomatous polyposis coli (APC) gene are responsible for familial adenomatous polyposis (FAP). Genotype-phenotype correlation studies in patients with FAP have demonstrated associations of certain variants of the disease with mutations at specific sites within the APC gene. In a large FAP family, we identified a frameshift mutation located in the alternatively spliced region of exon 9. Phenotypic studies of affected family members showed that the clinical course of FAP was delayed, with gastrointestinal symptoms and death from colorectal carcinoma occurring on average 25 and 20 years later than usual, respectively. The numbers of colorectal adenomas differed markedly among affected individuals and the location of colorectal cancer lay frequently in the proximal colon. Our findings suggest that the exon 9 mutation identified in the pedigree is associated with late onset of FAP. The atypical phenotype may be explained by the site of the mutation in the APC gene. Analysis of the APC protein product indicated that the exon 9 mutation did not result in a detectable truncated APC protein. Given the location of the mutation within an alternatively spliced exon of APC, it is conceivable that normal APC proteins are produced from the mutant allele by alternative splicing.     

Sulfoxide configuration in sparsomycin determines time-dependent and competitive inhibition of peptidyl transferase

Sparsomycin, S_cR_s configuration, was the most potent of the four possible stereoisomers as a competitive inhibitor of peptide bond formation. In addition, the configuration of the two chiral centers dictated whether the compound exhibited time- and temperature-dependent inhibition of peptidyl transferase when incubated with polysomes prior to enzyme assay. The data corroborate the thesis that a peptidyl transferase-mediated acylation of the pivotal sulfoxide moiety and subsequent Pummerer rearrangement play a significant role in the inhibitory properties of sparsomycin.     

Zinc mediated effects on leaf CO2 diffusion conductances and net photosynthesis in Phaseolus vulgaris L.

Supra-optimal levels of zinc in primary leaves of Phaseolus vulgaris increased the CO₂ compensation point and inhibited net photosynthesis. Leaf morphology was modified: mesophyll intercellular area, stomatal slit length and interstomatal distance were reduced, but stomatal density increased. Internal and stomatal conductances to CO₂ diffusion decreased. These changes are discussed in relation to the observed effects on leaf gas exchange and to the previously reported inhibition of different photosynthetic and photorespiratory enzymes.     

Control of glycolysis in the posterior adductor muscle of the sea musselMytilus edulis

Summary Concentrations of glycolytic intermediates, lactate, adenine nucleotides, inorganic phosphate, phosphoarginine and citrate have been estimated after various periods of valve closure (Table 1 and Fig. 1). Mass action ratios of enzyme steps involved in the metabolism of these components are compared with their equilibrium constants. This reveals glycogen phosphorylase, phosphofructokinase, hexosediphosphatase and pyruvate kinase catalyze non-equilibrium reactions. The first three enzymes possess relatively low activities (Table 2).From the changes in concentrations of the glycolytic intermediates it is concluded that phosphofructokinase controls the carbon flow during the first hours after valve closure, whereas later on the rate of conversion of phosphoenolpyruvate is determining this flow. In skeletal muscle phosphofructokinase controls the carbon flow during the whole period of exercise.The concentrations of ADP, AMP and inorganic phosphate increase, whereas the concentrations of ATP, phosphoarginine and citrate decrease during valve closure (Table 1 and Fig. 2). In contrast to skeletal muscle, these changes do not result in a strong increase in the glycolytic flux.There is a much greater potential for ATP hydrolysis by the myofibrillar ATPase system than is actually realized by the adductor muscle during valve closure.     

Vegetative multiplication of sugarbeet through in vitro culture of inflorescence pieces

In vitro vegetative multiplication of sugarbeet was obtained by culturing of inflorescence explants. Subapical segments or 5-mm-long tips from nine varieties developed axillary shoots (up to 50 per tip) on a medium containing indolebutyric acid (IBA) and benzylaminopurine (BAP). Zeatin was ineffective as cytokinin. Gibberellic acid (GA₃) enhanced the process. Such vegetative shoots were subsequently isolated and were each allowed to develop up to 20 supplementary axillary shoots on a multiplication medium containing IBA, BAP, and naphthaleneacetic acid (NAA). Rooting of shoots was obtained in the absence of growth regulators and plants were established.     

Agrobacterium and plant genetic engineering

Erratum

Agrobacterium and plant genetic engineering     

Community structure and functional roles of meiofauna in the North Sea

Knowiedge on community structure of North Sea meiofauna has greatly increased recently. A quasisynoptic picture of meiofauna densities and copepod community structure from 171 stations of the southern North Sea, sampled in April–May 1986, has been obtained during the North Sea Benthos Survey. Latitudinal patterns in meiofauna abundance and copepod weight, abundance and diversity exist in an area between 51°30′N and 58°30′N. Using TWINSPAN-classification five major groups of copepod species can be recognized which are related to sediment type, latitude and depth. The part of the meiofauna in total benthic energy flow, their role in the benthic food web and in biogeochemical cycles is discussed based on existing literature. There are still considerable gaps in knowledge and the field is not progressing rapidly. Publication no. 599 Netherlands Institute of Ecology, Centre for Estuarine and Coastal Ecology, Yerseke, The Netherlands.     

Histology and histochemistry of the testis and ovary of the platyfish,Xiphophorus maculatus,from birth to sexual maturity

Summary The gonads of 3-day- to 7-month-old male and female platyfish (Xiphophorus maculatus) were examined for the presence of 5-3-hydroxysteroid dehydrogenase (3-HSD) and glucose-6-phosphate dehydrogenase (G6PD) by histochemical means. In 3-day-old males a positive response for both enzymes is localized in the Leydig cells. With subsequent testicular development, these cells increase in number and display greater activity at the periphery of the testis and around the efferent ducts. In 3-day-old females 3-HSD and G6PD are localized in the stromal cells of the ovary. These cells increase in number and activity as the animals become sexually mature. Sertoli cells, efferent duct epithelium, and ovarian granulosa cells are negative at all stages of development examined. Our findings suggest that the gonads of neonatal fish possess the potential for steroidogenesis. The role played by sexsteroid hormones in the maturation of the brain-pituitary-gonad axis is discussed.