Chlamydosporol,a new metabolite from Fusarium chlamydosporum

Extracts of rice on which an isolate of Fusarium chlamydosporum had been cultured were toxic to brine shrimps. The toxic fraction was purified by flash chromatography to give two compounds which were identified by UV, IR, NMR and mass spectroscopy at the 6 and 6 isomers of 5-hydroxy-4-methoxy-6, 8a-dimethyl-6,7-dihydro-2H,8aH-pyrano[2,3-b]pyran-2-one. These lactones for which the name chlamydosporol is proposed have not been reported previously. When tested in brine shrimp and HeLa cell assays, the LC₅₀ concentration for a mixture of the isomers was approximately 400 g/ml in both systems.     

Proportionality of ELF electric field-induced growth inhibition to induced membrane potential inZea mays andVicia faba roots

Summary The postulate that 60-Hz electric field-induced bioeffect severity is proportional to induced transmembrane potential [ ] magnitude was tested and supported using a plant root model cell system. Statistically significant correlations were obtained upon regression of the relative rates of exposedVicia faba andZea mays root segment growth on the average (calculated) arising in those segments under specified 60 Hz field exposure conditions. The associated with the apparent threshold for growth inhibition was similar inZea andVicia roots (2.5 vs 2.4 mV, respectively). At greater than this threshold,Zea root growth declined by about 9% per mV, andVicia root growth by about 19% per mV induced potential.Abbreviations EF electric field - RGR relative growth rate - RSGR relative segmental growth rate - induced membrane potential - segmental-average induced membrane potential - VC _d region of root tip in which a complete, nascent vascular cylinder is first distinguishable in histological sections     

Intrinsic potential for high fetal hemoglobin production in a Druze family with β-thalassemia is due to an unlinked genetic determinant

Summary The mechanism for elevated production of fetal hemoglobin (Hb F) in a Druze patient with °-thalassemia intermedia was investigated. Heterozygous family members exhibited normal Hb F levels, suggesting that the increase in -gene expression in the propositus may be partly due to anemic stress. Erythroid progenitors of these family members cultured in vitro [burst forming units (erythroid); (BFUe)] showed elevated synthesis of Hb F, indicating the existence of a genetically determined intrinsic capacity for high Hb F production in this family. The propositus was found to be homozygous for a IVS2-position 1 mutation, on the background of Mediterranean haplotype I, which is not known to be linked to high Hb F production. Moreover, extensive molecular studies of the -globin gene cluster, including sequence analysis of the promoter regions of the -globin genes, did not reveal any cisacting mechanism that could account for the high Hb F production in the propositus. A young niece of the propositus with °-thalassemia major was recently discovered, who was homozygous for the same -globin allele and haplotype as the propositus. However, unlike her uncle, she does not have a high Hb F level and presents with a severe clinical course. Her inability to produce high Hb F suggests that the genetic determinant for increased -gene expression in the propositus is unlinked to the -globin gene cluster.     

Ultrastructure of pericytes in early stages of histamine-induced inflammation

Physiological and ultrastructural assessment of changes in the walls of venules in the rat cremaster muscle after administration of histamine indicates that pericytes have essential roles in the normal functioning of venules during inflammation. Fluorescein-labelled albumin was used to quantitate macromolecular leakage and to select suitable venules for ultrastructural analysis 4 and 7 minutes after addition of histamine. Pericytes were concentrated over endothelial cell junctions and gaps. At 4 minutes, when albumin leakage was becoming detectable, gaps between endothelial cells were observed in the venule wall. In 24 serially sectioned gaps, pericytes formed covers, with contact points to the endothelial cells along the sides of the gaps. At 7 minutes, when albumin leakage was maximal, gaps with pericyte covers were still evident, but more commonly observed were pericyte covers over closed endothelial cell junctions. Spaces between the innermost pericytes and endothelial cells were enlarged by an order of magnitude, from 95 nm in controls to 872 nm at 4 minutes and 958 nm at 7 minutes. Pericytes formed coverings or bridges over inclusions of extravasated cells, fluid, proteins, and the vascular label monastral blue. The data indicate that pericytes protect the endothelial lining of venules during histamine-induced inflammation by forming a cohesive covering across gaps.     

Summer feeding ecology of harp seals (Phoca groenlandica) in relation to arctic cod (Boreogadus saida) in the Canadian high arctic

Summary The diet and feeding behaviour of harp seals, Phoca groenlandica, was examined in two high arctic locations. Fish otoliths were used to evaluate dietary composition and aspects of the population dynamics of the major prey species, arctic cod, Boreogadus saida. Harp seals, primarily adults, arrive in the high arctic in mid to late June and depart by early October. Their migration is undertaken specifically for feeding. Harp seals feed intensively on arctic cod, often occurring in dense multispecies aggregations in late summer. The average weight of harp seal stomach contents was high; glutted individuals contained as much as 6% of their body weight in food. Although arctic cod declined in abundance between years, size of cod ingested was similar between areas and years, and overlapped completely with cod taken by other marine mammals. Age/size segregation of arctic cod may account for poor representation of fish <3 years old in the seal diet. Widespread reproductive failure of arctic cod could have a profound influence on the energy balance of adult harp seals since there does not appear to be an alternate food source of equivalent energy value and abundance in arctic waters. Increasing harp seal populations will likely result in increased competition with a host of arctic cod predators, particularly ringed seals.     

Human aminoacylase-1: cloning, regional assignment to distal chromosome 3p21.1, and identification of a cross-hybridizing sequence on chromosome 18.

Aminoacylase-1 (ACY1, EC 3.5.1.14) is a cytosolic enzyme with a wide range of tissue expression and has been postulated to function in the catabolism and salvage of acylated amino acids. ACY1 has been assigned to chromosome 3p21, a region reduced to homozygosity in small-cell lung cancer and renal cell carcinoma, and has been reported to exhibit reduced or absent expression in small-cell lung cancer cell lines and tumors. Using monoclonal antibodies to human ACY1, we have isolated cDNA clones from a liver lambda gt11 cDNA library. As proof of identity, the fusion protein encoded by a putative ACY1 cDNA displayed ACY1 enzymatic activity. Additionally, it was determined that the putative ACY1 cDNA clones hybridize to an EcoR1 restriction fragment that has been mapped to chromosome 3p. Both ACY1 activity and this restriction fragment have been further demonstrated to be syntenic to distal 3p21.1 through the use of a panel of human-rodent somatic cell hybrids containing fragments of chromosome 3. An additional EcoR1 restriction fragment to which the probe hybridizes has been assigned to chromosome 18. The major mRNA species to which the ACY1 cDNA hybridizes is 0.9 kb; faint hybridization to a 4.2-kb mRNA species is also detected. These studies further refine a region of interest in the investigation of gene inactivation in small-cell lung cancer and provide a new marker on chromosome 18.     

Chromosome-specific subsets of human alphoid DNA identified by a chromosome 2-derived clone

We have cloned an alphoid DNA fragment, pBS4D, from the DNA of a human-hamster hybrid cell line containing chromosome 2 as its only cytologically detectable human component. Under high stringency conditions, pBS4D hybridized in situ mostly to chromosome 2 and to a lesser extent to chromosomes 18 and 20. Restriction analysis using the DNA from selected somatic hybrid cell lines revealed that the genomic organization of this alphoid DNA differs on each of these three chromosomes.     

Endocrine treatment for breast cancers: biological rationale and current progress

Endocrine therapy is a major treatment modality for the systemic management of breast cancer. In comparison with alternatives such as chemotherapy, hormone manipulations have the advantage of lower toxicity but suffer from the disadvantages of producing responses in only 30-40% of patients with metastatic disease and seldom being curative. Nevertheless in recent years there have been significant advances in the endocrine treatment of breast cancer which have stemmed from a better understanding of the sources from which breast tumours may be supplied with hormones, the mechanism by which hormones regulate tumour proliferation and the more accurate identification of hormone sensitive tumours. As a result agents such as antioestrogens, aromatase inhibitors. LHRH agonists have largely superseded surgical and radiological ablation of endocrine organs. The major reduction in morbidity associated with these medical regimes means that they are much more acceptable to patients and may be used as adjuvants to local treatment of the breast in patients with "earlier" stages of the disease. At the same time patients can now be offered rational treatment selected on the basis of tumour biology rather than on more empirical criteria. The aims of this review are to provide details of the research which has led to this progress in endocrine treatment of breast cancer and to put into perspective the prospects for further advances.     

Rat liver beta-glucuronidase. cDNA cloning, sequence comparisons and expression of a chimeric protein in COS cells.

A cDNA for rat liver beta-glucuronidase was isolated, its sequence determined and its expression after transfection into COS cells studied. The deduced amino acid sequence of the rat liver clone showed 77% homology with that from the cDNA for human placental beta-glucuronidase and 47% homology with that deduced from the cDNA for Escherichia coli beta-glucuronidase. Several differences were found between the cDNA from rat liver and that previously reported from rat preputial gland. Only one change leads to an amino acid difference in the mature enzyme. A chimeric clone was constructed by using a fragment encoding the first 18 amino acid residues of the signal sequence from the human placental cDNA clone and a fragment from the rat clone encoding four amino acid residues of the signal sequence, all 626 amino acid residues of the mature rat enzyme, and all of the 3' untranslated region. After transfection into COS cells the chimeric clone expressed beta-glucuronidase activity that was specifically immunoprecipitated by antibody to rat beta-glucuronidase. The Mr value of 76,000 of the expressed gene product was characteristic of the glycosylated rat enzyme. It was proteolytically processed in COS cells to Mr 75,000 6 h after metabolic labelling. At least 50% of the expressed enzyme was secreted at 60 h post-transfection, but the secreted enzyme did not undergo proteolytic processing. These results provide evidence that the partial cDNA isolated from a rat liver library contains the complete coding sequence for the mature rat liver enzyme and that the chimeric signal sequence allows normal biosynthesis and processing of the transfected rat liver enzyme in COS cells.