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.     

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.     

Meclofenamate blocks the pulmonary arterial vasopressor effects of leukotriene B4 in awake sheep

This study examined the hemodynamic effects of leukotriene B4 (LTB4) in chronically instrumented awake sheep, and the role of cyclooxygenase products in the sheep's response to LTB4. LTB4 (25 micrograms) was given as a bolus into the pulmonary artery. Six sheep were studied with LTB4, both before and after pretreatment with meclofenamate (5 mg/kg load, 3 mg/kg/hr maintenance infusion). LTB4 alone caused a rapid rise in pulmonary arterial pressure from 15 +/- 1 to 42 +/- 11 cm H2O. LTB4 had no effect on pulmonary arterial pressure following pretreatment with meclofenamate. LTB4 alone caused an increase in serum thromboxane B2 (TxB2) from 130 +/- 35 to 320 +/- 17 pg/ml 3 minutes after dosing but did not increase TxB2 following pre-treatment with meclofenamate. LTB4 caused a slight decrease in mean systemic arterial pressure and a transient fall in circulating white blood cells, both of which were unaffected by meclofenamate pre-treatment. The vasoactive effects of LTB4 in the pulmonary circulation appear to be mediated indirectly through the production of cyclooxygenase metabolites of arachidonic acid.     

Conjugal transfer of R68.45 and FP5 between Pseudomonas aeruginosa strains in a freshwater environment

Recent concern over the release of genetically engineered organisms has resulted in a need for information about the potential for gene transfer in the environment. In this study, the conjugal transfer in Pseudomonas aeruginosa of the plasmids R68.45 and FP5 was demonstrated in the freshwater environment of Fort Loudoun Resevoir, Knoxville, Tenn. When genetically well defined plasmid donor and recipient strains were introduced into test chambers suspended in Fort Loudoun Lake, transfer of both plasmids was observed. Conjugation occurred in both the presence and absence of the natural microbial community. The number of transconjugants recovered was lower when the natural community was present. Transfer of the broad-host-range plasmid R68.45 to organisms other than the introduced recipient was not observed in these chambers but was observed in laboratory simulations when an organism isolated from lakewater was used as the recipient strain. Although the plasmids transferred in laboratory studies were genetically and physically stable, a significant number of transconjugants recovered from the field trials contained deletions and other genetic rearrangements, suggesting that factors which increase gene instability are operating in the environment. The potential for conjugal transfer of genetic material must be considered in evaluating the release of any genetically engineered microorganism into a freshwater environment.     

Expression and Secretion of a Cellulomonas fimi Exoglucanase in Saccharomyces cerevisiae

We used the yeast MEL1 gene for secreted alpha-galactosidase to construct cartridges for the regulated expression of foreign proteins from Saccharomyces cerevisiae. The gene for a Cellulomonas fimi beta-1,4-exoglucanase was inserted into one cartridge to create a fusion of the alpha-galactosidase signal peptide to the exoglucanase. Yeast transformed with plasmids containing this construction produced active extracellular exoglucanase when grown under conditions appropriate to MEL1 promoter function. The cells also produced active intracellular enzyme. The secreted exoglucanase was N-glycosylated and was produced continuously during culture growth. It hydrolyzed xylan, carboxymethyl cellulose, 4-methylumbelliferyl-beta-d-cellobiose, and p-nitrophenyl-beta-d-cellobiose. A comparison of the recombinant S. cerevisiae enzyme with the native C. fimi enzyme showed the yeast version to have an identical K(m) and pH optimum but to be more thermostable.     

Selective solubilization of xylan in pulp using a purified xylanase fromTrichoderma harzianum

Summary The specificity of action of a cellulase-free xylanase preparation on pulp fibers was revealed by the composition of the solubilized products after enzyme treatment. The neutral carbohydrates released by the treatment of two hardwood kraft pulps were composed exclusively of xylooligomers. A similar treatment of Solka Floc showed no detrimental effect on the degree of polymerization of the cellulose fibers, as determined by size exclusion chromatographic analysis.