Nystatin and killer toxin sensitivity of free and immobilizedSaccharomyces cerevisiae

The inhibitory effect of nystatin and killer toxin on the growth of free and covalently-immobilizedSaccharomyces cerevisiae cells was studied. The resistance of immobilized cells to both agents was accompanied by increased amounts of phospholipids and sterols. The possible relationship between these changes in the membrane composition and the transduction of a signal across the cytoplasmic membrane is discussed.     

Hydrogen evolution by subchloroplast preparations of photosystem II from pea and spinach,

Covalent coupling of bovine rhodopsin to CPG-thiol glass was used for separation of CNBr peptides. It is shown that cysteine residues 322 and 323 in the C-terminal cytoplasmic fragment of rhodopsin are modified with palmitic acid.     

Metabolic activation of unsaturated derivatives of valproic acid. Identification of novel glutathione adducts formed through coenzyme A-dependent and -independent processes

The ability of 2-n-propyl-4-pentenoic acid (Δ⁴-VPA) and 2-n-propyl-2(E)-pentenoic acid ([E]-Δ²-VPA), two unsaturated metabolites of valproic acid (VPA), to form reactive intermediates, deplete hepatic glutathione (GSH) and cause accumulation of liver triglycerides was investigated in the rat. With the aid of ionspray liquid chromatography-tandem mass spectrometry (LC-MS/MS), three GSH adducts were detected in the bile of Δ⁴-VPA-treated animals and were identified as 4-hydroxy-5-glutathion-S-yl-VPA-γ-lactone, 5-glutathion-S-yl-(E)-Δ³-VPA and 3-oxo-5-glutathion-S-yl-VPA. A fourth conjugate was identified tentatively as 4-glutathion-S-yl-5-hydroxy-VPA. Quantitative analysis of the corresponding N-acetylcysteine (NAC) conjugates in urine indicated that metabolism of Δ⁴-VPA via the GSH-dependent pathways accounted for approximately 20% of an acute dose (100 mg kg⁻¹ i.p.). In contrast, when rats were given an equivalent dose of (E)-Δ²-VPA, only one GSH adduct (5-glutathion-S-yl-(E)-Δ³-VPA) was detected at low concentrations in bile. In vitro experiments with rat liver mitochondria demonstrated that Δ⁴-VPA undergoes coenzyme A- and ATP-dependent metabolic activation in this organelle via the β-oxidation pathway to intermediates which bind covalently to proteins. When liver homogenates and hepatic mitochondria from rats injected with Δ⁴-VPA, (E)-Δ²-VPA or VPA were analyzed for GSH content, it was found that only Δ⁴-VPA depleted GSH pools significantly. Treatment of rats with Δ⁴-VPA and (to a lesser extent) VPA led to an accumulation of liver triglycerides, whereas (E)-Δ²-VPA had no measurable effect. It is concluded that Δ⁴-VPA undergoes metabolic activation by both microsomal cytochrome P-450-dependent and mitochondrial coenzyme A-dependent processes, and that the resulting electrophilic intermediates, which are trapped in part by GSH, may mediate the hepatotoxic effects of this compound. In contrast, (E)-Δ²-VPA is not transformed to any appreciable extent to reactive metabolites, which thus accounts for the apparent lack of hepatotoxicity of this positional isomer in the rat.     

The functioning of ectomycorrhizal fungi in the field: linkages in space and time

Individual trees, either of the same or different species, can be linked spatially and temporally by the hyphae of ectomycorrhizal (ECM) fungi that allow carbon and nutrients to pass among them and promote forest establishment following disturbance. Spatial and temporal linkages between plants influence the function of ECM fungi in the field. Studies indicate that ECM linkages can reduce plant competition for resources, promote forest recovery, and influence the pattern of plant succession. The degree of influence depends on many factors, including the composition and arrangement of the vegetative community and soil and climatic conditions. Management practices that create intense disturbance and loss of organic matter or promote the introduction of non-ectomycorrhizal host species can decrease the ability of plants to form linkages with ECM fungi. Management practices that retain living trees and shrubs and input of organic matter provide the energy source and substrate necessary for ECM linkages. More research is needed to determine the degree to which ECM fungal linkages occur in the field and their role in ecosystem function and long-term health.     

Time linkages between pollination onsets of different taxa over an 11-year period in Perugia,Central Italy

Times of pollination of different taxa in the atmosphere of Perugia (Central Italy) over an 11-year period (1982–1992) were recorded and analysed by means of a 7-day volumetric Hirst-type pollen trap. For some taxa, the pollination period varied from year to year from a chronological and/or quantitative point of view. Several taxa showed a linkage in their starting dates of pollination. Knowledge of this kind of linkage allows us to build a forecasting model.     

Human β-glucuronidase: Assignment of the structural gene to chromosome 7 using somatic cell hybrids

-Glucuronidase (GUS) has become an important enzyme model for the genetic study of molecular disease, enzyme realization, and therapy, and for the biogenesis and function of the lysosome and lysosomal enzymes. The genetics of human -glucuronidase was investigated utilizing 188 primary man-mouse and man-Chinese hamster somatic cell hybrids segregating human chromosomes. Cell hybrids were derived from 16 different fusion experiments involving cells from ten different and unrelated individuals and six different rodent cell lines. The genetic relationship of GUS to 28 enzyme markers representing 19 linkage groups was determined, and chromosome studies on selected cell hybrids were performed. The evidence indicates that the -glucuronidase gene is assigned to chromosome 7 in man. Comparative linkage data in man and mouse indicate that the structural gene GUS is located in a region on chromosome 7 that has remained conserved during evolution. Involvement of other chromosomes whose genes may be important in the final expression of GUS was not observed. A tetrameric structure of human -glucuronidase was demonstrated by the formation of three heteropolymers migrating between the human and mouse molecular forms in chromosome 7 positive cell hybrids. Linkage of GUS to other lysosomal enzyme genes was investigated. -Hexosaminidase HEX _B) was assigned to chromosome 5; acid phosphatase₂ (ACP ₂) and esterase A₄ (ES-A ₄) were assigned to chromosome 11; HEX _A was not linked to GUS; and -galactosidase (-GAL) was localized on the X chromosome. These assignments are consistent with previous reports. Evidence was not obtained for a cluster of lysosomal enzyme structural genes. In demonstrating that GUS was not assigned to chromosome 9 utilizing an X/9 translocation segregating in cell hybrids, the gene coding for human adenylate kinase₁ was confirmed to be located on chromosome 9.Supported by NIH Grants HD 05196, GM 20454, and GM 06321, by NSF Grant BMS 73-07072, and by HEW Maternal and Child Health Service, Project 417.     

7,9-Diaryl-1,6,8-trioxaspiro[4.5]dec-3-en-2-ones: Readily accessible and highly potent anticancer compounds

7,9-Diaryl-1,6,8-trioxaspiro[4.5]dec-3-en-2-ones are a recently described group of spirocyclic butenolides that can be generated rapidly and as a single diastereomer through a cascade process between γ-hydroxybutenolides and aromatic aldehydes. The following outlines our findings that these spirocycles are potently cytotoxic and have a dramatic structure–function profile that provides excellent insight into the structural features required for this potency.     

High throughput covalent immobilization process for improvement of shelf-life,operational cycles,relative activity in organic media and enzymatic kinetics of urease and its application for urea removal from water samples

High throughput covalent urease immobilization was performed through the amide bond formation between the urease and the amino-functional MNPs. The enzyme’s performances, including shelf-life, reusability, enzymatic kinetics, and the enzyme relative activity in organic media was improved. At optimal conditions, the immobilization efficiency was calculated about 95.0% with keeping 94.7% of the urease initial specific activity. The optimal pH for maximum activity of the free and immobilized urease was calculated as 7.0 at 37.0 °C and 8.0 at 60.0 °C, respectively. The kinetics studies showed the K_m of 26.0 mM and 8.0 mM and the V_max of 5.31 μmol mg⁻¹ min⁻¹ and 3.93 μmol mg⁻¹ min⁻¹ for the free and immobilized urease, respectively. The ratio K_cat/K_m as a measure of catalytic efficiency and enzyme specificity was calculated as 0.09 mg mL⁻¹ min⁻¹ and 0.22 mg mL⁻¹ min⁻¹ for the free and immobilized urease, respectively, indicating an improvement in the enzymatic kinetics. The shelf-life and operational studies of immobilized urease indicated that approximately 97.7% and 88.5% of its initial activity was retained after 40 days and 17 operational cycles, respectively. The immobilized urease was utilized to urea removal from water samples with an efficiency between 91.5–95.0%.     

Discovery of quinoline-based irreversible BTK inhibitors

Bruton tyrosine kinase (BTK) is an important target in oncology and (auto)immunity. Various BTK inhibitors have been approved or are currently in clinical development. A novel BTK inhibitor series was developed starting with a quinazoline core. Moving from a quinazoline to a quinoline core provided a handle for selectivity for BTK over EGFR and resulted in the identification of potent and selective BTK inhibitors with good potency in human whole blood assay. Furthermore, proof of concept of this series for BTK inhibition was shown in an in vivo mouse model using one of the compounds identified.