Needle aspiration cytology of a benign and a malignant schwannoma

The histologic and cytologic features of an uncommon solitary, malignant schwannoma and a benign schwannoma are presented. The benign tumor revealed characteristic interlacing fascicles of spindle-shaped cells on both histology and cytology. The malignant schwannoma produced a variable histologic pattern that was selectively sampled from a recurrence in a scar; only obviously malignant, undifferentiated, spindle-shaped cells not capable of further characterization were seen on cytology. Preliminary experience with immunoperoxidase staining for the neural crest marker S-100 protein has been encouraging and may permit identification of these tumors on aspiration smears.     

Effects of temperature,ph, salinity,and inorganic nitrogen on the rate of ammonium oxidation by nitrifiers isolated from wetland environments

Ammonium-oxidizing bacteria were examined in two wetland environments, a freshwater marsh and an estuarine bay, during a 2-year period. Two predominant types were consistently isolated, one from each environment. Both isolates were identified as species ofNitrosomonas. Using a closed culture, high cell density assay, the effects of temperature, pH, salinity, Na⁺, K⁺, nitrite, nitrate, and ammonium concentrations on ammonium oxidation were determined. Maximum activity was observed for the freshwater isolate at 35°C, pH 8.5, salinities of 0.3 to 0.5% Na⁺ and K⁺, and ammonium concentrations greater than 0.5 g/l. For the estuarine isolate, maximum activity was observed at 40°C, pH 8.0, salinities of 0.5 to 1.0%, 1.0% Na⁺ and K⁺, and 0.2 g/l ammonium. The estuarine isolate had a Na⁺ requirement which could be partially substituted by the K⁺, suggesting that the organism is a true estuarine bacterium. Nitrite inhibited both isolates at concentrations greater than 5 mg/l, whereas nitrate had no significant effect on either isolate.     

Peptide map comparisons of epidermal and spleen H-2 molecules

Peptide map comparisons of molecules encoded in the mouseH-2 complex isolated from epidermal cell preparations have been carried out. We previously showed that the Ia molecules from both theI-A andI-E subregions are synthesized by nonlymphoid bone-marrow-derived cells, probably Langerhans cells. The K and D or transplantation molecules are synthesized by both true epidermal cells and nonlymphoid bone-marrow-derived cells. The tryptic maps generated by separating tryptic peptides by high pressure liquid chromatography (HPLC) of epidermal H-2 molecules are identical to their spleen-cell counterparts. The biological significance of this finding is discussed.     

Increased susceptibility of carbamylated glutamate dehydrogenase to proteolysis

Glutamate dehydrogenase is very susceptible to carbamylation which results in loss of activity. The effect of a number of proteolytic enzymes (pronase, trypsin and chymotrypsin) on native and carbamylated glutamate dehydrogenase was tested. In all cases, the carbamylated enzyme was at least twice as susceptible to proteolysis as the native enzyme. Antibodies were prepared against glutamate dehydrogenase and carbamylated glutamate dehydrogenase; the carbamylated enzyme was antigenically indistinguishable from the native enzyme. Preliminary experiments indicate that the carbamylated glutamate dehydrogenase is taken up by ascites tumor cells while glutamate dehydrogenase is not. It seems possible that the effects described can be extrapolated to degradation by lysosomes and to other covalently modified enzymes.     

Glycosaparaginase from human leukocytes. Inactivation and covalent modification with diazo-oxonorvaline

The apparent active site of human leukocyte glycoasparaginase (N4-(beta-acetylglucosaminyl)-L-asparaginase EC 3.5.1.26) has been studied by labeling with an asparagine analogue, 5-diazo-4-oxo-L-norvaline. Glycoasparaginase was purified 4,600-fold from human leukocytes with an overall recovery of 12%. The purified enzyme has a Km of 110 microM, a Vmax of 34 mumol x l-1 x min-1, and a specific activity of 2.2 units/mg protein with N4-(beta-N-acetylglucosaminyl)-L-asparagine as substrate. The carbohydrate content of the enzyme is 15%, and it exhibits a broad pH maximum between 7 and 9. The 88-kDa native enzyme is composed of 19-kDa light (L) chains and 25-kDa heavy (H) chains and it has a heterotetrameric structure of L2H2-type. The glycoasparaginase activity decreases rapidly and irreversibly in the presence of 5-diazo-4-oxo-L-norvaline. At any one concentration of the compound, the inactivation of the enzyme is pseudo-first-order with time. The inhibitory constant, K1, is 80 microM and the second-order rate constant 1.25 x 10(3) M-1 min-1 at pH 7.5. The enzyme activity is competitively protected against this inactivation by its natural substrate, aspartylglucosamine, indicating that this inhibitor binds to the active site or very close to it. The covalent incorporation of [5-14C]diazo-4-oxo-L-norvaline paralleled the loss of the enzymatic activity and one inhibitor binding site was localized to each L-subunit of the heterotetrameric enzyme. Four peptides with the radioactive label were generated, purified by high performance liquid chromatography, and sequenced by Edman degradation. The sequences were overlapping and all contained the amino-terminal tripeptide of the L-chain. By mass spectrometry, the reacting group of 5-diazo-4-oxo-L-norvaline was characterized as 4-oxo-L-norvaline that was bound through an alpha-ketone ether linkage to the hydroxyl group of the amino-terminal amino acid threonine.     

Characterization of thromboxane receptor blocking effects of SQ 29548 in the feline pulmonary vascular bed.

The effects of SQ 29548, a thromboxane (Tx) A2 receptor blocking agent, on responses to the TxA2 mimic U46619 were investigated in the pulmonary vascular bed of the intact-chest cat under constant-flow conditions. The administration of SQ 29548 in doses of 0.25-1 mg/kg iv reduced vasoconstrictor responses to U-46619; however, responses to prostaglandins (PG) F2 alpha and D2 and to serotonin were also decreased. After administration of SQ 29548 in doses of 0.05-0.1 mg/kg iv, responses to U-46619 and U-44069 were reduced significantly, and the dose-response curves for these TxA2 mimics were shifted to the right in a parallel manner at a time when responses to PGF2 alpha and PGD2 were not altered. The low doses of the TxA2 receptor blocking agent significantly reduced responses to the PG and TxA2 precursor arachidonic acid but were without significant effect on vasoconstrictor responses to serotonin; histamine; norepinephrine; angiotensin II; the major PGD2 metabolite 9 alpha,11 beta-PGF2; BAY K 8644, an agent that enhances calcium entry; and endothelin-1. The present data show that at low doses SQ 29548 selectively blocks TxA2 receptor-mediated responses in a competitive and reversible manner in the pulmonary vascular bed. These data suggest that responses to arachidonic acid are mediated in large part by the formation of TxA2 and provide evidence in support of the hypothesis that a discrete TxA2 receptor unrelated to PGF2 alpha or PGD2 receptors is present in undefined resistance vessel elements in the feline pulmonary vascular bed.     

Species turnover in ant assemblages is greater horizontally than vertically in the world's tallest tropical forest

Abiotic and biotic factors structure species assembly in ecosystems both horizontally and vertically. However, the way community composition changes along comparable horizontal and vertical distances in complex three‐dimensional habitats, and the factors driving these patterns, remains poorly understood. By sampling ant assemblages at comparable vertical and horizontal spatial scales in a tropical rainforest, we tested hypotheses that predicted differences in vertical and horizontal turnover explained by different drivers in vertical and horizontal space. These drivers included environmental filtering, such as microclimate (temperature, humidity, and photosynthetic photon flux density) and microhabitat connectivity (leaf area), which are structured differently across vertical and horizontal space. We found that both ant abundance and richness decreased significantly with increasing vertical height. Although the dissimilarity between ant assemblages increased with vertical distance, indicating a clear distance‐decay pattern, the dissimilarity was higher horizontally where it appeared independent of distance. The pronounced horizontal and vertical structuring of ant assemblages across short distances is likely explained by a combination of microclimate and microhabitat connectivity. Our results demonstrate the importance of considering three‐dimensional spatial variation in local assemblages and reveal how highly diverse communities can be supported by complex habitats.     

Heterologous expression of cellobiohydrolase II (Cel6A) in maize endosperm

The technology of converting lignocellulose to biofuels has advanced swiftly over the past few years, and enzymes are a significant constituent of this technology. In this regard, cost effective production of cellulases has been the focus of research for many years. One approach to reach cost targets of these enzymes involves the use of plants as bio-factories. The application of this technology to plant biomass conversion for biofuels and biobased products has the potential for significantly lowering the cost of these products due to lower enzyme production costs. Cel6A, one of the two cellobiohydrolases (CBH II) produced by Hypocrea jecorina, is an exoglucanase that cleaves primarily cellobiose units from the non-reducing end of cellulose microfibrils. In this work we describe the expression of Cel6A in maize endosperm as part of the process to lower the cost of this dominant enzyme for the bioconversion process. The enzyme is active on microcrystalline cellulose as exponential microbial growth was observed in the mixture of cellulose, cellulases, yeast and Cel6A, Cel7A (endoglucanase), and Cel5A (cellobiohydrolase I) expressed in maize seeds. We quantify the amount accumulated and the activity of the enzyme. Cel6A expressed in maize endosperm was purified to homogeneity and verified using peptide mass finger printing.