Small cell carcinoma of the stomach: an immunohistochemical and electron microscopic study.

A 4 x 6 cm ulcerative mass in the antrum was found to consist of papillary adenocarcinoma in the surrounding wall and the small round cell neoplasm at its base. Immunohistochemical staining revealed that elements of the papillary adenocarcinoma were positive for carcinoembryonic antigen, epithelial membrane antigen, keratin, endocrine granule constituent, and CA19-9, while components of the small cell carcinoma were weakly positive only for neuron-specific enolase. In one portion of the small cell carcinoma, particularly large cells with pleomorphic nuclei which were intensely positive for desmin were detected. Electron microscopic examination revealed dense-cored granules and intercellular junctions in the small neoplastic cells and bundles of intermediate filaments in the desmin-positive large cells. These findings suggest that ultrastructural examination is vital in diagnosis of small cell carcinoma and they reveal the capability of this carcinoma toward multidirectional differentiation.     

Complete nucleotide sequence of the mitochondrial DNA from a liverwort,Marchantia polymorpha

Libraries of cosmid and plasmid clones covering the entire region of mtDNA from the liverwortMarchantia polymorpha were constructed. These clones were used for the determination of the complete nucleotide sequence of the liverwort mtDNA totally 186,608 bp (GenBank no. M68929) and including genes for 3 species of ribosomal RNAs, 29 genes for 27 species of transfer RNAs, and 30 genes for functionally known proteins (16 ribosomal proteins, 3 subunits of cytochromec oxidase, apocytochromeb protein, 3 subunits of H⁺-ATPase, and 7 subunits of NADH ubiquinone oxidoreductase). The genome also contains 32 unidentified open reading frames. Thus the complete nucleotide sequences from both chloroplast and mitochondrial genomes have been determined in the same organism. Plasmid clones are available upon the request. Gene names are represented according to Lonsdale and Leaver (1988) with modifications recommended by Lonsdale (personal communication).     

Enclosure experiment on the control mechanism of planktonic bacterial standing stock

In order to understand the control mechanisms of a large, stable bacterial standing stock, enclosure experiments were conducted in a eutrophic lake, where both bacterial productivity and grazing pressure were very high. Total bacterial number in the different enclosures ranged from 1.2 to 2.7×10⁷ cells mL⁻¹ throughout the experiment. The average bacterial cell production rate estimated from a grazer eliminating experiment was 6.3×10⁵ cells mL⁻¹ h⁻¹. Difference in the bacterial cell production rate between shaded and unshaded enclosures was not apparent. Bacteria showed a reduction in standing stock of only about 25–30% even after the supply of light was cut to 1%. Bacteria in the shaded enclosures then recovered their production rate in the first 12 days of perturbation. Grazing pressure in the shaded enclosures was not less than that for the control. Thus, it was considered a control mechanism of bacterial stable standing stock that the bacteria shifted their organic substrate from extracellular dissolved organic carbon freshly released from phytoplankton to that already stocked in the water column, though it is not known whether the dominant bacteria were the same.     

Mutations in a Saccharomyces cerevisme host showing increased holding stability of the heterologous plasmid pSRI

Summary We have isolated Saccharomyces cerevisiae mutants, smp, showing stable maintenance of plasmid pSRI, a Zygosaccharomyces rouxii plasmid. The smp mutants were recessive and were classified into at least three different complementation groups. The three mutants also showed increased stability of YRp plasmids and the mutations are additive for plasmid stability. One mutation, smp1, confers a respiration-deficient (rho ⁰) phenotype and several Rho^– mutants independently isolated by ethidium bromide treatment of the same yeast strain also showed increased stabilities of pSR1 and YRp plasmids. The wild-type S. cerevisiae cells showed a strongly biased distribution of pSR1 molecules as well as YRp plasmids to the mother cells at mitosis, while the smpf mutant did not show this bias. Another mutation, smp3, at a locus linked to ade2 on chromosome XV, confers temperature-sensitive growth. The SMP3 gene encodes a 59.9 kDa hydrophobic protein and disruption of the gene is lethal.     

Increased yield of fructose from glucose employing thermophilic xylose isomerase in water-ethanol mixtures

Summary The isomerization of D-glucose in mixed ethanol-water was studied at various reaction temperatures (40–70 °C), employing glucose isomerase fromStreptomyces phaeochromogenes andClostridium thermohydrosulfuricum, respectively. The thermophilicClostridium enzyme was considerably, more stable towards the combination of organic cosolvent and increased temperature and with this enzyme a 55% yield of fructose from glucose was obtained at relatively low concentration of ethanol (40 %).     

Morphological effects of cadmium on proximal tubular cells in rats

Twenty-four male rats of the Wistar strain divided into four groups were injected sc with a dose of 0.8, 1.5, and 3.0 mg Cd/kg body wt as CdCl₂ in saline, and saline alone to the control rats, three times a week for 3 wk. Cadmium levels of whole kidney homogenate, supernatant (cytosol), precipitate, and metallothionein (MT) fraction were measured. Histological changes of the renal proximal tubules were investigated by optical and electron microscopy. In the kidneys, Cd levels were increased with the increment of Cd dosage; 80–90% of Cd was contained in cytosol, and 55–75% was in MT fraction. Non-MT-Cd reached a maximum in the 1.5 mg Cd group, whereas that of the 3.0 mg Cd group showed some decline. With increasing Cd doses, the size of nuclei and nucleoli in the cells of proximal tubule showed significant enlargement and also an increase in the number of nucleoli on light microscopy. At higher doses, chromatin condensation of the tubular nuclei and vacuolar degeneration of the tubular cells were evident. On electron microscopy, perichromatin granules of the proximal tubular nuclei were increased in number, especially in the rats of Cd 0.8 mg and 1.5 mg/kg groups. As the Cd doses increased, ring-shaped nucleoli were increased in number and nucleolar segregation was observed more clearly. Moreover, in the 3.0 mg/kg Cd group, nuclear indentation and nucleoli containing compact dense granules were observed. In the cytoplasm, there was an increase of lysosomes, myelin bodies, ring-shaped mitochondria, and vesiculation; ultimate changes were degeneration and cell necrosis. The injured cells were heterogenously distributed in each nephron and this heterogeneity was attributed in the difference in Cd content and cell cycle in each cell of the nephron.     

Mutual interactions between optic lobe circadian pacemakers in the cricket Gryllus bimaculatus

The coupling mechanism between the bilaterally paired optic lobe circadian pacemakers in the cricket Gryllus bimaculatus was investigated by recording locomotor activity, under constant light or constant red light, after the optic nerve was unilaterally severed.

Subcellular distribution and properties of carbonyl reductase in guinea pig lung

On subcellular fractionation, carbonyl reductase (EC 1.1.1.184) activity in guinea pig lung was found in the mitochondrial, microsomal, and cytosolic fractions; the specific activity in the mitochondrial fraction was more than five times higher than those in the microsomal and cytosolic fractions. Further separation of the mitochondrial fraction on a sucrose gradient revealed that about half of the reductase activity is localized in mitochondria and one-third in a peroxidase-rich fraction. Although carbonyl reductase in both the mitochondrial and microsomal fractions was solubilized effectively by mixing with 1% Triton X-100 and 1 M KCl, the enzyme activity in the mitochondrial fraction was more highly enhanced by the solubilization than was that in the microsomal fraction. Carbonyl reductases were purified to homogeneity from the mitochondrial, microsomal, and cytosolic fractions. The three enzymes were almost identical in catalytic, structural, and immunological properties. Carbonyl reductase, synthesized in a rabbit reticulocyte lysate cell-free system, was apparently the same in molecular size as the subunit of the mature enzyme purified from cytosol. These results indicate that the same enzyme species is localized in the three different subcellular compartments of lung.     

Inhibition of cell proliferation with antibody-targeted liposomes containing methotrexate-γ-dimyristoylphosphatidylethanolamine

We have prepared liposomes containing methotrexate-γ-dimyristoylphosphatidylethanolamine (MTX-DMPE liposomes), to which protein A was covalently coupled, permitting specific association of these liposomes in vitro with murine cells preincubated with relevant protein A-binding monoclonal antibodies. In the absence of antibody the presence of externally-oriented methotrexate (MTX) in MTX-DMPE liposomes did not result in greater binding to cells than liposomes made without MTX-γ-DMPE. Derivation of methotrexate with phospholipid permits enhanced drug-liposome association. These liposomes are more resistant than conventional liposomes to repeated cycles of freezing and thawing. MTX-DMPE liposomes are comparable to antibody-targeted liposomes made with encapsulated water-soluble methotrexate both with respect to specific binding to target cells and drug effect. The inhibitory effects off MTX-liposomes, as well as free MTX, were reversible by either thiamin pyrophosphate (Tpp) or N⁵-formyltetrahydrofolate (F-THF), while the effects of MTX-DMPE liposomes were reversed only by N⁵-formyltetrahydrofolate. This suggests that the toxicity of non-targeted MTX-liposomes may be due to leakage of the encapsulated MTX. The absence of an effect of thiamin pyrophosphate on non-targeted MTX-DMPE liposomes indicates that they do not enter into the cell via the normal folate transport system.     

Inhibition of cell proliferation with antibody-targeted liposomes containing methotrexate-gamma-dimyristoylphosphatidylethanolamine

We have prepared liposomes containing methotrexate-gamma-dimyristoylphosphatidylethanolamine (MTX-DMPE liposomes), to which protein A was covalently coupled, permitting specific association of these liposomes in vitro with murine cells preincubated with relevant protein A-binding monoclonal antibodies. In the absence of antibody the presence of externally-oriented methotrexate (MTX) in MTX-DMPE liposomes did not result in greater binding to cells than liposomes made without MTX-gamma-DMPE. Derivation of methotrexate with phospholipid permits enhanced drug-liposome association. These liposomes are more resistant than conventional liposomes to repeated cycles of freezing and thawing. MTX-DMPE liposomes are comparable to antibody-targeted liposomes made with encapsulated water-soluble methotrexate both with respect to specific binding to target cells and drug effect. The inhibitory effects of MTX-liposomes, as well as free MTX, were reversible by either thiamin pyrophosphate (Tpp) or N5-formyltetrahydrofolate (F-THF), while the effects of MTX-DMPE liposomes were reversed only by N5-formyltetrahydrofolate. This suggests that the toxicity of non-targeted MTX-liposomes may be due to leakage of the encapsulated MTX. The absence of an effect of thiamin pyrophosphate on non-targeted MTX-DMPE liposomes indicates that they do not enter into the cell via the normal folate transport system.