Studies on the N-acetyl-beta-D-hexosaminidase B from germinating Lupinus luteus L. seeds. I. Purification and characterization

The N-acetyl-beta-D-hexosaminidase B of germinating Lupinus luteus L. seeds (McFarlane et al. (1984) Phytochemistry 23, 2431-2433) was partially purified with a six-step purification procedure following extraction. This enzyme consists of one protein chain (Mr 69,000, as determined by SDS-PAGE and 62,500, as obtained by gel filtration on Bio-Gel P-60 Gel) and has a neutral isoelectric point (pI = 7.05, as determined by chromatofocusing). Moreover, it was found to be very sensitive to low ionic strength, especially in the presence of different gels based on Sephadex. Considering the substrate specificity, the enzyme splits both p-nitrophenyl-2-acetamido-2-deoxy-beta-D-glucosaminide and -galactosaminide substrates, but lacks N,N'-diacetylchitobiase activity. A new mixed-substrate procedure was developed and is presented here to demonstrate that a common active site is responsible for the splitting of both synthetic substrates.     

Cyclic AMP-like effects of polyamines on phosphatidylcholine synthesis and protein phosphorylation in human promyelocytic leukemia HL60 cells. Comparison with the effects of phorbol ester

Spermine or putrescine increased cAMP levels through a catalase-sensitive mechanism, resulting in, most notably, a dephosphorylation of protein A (Mr 45,000, pI 5.15) and protein B (Mr 45,000, pI 4.9) and slightly increased phosphatidylcholine (PC) synthesis in HL60 cells. Exogenous dibutyryl cAMP mimicked the polyamine effects. 12-O-Tetradecanoyl phorbol-13-acetate (TPA) also promoted the protein dephosphorylation and PC synthesis, the effects augmented by R59022 and mimicked by exogenous 1-oleoyl-2-acetylglycerol. The effects of spermine (or dibutyryl cAMP) and TPA on PC synthesis were synergistic. It was suggested that cAMP-dependent protein kinase and protein kinase C might mediate, in an independent but inter-related manner, the effects of polyamines and TPA.     

Structural and functional properties of Drosophila melanogaster phosphorylase: comparison with the rabbit skeletal muscle enzyme

Glycogen phosphorylase isolated from Drosophila melanogaster contains one pyridoxal 5'-phosphate per subunit; the coenzyme is in a hydrophobic environment. Fruit-fly phosphorylase a has lower KM for glucose-1-phosphate and is less sensitive to allosteric inhibitors than the b form of the enzyme. The amino acid composition of Drosophila phosphorylase differs from that of rabbit skeletal muscle phosphorylase. These two enzymes give distinct one dimensional peptide maps. The distribution of reactive SH-groups is markedly different in the insect and vertebrate phosphorylase. Fruit-fly phosphorylase a is dephosphorylated by either rabbit or Drosophila protein phosphatase-1 at a slower rate than rabbit muscle phosphorylase a.     

Do terrestrial gastropods use olfactory cues to locate and select food actively?

Having been investigated for over 40 years, some aspects of the biology of terrestrial gastropod’s olfactory system have been challenging and highly contentious, while others still remain unresolved. For example, a number of terrestrial gastropod species can track the odor of food, while others have no strong preferences toward food odor; rather they find it by random encounter. Here, while assessing the most recent findings and comparing them with earlier studies, the aspects of the food selection based on olfactory cues are examined critically to highlight the speculations and controversies that have arisen. We analyzed and compared the potential role of airborne odors in the feeding behavior of several terrestrial gastropod species. The available results indicate that in the foraging of most of the terrestrial gastropod species odor cues contribute substantially to food finding and selection. The results also suggest, however, that what they will actually consume largely depends on where they live and the species of gastropod that they are. Due to the voluminous literature relevant to this object, this review is not intended to be exhaustive. Instead, I selected what I consider to be the most important or critical in studies regarding the role of the olfaction in feeding of terrestrial gastropods.     

Digital cell image analysis of Ewing's sarcoma.

We analyzed the lesional tissue in Ewing's sarcoma by means of a cell image processor computing 15 nuclear parameters in order to quantify the morphologic variability of the tumor cell nuclei. To this end we combined 32 cases (350-400 Feulgen-stained nuclei analyzed per case) in a data file, which was then subjected to principal component and canonical analyses. We found considerable heterogeneity within the cell nucleus population of Ewing's sarcomas. Indeed, after the arbitrary subdivision of the file into two cell classifiers (CC1 and CC2 cell types) on the basis of the first canonical function, the 32 Ewing's sarcomas showed a great deal of variability in the proportion of CC1 and CC2 cell nucleus types. The nuclei of the CC1 type had a more finely textured chromatin when compared to the CC2 type, the nuclei of which exhibited a more granular chromatin pattern. Additionally, these 32 Ewing's sarcomas were characterized by three distinct DNA histogram types. Eight tumors displayed a diploid nonproliferating DNA histogram pattern (type A), 11 a diploid proliferating (type B) and 13 an aneuploid (type C) DNA histogram profile. We found a highly significant relationship between these DNA histogram types and the CC1:CC2 cell type percentage ratio. The eight Ewing's sarcomas with a type A DNA histogram contained a significantly higher proportion of CC1 cell type nuclei as compared to the 13 tumors with a type C DNA histogram, which contained a great proportion of CC2 cell type nuclei.     

Neomorph and leaf differentiation as alternative morphogenetic pathways in soybean tissue culture.

Somatic embryogenesis and organogenesis were induced on immature cotyledons of different soybean cultivars. The anatomical investigation of morphogenesis proved neomorph differentiation instead of somatic embryos, and leaf formation instead of shoot development. While normal embryos were induced in 0-3.1% of the explants, neomorphs developed at a much higher rate i.e. in 10.5-78.9% depending on the genotype. Likewise organogenesis preferably followed the pathway of leaflet development (3.1-26.3%) than that of shoot tip formation (0-2.6%). Low plant regeneration frequency of soybean can partly be explained with these two alternative abortive pathways of morphogenesis probably induced with higher frequency than the normal pathways by the generally used in vitro methods.     

Regulation of phospholipase D by protein kinase C

In nearly all mammalian cells and tissues examined, protein kinase C (PKC) has been shown to serve as a major regulator of a phosphatidylcholine-specific phospholipase D (PLD) activity, At least 12 distinct isoforms of PKC have been described so far; of these enzymes only the α- and β-isoform were found to regulate PLD activity, While the mechanism of this regulation has remained unknown, available evidence suggests that both phosphorylating and non-phosphorylating mechanisms may be involved. A phosphatidylcholine-specific PLD activity was recently purified from pig lung, but its possible regulation by PKC has not been reported yet. Several cell types and tissues appear to express additional forms of PLD which can hydrolyze either phosphatidylethanolamine or phosphatidylinositol. It has also been reported that at least one form of PLD can be activated by oncogenes, but not by PKC activators, Similar to activated PKC, some of the primary and secondary products of PLD-mediated phospholipid hydrolysis, including phosphatidic acid, 1,2-diacylglycerol, choline phosphate and ethanolamine, also exhibit mitogenic/co-mitogenic effects in cultured cells. Furthermore, both the PLD and PKC systems have been implicated in the regulation of vesicle transport and exocytosis. Recently the PLD enzyme has been cloned and the tools of molecular biology to study its biological roles will soon be available. Using specific inhibitors of growth regulating signals and vesicle transport, so far no convincing evidence has been reported to support the role of PLD in the mediation of any of the above cellular effects of activated PKC.