Inhibition of rabbit liver fructose 1,6-biphosphatase by AMP: effect of temperature and physiological concentrations of cations and anions

Turkey gizzard smooth muscle myofibrils, the actin of which is composed of 75% smooth muscle γ-isoactin and 25% nonmuscle β-isoactin, were separated into an actomyosin and a cytoskeletal fraction. Isoelectric focusing analysis of the actomyosin actin showed it was 80% γ-isoactin and 20% β-isoactin. It thus appears that the major actin in the tissue is also the major form involved in force generation. When the cytoskeletal material was extracted with low-ionic-strength solution for 18 h at 4 °C, the actin released was 95% γ and 5% β compared with the 75:25 ratio found in the original cytoskeletal material. The extracted material revealed the presence of F-actin filaments and high-molecular-weight aggregates. Little of the material was in a low-molecular-weight form. On the other hand, extraction of the cytoskeletal material with 0.6 m KI resulted in the two isoactins being extracted in the same proportions in which they were found in the original cytoskeletal material. However, when this KI-extracted material was subsequently chromatographed on Bio-Gel A-5m equilibrated with 0.6 m KCl, the γ-isoactin migrated predominantly as a very high molecular weight form while the β-isomer moved in the lower-molecular-weight range of the elution profile. This aggregation behavior displayed by the γ-isoactin was not observed with the γ-isoactin in the actomyosin fraction. These results show that the two gizzard isoactins in the cytoskeletal residue behave very differently in response to various extraction media, and are consistent with possible differential isoactin utilization in gizzard smooth muscle.     

Human glioma tumour-associated antigens

Conclusion From this brief review it appears that at least three categories of human glioma-associated antigens may exist. The first seems to be restricted and common to gliomas. The second is shared between gliomas, normal adult brain, and fetal brain. The third is present on cells from adult and fetal tissue and on cells from tumours derived from the neural crest. The expression of glioma-associated antigens is highly variable from one tumour, or tumour cell line, to another, and reflects the phenotypic heterogeneity of the glioma group. Moreover, this heterogeneity has been found in different clones of individual glioma cell lines [1]. The fact that gliomas share some antigens with normal brain is of critical importance for immunodiagnosis or immunotherapy. It is evident that active immunotherapy for gliomas should be performed with cultured cells and not with tumour extracts, because such extracts may contain MBP.The exact nature of the various glioma-associated antigens remains to be clearly defined, however. They may belong to a group of surface glycoproteins such as those described by Lloyd et al. [24] for melanoma or more recently by Lubitz et al. [25] for glial cells.     

Effects of anti-embryonal carcinoma serum on aggregation and metabolic cooperation between teratocarcinoma cells

Effects of rabbit anti-embryonal carcinoma IgG on embryonal carcinoma cells and their differentiated derivatives were studied at different levels of cell-cell interaction. Fab fragments of anti-EC IgG were found to inhibit aggregation of the majority of EC cell lines. Two, however, were insensitive. Anti-EC Fab fragments act also on the transfer of metabolites between EC cells: the rescue of HPRT^? EC cells by HPRT⁺ EC cells in selective medium is abolished. These findings are correlated with the disappearance of tight and gap junctions from the surface of EC cells (Dunia et al., 1979). The presence of the surface structure involved in the action of anti-EC Fab fragments was tested by absorption experiments followed by decompaction test on PCC4 Aza R1 cells. All EC cell lines and two embryonic cell lines—a trophectodermal and an endodermal line—were found to bear material absorbing the decompacting activity. The results are discussed in terms of state of differentiation of the cell lines and of complexity of aggregation of embyronic cells.     

Insect sociality and its consequential effects on intraspecific competition

Summary The phenomenon of colonialism which characterizes many insect groups is considered in terms of its potential effect on intraspecific competition. Intraspecific competition is assumed to be a function of the number of distinct pair encounters between 2 individuals of differing colony origin. A model is offered which describes the reduction in the number of potential competing encounters as a result of colonialism, and as such, combinatorial formulae are appropriate. For 2-colony and multi-colony systems, there is a proportionately smaller number of potential competing encounters as the size of the colonies becomes more inequitable and greater than 100 individuals in combined total. As a consequence, large inequitabilities in colony sizes are expected for nearest neighbor pairs, and thus a generally large variance in colony size for groups of colonies is also expected. Empirical data from various sources is presented and in good agreement with the predictions generated from the model.     

Unprecedented Therapeutic Potential with a Combination of A2A/NR2B Receptor Antagonists as Observed in the 6-OHDA Lesioned Rat Model of Parkinson's Disease

In Parkinson''s disease, the long-term use of dopamine replacing agents is associated with the development of motor complications; therefore, there is a need for non-dopaminergic drugs. This study evaluated the potential therapeutic impact of six different NR2B and A_2A receptor antagonists given either alone or in combination in unilateral 6-OHDA-lesioned rats without (monotherapy) or with (add-on therapy) the co-administration of L-Dopa: Sch-58261+ Merck 22; Sch-58261+Co-101244; Preladenant + Merck 22; Preladenant + Radiprodil; Tozadenant + Radiprodil; Istradefylline + Co-101244. Animals given monotherapy were assessed on distance traveled and rearing, whereas those given add-on therapy were assessed on contralateral rotations. Three-way mixed ANOVA were conducted to assess the main effect of each drug separately and to determine whether any interaction between two drugs was additive or synergistic. Additional post hoc analyses were conducted to compare the effect of the combination with the effect of the drugs alone. Motor activity improved significantly and was sustained for longer when the drugs were given in combination than when administered separately at the same dose. Similarly, when tested as add-on treatment to L-Dopa, the combinations resulted in higher levels of contralateral rotation in comparison to the single drugs. Of special interest, the activity observed with some combinations could not be described by a simplistic additive effect and involved more subtle synergistic pharmacological interactions. The combined administration of A_2A/NR2B-receptor antagonists improved motor behaviour in 6-OHDA rats. Given the proven translatability of this model such a combination may be expected to be effective in improving motor symptoms in patients.     

Diverse phylogeny and morphology of magnetite biomineralized by magnetotactic cocci

Magnetotactic bacteria (MTB) are diverse prokaryotes that produce magnetic nanocrystals within intracellular membranes (magnetosomes). Here, we present a large-scale analysis of diversity and magnetosome biomineralization in modern magnetotactic cocci, which are the most abundant MTB morphotypes in nature. Nineteen novel magnetotactic cocci species are identified phylogenetically and structurally at the single-cell level. Phylogenetic analysis demonstrates that the cocci cluster into an independent branch from other Alphaproteobacteria MTB, that is, within the Etaproteobacteria class in the Proteobacteria phylum. Statistical analysis reveals species-specific biomineralization of magnetosomal magnetite morphologies. This further confirms that magnetosome biomineralization is controlled strictly by the MTB cell and differs among species or strains. The post-mortem remains of MTB are often preserved as magnetofossils within sediments or sedimentary rocks, yet paleobiological and geological interpretation of their fossil record remains challenging. Our results indicate that magnetofossil morphology could be a promising proxy for retrieving paleobiological information about ancient MTB.     

Bakers' yeast uridine nucleosidase is a regulatory copper containing protein.

The enzymatic properties of homogeneous bakers' yeast uridine nucleosidase, prepared as previously described (G. Magni et al., J. Biol. Chem. 1975 $\text{250}$, 9–13) have been further investigated, and in addition to glucose-6-phosphate and ribose the enzyme activity was inhibited by ribose-5-phosphate and ribulose-5-phosphate. The curves describing this inhibitions were sigmoidal and when the data were plotted according to Hill, n′ values different from 1 were observed suggesting the existence of interactions among the inhibitory molecules binding sites. Furthermore the percentage of inhibition exerted by glucose-6-phosphate, ribose and ribose-5-phosphate on the enzyme activity varied at different pH values. The addition of various chelating agents to the activity assay mixture caused a strong inhibition of the enzyme activity and metal analysis by atomic absorption spectrophotometry, colorimetric methods and electronic paramagnetic resonance, indicated the presence of 1 copper atom per enzyme molecule. Finally the inhibition exerted by metal ions on the enzyme activity was described.