Kinetics and mechanism of the substitution reactions of [PtCl(bpma)]<Superscript>+</Superscript>, [PtCl(gly-met-<Emphasis Type="Italic">S,N,N</Emphasis>)] and their aqua analogues with <Emphasis Type="SmallCaps">l</Emphasis>-methionine,glutathione and 5′-GMP

The substitution reactions of [PtCl(bpma)]+, [PtCl(gly-met-S,N,N)], [Pt(bpma)(H(2)O)](2+) and [Pt(gly-met-S,N,N)(H(2)O)](+) [where bpma is bis(2-pyridylmethyl)amine and gly-met-S,N,N is glycylmethionine] with L-methionine, glutathione and guanosine 5'-monophosphate (5'-GMP) were studied in aqueous solutions in 0.10 M NaClO(4) under pseudo-first-order conditions as a function of concentration and temperature using UV-vis spectrophotometry. The reactions of the chloro complexes were followed in the presence of 10 mM NaCl and at pH approximately 5, whereas the reactions of the aqua complexes were studied at pH 2.5. The [PtCl(bpma)]+ complex is more reactive towards the chosen nucleophiles than [PtCl(gly-met-S,N,N)]. Also, the aqua complexes are more reactive than the corresponding chloro complexes. The activation parameters for all the reactions studied suggest an associative substitution mechanism. The reactions of [PtCl(bpma)]+ and [PtCl(gly-met-S,N,N)] with 5'-GMP were studied by using (1)H NMR spectroscopy at 298 K. The pK (a) value of the [Pt(gly-met-S,N,N)(H(2)O)]+ complex is 5.95. Density functional theory calculations (B3LYP/LANL2DZp) show that in all cases guanine coordination to the L(3)Pt fragment (L(3) is terpyridine, bpma, diethylenetriamine, gly-met-S,N,N) is much more favorable than the thioether-coordinated form. The calculations collectively support the experimentally observed substitution of thioethers from Pt(II) complexes by N7-GMP. This study throws more light on the mechanistic behavior of platinum antitumor complexes.     

Weitere Untersuchungen über das Wachstum beim absoluten hungern

Ohne Zusammenfassung     

Beitrag zur Samenmorphologie der FamilieFabaceae

Die Autorinnen legen drei neuen Fachausdrücke für die an Samen der FamilieFabaceae festgestellten Gebilde for. Macula cicatricularis—ein Makel um die Narbe (cicatricula), macula raphalis—ein Makel um die Sammennaht (raphe), und fissum hilare—eine linienförmige Vertiefung inmitten des Nabels (hilum).     

Photodissociation Dynamics of DNA Bases

In order to access the damaging mechanismsof DNA and its bases on themolecular level by T Hz radiation, it isnecessary to create a database of assessingdamage at different spectral regions.Possible damage by T Hz radiation will beassessed by comparison. Furthermore, theexpose of the cytosine to radiation at157 nm, suggest that photochemical bondbreaking is the only damaging mechanism inthe vacuum ultraviolet region of thespectrum, (157–170) nm where one photonbreaks one chemical bond.     

Comparison of the regeneration of the hypostome with the budding process inHydra littoralis

Summary One group of animals has been cut close behind the tentacles and another group in the central part of the gastral region.Hydras have been fixed in Bouin in various time intervals after amputation (from 30 min to 46 h).When the hypostome is entirely closed and when both layers are conspicuous, then the hypostome looks very much like a top of the bud in development. These similarites refer to the position of the cells and their qualitative and quantitative composition.The results lead to a conclusion that zymogen cells can easily move and that in different forms of differentiation can be found in a few hours either at the place of the formation of buds or at the place of the regeneration of the hypostome.Their dedifferentiation into interstitial gastrodermal cells permitted the migration of these cells into the layer of the ectoderm and in this way the growth of the bud and the regeneration of the hypostome are made possible.The vacuolization of these cells and their change into mucous cells created the condition for the formation of new parts of the gastrodermal hypostome and for the formation of tentacles.

---

Zusammenfassung Eine Gruppe Versuchstiere wurde nahe hinter den Tentakeln und die andere Gruppe im zentralen Teil der Gastralregion durchschnitten. Die Hydren wurden in Bouin zu verschiedenen Zeitintervallen nach Amputation fixiert (zwischen 30 min und 46 Std). Wenn das Hypostom gänzlich geschlossen ist und beide Zell-Lagen augenfällig sind, dann sieht das Hypostom der Oberseite einer Knospe sehr ähnlich. Diese Ähnlichkeiten beziehen sich auf die Lage der Zellen und auf ihre qualitative und quantitative Zusammensetzung. Die Ergebnisse erlauben den Schluß, daß Zymogenzellen mit Leichtigkeit sich bewegen und innerhalb weniger Stunden als verschieden differenzierte Formen entweder an der Bildungsstelle von Knospen oder am Regenerationsort des Hypostoms gefunden werden können. Ihre Dedifferenzierung in interstitiale Gastroderm-Zellen erlaubt die Wanderung dieser Zellen in die Ectoderm-Schicht und auf diese Weise das Wachstum der Knospe und die Regeneration des Hypostoms. Die Vakuolisierung dieser Zellen und ihre Umwandlung in Schleimzellen schafft die Bedingungen für die Bildung neuer Teile des gastrodermalen Hypostoms und der Tentakeln.

---

---

The work has been partly effected in Middlesex Hospital Medical School, London, where I practised as the British Council scholar.     

Inhibition of the puromycin reaction with benzamidine and related compounds

Incubation of mouse cells with N-methyl-N′-nitro-N-nitrosoguanidine causes a strong inhibition of DNA replication the extent of which varies with the cell line used. Analysis of the products synthesized in drug-treated cells indicates a particularly severe effect on the joining of replicons while other steps in DNA synthesis like initiation and chain elongation are much less affected. The data indicate that replicon fusion may be extremely sensitive to changes in the topology of DNA induced by the introduction of rare single-strand breaks during repair of N-methylated purines produced by incubation of cells with small amounts of the methylating agent     

Adaptive superparasitism and host-parasitoid dynamics

We consider a host-solitary parasitoid system with three categories of individuals: parasitoids, healthy hosts and parasitized hosts. Parasitoids are assumed to discriminate perfectly between the two kinds of hosts and they can reject those which are already parasitized. If parasitoids systematically accept or reject superparasitism or behave randomly, the system is always unstable. Using an optimal foraging model, we determine the behavior of parasitoids which leads to maximization of the instantaneous reproductive rate. When following this adaptive decision rule, parasitoids accept or refuse superparasitism according to the densities of both healthy and parasitized hosts. We study the dynamics of the system when parasitoids follow the optimal rule and show that under certain conditions it possesses a locally stable equilibrium point. In addition, our model predicts that at equilibrium parasitoids show partial preferences for superparasitism.     

Survey of susceptibility to selected antibiotics ofPseudomonas aeruginosa strains isolated from patients with tumor disease and their relationship to serotype

A total of 51Pseudomonas aeruginosa strains had been isolated over a year from patients with tumor diseases in theNational Institute of Oncology in Bratislava. All strains were subjected to serotyping; in 45 strains quantitative susceptibility to selected antibiotics was determined by the microdilution method. When comparing susceptibility of individual serotypes, resistance of strains belonging to serotype O12 to a number ofβ-lactam, aminoglycoside and quinolone antibiotics was found. In addition, resistant strains occurred even among serotype O4 and polyagglutinating strains. The resistant strains as causative agents of nosocomial infections may represent a serious risk particularly for patients of oncological wards.     

Critique of proportional hypotheses and methods for back-calculation of fish growth

Synopsis Hypotheses which assume a contant proportional deviation of the individual size of fish scales (S) or body (L) from mean size throughout life are biologically insignificant. Growth is considered and illustrated as a complex self-regulating process which continuously changes throughout ontogeny. Speed and form of changes of the growth of individual fish depend mainly on the initial size of the specimen and on the habitat.Consider five main types of changes of the L-S regression lines for individual fish with different initial sizes. They are basically different from the current proportional model of individual growth. The regression lines for individual fish cannot and should not be used for back-calculating L from S either by proportional or by regression methods, as individual L(S)/theoretical L(S) ratio, determined at the time of capture, are usually considerably different, compared to the previous years. For back-calculation of the average L values from average S values the use of separate equations for each age-group or for the whole subpopulation are recommended.