ALBERT

Notes: Axenically grown Giardia lamblia trophozoites treated with low concentrations of the benzimidazole carbamates albendazole and mebendazole detach from glass culture tubes and lose viability. Scanning electron microscopic observations revealed that these drugs produce grotesque modifications of the cell shape of the parasite and disassembly of the adhesive disc. Transmission electron microscopy showed several stages of the fragmentation of adhesive discs with dispersion of microtubules and microribbons in the cytoplasm. Flagella appeared undamaged. In drug-treated trophozoites electron-dense precipitates were selectively deposited on microtubules and microribbons. The results indicate that the antigiardial effect of benzimidazoles is the result of binding to microtubules and subsequent alterations of the cytoskeleton. The electron microscopic observations also suggest that the drugs may bind to microribbon components of the adhesive disc, possibly giardin proteins.

Notes: Some characterizations of the conjugate of a Banach–Stone map T : C(X) → C(Y) between the non–Archimedean spaces of continuous functions C(X) and C(Y) are studied. The main result that T′ : C(Y)′→ C(X)′ is a Banach–Stone map if and only if T is a Banach–Stone map is proved.

Notes: Miguel Martinez Lucio and Syd Weston, who are Lecturers in Human Resource Management at the Cardiff Business School, emphasise that, in seeking to understand trade union responses to HRM and new management practices, it is important to take into account their traditions and internal decision-making processes as well as external influences. They suggest, in particular, that it is possible to identify three main ‘clusters’ of opinion which have emerged in recent years and which go to make up the complex position of the TUC. They go on to argue that, as unions learn more about HRM and new management practices, they will tend to exert a more significant influence on the form and implementation of such initiatives.

Notes: Juveniles of Pinctada mazatlanica and Pteria sterna were collected with artificial collectors from Falsa Bay, Baja California Sur, Mexico during a 12 month experimental period. Filament substrate artificial collectors contained in 2 mm plastic mesh bags (25 ± 25 cm) were deployed from the surface to 17 m of depth, and replaced monthly. Pinctada mazatlanica had the greatest recruitment (12 juveniles/cm2) in late summer and P. sterna (5 juveniles/cm2) in winter. Maximum spat collection from September 1986 to April 1987 occurred at 10 m depth for P. mazatlanica and at 4–7 m depth for P. sterna. However, peak spatfall under 11m depth occurred from late July to August 1987. The mean prodissoconch shell height was 254 μm (SE = 0.003; N = 50) for P. mazatlanica and 313 μm (SE = 0.004; N= 50) for P. sterna. The growth equations for the first five weeks of both species, based on the prodissoconch shell height and the maximum spat height (measured from the umbo to distal edge) are presented.

Notes: The reroductive biology and growth of the Central American cichlid, Cichlasoma urophthalmus, was studieg in a brackish water lagoon in Celestun, Yucatan, Mexico, between spring 1985 and spring 1986. The fish is strongly euryhaline and reproduces in brackish waters as well as in fresh water, having clear thermophilic habits, and resisting low oxygen levels. The population in the lagoon is constituted by fast growing fish which have one, or exceptionally two, reroductive seasons in their lifetimes. The mean standard length of catured fish was 134.7 mm for mais and 135.3 mm for females but no significant difference was found getween them. A significant difference in the sex ratio was found between summer and autumn, presumably due to the type of parental care exhibited by this species. Examination of ovaries showed that the reproductive season starts in mid-April and extends until mid-November, with reproductive peaks in sprin and summer. The fecundity ranged from 2085 to 6615 ova/female. The minimum size of maturity of females was 102 mm (50 g). Specific attributes of this species are compared with those of some African cichlids and are discussed in terms of aquaculture.〈section xml:id="abs1-2"〉〈title type="main"〉Zusammenfassung Die Reproduktionsbiologie und das Wachstum des zentralamerikanischen Cichliden Cichlasoma urophthalmus (Günther)Die Reproduktionsbiologie und das Wachstum des zentralamerikanischen Cihliden Cichlasoma urophthalmus wurden in einer Brackwasserlagune in Celestun, Yucatan, Mexiko untersucht. Diese Arbeiten fanden im Zeitraum zwischen dem Frühjahr 1985 und Frühjahr 1986 start. Diese stark euryhaline Fischart vermehrt sich sowohl in Brack- als auch in Säßwasser, wobei thermophile Eigenschaften sowie eine deutliche Widerstandsfähigkeit gegen niedrige Sauerstoffgehalte des Wassers beobachtet wurden. Die Population, die in der Lagune lebte, bestand aus schnell wachsenden Individuen, die sich ein oder maximal zweimal während ihres Lebenszyklus vermehren. Die mittlere Standardlänge der gefangenen Tiere betrug 134,7 mm für die Männchen, sowie 135,3 mm für die Weibchen, die Unterschiede der mittleren Länge waren nicht signifikant. Ein signifikanter Unterschied bestand zwischen dem Verhältnis von Männchen zu Weibchen im Sommer und Herbst, was wahrscheinlich auf die Art vom Brutpflegeverhalten dieser Art zurückzuführen ist. Untersuchungen der Ovarien zeigten, daß die Reproduktion gegen Mitte April einsetzt und bis Mitte November andauert. Die Höhepunkte in der Vermehrung liegen im Frühjahr und Sommer. Die Fruchtbarkeit schwankte zwischen 2085 und 6615 Eiern pro Weibchen. Die Mindestgröße der Weibchen urn die Geschlechtsreife zu erlangen betrug 102 mm (50 g). Spezifische Eigenschaften dieser Fischart werden mit denen afrikanischer Cichliden verglichen und unter aquakulturtechnischen Gesichtspunkten diskutiert.

Notes: Abstract The molecular mass of cruzipain, the major cysteine proteinase from Trypanosoma cruzi epimastigotes, is 36.3 kDa as calculated from its sequence; this value can increase to about 41 kDa if the three potential N-glycosylation sites are glycosylated in vivo. Yet the apparent molecular mass of the enzyme, as determined by SDS-polyacrylamide gel electrophoresis, has been reported in a range of values from 60 to 40 kDa. We show that the purified enzyme had apparent molecular masses ranging from 51 to 33 kDa, depending on the experimental conditions. This variation is likely to be due to both N-glycosylation and the presence of several disulfide bridges, which make electrophoretic mobility dependent on acrylamide concentration, and reduction and/or boiling of the sample.

Notes: Abstract To further study the ribosomal RNA genetic system in Trypanosoma cruzi, the 5S rRNA gene family was characterized. We found that this gene family is reiterated about 1600 times per diploid nuclei and is mostly organized as a tandem repeat of 481 base pairs. These gene clusters were assigned to two chromosomes of about 1500 and 1400 kilobase pairs. We found that the 5S rRNA-coding region is comprised of 120 nucleotides, and contains the well-known internal control regions of eukaryotic RNA polymerase III. The two gene-spacer regions analysed exhibit a putative signal for transcription termination and six sites homologous to the consensus sequence for the binding of transcription factor Sp1.

Notes: Abstract From autolysed cultures of Mucor rouxii, two chitosanases, A and B, were purified to electrophoretic homogeneity. Apparent Mr values of 76 000 and 58 000 and pI values of 4.9 and 4.7 were determined for A and B, respectively. Both chitosanases showed a high specificity for chitosan and chitosan derivatives. They had optimum activities at pH 5.0 and at temperatures of 55°C and 50°C for A and B, respectively. Enzyme A was inhibited by acetate ions and enzyme B by high substrate concentration. Both enzymes showed an endo-splitting type of activity, and the end product of chitosan degradation contained a mixture of dimer, trimer and higher molecular mass oligomers of glucosamine. Glucosamine oligosaccharides were poorly hydrolysed by these enzymes. Both enzymes extensively degraded the chitosan extracted from M. rouxii cell walls.