Stereochemistry and kinetics of interaction with DNA of the antineoplastic antibiotic olivomycin

The kinetics of interaction of antitumor glycoside antibiotic olivomycin with DNA has been investigated. The existence of two relaxation times in the experimental kinetics curves indicates that two types of antibiotic--DNA complex are formed. We have measured the rate constants of association and dissociation processes and determined their temperature dependences. It is suggested, that one of the complex form results from nonspecific interaction between glycoside residues of the antibiotic molecule and sugar-phosphate backbone of DNA whereas the other type of complex exhibits a pronounced specificity for GC-rich regions on DNA. The binding specificity probably results from formation of a H-bond between the antibiotic chromophore ring and guanine 2-amino group. A stereochemical model for olivomycin-DNA complex is proposed. According to this model the antibiotic chromophore and glycoside residues are located in the narrow groove of DNA.     

Cleavage beyond the block stage and survival after transfer of early bovine embryos cultured with trophoblastic vesicles

Early bovine embryos (1- to 8-cell stages) were recovered from superovulated heifers at slaughter on Days 2 or 3. Embryos were cultured for 3-4 days in Medium B2 supplemented with 15% (v/v) fetal calf serum in the absence (B2SS, 106 embryos) or presence of trophoblastic vesicles (B2SS + TV, 190 embryos). At the end of culture, there were more (P less than 0.001) morulae (greater than or equal to 16 cells) in B2SS X TV (46%) than in B2SS alone (18%) irrespective of the initial cell stage. More 8-cell embryos reached the 16-cell stage than did embryos with less than 8 cells (30% vs 15% in B2SS, P greater than 0.05; 70% vs 41% in B2SS + TV, P less than 0.005). After culture, 102 morulae were transferred non-surgically to temporary recipient heifers (84 embryos cultured in B2SS + TV and 18 in B2SS). After 2 or 3 days, 14 out of 58 embryos from the B2SS + TV group and 3 out of 10 embryos from the B2SS group were recovered as blastocysts. Most blastocysts were deep-frozen and stored for several weeks. After thawing, 10 apparently normal embryos from the B2SS + TV group were transferred non-surgically into 10 recipient heifers. Four pregnancies were induced, but only one embryo survived to term (birth of a normal male calf). It is concluded that trophoblastic vesicles release one or several unknown compound(s) normally present in vivo, promoting the cleavage of early bovine embryos.     

Phytosociological characteristics of theRondeletio correifoliae-Andropogonetum multinervosi ass. nova (Sierra de la Siguanea,Isla de la Juventud,Cuba)

The contribution deals with the phytocenological analysis of theRondeletio correifoliae-Andropogonetum multinervosi, an endemic savanna association occuring on the Siguanea Hills (Sierra de la Siguanea) near the Colony Hotel.     

Foliicole flechten aus zaire (III) Die GattungByssoloma Trevisan

Nine species ofByssoloma Trevisan (Pilocarpaceae) are reported from a collection of foliicolous lichens from Zaire, and includeB. murinum sp. n. In addition,B. usambarense sp. n. is described from adjacent Tanzania. A determination key is provided to all the known African species, and each species is briefly characterized.     

Seroresponse (IgG) after Vaccination and Natural Infection of Cattle with Babesia Divergens

The antibody response against Babesia divergens in vaccinated calves and in unvaccinated sentinels on farms where vaccination had been practiced routinely, was investigated using a live vaccine. Sera were obtained before and 3 weeks after vaccination in March and April, approximately 1 month before the animals were put out on pasture. Additional blood samples were collected at the end of the grazing season and again the next spring. At that time previously unvaccinated sentinel calves were vaccinated and their antibody response was tested 3 weeks later. All sera were analysed by an IF-technique. All of the vaccinated calves (100%) were seropositive 3 weeks after vaccination. The seroresponse did not differ signifacantly between animals vaccinated before their first or second grazing season although the age difference was about 12 months. No clinical symptoms of babesiosis were seen in vaccinated animals. The titres were, however, significantly higher 3 weeks after vaccination than 6 months later. After the grazing season about 42% of the unvaccinated sentinel calves were sero–positve. Two of these calves had clinical babesiosis on pasture in July and September respectively. The number of sentinel calves which became infected on pasture showed a large farm-to-farm variation although all cattle on the farms once had been infected-/vaccinated with B. divergens. Probably the different number of calves infected was a reflection of a variation in tick density on the different pastures. All calves, which were seropositive after the grazing season, were also seropositive after 6 months indoors. The titres declined during the winter period, but they were still within the range of 2 doubling dilution steps.     

Effect of Eimeria falciformis infection on the development of toxoplasmosis in mice

White mice previously infected with 10(2), 10(3) or 10(4) Eimeria falciformis oocysts on days 0, 5, 10 or 30 were inoculated per os with 10(1), 10(2), 10(3) or 10(4) Toxoplasma oocysts. While the results obtained for mice with higher Toxoplasma inocula were consistent, animals with 10(1) and 10(2) oocysts previous inoculation with Eimeria showed important differences related with those infected only with Toxoplasma. For example, survival time was higher in animals infected with both parasites, especially if inoculated with Eimeria 30 days before Toxoplasma infection. Furthermore the number of T. gondii cysts found in the animals previously infected with Eimeria was lower compared with mice inoculated with Toxoplasma only. Body weight of mice infected with Toxoplasma previous infection with Eimeria was almost normal in relation to those infected only with Toxoplasma, indicating a probable pathological effect due to the parasite, more evident in "non immunized" mice.     

Giemsa stain applied to deplasticized sections to identify pancreatic islet cells

A new application of the Giemsa stain to demonstrate endocrine cells in deplasticized sections of Epon embedded material is described. Its application to the pancreas of Rana temporaria is illustrated. The technique does not require postfixation with OsO4 and is easily performed in 30 min. It allows the easy identification of three types of endocrine cells (A, B, and D). A cells, preferentially located at the islet periphery, stain purple-blue. B cells, which occupy the interior of the islet, display a lilac color. D cells give a strong purple color; they are located both in the periphery of the islets and scattered among acinar cells. Positive identification of the cell types was made by immunocytochemistry and electron microscopy.