TAXOL REDUCES THE RATE OF CYTOKINESIS IN PtK1CELLS

Mitotic PtK₁cells were treated both during mid-anaphase and at furrow initiation with the potent microtubule (MT) stabilizing agent, taxol, to determine the role of MTs in the rate of cytokinetic events. Rates of cytokinesis (μm/min) were measured by changes in furrow diameter. Incubation of PtK₁cells during mid-anaphase with 5 μg/ml taxol slows the rate of cytokinesis by an average of 43%. Instead of furrow initiation to midbody formation taking an average of 10.7 min (1.6 μm/min), furrowing to midbody formation was completed in an average of 19.0 min (0.9 μm/min), which does not include the 7-min period between taxol application in mid-anaphase and furrow initiation. Application of 5 μg/ml taxol to cells at furrow initiation had a reduced effect on decreasing the rate of cytokinesis and midbody formation; furrowing to midbody formation took an average of 14.6 min (1.2 μm/min). These data suggest that delays in the rate of cytokinesis is dependent on the mitotic stage at which taxol is applied. Ultrastructural analysis shows that taxol treatment of anaphase cells prevents midbody formation during early G₁, yet MT number and organization in the furrowed region is not significantly altered from untreated cells. There is little change in the organization and amount of contractile ring microfilaments, yet filaments are also found parallel to midbody MTs. Our results may be explained by the fact that taxol tends to stabilize MTs which probably affects the rate at which they depolymerize in the terminal phases of cytokinesis. Reduction in depolymerization rates of a stable population of MTs could serve to regulate the rate of cytokinesis.     

Antigenic Differences Among Epimastigotes,Amastigotes and Trypomastigotes of Trypanosoma cruzi*

Antigenic differences were demonstrated among trypomastigotes, amastigotes, and epimastigotes of Trypanosoma cruzi by the indirect fluorescent antibody method. Tests using cross-absorbed sera were included in the study.     

Separate Factors in Phytohaem-agglutinin induce Lymphotoxin,Interferon and Nucleic Acid Synthesis

PHYTOHAEMAGGLUTININ (PHA) has many different biological activities, for example, erythroagglutination¹, leucoagglutination¹, stimulation of RNA and DNA synthesis¹ and induction of interferon¹ and lymphotoxin (LT)². We demonstrate here that the induction of interferon and lymphotoxin by PHA is caused by factors separate from those stimulating nucleic acid synthesis.     

Eurycea bislineata (Green), the Two-Lined Salamander, a New Host of Myxidium serotinum Kudo & Sprague, 1940 (Myxosporida, Myxidiidae)

SYNOPSIS. Myxidium serotinum was found in 51 of 58 (87.9%) specimens of the two-lined salamander, Eurycea bislineata , from West Virginia. This constitutes a new host record. No specimens of the order Salientia, or other species of the order Caudata were infected. Eurycea bislineata appears to be the normal host of M. serotinum , which is specific for the gallbladder in a variety of amphibian hosts. Apparently, larval E. bislineata becomes infected with M. serotinum , and the parasite does not become a mature trophozoite until after the tadpoles metamorphose to the adult salamander. Certain host hormonal factors may be important to the maturation of M. serotinum.     

The Effect of External Conditions on Coremium Production in Paecilomyces farinosus Bainier

Paecilomyces farinosus grew and produced coremia under laboratoryconditions on media containing wide ranges of carbon and nitrogensources. The fungus tolerated higher concentrations of complexcarbon and nitrogen sources than of simple ones. Sustained lowconcentrations of simple carbon and nitrogen nutrients favouredcoremium production. Once P. farinosus colonies had consumedsufficient nutriment, coremium production could take place withoutfurther access to external nutrients. Light was essential for initiation and development of coremia.The tips of the coremia were photosensitive throughout theirgrowth. After growth in darkness during the initial trophicphase of development, P. farinosus required exposure to lightfor at least 8 days before coremia were initiated. The isolate used produced non-coremial strains spontaneously.These usually also lacked the orange, alcohol soluble, pH sensitivepigment found in the coremial strains.     

Characterization of the Malaria Pigment (Hemozoin) from the Avian Malaria Parasite Plasmodium lophurae*

SYNOPSIS. Plasmodium lophurae hemozoin (malaria pigment) is a heme-containing protein which is distinctly different from hemoglobin and hematin by immunologic, spectrophotometric, fingerprint, heme-iron, gel filtration, and starch gel electrophoretic analyses. The calculated average molecular weight of P. lophurae hemozoin is ca. 40,000. Hemozoin contains at least 3 antigenic components and shows some indication of cross-reaction with hemoglobin.     

The differentiation of bunodont Listriodontinae (Mammalia,Suidae) of Africa: new data from Kalodirr and Moruorot,Kenya

The early Miocene sites of Moruorot and Kalodirr (Kenya, 17.5 Myr) have yielded a rich collection of mammals. New listriodont material from these localities, including a complete skull and a partial mandible, provide long awaited information on cranial features of early bunodont Listriodontinae. The evolution and systematics of the group are highly debated, especially regarding its first representatives. The new material described here sheds light on the differentiation of bunodont Listriodontinae in Africa and clarifies the systematics of the group. The first phylogenetic analysis of the Listriodontinae is here performed and supports close relationships between Kubanochoerus and a clade (Eurolistriodon, Listriodon). Lopholistriodon is the most basal representative of the listriodontine clade. These first results stress the role of the African continent in the biogeographical history of the Listriodontinae. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 157 , 653–678.     

Speciation in the greater galagos (Prosimii: Galaginae): review and synthesis*

A marked morphological and genetical discontinuity among the greater galagos points to the existence of two genetical species within the taxon, Galago crassicaudatus E. Geofl'roy 1812. This contribution investigates the conditions surrounding this speciation event, and places it within a phylogenetic context. Information pertaining to body size, litter size, sexual dimorphism, locomotor mode and karyotypic structure is assessed. It is hypothesized that G. crassicaudatus diverged from its more gracile sibling, G. garnettii, approximately 2 million years ago, in respotise lo the increasing aridification of Africa that accompanied the Northern Hemisphere Pleistocene glaciations.     

Juvenile Hormone: The Status of "Status Quo"

SYNOPSIS. Cuticular proteins show specificity for stage, age,and anatomical region. Analysis of the cuticular proteins ofsecond pupae created by application of juvenile hormone demonstratesthat the hormone prevents the onset of new sequences of synthesesand favors repetition of the region-specific, temporal patternof syntheses used in the previous stage. The argument made isthat juvenile hormone might exert this "status quo" action bypreventing alterations in chromatin configuration. Evidencefrom a wide variety of systems shows that polyamines might beinvolved in reprogramming chromatin. Ecdysterone induces ornithinedecarboxylase, the rate limiting enzyme in animal polyaminesynthesis. I suggest that juvenile hormone might be exertingits status quo action by inhibiting this induction. Preliminarystudies of ornithine decarboxylase induction support this specifichypothesis; experiments with an inhibitor of this enzyme, -difluoromethylornithine, however, do not show the expected juvenile hormonemimicry. Further studies are needed to define the control ofpolyamine biosynthesis in insects and to discover whether juvenilehormone plays a role in this control.