Mitochondrial DNA divergence in populations of the tapeworm Diphyllobothrium nihonkaiense and its phylogenetic relationship with Diphyllobothrium klebanovskii

Diphyllobothrium nihonkaiense [Y. Yamane, H. Kamo, G. Bylund, J.P. Wilkgren. Diphyllobothrium nihonkaiense sp. nov (Cestoda: Diphyllobothriidae)- revised identification of Japanese broad tapeworm. Shimane J Med Sci 1986;10:29-48.] and Diphyllobothrium klebanovskii [I.V. Muratov, P.S. Posokhov. Causative agent of human diphyllobothriasis - Diphyllobothrium klebanovskii sp. n. Parazitologiia. 1988;22:165-170.] are two major species of human diphyllobothriasis in Japan and Far East Russia, respectively, but their taxonomical relationship remains unclear. In this study, we analysed the DNA sequences of 16 clinical isolates of D. nihonkaiense from Japanese people, 3 isolates of D. klebanovskii from a bear in Kamchatka, and 4 clinical isolates of D. klebanovskii from native Udygeyci people in Russia, as well as 4 plerocercoids from Oncorhynchus spp. 18S rDNA and internal transcribed spacer 1 (ITS1) sequences from D. nihonkaiense and D. klebanovskii showed a high level of similarity, indicating synonymy of the two species. Analyses of mitochondrial DNA (mtDNA) sequence polymorphisms in the cox1 and nad3 genes of D. nihonkaiense (D. klebanovskii) revealed two deeply divergent lineages, A and B, with genetic distances (Kimura-2 parameter) of 0.018-0.022. Furthermore, the distinct monophyletic groupings of cox1 haplotypes corresponded to the distinct monophyletic groupings of nad3 haplotypes. The two lineages were neither distinguished by morphological features nor defined by the localities of the samples. These results suggest that the two morphologically cryptic lineages have diverged and coexisted over a long period of time.     

Some advantages and limitations of mitosis as a phylogenetic criterion

The advantages and disadvantages of mitosis as a phylogenetic character are discussed. Mitosis is suggested to be a good character on the grounds that it is universally applicable and that it reflects features of the basic organism since it is unlikely to have arisen through multiple endosymbiotic events. Since mitosis is an absolutely essential feature of the cell cycle it is subject to a great deal of evolutionary pressure and one would not expect a priori that relatively inefficient mitotic apparatuses would persist. It is suggested that supposedly primitive mitotic apparatuses are not inefficient and that the evidence that they are functionally different from those of higher organisms is largely negative electron microscopic evidence. This type of evidence is not very satisfactory since it can result from poor preservation and consequently it should be continually retested. Another weakness of mitosis as a phylogenetic criterion (shared with other essentially morphological criteria) is that there is no easy way to relate structural change with genetic change. Thus, while mitosis is a useful phylogenetic character, its usefulness is limited.     

Studies on the in situ physiology of Thiothrix spp. present in activated sludge

The in situ physiology of the filamentous sulphur bacterium Thiothrix spp. was investigated in an industrial wastewater treatment plant with severe bulking problems as a result of overgrowth of Thiothrix. Identification and enumeration using fluorescence in situ hybridization (FISH) with species-specific 16S and 23S rRNA probes revealed that 5–10% of the bacteria in the activated sludge were Thiothrix spp. By using a combination of FISH and microautoradiography it was possible to study the in situ physiology of probe-defined Thiothrix filaments under different environmental conditions. The Thiothrix filaments were very versatile and showed incorporation of radiolabelled acetate and/or bicarbonate under heterotrophic, mixotrophic and chemolithoautotrophic conditions. The Thiothrix filaments were active under anaerobic conditions (with or without nitrate) in which intracellular sulphur globules were formed from thiosulphate and acetate was taken up. Thiothrix -specific substrate uptake rates and growth rates in activated sludge samples were determined under different conditions. Doubling times of 6–9 h under mixotrophic conditions and 15–30 h under autotrophic conditions were estimated. The key properties that Thiothrix might be employing to outcompete other microorganisms in activated sludge were probably related to the mixotrophic growth potential with strong stimulation of acetate uptake by thiosulphate, as well as stimulation of bicarbonate incorporation by acetate in the presence of thiosulphate.     

Never ending growth and a growth factor. II. Immunocytochemical evidence for the presence of epidermal growth factor in a tapeworm

Flatworm growth patterns are interesting and the guiding principles behind them have long been sought. Epidermal growth factor immunoreactivity (EGF-IR) was detected in a dispersed population of nerve cells of the constantly growing adult gull-tapeworm Diphyllobothrium dendriticum (Cestoda, Pseudophyllidea). The EGF-IR cells are located close to regions characterized by active growth and the presence of mitotically competent cells. As no EGF-IR was observed in the non-growing plerocercoid larva a correlation with the growth rate of the worm and the presence of EGF-IR is suggested.     

The phased division of the freshwater dinoflagellate Ceratium hirundinella and its use as a method of assessing growth in natural populations

SUMMARY. The nocturnal phasing and partial synchrony of cell division in Ceratium hirundinella was investigated on four occasions for dense planktonic populations in a small productive lake (Esthwaite Water). The population growth rates deduced from the proportion of cells dividing per day are compared with the rates of increase of cell density in the lake. The maximum proportion of Ceratium cells found dividing at any time was 5.8 ± 1.0%, and the time of optimum division was 03.00 hours G.M.T. The daily rate of division during the main phase of population increases was similar to that deduced from the overall population increments at that time, although during the week of collection the increase had apparently ceased temporarily. On the other three occasions, either increase of cell numbers had ceased or the population was declining, but a continued low rate of division ( c . 3% day⁻¹) was found.
The nocturnal division of Ceratium in Esthwaite Water is compared with the division phasing of dinaflagellates described from elsewhere. Some general problems associated with the derivation of estimates of population growth rate from division frequency are also considered.     

Studies on genus Pleurotus. VIII. Interaction between mycelial growth and yield

This project studies the relationship between mycelial growth rate and production of basidiomata of 19 Pleurotus strains. Firstly, monosporic cultures were isolated of five strains from the following species: Pleurotus djamor (3), Pleurotus ostreatus (1) and Pleurotus pulmonarius (1). These were self-crossed in order to obtain 25 infraspecific dikaryons from which their mycelial growth rate was estimated. The parent strains and the 14 fastest growing crosses were cultivated in the pilot plant on barley straw with the following data recorded: days of incubation, primordia initiation, number of harvests, biological efficiency (BE), production rates (PR) and size of the basidiomes. The BE's fluctuated between 16.8 to 75.6% and the PR's between 0.34 to 1.68%. Most of the basidiomata presented a pileus diameter of 5-15 cm. With the exception of one cross with P. djamor, no increase was observed in the productivity and size of the carphophores of the crosses with respect to the parent strains, suggesting that the rapid mycelial growth rate of the strains was not reflected in the development of the fruiting bodies.     

Phase transitions of phospholipids as a criterion for assessing the capacity for thermal adaptation in fish

This study examines the crystal-liquid crystal phase transitions of the major phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), from muscle tissue of marine fish living at temperatures of 0–4.1°C (the Pacific cod Gadus macrocephalus, banded Irish lord Hemilepidotus gilberti, Pacific halibut Hippoglossus hippoglossus, black edged sculpin Gymnocanthus herzensteini, dark colored flounder Pleuronectes obscurus, and plain sculpin Myoxocephalus jaok), as well as of fish living at 14 and 18°C (Pacific redfin Tribolodon brandti). The PC and PE phase-transition thermograms of all the investigated species displayed specific profiles. The largest share of the thermogram area at temperatures higher than those of the habitat was found for the PC (28–40%) and PE (47–82%) of the black-edged sculpin, dark-colored flounder, and the plain sculpin, which have reduced physiological activity at low temperatures. In the Pacific cod, banded Irish lord, and the Pacific redfin, this parameter was much lower, 0–18% (PC) and 0–39% (PE). The thermotropic behavior PC and PE was symbate in all fish, except for the cod and the plain sculpin. The transition enthalpy of PC in all the investigated species was 2.8 times higher than that of PE. To interpret the varied PC and PE thermogram profiles of fish with similar fatty-acid compositions, the data on the composition of the molecular species of these phospholipids appeared to be the most informative. This study suggests that each fish species has its own strategy for thermal adaptation, which is realized through a certain set of phospholipid molecular species.     

The survival of chloroplasts in vitro: Particle volume distribution patterns as a criterion for assessing the degree of integrity of isolated chloroplasts

Summary Volume distribution patterns of chloroplast suspensions obtained electronically with a Coulter counter have been compared with the corresponding diameter measurements and with the appearance of chloroplasts observed by phase-contrast microscopy. It was found that the Coulter counter pattern could be used to detect gross morphological changes of chloroplasts in isolation, but could not be used for the quantitative determination of the properties of chloroplasts in different morphological states. The pattern for a suspension containing both intact and damaged chloroplasts in approximately equal numbers has only one maximum. Two maxima are present if the proportion of intact chloroplasts is considerably greater than 50%. Chloroplasts which have lost both their outer limiting membrane and also their stroma (i.e. naked, but intact, lamellae systems) make only a very small contribution to the size distribution pattern in the region recording apparent volumes between 0 and 11.2 µ³.Previous workers have described intact chloroplasts as Class I, and damaged chloroplasts lacking limiting membrane and stroma as Class II. We suggest that a third Intermediate Class should be recognized for chloroplasts devoid of their limiting membrane, but still retaining stroma. Such chloroplasts can be distinguished from Class II chloroplasts by their less clearly visible grana, and slightly lighter appearance under phase contrast, and also by their considerable contribution to Coulter counter volume distribution patterns with a peak maximum between 35 and 55 µ³. Such Intermediate Class chloroplasts would also be expected to have biochemical properties differing considerably from those of both Class I and Class II chloroplasts.Salters' Scholar 1967/68.     

Construction of a cytogenetically characterized porcine somatic cell hybrid panel and its use as a mapping tool

A new panel of cytogenetically characterized pig–rodent somatic cell hybrids was constructed and tested for twelve microsatellite markers with PCR. Cytogenetic characterization of hybrids was accomplished by fluorescence painting and GTG-banding of metaphase chromosomes. The panel consists of 15 independent pig–hamster and 6 independent pig–mouse cell lines. In the panel, all pig autosomes and the X Chromosome (Chr) are represented, and it is informative for all chromosome pairs except 2–14, 2–15, 3–9, 14–15, 14–16, and 16–17. The microsatellites tested were S0022, S0023, S0084, S0098, S0112, S0113, S0114, S0115, S0117, S0118, S0119, and S0120. The PCR results obtained in the 21 hybrids were compared with the cytogenetic data and analyzed for concordancy and correlation. Eight microsatellites could be assigned to specific pig chromosomes, confirming seven assignments based on linkage analysis. Received: 25 September 1995 / Accepted: 11 December 1995     

Displacement of chromosomes in mitosis: a technique for assessing differential chromosome error

To assess whether displacement--the appearance of individual chromosomes inside of the ring of chromosomes attached to spindle fibers--is a valid method of analyzing chromosome misdivision, displacement data from six healthy female subjects were compared with data for mitotic and meiotic nondisjunction. Statistical analysis indicated that nondisjunction and displacement are equivalent methods of assessing differential chromosome error. Tests for homogeneity of the data sets showed no significant heterogeneity for the mitotic data, but chromosomes 1, 2, 11, 16, 17, 19, and 20 were responsible for significant heterogeneity in the meiotic data.