CELL DIVISION IN THE FILAMENTOUS PLEURASTRUM AND ITS COMPARISON WITH THE UNICELLULAR PLATYMONAS (CHLOROPHYCEAE)1

At prophase in Pleurastrum, extranuclear spindle microtubules develop from the region of centrioles, which lie lateral to the nucleus midway between the future sites of the metaphase spindle poles. The microtubules then move laterally to overarch the nucleus and finally become incorporated into the spindle. The centrioles do not migrate and therefore lie in the same plane as the chromosomes at metaphase. At telophase, 2, more different systems of microtubules develop from the vicinity of the centrioles—a phycoplast and extensive arrays of microtubules that ensheath the daughter nuclei. Cell division in the filamentous Pleurastrum is compared to that in the green flagellate, Platymonas. The similarities between cell division in the 2 algae are interpreted as evidence: (i) that rhizoplasts (which in Platymonas resemble myofibrils) are somehow homologous to microtubules; and, (ii) that cell division in Pleurastrum differs from cell division in other examined filamentous chlorophycean genera because Pleurastrum has an independent evolutionary origin from a monad with Platymonas-like characteristics.     

Species specificity and intraspecific variation in the chemical profiles of Heliconius butterflies across a large geographic range

In many animals, mate choice is important for the maintenance of reproductive isolation between species. Traits important for mate choice and behavioral isolation are predicted to be under strong stabilizing selection within species; however, such traits can also exhibit variation at the population level driven by neutral and adaptive evolutionary processes. Here, we describe patterns of divergence among androconial and genital chemical profiles at inter‐ and intraspecific levels in mimetic Heliconius butterflies. Most variation in chemical bouquets was found between species, but there were also quantitative differences at the population level. We found a strong correlation between interspecific chemical and genetic divergence, but this correlation varied in intraspecific comparisons. We identified “indicator” compounds characteristic of particular species that included compounds already known to elicit a behavioral response, suggesting an approach for identification of candidate compounds for future behavioral studies in novel systems. Overall, the strong signal of species identity suggests a role for these compounds in species recognition, but with additional potentially neutral variation at the population level.     

Direct detection of 16S rRNA in soil extracts by using oligonucleotide microarrays

We report on the development and validation of a simple microarray method for the direct detection of intact 16S rRNA from unpurified soil extracts. Total RNAs from Geobacter chapellei and Desulfovibrio desulfuricans were hybridized to an oligonucleotide array consisting of universal and species-specific 16S rRNA probes. PCR-amplified products from Geobacter and Desulfovibrio were easily and specifically detected under a range of hybridization times, temperatures, and buffers. However, reproducible, specific hybridization and detection of intact rRNA could be accomplished only by using a chaperone-detector probe strategy. With this knowledge, assay conditions were developed for rRNA detection using a 2-h hybridization time at room temperature. Hybridization specificity and signal intensity were enhanced using fragmented RNA. Formamide was required in the hybridization buffer in order to achieve species-specific detection of intact rRNA. With the chaperone detection strategy, we were able to specifically hybridize and detect G. chapellei 16S rRNA directly from a total-RNA soil extract, without further purification or removal of soluble soil constituents. The detection sensitivity for G. chapellei 16S rRNA in soil extracts was at least 0.5 microg of total RNA, representing approximately 7.5 x 10(6) Geobacter cell equivalents of RNA. These results suggest that it is now possible to apply microarray technology to the direct detection of microorganisms in environmental samples, without using PCR.     

Reliance on head versus eyes in the gaze following of great apes and human infants: the cooperative eye hypothesis

As compared with other primates, humans have especially visible eyes (e.g., white sclera). One hypothesis is that this feature of human eyes evolved to make it easier for conspecifics to follow an individual's gaze direction in close-range joint attentional and communicative interactions, which would seem to imply especially cooperative (mututalistic) conspecifics. In the current study, we tested one aspect of this cooperative eye hypothesis by comparing the gaze following behavior of great apes to that of human infants. A human experimenter "looked" to the ceiling either with his eyes only, head only (eyes closed), both head and eyes, or neither. Great apes followed gaze to the ceiling based mainly on the human's head direction (although eye direction played some role as well). In contrast, human infants relied almost exclusively on eye direction in these same situations. These results demonstrate that humans are especially reliant on eyes in gaze following situations, and thus, suggest that eyes evolved a new social function in human evolution, most likely to support cooperative (mututalistic) social interactions.     

Influence of ploidy level on morphology,growth and drought susceptibility in <Emphasis Type="Italic">Spathiphyllum wallisii</Emphasis>

In this study, we analysed morphological, anatomical and physiological effects of polyploidisation in Spathiphyllum wallisii in order to evaluate possible interesting advantages of polyploids for ornamental breeding. Stomatal density was negatively correlated with increased ploidy level. Stomatal size increased in polyploids. Tetraploid Spathiphyllum plants had more ovate and thicker leaves. The inflorescence of tetraploids had a more ovate and thicker spathum, a more cylindrical spadix and a thicker but shorter flower stalk. Biomass production of the tetraploids was reduced, as expressed by lower total dry weights, and tetraploids produced fewer shoots and leaves compared with their diploid progenitors. Furthermore, tetraploid Spathiphyllum plants were more resistant to drought stress compared with diploid plants. After 15 days of drought stress, diploids showed symptoms of wilting, while the tetraploids showed almost no symptoms. Further, measurements of stomatal resistance, leaf water potential, relative water content and proline content indicated that the tetraploid genotypes were more resistant to drought stress compared with the diploids.     

Demography of an alpine population of Savannah Sparrows

ABSTRACT.   Although Savannah Sparrows ( Passerculus sandwichensis ) have been well studied across their North American range, few data are available for populations that breed in high-elevation habitats. We collected data over six years on the demography of a population of Savannah Sparrows ( P. s. anthinus ) breeding in alpine tundra and sub-alpine meadows in northern British Columbia, Canada. The mean duration of the breeding season at our site was 45.5 d, and pairs produced a maximum of one brood per season. Clutch sizes varied annually (mean = 4.37, range = 3.90 – 4.71 eggs). Nest fate also varied among years (range = 33 – 92%) due to variation in abiotic (weather) and biotic (predators) conditions. Uncorrected return rates of banded birds were 68% for adults and 17% for juveniles ( N = 22 and 102, respectively). However, when resighting probability was taken into account, apparent annual survival was 75% for adults and 34% for juveniles. Compared to populations at lower elevations, Savannah Sparrows in our study had shorter breeding seasons, fewer broods per season, larger clutches, and higher adult and juvenile return rates. Our results suggest that Savannah Sparrows that breed in high-elevation habitats have adopted a low fecundity, high survival life history strategy that enables their persistence in these challenging environments.     

Secretion of the STA3 heat-stable enterotoxin of Escherichia coli: extracellular delivery of Pro-STA is accomplished by either Pro or STA

The methanol-soluble, heat-stable enterotoxin of Escherichia coli is a protease-resistant extracellular peptide which is synthesized as a 72-amino-acid precursor Pre-Pro-STA3. The specific roles of Pre (19 amino acids), Pro (34 amino acids) and STA3 (19 amino acids) in the secretion process were studied by functionally deleting each of the three domains. Deletion of the Pre signal sequence resulted in a short-lived cell-associated molecule with an M(r) equivalent to that of Pro-STA3. Deletion of Pro (i.e., Pre-STA3) resulted in the rapid extracellular accumulation of STA3; the periplasmic intermediate found in the secretion of the wild-type toxin was undetected. Deletion of the STA3 domain resulted in a cell-associated Pre-Pro peptide; with time this form converted to periplasmic Pro which later became extracellular. When DNA encoding either STA3, by itself, or Pro-STA3 (lacking the signal peptide) was expressed, these peptides were degraded intracellularly, with no periplasmic or extracellular forms detected. The results presented demonstrate that the signal peptide (Pre) is essential even for the export of small peptides to the periplasm, and that its absence causes the STA3 domain to become susceptible to intracellular proteases. The rapid degradation of intracellular STA3 indicates that its proteolytic resistance is acquired in a compartment other than the cytoplasm. The results also show that after the Pre domain is proteolytically cleaved from Pre-STA3 and Pre-Pro, the STA3 and Pro peptides can exit to the culture supernatant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevalence,Types, Risk Factors and Clinical Correlates of Anaemia in Older People in a Rural Ugandan Population

Background

Studies conducted in high income countries have shown that anaemia is a common medical condition among older people, but such data are scarce in Africa. The objectives of this study were to estimate the prevalence, types, risk factors and clinical correlates of anaemia in older people.

Methods

Participants were aged (≥ 50) years recruited from a general population cohort from January 2012 to January 2013. Blood samples were collected for assessing hemoglobin, serum ferritin, serum vitamin B12, serum folate, C-reactive protein, malaria infection and stool samples for assessment of hookworm infection. HIV status was assessed using an algorithm for HIV rapid testing. Questionnaires were used to collect data on sociodemographic characteristics and other risk factors for anaemia.

Results

In total, 1449 people participated (response rate 72.3%). The overall prevalence of anaemia was 20.3 % (95% CI 18.2-22.3%), and this was higher for males (24.1%, 95% CI=20.7-27.7%) than females (17.5%, 95% CI=15.0-20.1%). In males, the prevalence of anaemia increased rapidly with age almost doubling between 50 and 65 years (p-trend<0.001). Unexplained anaemia was responsible for more than half of all cases (59.7%). Anaemia was independently associated with infections including malaria (OR 3.49, 95% CI 1.78-6.82), HIV (OR 2.17, 1.32-3.57) heavy hookworm infection (OR 3.45, 1.73-6.91), low fruit consumption (OR 1.55, 1.05-2.29) and being unmarried (OR 1.37 , 95% CI 1.01-1.89). However, the odds of anaemia were lower among older people with elevated blood pressure (OR 0.47, 95% CI 0.29-0.77).

Conclusion

Anaemia control programmes in Uganda should target older people and should include interventions to treat and control hookworms and educational programs on diets that enhance iron absorption. Clinicians should consider screening older people with HIV or malaria for anaemia. Further studies should be done on unexplained anaemia and serum ferritin levels that predict iron deficiency anaemia in older people.