Leishmania chagasi: in vitro differentiation of promastigotes monitored by flow cytometry

A sequential development from a less infective to an infective stage of Leishmania promastigotes growing in culture has been previously reported. The aim of this work was to investigate whether freeze-fracture electron microscopy and flow cytometry would be able to provide some reliable morphological markers of in vitro differentiation of Leishmania chagasi promastigotes. The flow cytometry technique discriminates between the L. chagasi promastigotes from the different stages of their in vitro differentiation. The "forward scatter" intensity of the parasite, very high 15 hr after seeding when the parasites were very condensed and with a high DNA content per particle, strongly decreased during the culture course. Parallel experiments have shown a striking correlation between forward scatter intensity, growth curves, and infectivity of promastigote populations. By contrast, freeze-fracture techniques showed that in either less infective or infective promastigote plasma membranes, the intramembrane particles density in protoplasmic fracture faces (about 2800/micron 2) and in exoplasmic fracture faces (about 1000/micron 2) was independent of the time of cultivation. The amount of filipin lesions, which reflects the cholesterol content within the plasma membrane, was also constant throughout the culture course. Both data suggest that the architecture of the plasma membrane is an intrinsic characteristic of the promastigote stage. This study shows that whereas freeze-fracture electron microscopy does not provide markers for the differentiation of Leishmania promastigotes, flow cytometry may on the other hand be of value as a screening test for promastigote populations allowing the characterization of their developmental stages in in vitro cultures.     

Biogeochemical Stoichiometry Reveals P and N Limitation Across the Post-glacial Landscape of Denali National Park,Alaska

Global warming has accelerated glacial retreat in high-elevation and high-latitude ecosystems, exposing new terrain that can undergo predictable patterns of ecosystem succession, especially in coastal areas with relatively mild climates. However, little work has been done in harsher high-elevation and inland areas where the rate of plant and microbial succession may be greatly slowed by dryness and low temperatures. The present study is the first to address microbial succession at a major glacial foreland (the Middle Fork Toklat Glacier) in the interior of Alaska. We used a spatially nested sampling regime to reveal the landscape patterns in microbial activity and biogeochemical pools during the pre-plant stage of primary succession along this high-elevation and high-latitude chronosequence. Recently deglaciated soils (0–10 years) were colonized by a diverse microbial community that included many chemoautotrophs that likely subsist on high levels of un-weathered minerals (for example, pyrite) found at this site. Rates of N-fixation and extracellular enzyme activities were very low in the youngest soils sampled, but increased during the first 20 years of succession coinciding with a decrease in TOC and C:N levels. In older soils (20–54 years), TOC and TON increased and IN became undetectable perhaps indicating N limitation. Indicators of microbial activity stopped increasing 20 years post de-glaciation and remained at levels well below those seen at lower elevation and lower latitude sites, perhaps indicating severe nutrient limitations. Stoichiometric analyses also indicated phosphorus and nitrogen limitation across the entire chronosequence, with no indication of carbon limitation of microbial activity. These results indicate that nutrient limitation, rather than the constraints of a severe climate, may be the dominant factor slowing the rate of succession at high-latitude and high-altitude glacial forelands.     

An Enigmatic Hypoplastic Defect of the Maxillary Lateral Incisor in Recent and Fossil Orangutans from Sumatra (<Emphasis Type="Italic">Pongo abelii</Emphasis>) and Borneo (<Emphasis Type="Italic">Pongo pygmaeus</Emphasis>)

Developmental dental pathologies provide insight into health of primates during ontogeny, and are particularly useful for elucidating the environment in which extant and extinct primates matured. Our aim is to evaluate whether the prevalence of an unusual dental defect on the mesiolabial enamel of the upper lateral incisor, thought to reflect dental crowding during maturation, is lesser in female orangutans, with their smaller teeth, than in males; and in Sumatran orangutans, from more optimal developmental habitats, than in those from Borneo. Our sample includes 49 Pongo pygmaeus (87 teeth), 21 P. abelii (38 teeth), Late Pleistocene paleo-orangutans from Sumatra and Vietnam (67 teeth), Late Miocene catarrhines Lufengpithecus lufengensis (2 teeth), and Anapithecus hernyaki (7 teeth). Methods include micro-CT scans, radiography, and dental metrics of anterior teeth. We observed fenestration between incisor crypts and marked crowding of unerupted crowns, which could allow tooth-to-tooth contact. Tooth size does not differ significantly in animals with or without the defect, implicating undergrowth of the jaw as the proximate cause of dental crowding and defect presence. Male orangutans from both islands show more defects than do females. The defect is significantly more common in Bornean orangutans (71 %) compared to Sumatran (29 %). Prevalence among fossil forms falls between these extremes, except that all five individual Anapithecus show one or both incisors with the defect. We conclude that maxillary lateral incisor defect is a common developmental pathology of apes that is minimized in optimal habitats and that such evidence can be used to infer habitat quality in extant and fossil apes.     

Goniatiten mit Radula und Kieferapparat in der Itararé-Formation von Uruguay

Radula and jaws were found in the livng chamber of eight goniatites from a marine transgression of the Itararé formation of northern Uruguay. The goniatites are preserved in phosphorite concretions und belong to the genusEoasianites, subgenusGlaphyrites. The radula presents a large number of tooth rows with 7 teeth in each row. The formula 3. 1. 3 is present in recent mollusks only among the dibranchiates. The form and disposition of the teeth resembles those observed in some teuthoids and sepiids. The jaws show morphological features of both dibranchiates and tetrabranchiates. The lack of the calcareous layer as well as the morphology of the lateral wings puts them closer to the dibranchiates. Although the goniatite radula is comparable to those of recent dibranchiates the author proposes that ammonoids should be placed among the Ectocochlia.     

Benzothiopyran-4-one based reversible inhibitors of the human cytomegalovirus (HCMV) protease

A novel class of CMV protease inhibitors based on a benzothiopyran-S,S-dioxide nucleus has been discovered. Enzyme kinetic data supports a reversible mode of inhibition for a representative member of this class, 2-(3-pyridyl-N-oxide)benzothiopyran-4-one-S,S-dioxide, 1. Experiments in the presence and absence of the disulfide reducing agent DTT suggest that the inhibition by 1 is not due to oxidative inactivation of the enzyme. Also presented are results of some SAR studies of the benzothiopyranone ring system.     

Targeted ITS1 sequencing unravels the mycodiversity of deep-sea sediments from the Gulf of Mexico

Fungi from marine environments have been significantly less studied than terrestrial fungi. This study describes distribution patterns and associated habitat characteristics of the mycobiota of deep-sea sediments collected from the Mexican exclusive economic zone (EEZ) of the Gulf of Mexico (GoM), ranging between 1000 and > 3500 m depth. Internal Transcribed Spacer 1 (ITS1) amplicons were sequenced by Illumina MiSeq. From 29 stations sampled across three annual campaigns, a total of 4421 operational taxonomic units (OTUs) were obtained, indicating a high fungal richness. Most OTUs assignments corresponded to Ascomycota, unidentified fungi and Basidiomycota. The majority of the stations shared a mere 31 OTUs, including the worldwide reported genera Penicillium, Rhodotorula and Cladosporium. Both a transient and a conserved community were identified, suggesting their dependence on or adaptation to the habitat dynamics, respectively. The differences found in fungal richness and taxonomic compositions were correlated principally with latitude, carbon and carbonates content, and terrigenous content, which could be the potential drivers that delimit fungal distribution. This study represents an expansion of our current knowledge on the biogeography of the fungal community from deep-sea sediments, and identifies the geographic and physicochemical properties that delimit fungal composition and distribution in the GoM.