Stability in controlling viral replication identifies long-term nonprogressors as a distinct subgroup among human immunodeficiency virus type 1-infected persons.

Long-term nonprogressors (LTNPs) of human immunodeficiency virus type 1 (HIV-1) infection are characterized by low levels of HIV-1 replication and viral load. However, it has not been established whether they differ in this regard from progressors from the very early stage of infection. By studying peripheral blood mononuclear cell (PBMC) specimens from a longitudinally monitored cohort of HIV-1-infected men, we found that HIV-1 proviral copy numbers and HIV-1 mRNA expression levels as low or lower than those seen in seven carefully selected LTNPs were commonly observed in specimens collected soon after seroconversion from 28 subjects who became infected while under observation. However, only the LTNPs were able to stably maintain such an efficient viral control over time. Because of the instability of the early control of HIV-1 replication, the predictive value of HIV-1 mRNA expression in PBMCs at postseroconversion was found to be limited but significantly increased during the first year of infection. Besides their diagnostic implications, these data support the idea that LTNPs may be a pathophysiologically distinct subgroup among persons infected with HIV-1.     

Synergy of human neutrophils with fluconazole in killing Candida species

The killing of Candida species by human neutrophils in a long-term 24-h assay and possible synergy with fluconazole (FCZ) for killing was investigated. The test medium (TM) consisted of RPMI-1640, penicillin and streptomycin (P/S), and 10% fresh autologous serum. TM alone was highly fungistatic for Candida species compared to TM without serum. When neutrophils were cocultured in TM with Candida species for 24 h the inoculum colony-forming units (CFU) were always significantly reduced (killing) by 58 to 99%. FCZ was tested over a range of 1–500 g/ml, and though almost always fungistatic itself, it synergized with neutrophils for significantly increased killing of C. albicans (isolate Sh27) (P<0.01) and C. albicans (isolate 94-20) (P<0.05). Killing of non-albicans Candida species was so efficient in the absence of FCZ that demonstration of synergy with FCZ was difficult.     

The potential energy surface of methyl 2-O-(α-D-mannopyranosyl)-α-D-mannopyranoside in aqueous solution: Conclusions derived from optical rotation

The optical rotation of methyl 2-O -(α-D -mannopyranosyl)-α-D -mannopyranoside is calculated semiempirically as a function of the linkage dihedral angles ? (H1-C1-O1-C2′) and ψ (C1-O1-C2′-H2′). Although the rotation calculated for the global energy minimum conformation found in several rigid-residue modeling calculations (?,ψ = ?40°,?20°) is in good agreement with the observed solution rotation, the observed rotation is also compatible with the limited flexibility inferred from more recent relaxed residue modeling calculations on a structurally related rhamnose disaccharide © 1994 John Wiley & Sons, Inc.     

Effects of ethanol,octanoic and decanoic acids on fermentation and the passive influx of protons through the plasma membrane of Saccharomyces cerevisiae

Ethanol, octanoic and decanoic acids are known toxic products of alcoholic fermentation and inhibit yeast functions such as growth and fermentation. pH-stat measurements showed that, in a concentration range up to 20 mg/l, octanoic and decanoic acids increase the rate of passive H⁺ influx across the plasma membrane of Saccharomyces cerevisiae IGC 3507. Decanoic acid was more active than octanoic acid, which agrees with its higher liposolubility. The fatty acids probably act as H⁺ carriers, since the magnitude of the effect depended on pH and correlated with the concentration of protonated fatty acids. Esterification of the fatty acids partially abolished the enhancing effect on passive H⁺ influx. Passive H⁺ influx showed saturation kinetics with half-maximal activity at 6.6 M H⁺ (pH 5.2). Contrary to previous findings, ethanol inhibited H⁺ influx exponentially up to a concentration of 8% (v/v). At higher concentrations, ethanol reactivated H⁺ influx; the original rate of H⁺ uptake was reached at 14% (v/v) ethanol. In the same concentration ranges that affected passive H⁺ influx, ethanol, octanoic and decanoic acids inhibited the fermentation rate. This inhibitory effect of the fatty acids on fermentation rate depended on liposolubility, pH, and esterification in the same way as that found for their effect on passive H⁺ influx. Inhibition of fermentation by octanoic and decanoic acids could therefore result from their effect on the rate of passive H⁺ influx. Correspondence to: S. Stevens     

Mortality rates of desert vegetation during high-intensity drought at Uluru-Kata Tjuta National Park,Central Australia

Precipitation variability and heatwaves are expected to intensify over much of inland Australia under most projected climate change scenarios. This will undoubtedly have impacts on the biota of Australian dryland systems. However, accurate modelling of these impacts is presently impeded by a lack of empirical research on drought/heatwave effects on native arid flora and fauna. During the 2018–2021 Australian drought, many parts of the continent's inland experienced their hottest, driest period on record. Here, we present the results of a field survey in 2021 involving indigenous rangers, scientists and national parks staff who assessed plant dieback during this drought at Ulur u-Kata Tjut a National Park (UKTNP), central Australia. Spatially randomized quadrat sampling of eight common and culturally important plants indicated the following plant death rates across UKTNP (in order of drought susceptibility): desert myrtle (Aluta maisonneuvei subsp. maisonneuvei) (91%), yellow flame grevillea (Grevillea eriostachya) (79%), Maitland's wattle (Acacia maitlandii) (67%), waxy wattle (A. melleodora) (65%), soft spinifex grass (Triodia pungens) (53%), mulga (A. aneura) (42%), desert oak (Allocasuarina decaisneana) (22%) and quandong (Santalum acuminatum) (0%). The sampling also detected that seedling recruitment was absent or minimal for all plants except soft spinifex, while a generalized linear mixed model (GLMM) indicated two-way interactions among species, plant size and stand density as important predictors of drought survival of adult plants. A substantial loss of biodiversity has occurred at UKTNP during the recent drought, with likely drivers of widespread plant mortality being extreme multi-year rainfall deficit (2019 recorded the lowest-ever annual rainfall at UKTNP [27 mm]) and record high summer temperatures (December 2019 recorded the highest-ever temperature [47.1°C]). Our findings indicate that widespread plant death and extensive vegetation restructuring will occur across arid Australia if the severity and frequency of droughts increase under climate change.     

Photo-induction of electrical current with the cyanobacteriumAgmenellum quadruplicatum PR-6

We investigated the possibility of eliciting a measurable photoinduced electrical current from the cyanobacteriumAgmenellum quadruplicatum PR-6 (Synechococcus PCC 7002). This proved virtually impossible for intact cells. However, treated PR-6 cells fixed in an alginate matrix on tin oxide as the active electrode in a three electrode electrochemical cell gave rise to a significant light response. Cell treatments involving toluene, chloroform or detergents were effective and gave current responses up to 250 nA. Drying the cyanobacterial matrix increased the current yield at least fifty-fold. These effects were observed for light wavelengths > 650 nm and were not influenced by inhibitors or enhancers of photosynthesis nor by sustained argon bubbling of the electrolyte.French pressure cell lysates facilitated distinction between two light induced current components. Lysates prepared without CaCl₂ gave current induction kinetics that were indistinguishable from those on chemically treated cells i.e. slowly rising to a stable maximum in 10–15 min. When CaCl₂ was present during lysis, a rapidly induced (<1 s) unstable component was observed. Toluenization of PR-6 either prior to or post lysing abolished the CaCl₂ related effect. CaCl₂ had no effect on current induction in strain PR-6008, which lacked the and subunits of phycocyanin and exhibited slow current induction kinetics.The observed effects are interpreted as responses of components of the photosystems of PR-6 rather than in terms of an integrated photosynthetic process.     

Influences of habitat features and human disturbance on use of breeding sites by a declining population of southern fur seals (Arctocephalus australis)

Southern fur seals Arctocephalus australis in Peru have declined gradually over the past decade, and declined dramatically (72%) as a result of low food availability during the severe El Niño in 1997–98. In 1999, seals abandoned some historically important breeding sites. This is particularly alarming because new sites were not colonized. Our objective was to examine how habitat features and human disturbance influenced whether sites were currently used, abandoned or apparently not used in the past by fur seals for breeding. Data were collected on 14 variables at 70 potential breeding sites at three guano reserves in Peru. Discriminant analysis revealed significant multivariate differences among sites currently used for breeding, abandoned sites and unused sites ( F =5.97, P <0.00001), and the model classified 74% of sites correctly. Currently used sites were less likely to have human disturbance and more likely to have offshore islands, stacked rocks, tide pools and abundant shade. Separate discriminant analyses for each reserve produced similar results. Habitat associated with thermoregulation (e.g. shade or pools) may be more important to fur seals in Peru, which breed at lower latitudes and are at greater risk of overheating on land than other populations. Habitat with minimized human access may be especially important to seals in small populations in which individuals may perceive themselves as more vulnerable because of decreased vigilance and dilution effects. Seals in our study selected breeding habitat with stacked rocks, which create shade and tide pools for thermoregulation and make human access difficult; but pups might suffer higher mortality in this habitat. We hypothesize that fur seals in Peru may exhibit an Allee effect, whereby suitability of habitat varies with population abundance.     

Quaternary structure,Mg2+ interactions,and some kinetic properties of the (β-galactosidase fromThermoanaerobacterium thermosulfurigenes EM1

Theβ-galactosidase fromThermoanaerobacterium thermosulfurigenes EM1 was found to be a dimer with a monomer molecular weight of about 85,000. It lacks theα-peptide and an importantα-helix that are both needed for dimer-dimer interaction and there is no homology in other important dimer-dimer interaction areas. These differences in structure probably account for the dimeric (rather than tetrameric) structure. Only 0.19 Mg²⁺ bound per monomer and Mg²⁺ had only small effects on the activity and heat stability. The absence of residues equivalent to Glu-416 and His-418 (two of the three ligands to Mg²⁺ in theβ-galactosidase fromEscherichia coli) probably accounts for the low level of Mg²⁺ binding and the consequent lack of response to Mg²⁺. Both Na⁺ and K⁺ also had no effect on the activity. The enzyme activity witho-nitrophenyl-β-D-galactopyanoside (ONPG) was very similar to that withp-nitrophenyl-β-D-β-D-galactopyranoside (PNPG) and the ONPG pH profile was very similar to the PNPG pH profile. These differences are in contrast to theE. coli β-galactosidase, which dramatically discriminates between these two substrates. The lack of discrimination by theT. thermosulfurigenes β-galactosidase could be due to the absence of the sequence equivalent to residues 910-1023 of theE. coli β-galactosidase. Trp-999 is probably of the most importance. Trp-999 of theE. coli β-galactosidase is important for aglycone binding and ONPG and PNPG differ only in their aglycones. The suggestion that the aglycone site of theT. thermosulfurigenes β-galactosidase is different was strengthened by competitive inhibition studies. Compared toE. coli β-galactosidase, D-galactonolactone was a very good inhibitor of theT. thermosulfurigenes enzyme, while L-ribose inhibited poorly. These are transition-state analogs and the results indicate thatT. thermosulfurigenes β-galactosidase binds the transition state differently than doesE. coli β-galactosidase. Methanol and glucose were good acceptors of galactose, and allolactose was formed when glucose was the acceptor. Allolactose could not, however, be detected by TLC when lactose was the substrate. The differences noted may be due to the thermophilic nature ofT. thermosulfurigenes.     

Isolation of carp cDNA clones,representing developmentally-regulated genes,using a subtractive-hybridization strategy

A subtractive-hybridization technique, combined with differential screenings and subsequent whole mount in situ hybridization (ISH) reactions, was used to isolate novel cDNA clones representing developmentally-regulated genes of carp. Small-scale differential screenings of an oocyte and a segmentation-stage cDNA library using oocyte-specific and segmentation stage-specific enriched probes, yielded 75 positive clones. ISH screening showed that 65% (15) of the oocyte-stage clones and 50% (26) of the segmentation-stage clones were indeed stage-specific. Partial sequence analysis suggests that approximately 65% of the 41 stage-specific clones represent novel genes. In addition, an Otxl clone was isolated. Two novel clones and the Otxl clone are of special interest for developmental studies. The clones represent genes that are locally expressed during embryonic development. The expression patterns of Otxl and one of the novel clones suggest functions in specification of the anterior-posterior axis. The three clones provide molecular markers for the study of gastrulation and the patterning of the a-p axis in teleosts.