Estrogen dependent ciliogenesis in the chick oviduct

Both the hormone dependency and the morphological details of estrogen-dependent ciliogenesis in the shell gland of the chick oviduct were investigated. Ciliogenesis was initiated on day 3 of estrogen treatment, and progressively more cells became differentiated until, on day 10, 55% ciliation occurred with 17-estradiol (1 mg/day) and 75% ciliation occurred with diethylstilbestrol (1 mg/day). Simultaneous administration of progesterone with diethylstilbestrol (1 mg each/day for 10 days) caused a 50% depression in the number of ciliated cells on day 10. The rate of ciliogenesis was found to be affected by progesterone and the type of estrogen administered. The minimum stimulatory dose of estradiol was found to be between 0.01 mg/day and 0.05 mg/day. Ciliogenic cells were first recognized by the appearance of pro-basal bodies in the apical portion of the cell. Pro-basal body maturation and cilium formation were the same as those described for the chick trachea. Ciliogenesis in the chick was found to be homologous to estrogen-dependent ciliogenesis in various mammalian oviducts.     

Proton relay mechanism of general acid catalysis by DNA topoisomerase IB.

Type IB topoisomerases cleave and rejoin DNA through a DNA-(3'-phosphotyrosyl)-enzyme intermediate. A constellation of conserved amino acids (Arg-130, Lys-167, Arg-223, and His-265 in vaccinia topoisomerase) catalyzes the attack of the tyrosine nucleophile (Tyr-274) at the scissile phosphodiester. Previous studies implicated Arg-223 and His-265 in transition state stabilization and Lys-167 in proton donation to the 5'-O of the leaving DNA strand. Here we find that Arg-130 also plays a major role in leaving group expulsion. The rate of DNA cleavage by vaccinia topoisomerase mutant R130K, which was slower than wild-type topoisomerase by a factor of 10(-4.3), was stimulated 2600-fold by a 5'-bridging phosphorothiolate at the cleavage site. The catalytic defect of the R130A mutant was also rescued by the 5'-S modification (190-fold stimulation), albeit to a lesser degree than R130K. We surmise that Arg-130 plays dual roles in transition state stabilization and general acid catalysis. Whereas the R130A mutation abolishes both functions, R130K permits the transition state stabilization function (via contact of lysine with the scissile phosphate) but not the proton transfer function. Our results show that the process of general acid catalysis is complex and suggest that Lys-167 and Arg-130 comprise a proton relay from the topoisomerase to the 5'-O of the leaving DNA strand.     

Sociosexual behavioral patterns involving nulliparous female orangutans (Pongo sp.) reflect unique challenges during the adolescent period

The primate adolescent period is characterized by a series of changes in physiology, behavior, and social relationships. Orangutans have the slowest life history and the longest period of dependency of all primates. As members of a semisolitary species with high levels of sexual coercion, adolescent female orangutans face a unique combination of challenges when achieving independence from their mother. This study examined the mating behavior of adolescent female orangutans and compared it with that of adult females to assess whether mating behavior reflects distinct strategies at these different points in the life cycle. Data were collected in Gunung Palung National Park on the island of Borneo over 20 years. Mating events from adolescent (n = 19) and adult females (n = 26) were scored and compared. Adolescent female mating events had significantly higher mating scores (indicating more proceptivity) than those of adult females (β = 1.948, p = .001). Adolescent females also engaged in elaborate sociosexual interactions with different flanged males, behaviors that were never observed during mating events of adult females. These interactions involved characteristic behavior on the part of both the adolescent females and the flanged males. Given these findings and the documentation of similar accounts of adolescent female–flanged male mating from the island of Sumatra, we propose that adolescent female orangutans display distinctive behavioral repertoires throughout the genus Pongo which serves to overcome male ambivalence toward nulliparous females, establish familiarity, and evaluate coercive tendencies in flanged males. We suggest that these behavioral patterns are an integral part of female social development in a female philopatric, but highly dispersed species where consistent social support is absent after ranging independence is achieved.     

Disease hotspots or hot species? Infection dynamics in multi‐host metacommunities controlled by species identity,not source location

Pathogen persistence in host communities is influenced by processes operating at the individual host to landscape‐level scale, but isolating the relative contributions of these processes is challenging. We developed theory to partition the influence of host species, habitat patches and landscape connectivity on pathogen persistence within metacommunities of hosts and pathogens. We used this framework to quantify the contributions of host species composition and habitat patch identity on the persistence of an amphibian pathogen across the landscape. By sampling over 11 000 hosts of six amphibian species, we found that a single host species could maintain the pathogen in 91% of observed metacommunities. Moreover, this dominant maintenance species contributed, on average, twice as much to landscape‐level pathogen persistence compared to the most influential source patch in a metacommunity. Our analysis demonstrates substantial inequality in how species and patches contribute to pathogen persistence, with important implications for targeted disease management.     

Forging a path to mesoscopic imaging success with ultra-high field functional magnetic resonance imaging

Functional magnetic resonance imaging (fMRI) studies with ultra-high field (UHF, 7+ Tesla) technology enable the acquisition of high-resolution images. In this work, we discuss recent achievements in UHF fMRI at the mesoscopic scale, on the order of cortical columns and layers, and examine approaches to addressing common challenges. As researchers push to smaller and smaller voxel sizes, acquisition and analysis decisions have greater potential to degrade spatial accuracy, and UHF fMRI data must be carefully interpreted. We consider the impact of acquisition decisions on the spatial specificity of the MR signal with a representative dataset with 0.8 mm isotropic resolution. We illustrate the trade-offs in contrast with noise ratio and spatial specificity of different acquisition techniques and show that acquisition blurring can increase the effective voxel size by as much as 50% in some dimensions. We further describe how different sources of degradations to spatial resolution in functional data may be characterized. Finally, we emphasize that progress in UHF fMRI depends not only on scientific discovery and technical advancement, but also on informal discussions and documentation of challenges researchers face and overcome in pursuit of their goals.This article is part of the theme issue ‘Key relationships between non-invasive functional neuroimaging and the underlying neuronal activity’.     

Changes in knee joint muscle activation patterns during walking associated with increased structural severity in knee osteoarthritis

PurposeTo determine whether alterations in knee joint muscle activation patterns during gait were related to structural severity determined by Kellgren–Lawrence (KL) radiographic grades, for those with a moderate knee OA classification.ScopeEighty-two individuals with knee OA, classified as moderate using a functional and clinical criterion were stratified on KL-grade (KL II, KL III and KL IV). Thirty-five asymptomatic individuals were matched for age and walking velocity. Lower limb motion and surface electromyograms from rectus femoris plus lateral and medial sites for the gastrocnemii, vastii and hamstring muscles were recorded during self-selected walking. Gait velocity and characteristics from sagittal plane knee angular displacement waveforms were calculated. Principal component analysis extracted amplitude and temporal features from electromyographic waveform. Analysis of variance models tested for main effects (group, muscle) and interactions (α = 0.05) for these features. No differences in anthropometrics, velocity, knee muscle strength and symptoms were found among the three OA groups (p > 0.05). Specific features from medial gastrocnemius, lateral hamstring and quadriceps amplitude and temporal patterns were significantly different among OA groups (p < 0.05).ConclusionsSystematic alterations in specific knee joint muscle activation patterns were associated with increasing structural severity based on KL-grades whereas other alterations were associated with the presence of OA.     

Antiviral Nucleoside Drug Delivery via Amino Acid Phosphoramidates

Abstract

Stable and water soluble amino acid phosphomonoester amidates of AZT were synthesized and shown to have potent anti-HIV-1 activity. Intracellular and cell extract metabolism studies revealed that these compounds are likely to be enzymatically converted to the corresponding monophosphates. In addition, we have shown that the half life and tissue distribution of a phosphoramidate of AZT is 5 and 10-fold greater, respectively, than AZT.     

Influence of community structure on the spatial distribution of critically endangered Dicerandra immaculata var. immaculata (Lamiaceae) at wild, introduced, and extirpated locations in Florida scrub

Community structure at local scales is a major factor controlling population and community dynamics of plant species. Dicerandra immaculata Lakela var. immaculata (Lamiaceae) is a critically endangered plant known only from a few locations in scrub habitat in Florida. Using seven sites where populations of D. immaculata were wild, introduced, and/or extirpated, we sought to answer the following questions: (1) how do habitat characteristics at locations supporting wild D. immaculata plants vary from random locations within the same habitat; (2) how do habitat characteristics differ between wild and extirpated populations; and (3) how do habitat characteristics differ between wild and introduced populations? At locations of wild D. immaculata, community structure had fewer woody stems, shorter understory vegetation, lower percent canopy coverage, and lower percent ground cover of detritus than random locations and locations with extirpated D. immaculata. In addition, bare ground decreased at extirpated locations because other plant species expanded their coverage, water saturation of the soil increased, diversity of shrubs decreased, and composition of the overstory changed compared to that of wild locations. Habitat characteristics associated with introduced plants were more similar to characteristics at randomly chosen locations than those with wild plants. However, introduced plants tended to occupy locations that had drier soil, a higher abundance of conspecifics, and a higher proportion of woody understory plants than that of random locations. Overall, gaps in the canopy and at ground level are likely essential for survival and recruitment of D. immaculata.     

No cumulative effect of 10 years of elevated [CO2] on perennial plant biomass components in the Mojave Desert

Elevated atmospheric CO₂ concentrations ([CO₂]) generally increase primary production of terrestrial ecosystems. Production responses to elevated [CO₂] may be particularly large in deserts, but information on their long‐term response is unknown. We evaluated the cumulative effects of elevated [CO₂] on primary production at the Nevada Desert FACE (free‐air carbon dioxide enrichment) Facility. Aboveground and belowground perennial plant biomass was harvested in an intact Mojave Desert ecosystem at the end of a 10‐year elevated [CO₂] experiment. We measured community standing biomass, biomass allocation, canopy cover, leaf area index (LAI), carbon and nitrogen content, and isotopic composition of plant tissues for five to eight dominant species. We provide the first long‐term results of elevated [CO₂] on biomass components of a desert ecosystem and offer information on understudied Mojave Desert species. In contrast to initial expectations, 10 years of elevated [CO₂] had no significant effect on standing biomass, biomass allocation, canopy cover, and C : N ratios of above‐ and belowground components. However, elevated [CO₂] increased short‐term responses, including leaf water‐use efficiency (WUE) as measured by carbon isotope discrimination and increased plot‐level LAI. Standing biomass, biomass allocation, canopy cover, and C : N ratios of above‐ and belowground pools significantly differed among dominant species, but responses to elevated [CO₂] did not vary among species, photosynthetic pathway (C₃ vs. C₄), or growth form (drought‐deciduous shrub vs. evergreen shrub vs. grass). Thus, even though previous and current results occasionally show increased leaf‐level photosynthetic rates, WUE, LAI, and plant growth under elevated [CO₂] during the 10‐year experiment, most responses were in wet years and did not lead to sustained increases in community biomass. We presume that the lack of sustained biomass responses to elevated [CO₂] is explained by inter‐annual differences in water availability. Therefore, the high frequency of low precipitation years may constrain cumulative biomass responses to elevated [CO₂] in desert environments.