Ultracytochemistry of cholera-toxin binding sites in ciliary processes

Summary Cholera toxin reduces the rate of formation of aqueous humor in concentrations (10^–11 M) that do not disturb the morphology of the aqueoushumor forming epithelial cells of the ciliary processes of the rabbit eye. The search for an endogenous mediator of aqueous-humor formation comparable to cholera toxin in its mode of operation prompted us to map the distribution of cell surface receptors for cholera toxin in the ciliary processes of the eyes of rabbits. Cytochemical studies were carried out with the use of conjugates of cholera toxin to fluorescein isothiocyanate (CT-FITC) and to horseradish peroxidase (CT-HRP), and of the B subunit of cholera toxin to horseradish peroxidase (B-HRP). Multiple fluorescent CT-FITC binding sites were observed on the outer nonpigmented epithelial layer near the crests of the processes. Processes incubated with CT-HRP in vitro showed surface staining of 30–40% of the nonpigmented epithelial cells. A prominent reaction product was observed along the basal and lateral plasma membranes of these cells. In vivo studies carried out after arterial infusion of B-HRP showed a reproducible dense reaction product between the apical surfaces of the pigmented epithelium (PE) and of the nonpigmented epithelium (NPE) facing each other. Aggregations of reaction product were observed with the electron microscope in the extracellular space between the apices of PE and NPE. The apical plasma membrane of the endothelium of the blood vessels near the crests of the ciliary processes was stained after either in vivo or in vitro exposure to peroxidase conjugates. These findings indicate that the cell-surface receptors which mediate the action of cholera toxin on aqueous humor formation are very likely localized in the apical plasma membranes of the epithelium of the ciliary processes.Supported in part by USPHS grant # EY-00237, the Connecticut Lions Eye Research Foundation, Inc., and Research to Prevent Blindness, Inc.     

Thermoregulation in premature infants: A mathematical model

PurposeIn 2010, approximately 14.9 million babies (11.1%) were born preterm. Because preterm infants suffer from an immature thermoregulatory system they have difficulty maintaining their core body temperature at a constant level. Therefore, it is essential to maintain their temperature at, ideally, around 37 °C. For this, mathematical models can provide detailed insight into heat transfer processes and body-environment interactions for clinical applications.MethodsA new multi-node mathematical model of the thermoregulatory system of newborn infants is presented. It comprises seven compartments, one spherical and six cylindrical, which represent the head, thorax, abdomen, arms and legs, respectively. The model is customizable, i.e. it meets individual characteristics of the neonate (e.g. gestational age, postnatal age, weight and length) which play an important role in heat transfer mechanisms. The model was validated during thermal neutrality and in a transient thermal environment.ResultsDuring thermal neutrality the model accurately predicted skin and core temperatures. The difference in mean core temperature between measurements and simulations averaged 0.25±0.21 °C and that of skin temperature averaged 0.36±0.36 °C. During transient thermal conditions, our approach simulated the thermoregulatory dynamics/responses. Here, for all infants, the mean absolute error between core temperatures averaged 0.12±0.11 °C and that of skin temperatures hovered around 0.30 °C.ConclusionsThe mathematical model appears able to predict core and skin temperatures during thermal neutrality and in case of a transient thermal conditions.     

The discursive detachment of race from gentrification in Cartagena de Indias,Colombia

In this article, I provide an ethnographic account of the gentrification process and its relationship to race and racism in the community of Getsemaní in Cartagena de Indias, Colombia. I introduce Racial Attachment Processes as a conceptual framework for understanding how individuals reconcile Latin American discourses that suggest that race is not a primary stratifying principle with the material spatial realities of racial hierarchies that counter such discourses. Drawing on ethnographic participant observation and semi-structured interviews, including those employing photo-elicitation, I demonstrate how people discursively mobilize race in everyday life, yet selectively detach race in ways that allow them to interpret processes of gentrification as untethered to their racial underpinnings. This paper ultimately demonstrates how the discursive detachment of race from understandings of Colombian socio-spatial, political and economic relations obscures the relationship between racial domination and social inequality.     

Microbial activities in soils of a healthy and a declining reed stand

Microbial processes were investigated in the soil of a declining, more eutrophic (Romberk West) and a healthy looking, less eutrophic (Romberk East) freshwater reed stand. Soil was sampled monthly from June to September 1997. Glucose induced carbon dioxide (CO₂) production in oxic and anoxic conditions, methane (CH₄) production, nitrification and denitrification activities were measured in laboratory conditions in suspensions prepared from homogenised soil samples. Within a stand the proportion of anaerobic (as opposed to aerobic) microbial activity was greatest in June. Potential methanogenesis was highest in June and decreased later in both stands. Methane production was approximately the same in June at both stands but it was higher at Romberk East than at Romberk West stand in later months. Denitrifying activity was higher in August than July at both stands. Nitrifying activity was undetectable at both stands over the entire study period. Generally Romberk West was more anaerobic than Romberk East, with lower redox potential, higher amounts of oxygen-consuming organic matter and a lower ratio of CO₂ production in oxic conditions to CO₂ production in anoxic conditions. Microbial activity was apparently restricted at Romberk West stand in comparison to Romberk East. The shift from aerobic to anaerobic microbial metabolism and a coinciding restriction of metabolic activities at Romberk West are thought to be indicative of a strengthened oxygen stress in the soil, associated with accumulation of metabolites toxic to both the microorganisms and the reed. Possible links between eutrophication, microbial characteristics and reed performance are discussed.     

Carbon nanotubes promote Cr(VI) reduction by alginate-immobilized Shewanella oneidensis MR-1

Bioreduction of hexavalent chromium (Cr(VI)) into trivalent one (Cr(III)) based on microbial immobilization techniques has been recognized as a promising way to remove Cr contaminants from wastewater. However, such a bioreduction process is inefficient due to limited electron transfer through the immobilization matrix. In this study, a modified immobilization process was proposed by impregnating carbon nanotubes (CNTs) into Ca-alginate beads, which were then used to immobilize Shewanella oneidensis MR-1 for enhanced Cr(VI) reduction. Compared with the free cells and the beads without CNTs, the AL/CNT/cell beads showed up to 4 times higher reduction rates, mainly attributed to an enhanced electron transfer by the CNTs. In addition, the dose of CNTs greatly improved the stability of beads, suggesting a high feasibility of the AL/CNT/cell beads for repeated use. The optimized CNT concentration, temperature and pH for Cr(VI) reduction by the AL/CNT/cell beads were 0.5%, 30 °C and 6.0–7.0, respectively.     

Exact results for fixation probability of bithermal evolutionary graphs

One of the most fundamental concepts of evolutionary dynamics is the “fixation” probability, i.e. the probability that a mutant spreads through the whole population. Most natural communities are geographically structured into habitats exchanging individuals among each other and can be modeled by an evolutionary graph (EG), where directed links weight the probability for the offspring of one individual to replace another individual in the community. EGs have recently spurred huge interest, as it has been shown that some topology can amplify or suppress the effect of beneficial mutations. Very few exact analytical results however are known for EGs. In this article we show that the use of a new technique, the fixed point of probability generating function, allows us to compute the exact fixation probability for a large subset of bithermal graphs. We also show by numerical simulations that the computed solution holds for all bithermal graphs. Moreover, the analytical solution allows us to clarify the opposing consequences of birth–death versus death–birth processes as amplifier or suppressor of beneficial mutations for the same bithermal topology.     

Practical considerations in the study of spectral analysis of discrete processes

Abstract

Clock hour independent groups of young female rats received a series of 3 alternate day intra‐articular injections of methylprednisolone acetate. All rats lost body weight, but the change was minimal when the injections were given in the late afternoon (‐30.8 g) vs the night (‐42.4 g, P < .02). The data imply that methylprednisolone acetate, which is designed to be locally active in joint spaces, can be absorbed into the circulation and that the rate of absorption is subject to circadian control.     

Turning food waste to energy and resources towards a great environmental and economic sustainability: An innovative integrated biological approach

Food waste (FW) management is a global conundrum because of the rapid population growth and growing economic activity. Currently, incineration and landfill are still the main means for FW management, while their environmental sustainability and economic viability have been in question. Recently, the biological processes including anaerobic digestion, aerobic composting, bioethanol fermentation, feed fermentation etc. have attracted increasing interest with the aims for energy and resource recovery from FW. However, these biological approaches have inherent drawbacks, and cannot provide a comprehensive solution for future FW management. Therefore, this review attempts to offer a critical and holistic analysis of current biotechnologies for FW management with the focus on the challenges and solutions forward. The biological approaches towards future FW management should be able to achieve both environmental sustainability and economic viability. In this instance, the concept of zero solid discharge-driven resource recovery has thus been put forward. According to which, several innovative biological processes for FW management are further elucidated with critical analysis on their engineering feasibility and environmental sustainability. It turns out that is an urgent need for turning current single task-orientated bioprocess to an integrated biological process with multiple tasks of concurrent recovery of water, resource and energy together with zero-solid discharge.