Snapshot prediction of carbon productivity,carbon and protein content in a Southern Ocean diatom using FTIR spectroscopy

Diatoms, an important group of phytoplankton, bloom annually in the Southern Ocean, covering thousands of square kilometers and dominating the region''s phytoplankton communities. In their role as the major food source to marine grazers, diatoms supply carbon, nutrients and energy to the Southern Ocean food web. Prevailing environmental conditions influence diatom phenotypic traits (for example, photophysiology, macromolecular composition and morphology), which in turn affect the transfer of energy, carbon and nutrients to grazers and higher trophic levels, as well as oceanic biogeochemical cycles. The paucity of phenotypic data on Southern Ocean phytoplankton limits our understanding of the ecosystem and how it may respond to future environmental change. Here we used a novel approach to create a ‘snapshot'' of cell phenotype. Using mass spectrometry, we measured nitrogen (a proxy for protein), total carbon and carbon-13 enrichment (carbon productivity), then used this data to build spectroscopy-based predictive models. The models were used to provide phenotypic data for samples from a third sample set. Importantly, this approach enabled the first ever rate determination of carbon productivity from a single time point, circumventing the need for time-series measurements. This study showed that Chaetoceros simplex was less productive and had lower protein and carbon content during short-term periods of high salinity. Applying this new phenomics approach to natural phytoplankton samples could provide valuable insight into understanding phytoplankton productivity and function in the marine system.     

Reducing HIV Risk among Transgender Women in Thailand: A Quasi-Experimental Evaluation of the Sisters Program

Transgender women are particularly at risk of HIV infection, but little evidence exists on effective HIV prevention strategies with this population. We evaluated whether Sisters, a peer-led program for transgender women, could reduce HIV risks in Pattaya, Thailand. The study used time-location sampling to recruit 308 transgender women in Pattaya into a behavioral survey in 2011. Coarsened exact matching was used to create statistically equivalent groups of program participants and non-participants, based on factors influencing likelihood of program participation. Using multivariable logistic regression, we estimated effects of any program participation and participation by delivery channel on: condom use at last sex; consistent condom and condom/water-based lubricant use in the past 3 months with commercial, casual, and regular partners; and receipt of HIV testing in the past 6 months. Program coverage reached 75% of the population. In a matched sub-sample (n = 238), participation in outreach was associated with consistent condom/water-based lubricant use with commercial partners (AOR 3.22, 95% CI 1.64–6.31). Attendance at the Sisters drop-in center was associated with receiving an HIV test (AOR 2.58, 95% CI 1.47–4.52). Dedicated transgender-friendly programs are effective at reducing HIV risks and require expansion to better serve this key population and improve HIV prevention strategies.     

Studies on the Development of the Desiccation-sensitive (Recalcitrant) Seeds of Avicennia marina (Forssk.) Vierh.: The Acquisition of Germinability and Response to Storage and Dehydration

Germinability and responses to storage and dehydration werestudied throughout the development of the desiccation-sensitiveseeds of Avicennia marina. Seeds acquired the ability to produceroots at 55 d after fruit set (DAFS) which is shortly afterhistodifferentiation, but the capacity for full germinability(seedling establishment) was not attained until 70 DAFS, whichis midway through the phase of growth and reserve accumulation.Pre-mature seeds showed a germination lag that was equivalentto the period between harvest and full maturity, but, followingshort-term storage, this was reduced to that of mature seeds.At no stage, however, would seeds with an intact pericarp germinate. Once seeds were fully germinated, storage lifespan under non-desiccatingconditions was independent of developmental stage, but was considerablyreduce by the presence of the pericarp, probably because offungal contamination. Prior to the acquisition of full germinationcapacity, the seeds were unable to tolerate any dehydrationbut became tolerant to slight water loss once they became fullygerminable, after which desiccation sensitivity was not influencedby the stage of development. If rapidly dried, excised axesof germinable seeds survived to lower water contents than didaxes removed from seeds following slower drying.Copyright 1993,1999 Academic Press Desiccation-tolerance/sensitivity, germination, mangrove, recalcitrant, seed development, seed storage     

Scanning and transmission electron microscopic study of the supraependymal macrophages in the lateral ventricles of the toad brain

Transmission and scanning electron microscopy of the lateral ventricles of the toad brain revealed the presence of supraependymal cells that have the features of macrophages. Based solely on their surface morphology three different cell forms could be identified. The most frequently observed cells are flat and multipolar, and have a smooth or ruffled surface. The second type is spherical with a ruffled surface and occurs either singly, in which case it lacks processes, or in clusters from which processes radiate. The third type has surface blebs and numerous thin, smooth processes. However, when specimens that had been examined in the scanning electron microscope are viewed in the transmission electron microscope, all cells appear to belong to a single cell type. All cells viewed closely resemble macrophages in that they contain nuclei with clumped chromaffin, single cisternae of rough endoplasmic reticulum, numerous dense bodies, and many Golgi complexes. In addition, when horseradish peroxidase (HRP) was perfused into the ventricles, reaction product was found a short time thereafter within cytoplasmic vacuoles, and after a longer period within dense bodies. Because of their ultrastructural resemblance to macrophages and their capacity to ingest HRP, we suggest that these cells function as phagocytes and, as such, act to remove foreign materials from the cerbrospinal fluid.     

Excitatory amino acid receptor-channels in Purkinje cells in thin cerebellar slices.

Glutamate receptors of the N-methyl-D-aspartate (NMDA) and non-NMDA type serve different functions during excitatory synaptic transmission. Although many central neurons bear both types of receptor, the evidence concerning the sensitivity of cerebellar Purkinje cells to NMDA is contradictory. To investigate the receptor types present in Purkinje cells, we have used whole-cell and outside-out patch-clamp methods to record from cells in thin cerebellar slices from young rats. At a holding potential of -70 mV (in nominally Mg(2+)-free medium, with added glycine) NMDA caused a whole-cell current response which consisted of a dramatic increase in the frequency of synaptic currents. In the presence of tetrodotoxin (TTX) and the gamma-aminobutyric acidA (GABAA) receptor antagonist bicuculline, spontaneous synaptic currents and responses to NMDA were inhibited. In a proportion of cells a small polysynaptic response to NMDA persisted, which was further reduced by the non-NMDA receptor antagonist 6-cyano-2,3-dihydro-7-nitroquinoxalinedione (CNQX). The non-NMDA glutamate receptor agonists kainate (KA), quisqualate (QA) and s-alpha-amino-3-hydroxy-5-methyl-4-isoazolepropionic acid (s-AMPA), evoked large inward currents due to the direct activation of receptors in Purkinje cells. NMDA applied to excised membrane patches failed to evoke any single-channel currents, whereas s-AMPA and QA caused small inward currents accompanied by marked increases in current noise. Spectral analysis of the s-AMPA noise in patches gave an estimated mean channel conductance of approximately 4 pS.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evidence for cytosolic benzo(a)pyrene carrier proteins which function in cytochrome P450 oxidation in rat liver

Solutions of cytosolic proteins from rat liver contain benzo(a)pyrene solubilizing activity capable of serving as a carrier between solid state benzo(a)pyrene and microsomal cytochrome P₄₅₀. Fractionation of benzo(a)pyrene-saturated cytosolic proteins on a Sephadex G-100 column or by sucrose density gradients produced benzo(a)pyrene peaks of about 46,000 daltons and a very high molecular weight material. The protein-bound benzo(a)pyrene obtained in both peaks was oxidized rapidly by microsomes in the presence of NADPH, indicating that the benzo(a)pyrene carrier activity is capable of presenting the substrate to the cytochrome P₄₅₀. Liver cytosolic proteins from rats receiving intraperitoneal injection of [¹⁴C] benzo(a)pyrene was chromatographed on a column of Sephadex G-75. Radioactivity eluted at the same positions of the chromatogram as did the carrier activities described above. These results indicate that these benzo(a)pyrene carrier proteins may have an $\text{in}\text{vivo}$ role in the metabolism of benzo(a)pyrene.     

Stimulation of sugar transport in rat diaphragm by 8-bromoguanosine 3′,5′-monophosphate

The cyclic GMP derivative, 8-bromo cyclic GMP, increases the uptake of D-xylose and of 2-deoxy D-glucose into intact rat diaphragm incubated in vitro. 8-Bromo cyclic GMP does not stimulate the incorporation of [¹⁴C] glucose into glycogen in the diaphragm, or the uptake of α-amino isobutyric acid into this tissue. The effect of 8-bromo cyclic GMP on the diaphragm is consistent with the hypothesis that cyclic GMP plays a role in the regulation of sugar transport in muscle.