Light-induced membrane protein phosphorylation in the bovine rod outer segment. A magic angle spinning 31P-NMR study

Magic angle spinning 31P-NMR (MAS 31P-NMR) spectra of bovine rod outer segments, unphosphorylated and phosphorylated, were obtained. In the phosphorylated samples the spectra showed new resonances not assignable to phospholipids. These signals were present only when stimulation of receptor phosphorylation occurred. These resonances were not due to exogenous, soluble phosphorus-containing compounds. Limited proteolysis to remove the carboxyl-terminal region of the photoreceptor that contains the phosphorylation sites removed these resonances. The chemical shifts were in the usual range for serine phosphate and threonine phosphate. The pKa obtained from a pH titration of the 31P chemical shift was typical of serine phosphate. Therefore, these 31P-NMR resonances were assigned to the phosphorylation sites on membrane proteins in the rod outer segment disk membranes. Static 31P-NMR measurements revealed that at least some of these sites gave rise to relatively narrow resonances, indicative of considerable motional freedom of the carboxyl-terminal segment of the photoreceptor when phosphorylated. These data indicate that it is possible to study phosphorylation sites on membrane proteins using MAS 31P-NMR, and that using in vivo 31P 'spin labelling' one can study directly and selectively regions of receptors crucial to receptor function.     

Modeling perimenopause in Sprague-Dawley rats by chemical manipulation of the transition to ovarian failure

Various age-related diseases increase in incidence during perimenopause. However, our understanding of the effects of aging compared with hormonal changes of perimenopause in mediating these disease risks is incomplete, in part due to the lack of an experimental perimenopause model. We therefore aimed to determine whether manipulation of the transition to ovarian failure in rats via the use of 4-vinylcyclohexene diepoxide (VCD) could be used to model and accelerate hormonal changes characteristic of perimenopause. We examined long-term (11 to 20 mo), dose-dependent effects of VCD on reproductive function in 1- and 3-mo-old female Sprague-Dawley rats. Twenty-five daily doses of VCD (80 or 160 mg/kg daily compared with vehicle alone) depleted ovarian follicles in a dose-dependent fashion in rats of both ages, accelerated the onset of acyclicity, and caused dose-dependent increases in follicle-stimulating hormone that exceeded those naturally occurring with age in control rats but left serum levels of 17β-estradiol unchanged, with continued ovarian production of androstenedione. High-dose VCD caused considerable nonovarian toxicities in 3-mo-old Sprague-Dawley rats, making this an unsuitable model. In contrast, 1-mo-old rats had more robust dose-dependent increases in follicle-stimulating hormone without evidence of systemic toxicity in response to either VCD dose. Because perimenopause is characterized by an increase in follicle-stimulating hormone with continued secretion of ovarian steroids, VCD acceleration of an analogous hormonal milieu in 1-mo-old Sprague-Dawley rats may be useful for probing the hormonal effects of perimenopause on age-related disease risk.     

Sex differences in salivary cortisol in response to acute stressors among healthy participants, in recreational or pathological gamblers, and in those with posttraumatic stress disorder

Sex differences in incidence and severity of some stress-related, neuropsychiatric disorders are often reported to favor men, suggesting that women may be more vulnerable to aberrant hypothalamic-pituitary-adrenal (HPA) axis responses to stress. In this review, we discuss several investigations that we, and others, have conducted assessing salivary cortisol as a measure of HPA function. We have examined basal cortisol among healthy men and women and also following acute exposure to stressors. Among healthy participants, men had higher basal cortisol levels than did women. In response to acute stressors, such as carbon dioxide or noise, respectively, cortisol levels were comparable between men and women or higher among women. We have also examined cortisol levels among those with problem eating, gambling, or posttraumatic stress disorder (PTSD). Women with restrained eating habits have higher basal cortisol levels than do women without restrained eating habits. Pathological gamblers have more aberrant stress response to gambling stimuli than do recreational gamblers, and these effects are more prominent among men than women. Men who have motor vehicle accident related PTSD, demonstrate more aberrant cortisol function, than do their female counterparts. Although these sex differences in cortisol seem to vary with type of stress exposure and/or pathophysiological status of the individual, other hormones may influence cortisol response. To address this, cortisol levels among boys and girls with different stress-related experiences, will be the subject of future investigation.     

Characterization of groups of the zygomycete genusRhizopus

Rhizopus is a zygomycetous genus. Several species of this taxon may infect humans and lower animals. Seventeen isolates ofRhizopus species in three distinct morphological groups were studied: the stolonifer group (sporangiophores greater than 1 mm in height, sporangial diameters of 100–275 µm, branched rhizoids); the arrhizus group (sporangiophores greater than 1 mm in height, branched rhizoids, sporangial diameters of 100–240 µm); and the microsporus group (sporangiophores less than 0.8 mm in height, sporangial diameters less than 100 µm, simple rhizoids). Maximal growth temperatures were characteristic: the stolonifer group grew at 30°C, the arrhizus group grew at 36°C, and the microsporus group grew at 45°C. The DNA mol% G + C base composition of all isolates ranged from 34.9 to 40.2% Species within the three groups were grouped by DNA differences. The arrhizus group was most distinctive with a value of 34.9–36.3%; the stolonifer and microsporus groups had G + C values of 37.0–39.3% and 37.8–40.2%, respectively. Our research clarifies and defines the G-C values of the three important groups ofRhizopus species.     

Figure tracking by flies is supported by parallel visual streams

Visual figures may be distinguished based on elementary motion or higher-order non-Fourier features, and flies track both. The canonical elementary motion detector, a compact computation for Fourier motion direction and amplitude, can also encode higher-order signals provided elaborate preprocessing. However, the way in which a fly tracks a moving figure containing both elementary and higher-order signals has not been investigated. Using a novel white noise approach, we demonstrate that (1) the composite response to an object containing both elementary motion (EM) and uncorrelated higher-order figure motion (FM) reflects the linear superposition of each component; (2) the EM-driven component is velocity-dependent, whereas the FM component is driven by retinal position; (3) retinotopic variation in EM and FM responses are different from one another; (4) the FM subsystem superimposes saccadic turns upon smooth pursuit; and (5) the two systems in combination are necessary and sufficient to predict the full range of figure tracking behaviors, including those that generate no EM cues at all. This analysis requires an extension of the model that fly motion vision is based on simple elementary motion detectors and provides a novel method to characterize the subsystems responsible for the pursuit of visual figures.     

Fly flight: a model for the neural control of complex behavior.

Flies exhibit a repertoire of aerial acrobatics unmatched in robustness and aerodynamic sophistication. The exquisite control of this complex behavior emerges from encoding intricate patterns of optic flow, and the translation of these visual signals into the mechanical language of the motor system. Recent advances in experimental design toward more naturalistic visual and mechanosensory stimuli have served to reinforce fly flight as a key model system for understanding how feedback from multiple sensory modalities is integrated to control complex and robust motor behaviors across taxa.     

Expression and sequence analysis of a Treponema pallidum gene, tpn38(b), encoding an exported protein with homology to T. pallidum and Borrelia burgdorferi proteins

Abstract An Escherichia coli clone containing recombinant plasmid C19 was identified from a Treponema pallidum genomic DNA library by in situ immunoassay. E. coli maxicells containing pC19 synthesized a treponemal protein doublet of 39.2 and 38.2 kDa, designated TpN38(b). Pulse-chase and protein processing studies showed that TpN38(b) is synthesized with a cleavable amino-terminal signal peptide. A 2.0-kb fragment of pC19 containing the tpn38(b) gene was subcloned and sequenced. The tpn38(b) gene is 1029 nucleotides long and encodes a protein of 343 amino acids with a calculated molecular mass of 37.9 kDa. The deduced amino acid sequence of TpN38(b) has homology with the T. pallidum TpN35 lipoprotein and the Borrelia burgdorferi BmpA, BmpB, BmpC, and BmpD proteins.