Fourth-derivative spectrophotometry of proteins

Fourth-derivative spectrophotometry offers several advantages over classical absorption or difference spectrophotometry in examining the characteristics of aromatic amino acids in proteins. The basic principles of the technique and its applications are outlined.     

Induction of the blue form of bacteriohodopsin by low concentrations of sodium dodecyl sulfate

The effects produced on bacteriorhodopsin by low concentrations of several detergents have been studied by absorption and fourth-derivative spectrophotometry. Sodium dodecyl sulfate induces the appearance of the blue form of bacteriorhodopsin (λ_max = 600 nm) at pH values up to 7.0 in a reversible manner. The apparent pK of the purple-to-blue transition raised with increasing concentration of SDS. Of the other detergents tested, only sodium dodecyl-N-sarcosinate showed a slight red-shift of the absorption band to 580 nm, whereas sodium taurocholate, Triton X-100 and cetyltrimethylammonium bromide did not favour the appearance of the blue form. The effect of SDS was found to be consistent with a localized conformational change that moves away the counter-ion of the protonated Schiff base.     

Beta 1 and beta 2 adrenergic agonists in exocrine pancreatic secretion in the rabbit

The effect of Dobutamine (a beta 1-adrenergic agonist) and Terbutaline (a beta 2-adrenergic agonist) on exocrine pancreatic secretion was studied in anaesthetized rabbits, simultaneously controlling pancreatic blood flow and blood pressure. The secretion of fluid and ions (bicarbonate, sodium and potassium) was unaffected by the infusion of Dobutamine (8 micrograms.kg-1.min-1) or Terbutaline (10 micrograms.kg-1.min-1). Neither were pancreatic blood flow or mean blood pressure altered. Dobutamine or Terbutaline depress the function of the acinar cells, amylase secretion being more affected by the action of Terbutaline. The results show that beta 1 and beta 2-adrenergic stimulation has no effect on the ductular cells but does decrease the secretion by the acinar cells.     

A new technique for the treatment of palpebral bags

A new technique for the treatment of palpebral bags is presented. The technique consists of returning fat to the orbital cavity and retaining it by means of a continuous suture (with nonabsorbable filament) of the capsulopalpebral fascia to the periosteum of the lower orbital rim. The anatomic basis for the technique, after examination of the relevant literature and dissection on fresh cadavers, is analyzed. The procedure followed and results obtained are described in detail. Evaluation of the results suggests to the authors that this might be the method to be applied in the majority of patients.     

Soils in warmer and less developed countries have less micronutrients globally

Soil micronutrients are capital for the delivery of ecosystem functioning and food provision worldwide. Yet, despite their importance, the global biogeography and ecological drivers of soil micronutrients remain virtually unknown, limiting our capacity to anticipate abrupt unexpected changes in soil micronutrients in the face of climate change. Here, we analyzed >1300 topsoil samples to examine the global distribution of six metallic micronutrients (Cu, Fe, Mn, Zn, Co and Ni) across all continents, climates and vegetation types. We found that warmer arid and tropical ecosystems, present in the least developed countries, sustain the lowest contents of multiple soil micronutrients. We further provide evidence that temperature increases may potentially result in abrupt and simultaneous reductions in the content of multiple soil micronutrients when a temperature threshold of 12–14°C is crossed, which may be occurring on 3% of the planet over the next century. Altogether, our findings provide fundamental understanding of the global distribution of soil micronutrients, with direct implications for the maintenance of ecosystem functioning, rangeland management and food production in the warmest and poorest regions of the planet.     

Quail Pax-6 (Pax-QNR) mRNAs are expressed from two promoters used differentially during retina development and neuronal differentiation.

During investigations on the regulation of the Pax-6 gene, we characterized a cDNA from quail neuroretina showing a 5' untranslated region distinct from that previously described and initiated from an internal promoter. Using RNase protection and primer extension mapping, we localized this second quail Pax-6 promoter, termed P1. As reported for the already described P0 promoter, P1 was also transactivated in vitro by the p46Pax-QNR protein. RNase protection assays performed with quail neuroretina RNA showed that P1-initiated mRNAs were detected before the P0-initiated mRNAs, remained constant up to embryonic day 8, and decreased slowly thereafter whereas, P0-initiated mRNAs accumulated up to embryonic day 8. In contrast, quail retinal pigmented epithelium expressed only the P1-initiated mRNAs. Transformation of these cells by the v-myc oncogene induced neuronal traits in the culture, which thereafter, in addition to the P1-initiated mRNAs, expressed Pax-QNR from the P0 promoter. These results suggest that expression of the quail Pax-6 gene is under the control of different regulators through alternate promoters, P0 being activated at the onset of neuronal differentiation.     

Drug resistance-conferring mutations in Mycobacterium tuberculosis from Madang, Papua New Guinea

ABSTRACT: BACKGROUND: Monitoring drug resistance in Mycobacterium tuberculosis is essential to curb the spread of tuberculosis (TB). Unfortunately, drug susceptibility testing is currently not available in Papua New Guinea (PNG) and that impairs TB control in this country. We report for the first time M. tuberculosis mutations associated with resistance to first and second-line anti-TB drugs in Madang, PNG. A molecular cluster analysis was performed to identify M. tuberculosis transmission in that region. RESULTS: Phenotypic drug susceptibility tests showed 15.7% resistance to at least one drug and 5.2% multidrug resistant (MDR) TB. Rifampicin resistant strains had the rpoB mutations D516F, D516Y or S531L; isoniazid resistant strains had the mutations katG S315T or inhA promoter C15T; streptomycin resistant strains had the mutations rpsL K43R, K88Q, K88R), rrs A514C or gidB V77G. The molecular cluster analysis indicated evidence for transmission of resistant strain. CONCLUSIONS: We observed a substantial rate of MDR-TB in the Madang area of PNG associated with mutations in specific genes. A close monitoring of drug resistance is therefore urgently required, particularly in the presence of drug-resistant M. tuberculosis transmission. In the absence of phenotypic drug susceptibility testing in PNG, molecular assays for drug resistance monitoring would be of advantage.     

Targeting CB2-GPR55 Receptor Heteromers Modulates Cancer Cell Signaling

The G protein-coupled receptors CB₂ (CB₂R) and GPR55 are overexpressed in cancer cells and human tumors. Because a modulation of GPR55 activity by cannabinoids has been suggested, we analyzed whether this receptor participates in cannabinoid effects on cancer cells. Here we show that CB₂R and GPR55 form heteromers in cancer cells, that these structures possess unique signaling properties, and that modulation of these heteromers can modify the antitumoral activity of cannabinoids in vivo. These findings unveil the existence of previously unknown signaling platforms that help explain the complex behavior of cannabinoids and may constitute new targets for therapeutic intervention in oncology.