Photoreceptor-specific efficiencies of β-carotene,zeaxanthin and lutein for photopigment formation deduced from receptor mutant Drosophila melanogaster

Summary Drosophila rearing media had only -carotene, zeaxanthin or lutein as precursors for photopigment chromophores. Zeaxanthin and lutein are potentially optimum sources of the 3-hydroxylated retinoids of visual and accessory photopigments. Mutants made the electroretinogram in white (w) eyes selective for compound eye photoreceptors R1–6, R7 and R8: R1–6 domiantes w's electroretinogram; R7/8 generates w;ora's (ora = outer rhabdomeres absent); R8 generates w sev;- ora's (sev = sevenless). Microspectrophotometry revealed R1-6's visual pigment. In w, all 3 carotenoids yielded monotonic dose-responses for sensitivity (Fig. 4) or visual pigment (Fig. 7). An ultraviolet sensitivity peak from R1-6's sensitizing pigment was present at high but not low doses (Fig. 1). In w;ora, all 3 carotenoids gave similar spectra dominated by R7's high ultraviolet sensitivity (Fig. 2). For w sev;ora, all spectra were the shape expected for R8, peaking around 510 nm (Fig. 3). The sensitivity dose-response was at its ceiling except for low doses in w;ora (Fig. 5) and zero supplementation in w sev;ora (Fig. 6). Hence, without R1-6, most of our dose range mediated maximal visual pigment formation. In Drosophila, -carotene, zeaxanthin and lutein mediate the formation of all major photopigments in R1-6, R7 and R8.Abbreviations ERG electroretinogram - MSP microspectrophotometry - HPLC high pressure liquid chromatography - n.a. numerical aperture - w, sev, ora Drosophila mutants - y, p, r marg types of R7 and R8     

An Ustilago maydis Mutant Partially Blocked in P45014DM Activity Is Hypersensitive to Azole Fungicides

An Ustilago maydis ergosterol biosynthesis mutant (A14) which is partially blocked in sterol 14alpha-demethylase (P45014DM) activity is described. This mutant accumulated the abnormal 14alpha-methyl sterols, eburicol, 14alpha-methylfecosterol, and obtusifoliol, along with significant amounts of ergosterol. Although the A14 mutant grew nearly as well as the wild type, it was impaired in cell extension growth, which indicated a dysfunction in apical cell wall synthesis. The mutant was also found to be hypersensitive to the azole fungicides penconazole and tebuconazole.     

Ultrasonic characteristics of frozen liver

The recent development of new ultrasound probes has made real-time intraoperative monitoring of cryosurgery, and thermocouple placement a possibility. It is shown that frozen tissue and thermocouple needles have acoustic characteristics that enable them to be easily visualized by ultrasound examination. Further in vivo animal studies are needed to examine temperature characteristics of visualized cryolesions, to develop scanning techniques, and to correlate ultrasonic findings with histologic changes in tissue.     

Thyroid antibodies as a risk factor for Down syndrome and other trisomies.

To test whether the presence of thyroid antibodies in a parent is a risk factor for meiotic nondisjunction, we measured the levels of thyroid antibodies in serum samples drawn during early pregnancy from 101 gravidas who delivered a child with a trisomy, from 11 gravidas who had had a trisomic child in a previous pregnancy, and from 44 of their husbands. For each case mother, three controls were randomly selected from the same population and matched for age, race, sex of the child, and hospital of birth. Cases and controls came from two longitudinal populations, the Child Health and Development Studies (CHDS) and the national Collaborative Perinatal Project (CPP), together comprising more than 70,000 live births. All cases with both a definite diagnosis of trisomy-Down syndrome (DS) or other-and available serum were included. Overall, there was no association between the presence of thyroid antibodies in a mother and a trisomy in her offspring (odds ratio [OR] = .98, confidence interval [CI] = .54-1.85). The lack of association was seen in all three subgroups (DS only, other trisomies, and DS in a previous pregnancy), in all ethnic groups, and in the age groups of white mothers either less than 30 years of age (OR = .80, CI = .40-1.6) or greater than or equal to 30 years of age (OR = 1.26, CI = .82-1.9). In the CHDS population, case fathers, as compared with control fathers, did not have a higher prevalence of thyroid antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mapping genes for resistance to Leptosphaeria maculans in Brassica juncea.

Blackleg disease of crucifers, caused by the fungus Leptosphaeria maculans, is a major concern to oilseed rape producers worldwide. Brassica species containing the B genome have high levels of resistance to blackleg. Brassica juncea F2 and first-backcross (B1) populations segregating for resistance to a PG2 isolate of L. maculans were created. Segregation for resistance to L. maculans in these populations suggested that resistance was controlled by two independent genes, one dominant and one recessive in nature. A map of the B. juncea genome was constructed using segregation in the F2 population of a combination of restriction fragment length polymorphism (RFLP) and microsatel lite markers. The B. juncea map consisted of 325 loci and was aligned with previous maps of the Brassica A and B genomes. The gene controlling dominant resistance to L. maculans was positioned on linkage group J13 based on segregation for resistance in the F2 population. This position was confirmed in the B1 population in which the resistance gene was definitively mapped in the interval flanked by pN199RV and sB31143F. The provisional location of the recessive gene controlling resistance to L. maculans on linkage group J18 was identified using a subset of informative F2 individuals.     

Hexazonium pararosaniline as a fixative for animal tissues

Hexazonium pararosaniline is a valuable reagent that has been used in enzyme activity histochemistry for 50 years. It is an aqueous solution containing the tris-diazonium ion derived from pararosaniline, an aminotriarylmethane dye, and it contains an excess of nitrous acid that was not consumed in the diazotization reaction. Other investigators have found that immersion for 2 min in an acidic (pH 3.5) 0.0015 M hexazonium pararosaniline solution can protect cryostat sections of unfixed animal tissues from the deleterious effects of aqueous reagents such as buffered solutions used in immunohistochemistry, while preserving specific affinities for antibodies. In the present investigation hexazonium pararosaniline protected lymphoid tissue and striated muscle against the damaging effects of water or saline. The same protection was conferred on unfixed sections treated with dilute nitrous or hydrochloric acid in concentrations similar to those in hexazonium pararosaniline solutions. Model tissues (solutions, gels or films containing gelatin and/or bovine albumin) responded predictably to well known cross-linking (formaldehyde) or coagulant (mercuric chloride) fixatives. Hexazonium pararosaniline solutions prevented the dissolution of protein gels in water only after 9 or more days of contact, during which time considerable swelling occurred. It is concluded that there is no evidence for a “fixative” action of hexazonium pararosaniline. The protective effect on frozen sections of unfixed tissue is attributable probably to the low pH of the solution.