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.     

Experimental Mycoplasma gallisepticum infections in captive-reared wild turkeys

The effects of Mycoplasma gallisepticum (MG) infections on egg production, fertility, and hatchability were studied in captive-reared wild turkeys (Meleagris gallopavo). Three groups of adult birds, each consisting of four hens and two toms, were exposed to MG by the respiratory route at the beginning of their breeding season. Fourteen control birds received sterile growth medium. Although no mortality of infected or control birds occurred, egg production during the first breeding season after infection was reduced. The mean number of eggs/hen/day produced by infected groups the first breeding season postexposure (PE) was significantly lower than the control value. The mean number of eggs produced daily by the same hens 1 yr later was unaffected by MG infection. The percentage of fertile eggs produced by infected groups was slightly reduced in both the first and second breeding seasons PE. Hatchability of fertile eggs from infected hens was significantly lower than eggs from control hens. Productivity may be impaired if MG infections occur in free-ranging wild turkey populations.     

Photochemical covalent binding of urocanic acid to polynucleic acids

Photolysis of E-[ring-2-14C]urocanic acid (UA) with native or denatured calf thymus DNA leads to covalent binding of the radiolabel to the nucleic acid. A similar observation is made upon photolysis of the labeled UA with the polyribonucleotides, in which case a strong preference is observed for binding to poly[U]. DNA or poly[U], which had been reacted with UA and purified by dialysis and multiple precipitations, releases UA upon further irradiation with 254 nm light (as expected for cyclobutane adducts). Quantum efficiencies for binding of the UA to native DNA have been measured at 308 and 266 nm and are 0.30 x 10(-5) and 1.3 x 10(-4), respectively, at comparable reactant concentrations. The large increase at the shorter wavelength (where DNA absorption is more competitive) is taken as evidence for the primary role of a DNA excited state in initiating the binding reaction(s).     

Failure of two progesterone antagonists, mifepristone and onapristone, to affect luteal activity in lactating rats

The progesterone antagonists, mifepristone (RU-38,486) and onapristone (ZK-98,299), given as 2 mg daily, did not markedly affect lactation in rats. Both litter growth and time spent by 10-pup litters attached to their mothers were similar in antagonist-treated mothers and in solvent-treated controls. The progesterone antagonists did not affect the steroid content in corpora lutea remaining from the preceding pregnancy. Corpora lutea formed after post-partum ovulation also showed nearly normal function throughout the first 17 days of lactation. It is concluded that progesterone itself plays no role in the initiation or maintenance of luteal function when prolactin secretion is governed through an action independent of the ovaries, as through suckling. Antagonist-treated rats ovulated around Day 13 of lactation despite suckling. This ovulation was not associated with a decrease of progesterone production by the corpora lutea formed after post-partum ovulation. Apparently, elimination of progesterone action may protect corpora lutea from luteolysis. The latter finding indicates a possible role of progesterone in luteolysis and deserves further analysis.     

A comparative study of chromatin from lymphocyte nuclei upon activation of transcription by irradiation from an He-Ne-laser or phytohemagglutinin]

The influence of He-Ne laser radiation (632.8 nm, 56 J/m2, t = 10 s) and phytohaemagglutinin (PHA, 2 micrograms/ml) on chromatin structure in human lymphocytes was studied by electron microscopy using ultrathin cell sections. Morphometric analysis of extranuclear condensed chromatin masses was performed 1 h after the irradiation or after the beginning of PHA treatment. In the irradiated cells the following insignificant changes were revealed: decrease in the relative area of the nucleoplasmic chromatin, increase in the relative area of decondensation zones as well as increase in the number of clumps of nucleoplasmic chromatin and relative length at their boundary with nucleoplasma. The tendency of these morphological changes may be interpreted as functional activation of extranucleolar RNA synthesis in response to irradiation by red laser light. Action of PHA results in significant changes of the surfaces of chromatin clumps, namely increase in relative length of nucleoplasmic chromatin boundary and decrease in relative length of perimembranous chromatin boundary with nucleoplasma as well as some less expressed delamination of the chromatin masses from the nuclear membrane. These essential changes may reflect chromatin activation by proliferative stimulus. Peculiarities of the ultrastructural reorganisation in the condensed chromatin after irradiation and PHA-treatment probably reflect the differences in the processes of gene activation caused by the two agents.     

Expression of sialic acid on the alveolar surface of adult and fetal human lungs

Lung alveoli are coated by a thin layer of extracellular material rich in anionic charges. The nature of this acid layer and its relationship to the phospholipid surfactant are not known. We investigated the possible presence of sialic acid groups by light and electron microscopy in tissues from normal fetal and adult lungs, using neuraminidase treatment followed by staining with the galactose-binding lectin from peanut, labeled with peroxidase. Our results showed that adult lung does not bear peanut lectin-reactive sites but that a very thin and distinct reactive layer becomes evident after neuraminidase treatment, especially on type II pneumocytes. In fetal lung, the entire surface of the developing respiratory tree is outlined by a strongly peanut lectin-reactive layer even if neuraminidase digestion is not performed. We conclude that the acid coat of the alveolar lining is in part composed of sialic acid residues and that sialic acid is added to the fetal lung as the alveoli mature.