Abundant alkali-sensitive sites in DNA of human and mouse sperm

The DNA of human and mouse sperm cells was analyzed by single-cell microgel electrophoresis, by agarose gel electrophoresis, and by alkaline elution--three techniques that can detect single-strand DNA breaks and/or labile sites. Under these conditions a surprisingly large number of single-strand DNA breaks, approximately 10(6) to 10(7) per genome, were detected in human and mouse sperm but not in human lymphocytes or in mouse bone marrow cells. These breaks were also present in chicken erythrocyte DNA, which is also highly condensed. These breaks were not observed under neutral pH conditions nor under denaturing conditions not involving alkali, suggesting that these sites are alkali-sensitive and do not represent preexisting single-strand breaks. The high frequency of such sites in sperm from healthy mouse and human donors suggests that they represent a functional characteristic of condensed chromatin rather than DNA damage.     

Rat pineal S-antigen: sequence analysis reveals presence of alpha-transducin homologous sequence

S-antigen (S-Ag) is a soluble, highly antigenic protein, the administration of which induces autoimmune uveitis. This protein is found in the retina and pineal. Retinal S-Ag from three species has been sequenced. In this study rat pineal S-Ag was sequenced. Clones were isolated from a rat pineal lambda gt11 cDNA library by probing with a 300 bp fragment of mouse retinal S-Ag cDNA containing the 5'-coding region. The largest clone isolated (RPS-118; 1364 bp) contained the entire coding sequence. Comparison of the rat pineal and mouse retinal S-Ag nucleotide sequences indicated a high homology (95%). The deduced amino acid sequence was found to contain 403 residues (congruent to 44 992 Da). Comparison of the rat pineal and mouse retinal S-Ag amino acid sequences also revealed high homology (97%). The similarity of both the nucleotide and amino acid sequences of rat pineal and mouse retinal S-Ag indicates that expression of the S-Ag gene in both tissues is similar. Further analysis of the rat pineal S-Ag sequence indicated that it contained essentially the same major uveitopathogenic region of S-Ag present in bovine retina; minor uveitopathogenic sites were somewhat different. As is true of retinal S-Ag, rat pineal S-Ag contains the same consensus phosphoryl-binding site present in many GTP/GDP-binding proteins and a homologous sequence found in the C-terminus of alpha-transducin. These sequences may play a role in the action of pineal S-Ag in transmembrane signal transduction.     

A SEM study of the olfactory lamellae of the catfish Heteropneustes fossilis (Bl.)

The olfactory lamellae of the catfish H. fossilis (Bl.) was studied in the scanning electron microscope. The olfactory lamellae are composed of sensory and non-sensory epithelium. The sensory epithelium contains large numbers of ciliated receptor cells, whereas the non-sensory raphe epithelium is covered with a dense mat of non-sensory cilia. It is not known whether the olfactory cilia possess receptor sites.     

Development of the neo-morphic air breathing organs in three genera of estuarine gobies

The rudiment of the neo-morphic organ for O2 uptake arises in the form of a gill mass formed by the gill material of the embryonic 5th gill arch. Ectodermal induction to the gill mass takes place in the post-embryonic stage of development to produce a respiratory epithelium of the neo-morphic air breathing organ. The respiratory epithelium of the opercular chamber and the buccal cavity is formed by the cells of the gill mass alone. The respiratory epithelium of the suprabranchial chamber is formed by the cells of the gill mass as well as the gill lamellae derived from the dorsal aspects of the functional gill arches (1 to 4). Extension of the suprabranchial chamber into the buccal region anteriorly is a device to increase the respiratory surface area available for O2 uptake by air. The epithelial position of the blood capillaries in the suprabranchial chamber of Periophthalmodon schlosseri signifies terrestrial nature of the fish.     

Primary photoprocesses of phytochrome. Picosecond fluorescence kinetics of oat and pea phytochromes

The primary photoprocesses of etiolated oat and pea phytochromes (Pr forms) are diffusion-modulated by the microscopic viscosity within the chromophore pocket. The chromophore pocket is preferentially accessible to glycerol but not to Ficoll. Glycerol preferentially retarded the rate (rate constant ca. 1-2 X 10(10) s-1) of the initial reaction from the Qy excited state of phytochrome, whereas it increased the long fluorescence lifetime (nanosecond) component that can be attributed to either an emitting intermediate or to modified/conformationally heterogeneous phytochrome populations. The picosecond time-resolved fluorescence spectra of different phytochrome preparations (i.e., full-length vs 6/10-kDa NH2-terminus truncated forms of phytochromes from monocot and dicot plants) revealed no significant differences. The spectra in the picosecond time scale showed no spectral shifts, but at longer time scales of up to approximately 1.90 ns, significant blue spectral shifts were observed. The shifts were more in the truncated than in the full-length pea phytochrome. Comparison of the fluorescence decay data and the picosecond time-resolved fluorescence spectra suggests differences in conformational flexibility/heterogeneity among the preparations of the monocot vs dicot phytochromes and the full-length native vs the amino terminus truncated phytochromes.     

Algal epilithon and water quality of a stream receiving oil refinery effluent

Changes in epilithic algal communities colonizing introduced substrata were determined in a stream polluted with oil refinery effluent at Digboi (Assam, India). The number of algal taxa was reduced but the growth of blue-green algae, particularly two species ofOscillatoria, was encouraged. Epilithic biomass (as chlorophylla) also declined at polluted stations. The algal community of the upstream station was markedly different from the community occurring just after the confluence of effluent; however, the differences were gradually reduced downstream, indicating improvement in water quality. Of the various criteria tested for possible relationships with the level of pollutants, species richness, Shannon diversity and biomass showed significant relationships. The study demonstrates the usefulness of algal criteria for monitoring oil pollution in running waters.     

Differential effects of cisplatin on mouse hepatic and renal mitochrondrial DNA

The objective of this study was to determine if the nephrotoxic effects induced by cisplatin were correlated to mitochondrial DNA damage. Comparisons were made with the liver since hepatotoxicity is rarely observed. Cisplatin doses of 10, 20 and 40 mg/kg were administered intraperitoneally to C57BL/6J mice. Mitochrondrial DNA was isolated from both the hepatic and renal tissues and quantitated by hybridization with a specific mitochondrial probe. Cisplatin caused differential effects on mouse hepatic and renal mitochondrial DNA. The 10 and 20 mg/kg dose caused an elevation in mitochondrial DNA levels in the hepatic, but no increase in the renal tissue was observed. This is the first study demonstrating an organ specific effect of cisplatin at the DNA level.