Human atrial natriuretic peptide receptor defines a new paradigm for second messenger signal transduction.

We isolated cDNAs encoding a 115 kd human atrial natriuretic peptide (alpha ANP) receptor (ANP-A receptor) that possesses guanylate cyclase activity, by low-stringency hybridization with sea urchin Arbacia punctulata membrane guanylate cyclase probes. The human ANP-A receptor has a 32 residue signal sequence followed by a 441 residue extracellular domain homologous to the 60 kd ANP-C receptor. A 21 residue transmembrane domain precedes a 568 residue cytoplasmic domain with homology to the protein kinase family and to a subunit of the soluble guanylate cyclase. COS-7 cells transfected with an ANP-A receptor expression vector displayed specific [125I]alpha ANP binding, and exhibited alpha ANP stimulated cGMP production. These data demonstrate a new paradigm of cellular signal transduction where extracellular ligand binding allosterically regulates cyclic nucleotide second-messenger production by a receptor cytoplasmic catalytic domain.     

Molecular mimicry between uveitopathogenic site of retinal S-antigen and Escherichia coli protein: induction of experimental autoimmune uveitis and lymphocyte cross-reaction

Experimental autoimmune uveitis (EAU) is caused by the immunization of microgram amounts of a soluble retinal protein, known as S-antigen, in susceptible animal strains including primates. The disease serves as an animal model of ocular inflammation. We induced EAU and pinealitis in Lewis rats with small synthetic peptides, corresponding to the amino acid sequence in Escherichia coli protein, which contains six consecutive amino acids identical to a uveitopathogenic site in human S-antigen (peptide M). EAU and pinealitis induced in rats by synthetic peptide derived from E. coli was indistinguishable from those induced by native S-antigen or other uveitopathogenic synthetic peptides corresponding to the amino acid sequence of S-antigen. Furthermore, lymph node cells from animals immunized with either peptide M or peptide derived from E. coli protein showed significant proliferation in the presence of either peptide when tested in vitro for lymphocyte mitogenesis using [3H]thymidine. Thus, molecular mimicry, a process by which an immune response directed against a nonself protein cross-reacts with a normal host protein, may play a role in autoimmunity.     

Sequence homology between yeast histone H3 and uveitopathogenic site of S-antigen: lymphocyte cross-reaction and adoptive transfer of the disease

Experimental autoimmune uveitis (EAU) serves as an animal model of ocular inflammation. The disease is caused by the immunization of microgram amounts of a soluble retinal protein, designated S-antigen, in susceptible animal strains, including primates. We induced EAU and experimental autoimmune pinealitis (EAP) in Lewis rats with a small synthetic peptide corresponding to amino acid positions 106-121 in yeast histone H3. This peptide contains five consecutive amino acids identical to a uveitopathogenic site (peptide M) in human S-antigen. Lymph node or mononuclear cells from different species of animals immunized either with histone H3 or with peptide M showed significant cross-reaction as measured by in vitro lymphocyte mitogenesis assay using [3H]thymidine. Also, we adoptively transferred the EAU and EAP in naive rats by immune lymph node cells. These findings support the fact that selected bacterial, viral, or fungal proteins with amino acid sequence homologies to normal retinal proteins are uveitopathogenic and, as such, provide a basis for autoimmune inflammatory diseases.     

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.