Biomedical subjects

J P Franck

Publications and source records attributed to J P Franck.

At least 19 recordsLinked to original sources

PubMed2002

Oxygen isotope effect in the ab-plane reflectance of underdoped YBa(2)Cu(3)O(7-delta).

We have measured the effect of oxygen isotope substitution on the ab-plane reflectance of underdoped YBa(2)Cu(3)O(7-delta). The frequency shift of the transverse optic phonons due to the substitution of 16O by 18O yields an isotope effect of the expected magnitude for copper-oxygen stretching modes with alpha=0.5+/-0.1. The reflectance shoulder at 400-500 cm(-1) shows a much smaller exponent of alpha=0.1+/-0.1 in the normal state and alpha=0.23+/-0.1 in the superconducting state. These observations suggest that the shoulder is of electronic origin and not due to a phonon mode as has been suggested recently.

Journal Article↗

PubMed2001

Evidence for two superconducting gaps in MgB2.

We have measured the Raman spectra of polycrystalline MgB2 from 25 to 1200 cm(-1). A superconductivity-induced redistribution in the electronic Raman continuum was observed. Two pair-breaking peaks appear in the spectra, suggesting the presence of two superconducting gaps. The measured spectra were analyzed using a quasi-two-dimensional model in which two s-wave superconducting gaps open on two sheets of Fermi surface. For the gap values we have obtained Delta(1) = 22 cm(-1) ( 2.7 meV) and Delta(2) = 50 cm(-1) ( 6.2 meV). Our results suggest that a conventional phonon-mediated pairing mechanism occurs in the planar boron sigma bands and is responsible for the superconductivity of MgB2.

Journal Article↗

PubMed2001

On the status of the Serranid fish genus Epinephelus: evidence for paraphyly based upon 16S rDNA sequence.

Historically, attempts to elucidate evolutionary relationships among members of the genus Epinephelus (Teleostei: Serranidae), commonly known as groupers, have been hindered by the overwhelming number of species (98, sensu stricto), a pan global distribution, and the lack of morphological specializations traditionally used in ichthyological classification. To date, no comprehensive phylogenetic study, morphological or molecular, to evaluate the monophyly of this genus has been presented. In this study, previous hypotheses regarding the relationships among the American grouper species and the allied genera were evaluated by examination of mitochondrial DNA sequences of the 16S ribosomal DNA region. A 590-bp region of the 16S rDNA gene was amplified using a universal primer pair for 42 serranid species, including members of the genera Epinephelus, Mycteroperca, and Paranthias from the New World and selected Indo-Pacific congeners. Maximum-parsimony criteria and neighbor-joining analysis dispute the monophyly of the American Epinephelus species as previously hypothesized. The data support the monophyly of Cephalopholis only with the inclusion of the morphologically distinct Paranthias and the monophyly of Mycteroperca with the inclusion of the Indo-Pacific Anyperodon leucogrammicus.

Animals↗

PubMed2000

Cloning of a neonatal calcium atpase isoform (SERCA 1B) from extraocular muscle of adult blue marlin (Makaira nigricans).

Complete cDNAs for the fast-twitch Ca2+ -ATPase isoform (SERCA 1) were cloned and sequenced from blue marlin (Makaira nigricans) extraocular muscle (EOM). Complete cDNAs for SERCA 1 were also cloned from fast-twitch skeletal muscle of the same species. The two sequences are identical over the coding region except for the last five codons on the carboxyl end; EOM SERCA 1 cDNA codes for 996 amino acids and the fast-twitch cDNAs code for 991 aa. Phylogenetic analysis revealed that EOM SERCA 1 clusters with an isoform of Ca2+ -ATPase normally expressed in early development of mammals (SERCA 1B). This is the first report of SERCA 1B in an adult vertebrate. RNA hybridization assays indicate that 1B expression is limited to extraocular muscles. Because EOM gives rise to the thermogenic heater organ in marlin, we investigated whether SERCA 1B may play a role in heat generation, or if 1B expression is common in EOM among vertebrates. Chicken also expresses SERCA 1B in EOM, but rat expresses SERCA 1A; because SERCA 1B is not specific to heater tissue we conclude it is unlikely that it plays a specific role in intracellular heat production. Comparative sequence analysis does reveal, however, several sites that may be the source of functional differences between fish and mammalian SERCAs.

Amino Acid Sequence↗

PubMed1998

Cloning and characterization of fiber type-specific ryanodine receptor isoforms in skeletal muscles of fish.

We have cloned a group of cDNAs that encodes the skeletal ryanodine receptor isoform (RyR1) of fish from a blue marlin extraocular muscle library. The cDNAs encode a protein of 5,081 amino acids with a calculated molecular mass of 576,302 Da. The deduced amino acid sequence shows strong sequence identity to previously characterized RyR1 isoforms. An RNA probe derived from a clone of the full-length marlin RyR1 isoform hybridizes to RNA preparations from extraocular muscle and slow-twitch skeletal muscle but not to RNA preparations from fast-twitch skeletal or cardiac muscle. We have also isolated a partial RyR clone from marlin and toadfish fast-twitch muscles that shares 80% sequence identity with the corresponding region of the full-length RyR1 isoform, and a RNA probe derived from this clone hybridizes to RNA preparations from fast-twitch muscle but not to slow-twitch muscle preparations. Western blot analysis of slow-twitch muscles in fish indicates the presence of only a single high-molecular-mass RyR protein corresponding to RyR1. [3H]ryanodine binding assays revealed the fish slow-twitch muscle RyR1 had a greater sensitivity for Ca2+ than the fast-twitch muscle RyR1. The results indicate that, in fish muscle, fiber type-specific RyR1 isoforms are expressed and the two proteins are physiologically distinct.

Amino Acid Sequence↗

PubMed1994

The utility of SATA satellite DNA sequences for inferring phylogenetic relationships among the three major genera of tilapiine cichlid fishes.

The SATA satellite DNA family of sequences, composed of three size variants of approximately 237, 230, and 209 bp, is conserved in the genomes of tilapiine and haplochromine cichlid fishes. In the present study we examined the utility of the SATA sequences for inferring phylogenetic relationships among the three major genera of tilapiine fishes, Oreochromis, Sarotherodon, and Tilapia. Hybridization of the monomer SATA repeat to genomic DNA of representative cichlid species established conservation of the sequence in the African tilapine and haplochromine lineages and its absence from other cichlid lineages. Bootstrapped DNA parsimony and neighbor-joining analyses of derived consensus sequences revealed two distinct clades, one containing the mouthbrooding genera Oreochromis and Sarotherodon, and the other containing the substrate spawning genus Tilapia. These results are consistent with recent independent studies using mitochondrial DNA and establish the utility of the SATA satellite DNA family for phylogenetic reconstruction. Concerted evolution of the SATA sequences was also demonstrated within the tilapiine tribe.

Animals↗

PubMed1993

Conservation of a satellite DNA sequence (SATB) in the tilapiine and haplochromine genome (Pisces: Cichlidae).

We have cloned and sequenced a 1900-bp EcoRI fragment (SATB) from the tilapiine fish Oreochromis niloticus. The SATB sequence is highly reiterated in the tilapiine genome and organized in long tandem arrays. A 760-bp HindIII fragment, an internal component of SATB, has also been cloned and sequenced from the related tilapiine species Oreochromis hornorum. Hybridization of the radiolabelled 760-bp HindIII repeat detected the presence of the SATB repeat in the genomes of several tilapiine species as well as the haplochromine species Haplochromis (Protomelas) similis. The 760-bp HindIII fragment did not hybridize to genomic DNA of Etroplus maculatus (an Asian cichlid) or to that of Cichlasoma meeki (a South American cichlid). The SATB repeat sequence is 56% AT and constitutes 0.2-5% of the tilapiine genome depending on the species examined. Four imperfect 21-bp direct repeat sequences are present within the cloned 1900-bp EcoRI repeat. Alignment of the four direct repeats from the O. niloticus cloned 1900-bp DNA and the two homologous direct repeats from the O. hornorum 760-bp HindIII repeat revealed a core motif of 11 bp that exhibits 100% sequence identity between all of the direct repeats. The conservation of this motif in the SATB repeat suggests that this sequence may be under selective constraint.

Animals↗

PubMed1992

Genetic variability in a family of satellite DNAs from tilapia (Pisces: Cichlidae).

We have cloned and sequenced members of a family of satellite DNAs from three genera of the tilapiine tribe of fishes: Oreochromis, Sarotherodon, and Tilapia. The satellite DNAs, visualized as intensely staining bands following electrophoretic separation of EcoRI-digested genomic DNA, consist of three size variants differentially distributed in the various tilapiine species. The sizes of the monomers are approximately 237 bp (type I), 230 bp (type II), and 209 bp (type III). Several cloned monomers were sequenced from Oreochromis niloticus (type III), Oreochromis placidus (types I and II), Sarotherodon galilaeus (type I), Tilapia zillii (type I), and Tilapia rendalli (type I). Comparison of derived consensus sequences for the monomer units of the satellite DNAs revealed sequence identities within and between species that ranged from 89 to 96%. The type II and type III size variants appear to have arisen by deletions of 9 and 29 bp, respectively, within different regions of the type I satellite. Hybridization of a cloned monomer satellite from O. niloticus (type III) to PalI digests of genomic DNA from all three genera detected polymorphic, high molecular weight restriction fragments that produced fingerprint-like patterns. The complexity of these DNA fingerprints varied from one species to another, suggesting a markedly different genomic organization for these polymorphic satellite DNAs.

Animals↗

PubMed1991