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C Collet

Publications and source records attributed to C Collet.

At least 55 records · Page 3Linked to original sources
PubMed1994

Autonomic responses correlate to motor anticipation.

New findings have stated that autonomic nervous system (ANS) functioning may reflect some cognitive processes observed in real time analysis. Four ANS variables plus instantaneous heart rate and respiratory frequency were quantified by original techniques and indices on 11 subjects during a coincidence-anticipation task, performed on a computer screen under six different, randomly-presented modalities (3 modalities describing the spot moving along a parabola at 2 speeds). Tonic levels and phasic responses corresponding to each trial were recorded continuously. Results showed that skin resistance tonic level evolution gave evidence of vigilance changes. Thus, performance can be related to subjects' vigilance. An autonomic response was always observed during performance of an anticipation task. The six task modalities were distinguished by performance values. Simultaneously recorded ANS responses fully differentiated these same modalities for 10 subjects out of 11. These ANS responses were furthermore related to performance. Ten subjects out of 11 possess at least one Autonomic variable which can differentiate the six task modalities, confirming Lacey's hypothesis on ANS preferential response, and suggesting ANS specificity. ANS functioning may reveal some brain functions through a specific autonomic channel, characterizing each subject. The behavioral output of an individual may thus be reflected by such a functioning.

Adolescent↗
PubMed1994

The identification of nuclear and mitochondrial genes by sequencing randomly chosen clones from a marsupial mammary gland cDNA library.

To increase the number of genes that can be mapped to the genome of the tammar wallaby (Macropus eugenii), we sequenced 100 randomly chosen clones from a mammary gland cDNA library. Provisional identifications were made of seven nuclear genes and one mitochondrial gene encoding two caseins, beta-galactosidase, acetyl-coenzyme A synthetase, lipoprotein lipase, inorganic pyrophosphatase, an ATP-dependent RNA helicase, and cytochrome c oxidase I. Highly conserved genes, such as that encoding acetyl-coenzyme A synthetase, were easily identified even from cross-kingdom matches. Genes which are highly divergent, however, such as those encoding the mature casein peptides, could not be aligned with homologues in the databases. Even in an organ where there is high mRNA species redundancy, the sequence characterization of expressed sequence tags provides a rapid means of gene identification for mapping purposes.

Amino Acid Sequence↗
PubMed1994

Consistent variation in amino-acid substitution rate, despite uniformity of mutation rate: protein evolution in mammals is not neutral.

Variation in mutation rate, attributed to differences in both generation time and in metabolic rate, has been invoked under the neutral theory of molecular evolution to account for differences in substitution rate among mammalian lineages. We show that substitution rates at fourfold-degenerate sites and at sites in noncoding regions do not vary between the primate and rodent lineages, implying mutation-rate uniformity. In contrast, the substitution rates at nondegenerate sites vary both within and between lineages. This difference in substitution-rate pattern between the two types of site is incompatible with neutral theory but may result from substitutions occurring by fixation of slightly deleterious mutations. Variation in the rate of protein evolution among mammalian lineages appears to be due more to differences in population fixation rates than to biochemical or physiological differences affecting mutation rates.

Animals↗
PubMed1994

Double staining in situ study of mRNAs encoding milk proteins in the mammary gland of the tammar wallaby (Macropus eugenii).

Oligonucleotides, differentially tagged with fluorochromes, were used to determine whether the distribution of mRNAs encoding the major milk proteins is heterogeneous within the mammary gland of the tammar wallaby (Macropus eugenii). This method also allowed direct visualization of two species of mRNA within the same cell. Sections of early and late lactating glands of tammar wallabies were hybridized with oligonucleotides labelled with fluorescein isothiocyanate or rhodamine isothiocyanate either alone or in combination. The results support the hypothesis that milk secretion is an all-or-none process with all epithelial cells in a given alveolus producing the same suite of milk proteins. In tammar wallabies, a gene encoding a protein specific to the latter phase of lactation appears to be expressed in those cells already secreting the other major milk proteins.

Animals↗
PubMed1994

[Immunoassay and measurement of the biological activity of serum hLH: results obtained of a multicenter study].

The discrepancy between results obtained using different anti-hLH antibodies available on the market led us (in the context of a contract with the CNAMTS) to compare the results of hLH immunoassays (eight different reagents) with those of hLH bioassays based on the measurement of the steroidal activity of this hormone on mouse, rat or pig testicular preparations (five methodologies). Twenty-nine samples of serum or human serum pools were tested. The values resulting from these tests reveal differences linked to the nature of the antibodies or to the methodological conditions used for the testicular preparations. Some antibodies seem unable to identify some hLH forms which, however, can be detected by biological methods.

Adult↗
PubMed1993

A novel member of the lipocalin superfamily: tammar wallaby late-lactation protein.

The finding that tammar wallaby late-lactation protein is linked to beta-lactoglobulin prompted a search of current GenPeptide and NBRF-PIR protein databases for sequence similarities to late-lactation protein. Similarities were found to von Ebner's gland protein and other members of the lipocalin superfamily of proteins. A conservative replacement of Trp with Tyr suggests that late-lactation protein may represent an unusual member of this protein superfamily.

Amino Acid Sequence↗
PubMed1993

Hypothalamic-pituitary activation does not differ during human and porcine insulin-induced hypoglycemia in insulin-dependent diabetes mellitus.

Although pituitary hormones play only a minor role in acute hormonal counterregulation during insulin-induced hypoglycemia, their concomitant secretion with the profound sympathoadrenal response provides an indicator of hypothalamic-pituitary activation. The release of different amounts of beta-endorphin, growth hormone, and adrenocorticotropin during human (HI) and porcine (PI) insulin-induced hypoglycemia would serve as a pointer to a different insulin species effect on hypothalamic-pituitary response. We performed a controlled, double-blind study with randomization to either HI or PI to compare insulin effects during developing and established hypoglycemia. The glucose clamp technique was used to lower the blood glucose concentration stepwise (3.3, 2.2, 1.7 mmol/l) over similar periods in ten patients with insulin-dependent diabetes mellitus. beta-endorphin, growth hormone, and adrenocorticotropin levels were determined by radioimmunoassay from arterialized blood at the above plateaus. A different action of HI or PI on peripheral glucose metabolism was not found. Pituitary hormones increased significantly during hypoglycemia (analysis of variance for hypoglycemic effects: beta-endorphin, P < 0.02; growth hormone, P < 0.04; adrenocorticotropin, P < 0.05). No insulin species effect was detected. Hypothalamic-pituitary activation during insulin-induced hypoglycemia is independent of the insulin species used, which supports earlier observations of an identical sympathoadrenal response during HI- and PI-induced hypoglycemia.

Adrenocorticotropic Hormone↗
PubMed1993

Use of a subspecies cross for efficient development of a linkage map for a marsupial mammal, the tammar wallaby (Macropus eugenii).

The tammar wallaby (Macropus eugenii) has a 2n = 16 karyotype with an XX/XY female/male sex dimorphism. Female reproduction can be manipulated to produce up to five offspring per year. We have crossed two genetically distant subspecies of tammars, one from Kangaroo Island in South Australia, the other from Garden Island in Western Australia, to produce fertile F1 offspring of both sexes. Male F1 hybrids were crossed with female Kangaroo Island tammars to produce over 80 phase-known backcross progeny for linkage studies. Here we report detection of two linkage groups derived from these male recombination values. The first consists of alpha-lactalbumin and an anonymous tammar cDNA clone, pB72; the second contains the gene for a marsupial-specific milk protein (late lactation protein), the gene for lipoprotein lipase, and an anonymous cDNA clone, pB65. The gene for late lactation protein has previously been assigned to tammar chromosome 3.

Animals↗
PubMed1992

Molecular characterization and in-vitro hormonal requirements for expression of two casein genes from a marsupial.

Two marsupial casein genes have been isolated from a tammar wallaby (Macropus eugenii) mammary gland cDNA library. Comparisons of the tammar alpha- and beta-casein genes with their eutherian homologous reveal extensive divergence at the levels of nucleotide and amino acid sequences. Regions of similarity between the tammar and eutherian Ca(2+)-sensitive caseins are restricted to the major phosphorylation sites and the signal peptides. Quantification of casein mRNA levels in hormone-stimulated mammary gland explants from tammars in late pregnancy suggests that maximal induction of the beta-casein gene is dependent upon prolactin and insulin, while maximal induction of the alpha-casein gene is dependent upon prolactin, insulin and cortisol. These results are in contrast to earlier studies which show that the maximal induction of a putative 19 kDa casein, alpha-lactalbumin and beta-lactoglobulin in the tammar mammary gland is dependent upon prolactin alone. The expression of the latter three genes is not modulated by other hormones known to play a role in the in-vitro initiation of lactation in eutherians.

Amino Acid Sequence↗
PubMed1991

Hormone-responsive survival of mammary gland explants from the pregnant tammar wallaby (Macropus eugenii) in the absence of exogenous hormones and growth factors.

1. The level of beta-lactoglobulin mRNA increased maximally in mammary explants from late pregnant tammars cultured for 3 days in media containing either prolactin or insulin, cortisol and prolactin. 2. The same level of accumulation occurred when explants were first cultured for 4 days in a chemically defined medium with no exogenous hormones, serum or growth factors, suggesting that the tissue remains viable and hormone-responsive during the initial incubation. 3. Mammary explants cultured for 4 days in medium with no hormones demonstrated a progressive increase in the rate of RNA and DNA synthesis suggesting that the tissue is under a positive autocrine/paracrine stimulus.

Animals↗
PubMed1991

A marsupial beta-lactoglobulin gene: characterization and prolactin-dependent expression.

Analysis of the tammar wallaby beta-lactoglobulin cDNA and inferred amino acid sequences reveal extensive sequence divergence from the eutherian beta-lactoglobulins. Conserved residues include the cysteines and a number of individual amino acids involved in structure and ligand-binding. The only region of extended similarity is a heptapeptide sequence which may impart specificity to its interaction with a receptor protein. Northern analysis of total mammary RNA revealed two transcripts which result from differential utilization of polyadenylation signals. The concentration of beta-lactoglobulin mRNA increased in late lactation and correlates with increases in milk production and levels of milk fat. Quantification of beta-lactoglobulin mRNA levels in hormone-stimulated mammary gland explants from tammars in late pregnancy suggests that maximal induction of the gene is dependent on prolactin alone and that expression is not modulated by other hormones known to play a role in the initiation of lactation in eutherians.

Amino Acid Sequence↗
PubMed1990

Cloning, cDNA analysis and prolactin-dependent expression of a marsupial alpha-lactalbumin.

The gene for alpha-lactalbumin has been cloned from a tammar wallaby (Macropus eugenii) mammary gland cDNA library. Tammar alpha-lactalbumin has approximately 50 and 30% homology to the alpha-lactalbumins of eutherians at the levels of nucleotide and protein sequence respectively. Comparison of the inferred tammar polypeptide sequence with the sequence of the eutherian proteins reveals extensive divergence at almost all of the non-essential amino acid residues. However, the hydropathy plots of the tammar protein are almost identical to those of eutherian alpha-lactalbumins, suggesting that protein conformation is conserved. The tammar gene encodes a transcript of approximately 975 bases. Northern blot analysis of hormone-stimulated mammary gland explants shows that maximal induction of alpha-lactalbumin mRNA is dependent on prolactin and that expression is not modulated by other hormones that play a role in the initiation of lactation in eutherians.

Amino Acid Sequence↗
PubMed1990

Molecular analysis of duplicated esterase genes in Drosophila melanogaster.

Genomic clones containing sequences homologous to an esterase 6 (Est-6) cDNA clone were isolated from a library of Drosophila melanogaster DNA. Comparison of the genomic and cDNA sequences revealed that the Est-6 gene comprises two exons, one of 1,387 bp and one of 248 bp, separated by a short intron of 51 bp. Further sequencing revealed the presence of a tandem duplication of the Est-6 gene (denoted Est-P) which also has an exon of 1,387 bp and an exon of 248 bp, separated by a short intron of 56 bp. The two genes show similarities of 64% and 60% at the DNA and protein levels, respectively. The coding regions of the genes are 197 bases apart, and presumptive 5' regulatory sequences of Est-P overlap at least the 3' noncoding region of Est-6. Transcripts homologous to Est-P were detected in late larvae and adults of each sex, whereas Est-6 transcripts are present in all life stages but are predominant in adult males. This suggests different physiological functions for the products of the two genes. Southern and Northern blot hybridization analyses of the 20-kb region surrounding the Est-6/Est-P duplication failed to detect any other duplicated esterase genes, although this region is actively transcribed.

Amino Acid Sequence↗
PubMed1989

Molecular cloning and characterization of a novel marsupial milk protein gene.

The tammar wallaby (Macropus eugenii) produces two different types of milk; "early" milk for the first 180 days and "late" milk for the remaining 150 days of lactation. We report the cloning of the cDNA of a novel whey protein, Late-Lactation Protein (LLP), which is produced during the late phase of lactation. The cDNA was cloned using an oligonucleotide probe deduced from the published partial protein sequence. The cDNA encodes an open-reading frame of 176 amino acids of which the first 18 residues represent a signal peptide. Northern blot analysis revealed a 1kb transcript in late phase lactation but not in the early phase.

Amino Acid Sequence↗
PubMed1988

Recent origin for a thermostable alcohol dehydrogenase allele of Drosophila melanogaster.

The nucleotide sequence of the Fast-Chateau Douglas isolate of the thermostable alcohol dehydrogenase allele is compared with the sequences of the Slow and Fast alleles of Drosophila melanogaster. Conceptual translation of the FChD sequence indicates that the thermostable polypeptide has the diagnostic FAST amino acid replacement at residue 192 and an additional replacement of serine for proline at residue 214. This suggests a Fast origin for the thermostable Adh allele. However, some of the biochemical properties of the FCHD protein resemble those of the SLOW rather than the FAST polypeptides. The serine for proline replacement confers upon the thermostable polypeptide substrate specificities and some kinetic parameters similar to the SLOW protein. The same replacement substitution within the third coding exon also appears to alter the ADH protein concentration to a level similar to the SLOW polypeptide and the probable effect is at the level of mRNA concentration. The low level of nucleotide sequence variation, other than that leading to the amino acid substitution, suggests a recent origin for the thermostable allele. The time since divergence of the FChD sequence from Fast is estimated to be approximately 260,000-470,000 years.

Alcohol Dehydrogenase↗