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S Lien

Publications and source records attributed to S Lien.

At least 55 records · Page 3Linked to original sources
PubMed1996

Multipoint linkage map from sperm typing data.

Sperm typing makes it possible to construct accurate multipoint linkage maps based on a theoretically unlimited number of meioses. The high sperm number from single individuals enables the dissection of hyper-recombinant regions and presents an ideal situation for studying recombination rate variability in mammals. Of particular relevance for livestock is the fact that fine structure mapping of functional genes by sperm typing can be used to identify the breakpoints between conserved syntenic groups in different species. This is important for the extrapolation of positional information from the highly developed human map to the lower density maps in farm animals.

Animals↗
PubMed1995

The role of melanocyte-stimulating hormone (MSH) receptor in bovine coat color determination.

The melanocyte-stimulating hormone (MSH) receptor has a major function in the regulation of black (eumelanin) versus red (phaeomelanin) pigment synthesis within melanocytes. We report three alleles of the MSH-receptor gene found in cattle. A point mutation in the dominant allele ED gives black coat color, whereas a frameshift mutation, producing a prematurely terminated receptor, in homozygous e/e animals, produces red coat color. The wild-type allele E+ produces a variety of colors, reflecting the possibilities for regulating the normal receptor. Microsatellite analysis, RFLP studies, and coat color information were used to localize the MSH-receptor to bovine Chromosome (Chr) 18.

Alleles↗
PubMed1995

Associations between casein haplotypes and milk yield traits.

The genotyping of 13 sires and 250 of their sons for casein polymorphisms revealed 10 different haplotypes for Norwegian Cattle. Associations between haplotypes and yields of protein, milk, and fat were studied using a granddaughter design. Three subsets of data containing families with haplotypes 1, 5, and 10 were analyzed independently and denoted by analyses 1, 5, and 10, respectively. In addition, all sire families of all haplotypes were pooled and analyzed in analysis T. No associations were found between haplotypes and traits for milk yield in analyses 1, 10, and T. However, the null hypothesis of an equal effect within sire of bulls was rejected in analysis 5 for yields of protein and milk. The increase in protein yield associated with haplotype 5 ranged from 2.52 to 14.58 kg (from .09 to .51 phenotypic standard deviations). These results may indicate the presence of at least one quantitative trait locus in the region of the casein genes that affects protein yield of Norwegian Cattle. The findings were confirmed with a new analysis of two large sire families segregating haplotype 5 (analysis 5N).

Animals↗
PubMed1994

Chromosomal localization and detection of DNA polymorphisms in the bovine polymeric immunoglobulin receptor gene.

Polymeric immunoglobulin receptor (PIGR) mediates transcellular transport of secretory antibodies in glandular and mucosal epithelial cells. By use of a bovine-rodent somatic cell hybrid panel the bovine PIGR locus has been assigned to syntenic group U1. Using in situ hybridization, PIGR was localized to bovine chromosome 16, segment q13, thus confirming the recent assignment of syntenic group U1 to this chromosome. Two common restriction fragment length polymorphisms (RFLPs) with the enzymes BamHI and MspI were detected using the PIGR cDNA as probe. Direct PCR sequencing of a segment in the PIGR coding region (nucleotides 162-413) from 13 bulls of Norwegian Cattle revealed single nucleotide exchanges at two positions. An efficient PCR-RFLP method for detection of these mutations was developed.

Animals↗
PubMed1993

A simple and powerful method for linkage analysis by amplification of DNA from single sperm cells.

Haplotypes of three bovine casein loci were analyzed as a way of determining genetic linkage. A total of 330 individual sperm cells from a triply heterozygous bull were selected by means of a new method involving fixing the sperm cells into low-melting-point agarose gels. The method is simple and very accurate with an efficiency close to 100% for picking sperm cells and producing amplifiable DNA templates, circumventing the complicated statistical analysis mandated by automated cell sorting. The DNA was amplified in a two-step polymerase chain reaction (PCR) to achieve the necessary high specificity of amplification. In the first reaction, primers flanking the polymorphic site at each locus were used. The PCR product from the first reaction was then reamplified in a second PCR using primers that create allele-specific restriction sites (ACRS) in the PCR products for two of the three loci, allowing the alleles to be determined by gel electrophoresis. No recombinants were found among the 330 single sperm cells analyzed, giving a lod score higher than 30 and proving a very strong linkage between bovine casein genes.

Animals↗
PubMed1993

Bovine casein haplotypes: number, frequencies and applicability as genetic markers.

Three casein loci, tightly linked on bovine chromosome 6, have been studied as haplotypes within families of bulls. The polymorphisms included in the study were CASAS1 (B, C), CASB (A1, A, A5, B), CASK (A, B, E) and a microsatellite in intron III of CASK. A new A5 variant of CASB, caused by a silent mutation in the triplet coding for amino acid 110, was detected by direct polymerase chain reaction sequencing. Our analysis of 306 sons and 15 sires revealed 10 different casein haplotypes with a cumulative polymorphic information content (PIC) of 0.78.

Animals↗
PubMed1992

Detection of multiple beta-casein (CASB) alleles by amplification created restriction sites (ACRS).

Direct sequencing of polymerase chain reaction (PCR) amplified DNA has been used to detect the DNA sequences for bovine beta-casein (CASB) A3 and B variants. Based on these sequences we have designed primers which create allele-specific restriction sites in the PCR product. Restriction analysis of PCR product generated in one reaction enable us to identify the A1, A2, A3 and B alleles of CASB rapidly without the use of radioactivity.

Alleles↗
PubMed1989

A method for kappa-casein genotyping of bulls.

A method for kappa-casein genotyping in bulls has been developed. By analysis of DNA polymorphisms we are able to discriminate between the kappa-casein variant A and B in the bulls. This method will be an efficient tool in selection for the most desirable kappa-casein variant.

Animals↗
PubMed1984

Effects of electron mediator charge properties on the reaction kinetics of hydrogenase from Chlamydomonas.

Anions modulate hydrogenase activity in cell-free preparations of Chlamydomonas reinhardtii, and this modulation is greatly influenced by the charge properties of the redox agent included to mediate electron transfer to hydrogenase. With cationic methyl viologen as the electron mediator, anions stimulate the maximum velocity of H2 production (e.g., a 320% increase in the presence of 1 M NaCl) but have little effect on the Km for methyl viologen. Conversely, when hydrogenase activity is mediated by polyanionic metatungstate or ferredoxin, H2 production is strongly inhibited by anions (e.g., 70-77% inhibition by 0.2 M NaCl). This inhibition is primarily due to a reduced affinity of hydrogenase for these mediators (as evidenced by a large increase in Km values), rather than a change in the maximum velocity of the reaction. Anions have little effect on the kinetics of hydrogenase activity mediated by zwitterionic sulfonatopropyl viologen, a redox agent with a nearly neutral net charge. These results suggest the presence of a cationic region near the active site of hydrogenase. This cationic region, probably due to lysine and/or arginine residues, may serve in vivo to facilitate the interaction between hydrogenase and ferredoxin, the polyanionic, physiological electron mediator.

Anions↗
PubMed1984

Purification of Hydrogenase from Chlamydomonas reinhardtii.

A method is described which results in a 2750-fold purification of hydrogenase from Chlamydomonas reinhardtii, yielding a preparation which is approximately 40% pure. With a saturating amount of ferredoxin as the electron mediator, the specific activity of pure enzyme was calculated to be 1800 micromoles H(2) produced per milligram protein per minute. The molecular weight was determined to be 4.5 x 10(4) by gel filtration and 4.75 x 10(4) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme has an abundance of acidic side groups, contains iron, and has an activation energy of 55.1 kilojoules per mole for H(2) production; these properties are similar to those of bacterial hydrogenases. The enzyme is less thermally stable than most bacterial hydrogenases, however, losing 50% of its activity in 1 hour at 55 degrees C. The K(m) of purified hydrogenase for ferredoxin is 10 micromolar, and the binding of these proteins to each other is enhanced under slightly acidic conditions. Purified hydrogenase also accepts electrons from a variety of artificial electron mediators, including sodium metatungstate, sodium silicotungstate, and several viologen dyes. A lag period is frequently observed before maximal activity is expressed with these artificial electron mediators, although the addition of sodium thiosulfate at least partially overcomes this lag.

Journal Article↗
PubMed1984

Activation and de novo synthesis of hydrogenase in chlamydomonas.

Two distinct processes are involved in the formation of active hydrogenase during anaerobic adaptation of Chlamydomonas reinhardtii cells. In the first 30 minutes of anaerobiosis, nearly all of the hydrogenase activity can be attributed to activation of a constituitive polypeptide precursor, based on the insensitivity of the process to treatment with cycloheximide (15 micrograms per milliliter). This concentration of cycloheximide inhibits protein synthesis by greater than 98%. After the initial activation period, de novo protein synthesis plays a critical role in the adaptation process since cycloheximide inhibits the expression of hydrogense in maximally adapted cells by 70%. Chloramphenicol (500 micrograms per milliliter) has a much lesser effect on the adaptation process.Incubation of cell-free extracts under anaerobic conditions in the presence of dithionite, dithiothreitol, NADH, NADP, ferredoxin, ATP, Mg(2+), Ca(2+), and iron does not lead to active hydrogenase formation. Futhermore, in vivo reactivation of oxygen-inactivated hydrogenase does not appear to take place.The adaptation process is very sensitive to the availability of iron. Iron-deficient cultures lose the ability to form active hydrogenase before growth, photosynthesis, and respiration are significantly affected. Preincubation of iron-deficient cells with iron 2 hours prior to the adaptation period fully restores the capacity of the cells to synthesize functional hydrogenase.

Journal Article↗