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At least 73 records · Page 4Linked to original sources
PubMed1995

Phase polymorphism, molecular interactions, and miscibility of binary mixtures of dimyristoyl-N-biotinylphosphatidylethanolamine with dimyristoylphosphatidylcholine.

The phase diagram of hydrated binary mixtures of dimyristoyl-N-biotinylphosphatidylethanolamine with dimyristoylphosphatidylcholine in 1 M NaCl has been established by differential scanning calorimetry. Identification of the structures of the phases involved has been made by using X-ray diffraction, spin label ESR spectroscopy, and 31P NMR spectroscopy. On the composition axis, the phase diagram is divided into three regions corresponding to formation of compounds in the gel phase with biotinyl lipid to phosphatidylcholine stoichiometries of approximately 1:1 and 1:3 mol/mol. For the first two regions (up to 75 mol % phosphatidylcholine), the lipids in the gel phase have interdigitated chains (L beta i), whereas in the third region the gel phase is not interdigitated (L beta' or L beta). For the first region (up to 50 mol % phosphatidylcholine), the fluid phase is of the novel isotropic type (IMI) composed of aggregated normal micelles that is characteristic of shorter chainlength biotinylated lipids [Swamy, M.J., Würz, U., & Marsh, D. (1993) Biochemistry 32, 9960-9967], whereas for the other two regions a normal fluid lamellar (L alpha) phase obtains. The equimolar mixture, which lies at a stoichiometric phase boundary, melts isothermally and then undergoes a transition from the isotropic IMI structure to the lamellar L alpha structure with increasing temperature in the fluid phase.

Biotin↗
PubMed2002

Cellular, serological, and molecular polymorphism of the class I and class II loci of the canine Major Histocompatibility Complex.

This study was undertaken to determine the relationships between canine cellular and serological determinants and more recently described genes. Such relationships might reveal information about immunological reactivity or function of various proteins. To do this we studied the haplotypic associations of dog leukocyte antigen (DLA) class I and class II alleles determined from a panel of 14 DLA-D homozygous dogs. This panel of dogs was typed for the serological determinants DLA-A, DLA-B and DLA-C. Polymorphisms for DLA-DQA1, DLA-DQB1, DLA-DRB1 and DLA-88 were also determined. The number of alleles (one or two) for two microsatellite markers in the DLA region were also determined. Analyses of the nucleotide sequences and of the serological and cellular typing data revealed that phenotypic homozygosity, as defined by the DLA-D type in mixed leukocyte culture (MLC), tended to correlate with homozygosity at the DLA-DRB1 locus but not necessarily at the DLA-DQB1 locus. Furthermore, MLC specificity was determined by other loci besides DLA-DRB1 and DLA-DQB1. The amino acid at position 63 of the DR beta chain could contribute to the DLA-B serological specificity. DLA-88, the most polymorphic class I gene characterized to date, did not have an easily identifiable association with either the DLA-A or DLA-C class I serological specificities. Homozygosity or heterozygosity of each of two microsatellite markers, FH 2200 and FH 2202, located in the class I or class II region, respectively, did not correlate with homozygosity or heterozygosity of the most polymorphic known class I (DLA-88) or class II (DLA-DRB1) genes.

Animals↗
PubMed1997

Effect of the molecular polymorphisms of human paraoxonase (PON1) on the rate of hydrolysis of paraoxon.

1. The hydrolysis of organophosphate pesticides (OP) and nerve gases by serum paraoxonase (PON1) is an important factor determining their toxicity to mammals including man. The PON1 gene contains 2 polymorphic sites at amino acid positions 55 (L-->M) and 192 (G-->A, classically defined as the A and B genotypes) which result in several alloenzymes of PON1 in human serum. 2. The 192 polymorphism has previously been shown to affect PON1 activity. We have investigated the effect of both polymorphisms on the hydrolysis of paraoxon by serum from 279 healthy human subjects. 3. The 55 polymorphism significantly influenced PON1 activity. MM homozygotes had over 50% less activity towards paraoxon compared to the LL and LM genotypes regardless of the 192 genotype (P < 0.001). 4. Multiple regression analysis indicated that the 192 polymorphism, 55 polymorphism and serum PON1 concentration were responsible for 46, 16 and 13% of the variation in PON1 activity, respectively (all P < 0.001). None of the other parameters investigated significantly affected PON1 activity. 5. Therefore both PON1 polymorphisms affect the hydrolysis of paraoxon. AA/MM and AB/MM individuals may be potentially more susceptible to OP intoxication. 6. Genotyping individuals for both PON1 polymorphisms may provide a method for identifying those individuals at most risk of OP poisoning. The effect of PON1 polymorphisms on activity may also explain why some Gulf War Veterans have developed Gulf War Syndrome and some have not.

Adult↗
PubMed1992

Molecular polymorphism and epidemiology of Neisseria meningitidis immunoglobulin A1 proteases.

Neisseria meningitidis is one of several important bacterial pathogens that secrete a specific protease capable of cleaving human immunoglobulin A1 (IgA1) in the hinge region. To obtain further information on this putative virulence factor, we examined the IgA1 protease and iga gene region of 133 isolates of N. meningitidis assigned to 88 multilocus enzyme genotypes and representing major epidemics and carrier strains from 19 countries. Of the two IgA1 cleavage specificities previously observed, isolates associated with epidemics of meningococcal disease showed exclusively type 1 IgA1 protease activity. Considerable heterogeneity of the N. meningitidis IgA1 protease was demonstrated at both the protein and gene levels. Thus, five different forms of IgA1 protease were detected with enzyme-neutralizing antibodies raised in rabbits. An antiserum raised against a single type 2 IgA1 protease inhibited the enzyme activity of all strains examined, a finding of potential significance for the possible application of IgA1 protease in a vaccine against meningococcal disease. Examination of the iga gene region with restriction endonucleases revealed a high degree of polymorphism among strains belonging to some multilocus enzyme genotypes. The different iga gene types did not correlate with cleavage type or inhibition of the IgA1 protease. Our findings indicate that horizontal genetic exchange occurs in vivo with considerably different frequency in different clones of meningococci.

Carrier State↗
PubMed2004

Molecular polymorphism of ABO blood group gene in Austronesian and non-Austronesian populations in Oceania.

A number of archeological, linguistic, and genetic studies have been carried out on the peopling of the Pacific, while the origin of Polynesians or the Lapita people is still open to debate. The Lapita people are believed to have populated the Bismarck Archipelago more than 3600 years ago. However, their Melanesian descendants still living in the Bismarck Archipelago have not been genetically clarified yet. To address this question, polymorphism of the ABO blood group gene was investigated in the following three populations who are considered to be almost free from recent admixtures: (i) Balopa islanders as Austronesian (AN)-speaking Melanesians living in the northwestern end of the Bismarck Archipelago; (ii) Gidra as non-Austronesian (NAN)-speaking Melanesians in southwestern lowlands of Papua New Guinea; and (iii) Tongan living in Ha'apai island as AN-speaking Polynesians. Interestingly, there were marked differences in allele frequencies of ABO*A101 and ABO*A102 among the three populations. The allele frequencies of ABO*A101 and ABO*A102 were 7.9 and 19.3% in Balopa, 23.2 and 0.0% in Gidra, and 2.9 and 25.0% in Tongan. Both phylogenetic and correspondence analyses suggested that Balopa was more close to Tongan than to Gidra and that Balopa was genetically placed between Tongan and Asian populations. Our results imply that Balopa may be Melanesian descendants of the Lapita people who populated the Bismarck Archipelago.

ABO Blood-Group System↗
PubMed2005

Molecular polymorphism of native gonadotropin-releasing hormone (GnRH) is restricted to mammalian GnRH and [hydroxyproline9] GnRH in the developing rat brain.

Although chicken gonadotropin-releasing hormone (GnRH)-II is thought to occur in most animal species, its presence and that of two other variants (lamprey GnRH-III, salmon GnRH) is questionable in rodents. Here we report on the GnRH peptides present in the hypothalamus and the remaining brain of rat of both sexes during development. No immunoreactivity was detected in the elution zone of either native or hydroxylated forms of the above three variants in any of brain extracts chromatographed. The main peptides detected were mammalian GnRH (mGnRH) and m[hydroxyproline9]GnRH (mHypGnRH). In the hypothalamus, these peptides were associated with their free acid and precursor forms. N-terminal fragments from both native decapeptides (GnRH) and mGnRH (GnRH) were observed only in the hypothalamus. C-terminal fragments were detected in both tissues. The relative proportions of mGnRH and mHypGnRH showed no developmental changes in the remaining brain. The hypothalamic proportions of mHypGnRH were high on day 5, and decreased from day 15 onwards. The [Gly11]-precursor to mHypGnRH molar ratio was twofold lower than with the non-hydroxylated peptides. The mGnRH to GnRH molar ratio increased in males but decreased in females during development. No sex-related differences were observed in the native decapeptide to GnRH molar ratio. It was concluded that (1) chicken GnRH-II is not present in all mammals, (2) mGnRH and mHypGnRH are the main GnRH isoforms present in the rat brain, (3) the processing of [Gly11]-precursor into mHypGnRH occurs at a higher rate than that of mGnRH, and (4) the catabolism does not interfere with the developmental changes undergone by the mGnRH and mHypGnRH brain contents.

Age Factors↗
PubMed2005

Molecular polymorphism of strains within Paramecium septaurelia (Ciliophora, Oligohymenophorea).

RAPD-PCR fingerprinting and ARDRA riboprinting revealed polymorphism within P. septaurelia strains from Russia (4 strains from Lower Volga Basin), and one strain from USA, Florida. However, the first method showed the existence of four RAPD genotypes while the second revealed only two groups of strains with different band patterns. All studied strains had a high percentage of surviving hybrid clones in the inter-strain crosses, with little differentiation of strains within species. Intra-species differentiation of strains in RAPD band patterns may be connected with the degree of inbreeding for the studied species. Species of the P. aurelia complex can be arranged according to the degree of inbreeding characteristic for each, which is correlated with the degree of DNA polymorphism revealed by the RAPD method from extreme inbreeders (e.g. P. sexaurelia), moderate inbreeders (e.g. P. triaurelia) to weak inbreeders (e.g. P. pentaurelia). P. septaurelia of the P. aurelia complex should be included in the group of extreme inbreeder.

Animals↗
PubMed2005

[Molecular polymorphism of viral dsRNA of yeast Saccharomyces paradoxus].

An analysis of 53 strains of yeast Saccharomyces paradoxus (YSP) of different geographic origins enabled us, for the first time, to find viral double-stranded RNA (L and M fractions) in YSP and to study natural polymorphism. As in the cultured Scerevisiae, the size of L dsRNA was constant (4.5 kb). The size of minor M dsRNA varied from 1.5 to 2.4 k.b. In YSP, we determined 7 types of M dsRNA (M1-M7), which were not connected with the source of isolation or geographic origin of the host strains.

Asia↗
PubMed1988

I-J as a second T cell receptor for self--molecular polymorphism and the role in suppressive signal transduction.

We have been able to demonstrate an I-J epitope on the cell surface of interleukin 2 (IL-2) dependent T cell clones of both T helper (Th) and suppressor T cells (Ts) lineages by flow microfluorometry with fluoresceinated anti-I-Jk, and to identify the molecule by the specific immunoprecipitation and the gel analysis. The I-J molecule thus detected is a novel 90K dimeric molecule composed of 45K glycopeptide subunits distinct from conventional T cell receptor (TcR) or CD28. The molecule is not comodulated with TcR or T3 on the cell surface. Monoclonal anti-I-J can inhibit various major histocompatibility complex (MHC)-restricted T cell functions including Ca2+ influx, antigen-induced T cell proliferation and IL-2 production, indicating that the ligation of I-J molecules results in a negative signal transduction. Since it has been reported that the I-J phenotype undergoes a systematic adaptive alteration in radiation bone marrow chimeras in association with the acquired class II restriction, it is likely that I-J is a novel receptor for self MHC apart from TcR heterodimer and is required for a negative signal transduction.

Animals↗
PubMed1994

Molecular polymorphism of lumican during corneal development.

PURPOSE: To evaluate the expression of lumican and decorin, the major proteoglycans of the adult corneal stroma, during the acquisition of corneal transparency in developing chick embryos. METHODS: mRNA levels of decorin and lumican were measured in total RNA extracted from corneas of days 9 to 18 of development by Northern blot analysis using a 32P-labeled cDNA clone to each proteoglycan. The synthesis lumican and decorin precursor proteins were determined by biosynthetically radiolabeling corneas from day 7 to 18 chick embryos with 35S-methionine, and then using antibodies specific for lumican and decorin core proteins to precipitate the radiolabeled precursor proteins. The accumulation of lumican and decorin was determined by fractionating extracts of day 7 to 18 embryonic corneas by DEAE chromatography into glycoprotein and proteoglycan fractions, and then analyzing each fraction by Western blot using antibodies to lumican and decorin. RESULTS: Lumican and decorin mRNA increased from day 9 to day 18, with respect to beta-actin. The rate of decorin precursor protein synthesis remained relatively low and constant throughout development, but lumican precursor protein synthesis increased dramatically between days 7 and 9 of embryonic development, to a value 80-fold higher than that of decorin, and then decreased exponentially through day 18. Lumican with polylactosamine (nonsulfated keratan sulfate) side chains was detected in extracts of corneas as early as day 7 of embryonic development, and continued to accumulate within the cornea through day 18. Decorin and lumican with sulfated glycosaminoglycan side chains (ie, proteoglycans), however, were not detected in corneal extracts until day 15, when transparency starts to increase, and then accumulated considerably within the cornea by day 18. CONCLUSIONS: The results of these studies suggest that decorin and lumican expression are independently regulated during the period of acquisition of corneal transparency. The switch in production of the polylactosamine form of lumican to the proteoglycan form of lumican at the onset of increasing corneal transparency suggests that the sulfation of lumican may be important for the development of corneal transparency.

Actins↗
PubMed1998

Evolution towards hormone independence of the MXT mouse mammary tumor is associated with a gradual change in its estrogen receptor molecular polymorphism.

Using a method based on [3H]tamoxifenaziridine ([3H]TAZ) labeling, sequential immunoadsorption with anti-ER monoclonal antibodies, sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE) and fluorography, we observed a striking change inthe estrogen receptor (ER) electrophoresis pattern of the transplantable MXT mouse mammary tumor. Early, ER "rich" tumors (approximately 100 fmol/mg prot) displayed classical cytosolic 67 and 50 KDa bands. These bands disappeared in favor of a "cytosolic" 35 KDa band during progression towards undifferentiated ER "poor" tumors (approximately 25 fmol/mg prot). Although we can not rule out that this 35 KDa peptide results from in vivo ER proteolysis, it seems unique in view of the following: 1. It is immunoadsorbed not only by an anti-ER monoclonal antibody (H-222) directed to the hormone-binding domain, but also by an anti-ER monoclonal antibody (H-226) which interacts with an epitope in the A/B region close to the DNA-binding domain and is mainly exposed under activation conditions. 2. It does not bind [3H]estradiol([3H]E2) and a tentative to restore its [3H]E2 binding capacity with calmodulin and ATP was unsuccessful. The observation of similar approximately 35 KDa ERs in the nuclear fraction of early tumor transplants and in control uterus suggests that this peptide is already in an activated form. Structural alterations of ER and/or associated "anchorage" nuclear proteins may beat the origin of its cytosolic localization. Moreover, the fact that the addition of calmodulin and ATP to late MXT transplants cytosols fails to increase their [3H]E2 binding capacity indicates that the low ER content of these tumors does not result from a deficiency in the phosphorylation status of the receptor.

Animals↗
PubMed1987

Human complement C3b/C4b receptor (CR1) mRNA polymorphism that correlates with the CR1 allelic molecular weight polymorphism.

The human C3b/C4b receptor (CR1) is a Mr approximately equal to 200,000 single-chain integral membrane glycoprotein of human erythrocytes and leukocytes. It functions both as a receptor for C3b- and C4b-coated ligands and as a regulator of complement activation. Prior structural studies have defined an unusual molecular weight allelic polymorphism in which the allelic products differ in molecular weight by as much as 90,000. On peripheral blood cells there is codominant expression of CR1 gene products of Mr 190,000 (A), 220,000 (B), 160,000 (C), and 250,000 (D). Results of prior biosynthetic and tryptic peptide mapping experiments have suggested that the most likely basis for the allelic molecular weight differences is at the polypeptide level. In order to define further the molecular basis for these molecular weight differences, human CR1 was purified to homogeneity, tryptic peptide fragments were isolated by HPLC and sequenced, oligonucleotide probes were prepared, and a CR1 cDNA was identified. A subclone of this CR1 cDNA was used as a probe of RNA blots of Epstein-Barr virus-transformed cell lines expressing the allelic variants. Each allelic variant encodes two distinct transcripts. A mRNA size polymorphism was identified that correlated with the gene product molecular weight polymorphism. This finding, in addition to a prior report of several homologous repeats in CR1, is consistent with the hypothesis that the molecular weight polymorphism is determined at the genomic level and may have been generated by unequal crossing-over.

Alleles↗