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PubMed1991

Molecular structure, polymorphism, and toxicity of lantadene A, the pentacyclic triterpenoid from the hepatotoxic plant Lantana camara.

Lantadene A (22 beta-angeloyloxy-3-oxo-olean-12-en-28-oic acid), a pentacyclic triterpenoid compound from lantana (Lantana camara) leaves has been obtained in two polymorphic forms I and II. Form I had white, fluffy, and rod-shaped uniform crystals. Form II particles were irregular, shining, and polyhedral. The two forms differed in melting behavior. The powder x-ray diffraction of form I showed sharp peaks whereas from II did not contain distinct peaks. From single-crystal three-dimensional x-ray structure determination, the molecular structure of form I has been established. A/B and B/C rings of the molecule are trans fused while D/E rings are cis fused. The packing of the molecule is stabilized by hydrogen bonding. Form I of lantadene A was non-toxic to guinea pigs on oral administration. Form II induced ictericity and toxicity associated with decrease in feed intake and fecal output, hepatomegaly, increase in plasma bilirubin, and acid phosphatase activity.

Animals↗
PubMed1992

Organization, polymorphism, and molecular cytogenetics of chromosome-specific alpha-satellite DNA from the centromere of chromosome 2.

The general usefulness of alpha-satellite DNA probes for the molecular, genetic, and cytogenetic analysis of the human genome is enhanced by their being chromosome specific. Here, we describe the isolation and characterization of an alpha-satellite subset specific for human chromosome 2. Three clones, p2-7, p2-8, and p2-11, obtained from an EcoRI-digested lambda phage library from flow-sorted chromosome 2, are specific for the centromere of chromosome 2 by somatic cell hybrid mapping and chromosomal in situ hybridization. Nucleotide sequence analysis identifies the chromosome 2-specific alpha-satellite subset D2Z1 as a member of the suprachromosomal subfamily II, which is based on a characteristic two-monomer repeat. The D2Z1 subset is further organized as a series of diverged 680-bp tetramers, revealed after digestion of genomic DNA with HaeIII, HindIII, HinfI, StuI, and XbaI. Using pulsed-field gel electrophoresis (PFGE), probes p2-7, p2-8, and p2-11 detect polymorphic restriction patterns within the alpha-satellite array. Among 15 different chromosomes 2 (in two two-generation families and one three-generation family), the length of the D2Z1 alpha-satellite array varied between 1050 and 2900 kb (mean = 1850 kb, SD = 550 kb). The inheritance of the chromosome 2 alpha-satellite arrays and their associated polymorphisms was strictly Mendelian.

Aneuploidy↗
PubMed1993

Molecular variation of Adh and P6 genes in an African population of Drosophila melanogaster and its relation to chromosomal inversions.

Four-cutter molecular polymorphism of Adh and P6, and chromosome inversion polymorphism of chromosome II were investigated in 95 isogenic lines of an Ivory Coast population of Drosophila melanogaster, a species assumed to have recently spread throughout the world from a West African origin. The P6 gene showed little linkage disequilibrium with the In(2L)t inversion, although it is located within this inversion. This suggests that the inversion and the P6 locus have extensively exchanged genetic information through either double crossover or gene conversion. Allozymic variation in ADH was in linkage disequilibrium with In(2L)t and In(2R)NS inversions. Evidence suggests either that inversion linkage with the Fast allele is selectively maintained, or that this allele only recently appeared. Molecular polymorphism at the Adh locus in the Ivory Coast is not higher than in North American populations. New haplotypes specific to the African population were found, some of them connect the "WaS-like" haplotypes found at high frequencies in the United States to the other slow haplotypes. Their relation with In(2L)t supports the hypothesis that WaS recently recombined away from an In(2L)t chromosome which may be the cause of its divergence from the other haplotypes.

Africa, Western↗
PubMed2005

Controlling molecular crystal polymorphism with self-assembled monolayer templates.

The control of crystal polymorphism is a long-standing issue in solid-state chemistry, which has many practical implications for a variety of commercial applications. At least four different crystalline forms of 1,3-bis(m-nitrophenyl) urea (MNPU), a classic molecular crystal system, are known to crystallize from solution in various concomitant combinations. Herein we demonstrate that the introduction of gold-thiol self-assembled monolayers (SAMs) of substituted 4'-X-mercaptobiphenyls (X = H, I, and Br) into the crystallization solution can serve as an effective means to selectively template the nucleation and growth of alpha-, beta-, and gamma-MNPU phases, respectively. Polymorph control in the presence of SAM surfaces persists under a variety of solution conditions and consistently results in crystalline materials with high phase purity. The observed selectivity is rationalized on the basis of long-range two-dimensional geometric lattice matching and local complementary chemical interactions at the SAM/crystal interfaces.

Journal Article↗
PubMed2004

The genetic architecture of quantitative traits: lessons from Drosophila.

Understanding the genetic architecture of quantitative traits begins with identifying the genes regulating these traits, mapping the subset of genetically varying quantitative trait loci (QTLs) in natural populations, and pinpointing the molecular polymorphisms defining QTL alleles. Studies in Drosophila have revealed large numbers of pleiotropic genes that interact epistatically to regulate quantitative traits, and large numbers of QTLs with sex-, environment- and genotype-specific effects. Multiple molecular polymorphisms in regulatory regions of candidate genes are often associated with variation for complex traits. These observations offer valuable lessons for understanding the genetic basis of variation for complex traits in other organisms, including humans.

Animals↗
PubMed2005

DNA polymorphism and molecular subtyping of the capsular gene cluster of group B streptococcus.

Serotyping and other phenotypic methods are often used to characterize the capsular polysaccharide of group B streptococci (GBS). We describe a capsular genotyping method that utilizes PCR of capsular polysaccharide synthesis genes (cps) and restriction enzyme digestion. This method facilitates the detection of DNA polymorphism in cps genes and correlates well with serotyping.

Bacterial Capsules↗
PubMed1993

Linkage disequilibrium in the white locus region of Drosophila melanogaster.

Linkage disequilibrium between molecular polymorphisms in a 10 kb region in the white locus of Drosophila melanogaster, revealed with a battery of four-cutter restriction enzymes, was investigated in 266 lines sampled from seven natural populations around the world. A total of 73 (35 restriction site, 37 insertion/deletion and 1 inversion) polymorphisms were detected, of which 55 non-unique polymorphisms were analysed for linkage disequilibrium. Clustering of significant linkage disequilibrium was observed in the transcriptional unit of the white locus as in Miyashita & Langley (1988). It was shown that about two thirds of the 2-locus combinations showing significant linkage disequilibrium have similar degree and direction of association over different populations. Despite lower divergence in allelic frequencies of molecular polymorphisms among populations, an increase in the proportion of 2-locus pairs showing significant linkage disequilibrium is observed in the transcriptional unit. Large values of Ohta's D measure ratio (1982a, b) cluster in the transcriptional unit, and correspond to significant linkage disequilibria. Although the exact molecular mechanism is not clear, these results suggest that epistatic selection is responsible for significant linkage disequilibrium in the transcriptional unit of this locus.

Animals↗
PubMed2005

Pulsed field gel electrophoresis and random amplified polymorphic DNA molecular characterization of Ralstonia pickettii isolates from patients with nosocomial central venous catheter related bacteremia.

Over a period of 18 months 3 clusters of central venous catheter-related Ralstonia pickettii bacteremia occurred in 3 different units of the same hospital. In order to investigate the relatedness of the clinical isolates we studied 15 strains using pulsed-field gel electrophoresis (PFGE) and randomly amplified polymorphic DNA (RAPD) techniques. The combined analysis of the results obtained by these two methods led us to conclude that all the patients except one were infected by a single clone comprising two variants circulating in the units. Only one case was due to a different strain, probably originating outside the ward. PFGE and RAPD appear to be discriminatory techniques to study the clonal relationship among the isolates and can represent a good tool to perform the epidemiological investigation of an outbreak.

Bacteremia↗
PubMed2005

Self-propagating, molecular-level polymorphism in Alzheimer's beta-amyloid fibrils.

Amyloid fibrils commonly exhibit multiple distinct morphologies in electron microscope and atomic force microscope images, often within a single image field. By using electron microscopy and solid-state nuclear magnetic resonance measurements on fibrils formed by the 40-residue beta-amyloid peptide of Alzheimer's disease (Abeta(1-40)), we show that different fibril morphologies have different underlying molecular structures, that the predominant structure can be controlled by subtle variations in fibril growth conditions, and that both morphology and molecular structure are self-propagating when fibrils grow from preformed seeds. Different Abeta(1-40) fibril morphologies also have significantly different toxicities in neuronal cell cultures. These results have implications for the mechanism of amyloid formation, the phenomenon of strains in prion diseases, the role of amyloid fibrils in amyloid diseases, and the development of amyloid-based nano-materials.

Amino Acid Motifs↗
PubMed2003

The use of amplified fragment length polymorphism for molecular analysis of Beauveria bassiana isolates from Kenya and other countries, and their correlation with host and geographical origin.

Beauveria spp. (one Beauveria sp., two B. brongniartii, and 47 B. bassiana) isolated from insects and soil from Kenya and other 16 different countries, were obtained from the CABI Bioscience Genetic Resource Collection. DNA was extracted from the 50 isolates and their genetic variability was investigated using restriction analysis of the internal-transcribed-spacer ribosomal region restriction fragment length polymorphism (ITS-RFLP), ITS sequencing, and amplified fragment length polymorphism (AFLP). The B. bassiana isolates could not be distinguished by ITS-RFLP as all of them showed the same banding pattern. However, the AFLP technique provided more information on polymorphism between the isolates, allowing them to be clustered by relative similarity using band matching and unweighted pair group method with arithmetic mean analysis. Although no significant correlation between the isolates and host and geographical origins were observed, the technique revealed clonal populations of B. bassiana within Kenya.

Acrylic Resins↗
PubMed1985

DNA polymorphism and molecular pathology of the human globin gene clusters.

In the past few years there has been intensive study of the human globin genes. This study has provided important insights into normal gene structure and function and the nature of molecular defects leading to a set of inherited diseases. In turn, this information forms the basis for rational design of specific tests for prenatal diagnosis of particular forms of beta-thalassemia. Several areas demand further investigation. First, we need to know more about the region within the beta-gene cluster in which recombination appears to be more frequent than in areas surrounding it. This will provide new insights into the evolution of a segment of the genome and aid in explaining how particular mutations are dispersed to numerous chromosome types. Second, study of additional beta-thalassemia genes from human populations not previously studied will provide new gene defects, some of which may yield further clues about RNA transcription and processing. In addition, some (e.g., the coding region substitutions that affect RNA processing) may allow identification of new mechanisms of gene dysfunction. Third, we need further refinement of prenatal diagnostic tests so that early, accurate, and simplified assessment of pregnancies at risk can be accomplished widely, particularly in those geographic regions where beta-thalassemia is especially prevalent.

Alleles↗
PubMed2006

Insights into the molecular mechanism underlying polymorph selection.

We use molecular simulations to study polymorph selection during the crystallization of charge-stabilized colloidal suspension. By modifying the conditions of crystallization, we invert the stability of two polymorphs and induce the formation of crystallites whose structure is predominantly that of the stable polymorph. However, our simulations reveal that kinetics play a major role not only during the nucleation step but also in the growth mechanism. The growth of postcritical crystallites of the stable polymorph proceeds through a complex mechanism involving the cross-nucleation of a third metastable polymorph followed by the conversion of this third polymorph into the stable structure.

Journal Article↗
PubMed2003

[Molecular-genetic polymorphisms of cultivars of common hops (Humulus lupulus L.) using ISSR-PCR analysis].

Genetic diversity among 26 Russian and European cultivars of the common hop (Humulus lupulus L.) was studied using the ISSR-PCR technique. Twenty-one primers used provided amplification of 183 DNA fragments, 106 of which (57.9%) were found to be polymorphic. The ISSR markers, specific for certain cultivars were revealed. Based on the coefficient of dissimilarity values, cluster analysis was performed and a dendrogram was constructed, on which most of the hop cultivars formed two clusters according to their origin. Advantages of the ISSR-PCR analysis in selective studies aimed at the classification and identification of common hop cultivars are discussed.

Humulus↗
PubMed1983

Scanning electron microscopy of the human hippocampus.

The human hippocampus was studied by means of scanning electron microscopy (SEM) because further investigation of its neuroanatomy has been stimulated by increasing evidence of its functional significance. Human brains were removed within 2 hours of demise and were fixed in 10% buffered formalin for several weeks. After routine coronal sections of the cerebral hemispheres, blocks were taken of the hippocampal region for light microscopy (LM), transmission electron microscopy (TEM) and SEM. At low magnifications, the different anatomical regions can be clearly identified as well as the interlocking of the dentate gyrus and the cornu Ammonis. At higher magnifications, the detailed micro-anatomical structures can be resolved. The fimbria and alveus are composed of a closely packed network of fibrils. Within the lateral ventricle, the ependymal cells are ciliated. The choroid plexus shows clusters of polygonal cells which have a brushlike border due to the presence of numerous stubby microvilli on the surface of the cells. The granular layer of the dentate gyrus is compact due to the intimate but irregular apposition of the cells resembling the dentition in malocclusion. The neuronal bodies are mostly fusiform but may taper into a flask shape. The neurons of the molecular and of the polymorphic molecular layers are much smaller and they are more widely scattered. In the hippocampal formation, the pyramidal layer stands out most clearly as its cells are larger and more angular than those of the other layers. A classical pyramidal morphology may be well shown. A very rich plexus of fibers is found in the stratum lacunosum.

Adult↗
PubMed1975

Molecular conformation prostaglandin A1 monoclinic crystalline polymorph.

The molecular conformation of the monoclinic crystalline polymorph of prostaglandin A1 has been determined by X-ray diffraction techniques. The space group is P21 with a = 13.637(2), b = 7.567(1), c = 10.576(2) A, beta = 107.37(3) degrees; Dc = 1.073 g.cm-3 for Z = 2. The molecular conformation is characterized by the nearly parallel arrangement of the C1-C7 and C13-C20 side chains, with a general flattening of the overall structure when compared with the orthorhombic polymorph. The cyclopentenone moiety assumes a C8 envelope conformation with C8 and O9 displaced +0.29 A and -0.18 A from the C9-C10=C11-C12 plane respectively. Concerted, small varations of the torsion angles, primarily about the C8-C12, C14-C15 and C16-C17 bonds, bring the monoclinic and orthorhombic conformations into coincidence.

Models, Molecular↗