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PubMed1998

Rapid hybrid speciation in wild sunflowers.

Hybrid or "recombinational" speciation refers to the origin of a new homoploid species via hybridization between chromosomally or genetically divergent parental species. Theory predicts that this mode of speciation is punctuated, but there has been little empirical evidence to support this claim. Here, we test the hypothesis of rapid hybrid speciation by estimating the sizes of parental species chromosomal blocks in Helianthus anomalus, a wild sunflower species derived via hybridization between H. annuus and H. petiolaris. Analysis of the frequency spectrum of parental species chromosomal blocks with respect to predictions based on R. A. Fisher's [Fisher, R. A. (1953) Heredity 8, 187-197] junctions approach, suggests that H. anomalus arose rapidly, probably in fewer than 60 generations. This result is corroborated by independent lines of evidence demonstrating (i) a significant concordance between the genomes of H. anomalus and early generation H. annuus x H. petiolaris synthetic hybrids, and (ii) a rapid recovery of pollen fertility in these synthetic hybrid lineages. These results are not only consistent with theory but also provide a new and general method for estimating the tempo of hybrid speciation and dating the origin of hybrid zones.

Biological Evolution↗
PubMed2000

[Value of the immunochromatographic assay for detecting IgG antibodies against 38 kDa mycobacterial antigen in diagnosis of tuberculosis].

Despite of a fast development in the techniques of rapid identification of mycobacteria by molecular genetic techniques, serodiagnosis may be of special values as non-expensive, easy to perform method. Several serodiagnostic tests, principally those using immunoenzymatic (ELISA) methodology are available. The goal of our study was to evaluate one step coloured immunochromatographic assay detecting IgG antibodies against antigen 38 kDa (Rapid Test TB). Our material consisted of 278 serum samples--tuberculosis (n = 155), healthy (n = 36), sarcoidosis (n = 50), lung cancer (n = 25) mycobacterial infections other than tuberculosis (n = 12). Tuberculosis group consisted of new culture positive cases (n = 66), new culture negative cases (n = 23), chronic cases (n = 43) and extrapulmonary TB (n = 23). Specificity of 96% and sensitivity of 54% was obtained. In pulmonary TB sensitivity of 50% and in extrapulmonary TB of 74% was obtained. In chronic cases sensitivity of 70% and in new cases of 40% was received. Sensitivity of 44% in new culture positive cases and 30% in new culture negative cases was obtained. We conclude that immunochromatographic test may be a very useful tool improving tuberculosis diagnosis, especially in extrapulmonary tuberculosis. Strip test may be an interesting alternative as it is an extremely simple, rapid, and cheap technique.

Chromatography↗
PubMed2000

Hereditary non-polyposis colorectal cancer: an updated review.

INTRODUCTION: Colorectal cancer is the commonest cause of death due to malignancy in non-smokers in the western countries. The two main hereditary types of colorectal cancer are familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC), constituting approximately 10% of all cases of colorectal cancer. The main aim of this review is to reappraise the current advances in the genetics and diagnosis of HNPCC. METHODS: A Medline search was carried out to identify papers published from 1970 to 1999 on HNPCC. Embase and Cochrane databases were also searched. Reference lists of retrieved articles were carefully searched for additional articles. RESULTS AND CONCLUSIONS: Recent technological advances in the genetics of HNPCC have refined the criteria for diagnosis and management of HNPCC, however current policies regarding the testing of pedigrees are not clearly established. We believe that with the rapid development in this area definitive clinical guidelines will need to be available in future for the management of HNPCC.

Colorectal Neoplasms, Hereditary Nonpolyposis↗
PubMed2005

Rapid mood switching and suicidality in familial bipolar disorder.

OBJECTIVES: Rapidly alternating or mixed mood states in bipolar disorder are associated with a particularly high risk for suicidal behavior. Are individuals with these patterns of illness more likely to develop suicidal intentions, or are they less able to resist them? This analysis examines the specific contribution of rapid switching and other variables to the relative likelihood of having or acting on self-reported suicidal thought and action, in a large group of individuals with bipolar disorder. METHODS: The analysis included 1574 family members with bipolar disorder interviewed for a multi-site bipolar disorder genetic linkage study. Two models were tested, using the same set of demographic and clinical data points as independent variables. One model tested the influence of rapid switching and other variables on self-reported suicidal thought or action (i.e., suicidality), while the other tested the influences on suicidal action only among those who reported a history of suicidality. RESULTS: Over 75% of subjects had contemplated suicide and 38% reported a history of suicidal behavior. A history of rapid switching was associated with higher likelihood of a history of suicidality, as was panic disorder. Familial suicidal behavior, as well as drug abuse, increased the likelihood of suicidal action among suicidal individuals, but did not increase the likelihood of becoming suicidal. Female sex, early age at onset, and several demographic factors were associated with both facets of suicidality. CONCLUSIONS: Factors associated with high acuity of distress, such as panic attacks and unstable moods, appear to enhance the risk of suicidality in general. Factors that affected the threshold for action without increasing suicidality overall can also be seen as markers of impulsive decision-making. Of the two distinct kinds of suicidal risk, the latter - the likelihood of action given intent - appears to be the more familial.

Adult↗
PubMed1975

Genetic studies on walking behavior in Drosophila melanogaster. I. Selection and hybridization analysis.

Rapid vs. slow types of walking behavior in Drosophila melanogaster were tested in response to light in a connected test-tube apparatus. The effect of selection for both types of behavior was clearly recognized after only a few generation. The heritability of the two traits of walking behavior was remarkably different; the former was estimated to be about 7%, the latter 26%. Walking behavior is possibly controlled by a major gene with the behavior manifesting slow response to light being dominant to that manifesting rapid walking behavior.

Animals↗
PubMed2005

Genetic identification and detection of human pathogenic Rhizopus species, a major mucormycosis agent, by multiplex PCR based on internal transcribed spacer region of rRNA gene.

BACKGROUND: Mucormycosis is an invasive opportunistic infection caused by fungi belonging to the order Mucorales. Due to the lack of laboratory tests, the diagnosis of mucormycosis is notoriously difficult. Added with its rapid progression as well as the debilitated state of the patients who contract the disease, mortality is extremely high. OBJECTIVE: The goal of this study was to genetically identify human pathogenic Rhizopus species, a major mucormycosis agent, by the internal transcribed spacer (ITS) region of rRNA gene. METHODS: Primers were designed to identify five Rhizopus species known to cause human disease by multiplex PCR. PCR was done not only with test strains and clinical isolates, but also with clinical samples from cutaneous mucormycosis patients. Sporangiospore morphology was observed by scanning electron microscopy to confirm the correlation of phenotypic and genotypic features. RESULTS: Multiplex PCR identified five Rhizopus species including Rhizopus oryzae, where R. azygosporus could only be distinguished from R. microsporus by certain polymorphisms that were present in its sequence. When this multiplex PCR was applied to clinical samples from three mucormycosis patients (paraffin sections from all and sera from one patient), Rhizopus DNA corresponding to the isolated pathogens were specifically detected. CONCLUSION: While fungal DNA detection from clinical samples is a rigorously studied area, this is the first report to genetically identify and detect Rhizopus species from human mucormycosis specimens. This may expand the possibility of this multiplex PCR system not only to identify isolated fungi, but also as a screening method for visceral mucormycosis.

Adolescent↗
PubMed1998

Overview of RB gene mutations in patients with retinoblastoma. Implications for clinical genetic screening.

OBJECTIVE: This study aimed to determine the distribution of germline mutations in the retinoblastoma (RB) gene in patients with retinoblastoma to design more effective genetic testing. DESIGN: A meta-analysis. PARTICIPANTS: 192 cases identified from literature. METHODS: All identifiable reported cases of bilateral retinoblastoma, which included DNA sequence analysis of the RB gene, were reviewed. MAIN OUTCOME MEASURE: Type of genetic mutation. RESULTS: Among 192 patients with retinoblastoma with identifiable germline mutations in the RB gene, the DNA alteration was a nonsense mutation in 83 (43%), frameshift in 67 (35%), intron mutation in 23 (12%), missense mutation in 11 (6%), in-frame deletion in 5 (3%), and promoter mutation in 3 (2%). Mutations were distributed throughout 24 of the 27 exons of the RB gene with no single mutational "hotspot." Exons 8, 17, 18, and 23 were involved most often, and 189 (98%) of the mutations were predicted to affect the RB large pocket domain. CONCLUSIONS: A single genetic test is unlikely to detect all germline RB gene mutations in patients with retinoblastoma because of the variety of types and locations of mutations that occur. However, a series of complementary tests may be able to rapidly detect mutations based on the observation that most mutations alter the protein size and disrupt the large pocket domain.

Americas↗
PubMed2004

Evidence for mycorrhizal races in a cheating orchid.

Disruptive selection on habitat or host-specificity has contributed to the diversification of several animal groups, especially plant-feeding insects. Photosynthetic plants typically associate with a broad range of mycorrhizal fungi, while non-photosynthetic plants that capture energy from mycorrhizal fungi ('mycoheterotrophs') are often specialized towards particular taxa. Sister myco-heterotroph species are often specialized towards different fungal taxa, suggesting rapid evolutionary shifts in specificity. Within-species variation in specificity has not been explored. Here, we tested whether genetic variation for mycorrhizal specificity occurs within the myco-heterotrophic orchid Corallorhiza maculata. Variation across three single-nucleotide polymorphisms revealed six multilocus genotypes across 122 orchids from 30 sites. These orchids were associated with 22 different fungal species distributed across the Russulaceae (ectomycorrhizal basidiomycetes) according to internal-transcribed-spacer sequence analysis. The fungi associated with four out of the six orchid genotypes fell predominantly within distinct subclades of the Russulaceae. This result was supported by Monte Carlo simulation and analyses of molecular variance of fungal sequence diversity. Different orchid genotypes were often found growing in close proximity, but maintained their distinct fungal associations. Similar patterns are characteristic of insect populations diversifying onto multiple hosts. We suggest that diversification and specialization of mycorrhizal associations have contributed to the rapid radiation of the Orchidaceae.

Base Sequence↗
PubMed2025

Molecular insights into the persistence and co-occurrence of two different carbapenem-resistant Pseudomonas aeruginosa lineages within a hospital setting.

UNLABELLED: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) represents a critical-priority pathogen capable of causing life-threatening, multidrug-resistant infections. We performed susceptibility testing, whole-genome sequencing, and bioinformatic analyses on 137 CRPA isolates from a Guangdong hospital. We found that the major specimen types were respiratory specimens (57/137, 41.6%) and bronchoalveolar lavage (42/137, 30.7%). All isolates were carbapenem-resistant but had low resistance to polymyxin B (0.7%, 1/137). IncP-6-positive isolates exhibited &#x2265;2- to 32-fold higher resistance to 9/12 antibiotics (P < 0.05), with no difference to imipenem and meropenem. Fifty-four sequence types and 11 O-serogroups were identified, with ST1971 (6.6%) and O11 (29.9%) being predominant. Temporal and spatial patterns suggest persistent co-occurrence of clade 1 and clade 2 isolates, indicating potential nosocomial outbreak and clonal transmission. IMPORTANCE: The prevalence of carbapenem-resistant Pseudomonas aeruginosa (CRPA) has increased rapidly in recent years, yet few genetic and epidemiological studies on CRPA isolates have been performed. We performed susceptibility testing, whole-genome sequencing, and bioinformatic analyses on hospital isolates to investigate their resistance profiles and molecular epidemiology. These findings may offer new insights for developing effective global strategies to control CRPA and reduce untreatable infections in clinical settings.

Pseudomonas aeruginosa↗
PubMed2002

Genetic testing in the workplace: the employer's coin toss.

A toss of the coin by the modern-day employer reveals two options regarding genetic testing in the workplace. The employer may choose to take advantage of increasingly precise, available, and affordable genetic testing in order to ascertain the genetic characteristics--and deficiencies--of its employees. This outcome exposes the employer to a vast array of potential litigation and liability relating to the Americans with Disabilities Act, the Fourth Amendment, Title VII of the Civil Rights Act, and state legislation designed to protect genetic privacy. Alternatively, the employer may neglect to indulge in this trend of genetic testing and may face liability for employer negligence, violations of federal legislation such as OSHA regulations, and increased costs associated with insuring the health of genetically endangered employees. In the rapidly developing universe of genetic intelligence, the employer is faced with a staggering dilemma.

Carpal Tunnel Syndrome↗
PubMed2026

Guidelines for Genetic Testing of Peripheral Nerve Disorders.

Inherited peripheral neuropathies (IPNs) comprise a clinically and genetically heterogeneous group of disorders affecting approximately 1 in 2500 individuals and represent one of the most common inherited neurologic diseases. The rapidly expanding identification of disease-causing genes and the widespread implementation of next-generation sequencing (NGS) have fundamentally transformed the diagnostic evaluation of these disorders. Contemporary molecular testing has substantially increased diagnostic yield, shortened the diagnostic delay, refined disease classification, and strengthened genotype-phenotype correlations. In the United States, NGS-based multigene panels have become the most cost-effective first-line molecular diagnostic approach for most patients with suspected inherited neuropathies, whereas phenotype-directed single-gene testing remains appropriate in selected clinical circumstances and in healthcare systems in which access to comprehensive sequencing is limited. Despite these advances, challenges continue to affect diagnostic accuracy, including interpretation of variants of uncertain significance, detection of copy number variants and repeat expansions, technical limitations associated with highly homologous genomic regions such as SORD, and variability in gene content and analytic performance among commercially available testing platforms. Accurate diagnosis therefore requires integration of clinical phenotype, electrodiagnostic findings, family history, and molecular data. Establishing a precise genetic diagnosis has become increasingly important because it improves prognostic accuracy, guides genetic counseling and cascade testing, identifies patients with treatable hereditary neuropathies such as transthyretin amyloidosis, and facilitates enrollment in gene-specific clinical trials and emerging precision therapies. An evidence-based, phenotype-driven approach that incorporates contemporary molecular technologies is essential to maximize diagnostic efficiency while recognizing the strengths and limitations of currently available genetic testing strategies.

Charcot&#x2013;Marie&#x2013;tooth disease↗
PubMed2006

A laboratory strategy for genotyping haemoglobin H disease in the Chinese.

BACKGROUND: The thalassaemias are the commonest blood disorders worldwide, with South East Asia and southern China as areas of high prevalence. Accurate diagnosis of these disorders helps in clinical management with improved outcome. METHODS: The alpha-globin genotypes of 100 Chinese patients in Hong Kong with haemoglobin H (Hb H) disease were characterised. Single-tube multiplex gap-PCR was used to detect --(SEA), -alpha(3.7) and -alpha(4.2), while Hb CS, Hb QS and codon 30 (DeltaGAG) were identified by single-tube multiplex amplification refractory mutation system (ARMS). Automated direct nucleotide sequencing of the amplified alpha2- and alpha1-globin genes was performed to characterise other non-deletional alpha-thalassaemia determinants. RESULTS: In the 100 cases studied, 99 cases had --(SEA) in combination with deletional alpha(+)-thalassaemia or non-deletional alpha-globin gene mutation involving the alpha2-globin gene. In 70 cases of the deletional form, 43 cases showed the genotype of (--(SEA)/-alpha(3.7)) and 27 cases of (--(SEA)/-alpha(4.2)). Three of the 27 cases of (--(SEA)/-alpha(4.2)) were found to have Hb Q-Thailand linked in-cis with -alpha(4.2). The remaining 30 cases were of non-deletional form with the following genotypes: 11 cases of (--(SEA)/alpha(HbCS)alpha), 9 cases of (--(SEA)/alpha(HbQS)alpha), 3 cases of (--(SEA)/alpha(cd30 (DeltaGAG))alpha), 3 cases of (--(SEA)/alpha(cd31)alpha), 2 cases of (--(SEA)/alpha(poly-A)alpha), 1 case of (--(SEA)/alpha(HbWestmead)alpha) and 1 case of (--(non-SEA)/alpha(HbQS)alpha). CONCLUSIONS: Based on two rapid diagnostic tests, multiplex gap-PCR and multiplex ARMS, more than 90% of the cases were genetically characterised. This laboratory strategy should be widely applicable for genetic diagnosis of alpha-thalassaemia.

Adolescent↗
PubMed1965

A rapid plaque method using vertical tube cultures for titration of viruses and neutralizing antibodies.

Standard methods for titrating and typing enteroviruses and other viruses, or for assaying antibodies against them, are based on observation of metabolic inhibition of infected cells or on direct microscopic reading of cytopathogenic effects. Incubation of cell cultures for at least a week, with two or three readings during this period, is usually required before assessment is completed. This report describes a vertical-tube method in which cell monolayers are confined to the bottom end of a serological tube; an agar overlay is used after virus or virus-serum inoculation. The reduced monolayer area allows seeding with only about 30% of the cells required for standard tube cultures, and 5% of those required for plaque assay in bottle cultures. The new method requires only a single macroscopic reading one to three days after the test is set up. This method has proved economical, simple and rapid in epidemiological studies on rapidly growing viruses of the entero-, reo-, herpes-, myxo- and poxvirus groups, and for tests of the genetic markers of live poliovirus vaccine.

Culture Techniques↗
PubMed1996

The recognition and investigation of X-linked learning disability syndromes.

X-linked learning disability syndromes occur in approximately one per 600 live male births and account for 20-30% of all learning disability. Fragile-X syndrome comprises some 40% of all X-linked learning disability, and there are currently about 95 recognized syndromes comprising the rest. Clinicians should be alert to these other forms of X-linked learning disability: families should be offered genetic counselling, including dysmorphology opinion and cytogenetic testing. Gene mapping on the X chromosome is advancing very rapidly and some causative genes for X-linked learning disability are now known. Clinicians involved in the care of patients with X-linked learning disability are encouraged to investigate all families, report new syndromes and those with cytogenetic abnormalities, and collaborate with clinical geneticists and laboratory scientists working on X chromosome gene mapping.

Chromosome Aberrations↗
PubMed1981

Evolution of cytochrome C investigated by the maximum parsimony method.

Rates of evolution for cytochrome c over the past one billion years were calculated from a maximum parsimony dendrogram which approximates the phylogeny of 87 lineages. Two periods of evolutionary acceleration and deceleration apparently occurred for the cytochrome c molecule. The tempo of evolutionary change indicated by this analysis was compared to the patterns of acceleration and deceleration in the ancestry of several other proteins. The synchrony of these tempos of molecular change supports the notion that rapid genetic evolution accompanied periods of major adaptive radiations. Rates of change at different time in several structural-functional areas of cytochrome c were also investigated in order to test the Darwinian hypothesis that during periods of rapid evolution, functional sites accumulate proportionately more substitutions than areas with no known functions. Rates of change in four proposed functional groupings of sites were therefore compared to rates in areas of unknown function for several different time periods. This analysis revealed a significant increase in the rate of evolution for sites associated with the regions of cytochrome c oxidase and reductase interaction during the period between the emergence of the eutherian ancestor to the emergence of the anthropoid ancestor.

Animals↗
PubMed1999

The current social, political, and medical role of genetic testing in familial breast and ovarian carcinomas.

Few advances in medical science have yielded as much publicity and controversy as discoveries in genetics. Moving quickly from the bench to the bedside, genetic testing for inherited susceptibility to breast and ovarian cancer has had a significant impact on our paradigms for decisions about the treatment and prevention of disease. Assessment of cancer risk is developing into a distinct discipline, with rapidly evolving genetic technologies and models for estimating an individual's risk of cancer. Exciting developments in chemoprevention of breast cancer demonstrate the potential to offer a broader range of options for decreasing cancer risk. This article will consider recent advances in the understanding of cancer genetics, and describe the state-of-the-art in terms of management of individuals with inherited susceptibility to breast and ovarian cancer.

Breast Neoplasms↗
PubMed1998

Bacterial complementation as a means to test enzyme-ligand interactions.

A bacterial complementation assay has been developed for the rapid screening of a large number of compounds to identify those that inhibit an enzyme target for structure-based inhibitor design. The target enzyme is the hypoxanthine phosphoribosyltransferase (HPRT). This enzyme has been proposed as a potential target for inhibitors that may be developed into drugs for the treatment of diseases caused by several parasites. The screening assay utilizes genetically deficient bacteria complemented by active, recombinant enzyme grown in selective medium in microtiter plates. By comparing absorbance measurements of bacteria grown in the presence and absence of test compounds, the effect of the compounds on bacterial growth can be rapidly assayed. IC50 values for inhibition of bacterial growth are a reflection of the ability of the compounds to bind and/or inhibit the recombinant enzyme. We have tested this bacterial complementation screening assay using recombinant HPRT from the parasites. Plasmodium falciparum and Trypanosoma cruzi, as well as the human enzyme. The results of these studies demonstrate that a screening assay using bacterial complement selection can be used to identify compounds that target enzymes and can become an important part of structure-based drug design efforts.

Animals↗
PubMed1978

Somatic mosaicism in plants with special reference to somatic crossing over.

Plant systems in use for the detection of environmental mutagens appear capable of detecting all types of genetic effects which can be studied in animals. The study of somatic mosaicism, however, is better developed in plants than in higher animals. A case is presented here which shows the ability of plant systems in analyzing a host of genetic end points, including chromosome aberrations like deletions, somatic crossing over, numerical inequality, gene conversion, paramutations and point mutations. The systems in general use utilize certain varieties of Tradescantia, Glycine max, Nicotiana tabacum, Antirrhinum majus, Petunia hybrida, and Arabidopsis thaliana. Heterozygous plants or their homozygous counterparts with gene markers affecting chlorophyll development or anthocyanin in floral parts are exploited in these studies. Mutagens produce different frequencies of different types of spots typical of the mode of action of the agent. Analysis of these parameters may be used to predict, at least qualitatively, the kind of genetic damage that might be produced in man. Besides, one can test the validity of interpretation by traditional progeny tests of plants raised from tissue culture from sectors as in Nicotiana and/or by precursor analysis as done in Antirrhinum. The study of mosaicism in plants offers quite inexpensive, rapid, and reliable tests of mutagenicity at least as a preliminary eukaryotic test system.

Biotransformation↗