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Biomedical subjects

C S Richards

Publications and source records attributed to C S Richards.

At least 19 recordsLinked to original sources
PubMed2003

Oviposition by small hive beetles elicits hygienic responses from Cape honeybees.

Two novel behaviours, both adaptations of small hive beetles ( Aethina tumida Murray) and Cape honeybees ( Apis mellifera capensis Esch.), are described. Beetles puncture the sides of empty cells and oviposit under the pupae in adjoining cells. However, bees detect this ruse and remove infested brood (hygienic behaviour), even under such well-disguised conditions. Indeed, bees removed 91% of treatment brood (brood cells with punctured walls caused by beetles) but only 2% of control brood (brood not exposed to beetles). Only 91% of treatment brood actually contained beetle eggs; the data therefore suggest that bees remove only that brood containing beetle eggs and leave uninfected brood alone, even if beetles have accessed (but not oviposited on) the brood. Although this unique oviposition strategy by beetles appears both elusive and adaptive, Cape honeybees are able to detect and remove virtually all of the infested brood.

Animal Diseases↗
PubMed2002

Diagnostic DNA testing for X-linked ocular albinism (OA1) with a hierarchical mutation screening protocol.

Albinism is a group of inherited conditions in which affected individuals have less than normal pigment in the eyes, skin, and hair compared to others of the same race and ethnic background. The prevalence of all types of albinism in the United States is estimated at 1 in 20,000, based on poor epidemiological data. X-linked Nettleship-Falls ocular albinism (XLOA, OA1) affects approximately 1/150,000 males in the population. XLOA effects reduce visual acuity and nystagmus, result in a mild skin and hair phenotype, and occur mostly in XY males. Female carriers of XLOA have normal visual acuity, but often show iris punctate transillumination and a classic pattern of mosaic retinal pigmentation, coarse and grainy in the macula and becoming increasingly reticular into the periphery of the retinal pigment epithelium. Studies of OA1 have shown linkage of a single gene to markers at Xp22.3-p22.2. About 48% of the reported mutations in the OA1 gene are intragenic deletions and about 43% are point mutations. We present a hierarchical strategy for mutation screening for diagnostic testing for OA1 that comprises two tiers: first, multiplex PCR to detect intragenic deletions in the OA1 gene with denaturing high-performance liquid chromatography (dHPLC), and, second, heteroduplex analysis with dHPLC to scan for mutations, with subsequent sequencing of variants to confirm putative mutations in the OA1 gene. Prenatal diagnosis can be provided for families when the mutation has been firmly identified. We have validated this procedure with positive controls that were identified in patients by Southern blot, single-stranded conformation polymorphism (SSCP), and sequencing. In this hierarchical strategy, these procedures have an analytical sensitivity of > 99%.

Albinism, Ocular↗
PubMed2001

The relationship between Schistosoma mansoni and Biomphalaria glabrata: genetic and molecular approaches.

Biomphalaria glabrata is a major intermediate host for the helminth parasite Schistosoma mansoni. Beginning in the mid-20th century, studies were carried out with this snail species to identify the immunological and genetic components that might be involved in controlling schistosome development. A number of genetically well-defined snail stocks were derived as a direct result of these studies and have since played major roles in helping investigators to identify important cellular and humoral components in the snail/schistosome relationship. This review will explore the historical development of these stocks and describe some of the major advances in several areas of medical malacology that hawe been made possible be their use.

Animals↗
PubMed2001

Detection of sequence variations in the adenomatous polyposis coli (APC) gene using denaturing high-performance liquid chromatography.

We have evaluated the usefulness of denaturing high performance liquid chromatography (dHPLC) for scanning the adenomatous polyposis coli (APC) gene for point mutations, small deletions, and insertions. Our assay consists of 28 sets of primers to amplify the 15 exons of the APC gene. All PCR reactions were amplified simultaneously using the same reaction conditions in a 96-well format and then analyzed by dHPLC, using empirically determined optimum temperatures for partial fragment denaturation. Previously studied DNA specimens from 47 familial adenomatous polyposis (FAP) patients were analyzed by dHPLC and all mutations were correctly identified and confirmed by sequence analysis. This approach identified a single-base substitution in exon 6 and a 2-bp insertion in exon 15 that initially had not been detected by single-strand conformational polymorphism (SSCP) analysis. A novel mutation in exon 15 of the APC gene, 2065delG (codon 689) that had previously been undetected by the protein truncation test (PTT) was also identified by dHPLC. We present our validation studies of dHPLC technology for APC gene analysis in terms of sensitivity and specificity and compare it to current standard scanning technologies including PTT, SSCP, and conformational sensitive gel electrophoresis (CSGE).

Adenomatous Polyposis Coli↗
PubMed2001

Abnormal uterine bleeding. Diagnostic considerations, management options.

The approach to diagnosis of abnormal uterine bleeding is guided by a sound knowledge of menstrual physiology and differential diagnosis. Often, simple anovulation is the underlying problem, although the possibility of pregnancy, endometrial hyperplasia with atypia, or benign reproductive tract disease must be considered. In the majority of cases, abnormal uterine bleeding can be fully evaluated and effectively treated medically without the need for gynecologic referral.

Acute Disease↗
PubMed2000

Identification of female carriers for Duchenne and Becker muscular dystrophies using a FISH-based approach.

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive neuromuscular diseases caused by dystrophin gene mutations. Deletions, or more rarely duplications, of single or multiple exons within the dystrophin gene can be detected by current molecular methods in approximately 65% of DMD patients. Mothers of affected males have a two-thirds chance of carrying a dystrophin mutation, whilst approximately one-third of affected males have de novo mutations. Currently, Southern blot analysis and multiplex PCR directed against exons in deletion hot spots are used to determine female carrier status. However, both of these assays depend on dosage assessment to accurately identify carriers since, in females, the normal X chromosome is also present. To obviate quantitation of gene dosage, we have developed exon-specific probes from the dystrophin gene and applied them to a screen for potential carrier females using fluorescence in situ hybridization (FISH). Cosmid clones, representing 16 exons, were identified and used in FISH analysis of DMD/BMD families. Our preliminary work has identified multiple, informative probes for several families with dystrophin deletions and has shown that a FISH-based assay can be an effective and direct method for establishing the DMD/BMD carrier status of females.

Dystrophin↗
PubMed1999

Fragile X syndrome and an isodicentric X chromosome in a woman with multiple anomalies, developmental delay, and normal pubertal development.

We report on an individual with developmental delays, short stature, skeletal abnormalities, normal pubertal development, expansion of the fragile X triplet repeat, as well as an isodicentric X chromosome. S is a 19-year-old woman who presented for evaluation of developmental delay. Pregnancy was complicated by a threatened miscarriage. She was a healthy child with intellectual impairment noted in infancy. Although she had global delays, speech was noted to be disproportionately delayed with few words until age 3.5 years. Facial appearance was consistent with fragile X syndrome. Age of onset of menses was 11 years with normal breast development. A maternal male second cousin had been identified with fragile X syndrome based on DNA studies. The mother of this child (S's maternal first cousin) and the grandfather (S's maternal uncle) were both intellectually normal but were identified as carrying triplet expansions in the premutation range. S's mother had some school difficulties but was not identified as having global delays. Molecular analysis of S's fragile X alleles noted an expansion of more than 400 CGG repeats in one allele. Routine cytogenetic studies of peripheral blood noted the presence of an isodicentric X in 81of 86 cells scored. Five of 86 cells were noted to be 45,X. Cytogenetic fra(X) studies from peripheral blood showed that the structurally normal chromosome had the fragile site in approximately 16% of the cells. Analysis of maternal fragile X alleles identified an allele with an expansion to approximately 110 repeats. FMRP studies detected the expression of the protein in 24% of cells studied. To our knowledge, this is the first patient reported with an isodicentric X and fragile X syndrome. Whereas her clinical phenotype is suggestive of fragile X syndrome, her skeletal abnormalities may represent the presence of the isodicentric X. Treatment of S with 20 mg/day of Prozac improved her behavior. In the climate of cost con trol, this individual reinforces the recommendation of obtaining chromosomes on individuals with developmental delay even with a family history of fragile X syndrome.

Abnormalities, Multiple↗
PubMed1999

The identification of markers segregating with resistance to Schistosoma mansoni infection in the snail Biomphalaria glabrata.

Both snail and parasite genes determine the susceptibility of the snail Biomphalaria glabrata to infection with the trematode Schistosoma mansoni. To identify molecular markers associated with resistance to the parasite in the snail host, we performed genetic crosses between parasite-resistant and -susceptible isogenic snails. Because resistance to infection in adult snails is controlled by a single locus, DNA samples from individual F2 and F1 backcross progeny, segregating for either the resistant or susceptible phenotypes, were pooled (bulked segregant). Genotypes for both parents were determined with 205 arbitrary decamer primers by random amplified polymorphic DNA-PCR. Of the 205 primers, 144 were informative, and the relative allele frequencies between the pools for these primers were determined. Two primers, OPM-04 and OPZ-11, produced fragments in the resistant parent of one cross that were inherited in a dominant fashion in the resistant F2 and backcross-bulked segregant progeny. Subsequent typing of DNA samples of individual progeny snails showed that the 1.2-kb marker amplified by primer OPM-04 and the 1.0-kb marker produced by primer OPZ-11 segregated in the same dominant fashion with the resistant phenotype. Sequence analysis of the 1.2-kb marker showed that it corresponds to a repetitive sequence in the snail genome with no homology to existing DNA sequences in the public databases. Analysis of the 1. 0-kb marker showed that it also corresponds to a repetitive sequence in the B. glabrata genome that contains an imperfect ORF, with homology to retrovirus-related group-specific antigens (gag) polyprotein.

Animals↗
PubMed1999

Psychological and behavioral factors associated with colorectal cancer screening among Ashkenazim.

BACKGROUND: Psychological and behavioral factors related to annual colorectal cancer (CRC) screening were examined in a sample of Ashkenazi Jewish individuals. Identification of factors related to regular CRC screening in this population is important because of the possibility of a heightened incidence of CRC. METHODS: Eligible participants were 171 Ashkenazi Jewish adults 40 years or older attending an educational program about breast cancer genetics. Compliance with recommended guidelines for digital rectal examination and fecal occult blood test in the past year were dependent measures. Demographic variables, family history of CRC, perceived risk, physician recommendation, and worry about cancer were independent measures. RESULTS: Digital rectal examinations and fecal occult blood tests had been obtained in the past year by 46 and 31% of the participants, respectively. A logistic regression showed that physician recommendation was related significantly to obtaining digital rectal examinations. Physician recommendation and education were related significantly to obtaining fecal occult blood tests. Although participants with family histories of CRC perceived themselves as being at increased risk of developing CRC, and were more worried about developing colon cancer, they were no more likely to adhere to CRC screening guidelines than those without such histories. CONCLUSIONS: Overall, compliance with recommended CRC screening was low even among high-risk individuals. Physicians play a key role in motivating people to comply with CRC screening. Physicians need to en courage all asymptomatic patients 50 years and older to be screened for CRC.

Adult↗
PubMed1999

Ashkenazi Jewish population frequency of the Bloom syndrome gene 2281 delta 6ins7 mutation.

Bloom syndrome is an autosomal recessive disorder characterized clinically by small size, sun-sensitive facial erythema, and immunodeficiency, and cytogenetically by increased chromosome breakage and sister chromatid exchange. Genomic instability renders Bloom syndrome patients at elevated risk for multiple cancers. Bloom syndrome occurs most commonly in the Ashkenazi Jewish population due to an apparent founder effect. The BLM gene on chromosome 15q26.1 was identified to encode a RecQ DNA helicase. Multiple mutations were identified, with Ashkenazi Jewish Bloom syndrome patients almost exclusively homozygous for a complex frameshift mutation (6-bp deletion/7-bp insertion at BLM nucleotide 2,281). This molecular genetic study seeks to verify the Ashkenazi Jewish carrier frequency of the BLM 2281 delta 6ins7 allele using semiautomated allele-specific oligonucleotide (ASO) analysis. Anonymized DNA samples from 1,016 Ashkenazi Jewish individuals and 307 non-Jewish individuals were screened. Ten Ashkenazi heterozygote carriers for the 2281 delta 6ins7 mutation were identified, giving a carrier frequency estimate of 0.98%, or approximately 1 carrier out of 102 individuals in the Ashkenazi Jewish population. These results are consistent with previous estimates, and combining our findings with the published molecular data collectively yields an Ashkenazi Jewish carrier frequency of approximately 1 in 104. Given its high population frequency and detection rate among Ashkenazi Jewish patients, the blmAsh mutation constitutes an appropriate addition to screening panels for Ashkenazi Jewish disease testing.

Adenosine Triphosphatases↗
PubMed1998

Relative stability of a minimal CTG repeat expansion in a large kindred with myotonic dystrophy.

The genetic basis for myotonic dystrophy (DM) is a CTG trinucleotide repeat expansion. The number of CTG repeats commonly increases in affected individuals of successive generations, in association with anticipation. We identified a large DM family in which multiple members had minimal CTG repeat expansions, and in which the number of CTG repeats remained in the minimally expanded range through at least three, and possibly four, generations. This relative stability of minimal CTG repeat expansions may help to maintain the DM mutation in the population.

Aged↗
PubMed1997

Prenatal diagnosis of a fetus with a homologous Robertsonian translocation of chromosomes 15.

We present a prenatal diagnosis of a de novo homologous Robertsonian translocation involving both chromosomes 15. Amniocentesis was performed on a 36-year-old woman at 16.5 weeks of gestation. Chromosome analysis documented a 45,XX,der(15;15) (q10;q10) chromosome pattern. No evidence of a deletion was observed by FISH using a SNRPN DNA probe associated with the Prader-Willi/Angelman syndrome critical region. Molecular studies in the family using six polymorphic markers for chromosome 15 and Southern blot analysis of DNA methylation for the CpG island near the SNRPN gene showed normal biparental inheritance of chromosome 15, excluding uniparental disomy. The patient was counseled that her child would not be able to bear off-spring without clinical assistance. Otherwise the health and intellect of her child were not expected to be affected by the translocation. We consider this to be the first prenatal case identified with a balanced der(15;15)(q10;q10) Robertsonian translocation and a phenotypically normal female outcome. Prenatally identified cases of der(15;15)(q10;q10) warrant further investigation by molecular methodology.

Adult↗
PubMed1997

Southern analysis for detection of CAG repeat expansions associated with dentatorubral pallidoluysian atrophy.

Dentatorubral pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder caused by expansion of an unstable, tandemly repeated trinucleotide sequence, (CAG)n, in a novel gene on human chromosome 12p12-pter. Molecular diagnosis of DRPLA uses the polymerase chain reaction (PCR) to amplify and characterize the number of CAG repeats carried by individuals. The PCR analysis is fairly straightforward when two alleles are identified. However, when only a single allele is observed, it is difficult to know whether the sample is homozygous or whether there was failure to amplify the second allele. We describe a Southern analysis for detection of the DRPLA CAG repeat, providing an independent method for the assessment of expanded alleles.

Atrophy↗
PubMed1997

DMD-specific FISH probes are diagnostically useful in the detection of female carriers of DMD gene deletions.

The challenge of Duchenne muscular dystrophy (DMD) carrier identification resides in the ability to identify the presence of a mutant gene over the background contributed by the normal allele. Current diagnosis of carrier status when a deletion has been identified in a proband is based on an analysis of a gene dosage. We present a diagnostic strategy that uses fluorescence in situ hybridization (FISH) to detect female carriers with major deletions in the dystrophin gene. We screened a human X-chromosome-derived genomic library with a full-length dystrophin cDNA and isolated 15 dystrophin-specific cosmids that contain DMD gene exons. Six cosmids were further tested as FISH probes in control individuals and subsequently applied on chromosomes from eight males with DMD and known deletions and on samples from three female carriers. As expected, X chromosomes in normal females displayed four signals, two for the DMD-specific probe and two for the X-chromosome centromeric probe. Hybridization on chromosomal spreads from carriers of deletions revealed only one signal from the DMD-specific probe and two from the control centromeric probe. Males carrying deletions showed no DMD-specific signal for the deleted exons tested. Our data indicate that FISH could represent an alternative method for the detection of female carriers with DMD gene deletions.

Cosmids↗
PubMed1997

Congenital myotonic dystrophy pathology and somatic mosaicism.

We present the pathology and molecular genetic analysis of an infant with congenital myotonic dystrophy. The proband/infant, born at 35 weeks' gestational age to a mother with myotonic dystrophy and 750 CTG repeats, was markedly hypotonic and had severe cardiomyopathy. She died after 16 days of life. At autopsy, skeletal and heart muscles were immature and had a decrease in contractile elements. DNA CTG trinucleotide repeat analysis of the proband demonstrated 2,480 repeats in blood and a slightly greater number of repeats in skeletal muscles, viscera, and gray matter. Corresponding to the clinical course and pathology, cardiac tissues displayed somatic mosaicism, with repeats ranging from 2,760 to 3,220.

Adult↗
PubMed1997

Screening for 185delAG in the Ashkenazim.

A study was initiated to assess interest, educational effectiveness, and implications of genetic testing for the common BRCA1 mutation, 185delAG, in the Ashkenazim. Of 333 individuals who attended group sessions, 309 (92%) participated in the study. Participants were categorized as having negative family history (67%), positive family history (defined, by a relaxed criterion, as one first-degree relative or two second-degree relatives with breast [premenopausal] or ovarian cancer) (22%), positive personal history (7%), and both positive personal history and positive family history (4%). Group education was effective, as shown by the improvement in participant scores from pre- to posteducation tests. For the 289 individuals (94%) who requested testing, the major reasons included concern for their own risk, concern for the risk of their children, and desire to learn about surveillance options. The most common reason given by participants who declined testing was concern about health insurance. Six participants found to be heterozygous for the 185delAG mutation received results and were offered genetic counseling. Participants had consented for additional testing without receiving results and were screened for the 6174delT mutation in BRCA2, and seven were found to be positive. All identified carriers reported at least one first- or second-degree relative with a history of breast or ovarian cancer, although they did not all meet our study criteria for positive family history. Given these outcomes, we conclude that screening for breast and ovarian cancer susceptibility is most appropriate for individuals with a positive personal or positive family cancer history. We propose a guideline for future studies designed to identify individuals who may benefit from genetic testing for inherited breast and ovarian cancer.

Adult↗