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Biomedical subjects

L J Sheffield

Publications and source records attributed to L J Sheffield.

At least 19 recordsLinked to original sources
PubMed2005

Pharmacogenomics education: International Society of Pharmacogenomics recommendations for medical, pharmaceutical, and health schools deans of education.

Pharmacogenomics would be instrumental for the realization of personalized medicine in coming decades. Efforts are evident to clarify the potential bioethical, societal, and legal implications of key pharmacogenomics-based technologies projected to be soon introduced into the core practice of medicine. In sharp contrast, a lack of sufficient attention to educational aspects of pharmacogenomics, both for professionals and for society at large, is evident. In order to contribute to this discussion, a 'Pharmacogenomics Education Forum' was held on October 2, 2004 during the 3rd Annual Meeting of the International Society of Pharmacogenomics (ISP) at Santorini, Greece. The participants, members of the ISP Pharmacogenomics Education Forum, after deliberate discussions, proposed a document of 'Background Statement' and 'Recommendations and Call for Action' addressed to Deans of Education at Medical, Pharmaceutical, and Health Schools globally. This document has been considered by the education committee of the International Society of Pharmacogenomics and the result is presented here. We hope that this call would be listened to, and soon followed by beneficial action, ultimately leading to enhanced implementation of personalized medicine into core medical education and practice.

Curriculum↗
PubMed2001

Strategies to find new genes involved in drug metabolism.

Pharmacogenomics is a field that is applying the new methods of molecular genetics to explain the genetic basis of an individual's reaction to drugs. One example from the literature of variations in a single gene being predictive of drug metabolism is described, in addition to methods of testing a gene to see if it is associated with poor metabolism of the drug. An explanation is given of why linkage and association studies are used. Candidate gene studies are most frequently used but whole-genome scans are also described. Case-control studies or transmission disequilibrium tests are used to investigate phenotype and genotype association.

Cytochrome P-450 CYP2D6↗
PubMed1999

Analyses of the COGA data set in one ethnic group with examinations of alternative definitions of alcoholism.

We used GENEHUNTER and GENEHUNTER-PLUS to search for linkage with the markers in the Collaborative Study on the Genetics of Alcoholism (COGA) data set in a single ethnic group. Analyses of a complex disorder such as alcoholism depend on the definition of affection status. The COGA study provides two definitions of alcoholism (variables ALDX1 and ALDX2). To identify more severely affected alcoholics that might be more homogeneous genetically, we developed two other ways of characterizing subjects as alcohol dependent: (1) by combining the symptom variable values equally into a 24-point scale and (2) by weighting optimally the symptoms and other descriptive variables into a single score using logistic regression. We applied these definitions within a single ethnic group to map alcoholism-related loci. We found two regions on chromosome 1 that have adjacent markers significant at p-values < or = 0.05. ALDX1 provided the highest Z-scores compared to the alternatives.

Alcoholism↗
PubMed1999

A more powerful method to evaluate p-values in GENEHUNTER.

The determination of statistical significance in genetic linkage studies is complicated by many factors, such as missing individuals or uninformative markers, and the validity of theoretical results is often questionable. Although many simulation-based methods have been proposed to determine empirically the statistical significance, they are either not generally applicable to complex pedigree structures, or not able to preserve the observed genetic information content at each locus in the pedigrees. We have developed and implemented a general and computationally efficient randomization procedure in GENEHUNTER that applies to arbitrary pedigree structure and preserves the observed information content at each locus. We applied this method to the Problem 1 data set of the Genetic Analysis Workshop 11. The performance of this new method was similar to the method implemented in GENEHUNTER-PLUS, and both outperformed the conservative approach in GENEHUNTER.

Alcoholism↗
PubMed1999

Late diagnosis of maternal PKU in a family segregating an arylsulfatase [corrected] E mutation causing symmetrical chondrodysplasia punctata.

Mutations in the arylsulfatase E gene, located on the X chromosome, have been shown to cause chondrodysplasia punctata (CDP). A substitution of arginine with serine at amino acid 12 (R12S) was identified in a patient with typical features of mild symmetrical CDP including mild mental retardation. The proband was institutionalized and was found to have seven full and half siblings all of whom were microcephalic. Six siblings are alive and all are mentally retarded. The mother is borderline retarded. The mother and three daughters are carriers of the R12S change, but do not appear to have CDP. A son and three other daughters do not carry the R12S change. Further studies revealed that the mother had phenylketonuria (PKU) and the children maternal PKU. This suggests that the R12S change is not the primary cause of short stature, microcephaly, and mental retardation in this family. The relationship between CDP and PKU, both of which can cause short statue and mental retardation, is discussed.

Amino Acid Substitution↗
PubMed1998

Segregation of mutations in arylsulphatase E and correlation with the clinical presentation of chondrodysplasia punctata.

Sixteen males and two females with symmetrical (mild) type of chondrodysplasia punctata were tested for mutations in the X chromosome located arylsulphatase D and E genes. We identified one nonsense and two missense mutations in the arylsulphatase E gene in three males. No mutations were detected in the arylsulphatase D gene. Family studies showed segregation of the mutant genes establishing X linked inheritance for these families. Asymptomatic females and males were found in these studies. The clinical presentation varies not only between unrelated affected males, but also between affected males within the same family. We also conclude that clinical diagnosis of chondrodysplasia punctata in adults can be difficult. Finally, our results indicate that brachytelephalangy is not necessarily a feature of X linked symmetrical chondrodysplasia punctata.

Amino Acid Sequence↗
PubMed1998

Fetal outcome and maternal morbidity after early amniocentesis.

We have studied a large population-based cohort of women who had amniocentesis at 14 weeks' gestation (early amniocentesis) in Victoria, a state of Australia, to determine fetal loss rates and maternal morbidity. This was done by linking two registers--one containing information on all prenatal diagnostic tests in the state, and the other a register of all births at or after 20 weeks' gestation. Almost complete follow-up was achieved. The spontaneous fetal loss rate was significantly higher for women of age 37 years and over having early amniocentesis (2.5 per cent), as compared with the fetal loss rate found previously on the same geographically defined population who had amniocentesis at about 16 weeks' gestational age (1.1 per cent). Three classes of maternal morbidity reported to the birth register (post 20 weeks' gestation) were also analysed. The most significant finding was a reduced rate of premature rupture of membranes with early amniocentesis when compared with a group having later amniocentesis, or the background population not having any amniocentesis. There was no significant increase in the occurrence of antepartum bleeding or genito-urinary tract infection for women having early amniocentesis. These data agree with other studies in showing that early amniocentesis is associated with a significant increased risk of fetal loss, as compared with later amniocentesis. In addition we have shown no significant increase in the occurrence of three indicators of maternal morbidity, reported at or after 20 weeks' gestation.

Adult↗
PubMed1997

The elusive Angelman syndrome critical region.

DNA mapping studies in two families provide further information on the Angelman syndrome critical region, which has recently been defined by the gene UBE3A. The first family has probable familial Angelman syndrome with a maternally imprinted inheritance pattern. A 5 year old girl with this disorder has a 14 year old brother and an 11 year old male cousin who have less typical clinical features. DNA microsatellite analysis has shown that the three share a common segment of the same grandpaternal chromosome 15q11-q13 that overlaps with UBE3A. The child with typical Angelman syndrome has an additional maternal recombination 5' to UBE3A. The second family is a mother and son both of whom have mental retardation but no other features of Angelman syndrome despite an extensive DNA deletion on the telomeric side of UBE3A. Together, the two families identify a region between loci D15S210 and D15S986 which forms part of the Angelman syndrome critical region. A new microsatellite (D15S1234) is described which can be used in place of the LS6-1 marker at locus D15S113.

Adolescent↗
PubMed1996

Familial temporal lobe epilepsy: a common disorder identified in twins.

We describe a new syndrome of familial temporal lobe epilepsy in 38 individuals from 13 unrelated white families. The disorder was first identified in 5 concordant monozygotic twin pairs as part of a large-scale twin study of epilepsy. When idiopathic partial epilepsy syndromes were excluded, the 5 pairs accounted for 23% of monozygotic pairs with partial epilepsies, and 38% of monozygotic pairs with partial epilepsy and no known etiology. Seizure onset for twin and nontwin subjects usually occurred during adolescence or early adult life. Seizure types were simple partial seizures with psychic or autonomic symptoms, infrequent complex partial seizures, and rare secondarily generalized seizures. Electroencephalograms revealed sparse focal temporal interictal epileptiform discharges in 22% of subjects. Magnetic resonance images appeared normal. Nine affected family members (24%) had not been diagnosed prior to the study. Pedigree analysis suggested autosomal dominant inheritance with age-dependent penetrance. The estimated segregation ratio was 0.3, indicating an overall penetrance of 60% assuming autosomal dominant inheritance. The mild and often subtle nature of the symptoms in some family members may account for lack of prior recognition of this common familial partial epilepsy. This disorder has similarities to the El mouse, a genetic model of temporal lobe epilepsy with a major gene on mouse chromosome 9, which is homologous with a region on human chromosome 3.

Adolescent↗
PubMed1996

Detection of carriers of haemophilia A: use of bioassays and restriction fragment length polymorphisms (RFLP).

BACKGROUND: Haemophilia A is a sex-linked bleeding disorder carried by unaffected females. Currently, the two main methods used for the determination of carrier status in women from families with haemophilia A are bioassays and DNA-based assays using restriction fragment length polymorphisms (RFLP). AIM: The aim of this paper was to assess the current usefulness of these two methods. METHODS: Bioassays measured factor VIII coagulation activity by a two-stage coagulation assay and von Willebrand antigen by immunoelectrophoresis. RFLP were determined with two intragenic probes (p114 and p486) and two linked probes (St14 and DX13). Data were analysed using a Bayesian analysis to allow for all possible recombination events. We also incorporated an estimate for the risk of mosaicism into calculations in isolated haemophilia families. Both bioassays and RFLP were used to determine carrier status in 63 women, 31 from known haemophilia families and 32 from families of isolated cases. The techniques were assessed for their ability to classify the patients as normal (p < 0.2) or carrier (p > 0.7). Where applicable, intron 22 inversion was also tested. RESULTS: In the known families, six women could not be classified after bioassay, but all could be classified by RFLP. Of the 32 women from families of isolated cases, eight were unclassified by bioassay and 12 were not definitely classified using RFLP. However, RFLP was useful in determining that a recent mutation had occurred in six of the eight families in which DNA from the grandparents was available. CONCLUSION: For diagnosis of carriers of haemophilia, RFLP is the preferred method in familial haemophilia, but is less useful in isolated haemophilia.

Blood Coagulation Tests↗
PubMed1995

Prenatal exposure to phenytoin, facial development, and a possible role for vitamin K.

Ten patients with maxillonasal hypoplasia (Binder "syndrome"), who were prenatally exposed to phenytoin (usually in combination with other anticonvulsants), were identified retrospectively. In addition to their facial anomalies, 6 of the patients were radiographed neonatally and showed punctate calcification, characteristic of chondrodysplasia punctata. Evidence is presented that the facial abnormalities seen in these children are due to anticonvulsant-induced vitamin K deficiency, causing abnormal development of the cartilaginous nasal septum. We propose that early vitamin K supplementation of at-risk pregnancies may prevent the development of maxillonasal hypoplasia, which in some patients is severely disfiguring and causes great emotional distress. Correction of this facial defect requires surgical and dental treatment over a long period of time.

Abnormalities, Drug-Induced↗
PubMed1995

New estimates of Down syndrome risks at chorionic villus sampling, amniocentesis, and livebirth in women of advanced maternal age from a uniquely defined population.

Current measures of livebirth prevalence of Down syndrome are derived from data obtained up to 20 years ago, before the introduction of the prenatal diagnostic tests amniocentesis and chorionic villus sampling (CVS). For women aged 36-52 years, but who were not tested prenatally, we proposed to make a direct estimate of current livebirth prevalence of Down syndrome. We could also determine prevalence at the time of CVS and amniocentesis in women of the same age undergoing prenatal testing. Differences in these prevalences allow an estimation of the relative loss of Down syndrome during pregnancy. In Victoria, Australia, we identified 3041 women having CVS, 7504 having amniocentesis, and 13,139 having no test. Smoothed regression estimates of age-specific livebirth prevalence were found to be higher than in the early studies. The estimate of spontaneous loss was 17 per cent between the time of CVS and amniocentesis, and 18 per cent after the time of amniocentesis. The latter figure is lower than previous estimates and may be explained by a greater likelihood of a Down syndrome fetus surviving to be liveborn, given the modern approach to early obstetric intervention. These current risk estimates of livebirth may be useful updates for genetic counselling, but perhaps more importantly, may be used as precise maternal age-related risk figures, necessary in the design and implementation of prenatal screening programmes for Down syndrome.

Adult↗
PubMed1995

A low allergen diet is a significant intervention in infantile colic: results of a community-based study.

BACKGROUND: The effect of diet change in 38 bottle-fed and 77 breast-fed "colicky" infants, referred from community-based pediatric facilities was studied over a 1-week period in a double-blind (within each feeding mode), randomized, placebo-controlled trial. METHODS: Bottle-fed infants were assigned to either casein hydrolysate or cow's milk formula. All mothers of breast-fed infants were started on an artificial color-free, preservative-free, additive-free diet and also randomized to an active low allergen diet (milk-, egg-, wheat-, nut-free) or a control diet. RESULTS: The response to diet was assessed on day 1 and day 8 with the use of a previously validated infant distress chart on which parents recorded distress levels. If successful outcome was defined as a reduction in distress of 25% or more, after adjusting for age and feeding mode, infants on active diet had a significantly higher rate of improvement than those on the control diet (odds ratio, 2.32; 95% confidence interval, 1.07-5.0; p = 0.03). Analysis of the day 8 to day 1 distress ratio, again adjusted for age and feeding mode, showed that infants on the active diet had distress reduced by 39% (95% confidence interval, 26-50) compared with 16% (95% confidence interval, 0-30) for those on the control diet (p = 0.012). CONCLUSION: The results suggest a period of dietary modification with a low allergen diet and appropriate nutritional support should be considered in healthy infants with colic.

Age Factors↗
PubMed1995

'Disorganization-like syndrome' with 47,XXY and unilateral narrowing of the common iliac artery.

We described a male infant with a spectrum of anomalies compatible with the diagnosis of 'disorganization-like syndrome'. The infant had a partial foot arising from the right buttock, an absent right kidney, and a shortened right leg with severe non-positional talipes equinovarus. The infant's karyotype was 47,XXY. The right common iliac artery was one half of the expected diameter. The limb reduction defect seen in this case of disorganization (Ds) may have had a vascular aetiology.

Abnormalities, Multiple↗