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Biomedical subjects

R D Wilson

Publications and source records attributed to R D Wilson.

At least 19 recordsLinked to original sources
PubMed1998

Antibiotic resistance and genomic analysis of enterococci in an intensive care unit and general wards.

Fifty-nine enterococci isolated from 18 patients in an intensive care unit (ICU) and 21 patients in general wards (GW) at Royal Perth Hospital (RPH) during a period of 14 months were examined for antibiotic resistance by susceptibility testing and DNA polymorphism by pulsed-field gel electrophoresis. The study showed that penicillin-resistant Enterococcus faecium is a common nosocomial isolate in ICU. The DNA patterns of various strains of E. faecium and E. faecalis were closely related in most consecutive isolates from the same patients but were generally different for isolates from different patients. Thirty two different DNA patterns were identified for 59 isolates from 39 patients. Identical or similar DNA patterns were also identified for some isolates from different patients, suggesting that cross-infection had occurred between patients in ICU and GW. These data suggest that cross-infection occurred more commonly in ICU than in GW and are consistent with the known higher risk of ICU patients for nosocomial infection.

Bacterial Typing Techniques↗
PubMed1997

Frequency of fetal cells in sorted subpopulations of nucleated erythroid and CD34+ hematopoietic progenitor cells from maternal peripheral blood.

Fetal cells that circulate in maternal peripheral blood (PB) during pregnancy offer a potential source of nucleated fetal material for noninvasive prenatal diagnosis. Fluorescence-activated cell sorting was used to target two populations of fetal cells: nucleated erythroid cells (NECs; CD71/glycophorin-A+ CD45(lo-int) CD34-) and hematopoietic progenitor cells (CD34+ cells; CD34++ CD71/glycophorin-A- CD45(int)). Fetal cells were detected by fluorescence in situ hybridization (FISH) using directly conjugated chromosome X and Y probes in 65% (13 of 20) of the maternal PBs (fetal karyotype 46,XY). The frequency of fetal cells isolated from the NEC and CD34+ fractions was, respectively, 0 to 14 and 0 to 7 cells per 2 x 10(7) previously frozen maternal cells (approximately 20 mL of blood). In nonfrozen samples, the yield and recovery of fetal cells was moderately improved. Culturing the CD34+ sorted fractions in serum-free media with cytokines improved the quality of the FISH preparations and resulted in a slight expansion in detectable fetal cells. The frequency of fetal cells isolated from cultured CD34+ fractions was 0 to 35 and 0 to 93 cells per 2 x 10(7) previously frozen and nonfrozen maternal PB cells, respectively. These results document the isolation, characterization, and enumeration of fetal cells from the maternal periphery that appear to be present in most, but not all, samples analyzed.

Antigens, CD34↗
PubMed1997

Fetal pyelectasis: comparison of postnatal renal pathology with unilateral and bilateral pyelectasis.

The aim of this study was to determine the prenatal fetal pyelectasis which requires postnatal evaluation. This was a retrospective analysis involving 65 infants with complete urological follow-up; 59 had shown prenatal evidence of pyelectasis using previously published standards. Males were more common in both the normal (75 per cent) and the abnormal (77 per cent) postnatal outcome groups. Unilateral prenatal lesions were less common than bilateral, but had significant postnatal pathology in 47 and 26 per cent, respectively (n.s.). Persistent dilatation was likely to be associated with postnatal pathology. A 6 mm threshold of dilatation predicted the 19 infants with significant postnatal pathology. The majority of fetuses with pyelectasis in the study had normal outcomes, with males often showing 'transitory pyelectasis'. A repeat prenatal scan at 30-40 weeks' gestation is recommended for all fetuses where 6 mm or more of renal pelvic dilatation is detected prior to 28 weeks. Postnatal follow-up is required for persistent pyelectasis.

Dilatation, Pathologic↗
PubMed1997

Single-dose and chronic dietary neurotoxicity screening studies on 2,4-dichlorophenoxyacetic acid in rats.

Forms of 2,4-dichlorophenoxyacetic acid (collectively known as 2,4-D) are herbicides used to control a wide variety of broadleaf and woody plants. Single-dose acute and 1-year chronic neurotoxicity screening studies in male and female Fischer 344 rats (10/sex/dose) were conducted on 2,4-D according to the U.S. EPA 1991 guidelines. The studies emphasized a Functional Observational Battery (which included grip performance and hindlimb splay tests), automated motor activity testing, and comprehensive neurohistopathology of perfused tissues. Dosages were up to 250 mg/kg by gavage for the single-dose study, and up to 150 mg/kg/day in the diet for 52 weeks in the repeated-dose study. In the acute study, gavage with 250 mg/kg test material caused slight transient gait and coordination changes and clearly decreased motor activity at the time of maximal effect on the day of treatment (day 1). Mild locomotor effects occurred in one mid-dose rat (75 mg/kg), on Day 1 only. No gait, coordination, or motor activity effects were noted by day 8. In the chronic study, the only finding of neurotoxicologic significance was retinal degeneration in females in the high-dose group (150 mg/kg/day). Body weights of both sexes were slightly less than controls in the mid-dose group, and 10% less than controls in the high-dose group. In summary, the findings of these studies indicated a mild, transient locomotor effect from high-level acute exposure, and retinal degeneration in female rats from high-level chronic exposure. Based on the results from these two studies, the no-observed-adverse-effect level for acute neurotoxicity was 15 mg/kg/day and for chronic neurotoxicity was 75 mg/kg/day.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1997

Suspected skeletal dysplasias: femur length to abdominal circumference ratio can be used in ultrasonographic prediction of fetal outcome.

OBJECTIVES: Skeletal dysplasias are a group of bone growth disorders, some of which can be recognized prenatally. Certain types of skeletal dysplasias result in a lethal fetal outcome. The ability to predict this outcome prenatally would be important in counseling parents. This study evaluated the ratio of femur length to abdominal circumference as a predictor of fetal outcome in cases of suspected skeletal dysplasia. STUDY DESIGN: This 3-year retrospective study identified 18 cases of prenatally suspected skeletal dysplasia from a population of approximately 35,000 fetuses undergoing prenatal ultrasonography. The femur length/abdominal circumference ratio was calculated and compared with fetal-neonatal outcomes and diagnoses. RESULTS: Eighteen cases of suspected skeletal dysplasia were identified, and the femur length/abdominal circumference ratio was found to be a good predictor of fetal outcome independent of gestational age. A ratio < 0.16 resulted in a lethal outcome in nine of nine cases. Conversely, a ratio > or = 0.16 resulted in a diagnosis of a nonlethal form of skeletal dysplasia or a diagnosis that ruled out any form of skeletal dysplasia in nine of nine cases. CONCLUSIONS: The femur length/abdominal circumference ratio may be useful to predict a lethal fetal outcome when ultrasonography indicates a possible skeletal dysplasia.

Abdomen↗
PubMed1997

Fetal anomalies: what is the diagnosis when the chromosomes are normal?

A retrospective study of cases of fetal anomalies associated with a normal karyotype was conducted (1) to evaluate the accuracy of prenatal diagnosis; and (2) to assess two different tools to assist in determining the correct diagnosis. A total of 201 charts were reviewed. The accuracy of the prenatal diagnosis was assessed subjectively by one physician. The London Dysmorphology Database and a locally developed non-computerized tool (Appendix) were assessed retrospectively using 36 test cases. The population studied presented a spectrum of 97 different groups of single (67%) or multiple (33%) anomalies. The prenatal diagnosis was accurate in 57% of the cases. The two proposed tools generated an average of 146 and 15 different diagnoses, respectively and the correct one in 26 and 22 of the 36 test cases. The two studied tools have the potential to generate a differential diagnosis in the presence of a fetal anomaly prior to and following normal karyotype analysis. The non-computerized tool presents the advantages of listing antenatal features and creating a shorter differential diagnosis list with a minimal decrease in the identification rate of the correct diagnosis. Its use should be studied prospectively.

Chromosome Aberrations↗
PubMed1997

Complications of long-term drainage of fetal pleural effusion: case report and review of the literature.

Severe fetal pleural effusion and ascites in the second trimester are associated with poor prognosis. We present a case where long-term drainage of several pleural effusion by a double reverse pig tail stent was achieved. Although the ultimate outcome was successful, complications seen in this case include accidental placement of the proximal opening of the catheter, first into the myometrium, then between amnion and chorion; development of oligohydramnios; intrathoracic migration of the catheter. Review of the literature reveals a multitude of other complications associated with this procedure, specifically difficulties at the time of placement and failure of function due to obstruction, migration of the catheter, or removal by the fetus. It is important to consider these complications in the counseling and management of the patients. Ongoing research is required to further improve the design of the catheters.

Adult↗
PubMed1997

Meiotic origin of trisomy in confined placental mosaicism is correlated with presence of fetal uniparental disomy, high levels of trisomy in trophoblast, and increased risk of fetal intrauterine growth restriction.

Molecular studies were performed on 101 cases of confined placental mosaicism (CPM) involving autosomal trisomy. The origin of the trisomic cell line was determined in 54 cases (from 51 pregnancies), 47 of which were also analyzed for the presence of uniparental disomy (UPD) in the disomic cell line. An additional 47 cases were analyzed for parental origin in the disomic cell line only. A somatic (postmeiotic) origin of the trisomy was observed in 22 cases and included the majority of cases with CPM for trisomy 2, 7, 8, 10, and 12. Most cases of CPM involving trisomy 9, 16, and 22 were determined to be meiotic. Fetal maternal UPD was found in 17 of 94 informative CPM cases, involving trisomy 2 (1 case), 7 (1 case), 16 (13 cases), and 22 (2 cases). The placental trisomy was of meiotic origin in all 17 cases associated with fetal UPD (P = .00005). A meiotic origin also correlated with the levels of trisomy in cultured chorionic villi samples (CVS) (P = .0002) and trophoblast (P = .00005). Abnormal pregnancy outcome (usually IUGR) correlated with meiotic origin (P = .0003), the presence of fetal UPD (P = 4 x 10(-7)), and the level of trisomy in trophoblast (P = 3 x 10(-7)) but not with the level of trisomy in CVS or term chorion. The good fit of somatic errors with the expected results could have been observed only if few true meiotic errors were misclassified by these methods as a somatic error. These data indicate that molecular determination of origin is a useful predictor of pregnancy outcome, whereas the level of trisomy observed in cultured CVS is not. In addition, UPD for some chromosomes may affect prenatal, but not postnatal, development, possibly indicating that imprinting effects for these chromosomes are confined to placental tissues.

Cells, Cultured↗
PubMed1997

Fee-for-service dentistry or managed care: one dentist's opinion.

Contrasts are drawn between dental care based on fee-for-service and managed care financial arrangements. The advantages of fee-for-service include (for the profession) slow acceptance of managed care in dentistry compared to medicine; (for society and the patient) more community service, higher technical quality of work, and stimulation of innovations; and (for the individual dentist) the strong dentist-patient bond as well as professionalism.

Attitude of Health Personnel↗
PubMed1996

Trisomy 7 CVS mosaicism: pregnancy outcome, placental and DNA analysis in 14 cases.

Prenatal diagnosis by chorionic villus sampling (CVS) documents placental chromosomal mosaicism in approximately 2% of viable pregnancies at 9-12 weeks of gestation and can involve various chromosomes and placental cell lineages. Confined placental mosaicism (CPM) is the result of postzygotic mitotic errors occurring in either diploid or trisomic zygotes. With trisomic zygote rescue, depending on the parental origin of the chromosome which is lost, uniparental disomy (UPD) or biparental disomy (BPD) may arise [Kalousek et al., Am J Hum Genet 52: 8-16, 1993]. In this paper, we present 14 pregnancies which were diagnosed by CVS as mosaic trisomy 7. All follow-up amniocenteses showed a normal diploid karyotype. Using both classical cytogenetics and interphase analysis, studies of term placentae showed variable levels of trisomy 7. DNA analysis was performed in nine cases to determine whether the diploid fetus had BPD 7 or UPD 7. Fetal UPD 7 was present only in one case; in eight other cases biparental inheritance was demonstrated. DNA analysis to establish the origin of trisomy 7 in the placenta was fully informative in six cases. One trisomy resulted from a meiotic error and was associated with fetal UPD 7, while the rest were somatic in origin. It is difficult to compare the effect of CPM for trisomy 7 to other trisomies confined to the placenta, as for most chromosomes there are few available cases. It appears that intrauterine fetal growth is not greatly affected by the presence of a trisomy 7 cell line in the placenta. This finding is in contrast to the serious effect of high levels of trisomy 16 within the placenta on fetal intrauterine growth in a series of well-documented cases of CPM 16 [Kalousek et al. 1993].

Chorionic Villi Sampling↗
PubMed1996

Comparative subchronic and chronic dietary toxicity studies on 2,4-dichlorophenoxyacetic acid, amine, and ester in the dog.

Forms of 2,4-dichlorophenoxyacetic acid (2,4-D) are herbicides used in the control of a wide variety of broadleaf and woody plants. Subchronic toxicity studies in dogs were conducted on three forms of 2,4-D: the parent form, 2,4-D acid (ACID); 2,4-D dimethylamine salt (DMA); and 2,4-D 2-ethylhexyl ester (2-EHE). The three studies were designed to allow for comparison of the toxicity of the three forms. Doses in the subchronic studies, on an acid equivalent basis, were 0, 0.5 (ACID only), 1.0, 3.75, and 7.5 mg/kg/day. Treatment related findings in the three studies included reductions in body weight gain, and food consumption, and minor increases in blood urea nitrogen, creatinine, and alanine aminotransferase. The data from the three subchronic studies demonstrated the comparable toxicity of ACID, DMA, and 2-EHE and support a subchronic no observed adverse effect level (NOAEL) of 1.0 mg/kg/day for all three forms. Due to the similarity in toxicity of the three forms of 2,4-D, a 1-year chronic toxicity study was performed on the parent ACID to fully characterize the potential toxicity of 2,4-D in the dog. ACID was well tolerated at doses of 0, 1.0, 5.0, and 7.5 mg/kg/day. The clinical pathology alterations were similar to those seen in the subchronic studies and were not progressive. The histopathology alterations observed were not severe in nature and the no observed effect level in the chronic study was determined to be 1.0 mg/kg/day. There was no indication of any immunotoxic or oncogenic response in the studies. In conclusion, the findings of these studies indicate comparable toxicity among representative forms of 2,4-D and their generally low toxicity following subchronic and chronic dietary exposure in the dog.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1996

Comparative subchronic studies on 2,4-dichlorophenoxyacetic acid, amine, and ester in rats.

Forms of 2,4-dichlorophenoxyacetic acid (collectively known as 2,4-D) are herbicides used to control a wide variety of broadleaf and woody plants. Subchronic toxicity studies in rats were conducted on three forms of 2,4-D: the parent form, 2,4-D acid; 2,4-D dimethylamine salt (DMA); and 2,4-D 2-ethylhexyl ester (2-EHE). Doses in the subchronic studies (on an acid equivalent basis) were 0, 1, 15, 100, and 300 mg/kg/day. Major treatment related findings in the three studies included decreases in red cell mass, decreases in T3 and T4 levels, decreases in ovary and testes weights, increases in liver, kidney, and thyroid weights, and cataracts and retinal degeneration (high-dose females). These data demonstrated the comparable toxicities of 2,4-D acid, DMA, and 2-EHE and support a subchronic no-observed-effect level of 15 mg/kg/day for all three forms. In summary, the findings of these studies indicate comparable low subchronic toxicity potentials among representative forms of 2,4-D.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1996

Chronic dietary toxicity/oncogenicity studies on 2,4-dichlorophenoxyacetic acid in rodents.

Forms of 2,4-dichlorophenoxyacetic acid (collectively known as 2,4-D) are herbicides used to control a wide variety of broadleaf and woody plants. Doses in the 2-year chronic/oncogenicity rat study were 0, 5, 75, and 150 mg/kg/day. The chronic toxicity paralleled subchronic findings, and a NOEL of 5 mg/kg/day was established. A slight increase in astrocytomas observed (in males only) at 45 mg/kg/day in a previously conducted chronic rat study was not confirmed in the present study at the high dose of 150 mg/kg/ day. Doses in the 2-year mouse oncogenicity studies were 0, 5, 150, and 300 mg/kg/day for females and 0, 5, 62.5, and 125 mg/ kg/day for males. No oncogenic effect was noted in the study. In summary, the findings of these studies indicate low chronic toxicity of 2,4-D and the lack of oncogenic response to 2,4-D following chronic dietary exposure of 2,4-D in the rat and mouse.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1996

Distribution of mosaicism in human placentae.

Traditional first trimester chorionic villus sampling (CVS) for prenatal diagnosis can be performed by cytogenetic analysis of cytotrophoblast or chorionic villous stroma. Approximately 2% of pregnancies studied by CVS show confined placental mosaicism (CPM) involving either cytotrophoblast, stroma or both. We present the results of a cytogenetic study of nine term placentae from pregnancies with prenatally diagnosed CPM. The aneuploid++ cell lines involved trisomies for chromosomes 7,9,16, and X. The cytotrophoblast and villous stroma from multiple biopsies of these placentae were examined using a combination of interphase and metaphase cytogenetic analysis. CPM was detected in all nine of the term placentae and both tissue-specific and site-specific patterns of mosaicism could be discerned. These results indicate that the analysis of villous stroma and cytotrophoblast from multiple placental biopsies is necessary to improve our understanding of the evolution of CPM during pregnancy and its effect on the fetus.

Biopsy↗
PubMed1995

Early amniocentesis: a clinical review.

Early amniocentesis at less than 14 weeks gestation is becoming more common in prenatal diagnosis populations. Randomized studies are minimal and have not had the power to determine the accuracy and safety of the procedure compared to chorionic villus sampling or mid-trimester amniocentesis. Procedures at 11+0-12+6 weeks should be considered experimental. This clinical review considers the ethics, embryology, and clinical experience (cytogenetics, AFP, AChE, procedure and cytogenetic failures, spontaneous and therapeutic pregnancy losses, congenital anomalies) of early amniocentesis.

Amniocentesis↗
PubMed1995

Prenatal and postnatal growth failure associated with maternal heterodisomy for chromosome 7.

The association of maternal uniparental disomy for chromosome 7 and postnatal growth failure has been reported in four cases and suggests the presence of genomic imprinting of one or more growth related genes on chromosome 7. However, in the reported cases, the possibility of homozygosity for a recessive mutation could not be excluded as the cause of the growth failure as in all cases isodisomy rather than heterodisomy for chromosome 7 was present. We report a case of prenatal and postnatal growth retardation associated with a prenatal diagnosis of mosaicism for trisomy 7 confined to the placenta. DNA typing of polymorphic markers on chromosome 7 has established that the zygote originated as a trisomy 7 with two maternal and one paternal chromosomes 7 with subsequent loss of the paternal chromosome resulting in a disomic child with maternal heterodisomy for chromosome 7. The growth failure seen in this child with heterodisomy 7 lends strong support to the hypothesis of imprinted gene(s) on chromosome 7.

Adult↗