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L Strain

Publications and source records attributed to L Strain.

At least 37 records · Page 2Linked to original sources
PubMed1994

Prenatal diagnosis of fragile X syndrome: management of the male fetus with a premutation.

Direct detection of the fragile X mutation by DNA analysis has greatly simplified prenatal diagnosis of this disease. However, women carrying a fragile X premutation may pass their expanded trinucleotide repeat to sons without expansion to a full mutation. Such sons are predicted to be intellectually normal. In this situation, the accuracy with which the fetal status can be inferred from analysis of chorionic villus sample (CVS) DNA is unclear. We describe such a case, in which it was felt necessary to proceed to fetal blood sampling despite technically unambiguous DNA results from the CVS. The lack of prospective data means that this dilemma may be expected to recur over the next few years when performing prenatal diagnosis on fragile X premutation carriers.

Adult↗
PubMed1994

Heterogeneity analysis in 40 X-linked retinitis pigmentosa families.

Analysis of genetic heterogeneity in 40 kindreds with X-linked retinitis pigmentosa (XLRP), with 20 polymorphic markers, showed that significant heterogeneity is present (P = .001) and that 56% of kindreds are of RP3 type and that 26% are of RP2 type. The location of the RP3 locus was found to be 0.4 cM distal to OTC in the Xp21.1 region, and that of the RP2 locus was 6.5 cM proximal to DXS7 in Xp11.2-p11.3. Bayesian probabilities of linkage to RP2, RP3, or to neither locus were calculated. This showed that 20 of 40 kindreds could be assigned to one or the other locus, with a probability > .70 (14 kindreds with RP3 and 6 kindreds with RP2 disease). A further three kindreds were found to be unlinked to either locus, with a probability > .8. The remaining 17 kindreds could not be classified unambiguously. This highlights the difficulty of classifying families in the presence of genetic heterogeneity, where the two loci are separated by an estimated 16 cM.

Bayes Theorem↗
PubMed1994

Genetic heterogeneity in X-linked hydrocephalus: linkage to markers within Xq27.3.

X-linked hydrocephalus is a well-defined disorder which accounts for > or = 7% of hydrocephalus in males. Pathologically, the condition is characterized by stenosis or obliteration of the aqueduct of Sylvius. Previous genetic linkage studies have suggested the likelihood of genetic homogeneity for this condition, with close linkage to the DXS52 and F8C markers in Xq28. We have investigated a family with typical X-linked aqueductal stenosis, in which no linkage to these markers was present. In this family, close linkage was established to the DXS548 and FRAXA loci in Xq27.3. Our findings demonstrate that X-linked aqueductal stenosis may result from mutations at two different loci on the X chromosome. Caution is indicated in using linkage for the prenatal diagnosis of X-linked hydrocephalus.

Cells, Cultured↗
PubMed1988

First-trimester prenatal diagnosis of cystic fibrosis using fibroblasts from a deceased index child to establish haplotypes.

First-trimester prenatal diagnosis of cystic fibrosis (CF) using linked DNA markers is usually only possible if there is an index affected child to establish the haplotype of the parental chromosomes. We describe a prenatal diagnosis where fibroblasts, cultured from the skin of a deceased affected child and then held in frozen storage for 3 years, were used as the starting point for tracking the CF gene. The fetus was diagnosed as a homozygous normal and the diagnosis confirmed by immunoreactive trypsin testing after birth. It was also possible to establish heterozygosity in the aunt of the affected child.

Adult↗
PubMed1988

Use of linkage disequilibrium data in prenatal diagnosis of cystic fibrosis.

Parents at risk of bearing a child with cystic fibrosis, and who have no living affected child, often use prenatal diagnosis based on microvillar enzyme assay in second-trimester amniotic fluid samples. If enzyme levels are abnormal and the pregnancy is terminated, it is possible in principle to use the fetal tissues to establish the phase relationship of linked DNA markers for a subsequent first-trimester prenatal diagnosis. However, the probability of a fetus being affected after an abnormal microvillar enzyme test may be no greater than 80%. The strong linkage disequilibrium between haplotypes at the D7S23 locus and the cystic fibrosis gene may be used to increase this probability. If fetal tissues are homozygous for the 6.6-kb band defined by pKM.19 and PstI and also homozygous for the 2.1-kb band with pXV-2c and TaqI, the chance of being affected increases from 80% to between 95% and 97%. We regard this as being sufficiently certain for use in phase determination.

Cystic Fibrosis↗
PubMed1988

Genotyping of cystic fibrosis families with linked DNA probes.

Forty-six British families, containing at least one child affected with cystic fibrosis, were typed for restriction fragment length polymorphisms (RFLPs) by the probes pmet H, pmet D, pJ3.11 and 7c22. Thirty-five (76%) were fully informative for prenatal diagnosis and carrier detection, while in the remainder prenatal exclusion of an affected fetus could be carried out in half the pregnancies. The frequencies of individual alleles did not differ between cystic fibrosis and normal chromosomes. However, the previously noted excess of one haplotype on chromosomes carrying the cystic fibrosis gene was confirmed.

Cystic Fibrosis↗
PubMed1988

Confirmation of prenatal diagnosis of cystic fibrosis by DNA typing of fetal tissues.

Tissues from eight fetuses, diagnosed on the basis of amniotic fluid microvillar enzyme assay as having cystic fibrosis, were conserved in frozen storage for up to three years. Adequate samples of undegraded DNA could be extracted from small intestine, lung, and liver. DNA typing, with restriction fragment length polymorphisms tightly linked to the cystic fibrosis gene, showed all eight diagnoses to have been correct. Determining the DNA genotype of fetal material can also be used to establish the linkage relationship between markers and the cystic fibrosis gene, and will permit subsequent first trimester prenatal diagnosis for couples who have no living affected child.

Amniocentesis↗
PubMed1987

Reliability of a single beta-thromboglobulin measurement in a diabetic population: importance of PGE1 in anticoagulant mixture. Damad Study Group.

During the collection of samples for plasma beta-thromboglobulin (beta-TG) determination, it is well established that artificially high values can be observed due to in-vitro release. To estimate the reliability of a single beta-TG measurement, blood samples were collected simultaneously from both arms on two separate occasions in 56 diabetic patients selected for a clinical trial. From each arm, blood was taken into two tubes containing an anticoagulant mixture with (tube A) and without (tube B) PGE1. The overall mean value of B-TG in tube B was 1.14 times higher than in tube A (p less than 0.01). The markedly large between-arms variation accounted for the most part of within-subject variation in both tubes and was significantly greater in tube B than in tube A. Based on the difference between B-TG values from both arms, the number of subjects with artificially high B-TG values was significantly higher in tube B than in tube A on each occasion (overall rate: 28% and 14% respectively). Estimate of between-occasions variation showed that B-TG levels were relatively stable for each subject between two occasions in each tube. It is concluded that the use of PGE1 decreases falsely high B-TG levels, but a single measurement of B-TG does not provide a reliable estimate of the true B-TG value in vivo.

Adult↗
PubMed1986

Platelet-density analysis and intraplatelet granule content in young insulin-dependent diabetics.

This study was designed to assess the density characteristics of platelets from controls (N = 10) and three groups of diabetics (N = 32) exhibiting various degrees of glycemic control. With continuous gradients of Percoll, platelets from controls and diabetics (N = 8) with an HbA1 less than or equal to 9% formed a band extending from 1.0625 g/ml to 1.0925 g/ml with a mean platelet density of 1.0775 g/ml. In the two groups of diabetics with HbA1 greater than or equal to 10%, there was an increase in the proportion of low-density platelets recovered on the gradients and the mean platelet density was reduced to 1.0750 g/ml (HbA1 = 10-13%) and 1.070 g/ml (HbA1 greater than or equal to 14%). All three groups of diabetics had normal levels of intraplatelet ATP/ADP and beta-thromboglobulin. It is unlikely that in vivo degranulation of platelets after activation was responsible for the altered density profiles. We propose that abnormal platelet subpopulations with low density but normal intraplatelet granule content were responsible for the changed density profiles.

Adult↗
PubMed1978

Small inclusions in the cytoplasm of leukocytes in LE cell tests.

Small homogeneous basophilic and eosinophilic particles varying in size from 0.7 to 3.0 micra were seen in cytoplasm of monocytes and polymorphonuclear cells of leukocytes in LE cell tests. The aim of this investigation was to determine their frequency and diagnostic significance. Inclusions were found in one-third of LE cell tests on patients with rheumatic diseases and were not observed in normals. In 19.1% of 161 patients with SLE, they were present before LE cells were found. Sixty-eight% of patients who had particles had SLE, 8% had rheumatoid arthritis with LE cells, and 3% had nonrheumatic diseases.

Adult↗