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Biomedical subjects

E C Jenkins

Publications and source records attributed to E C Jenkins.

At least 73 records · Page 4Linked to original sources
PubMed1986

Low frequencies of apparently fragile X chromosomes in normal control cultures: a possible explanation.

Low frequencies of apparently fragile X [fra(X)] chromosomes have been reported in normal control, short-term, whole blood cultures, and they have been noted in both amniocyte and fetal blood cultures. However, there is currently no universal agreement on the lowest frequency for fra(X)(q27) that is diagnostic for the fragile X syndrome. Here, we present our observations on low levels of apparently fra(X) chromosomes in normal samples. We observed frequencies of 0.5% in short-term whole blood cultures and 0.9% in amniotic fluid cell cultures. In 1982, Steinbach et al. described nonspecific telomeric structural changes (TSC) and suggested that such low frequencies of apparently fra(X) chromosomes in normal material may be occurring by the same mechanism that is responsible for TSC formation. To determine if TSC formation can explain the significant baseline frequencies of fra(X) in normal controls, 10,457 cells were screened from 178 individuals referred for fra(X) analysis. Our findings indicated that TSC are not randomly distributed across chromosomes but tend to occur at specific sites. Based on our observations, we offer the hypothesis that the low frequency of apparent fra(X) in normal individuals may be due to nonrandom TSC distribution.

Amnion↗
PubMed1986

Autism and the fragile X syndrome.

The fragile X chromosome is an important factor in inherited mental retardation in males. It has also been reported that infantile autism is associated with fragile X. Recently, an article reported an examination of a small sample of autistic children in whom the fragile X chromosome was not found. Its authors concluded that if an association between fragile X and autism exists, it is infrequent. In the present study of 144 autistic male subjects, 18 were found to have the fragile X chromosome, supporting other (epidemiological) findings that the association between fragile X and autism occurs relatively frequently.

Adolescent↗
PubMed1985

Fragile X syndrome: associated neurological abnormalities and developmental disabilities.

The fragile X syndrome is a frequent cause of developmental disabilities. It is associated primarily with nonprogressive X-linked mental retardation. The neurodevelopmental abnormalities of 25 males and 3 females are described. Mental retardation was mild in 4, moderate in 11, severe in 6, and profound in 2 patients, while 4 patients had only learning disabilities. The presence or absence of a developmental disability could not be determined in the youngest (8 months). Seven patients had had infantile autism and 7 had epilepsy. Generally no major focal neurological abnormalities were observed but most of the patients exhibited minor signs. The severity of developmental disabilities in our patients varied between and within families and between genders. All adult males had macroorchidism. Unusual facial features were present in 13 males but none were seen in the females. Familial occurrences were found in 18 cases (64%); 10 cases (36%) were sporadic. Overall, males were more severely affected than females. Diagnostic tests including computed tomographic scans, electroencephalograms, and evoked potentials did not disclose any specific abnormalities.

Adolescent↗
PubMed1985

Analysis of the fragile-X chromosome: localization and detection of the fragile site in high resolution preparations.

Fragile X chromosome preparations were analyzed at levels of up to 850 bands per haploid set. We were able to consistently sublocalize the Xqter fragile site to band Xq27.3 using high-resolution methods. Chromosome length versus the frequency of fragile X expression was also compared. The fragile site appeared at a higher percentage in more condensed chromosome preparations. The importance of this finding is that high-resolution chromosome preparations do not optimize fragile-X detection.

Chromosome Banding↗
PubMed1985

Genetic linkage heterogeneity in the fragile X syndrome.

Genetic linkage between a factor IX DNA restriction fragment length polymorphism (RFLP) and the fragile X chromosome marker was analyzed in eight fragile X pedigrees and compared to eight previously reported pedigrees. A large pedigree with apparently full penetrance in all male members showed a high frequency of recombination. A lod score of -7.39 at theta = 0 and a maximum score of 0.26 at theta = 0.32 were calculated. A second large pedigree with a nonpenetrant male showed tight linkage with a maximum lod score of 3.13 at theta = 0, a result similar to one large pedigree with a nonpenetrant male previously reported. The differences in lod scores seen in these large pedigrees suggested there was genetic heterogeneity in linkage between families which appeared to relate to the presence of nonpenetrant males. The combined lod score for the three pedigrees with nonpenetrant males was 6.84 at theta = 0. For the 13 other pedigrees without nonpenetrant males the combined lod score was -21.81 at theta = 0, with a peak of 0.98 at theta = 0.28. When lod scores from all 16 families were combined, the value was -15.14 at theta = 0 and the overall maximum was 5.13 at theta = 0.17. To determine whether genetic heterogeneity was present, three statistical tests for heterogeneity were employed. First, a "predivided-sample" test was used. The 16 pedigrees were divided into two classes, NP and P, based upon whether or not any nonpenetrant males were detected in the pedigree. This test gave evidence for significant genetic heterogeneity whether the three large pedigrees with seven or more informative males (P less than 0.005), the eight pedigrees with three informative males (P less than 0.001), or all 16 pedigrees (P less than 0.001) were included in the analysis. Second, Morton's large sample test was employed. Significant heterogeneity was present when the analysis was restricted to the three large pedigrees (P less than 0.025), or to the eight pedigrees with informative males (P less than 0.05) but not when smaller, less informative pedigrees were also included. Third, an "admixture" test for heterogeneity was employed which tests for linkage versus no linkage. A trend toward significance was seen (0.05 less than P less than 0.10) which increased when the analysis was restricted to the larger, more informative pedigrees.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1985

Adult fragile X syndrome. Clinico-neuropathologic findings.

Fragile X syndrome [fra (X)] is currently accepted as the second most frequent chromosomal disorder associated with developmental disability. Although next to Down syndrome in frequency, no postmortem studies of confirmed adult cases had been reported. The autopsy examination of a 62-year-old, moderately retarded man with the fra (X) syndrome confirmed the preferential involvement of cerebral and testicular structures in this disorder. Dendritic spine abnormalities of the type observed in trisomic chromosomal disorders were associated with synaptic immaturity. Severe testicular hypogonadism accompanied bilateral macro-orchidism, normal penis, and unilateral hydrocele. Valvular, articular, and testicular interstitial compartments showed normal histochemical staining characteristics for glycoproteins and lipids.

Brain↗
PubMed1985

Chromosomal localization of several families of repetitive sequences by in situ hybridization.

Four recombinant DNA clones (H1, H7, H12, and H15) carrying low-repetitive human DNA were previously isolated from a human genomic library based on their specificity for chromosome 21 and were studied for their distribution as determined by in situ hybridization. Clone H7 hybridized to the satellite regions of chromosomes 13, 14, 15, 21, and 22 as well as to the centromere region of chromosome 1. Clone H12 hybridized strongly to chromosomes 11 and 17 and the centromere of the X. Clones H1 and H15 had a very widespread distribution throughout the genome. Clone H15 hybridized significantly more to the short arm of chromosome 18 than to any other chromosomal segment. Clone H1 hybridized strongly to the centromere of chromosome 19 and also showed random distribution on all the other human chromosomes. We conclude that these probes appear to represent four repetitive families that demonstrate in situ hybridization patterns that do not correspond with those of any other repetitive family. Further, the in situ hybridization patterns do not show the strong chromosome 21 specificity originally defined by Southern blot analysis. The nature and chromosomal localization of these repetitive families should be useful in regional mapping and evolutionary studies and give additional insight into chromosomal organization.

Chromosome Banding↗
PubMed1984

Isolation and regional localization by in situ hybridization of a unique gene segment to chromosome 21.

V chromosome 21 (ch. 21) flow-sorted library was screened for the presence of unique DNA segments which are specific for the 21st chromosome. By combining the techniques of somatic cell genetics and in situ hybridization, we have identified several of these recombinant probes and have regionally mapped one of them to the distal half of the long arm of chromosome 21 (q22.1- greater than qter). This represents the first report of the sublocalization of a unique DNA segment to chromosome 21 by in situ hybridization.

Animals↗
PubMed1984

Experience with prenatal fragile X detection.

We have attempted the prenatal detection of the fra(X) 9 times. Three fra(X) positive fetuses have been diagnosed: 2 males and one female. The diagnosis on the 2 males has been confirmed. The testes of the 2 fra(X) positive fetuses appeared large for gestational age. However, results of anthropometric, bone age, anatomical and neurohistological studies were normal. Normal outcome was confirmed after birth in 2 males and one female on the basis of whole blood fra(X) studies. A presumptively positive female and a presumptively negative female await confirmation. Two presumptively negative males remain unborn. Further experience is needed to establish the reliability of the prenatal detection of fra(X) (q27).

Adrenal Cortex↗
PubMed1984

Folic acid therapy in the fragile X syndrome.

Two brothers with fra(X) positive X-linked mental retardation (XLMR) were treated with folic acid. Initially a double blind cross-over design was employed followed by a long-term high dose trial. A decrease in the frequency of fra(X) positive cells was observed when low folic acid culture medium was used but not when an FUdR induction system was employed. Selected behavioral characteristics improved in both while receiving folic acid. Decreased hyperactivity, greater attention span, increased motor coordination, increased quantity and quality of speech were noted. Improvement in Leiter mental age and regression after cessation of treatment was seen in one subject but not in the other. Further controlled trials with larger numbers of subjects using high doses of folic acid over longer periods of time are needed to assess the possible benefits of this experimental form of treatment.

Adolescent↗
PubMed1984

Distal duplication 14q: report of three cases and further delineation of the syndrome.

Three cases of distal duplication 14q are presented. The first two cases are cousins in a kindred segregating a balanced translocation t(14;18)(q31;q23). The third case resulted from a maternal translocation t(14;18)(q24;p11). By review of these cases and those previously reported, a distal duplication 14q syndrome is further delineated. Common features include postnatal growth retardation, mental retardation, hypotonia, microcephaly, slanted palpebral fissures, ocular hypertelorism, sparse eyelashes and eyebrows, nasal dysmorphism, tented lip, micrognathia, posteriorly rotated ears, and minor skeletal anomalies.

Adult↗
PubMed1983

Monosomy 21 syndrome: further delineation including clinical, neuropathological, cytogenetic and biochemical studies.

Only six cases of living newborns with apparently complete monosomy 21 have been reported. All the previous cases with the exception of the present case died between 3 weeks and 20 months. Only one of these cases had a postmortem examination. The subject of this report was previously described at the age of 6 years (Davis et al. 1976). He survived until 11 years old and is the oldest known case of complete monosomy 21. We report here the clinical presentation over 11 years, results of gene dosage studies, cytogenetic analysis, and the neuropathological postmortem examination.

Aneuploidy↗
PubMed1983

The strength of association between fragile (X) chromosome presence and mental retardation.

In order to obtain a quantitative estimate of the degree of association between presence of fragile X chromosome (fra(X] and mental retardation (MR), existing data from nonretarded males were analyzed. Clearly, fra(X) occurs less frequently among nonretarded compared to MR males. However, incidence estimates for fra(X) based upon existing data hold open the possibility that there may be significant numbers of nonretarded males with fra(X). Additional analyses of data from families with a pattern of fra(X) linked MR showed: (a) the probability that nonretarded male offspring will have fra(X) is very small, and (b) the probability that MR male offspring will have fra(X) is very large. Thus, accurate prognostic decisions can be based upon prenatal diagnosis of fra(X) presence, especially in families with a pattern of fra(X) linked MR.

Female↗
PubMed1983

Atypical Down syndrome and partial trisomy 21.

A case of "atypical" Down Syndrome (DS), where the proposita did not exhibit all of the clinical features of DS and had de novo partial trisomy 21, was studied. Results from phenotypic, chromosome banding and superoxide dismutase (SOD) gene dosage studies suggest a karyotype of 46,XX,-12,+t(12pter to 12qter::21q21 to 21q22.?2). Additional studies of such atypical cases will provide more precise sublocalization for both gene and phenotypic mapping of the bands that are responsible for the DS phenotype.

Child↗