Biomedical subjects
Publications and source records attributed to S A Farrell.
A direct intrachromosome insertion of chromosome 7 is described, and previous reports of intrachromosomal insertions are listed. All others were ascertained through a phenotypically abnormal proband. Ours is the first presenting with multiple pregnancy losses. Since the risk of chromosomally abnormal liveborns is appreciable, prenatal diagnosis should be made available to known carriers of chromosome insertions.
Mosaicism for a balanced reciprocal translocation is uncommon. These two new cases were detected during investigation of infertility and miscarriages. Otherwise, the probands were normal. Of five previously described cases, only one was possibly syndromal. More reports of this class of chromosomal aberration are needed to assess accurately the risk of phenotypic abnormalities.
Human CR1 is composed of tandem long homologous repeating (LHR) segments that encode separate binding sites for C3b or C4b. Homologous recombination with unequal crossover has been proposed as the genetic mechanism that gave rise to the CR1 alleles that differed in their total numbers of LHR. The F allotype has four LHR, named LHR-A, -B, -C, -D, 5' to 3'. The site in LHR-A preferentially binds C4b and those in LHR-B and -C prefer C3b. A previous study revealed the presence of a fifth LHR with sequences similar to LHR-B and a third C3b binding site in the S allotype of higher m.w. In the present study, an 18-kb EcoRV fragment that was associated with the expression of the lower m.w. F' allotype hybridized with a unique pattern of cDNA and intron probes specific for LHR-C. Deletion of LHR-B and one C3b binding site was proposed as the mechanism for the appearance of this F'-specific fragment. Functional differences among the CR1 variants were sought by comparative analyses of soluble rCR1 having one, two or three C3b binding sites. Although these three variants did not exhibit any significant differences in their capacities to act as cofactors for the cleavage of monomeric C3b, their relative affinities for dimeric ligand varied more than 100-fold. Furthermore, the variant with only one C3b binding site was at least 10-fold less effective in the inhibition of the alternative pathway C3 and C5 convertases. These observations suggested that the F' allotype may be impaired in its capacity to bind opsonized immune complexes, to inhibit the formation of the alternative pathway C3 and C5 convertases, and perhaps to mediate other CR1-dependent cellular responses.
Three children with deletions involving the 9q22q34 region are described. A review of clinical features of these three new patients and seven previously reported ones did not demonstrate a recognizable dysmorphic pattern. Our cases illustrate the need for repeat karyotyping at higher levels of resolution when there is a suspicion of a chromosome anomaly, since each deletion was missed on initial analysis.
This report describes a spontaneous vaginal vault prolapse in association with massive evisceration following sacrospinous vaginal vault fixation. Careful attention to surgical technique is critical to the success of the operation. In particular, good apposition of the vaginal vault to the sacrospinous ligament and adequate repair of an enterocele should avoid this complication.
Megacystis-microcolon-intestinal hypoperistalsis syndrome is an uncommon condition, possibly inherited as an autosomal recessive trait. This report describes an affected sib pair with intrauterine death of one of the sibs.
Schwartz-Jampel syndrome generally presents in childhood with short stature, limited joint mobility, masklike facies with blepharophimosis, myotonia, and often muscle hypertrophy. Few cases with neonatal manifestations have been described. A newborn with severe manifestations is reported and the literature is reviewed.
Lissencephaly, hydrocephalus, and eye abnormalities characterize patients with the Walker-Warburg syndrome, an uncommon autosomal recessive condition. Encephaloceles occur in about 50% of patients. We describe the prenatal diagnosis of this condition based on the ultrasonographic findings of retinal detachment, hydrocephalus, and an encephalocele in a fetus not known to be at risk.
A female infant with Kaufman-McKusick syndrome redeveloped respiratory distress and abdominal distention at 5 weeks of age. Ultrasonography demonstrated recurrence of peritoneal cysts and hydrometrocolpos. It is postulated that refluxing vaginal secretions may contribute to the abdominal distention seen in many infants with Kaufman-McKusick syndrome.
Few cases have been described of the Weaver syndrome, an overgrowth syndrome with advanced skeletal age. Here we report bilateral pes cavus in an affected girl.
The phenomenon of segregation of gene expression has been examined in intraspecific somatic cell hybrids. Specifically, segregation at the hypoxanthine guanine phosphoribosyltransferase (HPRT) locus has been studied in hybrids of Chinese hamster cell lines. The role of chromosome segregation, or other chromosomal events has been assessed by detailed comparison of karyotypes in the 6-thioguanine resistant segregants with those of the parental hybrid lines. The results clearly demonstrate that loss of an entire X chromosome is the primary event responsible for segregation at the HPRT locus, while deletion of a portion of the short arm of an X chromosome was also a frequent event. The results provide the first direct evidence for the assignment of the mapping of this locus to the distal region of the short arm. Analysis of chromosome number distributions in the hybrids and segregants suggests that in selecting chromosomal segregants one may also select for hybrid lines with reduced chromosome stability.