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Biomedical subjects

L G Brown

Publications and source records attributed to L G Brown.

At least 55 records · Page 3Linked to original sources
PubMed1989

ZFX has a gene structure similar to ZFY, the putative human sex determinant, and escapes X inactivation.

The ZFX gene on the human X chromosome is structurally similar to the ZFY gene, which may constitute the sex-determining signal on the human Y chromosome. ZFY and ZFX diverged from a common ancestral gene, as evidenced by similarities in their intron/exon organization and exon DNA sequences. The carboxy-terminal exons of ZFY and ZFX both encode 13 zinc fingers; 383 of 393 amino acid residues are identical, and there are no insertions or deletions. Thus, the ZFY and ZFX proteins may bind to the same nucleic acid sequences. ZFY and ZFX are transcribed in a wide variety of XY and (in the case of ZFX) XX cell lines. Transcription analysis of human-rodent hybrid cell lines containing "inactive" human X chromosomes suggests that ZFX escapes X inactivation. This result contradicts the "dosage/X-inactivation" model, which postulated that sex is determined by the total amount of functionally interchangeable ZFY and ZFX proteins.

Base Sequence↗
PubMed1989

Distal interphalangeal joint flexible implant arthroplasty.

Twenty-one osteoarthritic distal interphalangeal joints in 13 patients were treated by flexible implant arthroplasty. Follow-up to 5 years showed results that were good to excellent, with only one complication, and a high degree of patient satisfaction. The procedure should be considered a good alternative to the more traditional distal interphalangeal joint arthrodesis.

Aged↗
PubMed1989

Percutaneous peritoneal lavage in blunt trauma patients: a safe and accurate diagnostic method.

We reviewed the records of 395 patients seen from January 1983 through May 1988, who after sustaining blunt thoracoabdominal trauma had diagnostic peritoneal lavage (DPL) performed percutaneously by the Seldinger wire technique of Lazarus and Nelson. The test was considered grossly positive if 10 cc of blood were aspirated from the catheter immediately after its insertion into the peritoneal cavity. Microscopic criteria for positivity included more than 100,000 RBC or 500 WBC/cc of lavage return, elevated amylase or bilirubin, or the presence of vegetable fibers or bacteria. Seventy-two (18%) of the patients were true positives and 315 (80%) were true negatives. There were four false positives (1.3%) and one false negative (0.2%), giving the test a sensitivity of 99% and a specificity of 98%. Complications occurred in three patients, for a rate of 0.8%, and included catheter insertion into a large ovarian dermoid cyst, needle perforation of the ileum, and needle perforation of the sigmoid colon. This technique of DPL can consistently be performed much more rapidly than the open method. Therefore we conclude that percutaneous DPL is as accurate as, as safe as, and quicker than open DPL for determining intra-abdominal injury in blunt trauma patients.

Abdominal Injuries↗
PubMed1988

Characterization of a (Y;4) translocation by DNA hybridization.

A phenotypically normal male with azoospermia was found to have a translocation between the short arm of the Y chromosome and the distal long arm of a chromosome 4. By cytogenetic analysis it could not be determined whether the translocation was reciprocal, nor whether it was balanced. In situ DNA hybridization with two pseudoautosomal and one Y-specific probe demonstrated that the breakpoint was on distal Yp and that there was Y chromosome material on 4q. Thus the translocation was reciprocal and could be characterized as t(Y;4)(pll;q32). There was no evidence for loss of Y-DNA sequences as judged by Southern blotting with Y-DNA probes. Thus the translocation may be balanced. We conclude that DNA hybridization can be used to refine considerably the cytogenetic analysis of such translocations.

Adult↗
PubMed1988

Molecular detection of a Yp/18 translocation in a 45,X holoprosencephalic male.

Prenatal diagnosis in a fetus with holoprosencephaly showed a 45,X karyotype and a suspected 18p abnormality. At birth, the fetus presented with normal male genitalia. Y chromatin was not cytogenetically detectable by Q-, G-, or G11-banding. Mosaicism for a cell line containing a Y chromosome was not observed in amniocytes, lymphocytes, or skin fibroblasts. Southern blot analysis for 11 different Y-DNA loci demonstrated the presence in the patient's genome of sequences derived from the short arm, centromeric region, and proximal long arm of the Y chromosome (intervals 1-5). The distal long arm of the Y (intervals 6 and 7) was absent. In situ hybridization with the Y-derived probe pDP105 showed silver grains over the short arm of the del(18) chromosome, suggesting a Y/18 translocation with loss of 18p and distal Yq material.

Abnormalities, Multiple↗
PubMed1987

The sex-determining region of the human Y chromosome encodes a finger protein.

The presence or absence of the Y chromosome determines whether a mammalian embryo develops as a male or female. In humans, genetic deletion analysis of "sex-reversed" individuals has identified a small portion of the Y chromosome necessary and sufficient to induce testicular differentiation of the bipotential gonad. We report the cloning of a 230-kilobase segment of the human Y chromosome that contains some or all of the testis-determining factor gene (TDF), the master sex-determining locus. The cloned region spans the deletion in a female who carries all but 160 kilobases of the Y. Certain DNA sequences within this region were highly conserved during evolution; homologs occur on the Y chromosomes of all mammals examined. In particular, homologous sequences are found within the sex-determining region of the mouse Y chromosome. The nucleotide sequence of this conserved DNA on the human Y chromosome suggests that it encodes a protein with multiple "finger" domains, as first described in frog transcription factor IIIA. The encoded protein probably binds to nucleic acids in a sequence-specific manner, and may regulate transcription. Very similar DNA sequences occur on the X chromosome of humans and other mammals. We discuss the possibility that the Y-encoded finger protein is the testis-determining factor, and propose models of sex determination accommodating the finding of a related locus on the X chromosome. The presence of similar sequences in birds suggests a possible role not only in the XX/XY sex determination system of mammals, but also in the ZZ/ZW system of birds.

Amino Acid Sequence↗
PubMed1987

Familial premature ovarian failure due to an interstitial deletion of the long arm of the X chromosome.

We describe a family in which four women had menstrual irregularities and a partial deletion of the long arm of the X chromosome (Xq). Three of the four women had premature ovarian failure (at the ages of 24 to 37 years). Chromosome-banding studies initially suggested that a terminal portion of Xq was deleted. However, DNA-hybridization studies showed that an interstitial portion of Xq was deleted and that the affected women had a 46,XX,del(X)(pter-q21.3::q27-qter) karyotype. These findings help clarify the role of Xq in ovarian function and indicate that the accurate description of such abnormalities requires a combination of cytogenetic and DNA-hybridization analysis.

Adult↗
PubMed1987

Linkage, physical mapping, and DNA sequence analysis of pseudoautosomal loci on the human X and Y chromosomes.

The pseudoautosomal region of the human X and Y chromosomes is subject to frequent X-Y recombination during male meiosis. We report the finding of two pseudoautosomal loci, DXYS20 and DXYS28, characterized by highly informative restriction fragment length polymorphisms (RFLPs). The pseudoautosomal character of DXYS20 and DXYS28 was formally demonstrated by comparing their transmission to 45,X and to normal individuals. Studies of the inheritance of these loci reveal that the pseudoautosomal region, though highly recombinogenic, is subject to marked recombinational interference in male meiosis; no double recombinants were observed in 143 triply informative meioses, and the coefficient of coincidence is likely less than 0.45. In female meiosis, linkage of these pseudoautosomal RFLPs to strictly sex-linked RFLPs on the short arm of the X is readily detected; the genetic length of the pseudoautosomal region in female meiosis is at least 4 cM but not more than 18 cM. The genetic map of the human X chromosome is now defined from near the short-arm telomere to band q28 on the long arm. Locus DXYS20, which maps near the X and Y short-arm telomeres, is composed of long tandem arrays of 61-bp repeats. Occasional, seemingly random base-pair substitutions within these arrays of 61-bp repeats, in combination with marked variation in the size of the array, generate the high degree of DNA polymorphism at DXYS20.

Base Sequence↗
PubMed1987

An XXX male resulting from paternal X-Y interchange and maternal X-X nondisjunction.

A 2-year-old boy was found to have a 47,XXX karyotype. Restriction-fragment-length-polymorphism analysis showed that, of his three X chromosomes, one is of paternal and two are of maternal origin. The results of Y-DNA hybridization were reminiscent of those in XX males in two respects. First, hybridization to Southern transfers revealed the presence in this XXX male of sequences derived from the Y-chromosomal short arm. Second, in situ hybridization showed that this Y DNA was located on the tip of the X-chromosomal short arm. We conclude that this XXX male resulted from the coincidence of X-X nondisjunction during maternal meiosis and aberrant X-Y interchange either during or prior to paternal meiosis.

Child, Preschool↗
PubMed1986

Fetal outcome with oligohydramnios in the second trimester.

Thirty-four cases of oligohydramnios in the second trimester were diagnosed by ultrasonography. Nine of these pregnancies were associated with fetal anomalies including Potter syndrome (three), atrioventricular dissociation (two), congenital absence of thyroid (one), and multiple anomalies (three). There were ten unexplained stillbirths, one demise due to abruptio placentae, eight with perinatal morbidity after premature labor or abruptio placentae, and six with live-born term infants. Although oligohydramnios in the second trimester is associated with increased perinatal morbidity, this finding is not associated with a universally poor outcome.

Amniotic Fluid↗
PubMed1985

Pregnancy complicated by intraamniotic infection by Salmonella typhi.

There are few reports of transplacental infection by Salmonella typhi. A case of a primagravida at 26 weeks' gestation with severe S typhi gastroenteritis, sepsis, and disseminated intravascular coagulation is presented. Shortly after institution of antibiotic therapy, she spontaneously aborted a previable infant. Amniotic fluid was turbid and subsequently grew S typhi.

Abortion, Spontaneous↗
PubMed1984

A survey of pregnancies complicated by decreased amniotic fluid.

Four hundred seventy-one patients undergoing diagnostic ultrasonography were identified as having moderately decreased amniotic fluid or oligohydramnios, and 339 of these cases were reviewed. Ninety-two of the patients were excluded from further statistical analysis because their decreased fluid was attributed to rupture of the membranes only. Of the remaining patients there was a 7% neonatal malformation rate. Decreased amniotic fluid before 27 weeks of gestation was associated with a significantly poor outcome. Of all the live births, infants of patients with oligohydramnios had lower Apgar scores at 1 minute and 5 minutes than did infants of patients with moderately decreased amniotic fluid. Of cases of patients with decreased fluid, 10% involved fetal distress during labor and in 17% meconium was present. Decreased levels of fluid were associated with an increased rate of abdominal deliveries. Preeclampsia was present in 24.7% of patients with decreased fluid. There was no correlation between the quantitative fluid amounts and the severity of the disease. In view of normative data and clinical experience, these observations suggest that the diagnosis of decreased amniotic fluid on routine ultrasonography requires a fetal scan to rule out anomalies, close antepartum observation to detect complications that may arise in the pregnancy, and delivery under conditions that allow appropriate support and intervention on behalf of the fetus.

Amniotic Fluid↗
PubMed1976

Post-traumatic trapped dislocations of the proximal interphalangeal joint.

This paper deals with the uncommon and frequently unrecognized problem of trapped dislocations of the proximal interphalangeal joint. These may be dorsal or volar. Soft tissue forming a noose, or interposed in the joint, is implicated. There is injury to one or more of the following structures: 1) extensor mechanism, 2) collateral ligament, 3) volar plate, 4) flexor tendon sheath, and 5) skin (compound dislocations). Open reduction and appropriate soft tissue repair are mandatory the essential features of diagnosis and management are discussed and four illustrative cases are presented.

Adolescent↗
PubMed1975

Treatment of felons.

The pitfalls of traditional concepts in the management of a felon are reviewed. A more rational and uniformly successful method is detailed. This consists of a midvolar, longitudinal incision of the fat pad where the majority of abscesses point. Other incisions are reserved for the few cases in which maximal tenderness is shown elsewhere. An abscess should always be drained where it points. It has not been our intent in this report to discuss the problems of extension of infection beyond the closed space of the distal fat pad or to deal with paronychias and eponychias that simulate a felon by their extension.

Adipose Tissue↗