Twin-to-twin transfusion syndrome--debates on the etiology, natural history and management.
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Arteriovenous Anastomosis↗
Biomedical subjects
G Machin
Publications and source records attributed to G Machin.
The highly protective effect of newborn circumcision against invasive penile cancer.
OBJECTIVE: We determined the relation between newborn circumcision and both invasive penile cancer (IPC) and carcinoma in situ (CIS) among adult male members of a large health maintenance organization. SUBJECTS AND METHODS: Circumcision status was ascertained by a combination of pathology reports, medical record review, and questionnaires for 213 adult male members of a large prepaid health plan who were diagnosed with IPC or CIS. RESULTS: Of 89 men with IPC whose circumcision status was known, 2 (2.3%) had been circumcised as newborns, and 87 were not circumcised. Of 118 men with CIS whose circumcision status was known, 16 (15.7%) had been circumcised as newborns. CONCLUSIONS: Our results confirm the highly protective effect of newborn circumcision against IPC and the less protective effect against CIS.
Age of Onset↗
A twin-pronged attack on complex traits.
Before one starts the hunt for quantitative trait loci (QTLs) for a complex trait, it is necessary to show that the trait is genetically influenced. This evidence is most likely to come from the classical twin study--the demonstration that monozygotic twins are more similar for the trait than dizygotic twins. The strengths and weaknesses of twin studies are discussed, and it is suggested that, far from becoming irrelevant with advances in molecular biology, they can improve the efficiency of QTL detection and play an important role in unravelling developmental genetic mechanisms.
Diseases in Twins↗
Zygosity testing. Current status and evolving issues.
This paper reviews the current status and evolving issues in the field of zygosity testing. Monozygotic twins are seldom absolutely identical. Traditional methods of zygosity testing, mathematical ones and assessment of physical characteristics are reviewed. The proper delineation of zygosity based on placentation and chorionicity is outlined. Genetic and environmental discordance patterns are described, with a discussion of why "identical" twins are never identical preceding specific guidelines for clinical practice.
Diseases in Twins↗
X-chromosome inactivation is mostly random in placental tissues of female monozygotic twins and triplets.
Patterns of X-chromosome inactivation in chorion, amnion, and cord from 79 pairs of twins were examined. Seven sets of triplets were included in the analysis, both as twin pairs and triplets. Twins were stratified as dizygotic (DZ), monozygotic (MZ), monochorionic, and dichorionic and were selected for birth weight discordance, discordance for congenital anomalies, twin-twin transfusion syndrome, and various patterns of vascular anastomosis. X-inactivation was predominantly symmetric. Chorion was the most likely tissue to show asymmetric X-inactivation and was found most frequently in MZ dichorionic twins. There was no correlation of X-inactivation pattern with the selected clinical criteria. This study does not confirm that asymmetric X-inactivation in embryonic tissues is a common phenomenon in female twins, including monozygotic twins.
Amnion↗
Correlations of placental vascular anatomy and clinical outcomes in 69 monochorionic twin pregnancies.
Monochorionic monozygotic twins frequently suffer complications from the presence of vascular anastomoses in their monochorionic placentas. Also, sharing of perfusion zones may be unequal, leading to marked growth discordance. This paper analyzes four measures of perinatal outcome (gestational age at delivery, perinatal mortality, birth weight discordance, and presence/absence of hydramnios) according to the vascular patterns of the monochorionic placentas. The worst clinical outcomes were associated with arteriovenous anastomoses in the absence of arterio-arterial and veno-venous anastomoses. The vascular patterns of monochorionic placentas cause significant fetal environmental differences within pairs of monochorionic monozygotic twins. These differences may cause life-long discordance for several phenotypic traits that are not genetically based, and which cause monochorionic monozygotic twins to be "non-identical."
Birth Weight↗
Some perinatal characteristics of monozygotic twins who are dichorionic.
Zygosity testing of all multiple births allowed the identification of a subgroup of 42 monozygotic twin pairs who have dichorionic placentas, fused and separate. Perinatal outcomes of this group were compared with 110 pairs of monochorionic monozygotic twins and 148 pairs of dizygotic twins. Dichorionic monozygotic twins had the lowest incidence of preterm birth, perinatal mortality, and birth weight discordance. There was an excess of like-sexed over unlike-sexed pairs among the dizygotic twins.
Birth Weight↗
Prostaglandin endoperoxide-H synthase (PGHS) activity and immunoreactive PGHS-1 and PGHS-2 levels in human amnion throughout gestation, at term, and during labor.
Prostaglandins (PGs) are of primary importance in the initiation and maintenance of labor in women. A major intrauterine source of prostaglandins is the amnion, which synthesizes increased amounts of PGE2 at term labor. Because PG endoperoxide-H synthase (PGHS) catalyzes the rate-limiting step of PG synthesis from arachidonic acid, we investigated the changes in amniotic PGHS specific activity during gestation and at term and preterm labor. Also, we determined the level of immunoreactive PGHS protein in the amnion to evaluate the mechanisms by which PGHS activity may be regulated. PGHS specific activity, measured at the amount of PGE2 produced by amnion microsomes under optimal conditions, was 18.2 +/- 3.7 pg PGE2/micrograms protein.min (mean +/- SE; n = 19) at term (37-42 weeks gestation) before the spontaneous onset of labor. PGHS specific activity was significantly higher after spontaneous term labor (38.9 +/- 6.0 pg PGE2/micrograms protein.min; n = 19; P < 0.05). Amnion samples from preterm (< 36 weeks gestation) nonlaboring patients contained low levels of PGHS specific activity (5.9 +/- 1.8 pg PGE2/micrograms protein.min; n = 9), which increased significantly with spontaneous preterm labor (28.3 +/- 6.8 pg PGE2/micrograms protein.min; n = 10; P < 0.05). Longitudinal analysis of the data showed that PGHS specific activity was low in the first and second trimesters of gestation, but increased dramatically before labor onset at term. We detected PGHS protein in all microsomal samples, with an antiovine PGHS antibody recognizing both PGHS-1 and -2 isoforms of the enzyme. However, there was no correlation between PGHS specific activity and the amount of immunoreactive PGHS protein. Using an antibody specific for PGHS-2, we detected immunoreactive protein in only 9 of the 25 tissues examined and found no correlation between PGHS specific activity and the amount of PGHS-2 protein. These results suggest that 1) PGHS specific activity in the amnion increases sharply before the onset of labor at term; 2) further increases in specific activity occur during term and preterm labor; and 3) the specific activity of PGHS in the amnion is not related directly to the amount of immunoreactive enzyme protein.
Amnion↗
Evaluation of effects of PAF on alveolar fluid clearance with use of NMR imaging.
Autologous serum with or without platelet-activating factor (PAF) was instilled into one lung lobe of an anesthetized cat, and changes in the regional lung water content were monitored for 4 h with proton nuclear magnetic resonance (NMR) images and relaxation time measurements. With serum as an instillate, water was cleared with a half time of approximately 670 min; after 4 h, 86 +/- 6% of that instilled remained. With PAF added to the instillate, clearance was biphasic with an initial clearance half time of approximately 30 min followed by clearance similar to that observed after serum instillation; after 4 h, 35 +/- 4% of that instilled remained. In contrast, 4 h after instillation of serum or serum plus PAF, 91 +/- 3% and 82 +/- 5%, respectively, of the instilled 125I-labeled albumin remained in the lung (P = 0.06). From transverse magnetization relaxation curves we were able to resolve two relaxation components, which we have attributed to the instilled fluid in the air spaces (relaxation time = 177 +/- 7 ms) and the tissue-bound fluid (relaxation time = 25 +/- 1 ms).
Animals↗
Poland anomaly with a limb body wall disruption defect: case report and review.
We describe a female infant with apparent Poland anomaly (PA) and limb body wall defect. Analysis of the defects suggest that a disruption of the lateral embryonic plate mesoderm may have been responsible for the observed lesions. Because of the overlap of this case with PA, we re-examined previous reports of this syndrome. We think that the lesions could be equally well explained as a mesodermal disruption, and point out a previously unrecognised discrepancy between sex and affected side in sporadic PA and inherited PA which supports this view.
Diaphragmatic Eventration↗
Benefits of orotracheal and nasotracheal intubation in neonates requiring ventilatory assistance.
To investigate differences in orotracheal (OT) and nasotracheal (NT) intubation for ventilatory assistance, we randomly assigned 91 neonates to be intubated via either of the two routes: 46 infants were assigned to the OT group and 45 infants were assigned to the NT group. Inability to intubate the nostril in three neonates, and respiratory or cardiac instability during attempted NT intubation in three neonates, resulted in the assignment of 52 infants to the OT group and 39 infants to the NT group; patients in both groups were of comparable size, sex, and clinical problems. Initial malposition of the endotracheal tube and need to retape, reposition, or replace the tube during the mean duration of intubation of 247 +/- 42 hours for the OT group and 273 +/- 57 hours for the NT group were similar. Daily Gram stains of tracheal aspirates showed that inflammation (greater than or equal to ten polymorphonuclear cells per 400 power fields) was common (51% OT group, 53% NT group). Cultures grew potential pathogens in 37% of the patients from the OT group and 31% of the NT group. There was no difference in the clinical or radiologic incidence of pneumonia. Postextubation problems were comparable: atelectasis, 48% OT and 59% NT; stridor, 15% OT and 26% NT. OT intubation may be preferred for prolonged ventilatory assistance in neonates because of the relative ease of initial intubation.
Female↗
In utero evaluation of fetal cardiac structure: a preliminary report.
Fetal echocardiography as a tool for the prenatal diagnosis of cardiac structural abnormalities was utilized in 27 consecutive patients who were referred for evaluation. Four abnormalities were recognized prenatally and confirmed postnatally. A fifth was identified postnatally. The sensitivity and specificity of this diagnostic test were 80% and 100%, respectively. The utilization of this tool in a tertiary care setting by an adequately trained team has proved to be helpful and is recommended.
Echocardiography↗
The effect of very prolonged membrane rupture on fetal development.
This retrospective study examined the effects of very prolonged membrane rupture of more than 1 week on the development of pulmonary hypoplasia and positional deformities in the infants of 100 consecutive women. A control group of infants who were matched for gestational age at delivery, sex, and time of delivery was identified. The results indicate that there was a statistically significant difference (p less than 0.001) in the occurrence of pulmonary hypoplasia and positional deformities. The greatest impact of prolonged membrane rupture on fetal development was seen in the patients in whom membrane rupture occurred prior to 26 weeks' gestation and the duration of rupture was more than 5 weeks.
Bone and Bones↗
Mitochondrial myopathy of cerebro-hepato-renal (Zellweger) syndrome.
The muscles of four infants with cerebro-hepato-renal (Zellweger) syndrome were studied during life and/or at necropsy. A mitochondrial myopathy was demonstrated, similar to mitochondrial alterations demonstrated in liver and brain in this disease. Muscle fibers with red-staining subsarcolemmal aggregates were identified with Gomori trichrome stain in two cases. Subsarcolemmal and intermyofibrillar zones of increased concentrations of NADH-TR, SDH, and cytochrome-c-oxidase activity were demonstrated histochemically in all four cases. Degenerative and cytoarchitectural changes in muscle fibers were not found. Ultrastructural studies showed large aggregates of mitochondria and increased lipid in the subsarcolemmal and intermyofibrillar spaces. Degenerative changes in mitochondria and lipid also were demonstrated, but paracrystalline inclusions were not seen. The distribution of these changes was not uniform between patients or between different muscles in the same patient. The diaphragm was affected more severely than proximal or distal muscles of the extremities. Direct involvement of muscle mitochondria in this disease may interfere with energy metabolism and contribute to the clinical findings of hypotonia, weakness, and respiratory insufficiency. The muscle biopsy with histochemistry and electron microscopy may be used as a diagnostic adjunct in suspected cases, but the variation encountered dictates dictates caution in the interpretation of negative findings.
Brain Diseases↗
Prostaglandin endoperoxide H synthase (PGHS) activity increases with gestation and labour in human amnion.
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Amnion↗
A case of aplasia cutis congenita in dizygotic twins.
We report a newborn infant with extensive aplasia cutis congenita of the flanks and thighs, associated with a co-twin fetus papyraceus. DNA restriction fragment polymorphism analysis of the twins proved dizygosity. The association of these two conditions in twins is reviewed.
Diseases in Twins↗