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Biomedical subjects

K Tabsh

Publications and source records attributed to K Tabsh.

At least 19 recordsLinked to original sources

Prenatal diagnosis of Sjögren-Larsson syndrome using enzymatic methods.

Sjögren-Larsson syndrome (SLS) is an autosomal recessive disorder characterized by the presence of congenital ichthyosis, mental retardation, and spasticity. The primary biochemical defect in SLS has recently been identified to be a deficiency of fatty aldehyde dehydrogenase (FALDH), which is a component of fatty alcohol:NAD+ oxidoreductase (FAO). We monitored four pregnancies at risk for SLS by measuring FAO and FALDH in cultured amniocytes or cultured chorionic villus cells. The enzymatic results in one case using amniocytes obtained during the second trimester predicted an affected SLS fetus, which was confirmed at termination of the pregnancy. Another at-risk fetus was predicted to be affected with SLS using cultured chorionic villus cells obtained in the first trimester, and fetal skin fibroblasts confirmed a profound deficiency of FAO and FALDH. Two other fetuses were correctly predicted to be unaffected. These results demonstrate that SLS can be diagnosed prenatally using enzymatic methods.

Alcohol Oxidoreductases↗

Risk assessment of amniocentesis between 11 and 15 weeks: comparison to later amniocentesis controls.

We studied 693 consecutive early amniocenteses (prior to 15 weeks) and found a spontaneous abortion rate to 28 weeks' gestation of 1.5 per cent. A control group of women having standard amniocentesis (15-20 weeks) experienced a 0.6 per cent fetal loss in the same period. There were no other apparent differences between the two groups. Early amniocentesis results are generally available 4-6 weeks before standard amniocentesis and 1-3 weeks after chorionic villus sampling (CVS). Alpha-fetoprotein (AFP) can be accurately assayed in 11- to 15-week amniotic fluid samples but additional studies are necessary to determine the accuracy of neural tube defect (NTD) detection. Including the present study, over 5800 early amniocenteses have been reported and the results suggest that this is a relatively safe prenatal diagnostic test and an alternative to CVS and later amniocentesis.

Abortion, Spontaneous↗

Detection of complex gangliosides in human amniotic fluid.

Gangliosides are possibly very potent immunosuppressive molecules. Here we show that human amniotic fluid contains high concentrations of a number of previously unnoted, structurally complex and highly polar gangliosides. These unusual molecules are present early in pregnancy (first trimester), increase in concentration with gestational age, and reach maximum levels (0.8 microM) at term. Since similar gangliosides have been detected in human placenta, trophoblast, and amnion, we suggest that these molecules are shed into the amniotic fluid bathing these tissues.

Amnion↗

Sjögren-Larsson syndrome: technique and timing of prenatal diagnosis.

BACKGROUND: Sjögren-Larsson syndrome is an autosomal recessive disease with sequelae including ichthyosis, mental retardation, and spasticity. Although fetal skin biopsy has permitted prenatal diagnosis of Sjögren-Larsson syndrome in the late second trimester, it is accompanied by substantial risks, including fetal loss, premature labor, and detection at a gestational age close to the legal limit for pregnancy termination in most states. A new technique involving biochemical assay of cultured amniocytes for reduced levels of fatty alcohol:oxidized nicotinamide-adenine dinucleotide (NAD+)-oxidoreductase may allow earlier and less invasive detection of Sjögren-Larsson syndrome. CASE: A 38-year-old Lebanese woman, gravida 6, para 3, presented for prenatal diagnosis of Sjögren-Larsson syndrome following a history of two children born with the disease. At 19 weeks' gestation, multiple fetal skin biopsies were obtained by ultrasound-guided transabdominal percutaneous insertion of biopsy forceps. Histologic examination of the specimen revealed no evidence of Sjögren-Larsson syndrome. However, assay of fatty alcohol:NAD(+)-oxidoreductase in cultured amniocytes obtained at fetal skin biopsy showed a profound enzymatic deficiency. Additional fetal skin biopsies were obtained at 23.5 weeks' gestation, and histologic examination was positive for Sjögren-Larsson syndrome. The patient elected to terminate the pregnancy, and a subsequent autopsy on the fetus confirmed Sjögren-Larsson syndrome. CONCLUSION: This case demonstrates the limitations of histologic examination of fetal skin specimens for the diagnosis of Sjögren-Larsson syndrome and indicates the potential value of biochemical detection from fetal amniocytes. This new technique may allow earlier diagnosis of Sjögren-Larsson syndrome, is less invasive, and may be less psychologically traumatic for the patient if she elects to terminate the pregnancy.

Adult↗

Prenatal diagnosis of glucose-6-phosphate-dehydrogenase deficiency.

Prior to the development of the DNA-based technology reliable prenatal diagnosis of G6PD deficiency was not possible. We show that, using PCR amplification and restriction endonuclease digestion, prenatal diagnosis is possible. We have now been able to determine that the male fetus of a mother heterozygous for G6PD Mediterranean had inherited the maternal X chromosome with the normal G6PD gene.

Adult↗

Elevated maternal serum alpha-fetoprotein and amniotic fluid alpha-fetoprotein after multifetal pregnancy reduction.

Forty patients underwent fetal reduction at approximately 12 weeks' gestation for multiple pregnancy. Twenty-two had maternal serum alpha-fetoprotein (MSAFP) determinations and all but one was elevated, with a mean value of 9.41 multiples of the median (MOM). A total of 53 amniotic fluid specimens were evaluated for AFP; 25% were elevated above 2.0 MOM and one sample was positive for acetylcholinesterase. None of these elevations were associated with a neural tube defect, although two neural tube defects were detected by other means. Routine MSAFP is not recommended for patients with multifetal pregnancy reduction.

Abortion, Induced↗

Heparin therapy for pregnant women with lupus anticoagulant or anticardiolipin antibodies.

Maternal lupus anticoagulants and anticardiolipin antibodies are associated with a syndrome of recurrent pregnancy loss or preterm birth in live-borns, fetal growth retardation, and placental infarction. Fourteen women with one or more abnormal pregnancy outcomes (total 28 losses, one severely growth-retarded premature live-born) and no normal outcomes were treated with full-dose, subcutaneous, twice-daily heparin therapy in subsequent pregnancies. Treatment was started at an estimated gestational age of 10.3 +/- 4.0 (mean +/- SD) weeks (range 6-18), in a mean total daily dosage of 24,700 +/- 7400 units (range 10,000-36,000). Fourteen of 15 pregnancies resulted in live births at 36.1 +/- 1.7 weeks (range 33-39). The mean birth weight percentile was 57 +/- 21 (range 10-90), and Apgar scores were good to excellent. The number of placental infarcts was fewer in treated cases than in previous deliveries. Five fetuses had third-trimester or perinatal problems with no sequelae, four discovered by close maternal-fetal monitoring. There was an increased rate of preterm and cesarean deliveries. Maternal complications of treatment were few and minor, with no hypertension, preeclampsia, or serious drug-related complications. Heparin appears suitable for further investigation in the treatment of this obstetric syndrome.

Abortion, Spontaneous↗

Second-trimester sonographic diagnosis of Down syndrome: role of femur-length shortening and nuchal-fold thickening.

Relative shortening of femur length and nuchal-fold thickening were evaluated as sonographic signs for the prenatal detection of Down syndrome. The sonograms of 28 fetuses identified by amniocentesis as having trisomy 21 were reviewed. The sonograms of 128 fetuses with a normal karyotype were evaluated as a control group. The finding of either an actual-to-expected femur-length ratio of 0.91 or less or a nuchal-fold measurement of 6 mm or more detected Down syndrome with a sensitivity of 42% and a specificity of 88%. The positive predictive value for Down syndrome detection when using femur-length shortening alone was greater than that when using the combination of femur-length shortening and nuchal-fold thickness. We conclude that femur-length shortening may be potentially useful for the detection of Down syndrome, whereas nuchal-fold thickening has a limited role.

Down Syndrome↗

Circulatory responses to hypovolemia in the pregnant and nonpregnant sheep after pharmacologic sympathectomy.

Circulatory responses to progressive hypovolemia, hypotensive shock, blood reinfusion, and recovery were studied in pregnant and nonpregnant sheep with an intact or pharmacologically ablated sympathetic nervous system produced by administration of 6-hydroxydopamine. These studies also provided an opportunity to assess the contribution of the sympathetic nervous system to the maintenance of vasomotor tone in the pregnant animal at rest. The results show the following: (1) Although there were some differences in the circulatory adjustments to the initial period of blood loss between intact and "sympathectomized" animals, the overall circulatory responses to progressive hypovolemia, shock, blood reinfusion, and recovery were not significantly different in animals with intact or ablated sympathetic nervous systems whether or not they were pregnant. (2) The reasons for the similarity of cardiovascular responses to hypovolemia are the marked increase in catecholamine outputs by the adrenal medulla, which was not affected by 6-hydroxydopamine, and the supersensitivity of the systemic vascular beds of the sympathectomized animal to catecholamines. (3) The contribution of the sympathetic nervous system to the maintenance of the resting vasomotor tone is considerably enhanced during pregnancy, as demonstrated by the chronic effects of adrenergic ablation on the resting arterial pressure. (4) The circulation of the pregnant uterus possesses the ability of autoregulation during chronic changes of perfusing pressure as demonstrated by the differences in the arterial pressure and uteroplacental vascular resistance between intact and sympathectomized animals.

Adrenal Medulla↗

Heat flux and oxygen consumption of the pregnant uterus.

Heat flux (conductive and convective heat) and oxygen consumption of the pregnant uterus and its content were measured simultaneously in the same group of pregnant ewes during the acute postoperative period, during a chronic resting period, and during alpha- and beta-adrenergic-receptor stimulation with norepinephrine and ritodrine. Results indicated four conclusions. First, an excellent correlation existed between heat flux and oxygen consumption in the acute and chronic resting condition as well as during increasing uteroplacental vascular resistance and decreasing blood flow produced by norepinephrine infusion; the correlation was not as good during ritodrine infusion. Second, during rest, about 85% of heat generated by the pregnant uterus is eliminated through the uteroplacental circulation while the remaining heat diffuses through the myometrium. Third, during decreasing uteroplacental blood flow and elevated resistance, the pregnant uterus is able to maintain a normal thermostasis by widening the temperature difference in the blood entering and leaving the uterus and by increasing the myometrial heat exchange; oxygen consumption also is maintained at normal level through increase in oxygen extraction. Fourth, with the exception of uteroplacental circulation, the circulatory, metabolic, and thermal conditions of the pregnant ewe are not different after 5 hours from 5 to 7 days after the surgical procedure.

Animals↗

Circulatory and renal effects of beta-adrenergic-receptor stimulation in pregnant sheep.

The effects of beta-adrenergic-receptor stimulation with ritodrine on systemic and pulmonary hemodynamics and on renal handling of water and electrolytes were studied in unanesthetized, chronically instrumented pregnant sheep. Each animal was studied during control, ritodrine, and recovery periods, each lasting 60 minutes, with the use of three different modes of hydration. beta-receptor stimulation produced a significant increase in heart rate and cardiac output and a decrease in systemic vascular resistance. Pulmonary arterial and wedge pressures tended to increase. These circulatory effects were similar for the three types of hydration and they persisted after cessation of infusion. In terms of its renal effects, beta-receptor stimulation elicited a profound decrease in urine flow and in the excretions of sodium and potassium, irrespective of the mode of hydration. The antidiuresis and antinatriuresis were accompanied by no changes in plasma osmolality and sodium concentration, whereas plasma potassium levels decreased. All of these effects persisted for 60 minutes after the cessation of infusion. In the water-loaded experiments, the antidiuresis seemed to be related to increased antidiuretic hormone secretion; in the saline-loaded experiments, however, both the antidiuresis and antinatriuresis appeared to be related to increased renal reabsorption. The changes in renal hemodynamics seemed to have an insignificant role. The amount of fluid retained in the body was greater when ritodrine was infused with saline solution than with dextrose solution. These cardiovascular and renal studies suggest that a circulatory overload may be the major factor in the pathogenesis of pulmonary edema observed during beta-adrenergic-receptor stimulation.

Animals↗

The contribution of the beta-adrenergic system to the cardiovascular response to hypovolemia.

Unanesthetized, chronically instrumented, nonpregnant sheep were studied in periods of progressive blood withdrawal, hypovolemic shock, blood reinfusion, and recovery. Hemodynamic responses were recorded during experiments with an intact beta-adrenergic system (saline solution), beta-adrenergic blockage (propranolol), and beta-adrenergic stimulation (isoxsuprine). With an intact beta-adrenergic system, stepwise bleeding produced a progressive decrease in arterial pressure, stroke volume, and cardiac output and an increase in systemic vascular resistance; heart rate increased initially but fell when hypovolemia became severe. All circulatory parameters returned toward control valves during blood reinfusion and recovery. In animals deprived of beta-adrenergic control, the hemodynamic response to progressive hypovolemia and blood reinfusion was not greatly different from that of control animals, despite abolition of tachycardia. During beta-adrenergic stimulation, arterial pressure and cardiac output fell more rapidly than in control and tachycardia was relatively small; cardiac output and stroke volume rebounded strikingly during reinfusion and recovery. These results support findings of others that the role of the beta-adrenergic system is minor during hypovolemia. When pharmacologically activated, it might play a significant role in the posthypovolemia compensatory mechanisms.

Animals↗

Malfunction of ventriculoperitoneal shunts during pregnancy.

Two cases of successful pregnancy in patients with a ventriculoperitoneal shunt are presented. Both patients experienced shunt malfunction early in the third trimester which was apparently related to anatomic changes in the abdomen associated with pregnancy. All symptoms resolved with conservative management. The obstetric and neurologic management of such patients is discussed.

Adult↗

Mixing problems in using indicators for measuring regional blood flow.

A basic requirement for using indicators for measuring blood flow is adequate mixing of the indicator with blood prior to sampling the site. This requirement has been met by depositing the indicator in the heart and sampling from an artery. Recently, authors have injected microspheres into veins and sampled from venous sites. The present studies were designed to investigate the mixing problems in sheep and rabbits by means of Cardio-Green and labeled microspheres. The indicators were injected at different points in the circulatory system, and blood was sampled at different levels of the venous and arterial systems. Results show the following. (a) When an indicator of small molecular size (Cardio-Green) is allowed to pass through the heart chambers, adequate mixing is achieved, yielding accurate and reproducible results. (b) When any indicator (Cardio-Green or microspheres) is injected into veins, and sampling is done at any point in the venous system, mixing is inadequate, yielding flow results which are inconsistent and erratic. (c) For an indicator or large molecular size (microspheres), injecting into the left side of the heart and sampling from arterial sites yield accurate and reproducible results regardless of whether blood is sampled continuously or intermittently.

Animals↗