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At least 199 records · Page 11Linked to original sources
PubMed1986

Improved characterization of plasma von Willebrand factor heterogeneity when using 2.5% agarose gel electrophoresis.

Discontinuous sodium dodecyl sulfate electrophoresis in large pore gels, followed by overlay with radiolabelled anti-von Willebrand factor (vWF) antibodies and by autoradiography, permits to analyze the multimeric structure of vWF. The aim of this study was to improve experimental conditions of this technique to satisfactorily resolve the minor forms of plasma vWF while still separating its high, intermediate, and low molecular weight predominant multimers. By using a 2.5% mixture of two selected agaroses, a single electrophoretic analysis of plasma clearly reveals the extreme complexity of the molecular forms of circulating vWF: each multimeric unit of plasma vWF may be separated into five bands, the central one being predominant. The multimeric distribution and "quintuplet" pattern obtained in the electrophoretic system described here permit a convenient classification of the different subtypes of von Willebrand's disease.

Electrophoresis, Agar Gel↗
PubMed1994

Modulation of gap junctional mechanisms during calcium-free induced field burst activity: a possible role for electrotonic coupling in epileptogenesis.

To date, there is little experimental evidence supporting or refuting electrotonic interactions through gap junctions in the generation and/or spread of seizure activity in the mammalian brain. We have studied gap junctional mechanisms in the in vitro calcium-free induced model of epilepsy using electrophysiological and staining techniques in the CA1 area of the hippocampus. Lucifer yellow staining of CA1 pyramidal neurons revealed that dye coupling was increased 2.3 times in hippocampal slices made hyperexcitable by perfusion with calcium-free artificial cerebrospinal fluid (aCSF). Furthermore, multiple neuronal dye coupling (triplets, quintuplets) was observed in these conditions but never in control (standard aCSF). Under conditions that reduce gap junctional conductance (intracellular acidification, octanol, halothane), seizure-like activity was suppressed in the CA1 area in this epilepsy model, whereas increasing gap junctional conductance by intracellular alkalinization increased the frequency and duration of field burst events. Intracellular acidification also reduced dye coupling as well as the frequency of fast prepotentials (electrotonic potentials) without altering neuronal firing frequency. Simultaneous extracellular field and single whole-cell recordings revealed suppression of synchronization between neuronal firing and spontaneous field burst activity during acidification. These observations indicate an apparent increase in electrotonic coupling during calcium-free induced spontaneous rhythmic field burst activity in the CA1 area of the hippocampus and that electrotonic coupling may contribute substantially to the synchronization of neuronal firing underlying seizure-like events.

Acids↗
PubMed1993

Modulation of mechanosensitive calcium-selective cation channels by temperature.

Gating of associations of mechanosensitive Ca(2+)-selective cation co-channels in the plasmalemma of onion epidermis has a strong and unusual temperature dependence. Tension-dependent activity rises steeply as temperature is lowered from 25 degrees C to about 6 degrees C, but drops to a low level at about 5 degrees C. Under the conditions tested (with Mg2+ and K+ at the cytosolic face of outside-out membrane patches), promotion results both from more bursting at all observed linkage levels and from longer duration of bursts of co-channels linked as quadruplets and quintuplets. Co-channel conductance decreases linearly, but only modestly, with declining temperature. It is proposed that these and related mechanosensitive channels may participate in a variety of responses to temperature, including thermonasty, thermotropism, hydrotropism, and both cold damage and cold acclimation.

Allium↗
PubMed1993

Mechanosensory calcium-selective cation channels in epidermal cells.

This paper explores the properties and likely functions of an epidermal Ca(2+)-selective cation channel complex activated by tension. As many as eight or nine linked or linkable equivalent conductance units or co-channels can open together. Open time for co-channel quadruplets and quintuplets tends to be relatively long with millimolar Mg2+ (but not millimolar Ca2+) at the cytosolic face of excised plasma membrane. Sensitivity to tension is regulated by transmembrane voltage and temperature. Under some circumstances channel activity is synchronized in rhythmic pulses. Certain lanthanides and a cytoskeleton-disturbing herbicide that inhibit gravitropic reception act on the channel system at low concentrations. Specifically, ethyl-N-phenylcarbamate promotes tension-dependent activity at micromolar levels. With moderate suction, Gd3+ provided at about 0.5 microM at the extracellular face of the membrane promotes for several seconds but may then become inhibitory. Provision at 1-2 microM promotes and subsequently inhibits more vigorously (often abruptly and totally), and at high levels inhibits immediately. La3+, a poor gravitropic inhibitor, acts similarly but much more gradually and only at much higher concentrations. These properties, particularly these susceptibilities to modulation, indicate that in vivo the mechanosensitive channel must be mechanosensory and mechanoregulatory. It could serve to transduce the shear forces generated in the integrated wall-membrane-cytoskeleton system during turgor changes and cell expansion as well as transducing the stresses induced by gravity, touch and flexure. In so far as such transduction is modulated by voltage and temperature, the channels would also be sensors for these modalities as long as the wall-membrane-cytoskeleton system experiences mechanical stress.

Allium↗
PubMed1997

Triplet births: trends and outcomes, 1971-94.

OBJECTIVES: This report describes changes in the number and ratio of live births in triplet and other higher order multiple deliveries from 1971 to 1994 by maternal race, age, education, and marital status. The report also examines the birth outcomes of triplets compared with singletons, including overall gestation specific, and birthweight specific infant mortality rates. METHODS: Birth data are obtained from the U.S. certificates of live birth. Mortality data were obtained from the Linked Birth and Infant Death Data Sets for the 1983-91 birth cohorts. Most analyses are based on triplet and other higher-order multiple births (quadruplet and quintuplet and greater births) in the aggregate. (Triplet births comprise about 92 percent of all higher order multiple births.) Triplet and other higher order birth ratios for most variables are computed by combining data for years 1982-84 and 1992-94, and for infant mortality by combining birth cohorts for years 1987-91. FINDINGS: Between 1971 and 1994 the number and ratio of triplet births quadrupled, rising from 1,034 to 4,594, and from 29.1 to 116.2 per 100,000 live births. Most of the increase was among births to white mothers, particularly among married and more educated mothers. Only about one-third of the increase in triplet birthing among white mothers between 1989 and 1994 could be attributed to changes in the maternal age distribution. Massachusetts reported the highest triplet birth ratio (215.9), more than twice the U.S. ratio (105.5). Other States with comparatively high ratios were New Hampshire, New Jersey, and Iowa. Nine of 10 triplets were born preterm compared with 1 of 10 singletons. The average triplet weighed 1,698 grams at birth, one-half that of the average singleton (3,358 grams). Triplets were about 12 times more likely to die during the first year of life as singletons, but had a survival advantage over singletons at lower gestations and birthweights.

Adult↗
PubMed1997

Comparison of pregnancy outcome of natural twin pregnancies versus multifetal pregnancies selectively reduced to twins.

The high rate of multiple gestations following ovulation induction with and without assisted reproductive technologies (ART) has led to an increased interest in selective reduction. The aim of this study was to compare pregnancy outcome of 6 triplet and 2 quintuplet pregnancies following selective reduction to twins to a group of 30 natural twin pregnancies delivered during the same time period. Outcome variables compared included birth weights, gender, gestational age at delivery, route of delivery, and neonatal complications. Results failed to demonstrate an adverse effect of selective reduction on pregnancy outcome.

Adult↗
PubMedDate not supplied

[Neonatal, neurologic and psychosocial findings in higher order multiple births. Follow-up for 3 to 10 years].

We examined the outcome of 9 triplet, 3 quadruplet, 1 quintuplet and 1 sixtuplet pregnancies delivered between 1979-1989 at the perinatal center of the RWTH Aachen. The course of pregnancy and neonatal period were retrospectively analysed. The follow-up program covered at least 3, up to a maximum of 10 years. 12 families could be interviewed concerning psychosocial effects. The neonatal mortality was 4%. Neonatal morbidity; hyaline membrane disease (n = 18), intraventricular hemorrhage (n = 9), pneumothorax (n = 7), patent ductus arteriosus (n = 7), bronchopulmonary dysplasia (n = 8). At the age of 2 years 63% of the children were considered to be normal on developmental assessment, 17% showed mild, 20% severe developmental delay. With 3 to 10 years 83% were normal, 17% severely handicapped. In total 20% of the children died or showed severe handicap. Higher order multiple pregnancies make great demands on the perinatal medicine and lead in spite of an improved prognosis to a remaining burden for the children and their parents.

Brain Damage, Chronic↗
PubMed1998

[Intracellular calcium channels, hormone receptors and intercellular calcium waves].

The hormone-mediated intercellular Ca2+ waves were analyzed in multiplets of rat hepatocytes by video imaging of fura2 fluorescence. These multicellular systems are composed of groups of several cells (doublets to quintuplets) issued from the liver cell plate, a one cell-thick cord of about 20 hepatocytes long between portal and centrolobular veins. When the multiplets were homogeneously bathed with the glycogenolytic agonists vasopressin, noradrenaline, angiotensin II and ATP, they showed highly organized Ca2+ signals. Surprisingly, for a given agonist, the primary rises in intracellular Ca2+ concentration ([Ca2+]i) originated invariably in the same hepatocyte, then was propagated in a sequential manner to the nearest connected cells (cell 2, then 3, cell 4 in a quadruplet, for example). The sequential activation of the cells appeared to be an intrinsic property of multiplets of rat hepatocytes. The same sequence was observed at each train of oscillations occurring between cells. The order of [Ca2+]i responses was modified neither by repeated additions of hormones nor by the hormonal dose. The mechanical disruption of an intermediate cell did not prevent the activation of the next cell. These results suggest that each hepatocyte in the multiplet displays its own sensitivity to the hormone and that a gradient of sensitivity between each cell could be responsible for directing the intercellular Ca2+ wave. To test this hypothesis, we selectively isolated rat hepatocytes from periportal (PP) and perivenous (PV) areas of the liver cell plate. Periportal (PP) and perivenous (PV) rat hepatocyte suspensions were loaded with quin2/AM and hormonal responses were studied in a spectrofluorimeter. Noradrenaline, angiotensin II, and vasopressin-induced [Ca2+]i rises were greater in PV than in PP hepatocytes. In contrast, PP cells were more responsive than PV cells to ATP. The function of the InsP3 receptor (InsP3R) was also studied by measuring the InsP3-mediated 45Ca2+ release from permeabilized PP and PV hepatocytes. In permeabilized PP and PV hepatocytes, internal Ca2+ stores displayed the same loading-kinetics, the responses to InsP3 were similar, and the sizes of InsP3-sensitive compartment were not different. In a further study, we investigated by video microscopy in fura2-loaded multicellular systems of rat hepatocytes, the mechanisms controlling intercellular propagation of the Ca2+ wave and coordination of Ca2+ signals induced by the different hormones. Using focal microperfusion which allows local perfusion of any cell of the multiplet, rapid agonist removal during the Ca2+ response and microinjection, we found that second messengers and [Ca2+]i rises in one hepatocyte cannot trigger Ca2+ responses in connected adjacent cells, suggesting that diffusion across gap junctions, while required for coordination, is not sufficient by itself for the propagation of the intercellular Ca2+ wave. In addition, focal microperfusion and intermediate cell disruption experiments revealed very fine functional differences (hormonal delay, frequency of [Ca2+]i oscillations) between hormone-induced Ca2+ signals, even between two adjacent connected hepatocytes. Recent unpublished results performed in suspensions of PP and PV rat hepatocytes supported the view of a major role played by vasopressin receptors (V1a) in genesis and orientation of the Ca2+ wave. Vasopressin binding sites, V1a mRNAs detected by RNAse Protection Assay, and vasopressin-induced InsP3 production, were more abundant in PV than in PP cells. A gradient of hormone receptors could orientate the propagation of the Ca2+ wave in multicellular systems and in liver cell plate. These results suggest that the intercellular Ca2+ wave in multicellular systems of rat hepatocytes is propagated through mechanisms involving at least three factors. (ABSTRACT TRUNCATED)

Animals↗
PubMed1992

Triplets and higher-order multiple births. Time trends and infant mortality.

OBJECTIVES: To describe changes in rates of higher-order multiple births (triplets and higher) between 1972 and 1989, to compare infant mortality rates in infants of higher-order multiple births and singletons born from 1983 through 1985, and to compare infant mortality rates among higher-order multiples born from 1983 through 1985 with rates among those born in 1960. RESEARCH DESIGN: Population-based analysis of live births (1972 through 1989) and infant deaths (1960 and 1983 through 1985) in the United States. The rate of higher-order multiple births was calculated per 100,000 live births. DATA SOURCE: Computerized national natality files for 1972 through 1989 and national linked birth/infant death data sets for 1960 and 1983 through 1985 from the National Center for Health Statistics, Centers for Disease Control. POPULATION: Live births to white and black women in the United States. INTERVENTIONS: None. MAIN RESULTS: Between 1972 through 1974 and 1985 through 1989 the rate of higher-order multiple births increased by 113% among infants of white mothers and by 22% among infants of black mothers. In whites the increase was mostly age specific and was not due to the upward shift in the maternal age distribution. The increase was particularly large in white women aged 30 through 34 years (152%) and 35 through 39 years (165%) and in more highly educated mothers. In blacks the modest increase in the rate of higher-order multiple births was mostly due to an upward shift in the maternal age distribution. From 1983 through 1985, mortality of infants of higher-order multiple births was about 15 times that of singletons. This was due almost entirely to the lower birth weight distribution of infants of higher-order multiple births. Their weight-specific mortality compared favorably with that of singletons. At 500 through 999 g, mortality was about the same. In weight categories between 1000 and 1999 g, mortality rates in higher-order multiple births were much lower: weight-specific relative risks ranged from 0.30 to 0.73. Between 1960 and 1983 through 1985 infant mortality in higher-order multiple births declined by about 50%. CONCLUSIONS: It is likely that much of the increase in the incidence of higher-order multiple births is due to the rise in the use of ovulation-inducing drugs for the treatment of infertility. This increase and the decline in mortality risk have created a much greater need for medical and social services for infants of higher-order multiple births and their families.

Black or African American↗
PubMed2002

Monochorionic high-order multiple pregnancies and multifetal pregnancy reduction.

OBJECTIVE: To study the frequency and obstetric outcome of monochorionic multiple pregnancies in a population referred for fetal reduction. METHODS: Data charts of all patients with multifetal (> or =3) pregnancies referred for fetal reduction over the last 10 years were reviewed for the presence of monochorionic twin pairs or triplets. RESULTS: Twenty-nine of 239 high-order multiple pregnancies contained a monochorionic component (12.1%), eight of which were monochorionic triplets. Half of all naturally conceived pregnancies contained a monochorionic component. High-order multiple pregnancies with a monochorionic component resulted significantly more frequently from natural conceptions (7 of 29) than multichorionic pregnancies (7 of 210) (P =.001). Fetal reduction of the monochorionic twin pair in 21 pregnancies resulted in eight twin and 13 singleton pregnancies; mean gestational age at delivery was, respectively, 34.3 +/- 2.9 and 39.2 +/- 1.4 weeks. Pregnancy loss rate was one of 21 (4.8%). In the remaining eight multiple pregnancies with a monochorionic triplet present, three were complicated by a twin reversed arterial perfusion sequence, and two couples requested a first trimester termination of pregnancy. Fetal reduction of the monochorionic triplet in a dichorionic quadruplet pregnancy resulted in a normal pregnancy outcome. In two monochorionic triplet pregnancies, fetal reduction to monochorionic twin pregnancies with bipolar coagulation of the umbilical cord resulted in a favorable pregnancy outcome. CONCLUSION: Monochorionic twins or triplets are frequently part of naturally conceived high-order multiple pregnancies. Reduction of the monochorionic twin pairs improves pregnancy outcome. Monochorionic triplet pregnancies show a high complication rate, but may benefit from fetal reduction by cord coagulation.

Adult↗
PubMed2004

Simultaneous bilateral tubal pregnancies and intrauterine pregnancy with five fetuses.

A 28-year-old woman with severe right lower abdominal pain and vaginal bleeding at 7 weeks' (+/- 2 days') gestation was seen in the emergency room of our institution. The pregnancy was the result of natural conception after ovarian stimulation with gonadotropins. Transvaginal sonography revealed five intrauterine gestational sacs containing five live embryos. A positive fetal heartbeat was detected in the fallopian tube on the right. Laparoscopic findings disclosed the enlarged uterus with the unruptured right ectopic pregnancy in the ampullary region and an extrauterine pregnancy in the left tube as well. A linear salpingotomy was performed on the right tubal pregnancy. We decided to perform salpingectomy on the left tube because it was impossible to preserve the tube, and exploration of it showed the existence of another gestational sac. It is necessary to decry inappropriate and injudicious use of assisted reproductive technologies, especially by individuals with little or no training in monitoring the agents and treatments prescribed. In 2003, still waiting for official legislation from the Italian Parliament on assisted reproductive technology, we have to face dramatic situations, such as this very unique case of heterotopic pregnancy.

Adult↗
PubMed1990

Higher order multiple births: natural wonder or failure of therapy?

Data of 601 families with triplets and higher multiples have been collected. Since about nine years the number of higher-order births has been increasing enormously. The average pregnancy duration and the average birthweight of these mostly premature children have been declining from year to year. Despite the progress in neonatology, the death rate and the rate of handicapped children is very high. To prevent such disastrous outcomes, treatments for infertility should be performed only by physicians in centers with strong controls. Selective abortions are no regular solution to the problem of higher multiple gestation.

Birth Weight↗
PubMed1987

Growth characteristics in twins and higher order multiple births.

Measurements of height and weight have been undertaken on 201 pairs of twins and 46 sets of higher multiples once each at various ages through childhood. The heights of twins are comparable to the overall population of singletons, those of higher multiples are slightly undersized. However, the total group of twins were shorter than expected when compared with the heights of parents and siblings, but this was entirely accounted for by that component of the group who at birth had been very light for dates. The children in all groups of multiples were underweight for their height in comparison with standards of a comparable population and with their own siblings.

Adolescent↗