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Biomedical subjects

H Schulman

Publications and source records attributed to H Schulman.

At least 145 records · Page 8Linked to original sources
PubMed1988

Sphingosine inhibits calmodulin-dependent enzymes.

Sphingosine is a potent inhibitor of several calmodulin-dependent enzymes. The multifunctional Ca2+/calmodulin-dependent protein kinase, a Ca2+/calmodulin-dependent phosphodiesterase, and smooth muscle myosin light chain kinase are inhibited in vitro at concentrations previously shown to inhibit protein kinase C. Inhibition of each of the enzymes is competitive with calmodulin, suggesting that sphingosine may be a calmodulin antagonist. In the pituitary cell line GH3, sphingosine inhibits the phosphorylation of microtubule-associated protein 2 by the multifunctional Ca2+/calmodulin-dependent protein kinase and the phosphorylation of elongation factor 2 by Ca2+/calmodulin-dependent kinase III. These findings suggest that sphingosine, in blocking the effects of both the Ca2+.calmodulin complex and of diacylglycerol, may be a very effective inhibitor of both branches of the phosphatidylinositol signaling pathway. By extension, caution should be exercised in the use of sphingosine as a diagnostic test for the involvement of protein kinase C in biological processes.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1988

The multifunctional Ca2+/calmodulin-dependent protein kinase mediates Ca2+-dependent phosphorylation of tyrosine hydroxylase.

Stimulation of rat pheochromocytoma PC12 cells with ionophore A23187, carbachol, or high K+ medium, agents which increase intracellular Ca2+, results in the phosphorylation and activation of tyrosine hydroxylase (Nose, P., Griffith, L. C., and Schulman, H. (1985) J. Cell Biol. 101, 1182-1190). We have identified three major protein kinases in PC12 cells and investigated their roles in the Ca2+-dependent phosphorylation of tyrosine hydroxylase and other cytosolic proteins. A set of PC12 proteins were phosphorylated in response to both elevation of intracellular Ca2+ and to protein kinase C (Ca2+/phospholipid-dependent protein kinase) activators. In addition, distinct sets of proteins responded to either one or the other stimulus. The three major regulatory kinases, the multifunctional Ca2+/calmodulin-dependent protein kinase, the cAMP-dependent protein kinase, and protein kinase C all phosphorylate tyrosine hydroxylase in vitro. Neither the agents which increase Ca2+ nor the agents which directly activate kinase C (12-O-tetradecanoylphorbol-13-acetate or 1-oleyl-2-acetylglycerol) increase cAMP or activate the cAMP-dependent protein kinase, thereby excluding this pathway as a mediator of these stimuli. The role of protein kinase C was assessed by long term treatment of PC12 cells with 12-O-tetradecanoylphorbol-13-acetate, which causes its "desensitization." In cells pretreated in this manner, agents which increase Ca2+ influx continue to stimulate tyrosine hydroxylase phosphorylation maximally, while protein kinase C activators are completely ineffective. Comparison of tryptic peptide maps of tyrosine hydroxylase phosphorylated by the three protein kinases in vitro with phosphopeptide maps generated from tyrosine hydroxylase phosphorylated in vivo indicates that phosphorylation by the Ca2+/calmodulin-dependent kinase most closely mirrors the in vivo phosphorylation pattern. These results indicate that the multifunctional Ca2+/calmodulin-dependent protein kinase mediates phosphorylation of tyrosine hydroxylase by hormonal and electrical stimuli which elevate intracellular Ca2+ in PC12 cells.

Adenosine↗
PubMed1988

Hormone receptors on cloned T lymphocytes. Increased responsiveness to histamine, prostaglandins, and beta-adrenergic agents as a late stage event in T cell activation.

Lymphocytes have surface receptors for a variety of hormones that play an important part in modulating the immune response. Most previous studies, however, have examined the effects of hormone agonists on heterogeneous bulk populations of cells, making it difficult to precisely identify the responding target cells. We have therefore studied a set of well characterized T cell clones for a series of adenylate cyclase-linked hormone receptors and examined changes in receptor expression that occur after cell activation. All clones tested had receptors for histamine, isoproterenol, and PGE1, but not for several other cAMP-active hormone agonists. The apparent receptor affinities and their specificities were characteristic of typical histamine H2, beta 2-adrenergic, and PGE receptors. The cAMP response to PG was higher and longer lasting than that to histamine or isoproterenol, both of which appear to undergo receptor desensitization. After activation of quiescent cells in IL-2-containing media, the cAMP response to all three ligands increased, peaking 4 to 5 days after stimulation, and then returned to basal levels as the cells ceased proliferating. Inasmuch as this effect did not require Ag, it appears that the coordinate regulation of responsiveness to these ligands is a direct result of lymphocyte activation. This increase in hormone receptor activity is functionally analogous to the up-regulation of receptors for other ligands that occurs after lymphocyte activation and further demonstrates the important immunoregulatory role played by the changing repertoire of surface receptors that is associated with activation.

Animals↗
PubMed1988

Prenatal surveillance using nonstress testing and Doppler velocimetry.

One hundred forty pregnant women referred to our prenatal testing laboratory for conventional nonstress testing (NST) also had a Doppler study of the umbilical arteries. The outcomes of 88 women with abnormal testing (NST or Doppler) were compared with the outcomes of 52 women who had normal results on both tests. The results demonstrated that 50% of the fetuses with decreased flow velocity who later developed an abnormal NST were growth-retarded, 75% required a cesarean section, and 63% were admitted to the neonatal intensive care unit. Development of an abnormal NST in the presence of normal velocimetry studies occurred most frequently in the postdates pregnancy; 32% required cesarean section for fetal distress. Knowledge of the umbilical circulation through Doppler studies may be of benefit when selecting patients for NST and when interpreting results.

Blood Flow Velocity↗
PubMed1988

Uterine and umbilical artery Doppler velocimetry in postterm pregnancy.

Uterine and umbilical artery Doppler velocimetry was carried out on 149 women whose pregnancies went to 41 weeks or beyond. Flow velocity was not altered even in the presence of other signs suggestive of fetal compromise. It appears that the postdate syndrome is not associated with significant alterations in the maternal or umbilical blood flow prior to the onset of labor.

Arteries↗
PubMed1988

Pregnancy termination after detection of fetal chromosomal or metabolic abnormalities.

In 3400 midtrimester amniocenteses, 68 fetuses had abnormal findings. Three women elected to continue their pregnancies and the remainder chose terminations. Of these, 29 were cared for in our hospitals. Pregnancy termination was carried out in gestations averaging 21.6 +/- 2.3 weeks and fetal weights averaging 531 +/- 351 g. Three prostaglandins techniques were used, two of which proved to be effective. Dosages employed were comparable to those used in early second trimester pregnancy terminations. Side effects were similar; one retained placenta occurred. We have used a multidisciplinary counseling approach for these couples and have restricted ourselves to the medical aspects of their problems. Techniques are described for the psychologic support of the couple during this stressful period.

Abortion, Induced↗
PubMed1988

Developmental changes in Ca2+/calmodulin-dependent protein kinase II in cultures of hippocampal pyramidal neurons and astrocytes.

We have analyzed Ca2+/calmodulin-dependent protein kinase II (CaM-kinase II) localization, activity, and endogenous protein substrates during differentiation and synaptogenesis in cultured hippocampal neurons. Primary cultures from hippocampi from 18 d embryonic rats are composed primarily of pyramidal neurons, with minimal contamination by nonneuronal cells. We have used monoclonal (Mab) and affinity-purified polyclonal antibodies that recognize either or both of the subunits of CaM-kinase II in order to localize the enzyme at progressive stages of neuronal differentiation. Diffuse but specific binding, determined by indirect immunofluorescence analyses, was first detected in cell bodies and growth cones of pyramidal neurons after 4 d in culture. Immunoreactivity increased during the next 3 d of culture, at which time fluorescent, labeling was patchy along neuritic processes. By 10 d, intensely fluorescent, discrete spots were observed along processes and on cell bodies. Astrocyte cultures prepared from newborn rat cortex showed no detectable immunofluorescence with anti-CaM-kinase II antibodies. Cytosolic and particulate fractions from cultured pyramidal neurons and astrocytes were analyzed using immunoblot, in vitro phosphorylation, 2-dimensional gel electrophoresis, and phosphopeptide mapping techniques. Although pure astrocyte cultures contained low levels of Ca2+/CaM-stimulated protein kinase activity, they did not display detectable levels of immunoreactive 50 kDa subunit nor 50 and 60 kDa phosphoproteins analogous to the autophosphorylated subunits of CaM-kinase II. Immunoblot analysis detected the 60 kDa kinase subunit in particulate and cytosolic fractions from 2 d neurons. By contrast, the 50 kDa subunit of CaM-kinase II was not detected in cytosolic or particulate fractions of pyramidal neurons before 4 d in culture. In 2 d pyramidal neuron cultures, only low levels of Ca2+/CaM-stimulated protein phosphorylation were observed. Ca2+/CaM-dependent phosphorylation of 10 d pyramidal cell proteins was 3-5-fold greater than that of 2 d cultures, and included major phosphoproteins of 48, 50, 56, 58/60, 80-86, 90, 120, 138, 175, and 190 kDa. Phosphopeptide maps of 58/60 and 50 kDa phosphoproteins gave patterns very similar to those of the autophosphorylated 60 and 50 kDa subunits, respectively, of purified CaM-kinase II. A phosphoprotein doublet of 83 kDa was identified as synapsin I. Developmental changes in Ca2+/CaM-dependent phosphorylation in pyramidal neuron cultures were very similar to those previously described in subcellular fractions from postnatal rat forebrain.

Animals↗
PubMed1987

Evidence for the activation of the multifunctional Ca2+/calmodulin-dependent protein kinase in response to hormones that increase intracellular Ca2+.

The phosphorylation state of six cytoplasmic proteins is increased following treatment of isolated rat hepatocytes with hormones that elevate free intracellular Ca2+ levels (Garrison, J. C. and Wagner, J. D. (1982) J. Biol. Chem. 257, 13135-13143). Tryptic 32P-phosphopeptide maps of two of the substrates, pyruvate kinase and a 49,000-dalton protein, the major 32P-labeled protein in hepatocytes, were prepared following stimulation of cells with vasopressin, a Ca2+-linked hormone. Peptide maps of the 49,000-dalton protein phosphorylated in vitro with the recently identified multifunctional Ca2+/calmodulin-dependent protein kinase contained phosphopeptides identical to those observed in the intact cell, suggesting that this kinase is activated in response to Ca2+-mobilizing hormones. Similar in vitro phosphorylation experiments with pyruvate kinase suggested that the Ca2+/calmodulin-dependent protein kinase can phosphorylate not only the serine residues observed following vasopressin stimulation of the intact cell but also additional threonine residues. Both pyruvate kinase and the 49,000-dalton protein are also phosphorylated in the hepatocyte in response to glucagon and in vitro by the cAMP-dependent protein kinase. Both vasopressin and glucagon appear to stimulate the phosphorylation of identical serine residues in pyruvate kinase but only vasopressin enhances the phosphorylation of certain sites in the 49,000-dalton protein. Comparison of the tryptic phosphopeptide maps of these substrates phosphorylated in vitro with either the Ca2+/calmodulin-dependent protein kinase or the cAMP-dependent protein kinase suggests that the Ca2+-dependent kinase can phosphorylate unique sites in both substrates. It appears to share specificity at other sites with the cAMP-dependent protein kinase. Overall, the results suggest that the multifunctional Ca2+/calmodulin-dependent protein kinase plays an important role in the response of the hepatocyte to a Ca2+ signal.

Calcium↗
PubMed1987

Vaginal birth after two or more previous cesarean sections.

The recommendation from the American College of Obstetricians and Gynecologists is to allow vaginal delivery after one cesarean section. This report is an update of our experience of 57 women with two or more cesarean sections who were allowed to labor.

Cesarean Section↗
PubMed1987

The significance of absent end-diastolic velocity in umbilical artery velocity waveforms.

Doppler umbilical artery velocimetry has been used to study high-risk pregnancies. The most extreme waveform abnormality is the absence of end-diastolic velocity. To examine the significance of this finding, events outcome was evaluated in 161 women studied between 31 and 36 weeks. Ten had absence of end-diastolic velocity. When compared with fetuses with normal and less severely abnormal waveforms, there was a higher incidence of intrauterine growth retardation, pregnancy-induced hypertension, cesarean section for fetal distress, neonatal intensive care unit admission, and low Apgar scores. Average birth weight and gestational age at delivery were lower. Five other fetuses with absence of end-diastolic velocity were identified that were delivered between 27 and 30 weeks, making a total of 15 patients with absence of end-diastolic velocity. Of 12 patients monitored, 11 had an abnormal fetal heart rate pattern. Four fetuses had lethal anomalies. There were eight perinatal deaths. Acute or chronic hypoxia was evident in all fetuses with absence of end-diastolic velocity. Absent end-diastolic velocity represents a unique and severe fetal condition that cannot be identified by present surveillance methods and requires a Doppler study for diagnosis.

Blood Flow Velocity↗
PubMed1987

Uterine-umbilical velocimetry in open heart surgery.

The effect of the nonpulsating cardiac pump in uterine and umbilical circulation has not been studied extensively by measuring the resistance of the uterine and umbilical circulation with velocimetry. During open heart surgery, we were able to demonstrate the effects of the nonpulsatile cardiac pump.

Adult↗
PubMed1987

The clinical significance of Doppler umbilical artery velocimetry in the small for gestational age fetus.

Fifty-four women who were delivered of small for gestational age infants were studied antenatally by serially continuous-wave Doppler velocimetry. Outcomes were compared in the normal and abnormal systolic/diastolic ratio groups. Seventy-eight percent had an abnormal systolic/diastolic ratio. The group with an elevated systolic/diastolic ratio had a significantly higher incidence of abnormal fetal heart rate, pregnancy-induced hypertension, oligohydramnios, cesarean section for fetal distress, and admission into the neonatal intensive care unit. One third of the newborns required intermittent positive pressure ventilation. Average birth weight and gestational age at delivery were significantly lower and there were six perinatal deaths in the group with an elevated systolic/diastolic ratio and none in the group with a normal systolic/diastolic ratio. These data suggest that the small for gestational age fetus with normal umbilical artery velocimetry is at significantly lower risk than are those with abnormal ratios. This implies that management of the small for gestational age fetus may now be aided by a functional classification based on the umbilical artery velocity waveform.

Blood Flow Velocity↗
PubMed1987

The clinical implications of Doppler ultrasound analysis of the uterine and umbilical arteries.

Serial Doppler velocimetry of the umbilical and uterine arteries has revealed a relatively clear separation between normal and abnormal waveforms. Abnormal umbilical artery waveforms are defined by a systolic/diastolic ratio greater than or equal to 3 in the last 10 weeks of pregnancy. When abnormal waveforms persist, fetal growth retardation and adverse perinatal outcome are likely. Abnormal uterine artery waveforms are also recognized by a systolic/diastolic ratio averaged from both vessels of more than 2.6 after 26 weeks. In addition, the abnormal vessel will usually contain a persistent diastolic notching. Abnormal uterine vessels strongly correlate with the presence or subsequent development of preeclampsia and fetal growth retardation. Doppler velocity flow provides valuable insights into the pathophysiology of various disease states. It provides a basis for new clinical and basic research into disease mechanisms and methods for improving perinatal and maternal morbidity.

Arteries↗
PubMed1987

A classification of hypertension in pregnancy based on Doppler velocimetry.

We studied 136 pregnant women with hypertension with Doppler velocimetry of the uterine and umbilical arteries. The patients were classified into four groups according to the values of the systolic/diastolic ratios. The first group had normal ratios in both the umbilical and uterine arteries. The second group had elevated umbilical ratios and normal ratios in the uterine arteries. The third group had elevated uterine artery systolic/diastolic ratios with normal umbilical artery values, and the fourth group had elevated systolic/diastolic ratios in both vessels. Women in the group with normal ratios in both the umbilical and uterine arteries were delivered of infants with a birth weight (mean +/- SD) of 3261 +/- 522 gm and gestational age of 39 +/- 2 weeks. The values for the three groups with abnormal velocimetry were: those with elevated umbilical ratios and normal ratios in the uterine arteries: body weight = 2098 +/- 811 gm, gestational age = 35.7 +/- 3.2 weeks; those with elevated uterine artery ratios with normal umbilical artery values: 2464 +/- 722 gm, gestational age = 36.3 +/- 3 weeks; and those with elevated systolic/diastolic ratios in both vessels: body weight = 1627 +/- 697 gm, gestational age = 33.3 +/- 2.7 weeks (p less than 0.01; p less than 0.001). There were 27 small for gestational age infants delivered during this study. Doppler velocimetry studies were abnormal in 26 of them (96%). Results show that Doppler-derived vascular patterns correlate well with normal and adverse perinatal outcome. A description of the uterine and umbilical systolic/diastolic ratios should be part of the clinical evaluation of all pregnant women with hypertension. This should lead to better treatment protocols and improved clinical outcome.

Adult↗
PubMed1987

Uterine artery Doppler velocimetry: the significance of divergent systolic/diastolic ratios.

Continuous wave Doppler studies were carried out on both uterine arteries in 71 pregnant women from the twentieth week of gestation onward. Analysis of the waveform included the systolic/diastolic ratio and the presence or absence of a diastolic notch. In the current study, these ratios from 31 women with left/right systolic/diastolic difference, (between left and right uterine arteries) were compared with those of women having normal ratios. A normal left/right systolic/diastolic ratio difference of 0.3 with SD of 0.3 was found. When the left/right difference was plotted against the left/right averaged systolic/diastolic ratio, a correlation coefficient of 0.7 was noted (p less than 0.001). Significant outcome differences were noted between normal and abnormal left/right difference systolic/diastolic ratios in the perinatal parameters of gestational age at delivery, fetal weight, pregnancy-induced hypertension, proteinuria, and intrauterine growth retardation. Divergent uterine artery ratio findings are a result of one artery being the dominant supplier to the placenta. The majority of women with an elevated systolic/diastolic ratio seem to have divergent uterine blood supply to the uterus and placenta. These data suggest that errors in placentation site contribute to the development of preeclampsia and growth retardation in the fetus.

Arteries↗
PubMed1987

Uterine and umbilical artery velocimetry during normal labor.

Twelve normal parturients were studied with a continuous wave Doppler unit to assess changes in uterine and umbilical velocity waveforms during labor. The analysis of these waveforms included the peak systolic/end-diastolic ratio and the evaluation of a diastolic notch. Each woman served as her own control, and all fetal heart rate tracings were normal. In latent phase labor and intact membranes, the umbilical artery systolic/end diastolic ratios before, during, and after a contraction were 2 +/- 0.2, 2 +/- 0.3 and 1.95 +/- 0.3 (N.S.). Similar results were obtained in the active phase, after rupture of membranes, or during oxytocin stimulation. This stability of the fetal cardiovascular system ensures an uninterrupted gas exchange process during the contractions (on the fetal side), enabling the great majority of term fetuses to tolerate labor with minimal if any metabolic changes. The uterine artery end-diastolic velocity fell progressively during the contraction, reaching 0 when the intrauterine pressure exceeded 35 mm Hg. Despite intrauterine pressure of greater than 60 mm Hg, the diastolic notch did not appear. Thus at term, the umbilical artery velocity waveform does not change over a wide range of uterine pressures. The changes seen in the uterine artery waveforms suggest that the end-diastolic component is primarily determined by changes in the arcuate and spiral arteries, both of which are affected during the uterine contraction.

Blood Flow Velocity↗
PubMed1987

Molecular cloning of a brain-specific calcium/calmodulin-dependent protein kinase.

A calcium/calmodulin-dependent protein kinase type II (CaM-K) alpha-subunit cDNA has been cloned from rat brain. This enzyme is encoded by a 5.1-kilobase mRNA expressed exclusively in the brain. Hybridization histochemistry reveals that the CaM-K mRNA expression corresponds to the distribution of the immunoreactive alpha-subunit protein, suggesting that the high enzyme levels in specific brain areas reflect regional differences in gene expression. The sequence of CaM-K alpha-subunit cDNA indicates a 478-amino acid (54-kDa) protein with three functional domains. The domain organization suggests a structural model for calcium/calmodulin-dependent and independent states that might subserve short- and long-term responses to transient stimuli.

Amino Acid Sequence↗