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Biomedical subjects

H Schulman

Publications and source records attributed to H Schulman.

At least 127 records · Page 7Linked to original sources
PubMed1990

Multifunctional Ca2+/calmodulin-dependent protein kinase made Ca2+ independent for functional studies.

Multifunctional Ca2+/calmodulin-dependent protein kinase (CaM kinase) that is transiently expressed in COS-7 cells is essentially inactive when assayed without Ca2+. Physiological activation of the kinase occurs by binding of Ca2+/calmodulin near a putative autoinhibitory subdomain that contains the sequence His282-Arg-Gln-Glu-Thr286. We have markedly increased the Ca2(+)-independent activity of CaM kinase by altering the charge of this sequence by site-directed mutagenesis. The mutant containing Asp282-Gly-Glu-Glu-Thr286 is 67% Ca2+ independent. We also mimicked the effect of autophosphorylation at Thr286 by the mutant containing His282-Arg-Gln-Glu-Asp286, which is 36% Ca2+ independent. In addition to delineating the autoinhibitory domain by use of mutations that disable it, these constructs are of immediate practical value for simulating CaM kinase action in vivo without elevating Ca2+. To this end, we show that nuclear microinjection of cDNA of a constitutive mutant, but not of the wild-type kinase, initiates maturation of Xenopus oocytes.

Amino Acid Sequence↗
PubMed1990

Doppler umbilical artery velocimetry in fetuses with polyhydramnios.

Polyhydramnios is a condition of multiple etiologies, many of a benign nature, but some of which are incompatible with life. To evaluate Doppler velocimetry results as a prognostic parameter in these fetuses, we reviewed all of our cases of polyhydramnios that underwent Doppler analysis in the third trimester. Fifty-four fetuses were studied. Eleven (20.4%) had abnormal waveforms and 43 (79.6%) had normal waveforms. An abnormal waveform was associated with a significantly higher incidence of congenital anomalies, perinatal mortality and intrauterine growth retardation. Six of the 11 fetuses had abnormal karyotypes. Macrosomia was present in 37.2% of fetuses with normal waveforms and in no fetus with an abnormal waveform. Doppler analysis may aid in the counseling and management of patients with polyhydramnios. In cases with an abnormal ratio, the physician and patients should be prepared for a poor outcome and third trimester genetic analysis should be strongly considered.

Chi-Square Distribution↗
PubMed1990

Multifunctional Ca2+/calmodulin-dependent protein kinase is necessary for nuclear envelope breakdown.

The role of multifunctional Ca2+/calmodulin-dependent protein kinase (CaM kinase) in nuclear envelope breakdown (NEB) was investigated in sea urchin eggs. The eggs contain a 56-kD polypeptide which appears to be a homologue of neuronal CaM kinase. For example, it undergoes Ca2+/calmodulin-dependent autophosphorylation that converts it to a Ca2(+)-independent species, a hallmark of multifunctional CaM kinase. It is homologous to the alpha subunit of rat brain CaM kinase. Autophosphorylation and substrate phosphorylation by the sea urchin egg kinase are inhibited in vitro by CaMK(273-302), a synthetic peptide corresponding to the autoinhibitory domain of the neuronal CaM kinase. This peptide inhibited NEB when microinjected into sea urchin eggs. Only one mAb to the neuronal enzyme immunoprecipitated the 56-kD polypeptide. Only this antibody blocked or significantly delayed NEB when microinjected into sea urchin eggs. These results suggest that sea urchin eggs contain multifunctional CaM kinase, and that this enzyme is involved in the control of NEB during mitotic division.

Animals↗
PubMed1990

Doppler velocimetry of the umbilical and uteroplacental circulation: a critical review.

During the past 8 years, there have been more than 300 articles published describing Doppler studies in the field of obstetrics. This review will analyze the data dealing with the umbilical and uteroplacental circulation. This is being done with the goal of formulating an opinion of the role of Doppler in the practice of clinical obstetrics. We have concluded from prospective studies that there is no clear definition of abnormal umbilical flow velocity before 30 weeks, except for absent end-diastolic velocity after the 20th week. Most of the prospective studies on the uteroplacental circulation have suffered from a lack of knowledge of the umbilical circulation, or only one uterine artery was studied. Most investigations until now have focused on demonstrating the pathophysiological correlations with Doppler studies. With the exception of a few dissenting voices, most have demonstrated strong correlations at probability levels of less than 0.01. A few studies have emerged that have attempted to evaluate Doppler as a screening or surveillance tool. The results have not been encouraging. In populations with a low perinatal mortality, it will be difficult to prove that Doppler will reduce perinatal mortality. Studies of Doppler efficacy will have to be designed to show improved usage and efficacy of fetal surveillance. Since Doppler uniquely identifies the fetus at risk for hypoxia before term, it could replace our current risking system for the detection of fetal disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1990

Umbilical artery Doppler velocimetry in pregnancies of less than 21 weeks' duration.

Most Doppler ultrasound investigations of the umbilical artery circulation have been confined to beyond 16 weeks' gestation. The purpose of this study is to explore the evolution of this circulation in human pregnancies of less than 21 weeks' gestation. We studied 169 low-risk pregnant women (125 longitudinally and 44 cross-sectionally) with a pulsed Doppler system on 357 separate occasions between 9 and 20 weeks of gestation. Systolic/diastolic (S/D) ratios were used for waveform analysis. We obtained umbilical waveforms as early as 9 weeks. Before 13 weeks, all fetuses had absent end-diastolic velocity (AEDV), then progressive development of end-diastolic velocity (EDV) appeared from 13 to 18 weeks. At 18 weeks, all fetuses had developed EDV. S/D ratios progressively declined from 13 to 20 weeks (y = 17.67 - 1.26x + 0.3x2; r2 = .95). A cross-sectional evaluation of fetal heart rate in 136 fetuses revealed a significant negative second-order polynomial relationship with gestational age between 9 and 20 weeks y = 245.84 - 10.33x + 0.27x2; r2 = .93). In 136 fetuses, 185 measurements of S/D ratios and their corresponding fetal heart rate revealed no relationship (weighted linear regression, r2 = .005). Mean fetal heart rate was significantly higher when EDV was absent (164.6 +/- 10.8 standard deviation [SD], n = 74) than when EDV was present (150.1 +/- 5.8 SD; n = 62; P = .000). Thus, upstream factors may be of little importance in the generation of umbilical artery velocity waveforms in early pregnancy. Umbilical Doppler velocimetry in the first half of pregnancy gives a functional assessment of the vascular development of the umbilical-placental circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1990

Value of a screening fetal heart rate tracing in the latent phase of labor.

We studied the value of a screening fetal heart rate (FHR) tracing obtained on 405 women in the latent phase of labor on presentation to the labor-and-delivery suite. All pregnancies were at term and had a cephalic presentation. Thirty-two women in the sample studied underwent a cesarean section for fetal distress. Using that end point, a screening FHR tracing in the admitting room had a sensitivity of 57%, specificity of 98%, positive predictive value of 75% and overall efficiency of 95%. One- and five-minute Apgar scores and thick meconium staining of the amniotic fluid were also examined. While no statistically significant differences were found (P less than .2 for Apgar score and less than .06 for meconium), there was a trend that might have been significant if more women had been studied. A screening FHR tracing on all women at term in the latent phase of labor will identify the majority of those who will develop fetal distress in labor. Women with an abnormal screening tracing should be admitted to the hospital and the fetal status evaluated further.

Female↗
PubMed1989

Inhibition of postsynaptic PKC or CaMKII blocks induction but not expression of LTP.

Long-term potentiation (LTP) of synaptic transmission is a widely studied cellular example of synaptic plasticity. However, the identity, localization, and interplay among the biochemical signals underlying LTP remain unclear. Intracellular microelectrodes have been used to record synaptic potentials and deliver protein kinase inhibitors to postsynaptic CA1 pyramidal cells. Induction of LTP is blocked by intracellular delivery of H-7, a general protein kinase inhibitor, or PKC(19-31), a selective protein kinase C (PKC) inhibitor, or CaMKII(273-302), a selective inhibitor of the multifunctional Ca2+-calmodulin-dependent protein kinase (CaMKII). After its establishment, LTP appears unresponsive to postsynaptic H-7, although it remains sensitive to externally applied H-7. Thus both postsynaptic PKC and CaMKII are required for the induction of LTP and a presynaptic protein kinase appears to be necessary for the expression of LTP.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

In vivo and in vitro phosphorylation of murine lymphocyte differentiation antigen CD5.

Ly-1, the murine lymphocyte differentiation antigen CD5, is phosphorylated constitutively in vivo. This phosphorylation is enhanced by phorbol 12-myristate 13-acetate (PMA) treatment, but not by concanavalin A, Ca2+ ionophore or dibutyryl cAMP. Prolonged PMA treatment abolished PMA-induced Ly-1 phosphorylation but not constitutive phosphorylation, suggesting that protein kinase C (PKC) is responsible for this enhanced phosphorylation, but not the basal phosphorylation of Ly-1. Ly-1 is phosphorylated by PKC added to membranes, further supporting a role for protein kinase C in the in vivo phosphorylation of Ly-1.

Amino Acids↗
PubMed1989

A cAMP-regulated chloride channel in lymphocytes that is affected in cystic fibrosis.

A defect in regulation of a chloride channel appears to be the molecular basis for cystic fibrosis (CF), a common lethal genetic disease. It is shown here that a chloride channel with kinetic and regulatory properties similar to those described for secretory epithelial cells is present in both T and B lymphocyte cell lines. The regulation of the channels by adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase in transformed B cells from CF patients is defective. Thus, lymphocytes may be an accessible source of CF tissue for study of this defect, for cloning of the chloride channel complex, and for diagnosis of the disease.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1989

Pregnancy surveillance with Doppler velocimetry of uterine and umbilical arteries.

Previous studies with Doppler velocimetry have demonstrated a strong correlation between abnormal waveforms and fetal-maternal disease. This study was designed to evaluate the potential role of Doppler velocimetry as a screening test in routine prenatal care. Two hundred fifty-five pregnant women had routine monthly Doppler (systolic/end-diastolic ratio) studies on the uterine and umbilical arteries starting in the twentieth week of gestation. When a cutoff value of 3 was used at 30 weeks for the umbilical arteries, there were 35 (13%) positive tests. In 20 of these values fell to less than 3 in the ensuing weeks and were considered false positive. The remaining 15 babies demonstrated positive clinical pathologic correlates. When a value of 2.6 was used at 26 weeks for uterine arteries, there were nine positive results, seven of which had clinical pathologic correlates. This study suggested an overall positivity rate of 7%; therefore it provides encouragement for a larger venture in which screening and impact on decision making are evaluated.

Adult↗
PubMed1989

Doppler velocimetry and placental disease.

Quantitative placental examinations were performed on 47 women who had Doppler flow velocity studies of the umbilical artery during their pregnancy. The systolic-diastolic ratio of the umbilical artery was used as the measurement parameter to divide the study population into two groups. Group 1 consisted of women with normal systolic-diastolic ratios (systolic-diastolic less than 3), and group 2 consisted of women with an elevated systolic-diastolic ratio (systolic-diastolic greater than or equal to 3). The group with an increase in systolic-diastolic ratio had more perinatal complications as demonstrated by two stillbirths, a higher incidence of cesarean deliveries for fetal distress, and more admissions to the neonatal intensive care unit. Significant differences were found when gestational age at delivery, placental weight, birth weight, and the number of small muscular arteries in the placenta were compared. Since gestational age may have accounted for the difference in placental findings, patients were matched for gestational age. The placental weights were comparable, but there were fewer small muscular arteries in those patients with an increase in systolic-diastolic ratio (p less than 0.001). In addition, when these findings were examined to determine the influence of diminished uterine flow velocity, none was found.

Blood Flow Velocity↗
PubMed1989

Expression of a multifunctional Ca2+/calmodulin-dependent protein kinase and mutational analysis of its autoregulation.

Autophosphorylation of multifunctional Ca2+/calmodulin-dependent protein kinase converts it from a Ca2(+)-dependent to a Ca2(+)-independent or autonomous kinase, a process that may underlie some long-term enhancement of transient Ca2+ signals. We demonstrate that the neuronal alpha subunit clone expressed in COS-7 cells (alpha-CaM kinase) is sufficient to encode the regulatory phenomena characteristic of the multisubunit kinase isolated from brain. Activity of alpha-CaM kinase is highly dependent on Ca2+/calmodulin. It is converted by autophosphorylation to an enzyme capable of Ca2(+)-independent (autonomous) substrate phosphorylation and autophosphorylation. Using site-directed mutagenesis, we separately eliminate five putative autophosphorylation sites within the regulatory domain and directly examine their individual roles. Ca2+/calmodulin-dependent kinase activity is fully retained by each mutant, but Thr286 is unique among the sites in being indispensable for generation of an autonomous kinase.

Amino Acid Sequence↗
PubMed1989

Multifunctional Ca2+/calmodulin-dependent protein kinase: domain structure and regulation.

Cells respond to many hormones, neurotransmitters and growth factors by increasing intracellular Ca2+. This second messenger, in turn, affects cellular function via activation of a novel multifunctional Ca2+/calmodulin-dependent protein kinase. The kinase displays an interesting form of biochemical 'memory'; activation elicits an autophosphorylation which converts it to a Ca2+-independent enzyme that can continue to phosphorylate cellular proteins for some time following termination of the initial Ca2+ stimulus.

Animals↗
PubMed1989

Distinct autophosphorylation sites sequentially produce autonomy and inhibition of the multifunctional Ca2+/calmodulin-dependent protein kinase.

The multifunctional Ca2+/calmodulin-dependent protein kinase (multifunctional CaM kinase) may be an important mediator for neurotransmitters and hormones that utilize Ca2+ as a "second messenger." We examined the ability of autophosphorylation to convert the multifunctional CaM kinase to a Ca2+/calmodulin-independent (autonomous) form to determine whether autophosphorylation is a mechanism for short- or long-term enhancement of Ca2+ action. As the kinase incorporates phosphate during continuous stimulation by Ca2+/calmodulin, its ability to phosphorylate exogenous substrates becomes increasingly autonomous. Withdrawal of Ca2+ after a critical level of phosphate incorporation is reached leads to a "burst" or rapid increase in Ca2+-independent autophosphorylation. The "burst" of autophosphorylation is distinct from the initial Ca2+-dependent autophosphorylation, however, since it inhibits substrate phosphorylation. Both Ca2+-dependent and Ca2+-independent substrate phosphorylation are inhibited by this autonomous autophosphorylation. Thus, autophosphorylation has a dual role in modulating the activity of multifunctional CaM kinase. It initially enables the kinase to continue phosphorylating substrates after Ca2+ levels decline, but it eventually suppresses this autonomous activity. Tryptic phosphopeptide mapping demonstrates that appearance of phosphothreonine-containing peptides is common to several conditions used to generate an autonomous enzyme. Sequencing reveals the critical "autonomy" site to be threonine286. The inhibitory mode of autophosphorylation involves 3 additional phosphopeptides containing a serine and a threonine residue.

Animals↗