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Biomedical subjects

A Steinschneider

Publications and source records attributed to A Steinschneider.

At least 19 recordsLinked to original sources
PubMed1991

Inhibition and stimulation of rat luteal protein phosphorylation by protein kinase effectors.

Estradiol-17 beta (E2) predetermined protein phosphorylation systems have been identified recently in midpregnant rat corpus luteum. Major type protein kinase activities in these systems were explored here using as probes protein kinase inhibitors. Luteal nuclear, mitochondrial, microsomal and cytosolic fractions were obtained from rats hysterectomized and hypophysectomized on day 12 of pregnancy and then treated for 72 h with E2. In vitro phosphate transfer from [gamma-32P]ATP was monitored by SDS-PAGE followed by autoradiography. Polymyxin B (PMB), 1-200 microM, a PKC inhibitor, completely blocked, in a dose dependent manner, the Ca2+ phospholipid (PL) stimulated radiolabeling of nuclear fraction Mr 79,000 substrate(s) as expected. Similarly, the calmodulin (CaM) antagonist compound 48/80, 1-20 micrograms/ml, inhibited the Ca2+/CaM-dependent phosphorylation of the microsomal fraction Mr 60,000 and Mr 56,000 proteins. The Ca2+ PL-enhanced labeling of mitochondrial fraction Mr 76,000 substrate(s) was only partially susceptible to inhibition by PMB or compound 48/80. Studies of microsomal fraction phosphoprotein bands not stimulated by added cofactors indicated that the radiolabeling of Mr 75,000 protein(s) was partially blocked by compound 48/80 but not by PMB. Phosphate transfer to Mr 41,000 protein(s) was inhibited by the cAMP-dependent kinase protein inhibitor (PKI), while the phosphorylation of Mr 31,000 protein(s) was refractory to all inhibitors employed here. Surprisingly, regardless of hormonal pretreatment, PMB and compound 48/80 activated in every subcellular fraction the cofactor independent appearance of at least one phosphoprotein band, between Mr 87,000-99,000. This novel observation should be instrumental in understanding the actions of these compounds towards living cells.

Animals↗
PubMed1991

Effect of diphtheria-tetanus-pertussis immunization on prolonged apnea or bradycardia in siblings of sudden infant death syndrome victims.

To determine whether the incidence of apnea or bradycardia increased after the first diphtheria-tetanus-pertussis (DTP) immunization in 100 subsequent siblings of victims of sudden infant death syndrome, we examined data obtained from floppy disk recordings attached to apnea-bradycardia monitors for episodes of apnea lasting 15 seconds or longer and episodes of bradycardia lasting 10 seconds or longer. The data were divided into three periods: (1) 10 days before the first DTP immunization was received (pre-DTP period), (2) 10 days immediately after the DTP (DTP period), and (3) 10 days after the DTP period (post-DTP period). Seventeen infants had at least one episode of prolonged apnea or prolonged bradycardia either before or after the 30-day study period (eight before only, eight after only, and one before and after). None of the infants had episodes of apnea lasting 15 seconds or more or bradycardia lasting 10 seconds or more during the pre-DTP or DTP period. One episode of apnea, 16 seconds long, and one episode of bradycardia lasting 11 seconds occurred in the post-DTP period. These results failed to confirm the clinical impression that DTP immunizations are associated with an increased frequency and severity of prolonged apnea. They also place in question the utility of assessing an infant's response to a DTP immunization to determine continued risk of apnea and bradycardia before home monitoring is discontinued.

Apnea↗
PubMed1991

Calcium-calmodulin and calcium-phospholipid dependent phosphorylation of membranous fraction proteins related to the tropic regulation by estradiol in the corpus luteum.

Estradiol assumes a major role in the regulation of growth, vascularization, and progesterone synthesis in the midpregnant rat corpus luteum. To explore whether molecular events triggered by estradiol could be mediated, at least in part, by protein phosphorylation, we investigated whether estradiol treatment in vivo affects endogenous luteal protein phosphorylation systems detectable in vitro. Luteal nuclear, mitochondrial, and microsomal fractions were obtained by differential centrifugation from rats hypophysectomized and hysterectomized on day 12 of pregnancy and treated with or without estradiol for 72 h. Using [gamma-32P]ATP as phosphate donor, proteins were phosphorylated in the presence or absence of either calcium (Ca), Ca plus calmodulin, or Ca plus phospholipid. Phosphoproteins were separated by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and visualized by autoradiography. The Coomassie blue stained proteins and phosphoprotein profiles were markedly different in the various fractions. Estradiol treatment in vivo caused an increase in the basal endogenous phosphorylation of several proteins in vitro. It also substantially enhanced the protein kinase C (PKC) and Ca-calmodulin kinase-dependent phosphorylation of selected proteins in subcellular fractions. The Ca-calmodulin kinase catalyzed phosphorylation of microsomal 56 and 60 kilodalton (kDa) proteins was remarkably increased by estradiol. Proteins (56 and 60 kDa) were also phosphorylated when Ca-calmodulin was added to the nuclear fraction, however, this phosphorylation did not appear to be affected by estradiol treatment. A major PKC substrate in the nuclear fraction was an 80 kDa protein whose phosphorylation was increased remarkably by estradiol treatment. In the mitochondrial fraction the most striking effect of estradiol was a marked increase in PKC-mediated phosphate transfer into a 76 kDa substrate. To determine whether estradiol action on protein phosphorylation was related to its tropic effect in the corpus luteum, the hormone was administered to day 10 hypophysectomized and hysterectomized pregnant rats. In this rat model, where estradiol has no stimulatory effect on either luteal steroidogenesis or growth, neither endogenous nor kinase-mediated phosphorylation was affected by this steroid. In summary, the present investigation has revealed that in vivo treatment with estradiol affects the PKC and the Ca-calmodulin dependent in vitro phosphorylation of selected proteins localized in different subcellular compartments and further suggests that phosphorylation systems are potential control points for estradiol regulation of rat corpus luteum function.

Animals↗
PubMed1991

Parental reports of apnea and bradycardia: temporal characteristics and accuracy.

A prospective examination was made of the temporal course of parental observations in response to a monitor alarm of apnea (apnea setting of 20 seconds) or bradycardia (bradycardia setting of 80 beats per minute). Data were obtained from 155 subsequent sudden infant death syndrome siblings followed up at home, during the first 20 weeks of life, on an apnea/bradycardia monitor with an attached event recorder. In addition, parental reports were compared to an objective recording of the pattern of cardiorespiratory activity surrounding each monitor alarm. Only those parental observations were considered which reported the infant to be asleep with no apparent equipment malfunction following an apnea alarm (with or without pallor, cyanosis, or the provision of external stimulation) or a low heart rate alarm associated with pallor, cyanosis, or stimulation. Observations were analyzed within each of five age periods (less than 29, 29 through 56, 57 through 84, 85 through 112, 113 through 140 days). The percentage of infants reported to have prolonged apnea, prolonged apnea with stimulation, or bradycardia with stimulation was found to decrease with age. An examination of the linked event recordings failed to document an episode of apnea as long as 15 seconds for any of the reported episodes of apnea. Furthermore, bradycardia as long as 5 seconds in duration could be documented in only 3 of 422 reported episodes of bradycardia. These results indicate the potential for considerable error when total reliance is placed on parental observations and point to the necessity for objective event recordings when using home monitors in the clinical management of at-risk infants.

Apnea↗
PubMed1990

Identification and characterization of an abundant phosphoprotein specific to the large luteal cell.

An abundant protein with a relative mol wt of 32K present specifically in the large cells of the pregnant rat corpus luteum has been identified. Separation of large and small luteal cells by elutriation, followed by protein analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), have revealed that the 32K protein was present as a major protein in the large luteal cells but was practically absent in the small cell population. This protein appears to be highly tissue and cell specific and resolves into three protein species by two-dimensional SDS-PAGE with the major protein having an isoelectric point (pI) greater than or equal to 8.5. It was not detected in preantral follicles or placentas of the same pregnant rats, or in any other tissue examined. After subcellular fractionation, the 32K protein(s) was found in the particulate fraction and was localized principally in the microsomal compartment. Autoradiographic analysis of 35S-amino acid-labeled tissue demonstrated that the 32K protein(s) is synthesized in the corpus luteum. When particulate fractions from small and large cells were incubated in the presence of [gamma-32P]ATP followed by SDS-PAGE, phosphorylation of the 32K protein was apparent. Phosphorylation of this protein was not enhanced by the addition of cofactors for cAMP, Ca2(+)-calmodulin- or Ca2(+)-phospholipid-dependent kinases. Experimental inhibition of steroidogenesis with amino-glutethimide caused a remarkable reduction in the luteal content of this 32K protein whereas estradiol and human CG treatment increased its content. In summary, we have discovered and partially characterized a unique 32K protein(s) which is expressed and phosphorylated only in large luteal cells of the corpus luteum. This protein(s), which is regulated by estradiol formed locally, may serve as a powerful marker for both the large luteal cell and estrogen action in the corpus luteum.

Animals↗
PubMed1989

Protein kinase C catalyzed phosphorylation of sterol carrier protein 2.

The transport of cholesterol to the inner mitochondrial membrane, a key step in steroidogenesis, is subject to hormonal modulation that, at least in part, could be mediated by protein phosphorylation. This step is stimulated by sterol carrier protein 2 (SCP2) and Ca2+. To explore whether SCP2 itself is a potential control point for regulation by Ca2+-dependent phosphorylation we investigated whether highly purified SCP2 could serve as a substrate for major type Ca2+ and non-Ca2+-dependent protein kinases. Phosphorylation by calmodulin protein kinase II (CaM-PK II), myosin light chain kinase (MLCK), cAMP-dependent kinase (PKA) and protein kinase C (PKC) was monitored under optimal conditions for each enzyme. PKA, CaM-PK II and MLCK catalyzed the radiolabeling of histone 2A, synapsin I and myosin light chain (MLC), known substrates for these kinases, respectively, yet no phosphate transfer to SCP2 was observed. In contrast, PKC from two different sources (rat and calf brain) effectively catalyzed the phosphorylation of the highly purified SCP2. The phosphorylation of SCP2 depended on the addition of Ca2+ and phospholipids and was completely blocked by Polymyxin B, a PKC inhibitor. PKC catalyzed phosphorylation of SCP2 displayed a similar dependence on the concentration of ATP. Lineweaver Burk plots of the data indicate Km values for ATP of approximately 6 microM for the phosphorylation of SCP2. Our results, which have revealed for the first time that SCP2 is a substrate for PKC, are consistent with the possibilities that the control of steroidogenesis by tropic hormones and by PKC activation are mediated, at least in part, by the phosphorylation/dephosphorylation of SCP2.

Adenosine Triphosphate↗
PubMed1979

Neonatal respiratory instability and infant development.

This study examines the relationships between neonatal sleep respiratory instability and infant development. A group of 122 full-term healthy infants was observed during a nap within the first and fourth weeks of life. During each nap, a continuous polygraphic recording was obtained of respiratory activity and extraocular movements. The relative frequency and average duration of apneic pauses (greater than or equal to 2 sec) in each testing session for an infant were employed to calculate a measure of respiratory instability (PSA4) previously found to be related to the occurrence of prolonged sleep apnea. 28 of the infants in this study were maintained at home on apnea monitors. The Bayley Scales of Infant Development were administered to each infant at approximately 9 months of age. Comparisons of infants with high versus low PSA4 values and of monitored versus unmonitored infants were not strongly distorted by imbalances in birth weight, sex, race, birth order, method of feeding, Sudden Infant Death Syndrome (SIDS) sibship, parental education, age at developmental assessment, and developmental tester. Those with increased respiratory instability (PSA4 greater than or equal to -0.04) within the first week of life averaged significantly lower in mental and psychomotor development. Utilization of home apnea monitors was not significantly associated with developmental scores.

Child Development↗
PubMed1978

Glucose in vertebrate skeletal muscle proteins.

Neutral sugar was found in proteins extracted with acid chloroform/methanol from skeletal muscle of frog, normal and dystrophic chicken as well as in conventional preparations of frog tropomyosin and rabbit myosin. Whenever tested, the sugar content remained unaffected by two extractions with 5% trichloroacetic acid and by treatment with acid (0.1 N hydrochloric acid) or alkali (0.1 N sodium hydroxide, 60--90 min, 100 degrees C). These and other chemical properties favor the notion that sugar is present in covalent linkage to protein rather than as an attending contaminant. In every protein studied sugar profiles consisted of glucose only except rabbit myosin where it was accompanied by another sugar, presumably ribose.

Animals↗
PubMed1978

Sudden infant death syndrome and prolongation of the QT interval.

A standard lead II ECG was recorded during either the first or the fourth week of life or at both ages from 30 neonates whose sibling had died of the sudden infant death syndrome (SIDS). Electrocardiographic recordings also were obtained from 75 control neonates and from 52 adults who had had an infant who died of SIDS. The neonatal data revealed that the QT interval, corrected for heart rate (QTC), was longest during NREM (vs rapid eye movement [REM]) sleep. Furthermore, the QTC interval was longer within the fourth week than in the first week of life. However, the QTC interval of siblings of SIDS victims did not differ from that of the control infants, nor did the QT interval of parents of SIDS victims differ from published normal values. One neonate who subsequently died of SIDS did not have an abnormally long QTC interval. These data do not support the hypothesis that genetically determined prolongation of the QT interval plays a major role in SIDS.

Adult↗
PubMed1977

Isolation of phosphorylated acid chloroform/methanol-soluble proteins from live frog muscle.

About 6-7% of the total proteins from trichloroacetic acid-washed and freeze-dried frog muscle could be extracted with acid chloroform/methanol. Three of these proteins were found to be phosphorylated in the live frog. They were purified to apparent homogeneity by gel chromatography and preparative gel electrophoresis. The apparent molecular weights, determined by sodium dodecyl sulfate gel electrophoresis, were 34 000, 19 000 and 10 000. Each phosphorylated protein contained 3 mol of a covalently bound neutral sugar but they did not contain any tightly bound lipids. All three proteins incorporated 32P into serine phosphate. The 10 000 dalton protein, which had the highest specific radioactivity contained an unusually high proportion of serine, 14% of the total amino acids. It also did not stain with Coomassie Blue.

Amino Acids↗
PubMed1977

Prolonged sleep apnea and respiratory instability: a discriminative study.

This report is based on a study of 53 infants, 28 of whom had clinically observed prolonged apnea (greater than or equal to 20 seconds) during sleep whereas the remaining did not. In addition to the clinical observations, each infant was studied in a sleep laboratory during a complete nap, and a continuous recording was made of respiratory activity and rapid eye movements. Measurements were made of all apneic pauses (greater than or equal to 2 seconds) observed in the laboratory and the two groups of infants were compared in terms of the frequency and average duration of apneic pauses, the longest apneic pause, the amount of periodic apnea, and the relative amount of apnea. The infants with prolonged sleep apnea had, during a single nap, more frequent and longer apneic pauses and more periodic apnea. This supports the hypothesis that respiratory instability during sleep and prolonged apnea have a common etiology. By employing a multiple linear regression model and including all laboratory apnea measures in a single analysis, a composite laboratory score was developed to differentiate members of the two groups. It would thus appear that the study of infants during a single nap could assist in the identification of infants at risk for prolonged sleep apnea and provide an indirect method for determining the influence of a number of variables on the occurrence of prolonged sleep apnea. Pediatrics, 59:962-970, 1977, SLEEP, APNEA, RESPIRATORY INSTABILITY.

Apnea↗
PubMed1977

Nasopharyngitis and the sudden infant death syndrome.

Infants who died of SIDS in Onondaga County (New York) were classified into a Nasopharyngitis Group (N = 59) or a No Nasopharyngitis Group (N = 57) on the basis of symptoms, within one week prior to death, referable to the upper respiratory tract. Examination of the postnatal age of death revealed that infants in the Nasopharyngitis Group tended to be older than those in the No Nasopharyngitis Group. These results are consistent with a prediction derived from the hypothesis that prolonged sleep apnea is part of a pathophysiologic process resulting in SIDS.

Age Factors↗
PubMed1976

Apnea and airway obstruction during feeding and sleep.

Recent awareness of the magnitude of sudden unexplained deaths in apparently healthy infants has lead to an increased interest in those circumstances that are associated with or can elicit prolonged and serious apneic episodes. In the present studies, attention was directed toward the study of physiologic activity during sleep and feeding. Apneic episodes of varying durations occur during sleep which, in some instances, can be of sufficient length to warrant resuscitative intervention. A number of infants also reveal transient upper airway obstruction following brief periods of sleep apnea. This functional airway obstruction produces sudden and severe bradycardia. Similarly, infant feeding can induce dangerously prolonged periods of apnea and, in some infants, transient airway obstruction. Few detailed studies have been performed to identify the anatomical level or characteristics of the obstruction. Available evidence suggests that this can take the form either of muscle hypotonicity or hypertonicity. Two infants observed by means of direct laryngoscopy revealed transient failure of vocal cord abduction. These results have provided for the development of two theoretical models that can result in the sudden infant death syndrome; furthermore, continuous recordings of respiratory and cardiac activity during feeding and sleep can be extremely valuable in elucidating the mechanisms responsible for the sudden development of apneic and cyanotic episodes in infants.

Airway Obstruction↗
PubMed1975

Kinetic demonstration of the intermediate role of aminoacyl-adenylate-enzyme in the formation of valyl transfer ribonucleic acid.

The question whether aminoacyl-tRNA synthetases act in a stepwise or in a concerted mechanism has been investigated kinetically with the valine enzyme of Escherichia coli, which had been used in previous studies by others who concluded that the physiological mechanism is concerted. An exchange between aminoacyl-tRNA and tRNA, dependent upon AMP, was studied. PP-i inhibits this exchange completely in the presence of Mg2+ and AMP but in the absence of added Mg2+ or with dAMP as the nucleotide the inhibition by PP-i is only partial; this is compatible with a stepwise, not a concerted, reaction. Exchange of isotopically labeled substrates in a system at chemical equilibrium also shows effects of substrate concentrations on rates in agreement with the predictions of a stepwise mechanism.

Adenosine Monophosphate↗