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Biomedical subjects

A Steinschneider

Publications and source records attributed to A Steinschneider.

At least 37 records · Page 2Linked to original sources
PubMed1982

Pulmonary artery changes in response to recurrent episodes of anoxia.

Newborn rats exposed to anoxia for 30 seconds twice daily for 4 weeks developed thickening of the media of small muscular pulmonary arteries as measured by point-counting morphometric techniques. These findings are similar to those described in postmortem studies on the lungs of victims of sudden infant death syndrome and support the hypothesis that repeated episodes of apnea alone are a sufficient respiratory abnormality to produce some of the morphometric changes described in victims of sudden infant death syndrome.

Aging↗
PubMed1982

The sudden infant death syndrome and apnea/obstruction during neonatal sleep and feeding.

Respiratory observations made during nutritive feeding and a complete daytime nap within the first week of life on ten newborns who subsequently were victims of sudden infant death syndrome (SIDS) were compared with normative data based on 1,301 infants of comparable ages. Measurements were obtained of all apneic pauses and/or transient respiratory obstructive events at least two seconds in duration. A statistically significant increased number of future SIDS victims were found to have an unusual amount of apnea/obstruction episodes during nutritive feeding when compared with the normative group. Future SIDS victims, as a group, also had an increased frequency of apneic pauses during sleep. Furthermore, all SIDS victims demonstrated either an unusual amount of apnea/obstruction during nutritive feeding or apneic pauses during sleep. None of the airway obstruction measures during sleep differentiated the SIDS infants from the normative group. These results are consistent with the general hypothesis that prolonged apnea or airway obstruction is part of the pathophysiologic process resulting in SIDS and those hypotheses implicating unstable respiratory activity during sleep as well as apnea and pharyngeal/laryngeal dysfunction induced by liquid stimulation of the upper airway. They are also compatible with the growing body of evidence indicating that factors that predispose an infant to SIDS originate in the perinatal period.

Humans↗
PubMed1981

The cry characteristics of an infant who died of the sudden infant death syndrome.

Fourteen cries of a four day old infant who subsequently died suddenly of unexplained causes were analyzed on nine acoustic characteristics including fo, duration, formant frequencies and sound pressure level. In comparison to a group of newborn controls, the Sudden Infant Death Syndrome (SIDS) victim's cries exhibited a lower fo, longer duration, lower formant frequencies and greater sound pressure level throughout the spectrum. Cry duration and sound pressure levels, however, deviated in excess on one standard deviation from the mean of the other newborns. Similar findings resulted when the SIDS infant was compared to a group of full term infants who were siblings of SIDS victims, although the magnitude of the differences was slightly less especially with respect to sound pressure level. Measurement of selected acoustic variables in a newborn's cry may be of value in our understanding of SIDS and for identifying infants at risk.

Acoustics↗
PubMed1981

Labeling of amino acids and peptides with isotopic oxygen as followed by 17O-N.M.R.

17O was introduced into the respective alpha- and gamma-COOH groups of Boc-Gly and Boc-Glu by saponification of the corresponding O-methyl esters with 1N NaOH in H2 17O. Other 17O enriched Boc-amino acids were prepared by acid catalyzed exchange into the amino acid alpha-COOH group followed by t-butyloxycarbonylation with t-butyl S-4, 6-dimethylpyrimidin-2-ylthio carbonate. Final enrichment, by approximately three orders of magnitude over natural abundance, was 60-100% of the possible maximum. The synthesis of [17O]-Gly-Ala, [17O]-Gly-Leu and [17O]-Gly-Glu by DCC/HBT mediated coupling of Boc-Gly-[17O]-alpha-COOH with amino acid-O-t-butyl esters followed by deprotection with HCl/EtOAc proceeded without undue loss of the isotope. Boc-[17O]-Pro-Leu-Gly-NH2 was prepared by a similar procedure. [Tyr2-17O]-, [Pro7-17O]- and [Gly4-17O]-oxytocin were synthesized using solid phase support. 17O-chemical shifts of synthetic intermediates and of the final products were as expected for each functional group. Linewidth data correlate with the molecular weights of the compounds prepared.

Amino Acids↗
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↗
PubMed1975

The role of divalent cations in the reactions of valyl transfer ribonucleic acid synthetase of Escherichia coli. Effects of spermine and ethylenediaminetetraacetate.

We have analyzed the function of spermine in the aminoacylation of tRNA-Val by the valyl-tRNA synthetase of Escherichia coli. Our results indicate that Mg2+ is required for the aminoacylation reaction as well as for the ATP-PP-i exchange catalyzed by this enzyme. The apparent stimulation by spermine is a function of the tRNA used, which appears to contain bound cations even after dialysis against 10 minus 4 M EDTA. Higher concentrations of EDTA totally abolish spermine-stimulated esterification of tRNA-Val.

Amino Acyl-tRNA Synthetases↗
PubMed1975

Thermal chromatography of lysine-specific transfer ribonucleic acid from Escherichia coli B.

Two Escherichia coli B tRNALys isoacceptors have been separated by thermal chromatography on hydroxyapatite demonstrating the potential of this approach in the fractionation of single-stranded polynucleotides. Elution temperatures were reproducible and depended primarily on the cation present and its concentration. Cesium phosphate was a more effective eluent than sodium phosphate. The integrity of the polynucleotide following thermal chromatography was examined by ultracentrifugation in a 60% dimethyl sulfoxide solvent, electrophoresis on polyacrylamide gels containing urea and oligonucleotide mapping. Adsorption to hydroxyapatite did not noticeably increase phosphodiester bond breakage compared with that in solution. Minimal, if any, rupture of covalent linkages was detected under the conditions of preparative separation of the isoacceptors. Several observations suggest that only one tRNALys was transcribed by the E. coli B cell.

Adsorption↗
PubMed1975

Primary structure of tRNA-Lys of E. coli B.

The primary structure of tRNALys of E. coli was determined by use of [32P]-tRNA. The sequence is pGGGUCGUUAGCUCAGDDGGDAGAGCAGUUGACUmam5-s2-UUU-t6AApsiCAAUUGm7GXCGCAGGTpsiCGAAUCCUGCACGACCCACCA. No s4-U was detected in position 8. No other lysine tRNA was detected but the existence of another species has not been ruled out.

Autoradiography↗