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Biomedical subjects

E Yang

Publications and source records attributed to E Yang.

At least 73 records · Page 4Linked to original sources

Safety of casein hydrolysate formula in children with cow milk allergy.

The purpose of this study was to determine whether a new casein hydrolysate infant formula, Alimentum, could be administered safely to children with cow milk hypersensitivity. The formula was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and with a sensitive enzyme-linked inhibition immunoassay, and it was judged to be safe for clinical trials in children allergic to cow milk. Twenty-five such children underwent double-blind placebo-controlled oral food challenges with 10 gm of powdered cow milk and casein hydrolysate formula. All children were highly atopic and had positive skin prick reactions to cow milk. No patient reacted to placebo during a double-blind, placebo-controlled food challenge. Two patients lost their allergy to cow milk and did not react during the challenge; the remaining patients reacted with a variety of cutaneous, respiratory, and gastrointestinal symptoms within 15 to 90 minutes of challenge. All children tolerated the blinded challenge to the casein hydrolysate and were fed the hydrolysate openly without difficulty. We conclude that this casein hydrolysate is generally safe to feed to children with immediate hypersensitivity to cow milk. We recommend that all infant formulas promoted as "hypoallergenic" be tested in milk-allergic patients to assess their allergenic potential, in addition to standard nutritional evaluation and animal testing for antigenicity.

Caseins↗

Renal alpha 1-adrenergic receptor response coupling in spontaneously hypertensive rats.

Renal sympathetic antidiuretic, antinatriuretic, and vasoconstrictor responses are mediated by alpha 1-adrenergic receptors in the normal rat. Since the renal nerve has been implicated in the pathogenesis of rat genetic hypertension, we investigated renal alpha 1-adrenergic receptor coupling to phosphoinositide turnover in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). In cortical slices from adult (13-week-old) SHR and WKY, stimulation with norepinephrine (10(-7)-10(-3) M) caused a concentration-dependent increase in accumulation of [3H]inositol phosphates. However, dose-response curves for SHR characteristically displayed a depression of the maximum response as compared with those for WKY. Baseline accumulation of [3H]inositol phosphates was not different between strains (39.4 +/- 2.2 cpm/mg tissue/hr for WKY and 34.4 +/- 2.1 cpm/mg tissue/hr for SHR slices; n = 5 rats/group, determined in triplicate). Antagonist competition studies revealed that norepinephrine-stimulated (10(-4) M) [3H]inositol phosphate accumulation was mediated by alpha 1-adrenergic receptors (IC50) for prazosin: 65 +/- 11 nM for SHR and 64 +/- 5 nM for WKY). The reduction in norepinephrine-stimulated [3H]inositol phosphate accumulation in SHR cortex was not the result of the hypertension, since it was also present in cortical slices from young (4-week-old) SHR in which the blood pressure was not yet significantly different from that in WKY and since [3H]inositol phosphate accumulation was unchanged from control values in rats made hypertensive by treatment with deoxycorticosterone acetate. Scatchard analysis of [3H]prazosin binding in renal cortical membranes of young and adult SHR and WKY revealed no significant differences in alpha 1-adrenergic receptor density or affinity between strains at either age. Our results suggest that renal alpha 1-adrenergic receptor coupling to phospholipase C is less efficient in SHR than in WKY. This impaired response is not the result of hypertension or changes in receptor density; this defect may play a role in increased renal sympathetic nerve activity and in the development or maintenance of hypertension in SHR.

Angiotensin II↗

Inhibition of renin release by alpha-adrenoceptor stimulation in the isolated perfused rat kidney.

The effect of the specific alpha 2-adrenoceptor agonist BHT 933 on stimulated renin release was investigated in the isolated perfused rat kidney preparation. Renin release was stimulated with N-ethylcarboxamide adenosine (NECA) (3 microM) a specific A2-adenosine receptor agonist. alpha 2-Adrenoceptor stimulation with BHT 933 (1 microM) attenuated the stimulation of renin release by NECA. Yohimbine (300 nM) or prazosin (28 nM) at alpha 2- and alpha 1-adrenoceptor specific concentrations respectively, blocked this inhibition of renin release by BHT 933. In all groups studied there was no significant effect of these experimental treatments on renal hemodynamics or electrolyte excretion. The ability of yohimbine or prazosin, at alpha 2- and alpha 1-adrenoceptor specific concentrations respectively, to antagonize the effects of BHT 933 suggests a lack of agonist specificity for these receptor effect as previously suggested for the mesenteric artery.

Adenosine↗

Nucleotide excision repair genes from the yeast Saccharomyces cerevisiae.

The genetics of nucleotide excision repair in the yeast Saccharomyces cerevisiae is complex, apparently requiring at least 10 genes. We have isolated 5 of these genes (designated RAD1, RAD2, RAD3, RAD4, and RAD10) by molecular cloning and plan to overexpress them in order to generate proteins for biochemical study. We have sequenced four of these five genes and have noted regions of homology with other proteins in the predicted amino acid sequence of some of them. In particular, there is striking homology between Rad3 protein and a number of prokaryotic and eukaryotic proteins that bind nucleotides and hydrolyze ATP or GTP. Mutations in this region of the RAD3 gene render cells defective in the nucleotide excision repair function. In addition to its role in nucleotide excision repair, the RAD3 gene is essential for the viability of haploid cells in the absence of DNA damage. The nature of the essential function is unknown. The RAD1 and RAD3 genes are not inducible by DNA damaging agents. However, exposure of cells to UV radiation, 4-nitroquinoline 1-oxide, or gamma radiation results in 4- to 6-fold enhanced expression of the RAD2 gene.

Amino Acid Sequence↗

Methods for determining auditory evoked brain-stem response thresholds in human newborns.

Previous investigators have reported that newborn auditory evoked brain-stem responses (ABRs) are 20-30 dB higher than adult psychophysical thresholds to the same stimuli. These investigators reduced the intensity of the stimulus until they no longer reported an ABR to the stimulus. We adapted 2 widely used psychophysical methods, the up-down-transformed response (UDTR) method and the method of constant stimuli, for ABR threshold determination of human newborns. Response judgments were made blindly. ABR thresholds of healthy normal newborns by both procedures were no more than 10-15 dB higher than adult psychophysical thresholds. The differences between the newborn ABR thresholds we reported and those in the literature were probably explained by different procedures including the method used to estimate adult psychophysical thresholds. The correlations between ABR thresholds and suprathreshold ABR latencies and amplitudes and latency and amplitude/intensity functions were modest at best. In normal newborns suprathreshold ABR measurements are of little value in predicting ABR thresholds.

Brain Stem↗

Molecular cloning and nucleotide sequence analysis of the Saccharomyces cerevisiae RAD1 gene.

We have screened a yeast genomic library for complementation of the UV sensitivity of mutants defective in the RAD1 gene and isolated a plasmid designated pNF1000 with an 8.9-kilobase insert. This multicopy plasmid quantitatively complemented the UV sensitivity of two rad1 mutants tested but did not affect the UV resistance of other rad mutants. The location of the UV resistance function in pNF1000 was determined by deletion analysis, and an internal fragment of the putative RAD1 gene was integrated into the genome of a RAD1 strain. Genetic analysis of several integrants showed that integration occurred at the chromosomal RAD1 site, demonstrating that the internal fragment was derived from the RAD1 gene. A 3.88-kilobase region of pNF1000 was sequenced and showed the presence of a small open reading frame 243 nucleotides long that is apparently unrelated to RAD1, as well as a 2,916-nucleotide larger open reading frame presumed to encode RAD1 protein. Depending on which of two possible ATG codons initiates translation, the size of the RAD1 protein is calculated at 110 or 97 kilodaltons.

Amino Acid Sequence↗

Schedule-dependent enhancement of 1-beta-D-arabinofuranosylcytosine incorporation into HL-60 DNA by deoxyguanosine.

We studied the ability of the purine deoxynucleoside deoxyguanosine (dGuo) to enhance 1-beta-D-arabinofuranosylcytosine (ara-C) incorporation into DNA of HL-60 cultured human leukemia cells. The effects of dGuo on ara-C incorporation into DNA were compared to those of thymidine (dThd), a pyrimidine deoxynucleoside known to augment ara-C effects both in vitro and in vivo. Both deoxynucleosides doubled the cells in the S phase of the cell cycle within the exposure periods (up to 48 hr) and concentrations (10 to 1000 microM) tested. Both deoxynucleosides enhanced ara-C incorporation into DNA equally. However, dThd and dGuo differed in the schedule required to achieve this effect. Simultaneous exposure of cells to ara-C and dThd increased ara-C incorporation into DNA approximately 3.5-fold. Preincubation of cells with dThd for 16 hr prior to the addition of ara-C further enhanced ara-C incorporation into DNA (to approximately 5-fold) in direct proportion to the dThd-induced increase in cells in S phase. Preincubation was essential for dGuo, since 16-hr preincubation of cells with concentrations as low as 30 microM caused augmentation of ara-C incorporation into DNA; but simultaneous exposure of cells to dGuo and ara-C caused no augmentation of ara-C incorporation into DNA. The augmentation of ara-C incorporation into DNA caused by preincubation of the cells with dGuo results from a number of factors, including the cytokinetic effect of increasing the percentage of cells in S phase and the reduction of intracellular dCTP pools. Maximal dGuo enhancement of ara-C incorporation into DNA (approximately 5-fold) required greater than 100 microM dGuo, 16-hr preincubation with dGuo, and final incubation of cells with ara-C after removal of dGuo. We explain this further augmentation of ara-C incorporation into DNA caused by the removal of dGuo prior to adding ara-C by our observed inhibition of ara-C phosphorylation by dGuo concentrations greater than 100 microM.

Cell Line↗

Neuromuscular blocking effects of tobramycin, gentamicin, and cefazolin.

Forty patients (A.S.A. class I or II), 18 to 75 years of age, who were undergoing elective surgery were studied to determine the clinical and subclinical neuromuscular blocking effects of two antibiotics, tobramycin and gentamicin and to compare these effects with those produced by cefazolin, an aminoglycoside not known to produce paralysis. Patients were prospectively and randomly assigned in approximately equal numbers to one of four groups: group A received 1 mg/kg of tobramycin; group B, 1 mg/kg of gentamicin; group C, 500 mg of cefazolin; or group D, control (no antibiotic). Antibiotics were administered intravenously 45 minutes immediately preceding the study. The ulnar nerve was stimulated supramaximally and neuromuscular function was measured electromyographically. Anesthesia was induced with thiopental, 4 mg/kg IV, and maintained with endotracheal enflurane 1.0% to 1.5% (inspired) and N2O-O2 (2 L:1 L) after intubation. Succinylcholine (1 mg/kg) was administered after induction of anesthesia and the magnitude and duration of neuromuscular block monitored. d-Tubocurarine (0.1 mg/kg) was given 5 to 10 minutes after full recovery from succinylcholine and repeated as required. At the end of the operation, atropine, 0.02 mg/kg, and neostigmine, 0.4 mg/kg, were used to reverse the block. Base line neuromuscular data, duration of block of succinylcholine, and potency, duration of block, recovery rate, train-of-four fade, tetanic trend, response to double stimuli, post-tetanic effect, and reversibility of the subsequent d--tubocurarine-induced neuromuscular block were not significantly different (p less than 0.01) between any two groups. Tobramycin, gentamicin, and cefazolin, in recommended single doses, lack clinical neuromuscular blocking and subclinical relaxant-potentiating effects.

Adolescent↗

Constrictive effect of pancuronium on capacitance vessels.

The effects of pancuronium 0.08 mg kg-1, metocurine 0.4 mg kg-1 and tubocurarine 0.4 mg kg-1 on vascular tone were studied in 26 patients undergoing open heart surgery during total cardiopulmonary bypass. With a fixed rate of perfusion, arterial pressure is related directly to total peripheral resistance, while the volume of blood remaining in the extracorporeal reservoir is related inversely to vascular capacity, which depends primarily on venous tone. Pancuronium increased the reservoir volume (average of 780 +/- SEM 250 ml (P less than 0.01). We conclude that under certain circumstances pancuronium constricts capacitance vessels in man.

Adult↗

Predetermination of dose requirement of pancuronium.

The neuromuscular sensitivity of 71 patients (A.S.A. class I or II) was tested by scoring on a scale from 1 to 6 the ability to lift the upper eyelid 2 minutes after pretreatment with 1 mg of pancuronium. Subsequently, each patient also received an additional "intubation dose" pancuronium (in milligrams) equal to the eye-opening test score (group I), or either 1 mg (group II) or 2 mg (group III) in excess. The resultant depression of the neurally evoked muscle response of the little finger was quantified by another score (the response score) which allowed for assessment of neuromuscular block beyond the limit of 100% depression of the twitch. The criteria for the response score, in the response score, in the order of increasing magnitude of block, were: (1) visible twitch responses to all 4 of the train-of-four stimulation remained; (2) part of the train-of-four twitches was eliminated; (3) all twitches were eliminated; (4) tetanus was eliminated; (5) post-tetanic twitch following a 5-second 50 Hz tetanus was also eliminated; and (6) not even the post-tetanic twitch became elicitable again in 30 minutes. It was found that 1 mg of pancuronium depressed the eye-opening score to 4.0 +/- 0.2, from 5.1 +/- 0.1 (mean +/- SEM, p < 0.01). Following the additional "intubation dose" of pancuronium, patients in group I had an average response score of 2.2 +/- 0.3, those in group II a score of 3.4 +/- 0.2, and those in group III, a score of 4.8 +/- 0.6. Each additional 1 mg of pancuronium (increasing from group I to III) linearly increased the average response score. In terms of frequency response, patients in group I had more than a 50% change of being scored 1, while those in group II had a greater than 50% chance of being scored 3, 4, or 5, and those in group III had more than a 50% chance of being scored 6. It is concluded that sensitivity to pancuronium can be quantified by the ptotic response to a 1-mg test dose of pancuronium, and that a sensitivity-adjusted additional "intubation dose" of pancuronium can be predetermined in individual patients.

Adult↗

Interactions of neuromuscular effects of edrophonium, alpha-bungarotoxin and beta-bungarotoxin.

Interactions of neuromuscular effects of edrophonium, alpha-bungarotoxin, and beta-bungarotoxin were studied in 12 chickens using the sciatic-gastrocnemius nerve-muscle preparation to elucidate the mechanism of action of each drug. Modification by the toxins of neuromuscular effects of edrophonium depended on the level of block pre-established by the toxins. Edrophonium-induced augmentation of muscle twitch ("facilitation") was decreased by both toxins. As the block reached 50 per cent, the facilitation was nearly abolished. Edrophonium-induced contracture of the muscle was blocked by alpha-bungarotoxin only. At 25 per cent block, it was no longer observable in five of six preparations. Beta-bungarotoxin enhanced the contracture. At complete block, the contracture reached 156 (SE 11, n = 6) per cent of control. The authors conclude that edrophonium facilitates neuromuscular transmission by a prejunctional mechanism and causes contracture of the chicken muscle by a post-junctional activation. The beta-bungarotoxin-blocked nerve-muscle preparation of the chicken is a model of acute denervation potentially useful for the study of drug effects on the postjunctional membrane.

Animals↗

Neuromuscular block by circulating D-tubocurarine residue following uptake and distribution.

Serum concentration of d-tubocurarine decreases rapidly after intravenous injection because of uptake and distribution. The circulating residue of an ED 50 dose of d-tubocurarine five minutes after injection will produce no block in a previously unexposed neuromuscular junction. To produce a 50 per cent block with the circulating d-tubocurarine residue in a previously unexposed neuromuscular junction requires an initial injection of 2.5 x ED 50 dose. Five minutes after a dose 5 to 6 times the ED 50, the plasma d-tubocurarine residue is sufficient to produce a total block.

Animals↗

Focal contracture following injection of succinylcholine in patients with peripheral nerve injury.

Focal muscle contracture in the limb following sytemic administration of depolarizing neuromuscular blocking agents have been demonstrated experimentally with transection or crush injury of the nerve, but has rarely been observed clinically in patients with partial peripheral nerve injury. Three cases of spastic response in the hand and wrist are described in patients with subclinical chronic, subacute, and acute nerve injury, to document the occurrence of this phenomenon under various circumstances.

Adult↗

Neuromuscular facilitation during train-of-four and tetanic stimulation in healthy volunteers: observations with half-refractory paired responses.

The compound electromyographic response of the thenar musculature was elicited by supramaximal stimulation of the ulnar nerve in 12 awake healthy volunteers. The half-refractory period of the neuromuscular transmission was determined. Twin stimuli separated by the half-refractory interval were repeated as a unit at 2 Hz and at 50 Hz. Thus two trains of responses, one beginning with a maximal response, the other with a half-maximal response, were obtained with each frequently of stimulation. Marked facilitation of the electromyographic response began with the train of stimulation, especially with tetanic stimulation. A secondary fade occurred occasionally. These changes were more remarkable in the train of half-refractory responses. We conclude that nerve stimulation facilitates neuromuscular transmission and deduce that the characteristic fade observed with a curariform block, rather than being an uncovered physiological phenomenon, is caused by tubocurarine and related drugs.

Action Potentials↗