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Biomedical subjects

H Edwards

Publications and source records attributed to H Edwards.

At least 37 records · Page 2Linked to original sources
PubMed1992

Continuous arteriovenous hemofiltration after cardiac operations in infants and children.

Acute renal insufficiency after cardiopulmonary bypass can lead to a significant morbidity from fluid overload and electrolyte disturbance, impede pulmonary gas exchange, and postpone weaning from mechanical ventilation. The limitations placed on free water intake result in severe restriction of nutrition while diuretic therapy causes electrolyte imbalance. Artificial renal support either in the form of peritoneal dialysis or hemodialysis may be complicated by sepsis and hemodynamic instability. We reviewed our experience with the use of continuous arteriovenous hemofiltration, an extracorporeal technique for removal of solutes, toxins, and water in critically ill patients with cardiac failure complicated by acute renal insufficiency and hemodynamic instability after cardiopulmonary bypass. Ten infants and children with renal insufficiency caused by low cardiac output had continuous arteriovenous hemofiltration instituted for indications including sepsis, volume overload, oliguria for more than 24 hours nonresponsive to diuretic therapy, and the need for hyperalimentation. All were supported by mechanical ventilation and receiving high-dose inotropic support. Arterial and venous vascular access was successfully obtained by cannulation of the femoral artery and vein in nine patients. Anticoagulation of the circuit was achieved with heparin infusion (6 to 20 micrograms/kg/hr) and monitored by measurement of activated clotting time. The continuous arteriovenous hemofiltration circuit was replaced if there was clot formation, or at 3 days after placement. Dialysis solution (Dianeal) 1.5% or 0.5% was infused as prefilter dilution. With the use of continuous arteriovenous hemofiltration, 20 to 100 m/hr of ultrafiltrate was removed, which allowed correction of hypervolemia, and caloric intake increased from 13.5 kcal/kg/day to 79.5 kcal/kg/day. Continuous arteriovenous hemofiltration was maintained between 5 hours and 8 days and was well tolerated in all patients. Serum urea and creatinine levels declined during continuous arteriovenous hemofiltration. We conclude that continuous arteriovenous hemofiltration is a safe and effective method for fluid and electrolyte homeostasis and that it thus allows hyperalimentation in infants and children after cardiac operations.

Acute Kidney Injury↗
PubMed1991

An Escherichia coli tyrosine transfer RNA is a leucine-specific transfer RNA in the yeast Saccharomyces cerevisiae.

While the Escherichia coli Su-3 (tyrT) tyrosine tRNA suppressor inserts only tyrosine at amber codons in E. coli, we show here that in Saccharomyces cerevisiae this tRNA inserts leucine and no significant amounts of any other amino acid. Thus, the E. coli tyrosine tRNA is functionally a leucine tRNA in yeast cytoplasm. This functional identity may correlate with a structural relationship between the E. coli tyrosine and yeast leucine tRNAs, which are both members of the uncommon type II class of tRNA structures. The results raise the possibility that in evolution a tRNA may be more closely related to a tRNA of different acceptor specificity, but of the same type class, than to one with the same amino acid specificity, but of a different type class.

Alleles↗
PubMed1991

A single base pair dominates over the novel identity of an Escherichia coli tyrosine tRNA in Saccharomyces cerevisiae.

The Escherichia coli su+3 tyrosine tRNA was shown recently to be a leucine-specific tRNA in Saccharomyces cerevisiae. This finding raises the possibility that some determinants for tRNA identity in E. coli may be different in S. cerevisiae. To investigate whether the fungal system is sensitive to the major determinant for alanine acceptance in E. coli, a single G3 . U70 base pair was introduced into the acceptor helix of the su+3 tyrosine tRNA. This substitution converts the identity of the E. coli suppressor in S. cerevisiae from leucine to alanine. Thus, as in E. coli, G3 . U70 is a strong determinant for alanine acceptance that can dominate over other features in a tRNA that might be recognized by alternative charging enzymes.

Amino Acid Sequence↗
PubMed1990

A bacterial amber suppressor in Saccharomyces cerevisiae is selectively recognized by a bacterial aminoacyl-tRNA synthetase.

Little is known about the conservation of determinants for the identities of tRNAs between organisms. We showed previously that Escherichia coli tyrosine tRNA synthetase can charge the Saccharomyces cerevisiae mitochondrial tyrosine tRNA in vivo, even though there are substantial sequence differences between the yeast mitochondrial and bacterial tRNAs. The S. cerevisiae cytoplasmic tyrosine tRNA differs in sequence from both its yeast mitochondrial and E. coli counterparts. To test whether the yeast cytoplasmic tyrosyl-tRNA synthetase recognizes the E. coli tRNA, we expressed various amounts of an E. coli tyrosine tRNA amber suppressor in S. cerevisiae. The bacterial tRNA did not suppress any of three yeast amber alleles, suggesting that the yeast enzymes retain high specificity in vivo for their homologous tRNAs. Moreover, the nucleotides in the sequence of the E. coli suppressor that are not shared with the yeast cytoplasmic tyrosine tRNA do not create determinants which are efficiently recognized by other yeast charging enzymes. Therefore, at least some of the determinants that influence in vivo recognition of the tyrosine tRNA are specific to the cell compartment and organism. In contrast, expression of the cognate bacterial tyrosyl-tRNA synthetase together with the bacterial suppressor tRNA led to suppression of all three amber alleles. The bacterial enzyme recognized its substrate in vivo, even when the amount of bacterial tRNA was less than about 0.05% of that of the total cytoplasmic tRNA.

Amino Acyl-tRNA Synthetases↗
PubMed1988

Haptic identification of letters using the left or right hand.

The present study investigated the effects of the use of the right and left hands on haptic identification of letters of the alphabet. Each of the 64 right-handed subjects was given three series of randomly ordered presentations of the 26 letters of the alphabet. The subjects were asked to feel each letter and name correctly each letter as quickly but as accurately as possible. Analysis showed faster identification by those subjects using their left hands on Series 1 with no hand-differences appearing on Series 2 and 3. Significant over-all improvement in identification time occurred with practice. The results were interpreted in terms of a novelty hypothesis of right-hemisphere function and an explanation of perceptual learning of letter identification.

Adolescent↗
PubMed1987

An E. coli aminoacyl-tRNA synthetase can substitute for yeast mitochondrial enzyme function in vivo.

We have investigated the function of an E. coli aminoacyl-tRNA synthetase in S. cerevisiae strains that are respiration-deficient because of a mutation or a gene disruption in the nuclear encoded gene for the mitochondrial tyrosyl-tRNA synthetase. Although the yeast mitochondrial and E. coli tyrosine tRNAs differ significantly in sequence, expression of the E. coli tyrosyl-tRNA synthetase from a gene fusion restores respiration. The fusion gene contains a presumptive sequence for mitochondrial import from the mitochondrial tyrosyl-tRNA synthetase gene fused to the E. coli coding region. The fusion protein is incorporated into mitochondria. This incorporation and the rescue of the respiratory defect require the presumptive sequence for mitochondrial import. These experiments suggest a more limited definition of the identity of a tyrosine tRNA.

Amino Acyl-tRNA Synthetases↗
PubMed1987

New assignment of the adenosine deaminase gene locus to chromosome 20q13 X 11 by study of a patient with interstitial deletion 20q.

A karyotype 46,XY,del(20)(q11 X 23q13 X 11) was found in a three year old boy with mental and growth retardation, low set ears, broad nasal bridge, and macrostomia. Adenosine deaminase (ADA) activity was reduced by about 50%, assigning the gene locus to the deleted segment. A review of the previously reported regional assignments suggests that the ADA gene is in the region of band 20q13 X 11.

Adenosine Deaminase↗
PubMed1986

Evaluation of an introductory course in neurology.

The aim of this study was to distinguish factors which may influence student perception of what constitutes a good introductory course in clinical neurology. This should lead to the development of improved teaching techniques. Previous work has shown that even those students who retain accessible knowledge of preclinical subjects, such as neuro-anatomy, find it difficult to use this in a clinical context. This study is preliminary to looking at correlations between student perception of what they like about a clinical topic and the ability to integrate clinical knowledge with pre-existing knowledge structures. The evaluation was carried out on 36 fifth year students who were taught clinical neurology in small groups concurrently with another topic, clinical decision making (CDM), by the same teacher. Neurology consistently rated at over 80% for enjoyment, interest and perceived clinical relevance. This contrasted with low ratings of less than 25% on all these parameters for CDM. An analysis of teaching methods showed that in neurology, contrasting with CDM, procedural rules were supplied for the application of preclinical knowledge at the bedside, students had an opportunity for active participation and problem solving in class, as well as frequent patient interaction. All these factors are important for student acceptance of a course, but further studies are needed to look at the interplay of preclinical knowledge and the acquisition of clinical expertise. The findings of this preliminary work may have significant implications for curriculum planners when developing introductory clinical courses.

Education, Medical↗
PubMed1983

Surgical management of subaortic stenosis.

The two most common causes for left ventricular outflow tract obstruction are discrete fibromuscular membrane (DMS) and idiopathic hypertrophic subaortic stenosis (IHSS). From 1955 to 1980, 195 patients were seen with subaortic obstruction, 50 of whom required operation. Thirty patients had excision of a subaortic membrane; 20 had resection of the hypertrophic muscular obstruction. The average preoperative gradient across the left ventricular outflow tract was 79 mm Hg. Postoperatively 40 patients were catheterized; two had gradients over 40 mm Hg, and both were in the DMS group. There were four operative and six late deaths (mean follow-up, 8.5 years), five occurring in the IHSS group (25%) and one in the DMS group (3.5%). Recurrent symptoms required reoperation in three patients with IHSS and one with DMS. Both groups benefitted from operation, but those with DMS had a better overall survival rate and fewer postoperative symptoms than those with IHSS.

Adolescent↗
PubMed1983

Thymectomy for myasthenia gravis.

Thymectomy was performed on 249 patients with myasthenia gravis between 1957 and 1981. During a follow-up period that ranged from 2 months to 24 years (mean 7.5 years), the remission rate for the entire group was 51 percent, and an additional 36 percent had improvement (87 percent benefited). In those 51 patients with thymoma, the remission rate was 37 percent, with 68 percent of the patients benefiting from operations. The remaining 198 patients fared better after the operation: 54 percent had remission and a total of 91 percent benefited. The female patients within this group had a 94 percent probability of benefit from operation. We conclude that most patients with myasthenia gravis will benefit from thymectomy, and that the improvement persists over an extended period of time in a high percentage of patients.

Adolescent↗
PubMed1983

Dental caries prevalence in children with a diet free of refined sugar.

A study of the caries and dental hygiene status of 73 children living in the Synanon community revealed a mean DMF-S score at 0.53 for the 5-10 year old group and 3.33 for the 11-17 year old group. In spite of poor oral hygiene, 53 per cent of the children were caries-free and none of the children was missing permanent teeth. The children had consumed a diet free of refined carbohydrates for five years and had received optimal fluoride supplementation since birth or joining Synanon.

Adolescent↗
PubMed1982

Novel evolutionary variation in transcription and location of two chloroplast genes.

We have found major evolutionary changes in the types of transcripts produced by specific chloroplast genes, in particular those encoding the large subunit (LS) of ribulose-1,5-bisphosphate carboxylase and a photosystem II polypeptide (PII). Two distinct patterns of LS gene transcripts are revealed by hybridizing an LS gene probe to electrophoretically separated RNA from 19 angiosperms. Most species, including pea, contain the single transcript of approximately 1.6 kb previously observed in corn, spinach and mustard. However, in mung bean and other members of the legume genera Vigna and Phaseolus, the 1.6 kb transcript represents only a minor fraction of LS transcripts, and instead, two larger LS transcripts of approximately 2.4 and 2.6 kb predominate. The PII gene produces a single transcript in pea and most other species examined, while members of the related legume genera Vigna, Phaseolus and Glycine contain two additional transcripts which are smaller in size and probably represent specific RNA breakdown products. A single species, sweet pea (Lathyrus odoratus), contains a second PII transcript which is 0.2 kb larger than the approximately 1.2 kb transcript found in all species. The LS and PII genes map to the same 5 kb region in both pea and mung bean and are transcribed off the same DNA strand. In contrast, published studies indicate that the two genes are approximately 50 kb apart and are transcribed off opposite DNA strands in five other chloroplast genomes. These differences are probably the consequence of an approximately 50 kb inversion which distinguishes the pea and mung bean genomes from those of most other angiosperms (1).

Biological Evolution↗
PubMed1982

Postoperative deterioration in muscular function.

To clarify the postoperative fatigue state, we analyzed some components of muscular function before and after surgical procedures. Eleven subjects undergoing elective surgery were studied for test periods of up to 35 days. Significant impairment of muscular functioning, particularly muscle endurance, developed postoperatively. Maximum deterioration was noted on postoperative days 8 and 9. Isometric strength was affected more than isokinetic strength. Changes in muscular functioning in two young volunteers undergoing bed rest were surprisingly similar to those observed in postoperative patients.

Adult↗
PubMed1982

Nonoperative management of a traumatic peroneal artery false aneurysm.

The standard approach to management of traumatic false aneurysms is operative. This report describes successful treatment of a traumatic peroneal artery aneurysm following a gunshot wound in a 29-year-old man by an intraluminal steel coil occlusion technique. The coil was guided through the popliteal artery and aneurysm into the distal peroneal artery via a percutaneously placed catheter: following disengagement of the coil the outflow tract of the aneurysm was occluded, and another passed and released into the proximal peroneal artery occluded the inflow tract.

Adult↗
PubMed1982

Massive perioperative polyuria.

A 25-year-old man with a spinal cord transection secondary to a gunshot wound underwent surgical repair of a perforated prepyloric ulcer on the eighth hospital day. He received 68 liters and excreted 43 liters of intravenous fluid during the perioperative period. Causes of this massive polyuria during and after the second operation are unknown, although iatrogenically induced glycosuria and natriuresis may have contributed to its severity. The problems and their management are discussed.

Adult↗