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Biomedical subjects

E J Baker

Publications and source records attributed to E J Baker.

At least 73 records · Page 4Linked to original sources
PubMed1988

The cross sectional anatomy of ventricular septal defects: a reappraisal.

The cross sectional echocardiographic description of holes in the ventricular septum has been unsatisfactory, chiefly because there are so many classifications of this defect. The accurate description of the anatomy of individual defects, from cross sectional images, is more important than attempts to fit them into a preconceived classification. One hundred specimens of hearts with a ventricular septal defect were reviewed to identify those features that are of value in the interpretation of cross sectional images. Three groups of defect were identified: those which abutted the central fibrous body, those with a margin partly formed by an area of fibrous continuity between the leaflets of the aortic and pulmonary valves, and those with entirely muscular margins. Each group had features that were readily discernible in cross section. Other features of the defects seen in the cross sectional images identified defects that opened between the two ventricular inlets, defects that opened between the two subarterial outlets, and those that extended solely into the trabecular septum. The criteria for describing the anatomy of defects were established in hearts with normal connections, but they were found to be equally applicable in hearts with discordant atrioventricular connection, discordant ventriculoarterial connection, common arterial trunk, and double outlet from the morphologically right ventricle. Cross sectional imaging, by echocardiography and potentially by other techniques, provided a uniquely detailed and precise description of the morphology of ventricular septal defects.

Abnormalities, Multiple↗
PubMed1987

The pathology of balloon pulmonary valvoplasty.

The pulmonary valve was examined following balloon dilation of pulmonary valve stenosis in six children. Stenosis was due to commissural fusion in two. In these patients, cineangiography showed that the valve was slightly thickened and "domed" during systole. Balloon valvoplasty produced complete separation of fused commissures in one and partial separation in the other. Commissural splitting is likely to be the most common mechanism of relief of pulmonary stenosis by balloon dilation. Incomplete separation could account for the partial reduction of the gradient in most children treated with this technique. Four children had pulmonary valve dysplasia. Balloon valvoplasty did not produce haemodynamic improvement or morphological changes that were identifiable at the time of surgical correction. Tearing of pulmonary valve tissue and avulsion of pulmonary cusps were not seen in this series.

Adolescent↗
PubMed1986

Radionuclide measurement of right ventricular function in atrial septal defect, ventricular septal defect and complete transposition of the great arteries.

Right ventricular (RV) function was assessed in 80 patients with congenital heart disease by first-pass and gated equilibrium radionuclide angiography. In 30 patients with a ventricular septal defect (VSD) the mean RV ejection fraction (+/- standard deviation) was 64 +/- 7%. In 30 patients with a secundum atrial septal defect it was 61 +/- 9% and in 20 patients with surgically corrected complete transposition of the great arteries it was 49 +/- 13%. These values are in close agreement with values established with cineangiography for similar groups of patients. The mean ejection fraction in the group with transposition of the great arteries was significantly less than in the group with VSD (p less than 0.001). Phase analysis of the equilibrium studies showed that there was delayed RV contraction in many patients in the absence of conduction abnormalities. This delay was significantly greater in patients with atrial septal defect than in those with VSD (p less than 0.05). There was a strong correlation between size of left-to-right shunt and phase delay in patients with VSD (r = -0.72). Thus, first-pass gated radionuclide angiography provides a valid measurement of RV ejection fraction, and delayed RV contraction on phase analysis may be a sensitive index of early RV dysfunction.

Adolescent↗
PubMed1986

Balloon aortoplasty for recoarctation following the subclavian flap operation.

Transluminal balloon aortoplasty was successfully performed 7 times in 5 children between 3 and 14 months of age who had had the subclavian flap operation for coarctation of the aorta in the neonatal period. In two the balloon aortoplasty was performed twice. All recoarctations presented with upper limp hypertension and marked upper to lower limb pressure gradients. The pressure gradient decreased immediately after the procedure from 57.1 +/- 13.8 mm Hg to 17.9 +/- 15.5 mm Hg, P less than 0.001. The diameter of the recoarcted region increased from 2.67 +/- 1.0 mm to 3.85 +/- 1.23 mm, P less than 0.05. There were no complications attributable to the dilatation technique. Intermediate term success was unpredictable from the initial results or the angiographic appearance of the recoarctation. Follow-up has been for an average of 12.7 months (range 2-30 months). Four patients have pressure gradients from upper to lower limbs of 20 mm Hg or less. In one this has been achieved by repeat balloon aortoplasty. Severe restenosis has occurred in one other patient despite repeating the angioplasty. The procedure is safe and although intermediate term success cannot be predicted in all cases, we propose that balloon aortoplasty be the initial treatment of choice for recoarctation of the aorta. The place of repeating the procedure when early restenosis occurs has yet to be defined.

Angioplasty, Balloon↗
PubMed1986

Measurement of plasma disopyramide as a guide to paediatric use.

We have studied the relationship between age, daily dose, plasma concentration and clinical efficacy of disopyramide in a group of paediatric patients. Twelve children with ventricular and 3 with supraventricular arrhythmias were treated with oral disopyramide. The initial dose was 3-6 mg/kg per day. This was adjusted until a pre-dose plasma concentration greater than 2 mg/I was achieved. Seven patients were judged to have responded to the treatment on clinical criteria. No symptoms or signs of toxicity were observed. In some of the children the dose of disopyramide required to achieve a plasma concentration greater than 2 mg/l was greatly in excess of the normal adult dose. Generally the youngest children required the highest dose, but the variation was wide. The dose could not be predicted from the age, the body weight or the surface area of the patient. In children high doses of disopyramide may be needed to achieve effective plasma concentrations of the drug; such doses are not associated with adverse effects. Measurement of the plasma concentration is necessary to guard against premature termination of therapy.

Administration, Oral↗
PubMed1986

Protein synthesis is required for rapid degradation of tubulin mRNA and other deflagellation-induced RNAs in Chlamydomonas reinhardi.

After flagellar detachment in Chlamydomonas reinhardi, there is a rapid synthesis and accumulation of mRNAs for tubulin and other flagellar proteins. Maximum levels of these mRNAs (flagellar RNAs) are reached within 1 h after deflagellation, after which they are rapidly degraded to their predeflagellation levels. The degradation of alpha- and beta-tubulin RNAs was shown to be due to the shortening of their half-lives after accumulation (Baker et al., J. Cell Biol. 99:2074-2081, 1984). Deflagellation in the presence of protein synthesis inhibitors results in the accumulation of tubulin and other flagellar mRNAs by kinetics similar to those of controls. However, unlike controls, in which the accumulated mRNAs are rapidly degraded, these mRNAs are stabilized in cycloheximide. The stabilization by cycloheximide is specific for the flagellar mRNAs accumulated after deflagellation, since there is no change in the levels of flagellar mRNAs in nondeflagellated (uninduced) cells in the presence of cycloheximide. The kinetics of flagellar mRNA synthesis after deflagellation are shown to be the same in cycloheximide-treated and control cells by in vivo labeling and in vitro nuclear runoff experiments. These results show that protein synthesis is not required for the induced synthesis of flagellar mRNAs, and that all necessary transcriptional control factors are present in the cell before deflagellation, but that protein synthesis is required for the accelerated degradation of the accumulated flagellar mRNAs. Since cycloheximide prevents the induced synthesis and accumulation of flagellar proteins, it is possible that the product(s) of protein synthesis required for the accelerated decay of these mRNAs is a flagellar protein(s). The possibility that one or more flagellar proteins autoregulate the stability of the flagellar mRNAs is discussed.

Bacterial Proteins↗
PubMed1985

First-pass measurement of left ventricular function in infants and children.

The left ventricular ejection fraction was measured in 57 infants and children with congenital heart disease by both first-pass radionuclide angiography and left ventricular cineangiography. The correlation coefficient for the two sets of measurements was 0.79. In subgroups without left to right shunts (n = 21) and with left to right shunts (n = 36) it was 0.93 and 0.37, respectively. It is concluded that measurement of the left ventricular ejection fraction by the first-pass method is valid in children, provided there is no left-to-right shunt.

Adolescent↗
PubMed1985

Percutaneous balloon pulmonary valvuloplasty.

Percutaneous pulmonary valvuloplasty was performed in 27 patients with congenital pulmonary valve stenosis. A fall in the transvalve gradient of at least 15 mm Hg occurred in 22 patients. In five there was little change in the severity of the stenosis; in three of these the pulmonary valve was dysplastic. None of the successfully treated patients had a dysplastic valve. The two other failures, early in the series, were probably due to inadequate balloon size. In one patient the procedure was performed twice, with a successful result from the second dilatation with a larger balloon. Follow up studies in a further six patients showed no evidence of restenosis in those who had been successfully treated and no late improvement in the remainder. There were no important complications. Percutaneous pulmonary valvuloplasty should be the initial treatment for congenital pulmonary valve stenosis, although when the valve is dysplastic the result is less likely to be satisfactory.

Adolescent↗
PubMed1985

Superiority of radionuclide over oximetric measurement of left to right shunts.

In 100 children with suspected left to right shunts the ratio of pulmonary to systemic flow was measured both by oximetry and first pass radionuclide angiography. The pulmonary time activity curve from the radionuclide study was analysed by the method of gamma variate fits. There was strong correlation between the two techniques; weaker correlation was found when the shunt was at atrial rather than ventricular level. This difference can be explained only by problems with the oximetric rather than the radionuclide technique. Although there are important limitations to the radionuclide method, it is the more precise and less invasive of the two and is to be preferred when the accurate measurement of left to right shunts is required.

Adolescent↗
PubMed1985

Embolisation procedures in congenital heart disease.

Eight therapeutic embolisation procedures were performed by the transcutaneous catheter technique in seven patients with congenital heart disease. After surgical correction of tetralogy of Fallot (four patients), catheter embolisation was used to occlude two large aortopulmonary collaterals (one patient), three small aortopulmonary collaterals (one patient), and two Blalock-Taussig shunts (two patients). In two patients congenital coronary anomalies were occluded--a coronary arteriovenous malformation and a coronary artery/bronchial artery anastomosis. In one patient a pulmonary arteriovenous malformation was embolised. Detachable balloons were used to occlude six large arteries, the three small arteries were occluded with small gelfoam fragments, and the pulmonary arteriovenous malformation was occluded with multiple steel coils and large gelfoam pieces. Successful occlusion was achieved in all cases. No complications were encountered and the procedure was well tolerated even in the two patients receiving postoperative intensive care. Therapeutic embolisation in suitable cases is a safe and effective alternative to surgery and the detachable balloon technique is effective in occluding high flow vessels.

Adolescent↗
PubMed1984

Rapid changes in tubulin RNA synthesis and stability induced by deflagellation in Chlamydomonas.

Detachment of the flagella of Chlamydomonas induces a rapid accumulation of mRNAs for tubulin and other flagellar proteins. Measurement of the rate of alpha and beta tubulin RNA synthesis during flagellar regeneration shows that deflagellation elicits a rapid, 4-7-fold burst in tubulin RNA synthesis. The synthesis rate peaks within 10-15 min, then declines back to the predeflagellation rate. Redeflagellation of cells at times before the first flagellar regeneration is completed (and when cells have already accumulated elevated levels of tubulin RNA) induces another burst in tubulin RNA synthesis which is identical to the first in magnitude and duration. This finding indicates that the induction signal may act to simply reprogram the tubulin genes for a transient burst of maximal synthesis. Evidence is presented that the stability of the tubulin RNAs changes during regeneration. Stability changes include both an apparent stabilization during regeneration and accelerated decay following regeneration.

Chlamydomonas↗
PubMed1984

Radionuclide measurement of left ventricular ejection fraction in infants and children.

The left ventricular ejection fraction was measured in 60 infants and children with congenital heart disease by both the equilibrium gated radionuclide technique and biplane left ventricular cineangiography. The median age of the patients studied was 2.25 years, and 17 were less than 1 year old. The correlation coefficient for the two sets of measurements was good and did not deteriorate in subgroups under 1 year old and with a large left to right shunt. In those infants with a right to left shunt the correlation was weak. Equilibrium gated radionuclide angiography is a valid and clinically valuable method of measuring left ventricular function in infants and children with congenital heart disease.

Adolescent↗
PubMed1984

Balloon atrial septostomy in the neonatal intensive care unit.

In eight infants with complete transposition of the great arteries balloon atrial septostomy was performed in the neonatal intensive care unit solely under cross sectional echocardiographic control. One infant developed necrotising enterocolitis; otherwise there were no complications. This technique eliminates the need for radiographic screening during the procedure, is quick, and causes little disturbance to the infant who does not have to be removed from the incubator.

Echocardiography↗
PubMed1984

Use of radionuclide labelled microspheres to show the distribution of the pulmonary perfusion with multifocal pulmonary blood supply.

In pulmonary atresia with a ventricular septal defect and similar congenital heart disorders the pulmonary blood supply is often multifocal. The relative distribution of pulmonary perfusion from individual sources is usually demonstrated by selective angiography. A new technique using a selective injection of radionuclide labelled human albumin microspheres was performed in four patients with a complex pulmonary blood supply. In these cases the physiological distribution of each of the multiple sources of pulmonary perfusion was demonstrated. This is a useful additional technique in the assessment of such patients.

Adolescent↗
PubMed1984

Radionuclide measurement of left ventricular ejection fraction in tricuspid atresia.

In 15 patients with tricuspid atresia and one with tricuspid stenosis the left ventricular ejection fraction was measured by equilibrium gated radionuclide angiography and the results compared with those from a control group of 16 patients. The patients with tricuspid atresia had a significantly depressed ejection fraction. Those who had a surgical shunt or who had had pulmonary artery banding had significantly lower ejection fractions than the remainder. There was no significant correlation between the ejection fraction and age, the arterial oxygen saturation, or the haemoglobin concentration. Five patients were also studied during isometric exercise; three had an abnormal response. Volume overload of the ventricle is identified as one cause of the dysfunction, but other factors may be important. Radionuclide angiography offers a non-invasive method of studying ventricular function in this condition.

Adolescent↗
PubMed1983

Individual regulation of the accumulation of H1 mRNA and core histone mRNAs in sea urchin embryos.

The relative cytoplasmic accumulation of the individual histone mRNAs in sea urchins was determined by gel analysis of 3H-labeled cytoplasmic RNA isolated from embryos of the early cleavage through the mesenchyme blastula stages. A number of separate determinations showed that H1 mRNA accumulates at a molar ratio of 0.5 or less compared with each of the H2 or H3 core histone mRNAs through approximately the first 12 h of embryonic development. After this time, the accumulation of H1 mRNA increases relative to the core histone mRNAs, and approximately equimolar amounts of the histone mRNAs are produced by about the 14-h stage. The equimolar synthesis of H1 mRNA appears to be transient, returning to 0.5-molar levels several hours later. The increase in H1 mRNA accumulation, relative to the core histone RNAs, is coincident with the transition from expression of the early (alpha) sea urchin histone gene set to the late histone genes. Since all five of the early histone genes occur in a 1:1 ratio within repeating units, the data suggest that the genes within a single repeat, or their immediate products, are individually regulated. Gel analysis of the proteins synthesized in vivo by embryos demonstrates that the pattern of synthesis of the histone proteins reflects the changing ratios of the histone mRNAs.

Age Factors↗