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Biomedical subjects

J Hess

Publications and source records attributed to J Hess.

At least 217 records · Page 12Linked to original sources
PubMed1990

Change in the cellular localization of alkaline phosphatase by alteration of its carboxy-terminal sequence.

Alkaline phosphatase (AP) is secreted into the medium when the carboxy-terminal 25 amino acids are replaced by the 60 amino acid carboxy-terminal signal peptide (HlyAs) of Escherichia coli haemolysin (HlyA). Secretion of the AP-HlyAs fusion protein is dependent on HlyB and HlyD but independent of SecA and SecY. The efficiency of secretion by HlyB/HlyD is decreased when AP carries its own N-terminal signal peptide. Translocation of this fusion protein into the periplasm is not observed even in the absence of HlyB/HlyD. The failure of the Sec export machinery to transport the latter protein into the periplasm seems to be due in part to the loss of the carboxy-terminal sequence of AP since even AP derivatives which do not carry the HlyA signal peptide but lack the 25 C-terminal amino acids of AP are localized in the membrane but not translocated into the periplasm.

Alkaline Phosphatase↗
PubMed1990

Subaortic obstruction: intraoperative echocardiography as an adjunct to operation.

Fourteen patients undergoing operation for subaortic obstruction (membranous obstruction in 11 patients, tunnel obstruction in 2 patients, obstruction due to reduplicated mitral valve tissue in 1 patient) were evaluated by intraoperative epicardial echocardiography. In all 9 patients with "discrete" obstruction who underwent prebypass epicardial echocardiography, the septal and lateral attachments of the lesion were correctly demonstrated. The precise extent of tunnel stenosis was seen in both patients. The lateral attachment of the membrane in 4 patients and multiple extensions in another 2 were identified by the epicardial study (having been missed on precordial echocardiography). The discrete membrane was enucleated in 10 of the 11 patients and was partially resected in 1. One tunnel obstruction was completely relieved; the other was partially relieved. Reduplicated mitral valve tissue in the remaining patient was completely resected. Epicardial imaging after bypass showed remnants of the membrane in 2 patients. Intraoperative Doppler echocardiography and color flow imaging confirmed the absence of clinically significant residual gradients (less than 20 mm Hg) in all but 1 patient with tunnel obstruction. Epicardial imaging provided excellent morphological information about obstructive lesions of the left ventricular outflow tract and enabled immediate assessment of surgical repair.

Aortic Valve Stenosis↗
PubMed1990

The assessment of juxtaposed atrial appendages by transoesophageal echocardiography.

As part of a prospective study into the diagnostic role of transoesophageal echocardiography in children with complex congenital heart disease, the atrial morphology was assessed in 62 children. Using the direct visualization of atrial appendage morphology, 58 were shown to have usual atrial arrangement, two were documented to have isomerism of the right and two isomerism of the left appendages. Of those with usual arrangement, four children were demonstrated to have left juxtaposition of the atrial appendages. Only two of these patients were identified during praecordial echocardiographic re-evaluation, and three on angiocardiographic examination. Surgical confirmation was obtained in three, and juxtaposition was excluded in the remaining cases. The transoesophageal cross-sectional imaging features of left juxtaposition of the atrial appendages are unique and readily diagnostic of this entity. They include, first, a lateral deviation of the acid-portion of the atrial septum and, second, a frontal orientation of the antero-superior portion forming the floor and the posterior wall of the junction of the right-sided atrial appendage with the venous component of the atrial cavity. The knowledge of these morphologic characteristics is important, as, otherwise, this malformation may be misinterpreted as representing an atrial septal defect. The results suggest that transoesophageal echocardiography will be the most sensitive preoperative diagnostic technique in detecting or excluding juxtaposed atrial appendages.

Adolescent↗
PubMed1990

Comparative values of the precordial and transesophageal approaches in the echocardiographic evaluation of atrial baffle function after an atrial correction procedure.

Previous methods used to assess atrial baffle function after correction of transposition of the great arteries have included precordial echocardiography and cardiac catheterization. To evaluate whether single plane transesophageal echocardiography might provide additional information, its findings were correlated with information derived from both precordial echocardiography and cardiac catheterization in 15 patients (14 Mustard procedures, 1 Senning procedure) aged 4.2 to 33 years (mean 16.3). Precordial ultrasound with combined imaging, color flow mapping and pulsed Doppler ultrasound visualized the supramitral portion of the common systemic venous atrium in every case but could identify only superior limb obstruction in three of six patients, mid-baffle obstruction in zero of two and inferior limb obstruction in zero of two patients. Transesophageal studies with use of the same range of ultrasound methods demonstrated superior limb obstruction (severe in four, mild in two) in six of six patients, mid-baffle obstruction in two of two and inferior limb obstruction in two of two patients. The entire pulmonary venous atrium was equally well interrogated by either ultrasound approach, with both identifying three cases (two mild, one moderate) of mid-pulmonary venous atrium obstruction. However, individual pulmonary vein velocity profiles could only be recorded by transesophageal pulsed Doppler ultrasound. Precordial studies identified baffle leaks (1 large, 2 small) in only three patients, whereas transesophageal studies identified 11 such baffle leaks (1 large, 10 small), which were multiple in two patients. It is concluded that transesophageal echocardiography provides a more detailed and accurate assessment of atrial baffle morphology and function than is provided by either precordial ultrasound or cardiac catheterization.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Comparative value of transthoracic and transesophageal echocardiography in the assessment of congenital abnormalities of the atrioventricular junction.

Information obtained from transthoracic and transesophageal echocardiography (two-dimensional echocardiography with spectral Doppler and color flow imaging) was compared in 17 patients with major congenital abnormalities of the atrioventricular (AV) junction (10 discordant AV connections, 1 criss-cross connection, 5 absent right connections and 1 absent left connection). The findings by either technique were correlated with findings at cardiac catheterization (12 patients) and at surgery (5 patients). In two of six patients with an absent AV connection as defined by transthoracic echocardiography, transesophageal imaging demonstrated an imperforate AV valve. In 11 of 11 patients with a discordant or criss-cross connection, assessment of AV valve and ventricular morphology (by defining the chordal attachments of both AV valves) was possible with transesophageal echocardiography (3 of 11 patients by transthoracic echocardiography); chordal straddling was detected in 1 patient and excluded in 3 others with an associated inlet ventricular septal defect. Anomalous pulmonary venous connection (one patient), atrial septal defect (three patients) and subpulmonary stenosis (five patients) were better assessed by transesophageal imaging, and atrial appendage morphology could be demonstrated in all. The transesophageal technique was less useful in demonstrating the anterior subaortic infundibulum or aortopulmonary shunt (two patients). Although systemic ventricular function could be assessed by either method with use of short-axis M-mode scans, transesophageal pulsed Doppler interrogation of AV valve and pulmonary venous flow patterns provided clues to diastolic dysfunction of the systemic ventricle.

Adolescent↗
PubMed1990

Transesophageal echocardiography in children with congenital heart disease: an initial experience.

Transesophageal echocardiography with a single plane (transverse axis), dedicated pediatric probe was performed prospectively in 25 anesthetized children undergoing routine cardiac catheterization or intracardiac surgery, to assess the potential role of this technique in the initial diagnosis, perioperative management and postoperative follow-up of children with congenital heart disease. The group ranged in age from 1 year to 14.8 years (mean 6.1) and weight from 6.5 to 52 kg (mean 22.4). Studies were successful in all patients and no complications were encountered. The results of the transesophageal studies (combined imaging, color flow mapping and pulsed wave Doppler sampling) were correlated both with the results of prior precordial studies and the information obtained at cardiac catheterization. Transesophageal echocardiography provided a more detailed evaluation of the morphology and function of systemic and pulmonary venous return, the atria, interatrial baffles, atrioventricular valves and the left ventricular outflow tract. Additional information was obtained in 15 patients (60%). Problem areas for single plane transesophageal imaging were the apical interventricular septum, the right ventricular outflow tract and the left pulmonary artery. The intraoperative use of transesophageal echocardiography allowed assessment of the surgical repair and monitoring of ventricular function and volume status while the patient was weaned from cardiopulmonary bypass. Transesophageal echocardiography in pediatric patients is of additional value in three main areas: 1) the precise morphologic diagnosis of congenital heart disease, 2) perioperative monitoring, and 3) postsurgical follow-up.

Cardiac Catheterization↗
PubMed1990

Comparative roles of intraoperative epicardial and early postoperative transthoracic echocardiography in the assessment of surgical repair of congenital heart defects.

In 94 consecutive patients undergoing surgical repair of congenital heart defects the results of intraoperative (after cardiopulmonary bypass) epicardial two-dimensional and Doppler color flow imaging were compared with those of sequential transthoracic echocardiography performed within 24 h of surgery and again before hospital discharge to define the precise role of intraoperative imaging. In 6 of 7 patients with a residual defect requiring immediate surgical revision, intraoperative imaging correctly identified the defect; spectral Doppler imaging underestimated or did not identify a residual outflow tract gradient in 17 patients. Left atrioventricular (AV) valve regurgitation after repair of complete AV septal defect was underestimated in three patients. Although intraoperative documentation of good ventricular function was usually associated with a good outcome, in three patients poor systemic ventricular function after cardiopulmonary bypass was not associated with early mortality. A minor degree of shunting around the patch was a common finding on epicardial and early postoperative imaging and persisted at the time of hospital discharge in 17 of 46 patients who had undergone patch closure of a ventricular septal defect as part of the surgical procedure. Additional trabecular septal defects were missed on color flow imaging after cardiopulmonary bypass in three patients, one of whom required subsequent reoperation. Although intraoperative two-dimensional and color flow imaging permitted the recognition of the majority of residual defects requiring immediate revision, residual outflow obstruction or AV valve regurgitation was usually underestimated.

Child↗
PubMed1990

Respiratory infections and vascular rings.

Recurrent respiratory infections after the first years of life are not easily related to vascular rings as the cause of these infections. Therefore six cases of older children are presented in whom a vascular ring was the cause of their respiratory problems. None of them ever had stridor or swallowing problems in early infancy, and recurrent respiratory infections occurred later in life as a symptom of a vascular ring. Unfamiliarity with this association caused a delay in diagnosis and treatment in two patients and persistent lung damage in one child. Five of the 6 children recovered well after operation. The diagnosis can be made at an early stage if close inspection of the outline of the trachea on the chest radiograph shows an impression from the right side.

Aorta↗
PubMed1990

Streptokinase treatment for femoral artery thrombosis after arterial cardiac catheterisation in infants and children.

Data on 205 children who underwent retrograde arterial catheterisation were studied to assess the frequency of femoral artery thrombosis and the safety and efficacy of systemic streptokinase treatment for this complication. In 29 (14%) a transarterial balloon dilatation was performed. In 15 (7.3%) patients impaired arterial perfusion due to vascular spasm with or without thrombus formation was seen in the cannulated leg after catheterisation. Despite heparinisation, signs of impaired arterial circulation persisted in nine patients (4.4% of the total). In these patients femoral artery thrombosis was strongly suspected. Six (53%) of these had undergone a balloon dilatation. Therefore in this study the risk of femoral artery thrombosis developing was 12 times greater after transarterial balloon dilatation than after arterial catheterisation without dilatation (20.6% v 1.7%). Systemic infusion of streptokinase was started in all patients with femoral artery thrombosis. Arterial perfusion became normal in all patients, though in one this was delayed. Haematological monitoring showed lengthening of the thrombin time and a decrease of the fibrinogen concentration during streptokinase treatment. There were no serious complications. Systemic infusion of streptokinase is a safe and useful treatment in children with persistent femoral artery thrombosis after arterial cardiac catheterisation.

Cardiac Catheterization↗
PubMed1989

Complete atrioventricular dissociation and His bundle tachycardia in a newborn: problems in prenatal diagnosis and postnatal management.

A newborn infant with complete atrioventricular dissociation and infranodal tachycardia, detected at 33 weeks gestation by fetal echocardiography, is described. In the perinatal period, infra or juxta-nodal tachycardia was noted, compromising the hemodynamic state of the newborn. A combination of flecainide and propranolol terminated the arrhythmia.

Atrioventricular Node↗
PubMed1989

Calcium-imaging with Fura-2 in isolated cerebral microvessels.

Cerebral microvessels were isolated from rat hippocampus with a modified, mild collagenase digestion and loaded with the calcium fluoroprobe, Fura-2. Using a fluorescence microscope with quartz optics and an image analyser, it was possible to measure the intracellular concentration of free calcium ions [Ca2+]i in single microvessels for the first time. A resting level of (90 +/- 28) nmol/l (+/- SD, n = 24) was calculated which immediately rose after ionomycin application. The temporal resolution for [Ca2+]i of our set-up was 0.7 s. By image processing, sequences of digitized fluorescence images of single microvessels were colour-coded in terms of [Ca2+]i with a spatial resolution up to 1.5 microns (pixel size). Both the temporal and spatial resolution make our system suitable for investigation of calcium-mobilizing receptors of the blood-brain barrier.

Animals↗
PubMed1989

The visna virus long terminal repeat directs expression of a reporter gene in activated macrophages, lymphocytes, and the central nervous systems of transgenic mice.

Visna virus is a lentivirus which causes a slow progressive disease involving the immune system and the central nervous system. To determine the role of the viral long terminal repeat (LTR) in targeting the virus to specific host cells and tissues, transgenic mice were constructed which contained the visna virus LTR directing expression of the bacterial gene encoding chloramphenicol acetyltransferase (CAT). Analysis of the transgenic mouse tissues for CAT activity revealed that the viral LTR was responsible, in part, for the tropism of visna virus for macrophages and the central nervous system. Expression of the LTR required the macrophage to be in an activated state both in vivo and in vitro. Thioglycolate activation of peritoneal macrophages in vivo and 12-O-tetradecanoylphorbol 13-acetate treatment in vitro induced expression of the visna virus LTR. Lymphocytes from the spleens of the transgenic mice expressed CAT activity, suggesting that visna virus was able to replicate in lymphocytes, as did human immunodeficiency virus and simian immunodeficiency virus. These studies demonstrated that the lentivirus LTR was responsible, in part, for cell and tissue tropism in vivo.

Animals↗
PubMed1989

[Morphometric studies of histologically classified chorionic villi of human placentas. 1. Placentas of eutrophic and hypotrophic full-term infants].

Occurrence of mature and immature chorionic villi was morphometrically analysed in 30 human placentae of children born on term. The following results were obtained from a method specially developed for surface determination of villus cross-section: The surface of mature villi (end or absorption villi) in children born on term with low birth weight was much smaller than that of immature villi. Total surfaces of mature and immature villi were almost equal in size as of the 25th percentile of child weight. The importance is underlined of a "transitional" class between hypotrophic and eutrophic children born on term, and a pattern of results is suggested.

Chorionic Villi↗
PubMed1988

Quantitative selected ion monitoring processing system: software and hardware for the automated collection and analysis of selected ion monitoring data acquired for use in pharmacokinetic studies.

The Quantitative Selected Ion Monitoring Processing System (QSIMPS) is a collection of software and hardware which was designed with the capacity to analyze 30,600 samples per year in support of pharmacokinetic studies. On a per sample basis, QSIMPS was designed to inject a sample into the GC, control the GC divert valve, collect selected ion monitoring data, identify the peaks for the drug and one metabolite and each compound's reference standard, fit the peaks to a relevant chromatographic model, calculate chromatographic features of merit, calculate the peak heights and ratio of the drug and its reference standard and the metabolite and its reference standard, and, using calibration data, convert the ratio to an amount of drug. On a per tray (batch) basis, QSIMPS was designed to fit all the peak height ratios from the calibration standards to either a linear equation, or a generalized nonlinear isotope dilution equation, report a statistical analysis of the fit, and, using aliquot factors, convert the measured amount of drug into concentrations. On a per project basis, QSIMPS prints reports summarizing statistical data on the calibration standards and the quality assurance samples, and prints reports presenting the concentration data as a function of, for examples, subject, drug treatment, time postdose, etc., along with other ancillary data such as subject sex, weight, species, etc. In addition, QSIMPS can fit the concentration data to a number of common pharmacokinetic model-derived equations, and report the resulting pharmacokinetic parameters along with a statistical comparison of the parameters.

Chromatography, Gas↗
PubMed1988

Frequent detection of antibodies to hepatitis B virus x-protein in acute, chronic and resolved infections.

Recombinant MS2- or beta gal fusion proteins containing parts of hepatitis B virus (HBV) HBx-, HBc-, and HBs-amino acid sequences were expressed in Escherichia coli and were used to screen 96 and 60 serum samples of HBV infected and uninfected patients, respectively, for the corresponding antibodies by immunoblotting. Antibodies against HBx were detected in 20 out of 65 sera of patients with previous resolved HBV-infection, in 3 out of 7 patients with persistent infection, and in 9 out of 24 sera of patients with acute HBV infection. The specificity of the immune reaction was confirmed by competition experiments with MS2- and beta gal-HBx fusion proteins, and by the lack of HBx antibodies in the sera of uninfected patients. Hbs and HBc antibodies were detected less frequently by immunoblotting with recombinant fusion proteins than by a commercial immunoassay. Our results indicate that HBx antibodies are induced early and frequently during HBV infection suggesting that the HBx protein is an early antigenic protein expressed in vivo.

Cloning, Molecular↗
PubMed1988

Characterization of a sequence (hlyR) which enhances synthesis and secretion of hemolysin in Escherichia coli.

A sequence (hlyR) of about 600 bp which enhances the expression of hemolysin (HlyA) more than 50-fold was identified in the plasmid pHly152-specific hemolysin (hly) determinant. Deletion of this entire hlyR sequence led to the same low level of hemolysin synthesis and excretion as that expressed by the recombinant plasmid pANN202-312. HlyR was active in cis but its activity was orientation-dependent. The enhancing sequence, hlyR, is separated from the promoter phlyI transcribing hlyC, hlyA and possibly hlyB by more than 1.5 kb including an IS2 element. Stepwise removal of the hlyR sequence from its 5' end by exonuclease III (ExoIII) digestion yielded several types of deletion mutants which expressed decreasing amounts of hemolysin. A similar observation was made when hlyR was shortened by ExoIII from its 3' end, which suggests that more than one functional region may be present in the hlyR sequence. A deletion of 717 bp within the adjacent IS2 element reduced the activity of hlyR only slightly, indicating that IS2 is not directly involved in the enhancement mechanism but that it may support an optimal positioning in hlyR relative to the hly promoter. The nucleotide sequence of hlyR is rich in A + T and does not contain an extended open reading frame, but exhibits several sequence motives that may represent sites for protein binding and DNA bending.

Base Sequence↗