Biomedical subjects

H Stam

Publications and source records attributed to H Stam.

At least 37 records · Page 2Linked to original sources

PubMed1996

Kinetics of mRNA and protein synthesis of genes controlled by the 1,4-beta-endoxylanase A promoter in controlled fermentations of Aspergillus awamori.

In this study, induction and repression kinetics of the expression of the Aspergillus awamori 1,4-beta-endoxylanase A (exlA) gene under defined physiological conditions was analyzed at the mRNA and the protein levels. Induction was analyzed by pulsing D-xylose to a sucrose-limited continuous culture of an A. awamori 1,4-beta-endoxylanase A (EXLA)-overproducing strain. Directly after the D-xylose pulse, exIA mRNA was synthesized, and it reached a constant maximal level after 45 to 60 min. This level was maintained as long as D-xylose was present. The kinetics of mRNA synthesis of the genes encoding Thermomyces lanuginosa lipase (lplA) and Escherichia coli beta-glucuronidase (uidA), which were also under the control of the exlA promoter, were similar to those observed for exlA mRNA. The repression of exlA expression was analyzed by pulsing D-glucose to a D-xylose-limited continuous culture. Immediately after the glucose pulse, the exlA mRNA level declined rapidly, with a half-life of approximately 20 to 30 min, and it reached a minimal level after 60 to 90 min. The time span between mRNA synthesis and the secretion of proteins was determined for EXLA and lipase. In both cases, mRNA became visible after approximately 7.5 min. After 1 h, both proteins became detectable in the medium but the rate of secretion of EXLA was faster than that of lipase.

Aspergillus↗

PubMed1995

A novel strategy for the isolation of defined pyrG mutants and the development of a site-specific integration system for Aspergillus awamori.

A homologous gene transfer system for Aspergillus awamori for site-specific integration is described, based on two components. First, a defined A. awamori pyrG mutant strain constructed by a selection strategy for gene-replacement in fungi. Second, a vector with a homologous pyrG selection marker containing a defined mutation at a site different from that of the mutations in the pyrG gene of the defined mutant strain. Defined mutation in the A. awamori pyrG gene, isolated from a genomic library by heterologous hybridisation with the A. niger pyrG gene as a probe, were introduced by specifically altering sequences at restriction sites in the coding region of the gene. After transformation of the A. awamori wild-type strain with vectors containing these mutated pyrG genes, and selection for 5-fluoro-orotic acid resistance (5-FOAR), on the average 60% of the 5-FOAR colonies originated from replacement of the wild-type pyrG gene by the mutated pyrG allele. After transformation of a mutant strain, carrying a mutation near the 5' end of the pyrG gene with vectors containing a mutation near the 3' end of the pyrG gene, 35% of the resulting transformants contained one copy of the vector at the pyrG locus.

Amino Acid Sequence↗

PubMed1995

Cloning, sequence and expression of the gene coding for rhamnogalacturonase of Aspergillus aculeatus; a novel pectinolytic enzyme.

Rhamnogalacturonase was purified from culture filtrate of Aspergillus aculeatus after growth in medium with sugar-beet pulp as carbon source. Purified protein was used to raise antibodies in mice and with the antiserum obtained a gene coding for rhamnogalacturonase (rhgA) was isolated from a lambda cDNA expression library. The cloned rhgA gene has an open-reading frame of 1320 base pairs encoding a protein of 440 amino acids with a predicted molecular mass of 45 962 Da. The protein contains a potential signal peptidase cleavage site behind Gly-18 and three potential sites for N-glycosylation. Limited homology with A. niger polygalacturonase amino acid sequences is found. A genomic clone of rhgA was isolated from a recombinant phage lambda genomic library. Comparison of the genomic and cDNA sequences revealed that the coding region of the gene is interrupted by three introns. Furthermore, amino acid sequences of four different peptides, derived from purified A. aculeatus rhamnogalacturonase, were also found in the deduced amino acid sequence of rhgA. A. aculeatus strains overexpressing rhamnogalacturonase were obtained by cotransformation using either the A. niger pyrA gene or the A. aculeatus pyrA gene as selection marker. For expression of rhamnogalacturonase in A. awamori the A. awamori pyrA gene was used as selection marker. Degradation patterns of modified hairy regions, determined by HPLC, show the recombinant rhamnogalacturonase to be active, and the enzyme was found to have a positive effect in the apple hot-mash liquefaction process.

Amino Acid Sequence↗

PubMed1995

Can one patient record accommodate the diversity of specialized care?

Despite a quarter century of developments, few specialists directly use a computerized patient record, that fully replaces the paper chart. Because of the diversity of domains in specialized care, medical decision-making and the continuity of care may suffer from scattering of patient data over various records. The challenge was to develop a computerized patient record, that would be versatile enough to tailor it to specific needs, while keeping it uniform enough to permit physicians to share data on the same patient. In our CPR, the key that reconciles versatility with uniformity lies in the design of the data model. The CPR consists of a mother record with specialized sub-records, that all share the same data model. A physician can enlarge his scope for decision-making by consulting other specialized records on the same patient or by viewing the combined information of all sub-records without the need to convert data or to familiarize himself with different interfaces.

Humans↗

PubMed1995

ARIS: integrating multi-source data for research in andrology.

Although the concept of distributed systems for the storage of patient data is more and more commonly accepted, for some considerable time yet most patient data will be stored in centralized rather than departmental systems. An important advantage of storage in a central system is hospital-wide access to much of the patient data. Disadvantages are however that these data cannot be reviewed through one user interface, and that the structure of the data does not lend itself to exploitation for other purposes. We describe the implementation of an Andrology Research Information System in which these data are integrated in a well-structured database facilitating multiple views on the patient data through a graphical user interface, and clinical research, quality control and summary reports. The data can be analyzed directly using the Hermes workstation. In this way the strengths of the centralized system are combined with those of the dedicated ARIS system.

Computer Graphics↗

PubMed1995

A multi-strategy approach for medical records of specialists.

Despite a number of well recognized shortcomings of paper medical records, the use of Computer Patient Records (CPR) is not widespread among specialists. The complexity of specialized care combined with the diversity of their domains of expertise make it a challenge to design a CPR that satisfies the needs of a specialist. Ideally, CPRs are tailored to the specific tasks of each user, yet general enough to permit the exchange and sharing of information. The basic philosophy behind our CPR is a "mother" record, extended with specialized sub-records. Two different types of subrecords are discussed: one to accommodate standardized data entry in the context of a specialty or research protocol, and another for structured recording of accidental findings outside one's own domain of expertise. The CPR does not impose structured data entry on the physician, but stimulates her to do so by confronting her with the benefits of a structured CPR.

Medical Records↗

PubMed1995

Computer-based patient record with a cardiologic extension.

Shortcomings of Paper Medical Records have been well recognized: limited readability, completeness, consistency, availability, structure, etc. Although electronic storage solves the problems of availability and legibility, data analysis and decision support require more than free text in electronic form. Although many information systems contain diagnoses and lab data in coded form, findings have often been left to free text. Even though the shortcomings of paper records are more pronounced in specialized care than in primary care, Dutch general practitioners have proven far more receptive to the use of computerized records. Specialists are very diverse in their domains of expertise and usually work in a complex environment: no single record would satisfy them all. Our objective is to support the specialist with the acquisition of patient data in a structured format with emphasis on history and physical exam. Important considerations have been that it will benefit physician and patient if record data can be shared, and that every specialist can record both data within, as well as outside, his domain of expertise. The philosophy of our Computer-based Patient Record model is based on two main principles: 1) A 'mother' record that can be extended with specialized subrecords. 2) A structure that supports flexible retrieval, efficient data entry and data analysis. The mother record contains information that all records have in common, but also offers the option of entering information, which has not been modeled in a subrecord. The 'face' of the mother record is the patient profile which offers the physician an overview of the status of the patient on any specified date. The profile includes diagnoses, medication, test results, and dates of previous visits. From this overview, the physician can directly access the subrecords, zoom in on data, or call another view. To avoid abrupt change in the daily routine of the physician, the interface allows the user to keep records in a rather conventional way, i.e., as free text. Yet, the interface constantly brings to attention the benefits of structured data, which will stimulate the physician to enter the data in a structured way; when most fields in the patient profile are empty, such as medication and past history, he may regret to have only entered free text in a 'summary' field. The mother record and a specialized record for the out-patient clinic of cardiac failure have been developed with the Department of Internal Medicine and the Thorax Centre of the Academic Hospital Rotterdam. The demonstration will show the versatility of both records. The application runs on a Unix platform with the use of an Interbase DBMS, OSF-Motif windows, and the Hermes kernel.

Cardiology Service, Hospital↗

PubMed1994

Diffusing capacity dependent on lung volume and age in normal subjects.

In this study we determined reference values of total diffusing capacity of carbon monoxide (DLCO) and DLCO per liter alveolar volume (DLCO/VA) at total lung capacity (TLC) and at lung volumes below TLC in sitting position. In 55 healthy nonsmoking volunteers (20-85 yr old), we determined reference values at TLC level in which age was the only parameter. In a subgroup (n = 16) these references did not change by correction for normal variability in hemoglobin concentration. In all volunteers DLCO decreased and DLCO/VA increased with decreasing VA. The increase in DLCO/VA was linear and less in older subjects. We derived equations to calculate reference values of DLCO/VA for lung volumes at and below TLC with two methods: 1) "random coefficients linear" model, which calculates the reference values directly, and 2) a conversion method, which calculates DLCO/VA for lower VA levels from reference values at TLC. An advantage of the conversion method is the suitability of DLCO/VA reference values at TLC of other populations. A disadvantage is the greater standard deviation of these reference values compared with those obtained by the random coefficients linear method. DLCO can be found by multiplying DLCO/VA with VA.

Adult↗

PubMed1994

A powerful macro-model for the computer patient record.

Especially in the Netherlands, the introduction of computer patient records (CPRs) in primary care has been relatively successful. Specialists usually maintain more extensive records than general practitioners and it has proven to be a great challenge to design a CPR that is useful and practical for specialized care. In this paper, we present the design of a CPR for use by specialists in an out-patient clinic. The philosophy underlying the design is that specialists may keep record in a relatively conventional way, while, at the same time, the system motivates them to add structure to their data. Data can be presented in various views, each suitable for one or more specific tasks. The potential to benefit from these views depends on the degree of structure in the recorded data. Since a CPR has to be faithful and permanent, explicit representation of observations, insights, and evolution of insight is also supported. The CPR system is in a final stage of implementation and will be evaluated in a clinical setting in summer 1994.

Computer Systems↗

PubMed1993

Diclofenac for pain relief after arthroscopy: a comparison of early and delayed treatment.

The effect of diclofenac on pain after arthroscopy of the knee joint was investigated in 64 patients. The aim of this double-blind, placebo-controlled, randomised study was to compare administration before surgery with delayed treatment. The effect on postoperative pain was evaluated by means of a Visual Analogue Scale and recording of the need for additional analgesics postoperatively. After surgery, hourly assessments were performed within 6 h after the anaesthetic block (approximately 5 h after start of surgery), and on the morning after surgery. Both treatment with diclofenac before surgery and delayed treatment were superior to placebo concerning pain scores within 6 h after onset of anaesthesia (P < 0.0065 and P < 0.0005, respectively). On the morning after surgery, only delayed treatment was superior to placebo (P < 0.02). No differences in pain scores were evident between the different groups treated with diclofenac. No differences in the need for additional analgesics were found.

Arthroscopy↗

PubMed1992

Lipid metabolism of myocardial endothelial cells.

The vascular endothelium can be regarded as a widely distributed organ, interposed between the intravascular and extravascular spaces, with a pluripotent function in the regulation of capillary diameter, vascular homeostasis, lipoprotein metabolism and the vascular response to injury. In the basal physiological state these processes provide a non-thrombotic, non-inflammatory vascular lining preventing uncontrolled inflammation and coagulation. Endothelial cells respond to potential harmful conditions (mechanical stress, anoxia, ischemia and oxidative stress) and a variety of hormones and vasoactive mediators by inducing coagulation and production of inflammatory mediators through the production of 'bioactive' lipids. Although the number of studies in isolated myocardial endothelial cells is limited, from the presumed metabolic analogy with endothelial cells isolated (and cultured) from other organs, one may conclude that the bioactive lipids include oxygenated arachidonate metabolites (eicosanoids) and the platelet activating factor (1--O-alkyl-2-acetyl-sn-glycerol-3-phosphocholine; PAF). All aspects of lipid metabolism, related to the production of eicosanoids and PAF, are present within myocardial endothelial cells. There is uptake and incorporation of fatty acids by endothelial cells and liberation from endogenous triacylglycerol and (membrane) phospholipid stores by (phospho)lipases. Endothelial cells oxidize fatty acids in a carnitine-dependent, mitochondrial, pathway. Endothelial cells actively interact with high density lipoprotein (HDL) and low density lipoprotein (LDL) leading to uptake of cholesterol(esters) that undergo intracellular hydrolysis, and re-esterification to phospho- and neutral lipids, and leaving the LDL-particle modified in a way that makes them bind to the scavenger receptor on macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Interscalene plexus block for arthroscopy of the humero-scapular joint.

Interscalene plexus block was performed in nine patients subjected to shoulder arthroscopy. The operating conditions, including muscle relaxation, were fully adequate in all patients (after additional local anaesthesia of the skin in four patients). With the exception of one patient who experienced temporary hoarseness (probably due to a concomitant block of the recurrent laryngeal nerve), no side effects were found and the patients tolerated the surgical procedure well. Interscalene block might be a suitable alternative to general anaesthesia for shoulder arthroscopy. However, additional local anaesthesia at the site where the arthroscope is to be inserted is frequently required.

Adult↗

PubMed1991

Effect of lung volume and positional changes on pulmonary diffusing capacity and its components.

Normal subjects have a larger diffusing capacity normalized per liter alveolar volume (DL/VA) in the supine than in the sitting position. Body position changes total lung diffusing capacity (DL), DL/VA, membrane conductance (Dm), and effective pulmonary capillary blood volume (Qc) as a function of alveolar volume (VA). These functions were studied in 37 healthy volunteers. DL/VA vs. VA yields a linear relationship in sitting as well as in supine position. Both have a negative slope but usually do not run parallel. In normal subjects up to 50 yr old DL/VA and DL increased significantly when subjects moved from a sitting to a supine posture at volumes between 50 and 100% of total lung capacity (TLC). In subjects greater than 50 yr old the responses of DL/VA and DL to change in body position were not significant at TLC. Functional residual capacity (FRC) decreases and DL/VA increases in all normal subjects when they change position from sitting to supine. When DL/VA increases more than predicted from the DL/VA vs. VA relationship in a sitting position, we may infer an increase in effective Qc in the supine position. In 56% of the volunteers, supine DL was smaller than sitting DL despite a higher DL/VA at FRC in the supine position because of the relatively larger decrease in FRC. When the positional response at TLC is studied, an estimation obtained accidentally at a volume lower than TLC may influence results. Above 80% of TLC, Dm decreased significantly from sitting to supine. Below this lung volume the decrease was not significant. The relationship between Qc and VA was best described by a second-order polynomial characterized by a maximum Qc at a VA greater than 60% of TLC. Qc was significantly higher in the supine position than in the sitting position, but the difference became smaller with increasing age. In observing the sitting and supine positions, we saw a decrease in maximum Qc normalized per square meter of body surface area with age.

Adolescent↗

PubMed1991

Effects of PEEP on respiratory mechanics in patients with COPD on mechanical ventilation.

We studied the effects of positive end-expiratory pressure (PEEP) applied by the ventilator on respiratory mechanics in ventilated patients with chronic obstructive pulmonary disease (COPD). Airway pressures, relaxed expiratory flow-volume curves and end-expiratory volumes (EEV) were measured. In all patients investigated without PEEP applied by the ventilator, an intrinsic PEEP level (PEEPi) and a concavity in the flow-volume curve was present. Ventilator-PEEP caused a significant decrease in PEEPi in all patients (p less than 0.01). In patients in whom ventilator-PEEP exceeded PEEPi, significant increases occurred in airway pressures and EEV (p less than 0.05) and moreover the shape of the flow-volume curve was changing. In patients in whom the level of ventilator-PEEP was below the PEEPi level, no significant changes in airway pressures, EEV or flow-volume curves were found. We conclude: 1) PEEP applied by the ventilator can reduce PEEPi in ventilated patients with COPD without significant changes in airway pressures, EEV or flow-volume curves. 2) Expiratory flow-volume curves can be used to estimate the effects of ventilator-PEEP on EEV.

Aged↗

PubMed1990

Hormonal control of cardiac lipolysis by glyco(geno)lysis.

The importance of the glucose/fatty acid cycle in the control of cardiac lipolysis is emphasized by the following observations. Addition of the glycogen debranching inhibitor deoxynojirimycin or an O2-vehicle, fluorocarbon F-43, to media perfusing paced, lipid-enriched, Langendorff hearts lower cardiac lactate and glycerol 3-phosphate levels together with inhibition of glucagon-stimulated glycerol (and lactate) release. The absence of fluorocarbon during perfusion of 5 Hz paced langendorff hearts probably results in limited tissue oxygenation, resulting in glycogenolysis and lipolysis. The results indicate hormonal control of cardiac lipolysis by glyco(geno)lysis.

1-Deoxynojirimycin↗

PubMed1990

Properties of phosphatidate phosphohydrolase and diacylglycerol acyltransferase activities in the isolated rat heart. Effect of glucagon, ischaemia and diabetes.

Myocardial triacylglycerol hydrolysis is subject to product inhibition. After hydrolysis of endogenous triacylglycerols, the main proportion of the liberated fatty acids is re-esterified to triacylglycerol, indicating the importance of fatty acid re-esterification in the regulation of myocardial triacylglycerol homoeostasis. Therefore, we characterized phosphatidate phosphohydrolase (PAP) and diacylglycerol acyltransferase (DGAT) activities, enzymes catalysing the final steps in the re-esterification of fatty acids to triacylglycerols in the isolated rat heart. The PAP activity was mainly recovered in the microsomal and soluble cell fractions, with an apparent Km of 0.14 mM for both the microsomal and the soluble enzyme. PAP was stimulated by Mg2+ and oleic acid. Oleic acid, like a high concentration of KCl, stimulated the translocation of PAP activity from the soluble to the particulate (microsomal) fraction. Myocardial DGAT had an apparent Km of 3.8 microM and was predominantly recovered in the particulate (microsomal) fraction. Both enzyme activities were significantly increased after acute streptozotocin-induced diabetes, PAP from 15.6 +/- 1.1 to 28.1 +/- 3.6 m-units/g wet wt. (P less than 0.01) and DGAT from 2.23 +/- 0.11 to 3.01 +/- 0.11 m-units/g wet wt. (P less than 0.01). In contrast with diabetes, low-flow ischaemia during 30 min did not affect PAP and DGAT activity in rat hearts. Perfusion with glucagon (0.1 microM) during 30 min did not affect total PAP activity, but changed the subcellular distribution. More PAP activity was recovered in the particulate fraction. DGAT activity was lowered by glucagon treatment from 0.37 +/- 0.03 to 0.23 +/- 0.02 m-unit/mg of microsomal protein (P less than 0.05). The role of PAP and DGAT activity and PAP distribution in the myocardial glucose/fatty acid cycle is discussed.

Acyltransferases↗

PubMed1990

Design and validation of an indicator gas injector for multiple gas washout tests in mechanically ventilated patients.

A device to produce a stepwise indicator gas fraction variation to initiate a washout test in mechanically ventilated patients is described. The device, which can be used in conjunction with the commonly used Siemens-Elema series 900 ventilators, is based on simple, off-the-shelf technology. It features the simultaneous use of two indicator gases (so that the influence of diffusion processes in the gas exchange to the patient can be measured) and maintains a nearly constant FIO2 during a washout procedure. With this indicator gas injector, the transition time of the indicator gas fraction at the beginning of a washout proved to be short enough to detect ventilation inhomogeneity by visual inspection of the washout curves. Functional residual capacity measurements using this device are presented on a test lung with known volume, on healthy volunteers, and on critically ill patients.

Adolescent↗

PubMed1990

Relationship between airway obstruction, desaturation during exercise and nocturnal hypoxaemia in cystic fibrosis patients.

We measured pulmonary function, responses to exercise and oxygen saturation (So2) at rest, and also before and during sleep in 24 patients with cystic fibrosis in a varying degree of severity. The pulmonary function indices analysed were forced expiratory volume in one second (FEV1), total lung capacity (TLC), measured by body plethysmography (TLC box) and Helium dilution (TLC He), residual volume measured by body plethysmography (RV) and the amount of trapped air (TA = TLC box-TLC He). The exercise variables included symptom limited maximal oxygen uptake (Vo2max), maximum minute ventilation (VEmax) and So2, at rest in sitting position and during maximal exercise. So2 was measured by ear oximetry. The lowest mean So2 obtained in two consecutive nights over a period of 1 hour was taken as the indicator of nocturnal oxygen saturation. A high correlation existed between resting supine and sitting So2, and the degree of nocturnal hypoxaemia (0.84 and 0.76, respectively). Highly significant correlations existed also for the indices of airway obstruction, Vo2 max and lowest So2 at exercise versus the nocturnal lowest hourly mean So2. From all variables a resting So2 in the sitting position lower than 94% appeared to be most predictive of nocturnal desaturation and indicates a risk of nocturnal hypoxaemia in patients with cystic fibrosis.

Adolescent↗