Showing papers by "Maastricht University published in 1993"

Understanding the rationale of strategic technology partnering: Interorganizational modes of cooperation and sectoral differences

Abstract: Interfirm strategic alliances appear to have become more important as a part of (international) business. In this contribution an attempt is made to clarify our understanding of the motives that lead firms to cooperate in their innovative efforts. Going beyond general theoretical statements and case studies, attention is paid to both sectoral differences in the motivation for partnerships as well as to contrasts in interorganizational features of technology cooperation. Based on a large sample of alliances the analysis reveals some major differences regarding the research orientation of contractual arrangements and organizationally complex alliances.

On the origin of intermediate effects in clinical case recall

Abstract: In two experiments, the effects of level of medical expertise and study time on free recall of a clinical case were assessed. In Experiment 1, a nonmonotonic relationship between level of ex­ pertise and recall was found: Subjects of intermediate levels of expertise remembered more in­ formation from the case than both experts and novices. This "intermediate effect" disappeared, however, when study time was restricted. Analysis of post hoc acquired protocols ofpathophysio­ logical knowledge active during case processing suggested that this phenomenon could be at­ tributed to the nature of the pathophysiological knowledge mobilized to comprehend the case. In Experiment 2, this assumption was directly tested by priming relevant pathophysiological knowledge for either a short or a longer period, before enabling subjects to study the case briefly. Free-recall data confirmed and extended the results of Experiment 1. Again, an intermediate effect was found; this time, however, it was generated experimentally. The findings were inter­ preted in terms of qualitative differences in the nature of the knowledge structures underlying performance between novices, advanced students, and medical experts: Experts use knowledge in an encapsulated mode while comprehending a case, whereas students use elaborated knowledge. The intermediate effect in clinical case representation studies is among the best-known, stable, and hitherto un­ explained phenomena in medical expertise research. The quasi-experimental paradigm that produces this phenom­ enon is described as follows: Subjects differing in level of expertise are requested to study, for about 2 or 3 min, half a page oftext describing a patient's history, present­ ing complaint and some additional findings such as re­ sults of laboratory tests and physical examination. The text is removed, and the subjects are asked to recall every­ thing they can remember from the text. Subjects of inter­ mediate levels of expertise consistently produce more elaborate recalls than either experts (e.g., experienced physicians) or novices. This phenomenon has been dem­ onstrated under various conditions, with different cases and in different populations (Claessen & Boshuizen, 1985; Hassebrock, Bullemer, & Johnson, 1988; Muzzin, Nor­ man, Feightner, & Tugwell, 1983; Patel & Groen, 1986b). The intermediate effect has also been demon­ strated in expertise-related tasks other than text process­ ing (Grant & Marsden, 1988; Patel, Evans, & Kaufman, 1988). These findings appear to be counterintuitive. Spilich, Vesonder, Chiesi, and Voss (1979), for instance, have

Adverse reactions to influenza vaccine in elderly people: randomised double blind placebo controlled trial.

Abstract: OBJECTIVE--To assess the frequency and type of side effects after influenza vaccination in elderly people. DESIGN--Randomised double blind placebo controlled study. SETTING--15 general practices in the southern Netherlands. SUBJECTS--1806 patients aged 60 or older, of whom 904 received influenza vaccine and 902 placebo. MAIN OUTCOME MEASURES--Adverse reactions reported on postal questionnaire completed four weeks after vaccination. RESULTS--210 (23%) patients given vaccine reported one or more adverse reactions compared with 127 (14%) given placebo. The frequency of local adverse reactions were 17.5% in the vaccine group and 7.3% in the placebo group (p

Regional entrainment of atrial fibrillation studied by high-resolution mapping in open-chest dogs.

Abstract: BACKGROUND It recently has been demonstrated that during atrial fibrillation, a short and variable excitable gap exists, allowing regional control of atrial fibrillation by local stimulation. In the present study, we visualized the process of excitation during regional entrainment of atrial fibrillation by rapid pacing. METHODS AND RESULTS In six open-chest dogs, the excitation of the left atrial free wall was mapped using a spoon-shaped mapping electrode (248 points). Episodes of atrial fibrillation were induced by burst pacing (50 Hz, 2 seconds). During atrial fibrillation, the electrograms showed rapid irregular activity with a median cycle length of 98 +/- 16 ms (mean +/- SD, n = 6). Rapid pacing in the center of the mapping electrode at intervals slightly shorter or longer than the median atrial fibrillation interval resulted in regional capture of atrial fibrillation. The window of entrainment was 16 +/- 5 ms. Mapping of atrial fibrillation showed that the left atrium was activated by fibrillatory wavelets coming from different directions. During entrainment, a relatively large area with a diameter of about 4 cm was activated by uniform wave fronts propagating away from the site of stimulation. The area of entrainment was limited by intra-atrial conduction block and by collision with fibrillation waves. Regional control of atrial fibrillation was lost by pacing either too slowly or too rapidly. In the first case, retrograde invasion of the area of entrainment by fibrillatory waves resulted in depolarization of the pacing site prior to the stimulus. Pacing too rapidly caused acceleration of atrial fibrillation by induction of local intra-atrial reentry circuits with a revolution time shorter than the pacing interval. CONCLUSIONS During atrial fibrillation, an area with a diameter of about 4 cm can be entrained by local pacing. The resulting reduction in fibrillating tissue mass was not sufficient to terminate atrial fibrillation. Extension of the area of entrainment was limited by intra-atrial conduction block, whereas entrainment at a too high rate resulted in acceleration of atrial fibrillation by induction of local microreentry.

Determinants of consistent condom use by adolescents: the impact of experience of sexual intercourse

Abstract: The determinants of consistent condom use were investigated in a cross-sectional study of 1018 students 12-19 years of age from 18 Dutch secondary schools. The study was prompted by concern over the lack of acceptance of condoms on the part of young people in The Netherlands despite extensive acquired immunodeficiency syndrome (AIDS) prevention campaigns. Components of the variance in behavioral intention to use condoms included intuitive attitude regarding personal consequences 34%; self-efficacy (degree to which students considered themselves able to obtain and negotiate condom use) 12%; subjective social norms derived from parents peers and sexual partners 3%; perceived vulnerability to AIDS 2%; and perceived beliefs and behaviors of peer 2%. Adolescents with significant sexual experience (intercourse more than 5 times) were less likely than their inexperienced counterparts to respond positively to condom use as a means of avoiding transmission of AIDS. Students with extensive sexual experience were less likely to express discomfort with the idea of raising the subject of condom use with a new partner than their inexperienced peers but were likely to anticipate problems with consistent condom use with a well-known sexual partner. Those who reported consistent condom use also expressed confidence in their ability to use condoms even when drunk and to interrupt lovemaking to apply a condom. In addition consistent users were less likely to focus on the unpleasant aspects of condom use (decreased sexual stimulation messiness) and to perceive a positive social norm regarding this method of AIDS prevention. Given the finding that condoms decline in popularity as adolescents gain sexual experience behavioral skills programs that increase confidence in purchasing condoms and negotiating their use with sex partners should be implemented.

Is the gut an athletic organ? Digestion, absorption and exercise.

Abstract: Digestion is a process which takes place in resting conditions Exercise is characterised by a shift in blood flow away from the gastrointestinal (GI) tract towards the active muscle and the lungs Changes in nervous activity, in circulating hormones, peptides and metabolic end products lead to changes in GI motility, blood flow, absorption and secretion In exhausting endurance events, 30 to 50% of participants may suffer from 1 or more GI symptoms, which have often been interpreted as being a result of maldigestion, malabsorption, changes in small intestinal transit, and improper food and fluid intake Results of field and laboratory studies show that pre-exercise ingestion of foods rich in dietary fibre, fat and protein, as well as strongly hypertonic drinks, may cause upper GI symptoms such as stomach ache, vomiting and reflux or heartburn There is no evidence that the ingestion of nonhypertonic drinks during exercise induces GI distress and diarrhoea In contrast, dehydration because of insufficient fluid replacement has been shown to increase the frequency of GI symptoms Lower GI symptoms, such as intestinal cramps, diarrhoea — sometimes bloody — and urge to defecate seem to be more related to changes in gut motility and tone, as well as a secretion These symptoms are to a large extent induced by the degree of decrease in GI blood flow and the secretion of secretory substances such as vasoactive intestinal peptide, secretin and peptide-histidine-methionine Intensive exercise causes considerable reflux, delays small intestinal transit, reduces absorption and tends to increase colonic transit The latter may reduce whole gut transit time The gut is not an athletic organ in the sense that it adapts to increased exercise-induced physiological stress However, adequate training leads to a less dramatic decrease of GI blood flow at submaximal exercise intensities and is important in the prevention of GI symptoms

Two clinically distinct lacunar infarct entities? A hypothesis.

Abstract: We investigated the hypothesis that patients with one or more asymptomatic lacunar infarcts and those with only one symptomatic lacunar infarct represent two clinically distinct lacunar infarct entities.In a prospective series of 100 lacunar infarct patients, univariate and multivariate logistic regression analysis was performed on clinical features, vascular risk factors, and leukoaraiosis between patients with and without asymptomatic lacunar infarcts.Patients with asymptomatic lacunar infarcts had hypertension significantly more often (71% versus 43%; [crude] odds ratio, 3.31; 95% confidence intervals, 1.16-9.43; p < 0.05) and had leukoaraiosis significantly more often (71% versus 19%; [crude] odds ratio, 10.67; 95% confidence intervals, 3.81-32.10; p < 0.001) than those with only a symptomatic lacunar infarct. After multivariate logistic regression analysis, only leukoaraiosis was significantly associated with the presence of asymptomatic lacunar infarcts. The asymptomatic lacunar infarcts differed in...

Alcohol consumption in the European Community: uniformity and diversity in drinking patterns

Abstract: Within the European Community (EC) drinking patterns in the southern countries can be characterised by daily consumption of wine at meals, and in the northern countries by less frequent consumption of beer outside meals. Yet, as in past decades in the southern countries beer consumption and in the northern countries wine consumption strongly increased, the question is whether the distinction in drinking patterns still applies. This paper (1) describes for each country of the EC total alcohol consumption, (2) examines the frequency and the context of consumption of the new beverage type and (3) analyses whether subpopulations, defined by sex, age and educational level, differ in the adoption of the new beverage type. In all countries wine is consumed more often at meals compared to beer. Older people consume wine in greater numbers and more frequently than younger people, who consume beer in greater numbers. People of higher educational level consume the new beverage type more often compared to people of lower educational level, who consume the traditional beverage type more frequently. Finally, males and females differ less in the frequency of consumption of the new beverage type than in the frequency of the traditional beverage type.

Oxidation rates of orally ingested carbohydrates during prolonged exercise in men

Abstract: Six male volunteers exercised on a cycle ergometer at 65% of maximal work load for 120 min on six occasions while ingesting water (W) only, four doses of maltodextrin (M) [0.92, 1.85, 2.77, and 3.7...

Nuclear A-type lamins are differentially expressed in human lung cancer subtypes.

Abstract: Nuclear A-type and B-type lamin expression was investigated in the major human lung cancer subtypes: small cell lung cancer (SCLC), squamous cell carcinomas, and adenocarcinomas (both non-SCLC). Twenty-two human lung cancer cell lines and 46 fresh frozen human lung cancer specimens were examined. Expression of B-type lamins was found in all the different cell lines. A-type lamins were expressed in all non-SCLC cell lines but were absent or only weakly expressed in 14 out of 16 SCLC cell lines. The immunocytochemical results were confirmed by immunoblotting and Northern blot analyses. In sections of SCLCs and non-SCLCs, B-type lamins were found to be expressed in all tumors. However, in some non-SCLCs, particularly in adenocarcinomas, a considerable proportion of the tumor cells were negative for B-type lamins. A-type lamin expression in SCLCs was weakly positive or negative in 14 out of 15 cases. In contrast, all non-SCLCs displayed A-type lamins, but in several of these samples, both cytoplasmic and nuclear staining was observed.

Evidence for a novel angiotensin II receptor involved in angiogenesis in chick embryo chorioallantoic membrane

Abstract: Angiotensin II acts as a growth factor in the cardiovascular system and has been implicated in angiogenesis. The existence of at least two types of angiotensin II receptors, the AT1 and the AT2 receptors, has been suggested by ligand binding studies. We used three different AT receptor antagonists to study the receptor mediating angiotensin II-induced angiogenesis in the chorioallantoic membrane (CAM) of the chick embryo. Angiotensin II caused pronounced angiogenesis of pre- and postcapillary vessels of 30-40%. This response could only be blocked by adding the peptidergic AT2 antagonist CGP-42112A. The nonpeptidergic AT2 antagonist PD123319 and AT1 antagonist losartan (DuP 753) were not effective. In addition, we used radioligand binding studies with a range of ligands to define the nature of the receptor. Our results show a high density of specific single class AT receptor with a total number of binding sites of 1,190 fmol/mg protein and an affinity constant for angiotensin II of 2.7 nM. The inhibitory concentrations (IC50) for CGP-42112A, PD 123319 and losartan were 724, > 100,000, and 59,000 nM, respectively. Our studies suggest that these binding sites act as receptors for angiotensin II-induced angiogenesis. Both functional and radioligand binding studies suggest that the receptor is different from the classical mammalian AT1 and AT2 receptors.

Problem effectiveness in a course using problem-based learning

Abstract: textBackground. Problem-based learning (PBL) emphasizes active generation of learning issues by students. Both students and reachers, however, tend to worry that not all important knowledge will be acquired. To explore this question, problem effectiveness (i.e., for each problem, the degree of correspondence between student-generated learning issues and preset faculty objectives) was examined in three interdependent studies. Method. The three studies used the same participants: about 120 second-year students and 12 faculty tutors in a six-week course on normal pregnancy, delivery, and child development at the medical school of the University of Limburg in The Netherlands, 1990-91. The participants were randomly assigned to 12 tutorial groups that were each given the same 12 problems; the problems were based on 51 faculty objectives; the tutors were asked to record all learning issues generated by their groups. Study 1 addressed this question: To what degree are faculty objectives reflected by student-generated learning issues? Study 2: To what extent do students miss certain objectives, and are these objectives classifiable? Study 3: Do students generate learning issues not expected by the faculty, and are these issues relevant to course content, and finally, why do students generate these issues? To help answer these questions, the studies employed expert raters and a teacher familiar with the course content. Results. Study 1: For the set of 12 problems, the average overlap between learning issues and faculty objectives was 64.2%, with the percentages for individual problems ranging from 27.7% to 100%. Study 2: Of the 51 objectives, 30 were not identified by at least one tutorial group; these objectives were grouped into three categories; on average, each group failed to identify 7.4 objectives (15%). Study 3: Of 520 learning issues, 32 (6%) were unexpected; 15 of these were judged to be at least fairly relevant to course content; they were grouped into four categories. Conclusions. The students' learning activities covered an average of 64% of the intended course content; in addition, the students generated learning issues not expected by the faculty, and half of these issues were judged relevant to the course content. Thus, PBL seems to permit students to adapt learning activities to their own needs and interests.

Comparison of the performance of the RF cross correlation and Doppler autocorrelation technique to estimate the mean velocity of simulated ultrasound signals

Abstract: In pulsed Doppler systems the received RF (radio frequency) signal is multiplied by a quadrature reference signal and subsequently averaged over a short depth range to obtain a sample of the complex Doppler signal. The mean frequency of the sampled Doppler signal, obtained with the autocorrelation function, reflects the mean velocity of the scatterers moving through the sample volume. An alternative is to evaluate the two-dimensional cross correlation function of a short segment of the RF signals over subsequent lines, giving the mean velocity of the scatterers. Both methods of velocity estimation were applied to computer-generated RF signals with varying RF bandwidth, signal-to-noise ratio, and mean and width of the imposed velocity distribution. The length of the RF signal segment and the number of lines for velocity estimation (package length) affects the accuracy of the velocity estimate. It can be concluded that the cross correlation technique behaves superiorly especially for a low velocity dispersion. Furthermore, the standard deviation of the velocity estimate decreases for an increasing sample volume length and package length, while the performance of the conventional Doppler technique is rather independent of the length of the sample volume. The difference between both techniques decreases for a greater package length or for signals simulating a wide velocity distribution.

Mechanism and function of changes in membrane-phospholipid asymmetry in platelets and erythrocytes.

Abstract: Introduction In the two decades since it was first proposed by Hretscher [ 11, ample evidence has accumulated to support the general view that both leaflets of the lipid bilayer of most, if not all, biological membranes have distinctly different lipid compositions (see [2] for a recent review). Whereas the outer leaflet is generally rich in cholinephospholipids, sphingomyelin and phosphatidylcholine, the inner leaflet is preferentially occupied by aminophospholipids, phosphatidylethanolamine and phosphatidylserine. Despite the fact that membrane-phospholipid asymmetry has become widely appreciated as a ubiquitous phenomenon, the mechanisms involved in its regulation and maintenance have begun to be addressed only recently. The discovery of an ATP-dependent aminophospholipid-specific transporter, which shuttles phosphatidylserine and phosphatidylethanolamine across the bilayer membrane towards the inner leaflet [3], suggests that a specific transmembrane orientation of these lipids is of major importance for cell function. Although our understanding of the physiological role of membrane lipid asymmetry is still fragmentary, there is evidence to suggest that exposure of phosphatidylserine at the cell surface which can occur during cell activation provides a signal for cell-cell recognition [4, 51 and is instrumental in promoting blood coagulation [6,7]. In this article we address the possible mechanisms which may play a role in the loss of membrane-phospholipid asymmetry that happens upon activation of blood platelets or upon CaZ+entry into red blood cells. In addition we will highlight an experiment of nature by featuring a rare bleeding disorder in which these phenomena do not occur.

Vitamin K-induced changes in markers for osteoblast activity and urinary calcium loss

Abstract: The objective of this study was to identify subjects in whom vitamin K has an effect on markers for calcium and bone metabolism and to detect hitherto-unnoticed correlations between vitamin K-induced changes in these markers. Participants in our studies were apparently healthy women, in whom we measured serum-immunoreactive osteocalcin (irOC) before and after adsorption to hydroxylapatite; total serum alkaline phosphatase (T-AP) and bone-specific alkaline phosphatase (B-AP); and fasting urinary calcium and creatinine. We describe a trial among 145 women who were treated with vitamin K (1 mg/day) for 2 weeks, and a prospective placebo-controlled trial among two groups each of 70 postmenopausal women with a treatment period of 3 months. It turned out that in elderly women vitamin K induced increased levels of serum irOC with a high affinity for hydroxylapatite (irOCbound), whereas that with low affinity (irOCfree) remained unaffected. In placebo-treated women the ratio irOCfree/irOCbound shifted from 0.38 to 0.65 around the 50th year of age. This shift was not found in vitamin K-treated women. After 3 months of treatment the vitamin K-induced changes in irOCbound were correlated with changes in B-AP, whereas irOCfree was correlated to urinary calcium excretion. In fast losers of urinary calcium vitamin K induced a 30% decrease of calcium excretion. The hypothesis is put forward that irOCbound may be a marker for bone formation, that serum irOCfree may be a marker for bone resorption, and that the serum irOCfree/irOCbound ratio may become a marker for skeletal remodeling.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of factors influencing the prognosis of Japanese, German, and Dutch gastric cancer patients

Abstract: As a result of Japanese reports of improved survival of gastric cancer patients after extended lymph node dissection, a study was undertaken to evaluate factors that might influence these results. The influence of staging was evaluated by stratifying 1085 patients of the National Cancer Center of Japan and grouping them according to the three commonly used systems; UICC's old and new TNM systems (fourth edition) and the system of the Japanese Research Society for the study of Gastric Cancer (JRSGC). No survival difference was found between the stages of the three systems, except for stage II, where the new TNM and the JRSGC differed (p<0.05). In a second analysis, the incidence of the most important prognostic factors for advanced gastric cancer was compared among three institutions: the National Cancer Center Tokyo, Japan (NCC), the University Hospital Erlangen, Germany (UHE) and the University Hospital Maastricht in The Netherlands (UHM). Japanese patients were on average 3 years younger than the German patients and 8 years younger than the Dutch patients, and had a higher proportion of advanced (T4) carcinomas. Male-female distribution, histology, and lymph node invasion were comparable in the three groups. From these data a rather worse prognosis for Japanese advanced gastric cancer patients could be expected. However, the observed 5-year survival rates show a marked advantage for the Japanese patients: 57% (NCC) versus 34% (UHE) and 31% (UHM). The survival difference for stage II patients between the new TNM and the JRSGC staging systems is not sufficient to explain this advantage. This result underlines the importance of the Japanese therapeutic approach. Whether this approach (i.e., extended lymph node dissection) actually improves survival or merely improves classification, is currently the subject of a prospective randomized trial in The Netherlands.

A physiological/psychological indicator of over-reaching during intensive training

Abstract: Many indicators of over-reaching and over-training have been proposed, using both physiological and psychological techniques. Field testing of athletes has led us to believe that a decrease in the ratio of blood lactate concentration to ratings of perceived exertion indicates a fatigued and/or over-reached state following intensive training. The purpose of this study, therefore, was to test the hypothesis that a decrease in the ratio of blood lactate concentration to ratings of perceived exertion would indicate an over-reached state. Seven well-trained male cyclists performed two weeks each of: normal (moderate) training, overtraining and recovery. During each time period an incremental exercise test was performed to maximal effort with blood lactate concentration (HLa) and ratings of perceived exertion (RPE) obtained for each workload. All seven subjects became over-reached during the two week period of intensive interval training. The ratio of HLa:RPE (multiplied by 100) decreased with all workloads following both one (mean decrease 29.1 +/- 3.0%) and two (mean decrease 48.7 +/- 2.5%) weeks of overtraining. However, only the decrease at the maximal workload was statistically significant. Examining the individual data revealed that at maximal workload all seven subjects had HLa:RPE ratios of less than 100 when over-reached. The ease and speed at which the HLa:RPE ratio can be determined may make it useful for coaches and athletes in monitoring intensive exercise training and recovery.