Flexible electronic feedback using the virtues of progress testing.

The potential richness of the feedback for learners and teachers is one of the educational advantages of progress tests (PTs). Every test administration yields information on a student's knowledge level in each sub-domain of the test (cross-sectional information), and it adds a next point to the corresponding knowledge growth curve (longitudinal information). Traditional paper-based feedback has severe limitations and requires considerable effort from the learners to give meaning to the data.

Collaboration on progress testing in medical schools in the Netherlands.

Progress testing in the Netherlands was originally developed at Maastricht University. Since the late 1990s, a collaboration has started between three medical schools to jointly produce and administer the progress test. Currently, the progress test is administered to five out of eight medical schools in the Netherlands.

Results of surgical repair of atrioventricular septal defect with double-orifice left atrioventricular valve.

Objective: The outcome of surgical correction of atrioventricular septal defect with double-orifice left atrioventricular valve has improved in recent years but is still reported to be associated with high mortality and reoperation rates. Controversy exists about the management of the accessory orifice. We evaluated our results with correction of atrioventricular septal defect with double-orifice left atrioventricular valve.

Chronic right ventricular pressure overload results in a hyperplastic rather than a hypertrophic myocardial response.

Myocardial hyperplasia is generally considered to occur only during fetal development. However, recent evidence suggests that this type of response may also be triggered by cardiac overload after birth. In congenital heart disease, loading conditions are frequently abnormal, thereby affecting ventricular function.

Development of the cardiac conduction system in atrioventricular septal defect in human trisomy 21.

In patients with atrioventricular septal defect (AVSD), the occurrence of nonsurgical AV block has been reported. We have looked for an explanation in the development of the AV conduction system. Human embryos with AVSD and trisomy 21 and normal embryos were examined (age 5-16 wk gestation).

The role of neural crest and epicardium-derived cells in conduction system formation.

During cardiac development the heart tube loops and is septated into a four-chambered structure. The initial peristaltic contraction of the primitive myocardium is replaced by a system of working myocardium and a myocardial-derived central and peripheral conduction system. The genes guiding this differentiation process are still under investigation and it has yet to be decided whether we are dealing with a recruitment or a specification model.

Deficiency of the vestibular spine in atrioventricular septal defects in human fetuses with down syndrome.

Data on the morphogenesis of atrioventricular septal defect (AVSD) in Down syndrome are lacking to support molecular studies on Down syndrome heart critical region. Therefore, we studied the development of complete AVSD in human embryos and fetuses with trisomy 21 using 3-dimensional graphic reconstructions and immunohistochemical markers. Eight trisomic hearts with AVSD and 10 normal hearts, ranging from 5 to 16 weeks' gestation, were examined.

HNK-1 expression patterns in the embryonic rat heart distinguish between sinuatrial tissues and atrial myocardium.

HNK-1 expression was studied by immunohistochemistry in serial sections of embryonic and fetal rat hearts from 11.5 to 16.5 embryonic days.

Development of the atrioventricular valve tension apparatus in the human heart.

Using various microscopical techniques we studied the development of the atrioventricular valves in human hearts between 5 and 19 weeks of development. Within the atrioventricular cushions two different layers could be recognized that remained present in all ages studied. The atrial layer, being present at the side of the atrioventricular orifice, was positive for laminin while the ventricular layer, that was connected to the myocardium, was positive for fibronectin and collagen III.

Diminished growth of atrioventricular cushion tissue in stage 24 retinoic acid-treated chicken embryos.

Stage 34 chicken hearts have shown a spectrum of looping disturbances, changed hemodynamics, and changed growth of both right ventricular myocardium and atrioventricular cushion tissue after retinoic acid treatment. To obtain more information about the onset of the malformations we studied stage 24, the stage between the previously studied stage 34 and the moment of treatment. Sixteen stage 24 chicken embryos were examined after treatment with 1 microg all-trans retinoic acid at stage 15 and compared with 6 sham operated embryos.

Development of the papillary muscles of the mitral valve: morphogenetic background of parachute-like asymmetric mitral valves and other mitral valve anomalies.

Objectives: To understand papillary muscle malformations, such as in parachute mitral valves or parachute-like asymmetric mitral valves, we studied the development of papillary muscles.

Methods: Normal human hearts at between 5 and 19 weeks of development were studied with immunohistochemistry, three-dimensional reconstructions, and gross inspection. Scanning electron microscopy was used to study human and rat hearts.

The parachute-like asymmetric mitral valve and its two papillary muscles.

Objectives: The morphologic features of parachute-like asymmetric mitral valves are described to discriminate this anomaly from parachute mitral valves.

Background: Mitral valves with unifocal attachment of chords have been called "parachute valves," independent of the number of papillary muscles. Therefore the anomaly involving two papillary muscles has not received separate attention.

Stereological study of stage 34 chicken hearts with looping disturbances after retinoic acid treatment: disturbed growth of myocardium and atrioventricular cushion tissue.

Background: In a previous study retinoic acid treatment of chicken hearts has resulted in a spectrum of looping disturbances. Because of a decrease in contraction force of these hearts, the myocardial volume was hypothesized to be altered. Because retinoic acid has been suggested to influence endocardial cushion volumes, these were estimated as well.

Ultrastructural changes of the myocardium in the embryonic rat heart.

Background: Ultrastructural changes of the embryonic heart have been described, and quantitative studies have reported the changes of cellular organelles in late fetal and postnatal development. However, no specific data are available on the quantitative morphology of the individual segments and intersegmental junctions of the early embryonic heart, although these components must have different functions.

Methods: We measured the absolute volumes of glycogen, Golgi complex, myofibrils, mitochondria, and the surface areas of the rough endoplasmic reticulum and mitochondrial cristae in the different regions of the embryonic rat heart by using stereological tools.

Development of myocardial fiber organization in the rat heart.

Confocal laser-scanning microscopy of phalloidine-stained actin fibers is a relatively new tool for studying the development of myocardial fiber organization. It seems to show orientation of myocytes in rather early embryonic stages. To further evaluate the differentiation of the myocardium, this technique was compared with transmission electron microscopy in rat embryos aged between 11 and 18 days.

MRI appearance of a double inlet and double outlet right ventricle with supero-inferior ventricular relationship.

This patient was diagnosed with a double inlet and double outlet RV with supero-inferior ventricular relationship, ventricular inversion was diagnosed on the basis of left-handed topology of the RV, and the straddling of the right-sided mitral valve over an anterior VSD, with its tension apparatus extending into the outflow tract of the RV. MRI was found to be superior to color Doppler echocardiography and contrast ventriculography in the segmental analysis leading to a full understanding of this complex case.

Nuclear and cellular size of myocytes in different segments of the developing rat heart.

Background: In the embryonic heart, the individual cardiac segments show different growth rates. For the analysis of changing form in relation with changing function, data on number and shape of cardiomyocytes are necessary. Such data will give insight into the process of hypertrophy and/or hyperplasia as they may take place in the myocardium in the embryonic period.

Growth of the myocardial volumes of the individual cardiac segments in the rat embryo.

Background: Although the growth of the developing heart in relation to an increase of ventricular systolic pressure and the growth of the entire embryo during development has been described, no data are available on the growth of the individual segments and intersegmental junctions. Because these different portions are known to function differently, the need for data on their individual development is obvious.

Methods: We have measured the volumes of these different compartments by Cavalieri's point counting method in rat embryos from 11 to 17 days.

In normal development pulmonary veins are connected to the sinus venosus segment in the left atrium.

Background: Classic theories describe that the common pulmonary vein develops as an outgrowth from either the sinus venosus or atrial segment. Recent studies show that the pulmonary veins are connected to the sinu-atrial region before its differentiation into a sinus venosus and atrial segment.

Methods: The development of the sinu-atrial region with regard to the developing common pulmonary vein and the growth of the atrial septum was investigated in avian embryos, using both scanning electron microscopy and immunohistochemistry.

Spectrum of looping disturbances in stage 34 chicken hearts after retinoic acid treatment.

Background: In a recently developed chick model the teratogen retinoic acid has appeared to induce a spectrum of double outlet right ventricle, which needs further detailed evaluation. It is known that retinoic acid is able to induce cardiac malformations. Although the exact mechanism is not known, an interaction with neural crest cell function is thought to exist.

Origin of subepicardial cells in rat embryos.

Background: The role of the villi and vesicles of the epicardium primordium in the formation of the epicardium has been extensively studied over the last decades. With regard to the cellular contents of the villi and vesicles of the epicardium primordium, in quail the presence of mesenchymal cells in the villi recently has been described. In the present study, we have determined whether the villi and vesicles of the epicardium primordium in rat embryos contain mesenchymal cells that originate from the transverse septum and if so, whether these cells will become part of the subepicardium.