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Biomedical subjects

I Heyman

Publications and source records attributed to I Heyman.

17 recordsLinked to original sources
PubMed1996

Different paradigms in a new research domain. The case of nursing research on diabetes in Sweden.

The aim of this study was to examine doctoral theses written by nurses on the same subject, namely diabetes. The five theses were published during three years. The text analysis emphasized the purposes, theoretical framing, methods for collection and analyzing the data, ways of presenting the texts and, finally, the references in the five theses. The findings indicate that the authors make use of different paradigms. Experimental approach was used in some theses and one thesis was based on grounded theory. Two theses could be said to be more concise that the others because they made use of only one technique each--physiological measurements and an open-ended interview. The remainder used of a number of methods--in other words, they were eclectic in approach. The conclusion is that there is a freedom for nurse researcher to affiliate to different scientific traditions inside academia--the two in question here are biomedical research and interpretative traditions inside social science. The author encourage all researchers inside the nursing domain to subject herself to criticism and reflection to the same extent as she analyzes other people or phenomena in order to increase epistemological awareness of the use of research tools, perspectives and theories.

Authorship↗
PubMed1995

Cell and matrix specialisations of rhombomere boundaries.

Hindbrain segments, rhombomeres, define distinct cellular and molecular domains which furnish the ground plan for important aspects of neural and cranial development. In this study, further evidence is presented that the interfaces between rhombomeres, rhombomere boundaries, contain both cells and extracellular matrix with specialised characteristics. Cells at rhombomere boundaries show temporally and spatially distinct expression patterns of developmentally important genes. Towards the end of the developmental period when rhombomeres are present, a fan-shaped array of cells at rhombomere boundaries, that constitute the ventricular ridge, shows decreased expression of two genes (Hoxb-1 and Krox-20), which earlier in development were expressed in all cells of specific rhombomeres. In contrast, these boundary cells show increased expression of another gene, Pax-6, which earlier in development has a rhombomere-specific expression pattern. A specialised identity for boundary cells is further suggested by increased labelling with an anti-vimentin antibody at rhombomere boundaries, indicating that at least some boundary cells are radial glia or glial precursors. In addition to distinct cellular properties, the extracellular domain at rhombomere boundaries is also specialised. Chondroitin sulphate proteoglycan (CSPG) immunoreactivity is increased and, as revealed by immuno-electron microscopy, localised to extracellular spaces. CSPG is also enriched in boundaries regenerated after ablation, or boundaries generated ectopically by rhombomere transplantation. We propose that rhombomere boundaries form their characteristic morphology at the interface between groups of cells with differing molecular characteristics, representing different cell states. A specialised band of cells then develops at the interface. Both the boundary cells and extracellur matrix have characteristics which could be important in later events of neural development such as axon guidance and cell migration.

Animals↗
PubMed1993

Cellular morphology and extracellular space at rhombomere boundaries in the chick embryo hindbrain.

The chick embryo hindbrain is a segmented region of the CNS characterised by repeated blocks of neuroepithelial cells, known as rhombomeres. Individual rhombomeres are polyclonal compartments, defined both by cell lineage restriction and by the restricted expression of development control genes, that later acquire specific patterns of neuronal differentiation and axon outgrowth. The interfaces between adjacent rhombomeres are defined by boundaries across which cells do not move; the boundaries contain specialised cells and are preferentially colonised at early stages of development by extending axons. In this study, routine electron microscopy and high-pressure cryopreservation, a technique that avoids artifacts of chemical fixation, have been used to examine the morphology of rhombomere boundaries through a staged series of chick embryos. We find that the boundary regions contain enlarged extracellular spaces and that these form conduits for axons subsequently extending in the circumferential plane of the hindbrain. Labeling the ventricular surface of the neuroepithelium with DiI crystals in aqueous suspension revealed the morphology of individual cells in the intact neural tube, and demonstrated unusual fan-shaped arrays of cells at the boundaries. These findings contribute further to the evidence that cells at rhombomere boundaries differ from those in rhombomere centres, and leads to hypotheses about both the mechanism of development of the boundaries, and the role they may play in hindbrain patterning.

Animals↗
PubMed1993

Even-numbered rhombomeres control the apoptotic elimination of neural crest cells from odd-numbered rhombomeres in the chick hindbrain.

Neural crest cells originate at three discontinuous levels along the rostrocaudal axis of the chick rhombencephalon, centred on rhombomeres 1 and 2, 4 and 6, respectively. These are separated by the odd-numbered rhombomeres r3 and r5 which are depleted of migratory neural crest cells. Here we show elevated levels of apoptosis in the dorsal midline of r3 and r5, immediately following the formation of these rhombomeres at the developmental stage (10-12) when neural crest cells would be expected to emerge at these neuraxial levels. These regions are also marked by their expression of members of the msx family of homeobox genes with msx-2 expression preceding apoptosis in a precisely colocalised pattern. In vitro and in ovo experiments have revealed that r3 and r5 are depleted of neural crest cells by an interaction within the neural epithelium: if isolated or distanced from their normal juxtaposition with even-numbered rhombomeres, both r3 and r5 produce migrating neural crest cells. When r3 or r5 are unconstrained in this way, allowing production of crest, msx-2 expression is concomitantly down regulated. This suggests a correlation between msx-2 and the programming of apoptosis in this system. The hindbrain neural crest is thus produced in discrete streams by mechanisms intrinsic to the neural epithelium. The crest cells that enter the underlying branchial region are organised into streams before they encounter the mesodermal environment lateral to the neural tube. This contrasts sharply with the situation in the trunk where neural crest production is uninterrupted along the neuraxis and the segmental accumulation of neurogenic crest cells is subsequently founded on an alternation of permissive and non-permissive qualities of the local mesodermal environment.

Animals↗
PubMed1992

Schizophrenia and neurodevelopment.

Schizophrenia is characterised by the psychotic symptoms of hallucinations and delusions, accompanied by variable degrees of loss of insight. Whilst there is heterogeneity in the clinical profile, and presumably in the pathogenesis of what is currently called 'schizophrenia', it has become absolutely clear over the past decade that schizophrenic symptoms are consequent upon serious brain dysfunction. This new perspective has laid to rest a variety of 'crazy' theories, including the notion that mental illness was a myth, or that schizophrenia could be caused by faulty child rearing. The use of dopamine-blocking drugs has led to an improvement in symptom control, and diminished the need for prolonged hospital stays. It was hoped that the clear relationship between antipsychotic activity and dopamine blockade would help to elucidate the pathophysiology of schizophrenia, but to date no consistent abnormalities of the dopamine system have been found. Nevertheless, we have learned much about both the aetiology of schizophrenia and the origin of particular symptoms. Much of this has stemmed from increased understanding of the brain abnormalities underlying the disorder.

Adolescent↗
PubMed1990

The work of practical nursing educators. A case study report.

In 1987 a study was carried out at two upper secondary schools. The aim was to study the working conditions of teachers in a changing environment by interviewing different professionals in the school as well as students. In the last five years, the average age of students was found to have fallen by two to four years. Another finding was that the entrance requirements had been lowered. In the same five-year period the drop-out rates at one of the two schools had risen from 5/60 to 18/81. At the other school 5/30 dropped out in 1987. Many of the teachers interviewed reported their students to be open-minded and spontaneous but at the same time too immature to work in the medicare sector, especially in the psychiatric field. A tendency appeared for teachers to take on a more curative and supportive role. The teachers maintained certain minimum standards and students who did not pass their examinations were required to withdraw.

Age Factors↗
PubMed1985

Depolarizing responses to capsaicin in a subpopulation of rat dorsal root ganglion cells.

Microelectrode recordings from the somata of rat dorsal root ganglion (DRG) cells were used to correlate their electrophysiological characteristics with sensitivity to locally applied capsaicin. Of the 80 cells tested, 17 responded to capsaicin by a rapid depolarization. These cells had low axonal conduction velocities (less than 1.4 m/s) and long duration action potentials, characteristic of C-cells. Some C-cells did not respond to capsaicin, and no A-cells, which had high conduction velocities and brief action potentials, did so. The effect of capsaicin on the current-voltage curve of C-cells suggested that it produced a conductance increase as well as a change in delayed rectification.

Action Potentials↗
PubMed1985

Does 1,25-dihydroxyvitamin D participate in the regulation of hormone release from endocrine glands?

The presence of receptors for 1,25-dihydroxyvitamin D3 in the pituitary, pancreas, testis, and ovary has raised the question of a possible direct role for 1,25-dihydroxyvitamin D (1,25(OH)2D) in the regulation of hormone synthesis and secretion. To evaluate this problem, six children with the syndrome of resistance to 1,25(OH)2D with rickets and alopecia underwent dynamic tests of insulin, TSH, PRL, GH, and testosterone secretion. Oral glucose loading resulted in normal glucose curves, subnormal peak insulin responses of 12-20 microU/ml in three hypocalcemic patients, and normal peak serum insulin values of 30-40 microU/ml in two normocalcemic patients. Basal serum, TSH, PRL, T4, and T3 concentrations were normal in all patients. Peak serum TSH values after TRH were 11-17 and 16-32 microU/ml in the hypo- and normocalcemic patients, respectively. The PRL response to TRH stimulation in either hypocalcemic or normocalcemic patients was normal [mean 26.2 +/- 5.1 (SD) ng/ml]. Peak serum GH levels were greater than 8 ng/ml in all five patients studied after one or more of the various stimuli. Serum testosterone concentrations after hCG stimulation were normal in the three patients studied (4.1-8.0 ng/ml). Thus, in children with resistance to 1,25(OH)2D, we could find no significant abnormalities in hormone secretion from the pituitary, pancreas, and testis apart from those presumably due to the hypocalcemia itself.

Calcitriol↗
PubMed1977

Recurrent hemolytic-uremic syndrome. A report of two cases.

Two boys suffering from the hemolytic-uremic syndrome (HUS) are presented. One of them developed four episodes of the disease beginning at infancy, the other one had at least two episodes which were associated with mild portal fibrosis of the liver. Between the attacks of the disease, the children were completely healthy, and no renal or hematological abnormalities were detected. Both patients are now physically and mentally well developed healthy young men. The relatioship between HUS and thrombotic thrombocytopenic purpura is briefly discussed.

Child↗
PubMedDate not supplied

Correlation of human hepatotoxicants with hepatic damage in animals.

Substances that cause liver damage in humans were identified through a literature search conducted on Toxline and Medline. Using the same search strategy, species other than man were selected, in whom hepatic injury could be attributed to exposure to the identified substances. A total of 38 substances were identified as producing liver damage, manifested by either clinical chemistry or histopathology. The substances included 24 drugs, 9 industrial chemicals, 3 environmental agents, 1 pesticide, and ethanol. Twelve of the 36 compounds have been toxicologically evaluated in man, rodent, and non-rodent. Histopathologic liver damage was reported in all three species for 11 of these compounds. Only carbencillin produced histopathologic damage in man but not in either the rodent or non-rodent. Where clinical chemistry changes were reported for all three species categories, only eight substances induced similar reactions in all three species. Only with two substances did man and rodent react similarly (both positive), while the non-rodent was negative. The two substances were polychlorinated biphenyl (PCB) and tetrachlorethane. In the majority of the cases in which either or both histopathologic or clinical chemistry changes were reported for man or for the rodent or non-rodent, the changes that occurred were qualitatively similar. The rodent was as sensitive a predictor for hepatic effects as the non-rodent. Although it is impossible to predict how liver damage observed in a laboratory animal is correlated with human liver damage, hepatotoxicity in the rodent must be considered as indicative of potential hepatic damage in man.

Animals↗