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Biomedical subjects

M Laufer

Publications and source records attributed to M Laufer.

At least 55 records · Page 3Linked to original sources
PubMed1989

Cyclic adenosine monophosphate as a second messenger in horizontal cell uncoupling in the teleost retina.

The reduction in the receptive field of horizontal cells of the teleost Eugerres plumieri observed upon dopamine (DA) superfusion is thought to be due to cell uncoupling. The possible mechanisms by which activation of DA receptors modify the electric coupling between horizontal cells were studied in the present work. It was found that the effect of DA in different preparations is mediated by a modification of intracellular concentration of cAMP and H+. The effects of intracellular injection of cAMP and H+ were studied in retinal horizontal cells of the teleost E. plumieri. A triple microelectrode was used to inject the ion iontophoretically, to pass current pulses, and to record voltages from the same cell, while a fourth microelectrode was used to record voltages from a neighboring cell in the same retinal layer. Responses evoked by light spots and annuli were evaluated simultaneously. Coupling ratios between neighboring horizontal cells ranged from 0.22 to 0.45. The intercellular resistance (Rc), 0.5-3.5 x 10(6) ohms, and that of the remaining cell membrane resistance (Rm), 2.5-18 x 10(6) ohms, were calculated by means of a passive electrical model that has a hexagonal array. The microinjection of H+ with injection current from +5 to +30 nA for 40 to 100 sec led to temporary and reversible light response reduction. The coupling ratio between two impaled cells was reduced by about 30%, and intercellular resistance (Rc) increment was 320% while cell membrane resistance (Rm) did not change consistently. There was also a temporary and reversible Rm reduction (70-85%) and an Rc increment of 170-330% when cyclic adenosine monophosphate was iontophoretically injected with current from -30 to -40 nA for 50 to 170 sec. The coupling ratio between two impaled cells was reduced by about 40%, and light responses recorded from the injected cell showed a reduction in amplitude with the same time course as that of the resistive changes. The injection of Lucifer yellow into a horizontal cell under normal conditions always results in pronounced fluorescence for more distant cells; however, under constant injection of H+ or cAMP only the injected cell is fluorescent, which provides direct evidence of the reduction in the effectiveness of coupling between horizontal cells. The observed effects of intracellular H+ or cAMP injection correspond to the resistive changes in Rc and coupling ratio that occur in the horizontal cell network upon superfusion with a dopamine (DA) solution.

Animals↗
PubMed1986

Adolescence and psychosis.

In this paper, I discuss how the specific developmental function of adolescence can result in behaviour and thought which resemble the adult psychoses but which, in most circumstances, are fundamentally different from the adult psychoses. Anybody who treats the seriously disturbed adolescent will be familiar with a simple and obvious characteristic of these adolescents--it is an irreconcilable, unanswerable quest to alter the image of the body. If we try to understand the psychotic manifestations or psychoses of adolescence, we must differentiate between (i) a psychotic episode, (ii) psychotic functioning, and (iii) psychosis. The assessment of psychosis must be reserved only for a very special category of disorder in adolescence and must not be confused with either a psychotic episode or psychotic functioning.

Adolescent↗
PubMed1983

Fine structure of regenerated ependyma and spinal cord in Sternarchus albifrons.

The caudal-most regenerated spinal cord in Sternarchus albifrons consists solely of an ependymal tube. Ependymal cells are enlarged radially and are more numerous than in unregenerated cord. Projections of ependymal cell cytoplasm and Reissner's fiber fill most of the central canal. Small groups of neurites and cell processes filled with dense-cored vesicles lie between abluminal processes of ependymal cells. Rostral to this, additional cells appear dorsal and lateral to the inner ependymal layer. Some cell bodies contain numerous dense-cored vesicles. Larger bundles of neurites, some with synapses, are present. Invaginations of the peripheral edge of the cord create enclosed spaces lined with basal lamina. In the peripheral region, longitudinally oriented neurites extend through extracellular spaces or channels. The ventral portion at some levels of regenerated cord is completely filled with neurites, processes containing dense-cord vesicles, and capillaries. Similar masses of neurites and processes containing dense-cored vesicles lie outside the cord proper, in or near the meningeal layer. In rostral-most sections, the organization of regenerated spinal cord approaches that of normal cord, with the regenerated cord exhibiting groups of myelinated axons, differentiated fibrous astrocytes and oligodendroglia, cell bodies containing dense-cored vesicles, and differentiated electromotor neurons. These observations indicate a degree of pluripotency in some of the ependymal cells in adult Sternarchus. Moreover, they are consistent with a role of ependymal cells in the guidance of regenerating neurites.

Animals↗
PubMed1982

The formation and shaping of the Oedipus complex: clinical observations and assumptions.

Freud maintained that the Oedipus complex as a development landmark could be conceptualized as taking place only at the time of the phallic phase. Freud's theory is that it is the culmination of a very long process whose primary result, in developmental terms, was that the ego now had to act as an organizing and unifying agent of all of one's past, while at the same time adding a new agency of the mind which he called the superego. With the resolution of the Oedipus complex, infantile sexuality would begin to be left behind. Since Freud, there have been a number of developments and controversies related to the Oedipus complex. The confusion which has arisen is that some of us use the insights we have gained about pre-oedipal life as themselves holding the answers to many of the psychopathologies we meet with clinically. My own view is that unless these insights about pre-oedipal life become part of a development framework, culminating in the Oedipus complex and, through its resolution, in the internalization of the superego, then we miss something which is fundamental in our understanding and in our efforts to undo psychopathology. For Freud, the relationship between sexuality and the Oedipus complex was inseparable. The assumption I put forward about the Oedipus complex is that the image of one's own body which has been organized by the end of the phallic-oedipal period determines the form of the oedipal resolution, and remains central to one's later sexual life and psychopathology. If, in our clinical work, we avoid the meaning of genital sexuality and the meaning of the sexual body image, but interpret mainly those aspects of the patient's life which are pre-oedipal (and therefore non-incestuous), then we lose the chance of creating the possibility of the patient having an active relationship to his sexual/genital body, and the patient loses the chance of ever feeling himself to be the owner of his own sexuality.

Adolescent↗
PubMed1981

Adolescent breakdown and the transference neurosis.

Adolescent pathology should be viewed as a breakdown in the development process, and it is a breakdown which takes place at puberty or during adolescence. It seems that the acute breakdown at puberty is potentially the more serious. This breakdown in the development process is understood in relation to the function of adolescence developmentally, and is linked to the establishment of a final sexual organization by the end of adolescence. Clinically, there are certain problems which are specific to the adolescent patient. Core fantasies in adolescence tell us the direction of the person's psychosexual development and the potential of abnormality. In the transference neurosis of the adolescent patient, the development breakdown has to be re-experienced and re-enacted with the analyst, but it is the core fantasies which contain the clue to the nature of the pathology and to the direction of the abnormality in terms of sexual functioning and of object relationships.

Adolescent↗
PubMed1980

Drug-induced changes in catecholaminergic cells of the fish retina.

The changes in fluorescence intensity and number of visible catecholaminergic cells (CA-cells), as revealed by means of a histofluorescence technique, were used as indicators of the effects of various pharmacological agents upon CA-cells in the retina of fishes (Cyprinus carpio and Eugerres plumieri). The study includes in vivo and in vitro experiments. In the in vivo experiments, intravitreal injection, two or three hours before eye enucleation, of 10 microgram L-DOPA, dopamine, or noradrenaline accentuated CA-cell fluorescence and increased the number of visible cells, whereas 10 microgram of tyramine, octopamine, synephrine, or adrenaline reduced the endogenous fluorescence. Intramuscular injection of reserpine (3 mg/kg) abolished CA-cell fluorescence. In the in vitro experiments, pieces of isolated retinas were incubated for three or 30 minutes in media containing different drugs. Only minor changes in fluorescence were detected after three minutes of incubation, but after 30 minutes, dopamine (20 microM) markedly enhanced CA-cell fluorescence. Carbachol (20 mM), acetylcholine (10 mM) plus BW-anticholinesterase (1 mM) or substance P(1.6 x 10(-2) mM), all reduced CA-cell fluorescence. Kainic acid (20 mM) abolished fluorescence from CA-cell somata, while fluorescent fiber networks remain unchanged. L-aspartate (5 mM) and GABA (10 mM) in the incubation medium did not influence fluorescence intensity. The results are relevant to, and consistent with, electrophysiological observations of dopamine-mediated spatial effects on horizontal cell potentials.

Acetylcholine↗
PubMed1980

Spatial distribution of catecholaminergic cells in the fish retina.

The cell density, distribution pattern, and morphology of catecholaminergic (CA) cells have been studied by fluorescence microscopy of retinal flat-mounted preparations from various species of fresh water, estuary, and marine is lowest in the central region surrounding the optic disc, slightly higher in the intermediate region, and highest in the periphery. The size of CA-cells is smaller the higher their density. Following administration of L-Dopa, dompamine, or noradrenaline, the density of CA-cells approximately doubled, due to the appearance of small fluorescent cells. CA-cells are arranged in rows along radial lines which fan out from the optic disc. In large cells of the central and intermediate regions three to five processes arise from the some and extend and ramify irregularly in the inner plexiform layer, while in small cells from the intermediate and peripheral regions two processes arise from opposite poles and extend regularly in a direction perpendicular to the rows of cells and parallel to the retinal margin. In the retina of the marine fish Holocentrus sp CA-cells are fewer in number compared to other fish studied and their processes extend without any regular pattern. In the toad their size and density are homogenous throughout the retina, and their processes show a regular arrangement.

Animals↗