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D L Meyer

Publications and source records attributed to D L Meyer.

At least 55 records · Page 3Linked to original sources
PubMed1992

Peripheral origin of olfactory nerve fibers by-passing the olfactory bulb in Xenopus laevis.

After DiI injections into the diencephalon of Xenopus, two types of retrogradely labelled cells were found in the nasal area: (i) receptor cells in the olfactory epithelium and (ii) a small cell group located between the main olfactory epithelium and the vomeronasal system. These results reveal an extensive extrabulbar olfactory projection of olfactory receptor cells. Fibers of these cells do not terminate in the olfactory bulb but innervate targets in the diencephalon directly. The other type of retrogradely labelled cells, apparently, are not part of any epithelium. They resemble similar cell groups which have previously been regarded as part of the nervus terminalis system in other vertebrates.

Animals↗
PubMed1992

Changes in ligand binding to GABAA receptor sites in pacific salmon (Oncorhynchus) brain during spawning migration and "aging".

When several years old, pacific salmon return to the site of birth, to spawn. At this time, a rapid aging process begins and the fish die within a few weeks after reproducing. Age-related changes of high and low affinity GABA binding sites were studied in salmon brains at three different phases of the spawning migration, i.e. shortly after returning to the natal stream, at the time of spawning, and thereafter. High affinity GABA binding slightly increased while the fish deteriorated. The low affinity component showed a remarkable decrease in density and a concomitant increase in affinity during this final episode of salmon life.

Aging↗
PubMed1991

Functional subdivisions of the olfactory system correlate with lectin-binding properties in Xenopus.

Soybean agglutinin (SBA) is known to selectively label a portion of neurons in amphibian and mammalian primary olfactory systems. Hitherto, no other distinctive features have been found to correlate with the two neuronal populations. Investigating SBA-HRP binding in olfactory mucosa and CNS of Xenopus, we noted that labelled and unlabelled structures can readily be assigned to different olfactory subsystems. The SBA negative one is utilized to detect air-borne odors, whereas major SBA-positive structures serve a role in the perception of water dissolved molecules. Some labelled fibers by-pass the olfactory bulb, traverse the telencephalon and innervate prosencephalic structures. They are considered to be aberrant olfactory nerve fibers, rather than being part of the terminal nerve.

Animals↗
PubMed1991

The visually related posterior pretectal nucleus in the non-percomorph teleost Osteoglossum bicirrhosum projects to the hypothalamus: a DiI study.

This study was done to elucidate the ancestral (plesiomorphic) condition for visual pathways to the hypothalamus in teleost fishes. Three patterns of pretectal organization can be discerned morphologically and histochemically in teleosts. Their taxonomic distribution suggests that the intermediately complex pattern (seen in most teleost groups) is ancestral to both the elaborate pattern (seen in percomorphs) and the simple pattern (seen in cyprinids). The pretectal nuclei involved can be demonstrated with acetylcholinesterase histochemistry selectively and reliably in different species of teleosts, suggesting that the same-named nuclei are homologous in representatives of the three different patterns. Whereas there are visual pathways to the hypothalamus in both the elaborate (percomorph) and the simple (cyprinid) patterns, different pretectal and hypothalamic nuclei are involved. Thus visual hypothalamic pathways in these two patterns would not appear to be homologous. In this study, circuitry within the third, i.e., the intermediately complex, pattern is investigated. It is demonstrated that visual pathways project via the pretectum to the hypothalamus in Osteoglossum bicirrhosum and that they are very similar to the visual pathways in the elaborate pattern. This suggests that the circuitry in the intermediately complex pattern, as represented by Osteoglossum, is plesiomorphic (evolutionarily primitive) and the circuitry in both the simple pattern (seen in cyprinids) and the elaborate pattern (seen in percomorphs) is apomorphic (evolutionarily derived) for teleosts.

Animals↗
PubMed1991

Ontogeny of the olfacto-retinalis projection in coho salmon (Oncorhynchus kisutch).

Filling of nucleus olfacto-retinalis neurons by cobaltous lysine injections into one eye of coho salmon of different ages revealed that the terminal nerve projection to the retina is established when the fish leave their freshwater environment. At this time salmons go through a metamorphosis termed "smoltification." FMRF-amide-like immunoreactive neurons in the nucleus olfacto-retinalis already exist in pre-smolts before the retino-petal projection is established. Thus, for the first time in any vertebrate, a projection of the terminal nerve is shown to develop during an advanced ontogenetic state.

Animals↗
PubMed1991

Subdivisions of the terminal nerve in Xenopus laevis.

The majority of recent studies on the terminal nerve (nt) in various vertebrates either involved tracer injections into the nasal cavity or made use of the LHRH-/FMRFamide-like immunoreactivity (ir) of a portion of its fibers. The present investigation was designed to determine the extent of overlap between data rendered by the two methods in Xenopus. The findings reveal no overlap of nt projections visualized by the two experimental techniques. This result sheds doubt on the validity of current definitions of the nt system.

Animals↗
PubMed1991

Misinterpretation of interaction effects: a reply to Rosnow and Rosenthal.

The structural model of analysis of variance for multiway tables, with main effects and interaction parameters, is overspecified. Only the set of estimable functions of the cell means is useful. The individual estimates of the parameters are artificial as regards the underlying scientific process. Rosnow and Rosenthal (1989a) stated that it is "absolutely necessary" (pg 146) that interactions should be interpreted by examining the usual estimates of the interaction parameters. This is incorrect.

Analysis of Variance↗
PubMed1991

Histochemical, connectional and cytoarchitectonic evidence for a secondary reduction of the pretectum in the European eel, Anguilla anguilla: a case of parallel evolution.

There are at least three different patterns of pretectal organization in teleost fishes: a simple pattern observed in cyprinids, an elaborate pattern present in percomorphs, and an intermediately complex pattern seen in many other teleost groups. The taxonomic distribution of the pretectal patterns indicates that the simple and the elaborate patterns are both evolutionarily derived (apomorphic) from the primitive (plesiomorphic) intermediately complex one. In anguillids, the pretectal pattern observed cytoarchitectonically has an anatomical configuration similar to that of the simple pattern in cyprinids. The distribution of acetylcholinesterase positivity in the pretectum (namely acetylcholinesterase positivity in the parvo- and magnocellular superficial and posterior pretectal nuclei, and acetylcholinesterase negativity in the pretectal cell plate and the ovoid preglomerular cell aggregate), as well as the retinal projections (namely retinal terminals in the parvocellular superficial and central pretectal nuclei, and absence of such terminals in the magnocellular superficial and posterior pretectal nuclei and the pretectal cell plate), strongly supports the interpretation suggested by the cytoarchitectonic analysis. As anguillids (elopomorpha) and cyprinids (ostariophysi) are related only distantly, this secondary simplification in the pretectum likely occurred independently, i.e. this simplification represents a case of parallel reduction.

Acetylcholinesterase↗
PubMed1991

Conducting family meetings in nursing homes: resident, nurse, and family perceptions.

One facet of the teaching nursing home activities of the Maine-Dartmouth Family Practice Residency Program involves requiring residents to schedule a yearly family meeting in collaboration with nursing staff for each of the three to six nursing home patients for whom they are primarily responsible. During a one-year period, meetings were held for 45 of 63 nursing home patients (71%). All participants used a simple instrument to evaluate the experience. A general outline of the content and process of successful meetings is described. Results indicate that families, patients, nurses, and physicians found the meetings useful for sharing medical information and providing emotional support. Meetings typically reinforced or made only minor refinements in the ongoing plan of care. The implementation methods of the project are briefly described so that others might consider making yearly family meetings in nursing homes a part of their training programs.

Communication↗
PubMed1990

Paraventricular organ of the lungfish Protopterus dolloi: morphology and projections of CSF-contacting neurons.

The morphology and projections of neurons in the paraventricular organ (PVO) were studied by means of silver impregnation after intraocular application of cobaltous lysine in the lungfish Protopterus dolloi. Cobalt-labeled neurons were found exclusively in the PVO in the dorsal and infundibular hypothalamus. These bipolar neurons possess one CSF-contacting process that protrudes into the ventricular lumen with a club-shape ending and a thick, ramifying process directed into the hypothalamic neuropil; the ependymofugal processes form intra- and extrahypothalamic projections. Impregnated fibers from paraventricular neurons cross in infundibular and hypothalamic commissures, the commissure of the posterior tuberculum, the postoptic, the habenular, and the anterior commissures. Projections to the infundibulum and the median eminence are relatively sparse; no fibers are labeled in the pituitary gland. Ascending projections to the forebrain are extensive. Major targets include the dorsal hypothalamus, the periventricular preoptic nuclei, the habenula, the subhabenular region, the anterodorsal thalamus, and the medial telencephalic hemisphere (septum). Most ascending fibers follow the medial forebrain bundle; others course in the fasciculus retroflexus and terminate in rostral parts of the ipsilateral habenula. Descending fibers run caudally along the ventral floor of the brainstem. They terminate in the neuropil of the mesencephalic tegmentum, ventral tectum, isthmic region, ventral portions of the reticular formation throughout the rhombencephalon, and extend into the spinal cord. Intraocular application of cobaltous lysine results in selective impregnation of neurons in the PVO and their ascending and descending projections, presumably via uptake of tracer from vascular circulation. These projections do not represent retinofugal or retinopetal projections. We provide conclusive evidence for the existence of a PVO in Protopterus. On the basis of PVO location and acetylcholinesterase histochemistry, we propose subdivisions of the infundibular hypothalamus corresponding to those in amphibians. Ascending PVO projections appear to be particularly well developed in lungfish compared with other species and may be related to specialized endocrine mechanisms in this group of vertebrates.

Acetylcholinesterase↗
PubMed1990

Dorsomedial telencephalon of lungfishes: a pallial or subpallial structure? Criteria based on histology, connectivity, and histochemistry.

The dorsomedial telencephalon of lepidosirenid lungfishes has been interpreted in two divergent ways: earlier investigators regarded it as a subpallial (septal) structure; more recently, it has been reinterpreted as the medial pallium (hippocampus). To resolve this question, we identified parameters that are conclusive in their association with either the medial pallium or the septum in anamniotes. The present study examines the position of ependymal thickenings and the distribution of acetylcholinesterase (AchE) in the cerebral hemispheres of the African lungfish Protopterus, the Australian lungfish Neoceratodus, and the amphibian species Xenopus and Ambystoma. In addition, projections from the hypothalamus (paraventricular organ) to the telencephalon are investigated in Protopterus. Ependymal specializations are located dorsally and ventrally in the lateral ventricles of amphibians, but laterally and medially in lungfishes. In Protopterus, the paraventricular organ projects to the medial telencephalic hemisphere, but not to the dorsal roof. High levels of AchE are present in restricted neuropil regions of the medial hemisphere and in the ventral and ventrolateral telencephalon, but they are lacking in the dorsal roof. Intensely AchE-stained neuronal cell bodies are located in the ventral telencephalon (rostrally) and the dorsomedial telencephalon (at mid-level). In Neoceratodus, AchE staining is pronounced in the septal area, but absent in the pallium. The terminal nerve proper lacks AchE stain in Protopterus; nerve fibres of the preoptic nerve are AchE-positive in both lungfish species. In Xenopus, AchE staining of fibers and terminals is restricted to the subpallium (medial septum, tuberculum olfactorium, striatum, nucleus accumbens, and medial amygdala); cell bodies are AchE positive in parts of the subpallium and rostral pallium. Comparison of cytological, histochemical, and "connectional" parameters substantiates the interpretation that the dorsomedial telencephalon of lungfishes represents a subpallial, but not a "medial pallial" structure. The dorsomedial part of the lepidosirenid telencephalon corresponds to the septum in the most plesiomorphic living lungfish, Neoceratodus forsteri, but it differs considerably from the dorsomedial telencephalon (medial pallium) in amphibians.

Acetylcholinesterase↗
PubMed1990

Phylogeny of putative cholinergic visual pathways through the pretectum to the hypothalamus in teleost fish.

Three patterns of pretectal organization can be discerned morphologically in teleosts. The taxonomic distribution of these pretectal patterns suggests that the intermediately complex pattern (seen in most teleost groups) has given rise to both the elaborate pattern (seen in percomorphs) and the simple pattern (seen in cyprinids). Two pretectal patterns (intermediately complex and elaborate) form part of similar, homologous visual pathways to the hypothalamus; the third pattern is involved in a nonhomologous pathway to the hypothalamus. Acetylcholinesterase (AChE) histochemistry was used in the present study in order to characterize these pretectal patterns further. It is demonstrated that AChE is a highly selective and reliable interspecific marker for all divisions of the superficial pretectum, the nucleus corticalis, the posterior pretectal nucleus (or nucleus glomerulosus) and portions of the inferior lobe. Therefore, the histochemical data support the hypothesis of a homology between the three patterns of pretectal organization in teleosts. Furthermore, the present data provide a basis for more specific investigations regarding the involvement of acetylcholine as a neurotransmitter within the visual pathways to the hypothalamus in teleosts.

Acetylcholinesterase↗
PubMed1990

Tectal afferents in Rana pipiens. A reassessment questioning the comparability of HRP-results.

Studying afferents to the optic tectum in Rana pipiens by means of retrograde HRP transport, results were obtained, that cast doubt on the reliability of this neuronal tract tracing technique. The tectum was found to receive afferents from e.g. lateral mesencephalic tegmentum, torus semicircularis, contralateral large-celled pretectal nucleus, and ipsilateral thalamic nuclei, which have not previously been demonstrated. In addition, the data obtained lack evidence of projections reported earlier. We suggest, that neuronal projections may be subject to hormone and/or activity dependent changes, that alter the probability of accumulating sufficient amounts of the tracer to become labeled.

Animals↗
PubMed1990

Sex of physician: patients' preferences and stereotypes.

Patients' preferences for physicians of a particular sex tend to skew sex distributions of clinical populations in training and practice settings. A study was developed to explore these preferences and potential reasons for them. Of 185 adult patients surveyed at four family practice residency clinics, 45% expressed a preference for sex of physician; 43% of women and 12% of men preferred a female physician, while 31% of men and 9% of women preferred a male physician. Patients who stated no overall preference often expressed one in specific clinical situations, eg, anal or genital examinations. Patients who preferred female physicians reported humane behaviors as more characteristic of female physicians, and those who preferred male physicians reported humane behaviors as more characteristic of men; patients who had no overall sex preference did not sex stereotype physicians on these behaviors (F = 59.34, P less than .01). Patients who preferred male physicians reported technical competence behaviors as more characteristic of male physicians; others did not sex stereotype physicians on these behaviors (F = 15.4, P less than .01). Patients rated humaneness and comprehensiveness as being of high priority, but no relationship was found between priorities for aspects of care and preferences for sex of physician. Areas for future investigation include assessing preferences in other populations and exploring sex differences in physician behavior during office encounters and correlating these differences with patient satisfaction.

Adult↗
PubMed1990

Perceived social support and family meeting attendance preferences among family medicine outpatients.

Although there is much social science literature about social support, relatively little is known about the extent and sources of support that family medicine patients perceive to be available to them. A questionnaire requesting ratings of perceived informational, instrumental, emotional, and crisis support in a variety of relationships was administered to 101 family practice center outpatients. Results indicated strong perceptions of available support overall, with highest levels perceived from partners and parents. Notably, however, strong support was also perceived from extrafamilial sources, surpassing that of other categories of biological relatives. Levels of perceived support from particular people also varied according to type of support being rated. Finally, patients expressed strong preferences for inviting both immediate family members and supportive extrafamilial persons to hospital meetings with physicians to discuss serious medical problems. Results are consistent with a multifactorial model of social support and suggest that physicians should take a broad social systems perspective in assessing patient resources and negotiating attendance at family meetings.

Adolescent↗
PubMed1989

Retino-petal neurons in the diencephalon of juvenile Lobotes surinamensis (teleostei).

Diencephalic retino-petal neurons in juvenile specimens of the teleost Lobotes surinamensis are not segregated into subpopulations that form discrete nuclei. A continuous band of such cells extends from the rostral to the caudal diencephalon. It includes some locations previously described as retino-petal nuclei in other teleosts. The vast majority of diencephalic retino-petal cells only projects to the contralateral eye in Lobotes.

Animals↗
PubMed1989

Retinopetal cells exist in the optic tectum of steelhead trout.

The existence of retinopetal cells in the tectum of various teleost fishes as been claimed by several authors. Others, however, have been unable to verify such observations and attribute the findings of retrogradely labelled tectal cells to methodological problems. In this study cobalt-lysine and HRP have been used as neuronal tracers. Evidence is provided for the presence of retinopetal cells in the tectum of steelhead trout. Dendritic arborizations of some of the cells are extremely elaborate. In salmon no such findings were made.

Animals↗