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Biomedical subjects

G Schlosser

Publications and source records attributed to G Schlosser.

9 recordsLinked to original sources
PubMed1997

Development of the retina is altered in the directly developing frog Eleutherodactylus coqui (Leptodactylidae).

The loss of a free-living larval stage during the evolution of directly developing frogs of the genus Eleutherodactylus resulted in dramatic alterations in ontogeny. Immunostaining for proliferating cell nuclear antigen reveals that in the directly developing frog Eleutherodactylus coqui pervasive cell proliferation occurs throughout the retina even after the plexiform layers have formed. In striking contrast to biphasically developing frogs (e.g. Discoglossus pictus or Xenopus laevis), in E. coqui proliferation becomes restricted to the ciliary margin only after the eye has reached the size typical of a postmetamorphic froglet and after its laminar structure has developed. As a consequence, the retina of E. coqui develops rapidly without recapitulating larva-typical stages. Our results suggest that dissociation of cell proliferation and differentiation can lead to the abbreviation of ontogenies during evolution.

Animals↗
PubMed1997

Evolution of nerve development in frogs. I. The development of the peripheral nervous system in Discoglossus pictus (Discoglossidae).

The gross anatomical development of the peripheral nervous system (PNS) during embryogenesis and metamorphosis in the frog Discoglossus pictus is described based on whole-mount immunostaining for nerves and muscles. In the head, neurite outgrowth starts with the mandibular ramus of the trigeminal nerve at the tailbud stage. Cranial muscles are innervated as soon as they differentiate, beginning at mid-embryonic stages. During late embryonic stages, the course of the trigeminal and facial nerves becomes greatly distorted and changes again drastically during metamorphosis accompanying the reorganization of the jaw muscles. Two occipital somites and nerves develop transitorily but degenerate at late embryonic stages. The hypoglossal nerve develops by fusion of the first and second spinal nerves and receives a transitory contribution of the third and fourth spinal nerve at embryonic stages. In the trunk, several classes of Rohon-Beard neurites could be identified at embryonic stages, one of which forms intersegmental sensory nerves that prefigure the course of the sensory rami of spinal nerves at later stages. We give detailed schedules of PNS and cranial muscle development which, in comparison with data on other frog species described in a companion paper, will serve as a basis to evaluate heterochronic shift during evolution of PNS development in frogs.

Animals↗
PubMed1997

Evolution of nerve development in frogs. II. Modified development of the peripheral nervous system in the direct-developing frog Eleutherodactylus coqui (Leptodactylidae).

We use whole-mount immunohistochemistry to describe the pattern of development of cranial nerves and muscles in the direct-developing leptodactylid frog Eleutherodactylus coqui. Comparison with nerve development in the biphasically developing frogs Physalaemus pustulosus (Leptodactylidae) and Discoglossus pictus (Discoglossidae; described in a companion paper) allows us to infer the ancestral leptodactylid ontogenetic pattern and the extent to which it has been modified during the evolution of direct development in Eleutherodactylus. While early embryonic development of cranial nerves and muscles is remarkably conserved in E. coqui, most transitory embryonic and larval characters (e.g., occipital and spinal myotomes together with their innervation, the distorted course of trigeminal and facial nerves, ventral branchial arch muscles, a subset of branchial-nerve rami and the lateral-line system) never develop. However, a few larva-typical characters are recapitulated, including Rohon-Beard cells and an anastomosis between the vagal and hypoglossal nerve. In addition to the abbreviation of ontogeny by loss of larva-specific traits, dramatic dissociations and heterochronic shifts of characters can be observed in E. coqui. The onset of development of limb and trunk innervation has been pre-displaced to early embryonic stage. Moreover, the reorientation of cranial muscles and nerves corresponding to late metamorphic events in biphasically developing anurans occurs relatively much earlier and is less pronounced in E. coqui resulting in an extreme condensation of ontogeny.

Animals↗
PubMed1995

Distribution of cranial and rostral spinal nerves in tadpoles of the frog Discoglossus pictus (Discoglossidae).

We studied the peripheral nervous system of early tadpoles of the frog Discoglossus pictus using whole-mount immunohistochemistry. Double-labeling of muscles and nerves allowed us to determine the innervation of all cranial muscles supplied by the trigeminal, facial, glossopharyngeal, vagal, and hypoglossal nerves. The gross anatomical pattern of visceral, cutaneous, and lateral-line innervation was also assessed. Most muscles of the visceral arches are exclusively supplied by posttrematic rami of the corresponding branchiomeric nerves, the only exceptions being some ventral muscles (intermandibular, interhyoid, and subarcual rectus muscles). In the mandibular arch, the pattern of motor ramules of the trigeminal nerve prefigures in a condensed form the adult pattern, but the muscles of the hyoid arch are innervated by ramules of the facial nerve in a pattern that differs from that of postmetamorphic frogs. With respect to the nerves of the branchial arches, pretrematic visceral rami, typical of other gnathostomes, are absent in D. pictus. Instead, we find a separate series of posttrematic profundal visceral rami. Pharyngeal rami of all branchial nerves contribute to Jacobson's anastomosis. We provide a detailed description of the lateral-line innervation and describe a new ramus of the middle lateral-line nerve (ramus suprabranchialis). We confirm the presence of a first spinal nerve and its contribution to the hypoglossal nerve in D. pictus tadpoles.

Animals↗
PubMed1993

Lipoprotein (a), low-density, intermediate-density lipoprotein, and blood pressure in a young male population.

Both hypercholesterolemia and hypertension are risk factors for atherosclerotic vascular disease, and elevated cholesterol levels occur more frequently than expected in patients with hypertension. Elevated levels of intermediate-density lipoproteins (IDL) and low-density lipoproteins (LDL) were shown to be atherogenic, and LDL, comprising the major cholesterol-carrying fraction in human plasma, are structurally related to lipoprotein (a)[Lp(a)], a further risk factor for atherosclerosis. In the present study we investigated 200 male employees (mean age 26 +/- 7 years) to determine whether the relationship of IDL and Lp(a) to systemic blood pressure is similar to the reported correlations between total and LDL cholesterol and systemic blood pressure. To this end blood pressure was measured several times in each individual, and lipids, lipoprotein-cholesterol, apolipoprotein B (apo B), and Lp(a) were determined in fasting serum. IDL cholesterol and apo B, the main protein component of IDL and LDL correlated with blood pressure. However, levels of Lp(a) correlated neither with systolic or diastolic blood pressure nor with lipoprotein cholesterol, body weight, or age. Although IDL and Lp(a) are considered lipoprotein risk factors for atherosclerosis, levels of Lp(a), unlike IDL, are not related to blood pressure, body weight, or age. Our data suggest different metabolic and pathophysiological mechanisms of the risk factors, IDL, LDL, and Lp(a).

Adult↗
PubMed1988

An analysis of rheumatology cases presenting to the emergency room of a teaching hospital.

We surveyed diagnoses on 5592 consecutive new cases presenting to a general hospital emergency room. The number of cases that could be judged "rheumatic" were analyzed further to determine the spectrum of rheumatologic problems that were seen in this facility. Four hundred eighty-three cases were studied. Precise diagnosis frequently could not be determined, but the largest group was soft tissue rheumatism. A wide variety of "rheumatologic" cases were seen initially in the emergency room. The clinical disposition and followup on these patients was also determined.

Emergency Medical Services↗
PubMedDate not supplied

Projection-neurons that send axons through the lumbar spinal cord of the chick embryo are not obviously distributed in a segmentally repetitive pattern.

Earlier studies have shown that the formation of the segmentally repetitive pattern of spinal nerves in avian embryos depends upon the segmental arrangement of the somites and does not reflect an intrinsic pattern of the spinal cord. These studies could not, however, rule out the possibility that some elements of the central nervous system are intrinsically segmented. The question remained, for instance, whether projection-neurons are distributed in a segmentally repetitive pattern within the spinal cord. To address this question, horseradish peroxidase was injected into one or two segments of the lumbar spinal cord of chick embryos, thereby labeling projection-neurons that had ascending or descending axons passing through the injection site. In all stages examined, the number of labeled projection-neurons in the anterior and posterior halves of each segment did not differ significantly. In addition, segmentally repetitive peaks or troughs in the numbers of labeled projection-neurons were not detected in the center of each segment. Three subpopulations of projection-neurons, defined by their position along the dorsal-ventral axis of the spinal cord, were also not segmentally distributed by these criteria. While these results do not rule out the possibility that subpopulations of projection-neurons defined by dendritic morphology, functional class, or some other parameter are segmentally arranged or that there is a basic modular repetition of neural populations from segment to segment, they do show that projection-neurons as a class and subpopulations of these neurons defined by their dorsal-ventral position are not obviously distributed in a repetitive segmental pattern.

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