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Biomedical subjects

L R Page

Publications and source records attributed to L R Page.

At least 19 recordsLinked to original sources
PubMed2002

Larval and metamorphic development of the foregut and proboscis in the caenogastropod Marsenina (Lamellaria) stearnsii.

The specialized, postmetamorphic feeding structures of predatory caenogastropods evolved by changes to an ancestral caenogastropod developmental program that generated a planktotrophic larval stage followed by a herbivorous postmetamorphic stage. As part of a program of comparative studies aimed at reconstructing these developmental changes, I studied the development of the postmetamorphic feeding system of Marsenina stearnsii using histological sections for light microscopy and scanning and transmission electron microscopy. The feeding system of this species has two very different designs during ontogeny. The larval system uses ciliary effectors to capture and ingest microalgae, whereas the juvenile/adult system includes a proboscis, jaws, and radular apparatus for predation on ascidian zooids. The postmetamorphic foregut begins to develop during the early larval phase, but the anlagen does not interfere with larval feeding because it develops as an increasingly elaborate outpocketing from the ventral wall of the larval esophagus. At metamorphosis, an opening is created in the anterior tip of the prospective, postmetamorphic buccal cavity and the margins of this opening anneal with the metamorphically remodeled lips of the larval mouth. This process exposes the jaws, which differentiate within the buccal cavity prior to metamorphosis. As a working hypothesis, I suggest that rupture of the buccal cavity to the outside at metamorphosis was selected as a mechanism to allow precocious development of jaws in species where jaws enhanced feeding performance by young juveniles. The larval esophagus of M. stearnsii appears to be completely destroyed at metamorphosis. Larval esophageal cells have distinctive apical characteristics (cilia, blebbed microvilli, stacks of lamellae within the glycocalyx) and no cells having this signature persist through metamorphosis. Development of the proboscis and proboscis sac, which begins prior to metamorphosis, conforms to previous descriptions of pleurembolic proboscis development, although an acrembolic proboscis has been ascribed to members of the Lamellaroidea.

Animals↗
PubMed2000

Comparative study of the apical ganglion in planktotrophic caenogastropod larvae: ultrastructure and immunoreactivity to serotonin.

Previous research suggests that a major role of the apical ganglion (also called the apical or cephalic sensory organ) in gastropod larvae is detection and integration of sensory information and relay of motor signals to effectors in the velum. However, the relative impact of ancestry versus velum size and life history on characteristics of the apical ganglion is unresolved. We address this issue by contributing data on the apical ganglion and overlying epidermis in planktotrophic larvae of four caenogastropod species (Euspira [Polinices] lewisii, Lacuna vincta, Trichotropis cancellata, and Amphissa versicolor) derived from light microscopy, scanning and transmission electron microscopy, and immunohistochemical localization of serotonin-like antigenicity. Ultrastructure of the apical ganglion is similar in these caenogastropods, and the basic plan corresponds to previous descriptions of the apical ganglion in planktotrophic opisthobranch larvae (subgroup of Heterobranchia). The only identified structural feature that is unique to all these caenogastropods, relative to opisthobranchs, is modified ciliary axonemes for the ampullary cells, a distinctive type of sensory neuron. Like opisthobranch larvae, caenogastropod larvae have serotonin-immunoreactive neurons within the apical ganglion; the number ranges from three to six, but a lateral pair of serotonergic, nonsensory neurons is common to all species. The pattern of serotonergic neurons in E. lewisii, which develops large, subdivided velar lobes, is the same as that of opisthobranch larvae, which have a relatively small, unelaborated velum. These and other data suggest that common ancestry is a major determinant of overall structural design for the apical ganglion in caenogastropods and heterobranchs, which are sister groups within the Gastropoda. Velum size and life history strategy may account for some, but not all, cases of interspecific differences in the serotonergic component.

Animals↗
PubMed1997

Development of serotonin-like immunoreactivity in the embryos and larvae of nudibranch mollusks with emphasis on the structure and possible function of the apical sensory organ.

This investigation provides a light and electron microscopic examination of the development of serotonin-like immunoreactivity and structure of the apical sensory organ (ASO) in embryos and/or larvae of four nudibranch species: Berghia verrucicornis, Phestilla sibogae, Melibe leonina, and Tritonia diomedea. Serotonin-like immunoreactivity is first expressed in somata, dendrites, and axons of a group of five distinct neurons within the ASO. These neurons extend axons into an apical neuropil, a structure that is situated centrally and immediately dorsal to the cerebral commissure. Three of these neurons possess sensory dendrites that extend through the pretrochal epithelium, each supporting two cilia at their distal ends. Later development of serotonin-like immunoreactivity includes 1) axons from the apical neuropil that extend into each of the velar lobes; 2) neuron perikarya in the cerebral and pedal ganglia; 3) axons that extend through the cerebral commissure, cerebral-pedal connectives, pedal commissure, and possibly the visceral loop connective; and 4) axons extending from each pedal ganglion into the larval foot. Ultrastructurally, the ASO can be seen to be composed of three lobes and an apical neuropil that is separately delineated from the cerebral commissure. Four cell types are present within the ASO: ciliary tuft cells, type I and type II parampullary neurons, and ampullary neurons. Immunofluorescence and 3,3' diaminobenzidine tetrahydrochloride (DAB) labeling verify that the serotonergic neurons of the ASO are type I and type II parampullary neurons. The ampullary and type I parampullary neurons possess dendrites that extend through the pretrochal epithelium. These dendrites are partitioned into three bundles, one on either side of the ciliary tuft cells and a third bundle penetrating the pretrochal epithelium centrally between the ciliary tuft cells. One serotonergic type I parampullary neuron is associated with each of these bundles. Two ampullary neurons are associated with each of the lateral dendritic bundles, while the central bundle includes only one. Ultrastructural analyses of serotonergic axonal innervation arising from the ASO agree with those determined from fluorescently labeled material. The structure of the ASO and its associated serotonergic axons suggest that the serotonergic component of this structure senses environmental stimuli affecting velar function, possibly the contractility of muscle fibers in the velar lobes. Similarities and differences among the ASOs of embryos and larvae from various invertebrate phyla may provide useful data that will assist in the reconstruction of phylogenetic relationships.

Animals↗
PubMed1993

Developmental analysis reveals labial and subradular ganglia and the primary framework of the nervous system in nudibranch gastropods.

Previous ultrastructural observations on late stage larvae of dorid nudibranchs (Gastropoda, Opisthobranchia) revealed two pairs of ganglia within the base of the foot that do not have obvious counterparts in existing descriptions of other gastropod larvae [Chia and Koss (1989). Cell Tiss. Res. 256:17-26.] One of these ganglionic pairs has been implicated in the initiation of settlement preceding metamorphosis [Arkett et al. (1989). Biol. Bull. 176:155-160.] By examining neurogenesis in sequential larval stages, I have found that the pattern of connectives and commissures associated with these enigmatic ganglia is comparable to patterns found in less consolidated adult nervous systems of chitons, monoplacophorans, and archaeogastropods. These comparative data suggest that the two pairs of ganglia in dorid nudibranch larvae are homologues of labial and subradular ganglia. The labial ganglia become incorporated into the cerebral ganglia at metamorphosis. In an attempt to integrate anatomical and developmental observations with behavioral and neurophysiological results, I suggest that receptor cells of the larval labial ganglia may become postmetamorphic primary mechanoreceptors of the oral tube, which have central cell bodies within the "cerebral" ganglia and which help coordinate feeding. Results of this study also address a larger evolutionary issue by questioning the traditional model of an ancestral molluscan nervous system that consists of four longitudinal nerve cords that arise from separate sites along a circumesophageal nerve ring. This pattern results from secondary connections in nudibranchs and possibly other molluscs. The primary condition of a single axon bundle emerging from each cerebral ganglion is more similar to the developing nervous system in polychaete annelids than what has been recognized previously.

Animals↗
PubMed1980

Acute recurrent gingivitis. A clinical entity.

A typical case of a previously undescribed form of gingivitis which is self-limiting and recurrent is discussed. The signs and symptoms include acute pain and swelling of interdental papillae with regional lymphadenopathy. As the disease progresses the localized swelling quickly spreads to the adjacent marginal and papillary gingiva. Ulceration is infrequent and without pseudomembrane formation or interdental cratering. We believe this to be a unique form of gingivitis and suggest the name acute recurrent gingivitis (ARG).

Acute Disease↗
PubMed1979

Cancellous bone marrow grafts in irradiated dog and monkey mandibles.

A pilot study was conducted to investigate the osteogenic potential of autogenous cancellous marrow grafts placed in irradiated tissue. Five dogs and three monkeys received either 4,100 or 6,520 rads of cobalt-60 irradiation during a 5- or 8-week period. Postirradiation discontinuity mandibular defects were created surgically and restored with autogenous cancellous bone marrow grafts held in position by a titanium mesh basket. Bony union occurred in all the mandibles. Intraoral ulceration was common in the dogs, and extraoral wound dehiscence was found in the monkeys. Hematopoietic marrow was present in the graft sites of both species 6 months to 1 year after surgery.

Animals↗
PubMed1979

Blastomycosis with oral lesions. Report of two cases.

The recent literature suggests that blastomycosis (previously known as North American blastomycosis) with oral lesions may be more common than is generally realized. This report discusses two cases of blastomycosis in which oral lesions played a critical role in the ultimate diagnosis of the disease. The potential importance or oral lesions in early diagnosis and the necessity of culturing the organisms for definitive diagnosis are emphasized.

Adult↗
PubMed1977

The oral melanotic macule.

A clinical and histologic study of eighty oral melanotic lesions which do not readily fit into recognized categories of melanotic lesions was conducted. These lesions tend to occur in the fifth decade of life and are most frequently seen on the gingiva, with the buccal mucosa and palate the next most frequent sites. The lesions are usually single, smaller than 1 cm., but they may also occur as multiple lesions. There is no sex bias, and there seems to be a number of etiologic factors. In a few cases long-term follow-up was possible. There is no indication of a tendency toward recurrence or development of malignant lesions. Histologically, none of the lesions shows atypia. Melanin pigmentation tends to be present in significant amounts in the basal-cell layer and less often in the lamina propria. There are no outstanding histologic differences among the eighty specimens. It is suggested that the term oral melanotic macule be used for these lesions, unless a specific cause can be confirmed by clinical data. Although these lesions should not be considered premalignant, it would be prudent to remove them for histologic confirmation of clinical impressions.

Adolescent↗
PubMed1977

Aspergillosis of the maxillary sinus. Review of the literature and report of a case.

Aspergillosis of the paranasal sinuses is an infrequently reported disease which can occur in two forms: (1) a noninvasive form that can clinically mimic nonspecific chronic sinusitis and (2) an invasive form that can simulate malignant disease of the sinuses. The disease occurs without known predisposing systemic disease. Primary treatment consists of surgical eradication of infected tissue. The question of whether concomitant antifungal chemotherapy should be used in the noninvasive form of aspergillosis has not been definitely resolved. Presented is a review of the literature, the report of a case, and a discussion of possible pathogenic mechanisms.

Adult↗
PubMed1976

The labial melanotic macule.

Fifty-five cases of a melanotic lesion of the lips which is well known, but not well described, are reported. The lesions characteristically occur on the lower lips of young adults. Males and females are equally affected. These lesions may be ephelides, postinflammatory melanoses, or unique lesions for which there is no exact cutaneous counterpart. We suggest the term labial melanotic macule as a descriptive one which would encompass the three different constituent entities. On the basis of follow-up information obtained and the histopathologic character of the lesions, this entity is benign and does not, in our opinion, have any malignant potential.

Adolescent↗
PubMedDate not supplied

Development and evolution of adult feeding structures in Caenogastropods: overcoming larval functional constraints.

Comparative study of the developing foregut in three species of caenogastropods, including an herbivorous grazer (Lacuna vincta) and two carnivores (Euspira [Polinices] lewisii and Nassarius mendicus), suggests how the specialized adult foregut of a carnivorous neogastropod evolved within a life cycle having a planktotrophic larva. Postmetamorphic feeding structures (buccal cavity and radular sac) in all three species achieve advanced differentiation in the larval stage, permitting juvenile feeding at 3 days postmetamorphosis. Recent phylogenetic hypotheses for the Gastropoda predict that foregut developmental patterns in E. lewisii and N. mendicus are derived, relative to that of L. vincta. In hatching larvae of these three, the anlage of postmetamorphic feeding structures is a small patch of nonciliated cells embedded in the ventral wall of the larval foregut and the patch soon forms an outpocketing. During subsequent morphogenesis, Euspira lewisii and N. mendicus share a developmental novelty that involves semi-isolation of the developing, postmetamorphic buccal cavity and radular sac from the larval foregut and formation of a new, definitive mouth at metamorphosis. Nassarius mendicus, a neogastropod, embellishes this novelty by adding the entire anterior esophagus and valve of Leiblein (de novo structures) to the semi-isolated buccal cavity. Therefore, a valve and long stretch of muscular anterior esophagus, which are necessary for feeding with a pleurembolic proboscis, are preformed in the larval stage of this neogastropod without interfering with larval feeding. The inferred evolutionary events leading to postmetamorphic feeding specialization in N. mendicus are invisible in adults; they require reconstruction from comparative developmental analysis.

Animals↗