Biomedical subjects
Publications and source records attributed to T A Weidman.
The preperitoneal space is presented from an embryologic, anatomic, and surgical standpoint in detail. Because this space is one of the most used areas for the repair of groin hernias, knowledge of its embryology and anatomy is essential.
PURPOSE: This study demonstrates the effects of eye rubbing on ocular surface tissue. METHODS: Rabbits (3-4 kg; n = 24) were killed at 0, 4-h, 8-h, and 12-h intervals after a 5-min period of eye rubbing. Ocular surface tissues were studied by light and scanning electron microscopy. Contralateral eyes served as controls. Eye rubbing was accomplished by using digital pressure over the closed eyelid with a force sufficient to appreciate by palpation the orbital rim. Biomicroscopic examination revealed marked vascular injection of the conjunctiva. Ocular surface tissues studied included the lid margins, the upper and lower tarsal conjunctivae, the bulbar conjunctiva, and the cornea. RESULTS: Changes in the ocular surface included dramatic alteration in the upper tarsal conjunctiva when compared with controls. The cornea and bulbar and lower tarsal conjunctiva were not altered when compared with control tissues, except for some increase in exfoliating cells in the cornea. The surface epithelial cells of the upper tarsal conjunctiva had a spheroidal structure and were markedly elevated, the microprojections were altered, and there was evidence of increased cellular exfoliation. These changes were most pronounced at the 0 and 4-h time points, less noticeable at 8 h, and no appreciable changes were observed when compared with control tissues at 12 h. CONCLUSION: This study demonstrates that eye rubbing causes surface alterations in the stratified cuboidal to columnar epithelial surface of the upper tarsal conjunctiva while sparing the stratified squamous epithelial surface of the distal lid margins and cornea.
We documented the comparative histogenesis and timing of development of Bruch's membrane (complexus basalis) in five mammalian models with different lengths of gestation. Retinas with attached choroid from the central posterior pole of the eye were obtained from hamster, vole, rabbit, ferret and cat, from mid-gestation onward until the time at which all components of Bruch's membrane could be detected. The sequence of events in the development of Bruch's membrane was similar among species, however the time of appearance of the components varied. At mid-gestation, the basement membrane of the retinal pigment epithelium (RPE) was present to some degree in all species and microfibrils were developing in the connective tissue space external to the RPE basement membrane. The appearance of an initially scant endothelial basement membrane around the choriocapillaries occurred on post-natal (P) day 1 (P1) in hamster, pre-natal (E) day 20 (E20) in vole, E16 in rabbit, P2 in ferret, and E48 in cat. Among the microfibrils within the connective tissue space external to the RPE, electron-dense islands presumed to be elastin were detected on P7 in hamster, P9 in vole, E24 in rabbit, P19 in ferret, and P1 in cat. Relative to birth date and eye opening, the components of Bruch's membrane in the ferret were detected at a later date than that of the other species studied. However, relative to the interval from conception to the appearance of the components of Bruch's membrane, the ferret and cat are similar, paralleling their similar intervals from conception to eye opening.
An Alcian-blue/Periodic acid Schiff reagent (AB/PAS) pH dependent staining method was used to identify the mucus content of secretory vesicles of non-goblet epithelial cells of the human conjunctiva. Twenty subjects were selected for biopsy of the midcentral upper tarsal conjunctiva: 10 subjects had no contact lens wearing experience, and 10 subjects wore contact lenses. Human respiratory epithelium was used as a control for the staining procedure. Four-micron paraffin sections of conjunctival and control tissues were stained with Alcian blue at pH 2.5 and 1.0 and counterstained with PAS. Non-goblet epithelial cell secretory vesicles contained neutral mucin, sialmucin, and sulphomucin. This study provides evidence for a 'second' mucus system of the conjunctiva, that this system is in the non-goblet epithelial cells, and that the mucus of this system has sulphomucins, sialomucins and neutral mucins.
The retina of the adult ferret, Mustelo furo, was studied with light and transmission electron microscopy to provide an anatomical basis for use of the ferret as a model for retinal research. The pigment epithelium is a simple cuboidal layer of cells characterized by a zone of basal folds, apical microvilli, and pigment granules at various stages of maturation. The distinction between rod and cone photoreceptor cells is based on their location, morphology, heterochromatin pattern and the electron density of their inner segments. The round, light-staining cone cell nuclei occupy the layer of perikarya along the apical border of the outer nuclear layer. The remainder of the outer nuclear layer consists of oblong, deeply-stained rod cell nuclei. Ribbon type synaptic complexes involving photoreceptor cell axons, horizontal cell processes, and bipolar cell dendrites characterize the outer plexiform layer. The inner nuclear layer is comprised of horizontal, bipolar, and amacrine cell perikarya as well as the perikarya of the Müller cells. The light-staining horizontal cell nuclei are prominent along the apical border of the inner nuclear layer. The light-staining amacrine cell nuclei form a more or less continuous layer along the basal border of the inner nuclear layer. Both conventional and ribbon-type synapses characterize the inner plexiform layer. The ganglion cells form a single cell layer. The optic fiber layer contains bundles of axons surrounded by Müller cell processes. Small blood vessels and capillaries are present in the basal portion of the retina throughout the region extending from the internal limiting membrane to the outer plexiform layer. The adult one-year-old retina is compared with the retina at the time of eye opening.
Pericentriolar processes (arm-like fibers) of the migrating centrioles (diplosome) in differentiating retinal photoreceptor cells were examined in six mammalian species (hamster, vole, rat, rabbit, ferret, cat). These processes emanate in a radial fashion from one end of the centrioles comprising the photoreceptor diplosome. The pericentriolar processes of the basal body are first observed as the diplosome migrates toward the apical plasmalemma, suggesting that centrioles are committed early-on to developing such processes. One pericentriolar process arises from each set of microtubular triplets comprising the centriole and are apicoexternally oriented at an angle of between 30 and 60 degrees with the centriolar axis. Prior to the arrival of one of the centrioles at the apical plasmalemma these processes connect with an electron-dense portion of a centriole-associated vacuole. The diplosome migrates to the apical plasmalemma where one centriole (the presumptive basal body) orients perpendicularly to the apical plasmalemma. The centriole-associated vacuole appears to fuse with the plasmalemma. The pericentriolar processes appear to attach to this fusion site on the plasmalemma which is a region of the membrane characterized by increased electron density (the basilar plate). Invagination of the apical membrane, which occurs at this same site, is accompanied by a lengthening of the microtubules forming a cilium and is observed as an outpouching of the plasmalemma within the aforementioned invagination. The associated vacuole apparently becomes continuous with the apical plasmalemma. These pericentriolar processes appear to be functionally involved in ciliogenesis and offer structural stability between the basal body, the plasmalemma and indirectly the cilium.
Explore the source record for details and available documents.
Fifteen specimens of the upper tarsal conjunctiva were obtained from subjects with biomicroscopically normal conjunctivae. Ten specimens were examined by scanning electron microscopy and five by transmission electron microscopy. This examination was performed to examine cells with variant surface morphologic appearance that may be signs of the initial changes typical of those seen in the diseased conjunctiva. Although most specimens had cells with a characteristic uniform distribution of microvilli, seven specimens had cells with nonuniform microvillar patterns. In these seven specimens, less than 5% of the cells showed these changes. Cell surface variations marked by reduced cell diameters and alterations in the microvillar distribution were categorized into two groups: cells with microvilli that were grouped together to form tufts of varying height and number, and cells with a single, centralized group of microvilli. These variations were seen with increased frequency in disease, and it is postulated that the microvillar changes described in this study represent a continuum of adaptive responses of cells to insult and disease.
We correlated histologic findings concerning conjunctival goblet cells with findings concerning the mucous membrane surfaces of the conjunctiva. Ten biopsy specimens were obtained from the upper tarsal conjunctiva and ten from the perilimbal bulbar conjunctiva. Changes in goblet cells just before and during secretion included changes in surface cell diameter, evagination of the apical surface of the cell membrane, decrease in the number of microvilli, and alteration in the arrangement and morphologic characteristics of microvilli. Changes seen by light and transmission electron microscopy correlated with those observed by scanning electron microscopy. Goblet cells were often associated with crypt openings; some crypts served as conduits for the secretion of mucus from underlying goblet cells. This study supports the hypothesis that crypts in the conjunctiva seen by scanning electron microscopy are often associated with goblet cells and their mucus secretion.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Biopsy specimens were obtained from the upper tarsal and limbal conjunctivae of ten normal persons and from the upper tarsal conjunctivae of five asymptomatic contact lens wearers and five patients with giant papillary conjunctivitis (GPC) associated with contact lens wear. The microvillar surface of the conjunctival epithelium was studied by transmission and scanning electron microscopy. Branches often stemmed from the side of a straight tubular microvillus and formed an acute angle with the main process. Branches sprouted at various distances from the origin of the microvillus. The most common branching pattern was the bifurcated (bifid) form. Occasionally, both primary and secondary bifurcations were primary and secondary bifurcations were observed on the same microvillus. Some microvilli were branched in the normal conjunctivae, but the conjunctivae of asymptomatic contact lens wearers and patients with GPC had more branched microvilli and greater polymorphism, which correlated with the degree of alteration. This report demonstrates the presence of branched microvilli and describes the types seen in normal conjunctivae and compares the frequency with which branched microvilli are seen in altered conjunctival surfaces.
Biopsy specimens from the upper tarsal conjunctivae of ten patients with clinically evident contact-lens-associated giant papillary conjunctivitis (GPC) and eight asymptomatic contact lens wearers without clinically evident conjunctival changes were compared by light and transmission electron microscopy to determine the contribution of nongoblet epithelial cells to increased mucus. A control group consisted of five subjects who had never worn contact lenses. The apical cytoplasm of superficial nongoblet epithelial cells in specimens from all groups showed single-membrane-limited vesicular inclusions that stained metachromatically with toluidine blue and were positive with PAS staining, which indicated muco-protein content. Some vesicles appeared to discharge their contents into the conjunctival sac. More vesicles were found in the GPC subjects and the asymptomatic contact lens wearers than in the normal subjects. These observations, coupled with the sign of increased or excessive mucus discharge in GPC subjects and in asymptomatic lens wearers, support the premise that the superficial layers of non-goblet conjunctival epithelial cells can contribute to an increase in mucus production.
The available descriptions of the development of sympathetic innervation of the chick heart conflict with the known sympathetic innervation of the adult chicken heart. The adult heart is innervated by bilateral sympathetic cardiac nerves originating from the first thoracic sympathetic ganglia. These nerves travel lateral and anterior to the lung and join the vagi just before entering the pericardium along the great vessels. Using catecholamine histofluorescence techniques and silver preparations, we have observed the development of the sympathetic cardiac nerves. The sympathetic cardiac nerves arise from the first thoracic sympathetic ganglia on the 7th day of incubation. They grow lateral and then ventral to the developing lungs to join the vagi, and are found in the bulbar region of the heart and atrium on the 10th day of incubation. FLuorescent cells without processes mark the course of the sympathetic cardiac nerves and are present in the bulbar region on the 10th day and thereafter. Sympathetic ganglion cells lose their fluorescence between day 8 and day 16 of incubation. This is presumably due to dilution of the transmitter in the rapidly increasing volume of cytoplasm in the sprouting neurons. Small intensely fluorescent (SIF) and adrenal medullary cells do not undergo a diminution of fluorescence during this period. SIF cells appear well differentiated at 16 days.
Explore the source record for details and available documents.
The development of the chick bulbar cardiac ganglia has been studied ultrastructurally from the 3rd day of incubation to hatching. For descriptive purposes, their development has been divided into three phases. The first phase includes migration and aggregation of undifferentiated neuroblasts, stages 21-26 (day 3.5-5). Cardiac branches of the vagus first grow toward the heart at 3.5 days of incubation. The nerves are accompanied by migrating neural crest neuroblasts. The neuroblasts begin to aggregate at 4.5 days around the aortic arch arteries and truncus arteriosus. Some of these cells sprout axonal processes by day 5. A sparse population of developing supporting cells can be found near some neuroblasts and nerves. During the second phase of development, stages 27-36 (days 5-10), the neuroblasts assume a globular shape and have eccentric, indented nuclei. Supporting cells become more numerous as this phase of development progresses. Axodendritic synapses appear first at stage 34 in the ganglia. The neurons and supporting cells in the ganglia undergo maturation during the final phase from stage 37 to hatching (11-21 days). The immature/mature ganglion cells are large ovoid to pyriform neurons which become rounder as the cytoplasm accumulates. Axosomatic synapses are seen first at stage 38. Small supporting cells become more numerous. Clusters of catecholamine-containing cells near the cardiac ganglia are present during the final phase of development.
Development of the trochlear nerve from day 11 of incubation through hatching was studied in white Peking duck embryos. Counts of fibers from the electron micrograph montages indicate that initially there is an abundant collateral sprouting which roughly coincides with the time of neuromuscular contacts, suggesting some sort of interaction between the developing nerve and the periphery. The maximum number of trochlear cells and fibers is present on day 12. Average cell and fiber counts on this day are 2325 and 47,386 respectively. Assuming all cells send their axons into the nerve and that all cell bodies are present within the trochlear nucleus, the ration of cells to fibers is 1:20. Average cell and fiber counts at hatching are 1338 and 1506 respectively. Thus, losses of approximately half the trochlear cells and of 97% of the fibers occur during normal development. Degenerating cells and fibers are first observed on day 13. Degeneration involves both the myelinated and the unmyelinated axons. The actual number of degenerating fibers which were observed, however, was very small compared to the number of fibers lost during development; thus, it is suggested that, in the majority of cases, fiber loss is perhaps via retraction of axon collaterals. In general, cell death slightly precedes axon loss, which suggests that the direction of the degeneration is from cell body to the axon. A cell/fiber ratio of approximately 1:1 is first observed on day 18 and remains so thereafter. Indirect evidence is discussed, suggesting that at least some cells which die during normal devleopment had sent their axon into the nerve prior to their death. Whether these axons make meaningful connections with the muscle is uncertain.
Explore the source record for details and available documents.