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Biomedical subjects

G M Wright

Publications and source records attributed to G M Wright.

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

The presence of corticotropin-like and opiate-like activities in tissues of adult sea lamprey, Petromyzon marinus L.

Sexually mature landlocked sea lamprey were captured during their upstream migration. Different tissues, including the brain, pituitary, heart, liver, gut, testis, and ovary, were dissected from the animals and an acetone powder was prepared from each tissue. The tissue acetone powders were subjected to heat treatment and were then extracted with an acidic medium in order to inactivate any proteases present. The resulting acid acetone powders were then tested for their ability to stimulate corticosterone production from isolated rat adrenal cells and to displace the binding of D-Ala2-D-Leu5-[tyrosyl-3,5-3H]-enkephalin to rat brain membranes. It was found that the brain and liver contained steroidogenic activity while opiate activity was detected in the heart, liver, gut, brain, and pituitary. No steroidogenic activity was found in the heart, ovary, testis, gut, and pituitary while ovary and testis did not contain assayable opiate activity. None of the tissues contained beta-endorphin-like immunoreactivity.

Adrenocorticotropic Hormone↗
PubMed1989

Pharmacokinetic and pharmacodynamic interaction of N-acetyl procainamide and procainamide in humans.

Procainamide is a sodium channel blocker which prolongs QRS and QTc intervals, yet its major active metabolite, N-acetylprocainamide (NAPA), generally prolongs only QTc and has very different electrophysiologic and antiarrhythmic actions. In greater than 50% of patients receiving chronic treatment with procainamide, plasma concentrations of NAPA exceed those of procainamide. In this study, we examined the hypothesis that NAPA might alter the disposition kinetics or pharmacologic actions of procainamide. Ten patients with frequent ventricular extrasystoles received intravenous (i.v.) infusions of procainamide alone (study day 1), procainamide and NAPA (study day 2), and NAPA alone (study day 3) at least 48 h apart. On study days 1 and 2, procainamide was administered at a constant rate for 4 h. On study days 2 and 3, NAPA was administered as a loading and maintenance infusion designed to reach a target pseudo-equilibrium plasma concentration of 8 micrograms/ml. NAPA increased procainamide elimination half-life (t1/2) from 275 +/- 42 min (mean +/- SD) on day 1 to 340 +/- 74 min on day 2 (p less than 0.01). A significant correlations was noted between the change in procainamide total clearance on day 2 relative to day 1 and the initial procainamide total clearance on day 1 (r = -0.77, p = 0.009). Findings were similar when procainamide fractional urinary excretion was considered (r = -0.89, p = 0.007). NAPA did not alter procainamide-induced QRS prolongation, but potentiated procainamide-induced QTc prolongation. The antiarrhythmic response to procainamide was not significantly altered by NAPA in seven of nine patients. One patient had greater arrhythmia suppression when NAPA and procainamide were combined than when either was administered alone. In one patient, NAPA apparently antagonized procainamide-induced arrhythmia suppression, but this effect was not reproducible. We conclude that accumulation of NAPA during procainamide therapy can alter both procainamide elimination as well as its electrophysiologic actions.

Acecainide↗
PubMed1988

Trabecular, nasal, branchial, and pericardial cartilages in the sea lamprey, Petromyzon marinus: fine structure and immunohistochemical detection of elastin.

Immunohistochemical and ultrastructural methods were used to examine the distribution of elastin and the fine structure of the trabecular, nasal, branchial, and pericardial cartilages in the sea lamprey, Petromyzon marinus. The cells and matrix, as well as the overall organization of these components, in larval and adult trabecular cartilage resemble those of adult annular and piston cartilages (Wright and Youson: Am. J. Anat., 167:59-70, 1983) Chondrocytes are similar to those in hyaline cartilage. Lamprin fibrils and matrix granules, but no collagen fibrils, are found in a matrix arranged into pericellular, territorial, and interterritorial zones. Branchial, pericardial, and nasal cartilages differ from trabecular, annular, and piston cartilages in the organization of their matrix and in the structural components of their matrix and perichondria. Furthermore, immunoreactive elastin-like material is present within the perichondria and peripheral matrices of nasal, branchial, and pericardial cartilages in both larval and adult lampreys. Oxytalan, elaunin, and elastic-like fibers are dispersed between collagen fibers in the perichondrium. The matrix contains lamprin fibrils, matrix granules, and a band of amorphous material, which is reminiscent of elastin, in the periphery bordering the perichondrium. The presence of elastic-like fibers and elastin-like material within some lamprey cartilages implies that this protein may have evolved earlier in vertebrate history than has been previously suggested.

Animals↗
PubMed1988

Relationship between the P300 auditory event-related potential and automated psychometric tests.

Event-related potentials particularly the P3 component have been noted to be abnormal in illnesses affecting cognitive processes, such as dementia. The relationship between the P3 latency and objective tests of mental function in patients with Alzheimer's disease and vascular dementia has been studied. A significant correlation was demonstrated between P3 latency and automated psychometric tests in patients with Alzheimer's disease.

Aged↗
PubMed1986

Immunocytochemical study of fibronectin in the sea lamprey, Petromyzon marinus, and the Atlantic hagfish, Myxine glutinosa.

Immunoreactive fibronectin-like material was localized within tissues of agnathans (hagfishes and lampreys) by an immunoperoxidase technique. Fibronectin was detected in basement membranes and in loose and dense connective tissues throughout the agnathan body. A fibronectin-like component was also identified in the plasma of both lampreys and hagfishes. The results indicate that fibronectin or a fibronectin-like material is a major component of agnathan connective tissues. Although there were some variations in the localization of fibronectin both between the lamprey and the hagfish and between agnathan and other vertebrate tissues, the generalized pattern of distribution of fibronectin in the agnathans supports the view that this protein, like that in higher vertebrates, plays a role in cell-matrix adhesion and tissue organization.

Animals↗
PubMed1986

Immunocytochemical demonstration of growth hormone, prolactin and somatostatin-like immunoreactivities in the brain of larval, young adult and upstream migrant adult sea lamprey, Petromyzon marinus.

Growth hormone, prolactin and somatostatin-like immunoreactivities were demonstrated in the brains of larval, young adult (parasitic) and upstream migrant adult sea lampreys, Petromyzon marinus, by means of immunoperoxidase techniques. Growth hormone (GH) and prolactin (PRL) were observed within separate perikarya in the nucleus praeopticus, within fibers in the commissura praeinfundibularis, and in nerve endings within the neurohypophysis of larval and adult-stage lampreys. Cell bodies demonstrating immunoreactive growth hormone were more numerous than those reactive for prolactin. Unlike in the upstream migrant adult lamprey, no GH or PRL was demonstrated in the adenohypophysis of larval or parasitic lamprey. Somatostatin (SRIF)-like immunoreactive neurons were demonstrated in the nucleus commissurae praeinfundibularis, anterior and posterior pars ventralis hypothalami, pars dorsalis thalami, and the tegmentum motorium rhombencephali of larval, parasitic and upstream migrant adult lampreys. Many of the SRIF containing neurons within the hypothalamus were cerebrospinal fluid (CSF)-contacting cells. SRIF fibers were found throughout most of the brain predominating within the nucleus praeopticus, pars ventralis hypothalami, and the nucleus interpeduncularis. No SRIF immunoreactivity was found within the neurophyophysis. The possible functions of these peptides within the brain of the lamprey are discussed.

Aging↗
PubMed1984

Cartilage in the Atlantic hagfish, Myxine glutinosa.

Light and electron microscopic observations and biochemical analysis of the lingual cartilages from the Atlantic hagfish, Myxine glutinosa, reveal two different types of cartilage, designated types 1 and 2, respectively. The anterior and medial lingual are type 1, while the posterior lingual cartilage is type 2. Chondrocytes in type 1 cartilage are similar to those found in other vertebrate cartilages. The presence within the Golgi elements of material that resembles a component of the extracellular matrix suggests the involvement of active chondrocytes in the synthesis of the matrix. The matrix of the type 1 cartilage contains fibrils arranged to form concentric lamellae in the territorial matrix and irregularly arranged, branched fibrils in the interterritorial matrix. Biochemical analysis of the type 1 cartilage reveals that it is composed primarily of a cyanogen bromide (CNBr)-insoluble protein of unique composition that we have termed " myxinin ." Myxinin appears to be similar, but not identical, to lamprin . Type 2 cartilage bears no resemblance to any other known vertebrate cartilage. The principal cells are hypertrophied and are characterized by masses of cytoplasmic filaments. The appearance of the organelles in smaller nest cells suggests that nest cells are active in the production of some of the matrix, which consists primarily of collagen. Microfibrils and a basal lamina-like material are also present. Biochemical analysis of the type 2 cartilage reveals that the CNBr-insoluble material is different from myxinin . Comparisons of lamprey and hagfish cartilages prompt the concept that these two agnathans probably followed long-independent evolutionary histories.

Animals↗
PubMed1984

Immunocytochemical study of growth hormone, prolactin, and thyroid-stimulating hormone in the adenohypophysis of the sea lamprey, Petromyzon marinus L., during its upstream migration.

Immunoreactivity to growth hormone (GH), prolactin (PRL), and thyroid-stimulating hormone (TSH) was found in the adenohypophysis of the sea lamprey, Petromyzon marinus L., during its upstream migration, by immunoperoxidase techniques with antisera to mammalian pituitary hormones. Cross-reactivity to GH and PRL was found in two different cell populations in the proximal pars distalis. Specific immunostaining for GH and PRL was absent in other parts of the lamprey pituitary. Immunoreactive TSH cells were located only in the rostral pars distalis, and corresponded in shape and size to the large basophils in this region of the lamprey pituitary. These results suggest that mammalian-like GH, PRL, and TSH are produced in the pituitary of the lamprey.

Animals↗
PubMed1983

Ultrastructure of cartilage from young adult sea lamprey, Petromyzon marinus L: a new type of vertebrate cartilage.

Ultrastructural observations of cartilage from adult sea lamprey, Petromyzon marinus, reveal a highly cellular cartilage with an unusual extracellular matrix. The avascular cartilage is surrounded by a vascular perichondrium, which consists of dense connective tissue containing fibroblasts, collagen fibrils, and microfibrils. The cells (chondrocytes) vary in morphology in different parts of the cartilage in a way that may reflect their state of activity. Chondrocytes within the peripheral cartilage contain tubulo-vesicular structures along the cell surface, an extensive lamellar rough endoplasmic reticulum, and a well-developed Golgi complex with associated vesicles and vacuoles. The presence of material within the Golgi elements that resembles components of the extracellular matrix suggests the involvement of the peripheral chondrocytes in the synthesis and secretion of the matrix components. Chondrocytes within the central cartilage are hypertrophied and contain a pale cytoplasm with a reduced number of organelles that are widely spaced throughout the cell. The appearance of the organelles within these cells suggests that they are not as actively involved in the production of the matrix as those of the peripheral cartilage. The extracellular matrix consists of a dense network of randomly arranged, branched, noncollagenous matrix fibrils 15-40 nm in diameter and varying amounts of electron-dense matrix granules. Due to the unique nature of its extracellular matrix, the cartilage of the lamprey cannot be likened to any of the known vertebrate cartilages and, therefore, must be considered a new type of vertebrate cartilage.

Animals↗
PubMed1983

Ultrastructure of the adenohypophysis in the larval anadromous sea lamprey, Petromyzon marinus L.

The ultrastructure of the adenohypophysis (AH) in the larval anadromous sea lamprey, Petromyzon marinus L., was examined. The AH is subdivided into three regions, the pro-, meso-, and meta-AH. Cells of the nasopharyngeal stalk extend directly beneath the pro- and meso-AH to form the ventral surface of the gland. Some cells in the pro- and meso-AH are arranged into small follicles. Each region of the AH is characterized by a single granulated (secretory) cell type. Granulated cells constitute 80-90% of the pro-AH and contain secretory granules that range from 800 to 2400 A in diameter. Only 10-20% of the cells in the meso-AH are granulated and they contain much smaller secretory granules (400 to 1250 A diameter) than those in the pro-AH. Granulated cells constitute 80-90% of the meta-AH and contain only a few secretory granules, ranging from 1000 to 2500 A in diameter, and many vesicles containing either a loose flocculent or dense granular material. Non-granulated (stellate) cells are found in all regions. They are characterized by their long cell processes, abundant cytoplasmic filaments, and variable electron density. The appearance of organelles in these cells suggests they are nonsecretory. They may play a role in maintaining the structural integrity of the gland and the regulation of granule release in the pro-AH. Two types of nongranulated cells make up 80-90% of the meso-AH. Type I are stellate cells, type II may be undifferentiated cells. The functional significance of the secretory cells in the larval AH is discussed.

Animals↗
PubMed1982

Ultrastructure of mucocartilage in the larval anadromous sea lamprey, Petromyzon marinus L.

The fine structure of mucocartilage, a tissue unique to larval lampreys, was examined in Petromyzon marinus L. This tissue is surrounded by a perichondrium of vascularized, dense connective tissue composed of fibroblasts, collagen fibrils, and elastic-like microfibrils, but it is avascular itself and consists of elastic-like microfibrils, ground substance, and a few diffusely scattered fibroblasts. Fibroblasts possess rough endoplasmic reticulum, may free ribosomes, a well-developed Golgi apparatus, a tubulo-vesicular network, and a number of secondary lysosomes containing crystalline material. The appearance of the organelles suggests the involvement of the cell in the synthesis and secretion of the ground substance and microfibrils. Tubular microfibrils, 11-13 nm in diameter, comprise the major portion of the matrix, and they are similar to those described in developing mammalian elastic tissue (Ross and Bornstein, 1969). The retention of the microfibrils may represent either a primitive form of elastic fiber in this "primitive" vertebrate or reflect the larval condition of the lampreys under examination. Scattered spherical to polyhedral-shaped mitrix granules and intergranular filaments make up the remainder of the matrix. It was concluded that mucocartilage in larval lampreys is not a conventional type of vertebrate connective tissue.

Animals↗