PubMed Health⌕ Search

Biomedical subjects

J Wharton

Publications and source records attributed to J Wharton.

At least 73 records · Page 4Linked to original sources
PubMed1992

Autoradiographic localization and analysis of endothelin-1 binding sites in human synovial tissue.

OBJECTIVE: To determine the localization of endothelin binding sites and immunoreactivity in human synovial tissues. METHODS: Quantitative in vitro autoradiographic and immunohistochemical techniques were used to localize and characterize 125I-labeled endothelin-1 (125I-ET-1) binding sites and endothelin-like immunoreactivity in sections of rheumatoid, osteoarthritic, and normal synovium. RESULTS: Specific 125I-ET-1-binding sites, characteristic of the ETA receptor, were localized to the media of synovial blood vessels in all 3 groups. No difference was found in vascular binding site density in rheumatoid and osteoarthritic synovium. Endothelin-like immunoreactivity was localized to endothelial cells in blood vessels displaying 125I-ET-1 binding sites. CONCLUSION: We conclude that endothelin may act locally, modulating synovial perfusion and exacerbating hypoxia in chronic arthritis.

Aged↗
PubMed1992

Localization of brain and atrial natriuretic peptide in human and porcine heart.

We have compared the localization of brain and atrial natriuretic peptide-like immunoreactivity in human and porcine hearts, using immunohistochemical techniques at both the light and ultrastructural level and specific antisera to amino-(cardiodilatin) and carboxy-terminal regions of the atrial natriuretic precursor molecule and to brain natriuretic peptide. Atrial myocardial cells in human fetal, normal adult and failing explanted hearts, displayed immunoreactivity for both brain and atrial natriuretic peptide-like sequences. At the subcellular level, brain natriuretic peptide-, cardiodilatin- and alpha-atrial natriuretic peptide-like immunoreactivity were co-localized to secretory granules in atrial myocardial cells. Immunoreactivity was also detected in the left (64%) and right ventricular free walls (23%) of 22 failing explanted hearts, but not in donor cardiac tissues. A gradient of natriuretic peptide immunostaining was observed across ventricular free walls and immunoreactivity for both natriuretic peptide sequences co-localized to secretory granules in a subpopulation of myocardial cells, concentrated in subendocardial regions of the ventricular walls. Brain and atrial natriuretic peptide-like immunoreactivity were also demonstrated in porcine atrial myocardium and cells of the ventricular conduction system. The parallel distribution of cardiac brain and atrial natriuretic peptide-like immunoreactivity suggests a dual regulation and co-storage of the natriuretic peptides in human and porcine hearts.

Adolescent↗
PubMed1992

Cardiac denervation in the calf using cryoablation: functional evidence and regional tissue catecholamine content.

Twenty-six calves were subjected to a technique of cryoablation in order to establish an animal model of complete cardiac denervation. All 26 survived the procedure, and 20 were alive to be re-evaluated 2-4 weeks later. Mean heart rate in the denervated animals rose from 77 +/- 7.8 beats/min to 102 +/- 16.4 (P less than 0.01). Cryoablation abolished the heart rate responses to electrical stimulation of the vagus nerve and thoracic sympathetic trunk. The reduction in myocardial noradrenaline concentrations averaged 99% in the right atrium, 90% in the left atrium, 85% in the right ventricle and 90% in the left ventricle, when compared with tissue obtained from control animals. Cryoablation is a relatively simple means of accomplishing complete functional cardiac denervation in the calf. On the basis of the observed change in heart rate, the calf model appears to be more comparable with human heart transplant recipients than the dog.

Animals↗
PubMed1992

Occurrence of auditory evoked field (AEF) N1M and P2M components in a sample of normal subjects.

A great deal of information about the characteristics of components N1m and P2m of the auditory evoked cortical fields (AEFs) has accumulated since the late 1970s. However, a number of fundamental issues have not been addressed. For instance, some previous investigators have suggested that P2m is present consistently in normals, whereas others suggest that when present, P2m is small in amplitude. Preliminary observations in this laboratory suggested that P2m is not observed consistently in normal subjects. Therefore, the specific aim of this investigation was to estimate the frequency of occurrence of the contralaterally recorded N1m and P2m after stimulation of right and left ears in normal subjects. Results demonstrated N1m to be present in all circumstances. Consistent with our preliminary observations, P2m was often absent, and moreso after stimulation of the left ear.

Adult↗
PubMed1992

Localisation and characterisation of substance P binding to human synovial tissue in rheumatoid arthritis.

The neuropeptide substance P is found in perivascular and free unmyelinated nerve fibres in human synovial tissue. Quantitative receptor autoradiography was used to show specific, high affinity (Kd = 0.75 (0.21), nmol/l (mean (standard error of the mean)), low capacity (Bmax = 27.8 (7.9) amol/mm2) binding sites for substance P Bolton Hunter-labelled with iodine-125 localised to vascular endothelial cells in human synovial tissue. The binding could be saturated, was reversible, and was dependent on the magnesium concentration. Unlabelled substance P and neurokinin A competitively inhibited specific binding with 50% inhibition at concentrations of 1.25 (0.21) and 175 (29) nmol/l respectively. Neurokinin B (mumol/l) and calcitonin gene related peptide (1 mumol/l) did not inhibit binding. These binding sites show characteristics of the neurokinin 1 tachykinin receptor subtype. This provides further evidence that substance P may play a part in the vascular control of human synovium and may influence inflammatory processes in joints.

Adult↗
PubMed1992

Neural and endothelial regulatory peptides, their possible involvement in inflammation.

The vasoactive regulatory peptides produced by neural and endothelial tissues contribute to normal vascular function and can modify the inflammatory process. Modern microscopic imaging techniques are revealing the plasticity of this neurovascular peptidergic system, highlighting changes in the synthesis, release, binding and degradation of vasoactive peptides during the inflammatory process. Initial changes may represent normal protective mechanisms against tissue injury, while subsequently a loss of neurovascular regulation may contribute to the pathogenesis of some inflammatory conditions. Understanding the complexity of these regulatory systems provides novel insights into the inflammatory process and suggests new possibilities for therapeutic approaches to human disease. In this review we examine the potential for modern microscopic imaging techniques to help elucidate the complexity of the inflammatory process, as illustrated by the involvement of the vasoactive neural- and endothelial-derived regulatory peptides substance P, calcitonin gene-related peptide, neuropeptide Y and endothelin.

Animals↗
PubMed1991

Autoradiographic discrimination of brain and atrial natriuretic peptide-binding sites in the rat kidney.

Brain (BNP) and atrial natriuretic peptides (ANP) have been identified which may represent endogenous agonists of kidney receptor subtypes. Quantitative in vitro autoradiography was used to investigate the regional distribution of receptor subpopulations and the competitive inhibition of 125I porcine BNP1-26 (pBNP1-26) and 125I rat alpha-ANP1-28 (rANP1-28) renal binding sites. Specific, high affinity binding (Kd 0.2-1.37 nM range) was localized to glomeruli, inner medulla, interlobar and arcuate arteries, vasa recta bundles, and smooth muscle in the renal pelvis. pBNP1-26 competed for the same sites as rANP1-28 but displayed a lower potency and was less selective for nonclearance sites. Clearance binding sites were discriminated by competitive inhibition with C-ANP4-23 and comprised some 65% of glomerular sites as well as the vast majority of sites in the renal pelvis. Nonclearance sites predominated in the inner medulla and intrarenal arteries. C-terminal changes in amino acid sequence induced a significant loss of inhibitory potency. Immunohistochemical studies identified a distinct population of BNP-like immunoreactive renal nerve fibers, associated with intra-renal arteries. Circulating natriuretic peptides and BNP sequences derived from renal nerves may influence renal function by interacting with specific receptor subpopulations in the kidney.

Amino Acid Sequence↗
PubMed1991

Atrial amyloid deposits in the failing human heart display both atrial and brain natriuretic peptide-like immunoreactivity.

Atrial amyloid deposits are common in the ageing human heart and contain alpha-atrial natriuretic peptide (proANP99-126) immunoreactivity. However, atrial myocytes secrete both amino and carboxy terminal fragments of the ANP prohormone (proANP1-126) and also express an homologous, but separate brain natriuretic peptide (BNP). Characteristic amyloid deposits were identified in the atria of 9/22 patients (26-63 years of age) with end-stage heart failure. Amyloid fibrils displayed immunoreactivity for both amino and carboxy terminal fragments of proANP1-126 and for the distinct BNP sequence. As in other endocrine organs, both mature and precursor peptide sequences appear to be constituents of amyloid fibrils. Whilst immunoreactivity for cardiac peptide hormones is co-localized in atrial amyloid deposits, it is uncertain whether the increase in natriuretic peptide expression which accompanies cardiac failure contributes to the incidence of isolated atrial amyloidosis.

Adolescent↗
PubMed1991

Localization of endothelinlike immunoreactivity and endothelin binding sites in human colon.

The potent vasoconstrictor endothelin was originally isolated from vascular endothelial cells but has since been found in several other tissues. The aim of this study was to establish whether endothelinlike immunoreactivity occurs in human enteric nerves and to identify endothelin binding sites using immunocytochemical and in vitro autoradiographic techniques. Endothelinlike immunoreactivity was localized to nerve bundles throughout the colon and to most of the ganglion cells of the two major plexuses, many of which costored vasoactive intestinal polypeptide. High-affinity (dissociation constant = 0.35 +/- 0.014 nmol/L; mean +/- SEM) binding sites for endothelin 1, with an apparent binding capacity of 92 +/- 6.3 amol/mm2 (mean +/- SEM), were demonstrated in the myenteric plexus, with less dense binding being found in the submucous plexus, mucosa, muscle layers, and blood vessel walls. Competition data suggested two populations of binding sites, both showing high affinities for endothelins 1 and 2, vasoactive intestinal constrictor, and sarafatoxin b but differentiated by their affinity for endothelin 3 and sarafatoxin c. This study provides evidence that endothelin is a neuropeptide in the human intestine with binding sites on neural plexuses and mucosa, suggesting a role in the modulation of intestinal motility and secretion.

Adult↗
PubMed1991

Auditory evoked cortical magnetic field (M100-M200) measurements in tinnitus and normal groups.

Recently, Hoke et al. (1989) and Pantev et al. (1989) demonstrated that the auditory evoked cortical magnetic field (AECMF) M100 component was larger, and M200 was smaller and occurred later in subjects with unilateral tinnitus compared with normal subjects. These group amplitude differences resulted in an M200/M100 amplitude ratio that was smaller for the subjects with tinnitus. The purposes of the present investigation were to: 1) extend the observations of Hoke et al. (1989), and, 2) determine whether contralateral AECMF differences existed following stimulation of the non-tinnitus and tinnitus ears of patients with tinnitus. Neuromagnetic AECMF recordings were recorded from 25 young normal hearing and 14 patients with unilateral tinnitus and hearing loss. The results failed to support the findings of Hoke et al. (1989). Specifically, there is no evidence suggesting that the M100 amplitude is larger, the M200 latency later, or, the M200/M100 amplitude ratios smaller, when the two samples are compared. Additionally, there were no differences in the amplitudes or latencies of M100 or M200 when results from stimulation of the tinnitus and non-tinnitus ears of tinnitus subjects were compared.

Adult↗
PubMed1991

Localization of endothelin binding sites and endothelin-like immunoreactivity in human fetal heart.

The localization of [125I]endothelin-1 ([125I]ET-1) and [125I]endothelin-3 ([125I]ET-3) binding sites, as well as ET-like immunoreactivity, was investigated in sections of human fetal heart, using in vitro autoradiographic and immunohistochemical techniques. High-affinity [125I]ET-1 binding sites showed a tissue-specific distribution pattern, with high-density binding to the atria, ventricles (77-100 amol/mm2), and cardiac valve cusps (120.6 +/- 2.6 amol/mm2). Specific high-density binding of [125I]ET-3 was also exhibited on valve cusps (143.2 +/- 2 amol/mm2), whereas a much lower density of binding was displayed on atria and ventricles (10-15 amol/mm2). Microautoradiographic examination demonstrated binding sites on the wall of the aorta, pulmonary and coronary arteries, myocardium, ventricular conduction system, endocardium, and endothelial lining of valve cusps. Regional differences in the density and affinity of ET binding sites suggest that subpopulations of receptors are present in the human fetal heart. ET-like immunoreactivity was localized to a heterogeneous population of endothelial, endocardial, and epicardial mesothelial cells. The concordant localization of specific binding sites and ET-like immunoreactive cells indicates that locally released peptide might have a paracrine or autocrine role, possibly influencing cardiovascular development and function.

Autoradiography↗
PubMed1991

Autoradiographic localization of endothelin-1 binding sites in porcine skin.

Autoradiographic techniques and 125I-labeled endothelin-1 were used to study the distribution of endothelin-1 binding sites in porcine skin. Specific endothelin-1 binding sites were localized to blood vessels (capillaries, deep cutaneous vascular plexus, arteries, and arterioles), the deep dermal and connective tissue sheath of hair follicles, sebaceous and sweat glands, and arrector pili muscle. Specific binding was inhibited by endothelin-2 and endothelin-3 as well as endothelin-1. Non-specific binding was found in the epidermis and the medulla of hair follicles. No binding was found in connective tissue or fat. These vascular binding sites may represent endothelin receptors, in keeping with the known cutaneous vasoconstrictor actions of the peptide. If all binding sites are receptors, the results suggest that endothelin could also regulate the function of sweat glands and may have trophic effects in the skin.

Animals↗
PubMed1991

Heterogeneous binding sites for alpha-atrial natriuretic peptide in human umbilical cord and placenta.

The distributions of atrial natriuretic peptide (ANP) clearance receptors in human umbilical cord and placenta were investigated by using des[Gln18,Ser19,Gly20,Leu21,Gly22]ANP-(4-2 3) (C-ANP) as a specific ligand of this receptor to displace bound alpha-125I-labeled ANP. alpha-125I-ANP bound reversibly to umbilical venous and arterial intima and to fetal placental and maternal decidual tissues, with dissociation constants of 1.24 +/- 0.51, 0.58 +/- 0.19, 1.86 +/- 0.51, and 1.07 +/- 0.25 mM, respectively. Binding was reversed by 1 microM unlabeled alpha-ANP but not by unrelated peptides such as gastrin. The 1 microM C-ANP displaced bound alpha-125I-ANP from the intima of umbilical artery but not that of the vein. The specific reversible binding of alpha-125I-ANP to placental decidua but not to fetal placenta was also displaced by 1 microM C-ANP. Therefore high-affinity binding sites for alpha-ANP on the intima of the umbilical artery and on placental decidua differ from those on the umbilical vein and on fetal placental tissue; the binding sites of the intima of the umbilical artery and of the decidua in humans are consistent with clearance receptors for alpha-ANP.

Adult↗
PubMed1991

Endothelin-1 in human skin: immunohistochemical, receptor binding, and functional studies.

The morphological distribution of endothelin-1 (ET-1) was investigated in human digital skin biopsies by immunohistochemistry using endothelin antisera, and by in vitro autoradiographic binding studies with 125I-labeled ET-1. In vitro studies on the responsiveness of cutaneous microvascular endothelium were carried out using human dermal microvascular endothelial cells (HDMEC) cultured from neonatal foreskin. Endothelin immunoreactivity was present in the endothelial cells of cutaneous blood vessels, in large and small arteries, veins in the dermis and capillaries, including those of the dermal papillae. Autoradiographic studies showed the presence of 125I-labeled ET-1 binding sites on the blood vessels and sweat glands. In confluent monolayers of HDMEC, ET-1 (100 pM-100 nM) significantly inhibited basal release of prostaglandin E2 (PGE2) (p less than 0.05), while causing a dose-dependent increase of intracellular cyclic adenosine monophosphate (cAMP) levels. cAMP accumulation, induced by 100 nM ET-1, was blocked by extracellular Ca2+ chelator EGTA, the intracellular Ca2+ chelator TMB-8, and dihydropyridine Ca(2+)-channel antagonist nifedipine (p less than 0.05), whereas ET-1 inhibition of PGE2 release was unaffected. These findings indicate that ET-1 may be important in the control of blood flow and vascular tone in the cutaneous microvasculature.

Adult↗
PubMed1990

Expression of neural cell adhesion molecule immunoreactivity in hypertrophic myocardium.

Myocardial neural cell adhesion molecule (N-CAM) is temporally regulated, being expressed during cardiac morphogenesis and innervation and suppressed in the adult heart. We have investigated the plasticity of N-CAM expression in hypertrophic muscle using the rat model of chronic hypoxia to selectively induce right ventricular hypertrophy over a 14 day time course. Sarcolemmal and intercalated disc N-CAM immunostaining was more extensive in the ventricular myocardium of hypoxic rats compared to normoxic controls. Quantitative assessment of the immunoreactivity in tissue extracts demonstrated a selective increase in the amount of N-CAM immunoreactivity in the hypertrophic myocardium of the right ventricle of rats exposed to hypoxia and this was associated with an increase of the 125 kDa isoform. We conclude that myocardial hypertrophy may be a factor influencing N-CAM expression in the heart and adhesion molecules may have a role in cardiac remodelling.

Animals↗
PubMed1990

Peptide-containing nerve fibres in guinea-pig coronary arteries: immunohistochemistry, ultrastructure and vasomotility.

The peptidergic innervation of guinea-pig coronary arteries was investigated by means of immunohistochemical, ultrastructural and in vitro pharmacological techniques. A network of nerves was demonstrated in all major epicardial arteries by means of an antiserum to the neuronal marker protein gene product 9.5. The majority of nerve fibres possessed neuropeptide Y (NPY) and tyrosine hydroxylase (TH) immunoreactivity, the number and distribution of nerves immunoreactive for NPY being similar to that of nerves containing TH immunoreactivity. Numerous nerve fibres displaying immunoreactivity for substance P, neuropeptide K and calcitonin gene-related peptide (CGRP) were also found. In double-stained preparations substance P immunoreactivity was co-localized with CGRP and with neuropeptide K immunoreactivities in the same varicose nerve fibres. Ultrastructural studies revealed the presence of numerous axon varicosities at the adventitial-medial border. NPY immunoreactivity was localized in large granular vesicles in nerve varicosities which also contained numerous small granular vesicles. Large granular vesicle-containing nerves also displayed immunoreactivity for dopamine-beta-hydroxylase. With an in vitro method, the vasomotor responses to perivascular peptides were characterized in epicardial and intramyocardial arteries. In epicardial arteries neither noradrenaline nor NPY elicited a contractile response. Only in some intramyocardial arteries was an NPY-mediated contraction demonstrated. No potentiating effect of noradrenaline and NPY was observed in either epicardial or intramyocardial arterial segments. In contrast, CGRP, substance P and vasoactive intestinal peptide (VIP) all produced a concentration-dependent relaxation of both epicardial and intramyocardial arteries. These results suggest that peptide-containing nerves associated with guinea-pig coronary arteries may predominantly be involved in mediating vasodilation.

Animals↗
PubMed1990

Immunohistochemical demonstration of human cardiac innervation before and after transplantation.

Knowledge about the distribution and origins of peptide-containing nerves in the innervated and transplanted heart is lacking. Immunohistochemical and histochemical techniques were used to visualize human cardiac innervation before and after transplantation. In the recipient heart cardiac nerve fibers and fascicles displayed immunoreactivity for general neural (protein gene product 9.5 and synaptophysin) and Schwann cell markers (S-100). A major proportion of cardiac nerves displayed neuropeptide tyrosine and tyrosine hydroxylase immunofluorescence staining. Subpopulations of nerves contained somatostatin, vasoactive intestinal polypeptide, calcitonin gene-related peptide, substance P- or neurokinin-like immunoreactivity, and acetylcholinesterase activity. Tissues from cardiac allografts (5 weeks to 63 months after transplantation) contained nerves and ganglion cells that were acetylcholinesterase positive and immunoreactive for the general neural markers. These nerves were less numerous than in recipient hearts and rarely displayed neuropeptide immunostaining. Atrial natriuretic peptide immunoreactivity was localized to myocardial cells in transplanted hearts as well as explanted recipient and postmortem hearts. While most human cardiac allografts remain functionally extrinsically denervated, they appear to contain viable intrinsic nerves, and myocardial cells retain the capacity to produce atrial natriuretic peptide.

Adolescent↗