Search PubMed⌕ Search

Biomedical subjects

D R Lynch

Publications and source records attributed to D R Lynch.

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

Angiotensin II and atrial natriuretic factor-binding sites in various tissues in hypertension: comparative receptor localization and changes in different hypertension models in the rat.

The peptides angiotensin II (ANGII) and atrial natriuretic factor (ANF) regulate blood pressure and salt and water balance by producing antagonistic physiological effects in a variety of tissues. We used in vitro autoradiography with [125I] ANGII and [125I]ANF to compare receptor regulation for both peptides in various tissues in three experimental models of hypertension [two-kidney, one-clip (2K-1C); one-kidney, one-clip (1K-1C); desoxycorticosterone-salt (DOCA-SALT)] and three nonhypertensive control groups [two-kidney (2K-CON); one-kidney (1K-CON); salt-loaded (SALT-CON)]. Blood pressures at death were significantly higher in all three hypertensive groups compared to those in normotensive controls, but there were no significant differences among the hypertensive or normotensive groups, respectively. PRA was highest in the 2K-1C group and lowest in the DOCA-SALT and SALT-CON groups, but plasma ANF levels did not differ significantly among the hypertensive or normotensive groups. In the aorta, ANGII receptor binding was decreased in 2K-1C rats and increased in DOCA-SALT and SALT-CON rats; ANF receptor binding was moderately increased in all three hypertensive groups. Adrenal zona glomerulosa binding for ANGII was highest in the 2K-1C group and lowest in DOCA-SALT rats, while ANF binding was decreased in DOCA-SALT and SALT-CON animals. ANGII renal glomerular binding was increased in DOCA-SALT and SALT-CON groups, and ANF glomerular binding was decreased in the same two groups. In the brain, the subfornical organ showed increased binding for both ANGII and ANF in DOCA-SALT rats. Our results show that tissue receptor binding of ANGII and ANF is regulated in distinct patterns in different models of hypertension, and that these patterns are tissue specific and more complex than simple reciprocal regulation.

Adrenal Glands↗
PubMed1989

Neuropeptide Y receptor binding sites in rat brain: differential autoradiographic localizations with 125I-peptide YY and 125I-neuropeptide Y imply receptor heterogeneity.

Neuropeptide Y (NPY) receptor binding sites have been localized in the rat brain by in vitro autoradiography using picomolar concentrations of both 125I-NPY and 125I-peptide YY (PYY) and new evidence provided for differentially localized receptor subtypes. Equilibrium binding studies using membranes indicate that rat brain contains a small population of high-affinity binding sites and a large population of moderate-affinity binding sites. 125I-PYY (10 pM) is selective for high-affinity binding sites (KD = 23 pM), whereas 10 pM 125I-NPY labels both high- and moderate-affinity sites (KD = 54 pM and 920 pM). The peptide specificity and affinity of these ligands in autoradiographic experiments match those seen in homogenates. Binding sites for 125I-PYY are most concentrated in the lateral septum, stratum oriens, and radiatum of the hippocampus, amygdala, piriform cortex, entorhinal cortex, several thalamic nuclei, including the reuniens and lateral posterior nuclei, and substantia nigra, pars compacta, and pars lateralis. In the brain stem, 125I-PYY sites are densest in a variety of nuclei on the floor of the fourth ventricle, including the pontine central grey, the supragenual nucleus, and the area postrema. 125I-NPY binding sites are found in similar areas, but relative levels of NPY binding and PYY binding differ regionally, suggesting differences in sites labeled by the two ligands. These receptor localizations resemble the distribution of endogenous NPY in some areas, but others, such as the hypothalamus, contain NPY immunoreactivity but few binding sites.

Animals↗
PubMed1988

Enkephalin convertase: characterization and localization using [3H]guanidinoethylmercaptosuccinic acid.

Enkephalin convertase (carboxypeptidase E,H; EC 3.4.17.10) is a carboxypeptidase B-like enzyme which appears to be physiologically associated with the biosynthesis of the enkephalins and certain other peptides. We have localized enkephalin convertase in the brain and other tissues autoradiographically by labeling studies with [3H]guanidinoethylmercaptosuccinic acid ([3H]GEMSA). In the brain, [3H]GEMSA localizations parallel enkephalin distribution but with certain exceptions, suggesting a role in relation to other peptides. In the pancreas, [3H]GEMSA binding sites are localized to the islets suggesting an involvement in insulin, glucagon, or somatostatin formation. The selective concentration of [3H]GEMSA grains in cardiac atria suggests a link to atrial natriuretic factor.

Animals↗
PubMed1988

Enkephalin convertase in the heart: similar disposition to atrial natriuretic factor.

Enkephalin convertase (EC; carboxypeptidase-E or -H) is a carboxypeptidase-B-like enzyme proposed to be involved in the synthesis of enkephalins and other neuropeptides. In this study we have characterized and localized EC in the rat heart and examined its correspondence with atrial natriuretic factor. Heart homogenates bind [3H]guanidinoethylmercaptosuccinic acid ([ 3H]GEMSA), a selective ligand for enkephalin convertase, with specificity and high affinity (Kd = 5-10 nM). The pharmacology of these sites matches that of convertase catalytic activity and of [3H]GEMSA binding in other tissues. The binding sites in the heart can be purified 4000-fold using p-aminobenzoylarginine affinity chromatography, and the purified sites have Co2+ stimulated carboxypeptidase activity identical to EC. By subcellular fractionation studies [3H]GEMSA-binding sites are localized to the granule fraction with ANF immunoreactivity. [3H]GEMSA autoradiography localizes EC in the heart to the left and right atria, with very low levels in mature and ventricles. The distribution, biochemical properties, and developmental course of EC suggest that it may be involved in the synthesis of atrial natriuretic factor.

Aging↗
PubMed1987

Ontogeny of the serotonergic projection to rat neocortex: transient expression of a dense innervation to primary sensory areas.

The development of serotonergic innervation to rat cerebral cortex was characterized by immunohistochemical localization of serotonin combined with autoradiographic imaging of serotonin-uptake sites. In neonatal rat, a transient, dense, serotonergic innervation appears in all primary sensory areas of cortex. In somatosensory cortex, dense patches of serotonergic innervation are aligned with specialized cellular aggregates called barrels. The dense patches are not apparent after 3 weeks of age, and the serotonergic innervation becomes more uniform in adult neocortex. This precocious neonatal serotonergic innervation may play a transient physiologic role in sensory areas of cortex or may exert a trophic influence on the development of cortical circuitry and thalamocortical connections.

Aging↗
PubMed1987

Angiotensin-converting enzyme labeled with [3H]captopril. Tissue localizations and changes in different models of hypertension in the rat.

In vitro autoradiography with [3H]captopril was used to localize and quantitate angiotensin-converting enzyme (ACE) in various tissues in two-kidney, one-clip (2K-1C) hypertension, one-kidney, one-clip (1K-1C) hypertension, desoxycorticosterone acetate (DOCA)-salt hypertension, and a normotensive control group. There were no significant differences in mean systolic blood pressure among the hypertensive groups. Plasma renin activity (PRA) was highest in the 2K-1C group (6.20 +/- 2.17 ng/ml per h), intermediate in the 1K-1C group (2.19 +/- 0.62 ng/ml per h) and control group (3.20 +/- 0.53 ng/ml per h), and lowest in the DOCA-salt group (0.07 +/- 0.06 ng/ml per h). In the lungs, aorta, mesenteric arteries, and adrenal medulla, ACE labeling was highest in the 2K-1C group, intermediate in the 1K-1C and control groups, and lowest in the DOCA-salt group. ACE levels in these tissues correlated positively with PRA. In the kidney, anterior pituitary, testis, and choroid plexus of the brain, ACE levels correlated negatively with PRA, with lowest ACE levels in the 2K-1C group and highest levels in the DOCA-salt group. In the epididymis, posterior pituitary, and other regions of the brain, ACE levels did not differ significantly among the groups.

Animals↗
PubMed1987

Enkephalin convertase in the gastrointestinal tract an associated organs characterized and localized with [3H]guanidinoethylmercaptosuccinic acid.

Enkephalin convertase (carboxypeptidase EH; EC 3.4.17.10), a carboxypeptidase B-like enzyme which processes hormone and neuropeptide precursors, has been characterized in the gastrointestinal tract, submandibular gland, and pancreas using a binding assay with [3H]guanidinoethylmercaptosuccinic acid. Binding to homogenates of the membrane and soluble fractions of stomach, small intestine, colon, and submandibular gland is saturable, with Kd values of about 2 nM. Partial purification of the membrane fractions reveals a Co+2-stimulated carboxypeptidase B activity which is not detectable in crude homogenates. In vitro autoradiography with [3H]guanidinoethylmercaptosuccinic acid localizes enkephalin convertase to the epithelial cells of the stomach, colon, and intestine, the islet cells of the pancreas, and the acinar cells of the submandibular gland. This localization contrasts to the distribution of enkephalins and other neuropeptides in the gastrointestinal tract and associated organs, suggesting that enkephalin convertase may serve functions other than neuropeptide and prohormone processing.

Animals↗
PubMed1986

Differential ontogeny of rat brain peptidases: prenatal expression of enkephalin convertase and postnatal development of angiotensin-converting enzyme.

We quantitated the levels of two peptidases in the developing rat brain as a means to determine their function. Enkephalin convertase (EC 3.4.17.10), a carboxypeptidase B-like enzyme detected by [3H]guanidinoethylmercaptosuccinic acid (GEMSA) autoradiography, is present in high concentration throughout the brains of rat fetuses 3 days prior to birth. During the first 3 postnatal weeks, the density of [3H]GEMSA-labeled enkephalin convertase drops to adult levels. The expression of enkephalin convertase prior to that of most neuropeptides supports a role for this enzyme in propeptide processing. The regional distribution of [3H]GEMSA binding is similar in fetal and adult rats except that the thalamus exhibits the highest levels of [3H]GEMSA binding prenatally, and among the lowest levels in adult rats. Thus, peptide(s) formed in high concentration in the prenatal thalamus may be substrates for enkephalin convertase. Angiotensin-converting enzyme (ACE, EC 3.14.15.1) was visualized in the perinatal period by [3H]captopril autoradiography. Striatonigral ACE is undetectable at birth and increases to adult levels by two weeks of age. The expression of ACE after the initial presence of known peptides in the basal ganglia implies that the enzyme is not essential for peptide synthesis, suggesting instead a degradative role. In contrast to the striatonigral system, the choroid plexus contains high concentrations of ACE prior to birth, consistent with previous proposals of different substrates for ACE in the choroid plexus and the basal ganglia.

Age Factors↗
PubMed1986

Atrial natriuretic factor receptors in rat kidney, adrenal gland, and brain: autoradiographic localization and fluid balance dependent changes.

Mammalian atria contain natriuretic peptides designated atrial natriuretic factors (ANF). Using in vitro autoradiography with 125I-labeled ANF, we have localized high-affinity (Kd = 150 pM) ANF binding sites to the glomeruli of the kidney, zona glomerulosa of the adrenal gland, and choroid plexus of the brain. The numbers of sites in both kidney and adrenal are increased in rats deprived of water; increases are detectable within 72 hr of water deprivation in the kidney and within 24 hr in the adrenal gland. Receptor numbers decline in rats given 2.0% NaCl as drinking water and in diabetic rats. The discrete localizations and dynamic alterations of these receptors suggest that ANF regulates fluid balance through diverse but coordinated effects on receptors in numerous organs including the kidney, adrenal, and brain.

Adrenal Glands↗
PubMed1986

Angiotensin-converting enzyme localized in the rat pituitary and adrenal glands by [3H]captopril autoradiography.

We have localized angiotensin-converting enzyme (EC 3.14.5.1) in the rat pituitary and adrenal glands by [3H]captopril autoradiography. The maximal numbers of [3H] captopril-binding sites are: posterior pituitary, 4500 fmol/mg protein; anterior pituitary, 1950 fmol/mg; intermediate pituitary, less than 100 fmol/mg; adrenal medulla, 480 fmol/mg; and adrenal cortex, less than 25 fmol/mg. The distribution within the posterior pituitary and adrenal medulla is homogeneous, whereas that in the anterior pituitary is patchy. Subcellular fractionation of the bovine adrenal medulla reveals enrichment of angiotension-converting enzyme in plasma membrane fractions, but not in chromaffin granules. [3H]Captopril autoradiography in the rat pituitary gland is unaltered by dehydration, adrenalectomy, or reserpine treatment and in Brattleboro rats. [3H]Captopril binding in the adrenal medulla is increased by 75% 3 weeks after hypophysectomy and is elevated by 80% after reserpine treatment. The change after hypophysectomy is not reversed by dexamethasone treatment.

Adrenal Glands↗
PubMed1986

Enkephalin convertase: localization to specific neuronal pathways.

3H-Guanidinoethylmercaptosuccinic acid (GEMSA) selectively labels the carboxypeptidase B-like enzyme enkephalin convertase (EC) in rat brain tissue sections. We have used autoradiography with 3H-GEMSA to map membrane-bound EC in the rat forebrain and, in conjunction with lesioning techniques, to localize EC to specific neuronal pathways. The highest levels of EC are in the median eminence. High levels of EC also occur in the hypothalamic magnocellular nuclei, in several nuclei of the amygdala, the lateral septum, and the bed nuclei of the stria terminalis. Knife-cut lesions of the stria terminalis increase EC posterior to the lesion in the stria and deplete EC from the stria adjacent to the bed nucleus, suggesting that EC, like enkephalins, is axonally transported within the stria terminalis. Ibotenic acid lesions of the caudate nucleus destroy binding in the substantia nigra pars reticulata ipsilateral to the lesion, suggesting that nigral EC is associated with axons originating in the caudate nucleus. We have also mapped EC in detail in the hippocampus. EC levels are highest near pyramidal cells of CA 3-4 and the dentate gyrus granule cells. Quinolinic acid lesions destroy both the granule and pyramidal cells and destroy all of the 3H-GEMSA labeling except for a small amount in the molecular layer of the dentate gyrus. Selective destruction of CA 3-4 pyramidal cells with kainic acid eliminates EC in the pyramidal cell region. Destruction of granule cells of the dentate gyrus with colchicine depletes binding in the dentate gyrus without any change in the area surrounding field CA 3-4. High levels of 3H-GEMSA binding are present in the hippocampus at least 3 d before birth. These observations suggest that in the hippocampus the majority of EC is associated with pyramidal cells, which have not been shown to contain enkephalins. 3H-GEMSA autoradiography of the trigeminal ganglion localizes EC to the sensory neurons and not to white matter tracts there. These studies demonstrate that while EC is contained in enkephalinergic pathways, it is also present in some neurons that do not contain enkephalins.

Animals↗
PubMed1985

Comparative theoretical performance for two types of regional hyperthermia systems.

Regional hyperthermia systems have drawn attention because of their potential for depositing power noninvasively in deep-seated tumors. Two such systems that have received clinical attention because of their ability to deposit significant amounts of power in tissue are magnetic induction devices and annular phased array applicators. In this paper, theoretical calculations for the specific absorption rate (SAR) and the resulting temperature distributions for these systems are compared. The finite element method is used in the formulation of both the electromagnetic and thermal boundary value problems. Six detailed patient models based on CT-scan data from the pelvic, visceral, and thoracic regions are generated to simulate a variety of tumor locations. In general, the annular phased array deposited more power within the tumor and produced better temperature distributions than the magnetic induction device. However, the ratio of the maximum power absorbed by the tumor to the maximum power absorbed in normal tissue does not appear to be high enough for either device to heat significant portions of perfused tumors to therapeutic temperatures under a wide range of physiological conditions. The results contained herein should aid the physician in comparative treatment planning with existing regional hyperthermia systems.

Electromagnetic Fields↗
PubMed1985

Enkephalin convertase demonstrated in the pituitary and adrenal gland by [3H]guanidinoethylmercaptosuccinic acid autoradiography: dehydration decreases neurohypophyseal levels.

[3H]Guanidinoethylmercaptosuccinic acid (GEMSA) autoradiography demonstrates the particulate form of a carboxypeptidase B-like peptide processing enzyme, enkephalin convertase (EC 3.4.17.10), in the rat pituitary and adrenal glands. The maximal number of binding sites (Bmax) for [3H]GEMSA is 20 pmol/mg protein in the intermediate lobe of the pituitary, 12.0 pmol/mg protein in the posterior pituitary lobe, 15 pmol/mg protein in the anterior pituitary lobe, 5.8 pmol/mg protein in the adrenal medulla, and less than 0.3 pmol/mg protein in the adrenal cortex. The labeling pattern is homogeneous within each of these regions. Subcellular fractionation of the bovine adrenal medulla demonstrates that [3H] GEMSA-binding sites are localized to chromaffin granules. In Brattleboro rats and dehydrated rats, the level of posterior pituitary [3H]GEMSA binding is less than 25% of that in control animals. This decrease is abolished by arginine vasopressin treatment of Brattleboro rats or rehydration of dehydrated rats. There are no changes in [3H] GEMSA binding in the supraoptic nucleus or magnocellular portion of the paraventricular nucleus of the hypothalamus under any of these conditions, suggesting that the alterations observed in the neurohypophysis result from an increased rate of loss of enkephalin convertase. The level of anterior pituitary enkephalin convertase is unchanged by dehydration, adrenalectomy, or dexamethasone or in Brattleboro rats. [3H]GEMSA labeling in the intermediate pituitary lobe is unaffected by dehydration and haloperidol treatment and in Brattleboro rats. The adrenal medullary enzyme is not altered by reserpine, hypophysectomy, or splanchnic denervation or in Brattleboro rats.

Adrenal Glands↗
PubMed1984

[3H]guanidinoethylmercaptosuccinic acid binding to tissue homogenates. Selective labeling of enkephalin convertase.

[3H]Guanidinoethylmercaptosuccinic acid (GEMSA), a potent inhibitor of enkephalin convertase, binds to membrane and soluble fractions of tissue homogenates saturably and reversibly with a KD of 6 nM. Specific binding accounts for greater than 95% of total binding. The highest levels of [3H]GEMSA binding occur in the pituitary gland and the brain, with much lower levels in peripheral tissues. GEMSA, guanidinopropylsuccinic acid, 2-mercaptomethyl-3-guanidinothiopropionic acid, aminopropylmercaptosuccinic acid, [Leu] enkephalin-Arg, and [Met]enkephalin-Arg inhibit [3H] GEMSA binding to crude rat brain homogenates, to crude bovine pituitary homogenates, and to pure enkephalin convertase with equal potencies. Their Ki values against [3H]GEMSA binding are similar to their Ki values against enkephalin convertase activity. EDTA and 1,10-phenanthroline markedly inhibit both binding and enzymatic activity. The ratio of the Vmax for 5-dimethylaminonaphthalene-1-sulfonyl-Phe-Leu-Arg to the Bmax (maximal number of binding sites) for [3H]GEMSA is about 2,000 min-1 in both pure enzyme preparations and crude tissue homogenates. [3H] GEMSA binding activity is found only in fractions containing enkephalin convertase during enzyme purification from bovine pituitary by L-arginine affinity chromatography. These data confirm that [3H]GEMSA binds only to enkephalin convertase in crude homogenates under our assay conditions. CoCl2 activates enzyme activity without altering the Ki of GEMSA against enzymatic hydrolysis and weakly inhibits [3H] GEMSA binding by increasing the KD.

Animals↗
PubMed1984

Theoretical temperature profiles for concentric coil induction heating devices in a two-dimensional, axi-asymmetric, inhomogeneous patient model.

In this paper we report on theoretical calculations for the temperature distributions produced by an rf magnetic induction device that is placed concentrically about the long axis of the patient. A two-dimensional, axi-asymmetric, inhomogeneous patient model was used in conjunction with a numerical moment method for calculating the electric fields in the tissues of the model and a numerical finite element method for calculating the resulting temperature distributions. The electric fields and the absorbed power per unit volume of tissue were calculated for both a thorax and viscera model, each of which included a tumor volume. The absorbed power values were input into the bioheat transfer equation and the temperature distributions were calculated for a wide range of blood flow rates. Based on the steady-state and transient results, our computer simulations predict poor therapeutic temperature profiles for tumors embedded deeply in the thorax and viscera. This heating technique appears to produce significant therapeutic volumes in superficial tumors located not greater than 7 cm in depth. These theoretical calculations should aid the clinician in the evaluation of induction heating devices for their effectiveness in heating deep-seated and superficial tumors.

Humans↗
PubMed1984

Enkephalin convertase localization by [3H]guanidinoethylmercaptosuccinic acid autoradiography: selective association with enkephalin-containing neurons.

Enkephalin convertase, an enkephalin-forming carboxypeptidase, is potently inhibited by guanidinoethylmercaptosuccinic acid (GEMSA). We have localized enkephalin convertase in rat brain by in vitro autoradiography with [3H]GEMSA. [3H]GEMSA-associated silver grains are highly concentrated in the median eminence, bed nucleus of the stria terminalis, lateral septum, dentate gyrus, hippocampus, central nucleus of the amygdala, preoptic hypothalamus, magnocellular nuclei of the hypothalamus, interpeduncular nucleus, dorsal parabrachial nucleus, locus coeruleus, nucleus of the solitary tract, and the substantia gelatinosa of the spinal trigeminal tract. This distribution corresponds closely with immunocytochemical localizations of enkephalin-containing cells and axons, indicating that enkephalin convertase is selectively involved in enkephalin biosynthesis.

Animals↗