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Biomedical subjects

K Barnes

Publications and source records attributed to K Barnes.

At least 73 records · Page 4Linked to original sources
PubMed1993

The effect of imposed leg length difference on pelvic bone symmetry.

This study was designed to examine the effect of varying degrees of imposed leg length difference on symmetry of the innominate bones in healthy college women with relatively equal leg lengths. Subjects' leg length was determined by clinical and roentgenographic procedures. Position of the innominate bones with and without lifts under one foot was measured with respect to the transverse plane using the Waterloo Spatial Motion and Recording Technique (WATSMART; Northern Digital, Inc., Waterloo, Ontario, Canada), which allows very high spatial resolution. Our results show that posterior innominate bone rotation occurs on the side of the lengthened limb, and anterior rotation occurs on the shorter limb. The amount of pelvic obliquity increased in an approximately linear fashion as the leg length difference was increased from 2/8 to 7/8 inch. Some individual differences were evident.

Adult↗
PubMed1993

An immunoelectron microscopic study of pig substantia nigra shows co-localization of endopeptidase-24.11 with substance P.

Endopeptidase-24.11 is a widely distributed cell surface enzyme with a role in inactivating some neuropeptides and peptide hormones. In the central nervous system it has been implicated in the metabolism of enkephalins and tachykinins, neuropeptides which are expressed by neurons projecting to the substantia nigra. Two immunochemical methods have been used to reveal the ultrastructural localization of endopeptidase-24.11 and substance P in the substantia nigra of piglets. In the first approach, substance P was revealed by immunoperoxidase staining using the rat monoclonal antibody, NC1, and endopeptidase-24.11 by 1 nm colloidal gold using an affinity-purified rabbit polyclonal antibody, both being applied at the pre-embedding stage. NC1 was shown to be highly specific for substance P, with negligible cross-reactivity with neurokinins A and B. The specificity of the immunostaining was confirmed by processing all sections for both markers, even when only one primary antibody was applied. In the second approach, ultrathin cryosections were immunostained using gold particles of different diameters. In a survey of electron micrographs, 80% of the silver-enhanced gold particles were touching neuronal membranes, consistent with the known topology of endopeptidase-24.11. Endopeptidase-24.11 immunoreactivity was observed both on membranes of axons and on pre- and postsynaptic elements. Substance P immunoreactivity was seen within some boutons, apparently associated with vesicles, and in axons. In doubly stained sections, many examples of immunopositive gold-labelled boutons (i.e. endopeptidase-24.11-immunoreactive-positive) containing immunoperoxidase reaction product (i.e. substance P-immunoreactive-positive) were recorded. In ultrathin cryosections, substance P immunoreactivity was mainly observed in dense-core vesicles within boutons, some of which also showed membrane-associated gold particles marking endopeptidase-24.11 immunoreactivity. This is the first demonstration of endopeptidase-24.11 by immunogold at the electron microscopic level and the first demonstration of the ultrastructural co-localization of a membrane peptidase and its putative neuropeptide target. The results lend strong support to the view that endopeptidase-24.11 has a physiological role in the metabolism of substance P, but do not exclude a role in the inactivation of other neuropeptides.

Animals↗
PubMed1993

Who becomes an "at-risk" student? The predictive value of a Kindergarten Screening Battery.

This study was undertaken to determine whether a preschool screening instrument could predict whether kindergarten students would later be retained, referred to special education, or placed in special education. The results of Early Prevention of School Failure (EPSF) screening on 161 kindergarten students were examined. Students who had been retained, referred to special education, or placed in special education demonstrated significantly lower EPSF pretest scores except in the gross motor modality. All EPSF modalities were statistically significant predictors of students' status; however, other factors such as family support network, preschool experiences, and motivational factors must be considered in evaluating whether a student is "at risk" of later school failure.

Child↗
PubMed1993

Endocrine profile of catch-up growth in the cynomolgus monkey.

We studied catch-up growth following withdrawal of glucocorticoid administration in seven intact prepubertal cynomolgus monkeys. To reduce stress during blood sampling, a vascular access port was implanted subcutaneously in each animal for the duration of the study. After a baseline observation period of 50 weeks, the monkeys received injections of dexamethasone at a dose of 100 micrograms.kg-1.day-1 for 15 weeks. Growth velocity was monitored every 3 weeks by measuring lower leg length and body weight. Spontaneous serum growth hormone (GH) concentrations and GH levels after insulin and L-dopa stimulation, as well as serum insulin-like growth factor I (IGF-I) and plasma thyrotropin, triiodothyronine and thyroxine, were measured during the study. Differences between animals were analyzed by repeated measures analysis of variance and Student's paired t-test. Mean +/- SEM growth velocity (mm/3 weeks) decreased from 0.90 +/- 0.08 during the baseline period to 0.29 +/- 0.07 (p < 0.001) during the period of growth retardation, and increased to 1.23 +/- 0.2 (p < 0.001) during the period of catch-up growth. Spontaneous GH and peak GH levels following insulin did not show any significant variation during the study. Peak GH during the L-dopa test decreased from 15.4 +/- 3.2 micrograms/l during the baseline period to 6.2 +/- 2.4 micrograms/l during the period of growth retardation (p < 0.05), and increased to 23.0 +/- 5.9 micrograms/l during the period of catch-up growth (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A comparison of the zinc contents and substrate specificities of the endothelial and testicular forms of porcine angiotensin converting enzyme and the preparation of isoenzyme-specific antisera.

Angiotensin converting enzyme (ACE; EC 3.4.15.1) was purified from porcine kidney and lung (endothelial isoenzyme) and testis (testicular isoenzyme) by affinity chromatography on lisinopril-2.8 nm-Sepharose. Atomic-absorption spectroscopy revealed that ACE purified from kidney and lung contained 2.58 and 2.35 atoms of zinc per molecule of enzyme (M(r) 147,000) respectively. In contrast, ACE purified from testis contained only 1.58 atoms of zinc per molecule of enzyme (M(r) 80,000). Thus it would appear that both putative zinc-binding sites in endothelial ACE contain zinc and may therefore be catalytically active. No differences were observed in the pattern of products generated on hydrolysis of benzoyl (Bz)-Gly-His-Leu, substance P, luteinizing-hormone-releasing hormone (LH-RH) and its analogue, des-Gly10-LH-RH-ethylamide, by kidney and testicular ACE. There was also no difference in the initial rates of hydrolysis of Bz-Gly-His-Leu or substance P by the two isoenzymes, although LH-RH and its analogue were hydrolysed twice as rapidly by kidney ACE. It is therefore unlikely that the N-terminal catalytic site in porcine endothelial ACE is predominantly responsible for the atypical cleavage of LH-RH generating the N-terminal tripeptide. Two polyclonal antisera were raised to the affinity-purified forms of pig kidney and testicular ACE. Isoenzyme-specific antisera were then isolated from these by absorbing out those antibodies recognizing determinants on the other isoenzyme. Immunoelectrophoretic blot analyses and immunofluorescent staining of sections of pig kidney were used to demonstrate the specificity of the antisera. Immunofluorescent staining of sections of pig testis with the antiserum specific to testicular ACE localized testicular ACE solely to the lumen of the seminiferous tubules, whereas the antiserum specific to endothelial ACE revealed the presence of this isoenzyme only in blood vessels. The antiserum to endothelial ACE, which recognizes determinants in the unique N-terminal domain, was investigated as a possible specific inhibitor of the N-terminal catalytic site. Although this antiserum failed to inhibit testicular ACE, the effect on the activity of endothelial ACE appeared to be due to inhibition of both the N- and C-terminal catalytic sites.

Amino Acid Sequence↗
PubMed1992

Endoscopic carpal tunnel release: an anatomic study of the two-incision method in human cadavers.

To determine the relationship of neurovascular structures to the sites of portal placement and transverse carpal ligament division during two-portal endoscopic carpal tunnel release, a study of 20 fresh cadaver specimens was carried out. Open dissection of the carpal tunnel after endoscopic surgery showed complete ligamentous release in 18 hands (90%). In 10 specimens, the procedure was performed as described by Chow. There was one partial transection of the superficial palmar arch (5%), and five specimens (50%) had complete divisions of the superficial palmar fascia with considerable pressure placed on the ulnar nerve at the wrist. A modified technique was used in 10 specimens in which the proximal incision was made in a more distal location and a distally based ligamentous flap was created. The superficial palmar arch and the distal edge of the transverse carpal ligament were visualized directly before passage of the trocar. No complications were noted with this method.

Anthropometry↗
PubMed1992

Membrane localization of endopeptidase-24.11 and peptidyl dipeptidase A (angiotensin converting enzyme) in the pig brain: a study using subcellular fractionation and electron microscopic immunocytochemistry.

Brains from piglets were dissected and a block of tissue including the substantia nigra, globus pallidus, and entopeduncular nucleus was homogenized and then fractionated on discontinuous Percoll gradients. Ligand-binding assays using (-)-[3H]nicotine and [3H]quinuclidinyl benzilate served to delineate fractions containing nicotinic and muscarinic acetylcholine receptors. In this system endopeptidase-24.11 exhibited a biphasic distribution, consistent with its presence on both pre- and postsynaptic membranes. Peptidyl dipeptidase A (angiotensin converting enzyme; ACE) was associated with membrane fractions containing muscarinic receptors. An immunoblot of these fractions with an affinity-purified polyclonal antibody to ACE revealed only the neuronal form of ACE (Mr 170,000), the endothelial form (Mr 180,000) being undetectable. Electron microscopic immunoperoxidase staining of the substantia nigra, with an affinity-purified antibody to endopeptidase-24.11 at the preembedding stage, showed this antigen to be confined to the plasma membranes of boutons, axons, and some dendrites. Both pre- and postsynaptic membranes were stained, and occasionally other regions of the dendritic membrane were positive. No staining of synaptic vesicles within the boutons was observed. Thus, two independent approaches indicate that endopeptidase-24.11 is present on both pre- and postsynaptic membranes in the pig substantia nigra. The subcellular fractionation suggests that neuronal ACE is confined to dendritic membranes.

Animals↗
PubMed1991

Membrane peptidases in the peripheral nervous system of the pig: their localization by immunohistochemistry at light and electron microscopic levels.

The presence and cellular localization of five membrane peptidases has been investigated in peripheral nerves, including those of the autonomic nervous system, in the pig. Endopeptidase-24.11 ("enkephalinase") peptidyl dipeptidase A, aminopeptidase N, aminopeptidase W and dipeptidyl peptidase IV were studied by both enzymic assays of membranes prepared from samples of nerve and by immunoperoxidase histochemistry at light and in two cases, endopeptidase-24.11 and aminopeptidase W, at electron microscopic levels. All five peptidases could be quantified by enzymic assay, though the activities were about 1% of those in renal microvilli and less than those of choroid plexus membranes. Endopeptidase-24.11 was associated with Schwann cell membranes in all types of nerve examined, including major nerves containing predominantly myelinated fibres as well as autonomic nerves, such as the vagus and splenic nerves and the sympathetic chain, staining being observed in membranes associated with myelinated and unmyelinated fibres. The Schwann cell location of endopeptidase-24.11 was confirmed by correlation with immunostaining for glial fibrillary acidic protein and by electron microscopy. This peptidase is known to have a wide repertoire of susceptible substrates among neuropeptides which was here shown to include vasoactive intestinal polypeptide (Km 268 microM, kcat 568 min-1), one of a number of neuropeptides present in peripheral nerve fibres. Three of the peptidases, peptidyl dipeptidase A, aminopeptidase N and dipeptidyl peptidase IV, were associated with microvessels of peripheral nerves. Aminopeptidase N was also observed in connective tissue elements, including the perineurium. Aminopeptidase W was unique among the five peptidases in having a neuronal localization. This was observed in unmyelinated and myelinated nerves and was supported by comparison with the pattern of staining observed for neurofilament protein and by electron microscopic immunoperoxidase staining. This observation was unexpected since aminopeptidase W has not been detected as a neuronal marker in the brain. Some possible roles for the membrane peptidases in peripheral nerves are discussed.

Animals↗
PubMed1990

Effect of chronic treatment with the glucocorticoid antagonist RU 486 in man: toxicity, immunological, and hormonal aspects.

Suppression of immune function was traditionally thought to occur only with pharmacological levels of glucocorticoids. However, recent studies in rodents have suggested that glucocorticoids exert tonic antiinflammatory/immunosuppressive effects even at basal nonstress concentrations. To examine whether basal glucocorticoid secretion modulates immune function in man we employed the specific glucocorticoid receptor antagonist RU 486. If a tonic level of inhibition of the immune system by basal glucocorticoid levels was present, then a potentiation or enhancement of immune function might evolve in the absence of glucocorticoid action. To examine this hypothesis, we studied 11 healthy male normal volunteers who received RU 486 (10 mg/kg.day) or placebo vehicle, divided into 2 daily oral doses, for 7-14 days. Blood samples were collected every 2 days for measurement of plasma ACTH and cortisol concentrations along with 24-h urine samples for measurement of 17-hydroxysteroid and free cortisol excretion. Complete and differential blood counts, erythrocyte sedimentation rates, C-reactive protein, antinuclear antibodies, rheumatoid factor, and quantitative immunoglobulins were also determined at 2-day intervals. Leukocytes were obtained by leukopheresis for phenotypic characterization and functional analysis before and 7 days after the initiation of RU 486 or placebo therapy. Blockade of cortisol receptors with RU 486 was associated with marked compensatory elevations of plasma ACTH and cortisol and increases in 24-h urinary excretion of 17-hydroxysteroids and free cortisol. Unexpectedly, 8 of the 11 subjects developed generalized exanthem after 9 days of RU 486 treatment. One subject developed symptoms and signs consistent with the diagnosis of adrenal insufficiency. Total white blood cell counts, absolute lymphocyte, neutrophil and eosinophil counts, erythrocyte sedimentation rate, and quantitative immunoglobulins did not change with RU 486 therapy. Similarly, T-, B-, and natural killer cell subsets did not change during RU 486 treatment. Furthermore, functional evaluation of lymphocyte cytotoxicity and proliferation revealed no changes. We conclude that administration of high doses of RU 486 to normal volunteers does not result in measurable enhancement of immune function. This suggests that in man, glucocorticoids may not exert a tonic inhibitory effect on the immune system as they appear to do in rodents. Alternatively, the compensatory increase in endogenous cortisol may obviate any effect of the glucocorticoid antagonist on the immune system.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Insufficiency↗
PubMed1989

Proteins of the kidney microvillar membrane. Structural and immunochemical properties of rat endopeptidase-2 and its immunohistochemical localization in tissues of rat and mouse.

The phosphoramidon-insensitive endopeptidase-2 in rat renal brush borders was investigated by immunochemical approaches with a rabbit polyclonal antibody raised to the purified enzyme released from the membrane by papain. An immunoaffinity column successfully purified the detergent-solubilized form of endopeptidase-2. This preparation had an apparent subunit Mr of 80,000, and did not show the two subunits, of Mr 80,000 and 74,000, consistently found in the papain-solubilized forms, indicating that the latter resulted from proteolysis by papain. SDS/polyacrylamide-gel electrophoresis of non-reduced samples of the enzyme revealed a band of Mr 220,000, confirming the presence of disulphide-bridged subunits. Treatment with endoglycosidases H and F generated smaller molecular forms, indicating that endopeptidase-2 contained about 30% asparagine-linked carbohydrate and that a few of these oligosaccharide chains were of the high-mannose type. Treatment with phosphatidylinositol-specific phospholipase indicated that the enzyme did not possess a glycolipid membrane anchor. A survey of rat tissues examined immunohistochemically and by immunoblotting revealed that only the kidney and intestinal tract expressed the antigen in significant amounts. Although some weak staining was seen in salivary glands and thyroid, other organs and tissues including brain and spinal cord were negative by both immunochemical techniques. In the kidney the antigen was confined to the lumen of the proximal tubule and was seen mainly in the population of juxtamedullary nephrons. In the gut, luminal staining was observed throughout its whole length, from duodenum to rectum. Excellent cross-reactivity of the antibody with Balb/c mouse tissues was observed. Immunohistochemistry of mouse kidney and gut revealed a distribution identical with that observed in the rat. Immunopurification of the detergent-solubilized mouse kidney antigen showed it to be a protein containing disulphide-linked subunits of Mr 90,000. It possessed endopeptidase-2-like activity, but was more efficient in hydrolysing azo-casein and less efficient in hydrolysing a model substrate than the rat enzyme. The close similarity between rat endopeptidase-2 and mouse meprin is further supported by these results.

Animals↗
PubMed1989

Membrane peptidases in the pig choroid plexus and on other cell surfaces in contact with the cerebrospinal fluid.

A comprehensive survey of 11 peptidases, all of which are markers for renal microvillar membranes, has been made in membrane fractions prepared from pig choroid plexus. Two fractionation schemes were explored, both depending on a MgCl2-precipitation step, the preferred one having advantages in speed and yield of the activities. The specific activities of the peptidases in the choroid-plexus membranes were, with the exception of carboxypeptidase M, lower than in renal microvillar membranes: those of aminopeptidase N, peptidyl dipeptidase A ('angiotensin-converting enzyme') and gamma-glutamyltransferase were 3-5-fold lower, those of aminopeptidase A and endopeptidase-24.11 were 12-15 fold lower, and those of dipeptidyl peptidase IV and aminopeptidase W were 50-70-fold lower. Carboxypeptidase M had a similar activity in both membranes. Alkaline phosphatase and (Na+ + K+)-activated ATPase were more active in the choroid-plexus membranes. No activity for microsomal dipeptidase, aminopeptidase P and carboxypeptidase P could be detected. Six of the peptidases and (Na+ + K+)-activated ATPase were also studied by immunoperoxidase histochemistry at light- and electron-microscopic levels. Endopeptidase-24.11 and (Na+ + K+)-activated ATPase were uniquely located on the brush border, and the other two peptidases appeared to be much more abundant on the endothelial lining of microvessels. Dipeptidyl peptidase IV and aminopeptidase W were also detected in microvasculature. Pial membranes associated with the brain and spinal cord also stained positively for endopeptidase-24.11, aminopeptidase N and peptidyl dipeptidase A. The immunohistochemical studies indicated the subcellular fractionation did not discriminate between membranes derived from epithelial cells (i.e. microvilli) and those from endothelial cells. The possible significance of these studies in relation to neuropeptide metabolism and the control of cerebrospinal fluid production is discussed.

Animals↗
PubMed1988

Electronmicroscopic immunocytochemistry of pig brain shows that endopeptidase-24.11 is localized in neuronal membranes.

An ultrastructural study of endopeptidase-24.11 in the globus pallidus from the brain of a newborn pig is reported. The antigen was localized by an immunoperoxidase method using an affinity-purified polyclonal antibody in which staining was performed on thick vibratome sections prior to osmication and flat embedding. When areas selected by light microscopy for re-embedding were examined in the electron microscope a minority of the axonal membranes in the fields examined were observed to be immunostained for endopeptidase-24.11. These were unmyelinated fibres and the membrane staining included not only the length of an axon but also some boutons synapsing with dendrites. Positively staining dendritic and glial membranes were not observed. These results support the view that endopeptidase-24.11 may play a role in inactivating some neuropeptides after their release at the synapse.

Animals↗
PubMed1988

Receptor-mediated effects of glucocorticoids on inflammation: enhancement of the inflammatory response with a glucocorticoid antagonist.

Glucocorticoids suppress the inflammatory response by altering leukocyte traffic and function, cytokine secretion and action, and phospholipid metabolism. We employed the glucocorticoid receptor antagonist RU 486, to examine whether glucocorticoids suppress the inflammatory response through a receptor-mediated mechanism and whether basal glucocorticoid secretion exerts antiinflammatory effects in the resting (non-stress) state. To test these hypotheses we evaluated the effects of increasing doses of dexamethasone, RU 486, or dexamethasone plus RU 486 on the exudate volume and concentrations of leukocytes, prostaglandin E2, (PGE2) and leukotriene B4 (LTB4) in intact rats that received subcutaneous carrageenin. Exudate volume, leukocyte concentration and LTB4 and PGE2 levels were all suppressed by dexamethasone in a dose-dependent fashion (P less than 0.005). RU 486 was able to antagonize fully the suppressive effects of dexamethasone on the inflammatory response (P less than 0.001) and to cause increases of exudate volume and leukocyte, PGE2 and LTB4 concentrations when given alone (P less than 0.05). These increases ranged between 30 and 100% above the basal inflammatory response. We conclude that glucocorticoids most likely suppress the inflammatory response by a glucocorticoid receptor-mediated mechanism and under basal conditions exert tonic antiinflammatory effects.

Alprostadil↗