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Biomedical subjects

D M Smith

Publications and source records attributed to D M Smith.

At least 109 records · Page 6Linked to original sources
PubMed1999

Rat-2 fibroblasts express specific adrenomedullin receptors, but not calcitonin-gene-related-peptide receptors, which mediate increased intracellular cAMP and inhibit mitogen-activated protein kinase activity.

Rat-2 fibroblasts demonstrate specific binding of 125I-labelled rat adrenomedullin (KD=0.43 nM; Bmax=50 fmol/mg of protein) in the absence of 125I-labelled calcitonin-gene-related peptide (CGRP) binding. Therefore Rat-2 cells were used to examine the pharmacology and signal transduction pathways of adrenomedullin receptors. We examined the effects of adrenomedullin, the CGRP receptor antagonist CGRP-(8-37) and the amylin antagonists AC187 and AC253 on receptor binding and cAMP production. AC253, AC187 and CGRP-(8-37) inhibited 125I-adrenomedullin binding, with respective IC50 values of 25+/-8, 129+/-39 and 214+/-56 nM. Adrenomedullin dose-dependently increased intracellular cAMP (approximate EC50=1.0 nM). CGRP-(8-37), AC253 and AC187 antagonized adrenomedullin-stimulated cAMP production at micromolar concentrations. Using kinase-substrate assays, Mono Q FPLC and 'phospho-specific' Western blotting, we found that adrenomedullin alone abolished basal mitogen-activated protein kinase (MAPK) activity and dose-dependently inhibited platelet-derived-growth-factor-stimulated MAPK activity. Radioimmunoassay for adrenomedullin of media from Rat-2 cells showed a linear release of adrenomedullin-like immunoreactivity of 3.1 fmol/h per 2x10(6) cells. Gel-filtration chromatography showed that this adrenomedullin-like immunoreactivity co-eluted with synthetic rat adrenomedullin. Northern blotting with a rat adrenomedullin cDNA probe was used to confirm the presence of adrenomedullin mRNA. However, neither Northern blotting nor reverse transcriptase-PCR showed the presence of the cloned adrenomedullin receptor (L1). We conclude that the Rat-2 cell line expresses a specific adrenomedullin receptor (coupled to cAMP production and regulation of MAPK) and secretes adrenomedullin, which may participate in a regulatory control loop.

Animals↗
PubMed1999

HLA-G expression protects porcine endothelial cells against natural killer cell-mediated xenogeneic cytotoxicity.

BACKGROUND: Natural killer (NK) cells are major component of the cellular response in xenotransplantation. NK cell activation and NK cell-mediated cytotoxicity can be a direct barrier to the potential use of xenogeneic organs in human transplantation. METHODS: To determine if HLA-G would protect porcine xenogeneic cells from human NK cell lysis, human full-length HLA-G genomic DNA was transfected into porcine aortic endothelial cell (PAECs) by the lipofection method. Surface expression of HLA-G in transfected PAECs was confirmed by immunofluorescense staining with anti-HLA class I framework antibody, PA2.6. Fresh human peripheral blood lymphocytes were used as NK effector cells with HLA-G-transfected PAECs as targets in a 51Cr release assay. The inhibition of human polyclonal NK cells by HLA-G expression on PAECs was confirmed by antibody blocking using purified F(ab')2 portion of anti-human HLA class I antibody PA2.6. RESULTS: Expression of HLA-G on PAECs conferred a significant protection against NK-mediated lysis (range: 52-100% inhibition) when peripheral blood lymphocytes from seven healthy donors, bearing either homozygous HLA-Cw3 or -Cw4 used as NK effector cells. Such protection was inhibited by purified F(ab')2 portion of anti-HLA class I antibody, indicating that the protection of PAECs was directly mediated by HLA-G expression. CONCLUSIONS: Expression of HLA-G on PAECs protected xenogeneic PAECs against human polyclonal NK cell-mediated lysis. These results indicate that the expression of HLA-G alone in the absence of other nonclassical HLA class I molecules is sufficient to inhibit human NK cell lysis. These findings suggest methods utilizing HLA-G to overcome NK cell-mediated cytotoxicity against porcine endothelial cells, considered the first cell type effected during xenograft cellular rejection.

Animals↗
PubMed1999

Effect of steroids and the estrous cycle on uterine neuromedin U receptor expression.

We investigated the role of estrogen and progesterone on rat uterine NmU receptor expression in both intact and ovariectomized animals and examined receptor expression through the estrous cycle. Chronic administration of beta-estradiol 3-benzoate (E2) or progesterone in intact animals was devoid of any effect. RU486 caused a 2-fold up-regulation in NmU receptor density. Ovariectomy caused a 60% decrease in receptor density, but chronic E2 administration to ovariectomized rats significantly increased NmU receptor density. The estrous cycle had no significant effect on NmU receptor density. These results suggest that NmU receptor expression is estrogen-dependent, whereas progesterone or a progestin-induced factor is involved in the modulation of this expression.

Animals↗
PubMed1999

Chick Barx2b, a marker for myogenic cells also expressed in branchial arches and neural structures.

We have isolated a new chicken gene, cBarx2b, which is related to mBarx2 in sequence, although the expression patterns of the two genes are quite different from one another. The cBarx2b gene is expressed in craniofacial structures, regions of the neural tube, and muscle groups in the limb, neck and cloaca. Perturbation of anterior muscle pattern by application of Sonic Hedgehog protein results in a posteriorization of cBarx2b expression.

Amino Acid Sequence↗
PubMed1999

Production and specificity of polyclonal antibodies to hexanal-lysine adducts.

Hexanal content is a widely used index of lipid oxidation in foods. The objectives of this study were to develop antibodies to hexanal-lysine adducts, devise an ELISA, and characterize antibody specificity. Hexanal was made immunogenic by covalent attachment to lysine side chains of bovine serum albumin via reductive alkylation. Polyclonal antibodies had antiserum titers as high as 6.15 x 10(5). A competitive indirect ELISA was developed with a detection limit of 0.7 ng of hexanal/mL. Antibodies were carrier-independent, reacting with hexanal conjugates of several proteins but not with the corresponding native proteins. Cross-reactivities with chicken serum albumin conjugates of n-heptanal, n-pentanal, and n-octanal were 86. 3, 11.8, and 2.2%, respectively. Antibodies reacted strongly with hexanal-modified lysine and hexanal-modified epsilon-aminocaproic acid but did not recognize free amino acids or free hexanal. It may be feasible to use this ELISA to monitor lipid oxidation in food provided hexanal is alkylated to a carrier protein prior to analysis.

Aldehydes↗
PubMed1999

Characterization of receptors for calcitonin gene-related peptide and adrenomedullin on the guinea-pig vas deferens.

1. The receptors which mediate the effects of calcitonin gene-related peptide (CGRP), amylin and adrenomedullin on the guinea-pig vas deferens have been investigated. 2. All three peptides cause concentration dependant inhibitions of the electrically stimulated twitch response (pD2s for CGRP, amylin and adrenomedullin of 7.90+/-0.11, 7.70+/-0.19 and 7.25+/-0.10 respectively). 3. CGRP8-37 (1 microM) and AC187 (10 microM) showed little antagonist activity against adrenomedullin. 4. Adrenomedullin22-52 by itself inhibited the electrically stimulated contractions of the vas deferens and also antagonized the responses to CGRP, amylin and adrenomedullin. 5. [125I]-adrenomedullin labelled a single population of binding sites in vas deferens membranes with a pIC50 of 8.91 and a capacity of 643 fmol mg(-1). Its selectivity profile was adrenomedullin> AC187>CGRP=amylin. It was clearly distinct from a site labelled by [125I]-CGRP (pIC50=8.73, capacity=114 fmol mg(-1), selectivity CGRP>amylin=AC187>adrenomedullin). [125I]-amylin bound to two sites with a total capacity of 882 fmol mg(-1). 6. Although CGRP has been shown to act at a CGRP2 receptor on the vas deferens with low sensitivity to CGRP8-37, this antagonist displaced [125I]-CGRP with high affinity from vas deferens membranes. This affinity was unaltered by increasing the temperature from 4 degrees C to 25 degrees C, suggesting the anomalous behaviour of CGRP8-37 is not due to temperature differences between binding and functional assays.

Adrenomedullin↗
PubMed1999

Towards excellence in quality patient care: a clinical pathway for myocardial infarction.

A major initiative to implement a clinical pathway for myocardial infarction has provided a model on which to further develop pathways within our organization. Two of the primary objectives were to reduce time to thrombolysis and length of stay. Two years after the implementation of the myocardial infarction pathway there has been a reduction in the thrombolysis times from 80 to 49 min and in length of stay from 7.28 to 6.13 days. These results highlight significant improvements in patient and process outcomes. There is heightened awareness about best practice for patients who have sustained myocardial infarctions.

Critical Pathways↗
PubMed1999

Prevention and control of epidemic keratoconjunctivitis in a teaching eye institute.

PURPOSE: To determine if an ongoing infection control program is associated with a reduction in rates of nosocomial outbreaks of epidemic keratoconjunctivitis (EKC) and outbreak morbidity from nosocomial EKC in a large teaching eye institute. METHODS: The number of nosocomial EKC outbreaks, the number of affected patients, and the total number of patient visits were collected for each year between 1984 and 1997. An infection control program was implemented in 1992. The program included specified methods of patient screening and isolation, handwashing, instrument disinfection, medication distribution, and furlough of infected employees. The program included two levels of intensity of infection control measures, for non-outbreak and outbreak conditions. We compared rates per 100,000 patient visits of nosocomial outbreaks of EKC and affected patients for the 6-year period after the program was implemented, 1992-1997, with corresponding rates for 1984-1991. RESULTS: One, to three nosocomial outbreaks of EKC occurred annually in the period 1984-1991. After the implementation of the infection control program, no nosocomial outbreaks occurred in three of six years studied. In the pre-infection control years 1984-1991, there were 3.89 outbreaks and 54.09 affected patients per 100,000 visits, respectively. For the post-infection control years 1992-1997, the corresponding rates were 0.54 outbreaks and 5.66 affected patients per 100,000 patient visits. Rates for both outbreaks and affected patients were significantly lower for the post-implementation period (p < 0.005 and p < 0.0005, respectively). CONCLUSIONS: An ongoing infection control program was associated with decreased rates of nosocomial EKC outbreaks and outbreak morbidity from nosocomial EKC in our institute. Although several reports have described infection control measures that terminated individual outbreaks of nosocomial EKC, this study demonstrates that an ongoing infection control program may preemptively reduce nosocomial EKC outbreaks.

Baltimore↗
PubMed1999

Mailed reminders for area-wide influenza immunization: a randomized controlled trial.

OBJECTIVE: To determine if mailed reminders would increase area-wide influenza immunization for persons aged 65 and older. DESIGN: A randomized, controlled trial. SETTING: Ten counties in Indiana. PARTICIPANTS: Using a Medicare database, 10,000 subjects were selected randomly from 10 counties in Indiana and randomized for the study. Using pre-established criteria, 4503 persons in the control group and 4508 in the intervention group were eligible for study. INTERVENTION: Intervention subjects received mailed reminders during the immunization season of 1995. MEASUREMENTS: Data from mailed surveys, Medicare claims, and phone calls were used to determine immunization rates. RESULTS: Of those surveyed who received immunization, only 63.4% filed a Medicare claim. Immunization rates were high in both groups but higher in the intervention group, 69.0% versus 64.2%. Age, presence of lung disease, assignment to the intervention group, presence of heart disease, and an age-sex interaction term were significantly and independently related to immunization. CONCLUSIONS: The Healthy People Year 2000 goal (60% immunization for persons 65 and older) was exceeded in this population. Medicare claims data do not reflect immunization rates accurately. Mailed reminders, an inexpensive intervention, increased immunization rates area-wide and have potential for cost savings.

Age Factors↗
PubMed1999

Residual triose phosphate isomerase activity and color measurements to determine adequate cooking of ground beef patties.

The objectives were to (i) compare the use of triose phosphate isomerase (TPI) activity and internal color scores for determination of cooking adequacy of beef patties and (ii) determine the effect of frozen storage and fat content on residual TPI activity in ground beef. Ground beef patties (24.4% fat) were cooked to five temperatures ranging from 60.0 to 82.2 degrees C. TPI activity decreased as beef patty cooking temperature was increased from 60.0 to 71.1 degrees C; however, no difference (P > 0.05) in activity (6.3 U/kg meat) was observed in patties cooked to 71.1 degrees C and above. Degree of doneness color scores, a* values and b* values, of ground beef patties decreased as internal temperature was increased from 60.0 to 71.1 degrees C; however, temperature had no effect on L* values. TPI activity in raw ground beef after five freeze-thaw cycles did not differ from the control. Three freeze-thaw cycles of raw ground beef resulted in a 57.2% decrease in TPI activity after cooking. TPI activity of cooked beef increased during 2 months of frozen storage, but TPI activity in ground beef stored for 3 months or longer did not differ from the unfrozen control. While past research has shown color to be a poor indicator of adequate thermal processing, our results suggest that undercooked ground beef patties could be distinguished from those that had been adequately cooked following U.S. Department of Agriculture guidelines using residual TPI activity as a marker.

Animals↗
PubMed1999

Performance improvement in a hospital transfusion service.

Blood bankers have always embraced the concepts of quality exemplified by the American Association of Blood Banks' Standards for Blood Banks and Transfusion Services and its accreditation program. The emergence of a quality management system based on a set of quality system essentials represents a natural evolution of these quality initiatives. When fully implemented, a quality system provides a powerful tool with which to improve the quality of both intralaboratory and, importantly, extralaboratory processes related to transfusion medicine. In addition, a functional quality system enhances a transfusion service's ability to meet current and proposed requirements of the American Association of Blood Banks, the Food and Drug Administration, the Joint Commission on Accreditation of Healthcare Organizations, and the National Committee for Clinical Laboratory Standards.

Blood Banks↗
PubMed1999

Improving educational needs assessment for general practitioners.

OBJECTIVE: To improve the quality of educational needs analysis for groups of general practitioners through the development of a range of simple, inexpensive practice based performance measures of general practice. METHOD: Members of one volunteer semi rural division of general practice were allocated randomly to groups that collected or provided data on: local referral patterns; consulting, prescribing and ordering, as collected by the Health Insurance Commission; and age, gender, reasons for encounter and management of a sample of patients. Other information was provided by a recent division community needs analysis, a consumer survey, national health targets and local health professionals. These data were combined to develop a list of educational topics that deserved attention. RESULTS: A total of 56% of GPs agreed to participate, providing Health Insurance Commission data for seven GPs, referral patterns for 11 GPs and BEACH surveys for five GPs. Much of the data collected for other purposes proved to be of little value in determining specific educational needs and the more time consuming methods attracted poor participation rates. The most useful data were those collected locally by the division. CONCLUSION: Educational needs analyses for groups of GPs should consider the perspectives of the profession, funders and patients, in addition to those of individual GPs. Practice based measures of GP performance need to be made more relevant to current practice, while remaining inexpensive and not intruding too much into GPs' time. A range of potential measures is provided.

Australia↗
PubMed1998

Neuropeptide Y (NPY) actions on the corticotroph cell of the anterior pituitary gland are not mediated by a direct effect.

Neuropeptide Y has been implicated in the activation of the hypothalamic-pituitary-adrenal (HPA) axis, the regulation of growth and sexual function, and is the most potent stimulant of feeding yet reported. The actions of NPY on the HPA axis are thought to be mediated via an activation of the corticotrophin releasing hormone (CRH) neurones within the paraventricular nucleus of the hypothalamus. The ability of NPY to directly influence the corticotroph cell is currently controversial. These studies investigated whether NPY could have a direct influence on anterior pituitary adrenocorticotrophic hormone (ACTH) release. In dispersed male rat anterior pituitary cells, NPY (1-1000 nM) had no effect on either basal or CRH (1 nM) stimulated ACTH release. Basal release, NPY (1000 nM) 111 +/- 6% vs. control 103 +/- 5%. CRH stimulated release, CRH (1 nM) with NPY (1000 nM) 226 +/- 23% vs. CRH (1 nM) alone 228 +/- 20%. In addition, NPY (1000 nM) had no effect on either basal or CRH (1 nM) stimulated ACTH release in the mouse corticotroph cell line, AtT-20. Thus, in two models of the anterior pituitary corticotroph NPY had no effect on ACTH release. NPY induced activation of the HPA axis is likely to be mediated via a modulation of hypothalamic CRH and not via a direct action at the level of the anterior pituitary.

Adrenocorticotropic Hormone↗
PubMed1998

The NPY Y1 receptor antagonist BIBP 3226 blocks NPY induced feeding via a non-specific mechanism.

We have previously shown that intracerebroventricular BIBP 3226 inhibits NPY induced feeding in rats. However, this was associated with abnormal behaviour, likely to be due to interaction with Y1 receptors involved in mechanisms other than the control of food intake. In order to minimise such interactions we investigated the effects of paraventricular nucleus (PVN) injections of BIBP 3226 and its inactive enantiomer BIBP 3435. Intra-PVN injection of NPY (0.1-2.5 nmol/animal) increased food intake, with an EC50 of approximately 0.15 nmol/animal. Injections of BIBP 3226 and BIBP 3435 (0.25-25 nmol) reduced NPY-induced food intake in a dose responsive manner, with BIBP 3226 reducing food intake by 95%, and BIBP 3435 by 65% at the highest dose tested. The reversibility of the effect of BIBP 3226 was investigated by measuring the feeding response to NPY (0.5 nmol) in animals 1 week after BIBP 3226 injection. The response to NPY was less in animals which had received high doses of BIBP 3226. Animals previously injected with saline vehicle alone showed a normal NPY feeding response. These results suggest that BIBP 3226 may be inhibiting NPY-induced food intake in a non-specific manner, not secondary to inhibition of the Y1 receptor. This does not, however rule out a role for the Y1 receptor in the control of food intake by NPY.

Animals↗
PubMed1998

The transcription factor Pitx2 mediates situs-specific morphogenesis in response to left-right asymmetric signals.

The mechanism by which asymmetric signals induce left-right-specific morphogenesis has been elusive. Pitx2 encodes a transcription factor expressed throughout the left lateral plate mesoderm and subsequently on the left side of asymmetric organs such as the heart and gut during organogenesis in the chick embryo. Pitx2 is induced by the asymmetric signals encoded by Nodal and Sonic hedgehog, and its expression is blocked by prior treatment with an antibody against Sonic hedgehog. Misexpression of Pitx2 on the right side of the embryo is sufficient to produce reversed heart looping and heart isomerisms, reversed body rotation, and reversed gut situs.

Amino Acid Sequence↗
PubMed1998

Organizing principles of cortical integration in the rat neostriatum: corticostriate map of the body surface is an ordered lattice of curved laminae and radial points.

The neuroanatomic organizing principles underlying integrative functions in the striatum are only partially understood. Within the three major subdivisions of the striatum-sensorimotor, associative, and limbic--longitudinal zones of axonal plexuses from the cerebral cortex end in bands and clusters that innervate cell groups. To identify organizing principles of the corticostriate bands and clusters, we localized somatosensory cortical cells receptive to light touch on the hindlimb, forelimb, or vibrissae by extracellular recording, and we labeled their projections by iontophoretic application of dextran anterograde tracers. The results show that cortical cells in columnar groups project to the striatum in the form of successive strips, or laminae, that parallel the curve of the external capsule. The vibrissae somatosensory cortex projects to the most lateral lamina. Just medial to the vibrissae projection, the major axonal arborizations arising from hindlimb and forelimb somatosensory cortex are organized within a common lamina, where they interdigitate and overlap as well as remain separate. In addition, the hindlimb and forelimb cortex send small projections to the vibrissae lamina, and vice versa, forming broken, radially oriented lines of points across the laminar strips. The major somatosensory projections are in the dorsolateral, calbindin-poor sensorimotor striatum, whereas the radially oriented projection points extend into the medial, calbindin-rich associative striatum. Extending previous studies of corticostriate projections, this report shows a grid translation of columnar somatosensory cortical inputs into striatum and a detailed map for the rat sensorimotor zone. The lattice-like grid is a novel functional/neuroanatomic organization that is ideal for distributing, combining, and integrating information for sensorimotor and cognitive processing.

Animals↗