Search PubMed⌕ Search

Biomedical subjects

P Gardner

Publications and source records attributed to P Gardner.

At least 37 records · Page 2Linked to original sources
PubMed1997

Non-capacitative calcium entry in Chinese hamster ovary cells expressing the platelet-derived growth factor receptor.

Platelet-derived growth factor (PDGF) is believed to produce intracellular calcium (Ca2+i) transients by inositol trisphosphate (InsP3)-mediated release of intracellular Ca2+ stores followed by "capacitative" Ca2+ entry due to emptying of these stores. We examined the roles for the phospholipase Cgamma-InsP3 pathway and the emptying of InsP3-dependent intracellular Ca2+ stores in PDGF-mediated Ca2+ entry. Intracellular Ca2+ release and Ca2+ entry were measured with fluorometric methods in Chinese hamster ovary cells expressing wild type or mutant PDGF receptors. Activation of the wild type PDGF receptor caused both intracellular "Ca2+ release, " measured in nominally 0 Ca2+ extracellular medium, and "Ca2+ entry, " measured upon addition of 2 mM Ca2+ medium. Both phases were absent in Chinese hamster ovary cells expressing a PDGF receptor mutant (Y977F,Y989F) that fails to bind phospholipase Cgamma. Blockade of the InsP3 receptor, by microinjection of single cells with low molecular weight heparin (5-50 mg/ml), blocked only Ca2+i release (following PDGF or flash photolysis of caged InsP3) and had no effect on PDGF-induced Ca2+ entry. In whole cell patch-clamp experiments, intracellular heparin also failed to block PDGF-evoked ion currents. Release of InsP3-dependent intracellular Ca2+ stores, by flash photolysis of caged InsP3, was apparently not sufficient to maximally activate Ca2+ entry. Intracellular InsP3 caused significantly less Ca2+ entry than PDGF alone. These data suggest that InsP3 alone is not sufficient to maximally activate Ca2+ entry by the capacitative pathway and that products of phosphatidylinositol 4,5-bisphosphate breakdown other than InsP3 probably play a role in PDGF-mediated Ca2+ entry.

Animals↗
PubMed1997

Nuclear export of NF-ATc enhanced by glycogen synthase kinase-3.

The transcription factor NF-AT responds to Ca2+-calcineurin signals by translocating to the nucleus, where it participates in the activation of early immune response genes. Calcineurin dephosphorylates conserved serine residues in the amino terminus of NF-AT, resulting in nuclear import. Purification of the NF-AT kinase revealed that it is composed of a priming kinase activity and glycogen synthase kinase-3 (GSK-3). GSK-3 phosphorylates conserved serines necessary for nuclear export, promotes nuclear exit, and thereby opposes Ca2+-calcineurin signaling. Because GSK-3 responds to signals initiated by Wnt and other ligands, NF-AT family members could be effectors of these pathways.

Amino Acid Sequence↗
PubMed1997

Involvement of the IP3 cascade in the damage to guinea-pig ventricular myocytes induced by cytotoxic T lymphocytes.

We have shown previously that the interaction between cytotoxic T lymphocytes (CTL) and ventricular myocytes, an in vitro model for heart transplant rejection, results in electrophysiological and morphological alterations indicative of overload of the intracellular [Ca2+] ([Ca2+]i). Since these deleterious effects cannot be accounted for by increased L-type Ca2+ current (ICa,L), we hypothesize that [Ca2+]i overload due to Ca2+ release from intracellular stores, e.g. sarcoplasmic reticulum (SR), is initiated by CTL-induced activation of the inositol trisphosphate (IP3) cascade. Patch-clamp and fura-2-fluorescence techniques were utilized to record transmembrane potentials and [Ca2+]i from ventricular myocytes bound to peritoneal exudate CTL (PEL). In ventricular myocyte-PEL conjugates (after 60 min), resting potential was reduced (compared with the nonconjugated state) from -80.9 +/- 0.7 to -59.9 +/- 2.5 mV, action potential amplitude from 139.5 +/- 1.4 to 80.6 +/- 1.7 mV and action potential duration to 50% repolarization (APD50) from 797 +/- 97 to 52 +/- 12 ms. The ratio of fluorescence at 340 and 380 nm (R340/380) increased from a control value (in nonconjugated myocytes) of 0.71 +/- 0.02 to 2.07 +/- 0.03, 30 min, after conjugate formation, and exceeded 4.0 at 60 min, before myocyte destruction. Heparin (50 micrograms/ml), an antagonist of IP3-induced Ca2+ release from SR channels, or U-73122 (2 microM), a phospholipase C (PLC) inhibitor (drugs were included in the pipette solution), prevented PEL-induced morphological and electrophysiological alterations. Accordingly, heparin attenuated the PEL-induced increase in [Ca2+]i; after 60 min of PEL-myocyte interaction, R340/380 was 1.15 +/- 0.09 (compared with approximately 4.0 in the absence of heparin). The results indicate that CTL-mediated damage to ventricular myocytes is, at least partially, mediated by PLC activation and IP3-induced Ca2+ release from intracellular stores. Pharmacological targeting of IP3 in heart transplant rejection is thus suggested.

Animals↗
PubMed1997

Cystic fibrosis, nutrition, and the health care team.

Because of the multiple systems involved in cystic fibrosis, the variability and chronicity of the disease, and the increased survival of this population, a specialty team of experts for care has evolved. A multidisciplinary approach is essential to assist patients and their families in adjusting to the disease and to optimize treatment interventions. The dietitian is responsible for assessment of nutritional status, including the determination of energy requirements and eating habits, interpretation of anthropometric data, and evaluation of nutritional adequacy. The nutrition care plan forms an integral part of the overall treatment objectives and is reported to other team members as it is devised, implemented, and monitored. A consensus report issued in April 1990 by the Cystic Fibrosis Foundation includes both general nutrition guidelines and detailed recommended treatment standards aimed at providing optimal nutrition care.

Child, Preschool↗
PubMed1997

Quality standards for immunization. Guidelines from the Infectious Diseases Society of America.

This is the third in a series of guidelines commissioned by the Infectious Diseases Society of America through its Practice Guidelines Committee. It is presented as a standard of care rather than a practice guideline because the case for following these recommendations is very strong and it should be followed with rare exceptions. The purpose of this guideline is to provide assistance to clinicians when making decisions on providing immunizations to healthy infants, children, and adults. The document is a summary of guidelines already developed by national organizations. The targeted providers are pediatricians, family practitioners, internists, and other physicians who provide immunizations. The IDSA provided the funding. Panel members represent experts in adult and pediatric infectious diseases. The guidelines are evidence-based. A standard ranking system is used for the strength of the recommendations and the quality of the evidence cited in the literature reviewed. The document has been subjected to external review by peer reviewers as well as by the Practice Guidelines Committee and was approved by the IDSA Council. An executive summary and tables highlight the major recommendations. Indicators for measuring compliance with the standards are included.

Adolescent↗
PubMed1997

Toward cystic fibrosis gene therapy.

Cystic fibrosis (CF) is a common genetic disorder characterized by defective epithelial chloride transport and progressive lung disease. Although great strides have been made in the treatment of CF, it remains lethal, often by early adulthood. CF is one of the most extensively researched genetic diseases as a target for gene therapy development. It may also serve as an important model for gene therapy of other diseases. Preclinical and clinical research has lead to the rapid development of a variety of vectors designed to correct the basic defect in CF, including adenovirus, adeno-associated virus, and liposomes. Clinical studies have identified the host immune response and low vector efficiency as key impediments to effective CF gene therapy. Further research promises to refine vector technology and bring CF gene therapy to the bedside.

Adolescent↗
PubMed1996

Adult immunizations.

New vaccines have been licensed for hepatitis A, varicella, and typhoid. This paper reviews these vaccines and their recommended uses in adults. Special attention is given to a new national policy establishing age 50 years as a time for review of preventive health measures with emphasis on evaluating risk factors that indicate a need for pneumococcal vaccine and the initiation of annual influenza immunization.

Adult↗
PubMed1996

Carotid body tumors, inheritance, and a high incidence of associated cervical paragangliomas.

BACKGROUND: Current experience with carotid body tumors suggesting a high prevalence of associated cervical paragangliomas prompted this review. PATIENTS AND METHODS: An 8-year retrospective study of patients with carotid body tumors was undertaken, detailing presentation, diagnosis, and treatment. RESULTS: Eleven patients harboring 17 carotid body tumors were discovered. All patients had a neck mass. Seven patients (64%) had bilateral carotid body tumors. Six (55%) reported a positive family history-4 were first-generation relatives, 5 had bilateral tumors, and 3 had other head and neck paragangliomas. Angiography documented 4 associated vagal and 2 glomus jugulare paragangliomas in addition to the carotid body tumors. Precise surgical care limited blood loss to an average of 590 cc. The carotid artery was repaired during 5 resections (29%). Cranial nerve injury occurred in 3 cases, all following vagal body or glomus jugulare resection. Every patient is currently alive, stroke free, and functioning without major disability. CONCLUSIONS: Patients with carotid body tumors have a propensity for multiple head and neck paragangliomas. Angiography is diagnostic. The need for associated paraganglioma resection dramatically increases the risk of cranial nerve injury.

Adult↗
PubMed1996

Reduced IL-10 secretion by CD4+ T lymphocytes expressing mutant cystic fibrosis transmembrane conductance regulator (CFTR).

Expression of the CFTR protein is thought to be physiologically important only in exocrine epithelial cells. However, chronic respiratory inflammation and infection remain unexplained phenomena in disease pathogenesis. Non-transformed, antigen-responsive CD4+ T cells cloned from healthy controls and CF patients homozygous or heterozygous for the delta F508 mutation transcribed CFTR mRNA and expressed immunoreactive cytoplasmic CFTR protein. T cell clones (TCC) from controls and CF patients displayed equivalent Ca(2+)-mediated Cl- current; however, TCC from patients with CF but not controls displayed defective cAMP-mediated Cl-current. Although CF-derived TCC preserved mitogen and antigen proliferative responses and specificity to tetanus toxoid epitopes, they selectively secreted approximately 45% less IL-10 compared with control TCC after activation with concanavalin A (Con A) (624 +/- 101 versus 1564 +/- 401 pg/ml per 10(6) cells, respectively; P = 0.04) or anti-CD3/phorbol ester (5148 +/- 1634 versus 11788 +/- 2390 pg/ml; P = 0.05). This difference was independent of atopy. Secretion of interferon-gamma, IL-2, and IL-4 was comparable in CF and control TCC after both forms of activation, while IL-5 was reduced in CF TCC following anti-CD3/phorbol myristate acetate (PMA) but not after Con A. We conclude that expression of mutant CFTR in human TCC is accompanied by ion channel dysfunction characteristic of the CF phenotype, and is accompanied by a reduction in IL-10 secretion after polyclonal activation. It is possible that disruption of IL-10-mediated anti-inflammatory homeostasis may contribute to early onset sustained inflammation in CF airways.

Animals↗
PubMed1996

Interaction of cytotoxic T lymphocytes and guinea pig ventricular myocytes. Pharmacological modulation by blocking K+ currents in cytotoxic T lymphocytes.

Infiltrating cytotoxic T lymphocytes (CTLs) are important immune effectors that damage the myocardium during heart transplant rejection as well as in cardiomyopathy and Chagas' heart disease. We have previously shown that in an in vitro model of murine-derived peritoneal exudate CTL (PEL)-guinea pig ventricular myocyte interaction, PEL induced in conjugated myocytes reduction of resting membrane potential and action potential (AP) amplitude, shortening of AP duration, delayed afterdepolarizations (DADs), and myocyte contracture and destruction. Since these findings indicated that cytotoxicity was largely caused by [Ca2+]i overload, in the present study we tested the hypothesis that blocking the L-type Ca2+ current (ICa,L) in the myocyte will eliminate the trigger for Ca2+ release from intracellular stores and will reduce [Ca2+]i overload and subsequent myocyte deterioration. CoCl2 (3 mmol/L) prevented PEL-induced AP changes, induction of DADs, and myocyte destruction. Since verapamil (2 mumol/L) was ineffective, indicating that the CoCl2 protection was not due to block of ICa,L, we tested whether the different action of these Ca2+ channel blockers was due to their differential effect on the PEL's K+ current (IK), previously shown to participate in lymphocyte activation and cytotoxicity. In agreement with their protective efficacy, CoCl2 but not verapamil blocked IK in PELs, suggesting that this is the mechanism for the protection provided by CoCl2. To support this notion, we tested the effect of the scorpion-derived peptide margatoxin (10 nmol/L), a specific K+ channel blocker in lymphocytes, on PEL-myocyte interaction and on PEL's IK; margatoxin prevented PEL-induced cytotoxicity and also blocked IK in PEL. Based on these findings, an alternative modality for attenuating CTL-induced lymphocytotoxicity is proposed.

Animals↗
PubMed1995

Activation of dual T cell signaling pathways by the chemokine RANTES.

The chemokine RANTES induced biphasic mobilization of Ca2+ in T cells. The initial peak, a transient increase in cytosolic Ca2+ mediated by a heterotrimeric guanine nucleotide-binding protein (G protein)--coupled pathway, was associated predominantly with chemotaxis. The second peak, Ca2+ release and sustained influx dependent on protein tyrosine kinases, was associated with a spectrum of cellular responses--Ca2+ channel opening, interleukin-2 receptor expression, cytokine release, and T cell proliferation--characteristic of T cell receptor activation. Other chemokines did not produce these responses. Thus, in addition to inducing chemotaxis, RANTES can act as an antigen-independent activator of T cells in vitro.

Benzoquinones↗
PubMed1995

Activation of CFTR chloride current by nitric oxide in human T lymphocytes.

Nitric oxide, which is produced by cytokine-activated mononuclear cells, is thought to play an important role in inflammation and immunity. While the function of nitric oxide as a direct cytotoxic effector molecule is well established, its function as a transducer molecule in immune cells is not. By use of whole-cell patch clamp recordings, we show that nitric oxide activates cystic fibrosis transmembrane conductance regulator CI- currents in normal human cloned T cells by a cGMP-dependent mechanism. This pathway is defective in cystic fibrosis-derived human cloned T cells. These findings not only delineate a novel transduction mechanism for nitric oxide but also support the hypothesis that an intrinsic immune defect may exist in cystic fibrosis.

Aminoquinolines↗