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Biomedical subjects

D Gordon

Publications and source records attributed to D Gordon.

At least 19 recordsLinked to original sources
PubMed1992

T-cell activation by the CD28 ligand B7 is required for cardiac allograft rejection in vivo.

Organ graft rejection is a T-cell-dependent process. The activation of alloreactive T cells requires stimulation of the T-cell receptor/CD3 complex by foreign major histocompatibility complex (MHC)-encoded gene products. However, accumulating evidence suggests that, in addition to T-cell receptor occupancy, other costimulatory signals are required to induce T-cell activation. Previously, the CD28 receptor expressed on T cells has been shown to serve as a surface component of a signal transduction pathway that can provide costimulation. In vitro, interaction of CD28 with its natural ligand B7 expressed on the surface of activated B cells or macrophages can act as a costimulus to induce proliferation and lymphokine production in antigen receptor-activated T cells. We now report evidence that stimulation of T cells by the CD28 ligand B7 is a required costimulatory event for the rejection of a MHC-incompatible cardiac allograft in vivo. These results demonstrate that the B7/CD28 activation pathway plays an important role in regulating in vivo T-cell responses.

Animals↗
PubMed1992

Localization of receptor sites for insect-selective toxins on sodium channels by site-directed antibodies.

Site-directed antibodies corresponding to conserved putative extracellular segments of sodium channels, coupled with binding studies of radiolabeled insect-selective scorpion neurotoxins, were employed to clarify the relationship between the toxins' receptor sites and the insect sodium channel. (1) The depressant insect toxin LqhIT2 was shown to possess two noninteracting binding sites in locust neuronal membranes: a high-affinity (KD1 = 0.9 +/- 0.6 nM) and low-capacity (Bmax1 = 0.1 +/- 0.07 pmol/mg) binding site as well as a low-affinity (KD2 = 185 +/- 13 nM) and high-capacity (Bmax2 = 10.0 +/- 0.6 pmol/mg) binding site. (2) The high-affinity site serves as a target for binding competition by the excitatory insect toxin AaIT. (3) The binding of LqhIT2 was significantly inhibited in a dose-dependent manner by each of four site-directed antibodies. The binding inhibition resulted from reduction in the number of binding sites. (4) The antibody-mediated inhibition of [125I]AaIT binding differs from that of LqhIT2: three out of the four antibodies which inhibited LqhIT2 binding only partially affected AaIT binding. Two antibodies, one corresponding to extracellular and one to intracellular segments of the channel, did not affect the binding of either toxin. These data suggest that the receptors to the depressant and excitatory insect toxins (a) comprise an integral part of the insect sodium channel, (b) are formed by segments of external loops in domains I, III, and IV of the sodium channel, and (c) are localized in close proximity but are not identical in spite of the competitive interaction between these toxins.

Animals↗
PubMed1992

Spectral analysis of heart rate variability in bronchial asthma.

Sympathetic and parasympathetic activity was evaluated in ten healthy controls, nine asymptomatic, untreated asthmatic subjects and ten asthmatic patients during treatment for acute asthma, by measurement of the variation in resting heart rate using frequency spectrum analysis. Heart rate was recorded by ECG and respiratory rate by impedance plethysmography. Spectral density of the beat-to-beat heart rate was measured within the low frequency band 0.04 to 0.10 Hz (low frequency power) modulated by sympathetic and parasympathetic activity, and within a 0.12 Hz band width at the respiratory frequency mode (respiratory frequency power) modulated by parasympathetic activity. Acute asthmatics had higher heart rates than either of the other two groups; this was probably related to the effects of beta-adrenoceptor agonist medication. Sympathetically mediated heart rate variability (normalized low frequency power) was significantly lower in both asymptomatic (p less than 0.002) and acute (p less than 0.02) asthma subjects compared to controls. This is consistent with altered sympathetic/parasympathetic regulation of heart rate in subjects with bronchial asthma.

Adult↗
PubMed1992

Audit of multiple insulin injection regimens in a large outpatient diabetic population.

One hundred out-patients treated by multiple insulin injection regimens underwent clinical audit by retrospective analysis of their case-notes. Patients had been on multiple insulin injection therapy (MIIT) for 1.0-4.5 years (median, 3.6 years) and had had diabetes for 2 months-33 years (median, 8.7 years) at the time of starting pen therapy. Median daily insulin dose per patient did not differ significantly following stabilisation on MIIT or at latest follow-up. The median glycated haemoglobin did not change during each of the 4 years of follow-up. During the year prior to commencing MIIT the patients showed no significant alteration in body weight. Patients' weights rose significantly during each subsequent year. Median weight gains were 0.9 kg (P less than 0.005) during the first year, 1.4 kg (P less than 0.005) during the second year, 0.9 kg (P less than 0.05) during the third year and 1.4 kg (P less than 0.05) during year 4. No such weight gain was recorded in a control group of 30 patients matched for age and duration of diabetes and treated by twice daily insulin injections. Multiple insulin injection regimens used over prolonged periods in a routine clinic setting do not alter metabolic control. However, continuing weight gain appears to occur despite similar daily insulin doses.

Adolescent↗
PubMed1992

Gene transfer in vivo with DNA-liposome complexes: lack of autoimmunity and gonadal localization.

Direct gene transfer into localized arterial segments can be performed in vivo by transfection with DNA-liposome complexes. This technique holds promise for the treatment of human diseases, including malignancy and cardiovascular disorders. We have previously characterized the potential toxicity of this form of treatment in mice in vivo (Stewart et al., 1992). In this report, we examined two issues relevant to long-term expression of foreign recombinant genes: (i) the potential for autoimmune damage to major organs and (ii) DNA localization in gonadal tissue. Autoimmunity and toxicity of allogeneic major histocompatibility (MHC) gene transfer was assessed in mice after induction of an immune response to a recombinant murine class I MHC gene by direct gene transfer in vivo. Histological examination of brain, heart, lung, liver, kidney, spleen, and skeletal muscle revealed no clinically significant immunopathology or organ damage. The toxicity of gene delivery by DNA liposomes was also analyzed in pigs and rabbits in vivo. No histopathology was observed following the introduction of plasmids encoding several different gene products, and analysis of serum following DNA liposome delivery revealed no abnormalities of serum biochemical parameters. The potential for transfer of recombinant DNA into testes and ovary in animals was evaluated by the polymerase chain reaction. Although evidence of recombinant plasmid was consistently observed in transfected, but not untransfected, arterial sites and occasionally in lung, kidney, spleen, and liver, no plasmid DNA was detected in testes or ovary. These studies suggest that uptake of recombinant DNA following direct gene transfer by liposomal transfection in major organs is not associated with autoimmunity, toxicity, or gonadal localization.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Lipoprotein lipase is synthesized by macrophage-derived foam cells in human coronary atherosclerotic plaques.

Lipoprotein lipase (LPL), hydrolyzes the core triglycerides of lipoproteins, thereby playing a role in their maturation. LPL may be important in the metabolic pathways that lead to atherosclerosis, since it is secreted in vitro by both of the predominant cell types of the atherosclerotic plaque, i.e., macrophages and smooth muscle cells. Because of uncertainty concerning the primary cellular source of LPL in atherosclerotic lesions, in situ hybridization assays for LPL mRNA were performed on 12 coronary arteries obtained from six cardiac allograft recipients. Macrophages and smooth muscle cells were identified on adjacent sections with cell-specific antibodies and foam cells were identified morphologically. LPL protein was localized using a polyclonal antibody. LPL mRNA was produced by a proportion of plaque macrophages, particularly macrophage-derived foam cells, but was not detected in association with any intimal or medial smooth muscle cells. These findings were confirmed by combined immunocytochemistry and in situ hybridization on the same tissue sections. LPL protein was detected in association with macrophage-derived foam cells, endothelial cells, adventitial adipocytes, and medial smooth muscle cells, and, to a lesser extent, in intimal smooth muscle cells and media underlying well-developed plaque. These results indicate that macrophage-derived foam cells are the primary source of LPL in atherosclerotic plaques and are consistent with a role for LPL in the pathogenesis of atherosclerosis.

Arteriosclerosis↗
PubMed1992

Preservation of RNA for in situ hybridization: Carnoy's versus formaldehyde fixation.

Tissues fixed with organic solvent fixatives such as Carnoy's solution are known to give poor and erratic results with in situ hybridization, whereas those fixed with paraformaldehyde produce more consistent results. To understand this difference and to improve the utility of Carnoy's-fixed tissue for in situ hybridization, we explored several parameters of RNA integrity and preservation. Carnoy's-fixed, paraffin-embedded livers and paraformaldehyde-fixed, paraffin-embedded livers of mice were compared for RNA extractability, degradation, and hybridizability. In addition, retention of RNA in tissue sections after sequential in situ hybridization treatments was compared. RNA was found to be easily extractable from Carnoy's-fixed liver and was well preserved, with only slight degradation of high molecular weight RNA. Conversely, only a small percentage of the RNA was extractable from paraformaldehyde-fixed liver unless the tissue was digested with protease. The extracted RNA was well preserved, without detectable degradation. Sections of tissue fixed in Carnoy's solution subjected to in situ hybridization retained only about 10% of their original RNA content and gave correspondingly weak in situ hybridization signals. Formaldehyde-fixed tissues retained much more of the RNA (about 45%) and produced strong in situ hybridization signals. Treatment of Carnoy's-fixed tissue sections with vaporous formaldehyde increased retention of RNA and provided in situ hybridization signals comparable with those of paraformaldehyde-fixed tissues.

Acetates↗
PubMed1992

Measurement of oxybutynin and its N-desethyl metabolite in plasma, and its application to pharmacokinetic studies in young, elderly and frail elderly volunteers.

1. A quantitative h.p.l.c. plasma assay for oxybutynin (OB) and its active metabolite, N-desethyl oxybutynin (DEOB) is described. The method is linear with coefficients of variation ranging between 4 and 11.8% for OB and 4.6-9.1% for DEOB over the typical concentration range measured. Minimum detectable levels were 0.5 and 5 ng/ml for OB and DEOB respectively from a 2 ml sample. 2. Pharmacokinetic parameters were obtained after a single oral dose of OB and after administration two or three times daily to frail elderly and elderly volunteer groups respectively. Single dose results were also compared with data from young healthy volunteers. 3. There was a wide range in peak blood levels and high levels of parent drug were matched by high DEOB metabolite levels. Plasma levels on repeated administration were as would be predicted from the single dose kinetics. 4. Area under the plasma time course curve for DEOB metabolite was less than or equal to 5 than that of the parent drug. 5. A trend of increasing peak plasma levels and bioavailability was observed with increasing age and frailty, with the differences more apparent between the active elderly and frail elderly groups than between the active elderly and young volunteers. 6. Results indicate that for frail elderly patients a lower initial starting dose of 2.5 mg OB given two or three times a day may provide adequate therapeutic blood levels of the drug.

Administration, Oral↗
PubMed1992

Proliferating cell nuclear antigen. A marker for cell proliferation in autopsy tissues.

Antibodies to the proliferating cell nuclear antigen allow identification of proliferating cells in fresh tissue specimens using routine immunocytochemical methods. However, the use of such proliferation markers has not been verified for autopsy-derived tissue specimens, in which there is often a significant delay between the time of death and tissue specimen fixation. To assess the reliability of anti-proliferating cell nuclear antigen antibodies to identify proliferating cells in autopsy tissue specimens, an autopsy simulation was performed using fresh monkey and rat tissue specimens. These tissue specimens were kept at room temperature for predetermined numbers of hours before fixation. The proliferation specific staining was most reliable for tissue specimens obtained within 6 hours of death. There was reliable staining of proliferating regions up to 12 hours, although sensitivity was decreased. The only exception was skin, which was able to withstand much longer periods. Quantitative data from monkey spleen white-pulp regions showed 63% of the cells to stain for proliferating cell nuclear antigen when fixed immediately; this decreased to 29% of the cells after 12 hours and only 19% by 18 hours of postmortem simulation. Representative tissue specimens obtained from human autopsy material revealed similar postmortem staining patterns. Rapid procurement and fixation of tissue specimens and the use of control tissue specimens derived from the same autopsy material (eg, lymph node tissue) are recommended. These studies do suggest that anti-proliferating cell nuclear antigen antibodies can be used to identify proliferating cells in human autopsy tissue specimens obtained within approximately 12 hours of death, with some compromise in overall sensitivity.

Animals↗
PubMed1992

Transplant arteriosclerosis in a rat aortic model.

Transplant arteriosclerosis (TA) has emerged as an obstacle to the long-term survival of transplanted organs, especially cardiac transplants. The animal models that have been used to study TA have not been fully characterized with regard to features such as the time course of cell proliferation and the sequence of cell types arriving in the developing intimal lesion. We present a model of TA based on a transplanted segment of abdominal aorta that helps address these questions. Two strains of rats (PVG x DA) underwent orthotopic aortic transplantation without immunosuppression and were killed at 14, 20, 40, and 60 days after transplantation. The within-strain control group displayed minimal evidence of cellular rejection with minimal to absent intimal lesions. In contrast, the allograft group showed a linearly increasing intimal lesion, up through 60 days after transplantation. The mechanism of intimal thickening was by an increase in cell number at the earlier time points with the later deposition of extracellular matrix. The early intimal lesion consisted mostly of mononuclear inflammatory cells (45%) with gradually increasing presence of smooth muscle cells (SMC) in the intima between 20 and 60 days. Conversely, the media showed gradual infiltration by macrophage-type cells with virtual loss of all SMC from the media by 40 days. The proliferative index showed a peak of 6% and 8% at 20 days in both the intima and media, respectively, and was preceded by the presence of macrophages. In fact, most of the proliferating cells at the earlier time points were either monocytes/macrophages, or were immediately adjacent to monocyte-/macrophage-rich regions. This straight artery segment model of transplant arteriosclerosis provides an easily quantifiable system in which the effects of different interventions (e.g., immunosuppressive regimens) can be tested.

Animals↗
PubMed1992

Prostaglandin for enhancing bladder function after vaginal surgery. Does it work?

Fifty women underwent vaginal hysterectomy with or without anterior and posterior colporrhaphy. After the operations the women were allocated randomly to one of three groups. One group (17 patients) received daily vaginal suppositories of 10 mg of prostaglandin E2. The second group (15) received a daily intravesical solution of 50 micrograms of prostaglandin F2 alpha dissolved in 100 mL of normal saline. The third group (18) received a daily instillation of 100 mL of saline and served as the control group. The postvoiding residual urinary volume was checked daily through a suprapubic catheter, which was removed once the residual volume was less than 50 mL. The prostaglandin did not shorten the time required for postoperative bladder drainage. The rates of febrile morbidity and hospital stay were the same in all three groups. Since most of the women in the study voided spontaneously within three days, the "sit and wait" approach seems reasonable in such patients, and prophylactic treatment to enhance bladder function after vaginal operations does not seem justified.

Administration, Intravesical↗
PubMed1991

Mollusc-specific toxins from the venom of Conus textile neovicarius.

Three peptide toxins exhibiting strong paralytic activity to molluscs, but with no paralytic effects on arthropods or vertebrates, were purified from the venom of the molluscivorous snail Conus textile neovicarius from the Red Sea. The amino acid sequences of these mollusc specific toxins are: TxIA, WCKQSGEMCNLLDQNCCDGYCI-VLVCT (identical to the so called 'King Kong peptide'); TxIB, WCKQSGEMCNVLDQNCCDGYCIVFVCT; TxIIA, WGGYSTYC gamma VDS gamma CCSDNCVRSYCT (gamma = gamma-carboxyglutamate). There is a similarity of the Cys framework of these toxins to that of the omega-conotoxins; however, their net negative charges, high content of hydrophobic residues and uneven number of Cys residues in TxIIA, are highly unusual for conotoxins. When assayed on isolated cultured Aplysia neurons, all three toxins induced membrane depolarization and spontaneous repetitive firing. The TxI toxins also induce a marked prolongation of the action potential duration, which is sodium dependent. These effects differ significantly from the blocking activities of piscivorous venom conotoxins. These mollusc specific conotoxins may therefore serve as new and selective probes for ion-channel functions in molluscan neuronal systems.

Amino Acid Sequence↗
PubMed1991

Solubilization and characterization of the insect neuronal sodium channel.

Locust neuronal sodium channels were solubilized by 1% cholate and 0.2% Triton X-100, and their functionality was monitored by [3H]saxitoxin (STX) binding assays. About 40% of STX binding activity was recovered in the solubilized fraction without affecting affinity (Kd = 0.5 nM) and the time and temperature dependent STX binding activity was significantly stabilized in the presence of 20 nM STX. Partial purification by an anion exchange resin yielded a 20% recovery and a 3.5 times increase in the specific STX binding activity. Identification of the locust solubilized sodium channels by immunoprecipitation and radiophosphorylation revealed a Mr of 245,000 on SDS-PAGE. The present solubilized preparation will enable the study of the unique pharmacology of insect sodium channels.

Animals↗
PubMed1991

Modelling length bias in a longitudinally-linked record system of HIV cases.

We compare numbers of hospital admissions for intravenous drug using (IVDU) HIV patients and other HIV patients in acute-care facilities in New York State. Data consist of routinely collected hospital-discharge reports from New York's Statewide Planning and Research Cooperative System, linked into longitudinal case histories. Because recognition of an IVDU depends on an opioid diagnosis on any record in the case history, the observed distribution of the number of admissions per case for recognized IVDU's is biased towards greater numbers of admissions. We develop and apply a model to overcome this biasing. Our findings reveal that the mean numbers of admissions for the two groups differ significantly, but less so than without recognition of the length biasing.

Bias↗
PubMed1991

Growth of tracheal anastomoses: advantage of absorbable interrupted sutures.

Growth of the trachea after complete transection and anastomosis was studied in four groups of 1-month-old New Zealand white rabbits. The trachea was transected at the fifth cartilaginous ring and then anastomosed with continuous 6-0 polypropylene (Prolene) (group 1), interrupted 6-0 polypropylene (group 2), continuous 6-0 polydioxanone (PDS) (group 3), or interrupted 6-0 PDS (group 4). The animals were followed up for 90 to 103 days (mean follow-up, 95 days). At the time the animals were killed, body weight had increased 125% (1.2 to 2.7 +/- 0.18 kg). Growth of the trachea was assessed at the time of death. Results from this study suggest that growth of a tracheal anastomosis is retarded in a growing animal model. The degree of resultant stenosis was significantly less when an absorbable suture material (PDS) and an interrupted suturing technique were used.

Anastomosis, Surgical↗