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Biomedical subjects

J Connor

Publications and source records attributed to J Connor.

At least 55 records · Page 3Linked to original sources
PubMed1996

Recovery of in vitro functional activity of platelet concentrates stored at 4 degrees C and treated with second-messenger effectors.

BACKGROUND: The potential for bacterial contamination limits the storage of platelets at 22 degrees C to 5 days. Refrigerated storage at 4 degrees C would abrogate this problem but would also result in a rapid loss of in vitro viability and functional activity and in vivo viability. The inhibition of platelets during storage by a combination of specific, reversible, second-messenger effectors has been investigated to allow prolonged storage at 4 degrees C with significant retention of in vitro viability and functional activity. STUDY DESIGN AND METHODS: The combination of effectors was added directly to platelet concentrates, and this step was followed by storage at 4 degrees C. Control units were incubated at 4 degrees C without the effectors and at 22 degrees C according to standard blood-banking techniques. At 1, 5, and 9 days, the units were tested for recovery of cell number, recovery of in vitro functional activity and viability, and expression of platelet surface markers. RESULTS: Treated platelets stored at 4 degrees C for 9 days, while spherical in shape, displayed no loss of cell number and had a recovery of viability and functional activity, as compared with control platelets stored at 22 degrees C for 5 days, as follows: ADP and collagen aggregation responses of 250 and 100 percent, respectively; a 70-percent recovery of hypotonic shock response; and a 60-percent recovery of extent of shape change. The treated platelets also expressed an equivalent amount of the surface marker glycoprotein lb and a lower amount of the activation marker alpha-granule membrane protein-140 on the membrane surface. CONCLUSION: Second-messenger effectors added to platelets significantly maintained in vitro functional activity with storage at 4 degrees C. In vitro analysis demonstrates the potential for extended 4 degrees C storage of platelets with numerical and functional recovery comparable to that achieved with current methods. Refrigerated storage of platelet concentrates has the potential to reduce the risk of bacterial contamination.

Blood Platelets↗
PubMed1996

A ureteric bud cell line induces nephrogenesis in two steps by two distinct signals.

Nephrons develop from mesenchymal cells that have contacted the ureteric bud (UB). To determine whether cell associated or secreted ureteric molecules induce the mesenchyme, we have isolated UB cell lines from mice transgenic for T antigen. These cells express epithelial and ureteric (Dolichos lectin staining, c-ret, c-met without hepatocyte growth factor) specific markers, which identifies them as authentic UB cells. Medium conditioned by our cells rescues mesenchyme from apoptosis without inducing the appearance of epithelial aggregates. The same was found by culturing mesenchymes upon the apical surface of a UB monolayer. In contrast, tubules were induced in mesenchymes contacting trypsinized pellets of UB cells. As revealed by staining for T antigen and Dolichos lectin or by prelabeling UB cells with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI), we found that our cells encapsulated the mesenchyme but did not incorporate in the tubules. These data demonstrate that nephrogenesis is stimulated by two distinct ureteric signals, secreted molecules rescue the mesenchyme from apoptosis, whereas diffusion-limited basolateral molecules trigger mesenchymal/epithelial conversion.

Animals↗
PubMed1996

The expression of ferritin subunits and iron in oligodendrocytes in neonatal porcine brains.

Myelination is an essential component of normal development in the brain. Thus, the factors which influence the onset of myelination need to be identified and monitored during development to insure adequate myelination. These factors may also play a role in remyelination attempts which occur as a result of demyelinating diseases. One factor known to be involved in myelination is iron. In this study, the cellular deposition of iron and the intracellular iron storage protein ferritin are examined in the brains of 1-month-old piglets. Ferritin consists of 2 subunits (H and L chains) which occur in different ratios in different organs. The subunits are functionally distinct so their pattern of expression at the cellular level reveals information about the iron requirement of the cell and utilization versus storage. The H subunit of ferritin is expressed in abundance in oligodendrocytes within white-matter tracts whereas the L subunit in this region is found only in endothelial cells of blood vessels. H-ferritin-positive cells occur in clearly defined patches which are scattered throughout the white-matter tracts. The cellular distribution of iron is identical to that of H ferritin. H-ferritin-positive cells are identified as oligodendrocytes on the basis of immunofluorescent colocalization with CNPase. Also, some of the H-ferritin-positive cells are positive for myelin basic protein. However, the distribution of CNPase-positive cells is more even in the white matter than the patches of H-ferritin/iron-positive cells. The relationship between H-ferritin- and CNPase-positive cells indicates that the former are oligodendrocytes, but also reveals a subset of oligodendrocytes in the white matter. The results of this study provide insight into how the intracellular iron is managed in oligodendrocytes. The factors which initiate iron uptake and ferritin expression in a select population of oligodendrocytes, and the relationship of this select population to myelinogenesis and myelin maintenance, have yet to be identified.

Animals↗
PubMed1996

Genetic analysis of thyroid hormone receptors in development and disease.

Thyroid hormone (T3) fulfills diverse functions in vertebrate development and physiology. These functions are thought to be mediated by two genes encoding the related T3 receptors. TR alpha and TR beta. The use of homologous recombination in embryonic stem cells to generate defined, single-gene mutations provides a powerful means to investigate the individual functions of TR alpha and TR beta in mice. We have shown that targeted inactivation of the TR beta gene results in goiter and elevated levels of thyroid hormone. Thyroid stimulating hormone (TSH), which is released by pituitary thyrotropes and is normally suppressed by increased levels of thyroid hormone, was present at elevated levels in homozygous mutant (Thrb-/-) mice. These findings suggest a unique role for TR beta that cannot be substituted by TR alpha in the T3-dependent feedback regulation of TSH transcription. Thrb-/- mice provide a recessive model for the human syndrome of resistance to thyroid hormone (RTH). Typically, RTH is associated with dominant mutations in TR beta. It is unknown whether TR alpha, TR beta, or other receptors are targets for inhibition in dominant RTH; however, the analysis of Thrb-/- mice suggests that antagonism of TR beta-mediated pathways underlies the disorder of the pituitary-thyroid axis. Thrb-/- mice also display defective maturation of auditory function, demonstrating that TR beta is essential for the development of hearing. Interestingly, hearing defects are generally absent in dominant RTH, indicating that in the auditory system, a dominant TR beta mutant cannot mimic the defect caused by loss of TR beta. This suggests the existence of tissue-specific mechanisms that modulate the activity of TR beta. These results define in vivo functions for TR beta and indicate that specificity in T3 signaling is conferred by distinct receptor genes.

Animals↗
PubMed1995

Current recommendations for surgery of the rheumatoid hand and wrist.

Treatment of the hand with rheumatoid arthritis has not changed significantly over the past year. Two studies indicated that methotrexate administration need not be discontinued prior to surgery. Electron microscopy has shown that rheumatoid tendons are morphologically different from normal tendons. Early synovectomy has been reintroduced as a valuable technique, and the need for a team approach in disease management has been emphasized. Several authors emphasized rigid surgical fixation to improve digital and wrist fusions. Three studies reported good long-term results from metacarpophalangeal joint arthroplasty. Derangements of the distal radioulnar joint can benefit from the Sauve-Kapandji procedure. A newer technique to stabilize the distal ulna following the Darrach procedure was introduced, also, the treatment of swan-neck and boutonniere deformities, the results of which were somewhat disappointing, was reviewed.

Arthritis, Rheumatoid↗
PubMed1995

Dual inhibition of nitric oxide and prostaglandin production contributes to the antiinflammatory properties of nitric oxide synthase inhibitors.

We have recently put forward the hypothesis that the dual inhibition of proinflammatory nitric oxide (NO) and prostaglandins (PG) may contribute to the antiinflammatory properties of nitric oxide synthase (NOS) inhibitors. This hypothesis was tested in the present study. A rapid inflammatory response characterized by edema, high levels of nitrites (NO2-, a breakdown product of NO), PG, and cellular infiltration into a fluid exudate was induced by the administration of carrageenan into the subcutaneous rat air pouch. The time course of the induction of inducible nitric oxide synthase (iNOS) protein in the pouch tissue was found to coincide with the production of NO2-. Dexamethasone inhibited both iNOS protein expression and NO2- synthesis in the fluid exudate (IC50 = 0.16 mg/kg). Oral administration of N-iminoethyl-L-lysine (L-NIL) or NG-nitro-L-arginine methyl ester (NO2Arg) not only blocked nitrite accumulation in the pouch fluid in a dose-dependent fashion but also attenuated the elevated release of PG. Finally, carrageenan administration produced a time-dependent increase in cellular infiltration into the pouch exudate that was inhibited by dexamethasone and NOS inhibitors. At early times, i.e., 6 h, the cellular infiltrate is composed primarily of neutrophils (98%). Pretreatment with colchicine reduced both neutrophil infiltration and leukotriene B4 accumulation in the air pouch by 98% but did not affect either NO2- or PG levels. In conclusion, the major findings of this paper are that (a) selective inhibitors of iNOS are clearly antiinflammatory agents by inhibiting not only NO but also PG and cellular infiltration and (b) that neutrophils are not responsible for high levels of NO and PG produced.

Amino Acid Oxidoreductases↗
PubMed1994

Exposure of phosphatidylserine in the outer leaflet of human red blood cells. Relationship to cell density, cell age, and clearance by mononuclear cells.

Human red blood cells (RBC) were separated by density on self-forming Percoll gradients into five distinct populations. The transbilayer movement and equilibrium distribution of 1-oleoyl-2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4- yl)aminocaproyl)phosphatidylserine (NBD-PS) was slower in dense cells and equilibrated in the inner leaflet of these cells to a lesser degree than in light cells. Conversely, the outward movement of the lipid was slower in light cells. Assessment of endogenous PS in the cells' outer leaflet by the prothrombinase activity of externalized PS revealed an increase in its presence at the cell surface with increasing cell density. The presence of PS on the cell surface directly correlated with the propensity of the RBC to bound by autologous monocytes. To determine whether increased cell density is associated with increased cell age, the in vivo clearance of density-separated murine RBC was monitored in syngeneic mice. The T1/2 of circulation of light cells was about twice that of dense cells. The majority of the cleared cells localized in the spleen. Studies carried out in antibody-deficient SCID mice indicated that RBC were cleared via a mechanism that was independent of antibody. These data suggest that cell age is related to cell density and that cells of increasing age and density display higher amounts of PS in their outer leaflet.

4-Chloro-7-nitrobenzofurazan↗
PubMed1994

Altered monamine metabolism in caudate-putamen of iron-deficient rats.

The effect of iron deficiency on brain monoamine metabolism using in vivo microdialysis techniques has not been previously reported. We, therefore, examined the monoamines, dopamine and norepinephrine, and their metabolites at steady state by in vivo microdialysis in rat brain caudate-putamen in 11-week-old iron-deficient anemic (hemoglobin < 7 g/dl) and control rats (Hb > 14 g/dl). Caudate-putamen dopamine (DA), dihydroxyphenyl acetic acid (DOPAC), and homovanillic acid (HVA) concentrations were increased by 53%, 57%, and 30% (p < 0.001), respectively, in iron-deficient rats in samples collected over a 4-h period. While diminished numbers of D2 receptors have been previously reported, the present findings suggest an additional defect in monoamine uptake and catabolism.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

A new keyed vaporizer filler.

A new design of keyed filler with a dead space of 1.1 ml was used with 50 bottles of isoflurane to fill vaporizers. The volume of isoflurane remaining in the 'empty' bottle, the residual volume, was measured. The trial was repeated using the old style filler which has a dead space of 3.3 ml. The new filler reduced the mean residual volume by 73% but still did not completely empty the bottle.

Anesthesia, Inhalation↗
PubMed1993

Regression of bladder tumors in mice treated with interleukin 2 gene-modified tumor cells.

This study explored the use of interleukin 2 (IL-2) and interferon gamma (IFN-gamma) gene-modified tumor cells as cellular vaccines for the treatment of bladder cancer. The mouse MBT-2 tumor used is an excellent model for human bladder cancer. This carcinogen-induced tumor of bladder origin resembles human bladder cancer in its etiology and histology, and responds to treatment in a manner similar to its human counterpart. Using retroviral vectors, the human IL-2 and mouse IFN-gamma genes were introduced and expressed in MBT-2 cells. The tumor-forming capacity of the cytokine gene-modified MBT-2 cells was significantly impaired, since no tumors formed in mice injected intradermally with either IL-2- or IFN-gamma-secreting cells, using cell doses far exceeding the minimal tumorigenic dose of parental MBT-2 cells. Furthermore, mice that rejected the IL-2- or IFN-gamma-secreting tumor cells became highly resistant to a subsequent challenge with parental MBT-2 cells, but not to 38C13 cells, a B cell lymphoma of the same genetic background. To approximate the conditions as closely as possible to the conditions prevailing in the cancer patient, inactivated cytokine-secreting cells were used to treat animals bearing tumors established by orthotopic implantation of MBT-2 cells into the bladder wall of the animal. Treatment of mice carrying a significant tumor burden with IL-2-secreting MBT-2 cells had a significant inhibitory effect on tumor progression with extended survival. Moreover, in 60% of the mice the tumor regressed completely and the animals remained alive and free of detectable tumor for the duration of the observation period. Treatment of tumor-bearing animals with IL-2-secreting MBT-2 cells was superior to the use of cisplatin, a chemotherapeutic agent used in the treatment of bladder cancer. The therapeutic effect of IFN-gamma-secreting cells was minimal and treatment with unmodified MBT-2 cells had no effect on tumor growth or survival, showing that the parental MBT-2 cells were nonimmunogenic in this experimental setting. Most importantly, mice that exhibited complete tumor regression after treatment with IL-2-secreting MBT-2 cells became resistant to a subsequent challenge with a highly tumorigenic dose of parental MBT-2 cells, indicating that long-term immunological memory was established in the "cured" mice.

Animals↗
PubMed1993

Safety, tolerance, and pharmacokinetics of systemic ribavirin in children with human immunodeficiency virus infection.

Eleven pediatric patients, aged 1 to 10 years and with symptomatic human immunodeficiency virus infection, were treated with 6 or 10 mg of oral ribavirin per kg of body weight daily for 60 days. Safety and pharmacokinetic parameters were monitored; five children had comprehensive pharmacokinetic evaluations. The children tolerated the drug well, and treatment was not associated with any clinically significant adverse effects. Peak concentrations in plasma of 2.5 and 3.0 microM were reached at 90 min after single oral doses of 6 and 10 mg/kg, respectively. The mean systemic availability of oral ribavirin was 42.3%. After 60 days of ribavirin administration, mean trough concentrations in plasma of 2.6 and 4.1 microM were obtained. Ribavirin penetrated well into the cerebrospinal fluid, achieving 70% of the concentration in plasma at steady state.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Evidence for a structurally homologous Rh-like polypeptide in Rhnull erythrocytes.

Human Rhnull red blood cells fail to react with Rh antibodies, indicating that these cells are either devoid of Rh protein or, like other species, possess antigenically distinct variants. To determine whether Rhnull cells possess an Rh-like polypeptide, 32-kDa proteins from D--, rr, and Rhnull cells were labeled with the cysteine-specific probe, 125I-labeled pyridyldithioethylamine. Size comparisons of labeled proteins in Triton X-100-solubilized membranes from Rh-bearing and Rhnull cells showed similar sedimentation coefficients and Stoke's radii. Immunoprecipitated Rh(D) from D-- cells, Rh(c) from rr cells, and purified 32-kDa proteins from Rhnull cells were digested with alpha-chymotrypsin and examined by high-performance liquid chromatography and by two-dimensional iodopeptide mapping. Analysis of 125I-labeled chymotryptic fragments from immunoprecipitated Rh(D) and Rh(c) showed the labeled peptides from both phenotypes to be virtually identical. High-performance liquid chromatography profiles and iodopeptide maps of 32-kDa Rhnull proteins yielded patterns identical to 32-kDa proteins isolated from D-- cells and rr cells with the exception of one missing 125I-labeled peptide. Further analysis of the Rh-related fragments from Rhnull cells showed significant homology with immunoprecipitated Rh(D) and Rh(c). DNA sequence analysis of cysteine-encoding regions from Rh-bearing and Rhnull cells showed complete identity. These data suggest that Rhnull red blood cells, although serologically distinct, possess an Rh-like protein that is structurally very similar to Rh(D) and Rh(c).

Amino Acid Sequence↗
PubMed1992

Bidirectional transbilayer movement of phospholipid analogs in human red blood cells. Evidence for an ATP-dependent and protein-mediated process.

The transbilayer movement of fluorescent and isotopically labeled analogs of phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylcholine (PC) from the outer to the inner leaflet (flip) and from the inner to the outer leaflet (flop) of human red blood cells (RBC) was examined. The inward movement of 1-oleoyl-2-(N-4-nitrobenzo-2-oxa-1,3-diazole-aminocaproyl)- (C6-NBD-), 1-oleoyl-2-(N-(3-(3-[125I]iodo-4-hydroxyphenyl)propionyl)aminocaproyl)- (C6-125I-), or 1-oleoyl-2-(N-(3-3-[125I]iodo-4-azido-phenyl)propionyl)aminocaproyl- (C6-125I-N3-) analogs of PC and PE were relatively slow. In contrast, all analogs of PS and PE analogs containing aminododecanoic acid (C12 lipids) were rapidly transported to the cell's inner leaflet. Analysis of 125I-N3 lipids cross-linked to membrane proteins revealed labeling of 32-kDa Rh polypeptides that was dependent on the lipid's capacity to be transported to the inner leaflet but was independent of lipid species. To investigate whether lipids could also be transported from the inner to the outer leaflet, lipid probes residing exclusively in the inner leaflet were monitored for their appearance in the outer leaflet. Lipid movement could not be detected at 0 degrees C. At 37 degrees C, however, approximately 70% of the PC, 40% of the PE, and 15% of the PS redistributed to the cells outer leaflet, thereby attaining their normal asymmetric distribution. Continuous incubation in the presence of bovine serum albumin depleted the cells of the analogs (t1/2 approximately 1.5 h) in a manner that was independent of lipid species. Similar to the inward movement of aminophospholipids, the outward movement of PC, PE, and PS was ATP-dependent and could be blocked by oxidation of membrane sulfhydryls and by the histidine reagent bromophenacyl bromide. Evidence is presented which suggests that the outward movement of lipids is an intrinsic property of the cells unrelated to compensatory mechanisms due to an imbalance in lipid distribution.

Amines↗
PubMed1992

Recombinant alpha-2 interferon gel treatment of recurrent herpes genitalis.

Topical recombinant alpha-2 interferon treatment of recurrent genital herpes was studied in a randomized, double-blind, placebo controlled clinical trial. Three hundred and eighty-seven patients were treated at eight study centers with either interferon gel or placebo four times daily for four days. Interferon therapy caused a 26% decrease in the duration of viral shedding. For male patients, there were also significant decreases in the time to crusting (17%) and duration of pain (34%) and itching (21%). For patients with recurrent genital herpes, treatment with topical interferon was found to be effective in decreasing the duration of viral shedding and, for males, pain, itching and time to crusting.

Administration, Cutaneous↗
PubMed1992

Morphologic, biochemical, and molecular evidence of apoptosis during the reperfusion phase after brief periods of renal ischemia.

A multiparametric analysis to demonstrate that even brief periods of arterial clamping can initiate extensive cell loss in a rat kidney through the process of apoptosis during the 48-hour period after reperfusion was performed. Microscopic examination of rat renal tissues subject to a 5-, 30-, or 45-minute period of complete ischemia showed the presence of apoptotic bodies both within and occasionally between renal tubules, appearing as early 12 hours after reperfusion, and increasing in numbers at 24 hours. Furthermore, DNA extracted from such reperfused renal tissue demonstrated the appearance of a distinct "ladder" pattern of DNA fragments after electrophoresis in agarose gels, a phenomenon commonly associated with cells undergoing apoptosis and in contrast to the predominant smear pattern obtained after electrophoresis of DNA extracted from necrotic renal tissue. Finally, messenger RNA (mRNA) encoding sulfated glycoprotein-2, a gene product previously identified to apoptotic renal cells, was found to be highly expressed in the 30-minute arterial clamped rat kidney after 24 hours of reperfusion, but was not detectable in mRNA extracted from renal tissue after 24 hours chronic infarction. This study demonstrates that a combination of morphologic, biochemical, and molecular markers can be used to distinguish predominant modes of cell death in varying forms of tissue injury. Application of these analytical techniques to renal vascular injury has distinguished that brief periods of complete ischemia initiates a form of cell death (apoptosis) during a subsequent reperfusion phase that is drastically different from cellular necrosis induced by prolonged severe ischemia.

Animals↗