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Biomedical subjects

R Sargeant

Publications and source records attributed to R Sargeant.

15 recordsLinked to original sources
PubMed2000

Down-regulation of the chemokine receptor CCR5 by activation of chemotactic formyl peptide receptor in human monocytes.

Interactions between cell surface receptors are important regulatory elements in the complex host responses to infections. In this study, it is shown that a classic chemotactic factor, the bacterial chemotactic peptide N-formyl-methionyl-leucylphenyl-alanine (fMLF), rapidly induced a protein-kinase-C-mediated serine phosphorylation and down-regulation of the chemokine receptor CCR5, which serves as a major human immunodeficiency virus (HIV)-1 coreceptor. The fMLF binding to its receptor, formyl peptide receptor (FPR), resulted in significant attenuation of cell responses to CCR5 ligands and in inhibition of HIV-1-envelope-glycoprotein-mediated fusion and infection of cells expressing CD4, CCR5, and FPR. The finding that the expression and function of CCR5 can be regulated by peptides that use an unrelated receptor may provide a novel approach to the design of anti-inflamatory and antiretroviral agents. (Blood. 2000;96:2887-2894)

Anti-HIV Agents↗
PubMed2000

Activation of the chemotactic peptide receptor FPRL1 in monocytes phosphorylates the chemokine receptor CCR5 and attenuates cell responses to selected chemokines.

FPRL1 is a seven-transmembrane (STM), G-protein coupled receptor which was originally identified as a low affinity receptor for the bacterial chemotactic formyl peptide and a high affinity receptor for the lipid metabolite lipoxin A4. We recently discovered that a number of peptides, including several synthetic domains of the HIV-1 envelope proteins and the serum amyloid A, use FPRL1 to induce migration and calcium mobilization in human monocytes and neutrophils. In this study, we report that a synthetic peptide domain of the V3 region of the HIV-1 envelope gp120, activates the FPRL1 receptor in monocytes and neutrophils. Furthermore, monocytes prestimulated with V3 peptide showed reduced response to several chemokines that use multiple cell receptors. This is associated with a rapid phosphorylation of the chemokine receptor CCR5 on the serine residues. Our study suggests that FPRL1, as a classical chemoattractant receptor, may play an important role in modulating monocyte activation in the presence of multiple stimuli.

Amino Acid Sequence↗
PubMed2000

Surgeon perspectives on surgical options for early-stage breast cancer.

To evaluate the practice patterns of general and plastic surgeons regarding patients with early-stage breast cancer, all general and plastic surgeons in Quebec and Maryland were mailed self-administered questionnaires evaluating surgeon demographics, practice patterns, treatment preferences, and satisfaction with the results of lumpectomy and radiation therapy or breast reconstruction. Response rates of 38.3 percent and 26.7 percent were obtained for general surgeons in Quebec and Maryland, respectively. The ratio of reported mastectomies to lumpectomies was 1:2 in Maryland and 1:5 in Quebec. All general surgeons considered lumpectomy an important option. Ninety percent of Maryland surgeons versus 44 percent of Quebec surgeons considered mastectomy important. A total of 53.6 percent versus 24.9 percent of general surgeons in Maryland and Quebec, respectively, considered delayed reconstruction an important option. Additionally, 81.3 percent of Maryland surgeons considered immediate reconstruction important, and 79.6 percent discussed it with all stage I or II patients. More than 75 percent of Quebec general surgeons reported discussing immediate or delayed reconstruction with < or =50 percent of these women. Response rates of 53.6 percent and 48.8 percent were obtained for plastic surgeons in Quebec and Maryland, respectively. In one year Quebec plastic surgeons reported that they performed less than half the number of reconstructions performed by Maryland plastic surgeons (7.2 versus 17.3). In Quebec, 82.3 percent of surgeons reported that they frequently discuss delayed reconstruction, 25.1 percent immediate, 62.5 percent pedicled TRAM, and 51.7 percent nonautogenous options. In Maryland, 74.3 percent of plastic surgeons frequently discuss delayed reconstruction, 95.7 percent immediate, 89.9 percent pedicled TRAM, and 85.9 percent nonautogenous options. For women with early-stage breast cancer, regional variations exist in the surgical options discussed and provided.

Attitude of Health Personnel↗
PubMed1999

Inhibition of tyrosine kinase activation blocks the down-regulation of CXC chemokine receptor 4 by HIV-1 gp120 in CD4+ T cells.

Because the binding of HIV-1 envelope to CD4 initiates a configurational change in glycoprotein 120 (gp120), enabling it to interact with fusion coreceptors, we investigated how this process interferes with the expression and function of CXC chemokine receptor 4 (CXCR4) in CD4+ T lymphocytes. A recombinant gp120 (MN), after preincubation with CD4+ T lymphocytes, significantly inhibited the binding and chemotaxis of the cells in response to the CXCR4 ligand stromal cell-derived factor-1alpha (SDF-1alpha), accompanied by a markedly reduced surface expression of CXCR4. gp120, but not SDF-1alpha, induced rapid tyrosine phosphorylation of src-like kinase p56lck in CD4+ T cells, whereas both gp120 and SDF-1alpha caused phosphorylation of the CXCR4. The tyrosine kinase inhibitor herbimycin A abolished the phosphorylation of p56lck and CXCR4 induced by gp120 in association with maintenance of normal expression of cell surface CXCR4 and a migratory response to SDF-1alpha. Thus, a CD4-associated signaling molecule(s) including p56lck is activated by gp120 and is required for the down-regulation of CXCR4.

Benzoquinones↗
PubMed1999

Surgical options for the early-stage breast cancer: factors associated with patient choice and postoperative quality of life.

Patients with early-stage breast cancer have three surgical options: lumpectomy with radiotherapy, mastectomy alone, and mastectomy with breast reconstruction. Our objective was to compare women in these three groups with respect to demographics, preoperative counseling, postoperative body image, and quality of life. Women having undergone surgery for stage 1 or 2 breast cancer between 1990 and 1995 were selected by random sampling of hospital tumor registries and were mailed a self-administered questionnaire, which included the Medical Outcomes Survey Short Form 36. Patients were stratified into three mutually exclusive groups: lumpectomy with axillary node dissection and radiotherapy, modified radical mastectomy, and modified radical mastectomy with breast reconstruction. In total, 267 of 525 surveys were returned (50.9 percent). Compared with mastectomy patients, breast reconstruction patients were younger (p < 0.001), better educated (p = 0.001), and more likely Caucasian (p = 0.02). Among mastectomy patients, 54.9 percent recalled that lumpectomy had been discussed preoperatively and 39.7 percent recalled discussion of breast reconstruction. Post-operative comfort with appearance was significantly lower for mastectomy patients. The relationship between type of surgery and postoperative quality of life varied with age. Under 55, quality of life was lowest for mastectomy patients on all but two Medical Outcomes Survey Short Form 36 subscales. Over 55, quality of life was lowest for lumpectomy patients on all subscales (p < 0.05 for all subscales except social functioning and role-emotional). Treatment choice may be related to age, race, education, and preoperative counseling. Whereas the effect of breast cancer on a woman's life is complex and individual, the type of surgery performed is a significant variable, whose impact may be related to patient age.

Adult↗
PubMed1998

Late capsular hematoma after breast reconstruction with polyurethane-covered implants.

We report two patients who developed late hematomas after breast reconstruction with polyurethane-covered implants. Although the cause of these hematomas is not absolutely clear, they are believed to have been caused by the intense, highly vascular inflammatory response that polyurethane coating is known to elicit. The development of late hematoma has not been previously stressed in the literature as a late complication of polyurethane-covered breast implants.

Adult↗
PubMed1997

Modulation of macrophage function for defence of the lung against Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a common respiratory tract pathogen in certain groups of compromised hosts, most notably those with cystic fibrosis. The pathogenicity of P. aeruginosa may depend in part upon its capacity to resist normal phagocytic cell clearance. We have recently shown that phagocytosis of P. aeruginosa by macrophages is a unique two-step process; binding is glucose-independent but ingestion occurs only in the presence of D-glucose or D-mannose. P. aeruginosa is the only particle we have found which is ingested by macrophages in a glucose-dependent manner. Since glucose is present in only negligible quantities in the endobronchial space, P. aeruginosa may be pathogenic by virtue of its capacity to exploit the opportunity presented in the lower airway to resist normal nonspecific phagocytic defences. The purpose of the studies reported here is to better understand the glucose-dependent phagocytosis of P. aeruginosa and to design novel therapies to facilitate phagocytic cell clearance of it from the lower respiratory tract. We have shown that phagocytosis of unopsonized P. aeruginosa depends upon facilitated transport of glucose into macrophages via the GLUT1 isoform. After transport into the macrophage, the glucose must be metabolized to trigger phagocytosis of P. aeruginosa; pretreatment with 2-deoxyglucose or 5-thioglucose abrogates glucose-dependent ingestion. We have recently demonstrated that pulmonary alveolar macrophages (as opposed to all other macrophage phenotypes studied) lack the capacity to transport glucose and to phagocytose unopsonized P. aeruginosa; however, after the cells have been cultured in vitro for 48 hours, they are able to perform both functions. Whereas most macrophages (such as peritoneal cells) primarily depend upon glycolysis for metabolic energy, pulmonary alveolar macrophages reside in a high oxygen tension environment and appear to utilize oxidative phosphorylation. Treatment of freshly explanted pulmonary alveolar macrophages with sodium azide (to poison oxidative respiration) dramatically enhances both glucose transport and glucose-dependent phagocytosis of P. aeruginosa. We are currently investigating the compromised phagocytic function of pulmonary alveolar macrophages and the mechanism by which azide enhances glucose transport and phagocytosis of P. aeruginosa. Although physiological measurements have indicated that glucose is removed from the endobronchial space by an active transport process of the lung epithelium, the types of glucose transporters that are expressed in the lung are as yet unknown. Using RT-PCR, we have amplified a product from human and murine lung RNA which has a high degree of homology with members of the sodium-dependent glucose transporter (SGLT) family. The ultimate goal of these studies is to design novel agents for enhancing the phagocytic function of pulmonary alveolar macrophages. Delivery of simple glucose by aerosol would not be effective because (i) it would be exported by sodium-dependent active transport and (ii) pulmonary alveolar macrophages lack the capacity to transport glucose. Various approaches for targeting glucose to alveolar macrophages by receptor-mediated endocytosis are under investigation.

Animals↗
PubMed1996

Delusional misidentification syndromes: a descriptive study.

Twenty-three patients with one or more delusional misidentification syndromes were studied. The majority of the subjects were females and the Capgras syndrome was the most common delusional misidentification syndrome in our sample. The Capgras syndrome cases were significant older than the Fregoli syndrome cases. Schizophrenia and schizo-affective psychosis were significantly associated with Fregoli syndrome. Discriminant function analysis was carried out on the sample and showed that age and symptoms of nuclear schizophrenia were the variables most predictive of the type of delusional misidentification. These findings are discussed in the light of current literature.

Adult↗
PubMed1995

Cellubrevin is a resident protein of insulin-sensitive GLUT4 glucose transporter vesicles in 3T3-L1 adipocytes.

Insulin stimulates glucose transport in muscle and fat cells by inducing translocation of GLUT4 glucose transporters from a storage site to the cell surface. The mechanism of this translocation and the identity of the storage site are unknown, but it has been hypothesized that transporters recycle between an insulin-sensitive pool, endosomes, and the cell surface. Upon cell homogenization and fractionation, the storage site migrates with light microsomes (LDM) separate from the plasma membrane fraction (PM). Cellubrevin is a recently identified endosomal protein that may be involved in the reexocytosis of recycling endosomes. Here we describe that cellubrevin is expressed in 3T3-L1 adipocytes and is more abundant in the LDM than in the PM. Cellubrevin was markedly induced during differentiation of 3T3-L1 fibroblasts into adipocytes, in parallel with GLUT4, and the development of insulin regulated traffic. In response to insulin, the cellubrevin content decreased in the LDM and increased in the PM, suggesting translocation akin to that of the GLUT4 glucose transporter. Vesicle-associated membrane protein 2 (VAMP-2)/synaptobrevin-II, a protein associated with regulated exocytosis in secretory cells, also redistributed in response to insulin. Both cellubrevin and VAMP-2 were susceptible to cleavage by tetanus toxin. Immunopurified GLUT4-containing vesicles contained cellubrevin and VAMP-2, and immunopurified cellubrevin-containing vesicles contained GLUT4 protein, but undiscernible amounts of VAMP-2. These observations suggest that cellubrevin and VAMP-2 are constituents of the insulin-regulated pathway of membrane traffic. These results are the first demonstration that cellubrevin is present in a regulated intracellular compartment. We hypothesize that cellubrevin and VAMP-2 may be present in different subsets of GLUT4-containing vesicles.

3T3 Cells↗
PubMed1993

Chloroquine inhibits glucose-transporter recruitment induced by insulin in rat adipocytes independently of its action on endomembrane pH.

In adipocytes, stimulation of glucose transport by insulin is mediated largely by translocation of the GLUT4 isoform of glucose transporters from an intracellular store to the plasma membrane. Most endomembrane compartments are endowed with H(+)-pumping ATPases, and the resulting luminal acidification is thought to play a role in vesicular traffic. Chloroquine (Clq), a permeant weak base, was used to test whether endomembrane pH is an important factor in GLUT4 translocation. Under conditions chosen to optimize Clq uptake, the weak base precluded insulin-induced GLUT4 translocation and the associated stimulation of glucose transport. Clq also effectively dissipated the delta pH of acidic endomembrane compartments, assessed fluorimetrically. To define whether the intracellular GLUT4 storage compartment is acidic, immunoadsorption and immunoblotting experiments were performed to determine whether glucose transporters and vacuolar-type H+ pumps coexist in the same membranes. Unexpectedly, H+ pumps were not detectable in vesicles bearing GLUT4. Moreover, dissipation of endomembrane delta pH by monensin failed to inhibit insulin-stimulated GLUT4 translocation and hexose transport. Finally, the inhibitory effect of Clq persisted in the presence of monensin. We conclude that GLUT4 resides in an intracellular compartment devoid of H+ pumps. The insertion of this compartment into the plasmalemma is not regulated by transmembrane pH gradients. Clq impairs the stimulation of glucose transport by blocking translocation of GLUT4 by a pH-independent mechanism. Clq may provide a useful tool to elucidate the signalling or fusion steps involved in insulin-induced GLUT4 translocation.

Adipocytes↗
PubMed1993

Mechanisms of adaptation of glucose transporters to changes in the oxidative chain of muscle and fat cells.

Cells in which glucose uptake is rate limiting respond to hypoxic insults with an increase in glucose transport activity. To understand the underlying cellular mechanisms involved in this adaptive response, the effects of an uncoupler of oxidative phosphorylation, 2,4-dinitrophenol (DNP), and of an inhibitor of the electron transport chain, rotenone, were compared with the effect of hypoxia in L6 muscle cells and 3T3-L1 adipocytes. All three conditions (DNP, rotenone, and 3% oxygen) elevated hexose uptake by approximately twofold in 4 h relative to control cells. All three insults decreased cellular ATP levels rapidly. A subsequent recovery was observed within 1-2 h in the presence of DNP or 3% oxygen, probably as a result of anaerobic production of ATP through increased glucose uptake and glycolysis. DNP and rotenone elevated the content of GLUT-1 protein in isolated plasma membranes and decreased it in intracellular light microsomes, suggestive of translocation of this transporter isoform. No change in GLUT-4 protein distribution was detected. In contrast, 3% oxygen caused a marked specific increase in GLUT-1 protein in both plasma membranes and microsomes. Consistently, cycloheximide had no effect on the hexose transport responses to DNP or rotenone, but prevented the response to hypoxia. However, GLUT-1 mRNA and the total cell content of GLUT-1 protein were elevated by all three treatments. It is proposed that within the time frame studied, reductions in the energy charge may activate the glucose transport system in L6 myotubes and 3T3-L1 adipocytes by GLUT-1 protein biosynthesis and translocation. When both responses exist, the biosynthetic pathway is dispensable, and posttranslational mechanisms, including transporter translocation suffice to sustain the adaptive elevation in glucose transport activity for several hours.

2,4-Dinitrophenol↗
PubMed1978

Motorized minitrack for exercising large animals.

A simply constructed device for exercise training large animals, e.g., swine, is described. Basically the device is a small, circular, enclosed track constructed of plywood and metal fence material. A centrally located, vertical shaft powered by a DC motor rotates at a variable speed. Attached to each of four horizontal metal beams extending from the shaft are four suspended partitions which hang freely above the enclosed track surface. As the shaft rotates, the four partitions move in unison, thus forcing animals in each compartment to move at the same pace. The advantages of this device are its cost, low maintenance, and the flexibility to train eight animals by one person. Preliminary results of a study on training pigs are discussed.

Animals↗