PubMed Health⌕ Search

Biomedical subjects

P Friedman

Publications and source records attributed to P Friedman.

At least 19 recordsLinked to original sources
PubMed1999

Receptors for oxidized low-density lipoprotein on elicited mouse peritoneal macrophages can recognize both the modified lipid moieties and the modified protein moieties: implications with respect to macrophage recognition of apoptotic cells.

It has been shown previously that the binding of oxidized low-density lipoprotein (OxLDL) to resident mouse peritoneal macrophages can be inhibited (up to 70%) by the apoprotein B (apoB) isolated from OxLDL, suggesting that macrophage recognition of OxLDL is primarily dependent on its modified protein moiety. However, recent experiments have demonstrated that the lipids isolated from OxLDL and reconstituted into a microemulsion can also strongly inhibit uptake of OxLDL (up to 80%). The present studies show that lipid microemulsions prepared from OxLDL bind to thioglycollate-elicited macrophages at 4 degrees C in a saturable fashion and inhibit the binding of intact OxLDL and also of the apoB from OxLDL. Reciprocally, the binding of the OxLDL-lipid microemulsions was strongly inhibited by intact OxLDL. A conjugate of synthetic 1-palmitoyl 2(5-oxovaleroyl) phosphatidylcholine (an oxidation product of 1-palmitoyl 2-arachidonoyl phosphatidylcholine) with serum albumin, shown previously to inhibit macrophage binding of intact OxLDL, also inhibited the binding of both the apoprotein and the lipid microemulsions prepared from OxLDL. Finally, a monoclonal antibody against oxidized phospholipids, one that inhibits binding of intact OxLDL to macrophages, also inhibited the binding of both the resolubilized apoB and the lipid microemulsions prepared from OxLDL. These studies support the conclusions that: (i) at least some of the macrophage receptors for oxidized LDL can recognize both the lipid and the protein moieties; and (ii) oxidized phospholipids, in the lipid phase of the lipoprotein and/or covalently linked to the apoB of OxLDL, likely play a role in that recognition.

Animals↗
PubMed1999

Monoclonal antibodies against oxidized low-density lipoprotein bind to apoptotic cells and inhibit their phagocytosis by elicited macrophages: evidence that oxidation-specific epitopes mediate macrophage recognition.

Apoptosis is recognized as important for normal cellular homeostasis in multicellular organisms. Although there have been great advances in our knowledge of the molecular events regulating apoptosis, much less is known about the receptors on phagocytes responsible for apoptotic cell recognition and phagocytosis or the ligands on apoptotic cells mediating such recognition. The observations that apoptotic cells are under increased oxidative stress and that oxidized low-density lipoprotein (OxLDL) competes with apoptotic cells for macrophage binding suggested the hypothesis that both OxLDL and apoptotic cells share oxidatively modified moieties on their surfaces that serve as ligands for macrophage recognition. To test this hypothesis, we used murine monoclonal autoantibodies that bind to oxidation-specific epitopes on OxLDL. In particular, antibodies EO6 and EO3 recognize oxidized phospholipids, including 1-palmitoyl 2-(5-oxovaleroyl) phosphatidylcholine (POVPC), and antibodies EO12 and EO14 recognize malondialdehyde-lysine, as in malondialdehyde-LDL. Using FACS analysis, we demonstrated that each of these EO antibodies bound to apoptotic cells but not to normal cells, whereas control IgM antibodies did not. Confocal microscopy demonstrated cell-surface expression of the oxidation-specific epitopes on apoptotic cells. Furthermore, each of these antibodies inhibited the phagocytosis of apoptotic cells by elicited peritoneal macrophages, as did OxLDL. In addition, an adduct of POVPC with BSA also effectively prevented phagocytosis. These data demonstrate that apoptotic cells express oxidation-specific epitopes-including oxidized phospholipids-on their cell surface, and that these serve as ligands for recognition and phagocytosis by elicited macrophages.

Animals↗
PubMed1999

A specific human lysophospholipase: cDNA cloning, tissue distribution and kinetic characterization.

Lysophospholipases are critical enzymes that act on biological membranes to regulate the multifunctional lysophospholipids; increased levels of lysophospholipids are associated with a host of diseases. Herein we report the cDNA cloning of a human brain 25 kDa lysophospholipid-specific lysophospholipase (hLysoPLA). The enzyme (at both mRNA and protein levels) is widely distributed in tissues, but with quite different abundances. The hLysoPLA hydrolyzes lysophosphatidylcholine in both monomeric and micellar forms, and exhibits apparent cooperativity and surface dilution kinetics, but not interfacial activation. Detailed kinetic analysis indicates that the hLysoPLA binds first to the micellar surface and then to the substrate presented on the surface. The kinetic parameters associated with this surface dilution kinetic model are reported, and it is concluded that hLysoPLA has a single substrate binding site and a surface recognition site. The apparent cooperativity observed is likely due to the change of substrate presentation. In contrast to many non-specific lipolytic enzymes that exhibit lysophospholipase activity, hLysoPLA hydrolyzes only lysophospholipids and has no other significant enzymatic activity. Of special interest, hLysoPLA does not act on plasmenylcholine. Of the several inhibitors tested, only methyl arachidonyl fluorophosphonate (MAFP) potently and irreversibly inhibits the enzymatic activity. The inhibition by MAFP is consistent with the catalytic mechanism proposed for the enzyme - a serine hydrolase with a catalytic triad composed of Ser-119, Asp-174 and His-208.

Amino Acid Sequence↗
PubMed1999

Radiographic evidence of interstitial pulmonary edema after exercise at altitude.

Pulmonary function abnormalities after exercise are suggestive of pulmonary edema; however, radiographic evidence is lacking. Well-trained cyclists were studied to determine whether there is radiographic evidence of pulmonary edema after endurance exercise (cycling distance 5.3-131.5 km) at altitude. Chest radiographs obtained before exercise were coded for later interpretation. Films obtained after exercise were coded with a different number. A total of 74 sets of posteroanterior and lateral films were analyzed by three radiologists for signs of pulmonary edema. Radiographic changes were graded on a three-point scale. An edema score was calculated by summing the score for each individual radiographic finding for each radiologist and an overall edema score representing the mean scores from all three radiologists. The overall edema score increased from 0.8 +/- 1.2 before exercise to 1.8 +/- 1.6 after exercise (P < 0.01). These results suggest that, after prolonged high-intensity exercise at moderate altitude, there is radiographic evidence of early pulmonary edema in some cyclists.

Adolescent↗
PubMed1999

GB virus type C viremia and envelope antibodies among population subsets in The Netherlands.

BACKGROUND AND OBJECTIVES: Two new flaviviruses, hepatitis G virus and GB virus type C (GBV-C), are possible causative agents for non-A-E hepatitis. In this study we established the prevalence of GBV-C markers in various population subsets in The Netherlands by assays for GBV-C antibodies and GBV-C nucleic acid. MATERIALS AND METHODS: We tested specimens from groups of patients with hepatitis of various causes, intravenous drug users (IVDUs), and blood donors for GBV-C RNA (LCx(R) GBV-C assay, Abbott Laboratories), and for antibodies to the GBV-C envelope E2 protein (GBV-C anti-E2) with an enzyme immunoassay (Abbott Laboratories). Patients and donors were represented in one group only. RESULTS: GBV-C RNA and GBV-C anti-E2 prevalence were, respectively, 2/34 (6%) and 3/34 (9%) among patients with non-A-E hepatitis, 2/10 (20%) and 0/10 (0%) among hepatitis B virus patients, 10/40 (25%) and 19/40 (48%) among hepatitis C virus (HCV) patients, 1/8 (13%) and 0/8 (0%) among patients with autoimmune hepatitis (AIH), 24/102 (24%) and 72/102 (71%) among IVDUs, 1/34 (3%) and 2/34 (6%) among blood donors with indeterminate anti-HCV recombinant immunoblot assay reactivity, and 3/250 (1.2%) and 8/250 (3.2%) among first-time blood donors. The profile of simultaneous GBV-C RNA positivity plus GBV-C anti-E2 positivity was found in 2/40 (5%) HCV patients, 4/102 (4%) IVDUs, and 1/250 (0.4%) first time blood donors. CONCLUSION: GBV-C infection appears not to be a major cause of non-A-E hepatitis and AIH, but is associated with parenteral risk. The prevalence of GBV-C viremia in first time blood donors is higher than that of HCV (1.2 vs. 0.04%), but GBV-C viremia in IVDUs is lower than HCV (24 vs. 59%). Most IVDUs have probably previously been exposed to GBV-C given the very high prevalence of GBV-C anti-E2 (71%). Most persons with GBV-C markers are GBV-C RNA-negative and anti-E2-confirmed positive, suggesting that GBV-C infection is transient.

Blood Donors↗
PubMed1999

Monoclonal autoantibodies specific for oxidized phospholipids or oxidized phospholipid-protein adducts inhibit macrophage uptake of oxidized low-density lipoproteins.

We recently cloned monoclonal IgM autoantibodies which bind to epitopes of oxidized low-density lipoprotein (OxLDL) from apoE-deficient mice (EO- autoantibodies). We now demonstrate that those EO- autoantibodies that were originally selected for binding to copper-oxidized low-density lipoproteins (CuOx-LDL), also bound both to the oxidized protein and to the oxidized lipid moieties of CuOx-LDL. The same EO- autoantibodies showed specific binding to products of oxidized 1-palmitoyl-2-arachidonoyl-phosphatidylcholine (OxPAPC) and to the specific oxidized phospholipid, 1-palmitoyl-2-(5-oxovaleroyl)-phosphatidyl-choline (POVPC), whereas oxidation of fatty acids (linoleic or arachidonic acid) or cholesteryl esters (cholesteryl-oleate or cholesteryl-linoleate) did not yield any binding activity. Those EO- autoantibodies that bound to oxidized phospholipids (e.g., EO6) inhibited the binding and degradation of CuOx-LDL by mouse peritoneal macrophages up to 91%, whereas other IgM EO- autoantibodies, selected for binding to malondialdehyde (MDA)-LDL, had no influence on binding of either CuOx-LDL or MDA-LDL by macrophages. F(ab')2 fragments of EO6 were equally effective as the intact EO6 in preventing the binding of CuOx-LDL by macrophages. The molar ratios of IgM to LDL needed to maximally inhibit the binding varied from approximately 8 to 25 with different CuOx-LDL preparations. Finally, a POVPC-bovine serum albumin (BSA) adduct also inhibited CuOx-LDL uptake by macrophages. These data suggest that oxidized phospholipid epitopes, present either as lipids or as lipid-protein adducts, represent one class of ligands involved in the recognition of OxLDL by macrophages, and that apoE-deficient mice have IgM autoantibodies that can bind to these neoepitopes and inhibit OxLDL uptake.

Animals↗
PubMed1998

Multicenter trial on mother-to-infant transmission of GBV-C virus. The Lombardy Study Group on Vertical/Perinatal Hepatitis Viruses Transmission.

Evidence indicates that the GBV-C or hepatitis G virus can cause persistent infection in humans, but little is known on the importance of vertical transmission. To assess the risk of mother-to-infant transmission and the clinical outcome of infected babies, we investigated 175 anti-HCV positive mothers and followed-up their children for 3-33 months. GBV-C RNA was detected by RT-PCR and anti-E2 antibody was assayed by EIA. Thirty-four (19.4%) women were GBV-C RNA positive and transmission occurred to 21 (61.8%) babies; 20 (95.2%) acquired GBV-C alone, and one (4.8%) GBV-C and HCV. Maternal factors such as intravenous drug use, HIV coinfection, HCV-RNA positivity, and type of feeding were not correlated with GBV-C transmission. GBV-C RNA remained persistently positive in all infected babies but one baby who seroconverted to anti-E2. Seven (35%) babies with GBV-C alone developed marginally elevated ALT; the baby with HCV and GBV-C co-infection had the highest ALT peak value (664 IU/l). Seven of the 141 (5%) babies born to the GBV-C RNA negative mothers acquired HCV and six (85.7%) had abnormal ALT. The mean ALT peak value was significantly higher (P < 0.05) for babies with HCV than for those with GBV-C. None of the children with GBV-C or with HCV became icteric. GBV-C is frequently present in anti-HCV positive women. The infection is transmitted efficiently from mother to baby and rate of transmission is much higher than that for HCV. GBV-C can cause persistent infection in babies but usually without clear evidence of liver disease.

Adult↗
PubMed1998

Detection of GB virus C by the RT-PCR LCx system.

The recent publication of representative genomic sequences of GBV-C has permitted the selection of PCR primers for detection of GBV-C in clinical samples by PCR techniques. Traditional amplification methodologies which couple reverse transcription polymerase chain reaction (RT-PCR) and Southern blot detection are slow, cumbersome, and can be technique dependent. This has hampered studies to determine the clinical significance of GBV-C. We report the selection of highly conserved PCR primers and a probe useful for semi-automated RT-PCR using the Abbott LCx system. This adaptation of the LCx system expands its capabilities to include the detection of RNA by RT-PCR, in addition to DNA detection by ligase chain reaction (LCR).

Automation↗
PubMed1998

Design and implementation of the Dual Site Atrial Pacing to Prevent Atrial Fibrillation (DAPPAF) clinical trial. DAPPAF Phase 1 Investigators.

The Dual Site Atrial Pacing to Prevent Atrial Fibrillation (DAPPAF) study compares dual site, single site and support pacing modalities in the prevention of atrial fibrillation (AF) in patients with a history of paroxysmal AF (PAF) and a bradyarrhythmic indication for pacing. The trial is a randomized crossover comparison of dual site atrial pacing, single site atrial pacing, and a support pacing control period (DDI at 50 ppm or VDI) done in six month intervals. Patient inclusion requires at least 2 documented AF episodes in the three months prior to enrollment. The patients can be on concurrent antiarrhythmic drug regimens but this regimen must remain constant throughout the protocol. Patients with AV nodal ablation are excluded from this study. The primary endpoints of the study compare the time to first recurrence of clinically significant symptomatic AF with ECG verification, and quality of life among the three treatment modes. Secondary endpoints include time to first recurrence of all AF episodes as monitored by the pacemaker, the measurement of echocardiographic parameters, and symptoms logged by the patients. This trial was designed after pilot studies showed dual site pacing to be safe, feasible and preliminary results suggested increased maintenance of sinus rhythm with atrial pacing.

Adult↗
PubMed1996

Conversion of lysophospholipids to cyclic lysophosphatidic acid by phospholipase D.

Phospholipase D from Streptomyces chromofuscus hydrolyzes lysophosphatidylcholine or lysophosphatidylethanolamine in aqueous 1% Triton X-100 solution. In situ monitoring of this reaction by 31P NMR revealed the formation of cyclic lysophosphatidic acid (1-acyl 2,3-cyclic glycerophosphate) as an intermediate which was hydrolyzed further by the enzyme at a functionally distinct active site to lysophosphatidic acid (lyso-PA). Synthetic cyclic lyso-PA (1-octanoyl 2,3-cyclic glycerophosphate) was found to be stable in aqueous neutral solutions at room temperature. It was hydrolyzed by the bacterial phospholipase D to lyso-PA at a rate which was approximately 4-fold slower than the rate of formation of cyclic lyso-PA. The addition of 5-10 mM sodium vanadate could partially inhibit the ring opening reaction and thus increase substantially the cyclic lyso-PA accumulation. Cyclic lyso-PA may act as a dormant configuration of the physiologically active lyso-PA or may even possess specific activities which await verification.

Hydrolysis↗
PubMed1996

Cell attachment to frozen sections of injured adult mouse brain: effects of tenascin antibody and lectin perturbation of wound-related extracellular matrix molecules.

Previous studies describing the use of cryoculture methods have focused on the efficacy of the method for studying neuron attachment and neurite outgrowth on intact sections of nerve, and rodent and even human brain. The cryoculture method has shown promise for determining the presence of cell attachment- and neurite-growth-inhibiting molecules in such specimens, and some studies have also attempted to neutralize such molecules with antibodies to myelin inhibitory proteins, nerve growth factor, or factors present in conditioned media that may counteract the repulsiveness of some of these molecules preserved in sections of, for example, myelinated nerves or adult brain white matter. The present study describes the novel use of lesioned central nervous system cryocultures as substrates for investigating the attachment of embryonic neurons and PC12 cells. In addition to demonstrating the use of this novel scar substrate to extend previous 'scar-in-a-dish' models (David et al. (1990) Neuron, 5:463-469; Rudge and Silver (1990) J. Neurosci., 10: 3594-3603; Rudge et al. (1989) Exp. Neurol., 103: 1-16), the present study also describes antibody and lectin perturbations of putative inhibitory molecules that result in an enhanced attachment of cells to cryosection cultures of brain and spinal cord wounds.

Animals↗
PubMed1994

Severe factor VII deficiency caused by mutations abolishing the cleavage site for activation and altering binding to tissue factor.

Factor VII (F.VII) is a vitamin-K-dependent serine protease required in the early stages of blood coagulation. We describe here a patient with severe F.VII deficiency, with a normal plasma F.VII antigen level (452 ng/mL) and F.VII activity less than 1%, who is homozygous for two defects: a G-->A transition at nucleotide 6055 in exon 4, which results in an Arg-->Gln change at amino acid 79 (R79Q); and a G-->A transition at nucleotide 8961 in exon 6, which results in an Arg-->Gln substitution at amino acid 152 (R152Q). The R79Q mutation occurs in the first epidermal growth factor (EGF)-like domain, which has previously been implicated in binding to tissue factor. The R152Q mutation occurs at a site (Arg 152-Ile 153) that is normally cleaved to generate activated F.VII (F.VIIa). Analysis of purified F.VII from patient plasma shows that the material cannot be activated by F.Xa and cofactors. In addition, in an in vitro binding assay using relipidated recombinant tissue factor, patient plasma showed markedly reduced binding to tissue factor at all concentrations tested. In an effort to separate the contributions of the two mutations, three recombinant variants, wild-type, R79Q, and R152Q, were prepared and analyzed. The R152Q variant had markedly reduced activity in a clotting assay, whereas R79Q showed a milder, concentration-dependent reduction. The R152Q variant exhibited nearly normal binding in the tissue factor binding assay, whereas the R79Q variant had markedly reduced binding. The time course of activation of the R79Q variant was slowed compared with wild-type. Our results suggest that the first EGF-like domain is required for binding to tissue factor and that the F.VII zymogen lacks activity and requires activation for expression of biologic activity.

Adult↗
PubMed1994

Predictors of survival after cerebral infarction: importance of cardiac factors.

BACKGROUND: Stroke is the third leading cause of death in much of the developed world. There are two approaches to lowering mortality from stroke: reducing the incidence of stroke and reducing case fatality rate. AIMS: To determine factors, identified at presentation, that were predictive of mortality in elderly persons with acute cerebral infarction. METHODS: A consecutive series of 215 elderly persons admitted to hospital with acute cerebral infarction, confirmed by computerised tomography, were followed for an average of one year. A proportional hazards model was used to identify predictors of mortality. RESULTS: The following variables were identified on univariate analysis as predictors of death: raised serum creatinine, interstitial oedema on chest radiograph, low score on the Mini-Mental State Examination, atrial fibrillation, advanced age, cardiomegaly, raised leucocyte count, pulmonary venous congestion and homonymous hemianopia. Interstitial oedema was the most powerful predictor of death among the four measures of cardiac status. Two successful multivariate models included: 1) interstitial oedema, serum creatinine, age and homonymous hemianopia; 2) serum creatinine and Mini-Mental State Score. Further studies are required to assess the relationship between elevated serum creatinine and poor survival following stroke.

Aged↗