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Biomedical subjects

M Laposata

Publications and source records attributed to M Laposata.

At least 55 records · Page 3Linked to original sources
PubMed1997

Effects of fasting and glucose infusion on basal and overnight leptin concentrations in normal-weight women.

The plasma concentration of leptin is reduced in association with chronic energy restriction and weight loss in humans, but little is known about the acute effects of fasting and glucose infusion on leptin. In this study, plasma leptin, insulin, glucose, and fatty acid concentrations were measured daily in 14 healthy, normal-weight, female volunteers aged 24 +/- 4 y with a body mass index (kg/m2) of 24.2 +/- 3.6 during a 4-d fast. The mean plasma leptin concentration decreased by 54 +/- 8% with fasting (P = 0.0006, ANOVA). In a stepwise-regression model, the change in leptin concentration with fasting correlated most significantly with the change in insulin (R2 = 0.48, P = 0.0057) and to a lesser extent with the change in body fat by bioimpedance analysis (R2 = 0.19, P = 0.03). Plasma leptin concentrations measured every 20 min from 2000 to 0800 on the fourth night of the fast did not show a time-dependent rise. A continuous intravenous infusion of 5% glucose providing 1414 +/- 323 kJ/d (338 +/- 78 kcal/d) was begun after 4 d of fasting in seven subjects who continued to fast for an additional 6 d. Within 24 h of the glucose infusion, leptin concentrations increased significantly by 80 +/- 52% (P < 0.05). These data show the sensitivity of plasma leptin concentrations to small changes in energy supply and suggest a basic role of substrate metabolism in the short-term regulation of leptin.

Adult↗
PubMed1997

Rapid in vivo hydrolysis of fatty acid ethyl esters, toxic nonoxidative ethanol metabolites.

Fatty acid ethyl esters (FAEE), esterification products of fatty acids and ethanol, are in use as fatty acid supplements, but they also have been implicated as toxic mediators of ethanol ingestion. We hypothesized that hydrolysis of orally ingested FAEE occurs in the gastrointestinal (GI) tract and in the blood to explain their apparent lack of toxicity. To study the in vivo inactivation of FAEE by hydrolysis to free fatty acids and ethanol, we assessed the hydrolysis of FAEE administered as an oil directly into the rat stomach and when injected within the core of low-density lipoprotein particles into the circulation of rats. Our studies demonstrate that FAEE are rapidly degraded to free fatty acids and ethanol in the GI tract at the level of the duodenum with limited hydrolysis in the stomach. In addition, FAEE are rapidly degraded in the circulation, with a half-life of only 58 s. Thus the degradation of FAEE in the GI tract and in the blood provides an explanation for the apparent lack of toxicity of orally ingested FAEE.

Administration, Oral↗
PubMed1997

Ethyl palmitate and ethyl oleate are the predominant fatty acid ethyl esters in the blood after ethanol ingestion and their synthesis is differentially influenced by the extracellular concentrations of their corresponding fatty acids.

The possibility that fatty acid ethyl esters (FAEEs), esterification products of fatty acids and ethanol, are mediators of ethanol-induced organ damage was suggested by an autopsy study in which individuals who died while acutely intoxicated were found to have FAEEs predominantly in the organs damaged by ethanol abuse. We initially observed in human subjects after ethanol consumption that there is a marked preference for the synthesis of ethyl palmitate and ethyl oleate over other FAEEs. To investigate the basis for this relative fatty acid specificity for FAEE synthesis, we used an in vitro system of Hep G2 cells incubated with ethanol. The cells were capable of synthesizing FAEEs upon exposure to ethanol and they showed a preference for synthesis of ethyl palmitate and ethyl oleate, as was found in human plasma after ethanol ingestion. This finding allowed us to explore the metabolic preference for palmitate and oleate for FAEE synthesis at the biochemical level using intact cells. We demonstrated that the preferential selection of palmitate and oleate for FAEE synthesis was not likely to be the result of specificity for palmitate and oleate by FAEE synthase or preferential uptake of palmitate and oleate by Hep G2 cells. In studies to determine whether the preference for ethyl palmitate and ethyl oleate synthesis was a result of higher concentrations of palmitate and oleate in the extracellular medium, we observed that the synthesis of ethyl oleate, ethyl linoleate, and ethyl arachidonate, but not ethyl palmitate, is influenced by the extracellular concentration of its corresponding fatty acid. The results of our studies indicate that ethyl palmitate and ethyl oleate are the predominant ethyl esters synthesized, that there is no preferential uptake or enzyme affinity for their fatty acid precursors to explain the predominance, and that ethyl palmitate synthesis is uniquely unaffected by the concentration of palmitate in the extracellular medium.

Acyltransferases↗
PubMed1997

The distribution of fatty acid ethyl esters among lipoproteins and albumin in human serum.

Fatty acid ethyl esters (FAEEs) are nonoxidative products of ethanol metabolism and have been implicated as mediators of ethanol-induced organ damage. Previous studies have demonstrated that FAEEs bind to lipoproteins and albumin in human plasma after ethanol ingestion. Analysis of human serum with varying blood ethanol levels and endogenously formed FAEEs revealed a positive correlation between serum FAEE concentration and the percentage of FAEEs associated with lipoproteins, predominantly very low density and low density lipoprotein. Similar results were obtained when increasing amounts of FAEEs were added to serum with zero blood ethanol. Additional studies indicated that free fatty acids and FAEEs do not compete for binding to albumin or lipoproteins. Data support the conclusion that the distribution of FAEEs among their carriers in the serum is dependent on serum FAEE concentration.

Acyltransferases↗
PubMed1997

Fatty acid ethyl esters: short-term and long-term serum markers of ethanol intake.

This review includes a description of short-term and long-term markers of ethanol intake and their clinical utility. The major portion of this report is a summary of studies on fatty acid ethyl ester, a new marker for monitoring both acute and chronic ethanol intake. With the markers described in the review, algorithms to assess recent ethanol intake, chronic ethanol intake, and end organ damage are included to provide a practical approach to the evaluation of the patient.

Alcohol Drinking↗
PubMed1997

The nature and extent of training activities in clinical pathology required for effective consultation on laboratory test selection and interpretation.

OBJECTIVE: The goal of this study was to identify the activities in clinical pathology training and the length of time required in each to effectively train residents as consultants on laboratory test selection and interpretation. METHODS: The information needed to address these questions was obtained from a study of 20 residents in clinical pathology at our institution between 1990 and 1996. In the survey participants were asked to assess the value of specific training activities in developing their confidence when addressing consultative questions on laboratory test use and interpretation. Participants were also asked to assess the length of time required to gain confidence in performing this role. RESULTS: The results of the study demonstrate that confidence in providing advice on clinical laboratory test selection and interpretation is acquired to a significant but not absolute degree after an intense 8-week experience in a single clinical laboratory subspecialty, during which time no other responsibilities are assigned. The data also indicate that interactions with clinical pathologists and formal lectures provided to the trainees during their rotations are critical components of the consultation service. There was a significant decrease in the length of time required to provide effective information on test selection and interpretation as the residents progressed through their training. CONCLUSIONS: For all of the major subspecialties in clinical pathology, the residents gained significant confidence by 4 weeks of intense training, and by 8 weeks participants were very confident in answering consultation questions. Even after 8 weeks, however, fewer than 10% of the residents felt absolutely confident in their own decisions regarding laboratory test use and interpretation prior to discussion with senior residents and faculty. Thus, acquisition of expertise to effectively provide advice on laboratory test selection and interpretation required up to 8 weeks of focused training in each clinical laboratory subspecialty. Gaining confidence in multiple areas requires a significant commitment of full-time training. This study provides an understanding of the type and extent of training required to attain the skills necessary to effectively provide consultation in clinical pathology.

Clinical Competence↗
PubMed1996

Fatty acid ethyl esters in the blood as markers for ethanol intake.

OBJECTIVE: To determine the clinical utility of fatty acid ethyl esters (FAEEs) in the blood as a short-term confirmatory marker for ethanol intake and a longer-term marker for ethanol intake after ethanol is no longer detectable. DESIGN: Single-center controlled clinical trial and a blinded comparison involving 48 blood samples that were positive, negative, or equivocal for blood ethanol. PARTICIPANTS: Seven healthy subjects (4 men and 3 women, aged 21 to 23 years) participated in the clinical trial. Blood samples from participants for the blinded comparison portion of the study were numbered from 1 to 48 and not identified by name. INTERVENTION: The 7 healthy subjects ingested a known amount of ethanol at a fixed rate. The concentration of FAEEs in the blood after ethanol intake was determined for a period of up to 24 hours. There was no intervention in the blinded comparison study. MAIN OUTCOME MEASURES: In the clinical trial, a pharmacokinetic analysis of FAEE concentration in the blood after ethanol intake was completed for 7 individuals whose blood ethanol level was elevated from 25 to 35 mmol/L. In the blinded comparison, the 48 blood samples that were positive, negative, or equivocal for blood ethanol were analyzed for FAEE concentration. RESULTS: In the clinical trial, the disappearance of FAEEs from the blood followed a decay curve that initially resembled the decay curve for blood ethanol. However, because of a very slow secondary elimination phase, the FAEEs were found to persist in the blood for at least 24 hours after ethanol intake was completed. In the blinded comparison, all 20 samples that were positive for ethanol were positive for FAEEs, 7 of 7 samples equivocal for ethanol were positive for FAEEs, and 21 of 21 negative samples for ethanol were negative for FAEEs. CONCLUSIONS: Serum concentration of FAEEs can serve as an excellent short-term confirmatory test for ethanol intake as well as a longer-term marker of ethanol ingestion. Measurement of FAEEs in the blood may be a more sensitive indicator of ethanol ingestion than the measurement of blood ethanol .

Adult↗
PubMed1996

Purification of fatty acid ethyl esters by solid-phase extraction and high-performance liquid chromatography.

We have developed a two-step method to purify fatty acid ethyl esters (FAEE) using solid-phase extraction (SPE), with a recovery of 70 +/- 3% (mean +/- S.E.M.) as assessed using ethyl oleate as a recovery marker from a standard lipid mixture in hexane. The first step of the SPE procedure involves application of a lipid mixture to an aminopropyl-silica column with simultaneous elution of FAEE and cholesteryl esters from the column with hexane. Gas chromatographic analysis of FAEE without interference from cholesteryl esters may be performed using the eluate from the aminopropyl-silica column, thus eliminating the need for an octadecylsilyl (ODS) column in this case. The FAEE can then be separated from the cholesteryl esters, if necessary, by chromatography on an ODS column and elution with isopropanol-water (5:1, v/v). Both the aminopropyl-silica and ODS columns were found to be effective for up to four uses. To permit isolation of specific FAEE species following isolation of total FAEE by the two-step SPE method, we have also developed a purification scheme for individual FAEE by high-performance liquid chromatography (HPLC). Thus, this simple method allows for reproducible isolation of total FAEE by SPE and isolation of individual FAEE species by HPLC.

Chromatography, High Pressure Liquid↗
PubMed1996

gamma-Linolenic acid treatment of rheumatoid arthritis. A randomized, placebo-controlled trial.

OBJECTIVE: To assess the clinical efficacy and adverse effects of gamma-linolenic acid (GLA), a plant seed oil-derived unsaturated fatty acid that suppresses inflammation and joint tissue injury in animal models, in the treatment of active rheumatoid arthritis (RA). METHODS: Fifty-six patients with active RA were randomized to treatment groups in a 6-month, double-blind trial of GLA versus placebo. This was followed by a 6-month, single-blind trial during which all patients received GLA. Patients were treated with 2.8 gm/day of GLA as the free fatty acid or with sunflower seed oil (placebo) administered in identical capsules. RESULTS: Treatment with GLA for 6 months resulted in statistically significant and clinically relevant reductions in the signs and symptoms of disease activity in patients with RA. Overall meaningful responses (at least 25% improvement in 4 measures) were also better in the GLA treatment group (14 of 22 patients versus 4 of 19 in the placebo group; P = 0.015). During the second 6 months, both groups exhibited improvement in disease activity. Thus, patients taking GLA during the entire study showed progressive improvement during the second 6 months. In this group, 16 of 21 patients showed meaningful improvement at 12 months compared with study entry. CONCLUSION: GLA at doses used in this study is a well-tolerated and effective treatment for active RA. GLA is available as a component of several plant seed oils and is usually taken in far lower doses than were used in this trial. It is not approved in the United States for the treatment of any condition, and should not be viewed as therapy for any disease. Further controlled studies of its in RA are warranted.

Adolescent↗
PubMed1996

Thioesterification of platelet proteins with saturated and polyunsaturated fatty acids.

We have demonstrated that more than 20 platelet proteins can be acylated with fatty acids via thioester linkages. These include the glycoprotein IX beta chain of glycoprotein Ib, components of the von Willebrand factor receptor on the platelet surface, P-selectin, and alpha subunits of Gz, Gq, and Gi. Our studies have shown that platelet proteins can be posttranslationally acylated in thioester linkages not only with palmitate but with myristate and also with the eicosanoid precursor fatty acids arachidonate and eicosapentaenoate. Thioesterification of platelet proteins with fatty acids other than palmitate may have significant functional consequences for reversible binding of proteins to membranes.

Arachidonic Acid↗
PubMed1996

Coagulation changes during thoracoabdominal aneurysm repair.

PURPOSE: The cause of coagulopathic hemorrhage during thoracoabdominal aneurysm (TAA) repair has not been well defined in human studies. We investigated changes in the coagulation system associated with supraceliac versus infrarenal cross-clamping to address this critical issue. METHODS: Blood levels of fibrinogen, the prothrombin fragment F1.2, D-dimer, and factors II, V, VII, VIII, IX, X, XI, and XII were analyzed in 19 patients with TAAs and four patients with abdominal aortic aneurysms (AAAs) at: (A) induction; (B) 30 minutes into supraceliac (TAA) or infrarenal (AAA) clamping; (C) 30 minutes after release of supraceliac or infrarenal clamps; and (D) immediately after surgery. Preoperative and intraoperative variables, including but not limited to aneurysm type, pathologic findings, comorbid conditions, clamp times, volume and timing of blood products, and clinical outcome, were prospectively recorded. Significance was determined by analysis of variance, Student's t test, and univariate linear regression. RESULTS: Levels of fibrinogen and factors II, V, VIII, VIII, IX, X, XI, and XII decreased (p < 0.05) at time B versus time A and returned to near baseline by time D. D-dimer and F1.2 increased starting at time B and reached significance (p < 0.05) by time D. Data points were compared for the TAA and AAA groups. Although AAA groups demonstrated a trend to factor activity reduction and increased fibrinolysis, the effect was much less pronounced than in TAA and did not approach significance. No correlation of coagulation change with clamping time was present; however, visceral clamping times were all less than 65 minutes (mean, 44 minutes). Blood and factor replacement was initiated after time B. Univariate regression analysis of factor level versus total blood replacement demonstrated a significant (p < 0.04) correlation between the reduction in the levels of factors II, V, VII, VIII, X, and XII, and the increase in the level of D-dimer at time B and subsequent total blood replacement. CONCLUSIONS: Thoracoabdominal aneurysm repair is associated with a reduction in clotting factor activity and an increase in fibrinolytic function, which occurs after placement of the supraceliac clamp. Explanations include visceral ischemia or a greater and longer ischemic tissue burden as the likely cause of coagulation alterations. Total blood replacement during TAA procedures was correlated to the degree of factor reduction and fibrinolysis at the time of visceral cross-clamping. An aggressive approach to early blood component replacement and to coagulation monitoring could lessen blood loss during TAA repair and avoid potentially disastrous bleeding complications.

Aortic Aneurysm, Abdominal↗
PubMed1996

What many of us are doing or should be doing in clinical pathology: a list of the activities of the pathologist in the clinical laboratory.

Mr. Paul Mango, Chief Operating Officer of a hospital-based clinical laboratory network in Pittsburgh, recently performed a survey of patients presenting for phlebotomy. The survey included the question, "What does a pathologist do?" The results were that 50% of the patients had no idea what a pathologist did, and 30% of the patients stated that pathologists examined dead bodies. It is not surprising that there is a limited understanding by patients of the activities of pathologists because patients do not usually see pathologists. However, beyond autopsy and surgical pathology, the activities of pathologists are also not well known to nonpathologist physicians and hospital administrators. A poor understanding of activities in clinical pathology have placed these clinical responsibilities of the pathologist under particular scrutiny for cost reduction. The quantitation of output from anatomic pathology, in number of slides reviewed or number of autopsies performed, is objective and easily understood. As noted in the list of clinical pathology activities that follows, the responsibilities within the clinical laboratory are highly diverse and, if the pathologist handles them successfully, highly contributory to patient care. Thus, it is timely that a compilation of activities in clinical pathology be issued for review by the pathologist community. I would hope that this list will serve as a starting point for a universally accepted group of activities that describes clinical pathology today and that it will be useful for pathologists to make their significant contributions in the clinical laboratory apparent to administrators, fellow physicians, and patients. The clinical laboratory responsibilities should also be valuable to directors of residency training programs to focus training in clinical pathology toward the development of currently desirable expertise.

Clinical Laboratory Techniques↗
PubMed1996

Reduced fatty acid ethyl ester synthase activity in the white blood cells of alcoholics.

PURPOSE: Fatty acid ethyl esters (FAEEs), esterification products of ethanol and fatty acids, have been implicated as mediators of ethanol-induced organ damage. It has been shown that FAEE synthase, the enzyme responsible for the formation of FAEE, is present selectively in the organs commonly damaged by ethanol abuse. Recently, we have made the observation that FAEEs are also present in the serum after ethanol ingestion. The current study was performed to determine whether cellular elements of the blood and/or plasma are capable of synthesizing FAEEs from fatty acids and ethanol. MATERIALS AND METHODS: Heparinized blood samples were collected from 10 healthy volunteers, and the red blood cells, platelets, plasma, and several white blood cell populations were assayed for FAEE synthase activity. Blood samples from control subjects and individuals admitted to an alcoholic detoxification unit at a local hospital were also assayed for FAEE synthase activity. RESULTS: We observed that the FAEE synthase activity is present in whole blood, primarily within white blood cells. Fractionation of the white blood cells revealed that the lymphocyte-monocyte fraction isolated using Ficoll-hypaque contained approximately 3.5-fold higher activity than the granulocyte fraction. The cell type that contained the highest FAEE synthase activity (1220 pmol/hr/10(6) cells) was the natural killer (NK) cell population. B cells contained approximately 40% of the enzyme activity found in NK cells, and the B-cell activity was slightly greater than that found in CD4+ and CD8+ T cells. Having shown that FAEE synthase exists in a blood cell, we subsequently demonstrated that alcoholic individuals have approximately half the white blood cell FAEE synthase activity of that found in normal controls. We also demonstrated that white blood cell FAEE synthase could be induced nearly 2-fold upon ingestion of 2 oz of scotch whiskey for 6 days. The enzyme activity returned to baseline levels despite ingestion of 2 oz of scotch whiskey/day for 3 additional days. CONCLUSIONS: These data indicate that ethanol ingestion results in increased FAEE production, particularly by NK cells. FAEE synthesis after ethanol ingestion may explain the presence of FAEE in the serum. The lower enzyme activity observed in white blood cells of alcoholics from a detoxification center may be the result of years of ethanol abuse or it may be that alcoholics congenitally have low levels of FAEE synthase. If the latter is true, this finding may explain in part the genetic predisposition of many alcoholic individuals to ethanol abuse.

Acyltransferases↗
PubMed1996

Fatty acid ethyl ester synthase, an enzyme for nonoxidative ethanol metabolism, is present in serum after liver and pancreatic injury.

Fatty acid ethyl esters (FAEE), esterification products of ethanol and fatty acids, have been implicated as mediators of ethanol-induced organ damage. Because cytosolic enzymes such as aspartate aminotransferase, lipase, and amylase appear in the blood after liver or pancreatic damage, we hypothesized that FAEE synthase, which is both cytosolic and membrane bound, is also released into the blood of patients with liver or pancreatic disease. We used a method involving thin-layer chromatography coupled with gas chromatography-mass spectrometry to reliably identify and quantify FAEE. In this study, we demonstrated that patients with liver or pancreatic disease release FAEE synthase into their plasma in amounts proportional to the amount of aspartate aminotransferase (r = 0.78), amylase (r = 0.65), and lipase (r = 0.63). These data indicate that liver and pancreatic damage results in release of FAEE synthase into the blood. The presence of FAEE synthase in plasma permits nonoxidative ethanol metabolism in the plasma.

Acyltransferases↗
PubMed1996

Binding of ethyl oleate to low density lipoprotein, phospholipid vesicles, and albumin: a 13C NMR study.

Fatty acid ethyl esters (FAEE), esterification products of ethanol and fatty acids, have been implicated as mediators of ethanol-induced organ damage. After ethanol ingestion in humans, FAEE circulate in blood, bound to lipoproteins and albumin. We have analyzed the binding of ethyl (1-13C, 99%) oleate (EO) to small unilamellar phospholipid vesicles (SUV), human low density lipoprotein (LDL), and bovine serum albumin (BSA) by 13C-NMR spectroscopy. Binding of < or = 25 mol% EO to SUV yielded a single EO carbonyl peak (172.6-172.9 ppm) downfield from that of EO oil (171.9 ppm). Thus, the carbonyl forms hydrogen bonds with water in the SUV aqueous interface. At 30 mol% EO in SUV, a second EO carbonyl peak appeared, indicating a limit in FAEE solubility in SUV. Addition of EO to isolated human LDL yielded a peak at 171.9 ppm, suggesting that the EO exists in an unhydrated environment, most likely the core of the lipoprotein. This binding was also observed using high levels of EO added to human serum. The addition of EO dissolved in ethanol or as an oil to a solution of BSA yielded no visible EO peak, whereas addition of (1-13C, 99%) oleic acid resulted in several narrow peaks, demonstrating a much greater affinity of BSA for oleic acid than for EO. Bidirectional transfer of EO between LDL and SUV was observed and was 85% complete within 30 min. There was no measurable transfer of EO from LDL or SUV to albumin. The weak binding of EO to albumin will result in increased transport of EO by lipoproteins as plasma levels of EO increase.

Carbon Isotopes↗
PubMed1995

Fatty acid ethyl ester synthase catalyzes the esterification of ethanol to cocaine.

Fatty acid ethyl esters (FAEE), esterification products of ethanol and fatty acids, have been implicated as mediators of ethanol induced organ damage. It has been shown that FAEE synthase, the enzyme responsible for the formation of FAEE, is present selectively in the organs damaged by ethanol abuse. Cocaethylene is a cocaine metabolite generated in the presence of ethanol which has been established as enhancing cocaine toxicity. In the present study we show that purified FAEE synthase also catalyzes the formation of cocaethylene. A linear relationship (r = 0.998) was demonstrated between the amount of purified FAEE synthase (microgram) and cocaethylene synthesis (nmol/hr). We further showed a correlation (r = 0.804) between the two enzyme activities in selected tissues. These findings provide evidence that purified FAEE synthase has cocaethylene synthetic ability and FAEE synthase may be responsible for a portion of cocaethylene synthesis in vivo.

Acyltransferases↗
PubMed1995

Differential regulation of human T lymphocyte protein kinase C activity by unsaturated fatty acids.

Administration of gamma-linolenic acid suppresses active synovitis in patients with rheumatoid arthritis. We therefore examined the effects of gamma-linolenic acid and its first metabolite, dihomo-gamma-linolenic acid, on protein kinase C, a key element in transduction of signals from cell surface to nucleus. We report here that gamma-linolenic acid and dihomo-gamma-linolenic acid suppress total protein kinase C activity, but facilitate translocation of protein kinase C activity from cytosol to membrane in human peripheral blood T lymphocytes stimulated with phorbol 12-myristate 13-acetate. Arachidonic acid and eicosapentaenoic acid do not influence total protein kinase C activity and have only modest effects on enzyme translocation. These findings in whole cells are in contrast to results of experiments performed with isolated protein kinase C, in which unsaturated fatty acids uniformly enhance protein kinase C activity. The differential effects of unsaturated fatty acids underscore the complexity of protein kinase C regulation and indicate that gamma-linolenic and dihomo-gamma-linolenic acids influence T lymphocyte protein kinase C metabolism in a manner that is unique among unsaturated fatty acid precursors of eicosanoids.

8,11,14-Eicosatrienoic Acid↗