Proteomics: applications in basic and applied biology

The rapid evolution of proteomics has continued during the past year, with a series of innovations in the core technologies of two-dimensional electrophoresis and mass spectrometry, and a diversity of productive research programmes. Well-annotated proteomics databases are now emerging in a number of fields to provide a platform for systematic research, with particularly promising progress in clinical applications such as cardiology and oncology. Large-scale quantitative research, comparable in power and sensitivity to that achieved for gene expression, is thus becoming a reality at the protein level.

Proteomics: applications and opportunities in preclinical drug development

Advances in DNA sequencing and the near-term availability of whole genome sequences for several pharmaceutically relevant organisms promise to dramatically alter the breadth and scale of high-throughput proteomic studies. The substantial amount of literature is available in the public domain, demonstrate the potential of proteomics in the preclinical phases of pharmaceutical development. Over the next few years, it is anticipated that functional genomics and proteomics will have major impacts on the clinical phases of drug development. Expected benefits are earlier proof-of-concept studies in man and increased efficiency of clinical trials through the availability of biologically relevant markers for drug efficacy and safety.

Proteomics to display lovastatin-induced protein and pathway regulation in rat liver

Lovastatin is a lipid lowering agent that acts by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, a key regulatory enzyme in cholesterol biosynthesis. In this study the pattern of gene network regulation induced in hepatic proteins as a response to lovastatin treatment was analyzed by proteomics. In livers of male F344 rats treated with 1.6 mg/kg/day lovastatin or 150 mg/kg/day lovastatin for seven days, 36 proteins were found to be significantly altered (p<0.001) in relation to treatment. The changed proteins were classified according to their cellular function and participation in biochemical pathways. The following observations were made: (i) inhibition of HMG-CoA reductase provoked a regulatory response in the cholesterol synthesis pathway including the induction of cytosolic HMG-CoA synthase and of isopentenyl-diphosphate delta-isomerase, (ii) manipulation of the lipid metabolism triggered alterations in key enzymes of the carbohydrate metabolism, and (iii) lovastatin treatment was associated with signs of toxicity as reflected by changes in a heterogeneous set of cellular stress proteins involved in functions such as cytoskeletal structure, calcium homeostasis, protease inhibition, cell signaling or apoptosis. These results present new insights into liver gene network regulations induced by lovastatin and illustrate a yet unexplored application of proteomics to discover new targets by analysis of existing drugs and the pathways that they regulate.

Two-dimensional electrophoresis of liver proteins: characterization of a drug-induced hepatomegaly in rats

Two-dimensional electrophoresis (2-DE) of liver proteins was applied to further characterize an unusual drug-induced increase in hepatocellular rough endoplasmic reticulum (RER) in Sprague-Dawley rats given a substituted pyrimidine derivative. Absolute liver weights of drug-treated rats (9.9 +/- 0.4 g) increased above vehicle-treated controls (7.2 +/- 0.2 g) by 37%. Light microscopy revealed diffuse granular basophilia of the hepatocellular cytoplasm, uncharacteristic of hepatocytes and suggested cells rich in ribosomes, which was confirmed by electron microscopy. Immunostaining for cell proliferation, viz., 5-bromo-2'-deoxyuridine (BrdU) and proliferating cell nuclear antigen (PCNA), indicated marked hepatocellular proliferative activity. 2-DE of solubilized liver using an ISO-DALT gel system indicated significant (p<0.001) quantitative changes in at least 17 liver proteins (12 increased, 5 decreased) compared to controls. The protein with the largest increase was homologous to acute-phase reactant, contrapsin-like protein inhibitor-6. Other markedly upregulated proteins were methionine adenosyltransferase, a catalyst in methionine/ATP metabolism and mitochondrial HMG-CoA synthase, involved in cholesterol synthesis. The complementary strategies of 2-DE coupled either with database spot mapping or protein isolation and amino acid sequencing successfully identified a subset of proteins from xenobiotic-damaged rodent livers, the expression of which differed from controls. However, the current bioinformatics platform for rodent hepatic proteins and limited knowledge of specific protein functionality restricted application of this proteomics profile to further define a mechanistic basis for this unusual hepatotoxicity.

Two-dimensional electrophoresis of liver proteins: characterization of a drug-induced hepatomegaly in rats

Two-dimensional electrophoresis (2-DE) of liver proteins was applied to further characterize an unusual drug-induced increase in hepatocellular rough endoplasmic reticulum (RER) in Sprague-Dawley rats given a substituted pyrimidine derivative. Absolute liver weights of drug-treated rats (9.9 +/- 0.4 g) increased above vehicle-treated controls (7.2 +/- 0.2 g) by 37%. Light microscopy revealed diffuse granular basophilia of the hepatocellular cytoplasm, uncharacteristic of hepatocytes and suggested cells rich in ribosomes, which was confirmed by electron microscopy. Immunostaining for cell proliferation, viz., 5-bromo-2'-deoxyuridine (BrdU) and proliferating cell nuclear antigen (PCNA), indicated marked hepatocellular proliferative activity. 2-DE of solubilized liver using an ISO-DALT gel system indicated significant (p<0.001) quantitative changes in at least 17 liver proteins (12 increased, 5 decreased) compared to controls. The protein with the largest increase was homologous to acute-phase reactant, contrapsin-like protein inhibitor-6. Other markedly upregulated proteins were methionine adenosyltransferase, a catalyst in methionine/ATP metabolism and mitochondrial HMG-CoA synthase, involved in cholesterol synthesis. The complementary strategies of 2-DE coupled either with database spot mapping or protein isolation and amino acid sequencing successfully identified a subset of proteins from xenobiotic-damaged rodent livers, the expression of which differed from controls. However, the current bioinformatics platform for rodent hepatic proteins and limited knowledge of specific protein functionality restricted application of this proteomics profile to further define a mechanistic basis for this unusual hepatotoxicity.

Expression profiling in toxicology--potentials and limitations

Recent progress in genomics and proteomics technologies has created a unique opportunity to significantly impact the pharmaceutical drug development processes. The perception that cells and whole organisms express specific inducible responses to stimuli such as drug treatment implies that unique expression patterns, molecular fingerprints, indicative of a drug's efficacy and potential toxicity are accessible. The integration into state-of-the-art toxicology of assays allowing one to profile treatment-related changes in gene expression patterns promises new insights into mechanisms of drug action and toxicity. The benefits will be improved lead selection, and optimized monitoring of drug efficacy and safety in pre-clinical and clinical studies based on biologically relevant tissue and surrogate markers.

Sudden onset of EDTA-dependent pseudothrombocytopenia after therapy with the glycoprotein IIb/IIIa antagonist c7E3 Fab

The development of thrombocytopenia following exposure to the platelet glycoprotein (GP) IIb/ IIIa receptor antagonist abciximab (c7E3 Fab, ReoPro) is associated with adverse clinical outcome and excessive bleeding. Pseudothrombocytopenia is an important differential diagnosis in sudden onset of thrombocytopenia in a patient treated with c7E3 Fab. We report on a case of documented sudden onset of EDTA-dependent pseudothrombocytopenia in a 63-year-old woman who was admitted for emergency coronary intervention. Four hours after bolus administration of c7E3 Fab, the platelet concentration in EDTA-anticoagulated blood decreased from 385 x 10(9)/l to 119 x 10(9)/l, and it showed a further decrease to 57 x 10(9)/l at the end of a 12-h infusion. Despite no warnings or abnormalities of the automated cell counter, platelet aggregates were observed by microscopic evaluation of the blood smear. Repeated platelet counts in citrate-anticoagulated samples revealed platelet concentrations within the reference range. EDTA-dependent pseudothrombocytopenia due to therapy with c7E3 Fab is an important differential diagnosis that needs to be excluded rapidly from other causes of thrombocytopenia to avoid unnecessary further examinations, discontinuation of therapy, or even initiation of inappropriate therapy.

Evidence for the impairment of the vitamin D activation pathway by cyclosporine A

Cyclosporine A (CsA) is a potent immunosuppressant with the drawback of renal side effects. We reported that CsA markedly decreases calcium-binding protein calbindin-D28k mRNA levels in rat kidneys, and showed that this decrease is associated with its adverse renal effects. The transcription of the calbindin-D28k gene is activated via the vitamin D pathway. In this work, the potential CsA-mediated impairment of the vitamin D pathway was investigated. Wistar rats were treated for 12 days with 50 mg/kg/day CsA or for 20 days with 50 mg/kg/day of the non-immunosuppressant and non-nephrotoxic SDZ PSC 833, which had been previously shown not to affect calbindin-D28k mRNA levels. The expression of the three vitamin D-regulated genes calbindin-D28k, 1,25-dihydroxyvitamin D3-24-hydroxylase (24-OHase), and vitamin D receptor (VDR) were quantified in rat kidney homogenates by real-time reverse transcription-polymerase chain reaction. Plasma parathyroid hormone (PTH) as well as plasma and kidney 1,25 dihydroxyvitamin D3 (calcitriol) levels were monitored in all animals. CsA induced a 85% decrease in calbindin-D28k mRNA levels as well as a 40% and 69% decrease in VDR and 24-OHase mRNA levels, respectively. Plasma and kidney 1,25 dihydroxyvitamin D3 as well as plasma PTH levels were increased by CsA, but not by SDZ PSC 833. The treatment with SDZ PSC 833 did not affect calbindin-D28k or VDR expression, but did cause a 73% decrease in 24-OHase mRNA levels. Taken together, these results indicate an association between CsA-mediated down-regulation of rat renal calbindin-D28k mRNA and the decrease in other 1,25 dihydroxyvitamin D3-regulated genes, suggesting an impairment of the vitamin D pathway by CsA which may be related to its adverse renal side effects and its immunosuppressive activity.

4-chloro-o-phenylenediamine induces a dose-related increase in G:C > T:A transversions and one major DNA adduct in the liver of Big Blue mice after 26 weeks in feed treatment

The monocyclic aromatic amine 4-chloro-o-phenylenediamine (4-C-o-PDA), a known mutagen and mouse hepatocarcinogen, was tested for its in vivo mutagenic potential in the Big Blue transgenic mouse assay system. Genomic DNA was isolated from liver tissue of control and treated animals and lacI mutants were recovered. In an initial 2-week study 4-C-o-PDA was administered daily per os to groups of male and female C57BL/6 Big Blue mice at doses of 0 and 200 mg/kg for 2 weeks (on working days) followed by a treatment free expression time of 10 days. Only a weak increase in the mutant frequencies in females was observed. In a 26-week study, where 4-C-o-PDA was given to groups of male and female Big Blue mice in feed at dietary concentrations of 0, 5,000 and 10,000 ppm, 4-C-o-PDA was found to induce a pronounced dose-dependent increase in mutant frequencies in either sex. In the present work, we analyzed the mutation spectrum by automated DNA sequencing of lacI mutants from both studies. Following the 2-week administration of 4-C-oT:A transversions in both sexes. In addition, upon 26-week treatment with 4-C-o-PDA, one major DNA adduct was detected by 33P postlabelling and subsequent multidimensional thin layer chromatography. It is concluded that 4-C-oT:A transversions after 26 weeks in feed treatment. This result indicates that the sensitivity of the Big Blue transgenic assay system, in detecting a unique chemically induced mutation spectrum, is dependent on experimental parameters, such as treatment time. The data suggest that the formation of one major DNA adduct upon 4-C-o-PDA treatment may be critical for its mutagenicity.

[Development of evidence-based clinical practice guidelines; a model project integrating external evidence and clinical expertise]

BACKGROUND

Internationally, evidence-based clinical practice guidelines have been established for several years. In Germany, they are now gaining increasing importance.

OWN STUDIES

The Institute of Health Economics and Clinical Epidemiology at the University of Cologne has developed a mostly standardized process for evidence-based guideline development. This process has been implemented in such a way that reproducibility, validity and practicability of guidelines can be assured: evidence from research (external evidence) has been searched and evaluated according to the criteria of the Agency of Health Care Policy and Research (AHCPR). Through cooperation with clinical experts, this evidence has been transferred into practicable recommendations. In addition, acceptance of guideline users and patients was improved by applying this method.

CONCLUSION

Evidence-based guidelines are considered as an appropriate tool to assist medical decision-making of all stakeholders involved. The process will be demonstrated developing an evidence-based guideline for obesity treatment.

Congenital asplenia detected in a 60 year old patient with septicemia

A 60 year-old female who had never been seriously ill, was brought to the emergency ward after she had been found somnolent at home. She developed renal failure, meningitis, respiratory distress and disseminated intravascular coagulation. Overwhelming septicemia was evident, and streptococcus pneumoniae was isolated from blood and cerebrospinal fluid. Surprisingly, peripheral blood smears showed numerous Howell-Jolly-bodies, indicating severe impairment of splenic function. On abdominal ultrasound, CT-scan, and scintigraphy no spleen could be detected. There was no history of abdominal surgery. Apparently, congenital asplenia, which was not noticed until the age of 60, was responsible for the patient's life-threatening septicemia. We suggest that, in cases of severe septicemia, the examination of a blood smear is useful to detect functional (or congenital) asplenia.

Compact organization of rRNA genes in the filamentous fungus Ashbya gossypii

The rDNA cluster in the phytopathogenic fungus Ashbya gossypii consists of approximately 50 tandem repeat units of 8197 bp. Each unit carries a gene for the 35S pre-rRNA, processed into 18S, 5.8S and 25S rRNA, and a divergently transcribed gene for 5S rRNA. The well-characterized rDNA of the yeast Saccharomyces cerevisiae is the only other example of a completely sequenced rDNA unit (9137 bp) carrying both a 35S pre-rRNA and a 5S rRNA gene. The coding regions for the 5S, 5.8S, 18S and 25S rRNAs are 95-100% identical whereas transcribed and non-transcribed spacers show 43-66% sequence identity. Functionally characterized rDNA and rRNA elements of S. cerevisiae can be unambiguously recognized in the A. gossypii sequence, including the RNA polymerase-I transcription start site, two Reb1p enhancer binding sites and numerous recognition sequences for rRNA modification and processing. In addition to these functionally characterized sequences eight highly conserved elements from 10 to 71 bp were detected in the over 600-bp transcribed region upstream of the 18S rRNA gene which most likely play as yet uncharacterized functions at the DNA or RNA level. In addition to this work we started to identify A. gossypii homologs of S. cerevisiae nucleolar proteins involved in rDNA maturation.

[Influence of pulmonary hemodynamics on right ventricular ejection fraction in chronic obstructive pulmonary disease]

Right ventricular dysfunction is common in patients with chronic obstructive pulmonary disease. Right ventricular function might be influenced by the afterload, which depends on pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR). To evaluate the influence of the right ventricular afterload on right ventricular performance, we investigated 30 patients with chronic obstructive pulmonary disease without clinical signs or history of left heart failure or coronary heart disease. The study includes lung function tests, analysis of blood gases and right heart catheterisation. RV function was assessed by a thermodilution technique using a pulmonary artery catheter equipped with a rapid response thermistor (produced by Baxter, USA). There are 9 patients with normal, 12 with latent and 9 with fixed pulmonary hypertension. Median RVEF was measured to be 33.3% (19-44%). There was a significant correlation between RVEF and PAP (r = -0.66; p < 0.0001) and RVEF and PVR (r = -0.54; p < 0.0018). RVEF was not directly influenced by lungfunction or pulmonary capillary wedge pressure (PCWP). Under treadmill exercise RVEF and cardiac index increased without a change of PCWP. A low RVEF at rest seems to be a predictive value for a reduced exercise capacity. A reduced RVEF has a predictive value of pulmonary hypertension with a sensitivity of 66% in patients with unstable and 89% in patients with lasting pulmonary hypertension. In a subgroup of 6 cases treadmill exercise led to a RVEF decrease. These patients showed no difference in afterload, blood gases or lung function-tests compared with the total group. In conclusion, right ventricular ejection fraction seems to be influenced by PVR and PAP which determinate the right ventricular afterload. The validity of the method depends on the severity of pulmonary hypertension, and hence measurement of RVEF might not provide a reliable estimation of pulmonary arterial pressure in patients suffering from mild to moderate pulmonary hypertension.

Changes in the liver protein pattern of female Wistar rats treated with the hypoglycemic agent SDZ PGU 693

SDZ PGU 693 acts as a hypoglycemic agent by stimulating glucose utilisation in insulin-sensitive peripheral tissues, such as skeletal muscle and fat. In a 28 day toxicity study the compound was found to induce hepatocellular hypertrophy in Wistar rats treated with 300 mg/kg/day. To gain insights into the pathomechanism of these alterations, aliquots of liver samples from control and treated female Wistar rats were separated by two-dimensional protein gel electrophoresis and the digitized images of the protein patterns were searched for protein abundance changes. Significant treatment-related quantitative changes (P < 0.001) were found in 29 liver proteins. Major increases were observed in several microsomal proteins, including NADPH cytochrome P-450 reductase, cytochrome b5 and serine protease inhibitor. The changes in the cytochrome related enzymes, both known co-factors of the P-450 enzyme system, strongly suggest that SDZ PGU 693 induces microsomal proliferation and induction of the P-450 enzyme system. Decreases were observed in a series of mitochondrial proteins, such as F1ATPase-delta subunit and ornithine aminotransferase precursor as well as in several cytosolic proteins such as the liver fatty acid binding protein, arylsulfotransferase and the senescence marker protein-30. The changes in F1ATPase-delta subunit and liver fatty acid binding protein together suggest a down-regulation of the mitochondrial liver fatty acid metabolism, likely reflecting the pharmacological action of the compound. These results show that SDZ PGU 693 produces a complex pattern of gene expression changes which give insights into the molecular mechanisms of both its pharmacological action and a toxic response.

Efficient identification of point mutations by automated DNA sequencing of artificial heterozygote samples

DNA sequencing templates of individual point mutants of the lacI target gene were amplified by polymerase chain reaction (PCR). By mixing the PCR fragments from two individual mutants in a defined ratio, samples of artificial heterozygous composition were prepared. These samples were then submitted to automated DNA sequencing. The simultaneous, visual comparison of the mixed mutant traces using a graphics program efficiently revealed all heterozygous positions. Based on the individual intensities of the heterozygous base signals the identified point mutations could be assigned to the corresponding mutants. This efficient approach doubles the sample throughput for both the sequencing reactions and the gel electrophoresis using an automated DNA sequencing system.

[Results and complications of fiber bronchoscopy in HIV positive patients]

Fibreoptic bronchoscopy is an established diagnostic procedure for HIV-associated pulmonary infections. We retrospectively evaluated the diagnostic effectivity and safety of fibreoptic bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial biopsy (TBB) in 153 patients with late-stage HIV infection and clinical signs of pulmonary infection or abnormal chest radiograph. Bronchoscopy leads to diagnosis in 82.4% and changed therapy in 54%. 45 patients (30%) were found to have pneumocystis carinii pneumonia (PCP), the most common bronchoscopic finding, followed by bacterial lung disease (29.3%). BAL had a sensitivity of 78% for PCP. Diagnostic yield of BAL for PCP was higher in patients without previous treatment (positive results in 82%) with regard to PCP independend of the prior treatment. Serious complication occurred in 22 cases (pneumothorax: 6 (3.9%), bleeding: 12 (7.8%), hypoxaemia: 4 (2.6%)). High serum levels of lactate dehydrogenase (LDH) correlated with pulmonary complications like pneumothorax. Age, sex and kind of pulmonary infection did not influence complication rates. 6 (3.9%) episodes of spontaneous pneumothorax occurred in the further course, 3 of them concurrently with PCP or prior history of PCP. We conclude that fibreoptic bronchoscopy is of great value for diagnosing pulmonary infection in HIV-seropositive patients. TBB provides incremental diagnostic information not available from BAL, especially in patients pretreated with cotrimoxazol or pentamidin. For that reason we believe that TBB should be performed in these patients.

New insights into cyclosporine A nephrotoxicity by proteome analysis

Using two-dimensional gel electrophoresis (2-DE), we recently discovered an association between decreased calcium-binding protein, calbindin-D 28 kDa, urinary calcium wasting and intratubular corticomedullary calcifications in rat kidney. This observation prompted us to investigate kidney tissues of other species, including man. In this paper we show that in dogs and monkeys, which are generally devoid of cyclosporine A (CsA)-mediated nephrotoxicity, renal calbindin levels were not affected by the CsA treatment whereas in CsA-treated human kidney-transplant recipients with renal vascular or tubular toxicity, a marked decrease in renal calbindin-D 28 kDa protein level was found in most of the kidney biopsy sections. The present results strongly suggest that calbindin is a marker for CsA-nephrotoxicity. The discovery of calbindin-D 28 kDa being involved in CsA toxicity has evolved from the application of 2-DE and has not been reported previously, proving that proteomics can provide essential information in mechanistic toxicology. Considering the current improvements in proteome methods it is expected that high throughput proteomics will become an indispensable tool in preclinical safety testing.

Cyclosporine A-induced decrease in calbindin-D 28 kDa in rat kidney but not in cerebral cortex and cerebellum

Recently, we reported that in rat, cyclosporine A (CsA) markedly decreases the levels of calbindin-D (CABP-D) 28 kDa in kidney. CABP-D 28 kDa is a calcium-binding protein which is highly expressed in calcium-transporting tissues such as kidney or brain. In this study, we investigated whether, in addition to the kidney, CsA also has an effect on CABP-D 28 kDa in rat brain. Three groups of male Wistar rats received 15 mg/kg/day or 50 mg/kg/day of CsA orally for 12 days, whereas controls received vehicle solution for the same period. CABP-D 28-kDa protein and CsA were quantified in homogenates of kidney, cerebral cortex and cerebellum, and the localization of CABP-D 28 kDa was assessed in the different tissue sections by immunohistochemistry. In kidney, CABP-D 28 kDa was strongly and dose dependently decreased, and was located in tubular epithelial cells. In brain, CABP-D 28 kDa was not changed and was mainly located in pyramidal cells of the cortex and in cerebellum exclusively in Purkinje cells. High CsA concentrations were measured in kidney, more than 17-fold greater than those found in cortex. In cerebellum, CsA was below the limit of detection. These data suggest that at clinically relevant doses, CsA may not affect CABP-D 28-kDa levels in brain.

The cyclosporine A-induced decrease in rat renal calbindin-D28kDa protein as a consequence of a decrease in its mRNA

Cyclosporine A (CsA) is a potent immunosuppressant with the drawback of renal side-effects. We recently reported that relatively high doses of CsA markedly decreased the calcium-binding protein calbindin-D28kDa in kidneys of male Wistar rats, and showed that this decrease could be associated with some of the drug-induced adverse renal effects. To investigate the events leading to this decrease, the calbindin-D28kDa mRNA level in kidneys of rats treated with 15 or 50 mg/kg/day CsA for 12 days was analysed by reverse transcription followed by polymerase chain reaction. At both doses, a marked dose-dependent decrease in the calbindin-D28kDa mRNA level was found, one very similar to the decrease measured in the calbindin-D28kDa protein abundance. Thus, the CsA-mediated down-regulation of the renal calbindin-D28kDa protein is most likely the result of a decrease in the calbindin-D28kDa mRNA level.

[Prognostically relevant parameters in patients with coronary heart disease, arterial hypertension and sleep apnea disorders]

Patients with untreated sleep apnea syndrome have a higher cardiovascular mortality. It is not known which mechanisms lead to this increase in mortality and whether it is independent from the often associated coronary heart disease and systemic hypertension. In 48 consecutive patients with coronary heart disease confirmed by angiography, exercise-ECG, Holter-ECG, echocardiography, spirometric tests, analysis of ventricular late potentials, heart rate variability and a test for sleep-disordered breathing with a screening device were performed. Seventeen patients showed disordered breathing during sleep (obstructive sleep apnea) with a desaturation index of > or = 10 (mean desaturation index 17.3 +/- 9.3 vs. 2.6 +/- 3.1 in the patients without sleep-disordered breathing). There are no significant differences in age (58.9 +/- 6.1 vs. 59.7 +/- 7.6 years), body-mass-index (28.6 +/- 3.7 vs. 27.7 +/- 3.3 kg/m2), left ventricular ejection fraction (57.2 +/- 13.6 vs. 64.0 +/- 14.6%), forced expiratory volume in 1 second/vital capacity 95.4 +/- 13.9 vs. 92.9 +/- 11.2% predicted, heart rate variability (standard deviation of the RR-intervals 39.4 +/- 29.4 vs. 37.2 +/- 17.0 ms), the frequency of premature ventricular beats over 24 h and at night, the frequency of multivessel disease (71 vs. 68%), additional hypertension 53 vs. 48%), status postmyocardial infarction (47 vs. 48%) and positive late potential analysis (24 vs. 13%). There were no ST segment depressions during the night. Patients with coronary heart disease and mild sleep-disordered breathing show no significant differences in the investigated parameters compared with patients without obstructive sleep apnea or sleep-disordered breathing.

Decrease in kidney calbindin-D 28kDa as a possible mechanism mediating cyclosporine A- and FK-506-induced calciuria and tubular mineralization

The use of the immunosuppressant cyclosporine A (CsA) is limited by its adverse renal effects. Most recently, we reported that the drug markedly decreases the levels of the calcium-binding protein calbindin-D 28kDa in kidneys of male Wistar rats. In the present study, the potential relationship between drug-induced nephrotoxicity and the decrease in kidney calbindin-D 28kDa was investigated. Four groups of male Wistar rats were treated for 10 or 31 days with either the immunosuppressant CsA (50 mg/kg/day), FK-506 (5 mg/kg/day), rapamycin (5 mg/kg/day) or with the nonimmunosuppressive cyclosporine derivative 3'keto-[Bmt1]-[Val2]-CsA (SDZ PSC-833) (50 mg/kg/day), and the effects on calcium homeostasis, kidney histology and renal calbindin-D 28kDa were examined. Similar effects were found with CsA and FK-506; both drugs strongly reduced kidney calbindin-D 28kDa protein levels, increased urine calcium excretion, caused intratubular calcification, and induced basophilic tubules. In contrast, rapamycin and SDZ PSC-833 caused no decrease in renal calbindin-D 28kDa levels, no noticeable alterations in calcium metabolism, and no renal calcification. The results provide evidence for a link between decreased renal calbindin, increased calcium urine excretion, and intratubular kidney calcification. The present data show no correlation between the decrease in renal calbindin and the induction of basophilic tubules; however, it needs to be investigated if these apparently independent kidney effects may have a common origin upstream of calbindin expression.

[Skull injury in childhood: comparison of ultrasonography with conventional X-rays and computerized tomography]

PURPOSE

The purpose of our study was to compare the value of ultrasound, conventional x-ray diagnosis and CT in detecting skull fractures and intracranial haemorrhage in children suffering from a head injury.

MATERIAL AND METHODS

We examined 210 children who had a head injury. In all cases the calvarium was investigated by ultrasound using a 7.0 MHz linear transducer. In children with an open fontanel (n = 190) the cerebrum was screened additionally by ultrasound following a standard protocol. The sonographic findings were correlated to the x-ray examination (n = 21) and CT (n = 13).

RESULTS

Ultrasound enabled diagnosis of linear calvarial fractures (n = 29), depressed fractures (n = 6) and intracranial haemorrhage (n = 8). X-Ray and CT examination confirmed the diagnosis of linear calvarial fractures in 16 cases, of depressed fractures in 6 cases. CT confirmed the sonographic diagnosis of intracranial haemorrhage in 8 cases.

CONCLUSION

Ultrasound as a primary method can replace the conventional x-ray in detecting calvarial fracture and posttraumatic sequelae. Additional CT examination depends on the sonographic and neurological status.

Cyclosporine A decreases the protein level of the calcium-binding protein calbindin-D 28kDa in rat kidney

Despite the widespread use of cyclosporine A (CsA), its mechanism of action and side effects are not yet completely understood. There exists a large body of evidence suggesting that disturbance of calcium homeostasis is a critical step in the cascade of cellular and molecular events induced by the drug. As recently shown in our laboratory by two-dimensional protein gel electrophoresis (2-DE) analysis of kidney homogenates, CsA induced numerous changes in several kidney proteins. One kidney protein in particular was shown to be strongly down-regulated by the drug. In this work we report the identification of the strongly decreased kidney protein as calbindin-D 28kDa, a vitamin D-dependent calcium-binding protein associated with calcium handling by cells. The assignment of the down-regulated protein spot is based on its internal amino acid sequence analysis and its specific reaction with a monoclonal antibody raised against calbindin-D 28kDa. In kidney homogenates of male Wistar rats treated with 50 mg/kg/d CsA for up to 28 days, calbindin levels were measured by ELISA and were shown to be continuously decreased with prolonged CsA treatment. To our knowledge, this is the first report describing the effect of CsA on kidney calbindin-D 28kDa protein levels. Further studies are needed to elucidate whether the CsA-mediated down-regulation of the calcium-binding protein calbindin-D 28kDa may be a critical factor for the renal adverse effects induced by this drug.

Induction of the adipose differentiation-related protein in liver of etomoxir-treated rats

The effects of etomoxir, an irreversible carnitine palmitoyltransferase I inhibitor, on the liver protein pattern and on liver morphology were examined by two-dimensional gel electrophoresis in female Sprague-Dawley rats treated with 125 mg/kg/day etomoxir for 28 days. In livers of treated animals a protein spot was found which was not present in controls. The spot was identified by internal amino acid sequence analysis as the adipose differentiation-related protein (ADRP). The expression of ADRP in liver is a novel finding as the protein has been described previously as adipocyte-specific. Additionally we found histopathologic evidence of lipid accumulation in the livers of etomoxir rats. The data show that for each treated rat there was a good correlation between ADRP levels and degree of lipid droplet formation. This observation may suggest a potential relationship between drug-induced expression of ADRP in liver and lipid accumulation.

Protein variability in male and female Wistar rat liver proteins

In the emerging field of mechanistic toxicology, growing attention is being paid to the interpretation of sex-related toxic responses. The Wistar rat outbred stock is a frequently used rodent for toxicity testing. Outbred strains, which display a relatively high degree of genetic variability between the individual animals are often used in risk assessment, as they are considered to best approximate the variability present in a human population. In this study two-dimensional (2-D) protein gel electrophoresis was applied to investigate the liver protein patterns of male and female Wistar rats and to search for (i) sex-related and (ii) interindividual qualitative and quantitative differences in protein expression. Among the sexes, six proteins were detected that were shown to be exclusively present in male rats and one that was present only in females. A male-specific protein was tentatively assigned to alpha 2u globulin. Seven protein spots showed statistically significant abundance changes (p < 0.001) between males and females, one was tentatively assigned to heme oxygenase 1 and another to the 23 kDa morphin-binding protein. Four sets of protein spots were detected that showed positional shifts in the individual patterns and are likely to represent polymorphic proteins inherent in the Wistar rat. These results form a valuable basis for future investigations of drug-induced changes in the male and female Wistar rat liver pattern.

An updated two-dimensional gel database of rat liver proteins useful in gene regulation and drug effect studies

We have improved upon the reference two-dimensional (2-D) electrophoretic map of rat liver proteins originally published in 1991 (N. L. Anderson et al., Electrophoresis 1991, 12, 907-930). A total of 53 proteins (102 spots) are now identified, many by microsequencing. In most cases, spots cut from wet, Coomassie Blue stained 2-D gels were submitted to internal tryptic digestion [2], and individual peptides, separated by high-performance liquid chromatography (HPLC), were sequenced using a Perkin-Elmer 477A sequenator. Additional spots were identified using specific antibodies.

[Diagnosis of cerebral metastasis with standard dose gadobutrol vs. a high dose protocol. Intraindividual evaluation of a phase II high dose study]

PURPOSE

To assess the effectiveness and safety of normal and high doses of Gadobutrol versus a standard dose of Gadolinium DTPA in the MR evaluation of patients with brain metastases.

MATERIAL AND METHODS

In a clinical phase-II study 20 patients who had been diagnosed as having brain metastases with CT or MRT were studied prospectively with Gadobutrol, a new nonionic, low osmolality contrast agent. Each patient received an initial injection of 0.1 mmol/kg body weight and an additional dose of 0.2 mmol/kg Gadobutrol 10 min later. Spin-echo images were obtained before and after the two applications of Gadobutrol. Dynamic scanning (Turbo-FLASH) was performed for 3 min after each injection of the contrast agent. Both quantitative and qualitative data were intraindividually evaluated. The primary tumor was a bronchial carcinoma in 11 cases; in 9 other cases there were different primary tumors.

RESULTS

Forty-eight hours after the use of Gadobutrol there were no adverse signs in the clinical examination, vital signs or blood and urine chemistry. Statistical analysis (Friedman test and Wilcoxon test) of the C/N ratios between tumor and white matter, percentage enhancement, and visual assessment rating revealed statistically significant superiority of high-dose Gadobutrol injection in comparison to the standard dose. The percentage enhancement increased on average from 104% after 0.1 mmol/kg to 162% after 0.3 mmol/kg Gadobutrol. Qualitative delineation and contrast of the lesions increased significantly. The use of high-dose Gadobutrol improved the detection of 36 additional lesions in 6 patients.

CONCLUSION

The first in vivo results prove the excellent contrast capacity of the nonionic contrast agent Gadobutrol for the diagnosis of intracerebral metastases.

[MRI of focal liver lesions using a 1.5 turbo-spin-echo technique compared with spin-echo technique]

AIM

The aim of our study was to evaluate a T2-weighted turbo-spinecho sequence in comparison to a T2-weighted spinecho sequence in imaging focal liver lesions.

METHODS

In our study 35 patients with suspected focal liver lesions were examined. Standardised imaging protocol included a conventional T2-weighted SE sequence (TR/TE = 2000/90/45, acquisition time = 10.20) as well as a T2-weighted TSE sequence (TR/TE = 4700/90, acquisition time = 6.33). Calculation of S/N and C/N ratio as a basis of quantitative evaluation was done using standard methods. A diagnostic score was implemented to enable qualitative assessment.

RESULTS

In 7% (n = 2) the TSE sequence enabled detection of further liver lesions showing a size of less than 1 cm in diameter. Comparing anatomical details the TSE sequence was superior. S/N and C/N ratio of anatomic and pathologic structures of the TSE sequence were higher compared to results of the SE sequence.

CONCLUSION

Our results indicate that the T2-weighted turbo-spinecho sequence is well appropriate for imaging focal liver lesions, and leads to reduction of imaging time.

Homologous recombination as the main mechanism for DNA integration and cause of rearrangements in the filamentous ascomycete Ashbya gossypii

A slow and a fast growth phenotype were observed after transformation of the phytopathogenic fungus Ashbya gossypii using a plasmid carrying homologous DNA and as selectable marker the Tn903 aminoglycoside resistance gene expressed from a strong A. gossypii promoter. Transformations with circular plasmids yielded slowly and irregularly growing geneticin-resistant mycelia in which 1% of nuclei contained plasmid sequences. Occasionally, fast growing sectors appeared which were shown to be initiated by homologous integration of the transforming DNA. Transformants obtained with plasmids linearized within the homology region immediately exhibited fast radial growth. In all 28 transformants analyzed plasmid DNA was integrated homologously. Such apparent lack of nonhomologous recombination has so far not been observed in filamentous ascomycetes. In 14 transformants two to four tandemly integrated plasmid copies were found. They underwent several types of genetic changes, mainly in the older mycelium: excision of whole plasmid copies and rearrangements within the integrated DNA (inversions and deletions). These internal rearrangements involved 360-bp inverted repeats, remnants of IS-elements flanking the resistance gene, and 156-bp direct repeats, originating from the strong A. gossypii promoter. Improved vectors lacking sequence repetitions were constructed and used for stable one-step gene replacement in A. gossypii.

Effects of cyclosporine A on the rat liver and kidney protein pattern, and the influence of vitamin E and C coadministration

The effects of cyclosporine A (CsA), a potent immunosuppressive drug, were examined in rat liver and kidney samples using two-dimensional electrophoretic protein analysis. Of a total of 370 liver and 336 kidney spots analyzed, 8% (29 spots) and 6% (19 spots), respectively, showed a significant drug-induced change (p < 0.01), which was predominantly reflected in increased protein abundance (62% and 74% of the changes, respectively). Of the 48 proteins changed in either organ, 14 were most probably common to both tissues and one of these was significantly increased in both the liver and the kidney. Most of the other 13 showed similar trends (either increases or decreases) in both organs. However, the most striking drug effect seen in this study concerned an unidentified protein present only in the kidney, which completely disappeared upon CsA treatment. It was also investigated whether the drug-induced changes could be prevented by the coadministration of the radical scavengers vitamin E and C with CsA. Spots changed by the administration of the drug were classified according to three different categories, based on their response profiles in rats treated with CsA in combination with the vitamins: (i) spots which were changed by CsA as well as by CsA in combination with the vitamins (12 liver and 4 kidney spots), (ii) spots which were changed by CsA and showed an additional increase of this change by CsA plus the vitamins (no liver and 4 kidney spots), and (iii) spots which were changed by CsA but not by CsA in combination with the vitamins (8 liver and 6 kidney spots). These results showed that in both organs the vitamins were able to prevent around 30% of the effects caused by CsA, and that two-dimensional gel electrophoresis is an excellent tool to demonstrate such drug interactions at the molecular level.

Cloning and sequencing of a gene coding for an actin binding protein of Saccharomyces exiguus

The actin binding protein Abp1p of the yeast Saccharomyces cervisiae is thought to be involved in the spatial organisation of cell surface growth. It contains a potential actin binding domain and an SH-3 region, a common motif of many signal transduction proteins [1]. We have cloned and sequenced an ABP1 homologous gene of Saccharomyces exiguus, a yeast which is only distantly related to S. cerevisiae. The protein encoded by this gene is slightly larger than the respective S. cerevisiae protein (617 versus 592 amino acids). The two genes are 67.4% identical and the deduced amino acid sequences share an overall identity of 59.8%. The most conserved regions are the 148 N-terminal amino acids containing the potential actin binding site and the 58 C-terminal amino acids including the SH3 domain. In addition, both proteins contain a repeated motif of unknown function which is rich in glutamic acids with the sequence EEEEEEEAPAPSLPSR in the S. exiguus Abp1p.

Sequence and promoter analysis of the highly expressed TEF gene of the filamentous fungus Ashbya gossypii

Ashbya gossypii carries only a single gene (TEF) coding for the abundant translation elongation factor 1 alpha. Cloning and sequencing of this gene and deletion analysis of the promoter region revealed an extremely high degree of similarity with the well studied TEF genes of the yeast Saccharomyces cerevisiae including promoter upstream activation sequence (UAS) elements. The open reading frames in both species are 458 codons long and show 88.6% identity at the DNA level and 93.7% identity at the protein level. A short DNA segment in the promoter, between nucleotides -268 and -213 upstream of the ATG start codon, is essential for high-level expression of the A. gossypii TEF gene. It carries two sequences, GCCCATACAT and ATCCATACAT, with high homology to the UASrpg sequence of S. cerevisiae, which is an essential promoter element in genes coding for highly expressed components of the translational apparatus. UASrpg sequences are binding sites for the S. cerevisiae protein TUF, also called RAP1 or GRF1. In gel retardation with A. gossypii protein extracts we demonstrated specific protein binding to the short TEF promoter segment carrying the UASrpg homologous sequences.

Risk behavior for HIV transmission among gay men surveyed in Seattle bars

Men attending four Seattle gay bars were asked to complete a self-administered questionnaire including measures of sexual behavior, perceptions of peer norms in the area of sexual safety, personal human immunodeficiency virus (HIV) risk estimate, and knowledge and use of a variety of acquired immunodeficiency syndrome (AIDS) prevention services. Twenty-nine percent of the sample reported engaging in unprotected anal intercourse at least once during the 2 months before the survey. Differences in peer norm perceptions, age, HIV risk estimate, and intent to be sexually safe in the future were found between those engaging in unprotected anal intercourse and those not reporting unprotected anal intercourse. No significant differences were found in level of education, use of AIDS prevention services, and whether or not a person had been tested for HIV. Implications for prevention programs are discussed.

[MRT of the liver in Wilson's disease]

To show that Wilson's disease is one likely cause of multiple low-intensity nodules of the liver we obtained MR images in 16 patients with clinically and histopathologically confirmed Wilson's disease. Corresponding to morphological changes MRI enabled the subdivision of the patients into two groups. Using a T2-weighted spin-echo sequence (TR/TE = 2000/45-90) liver parenchyma showed multiple tiny low-intensity-nodules surrounded by high-intensity septa in 10 out of 16 patients. 5 patients had also low-intensity nodules in T1-weighted images (TR/TE = 600/20). In patients of this group histopathology revealed liver cirrhosis (n = 7) and fibrosis (n = 2). Common feature of this patient group was marked inflammatory cell infiltration into fibrous septa, increase of copper concentration in liver parenchyma and distinct pathological changes of laboratory data. In the remaining 6 patients no pathological change of liver morphology was demonstrated by MRI corresponding to slight histopathological changes of parenchyma and normal laboratory data. As low-intensity nodules surrounded by high intensity septa can be demonstrated in patients with marked inflammatory infiltration of liver parenchyma MRI may help to define Wilson patients with poorer prognosis. In patients with low-intensity nodules of the liver and unknown cause of liver cirrhosis laboratory data and histopathology should be checked when searching for disorders of copper metabolism.

Molecular dosimetry of DNA adducts in C3H mice treated with bisphenol A diglycidylether

The formation of a glycidaldehyde-DNA adduct in skin of C3H mice treated with [14C]bisphenol A diglycidylether has been previously reported and it was assumed that the modification occurred on guanine residues. We were interested in elucidating the structure of this glycidaldehyde-DNA adduct by using a non-radioactive approach. Male C3H mice were treated with a single topical dose of 2 mg bisphenol A diglycidylether in acetone for 48, 96 or 192 h. An additional two mice were treated with 2 mg glycidaldehyde in acetone for 24 h. Epidermal DNA was isolated and enzymatically digested to nucleoside-3'-monophosphates. Aliquots of the DNA hydrolysates were separated on HPLC using a reverse-phase column with a potassium dihydrogen phosphate/methanol gradient. Fluorescence analysis of the eluent indicated the presence of a fluorescent DNA adduct, which was identified as hydroxymethylethenodeoxyadenosine-3'-monophosphate by comparison with a synthetic reference standard. Amounts of adducts were determined by fluorescence measurements using a calibration curve obtained with the authentic adduct standard. Irrespective of duration of exposure, all DNA hydrolysates of treated mice contained similar amounts of the deoxyadenosine adduct. The alkylation frequency was 0.1-0.8 and 166 adducts/10(6) normal nucleotides for the treatment with bisphenol A diglycidylether and glycidaldehyde respectively. The limit of detection using 500 micrograms DNA samples for analysis was approximately 0.03 adducts/10(6) normal nucleotides.

Molecular dosimetry of DNA adducts in C3H mice treated with glycidaldehyde

The formation of DNA adducts in the skin of male C3H mice treated cutaneously with glycidaldehyde (2 or 10 mg/animal) in acetone has been investigated by HPLC coupled with fluorescence detection and 32P-postlabelling analysis. Following a 24 h exposure period, epidermal DNA was isolated from treated dorsal skin and enzymically digested to nucleoside-3'-monophosphates. HPLC-32P-postlabelling analysis of the DNA hydrolysate indicated that a single major cyclic adduct was formed from the reaction of glycidaldehyde with deoxyadenosine residues in mouse skin DNA. This adduct was identified as 3-beta-D-deoxyribofuranosyl-7-(hydroxymethyl)-3H- imidazo[2,1-i]purine-3'-monophosphate by comparison with a synthetic standard. This adduct was stable, strongly fluorescent and readily detected by HPLC with fluorescence detection. There was no evidence for the formation of deoxyguanosine adducts in epidermal DNA of treated animals. Glycidaldehyde also reacted with calf thymus DNA in vitro at pH 7.0 to give the same deoxyadenosine adduct observed in vivo. At pH 10, however, this was a relatively minor product and the major adduct was 5,9-dihydro-7-(hydroxymethyl)-9- oxo-3-beta-D-deoxyribofuranosyl-3H-imidazo[1,2-a]purine-3'- monophosphate formed by the initial reaction of glycidaldehyde with deoxyguanosine residues.

[The clinical value of Mn-DPDP: a new paramagnetic hepatobiliary contrast medium for magnetic resonance tomography of the liver]

In an open prospective study the tolerance and diagnostic value of the new hepatobiliary contrast agent Mn-DPDP in MR imaging was evaluated in 20 patients suspected of having focal liver lesions. T1- and T2-weighted spin-echo sequences and T1-weighted gradient-echo sequences were obtained before and after intravenous application of Mn-DPDP. In all patients the signal to noise (S/N) values of normal liver tissue increased significantly after application of Mn-DPDP. All focal lesions could be better localized and differentiated due to increased contrast to noise ratios of lesion to liver. Pathological examination revealed in 14 patients malignant and in 5 patients benign liver lesions; one patient had no pathological findings. In metastatic disease of the liver 25-120% more lesions could be detected in MRI after Mn-DPDP-application, compared with the unenhanced images. In 5 patients the lesions showed significant enhancement of Mn-DPDP (2 cirrhotic nodules, 2 hepatocellular carcinomas, 1 focal nodular hyperplasia). Our preliminary results indicate that Mn-DPDP is a well-tolerated contrast agent useful for the detection and differentiation of liver lesions in MR imaging.

[Resistance and defense in supervision. From clinical practice of individual and team supervision (with special reference to institutional aspects)]

This paper presents a contribution to the techniques of supervision. At the beginning of any supervision it is necessary to clarify the condition which have lead to that particular supervision. Motivation and setting are mentioned. Against the declared goal of the supervision the teams develops regularly different kinds of resistance; these are carefully discussed. Every form of resistance is presented from the point of view of groupdynamics and clinic organisation. The last paragraph is dedicated to the dealing with resistance.

[Diffuse liver parenchymal diseases: the value of MRI compared to sonography and CT]

29 patients with diffuse liver disease were examined by ultrasound, CT and MRI. MRI imaging was performed using T1-and t2-weighted spin-echo-sequences and fast gradient-echo-sequences. The paramagnetic contrast agent Gd-DTPA was applied intravenously (0.1 mmol/kg). In all patients with hepatitis MRI enabled exact liver biopsy by delineation of inflammatory changes in cases of chronic or focal hepatitis. CT and ultrasound were superior to MRI in the detection of focal or diffuse fatty degeneration. However, MRI enabled an exact differentiation of fatty changes from neoplasm. In cases of fibrotic changes the most accurate findings could be shown by MRI. In patients suffering from hemochromatosis MRI supplied additional information compared to CT and ultrasound revealing significant reduction of signal intensity due to reinforced enhancement of iron. Concerning Wilson's disease MRI showed a characteristic pattern of parenchymal changes. The application of Gd-DTPA in cases of diffuse liver disease adds supplementary information about perfusion of liver parenchyma, but its value for diagnostic accuracy is only secondary.

[Therapy of borderline personality disorder]

A short clarification of the diagnosis "Borderline Personality Disorder" is followed by a review of different therapeutic concepts. The patients usually have many social problems, therefore social rehabilitation can be the most important therapeutic measure. The concept of family-therapy is deemed important to counteract splitting phenomena in the triangle patient-family-medical doctor. Various pharmacological treatments are discussed. In the process of psychotherapy the physician should learn how to deal with impulsivity, unstable and intense interpersonal relationships, affective instability, and the tendency for physically self-damaging behavior in his patients.

Mouse skin inflammation induced by multiple topical applications of 12-O-tetradecanoylphorbol-13-acetate

It is well known that applications of a single dose of 12-O-tetradecanoylphorbol-13-acetate (TPA) to mouse ears induces an acute inflammatory reaction consisting of erythema, edema and polymorphonuclear leukocyte (PMN) infiltration. We report here that multiple topical applications of TPA to mouse ears produce a prolonged inflammatory reaction characterized by increases in ear weight, inflammatory cell infiltration and epidermal hyperplasia. TPA was applied 5 times over 10 days to mouse ears. Epidermal thickness and PMN infiltration (myeloperoxidase content) increased 3- and 160-fold, respectively, by day 3 and remained elevated over control values throughout the test period. Ear weight was elevated from day 1 and remained high. Hydrocortisone 17-valerate and betamethasone dipropionate significantly reduced all three parameters of inflammation. Indomethacin and two other cyclo-oxygenase inhibitors, and an antihistamine had little or no effect on any of the parameters. This chronic skin inflammation model may be more relevant for evaluating anti-inflammatory compounds than the acute TPA model because the test compounds are applied after the inflammatory lesion is established, which mirrors the use of clinical anti-inflammatory drugs. Also this model may be more selective than the acute TPA model for compounds which affect leukotriene production since other pharmacological agents which are active in the acute model are not active in the multiple-application model.

The role of fatty acid metabolites in the differentiation of the human monocyte-like cell line U937

The human monocyte cell line, U937, can be induced to terminally differentiate into macrophage-like cells when treated with gamma-interferon. However, if these cells were treated with gamma-interferon and esculetin, an inhibitor of the lipoxygenase pathway, or BW755C, an inhibitor of both the lipoxygenase and the cyclooxygenase pathways, a marked inhibition in cellular differentiation occurred. In contrast, inhibitors of only the cyclooxygenase pathway had no effect on differentiation. These studies suggest a role for lipoxygenase products of arachidonic acid in the differentiation of the human U937 cell line. Arachidonic acid utilized in the production of eicosanoids is derived from phospholipids by the action of phospholipase A2 and phospholipase C. When U937 cells were cultured in medium supplemented with gamma-interferon, there was a striking increase in the level of phosphatidylcholine and phosphatidylethanolamine-specific phospholipase A2 activities and phosphatidylinositol-specific phospholipase C activity as compared to control cells. More ever, although there was not a significant difference in the incorporation of labeled arachidonic acid or linoleic acid into the major phospholipids of differentiated U937 cells as compared to undifferentiated control cells, there was a marked increase in the relative amount of the labeled arachidonic acid released from the differentiated cells as lipoxygenase products compared to cyclooxygenase products. These data suggest that lipoxygenase products may be essential in the differentiation process of U937 cells and that enhanced phospholipase enzyme activities that occur during differentiation help explain how arachidonic acid becomes available to form lipoxygenase products.