Phosphorylation of ELYS promotes its interaction with VAPB at decondensing chromosomes during mitosis

ELYS is a nucleoporin that localizes to the nuclear side of the nuclear pore complex (NPC) in interphase cells. In mitosis, it serves as an assembly platform that interacts with chromatin and then with nucleoporin subcomplexes to initiate post-mitotic NPC assembly. Here we identify ELYS as a major binding partner of the membrane protein VAPB during mitosis. In mitosis, ELYS becomes phosphorylated at many sites, including a predicted FFAT (two phenylalanines in an acidic tract) motif, which mediates interaction with the MSP (major sperm protein)-domain of VAPB. Binding assays using recombinant proteins or cell lysates and co-immunoprecipitation experiments show that VAPB binds the FFAT motif of ELYS in a phosphorylation-dependent manner. In anaphase, the two proteins co-localize to the non-core region of the newly forming nuclear envelope. Depletion of VAPB results in prolonged mitosis, slow progression from meta- to anaphase and in chromosome segregation defects. Together, our results suggest a role of VAPB in mitosis upon recruitment to or release from ELYS at the non-core region of the chromatin in a phosphorylation-dependent manner.

Transcriptional regulation of plasminogen activator inhibitor-1 expression by insulin-like growth factor-1 via MAP kinases and hypoxia-inducible factor-1 in HepG2 cells

Insulin-like growth factor 1 (IGF-1) and plasminogen activator inhibitor-1 (PAI-1) appear to play a crucial role in a number of processes associated with growth and tissue remodelling. IGF-1 was shown to enhance PAI-1 expression in primary hepatocytes and HepG2 hepatoma cells, but the molecular mechanisms underlying this effect have not been fully elucidated. In this study, we investigated the transcriptional mechanism and the signaling pathway by which IGF-1 mediates induction of PAI-1 expression in HepG2 cells. By using human PAI-1 promoter reporter gene assays we found that mutation of the hypoxia responsive element (HRE), which could bind hypoxia-inducible factor-1 (HIF-1), nearly abolished the induction by IGF-1. We found that IGF-1-induced up-regulation of PAI-1 expression was associated with activation of HIF-1α. Furthermore, IGF-1 enhanced HIF-1α protein levels and HIF-1 DNA-binding to each HRE, E4 and E5 as shown by EMSA. Mutation of the E-boxes, E4 and E5, did not affect the IGF-1-dependent induction of PAI-1 promoter constructs under normoxia but abolished the effect of IGF-1 under hypoxia. Inhibition of either the PI3K by LY294002 or ERK1/2 by U0126 reduced HIF-1α protein levels while both inhibitors together completely abolished the IGF-1 effect on HIF-1α. Remarkably, transfection of HepG2 cells with vectors expressing a dominant-negative PDK1 or the PKB inhibitor, TRB3, did not influence while dominant-negative Raf inhibited the IGF-1 effect on HIF-1α. Thus, IGF-1 activates human PAI-1 gene expression through activation of the PI3-kinase and ERK1/2 via HIF-1α.

DPP9 is a novel component of the N-end rule pathway targeting the tyrosine kinase Syk

The aminopeptidase DPP9 removes dipeptides from N-termini of substrates having a proline or alanine in second position. Although linked to several pathways including cell survival and metabolism, the molecular mechanisms underlying these outcomes are poorly understood. We identified a novel interaction of DPP9 with Filamin A, which recruits DPP9 to Syk, a central kinase in B-cell signalling. Syk signalling can be terminated by degradation, requiring the ubiquitin E3 ligase Cbl. We show that DPP9 cleaves Syk to produce a neo N-terminus with serine in position 1. Pulse-chases combined with mutagenesis studies reveal that Ser1 strongly influences Syk stability. Furthermore, DPP9 silencing reduces Cbl interaction with Syk, suggesting that DPP9 processing is a prerequisite for Syk ubiquitination. Consistently, DPP9 inhibition stabilizes Syk, thereby modulating Syk signalling. Taken together, we demonstrate DPP9 as a negative regulator of Syk and conclude that DPP9 is a novel integral aminopeptidase of the N-end rule pathway.

The amino terminus extension in the long dipeptidyl peptidase 9 isoform contains a nuclear localization signal targeting the active peptidase to the nucleus

The intracellular prolyl peptidase DPP9 is implied to be involved in various cellular pathways including amino acid recycling, antigen maturation, cellular homeostasis, and viability. Interestingly, the major RNA transcript of DPP9 contains two possible translation initiation sites, which could potentially generate a longer (892 aa) and a shorter version (863 aa) of DPP9. Although the endogenous expression of the shorter DPP9 form has been previously verified, it is unknown whether the longer version is expressed, and what is its biological significance. By developing specific antibodies against the amino-terminal extension of the putative DPP9-long form, we demonstrate for the first time the endogenous expression of this longer isoform within cells. Furthermore, we show that DPP9-long represents a significant fraction of total DPP9 in cells, under steady-state conditions. Using biochemical cell fractionation assays in combination with immunofluorescence studies, we find the two isoforms localize to separate subcellular compartments. Whereas DPP9-short is present in the cytosol, DPP9-long localizes preferentially to the nucleus. This differential localization is attributed to a classical monopartite nuclear localization signal (K(K/R)X(K/R)) in the N-terminal extension of DPP9-long. Furthermore, we detect prolyl peptidase activity in nuclear fractions, which can be inhibited by specific DPP8/9 inhibitors. In conclusion, a considerable fraction of DPP9, which was previously considered as a purely cytosolic peptidase, localizes to the nucleus and is active there, raising the intriguing possibility that the longer DPP9 isoform may regulate the activity or stability of nuclear proteins, such as transcription factors.

Kernresonanz-Untersuchung am System (CH3)3P/BF3 / N.M.R. Study of the System (CH3)3P/BF3

The 2J (PH) coupling constant of mixtures of (CH3)3SiCH2CH2P(CH3)2 and BF3 depends on the ratio of the two components. During the investigation of the simpler system (CH3)3P/BF3the following results were obtained: 1. τH[P(CH3)3] and 2J(PH) vary steadily with the ratio (CH3)3P/BF3, 2. Only one doublet is observed even for mixtures with excess P(CH3)3, 3. 2J (PH) becomes zero for the given ratio BF3: P(CH3)3 = 0.4. The results can be explained by assuming a fast exchange according to equation (2) and opposite signs for the coupling constants of P(CH3)3 [2J (PH) = +2.5 Hz] and the adduct (CH3)3P →BF3[2J(PH) = -11.3 Hz].

A novel SUMO1-specific interacting motif in dipeptidyl peptidase 9 (DPP9) that is important for enzymatic regulation

Sumoylation affects many cellular processes by regulating the interactions of modified targets with downstream effectors. Here we identified the cytosolic dipeptidyl peptidase 9 (DPP9) as a SUMO1 interacting protein. Surprisingly, DPP9 binds to SUMO1 independent of the well known SUMO interacting motif, but instead interacts with a loop involving Glu(67) of SUMO1. Intriguingly, DPP9 selectively associates with SUMO1 and not SUMO2, due to a more positive charge in the SUMO1-loop. We mapped the SUMO-binding site of DPP9 to an extended arm structure, predicted to directly flank the substrate entry site. Importantly, whereas mutants in the SUMO1-binding arm are less active compared with wild-type DPP9, SUMO1 stimulates DPP9 activity. Consistent with this, silencing of SUMO1 leads to a reduced cytosolic prolyl-peptidase activity. Taken together, these results suggest that SUMO1, or more likely, a sumoylated protein, acts as an allosteric regulator of DPP9.

The cytoplasmic peptidase DPP9 is rate-limiting for degradation of proline-containing peptides

Protein degradation is an essential process that continuously takes place in all living cells. Regulated degradation of most cellular proteins is initiated by proteasomes, which produce peptides of varying length. These peptides are rapidly cleaved to single amino acids by cytoplasmic peptidases. Proline-containing peptides pose a specific problem due to structural constrains imposed by the pyrrolidine ring that prevents most peptidases from cleavage. Here we show that DPP9, a poorly characterized cytoplasmic prolyl-peptidase, is rate-limiting for destruction of proline-containing substrates both in cell extracts and in intact cells. We identified the first natural substrate for DPP9, the RU1(34-42) antigenic peptide (VPYGSFKHV). RU1(34-42) is degraded in vitro by DPP9, and down-regulation of DPP9 in intact cells results in increased presentation of this antigen. Together our findings demonstrate an important role for DPP9 in peptide turnover and antigen presentation.

Performing in vitro sumoylation reactions using recombinant enzymes

Sumoylation of proteins in vitro has evolved as an indispensable tool for the functional analysis of this post-translational modification. In this article we present detailed protocols for bacterial production of mammalian proteins necessary to perform in vitro sumoylation reactions, namely the E1 activating enzyme Aos1/Uba2 (SAE1/SAE2), the E2 conjugating enzyme Ubc9, SUMO-1 (identical protocols can be used for SUMO-2/3), and the catalytic domain of the E3 ligase RanBP2/Nup358. Two alternative procedures are described for the E1 enzyme, one depending on co-expression of His-Aos1 and untagged Uba2, and a second protocol for separate expression of His-Aos1 and Uba2-His and subsequent reconstitution of the active dimer. Two example conditions for in vitro sumoylation of RanGAP1 and Sp100 in the absence or presence of the SUMO E3 ligase RanBP2, respectively, are provided. Both protocols can be adapted easily to test in vitro conjugation of other target proteins and/or E3 ligases.

Neonatal and maternal immunological responses to conserved epitopes within the DBL-gamma3 chondroitin sulfate A-binding domain of Plasmodium falciparum erythrocyte membrane protein 1

Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) mediates the adherence of P. falciparum-infected erythrocytes to placental syncytiotrophoblasts via interactions with chondroitin sulfate A (CSA), a characteristic of pregnancy-associated malaria. Pregnancy-associated malaria predicts increased susceptibility of newborns to malaria, and it is postulated that transplacental passage of parasite antigen induces immune regulatory activity in the neonate. We wished to examine the immune responsiveness to a CSA-binding domain of PfEMP1, the DBL-gamma3 domain, in cord and maternal venous blood obtained from pregnancies with various histories of P. falciparum infection. We assessed in vitro T-cell cytokine and plasma immunoglobulin G (IgG) and IgM responses to four peptides corresponding to highly conserved regions of a DBL-gamma3 domain common to central African parasite isolates. The presence of placental P. falciparum infection at delivery was associated with elevated frequencies of DBL-gamma3 peptide-specific CD3+ interleukin-10-positive T cells in cord blood, while treatment and clearance of infection prior to delivery was associated with elevated frequencies of CD3+ gamma interferon-positive T cells. DBL-gamma3 peptide-specific IgM antibodies were detected in 12 of 60 (20%) cord plasma samples from those born to mothers with P. falciparum infection during pregnancy. Consistent with polyclonal anti-PfEMP1 antibody responses that are associated with protection against pregnancy-associated malaria, the presence of maternal IgG antibodies with specificity for one of the DBL-gamma3 peptides showed a parity-dependent profile. These data demonstrate that peptides corresponding to conserved regions of the DBL-gamma3 domain of PfEMP1 are immunogenic in P. falciparum-infected mothers and their offspring.

IFN-gamma and IL-10 mediate parasite-specific immune responses of cord blood cells induced by pregnancy-associated Plasmodium falciparum malaria

Available evidence suggests that immune cells from neonates born to mothers with placental Plasmodium falciparum (Pf) infection are sensitized to parasite Ag in utero but have reduced ability to generate protective Th1 responses. In this study, we detected Pf Ag-specific IFN-gamma(+) T cells in cord blood from human neonates whose mothers had received treatment for malaria or who had active placental Pf infection at delivery, with responses being significantly reduced in the latter group. Active placental malaria at delivery was also associated with reduced expression of monocyte MHC class I and II in vivo and following short term in vitro coculture with Pf Ag compared with levels seen in neonates whose mothers had received treatment during pregnancy. Given that APC activation and Th1 responses are driven in part by IFN-gamma and down-regulated by IL-10, we examined the role of these cytokines in modulating the Pf Ag-specific immune responses in cord blood samples. Exogenous recombinant human IFN-gamma and neutralizing anti-human IL-10 enhanced T cell IFN-gamma production, whereas recombinant human IFN-gamma also restored MHC class I and II expression on monocytes from cord blood mononuclear cells cocultured with Pf Ag. Accordingly, active placental malaria at delivery was associated with increased frequencies of Pf Ag-specific IL-10(+)CD4(+) T cells in cord blood mononuclear cell cultures from these neonates. Generation and maintenance of IL-10(+) T cells in utero may thus contribute to suppression of APC function and Pf Ag-induced Th1 responses in newborns born to mothers with placental malaria at delivery, which may increase susceptibility to infection later in life.

Clinical and Parasitological Characteristics of Puerperal Malaria

BACKGROUND

Women with semi-immunity to malaria who live in regions where the disease is endemic are at increased risk for more frequent and severe episodes of malaria during pregnancy. Recent findings indicate that this increased risk might persist beyond delivery, but the underlying mechanisms for this change in risk are poorly understood.

METHODS

One hundred fifty women were included in a cohort study in Lambaréné, Gabon, and were actively followed up weekly for 10 weeks after delivery, as were nonpregnant control women who had been matched to them by location and age. Parasites in samples of placenta and blood were genotyped by use of polymerase chain reaction amplification of the merozoite surface antigen 2 gene and the subtelomeric variable open reading frame gene of Plasmodium falciparum.

RESULTS

Eleven puerperal women had cases of clinical malaria, compared with 1 control woman (rate ratio, 9.8; P=.006). Eighteen puerperal women had P. falciparum parasitemia, compared with 6 control women (rate ratio, 2.7; P=.03). Five of 16 puerperal women (31%) with parasitemia on follow-up had identical parasites in their placentas and blood, and 11 of these cases (69%) were the result of reinfection. Puerperal women remained at equal risk for the development of parasitemia throughout the first 10 weeks after delivery. Use of bed nets, use of chloroquine prophylaxis during pregnancy, presence of malaria episodes during pregnancy, gravidity, and age were not associated with the acquisition of parasitemia during follow-up.

CONCLUSIONS

Compared with nonpregnant women, puerperal women have a considerably increased risk for the development of malaria and/or parasitemia. This increased risk is caused both by the recurrence of P. falciparum parasitemia and by the increased susceptibility to new infections, although the latter plays a more significant role.

Metabolic power of European starlings Sturnus vulgaris during flight in a wind tunnel, estimated from heat transfer modelling, doubly labelled water and mask respirometry

It is technically demanding to measure the energetic cost of animal flight. Each of the previously available techniques has some disadvantage as well advantages. We compared measurements of the energetic cost of flight in a wind tunnel by four European starlings Sturnus vulgaris made using three independent techniques: heat transfer modelling, doubly labelled water (DLW) and mask respirometry. We based our heat transfer model on thermal images of the surface temperature of the birds and air flow past the body and wings calculated from wing beat kinematics. Metabolic power was not sensitive to uncertainty in the value of efficiency when estimated from heat transfer modelling. A change in the assumed value of whole animal efficiency from 0.19 to 0.07 (the range of estimates in previous studies) only altered metabolic power predicted from heat transfer modelling by 13%. The same change in the assumed value of efficiency would cause a 2.7-fold change in metabolic power if it were predicted from mechanical power. Metabolic power did not differ significantly between measurements made using the three techniques when we assumed an efficiency in the range 0.11-0.19, although the DLW results appeared to form a U-shaped power-speed curve while the heat transfer model and respirometry results increased linearly with speed. This is the first time that techniques for determining metabolic power have been compared using data from the same birds flying under the same conditions. Our data provide reassurance that all the techniques produce similar results and suggest that heat transfer modelling may be a useful method for estimating metabolic rate.

Pilot Study: Tendency of Increasing Iodine Content in Human Milk and Cow's Milk

The iodine supply in Germany has improved throughout the last decade, albeit with enormous differences between individuals and regions. In the Thuringian city of Jena, analyses of the iodine content of human milk have been undertaken regularly since 1982. Significantly increasing iodine concentrations in human and cow's milk have been found. Therefore, the current situation and the effectiveness of measures to prevent iodine deficiency demands re-evaluation. The iodine content of human milk from 32 lactating mothers was analysed on the 5th day (mean) postpartum and mothers' dietary iodine intake during the last two months of pregnancy was assessed by means of a food frequency questionnaire. To corroborate the assumption that the increasing iodine levels of cow's milk are one of the main reasons for the improved iodine supply, the iodine concentration of 34 cow's milk bulk-samples was also determined. Both human and cow's milk samples were analysed by the ICP-MS method. Twenty women took iodine supplements (mean daily intake = 175 microg). The average daily iodine intake of the 20 supplemented and 12 non-supplemented women was 258 microg and 116 microg, respectively. Daily iodine intake from food and beverages was significantly lower in supplemented women (83 microg/day). The average iodine content of human milk was 169 +/- 88 microg/l with a range of 33 - 348 microg/l. This content is two times higher than levels from 1994 in the same area. There was no difference in the human milk iodine content between mothers taking supplements and those who did not. Cow's milk samples showed a mean iodine concentration of 178 +/- 131 microg/l (range 48 - 661 microg/l).

Induction of plasminogen activator inhibitor I gene expression by intracellular calcium via hypoxia-inducible factor-1

The plasminogen activator inhibitor-1 (PAI-1) expression can be enhanced by hypoxia and other stimuli leading to the mobilization of intracellular calcium. Thus, it was the aim of the present study to investigate the role of calcium in the hypoxia-dependent PAI-1 expression. It was shown that the Ca2+-ionophore A23187 and the cell permeable Ca2+-chelator BAPTA-am (1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid-acetoxymethyl ester) induced PAI-1 mRNA and protein expression under normoxia and hypoxia in HepG2 cells. Transfection experiments with wild-type and hypoxia response element (HRE)-mutated PAI promoter constructs revealed that the HRE binding hypoxiainducible factor-1 (HIF-1) mediated the response to A23187 and BAPTA-am. Although A23187 induced a striking and stable induction of HIF-1α, BAPTA-am only mediated a fast and transient increase. By using actinomycin D and cycloheximide we showed that A23187 induced HIF-1α mRNA expression, whereas BAPTA-am acted after transcription. Although A23187 activated extracellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK), as well as protein kinase B, it appeared that the enhancement of HIF-1α by A23187 was only mediated via the ERK pathway. By contrast, BAPTA-am exerted its effects via inhibition of HIF-prolyl hydroxylase activity and von Hippel-Lindau tumor repressor protein (VHL) interaction. Thus, calcium appeared to have a critical role in the regulation of the HIF system and subsequent activation of the PAI-1 gene expression. (Blood. 2004;104:3993-4001)

A Fenton reaction at the endoplasmic reticulum is involved in the redox control of hypoxia-inducible gene expression

It has been proposed that hydroxyl radicals (.OH) generated in a perinuclear iron-dependent Fenton reaction are involved in O(2)-dependent gene expression. Thus, it was the aim of this study to localize the cellular compartment in which the Fenton reaction takes place and to determine whether scavenging of.OH can modulate hypoxia-inducible factor 1 (HIF-1)-dependent gene expression. The Fenton reaction was localized by using the nonfluorescent dihydrorhodamine (DHR) 123 that is irreversibly oxidized to fluorescent rhodamine 123 while scavenging.OH together with gene constructs allowing fluorescent labeling of mitochondria, endoplasmic reticulum (ER), Golgi apparatus, peroxisomes, or lysosomes. A 3D two-photon confocal laser scanning microscopy showed.OH generation in distinct hot spots of perinuclear ER pockets. This ER-based Fenton reaction was strictly pO(2)-dependent. Further colocalization experiments showed that the O(2)-sensitive transcription factor HIF-1alpha was present at the ER under normoxia, whereas HIF-1alpha was present only in the nucleus under hypoxia. Inhibition of the Fenton reaction by the.OH scavenger DHR attenuated HIF-prolyl hydroxylase activity and interaction with von Hippel-Lindau protein, leading to enhanced HIF-1alpha levels, HIF-1alpha transactivation, and activated expression of the HIF-1 target genes plasminogen activator inhibitor 1 and heme oxygenase 1. Further,.OH scavenging appeared to enhance redox factor 1 (Ref-1) binding and, thus, recruitment of p300 to the transactivation domain C because mutation of the Ref-1 binding site cysteine 800 abolished DHR-induced transactivation. Thus, the localized Fenton reaction appears to impact the expression of hypoxia-regulated genes by means of HIF-1alpha stabilization and coactivator recruitment.

Zerebrale Vasospasmen mit h�modynamischen Infarkten als Komplikation eines HELLP-Syndroms

Sinal thrombosis, intracerebral bleeding, cerebral edema, and cerebral vasospasm are typical neurological complications in pre- and eclampsia. Hemolysis, elevated liver enzyme, and low platelet (HELLP) syndrome is a rare, severe complication of pre-eclampsia. We present the case of a 33-year-old woman with HELLP syndrome. After a cesarean section, generalized epileptic seizure occurred and intubation was necessary due to sustained unconsciousness. Despite magnesium therapy, bilateral hemodynamic ischemic infarctions and narrowing of the circle of Willis were visible on MRI, and vasospasm of all large basal cerebral arteries was confirmed by cerebral angiography and transcranial Doppler sonography. During the following 2 weeks, the cerebral vasospasm resolved with application of high-dose methyl prednisolone and nimodipine. After extubation, the patient initially suffered from mild psychosyndrome and ataxia but recovered completely after 3 months. The HELLP syndrome may be complicated by cerebral vasospasm with subsequent hemodynamic strokes. Combined treatment with magnesium, corticosteroids, and nimodipine can be recommended. In our case, this regimen led to resolution of the cerebral vasospasm and complete clinical recovery.

[Current aspects of the Thuringia prematurity prevention campaign 2000]

In two prospective investigations the effectiveness of the self- care program for prematurity prevention, developed by Saling, was investigated. Pregnant women in Erfurt have been offered to perform self-measurements of their vaginal pH by means of test gloves (Careplan VpH) twice a week. The women were instructed to see their physician immediately, if abnormal values (pH > or = 4.7) or other risk factors were present. 73 out of 381 women in the intervention group have been identified as risk cases. 58 of them were treated with a lactobacillus preparation, and 24 with clindamycin cream for bacterial vaginosis, 3 patients refused to have any therapy. In this study the prematurity rate was 8.1 % in the self-measurement/intervention group vs. 12.3 % in the control group (N=2 341, P < 0.05); 0.3 % vs. 3.3 % of the neonates belonged to the group of early prematures with a gestational age of < 32 + 0 weeks (P < 0.01). PROM was registered in 22.8 % vs. 30.8 % (P < 0.001) respectively. Starting March 1, 2000 a similar statewide pH-screening program was initiated in Thuringia. According to the study design a significant decrease of prematurity was hypothetically expected for the second half of the year 2000. In Erfurt an overall decrease of prematurity from 7.68 to 6.81 % and a reduction of cases < 32 + 0 weeks from 3.22 to 2.39 % was observed (N=1,600). Data from 16,276 women are available for the state of Thuringia. On this basis a significant reduction of early prematurity from 1.58 to 0.99 % was seen respectively (P < 0.001). Comparing low birthweights a significant reduction of cases was achieved as well in all groups. On the basis of the data obtained we recommend the extension of the campaign in the whole of Germany.

[In vitro studies into the influence of ochratoxin A on the production of tumor necrosis factor alpha by the human monocytic cell line THP-1]

The influence of pure OTA and an Aspergillus-ochraceus crude toxin on the intracellular expression and the secretion of tumor necrosis factor (TNF) alpha by the monocytic cell line THP-1 was studied in vitro. After 4 hours exposure, the secretion of TNF alpha was inhibited to 50% by pure OTA in a concentration of 400 ng/ml and by crude toxin in a concentration of 100 ng/ml. The same concentrations of mycotoxins impaired the mitochondrial activity of THP-1 cells only marginally. The intracellular expression of TNF alpha was not disturbed by pure OTA in the concentrations tested, whereas crude toxin showed an inhibitory effect. The possible reasons for these findings are discussed.

[HELLP Syndrome as an indication for liver transplantation]

Liver rupture followed by multiorgan failure is perhaps the most catastrophic complication of the HELLP syndrome (hemolysis, elevated liver function, low platelets). Specific treatment options are currently limited and not routinely clarified. Here, we present a patient successfully managed by an innovative surgical approach consisting of combined total hepatectomy, portacaval shunt, and liver transplantation. A 26-year-old primipara (39th week of gestation) who suffered liver rupture as a complication of HELLP syndrome after delivery underwent a portacaval shunt after total hepatectomy. This combination was sufficient until the patient underwent orthotopic liver transplantation. The patient was discharged from the hospital after a dramatic recovery. Bridging portacaval shunt and consecutive orthotopic liver transplantation represented an effective therapy for this patient and should be considered early as a treatment option in patients with liver rupture complicating severe HELLP syndrome.

Metabolic power, mechanical power and efficiency during wind tunnel flight by the European starlingSturnus vulgaris

We trained two starlings (Sturnus vulgaris) to fly in a wind tunnel whilst wearing respirometry masks. We measured the metabolic power (Pmet) from the rates of oxygen consumption and carbon dioxide production and calculated the mechanical power (Pmech) from two aerodynamic models using wingbeat kinematics measured by high-speed cinematography. Pmet increased from 10.4 to 14.9 W as flight speed was increased from 6.3 to 14.4 m s–1 and was compatible with the U-shaped power/speed curve predicted by the aerodynamic models. Flight muscle efficiency varied between 0.13 and 0.23 depending upon the bird, the flight speed and the aerodynamic model used to calculate Pmech. Pmet during flight is often estimated by extrapolation from the mechanical power predicted by aerodynamic models by dividing Pmech by a flight muscle efficiency of 0.23 and adding the costs of basal metabolism, circulation and respiration. This method would underestimate measured Pmet by 15–25 % in our birds. The mean discrepancy between measured and predicted Pmet could be reduced to 0.1±1.5 % if flight muscle efficiency was altered to a value of 0.18. A flight muscle efficiency of 0.18 rather than 0.23 should be used to calculate the flight costs of birds in the size range of starlings (approximately 0.1 kg) if Pmet is calculated from Pmech derived from aerodynamic models.

[Nitroglycerin patch for tocolysis--a prospective randomized comparison with fenoterol by infusion]

OBJECTIVE

To evaluate tocolytic efficacy of transdermal glyceryl trinitrate (GTN) in comparison to fenoterol per infusionem in a prospective randomized multicenter study.

PATIENTS AND METHODS

50 pregnant women between 27 and 35 weeks of gestation with preterm labour were treated with either GTN patches (0.4-0.8 mg/h) or fenoterol per infusionem (60-120 micrograms/h) up to stop of contractions or 35 weeks in maximum. The primary outcomes were the prolongation of gestation by 48 h, 7 days or up to 37 weeks of gestation as well as the neonatal outcome. The progression of cervical ripening and maternal side effects during tocolysis were assessed as secondary outcome criteria.

RESULTS

There was no difference in successful tocolysis for 48 h and 7 days in both groups, whereas significantly more women passed 37 weeks after GTN therapy. So mean duration of pregnancy, birth weight and height were greater, whereas transfer into neonatal care unit was significantly rare after GTN. There were no differences in neonatal outcome and progression of cervical ripening during tocolysis. Maternal side effects during GTN were fewer and weaker compared with fenoterol. Circa 70% of GTN treated women had a headache temporary, whereas more than 90% of the patients with fenoterol suffered from tachycardia and tremor.

CONCLUSIONS

Tocolytic efficacy of transdermal GTN was at least equivalent to the established beta-mimetic therapy with fenoterol. Because of the lower preterm delivery rate transfer into neonatal care for control was significantly rarer after GTN with equally good neonatal outcome in both groups. Beside the headache transdermal GTN therapy had lower maternal side effects in comparison to fenoterol.

Pitfalls in the clustering of neuroimage data and improvements by global optimization strategies

In this paper, we examined three vector quantization (VQ) methods used for the unsupervised classification (clustering) of functional magnetic resonance imaging (fMRI) data. Classification means that each brain volume element (voxel), according to a given scanning raster, was assigned to one group of voxels based on similarity of the fMRI signal patterns. It was investigated how the VQ methods can isolate a cluster that describes the region involved in a particular brain function. As an example, word processing was stimulated by a word comparison task. VQ analysis methodology was verified using simulated fMRI response patterns. It was demonstrated in detail that VQ based on global rather than local optimization of the objective function yielded a higher performance. Performance was measured in statistically relevant series of VQ attempts using several indices for goodness, reliability and efficiency of VQ solutions. Furthermore, it was shown that a poor local optimization caused either an underestimation or an overestimation of the stimulus-induced brain activation. However, this was not observed if the cluster analysis was based upon a global optimization strategy.

Structure of the 5'-flanking region of the rat prostaglandin F(2alpha) receptor gene and its transcriptional control functions in hepatocytes

Prostaglandin F(2alpha) (PGF(2alpha)), modulates hepatocyte functions via a heptahelical G(q)-coupled PGF(2alpha)-receptor (FP-R) which in liver is expressed exclusively in hepatocytes. The aim of the present study was to isolate the 5'-flanking region of the rat FP-R gene and to elucidate its basal and IL-6-modulated transcription control function in rat hepatocytes. The 5'-non-translated region of the rat hepatocyte FP-R mRNA differed from the corresponding region in rat fetal astrocyte or corpus luteum. It was encoded by exons 1a and 2 which were separated by a 1. 4 kb intron containing the exons 1b and 1c coding for the 5'-untranslated region of rat fetal astrocyte and corpus luteum FP-R mRNA, respectively. The transcription initiation site in hepatocytes was localized 263 bp upstream of the start ATG by 5'-RACE. A DNA-fragment covering the 5'-flanking region of the rFP-R gene from -1 of the transcription initiation site to -2590 bp was cloned and sequenced. Its 3'-two thirds had a 65% sequence identity to the mouse FP-R promoter however no homology to the bovine FP-R promoter. In the overlapping sequence most of the putative transcription factor binding sites were conserved between mouse and rat. The rat promoter contained no classical TATA- or CAAT-boxes but putative binding sites for the transcription factors C/EBP, GATA-1, HNF-1, HNF-3beta, SP-1, and USF. Luciferase reporter gene constructs containing portions of the 5'-flanking region were transfected into rat hepatocytes. Luciferase expression ranked -181 >/= -608 < -1418 > -1821 >/= -2590. The strongest transcriptional activity was conferred by the region between -608 and -1418 containing a cluster of potential HNF-1 and HNF-3beta binding sites that might allow the exclusive expression of FP-R mRNA in hepatocytes. The amount of FP-R mRNA and the luciferase expression under control of the -2590 promoter fragment were reduced by IL-6 in hepatocytes.

Requirement of N-glycosylation of the prostaglandin E2 receptor EP3beta for correct sorting to the plasma membrane but not for correct folding

Eight heptahelical receptors have been characterized for prostaglandin (PG) D(2), PGE(2), PGF(2alpha), prostacyclin and thromboxane A(2). They share a sequence identity of 40%. All of them have potential N-glycosylation sites. The current study analysed the role of the two N-glycosylation sites in the rat EP3beta-subtype PGE(2) receptor for protein folding and sorting. The N-glycosylation consensus sequences were eliminated by site-directed mutagenesis and receptors expressed in HEK-293 cells. Both potential N-glycosylation sites were used. Their joint elimination resulted in the synthesis of a receptor protein with full binding competence, biological activity and no reduction of affinity; however, the half-life of the non-glycosylated receptor was slightly reduced. Ligand binding to intact stably transfected cells and confocal laser microscopic immunocytochemistry showed that the glycosylated receptor was correctly inserted into the plasma membrane to a much larger extent than the non-glycosylated receptor, which tended to accumulate in the perinuclear zone of the endoplasmic reticulum. Inhibition of N-glycosylation with tunicamycin resulted in a similar perinuclear distribution of the wild-type receptor. Therefore, glycosylation of the EP3beta receptor seems not to be necessary for correct folding of the receptor protein but for the efficient transport of the receptor protein to the plasma membrane. This contrasts with a previous finding which described a reduction of the affinity for PGE(2) of the EP3alpha receptor by elimination of the distal glycosylation site when the receptor protein was expressed in insect cells.

Phospholipase D stimulation by receptor tyrosine kinases mediated by protein kinase C and a Ras/Ral signaling cascade

Stimulation of phospholipase D (PLD) in HEK-293 cells expressing the M(3) muscarinic receptor by phorbol ester-activated protein kinase C (PKC) apparently involves Ral GTPases. We report here that PKC, but not muscarinic receptor-induced PLD stimulation in these cells, is strongly and specifically reduced by expression of dominant-negative RalA, G26A RalA, as well as dominant-negative Ras, S17N Ras. In contrast, overexpression of the Ras-activated Ral-specific guanine nucleotide exchange factor, Ral-GDS, specifically enhanced PKC-induced PLD stimulation. Moreover, recombinant Ral-GDS potentiated Ral-dependent PKC-induced PLD stimulation in membranes. Epidermal growth factor, platelet-derived growth factor, and insulin, ligands for receptor tyrosine kinases (RTKs) endogenously expressed in HEK-293 cells, apparently use the PKC- and Ras/Ral-dependent pathway for PLD stimulation. First, PLD stimulation by the RTK agonists was prevented by PKC inhibition and PKC down-regulation. Second, expression of dominant-negative RalA and Ras mutants strongly reduced RTK-induced PLD stimulation. Third, overexpression of Ral-GDS largely potentiated PLD stimulation by the RTK agonists. Finally, using the Ral binding domain of the Ral effector RLIP as an activation-specific probe for Ral proteins, it is demonstrated that endogenous RalA is activated by phorbol ester and RTK agonists. Taken together, strong evidence is provided that RTK-induced PLD stimulation in HEK-293 cells is mediated by PKC and a Ras/Ral signaling cascade.

Agonist-induced phosphorylation by G protein-coupled receptor kinases of the EP4 receptor carboxyl-terminal domain in an EP3/EP4 prostaglandin E(2) receptor hybrid

Prostaglandin E(2) receptors (EP-Rs) belong to the family of heterotrimeric G protein-coupled ectoreceptors with seven transmembrane domains. They can be subdivided into four subtypes according to their ligand-binding and G protein-coupling specificity: EP1 couple to G(q), EP2 and EP4 to G(s), and EP3 to G(i). The EP4-R, in contrast to the EP3beta-R, shows rapid agonist-induced desensitization. The agonist-induced desensitization depends on the presence of the EP4-R carboxyl-terminal domain, which also confers desensitization in a G(i)-coupled rEP3hEP4 carboxyl-terminal domain receptor hybrid (rEP3hEP4-Ct-R). To elucidate the possible mechanism of this desensitization, in vivo phosphorylation stimulated by activators of second messenger kinases, by prostaglandin E(2), or by the EP3-R agonist M&B28767 was investigated in COS-7 cells expressing FLAG-epitope-tagged rat EP3beta-R (rEP3beta-R), hEP4-R, or rEP3hEP4-Ct-R. Stimulation of protein kinase C with phorbol-12-myristate-13-acetate led to a slight phosphorylation of the FLAG-rEP3beta-R but to a strong phosphorylation of the FLAG-hEP4-R and the FLAG-rEP3hEP4-Ct-R, which was suppressed by the protein kinase A and protein kinase C inhibitor staurosporine. Prostaglandin E(2) stimulated phosphorylation of the FLAG-hEP4-R in its carboxyl-terminal receptor domain. The EP3-R agonist M&B28767 induced a time- and dose-dependent phosphorylation of the FLAG-rEP3hEP4-Ct-R but not of the FLAG-rEP3beta-R. Agonist-induced phosphorylation of the FLAG-hEP4-R and the FLAG-rEP3hEP4-Ct-R were not inhibited by staurosporine, which implies a role of G protein-coupled receptor kinases (GRKs) in agonist-induced receptor phosphorylation. Overexpression of GRKs in FLAG-rEP3hEP4-Ct-R-expressing COS-7 cells augmented the M&B28767-induced receptor phosphorylation and receptor sequestration. These findings indicate that phosphorylation of the carboxyl-terminal hEP4-R domain possibly by GRKs but not by second messenger kinases may be involved in rapid agonist-induced desensitization of the hEP4-R and the rEP3hEP4-Ct-R.

Application of correlation dimension and pointwise dimension for non-linear topographical analysis of focal onset seizures

For many patients who are candidates for epilepsy surgery, non-invasive evaluation fails to provide sufficient information to permit surgical treatment. Since there are also definite risks and considerable costs associated with invasive procedures, new (non-invasive) techniques are required. This study provides empirical evidence that a non-linear approach applied to ictal surface electroencephalograms (EEGs) can help to delineate the area of seizure onset and may prove useful in complementing visual analysis of the EEG. Multichannel EEGs, recorded from eight patients with different drug-resistant localisation-related epilepsies, were analysed using the concept of correlation dimension and two extensions based on the pointwise dimension. The latter also provided results in cases where assessment of the correlation dimension was not feasible. Comparative values between 2 and 6 were accepted as the result of the algorithms, mostly 3-4 for the EEG channels strongly reflecting epileptic activity, and 4-6 for the other signals. The proportion of accepted pointwise values was usually 200-800% for strong epileptic EEG activity compared to the other data. The approach permitted the characterisation of the scalp area reflecting epileptic activity. The results obtained were in perfect concordance with those obtained during pre-surgical work-up and confirmed by the post-operative outcome.

Nonlinear dynamics of 3 Hz spike-and-wave discharges recorded during typical absence seizures in children

One-channel routine recordings of the scalp electroencephalogram (EEG) from unmedicated children strictly classified as unprovoked typical (3 c/s) absence seizures were selected. The dynamics of spike-and-wave discharges (SWD) were then examined by means of autocorrelation, correlation dimension, averaged pointwise dimension and largest Lyapunov exponent. For one EEG signal with pronounced spike-and-wave (SW) patterns, these measures were used complementary to a surrogate data method, a nonlinear (SETAR) modeling approach, and a SW simulation procedure providing five types of SW test signals. The SETAR model exhibited stationary SW dynamics, visually very similar to the EEG target signal, and with clear nonlinear structure. According to the results, the EEG episodes investigated represent low-dimensional dynamics, possibly recorded during nonstationary periods. Arguments that justify the assumption of deterministic chaos in our EEG signals were not obtained with the current methods. From the results one may conclude that two global oscillatory modes are present for the model, and three modes are active during the EEG recording period.

Immunochemical detection of CoA-modified mitochondrial matrix proteins

An in vitro assay mixture consisting of mitochondrial matrix proteins from rat liver and CoA resulted in the formation of CoA-modified proteins. CoA-modified proteins were demonstrated by detection of CoA. CoA was released from the proteins by dithioerythritol treatment under denaturing conditions and was identified by (a) its retention time on HPLC, (b) its absorption spectrum and (c) its activity in a CoA-specific assay. This CoA represents protein-bound CoA and, in addition, protein-bound palmitoyl-CoA when MgATP was also present in the in vitro assay. The detection of immunoreactive proteins using mono-specific anti-CoA antibodies exclusively identifies CoA-modified proteins. The specificity of these antibodies can be used to identify both endogenously occurring CoA-modified proteins and proteins that have been modified in the in vitro assay. An intact thiol group of CoA is an essential precondition for the modification to occur.

Non-radioactive detection of oligonucleotide probes by photochemical amplification of dioxetanes

We describe a new method of non-radioactive labelling and detection of oligonucleotide probes. The approach is based on a simple chemical principle. Oligonucleotides labelled with methylene blue (a photosensitizer) are hybridized on a membrane to immobilized DNA target sequences. After hybridization and stringency washing 2(-)[3-(hydroxyphenyl)methoxymethylene] adamantane is added to the membrane and the membrane is irradiated with a tungsten lamp light source through a cut-off filter. Thermally stable dioxetanes are amplified during irradiation at the positions of the labelled probe. These amplified dioxetanes are detected using chemically triggered chemiluminescent decay. Signals are recorded on commercial X-ray film. Detection is possible immediately after the last washing step and a hard copy of the blot is obtained within 1 h. Dependent on the level of the target sequences, the sensitivity of the method allows detection of 0.3 pg single-stranded M13mp18(+) plasmid DNA in dot blots and 75 pg in Southern blots. Additional immunological reaction steps and washing steps with blocking reagents and buffers are avoided. Furthermore, expensive reagents and equipment for physical detection are not necessary. The method might be particularly useful for fast routine analysis in forensic and medical applications. The synthesis of the olefin, conditions of hybridization and the protocol of detection are described in detail.

Versatile procedure of multiple introduction of 8-aminomethylene blue into oligonucleotides

The coupling of 8-aminomethylene blue to oligonucleotides via poly-L-glutamic acid linker using carboxy-anchor groups will be described. The introduction of carboxy-anchor groups into oligonucleotides proceeds both during automated synthesis using 6-(ethoxycarbonyl)hexyl 1-O-phosphoramidite and by reaction of 5'-amino-functionalized oligonucleotides with succinic anhydride. O-(N-Succinimidyl)-1,1,3,3-tetramethyluronium tetrafluoroborate was used as activating reagent for binding of poly-L-glutamic acid to the carboxylated oligonucleotides. The successful 5'-carboxylation and poly-L-glutamic acid coupling were proven both by polyacrylamide gel electrophoreses and HPLC. 8-Aminomethylene blue in its leucoform was covalently coupled to the oligonucleotides in the presence of water soluble carbodiimide.

Modified cerium-based and Gomori-based cerium methods for light microscopic phosphatase histochemistry: the cerium-perhydroxide-diaminobenzidine-nickel (Ce-H2O2-DAB-Ni and Ce/Ce-H2O2-DAB-Ni) two-step procedures

Some modified cerium-based and Gomori-based cerium methods for the demonstration of phosphatase activity in cryostat sections were described. Dextrane as stabilizing agent was added to the incubation media for ATPase, 5'-Nase, and TPPase. The oxidation of the CeIII-phosphate primary reaction product in a separate step by H2O2 before the DAB incubation yielded an increase of the intensity of the DAB-based visualization reaction (Ce-H2O2-DAB-Ni two step method). The sensitivity of the histochemical enzyme reaction was remarkably increased if CeIII-ions were employed as amplifying agent (Ce/Ce-H2O2-DAB-Ni two-step method). A new suitable DAB medium consisting of 0.015% DAB, 2.0% Ni-sulphate, 15% methanol, and 0.005% H2O2 in 0.1 mol/l acetate buffer, pH = 5.2, was used. The disadvantage of diffuse background staining has been overcome by addition of 15% methanol to the DAB solution. Electrovalently bound CeIII (cerophilia) was removed by treatment of the incubated sections with CeIII-citrate (CeIII-complexation). In addition, a novel membrane floating incubation for sections is proposed. At present, the modified procedures are some of the most sensitive modes for the demonstration of phosphatases and improve the earlier described cerium-DAB one-step technique (Halbhuber et al. 1988b).

Identification of the CoA-modified forms of mitochondrial acetyl-CoA acetyltransferase and of glutamate dehydrogenase as nearest-neighbour proteins

A 52 kDa protein could only be co-purified with the CoA-modified forms of acetyl-CoA acetyltransferase (acetoacetyl-CoA thiolase) (EC 2.3.1.9) from rat liver mitochondria. Immunoprecipitations of these modified forms with anti-(acetyl-CoA acetyltransferase) IgG or anti-(52 kDa protein) IgG yielded, in addition to the appropriate proteins, the 52 kDa protein or the CoA-modified form of acetyl-CoA acetyltransferase (41 kDa) respectively. This was demonstrated by SDS/PAGE and immunoblots. The modified forms containing the 52 kDa protein could be cross-linked by 1,5-difluoro-2,4-dinitrobenzene to a high-molecular-mass complex containing both the 41 kDa and 52 kDa proteins. The 52 kDa protein was identified as mitochondrial glutamate dehydrogenase (EC 1.4.1.3) by amino acid sequence analysis. The results of co-immunoprecipitation and cross-linking characterize the CoA-modified forms of acetyl-CoA acetyltransferase and the glutamate dehydrogenase as nearest-neighbour proteins.

[Parathyroid sonography in long-term dialysis]

In a prospective study the prevalence of sonographically enlarged parathyroid glands in patients on maintenance hemodialysis was investigated and correlated with clinical and laboratory findings of secondary hyperparathyroidism. We examined 97 unselected patients with a 5 MHz probe. In 34% (33/97) a total of 69 parathyroid glands were detected with a statistically significant correlation between the period of dialysis and the incidence of parathyroid enlargement; 47.8% of the glands were hypoechoic, 34.8% moderately echogenic and 17.3% gave echoes similar to the normal thyroid parenchyma. A correlation was found between the finding of enlarged parathyroid glands and blood levels of calcium and alkaline phosphatase. Parathyroid enlargement was found sonographically before, or in the absence of clinical and laboratory findings of secondary hyperparathyroidism. Sonography is therefore a useful technique for early diagnosis of hyperparathyroidism in patients on maintenance dialysis.

Evidence for an in vivo modification of mitochondrial proteins by coenzyme A

Following denaturation of mitochondrial proteins by sodium dodecyl sulfate, a [1-14C]pantothenic acid-derived radioactivity proved to be acid precipitable in the outer membrane, the intermembrane space, the inner membrane and in the matrix of rat liver mitochondria, where it had the highest specific radioactivity of 541 +/- 29 cpm/100 micrograms protein. This tightly and/or covalently bound protein radioactivity could be released by incubation in the presence of dithioerythreitol; it was identified as [14C]coenzyme A by its HPLC retention time, its absorption spectrum and its radioactivity. This acid-stable and thiol-labile coenzyme A-binding apparently refers to specific protein binding sites. With the purified, homogeneous mitochondrial matrix enzymes acetyl-CoA acetyltransferase (acetoacetyl-CoA thiolase) (EC 2.3.1.9, acetyl-CoA:acetyl-CoA C-acetyltransferase) and 3-oxoacyl-CoA thiolase (EC 2.3.1.16) coenzyme A was found exclusively, e.g., in the modified, partially-active forms A1 und A2 of acetyl-CoA acetyltransferase and not in the unmodified fully-active enzyme. Thus it is evident that this coenzyme A modification is transient. We suggest that coenzyme A-modification is a signal involved in the assembly or the degradation process of distinct mitochondrial matrix proteins.

[The action of trypsin and zymosan on the respiration of cultivated endothelial cells]

Trypsin and Zymosan induce an increase in respiration activity of cultivated endothelial cells. These effects are not due to the production of oxygen radicals. The effect of trypsin will be explained by interfering with the cellular homeostasis of calcium. The stimulated respiration after incubation with zymosan may be connected with the increased phagocytosis.

[Fetal movement and acceleration behavior in unimpaired and impaired newborn infants]

The following biophysical examination parameters were found by CTG-synchronous registration of fetal body and respiratory movements and compared in 7 fetuses impaired at birth (pHa less than 7.20, 1- and 5-minute Apgar scores less than or equal to 7 points) and 76 unimpaired born fetuses (pHa greater than or equal to 7.20, 1- and 5-minute Apgar scores greater than or equal to 8 points): number of fetal body movements per 10 minutes examination time; total and mean durations of these movements per 10 minutes; number of fetal respiratory movements per 10 minutes; number and total duration of fetal respiratory movement periods per 10 minutes; frequency of fetal respiratory movements; proportion of 10-minute periods with and without fetal body and/or respiratory movements and the amounts of the quotients from the amplitude of accelerations in fetal heart rate resulting from fetal body movements and the durations of these body movements. The mean interval between biophysical examination and childbirth was 11 days. Principally, the impaired born fetuses were less active in their movements than were unimpaired born fetuses. Apart from the frequency of fetal respiratory movements and the proportion of 10-minute periods without fetal body movements, the above mentioned parameters differ significantly with a probable error of alpha = 0.05. All biophysical parameters were registered on an uterus without labour and the cardiogram as well as the biophysical profile--with the exception of one fetus from the group of impaired borns--being unremarkable. The 10-minute periods without fetal body or respiratory movements were excluded from analysis.

[Movement and acceleration behavior of eutrophic and hypotrophic fetuses sub partu]

Cardiogram synchronous registration of fetal body and respiratory movements (real-time ultrasonic examination) was employed to compare the movement and acceleration behaviour of 130 normotrophic fetuses to that of 13 fetuses with body weights between the 6th and the 10th weight percentiles according to Kyank and of 13 fetuses with body weights less than or equal to the 5th percentile. The mean duration of examination was 80 minutes. The normotrophic fetuses exhibited the highest movement activity and reactivity of the cardiovascular system. In 88.6%, accelerations of fetal heart rate were associated with fetal body movements and were independent of fetal weight. Comparison with a previous communication of the authors revealed that intranatal fetal movement activity and reactivity of the cardiovascular system were only slightly below that with a uterus without labour. The only exception were fetal respiratory movements with significantly fewer intranasal observations.

Identification of [1-14C]pantothenic-acid-mediated modified mitochondrial proteins

The in vivo administration of [1-14C]pantothenic acid, which is the precursor of coenzyme A, resulted in the radioactive labelling of several mitochondrial proteins in rat liver. The incorporated radioactivity could be released by glutathione or 2-mercaptoethanol. Two mitochondrial matrix proteins acetyl-CoA acetyltransferase (liver and heart), an enzyme involved in the biosynthesis or degradation of ketone bodies, and 3-oxoacyl-CoA thiolase (liver), a protein participating in fatty acid oxidation were identified as modified proteins. The radioactivity was localized exclusively in forms A1 and A2 indicating that these forms represent the modified states of the acetyl-CoA acetyltransferase protein. Kinetics of incorporation of radioactivity revealed an accumulation of the modified forms. The ratio of specific radioactivities of A2 compared to A1 was 2.41 +/- 0.15 (n = 10). After in vivo labelling with [14C]leucine, the specific radioactivity of acetyl-CoA acetyltransferase depended on the state of the enzyme protein. The unmodified enzyme exhibited a lower specific radioactivity than its modified forms suggesting different turnover rates of these proteins.