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Biomedical subjects

J Biermann

Publications and source records attributed to J Biermann.

At least 19 recordsLinked to original sources
PubMed1999

In vitro processing of the human alkyl-dihydroxyacetonephosphate synthase precursor.

Alkyl-dihydroxyacetonephosphate synthase, a peroxisomal enzyme involved in the biosynthesis of ether phospholipids, is synthesized with a cleavable N-terminal presequence containing the peroxisomal targeting signal type 2. The human alkyl-dihydroxyacetonephosphate synthase precursor produced in vitro or expressed in Escherichia coli could be processed to a lower molecular weight protein by incubation at 37 degrees C with a guinea pig liver fraction, enriched in mitochondria, lysosomes, and peroxisomes. This lower molecular weight protein was identified as the mature human alkyl-dihydroxyacetonephosphate synthase by radiosequencing, indicating that the processing protease is present in this organellar fraction. Characterization of the processing protease indicated that it is a cysteine protease with a pH optimum of 6.5. Furthermore, it was demonstrated that exogenously added pre-alkyl-dihydroxyacetonephosphate synthase was imported and processed in purified peroxisomes in vitro. Processing of alkyl-dihydroxyacetonephosphate synthase did not increase the activity of the enzyme. This indicates that the presence of the presequence does not affect the activity of the enzyme.

Alkyl and Aryl Transferases↗
PubMed1999

Immunological analyses of alkyl-dihydroxyacetone-phosphate synthase in human peroxisomal disorders.

Alkyl-dihydroxyacetonephosphate synthase (alkyl-DHAP synthase) is a peroxisomal enzyme involved in the biosynthesis of ether phospholipids. To localize the enzyme in human peroxisomal disorders, indirect immunofluorescence and immunoblot analysis was performed. In Zellweger syndrome and rhizomelic chondrodysplasia punctata fibroblast cell lines, alkyl-DHAP synthase protein levels on immunoblots were strongly decreased and residual immunofluorescence was diffusely localized throughout the cytoplasm. In a particular neonatal adrenoleukodystrophy cell line, characterized by the absence of a functional peroxisomal targeting signal 1 receptor, the precursor form of the enzyme was detected in Western blots at levels comparable to that of the mature enzyme in control fibroblasts. Similarly, fibroblasts from patients with a single deficiency in the activity of either alkyl-DHAP synthase or DHAP-acyltransferase showed normal levels of the mature alkyl-DHAP synthase protein on immunoblots. Immunofluorescence experiments revealed a peroxisomal localization of both the precursor and the mature form of the enzyme. Collectively, these results visualize the peroxisomal localization of alkyl-DHAP synthase, indicate that the enzyme is unstable outside its target organelle and explain that normal enzyme protein levels found in some peroxisomal disorders result from protection against cytoplasmic degradation through import into peroxisomes. Additionally, alkyl-DHAP synthase could be detected in rat mesangial cells and murine NIH-3R3 fibroblasts by immunofluorescence as well as immunoblot analysis. Immunoelectron microscopy showed that the enzyme is predominantly located on the lumenal side of the peroxisomal membrane in rat and guinea pig liver.

3T3 Cells↗
PubMed1999

Alkyl-dihydroxyacetone phosphate synthase and dihydroxyacetone phosphate acyltransferase form a protein complex in peroxisomes.

Dihydroxyacetone phosphate (GrnP) acyltransferase and alkyl-GrnP synthase are the key enzymes involved in the biosynthesis of ether phospholipids. Both enzymes are located on the inside of the peroxisomal membrane. Here we report evidence for a direct interaction between these enzymes obtained by the use of chemical cross-linking. After cross-linking and immunoblot analysis alkyl-GrnP synthase could be detected in a 210-kDa complex which was located entirely on the lumenal side of the peroxisomal membrane. Two-dimensional SDS/PAGE demonstrated that GrnP-acyltransferase is also cross-linked in a 210-kDa complex. Co-immunoprecipitation confirmed that the two enzymes interact, in a heterotrimeric complex. Furthermore, alkyl-GrnP synthase can form a homotrimeric complex in the absence of GrnP-acyltransferase as was demonstrated by immunoblot analysis after cross-linking experiments with either GrnP-acyltransferase deficient human fibroblast homogenates or recombinant (His)6-tagged alkyl-GrnP synthase. We conclude that alkyl-GrnP synthase interacts selectively with GrnP-acyltransferase in a heterotrimeric complex and in the absence of GrnP-acyltransferase can also form a homotrimeric complex.

Acyltransferases↗
PubMed1999

The oncostatic action of melatonin in an ovarian carcinoma cell line.

Melatonin is reported to reduce proliferation in many cell types, but the effect is small and the results are inconsistent. Information on the mechanism by which melatonin exerts its antiproliferative effects might provide insight into the variability of the response. In an ovarian adenocarcinoma cell line (BG-1), we find that melatonin at concentrations of 10(-9)-10(-7) M caused a 20-25% reduction in cell number. Melatonin also resulted in a similar reduction in [3H]-thymidine incorporation with no significant increase in cell death as measured by trypan blue incorporation. The Kd for melatonin reduction in cell number was approximately 5 x 10(-10) M. Melatonin ML2 receptors have a Kd for melatonin binding in the low nM range and are linked to the production of the calcium mobilizing agent inositol-1,4,5-trisphosphate (IP3). To investigate whether melatonin signaling involves an increase in cytosolic-free calcium. BG-1 cells were loaded with the calcium sensitive indicator, fura-2. Acute addition of melatonin (10(-5)-10(-9) M) did not alter cytosolic calcium. Addition of the putative nuclear receptor agonist CGP52608 caused a dose-dependent inhibition of cell number with a Kd of approximately 2 x 10(-9) M. Addition of CGP52608 caused a similar reduction in [3H]-thymidine incorporation. Neither melatonin (10(-8) M-10(-5) M) nor CGP52608 at concentrations below 10(-7) M induced cell death associated with the inhibition of cell proliferation; however, addition of CGP52608 at a high dose (10(-7) M) caused an increase in cell death, consistent with apoptosis. Growth inhibition by melatonin or CGP52608 did not alter the percentage of cells in G1 versus S/G2/M.

Adenocarcinoma↗
PubMed1998

The native molecular size of alkyl-dihydroxyacetonephosphate synthase and dihydroxyacetonephosphate acyltransferase.

Dihydroxyacetonephosphate acyltransferase (DHAP-acyltransferase) and alkyl-dihydroxyacetonephosphate synthase (alkyl-DHAP synthase) are the first two enzymes involved in the biosynthesis of ether phospholipids. Both peroxisomal enzymes have recently been purified to homogeneity and their molecular weights under denaturing conditions were reported. To determine the in situ functional size of both enzymes, radiation inactivation experiments were performed. Alkyl-DHAP synthase showed single exponential decays, both when enzymatic activity and when immunoreactive protein levels were measured, from which target sizes of 79+/-2 kDa and 78+/-4 kDa, respectively, were calculated. DHAP-acyltransferase activity increased at lower doses and decayed upon further irradiation with an apparent target size of 62+/-7 kDa. We conclude from these data that the functional unit sizes for both enzymes in situ are represented by their single polypeptide chains.

Activation Analysis↗
PubMed1998

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Clinical Competence↗
PubMed1997

Immunological localization and tissue distribution of alkyldihydroxyacetonephosphate synthase and deficiency of the enzyme in peroxisomal disorders.

Alkyldihydroxyacetonephosphate synthase (alkylglycerone-phosphate synthase) is a peroxisomal enzyme involved in ether phospholipid biosynthesis. The recent cloning of the cDNA encoding this enzyme from guinea pig liver enabled the raising of specific antisera against this enzyme. Both a synthetic peptide corresponding to a predicted epitope and a recombinant protein expressed in Escherichia coli were used for that purpose. Using western blot techniques, the solubilization of the enzyme from the peroxisomal membrane by Triton X-100 in the presence of salt was confirmed. Neutral hydroxylamine treatment of peroxisomes resulted in almost no release of the protein from the membrane. The complete polypeptide chain of the enzyme was resistant to proteolysis by trypsin when intact peroxisomes were studied. Carbonate treatment released alkyldihydroxyacetonephosphate synthase from the membrane indicating that the enzyme is not an integral membrane protein. This idea is in accord with the absence of a clear hydrophobic transmembrane domain in the deduced amino acid sequence of the enzyme. Alkyldihydroxyacetonephosphate synthase, as well as its mRNA, could be detected in all five guinea pig tissues examined. When using the antiserum against guinea pig recombinant alkyldihydroxyacetonephosphate synthase, a cross-reactive protein was detected in a human liver homogenate that runs at a slightly higher molecular mass. The absence of this band in liver of Zellweger syndrome and Rhizomelic chondrodysplasia punctata patients provides strong evidence that it represents the human homolog of this enzyme.

Alkyl and Aryl Transferases↗
PubMed1995

Comparison of effects of N-3 to N-6 fatty acids on serum level of lipoprotein(a) in patients with coronary artery disease.

The influence of dietary supplementation with n-3 versus n-6 fatty acids on plasma lipoprotein(a) (Lp[a]) levels was studied. Thirty-five male hospitalized patients with coronary artery disease were treated for 4 weeks with 12 g/day of fish oil (approximately 8.5 g of n-3 fatty acids) in combination with a 5,000 kilojoule, 30% fat diet and moderate exercise. Eighteen control patients given the same dietary and training program were treated with 12 g/day of rapeseed oil. Plasma Lp(a), in addition to several lipids and lipoproteins, blood clotting factors, and platelet reactivity, were measured before and at the end of therapy. Results can be summarized as follows: total cholesterol, low-density lipoprotein cholesterol, and apolipoprotein B levels decreased significantly in both the rapeseed oil (-14.4%, -20.3%, -15.2%, respectively) and fish oil (-12.2%, -16.0%, and -14.2%, respectively) groups. Triglycerides decreased (-20.3%) and high-density lipoprotein cholesterol increased (+8.3%) significantly only in patients treated with fish oil. Plasma Lp(a) levels were reduced by 14% in the fish oil group, but unaffected in the rapeseed oil group. Patients treated with fish oil could be categorized into 2 subgroups: "responders," with a reduction in Lp(a) by 24% and "nonresponders," with a small nonsignificant increase in serum Lp(a). Responders and nonresponders exhibited a marked reduction in cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, and triglycerides, and an increase in high-density lipoprotein3 cholesterol. There was a large reduction in tissue plasminogen activator in the fish oil group, which correlated significantly with reduction in Lp(a).(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoproteins B↗
PubMed1992

[Effect of fish oil concentrate on the lipoprotein profile of patients with type II diabetes mellitus].

Non-insulin-dependent diabetes mellitus (NIDDM) is associated with increased very-low-density lipoprotein (VLDL) and triglyceride concentrations as abnormalities of low-density lipoprotein (LDL) composition. Because fish oil has a strong triglyceride lowering effect in case of normolipemic subjects, we investigated the influence of supplementary fish oil diet in patients suffering from NIDDM (n = 19), who until now were not treated by drugs but only by diet. The study was started with a placebo-run-in-period for four weeks (phase I, 6 g rape seed oil capsules/d), followed by a verum period for twelve weeks (phase II, 6 g fish oil concentrate capsules/d), and a wash-out-period for four weeks (phase III, 6 g rape seed oil capsules/d). The fish oil supplementation contained at least 3 g eicosapentenoic and docosahexenoic acid. The lipoproteins, apolipoproteins, blood glucose, and insulin level (fasting and after load test) were checked at the beginning and at the end of each phase. In comparison to the placebo rape seed oil supplementation, the fish oil diet effected a decrease of serum triglycerides by 29%. LDL-cholesterol increased by 9%, HDL-cholesterol by 9% (especially HDL2-cholesterol), and apolipoprotein B by 4%. Apolipoprotein A-I was reduced by 9%. The fasting blood glucose and the glucose load test as the insulin level (fasting and after load test) showed no significant changes at the end of the verum period in comparison to the run-in-phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol, HDL↗
PubMed1991

[Therapy-refractory primary intestinal lymphangiectasis].

A 20-year-old man with severe physical weakness (from which he soon recovered spontaneously) was found to have hypoproteinaemia and lymphocytopenia (768/microliters). Ten years later, after having been free of symptoms in the meantime, oedema, ascites and abdominal pain occurred, associated with loss of physical capacity. Enteric loss of protein (alpha 1-antitrypsin clearance increased about thirtyfold) with a total serum protein concentration of only 3.7 g/dl, as well as histological evidence of lymphangiectasia of the small and large intestines provided the diagnosis of primary intestinal lymphangiectasia. In the course of the disease cholelithiasis and (after treatment with tranexamic acid) thrombosis of the axillary vein occurred. No treatment has been of any avail and the patient has been unable to work for three years.

Adult↗
PubMed1991

High incidence of antibodies to hepatitis C virus in alcoholic cirrhosis: fact or fiction?

An enzyme immunoassay (Ortho-HCV ELISA) for antibodies against the hepatitis C virus was used to test serum samples from 39 patients with alcoholic cirrhosis and 34 patients with alcoholic hepatitis or fatty liver. The frequency of a positive result in the cirrhotics was significantly higher than in the alcoholics without cirrhosis (38.5% vs 8.8%, P less than 0.01). However, the positive results in the cirrhotics were associated with high gammaglobulin concentrations, and optical density values in the assay correlated closely with serum globulin (r = 0.73, P less than 0.01). The findings suggest that serum from patients with alcoholic cirrhosis may contain a component that give false-positive results in the assay.

Biopsy↗
PubMed1990

[Modification of selected lipoproteins and blood pressure by different dosages of n-3-fatty acids].

125 male patients with cardiovascular diseases (51.0 +/- 5.1 years) were treated with supplementary fish oil diet (gelatin capsules 2 g or 6 g PUFA/a day) and arachis oil gelatin capsules, respectively, as well as simultaneous fat- and energy-reduced diet at a moderate body-training during a four-week cure. N-3 PUFA-rich fish oil diet caused a significant decrease of the triglycerides and the Apo B with increase of the HDL2 cholesterol. By addition of reduction diet the effect became clearer by additional ascertained decrease of total and LDL-cholesterol. The blood pressure-reducing effect of n-3 PUFA, but not n-6 PUFA, at test as well as on exertion was present with 2 g and 6 g/a day, however, it was more conspicuous with the higher dosage.

Angina Pectoris↗
PubMed1989

[Modification of the atherogenic risk factor Lp(a) by supplementary fish oil administration in patients with moderate physical training].

Influence of supplementary fish oil diet in patients with moderate physical training on the atherogenic risk factor Lp(a) 32 male patients (mean age 54.0 +/- 5.8 years) were treated with supplementary fish oil intake (8 ml/d) and daily moderate swim training (20 to 30 min) for four weeks. In 22 of the 32 patients lipoprotein Lp(a) was reduced significantly by 25.0%, apolipoprotein (apo) B by 11.4%, apo A I by 7.8%, triglycerides by 38.3%, and cholesterol by 12.3%. Possibly caused by too low dosed fish oil no drop of Lp(a) was seen in ten patients. Caloric reduced diet (5000 kJ/d) did not effect additional decrease of the Lp(a) level. A control group of 22 male patients (52.9 +/- 5.7 control group of 22 male patients (52.9 +/- 5.7 years) trained in the same way received a supplementary peanut oil diet (8 ml/d). There was no influence on Lp(a) by n-6 PUFA but cholesterol and triglycerides dropped significantly.

Combined Modality Therapy↗
PubMed1987

[Sports therapy in obesity and lipid metabolism disorders].

Lack of movement is an essential cause for the development of obesity and dys- and hyperlipoproteinaemias. These disturbances of metabolism are risk factors for the development of the early coronary heart disease. The medicamentous treatment of these diseases can be decisively supported by dosed application of athletic exercises (sports therapy). Persevering athletic exercises of at least 30 min duration increase the activity of lipocatabolic enzymes (lipoprotein lipase, serum-lecithin-cholesterol-acyl transferase). As measure of exercise in sports therapy perseverance-orientated kinds of sport of altogether 2 hours a week are recommended.

Cholesterol↗
PubMed1987

[An eicosapentaenoic acid-rich diet in relation to a reducing diet and physical training].

The effect of a mackerel diet alone or in connection with reducing diet and physical training has been tested during 4 weeks in 49 male patients with cardiovascular diseases undergoing a cure and in 45 males with healthy metabolism. 1st group: 15 persons with healthy metabolism, 240 g/die supplementary mackerel diet, no physical training; 2nd group: 16 cure patients with reducing diet (5,000 kJ/d), no mackerel diet, no physical training; 3rd group: 14 cure patients with reducing diet and a proportion of mackerels of 125 g/d, no physical training; 4th group: 19 cure patients with reducing diet and mackerel diet 125 g/d as well as daily swimming training (20 to 30 min). The decrease of beta-C and Apo B was most distinct in groups 3 and 4 and lay between 21 and 35%. The combination reducing diet with proportion of mackerels proved to be most effectively for the decrease of the atherogenic LDL and was superior to the monotherapies. A significant increase of the HDL (measured in alpha-C and Apo A) took place only in group 4 with simultaneous performance of physical training, alpha-C increased by 31 and Apo A by 8%.

Adult↗