Defective regulation of the cytosolic Ca2+ activity in parathyroid cells from patients with hyperparathyroidism

The parathyroid hormone (PTH) release and cytosolic Ca²⁺ activity were determined in normal bovine parathyroid cells and parathyroid cells obtained from patients with hyperparathyroidism (HPT). There was a sigmoid relation between the cytosolic Ca²⁺ activity and the extracellular calcium concentration between 0.5 and 6.0 mmol/l. The PTH release was inhibited in parallel with the rise in the cytosolic Ca²⁺ activity. Both the hormone release and the cytosolic Ca²⁺ activity were lower in cells from human adenomas and hyperplastic glands~ and in comparison with the bovine preparations these ceils had higher set points for the cytosolic Ca²⁺ activity and PTH release. There was a close correlation between the individual set points for the cytosolic Ca²⁺ activity and PTH release in a material containing both normal and pathological cells. The results indicate that the abnormal PTH release characteristic of HPT is due to a defective regulation of the cytosolic Ca²⁺ activity.     

Methanol conversion in Eubacterium limosum

The conversion of methanol by cell-free extracts of the acetogenic bacterium Eubacterium limosum was studied. Incubation of mixed cell-free extracts of both E. limosum and Methanobacterium formicicum resulted in methane formation from methanol in the presence of ATP and 2-mercaptoethanesulfonic acid. The separate extracts were not able to perform this reaction. Addition of ferredoxin obtained from Methanosarcina barkeri to the mixed extracts resulted in increased methane formation. The enzyme, responsible for methanol binding in cell-free extract of E. limosum, was inactivated by FAD under N₂ and exhibited maximal activity under an atmosphere of H₂. This enzyme contains a firmly bound cobalamin which was methylated by methanol in the presence of ATP. It was demethylated in the presence of methylcobalamin: coenzyme M methyltransferase obtained from M. barkeri under concomitant formation of methylated coenzyme M. These properties are similar to those of methanol: 5-hydroxybenzimidazolylcobamide methyltransferase from M. barkeri. It was proposed that methylotrophic acetogens and methylotrophic methanogens use similar enzymes in the first step of methanol conversion.Abbreviations HS-CoM 2-mercaptoethanesulfonic acid - CH₃S-CoM 2-(methylthio)ethanesulfonic acid - BrES 2-bromoethanesulfonic acid - TES N-tris(hydroxymethyl)-methyl-2-aminoethanesulfonic acid - MT₁ methanol: 5-hydroxybenzimidazolylcobamide methyltransferase - MT₂ methylcobalamin - HS-CoM methyltransferase - DMBI 5,6-dimethylbenzimidazole and HBI, 5-hydroxybenzimidazole, are -ligands of corrinoids - (S-CoM)₂ 2,2-dithiodiethanesulfonic acid     

Effect of carbon source on enzymes involved in glycerol metabolism inNeurospora crassa

Specific activities of eight enzymes involved in glycerol metabolism were determined in crude extracts of three strains ofNeurospora crassa after growth on six different carbon sources. One of the strains was wild type, which grew poorly on glycerol as sole carbon source; the other two were mutant strains which were efficient glycerol utilizers. A possible basis for this greater effeciency of glycerol utilization was catabolite repression of glyceraldehyde kinase by glycerol in wild type, and two-fold higher glycerate kinase activity in the mutant strains after growth on glycerol, thus apparently allowing two routes for glyceraldehyde to enter the glycolytic pathway in the mutant strains but only one in wild type. The preferential entry of glyceraldehyde to the glycolytic pathway through glycerate was suggested by the lack of glyceraldehyde kinase in all three strains after growth on one or more of the carbon sources and the generally higher levels of aldehyde dehydrogenase and of glycerate kinase than of glyceraldehyde kinase.     

Lysozyme-promoted association of protein I molecules in the outer membrane of Escherichia coli.

Incubation of whole envelopes prepared from sonically oscillated Escherichia coli K-12 cultures with lysozyme in vitro resulted in the appearance of a protein species with an apparent molecular weight double that of outer membrane protein I. Similar dimers were also detected in purified outer membranes and whole envelopes from lysozyme-induced spheroplasts of E. coli K-12. This was confirmed by two-dimensional electrophoresis in which the dimers were resolved in the second dimension to run as single polypeptides of protein I. Formation of dimers was correlated with peptidoglycan degradation, but the ability of protein I molecules to associate may vary between strains of E. coli, since dimers were found only in outer membranes from E. coli W7. We suggest that extensive degradation of peptidoglycan leads to nonspecific formation of protein I aggregates, but that these aggregates do not occur in vivo.     

Origin of the left anterior descending coronary artery from the pulmonary artery: An unusual cause of angina in a middle-aged woman

A 48-year-old woman was admitted to our institution with angina pectoris and a systolic murmur. At cardiac catheterization, she was found to have an anomalous origin of the left anterior descending coronary artery from the pulmonary trunk. There was also an associated atrial septal defect and a bicuspid aortic valve.     

Identification of noncollagenous basement membrane glycopolypeptides synthesized by mouse parietal entoderm and an entodermal cell line

Using two-dimensional gel electrophoresis, we have identified two noncollagenous basement membrane (BM) glycopolypeptides which are synthesized by the mouse teratocarcinoma-derived parietal yolk sac (PYS) cell line. These glycopolypeptides have molecular weights of about 200,000 and isoelectric points of about 5.6. Polypeptides with identical parameters are synthesized by the parietal entodermal cells of mouse embryos and are found in Reichert's membrane. Pluripotent embryonal carcinoma cells (ECC) synthesize considerable amounts of the two polypeptides, whereas the yield from nullipotent ECC is negligible. The treatment of nullipotent F9 cells with retinoic acid, which induces entodermal differentiation, activates the synthesis of these polypeptides. These results indicate that the two polypeptides can be used as markers of parietal entoderm differentiation.     

Partial hypoxanthine-guanine phosphoribosyl transferase deficiency with full expression of the Lesch-Nyhan syndrome

Summary A patient with the full clinical expression of the classical Lesch-Nyhan syndrome is presented with a residual hypoxanthine-guanine phosphoribosyl transferase (HGPRT) activity of 5–10% in erythrocyte lysate and about 30% in fibroblast lysate. The activities of other erythrocyte enzymes of purine metabolism were typical for a classical Lesch-Nyhan patient. The effects of allopurinol therapy on the excretion of urinary purine metabolites were studied by a newly developed isotachophoretic technique.The unusually high residual activity of HGPRT in erythrodytes and fibroblasts of the patient enabled the enzymologic characterization of the mutant enzyme: in fibroblasts the affinities for the substrates hypoxanthine and guanine were normal. However, there was an increased apparent K _m for phosphoribosylpyrophosphate (PRPP), a complete absence of product inhibition by IMP and GMP, and a decreased heat stability. Addition of PRPP did not stabilize the mutant enzyme. In addition to the altered properties of the fibroblast enzyme, the K _m of the erythrocyte enzyme for hypoxanthine was also increased.Immunoprecipitation experiments revealed the presence of an approximately normal amount of material cross-reacting with anti-human HGPRT antiserum. However, it appeared that this cross-reacting material had a decreased stability. When intact erythrocytes were incubated with radiolabeled purine bases, no formation of IMP or GMP could be detected, despite the relatively high residual activity of HGPRT in the hemolysate. The results fit the following hypothesis: as a consequence of a structural mutation affecting the PRPP-site of the enzyme and a decreased heat stability, the activity of the mutant enzyme under in vivo conditions is virtually zero.In the erythrocytes of the patient's mother a normal HGPRT-activity was found. However, the activity in her fibroblasts was lower than normal, while a decreased heat stability and an intermediate behavior towards IMP could be shown.Hair root analysis of several members of the patient's family confirmed the heterozygosity of the mother, whereas no other heterozygotes could be detected. The family anamnesis did not show other cases of Lesch-Nyhan syndrome. These findings were taken as evidence that the patient described in this paper might represent a mutation orginating from the gametes in either of the maternal grandparents.