Renal responsiveness to parathyroid hormone in a case of nonfamilial hypophosphatemic osteomalacia

Summary Plasma immunoreactive parathyroid hormone level, urinary excretion of adenosine cyclic 3,5-monophosphate (cyclic AMP) and the sensitivity of the renal tubule to calcium infusion and to parathyroid extract were investigated in a patient with nonfamilial hypophosphatemic osteomalacia. Plasma immunoreactive parathyroid hormone concentration was normal and basal urinary excretion of cyclic AMP was increased. Renal cortical adenylate cyclase, as measured by urinary cyclic AMP excretion, was certainly as sensitive to exogenous parathyroid extract as in normal subjects. After a previous calcium infusion, a greater parathyroid-hormone-sensitive component of phosphorus transport in the kidney was present than in two control subjects. Our results indicate that in nonfamilial hypophosphatemic osteomalacia the renal tubule could be hyperresponsive to parathyroid hormone.This work was supported by a grant (n^o 20,463) from the Belgian Nationaal Fonds voor Geneeskundig Wetenschappelijk Onderzoek     

On the secretagogue effect of dibutyryl cyclic AMP in the rat exocrine pancreas

Summary DbcAMP0.1 mM induces the discharge of exportable enzymes from rat pancreas fragments incubated in vitro. This effect is qualitatively similar to the action of physiological secretagogues acting via hormone receptors: 1) it is accompanied by the appearance of exocytotic images at the acinar cell apex; 2) it is energy dependent but energy supply is low while that required for the carbamylcholine or caerulein response is high and can only be afforded by oxidative phosphorylation; 3) it is calcium dependent, but no alteration of inward or outward calcium movement can be observed; 4) it is altered by agents known to disrupt the microfilamentous microtubular system [41]. However, the secretory response to DbcAMP is quantitatively less than that obtained with hormonal stimuli. A damaging effect of DbcAMP on pancreatic acinar cells is ruled out on histological and biochemical grounds: there is no significant leakage of LDH; protein synthesis, 2-deoxy-d-glucose andl-leucine uptake are unaltered. The secretagogue effect of DbcAMP is reversible, dose-related and specific. It is not mediated by neuro-transmitter release or by interaction with their receptors. The evidence presented points to a direct interaction of DbcAMP on the pancreatic acinar cell and suggests the last step of the secretory cycle as the most probable site of action of the nucleotide derivative.Abbreviations cAMP Adenosine-3,5-monophosphate - cyclic DbcAMP: N⁶-2-O-Dibutyryl-adenosine-3,5-monophosphate, cyclic - DbcGMP N²-2-O-Dibutyryl-guanosine-3,5-monophosphate, cyclic - 5-AMP Adenosine-5-monophosphate - TCA Trichloracetic acid - ATP Adenosine triphosphate - NADH Nicotinamide-adenine dinucleotide - Tris Tris-(hydroxy-methyl) amino-methane - EGTA Ethylene glycol-bis ( aminoethylether)-NN-tetraacetic acid - LDH Lactic dehydrogenase Part of this work has been presented in abstract from at the VIIIth Symposium of the European Pancreatic Club, Toulouse, France, October, 1975, 23rd–25th and at the Biochemical Society of Belgium [40]This work was partially carried out under contracts from the Ministère de la Politique Scientifique within the framework of the Association Euratom—University of Brussels—University of Pisa, and the Institut National de la Santé et de la Recherche Médicale (France)     

Parathyroid hormone, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D concentration in elderly patients

Summary In 50 patients of a geriatric hospital (33 women, aged 65–96 years, mean age 80 years, and 17 men, aged 68–91, mean age 78.3 years) calcium, albumin, phosphate, urea, creatinine, parathyroid hormone, 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D were determined. Forty patients with serum creatinine levels up to 1.4 mg/dl (124 mol/l) and 10 patients with creatinine concentrations 1.5 mg/dl (132mol/l) were evaluated. In patients with normal creatinine, a positive correlation was found between parathyroid hormone and age (r=0.41;P<0.01). In patients with elevated creatinine, negative correlations were found in 1,25-dihydroxyvitamin D and calcium (r=–0.724;P<0.05), 1,25dihydroxyvitamin D and creatinine (r=–0.79;P<0.01) and 1,25-dihydroxyvitamin D and phosphate (r=–0.87;P< 0.002). The best correlation was observed in patients with elevated serum creatinine for 1,25-dihydroxyvitamin D and phosphate (r=–0.91;P< 0.001). The results suggest that low levels of calcium and phosphate stimulate the 1-hydroxylation of 25-hydroxyvitamin D even in advanced age and that the calcium metabolism of these patients is frequently disturbed. Nineteen patients had low levels of 25-hydroxyvitamin D, indicating an insufficient supply of vitamin D or rare exposure to sunlight. In 49 of 50 patients, one ore more of the parameters of calcium metabolism were outside the normal range.Abbreviations 25-OH-D 25-hydroxyvitamin D - 1,25(OH)₂D 1,25-dihydroxyvitamin D - PTH parathyroid hormone Supported by the Deutsche Forschungsgemeinschaft (Schm 405–407)     

Characteristics of aggregated immunoglobulin G as an immunologic phagocytic stimulus for granule enzyme release from human neutrophils

Aggregated immunoglobulin G (AggIgG) induced a time- and concentration-dependent phagocytic release of granule-associated lysozyme and myeloperoxidase (MPO) from human neutrophils. Degranulation was significantly enhanced in the presence of calcium or magnesium, and maximum granule exocytosis was observed when both divalent cations were present. AggIgG-stimulated enzyme release was inhibited with the intracellular calcium antagonist, TMB-8[8-(N, N-diethyl-amino)-octyl-(3,4,5-trimethoxy)benzoate] in the absence of extracellular calcium, DIDS (4,4-diisothiocyano-2,2-disulfonic acid stilbene), a permeant anion channel blocker, also suppressed AggIgG-induced degranulation. Cycloheximide, an inhibitor of protein synthesis, enhanced granule exocytosis from AggIgG-treated neutrophils. Two inhibitors of transmethylation reactions, 3-deazaadenosine (3-DZA) and homocysteine thiolactone (HCTL) in combination, suppressed AggIgG-elicited granule enzyme release. These data indicate that AggIgG is a useful probe for investigating the requirements for phagocytic enzyme release from human neutrophils.     

Differences in antigenic properties of Fc-binding activity during infection with herpes simplex virus type 1

Summary The antigenic properties of the Fc receptor induced by herpes simplex virus type 1 (HSV-1) were studied with anti-HSV F(ab)₂ and pFc from infected rabbits.It appeared that the HSV-induced Fc-binding receptor had different antigenic characteristics at different times after infection. The Fc receptor present early in the infection (0.5 hours), during the adsorption period, most probably is the result of a fusion event between the virus envelope and the infected cell. We found that this Fc receptor reacted with anti-HSV F(ab)₂ and thus showed HSV-antigenic properties in such a way that binding of anti-HSV F(ab)₂ prevented the binding of pFc fragments.Later on in the infection (5 hours), the Fc-binding activity present on the surface of the infected cell is the result of newly synthesized and in the plasma membrane integrated polypeptides. The Fc-binding activity present on the cell surface of 5 hours infected cells could not be inhibited by anti-HSV F(ab)₂ and did not interfere with the binding of pFc to the Fc receptor.With 1 Figure     

Dissociation of acetylcholine- and cyclic GMP-induced currents inXenopu oocytes

InXenopus follicular oocytes, activation of muscarinic receptors evokes a slow potassium current (H-response); a similar current is evoked by intracellular injection of cyclic guanosine 3,5-monophosphate, cGMP (Dascal et al. 1984). We have tested the hypothesis that cGMP may be the second messenger that mediates the opening of K channel by acetylcholine (ACh). ACh elevated the intracellular level of cGMP with a time course similar to that of the development of the muscarinic H-response; maximal increase in cGMP concentration above the control was about 0.2 pmole/oocyte. The amount of injected cGMP that produced a detectable K current (threshold dose) varied between 0.5 and 3 pmole/oocyte. At low doses of cGMP, the slope of log dose-log response curve was about 2.5, suggesting involvement of a biochemical process with a positive cooperativity of at least 3. Higher doses of cGMP evoked, in addition to the outward current, an irregular, rapidly developing, long-lasting inward current, that never reached amplitudes comparable to those of ACh-evoked Cl currents. The K current elicited by cGMP was insensitive to elevation or depletion of external Ca. It was potentiated by isobutylmethylxanthine (IBMX). ACh strongly inhibited the cGMP-evoked K current when applied at the plateau of the latter. 4-Phorbol 12,13-dibutyrate (PDBu) (1 M) rapidly and completely inhibited the cGMP response. It is concluded, that most of the results presented in this report contradict the hyothesis that cGMP is the intracellular mediator of ACh-induced changes in membrane conductance in the oocytes.Abbreviations ACh acetylcholine - cAMP cyclic adenosine 3,5-monophosphate - cGMP cyclic guanosine 3,5-monophosphate - EGTA ethylenediaminetetraacetic acid - Hepes N-2-hydroxyethyl-piperazinc-N-2-hydroxypropanesulphonic acid - IBMX 3-isobutyl-l-methylxanthine - IP₃ inositol 1,4,5-trisphosphate - PDBu 4-phorbol 12,13-dibutyrate     

Specific Interaction of a 25-kilodalton Cellular Protein,a 40S Ribosomal Subunit Protein,with the Internal Ribosome Entry Site of Hepatitis C Virus Genome

Translation initiation of hepatitis C virus (HCV) RNA is controlled by an internal ribosome entry site (IRES) contained in 5 noncoding region (NCR) and in several nucleotides of the coding region. The ability of a 25-kilodalton cellular protein (p25) to bind the HCV 5 NCR is correlated with the efficiency of translation initiation of HCV RNA, indicating that this protein plays a critical role in HCV translation (S. Fukushi, C. Kurihara, N. Ishiyama, F. B. Hoshino, A. Oya, and K. Katayama, J Virol 71, 1662–1666, 1997). We have extended the study for identification of the IRES region required for p25 binding. For this purpose, we have performed UV cross-linking competition analyses using 5- or 3- deleted mutants of the HCV 5 NCR as competitor RNAs for binding of p25 to wild-type HCV 5 NCR. Competitor RNAs lacking nucleotides (nt) 47–74 or nt 279–331 did not inhibit p25 binding to the HCV IRES, indicating that these regions are necessary for interaction of the p25 and HCV IRES. Since p25 binding was not observed in the IRES elements of encephalomyocarditis virus and poliovirus in UV cross-linking competition analyses, the p25 binding may be specific for the HCV IRES. p25 bound to the HCV IRES was detected when a purified 40S ribosomal subunit was used for UV cross-linking experiment, indicating that p25 is one of 40S ribosomal subunit proteins. These results reveal an unique interaction between the 40S ribosomal subunit and HCV IRES to contribute to translation initiation of the HCV genome.     

Stereochemical aspects of the interaction of myosin and actomyosin with nucleotides

Summary The five possible analogues of ATP and the three possible analogues of ADP which contain single non-bridging sulphur atoms instead of oxygen in the polyphosphate structure have been used as probes of the interaction of nucleotides with myosin and actomyosin. Evidence is presented for the requirement of an , , -tridentate complex of magnesium and ATP as the substrate for myosin. Of the four possible tridentate MgATP diastereomers, the exo isomer (nomenclature of Cornelius & Cleland, 1978) appears to be the actual substrate.Abbreviations ATP Adenosine-5-O-triphosphate - ATP(-S) Adenosine-5-O-(1-thiotriphosphate) - ATP(-S) Adenosine-5-O-(2-thiotriphosphate) - ATP(-S) Adenosine-5-O-(3-thiotriphosphate) - ADP Adenosine-5-O-diphosphate - ADP(-S) Adenosine-5-O-(1-thiodiphosphate) - ADP(-S) Adenosine-5-O-(2-thiodiphosphate) - Enzyme Myosin ATPase (EC 3.6.1.3)     

Further characterization of the slow muscarinic responses inXenopus oocytes

In immature follicular ocytes of the frogXenopus laevis, application of muscarinic agonists evokes a complex response consisting of a fast and a slow Cl currents (the dominant responses), Cl current fluctuations, and a less prominent slow K current. The characteristics of the slow ACh-evoked potassium current were studied using the two-electrode voltage clamp method, and compared to those of the ACh-evoked Cl currents. In experiments designed to study the K current response separately, without the interference of ACh-evoked Cl currents, the holding potential was set close or equal to Cl equilibrium potential (measured as the reversal potential of the ACh-evoked Cl current). The Cl current responses were studied in cells that had negligible K current response. The dose-response curve of the potassium response followed classical Michaelis-Menten kinetics. The dose-response characteristics of the slow ACh-evoked Cl current displayed a positive cooperativity of at least 3. In spite of this difference, kinetic analysis revealed that these two responses, as well as the fast Cl current response that was characterized earlier (Dascal and Landau 1982), had almost identical apparent equilibrium dissociation constants (0.29–0.39 M), suggesting involvement of a single receptor class. Both K and Cl currents were reduced (to 32–56% of control) by millimolar concentrations of phosphodiesterase (PDE) inhibitors, theophylline and isobutylmethylxanthine. Elevation of extracellular Ca concentration from 1 to 10 mM doubled the K current; depletion of external Ca caused a partial inhibition of this response. The K current was potentiated by 0.1 M 4-phorbol 12,13-dibutyrate (PDBu). Ca-dependence of the ACh-evoked K current resembles that of ACh-evoked Cl currents, described earlier, and suggests mediation by a similar mechanism, i.e. mobilization of Ca from intracellular stores. On the other hand, most of the features described here are in a sharp contrast to those reported for adenosine-evoked, cAMP-mediated slow K current. Thus, we suggest that purinergic and muscarinic receptors inXenopus follicular oocytes are coupled to potassium channels through different molecular mechanisms.Abbreviations ACh acetylcholine - cAMP cyclic adenosine 3,5-monophosphate - cGMP cyclic guanosine 3,5-monophosphate - EGTA ethylenediaminetraacetic acid - Hepes N-2-hydroxyethylpiperazine-N-2-hydroxypropanesulphonic acid - IBMX 3-isobutyl-1-methylxanthine - IP₃ inositol 1,4,5-trisphosphate - PDBu 4-phorbol 12,13-dibutyrate - PDE phosphodiesterase     

Concomitant increase in plasma atrial natriuretic peptide and cyclic GMP during volume loading

Summary To investigate the effects of fluid expansion on endogenous atrial natriuretic peptide (ANP) and cyclic 3,5-guanosine monophosphate (cGMP), four male volunteers were studied before, during and after intravasal volume loading. Volume expansion was performed by intravenous infusion of 2,000 ml isotonic saline solution within 30 min. Mean plasma ANP levels increased 2.5-fold from 31.2 pg/ml to 81.7 pg/ml 40 min after the start of infusion. Plasma cGMP levels paralleled the rise in ANP, shwoing a mean cGMP increment from 2.7 pmol/ml to a maximum of 8.2 pmol/ml. Both ANP and cGMP levels were back to basal levels 120 min after termination of the infusion. Stimulation of endogenous ANP release by volume loading suggests that ANP is involved in the regulation of fluid homeostasis in man. The parallel rise in plasma cGMP levels supports the idea that cGMP is a mediator for the effects of ANP.Abbreviations ANP atrial natriuretic peptid - cGMP cyclic 3,5-guanosine monophosphate - PRA plasma renin activity     

Impermeant stilbene disulfonic acids block chemotactic peptide receptor function on human granulocytes

Anion transport is important in a variety of cell functions. 4,4-Diisothiocyanostilbene-2,2-disulfonic acid (DIDS) and 4-acetamido-4-isothiocyanostilbene2,2-disulfonic acid (SITS) are two impermeant agents that have been reported to specifically block the anion channel in erythrocytes. These agents block several responses of human neutrophils to stimulation by immune complexes, the synthetic chemotaxinN-formyl-met-leu-phe (FMLP), and a calcium ionophore. They also alter the function of C3b receptors on the neutrophil surface. We studied the effects of DIDS and SITS on the aggregation of human neutrophils, a process that has been implicated in a number of diverse clinical syndromes. Both DIDS and SITS inhibited granulocyte aggregation induced by FMLP, zymosan-activated plasma, 12-O-tetra-decanoylphorbolmyristate acetate (TPA), and the calcium ionophore A23187. To further study the mechanism of inhibition the effects of DIDS and SITS on FMLP-receptor function were tested. Similar concentrations of the anion channel blockers also inhibited binding of radiolabeled FMLP to its specific receptor on the neutrophil surface. Inhibition of binding was due to a decrease in both the number and affinity of the surface receptors available for FMLP; DIDS did not inactivate FMLP. The effects of stilbene disulfonic acid on cell function may be due to effects of these agents on other cell-surface structures in addition to the anion channel.Supported in part by National Institutes of Health grant R01-CA 36248, the University of Minnesota Graduate School Grant-in-Aid 0325-4909-73, the Leukemia Task Force, and the Masonic Memorial Hospital Fund, Inc. Appears in part in abstract form inClin. Res. 28: 312, 1980 and34: 958A, 1986.     

Selection and characterization of pyrG mutants of Penicillium chrysogenum lacking orotidine-5′-phosphate decarboxylase and complementation by the pyr4 gene of Neurospora crassaa

Summary Pyrimidine auxotrophs of Penicillium chrysogenum have been isolated at a high frequency among mutants resistant to 5-fluoroorotic acid (5.2 mM). Some of the pyrimidine auxotrophs (e.g. strain pyrG1) showed no reversion. A radiometric assay based on the conversion of (6-¹⁴C)orotidine 5-monophosphate (OMP) into (6-¹⁴C)uridine 5-monophosphate (UMP) was developed to determine OMP-decarboxylase activity. One of the pyrimidine auxotrophs (P. chrysogenum pyrGl) was studied in detail. It was deficient in OMP-decarboxylase activity, whereas the parental strain (P. chrysogenum Wis. 54-1255) showed a normal enzyme activity. A five-fold higher OMP-decarboxylase activity was found in a P. chrysogenum pyrGI clone transformed with plasmids containing the Neurospora crassa pyr4 gene (which codes for the same enzyme).Abbreviations OMP orotidine 5-monophosphate - UMP uridine 5-monophosphate     

Parathyroid Hormone Secretion by Brain and Pituitary of Sheep

Summary The secretion of immunoreactive PTH by different brain regions and pituitary of sheep was studied in vitro. Separate tissue samples of gyrus, internal capsule, basal ganglia, cerebellum, and pituitary were incubated in culture medium with low, normal, and high Calcium (Ca) (0.7 mM, 1.2 mM and 2.4 mM) concentrations. PTH release in medium containing low Ca were observed by all samples. The concentrations increased in the fifth and sixth hour from 100% (1st hour basis value) up to 300%. The PTH release showed an inverse relationship to the Ca concentration in the culture medium. To induce any significant decrease in medium concentrations of PTH, 1.25(OH)₂D (100 ng/ml) was added to the culture medium. This effect could be reversed by DB-cAMP. Our results indicate that secretion of immunoreactive PTH by brain and pituitary of sheep may occur in vitro. The secretion depends on the content of Ca, 1.25(OH)₂D, and DB-cAMP.Abbreviations ACTH Adrenocorticotrophic hormone - Ca Calcium - CNS Central nervous system - cAMP Cyclic adenosine 3,5-monophosphate - CT Calcitonin - DB-cAMP Dibutyryl-cyclic adenosine 3,5-monophosphate - 1.25(OH)₂D Dihydroxyvitamin D - Leu-ENK Leucine-enkephalin - Mg Magnesium - Met-ENK Methionine-enkephalin - PTH Immunorective parathyroid hormone - TSH Thyroid stimulating hormone - T₄ Thyroxine - T₃ Triiodothyronine     

Two polymorphicAvaI andHhaI sites in a differentially methylated region of the human H19 gene

Summary The H19 gene is paternally imprinted both in the human and mouse (Bartolomeiet al., 1991; Zhang and Tycko, 1992), although its expression pattern seems somewhat different between the two species (Jinno,et al., 1995). DNA-methylation is a promising candidate for a parent-of-origin mark of the gene, and a paternal allele-specific methylation imprint was recently identified at the mouse H19 locus (Tremblayet al., 1995). We found a 50% methylated region in the human H19 gene (Jinno, unpublished data). A search for polymorphisms in this region revealed two novelAvaI andHhaI RFLPs, which contribute to the detection of allele-specific methylation at the human H19 locus.PCR primers for the AvaI-site PANL2 5-GAGCCTGCCAAGCAGAGCG-3 - PANR2 5-CACATAAGTAGGCGTGACTTGA-3 PCR primers for the HhaI-site ASMA 5-CAATGAGGTGTCCCAGTTCCA-3 - PANR2 5-CACATAAGTAGGCGTGACTTGA-3     

Reduced bone mineral density and low parathyroid hormone levels in patients with the adult form of hypophosphatasia

Summary Hypophosphatasia is a heritable metabolic bone disease with characteristically reduced levels of alkaline phosphatase (ALP) in the blood, liver, kidney and bone. ALP levels are normal in the intestine and placenta. About 300 patients have been reported so far in the literature. Three kindreds with 52 known subjects are described here, whereby 12 subjects could be examined osteologically. Four subjects were patients and had clinical signs of the disease: spontaneous fractures of the metatarsals or femora and low ALP serum levels ranging between 8 and 23 U/1 (normal range 40–170 U/1). Four other members without fractures had reduced ALP levels; they might be carriers of the disease and develop symptoms later in life. The four remaining subjects had normal ALP levels and no signs of the disease. Serum levels of intact parathyroid hormone (iPTH) were found to be in the lower normal range and serum calcium levels in the upper normal range. There was a significant (P<0.05) negative correlation between iPTH and serum calcium levels (r=–0.78). Urinary calcium excretion was increased in 3 subjects with fractures. 25-OH-D₃ levels were increased in 6 of 8 subjects without any treatment. The bone mineral density (BMD) was measured using dual X-ray absorptiometry of the lumbar spine, representing mainly trabecular bone, and single-photon absorptiometry of the forearm, measuring mainly cortical bone. Z-scores of the spinal bone mass ranged between 0.38 and –1.95 SD; Z-scores of the forearm bone mass ranged between 0.53 and –2.47 SD with the lowest values in patients with fractures. There was a significant (P<0.05) correlation between serum ALP levels and forearm BMD (r=0.83). We conclude from these data that patients with the adult form of hypophosphatasia have decreased forearm and subnormal spinal bone mass, as well as reduced serum levels of iPTH.Abbreviations BMD bone mineral density - ALP alkaline phosphatase - iPTH intact parathyroid hormone - 25-OHD₃ 25-hydroxyvitamin D₃ - SD standard deviation - PEA phosphoethanolamine - PPi inorganic pyrophosphate - PLP pyridoxal-5-phosphate - cDNA clonal desoxyribonucleic acid - U/S Ca²⁺ urinary/serum calcium - DXA dual X-ray absorptiometry - DPA dual photon absorptiometry - SPAD bone density of distal forearm measured by single photon absorptiometry - SPAP bone density of proximal forearm measured by single photon absorptiometry     

Translation enhancer in the 3′-untranslated region of rotavirus gene 6 mRNA promotes expression of the major capsid protein VP6

Summary. The eleven rotavirus mRNAs contain 5-cap structures and most end with the 3-consensus sequence 5-UGACC-3. The UGACC functions as a common translation enhancer (3-TE-con) that upregulates viral protein expression through a process mediated by the nonstructural protein NSP3. To address the possibility that gene-specific enhancers are also contained in the untranslated regions (UTRs) of the rotavirus mRNAs, we used rabbit reticulocyte lysates to investigate the translation efficiencies of analog RNAs containing viral-specific 5-and 3-UTRs and the open reading frame for chloramphenicol acetyltransferase. These experiments combined with the analysis of full-length viral RNAs and RNAs containing 3-truncations showed that a highly active enhancer was present near the 5-end of the 139-nucleotide 3-UTR of the gene 6 mRNA (3-TEg6). The 3-TEg6 represents a functionally independent enhancer, as no other portion of the gene 6 mRNA was required for its activity. The 3-TEg6 differs significantly from the 3-TE-con in that the gene 6-specific enhancer does not require viral protein for activity and is formed by a sequence unique to only one of the eleven viral mRNAs. Together, our findings suggest that the 3-UTR of the gene 6 mRNA contains two TEs, one is gene-specific (3-TEg6) and the other is common to nearly all rotavirus genes (3-TE-con). The activity of the 3-TEg6 is likely important for directing the efficient translation of the gene 6 mRNA at levels sufficient to provide the 780 copies of VP6 necessary for the assembly of each progeny virion.     

Molecular mechanisms of neuronal plasticity during learning: The role of secondary messengers

We present published data along with our own results concerning the role of second messengers and their intracellular receptors in molecular mechanisms associated with the plasticity of neurons during learning. The participation of cyclic 3,5-adenosine monophosphate, cyclic 35-guanosine monophosphate, calcium, calmodulin, and also the metabolic products of inositol phospholipids, inositol-1,4,5-triphosphate, diacylglycerol and the protein kinase C activated by it, arachidonic acid, and the products of its lipoxygenase oxidation during the regulation of neuronal plasticity over the course of prolonged potentiation, sensitization, habituation, and classical associative training are discussed.Translated from Zhurnal Vysshei Nervnoi Deyatel'nostiimeni I. P. Pavlova, Vol. 39, No. 2, pp. 195–214, March–April, 1989.     

Prostaglandin-mediated hypercalcemia: A paraneoplastic syndrome

Summary Evidence has been presented for prostaglandin-mediated hypercalcemia and bone resorption in malignancies of both, experimental animals and man. Occurrence of hypercalcemia in cancer patients is known for a long time, but its pathogenesis has been poorly understood so far. Besides ectopic parathyroid hormone secretion by tumors, an osteoclastactivating factor released from leukocytes and direct bone destruction by tumor cells, prostaglandins of the E series have to be considered as one of the candicates involved in the pathomechanism of hypercalcemia and osteoclastic osteolysis in cancer patients. This new concept on the pathophysiology of cancer-associated hypercalcemia has implications for the diagnosis and management of this common complication of neoplastic disease.

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Abbreviations used cAMP cyclic adenosine 3:5-monophosphate - cr creatinine - NSAI drugs nonsteroidal antiinflammatory drugs - OAF osteoclast-activating factor - PG prostaglandin - 15-K-H₂-PG's 15-keto-13,14-dihydro-PG's - H₂-PGE₂ 13,14-dihydro-PGE₂ - PGE-M 7-hydroxy-5,11-diketotetranorprostane-1,16-dioic acid - PGF-M 5, 7-dihydroxy-11-ketotetranorprostane-1,16-dioic acid - PTH parathyroid hormone - Tx thromboxane     

Studies on sarcoplasmic reticulum from slow-twitch muscle

Summary Vesicles were isolated from membranes of the sarcoplasmic reticulum (SR) of rabbit slow-twitch muscle by differential and sucrose density gradient centrifugation after homogenization. In some experiments, the vesicles were further fractionated by loading them with calcium oxalate followed by centrifugation in a sucrose density gradient.Protein composition of the isolated vesicles was complex and differed from the protein composition of fast-twitch muscle vesicles. However, other protein components, which were also present in fast-twitch muscle SR vesicles, have been identified: Ca²⁺-dependent ATPase, calsequestrin, 160 000 molecular weight glycoprotein and 53 000 molecular weight glycoprotein. The amount of the Ca²⁺-dependent ATPase and calsequestrin was several times lower in the slow-twitch muscle SR vesicles. This has been observed in both the original and the loaded vesicles.The slow-twitch muscle SR vesicles showed active calcium transport, Ca²⁺-dependent ATPase activity, and the formation of the phosphorylated intermediate under conditions similar to those established for fast-twitch muscle SR. However, these activities, when expressed per mg of total protein, were several times lower than the analogous activities in the SR vesicles isolated from fast-twitch skeletal muscle. When the same enzyme activities were expressed per mg of the 105 000 molecular weight ATPase, the values obtained were very similar in both kinds of vesicles.The results indicate that the slow rate of calcium transport, found in slow-twitch muscle SR vesicles, may be related to a low content of the calcium-transporting ATPase in the membrane.Abbreviations Acid phosphatase Orthophosphoric monoester phosphohydrolase (EC 3.1.3.2) - ATP Adenosine triphosphate - ATPase Adenosine triphosphatase (EC 3.6.1.3) - DFP Di-isopropylfluorophosphate - EGTA Ethylene glycol bis (-aminoethyl ether)-N,N-tetraacetic acid - ENDO H ENDO-B-N-acetylglucosaminidase H (Streptomyces griseus) (Health Research, Inc., Albany, New York, U.S.A.) - Glucose-6-phosphatase d-Glucose-6-phosphate phosphorylase (EC 3.1.3.9) - 5-Nucleotidase 5-Ribonucleotide phosphohydrolase (EC 3.1.3.5) - PMSF Phenylmethyl sulphonylfluoride - Phosphorylaseb Glycogen phosphorylaseb (EC 2.4.1.1) - SDS Sodium dodecyl sulphate - Stains-all [1-Ethyl-2-[3-(1-ethylnaphthol[1,2d]thiazolin-2-ylidene)-2-methylpropenyl]-naphthol[1,2d]-thiazolium bromide (Kodak Organic Chemicals) - Succinate dehydrogenase succinate cytochromec reductase (EC 1.3.3.99.1)     

Ca2+-Mg2+-ATPase activity of human red blood cells in healthy and diabetic volunteers

Summary The present investigation was dedicated to support biochemical interpretations of well-known long-term microvascular complications in diabetes. Provided the hypothetical correlation between erythrocyte membrane rigidity and increased intracellular calcium content holds true, a reduced Ca²⁺-Mg²⁺-ATPase activity in diabetic subjects could represent the underlying biochemical mechanism. Thus, we have compared basal and calmodulin-activated ATPase activity in healthy and diabetic volunteers. We could demonstrate a significant reduction of basal and stimulated enzyme activity in diabetic subjects. Furthermore, partial purification of calmodulin from erythrocytes of diabetic patients and healthy subjects yielded experimental evidence that reduced enzyme activity in diabetic volunteers is due to an altered basal activity as well as to a reduced stimulation by calmodulin.Abbreviations ATP Adenosine 5-triphosphate - ATPase Adenosine 5-triphosphatase - DEAE Diethylaminoethyl - EDTA Ethylenediamine tetraacetate - EGTA Ethyleneglycol-bis-(-aminoethyl ether)N,N-tetraacetic acid - P_i Inorganic phosphate - Tris Tris(hydroxymethyl)aminomethane