Serum biochemistry of the Arrau turtle (Podocnemis expansa): Frozen analyte stability and the effects of long-term storage.

BACKGROUND: Turtles are a major source of protein for riverside human populations in Brazil. The encouragement of commercial breeding meets conservation efforts for these animals, and it is, therefore, crucial to understand the physiologic and behavioral aspects of semi-aquatic species in captive conditions. Serum biochemical tests are ancillary diagnostic tools, and sample storage is a main problem since clinical laboratories are not always available near the habitats of these species. OBJECTIVES: The aim of this study was to provide information about the stability of albumin, aspartate aminotransferase (AST), calcium, creatinine kinase (CK), total cholesterol (Chol), alkaline phosphatase (ALP), gamma glutamyltransferase (GGT), total protein (TP), and urea at different storage times. METHODS: In all, 17 Arrau turtles (Podocnemis expansa) were used, and the serum obtained was separated into aliquots and analyzed at 0, 4, 8, 16, and 32 days after being stored at -20°C. RESULTS: The results showed that albumin, AST, CK, GGT, and TP suffered interference due to the long storage times. CONCLUSION: Analytes such as ALP, calcium, Chol, and urea can be evaluated for up to 1 month after freezing. Albumin, AST, and TP can be analyzed up to 1 week after freezing without alterations, and CK GGT are best evaluated on fresh samples.

Pediatric influenza-associated myositis - Nebraska, 2001-2007.

OBJECTIVE: Influenza-associated myositis (IAM), characterized by severe lower-extremity myalgia and reluctance to walk, is a complication of influenza among children. We investigated IAM in Nebraska during six influenza seasons, 2001-2007. METHODS: During 2006-2007, we requested reports of severe influenza illness among persons aged <18 years and investigated medical records to identify and confirm IAM cases defined as severe myalgia with elevated serum creatinine kinase level in a patient aged <18 years, occurring within 7 days of laboratory confirmed influenza illness onset. Statewide hospital discharge data (HDD) were reviewed to identify retrospectively confirmed IAM cases during 2006-2007 and five previous seasons, by using surveillance data to define periods of influenza activity. Statewide IAM incidence was estimated for 2001-2002 through 2006-2007. RESULTS: During 2006-2007, a total of 13 IAM cases were confirmed by enhanced surveillance. Median age was 6 years (range, 4-11 years). Influenza diagnosis was established by viral isolation from six patients (one influenza A and five influenza B) and rapid diagnostic tests for seven. Twelve (92%) patients, including one who died, were hospitalized for a median of 3 days (range, 1-4 days). Review of HDD identified 12 retrospectively confirmed IAM cases during 2006-2007, including four not reported through enhanced surveillance, and only one during five previous seasons (2003-2004). The HDD-derived, retrospectively confirmed statewide IAM incidence estimates/100,000 population aged <18 years were 2.693 and 0.225 during 2006-2007 and 2003-2004, respectively. CONCLUSION: An IAM epidemic occurred in Nebraska during the 2006-2007 influenza season.

Development of a comprehensive red blood cell enzymopathy laboratory in Thailand: the study of normal activity in eight erythroenzymes in Thais.

In order to provide a reference range for normal red blood cell enzyme activities in Thai, we analyzed data from 113 healthy non-anemic Thai people (55 males and 58 females) age 1-42 years, who all had a normal pattern of hemoglobin typing (HbA and HbA2 less than 3.5%). Hematological analysis was performed using an automated cell counter and the hemoglobin studies were carried out by low pressure liquid chromatography. Owing to a high frequency of alpha-thalassemia in Thailand, cases with an MCV < 75 fl were excluded from the study since these cases were likely to be heterozygotes for alpha0-thalassemia. Cases with reticulocytes > 2.5% were excluded from the study since reticulocytes have a higher enzyme activity than mature erythrocytes. Cases with abnormal red blood cell morphology, such as spherocytes and ovalocytes, were also excluded. These criteria were applied to select "normal" controls for our analysis. We assayed eight red blood cell enzyme activities in normal subjects: glucose-6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6PGD), pyruvate kinase (PK), hexokinase (HK), glucose phosphate isomerase (GPI), phosphofructokinase (PFK), aldolase (ALD) and phosphoglycerate kinase (PGK). The mean normal ranges (+/- SD) for G6PD, 6PGD, PK, HK, GPI, PFK, ALD and PGK were 12.7 (+/-2.2), 10.7 (+/-1.3), 18.5 (+/-4.0), 1.5 (+/-0.4), 80.5 (+/-11.8), 11.8 (+/-2.1), 4.5 (+/-1.6) and 370 (+/-43) IU/gHb, respectively. Age-dependent differences for the reference values for these enzyme activities were summarized. All red blood cell enzyme activities were highest during the early childhood period and slightly lower in the adult period. These values will be of clinically useful for future reference.

Typhoid myopathy or typhoid hepatitis: a matter of debate.

PURPOSE: The aim of the present study was to evaluate the major source of increased serum enzyme level in typhoid fever and to determine the most relevant clinical entity, hepatitis or myopathy, during typhoid fever. METHODS: A total of 118 subjects proved to have typhoid fever were evaluated for serum enzymes such as transaminases, alkaline phosphatase, lactate dehydrogenase (LDH) and creatinine kinase (CK); and their relation with each other, clinical symptoms and serum bilirubin were evaluated by regression methods. RESULTS: Hepatomegaly was revealed in 14% of the cases and was correlated with elevated serum biliribin (5.05 +/- 13.03 mg/dL in hepatomegalic subjects). Alanine aminotransferase (ALT) and CK were elevated in 22 and 60% of the cases, respectively. Correlation coefficient of CK with aspartate aminotransferase (AST) and LDH was R2 = 0.68 and 0.75, respectively, which were higher than that of ALT with that two enzymes. CONCLUSIONS: In conclusion, elevation of serum enzymes in typhoid is mostly of muscular origin.

The purine metabolism of human erythrocytes.

This review summarizes currently available information about a crucial part of erythrocyte metabolism, that is, purine nucleotide conversions and their relationships with other conversion pathways. We describe the cellular resynthesis, interconversion, and degradation of purine compounds, and also the regulatory mechanisms in the conversion pathways. We also mention purine metabolism disorders and their clinical consequences. The literature is fragmentary because studies have concentrated only on selected aspects of purine metabolism; hence the need for a synthetic approach.

Soluble purine-converting enzymes circulate in human blood and regulate extracellular ATP level via counteracting pyrophosphatase and phosphotransfer reactions.

Extracellular ATP and other purines play a crucial role in the vasculature, and their turnover is selectively governed by a network of ectoenzymes expressed both on endothelial and hematopoietic cells. By studying the whole pattern of purine metabolism in human serum, we revealed the existence of soluble enzymes capable of both inactivating and transphosphorylating circulating purines. Evidence for this was obtained by using independent assays, including chromatographic analyses with 3H-labeled and unlabeled nucleotides and adenosine, direct transfer of gamma-terminal phosphate from [gamma-32P]ATP to NDP/AMP, and bioluminescent measurement of ATP metabolism. Based on substrate-specificity and competitive studies, we identified three purine-inactivating enzymes in human serum, nucleotide pyrophosphatase (EC 3.6.1.9), 5'-nucleotidase (EC 3.1.3.5), and adenosine deaminase (EC 3.5.4.4), whereas an opposite ATP-generating pathway is represented by adenylate kinase (EC 2.7.4.3) and NDP kinase (EC 2.7.4.6). Comparative kinetic analysis revealed that the Vmax values for soluble nucleotide kinases significantly exceed those of counteracting nucleotidases, whereas the apparent Km values for serum enzymes were fairly comparable and varied within a range of 40-70 micro mol/l. Identification of soluble enzymes contributing, along with membrane-bound ectoenzymes, to the active cycling between circulating ATP and other purines provides a novel insight into the regulatory mechanisms of purine homeostasis in the blood.

Pyrimidine nucleotidases/phosphotransferases from human erythrocyte.

Two cytoplasmic pyrimidine 5'-nucleotidase have been purified from human erythrocytes to homogeneity and partially characterized. The two enzymes, indicated as PN-I and PN-II, preferentially hydrolyse pyrimidine 5'-monophosphates and 3'-monophosphates, respectively. The kinetic analysis demonstrate that pyrimidine 5'-nucleotidases, in the presence of suitable nucleoside substrates, can operate as phosphotransferases by transferring phosphate to various nucleoside acceptors, including nucleoside analogues known as important drugs widely used in chemotherapy.

Direct labelling of hormone-sensitive phosphoinositides by a plasma-membrane-associated PtdIns synthase in turkey erythrocytes.

We have previously characterized phosphatidylinositol (PtdIns) synthase and PtdIns/myo-inositol-exchange enzyme activities in ghost membranes prepared by hypotonic lysis of turkey erythrocytes [McPhee, Lowe, Vaziri and Downes (1991) Biochem. J. 275, 187-192]. Here we show that PtdIns synthase activity is relatively enriched in plasma-membrane preparations of turkey erythrocytes and that inositol phospholipids labelled by both PtdIns synthase and PtdIns myo-inositol exchange enzymes are susceptible to hydrolysis by the receptor- and G-protein-regulated phospholipase C (PLC), which is present also in ghost preparations. Specific-radioactivity measurements of [3H]PtdIns from ghosts labelled to equilibrium under conditions favouring [3H]inositol incorporation by PtdIns synthase activity indicate that PtdIns synthase can directly access approx. 14% of the total erythrocyte ghost PtdIns. Approx. 16% of the [3H]PtdIns labelled by the PtdIns synthase reaction can be phosphorylated to polyphosphoinositides, which are then hydrolysed by the receptor- and G-protein-stimulated PLC. Since the mass of PtdIns declines to a similar extent as [3H]PtdIns during stimulation in the presence of guanine nucleotides and ATP, it is evident that both the labelled and unlabelled phosphoinositides are susceptible to hydrolysis by the relevant PLC. Phosphoinositides present in nuclei-free plasma membranes were also labelled by [3H]inositol under conditions favouring PtdIns synthase and PtdIns/myo-inositol-exchange enzyme activities respectively. These membranes lack PLC activity [Vaziri and Downes (1992) J. Biol. Chem. 267, 22973-22981], but the labelled lipids were sensitive to purinergic-receptor-stimulated hydrolysis in reconstitution assays using partially purified turkey erythrocyte PLC. The results strongly suggest that at least a portion of the PtdIns synthase in turkey erythrocytes is located in the plasma membrane and has direct access to an agonist-sensitive pool of inositol phospholipids.

Tyrosine kinases and phosphoinositide metabolism in thrombin-stimulated human platelets.

In this study we have examined the implication of tyrosine kinase activities in aggregation, 5-hydroxytryptamine secretion and mainly phosphoinositide metabolism in response to human platelet stimulation by thrombin. Using the potent tyrosine kinase inhibitor tyrphostin AG-213, we have observed a significant inhibition of aggregation and 5-hydroxytryptamine release; however, this percentage inhibition was lower at high thrombin concentrations. On the other hand, tyrphostin treatment of metabolically 32P-labelled platelets significantly inhibited the thrombin-dependent accumulation of PtdIns(3,4)P2, which involves at least a PtdIns 3-kinase and/or a PtdIns3P 4-kinase, whereas the synthesis of phosphatidic acid (PtdOH), a good reflection of the phospholipase C (PLC) activation in platelets, was partially blocked. Inositol phosphate production was also inhibited by about 40% when tyrphostin-treated platelets were stimulated with thrombin. In addition, we show by Western-blot analysis that PLC gamma 1, as well as the regulatory subunit (p85) of the PtdIns 3-kinase, were present in the anti-phosphotyrosine immunoprecipitate isolated from thrombin-stimulated platelets. Furthermore, tyrphostin treatment clearly decreased the PLC gamma 1 and p85 contents in such an anti-phosphotyrosine immunoprecipitate. Our results provide the first evidence for a direct or indirect regulation of PtdIns(3,4)P2 accumulation and PLC gamma 1 activity by tyrosine phosphorylation during thrombin stimulation of human platelets.

Purification and properties of a human platelet inositol 1,4,5-trisphosphate 3-kinase.

An inositol 1,4,5-trisphosphate 3-kinase (Ins(1,4,5)P3 3-kinase) has been purified 943-fold from a 30,000g human platelet extract and has a specific activity of 283 nmol/min/mg protein and an apparent Km for inositol 1,4,5-trisphosphate of 0.76 microM; the optimal pH for the enzymatic activity was 7.2. Under both denaturing and nondenaturing conditions, the kinase preparation contained two polypeptides, both of which exhibited Ca2+/calmodulin-dependent Ins(1,4,5)P3 3-kinase activity. In the presence and absence of calmodulin, Ins(1,4,5)P3 3-kinase exhibited a biphasic response to Ca2+, being stimulated between 10(-7) and 10(-6) M Ca2+ and inhibited when the Ca2+ level was further increased. Ins(1,4,5)P3 3-kinase was stimulated by calmodulin approximately 10-fold, requiring 55 nM calmodulin for a half-maximal effect. Calmodulin stimulation was immediately reversed upon chelation of Ca2+ by ethylene glycol bis (beta-amino-ethyl ether) N,N'-tetraacetic acid consistent with a mechanism of activation involving a direct interaction of calmodulin with Ins(1,4,5)P3 3-kinase. Since we have previously shown that Ins(1,4,5)P3 3-kinase can also be phosphorylated and consequently inactivated by protein kinase C in vitro (Lin, A. N., Barnes, S., and Wallace, R. W., 1990, Biochem. Biophys. Res. Commun. 170, 1369-1376), Ins(1,4,5)P3 3-kinase appears to be a key enzyme in the inositol phosphate signaling pathway and as such may play an important role in human platelet function.

Purification and characterization of human erythrocyte phosphatidylinositol 4-kinase. Phosphatidylinositol 4-kinase and phosphatidylinositol 3-monophosphate 4-kinase are distinct enzymes.

PtdIns 4-kinase has been purified 83,000-fold from human erythrocyte membranes. The major protein detected by SDS/PAGE is of molecular mass 56 kDa, and enzymic activity can be renatured from this band of the gel. The characteristics of this enzyme are similar to other type II PtdIns kinases previously described: PtdIns presented in Triton X-100 micelles is preferred as a substrate over PtdIns vesicles, the enzyme possesses a relatively low Km for ATP (20 microM), and adenosine is an effective inhibitor. A monoclonal antibody raised against bovine brain type II PtdIns 4-kinase is an effective inhibitor of the purified enzyme. PtdIns(4,5)P2 inhibits by approx. 50% when added in equimolar amounts with PtdIns; PtdIns4P has little effect on activity. A PtdIns3P 4-kinase activity has also been detected in erythrocyte lysates. Approximately two-thirds of this activity is in the cytosolic fraction and one-third in the membrane fraction. No PtdIns3P 4-kinase activity could be detected in the purified type II PtdIns 4-kinase preparation, nor could this activity be detected in a bovine brain type III PtdIns 4-kinase preparation. The monoclonal antibody that inhibits the type II PtdIns 4-kinase does not affect the PtdIns3P 4-kinase activity in the membrane fraction. The cytosolic PtdIns3P 4-kinase can be efficiently recovered from a 60%-satd.-(NH4)2SO4 precipitate that is virtually free of PtdIns 4-kinase activity. We conclude that PtdIns3P 4-kinase is a new enzyme distinct from previously characterized PtdIns 4-kinases, and that this enzyme prefers PtdIns3P over PtdIns as a substrate.

Transferrin binding of bone marrow cells and metabolic activity of erythrocytes after 5 Gy irradiation.

The effect of total body irradiation (5 Gy) on functional mouse erythroid lineage has been studied. The transferrin binding capacity by bone marrow cells and the activity of glycolytic regulatory enzymes and intracellular levels of 2,3 bisphosphoglycerate in peripheral blood erythrocytes have been determined. Results obtained along one year post-irradiation period suggest a complete recovery in the erythroid cell lineage with respect to the biological endpoints investigated.

Partial purification and characterization of two forms of phosphatidylinositol 4-phosphate 5-kinase from human platelet membrane.

The phosphatidylinositol 4-phosphate 5-kinase (PIP kinase) was isolated from the cholate extract of human platelet membranes. Two major activity peaks (PIP kinase I and PIP kinase II) were resolved by successive chromatographies on Fast Q-Sepharose, heparin-Sepharose, Mono Q and heparin-agarose columns. The PIP kinase I appears to be distinct from the PIP kinase II with regard to Mr (51 kDa and 47 kDa as determined by SDS-PAGE). The two forms of PIP kinase showed similarity in Km for ATP and Mg2+ dependency, but some differences were observed in effects of Mn2+ and phosphatidylethanolamine on the activity.

Hereditary erythrocyte adenylate kinase deficiency: a defect of multiple phosphotransferases?

Adenylate kinase (AK) modulates the interconversion of adenine nucleotides (AMP + adenosine triphosphate----2 ADP). We evaluated the fifth kindred with hereditary erythrocyte (RBC) AK deficiency. The proband had chronic hemolytic anemia. Her RBC had undetectable AK activity when measured spectrophotometrically, whereas those of her parents had half-normal AK activity. AK electrophoresis showed only AK-1 in the parents. The activities of pyruvate kinase and phosphoribosylpyrophosphate synthetase were decreased given the young age of the proband's RBC. Despite the absence of spectrophotometric AK activity, the proband's RBC were able to incorporate 14C-adenine into 14C-adenine nucleotides at 50% of the rate expected for her young RBC population, suggesting the possibility of an alternative pathway for the formation of ADP from AMP. Normal hemolysate had AMP:guanosine triphosphate (GTP) phosphotransferase activity, which produced ADP at 8% to 9% of the rate of AK (6.8 +/- 0.8 IU/mL RBC). AMP:GTP phosphotransferase activity was not detectable in the proband's or parent's hemolysates. These additional biochemical defects in the AK-deficient RBC further support the concept that AK deficiency per se may not cause hemolytic anemia. We propose that defects occur in multiple phosphotransferases in the AK-deficient RBC and that these other biochemical defects may produce deleterious lesions that promote the shortened RBC survival in AK deficiency.

Phosphatidylinositol synthase and phosphatidylinositol/inositol exchange reactions in turkey erythrocyte membranes.

Unlike human erythrocytes, those from avian species, such as turkeys and chicks, rapidly incorporate myo-[3H]inositol into membrane phospholipids. The mechanisms regulating [3H]Ins labelling of phosphatidylinositol have been investigated using turkey erythrocyte membranes. In the absence of added nucleotides, [3H]inositol incorporation appears to proceed via phosphatidylinositol/inositol exchange, with a Km for inositol of 0.01 mM. The reaction was dependent upon divalent cations, either Mg2+ or Mn2+, with the latter metal ion being the more effective. [3H]Inositol incorporation was accelerated by CMP, especially when the concentration of Ins was greater than the Km for the exchange reaction. CMP-dependent labelling of PtdIns had a Km for inositol of 0.3 mM and for CMP of 0.015 mM. Divalent cations were also required for this reaction: activity peaked at 0.5 mM-Mn2+ and declined at higher concentrations. At relatively high concentrations, Mg2+ was more effective than Mn2+, with peak activity being achieved above 10 mM. CMP-dependent incorporation of [3H]inositol appears to reflect an exchange reaction catalysed by PtdIns synthase. Definitive evidence for the occurrence of PtdIns synthase in turkey erythrocyte membranes was obtained by demonstrating the formation of [14C]CMP-phosphatidate from [14C]CMP. The radioactivity could be efficiently chased from [14C]CMP-phosphatidate in the presence of unlabelled inositol. The detection of PtdIns synthase activity in morphologically simple turkey erythrocytes should help to clarify the subcellular distribution of this important component of the phosphatidylinositol cycle.

Erythrocyte fructose 2,6-bisphosphate content in congenital hemolytic anemias.

We have investigated the levels of fructose 2,6-bisphosphate and its synthesizing enzyme 6-phosphofructo-2-kinase in red blood cells from different congenital anemias. Fructose 2,6-bisphosphate concentration and 6-phosphofructo-2-kinase activity are markedly influenced by the number of reticulocytes in all the cases studied with the exception of homozygous pyruvate kinase deficiency, where no correlation was observed with the percentage of reticulocytes.

Increased N-acetylglucosamine-1-phosphotransferase activity in sera from patients with leukemia.

In human cancer, lysosomal hydrolases contain increased amounts of phosphorylated sugar chains. Sugar chains of the hydrolases undergo post-translational processing which is catalyzed by N-acetylglucosamine-1-phosphotransferase (GlcNAc-phosphotransferase) at the first step. In the present study we estimated serum GlcNAc-phosphotransferase in 50 adults suffering from leukemia and myelodysplastic syndrome. The serum GlcNAc-phosphotransferase was increased to moderate or high levels in patients with acute nonlymphocytic leukemia (ANLL), acute lymphoblastic leukemia and chronic myelogenous leukemia, suggesting that the serum transferase is released from leukemic cells. In many cases of ANLL examined, activity of the transferase was decreased concomitantly with reduction of peripheral blastic cells by effective chemotherapy.

A novel pathway for the formation of phosphatidylinositol 3,4-bisphosphate. Phosphorylation of phosphatidylinositol 3-monophosphate by phosphatidylinositol-3-monophosphate 4-kinase.

Three polyphosphoinositides containing phosphate at the D-3 position of the inositol ring can be generated in vitro by phosphorylation of phosphatidylinositol, phosphatidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate by a phosphatidylinositol-3-kinase (Auger, K. R., Serunian L. A., Soltoff, S. P., Libby, P., and Cantley, L. C. (1989) Cell 57, 167-175. An alternative pathway for in vivo synthesis of one of these lipids was recently suggested: phosphatidylinositol 3,4-bisphosphate could be produced by phosphorylation of phosphatidylinositol 3-phosphate at the D-4 position of the inositol ring (Yamamoto, K., and Lapetina, E. G. (1990) Biochem. Biophys. Res. Commun. 168, 466-472). Here we demonstrate the presence of an enzyme in human platelets that phosphorylates [32P]phosphatidylinositol 3-phosphate to produce [32P]phosphatidylinositol 3,4-bisphosphate. This enzyme is Mg2(+)-dependent and its apparent molecular mass is approximately 150 kDa as estimated by sucrose gradient centrifugation and gel filtration chromatography. Unlike the major phosphatidylinositol-4-kinase in platelets that is stimulated by the detergent Nonidet P-40, the phosphatidylinositol-3-phosphate-4-kinase is inhibited by Nonidet P-40. Both activities are also differentiated by the action of adenosine. The discovery of this new enzyme raises the possibility that multiple pathways exists for generating D-3 phosphorylated phosphoinositides.

Thrombin-stimulated immunoprecipitation of phosphatidylinositol 3-kinase from human platelets.

Growth factors and transforming proteins that activate tyrosine phosphorylation have been shown to cause an increased labeling of 3-phosphate-containing phosphatidylinositols. Turnover correlates with the formation of a complex between phosphatidylinositol 3-kinase, the activated protein-tyrosine kinase, and other proteins thought to participate in transmembrane signaling. When human platelets are treated with thrombin, labeling of 3-phosphate-containing phosphatidylinositols is stimulated with a time course and concentration dependence consistent with a role for these lipids in platelet activation. We now report that when human platelets are stimulated with thrombin, a complex forms between phosphatidylinositol 3-kinase, a protein-serine/threonine kinase, and an uncharacterized platelet membrane protein. The complex is immunoprecipitated from detergent lysates of thrombinstimulated platelets by a rabbit antiserum prepared against a peptide from the cytoplasmic domain of the mouse platelet-derived growth factor (PDGF) receptor. The antigen is not the PDGF receptor, since complex formation is not stimulated by PDGF and thrombin-induced complexes are not precipitated by another rabbit antiserum against the same peptide or by monoclonal anti-human PDGF receptor antibodies. Formation of the complex is rapid (within 30 sec) and occurs at thrombin concentrations that stimulate platelet aggregation and secretion (50% of maximal complex formation at 0.03 unit of thrombin per ml). We propose that the complex initiates formation of 3-phosphate-containing phosphatidylinositols that may function in platelet activation.