Hypoxanthine Values Research Articles

Effects of bioactive substances to prolong the shelf‐life and inhibit the formation of black spots in black tiger shrimp (Penaeus monodon) preserved at 0 degree C

AbstractThe objective of this study was to extend the shelf‐life and inhibit the process of black spots formation in giant black tiger shrimp (Penaeus monodon) by using 1.5 % solutions of the bioactives including: gallic acid, caffelic acid and cinnamaldehyde. Shrimp samples were dipped in the solutions for ten minutes, at 4°C and stored at 0°C for 15 days. Total viable count (TVC), melanosis evaluation method, chemical quality indexes including total volatile base nitrogen (TVB‐N), trimethylamine nitrogen (TMA‐N), pH and hypoxanthine values were used to evaluate the effectiveness of the treatments. TVC values, melanosis score of shrimp samples treated with bioactive compounds appeared more slowly, TVB‐N and TMA‐N values changed exponentially, hypoxanthine values increased linearly with storage time, and pH decreased on day 2, then increased gradually. Shelf life of treated samples were found to be longer than that of the control sample (8 days), and had a better ability to inhibit melanosis, in particular, the samples treated with a solution of cinnamaldehyde had the longest shelf life of 14 days, compared with 13 days of samples treated with caffelic acid and 12 days of the ones treated with gallic acid.

Differential Metabolites in Chinese Autistic Children: A Multi-Center Study Based on Urinary 1H-NMR Metabolomics Analysis.

Background: Autism spectrum disorder (ASD) is a group of early-onset neurodevelopmental disorders. However, there is no valuable biomarker for the early diagnosis of ASD. Our large-scale and multi-center study aims to identify metabolic variations between ASD and healthy children and to investigate differential metabolites and associated pathogenic mechanisms.Methods: One hundred and seventeen autistic children and 119 healthy children were recruited from research centers of 7 cities. Urine samples were assayed by 1H-NMR metabolomics analysis to detect metabolic variations. Multivariate statistical analysis, including principal component analysis (PCA), and orthogonal projection to latent structure discriminant analysis (OPLS-DA), as well as univariate analysis were used to assess differential metabolites between the ASD and control groups. The differential metabolites were further analyzed by receiver operating characteristics (ROC) curve analysis and metabolic pathways analysis.Results: Compared with the control group, the ASD group showed higher levels of glycine, guanidinoacetic acid, creatine, hydroxyphenylacetylglycine, phenylacetylglycine, and formate and lower levels of 3-aminoisobutanoic acid, alanine, taurine, creatinine, hypoxanthine, and N-methylnicotinamide. ROC curve showed relatively significant diagnostic values for hypoxanthine [area under the curve (AUC) = 0.657, 95% CI 0.588 to 0.726], creatinine (AUC = 0.639, 95% CI 0.569 to 0.709), creatine (AUC = 0.623, 95% CI 0.552 to 0.694), N-methylnicotinamide (AUC = 0.595, 95% CI 0.523 to 0.668), and guanidinoacetic acid (AUC = 0.574, 95% CI 0.501 to 0.647) in the ASD group. Combining the metabolites creatine, creatinine and hypoxanthine, the AUC of the ROC curve reached 0.720 (95% CI 0.659 to 0.777). Significantly altered metabolite pathways associated with differential metabolites were glycine, serine and threonine metabolism, arginine and proline metabolism, and taurine and hypotaurine metabolism.Conclusions: Urinary amino acid metabolites were significantly altered in children with ASD. Amino acid metabolic pathways might play important roles in the pathogenic mechanisms of ASD.

Abstract 9936: Hypoxanthine is a Biomarker of Ischemia

We hypothesize that hypoxanthine (HX) is an early biomarker of ischemia. Our goal was to assess early HX values in patients presenting with acute chest pain (ACP) and late troponin elevation (n=27) compared to those with known coronary artery disease (CAD) presenting for elective CABG (n=10) and normal controls without known CAD (n=24). Methods: In a retrospective manner after IRB approval was obtained, we examined residual plasma for HX in 27 patients presenting to the emergency room with troponin samples requested by the clinician as per routine clinical practice. Patients with a non diagnostic troponin level for myocardial infarction (MI) at the time of presentation but who subsequently ruled in for MI (troponin of > .39 μg/L) were included in the study. Significant differences between the groups was determined using a standard t test. Results: Initial sample results for the ACP patient group who subsequently ruled in for MI by troponin show a mean troponin of 0.07+/-0.014(SEM)μg/L and a mean HX level of 27.38 +/- 3.53 μM compared to normal controls whose mean HX was 4.03 +/- 0.32 μM (p<.05). Ten patients without ACP presenting for elective CABG had a mean HX of 5.09+/- 0.67 μM. In the figure below, we demonstrate that HX is elevated in ACP patients who on subsequent sampling rule in by troponin criteria for MI. Reported HX levels in normal volunteers are approximately 3.5 μM consistent with our controls. Conclusion: HX is elevated prior to troponin elevation in patients presenting with ACP that subsequently rule in for MI by troponin criteria. These levels were elevated relative to normal control patients as well as in 10 patients with known CAD without ACP presenting for elective CABG. Therefore, HX is potentially an early maker of ischemia in the acute clinical setting.

Consumption of green tea favorably affects oxidative stress markers in weight-trained men

Objective This study investigated the effects of the consumption of green tea (GT) for 7 d on biomarkers of oxidative stress in young men undergoing resistance exercise. Methods Fourteen subjects performed a bench press exercise (four sets, 10 to 4 repetitions) after undergoing a period without (control group) or with the intake of GT (GT group; 2 g of leaves in 200 mL of water, three times per day). Blood samples were obtained before and after exercise and analyzed for total antioxidant capacity (ferric reducing ability of plasma [FRAP]), total polyphenols, reduced glutathione (GSH), lipid hydroperoxide (LH) and thiobarbituric acid–reactive substances, creatine kinase (CK), aspartate aminotransferase (AST), xanthine oxidase (XO), hypoxanthine, and uric acid (UA). Results In the control group, exercise did not affect the values of LH, thiobarbituric acid–reactive substances, and FRAP, although it did reduce the levels of GSH ( P < 0.05). In addition, exercise increased CK, AST, and XO activities, although it did not change the values for hypoxanthine or UA. Green tea reduced the postexercise concentration of LH and increased the values of total polyphenols, GSH, and FRAP. GT also inhibited a significant rise in CK and XO activities induced by exercise. Furthermore, GT decreased the AST activity and hypoxanthine and UA concentrations before and after exercise. The assessment of food consumption revealed that the participants had an unbalanced diet, particularly in relation to vitamin E and carotenoids. Conclusion Consumption of GT, a beverage rich in polyphenols, may offer protection against the oxidative damage caused by exercise, and dietary guidance for sports participants should be emphasized.

Functional expression and characterization of a purine nucleobase transporter gene from Leishmania major.

Leishmania major, like all the other kinetoplastid protozoa, are unable to synthesize purines and rely on purine nucleobase and nucleoside acquisition across the parasite plasma membrane by specific permeases. Although, several genes have been cloned that encode nucleoside transporters in Leishmania and Trypanosoma brucei, much less progress has been made on nucleobase transporters, especially at the molecular level. The studies reported here have cloned and expressed the first gene for a L. major nucleobase transporter, designated LmaNT3. The LmaNT3 permease shows 33% identity to L. donovani nucleoside transporter 1.1 (LdNT1.1) and is, thus, a member of the equilibrative nucleoside transporter (ENT) family. ENT family members identified to date are nucleoside transporters, some of which also transport one or several nucleobases. Functional expression studies in Xenopus laevis oocytes revealed that LmaNT3 mediates high levels of uptake of hypoxanthine, xanthine, adenine and guanine. Moreover, LmaNT3 is an high affinity transporter with K(m) values for hypoxanthine, xanthine, adenine and guanine of 16.5 +/- 1.5, 8.5 +/- 0.6, 8.5 +/- 1.1, and 8.8 +/- 4.0 microM, respectively. LmaNT3 is, thus, the first member of the ENT family identified in any organism that functions as a nucleobase rather than nucleoside or nucleoside/nucleobase transporter.

Hypoxia‐induced free iron release in the red cells of newborn infants*

Heparinized blood samples were obtained at birth from 164 newborn infants (101 full term; 63 preterm). Intra‐erythrocyte free iron concentration and hypoxanthine plasma levels were determined by high‐pressure liquid chromatography. Intra‐erythrocyte free iron concentration was higher in preterm than in full term babies (p &lt; 0:0001) and adults (p &lt; 0:0001). Statistically significant correlations were observed between intra‐erythrocyte free iron concentration and hypoxanthine levels (r = 0:66; p= 0:0001), pH (r = ‐ 0:76; p = 0:0001), base excess (r = ‐ 0:79; p= 0:0001), and gestational age (r = ‐ 0:44; p= 0:0001) in both infant populations. Multiple regression analysis between intra‐erythrocyte free iron concentration in cord blood, as an independent variable, and Apgar score at 1 min, pH, base excess, hypoxanthine values, FiO2 needed for resuscitation immediately after delivery, and gestational age, as dependent variables, identified hypoxanthine levels (p= 0:0003; partial F‐test = 15.4) as the best single predictor of intra‐erythrocyte free iron concentration. In conclusion, hypoxia induces intra‐erythrocyte free iron release, and therefore enhances the risk of oxidative injury due to hydroxyl radical generation.

Tissue hypoxia in ipsilateral and contralateral testes undergoing surgically induced maldescent.

The mechanism of deterioration of ipsilateral and contralateral testes during unilateral maldescent remains controversial. Proposing that alterations in tissue perfusion may play a role in ipsilateral and contralateral testicular deteriorations, an experimental study has been planned to evaluate the status of parameters of tissue hypoxia in ipsilateral and contralateral testes following surgically induced maldescent, in rats which preoperatively underwent placebo or chemical sympathectomy. 60 male albino rats were used for the experiment. At the age of 21 days each 30 rats that were treated by placebo or chemical sympathectomy agent were divided into 3 groups undergoing sham operation, abdominal fixation of one testis or abdominal fixation of both testes. At the age of 3 months the rats underwent bilateral orchidectomies and lactic acid (LA) and hypoxanthine (HX) levels were measured in testicular tissues. Maldescent of the testis resulted in a marked increase of LA and HX values in the ipsilateral testis compared to controls, and also resulted in increased levels of LA and HX in the contralateral testis. Although the levels of LA and HX were lower compared to ipsilateral undescended counterparts the levels in contralateral testis were significantly elevated compared to the contralateral testes of rats undergoing sham operation following placebo treatment. Bilateral maldescent resulted in similar elevations of LA and HX in both of the testes. Administration of 6-hydroxydopamine did not result in decreased levels of LA and HX values in the ipsilateral testis following unilateral testicular undescendence. However the LA levels in the contralateral descended testis did not reveal a significant difference compared to the contralateral testis of rats undergoing sham operation. The present experimental design reveals that abdominal fixation of the testis results in tissue hypoxia not only in the ipsilateral but also in the contralateral testis. Chemical sympathectomy has some protective effects on contralateral testicular hypoxia during unilateral maldescent. Tissue hypoxia during maldescent may result from relative inadequacy of testicular blood flow to overcome the increased metabolic demands under hyperthermic conditions.

Chemical and sensory changes in haddock and herring stored under modified atmosphere

The effectiveness of storage in atmospheres with increased proportions of CO2 to extend the shelf‐life of haddock and herring was examined. Using a 40: 30: 30/CO2: O2: N2 atmosphere with haddock no useful extension of shelf‐life was achieved at +5°C and only limited extension at 0°C. A more useful extension of shelf‐life at 0°C was obtained by storing haddock in a 60: 20: 2O/CO2: O2: N2 atmosphere and with herring in a 60:40/CO2::N2: atmosphere. Total volatile bases (TVB) and hypoxanthine values (Hx) correlated with the cooked flavour. There were no significant differences in drip‐loss between the modified atmosphere packaging (MAP) stored samples and the controls. Peroxide values (PV) in herring were lower in MAP stored samples. Whole haddock and whole herring were found to have a longer shelf‐life when stored in MAP at 0°C than when stored as fillets.

O2 Uptake Kinetics in Response to Exercise: A Measure of Tissue Anaerobiosis in Heart Failure

Oxygen uptake (VO2) reflects the rate of aerobic regeneration of high-energy phosphate compounds (primarily adenosine triphosphate [ATP]). Since lactate increase is thought to result from an inadequate rate of aerobic ATP regeneration, it might be expected that lactate increase would be associated with a delayed attainment of steady state for VO2 in response to constant load exercise. Similarly if mitochondrial ATP regeneration during exercise is inadequately supported by O2 transport mechanisms, adenosine diphosphate (ADP) and purine nucleotide by-products, such as hypoxanthine, should increase. This study investigated the relationship between VO2 kinetics during exercise and accompanying changes in blood lactate and hypoxanthine values in heart failure patients, as a model of compromised O2 transport. Twenty-five patients with chronic heart failure performed cycle ergometry for 6 min at 25 W and at a work rate midway (50 percent delta) between their lactic acidosis threshold (LAT) and peak VO2. Ventilation and gas exchange were measured breath by breath, and venous lactate, hypoxanthine, norepinephrine, and epinephrine were determined at rest and 2 min after each test. The slow component of VO2 kinetics was quantified as the rise in VO2 from the third to the sixth minute of exercise (delta VO2 [6-3]). Ten age- and size-matched normal subjects served as control subjects. delta VO2 (6-3) was correlated with the increase in lactate (r = 0.71, p < 0.001), hypoxanthine (r = 0.61, p < 0.001), and norepinephrine (r = 0.41, p < 0.01) but not epinephrine in response to exercise in the heart failure patients. The delta VO2 (6-3) and delta lactate were both greater in the patients than in the control subjects at similar absolute work rates (54 +/- 20 and 60 W, respectively). However, the slope of the relationship between delta La and delta VO2 (6-3) for the patient and normal groups was indistinguishable. The lactate increase was correlated with hypoxanthine increase (r = 0.66, p < 0.001), but not norepinephrine or epinephrine. In summary, VO2 kinetics in response to exercise reflects delayed attainment of the steady state in heart failure patients, which is correlated with increases in lactate and hypoxanthine, markers of increased anaerobic metabolism.

Valuable indicators of physical stress in porcine plasma.

Various markers for stress were evaluated in the plasma of pigs. Treadmill exercise was chosen as a well defined and quantifiable stressor. One group of non-stress-susceptible pigs had to carry out two intense exercise bouts at a one-week interval, and another group remained in their pens and served as controls. Large interindividual differences in the performance and in the hormonal and metabolic responses to exercise were observed. The exercise stress resulted in an immediate increase in the plasma concentrations of cortisol, lactate and hypoxanthine, with a return to the pre-exercise levels within one hour. No direct effect of physical stress on CBG binding capacity or on the concentrations of xanthine and uric acid was observed. In two very nervous pigs, even mild stress in connection with the first blood sampling resulted in an elevated concentration of lactate, but the cortisol and hypoxanthine values remained at the basal level. It is concluded that plasma concentrations of cortisol, lactate and hypoxanthine are valuable markers for physical stress.

Transport of hypoxanthine from plasma to cerebrospinal fluid and vitreous humor in newborn pigs

To determine whether an elevated level of hypoxanthine in cerebrospinal fluid or vitreous humor might reflect a high plasma hypoxanthine concentration, or whether it necessarily represents local tissue hypoxia, we infused hypoxanthine intravenously to normoxemic and normotensive piglets (n = 6). Hypoxanthine was measured in different body fluids using HPLC. During the 8 hours of infusion hypoxanthine increased in plasma (from 30 +/- 6 mumol/l (mean +/- SD) before the infusion to 68 +/- 20 mumol/l at the end of the infusion, p < 0.01), cerebrospinal fluid (CSF) (19 +/- 8 to 43 +/- 9 mumol/l, p < 0.05) and vitreous humor (15 +/- 5 to 30 +/- 6 mumol/l, p < 0.05). After infusion, hypoxanthine values in all three fluids were similar to those seen in pigs after severe hypoxia. Hypoxanthine in vitreous humor and plasma were significantly correlated (r = 0.80, 95% confidence interval 0.47-0.93, p < 0.001). Urinary excretion of hypoxanthine increased almost 40 times from 0.12 +/- 0.14 to 4.6 +/- 2.9 mumol/kg/h indicating that renal excretion of hypoxanthine is not achieved just by passive filtration. We conclude that in newborn piglets hypoxanthine can pass from plasma to CSF and vitreous humor. Thus an increased CSF hypoxanthine concentration is not definite proof that significant cerebral hypoxia has occurred.

Physical, chemical and sensory analysis of sardine (Sardina pilchardus) stored in ice

AbstractThe shelf‐life of iced sardine (Sardina pilchardus) was studied. The main changes which take place in raw fish were investigated by means of organoleptic assessments, chemical analyses (total volatile nitrogen (TVB‐N), trimethylamine (TMA‐N), trimethylamine oxide (OTMA‐N) and hypoxanthine) and physical measurements (GR Torrymeter readings and pH). The influence of both seasonal changes and fat deterioration were also considered. The results obtained indicate that TVB‐N and TMA‐N parameters are not good freshness indicators for this species, but Torrymeter readings and hypoxanthine values can be used as indicators of freshness. However, they must always be confirmed by a sensory evaluation. From the different combinations tried, the most highly significant degree of correlation was obtained between sensory evaluation and Torrymeter readings.

Simultaneous determination of inosine, hypoxanthine, xanthine, and uric acid and the effect of metal chelators

We describe a sensitive, reproducible method for the simultaneous determination of the ATP catabolites inosine, hypoxanthine, xanthine, and uric acid in biological samples and organ perfusate using reverse-phase chromatography and multiwavelength detection at 254, 270, and 292 nm. Sample preparation includes precipitating proteins with perchloric acid, neutralizing the sample, passing the supernatant over a polyethyleneimine column, and analyzing the collected fractions by high-performance liquid chromatography. Addition of metal chelators to the perchloric acid resulted in increased values for xanthine, hypoxanthine, and uric acid. The method was sensitive (limit of detection, 0.08 nmol on column; S N = 4 ) and linear over the range 0.5–30 μ m. Precision and accuracy of the method were evaluated for lung tissue and lung perfusate. Coefficients of variation ranged from 2.8 to 6.1% for perfusate and from 1.7 to 12.6% for tissue. Recoveries for all compounds exceeded 90%. We applied this method to rat lung tissue, lung perfusate, and rat and human blood. Advantages of this method are simultaneous quantitation with excellent sensitivity of all compounds, simplified peak identification by using multiwavelength detection, and improved accuracy by preventing loss of compounds with metal chelators.

Prediction of perinatal brain damage by cord plasma vasopressin, erythropoietin, and hypoxanthine values

For an assessment of whether cord plasma arginine vasopressin, erythropoietin, and hypoxanthine concentrations are predictors of perinatal brain damage, these concentrations were measured in 62 infants born after preeclampsia of pregnancy, 31 acutely asphyxiated infants, and 38 control infants. Follow-up at 2 years included neurologic examination and the determination of a Bayley mental score. Clear abnormality (death, cerebral palsy, or developmental delay) was found in four infants in the preeclampsia group and five in the asphyxia group; slight abnormality was found in 12 and 6 infants, respectively; and no abnormality was found in the remainder. Neither arginine vasopressin values nor hypoxanthine values predicted adverse outcome in either study group. A high erythropoietin level was found in infants born after preeclampsia regardless of outcome: normal outcome (geometric mean (GM), 102; 95% confidence interval [CI], 69 to 153 mU/ml), slightly abnormal outcome (GM, 100; 95% CI, 37 to 270 mU/ml) or clearly abnormal outcome (GM, 84; 95% CI, 19 to 378 mU/ml). However, asphyxiated infants with clearly abnormal outcome had higher erythropoietin values (GM, 67; 95% CI, 33 to 137 mU/ml; p less than 0.05) than the normal infants (GM, 37; 95% CI, 23 to 59 mU/ml). We conclude that a high erythropoietin level after normal pregnancy, but not after preeclampsia, indicates an increased risk for cerebral palsy or death.

Properties and substrate specificity of a purine phosphoribosyltransferase from the human malaria parasite, Plasmodium falciparum

The properties of a purine phosphoribosyltransferase from late trophozoites of the human malaria parasite, Plasmodium falciparum, are described. Enzyme activity with hypoxanthine, guanine and xanthine as substrates eluted in parallel during hydroxylapatite, size exclusion and DEAE-Sephadex chromatography as well as during chromatofocusing experiments. Furthermore, enzyme activity with all three purine substrates changed in parallel during heat inactivation of enzyme preparations and upon cold storage (4°C) of the enzyme. When considered together, these results support the view that the phosphoribosyltransferase is capable of utilizing all three purine bases as substrates. Additional characterization revealed that the apparent molecular weight and isoelectric point of this enzyme are 55 500 and 6.2, respectively, and that the apparent K m for 5-phosphoribosyl-1-pyrophospate ranges from 13.3 to 21.4 μM, depending on the purine base serving as substrate. The apparent K m values for hypoxanthine, guanine and xanthine were found to be 0.46, 0.30 and 29 μM, respectively. Other experiments showed that several divalent cations and sulfhydryl reagents produce a marked reduction of enzyme activity whereas dithiothreitol activates the enzyme. It should be noted that the ability to utilize xanthine as a substrate serves to distinguish the P. falciparum enzyme from its counterpart in the parasite's host cell, the human erythrocyte. The human enzyme shows only barely detectable activity with xanthine while the parasite enzyme displays similarly high levels of activity with all three purine substrates. Thus, the parasite enzyme might prove to be selectively susceptible to inhibition by xanthine analogs and related compounds.

Concentration of hypoxanthine in both cerebrospinal fluid and brain tissue increases under intensive hypoxia only.

The relationships between the concentrations of glycogen, glucose, lactate, adenosine triphosphate (ATP) and hypoxanthine in the brain tissue, and the hypoxanthine and lactate concentration in cerebrospinal fluid and blood were examined after exposure of rats to hypoxia. The animals (1 and 10 days old) were exposed to hypobaric hypoxia for 1-12 h, pO2 11.3 kPa (mild), pO2 8.6 kPa (moderate), pO2 6.4 (strong) and pO2 4.7 kPa (severe) in inspired air. The concentration of hypoxanthine in both cerebrospinal fluid and brain tissue increases in severe hypoxia. This severe hypoxia was related to a decrease of ATP level in brain tissue. This study showed that the level of hypoxanthine in blood did not closely correlate to the level of hypoxanthine in brain tissue and cerebrospinal fluid. Extremely high hypoxanthine values in the blood might indicate a decrease in ATP content in brain tissue.

Quality of rainbow trout chilled‐stored after post‐catch holding

AbstractThe shelf‐life of headed and gutted rainbow trout (Salmo gairdneri) was evaluated over period of storage at 0°C. There were three groups of samples: (i) fish held at 10°C for 6h and iced, (ii) fish held at 20°C for 6h and iced and (iii) fish held at 30°C for 6h and iced. Quality was assessed over the period of iced storage by measurements of total volatile bases (TVB), hypoxanthine, thiobarbituric acid, pH, water holding capacity (WHC) and tissue compressibility (TC). The results indicated that holding at various time/temperature periods before icing influences quality over the period of iced storage. Deterioration in quality was most pronounced when the fish had been held at high ambient temperatures of 30°C. Hypoxanthine values appeared to give an accurate indication of quality of freshwater fish. There was a linear increase in hypoxanthine values over the period of iced storage for all samples. However, for trout held at 30°C for 6 h before icing the values appeared to be highest. The coefficients of linear regression for fish iced immediately on receipt were lowest per day. It is suggested that hypoxanthine values may be used as chemical indicators of quality of freshwater trout.

Human brain hypoxanthine guanine phosphoribosyltransferase: Structural and functional comparison with erythrocyte hypoxanthine guanine phosphoribosyltransferase

1. 1. A rapid and simple method, based on GMP Sepharose affinity chromatography, was used for the purification of human brain hypoxanthine guanine phosphoribosyltransferase. 2. 2. A single protein band was detected by polyacrylamide gel electrophoresis of the native purified enzyme. A subunit molecular weight of 25,000 was estimated by SDS gel electrophoresis. 3. 3. The K m values for hypoxanthine and phosphoribosyl pyrophosphate were 50 and 111μM, respectively. The K i values for GMP and IMP with phosphoribosyl pyrophosphate were 21 and 37 μM, respectively. 4. 4. The purified enzyme from human brain did not differ significantly from the human erythrocyte one in amino acid composition. 5. 5. The brain and erythrocyte hypoxanthine guanine phosphoribosyltransferases showed complete immunochemical identity on Ouchterlony double diffusion.

Purification and characterisation of chicken brain hypoxanthine-guaninephosphoribosyltransferase

Hypoxanthine-guanine phosphoribosyltransferase enzyme (EC 2.4.2.8) from chicken brain has been purified 10000-fold to homogeneity. The molecular mass of the native enzyme is 85 kDa, with four subunits, each of 26 kDa, and exerts its maximum activity at pH 10.0. The K m values for hypoxanthine and guanine are 5.2 and 1.8 μM, respectively. The half-life of the enzyme is 30 min at 85°C. Monoclonal antibodies were raised against the native purified enzyme and were used for purification of enzyme to homogeneity. The monoclonal antibody did not bind to the active centre of the enzyme.

The concentration of hypoxanthine and lactate in the blood of healthy and hypoxic newborns.

This work examines the correlation between the concentration of hypoxanthine and lactate, the clinical course, and the parameters of the acid-base metabolism in newborns. In order to obtain normal values in mature, healthy newborns (Group A) 136 determinations of hypoxanthine and 126 determinations of lactate in blood were performed in the first five postnatal days. In well prematures (Group B) hypoxanthine was determined 18 times and lactate 16 times. In newborns requiring oxygen therapy including ventilator support (Group C) hypoxanthine and lactate were determined 36 and 31 times respectively. Hypoxanthine levels in the blood of mature healthy newborns decreased with increasing age. A similar course is known for lactate levels. In the group of well prematures (Group B), hypoxanthine and lactate levels have an age dependent course similar to that in group A. Correlations between hypoxanthine and lactate concentrations were observed in all three groups but were not noted to be as well defined as has been seen experimentally (e.g., by SAUGSTAD) and thus confirm the clinical results of other authors. Among the newborns requiring oxygen therapy (Group C) 7 of 36 hypoxanthine values were more than two standard deviations above those in the normal group. For lactate group C infants were in 12 of 31 cases above the two standard deviation range. The hypoxanthine and lactate concentrations of group C newborns were correlated with clinical and biochemical indicators of hypoxia. Infants with unequivocal signs of hypoxia showed elevated as well as normal hypoxanthine and lactate levels. Conversely, infants without clinical, pathological or biochemical hypoxia indicators showed in some cases elevated hypoxanthine and lactate values.(ABSTRACT TRUNCATED AT 250 WORDS)