Can SCSA and TUNEL forecast apoptosis-related motility depletion in Asthenozoospermia?

This study is an attempt to determine the power of SCSA and TUNEL for the evaluation of apoptosis status and apoptosis-related motility depletion in Asthenozoospermia. Fifty-one semen samples from Asthenozoospermic and 20 samples from fertile men participated in this study. SCSA and TUNEL were applied for the assessment of DNA integrity by flow cytometry. Annexin V conjugated with FITC labelling and FLICA method were used for the assessment of externalisation of phosphatidylserine and spermatozoon with active Caspase 3 respectively. SCSA results were shown to have a significant correlation with EPS in live spermatozoon (r = .85, p value = .00) and spermatozoon with active Caspase 3 (r = .633, p value = .00). TUNEL result was revealed to have a nonsignificant positive correlation with them. Then, Asthenozoospermic individuals were divided into two groups, SCSA higher and SCSA lower than 27%. Results interestingly indicated that the two groups significantly differed from each other in terms of TUNEL, EPS in live spermatozoon, spermatozoon with active Caspase 3 and sperm vitality (p value = .00). Both SCSA and TUNEL were correlated with apoptosis-related motility depletion in Asthenozoospermia. However, SCSA might be more powerful than TUNEL and could provide reliable information about DNA, chromatin integrity and apoptosis status in Asthenozoospermia.

Dynamic polarization flip in nanoripples on photoexcited Ti surface near its surface plasmon resonance.

Both normal and abnormal sub-100-nanometer ripples (wavenumber ∼10 µm(-1)) were separately observed on Ti surfaces excited by linearly polarized IR femtosecond laser pulses at lower and higher fluences. Numerical modeling of dispersion curves for surface plasmon-polaritons on the photoexcited Ti surfaces demonstrates its surface plasmon resonance with the peak wavenumber ∼8 µm(-1) spectrally tuned by prompt surface optical response, prompt surface charging, and pre-oxidation, with normal/abnormal nanoripples appearing at its red/blue shoulders, respectively.

Changes in serum levels of brain derived neurotrophic factor and nerve growth factor-beta in schizophrenic patients before and after treatment.

Schizophrenia is one of the most debilitating diseases among psychiatric disorders. Recent studies suggest the existence of effective immunological changes in the pathophysiology of this disease. The purpose of the current study was to determine the changes in serum levels of Brain Derived Neurotrophic Factor (BDNF) and Nerve Growth Factor-beta (NGF) in schizophrenic patients before treatment and 40 days after treatment. In this case-control study, serum levels of BDNF and NGF were measured by ELISA in 26 patients with schizophrenia and 26 healthy controls. All patients were treated with clozapine or risperidone for 40 days. A positive and negative syndrome scale (PANSS) questionnaire has been used to recognize the severity of the disease and to assess the response to treatment. Neurotrophin concentrations were compared before and after the treatment and with control groups using paired t-test and ANOVA test. BDNF and NGF levels in the case group were more than levels after treatment, but these differences were significant only for NGF. Concentrations in both neurotrophins were higher than the control group. The statistically significant difference was observed between changes in the NGF levels in the case and the control group, while no significant difference was seen in changes of BDNF. The main conclusion to be drawn from this study was that the increase in BDNF and particularly NGF may have an important role in causing schizophrenia. And possibly drugs clozapine and risperidone help to treat the disease by reducing the concentration of Neurotrophins.

Age-specific seroprevalence of hepatitis A in Sari, northern Islamic Republic of Iran.

The declining incidence of hepatitis A virus (HAV) infection in the Islamic Republic of Iran may be reducing the population's natural immunity. This was the first systemized, population-based survey of the seroprevalence of HAV antibodies in urban and rural inhabitants of Sari, Mazandaran province. Serum from 1034 individuals aged 1-25 years in 2007 were tested for anti-HAV lgG antibody using a commercial enzyme immunoassay kit. The overall seroprevalence was 38.9%. The lowest prevalence (5.2%) was among the younger age group (1-5 years) from urban areas and the highest prevalence (82.0%) in the older age group (15-25 years) from rural areas. Seropositivity was significantly higher at higher age, among females and in rural areas. Sari is no longer classified as an area of high endemicity, and immunization against HAV may be needed in our population in the future.

The impact of maternal measles-rubella immunization on the 12-month-old infant's immune response to measles-mumps-rubella vaccine immunogenicity.

This study was conducted to assess the roles of maternal measles-rubella (MR) vaccination before pregnancy on the persistence of passive immunity against MR in their infant before measles-mumps-rubella (MMR) immunization and the effects on the immunogenicity of MMR vaccine. Before and 4-8 weeks after MMR immunization of all healthy 12-month-old infants, sera samples were prepared. According to their mother's history of MR vaccination, infants were divided into two groups. Anti-MR antibodies were measured by the quantitative enzyme-linked immunosorbent assay (ELISA) method. The difference in seroconversion rates and the mean concentration of antibodies (MCA) between the two groups of infants were analyzed by descriptive statistical methods. In total, 7 and 12 sera, all from infants born from MR-vaccinated mothers, were positive against measles and rubella, respectively. The seroconversion rates were 90.5 and 53% in seronegative infants against measles and rubella, respectively, without statistically significant differences between the two groups of infants. However, the MCA differences were significant; measles P = 0.000, rubella P = 0.019. The MR vaccination of mothers may cause the prolongation of passive immunity in their infants, and may influence the immunogenicity of MMR vaccination. This finding should be considered for the optimal scheduling of the first dose of MMR vaccine. Also, the results showed that the immunogenicity of the rubella component of the MMR vaccine was lower than that reported.

Seroepidemiology of hepatitis E virus infection in 2-25-year-olds in Sari district, Islamic Republic of Iran.

The seroprevalence of hepatitis E virus infection (HEV) in children and young adults was determined in a community-based survey in an area of northern Islamic Republic of Iran. Serum samples were taken from 1080 randomly selected apparently healthy 2-25-year-olds from urban and rural regions of Sari district. Anti-HEV IgG antibodies were detected in 25 individuals (2.3%). Seroprevalence increased significantly with age from 3/255 (1.2%) in children < 10 years to 8/110 (7.3%) in those aged 20-25 years. No differences in HEV status were noted between the sexes. Earlier age at exposure to infection and a higher infection rate were found in people residing in rural areas than in urban areas.

Arginine, citrulline, and nitric oxide metabolism in end-stage renal disease patients.

The kidneys are thought to be a major site of net de novo arginine synthesis, but the quantitative status of arginine metabolism and its substrate precursor relationship to nitric oxide (NO) synthesis in end stage renal disease (ESRD) patients have not been characterized. We have investigated kinetic aspects of whole body arginine metabolism in six patients with ESRD. They received two pre- and two post-hemodialysis intravenous tracer infusion studies with L-[guanidino-(15)N(2)]arginine and L-[(13)C]leucine during the first study, and L-[5-(13)C]arginine and L-[5-(13)C-ureido,5,5, (2)H(2)]citrulline during the second study. Arginine homeostasis in ESRD patients was found to be associated with a lower rate of arginine oxidation, and despite the decrease in renal function, the rate of de novo arginine synthesis appeared to be preserved. Plasma citrulline concentrations and flux were also elevated in these subjects compared with healthy adults. The rate of whole body NO synthesis was increased in the ESRD patients, but apparently not different pre- and post-hemodialysis therapy. The anatomic site(s) responsible for the maintenance of net de novo arginine synthesis and for the elevated NO synthesis and its pathophysiological importance in ESRD remain to be established.

Seroepidemiological study of toxoplasmosis in intellectual disability children in rehabilitation centers of northern Iran.

Serological studies revealed that toxoplasmosis has world wide distribution. Although the infection by Toxoplasma gondii is widely prevalent in humans and animals, the disease is uncommon and most of the acquired infections are asymptomatic. The important aspect of this parasitic infection is the probable danger of congenital transmission and its severe effects on the fetus. There have been many reports about the prevalence of anti-T. gondii antibody among different groups of people in Iran; however the epidemiological data in intellectual disability (ID) persons are rare. This study was performed to evaluate the seroprevalence of toxoplasmosis among the inhabitants of rehabilitation centers of northern Iran. A total of 336 serum samples (161 males, 175 females) were examined for the IgG antibodies by indirect immunofluorescense technique. First of all, 1:50 titer dilution was tested, in the cases of positive result, further dilutions (1:100, 1:200, 1:400, 1:800, 1:1600, and 1:3200) were prepared and the last dilution was recorded. Among 336 sera, 77.4% showed seropositivity by IFAT. The positive rates of males and females were 77.6% (125/161) and 80% (140/175), respectively. However, there were no significant differences between sexes. Comparing the age groups, the highest seropositive rate showed in 19 or higher, and their rates had a tendency to increase with age. Prevalence of the infection in 10 rehabilitation centers was not significant either. Nevertheless, our data (77.4%) in rehabilitation centers in northern Iran suggest that infection is the same as in many other reports in normal population in this area, therefore toxoplasmosis is not a major problem in rehabilitation centers of this geographical area.

Pertussis seroimmunity among mother-infant pairs and infant immune response to pertussis vaccination.

This study was designed to evaluate seroprevalence rates of antibodies to pertussis in mothers and their infants, and the immunogenicity of pertussis vaccine in the presence or absence of pertussis antibodies in infants. Blood samples were collected from 110 mother-infants pairs before the first dose of pertussis vaccination and from 69 infants 4-8 weeks after administration of the third dose of DTwP vaccine. Pertussis antibodies were >25 U/mL in 88(78.9%) mothers and 50(45.3%) infants with a mean titer of 67(SD 48.1) and 33.5 (34.7) U/mL, respectively. After administration of three doses of DTwP vaccine, 53(76.8%) infants were seroconverted (MCA titer 87.4 (51.3)U/mL. Immunologic response to vaccination was similar between the two groups of infants; 30/37 (81.1%) of seronegative infants and 23/32 (71.9%) of seropositive infants at pre-vaccination, showed seroconversion after the vaccination (P = 0.36). The results of this study demonstrated that most of the studied mothers were serologically immune to pertussis, and this immunity was transferred to their infants. Pre-vaccination antibody did not affect infants immune response to vaccination.

Frequencies and phenotypic consequences of association of α- and ß-thalassemia alleles with sickle-cell disease in Bahrain.

INTRODUCTION: Bahrain has high prevalence rates of sickle cell and thalassemia in the population. This study reports the frequencies and phenotypic characteristics of α- and/or ß-thalassemia associated with sickle-cell disease (SCD) in a tertiary care hospital. METHODS: Adult SCD patients (n = 200) were screened for the common α- and ß-thalassemia alleles prevalent in the region using molecular techniques. Results of CBC, hemoglobin analysis, and average annual frequencies of severe pain episodes and numbers of transfused red cell units were documented. RESULTS: Patients were grouped on the basis of molecular studies as sickle-cell anemia (SS, n = 131), SS/α-thalassemia with three normal genes (n = 27), SS/α-thalassemia with two normal genes (n = 11), sickle-ß-thalassemia (Sß, n = 23), and Sß with co-inherited α-thalassemia (n = 8). Identified α-thalassemia determinants were -α3.7 (n = 52), -α4.2 (n = 4), αT-Saudi α (n = 1), and αHph α (n = 1). All ß-thalassemia alleles were ß0 defects. Sickle-thalassemia association resulted in higher hemoglobin, hematocrit, and erythrocyte counts with reduced MCV and reticulocytes. Significant clinical associations were as follows: increased severe pain frequency with α-thalassemia (three-gene group); red cell transfusion with ß-thalassemia alleles and female gender. CONCLUSION: One-third of patients with SCD co-inherited α- and/or ß-thalassemia alleles and these associations explained some of the observed phenotypic variability. A low prevalence of nondeletion α-thalassemia alleles was observed in these patients. The most significant disease amelioration occurred in SCD associated with two α-thalassemia alleles.

Sickle cell disease and pregnancy in Bahrain.

OBJECTIVE: To determine the morbidity and outcome of pregnancies complicated by homozygous sickle cell disease (SCD) in Bahrain. METHODS: A controlled study was conducted of all the pregnancies of women with SCD who were delivered at Salmaniya Medical Complex and affiliate hospitals in Bahrain between January 1, 1998, and December 31, 2002. RESULTS: There were 351 pregnancies with SCD, giving an incidence of 0.67%. The mean+/-S.D. age of women with SCD was 28.8+/-5.7 years. These women, who were mostly from Shia villages, had more spontaneous abortions than the 351 controls (32% and 12%, respectively). Compared with the control group, the mean+/-S.D. number of pregnancies among women with SCD was 5.0+/-1.9 vs. 5.7+/-3.1; birth weight, 2,965+/-540 g vs. 3,457+/-497 g; rate of preterm deliveries, 25.9% vs. 12%; incidence of intrauterine growth restriction, 10% to 13% vs. 4% to 7%; Apgar scores at 1 and 10 min, 8.1+/-0.8 and 8.8+/-0.8; and cesarean section rate, 19.0% vs. 12.7%. There were no differences in the rates of pre-eclampsia, antepartum and postpartum hemorrhage, or stillbirth. There were 4 maternal deaths directly related to SCD complications. Hemoglobin analysis was performed in 86% of the women with SCD. Of these women, 60.6% had homozygous SCD with raised levels of fetal hemoglobin (more than 5% HbF); 9.6% had sickle cell hemoglobin with beta-thalassemia disease; and 1.4% had sickle cell hemoglobin only. Vaso-occlusive crises were the most common cause of hospital admissions during pregnancy (42.2%), while hemolytic and sequestration crises accounted for 28.0% and 0.6% of admissions. CONCLUSION: Mortality, morbidity, and perinatal loss are still considerable among women with SCD in Bahrain. To reduce mortality and morbidity, there is a need for a multidisciplinary team able to deal with pregnancy complications due to SCD.

Measles seroepidemiology among adolescents and young adults: response to revaccination.

We evaluated the seroprevalence of measles antibody and response to measles reimmunization in 590 previously vaccinated adolescents and young adults; 263 were seronegative. To differentiate between primary and secondary vaccine failure, anti-measles IgM and IgG titres were assessed again 2-4 weeks after revaccination in 144 (105 seronegative, 39 seropositive) individuals: 75 seronegative participants responded to revaccination anamnestically (P < 0.001) and developed immunity, 11 also showed IgM response (probably primary vaccine failure); 38 seropositive participants remained seroprotected without significant increase in antibody titre (P = 0.577). Primary vaccine failure was 4.7%; secondary vaccine failure was 27.1%. After revaccination, 87.3% were seroprotected.

Effect of cystine intake on methionine kinetics and oxidation determined with oral tracers of methionine and cysteine in healthy adults.

There is evidence based on nitrogen balance that dietary cystine spares, from approximately 16% to 89%, the total methionine requirement. In a previous study we did not detect, by tracer techniques, a sparing effect of cystine when the diet provided methionine at a limiting intake (requirement level: 13 mg.kg-1.d-1). One reason could be that we used an intravenous infusion of the tracer, which may not, therefore, have labeled the carbon dioxide derived from the splanchnic oxidation of dietary methionine. The aim of this study was to compare methionine metabolism and oxidation in eight healthy adults given for 6 d each of three different diets: 13 mg (87.0 mumol) methionine.kg-1.d-1 and no cystine (diet A); 5 mg (33.5 mumol) methionine.kg-1.d-1 and no cystine (diet B); and 5 mg (33.5 mumol) methionine.kg-1.d-1 and 6.5 mg (52.4 mumol) cystine.kg-1.d-1 (diet C). On day 7, tracers ([1-13C, methyl-2H3]methionine and [2H2]cysteine) were administered orally at 30-min intervals for 8 h. Blood and breath samples were obtained for analysis during 3-h fasting and consecutive 5-h feeding periods. During fasting, methionine oxidation and methionine methyl (Qm) and carboxyl (Qc) fluxes and plasma concentrations were not affected by the amount of sulfur amino acids in the three diets. In the fed state methionine oxidation was significantly lower during diets B (3.0 +/- 0.5 mumol.kg-1.h-1) and C (2.8 +/- 0.6 mumol.kg-1.h-1) than during diet A (4.1 +/- 0.9 mumol.kg-1.h-1); there were no significant differences between diets B and C. Qm and Qc decreased with decreased methionine intake but no effect was observed by adding cystine. Cysteine flux (Qcys) was not affected by diet composition but it was lower during feeding than during fasting. In conclusion, replacing approximately 60% of the total requirement for methionine with cystine over a short diet period did not result in a detectable sparing of methionine oxidation.

An initial assessment, using 24-h [13C]leucine kinetics, of the lysine requirement of healthy adult Indian subjects.

The international 1985 FAO/WHO/UNU upper dietary requirement for lysine of 12 mg.kg-1.d-1 may be inadequate for healthy Indian adults. To test this, we used a modified indicator amino acid oxidation technique to assess the adequacy of lysine intake of 12 and 28 mg.kg-1.d-1. Seven healthy, male, Indian subjects were studied during each of two randomly assigned 6-d periods while receiving an otherwise adequate diet based on an L-amino acid mixture. Beginning at 1800 on day 6 of the diet, a 24-h infusion protocol in which a [13C]leucine tracer was administered intravenously was used to assess leucine oxidation and daily leucine balance at each test lysine intake. Mean 24-h leucine oxidation was 54.7 compared with 46.9 mg.kg-1.d-1 (P < 0.05) and mean 24-h leucine balances were -4.1 and 3.5 mg.kg-1.d-1 (P < 0.05) for lysine intakes of 12 and 28 mg, respectively. Leucine balances were significantly negative (0.025 < P < 0.05) with the 12-mg lysine intake and not significantly different (P > 0.10) from zero or equilibrium with the 28-mg intake. These findings indicate that the international requirement for lysine appears to be inadequate to maintain body amino acid homeostasis and function in apparently healthy subjects characteristic of the south Asia region. They further indicate that our previously proposed, tentative lysine requirement of 30 mg.kg-1.d-1 is probably adequate for this population.

Twenty-four-hour oral tracer studies with L-[1-13C]lysine at a low (15 mg.kg (-1).d (-1) and intermediate (29 mg.kg (-1).d(-1)) lysine intake in healthy adults.

BACKGROUND: We proposed previously that the mean lysine requirement value is approximately 30 mg * kg(-)(1) * d(-)(1) rather than the proposed 1985 FAO/WHO/UNU estimate of the upper range of the requirement, which is 12 mg * kg(-)(1) * d(-)(1). OBJECTIVE: Our objective was to explore the 24-h pattern and rate of whole-body lysine [l-(13)C]oxidation and status of whole-body lysine balance in healthy, young adults given an L-amino acid diet supplying either a low lysine intake (14-15 mg * kg(-)(1) * d(-)(1)) or an intermediate lysine intake (29 mg * kg(-)(1) * d(-)(1)) for 6 d before a continuous tracer study with L-[1-(13)C]lysine. DESIGN: Five subjects received the low lysine intake, 6 subjects received the intermediate intake, and all were studied by using a standard 24-h oral tracer protocol that was described earlier for studies at a generous lysine intake. RESULTS: The rate of lysine oxidation was not significantly different between the 12-h fasted and 12-h fed states. The daily oxidation rate (f1.gif" BORDER="0"> +/- SD) was 27. 9 +/- 8.8 and 27.3 +/- 17.6 mg lysine * kg(-)(1) * d(-)(1) for the low- and intermediate-intake groups, respectively (NS). Daily lysine balance was -12.4 +/- 92 and 1.8 +/- 17.7 mg * kg(-)(1) * d(-)(1), respectively (P < 0.025), for the low and intermediate intakes. The balance was significantly less than zero (P < 0.001) for the low intake. CONCLUSION: The FAO/WHO/UNU lysine requirement value is not sufficient to maintain lysine homeostasis in healthy adults. From the results of this and tracer studies done by others, the mean lysine requirement of healthy adults was determined to be 30 mg * kg(-)(1) * d(-)(1).

Twenty-four-hour intravenous and oral tracer studies with L-[1-13C]-2-aminoadipic acid and L-[1-13C]lysine as tracers at generous nitrogen and lysine intakes in healthy adults.

BACKGROUND: This is a continuation of investigations of the relations between amino acid kinetics and amino acid dietary requirements in healthy adults. OBJECTIVE: The aim was to investigate the 24-h pattern and rate of the metabolism of an L-[1-13C]-2-aminoadipic acid ([13C]AAA) tracer and of whole-body L-[1-13C]lysine ([13C]lysine) oxidation and balance in healthy, young adults receiving a generous intake of lysine. DESIGN: Thirteen healthy adults were given an adequate, L-amino acid-based diet supplying 77 mg lysine x kg(-1) x d(-1) for 6 d before the tracer studies. Two subjects received [13C]AAA intravenously and 2 received it orally; 3 subjects received [13C]lysine intravenously and 6 received it orally. We measured 13CO2 output, plasma [13C]AAA and [13C]lysine enrichment, and urinary [13C]AAA. RESULTS: [13C]AAA oxidation was estimated to be higher after the orally administered than after the intravenously administer tracer; plasma [13C]AAA was similar to urinary [13C]AAA. Whole-body lysine oxidation showed a rhythm that was induced by meal feeding. The intravenous [13C]lysine tracer gave mean estimates of lysine balances (lysine intake minus oxidation) that apparently were too low (-15.7 mg x kg(-1) x d(-1)) or too high (16.6 mg x kg(-1) x d(-1), P < 0.05 from zero balance) on the basis of urinary [13C]AAA or plasma [13C]lysine estimates of oxidation, respectively. For the orally administered tracer and plasma [13C]lysine enrichment, the mean balance was slightly positive (8.7 mg x kg(-1) x d(-1), P < 0.05 from zero). CONCLUSIONS: Use of urinary [13C]AAA as an index of the enrichment of the precursor pool did not appear to significantly improve the estimate of the fasting and feeding components of daily lysine balance. For estimates of daily, whole-body lysine oxidation, we propose use of plasma [13C]lysine with a 24-h, orally administered tracer protocol.

Phenylalanine conversion to tyrosine: comparative determination with L-[ring-2H5]phenylalanine and L-[1-13C]phenylalanine as tracers in man.

The in vivo rate of conversion of phenylalanine to tyrosine (PheOH) can be estimated using combinations of stable isotope-labeled phenylalanine and tyrosine. We have compared in four healthy adult men the rates of phenylalanine conversion to tyrosine based on the following pairs of primed, continuous tracer infusions administered simultaneously: (1) L-[ring-2H5]phenylalanine and 2H2-tyrosine with a 2H4-tyrosine prime, and (2) L-[1-13C]phenylalanine and 2H2-tyrosine with a 1-13C-tyrosine prime. Phenylalanine oxidation was determined from measurement of 13CO2 excretion in expired air. Tracers were given for 8 hours, with subjects being in the postabsorptive state during the first 3 hours and in the fed state during the remaining 5 hours. Mean (+/- SD) rates (mumol.kg-1.h-1) of phenylalanine conversion to tyrosine for fasted and fed states, respectively, were 5.1 +/- 2.9 and 6.8 +/- 3.4 with 2H5-phenylalanine and significantly higher (P < .05) at 11.1 +/- 5.6 and 12.7 +/- 7.7 with 13C-phenylalanine as tracer. Phenylalanine oxidation was 9.9 +/- 2.0 and 13.5 +/- 2.6, respectively, for fasted and fed states, and these mean values did not differ (P > .1) from the rate of phenylalanine conversion to tyrosine determined using 13C-phenylalanine. These results indicate the need for caution in interpreting kinetic aspects of phenylalanine metabolism when based on isotopic data from multideuterated phenylalanine.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma arginine kinetics in adult man: response to an arginine-free diet.

To explore the response of whole-body arginine metabolism to a change in arginine intake, plasma arginine kinetics were investigated in eight healthy adult men who received an L-amino acid diet supplying an Arg-rich or Arg-free intake for 6 days before undergoing a tracer study on day 7. The tracer protocol lasted for 8 hours. For the first 3 hours subjects remained in the postabsorptive (fasted) state, and during the following 5 hours they consumed small meals at 30-minute intervals. Primed continuous intravenous infusions of L-[guanidino-13C]arginine, L-[5,5,5-2H3]leucine, and [15N2]urea were administered to estimate plasma amino acid fluxes and the rate of urea production. For the fasted and fed states, plasma arginine fluxes (mumol.kg-1.h-1, mean +/- SD) were 69 +/- 8 and 87 +/- 12 (P < .01), respectively, for the Arg-rich diet and 63 +/- 14 and 51 +/- 7 (P < .01, from Arg-rich) for the Arg-free diet. Compared with the Arg-rich results, fed-state plasma arginine and ornithine concentrations were decreased (P < .01) and citrulline concentration was increased (P < .01) during the Arg-free diet period. Leucine fluxes and rates of urea production did not differ between the diet groups. The lower fed-state arginine flux in subjects receiving the Arg-free compared with the Arg-rich diet appears to be entirely due to the decreased rate of entry of arginine from the intestine in the former group.(ABSTRACT TRUNCATED AT 250 WORDS)

Performance of human mass balance studies with stable isotope-labeled drug and continuous flow-isotope ratio mass spectrometry: a progress report.

We propose performing human mass balance studies by administering stable isotope labeled (13C or 15N) drug and quantitating excess (above background) 13C or 15N in urine, serum, and feces by continuous flow-isotope ratio mass spectrometry (CF-IRMS). Theoretical calculations and empirical data (dynamic range, linearity, sensitivity, precision, accuracy) are presented to establish that commercially available CF-IRMS instruments can quantitate stable isotope labeled (one or two 15N or 13C labels) drug concentrations of 1.0 microg/mL or greater in urine, serum (15N), or feces. More than two 13C labels may be necessary to quantitate 1.0 microg/mL of drug in serum. Three volunteers received 650 mg of 15N13C2-acetaminophen, and urine was collected for 72 hours. Percent of administered label recovered in urine from the three subjects was 97.4, 78.9, and 95.4 for 13C and 90.3, 77.0, and 90.6 for 15N. Fecal recovery of label for one subject was 0.9% (13C2) and 1.1% (15N). Serum pharmacokinetic values obtained by counting 13C or 15N in one subject were as expected for acetaminophen. This method appears to be promising, and further validation is ongoing.

Alternatives to least squares linear regression analysis for computation of standard curves for quantitation by high performance liquid chromatography: applications to clinical pharmacology.

Standard curves and validation points for high-performance liquid chromatography (HPLC) determination of four drugs (carbamazepine and phenytoin at therapeutic drug monitoring concentrations and deuterium labeled carbamazepine and phenytoin at tracer dose concentrations) were computed using standard least squares linear regressions analysis and six alternative regression techniques (weighted 1/x, 1/y, 1/x2, 1/y2 least squares linear, log/log least squares linear, and robust). The coefficient of determination (R2) and the coefficient of prediction (R2pred) values for standard curves and the computed values for validation points did not differ significantly among the seven methods. The lower limit of quantitation (LLQ) values obtained with all six of the alternative regression methods were significantly (P < .01) lower than the LLQ values obtained with least squares linear regression analysis. The lowest LLQ values were obtained with 1/x2 and 1/y2 weighting and were threefold to tenfold less than the values obtained with unweighted least squares linear regression analysis (P < .001). The authors conclude that alternative regression analysis techniques (especially 1/x2 and 1/y2 weighting) offer significant advantages for clinical pharmacology studies when concentration values being measured by HPLC are near the LLQ of the method determined by unweighted least squares linear regression analysis. In other situations, alternative forms of regression analysis had no significant advantages in our study.