Biological and Molecular Characterization of Chenopodium quinoa Mitovirus 1 Reveals a Distinct Small RNA Response Compared to Those of Cytoplasmic RNA Viruses.

Indirect evidence of mitochondrial viruses in plants comes from discovery of genomic fragments integrated into the nuclear and mitochondrial DNA of a number of plant species. Here, we report the existence of replicating mitochondrial virus in plants: from transcriptome sequencing (RNA-seq) data of infected Chenopodium quinoa, a plant species commonly used as a test plant in virus host range experiments, among other virus contigs, we could assemble a 2.7-kb contig that had highest similarity to mitoviruses found in plant genomes. Northern blot analyses confirmed the existence of plus- and minus-strand RNA corresponding to the mitovirus genome. No DNA corresponding to the genomic RNA was detected, excluding the endogenization of such virus. We have tested a number of C. quinoa accessions, and the virus was present in a number of commercial varieties but absent from a large collection of Bolivian and Peruvian accessions. The virus could not be transmitted mechanically or by grafting, but it is transmitted vertically through seeds at a 100% rate. Small RNA analysis of a C. quinoa line carrying the mitovirus and infected by alfalfa mosaic virus showed that the typical antiviral silencing response active against cytoplasmic viruses (21- to 22-nucleotide [nt] vsRNA peaks) is not active against CqMV1, since in this specific case the longest accumulating vsRNA length is 16 nt, which is the same as that corresponding to RNA from mitochondrial genes. This is evidence of a distinct viral RNA degradation mechanism active inside mitochondria that also may have an antiviral effect.IMPORTANCE This paper reports the first biological characterization of a bona fide plant mitovirus in an important crop, Chenopodium quinoa, providing data supporting that mitoviruses have the typical features of cryptic (persistent) plant viruses. We, for the first time, demonstrate that plant mitoviruses are associated with mitochondria in plants. In contrast to fungal mitoviruses, plant mitoviruses are not substantially affected by the antiviral silencing pathway, and the most abundant mitovirus small RNA length is 16 nt.

Selenocysteine biosynthesis and insertion machinery in Naegleria gruberi.

Selenium (Se) is an essential trace element primarily found in selenoproteins as the 21st amino acid (selenocysteine, Sec, or U). Selenoproteins play an important role in growth and proliferation and are typically involved in cellular redox balance. Selenocysteine is encoded by an in-frame UGA codon specified by a stem-loop structure, the Sec insertion sequence element (SECIS), which, in eukaryotes, is located in the 3'-untranslated region (UTR). The availability of the Naegleria gruberi (ATCC 30224) genome sequence and the use of this organism as a model system for the pathogenic amoeba N. fowleri allowed us to investigate the Sec incorporation pathway in this primitive eukaryote. Using bioinformatics tools, we identified gene sequences encoding PSTK (O-phosphoseryl-tRNA(Sec) kinase), SepSecS (O-phosphoseryl-tRNA:selenocysteinyl-tRNA synthase), SelD/SPS2 (selenophosphate synthetase), EFSec (selenocysteine-specific elongation factor) and SBP (SECIS binding protein). These findings were confirmed by RT-PCR and by sequencing. A potential tRNA(Ser)Sec (SelC) gene and a putative selenoprotein with sequence similarity to a mitochondrial thioredoxin reductase (TR3) were also identified. Our results show that the selenocysteine incorporation machinery is indeed present in N. gruberi. Interestingly, the SelD/SPS2 gene is 2214 bp in length and contains two distinct domains. The N-terminal region shows sequence similarity to predicted methyltransferase proteins, and the C-terminal region is homologous to prokaryotic SelD/SPS2. Our results suggest the possibility of novel selenoproteins.

Blunted response of pituitary type 1 and brown adipose tissue type 2 deiodinases to swimming training in ovariectomized rats.

Ovariectomy leads to significant increase in body weight, but the possible peripheral mechanisms involved in weight gain are still unknown. Since exercise and thyroid hormones modulate energy balance, we aimed to study the effect of swimming training on body weight gain and brown adipose tissue (BAT) type 2 iodothyronine deiodinase responses in ovariectomized (Ox) or sham-operated (Sh) rats. Rats were submitted to a period of 8-week training, 5 days per week with progressive higher duration of exercise protocol. Swimming training program did not totally prevent the higher body mass gain that follows ovariectomy in rats (16.5% decrease in body mass gain in Ox trained rats compared to 22% decrease in sham operated trained animals, in relation to the respective sedentary groups), but training of Ox animals impaired the accumulation of subcutaneous fat pads. Interestingly, swimming training upregulates pituitary type 1 (p<0.001 vs. all groups) and BAT type 2 iodothyronine deiodinases (p<0.05 vs. ShS and OxS) in sham operated but not in Ox rats, indicating an impaired pituitary and peripheral response to exercise in Ox rats. However, BAT mitochondrial O2 consumption significantly increased by swimming training in both sham and Ox groups, indicating that Ox BAT mitochondria responds normally to exercise stimulus, but does not result in a significant reduction of body weight. In conclusion, increased body mass gain produced by Ox is not completely impaired by 8 weeks of high intensity physical training, showing that these animals sustain higher rate of body mass gain independent of being submitted to higher energy expenditure.

Telomere dynamics in mammals.

Telomeres are specialized structures found at the end of linear chromosomes. Telomere structure and functions are conserved throughout evolution and are essential for genome stability, preventing chromosome ends from being recognized as damaged DNA and from being fused or degraded by the DNA repair machinery. The structure of telomeres is intrinsically dynamic and affected by multiple processes that impact their length and nucleoprotein composition, thus leading to functional and structural heterogeneity. We review here the most significant facets of telomere metabolism and its dynamics, with an emphasis on human biology.

Estabilidad de la capacidad antioxidante y pH en leche humana refrigerada durante 72 horas: estudio longitudinal / Stability of the antioxidant capacity and ph of human milk refrigerated for 72 hours: longitudinal study

La leche materna es la vía óptima de alimentación del lactante durante, al menos, los primeros 6 meses de vida. Su elección se basa en el aporte de nutrientes y, de forma especial, en proporcionar al neonato diversos compuestos de acción beneficiosa que mejoran su crecimiento y le protegen frente a patologías propias de esta etapa. Estas propiedades de la leche materna justifican los procesos de manipulación previos a su ingesta, con el fin de promover y asegurar su seguimiento, tanto a nivel casero como a nivel hospitalario, de mayor importancia en lactantes prematuros y/o de bajo peso, por su destacada vulnerabilidad, a pesar de que durante estos procesos se pueden perder parcialmente algunas de sus propiedades. Es por ello que interesa conocer el efecto que los tratamientos aplicados a la leche humana ejercen sobre sus principales cualidades, como su capacidad antioxidante. Objetivo: Este trabajo analiza la estabilidad de la capacidad antioxidante de la leche humana durante su almacenamiento a 4ºC, de forma longitudinal desde su extracción hasta las 48 horas de refrigeración, así como las variaciones del pH. Método: Se analiza la leche madura procedente de 30 mujeres sanas. El poder antioxidante de la leche se evalúa a través de los parámetros: capacidad antioxidante total y concentración de malondialdehído. Los resultados obtenidos muestran que el pH disminuye de forma creciente desde el inicio del almacenamiento, mientras que la capacidad antioxidante, con diferente comportamiento según el parámetro evaluador considerado, permanece estable durante las primeras 24 horas, a partir de las cuales se presentan cambios significativos. Conclusiones: Cuando es preciso recurrir a la extracción y refrigeración de la leche antes de su ingesta es recomendable minimizar el tiempo de almacenamiento, procurando que no supere las 24 horas si se quiere preservar del estrés oxidativo (AU)

Maternal milk is the optimal feeding way for the infant at least for the first six months of life. Its properties include nutrients intake and, particularly, to provide the infant with several beneficial compounds improving his growth and protecting him from the diseases typical of this time period. These properties justify the manipulating processes before its intake in order to promote and warrant the adherence to it, both at the hospital and at home, being more important in premature infants and/or with low birth weight given their increased vulnerability, is spite of the fact that during these processes some of its properties may be partially lost. There exist, therefore, an interest in knowing the impact of the procedures applied to human milk on its qualitative properties, such as the antioxidant capacity. Objective: This work assesses the stability of the antioxidant capacity of human milk during its storage at 4º C, longitudinally from its extraction until 48 h of refrigeration, as well as the pH changes. Method: the milk from 30 healthy women was analyzed. The milk’s antioxidant capacity was assessed by the following parameters: total antioxidant capacity and level of malondialdehyde. The results obtained showed that pH decreases gradually from the storage beginning, where as the antioxidant capacity remains constant for the first 24 hours, with a different result depending on the parameter used, and there after significant changes were observed. Conclusions: In case of needing extraction and storage of maternal milk before its consumption, the storage time should be minimized, preferably less than 24 hours in order to preserve the oxidative stress (AU)

[Stability of the antioxidant capacity and pH of human milk refrigerated for 72 hours: longitudinal study]. / Estabilidad de la capacidad antioxidante y pH en leche humana refrigerada durante 72 horas: estudio longitudinal.

UNLABELLED: Maternal milk is the optimal feeding way for the infant at least for the first six months of life. Its properties include nutrients intake and, particularly, to provide the infant with several beneficial compounds improving his growth and protecting him from the diseases typical of this time period. These properties justify the manipulating processes before its intake in order to promote and warrant the adherence to it, both at the hospital and at home, being more important in premature infants and/or with low birth weight given their increased vulnerability, is spite of the fact that during these processes some of its properties may be partially lost. There exist, therefore, an interest in knowing the impact of the procedures applied to human milk on its qualitative properties, such as the antioxidant capacity. OBJECTIVE: This work assesses the stability of the antioxidant capacity of human milk during its storage at 4º C, longitudinally from its extraction until 48 h of refrigeration, as well as the pH changes. METHOD: the milk from 30 healthy women was analyzed. The milk's antioxidant capacity was assessed by the following parameters: total antioxidant capacity and level of malondialdehyde. The results obtained showed that pH decreases gradually from the storage beginning, whereas the antioxidant capacity remains constant for the first 24 hours, with a different result depending on the parameter used, and thereafter significant changes were observed. CONCLUSIONS: In case of needing extraction and storage of maternal milk before its consumption, the storage time should be minimized, preferably less than 24 hours in order to preserve the oxidative stress.

Conservation of hepatitis C virus nonstructural protein 3 amino acid sequence in viral isolates during liver transplantation.

As a consequence of selective pressure exerted by the immune response during hepatitis C virus (HCV) infection, a high rate of nucleotide mutations in the viral genome is observed which leads to the emergence of viral escape mutants. The aim of this study was to evaluate the evolution of the amino acid (aa) sequence of the HCV nonstructural protein 3 (NS3) in viral isolates after liver transplantation. Six patients with HCV-induced liver disease undergoing liver transplantation (LT) were followed up for sequence analysis. Hepatitis C recurrence was observed in all patients after LT. The rate of synonymous (dS) nucleotide substitutions was much higher than that of nonsynonymous (dN) ones in the NS3 encoding region. The high values of the dS/dN ratios suggest no sustained adaptive evolution selection pressure and, therefore, absence of specific NS3 viral populations. Clinical genotype assignments were supported by phylogenetic analysis. Serial samples from each patient showed lower mean nucleotide genetic distance when compared with samples of the same HCV genotype and subtype. The NS3 samples studied had an N-terminal aa sequence with several differences as compared with reference ones, mainly in genotype 1b-infected patients. After LT, as compared with the sequences before, a few reverted aa substitutions and several established aa substitutions were observed at the N-terminal of NS3. Sites described to be involved in important functions of NS3, notably those of the catalytic triad and zinc binding, remained unaltered in terms of aa sequence. Rare or frequent aa substitutions occurred indiscriminately in different positions. Several cytotoxic T lymphocyte epitopes described for HCV were present in our 1b samples. Nevertheless, the deduced secondary structure of the NS3 protease showed a few alterations in samples from genotype 3a patients, but none were seen in 1b cases. Our data, obtained from patients under important selective pressure during LT, show that the NS3 protease remains well conserved, mainly in HCV 3a patients. It reinforces its potential use as an antigenic candidate for further studies aiming at the development of a protective immune response.

Effect of pasteurization on the bactericidal capacity of human milk.

The use of human milk in milk banks requires thermal processing to eliminate microbiological hazards. An evaluation is made of the stability of overall human milk bactericidal capacity following 2 modalities of thermal pasteurization: 63 degrees C/30 minutes and 75 degrees C/15 seconds. Ten milk samples (mature milk) were analyzed. In each sample, the effect of both thermal treatments on bactericidal capacity against Escherichia coli was evaluated in relation to the capacity of fresh milk (control). All the samples analyzed possessed bactericidal capacity. Human milk pasteurization induced a significant loss of this capacity that was more pronounced after high-temperature treatment than after low-temperature processing. Untreated milk, low-pasteurized milk, and high-pasteurized milk yielded a reduction in E. coli growth of 70.10%, 52.27%, and 36.39%, respectively. In conclusion, human milk possesses antimicrobial activity that is lost in part as a result of thermal processing. Such bactericidal capacity is, moreover, better preserved by low-temperature, long-time pasteurization.

New approach for rapid detection of known hemoglobin variants using LC-MS/MS combined with a peptide database.

The identification of hemoglobin (Hb) variants is usually performed by means of different analytical steps and methodologies. Phenotypic methods, such as gel electrophoresis and high performance liquid chromatography, are used to detect the different electrophoretic or chromatographic behaviors of hemoglobin variants in comparison to HbA0 used as a control. These data often need to be combined with mass spectrometry analyses of intact globins and their tryptic peptide mixtures. As an alternative to a 'step-by-step' procedure, we have developed a 'single step' approach for the identification of Hb variants present in biological samples. This is based on the microHPLC-ESI-MS/MS analysis of the peptide mixture generated by a tryptic digestion of diluted Hb samples and an in-house new database containing solely the variant tryptic peptide of known human Hb variants. The experimental results (full MS and MS/MS spectra) are correlated with theoretical mass spectra generated from our in-house-built variant peptide database (Hbp) using the SEQUEST algorithm. Simple preparation of samples and an automated identification of the variant peptide are the main characteristics of this approach, making it an attractive method for the detection of Hb variants at the routine clinical level. We have analyzed 16 different samples, each containing a different known variant of hemoglobin.

Bactericidal activity of human milk: stability during storage.

Human milk provides infants with defensive factors against many illnesses. This study aims to analyse global bactericidal activity in fresh human milk and evaluate its stability in relation to milk manipulation and its possible alteration following refrigeration. Nineteen milk samples (mature milk) from 19 healthy women are analysed. Viability testing involving a strain of Escherichia coli NCTC 9111, serovar O111:K58(B4):H- was used to determine the bactericidal effect of human milk. Degree of bacteriolysis is calculated as the difference between E. coli counts in controls and in milk samples, expressed as a percentage of the control sample counts. An evaluation of the effect of refrigeration at 4-6 degrees C after 24, 48 and 72 hours, and at -20 degrees C for seven days on bactericidal capacity is made. Bactericidal activity was detected in all milk samples analysed (77.33 +/- 15.14%). This activity persisted after refrigeration for 48 hours and after freezing for 10 days, but showed a significant decrease after refrigeration for 72 hours. In conclusion, maternal milk has bactericidal capacity, providing defence and protection against infection for newborn infants. This property can be altered during the storage of milk. Consequently, if storage in excess of 48 hours is required, freezing is preferable to refrigeration.

Available lysine content in human milk: stability during manipulation prior to ingestion.

UNLABELLED: Available lysine content is an indicator of protein quality and nutritional value of milk. Many studies have examined the effects of extraction, treatment and storage of human milk upon its components, though no references are found regarding the possible changes in milk quality as defined by its content in essential amino acids such as lysine. The present study investigates the available lysine content in human milk and the variations in lysine resulting from milk manipulation as follows: (a) Cold storage (refrigeration at 4 degrees C for 48 hours, and frozen for 15 days at -20 degrees C); (b) Thermal treatment under conditions of low (Holder)(63 degrees C/30 minutes) and high pasteurization (75 degrees C/15 seconds). The results obtained show a decrease in milk lysine concentration after storage in both refrigerated and frozen samples. Pasteurization causes a highly significant loss of available lysine. The lysine losses were greater on applying low pasteurization versus the more gentle conditions of high pasteurization. CONCLUSIONS: While manipulation through cold storage or thermal treatment does not affect the protein content of human milk, its protein quality is modified. When human milk must be subjected to hygienization, it is preferable to apply high temperature treatment (75 degrees C, 15 seconds) than habitual pasteurization (63 degrees C, 30 minutes).

Copper, iron, and zinc contents in human milk during the first three months of lactation: a longitudinal study.

The aim of the study has been to analyze the evolution of copper, iron, and zinc contents in human milk, from colostrum to the third postpartum month, following a longitudinal design, under specific conditions of sample collection and to apply an analytical procedure previously optimized to reduce any variation outside physiological lactation. The copper, iron, and zinc concentrations in 144 milk samples from 39 healthy puerpera women, were analyzed in five stages by flame atomic absorption spectrometry, following a standardized protocol. Copper presented a gradual decrease from 0.38 mg/L to 0.19 mg/L by the 90th day; the particular analysis from colostrum to transitional milk manifested the following two tendencies. Whereas an increase from 0.19 to 0.42 mg/L was observed in some women, a decrease from 0.53 to 0.45 mg/L was detected in others; therefore, copper presented two significant behaviors in the evolution from colostrum to transitional milk. In both cases, the evaluated changes were significant. The iron content varied from 0.56 to 0.40 mg/L by the 30th day, remaining constant until the first trimester concluded. The average zinc concentration decreased sharply from 7.99 to 3.3 mg/L on d 15; the rate of decrease slowed down gradually until 1.05 mg/L.

[Incidence of hepatitis C infection among donors of femur heads to the tissue bank]. / Incidencia de infección por hepatitis C en donantes de cabezas femorales para el banco de tejidos.

Living donors of femoral heads belong to a highly specific group in terms of age and pathological characteristic, forming the core of the group who supply many tissue banks with spongy bone, to cover the needs of several specialties in the field of repair and corrective surgery. Analysis for the presence of the hepatitis C virus in this population was conducted as a part of quality control programs, while habitual blood donors from the same geographical location were used as the control group. Although the comparison of results could give rise to erroneous interpretations, due to the lack of qualitative fit between the groups, a much higher incidence of infection by VHC was found in the donors of spongy bone than was the case for blood donors (3.816% vs. 0.569%), although a smaller proportion of donors had hepatic alterations (measured by transaminases). In spite of the fact that the prevalence of VHC is almost 6 times that corresponding to the control group, the elimination of live donors of spongy bone would create serious problems with supply to tissue banks. We therefore propose that more severe exclusion criteria be applied to the selection of bone donors, and also that sterilisation techniques be employed, using physical-chemical procedures (liophilisation, dehydration, chemical treatment, irradiation) to process these tissues. We also recommend that younger multiple organ tissue donors be used as sources of spongy bone for cold storage that is not to be subjected to any additional sterilisation treatment.

[Cognition disorders in HIV infection. Validation of a brief neuropsychological evaluation battery]. / Troubles cognitifs au cours de l'infection par le VIH. Validation d'une batterie courte dévaluation neuropsychologique.

UNLABELLED: The objective of our study was the elaboration and the validation of a brief neuropsychological battery sensitive to the main cognitive and psychomotor deficits in HIV+ patients with HIV encephalopathy and cognitive impairment associated with seropositivity. We evaluated the sensitivity of this brief battery with respect to a large neuropsychological battery of standardized tests. METHODOLOGY: A brief battery (BB) (30 mn, with simple and portable material) of 5 standardized subtests and 7 new elaborated tests and a large battery (LB) (2 h to 2 h 30) of 16 standardized subtests, were constituted. Both screened 6 major cognitive areas (attention, memory, visuospatial function, psychomotor speed, motor dexterity, language). On the LB, subjects' age and educational level were considered while appraising performances to determine whether subjects had normal cognitive status (less than 4 abnormal test scores), borderline cognitive impairment (4 or 5 abnormal test scores); on the BB norms for the new tests were generated from the results of 24 HIV+ subjects with normal cognitive status on the LB and 15 HIV- subjects of a control group; performance on the BB was considered normal if less than 3 test scores were abnormal, or impaired if more than 3 test scores were abnormal. Conclusions deduced from the assessments with BB were compared to those obtained from LB. For all subjects, a possible anxio-depressive component was evaluated on the basis of DSM III-R criteria and clinical scales (MADRS and STAXI). Subjects were included in the study notwithstanding mode of contamination and stage of illness and anxiodepressive antecedents; patients with identified brain disease or evolutive non neurological pathology were not included. 102 evaluations were performed on a population of HIV+ patients comprising 89 men and 13 women: 19 CDC II, 35 CDC III or IV C 2 and 48 CDC IV; 76 homosexuals, 8 heterosexuals, 16 drug users and 2 transfused. RESULTS: the BB led to the same conclusions for 90.6% of the 53 impaired cases (on LB) and for 96% of the 24 normal cases. The reliability of the BB is therefore of 92%; there was only 1 false positive (less than 2%) and less than 6.5% false negatives. Among the 25 subjects with borderline cognitive impairment, half were impaired and half were normal on the BB; most (84%) presented with anxio-depressive symptoms. COMMENTS AND CONCLUSION: The brief battery (BB) testing 6 cognitive functions could be considered as a sensitive, practical instrument for rapid detection of cognitive impairment in HIV+ patients, with a few rate of false positive or negative diagnosis. However, it is not adequate for determining whether psychiatric or/and organic brain pathology is at the origin of the deficit. Evaluation and follow-up of a possible anxio-depressive component has to be considered together before concluding.

[Anxious-depressive state and cognitive deficit in HIV infection]. / Statut anxio-dépressif et déficit cognitif au cours de l'infection par le VIH.

UNLABELLED: This study tries to demonstrate the importance of using follow-up trials and taking anxio-depressive status into account while interpreting cognitive impairment in HIV-infected subjects. Subjects included were: 18 HIV carriers, mostly homosexual, belonging to CDC groups II (4), III or IVC2 (7) and IV (7), selected within a cohort of 63, as having been assessed 3 times, with no focal or identified brain disease at entry. Our methods were: 1) psychiatric interview based on DSM III-R criteria, clinical scales (Spielberger's STAXI and the MADRS) and cognitive questionnaires; 2) neuropsychological evaluation including 16 subtests screening attention, memory, visuo-spatial function, motor dexterity, psychomotor speed, and language; 3) repeated assessment within a period ranging from 6 to 21 months. RESULTS: At entry, cognitive status was impaired for 14 subjects (2 II, 5 III or IVC2, 7 IV). Disorders had disappeared for 7 subjects (2 II, 2 IVC2 and 3 IV) at following assessments allowing us to conclude on a psychogenic origin. For 7 subjects, cognitive status had either remained constant (3 III and 2 II) or had worsened within 7 to 17 months (2 IV), whereas psychiatric symptoms had decreased, implying HIV encephalopathy. Follow-up trials including 3 neuropsychological and psychiatric assessments and neuroimagery, if necessary, were required to ascertain the causes of cognitive impairment consequently attributed to anxio-depressive symptoms or HIV encephalopathy in 14 subjects.

DNA haplotype analyses of patients with hyperphenylalaninemia.

Linkage analysis of phenylketonurics has shown a strong association between the DNA haplotype at the phenylalanine hydroxylase (PAH) locus and phenylketonuria (PKU). Similarly, a genetic linkage between less severe forms of hyperphenylalaninemia (HPA) and the PAH locus has been suggested. In the present study we analyzed this linkage in more detail. Haplotypes at the PAH locus were determined for 19 individuals with moderately elevated plasma phenylalanine and normal urinary neopterin/biopterin ratios. Fourteen of these individuals had plasma phenylalanine levels of 4-10 mg/dl (mild HPA), and the other five had plasma phenylalanine levels of 10-19 mg/dl (atypical PKU). Thirteen of the 15 HPA families consisted of an affected child and at least one other sibling. Elevated plasma phenylalanine was seen to genetically segregate with specific PAH alleles in each family. Summation of the LOD scores for both categories of moderate plasma phenylalanine elevation gave a maximum value of 3.556 at theta = 0. At theta = 0 this gives a probability of linkage between the PAH locus and the locus for moderate phenylalanine elevations that is approximately 3,600:1. None of the alleles segregating with either mild HPA or atypical PKU were of haplotype 2 or 3, and 13/20 were of types 1 or 4. This is in agreement with the most deleterious mutations being on haplotypes 2 and 3 and with the less severe mutations being on haplotypes 1 and 4. chi 2 Analyses indicated no statistically significant correlation between HPA and a particular haplotype or restriction-enzyme site.

Distribution of zeranol in bovine tissues determined by selected ion monitoring capillary gas chromatography/mass spectrometry.

Bovine tissues, including liver, muscle, kidney, bile, serum, and urine, have been quantified by selected ion monitoring capillary gas chromatography/mass spectrometry to establish the distribution of the anabolic drug, zeranol, and its metabolites, taleranol and zearalanone, after administration of zeranol to 9 bovine animals. The method used to isolate, confirm, and quantify zeranol is undergoing validation by the United States Department of Agriculture, Food Safety Inspection Service (FSIS). Application of this method demonstrates utility in determining residue levels of zeranol in a variety of tissues with levels ranging over 4 orders of magnitude (i.e., 100 parts per trillion (ppt) to 1 part per million (ppm]. The analyte levels determined in this study complement previously reported pharmacokinetic data on the distribution of zeranol in addition to providing more specific information for taleranol and zearalanone. In this quantitative study it is shown that the liver is the main organ of deposition for zeranol, taleranol, and zearalanone, that taleranol is the main metabolite in the bovine, and that zeranol is efficiently eliminated.