Use of fetal biometry to determine fetal age in late pregnancy in llamas

Sixty-three pregnant llamas of known breeding date were used in this study. Forty-six of them were submitted to surgery between 186 and 320 days of gestation (52-91% of average gestation period, respectively). Under general anesthesia their fetuses were exteriorized and fetal weight (W), biparietal diameter (BPD) and femoral (F), tarsus-hoof (T-H), tibial (T)) and fronto-occipital (F-O) length were determined. Additionally, the same variables were determined on 16 newborn llamas. The weight was measured in kg and the length in cm. All the collected data was entered into a spreadsheet and different regression analyses as a function of gestational age (GA) were assessed. The best fit equations and their correlation for linear regression were the following: GA=169.448+16.66(*)W, r=0.99; GA=-51.713+44.77(*)BPD, r=0.88; GA=-72.139+39.48(*)F-O, r=0.71; GA=39.304+8.35(*)T-H, r=0.97; GA=91.276+8.23(*)T, r=0.86; GA=102.029+9.94(*)F, r=0.91. For multiple regression, the dependent variable GA can be predicted by the following equation: GA=67.462+11.163(*)W+20.297(*)BPD. Results of the present study indicated measured variables to be highly correlated with GA. This could be useful on daily basis in clinical examination of the neonates, in assessment of fetal growth and well being with cesarean sections, in the determination of GA in late gestation abortions, and in perinatal and reproductive research in the llama.

Low-dose inhaled carbon monoxide reduces pulmonary vascular resistance during acute hypoxemia in adult sheep

Carbon monoxide (CO) is produced by the action of the heme oxygenase (HO) complex through the oxidation of heme. CO, like nitric oxide (NO), is a molecular gas that among other actions stimulates guanylyl cyclase and increases cGMP levels in smooth muscle cells, regulating the vascular tone. Acute hypoxia generates pulmonary hypertension and increases the expression of inducible HO isoform (HO-1) in the vascular endothelium. Inhaled NO causes a potent pulmonary vasodilation. We hypothesized that inhaled CO might produce similar actions as NO on pulmonary vascular resistance (PVR). To test our contention, we studied the effects of inhaled CO (40 ppm) in the augmented PVR observed during hypoxemia. Five chronically instrumented German Merino sheep were submitted to a protocol consisting of 20 min of normoxemia (N), 20 min of isocapnic hypoxemia (H20), 20 min of isocapnic hypoxemia plus CO 40 ppm (H40), and 20 min of recovery (R). In the control protocol, we did not administer inhaled CO. Arterial gases and pH, percentage of carboxyhemoglobin (COHb), systemic and pulmonary arterial pressure, systemic and pulmonary vascular resistance, and cardiac output were measured during each period. During H20 period, there was a significant increase in cardiac output and PVR in sheep submitted to both protocols. The sheep treated with inhaled CO (H40 + CO) showed a modest but significant decrease (16%) in the elevated PVR. Our data indicate that inhaled CO decreases pulmonary vascular resistance associated with acute hypoxemia in adult sheep.

Cardiovascular responses to arginine vasopressin blockade during acute hypoxemia in the llama fetus

The fetal llama has a marked increase in the peripheral vascular resistance and no augmentation of brain blood flow during hypoxemia. In spite of the substantial plasma arginine-vasopressin (AVP) increase during hypoxemia, up to 8 times greater than in fetal sheep, there are no changes of carotid and femoral blood flows during hypoxemia with a V1 receptor blockade, as is seen in the fetal sheep. The aim of this study was to assess the role of AVP function in mediating the combined ventricular output and organ blood flow in the hypoxemic llama fetus. Six fetal llamas at 0.65 of gestation were instrumented under general anesthesia, and cardiorespiratory responses and blood flows determined under normoxemic and hypoxemic conditions. The AVP effect was determined using a V1 antagonist during normoxemic and hypoxemic conditions. Organ blood flows were measured with the radioactive microsphere technique. No significant differences in organ blood flow or in their vascular resistances were seen between the control and treated fetuses during hypoxemia. We conclude that V1 blockade did not have any important role in the cardiovascular response to acute hypoxemia in the llama fetus, in contrast with lowland fetuses. AVP may be playing a role in other regions, possibly in kidney or lung, during hypoxemia.

Differentiation between Mycobacterium tuberculosis and Mycobacterium bovis by a multiplex-polymerase chain reaction

A multiplex-polymerase chain reaction (PCR) assay, based on one-step amplification and detection of three different mycobacterial genomic fragments, was designed for differentiation between Mycobacterium bovis and Mycobacterium tuberculosis. The oligonucleotide primers were chosen from the groEL gene, present in the genus Mycobacterium sp., from the IS6110 insertion sequence, present in Myco. tuberculosis complex and from the mtp40 gene, identified as a specific-species Myco. tuberculosis genomic fragment. This amplification method allowed the detection of two fragments of 576 and 317 base pairs in Myco. bovis and three fragments of 576, 396 and 317 base pairs in Myco. tuberculosis strains, including atypical strains of Myco. tuberculosis where the copy number of the IS6110 element is low. The multiplex-PCR assay described may be a very useful tool for the rapid and specific differentiation of these related mycobacteria and easy to use in medical and veterinary microbiology laboratories.

Evaluation of mtp40 genomic fragment amplification for specific detection of Mycobacterium tuberculosis in clinical specimens

A PCR assay based on the species-specific mtp40 genomic fragment was developed for the specific detection and identification of Mycobacterium tuberculosis in different uncultured clinical specimens. The aim of the study was to evaluate the clinical applicability of this target DNA in comparison with those of conventional microbiological methods and to compare the results obtained with those obtained after amplification with the IS6110 repetitive element. Discrepant results were interpreted in conjunction with the patients' clinical data, medical histories, and response to therapy. A total of 172 specimens from 162 patients with respiratory symptoms were tested, 101 specimens were obtained from 92 patients clinically suspected of having tuberculosis, and 71 specimens were obtained from 70 patients without known mycobacterial infection. The results of our study suggest that PCR amplification with the mtp40 genomic fragment provides a highly sensitive and specific technique for the detection of M. tuberculosis strains in clinical samples. It allows for the differentiation between M. tuberculosis and other related mycobacteria, including M. bovis, and is more specific than the IS6110 target. For these and other reasons, we propose that the mtp40 assay is a possible alternative for the specific direct detection of M. tuberculosis in clinical laboratories.

[Comparative study of 2 rapid techniques (DNA hybridization and chromatography) for the identification of Mycobacterium tuberculosis complex isolated from clinical specimens]

We have compared the capacity of two combined chromatographic methods (gas chromatography and thin-layer chromatography) and a nucleic acid hybridization probe (Gen-Probe) to identify members of the Mycobacterium tuberculosis complex. The results of a single test show 6% of false-negatives with Gen-Probe and 8.5% doubtfuls with chromatography. After repeated, the specificity of both methods was improved to 100%. The advantages and disadvantages of the two methods in relation to its capacity to provide a rapid identification of Mycobacterium tuberculosis are discussed.