Recirculation in double lumen catheter veno-venous extracorporeal membrane oxygenation measured by an ultrasound dilution technique

Recirculation is a limiting factor for oxygen delivery in double lumen catheter veno-venous extracorporeal membrane oxygenation (DLVV-ECMO). This study compares three different methods for the determination of the recirculation fraction during double lumen catheter veno-venous ECMO at ECMO flow rates of 150, 125, 100, 75, and 50 ml/kg.min in nine lambs: (1) an ultrasound dilution method, in which the change in ultrasound velocity in blood after injection of a saline bolus as a marker is used for determination of recirculation; (2) an SvO2 method using real mixed venous blood oxygen saturation, the gold standard, for determination of recirculation fraction; and (3) the CVL method, in which oxygen saturation of a blood sample of the inferior vena cava is considered to represent mixed venous oxygen saturation. In all methods, the recirculation fraction increased with increasing ECMO flow rate. The correlation coefficient between the ultrasound dilution method and the SvO2 method was 0.68 (p < 0.01); mean difference was -2.4% (p = 0.6). Correlation coefficient between the ultrasound dilution method and the CVL method was 0.48 (p < 0.01); mean difference was -18.1% (p < 0.01). The correlation coefficient between the SvO2 method and the CVL method was 0.51 (p < 0.01); mean difference was -15.7% (p < 0.01). The ultrasound dilution method is a useful method for measurement of the recirculation fraction in DLVV-ECMO and is easier to use than the other methods.     

Lessons from a multicentre study of the detectability of viral genomes based on a two-round quality control of GB virus C (GBV-C)/hepatitis G virus (HGV) polymerase chain reaction assay

The aim of this study was to determine whether multicentre quality controls for the detectability of viral genomes could contribute to the improvement of diagnostic performance in the participating laboratories. The study was carried out during two successive rounds, during which 18 laboratories specialized in nucleic acid testing analyzed, through a polymerase chain reaction (PCR) assay, a common panel of GB virus C (GBV-C)/hepatitis G virus (HGV) RNA-positive and -negative samples. During the first round, the laboratories used either an 'in-house' PCR procedure or a partly standardized commercial test. After decoding the results of the first round, the procedures of the participating laboratories were compared in order to establish a consensus procedure deduced from those of the laboratories which provided the best results. During the second round, each participating laboratory could use the resulting consensus procedure, or its own procedure, or both. The results of this quality control study indicated that, whatever method used, even specialized and trained laboratories may give false-negative or false-positive results. The commercial assay did not guarantee a systematic high quality level of results. The striking heterogeneity of results observed among laboratories using the same commercial assay confirm that molecular biology methods need skilled technicians. The results of this quality control study suggest that full standardization of viral genome detection, including all steps of the procedure, is necessary and that the laboratories performing PCR should participate in repeated quality control studies, whatever technique is being used.     

Trisomy 13 and myelodysplastic syndrome

The clinical and cytogenetic data of a patient with myelodysplastic syndrome-refractory anemia with excess blasts (MDS-RAEB) and trisomy 13 as the sole abnormality are presented. This appears to be only the second report of such a patient. The presence of trisomy 13 is confirmed by in situ hybridization using an alphoid repeat probe L1.26, which is specific for the centromeres of both chromosomes 13 and 21.     

Human T hybridoma-derived immunoglobulin-binding factors

A human T hybridoma was generated lacking demonstrable low-affinity IgE surface receptors. This cell line produces spontaneously immunoglobulin-binding factors. The factors have an affinity for human IgE and IgG as well as for IgG from other species. The binding factors were purified by concanavalin A affinity chromatography, an IgE immunoaffinity column and SDS-PAGE. This purification procedure resulted in five major proteins bands at 13, 15, 30, 60 and less than 150 kilodaltons. As judged by Western blot analysis, all bands were variably glycosylated and were capable of binding IgE. Biological activity resided even within the small molecular weight (13 kilodaltons) peptide in terms of inhibiting IgE synthesis of the U266 B cell line and net IgE synthesis of B cells from atopic blood donors. Additionally, semipurified binding factor preparations also inhibited the Pokeweed mitogen-induced IgG synthesis while stimulating IgE synthesis at the same time. At present it is not clear whether the different molecular entities are dimers or polymers of the same protein, or are all derived from one larger protein (proteolytically cleaved), or whether they are completely different peptides mediating similar immunoglobulin-binding capacities as well as similar biological activities. Glycosylation of binding factors is not responsible for binding to immunoglobulins, but might be important for its biological activity.     

Hotspot for deletions in the CGG repeat region of FMR1 in fragile X patients

The fragile X syndrome is the most frequent cause of inheritedmental retardation. The molecular mechanism of the disorderis based on the expansion of a CGG repeat in the 5' UTR of theFMR1 gene In the majority of fragile X patients. The instabilityof this CGG repeat containing region is not restricted to theCGG repeat Itself but expands to the flanking region as well.We describe four unrelated fragile X patients that are mosaicfor both a full mutation and a small deletion in the CGG repeatcontaining region. Sequence analysis of the regions surroundingthe deletions showed that both the (CGG)_n repeat and some flankingsequences were missing in all four patients. The 5' breakpointsof the deletions were found to be located between 75–53bp proximal to the CGG repeat. This suggests the presence ofa hot spot region for deletions in the CGG repeat region ofthe FMR1 gene and emphasizes the instability of this regionIn the presence of an expanded CGG repeat.     

Prolactin and propranolol prevent the suckling-induced inhibition of lactation in rabbits

The normal once-a-day frequency of suckling in the rabbit was increased on day 31 (late lactation) by the addition of two extra sucklings (8 and 16 hr after) the daily suckling. In confirmation of previous data, two additional sucklings significantly decreased milk yield acutely on day 31 in comparison with the average 4-day milk yield before and after day 31. The decrease in milk secretion after the two additional sucklings was prevented by a single injection of 3 mg prolactin (given 24 hr before the two extra sucklings) and/or by injections of the beta-adrenergic-blocking drug, propranolol (100 micrograms/kg b. wt. given 30 min before each additional suckling). Since prolactin secretion is decreased in these species and the mammary gland is less responsive to the hormone during late lactation, the present results suggest that in addition to these factors, suckling-induced activation of sympathetic influences may contribute to the decline in milk production at this stage of lactation. Taken together, these results suggest that suckling may regulate lactation in the rabbit through antagonistic mechanisms at different stages of lactation.