Analysis of MR phase-contrast measurements of pulsatile velocity waveforms

Errors in the measurement of the mean velocity of pulsatile velocity waveforms with ungated phase-contrast techniques were studied theoretically and experimentally. Waveforms consisting of a constant and two sinusoidal components were analyzed. Variations in magnitude and phase of the vascular magnetic resonance (MR) signal resulted in errors, the severity of which increased when either factor increased. Magnitude variations always resulted in overestimation. The general shape of the waveform greatly influenced the error, with certain waveforms producing greater inherent error than others. Experimental measurements were performed, validating the predicted sensitivity of these errors to changes in imaging parameters, including TR and flow-encoding sensitivity. Errors generally became more severe with increased flow-encoding sensitivity. The theoretical and experimental results suggest that accurate mean velocity measurements in many vessels of the body--with acquisition times of less than 15 seconds--should be attainable with ungated imaging techniques and with careful selection of relevant imaging parameters.     

A small family of elements with long inverted repeats is located near sites of developmentally regulated DNA rearrangement in Tetrahymena thermophila

Extensive DNA rearrangement occurs during the development of the somatic macronucleus from the germ line micronucleus in ciliated protozoans. The micronuclear junctions and the macronuclear product of a developmentally regulated DNA rearrangement in Tetrahymena thermophila, Tlr1, have been cloned. The intrachromosomal rearrangement joins sequences that are separated by more than 13 kb in the micronucleus with the elimination of moderately repeated micronucleus-specific DNA sequences. There is a long, 825-bp, inverted repeat near the micronuclear junctions. The inverted repeat contains two different 19-bp tandem repeats. The 19-bp repeats are associated with each other and with DNA rearrangements at seven locations in the micronuclear genome. Southern blot analysis is consistent with the occurrence of the 19-bp repeats within pairs of larger repeated sequences. Another family member was isolated. The 19-mers in that clone are also in close proximity to a rearrangement junction. We propose that the 19-mers define a small family of developmentally regulated DNA rearrangements having elements with long inverted repeats near the junction sites. We discuss the possibility that transposable elements evolve by capture of molecular machinery required for essential cellular functions.     

Intrathecal clonidine and baclofen in the management of spasticity and neuropathic pain following spinal cord injury: a case study

Spasticity and pain are common disabling sequelae following spinal cord injury (SCI) and are often difficult to manage. The two problems are also not infrequently related. A variety of pharmacological and other approaches have been described for management of these problems in SCI. This case study reports a 32-year-old woman with an established incomplete C5 tetraplegia (anterior cord syndrome) who developed severe, intractable anal spasm following a hemorrhoidectomy, which persisted despite very good healing. This prevented evacuation of her bowels and resulted in severe rectal pain and episodes of autonomic dysreflexia. Attempts to modify the rate and mode of delivery of intrathecal baclofen through an existing programmable infusion pump failed to reduce anal sphincter spasm or improve symptoms. A right-sided pudendal block with lignocaine provided some relief. Clonidine was added to baclofen in the pump reservoir and both drugs were administered intrathecally in combination. This resulted in an immediate improvement in anal sphincter spasm and pain relief, allowing rapid reestablishment of her normal bowel pattern without need for any supplemental analgesia. It appears that intrathecal clonidine may have an important role in the treatment of spasticity, either as a single or an adjuvant agent, when intrathecal baclofen alone is ineffective or there is increasing tolerance to baclofen. Intrathecal clonidine may also prove useful in the management of intractable neuropathic pain.     

3-dimensional sonography in the diagnosis of meniscal lesions. An experimental and clinical study]

There is no consensus regarding the clinical significance of conventional two-dimensional ultrasound in the diagnosis of meniscal tears of the knee. Three-dimensional ultrasound spatially reconstructs a transparent image of subsequent ultrasound scans. In an experimental study of 96 menisci, radial and oblique tears were detected more often by three-dimensional ultrasound. In a clinical study of 60 menisci the two- and three-dimensional ultrasound reached a sensitivity of 92% and 100%, a specificity of 83% and 88%, a positive predictive value of 58% and 67%, and a negative predictive value of 98% and 100%, respectively. Altogether, there was no statistically significant difference between both methods. The high negative predictive value, however, shows that the three-dimensional ultrasound may be a clinically relevant examination for special questions in the diagnostics of meniscal tears.     

Comparison between reagent strips used for detection of urinary tract infection in the elderly

A comparison was made between the accuracy of Ames and Boehringer reagent strips for detecting urinary tract infections in 100 elderly patients (50 acutely ill patients admitted to hospital and 50 attending the day hospital). The results for urinary nitrite, blood and protein for both strips were documented. Nitrite provided the highest sensitivities and specificities. In the acute hospital patients, the sensitivities were 83% for the Ames and Boehringer strips respectively, while for the day hospital patients the sensitivities were 90% for both strips. Specificities were 100% for both strips in each group of patients. There was thus little difference between the accuracy of the Ames and Boehringer reagent strips in detecting urinary tract infection.     

Ketanserin in the treatment of protamine-induced pulmonary hypertension

The reversal of heparin by protamine may cause severe hemodynamic deterioration, characterized by systemic hypotension, pulmonary hypertension, and bronchoconstriction. A case report is presented concerning the administration of ketanserin in the treatment of pulmonary vasoconstriction and right ventricular failure following the infusion of protamine in a patient undergoing coronary artery bypass surgery and mitral valve replacement. The potential role of serotonin in the development of this serious complication is discussed.     

Clonotypic differences in signaling from CD94 (kp43) on NK cells lead to divergent cellular responses

Ligation of MHC class I-recognizing receptors on NK cells dramatically modulates their secretory and cytotoxic function. This study focuses on characterizing key signaling events regulating these activities after ligation of the C-type lectin superfamily member, CD94. We isolated separate clonal populations of human NK cells in which ligation of CD94 (kp43) either triggered cell-mediated cytotoxicity (group A clones) or potently inhibited NK cell activation (group B clones). We then evaluated the proximal signaling events that regulate these alternative responses. CD94 stimulation of group A clones induced the rapid activation of intracellular protein tyrosine kinases (i.e., lck and ZAP-70), phospholipase C, and phosphatidylinositol 3-kinase. In contrast, CD94 ligation on group B clones had none of the above noted effects and instead inhibited the FcR-induced tyrosine phosphorylations of ZAP-70 and phospholipase C-gamma 2, the formation of phospho-zeta/ZAP-70 complexes, and the release of inositol phosphates. These results define distinct proximal signaling events initiated after CD94 ligation and suggest that clonotypic differences in signaling generate fundamentally different NK cell-mediated responses.     

Rapid analysis of DNA methylation using new restriction enzyme sites created by bisulfite modification

Bisulfite converts non-methylated cytosine in DNA to uracil leaving 5-methylcytosine unaltered. Here, predicted changes in restriction enzyme sites following reaction of genomic DNA with bisulfite and amplification of the product by the polymerase chain reaction (PCR) were used to assess the methylation of CpG sites. This procedure differs from conventional DNA methylation analysis by methylation-sensitive restriction enzymes because it does not rely on an absence of cleavage to detect methylated sites, the two strands of DNA produce different restriction enzyme sites and may be differentially analyzed, and closely related sequences may be separately analyzed by using specific PCR primers.