Reliability of the transient hyperemic response test in detecting changes in cerebral autoregulation induced by the graded variations in end-tidal carbon dioxide

The transient hyperemic response (THR) in the middle cerebral artery (MCA) after the release of brief compression of the ipsilateral common carotid artery has been used to study cerebral autoregulation. We conducted the present study to evaluate the reliability of THR to detect changes in cerebral autoregulation induced by graded variations in PETCO2. Seven healthy adult volunteers were recruited. Fifteen THR tests were performed on every volunteer: three at baseline PETCO2, three each at PETCO2 of 7.5 mm Hg and 15 mm Hg above the baseline, and then three each at PETCO2 of 7.5 mm Hg and 15 mm Hg below the baseline. Transient hyperemic response ratio (THRR) and strength of autoregulation (SA) were calculated using established formulae. Both THRR and SA were highly sensitive (96%) in detecting the changes in cerebral autoregulation induced by graded changes in PETCO2. The within-individual variability of SA was significantly smaller than that of THRR at all levels of PETCO2. IMPLICATIONS: This study demonstrates the reliability of the THR test, when used for repetitive measurements, in detecting changes in cerebral autoregulation induced by graded changes in PETCO2. This test may provide a simple and noninvasive method of evaluating changes in cerebral autoregulation within an individual.     

Electro-optic properties of InGaAs/GaAs multiquantum wells for modulator applications

A study of the application of InGaAs/GaAs multiquantum wells for modulators using the electroabsorption ( Delta alpha ) and the electrofraction ( Delta n) effects is presented. The important parameters for these devices were measured directly in both waveguide and surface-normal configurations. The Delta n and Delta alpha spectra were shown to satisfy the Kramers-Kronig relations.<>     

Children of human immunodeficiency virus-infected members of the Army Reserve components

OBJECTIVES: Little is known about the numbers of children who will be left without one or both parents because of human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome. This report evaluates childbearing patterns among U.S. Army reserve component members, a group largely made up of men with limited contact with the military. METHODS: HIV status was determined from routinely collected data, with demographic information obtained from personnel records. Number of children was estimated from number of dependents reported. No information was available on the infection status of children or spouses of members. RESULTS: There were 1,884 HIV-positive members, with an estimated total of 843 children. Childbearing patterns varied across several demographic characteristics. Among 14 metropolitan statistical areas, the proportion reporting any children and the number of children of infected members per 100,000 varied substantially. CONCLUSIONS: This report documents the numbers of children of HIV-positive adults in this population and provides evidence that certain metropolitan areas will be disproportionately affected.     

An improved algorithm for finding the median distributively

Given two processes, each having a total-ordered set ofn elements, we present a distributed algorithm for finding median of these 2n elements using no more than logn +O(√logn) messages, but if the elements are distinct, only logn +O(1) messages will be required. The communication complexity of our algorithm is better than the previously known result which takes 2 logn messages.     

Thrombolytic therapy and proteolysis of factor V

OBJECTIVES: We sought to determine the extent of Factor V proteolysis during thrombolytic therapy. BACKGROUND: Thrombin- or Factor Xa-activated Factor V is an essential cofactor in the prothrombinase complex. In purified systems, plasmin, the major product of thrombolytic therapy, is known to first activate then inactivate Factor V. METHODS: We used quantitative gel electrophoresis and Western blotting to analyze the cleavages in plasma Factor V after thrombolytic therapy. RESULTS: The addition of streptokinase to plasma resulted in the activation then inactivation of Factor V, confirming previous results using purified reagents. We also identified the Factor V fragments resulting from the action of thrombin and plasmin. After thrombolytic therapy, there was considerable Factor V cleavage. The cleavage patterns were consistent with the action of plasmin, with little evidence for the action of thrombin. In the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries trial (n = 17), we observed an average 58% loss of intact Factor V at 6 h (range 1% to 91%). Samples from the Thrombolysis in Myocardial Infarction trial, Phase II (n = 12), collected on a shorter time scale, showed a loss of up to 99% at 50 min, with the loss of intact Factor V associated with the plasma concentration of plasminogen activator. Samples from patients with bleeding (n = 12) showed extensive Factor V cleavage. CONCLUSIONS: Factor V cleavage in thrombolytic therapy is primarily plasmin mediated, rapid and often extensive. It is likely that transient increases, as well as longer term losses, of Factor V cofactor activity play a role in both ischemic and hemorrhagic events subsequent to thrombolytic therapy. The extensive loss of Factor V in some patients may affect the estimation of heparinization.     

A nickel complex cleaves uridine in folded RNA structures: application to E. coli tmRNA and related engineered molecules

To gain more insight about Escherichia coli tmRNA structure, NiCR, a square planar macrocyclic nickel (II) complex, was used to probe guanine N7 exposure. On the basis of this additional structural information, a refined secondary structure of the molecule is proposed. In addition to its known specificity for guanine N7, we show here that the chemical probe can also cleave at specific uridine residues. In contrast to the alkaline-labile modification of guanine, the reactivity of NiCR at these uridine residues results in direct strand scission. To better characterize the uridine cleavage sites and assess the importance of the RNA structure for the reaction to occur, smaller RNA molecules derived from one pseudoknot (PK4) of E. coli tmRNA containing two uridine cleavage sites were engineered and probed. It is shown that this pseudoknot can fold by itself in solution and that the expected uridine residues are also cleaved by the nickel complex, suggesting that only a local sequence and/or structural context is required for cleavage. In E. coli tmRNA, the five uridine cleavage sites are located in double-stranded regions. These sites contain a G-U wobble base-pair and a downstream uridine which is cleaved. Using smaller RNAs derived from one stem of PK4, systematic changes in the proposed recognition motif indicate that the G-U pair is required for cleavage. Furthermore, there is no cleavage if the G-U pair is reversed. If the recognition motif is moved within the stem, the cleavage site moves accordingly. Additionally, if the recognition motif is changed such that the G-U pair is flanked by two uridine residues, the reactivity occurs only at the 3' uridine. Radical quenching studies have indicated that sulfate radical, as in the case of guanine oxidation, is involved in uridine oxidation. Although additional studies are required to better characterize the reaction, this paper reports a novel specificity for a chemical probe which may be useful for investigating structural motifs involving G-U pairs in folded RNAs.     

Natural variation within the principal arginine-specific protease gene, prpR1, of Porphyromonas gingivalis

Patients who were treated for fractures of the limbs were assigned to 1 of 2 groups for the management of postoperative pain. In Group 1 (postoperative patient-controlled analgesia group), 46 patients were given postoperative continuous epidural anaesthesia in combination with narcotic analgesics and this was regulated by the patient using a device. The 46 patients in Group 2 (control group) received suppositories or intramuscular injections of narcotic analgesics on their request. Patients in Group 1 needed suppositories and intramuscular injection of narcotic analgesics less often than those in Group 2, and had more satisfactory pain relief according to the visual analogue scale for pain assessment made on the first, second and third postoperative day. The time spent by nurses for pain management in Group 1 was less than that in Group 2. It appears that this patient-controlled method, combined with postoperative continuous epidural anaesthesia, is a safe, effective and efficient method for the management of postoperative pain.