Steady state of gradient echo sequences with radiofrequency phase cycling: Analytical solution,contrast enhancement with partial spoiling

Spoiled gradient echo sequences can only reach a homogeneous steady state if sufficiently strong crusher gradients are used in combination with RF phase cycling (RF spoiling). However, the signal depends quite sensitively on the chosen phase increment ? and—lacking analytical solutions—numerical simulations must be used to study the transient and steady‐state magnetization. For the steady state an exact analytical solution is derived, which holds for arbitrary sequence and tissue parameters. Besides a considerably improved computation performance, the analytical approach enables a better understanding of the complicated dependence on ?. For short repetition times (TR) the regime of small ? turns out to be particularly interesting: It is shown that the typical ?_c, where RF spoiling starts to become effective, is essentially inversely proportional to T₂. This tissue dependence implies that contrasts can be considerably larger with partial spoiling (? ≈ ?_c) than with conventional RF spoiling (? ? ?_c). As an example, the uptake of contrast agents in tissues is investigated. For typical parameters a considerably improved contrast enhancement can be obtained, both theoretically and experimentally. Magn Reson Med, 2006. © 2005 Wiley‐Liss, Inc.     

Adherence to continuous positive airway pressure treatment in patients with Alzheimer's disease and obstructive sleep apnea.

OBJECTIVE: This analysis examined whether patients with Alzheimer disease (AD) tolerate continuous positive airway pressure (CPAP). METHOD: Thirty patients with AD were randomized to CPAP or sham CPAP and completed sleep, depression, and quality-of-life questionnaires. Participants could choose to continue treatment after the trial. RESULTS: Patients wore CPAP for 4.8 hours per night. More depressive symptoms were associated with worse adherence (rS=-0.37; N=30, p<0.04). Patients who continued using CPAP had fewer depressive symptoms (t [19]=2.45, p=0.02) and better adherence (t [19]=2.32, p=0.03) during the trial. CONCLUSION: Patients with AD with obstructive sleep apnea can tolerate CPAP. Adherence and long-term use may be more difficult among those patients with more depressive symptoms.     

Osteocalcin 24-hour profiles during normal pregnancy.

The interpretation of previous data on osteocalcin during pregnancy has been complicated by the fact that serum levels, at least in nonpregnant women, display a significant circadian variation. In the present study, serum concentrations of osteocalcin were recorded for 24 h in 12 individual women. In 4 nonpregnant women, there were striking diurnal fluctuations during the sampling period, with values ranging from 0.5 to 4.0 ng/ml. One woman who was investigated in the 11th week of pregnancy showed similar fluctuations in osteocalcin concentrations whereas in the 15th and 17th week values were much lower with minor fluctuations. In 4 women investigated during late pregnancy (weeks 34-38), osteocalcin serum levels were extremely low (range 0.2-0.4 ng/ml), often below the detection limit of the assay, and there was no diurnal variation. Also, in 1 lactating woman, osteocalcin serum levels were low (0.3-0.8 ng/ml) and stable. Low osteocalcin values during pregnancy may indicate a reduced bone turnover possibly mediated via an altered estrogen and growth hormone secretion.     

Proximal radioulnar transposition in an elbow dislocation.

Proximal radioulnar transposition in an elbow dislocation is rare. Only three cases have been recorded. Translocation can easily be missed unless radiographs are carefully examined. Proximal radioulnar translocation has been believed to be iatrogenic. The injury we report was not iatrogenic, and mechanical locking of radial head and neck fracture necessitated open reduction.     

Disposition and pharmacokinetics of [14C]finasteride after oral administration in humans.

The disposition of [14C]finasteride, a competitive inhibitor of steroid 5 alpha-reductase, was investigated after oral administration of 38.1 mg (18.4 microCi) of drug in six healthy volunteers. Plasma, urine, and feces were collected for 7 days and assayed for total radioactivity. Concentrations of finasteride and its neutral metabolite, omega-hydroxyfinasteride (monohydroxylated on the t-butyl side chain), in plasma and urine were determined by HPLC assay. Mean excretion of radioactivity equivalents in urine and feces equaled 39.1 +/- 4.7% and 56.8 +/- 5.0% of the dose, respectively. The mean peak plasma concentrations reached for total radioactivity (ng equivalents), finasteride, and omega-hydroxyfinasteride were 596.5 +/- 88.3, 313.8 +/- 99.4, and 73.7 +/- 11.8 ng/ml, respectively, at approximately 2 hr; the mean terminal half-life for drug and metabolite was 5.9 +/- 1.3 and 8.4 +/- 1.7 hr, respectively. Of the 24-hr plasma radioactivity, 40.9% was finasteride, 11.8% was the neutral metabolite, and 26.7% was characterized as an acidic fraction of radioactivity. Binding of [14C]finasteride to plasma protein was extensive (91.3 to 89.8%), with a trend suggesting concentration dependency (range 0.02 to 2 micrograms/ml). Little of the dose was excreted in urine as parent (0.04%) or omega-hydroxyfinasteride (0.4%). Urinary excretion of radioactivity was largely in the form of acidic metabolite(s)--18.4 +/- 1.7% of the dose was eliminated as the omega-monocarboxylic acid metabolite. Finasteride was scarcely excreted unchanged in feces. In humans, finasteride is extensively metabolized through oxidative pathways.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ecological effects of hepatotoxic cyanobacteria

Many species of cyanobacteria produce hepatotoxic peptides called microcystins. Toxic cyanobacteria have caused fish, wildlife, and cattle mortality in many countries, but the distribution and fate of toxins and their ecological effects are poorly known. Toxic cyanobacteria may affect sensitive organisms and populations, but also fundamental ecological processes, e.g., primary production and microbial activity. Many studies show negative effects of cyanobacteria on zooplankton, but information on the type and quantity of toxin(s) involved is usually missing. Mussels accumulate peptide toxins but accumulation in other organisms remains to be studied. Cyanobacterial blooms often affect the littoral zones, which are important reproduction and feeding areas for fish and birds.     

Rehabilitation of a Spark Erosion Prosthesis: A Clinical Report

When complex prostheses are fabricated, it is expected that at some point maintenance will be necessary. This clinical report documents a 10-year-old maxillary spark erosion prosthesis that had been repaired many times, was discolored, and exhibited significant signs of wear. The metal superstructure was intact; therefore, only the acrylic resin base and teeth needed to be replaced. To reduce both cost and time without the prosthesis for the patient, the rehabilitation was completed within 24 hours.     

Adhesion of human platelets to albumin is synergistically increased by lysophosphatidic acid and adrenaline in a donor-dependent fashion.

Lysophosphatidic acid (LPA) and adrenaline are weak platelet activators considered important for thrombus formation, and were previously shown to synergistically increase platelet aggregation. Here we investigate synergistic activation by LPA and adrenaline when measuring platelet adhesion. Platelet-rich plasma from healthy blood donors together with adrenaline and/or LPA were added to protein-coated microplates. Platelets were allowed to adhere and the amount of adhesion detected enzymatically. The LPA and adrenaline combination induced a synergistic increase of platelet adhesion to a normally non-adhesive albumin surface. The degree of synergy varied markedly between individuals; these variations could not be explained by age, gender, blood type or different amounts of platelets, oxidized low-density lipoprotein, insulin or glucose in plasma. There was a trend indicating increased synergistic effect for platelets sensitive to adrenaline stimulation. The synergistic effect was blocked by the alpha2-adrenoceptor antagonist yohimbine and inhibited by the ADP scavenger system creatine phosphate/creatine phosphokinase and antibodies against alphaIIbbeta3. Furthermore, platelets adhering to albumin after adrenaline and LPA treatment expressed P-selectin. In conclusion, LPA and adrenaline act synergistically to increase alphaIIbbeta3-mediated platelet adhesion to albumin, dependent on alpha2-adrenoceptor signalling and platelet secretion. We also confirm that synergistic platelet activation achieved with LPA and adrenaline is highly donor dependent.     

13-cis-retinoic acid (NSC 122758) in the treatment of children with metastatic neuroblastoma unresponsive to conventional chemotherapy: Report from the childrens cancer study group

The Childrens Cancer Study Group evaluated daily oral 13-cis-retinoic acid to determine its therapeutic efficacy in 28 children with advanced neuroblastoma refractory to conventional therapy. Cheilitis and fissured lips were the most common side effects; however, fewer than 50% of the patients experienced any toxicity. Two of twenty-two evaluable children demonstrated positive response to therapy. In one case, a child received the drug for 11 months. Seventeen patients demonstrated progressive disease within 28 days of the start of treatment. Three other patients with stable disease, or removed from study at day 28, were considered nonresponsive. Our data demonstrate that, when given as a single daily oral dose of 100 mg/m², 13-cis-retinoic acid does not have significant activity in children with advanced neuroblastoma. © 1992 Wiley-Liss, Inc.