Enhancement of a 252Cf-based neutron beam via subcritical multiplication for neutron capture therapy.

Previous studies indicated that an epithermal-neutron beam based on bare 252Cf is not feasible for neutron capture therapy (NCT). It was reported that a clinically useful epithermal-neutron beam requires a minimum of 1.0 g of 252Cf, which is more than twice the US current annual supply. However, it was reasoned that the required quantity of 252Cf could be dramatically reduced when used with a subcritical multiplying assembly (SMA). This reasoning is based on the assumption that the epithermal-neutron beam intensity for NCT is directly proportional to the fission neutron population, and that the neutron multiplying factor of the SMA can be estimated by 1/(1 - k(eff)). We have performed detailed Monte Carlo calculations to investigate the validity of the above reasoning. Our results show that 1/(1 - k(eff)) grossly overestimates the beam enhancement factor for NCT. For example, Monte Carlo calculations predict a beam enhancement factor of 6.0 for an optimized SMA geometry with k(eff) = 0.968. This factor is much less than 31 predicted by 1/(1 - k(eff)). The overestimation is due to the fact that most of the neutrons produced in the SMA are self-shielded, whereas self-shielding is negligible in a bare 252Cf source. Since the beam intensity of a 0.1 g 252Cf with the optimized SMA enhancement is still more than an order of magnitude too low compared to the existing reactor beams, we conclude that the enhancement via an SMA for a 252Cf-based epithermal-neutron beam is inadequate for NCT.

Lipid peroxidation and the expressional regulation of the heat-shock response during ischemia-reperfusion of rat kidney.

Because of the continuing shortage of donor organs, 'marginal kidneys' are increasingly being used. The purpose of our experiments was to characterize the extent of lipid peroxidation after ischemia-reperfusion (IR) injury in rat kidney, to analyze the expressional regulation of the heat-shock response and now to discuss the clinical application of these results. After ischemia, xanthine oxidase (XO) is thought to be the main oxygen radical-generating system and malondialdehyde (MDA) is considered to be a marker of LPO. In young rats (10 weeks) a unilateral warm ischemia of 40 and 60 min duration with subsequent reperfusion up to 1 h was conducted. Beside the 'footprints' of oxidative stress, the cytosolic antioxidative capacity, expressed as superoxide anion (SOA) scavenging capacity, was investigated. There was only a moderate and transient increase of renal MDA 5 and 10 min after the onset of reoxygenation (133.57/70.67 and 97.84/91.57 vs. 49.47 nmol/g wet weight (ww) in preischemic controls). ATP breakdown (to 83/65 from 2,947 nmol/g ww) with consecutive accumulation of hypoxanthine (up to 1,105 nmol/g ww) at the end of the ischemic period and the subsequent rapid decline of hypoxanthine by XO during reperfusion were used for an assessment of the SOA-generating capacity of these kidneys. Only 1/25-1/50 of the kidney cytosol was able to scavenge the whole amount of SOA generated by the total XO activity of rat kidney. Thus, it could be analytically and stoichiometrically shown that after IR there is only a moderate oxidative stress in kidneys of young rats; this is due to their high SOA-scavenging capacity compared to their SOA-generating ability. We investigated the time course of HSP70-1 and -2 mRNA expression and its relation to cellular ATP levels in renal cortex after different periods of unilateral warm renal ischemia (10-60 min) and reperfusion (up to 60 min) in 10-week-old male Wistar rats, since IR is known to cause induction of both genes. Immediately after ischemia there was a significant induction of both HSP70i genes. While HSP70-1 expression constantly increased (up to 4-fold) during reperfusion, even to a higher extent with prolongation of ischemia, HSP70-2 mRNA - generally being expressed on a far lower level than HSP70-1 mRNA - was strongly induced (3-fold) during reperfusion only after brief periods (10 min) of ischemia. Cellular ATP levels rapidly dropped down to 5% with ischemia and the pattern of recovery during reperfusion significantly depended on the duration of the ischemic period thus showing a good relation to the heat-shock (protein) gene expression. We conclude that the HSP70-2 is the more sensitive gene with a lower threshold activation by mild injury, while the HSP70-1 gene mediates the big response of HSP induction after severe injury. Thus, the measurement of the cytosolic antioxidative capacity and the differential expression of HSP70-1 and -2 mRNA could be promising clinical tools to assess the donor viability.

Prevalence of GBV-C/hepatitis G virus viremia and anti-E2 in Canadian blood donors.

BACKGROUND AND OBJECTIVES: GB virus C (GBV-C)/hepatitis G virus (HGV) is a recently recognized parenterally and sexually transmitted agent. The prevalence of GBV-C/HGV markers in Canadian blood donors has not been previously studied and was therefore determined. MATERIALS AND METHODS: Blood donors [identity unlinked (IU), short-term temporarily deferred (STTD) and autologous groups] and donor samples with antibodies to hepatitis C (anti-HCV) or hepatitis B core were tested for GBV-C/HGV RNA and for antibodies to E2 antigen (anti-E2). RESULTS: GBV-C/HGV RNA was found in 1.1% and anti-E2 in 7.3% of the combined IU/STTD donor group. Viremia was much more common in anti-HCV-positive samples (12.5%); anti-E2 was present in >50% of this group. In the STTD group, female gender was significantly associated with viremia. CONCLUSION: GBV-C/HGV infection is relatively common in Canadian donors, and a small proportion are viremic. The association of female gender and viremia was unexpected. Further study is needed to clarify the epidemiology and natural history of GBV-C/HGV infection.

Evidence for only a moderate lipid peroxidation during ischemia-reperfusion of rat kidney due to its high antioxidative capacity.

The extent of lipid peroxidation after ischemia-reperfusion (I-R) injury in rat kidney has been controversial. After I, xanthine oxidase (XO) is thought to be the main oxygen radical-generating system and malondialdehyde (MDA) is considered to be a marker of lipid peroxidation (LPO). In young rats (10 weeks old) a unilateral warm I of 40 and 60 min duration with subsequent R up to 1 h was conducted. Beside the "footprints" of oxidative stress, the cytosolic antioxidative capacity, expressed as superoxide anion (SOA) scavenging capacity, and the renal catalase were also investigated. There was only a moderate and transient increase of renal MDA 5 and 10 min after the onset of reoxygenation (133.57/70. 67 and 97.84/91.57 vs. 49.47 nmol/g ww in preischemic controls). ATP breakdown (to 83/65 from 2947 nmol/g ww) with consecutive accumulation of hypoxanthine (up to 1105 nmol/g ww) at the end of ischemic period and the subsequent rapid decline of hypoxanthine by XO during reperfusion were used for an assessment of the SOA-generating capacity of these kidneys. Superoxide dismutase (SOD) activity, glutathione (GSH) and the high activity of catalase (18000 U/g ww) remained nearly unchanged during R. Only 1/25-1/50 of the kidney cytosol was able to scavenge the whole amount of SOA generated by the total XO activity of rat kidney. Thus, it could be analytically and stoichiometrically shown that after IR there is only a moderate oxidative stress in kidneys of young rats; this is due to their high SOA-scavenging capacity compared with their SOA-generating ability.

No association between hepatitis C and B-cell lymphoma.

Chronic viral infection has been implicated in the pathogenesis of B-cell lymphoma, and hepatitis C virus (HCV) infects lymphocytes. Chronic infection with HCV may result in B-cell proliferation. Individuals infected with hepatitis C are often co-infected with the RNA virus GB virus type C. Studies from Europe where hepatitis C infection is more common than in North America have shown a high prevalence of hepatitis C infection in patients with B-cell lymphoma. The aim of this study was to establish the prevalence of HCV and GBV-C infection in patients with B-cell lymphoma in an area of low HCV prevalence. One hundred patients with B-cell lymphoma (10 high grade, 46 intermediate grade, and 44 low grade) and 100 controls with nonhematological malignancies were studied. Serum was analyzed for HCV antibodies by third generation enzyme-linked immunosorbant assay, and HCV RNA and GBV-C RNA was analyzed by reverse transcriptase PCR. None of the controls or lymphoma patients had antibodies to HCV. HCV RNA was undetected in 60 out of 100 lymphoma patients tested. GBV-C RNA was detected in the serum of 5 out of 100 (5%) of lymphoma patients and in 3 out of 100 (3%) controls. Hepatitis C and GBV-C are, therefore, unlikely to play a major role in the pathogenesis of B-cell lymphoma in North America.

[Life-threatening swelling of the tongue in antihypertensive therapy with ACE inhibitors]. / Lebensbedrohliche Zungenschwellung bei antihypertensiver Therapie mit ACE-Hemmern.

Although generally showing a low incidence of side effects, inhibitors of angiotensin-converting enzyme (ACE) may in rare cases induce angioedemas, mainly located in the oro-facial area and larynx. The interval between the beginning of the ACE inhibitor therapy and the occurrence of such angioedemas may range from a few hours to a few years. Here, the case of a 53-year-old man with massive swelling of the tongue after dental surgery is presented who had started with ACE inhibitor therapy only 24 h before. At admission to the clinic, obstruction of the upper airway due to the tongue swelling had already progressed so far that fiberoptic intubation was necessary. Additionally, the patient was treated with corticosteroids, antihistaminics and epinephrine, avoiding any further administration of the ACE inhibitor. The swelling resolved within 48-72 h. Dentists and physicians should take into consideration this potential side effect in patients treated with ACE inhibitors.

Influence of assay method differences on multiple of the median distributions: maternal serum alpha-fetoprotein as an example.

A straightforward statistical explanation is provided to show how differences between assay methods can affect the distribution of the multiples of the median (MoM). Evaluation of the impact of assay method differences reveals that the upper tails of the MoM distribution are not affected to the same degree as the lower tails of the distribution. The disparities in MoM distributions due to assay method differences result in various sensitivity/specificity combinations for different assays having the same fixed MoM cutoffs. Disparities do not exist if risks are calculated with use of the distributions for affected and unaffected populations that are based on a center's own assay method. Applying published risk tables, however, can affect the accuracy of the risk estimates. We used maternal serum alpha-fetoprotein as an example of an assay with an established history of reporting results in MoM values; however, the concepts presented apply equally well to any assay for which results are reported in MoMs.

[Changes in blood flow velocity in the basal cerebral arteries following neck dissection]. / Veränderungen der Blutflussgeschwindigkeit in den basalen Hirnarterien nach Neck Dissection.

Cerebral blood-flow velocities (cm/s) and pulse index (PI) were studied pre- and postoperatively in a total of 15 male patients following bilateral radical/functional (group A; n = 10) or unilateral radical neck dissection (group B; n = 5) using a 2 MHz-pulsed transcranial Doppler ultrasonographical system (TCD), with a transtemporal approach to the middle cerebral artery. Systolic and mean flow velocities were significant reduced with subsequent increases in PI during the first postoperative sonography in group A-patients while no significant differences in TCD date developed in group B. Blood-flow velocities and PI reached control values within three days. General hemodynamic and respiratory parameters did not influence the changes in TCD flow profiles with the exception of moderate increases in arterial CO2 during the early postoperative period. It is concluded that the reductions in blood-flow velocities and concomitant increases in PI reflect a heightened resistance to flow in the arterial cerebral vasculature. The decrease in cerebral vascular compliance suggests increases in the cerebral venous outflow following the resection of essential drainage pathways. However, TCD does not provide any information about the adequacy of cerebral blood flow.

The absorption of tricalcium phosphate and its acute metabolic effects.

The use of calcium (Ca) supplements by postmenopausal women is growing rapidly. A commercial preparation of tricalcium phosphate (TCP) is available in the USA. Depending on the relative absorption of Ca versus phosphate, a rise in serum phosphorus (P) could stimulate parathyroid hormone (iPTH) secretion. We therefore compared Ca absorption and the metabolic responses following TCP to that of Ca carbonate (CC) on separate occasions in each of 10 women, aged 22-40 years. The subjects were fasted overnight for 12 hours while good hydration was maintained. Following a 2-hour baseline-urine collection, 1200 mg calcium (as CC or TCP) was ingested and two 2-hour postload urine collections were made. Blood was drawn at 1, 2, and 4 hours after the Ca load. Serum (S) and urine (U) Ca, P, and creatinine, and U cyclic AMP (cAMP) were determined. iPTH levels following TCP were also measured. Ca absorption was determined by the postload rise in Uca above baseline. Uca excretion increased significantly and was accompanied by significant rises in Sca after both preparations. Following TCP, S and U phosphorus increased. Urinary cAMP did not change after either preparation, and iPTH levels fell after oral TCP. We conclude that Ca taken as TCP is absorbed adequately and, thus, despite a rise in the S phosphorus level does not stimulate parathyroid activity.

Preoperative magnetic resonance imaging in Marfan syndrome.

We report one of the first cases in Israel of composite-graft repair of an aortic aneurysm in Marfan syndrome, in which preoperative evaluation was done noninvasively using magnetic resonance imaging (MRI). Because of the relatively favorable outcome of surgical compared with medical treatment of aortic aneurysm in patients with Marfan syndrome, surgery is now more frequently considered, even in asymptomatic patients. MRI is an excellent diagnostic tool for evaluating the thoracic aorta and has been suggested as a replacement for preoperative cardiac catheterization. In the case presented here, MRI preoperative confirmation of a 6.0-cm aortic aneurysm in an asymptomatic 38-year-old man with Marfan syndrome, was followed by composite ascending aorta and aortic valve replacement. The postoperative course was good. This case supports the view that aortic aneurysm replacement can be performed based on a noninvasive preoperative evaluation using MRI.

[Thoracic impedance in the determination of hydration following heart surgery under extracorporeal circulation]. / Thorakale Impedanz zur Bestimmung der Hydratation nach Herzoperationen in extrakorporaler Zirkulation.

Changes in thoracic water content are measurable by determining basic impedance (Zo). In 57 cardiac surgical patients Zo decreased postoperatively by an average 24% corresponding to water retention of about 1.51. On the second postoperative day the difference to the initial preoperative value was still 8.5% corresponding to a water amount of over 500 ml. A close mathematic correlation exists between changes in the basic impedance (delta Zo) and fluid balance with a correlation coefficient of 0.94. The simple, non-invasive method is suitable for therapeutic control of fluid balance and quantitative diagnosis of pulmonary hyperhydration forms of various causes.

[Pulse oximetry in surgery of the bronchial system]. / Pulsoximetrie bei Eingriffen im Bronchialsystem.

Oxygen saturation was determined by pulse oximetry in 35 children and adults during general anaesthesia using jet- or manually assisted ventilation for minor elective laryngeal and tracheo-bronchial surgery. The method is non-invasive and provides continuous information about the arterial oxygen saturation (saO2) and heart rate. Compromised arterial oxygenation during anaesthesia and the effects and brief ventilatory arrest are accurately detectable. Data such as pO2, pCO2 or pH cannot be assessed by pulse oximetry; carbon monoxide and methemoglobinaemia may lead to less accurate results. Pulse oximetry provides on-line information about sudden hypoxic events and allows early therapeutic intervention because arterial desaturation precedes the clinical signs and symptoms of hypoxia.

[High-frequency jet ventilation in emergency tracheal puncture]. / HF-Jet-Ventilation bei notfallmässiger Trachealpunktion.

A case of obstruction of the upper respiratory tract is reported, in which an intubation or insufflation by rigid tracheobronchoscopes was not possible. Due to the anatomical situation after multiple operations and irradiation, coniotomy could not be performed. Blind puncture of the trachea with subsequent High Frequency Jet Ventilation has proved successful as an emergency approach to maintain respiratory function.