Thrombotic microangiopathy with renal failure in two patients undergoing gemcitabine chemotherapy

Described here are 2 patients who developed thrombotic microangiopathy of the kidneys after receiving high cumulative doses of the new anticancer drug gemcitabine. The first patient, who received gemcitabine for treatment of a carcinoma of the pancreas, required hemodialysis for 6 months. In the second case, a woman suffering from a cholangiocellular carcinoma, end-stage renal disease was irreversible. Clinical awareness, timely detection and discontinuation of gemcitabine are mandatory to prevent this rare but disastrous complication of gemcitabine therapy.

Daily psychosocial stressors interfere with the dynamics of urine neopterin in a patient with systemic lupus erythematosus: an integrative single-case study

OBJECTIVE

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by flare-ups, the causes of which are not known. In accordance with new concepts in stress research, this study investigated whether daily psychosocial stressors interfere with immunological processes in SLE. Because such processes are unique to each individual, single-case design using time-series analysis (Box and Jenkins) was applied.

METHODS

A 40-year-old woman with SLE (last flare-up September 1995) was interviewed initially to determine major life events and difficulties (using the Life Events and Difficulties Schedule) in the previous 2 years. She was then observed for 63 days. Urine neopterin, an immunological parameter demonstrated to parallel disease activity in SLE patients, was measured in daily overnight urine. Daily incidents were identified weekly by the Incidents and Hassles Inventory and independently rated. Intervening factors, including infections, medication, and lifestyle, were controlled.

RESULTS

Retrospectively, data obtained from the Life Events and Difficulties Schedule indicated that major life events and difficulties had preceded the patient's last flare-up in 1995. Although there were no clinical signs of SLE during this prospective study of 63 days, cross-correlational analyses revealed that "moderately" stressful incidents associated with higher levels of emotional irritation (lag 0: +0.271, p < .05) predicted an increase in urine neopterin the following day (lag 1: +0.441, p < .05). Moreover, a 7-day cyclicity in neopterin levels that corresponded to the weekly examinations and interviews was found.

CONCLUSIONS

This study showed a causal relationship between psychosocial stressors and urine neopterin concentrations that may be related to SLE disease activity. Furthermore, the workability of an integrative approach using single-case design and time-series analysis in psychoneuroimmunology was demonstrated for the first time.

Cytochrome b558 (p22phox) in the guinea-pig adrenal medulla

Paraganglionic cells are sensitive to hypoxia, and the involvement of a plasmalemmal cytochrome b558-like protein in oxygen sensing by these cells has been suggested, but neither the identity of the immunoreactive protein detected by immunohistochemistry nor its anticipated subcellular (i.e., plasmalemmal) localization were directly proven. Thus, we extended these studies to the largest paraganglion, i.e., the adrenal medulla, in the guinea-pig, which, due to its size and accessibility, allowed us to address both of these issues utilizing antisera raised against synthetic peptides of the small (22 kD) subunit of cytochrome b558, p22phox. Cytochrome b558 was originally identified in granulocytes and macrophages, and antisera against this phagocyte p22phox were utilized. Immunoreactivity to p22phox was observed in all adrenal medullary endocrine cells, and the identity of the immunoreactive protein to the small cytochrome b558-subunit was confirmed by Western blotting. Immuno-electron microscopy of ultrathin cryosections and of resin-embedded tissue demonstrated its subcellular localization in the dense core vesicles of endocrine A-cells but not in the plasma membrane. In conclusion, the present study documents the presence of the small subunit of cytochrome b558 in guinea-pig adrenal medullary cells, but its subcellular vesicular localization does not support the initial interpretation of cytochrome b558 serving as a plasmalemmal oxygen sensor.

Aneurysmal portosystemic venous shunt: a case report

A case of an aneurysmal portosystemic venous shunt detected by colour Doppler ultrasound (CDUS) is presented. A young female patient complained of postprandial fatigue and had paroxysmal tachycardia. A direct vascular communication between right portal vein and right hepatic vein was found at CDUS and confirmed by direct portal angiogram. Using detachable coils a complete occlusion of the intrahepatic shunt was obtained. Reports from the literature regarding portovenous aneurysms are reviewed.

Combining nefazodone and midazolam during ECT

We report the case of a patient suffering from dysthymia. He underwent successful ECT treatment and was medicated with nefazodone and midazolam. Comparing the EEG and motor seizure duration in the periods with and without midazolam, no significant differences were recorded, but the dosage of thiopental and of succinylcholine had to be increased markedly after midazolam was discontinued (P < 0.05; ANOVA). This case indicates a substantial pharmacodynamic interaction between nefazodone, midazolam, thiopental, and succinylcholine.

On the directionality of cortical interactions studied by structural analysis of electrophysiological recordings

To investigate the directionality of neural interactions as assessed by electrophysiology, we adapted methods of structural analysis from the field of econometrics. In particular, within the framework of autoregressive modelling of the data, we considered quantitative measures of linear relationship between multiple time series adopting the Wiener-Granger concept of causality. The techniques were evaluated with local field potential measurements from the cat visual system. Here, several issues had to be addressed. First, out of several statistical tests of the stationarity of local field potentials considered, those based on the Kolmogorov-Smirnov and on the reverse arrangement statistics proved to be most powerful. The application of those tests to the experimental data showed that the large part of the local field potentials can be considered stationary on a time scale of 1 s. Second, out of the several investigated methods for the determination of an optimal order of the autoregressive model, the Akaike Information Criterion had the most suitable properties. The identified order of the model, across different repetitions of the trials, was consistently 5-8. Third, although the individual segments of field potentials used for the analysis were relatively short, the methods of structural analysis applied produced reliable results, confirming findings of simulations of data with similar properties. Furthermore the features of the estimated models were consistent among trials, so that the analysis of average measures of interaction appears to be a viable approach to investigate the relationship between the recording sites. In summary, the statistical methods considered have proved to be suitable for the study of the directionality of neuronal interactions.

On the role of biophysical properties of cortical neurons in binding and segmentation of visual scenes

Neuroscience is progressing vigorously, and knowledge at different levels of description is rapidly accumulating. To establish relationships between results found at these different levels is one of the central challenges. In this simulation study, we demonstrate how microscopic cellular properties, taking the example of the action of modulatory substances onto the membrane leakage current, can provide the basis for the perceptual functions reflected in the macroscopic behavior of a cortical network. In the first part, the action of the modulatory system on cortical dynamics is investigated. First, it is demonstrated that the inclusion of these biophysical properties in a model of the primary visual cortex leads to the dynamic formation of synchronously active neuronal assemblies reflecting a context-dependent binding and segmentation of image components. Second, it is shown that the differential regulation of the leakage current can be used to bias the interactions of multiple cortical modules. This allows the flexible use of different feature domains for scene segmentation. Third, we demonstrate how, within the proposed architecture, the mapping of a moving stimulus onto the spatial dimension of the network results in an increased speed of synchronization. In the second part, we demonstrate how the differential regulation of neuromodulatory activity can be achieved in a self-consistent system. Three different mechanisms are described and investigated. This study thus demonstrates how a modulatory system, affecting the biophysical properties of single cells, can be used to achieve context-dependent processing at the system level.

Lipoprotein(a) plasma concentrations after renal transplantation: a prospective evaluation after 4 years of follow-up

The highly atherogenic lipoprotein(a) [Lp(a)] is significantly elevated in patients with renal disease. It is discussed controversially whether Lp(a) concentrations decrease after renal transplantation and whether the mode of immunosuppressive therapy influences the Lp(a) concentrations. In a prospective study the Lp(a) concentrations before and on average 48 months after renal transplantation were measured in 145 patients. The determinants of the relative changes of Lp(a) concentrations were investigated in a multivariate analysis. Patients treated by CAPD showed a larger decrease of Lp(a) than hemodialysis patients, reflecting their markedly higher Lp(a) levels before transplantation. The relative decrease of Lp(a) was higher with increasing Lp(a) concentrations before transplantation in combination with an increasing molecular weight of apolipoprotein(a) [apo(a)]. That means that the relative decrease of Lp(a) is related to the Lp(a) concentration and the apo(a) size polymorphism. With increasing proteinuria and decreasing glomerular filtration rate, the relative decrease of Lp(a) became less pronounced. Neither prednisolone nor cyclosporine (CsA) had a significant impact on the Lp(a) concentration changes. Azathioprine (Aza) was the only immunosuppressive drug which had a dose-dependent influence on the relative decrease of Lp(a) levels. These data clearly demonstrate a decrease of Lp(a) following renal transplantation which is caused by the restoration of kidney function. The relative decrease is influenced by Aza but not by CsA or prednisolone.

Temporal binding, binocular rivalry, and consciousness

Cognitive functions like perception, memory, language, or consciousness are based on highly parallel and distributed information processing by the brain. One of the major unresolved questions is how information can be integrated and how coherent representational states can be established in the distributed neuronal systems subserving these functions. It has been suggested that this so-called "binding problem" may be solved in the temporal domain. The hypothesis is that synchronization of neuronal discharges can serve for the integration of distributed neurons into cell assemblies and that this process may underlie the selection of perceptually and behaviorally relevant information. As we intend to show here, this temporal binding hypothesis has implications for the search of the neural correlate of consciousness. We review experimental results, mainly obtained in the visual system, which support the notion of temporal binding. In particular, we discuss recent experiments on the neural mechanisms of binocular rivalry which suggest that appropriate synchronization among cortical neurons may be one of the necessary conditions for the buildup of perceptual states and awareness of sensory stimuli.

The low molecular weight apo(a) phenotype is an independent predictor for coronary artery disease in hemodialysis patients: a prospective follow-up

Patients with end-stage renal disease treated by hemodialysis have a tremendous risk for cardiovascular complications that cannot be explained by traditional atherosclerosis risk factors. Lipoprotein(a) (Lp(a)), a risk factor for these complications in the general population, is significantly elevated in these patients. In this study, it was determined whether Lp(a) and/or the genetically determined apo(a) phenotype are risk predictors for the development of coronary artery disease in these patients. A cohort of 440 unselected hemodialysis patients were followed for a period of 5 yr independent of the cause of renal disease, duration of preceding treatment, and the preexistence of coronary artery disease at study entry. Coronary events defined as definite myocardial infarction, percutaneous transluminal coronary angioplasty, aortocoronary bypass, or a stenosis >50% in the coronary angiography were the main outcome measure. Sixty-six (15%) of the 440 patients suffered a coronary event during follow-up. In univariate analysis, patients with events were significantly older and showed a trend to lower HDL cholesterol concentrations, and higher apolipoprotein B and Lp(a) concentrations without reaching significance. Apo(a) phenotypes of low molecular weight, however, were significantly more frequent in patients with compared to those without events (43.9% versus 21.9%, P<0.001). The other lipids, lipoproteins, and apolipoproteins were similar in both groups. Multiple Cox proportional hazards regression analysis found age and the apo(a) phenotype to be the best predictors for coronary events during the observation period, independent of whether patients with a preexisting coronary artery disease or an age >65 yr at the study entry or both were excluded from the analysis. Diabetes mellitus was a risk factor only in presence of a low molecular weight apo(a) phenotype. The genetically determined apo(a) phenotype is a strong and independent predictor for coronary events in hemodialysis patients. Apo(a) phenotyping might be helpful to identify hemodialysis patients at high risk for coronary artery disease.

Glomerular deposition of mannose-binding lectin in human glomerulonephritis

BACKGROUND

Mannose-binding lectin (MBL), a member of the collectin family, binds to various oligosaccharides and activates the classical pathway of complement independent from C1q. At present it is unknown whether this so-called lectin pathway of complement activation plays a role in the pathogenesis of human glomerulonephritis.

METHODS

Direct immunofluorescence of 84 renal biopsies using an MBL-specific monoclonal antibody and antibodies directed against IgG, IgA, IgM, C1q, C3, and terminal complement complex (TCC) was performed. Serum MBL levels of 50 patients were determined by enzyme-linked immunosorbent assay.

RESULTS

MBL was detected in the glomeruli of patients with lupus nephropathy (15 of 16), membranous nephropathy (10/15), membranoproliferative glomerulonephritis type I (5/6) and anti-GBM nephritis (2/4). MBL deposition paralleled that of immunoglobulins, C1q, C3, and TCC but was less intense as compared to C1q. Focal segmental deposits of MBL were present in focal segmental glomerulosclerosis (4/6), IgA nephropathy (3/11), amyloidosis AL (1/4), and advanced renal fibrosis (2/2). Here MBL staining was identical to IgM and C3 and considered an unspecific entrapment of MBL in sclerotic lesions in these cases. No significant difference in MBL serum levels was observed between normal controls and patients with lupus nephritis, membranous nephropathy, membranoproliferative glomerulonephritis, focal segmental sclerosis, minimal change disease or IgA nephropathy. In patients suffering from membranous nephropathy with (n=10) or without (n=5) glomerular MBL deposits serum creatinine, C3, C4, serum protein, and proteinuria were not statistically different.

CONCLUSION

MBL is present in the glomeruli of patients with glomerulonephritis involving deposition of IgG and activation of the classical pathway of complement. We propose that MBL binds to agalactosyl oligosaccharides of IgG that terminate in N-acetylglucosamine. The extent to which the lectin pathway of complement contributes to overall complement activation in the glomeruli remains unknown, but is likely to be marginal.

Risk assessment of a former military base contaminated with organoarsenic-based warfare agents: uptake of arsenic by terrestrial plants

Organoarsenic-based chemical warfare agents (CWAs) such as the sternutators diphenylchloroarsine (CLARK I), diphenylcyanoarsine (CLARK II) or phenyldichloroarsine (PFIFFIKUS) still pose a notable risk in countries where former military bases that have stored these weapons have not yet been reclaimed. In fact, this is the case for many countries of Eastern Europe and the CIS. One of the most important military bases of the former Third Reich, the Heeresmunitionsanstalt I and II, is situated close to the German-Polish border at Loecknitz (Fig. 1). The German army stored and decanted different compounds of CWAs at this military base until 1945. When the Soviet Army destroyed the base in 1946, large amounts of CWAs and other organoarsenic compounds polluted the soil. Today up to 250 g (!) of arsenic may be found in 1 kg of soil at some places in this area. Since 1991, a Government Working Group has been working on the risk assessment in order to define the scope of reclamation measures. This study investigates the contamination and the uptake of arsenic by plants because little is known about the bioavailability and metabolism of sternutators and their constituents. The total arsenic concentration of nine different species of terrestrial plants with at least six samples per species is presented. In spite of the considerable arsenic contamination of the soil (mean value 923 mg arsenic/kg soil) the plant contamination remained comparably low. The median value of arsenic contamination of the above-ground organs of velvet grass, Holcus lanatus, was 0.7 mg/kg dry wt. and the mean value was 4.3 mg/kg dry wt. due to some highly contaminated samples. The highest arsenic concentration registered was 26 mg/kg dry wt. in a sample of H. lanatus, which was most probably caused by soil particles adhering to the plant. The chemical structure of the arsenic compounds carried by the above-ground plant organs has been determined by gas chromatographic investigations and showed an uptake of triphenyl arsine by the plants.

Reinforced intradermal hepatitis B vaccination in hemodialysis patients is superior in antibody response to intramuscular or subcutaneous vaccination

Since 1960, hepatitis B virus-associated chronic liver disease has been considered an important problem in dialysis units in both Europe and North America. Separate dialysis facilities for hepatitis B-infected patients, the implementation of universal precautions for the prevention of transmission, and the active immunization against hepatitis B have now reduced the yearly incidence to less than 0.05% in Western countries. However, only 50% to 60% of patients with renal insufficiency develop sufficient immune response after intramuscular hepatitis B vaccination. The aim of the current study was to determine whether the mode of vaccine application plays a role in vaccination response and whether increasing the vaccine dose of primary intradermal hepatitis B vaccination can reduce the number of vaccine injections in hemodialysis patients. We designed a prospective, randomized study of antibody responses to hepatitis B vaccine given intradermally, subcutaneously, or intramuscularly in 81 hemodialysis patients. Outcome measures were rates of seroconversion, mean levels of anti-Hbs antibodies, and antibody levels 8 years after vaccination. The results show that intradermal hepatitis B vaccination response with a higher vaccination dose than previously used in hemodialysis patients is superior to conventional intramuscular and subcutaneous vaccination and is also well tolerated. Five intradermal injections of 20 microg each induced the development of sufficient anti-Hbs antibody titer, which persisted in 70% of the patients over 3 years.

Pressure sores and tube feeding in patients with a fracture of the hip: a randomized clinical trial

Pressure sores are a frequent problem, especially in elderly patients. Nutritional status may influence the incidence, progression and severity of pressure sores, data, however, are contradictory (1). The purpose of this study was to determine the effect of supplemental feeding on the nutritional status and the development and severity of pressure sores. The effect of supplemental feeding overnight (tube +) on patients with a fracture of the hip and a high pressure-sore risk score, was studied in a randomized clinical trial. The control group (tube -) had no supplemental feeding. After informed consent, 140 patients were randomized, and 129 of these took part in the trial (62 tube +, and 67 tube -). Protein and energy intake, haemoglobin, serum albumin, total serum protein and pressure-sore grade were measured at admission and after 1 and 2 weeks. Of the 62 patients randomized for tube feeding (tube +), only 25 tolerated their tube for more than 1 week and 16 for 2 weeks. Nevertheless, energy and protein intake was significantly higher in the tube + group (P < 0.001). This, however, did not significantly influence total serum protein, serum albumin and development and severity of pressure sores after 1 and 2 weeks. Comparison of the actually tube fed group (n=25 at 1 week, n = 16 at 2 weeks) and the control group showed a 2-3 times higher protein and energy intake (P < 0.0001), and a significantly higher total serum protein and serum albumin after 1 and 2 weeks in the actually tube fed group (all P < 0.001). Pressure-sore development and severity were not significantly influenced in the actually tube fed group. We conclude that we were not able to show a significant decrease in development and severity of pressure sores, because the nasogastric tube for supplemental feeding was not well tolerated in this patient group. Nevertheless, tube feeding overnight does result in a significant higher protein and energy intake, and has a significant effect on nutritional status in the actually tube-fed group. Other means of supplemental feeding will have to be used in order to answer the question of whether supplemental feeding can decrease development and severity of pressure sores.

Influence of hematocrit on the measurement of lipoproteins demonstrated by the example of lipoprotein(a)

BACKGROUND

The measurement of many parameters of human blood is usually performed in plasma or serum. Since lipoproteins or apolipoproteins, for example, are found almost exclusively in the plasma fraction after low-speed centrifugation, these parameters can be expected to be distributed in a different plasma volume depending on the hematocrit value. Therefore, the measured plasma levels might be relatively too low or too high in comparison to the whole blood concentrations in the case of abnormal hematocrit levels. The aim of our experiments was to evaluate the extent of differences between whole blood and plasma concentrations, taking as an example lipoprotein(a) [Lp(a)] in hemodialysis patients with documented decreased hematocrit values.

METHODS

Lp(a) was measured in plasma as well as whole blood of 15 hemodialysis patients with low hematocrit values (0.29 +/- 0.02) in comparison to 11 control subjects (0.45 +/- 0.04).

RESULTS

Plasma concentrations were 27% higher in patients than in controls (19.7 vs. 15.5 mg/dl). The relative difference was twice as high (59%) when measured in whole blood (13.5 vs. 8.5 mg/dl). Similar relative differences were observed when whole blood concentrations of 125 hemodialysis patients and 256 controls were calculated with the formula [Lp(a)plasma * (1-hematocrit)].

CONCLUSIONS

Our findings clearly demonstrate that hematocrit is a strong confounding variable of lipoprotein measurement in epidemiological studies when concentrations are measured in plasma, especially in cases of abnormal hematocrit values. Furthermore, studies investigating the longitudinal changes of lipoproteins should consider potential hematocrit changes.

Active sensing--closing multiple loops

In this contribution, it is argued that the prevailing view of the sensory system as an intricate, but passive processor of external information does not capture the full complexity of brain performance. Instead, we try to reinforce a notion that sees the brain as a system embedded within the environment and actively exploring it. We will attempt to emphasize the bidirectional interaction between brain and environment at all levels of processing and at different scales of the system description. This modified approach to the understanding of the brain has profound consequences for experimental investigations, starting with the experimental design and extending into data analysis and interpretation.