Magnetresonanztomographische Diagnostik der peripheren Durchblutung*

PURPOSE: This article describes the potential of dynamic contrast- enhanced magnetic resonance tomography (DCE-MRT) for the visualization and quantification of blood flow of lower leg muscles at rest and after individually adjusted muscular exercise. PATIENTS AND METHODS: Five cases were chosen to exemplify the qualitative and semi-quantitative blood flow evaluation in the lower leg muscles. The crural muscle state was determined with an isometric maximal strength measurement from a female patient with peripheral arterial occlusive disease (pAVK), a male patient with coronary heart disease (KHK) without clinical signs of a pAVK, a volunteer with sufficient physical activity in accordance with the Freiburg Questionnaire of Physical Activity and two professional athletes. After calibration of the plantarflexion ergometer MR-PEDALO (Figures 2a and 2b) for the execution of auxotonic muscle work a 1- minute alternating foot extension and flexion exercise on MRPEDALO was performed in the MR machine. Instead of the lower leg splint shown in Figures 2a and 2b the MR coil fits exactly in MR-PEDALO used for DCE-MRT. Mechanical work performed during the 1-minute exercise ranged from 52 watt seconds (Ws) to 244 Ws (0.65 W to 4.07 W), indicating similar interindividual work loads in relation to the individual maximum isometric strength. DCE-MRT was performed at rest and immediately after auxotonic exercise test (T1w 2DFLASH- GE sequence with TR/TE/alpha: 100 ms/6 ms/70 degrees; field of view: 400; matrix: 81 x 256; slice thickness: 10 mm; acquisitions: 73 at 8.3 s each; total examination time: 9.24 min; bolus application of Magnevist, Schering, 0.02 ml/kg kg, 20 ml bolus NaCl, flow 2 ml/s, 22G cannula in a cubital vein). Signal intensity (SI) curves were analyzed with DynaVision (MeVis gGmbH, Bremen, Germany). RESULTS: Measuring peripheral blood flow needs appropriate muscular stress tests. The SI-curves of the region of interest (ROI) representing the peroneus, tibialis anterior and gastrocnemius muscle run almost parallel at rest. Workloads between 52 Ws and 244 Ws (0.65 W and 4.07 W), similar in relation to the individual maximum isometric strength, induce distinctive changes of the upslope, wash-in, peak and washout of SI-curves preferably for the peroneus muscle and less predominant also for the tibialis anterior muscle and gastrocnemius muscle respectively. The first case, a 55-year-old female patient with peripheral arterial occlusive disease (pAVK) stage Fontaine IIb before (Figure 3a) and after (Figure 3b) percutaneous transluminal angioplasty (PTA) of a right femoral artery stenosis shows after interventional treatment a rapid post-exercise SI-increase in the peroneus muscle. The steeper SI-curve indicates a better contrast medium inflow due to an improved perfusion. The second case, a 65-year-old man suffering from coronary heart disease without clinical signs of pAVK (Figure 4) exercised with a workload of 92 Ws. After stress test the ROI for the peroneus muscle shows a clear intensity increase. After exercise the SI-curve for the tibialis anterior muscle shows a similar, but less predominant change while the shape of the SI-curve of the gastrocnemius muscle remains mainly identical. A 23-year-old male person with average physical activity (Figure 5) performed DCE-MRT of the left lower leg after stress test with 172 Ws demonstrating a rapid signal increase in the peroneus muscle while the synergistic tibialis anterior muscle and antagonistic gastrocnemius muscle show a comparatively slow contrast-medium wash-in. A 26-year-old male athlete (Figure 6) exercised with 196 Ws showing a rapid contrast medium inflow in the peroneus muscle and initially also in the synergistic tibialis anterior muscle. A contrast-medium wash-out appears in both muscles, while the shape of the gastrocnemius muscle SI-curve remains substantially unchanged. A 26-year-old female athlete (Figure 7) exercised with 244 Ws. Post exercise SI-curves show a distinctive and rapid increase of contrast medium wash-in with a sharp peak particularly in the peroneus muscle and similarly in the tibialis anterior and gastrocnemius muscle. After exercise all SI-curves show a wash-out phase. CONCLUSION: SI-curves show relative increase in correlation with Time-to-Peak (TTP) decrease and Mean-Intensity to Time Ratio (MITR) increase indicating blood flow reserve mobilization after exercise. Individual muscle state seems to be linked to muscle recruitment and muscle coordination reflected by post-exercise SI-curves. The gastrocnemius muscle shows comparatively low SI-curve changes after muscular load test. Further methodological standardization and optimization of the stress test is mandatory to assure intra- and interindividual comparisons. Due to direct visualization and quantitative evaluation of the peripheral microcirculation DCE-MRT has a diagnostic potential for monitoring therapeutic response in peripheral circulation disorders and sports medicine.     

The genome sequence of Clostridium tetani,the causative agent of tetanus disease

Tetanus disease is one of the most dramatic and globally prevalent diseases of humans and vertebrate animals, and has been reported for over 24 centuries. The manifestation of the disease, spastic paralysis, is caused by the second most poisonous substance known, the tetanus toxin, with a human lethal dose of approximately 1 ng/kg. Fortunately, this disease is successfully controlled through immunization with tetanus toxoid; nevertheless, according to the World Health Organization, an estimated 400,000 cases still occur each year, mainly of neonatal tetanus. The causative agent of tetanus disease is Clostridium tetani, an anaerobic spore-forming bacterium, whose natural habitat is soil, dust, and intestinal tracts of various animals. Here we report the complete genome sequence of toxigenic C. tetani E88, a variant of strain Massachusetts. The genome consists of a 2,799,250-bp chromosome encoding 2,372 ORFs. The tetanus toxin and a collagenase are encoded on a 74,082-bp plasmid, containing 61 ORFs. Additional virulence-related factors could be identified, such as an array of surface-layer and adhesion proteins (35 ORFs), some of them unique to C. tetani. Comparative genomics with the genomes of Clostridium perfringens, the causative agent of gas gangrene, and Clostridium acetobutylicum, a nonpathogenic solvent producer, revealed a remarkable capacity of C. tetani: The organism can rely on an extensive sodium ion bioenergetics. Additional candidate genes involved in the establishment and maintenance of a pathogenic lifestyle of C. tetani are presented.     

Assessment of Microvascular Abnormalities by Nailfold Capillaroscopy in Juvenile Dermatomyositis After Medium‐ to Long‐Term Followup

Objective

In juvenile dermatomyositis (DM), microvascular abnormalities, measured by nailfold capillaroscopy (NFC), are common early in the disease course. We aimed to compare the presence of NFC abnormalities in patients with medium‐ to long‐term juvenile DM with that of controls, and to explore associations between NFC abnormalities and disease activity and other disease characteristics.

Methods

Fifty‐eight juvenile DM patients with a median disease duration of 16.8 (range 2–38) years were clinically examined and compared with matched controls. By NFC, we assessed nailfold capillary density (NCD), giant capillaries, scleroderma, and neovascular pattern (defined as scleroderma active or late pattern). NFC was analyzed with researchers blinded to patient/control identity and disease characteristics. We measured disease activity and damage by validated tools, and patients were categorized as having active or inactive disease according to the Paediatric Rheumatology International Trials Organisation criteria.

Results

Compared to controls, patients had decreased NCD (mean ± SD 6.4 ± 2.1/mm versus 7.6 ± 0.8/mm; P = 0.001) and showed more abnormality in all other NFC parameters; 36% of patients versus 4% of controls had NCD <6/mm (P < 0.001). Giant capillaries, scleroderma, and neovascular pattern were found in 9%, 84%, and 41% of patients, respectively. Patients with active disease (n = 30) presented more frequently with neovascular pattern than patients with inactive disease (n = 28) (P = 0.041). Decreased NCD and neovascular pattern were associated with higher levels of disease activity and impaired muscle function.

Conclusion

After medium‐ to long‐term followup, juvenile DM patients had decreased NCD and, often, neovascular pattern; both were associated with higher levels of disease activity and impaired muscle function. This suggests that NFC can be a biomarker for disease activity in longstanding juvenile DM too.

     

Topotecan, a topoisomerase I inhibitor, is active in the treatment of myelodysplastic syndrome and chronic myelomonocytic leukemia

The aim of this study was to evaluate the activity of topotecan in patients with myelodysplastic syndrome (MDS) and chronic myelomonocytic leukemia (CMML). Forty-seven patients with a diagnosis of MDS (n = 22) or CMML (n = 25) were treated. The median age was 66 years. Chromosomal abnormalities were present in 70% and thrombocytopenia less than 50 x 10(3)/microL in 51%. Evaluation of outcome and of differences among subgroups was performed according to standard methods; the criteria for response were those used for acute leukemia. Topotecan was administered as 2 mg/ m2 by continuous infusion over 24 hours daily for 5 days (10 mg/m2 per course) every 3 to 4 weeks until remission, then once every month for a maximum of 12 courses. Thirteen patients (28%) achieved a complete response (CR) and six (13%) had hematologic improvement. A CR was achieved in six of 22 patients with MDS (27%) and in seven of 25 with CMML (28%). All eight patients who presented with cytogenetic abnormalities (five chromosome 5 or 7 abnormalities) who achieved CR were cytogenetically normal in CR. Characteristics for which there was evidence of association with a higher response rate were lack of prior chemotherapy, less than 10% marrow monocytes, and absence of RAS oncogene mutations. In contrast, CR rates were similar in patients with or without abnormal karyotypes. Mucositis occurred in 64% of patients (severe in 19%) and diarrhea in 32% (severe in 13%). Febrile episodes occurred in 85% of patients and documented infections in 47%. With a median follow-up duration of 8 months, the 12-month survival rate was 38%, median survival time 10.5 months, and median remission duration 7.5 months. We conclude that topotecan has significant activity in MDS and CMML, with acceptable side effects. Future studies will investigate topotecan combined with topoisomerase II reactive agents, cytarabine, or hypomethylating agents (azacytidine and decitabine).     

A cell-based screen for resistance of Bcr-Abl-positive leukemia identifies the mutation pattern for PD166326, an alternative Abl kinase inhibitor

In Philadelphia-positive (Ph(+)) leukemia, point mutations within the Bcr-Abl kinase domain emerged as a major mechanism of resistance to imatinib mesylate. We established a cell-based screening strategy for detection of clinically relevant point mutations using Bcr-Abl-transformed Ba/F3 cells. We identified 32 different single-point mutations within the kinase domain of Bcr-Abl. The pattern and frequency of mutations in this cell culture-based screen resembled the pattern and frequency observed in resistant patients. We then applied this screen to an alternative Abl kinase inhibitor. Using PD166326, the frequency of resistant colonies emerging at 5 to 10 times the median growth inhibition (IC50) of PD166326 was significantly lower than with imatinib. In addition, PD166326 produced a distinct pattern of Bcr-Abl mutations. The majority of mutations that came up with both imatinib and PD166326 could effectively be suppressed by increasing the dose of PD166326 to 50 to 500 nM. In contrast, only a few mutations could be suppressed by increasing the imatinib dose to 5 to 10 microM. However, 3 mutations affecting F317 displayed complete resistance to PD166326, but could be effectively inhibited by standard concentrations of imatinib. Thus, this robust and simple screening system provides a rational basis for combinatorial and sequential treatment strategies in targeted cancer therapy.     

Response to 2'-deoxycoformycin after failure of interferon-alpha in nonsplenectomized patients with hairy cell leukemia

Two patients with hairy cell leukemia with massive splenomegaly and severe pancytopenia were treated with recombinant alpha-A interferon (IFN-alpha-2a). There was no significant response to a trial of IFN- alpha-2a (11 and 20 weeks) with respect to blood counts or spleen size. Subsequent treatment with 2'-deoxycoformycin (dCF) for 8 consecutive weeks (4 mg/m2/wk) resulted in normalization of spleen size and a normalization of peripheral blood counts and bone marrow in one patient. The second patient demonstrated a reduction in spleen size and improved blood counts following 9 weeks of dCF therapy but eventually became refractory. This demonstrates that dCF is non-cross-resistant with interferon and confirms the efficacy of dCF in nonsplenectomized patients.     

Phase I study of Topotecan, a new topoisomerase I inhibitor, in patients with refractory or relapsed acute leukemia

The purpose of this study was to define, in a phase I study in leukemia, the maximally tolerated dose (MTD), major toxicities, and possible antitumor activity of Topotecan, a new topoisomerase I (topo I) inhibitor. Topotecan was delivered by a 5-day continuous infusion every 3 to 4 weeks to patients with refractory or relapsed acute leukemia, at doses ranging from 3.5 mg/m2 to 18 mg/m2 per course. Twenty-seven patients were treated, including 17 patients with acute myelogenous or undifferentiated leukemia, 7 with acute lymphocytic leukemia, and 3 with chronic myelogenous leukemia in blastic phase. Severe mucositis was the dose-limiting toxicity occurring in two of five patients treated with Topotecan 11.8 mg/m2 per course; a third patient had prolonged myelosuppression. At the MTD of 10 mg/m2 per course, 1 of 12 patients had severe mucositis and 5 had mild-to- moderate mucositis. Nausea, vomiting, diarrhea, and prolonged myelosuppression were uncommon. Three patients (11%) achieved a complete response, two (7%) had a partial response, and one (4%) had a hematologic improvement. The overall complete plus partial response rate was 19%, and 24% in acute myelogenous or undifferentiated leukemia. A novel in vitro assay that quantifies Topotecan-stabilized topo I-DNA complexes in patient samples was used, which demonstrated heterogeneity in the ability of Topotecan to interact with topo I, the intracellular target of Topotecan. This phase I study defined the MTD of Topotecan to be 10 mg/m2 by continuous infusion over 5 days every 3 to 4 weeks in patients with refractory or relapsed acute leukemia. Severe mucositis was the dose-limiting toxicity. Future studies will define the precise activity of Topotecan in different leukemia subsets, its efficacy in combination with other antileukemic drugs, and correlations between Topotecan-induced topo I-DNA complex formation and individual patient response to Topotecan.     

Convulsions and hypoglycemia due to tetramethyl succinonitrile intoxication in the polyvinyl chloride (PVC) industry: A 4-year follow-up

Objectives

Exposure and clinical data concerning cases of toxic convulsions and hypoglycemia due to tetramethyl succinonitrile (TMSN) exposure are reported.

Material and Methods

Forty-four workers exposed to TMSN in the PVC production plant participated in occupational health medical check-ups including medical history, clinical examination and clinical chemistry. A 4-year follow-up was performed. To evaluate occupational exposure, measurements of TMSN in the ambient air as well as personal air sampling were conducted.

Results

Four workers suffered from convulsions with reversible pathologic EEG and 16 other persons were hypoglycemic. Other frequent symptoms included headaches, dizziness and unpleasant taste sensations. TMSN levels had been clearly above the Swiss occupational exposure limit value (MAK). Occupational hygiene interventions resulted in a reduction of the TMSN concentration below the MAK value. TMSN related symptoms have not been observed anymore in the 4-year follow-up.

Conclusion

TMSN is a convulsive substance which in humans has also a hypoglycemic effect.