Toward understanding recurrent meningioma: the potential role of lysosomal cysteine proteases and their inhibitors.

OBJECT: The first aim of this study was to diagnose more aggressive and potentially recurrent meningiomas using an in vitro embryonic chick heart invasiveness assay in which lysosomal enzyme cathepsin B was used as the invasiveness marker. The second aim was to confirm if cathepsin B and/or cathepsin L and their endogenous inhibitors were also prognostic parameters in the clinical study of 119 patients with meningioma. METHODS: Primary meningioma cultured spheroids were "confronted" with embryonic chick heart spheroids in vitro, and cathepsin B was used as molecular marker to immunolabel the invasive tumor cells. In vitro invasion assays of the malignant meningioma cells were used to assess the invasive potential related to the cysteine cathepsins. As to the second aim, the possible association of cathepsin B along with selected molecular markers, cathepsin L, and endogenous cysteine protease inhibitors (stefins A and B and cystatin C) with meningioma malignancy was determined using enzyme-linked immunosorbent assays in tumor homogenates. Univariate and multivariate analyses were used to compare these parameters with established biological markers of meningioma recurrence in 119 patients with meningiomas. RESULTS: The more invasive tumors, which characteristically overgrew the normal tissue, were identified even within a group of histologically benign meningiomas. More intensive staining of cathepsin B in these tumors was not only found at the tumor front, but also in the invading pseudopodia of a single migrating tumor cells. Matrigel invasion of malignant meningioma cells was significantly altered by modulating cathepsin B activity and by stefin B silencing. In the clinical samples of meningioma, the levels of cathepsins B and L, stefin B, and cystatin C were highest in the tumors of higher histological grades, whereas stefin A and progesterone receptor were the only markers that were significantly increased and decreased, respectively, in WHO Grade III lesions. With respect to the prognosis of relapse, cathepsin L (p = 0.035), stefin B (p = 0.007), cystatin C (p = 0.008), and progesterone receptor (p = 0.049) levels were significant, whereas cathepsin B was not a prognosticator. As expected, WHO grade, age, and Simpson grade (complete tumor resection) were prognostic, with Simpson grade only relevant in the short term (up to 90 months) but not in longer-term follow-up. Of note, the impact of all these parameters was lost in multivariate analysis, due to overwhelming prognostic impact of stefin B (p = 0.039). CONCLUSIONS: The data indicate that the cysteine cathepsins and their inhibitors are involved in a process related to early meningioma recurrence, regardless of their histological classification. Of note, the known tumor invasiveness marker cathepsin B, measured in whole-tumor homogenates, was not prognostic, in contrast to its endogenous inhibitor stefin B, which was highly significant and the only independent prognostic factor to predict meningioma relapse in multivariate analysis and reported herein for the first time. Stefin B inhibition of local invasion was confirmed by in vitro invasion assay, although its other functions cannot be excluded.

Assessment of supra-additive effects of cytotoxic drugs and low dose rate irradiation in an in vitro model for hepatocellular carcinoma.

The use of 5-fluorouracil, topotecan, or gemcitabine was tested for enhancement of the effects of low dose rate (LDR) irradiation in an in vitro model for hepatocellular carcinoma. For comparison, all drugs were tested in combination with high dose rate (HDR) gamma-irradiation as well. Multicellular spheroids of HepG2 cells were exposed to HDR or LDR irradiation by means of external beam cobalt-60 or rhenium-188 (188Re), respectively, dissolved in the culture medium. Secondly, exposure to irradiation was combined with the cytotoxic drug. Toxicity was evaluated by means of a quantitative spheroid outgrowth assay and histology. For 5-fluorouracil, supra-additive effects were observed in combination with HDR irradiation. With 188Re, the supra-additive toxicity was only transient. For topotecan and 188Re, no supra-additive effects were seen, whereas the addition of HDR irradiation at the end of the topotecan exposure yielded lasting supra-additive effects. Incubation with gemcitabine followed by exposure to HDR irradiation, induced a synergistic toxicity on the outgrowth. No supra-additive effects were observed when HDR irradiation was added at the start of the incubation with gemcitabine or combined with LDR irradiation. For all drugs tested, supra-additive effects were observed with HDR irradiation if the timing of the irradiation was appropriate. For 188Re, no lasting supra-additive effects were observed.

Pulsatile tinnitus and the intrameatal vascular loop: why do we not hear our carotids?

OBJECTIVE: Pulsatile tinnitus is characterized by hearing the heart beat or respiration in one or both ears. In 15% of patients with pulsatile tinnitus, no cause can be found. Other investigators have suggested that a vascular loop entering the internal auditory meatus can be another cause of arterial, pulse synchronous tinnitus. If so, we should constantly hear the arterial pulsations of the carotid arteries passing through the petrous bone. METHODS: Using magnetic resonance imaging, 17 patients with unilateral pulsatile tinnitus and 46 with non-pulsatile tinnitus were analyzed for the presence of a vascular loop entering into the internal acoustic meatus. Four temporal bones were sectioned to find structural differences between the internal acoustic meatus and the pericarotid area. Four patients with intrameatal vascular loops and ipsilateral pulsatile tinnitus underwent surgery by Teflon interpositioning between the loop and the cochlea. RESULTS: In unilateral pulsatile tinnitus, a statistically highly significant amount of intrameatal vascular loops was noted in comparison to non-pulsatile tinnitus. A well-developed pericarotid venous plexus was found histologically. Three of the four patients who underwent surgery were initially tinnitus free, but pulsations recurred after 3 months in one patient. CONCLUSION: Vascular loops in the internal auditory canal may generate pulsatile tinnitus. It may be treated by placing Teflon between the cochlea and the intrameatal vascular loop. One then does not hear the pulsation of the carotids due to a dampening effect of a pericarotid venous plexus.

Radiation-induced damage to normal tissues after radiotherapy in patients treated for gynecologic tumors: association with single nucleotide polymorphisms in XRCC1, XRCC3, and OGG1 genes and in vitro chromosomal radiosensitivity in lymphocytes.

PURPOSE: To examine the association of polymorphisms in XRCC1 (194Arg/Trp, 280Arg/His, 399Arg/Gln, 632Gln/Gln), XRCC3 (5' UTR 4.541A>G, IVS5-14 17.893A>G, 241Thr/Met), and OGG1 (326Ser/Cys) with the development of late radiotherapy (RT) reactions and to assess the correlation between in vitro chromosomal radiosensitivity and clinical radiosensitivity. METHODS AND MATERIALS: Sixty-two women with cervical or endometrial cancer treated with RT were included in the study. According to the Common Terminology Criteria for Adverse Events, version 3.0, scale, 22 patients showed late adverse RT reactions. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assays were performed to examine polymorphic sites, the G2 assay was used to measure chromosomal radiosensitivity, and patient groups were compared using actuarial methods. RESULTS: The XRCC3 IVS5-14 polymorphic allele was significantly associated with the risk of developing late RT reactions (odds ratio 3.98, p = 0.025), and the XRCC1 codon 194 variant showed a significant protective effect (p = 0.028). Patients with three or more risk alleles in XRCC1 and XRCC3 had a significantly increased risk of developing normal tissue reactions (odds ratio 10.10, p = 0.001). The mean number of chromatid breaks per cell was significantly greater in patients with normal tissue reactions than in patients with no reactions (1.16 and 1.34, respectively; p = 0.002). Patients with high chromosomal radiosensitivity showed a 9.2-fold greater annual risk of complications than patients with intermediate chromosomal radiosensitivity. Combining the G2 analysis with the risk allele model allowed us to identify 23% of the patients with late normal tissue reactions, without false-positive results. CONCLUSION: The results of the present study showed that clinical radiosensitivity is associated with an enhanced G2 chromosomal radiosensitivity and is significantly associated with a combination of different polymorphisms in DNA repair genes.

Calcification as an indicator of osteoinductive capacity of biomaterials in osteoblastic cell cultures.

Mineralized extracellular matrix formation is representative for the osteoinductive capacity of biomaterials and is often tested in vitro. Characteristics of in vitro mineralization of primary rat osteoblastic cells (bone marrow, calvaria, periosteum, fetal and adult long bone) and UMR-106 cells were compared by von Kossa staining, FTIR, X-ray diffractometry, TEM and related to parameters of early (ALP and collagen I formation) and late (osteocalcin secretion) osteoblast expression. All cultures expressed high alkaline phosphatase activity and were able to form bone apatite. However, a nodular versus diffuse mineralization pattern was observed. Bone marrow, calvaria and periosteum (early passage) derived cells mineralized restrictively on the three-dimensional area of a nodule. The extracellular matrix consisted of collagen I fibers, among matrix vesicles loaded with needle-like crystals. Long bone, late passage periosteum derived and UMR-106 cells exhibited a diffuse mineralization pattern. Needle-like crystals were observed between the cells but collagen fibers and matrix vesicles could not be detected. Secretion of osteocalcin was detected in cultures derived from bone marrow and absent in UMR-106 and long bone derived cell cultures. The present study demonstrates that dystrophic calcification can not be distinguished from cell-mediated calcification with von Kossa, FTIR and X-ray diffractometry. Primary osteoblastic cells capable of forming nodules are recommended to evaluate the osteoinductive properties of biomaterials.

Chromosomal radiosensitivity in breast cancer patients: influence of age of onset of the disease.

The age dependency of onset of the disease on chromosomal radiosensitivity of an unselected group of breast cancer patients (n=100) was investigated and compared to a group of healthy women (n=100). The chromosomal radiosensitivity was assessed with the G2 and the G0 micro-nucleus (MN) assay. For the G2 assay lymphocytes were irradiated in vitro with a dose of 0.4 Gy 60Co gamma-rays after 70 h incubation and chromatid breaks were scored in 50 metaphases. For the G0 MN assay lymphocytes were exposed in vitro to 3.5 Gy 60Co gamma-rays at low dose rate (LDR). 72 h post-irradiation cultures were arrested and micronuclei were scored in 1000 binucleate cells. The results demonstrated that the group of breast cancer patients was more radiosensitive than a population of healthy women and this with both the G2 and the G0 MN assay. Analyses of the G2 and MN response in different age groups of the breast cancer patients revealed no significant differences in mean G2 and MN scores and suggest that the age of onset of the disease has no effect on chromosomal radiosensitivity in unselected breast cancer patients. Correlations with different clinical parameters were also investigated.

Isolation and Osteogenic Differentiation of Rat Periosteum-derived Cells.

Selection of appropriate cultures having an osteogenic potential is a necessity if cell/biomaterial interactions are studied in long-term cultures. Osteoblastic cells derived from rat long bones or calvaria have the disadvantage of being in an advanced differentiation stage which results in terminal differentiation within 21 days. In this regard, less differentiated periosteum-derived osteoprogenitors could be more suitable.Periosteum-derived cells were isolated from the tibiae of adult Wistar rats (n = 12). The osteogenic potential with regard to alkaline phosphatase activity, morphology, nodule formation and mineralization was studied by culturing them in an osteogenic medium for up to 4 months.Seventy-five percent of the cultures (n = 9) did not show any increase in alkaline phosphatase activity nor nodule formation during long-term culture for up to 4 months. Nevertheless, in 25% of the cultures, alkaline phosphatase activity started from negligible (<5 mM pNP/mg protein) and increased towards approximately 50 mM pNP/mg protein. Three-dimensional nodule formation was observed at passages 3-5. In further passages (P5-P7), nodule formation capacity decreased and a diffuse mineralization pattern was observed.Suitable cultures with osteogenic capacity, can be selected at early passages based on the presence of cuboidal cells. These cells have the advantage of retaining their osteogenic potential even after prolonged cultivation (6-7 passages) before final differentiation occurs. Although periosteal cells are suitable for long term in vitro evaluation of biomaterials, the isolation and selection is time consuming. Hence, a more appropriate source to study cell/biomaterial interactions should be more convenient.

Chromosomal radiosensitivity in secondary-progressive multiple sclerosis patients.

PURPOSE: To investigate chromosomal radiosensitivity of secondary progressive (SP) multiple sclerosis (MS) patients in comparison to a group of healthy individuals. MATERIAL AND METHODS: Chromosomal radiosensitivity was assessed in vitro with the G2 assay and the G0-micronucleus (MN) assay. For the G2 assay phytohaemagglutinin (PHA) stimulated blood cultures were irradiated with a dose of 0.4 Gy 60Co gamma rays in the G2 phase of the cell cycle. For the MN assay unstimulated diluted blood samples were exposed to 3.5 Gy 60Co gamma rays delivered at a high dose-rate (HDR = 1 Gy/min) or low dose-rate (LDR = 4 mGy/min). RESULTS: No significant differences in the number of chromatid breaks were observed between MS patients and healthy individuals. With the G0-MN assay a higher spontaneous MN yield was found in MS patients. At HDR irradiation no significant differences were shown, while at LDR irradiation, MS patients were found less sensitive than healthy controls. The dose-rate sparing index was higher for MS patients, pointing to a better repair capacity. CONCLUSIONS: MS patients are not characterised by an enhanced in vitro chromosomal radiosensitivity. The radioresistant response, which was only observed with the MN assay after LDR irradiation, may point to an adaptive response induced by in vivo oxidative stress in SPMS patients.

Primary resected meningiomas: relapses and proliferation markers.

UNLABELLED: Relapses of meningiomas are a well known phenomenon during follow-up. The significance of sex, age, surgical treatment and mitotic frequency with regard to relapses are still a matter of debate. PATIENTS AND METHODS: The study included 125 meningioma patients who underwent surgical intervention between 1986 and 1997 They were in follow-up for 3, 5, 10 and 15 years; they were grouped as "stable" or "relapsing" tumours. The follow-up was based on magnetic resonance image (MRI) and tomodensitometry (TDM). The labelling index for Ki67 and PCNA (proliferation markers) was scored at resection. Risk factors for relapse were reviewed using univariate analysis and Cox hazards model. RESULTS: One hundred and twenty-five patients were under medical control of whom 26 showed a relapse. Among them 25 arose from subtotal resected tumours and 1 was a recurrence. Relapses comprised 16 females and 10 males. Tumour relapses at 3,5,10 and 15 years were, respectively, 8.8%, 13.6%, 17.6% and 20.8%. Proliferation markers, at group level, were statistically significantly different to distinguish stable from relapsing and malignant from benign meningiomas. Factors significantly associated with tumour relapse in univariate analysis were incomplete resection, histopathology and proliferation markers. In multivariate analysis the proliferation markers and incomplete resection were the only significant risk factors (p<0.05) for relapse. CONCLUSION: To avoid relapses of meningiomas, total resection is recommended. The resection type and proliferation markers are predictive factors for tumour relapse. The proliferation markers cannot be applied at the individual level.

Can recurrence of meningiomas be predicted?

After resection of meningiomas the clinical evolution remains problematic, as no clear-cut predictive criteria are available. In vitro evaluation of meningiomas might help to predict their evolution in vivo after resection. For this goal a confrontation model was tested. A group of 105 patients operated for meningiomas between 1986 and 1997 were reviewed at 3, 5, 10 and 15 years for tumour evolution by tomodensitometry or magnetic resonance. At operation a fragment of these resected tumours was explanted for cell culture and was confronted with embryonic chick heart as a host tissue. The confrontation between tumour- derived cells and host tissue resulted in three different patterns: respectively a regressive, a non-invasive and an invasive pattern. Resection type, proliferation markers (Ki67 and PCNA) and in vitro confrontation patterns were significant (p<0.05) factors in predicting the postsurgical evolution of meningiomas. No correlation was found between proliferation markers and the behaviour in vitro, but invasion in vitro was strictly correlated with recurrence and malignancy of meningiomas.

Biologic dosimetry of 188Re-HDD/lipiodol versus 131I-lipiodol therapy in patients with hepatocellular carcinoma.

UNLABELLED: One approach to treatment of primary hepatocellular carcinoma (HCC) is intraarterial injection of (131)I-lipiodol. Although clinical results have been positive, the therapy can be improved by using (188)Re instead of (131)I as the radionuclide. (188)Re is a high-energy beta-emitter, has a shorter half-life than (131)I, and has only low-intensity gamma-rays in its decay. The present study compared the cytotoxic effect of the radionuclide therapy in HCC patients treated with (131)I-lipiodol and (188)Re-4-hexadecyl 2,2,9,9-tetramethyl-4,7-diaza-1,10-decanethiol (HDD)/lipiodol. To this end, dicentric chromosomes (DCs) were scored in metaphase spreads of peripheral blood cultures. The equivalent total-body dose was deduced from the DC yields using an in vitro dose-response curve. METHODS: Twenty (131)I-lipiodol treatments and 11 (188)Re-HDD/lipiodol treatments were performed on, respectively, 16 and 7 patients with inoperable HCC. Patients received a mean activity of 1.89 GBq of (131)I-lipiodol or 3.56 GBq of (188)Re-HDD/lipiodol into the liver artery by catheterization. For each patient, a blood sample was taken during the week before therapy. A blood sample was also taken 7 and 14 d after administration for the patients treated with (131)I-lipiodol and 1 or 2 d after administration for the patients treated with (188)Re-HDD/lipiodol. RESULTS: The mean DC yield of (188)Re-HDD/lipiodol therapy (0.087 DCs per cell) was significantly lower than that of (131)I-lipiodol therapy (0.144 DCs per cell) for the administered activities. Corresponding equivalent total-body doses were 1.04 Gy for (188)Re-HDD/lipiodol and 1.46 Gy for (131)I-lipiodol. Data analysis showed that, in comparison with (131)I-lipidol, (188)Re-HDD/lipiodol yielded a smaller cytotoxic effect and a lower radiation exposure for an expected higher tumor-killing effect. CONCLUSION: (188)Re is a valuable alternative for (131)I in the treatment of HCC with radiolabeled lipiodol, and a dose escalation study for (188)Re-HDD/lipiodol therapy is warranted.

Isolation, proliferation and differentiation of osteoblastic cells to study cell/biomaterial interactions: comparison of different isolation techniques and source.

A sufficient amount of easily obtained and well-characterized osteoblastic cells is a useful tool to study biomaterial/cell interactions essential for bone tissue engineering. Osteoblastic cells were derived from adult and fetal rat via different isolation techniques. The isolation and in vitro proliferation of primary cultures were compared. The osteogenic potential of subcultures was studied by culturing them in osteogenic medium and compared with respect to alkaline phosphatase activity, nodule formation and mineralization potential. Calvaria cells were easier to obtain and the amount of cells released by enzymatic isolation was higher than for the long bone cells. The expansion of the cells in primary culture was highest for fetal calvaria cells compared to fetal and adult long bone cells. All cultures expressed high alkaline phosphatase activity except for calvaria cells obtained by spontaneous outgrowth. Enzymatic isolation of fetal calvaria and long bone cells favoured the osteogenic differentiation. Enzymatically isolated calvaria cells formed well-defined three-dimensional nodules which mineralized restricted to this area. On the contrary, cultures derived from fetal as well as adult long bones mineralized in ill-defined deposits throughout the culture and only formed occasionally nodular-like structures. The mineral phase of all osteoblastic cultures was identified as a carbonate-containing apatite. The present study demonstrates that considering the isolation method, proliferation capacity and the osteogenic potential, the enzymatically released fetal calvaria cells are most satisfactory to study cell/biomaterial interactions.

Imaging of mild traumatic brain injury using 57Co and 99mTc HMPAO SPECT as compared to other diagnostic procedures.

BACKGROUND: Traumatic brain injury (TBI) is usually assessed with the Glasgow Coma Scale (GCS), CT and EEG. TBI can result from either the primary mechanical impact or secondary (ischemic) brain damage, in which calcium (Ca) plays a pivotal role. This study was undertaken to compare the applicability of SPECT using 57Co as a Ca-tracer in patients with mild traumatic brain injury. MATERIAL/METHODS: 8 patients with mild TBI (GCS 15) were clinically examined and studied with EEG, neuropsychological testing (NPT) and SPECT within 2 days post-TBI. After i.v.-administration of 37 MBq (1 mCi) 57Co (effective radiation dose 0.34 mSv x MBq(-1); 1.24 rem x mCi(-1); physical half-life 270 days, biological half-life 37.6 h), single-headed SPECT (12 h pi) was performed, consecutively followed by standard 925 MBq (25 mCi) Tc-99m HMPAO SPECT. RESULTS: In 6 of the 8 patients, baseline NPT and SPECT showed focal abnormalities in the affected frontal and temporal brain regions, which were in good topographical accordance. CT and EEG did not detect (structural) lesions in any of these cases. CONCLUSIONS: Single-headed 57Co-SPECT is able to show the site and extent of brain damage in patients with mild TBI, even in the absence of structural lesions. It may confirm and localize NPT findings. The predictive value of 57Co-SPECT should be assessed in larger patient series.

Antibiotic administration in an animal model of chronic peritoneal dialysate exposure.

OBJECTIVES: The high incidence of intraperitoneal infection remains an important problem in animal models of chronic dialysate exposure. Prophylactic antibiotic administration can be used to resolve this problem, but the isolated effects of antibiotics on peritoneal membrane function and structure are unknown. The present study examined the effects of prophylactic antibiotics on infection rate and peritoneal membrane function and structure in a rat model of chronic dialysate exposure. DESIGN: A first group of rats (A; n = 12) received 10 mL 3.86% glucose dialysate twice daily through a heparin-coated catheter. In a second group of animals (B; n = 12), oxacillin 2.5 mg/day and gentamicin 0.04 mg/day were added to the dialysate. Group C (n = 12) was injected twice daily with an identical dose of antibiotics dissolved in 1 mL of buffer solution. Group D (n = 12) was left untreated. Dialysate cultures were obtained regularly. After 8 weeks of exposure, peritoneal transport studies were performed and samples for histology were obtained. RESULTS: Technique survival was 92% in group A and 100% in the remaining groups. Five rats in group A but none of the animals in the other groups developed peritonitis. The transport rates of small solutes were elevated and net ultrafiltration was decreased in group A compared to the controls. Fibrosis, as evaluated by quantifying Picro Sirius Red staining with image analysis, was significantly elevated in group A (3.48% +/- 1.06% vs 0.72% +/- 0.51% in group D, p < 0.05) but not in group B (0.29% +/- 0.07%) or in group C (0.52% +/- 0.28%). Vascular density, measured by counting the number of blood vessels that stained positive for endothelial NO synthase, was increased in both groups that were exposed to dialysate: 153.0 +/- 12.9/microm2 in group A and 131.6 +/- 14.3/microm2 in group B, versus 76.76 +/- 12.37/microm2 in group C and 73.2 +/- 10.4/microm2 in group D (p < 0.01). CONCLUSIONS: Prophylactic administration of oxacillin and gentamicin adequately prevented intraperitoneal infection in an animal model of chronic dialysate exposure. In addition, fibrosis was absent, suggesting intraperitoneal infection rather than dialysate exposure is a causative factor.

Patient dosimetry for 131I-lipiodol therapy.

Patient dosimetry data for intra-arterial()iodine-131 lipiodol therapy for hepatocellular carcinoma (HCC) are scarce. The aim of this study was to determine the absorbed dose (D) to the tumour and healthy tissues, as well as the effective dose (E), by different methods for 17 therapies in 15 patients who received a mean activity of 1.9 GBq (SD 0.2) (131)I-lipiodol. Eight patients received thyroid blocking by potassium iodide (KI). Patient dosimetry was performed based on bi-planar total body scans using the Monte Carlo simulation program MCNP-4B and the MIRDOSE-3 standard software program. CT images of each patient were used to determine liver and tumour volume and position. The total body dose to the patient was also determined by biological dosimetry with the in vitro micronucleus (MN) assay. From the increase in micronucleus yield after therapy, the equivalent total body dose (ETBD) was calculated. Results for D and E were comparable between MCNP and MIRDOSE (liver: mean 7.8 Gy, SD 1.8, lungs: 6.8 Gy, SD 2.9, E: 2.01 Gy, SD 0.58). MIRDOSE gave a systematic overestimation for the tumour dose, especially for tumours <3 cm (15%). The MCNP method is more accurate since the dose contributions from tumour to organs and vice versa can be accounted for. The absorbed dose to the thyroid was significantly lower for patients who received KI (7.2 Gy, SD 2.2) than for the other patients (13.8 Gy, SD 5.0). MN yields could be obtained for only 12 of the 17 therapies due to hypersplenism. A mean ETBD of 1.66 Gy (SD 0.73) was obtained, but the MN results showed no correlation between the ETBD and the total body dose values of the physical dosimetry. Also, in all except one of the patients, no further reduction in the number of thrombocytes was observed after therapy, probably due to the existing hypersplenism. It is concluded that in view of the high E values, patient dosimetry is necessary for patients receiving (131)I-lipiodol therapy. Except in the case of the smaller tumours, comparable results were obtained with MCNP and MIRDOSE. Due to hypersplenism, biological dosimetry results based on the MN assay are not reliable.

The effects of heparin administration in an animal model of chronic peritoneal dialysate exposure.

Diverse modes of heparin administration have been used in animal models of chronic peritoneal dialysate exposure to maintain catheter patency and prevent fibrinous adhesions. Heparin has biological actions independent of its well-known anticoagulant activity, including the ability to modulate extracellular matrix synthesis, cellular proliferation, angiogenesis, and inflammation. These actions may interfere with peritoneal membrane homeostasis. The present study evaluated the influence of the mode of heparin administration on technique survival and infection rate in a rat model of chronic dialysate exposure. Further, the incorporation of heparin in the peritoneal membrane was examined. A 3.86% glucose dialysate was injected twice daily into Wistar rats with a heparin-coated catheter (group A1), or with a standard catheter with heparin injections during the entire exposure time (group A2) or only during 1 week (group A3). Sham manipulations were performed in a fourth group and a fifth group was left untreated. Technique survival was 80% in group A1, 60% in group A2, and 40% in group A3. The rate of infection was highest in group A1 and lowest in group A2. Intraperitoneally administered heparin accumulated in the peritoneal membrane, whereas dextran, with a molecular weight similar to that of heparin, was not incorporated in the peritoneum. In conclusion, intraperitoneal heparin reduced the incidence of infection in an animal model of chronic dialysate exposure. The best technique survival was, however, obtained using a heparin-coated catheter. Heparin is incorporated in the peritoneal membrane, where it may exert diverse biological actions and thus bias study results. The use of a heparin-coated catheter in combination with antibiotics may be the optimal approach to obtaining peritoneal access in animal models of chronic dialysate exposure.

Is the root entry/exit zone important in microvascular compression syndromes?

OBJECTIVE: Microvascular compression syndromes such as trigeminal neuralgia, hemifacial spasm, and disabling positional vertigo involve an artery or vein compressing a cranial nerve. A cranial nerve is composed of a central nervous system (CNS) segment and a peripheral nervous system (PNS) segment separated by the root entry/exit zone (REZ). Although vascular compression can occur at any point along the cranial nerve, it has been generally assumed that only vascular contact at the REZ of the affected cranial nerve can cause symptoms. On the basis of personal surgical experience, we propose that vascular compression of the CNS segment alone causes symptoms. This has important repercussions for the future diagnosis and treatment of microvascular compression syndromes, especially the cochleovestibular compression syndrome. METHODS: For the anatomic study, four autopsy specimens and one surgical biopsy specimen of the vestibulocochlear nerve were microscopically and ultramicroscopically analyzed for structural differences between the CNS and PNS segments. For the clinical study, five patients with the clinical picture of cochleovestibular compression syndrome were treated by microsurgical decompression at the level of the CNS segment and not the REZ. One patient underwent reoperation for recurrent symptoms 4 years later, and a 4-mm vestibular neurectomy was performed at that stage. We performed an epidemiological analysis to demonstrate that the known incidences of trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia are related to the length of their respective CNS segments. RESULTS: Histological differences between the PNS and CNS segments suggest that the PNS segment is more resistant to compression. This was confirmed by neurophysiological data from intraoperative monitoring in posterior fossa surgery and experimental studies. We found a clear epidemiological correlation between the length of the CNS segment, which differed among cranial nerves, and the incidence of the microvascular compression syndrome. Successful decompression of the CNS segment in patients without compression at the REZ of the vestibulocochlear nerve for disabling positional vertigo provides clinical support for this hypothesis. CONCLUSION: The evidence we present supports the hypothesis that vascular compression syndromes arise from vascular contact along the CNS segment of the cranial nerves.

Micronucleus assay reveals no radiation effects among nuclear power plant workers.

The micronucleus assay was applied as biomarker for exposure effect and radiosensitivity in a group of 99 radiation workers of the Nuclear Power Plant Doel (Belgium). The difference in micronucleus frequency between the group of radiation workers with annual dose exceeding 2 mSv and a non-exposed control population was statistically not significant. With respect to the micronucleus frequency after an in vitro challenge dose of 2 Gy, which can be considered as biomarker for radiosensitivity, the data of present study can be represented by a normal distribution without a high frequency tail. This means that a subpopulation of workers with elevated radiosensitivity could not be identified in the population under study.