Reduced laser-evoked potential habituation detects abnormal central pain processing in painful radiculopathy patients.

BACKGROUND: Repetitive painful laser stimuli lead to physiological laser-evoked potential (LEP) habituation, measurable by a decrement of the N2/P2 amplitude. The time course of LEP-habituation is reduced in the capsaicin model for peripheral and central sensitization and in patients with migraine and fibromyalgia. In the present investigation, we aimed to assess the time course of LEP-habituation in a neuropathic pain syndrome, i.e. painful radiculopathy. METHODS: At the side of radiating pain, four blocks of 25 painful laser stimuli each were applied to the ventral thigh at the L3 dermatome in 27 patients with painful radiculopathy. Inclusion criteria were (1) at least one neurological finding of radiculopathy, (2) low back pain with radiation into the foot and (3) a positive one-sided compression of the L5 and/or S1 root in the MRI. The time course of LEP-habituation was compared to 20 healthy height and age matched controls. Signs of peripheral (heat hyperalgesia) and central sensitization (dynamic mechanical allodynia and hyperalgesia) at the affected L5 or S1 dermatome were assessed with quantitative sensory testing. RESULTS: Painful radiculopathy patients showed decreased LEP-habituation compared to controls. Patients with signs of central sensitization showed a more prominent LEP-habituation decrease within the radiculopathy patient group. CONCLUSIONS: Laser-evoked potential habituation is reduced in painful radiculopathy patients, which indicates an abnormal central pain processing. Central sensitization seems to be a major contributor to abnormal LEP habituation. The LEP habituation paradigm might be useful as a clinical tool to assess central pain processing alterations in nociceptive and neuropathic pain conditions. SIGNIFICANCE: Abnormal central pain processing in neuropathic pain conditions may be revealed with the laser-evoked potential habituation paradigm. In painful radiculopathy patients, LEP-habituation is reduced compared to healthy controls.

Laser-evoked potentials in painful radiculopathy.

OBJECTIVE: The aims of this exploratory study were (1) to develop a standardized objective electrophysiological technique with laser-evoked potentials to assess dorsal root damage quantitatively and (2) to correlate these LEP measures with clinical parameters and sensory abnormalities (QST) in the affected dermatome. METHODS: Thirty-eight patients with painful radiculopathy and 20 healthy subjects were investigated with LEP recorded from the affected dermatome and control areas as well as with quantitative sensory testing. Questionnaires evaluating severity and functionality were applied. RESULTS: On average, LEP amplitudes and latencies from the affected dermatomes did not differ from the contralateral control side. In patients with left L5 radiculopathy (more severely affected) the N2 latency was longer and the amplitudes reduced. CONCLUSIONS: The N2P2 amplitude correlated with pinprick evoked sensations in QST. The N2 latency from the affected dermatome correlates with pain intensity, chronicity, clinical severity and with a decrease of physical function. SIGNIFICANCE: An increase in N2-latency indicates a more pronounced nerve root damage, which is associated with a decrease of function and an increase of severity and pain. LEP amplitudes are associated with the functional status of the nociceptive system and may distinguish between degeneration of neuronal systems and central sensitization processes.

Central habituation and distraction alter C-fibre-mediated laser-evoked potential amplitudes.

BACKGROUND: Recent studies applied laser-evoked potentials (LEP) for the analysis of small nerve fibre function and focused on the detection of stable C-fibre-mediated potentials (C-LEPs); high technical requirements were needed. The diagnostic significance is still controversially discussed. So far, only few studies focused on the susceptibility of C-LEPs to distraction and other influences. We hypothesized that C-LEPs are altered by habituation processes and distraction. METHODS: Twelve subjects were tested with a C-fibre laser set-up (neodymium:yttrium-aluminium-perovskite laser with a 10-mm beam diameter and 10-ms stimulus time) at the left perioral area. In condition I, the subjects received repetitive painful laser stimuli at the right hand to induce habituation. In condition II, the subjects had to fulfil an auditory discrimination task (where the subjects had to estimate the pitch of different tones on a scale for 20 min). C-LEPs were retrieved before and after the habituation or distraction paradigm. C-LEPs were also measured in a control group who was not influenced by laser stimuli or other disturbances during a 23-min break between the two test sessions. RESULTS: In both test conditions, there was significant C-LEP amplitude reduction. The LEP amplitudes of the control group remained unchanged. CONCLUSIONS: In the approach of detecting C-fibre-mediated potentials with LEP, future studies should take the high susceptibility to distraction and habituation into account.

Novel mutations in the RAD3 and SSL1 genes perturb genome stability by stimulating recombination between short repeats in Saccharomyces cerevisiae.

Maintaining genome stability requires that recombination between repetitive sequences be avoided. Because short, repetitive sequences are the most abundant, recombination between sequences that are below a certain length are selectively restricted. Novel alleles of the RAD3 and SSL1 genes, which code for components of a basal transcription and UV-damage-repair complex in Saccharomyces cerevisiae, have been found to stimulate recombination between short, repeated sequences. In double mutants, these effects are suppressed, indicating that the RAD3 and SSL1 gene products work together in influencing genome stability. Genetic analysis indicates that this function is independent of UV-damage repair and mutation avoidance, supporting the notion that RAD3 and SSL1 together play a novel role in the maintenance of genome integrity.

Summary of track D: social science: research, policy and action.

SCOPE: This review summarizes the main issues discussed during Track D, which examined the societal impact of HIV/AIDS, and responses to the epidemic by individuals, families, communities and societies worldwide. Micro- and macrolevel issues addressed included the development, implementation and evaluation of programmes for prevention and care; policy development and implementation; structural issues such as the impact of gender relations, development and migration on the development of the epidemic; and the social and economic impact of HIV/AIDS on affected societies and communities. RECURRENT THEMES: Presentations provided strong evidence that peer-led, community-based programmes offer particularly effective ways of working, and that participatory research involving affected communities provides useful results for the design and evaluation of programmes and policies. This is the case across settings, issues, populations and countries. FUTURE DIRECTIONS: Emerging needs include how best to ensure sustainability of national and international responses, how best to scale up successful interventions for wider reach, and how best to work with systematically marginalized, neglected groups and populations. Research priorities include the characterization of the multiple determinants of HIV-related vulnerability, and the evaluation of interventions that take these complex determinants as their starting point. A more coherent and strategic response requires less separation between the different constituencies involved in AIDS work, and the more sustained involvement of people living with HIV/AIDS themselves.

Soluble serum E-cadherin as a marker of tumour progression in colorectal cancer patients.

A pilot study was conducted to determine the concentrations of soluble serum E-cadherin in 36 patients with colorectal cancer or a high-grade dysplasia by the use of an ELISA technique. The results were compared with staging characteristics and concentrations of routine serum carcinoembryonic antigen (CEA). Sixteen patients with benign diseases and nine healthy volunteers served as internal or negative controls. Tumour specimens from seven patients were analysed by immunohistochemistry to compare concentrations of soluble serum E-cadherin with patterns of cell-bound E-cadherin or beta-catenin. Serum E-cadherin concentrations were increased in colorectal cancer patients (P = 0.009), but also in benign disease controls (P = 0.005), correlating with the T- (P < 0.05), but not N- or M-stage, and with serum CEA (P = 0.002) in case of existing liver metastases. Compared with other staining patterns, concentrations of soluble serum E-cadherin were higher in case of an exclusive membrane-bound localization of cellular beta-catenin (P = 0.071). The results suggest marker characteristics of soluble serum E-cadherin in colorectal cancer patients, but lacking specificity argues against a routine clinical use.

The product of the nuclear gene PET309 is required for translation of mature mRNA and stability or production of intron-containing RNAs derived from the mitochondrial COX1 locus of Saccharomyces cerevisiae.

Expression of the Saccharomyces cerevisiae mitochondrial COX1 locus, which contains several introns and is co-transcribed with the downstream genes AAP1, OLI2 and ENS2, is controlled by at least 18 nuclear-encoded proteins. The PET309 gene, encoding one of these proteins, was cloned, sequenced and shown to contain an open reading frame of 965 codons. Isonuclear PET309+ and delta pet309::URA3 strains carrying mitochondrial genomes that differ in the number of COX1 introns, were generated. Analysis of RNA species from these strains demonstrated an inverse relationship between the number of introns present in the precursor RNA and the amount of COX1 and AAP1/OLI2/ENS2 RNAs accumulated in a pet309 mutant. Hence, PET309 plays a role either in transcription of intron-containing primary transcripts from the COX1-AAP1-OLI2-ENS2 transcription unit or in stabilization of primary transcripts. PET309 is also required in translation of COX1 mRNA. A mitochondrial bypass suppressor of the pet309 deletion mutation was isolated, and shown to consist of a DNA rearrangement at the COX1 locus, such that the 5' untranslated leader region (UTR) of the COB gene was fused to COX1 at nucleotide -174 of its 5' UTR. This result suggests that Pet309p acts through the COX1 5' UTR to activate initiation of translation of the COX1 coding region.

The Saccharomyces cerevisiae Pet309 protein is embedded in the mitochondrial inner membrane.

The nuclear PET309 gene of Saccharomyces cerevisiae is necessary for expression of the mitochondrial COX1 gene, which encodes subunit I of cytochrome c oxidase. In a pet309 null mutant, there is a defect both in accumulation of COX1 pre-RNA, if it contains introns, and in translation of COX1 RNAs [Manthey, G. M. & McEwen, J. E. (1995) EMBO J. 14, 4031-4043]. To facilitate identification and intracellular localization of the protein Pet309p, that is encoded by the PET309 gene, Pet309p was tagged at the carboxy terminus with an epitope from the human c-myc protein. A monoclonal antibody against the c-myc epitope detected a 98-kDa protein in mitochondria of yeast cells that expressed the PET309-c-myc fusion protein from a high copy number plasmid. This protein was not detectable in cells that did not express the fusion protein, or that expressed it from a single copy centromeric vector. Additional analyses of mitochondrial subfractions demonstrated that the PET309-c-myc fusion protein is localized specifically in the inner mitochondrial membrane. It could not be extracted by alkaline sodium carbonate, yet it was susceptible to proteinase K digestion in mitoplasts (mitochondria with a disrupted outer membrane). These results indicate that Pet309p spans the inner membrane, with domain(s) exposed to the intermembrane space side of the membrane. How Pet309p may function in concert with other gene products necessary for COX1 RNA translation or accumulation, such as Mss51p or Nam1p, respectively, is discussed.

Raf-1 kinase, epidermal growth factor receptors, and mutant Ras proteins in colonic carcinomas.

Epidermal growth factor receptors (EGFR) and ras mutations are known to play a significant role in controlling cell growth and tumor promotion. Both of them transmit mitogenic signals to the nucleus by activation of Raf-1 kinase. In this study, the expression of EGFR and mutant Ras proteins, and, for the first time, the expression, phosphorylation and kinase activity of Raf-1 kinase have been determined in paired samples of colorectal cancer and mucosa. The tumor and mucosa samples did not differ significantly with regard to Raf-1 kinase content and activity. A major difference between tumors and mucosa was found, however, in the phosphorylation of Raf-1. Most of the mucosa samples (13/20), but only 1/20 of the cancer samples, contained hyperphosphorylated Raf-1. EGFR were significantly (p = 0.0025) decreased in the tumors. The decreased phosphorylation of Raf-1 in colonic carcinomas could be the result of activation of Raf-1 phosphatases or inactivation of kinases phosphorylating Raf-1. New forms of treatment based on EGFR overexpression do not seem to be suitable for the majority of colonic cancers.

Exocrine pancreatic function in insulin-dependent diabetes mellitus.

Exocrine pancreatic function was studied in patients with long-standing insulin-dependent diabetes mellitus using the secretin-pancreozymin test (n = 53), and estimation of immunoreactive trypsin (n = 43) and pancreatic isoamylase (n = 43). The secretin-pancreozymin test was abnormal in 23 patients (43%). The abnormalities found were a decreased output of lipase (37%), amylase (36%) or trypsin (26%) and bicarbonate (15%). Serum immunoreactive trypsin was below normal in only 6 (14%) and pancreatic isoamylase in 29 (67%) patients. There was no correlation between impairment of the secretin-pancreozymin test and decreased serum enzyme levels. It is concluded that an impairment of exocrine pancreatic function is frequent in insulin-dependent diabetics but that a decrease in serum enzymes, especially in pancreatic isoamylase, does not reflect an impairment of pancreatic function in these patients.

Expression and activity of mitogen activated protein kinases in human colorectal carcinoma.

BACKGROUND: Mitogen activated protein kinases (MAPKs) play a central role in the regulation of both cell growth and differentiation. They are involved in signal transduction of oncogenes and growth factors. The role of MAPK in colonic carcinoma is unknown. AIMS: To establish whether the expression and activity of p42/44 MAPKs are altered in colorectal tumours as compared with normal mucosa. METHODS: The expression and activity of p42/p44 MAPK were investigated in 22 colorectal carcinomas, four adenomas, and the corresponding normal colorectal mucosa by the use of western blotting, immunoprecipitation, and in vitro kinase assays. RESULTS: After immunoprecipitation with an antibody specific for p42 MAPK, we found significant inactivation of p42 MAPK in colonic carcinomas as well as in adenomas, whereas most sample pairs showed only minor differences in p42 MAPK expression. Investigation of MAPK with an antibody capable of detecting both p42 and p44 MAPK showed a slight but significant decrease in p44 MAPK content in malignant tissues. With this antibody, only minor alterations in MAPK activity and no correlation with p42 MAPK activity were found. CONCLUSIONS: Inactivation of p42 MAPK could be associated with colonic carcinogenesis.