SPring-8 in-vacuum undulator beam test at the ESRF

Before the commissioning of SPring-8, the in-vacuum hybrid undulator developed at SPring-8 had been brought to the ESRF for the first beam test in the summer of 1996. The purpose of this test was to investigate the influence of the in-vacuum undulator on the beam and check its vacuum system. However, heating by the resistive wall impedance turned out to be a critical issue for the in-vacuum undulators.

Cardiovascular effects of the alpha2-adrenergic receptor agonist medetomidine in clinically normal cats anesthetized with isoflurane

OBJECTIVE

To assess the cardiovascular effects of the alpha2-adrenergic receptor agonist medetomidine in healthy cats anesthetized with 2% isoflurane.

ANIMALS

11 clinically normal cats.

PROCEDURE

Cats were anesthetized with isoflurane, and catheters were inserted for measurement of aortic, left ventricular, and right atrial pressures. For data collection, end-tidal isoflurane concentration was reduced to 2%, and end-tidal CO2 was maintained at 35 to 40 mm of Hg by use of positive-pressure ventilation. After measurement of baseline data, medetomidine (0.01 mg/kg of body weight, i.m.) was administered and data were collected continuously for 75 minutes. At the end of data collection, incisions were closed and cats were allowed to recover from anesthesia.

RESULTS

Medetomidine significantly increased mean arterial pressure and systemic vascular resistance. The increase in mean arterial pressure was maximal at 17.8 +/- 7 minutes after medetomidine administration. Medetomidine also increased left ventricular peak systolic pressure, left ventricular end diastolic pressure, and right atrial pressure. Medetomidine significantly decreased heart rate and mean aortic flow.

CONCLUSIONS

The low dosage of medetomidine (0.01 mg/kg, i.m.) promoted severe vasoconstriction in isoflurane-anesthetized cats, and resulted in sustained increases in left ventricular preload and afterload.

Long-term experience with pentosanpolysulfate in interstitial cystitis

OBJECTIVES

An oral preparation of pentosanpolysulfate sodium (PPS) was recently approved by the Food and Drug Administration for interstitial cystitis (IC). Previously published articles have documented improvement in symptoms in 28% to 63% of patients, but no long-term studies have been published. No unique characteristics except for Hunner's ulcer have been found in patients experiencing relief from PPS. We report our experience with PPS following patients up to 116 months and analyze baseline parameters in an attempt to characterize long-term responders.

METHODS

Baseline and follow-up data from 97 patients with IC and enrolled in a compassionate use study with PPS at the University of Wisconsin from 1987 to 1995 are analyzed. Previous treatments had failed, and patients had to pay for PPS. Patients continuing treatment with PPS were monitored every 3 months with questionnaires and laboratory tests. In 1996 an update on medication and a questionnaire developed by the National Institutes of Health Interstitial Cystitis Database were sent to patients who had discontinued treatment.

RESULTS

By the end of the study period 11 (11.3%) of the patients were still taking PPS, with 6 (6.2%) doing so continuously for more than 18 months. Three (3%) patients who discontinued PPS were in long-term remission. An additional 15% had remission for a substantial period. Except for a weak correlation between less constant pain (P = 0.0439), no correlations were found between baseline parameters and duration of treatment with PPS.

CONCLUSIONS

On a long-term basis, between 6.2% and 18.7% of patients with IC benefit from PPS. The only baseline factor predicting response to PPS was less constant pain.

Neuroendocrine tumors of the uterus

Neuroendocrine tumors of the uterus are rare. When present, the majority is found in the uterine cervix. Several theories on the histogenesis of these tumors have been proposed including an origin from local neuroendocrine cells or from reserve cells. The latter hypothesis is supported by the fact that not too seldom uterine neuroendocrine tumors contain other histological components including adenocarcinoma and squamous cell carcinoma or even both. A firm diagnosis can usually the rendered when immunostainings and/or electron microscopy are performed, in addition to conventional light microscopy and Grimelius stain. The tumors react positively for a diversity of so-called neuroendocrine markers and several hormonal substances. Ultrastructurally, they contain dense- core neurosecretory granules. Prognosis is usually poor with most patients dying within one year from diagnosis. Survival can only be achieved in patients who present with early disease.

Iodine-123 alpha-methyl tyrosine single-photon emission tomography of cerebral gliomas: standardised evaluation of tumour uptake and extent

Single-photon emission tomography (SPET) with the amino acid analogue l-3-[123I]iodo-alpha-methyl tyrosine (IMT) is helpful in the diagnosis and monitoring of cerebral gliomas. Radiolabelled amino acids seem to reflect tumour infiltration more specifically than conventional methods like magnetic resonance imaging and computed tomography. Automatic tumour delineation based on maximal tumour uptake may cause an overestimation of mean tumour uptake and an underestimation of tumour extension in tumours with circumscribed peaks. The aim of this study was to develop a program for tumour delineation and calculation of mean tumour uptake which takes into account the mean background activity and is thus optimised to the problem of tumour definition in IMT SPET. Using the frequency distribution of pixel intensities of the tomograms a program was developed which automatically detects a reference brain region and draws an isocontour region around the tumour taking into account mean brain radioactivity. Tumour area and tumour/brain ratios were calculated. A three-compartment phantom was simulated to test the program. The program was applied to IMT SPET studies of 20 patients with cerebral gliomas and was compared to the results of manual analysis by three different investigators. Activity ratios and chamber extension of the phantom were correctly calculated by the automatic analysis. A method based on image maxima alone failed to determine chamber extension correctly. Manual region of interest analysis in patient studies resulted in a mean inter-observer standard deviation of 8.7% +/ -6.1% (range 2.7% -25.0%). The mean value of the results of the manual analysis showed a significant correlation to the results of the automatic analysis (r = 0.91, P<0. 0001 for the uptake ratio; r = 0.87, P<0.0001 for the tumour area). We conclude that the algorithm proposed simplifies the calculation of uptake ratios and may be used for observer-independent evaluation of IMT SPET studies. Three-dimensional tumour recognition and transfer to co-registered morphological images based on this program may be useful for the planning of surgical and radiation treatment.

BARE-1 insertion site preferences and evolutionary conservation of RNA and cDNA processing sites

The BARE-1 copia-like retrotransposon constitutes nearly 7% of the barley (Hordeum vulgare L.) genome as a family of more than 2 x 10(4) mostly full-length copies dispersed on all chromosomes. BARE-1 elements are transcribed in barley tissues from promoters within the LTR (long terminal repeat). The predicted, translated polyprotein contains conserved domains for GAG, aspartic proteinase, integrase, reverse-transcriptase, and RNase H. Here, we have used inverse PCR with LTR-based primers to establish the consensus sequences for the terminal region of the LTR, the external dinucleotides of the cDNA integration intermediate, and the minus- and plus-strand priming sites. These key functional entities are well-conserved in the BARE-1 family, including wheat Wis2, but differ from those of other plant retrotransposons. The target site duplication was established as 5 bp. Of the 13 integration sites identified here, 8 were other BARE-1 elements and 1 another retrotransposon; 59% of the total 17 identified BARE-1 insertion sites are retrotransposons. This nested insertion pattern may represent a basic feature of plant retrotransposons.

O-15-Butanol-PET-Aktivierungsstudie zur zerebralen Repräsentation deklarativer Gedächtnisvorgänge

Ziel: Untersuchungen zur zerebralen Repräsentation deklarativer Gedächtnisvorgänge mit der Positronen-Emissions-Tomographie an gesunden rechtshändigen Normalprobanden. Methoden: Bei sechs Probanden erfolgten sechs 0-15-Butanol-PET-Untersuchungen (jeweils 1500 MBq) mit einer GE 4096+ PET-Kamera. Die Gedächtnisaufgabe bestand darin, zwölf Wortpaare hoch bildhaften Gehaltes zu lernen (auditorische Präsentation über Kopfhörer). Bei der nachfolgenden Abfrage wurden randomisiert jeweils die ersten Worte präsentiert und die Probanden hatten dann die dazugehörenden Worte zu assoziieren. Als Referenzbedingungen wurden Nichtworte dargeboten. Die Datenanalyse erfolgte mit »Statistischem Parametrischem Mapping« (SPM 96) unter MatLab (Version 4.2). Ergebnisse: Die Gedächtnisleistung (Anteil der richtigen Assoziationen) der Probanden war hoch. Während des Lernvorganges wurden Aktivierungen - in Form von Anstiegen des rCBF - im anterioren Gyrus cinguli, sowie im linken und rechten präfrontalen Kortex beobachtet. Während der Abfrage zeigten sich Aktivierungen im linken und rechten Precuneus, im linken präfrontalen Kortex sowie im anterioren Gyrus cinguli. Schlußfolgerung: Die Untersuchung deklarativer Lern- und Gedächtnisvorgänge mittels 0-15-Butanol-PET weist auf die Beteiligung eines distribuierten Netzes von Hirnregionen hin. Darüber hinaus zeigt sich im Vergleich von Lernen und Abfrage eine unterschiedliche Involvierung der präfrontalen Gehirnregionen und eine wichtige Rolle des Precuneus bei der Erinnerung von Gedächtnisinhalten.

Macular-threatening traction detachment of the retina in diabetic proliferative retinopathy, treated by laser

PURPOSE

To treat patients with traction detachment of the central retina by laser in order to avoid vitrectomy.

METHODS

Focal treatment of and around the flat detached retinal area with the argon laser.

RESULTS

Seven patients were treated for macular-threatening traction detachment of the retina. The non-rhegmatogenous traction detachment was flat and circumscribed. Panretinal photocoagulation (PRP) with the argon laser was performed prior to treatment of the traction in three of the cases, in four it was carried out in addition to PRP. In each of the seven patients partial or complete reattachment and stabilization for many years was achieved, rendering vitrectomy unnecessary (mean follow-up after therapy: 40.1 months). In no case was a laser-induced hole produced, and in no patient did the visual acuity decrease.

CONCLUSION

The favourable results following photocoagulation can be explained by the tight retinal/choroidal scar formation (laserpexy). Laserpexy is only recommended for eyes with slight initial detachment.

Spontaneous autoimmune diabetes in monoclonal T cell nonobese diabetic mice

It has been established that insulin-dependent diabetes mellitus (IDDM) in nonobese diabetic (NOD) mice results from a CD4+ and CD8+ T cell-dependent autoimmune process directed against the pancreatic beta cells. The precise roles that beta cell-reactive CD8+ and CD4+ T cells play in the disease process, however, remain ill defined. Here we have investigated whether naive beta cell-specific CD8+ and CD4+ T cells can spontaneously accumulate in pancreatic islets, differentiate into effector cells, and destroy beta cells in the absence of other T cell specificities. This was done by introducing Kd- or I-Ag7-restricted beta cell-specific T cell receptor (TCR) transgenes that are highly diabetogenic in NOD mice (8.3- and 4.1-TCR, respectively), into recombination-activating gene (RAG)-2-deficient NOD mice, which cannot rearrange endogenous TCR genes and thus bear monoclonal TCR repertoires. We show that while RAG-2(-/-) 4.1-NOD mice, which only bear beta cell-specific CD4+ T cells, develop diabetes as early and as frequently as RAG-2+ 4.1-NOD mice, RAG-2(-/-) 8.3-NOD mice, which only bear beta cell-specific CD8+ T cells, develop diabetes less frequently and significantly later than RAG-2(+) 8.3-NOD mice. The monoclonal CD8+ T cells of RAG-2(-/-) 8.3-NOD mice mature properly, proliferate vigorously in response to antigenic stimulation in vitro, and can differentiate into beta cell-cytotoxic T cells in vivo, but do not efficiently accumulate in islets in the absence of a CD4+ T cell-derived signal, which can be provided by splenic CD4+ T cells from nontransgenic NOD mice. These results demonstrate that naive beta cell- specific CD8+ and CD4+ T cells can trigger diabetes in the absence of other T or B cell specificities, but suggest that efficient recruitment of naive diabetogenic beta cell-reactive CD8+ T cells to islets requires the assistance of beta cell-reactive CD4+ T cells.

Cerivastatin: pharmacology of a novel synthetic and highly active HMG-CoA reductase inhibitor

The pyridine derivative cerivastatin is a new entirely synthetic and enantiomerically pure inhibitor of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase. As a sodium salt cerivastatin is present in the active, open ring form. Cerivastatin inhibited the membrane-bound (non-solubilized) HMG-CoA reductase of the native microsomal fraction isolated from rat liver with a Ki value of 1.3 x 10(-9) M. The reference compound lovastatin was 100-fold less potent and exhibited a Ki value of 150 x 10(-9) M. Cerivastatin inhibited the cholesterol synthesis in the human hepatoma cell line HepG2 cells with a similar IC50 value of 1.0 x 10(-9) M. In vivo studies reflected its high in vitro activity. In both rats and dogs, cerivastatin inhibited the hepatic [14C]cholesterol synthesis from [14C]acetate with an oral ED50 value of 0.002 mg/kg body weight, while lovastatin exhibited an oral ED50 value of 0.3 mg/kg in rats, showing again the ratio of 100 or more between cerivastatin and lovastatin. In the small intestine and testes, cerivastatin was at least 50-fold less active with oral ED50 values higher than 0.1 mg/kg, which is indicative for a high liver selectivity of cerivastatin. In cholestyramine-primed dogs cerivastatin dose-dependently lowered the serum cholesterol concentrations by up to 59% with 0.1 mg/kg after 20 days. Interestingly, the serum triglycerides were markedly reduced by 53 and 76% with 0.03 and 0.1 mg/kg, respectively. In normal chow fed dogs the low density lipoprotein (LDL) concentrations were reduced by up to 75% after 0.1 mg cerivastatin/kg. The ratio of HDL/LDL increased by 81% compared with a change of only 14% in the placebo treated control group. The antiatherogenic effect of cerivastatin was shown in rabbits fed a diet enriched with 0.2% cholesterol. After 9 weeks on diet 0.1 mg cerivastatin/kg decreased the accumulation of cholesterol ester in the arterial tissue by 73%. In summary, these data as compared to published data on other HMG-CoA reductase inhibitors demonstrate cerivastatin to be the most active compound in this class. Vastatins used in therapy are effective in mg doses, while cerivastatin offers a new low dose therapy in the microg range.

A mechanism for the major histocompatibility complex-linked resistance to autoimmunity

Certain major histocompatibility complex (MHC) class II haplotypes encode elements providing either susceptibility or dominant resistance to the development of spontaneous autoimmune diseases via mechanisms that remain undefined. Here we show that a pancreatic beta cell-reactive, I-Ag7-restricted, transgenic TCR that is highly diabetogenic in nonobese diabetic mice (H-2(g7)) undergoes thymocyte negative selection in diabetes-resistant H-2(g7/b), H-2(g7/k), H-2(g7/q), and H-2(g7/nb1) NOD mice by engaging antidiabetogenic MHC class II molecules on thymic bone marrow-derived cells, independently of endogenous superantigens. Thymocyte deletion is complete in the presence of I-Ab, I-Ak + I-Ek or I-Anb1 + I-Enb1 molecules, partial in the presence of I-Aq or I-Ak molecules alone, and absent in the presence of I-As molecules. Mice that delete the transgenic TCR develop variable degrees of insulitis that correlate with the extent of thymocyte deletion, but are invariably resistant to diabetes development. These results provide an explanation as to how protective MHC class II genes carried on one haplotype can override the genetic susceptibility to an autoimmune disease provided by allelic MHC class II genes carried on a second haplotype.

The Heidelberg classification of renal cell tumours

This paper presents the conclusions of a workshop entitled 'Impact of Molecular Genetics on the Classification of Renal Cell Tumours', which was held in Heidelberg in October 1996. The focus on 'renal cell tumours' excludes any discussion of Wilms' tumour and its variants, or of tumours metastatic to the kidneys. The proposed classification subdivides renal cell tumours into benign and malignant parenchymal neoplasms and, where possible, limits each subcategory to the most commonly documented genetic abnormalities. Benign tumours are subclassified into metanephric adenoma and adenofibroma, papillary renal cell adenoma, and renal oncocytoma. Malignant tumours are subclassified into common or conventional renal cell carcinoma; papillary renal cell carcinoma; chromophobe renal cell carcinoma; collecting duct carcinoma, with medullary carcinoma of the kidney; and renal cell carcinoma, unclassified. This classification is based on current genetic knowledge, correlates with recognizable histological findings, and is applicable to routine diagnostic practice.

Citric acid-induced cough thresholds in normal subjects, patients with bronchial asthma, and smokers

Several challenge procedures have been developed to characterize the cough reflex in patients with airway diseases. This study was performed to compare the interindividual range of cough sensitivity in asthmatic and normal subjects as well as smokers using an identical method. Sixteen normal subjects, 20 patients with mild bronchial asthma, 6 patients with moderate to severe bronchial asthma, 9 current smokers, and 7 occasional smokers were included. In all subjects, methacholine challenges and standardized citric acid challenges were performed. Sensitivity of the cough reflex was expressed as cough threshold, i.e., as concentration at which coughing occurred. Reproducibility was assessed in 23 subjects. Within a concentration range of 0.625-320.0 mg/ml, inhaled citric acid caused cough in all subjects. Geometric mean (range) cough threshold was 13 (2.5-160) in normal subjects, 14 (5-40) in patients with mild, and 32 (20-40) mg/ml in patients with moderate to severe asthma, 40 (20-80) in current smokers, and 119 (80-160) in occasional smokers. Cough thresholds were reproducible within one doubling concentration. In normal subjects and patients with mild bronchial asthma, thresholds were not significantly different from each other but lower than those of the other groups (p<0.05 each). Cough thresholds in smokers and patients with moderate to severe asthma did also not differ significantly and were lower than in occasional smokers (p<0.05). There was no significant correlation between cough threshold, baseline FEV subset1 , and methacholine responsiveness. Our data indicate that (1) subjects with mild asthma showed on average similar cough thresholds as normal subjects, (2) there was a large variation in cough thresholds within groups, (3) the reproducibility of cough thresholds was within one doubling concentration, (4) cough thresholds did not correlate with methacholine responsiveness or baseline airway tone. In view of the prevalence of cough as a symptom of bronchial asthma, it appears that the determination of citric acid-induced cough thresholds does not yield additional diagnostic information in these subjects.

Nonclassical 2,4-diamino-5-aryl-6-ethylpyrimidine antifolates: activity as inhibitors of dihydrofolate reductase from Pneumocystis carinii and Toxoplasma gondii and as antitumor agents

Twelve novel 2,4-diamino-5-(4'-benzylamino)- and 2,4-diamino-5[4'-(N-methylbenzylamino)-3'-nitrophenyl]-6-ethylp yrimidines bearing 4-substituents on the benzylamino or N-methylbenzylamino aryl ring were synthesized and evaluated as nonclassical inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase (DHFR). Compounds were prepared by reaction of 2,4-diamino-5-(4'-chloro-3'-nitrophenyl)- (8) or 2,4-diamino-5-(4'-fluoro-3'-nitrophenyl)-6-ethylpyrimidine (15) with the appropriate 4-substituted (CO2H, CO2Me, SO2NH2, dioxolan-2-yl, CHO, dimethyloxazolin-2-yl) benzylamine or N-methylbenzylamine derivative. Compounds 25-29 were synthesized from 2,4-diamino-5-{4'-[N-(4"-carboxybenzyl)amino]-3'-nitrophenyl}-6- ethylpyrimidine (10) and the corresponding amine (NH3, MeNH2, Me2NH, piperidine, diethyl L-glutamate) via isobutyl mixed anhydride coupling; hydrolysis of the diethyl L-glutamate 29 afforded the L-glutamate analogue 30. The compounds exhibited potent inhibitory activity against T. gondii (IC50 values 0.0018-0.14 microM) and rat liver (IC50 values 0.0029-0.27 microM) DHFR, with a 4-substituent invariably enhancing binding to both enzymes relative to the unsubstituted benzoprim (5) or methylbenzoprim (6). Modest selectivity for T. gondii enzyme was observed with several analogues, whereas all of the compounds were relatively weak inhibitors of P. carinii DHFR and exhibited no selectivity. Selected analogues were evaluated for in vivo antitumor activity against the methotrexate-resistant M5076 murine reticulosarcoma, with 2,4-diamino-5-{4'-[N-[4"-(N"-methylcarbamoyl)benzyl]-N- methylamino]-3'-nitrophenyl}-6-ethylpyrimidine (14) (Ki for rat liver DHFR = 0.00035 +/- 0.00029 nM) combining significant antitumor activity with minimal toxicity.

Whole-body kinetics and dosimetry of L-3--123I-iodo-alpha-methyltyrosine

The synthetic amino acid L-3--123I-iodo-alpha-methyltyrosine (IMT) is currently under clinical evaluation as a single-photon emission tomography (SPET) tracer of amino acid uptake in brain tumours. So far, dosimetric data in respect of IMT are not available. Therefore we investigated the whole-body distribution of IMT in six patients with cerebral gliomas and the radiation doses were estimated. Whole-body scans were acquired at 1.5, 3 and 5 h after i.v. injection of 370-550 MBq IMT. The bladder was voided prior to each scan and the radioactivity excreted in the urine was measured. Based on the MIRD-11 method and the updated MIRDOSE3, the mean absorbed doses for various organs and the effective dose were calculated from geometric means of the anterior and posterior whole-body scans using seven source organs and the residence time. IMT was predominantly excreted by the kidneys (52.8%+/-11.5% at 1.5 h p.i., 63.0%+/-15.7% at 3 h p.i. and 74.6%+/-9.8% at 5 h p.i.). No organ system other than the urinary tract showed significant retention of the tracer. Early whole-body scans revealed slightly increased tracer uptake in the liver and in the bowel. Highest absorbed doses were found for the urinary bladder wall (0.047 mGy/MBq), the kidneys (0.010 mGy/MBq), the lower large intestinal wall (0.011 mGy/MBq) and the upper large intestinal wall (0.008 mGy/MBq). The effective dose according to ICRP 60 was estimated to be 0.0073 mSv/MBq for adults. This leads to an effective dose of 3.65 mSv in a typical brain SPET study using 500 MBq IMT. The MIRDOSE3 scheme yielded similar results. Thus, in spite of the relatively high tracer dose required for optimal brain scanning, radiation exposure in SPET studies with IMT is in the normal range of routine nuclear medicine investigations.

[Current status and analysis of diagnostic and therapeutic guidelines in the area of chronic obstructive respiratory tract diseases in adulthood]

GOAL OF THE INVESTIGATION: It was investigated (1) whether guidelines for the treatment of bronchial asthma and chronic obstructive pulmonary diseases (chronic obstructive bronchitis and lung emphysema) are distributed in Germany, (2) whether they are accepted by general practitioners and physicians for internal medicine without subspecialty, and (3) how much they are used.

METHODS

(1) The mostly read medical journals have been screened. (2) 1200 physicians have been questioned with regard to the main criteria of these guidelines. (3) 600 physicians were asked to write a documentation for two patients each with bronchial asthma and chronic obstructive pulmonary disease. 344 of the questionnaires (28.7%) and 544 of the documentations could be analyzed (22.7%).

RESULTS

Guidelines for the treatment of bronchial asthma are published in all leading journals. Substantially less references were found for the therapy of chronic obstructive bronchitis. The main concepts of training, diagnosis of the disease's severity, and physical therapy are all known by the practitioners. The training plays a sufficient role in only half of the questioned physicians. The self-measurement of the patient is not every where accepted. The treatment according to a stage by stage pharmacological therapy cannot be seen in one third of the questioned physicians.

CONCLUSIONS

Differential diagnosis and therapy are not sufficiently emphasized in the current guidelines. Practitioners should participate in the development of guidelines, to include the aspects of realization.

Prenatal diagnosis of the fetus with cystic fibrosis and meconium ileus

The sonographic finding of hyperechoic or dilated fetal bowel raises suspicion of a number of prenatal disorders including meconium ileus (MI), meconium peritonitis, congenital infection, neoplasm, or chromosomal trisomy. These findings may also represent transient normal variants. The following case report details the evaluation of one pregnancy with abnormal intestinal echogenic findings on serial sonograms (US), to demonstrate inherent diagnostic difficulties in such a case. A diagnostic algorithm is presented to aid in the proper use of US and DNA mutation analysis for cystic fibrosis (CF), so that the cause of an abnormal abdominal US can be established earlier and more accurately than suggested by previous management schemes. Earlier fetal diagnosis may help to anticipate postnatal problems associated with CF/MI, and therefore provide more optimal clinical management of the affected fetus.

Skn-1: evidence for a bipartite recognition helix in DNA binding

Skn-1 is a maternally expressed transcription factor that specifies the fate of certain blastomeres early in the development of Caenorhabditis elegans. This transcription factor contains a basic region, but it binds to DNA as a monomer. Because other transcription factors containing basic regions bind as dimers, this finding implied that Skn represents a new DNA recognition motif. It has been proposed that the basic region helix of Skn is stabilized for binding by tertiary contacts to other parts of the protein. We have tested this proposal by carrying out circular dichroism (CD) and NMR experiments on the Skn domain and five truncated proteins. Our results have shown that the basic region of Skn is unstructured in solution and does not contact other parts of the protein; like other basic region peptides, it folds into a helix only upon binding specifically to DNA. However, there is a stably folded helical module in the Skn domain, and one of the helices in this module terminates immediately before the start of the basic region. This pre-organized helix contains a surface rich in basic amino acids, and we propose that this helix contacts the DNA distal to the basic region proper, providing an extra long helical recognition surface which helps to stabilize monomeric binding. Homology between the Skn domain and several basic-region leucine zipper (bZIP) domains raises the possibility that the affinity and perhaps the specificity of DNA binding by bZIP proteins can be modulated by incorporating a stably folded helical segment that contacts the DNA just below the basic region proper.

Color vision tests for early detection of antiepileptic drug toxicity

A previous suggestion that antiepileptic drugs may induce color vision deficiencies prompted us to examine whether color vision deficiencies may occur at lower drug serum concentrations than those associated with symptoms of neurotoxicity. Eighty patients presenting with epilepsy received monotherapies of valproic acid, phenytoin, or carbamazepine; 18 patients did not receive antiepileptic drug therapy. Color vision was tested by the Farnsworth-Munsell 100-hue test, spectral sensitivity, and the newly developed tritan screening plates. Patients treated with phenytoin or carbamazepine developed blue-yellow color vision deficiencies. In contrast, patients exposed to valproic acid or receiving no drug treatment showed normal color vision. There was a significant correlation (p < 0.0001) between signs of neurotoxicity induced by phenytoin or carbamazepine and blue-yellow color vision deficiencies. In contrast, we found no correlation between these signs of neurotoxicity and the drug serum concentrations (p = 0.0637). Color vision testing in epileptic patients treated with phenytoin or carbamazepine appears to be a sensitive method for early detection and monitoring of clinical neurotoxicity.

Co-stimulatory pathways controlling activation and peripheral tolerance of human CD4+CD28- T cells

Co-stimulation mediated by the CD28 molecule is considered critical in the activation of CD4+ T cells. In patients with rheumatoid arthritis and infrequently in normal individuals, CD4+ T cells lacking CD28 expression are expanded and contain clonogenic populations. To analyze whether these cells are independent of co-stimulatory requirements or whether they use co-stimulatory signals distinct from the CD28 pathway, we have compared CD4+ CD28+ and CD4+ CD28- T cell clones isolated from rheumatoid arthritis patients. Accessory cells supported the induction of CD25 expression as well as of proliferative responses after anti-CD3 cross-linking and prevented the induction of anergy in CD4+ CD28- T cell clones. In contrast to CD4+CD28+ T cells, the presence of accessory cells did not enhance the secretion of interleukin (IL)-2, interferon-gamma, or IL-4. The co-stimulatory signals did not involve CD28/CTLA-4-CD80/CD86 receptor-ligand interactions. The proliferative response of CD4+CD28- T cells could not be blocked by anti-CD2, anti-CD18, and anti-CD58 antibodies, suggesting that these receptor-ligand interactions cannot provide CD28- independent co-stimulation. Our data suggest that CD4+CD28- T cells require co-stimulatory signals for optimal induction of cell growth and CD25 expression as well as for the prevention of anergy. The co-stimulatory receptor-ligand interaction is independent of the CD28 pathway and may be involved in the oligoclonal expansion of the CD4+ CD28- T cell subset in rheumatoid arthritis.