Magnetic resonance imaging white matter hyperintensities in clinically normal elderly individuals. Correlations with plasma concentrations of naturally occurring antioxidants

BACKGROUND AND PURPOSE

White matter hyperintensities are a common magnetic resonance imaging (MRI) observation in the elderly. They are believed to represent a subclinical form of ischemic brain damage, but the underlying pathophysiological mechanisms are still incompletely understood. We postulated that oxidative mechanisms may favor the development of these changes and therefore correlated their presence and extent with the plasma concentrations of 10 naturally occurring antioxidants.

METHODS

We studied 355 clinically normal volunteers 45 to 75 years of age who were randomly selected from the official community register. A 1.5-T MRI of the brain and measurements of the plasma concentrations of antioxidants including zeaxanthin, cryptoxanthin, canthaxanthin, lycopene, alpha- and beta-carotene, retinol, gamma- and alpha-tocopherol, as well as ascorbate were performed in all study participants. White matter hyperintensities were graded as punctate, beginning confluent, and confluent abnormalities.

RESULTS

Punctate, beginning confluent, and confluent white matter abnormalities occurred in 101 (28.5%), 44 (12.4%), and 14 (3.9%) individuals, respectively. Study participants with white matter damage were significantly older and had a higher frequency of arterial hypertension and cardiac disease but lower serum concentrations of total cholesterol. The plasma levels of lycopene and alpha-tocopherol were significantly lower in subjects with early confluent and confluent white matter hyperintensities, while individuals with punctate foci had an antioxidant status similar to those with normal MRI scans. Alpha-tocopherol was the only antioxidant that remained significantly and inversely related to the presence of beginning confluent and confluent white matter changes after adjustment for the between-group differences in age, arterial hypertension, cardiac disease, and cholesterol. The adjusted odds ratio for early confluent and confluent white matter abnormalities was 3.70 (95% CI, 1.69 to 8.10) in the lowest compared with the highest quartile of the alpha-tocopherol concentration. The odds ratio increased to 7.11 (95% CI, 1.63 to 22.84) when quintiles of the alpha-tocopherol level were compared.

CONCLUSIONS

These data do not prove a causal relation, but they provide evidence of an association between low plasma concentrations of vitamin E and a higher risk of cerebral white matter disease in elderly normal subjects.

Analysis of the occurrence and nature of repeated DNA in an 850 kb region of Arabidopsis thaliana chromosome 4

The occurrence and nature of repeated DNA sequences has been analysed within an 850 kb YAC contig on Arabidopsis thaliana chromosome 4. Hybridization analysis with seven RFLP markers, six cosmid contigs, 29 YAC end probes and eight YAC clones showed that a least 585 kb of the 850 kb contained only low-copy sequences. One YAC end probe, EG15C8LE, hybridized to multiple genomic fragments and contained a sequence with predicted protein homology to cytochrome P450 monooxygenases. Another one, EG11B7RE, was found to be non-contiguous with the other YAC clones and contained a dispersed repetitive sequence associated with centromeric regions.

Effect of aromatic amino acid substitutions in the 3-position of cyclic beta-casomorphin analogues on mu-opioid agonist/delta-opioid antagonist properties

The beta-casomorphin-5 analog H-Tyr-c[-D-Orn-2-Nal-D-Pro-Gly-] (2-Nal = 2-naphthylalanine) was the first reported cyclic opioid peptide with mixed mu agonist/delta antagonist properties [R. Schmidt et al. (1994) J. Med. Chem. 37, 1136-1144]. The 2-Nal3 residue in this peptide was replaced with benzothienylalanine (Bta) (3), His(Bzl) (4), Tyr(Bzl) (5), 4'-benzoylphenylalanine (Bpa) (6), 4'-benzylphenylalanine (Bzp) (7), thyronine (Thy) (8), thyroxine (Thx) (9), 4'-biphenylalanine (Bip) (10), 4'-biphenylglycine (Bpg) (12) and 3,3-diphenylalanine (Dip) (14), and the in vitro opioid activity profiles of the resulting compounds were determined in mu and delta receptor-representative binding assays and bioassays. Analogues 3, 12 and 14 were full agonists in the mu receptor-representative guinea-pig ileum (GPI) assay and also were agonists in the delta receptor-representative mouse vas deferens (MVD) assay. The agonist effects of the latter compounds in the MVD assay were antagonized by the highly selective delta antagonist H-Tyr-Tic-Phe-Phe-OH (TIPP), indicating that they were triggered by delta receptor activation. The Bzp3- and Bip3- containing peptides 7 and 10 turned out to be mu antagonists against the mu selective agonist H-Tyr-D-Ala-Phe-Phe-NH2 in the GPI assay. The other analogues were weak partial mu agonists which displayed remarkably decreased mu receptor affinity as compared to parent peptide 1. Compounds 4-10 were found to be delta antagonists in the MVD assay. Analogues 4 and 9 exhibited delta antagonist potency similar to that of parent peptide 1, while compounds 5-8 and 10 showed 3-12-fold higher delta antagonist potency against DPDPE and deltorphin I and, in most cases, increased delta receptor affinity. These results indicate that the delta receptor tolerates bulky aromatic side chains in the 3-position of cyclic beta-casomorphin analogs with either delta agonist or delta antagonist properties. However, these compounds displayed drastically reduced mu receptor affinity in nearly all cases.

Apolipoprotein E e4 allele in the normal elderly: neuropsychologic and brain MRI correlates

The presence of the apolipoprotein E e4 allele has been considered to be a risk factor for Alzheimer's disease and vascular dementia. We therefore used demanding neuropsychologic testing and brain MRI to determine if elderly normals with at least one e4 allele demonstrate subclinical changes in cognition and a higher frequency of brain atrophy or silent ischemic brain damage. The study population consisted of 214 randomly selected individuals aged 50 to 75 years without neuropsychiatric or general disease. There were 175 (81.8%) subjects without and 39 (18.2%) with at least one e4 allele. The two groups were comparable for age, length of education, verbal intelligence, mood and major vascular risk factors. Apolipoprotein E e4 carriers performed significantly worse than non-carriers when assessed for learning and memory abilities, while there were no differences in test results of conceptualization, attention, speed of mental processing and visuopractical skills. There were no between-group differences for thromboembolic and lacunar infarcts, white matter hyperintensity grading and the semiautomatically measured white matter hyperintensity area. The extent of sulcal and ventricular widening as well as hippocampal and parahippocampal volumes were also similar between the comparative subsets. We conclude that the apolipoprotein E e4 allele is associated with subtle learning and memory deficits in normal elderly persons and may therefore be suggested a marker for accelerated cognitive aging. In this group of subjects it was not associated with brain parenchymal changes as demonstrated by MRI.

Estrogen replacement therapy in older women: a neuropsychological and brain MRI study

OBJECTIVE

To determine if postmenopausal women receiving estrogen perform better on demanding cognitive tests than women without estrogen replacement and if this beneficial effect on cognition is caused by estrogen-related prevention of silent ischemic brain damage.

DESIGN

Cross-sectional study comparing postmenopausal estrogen users and non-users.

SETTING

Austrian Stroke Prevention Study.

PARTICIPANTS

A total of 70 women currently using estrogen and 140 women who have never used estrogen from a subset of 222 postmenopausal women without neuropsychiatric or general disease undergoing extensive diagnostic work-up in a large-scale stroke prevention study among randomly selected community members.

MEASUREMENTS

Neuropsychological test scores and focal brain abnormalities as well as size of ventricles and cortical sulci as assessed by 1.5 Tesla MRI.

RESULTS

Estrogen users performed better than non-users on almost all neuropsychological tests administered. When ANCOVA was used to correct for slight differences between groups in age, length of education, mean arterial blood pressure and self-reported activation, values of P < .05 were noted on tasks assessing conceptualization, attention, and visuopractical skills. After adjustment for multiple comparisons, the differences in conceptualization and visuopractical skills remained significant. MRI showed a lower rate and extent of white matter hyperintensities and a significantly smaller total white matter hyperintensity area in women treated with estrogen (P = .043). The total white matter hyperintensity area was inversely related to the duration of estrogen replacement therapy(P = .040). However, there was no difference in neuropsychological performance between estrogen users with and without white matter abnormalities, and this was also supported by the lack of an association between cognitive test results and the extent of white matter disease.

CONCLUSIONS

Our study demonstrated an association between estrogen replacement therapy and better cognitive functioning and a lower rate of clinically unsuspected ischemic brain damage in postmenopausal women.

The listerial exotoxins listeriolysin and phosphatidylinositol-specific phospholipase C synergize to elicit endothelial cell phosphoinositide metabolism

Exotoxins such as listeriolysin (LLO) and phosphatidylinositol-specific phospholipase C (PIcA) have been implicated in listerial infection and sepsis. Employing different Listeria strains, mutated in individually known virulence genes, we examined exotoxin-related induction of endothelial cell signaling. Listeria monocytogenes was a potent inductor of phosphatidylinositol (PtdIns) metabolism in HUVEC. This effect was completely absent in a LLO-negative strain. Using a recombinant Listeria innocua strain, engineered to produce high levels of LLO, PtdIns metabolism was restored to approximately 30% of that produced by the parental L. monocytogenes strain. A recombinant L. innocua strain expressing only PIcA did not induce any PtdIns metabolism. Even higher than wild-type levels of PtdIns hydrolysis products were, however, evoked when engineered bacteria secreted both LLO and PIcA. These effects occurred in the absence of bacterial uptake by the endothelial cells. Corresponding results were observed with regard to endothelial diacylglycerol (DAG) generation. The amplification of endothelial cell signaling could be reproduced by engaging purified LLO and PIcA in the absence of bacteria. In these experiments, the unrelated pore-forming agent staphylococcal alpha-toxin, a very weak stimulus for endothelial phosphoinositide metabolism by itself, substituted for LLO to allow marked PtdIns hydrolysis when co-applied with PIcA. We conclude that the listerial exotoxins LLO and PIcA cooperate to provoke potent second messenger synthesis in endothelial cells, in the absence of cell invasion by the bacteria. This is an impressive example of synergism between a pore-forming and an enzymatic bacterial exotoxin in provoking cell signaling and inflammatory events.

Long-term results of patients with clinical stage C prostate cancer treated by phototherapy and early orchiectomy. A retrospective analysis of 169 cases

BACKGROUND

To evaluate the value of radiotherapy and immediate hormonal therapy in the treatment of stage C prostate cancer.

PATIENTS AND METHOD

From 1977 to 1986, 169 patients with clinically stage C prostate cancer underwent irradiation with curative intent following early orchiectomy. Sixty-four patients had a transurethral resection, 22 patients a prostatectomy and 83 patients had only a biopsy. In 38 patients a grade Ia/b tumor was found, in 78 patients a grade IIa/b tumor and in 43 patients a grade IIIa/b tumor using the German grade of malignancy. Treatment fields included the prostate, the seminal vesicles and the locoregional lymphatics. Until 1979 the dose was 60 Gy for the tumor encompassing isodose and from then on 65 Gy with a single dose of 2 Gy.

RESULTS

With a median follow-up of 98 months, the overall survival rate for 8 and 10 years was 51% and 37% and the cause specific survival rate was 84% and 77%, respectively. Thirty-two patients (19%) developed distant metastases. Patients with local tumor control (n = 148) had a significantly better overall survival rate of 45% for 10 years compared to patients with clinical local progression of disease (n = 21) of 22% (p < 0.05). Multivariate analysis showed the grade of malignancy and local control as independent factors for overall survival and cause-specific survival (p < 0.05). Twenty-three patients (14%) had at least one late side effect for the rectum or the bladder, in almost all cases grade I or II. Five patients (3%) showed severe late side effects RTOG grade III (n = 2) or IV (n = 3). One patient had a colostomy, in 2 patients a severe haemorrhagic cystitis was seen.

CONCLUSIONS

Radiotherapy with photons and early orchiectomy for patients with stage C prostate cancer achieves high local control rates and a 30% to 40% 10-year survival rate with a low incidence of late side effects. The value of the radiotherapy of the locoregional lymphatics remains controversial.

[Is drug dependence an occupational risk for physicians?]

Physicians are probably a high-risk group for the development of dependency. In addition to the particular demands associated with the profession of medicine, another cause is to be sought in the specific aspects of a doctor's personality. Occupational stress and an inability to develop adequate compensatory mechanisms can lead to burnout and addiction. Over and beyond treatment, rational prophylaxis is urgently required, and this should not fail to include a critical consideration of the self-image of the medical profession.

The relation of cerebral magnetic resonance signal hyperintensities to Alzheimer's disease

To further elucidate the relation of cerebral magnetic resonance signal hyperintensities to Alzheimer's disease (AD) we performed a case-control comparison between 30 consecutive patients with probable AD (age range 49-76, mean 65 years) and 60 asymptomatic volunteers matched for age, sex, and major cerebrovascular risk factors. We used a 1.5T magnet and determined the extent of morphologic abnormalities both by visual grading and measurement. AD patients showed comparable grades of deep/subcortical white matter hyperintensities (WMH) and a similar extent of the total WMH area as controls (3.3 cm2 +/- 8.8 vs. 2.0 cm2 +/- 4.6). They had significantly more often a "halo' of periventricular hyperintensity (PVH) (p < 0.0005) and an increased mean PVH thickness (3.0 mm +/- 1.9 vs. 1.3 mm +/- 1.2; p < 0.001). This PVH thickness correlated significantly with measures of ventricular enlargement. While univariate logistic regression also suggested a significant association of PVH thickness with a diagnosis of AD this association was lost against atrophy measures in a multivariate analysis. Our results confirm a significantly greater extent of PVH in AD patients than controls even when matched for cerebrovascular risk factors. However, this abnormality was not independently related to the disease but rather appears to be an epiphenomenon of brain atrophy.

Rhesus thymic/liver xenografts in severe combined immunodeficient mice: immunologic reconstitution and intrathymic infection with simian immunodeficiency virus

By serving as host recipients of xenografts from both humans and animals, severe combined immunodeficient (SCID) mice have become valuable to many laboratories interested in examining the pathophysiology of different diseases. To gain insight into the usefulness of the SCID mutation in retrovirus research, rhesus monkey fetal hematolymphoid tissues (liver and thymus) were used to construct a SCID-rhesus chimeric mouse (SCID-rh) and were engrafted in the renal capsule. The size and maturation of the thymic engrafts were monitored grossly, histologically, and immunologically. SCID mice were tolerant to rhesus tissues, and thymic engrafts contained thymocytes at different stages of maturation and differentiation that had morphologic features similar to age-matched rhesus thymus. Mature single positive CD2+, CD4+, and CD8+ T lymphocytes that were phenotypically similar to rhesus T lymphocytes were present at low levels (2% to 5%) in the peripheral blood and at moderately higher levels (7% to 15%) in the spleens of SCID-rh mice obtained between 12 and 15 weeks after thymus/liver engraftment. Within 3 weeks after engraftment, > 85% of the thymocytes in the thymic engrafts were immature double positive CD4+CD8+ T cells. The highest number of positive cells were seen in thymic engrafts obtained at 12 to 18 weeks. During these weeks, > 90% of the cells were double positive (CD2+CD4+, CD2+CD8+, and CD4+CD8+). After infection of the engrafted thymus tissue with simian immonodeficiency virus (SIVmac239), PCR analysis revealed successful viral infection of engrafts at 2 and 4 weeks after infection. No significant histopathologic and flow cytometric changes were observed in the thymic engrafts at 2 and 4 weeks after infection. An unrelated lesion of thymic lymphomas involving the SCID host thymus was seen in 12% of the mice. The data presented herein suggest that the SCID-rh is a valuable model for specific studies related to thymus-retrovirus interaction and that it could be used for further studies. The results are discussed in relation to current knowledge of thymus involvement during simian and human immunodeficiency virus infection.

[Physicians as patients--on the problem of the mentally ill physician]

The phenomenon of mentally ill physicians is hardly noticed in Germany today-a fact that possibly indicates a taboo. This investigation is to reveal the importance of the subject by referring to the findings of several major studies. Epidemiological data turn out to be of little reliability regarding for instance the number of impaired physicians with a range between 0.5-46%. Addiction and substance abuse can be found in 90% of all cases of mental illness. Increased suicide (3-4x), divorce (20x) and addiction rates (according to some authors 30-100x) in comparison with the average population emphasise the necessity of further investigation. These facts imply the question whether doctors are mentally more vulnerable than their patients. Special difficulties in treating doctor-patients deserve attention as only little is known how appropriate "iatrotropic" (psycho-)therapy can be carried out effectively.

Identification and distribution of seven classes of middle-repetitive DNA in the Arabidopsis thaliana genome

In order to analyse further the genomic distribution of repetitive sequences in the Arabidopsis genome, we have identified and characterized seven novel repetitive sequences. Analysis of genomic representation, genomic location and DNA sequence divided the seven repeated sequences into two classes. The first was represented by three cosmid subclones (182A, 74A, 191A) carrying sequences that hybridised to up to 20 genomic fragments and showed sequence homology to the genes, Arabidopsis CCR2, Arabidopsis MYB and to various ATP-binding transport proteins. These multigene families mapped to various positions within the genome, as judged by hybridization to YAC clones constituting the Arabidopsis physical map. The second class was represented by four cosmid subclones (106B, 164A, 163A, 278A) that hybridised to between 20 and 300 genomic fragments. One of these, 106B, is a diverged, partial copy of the LTR of the Arabidopsis retrotransposon Athila. The other three sequences showed no homology to known genes or proteins. The distribution of these sequences on chromosome 4 was analysed and sequences hybridizing to 106B, 164A and 163A were found exclusively at the centromeric region of this chromosome. Their detailed arrangement at the centromeric region of chromosome 4, relative to other repeated sequence families and single copy sequences, was determined.

The aging glomerulus

Glomerular filtration rate (GFR) decreases with advancing age, particularly in men, although the rate of decrease in GFR is highly variable. Renal vasoconstriction contributes to the decrease in GFR because of increased renal nerve activity, angiotensin II, endothelin, and decreases in vasodilatory prostacyclin levels. Intrarenal nitric oxide activity may be enhanced during aging, perhaps as part of a compensatory response. The atrial natriuretic peptide system is altered during aging, but there is probably no net change in intrarenal hemodynamic actions. Glomerular damage also contributes to age-dependent decreases in GFR. The primary mechanisms are unknown, but they involve a buildup of mesangial extracellular matrix materials. Increases in vasoconstrictor, growth promoting factors, and/or decreases in vasodilator, growth inhibiting factors may contribute. Androgens provide a risk factor. Glomerular hypertension and/or hypertrophy are not primary factors in the development of age-dependent glomerulopathy, but will worsen the process when present.

Pattern of cerebral blood flow and cognition in patients undergoing chronic haemodialysis treatment

We studied 20 patients aged 46-69 years (mean 57 years) undergoing long-term haemodialysis (HD) and 20 age- and sex-matched controls with single photon emission tomography (SPET) and 99Tcm-hexamethyl-propyleneamine-oxime to look for regional abnormalities in cerebral blood flow (CBF) and their relation to cognitive dysfunction. Global hemispheric tracer uptake relative to the cerebellum was similar in both groups, but regional over cerebellar activity was significantly reduced in the frontal cortex (85.9 +/- 5.1 vs 90.4 +/- 5.3; P = 0.01) and thalamus (99.2 +/- 8.8 vs 104.9 +/- 8.4; P = 0.05) of the HD patients. Normalization to whole-brain activity also showed the frontal cortex to be hypoactive in the HD patients, while tracer uptake was increased occipitally. These regional differences were not explained by the presence of atrophy or cerebrovascular damage seen on brain magnetic resonance imaging. The HD patients scored significantly worse on cognitive tests such as the Mini Mental State Examination (23 +/- 4 vs 28 +/- 1; P < 0.001) and Mattis Dementia Rating Scale (114 +/- 24 vs 143 +/- 1; P < 0.001). Regional activity ratios did not correlate with cognitive test scores, however. Our results indicate a disturbed pattern of CBF in HD patients, although regional SPET abnormalities did not correspond to the severity of cognitive dysfunction.

[The "buried bumper" syndrome--a rare complication of percutaneous endoscopic gastrostomy]

Since initially being described in 1980, percutaneous endoscopic gastrostomy (PEG) has had a dramatic impact on enteral access and alimentation techniques. Knowledge of the problems makes it possible to lower the complication rate of this method. We report a case of partial penetration of the gastric wall by the internal bolster of the tube. We focus on the prevention, recognition, and management of this PEG-related problem.

Distinct conformational preferences of three cyclic beta-casomorphin-5 analogs determined using NMR spectroscopy and theoretical analysis

The conformational properties of three cyclic beta-casomorphin analogs based on the general formula H-Tyr-c[-D-Orn-2-Nal-D-Pro-Xaa-] (2-Nal = 2-naphthylalanine; Xaa = D-Ala, Sar or NMe-Ala) in DMSO solution were investigated using NMR spectroscopy in conjunction with molecular modeling techniques. The D-Ala5- and Sar5-analogs (compounds 1 and 2 respectively) are potent mixed mu-agonist/delta-antagonists with high mu- and delta-opioid receptor affinities, whereas the NMe-Ala5-analog (compound 3) is a potent mu-agonist and a weak partial delta-agonist. Distinct conformational differences emerged for the three compounds studied. Flexibility in the bare ring structures was found to increase in the order 3 < 2 < 1. The increased structural rigidity of 3 may be responsible for its low delta-receptor affinity as compared to the two other analogs. A low fractional population of conformers containing two cis peptide bonds was found for compound 2 but not for analog 1 or 3. Initial evidence for this observation was obtained from NMR differential line-broadening experiments and later confirmed by molecular mechanics simulations. Comparison of the temperature dependence of amide proton chemical shifts acquired for the three cyclic analogs indicate a large degree of intramolecular hydrogen bonding for 1 but not for the other two peptides.

The cytoskeletal linking proteins, moesin and radixin, are upregulated by platelet-derived growth factor, but not basic fibroblast growth factor in experimental mesangial proliferative glomerulonephritis

The expression of the two cytoskeletal linking proteins, moesin and radixin, was examined in experimental mesangial proliferative nephritis in rats (anti-Thy1 model). Moesin and radixin mRNA and protein are constitutively expressed in all cell types of normal rat glomeruli, except podocytes. In the anti-Thy1 model the expression of moesin and radixin was increased in infiltrating macrophages and in activated, alpha-smooth muscle actin-positive mesangial cells and was concentrated in the cellular extensions of mesangial cells in areas of glomerular remodelling. Studies using neutralizing antibodies demonstrated that the increase in moesin and radixin expression by mesangial cells is mediated by PDGF, but not bFGF. The increase in these cytoskeletal proteins appears to be regulated primarily (radixin) or partially (moesin) posttranscriptionally. The data suggest that PDGF mediated upregulation of the cytoskeletal proteins, moesin and radixin, is important for cell migration and other changes that accompany the coordinated restoration of glomerular architecture after injury.

[Drug dependence among physicians]

Physicians are at higher risk of addiction compared with the general population. Worldwide about 15% of physicians may be addicted to drugs or alcohol. In Germany, accurate epidemiological data are not available. The underlying issues of this occupational risk are the dangers of "role strain", features of a "typical" personality and a high rate of burnout among physicians. Most important is therefore prevention, the need to persuade physicians to "cherish themselves" and reduce work stress as far as possible. An US-program is described regarding identification and therapy of drug users among physicians.

Adhesion receptors in malignant transformation and dissemination of gastrointestinal tumors

Changes in the expression and function of adhesion molecules on the surface of cancer cells are important characteristics in the development of gastrointestinal malignancies and might be used in the future as prognostic factors or as new targets for diagnostic and therapeutic approaches. In esophageal cancer a down-regulation of the E-cadherin receptor and the cytoplasmic protein alpha-catenin is associated with tumor dedifferentiation, infiltrative growth and lymph-node metastasis. In gastric cancer a reduction of E-cadherin expression due to gene mutations is restricted to diffuse-type tumors while the occurrence of the CD44-standard and the CD44-9v isoform is significantly related to a higher tumor-induced mortality and a shorter survival time. The CD44-6v isoform is predominantly expressed by intestinal-type gastric carcinomas, giving these tumor cells the ability to perform lymph-node metastasis. In pancreatic cancer the expression of integrin adhesion receptors is significantly altered during the malignant transformation while a loss of the E-cadherin receptor can generate dedifferentiation and invasiveness of pancreas carcinoma cells. There is increasing evidence that integrin receptors as well as different isoforms of the CD44 receptor are altered following the malignant transformation of colonic mucosa into adenomas and invasive carcinomas. The expression of the CD44-6v isoform seems to be associated with an adverse prognosis in colorectal cancer due to the development of tumor metastases. A strong correlation has been observed between the expression of the 67-kDa laminin receptor and the degree of differentiation, the invasive phenotype and the metastatic abilities af colorectal cancer cells. Analyzing the expression of the E-cadherin receptor showed that this receptor may serve as an independent prognostic marker in Dukes' stage B colorectal cancer to identify patients with poor prognosis and designate them for intensive adjuvant therapy and clinical observation after curative surgical tumor treatment.

Detailed description of four YAC contigs representing 17 Mb of chromosome 4 of Arabidopsis thaliana ecotype Columbia

The detailed arrangement of 563 YAC clones comprising four contigs covering approximately 17 Mbp of chromosome 4 is presented. YAC clones were positioned relative to each other and to markers by taking into account marker and end fragment hybridization data and the sizes of all YAC clones. This analysis made it possible to estimate physical distances between the majority of chromosome 4 markers. It also identified a relatively large number of YAC clones containing chimaeric inserts. The YAC contig map of the Columbia ecotype presents an important resource for map-based cloning experiments, rapid mapping of DNA sequences and large-scale genomic sequencing programs.

Superficial siderosis of the central nervous system: MRI findings and clinical significance

We reviewed a 7-year series of brain MRI examinations to determine the frequency and clinical significance of superficial siderosis of the central nervous system (SS). SS was defined by widespread bilateral signal loss at the surfaces of the cerebral or cerebellar hemispheres, the brain stem and the spinal cord on T2-weighted images. Clinical data comprised a neurological examination of identified patients and a review of their case notes. Among 8843 consecutive studies we identified 13 (0.15%) patients with MRI evidence of SS. Only 2 had symptoms or signs characteristic of SS, such as cerebellar ataxia, hearing loss, myelopathy and dementia. Haemosiderin deposition was most widespread in both symptomatic individuals. A definite cause for SS was detected in 9 patients (69%). None of them had a full clinical picture of SS. These data indicate SS per se to be much more frequent than may be assumed from the literature. It appears to become symptomatic only with extensive amounts of widespread iron deposition which develop preferentially with cryptic or unidentified causes of bleeding.