Frailty as an indicator of postoperative complications following surgical excision of non-melanoma skin cancer on the head and neck.

INTRODUCTION: Non-melanoma skin cancer (NMSC) predominantly affects those aged over 90 years, with 85% of lesions arising on the head and neck, where surgical excision remains the treatment of choice. Frailty is a measure of physiologic age and can be used as a predictor of adverse treatment outcomes. The aim of this study was to determine if the Rockwood Frailty Index is predictive of complications following excision of NMSC. METHODS: Data were collected prospectively for patients who underwent an excision of a suspected NMSC from the head or neck across a two-month period. Details of the patient, lesion and procedure were recorded alongside ASA grade and Rockwood's Frailty score. Postoperative complications were recorded four weeks later. RESULTS: There was a total of 125 patients: 74 (60%) male, 51 (40%) female; mean age was 78 (±9.8) years. Of the excised sites, 61% were closed primarily, 26% with a full thickness skin graft (FTSG), 13% with a local flap. Frailty ranged from 1 to 7 (median = 4). ASA ranged from 1 to 4 (median = 3). A total of 21 (17%) patients reported postoperative complications. Within this group, the median frailty and ASA grades were 5 and 3. Both frailty and ASA were positively significantly associated with age (p ≤ 0.001). There was no significant difference between the frailty or ASA grades of patients that experienced complications and those who did not. Patients who had a FTSG were significantly more likely to experience complications (p ≤ 0.05). CONCLUSIONS: Frailty is not predictive of postoperative complications following excision of NMSC on the head and neck. Postoperative complications are significantly more associated with FTSG.

Prognostic indicators and outcomes following surgical management of metastatic cutaneous squamous cell carcinoma of the head and neck.

Metastatic cutaneous SCC carries a poor prognosis with five-year survival of 25%-57%. The aim of this study is to examine the outcomes following surgery with adjuvant therapy for management of metastatic cSCC in a UK-based population. This is a retrospective review of patients with metastatic cSCC of the head and neck who underwent primary surgery at a regional center during a six-year period. Overall and disease specific survival were calculated using Kaplan-Meier and log-rank tests. Results were reported as hazard ratios (HR) with 95% confidence intervals. Forty-five patients met the inclusion criteria. The mean time to discovery of metastases was 9.3 months (range, 0-40 months). Only two patients (4%) had discovery of metastases after two years, with none after 3.3 years. The overall five5-year survival was 31% (95% CI 15%to 48%) with two-year survival at 48% (95% CI 31%to 63%). The median OS survival was 722 days (95% CI 607to 1359). Patients aged >80 years had a decreased OS. This is the largest UK based study documenting the overall and disease specific survival associated with metastatic cutaneous SCC of the head and neck. Our overall survival is comparable to similar studies, but remains poor. Total number of involved nodes, and lymph node ratio were not statistically significant.

Chronic glucokinase activator treatment at clinically translatable exposures gives durable glucose lowering in two animal models of type 2 diabetes.

BACKGROUND AND PURPOSE: Pharmacological activation of glucokinase (GK) lowers blood glucose in animal models and humans, confirming proof of concept for this mechanism. However, recent clinical evidence from chronic studies suggests that the glucose-lowering effects mediated by glucokinase activators (GKAs) are not maintained in patients with type 2 diabetes (T2D). Existing preclinical data with GKAs do not explain this loss of sustained glucose-lowering efficacy in patients. Here, we have assessed the effects of chronic (up to 11 months) treatment with two different GKAs in two models of T2D. EXPERIMENTAL APPROACH: Two validated animal models of T2D, insulin-resistant obese Zucker rats and hyperglycaemic gk(wt/del) mice, were treated with two different GKAs for 1 or 11 months respectively at exposures that translate to clinical exposures in humans. Blood glucose, cholesterol, triglycerides and insulin were measured. GKA pharmacokinetics were also determined. KEY RESULTS: Treatment with either GKA provided sustained lowering of blood glucose for up to 1 month in the Zucker rat and up to 11 months in hyperglycaemic gk(wt/del) mice, with maintained compound exposures. This efficacy was achieved without increases in plasma or hepatic triglycerides, accumulation of hepatic glycogen or impairment of glucose-stimulated insulin secretion. CONCLUSIONS AND IMPLICATIONS: Chronic treatment with two GKAs in two animal models of diabetes provided sustained lowering of blood glucose, in marked contrast to clinical findings. Therefore, either these animal models of T2D are not good predictors of responses in human T2D or we need a better understanding of the consequences of GK activation in humans.

Papillary carcinoma within a thyroglossal duct cyst: significance of a central solid component on ultrasound imaging.

Malignancy within a thyroglossal duct cyst is rare (1.5% of cases), and most diagnoses are made postoperatively as clinically they are difficult to distinguish from benign neoplasms. We present a case in which a preoperative ultrasound scan showed the presence of a central solid component in a thyroglossal duct cyst, which contained papillary thyroid carcinoma.

Evaluation of novel renal biomarkers with a cisplatin model of kidney injury: gender and dosage differences.

A number of novel urinary biomarkers have been identified and partially qualified for use as markers for renal injury in rats. We use two novel multiplex assays to quantify biomarker concentration in multiple urine collections made prior to and following administration of cisplatin, a common nephrotoxicant, to rats. We investigate the correlation of the magnitude of biomarker changes with the severity of histopathological observations and explore the relationship of these to both dose and sex. The novel biomarkers evaluated are urinary albumin, alpha glutathione s-transferase (α-GST), glutathione S-transferase-yb1 (GSTYb1), lipocalin-2, kidney injury molecule-1 (KIM-1), osteopontin, and renal papillary antigen 1 (RPA-1) and plasma cystatin C, alongside the traditional biomarkers of plasma urea, creatinine, and urinary n-acetyl-beta-d-glucosaminidase (NAG), total protein, and glucose. We show for all time points, and for almost all doses, that male rats consistently had either more severely graded or a higher incidence of histologically observed lesions than females; that changes in urinary glucose, total urinary protein, NAG, and the novel urinary biomarkers albumin, osteopontin, and KIM-1 are clearly temporally associated; and that changes are related to the severity of injury. We also found that receiver operating characteristic curve analysis and area under the curve are significantly higher than urea or creatinine for all new biomarkers except aGST, GSTYb1, cystatin c, and total protein in both sexes.

The novel sodium glucose transporter 2 inhibitor dapagliflozin sustains pancreatic function and preserves islet morphology in obese, diabetic rats.

AIMS: To investigate whether glucose lowering with the selective sodium glucose transporter 2 (SGLT2) inhibitor dapagliflozin would prevent or reduce the decline of pancreatic function and disruption of normal islet morphology. METHODS: Female Zucker diabetic fatty (ZDF) rats, 7-8 weeks old, were placed on high-fat diet. Dapagliflozin (1 mg/kg/day, p.o.) was administered for ∼33 days either from initiation of high-fat diet or when rats were moderately hyperglycaemic. Insulin sensitivity and pancreatic function were evaluated using a hyperglycaemic clamp in anaesthetized animals (n = 5-6); ß-cell function was quantified using the disposition index (DI) to account for insulin resistance compensation. Pancreata from a matched subgroup (n = 7-8) were fixed and ß-cell mass and islet morphology investigated using immunohistochemical methods. RESULTS: Dapagliflozin, administered from initiation of high-fat feeding, reduced the development of hyperglycaemia; after 24 days, blood glucose was 8.6 ± 0.5 vs. 13.3 ± 1.3 mmol/l (p < 0.005 vs. vehicle) and glycated haemoglobin 3.6 ± 0.1 vs. 4.8 ± 0.26% (p < 0.003 vs. vehicle). Dapagliflozin improved insulin sensitivity index: 0.08 ± 0.01 vs. 0.02 ± 0.01 in obese controls (p < 0.03). DI was improved to the level of lean control rats (dapagliflozin 0.29 ± 0.04; obese control 0.15 ± 0.01; lean 0.28 ± 0.01). In dapagliflozin-treated rats, ß-cell mass was less variable and significant improvement in islet morphology was observed compared to vehicle-treated rats, although there was no change in mean ß-cell mass with dapagliflozin. Results were similar when dapagliflozin treatment was initiated when animals were already moderately hyperglycaemic. CONCLUSION: Sustained glucose lowering with dapagliflozin in this model of type 2 diabetes prevented the continued decline in functional adaptation of pancreatic ß-cells.

Cellular and histopathological changes in the infrapatellar fat pad in the monoiodoacetate model of osteoarthritis pain.

OBJECTIVE: The infrapatellar fat pad (IPFP) has been identified as a source of anterior knee pain. Fibrosis and marked inflammatory infiltrate in the IPFP of patients with arthritis of the knee and reduction in pain post knee replacement in patients following resection of the IPFP have been observed. We have investigated changes in the IPFP of rats undergoing the monoiodoacetate (MIA) model of degenerative joint disease, a model that exhibits some histopathological similarities to osteoarthritis (OA). METHODS: Rats were injected intra-articularly with MIA and the development of weight bearing asymmetry was followed for 21 days as compared to vehicle-injected animals. In addition, IPFPs were removed from both ipsilateral and contralateral joints. Both inflammatory infiltrate and histopathological changes were analysed. RESULTS: MIA injection caused marked weight bearing asymmetry. Ipsilateral IPFP wet weights were significantly increased on days 1 and 3 in MIA-treated animals. MIA treatment also resulted in significant increases in IPFP total white blood cells and monocytes on days 1, 3, and 7 and neutrophils on days 1 and 3. This was supported by histopathological findings at early time points which progressed to adipocyte necrosis, IPFP fibrosis, patellar cartilage and subchondral bone necrosis with synovial hyperplasia at later timepoints. CONCLUSIONS: The current study clearly demonstrated that marked inflammatory changes in the IPFP occur during the early stage of the MIA model of OA which may contribute to the pain observed at this early stage. The role of the IPFP in later stages of the model needs to be further explored.

The impact of lymphovascular invasion on survival in oral carcinoma.

Data was retrospectively analysed on 72 consecutive patients treated primarily with resection and concomitant neck dissection for intraoral carcinomas. Twenty prognostic variables were assessed by univariate analysis to assess their influence on survival. Seven variables were significant at the 5% level. Survival was negatively influenced by six tumour related factors, increasing T stage (P=0.039), increasing N stage (P=0.004), greater than two nodes histologically positive nodal disease (P=0.017), tumour size > 4 cm (P=0.022), residual disease at the primary site (P=0.012), extracapsular nodal spread (P=0.01) and the one treatment related factor analysed, adjuvant radiotherapy (P=0.039). Subsequent multivariate analysis was performed via the cox stepwise regression method to assess the influence on survival of all factors which achieved significance at the 20% level. There were only two variables which made a significant difference (P<0.05) to the multivariate model. The presence of lymphovascular invasion (P=0.015) and histological evidence of mandibular invasion (P=0.047). Lymphovascular invasion appeared in the final model despite not achieving statistical significance at the 5% level on univariate analysis. A final cox survival model was constructed. The relative risk of death for those with cervical metastases (N2 and above) at diagnosis was 3.74 (P=0.005). The addition of lymphovascular invasion to the cox model revealed an increase in the relative risk of death in the presence of lymphovascular invasion of 2.99 (P=0.015). Patients with nodal negative disease and one single node positive provided the baseline risk as there was no significant difference between these two groups. The presence of histological evidence of lymphovascular invasion in oral carcinoma surgical specimens has a significant impact on survival outcome in oral carcinoma patients.

Reduced expression of the KATP channel subunit, Kir6.2, is associated with decreased expression of neuropeptide Y and agouti-related protein in the hypothalami of Zucker diabetic fatty rats.

The link between obesity and diabetes is not fully understood but there is evidence to suggest that hypothalamic signalling pathways may be involved. The hypothalamic neuropeptides, pro-opiomelanocortin (POMC), neuropeptide Y (NPY) and agouti-related protein (AGRP) are central to the regulation of food intake and have been implicated in glucose homeostasis. Therefore, the expression of these genes was quantified in hypothalami from diabetic Zucker fatty (ZDF) rats and nondiabetic Zucker fatty (ZF) rats at 6, 8, 10 and 14 weeks of age. Although both strains are obese, only ZDF rats develop pancreatic degeneration and diabetes over this time period. In both ZF and ZDF rats, POMC gene expression was decreased in obese versus lean rats at all ages. By contrast, although there was the expected increase in both NPY and AGRP expression in obese 14-week-old ZF rats, the expression of NPY and AGRP was decreased in 6-week-old obese ZDF rats with hyperinsulinaemia and in 14-week-old rats with the additional hyperglycaemia. Therefore, candidate genes involved in glucose, and insulin signalling pathways were examined in obese ZDF rats over this age range. We found that expression of the ATP-sensitive potassium (K(ATP)) channel component, Kir6.2, was decreased in obese ZDF rats and was lower compared to ZF rats in each age group tested. Furthermore, immunofluorescence analysis showed that Kir6.2 protein expression was reduced in the dorsomedial and ventromedial hypothalamic nuclei of 6-week-old prediabetic ZDF rats compared to ZF rats. The Kir6.2 immunofluorescence colocalised with NPY throughout the hypothalamus. The differences in Kir6.2 expression in ZF and ZDF rats mimic those of NPY and AGRP, which could infer that the changes occur in the same neurones. Overall, these data suggest that chronic changes in hypothalamic Kir6.2 expression may be associated with the development of hyperinsulinaemia and hyperglycaemia in ZDF rats.

Current status and future directions for diagnostic markers of drug-induced vascular injury.

Recently, there has been an increased incidence of vascular toxicity in pre-clinical toxicology studies. This is of concern because of the uncertain relevance and extrapolation of this finding to humans. In dogs, profound heart rate (HR) and mean arterial pressure (MAP) changes were considered surrogate markers for drug-induced vascular injury until the early 1990s when endothelin receptor antagonists (ETRA) did not significantly alter HR or MAP but induced identical lesions in the coronary arteries of dogs. Thus significant alterations in HR and MAP were found not to be a prerequisite for this lesion. Clinically, the potential for vascular injury coupled with the lack of an unequivocal non-invasive diagnostic marker is an issue of concern to pharmaceutical companies and the regulatory authorities. Therefore, qualification and validation of biomarkers as diagnostic tools for drug-induced vascular injury would add great value to risk management and expedite the drug development process. This review focuses on the status, progress and future trends in vascular biology aimed at identification and development of diagnostic markers that are specific, sensitive and possess potential utility in both a pre-clinical and clinical setting.

Laparoscopic inguinal hernia repair: lessons learned after 1224 consecutive cases.

BACKGROUND: Despite numerous attempts to improve the techniques used for hernia repair, current published series show that recurrence rates are as high as 5-20%. The complexity of inguinal anatomy, combined with multiple potential areas of weakness, has contributed to the difficulty in preventing recurrences. However, the laparoscopic approach to inguinal herniorrhaphy has allowed clear visualization of all preperitoneal fascial planes and anatomic landmarks, as well as the hernia defect(s) and the peritoneal reflection. In the course of our performance of a series of 1,224 laparoscopic inguinal hernia repairs, we have developed a total extraperitoneal approach that yields excellent results with a low initial recurrence rate. Herein we describe our experience. METHODS: After our initial 300 transabdominal preperitoneal (TAPP) hernia repairs, which resulted in six recurrences, two bowel injuries, one bladder injury, and six cutaneous nerve injuries, the total extraperitoneal approach (TEP) was adopted. RESULTS: The first 300 TEP repairs resulted in one recurrence, two bowel injuries, one bladder injury, and two cutaneous nerve injuries. All major complications occurred in patients who had had previous lower abdominal surgery. In the last 624 TEP herniorrhaphies we implemented some modifications to the technique, especially for patients with previous lower abdominal surgery. In this group we recorded one bladder injury, no cutaneous nerve injuries, and one recurrence. CONCLUSIONS: The total extraperitoneal approach for laparoscopic herniorrhaphy allows for a safe and effective repair with low rates of complication and recurrence. A thorough knowledge of the anatomy of the extraperitoneal space and especially the two- and three-dimensional inguinal anatomy of this space contributed greatly to the evolution of our technique.

Role of genetic resistance in invasive pneumococcal infection: identification and study of susceptibility and resistance in inbred mouse strains.

From a panel of nine inbred mice strains intranasally infected with Streptococcus pneumoniae type 2 strain, BALB/c mice were resistant and CBA/Ca and SJL mice were susceptible to infection. Further investigation revealed that BALB/c mice were able to prevent proliferation of pneumococci in the lungs and blood, whereas CBA/Ca mice showed no bacterial clearance. Rapidly increasing numbers of bacteria in the blood was a feature of CBA/Ca but not BALB/c mice. In the lungs, BALB/c mice recruited significantly more neutrophils than CBA/Ca mice at 12 and 24 h postinfection. Inflammatory lesions in BALB/c mice were visible much earlier than in CBA/Ca mice, and there was a greater cellular infiltration into the lung tissue of BALB/c mice at the earlier time points. Our data suggest that resistance or susceptibility to intranasal pneumococci may have an association with recruitment and/or function of neutrophils.

Glycogenosomes in the aging rat brain: their occurrence in the visual pathways.

The significance of glycogenosomes (glycogen bodies), frequently seen in peripheral neurites of aging rats, is unknown and their occurrence elsewhere in nervous tissue is poorly documented. During the course of another study these bodies were observed by light microscopy in the visual pathways of aging rats where they have not previously been noted, and this report documents their occurrence, localisation and changes in density with age. Using the periodic acid-Schiff stain, small brightly red-staining bodies, digested by diastase and containing beta-glycogen particles, were seen in increasing numbers in the neuropil of the superior colliculi in brain sections from animals of 5 months of age onwards. From 1 year until more than 2 years of age they steadily became more numerous in the outer one third of the superior colliculus, but remained small, rarely exceeding 4 microm. They were also found at later times in small numbers lying singly in the optic tract, the optic chiasm and optic nerves, although rarely in lateral geniculate nuclei. Similar bodies were also found to accumulate with age in the retinal photoreceptor cell layer. Changes in their densities and size with age in both regions have been documented and it is suggested that, while their occurrence in retinal photoreceptor cells may be due to sustained light damage leading to mitochondrial oxidative stress, it is difficult to implicate this mechanism for their occurrence in retino-tectal nerve fibres. The role of physical trauma, suggested for the presence of these bodies in aging peripheral axons, can be excluded and they appear not to be related to polyglucosan bodies.

Characterisation of Candida albicans infections of haematogenous and mucosal origin in mice lacking the interferon gamma receptor protein.

Mice harbouring a null deletion mutation in the IFNgamma receptor gene were used to study the role of IFNgamma responsiveness during experimental systemic candidiasis of mucosal or haematogenous origin. After intravenous (i.v.) or intranasal (i.n.) challenge with Candida albicans the progression of infection and concomitant cellular and antibody anti-C. albicans immune responses were analysed. During the week following i.v. challenge, the rate of C. albicans multiplication in kidneys, liver and spleen was faster in IFNgammaR (-/-) than IFNgammaR (+/+) mice. As a result, IFNgammaR (-/-) mice perished earlier than IFNgammaR (+/+) mice when challenged with equal numbers of live yeast cells. However, the overall susceptibility of the two mouse strains, in terms of survival against different C. albicans challenge doses over a 60-day period, was similar. No differences were found in the cellular anti-C. albicans response generated by i.v. challenge in both mouse strains. In contrast the kinetics and strength of the serum anti-C. albicans antibody responses were markedly different. Significantly stronger, predominantly IgG2a antibody responses accompanied the eventual control of C. albicans infection in IFNgammaR (-/-) mice. Following intranasal challenge, there was no difference in the rate of C. albicans clearance from the lungs of IFNgammaR (-/-) and IFNgammaR (+/+) mice. However, 48 h after challenge, large, conspicuous abscesses appeared in the lungs, liver, kidneys and spleen of IFNgammaR (-/-) mice. These abscesses were characterised by the presence of C. albicans and abundant neutrophilic infiltrates, but very few macrophages. No such abscesses developed in i.n. challenged IFNgammaR (+/+) mice. In both mouse strains, i.n. challenge induced strong systemic anti-C. albicans cellular responses, but relatively low titre systemic antibody responses. Mucosal anti-C. albicans antibody responses were detected in IFNgammaR (+/+), but not IFNgammaR (-/-) mice. Splenic adherent macrophages obtained from IFNgammaR (-/-) mice exhibited a significantly lower candidacidal activity than those of IFNgammaR (+/+) mice, and as expected, were not responsive to IFNgamma. In summary, these data suggest that IFNgamma has a role in limiting C. albicans multiplication during the early stages of infection, as well as in preventing the development of C. albicans-associated abscesses. Activation of macrophages by IFNgamma might be pivotal in mediating this role.

No evidence for association of multiple sclerosis with the complement factors C6 and C7.

Four genome screens in multiple sclerosis have been completed and each has identified evidence for linkage in the pericentromeric region of chromosome 5. This region encodes a number of candidate genes including those for the complement components C6, C7 and C9. We have used a multiplexed oligoligation assay (OLA) to test single nucleotide polymorphisms (SNPs) from the C6 and C7 genes for evidence of association with multiple sclerosis in our sibling pair families. There was no statistically significant difference in the allele frequencies of these polymorphisms in the index cases from our families when compared with locally derived controls. No evidence for transmission distortion was seen with any of the polymorphisms, or with the haplotype built from the three SNPs from the C7 gene. Despite offering themselves as potential candidates these complement genes appear not to confer susceptibility to multiple sclerosis.

A screen of candidates from peaks of linkage: evidence for the involvement of myeloperoxidase in multiple sclerosis.

We tested 11 microsatellite markers for evidence of transmission distortion in 744 trio families with multiple sclerosis. Ten of the markers lie within or near to candidate genes selected on the basis that they map within the regions of potential linkage identified in our previously reported linkage genome screen, while the eleventh is an anonymous marker which had previously shown modest evidence for transmission distortion in our sibling pair families. Only the marker related to the myeloperoxidase (MPO) gene revealed tentative evidence for linkage disequilibrium and further work on this gene is clearly needed in order to resolve the status of this region in conferring susceptibility to multiple sclerosis.

Anti-inflammatory activity of c(ILDV-NH(CH2)5CO), a novel, selective, cyclic peptide inhibitor of VLA-4-mediated cell adhesion.

1. Small, N- to C-terminal cyclized peptides containing the leucyl-aspartyl-valine (LDV) motif from fibronectin connecting segment-1 (CS-1) have been investigated for their effects on the adhesion of human T-lymphoblastic leukaemia cells (MOLT-4) to human plasma fibronectin in vitro mediated by the integrin Very Late Antigen (VLA)-4 (alpha4beta1, CD49d/CD29). 2. Cyclo(-isoleucyl-leucyl-aspartyl-valyl-aminohexanoyl-) (c(ILDV-NH(CH2)5CO)) was approximately 5 fold more potent (IC50 3.6+/-0.44 microM) than the 25-amino acid linear CS-1 peptide. Cyclic peptides containing two more or one less methylene groups had similar potency to c(ILDV-NH(CH2)5CO) while a compound containing three less methylene groups, c(ILDV-NH(CH2)2CO), was inactive at 100 microM. 3. c(ILDV-NH(CH2)5CO) had little effect on cell adhesion mediated by two other integrins, VLA-5 (alpha5,beta1, CD49e/CD29) (K562 cell adhesion to fibronectin) or Leukocyte Function Associated molecule-1 (LFA-1, alphabeta2, CD11a/CD18) (U937 cell adhesion to Chinese hamster ovary cells transfected with intercellular adhesion molecule-1) at concentrations up to 300 microM. 4. c(ILDV-NH(CH2)5CO) inhibited ovalbumin delayed-type hypersensitivity or oxazolone contact hypersensitivity in Balb/c mice when dosed continuously from subcutaneous osmotic mini-pumps (0.1-10 mg kg(-1) day(-1)). Maximum inhibition (approximately 40%) was similar to that caused by the monoclonal antibody PS/2 (7.5 mg kg(-1) i.v.) directed against the alpha4 integrin subunit. 5. c(ILDV-NH(CH2)5CO) also inhibited oxazolone contact hypersensitivity when dosed intravenously 20 h after oxazolone challenge (1-10 mg kg(-1)). Ear swelling was reduced at 3 h and 4 h but not at 1 h and 2 h post-dose (10 mg kg(-1)). 6. Small molecule VLA-4 inhibitors derived from c(ILDV-NH(CH2)5CO) may be useful as anti-inflammatory agents.

Exploring the dense mapping of a region of potential linkage in complex disease: an example in multiple sclerosis.

In 1996 we reported the results of a genome screen in multiple sclerosis, in which potential linkage was identified in a total of twenty regions, including the centromeric region of chromosome 5. In order to investigate the efficiency of typing dense arrays of markers in regions of potential linkage, we have typed an additional nineteen microsatellite markers from this chromosome 5 region (D5S623 - D5S428) in the same sibling pair families. The mean additional information extracted per marker typed declined with increasing map density, while inaccuracies in the mapping and the density of genotyping errors increased. Our empirical results suggest that, in linkage-based experiments, there is a limit to the benefits that are gained from typing additional markers in the same families. Increasing map density up to the 2.5-5 cM level efficiently extracts valuable extra information; however, beyond this level efficiency declines while the confounding effects of mapping and genotyping errors accumulate. We, therefore, recommend that extra markers typed in linkage studies be limited to this level of resolution. Mapping regions beyond this density should only be initiated when searching for linkage disequilibrium.

Evidence that allelic variants of the spinocerebellar ataxia type 2 gene influence susceptibility to multiple sclerosis.

Expanded CAG trinucleotide repeats are known to be responsible for five of the autosomal dominant spinocerebellar ataxias (SCA1, SCA2, SCA3, SCA6, and SCA7). We have typed each of these repeats in 226 multiple sclerosis sibling pair families. No expanded repeats were seen, indicating an absence of SCA phenocopies in clinically defined familial multiple sclerosis. However, transmission disequilibrium testing for these repeats demonstrated significant excess transmission of the 22 repeat length allele of the SCA2 gene (P=4. 4E-06) in multiple sclerosis patients. This observation is consistent with pleiotropic effects of the SCA2 gene, with a non-dynamic mutation/polymorphism contributing epistatically to susceptibility in multiple sclerosis.