Mouse chromosome 19 and distal rat chromosome 1: a chromosome segment conserved in evolution

Through a combination of radiation hybrid mapping and studies by FISH and zoo-FISH we have made a comparative investigation of the distal portion of rat chromosome 1 (RNO1) and the entire mouse chromosome 19 (MMU19). It was found that homologous segments of RNO1 and MMU19 are similar in banding morphology and in length as determined by several different methods, and that the gene order of the 46 genes studied appears to be conserved across the homologous segments in the two species. High-resolution zoo-FISH techniques showed that MMU19 probes highlight only a continuous segment on RNO1 (1q43-qter), with no detectable signals on other rat chromosomes. We conclude that these data suggest the evolutionary conservation of a chromosomal segment from a common rodent ancestor. This segment now constitutes the entire MMU19 and a large segment distally on RNO1q in the mouse and rat, respectively.

Disappearance of the negative charge in giant DNA with a folding transition

In the present study we measure the electrophoretic mobility of giant T4 DNA (166 kbp) by electrophoretic light scattering for the elongated and folded compact states at different spermidine (trivalent cation) concentrations in 50 mM sodium maleate buffer (pH 6.0). It is found that the electrophoretic mobility of elongated DNA in the absence of the multivalent cation is seven times greater than that of fully folded compact DNA, where, with the increase of the concentration of spermidine, an abrupt transition is generated after a gradual decrease of the mobility. An analysis of the electrophoretic mobility suggests that the folded compact DNA chains almost completely lose their negative charges, by taking into account the difference of friction mechanism between an elongated and folded compact state. From the single chain observation by use of fluorescence microscopy, it is found that a phase-segregated structure is generated at intermediate concentrations of spermidine. The gradual decrease of the electrophoretic mobility in the transition region is, thus, attributed to the formation of the segregated state, exhibiting partial electroneutralization in the folded part. Disappearance of the negative charges in the completely folded compact DNAs is discussed in relation to the mechanism of transition, in terms of a first-order phase transition.

Tas-301, a new synthetic inhibitor of neointimal thickening after balloon injury, inhibits calcium-dependent signal transduction and cytoskeletal reorganization

We previously demonstrated that a recently synthesized drug, TAS-301 [3-bis(4-methoxyphenyl)methylene-2-indolinone], inhibited neointimal thickening after single-balloon injury to the rat common carotid artery by inhibiting both the migration and proliferation processes of vascular smooth muscle cells (VSMCs). The purpose of this current study was to elucidate the possible mechanism of action for its inhibition of the migration process of VSMCs. We also determined the efficacy of TAS-301 on second neointimal formation 14 days after a double-balloon injury to the rat common carotid artery. Neointimal thickening, 14 days after second balloon injury, was reduced by the oral administration of TAS-301 in a dose-dependent manner. In in vitro assays using rat VSMCs, Western blot analysis showed that TAS-301 inhibited platelet-derived growth factor (PDGF)-induced tyrosine phosphorylation of both focal adhesion kinase and paxillin. Tyrosine phosphorylation of these proteins depended on the increment of intracellular calcium concentration ([Ca2+]i). The PDGF-induced elevation of [Ca2+]i and activation of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) were also inhibited by TAS-301. Additionally, TAS-301 at 10 micromol/l reduced the extent of F-actin stress fiber depolymerization observed in response to PDGF. These results indicate that TAS-301 reduced the intimal thickening after denudation to a pre-existing lesion to the same extent as it reduced that after a single-balloon injury to the normal artery. Furthermore, the results of our in vitro experiments suggest that antimigratory mechanisms of TAS-301 that contribute to preventing the intimal thickening might be mediated by drug inhibition of Ca2+ -dependent signal molecules and the following cytoskeletal depolymerization.

Ultra-high-resolution scanning electron microscopic studies on the membrane system of the rat parietal cells after tetragastrin stimulation

The membrane system of the rat parietal cells in the resting state and after stimulation with tetragastrin (gastrin) was examined by ultra-high-resolution scanning electron microscopy after removal of the cytoplasmic matrix by the aldehyde-osmium-DMSO-osmium procedure. The intracellular canaliculus was lined with numerous microvilli. Viewed from the cytoplasmic side, the intracellular canaliculi appeared as an arborized system of cactus-like structures with numerous holes about 100 nm in diameter corresponding to the basal openings of the microvilli. The intracellular canaliculi were more developed after gastrin stimulation than in the resting state. In resting cells, most of the tubulovesicles were isolated, 100-200 nm in diameter, spherical or tubular in shape. After gastrin stimulation, these structures were interconnected by slender tubules of about 30 nm in diameter forming together tubulovesicular network. Stereo SEM views clearly demonstrated that the tubulovesicular network was connected with the intracellular canaliculus by the slender connecting tubulus. The increase in the canalicular membrane area and the depletion of tubulovesicles is explained by the transfer of the tubulovesicular membrane to the intracellular canaliculus. In the resting parietal cell, the microvilli are slender and their interior is packed with microfilaments. After gastrin stimulation, the microvilli are swollen and their interior is edematous. These morphological changes seem to indicate the accumulation of fluid in the microvilli after gastrin stimulation.

Effects of Dmo1 on obesity, dyslipidaemia and hyperglycaemia in the Otsuka Long Evans Tokushima Fatty strain

Whole-genome scans have identified Dmo1 as a major quantitative trait locus (QTL) for obesity and dyslipidaemia in the Otsuka Long Evans Tokushima Fatty (OLETF) rat. We have produced congenic rats for the Dmo1 locus, using marker-assisted speed congenic protocols, enforced by selective removal of other QTL regions (QTL-marker-assisted counterselection), to efficiently transfer chromosomal segments from non-diabetic Fischer 344 (F344) rats into the OLETF background. In the third generation of congenic animals, we observed a substantial therapeutic effect of the Dmo1 locus on lipid metabolism, obesity control and plasma glucose homeostasis. We conclude that single-allele correction of an impaired genetic pathway can generate a substantial therapeutic effect, despite the complex polygenic nature of type II diabetic syndromes.

Heart rate elevation and diabetic retinopathy in patients with type 2 diabetes mellitus and normoalbuminuria

To investigate the role of heart rate (HR) and blood pressure (BP) for diabetic retinopathy, 24-h ambulatory HR and BP were monitored for 162 in patients with type 2 diabetes and normoalbuminuria. The fundus was assessed as no retinopathy, simple diabetic retinopathy (SDR) and proliferative retinopathy (PDR). Comparing the highest with the lowest quartile of diabetic duration, the relative risk for retinopathy was 9.3 and for nocturnal HR, it was 3.6. Comparison among three retinopathy groups (no retinopathy, group 1, n=122; SDR, group 2, n=24; Pre-PDR or PDR, group 3, n=16) showed that 24-h and nocturnal HR were significantly higher in group 3 (80+/-9 and 71+/-9 beats per min) than in group 2 (73+/-8 and 64+/-8) and group 1 (72+/-7 and 60+/-7). In multiple logistic analysis, the odds ratio of diabetic duration and nocturnal HR to the existence of retinopathy was 1.17 (95% CI, 1.10-1.25, P=0.00001) and 1.11 (95% CI, 1.05-1.17, P=0.0002). We concluded that diabetic retinopathy is related to diabetic duration and high heart rate in type 2 diabetes mellitus with normoalbuminuria. Heart rate elevation may be a predictor of advanced retinopathy.

Human T-cell leukemia virus type I tax protein induces the expression of anti-apoptotic gene Bcl-xL in human T-cells through nuclear factor-kappaB and c-AMP responsive element binding protein pathways

Human T-cell leukemia virus type I (HTLV-I) is the etiologic agent of adult T-cell leukemia (ATL), which is an aggressive form of human T-cell malignancy. The viral protein, Tax, immortalizes human T-cells and inhibits various types of apoptosis, and is thought to play crucial roles in the development of ATL. We have recently demonstrated that Tax induces the constitutive expression of the anti-apoptotic protein, Bcl-xL, in a mouse T-cell line. The mouse, however, is not a natural host of HTLV-I, and HTLV-I does not induce this malignancy in mice. We thus examined whether Tax also activates the expression of Bcl-xL in human T-cells. Expression of Tax in a human T-cell line, Jurkat, induced the expression of the Bcl-xL gene, but did not significantly affect the expression of the other apoptosis-related genes, Bcl-2 and Bax. Transient transfection assays showed that Tax stimulated human Bcl-xL promoter activity in Jurkat cells. Deletion of the two potential nuclear factor (NF)-kappaB binding sites in the human Bcl-xL promoter significantly decreased Tax-induced transactivation. In addition to NF-kappaB, Tax activates transcription through the c-AMP responsive element binding protein (CREB). Tax mutants segregating these two pathways showed that both the NF-kappaB and CREB pathways of Tax are required for maximum activation of a human Bcl-xL promoter, nevertheless, NF-kappaB alone was sufficient for that of a mouse Bcl-xL promoter. Northern blot analysis showed that all the human T-cell lines expressing Tax had higher levels of Bcl-xL mRNA than HTLV-I-uninfected ones. Furthermore, the sample from one patient with ATL expressed higher levels of Bcl-xL mRNA compared with levels from uninfected peripheral blood mononuclear cells. Our results suggest that Tax induces the expression of Bc-xL through the NF-kappaB and CREB pathways in HTLV-I-infected human T-cells, and then inhibits apoptosis, and such inhibition is necessary for the infected cells to advance to the leukemia in vivo.

Oxidative stress is reduced by the long-term use of vitamin E-coated dialysis filters

BACKGROUND

Oxidative stress during hemodialysis is thought to promote the progression of vascular complications in hemodialysis patients. The protective role of vitamin E as a lipophilic antioxidant against oxidative stress has been widely investigated. Here we investigated the effects of a vitamin E-coated regenerated cellulose hollow fiber dialyzer (CL-EE) on oxidative stress compared with a polysulfone hollow fiber (CL-PS).

METHODS

For at least three months before beginning the protocol, 10 nondiabetic (NDM) patients (70.0 +/- 7.5 years; 6 males and 4 females) and 8 diabetic (DM) patients (65.0 +/- 7.4 years; 4 males, 4 females) were dialyzed with CL-PS. After that, we treated all of the patients with CL-EE for six months. Malondialdehyde (MDA), advanced glycation end products (AGEs), and 8-hydroxydeoxyguanosine (8-OHdG) were monitored as biomarkers for oxidative stress at the start and then at one, three, and six months into treatment with CL-EE.

RESULTS

Serum MDA, AGE, and 8-OHdG levels increased after the hemodialysis with CL-PS. The increase of the biomarkers was completely prevented by a single use of CL-EE. Long-term hemodialysis with CL-EE for six months significantly reduced the basal levels of the oxidant markers at one month for AGE and at six months for 8-OHdG in both DM and NDM patients. Serum MDA was reduced in only DM patients at three months. The improvement of the oxidative stress with CL-EE was more prominent in the DM patients.

CONCLUSIONS

Long-term treatment with CL-EE efficiently improves the oxidative stress associated with hemodialysis and potentially reduces dialysis complications due to oxidative stress.

Expression of survivin in HTLV-I-infected T-cell lines and primary ATL cells

Human T-cell leukemia virus type I (HTLV-I) is the etiological agent of adult T-cell leukemia (ATL), although the precise mechanisms involved in the transformation process have not yet been defined. Deregulated inhibition of apoptosis may facilitate the insurgence of leukemia. Survivin is an inhibitor of apoptosis and considered to play a role in oncogenesis. We investigated the expression of survivin in HTLV-I-infected T-cell lines and primary ATL cells. Northern blot analysis showed expression of survivin transcript in all 9 HTLV-I-positive T-cell lines. High survivin expression levels were detected in primary cells of patients with acute-type ATL, but no such expression was noted in the cells of chronic-type ATL or normal peripheral blood mononuclear cells. Treatment of an HTLV-I-infected T-cell line, MT-1, with survivin specific antisense oligonucleotide resulted in reduced cell growth. Our results suggest that expression of survivin may play an important role in the development and pathogenesis of ATL.

Translation and rotation of the mandible during habitual mouth opening movement in children with anterior reverse bite in the primary dentition

Translation and rotation of the mandible during habitual mouth opening movements were studied in 13 children with skeletal-based anterior reverse bite (reverse bite group) and in 13 children with normal occlusion (normal occlusion group) whose dental stage was the primary dentition. Movements were recorded by an opto-electronic movement-analyzing system that could measure mandibular movements with six degrees of freedom. Inferior translation of the mandible was analyzed at the left primary central incisor, both of the primary canines, and both of the primary second molars. Anterior translation of the mandible was analyzed at both of the condyles. Rotation of the mandible was measured in the sagittal plane. The results showed that the associations between the translation and rotation of the mandible during habitual mouth opening in the reverse bite group differed from those in the normal occlusion group. The reverse bite group had greater anterior translation of both of the condylar points than did the normal occlusion group. No significant differences were found in the inferior translation or rotation of the mandible between the two groups.

Weekly dosing with the platelet-derived growth factor receptor tyrosine kinase inhibitor SU9518 significantly inhibits arterial stenosis

The platelet-derived growth factor (PDGF) ligands and their receptors have been implicated as critical regulators of the formation of arterial lesions after tissue injury. SU9518 (3[5-(5-bromo-2-oxo-1,2-dihydroindol-3-ylidenemethyl)-2,4-dimethyl-1H-pyrrol-3-yl]propionic acid) is a novel synthetic indolinone that potently and selectively inhibits the cellular PDGF receptor kinase and PDGF receptor-induced cell proliferation. Inhibition of PDGF receptor phosphorylation in cell-based assays occurs within 5 minutes after drug exposure and persists for >6 hours after drug removal. The pharmacokinetics indicate plasma levels that exceeded the effective concentration required to inhibit the PDGF receptor in cells for up to 8 hours or 7 days after a single oral or subcutaneous administration, respectively. In the rat balloon arterial injury-induced stenosis model, once-daily oral or once-weekly subcutaneous administration of SU9518 reduced intimal thickening of the carotid artery (ratio of neointimal to medial area, 1.94+/-0.38 versus 1.03+/-0.29 [P<0.01] 2.21+/-0.32 versus 1.34+/-0.45 [P<0.01], respectively). These studies provide the rationale to evaluate PDGF receptor tyrosine kinase inhibitors, including inhibitors related to the indolinone, SU9518, for the treatment of arterial restenosis.

Advanced gastric cancer with liver metastasis effectively treated by intra-hepatic arterial infusion of 5-FU, MMC and peroral administration of 5-FU: a case report

We have experienced a case of advanced gastric cancer with liver metastasis effectively treated by intra-hepatic arterial infusion of 5-fluorouracil (5-FU), mitomycin C (MMC) and peroral administration of 5-FU. The patient was a 48-year-old male diagnosed as having advanced gastric cancer with multiple liver metastasis in the bilateral lobes of the liver. This patient was treated by intra-hepatic arterial infusion of 5-FU (250 mg/2 days x 8 doses), MMC (20 mg x 1 dose, 6 mg/2 weeks x 6 doses) and peroral administration of 5-FU (200 mg/day). At 14 weeks later, a CT revealed that the metastatic liver tumors had disappeared. However, at 7 months after the therapy, the patient eventually died of liver and brain metastasis. These results suggested that intra-hepatic arterial infusion of 5-FU and MMC was an effective therapy for metastatic tumors in the liver, but we need to perform intra-hepatic arterial infusion using a new prolonged regimen to treat the liver metastasis.

Multiple carcinoids in the stomach with hypergastrinemia and type A gastritis: a case report

We have experienced a case of the stomach with hypergastrinemia and type A gastritis with multiple carcinoids in a 37-year-old woman. An upper gastrointestinal series revealed multiple minute polyps in the upper body of the stomach. All polyps were diagnosed as carcinoid using endoscopic biopsies. She had neither symptom or signs of typical carcinoid disease. The serum gastrin level was as high as 725 pg/ml. Total gastrectomy was performed, and the diagnosis of multiple gastric carcinoids (sm, no) with type A gastritis was histologically confirmed. After the operation, the serum gastrin level returned to normal, and the patient has been doing well and is disease-free to date at 7 years after the operation. This case suggested that multiple gastric carcinoid lesions may be precipitated by chronic atrophic gastritis accompanying hypergastrinemia. In the treatment of multiple gastric carcinoids with type A gastritis, total gastrectomy with lymph node dissection should be standard operative procedure, in order to resect the fundic gland area completely which could be the origin of carcinoids and endocrine cell micronest.

Two cases of cancer in the remnant stomach derived from gastritis cystica polyposa

We have recently encountered two patients with early gastric cancer in the remnant stomach which resulted from gastritis cystica polyposa at the anastomosis site. The remnant stomach, which had been reconstructed with the Billroth II method, contained an elevated sessile lesion at the anastomosis site. One patient was a 73-year-old woman who had undergone gastrectomy for a gastric ulcer at 30 years earlier, cancer type I + IIa of the remnant stomach was diagnosed, and total remnant gastrectomy was performed. The other patient was a 59-year-old man who had undergone gastrectomy for a duodenal ulcer at 31 years earlier, cancer type I + IIa of the remnant stomach was diagnosed, and subtotal remnant gastrectomy was performed. Histological examination in each case showed that moderately differentiated adenocarcinoma had developed from gastritis cystica polyposa. These results suggested that this cancer has a close relationship with gastritis cystica polyposa.

Accumulation of 4-hydroxynonenal-modified proteins in hippocampal CA1 pyramidal neurons precedes delayed neuronal damage in the gerbil brain

It has been proposed that reactive oxygen species and lipid peroxidation have a role in the delayed neuronal death of pyramidal cells in the CA1 region. To explore the in situ localization and serial changes of 4-hydroxy-2-nonenal-modified proteins, which are major products of membrane peroxidation, we used immunohistochemistry of the gerbil hippocampus after transient forebrain ischemia with or without preconditioning ischemia. The normal gerbil hippocampus showed weak immunoreactivity for 4-hydroxy-2-nonenal-modified proteins in the cytoplasm of CA1 pyramidal cells. 4-hydroxy-2-nonenal immunoreactivity showed no marked changes after preconditioning ischemia. In the early period after ischemia and reperfusion, there was a transient increase of nuclear 4-hydroxy-2-nonenal immunoreactivity in CA1 pyramidal neurons. In contrast, cytoplasmic immunoreactivity transiently disappeared during same period and then increased markedly from 8h to seven days. One week after ischemia, 4-hydroxy-2-nonenal immunoreactivity was observed within reactive astrocytes in the CA1 region. Early nuclear accumulation of 4-hydroxy-2-nonenal in CA1 neurons may indicate a possible role in signal transduction between the nucleus and cytoplasm/mitochondria, while delayed accumulation of 4-hydroxy-2-nonenal-modified proteins in the cytoplasm may be related to mitochondrial damage. We conclude that 4-hydroxy-2-nonenal may be a key mediator of the oxidative stress-induced neuronal signaling pathway and may have an important role in modifying delayed neuronal death.

Immunohistochemical study on the expression of cyclin D1 and E in gastric cancer

Cyclin D1 and E have been found to be deregulated and overexpressed in various types of cancers. In order to study the cell cycle regulatory mechanisms in gastric cancer, we have analyzed the protein expression of cyclin D1 and cyclin E in 76 tumor specimens from patients with primary gastric cancer, using immunohistochemistry. Overexpression of cyclin D1 was observed in 38 cases (50.0%). Overexpression of cyclin E was observed in 40 cases (52.6%). There was no significant difference between the expression of cyclin D1 and any clinicopathological factor. Cyclin E overexpression was correlated with a high incidence of lymph node metastasis, a low incidence of T1, and with Stage I. There was no significant difference in survival curves between cyclin D1 (+) and cyclin D1 (-). The survival curves of cyclin E (-) were significantly higher than those of cyclin E (+). These results suggested that in gastric carcinoma, cyclin E overexpression was useful as a prognostic indicator, but cyclin D1 was not.

Single-allele correction of the Dmo1 locus in congenic animals substantially attenuates obesity, dyslipidaemia and diabetes phenotypes of the OLETF rat

1. Whole-genome scans have identified Dmo1 as a major quantitative trait locus for dyslipidaemia and obesity in the Otsuka Long Evans Tokushima Fatty (OLETF) rat. 2. We have produced congenic rats for the Dmo1 locus through successive back-cross breeding with diabetic OLETF rats. Marker-assisted speed congenic protocols were applied to efficiently transfer chromosomal segments from non-diabetic Brown Norway (BN) rats into the OLETF background. 3. In the fourth generation of congenic animals, we observed a substantial therapeutic effect of the Dmo1 locus on lipid metabolism, obesity control and plasma glucose homeostasis. 4. We have concluded that Dmo1 primarily affects lipid homeostasis, obesity control and/or glucose homeostasis at fasting and is secondarily involved in glucose homeostasis after loading. 5. The results of the present study show that single-allele correction of a genetic defect of the Dmo1 locus can generate a substantial therapeutic effect, despite the complex polygenic nature of type II diabetic syndromes.

Haemodynamic responses to the intubating laryngeal mask and timing of removal

We determined (a) the haemodynamic responses to intubating laryngeal mask (ILM) airway insertion/intubation and removal in anaesthetized patients, and (b) whether the timing of ILM removal influences these responses. One-hundred and twenty patients without cardiovascular disease were studied. ILM airway insertion/intubation was 5 min after induction with propofol 2 mg kg(-1) and maintenance of anaesthesia with sevoflurane 2% in oxygen 33% and nitrous oxide. Patients were randomly assigned for removal of the intubating laryngeal mask airway at 1, 3 and 5 min after successful intubation. Systolic and diastolic arterial pressures and heart rate were recorded preinduction (baseline), before ILM airway insertion/intubation, at 1-min intervals after insertion/intubation, and at 1-min intervals for 5 min after ILM removal. ILM insertion was successful at the first attempt in all patients, but 46 patients required more than one intubation attempt. Compared with baseline values, there were no increases in systolic or diastolic arterial pressure, but there was an increase in heart rate 1 min after ILM insertion/intubation (9%, P<0.001) and 1 min after ILM removal (8%, P<0.01). There was a significant increase in systolic and diastolic pressures and heart rate 1 min after ILM insertion/intubation (30%, 31% and 15%; all: P<0.002) compared with before ILM insertion/intubation values and 1 min after ILM removal (9%, 8% and 7%; all P<0.05) compared with 1 min after ILM insertion/intubation values. Removal of the ILM 1 min after successful intubation resulted in higher arterial pressure compared with removal at 3 min (systolic arterial pressure 10% higher for 1 min, P = 0.01) and 5 min (systolic arterial pressure 10-23% higher for 3 min, P<0.01; diastolic arterial pressure 10-20% higher for 4 min, P>0.02), but there were no differences in heart rate between groups. Systolic and diastolic arterial pressures were greater if more than one intubation attempt was required. Early removal or multiple intubation attempts did not exceed baseline haemodynamic values. We conclude that ILM insertion/intubation and removal in anaesthetized patients produces little or no haemodynamic response, even if multiple intubation attempts are required. The timing of removal exerts a small, but clinically unimportant influence on these responses.

Inhibitory effect of TAS-301, a new synthesized constrictive remodeling regulator, on renarrowing after balloon overstretch injury of porcine coronary artery

The purpose of this study was to determine the efficacy and the possible mechanism of action of a recently synthesized drug, TAS-301 [3-bis(4-methoxyphenyl)methylene-2-indolinone], on stenosis after balloon overstretch injury of porcine arteries. We measured the diameter of vessels by angiography and conducted histological analysis. The oral administration of TAS-301 kept dilated the angiographic luminal diameter of injured segment 4 weeks after overstretch injury and reduced calculated stenosis ratio in a dose-dependent manner, significantly reducing it at doses of 30 and 100 mg/kg. Histopathological analysis showed that TAS-301 significantly reduced the adventitial area at doses of 30 and 100 mg/kg with moderate reduction of the neointimal area, resulting in the larger residual lumen. In an in vitro assay, TAS-301 dose dependently inhibited the proliferation of adventitial fibroblasts stimulated by basic fibroblast growth factor or transforming growth factor-beta(1). In addition, the drug reduced adventitial fibroblast-mediated three-dimensional collagen gel contraction. These findings indicate that TAS-301, the first compound developed for targeting the constrictive remodeling, showed a high inhibitory potency on coronary artery stenosis of micropigs after injury, mainly due to inhibition of adventitial fibroblast proliferation and of the contractile ability of myofibroblasts. Our results suggest the strong possibility that TAS-301 may be efficacious for prevention of restenosis after angioplasty and the need to examine the therapeutic usefulness of this drug in clinical trials.

Quantitative trait loci for lipid metabolism in the study of OLETF x (OLETF x Fischer 344) backcross rats

1. The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is a model of type II diabetes with accompanying dyslipidaemia and obesity. 2. To define chromosomal intervals associated with obesity (abdominal fat weight and plasma leptin levels), dyslipidaemia (plasma triglyceride, cholesterol and free fatty acids) and hyperglycaemia (plasma glucose levels), we have performed genome-wide quantitative traits loci (QTL) analyses of 115 male OLETF x (OLETF x Fischer 344) backcross animals at 16 weeks of age. 3. The Diabetes Mellitus OLETF type I (Dmo1) locus on rat chromosome 1 showed statistically significant involvement in elevations of plasma levels of triglycerides (P = 4.87 x 10(-6) at D1Rat90) and total cholesterol (P = 1.16 x 10(-5) at D1Rat306). 4. No other loci produced significant linkage to these observed phenotypes. 5. These analyses have confirmed the importance of Dmo1 in lipid homeostasis at younger ages as well as during overt diabetes, which appears later. Thus, alterations at the Dmo1 locus are a major risk factor for pathogenesis in the strain, a finding that agrees with physiological studies that indicate a role for dyslipidaemia in the type II diabetic syndrome of OLETF rats.