Synthetic oleanane triterpenoid derivative CDDO-Me disrupts cellular bioenergetics to suppress pancreatic ductal adenocarcinoma via targeting SLC1A5.

To investigate the potential antitumor activity of synthetic triterpenoid, methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) in pancreatic ductal adenocarcinoma (PDAC), MTT cytotoxicity assay, and xenograft nude mice assay were performed to evaluate tumor growth in vitro and in vivo. Seahorse XFe96 bioenergetics analyzer was applied to determine aerobic glycolysis and mitochondrial respiration. Western blot and quantitative reverse transcription-polymerase chain reactions are used to detect protein and messenger RNA transcripts of SLC1A5 and metabolic enzymes. We confirmed the strong antitumor activity of CDDO-Me in suppressing PDAC growth. Mechanistically, we demonstrated CDDO-Me induced mitochondrial respiration and aerobic glycolysis dysfunction. We also verified CDDO-Me downregulated glutamine transporter SLC1A5, resulting in excessive reactive oxygen species (ROS) levels that suppressed tumor growth. Moreover, we confirmed that SLC1A5 depletion reduced the ratio of glutathione/oxidized glutathione. We also found CDDO-Me could inhibit N-linked glycosylation of SLC1A5, which promotes protease-mediated degradation. Finally, we confirmed SLC1A5 was significantly overexpressed in PDAC and closely correlated with the poor prognosis of PDAC patients. Our work uncovers CDDO-Me is effective at suppressing PDAC cell growth in vitro and in vivo and illuminates CDDO-Me caused excessive ROS and cellular bioenergetics disruption which contributed to CDDO-Me inhibited PDAC growth. Our data highlights CDDO-Me could be considered a potential compound for PDAC therapy, and SLC1A5 could be a novel biomarker for PDAC patients.

Anaesthesia and hospital links: strengthening healthcare through South-North hospital partnerships.

Health services can respond to the needs of the poorest people in developing countries if those who work in the front line of health care are supported and motivated and if development needs in services and training programmes can be filled. This can be achieved when a Health Link between a southern hospital and/or training school and its northern counterpart is designed to build a disciplined and long-term programme of staff development including the needs of anaesthetic services, which meets the needs identified by the southern partner. Development of anaesthetic practice is best carried out in the context of an institution-wide Health Link where not only the staff and systems involved in anaesthesia but all the essential 'back office' or support services are also supported and developed.

Reductions in cardiovascular risk in association with population screening: a 10-year longitudinal study.

BACKGROUND: This study was carried out in order to examine changes in cardiovascular risk associated with a population-based screening programme. METHOD: Cardiovascular disease (CVD) risk factor data from a representative sample of residents aged between 45 and 55 years who attended screening a total of three times over a 10-year period were chosen for analysis (n=4113). Cohorts were defined as either 'high risk' or 'normal risk' at baseline for risk factors including blood pressure, body mass index (BMI), cholesterol, smoking and alcohol intake. Mean changes were observed for both groups over three screening episodes, and results were stratified by gender. RESULTS: For the high-risk cohorts (after controlling for age and regression to the mean effects), there were significant decreases in all risk factors, except BMI. Conversely, the observed changes in the normal risk cohorts indicated significant increases in risk factors over the 10-year period. After adjusting for age, the pattern in the normal risk cohorts fluctuated and there were some decreases in risk, but they were not as large as the decreases in risk for the high-risk cohorts. CONCLUSIONS: Population screening for CVD is an effective strategy for identifying and reducing risk in high-risk individuals. These results have significant implications for the role of screening in preventing and controlling cardiovascular disease.

Comparative lymphatic, ocular, and metabolic phenotypes of Foxc2 haploinsufficient and aP2-FOXC2 transgenic mice.

FOXC2 mutations cause the lymphatic/ocular disorder Lymphedema-Distichiasis (LD), and Foxc2 haploinsufficient mice mimic this disorder. To determine if FOXC2 overexpression might also cause lymphatic and/or ocular abnormalities, we performed dynamic lymphatic imaging (Evans blue dye), ocular tissue examination, and metabolic profiles in mice: transgenic for FOXC2 with an adipocyte (aP2) promoter (aP2-FOXC2 Tg), heterozygous for targeted disruption of Foxc2 (Foxc2+/-), or compound heterozygous and transgenic (Foxc2+/-, Tg) compared to wild-type controls (WT). Foxc2+/-; aP2-FOXC2 Tg; and Foxc2+/-, Tg, exhibited LD's distinctive hyperplastic lymphatic phenotype characterized by increased number of lymphatic channels and lymph nodes as well as retrograde lymph reflux. Foxc2+/-, and Foxc2+/-, Tg but not aP2-FOXC2 Tg or WT showed an abnormal ocular phenotype. Previously described alterations in brown/ white fat distribution and lean phenotype in aP2-FOXC2 transgenics were confirmed. AP2-FOXC2 Tg immunohistochemistry disclosed aberrant FOXC2 expression in ectopic sites, especially embryonic heart. Lymphatic system links with fat metabolism are discussed.

Mixed multivariate generalized linear models for assessing lower-limb arterial stenoses.

Experiments and observational studies often involve gathering information on several response variables, enabling us to model their dependence on observable predictor variables. Despite associations between the response variables, they are often analysed separately using general and generalized linear models. This paper investigates applications of multivariate regression analysis to improve the accuracy of predictions and decisions, in the specific context of diagnosing arterial stenoses in human legs. Two basic models are developed for this application, using (i) four binary responses and (ii) a mixture of two binary and two normal responses. The results clearly demonstrate the potential advantages offered by this approach.

Role of cytoprotectants and nitric oxide inhibition in nonsteroidal anti-inflammatory drug-induced gastroduodenal injury in the rat.

BACKGROUND AND PURPOSE: Nonsteroidal anti-inflammatory drugs (NSAIDs) induce gastroduodenal injury and ulceration. The pathogenesis is uncertain, although reductions in cytoprotective prostaglandins and nitric oxide (NO) have been proposed. The effects of several cytoprotective agents on inhibition of gastroduodenal ulcerogenesis induced by CI-987, a novel NSAID, were evaluated in Wistar rats. METHODS: Male Wistar rats were given CI-987 orally (p.o.) at a dosage of 300 or 450 mg/kg of body weight or subcutaneously (s.c.) (3 x 50 mg/kg), alone or with misoprostol pretreatment (2 x 1 mg/kg, p.o.). In a second experiment, rats were pre-treated with 2 ml of gelusil p.o., 500 mg of sucralfate/kg, p.o., 100 mg of ranitidine/kg s.c., or 200 mg of N omega-nitro-L-arginine methyl ester (L-NAME)/kg, s.c.. Duodenal injury was induced by administration of 450 mg of CI-987/kg, p.o., 3 x 50 mg of CI-987/kg, s.c., or 300 mg of cysteamine/kg, s.c. Animals were euthanized within 24 to 48 hours, and the gastrointestinal tract was examined for evidence of gross or microscopic change. RESULTS: The L-NAME significantly reduced the incidence and severity of gastroduodenal injury induced by CI-987 and cysteamine. Prostaglandin ameliorated duodenal lesions induced by CI-987 given s.c., and Gelusil, ranitidine, and sucralfate were without effect on duodenal lesions induced by NSAID. CONCLUSIONS: Preemptive blockade of NO synthase is important in preventing NSAID-induced duodenal injury in rats. Inhibition of cytoprotective prostaglandins and enhanced acid-induced damage are unlikely to be primary mechanisms underlying NSAID-induced duodenal injury in rats.

Role of the C-terminal RDEL motif of the myxoma virus M-T4 protein in terms of apoptosis regulation and viral pathogenesis.

The purpose of this study was to investigate the significance of the C-terminal RDEL motif of the myxoma virus M-T4 protein in terms of apoptosis regulation and role in viral virulence. To accomplish this, a recombinant myxoma virus was created in which the C-terminal RDEL motif of M-T4 was deleted and a selectable marker (Ecogpt) was inserted immediately downstream. We hypothesized that removal of the RDEL motif from M-T4 would alter the subcellular localization of the protein and provide insight into its antiapoptotic role. Surprisingly, removal of the RDEL motif from M-T4 did not affect localization of the protein within the endoplasmic reticulum (ER), but it did reduce the stability of the mutant protein. Pulse-chase immunoprecipitation and endoglycosidase H analysis coupled with confocal fluorescent light microscopy demonstrated that the M-T4 RDEL(-) mutant protein is retained in the ER like wildtype M-T4 and suggests that the C-terminal RDEL motif is not the sole determinant for M-T4 localization to the ER. Infection of cultured rabbit lymphocytes with the M-T4 RDEL(-) mutant virus results in an intermediate apoptosis phenotype compared with the wildtype and M-T4 knockout mutant viruses. A novel myxomatosis phenotype was observed in European rabbits when infected with the recombinant M-T4 RDEL(-) mutant virus. Rabbits infected with the M-T4 RDEL(-) virus on day 9 postinfection exhibited an exacerbated edematous and inflammatory response at secondary sites of infections, particularly the ears. Our results indicate that the C-terminal RDEL motif may not be solely responsible for retention of M-T4 to the ER and that M-T4 may have a dual function in protecting infected lymphocytes from apoptosis and in modulating the inflammatory response to virus infection.

Estimation of breast volume and its variation during the menstrual cycle using MRI and stereology.

Unbiased estimates of breast volume may be obtained in vivo from systematic series of MR images acquired in accordance with the Cavalieri method of modern design-based stereology. The method does not require any assumptions to be made regarding breast shape. If point counting techniques are used to obtain the required breast section areas estimates, 10-15 min analysis (i.e. counting about 250 points on 12 to 16 images) ensures that the contribution of sectioning and point counting to the coefficient of error (CE) on the volume estimate is less than 3%. The methods were applied to measure breast volume in 15 healthy females aged between 22 and 44 years (mean 31.7 years; SD 8.2 years). One subject was studied on every fourth day during two consecutive cycles. The other 14 subjects were studied on three occasions corresponding to menses, ovulation and pre-menses during a single menstrual cycle. Repeat imaging after repositioning on three occasions within a period of 30 min and also at three different times of day for a single subject, both yielded a coefficient of variation (CV) of less than 3% in the estimation of breast volume. ANOVA indicates that there is no significant difference between the mean volume of the left and the right breast (p = 0.294). The mean volume of the left breast is 561 ml (95% confidence interval (CI): 553 ml, 569 ml) and the mean volume of the right breast is 567 ml (95% CI: 559 ml, 576 ml). There are highly significant differences between the three named stages of the menstrual cycle (p < 0.0005), whereby the mean volume at ovulation is 5.5% less than the mean volume at menses (95% CI: 3.0%, 7.9%) and the mean volume pre-menses is 8.1% greater than the mean volume at menses (95% CI: 5.3%, 10.9%). Overall, the volume of each breast varies by an average of 76 ml (95% CI: 61 ml, 92 ml) during the menstrual cycle, which corresponds to 13.6% of the volume at menses (95% CI: 13.3%, 13.8%). No significant interaction was found between the relative volumes of the left and right breast and the stage of the menstrual cycle (p = 0.277), nor between subjects and stages of cycle (p = 0.296). However, a significant interaction was observed between the volume of the left and right breasts in different subjects (p < 0.005). The average difference in the volume of the left and right breasts of all 15 subjects is 39.7 ml (95% CI: 21.3 ml, 58.1 ml), which is 7% of average breast volume and approximately 50% of the average variation in the volume of the breast during the menstrual cycle.

Evaluation of three lines of immunodeficient mice for the study of spontaneous metastatic tumors.

Various immunodeficient animals have been used as transplantation recipients for studying the growth of human tumors. We have been assessing the value of immunodeficiencies for the study of naturally arising tumors, using a model system of transgenic mice that spontaneously develop cancer of the pancreas as a result of elastase promoter-driven expression of the large tumor antigen gene of simian virus 40. We previously reported the establishment of transgenic mice that carried the SCID and/or beige mutations, eliminating B- and T-cell function and reducing lytic NK cell activity, respectively. In SCID beige animals, metastasis rates and target organs for metastases were similar to those observed in humans with pancreatic cancer. We describe here analysis of subsequent more highly inbred generations of these mice. The data show that inbreeding has almost negated the value of these immunodeficiencies for enhancing disease progression, and we observe high rates of metastasis even in immunocompetent animals. The data suggest that SCID and beige immunodeficiencies may not always have the same value for the modeling of spontaneous tumors as they do for the study of xenografts.

Experiences and career intentions of general practice registrars from The Netherlands.

For some years prospective general practitioners (GPs) from the Netherlands have come to Britain to complete their training. Not all report enjoying their time here, and many leave this country after training. The aim of this study was to examine reasons for coming to Britain, experiences, perceptions and career intentions. The sample consisted of 14 general practice registrars working in their practice year in Southern England. Data were collected through in-depth semistructured interviews and analysed by thematic qualitative analysis. The main reasons for training in this country were easier access, a quicker route to specialization and the quality of training provided. Most had positive professional and personal experiences and saw the British system of training GPs as up to date and supportive of their educational and professional needs. They highlighted some of the positive aspects of the British system, such as the emphasis on teamwork and collaboration with other primary care professionals. They did, however, point out problems and conflicts; for instance, they saw the health care system in Britain as more bureaucratic and as providing unequal access for different groups of the population. Despite their fear of litigation, which they saw as one of the drawbacks for British general practitioners, most looked favourably on the option of staying in or returning to this country if possible. All registrars valued their stay in Britain; however, personal circumstances often dictated a return to Holland. Our findings have implications for manpower planning and recruitment for general practice in both Britain and Holland.

A comparison of sleep detection by wrist actigraphy, behavioral response, and polysomnography.

Two alternative methods for detecting sleep, wrist actigraphy (ACT) and behavioral response monitoring (BRM), were compared to polysomnography (PSG). In the BRM paradigm, a threshold intensity visual or auditory stimulus generated by a palm-top computer was presented about once per minute, and subjects pressed a microswitch if the stimulus was detected. A response within 5 seconds of the stimulus was scored as "wake" and a failure to respond as "sleep." Four males and four females underwent two nights of simultaneous in-home PSG, BRM, and ACT. Each night, subjects underwent a protocol designed to generate five sleep latency trials. Subjects were awakened by alarm clocks at approximately 1-hour intervals and remained awake for 10 minutes before returning to bed for another sleep onset latency (SOL) trial. Minute-by-minute comparisons were made for PSG versus ACT and BRM. All measures were fairly sensitive in detecting sleep, but BRM was more accurate in determining SOL and subsequent wakefulness. Behavioral response monitoring using a tone resulted in more responses and arousals prior to and during light stages of sleep than BRM using a light. It is concluded that BRM has some important advantages as a simple, minimally invasive method for monitoring sleep.

Pathogenesis of Sendai virus infection in the Syrian hamster.

Young adult male Syrian hamsters were inoculated intranasally with Sendai virus, then killed and examined at postinoculation days (PID) 3, 5, 7, 9, 12, 16, and 21. Evaluation included clinical assessment, histologic examination, immunohistochemistry, viral isolation, and antibody response. Inoculated and control hamsters remained asymptomatic throughout the study. There was a focal to segmental rhinitis involving respiratory tract epithelium lining the dorsal and ventral meatus and nasal septum, and segmental lesions involving all regions of the trachea. At PID 5 and 7, there was focal bronchitis and bronchioloalveolitis, respectively. In general, most lesions had resolved by PID 12, although in hamsters examined at PID 21, residual lesions were present in the nasal passages in one of three, and in the trachea in two of three animals. In immunoperoxidase-stained preparations, viral antigen was present in the respiratory tract epithelium of the nasal passages and trachea beginning at PID 3, with extension to scattered bronchi at PID 5. Sendai virus was recovered from the lungs of inoculated animals at PID 5. Antibodies to Sendai virus were first detected at PID 7, and titers remained high throughout the remainder of the 21-day study. This report provides additional evidence that Syrian hamsters are susceptible to Sendai virus infection, and that the lesions and sites of replication in the upper and lower portions of the respiratory tract are similar to those observed in susceptible strains of laboratory mice.

Hominid thumb strength predicted by high resolution magnetic resonance imaging and force measurements in living subjects.

This study investigates whether in-vivo measurements of the morphology of the pollical distal phalanx (PDP) can be used to predict the maximum force that can be exerted by the thumb in flexion at the interphalangeal joint. A predictive equation was obtained via which measurements of fossil PDP's can be used to predict flexion force in hominids. A home-built insertable coil assembly, which increased the available magnetic field gradient strength from 10 to 40 (mT) m-1, was used to acquire high resolution T1-weighted 3D SPGR Magnetic Resonance (MR) images of the left and right thumbs of nine volunteers. The subjects' age, sex, weight, height and self-assessed hand-dominance were recorded. The MR images were transferred to a computer for reformatting of sections in the transverse and volar plane (VP). Measurements were made of the maximum length (ML), breadth (MB), tuft breadth (MT) and joint depth (JD) of the PDP. For each subject the maximum flexion force that could be exerted by each thumb was measured. The mean maximum flexion force generated was 8.21 kg (range 5.68-13.13 kg). Considerable inter-individual variability was observed in the magnitude of the force difference between the left and right thumbs and this is greatest in individuals with the strongest thumbs. The best model produced by multiple linear regression analysis of all the available data has a value of r = 0.77 and needs only the two covariates of sex and weight, i.e. FORCE = 2.217 + 0.6651 x WEIGHT + 2.488 x SEX. However, in order to be useful for predicting the maximum flexion force of the thumb in hominids the model should only contain those parameters which can be measured for fossil PDP's. Accordingly, the best predictive model has a value of r = 0.73 and needs only the two covariates of ML and JD, i.e. FORCE = -10.28 + 0.2053 x ML + 1.571 x JD. The maximum force predicted for any of the hominid fossil PDP's was not significantly different from those recorded for the volunteers in the present study, although they were on average somewhat lower than those obtained for modern humans. This may be a reflection of the hominid's overall smaller body weights.

Diagnostic evaluation of cats with seizure disorders: 30 cases (1991-1993).

OBJECTIVE: To investigate causes of seizure disorders in cats. DESIGN: Case series. ANIMALS: 30 cats referred to the Ontario Veterinary College for recurrent seizures. PROCEDURES: Signalment and seizure pattern were evaluated. Diagnostic procedures included physical, neurologic, and fundic examinations; CBC; serum biochemical analyses, including determination of pre- and postprandial bile acid concentrations; urinalysis; serologic assays for FeLV and feline immunodeficiency virus, feline infectious peritonitis, and Toxoplasma gondii, magnetic resonance imaging of the brain; CSF analysis; and neuropathologic examination of euthanatized cats and of surgical biopsy specimens. RESULTS: All cats were found to have structural brain diseases; nonsuppurative meningoencephalitis of unknown cause was found in 14 cats, feline ischemic encephalopathy in 6, meningioma in 2, polycythemia vera with secondary brain lesions in 2, posttraumatic epilepsy in 1, and cerebral abscess in 1. A definitive diagnosis could not be reached in 4 cats. CLINICAL IMPLICATIONS: The most common cause of seizures in cats is structural brain disease. Structural brain lesions often can be detected on the basis of seizure pattern and results of neurologic examination. Cerebrospinal fluid analysis and brain imaging are essential to determine the cause of these lesions. Causes of seizures found in the cats of this study differ from those reported to be the most common. Nonsuppurative meningoencephalitis of unknown origin appears to be a frequent cause of neurologic disorders in cats, including seizure disorders. Feline ischemic encephalopathy appears to exist in a milder form than the classic disease and may be a common cause of seizures in cats.

Phenotypic abnormalities in long-term surviving cystic fibrosis mice.

Mouse models for cystic fibrosis (CF) with no CFTR function (Cftr-/-) have the disadvantage that most animals die of intestinal obstruction shortly after weaning. The objective of this research was to extend the lifespan of CF mice and characterize their phenotype. Weanlings were placed on a nutrient liquid diet, and histologic and functional aspects of organs implicated in the disease were subsequently examined. Approximately 90% of Cftr-/- mice survived to 60 d, the majority beyond 100 d. Cftr-/- mice were underweight and had markedly abnormal intestinal histology. The intestinal epithelia did not respond to challenges with agents that raised intracellular cAMP, consistent with the absence of functional CFTR. No lesions or functional abnormalities were evident in the lungs. Liquid-fed Cftr-/- mice were infertile, although some males weaned to a solid diet were fertile before they died. Thus, we have succeeded in using dietary means to prolong the lives of Cftr-/- mice.

Attachment glycoproteins and receptor specificity of rat coronaviruses.

Murine coronavirus (MHV) and rat coronavirus (RCV) are antigenically related viruses that have different natural rodent hosts. Both MHV and RCV can be propagated in the L2(Percy) and CMT-93 mouse cell lines. In these cell lines MHV uses the MHV receptor (MHVR or Bgp1a) and several related murine Bgp glycoproteins in the immunoglobulin superfamily as receptors. To determine whether RCV also uses these murine glycoproteins as receptors, we characterized the envelope glycoproteins of two strains of RCV and compared the effects of anti-MHVR monoclonal antibody on susceptibility of the mouse cells to MHV and RCV. The Parker (RCV-P) and sialodacryoadenitis (RCV-SDAV) strains of RCV expressed the spike glycoprotein S, but only RCV-P expressed a hemagglutinin-esterase glycoprotein that had acetylesterase activity. Therefore RCV-SDAV must bind to cellular receptors by the viral S glycoprotein, whereas RCV-P might bind to cells by its hemagglutinin-esterase glycoprotein as well as by S. Pretreatment of L2(Percy) 41.a or CMT-93 cells with anti-MHVR monoclonal antibody blocked infection with MHV-A59 but did not prevent infection of these murine cells with RCV-P or RCV-SDAV. Baby hamster kidney cells transfected with cDNAs encoding MHVR (Bgp1a) or Bgp2 were susceptible to MHV-A59 but not to RCV-P or RCV-SDAV. Thus the RCV strains cannot use these murine coronavirus receptors and must be infecting murine cells by another, as yet unknown, receptor.

Inactivation of Fac in mice produces inducible chromosomal instability and reduced fertility reminiscent of Fanconi anaemia.

Fanconi anaemia (FA) is an autosomal recessive disease characterized by bone marrow failure, variable congenital malformations and predisposition to malignancies. Cells derived from FA patients show elevated levels of chromosomal breakage and an increased sensitivity to bifunctional alkylating agents such as mitomycin C (MMC) and diepoxybutane (DEB). Five complementation groups have been identified by somatic cell methods, and we have cloned the gene defective in group C (FAC)(7). To understand the in vivo role of this gene, we have disrupted murine Fac and generated mice homozygous for the targeted allele. The -/- mice did not exhibit developmental abnormalities nor haematologic defects up to 9 months of age. However, their spleen cells had dramatically increased numbers of chromosomal aberrations in response to MMC and DEB. Homozygous male and female mice also had compromised gametogenesis, leading to markedly impaired fertility, a characteristic of FA patients. Thus, inactivation of Fac replicates some of the features of the human disease.

Relative biological effectiveness of tritium for induction of myeloid leukemia in CBA/H mice.

To help resolve uncertainties as to the most appropriate weighting factor for tritium beta rays, a large experiment was carried out to measure the relative biological effectiveness (RBE) of tritiated water compared to X rays for the induction of myeloid leukemia in male mice of the CBA/H strain. The study was designed to estimate the lifetime incidence of myeloid leukemia in seven groups of about 750 mice each; radiation exposures were approximately 0, 1, 2 and 3 Gy both for tritiated water and for X rays. The lifetime incidence of leukemia in these mice increased from 0.13% in the control group to 6-8% in groups exposed to higher radiation doses. The results were fitted to various equations relating leukemia incidence to radiation dose, using both the raw data and data corrected for cumulative mouse-days at risk. The calculated RBE values for tritium beta rays compared to X rays ranged from 1.0 +/- 0.5 to 1.3 +/- 0.3. A best estimate of the RBE for this experiment was about 1.2 +/- 0.3. A wR value of 1 would thus appear to be more appropriate than a wR of 2 for tritium beta rays.

Familial dysmyelination in a Long Evans rat mutant.

Tremors were observed in 15 Long Evans rats beginning at 10 to 12 days of age. These were followed by progressively worsening ataxia, hind limb paresis, episodes of immobility, and seizures by 5 to 14 weeks. Gross lesions were not observed at necropsy in rats euthanized and perfused at 4 to 16 weeks of age. Neurohistologic examination revealed dysmyelination in the central nervous system. Astrogliosis in the white matter with marked increase of expression of the glial fibrillary acid protein marker was accompanied by diffuse microgliosis. Scattered glial cells, interpreted to be oligodendrocytes, contained minute periodic acid-Schiff-positive cytoplasmic granules. Large mineralized periodic acid-Schiff-positive and laminated structures were observed in the cerebellar white matter, midbrain, and thalamus of rats over 6 weeks old. Neuronal degeneration and loss was evident in the cortex, hippocampus, and midbrain. Large axonal spheroids were found in the ventral and lateral funiculi of the spinal cord. An ultrastructural study of four affected rats revealed an almost complete absence of myelinated axons and normal sheaths, and degeneration and necrosis of oligodendrocytes. The Long Evans shaker rat represents a novel myelin mutant with a remarkable survival period and appears to have an autosomal recessive mode of inheritance.