Wilmer L. Sibbitt

A novel technique to study the brain's response to pain: Proton magnetic resonance spectroscopy

Glutamate, a major excitatory neurotransmitter, has been implicated as an important mediator in the neurotransmission, potentiation, and negative affect associated with pain. We present results showing that a painful stimulus elicits a dynamic increase in glutamate (9.3% from baseline) concentrations in the anterior cingulate cortex, detectable using proton Magnetic Resonance Spectroscopy ((1)H-MRS). Increases in glutamine levels were also seen, which correlate strongly with the subjective level of pain experienced by participants (r(2) = 0.58, P < 0.01). These novel findings are the first time a dynamic change in glutamate and glutamine levels from baseline in response to an external stimuli has been measured in a single proton MRS scanning session. As such, this report demonstrates the efficacy of (1)H-MRS as a non-invasive tool for the study of neural responses to pain in vivo. The paradigm used in this study demonstrates that dynamic glutamate/glutamine changes due to stimulation are measurable by proton MRS, and could provide a means of testing novel pharmaceutical agents and other treatments for chronic pain.

Myths of Neuropsychology: Intelligence, Neurometabolism, and Cognitive Ability

Recently, Dodrill (1999) revised a previously described “Myth of neuropsychology” (1997) to state: “Just as below average performances on neuropsychological tests are found when intelligence is below average, to that same degree above average performances on neuropsychological tests are expected when intellectual abilities are above average.” This study addresses the relationship between intellectual and neuropsychological performance in the context of Magnetic Resonance Spectroscopy (MRS) measurements of the neurometabolite N-acetylaspartate (NAA). When subjects were stratified by Full Scale IQ (Average, High Average, Superior) they differed significantly in terms of total neuropsychological performance [F (2,47 = 17.63; p < .001] and the neuronal marker NAA [F (2,47) = 3.25; p < .05]. Regression analysis across groups demonstrated that FSIQ and NAA were independently related to Total z-score [F (1,47) = 29.43; p < .0001] and accounted for over half the variance (r 2 of model = .56). The concurrent relationship of FSIQ and NAA to total neuropsychological performance suggests that the relationship between measures sensitive to intellectual ability and neuropsychological performance is real, and does not reflect arbitrary psychometric or scaling properties of the WAIS-III.

Valvular Heart Disease by Transthoracic Echocardiography Is Associated with Focal Brain Injury and Central Neuropsychiatric Systemic Lupus Erythematosus

Background: Previous studies using transesophageal echocardiography (TEE) report an association of valvular heart disease (VHD) with cerebral infarcts and central neuropsychiatric systemic lupus erythematosus (NPSLE). However, TEE cannot be routinely used. Aim: To determine if VHD detected by transthoracic echocardiography (TTE) is associated with focal brain injury on magnetic resonance imaging (MRI) and secondarily with central NPSLE. Methods: Sixty-nine patients with systemic lupus erythematosus underwent general clinical, neuropsychiatric and laboratory evaluations followed by MRI of the brain and TTE. Results: Forty-one patients (59%) had NPSLE (stroke, transient ischemic attack, cognitive dysfunction, acute confusional state, seizures or psychosis); 46 (67%) had focal brain injury on MRI (cerebral infarcts, white matter lesions or small punctate lesions); 38 (55%) had VHD (vegetations, thickening or regurgitation). VHD was more common in patients with than in those without focal brain injury and NPSLE (all p < 0.05); focal brain lesions were more common in patients with than in those without NPSLE (all p < 0.04); and VHD was an independent predictor of focal brain lesions and NPSLE (both p < 0.04). Conclusion: In patients with systemic lupus erythematosus, VHD detected by TTE is associated with focal brain injury and NPSLE.

Libman-Sacks Endocarditis and Embolic Cerebrovascular Disease

OBJECTIVES The aim of this study was to determine whether Libman-Sacks endocarditis is a pathogenic factor for cerebrovascular disease (CVD) in systemic lupus erythematosus (SLE). BACKGROUND A cardioembolic pathogenesis of SLE CVD manifested as: 1) neuropsychiatric systemic lupus erythematosus (NPSLE), including stroke and transient ischemic attacks (TIA); 2) neurocognitive dysfunction; and 3) magnetic resonance imaging of focal brain lesions has not been established. METHODS A 6-year study of 30 patients with acute NPSLE (27 women, 38 ± 12 years of age), 46 age- and sex-matched SLE controls without NPSLE (42 women, 36 ± 12 years of age), and 26 age- and sex-matched healthy controls (22 women, 34 ± 11 years of age) who underwent clinical and laboratory evaluations, transesophageal echocardiography, carotid duplex ultrasound, transcranial Doppler ultrasound, neurocognitive testing, and brain magnetic resonance imaging/magnetic resonance angiography. Patients with NPSLE were re-evaluated after 4.5 months of therapy. All patients were followed clinically for a median of 52 months. RESULTS Libman-Sacks vegetations (87%), cerebromicroembolism (27% with 2.5 times more events per hour), neurocognitive dysfunction (60%), and cerebral infarcts (47%) were more common in NPSLE than in SLE (28%, 20%, 33%, and 0%) and healthy controls (8%, 0%, 4%, and 0%, respectively) (all p ≤ 0.009). Patients with vegetations had 3 times more cerebromicroemboli per hour, lower cerebral blood flow, more strokes/TIA and overall NPSLE events, neurocognitive dysfunction, cerebral infarcts, and brain lesion load than those without (all p ≤ 0.01). Libman-Sacks vegetations were independent risk factors of NPSLE (odds ratio [OR]: 13.4; p < 0.001), neurocognitive dysfunction (OR: 8.0; p = 0.01), brain lesions (OR: 5.6; p = 0.004), and all 3 outcomes combined (OR: 7.5; p < 0.001). Follow-up re-evaluations in 18 of 23 (78%) surviving patients with NPSLE demonstrated improvement of vegetations, microembolism, brain perfusion, neurocognitive dysfunction, and lesion load (all p ≤ 0.04). Finally, patients with vegetations had reduced event-free survival time to stroke/TIA, cognitive disability, or death (p = 0.007). CONCLUSIONS The presence of Libman-Sacks endocarditis in patients with SLE was associated with a higher risk for embolic CVD. This suggests that Libman-Sacks endocarditis may be a source of cerebral emboli.

Comparison of a self-report and performance-based test of disability in people with systemic lupus erythematosus

Purpose. The purpose of this study was to examine functional ability in people with SLE by comparing a self-report and a performance-based test. Method. Fifteen women with SLE and 15 healthy controls participated in this study. Participants completed a self report of daily living skills, the Health Assessment Questionnaire (HAQ). Actual performance during activities of daily living was evaluated with the Assessment of Motor and Process Skills (AMPS). Measures of cognition and disease activity were also collected. Results. HAQ scores of the participants with SLE indicated only very mild disability while scores on the AMPS indicated ineffective skill performance and potential safety risks. In the participants with SLE, cognitive status correlated significantly with the processing component (rs = 0.62, p < 0.05) and disease severity correlated with the motor component of the AMPS (rs = 0.84, p < 0.001). The HAQ did not correlate with the AMPS. Conclusions. This study suggests that cognitive deficits were more related to scores on the performance-based test of functional ability rather than the self-report. The performance-based test appeared to provide information that was not gained through self-report and measures of disease activity and gross cognition.

Purification of aldose reductase from human placenta and stabilization of the inhibitor binding site

Aldose reductase from human placenta was purified to homogeneity by a rapid (2 day) and efficient purification scheme involving Red Sepharose affinity chromatography, chromatofocusing and high performance liquid chromatography on a size-exclusion column. Addition of NADP+ at all steps in the purification of aldose reductase and during storage of the enzyme at -20 degrees stabilized both the enzyme active site and the major site for binding of aldose reductase inhibitors such as sorbinil and tolrestat. Aldose reductase is a monomer with a molecular mass of 38 kD by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, apparent pI 5.9. Placenta aldose reductase exhibited no cross-reactivity with aldehyde reductase from human liver in an ELISA assay. Aldose reductase showed broad specificity for aldehydes, was specific for NADPH, and was activated by sulfate.

Enrichment of natural killer cells by negative selection: comparison to Percoll gradient separation method.

A method is described for the preparation of human peripheral blood mononuclear cell (PBMC) suspensions containing highly enriched natural killer (NK) cell cytotoxicity. The technique involved the negative selection of OKM1+ cells by the selective removal of nylon wool nonadherent PBMC which are reactive with the Leu-1 monoclonal antibody. The Leu-1+ cells are removed by subsequent rosette formation with anti-mouse IgG coated bovine erythrocytes. The resultant OKM1+ cell suspension had a greater number of large granular lymphocytes, K562 target binding effector cells, and lytic activity than concomitantly prepared fractions of Percoll gradients.

Generation of natural killer cells and lymphokine-activated killer cells in human AB serum or fetal bovine serum

Interleukin 2 (IL-2) can induce or enhance the cytotoxic activity of natural killer (NK) cells and lymphokine-activated killer (LAK) cells. The effects of fetal bovine serum (FBS) and human AB serum (HABS) on the IL-2-induced NK cell and LAK cell activities of large granular lymphocytes (LGL) were measured, respectively, against the NK-sensitive cell line K562 and the LAK-sensitive cell line Daudi. FBS and HABS were essentially equivalent in their effects on IL-2-dependent NK activity with prolonged culture. However, with prolonged incubation from 1 to 5 days of PBMC in the presence of IL-2, there was considerably less generation of LAK cell activity in FBS (Day 3: 5.3 +/- 3.4 LU/10(7) cells) compared to HABS (Day 3: 44.6 +/- 4.2 LU/10(7) cells) (P less than 0.05). These differences in IL-2-dependent LAK cell generation did not appear to be due to the lot of the FBS or to activating factors present in individual samples of HABS. Similarly, the suppressive effects of FBS could not be reversed with increasing concentrations of IL-2 ranging from 10 to 100 U/ml. Importantly, the presence of FBS in the cultures resulted in more cell death (15.9 +/- 5.6%) at 4 days of culture compared to HABS (1.8 +/- 1.0%) (P less than 0.05). These results suggest that FBS may inhibit generation of LAK effector cells, but not NK cells in cultures containing IL-2 and that the use of HABS as a culture supplement is preferable to FBS in studies of human LAK cell function.

Inert particles inhibit natural killer cell function in vitro

Aqueous suspensions of inert particles were found to inhibit the baseline and interferon-enhanced natural killer (NK) cell activity of peripheral blood mononuclear cells (PBMC) and large granular lymphocytes (LGLs). This inhibition was induced with latex, silica, and Sephadex particles. The suppression of NK activity was not related to effector cell death as determined by trypan blue exclusion. The inhibition of NK cell function was more pronounced with prolonged incubation and could be partially reversed with monocyte depletion or the addition of indomethacin, a prostaglandin synthesis inhibitor, but not with the addition of the lipoxygenase inhibitors nordihydroguaiaretic acid and BW755C. Similarly, particle exposure inhibited the NK cell function of monocyte-depleted large granular lymphocytes with and without the add-back of glass adherent cells, implying that monocyte-independent NK suppressive mechanisms were also present. These data demonstrate that inert particles are immunosuppressive in vitro and can inhibit baseline and interferon-stimulated NK cell function of LGLs and PBMC through monocyte-dependent and independent pathways.

A possible role for MRI in polyarteritis nodosa: the creeping fat sign

We describe a case of polyarteritis nodosa with diffuse abnormalities in subcutaneous fat by magnetic resonance imaging. These abnormalities returned to normal following treatment. Magnetic resonance imaging may have a role in the identification and diagnosis of systemic vasculitis.