Instructional Bias: Ignoring One Side of the Classroom

A pronounced teaching bias away from the left side of the classroom (teacher's right) was observed in a time-sampling study of 19 teachers. Six male and 13 female teachers showed an instructional orientation toward the classroom right (teacher's left), and center. Teacher's relative inattention to students seated on the left of the classroom may be accounted for by teachers being conditioned to monitor students in the center and to the left, stable differences in left-right cerebral hemispheric attentional control or ease of classroom instruction.

3T diffusion-weighted MRI of the thyroid gland with reduced distortion: preliminary results

OBJECTIVE

Single-shot diffusion-weighted (DW) echo planar imaging (EPI), which is commonly used for imaging the thyroid, is characterised by severe blurring and distortion. The objectives of this work were: 1, to show that a reduced-field of view (r-FOV) DW EPI technique can improve image quality; and 2, to investigate the effect of different reconstruction strategies on the resulting apparent diffusion coefficients (ADCs).

METHODS

We implemented a single-shot, r-FOV DW EPI technique with a two-dimensional radiofrequency excitation pulse for DW imaging of the thyroid at 3T. Images were reconstructed using root sum of squares (SOS) and an optimal-B1 reconstruction (OBR). Phantom and in vivo experiments were performed to compare r-FOV and conventional full-FOV DW EPI with root SOS and OBR.

RESULTS

r-FOV with OBR substantially improved image quality at 3T. In phantoms, r-FOV gave more accurate ADCs than full-FOV. In vivo r-FOV always gave lower ADC values with respect to the full-FOV technique irrespective of the reconstruction used and whether only two or multiple b-values were used to compute the ADCs.

CONCLUSION

r-FOV DW EPI can reduce image blurring and distortion at the expense of a low signal-to-noise ratio. OBR is a promising reconstruction technique for accurate ADC measurements in lower signal-to-noise ratio regimes, although further studies are needed to characterise its performance.

ADVANCES IN KNOWLEDGE

DW imaging of the thyroid at 3T could potentially benefit from r-FOV acquisition strategies, such as the r-FOV DW EPI technique proposed in this paper.

DCE and DW MRI in monitoring response to androgen deprivation therapy in patients with prostate cancer: a feasibility study

Androgen deprivation therapy (ADT) is a key primary treatment for advanced and metastatic prostate cancer and is an important neoadjuvant before radiotherapy. We evaluated 3.0 T dynamic contrast-enhanced MRI and diffusion-weighted (DW) MRI in monitoring ADT response. Twenty-three consecutive patients with prostate cancer treated by primary ADT were included. Imaging was performed at baseline and 3 months posttreatment with ADT. After 3 months therapy there was a significant reduction in all dynamic contrast-enhanced MRI parameters measured in tumor regions of interest (K(trans), k(ep), v(p), IAUGC-90); P < 0.001. Areas of normal-appearing peripheral zone showed no significant change; P = 0.285-0.879. Post-ADT, there was no significant change in apparent diffusion coefficient values in tumors, whilst apparent diffusion coefficient values significantly decreased in areas of normal-appearing peripheral zone, from 1.786 × 10(-3) mm(2) /s to 1.561 × 10(-3) mm(2) /s; P = 0.007. As expected the median Prostate-Specific Antigen (PSA) significantly reduced from 30 ng/mL to 1.5 ng/mL posttreatment, and median prostate volume dropped from 47.6 cm(3) to 24.9 cm(3) ; P < 0.001. These results suggest that dynamic contrast-enhanced MRI and diffusion-weighted MRI offer different information but that both could prove useful adjuncts to the anatomical information provided by T2-weighted imaging. dynamic contrast-enhanced as a marker of angiogenesis may help demonstrate ADT resistance and diffusion-weighted imaging may be more accurate in determining presence of tumor cell death versus residual tumor.

Thalamic glutamate levels as a predictor of cortical response during executive functioning in subjects at high risk for psychosis

CONTEXT

Alterations in glutamatergic neurotransmission and cerebral cortical dysfunction are thought to be central to the pathophysiology of psychosis, but the relationship between these 2 factors is unclear.

OBJECTIVE

To investigate the relationship between brain glutamate levels and cortical response during executive functioning in people at high risk for psychosis (ie, with an at-risk mental state [ARMS]).

DESIGN

Subjects were studied using functional magnetic resonance imaging while they performed a verbal fluency task, and proton magnetic resonance spectroscopy was used to measure their brain regional glutamate levels.

SETTING

Maudsley Hospital, London, England.

PATIENTS AND OTHER PARTICIPANTS

A total of 41 subjects: 24 subjects with an ARMS and 17 healthy volunteers (controls).

MAIN OUTCOME MEASURES

Regional brain activation (blood oxygen level-dependent response); levels of glutamate in the anterior cingulate, left thalamus, and left hippocampus; and psychopathology ratings at the time of scanning.

RESULTS

During the verbal fluency task, subjects with an ARMS showed greater activation than did controls in the middle frontal gyrus bilaterally. Thalamic glutamate levels were lower in the ARMS group than in control group. Within the ARMS group, thalamic glutamate levels were negatively associated with activation in the right dorsolateral prefrontal and left orbitofrontal cortex, but positively associated with activation in the right hippocampus and in the temporal cortex bilaterally. There was also a significant group difference in the relationship between cortical activation and thalamic glutamate levels, with the control group showing correlations in the opposite direction to those in the ARMS group in the prefrontal cortex and in the right hippocampus and superior temporal gyrus.

CONCLUSIONS

Altered prefrontal, hippocampal, and temporal function in people with an ARMS is related to a reduction in thalamic glutamate levels, and this relationship is different from that in healthy controls.

Spinal cord repair in MS: does mitochondrial metabolism play a role?

OBJECTIVE

To investigate the mechanisms of spinal cord repair and their relative contribution to clinical recovery in patients with multiple sclerosis (MS) after a cervical cord relapse, using spinal cord (1)H-magnetic resonance spectroscopy (MRS) and volumetric imaging.

METHODS

Fourteen patients with MS and 13 controls underwent spinal cord imaging at baseline and at 1, 3, and 6 months. N-acetyl-aspartate (NAA) concentration, which reflects axonal count and metabolism in mitochondria, and the cord cross-sectional area, which indicates axonal count, were measured in the affected cervical region. Mixed effect linear regression models investigated the temporal evolution of these measures and their association with clinical changes. Ordinal logistic regressions identified predictors of recovery.

RESULTS

Patients who recovered showed a sustained increase in NAA after 1 month. In the whole patient group, a greater increase of NAA after 1 month was associated with greater recovery. Patients showed a significant decline in cord area during follow-up, which did not correlate with clinical changes. A worse recovery was predicted by a longer disease duration at study entry.

CONCLUSIONS

The partial recovery of N-acetyl-aspartate levels after the acute event, which is concurrent with a decline in cord cross-sectional area, may be driven by increased axonal mitochondrial metabolism. This possible repair mechanism is associated with clinical recovery, and is less efficient in patients with longer disease duration. These insights into the mechanisms of spinal cord repair highlight the need to extend spinal cord magnetic resonance spectroscopy to other spinal cord disorders, and explore therapies that enhance recovery by modulating mitochondrial activity.

Spinal cord spectroscopy and diffusion-based tractography to assess acute disability in multiple sclerosis

There is a need to assess spinal cord involvement in multiple sclerosis with new imaging techniques in order to understand better the underlying pathology. We aimed to evaluate whether quantitative MRI measures, obtained using single-voxel (1)H-MR spectroscopy of the cervical cord and diffusion-based tractography of the major spinal cord pathways, in patients with a cervical cord relapse, differed from controls and correlated with acute disability. Fourteen patients at the onset of a cervical cord relapse with at least one lesion between C1 and C3 were imaged on a 1.5 T scanner and clinically assessed on the Expanded Disability Status Scale (EDSS), 9-hole peg test (HPT) and timed 25-foot walk test. Thirteen age- and gender-matched control subjects were also scanned. Metabolite concentrations, including total N-acetyl-aspartate (tNAA), choline-containing compounds (Cho), creatine plus phosphocreatine (Cr) and myo-Inositol (m-Ins), were quantified at C1-C3. Probabilistic tractography was performed at C1-C3 to track the lateral cortico-spinal tracts in the lateral columns, the anterior cortico-spinal tracts and the anterior spino-thalamic fasciculi in the anterior columns, and the bilateral fasciculus gracilis and cuneatus in the posterior columns. Diffusion- and tractography-derived measures of these tracts, including fractional anisotropy and voxel-based connectivity, which reflect fibre integrity, were obtained. These MRI measures were compared between patients and controls using the Mann-Whitney test. Univariate correlations between MRI measures and disability were assessed using the Spearman's rho correlation coefficient. Multiple regression analyses were performed to investigate which MRI measures independently correlated with the clinical scores, adjusting also for cross-sectional cord area, age and gender. Patients showed lower tNAA of the cervical cord, lower connectivity and lower fractional anisotropy of the lateral cortico-spinal tracts and posterior tracts, than controls. In patients, there were significant correlations between: (i) EDSS and m-Ins, Cho, Cr and radial diffusivity of the lateral cortico-spinal tracts; (ii) HPT and Cr, radial diffusivity of the lateral cortico-spinal tracts, connectivity and fractional anisotropy of the posterior tracts, and connectivity of the anterior tracts. M-Ins was independently associated with the EDSS, while Cr, tNAA and connectivity of the posterior tracts were independently associated with the HPT. MR spectroscopy and diffusion-based tractography of the cervical cord provide measures that are sensitive to the tissue damage occurring in this area in patients with a cervical cord relapse. These measures were found to correlate with acute disability. Our findings suggest that it would be worthwhile performing longitudinal studies and extending these novel techniques to other neurological diseases affecting the spinal cord.

1H-MRS internal thermometry in test-objects (phantoms) to within 0.1 K for quality assurance in long-term quantitative MR studies

Many magnetic resonance test-object properties are temperature-dependent, with typical temperature coefficients of approximately 2-3% K(-1). Therefore, to achieve consistent quality assurance measurements to within 1%, test object temperatures should ideally be known to within 0.3 K. Proton magnetic resonance spectroscopy has previously been used to estimate accurately absolute tissue temperature in vivo, based on the linear temperature dependence of the chemical shift difference between water and temperature-stable reference metabolites such as N-acetylaspartate. In this study, this method of 'internal thermometry' in quality assurance test-objects was investigated, and in particular the value of sodium 3-(trimethylsilyl)propane-1-sulfonate (DSS) as a chemical shift reference was demonstrated. The relationship between the DSS-water chemical shift difference (sigma, expressed in ppm) and temperature tau (in K) was shown to be tau = 764.55 (+/-5.05) - 97.72 (+/-1.05) sigma (286 <or= tau <or= 309 K). Internal thermometry in MRI test-objects is feasible and straightforward, using readily available (1)H-MRS pulse sequences and standard spectroscopy evaluation packages, with a minimum detectable temperature difference of 100 (+/-20) mK.

Metabolite changes in early relapsing-remitting multiple sclerosis. A two year follow-up study

Previous in vivo proton magnetic resonance spectroscopic imaging ((1)H-MRSI) studies have found reduced levels of N-acetyl-aspartate (NAA) in multiple sclerosis (MS) lesions, the surrounding normal-appearing white matter (NAWM) and cortical grey matter (CGM), suggesting neuronal and axonal dysfunction and loss. Other metabolites, such as myoinositol (Ins), creatine (Cr), choline (Cho), and glutamate plus glutamine (Glx), can also be quantified by (1)H-MRSI, and studies have indicated that concentrations of these metabolites may also be altered in MS. Relatively little is known about the time course of such metabolite changes. This preliminary study aimed to characterise changes in total NAA (tNAA, the sum of NAA and N-acetyl-aspartyl-glutamate), Cr, Cho, Ins and Glx concentrations in NAWM and in CGM, and their relationship with clinical outcome, in subjects with clinically early relapsing-remitting MS (RRMS). Twenty RRMS subjects and 10 healthy control subjects underwent (1)H-MRSI examinations yearly for two years. Using the LCModel, tNAA, Cr, Cho, Ins and Glx concentrations were estimated both in NAWM and CGM. At baseline, the concentration of tNAA was significantly reduced in the NAWM of the MS patients compared to the control group (-7%, p = 0.003), as well as in the CGM (-8.7%, p = 0.009). NAWM tNAA concentrations tended to recover from baseline, but otherwise tissue metabolite profiles did not significantly change in the MS subjects, or relatively between MS and healthy control subjects. While neuronal and axonal damage is apparent from the early clinical stages of MS, this study suggests that initially it may be partly reversible. Compared with other MR imaging measures, serial (1)H-MRSI may be relatively less sensitive to progressive pathological tissue changes in early RRMS.

Metabolite Changes in Normal-Appearing Gray and White Matter Are Linked With Disability in Early Primary Progressive Multiple Sclerosis

BACKGROUND

Abnormalities in normal-appearing brain tissues may contribute to disability in primary progressive multiple sclerosis (PPMS), where few lesions are seen on conventional imaging.

OBJECTIVES

To evaluate the mechanisms underlying disease progression in the early phase of PPMS by measuring metabolite concentrations in normal-appearing white matter (NAWM) and cortical gray matter (CGM) and to assess their relationship with clinical outcomes.

DESIGN

Case-control study.

SETTING

Tertiary referral hospital. Patients Forty-three consecutive patients within 5 years of onset of PPMS and 44 healthy control subjects.

MAIN OUTCOME MEASURES

Concentrations of choline-containing compounds, phosphocreatine, myo-inositol, total N-acetyl-aspartate (tNAA), and glutamate-glutamine were estimated using proton magnetic resonance spectroscopic imaging. Brain parenchymal, white matter and gray matter fractions and proton density and gadolinium-enhancing lesion loads were calculated. The Expanded Disability Status Scale and Multiple Sclerosis Functional Composite scores were recorded.

RESULTS

In CGM, concentrations of the tNAA (P<.001) and glutamate-glutamine (P = .005) were lower in patients with PPMS than in controls. In NAWM, myo-inositol levels were higher (P = .002) and tNAA levels were lower (P = .005) in patients with PPMS than in controls. The Expanded Disability Status Scale score correlated with the tNAA concentration in CGM (r = -0.44; P = .03) and with myo-inositol (r = 0.41; P = .01) and glutamate-glutamine concentrations (r = 0.41; P = .01) in NAWM. Proton density lesion load correlated negatively with CGM tNAA concentration and positively with NAWM myo-inositol concentration.

CONCLUSION

Metabolite changes, which differ in CGM and NAWM, occur in early PPMS and are linked with disability.

Elevated white matter myo-inositol in clinically isolated syndromes suggestive of multiple sclerosis

Normal-appearing white matter (NAWM) in established multiple sclerosis has been shown to be abnormal using a variety of magnetic resonance (MR) techniques, including proton MR spectroscopy ((1)H-MRS), although the stage at which these changes first appear is less clear. Using a 1.5 T scanner and single-voxel (1)H-MRS [TR 3000 ms, TE 30 ms, point-resolved spectroscopy (PRESS) localization], we determined NAWM metabolite concentrations in 96 patients a mean of 19 weeks (range 12-28 weeks) after onset of a clinically isolated syndrome (CIS) suggestive of multiple sclerosis and in 44 healthy control subjects. Absolute concentrations of N-acetyl-aspartate, total creatine and phosphocreatine (Cr), choline-containing compounds, glutamate plus glutamine, and myo-inositol (Ins) were estimated automatically using the LCModel. Compared with control subjects, the concentration of Ins was elevated in CIS NAWM (mean 3.31 mM, SD 0.86 versus mean 3.82 mM, SD 1.06; P = 0.001). The increase in Ins was also seen in the patient subgroup with abnormal T2-weighted MRI (mean 3.88 mM, SD 1.10; P = 0.001) and in those who satisfied the McDonald criteria for multiple sclerosis (mean 4.04 mM, SD 1.31; P = 0.001). An increase in Cr was also observed in CIS NAWM (P = 0.023), but other metabolites did not significantly differ between the whole CIS group and control subjects. There was no significant correlation between NAWM Ins and T2 lesion load. The early increase in Ins may reflect a process of pathogenic importance in multiple sclerosis NAWM. Follow-up studies will investigate whether the increase in NAWM Ins is of prognostic importance for future relapses and disability.

Metabolic profiles of human brain tumors using quantitative in vivo 1H magnetic resonance spectroscopy

Proton spectroscopy can noninvasively provide useful information on brain tumor type and grade. Short- (30 ms) and long- (136 ms) echo time (TE) (1)H spectra were acquired from normal white matter (NWM), meningiomas, grade II astrocytomas, anaplastic astrocytomas, glioblastomas, and metastases. Very low myo-Inositol ([mI]) and creatine ([Cr]) were characteristic of meningiomas, and high [mI] characteristic of grade II astrocytomas. Tumor choline ([Cho]) was greater than NWM and increased with grade for grade II and anaplastic astrocytomas, but was highly variable for glioblastomas. Higher [Cho] and [Cr] correlated with low lipid and lactate (P < 0.05), indicating a dilution of metabolite concentrations due to necrosis in high-grade tumors. Metabolite peak area ratios showed no correlation with lipids and mI/Cho (at TE = 30 ms), and Cr/Cho (at TE = 136 ms) best correlated with tumor grade. The quantified lipid, macromolecule, and lactate levels increased with grade of tumor, consistent with progression from hypoxia to necrosis. Quantification of lipids and macromolecules at short TE provided a good marker for tumor grade, and a scatter plot of the sum of alanine, lactate, and delta 1.3 lipid signals vs. mI/Cho provided a simple way to separate most tumors by type and grade.

Brain metabolite changes in cortical grey and normal-appearing white matter in clinically early relapsing-remitting multiple sclerosis

While much work has concentrated on focal white matter (WM) lesions in multiple sclerosis, there is growing evidence to suggest that normal-appearing WM (NAWM) and grey matter (GM) are also involved in the disease process. This study investigated multiple sclerosis disease effects on NAWM and cortical GM (CGM) metabolite concentrations, and the relationships between these metabolite concentrations and clinical impairment. Proton magnetic resonance spectroscopic imaging ((1)H-MRSI) data acquired using point resolved spectroscopic (PRESS) localization (echo time 30 ms, repetition time 3000 ms, nominal voxel volume 2.3 ml) from 27 relapsing-remitting multiple sclerosis and 29 normal control (NC) subjects were processed using LCModel to estimate metabolite concentrations in millimoles per litre. (1)H-MRSI voxel tissue contents were estimated using SPM99 tissue and semi-automatic lesion segmentations of three-dimensional fast spoiled gradient recall scans acquired during the same scanning session. NAWM and CGM metabolite concentrations estimated were: choline-containing compounds (Cho); creatine and phosphocreatine (Cr); myo-inositol (Ins); N-acetyl-aspartate plus N-acetyl-aspartyl-glutamate (tNAA); and glutamate plus glutamine (Glx). CGM data came from 24 of the multiple sclerosis (mean age 35.2 years, mean disease duration 1.7 years) and 25 of the NC (mean age 34.9 years) subjects. NAWM data came from 25 of the multiple sclerosis (mean age 35.0 years, mean disease duration 1.7 years) and 28 of the NC (mean age 36.7 years) subjects. Metabolite concentrations were compared between multiple sclerosis and NC subjects using multiple (linear) regression models allowing for age, gender, (1)H-MRSI voxel tissue and CSF contents, and brain parenchymal volume. At a significance level of P < 0.05, CGM Cho, CGM and NAWM tNAA, and CGM Glx were all significantly reduced, and NAWM Ins was significantly elevated. Spearman correlations of multiple sclerosis functional composite scores with tissue metabolite concentrations were significant for the following: CGM Cr (r(s) = 0.524, P = 0.009), CGM Glx (r(s) = 0.580, P = 0.003) and NAWM Ins (r(s) = -0.559, P = 0.004). These results indicate that metabolite changes in NAWM and CGM can be detected early in the clinical course of multiple sclerosis, and that some of these changes relate to clinical status. The correlation of clinical impairment with CGM Cr and Glx but not tNAA suggests that it is more closely associated with neuronal metabolic dysfunction rather than loss in clinically early relapsing-remitting multiple sclerosis. The correlation of clinical impairment with a raised NAWM Ins may indicate that glial proliferation also relates to function at this stage of the disease.

In vivo GABA+ measurement at 1.5T using a PRESS-localized double quantum filter

A point-resolved spectroscopy (PRESS)-localized double quantum filter was implemented on a 1.5T clinical scanner for the estimation of gamma-amino butyric acid (GABA) concentrations in vivo. Several calibrations were found to be necessary for consistent results to be obtained. The apparent filter yield was approximately 38%; filter strength was sufficient to reduce the singlet metabolite peaks in vivo to below the level of the noise. Metabolite-nulled experiments were performed, which confirmed that significant overlap occurred between macromolecule signals and the GABA resonance at 3.1 ppm. Although the multiplet arm at 2.9 ppm was confirmed to be relatively free of contamination with macromolecules, some contribution from these and from peptides is likely to remain; therefore, the term GABA+ is used. GABA+ concentrations were estimated relative to creatine (Cr) at the same echo time (TE) in a group of controls, studied on two occasions. The GABA+ concentration in 35-ml regions of interest (ROIs) in the occipital lobe was found to be 1.4 +/- 0.2 mM, with scan-rescan repeatability of 38%.

Quantitative 1H MRS imaging 14 years after presenting with a clinically isolated syndrome suggestive of multiple sclerosis

clinically isolated syndromes (CIS) are events suggestive for emerging multiple sclerosis (MS). A majority of patients develop MS within months or years whilst others remain clinically isolated. The goal of this study was to investigate whether biochemical metabolites detectable by 'H magnetic resonance spectroscopy (MRS) may serve to distinguish between these two groups. We investigated 41 patients 14 years after presentation with a CIS and 21 controls with combined quantitative short echo 'H MRS and magnetic resonance imaging (MRI) and assessed disability according to the Expanded Disability Status Scale (EDSS). At follow-up, 32 had developed MS, and 9 still had CIS. Compared with controls, MS patients demonstrated significantly higher concentrations of myo-inositol (Ins) in normal appearing white matter (NAWM) and lesions. Lesions also demonstrated a reduced N-acetyl-aspartate (NAA) level and an increase in choline-containing compounds (Cho). The NAWM Ins concentration was correlated with EDSS (r = 0.48, p = 0.005). MS normal appearing cortical grey matter (CGM) exhibited a decreased NAA. Patients who remained CIS did not differ significantly from controls in any MRS measure. Metabolite changes in normal appearing white and grey matter in MS indicate diffuse involvement of the entire MS brain, which was not seen in the persisting CIS patients. Elevated Ins in MS NAWM appeared functionally relevant It may indicate glial cell proliferation or gliosis.

A comparison of some metabolic effects of N-methylaspartate stereoisomers, glutamate and depolarization: a multinuclear MRS study

Exposure of guinea pig brain slices to low concentrations (10 microM) of NMDA caused decreases in PCr and ATP within 30 min, with a slower decrease in NAA and increase in lactate, both detectable after 1 h. Exposure to NMDA for over 1 h or at higher concentrations caused further increases in lactate and decreases in NAA, with no further change in PCr or ATP. The L-isomer, NMLA, and the racemic mixture, NMDLA, caused similar changes in lactate and NAA, but both produced greater decreases in the energy state than NMDA, similar to those caused by prolonged exposure to glutamate. MK-801 prevented the changes in the energy state caused by NMDA, but not those caused by NMLA or by glutamate. The results are compared to previous studies on depolarization and discussed in terms of the role of the NMDA sub-type of glutamate receptor in the excitotoxic hypothesis of neuronal degeneration.

Characterization of the oxygenated intermediate of the thermophilic cytochrome P450 CYP119

Using UV-Vis, resonance Raman, and EPR spectroscopy we have studied the properties of the oxygenated ferrous cytochrome P450 from Sulfolobus solfataricus, (CYP119). The recently determined crystal structure of CYP119 is compared with other available structures of P450s, and detailed structural and spectroscopic analyses are reported. With several structural similarities to CYP102, such as in-plane iron position and a shorter iron-proximal ligand bond, CYP119 shows low-spin conformation preference in the ferric form and partially in the ferrous form at low temperatures. These structural features can explain the fast autoxidation of the oxyferrous complex of CYP119. Finally, we report the first UV-Vis and EPR spectra of the cryoradiolytically reduced oxygenated intermediate of CYP119. The primary reduced intermediate, a hydroperoxo-ferric complex of CYP119, undergoes a 'peroxide shunt' pathway during gradual annealing at 170-195 K and returns to the low-spin ferric form.

In vivo short echo time 1H-magnetic resonance spectroscopic imaging (MRSI) of the temporal lobes

Two different methodologies for obtaining PRESS-localized magnetic resonance spectroscopic imaging (MRSI) data from the mesial and lateral temporal lobes were investigated. The study used short echo times (30 ms) and long repetition times (3000 ms) to minimize relaxation effects. Inhomogeneity and spectral distortions from the proximity of the temporal bones precluded the attainment of consistently good-quality data from both temporal lobes at once. Even when the right and left temporal lobes were studied separately, distortions often disturbed spectra from the anterior lateral temporal lobe. Quantitative analysis using LCModel was therefore performed only on the posterior lateral temporal lobe, and the posterior, middle, and anterior mesial temporal lobe. No significant left-right differences in metabolite content were found in a series of 10 controls. Significantly higher concentrations of myoinositol and choline were found in the anterior mesial temporal lobe, even when grey matter content was included as a covariate. The concentration of N-acetyl aspartate plus N-acetyl aspartyl glutamate (NAc) was not found to vary significantly along the length of the hippocampus. The previously observed lower anterior ratios of NAA to creatine plus choline (NAA/(Cr + Cho) may instead have been due to higher anterior choline. Large differences in metabolite concentrations were seen between posterior lateral temporal lobe (predominantly subcortical white matter) and the posterior mesial temporal lobe, most notably lower creatine, glutamate/glutamine, and myo-inositol, and higher NAA/(Cr + Cho) in the lateral than mesial temporal lobe. This pattern was similar to that previously seen for grey/white matter differences in the frontal, parietal and occipital regions.

Analysis of residual trifluoroacetic acid in a phosphate-buffered saline matrix by ion chromatography with suppressed conductivity detection

As part of the formulation of a cell-based pharmaceutical product, cells were harvested from mice and incubated in a cocktail containing cell culture media and high levels of trifluoroacetic acid (TFA). The cells were washed with a phosphate-buffered saline solution to remove residual cell culture media and other reagents before the cells were infused back into the mice from which they originated. Because of the potentially toxic nature of the TFA, the cells were washed multiple times and the final wash was monitored for residual TFA in order to demonstrate the efficient removal of the reagent before the cell product could be reintroduced into the test animal. This report describes the method that was developed incorporating anion-exchange chromatography with suppressed conductivity detection for the analysis of residual TFA (down to 50 ng/ml) in the presence of high concentrations of phosphate and chloride interferences. The ultimate sensitivity of the method was improved by selectively removing halide anions using a silver cartridge before sample analysis. The method proved to be rugged and reproducible enough to be validated and used to monitor residual TFA levels in cell washes in support of an acute toxicological study. Results demonstrating the method's sensitivity, selectivity, precision and linearity were reported.

Preliminary evidence for neuronal damage in cortical grey matter and normal appearing white matter in short duration relapsing-remitting multiple sclerosis: a quantitative MR spectroscopic imaging study

Neuronal damage and loss is likely to underlie irreversible disability in multiple sclerosis (MS). The time of onset, location and extent of neuronal damage in early disease are all uncertain. To explore this issue 16 patients with short duration, mild relapsing-remitting disease (mean disease duration 1.8 years, median EDSS 1) were studied using short echo time proton magnetic resonance spectroscopic imaging (1H-MRSI) to quantify the concentration of the neuronal marker N-acetyl-aspartate (NAA). The data were compared with those from 12 age-matched controls. 1H-MRSI was obtained from a 1.5-cm-thick slice just above the lateral ventricles. The Linear Combination (LC) Model combined with locally developed software allowed automated measurement of absolute metabolite concentrations from lesions, normal-appearing white matter (NAWM) and cortical grey matter (CGM). MS CGM exhibited significantly lower NAA (P = 0.01) and myo-inositol (P = 0.04) than control CGM. MS NAWM exhibited a lower concentration of NAA (P = 0.01) and increased myo-inositol (P = 0.03) than control white matter. More marked reductions in NAA and increases in myo-inositol were seen in lesions. The reduced NAA in MS CGM and NAWM suggest that mild but widespread neuronal dysfunction or loss occurs early in the course of relapsing-remitting MS. This preliminary finding should be confirmed in a larger cohort, and follow-up studies are also needed to determine the prognostic and pathophysiological significance of these early changes.

Quantitative short echo time proton magnetic resonance spectroscopic imaging study of malformations of cortical development causing epilepsy

In patients with malformations of cortical development (MCD), widespread structural abnormalities of the brain have been demonstrated using volumetric MRI, and associated with poor post-surgical outcome in patients with localization-related epilepsy. Proton magnetic resonance spectroscopic imaging (1H-MRSI) studies permit the non-invasive measurement of concentrations of a variety of cerebral metabolites implicated in cerebral structure and function. There is a dearth of quantitative 1H-MRSI studies of MCD. Ten controls and 10 patients with localization-related epilepsy who were found to have MCD on high resolution MRI underwent 1H-MRSI on a 1.5 T GE Signa scanner [TE (echo time) = 30 ms, TR (repetition time) = 3 s]. In all patients, the axial area studied contained lesional and perilesional tissue. In seven unilaterally affected patients, the area studied contained also apparently normal contralateral grey and white matter; in three patients with bilateral but asymmetrical MCD, it contained visually normal and abnormal tissue from both hemispheres. N-acetyl aspartate + N-acetyl aspartyl glutamate (NAA), creatine + phosphocreatine (Cr), choline-containing compounds (Cho), glutamate + glutamine (Glx) and myo-inositol (Ins) were automatically quantified in voxels covering these different regions. Metabolite concentrations were corrected for CSF content and correlated with the grey and white matter of the MRSI voxels. In control subjects, there were significant positive correlations between grey matter content and concentrations of NAA, Glx, Ins and Cr. Compared with a normal range that took grey matter content into account, defined as the control mean +/- 2 SD, all lesions but one showed metabolic abnormalities. The most common abnormality was a decrease in NAA, but findings were heterogeneous and there was increased NAA in one lesion. Perilesional tissue was abnormal in eight patients, with increased NAA in three. Tissue contralateral to the main MCD was abnormal in all three patients with bilateral but asymmetrical MCD, and in six of the seven apparently unilaterally affected patients. Spectroscopic grey and white matter abnormalities in patients with MCD exceeded the apparently focal abnormality shown by MRI, indicating widespread abnormalities of cerebral function.

Quantitative analysis of short echo time (1)H-MRSI of cerebral gray and white matter

Quantitative analysis of (1)H-magnetic resonance spectroscopic imaging (MRSI) data was developed using the user-independent spectral analysis routine LCModel. Tissue segmentation was performed using statistical parametric mapping software (SPM 96), and the results were used to correct for cerebrospinal fluid contamination. A correction was developed for the imperfections in the spectroscopic excitation profile in order to improve the uniformity of metabolite images. After validation in phantoms, these techniques were applied to study differences in metabolite concentrations between gray and white matter in normal volunteers (n = 13). A positive correlation was found between concentration and gray matter content for most metabolites studied. The estimated ratios of metabolite concentration in gray vs. white matter were: N-acetyl aspartate + N-acetyl aspartyl glutamate (NAc) = 1.16+/- 0.11; creatine = 1.7+/-0.3; glutamate + glutamine = 2.4+/-0.5; myo-inositol = 1.6+/-0.3; choline = 0.9+/-0.2. The ratio of NAc/Cr was negatively correlated with gray matter content: gray/white = 0.69 +/-0.08. These methods will be useful in the evaluation of metabolite concentrations in MRSI voxels with mixed tissue composition in patient groups.

Multimodal MR imaging: functional, diffusion tensor, and chemical shift imaging in a patient with localization-related epilepsy

PURPOSE

To demonstrate the integration of complementary functional and structural data acquired with magnetic resonance imaging (MRI) in a patient with localization-related epilepsy.

METHODS

We studied a patient with partial and secondarily generalized seizures and a hemiparesis due to a malformation of cortical development (MCD) in the right hemisphere by using EEG-triggered functional MRI (fMRI), diffusion tensor imaging (DTI), and chemical shift imaging (CSI).

RESULTS

fMRI revealed significant changes in regional blood oxygenation associated with interictal epileptiform discharges within the MCD. DTI showed a heterogeneous microstructure of the MCD with reduced fractional anisotropy, a high mean diffusivity, and displacement of myelinated tracts. CSI demonstrated low N-acetyl aspartate (NAA) concentrations in parts of the MCD.

CONCLUSIONS

The applied MR methods described functional, microstructural, and biochemical characteristics of the epileptogenic tissue that cannot be obtained with other noninvasive means and thus improve the understanding of the pathophysiology of epilepsy.

Short echo time single-voxel 1H magnetic resonance spectroscopy in magnetic resonance imaging-negative temporal lobe epilepsy: different biochemical profile compared with hippocampal sclerosis

Single-voxel proton magnetic resonance spectroscopy (1H MRS) has shown abnormalities in patients with temporal lobe epilepsy (TLE) and hippocampal sclerosis (HS). Many TLE patients, however, do not have HS or other lesions on quantitative magnetic resonance imaging (MRI) (MRI-negative). Fifteen control subjects, 15 patients with unilateral HS, and 15 MRI-negative TLE patients underwent 1H MRS at an echo time of 30 msec on a 1.5-T GE Signa scanner. Voxels were tailored to the individual hippocampi. N-Acetylaspartate (NAA), creatine, choline, total glutamate plus glutamine (Glx), and myo-inositol (Ins) were quantitated by using an external standard and LCModel, a user-independent quantitation method. Normal ranges were defined as the control mean +/- 2.5 SD. In HS patients, 12 of 15 had abnormally low NAA in sclerotic hippocampi; 3 of these 12 also had abnormally low NAA contralaterally. Abnormally low NAA/Ins ratios lateralized the side affected by HS in 7 of 15 patients, without any bilateral abnormalities. In 15 MRI-negative TLE patients, 4 had abnormally low hippocampal NAA ipsilateral to seizure onset, 1 of whom had abnormally low NAA bilaterally. Analysis of groups of subjects showed a bilateral decrease in NAA, most marked in patients with HS and on the side of seizure onset. The mean NAA/Ins ratio was lower in patients with HS than in control subjects and in MRI-negative patients. The concentration of Glx was higher ipsilateral to seizure onset in MRI-negative patients than in HS patients. Quantitative short echo time 1H MRS identified abnormalities in 87% of patients with HS and 27% of MRI-negative TLE patients in concordance with other lateralizing data. In individual and group comparisons, 1H MRS described a metabolite profile in the hippocampi of MRI-negative TLE patients that was different from patients with HS, with an increase in Glx and a less marked decrease in NAA than was seen in HS.

Optical sensor to monitor and control temperature and build height of the laser direct-casting process

A nonintrusive optical sensor system is applied to real-time process control of the recently developed laser direct-casting process, in which a stream of metal powder is introduced into the beam of a high-power (500-W) cw laser to fabricate complex three-dimensional structures. The sensor system allows two critical parameters, temperature and build height, associated with this process to be monitored and controlled continuously. We achieved a height-sensing resolution of ?0.25 mm and temperature control with a resolution of ?10 degrees C at a typical working temperature of 1500 degrees C with an evident improvement in process quality, especially for complex workpieces comprising relatively high, thin walls at which the conductive heat transfer varies substantially as the process proceeds.

Characterization of a cytochrome P450 from the acidothermophilic archaea Sulfolobus solfataricus

We report the cloning, expression, purification, and molecular characterization of a cytochrome P450 (CYP119) from the thermophilic archaea Sulfolobus solfataricus. This protein displays an absorption spectra in the reduced, oxidized, and carbonyl adduct analogous to those of other P450 enzymes. We demonstrate that P450 (CYP119) exhibits remarkable thermo- and pressure stability, with a melting temperature 40 degrees higher than that of the extensively studied cytochrome P450cam (CYP101) and an optical spectra completely resistant to the formation of the inactive P420 by hydrostatic pressure up to 2 kbar. CO flash photolysis experiments, as well as construction of a CYP119 homology model, suggest an open active site with greater solvent access than P450 (CYP101) and similar to that of P450 (CYP102). This communication represents the first molecular characterization of an extremophilic cytochrome P450.

Photoacoustic calorimetry of proteins

We have described two examples of time-resolved photoacoustic calorimetry for the study of heme protein transient intermediates. Before photoacoustic calorimetry, determining thermodynamic information on short-lived intermediates was difficult. Along with being sensitive to enthalpic and volume changes, photoacoustic calorimetry can detect conformational changes in a time-resolved manner. In complex protein systems, the interpretation of the structural origins of a conformational change is sometimes difficult. Site-directed mutagenesis has been used successfully to identify the residues that play important roles in the ligand binding to both Mb and cytochrome P450cam. In both systems the hydration state of salt bridges gave rise to volume changes that were identified through mutagenesis of the residues involved. With its increasing popularity and the power of site-directed mutagenesis, time-resolved photoacoustic calorimetry is fast becoming a technique to probe conformational dynamics in proteins.

Decreased substrate affinity upon alteration of the substrate-docking region in cytochrome P450(BM-3)

A mutation at the surface of the substrate access channel which dramatically decreases the affinity for some fatty acids in P450(BM-3) was discovered by random mutagenesis. The mutation introduced, proline-25 to glutamine, is in close proximity to the arginine-47 residue thought to be responsible for the initial docking of fatty acid substrates. The P25Q mutant displays an affinity for palmitate which is approximately 100-fold weaker than the wild-type enzyme. In addition to its altered substrate affinity, P25Q also exhibits altered hydroxylation specificity and carbon monoxide recombination kinetics in the substrate-free form.

Carbon monoxide binding to cytochrome P450BM-3: evidence for a substrate-dependent conformational change

The kinetics of carbon monoxide binding to cytochrome P450BM-3 in the presence and absence of substrate has been investigated using flash photolysis. The second order kinetics for CO association with the substrate-free form of the protein appear biphasic. Deconvolution into two exponentials yields fast and slow rate constants of 11.1 +/- 0.6 x 10(6) M-1 s-1 and 3.5 +/- 0.2 x 10(6) M-1 s-1, respectively with 52% of the signal being attributed to the fast phase. Interestingly, upon binding of a substrate such as laurate, the second order kinetics become monophasic, with a value of 3.5 x 10(6) M-1 s-1, which are similar to the slow rate found in the substrate-free form of the protein. We have also examined the geminate CO rebinding kinetics in the presence and absence of various substrates. In the substrate-free form of the overall geminate yield is 30%, and addition of a substrate increases the geminate yield to roughly 50%. Both the substrate-free and substrate-bound forms exhibit complex geminate kinetics which cannot be described by a simple three-state kinetic model. Extension of this model to include four states is required. The addition of substrate causes an increase in the geminate rate constants resulting in a larger geminate amplitude when compared to the substrate-free form. There is also evidence for a correlation between the volume occupied by the substrate and the geminate rate constants. These results are discussed in terms of substrate-dependent conformational changes in cytochrome P450BM-3 and the overall energy landscape of the hemoprotein which couples to conformer equilibria.

Thermodynamic characterization of the interaction between cytochrome b5 and cytochrome c

In recent years many studies have been directed toward the elucidation of the interaction mechanisms within protein-protein complexes. One of the best studies protein-protein complexes has been the cytochrome b5 and cytochrome c electron transfer pair. Thermodynamic information about the association process has been obtained through methods which indirectly measure the binding between the proteins. We report here the use of Isothermal Titration Calorimetry to characterize the association of Rat cytochrome b5 and Horse cytochrome c. The association is accompanied by an unfavorable enthalpy change (+1.0 +/-0.1 Kcal/mole) and a large stabilizing change in entropy (33.9 +/-0.6 eu).

Continuing ischemic damage after acute middle cerebral artery infarction in humans demonstrated by short-echo proton spectroscopy

BACKGROUND AND PURPOSE

Proton MR spectroscopy is a noninvasive method of monitoring in vivo metabolite concentration changes over time. The aim of this work was to study the ischemic penumbra in humans by measuring the metabolic changes that occur after a middle cerebral artery territory infarction.

METHODS

Diagnostic MRI and short-echo time MR spectroscopy were performed on a 1.5-T system. Localized proton MR spectroscopy was performed within the area of cerebral infarction and in a homologous area of the contralateral hemisphere. The residual water resonance in the spectra was removed with the use of the Hankel Lanczos singular value decomposition method, after which peak area estimates were obtained by means of the variable projection time domain fitting analysis. The unsuppressed water signal was used as an internal concentration standard. Ten patients with acute middle cerebral artery infarction were studied within 28 hours of stroke onset and followed up for a period of up to 3 months.

RESULTS

Significant changes were seen in the initial spectra from the infarct compared with the contralateral spectra. Lactate, a marker of anaerobic metabolism, was present within the infarct but not detected in the contralateral hemisphere. N-Acetyl aspartate, a neuronal marker, and total creatine were significantly reduced. The initial choline signal, arising from choline-containing compounds within the cell and cell membrane, remained unchanged in the infarct core compared with the contralateral hemisphere. Further reductions in N-acetyl aspartate and total creatine concentrations occurred within the first week. A fall in the lactate concentration was seen within the infarct core during the first 7 to 10 days. Similar reductions in the choline concentration were observed during this period.

CONCLUSIONS

The demonstration of the continuing loss of cerebral metabolites within an infarct region suggests that further cell loss occurs up to 10 days after infarction. The continuing loss of neurons may represent continued ischemic damage after middle cerebral artery infarction.

Acute stroke in South Ayrshire: comparative study of pre and post stroke units

In September 1993 arrangements for managing acute stroke victims in South Ayrshire changed with the opening of a six bedded Acute Stroke Unit and a fifteen bedded Rehabilitation Stroke Unit. Previously all such patients were managed within general medical wards with a few being managed in geriatric assessment and rehabilitation facilities. This study compares the management and outcome from acute stroke before and after the establishment of these new Units. Fifty-eight patients' medical, nursing and paramedical records were studied for the period of investigation in 1992 and 68 for the same period in 1993. There was no significant difference in the age of the patients admitted or in the degree of neurological or functional impairment at the time of admission. There was a reduction in mortality from 37.9% in 1992 to 22.0% in 1993. This was not accomplished by an increase in the number of survivors requiring long term institutional care and there was no significant difference in the degree neurological or functional impairment at the time of discharge. A variety of specific management issues were also addressed by the study and in all areas there were improvements in the quality of care received by this group of patients in 1993. This study supports the view that management of acute stroke victims in specifically designated Stroke Units has a beneficial effect on outcome and quality of care.

Mutational analysis of the cucumber necrosis virus coat protein gene

A series of frameshift, deletion, and inversion mutations were made in the coat protein (CP) gene of the icosahedral cucumber necrosis tombusvirus (CNV) to investigate the role of the CP protruding (P) domain in the production of virus particles and, also, to investigate the basis for the accumulation of CP deletion derivatives previously reported in plants inoculated with PD(-), a P-domainless CNV CP mutant. P-domainless coat protein subunit could be detected in extracts of CP mutant-infected plants; however, virus-like particles could not, suggesting that the P domain is essential for tombusvirus particle assembly and/or stability. In addition, each of the P-domain mutants analyzed invariably produced coat protein deletion derivatives in infected plants whereas shell domain mutants rarely produced deletion derivatives. Finally, P-domain inversion and deletion mutants accumulated deletion derivatives very rapidly in comparison to P-domain frameshift mutants. Protoplast studies show that PD(-) RNA inoculum does not undergo further deletion in infected protoplasts, suggesting that PD(-) CP deletion derivatives preferentially accumulate in plants because they have a greater capacity for cell-to-cell movement.

Magnetic resonance neurography of the median nerve

A magnetic resonance imaging sequence, combining fat and flow suppression with T2 weighting, has been used to produce high conspicuity images of the median nerve within the carpal tunnel. Standard maximum intensity projection techniques were then used to produce three-dimensional (3D) reconstructions of the nerve. Comparison of 3D projections with the wrist in a neutral position and wrist flexed at 45 degrees depicted changes in the shape and course of the median nerve through the carpal tunnel of normal volunteers. In some cases of carpal tunnel syndrome evidence of a localized compression was observed. A 3D image of a nerve may help in the diagnosis of peripheral neuropathy and be an aid to surgery of or near major nerves.

Involvement of the cucumber necrosis virus coat protein in the specificity of fungus transmission by Olpidium bornovanus

Cucumber necrosis (CNV) and the cherry strain of tomato bushy stunt (TBSV-Ch) are tombusviruses which differ in transmissibility by the fungus Olpidium bornovanus (Sahtiyanci) Karling (= O. radicale Schwartz and Cook). Zoospores acquire and transmit CNV, but not TBSV-Ch, in the in vitro manner. To assess the role of the coat protein in the specificity of fungus transmission, reciprocal exchanges were made between the coat protein genes of these two viruses in full-length infectious cDNA clones. Virions containing a modified TBSV-Ch genome with the CNV coat protein gene were efficiently transmitted, but those containing a modified CNV genome with the TBSV-Ch coat protein gene were not. This is the first direct demonstration for the role of a viral coat protein in the specificity of transmission by a fungus.

Cognitive and neuropsychological response asymmetries for adults on the left-right seating axis

Six studies of the relationship between classroom seating and information processing were conducted with adult subjects. Findings converged to support a hemisphericity-based explanation of effects with right-side-sitters more inclined to a response style associated with the right hemisphere--perhaps, less analytical or less cautious in responding (Experiments 1-4), more "artistic" (Experiment 5), and less lateralized (Experiment 6), and vice versa for left side sitters. First, using incidental memory tasks, subjects (N = 164) with a right side seating preference (i.e., to the speaker's left side) were found, in their test-taking behavior, to respond more positively to inaccurate distractor words (Experiments 1 and 2), particularly those with an ambiguous semantic reference (Experiment 3). For different levels of processing, seating location did not influence auditory memory (Experiments 1 and 2) but right side sitters showed enhanced visual memory for accurate words (Experiment 3). In a sample of 366 subjects, males selecting right side seating were less successful on multiple-choice test performance (Experiment 4), but there were no Side differences in test taking speed or review time. In a sample of 286 subjects (Experiment 5), personality measures on the Vocational Preference Inventory revealed right sitters scored higher on the "Artistic" scale and on femininity on the Masculine-Feminine scale. The final study (N = 90) revealed reduced dichotic processing on verbal tasks (digits and voiced CVs) for right side sitters. Implications are discussed.

Symptomatology and movement of a cucumber necrosis virus mutant lacking the coat protein protruding domain

A cucumber necrosis virus (CNV) mutant which lacks the coding sequence for the coat protein protruding domain, PD(-), was constructed by site-directed mutagenesis of an infectious CNV cDNA clone, pK2/M5 (wild-type, 4701 nt). Transcripts of PD(-) were infectious on Nicotiana clevelandii; however, local lesions produced were significantly smaller than those on the corresponding leaves of plants inoculated with wild-type transcript. In addition, systemic symptoms took 8 to 12 days longer to develop than in wild-type-inoculated plants. The distinctive PD(-) phenotype was lost when N. clevelandii was inoculated with sap from systemically infected leaves of PD(-) transcript-inoculated plants and was replaced by symptoms that were the same as those with wild-type infections. High-molecular-weight RNA from mutant- and wild-type-infected plants was extracted and analyzed by Northern blotting. Full-length PD(-) RNA could be detected only rarely in RNA preparations from transcript-inoculated leaves; a further deleted, stable RNA species of approximately 3800 nucleotides was found in preparations from systemically infected leaves of PD(-) transcript- and sap-inoculated plants. CNV coat protein could not be detected by ELISA or ISEM in PD(-)-infected leaf material. The ca. 3.8-kb RNA, when cloned and sequenced, was found to have lost all but 74 of the 1140 nucleotides of the CNV coat protein open reading frame. Transcripts from this coat proteinless CNV cDNA clone produced wild-type symptoms on N. clevelandii. It would appear that CNV is able to replicate and move systemically, in both transcript-inoculated and sap-inoculated N. clevelandii, in the absence of a functional coat protein. Additionally, mechanical transmission of this virus occurs in the absence of the coat protein; however, such transmission is less efficient when compared with wild-type infections.

Mycoflora of strawberry in Ontario

Mycelial fungi associated with leaves, flowers, and fruits of strawberry (Fragaria × ananassa Duchesne) were monitored in a field plot from August 1986 to July 1987. The principal fungi found on leaves of various developmental stages were Alternaria alternata, Botrytis cinerea, Cladosporium spp., Colletotrichum dematium, Coniella fragariae, Epicoccum purpurascens, Gliocladium roseum, Gloeosporium sp., Gnomonia comari, Penicillium spp., Trichothecium roseum, and Verticillium spp. A majority of the fungi were observed more frequently on leaves that were washed and then plated on agar media than on leaves that were plated without washing. Trichothecium roseum, however, was found mainly on the unwashed leaves. Principal fungi on calyces, petals, and fruits were A. alternata, B. cinerea, Gloeosporium sp., Pencillium spp., T. roseum, and Verticillium spp. Other fungi variously found on the flowers and fruits included Rhizopus stolonifer, Paecilomyces spp., C. dematium, and Fusarium spp. Many of the fungi found frequently on the strawberry plants were present at most or all stages of development and decline of the various plant organs. The mycofloral observations are discussed in relation to the biocontrol of strawberry diseases. Key words: strawberry, mycoflora, Botrytis cinerea, population dynamics.

Intermediates in guanidine-HC1 unfolding of glutamine synthetase from the extreme thermophile, Bacillus caldolyticus

Glutamine synthetase is expressed in Bacillus caldolyticus as two isoforms that differ in physico-chemical and regulatory properties. Biphasic kinetics of thermal denaturation of E-I and E-II (Merkler, D.J., et al (1987) Biochemistry 26, 7805), suggested the formation of intermediates. CD spectral changes of E-II induced by guanidine-HC1 clearly indicate a three-state pathway for unfolding (N----I----D). Refolding of E-II from 6 M GuHCl led to only 15% recovery of activity, compared to greater than or equal to 90% with E-I.

Enhanced analysis of sulfonated azo dyes using liquid chromatography/thermospray mass spectrometry

Modifications to a thermospray vaporizer probe and ion source have been made that enhance ion evaporation resulting in increased sample ion current. These modifications include restricting the thermospray vaporizer exit orifice and the addition of a needle-tip repeller electrode to the thermospray ion source. The interaction and effect of probe-tip size, repeller voltage, and flow rate on sulfonated azo dye detection are reported. An increase in signal response for sulfonated azo dyes was observed. An efficient chromatographic separation procedure for sulfonated azo dyes, which is compatible with thermospray mass spectrometric detection, is also presented. Five disulfonated azo dyes were separated and detected by using selected ion monitoring. Mass spectra of disulfonated dyes show a number of molecular ions and adduct ions that provide unequivocal molecular weight information.

Pharmacokinetics of Amonafide in dogs

Amonafide, one of a series of imide derivatives of 1,8-naphthalic acid synthesized by Brana et al. has shown significant antitumor activity against a variety of experimental tumors, including L1210 leukemia and P388 leukemia. Along with the clinical trial at our institute, we have studied the disposition of Amonafide in dogs by HPLC and fluorometry. Six dogs received Amonafide i.v. at 5 mg/kg (100 mg/m2) over 15 min; three were sacrificed at 6 h, and three at 24 h. The initial plasma t1/2 of Amonafide was 2.4 +/- 0.4 min, the intermediate t1/2, 26.8 +/- 3.7 min, and the terminal t1/2, 21.7 +/- 4.0 h. The peak plasma concentration achieved was 6.3 +/- 1.7 micrograms/ml. The average apparent volume of distribution was 12.84 +/- 0.54 1/kg, and the total clearance was 0.56 +/- 0.16 1/kg/h. In 24 h, 9.5% +/- 0.2% of the administered dose was excreted in the urine as the parent drug, and 7.4% +/- 1.4% in the bile in 6 h. Amonafide penetrated the CSF readily and achieved the highest concentration 20-25 min after administration, which was 30% of the concurrent plasma level. Amonafide underwent extensive metabolism to at least three major metabolites and two or more minor metabolites. The alpha and beta plasma t1/2 of the major metabolite, an N-oxide derivative, were 24.8 min and 28.6 h, respectively. The 24-h cumulative urinary excretion was 1.4% of the injected dose, and the cumulative biliary excretion was 16.7% in 6 h. At autopsy 6 h after dosing, the liver contained the highest percentage (0.23% of administered dose) of unchanged Amonafide, followed by the stomach (0.11%), lung (0.04%), kidney (0.04%), and pancreas (0.03%). The rest of the major organs retained less than 0.02% of the Amonafide dose. One day after dosing, no detectable amount of Amonafide was found in any of these tissues, indicating that Amonafide appears to be extensively metabolized and not significantly retained in the dog.

Pharmacokinetics and metabolism of the antitumor drug amonafide (NSC-308847) in humans

Pharmacokinetics and urinary excretion of Amonafide (5-amino-2-[2-(dimethylamine)ethyl]-1H-benz[de]isoquinoline-1,3-(2H)- dione) were examined in seven patients who were administered 400 mg/m2 of drug as a 30-min infusion on a daily schedule for 5 consecutive days. Amonafide concentrations in plasma and urine were determined using reversed phase HPLC. Amonafide was eliminated from plasma with a terminal half-life of 3.5 hr. Renal excretion accounted for 23% of the administered dose. Amonafide pharmacokinetic parameters after the initial dose (day 1) were similar to those calculated after the fifth daily dose. Amonafide undergoes a significant amount of metabolism and eight urinary metabolites have been identified using a thermospray liquid chromatography-mass spectrometry (LC/MS) technique. Various N-acetylated species appear to be the major metabolites, although no evidence of N-acetylation was found in urine obtained from two patients. Two of the primary metabolites, the N(N5)-acetyl and N'(N1)-oxide metabolites of Amonafide, were tested in vitro for cytotoxicity against P388 murine leukemia cells. In this test system, the N-acetyl metabolite was observed to be only slightly less cytotoxic than the parent compound. The N'-oxide of Amonafide, however, proved to be inactive. These results are discussed together with the pharmacokinetic and metabolism data of this new investigational antitumor drug.