High-throughput ultra-high-performance liquid chromatography/tandem mass spectrometry quantitation of insulin-like growth factor-I and leucine-rich alpha-2-glycoprotein in serum as biomarkers of recombinant human growth hormone administration.

Insulin-like growth factor-I (IGF-I) is a known biomarker of recombinant human growth hormone (rhGH) abuse, and is also used clinically to confirm acromegaly. The protein leucine-rich alpha-2-glycoprotein (LRG) was recently identified as a putative biomarker of rhGH administration. The combination of an ACN depletion method and a 5-min ultra-high-performance liquid chromatography/tandem mass spectrometry (uHPLC/MS/MS)-based selected reaction monitoring (SRM) assay detected both IGF-I and LRG at endogenous concentrations. Four eight-point standard addition curves of IGF-I (16-2000 ng/mL) demonstrated good linearity (r(2) = 0.9991 and coefficients of variance (CVs) <13%). Serum samples from two rhGH administrations were extracted and their uHPLC/MS/MS-derived IGF-I concentrations correlated well against immunochemistry-derived values. Combining IGF-I and LRG data improved the separation of treated and placebo states compared with IGF-I alone, further strengthening the hypothesis that LRG is a biomarker of rhGH administration. Artificial neural networks (ANNs) analysis of the LRG and IGF-I data demonstrated an improved model over that developed using IGF-I alone, with a predictive accuracy of 97%, specificity of 96% and sensitivity of 100%. Receiver operator characteristic (ROC) analysis gave an AUC value of 0.98. This study demonstrates the first large scale and high throughput uHPLC/MS/MS-based quantitation of a medium abundance protein (IGF-I) in human serum. Furthermore, the data we have presented for the quantitative analysis of IGF-I suggest that, in this case, monitoring a single SRM transition to a trypsin peptide surrogate is a valid approach to protein quantitation by LC/MS/MS.

Late auditory magnetic sources may differ in the left hemisphere of schizophrenic patients. A preliminary report.

We recorded magnetoencephalographic auditory evoked fields from the left and right hemispheres of six medicated, paranoid schizophrenic subjects and six normal controls. The magnetic field data were used in estimating the location, orientation, and depth of the source generating the 100-millisecond latency evoked field component (M100). The M100 latencies were slightly shorter than simultaneously recorded vertex electroencephalographic evoked potential N100 latencies, suggesting that magnetoencephalographic and electroencephalographic recordings were examining slightly different aspects of the source(s). The M100 sources demonstrated substantial interhemispheric asymmetry in normal controls, and were located more posteriorly, with more nearly vertical orientations, over the left hemisphere. The M100 sources in schizophrenics did not exhibit the same interhemispheric asymmetry. Left hemisphere source orientation differed significantly between normal controls and schizophrenics. Discriminant function analysis correctly classified normal controls and schizophrenics at 100% using the conservative jackknife procedure on the basis of left hemisphere orientation alone. Our findings, while preliminary, support altered left hemisphere function, or possibly structure, in this group of schizophrenic subjects, and suggest that magnetoencephalographic recordings may be a useful research method in this major mental illness.

Magnetic source imaging evidence of sex differences in cerebral lateralization in schizophrenia.

BACKGROUND: It has been postulated that schizophrenia represents a disorder of anomalous cerebral lateralization. This study is a replication of earlier preliminary findings using a multichannel neuromagnetometer, suggesting altered lateralization in schizophrenia in male subjects, with an extension of the findings to female subjects. METHODS: We used magnetoencephalography-based magnetic source imaging to estimate the intracranial location of the 100-millisecond latency auditory-evoked field component (M100) in both left and right hemispheres of 20 patients with paranoid schizophrenia and 20 controls without schizophrenia. Neuroanatomical data were obtained by means of magnetic resonance imaging, from which we segmented and computed volumes of both total brain and left and right superior temporal gyri. RESULTS: Locations of M100 source were compatible with neuronal generators located in the transverse gyri of Heschl on the superior temporal gyri in both study groups; M100 sources were asymmetric in all the control subjects. The male patient subgroup exhibited significantly less asymmetry than the control group, while the female patient subgroup actually showed significantly more asymmetry. The male patient subgroup generally had smaller superior temporal gyri than the control group. No evidence of total brain volume differences was observed. CONCLUSIONS: Our findings support previous magnetoencephalography-based studies suggesting anomalous cerebral lateralization in schizophrenia. Further, in extending our studies to female patients, our data suggest that the nature of this anomaly is sex specific, a finding that, to our knowledge, has not previously been reported.

N-deethylation and N-oxidation of etamiphylline: identification of etamiphylline-N-oxide in greyhound urine by high performance liquid chromatography-mass spectrometry.

Millophyline-V, (etamiphylline camsylate) was administered intramuscularly to two racing greyhounds at a dose of 10 mg kg(-1). Unhydrolysed pre- and post-administration urine samples were extracted using mixed mode solid phase extraction (SPE) cartridges, the basic isolates derivatised as trimethylsilyl ethers and analysed by positive ion electron ionisation gas chromatography-mass spectrometry (GC/EI+/MS). The parent drug and one metabolite, N-desethyletamiphylline, were detected in urine for up to 72 h. For semi-quantification, urine samples were extracted on-line using a Prospekt sample handler. The analytes retained on the C2 SPE cartridge were eluted by the mobile phase directly on to the analytical high performance liquid chromatography column and analysed by positive ion atmospheric pressure chemical ionisation (LC/APCI+) MS in the multiple selective-ion recording mode. A major peak containing both ions (m/z) 280 and (m/z) 252 was observed. Full scan LC/APCI+/MS of the unknown indicated that the ion at (m/z) 280 was formed by the loss of an oxygen atom [MH+ -->(MH+-O)]. Samples were analysed by positive ion electrospray ionisation LC/MS on two different instruments and the unknown compound was identified as an N-oxide of the tert. nitrogen atom of the 2-(diethylamino)ethyl substituent on N7 of the theophylline nucleus. This compound has not been reported previously either as an in vivo or in vitro metabolite of etamiphylline in any species. Thermal decomposition of the N-oxide could lead to an increase the detection period of the parent drug during routine GC/MS screening of post-competition greyhound urine samples.

Magnetoencephalography: applications in psychiatry.

Magnetoencephalography (MEG) measures the extracranial magnetic fields produced by intraneuronal ionic current flow within appropriately oriented cortical pyramidal cells. Based upon superconducting quantum interference device technology operating at liquid helium temperatures (4 K), MEG offers excellent temporal and spatial resolution for selected sources, and complements information obtained from electroencephalograms and other functional imaging strategies. Current instrumentation permits recording up to several hundred channels simultaneously with head-shaped dewars, although the cost of such systems is high. The fact that magnetic fields fall off with the square of the distance from the source is both a benefit (when separating activity in the two hemispheres) and a limitation (when attempting to record deep sources). The lack of skin contact facilitates using MEG to record direct current and very high frequency (> 600 Hz) brain activity. The clinical utility of MEG includes presurgical mapping of sensory cortical areas and localization of epileptiform abnormalities, and localization of areas of brain hypoperfusion in stroke patients. MEG studies in psychiatric disorders have contributed materially to improved understanding of anomalous brain lateralization in the psychoses, have suggested that P50 abnormalities may reflect altered gamma band activity, and have provided evidence of hemisphere-specific abnormalities of short-term auditory memory function.

Schizoaffective disorder: evidence for reversed cerebral asymmetry.

BACKGROUND: Schizoaffective disorder is one of the most severe of the affective psychoses, but its pathophysiology is poorly understood. Because cerebral lateralization may be disturbed in psychotic disorders generally, studies examining cerebral asymmetry may improve understanding of the neurobiology specific to schizoaffective disorder. This study examines cerebral lateralization in this patient population using magnetic source localization. METHODS: We studied 16 subjects with schizoaffective disorder and 16 controls. Magnetic source localization was used to identify the location of the 20 msec latency somatosensory evoked field component (M20). RESULTS: In control subjects, the source location was further anterior in the right hemisphere. The subjects with schizoaffective disorder were reverse lateralized. CONCLUSIONS: The findings of a reversed asymmetry of the M20 in patients with schizoaffective disorder suggest an anatomical shift in the placement of the post central gyrus in this disorder, compatible with a disorder of cerebral lateralization. Whether this finding converges or diverges with measurement of the M20 in other psychotic disorders will require further investigation.

EEG correlates of methylphenidate response among children with ADHD: a preliminary report.

BACKGROUND: Recent electrophysiologic studies have found fairly consistent differences between children with attention-deficit/hyperactivity disorder (ADHD) and age-matched control subjects. The present study examined electroencephalogram (EEG) changes associated with a double blind, placebo-controlled administration of methylphenidate among children with ADHD. METHODS: Subjects were 10 children, ages 8 to 13, with a primary diagnosis of ADHD. Brain electrical activity was recorded with 7 electrodes in the frontal, central, and midline areas during baseline and cognitive activation conditions. RESULTS: Repeated-measures ANOVAs indicate that children exhibiting a positive medication response had reductions of theta and alpha as well as increased beta in the frontal regions, while nonresponders showed the opposite pattern (p < .05). Significant correlations between improvement on a vigilance task and changes in beta activity in the frontal electrodes emerged as well. CONCLUSIONS: These preliminary findings indicate that there are different electrophysiologic correlates to methylphenidate among ADHD children who are medication responders and nonresponders.

Fine structure of the auditory M100 in schizophrenia and schizoaffective disorder.

BACKGROUND: Several studies have demonstrated anomalous asymmetry of the 100-msec latency auditory-evoked field (M100) in schizophrenia. Recent evidence suggests this may be a compound component, however. Our study examines the localization of two M100 subcomponents in patients with schizophrenia and schizoaffective disorder. METHODS: Magnetoencephalographic recordings of auditory-evoked fields were obtained for 14 subjects with schizophrenia, 12 with schizoaffective disorder, and 23 control subjects. Two M100 subcomponents were identified and localized in each hemisphere. RESULTS: Both patient groups exhibited different lateralization compared with control subjects, with the second subcomponent tending to be less lateralized. CONCLUSIONS: The second subcomponent may be the major contributor to previously reported laterality differences. Future studies might benefit by separating M100 subcomponents so that specific functions could be addressed.

The thalamus and the schizophrenia phenotype: failure to replicate reduced volume.

BACKGROUND: Thalamic abnormalities resulting in impaired attention and information processing may form a foundation for cognitive and perceptual disturbances in schizophrenia. Measurements of the thalamus in patients with schizophrenia have shown reductions relative to normal comparison subjects. METHODS: In the current project, magnetic resonance images of the brain were obtained in 10 male and 11 female subjects with paranoid-type schizophrenia, and 15 male and 12 female normal comparison subjects. Total brain and bilateral thalamic volumes were calculated. RESULTS: There were no significant diagnosis, hemisphere, or gender differences in thalamic volumes. CONCLUSIONS: Structural thalamic abnormalities are not likely to universally and parsimoniously explain the schizophrenia phenotype. Abnormal thalamic size in patients with schizophrenia should be understood as reflecting one of several possible structural abnormalities contributing to production of the schizophrenia phenotype, but must be regarded with caution unless paired with functional studies.

Source origin of a 50-msec latency auditory evoked field component in young schizophrenic men.

We recorded auditory evoked magnetic fields in response to 128 15-msec duration 1-KHz tone pips from both hemispheres of 6 young schizophrenic men. Auditory evoked potentials were recorded conventionally from a vertex lead. The approximately 50-msec latency component was identified in both the magnetic (M50) and electroencephalographic (EEG) (P50) recordings. Isofield topographical contour maps were used to estimate M50 source location and depth. Magnetic resonance imaging was used to identify the neuroanatomical structure(s) present at the estimated source location. M50 sources appeared to reside in the planum temporale in both left and right hemispheres in all subjects. Normal inter-hemispheric asymmetry (with respect to external bony landmarks) of the M50 source was not found in this patient group. Additionally, left (but not right) hemisphere source anatomy differed in several respects from data previously reported in normals.

Bipolar disorder: anomalous brain asymmetry associated with psychosis.

OBJECTIVE: Anomalous cerebral asymmetry in schizophreniform disorders has been described, but its presence in psychotic mood disorders has not been established. Measures of cerebral asymmetry may distinguish patients with psychotic mood disorders from those with nonpsychotic mood disorders and from comparison subjects. To test this hypothesis, the authors examined functional cerebral asymmetry by using a metric based on magnetic source imaging. METHOD: A total of 33 subjects participated. Nine were patients with bipolar I disorder and a negative history of psychotic symptoms during mood disorder episodes, 12 were patients with bipolar I disorder and a positive history of psychotic symptoms during mood disorder episodes, and 12 were nonpsychiatric comparison subjects. Equivalent current dipole generators in both hemispheres were estimated for the 20-msec-latency somatosensory evoked field (M20) component produced by stimulation of the contralateral median nerve. RESULTS: The comparison subjects demonstrated asymmetry in anterior-posterior equivalent current dipole locations of the M20 (right anterior to left), and the bipolar subjects with no history of psychosis were similarly asymmetric. The bipolar subjects with a history of psychosis during mood episodes, however, demonstrated a reversal of cerebral asymmetry of the M20 (left anterior to right). CONCLUSIONS: Cerebral lateralization of the M20 distinguished bipolar subjects with psychosis from those without psychosis and comparison subjects. The M20 is generated in area 3b of the postcentral gyrus. These findings suggest anatomical displacement of the postcentral gyrus in psychotic disorders and support the hypothesis that anomalous cerebral asymmetry is a feature of psychotic disorders generally, including psychotic mood disorders.

Sex-specific expression of Heschl's gyrus functional and structural abnormalities in paranoid schizophrenia.

OBJECTIVE: Evidence supports abnormal temporal lobe structure and function in schizophrenia. Some abnormalities, particularly involving the auditory cortex, appear to be sex specific. These findings were extended to anatomical and physiological descriptors. METHOD: The authors quantified the volume, surface area, and three-dimensional location of Heschl's gyri on magnetic resonance imaging (MRI) images of 21 patients with paranoid schizophrenia and 24 healthy comparison subjects. Neuromagnetic localizations of the 100-msec latency auditory evoked field (M100) were compared with MRI-determined locations of Heschl's gyri, computed as the geometric center of mass of the volume. RESULTS: Volumetric measures revealed small Heschl's gyri only in male patients. Asymmetry was found in the location of the Heschl's gyrus centroid (more anterior on the right) across all groups. Male comparison subjects had M100 locations posterior to the Heschl's gyrus centroid in the left hemisphere and close to the Heschl's gyrus centroid on the right, while male patients had M100 sources anterior to the Heschl's gyrus centroid on the left. All women had M100 locations posterior to the Heschl's gyrus centroid on the left and anterior to it on the right. CONCLUSIONS: These results demonstrate that some temporal lobe abnormalities in schizophrenia are sex specific. They also suggest that the anomalous lateralization of the auditory evoked field cannot be explained by a shift in the underlying anatomy, since the anatomical substrate is lateralized in both comparison subjects and patients of both sexes. These findings may indicate a sex-specific functional reorganization in the auditory cortex in schizophrenia.

MEG based brain laterality: sex differences in normal adults.

Magnetoencephalographic (MEG) auditory evoked fields produced by short tone pips were recorded from 34 normal adults (17 males, 17 females) and the 100 msec latency component (M100) localized in left and right hemispheres. Absolute M100 location in the antero-posterior dimension was calculated for each subject. M100 sources were significantly further anterior in the right hemisphere of males. Magnetic resonance (MR) based anatomy of the superior temporal gyri (STG) in a subset of 17 subjects showed that in the left STG of both males and females M100 sources were located approximately midway on the STG. In the right hemisphere of males, however, M100 sources were significantly further anterior on the STG than was the case for females. The findings are compatible with a sex based difference in right STG functional anatomy, with evidence of greater hemispheric lateralization in males compared to females based upon a predominantly right hemisphere contribution.

Auditory M100 component 1: relationship to Heschl's gyri.

This study was designed to localize the neuroanatomic generator of the 100 ms latency magnetic auditory evoked field (EF) component (M100) activated by an unattended tone pip. Magnetic EFs in response to 25 ms duration, 90 dB, 1 kHz tone pips were recorded from both hemispheres of nine normal adults, five males and four females, using a seven-channel second-order gradiometer. The source of the M100 was estimated, with confidence intervals, by a least squares based inverse solution algorithm. Magnetic resonance (MR) images of the brain were acquired with a 1.5 T system using a standard head coil. The superior temporal gyri (STG) were manually segmented from 1.7 mm thick coronal images, and the superior surfaces were then rendered from the 3-D volume data. Translation and rotation matrices were identified to locate the magnetoencephalography (MEG) determined sources within the reconstructed STGs. This population of 18 STGs in 9 individuals demonstrated two transverse gyri in 4 of 9 left hemispheres, and 5 of 9 right hemispheres. All 9 left hemisphere M100 sources were in or included Heschl's gyrus(i) in the confidence intervals. Seven of the 9 included Heschl's gyrus(i) on the right: the remaining two, both males, had sources slightly anterior to Heschl's gyrus(i). We conclude that all M100 source location estimates were compatible with an auditory koniocortex source in or adjacent to Heschl's gyri.

Neuromagnetic alpha suppression during an auditory sternberg task. Evidence for a serial, self-terminating search of short-term memory.

Reaction times (RT) during the Sternberg memory paradigm generally increase with memory set size, but do not differ for positive and negative probe stimuli. Sternberg proposed that this indicated that short-term memory (STM) scanning is both exhaustive and serial. However, this notion has received much criticism, primarily because RT must also reflect response selection factors. Magnetoencephalographic (MEG) recordings of auditory alpha-suppression have previously demonstrated that suppression duration is correlated with set size, potentially providing a physiological index of memory scanning time related specifically to sensory cortices. The current study expands earlier research into this metric by separately analyzing positive and negative probes. Thirteen normal adults participated in an auditory Sternberg paradigm. Pure tones were presented in memory set/probe combinations where the probe had a 50 percent chance of being within the memory set, and RT and accuracy were measured. Magnetic alpha-band activity (8-12 Hz) was quantified for pre- and post-stimulus regions. Although RT did not differ for positive and negative probes, alpha-suppression duration was greater for negative probes than positive ones, potentially indicating that scanning time was slightly faster in the positive condition. This may indicate that STM scanning is serial, but self-terminates when matching occurs.

Sequential source of the M100 exhibits inter-hemispheric asymmetry.

The most prominent auditory evoked field component occurs at about 100 ms latency and is termed the M100. We recorded M100 data from 20 subjects, in both hemispheres. We modeled the generators with a single equivalent current dipole in a 10 ms sliding window from 0 to 245 ms post-stimulus. A residual error curve was plotted, and a search for local minima identified two latencies at about 75 and 100 ms. In the left hemisphere, the early generator was about 6 mm above the later source; in the right hemisphere the early source was about 3 mm above the later, and 11 mm posterior. The M100 is a compound source, and the model may provide additional information in cases with reported laterality differences.

Sex differences in the refractory period of the 100 ms auditory evoked magnetic field.

The 100 ms latency auditory evoked magnetic response (M100) has been implicated in the earliest stage of acoustic memory encoding in the brain. Sex differences in this response have been found in its location within the brain and its functional properties. We recorded the M100 in 25 adults in response to changes in interstimulus interval of an auditory stimulus. Response amplitudes of the M100 were used to compute a measure of the M100 refractory period, which has been proposed to index the decay time constant of echoic memory. This time constant was significantly longer in both hemispheres of the female participants when compared to the male participants. Possible implications of this for behavioral sex differences in human memory performance are discussed.

Developmental changes in refractoriness of the neuromagnetic M100 in children.

Considerable evidence exists for developmental changes in latency and amplitude of the auditory evoked potential termed N100. However, it is widely recognized that the N100 wave comprises multiple, temporally overlapping neural generators, and few data are available addressing either individual generator development or mechanisms behind such change. Using magnetoencelphalographic (MEG) measurements of the magnetic analog of the N100 termed the M100, which derives primarily from supra-temporal auditory generators, it is demonstrated here that changes in the response of that waveform to manipulation of interstimulus interval (ISI) occur between the ages of 6 and 18 years of age.

Auditory evoked magnetic fields in adults with fragile X syndrome.

Hyper-reactivity and anxiety to sensory stimuli have been described in patients with fragile X syndrome (FXS), and may be related to abnormal processing in afferent sensory pathways. We used magnetoencephalography (MEG) to measure auditory responses to pure tones in 11 adults with FXS and 11 non-FXS subjects. The amplitude for the N100m auditory evoked field component was significantly higher for patients with FXS than for subjects. FXS subjects also had less lateralized N100m anterior-posterior dipole locations. These data may suggest that more neurons are activated by acoustic stimuli in FXS, consistent with subjective experience of increased stimulus intensity. Anomalous cerebral lateralization may suggest an early critical window for effects on neocortical development of the fragile X mental retardation protein (FMRP) produced by the FMR1 gene in individuals with FXS.

Magnetic auditory source imaging in macaque monkey.

We recorded magnetic auditory evoked fields from the left hemisphere of a 2-year-old 3.4 kg Macaca nemestrina monkey. Three separate components were isolated from each of three data sets with latencies of approximately 22 ms, 46 ms, and 130 ms after stimulus onset. The 46 ms latency component had clear extrema values and was selected for localization. Field values from 21 recording points were used to estimate the 3-D source location of the 46 ms latency component, termed the M46. High resolution MR images of the brain provided information for correlation of neuroanatomic structure with source location. The neuroanatomic source was found to lie in the superior aspect of the temporal lobes bilaterally. We believe the M46 is the macaque analog of the human M100. Recording of auditory evoked fields in nonhuman primates offers a valuable animal model for studying neurophysiology of human magnetoencephalographically (MEG) determined auditory sources.