Quantitative and large-format histochemistry to characterize peripheral artery compositional gradients.

The femoropopliteal artery (FPA) is a long, flexible vessel that travels down the anteromedial compartment of the thigh as the femoral artery and then behind the kneecap as the popliteal artery. This artery undergoes various degrees of flexion, extension, and torsion during normal walking movements. The FPA is also the most susceptible peripheral artery to atherosclerosis and is where peripheral artery disease manifests in 80% of cases. The connection between peripheral artery location, its mechanical flexion, and its physiological or pathological biochemistry has been investigated for decades; however, histochemical methods remain poorly leveraged in their ability to spatially correlate normal or abnormal extracellular matrix and cells with regions of mechanical flexion. This study generates new histological image processing pipelines to quantitate tissue composition across high-resolution FPA regions-of-interest or low-resolution whole-section cross-sections in relation to their anatomical locations and flexions during normal movement. Comparing healthy ovine femoral, popliteal, and cranial-tibial artery sections as a pilot, substantial arterial contortion was observed in the distal popliteal and cranial tibial regions of the FPA which correlated with increased vascular smooth muscle cells and decreased elastin content. These methods aim to aid in the quantitative characterization of the spatial distribution of extracellular matrix and cells in large heterogeneous tissue sections such as the FPA. RESEARCH HIGHLIGHTS: Large-format histology preserves artery architecture. Elastin and smooth muscle content is correlated with distance from heart and contortion during flexion. Cell and protein analyses are sensitive to sectioning plane and image magnification.

Contrasting brain patterns of writing-related DTI parameters, fMRI connectivity, and DTI-fMRI connectivity correlations in children with and without dysgraphia or dyslexia.

Based on comprehensive testing and educational history, children in grades 4-9 (on average 12 years) were diagnosed with dysgraphia (persisting handwriting impairment) or dyslexia (persisting word spelling/reading impairment) or as typical writers and readers (controls). The dysgraphia group (n = 14) and dyslexia group (n = 17) were each compared to the control group (n = 9) and to each other in separate analyses. Four brain region seed points (left occipital temporal gyrus, supramarginal gyrus, precuneus, and inferior frontal gyrus) were used in these analyses which were shown in a metaanalysis to be related to written word production on four indicators of white matter integrity and fMRI functional connectivity for four tasks (self-guided mind wandering during resting state, writing letter that follows a visually displayed letter in alphabet, writing missing letter to create a correctly spelled real word, and planning for composing after scanning on topic specified by researcher). For those DTI indicators on which the dysgraphic group or dyslexic group differed from the control group (fractional anisotropy, relative anisotropy, axial diffusivity but not radial diffusivity), correlations were computed between the DTI parameter and fMRI functional connectivity for the two writing tasks (alphabet and spelling) by seed points. Analyses, controlled for multiple comparisons, showed that (a) the control group exhibited more white matter integrity than either the dysgraphic or dyslexic group; (b) the dysgraphic and dyslexic groups showed more functional connectivity than the control group but differed in patterns of functional connectivity for task and seed point; and (c) the dysgraphic and dyslexic groups showed different patterns of significant DTI-fMRI connectivity correlations for specific seed points and written language tasks. Thus, dysgraphia and dyslexia differ in white matter integrity, fMRI functional connectivity, and white matter-gray matter correlations. Of clinical relevance, brain differences were observed in dysgraphia and dyslexia on written language tasks yoked to their defining behavioral impairments in handwriting and/or in word spelling and on the cognitive mind wandering rest condition and composition planning.

Neurochemical changes within human early blind occipital cortex.

Early blindness results in occipital cortex neurons responding to a wide range of auditory and tactile stimuli. These changes in tuning properties are accompanied by an extensive reorganization of the occipital cortex that includes alterations in anatomical structure, neurochemical and metabolic pathways. Although it has been established in animal models that neurochemical pathways are heavily affected by early visual deprivation, the effects of blindness on these pathways in humans is still not well characterized. Here, using (1)H magnetic resonance spectroscopy in nine early blind and normally sighted subjects, we find that early blindness is associated with higher levels of creatine, choline and myo-Inositol and indications of lower levels of GABA within the occipital cortex. These results suggest that the cross-modal responses associated with early blindness may, at least in part, be driven by changes within occipital biochemical pathways.

Brain activation during face perception: evidence of a developmental change.

Behavioral studies suggest that children under age 10 process faces using a piecemeal strategy based on individual distinctive facial features, whereas older children use a configural strategy based on the spatial relations among the face's features. The purpose of this study was to determine whether activation of the fusiform gyrus, which is involved in face processing in adults, is greater during face processing in older children (12-14 years) than in younger children (8-10 years). Functional MRI scans were obtained while children viewed faces and houses. A developmental change was observed: Older children, but not younger children, showed significantly more activation in bilateral fusiform gyri for faces than for houses. Activation in the fusiform gyrus correlated significantly with age and with a behavioral measure of configural face processing. Regions believed to be involved in processing basic facial features were activated in both younger and older children. Some evidence was also observed for greater activation for houses versus faces for the older children than for the younger children, suggesting that processing of these two stimulus types becomes more differentiated as children age. The current results provide biological insight into changes in visual processing of faces that occur with normal development.

Instructional treatment associated with changes in brain activation in children with dyslexia.

OBJECTIVE: To assess the effects of reading instruction on fMRI brain activation in children with dyslexia. BACKGROUND: fMRI differences between dyslexic and control subjects have most often involved phonologic processing tasks. However, a growing body of research documents the role of morphologic awareness in reading and reading disability. METHODS: The authors developed tasks to probe brain activation during phoneme mapping (assigning sounds to letters) and morpheme mapping (understanding the relationship of suffixed words to their roots). Ten children with dyslexia and 11 normal readers performed these tasks during fMRI scanning. Children with dyslexia then completed 28 hours of comprehensive reading instruction. Scans were repeated on both dyslexic and control subjects using the same tasks. RESULTS: Before treatment, children with dyslexia showed less activation than controls in left middle and inferior frontal gyri, right superior frontal gyrus, left middle and inferior temporal gyri, and bilateral superior parietal regions for phoneme mapping. Activation was significantly reduced for children with dyslexia on the initial morpheme mapping scan in left middle frontal gyrus, right superior parietal, and fusiform/occipital region. Treatment was associated with improved reading scores and increased brain activation during both tasks, such that quantity and pattern of activation for children with dyslexia after treatment closely resembled that of controls. The elimination of group differences at follow-up was due to both increased activation for the children with dyslexia and decreased activation for controls, presumably reflecting practice effects. CONCLUSION: These results suggest that behavioral gains from comprehensive reading instruction are associated with changes in brain function during performance of language tasks. Furthermore, these brain changes are specific to different language processes and closely resemble patterns of neural processing characteristic of normal readers.

Regional brain chemical alterations in young children with autism spectrum disorder.

OBJECTIVE: The authors evaluated regional brain chemistry for evidence of increased neuronal packing density in autism. METHODS: Forty-five 3- to 4-year-old children with autism spectrum disorder (ASD), 13 children with typical development (TD), and 15 children with delayed development (DD) were studied using dual-echo proton echoplanar spectroscopic imaging (32 x 32 matrix-1 cm(3) voxels) to measure brain chemical concentrations and relaxation times. Chemical quantification was corrected for tissue partial volume and relative measures of chemical relaxation (T(2r)) were calculated from the paired echoes. Measures from averaged and individual regions were compared using analysis of variance corrected for multiple comparisons. RESULTS: ASD subjects demonstrated reduced N-acetylaspartate (NAA) (-10%), creatine (Cre) (-8%), and myo-inositol (-13%) concentrations compared to TD controls and prolonged NAA T(2r) relative to TD (7%) and DD (9%) groups. Compared to DD subjects, children with ASD also demonstrated prolonged T(2r) for choline (10%) and Cre (9%). Regional analyses demonstrated subtle patterns of chemical alterations in ASD compared to the TD and DD groups. CONCLUSIONS: Brain chemical abnormalities are present in ASD at 3 to 4 years of age. However, the direction and widespread distribution of these abnormalities do not support hypothesis of diffuse increased neuronal packing density in ASD.

fMRI auditory language differences between dyslexic and able reading children.

During fMRI, dyslexic and control boys completed auditory language tasks (judging whether pairs of real and/or pseudo words rhymed or were real words) in 30 s 'on' conditions alternating with a 30 s 'off' condition (judging whether tone pairs were same). During phonological judgment, dyslexics had more activity than controls in right than left inferior temporal gyrus and in left precentral gyrus. During lexical judgment, dyslexics were less active than controls in bilateral middle frontal gyrus and more active than controls in left orbital frontal cortex. Individual dyslexics were reliably less active than controls in left insula and left inferior temporal gyrus. Dyslexic and control children differ in brain activation during auditory language processing skills that do not require reading.

Effects of a phonologically driven treatment for dyslexia on lactate levels measured by proton MR spectroscopic imaging.

BACKGROUND AND PURPOSE: Dyslexia is a language disorder in which reading ability is compromised because of poor phonologic skills. The purpose of this study was to measure the effect of a phonologically driven treatment for dyslexia on brain lactate response to language stimulation as measured by proton MR spectroscopic imaging. METHODS: Brain lactate metabolism was measured at two different time points (1 year apart) during four different cognitive tasks (three language tasks and one nonlanguage task) in dyslexic participants (n = 8) and in control participants (n = 7) by using a fast MR spectroscopic imaging technique called proton echo-planar spectroscopic imaging (1 cm3 voxel resolution). The age range for both dyslexic and control participants was 10 to 13 years. Between the first and second imaging sessions, the dyslexic boys participated in an instructional intervention, which was a reading/science workshop. RESULTS: Before treatment, the dyslexic boys showed significantly greater lactate elevation compared with a control group in the left anterior quadrant (analysis of variance, P = .05) of the brain during a phonologic task. After treatment, however, brain lactate elevation was not significantly different from that of the control group in the left anterior quadrant during the same phonologic task. Behaviorally, the dyslexic participants improved in the phonologic aspects of reading. CONCLUSION: Instructional intervention that improved phonologic performance in dyslexic boys was associated with changes in brain lactate levels as measured by proton echo-planar spectroscopic imaging.

Modeling brain compartmental lactate response to metabolic challenge: a feasibility study.

Magnetic resonance spectroscopy has been used to characterize abnormal brain lactate response in panic disorder (PD) subjects following lactate infusion. The present study integrated water quantification and tissue segmentation to evaluate compartmental lactate response within brain and cerebrospinal fluid (CSF). As there is evidence of brain parenchymal pH changes during lactate infusion, water scans were collected at baseline and post-infusion to address brain water stability. Water levels remained essentially stable across the protocol suggesting internal water provides an improved reference signal for measuring dynamic changes in response to metabolic challenge paradigms such as lactate infusion. To model brain lactate changes by compartments, we took the null hypothesis that lactate rises occur only in tissue. The approach referenced lactate amplitude (potentially from both compartments) to 'voxel' water (water scan corrected for differential T(2) between CSF brain at long-echo times - synonymous to a short-echo water scan). If the magnitude of lactate rise in CSF was equal to or greater than brain, voxels with substantial CSF fractions should demonstrate an equivalent or elevated response to voxels comprised only of tissue. The magnitude of lactate increases paralleled voxel tissue fraction suggesting the abnormal lactate rise observed in PD is tissue-based. The feasibility of lactate quantification and compartmental modeling are discussed.

Dyslexic children have abnormal brain lactate response to reading-related language tasks.

BACKGROUND AND PURPOSE: Children with dyslexia have difficulty learning to recognize written words owing to subtle deficits in oral language related to processing sounds and accessing words automatically. The purpose of this study was to compare regional changes in brain lactate between dyslexic children and control subjects during oral language activation. METHODS: Brain lactate metabolism was measured during four different cognitive tasks (three language tasks and one nonlanguage task) in six dyslexic boys and in seven control subjects (age- and IQ-matched right-handed boys who are good readers) using a fast MR spectroscopic imaging technique called proton echo-planar spectroscopic imaging (1-cm3 voxel resolution). The area under the N-acetylaspartate (NAA) and lactate peaks was measured to calculate the lactate/NAA ratio in each voxel. RESULTS: Dyslexic boys showed a greater area of brain lactate elevation (2.33+/-SE 0.843 voxels) as compared with the control group (0.57+/-SE 0.30 voxels) during a phonological task in the left anterior quadrant. No significant differences were observed in the nonlanguage tasks. CONCLUSION: Dyslexic and control children differ in brain lactate metabolism when performing language tasks, but do not differ in nonlanguage auditory tasks.

Human brain metabolic response to caffeine and the effects of tolerance.

OBJECTIVE: Since there is limited information concerning caffeine's metabolic effects on the human brain, the authors applied a rapid proton echo-planar spectroscopic imaging technique to dynamically measure regional brain metabolic responses to caffeine ingestion. They specifically measured changes in brain lactate due to the combined effects of caffeine's stimulation of glycolysis and reduction of cerebral blood flow. METHOD: Nine heavy caffeine users and nine caffeine-intolerant individuals, who had previously discontinued or substantially curtailed use of caffeinated products because of associated anxiety and discomforting physiological arousal, were studied at baseline and then during 1 hour following ingestion of caffeine citrate (10 mg/kg). To assess state-trait contributions and the effects of caffeine tolerance, five of the caffeine users were restudied after a 1- to 2-month caffeine holiday. RESULTS: The caffeine-intolerant individuals, but not the regular caffeine users, experienced substantial psychological and physiological distress in response to caffeine ingestion. Significant increases in global and regionally specific brain lactate were observed only among the caffeine-intolerant subjects. Reexposure of the regular caffeine users to caffeine after a caffeine holiday resulted in little or no adverse clinical reaction but significant rises in brain lactate which were of a magnitude similar to that observed for the caffeine-intolerant group. CONCLUSIONS: These results provide direct evidence for the loss of caffeine tolerance in the human brain subsequent to caffeine discontinuation and suggest mechanisms for the phenomenon of caffeine intolerance other than its metabolic effects on elevating brain lactate.

Delayed unilateral post-traumatic tremor: localization studies using single-proton computed tomographic and magnetic resonance spectroscopy techniques.

We present the case of a 46-year-old former U.S. Marine who developed unilateral dystonic tremor responsive to anticholinergic medications 13 years after contralateral, combat-induced head trauma. Although conventional neuroimaging techniques showed normal brain anatomy, single-proton computed tomographic scans demonstrated hypometabolism ipsilateral to the area of old trauma. Proton echoplanar spectral imaging demonstrated decreased signal in this same area on creatine imaging, which normalized on anticholinergic medication. Choline imaging on medication showed a signal void in the clinically suspected basal ganglia-thalamus region. We believe that these results indirectly suggest a trans-synaptic origin of the patient's movement disorder.

Phase I study of a humanized anti-CD11/CD18 monoclonal antibody in multiple sclerosis.

OBJECTIVE: To evaluate the safety, pharmacokinetics, pharmacodynamics, and immunogenicity of a humanized anti-CD11/CD18 monoclonal antibody (Hu23F2G) in patients with multiple sclerosis. METHODS: In this phase I uncontrolled dose escalation study, patients (n = 24) with primary or secondary progressive multiple sclerosis received single intravenous infusions of Hu23F2G (0.01 to 4.0 mg/kg). Study parameters included safety, pharmacology, immunogenicity, and brain magnetic resonance imaging (MRI). RESULTS: Hu23F2G had few adverse effects, but 2 cases of urinary tract infection and 2 cases of gingivitis did occur. Transient leukocytes developed in some subjects receiving > or = 1.0 mg/kg. The pharmacokinetic response was nonlinear, with the area under the curve increasing out of proportion to the increase in dose. The mean terminal half-life increased with dose and was 21.9 (SD, 12.8) hours at the 4.0 mg/kg dose. High saturation (> 80%) of CD11/CD18 on circulating leukocytes was achieved with doses > or = 0.2 mg/kg. The duration of high leukocyte saturation was dose-dependent, persisting for more than a week at the 4.0 mg/kg dose. A marked decrease in leukocyte migration in response to cutaneous inflammation was observed. Antibodies against Hu23F2G were not detected. The neurologic examinations were stable except for 1 subject who had worsening weakness associated with an infection. No significant changes were noted on brain MRI scans. CONCLUSIONS: Hu23F2G was tolerated at doses that achieved high degrees of leukocyte CD11/CD118 saturation with in vivo inhibition of leukocyte migration. Because this phase I study was not designed to determine the clinical efficacy of Hu23F2G, further studies are needed.

Functional MR spectroscopy of the brain.

Functional MR spectroscopy is a technique for measuring brain activation that is based on metabolic changes in MR spectroscopy-detectable metabolites. This article covers functional MR spectroscopy applications in visual stimulation, auditory stimulation, language activation, cerebral metabolic rate, water MR spectroscopy, and in psychiatric disorders. Functional MR spectroscopy offers the ability to measure changes in the brain during neuronal activation that may be a more direct measure of cellular activation than functional magnetic resonance imaging. MR spectroscopy-detectable chemicals that are currently of greatest interest for measuring brain activation are also discussed.

Cerebral N-acetylaspartate is low in patients with multiple sclerosis and abnormal visual evoked potentials.

PURPOSE: Our purpose was to compare cerebral proton MR metabolite changes in patients with multiple sclerosis (MS) and abnormal visual evoked potentials (VEPs) with those in MS patients with normal VEPs. METHODS: Seventeen subjects with clinically definite MS were studied with VEPs and MR spectroscopic imaging. Proton MR metabolites were measured using a fast spectroscopic imaging technique called proton echo-planar spectroscopic imaging (PEPSI). Kurtzke's Expanded Disability Status Scale (EDSS) score was also ascertained for each subject to obtain a clinical rating. Twelve regions of interest within the visual pathway of the cerebrum were evaluated for levels of N-acetylaspartate (NAA), choline, creatine, and the presence or absence of MR-detectable lesions. RESULTS: PEPSI NAA values (water-normalized, CSF-corrected) were significantly lower in MS subjects with abnormal VEPs than in subjects with normal VEPs. MR-detectable lesion fractions and EDSS scores were also significantly different between the two VEP groups, but NAA comparison had a P value 100 times less than either of these measures. CONCLUSION: In patients with MS, NAA measurements in the optic pathways of the brain were sensitive to VEP abnormalities. NAA was more sensitive to VEP changes than were choline, creatine, MR-detectable lesions, and EDSS score.

Correlations of evoked potentials with MR imaging and MR spectroscopy in multiple sclerosis.

The current state-of-the-art imaging technique in multiple sclerosis (MS) is magnetic resonance (MR) imaging. With improved imaging technology, MR spectroscopy offers the capacity to identify those chemical changes associated with MS and promises to enhance our ability to understand this disease. Physiologic function in the central nervous system can be measured using evoked potentials. This article analyzes the correlation between these two techniques.

Bioelectromagnetic applications for multiple sclerosis.

There are EM effects on biology that are potentially both harmful and beneficial. We have reviewed applications of EM fields that are relevant to MS. It is possible that EM fields could be developed into a reproducible therapy for both symptom management and long-term care for MS. The long-term care for MS would have to include beneficial changes in the immune system and in nerve regeneration.

Activation of glycolysis in human muscle in vivo.

We tested the cytoplasmic control mechanisms for glycolytic ATP synthesis in human wrist flexor muscles. The forearm was made ischemic and activated by maximal twitch stimulation of the median and ulnar nerves in 10 subjects. Kinetic changes in phosphocreatine, Pi, ADP, ATP, sugar phosphates, and pH were measured by 31P magnetic resonance spectroscopy at 7.1-s intervals. Proton production was determined from pH and tissue buffer capacity during stimulation. Glycolysis was activated between 30 and 50 stimulations, and the rate did not significantly change through the stimulation period. The independence of glycolytic rate on [Pi], [ADP], or [AMP] indicates that feedback regulation by these metabolites could not account for this activation of glycolysis. However, glycolytic H+ and ATP production increased sixfold from 0.5 to 3 Hz, indicating that glycolytic rate reflected muscle activation frequency. This dependence of glycolytic rate on muscle stimulation frequency and independence on metabolite levels is consistent with control of glycolysis by Ca2+.

In vivo measurement of regional brain metabolic response to hyperventilation using magnetic resonance: proton echo planar spectroscopic imaging (PEPSI).

A new rapid spectroscopic imaging technique with improved sensitivity and lipid suppression, referred to as Proton Echo Planar Spectroscopic Imaging (PEPSI), has been developed to measure the 2-dimensional distribution of brain lactate increases during hyperventilation on a conventional clinical scanner equipped with a head surface coil phased array. PEPSI images (nominal voxel size: 1.125 cm3) in five healthy subjects from an axial section approximately 20 mm inferior to the intercommissural line were obtained during an 8.5-min baseline period of normocapnia and during the final 8.5 min of a 10-min period of capnometry-controlled hyperventilation (end-tidal PCO2 of 20 mmHg). The lactate/N-acetyl aspartate signal increased significantly from baseline during hyperventilation for the insular cortex, temporal cortex, and occipital regions of both the right and left hemisphere, but not in the basal ganglia. Regional or hemispheric right-to-left differences were not found. The study extends previous work using single-voxel MR spectroscopy to dynamically study hyperventilation effects on brain metabolism.

Functional MR spectroscopy of the auditory cortex in healthy subjects and patients with sudden hearing loss.

PURPOSE: To use MR spectroscopy to study the biochemical changes produced by auditory stimuli in patients with sudden sensorineural hearing loss and to compare these findings with the biochemical changes seen in healthy volunteers. METHODS: Single-voxel MR spectroscopy was used to study biochemical changes in the auditory cortex in 11 control subjects and 19 patients with sudden sensorineural hearing loss. MR spectroscopic signals were measured during three different sound conditions (scanner noise, music, and sirens). RESULTS: A lower MR spectroscopic lactate signal was observed in control subjects during the music stimulus than during the other sound conditions. This music-induced lactate change was not observed in patients with hearing loss. The other proton metabolites (choline, creatine, N-acetylaspartate [NAA]) remained stable during the different auditory stimuli. However, the NAA/creatine ratio was higher in the auditory cortex of patients than in the control subjects, and was not dependent on the sound condition. CONCLUSION: The detection of stimulus-induced and stable biochemical MR spectroscopic changes in patients with hearing loss may be useful in assessing disease activity.