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PubMed2003

How estrogen-specific proteins discriminate estrogens from androgens: a common steroid binding site architecture.

Steroid hormones play an essential role in a wide range of physiological and pathological processes, such as growth, metabolism, aging, and hormone-sensitive cancers. Estrogens are no exception and influence growth, differentiation, and functioning of many target tissues, such as the mammary gland, uterus, hypothalamus, pituitary, bone, and liver. Although very similar in structure, each steroid class (i.e., estrogens, androgens, progestins, mineral corticoids, or glucocorticoids) is responsible for distinct physiological processes. To permit specific biological responses for a given steroid class, specific proteins are responsible for steroid bioactivation, action, and inactivation, yet they have low or no affinity to other classes. Estrogens make no exception and possess their own set of related proteins. To understand the molecular basis underlying estrogen recognition from other steroids, structural features of estrogen-specific proteins were analyzed along with their ability to discriminate between steroid hormones belonging to different classes. Hence, the study of all estrogen-specific proteins for which an atomic structure has been determined demonstrated that a common steroid-binding pocket architecture is shared by these proteins. This architecture is composed of the following elements: i) a glutamate residue acting as a proton acceptor coupled with a proton donor that interact with the steroid O3; ii) a proton donor (His or Ser) that interacts with O17; iii) a highly conserved sandwich-like structure providing steric hindrance and preventing C19 steroid from binding; and iv) several amino acid residues interacting with the C18. As these different estrogen-specific proteins are not related in overall sequence, the inference is that the steroid binding site in these proteins has originated by convergent evolution.

17-Hydroxysteroid Dehydrogenases↗
PubMed2000

A binary architectural grading system for uterine endometrial endometrioid carcinoma has superior reproducibility compared with FIGO grading and identifies subsets of advance-stage tumors with favorable and unfavorable prognosis.

The International Federation of Gynecology and Obstetrics (FIGO) grading of uterine endometrial endometrioid carcinoma requires evaluation of histologic features that can be difficult to assess, including recognition of small amounts of solid growth, distinction of squamous from nonsquamous solid growth, and assessment of degree of nuclear atypia. The authors describe a novel, binary architectural grading system that uses low-magnification assessment of amount of solid growth, pattern of invasion, and presence of necrosis to divide endometrioid carcinomas into low- and high-grade tumors. The authors analyzed its performance for predicting prognosis and with respect to intra- and interobserver reproducibility. A total of 141 endometrioid carcinomas from hysterectomy specimens were graded according to the FIGO system, nuclear grading, and the binary architectural system. A tumor was classified as high grade if at least two of the following three criteria were present: (1) more than 50% solid growth (without distinction of squamous from nonsquamous epithelium); (2) a diffusely infiltrative, rather than expansive, growth pattern; and (3) tumor cell necrosis. For tumors that were confined to the endometrium, only percent solid growth and necrosis were evaluated, and those with both solid growth of more than 50% and necrosis were considered high grade. All tumors were graded independently by three pathologists on two separate occasions. Both inter- and intraobserver agreement using the binary grading system (kappa = 0.65 and 0.79) were superior compared with FIGO (kappa = 0.55 and 0.67) and nuclear grading (kappa = 0.22 and 0.41). The binary grading system stratified patients into three distinct prognostic groups. Patients with stage I low-grade tumors with invasion confined to the inner half of the myometrium (stages IA and IB) had a 100% 5-year survival rate. Patients with low-grade tumors that invaded beyond the outer half of the myometrium (stage IC and stages II-IV) and those with high-grade tumors with invasion confined to the myometrium (stages IB and IC) had a 5-year survival rate of 67% to 76%. In striking contrast to patients with advance-stage low-grade tumors, patients with advance-stage high-grade tumors had a 26% 5-year survival rate. This binary grading system has advantages over FIGO and nuclear grading that permit greater interobserver and intraobserver reproducibility and should be tested in other studies of endometrial endometrioid carcinomas to validate its reproducibility and use for segregating patients into different prognostic groups.

Adolescent↗
PubMed1995

The influence of bony architecture on fixed membranous bone graft survival.

The aim of this study was to examine the influence of membranous bone graft architecture on graft survival. Eighteen adult New Zealand rabbits underwent full-thickness harvesting of their zygoma, which was then divided into two parts, resulting in a wider, thicker anterior graft and a tapered posterior graft. The grafts were then rigidly fixed, one to each nasal bone, using titanium lag screws. On postgrafting days 15 and 45, 3 animals each were killed. The remaining 12 animals were killed on day 90. The graft, graft-host interface, and contralateral zygoma were assessed volumetrically, histologically (nondecalcified), and stereologically. Volumetrically, the anterior (thicker, wider) grafts demonstrated 100% survival while the posterior (thinner, more narrow) grafts demonstrated 80% survival (p = 0.004). Histologically, the anterior grafts demonstrated less resorption and porosity and greater labeling activity. At the graft-host interface, the anterior grafts exhibited a 2.5-fold increase in full incorporation of the grafts, and the posterior grafts had almost twice the incidence of nonincorporation. Stereological measurements, including interlabel width (20.3 microns anteriorly, 18.9 microns posteriorly), confirmed the enhanced survival of the anterior grafts. Using multiple forms of analyses, this study demonstrates that membranous bone graft architecture influences graft survival. To assist in understanding these differences, we also analyzed the normal contralateral zygoma. While the anterior and posterior halves had a relatively constant amount of bicortical bone, the thicker grafts had a proportionally greater trabecular component (i.e., increased diploë-to-cortical ratio). In the rabbit model, differences in membranous bone thickness imply differences in the cancellous portion of the graft, thereby influencing ultimate graft survival.

Animals↗
PubMed1999

Lymph node architecture preceding and following 6 months of potent antiviral therapy: follicular hyperplasia persists in parallel with p24 antigen restoration after involution and CD4 cell depletion in an AIDS patient.

OBJECTIVES: To evaluate changes in architecture, viral RNA, and viral protein over 6 months in lymph nodes from retroviral-naïve HIV-infected persons before and after commencing highly active antiretroviral therapy (HAART). METHODS: Nine antiretroviral-naïve HIV-infected persons had lymph nodes excised at baseline and at 2 and 6-8 months after beginning a four-drug combination regimen containing zidovudine, lamivudine, nevirapine, and indinavir. Two patients had AIDS. Lymph nodes were examined by immunohistochemical staining for Gag p24 HIV, CD3, CD21, CD20, HAM 56, and Ki67 antigens and by in-situ hybridization (ISH) for HIV RNA and H3-histone RNA. RESULTS: Eight of nine baseline lymph nodes showed follicular hyperplasia and germinal center and paracortical mononuclear cell activation. At 2 months, the lymph nodes from seven patients, including the AIDS patients, showed more follicular hyperplasia and activation than their baseline specimens but with decreased mononuclear cell activation. By 6 months, seven lymph nodes were less hyperplastic and activated than their corresponding 2 month specimens. Combined ISH/immunohistochemical staining of baseline lymph nodes revealed productively infected T (CD3) and B (CD20) cells and macrophages (HAM56+). HIV RNA-positive mononuclear cells were infrequent at 2 months, and rare at 6 months. HIV RNA was still associated with follicular dendritic cells (FDC) at 2 months, but not at 6 months. HIV p24-positive antigen in germinal centers persisted through all 6, and the one 8 month specimens. The baseline lymph nodes from one of the AIDS patients was involuted and T cell depleted, whereas the follow-up lymph nodes were hyperplastic with normal T cell levels. CONCLUSION: Follicular hyperplasia and cell activation, possibly caused by persistent viral protein in germinal centers, may help explain why HIV viremia rebounds so rapidly after the interruption of HAART. Restoration of architecture may follow the treatment of patients with AIDS who initially had involuted and CD4 cell-depleted lymph nodes.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Effect of testosterone administration and weight training on muscle architecture.

PURPOSE: The purpose of this study was to assess muscle architecture changes in subjects who were administered supraphysiologic doses of testosterone enanthate (TE) and concurrently performed heavy resistance training. METHODS: Ten subjects were randomly selected from the 21 subjects who participated in a previously published study (12). Subjects were allocated to one of two groups as per Giorgi et al. (12) and received either a saline-based placebo (nonTE) or a 3.5-mg.kg-1 body weight dose of TE by deep intramuscular injection once a week for 12 wk. Subjects also performed heavy resistance training using exercises that targeted the triceps brachii muscle. Before and after the training period, free-weight one-repetition-maximum (1-RM) bench press strength was tested, muscle thickness and pennation of the triceps brachii lateralis were measured using ultrasound imaging, and fascicle length was estimated from ultrasound photographs. RESULTS: There were no significant between-group differences in muscle thickness changes despite a trend toward increased thickness in TE subjects (TE, 23.5%, vs nonTE, 13.8%). However, 1-RM bench press performance and muscle pennation increased significantly in TE subjects compared with nonTE subjects (P < 0.05). There was also a trend toward longer fascicle lengths in the muscles of nonTE subjects. CONCLUSION: The results of the present study suggest that the use of TE in conjunction with heavy resistance training is associated with muscle architecture changes that are commonly associated with high-force production. Since there was little difference between the groups in muscle thickness, changes in pennation and possibly fascicle length may have contributed to strength gains seen in TE subjects.

Adult↗
PubMed1998

Volume maintenance of onlay bone grafts in the craniofacial skeleton: micro-architecture versus embryologic origin.

The superior volume maintenance of membranous over endochondral bone has been shown in several studies and provides the basis for its preferred clinical use as an onlay grafting material in the craniofacial skeleton. The scientific rationale for this seeming embryologic advantage, however, has never been proven. Our hypothesis is that the pattern of onlay bone graft resorption is primarily determined by a graft's micro-architecture (relative cortical and cancellous composition) rather than its embryologic origin (membranous versus endochondral). Twenty-five adult New Zealand, White rabbits were used for this study. Eight animals were killed at 3 weeks, eight animals at 8 weeks, and nine animals at 16 weeks. Three graft types were placed onto each rabbit cranium: cortical bone graft of membranous origin and cortical and cancellous bone graft of endochondral origin. Fluorochrome markers were injected into all living rabbits at 1, 6, and 14 weeks. Microcomputed tomography scanning was performed on all of the bone grafts to determine postsacrifice volumes and to obtain detailed information regarding the bone graft's trabecular architecture. In addition, specimens were examined histologically. Volume analysis showed a statistically greater resorption rate in the cancellous endochondral bone graft than in either the endochondral or membranous cortical bone grafts (p < 0.05) for all time points. In addition there was no significant difference in the resorption rates between the endochondral and membranous cortical bone grafts. A post-test power analysis (alpha = 5 percent) of the volume data comparing the two types of cortical bone grafts showed that a difference in resorption of 8.9 percent would be detected with a 90-percent probability. Previous studies, which have shown a seeming superiority of membranous over endochondral bone grafts, used composite grafts composed of both cortical and cancellous portions. By separating these components, we have shown that cortical bone grafts maintain their volumes significantly better than cancellous bone grafts. In addition, we found no statistical difference in the resorption rates between the two cortical onlay bone grafts of different embryologic origins, a finding that has never been previously published. From our results, we believe cortical bone to be a superior onlay grafting material, independent of its embryologic origin. We believe these results challenge the currently accepted theories of bone graft dynamics and may lead to a change in the way clinicians approach bone graft selections for craniofacial surgery.

Animals↗
PubMed1998

The internal bony architecture of the sacrum.

STUDY DESIGN: Radiographic and direct quantitative measurements were made of the cortical and the trabecular anatomy of the sacrum. OBJECTIVES: To define the trabecular patterns and the cortical thickness of the sacrum. SUMMARY OF BACKGROUND DATA: The sacrum is a frequent site of internal fixation. In previous anatomic studies, investigators have focused on specific dimensional measurements of the sacrum, whereas others have described the anatomic course of the anterior sacral neurovascular or visceral structures. Computed tomographic imaging also has been used to quantify the sacral trabecular bone density. The internal architecture of the sacrum has yet to be described in detail. METHODS: Seventeen cadaveric sacra were studied by computed tomographic imaging and then were sectioned at 3-mm intervals in the axial or sagittal plane. The cortical thickness of each section was measured under microscopic visualization. The sections were radiographed with high-resolution imaging to delineate their trabecular patterns. RESULTS: The trabecular bone was densest adjacent to the endplates. The sacral body trabeculae were arranged in a cruciate pattern, and bony atrophy occurred in a systematic fashion. An alar void was a consistent finding in all specimens with definable boundaries. The cortical thickness was uniform throughout the surface of each specimen. The computed tomographic images correlated with the anatomy observed in the cadaveric sections. CONCLUSION: The internal bony architecture of the sacrum has several consistent features. The relatively uniform cortical thickness seen in each sacral specimen may have clinical significance in the internal fixation of this region.

Aged↗
PubMed2001

The cortical shell architecture of human cervical vertebral bodies.

STUDY DESIGN: An anatomic study of cervical vertebral bodies. OBJECTIVES: To provide quantitative information on the cortical shell architecture of the middle and lower cervical vertebral bodies. SUMMARY OF BACKGROUND DATA: Some external dimensions have been measured, but little quantitative data exists for the cortical shell architecture of the vertebral bodies of the cervical spine. METHODS: Twenty-one human cervical vertebral bodies (C3-C7) were sectioned along parasagittal planes into five 1.7-mm thin slices for each vertebra. Radiographs of each slice were digitized, and external and internal dimensions were measured. Averages and standard deviations were computed. Single factor analysis of variance was used to determine significant (P < 0.05) differences between the vertebral levels. RESULTS: The superior endplate was thickest in the posterior region (range 0.74-0.89 mm) and thinnest in the anterior region (range 0.44-0.56 mm). The inferior endplate was thickest in the anterior region (range 0.61-0.81 mm) and thinnest in the posterior region (range 0.49-0.62 mm). In the central region, the superior endplate (range 0.42-0.58 mm) was thinner than the inferior endplate (range 0.53-0.64 mm). Variation with vertebral level was dependent on the dimension studied. CONCLUSIONS: Comprehensive quantitative anatomic data of the middle and lower cervical vertebral bodies have been obtained. This may be useful in improving the understanding of the three-column and other vertebral-fracture theories, the fidelity of the finite element models of cervical spine, and the designs of surgical instrumentation.

Cadaver↗
PubMedDate not supplied

Selective soft tissue release preserves growth plate architecture during limb lengthening.

Although distraction osteogenesis has proven successful in children, concerns remain regarding potential growth inhibition of the lengthened limb. Twenty-one 8-week-old New Zealand White rabbits underwent a unilateral 40% tibial lengthening with the contralateral tibia as control. The animals were divided into Achilles tendon release and non-release groups. Radiographs and histomorphometric analysis of the proximal tibial growth plate was performed 5 and 10 weeks after distraction. The corrected length of tibias without tenotomy was significantly shorter than the contralateral controls, whereas those with tenotomy were statistically equivalent to the contralateral control tibias. Histologically, the operated limbs without tenotomy showed a significant decrease in thickness and loss of cellular architecture of the proximal tibial growth plate compared with the tenotomy groups, which were of near-normal appearance. A concomitant tendo Achilles lengthening performed with 40% tibial lengthening preserves proximal tibial growth plate architecture in this model.

Achilles Tendon↗
PubMed2006

Quantification of topological changes in retinal vascular architecture in essential and malignant hypertension.

OBJECTIVE: Grading of hypertension severity by fundoscopic appearance is difficult and inaccurate. We investigated whether essential hypertension (EHT) and malignant phase hypertension (MHT) were associated with quantifiable abnormalities of the topology and architecture of the retinal circulation. METHODS: The topology and architecture of the retinal microvasculature were compared in images from 20 normotensive subjects, 20 patients with EHT and 20 patients with MHT. Digitized retinal photographs were analysed by a novel multiscale image analysis method using a semi-automated program to quantify geometrical and topological properties of arteriolar and venular trees. RESULTS: EHT was associated with an increase in the arteriolar length-to-diameter ratio (P < 0.01). There were also alterations in arteriolar topology indicative of rarefaction, including a marked reduction in the number of terminal branches in EHT (P < 0.01). These changes in the arteriolar network were exaggerated in MHT and there was also increased venular tortuosity and venular rarefaction in MHT compared with normotensive subjects. CONCLUSIONS: Hypertension is associated with marked topological alterations in the retinal vasculature, and quantification of these changes may be a useful novel approach to the assessment of target organ damage in hypertension.

Adult↗
PubMed2006

Hyalinizing trabecular adenoma of the thyroid revisited: a histologic and immunohistochemical study of thyroid lesions with prominent trabecular architecture and sclerosis.

BACKGROUND: Since its description, hyalinizing trabecular adenoma (HTA) of the thyroid has been a controversial entity. Some have considered it a unique entity, some have considered it a variant of papillary carcinoma (PC), and still others have considered it a nonspecific pattern that may be seen with a variety of thyroid lesions. Complicating the matter, studies demonstrating metastases have shown entities that do not appear to be HTAs as originally described, and molecular studies showing changes of PC have used methods that are not specific. This study reviews our experience with thyroid lesions that showed at least some histologic features of HTA and presents the immunohistochemical findings for these lesions using antibodies employed for the diagnosis of PC. DESIGN: Our files were reviewed for all thyroid resection reports describing lesions with hyalinized or sclerotic stroma and a trabecular architecture within the diagnosis or diagnostic comment. All cases were reviewed and classified as either HTA or as different lesions based upon histologic features. Immunohistochemistry with antibodies to HBME1, CK19 and p63 was performed with all lesions and with a series of controls. RESULTS: Eighteen thyroid lesions with prominent sclerosis or hyalinization and trabecular architecture were identified. Only 4 of these were found to completely match the histologic and cytologic descriptions of HTA by HE review. The other cases showed histologic features more compatible with other diagnoses including cellular adenomatoid nodule (5), follicular adenoma (4), follicular variant of PC (FVPC) (3), and epithelial neoplasm with features of FVPC (2). All HTAs lacked immunoreactivity for HBME1, CK19 and p63. All cases deemed to be adenomatoid nodules, follicular adenomas and epithelial neoplasms showed no immunoreactivity for HBME1 and CK19 and, of these, only a single AN showed immunoreactivity for p63. Cases deemed to be FVPCs showed diffuse immunoreactivity for HBME1 and CK19 and 1 reacted with antibodies to p63. Of control PCs and other thyroid lesions, reactivity for HBME1, CK19, and p63 was observed in 8/8, 7/7, and 7/8 and 3/27, 7/27, and 7/27 cases, respectively. CONCLUSIONS: A sclerotic or hyalinized stroma with a trabecular growth pattern may be seen in a number of different thyroid lesions and, when seen, is usually a focal feature of a lesion other than HTA. Immunohistochemistry may be of assistance as cases of FVPC with prominent hyalinization and trabeculation will show immunoreactivity for HBME1 and CK19, whereas HTAs and other thyroid lesions with hyalinization and trabeculation will not.

Adenoma↗
PubMed2005

Analyzing the vascular architecture of the free TRAM flap using intraoperative ex vivo angiography.

BACKGROUND: Using ex vivo intraoperative angiography to analyze 14 flaps from 12 breast reconstruction patients, the authors investigated the vascular architecture of free transverse rectus abdominis musculocutaneous (TRAM) flaps nourished by the deep inferior epigastric artery. METHODS: Contrast medium was injected through the deep inferior epigastric artery and flaps were radiographed to observe their vascular patterns. RESULTS: TRAM flaps showed one or two segmental arteries stained on their ipsilateral side (zones 1 and 3) and serving as the flap's axial artery. These segmental arteries directly connect to the large perforators (axial perforators) and emerge not only from the paraumbilical perforators but also from the caudal branches of the deep inferior epigastric artery. Arterial density is always lower in the contralateral area (zones 2 and 4) than in the ipsilateral area (zones 1 and 3). CONCLUSIONS: Because the cephalic half of zone 2 and all of zone 4 remain unstained, these areas are prone to skin or fat necrosis, especially in high-risk patients. Ex vivo angiography, by providing specific information about the individual flap and by reflecting its flow physiology, enables one to observe and to chart the vascular architecture of free TRAM flaps nourished by the deep inferior epigastric artery.

Angiography↗
PubMed2004

Recurrent cerebellar architecture solves the motor-error problem.

Current views of cerebellar function have been heavily influenced by the models of Marr and Albus, who suggested that the climbing fibre input to the cerebellum acts as a teaching signal for motor learning. It is commonly assumed that this teaching signal must be motor error (the difference between actual and correct motor command), but this approach requires complex neural structures to estimate unobservable motor error from its observed sensory consequences. We have proposed elsewhere a recurrent decorrelation control architecture in which Marr-Albus models learn without requiring motor error. Here, we prove convergence for this architecture and demonstrate important advantages for the modular control of systems with multiple degrees of freedom. These results are illustrated by modelling adaptive plant compensation for the three-dimensional vestibular ocular reflex. This provides a functional role for recurrent cerebellar connectivity, which may be a generic anatomical feature of projections between regions of cerebral and cerebellar cortex.

Cerebellum↗
PubMed1996

The prefrontal landscape: implications of functional architecture for understanding human mentation and the central executive.

The functional architecture of prefrontal cortex is central to our understanding of human mentation and cognitive prowess. This region of the brain is often treated as an undifferentiated structure, on the one hand, or as a mosaic of psychological faculties, on the other. This paper focuses on the working memory processor as a specialization of prefrontal cortex and argues that the different areas within prefrontal cortex represent iterations of this function for different information domains, including spatial cognition, object cognition and additionally, in humans, semantic processing. According to this parallel processing architecture, the 'central executive' could be considered an emergent property of multiple domain-specific processors operating interactively. These processors are specializations of different prefrontal cortical areas, each interconnected both with the domain-relevant long-term storage sites in posterior regions of the cortex and with appropriate output pathways.

Animals↗
PubMed1998

Tissue architecture: the ultimate regulator of epithelial function?

The architecture of a tissue is defined by the nature and the integrity of its cellular and extracellular compartments, and is based on proper adhesive cell-cell and cell-extracellular matrix interactions. Cadherins and integrins are major adhesion-mediators that assemble epithelial cells together laterally and attach them basally to a subepithelial basement membrane, respectively. Because cell adhesion complexes are linked to the cytoskeleton and to the cellular signalling pathways, they represent checkpoints for regulation of cell shape and gene expression and thus are instructive for cell behaviour and function. This organization allows a reciprocal flow of mechanical and biochemical information between the cell and its microenvironment, and necessitates that cells actively maintain a state of homeostasis within a given tissue context. The loss of the ability of tumour cells to establish correct adhesive interactions with their microenvironment results in disruption of tissue architecture with often fatal consequences for the host organism. This review discusses the role of cell adhesion in the maintenance of tissue structure and analyses how tissue structure regulates epithelial function.

Animals↗
PubMed2005

Dynamics of a neural system with a multiscale architecture.

The architecture of the brain is characterized by a modular organization repeated across a hierarchy of spatial scales-neurons, minicolumns, cortical columns, functional brain regions, and so on. It is important to consider that the processes governing neural dynamics at any given scale are not only determined by the behaviour of other neural structures at that scale, but also by the emergent behaviour of smaller scales, and the constraining influence of activity at larger scales. In this paper, we introduce a theoretical framework for neural systems in which the dynamics are nested within a multiscale architecture. In essence, the dynamics at each scale are determined by a coupled ensemble of nonlinear oscillators, which embody the principle scale-specific neurobiological processes. The dynamics at larger scales are 'slaved' to the emergent behaviour of smaller scales through a coupling function that depends on a multiscale wavelet decomposition. The approach is first explicated mathematically. Numerical examples are then given to illustrate phenomena such as between-scale bifurcations, and how synchronization in small-scale structures influences the dynamics in larger structures in an intuitive manner that cannot be captured by existing modelling approaches. A framework for relating the dynamical behaviour of the system to measured observables is presented and further extensions to capture wave phenomena and mode coupling are suggested.

Brain↗
PubMed2005

Q-ball imaging of macaque white matter architecture.

Diffusion-weighted magnetic resonance imaging holds substantial promise as a technique for non-invasive imaging of white matter (WM) axonal projections. For diffusion imaging to be capable of providing new insight into the connectional neuroanatomy of the human brain, it will be necessary to histologically validate the technique against established tracer methods such as horseradish peroxidase and biocytin histochemistry. The macaque monkey provides an ideal model for histological validation of the diffusion imaging method due to the phylogenetic proximity between humans and macaques, the gyrencephalic structure of the macaque cortex, the large body of knowledge on the neuroanatomic connectivity of the macaque brain and the ability to use comparable magnetic resonance acquisition protocols in both species. Recently, it has been shown that high angular resolution diffusion imaging (HARDI) can resolve multiple axon orientations within an individual imaging voxel in human WM. This capability promises to boost the accuracy of tract reconstructions from diffusion imaging. If the macaque is to serve as a model for histological validation of the diffusion tractography method, it will be necessary to show that HARDI can also resolve intravoxel architecture in macaque WM. The present study therefore sought to test whether the technique can resolve intravoxel structure in macaque WM. Using a HARDI method called q-ball imaging (QBI) it was possible to resolve composite intravoxel architecture in a number of anatomic regions. QBI resolved intravoxel structure in, for example, the dorsolateral convexity, the pontine decussation, the pulvinar and temporal subcortical WM. The paper concludes by reviewing remaining challenges for the diffusion tractography project.

Animals↗