Biomedical subjects

Robert A Clark

Publications and source records attributed to Robert A Clark.

At least 19 recordsLinked to original sources

PubMed2007

NAD(P)H oxidases regulate HIF-2alpha protein expression.

Biallelic inactivation of the von Hippel-Lindau tumor suppressor gene (VHL) is linked to the development of hereditary and sporadic renal cell carcinoma (RCC). In the absence of VHL, the alpha subunits of heterodimeric hypoxia-inducible transcription factors (HIF-1alpha and HIF-2alpha) are stabilized. Reactive oxygen species, generated by NAD(P)H oxidases, are involved in signaling cascades of malignant growth. We show that in VHL-deficient cells p22phox, Nox4 protein levels and NADPH-dependent superoxide generation are increased. Reintroduction of VHL into the VHL-deficient cells down-regulates the expression of p22phox and NADPH-dependent superoxide generation. Inhibition of the 26 S proteasome in VHL-expressing cells increased p22phox protein levels, which correlated with an increase of NADPH-dependent superoxide generation. We also show that p22phox co-immunoprecipitates with VHL in vivo. Moreover, p22phox is a target of ubiquitination. Importantly, in VHL-deficient cells, diphenyleneiodonium chloride (DPI), an inhibitor of Nox oxidases, decreased the expression of HIF-2alpha. Down-regulation of Nox1, Nox4, and p22phox expression by small interfering RNA also decreased HIF-2alpha protein expression and inhibited Akt and 4E-BP1 phosphorylation, suggesting that a translational mechanism is involved in maintaining HIF-2alpha in VHL-deficient cells. Colony formation by RCC 786-O in soft agar was markedly inhibited by DPI. Moreover, DPI significantly inhibited RCC 786-O tumor formation in athymic mice. Collectively, the data demonstrate that VHL protein exerts its tumor suppressor action, at least partially, via inhibition of p22phox-based Nox4/Nox1 NADPH oxidase-dependent reactive oxygen species generation.

Basic Helix-Loop-Helix Proteins↗

PubMed2007

Magnetic resonance imaging evidence for widespread orbital dysinnervation in dominant Duane's retraction syndrome linked to the DURS2 locus.

PURPOSE: High-resolution, multipositional magnetic resonance imaging (MRI) was used to demonstrate extraocular muscles (EOMs) and associated motor nerves in Duane retraction syndrome (DRS) linked to the DURS2 locus on chromosome 2. METHODS: Five male and three female affected members of two autosomal dominant DURS2 pedigrees were enrolled in the study. Coronal T(1)-weighted MRI of the orbits was obtained in multiple gaze positions, as well as with heavy T(2) weighting in the plane of the cranial nerves. MRI findings were correlated with motility. RESULTS: All subjects had unilateral or bilateral limitation of abduction, or of both abduction and adduction, with palpebral fissure narrowing and globe retraction in adduction. Orbital motor nerves were typically small, with the abducens nerve (cranial nerve [CN]6) often nondetectable. Lateral rectus (LR) muscles were structurally abnormal in seven subjects, with structural and motility evidence of oculomotor nerve (CN3) innervation from vertical rectus EOMs leading to A or V patterns of strabismus in three cases. Four cases had superior oblique, two cases superior rectus, and one case levator EOM hypoplasia. Only the medial and inferior rectus and inferior oblique EOMs were spared. Two cases had small CN3s. CONCLUSIONS: DRS linked to the DURS2 locus is associated with bilateral abnormalities of many orbital motor nerves, and structural abnormalities of all EOMs except those innervated by the inferior division of CN3. The LR may be coinnervated by CN3 branches normally destined for any other rectus EOMs. Therefore, DURS2-linked DRS is a diffuse congenital cranial dysinnervation disorder involving but not limited to CN6.

Abducens Nerve Diseases↗

PubMed2006

Development of a synthetic promoter for macrophage gene therapy.

Macrophages have the potential to deliver therapeutic genes to many target tissues. Macrophage-specific synthetic promoters (SPs) generated by random ligation of myeloid/macrophage cis elements had activity up to 100-fold that of a native macrophage promoter in macrophage cell lines, but were minimally active in nonmyeloid cells. Mouse bone marrow cells (BMCs) transduced ex vivo with lentivectors expressing green fluorescent protein (GFP) driven either by an SP (SP-GFP) or a cytomegalovirus (CMV) promoter (CMV-GFP) were used for syngeneic transplantation of lethally irradiated mice. Blood leukocytes showed stable GFP expression for up to 15 months after transplantation. SP-GFP expression was selective for CD11b+ macrophages, whereas CMV-GFP expression was observed in erythrocytes, as well as in both CD11b+ and CD11b- leukocytes. Furthermore, SP-GFP expression was much stronger than CMV-GFP expression in CD11b+ macrophages. apoE-/- BMCs transduced with the lentiviral vector encoding human apoE were used to transplant apoE-/- mice. Macrophage expression of apoE from 10 to 26 weeks of age significantly reduced atherosclerotic lesions in recipient apoE-/- mice. Thus, the novel SPs, especially when combined with lentivectors, are useful for macrophage-specific delivery of therapeutic genes.

Animals↗

PubMed2006

High-performance wavelet compression for mammography: localization response operating characteristic evaluation.

PURPOSE: To evaluate the accuracy of a visually lossless, image-adaptive, wavelet-based compression method for achievement of high compression rates at mammography. MATERIALS AND METHODS: The study was approved by the institutional review board of the University of South Florida as a research study with existing medical records and was exempt from individual patient consent requirements. Patient identifiers were obliterated from all images. The study was HIPAA compliant. An algorithm based on scale-specific quantization of biorthogonal wavelet coefficients was developed for the compression of digitized mammograms with high spatial and dynamic resolution. The method was applied to 500 normal and abnormal mammograms from 278 patients who were 32-85 years old, 85 of whom had biopsy-proved cancer. Film images were digitized with a charge-coupled device-based digitizer. The original and compressed reconstructed images were evaluated in a localization response operating characteristic experiment involving three radiologists with 2-10 years of experience in reading mammograms. RESULTS: Compression rates in the range of 14:1 to 2051:1 were achieved, and the rates were dependent on the degree of parenchymal density and the type of breast structure. Ranges of the area under the receiver operating characteristic curve were 0.70-0.83 and 0.72-0.86 for original and compressed reconstructed mammograms, respectively. Ranges of the area under the localization response operating characteristic curve were 0.39-0.65 and 0.43-0.71 for original and compressed reconstructed mammograms, respectively. The localization accuracy increased an average of 6% (0.04 of 0.67) with the compressed mammograms. Localization performance differences were statistically significant with P = .05 and favored interpretation with the wavelet-compressed reconstructed images. CONCLUSION: The tested wavelet-based compression method proved to be an accurate approach for digitized mammography and yielded visually lossless high-rate compression and improved tumor localization.

Adult↗

PubMed2006

Magnetic resonance imaging of the effects of horizontal rectus extraocular muscle surgery on pulley and globe positions and stability.

PURPOSE: Magnetic resonance imaging (MRI) was used to determine the effect of recessions and resections on horizontal extraocular muscle (EOM) paths and globe position. METHODS: Four adults with horizontal strabismus underwent contrast-enhanced, surface-coil MRI in central, secondary, and tertiary gazes, before and after horizontal EOM recessions and/or resections. EOM paths were determined from 2-mm thickness, quasicoronal MRI by analysis of cross-sectional area centroids in a normalized, oculocentric coordinate system. Globe displacement was determined by measuring the apparent shift of the bony orbit in eccentric gaze. RESULTS: In all subjects, the anteroposterior positions of the horizontal rectus pulleys shifted by less than 2 mm after surgery, indistinguishable from zero within measurement precision. In three subjects who underwent medial rectus (MR) recession or resection, postoperative globe position was similar in central gaze, but globe translation during vertical gaze shift changed markedly. There was no effect on globe translation in the subject who underwent only lateral rectus (LR) resection. CONCLUSIONS: Recessions and resections of horizontal EOMs have minimal effect on anteroposterior EOM pulley positions. Because the pulley does not shift appreciably despite large alterations in the EOM insertion, the proximity of a recessed EOM to its pulley would be expected to introduce torsional and vertical actions in tertiary gazes. Connective tissue dissection during MR surgery may destabilize the globe's vertical translational stability within the orbit, potentially changing the effective pulling directions of the rectus EOMs in vertical gazes. These changes may mimic oblique muscle dysfunction. LR surgery may avoid globe destabilization.

Adult↗

PubMed2005

Magnetic resonance imaging of human extraocular muscles during static ocular counter-rolling.

The rectus extraocular muscle (EOM) pulleys constrain EOM paths. During visual fixation with head immobile, actively controlled pulleys are known to maintain positions causing EOM pulling directions to change by one-half the change in eye position. This pulley behavior is consistent with Listing's law (LL) of ocular torsion as observed during fixation, saccades, and pursuit. However, pulley behavior during the vestibulo-ocular reflex (VOR) has been unstudied. This experiment studied ocular counter-rolling (OCR), a static torsional VOR that violates LL but can be evoked during MRI. Tri-planar MRI was performed in 10 adult humans during central target fixation while positioned in right and left side down positions known to evoke static OCR. EOM cross-sections and paths were determined from area centroids. Paths were used to locate pulleys in three dimensions. Significant (P < 0.025) counter-rotational repositioning of the rectus pulley arrays of both orbits was observed in the coronal plane averaging 4.1 degrees (maximum, 8.7 degrees ) from right to left side down positions for the inferior, medial, and superior rectus pulleys. There was a trend for the lateral rectus averaging 1.4 degrees . Torsional shift of the rectus pulley array was associated with significant contractile cross-section changes in the superior and inferior oblique muscles. Torsional rectus pulley shift during OCR, which changes pulling directions of the rectus EOMs, correlates with known insertions of the oblique EOM orbital layers on rectus pulleys. The amount of pulley reconfiguration is roughly one-half of published values of ocular torsion during static OCR, an arrangement that would cause rectus pulling directions to change by less than one-half the amount of ocular torsion.

Adult↗

PubMed2005

The influence of CCL3L1 gene-containing segmental duplications on HIV-1/AIDS susceptibility.

Segmental duplications in the human genome are selectively enriched for genes involved in immunity, although the phenotypic consequences for host defense are unknown. We show that there are significant interindividual and interpopulation differences in the copy number of a segmental duplication encompassing the gene encoding CCL3L1 (MIP-1alphaP), a potent human immunodeficiency virus-1 (HIV-1)-suppressive chemokine and ligand for the HIV coreceptor CCR5. Possession of a CCL3L1 copy number lower than the population average is associated with markedly enhanced HIV/acquired immunodeficiency syndrome (AIDS) susceptibility. This susceptibility is even greater in individuals who also possess disease-accelerating CCR5 genotypes. This relationship between CCL3L1 dose and altered HIV/AIDS susceptibility points to a central role for CCL3L1 in HIV/AIDS pathogenesis and indicates that differences in the dose of immune response genes may constitute a genetic basis for variable responses to infectious diseases.

Adolescent↗

PubMed2005

Magnetic resonance imaging evidence for widespread orbital dysinnervation in congenital fibrosis of extraocular muscles due to mutations in KIF21A.

PURPOSE: High-resolution orbital magnetic resonance imaging (MRI) was used to investigate the structural basis of ocular motility abnormalities in humans with congenital fibrosis of the extraocular muscles type 1 (CFEOM1) due to missense mutations in the developmental kinesin KIF21A. METHODS: Clinical ophthalmic and motility findings in 19 volunteers from six unrelated CFEOM1 pedigrees harboring four of the six reported KIF21A mutations and 23 normal control subjects were correlated with MRI studies demonstrating extraocular muscle (EOM) size, location, contractility, and innervation. RESULTS: Subjects with CFEOM1 had severe bilateral blepharoptosis, limited supraduction, and variable ophthalmoplegia. In affected subjects, MRI demonstrated atrophy of the levator palpebrae superioris and superior rectus EOMs and small or absent orbital motor nerves. The oculomotor nerve was most severely hypoplastic, but the abducens was also affected. EOMs exhibited variable atrophy and an abnormally bright T1 signal. Subjects with the R954W and R954Q substitutions frequently exhibited A-pattern strabismus, with misinnervation of the lateral rectus muscle by an oculomotor nerve branch. Rectus pulley locations were generally normal. Subjects with CFEOM1 exhibited subclinical but highly significant reduction from normal in mean optic nerve size (P < 0.001). Comparing clinical and MRI phenotypes did not reveal distinguishing features among KIF21A mutations. CONCLUSIONS: Orbital imaging in CFEOM1 due to various amino acid substitutions in the kinesin KIF21A demonstrates consistent abnormalities of motor and sensory innervation in the orbit. These findings suggest that neuronal disease is primary in CFEOM1, with myopathy arising secondary to abnormal innervation and minimal rectus pulley abnormality secondary to reduced EOM forces.

Adolescent↗

PubMed2004

Medial rectus pulley posterior fixation is as effective as scleral posterior fixation for acquired esotropia with a high AC/A ratio.

PURPOSE: To compare traditional medial rectus (MR) scleral posterior fixation versus MR pulley posterior fixation without scleral sutures for the treatment of acquired esotropia (ET) with a high accommodative convergence over accommodation (AC/A) ratio. DESIGN: Nonrandomized interventional case series. METHODS: Medical records were retrospectively reviewed for twenty-two patients who underwent bilateral MR posterior fixation for acquired ET with a high AC/A ratio, with or without associated MR recessions. The main outcome measure was the reduction in distance-near disparity created by MR scleral posterior fixation compared with MR pulley posterior fixation. RESULTS: Nine patients underwent MR scleral posterior fixation surgery, seven in combination with MR recessions for distance ET. Postoperatively, the distance-near disparity decreased an average of 11.8 prism diopters, stereoacuity improved in six patients, and eight patients no longer needed bifocals. Thirteen patients underwent MR pulley posterior fixation surgery, 10 in combination with MR recessions for distance ET. Postoperatively the distance-near disparity decreased an average of 14.4 prism diopters, stereoacuity improved in eight patients, and 12 patients no longer required bifocals. Statistically, the two procedures were equivalent. One patient in each group was undercorrected at near only, with the residual near ET controlled with bifocals. One patient who underwent MR pulley posterior fixation combined with large MR recessions was overcorrected at distance only. CONCLUSION: Traditional MR scleral posterior fixation and MR pulley posterior fixation are equally effective in treating acquired ET with a high AC/A ratio.

Accommodation, Ocular↗

PubMed2004

Data mining techniques for cancer detection using serum proteomic profiling.

OBJECTIVE: Pathological changes in an organ or tissue may be reflected in proteomic patterns in serum. It is possible that unique serum proteomic patterns could be used to discriminate cancer samples from non-cancer ones. Due to the complexity of proteomic profiling, a higher order analysis such as data mining is needed to uncover the differences in complex proteomic patterns. The objectives of this paper are (1) to briefly review the application of data mining techniques in proteomics for cancer detection/diagnosis; (2) to explore a novel analytic method with different feature selection methods; (3) to compare the results obtained on different datasets and that reported by Petricoin et al. in terms of detection performance and selected proteomic patterns. METHODS AND MATERIAL: Three serum SELDI MS data sets were used in this research to identify serum proteomic patterns that distinguish the serum of ovarian cancer cases from non-cancer controls. A support vector machine-based method is applied in this study, in which statistical testing and genetic algorithm-based methods are used for feature selection respectively. Leave-one-out cross validation with receiver operating characteristic (ROC) curve is used for evaluation and comparison of cancer detection performance. RESULTS AND CONCLUSIONS: The results showed that (1) data mining techniques can be successfully applied to ovarian cancer detection with a reasonably high performance; (2) the classification using features selected by the genetic algorithm consistently outperformed those selected by statistical testing in terms of accuracy and robustness; (3) the discriminatory features (proteomic patterns) can be very different from one selection method to another. In other words, the pattern selection and its classification efficiency are highly classifier dependent. Therefore, when using data mining techniques, the discrimination of cancer from normal does not depend solely upon the identity and origination of cancer-related proteins.

Biomarkers, Tumor↗

PubMed2004

Medial rectus pulley posterior fixation: a novel technique to augment recession.

PURPOSE: Medial rectus (MR) pulley posterior fixation, a technique of suturing the pulley to its muscle without scleral sutures, may be as effective as traditional scleral posterior fixation in primary treatment of acquired esotropia (ET) with a high AC/A ratio. This study examines the effectiveness of MR pulley posterior fixation for other variants of ET. METHODS: We retrospectively analyzed the pre- and postoperative alignment of 16 patients: 9 previously operated patients with excess near ET, 4 patients with sensory ET with excess near ET, and 3 patients with large-angle infantile ET. Surgeries involved extraocular muscle recessions and resections in standard doses combined with MR pulley posterior fixation. RESULTS: All 9 reoperated patients were between 0 and 10 prism diopters of distance ET postoperatively. The excess near ET decreased from an average of 12.1 prism diopters preoperatively (range 6-20) to 1.3 prism diopters postoperatively (range, 0-4). Two of the 4 patients with sensory ET were overcorrected at distance (exotropia of 10 and 15 prism diopters, respectively). The excess near ET of these 4 patients decreased from an average of 13.5 prism diopters preoperatively (range, 10-20) to 2.5 prism diopters postoperatively (range, 0-8). In patients with large-angle infantile ET, the addition of pulley posterior fixation resulted in a greater effect than would be predicted for standard MR recessions, particularly at near. Pooling data for all groups, pulley posterior fixation was associated with a highly significant reduction of excess near esotropia postoperatively (P < 0.00001). DISCUSSION: MR pulley posterior fixation augments MR recession with relatively greater effect at near. Surgical dosage for unilateral recessions and resections combined with MR pulley posterior fixation should be reduced in patients with poor potential for postoperative fusion.

Adolescent↗

PubMed2004

Regulation of the estrogen receptor alpha minimal promoter by Sp1, USF-1 and ERalpha.

The exact molecular mechanisms regulating estrogen receptor alpha (ERalpha) expression in breast tumors are unclear, but studies suggest that they are partly at the level of transcription. We have focused on the transcription factors that regulate the ERalpha minimal promoter, which we have previously shown to reside within the first 245 bp of the 5'-flanking region of the gene. Within this region are several elements essential for full ERalpha promoter transcriptional activity, including a GC box and an imperfect E box. In earlier studies we demonstrated an essential function for the Sp1 family of transcription factors in the regulation of ERalpha expression. We have now identified both USF-1 and ERalpha itself as components of a multi-protein complex of transcription factors that interacts at the ERalpha minimal promoter and is essential for its full transcriptional activity. Electrophoretic mobility shift assays demonstrated that Sp1 and USF-1, but not ERalpha, bind directly to the ERalpha minimal promoter. We showed by GST pull-down assays that ERalpha is able to interact in vitro with USF-1, suggesting, in addition to a possible interaction between ERalpha and Sp1, a mechanism whereby ERalpha is able to interact with the protein complex. Combined exogenous expression of the components of the complex in MCF-7 breast cancer cells resulted in a synergistic effect on transactivation of the ERalpha minimal promoter, suggesting that the importance of the protein complex is in the interactions among the components. Based upon these findings, we propose a possible model for transcription from the ERalpha minimal promoter.

Breast Neoplasms↗

PubMed2004

Demonstration of systematic variation in human intraorbital optic nerve size by quantitative magnetic resonance imaging and histology.

PURPOSE: To use magnetic resonance imaging (MRI) to measure the diameter along the course of the intraorbital optic nerve in living subjects and cadaveric specimens, and to validate measurements histologically in the same specimens. METHODS: Measurements of the intraorbital optic nerve were made in 23 living human subjects and in three formalin-fixed orbits using high-resolution, surface coil MRI in the coronal plane. Fixed orbits were then serially sectioned in the same plane, and stained by Masson's trichrome for digital morphometry of nerve diameter and densitometry of connective tissue constituents. RESULTS: In cadaveric specimens, MRI and histologic measurements of optic nerve dimensions were in close quantitative agreement, showing significant decrease in the average optic nerve diameter along its retrobulbar course. This finding was confirmed by MRI in living subjects, with average optic nerve diameter declining from 3.99 +/- 0.04 mm (SEM) just posterior to the globe, to 3.50 +/- 0.04 mm at 10 mm further to the posterior (P < 0.0001). Color densitometry demonstrated a consistent cross-sectional area of nervous tissue, but decreasing amounts of collagen posteriorly. CONCLUSIONS: There is a significant decrease in normal optic nerve diameter along its length in normal subjects, reflecting reduction in connective tissue. High-resolution MRI is a valid and sensitive method of detecting subtle changes in retrobulbar optic nerve size and can be useful in the investigation of structural optic nerve lesions. Optic nerve diameters must be measured, however, at similar distances posterior to the globe to allow meaningful comparisons.

Adult↗

PubMed2004

Improved interpretation of digitized mammography with wavelet processing: a localization response operating characteristic study.

OBJECTIVE: Our objective was the implementation and evaluation of a novel enhancement technique for improved interpretation of high-resolution digitized mammograms from computer monitors. MATERIALS AND METHODS: A wavelet algorithm was designed to attenuate the image spectral characteristics responsible for the long-range image correlation that often interferes with digital display. The algorithm was evaluated with a localization response operating characteristic (LROC) experiment with 500 negative, benign, and cancer cases with masses and calcification clusters. Three observers reviewed the original and wavelet-enhanced images on a 5-Mpixel monitor using a custom-made workstation user interface. RESULTS: Performance indexes were estimated for four different case combinations, each observer, and each interpretation mode. Wavelet enhancement improved the performance of all observers in all case combinations. Detection accuracy ranged from 0.678 to 0.827 for the unprocessed original data and 0.709-0.871 for the enhanced cases. Localization accuracy ranged from 0.547 to 0.785 for the original images and 0.568-0.847 for the enhanced cases, yielding increases of 5-15%. The difference between enhanced and original performances was statistically significant at the 0.10 level and in a few combinations at the 0.05 level. CONCLUSION: Soft-copy digitized mammography could replace standard film mammography under appropriate display parameters and conditions. The optimization of the soft-copy quality is expected to require more advanced processing techniques than standard gray-scale adjustments. Wavelet-based algorithms, such as the one proposed here, offer better soft-copy quality than the originals and a better starting point for additional manual gray-scale adjustments or automated postprocessing.

Algorithms↗

PubMed2004

Mechanisms of activation of NADPH oxidases.

The members of the NOX family of enzymes are expressed in a variety of tissues and serve a number of functions. There is a high level of conservation of primary protein sequence, as well as functional features, although specialized responses are beginning to emerge. In this context, our data demonstrate that the NOX1 cytoplasmic domains interact efficiently with the cytoplasmic subunits of the phagocyte NADPH oxidase and identify the second cytoplasmic loop of NOX electron transporters as a crucial domain for enzyme function. Studies of cytosolic co-factors showed that the C-terminal cytoplasmic domain of NOX1 was absolutely required for activation with NOXO1 and NOXA1 and that this activity required interaction of the putative NADPH-binding region of this domain with NOXA1. Finally, we have provided the first example of how alternative splicing of a NOX co-factor may be involved in the regulation of NADPH oxidase function.

Amino Acid Sequence↗

PubMed2003

Discovery of distinct protein profiles specific for lung tumors and pre-malignant lung lesions by SELDI mass spectrometry.

OBJECTIVES: Early lung cancer detection and treatment remain a challenge. The efficacy of surface-enhanced laser desorption/ionization (SELDI) technology in lung cancer detection, has not been defined. This study identifies specific protein peak patterns in malignant lung tumors, and in pre-malignant airways epithelium showing neoplastic transformation. METHODS: Lung tumor specimens taken from patients participating in a lung cancer screening study (H. Lee Moffitt Cancer Center, Tampa, FL) were laser capture microdissected to obtain pure cell populations from frozen sections of normal lung, atypical adenomatous hyperplasia (AAH) and malignant tumors. SELDI mass spectrometry was used to generate protein profiles in each epithelial cell type. RESULTS: SELDI mass spectroscopy is highly reproducible in detecting lung tumor-specific protein profiles. Three peaks at 17-23 kDa mass range from tumor cells showed markedly increased compared with normal cells. The peak at 17250 Da was not detected in any of the normal cells. This peak appeared to be present at low levels in the atypical cell samples. CONCLUSIONS: This study demonstrates the feasibility of detecting "malignant" protein signatures from lung tumor and pre-malignant pulmonary epithelium using SELDI mass spectrometry. Although additional study is necessary to validate these patterns as unique diagnostic tools, these "malignant" protein signatures lend themselves to identification of populations at high-risk for lung cancer and for monitoring response to lung cancer chemopreventive agents.

Carcinoma, Non-Small-Cell Lung↗

PubMed2003

Evidence for a pulley of the inferior oblique muscle.

PURPOSE: This study was undertaken to investigate evidence for a connective tissue pulley constraining the path of the inferior oblique (IO) muscle. METHODS: From magnetic resonance images, the cross-sectional area, path, and orbital relationships of the human IO were determined in multiple gaze positions. Rectus pulleys were directly imaged with intravenous gadodiamide contrast. Images were compared with serial histologic sections of IO muscles of humans and monkeys. RESULTS: The IO path from origin to the lateral border of the inferior rectus (IR) muscle was straight. Lateral to the IR, the IO curved to follow the globe. At the point of IR crossing, the IO moved anteriorly from infraduction to supraduction by approximately 53% of the IR insertion's travel. Gaze-related change in IO cross section was demonstrable near the IR center. The gaze-related inflection in IO path corresponded to its encirclement by a pulley consisting of a dense ring of collagen, stiffened by elastin and smooth muscle, and united with the IR pulley. Orbital layer fibers of the IO inserted on its pulley, the lateral rectus (LR) pulley, and associated connective tissues. CONCLUSIONS: Like the rectus muscles, the human and monkey IO has a connective tissue pulley serving as its functional origin. The position of the IO pulley is influenced by its coupling to the actively moving IR pulley, whereas in turn the IO orbital layer inserts on and presumably shifts the IR and LR pulleys. These intercouplings facilitate implementation by rectus extraocular muscle suspensions of a commutative ocular motor plant.

Adult↗

PubMed2002

Two novel proteins activate superoxide generation by the NADPH oxidase NOX1.

NOX1, an NADPH oxidase expressed predominantly in colon epithelium, shows a high degree of similarity to the phagocyte NADPH oxidase. However, superoxide generation by NOX1 has been difficult to demonstrate. Here we show that NOX1 generates superoxide when co-expressed with the p47(phox) and p67(phox) subunits of the phagocyte NADPH oxidase but not when expressed by itself. Since p47(phox) and p67(phox) are restricted mainly to myeloid cells, we searched for their homologues and identified two novel cDNAs. The mRNAs of both homologues were found predominantly in colon epithelium. Differences between the homologues and the phagocyte NADPH oxidase subunits included the lack of the autoinhibitory domain and the protein kinase C phosphorylation sites in the p47(phox) homologue as well as the absence of the first Src homology 3 domain and the presence of a hydrophobic stretch in the p67(phox) homologue. Co-expression of NOX1 with the two novel proteins led to stimulus-independent high level superoxide generation. Stimulus dependence of NOX1 was restored when p47(phox) was used to replace its homologue. In conclusion, NOX1 is a superoxide-generating enzyme that is activated by two novel proteins, which we propose to name NOXO1 (NOX organizer 1) and NOXA1 (NOX activator 1).

Adaptor Proteins, Signal Transducing↗