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PubMed2005

A novel method for determination of collagen orientation in cartilage by Fourier transform infrared imaging spectroscopy (FT-IRIS).

OBJECTIVE: The orientation of collagen molecules is an important determinant of their functionality in connective tissues. The objective of the current study is to establish a method to determine the alignment of collagen molecules in histological sections of cartilage by polarized Fourier transform infrared imaging spectroscopy (FT-IRIS), a method based on molecular vibrations. METHODS: Polarized FT-IRIS data obtained from highly oriented tendon collagen were utilized to calibrate the derived spectral parameters. The ratio of the integrated areas of the collagen amide I/II absorbances was used as an indicator of collagen orientation. These data were then applied to FT-IRIS analysis of the orientation of collagen molecules in equine articular cartilage, in equine repair cartilage after microfracture treatment, and in human osteoarthritic cartilage. Polarized light microscopy (PLM), the most frequently utilized technique to evaluate collagen fibril orientation in histological sections, was performed on picrosirius red-stained sections for comparison. RESULTS AND CONCLUSION: Thicknesses of each zone of normal equine cartilage (calculated based on differences in collagen orientation) were equivalent as determined by PLM and FT-IRIS. Comparable outcomes were obtained from the PLM and FT-IRIS analyses of repair and osteoarthritis tissues, whereby similar zonal variations in collagen orientation were apparent for the two methods. However, the PLM images of human osteoarthritic cartilage showed less obvious zonal discrimination and orientation compared to the FT-IRIS images, possibly attributable to the FT-IRIS method detecting molecular orientation changes prior to their manifestation at the microscopic level.

Animals↗
PubMed1998

Enhancement of spatial orientation of intravascular ultrasound images with side holes in guiding catheters.

BACKGROUND: Intravascular ultrasound (IVUS) images are typically viewed and recorded in an arbitrary rotational orientation. This study was performed to validate a new method for improved orientation of sonographic vascular cross-sections. METHODS AND RESULTS: We have tested a simple technique for rotational indexing of IVUS in cases in which guiding catheters with side holes are used. Although guiding catheters are opaque to ultrasonography, the side holes transmit the beam and therefore can be easily identified. The orientation of the side holes, which is characteristic for each make of guiding catheter, can be used to determine the anatomically appropriate rotational orientation of the IVUS image. In this study images of four commercially available side-hole guiding catheters were viewed in vitro to confirm the visibility of the side holes and to characterize their orientation for purposes of rotational orientation of images. Feasibility tests of rotational orientation based on side holes were then performed in canine coronary arteries (n = 3) and in six human coronary arteries. Three serial imaging runs in each clinical case yielded a mean variability in rotational orientation of 7.5 +/- 1.5 degrees. CONCLUSION: Validation testing of the side-hole technique demonstrates the potential for consistent and anatomically appropriate orientation of intravascular ultrasound images.

Animals↗
PubMed1994

Studies of highly asymmetric mixed-chain diacyl phosphatidylcholines that form mixed-interdigitated gel phases: Fourier transform infrared and 2H NMR spectroscopic studies of hydrocarbon chain conformation and orientational order in the liquid-crystalline state.

Hydrocarbon chain conformational and orientational order in liquid-crystalline bilayers of the highly chain-asymmetric 1-O-eicosanoyl, 2-O-dodecanoyl and 1-O-decanoyl, 2-O-docosanoyl phosphatidylcholines were studied by Fourier transform infrared (FTIR) and deuterium nuclear magnetic resonance (2H-NMR) spectroscopy, respectively, and compared with appropriate symmetric-chain phosphatidylcholines at comparable reduced temperatures. FTIR spectroscopy indicates that these two asymmetric-chain phospholipids contain a slightly greater number of kink, a considerably larger number of double-gauche, but a somewhat smaller number of end-gauche conformers than does dipalmitoylphosphatidylcholine, a symmetric-chain phospholipid having the same total number of carbon atoms in its hydrocarbon chains. Moreover, the asymmetric-chain phospholipids also contain a larger total number of gauche conformers, suggesting that their hydrocarbon chains are more disordered overall than are those of dipalmitoylphosphatidylcholine. 2H-NMR studies of the specifically chain-perdeuterated analogs of these asymmetric-chain lipids reveal that the orientational order parameter profiles of their shorter and longer chains differ both qualitatively and quantitatively, regardless of whether they are esterified at the sn1- or sn2 positions of the glycerol molecule. The longer hydrocarbon chains exhibit unusual orientational order profiles in which the order gradient is steepest in the middle of the chain and relatively shallower in regions adjacent to the carboxyl and methyl termini, whereas the short hydrocarbon chains exhibit orientational order profiles typical of those commonly observed with conventional symmetric chain lipids. When compared at equivalent depths in the bilayer, the shorter hydrocarbon chains of the asymmetric-chain lipids are more orientationally disordered than are their longer chain counterparts. At comparable reduced temperatures, the shorter and longer chains of the asymmetric-chain lipids are more orientationally disordered than those of appropriate short and long symmetric-chain lipids, but the chain-averaged orientational order of the symmetric-chain lipid decreases more sharply with increases in temperature than does that of the comparable chain of the asymmetric-chain species. Moreover, the order plateau regions adjacent to the carboxyl groups of the longer chains of the asymmetric-chain phosphatidylcholines are shorter than those of symmetric-chain lipids of comparable hydrocarbon chain length. Overall, the data indicate that the conformational and orientational order in the liquid-crystalline states of these highly asymmetric-chain lipids differ significantly from those of comparable symmetric-chain lipids. Also, the unusual shape of the orientational order profile of the longer chains of the former is attributed to interaction between the methyl termini regions of the long chains with hydrocarbon chains in opposing monolayers. The latter suggests that some form of hydrocarbon chain interdigitation exists in liquid-crystalline bilayers of these highly asymmetric-chain lipids.

Deuterium↗
PubMed2000

Effects of Different Types of Disparity Cues on the Response of Axis-orientation Selective Cells in the Monkey Parietal Cortex.

Purpose: To specify the cues for the discrimination of orientation in depth in axis orientation selective (AOS) neurons.Method: We analyzed the responses of AOS neurons in the monkey caudal intraparietal sulcus (cIPS) region using binocular disparity stimuli generated by stereoscopic 3 D computer graphics.Result: Most AOS neurons (20/27) were sensitive to binocular disparity and showed tuning to the orientation of a slit in the sagittal plane with orientation disparity cues. For 12 neurons we also used an array of discs or dots instead of slits to eliminate orientation disparity. Half of the neurons (6/12) responded better to the slits than to the discs or dots, suggesting that they were sensitive to orientation disparity. Five neurons (5/12) responded equally well to the discs or dots suggesting that they were more sensitive to the gradient of horizontal disparity than to the orientation disparity.Conclusion: Both orientation disparity and disparity gradient were likely to be integrated in the cIPS area to represent axis orientation of an object in space.

Journal Article↗
PubMed1998

Effects of contrast and temporal frequency on orientation discrimination for luminance and isoluminant stimuli.

We compared the mechanisms responsible for orientation discrimination of stimuli defined by luminance and red/green isoluminant contrast. A four-alternative forced-choice (4-AFC) paradigm was used to determine thresholds for discriminating 1 cpd sinewave gratings differing in orientation, contrast, or both. When measuring orientation thresholds as a function of stimulus contrast, we found a decrease in thresholds with increasing stimulus contrast. For three temporal frequencies (0, 1, and 8 Hz) the functions relating orientation thresholds to stimulus contrast had similar shapes for luminance and isoluminant gratings, indicating similar processing mechanisms. Thresholds for stationary or slowly moving gratings were consistently lower for isoluminant than for luminance gratings, when contrast was expressed on an absolute RMS-cone-contrast scale. When contrast was defined as multiples of detection thresholds, discrimination was slightly better for luminance gratings. Thresholds for fast moving gratings were similar, irrespective of the definition of contrast. In contrast to previous work, we found a marked "oblique-effect" for both luminance and isoluminant gratings, when measuring discrimination thresholds as a function of standard orientation. Finally, we measured discrimination thresholds for gratings that varied in contrast and orientation simultaneously. The shapes of the resulting two-dimensional threshold contours were similar for luminance and isoluminant gratings, indicating again that these stimuli undergo similar neuronal processing. Performance of the observers could be described by probability summation of the orientation and contrast cues, resulting in an elliptical shape of the two-dimensional threshold contours. In conclusion, our results show similar performance for luminance and isoluminant gratings in several orientation discrimination tasks. The similarity in shape of the different threshold functions presents strong evidence that similar mechanisms underlie orientation discrimination of luminance and isoluminant stimuli.

Color Perception↗
PubMed2000

Graded sparing of visually-guided orienting following primary visual cortex ablations within the first postnatal month.

We compared the abilities of intact cats and cats that incurred lesions of areas 17 and 18 in adulthood, at one month of age (P28), or on the day of birth (P1), to detect and orient towards visual stimuli either moved into or illuminated in the periphery of the visual field, and to detect and orient towards a stationary, broad-band white-noise auditory stimulus. For all groups of cats, movement of a stimulus into the visual field was a more potent stimulus for evoking visually-guided orienting movements than illumination of a static light-emitting diode (LED). The potency of the auditory stimulus was also extremely high. Proficiency on both visual tasks was graded according to the age at which areas 17 and 18 were ablated in the sequence: adult, P1, P28 and intact in the sequence worst-->best performance. The superior performance of the P1- and P28-groups provided evidence for sparing of visually-guided orienting, but the sparing was incomplete because it did not match performance of intact cats. Lesions of areas 17 and 18 incurred in adulthood had no significant impact on orienting to auditory white-noise stimuli. However, orienting performance to auditory stimuli presented in the peripheral quadrants was slightly superior in the P28 group and reduced in the P1 group. Thus, the visual sparing exhibited by the P1 group may be at the expense of highly proficient orienting to auditory cues. Overall, these results extend our knowledge by showing that in addition to P1-cats, cats that incur lesions of areas 17 and 18 at one month-of-age also exhibit sparing of visually-guided orienting, and that the sparing is not confined to a single stimulation paradigm. Finally, the covariation in the magnitude of pathway modifications with the scale of the orienting proficiency in P1- and P28 cats helps to solidify the linkage between rewired brain pathways and spared visually-guided behaviors.

Age Factors↗
PubMed1999

Biomechanics of mandibular distractor orientation: an animal model analysis.

PURPOSE: Previous reports suggest that device orientation may be one of the most important parameters affecting the successful application of osteodistraction. However, only computer models or cadaver mandibles have been used to investigate the biomechanical effects of device orientation during mandibular distraction osteogenesis. Therefore, the purpose of this study was to compare two different device orientations during bilateral mandibular osteodistraction in an animal model. MATERIALS AND METHODS: Fifteen skeletally mature beagle dogs underwent 10 mm of bilateral mandibular lengthening by intraoral distraction osteogenesis. The dogs were divided into two groups based on the orientation of the distraction device relative to the mandible when viewed occlusally: either parallel to the body of the mandible (group I) or parallel to the axis of distraction (group II). The effects of device orientation during osteodistraction were then analyzed clinically, radiographically, and by dental cast measurements. RESULTS: Distractors oriented parallel to the body of the mandible caused an increase in the anterior width of the proximal mandibular segments. This lateral displacement of the proximal segments led to several clinical complications, including screw fixation failure and bone resorption under the fixation plates. These effects were minimized when the device was oriented parallel to the axis of distraction. CONCLUSIONS: Device orientation plays an important role when applying distraction osteogenesis in a clinical setting. Although other intrinsic and extrinsic factors affect the success of osteodistraction, the devices should be oriented parallel to the axis of distraction to minimize adverse biomechanical effects during bilateral mandibular lengthening.

Animals↗
PubMed2001

Estrogen changes mitosis orientation in the uterine epithelia.

OBJECTIVES: Estrogens can lead to hyperplasia and cancer formation in the uterus, ovary and mammary gland. However, key factors involved in this process are not defined at present. It is possible that estrogens primarily affect more global tissue-organising parameters as composition of tissues in three-metric space, that is brought about changes in the orientation of the plane of cell division. There are no data about estrogen action on mitosis orientation in the uterus. STUDY DESIGN: Mitosis orientation, proliferative activity and general histology were examined in the uterus, jejunal and colonic crypts, and epidermis of ovariectomized rats 0, 24, 36 and 48h after a single injection of estradiol, and in the uterus of ovariectomized mice received injections with estradiol once-a-week for 30, 60 and 90 days. RESULTS: All mitoses in luminal and glandular epithelia of the uterus of ovariectomized rats aligned parallel to the basement membrane, and estradiol treatment leads to appearing of mitoses oriented perpendicular to the basement membrane of the epithelium. Together with increase in the proliferative activity, the number of perpendicular oriented mitoses in uterine epithelia of ovariectomized rats is significantly increased after a single injection of estradiol. During endometrial hyperplasia formation in mice, that is induced by chronic estrogen treatment, the number of perpendicular oriented mitoses in uterine epithelia become much more higher. In jejunal and colonic crypts, epidermis of ovariectomized rats, most of mitoses disposed parallel to the basement membrane and an injection of estradiol did not affect mitosis orientation and activity of proliferation. CONCLUSIONS: Estradiol effect on mitosis orientation may be considered as specific. Changes in mitosis orientation are probably responsible for estrogen-dependent hyperplasia and cancer formation in the uterus.

Animals↗
PubMed2002

Fibroblast orientation to stretch begins within three hours.

Most connective tissue cells align in response to stretch. Previous studies have shown these responses occur within 12-14 h of initiation of stretch, but do not identify the time at which this orientation occurs, nor whether the orientation continues after cessation of stretch. To ascertain the earliest times at which fibroblast orientation occurs, we cultured primary human fibroblasts on deformable culture dishes and stretched (1 Hz, 8% uniaxial strain) them for up to 24 h. We photographed the cells at 0.5, 1-6, 8, 10, 12, 14, 16, and 24 h. Similarly cells were photographed at 1-3, or 4 h after cessation of stretch for stretch durations of 1, 2, and 3 h. Orientation of cells were ascertained by an interactive computer program. The fibroblasts began to orient by 2-3 h and orientation appeared nearly complete by 24 h. Cultures stretched for 2 or 3 h continued to exhibit greater degrees of orientation (compared to controls) for 2 or 3 h respectively after cessation of stretch. We conclude fibroblasts begin to orient within 3 h of initiation of stretch, and that they continue to orient for several hours after cessation of stretch.

Adaptation, Physiological↗
PubMed1997

How the human visual system encodes the orientation of a texture, and why it makes mistakes.

Human observers are exquisitely sensitive to tilt in the orientation of a line. We can detect rotations away from the vertical of 0.5 degrees. It has been suggested [1,2] that this accuracy is a result of the orientation-selectivity of simple cells in the primary visual cortex (V1), many of which have receptive fields with an elliptical shape [3]. However, it is possible to sense the tilt of many stimuli that are unlikely to have their tilt directly encoded by such cells. For example, a garment such as a tie with diagonal stripes would predominantly stimulate cells in V1 tuned to an orientation of the stripes; yet we could tell whether or not the garment as a whole was tilted from the vertical. The perception of oriented textures is subject to systematic errors, however. A striking example is the Fraser 'twisted cord' illusion (Fig. 1) in which we see the global orientation of the horizontal texture-defined lines as being tilted in the direction of its locally tilted segments. If the component segments are at a larger angle (30 degrees) to the global orientation, on the other hand, the perceived shift is in the opposite direction. We have measured these effects psychophysically, and we propose a model in which second-order orientation units receive excitation from V1 units of similar orientation, but inhibition from V1 units of dissimilar orientation. Our model correctly predicts that making the textures different in average brightness from the background will reduce the illusions.

Humans↗
PubMed2005

Sexual orientation and mental health in a birth cohort of young adults.

BACKGROUND: This paper sought to examine the relationship between sexual orientation and mental health in a New Zealand birth cohort studied to age 25 years. METHOD: The analysis is based on a sample of 967 participants (469 males; 498 females) in the Christchurch Health and Development Study. As part of this study information was gathered on: (a) measures of sexual orientation, same-sex behaviour and sexual attraction obtained at ages 21 and 25 years; (b) measures of mental disorders and suicidal behaviours over the interval 21-25 years; (c) measures of childhood and family background. RESULTS: Latent class analysis was used to combine indicators of sexual orientation, same sex behaviour and attraction to form an empirically based classification of sexual orientation. The best-fitting model classified the sample into three groups: exclusively heterosexual orientation (87.6%); predominantly heterosexual but with same-sex inclinations or experience (9.6%); predominantly homosexual (2.8%). Proportionately more women than men were classified as predominantly heterosexual (14.2% v. 4.8% respectively) or predominantly homosexual (3.9% v. 1.5% respectively). Cohort members with a predominantly homosexual orientation had rates of mental disorder and suicidal behaviours that were between 1.5 and 12 times higher than for those with an exclusively heterosexual orientation. These associations persisted after adjustment for confounding. The associations between sexual orientation and mental health were more marked for males than females. CONCLUSIONS. The findings suggest a continuum of sexual preferences amongst young adults. Variations in sexual orientation were clearly associated with mental health. These associations tended to be stronger for males.

Adult↗
PubMed2000

Low-energy ion--surface reactions of pyrazine with two classes of self-assembled monolayers: influence of alkyl chain orientation

Collisions of pyrazine with two classes of self-assembled monolayer (SAM) films are employed to determine whether surface confinement and the resulting alkyl chain orientation, influences low-energy ion-surface reactions. SAM films formed from n-alkanethiols (CH3(CH2)n-S-Au, n = 14-17) and 4-(4-alkoxyphenylbenzenethiols (4-(4-CH3(CH2)mOC6H4)-C6H4-S-Au, m = 14-17) chemisorbed onto Au (111) substrates are known to exhibit a chain-length-dependent odd-even effect that places the terminal C-C bond into different orientations. Ion-surface collisions (20 eV) of pyrazine molecular ion (M = m/z 80) with these surfaces yield reaction product ions corresponding to the addition of hydrogen atoms ([M + H]+ = m/z 81) and methyl groups ([M + CH3]+ = m/z 95) from the surface to the probe ion. Differences in the relative abundance of the reaction product ions are measured as a function of chain length for both classes of SAM film. SAM films with odd chain lengths (n, m = 14 and 16) have a consistently higher abundance of H addition product ions than SAM films with even chain lengths (n, m = 15 and 17). Alternating reactivity is also observed for the addition of CH3, with methyl addition occurring more readily on even-chain-length films. The variations are consistent with the well-characterized orientation differences known to exist for films of this type. Specifically, odd-chain-length films are oriented such that the last C-C bond is more parallel to the plane of the surface than it is for even-chain-length films. The critical element of the parallel orientation is that it leaves, on average, one hydrogen atom on the terminal methyl and both hydrogen atoms on the first underlying methylene in more reactive positions compared to even chain lengths. Conversely, the trend in the relative abundance of CH3 addition indicates that the orientation produced by an even-chain-length film, with the last C-C bond more perpendicular to the surface, allows the probe ion better access to the methyl carbon. Reflection absorption IR spectroscopy (RAIRS) data independently confirm the orientational disposition of the films. The RAIRS data show that the odd-even effect is less dramatic for the n-alkanethiols when compared to 4-(4-alkoxyphenyl)benzenethiols. A smaller difference in ion-surface reactivity is measured for n-alkanethiols, demonstrating that ion-surface reactions can distinguish subtle differences in average orientation. In short, we report that the extent of ion-surface reactions of pyrazine ion with two classes of SAM films is directed by the spatial orientation of the surface-confined species that participate in the reaction.

Journal Article↗
PubMed1994

Analysis of circular dichroism spectra of oriented protein-lipid complexes: toward a general application.

A new application of circular dichroism on oriented films of protein-lipid complexes is presented in this work, which provides quantitative information on the orientation of alpha-helices with respect to the incident light beam. We used literature reference circular dichroism spectra for the various secondary structures to develop a new set of spectra, where the different directions of absorption within the molecular axis frame for each secondary structure type are taken into account. Using this new set of spectra, we could determine the orientation of the helical part of melittin in oriented films composed of various phospholipids. The orientation of the helix axis is found to be perpendicular to the membrane normal of films of dioleoylphosphatidylcholine, dioleoylphosphatidylglycerol, and dioleoylphosphatidylserine, whereas the helix was aligned preferentially parallel to the membrane normal for membranes composed of dimyristoylphosphatidylcholine and dimyristoylphosphatidylglycerol at a hydration of approximately 2-4 water molecules per lipid. The orientations found by circular dichroism at this low hydration for the various systems agreed very well with those obtained by Fourier transform infrared measurements on these samples. Upon increasing the hydration of the film (to approximately 20 water molecules per lipid), it is shown by circular dichroism that the orientation of the helix of melittin changes most in films of dioleoylphosphatidylserine, where it adopted, under these conditions, a preferred parallel orientation with respect to the membrane normal. Complications in the analysis of circular dichroism spectra of oriented samples are discussed and illustrated using patches of native purple membrane containing bacteriorhodopsin and films of alamethicin in dioleoylphosphatidylserine membranes.

Circular Dichroism↗
PubMed1988

Effect of pulsed and reversing electric fields on the orientation of linear and supercoiled DNA molecules in agarose gels.

When linear or supercoiled DNA molecules are imbedded in agarose gels and subjected to electric fields, they become oriented in the gel matrix and give rise to an electric birefringence signal. The sign of the birefringence is negative, indicating that the DNA molecules are oriented parallel to the electric field lines. If the DNA molecules are larger than about 1.5 kilobase pairs, a delay is observed before the birefringence signal appears. This time lag, which is roughly independent of DNA molecular weight, decreases with increasing electric field strength. The field-free decay of the birefringence is much slower for the DNA molecules imbedded in agarose gels than observed in free solution, indicating that orientation in the gel is accompanied by stretching. Both linear and supercoiled molecules become stretched, although the apparent change in conformation is much less pronounced for supercoiled molecules. When the electric field is rapidly reversed in polarity, very little change in the birefringence signal is observed for linear or supercoiled DNAs if the equilibrium orientation (i.e., birefringence) had been reached before field reversal. Apparently, completely stretched, oriented DNA molecules are able to reverse their direction of migration with little or no loss of orientation. If the steady-state birefringence had not been reached before the field reversal, complicated orientation patterns are observed after field reversal. Very large, partially stretched DNA molecules exhibit a rapid decrease in orientation at field reversal. The rate of decrease of the birefringence signal in the reversing field is faster than the field-free decay of the birefringence and is approximately equal to the rate of orientation in the field (after the lag period).(ABSTRACT TRUNCATED AT 250 WORDS)

Birefringence↗
PubMed2002

Gal4-VP16 and Gal4-AH increase the orientational and axial specificity of TATA box recognition by TATA box binding protein.

Previous work has shown that binding of the TATA box binding protein (TBP) to the TATA box is a rate-limiting step during pre-initiation complex (PIC) formation. Although the transcription of eukaryotic genes normally proceeds in one direction, studies in solution have shown that TBP lacks the information necessary to orient itself on the TATA box. Instead, yeast TBP binds TATA-containing promoters in two orientations that are related by a 180 rotation about TBP's pseudo-2-fold symmetry axis. Recruitment of PIC components by gene-specific activators is considered a primary mechanism of transcriptional enhancement. Here we ask whether activators might function, at least in part, by increasing the fraction of PICs assembled with TBP bound in the orientation necessary for transcription. We use DNA affinity cleavage and a TBP-phenanthroline-copper conjugate to monitor the orientation of TBP in the presence of the well-studied activators Gal4-VP16 and Gal4-AH. In the absence of a transcriptional activator, only 51% of the TBP x TATA box complexes were bound in the orientation necessary for the initiation of transcription. However, in the presence of saturating Gal4-VP16, 87% of the TBP bound to the TATA box was oriented correctly at equilibrium. This increase in orientational specificity corresponds to a free energy difference (Delta Delta G(obs)) of 1.1 kcal x mol(-1) and was accompanied by a dramatic increase in axial specificity, reminiscent of the effects of transcription factors TFIIB and TFIIA reported previously. Gal4-AH also enhanced the orientational and axial specificity of the TBP x TATA complex, although to a lesser extent. We suggest that these effects on specificity represent a variation of recruitment, since they require direct interactions between the activator and a PIC component but only increase the effective concentration of the correctly oriented PIC component. These findings add to increasing evidence that recruitment may encompass a broad range of mechanisms.

Binding Sites↗
PubMed2004

Cell orientation influences the biaxial mechanical properties of fibroblast populated collagen vessels.

Bioartificial tissues, composed of cells in a collagen matrix, can be fabricated with preferred cell orientations to mimic the histologic arrangement of biologic tissues. The influence of preferred cell orientations on the biaxial mechanical behavior of bioartificial tissues is unknown. Characterizing the biaxial mechanical behavior is necessary for better predicting the in vivo behavior of bioartificial tissues. Fibroblast populated collagen vessels (FPCVs) were fabricated with two different cell orientations by controlling the mechanical constraints during incubation. The cell orientation was verified by confocal microscopy and the collagen fiber organization was examined by confocal reflection and scanning electron microscopy (SEM). Pressure-diameter, force-length tests were performed to determine the influence of cell orientation on the biaxial mechanical behavior. FPCVs were more extensible in the direction perpendicular to the preferred cell orientation, than in the direction parallel to the cell orientation. Biaxial tests were also performed in the presence of Cytochalasin D (Cyto D) to minimize the mechanical contribution of the cells. After Cyto D treatment, the FPCVs remained more extensible in the direction perpendicular to the cell orientation, even though a preferred collagen fiber orientation was not observed in the microscopy images.

Animals↗
PubMed2001

Immune function in Swedish élite orienteers.

During 1979-1992 an increased frequency of sudden unexpected cardiac death (SUD) occurred among young male Swedish élite orienteers. Subacute-to-chronic myocarditis was found in 12/16 (75%) at autopsy and Chlamydia pneumoniae, or a cross-reacting agent, was suspected on the basis of diagnostic tests performed. Because myocarditis is an infrequent cause of SUD and clusters of SUD are rare, whereas Chlamydia pneumoniae infections are ubiquitous and seldom cause severe myocarditis, 119 top ranked élite orienteers (67 males and 52 females) and 36 highly trained male middle-distance runners and cross-country skiers, serving as controls, underwent immunologic screening in an effort to reveal possible immune dysfunction. Except for two orienteers and one runner/skier who showed genetic C3-deficiency or IgA-deficiency, the results showed no significant differences between the orienteers and controls with respect to immunoglobulin levels, complement activation, lymphocyte subsets, including activated T lymphocytes, and sIL-2r-alpha. IL-1 beta, IL-6, TNF-alpha, and sCD8, tested in the orienteers only, were normal. However, IFN-gamma was significantly higher in controls than in orienteers, who showed normal levels, whereas the orienteers had increased sELAM-1 and sICAM-1 levels. Finally, sIL-2 receptor-alpha was similarly elevated in orienteers and controls. We conclude that, with the tests employed, no immunologic disturbance could be revealed in the orienteers that may potentially have increased their susceptibility to myocarditis and SUD.

Adolescent↗
PubMed2006

Mechanisms underlying cross-orientation suppression in cat visual cortex.

In simple cells of the cat primary visual cortex, null-oriented stimuli, which by themselves evoke no response, can completely suppress the spiking response to optimally oriented stimuli. This cross-orientation suppression has been interpreted as evidence for cross-orientation inhibition: synaptic inhibition among cortical cells with different preferred orientations. In intracellular recordings from simple cells, however, we found that cross-oriented stimuli suppressed, rather than enhanced, synaptic inhibition and, at the same time, suppressed synaptic excitation. Much of the suppression of excitation could be accounted for by the behavior of geniculate relay cells: contrast saturation and rectification in relay cell responses, when applied to a linear feed-forward model, predicted cross-orientation suppression of the modulation (F1) component of excitation evoked in simple cells. In addition, we found that the suppression of the spike output of simple cells was almost twice the suppression of their synaptic inputs. Thus, cross-orientation suppression, like orientation selectivity, is strongly amplified by threshold.

Action Potentials↗