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PubMed2006

GABA(A) receptor diversity and pharmacology.

Because of its control of spike-timing and oscillatory network activity, gamma-aminobutyric acid (GABA)-ergic inhibition is a key element in the central regulation of somatic and mental functions. The recognition of GABA(A) receptor diversity has provided molecular tags for the analysis of distinct neuronal networks in the control of specific pharmacological and physiological brain functions. Neurons expressing alpha(1)GABA(A) receptors have been found to mediate sedation, whereas those expressing alpha(2)GABA(A) receptors mediate anxiolysis. Furthermore, associative temporal and spatial memory can be regulated by modulating the activity of hippocampal pyramidal cells via extrasynaptic alpha(5)GABA(A) receptors. In addition, neurons expressing alpha(3)GABA(A) receptors are instrumental in the processing of sensory motor information related to a schizophrenia endophenotype. Finally, during the postnatal development of the brain, the maturation of GABAergic interneurons seems to provide the trigger for the experience-dependent plasticity of neurons in the visual cortex, with alpha(1)GABA(A) receptors setting the time of onset of a critical period of plasticity. Thus, particular neuronal networks defined by respective GABA(A) receptor subtypes can now be linked to the regulation of various clearly defined behavioural patterns. These achievements are of obvious relevance for the pharmacotherapy of certain brain disorders, in particular sleep dysfunctions, anxiety disorders, schizophrenia and diseases associated with memory deficits.

Animals↗

PubMed1997

The effectiveness of orofacial myofunctional therapy in improving dental occlusion.

The most significant findings of this study definitively establish the beneficial effects of orofacial myofunctional therapy on improving dental occlusion, decreasing dental open bite, and decreasing dental overjet. The results reported are actually quite conservative because of the method of measuring. Measuring and recording every tooth unquestionably dilutes the results which would have been achieved if only the anterior teeth had been used in the calculations. Some may question the small millimeter change as being significant. The change is reflective of the overall relative value change of incorporating all teeth within the dental arches and not limiting the analysis to only the anterior teeth. The secondary findings of the study confirm that age is not necessarily a factor in predicting success of a therapy program. Further, this study indicates that improvement of open bite and overjet can result from OMT without prior or concurrent orthodontic intervention. Orofacial myofunctional therapy, from a public health standpoint, is a classic form of primary prevention to improve the overall health and well-being of the individual. The end result of OMT therapeutic programs is the establishment of new neuromuscular patterns, correction of functional and resting postures, correction of chewing/swallowing/feeding patterns and elimination of deleterious behaviors. Stabilization and maintenance of therapeutic goals become part of the lifelong learning and change process. Orofacial myofunctional therapy utilizes knowledge and skills acquired through multidisciplinary education and training. Licensed professionals, from dental hygiene, dentistry, speech pathology, medicine, nursing, and other allied health professions with advanced education and training in orofacial myofunctional therapy have demonstrated expertise in providing collaborative, integrated, and interdisciplinary primary care. Reference to earlier research works and anecdotal reports of ineffectiveness unfortunately perpetuate and reinforce the dichotomous quandary of form and function. Instead, recognition of the interrelationship of form and function, as conjoint fundamental processes, would encourage more pro-active patient referrals for orofacial myofunctional therapy services. This would allow the specialty area of orofacial myology to further validate the effectiveness of OMT on tooth movement in a positive, collaborative, and beneficial manner. Acknowledging the small sample size in this study may encourage other clinicians to conduct future research in this area. Additional research is needed on the physiologic adaptive capacity of the orofacial environment. Developmental aspects of orofacial and jaw neurophysiology, especially in children, are scant in the literature. Treatment recommendations for specific dental malocclusions are based on many factors. Each malocclusion classification presents opportunity for OMT research. A major research dilemma for the practicing clinician is the moral and ethical responsibility of providing treatment when dysfunction is diagnosed. Designing a study and identifying a "control group" is difficult due to the unethical aspect of knowingly withholding therapy when the benefits are statistically proven and available. A study design using the sample as its own control can infer and demonstrate validity. The next logical test is replication of this study to determine the level of reliability. This issue of the I.J.O.M. addresses the effectiveness of orofacial myology treatment in improving speech articulation, eliminating digit sucking, and improving dental occlusion. It is time the professions of dental hygiene, dentistry, medicine, and speech pathology move forward and acknowledge current substantive research and literature that supports the philosophies of prevention, early interception (intervention), and corrective treatment. The dark ages of disbelief only remain dark as long as we forget to turn on the light. (ABSTRACT TRU

Adolescent↗

PubMed1991

Striate cortical contribution to the surface-recorded pattern-reversal VEP in the alert monkey.

The striate cortical contribution to the surface pattern-reversal visual evoked potential (VEP) was investigated in awake monkeys during performance of a visual fixation task, by examining laminar profiles of VEP, current source density (CSD) and concomitant multiunit activity (MUA) in Area 17, recorded simultaneously at incremental depths using multicontact electrodes. Stimuli were black/white bar gratings centered on the fixation point. The typical surface pattern-reversal VEP over striate cortex consists of a prominent positivity peaking at 50-70 msec (P60), followed by a large negativity peaking at approx. 80 msec (N80), and then by a late broad positivity, peaking between 120 and 150 msec (P125). P60 is often preceded by a small negativity peaking at 45-55 msec (N50), and on rare occasions a small positivity (P40) is also observed. N50 is generated primarily by current sinks in Lamina 4C. P60 arises from large current sources in the supragranular laminae. N80 and P125 appear to be composite waveforms reflecting complex contributions from local activity and from activity occurring outside of the foveal/immediate parafoveal representation in Area 17. The basic physiologic sequence elicited by patterned stimulation is similar to that elicited by diffuse luminance or by electrical stimulation, but is characterized by more prominent supra- and infragranular activation. It is consistent with the cellular and synaptic anatomy of Area 17: initial activation of the thalamorecipient subdivisions of Lamina 4C, followed by activation of mid/upper Lamina 4 and of supra- and infragranular laminae. Our results suggest the possibility of differentiating synaptic stages and cellular processes reflected in the human VEP, based on homologies with simian VEP components.

Animals↗

PubMed1990

Conjunction search revisited.

Search for conjunctions of highly discriminable features can be rapid or even parallel. This article explores three possible accounts based on (a) perceptual segregation, (b) conjunction detectors, and (c) inhibition controlled separately by two or more distractor features. Search rates for conjunctions of color, size, orientation, and direction of motion correlated closely with an independent measure of perceptual segregation. However, they appeared unrelated to the physiology of single-unit responses. Each dimension contributed additively to conjunction search rates, suggesting that each was checked independently of the others. Unknown targets appear to be found only by serial search for each in turn. Searching through 4 sets of distractors was slower than searching through 2. The results suggest a modification of feature integration theory, in which attention is controlled not only by a unitary "window" but also by a form of feature-based inhibition.

Adult↗

PubMed2004

Enhanced occipital and anterior cingulate activation in men but not in women during exposure to angry and fearful male faces.

Blood-oxygenation-level-dependent signal was measured with functional magnetic resonance imaging in 24 healthy young subjects (12 men and 12 women) during viewing of angry, fearful, and neutral male and female face pictures. Exposure to angry male as opposed to angry female faces activated the visual cortex and the anterior cingulate gyrus significantly more in men than in women. A similar sex-differential brain activation pattern was present during exposure to fearful but not neutral faces. Previous behavioral studies indicate enhanced physiological arousal in men but not in women during exposure to angry male asopposed to female faces, and brain imaging studies have shown that the occipital cortex and the anterior cingulate gyrus are influenced by activity in the autonomic nervous system as well as by visualattention. Hence, we suggest that the elevated occipital and anterior cingulate activation in men during confrontation with other angry and fearful males may reflect enhanced vigilance in a potentially dangerous situation.

Adult↗

PubMed1999

DNA repeats in the human genome.

Repetitive DNA sequences, interspersed throughout the human genome, are capable of forming a wide variety of unusual DNA structures with simple and complex loopfolding patterns. The hairpin formed by the fragile X repeat, (CCG)n, and the bipartite triplex formed by the Friedreich's ataxia repeat, (GAA)n/(TTC)n, show simple loopfolding. On the other hand, the doubly folded hairpin formed by the human centromeric repeat, (AATGG)n, the hairpin G-quartet formed by (TTAGGG)n at the 3' telomere overhang, and the hairpin G-quartet, and hairpin C+.C paired i-motif formed by the insulin minisatellite, [formula: see text] show multiple and complex loopfolding. We have performed high resolution nuclear magnetic resonance (NMR) spectroscopy and in vitro replication to show that unique base-pairing and loopfolding render stability to these unusual structures under physiological conditions. The formation of such stable structures offers a mechanism of unwinding which is advantageous during transcription. For example, the formation of the hairpin G-quartet, and hairpin C+.C paired i-motif upstream of the insulin gene may facilitate transcription. These unusual DNA structures also provide unique 'protein recognition motifs' quite different from a Watson-Crick double helix. For example, the hairpin G-quartet formed by (TTAGGG)n at the 3' telomere overhang is specifically recognized and stabilized by the human repair protein, Ku70/Ku80 hetero-dimer, which may be important in the stability of the telomere. However, the formation of the same unusual DNA structures during replication is likely to cause instability in the lengths of the DNA repeats. If the altered (generally expanded) length enhances the probability of the unusual structure during the next cycle of replication, it further increases the instability of the repeat causing a 'dynamic mutation'. In fact, NMR and in vitro replication studies show that the longer the repeat length the higher is the probability of hairpin formation by the fragile X repeat, (CCG)n. In addition, the hairpin of the fragile X repeat, upstream of the FMR-1 gene, is more susceptible to CpG methylation than its duplex thereby leading to methyl-directed suppression of transcription. Thus, the selective advantage of the unusual structures formed by the DNA repeats in the regulation of gene expression may be offset by the genomic instability caused by the same structures during replication. The repeat number is a critical parameter that helps maintain a balance between the advantage gained from an unusual structure during gene expression and the disadvantage posed by the same structure during replication.

Antigens, Nuclear↗

PubMed2004

[The role of myeloid differential protein-2 in innate immunity].

As typical PRRs (pattern-recognition receptors), TLRs (Toll-like receptors) play an important role during innate immunity recognition. MD-2 (myeloid differential protein-2) may contain distinct functional domains that can separately and simultaneously bind TLRs (TLR4 or TLR2) and TLR ligands, such as lipopolysaccharide (LPS). The special structure of MD-2 may result in its three main functions: (1) An association with TLR4 that amplifies TLR4 responsiveness to ligands, especially LPS. (2) Enabling TLR2-mediated responses to LPS and enhancing TLR2-mediated responses to bacteria and their cell wall components. (3) Increasing the expression of TLR2 and TLR4 and possibly influencing the correct intracellular distribution of TLR4. Importantly, while MD-2 regulation of TLR expression and distribution is well established, determining whether the interaction is direct or not will require further study. Thus, MD-2 is not only an assistant molecule of TLR4 but is also a key regulatory molecule in innate immunity, and may play important roles during infection, inflammation, immune responses and many other pathologic and physiologic processes.

Animals↗

PubMed2006

Mycobacterium tuberculosis binding to human surfactant proteins A and D, fibronectin, and small airway epithelial cells under shear conditions.

A crucial step in infection is the initial attachment of a pathogen to host cells or tissue. Mycobacterium tuberculosis has evolved multiple strategies for establishing an infection within the host. The pulmonary microenvironment contains a complex milieu of pattern recognition molecules of the innate immune system that play a role in the primary response to inhaled pathogens. Encounters of M. tuberculosis with these recognition molecules likely influence the outcome of the bacillus-host interaction. Here we use a novel fluid shear assay to investigate the binding of M. tuberculosis to innate immune molecules that are produced by pulmonary epithelial cells and are thought to play a role in the lung innate immune response. Virulent and attenuated M. tuberculosis strains bound best to immobilized human fibronectin (FN) and surfactant protein A (SP-A) under this condition. Binding under fluid shear conditions was more consistent and significant compared to binding under static conditions. Soluble FN significantly increased the adherence of both virulent and attenuated M. tuberculosis strains to human primary small airway epithelial cells (SAEC) under fluid shear conditions. In contrast, SP-A and SP-D effects on bacterial adherence to SAEC differed between the two strains. The use of a fluid shear model to simulate physiological conditions within the lung and select for high-affinity binding interactions should prove useful for studies that investigate interactions between M. tuberculosis and host innate immune determinants.

Bacterial Adhesion↗

PubMed2006

The representation of noise vocoded speech in the auditory nerve of the chinchilla: physiological correlates of the perception of spectrally reduced speech.

This study investigated the neural representation of naturally produced and noise vocoded speech signals in the auditory nerve of the chinchilla. The syllables [see text] produced by male speakers were used to synthesize noise vocoded speech stimuli containing one, two, three and four bands of envelope modulated noise. The ensemble response of the auditory nerve, computed by pooling the PST histograms across many auditory nerve fibers, revealed temporal patterns in the responses to the natural tokens that uniquely identified the stop consonants. The responses to the 3- and 4-band noise vocoded tokens contained temporal patterns that were nearly identical to those observed for the natural tokens, while the responses to the 1- and 2-band tokens were significantly different (p<0.0001). The ALSR, ALIR and autocorrelation of the pooled PST histograms represented the detail of the frequency spectrum for a naturally produced vowel, while the driven rate was unreliable. Each of these spectral analyses failed to reveal significant information about the noise vocoded vowels. These results suggest that temporal patterns in the responses of the auditory nerve can provide the cues necessary for the recognition of noise vocoded stop consonants.

Acoustic Stimulation↗

PubMed1991

Vocal quality factors: analysis, synthesis, and perception.

The purpose of this study was to examine several factors of vocal quality that might be affected by changes in vocal fold vibratory patterns. Four voice types were examined: modal, vocal fry, falsetto, and breathy. Three categories of analysis techniques were developed to extract source-related features from speech and electroglottographic (EGG) signals. Four factors were found to be important for characterizing the glottal excitations for the four voice types: the glottal pulse width, the glottal pulse skewness, the abruptness of glottal closure, and the turbulent noise component. The significance of these factors for voice synthesis was studied and a new voice source model that accounted for certain physiological aspects of vocal fold motion was developed and tested using speech synthesis. Perceptual listening tests were conducted to evaluate the auditory effects of the source model parameters upon synthesized speech. The effects of the spectral slope of the source excitation, the shape of the glottal excitation pulse, and the characteristics of the turbulent noise source were considered. Applications for these research results include synthesis of natural sounding speech, synthesis and modeling of vocal disorders, and the development of speaker independent (or adaptive) speech recognition systems.

Adult↗

PubMed2005

Elucidating effective ways to identify and treat malnutrition.

There is a clear rationale for elucidating effective ways of identifying and treating disease-related malnutrition (DRM), given the physiological and financial consequences of this common condition and its treatability. Evidence indicates the efficacy of nutritional support methods (oral, tube and intravenous) in increasing total nutritional intake while having little effect on appetite, satiety, appetite mediators (e.g. leptin) and voluntary food intake. When used as the only source of nutrition, artificial nutrition can effectively maintain nutritional intake, and yet many patients find enteral or parenteral feeding alone is unable to relieve distressing appetite sensations, and unusual temporal patterns (including dissociation between hunger and desire to eat) occur. Despite the positive impact of these feeding methods on intake, controversy about whether nutritional support can affect patient outcome has remained. Systematic reviews and meta-analyses indicate that improvements in function and clinical (mortality, complication rates) outcome can occur in a number of patient groups (including hospitalised patients, the elderly, patients who have had gastrointestinal surgery, patients at risk of pressure ulcers). In order to target those patients who will benefit from nutritional support, and overcome the ongoing problem of poor detection and recognition of DRM, simple routine screening to identify risk followed by practical evidence-based treatment is recommended.

Evidence-Based Medicine↗

PubMed1997

Neoglycoprotein-binding sites (endogenous lectins) in the Fallopian tube, uterus and blastocyst of the rabbit during the preimplantation phase and implantation.

Regulation of the initial phase of embryo implantation may involve the recognition interplay of glycoconjugates and respective receptors such as endogenous lectins on both cellular surfaces. Whereas changes in glycoconjugate composition have been detected in preparation for embryo implantation and described in detail, knowledge on endogenous lectins has remained scant. Affinity probes (carrier-immobilized carbohydrate structures as ligand part on a histochemically inert backbone) are used in the present investigation in order to gain further insights in this area. Cryostat sections of rabbit Fallopian tubes and uteri in nonpregnant and early pregnant [tubes: 3 days post coitum (d p.c.); uteri: 3, 5, 7 and 9 d p.c.] states were studied for binding patterns of a series of biotinylated (neo)glycoproteins. A high density of binding sites was detected with beta-galactosides (with decreasing intensity: beta-D-galactose-BSA, asialofetuin with its triantennary glycan chains, lactose-BSA). Considerably less binding (but with the same pattern) was obtained with beta-N-acetyl-D-glucosaminide-BSA and is interpreted to originate from a cross-reactivity of such sites which may bind physiologically to Gal-beta1,3/4-GlcNAc sequences. In contrast, no evidence for the presence of binding molecules with specificities for a-D-mannose-BSA, maltose-BSA, N-acetyl-galactosaminide-BSA and N-acetyl-D-neuraminic acid-BSA was obtained in these tissues under the same conditions. The epithelium of the Fallopian tube showed a high density of beta-galactoside-binding sites at the apical cell poles (including the cytoplasm and membrane region) already in the nonpregnant state. At 3 d p.c., a strong reaction in all epithelial cells of the isthmus and a marked decrease in the ampulla were noted. The putative lectin(s) appear(s) to be synthesized and secreted by the tubal epithelium. A physiological role in forming the mucoprotein layer of the blastocyst coverings by precipitating the appropriate mucin-type molecules can be considered. Within the endometrium, the beta-galactoside-binding molecules were almost exclusively localized at the apical cell pole of epithelial cells, whereas there was hardly any binding in the epithelial cytoplasm or in the endometrial stroma. The reaction was very weak in the non-pregnant state but increased considerably until 5 d p.c., starting in the luminal-most parts of the epithelium. While the reaction was rather homogeneous at the surface of the luminal epithelium at 5 d p.c., the degree of heterogeneity increased stepwise from 7 to 9 d p.c. In the implantation chamber, the density of these beta-galactoside-specific 'receptors' was further enhanced in particular at the epithelial surface of the placental folds. In contrast, the reaction was less intense at the antimesometrial uterine epithelium and in interblastocyst segments of the uterus, and it remained weak in the middle and deep crypts. The trophoblast showed a high density of galactoside-binding sites at its surface, and less in the cytoplasm. Neoglycoprotein binding to the blastocyst coverings observed at 7 d p.c. was strong in particular at the outer and inner surfaces. Physical factors (e.g. differential texture at surfaces) are discussed to influence the staining patterns of these extracellular coverings. Nevertheless, the observations made on the tubal and the uterine mucosa suggest that the putative lectin(s) detected here is (are) secreted by these epithelia and could be involved in the structural organization of the various layers of the blastocyst coverings with their remarkable content of oligosaccharide chains. This effect on topological aspects of the zona pellucida equivalents may be important for the interplay between trophoblast and uterine epithelium and the cascade leading to implantation initiation.

Animals↗

PubMed2000

Diabetes mellitus in the pre-school child.

Diabetes mellitus presents rarely in the pre-school child and presents specific problems because of the peculiarity of the young child physiology. Pathogenesis involves the classic immunological mechanisms, with a higher incidence of other autoimmunity and family history of diabetes. Because of the rarity of the condition in this age group, the delay of the recognition of the signs and symptoms, which are often subtle at onset, determines the increased incidence of ketoacidosis. The reasons for the lower glycaemic control in this age group include the persistence of endogenous insulin, but also a more detailed involvement by the parents in organising diabetes. For the same reason ketoacidosis is an unusual occurrence after diagnosis. As to insulin therapy, three or more injections a day should be recommended, as in the older child, while the modern devices for blood glucose monitoring have proved useful to improve glycaemic control and to decrease the frequency of nocturnal hypoglycaemia, which gives particular concern given the vulnerability of the nervous system in this age group. Management of diabetes in the pre-school child may result very difficult for both parents and health carers because of the erratic daily pattern of activity, sleep and feeding; however, with a cautious strategy which involves insulin therapy, diet and monitoring it is possible to achieve satisfactorily the following aims: physical well-being of the young child, normal growth, lack of hyperglycaemia or hypoglycaemia, acceptable value of glycosilated haemoglobin.

Child, Preschool↗

PubMed1988

Diazepam binding inhibitor gene expression: location in brain and peripheral tissues of rat.

Diazepam binding inhibitor (DBI), an endogenous 10-kDa polypeptide was isolated from rat and human brain by monitoring displacement of radioactive diazepam bound to specific recognition sites in brain synaptic and mitochondrial membranes. The cellular location of DBI mRNA was studied in rat brain and selected peripheral tissues by in situ hybridization histochemistry with a 35S-labeled single-stranded complementary RNA probe. DBI mRNA was heterogeneously distributed in rat brain, with particularly high levels in the area postrema, the cerebellar cortex, and ependyma of the third ventricle. Intermediate levels were found in the olfactory bulb, pontine nuclei, inferior colliculi, arcuate nucleus, and pineal gland. Relatively low but significant levels of silver grains were observed overlying many mesencephalic and telencephalic areas that have previously been shown to contain numerous DBI-immunoreactive neurons and a high density of central benzodiazepine receptors. In situ hybridizations also revealed high levels of DBI mRNA in the posterior lobe of the pituitary gland, liver, and germinal center of the white pulp of spleen, all tissues that are rich in peripheral benzodiazepine binding sites. The tissue-specific pattern of DBI gene expression described here could be exploited to further understand the physiological function of DBI in the brain and periphery.

Animals↗

PubMed2005

Event-related potential component associated with the recognition of three-dimensional objects.

To understand the physiological process underlying view-invariant object recognition, we designed a delayed matching-to-sample task under two different conditions: in the first condition, the sample and test stimuli were presented in the same view, and in the second, the two stimuli were presented in different views. The event-related potential (ERP) component, posterior N1, exhibited a significantly larger amplitude when the test image was in the same view as the sample image than when the test and the sample images were in different views. The result indicates that the posterior N1 is significantly sensitive to view association, and clarifies the difference between the neuronal activity that occurs in 3D object recognition and 2D image identification at the level of N1.

Adult↗

PubMed1983

Contrast effects of the three primary colors on human visual evoked potentials.

In this study we evaluated in humans the question of whether contrast effects with patterned color stimuli varied in the same way as is known to occur with black-and-white stimuli. Using a counterphasing checkerboard pattern, we evaluated the steady-state visual evoked potential (VEP) in 10 subjects for the response to different contrast levels in each of the 3 primary colors. Overall mean luminance of each color was photometrically equated and kept constant during all trials. The VEP was computer-averaged for 90 consecutive 1 sec epochs of stimulation, and the power at the appropriate frequency was calculated. For each color, the contrast-response curves revealed small power values at low contrast (0.1) and larger power at the 3 high-contrast settings (0.3-0.5). Power varied markedly by color and by subject. The shape of the curves, depending on color and subject, often indicated a saturation of response. A given subject commonly had a physiologically 'preferred' color in that the power with that color was consistently larger. Most subjects had definite subjective color 'preferences,' believing that they perceived the contrast better for one or two colors. However, these impressions were often not validated by the VEP responses to the various colors. These results indicate that white-light VEP responses may not necessarily reflect the response characteristics of specific colors, nor do they necessarily reflect the large inter- and intra-subject differences in color responses noted in this study.

Adult↗

PubMed1997

Vernier step acuity and bisection acuity for texture-defined form.

Using as the stimulus a texture pattern of short lines, we compared positional acuity thresholds for an orientation-texture-defined (OTD) boundary and a luminance-defined (LD) boundary. Texture lines had different orientations but the same luminance on either side of the OTD boundary, and different luminances but the same orientation on either side of the LD boundary. For the LD boundary, both vernier step acuity threshold and bisection acuity threshold were inversely proportional to the number of texture lines per degree (i.e., the pattern's spatial sampling frequency) over the entire 1.9-59 samples/deg frequency range investigated, though thresholds were considerably lower than the distance between adjacent lines. For the OTD boundary, both thresholds were inversely proportional to spatial sampling frequency (though thresholds were again considerably less than the distance between adjacent lines) but only for sampling frequencies below 20 samples/deg. For sampling frequencies below 20 samples/deg, the ratio between positional acuity thresholds for OTD and LD boundaries was approximately constant (3.5:1 for vernier acuity and 1.4:1 for bisection acuity). As sampling frequency was increased beyond 20 samples/deg both vernier and bisection acuity thresholds for OTD boundaries rose steeply. Both thresholds fell to a minimum near 20 samples/deg. For vernier step acuity the minimum threshold was 2.3 and 2.4 min arc (two observers), and for bisection acuity 1.7 and 1.9 min arc. We propose that these minimum thresholds approach a physiological limit of positional acuity for an OTD boundary, and that the limit is determined by a balance between the progressive improvement of positional acuity caused by increasing the frequency of spatial sampling vs the progressive reduction in visibility of the OTD boundary caused by the associated reduction in the length of texture lines. These physiological limits are far higher than the corresponding limits for sharp-edged high-contrast LD targets (2-5 and 1-5 sec arc, respectively). For an OTD boundary the effect of orientation contrast on vernier step acuity threshold approximated a square root law, while the effect of orientation contrast on bisection acuity approximated a linear law. Observers can combine positional information carried by texture contrast with positional information carried by luminance contrast. As to the combination rule, our findings are consistent with probability summation between independent channels.

Adult↗

PubMed1988

A statistical study on left ventricular peak filling rate in diabetes.

The importance of non-invasive evaluation of cardiac function in diabetes is well known and radionuclide angiocardiography has become an accepted diagnostic procedure. While the pathophysiological interpretation of systolic parameters is clear, the meaning and determinants of peak filling rate (PFR) remain rather speculative. In the present study, a "pattern recognition" approach, including principal component analysis and hierarchical cluster analysis, has been adopted in order to evaluate the determinants of PFR in a series of 48 non-selected diabetic patients. The results of the study show that: PFR is inversely dependent on age which is its main determinant when systolic function is preserved; PFR is inversely dependent on combined effects of left ventricular dimensions, angina and wall motion; and the duration of diabetes in itself does not influence PFR. These results lead to the following clinically relevant conclusions: (a) It is unlikely that a young diabetic patient without anginal symptoms will have a significant PFR impairment even if the diabetes has been present for a long time. If such impairment is however present, ventricular latent dysfunction is likely to be the cause even if systolic parameters are still normal; (b) A decrease of PFR in a middle-aged diabetic patient without symptoms and with normal systolic function cannot be equated with latent ventricular dysfunction as it may represent only an age-related physiological change without special diagnostic meaning.

Adolescent↗