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PubMed1986

Nonaccommodative convergence excess.

Nonaccommodative convergence excess is a condition in which a patient has orthotropia or a small-angle esophoria or esotropia at distance and a large-angle esotropia at near, not significantly reduced by the addition of spherical plus lenses. The AC/A ratio, determined with the gradient method, is normal or subnormal. Tonic convergence is suspected of causing the convergence excess in these patients. Nonaccommodative convergence excess must be distinguished from esotropia with a high AC/A ratio and from hypoaccommodative esotropia. In 24 patients treated with recession of both medial recti muscles with and without posterior fixation or by posterior fixation alone, the mean correction of esotropia was 7.4 prism diopters at distance and 17 prism diopters at near.

Accommodation, Ocular↗
PubMed1996

Slow-velocity asymmetrical convergence: a decisive failure of "Hering's law".

With targets aligned in the midsagittal plane, six of seven subjects tested were often able to make smooth symmetrical convergence movements in which no detectable saccade occurred during the initial 300 msec of the eye movement (12-95% of their trials). With targets located in a plane parallel to, but appreciably to one side of the midsagittal plane, those same six subjects were also often able to make smooth, slow, "saccade-free" asymmetrical convergence movements that were appropriate in magnitude and velocity to the target location (ratio of excursions about 2 to 1). Vergence movements are thus more versatile than can be accounted for by a single generator of binocularly symmetrical input to the eye muscles (Hering's Law of Equal Innervation). The occurrence of "saccade-free" asymmetrical convergence suggests instead that during binocular viewing, each eye can respond independently to that eye's view of the target, resulting in binocularly simultaneous slow-velocity nasalward eye movements--which will represent symmetrical or asymmetrical convergence depending on the arrangement of the targets. A similar interpretation is also apparently demanded by recent data on the initiation of disjunctive smooth-pursuit movements in the monkey [King & Zhou (1995) Vision Research, 35, 3389-3400].

Adolescent↗
PubMed2026

Genomic contingence beneath ecological convergence: the tempo and mode of gene loss in parasitic bilaterians.

Parasitism has independently evolved hundreds of times among metazoans. Nonetheless, parasites have explored only a limited range of ecologies, and they display frequent convergence in morphological, behavioral, and life-history traits. Although gene loss in particular parasitic species has been documented, it is not known if gene loss converges along the same lines as these other traits. To test for convergent gene loss, we characterized the housekeeping, regulatory, and DNA-repair complements of 48 bilaterian species, including 20 parasites belonging to 6 different bilaterian phyla. We found that different parasitic strategies do not display characteristic tempos or modes of gene loss. Further, the accelerated rates of gene loss seen in some parasites were almost always shared with their free-living relatives, indicating that the increased rate of loss preceded the rise of parasitism. Therefore, the convergent ecological strategies and adaptations that have arisen in distantly related parasitic lineages overlay contingent gene losses, which largely reflect their phylogenetic history. These results have important implications for how ecologists and evolutionary biologists should model the acquisition of parasitism, especially regarding the long-held assumption that reversion from a parasitic to a free-living state is impossible.

Animals↗
PubMed2026

Direct link between convergent evolution at sequence level and phenotypic level of septal pore cap in Agaricomycotina.

Several homologous morphological characters, despite sharing apparently similar features, are known to have independently evolved in different lineages multiple times. However, the genetic backgrounds of such morphological convergences remain poorly understood. To detect any correlated amino acid substitutions potentially responsible for morphological convergence at the phenotypic level, we focused on the morphology of the septal pore cap (SPC), a structure involved in mycelia's complex multicellularity in fungi. SPCs are classified into 3 morphological types: perforate, imperforate, and vesiculate. To understand the evolutionary events that occurred at the sequence level during the morphological convergence of perforate SPCs in Agaricomycotina, we examined sequence differences among species with different SPC types by comparative genomic analysis using a single-copy gene dataset from 12 Agaricomycotina genomes with morphological literature of SPC. Our analysis revealed that sequences of 8 genes, including an SPC-related gene spc33, were clustered based on SPC morphology rather than species relationship. Additionally, same amino acid substitutions independently occurred in both lineages in which species with perforate SPCs emerged. These findings suggest that specific amino acid substitutions in spc33 were critical for the emergence of perforate SPCs in multiple lineages. Further, our gene search for spc33 across organisms suggests that spc33 evolved shortly before the emergence of imperforate SPC. This study represents the first step toward elucidating the genetic basis of the morphological evolution of SPC. It contributes to both clarifying the genetic basis underlying morphological convergence and advances the study of fungal evolutionary morphology.

Evolution, Molecular↗
PubMed2025

Genomic Insights Into Convergent Evolution: Adaptation to Rocky Habitats in Rock-Inhabiting Fungi.

Rock-inhabiting fungi (RIF), obligate colonizers of bare rocks, are primarily distributed across two major phylogenetic classes: Dothideomycetes and Eurotiomycetes. These fungi display striking convergence in morphology and physiology, characterized by meristematic growth, melanized cell walls, and extreme stress tolerance. However, the genomic underpinnings of this adaptive convergence remain poorly understood. Here, through comparative genomic analysis of 9 RIF and 18 non-RIF fungi, we revealed that RIF possess compact, gene-dense genomes marked by contraction of genes involved in nutrient uptake and secondary metabolism, alongside expansions in cell wall biosynthesis, lipid metabolism, and stress-responsive pathways. We identified two genes under positive selection across multiple RIF lineages: Ino80 ATPase (chromatin remodeling) and the ER chaperone BiP (protein folding). Further evidence of convergence was found in the mannosyltransferase Mnn9, a key enzyme in cell wall assembly, where two RIF-specific amino acid substitutions were predicted to enhance protein stability. Additionally, a unique Mnn9-like clade has expanded exclusively in RIF. RNAi-mediated knockdown of an Mnn9-like gene in Rachicladosporium sp. confirmed its role in cell wall mannosylation, osmotic stress response, and the transition from meristematic to filamentous growth. Our findings elucidate a set of common genomic adaptations and highlight the specialized evolution of the Mnn9 family in driving the convergent success of phylogenetically diverse RIF in rocky environments.

Phylogeny↗
PubMed1988

Variation of convergence limits with change in direction of gaze.

Until recently, convergence limits have been measured only in the primary position of gaze. A new instrument permits such measurements in all directions of gaze and at various angular distances from the primary straight-ahead position. Aberration and distortion-free stimuli based on Heine's principle were incorporated in the apparatus. For each of the nine subjects participating, convergence limits were obtained in the primary straight-ahead position, secondary, and tertiary positions and in varying degrees of obliquity of these directions of gaze. The convergence limits were measured in 10 degrees steps away from the straight-ahead position of gaze in 18 different meridians. It was found that convergence limits vary markedly with the direction of gaze, the maximal vergence range usually being found between 10 to 20 degrees below the primary horizontal plane in the lower right-half field, possibly because subjects spend most of their time looking in this direction.

Convergence, Ocular↗
PubMed1989

Convergence during human vertical saccades: probable causes and perceptual consequences.

1. When a downward saccade is made between equidistant targets, convergence consistently occurs during the saccade: about 1 deg overconvergence after an 8 deg saccade, with either binocular or monocular viewing, with either far (3 m) or near (30 cm) viewing distance. 2. During binocular viewing, this unnecessary convergence is corrected by divergence movement with a half-time of about 200 ms. During monocular viewing of far targets, similar post-saccadic divergence occurs, but for monocularly-seen near targets, recovery is considerably slower. 3. Vergence changes associated with upward saccades are much smaller and typically more variable among subjects. 4. The up-down asymmetry of intrasaccadic vergence changes can be accounted for by superposition of two plausible adventitious processes: co-contraction of the vertical recti, and tension increase (upward saccades) or tension release (downward saccades) in the superior oblique muscles. 5. During the 1000 ms after an upward saccade, constriction of the pupil consistently occurs; it apparently represents a near-triad response, for which concurrent convergence is masked. Such near-triad activation during upward gaze would presumably be necessary to counterbalance residual steady-state torques from the superior oblique muscles. 6. The up-down asymmetry of intrasaccadic vergence changes also arises when targets require both a vergence change and a vertical shift of gaze, thereby accelerating refixation for the typical natural spatial configuration, in which nearer objects are lower in the visual field. 7. During binocular viewing of equidistant targets, the convergence resulting from downward saccades produces large transient disparities, which can be expected to lead to biased evaluations of relative distances to targets. Several up-down illusions involving apparent distance may well be due to these disparities, including (a) backward tilt of the apparent vertical and of the vertical horopter, (b) the 'soup-bowl sky' illusion, and (c) the 'diverging sunbeams' illusion.

Accommodation, Ocular↗
PubMed1999

Does convergence, not accommodation, cause axial-length elongation at near? A biometric study in teens.

To determine whether convergence rather than accommodation has a primary effect on the changes in axial length and other biometric components during near fixation, we measured the anterior chamber depth, lens thickness, vitreous length and axial length in the right eyes of 124 young male subjects while their left eyes focused at distance (6 m) and near (20 cm). The measurements were performed before and after cycloplegia in the right eye, so we aimed to study biometric components of the eye in the states of accommodation and nonaccommodation, but converging at near. While the left eye focused at near, the axial length increased significantly with and without cycloplegia (p < 0.0005 and p < 0.0005). The vitreous length was the main increasing ocular biometric component at near both with and without cycloplegia (p < 0.044 and p = 0.001, respectively). At near, there was no difference between two mean axial length and two vitreous length measurements both with and without cycloplegia (p = 0.672 and p = 0.595, respectively). Under cycloplegia, anterior chamber depth also increased significantly at near fixation (p = 0. 012). Axial elongation at near fixation, mainly due to an increase in vitreous length, may result from the effect of accommodative convergence rather than accommodation itself. Much use of convergence, not accommodation, may be one of the contributing factors in adult onset and adult progression of myopia.

Accommodation, Ocular↗
PubMed2004

TMS over the left posterior parietal cortex prolongs latency of contralateral saccades and convergence.

PURPOSE: This study explored the role of the left posterior parietal cortex (PPC) in saccades, vergence, and combined saccade-vergence movements by means of transcranial magnetic stimulation (TMS) in humans. METHODS: TMS was applied over the left PPC for 80, 90, or 100 ms after target onset. In a control experiment, TMS was applied over the primary motor cortex at 90 ms after target onset. RESULTS: Relative to no TMS trials, TMS over the left PPC increased the latency of only certain types of eye movements: saccades to right, convergence, and convergence combined with rightward saccades. It had no such effect on saccades to the left, divergence, saccades combined with divergence, or left saccades combined with convergence. TMS over the vertex had no effect on the latency of any type of eye movement. Thus, the effects of TMS on latency are both area- and eye-movement specific. TMS of the left PPC or the motor cortex did not alter the accuracy of any type of eye movement. The results are in contrast to those of prior studies of the right PPC, which is involved in the initiation of any type of eye movement. CONCLUSIONS: The findings suggest that the right PPC is involved primarily in the processing of fixation disengagement, whereas the left PPC provides the signal that is also necessary to initiate eye movements and could occur in parallel with the process (model of Findlay and Walker). Such a functional role of the left PPC seems to be topographically organized and concerns a saccade to the right and convergence alone or combined with a saccade to the right.

Adult↗
PubMedDate not supplied

Convergence insufficiency in thyroid eye disease.

The incidence of convergence insufficiency in patients with thyroid ophthalmopathy and their response to convergence exercise is unknown. Twenty-seven consecutive patients with thyroid eye disease (TED) were evaluated prospectively. Six patients with symptomatic convergence insufficiency obtained varying degrees of subjective and objective benefit from treatment. None of the six had other TED-related complaints that required therapeutic intervention. The study findings should alert the clinician to consider convergence insufficiency in patients with TED and nonspecific ophthalmic symptoms.

Adolescent↗
PubMed1999

Acquired convergence-evoked pendular nystagmus in multiple sclerosis.

Nystagmus seen only with convergence is unusual. We describe four cases of acquired convergence-evoked pendular nystagmus in patients with multiple sclerosis. The nystagmus was horizontal and asymmetric in all patients. Eye movement recordings in one subject showed a conjugate rather than a convergent-divergent relationship of the phase of movement between the two eyes. All patients had evidence of optic neuropathy and cerebellar dysfunction. Occlusion of either eye during fixation of near targets led to divergent drift of the covered eye and a decrease in nystagmus. Intravenous scopolamine reduced nystagmus in one patient. Base-in prisms alleviated symptoms of oscillopsia at near and improving reading visual acuity. Convergence-evoked pendular nystagmus may be more common than currently appreciated, particularly among patients with multiple sclerosis.

Adult↗
PubMed1999

Efficacy of vision therapy for convergence insufficiency in an adult male population.

BACKGROUND: Although vision therapy has reportedly been very successful in elimination of asthenopic symptoms in adults with convergence insufficiency, controlled studies have not been performed, and a clinical bias exists against prescribing vision therapy for adults with convergence insufficiency. METHODS: Sixty adult males over the age of 40 years (median age, 65 years) with convergence insufficiency were divided into three treatment groups: office-based vision therapy with supplementary home therapy, home therapy only, and a control group. RESULTS: Vision therapy was successful in 61.9% of patients who received in-office plus home therapy, in 30% of patients who received home therapy only, and in 10.5% of the control group. The success rate for patients who received active in-office vision therapy supplemented with home procedures was significantly greater than that for controls. Home therapy alone was less successful than in-office therapy. The success rate obtained with home therapy alone was not significantly greater than that demonstrated by controls. CONCLUSIONS: Vision therapy is effective in eliminating asthenopia and improving convergence function in adult patients. In-office therapy combined with home therapy tends to produce better results than does home therapy alone.

Adult↗
PubMed1996

Neurophysiology of converging synaptic inputs from the rat prefrontal cortex, amygdala, midline thalamus, and hippocampal formation onto single neurons of the caudate/putamen and nucleus accumbens.

Neurophysiological responses mediated by projections from five telencephalic and diencephalic regions (the infra- and prelimbic portions of the prefrontal cortex, amygdala, midline and intralaminar thalamic nuclei, entorhinal cortex and subiculum/CA1) to the caudate/putamen (CPu) and nucleus accumbens (Acb) of the dorsal and ventral striatum were studied in chloral-hydrate-anesthetized rats. Both extra- and intracellular in vivo recording techniques were used. A retrograde tracer (wheatgerm agglutinin-apo-horseradish peroxidase-5 nm colloidal Gold) was deposited in some animals in the vicinity of recording sites to confirm that stimulating electrodes were located near cells that projected to the striatum. Electrical stimulation of these five regions, respectively, evoked excitatory responses in 60%, 22%, 51%, 25%, and 17% of striatal neurons. Some responses, particularly with thalamic stimulation, showed short-term frequency potentiation in which 5/s stimulation increased the probability of spike firing. About half of responsive cells showed convergent excitation to more than one stimulating site. It was possible with convergent excitatory responses to show synaptic interactions: simultaneous activation of more than one site produced spatial and temporal summation to increase the probability of spike firing. Up to 5-way convergence onto single striatal neurons and up to 3-way interactions could be shown. These results indicate that functional influences from the hippocampal formation can converge with other excitatory input onto single striatal neurons to effect synaptic integration.

Action Potentials↗
PubMed1995

Quantification of mitral regurgitation--comparison of the proximal flow convergence method and the jet area method.

A total of 92 patients with mitral regurgitation (age 63 +/- 13 years, 51 men, 41 women), quantified by angiography, were studied using color-flow Doppler imaging of isovelocity surface areas in the flow convergence region proximal to the regurgitant orifice (PISAs) and of the regurgitant jet in the left atrium. The PISA radii for the flow velocities (aliasing borders) of 28 and 41 cm/s, jet area, jet length, and relation of jet area to left atrial area were measured. A proximal flow convergence region was imaged in 98% (85%) of all patients for a flow velocity of 28 (41) cm/s. A regurgitant jet could be visualized in all patients. The PISA radii for both flow velocities correlated more closely with the angiographic grade (rSp = 0.79 for both flow velocities) than the jet area (rSp = 0.43), jet length (rSp = 0.39), and relation of jet area to left atrial area (rSp = 0.37). A correct differentiation of grade I-II from grade III-IV mitral regurgitation was provided in 95% of the patients by the proximal flow convergence method for both flow velocities and in up to 78% of the patients by the jet area method using the uncorrected jet area. The PISA radii correlated weakly with the parameters from the regurgitant jet (r = 0.5-0.58). It can be concluded that the proximal flow convergence method and the jet area method reach comparable sensitivity for the detection of mitral regurgitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Convergence of amino acid compositions of certain groups of protein aids in their identification on two-dimensional electrophoresis gels.

The amino acid composition (AAC) versus the protein identity (PI) method was used for establishment of the identities of proteins from bovine brain and kidneys which were prefractionated on a CM52 cation exchanger and by preparative flat-bed isoelectric focusing. Established identities of proteins whose AACs converge with those of other members of their proper superfamily are reliable. Groups of convergent AACs can be extracted from protein databases using the standard root-mean-square rule (Rmsd) with measures the difference between the AAC of chosen protein versus those in the database. Convergence of AACs of proteins is dependent on several factors such as the upper limit of Rmsd, the limits of variations of molecular mass (m) and isoelectric point (pI), the number of proteins with similar AACs present in protein databases, and the domain structure of proteins. AACs of many proteins remain unique if the Rmsd is maintained within 1.5-1.0 with m +/- 3kDA and pI +/- 4. Certain groups of multidomain proteins have quasi-unique AACs only if the Rmsd is restrained to a value within 1.0 and 0.7. Convergence of AACs of certain groups of proteins may indicate that a common biological function exists for some members of each group. The AAC-PI method may become an additional search tool for protein functions.

Amino Acid Isomerases↗
PubMed2006

Cancer mortality rates among first and second generation migrants in the Netherlands: Convergence toward the rates of the native Dutch population.

This study investigates the difference in cancer mortality rates between migrant groups and the native Dutch population, and determines the extent of convergence of cancer mortality rates according to migrants' generation, age at migration and duration of residence. Data were obtained from the national cause of death and population registries in the period 1995-2000. We used Poisson regression to compare the cancer mortality rates of migrants originating from Turkey, Morocco, Surinam, Netherlands Antilles and Aruba to the rates for the native Dutch. All-cancer mortality among all migrant groups combined was significantly lower when compared to that of the native Dutch population (RR = 0.55, CI: 0.52-0.58). For a large number of cancers, migrants had more than 50% lower risk of death, while elevated risks were found for stomach and liver cancers. Mortality rates for all cancers combined were higher among second generation migrants, among those with younger age at migration, and those with longer duration of residence. This effect was particularly pronounced in lung cancer and colorectal cancer. For most cancers, mortality among second generation migrants remained lower compared to the native Dutch population. Surinamese migrants showed the most consistent pattern of convergence of cancer mortality. The generally low cancer mortality rates among migrants showed some degree of convergence but did not yet reach the levels of the native Dutch population. This convergence implies that current levels of cancer mortality among migrants will gradually increase in future years if no specific preventive measurements are taken.

Adolescent↗
PubMed1992

Aberrant convergence of the neural folds in the mouse mutant vl.

Progressive changes in the dorsolateral angles (DA) and ventral angle (VA) during elevation and convergence of the caudal neural folds were morphometrically analyzed in normal and dysraphic abnormal embryos of the mouse mutant vacuolated lens (vl), and correlations with the configuration of microfilaments in the apices of neuroepithelial cells were made by means of ultrastructural cytochemistry. In 22-28 somite stage abnormal (vl/vl) embryos, the DA and VA are larger than those in their normal counterparts at each comparable level of the caudal neural folds, suggesting that defective convergence involves both the DA and VA in this mutant. In 30-35 somite stage abnormal embryos, the VA is likewise larger than that in normal embryos in which the neural folds have converged and closed; however, the DAs are much smaller, indicating that a medial collapse of the dorsal ends of the neural folds may occur secondary to the closure failure. At the DA, the ultrastructural configuration of microfilaments is similar in abnormal and normal embryos in terms of their circumferential arrangement around the perimeters of the neuroepithelial cell apices. In abnormal embryos, however, the bundles of microfilaments are more delicate and less prominent than in normal embryos; thus it is possible that a quantitative and/or functional deficiency in these elements may be involved in the failure of the abnormal neuroepithelium to bend properly during convergence of the neural folds.

Actin Cytoskeleton↗
PubMed2001

Directed Convergence in Stable Percept Acquisition.

We view a perceptual capacity as a nondeductive inference, represented as a function from a set of premises to a set of conclusions. The application of the function to a single premise to produce a single conclusion is called a "percept" or "instantaneous percept." We define a stable percept as a convergent sequence of instantaneous percepts. Assuming that the sets of premises and conclusions are metric spaces, we introduce a strategy for acquiring stable percepts, called directed convergence. We consider probabilistic inferences, where the premise and conclusion sets are spaces of probability measures, and in this context we study Bayesian probabilistic/recursive inference. In this type of Bayesian inference the premises are probability measures, and the prior as well as the posterior is updated nontrivially at each iteration. This type of Bayesian inference is distinguished from classical Bayesian statistical inference where the prior remains fixed, and the posterior evolves by conditioning on successively more punctual premises. We indicate how the directed convergence procedure may be implemented in the context of Bayesian probabilistic/recursive inference. We discuss how the L(infinity) metric can be used to give numerical control of this type of Bayesian directed convergence. Copyright 2001 Academic Press.

Journal Article↗