A hypothesis for robust polarization vision: an example from the Australian imperial blue butterfly, Jalmenus evagoras.

The Australian lycaenid butterfly Jalmenus evagoras has iridescent wings that are sexually dimorphic, spectrally and in their degree of polarization, suggesting that these properties are likely to be important in mate recognition. We first describe the results of a field experiment showing that free-flying individuals of J. evagoras discriminate between visual stimuli that vary in polarization content in blue wavelengths but not in others. We then present detailed reflectance spectrophotometry measurements of the polarization content of male and female wings, showing that female wings exhibit blue-shifted reflectance, with a lower degree of polarization relative to male wings. Finally, we describe a novel method for measuring alignment of ommatidial arrays: by measuring variation of depolarized eyeshine intensity from patches of ommatidia as a function of eye rotation, we show that (a) individual rhabdoms contain mutually perpendicular microvilli; (b) many rhabdoms in the array have their microvilli misaligned with respect to neighboring rhabdoms by as much as 45 deg; and (c) the misaligned ommatidia are useful for robust polarization detection. By mapping the distribution of the ommatidial misalignments in eye patches of J. evagoras, we show that males and females exhibit differences in the extent to which ommatidia are aligned. Both the number of misaligned ommatidia suitable for robust polarization detection and the number of aligned ommatidia suitable for edge detection vary with respect to both sex and eye patch elevation. Thus, J. evagoras exhibits finely tuned ommatidial arrays suitable for perception of polarized signals, likely to match sex-specific life history differences in the utility of polarized signals.

Use of a novel technique to assess impact of age-related denervation on mouse soleus muscle function.

Denervation contributes to loss of force-generating capacity in aged skeletal muscles, but problems with quantification of denervated fibers mean the precise impact of denervation on muscle function remains unclear. This study therefore looked to develop a reliable assay for identifying denervated muscle fibers, and used this to explore the impact of denervation on age-related force-generation in mouse skeletal muscle. Thirteen young (6-month-old) and 10 old (24-months-old) C57Bl/6 J female mice were utilized. Anaesthetized mice were infused with the fluorescent deoxyglucose analog 2[N-(7-nitrobenz-2-oxa-1,2-diaxol-4-yl)amino]-2-deoxyglucose (2-NBDG) and the tibial nerve was repeatedly stimulated to label active skeletal muscle fibers by activity-dependent uptake of 2-NBDG. Data on muscle force generation were acquired as part of the stimulation routine. Labeled muscles were removed, snap frozen, sectioned, and slide mounted. Sections were imaged to show accumulation of 2-NBDG in activated fibers and lack of 2-NBDG accumulation in quiescent (denervated) fibers, then processed using immunohistochemistry to allow collection of data on fiber number and morphology. Soleus muscles from older mice had nine times as many denervated fibers as those from young mice (average n = 36 vs 4, old vs young). Older muscles developed significantly more passive force and less specific force, but denervation only partly accounted for age-related deficits in specific force. Further investigations are required to definitively identify contributors to the decrease in force generation that remain unaccounted for.

Short-term Effects of Manual Therapy in Patients After Surgical Fixation of Ankle and/or Hindfoot Fracture: A Randomized Clinical Trial.

BACKGROUND: Patients with surgical fixation of ankle and/or hindfoot fractures often experience decreased range of motion and loss of function following surgery and postsurgical immobilization, yet there is minimal evidence to guide care for these patients. OBJECTIVES: To assess whether manual therapy may provide short-term improvements in range of motion, muscle stiffness, gait, and balance in patients who undergo operative fixation of an ankle and/or hindfoot fracture. METHODS: In this multisite, double-blind randomized clinical trial, 72 consecutive patients who underwent open reduction internal fixation of an ankle and/or hindfoot fracture and were receiving physical therapy treatment of exercise and gait training were randomized to receive either impairment-based manual therapy (manual therapy group) or a sham manual therapy treatment of light soft tissue mobilization and proximal tibiofibular joint mobilizations (control group). Participants in both groups received 3 treatment sessions over 7 to 10 days, and outcomes were assessed immediately post intervention. Outcomes included ankle joint range of motion, muscle stiffness, gait characteristics, and balance measures. Group-by-time effects were compared using linear mixed modeling. RESULTS: There were no significant differences between the manual therapy and control groups for range of motion, gait, or balance outcomes. There was a significant difference from baseline to the final follow-up in resting gastrocnemius muscle stiffness between the manual therapy and control groups (-47.9 N/m; 95% confidence interval: -86.1, -9.8; P = .01). There was no change in muscle stiffness for the manual therapy group between baseline and final follow-up, whereas muscle stiffness increased in the control group by 6.4%. CONCLUSION: A brief course of manual therapy consisting of 3 treatment sessions over 7 to 10 days did not lead to better short-term improvement than the application of sham manual therapy for most clinical outcomes in patients after ankle and/or hindfoot fracture who were already being treated with exercise and gait training. Our results, however, suggest that manual therapy might decrease aberrant resting muscle stiffness after ankle and/or hindfoot surgical fixation. LEVEL OF EVIDENCE: Therapy, level 2. J Orthop Sports Phys Ther 2019;49(5):310-319. Epub 13 Feb 2019. doi:10.2519/jospt.2019.8864.

Morphology of Cervical Spine Meniscoids in Individuals With Chronic Whiplash-Associated Disorder: A Case-Control Study.

Study Design Case-control study. Background Cervical spine meniscoids are thought to contribute to neck pain and hypomobility in individuals with chronic whiplash-associated disorder (WAD); however, their morphology has not been studied in a clinical population. Objectives To investigate cervical spine meniscoid morphology in individuals with chronic WAD. Methods Twenty volunteers with chronic WAD (mean ± SD age, 39.3 ± 11.0 years; 10 female) and 20 age- and sex-matched controls (age, 39.1 ± 10.6 years) underwent cervical spine magnetic resonance imaging. Lateral atlantoaxial and zygapophyseal joints (C2-3 to C6-7) were inspected for meniscoids. Length of meniscoid protrusion was measured and composition (adipose/fibrous/fibroadipose) assessed. Data were analyzed using Wilcoxon signed-rank tests and linear and logistic regression (P<.05). Results Meniscoids were identified in the chronic WAD (n = 317) and control (n = 296) groups. At the lateral atlantoaxial joints, median meniscoid length was greater in the control group (ventral, 6.07 mm; dorsal, 7.24 mm) than the WAD group (ventral, 5.01 mm; P = .06 and dorsal, 6.48 mm; P<.01). At the dorsal aspect of zygapophyseal joints, meniscoids were more frequently fibrous in the chronic WAD group (odds ratio = 2.38, P<.01; likelihood ratio test: χ22, 9.02; P = .01). Conclusion In individuals with chronic WAD, lateral atlantoaxial meniscoids were shorter and dorsal cervical zygapophyseal meniscoids were more fibrous, suggesting alterations in meniscoid composition. This may have pathoanatomical implications in chronic WAD. J Orthop Sports Phys Ther 2016;46(10):902-910. Epub 3 Sep 2016. doi:10.2519/jospt.2016.6702.

Effect of 11-cis 13-demethylretinal on phototransduction in bleach-adapted rod and cone photoreceptors.

We used 11-cis 13-demethylretinal to examine the physiological consequences of retinal's noncovalent interaction with opsin in intact rod and cone photoreceptors during visual pigment regeneration. 11-Cis 13-demethylretinal is an analog of 11-cis retinal in which the 13 position methyl group has been removed. Biochemical experiments have shown that it is capable of binding in the chromophore pocket of opsin, forming a Schiff-base linkage with the protein to produce a pigment, but at a much slower rate than the native 11-cis retinal (Nelson, R., J. Kim deReil, and A. Kropf. 1970. Proc. Nat. Acad. Sci. USA. 66:531-538). Experimentally, this slow rate of pigment formation should allow separate physiological examination of the effects of the initial binding of retinal in the pocket and the subsequent formation of the protonated Schiff-base linkage. Currents from solitary rods and cones from the tiger salamander were recorded in darkness before and after bleaching and then after exposure to 11-cis 13-demethylretinal. In bleach-adapted rods, 11-cis 13-demethylretinal caused transient activation of phototransduction, as evidenced by a decrease of the dark current and sensitivity, acceleration of the dim flash responses, and activation of cGMP phosphodiesterase and guanylyl cyclase. The steady state of phototransduction activity was still higher than that of the bleach-adapted rod. In contrast, exposure of bleach-adapted cones to 11-cis 13-demethylretinal resulted in an immediate deactivation of transduction as measured by the same parameters. These results extend the validity of a model for the effects of the noncovalent binding of a retinoid in the chromophore pockets of rod and cone opsins to analogs capable of forming a Schiff-base and imply that the noncovalent binding by itself may play a role for the dark adaptation of photoreceptors.

Evidence for the presence of high-mannose/hybrid oligosaccharide chain(s) on the mouse ZP2 and ZP3.

Previous studies from this laboratory have identified a novel alpha-D-mannosidase on plasma membranes of rat, mouse, hamster, and human spermatozoa [Tulsiani et al. J Cell Biol 1989; 109:1257; Biol Reprod 1990; 42:843]. Inhibition of the mouse sperm surface alpha-D-mannosidase inhibits sperm-egg binding in vitro, suggesting that the sperm enzyme may have a receptor-like role in binding to the complementary molecules (presumably mannose-containing oligosaccharide [OS] chains) on the mouse zona pellucida (ZP) glycoconjugates [Cornwall et al. Biol Reprod 1991; 44:913]. In the studies reported here, we demonstrate the presence of high-mannose/hybrid-type OS on mouse zona components. Zona-intact eggs, prepared from superovulated mice, were radioiodinated, and the individual zona components (ZP1, ZP2, and ZP3) were isolated by electrophoresis followed by electroelution. The purified ZP components, when resolved by immobilized concanavalin A column chromatography, showed the following results: 1) Nearly all of the ZP1 applied to the immobilized lectin eluted in the column flow-through (effluent) fractions, and no radioactivity eluted with alpha-methyl mannoside, suggesting that ZP1 may not contain high-mannose/hybrid OS. 2) A significant amount of both ZP2 and ZP3 bound to the immobilized lectin, and nearly 16% and 8% of the two components, respectively, were repeatedly eluted with alpha-methyl mannoside.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of the mouse sperm surface alpha-D-mannosidase inhibits sperm-egg binding in vitro.

In previous reports from this laboratory, we identified the presence of a novel alpha-D-mannosidase on the surface of rat, mouse, hamster, and human spermatozoa [J Cell Biol 1989; 109:1257-1267 and Biol Reprod 1990; 42:843-858]. Since it has been suggested that mannosyl residues on the egg zona pellucida may be important for sperm-egg binding, studies were undertaken to examine the potential role of the sperm alpha-D-mannosidase during fertilization. Incubation of mouse spermatozoa in the presence of increasing concentrations of the inhibitory sugars, alpha-methyl mannoside, alpha-methyl glucoside, D-mannose, or D-mannitol, resulted in a dose-dependent decrease in the number of spermatozoa bound per egg without a deleterious effect on sperm motility or on the sperm acrosome, and a dose-dependent inhibition of the sperm mannosidase activity. Galactose, however had no effect on sperm-egg binding or on sperm mannosidase activity. Two nucleotide sugars (UDP-GlcNAc and UDP-gal) were also tested and shown to reduce sperm-egg binding but with only a minimal effect on sperm mannosidase activity. In additional studies, spermatozoa incubated in the presence of a mannose-containing oligosaccharide exhibited a dramatic reduction in sperm-egg binding that correlated with a similar inhibition of sperm mannosidase activity. The oligosaccharide substrate did not affect sperm motility or the sperm acrosome. These studies suggest that the sperm alpha-D-mannosidase may play an important role during fertilization.

Effect of mental practice on isometric muscular strength.

This study was conducted in the Department of Physical Therapy, Louisiana State University Medical Center, New Orleans, LA 70112. The purpose of this study was to see if mental practice (MP) would increase voluntary isometric muscle strength in normal individuals. Twenty-four female subjects were randomly assigned to either a control group or a MP group. The study was conducted over a four-day period using a pretest, posttest, and control group design. The MP group participated in four, 30-minute covert practice sessions. During these sessions, subjects were instructed to cognitively practice isometric contractions of their right quadriceps muscle. Surface electromyography was applied during each practice session to ensure that subjects were not physically contracting their muscles. The data were analyzed using a two-way analysis of variance with repeated measures on one of the factors. The results of this study showed that the MP group significantly (p < .05) increased (12.6%) their quadriceps muscle strength compared to the control group. J Orthop Sports Phys Ther 1991;13(5):231-234.

Cellular mechanisms that underlie bleaching and background adaptation.

Experiments were performed on rod photoreceptors isolated from the eye of the larval tiger salamander to determine if the same or different mechanisms underlie the desensitization produced by dim background light (background adaptation) and that which persists in the steady state in darkness after a significant fraction of the photopigment is bleached (bleaching adaptation). We have examined adaptational effects after light that bleached between approximately 50% and 95% of the photopigment under conditions which preclude pigment regeneration. The steady-state desensitization, far greater than that predicted by quantum-catch loss, is relieved upon regeneration of the visual pigment with 11-cis retinal. We measured the spread of desensitization along the long axis of the rod after a local bright bleach at one end by comparing responses to dim local test flashes elicited in different regions of the outer segment, before and after bleaching. The space constant for this spread was less than 2.5 microns. We have previously measured the space constant for the longitudinal spread of desensitization during a local dim background in Ambystoma rods to be 7 microns. This is similar to a space constant of 6 microns measured under similar conditions in Bufo rods by Lamb et al. (1981. J. Physiol. 319:463-496). If calcium carries the signal for background desensitization, this difference in space constant for background and bleaching adaptation precludes it as the messenger for the steady component of bleaching adaptation. Experiments with isobutylmethyl xanthine (IBMX) also indicate that Ca2+ as well as c-GMP are unlikely regulators of bleaching desensitization, since elevation of cytosolic levels of both of these internal messengers by IBMX has little effect on sensitivity in bleach-adapted cells. All of our findings are consistent with the notion that bleaching adaptation is not mediated by a freely diffusible cytoplasmic messenger.

Effect of an Adjustable Pedal Shaft on ROM and Phasic Muscle Activity of the Knee during Bicycling.

From the Department of Physical Therapy, Louisiana State University Medical Center, New Orleans, LA. The purpose of this study was to determine if a shortened pedal shaft in comparison to a standard length pedal shaft significantly changed the amount of flexion required at the knee joint during cycling. In addition, was the phasic activity of the lower extremity musculature altered as a result of cycling under the two different conditions? Six healthy subjects pedaled at a steady rate of 75 rpm on a stationary bicycle with a standard (17.0 cm) and a shortened (8.9 cm) pedal shaft. The results of a paired t-test showed that significantly (p < 0.05) less knee flexion was needed with the shortened pedal shaft compared to the standard length shaft. Comparison of each muscle's phasic activity showed similar activity patterns between the two conditions. The onset of EMG activity, however, was found to be significantly later (p < 0.05) in the rectus femoris muscle while pedaling with the shortened shaft. In addition, the termination of EMG activity in the gastrocnemius muscle was found to occur significantly sooner (p < 0.05) during the shortened pedal shaft condition. The results of this study indicate that a shortened bicycle pedal shaft reduces the amount of knee flexion required for cycling without greatly altering the muscle contraction patterns of the muscles studied. It is the opinion of the authors that such a device will allow patients with moderately restricted ROM of the knee to utilize a stationary bicycle in their rehabilitation program. J Orthop Sports Phys Ther 1989;11(6):259-262.

The effect of physical activity on ligamentous strength: an overview*.

A brief review of the literature pertaining to the strengthening of ligamentous tissue through physical activity is presented. Although literature exists supporting both sides of the question, the predominence of evidence seems to be in favor of improved ligamentous strength following physical activity. Despite the general agreement, the exact mechanism involved is unclear. It is also unclear whether the ligament or the ligament-bone interface is the site of increased strength. A review of the possible mechanisms involved, as well as a discussion of the influence of immobility on the validity of the experimental results, is presented. J Orthop Sports Phys Ther 1984;5(5):275-277.