In vitro dark adaptation and preservation of electrical light responses in the retina from bovine eyes.

A method is described which allows the in vitro dark adaptation of rod photoreceptors from cattle eyes, enucleated under ambient light in the slaughterhouse. Without in vitro dark adaptation these eyes are light adapted and cannot be used for certain delicate biochemical studies and for an electrophysiological characterisation of rod responses. The method is very simple and yields large amounts of dark adapted retinal material, allowing experiments that require bulk amounts of photoreceptor cells. The only source of dark adapted photoreceptors so far have been retinae from dark adapted laboratory animals, which had to be killed and processed under infrared light. Eye cups were opened under red light as soon as possible after their enucleation. Their vitreous humor was removed and their retina thoroughly rinsed with ringer's. Then the eye cup was placed in a moist, light-tight box, where dark adaptation took place. Photoreceptors could thus be kept alive for more than 24 h without showing signs of deterioration. Humidity and free access of oxygen to the retina were the only prerequisites for their survival. The physiological intactness of the photoreceptors and their degree of dark adaptation was demonstrated by measuring mass receptor potentials (ERGs). A simple device is described which can be used for the electrophysiological characterisation of these eyes

Watching G proteins at work.

It has been known for over a century that rod photoreceptors in the living retina contract and swell in response to light. Although it is still not known whether this structural light-response is of any functional significance, it has recently been possible to correlate the underlying molecular processes with the activation and deactivation of the photoreceptor G protein, transducin. The technique of light-scattering allows the monitoring of minute changes in cell dimensions, and using this non-invasive experimental approach it can be shown that certain properties of the coupling between transducin and rhodopsin are different in a structurally well-preserved system as compared with rod material used for conventional biochemical studies. Thus, not unlike a psychiatrist, who often learns more about a patient's 'interiors' by observing the body language than by direct interrogation, a biochemist, studying the 'body language' of a cell, may extract information about delicate 'cell interior processes' that would be perturbed by more direct experimental approaches

Calcium regulates the rate of rhodopsin disactivation and the primary amplification step in visual transduction.

The kinetics of the light-induced activation of transducin as well as the subsequent disactivation process can be monitored by means of a specific light scattering transient PA. In this communication it is demonstrated that the rate of transducin disactivation is calcium dependent, increasing when the calcium concentration is decreased. As a consequence of the accelerated recovery in low calcium, the time to the peak of the transducin activation process is shortened and the gain of the primary amplification step, i.e. the number of transducin molecules activated per bleached rhodopsin, is reduced. Experiments using hydroxylamine as an artificial quencher of rhodopsin activity suggest that calcium acts upon rhodopsin kinase and not upon the rate of the GTPase. This would indicate that calcium may control visual adaptation not only by regulating guanine cyclase activity, but also by affecting the primary step in the transduction cascade, the rhodopsin-transducin couplin

A Literature Review of Studies Evaluating Rotator Cuff Activation during Early Rehabilitation Exercises for Post-Op Rotator Cuff Repair

Despite the modern advancement of surgical repair equipment and techniques, many rotator cuff repairs do not clinically heal. Prescribed rehabilitative exercises must appropriately load the repaired muscle-tendon complex to promote healing and prevent capsular adhesions without damaging the repair. The clinician must possess an understanding of the anatomy and physiology of the healing rotator cuff, and understand the importance of the plane of movement, speed of the movement, position of the extremity, level of assistance, and type of resistance used. Electromyography (EMG) provides a useful means to determine muscle activation levels during specific exercises. Descriptions of specific exercises and EMG activation as they relate to the rotator cuff muscles are described. The specific performance of the exercises, the reliability of such EMG measures, and the descriptive figures are described. Practicing clinicians will benefit from the correct interpretation of the EMG data, and how it can be used in the exercise prescription when formulating a treatment plan

Introductory biology undergraduate students\u27 mixed ideas about genetic information flow

The core concept of genetic information flow was identified in recent calls to improve undergraduate biology education. Previous work shows that students have difficulty differentiating between the three processes of the Central Dogma (CD; replication, transcription, and translation). We built upon this work by developing and applying an analytic coding rubric to 1050 student written responses to a three‐question item about the CD. Each response was previously coded only for correctness using a holistic rubric. Our rubric captures subtleties of student conceptual understanding of each process that previous work has not yet captured at a large scale. Regardless of holistic correctness scores, student responses included five or six distinct ideas. By analyzing common co‐occurring rubric categories in student responses, we found a common pair representing two normative ideas about the molecules produced by each CD process. By applying analytic coding to student responses preinstruction and postinstruction, we found student thinking about the processes involved was most prone to change. The combined strengths of analytic and holistic rubrics allow us to reveal mixed ideas about the CD processes and provide a detailed picture of which conceptual ideas students draw upon when explaining each CD process

Injury Rates in Major League Baseball during the 2020 COVID-19 Season

Background: The 2020 Major League Baseball (MLB) season was drastically altered because of the COVID-19 pandemic. The changes included an extended layoff between March and July as well as a shortened preseason. Purpose/Hypothesis: To determine the incidence and epidemiology of MLB injuries in the abbreviated 2020 season compared with prior seasons. We hypothesized that there was an increase in the overall injury rate in the 2020 season compared with the 2018-2019 seasons and that it equally affected all body regions. Study Design: Descriptive epidemiology study. Methods: The MLB transactions database was queried to find players who had been placed on the injury list between 2018 and 2020. Injuries were categorized into upper extremity, lower extremity, spine/core, and other injuries. Incidence per 1000 athlete-exposures was calculated for the prior 2 seasons (2018-2019) and for the 2020 season separately. Incidence for each category was also calculated separately for pitchers and fielders. Incidence rate ratios (IRRs) and confidence intervals were used to compare injury rates in 2018-2019 versus 2020. The z test for proportions was used to determine significant differences between injury incidences. Results: In 2020, the overall incidence rate per 1000 athlete-exposures was almost twice the rate compared with the 2 seasons before COVID-19 (8.66 vs 5.13; IRR, 1.69 [95% CI, 1.53-1.87]; P \u3c .001). Injury incidence increased similarly in 2020 for both pitchers (IRR, 1.68 [95% CI, 1.47-1.91]; P \u3c .001) and fielders (IRR, 1.68 [95% CI, 1.45-1.96]; P \u3c .001). Increases in injury incidence were seen in the upper extremity, spine/core, and other injury categories; however, the incidence of the lower extremity did not change significantly. Conclusion: There was a significant increase in injury incidence for both pitchers and fielders in 2020. Injury rates increased in anatomic zones of the upper extremity and spine/core but were not significantly changed in the lower extremity. The overall increase in injury rate suggests that irregular or insufficient sport-specific preparation prior to the start of the season placed athletes at a greater risk of injury when play resumed

More Elevated Fastballs Associated with Placement on the Injured List Due to Shoulder Injury

Purpose To evaluate whether impending shoulder injury was associated with changes in pitch location or velocity immediately preceding injury. Methods Pitchers placed on the injured list (IL) due to a shoulder injury between 2015 and 2020 were identified in the Major League Baseball transactions database. Four-seam fastball velocity and frequency of pitch location for each pitch type was collected for each player in the season before placement on the IL and within 1 month of placement on the IL with a minimum of 55 pitches thrown of 1 type. Pitch locations were collected as identified by Baseball Savant’s Game-Day Zones. Game-Day Zones were consolidated into high (above the strike zone midpoint) versus low, arm side (closer to the pitcher’s arm side of the plate) versus opposite side, and within the strike zone versus out of zone. Repeated measures analysis of variance determined differences in four-seam velocity and the location distribution of 4-seam fastballs, change-ups, and breaking balls among each group. Results In total, 267 pitchers were placed on the IL for a shoulder injury with the majority diagnosed with inflammation (89/267) followed by strain or sprain (69/267). Four-seam fastball locations significantly increased above the mid-point of the zone (45.9% vs 42.4%, P = .008) and out of the strike zone (48.5% vs 46.5%, P = .011) within a month before IL placement. There was no significant change in 4-seam fastball velocity immediately before IL placement. Conclusions Pitchers threw more elevated 4-seam fastballs and out-of-zone 4-seam fastballs in the month before IL placement for shoulder injury. These findings suggest that a loss of 4-seam fastball command decreases with impending shoulder injury. Level of Evidence IV, prognostic case series