Lipid alterations by oxidative stress increase detached acrosomes after cryopreservation of semen in Holstein bulls.

The nearly exclusive use of cryopreserved semen in cattle breeding enables long shipping distances, higher storage times, quarantine to avoid germ transmission and easy dispersal of high genetic value bulls. Spermatozoa from bulls are well freezable and improvement of cryopreservation protocols over decades has led to high semen quality. However, there is still some loss of spermatozoa in each semen dose due to detached acrosomes after thawing. There are even individual bulls with extremely high numbers of detached acrosomes after cryopreservation, called "bad freezers". This study screened 1092 ejaculates from 59 Holstein bulls for the difference in detached acrosomes before and after cryopreservation (ΔAC). The individual bull influenced ΔAC (P < 0.001) and allowed selection for individuals with repeatedly low ΔAC (good freezers) or high ΔAC (bad freezers). Good freezers were superior to bad freezers in a thermo-resistance test (78.2% vs. 33.6% total motility, respectively, P = 0.047) and had higher non-return rates (NRR: 46.8% vs. 40.8%, respectively, P = 0.016). Since oxidative stress is one possible explanation for premature acrosome reaction, the radical reduction capacity of the seminal fluid was measured, finding that this parameter was reduced in bad freezer bulls during cryopreservation (P = 0.043). Analysis of lipid species in sperm cells by matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS) showed a reduction of ether lipids and plasmalogens as well as an increase in formyl-lysophosphatidylcholines only within the bad freezers during cryopreservation (P = 0.043). In conclusion these findings show, that lipid alteration caused by oxidative stress is one essential reason for highly augmented acrosome reacted spermatozoa in bad freezer bulls. Therefore, increased use of antioxidants in the extender could be a possible starting point for developing individualized extenders for bad freezer bulls of high genetic value, in order to raise sperm quality after cryopreservation even in those bulls.

Adaptive finite element eye model for the compensation of biometric influences on acoustic tonometry.

BACKGROUND AND OBJECTIVE: Glaucoma is currently a major cause for irreversible blindness worldwide. A risk factor and the only therapeutic control parameter is the intraocular pressure (IOP). The IOP is determined with tonometers, whose measurements are inevitably influenced by the geometry of the eye. Even though the corneal mechanics have been investigated to improve accuracy of Goldmann and air pulse tonometry, influences of geometric properties of the eye on an acoustic self-tonometer approach are still unresolved. METHODS: In order to understand and compensate for measurement deviations resulting from the geometric uniqueness of eyes, a finite element eye model is designed that considers all relevant eye components and is adjustable to all physiological shapes of the human eye. RESULTS: The general IOP-dependent behavior of the eye model is validated by laboratory measurements on porcine eyes. The difference between simulation and measurement is below 8 µm for IOP levels from 5 to 40 mmHg. The adaptive eye model is then used to quantify systematic uncertainty contributions of a variation of eye length and central corneal thickness based on input statistics of a clinical trial series. The adaptive eye model provides the required relation between biometric eye parameters and the corneal deflection amplitude, which here is the measured quantity to trace back to the IOP. Implementing the relations provided by the eye model in a Gaussian uncertainty propagation calculation now allows the quantification of the uncertainty contributions of the biometric parameters on the overall measurement uncertainty of the acoustic self-tonometer. As a result, a systematic uncertainty contribution resulting from deviations in eye length dominate stochastic deviations of the sensor equipment by a factor of 3.5. CONCLUSION: As perspective, the proposed adaptive eye model provides the basis to compensate for systematic deviations of (but not only) the acoustic self-tonometer.

Results of First In Vivo Trial of an Acoustic Self-Tonometer.

Purpose: Glaucoma is the world's most common cause of irreversible blindness, which makes early diagnosis, with the goal of preserving vision, essential. The current medical intervention is to reduce intraocular pressure (IOP) to slow down progression of the disease. The main goal of this study was to test a novel handheld acoustic self-tonometer on humans. Methods: A sound pressure pulse generated by a loudspeaker causes the eye to vibrate. A pressure chamber is placed on the human orbit to form a coupled system comprised of the patient's eye, the enclosed air, and the loudspeaker. A displacement sensor in front of the loudspeaker membrane allows the dynamic behavior of the entire system to be detected. Results: For this clinical trial series, a prototype of the acoustic self-tonometer principle was applied. The resulting membrane oscillation data showed sensitivity of patient IOP, but direct allocation of the measured damping and frequency to the IOP was not significant. For this reason, an artificial neural network was used to find relationships among the subjects' biometric eye parameters in combination with the self-tonometer data for the IOP reference. An expanded measurement uncertainty (kp = 2) equal to 6.53 mm Hg was determined for the self-tonometer in a Bland-Altman analysis using Goldmann applanation tonometer reference measurements. Conclusions: The usability and success rate of producing valid measurement values with the device during self-measurements by test subjects was nearly 92%. The cross-sensitivities observed require compensation in a possible redesign phase to reduce the measurement uncertainty by at least 25% to the maximum of 5 mm Hg required to seek medical device approval. Translational Relevance: Building on successful laboratory experiments with pig eyes, this article reports the results of testing the acoustic tonometer on humans.

Methodical Approach for Determining the Length of Drill Channels in Osteosynthesis.

In order to fix a fracture in osteosynthesis, it is necessary to attach screws bicortically to the bone. The length of the screws must be selected correctly in 1-mm increments: otherwise, injury to the surrounding tissue structure or insufficient fixation will result. The drill channel length can only be determined preoperatively to a limited extent and with insufficient accuracy and is therefore determined intraoperatively with a mechanical caliper gauge. This length determination is error-prone, which often leads to a false screw selection and at the same time to considerable complications in the healing process. A novel approach based on a sensory drive train was pursued, with which all mechanical drilling parameters were recorded and evaluated in combination with a length measurement that allows for determining the drill channel length. In order to overcome the limitations of previous drill concepts, a precise length measurement of the drill channel was introduced. The amplitude of a stimulated linear oscillation of the drill was monitored for drilling channel length measurements in order to reliably detect the beginning of the drilling process. The method provides the information required for handheld drilling without the limitation of constant drilling parameters. With initial results from laboratory tests with pig bones, the measurement method for the drill channel length has been validated on a test bench of the drilling machine. With the laboratory tests, a measurement uncertainty of 0.3 mm was achieved, so screws with a 1-mm step width can be reliably selected.

Optical measurement of the corneal oscillation for the determination of the intraocular pressure.

Motivation Glaucoma is currently the most common irreversible cause of blindness worldwide. A significant risk factor is an individually increased intraocular pressure (IOP). A precise measurement method is needed to determine the IOP in order to support the diagnosis of the disease and to monitor the outcome of the IOP reduction as a medical intervention. A handheld device is under development with which the patient can perform self-measurements outside the clinical environment. Method For the measurement principle of the self-tonometer the eye is acoustically excited to oscillate, which is analyzed and attributed to the present IOP. In order to detect the corneal oscillation, an optical sensor is required which meets the demands of a compact, battery driven self-tonometer. A combination of an infrared diode and a phototransistor provides a high-resolution measurement of the corneal oscillation in the range of 10 µm-150 µm, which is compared to a reference sensor in the context of this study. By means of an angular arrangement of the emitter and the detector, the degree of reflected radiation of the cornea can be increased, allowing a measurement with a high signal-to-noise ratio. Results By adjusting the angle of incidence between the detector and the emitter, the signal-to-noise ratio was improved by 40 dB which now allows reasonable measurements of the corneal oscillation. For low amplitudes (10 µm) the signal-to-noise ratio is 10% higher than that of the commercial reference sensor. On the basis of amplitude variations at different IOP levels, the estimated standard uncertainty amounts to <0.5 mm Hg in the physiological pressure range with the proposed measuring approach. Conclusion With a compact and cost-effective approach, that suits the requirements for a handheld self-tonometer, the corneal oscillation can be detected with high temporal resolution. The cross-sensitivity of the sensor concept concerning a distance variation can be reduced by adding a distance sensor. Existing systematic influences of corneal biomechanics will be integrated in the sensor concept as a consecutive step.

Controlled ice nucleation--Is it really needed for large-volume sperm cryopreservation?

Controlled ice nucleation (CIN) is an integral stage of slow freezing process when relatively large volumes (usually 1 mL or larger) of biological samples in suspension are involved. Without it, a sample will supercool to way below its melting point before ice crystals start forming, resulting in multiple damaging processes. In this study, we tested the hypothesis that when freezing large volumes by the directional freezing technique, a CIN stage is not needed. Semen samples collected from ten bulls were frozen in 2.5-mL HollowTubes in a split-sample manner with and without a CIN stage. Thawed samples were evaluated for viability, acrosome integrity, rate of normal morphology, and, using computer-aided sperm analysis system, for a wide range of motility parameters that were also evaluated after 3 hours of incubation at 37 °C. Analysis of the results found no difference between freezing with and without CIN stage in any and all of the 29 parameters compared (P > 0.1 for all). This similarity was maintained through 3 hours of incubation at 37 °C. Possibly, because of its structure, the directional freezing device promotes continuous ice nucleation so a specific CIN stage is no longer needed, thus reducing costs, energy use, and carbon footprint.