Sperm melatonin receptors, seminal plasma melatonin and semen freezability in goats.

Goat bucks are seasonal breeders that show variation in sperm quality, endogenous melatonin (MLT), and presumably in the expression of MLT receptors on the sperm throughout the year, which may modify sperm freezability. The aim of this study was to determine whether sperm freezability is associated with (i) endogenous melatonin levels in seminal plasma and (ii) the expression of sperm plasma membrane melatonin receptors (MT1, MT2). To evaluate this, spermatozoa from seven Saanen goat bucks were cryopreserved throughout the year in Mexico using a standard freezing protocol. Seminal plasma MLT concentrations were determined by ELISA and the expression and localization of MT1 and MT2 were detected by immunocytochemistry and confirmed by western blotting. The recovery rate of progressive motility after thawing was higher in spring than autumn and winter; in contrast, the F pattern (CTC assay) was higher in winter than in the other seasons. A proportional increase in the AR pattern (CTC assay) was smaller in winter than in the other seasons and the proportion of sperm showing high plasma membrane fluidity was higher in spring than in summer and autumn. The seminal plasma MLT concentrations showed no significant interseasonal differences. The MT1 receptor was immunolocalised at the apical region of the sperm head, while MT2 was mainly localised in the neck. The relative expression of MLT receptors showed significant differences between summer and winter for all bands, except at 75 kDa of MT2. In conclusion, there was an association between the relative expression of MT1 and MT2 receptors throughout the year and sperm freezability in goat bucks in México. Post-thaw sperm quality is enhanced in semen samples collected during breeding season.

Sperm Incubation in Biggers-Whitten-Whittingham Medium Induces Capacitation-Related Changes in the Lizard Sceloporus torquatus.

Sperm capacitation involves biochemical and physiological changes that enable sperm to fertilize the oocyte. It can be induced in vitro under controlled conditions that simulate the environment of the oviduct. While extensively studied in mammals, its approach in lizards remains absent. Understanding the mechanisms that ensure reproduction is essential for advancing the implementation of assisted reproductive technologies in this group. We aimed to perform a sperm analysis to determine if capacitation-related changes were induced after incubation with capacitating media. Fifteen males of Sceloporus torquatus were collected during the early stage of the reproductive season. The sperm were isolated from the seminal plasma and then diluted up to a volume of 150 µL using BWW medium to incubate with 5% CO2 at 30 °C for a maximum duration of 3 h. A fraction was retrieved hourly for ongoing sperm assessment. The sperm analysis included assessments of its motility, viability, the capacitation status using the chlortetracycline (CTC) assay, and the acrosome integrity with the lectin binding assay to detect changes during incubation. We found that total motility was maintained up to 2 h post incubation, after which it decreased. However, sperm viability remained constant. From that moment on, we observed a transition to a deeper and less symmetrical flagellar bending in many spermatozoa. The CTC assay indicated a reduction in the percentage of sperm showing the full (F) pattern and an increase in those exhibiting the capacitated (B) and reactive (RA) patterns, accompanied by an elevation in the percentage of damaged acrosomes as revealed by the lectin binding assay. In mammals, these changes are often associated with sperm capacitation. Our observations support the notion that this process may also occur in saurian. While sperm analysis is a valuable method for assessing certain functional changes, additional approaches are required to validate this process.

Disruption of gonocyte development following neonatal exposure to di (2-ethylhexyl) phthalate.

Pre- and/or post-natal administrations of di(2-ethylhexyl) phthalate (DEHP) in experimental animals cause alterations in the spermatogenesis. However, the mechanism by which DEHP affects fertility is unknown and could be through alterations in the survival and differentiation of the gonocytes. The aim of the present study was to evaluate the effect of a single administration of DEHP in newborn mice on gonocytic proliferation, differentiation and survival and its long-term effects on seminiferous epithelium and sperm quality. BALB/c mice distributed into Control and DEHP groups were used. Each animal in the DEHP group was given a single dose of 500 mg/Kg at birth. The animals were analyzed at 1, 2, 4, 6, 8, 10 and 70 days postpartum (dpp). Testicular tissues were processed for morphological analysis to determine the different types of gonocytes, differentiation index, seminiferous epithelial alterations, and immunoreactivity to Stra8, Pcna and Vimentin proteins. Long-term evaluation of the seminiferous epithelium and sperm quality were carried out at 70 dpp. The DEHP animal group presented gonocytic degeneration with delayed differentiation, causing a reduction in the population of spermatogonia (Stra8 +) in the cellular proliferation (Pcna+) and disorganization of Vimentin filaments. These events had long-term repercussions on the quality of the seminiferous epithelium and semen. Our study demonstrates that at birth, there is a period that the testes are extremely sensitive to DEHP exposure, which leads to gonocytic degeneration and delay in their differentiation. This situation can have long-term repercussions or permanent effects on the quality of the seminiferous epithelium and sperm parameters.

Orthopaedic Simulation of a Morton's Extension to Test the Effect on Plantar Pressures of Each Metatarsal Head in Patients without Deformity: A Pre-Post-Test Study.

BACKGROUND: the area beneath the metatarsal heads is a common location of foot pain, which is often associated with high plantar pressures. The aim of this study was to determine the effect of the application of a Morton's extension on the pressure in the metatarsal bones of the foot using a pressure platform. METHODS: twenty-five subjects without musculoskeletal pathology were selected for this study, and an experiment was conducted with them as the subjects, before and after application of a Morton's extension. The foot regions were divided into the forefoot (transversely subdivided into six areas corresponding to the first, second, third, fourth, and fifth metatarsal heads, and the hallux), midfoot, and rearfoot, and then the maximum and average pressures exerted at each region were measured before and after placing a Morton's extension. MAIN FINDINGS: we found a pressure reduction, with a p-value less than (p < 0.05), in the head of the second and third metatarsals in statics and dynamics. CONCLUSIONS: we can conclude that the Morton's extension produces a variation in plantar pressures on the lesser metatarsals. The application of a Morton's extension may be beneficial for the management of forefoot pathology. This study will help clinicians consider various tools to treat forefoot disorders. NCT05879094 (ClinicalTrial.gov (accessed on 18 May 2023)).

The Effectiveness of Hard Insoles for Plantar Pressure in Cycling: A Crossover Study.

BACKGROUND: Hard insoles have been proposed to decrease plantar pressure and prevent foot pain and paresthesia due to repetitive loading. The aim of this research was to analyze the effect of three different hard insoles in cycling on healthy subjects. METHODS: A crossover randomized trial was carried out. The mean age of the subjects was 35 ± 3.19 years, and all of them were men. While the subjects were cycling on a stationary bicycle, their plantar pressure was recorded with nine in-shoe sensors placed in nine specific foot areas to test a standard ethylene-vinyl-acetate 52° Shore A hardness insole, a polypropylene 58° Shore D insole, and a polypropylene 580 Shore D insole with selective aluminum 60 HB Brinell hardness in the metatarsal head and hallux. RESULTS: The maximum plantar pressure decreased significantly with the polypropylene insole containing selective aluminum in the metatarsal head and hallux areas. The maximum plantar data of the polypropylene aluminum insole in the M2 area (5.56 kgF/cm2), fifth metatarsal styloid process (6.48 kgF/cm2), M3-M4 area (4.97 kgF/cm2), and hallux (8.91 kgF/cm2) were of particular interest compared to the other insoles. CONCLUSIONS: The use of insoles made of polypropylene with aluminum in the metatarsal head and hallux areas decreases the maximum plantar pressure in cycling compared to standard EVA and polypropylene insoles.

Implementation of a method for sperm cryopreservation in sceloporine lizards.

Actual loss of lizard biodiversity continues, even with the implementation of conventional conservation programs. An approach including assisted reproductive techniques such as sperm cryopreservation may contribute to the management of endangered species. We developed a method for sperm cryopreservation in sceloporine lizards and compared the response among the studied species. Prior to the mating season, we obtained semen from adult males of Sceloporus aeneus (n = 21), Sceloporus grammicus (n = 20) and Sceloporus torquatus (n = 21) via pressure of the genital papilla. Volume and sperm concentration were measured before semen dilution in a Tris-egg yolk (TEY) medium to evaluate progressive motility, sperm viability, morphology, plasma membrane and acrosome integrity. Then, we cooled the remaining volumes to 5°C at a rate of 0.1°C per minute to incorporate glycerol (8% v/v) in two fractions. Immediately afterwards, we placed 40 µl of the mix on solid CO2 to form pellets and immersed them in liquid nitrogen for storage. We thawed the pellets at 29°C for 3 minutes and diluted them 1:1 (v/v) in TEY medium to assess sperm quality. We found a positive relationship between body weight and seminal volume in S. grammicus and S. torquatus and a negative correlation with sperm concentration in S. grammicus (P < 0.05). Moreover, we observed that the freezing-thawing process decreased sperm quality in the three species, mostly affecting motility and viability. However, S. torquatus and S. aeneus showed a higher sperm tolerance than S. grammicus.

Cryptorchidism: The dog as a study model.

Cryptorchidism (CO) or undescended testicle is an abnormality of male gonadal development that can generate long-term repercussions in men, such as infertility and germ cell neoplasia in situ (GCNIS). The origin of these alterations in humans is not completely clear, due to the absence of an animal model with similar testicular development as in humans with CO. This work intends to describe the testicular histological development of dogs with congenital CO, and determine whether the species could adequately serve as a study model for this pathology in humans. The study was carried out with 36 dogs, equally distributed in two groups: healthy control (CTRL) and CO groups. The contralateral testis to the undescended one in CO group of the animals was considered and analyzed. Each group was subdivided in three stages of development: (1) peripubertal stage (6-8 months), (2) young adult (9-48 months) and (3) senile (49-130 months). Histological development, the presence of cells with gonocyte morphology, cell proliferation, testicular lipoperoxidation and hormonal concentrations of testosterone, estradiol, FSH and LH were evaluated and described. In the cryptorchid testes, the first histological alterations appeared from the first stage of development and were maintained until the senile stage. A pronounced testicular lipoperoxidation occurred only in the second stage of development. The histological alterations due to CO were markedly evident in the young adult stage. Testosterone concentrations witnessed a decrease starting from in the second stage and kept on until the last stage. The contralateral testes of the CO animals showed alterations that positioned them between the control and CO testes. Testicular development of dogs with CO is similar to that of humans. The results of the study suggest that this species could serve as a suitable model for the study of CO in humans.

Development and Validation of the Overall Foot Pain Questionnaire in Motorcycle Riders.

Objectives: Our primary aim was to develop a transcultural adaptation of a cycling questionnaire using the Borg CR-10 scale as a tool to describe the discomfort among motorcyclists during the riding process in two trial sessions. Design: A transcultural adaptation and descriptive cross-sectional study. Settings: Jarama motorcycling circuit (Madrid, Spain). Participants: The participants were riders recorded across in a final motorcycling race. Interventions: The study design is based in two tools, the adapted Motorcyclist Questionnaire (MQ-21) with 21 items and Borg CR10 Scale® was used to determine discomfort level during motorcycling performance. The translation procedure, reliability, and reproducibility were performed. Results: All items showed an almost perfect intraclass correlation coefficient (ICC) (ICC = 0.909-1.00), except for item 9 (ICC = 0.881). Almost perfect internal consistency was shown for the total score (Cronbach α = 0.899). No systematic differences existed among test and retest in all items (p > 0.05) according to Bland-Altman plots. Respondents experienced slight discomfort on their body parts during the test-retest 1 h riding process. Foot discomfort was scored as 1.20, being the eighth of the 12 studied body parts. Conclusions: Internal consistency and test-retest reliability of the MQ-21 questionnaire were excellent and this questionnaire may be recommended to be used in motorcycling sports and clinical settings to evaluate the discomfort.

Melatonin added to freezing diluent improves canine (Bulldog) sperm cryosurvival.

Cryopreservation compromises the capacity of sperm fertilizing due to a series of alterations in the structure and physiology of the sperm. The use of antioxidants, such as melatonin, added to freezing media, may help to reduce sperm cryoinjury. To test the effect of melatonin on Bulldog (Canis lupus familiaris) sperm cryosurvival, spermatozoa were diluted in a standard freezing medium and cooled to 5°C. Then, more freezing medium was added to obtain 200 × 106 cells/mL, and 5% glycerol. Diluted spermatozoa were treated with melatonin (0.0, 0.0005, 0.002, and 0.0035 mol/L), and packaged in 0.25 mL straws, which were further cooled to -5°C before freezing in liquid nitrogen. Thawing was carried out at 70°C for 5 s, and the progressive motility, viability, plasma membrane integrity, acrosome integrity, capacitation status, and plasma membrane fluidity of the spermatozoa (at 37°C) were assessed. Data were analyzed using ANOVA to detect differences between the melatonin doses. There were statistical differences (P < 0.05) in the percentage of sperm having hyper-fluid membranes, intact acrosome, capacitated acrosome-intact, and acrosome-reacted. The values for the high melatonin doses (0.002 and 0.0035 mol/L) were better than for the low melatonin doses (0.0 and 0.0005 mol/L). In conclusion, 0.002 and 0.0035 mol/L of melatonin improved the cryosurvival of sperm from male bulldogs. LAY SUMMARY: Preservation of sperm by freezing enables breeding of individuals geographically separated; protocols for the dog may be used to preserve the semen from threatened wild canids. To improve fertility of female dogs that become pregnant with frozen and then defrosted sperm, these cells must survive that process which can be damaging whilst keeping their ability to fertilize. Antioxidants are substances capable of retarding or preventing the oxidation of any oxidizing substrate such as lipids, proteins, and DNA, which are structural compounds of the sperm. The use of antioxidants, added to freezing media, may provide the sperm the capacity to neutralize oxidative compounds, such as reactive oxygen species, produced during the freezing and thawing process. In this work we tested different levels of melatonin, a natural antioxidant, on dog (English Bulldog) sperm survival and quality after freezing. We found that adding melatonin to the freezing media improved sperm quality after thawing.

A non-invasive method for semen collection and evaluation in small and median size lizards.

The aim of this study was to develop a non-invasive procedure to stimulate ejaculation in median and small lizards for semen collection. After semen collection, we applied a battery of tests to assess the motility (wave and progressive), viability (eosin-nigrosin stain), morphology (normal/abnormal), sperm concentration and ejaculate number, seminal volume and colour. We obtained this fluid from all males of the four species of sceloporine lizards (n = 30) and one species of Mexican horned lizards (n = 7). We found that semen from all males had a liquid-like consistency and a milky-white appearance. Ejaculate volume and sperm concentration varied among the males and the species studied. We also observed that although the mobility, viability and normal sperm morphology showed a wide variability, their average value in each species was high. We conclude that "genital papilla pressure" was an efficient and non-invasive semen obtaining method for small- and medium-sized lizards that does not imply damage to donors and could be used in other lizard species.

Effects of eccentric exercise in pressure pain threshold in subjects with functional ankle equinus condition.

Stretching exercises are widely used by the population before sporting activities. One of the most common technique is eccentric exercise. Here, we made a clinical examination of 98 subjects with equinus condition before activity and after 30 min of running (49 participants with previous eccentric exercise and 49 with no previously eccentric exercise). The clinical assessment of the Achilles tendon was based on the pressure pain threshold (PPT). We identified significant PPT changes between the previous eccentric stretching and the non-previous eccentric stretching group in the Achilles tendon evaluations. Based on our findings, we propose that subjects with equinus condition could use eccentric stretching in order to improve the Achilles tendon status.

Effects of eccentric exercise in pressure pain threshold in subjects with functional ankle equinus condition

SUMMARY Stretching exercises are widely used by the population before sporting activities. One of the most common technique is eccentric exercise. Here, we made a clinical examination of 98 subjects with equinus condition before activity and after 30 min of running (49 participants with previous eccentric exercise and 49 with no previously eccentric exercise). The clinical assessment of the Achilles tendon was based on the pressure pain threshold (PPT). We identified significant PPT changes between the previous eccentric stretching and the non-previous eccentric stretching group in the Achilles tendon evaluations. Based on our findings, we propose that subjects with equinus condition could use eccentric stretching in order to improve the Achilles tendon status.

RESUMO Exercícios de alongamento são amplamente utilizados pela população antes da atividade esportiva. Uma das técnicas mais comuns é o exercício excêntrico. Aqui, fizemos um exame clínico de 98 indivíduos com condição de pé equino antes da atividade e após 30 minutos de corrida (49 corredores com exercício excêntrico anterior e 49 sem exercício excêntrico anterior). A avaliação clínica do tendão de Aquiles foi baseada no limiar de dor à pressão (PPT). Identificamos modificações significativas no PPT entre alongamentos prévios excêntricos e nenhum exercício anterior excêntrico de alongamento para as avaliações do tendão de Aquiles. Com base em nossos achados, propomos que sujeitos com condição de pé equino poderiam fazer alongamentos com exercícios excêntricos para melhorar o status do tendão de Aquiles.

Quality of life improvement in aged patients after toenail surgery.

BACKGROUND: Patients of all ages can develop nail disorders, such as onychocryptosis, which are recurrent and painful conditions. OBJECTIVE: The aim of the study was to compare the quality of life in a group of aged patients with recurrent and painful ingrown toenails before and after chemical nail surgery to treat onychocryptosis. MATERIAL AND METHODS: The study design utilized a presurgery and a postsurgery questionnaire and examined prospective serial cases. The participants were drawn from an outpatient podiatric clinic from 1 January 2015 to 29 August 2016. The final sample of patients (>65 years old) underwent nail surgery with chemical matricectomy using phenol. In addition to the chemical nail surgical procedure, the patients completed the Manchester-Oxford Foot Questionnaire (MOXFQ) and the Borg CR-10 scale category ratio (CR) within 4 weeks prior to surgery. The patients completed both questionnaires again through mailing 3 months postsurgery. RESULTS: Lower MOXFQ scores were noted after surgery, demonstrating an improvement in quality of life after chemical nail surgery. Men and women exhibited similar results (p > 0.05), with the exception of the Borg CR-10 scale where women reported more residual pain compared with men, with scores of 1.26 ± 1.65 and 0.09 ± 0.20, respectively (p = 0.011). CONCLUSION: After a chemical nail surgery procedure, the quality of life improved in aged patients with recurrent and painful ingrown toenails.

Relationship Between Decreased Subcalcaneal Fat Pad Thickness and Plantar Heel Pain. A Case Control Study.

BACKGROUND: Heel pain is one of the most frequent complaints in medical clinical practice for conditions affecting the feet during weight-bearing tasks. OBJECTIVE: The goal of this study was to measure and compare the thickness of the fat pad in a sample of patients with current unilateral heel pain and patients without unilateral heel pain with normalized reference parameters. STUDY DESIGN: This was an observational case-control study. SETTINGS: The research took place in the podiatry department within a medical health care center. METHODS: A total of 375 patients were randomly selected from a pool of patients attending a medical health care center between the years 2008 and 2015 and diagnosed by a single medical podiatrist without having previous treatment. Patients were categorized in 2 groups: a heel pain group (n = 185) and a control group (asymptomatic; n = 190). The thickness of the plantar fat pad was measured with an ultrasonic probe (BodyMetrix® BX 2000; IntelaMetrix, Inc, Livermore, CA). RESULTS: Initial examination of both groups indicated no significant differences in age, height, weight, or body mass index (P > 0.01). There were, however, significant differences in the thickness of the fat pad between those in the heel pain group and those in the control group, when analyzed by group and by gender (P < 0.01; Cohen´s d = 0.465-1.959). LIMITATIONS: The study was not a randomized controlled trial. Although primary outcome data were self-reported, the assessor was not blinded. CONCLUSION: This study provides further evidence that people with unilateral heel pain showed a significantly decreased thickness of the subcalcaneal fat pad, regardless of gender. KEY WORDS: Heel pain, subcalcaneal fat, pain.

In vitro capacitation and acrosome reaction in sperm of the phyllostomid bat Artibeus jamaicensis.

Sperm capacitation occurs during the passage of sperm through the female reproductive tract. Once the sperm binds to the pellucid zone, the acrosome reaction to enable penetration of the oocyte is completed. In this study, sperm of Artibeus jamaicensis bat was used to evaluate both capacitation status and the acrosome reaction under in vitro conditions, incubating sperm at 32 and 37°C with and without progesterone. Sperm was incubated at different times to assess sperm cells' functionality in terms of capacitation and acrosome reaction, using the chlortetracycline staining, lectin fluoresceinisocyanate conjugate-Pisum sativum agglutinin (FITC-PSA), and transmission electron microscopy. Sperm cells that presented uniform fluorescence throughout the head and mid-piece were classified as non-capacitated. Subsequently, sperm cells, which were observed with fluorescence only in the anterior portion of the head and mid-piece, were classified as capacitated. Sperm cells with no fluorescence in the head, but fluorescence in the mid-piece, were categorized as sperm cells that have carried out the acrosome reaction. During the acrosome reaction, sperm cells showed changes in their morphology, so it was not possible to distinguish the plasma and acrosomal membranes. Around the entire head, it was not possible to distinguish the fusion points between these membranes that made it possible for the acrosomal reaction to take place and thus to release the enzymes necessary to penetrate the pellucid zone. In conclusion, under appropriate in vitro conditions and by supplementing the culture medium with progesterone, A. jamaicensis bat sperm cells are able to be capacitated in a period from 6 to 8 h and to carry out the acrosome reaction.

Optimal choice of footwear in the elderly population.

To discover whether changes in foot morphology and pain tolerance may favor the use of inadequate footwear in old age. 100 participants, mean age 81.60 ± 8.26 years attended an outpatient clinic where self-reported demographic data, frequency checked their feet, measurements of foot sensitivity, foot size and shoe size. Only 19% checked their feet every day, 73% revealed symptoms of neuropathy and 83% used inadequate footwear on at least one foot. In a bivariate analysis, no significant differences were observed. Distinct physical changes affect the feet in the elderly population. Decreased sensitivity and absence of regular foot checks can contribute to use of inadequate footwear. Often, it is necessary to use a different shoe size to ensure that the footwear matches the actual dimensions and true needs of each foot in order to improve functionality and prevent the onset of severe medical conditions and/or foot deformities.

Characterization of gametes in two phyllostomid bat species: Artibeus jamaicensis and Sturnira lilium.

Morphology of gametes is used to understand the physiological processes in reproduction among domestic and wild animals. These gametes are used in assisted reproductive technology (ART) and conservation programs. In the case of Artibeus jamaicensis and Sturnira lilium, few studies have been conducted related to these issues. The aim of this study was to describe the structure of spermatozoa, semen characteristics and also the morphology and quality of cumulus oocyte complexes (COC) of A. jamaicensis and S. lilium. Semen characteristics were: A. jamaicensis had a sperm concentration of 4.26×10(6)sperm/ml, progressive motility of 34.55%; viability of 73.23%; head, tail and mid-piece abnormalities of 12.50%. Head length was 6.26µm, mid-piece 18.61µm and tail 70.92µm. S. lilium, had a sperm concentration of 5.15×10(6)sperm/ml, progressive motility of 60.00%, viability of 83.82%; abnormalities in head, tail and mid-piece of 13.77%. Head length was 7.01µm, mid-piece 20.33µm and tail 70.50µm. On average 12.8 of right ovarian oocytes and 9.9 of left ovarian oocytes of A. jamaicensis were recovered. For S. lilium on average 10.7 oocytes from the right ovary and 10.9 oocytes from the left ovary were recovered, ranging in quality from excellent to poor. Sperm morphology and quality of COC were similar to those for other domestic and wild animals. Bat gametes can be used for the study of reproductive biology, in conservation programs and assisted reproductive technology (ART) among domestic and wild animals.

A simple osmotic stress test to predict boar sperm cryosurvival.

This work was carried out to test whether viability of pig spermatozoa subjected to an osmotic test is correlated to sperm cryosurvival. Spermatozoa were cooled from 22 degrees C to -5 degrees C, aliquots were exposed to a series of hyperosmotic solutions (300-2100 mOsm/kg) for 15 min, immediately spermatozoa were re-warmed to 37 degrees C and isosmolarity was restored. Spermatozoa were cooled from 22 degrees C to -5 degrees C and one aliquot was exposed to the osmotic test while diluted spermatozoa were frozen-thawed. Plasma membrane-intact spermatozoa decreased as osmolarity increased (P < 0.0001), a further decreased (P < 0.0001) was observed when isotonicity was restored. Proportions of plasma membrane-intact and acrosome-intact cells from the osmotic test were no different from those after freeze-thawing: 36% vs. 35%, 80% vs. 80%, respectively. A significant correlation was found between the proportion of acrosome-intact cells after freeze-thawing and that from the osmotic test (r = 0.81, P <0.01). This test provides a useful and economical mean to predict in vitro boar sperm cryosurvival.

The significance of cooling rates and animal variability for boar sperm cryopreservation: insights from the cryomicroscope.

Once the first methods for freezing mammalian semen had been established, research aimed at improving cryopreservation procedures became highly focused on the interactions between cooling rates and the permeability of the plasma membrane to water and cryoprotectants. This was based on the premise that cooling rates could be optimized from a theoretical basis for different species of interest. While this approach has stimulated considerable research, it has not achieved its original aim at the species level, largely because it overlooks inter-individual variation in sperm biochemical composition and physiology. If the underlying hypothesis is valid, however, optimal cooling rates should be identifiable for spermatozoa from individual animals. Experiments with the cryomicroscope revealed that while sperm survival after cryopreservation varied considerably between boars, there was little evidence that optimal freezing rates could be identified for individuals. Based on these findings, we tested the hypothesis that sperm susceptibility to cryoinjury is a consistent feature of each individual, but those individuals differ in susceptibility. This hypothesis was supported by evidence from an experiment with >100 boars; moreover, using genetic analyses, we demonstrated genomic differences between individual boars that correlated with post-thaw sperm quality.