Chemical synthesis and optical, structural, and surface characterization of InP-In2O3 quantum dots.

InP-In2O3 colloidal quantum dots (QDs) synthesized by a single-step chemical method without injection of hot precursors (one-pot) were investigated. Specifically, the effect of the tris(trimethylsilyl)phosphine, P(TMS)3, precursor concentration on the QDs properties was studied to effectively control the size and shape of the samples with a minimum size dispersion. The effect of the P(TMS)3 precursor concentration on the optical, structural, chemical surface, and electronic properties of InP-In2O3 QDs is discussed. The absorption spectra of InP-In2O3 colloids, obtained by both UV-Vis spectrophotometry and photoacoustic spectroscopy, showed a red-shift in the high-energy regime as the concentration of the P(TMS)3 increased. In addition, these results were used to determine the band-gap energy of the InP-In2O3 nanoparticles, which changed between 2.0 and 2.9 eV. This was confirmed by Photoluminescence spectroscopy, where a broad-band emission displayed from 2.0 to 2.9 eV is associated with the excitonic transition of the InP and In2O3 QDs. In2O3 and InP QDs with diameters ranging approximately from 8 to 10 nm and 6 to 9 nm were respectively found by HR-TEM. The formation of the InP and In2O3 phases was confirmed by X-ray Photoelectron Spectroscopy.

Male facial attractiveness and masculinity may provide sex- and culture-independent cues to semen quality.

Phenotype-linked fertility hypothesis (PLFH) predicts that male secondary sexual traits reveal honest information about male fertilization ability. However, PLFH has rarely been studied in humans. The aim of the present study was to test PLFH in humans and to investigate whether potential ability to select fertile partners is independent of sex or cultural background. We found that on the contrary to the hypothesis, facial masculinity was negatively associated with semen quality. As increased levels of testosterone have been demonstrated to impair sperm production, this finding may indicate a trade-off between investments in secondary sexual signalling (i.e. facial masculinity) and fertility or status-dependent differences in investments in semen quality. In both sexes and nationalities (Spanish and Colombian), ranked male facial attractiveness predicted male semen quality. However, Spanish males and females estimated facial images generally more attractive (gave higher ranks) than Colombian raters, and in both nationalities, males gave higher ranks than females. This suggests that male facial cues may provide culture- and sex-independent information about male fertility. However, our results also indicate that humans may be more sensitive to facial attractiveness cues within their own populations and also that males may generally overestimate the attractiveness of other men to females.

Squamous cell carcinoma of the lip. A retrospective study of 146 patients.

BACKGROUND: Squamous cell carcinoma of the lip (SCCL) accounts for 90% of all tumours of the oral cavity. We present a series of 146 patients with SCCL studied in our hospital. OBJECTIVE: To evaluate and identify the primary tumour parameters related to local and lymph node recurrence. METHODS: We retrospectively analysed the clinical characteristics, surgical procedures and tumour recurrences of the 146 patients diagnosed with SCCL in Hospital Universitario Fundación Alcorcón (Spain). RESULTS: A total of 122 of the 146 patients (91.7%) showed tumour stage ≤ T1N0M0 at diagnosis, and 11 (8.3%) showed stage >T1N0M0. Local recurrences were observed in 11 of the 146 patients (7.5%), and five patients (3.4%) developed lymph node metastases during follow-up. Kaplan-Meier survival analysis showed an increased tumour size to imply a greater risk of local recurrence (P = 0.025). The probability of local recurrence over the 24 months of follow-up was 1% for tumour stages ≤ T1N0M0 and 20% for stages ≥ T1N0M0. There appears to be a greater tendency towards local relapse in male patients, in smokers, patients living in rural areas, in lower lip tumours and in those patients showing infiltration at physical exploration. Eleven patients (8%) died during follow-up, although in only two of them (18%), SCCL was the cause of death. CONCLUSION: The low tumour stage of our patients may explain the few local and lymph node disease recurrences seen in our study. We have shown tumour size to be directly related to the probability of local recurrence.

Effect of aracnotoxin from Latrodectus mactans on bovine sperm function: modulatory action of bovine oviduct cells and their secretions.

Latrodectus mactans' aracnotoxin (Atx) induces changes in sperm function that could be used as a co-adjuvant in male contraceptive barrier methods. This effect includes the suppression of intracellular reactive oxygen species (ROS), an event necessary for capacitation, chemotaxis and acrosome reaction (AR). The sperm that are not trapped by the barrier method can reach the oviduct before fertilisation and be exposed to the secretions of the oviducts. This study evaluated the effect of bovine tubal explants (TU) and conditioned media (CM) from the ampullar and isthmal regions on spermatozoa exposed to Atx. Thawed bovine sperm were incubated with Atx, TU and CM from the ampullar and isthmal regions for 4 h and then DNA integrity, intracellular ROS and lysophosphatidylcholine-induced AR were determined. Spermatozoa exposed to Atx and co-incubated with TU and CM for 4 h produced an increase in sperm DNA damage, a decrease in ROS production and a decrease in %AR, compared with the control. A similar result was obtained from the co-incubation of spermatozoa with Atx. In conclusion, the effect of Atx is not modified by tubal cells or their secretions and this opens the door to future studies to evaluate the application of synthetic peptides obtained from Atx as a co-adjuvant of contraceptive barrier methods.

Activators of the nuclear receptor PPARgamma enhance colon polyp formation.

A high-fat diet increases the risk of colon, breast and prostate cancer. The molecular mechanism by which dietary lipids promote tumorigenesis is unknown. Their effects may be mediated at least in part by the peroxisome proliferator-activated receptors (PPARs). These ligand-activated nuclear receptors modulate gene expression in response to fatty acids, lipid-derived metabolites and antidiabetic drugs. To explore the role of the PPARs in diet-induced carcinogenesis, we treated mice predisposed to intestinal neoplasia with a synthetic PPARgamma ligand. Reflecting the pattern of expression of PPARgamma in the gastrointestinal tract, treated mice developed a considerably greater number of polyps in the colon but not in the small intestine, indicating that PPARgamma activation may provide a molecular link between a high-fat diet and increased risk of colorectal cancer.

Protective effect of fallopian tubal fluid against activated leucocyte-induced sperm DNA fragmentation: preliminary results.

The integrity of the paternal genome is of paramount importance in the initiation and maintenance of a viable pregnancy. Oxygen radicals (ROS) have been identified as one of the main factors responsible for the induction of sperm DNA damage. Spermatozoa are mainly protected against ROS-induced damage by seminal plasma. However, this protective effect disappears once spermatozoa enter the female genital tract. The fallopian tube mucosa may play a protective role against ROS-induced sperm damage. The main objective of this study was to determine whether human tubal explants and tubal fluid exert a protective effect on ROS-induced sperm DNA damage. Spermatozoa were exposed to tubal explants and/or tubal fluid in the presence of phorbol myristate acetate (PMA)-activated polymorphonuclear leucocytes or control medium and sperm DNA fragmentation was measured using the TdT-mediated dUTP-biotin nick end labelling (TUNEL) test. Exposure of human spermatozoa to PMA-activated leucocytes resulted in a 2-fold increase in sperm DNA fragmentation. Co-incubation of spermatozoa with tubal explants did not reduce this damage. However, pre-incubation of spermatozoa with tubal fluid resulted in a statistically significant reduction in sperm DNA fragmentation levels, comparable to those observed in control. In conclusion, tubal fluid appears to protect against activated leucocyte-induced sperm DNA fragmentation, thus preserving the integrity of the paternal genome.

Growth Mechanism and Properties of Self-Assembled InN Nanocolumns on Al Covered Si(111) Substrates by PA-MBE.

Self-assembled InN nanocolumns were grown at low temperatures by plasma-assisted molecular beam epitaxy with a high crystalline quality. The self-assembling procedure was carried out on AlN/Al layers on Si(111) substrates avoiding the masking process. The Al interlayer on the Si(111) substrate prevented the formation of amorphous SiN. We found that the growth mechanism at 400 ∘ C of InN nanocolumns started by a layer-layer (2D) nucleation, followed by the growth of 3D islands. This growth mechanism promoted the nanocolumn formation without strain. The nanocolumnar growth proceeded with cylindrical and conical shapes with heights between 250 and 380 nm. Detailed high-resolution transmission electron microscopy analysis showed that the InN nanocolumns have a hexagonal crystalline structure, free of dislocation and other defects. The analysis of the phonon modes also allowed us to identify the hexagonal structure of the nanocolumns. In addition, the photoluminescence spectrum showed an energy transition of 0.72 eV at 20 K for the InN nanocolumns, confirmed by photoreflectance spectroscopy.

Geographical differences in semen quality in a population of young healthy volunteers from the different regions of Spain.

Numerous studies have shown geographical differences in semen quality even within a given country. We have previously reported a low semen quality in volunteers from the province of Barcelona compared with the general population. The objective of this study was to determine the semen quality in a population of young healthy volunteers from the different regions of Spain. A total of 1239 volunteers between 18 and 30 years of age were enrolled. The parameters evaluated were semen volume, sperm concentration and progressive sperm motility. The results indicate that while there were no differences in semen volume or sperm motility, there were statistically significant differences in the rate of oligospermia in volunteers from the different regions studied. The prevalence of oligospermia was highest in Valencia (22.7%), Barcelona (22.7%) and Pais Vasco (18.7%), which are the regions of Spain with the highest degree of industrialisation for the last 50 years, and lowest in Galicia (8.5%) and Andalucía (13.7%), regions with a more recent industrial development. There were no differences in the rate of oligospermia as a function of age. These results support the hypothesis that exposure to environmental toxicants may affect the process of spermatogenesis leading to meiotic alterations, maturational arrest and oligospermia.

[Hypersensitivity reaction to systemic corticosteroids in a hemodialysis patients]. / Reacción de hipersensibilidad por corticoides sistémicos en una paciente en hemodiálisis.

Hypersensitivity reactions are a feared complication of hemodialysis considering their potential for a serious and eventually fatal course. This association could reflect a number of different exposures, including concomitant medications. Like this, systemic steroid-induced hypersensitivity reactions do occur, althought their incidence is extremely rare. A few reactions related to metylprednisolone have been reported in renal transplantation. The diagnosis could be confirmed by the patient history and performing skin testing, oral or parenteral challenge or by the evidence of specific IgE. We report on a 39-year-old woman undergoing dialysis therapy in whom severe bronchospasm was induced by corticosteroids. She has a positive systemic reaction on the oral steroid challenge test. A successful desensitization regimen for safe administration was achieved. The recognition of high-risk subjects and alternative therapeutic approach are critical, mainly in the management of patients while receiving corticosteroids or a renal allograft.

Properties of Particle Size Distribution from Milled White Nixtamalized Corn Kernels as a Function of Steeping Time.

This paper focuses on the particle size distribution (PSD) changes during nixtamalized corn kernels (NCK) as a function of the steeping time (ST). The process to obtain powder or corn flour from NCK was as follows: (i) the NCK with different STs were wet-milled in a stone mill, (ii) dehydrated by a Flash type dryer, and (iii) pulverized with a hammer mill and sieved with a 20 mesh. The powder was characterized by measuring the PSD percentage, calcium percentage (CP), peak viscosity at 90°C (PV), and crystallinity percentage (CP). The PSD of the powder as a function of ST was determined by sieving in Ro-TAP equipment. By sieving, five fractions of powder were obtained employing meshes 30, 40, 60, 80, and 100. The final weight of the PSD obtained from the sieving process follows a Gaussian profile with the maximum corresponding to the average particle obtained with mesh 60. The calcium percentage as a function of ST follows a behavior similar to the weight of the PSD. The study of crystallinity versus the mesh number shows that it decreases for smaller mesh number. A similar behavior is observed as steeping time increases, except around ST = 8 h where the gelatinization of starch is observed. The trend of increasing viscosity values of the powder samples occurs when increasing ST and decreasing particle size. The ST significantly changes the crystallinity and viscosity values of the powder and, in both cases, a minimum value is observed in the region 7-9 h. The experimental results show that the viscosity increases (decreases) if the particle size decreases (increases).

Organelle distribution in chick neuroepithelial cells: effects of colchicine and cytochalasin B.

The intracellular distribution of mitochondria, cytoplasmic inclusions and rough endoplasmic reticulum cisternae of chick neuroepithelial cells was investigated at neurulation stages 6, 8, 10 and 12. These neuroepithelial cells were subdivided into three zones: apical, median and basal and the distribution percentages of distribution of these organelles were obtained. Mitochondrial distribution was related to the energy supply that mitochondria provide for apical microfilament contraction. Cytoplasmic inclusions were distributed preferentially in the apical zone of the neuroepithelial cells during the four stages. Rough endoplasmic reticulum cisternae were homogeneously distributed in the three zones at stages 10 and 12, but at stages 6 and 8 there are more elevated percentages of rough endoplasmic reticulum in the apical zones than in the other zones. Experimental treatments with colchicine and cytochalasin B does not modify the patterns of mitochondria and rough endoplasmic reticulum cisternae but alters the distribution of cytoplasmic inclusions. Finally, there is a correlation in the normal neurulating neuroepithelial cells between the distributions of mitochondria and rough endoplasmic reticulum distribution and between the distributions of mitochondria and cytoplasmic inclusions distribution. This relationship is retained in the treated neuroepithelial cells.

Generation of regulatory oxysterols: 26-hydroxylation of cholesterol by ovarian mitochondria.

De novo synthesis of cholesterol and low-density lipoprotein (LDL) receptor levels are suppressed in the presence of cholesterol. Recent evidence suggests that a cholesterol metabolite (possibly a hydroxysterol), not cholesterol per se, is the effector that inhibits transcription of genes encoding enzymes involved in sterol synthesis and LDL receptors. We found that 26-hydroxycholesterol inhibits human ovarian cell sterol synthesis, and that luteinized human granulosa cells contain 26-hydroxylase messenger RNA (mRNA). We proceeded to characterize the enzyme generating 26-hydroxycholesterol in the rat ovary. Mitochondria derived from ovaries of PMSG-human CG (hCG) primed immature rats (day 3 post-hCG) metabolized [3H] cholesterol into [3H]26-hydroxycholesterol in the presence of nicotinamide adenine dinucleotide phosphate and aminoglutethimide (100 micrograms/ml), added to inhibit metabolism of sterols by the cholesterol side-chain cleavage system. The identity of the product was confirmed by chromatography in several systems; recrystallization to constant specific activity and mass spectrometry. Negligible 26-hydroxylase activity was detected in other ovarian subcellular fractions. 26-Hydroxycholesterol formation progressed at a linear rate for up to 40 min and was linearly related to mitochondrial protein added to the incubation mixture. 26-Hydroxylase was markedly stimulated (5-fold) by calcium (0.2 mM). Maximal rates of 26-hydroxycholesterol formation observed were 1 pmol/min.mg protein. This activity is substantially lower than cholesterol side-chain cleavage measured in the absence of aminoglutethimide. Ketoconazole (1-100 microM) inhibited 26-hydroxylase in a dose-dependent manner. Pregnenolone (1-1000 microM) and progesterone (1-100 microM) inhibited 26-hydroxylase in a dose-dependent manner, with appreciable inhibitory effects in the 1-10 microM range. We suggest that 26-hydroxycholesterol is an intracrine regulator that controls cellular sterol metabolism. Formation of 26-hydroxcholesterol in ovarian cells may be regulated by steroidogenic activity in such a way as to ensure availability of steroid hormone precursors. When steroidogenesis is active, 26-hydroxylase is inhibited by products of the side-chain cleavage system, allowing increased de novo sterol synthesis and LDL uptake. With reduced steroidogenic activity and less demand for cholesterol, 26-hydroxylase is not blocked, permitting formation of 26-hydroxycholesterol with attendant reduction in sterol synthesis and LDL receptor gene expression.

Prediction of respiratory distress syndrome by the novel dipalmitoyl phosphatidylcholine test.

OBJECTIVE: To determine the accuracy of a new test that measures the concentration in amniotic fluid (AF) of dipalmitoyl phosphatidylcholine (DPPC) in predicting respiratory distress syndrome (RDS). METHODS: The neonatal respiratory status of 176 newborns delivered within 72 hours of sampling was correlated with the concentration of DPPC, fluorescence polarization (TDx-FLM), lecithin-sphingomyelin ratio (L/S), and phosphatidyl-glycerol (Amniostat-FLM) in AF. RESULTS: Thirty infants developed RDS (17%), all correctly predicted with DPPC values less than 12 micrograms/mL (sensitivity 100%). Only six of the 146 cases with no RDS had DPPC values less than 12 micrograms/mL (specificity 96%). The overall accuracy of the DPPC test was 98% compared with 70% for TDx-FLM, 71% for the L/S, and 67% for Amniostat-FLM. Receiver operating characteristic analysis area was 0.98 +/- 0.01, indicating that the DPPC test is superior to both the TDx-FLM and L/S tests. CONCLUSION: The DPPC test is an accurate predictor of RDS and fetal lung maturity.

Performance of the dipalmitoyl phosphatidylcholine test in predicting respiratory distress syndrome in contaminated samples of amniotic fluid.

OBJECTIVE: To evaluate the reliability of the dipalmitoyl phosphatidylcholine test in predicting respiratory distress syndrome (RDS) in the presence of common contaminants of amniotic fluid. METHODS: Forty specimens of amniotic fluid collected within 72 hours of delivery were divided in five 25 microL aliquots and diluted with either phosphate-buffered saline (control), meconium, blood, vaginal fluid, or semen. The concentration of dipalmitoyl phosphatidylcholine in all five groups of samples, as measured by the dipalmitoyl phosphatidylcholine test, was compared by paired t test, Dunnett test, and analysis of variance, and correlated with the neonatal respiratory status of the newborns. RESULTS: No significant differences in the concentration of dipalmitoyl phosphatidylcholine were found between control and the corresponding contaminated samples (P = .33). Of the 200 samples evaluated, 80 had dipalmitoyl phosphatidylcholine concentrations below 12 micrograms/mL and 120 had at least 12 micrograms/mL. Using a cutoff dipalmitoyl phosphatidylcholine concentration of 12 micrograms/mL, the presence of RDS was predicted accurately in all 15 control and in 61 of 65 contaminated samples. The absence of RDS, as predicted by a dipalmitoyl phosphatidylcholine value at least 12 micrograms/mL, was predicted accurately in 24 of 25 control samples and 96 of 100 contaminated samples. The overall accuracy of the dipalmitoyl phosphatidylcholine test in predicting RDS in contaminated samples was 98%. CONCLUSION: The dipalmitoyl phosphatidylcholine test is a reliable predictor of RDS in contaminated samples.

Cost-effectiveness of fetal lung maturity testing in preterm labor.

OBJECTIVE: To determine the marginal cost-effectiveness of two strategies for preventing respiratory distress syndrome (RDS) resulting from preterm birth: 1) tocolysis with beta-mimetic agonists and treatment with corticosteroids (TREATALL), and 2) amniocentesis and testing for fetal lung maturity, with treatment based on test results (TESTALL), compared with no treatment. METHODS: We used a Markov decision analytic model to estimate the outcomes of each strategy, from a hospital-based perspective. Probability variables were obtained from the literature, whereas cost variables came from the Beth Israel-Deaconess Medical Center. Sensitivity analysis was performed on all variables. RESULTS: The most cost-effective strategy varied with the probability of RDS. TREATALL was the most cost-effective strategy above a probability of 17% (before 34 weeks' gestation), TESTALL was most cost-effective from 17% to 2% (34-36 weeks), and it was most cost-effective to use no treatment at probabilities less than 2% (after 36 weeks). TREATALL and TESTALL were both cost-saving compared with no treatment at probabilities of RDS above 2%. TREATALL was more highly favored as the costs of RDS and preterm birth increased, whereas TESTALL was more favored as the specificity of the test and the cost of maternal hospitalization increased. CONCLUSION: Although testing for fetal lung maturity is useful in many clinical situations, the cost-effectiveness of such testing in the setting of idiopathic preterm labor from a tertiary medical center perspective depends primarily on the probability and costs of RDS and the costs of non-RDS-related morbidity. At our institution, such testing is cost-effective between 34 and 36 weeks' gestation.

Amniotic fluid cholesteryl palmitate in pregnancies complicated by diabetes mellitus.

Amniotic fluid cholesteryl palmitate, as measured by thin-layer chromatography, appears to be a very sensitive and specific predictor for the risk of respiratory distress syndrome (RDS) in newborns of normal pregnancies. To assess the effect of diabetes mellitus on fetal pulmonary maturation, we measured cholesteryl palmitate concentration, the lung profile, and total phosphatidylcholine in amniotic fluid obtained from 35 well-controlled diabetic and 39 control pregnancies at term. In women with diabetes, the mean (+/- SD) third-trimester glycosylated hemoglobin level was 6.96 +/- 2.3% (normal 6-8%). Mean cholesteryl palmitate concentration in the diabetic population was 79.12 +/- 13.17 micrograms/mL, versus 153.71 +/- 16.77 micrograms/mL in the control group (P less than .001). The mean cholesteryl palmitate concentration was also significantly different for gestational diabetics and class B-R gravidas (112.75 +/- 26.2 versus 54.45 +/- 7.34 micrograms/mL; P less than .005). Cholesteryl palmitate was decreased despite the presence of a mature lecithin/sphingomyelin ratio and, in most cases, phosphatidylglycerol. These data suggest that even in well-controlled diabetic pregnancies, alterations in maternal metabolism may affect either the biosynthesis or degradation of cholesteryl palmitate.

Differential Behavior Between Isolated and Aggregated Rabbit Auricular Chondrocytes on Plastic Surfaces.

A knowledge of the behavior of chondrocytes in culture is relevant for tissue engineering. Chondrocytes dedifferentiate to a fibroblast-like phenotype on plastic surfaces. Dedifferentiation is reversible if these cells are then cultured in suspension. In this report a description is given of how when chondrocyte aggregates formed in suspension are next seeded on plastic, most of them attach as round or polygonal cells. This morphological differentiation, with synthesis of type II collagen, is stable for long culture periods. This simple method can be of use as a model for studies of chondrocyte behavior on plastic. The results indicate that in addition to culture conditions, such as cell isolation method or cell density, chondrocyte behavior on plastic depends on the presence of aggregates.

The sperm stress test: a novel test that predicts pregnancy in assisted reproductive technologies.

OBJECTIVE: To develop a reliable sperm test that would predict pregnancy rate in assisted reproductive technologies. DESIGN: Blind prospective cohort study. SETTING: Tertiary-care, university hospital-affiliated IVF program. PATIENTS: One hundred nineteen sperm samples were obtained from 110 males from couples undergoing IVF or GIFT (ART). Sperm samples were washed by Percoll, incubated at 24 degrees C for 4 hours, and an aliquot of the same sperm suspension was used for ART incubated at 40 degrees C for 4 hours (stress test). Stress test scores are expressed as the ratio of final to initial motility. RESULTS: Of 119 ART cycles, 24 resulted in pregnancy. Of 24 pregnancies, 23 occurred in cycles that used sperm samples with stress test scores > or = 0.75 and only one with a stress test score < 0.75. The negative predictive value of the test, defined as the absence of pregnancy with scores < 0.75, was 98% and the positive predictive value, defined as the occurrence of pregnancy with scores > or = 0.75, was 36%. Logistic regression analysis indicated that the stress test score alone was correlated significantly with pregnancy after ART. CONCLUSION: These results indicate that stress test scores < 0.75 are predictive of poor pregnancy outcome in ART.

Mechanisms to explain pancreatic dysfunction in cystic fibrosis.

This article focuses on three potential mechanisms by which pancreatic dysfunction occurs in cystic fibrosis. These include (1) obstruction of pancreatic ducts by inspissated plugs, (2) inhibition of endocytosis in acinar cells, and (3) imbalance in membrane lipids in cystic fibrosis regulated cells. Any of these abnormalities alone or in combination may explain the development of pancreatic exocrine insufficiency.

Evidence that membrane stress contributes more than lipid peroxidation to sublethal cryodamage in cryopreserved human sperm: glycerol and other polyols as sole cryoprotectant.

One effect of cryopreservation on human sperm is sublethal cryodamage, in which cell viability post-thaw is lost more rapidly at later times than in fresh cells. We hypothesized two modes of sublethal cryodamage: one is peroxidation-related involving plasma membrane damage due to lipid peroxidation; the other is membrane stress-related involving membrane embrittlement during phase transitions occurring during freeze-thaw. If the peroxidation-related mode contributed substantially to sublethal cryodamage, the hypothesis predicts that lipid peroxidation inhibitors should reduce this damage. To test this prediction, we examined the effect of the lipid peroxidation inhibitors, hypotaurine, bovine serum albumin (BSA), and alpha-tocopherol (Vit. E) on the time to loss of motility (TLM), taken as a measure of cell viability over time, for sperm samples cryopreserved in glycerol plus egg yolk medium. These agents had no effect on TLM of these samples, indicating that this mode contributes little to sublethal cryodamage. If the membrane stress-related mode contributed, the hypothesis predicts rapid recovery of motility in the presence of egg yolk plus glycerol, but slow recovery in the presence of glycerol alone. It also predicts that an appropriate polyol may be both necessary and sufficient for cryopreservation. In the presence of egg yolk plus glycerol, motility recovery was complete within 5 minutes, but the percent motile cells then decreased linearly with time. With glycerol alone in the range 3-12%, at 5 minutes post-thaw the percent motile cells was 5-10%, but by 40 minutes post-thaw had risen to 60-80%, approaching that in the fresh sample, and was maintained up to 4 hours. In the absence of glycerol, the percentage of motile cells post-thaw was nil and remained nil up to 4 hours. The polyols, erythritol, ribitol, and sorbitol had similar effects to that of glycerol, but the recovery of motility was not as complete. These results indicate that the membrane stress-related mode contributes substantially to sublethal cryodamage. They also indicate that glycerol and other polyols can function alone as cryoprotectants, but that recovery of motility is slow in these systems.