Reduction of oxidative changes in human spermatozoa by exogenous gangliosides

The effect of exogenous gangliosides, the sialic acid-containing glycosphingolipids, on oxidative changes in human spermatozoa was investigated. The incorporation of disialogangliosides or trisialogangliosides (GD1b and GT1b, respectively) into the iron/ascorbate promoter system for induction of lipid peroxidation decreased the release of malondialdehyde (MDA) from peroxidizing spermatozoa. The application of monosialogangliosides and disialogangliosides (GM1 and GD1a, respectively) did not have any effect under identical experimental conditions. GT1b, at a micromolar concentration, significantly inhibited the production of MDA, a breakdown product of lipid peroxide decomposition in spermatozoa of normozoospermic infertile men (P < 0.001; n = 51). An enhanced generation of MDA exhibited by the sperm population from the low-density Percoll fraction containing defective and/or immature spermatozoa was significantly reduced in the presence of GT1b. These results and the experiments on the influence of iron-chelating agent ethylenediamine tetraacetic acid (EDTA) as well as ferrous ion concentration itself on lipid peroxidation support the hypothesis that the protective effect of ganglioside against MDA generation could be the result of its chelating activity. Furthermore, superoxide anion release of phorbol myristate acetate-stimulated spermatozoa was significantly reduced in the presence of 50 and 100 micromol l(-1) GD1b (P < 0.05) and GT1b (P < 0.005). The inhibitory effect of 100 micromol l(-1) GT1b on spermatozoa from infertile normozoospermic men was statistically significant (P < 0.001; n = 21) and did not depend on the initial superoxide anion production. In conclusion, the protective action of GD1b and GT1b could be related to both scavenging of free radicals and metal-chelating properties, which might have relevance in the protection against oxidation-induced processes in human spermatozoa.

Serum sialic acid in subjects with impaired glucose tolerance and in newly diagnosed type 2 diabetic patients

Several general population studies and those carried out in diabetic patients with complications have pointed to serum sialic acid as a marker of inflammation in atherosclerosis. In this study we examined whether total sialic acid (TSA) was changed in the sera of 28 newly diagnosed subjects with type 2 diabetes (type 2 DM), 47 subjects with impaired glucose tolerance (IGT) and 72 subjects with normal glucose tolerance (NGT). The associations between sialic acid and other atherosclerotic risk factors such as lipid profile, baseline diene conjugates in low-density lipoproteins (LDL-BDC) and fasting insulin were also investigated. We found a trend to TSA increase in subjects with impaired glucose tolerance and a significant increase in TSA in newly diagnosed patients with type 2 DM (2.2+/-0.3 vs. 1.9+/-0.3 mmol/l; p<0.03) when compared to subjects with NGT. Lipid profile and LDL-BDC, as a marker of circulating oxidized LDL, did not differ among glucose tolerance categories. Significant associations between total sialic acid and 2-h post-load glucose level, fasting insulin, insulin sensitivity, HDL-cholesterol and log of triglycerides were found in the examined subjects. Multiple regression analysis showed significant correlations between serum sialic acid and 2-h post-load glucose levels and insulin sensitivity. This study indicates that measurement of TSA as a marker of subclinical inflammation may be valuable as an independent parameter in identifying subjects at higher risk of developing type 2 diabetes and those who might benefit from anti-inflammatory treatment.

Baseline diene conjugation in LDL lipids from newly diagnosed type 2 diabetic patients

BACKGROUND

To determine whether the susceptibility of low-density lipoproteins (LDL) to oxidation was altered in subjects with newly diagnosed type 2 diabetes mellitus and impaired glucose tolerance using the measurement of LDL baseline diene conjugation (LDL-BDC) as an indicator of circulating mildly oxidized LDL in vivo.

METHODS

LDL was isolated from sera of 26 newly diagnosed patients with type 2 diabetes mellitus (type 2 DM), 43 subjects with impaired glucose tolerance (IGT), and 67 subjects with normal glucose tolerance (NGT), who were matched for age, gender, body mass index and serum lipids. Twenty-seven healthy subjects with normal body mass index and normal values of lipids served as a control group. In all groups the LDL-BDC was compared with the production of conjugated dienes after copper-induced LDL oxidation, and with total antioxidative status.

RESULTS

The LDL-BDC levels (micromol/l; mean +/- SD) were similar in the three glucose tolerance categories (NGT 66.5 +/- 6.9; IGT 67.9 +/- 6.5; type 2 DM, 68.1 +/- 7.1 p = 0.52) and there was no difference in comparison with the control group (68.9 +/- 4.2 micromol/l). Also, no significant differences between the groups were observed in the susceptibility to LDL oxidation in vitro or total antioxidative status. There was no correlation between glycemia and mildly oxidized LDL in vivo, nor with any of the parameters of the LDL oxidation in vitro.

CONCLUSIONS

In the examined population of newly diagnosed diabetic patients with mild hyperglycemia, as evidenced by the level of glycated haemoglobin (HbA(1C)), a lack of changes in the susceptibility of LDL to oxidation both in vivo and in vitro was established.

Effect of creatine on erythrocyte rheology in vitro

To evaluate how creatine influences erythrocyte deformability, we determined its effect on erythrocyte filterability in 9 subjects with insulin dependent diabetes (IDDM) without complications, 14 diabetics with uremia and 10 non-diabetic controls. The short-term incubation (15 min at 37 degrees C) of diabetic erythrocytes with 3 mM creatine improved cell filterability (assessed according to the Reid method) from IDDM subjects without complications by 28.4% and that from diabetics with uremia by 18.9%. No rheological effect of creatine was found in erythrocytes from non-diabetic controls. However, a significant protective effect against erythrocyte filterability impairment induced by treatment of red blood cells from non-diabetic controls with hydrogen peroxide was observed with 3 mM (p < 0.04) and 5 mM (p < 0.01) creatine, respectively. Measurement of the thiobarbituric acid (TBA) reactivity was used to assess hydrogen peroxide induced formation of malondialdehyde (MDA). We found that creatine inhibits hydrogen peroxide-induced erythrocyte MDA-formation in a dose dependent manner by 20.4%, 22.3% and 41.4% for 1, 3 and 5 mM creatine, respectively. These results suggest that creatine by its ability to inhibit erythrocyte lipid peroxidation may contribute to the maintenance of normal cell deformability.

In vitro effect of zinc on superoxide anion production by polymorphonuclear leukocytes of diabetic patients

We evaluated the ability of zinc to modulate the superoxide anion released by isolated, phorbol myristate acetate (PMA)-stimulated polymorphonuclear leukocytes (PMNs). In the presence of zinc at physiological level (20 micromol/l), PMNs released 20% less superoxide anions than untreated cells, whereas at higher zinc concentration (200 micromol/l), a 40%-increase in superoxide anion production was detected. The direction (suppression or stimulation) of superoxide anion generation was dependent upon extracellular zinc level and did not discriminate type 1 and 2 diabetic subjects from normal controls. The mechanism(s) of dose-dependent pro- and antioxidative effects of zinc on isolated PMNs in vitro as well as the implication of this finding for the modulatory effect of Zn on PMN-superoxide anion production in vivo need further investigation.

Semen quality and reproductive endocrine function in relation to biomarkers of lead, cadmium, zinc, and copper in men

Blood lead (BPb), activity of delta-aminolevulinic acid dehydratase (ALAD), erythrocyte protoporphyrin (EP), blood cadmium (BCd), serum zinc (SZn), seminal fluid zinc (SfZn), serum copper (SCu), and parameters of semen quality and of reproductive endocrine function were measured in 149 healthy male industrial workers 20-43 years of age. The group contained 98 subjects with slight to moderate occupational exposure to Pb and 51 reference subjects. All of the subjects lived in Zagreb, Croatia. Significant (p < 0.05) correlations of BPb, ALAD, and/or EP with reproductive parameters indicated a Pb-related decrease in sperm density, in counts of total, motile, and viable sperm, in the percentage and count of progressively motile sperm, in parameters of prostate secretory function (SfZn, acid phosphatase, and citric acid in seminal fluid), and an increase in abnormal sperm head morphology, serum testosterone, and estradiol. These associations were confirmed by results of multiple regression, which also showed significant (p < 0. 05) influence of BCd, SZn, SCu, smoking habits, alcohol consumption, or age on certain reproductive parameters. These effects were mainly of lower rank and intensity as compared to Pb-related reproductive effects, whereas BCd contributed to a decrease in sperm motility and an increase in abnormal sperm morphology and serum testosterone. No significant Pb- or Cd-related influence was found on levels of the lactate dehydrogenase isoenzyme LDH-C(4) and fructose in seminal fluid or on follicle-stimulating hormone, luteinizing hormone, and prolactin in serum. The seminal fluid concentrations of Pb (SfPb) and Cd (SfCd) were measured in 118 of the 149 subjects, and a highly significant (p < 0.0001) correlation was found between BPb and SfPb levels (r = 0.571) and between BCd and SfCd levels (r = 0.490). The overall study results indicate that even moderate exposures to Pb (BPb < 400 microg/L) and Cd (BCd < 10 microg/L) can significantly reduce human semen quality without conclusive evidence of impairment of male reproductive endocrine function.

Antioxidative effect of melatonin on human spermatozoa

The ability of melatonin to suppress experimentally induced lipid peroxidation (LPO) in sperm membrane was investigated in 41 samples of infertile men. Iron/ascorbate (0.04/0.2 mmol)-induced LPO was measured by the formation of malondialdehyde (MDA) using the thiobarbituric acid method. Sperm incubated in the presence of melatonin (2-6 mmol) exhibited a concentration-dependent decrease of MDA generated from hydroperoxide of the sperm plasma membrane in the presence of promoter system. Addition of 6 mmol of melatonin significantly reduced the rate of lipid peroxidation in sperm of unselected donors (mean +/- SE in control samples = 26.4 +/- 2.9 vs. 6.5 +/- 1.1 nmol MDA/10(8) sperm in melatonin-treated samples: n = 16, p < .005). Inhibitory effect of melatonin was also significant in the presence of 0.015 mmol of ferrous ions (20.5 +/- 1.7 vs. 7.9 +/- 1.6 nmol MDA/10(8) sperm in melatonin-treated samples: n = 7, p < .02) and (.005 mmol of ferrous ions (20.2 +/- 2.8 vs. 9.9 +/- 2.4 nmol MDA/ 10(8) sperm: n = 6, p < .05). Comparing the effect of melatonin with that of Trolox, an analog of vitamin E. a similar effect at concentration of 0.1-0.2 mmol of Trolox was found (25.2 +/- 2.9 vs. 11.8 +/- 1.2 nmol MDA/10(8) sperm in Trolox-treated samples: n = 7, p < .005). The obtained data of in vitro experiments show that melatonin is 40-fold less efficient than Trolox in achieving the 50% reduction in LPO (4 vs. 0.1 mmol). Since the physiological concentration of melatonin in human semen is at the nanomolar level, its antioxidative role in vivo is probably of minor importance.

Effect of cisplatin and 6-bromo-6-deoxy-L-ascorbic acid on some biochemical and functional parameters in mice

The results of the present study demonstrate that 6-bromo-6-deoxy-L-ascorbic acid (6-BrAA), an antioxidative derivative of ascorbic acid, is capable of lowering the toxicity of cisplatin, cis-diaminedichloroplatinum (cis-DDP), an anticancerogenic drug. The biological aspects and pharmacological significance of a combined treatment of these two substances were investigated in a mouse model. The results indicate that the effectiveness of 6-BrAA on biological response(s) is strongly dependent on the dose of cis-DDP. Injection of 10 mg/kg body weight (bw) of cis-DDP following pretreatment with 6-BrAA (480 mg/kg bw) enhances the tissue-protecting effect of 6-BrAA and reduces, to some extent, the ensuing nephro-, liver and spleen toxicity. On the other hand, 6-BrAA in animals treated with a higher dose of cis-DDP (15 mg/kg bw) leads to exacerbation of the toxic cis-DDP effect and concurrent loss of the protective potential of 6-BrAA with respect to tissue damage. The exact mechanism(s) of 6-BrAA protection and exacerbation of the toxic cis-DDP effect is unclear, although scavenging or generating of free radicals may play an important role. The results obtained may be of importance in planning the rational use of cis-DDP and 6-BrAA administration in the potential treatment of cancer.

In vitro inhibition of superoxide anion production and superoxide dismutase activity by zinc in human spermatozoa

The in vitro effect of zinc on superoxide anion (O2-) generation and on SOD-like activity in spermatozoa of infertile men was investigated. The formation of superoxide anion was stimulated by NADPH and the level of superoxide anion was measured by the reduction of ferricytochrome c. Both Percoll-isolated (n = 14) and washed spermatozoa (n = 14) exposed to 1 mmol/L zinc (60 min, 37 degrees C), released less (p < 0.002 and p < 0.04, respectively) superoxide anions than did zinc-untreated spermatozoa. These results implicate a possible role for zinc as a scavenger of excessive superoxide anions produced by defective spermatozoa in semen after ejaculation. Additionally, zinc was found to dose-dependently inhibit superoxide dismutase (SOD)-like activity of spermatozoa in vitro. The inhibition of SOD-like activity by an equal concentration of zinc (1 mmol/L) was less pronounced in oligospermic (p < 0.002; n = 16) and asthenozoospermic (p < 0.0005; n = 20) than in normozoospermic samples (p < 0.0001; n = 20). This differential ability of zinc to inhibit SOD-like activity may be relevant to the physiological function of spermatozoa in fertilization. The evidence that zinc may elicit an inhibition of both superoxide anion production and SOD-like activity in human spermatozoa, indicate the existence of novel, zinc-related mechanism(s) involved in the oxidative events occurring after ejaculation, with a possible modulatory effect on germ cell function.

Paraoxonase and arylesterase activities in the serum of two hyperlipoproteinaemic patients after repeated extracorporal lipid precipitation

The effect of heparin-induced extracorporal lipid precipitation (HELP) on the activities of paraoxonase (EC 3.1.8.1) and arylesterase (EC 3.1.1.2) was studied in serum of a patient with hyperlipoproteinaemia (A) and of a patient with non-insulin dependent diabetes mellitus and hyperlipoproteinaemia (B). The enzyme activities were measured spectrophotometrically (Tris-HCl buffer, pH 7.4, 37 degrees C) with paraoxon and phenylacetate as substrates of paraoxonase and arylesterase, respectively. Both patients underwent HELP applications once a week over a period of 7 weeks. Over that period no overall change was observed either in enzyme activities or in the lipid and protein content of the sera. However, each HELP session caused an immediate decrease of EDTA-insensitive arylesterase activity (on average 56% in A and 42% in B), while EDTA-sensitive arylesterase remained almost unaltered. Paraoxonase remained unchanged in A, but decreased in B (approximately 60%). Of the atherogenic lipoprotein parameters, the most pronounced decrease was found in VLDL-cholesterol and in triglycerides (on average 45% in A and 32% in B), while the anti-atherogenic HDL-cholesterol decreased < 10%. Possible implications of the effect of HELP on the enzyme activities studied remain to be explained.

In vitro effect of zinc on oxidative changes in human semen

The in vitro effect of zinc on superoxide anion (O2-) generation and on experimentally induced lipid peroxidation (LPO) in spermatozoa of infertile men was investigated. Washed spermatozoa pre-incubated for 30 min at 37 degrees C in the presence of 1 or 3 mmol l-1 zinc, released less superoxide anions (P < 0.03 and P < 0.02, respectively; n = 9) than the untreated spermatozoa. Similar results were obtained using activated polymorphonuclear leukocytes (1 x 10(6) cells ml-1) in the presence of 1 or 3 mmol l-1 Zn (P < 0.001 and P < 0.0002, respectively; n = 9). The in vitro evidence of the inhibitory effect of zinc on O2- generation by human spermatozoa and leukocytes indicates that zinc may act in vivo as a scavenger of excessive O2- production by defective spermatozoa and/or leukocytes in semen after ejaculation. A significant stimulatory effect of Zn (3 mmol l-1) on iron-induced lipid peroxidation, measured by the formation of thiobarbituric acid reactive substances (TBARS), was detected in the spermatozoa of 16 normo- and 17 asthenozoospermic males (P < 0.0001 and P < 0.001, respectively). In 11 samples with sperm concentration 20.3 +/- 2.1 x 10(6) ml-1, exhibiting initial TBARS concentration two times higher than in normo- and asthenozoospermic samples (40.5 +/- 2.4 vs. 17.1 +/- 1.1 and 28.5 +/- 4.1 nmoles TBARS 10(-8) spermatozoa), no effect of zinc on the LPO rate was found. The observed inhibitory effect of zinc on superoxide anion regardless of the initial O2- level and stimulatory effect of zinc depending on the initial LPO rate in human spermatozoa suggests that this metal ion participates in the oxidative changes occurring after ejaculation and thus may modulate the properties of germ cells.

Superoxide dismutase activity in lymphocytes and polymorphonuclear cells of diabetic patients

Copper-zinc superoxide dismutase (Cu,Zn-superoxide dismutase) activity was evaluated in lymphocytes and polymorphonuclear cells of insulin-dependent (n = 33) and non-insulin-dependent (n = 34) diabetic patients. A commercial method for the measurement of superoxide dismutase activity was adapted for use on a discrete analyser and evaluated for interference by other antioxidants with superoxide anion-scavenging properties. In comparison to healthy control subjects (n = 32), a significantly lower Cu,Zn-superoxide dismutase activity was found in both lymphocytes and polymorphonuclear cells of insulin-dependent (2.08 +/- 0.58 vs. 1.70 +/- 0.46 U/mg protein, p < 0.05, and 1.06 +/- 0.46 vs. 0.64 +/- 0.40 U/mg protein, p < 0.001, respectively) and non-insulin-dependent diabetic patients (2.08 +/- 0.58 vs. 1.61 +/- 0.48 U/mg protein, p < 0.01, and 1.06 +/- 0.46 vs. 0.53 +/- 0.24 U/mg protein, p < 0.001, respectively). There was a week, but significant negative correlation between age and Cu,Zn-superoxide dismutase activity in lymphocytes and polymorphonuclear cells (r = -0.22 and r = -0.28, p < 0.05, respectively), whereas no influence of gender, diabetes duration and glycaemic control was observed. The results indicate that diabetes mellitus could elicit a significant disturbance in superoxide anion-scavenging potential of lymphocytes and polymorphonuclear cells.

Evaluation of ascorbate and urate antioxidant capacity in human semen

The ascorbate/urate ratio in the seminal plasma was studied in 76 randomly chosen infertile men. The levels of ascorbate and urate were found to vary widely (range: 93-954 mumol l-1 and 127-670 mumol l-1, respectively), while the ascorbate/urate ratio was 1.03 +/- 0.63 (mean +/- SD), indicating almost equimolar concentrations of both compounds in more than 60% of the subjects investigated. No relationship of ascorbate with any biochemical marker of accessory sex gland secretions was observed, whereas an inverse correlation of urate with some prostatic markers, acid phosphatase (-0.37; P < 0.001), zinc (-0.35; P < 0.002) and citric acid (-0.33; P < 0.003), was found. In vitro experiments were conducted on an artificial suspension containing ascorbate and urate at physiological levels and activated polymorphonuclear leukocytes in the normal range (as proposed by WHO) to determine the extent to which the presence of superoxide anion-generating leukocytes contribute to the depletion of ascorbate and urate. The ascorbate level did not change in the presence of 0.2 x 10(6) leukocytes ml-1, while higher amounts of activated polymorphonuclear leukocytes initiated ascorbate oxidation, the intensity of which was in correlation with the extent of leukocyte contamination. After incubation (37 degrees C, 30 min) in the presence of 0.4, 1.0 and 1.5 x 10(6) cells ml-1, the average decline from the initial ascorbic acid level was 24, 43 and 49%, respectively. However, exposure of whole semen, instead of buffer, to oxidants released from the same amount of activated polymorphonuclears led to only 2.6, 11 and 22% decrease of the ascorbic acid, most probably due to the action of other superoxide anion scavenger compounds present in semen. Excessive superoxide anion production due to the presence of activated leukocytes had no influence on urate level either in the artificial suspension or in semen. The ability of ascorbate to afford protection against leukocyte-associated superoxide anions is not hampered in the semen of infertile men, provided that leukocyte contamination does not exceed 1 x 10(6) cells ml-1. The possible role of urate in stabilizing the ascorbate antioxidant activity in seminal plasma should be further investigated.

Relationship of sperm superoxide dismutase-like activity with other sperm-specific enzymes and experimentally induced lipid peroxidation in infertile men

Superoxide dismutase-like activity (SOD-like), isoenzyme lactate dehydrogenase-C4 (LDH-C4) and NADH-diaphorase activities in spermatozoa have been investigated from 58 normozoospermic and 27 oligozoospermic men. Significantly higher SOD-like, LDH-C4 and diaphorase activities (P < 0.01, P < 0.005 and P < 0.0001, respectively) were detected in spermatozoa from oligozoospermic men, compared to the activities found in normozoospermic samples. SOD-like activity (mean +/- SE) in oligozoospermic samples amounted to 8.3 +/- 1.6 U 10(-8) spermatozoa, while in spermatozoa in normozoospermic men with a sperm concentration above 20 million of spermatozoa per ml amounted to 4.2 +/- 0.5 U 10(-8). There was a close correlation between the SOD-like activity and biochemical indicators of the presence of residual cytoplasm i.e. isoenzyme LDH-C4 and NADH-diaphorase (r = 0.53 and r = 0.66 in normozoospermic and r = 0.63 and r = 0.54 in oligozoospermic men, respectively). A positive relationship between SOD-like activity and experimentally-induced lipid peroxidation was detected in 54 infertile men (r = 0.30; P < 0.05). These findings suggest that a higher level of superoxide dismutase-like activity may reflect a defect in the development or maturation of spermatozoa and, thereby, a decreased fertility potential. Hence, determination of SOD-like activity may give information on the state of maturity of human spermatozoa, while its role in the antioxidative protection remains to be determined.

Superoxide anion scavenging capacity of human seminal plasma

This study has investigated the antioxidant capacity of human seminal plasma due to the presence of both high and low molecular weight antioxidant factors. Methods for the measurement of superoxide dismutase-like activity (SOD-like) and total antioxidant status (TAS) were automated, and had a within-run coefficient of variation of 7.3% for SOD-like activity and 4.8% for TAS. In 69 semen samples from unselected infertile men, SOD-like activity in seminal plasma ranged from 2 to 16 U/ml, with a mean of 6.9 +/- 2.8 U/ml. As SOD-like activity was correlated positively with levels of citric acid (p < 0.0001), zinc (p < 0.0002) and acid phosphatase activity (p < 0.0005), and there was no correlation with fructose levels, our results suggest that prostatic secretions are an important source of superoxide anion scavengers. Evaluation of SOD-like activity in infertile men with accessory sex gland infections (n = 12) showed significantly lower activity (p < 0.003) compared to values found in 12 infertile men without signs of infection. The values obtained for total antioxidant status (equivalent to the antioxidant capacity of alpha-tocopherol analogue) ranged from 1.7 to 2.3 mmol/L, with a mean of 2.1 +/- 0.1 (n = 40), reflecting the protective activity of ascorbate, urate and albumin, and to a very low extent of glutathione and taurine. The data obtained by TAS assay correlated with fructose, a major marker of vesicular secretion (p < 0.005), suggesting that low molecular weight components with antioxidant capacity derive partly from the seminal vesicles. The results indicate that the relative contribution of antioxidant defence systems capable of counteracting the deleterious action of superoxide anions, depends on the secretory activity of accessory sex glands and is independent of excessive ROS production due to increased oxidative stress.

Superoxide anion production and some sperm-specific enzyme activities in infertile men

The relationship between superoxide anion production and the activities of sperm specific NADH-diaphorase and isozyme LDH-C4 has been investigated in 25 normozoospermic and 17 oligozoospermic semen samples. The samples were separated into high and low density sperm populations on discontinuous, two step (40%:80%) Percoll gradients prior to analysis. Superoxide anion generation was significantly higher (P < 0.001) and diaphorase activity significantly increased (P < 0.01) in both low and high density sperm fractions from oligozoospermic patients compared to the values found in normozoospermic men. A significant positive correlation (P < 0.01) between diaphorase activity and superoxide anion production was established in the oligozoospermic samples of low density sperm fraction. A tendency of statistically insignificant increase in LDH-C4 isozyme activity was observed in the oligozoospermic samples. The activity of this isozyme appears to have no association with superoxide anion generation or diaphorase activity. These findings seem to suggest that excessive superoxide anion production along with increased diaphorase activity point to biochemical abnormalities which may affect the functional status of sperms. Hence, determination of these parameters may provide useful data in male infertility of unknown etiology.

Effect of pentoxifylline on experimentally induced lipid peroxidation in human spermatozoa

We demonstrated previously that pentoxifylline in millimolar concentrations can inhibit superoxide anion production by human spermatozoa. In the present study we have examined the effects of the same concentrations of pentoxifylline on experimentally induced lipid peroxidation, as measured by malondialdehyde formation in the thiobarbituric (TBA) assay. Under the experimental conditions used, preincubation of spermatozoa with pentoxifylline led to a significant dose-dependent stimulation (p < 0.005) of malondialdehyde production amounting to 10.77 +/- 2.35%, 13.45 +/- 2.99% and 17.4 +/- 1.99% (mean +/- SEM) for 1.9, 3.7 and 11.2 mmol/l pentoxifylline, respectively. In the presence of 11.2 mmol/l pentoxifylline, an increase in iron-catalysed lipid peroxidation potential was detected in samples of spermatozoa from 29 infertile men, regardless of their initial levels of malondialdehyde. The results of this study indicate that pentoxifylline might further augment the ferrous ion-stimulated decomposition of pre-accumulation lipid hydroperoxides in the sperm plasma membrane and thus promote malondialdehyde generation in the TBA assay. It is concluded that the stimulatory effect of pentoxifylline on iron-induced lipid peroxidation may have an adverse effect on the quality of sperm suspensions prepared for in vitro fertilization, a possibility which should be investigated further.

Side-effects of peptidoglycan monomer (PGM) treatment in mice

The influence of single (4 mg/mouse) and multiple (1 mg/mouse per day for 5 consecutive days) injections of PGM on some hepatic enzymes, lipid peroxide generation in serum and liver, sialic acid concentration in serum and spleen and hepatic lysosomal membrane permeability was investigated. The studies performed showed that a single injection of PGM in vivo changed temporarily the permeability of lysosomal membranes, lipid peroxidation products and sialic acid concentration, and when administered in vitro modulated superoxide anion production and did not affect the activity of lysosomal membrane enzymes. Multiple injections of PGM did not cause significant changes in the examined parameters. Although the metabolic changes were time-limited and from the toxicological point of view, provoked transient effects, the results obtained may be of importance when using PGM in combined chemo-immunotherapy.

Effect of sialic acid on glycation-induced fluorescence of albumin

The aims of this study were to determine whether in vitro nonenzymatic glycation of proteins by sialic acid (sialylation) induces the generation of fluorescence, and whether the presence of this keto sugar may affect the generation of fluorescence induced by other sugars. Incubation of bovine serum albumin (BSA; 1.5 mM) with sugars (50 mM in 0.2 M phosphate buffer, pH 7.4, at 37 degrees C) resulted in a time-dependent increase of formaldehyde release (moles/moles of protein). On the 17th day of incubation, the value was 0.53 +/- 0.06, 0.78 +/- 0.15 and 1.23 +/- 0.18 for sialic acid, fructose and glucose respectively, compared with 0.37 +/- 0.05 for BSA. The fluorescence intensity (arbitrary units/mg protein) was higher after 17 days of incubation with fructose (16.9 +/- 1.8) than with glucose (12.7 +/- 1.3), while no significant increase was noted with sialic acid compared with BSA (3.8 +/- 0.4). Fluorescence intensity increase by incubation with glucose (50 mM) was significantly reduced by sialic acid (20 mM) after both 10 (P < 0.001) and 14 (P < 0.001) days of incubation, while inhibition was weaker after 14 (P < 0.05) than after 10 (P < 0.001) days when fructose (50 mM) was used as the glycating agent. This indicates that sialic acid can be potentially used to limit the damage from adverse glycation-induced processes.

The effect of Met-enkephalin on mice liver lysosomes

The unsedimentable activities of acid phosphatase (AP) and beta-glucosidase (BG), from mice liver lysosomes significantly increased 6 h after a single i/p injection of Met-enkephalin (MENK). The activity of AP in the serum at the same time remained unchanged. Multiple injections of MENK (8 x 10 mg/kg) induced a significant decrease in AP activity in the serum and no change in the unsedimentable activities of AP or BG. MENK did not elicit any significant extracellular release of lactate dehydrogenase (LDH) either, indicating that, under the experimental conditions described, the cells remained intact. Other parameters, such as the activities of AP and BG in the liver and total sialic acid content in the serum and spleen remained unaltered. Moreover, MENK in concentrations of 10(-12) M, 10(-8) M, 10(-6) M or 10(-4) M did not change the activities of the lysosomal enzyme markers AP or BG in vitro. These data indicate far less pronounced transient effects of MENK on lysosomal membranes and enzymes compared to Leu-enkephalin which may be relevant for the use of MENK in combined chemo-immunotherapy.

Effect of leucocytes on the hypoosmotic swelling test of human sperm

The hypoosmotic swelling test was used to evaluate the size of physiologically competent sperm after their exposure to the influence of leucocyte-derived superoxide anions. In sperm suspensions, preincubated in the presence of 50 x 10(4)mL-1 leucocytes capable of producing 0.93 +/- 0.63 nmol of O2- (range 0.21-2.03 nmol) over 30 min at 37 degrees C, a significant decrease in the percentage of swollen sperm compared to that in the control sperm suspensions without added leucocytes was found (p < .001, n = 46). Addition of phorbol myristate acetate, an activator of the release of O2-, further diminished the ability of hypoosmotic sperm tail swelling (p < .001), while superoxide dismutase inhibited this effect. This study suggests that even very low amounts of superoxide anions may influence the functional integrity of sperm. Therefore, any source of superoxide anion production should be eliminated and/or inhibited in sperm suspensions used in assisted reproduction techniques.

Concentration of sialic acid in alloxan diabetic rat islets of Langerhans

A microanalytical procedure for the determination of total and surface sialic acid concentrations was employed to establish their changes in relation to the length of alloxan diabetes in rat islets of Langerhans. 14 and 60 days after alloxan administration (65 mg/kg), the number of Langerhans islets was significantly decreased (p < 0.001) compared to the control. According to their size, the distribution of islets displayed no significant difference in diabetic and control animals 14 days after alloxan administration, while after 60 days no large islets (dia > or = 128 microns) were found in diabetic animals. The surface sialic acid was significantly increased in the small islets (p < 0.001), whereas no change was found in the large islets 14 days after alloxan administration. After 60 days, the surface sialic acid of both small and large islets was significantly decreased (p < 0.001). These results demonstrate that chronic beta-cell destruction induces a decrease in the sialic acid content in the pancreatic islet cells, suggesting that sialic acid might play a role in insulin secretory regulation regarding chronic effects of alloxan beta-cytotoxicity.

NADH-dependent oxidoreductase (diaphorase) activity and isozyme pattern of sperm in infertile men

Diaphorase activities were measured in spermatozoa from 104 infertile men. The relationships between enzyme activity, sperm characteristics (density, motility, viability), and distribution of electrophoretic patterns were examined. There was a highly significant difference (p less than .001) between the sperm diaphorase activities in specimens with sperm concentration above 40 million per milliliter (0.685 +/- 0.5 mIU/10(6) sperm; n = 57) when compared with the diaphorase values of the oligospermic specimens with sperm density below 40 million per milliliter (1.53 +/- 1.5 mIU/10(6) sperm; n = 47). However, there was no evidence to support any relationship between sperm diaphorase activities, sperm motility, viability, and the distribution of three diaphorase electrophoretic patterns. This indicates that these parameters do not account for the differences between the diaphorase activity of spermatozoa of infertile men with sperm concentrations below and those above 40 million per milliliter.

Pentoxifylline-mediated reduction of superoxide anion production by human spermatozoa

The release of superoxide anions from sperm suspensions prepared for in vitro fertilization was measured by superoxide dismutase-inhibitable reduction of ferricytochrome C in response to phorbol myristate acetate. The superoxide anion production was found to be within the range of 0.21-3.76 nmoles O2- per 10(6) spermatozoa. Spermatozoa pre-incubated in the presence of 3.7 or 10 mM of pentoxifylline for 30 min at 37 degrees C released less (P less than 0.001) superoxide anions than did the untreated-control spermatozoa. It has been concluded that the inhibitory effect of pentoxifylline on superoxide anion production may be a factor contributing to the improvement of sperm preparation before insemination, and may, thereby, increase the fertility potential.

Effect of pentoxifylline on superoxide anion production by human sperm

The in-vitro effect of pentoxifylline, a methylxanthine derivative, on superoxide anion generation by sperm was studied in 27 men with superoxide anion production ranging from 0.57 to 13.8 nmoles 02-. per 10(6) sperm. Superoxide anion release stimulated by phorbol myristate acetate, a potent activator of oxygen radical generation, was reduced by 29-72% following the addition of 10 mM pentoxifylline. The inhibitory effect of this millimolar concentration of the drug did not depend on the initial superoxide production in the presence of phorbol myristate acetate. These results point to a potential use for pentoxifylline in the treatment of male infertility in men with an increased superoxide anion generation capacity.

Total and ganglioside-bound sialic acid content of lymphocytes from non-insulin-dependent diabetic patients

The total and ganglioside-bound sialic acid content of unfractionated blood lymphocytes obtained from normal-weight healthy subjects (n = 17) and non-insulin-dependent diabetic patients on oral hypoglycemic drugs arbitrarily divided into normal-weight (n = 11), moderately overweight (n = 14) and severely overweight (n = 17) subgroups were examined. In normal-weight diabetics the level of lipid-bound sialic acid (gangliosides) of lymphocytes was found to be reduced (p less than 0.01). A more pronounced decrease (p less than 0.001) was observed for the lymphocyte total sialic acid of normal-weight and moderately overweight diabetics as compared to healthy subjects. In severely overweight non-insulin-dependent diabetics the decrease of total sialic acid was less pronounced compared to that found in healthy subjects. Whether this finding was due to obesity in these patients remains to be clarified.

Leu-enkephalin induced alteration of enzymes and sialic acid levels in vivo

The influence in mice of 10 mg/kg Leu-enkephalin (LENK) on the activity of hepatic enzymes in serum and liver and sialic acid concentration in serum and spleen is described. The activity of acid and alkaline phosphatase and lactate dehydrogenase in serum was significantly enhanced 6 h after a single (10 mg/kg) LENK injection. This effect was not dose-dependent. The increase of acid phosphatase in serum was accompanied by a simultaneous decrease in the liver. While the level of serum sialic acid remained unchanged, it decreased in the spleen 6 h after a single LENK injection. The effect of LENK in the spleen and liver was dose-dependent; ie, the higher the dose the greater the effect. Multiple injections of Leu-enkephalin (6 x 10 mg/kg) induced the same degree of increase but an earlier rise in serum alkaline, acid phosphatase and lactate dehydrogenase levels than with a single injection. This was not accompanied by a change of activity in liver and spleen. These data may be relevant for use of LENK in combined chemo-immunotherapy, since liver enzyme changes may alter drug metabolism, and since sialic acid plays a regulatory role in immune processes.

Simple, rapid determination of zinc and acid phosphatase in seminal plasma with an ABA-100 bichromatic analyzer

I describe an automated assay for zinc and acid phosphatase in seminal plasma. These, which are markers of the function of the prostate, were assayed bichromatically with an Abbott ABA-100 analyzer. As many as 25 samples of human seminal plasma can be analyzed sequentially with CVs of 3.1% for zinc and 1.5% for acid phosphatase. The sensitivity, specificity, and speed of this assay system make it practicable for use in investigation of male infertility.

Simple, rapid determination of zinc and acid phosphatase in seminal plasma with an ABA-100 bichromatic analyzer

I describe an automated assay for zinc and acid phosphatase in seminal plasma. These, which are markers of the function of the prostate, were assayed bichromatically with an Abbott ABA-100 analyzer. As many as 25 samples of human seminal plasma can be analyzed sequentially with CVs of 3.1% for zinc and 1.5% for acid phosphatase. The sensitivity, specificity, and speed of this assay system make it practicable for use in investigation of male infertility.

A study of additional forms of the human sperm lactate dehydrogenase isoenzyme

Unusual isoenzymes of the sperm-specific lactate dehydrogenase detected in the seminal plasma of some infertile men were investigated using selective precipitation by antisera followed by electrophoretic resolution. The presence of two C subunit types was established: type I is a polymer of the four common C-subunits and type II consists of four C-subunits. Subunits of types I and II combine to form 5 sperm-specific binomially distributed lactate dehydrogenase isoenzymes. These results suggest the existence of two alleles at the c locus.

Seminal plasma LDH-X in testosterone rebound therapy

The changes in seminal plasma LDH-X isoenzyme were investigated in 27 oligozoospermic patients treated with large doses of testosterone. The increase in this isoenzyme, proven to occur prior to the sperm count elevation, might possibly serve as a predictor enabling the choice of an optimal term for affecting conception. A high percentage of responders has been found in patients with severe oligozoospermia (less than 0.1 x 10(6) spermatozoa/ml), but with a high initial relative percentage of seminal plasma LDH-X. The determination of this parameter could be one of the criteria for the selection of patients who will probably respond to the therapy.

Semen LDH-X deficiency and male infertility

Sperm-specific isozyme LDH-X (LDH-C4) in the semen of some infertile men with a normal sperm concentration was absent. This finding suggests a need for semen LDH-X isozyme determination in the evaluation of some causes of male infertility.

A simple automated method for determination of citric acid levels in semen

An automated enzymatic method for determination of seminal citric acid by using an Abbott ABA-100 bichromic analyzer is presented. The technique recommended in this communication is a rapid and simple micromethod which does not require semen deproteinization and which has been optimized to provide satisfactory precision and accuracy.

Seminal plasma isoenzyme LDH X in infertile men

The seminal plasma isoenzyme LDH X and hormonal profile were determined on 55 samples from patients with eigher azoo- or oligozoospermia. The correlation found between the value fo LDH X and the gonadotropins can be used as an indicator of germ cell differentiation. Surprisingly high values of LDH X which were found in patients with severe oligozoospermia could indicate that the patients have normal spermatogenesis and possibly may respond to hormonal therapy.