Serial analysis of chromosomal aberrations and proliferation kinetics of mouse spermatogonia after single or fractionated X-ray exposures

Dose-fractionation studies on translocation induction in stem-cell spermatogonia of mice, as measured by spermatocyte analysis many cell generations after irradiation, revealed that a small conditioning dose of X-rays sensitizes the stem cells to the induction of translocations by a second dose 24 h later (Van Buul and Léonard, 1974, 1980). To find out whether such sensitization effects also occur at other spermatogonial stages, a comparison was made of the effects of single (50, 100 and 150 rad) and fractionated (100 + 50 rad, with 24 h in between) doses of X-rays on the induction of chromosomal aberrations in spermatogonia by analysing spermatogonial metaphases shortly after irradiation at multiple sampling times (0–48 h; every 4 h). In addition, the kinetics of spermatogonial proliferation was studied by using, in vivo, a BrdU chromosome-labelling procedure. The recorded frequencies of chromosomal aberrations did not indicate any sensitization effect of dose fractionation. It is concluded that the sensitization effects, as observed for chromosomal aberrations in male premeiotic germ cells, are characteristic for the stem-cell spermatogonia and do not occur in the more differentiated spermatogonia.     

Translocation yield from mouse spermatogonial stem cells following unequal-sized x-ray fractionations: evidence of radiation-induced loss of heterogeneity.

Previous work has shown that a high yield of genetic damage can be recovered from stem spermatogonia exposed to a high (900 R) X-ray dose, despite extensive cell killing, when this follows 24 h after a smaller (100 R) radiation exposure. This differs from the response of the normal stem-cell population and has been interpreted to mean that the more radio-resistant cells surviving the first exposure become sensitive both to radiation-induced killing and genetic damage after this time interval and, as a consequence, lose the heterogeneity in radio-sensitivity that typifies a normal stem-cell population. Similar results have now been obtained with doses of 600 and 800 R given in fractions of 100 + 500 R and 100 + 700 R 24 h apart. Yields of translocations among spermatocytes were higher than obtained with the single doses and responses consistent with the fractions acting additively were obtained when the fractions were given in reverse order. Further analyses of the data provided support for the concept that 24 h after a radiation exposure there is a loss of heterogeneity in radio-sensitivity in the surviving stem-cell population.     

Chromosome aberration induction in murine spermatocytes in joint exposure to radiation and sodium nitrite and nitrate]

In studying the combined effect of single and fractionated exposure to gamma/neutron radiation (12.5-50 cGy) and sodium nitrite (100 mg/kg) and chronic irradiation with a mixture of radiation (25 cGy) and sodium nitrite, nitrate (10-100 mg/l) the synergistic effect was observed in inducing reciprocal translocations in mouse spermatocytes. The dose-response function of the reciprocal translocations occurrence in Af mouse spermatocytes was nonlinear; there was a "plateau" within the dose range from 25 to 50 cGy.     

Recycling spent larval food of Corcyra cephalonica stainton as a broiler feed ingredient

In commercial insectaries, large-scale production of rice moth, Corcyra cephalonica Stainton in pearl millet grain medium leads to an extensive accumulation of spent C. cephalonica larval medium (CLM). Experiments were conducted to determine whether inclusion of CLM for corn in the standard broiler diet (SBD) could ensure normal growth and development of broilers. Chemical analysis revealed that CLM diets met the nutritional requirements as of SBD. CLM diet contained no aflatoxin as well. Biological experiments were conducted to study the suitability of CLM diet in different combinations with SBD at 100% + 0%, 75% + 25%, 50% + 50%, 25% + 75% and 0% + 100% w/w without any nutritional change, and after nutritional modification with corn starch. CLM replacement was based on the corn content of the basal diet. Birds preferred SBD 100% and SBD 75% + CLM 25% nutritionally unchanged diets, and showed higher growth rate and weight gain. These parameters were significantly lower in other diet combinations. Modified isoenergetic CLM based diets in all the combinations, however, contributed higher feed intake and resulted in more weight gain as of SBD. Furthermore, none of treatments in both experiments yielded bird mortalities. The experimental CLM diets except SBD 75% + CLM 25% in both experiments were cost effective and contributed lower diet cost/kg weight gain.     

Composted grape marc as growing medium for hypostases (Hypostases phyllostagya)

The use of composted grape marc (CGM) as a plant growth medium was investigated with Hypostases (Hypostases phyllostagya). Seven media were prepared using CGM mixed, in different ratios, with native peat and perlite. The following mixtures were used: 100% CGM, 75% CGM + 25% peat, 50% CGM + 50% perlite, 25% CGM + 75% peat, 50% CGM + 25%) peat + 25% perlite, 25%, CGM + 50%, peat + 25% perlite and 100% peat. The experiment was arranged in a randomized plot design with four replicates under greenhouse conditions. After a growing period of three months, some horticultural parameters were measured. Besides, some physical and chemical properties of the growing medium were determined. The mixtures of 50% CGM + 50% peat, 25% CGM + 75% peat and 100% peat were found to be most suitable based on the horticultural parameters. This was confirmed through the physical characteristics. Up to 50% composted grape marc can be used in mixtures with peat on account of its low cost and high nutrient content.     

Effects of Dose on the Induction of Dominant-Lethal Mutations and Heritable Translocations with Ethyl Methanesulfonate in Male Mice

Genetic damage by ethyl methanesulfonate (EMS) in male mice was measured at doses ranging from 50 to 300 mg/kg with dominant-lethal mutations and reciprocal translocations as endpoints. No appreciable increase in dominant-lethal mutations was detected following a dose of 100 mg/kg. Dominant lethals induced by EMS were convincingly detected only after a dose of 150 mg/kg, but in the translocation experiment an increase in the genetic effect was detectable at the 50 mg/kg dose. It is likely that dominant lethals had also been induced at the 50 and 100 mg/kg doses, but were not detected due to the relative insensitivity of the dominant..lethal procedure. Thus, for detection of low levels of EMS-induced chromosome breakage, translocations are a much more reliable endpoint than are dominant-lethal mutations. A procedure for large-scale screening of induced translocations is described.—The dominant-lethal dose-response curve, plotted on the basis of living embryos as a percentage of the control value, is clearly not linear as it is markedly concave downward. Similarly, the translocation dose-response curve showed a more rapid increase in the number of translocations with dose than would be expected on the basis of dose-square kinetics. It is clear for both of these endpoints that the effectiveness of EMS in inducing chromosome breakage is proportionately much lower at low doses.     

Blood concentrations of vasopressin, neuropeptide FF and prolactin are increased by high-dose right unilateral ECT.

Electroconvulsive therapy (ECT) is known to stimulate subcortical brain regions and release hormones from the anterior and the posterior pituitary. To enhance the subcortical effect of ECT and the neuroendocrinological response we used high dose right unilateral ECT (RUL-ECT) in 11 depressive patients and studied its effect on the release of vasopressin, prolactin and neuropeptide FF. The RUL ECT stimulus for all studied patients was 5 times the individual seizure threshold and it led to immediate release of vasopressin in all studied patients. The release of prolactin was less uniform however in accordance with results from earlier studies. The ECT also stimulated a NPFF secretion peak that came approximately 5 min after ECT stimulus and preceded the prolactin peak. The maximal elevations in circulating vasopressin and prolactin concentrations were 680% and 950%, respectively. The neuropeptide FF concentration increased by 100% after ECT. There was a second rise in NPFF concentration at 25 min after the ECT treatment. The increases in all peptide concentrations were significant, but were not correlated with each other. The neuropeptide FF concentration returned to baseline level at 10 min and the vasopressin concentration at 25 min after ECT. The prolactin concentration remained increased during the 30 min follow up period. Our results complete earlier finding on ECT stimulated vasopressin and prolactin release and show that high intensity RUL-ECT releases neuropeptide FF into human blood. The modest rise of circulating NFFF most likely represents leakage from the CNS.     

The influence of exercise duration at VO2 max on the off-transient pulmonary oxygen uptake phase during high intensity running activity

The purpose of this study was to examine the influence of time run at maximal oxygen uptake (VO2 max) on the off-transient pulmonary oxygen uptake phase after supra-lactate threshold runs. We hypothesised: 1) that among the velocities eliciting VO2 max there is a velocity threshold from which there is a slow component in the VO2-off transient, and 2) that at this velocity the longer the duration of this time at VO2 max (associated with an accumulated oxygen kinetics since VO2 can not overlap VO2 max), the longer is the off-transient phase of oxygen uptake kinetics. Nine long-distance runners performed five maximal tests on a synthetic track (400 m) while breathing through the COSMED K4b2 portable, telemetric metabolic analyser: i) an incremental test which determined VO2 max, the minimal velocity associated with VO2 max (vVO2 max) and the velocity at the lactate threshold (vLT), ii) and in a random order, four supra-lactate threshold runs performed until exhaustion at vLT + 25, 50, 75 and 100% of the difference between vLT and vVO2 max (vdelta25, vdelta50, vdelta75, vdelta100). At vdelta25, vdelta50 (= 91.0 +/- 0.9% vVO2 max) and vdelta75, an asymmetry was found between the VO2 on (double exponential) and off-transient (mono exponential) phases. Only at vdelta75 there was at positive relationship between the time run at VO2 max (%tlimtot) and the VO2 recovery time constant (Z = 1.8, P = 0.05). In conclusion, this study showed that among the velocities eliciting VO2 max, vdelta75 is the velocity at which the longer the duration of the time at VO2 max, the longer is the off-transient phase of oxygen uptake kinetics. It may be possible that at vdelta50 there is not an accumulated oxygen deficit during the plateau of VO2 at VO2 max and that the duration of the time at VO2 max during the exhaustive runs at vdelta100, could be too short to induce an accumulating oxygen deficit affecting the oxygen recovery.     

The anaerobic degradability of thermoplastic starch: polyvinyl alcohol blends: potential biodegradable food packaging materials

A systematic study on the anaerobic degradability of a series of starch:polyvinyl alcohol (TPS:PVOH) blends was performed to determine their fate upon disposal in either anaerobic digesters or bioreactor landfills. The aims of the study were to measure the rate and extent of solubilisation of the plastics. The extent of substrate solubilisation on a COD basis reached 60% for a 90:10 (w/w) blend of TPS:PVOH, 40% for 75:25, 30% for 50:50 and 15% for PVOH only. The rate of substrate solubilisation was most rapid for the 90:10 blend (0.041 h(-1)) and decreased with the amount of starch in the blend in the following order 0.034 h(-1)(75:25); 0.023 h(-1)(50:50). The total solids that remained after 900 h were 10 wt.% (90:10); 23 wt.% (75:25); 55 wt.% (50:50); 90 wt.% (0:100). Starch containing substrates produced a higher concentration of volatile fatty acids (VFAs) and biogas, compared to the 0:100 substrate. The major outcome was that PVOH inhibited the degradation of the starch from the blend.     

Translocations in mouse spermatogonia after exposure to unequally fractionated doses of x-rays

The influence of various X-ray fractionation regimes on translocation induction in mouse spermatogonia was studied. Splitting a single exposure of 600 R into two fractions of 300 R separated by 24 h did not influence the translocation yield (7.58% vs. 8.35%). When the dose was given in the unequal fractions,100 R+500 R and 500 R+100 R, with the same 24 h between the fractions, the translocation frequency was significantly altered (10,19 and 4.94%, respectively). As a possible explanation of these findings it is assumed that the relatively resistant cells surviving the first fraction of the dose are sensitized towards translocation induction when receiving the second fraction of the dose.     

Translocation yield from the mouse spermatogonial stem cell following fractionated X-ray treatments: influence of unequal fraction size and of increasing fractionation interval

(1) The genetic response of the mouse spermatogonial stem cell to a high dose of X-rays given in two unequal fractions 24 h apart can be dependent upon the order in which the two fractions are given. When 1000 R was administered as 100 R followed by 900 R the recovered translocation yield (22%) was similar to that which can be obtained by extrapolation from lower doses and also to that of a 500 + 500 R 24 h fractionation. By contrast, when the 900 R preceded the 100 R the response was much lower (7.4%), yet still greater than that produced by a single 1000 R treatment (4.5%). The same order of effectiveness was observed for length of sterile period. (2) The sub-additive translocation yields previously obtained with 800 R treatments given in fractions of 500 R and 300 R at intervals of 3-12 days were found to be maintained with intervals up to at least 15 days but additivity was regained by the end of the third week. Sterile period data indicated that with these intervals the germinal epithelium had recovered sufficiently from the first fraction for spermatogenesis to restart before the second fraction was given. (3) It is concluded from the two experiments that (a) 24 h after a radiation exposure the surviving stem cells are more sensitive than formerly both to killing and genetic damage, (b) at this time they are no longer heterogeneous in their radiosensitivities, so that increasing yields of genetic damage may be obtained with increasing dose i.e. there is no fall in yield at higher doses, (c) the change in sensitivity could be a consequence of a synchronization to a sensitive stage in a cell cycle, or to a transitional phase preparatory to entering a different cell cycle. (d) to achieve rapid repopulation of the germinal epithelium the surviving stem cells are stimulated to enter a shorter cell cycle and this is the cause of the sub-additive translocation yields with fractionation intervals of 3-15 days, (e) the recommencement of spermatogenesis is associated with the reestablishment of the heterogeneity in radiosensitivity among the stem cells. At this time additive translocation yields can again be recovered.     

Effects of membrane potential on mechanical activation in skeletal muscle

The effect of subthreshold depolarization on mechanical threshold was investigated in tetrodotoxin-poisoned mammalian and amphibian skeletal muscle fibers using a two-microelectrode voltage-clamp technique. Mechanical threshold was determined with a 2-ms test pulse. The immediate effect of depolarization was inhibition of the mechanical system. The consequent increase in the test pulse threshold was linearly related to the size of the depolarization and there was, on the average, a 10% increase in threshold for a 10-mV depolarization in mammalian fibers. The duration of the inhibitory period was also related to the size of the depolarization. Inhibition was interrupted by the onset of activation (seen as a reduction in the test pulse threshold), and in rat soleus fibers this occurred within 100 ms with a 20-mV depolarization, inhibition decayed within 10 ms. The decay of activation after brief conditioning pulses was initially rapid (on the average, the test pulse threshold recovered to 80% of its control value within 1 ms) and then slow (full recovery took 100-500 ms). After long conditioning pulses, activation often decayed into a period of inhibition. When depolarization (of 20 mV or more) was maintained for several seconds, the fibers became inactivated. Rat extensor digitorum longus and sternomastoid fibers were strongly inactivated by depolarization to -40 mV and the test pulse to +40 mV did not cause contraction.     

不同配比红蓝LED光对黄瓜果实产量和品质的影响

以荧光灯为对照,研究不同配比红蓝LED光处理﹝包括100%红光、75%红光-25%蓝光( R31)、50%红光-50%蓝光(R11)、25%红光-75%蓝光(R13)和100%蓝光﹞对黄瓜(Cucumis sativus Linn.)果实性状、产量及营养品质的影响。结果表明：100%红光处理组黄瓜植株生长缓慢,果实发育异常,果实单株产量及VC、可溶性糖和可溶性蛋白质的含量均低于其他处理组。100%蓝光处理组的果实发育正常,果实单株产量显著低于红蓝LED光组合处理组,而果实中可溶性糖、蔗糖、游离氨基酸和可溶性固形物的含量总体上显著高于其他处理组,可溶性蛋白质含量也较高。 R31处理组黄瓜果实的单果鲜质量显著高于其他处理组;R31和R11处理组的果实单株产量显著高于其他处理组,R11处理组的黄瓜果实中VC和可溶性蛋白质含量明显高于其他处理组。上述研究结果显示：黄瓜果实的单株产量和营养品质受红蓝光协同作用的影响,设施栽培黄瓜生产的较适宜光照比例为50%红光-50%蓝光。     

Effects of astragalus polysaccharide on apoptosis of myocardial microvascular endothelial cells in rats undergoing hypoxia/reoxygenation by mediation of the PI3K/Akt/eNOS signaling pathway

The study explores the effect of astragalus polysaccharide (APS) mediating P13K/Akt/eNOS signaling pathway on apoptosis of myocardial microvascular endothelial cells (MMECs) in hypoxia/reoxygenation (H/R). MMECs were classified into blank, H/R, H/R + 25 mg/L APS, H/R + 50 mg/L APS, H/R + 100 mg/L APS, H/R + LY, and HR + 100 mg/L APS + LY groups. Cell viability was detected using MTT assay and apoptotic cell morphological changes by Hoechst staining. NO content, cell cycle and apoptosis, PI3K/Akt/eNOS signaling pathway proteins were detected using nitrate reductase assay, flow cytometry and Western blotting. An increased cell survival rate, NO content and expression of PI3K/Akt/eNOS signaling pathway associated proteins, and a decreased apoptosis rate was observed in the H/R + 50 mg/L APS and H/R + 100 mg/L APS groups compared with the H/R and H/R + 25 mg/L APS groups. Compared with the H/R + 50 mg/L APS group, the apoptosis rate decreased, whereas the cell survival rate, NO content and expression of PI3K/Akt/eNOS signaling pathway associated proteins increased in the H/R + 100 mg/L APS group. The H/R + LY and HR + 100 mg/L APS + LY groups followed opposite trends. In comparison to the HR + 100 mg/L APS group, the apoptosis rate in the H/R + LY and HR + 100 mg/L APS + LY groups increased, and the cell survival rate, NO content and expression of PI3K/Akt/eNOS signaling pathway associated proteins decreased. Collectively, APS improves the damage caused by H/P by mediating PI3K/Akt/eNOS signaling pathway.     

Calcium administration increases calcium-binding protein regucalcin concentration in the liver of rats

The alteration of regucalcin concentrations in the liver and serum of rats administered orally calcium is investigated. Rats received a single oral administration of calcium chloride solution (25, 50 and 75 mg Ca/100 g body weight). The administration of calcium (50 mg/100 g) produced a significant increase in liver regucalcin concentration between 30 and 180 min after the administration, while serum regucalcin concentration was not altered appreciably. The effect of calcium administration increasing liver regucalcin concentration was also seen with the dose of 25 mg/100 g. When liver cytosol prepared from normal rats was incubated for 6 h in the presence of 10 M Ca²⁺, the cytosolic regucalcin concentration at 3 and 6 h of incubation was decreased about 20% (p<0.05) as compared with the value at zero time point, indicating that the presence of Ca²⁺ does not inhibit the decomposition of liver cytosolic regucalcin. Moreover, serum regucalcin concentration was not significantly altered by the incubation for 6 h at 37°C, indicating a stability of regucalcin in rat serum. This suggests that the calcium administration-induced in liver regucalcin concentration is not based on the inhibition of regucalcin release from liver to serum. The present study demonstrates that regucalcin in the liver is clearly increased by calcium administration, presumably due to stimulating the protein synthesis.     

Resetting of the carotid arterial baroreflex during dynamic exercise in humans.

Recent investigations have demonstrated that at the onset of low-to-moderate-intensity leg cycling exercise (L) the carotid baroreflex (CBR) was classically reset in direct relation to the intensity of exercise. On the basis of these data, we proposed that the CBR would also be classically reset at the onset of moderate- to maximal-intensity L exercise. Therefore, CBR stimulus-response relationships were compared in seven male volunteers by using the neck pressure-neck suction technique during dynamic exercise that ranged in intensity from 50 to 100% of maximal oxygen uptake (VO(2 max)). L exercise alone was performed at 50 and 75% VO(2 max), and L exercise combined with arm (A) exercise (L + A) was performed at 75 and 100% VO(2 max). O(2) consumption and heart rate (HR) increased in direct relation with the increases in exercise intensity. The threshold and saturation pressures of the carotid-cardiac reflex at 100% VO(2 max) were >75% VO(2 max), which were in turn >50% VO(2 max) (P < 0.05), without a change in the maximal reflex gain (G(max)). In addition, the HR response value at threshold and saturation at 75% VO(2 max) was >50% VO(2 max) (P < 0.05) and 100% VO(2 max) was >75% VO(2 max) (P < 0.07). Similar changes were observed for the carotid-vasomotor reflex. In addition, as exercise intensity increased, the operating point (the prestimulus blood pressure) of the CBR was significantly relocated further from the centering point (G(max)) of the stimulus-response curve and was at threshold during 100% VO(2 max). These findings identify the continuous classic rightward and upward resetting of the CBR, without a change in G(max), during increases in dynamic exercise intensity to maximal effort.     

Nutritional value of waxy barleys for broiler chickens

Winter wheat was compared with a barley which has a normal amylopectin/amylose starch ratio, and waxy barleys which have essentially 100% amylopectin starch. In one trial, broiler chicks were fed on one of seven diets which had grain portions of all wheat (100W), 50% wheat–50% Compana (normal) barley (50W–50C), 25% wheat–75% Compana (25W–75C), 100% Compana (0W–100C), 50% wheat–50% Wapana (waxy) barley (50W–50Wa), 25% wheat–75% Wapana (25W–75Wa), or 100% Wapana (0W–100Wa). Body weights (g) at 7 weeks were (100W) 1659, (50W–50C) 1523, (25W–75C) 1401, (0W–100C) 1396, (50W–50Wa) 1503, (25W–75Wa) 1403 and (0W–100Wa) 1293. Dressing percentage was not affected by diet but mortality was greater on 0W–100C. Metabolizable energy (kJ/g dry matter) values determined on non-laying Leghorn hens were 12.93 ± 0.38 and 12.76 ± 0.46 for the Compana and Wapana barley, respectively. In a second trial, addition of a food-grade diastase at 2 g per kg of feed did not affect body weight on wheat-based diets, increased weights over corresponding control diets for Wapana-based diets but gave inconsistent results for Washunopana, a hull-less waxy barley with an active α-amylase-like activity on the starch granules. Group feed values indicated that enzyme supplements improved feed efficiency for barley diets but metabolizable energy values were similar for diets with or without diastase additions.     

The mutagenic effect of different types of irradiation on the sex cells of male mice. VIII. Frequency of development of reciprocal translocations in the spermatogonia of mice subjected to chronic gamma-irradiation]

The frequency of reciprocal translocations in mice spermatogonia after the exposure to chronic gamma-irradiation at doses of 100, 200, 300, 600, 920 r, at the dose rate of 4,2 r/day was investigated. It was shown that the mutation frequency increased insignificantly with the increase of the radiation dose (y =0,8+0.0011x). The comparison of the data obtained with earlier results revealed no changes in the yield of translocations at the reduction of the dose rate from 10 r/day to 4,2 r/day. The investigation of the genetic radiosensitivity of mice spermatogonia after a chronic gamma-irradiation showed a tendency to increase in their radioresistance.     

Mutagenic effect of different types of irradiation on the sex cells of male mice. IX. Duration of preservation of radiation-induced reciprocal translocations during the course of the reproductive period]

The rate of induction of reciprocal translocations by gamma-irradiation of mouse spermatogonia was studied by cytological examination of descendent spermatocytes. The CBA mice were given a total single acute dose of 300 r or 3 times per 300 r with 7 and 28 days intervals. The irradiated mice were killed within 3,7 and 12 month after the irradiation. The frequency of translocations in 3 and 7 month after the treatment was the same. A 25% decrease in the yield of reciprocal translocations was observed in 12 months after the irradiation. It suggests that the genetic risk from ionizing radiation remains high a year after the irradiation.     

Control of diapause in codling moth larvae

Diapause in a New Zealand strain of codling moth (Cydia pomonella Linnaeus [Lepidoptera: Olethreutidae]) was induced in larvae by photoperiods of 15 h or less. Once diapause had been initiated, it could not be terminated by any combination of conditions tested for at least 20 days after cocooning. In diapausing larvae a low rate of pupation occurred at 25 °C under a long day (18 h) photoperiod. A high rate of pupation was achieved under a long day regime when larvae were decocooned, and provided with apple as nourishment. Diapause could be terminated predictably in 94–100% of larvae by 1) conditioning at 15 °C and constant darkness for periods of 40–100 days, then 2) chilling at 2±2 °C and constant darkness for 20–50 days followed by 3) any post-chill condition periods at 25 °C, 18 h photoperiod. Complete diapause termination was achieved when 100 days conditioning was followed by 30 days or 50 days post-chill period. Under these conditions, 76% termination occurred in the post-chill period after 10 days, and 93% after 25 days.To terminate diapause in codling moth larvae, we recommend that a 100 days conditioning followed by 30 days chilling and 50 days post chilling periods be used.