首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
The interactions between freezing kinetics and subsequent storage temperatures and their effects on the biological activity of lactic acid bacteria have not been examined in studies to date. This paper investigates the effects of three freezing protocols and two storage temperatures on the viability and acidification activity of Lactobacillus delbrueckii subsp. bulgaricus CFL1 in the presence of glycerol. Samples were examined at −196°C and −20°C by freeze fracture and freeze substitution electron microscopy. Differential scanning calorimetry was used to measure proportions of ice and glass transition temperatures for each freezing condition tested. Following storage at low temperatures (−196°C and −80°C), the viability and acidification activity of L. delbrueckii subsp. bulgaricus decreased after freezing and were strongly dependent on freezing kinetics. High cooling rates obtained by direct immersion in liquid nitrogen resulted in the minimum loss of acidification activity and viability. The amount of ice formed in the freeze-concentrated matrix was determined by the freezing protocol, but no intracellular ice was observed in cells suspended in glycerol at any cooling rate. For samples stored at −20°C, the maximum loss of viability and acidification activity was observed with rapidly cooled cells. By scanning electron microscopy, these cells were not observed to contain intracellular ice, and they were observed to be plasmolyzed. It is suggested that the cell damage which occurs in rapidly cooled cells during storage at high subzero temperatures is caused by an osmotic imbalance during warming, not the formation of intracellular ice.  相似文献   

2.
Studies were conducted on the viability of Micrococcus varians strain M95 and Lactobacillus plantarum strain L4 upon freezing and freeze-drying using five cryoprotectants (sucrose, lactose, sodium glutamate, peptone, dry nonfat milk) singly or in combinations with gelatin, glutamic acid, and sodium acetate. The number of survivals was determined immediately after treatment and after storage at room temperature or refrigeration temperatures, under vacuum or in air. Dry nonfat milk and peptone introduced at the levels of 8 and 5%, respectively, to broth culture, were found to be the best cryoprotectants providing a 100% viability determined immediately after the treatment of the strains under investigation.Immediately after freezing and freeze-drying, the numbers of viable micrococci remain high, the percentage viability in the presence of almost all the protectants used being 100%. During storage, those numbers decrease rapidly, reaching zero in 3 months upon storage at room temperature in air. The storage ability of lactobacilli is considerably better and, regardless of the fact that the percentage viability decreases, sufficient numbers of viable cells remain after 6 months of storage at both test temperatures.The best results are obtained on storing the microoganisms under vacuum in ampoules under reduced temperatures (+5 °C).  相似文献   

3.
K Yamasato  D Okuno  T Otomo 《Cryobiology》1973,10(5):453-463
In order to get some basic information for the development of a long-term preservation method by freezing at moderately low temperatures, the viability of 259 strains belonging to 32 genera and 135 species was measured. Cells were suspended in 10% glycerol and stored at ?53 °C for 16 months. About 93%, 88%, and 74% of aerobic bacteria gave viable cell counts higher than 105/ml, 106/ml, and 107/ml, respectively. About 10% of gram-positives and 3% of gram-negatives gave viable cell counts lower than 105/ml. There seemed to be some species—and genus—specificity with respect to viability after frozen storage and liquid paraffin-seal storage. Strains of coryneform bacteria, genera of the family Enterobacteriaceae, and the genus Pseudomonas were generally resistant. Pseudomonas putrefaciens proved to be specifically sensitive. Lactic acid bacteria were subject to sublethal injury, requiring special recovery media. Psychrophilic bacteria were very susceptible to frozen storage. All the tested strains of acetic acid bacteria survived frozen storage well both in 10% glycerol and in 10% honey at ?28 °C for 4.5 years. Honey proved to be a better adjuvant for frozen storage than glycerol. It was suggested from the results that for many kinds of bacteria, long-term preservation by freezing at moderately low temperatures might be possible when appropriate procedures are applied.  相似文献   

4.
This study was conducted to identify optimal medium composition for freezing Oryzias dancena embryonic cell lines. Different freezing media consisting of various concentration of dimethyl sulfoxide (DMSO), fetal bovine serum (FBS), and trehalose were prepared and long-term cultured embryonic cell line was frozen in each freezing medium by conventional slow freezing program for 7 days. Through measurement of viability and growth of post-thaw cells frozen in each freezing medium, it was determined that optimal composition of three components was 10 % DMSO, 20 % FBS, and 0.1 M trehalose. The post-thaw cells frozen in optimal freezing medium showed similar morphology and growth rate with non-frozen cells. Next, this condition was applied to two different sets of experiment; (1) freezing of the same cells during expanded period (57 days) and (2) freezing of short-term cultured cells from other batches for 7 days. The viability of post-thaw cells was significantly low and comparable in set 1 and 2, respectively, when compared with the result of long term-cultured cells frozen in optimal freezing medium for 7 days and similar morphology and growth rate with non-frozen counterparts were detected in the post-thaw cells from both sets. In conclusion, this study first reports the optimal medium composition for freezing O. dancena embryonic cells, which can contribute to fish species preservation as well as improvement of cell-based biotechnology by providing stable cell storage.  相似文献   

5.
A simple, effective and economical method for the long-term preservation of bacteria in liquid nitrogen under anaerobic conditions is described. As a case example anaerobic photosynthetic bacteria were successfully preserved. Gas tight small screw-cap glass ampoules with butyl rubber septa were used for freezing the specimen anaerobically. During experimental manipulations no anaerobic chamber or glove boxes were required. All teste cultures yielded high recoveries after repeated thawing and during storage. After freezing, survival recoveries of Rhodospirillaceae range from 70–100%, whereas with strict anaerobic strains of Chlorobiaceae and Chromatiaceae a maximum loss of 1–2 log10 counts was observed. No further loss in viability occurred after 1–2 years of storage.The small size of the ampoules and the use of single ampoule for 15–20 repeated retrievals proved economical with respect to storage space and costs.The system is compact and suitable for the preservation of anaerobic phototropic bacteria and other fragile anaerobic microorganisms.  相似文献   

6.
After injury or death of a valuable male, recovery of epididymal spermatozoa may be the last chance to ensure preservation of its genetic material. The objective of this research was to study the effect of sperm storage, at 4 °C up to 96 h, in the epididymides obtained from castrated horses and its effect on different functional sperm parameters. Aims were to study the effect of (1) sperm storage on viability and chromatin condensation; (2) pre-incubation of recovered epididymal sperm in the freezing extender, prior cryopreservation, on viability and chromatin condensation; and (3) freezing–thawing on viability, chromatin condensation, ROS generation, protein tyrosine phosphorylation and heterologous fertilization rate (ICSI and IVF using bovine oocytes) of sperm recovered from the epididymis up to 96 h post castration. The average volume (720 ± 159 μL) and the concentration (6.5 ± 0.4 × 109 spermatozoa/mL) of sperm recovered from the epididymis were not affected by storage. Sperm viability after refrigeration at 4 °C for up to72 h was similar (P < 0.01). The effect of sperm dilution in the freezing media showed similar values up to 48 h, while viability was preserved up to 72 h (P < 0.01). Cryopreserved spermatozoa show similar viability between different storage times. Chromatin condensation was not affected by storage time; however, incubation for 30 min in freezing medium and freezing–thawing process induced an increase in the chromatin decondensation. ROS generation was not affected by storage up to 96 h. Epididymal storage did not affect sperm protein tyrosine phosphorylation patterns; although the pattern of phosphorylation changed to strong staining of the equatorial segment when the sperm where capacitated in sperm–TALP. Finally, successful and similar pronuclear formation (analyzed by ICSI) and in vitro penetration (evaluated with bovine zone free oocyte) was observed using cryopreserved sperm obtained from prolong epididymal storage at 4 °C. In conclusion, cryopreservation of epididymal stallion sperm stored for up to 72 h in the epididymis at 4 °C, maintain both viability and ability to fertilize in vitro.  相似文献   

7.
Nineteen strains of taxonomieally diverse yeast species tested survived freezing and subsequent five-year storage in liquid nitrogen at ™196 °C, using a medium M 2 composed of malt extract, yeast extract, peptone, calf serum and dimethyl sulfoxide. Viability of the yeast cultures after long-term storage ranged from 5 to 97 % (average 62 %) compared with the viability of the cultures prior to freezing. The use of liquid nitrogen refrigeration for preserving yeast cultures is strongly advocated.  相似文献   

8.
Long-term cryogenic storage of Neurospora crassa spores   总被引:1,自引:0,他引:1  
Neurospora crassa on agar slants in ampules were frozen by direct immersion into liquid nitrogen and stored at −196 °C for 0–5.5 years. The survival, estimated as percentage germination of conidia, after warming, varied between 81.1 and 97.6%. Although there was a slight decline in survival immediately after the freezing treatment, no further significant decline has been detected during 5.5 years storage. The regression coefficients, (0.43, control, and 0.97, liquid nitrogen storage for 5.5 years), do not predict extinction of viability.  相似文献   

9.
Settled zoospores of the green macroalga Enteromorpha intestinalis were subjected to several different freezing and storing treatments at both cryogenic and non-cryogenic temperatures after which their viability was assessed using a spore germination bioassay. Three different cooling rates were tested: slow cooling at –1°C min−1 and –0.5°C min−1 to end temperatures in the range –20°C to –40°C, and a two-step procedure whereby the spores were frozen to –30°C at a rate of –1°C min−1 prior to immersion in liquid nitrogen at –196°C. Spore viability was also investigated using the cryoprotectants glycerol and dimethyl suphoxide (DMSO), a reduced saline medium and various storage times. In the majority of experiments, the use of a cryoprotectant during the freezing process significantly increased the viability of the spores, with DMSO affording slightly greater protection than glycerol. All treatments produced high viabilities (ranging from 75.3–100.0%) after 5-min storage at the different end temperatures. However, progressively longer storage up to 7 days generally resulted in a marked reduction in viability. This was with the exception of spores frozen in a reduced saline medium; a medium of 75% seawater and either 5 or 10% DMSO greatly increased spore viability, with values of > 40% recorded for spores stored at –20°C for up to 5 weeks. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

10.
The aims of the present study were, to assess the effects of semen centrifugation, two different diluents and two different freezing methods on post-thaw semen quality in canine semen, and to elucidate the interdependence of these parameters. For this purpose, the sperm-rich fractions of ejaculates from 12 healthy male beagles were divided into four aliquots. Two aliquots were centrifuged and resuspended with two TRIS-egg yolk based extenders: with Uppsala and Gill extender (Gill). The diluents differed in the concentration of glycerol and in the admixture of Equex STM paste (Nova Chemical Sales Inc., Scituate, MA, USA). Diluted semen was frozen either in a styrofoam box or with a computerized freezing machine and an optimized freezing curve (IceCube 1,810; Sy-Lab, Purkersdorf, A). The change in temperature inside the straws was measured during the freezing procedure. Thawed semen samples were assessed for motility and viability (SYBR-14/PI) using the computer assisted sperm analyzer SpermVision (Minitüb, G) and a modified triple staining technique (flow cytometry). Deep freezing in the machine resulted in better motility and viability than in the box. The combination centrifugation-Uppsala extender-machine was superior to all other combinations, which was most evident after storage at +5 degrees C for 7 h (motility: 53.1%, viability: 64.9%). Post-thaw longevity and progressive motility were significantly improved by the use of the here introduced freezing curve. This was shown to be partly caused by less pronounced fluctuations of temperature inside the straws when compared to box-freezing.  相似文献   

11.
A method for the cryopreservation of third-stage infective juveniles (IJ) of Steinernema carpocapsae and Heterorhabiditis bacteriophora was developed. Cryoprotection was achieved by incubating the nematodes in 22% glycerol (S. carpocapsae) or 14% glycerol (H. bacteriophora) for 24 hours, followed by 70% methanol at 0 C for 10 minutes. The viability of S. carpocapsae frozen in liquid nitrogen as 20 μl volumes spread over cover slip glass was > 80%. Survival of H. bacteriophora frozen on glass varied from 10 to 60% but was improved to > 80% by replacing the glass with filter paper. Cryopreservation and storage of 1-ml aliqots of S. carpocapsae IJ resulted in > 50% survival after 8 months; pathogenicity was retained and normal in vitro development took place. Trehalose and glycerol levels increased and glycogen levels decreased during incubation of S. carpocapsae IJ in glycerol. Normal levels of trehalose, glycerol and glycogen were restored during post freezing rehydration.  相似文献   

12.
Aims: The frozen and dehydrated state transitions of lactose and trehalose were determined and studied as factors affecting the stability of probiotic bacteria to understand physicochemical aspects of protection against freezing and dehydration of probiotic cultures. Methods and Results: Lactobacillus rhamnosus GG was frozen (–22 or –43°C), freeze‐dried and stored under controlled water vapour pressure (0%, 11%, 23% and 33% relative vapour pressure) conditions. Lactose, trehalose and their mixture (1 : 1) were used as protective media. These systems were confirmed to exhibit relatively similar state transition and water plasticization behaviour in freeze‐concentrated and dehydrated states as determined by differential scanning calorimetry. Ice formation and dehydrated materials were studied using cold‐stage microscopy and scanning electron microscopy. Trehalose and lactose–trehalose gave the most effective protection of cell viability as observed from colony forming units after freezing, dehydration and storage. Enhanced cell viability was observed when the freezing temperature was ?43°C. Conclusions: State transitions of protective media affect ice formation and cell viability in freeze‐drying and storage. Formation of a maximally freeze‐concentrated matrix with entrapped microbial cells is essential in freezing prior to freeze‐drying. Freeze‐drying must retain a solid amorphous state of protectant matrices. Freeze‐dried matrices contain cells entrapped in the protective matrices in the freezing process. The retention of viability during storage seems to be controlled by water plasticization of the protectant matrix and possibly interactions of water with the dehydrated cells. Highest cell viability was obtained in glassy protective media. Significance and Impact of the Study: This study shows that physicochemical properties of protective media affect the stability of dehydrated cultures. Trehalose and lactose may be used in combination, which is particularly important for the stabilization of probiotic bacteria in dairy systems.  相似文献   

13.
The interactions between freezing kinetics and subsequent storage temperatures and their effects on the biological activity of lactic acid bacteria have not been examined in studies to date. This paper investigates the effects of three freezing protocols and two storage temperatures on the viability and acidification activity of Lactobacillus delbrueckii subsp. bulgaricus CFL1 in the presence of glycerol. Samples were examined at -196 degrees C and -20 degrees C by freeze fracture and freeze substitution electron microscopy. Differential scanning calorimetry was used to measure proportions of ice and glass transition temperatures for each freezing condition tested. Following storage at low temperatures (-196 degrees C and -80 degrees C), the viability and acidification activity of L. delbrueckii subsp. bulgaricus decreased after freezing and were strongly dependent on freezing kinetics. High cooling rates obtained by direct immersion in liquid nitrogen resulted in the minimum loss of acidification activity and viability. The amount of ice formed in the freeze-concentrated matrix was determined by the freezing protocol, but no intracellular ice was observed in cells suspended in glycerol at any cooling rate. For samples stored at -20 degrees C, the maximum loss of viability and acidification activity was observed with rapidly cooled cells. By scanning electron microscopy, these cells were not observed to contain intracellular ice, and they were observed to be plasmolyzed. It is suggested that the cell damage which occurs in rapidly cooled cells during storage at high subzero temperatures is caused by an osmotic imbalance during warming, not the formation of intracellular ice.  相似文献   

14.
The procedure described is applicable to 11 mutant strains of C. reinhardi Dangeard. In general, freezing resulted in 3-log loss of viable cells. Nevertheless, the phenotypic response of the recovered viable cells to selected media was the same as before freezing. There was no further reduction in viability after 6–17 months storage at liquid N2 temperatures.  相似文献   

15.
An evaluation of various refrigerated (4 °C) storage solutions and conditions was conducted using rabbit skin. Two in vitro methods to assay skin viability are presented: one which directly measures basal cell viability and one which assesses the skin's ability to grow in culture following storage. The superiority of storage in nutrient medium supplemented with fetal bovine serum over conventional storage in saline is clearly demonstrated. Storage in nutrient medium with 10% fetal calf serum resulted in basal cell viabilities which were over 30% higher than viabilities of skin stored by conventional methods in saline. Skin stored in saline failed to grow in culture, while 100% of the cultures of skin stored in medium plus fetal calf serum grew. Although addition of fetal calf serum to the saline improved the basal cell viability, growth in culture occurred only when the skin was stored in a capped tube. Skin stored in medium without serum gave viability results which were not significantly different from the unstored control, but growth rates in culture did differ significantly from the control values. Our study shows that the viability of rabbit skin and its ability to grow in vitro are depressed when the tissue is maintained at 4 °C in saline or in petri dishes, and optimal when refrigerated in nutrient medium supplemented with FBS in a sealed tube.  相似文献   

16.
The aim of this study was to develop short- and long-term preservation protocols for European eel ovarian stem cells (OSCs) through hypothermic storage and cryopreservation of ovarian fragments that will assist in current conservation programs of this critically endangered species. Firstly, a freezing procedure was developed by testing different cryomedia and technical aspects of freezing. Utilization of 1.5 M of dimethyl sulfoxide (Me2SO), 0.1 M glucose and 1.5% BSA yielded optimal OSCs survival. Additionally, equilibration of 50-mg ovarian fragments for 30 min and plunging into lN2 at −80 °C displayed the highest OSC viability. Different cooling rates ranging from −1 to −40 °C/min did not significantly affect OSC viability when thawing in a 10 °C water bath. In addition, application of needle-immersed vitrification (NIV), combining ES3 (1.5 M PG and 1.5 M Me2SO) with VS3 (3 M PG and 3 M Me2SO) yielded the highest viability rates. Finally, hypothermic storage (4 °C) of ovarian fragments and ovarian cell suspensions displayed favorable viability of ~90% after 48 h of storage and ~65% after 72 h of storage. The development of OSC preservation methods presents an onset of further development of germline stem cell (GSC) manipulation techniques in this species. Cryopreservation of OSCs can enable a continuous supply of cells for either transplantation or in vitro cell culture thus enabling new and improved management and conservation strategies for this endangered species.  相似文献   

17.
A free-living, marine dinoflagellate, Crypthecodinium cohnii, was successfully preserved by controlled and uncontrolled freezing. Tolerance testing to various concentrations of dimethylsulfoxide (DMSO) and glycerol established that 7.5% glycerol was the best cryoprotectant. Controlled freezing was accomplished by using a biological freezer to obtain a 1 °C/min cooling rate. After storage for a minimum of 7 days at ?150 °C material frozen by this method demonstrated a 47.7% mean recovery, and cells were viable through five subcultures. Uncontrolled freezing resulted from placing the ampoules on the bottom of a low temperature refrigerator at ?55 °C for 1 hr. This material demonstrated a mean recovery of 30.8% with a much wider range. Cells were initially nonmotile following recovery, and in those recovered after uncontrolled freezing motility was further delayed. One strain was viable after 6 years of storage with a 68% recovery following controlled freezing.The lack of motility immediately following recovery leads to inaccuracies when determining the percentage of cells recovered. Dilution techniques have been used for nonmotile recovered cells, but this method has been unsuccessful in our laboratory. Delayed motility has been reported for other flagellates and work in our laboratory indicates that flagellar shearing may be the cause.  相似文献   

18.
To increase the quality of cryopreserved sperm in white rhinoceros, the liquid nitrogen vapour (LN vapour) freezing and the multi-thermal gradient directional freezing methods were compared. Sixteen white rhinoceros (Ceratotherium simum sp.) were electro-ejaculated. Semen samples were diluted with cryoextender (Tris, lactose, egg-yolk, DMSO) and aliquoted into straws for LN vapour freezing, and glass hollow tubes for directional freezing. The sperm quality was evaluated before and after freezing by assessing the following parameters: motility, morphologic state, acrosomal integrity and plasma membrane function and integrity (i.e. sperm viability) as defined by the hypo-osmotic swelling. Directional freezing improved the sperm viability by 5.6% (p < 0.005), progressive motility score by 34.7% and sperm motility index (SMI) by 8.1% (p < 0.005) versus LN vapour freezing. When data was categorized into groups of low (<19%), moderate (20-39%) and high (>40%) percentages of morphologically normal, directional freezing (DF) resulted in 31.4% less abnormal acrosomes for the low quality group as well as 18.7% increase in intact acrosomes and 10.9% increase in motility for the high quality group compared to LN vapour freezing (LN) (p < 0.01, p < 0.03, p < 0.01, respectively). LN showed a significant reduction in sperm head volume (5.7%, p < 0.05) compared to the prefreeze; whereas, no significant reduction in head volume was demonstrated after DF. Several additives (xanthenuric acid, cytochalasin D, potassium, EDTA) to the basic cryoextender provided no significant improvement in spermatozoal survival after directional freezing. In conclusion, directional freezing proved to facilitate higher gamete survival compared to LN vapour freezing. This is especially effective in ejaculates of low sperm quality and is important in endangered species where high quality semen donors are often not accessible. These results suggest that directional freezing could be valuable particularly for species with limited freezability of spermatozoa.  相似文献   

19.
Biodiversity conservation programmes are underpinned by seed banking following drying to low water contents (WC), and supported by both the assessment and prediction of seed viability over time. The means of judging viability is thus crucial to the comprehension of seed vigour. We selected seeds of three species and one hybrid in the Salicaceae likely to have variation in tolerance to drying, processing and storage, including in relation to cryobanking, and compared survival growth as radicle emergence (germination) and normal seedling production. With three seed lots of Salix gracilistyla, air-drying to 8–10 % WC enhanced seed survival after 40 days’ storage at 5 °C as compared with non-treated seeds at 14–20 % WC. Four seed lots of Populus alba × P. glandulosa showed equally high germination (88–100 %) and proportions of normal seedlings (81–99 %) when stored at 5 °C for 7–10 weeks. Among seven seed lots of S. gracilistyla, two groups with different storage behaviour could be statistically distinguished with normal seedling production ranging from 0 to 45 % after storage at 5 °C for 13 weeks. Seed tolerance to WC manipulation and cryopreservation was very variable among species and seed lots. Seed lots of S. hallaisanensis and S. gracilistyla with ~80 % germination survived cryopreservation at 10 % WC, but were sensitive to lower WCs. In contrast, Populus seeds had greater desiccation tolerance combined with cryopreservation capability. With seed lots of all species and hybrids, cryopreservation had little effect on viability unless the high moisture freezing limit had been exceeded (~10–20 % WC, depending on seed lot). However, under all conditions of handling (drying, rehydration, storage at 5 °C or cryopreservation) using germination as the only indicator of viability over-estimated survival compared with normal seedling production.  相似文献   

20.
The limited availability of fresh osteochondral allograft tissues necessitates the use of banking for long-term storage. A vitrification solution containing a 55% cryoprotectant formulation, VS55, previously studied using rabbit articular cartilage, was evaluated using porcine articular cartilage. Specimens ranging from 2 to 6 mm in thickness were obtained from 6 mm distal femoral cartilage cores and cryopreserved by vitrification or freezing. The results of post-rewarming viability assessments employing alamarBlue demonstrated a large decrease (p < 0.001) in viability in all three sizes of cartilage specimen vitrified with VS55. This is in marked contrast with prior experience with full thickness, 0.6 mm rabbit cartilage. Microscopic examination following cryosubstitution confirmed ice formation in the chondrocytes of porcine cartilage vitrified using VS55. Experiments using a more concentrated vitrification formulation (83%), VS83, showed a significant treatment benefit for larger segments of articular cartilage. Differences between the VS55 and the VS83 treatment groups were significant at p < 0.001 for 2 mm and 4 mm plugs, and at p < 0.01 for full thickness, 6 mm plugs. The percentage viability in fresh controls, compared to VS55 and VS83, was 24.7% and 80.7% in the 2 mm size group, 18.2% and 55.5% in the 4 mm size group, and 5.2% and 43.6% in the 6 mm group, respectively. The results of this study continue to indicate that vitrification is superior to conventional cryopreservation with low concentrations of dimethyl sulfoxide by freezing for cartilage. The vitrification technology presented here may, with further process development, enable the long-term storage and transportation of living cartilage for repair of human articular surfaces.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号