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At least 19 recordsLinked to original sources
PubMed1979

The effect of freezing and storage in liquid nitrogen on the viability and growth of Mycobacterium leprae.

The effects of rapid and slow rates of freezing in liquid nitrogen, storage in liquid nitrogen for 12 months, and the rate of subsequent thawing on the viability and growth of M. leprae in the mouse footpad were studied. Some loss of viability of M. leprae was detected, and this was found to be associated with the freezing process, rather than with storage or thawing. Slow freezing was less deleterious than quick freezing, with a loss of viability of 90% compared with 98%. The growth pattern of M. leprae was unaffected except for a delay in the appearance of growth caused by the loss of viability, though there was some evidence of an increased lag phase of one strain, possibly due to the repair of sub-lethally damaged organisms.

Freezing↗
PubMed1975

Adenylate cyclase system of bovine adrenal plasma membranes.

The adenylate cyclase system present in a preparation enriched in plasma membranes derived from bovine adrenal cortex was investigated in considerable detail. This system is stimulated by adrenocorticotropic hormone (ACTH), by biologically active analogs of this hormone, and by fluoride ion. The preparation contains sodium-potassium- and magnesium-dependent ATPases that are markedly inhibited by 50 mM sodium fluoride. Incorporation of a pyruvate phosphokinase ATP generating system into the adenylate cyclase assay medium provided constant substrate levels. In the presence of the ATP generating system, the rate of cyclic AMP formation (basal, fluoride, and ACTH-activated) was proportional to enzyme concentration and was linear with time. Proportionality with respect to enzyme concentration as concerned the hormone-activated adenylate cyclase was achieved only when the ratio of hormone to enzyme protein was kept constant. The temperature optimum of the adenylate cyclase, basal or activated, was approximately 30 degrees. Michaelis-Menten kinetics were observed when the ratio of Mg2+ to ATP was approximately 6:1. Both calcium and ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid completely inhibited the adenylate cyclase system at concentrations of 5 and 0.5 mM, respectively. GTP was inhibitory at concentrations of 10-2 M but had little effect at lower concentrations. Freezing in liquid nitrogen and storage at -60 degrees exerted little effect on the fluoride-stimulated enzyme but lowered hormone stimulated activity. Preincubation in the presence of ACTH afforded a high degree of stabilization of the enzyme system while preincubation with a biologically inactive analog afforded no protection.

Adenosine Triphosphatases↗
PubMed1977

Effect of dimethyl sulphoxide on the expression of nitrogen fixation in bacteria.

Storage in dimethyl sulphoxide (DMSO) of Escherichia coli K12 hybrids carrying nif+ genes from Klebsiella pneumoniae can result in selection of a defective nitrogen-fixing phenotype. Similar results are obtained with E. coli K12 hybrids containing the nitrogen-fixing capacity from Rhizobium trifolii. DMSO appears to affect particular inner membrane proteins associated with energy metabolism in E. coli K12 and four chromosomal regions (chlD, chlG, his and unc) are associated with resistance to DMSO.

Chromosome Mapping↗
PubMed1978

Factors affecting the binding of polycyclic aromatic hydrocarbons to human embryo cells, and transformable and non-transformable hamster embryo cells.

The effects of various factors, including population doubling number, percent of confluence, serum concentration and storage in liquid nitrogen on the binding of several polycyclic aromatic hydrocarbons to human and hamster embryo cells were studied. The binding of 7,12-dimethylbenz[a]-anthracene (DMBA) to hamster embryo cells DNA, RNA and protein was maximal after 22 h of treatment. In contrast, binding to human embryo cell macromolecules increased for at least 55 h. Treatment of hamster embryo cells at 100% confluence resulted in much less binding than treatment at 70% confluence, whereas with human embryo cells the binding increased, or remained constant, following treatment at the greater confluence. The transforming frequency of hamster embryo cells decreases with increasing population doubling number. Accordingly, we found that the binding of DMBA to hamster embryo DNA, RNA and protein decreased approximately 100-fold between population doubling numbers 8 and 20. In transformable cell cultures, DMBA was bound to hamster embryo cell DNA to a greater extent than to RNA or protein. The binding of DMBA to nucleic acids was much greater than binding by either dibenz[a,h]anthracene (DB[a,h]A) or dibenz-[a,c]anthracene (DB[a,c]A), both of which had low binding values at all population doubling numbers tested. Therefore, the best correlation of binding with carcinogenicity and transforming activity was observed with DMBA. Storage of hamster embryo cells in liquid nitrogen did not alter their binding characteristics. Binding of all three hydrocarbons to human embryo cell nucleic acids was low during all population doubling numbers studied, while binding to cellular protein increased until population doubling number 70 and then decreased sharply.

9,10-Dimethyl-1,2-benzanthracene↗
PubMedDate not supplied

Cryopreservation of human lymphoid cells from various tissues.

Normal and pathological lymphoid cells, collected from different sources, were cryopreserved using a programmed freezing procedure. With this cryopreservation technique, the percentage of T and B cell surface markers and the proliferative response to mitogens were not influenced by 21 and 35 days of storage in liquid nitrogen. The recovery percentage of the lymphoid cells was satisfactory when fetal calf serum was added, as a protein source, to the medium during freezing and thawing phases, while a very low percentage of cells was recovered if the fetal calf serum was omitted.

Antigens, Surface↗
PubMed1979

Gametocytogenesis of Plasmodium falciparum in vitro: the cell-cycle.

Reproducible growth of gametocytes of Plasmodium falciparum in vitro was obtained from ring-stages taken directly from naturally infected patients and from the same material following storage in liquid nitrogen. Progressive sexual differentiation in vitro was examined for a finite period of 9 days in microcultures and was, for convenience, divided into 5 stages using established morphological criteria (Hawking, Wilson & Gammage, 1971). This microculture system was adapted as a bioassay for various anti-metabolites. Drug activity was measured by observing the inhibition of the established pattern of sequential development in experimental as compared to control cultures. Inhibitors used were directed against DNA, RNA and protein metabolism and microtubule assembly. As a result of these studies it is proposed that the sexual cell-cycle of P. falciparum is characterized by 4 phases. (1) A G1 period which lasts only a few hours. (2) The S phase, where DNA synthesis occurs, occupies the remainder of the first 2 days of development - both G1 and S are confined to stage I and II gametocytes. (3) G2, which is subdivided into 2 sections: G2A, characterized by stage II and III gametocytes, in which significant RNA and protein synthesis continue to occur; and G2B, where there is a progressive increase in transcription control resulting in the depression of both RNA and protein synthesis. Nonetheless, continued morphological differentiation occurs in the latter section transforming the parasites to stage IV and the morphologically and functionally mature stage V. The final M phase is marked by the brief and exposive events of gametogenesis, during which further protein synthesis occurs de novo. The proposed cell-cycle is examined as a model for studies on the activity of gametocytocidal compounds.

Animals↗
PubMed1979

Standardization of the human in vitro cell-mediated lympholysis technique.

Cytotoxic lymphocytes (CTL) can be generated in mixed lymphocyte culture and cryopreserved after a 6-day sensitization phase. CTL tested after storage in liquid nitrogen do not show lysis of autologous target cells and can mediate strong cytotoxicity against other target cells. This lysis shows the same specificity as that of the corresponding fresh CTL. The ability to cryopreserve CTL enables performance of sequential CML testing. Data from separate CML experiments can be pooled using a percent relative cytotoxic response (%RCR) to normalize values within individual experiments. Together, these methods provide a standardized cell-mediated lympholysis technique.

Cytotoxicity, Immunologic↗
PubMed1975

Characterization of the glucagon receptor in a pheochromocytoma.

Glucagon activated adenylate cyclase in a homogenate of a pheochromocytoma over the concentration range 1 times 10 minus 8M to 1 times 10 minus 6M. Several other hormones including adrenocorticotropin, thyrotropin, parathyroid hormone and histamine were without effect. The tumor glucagon receptor was characterized and found to be similar in several ways to the glucagon receptor previously reported in normal tissue such as liver and heart. One, the receptor specifically bound 125-I-glucagon. Two, solubilization of the pheochromocytoma abolished glucagon-activation of the adenylate cyclase. Three, glucagon-responsiveness of the adenylate cyclase was partially restored by the addition of phosphatidylserine to the incubations. One major difference was observed between the glucagon receptor in tumor tissue and that in liver and heart, namely, a marked lability in 125-I-glucagon binding and adenylate cyclase activity. Within four days, despite storage in liquid nitrogen, 75% of the binding activity and all of the adenylate cyclase activity in the solubilized preparation were lost. The factor(s) responsible for this lability remains unidentified.

Adenylyl Cyclases↗
PubMed1978

[Cryoresistance of rat liver endoplasmic reticulum membranes].

The effects of freezing of microsomes in liquid nitrogen and those of storage of microsomal suspensions at 2-4 degrees C and -3 - -5 degrees C for 24 hrs, on the enzymatic activities and hydrophobicity of membranes were studied. The hydrophobicity was determined by fluorescence of bound 1,8-anilino-naphthalene sulfonate. Rapid freezing of the microsomal suspension in liquid nitrogen followed by rapid warming did not change the hydrophobicity of the membranes, the rate of enzymatic lipid peroxidation, the level of cytochrome P-450 and the activity of NADH- and NADPH-cytochrome c reductase. A considerable decrease in the rate of enzymatic lipid peroxidation and membrane hydrophobicity was observed in the microsomes stored for 24 hrs at 2-4 degrees C. The 24-hr storage at -3 - -5 degrees C with subsequent thawing resulted in a rapid aggregation of the microsomes.

Adaptation, Physiological↗
PubMed1976

Biohazard potential: recovery of infectious virus from the liquid nitrogen of a virus repository.

Flame-sealed glass ampules containing vesicular stomatitis (VSV) were submerged in a liquid nitrogen (LN2) refrigerator for storage. Onseveral occasions cracked or shattered ampules were discovered upon removal from the refrigerator. Subsequently, VSV was recovered from the LN2 of the virus repository indicating a source of potential danger to those employing glass ampules submerged in LN2 for preservation of pathogenic organisms.

Laboratories↗
PubMed2025

Balancing nutrient remobilization and photosynthesis: proteomic insights into the dual role of lupin cotyledons after germination.

Efficient nutrient mobilization from seed storage tissues is essential for seedling establishment, particularly in legumes such as Lupinus albus (white lupin), which thrive in nutrient-poor soils. This study investigates the role of cotyledons in nitrogen (N) and mineral remobilization after germination during their transition from storage organs to photosynthetically active tissues, including the metabolic challenges posed by the coexistence of these two functions in epigeal germination. We cultivated white lupin seedlings under nitrogen-deficient conditions, analyzing cotyledon composition and function over 28 days. Our results indicate that 60% of cotyledon-stored proteins are degraded within the first 8 days, with free amino acids transiently accumulating before being redistributed to support growth. The progressive depletion of cotyledon reserves was accompanied by structural and metabolic changes, including an increase in photosynthetic proteins. However, cotyledon photosynthetic capacity remained lower than that of true leaves, suggesting a transient role in energy metabolism. The loss of cotyledons before day 12 significantly impaired seedling development, emphasizing their critical contribution to nitrogen, phosphate, and micronutrient supply during early growth. Comparative proteomic analysis revealed dynamic shifts in nutrient transport, amino acid metabolism, and stress response pathways following cotyledon removal. These findings underscore the significance of cotyledon nutrient remobilization in legume adaptation to low-fertility soils and highlight potential targets for breeding strategies aimed at improving nutrient use efficiency. By optimizing cotyledon nutrient composition and function, future breeding efforts could enhance seedling vigor, reduce fertilizer dependency, and improve the nutritional value of lupin-based foods.

Lupinus↗
PubMedDate not supplied

[Preservation of human lymphocytes in liquid nitrogen for the purpose of organ transplantation].

Repeated typing of organ receptors, indifferent of the technique employed, as well as the preparation of anti-sera of the HL-A type from multiple-pregnancy women (by repeated testing on known lymphocytes panels), suppose the storage for long periods of time of human lymphocytes at low temperatures. The authors present a technique adapted for the storage of lymphocytes in liquid nitrogen allowing for the survival of these cells, in very satisfactory conditions, for long periods of time.

Freezing↗
PubMed1979

Serum lipoprotein inhibitors of granulopoiesis in human bone marrow cultures.

Ammonium sulphate fractionation of human serum showed that two fractions contained an inhibitor of cluster and colony formation in agar cultures of human bone marrow cells. Further investigations demonstrated this inhibition to be caused by lipoproteins. When freshly prepared, only light density lipoproteins (LDL) were found to be inhibitory. During storage, very light density lipoproteins (VLDL) acquired inhibitory activity, while high density lipoproteins (HDL) did not show any inhibition of human bone marrow cultures. The possibility of toxic degradation of lipoproteins as an explanation for the inhibition was investigated by preincubation of human marrow cells with lipoproteins for 6 hours (37 degrees C) after storage of the lipoproteins under nitrogen (4 degrees C) for various intervals up to 48 days. Preincubation was found to be non-toxic (viable cell counts) and without colony/cluster-reducing ability for incubated marrow cells compared to controls. Addition of lipoproteins to mouse marrow cells and Ehrlich ascites tumour cells resulted in no change in colony formation by Ehrlich cells, whereas mouse marrow cells were inhibited, but to a lesser degree than human marrow cells.

Bone Marrow Cells↗
PubMedDate not supplied

Preservation of various microsomal drug metabolizing components in tissue preparations from the livers, lungs, and small intestines of rodents.

The livers, lungs, and small intestines of untreated rabbits and the livers of control rats were stored intact, or as microsomal suspensions, under liquid nitrogen at -196 degrees C. Aniline hydroxylase, aminopyrine demethylase, benzpyrene hydroxylase, biphenyl hydroxylase, NADPH-cytochrome c reductase, UDP-glucuronyltransferase activities, the microsomal content of cytochrome P-450, and the aniline- and benzphetamine-induced spectral changes were compared in fresh and stored preparations. Few significant changes in any of the above parameters resulted from storage of rabbit tissue preparations in liquid nitrogen for periods of up to 28 days. Pretreatment of rabbits with phenobarbital did not affect the stability of their stored microsomal preparations. Enzyme activities in the livers of untreated or 3-methylcholanthrene-pretreated rats were less stable to storage than in tissue preparations from rabbits stored under identical conditions. However, when rat hepatic microsomes were resuspended in KCl-HEPES supplemented with 1 mM EDTA before storage, enzyme activities were largely unaffected by freezing in liquid nitrogen.

Aminopyrine N-Demethylase↗
PubMed1975

[Immunocyte adherence and leukocyte migration inhibition tests in dogs infested with Leishmania donovani. Importance of lymphocyte conservation in liquid nitrogen].

A method of canine lymphocytes isolation and storage in liquid azote with DMSO is described. It was possible to use these lymphocytes in the immunocytoadherence and leucocytes migration inhibition tests in dogs infected with Leishmania donovani. The sensitisation was made with a soluble antigen from promastigotes of L. donovani braid by ultrasounds. The dogs with Leishmaniasis gave positive results. The controls without Leishmaniasis were negative. The tests with conserved lymphocytes were as satisfactory as the same tests with fresh lymphocytes.

Animals↗
PubMedDate not supplied

[Use of hydroxyethyl starch as a cryoprotective medium during platelet storage at low temperatures].

The effects of HES and HES + DMSO used as cryoprotective media for storage of human platelets in liquid nitrogen and vapor phase of liquid nitrogen were studied. Solution of 6% and 15% HES with molecular weight ranging from 65,000 to 250,000, and 10% DMSO were used. The criteria accepted for evaluation of the efficiency of these cryoprotective media were: 1. platelet counts, 2. participation of platelets in the processes of hemostasis measured in vitro by the ability of platelets to release adenine nucleotides (ATP + ADP) after thrombin stimulation. It was found that 15% HES is a more effective cryoprotective medium than 6% HES. The use of 15% HES + 10% DMSO gave similar results as the use of 10% DMSO alone.

Blood Cell Count↗