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PubMedDate not supplied

Long-term preservation of egg and tissue homogenates for determination of organochlorine compounds: freezing versus freeze-drying.

Storage of wet egg homogenates at temperatures from -18 degrees to -28 degrees C was more suitable for long-term preservation than freeze-drying. Changes in residue levels of heptachlor epoxide, oxychlordane, dieldrin, hexachlorobenzene,p,p'-DDE, mirex, and PCBs were not significant over a 3-year period in fresh herring gull egg homogenates stored at -18 degrees to -28 degrees C. Compounds with gas chromatographic retention times shorter than hexachlorobenzene vaporized during freeze-drying at a rate proportional to their volatility. Evaporative losses of components with vapor pressures less than hexachlorobenzene did not occur in naturally contaminated herring gull eggs after storage at room temperature for up to 1 year. Higher losses of all compounds, up to 25% for p,p'-DDE, occurred in freeze-dried whole-body herring gull homogenates. Easily dehydrochlorinated compounds were rapidly degraded in freeze-dried chicken egg homogenate at room temperature: The half-life of p,p'-DDT and p,p'-DDD was about 20 days, and that of alpha- and gamma-hexachlorocyclohexane was much less than 16 days. About one-third of oxychlordane in herring gull eggs was lost in 1 year under these conditions, but none was lost after freeze-drying when the homogenate was stored at -18 degrees to -28 degrees C.

Eggs↗
PubMed1988

Dehydrogenase enzyme histochemistry on freeze-dried or fixed resin-embedded tissue.

A method has been developed for the histochemical demonstration of a variety of dehydrogenases in freeze-dried or fixed resin-embedded tissue. Seven dehydrogenases were studied. Lactate dehydrogenase, NADH dehydrogenase and NADPH tetrazolium reductase were all demonstrable in sections of paraformaldehyde-fixed resin-embedded tissue. Freeze-dried specimens were embedded, without fixation, in glycol methacrylate resin or LR Gold resin at either 4 degrees C or -20 degrees C. All the dehydrogenases except succinate dehydrogenase retained their activity in freeze-dried, resin-embedded tissue. Enzyme activity was maximally preserved by embedding the freeze-dried tissue specimens in glycol methacrylate resin at -20 degrees C. The dehydrogenases were accurately localized without any diffusion when the tissue sections were incubated in aqueous media. Addition of a colloid stabilizer to the incubating medium was not required. Freeze-drying combined with low-temperature resin embedding permits accurate enzyme localization without diffusion, maintenance of enzyme activity and excellent tissue morphology.

Animals↗
PubMed2005

LENTICULE discs provide a homogenous format for external quality assessment samples: a comparison with freeze-dried samples for shellfish microbiology.

AIMS: The aim was to compare the variability in Escherichia coli enumeration data and detection of Salmonella spp. between four samples of LENTICULE discs and freeze-dried samples for the Health Protection Agency's External Quality Assessment (EQA) scheme for shellfish microbiology. METHODS AND RESULTS: Four samples of known but undisclosed microbiological content were dispatched in both freeze-dried and LENTICULE disc formats to 57 participating laboratories in 20 countries. Participants examined samples using their routine methods for the most probable number (MPN) of E. coli per 100 g and the presence/absence of Salmonella spp. There was no significant difference between the Food and Environmental Proficiency Testing Unit and participating laboratories for E. coli and Salmonella spp. results. There were significantly less outlying results using the LENTICULE discs than freeze-dried sample format and equivalent or less variance for the former for E. coli MPN. There was no significant difference between LENTICULE discs and freeze-dried samples for the presence/absence of Salmonella spp. CONCLUSIONS: Overall the results indicated that there was equivalent or less variance in results for the LENTICULE discs than for freeze-dried samples, therefore LENTICULE discs are a homogenous and stable matrix for EQA samples. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides validation data for the replacement of freeze-dried samples by LENTICULE discs for the Health Protection Agency Shellfish EQA Scheme.

Animals↗
PubMed2005

Effect of counterions on the physical properties of l-arginine in frozen solutions and freeze-dried solids.

The objective of this study was to elucidate the physical properties of L-arginine and various counterion combinations in frozen aqueous solutions and in freeze-dried solids. L-Arginine remains amorphous in the highly concentrated non-ice phase in frozen solutions with a Tg (glass transition temperature of maximally freeze-concentrated solutes) of -41.4 degrees C. Some acids and salts (e.g., H3PO4, H2SO4, HNO3, and NaH2PO4) raised the Tg , whereas others (e.g., HCl, CH3COOH, HCOOH, Na2HPO4, and NaCl) had little effect or lowered the L-arginine Tg . Co-lyophilization with phosphoric acid also raised the glass transition temperature (Tg) of amorphous freeze-dried L-arginine solids. Arginine-H3PO4 combinations exhibited properties that led to either the stabilization or destabilization of a model protein (lactate dehydrogenase: LDH) during freeze-drying, depending on their concentration ratios. Fourier-transform infrared (FT-IR) and diffusion reflectance near-infrared (NIR) spectra indicated the presence of interactions between the amino and/or guanidyl groups of L-arginine and phosphate ions in the amorphous freeze-dried cakes. It was postulated that the interaction between L-arginine and the multivalent counterions, as well as an increase in hydrogen bonding network, reduced the mobility of molecules in the frozen solutions and freeze-dried solids.

Animals↗
PubMed2003

A sensitive and rapid method to determine the viability of freeze-dried bacterial cells.

AIMS: To determine the potential use of flow cytometry for viability asssessment of freeze-dried bacterial cells. METHODS AND RESULTS: Escherichia coli CIP 54.8T and Vibrio metschnikovii CIP 104262 were analysed. The viability of freeze-dried cells resuspended in a nutrient broth was evaluated by culture whereas activity was determined by flow cytometry analysis of both esterase activity and cell death. Activity assessment by flow cytometry was found to be a rapid and good indicator of cell viability and was very efficient for quality control. For V. metschnikovii the fraction of active cells varies greatly depending on the freeze-drying procedure and within a given procedure. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: Bacterial activity assessment by flow cytometry is very efficient for the control of freeze-dried cells.

Bacteriological Techniques↗
PubMed1977

Deoxyribonucleic acid strand breaks during freeze-drying and their repair in Escherichia coli.

Freeze-drying of Escherichia coli cells caused strand breaks of deoxyribonucleic acid (DNA) in both radiation-sensitive and -resistant strains. However, in the radiation-resistant strain E. coli B/r the damaged DNA was repaired after rehydration, whereas in the radiation-sensitive strain E. coli Bs-1 the damaged DNA was not repaired and the DNA was degraded. Repeated freeze-drying did not break the damaged DNA into smaller pieces.

DNA Repair↗
PubMed1998

[The stability of freeze-drying lysosomal enzymes].

OBJECTIVE: Enzyme assays for the diagnosis of lysosomal storage diseases have been underway in China only in a few laboratories, and the specimens for enzyme assay must not be inactivated by environmental factors. To solve the problem, the stability of freeze-drying lysosomal enzymes was tested. METHODS: Three pools for samples were set up: control leucocytes pool and plasma pool(40 individuals in each pool), control fibroblasts pool( 3 cell lines). 4 groups of different dispositions of samples were designed for the pools:(1)pellets or plasma directly stored at -80 degrees C as routine(non-freeze-drying group or N);(2)after freeze-drying, pellets or plasma immediately stored at -80 degrees C (0 week or 0W); (3) after freeze-drying, pellets or plasma stayed at room temperature for 1 week(simulated mail) then stored at -80 degrees C (1 week or 1W);(4) the same with 1W but 3 weeks at room temperature(3 weeks or 3W). Microassay for enzyme activity was employed: 20 enzymes in leucocytes pool, 14 enzymes in fibroblasts pool and 7 in plasma pool. RESULTS: Enzyme activities among 4 groups in each sample pool were compared. Single factor analysis of variance (F test) showed no significance of differences (P>0.05) among 4 groups in leucocytes and fibroblasts pool, but highly significant differences (P<0.01) among 4 groups in plasma pool. "t test" showed no significance of differences (P> 0.05) between N and 3W in leucocytes and also fibroblasts pool, but very significant differences (P<0.01) between N and 3W in plasma pool. CONCLUSION: The results suggest that freeze-drying samples from leucocytes and fibro- blasts can provide a stable resource for enzyme assay and be simple for transportation of the diagnostic samples. Though freeze-drying is not appropriate for the plasma samples, it is still applicable for wide use since only a few kinds of lysosomal enzyme being indicated to use plasma for enzyme assay.

Clinical Enzyme Tests↗
PubMedDate not supplied

Particulate contamination from siliconized rubber closures for freeze drying.

It can be shown that siliconized closures for freeze drying may cause the opalescence and turbidity observed in freeze-dried products after reconstitution. Closures of different rubber composition show different intensities of turbidity when treated identically with the same quantity and type of silicone oil. Clear solutions are obtained after reconstitution if ETFE-coated closures are used instead of siliconized closures. Samples stored at 4 degrees C for up to 6 months show no change in the intensity of turbidity, while the turbidity of samples manufactured with siliconized closures and stored at higher temperatures increase with time. Samples with ETFE-coated closures show clear solutions when stored at 25 degrees C and 37 degrees C for up to 6 months and at 45 degrees C for 3 months. After 6 months only a very weak opalescence could be observed in these samples.

Drug Contamination↗
PubMed1972

Ultrastructural characteristics of freeze-dried human blood platelets.

Ultrastructural characteristics of freeze-dried human blood platelets were investigated. Extensive ice crystal formation was found in platelets frozen in the absence of cryoprotective agents. Platelet preservation was much improved by the addition of dimethyl sulfoxide, or dimethyl acetamide, with glucose or 0.25 M sodium glycerophosphate, to platelet-rich plasma prior to the freeze drying process. Platelet membranes and organelles were generally well preserved, and many granules demonstrated eccentric areas of electron density. Microtubules were not clearly identified, but some platelets showed tubule-like structures within platelet hyaloplasm. Pseudopods were often observed at the platelet surface, and often contained membrane-bound granule-like structures. Some pseudopods contained electrondense material which extended between adjacent platelets in interplatelet bridges and which was released to the surrounding medium. Interplatelet bridge formation was not prevented by chelation of calcium by ethylenediamine tetraacetic acid. The observations were consistent with the suggestion that contractile protein is present in interplatelet bridges and serves as a basis for clot retraction.

Acetamides↗
PubMed1985

An inexpensive device for freeze drying and plastic embedding tissues at low temperatures.

The preparation of biological tissues for electron microscopy by rapid freezing retains the original localization of ions and molecules. A reproducible freezing regime was established by quenching tissues in liquid propane according to the method of Elder et al. (1981). Tissue was thereafter freeze dried in a custom built freeze drying device with a liquid nitrogen cooled stage to prevent ice recrystallization during drying. The device was also designed to allow the vacuum embedding of tissue in low temperature resin such as Lowicryl and polymerization in situ. This paper describes the design of the device and an example of its use in the freeze drying of cartilage. The results show that minimal ice damage occurs to the chondrocytes and that intracellular organelles are clearly visible. The regime described may prove a useful and pragmatic alternative to cutting tissue in the frozen state. Translocation of elements is unlikely except perhaps in the case of very labile elements such as Na and K, but this remains to be fully elucidated.

Animals↗
PubMed1976

Clinical evaluation of freeze-dried bone allografts in periodontal osseous defects.

Freeze-dried cortical bone allografts of a fine particle size were implanted into wide three-wall, two-wall, one-wall, combination, and furcation defects. Of the 97 defects treated, 23 manifested complete bone regeneration; 39 showed greater than 50%; and 24, less than 50% osseous repair. Twelve defects failed to demonstrate any bony regeneration, of which nine were furcation involvements. From the preliminary data available, there is strong evidence which indicates that freeze-dried bone allografts have definite potential as grafting material in certain periodontal osseous defects. However, final determination must await the outcome of a larger number of cases and also histologic evidence.

Adult↗
PubMed2005

The effect of freeze-drying with different cryoprotectants and gamma-irradiation sterilization on the characteristics of ciprofloxacin HCl-loaded poly(D,L-lactide-glycolide) nanoparticles.

In the present study, the influence of freeze-drying with several cryoprotective agents and gamma (gamma)-irradiation sterilization on the physicochemical characteristics of ciprofloxacin HCl-loaded poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles was evaluated. Nanoparticles were prepared by W/O/W emulsification solvent evaporation followed by high-pressure homogenization. They were freeze-dried in the presence of 5.0% (w/v) mannitol, trehalose or glucose, with 5.0% (w/v) or 15.0% (w/v) dextran as cryoprotectants. The nanoparticles were irradiated at a dose of 25 kGy using a 60Co source. The following physicochemical properties of the formulations were investigated: the ratio of particle size before (initial) and after freeze-drying, the ease of reconstitution of the nanoparticle suspensions and the drug-release profiles of irradiated and non-irradiated nanoparticles. The antibacterial activity against Pseudomonas aeruginosa was measured. The freeze-drying process induced a significant increase in particle size when no cryoprotectant was employed. Similar results were observed when cryoprotectants were added to the formulation. Only when mannitol was used was no significant size increase measured. Moreover, for formulations with dextran, reconstitution after freeze-drying was difficult by manual agitation and particle size could not be determined because of aggregation. After gamma-sterilization no significant difference in mean particle size was observed, but reconstitution was more difficult and drug release was influenced negatively. Ciprofloxacin HCl incorporated in the nanoparticles was still effective against the micro-organism selected after freeze-drying and gamma-sterilization.

Anti-Bacterial Agents↗
PubMed1998

The importance of "like to like" ISI calibrations with freeze dried plasmas. European Concerted Action on Anticoagulation.

AIM: To assess reliability of like to like and cross species calibrations using two types of certified freeze dried plasma calibrants--artificially depleted of vitamin K clotting factors, and from coumarin treated patients. METHODS: Six ECAA national control laboratories provided certified values for the freeze dried plasmas in terms of the human plain international reference preparation (IRP) (BCT/441) with the manual prothrombin time technique. Eight other ECAA national laboratories determined international sensitivity index (ISI) values in full fresh plasma same species and cross species WHO calibrations against a low ISI human IRP (BCT/441) of the ECAA low ISI human thromboplastin and high ISI ECAA rabbit thromboplastin. Parallel calibrations were performed using the certified values. RESULTS: Calibrations on fresh plasmas of the human ECAA reference thromboplastin (stated ISI = 0.95) gave ISI of 0.957 against the human IRP and 1.66 against the rabbit IRP. The ECAA rabbit (stated ISI = 1.67) gave an identical value on the fresh plasma calibration v the human IRP. With freeze dried depleted plasmas certified in terms of the human IRP, the ISI of the ECAA human was 1.01, but the ECAA rabbit (stated ISI = 1.67) gave a low ISI of 1.47. The freeze dried coumarin plasmas gave an ISI of 0.943 for the ECAA human but only 1.493 for the ECAA rabbit. CONCLUSIONS: Fresh plasmas give reliable ISI when calibrating thromboplastins in same species and cross species calibrations. Freeze dried plasmas certified in terms of a single IRP, whether artificially depleted or of coumarin plasma origin, cannot be used for calibration of dissimilar thromboplastins.

Anticoagulants↗
PubMed2002

[A case of orchitis following vaccination with freeze-dried live attenuated mumps vaccine].

In Japan, freeze-dried live attenuated mumps vaccine has been used optionally since 1981. The effectiveness of mumps vaccination has been established by worldwide research since 1971. On the other hand, because of it's live activity several untoward effects have been reported. Vaccination-related mumps orchitis is a rare adverse effect of mumps vaccine. Only 9 cases of vaccination-related mumps orchitis have been reported in Japan. We describe a case of orchitis following mumps vaccination in adolescence. A 16 years-old male has admitted because of acute orchitis with high fever and painful swelling of right testis. The patient had received vaccination with freeze-dried live attenuated mumps vaccine 16 days before admission. After admission, the bed-rest had completely relieved the symptoms on 6th hospital day. The impaired testis has maintained normal size and consistency 6 months after discharge.

Adolescent↗
PubMed2003

Freeze-drying polymeric colloidal suspensions: nanocapsules, nanospheres and nanodispersion. A comparative study.

Different polymeric nanoparticles were freeze-dried and the powders compared to determine the influence of the lipophilic core (Miglyol 810) or benzyl benzoate) and polymeric material (poly(epsilon-caprolactone) or Eudragit S90) on their drug content and morphology. Diclofenac, a non-steroidal anti-inflammatory drug, was used as a model. To characterize the products, a biological experiment based on the evaluation of the mucosal toxicity of diclofenac was conducted. Nanocapsule and nanosphere suspensions were prepared by nanoprecipitation and freeze-dried after the addition of colloidal silicon dioxide. The powders were examined under scanning electron microscopy (SEM) and gastrointestinal tolerance of products was evaluated in rats. Powders presented drug contents between 90.2+/-5.5 and 101.1+/-1.9% (HPLC). SEM analyzes showed non-spherical microparticles and, at higher magnifications, the micro-powder surface presented a homogeneous nanocovering. Regarding the gastrointestinal tolerance, with the exception of benzyl benzoate-loaded formulations, powders presented lesional indexes lower than the diclofenac salt solution. In contrast to the literature, nanocapsules can be dried by freeze-drying without leakage of drug or breaking the capsule wall.

Animals↗
PubMed2000

Strategies for maintaining the particle size of peptide DNA condensates following freeze-drying.

The particle size of peptide DNA condensates were studied after freeze-drying and rehydration as a function of sugar excipient, concentration, pH, DNA concentration, and peptide condensing agent. In the absence of an excipient, freeze-dried 50 microg/ml AlkCWK(18) (iodoacetic acid alkylated Cys-Typ-Lys(18)) DNA condensates formed large fibrous flocculates on rehydration. Of the sugars tested as lyoprotectants, sucrose proved most effective at preserving particle size during rehydration. The addition of 5 wt/vol% sucrose preserved a mean particle diameter of less than 50 nm during rehydration of AlkCWK(18) DNA condensates prepared at DNA concentrations up to 200 microg/ml; however, higher DNA concentrations led to the formation of insoluble fibrous flocculates. Substitution of polyethylene glycol (PEG)-CWK(18) as a DNA condensing peptide eliminated the need for sucrose, resulting in peptide DNA condensates that retained particle size when rehydrated in water or normal saline at concentrations up to 5 mg/ml. The results suggest that sucrose functions primarily as a bulking agent during freeze-drying that only preserves the particle size of AlkCWK(18) DNA condensates up to a maximum concentration of 200 microg/ml. Alternatively, the steric layer created on the surface of PEG-CWK(18) DNA condensates provides far more efficient lyoprotection, preserving their particle size at a concentration of 5 mg/ml without a bulking agent.

DNA↗
PubMed1992

Freeze-drying of bone tissue: immunocytochemistry and enzyme histochemistry on paraffin embedded and low-temperature resin embedded specimens.

A simple protocol of tissue preparation was sought, which would enable marker enzymes of bone cells and extracellular matrix antigens to be localized in the same tissue section with high optical resolution. For this purpose, snap-frozen samples of rat fetal skeletal tissues were dried in a FDU 010 freeze-drying unit (Balzers) for 8-12 h at -50 to -40 degrees C and 0.02 bar. Freeze-dried tissues were either vacuum-infiltrated at 45 degrees C and embedded undemineralized in Paraplast, or vacuum-infiltrated overnight at 4 degrees C and embedded undemineralized in glycol methacrylate. These procedures enabled enzyme cytochemistry for alkaline phosphatase and tartrate-resistant acid phosphatase, and immunocytochemical staining for collagen types I, III, and laminin to be performed on the same sections. No pretreatment of the sections was necessary to reveal collagen antigenicity. This study reveals the possibility of complementing immunocytochemical studies of extracellular matrix with enzyme cytochemistry and, above all, with the excellent tissue preservation and high resolution afforded by plastic embedding.

Animals↗
PubMed2006

Identification of cyanidin glycosides as constituents of freeze-dried black raspberries which inhibit anti-benzo[a]pyrene-7,8-diol-9,10-epoxide induced NFkappaB and AP-1 activity.

Dietary freeze-dried black raspberries inhibit tumor induction by N-nitrosomethylbenzylamine in the rat esophagus, but the constituents responsible for this chemopreventive activity have not been identified. We fractionated freeze-dried black raspberries and used mouse epidermal JB6 Cl 41 cells stably transfected with either a nuclear factor kappa B (NFkappaB)- or an activator protein 1 (AP-1)-luciferase reporter, and treated with racemic anti-benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), to assess the inhibitory effects of the fractions. The ethanol and water extracts of the freeze-dried black raspberries had inhibitory activity and these extracts were fractionated by HPLC to give several bioactive fractions. Further HPLC analysis yielded multiple subfractions, some of which inhibited BPDE-induced NFkappaB activity. Major constituents of the most active subfractions were identified by their spectral properties and in comparison with standards as cyanidin-3-O-glucoside, cyanidin 3-O-(2(G)-xylosylrutinoside) and cyanidin 3-O-rutinoside. Analysis of freeze-dried black raspberries indicated that these three components comprised approximately 3.4% of the material by dry weight. Consistent with these results, standard cyanidin-3-O-glucoside and cyanidin chloride were also good inhibitors of BPDE-induced NFkappaB activity. The results of this study demonstrate that cyanidin glycosides of freeze-dried black raspberries are bioactive compounds which could account for at least some of the chemopreventive activity observed in animal models.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗