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At least 307 records · Page 17Linked to original sources
PubMed1986

The morphology of pial blood vessels of the frog, preserved by rapid freezing and freeze substitution.

Vesicular profiles in endothelial cells of frog meninges were examined in tissues preserved by rapid freezing or conventional chemical fixation. Tissues were frozen immediately after removal from the animal or after remaining in Ringers for several hours. Vesicular profiles with an average diameter of 240 nm were present in the endothelial cells in all experimental groups, demonstrating that they are not an artifact of chemical fixation or incubation in vitro. However, their concentration and morphology varied with the different preservation techniques.

Animals↗
PubMed1991

Direct determination of myosin filament symmetry in scallop striated adductor muscle by rapid freezing and freeze substitution.

Chemically skinned, relaxed bundles of fibers from the striated adductor muscle of the scallop Placopecten magellanicus were rapidly frozen and freeze-substituted. In the electron microscope, ultrathin transverse sections of embedded specimens showed, in many cases, clear regularly organized projections (crossbridges) protruding from the backbones of the myosin filaments. In the majority of cases the number of projections was directly observed to be seven: this was confirmed by alignment and averaging of the images using correlation methods. The rotational power spectrum of the average image showed a strong peak at N = 7. Tilting of sections in the electron microscope showed that the long-pitch crossbridge helices were right-handed. These and other observations confirm directly the essential features of the low-resolution three-dimensional helical reconstruction of negatively stained scallop filaments calculated previously.

Animals↗
PubMedDate not supplied

The purification of red cells for transfusion by freeze-preservation and washing. V. Red cell recovery and residual leukocytes after freeze-preservation with high concentrations of glycerol and washing in various systems.

Red blood cells freeze-preserved with 40% W/V glycerol in an ionic or low ionic medium at -80 C were washed in one of four commercially available systems: the Haemonetics Blood Processor 15 using a continuous-flow centrifugation procedure, the Fenwal Elutramatic using a continuous-flow centrifugation procedure, the IBM Blood Processor using an automated serial centrifugation procedure, and the Huggins Cytoglomerator using a dilution/agglomeration procedure. Determinations of red blood cell recovery and leukocyte and platelet removal were made for each of these groups. The dilution/agglomeration procedure produced lower red blood cell recovery values and poorer leukocyte and platelet removal than did any of the three wash systems using sodium chloride solutions. The values obtained with the systems using sodium chloride solutions were slightly but significantly different.

Blood Platelets↗
PubMed1981

Freeze-fracture cytochemistry: localization of wheat-germ agglutinin and concanavalin A binding sites on freeze-fractured pancreatic cells.

The combined application of thin-section and critical-point-drying "fracture-label" is used to determine the pattern of distribution and partition of wheat-germ agglutinin and concanavalin A binding sites on the membrane faces of freeze-fractured exocrine and endocrine rat pancreatic cells. Whereas the exoplasmic face of plasma membrane is preferentially labeled by both lectins, the endoplasmic reticulum and nuclear envelope are strongly and uniformly labeled by concanavalin A but not by wheat-germ agglutinin. The results support current views in the glycosylation of membrane proteins and do not support the backflow of sialidated glycoproteins to the endoplasmic reticulum.

Animals↗
PubMed1997

Effect of anti-freeze protein (AFP) on the cooling and freezing of equine embryos as measured by DAPI-staining.

Equine embryos recovered on Day 6 after ovulation were cooled to +4 degrees C, or frozen with AFP alone or together with glycerol. Twenty embryos (140-200 microm in diameter) were randomly assigned to 6 treatment groups. In the first 3 groups, the embryos were cooled from room temperature to +4 degrees C at a rate of 3 degrees C/min and warmed again at a rate of 32 degrees C/min in a programmable freezer. In the second 3 groups, the embryos were frozen using a standard protocol, stored in liquid nitrogen for 5-7 days and then thawed in a 37 degrees C waterbath. After cooling/warming or freezing/thawing all the embryos were stained with DAPI. The percentage of dead cell area was significantly lower in the cooling groups than in the freezing groups and no significant differences were apparent between the cryoprotectants used in the study.

Animals↗
PubMed1989

Immunocytochemical localization of amylase in gerbil salivary gland acinar cells processed by rapid freezing and freeze-substitution fixation.

We examined the immunocytochemical localization of amylase in cryofixed serous acinar cells of gerbil major salivary glands by indirect immunostaining, using anti-gerbil parotid amylase antibody and protein A-gold complex. Fresh tissue blocks were quickly frozen by the metal-contact method, using liquid helium, and were freeze-substituted with either osmium-acetone solution or glutaraldehyde-containing acetone. They were then embedded in an epoxy resin mixture which was polymerized at 60 degrees C. Some tissue blocks substituted with aldehyde-acetone solution were embedded in Lowicryl K4M, polymerized at -30 degrees C. Thin sections of epoxy resin-embedded materials were treated with an oxidizing agent before immunostaining. The labeling density on the materials processed by various protocols for preparatory procedures was quantitatively compared to examine the usefulness of application of cryofixation to immunocytochemistry. The central dense core of heterogeneous secretory granules in the serous acinar cells of the parotid and sublingual glands was heavily labeled with immunogold, regardless of substitution media and embedding resins employed. The immunolabeling pattern clearly distinguished between the dense core and the surrounding matrix. Labeling density in the cryofixed materials was about 1.5 times greater than in those processed by conventional chemical fixation. Seromucous secretory granules in the submandibular gland acinar cells were only faintly labeled. The results obtained indicate that application of immunostaining to quick-frozen, substitution-fixed tissues is useful for high-resolution immunocytochemistry.

Amylases↗
PubMed1990

[Biochemical values in erythrocytes before freezing and after freezing at low temperatures].

The authors tested three ways of freezing red cell concentrates with glycerin. At -30 degrees C in a deep freezer; on a Planer at the rate of 1 degree C per minute and by immersion into liquid nitrogen to -196 degrees C, stored in cryo-containers in liquid nitrogen. In samples processed in all three ways, incl. the follow-up of glycolysis in red cell concentrates in acid-citrate-dextrose solution, the levels of the following enzymes were assessed: glucose-6-phosphate dehydrogenase, glutathione reductase, pyruvate kinase. In addition also the levels of sodium, potassium, pH and glucose were assessed. The enzyme estimations of all three mentioned enzymes after triple rinsing with saline in the samples immersed in liquid nitrogen at -196 degrees C had the most acceptable values and smallest losses after rinsing.

Erythrocytes↗
PubMed1996

To freeze or not to freeze. A comparison of methods for the handling of breast biopsies with no palpable abnormality.

Recently there have been several editorials suggesting that breast biopsies with small or nonpalpable lesions should not be subjected to frozen section examination. In this study, the approach of routinely performing frozen sections on all breast biopsies was compared to the recommended approach of performing frozen sections only on cases with gross lesions < 1.0 cm. From July 1, 1992 through June 30, 1993, there were 444 breast biopsies submitted. Nearly all of these (98%) had frozen sections performed. Among these cases, there were 14 false-negative frozen section diagnoses equating to a frozen section sensitivity of 84%, and a frozen section false-negative rate of 3.3%. From July 1, 1994 through June 30, 1995, there were 601 breast biopsies submitted. Of these cases, 310 contained a gross lesion > 1.0 cm and were subjected to frozen section examination. The remaining 291 cases contained either no distinct lesion or a gross lesion < 1.0 cm. These cases were not frozen. Among the 310 cases that were frozen, there were 3 false-negative frozen section diagnoses equating to a frozen section sensitivity of 96%, and a frozen section false-negative rate of 1.0%. These findings indicate that careful gross examination combined with selective freezing of only cases containing a gross lesion > 1.0 cm improves frozen section accuracy. This study provides statistical support for previous recommendations that frozen section examination should be limited to cases with distinct gross lesions > 1.0 cm.

Biopsy↗
PubMed1991

Immunoelectron microscopy of acetylcholine receptors and 43 KD protein after rapid freezing, freeze-substitution, and low-temperature embedding in lowicryl K11M.

To label intracellular determinants of the acetylcholine receptor and associated cytoplasmic proteins while preserving optimal ultrastructure, we developed a post-embedment labeling technique that uses rapid-frozen specimens and freeze-substitution without chemical fixatives. This procedure has been made possible through the use of a low-temperature resin (Lowicryl K11M) that can be polymerized with UV light at -60 degrees C. Rapid-frozen muscle cells were used to evaluate the preservation of structure, and Torpedo electroplaque cells and purified postsynaptic membranes were used to quantitatively evaluate the labeling specificity, efficiency, and resolution of the technique. The labeling efficiency of seven different monoclonal antibodies (MAb) to the acetylcholine receptor varied from 3-13%; there was a correlation between the degree of efficiency and the number of epitopes with which the antibodies reacted. The resolution of the technique was not sufficient to determine whether the anti-acetylcholine receptor MAb were bound to the cytoplasmic or the extracellular surface, but was sufficient to correctly determine the location of the receptor-associated 43 KD protein on the cytoplasmic surface.

Acrylic Resins↗
PubMed1995

Immuno-gold-labelling of CUT-1, CUT-2 and cuticlin epitopes in Caenorhabditis elegans and Heterorhabditis sp. processed by high pressure freezing and freeze-substitution.

CUT-1 and CUT-2 are two distinct protein components of cuticlin, the insoluble residue of the cuticles of nematodes. In previous experiments of gold-immuno-labelling on sections of chemically fixed Caenorhabditis elegans, CUT-1 and CUT-2 epitopes were specifically lost. Cryo-immobilization of C. elegans under high pressure followed by freeze-substitution, however, resulted in a good preservation of these antigenic sites and of the ultrastructure of the worms. The entomopathogenic nematode Heterorhabditis sp. processed by the same cryopreparation protocol has shown a strong reactivity with anti-sera raised against CUT-1, CUT-2 and against the whole cuticlin residue of C. elegans. The localization of these epitopes was conserved across the two species.

Animals↗