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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

As has been known for several years, thoroughly purified ribosomes contain a firmly bound serine proteinase with an optimum of activity at neutral pH. The present paper shows that the activity is found in free cytoplasmic ribosomes as well as in ribosomes detached from the membranes of the endoplasmic reticulum of rat liver. After ribosome dissociation, the proteinase activity is found only on the 40 S subunits. Recovery of the proteinase in the proteins of whole ribosomes or of 40 S subunits amounts to 44 and 65%, respectively. Ribosomes purified both from plant (Euglena) and bacterial (Acinetobacter) cells contain a serine proteinase having an activity quite comparable to that of rat liver ribosomes. In view of the recommendations of BARRETT et al. ( in REICH, RIFKIN and SHAW (eds).: Proteinases and Biological Control, Cold Spring Harbour Lab., 1975, p. 481), who no longer restrict the name "cathepsin" to acid or even lysosomal proteinases, we propose the name " ccathepsin R" for this ribosomal serine proteinase.
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PMID:The ribosomal serine proteinase: cathepsin R. 4 62

The authors studied the ultrastructure of benign and malignant forms of the thyroid cold nodule. In the benign cold nodule the most striking feature was an irregular endoplasmic reticulum with large cisternae and scarce ribosomes, this meaning an impaired protein synthesis. Frequent lysosomes and phagolysosomes occurring in the apical zone of the cell were present. In the malignant form of the cold nodule, nuclear abnormalities, a reduced endoplasmic reticulum and a highly increased number of abnormal mitochondria were found. The increased number of mitochondria in the carcinoma is a compensatory reaction to the frequent abnormalities found in these organelles. No transitional ultrastructural stages could be established between benign and malignant cold nodules. In practice the nature of a cold nodule is established by thyroid surgery and histologic examination.
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PMID:Electronoptical aspects of the thyroid cold nodule. 52 46

Two forms of cellulase, buffer soluble (BS) and buffer insoluble (BI), are induced as a result of auxin treatment of dark-grown pea epicotyls. These two cellulases have been purified to homogeneity. Antibodies raised against the purified cellulases were conjugated with ferritin and were used to localize the two cellulases. Tissue sections were fixed in cold paraformaldehyde-glutaraldehyde and incubated for 1 h in the ferritin conjugates. The sections were washed with continuous shaking for 18 h and subsequently postfixed in osmium tetroxide. Tissue incubated in unconjugated ferritin was used as a control. A major part of BI cellulase is localized at the inner surface of the cell wall in close association with microfibrils. BS cellulase is localized mainly within the distended endoplasmic reticulum. Gogli complex and plasma membrane appear to be completely devoid of any cellulase activity. These observations are consistent with cytochemical localization and biochemical data on the distribution of these two cellulases among various cell and membrane fractions.
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PMID:Subcellular localization of cellulases in auxin-treated pea. 76 48

Glomeruli of canine kidneys were studied by light and electron microscopy to determine whether significant structural alterations occur during 24 hr of hypothermic perfusion. The kidneys of eight dogs were preserved by continuous pulsatile perfusion with cold cryoprecipitated plasma; they were subsequently reimplanted as autographs and contralateral nephrectomy was performed at that time. Biopsies of the experimental kidneys were taken before nephrectomy, after 24 hr of perfusion, and at 1 hr postanastomosis. Tissue samples from two animals were studied at autopsy. Structural changes observed in the glomeruli after preservation were: margination of nuclear chromatin, nuclear pyknosis, and dilation of smooth and rough endoplasmic reticulum membranes. These changes were observed in all cell types, but were more severe in the endothelial cells. The basement membrane in four cases was edematous and thickened. At 1 hr postanastomosis the glomerular ultrastructural appearance was greatly improved. Blood urea nitrogen, serum creatinine, and the ability of the kidney to sustain the life of the recipient were used as criteria for determining the viability of the preserved kidneys. Blood urea nitrogen and serum creatinine returned to a normal range in five dogs. The physiologic tests and the length of survival attest to the functional capability of the preserved kidneys. Study of tissue samples at autopsy indicated that, although a number of the structural alterations observed after preservation were reversible, some changes persisted.
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PMID:Canine renal glomerular ultrastructural changes after preservation and autotransplantation. 87 Apr 41

Ultrastructural investigations have been carried out on parthenogenetic rabbit eggs in an effort to elucidate events occurring during artificial activation and their similarity to processes of fertilization and embryogenesis. Rabbit eggs were artificially activated by culturing at 10 degrees C for 24 hours followed by incubation at 37 degrees C for 2 to 24 hours. Examination of eggs immediately after incubation at 10 degrees C for 24 hours indicates that activation is initiated when the chromosomes coalesce to form a reticulum which is either surrounded completely by two parallel membranes or incompletely by cisternae of smooth endoplasmic reticulum. Aggregation of the chromosomes occurs as a result of a reduction in the number of microtubules making up the meiotic spindle. When cold treated ova are subsequently incubated at 37 degrees C a nucleus is formed which moves central where it may participate in the cleavage of the egg. Formation of a second polar body and release of the contents of the cortical granules as reported for inseminated eggs was not found to be a part of activation of the egg by cold treatment. Approximately 95% of the ova cultured at 10 degrees C for 24 hours followed by 37 degrees C for 12 hours were activated, i.e., they possessed a nucleus or they had cleaved. Many of the activated eggs cultured for short periods at 37 degrees C were structurally similar to fertilized ova, with further incubation fragmented eggs and abnormal multicellular stages predominated.
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PMID:Ultrastructural analysis of artificially activated rabbit eggs. 112 13

In lizards (Sceloporus undulatus), long term (13 or 19 weeks) acclimation to an environment of 6 degrees C produces a striking increase in the argyrophilic neurofibrillar network in most large perikarya of the trochlear nucleus. In electron micrographs the cells contain numerous bundles of 10-30 regularly-spaced 90 A neurofilaments. In the cells from warm acclimated animals, a plexus of neurofibrils is seen by light microscopy. The electron micrographs show scattered neurofilaments and fewer, thinner bundles than in the cold. Within the cell bodies of the cold animals, glycogen particles are organized in regional accumulations from which other organelles are excluded except for the bundles of neurofilaments which are distributed throughout the cytoplasm. The aggregations of rough endoplasmic reticulum (RER) are also penetrated by the neurofilament bundles. The increased neurofilamentous network in the cold is not accompanied by obvious changes in the amount or distribution of RER or of microtubules which are present in limited numbers in both conditions. The dendrites of trochlear cells and axon terminals within the nucleus also show a cold induced increase in neurofilaments, as well as in the distinctive accumulations of glycogen particles.
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PMID:Neurofilament and glycogen changes during cold acclimation in the trochlear nucleus of lizards (Sceloporus undulatus). 115 43

Cytochrome c, a "mobile electron carrier" of the mitochondrial respiratory chain, also occurs in detectable amounts in the cytosol, and can receive electrons from cytochromes present in endoplasmic reticulum and plasma membranes as well as from superoxide and ascorbate. The pigment was found to dissociate from mitochondrial membranes in liver and kidney when rats were subjected to heat exposure and starvation, respectively. Treating cytochrome c with hydroxylamine gives a partially deaminated product with altered redox properties; decreased stimulation of respiration by deficient mitochondria, increased reduction by superoxide, and complete loss of reducibility by plasma membranes. Mitochondria isolated from brown adipose tissue of cold-exposed rats are found to be sub-saturated with cytochrome c. The ability of cytochrome c to reactivate reduced ribonuclease is now reinterpreted as a molecular chaperone role for the hemoprotein.
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PMID:Functions of cytochrome c in regulation of electron transfer and protein folding. 132 35

The influence of different temperature and nutrition regimes on the acute toxicity of 4-chloroaniline to golden ide (Leuciscus idus melanotus) was investigated. Acute toxicity was determined over 48 hr at 20 degrees C without feeding after a 2-day acclimation period. In an attempt to reveal underlying mechanisms accounting for diet- and temperature-related differences in the toxicant resistance of golden ide, biochemical and quantitative morphological parameters of the liver, a central organ in the xenobiotic metabolism of fish, were recorded throughout the 12-week acclimation period. In cold-acclimated fish, acute toxicity of 4-chloroaniline was 40% higher than in fish acclimated to 20 degrees C. If compared to 20 degrees C, preacclimation to 14 degrees C was characterized by a lower specific growth rate, an increase of hepatic glycogen, and a decrease of body and liver lipid deposits. The organelle composition of hepatocytes was not significantly altered by temperature acclimation. For the nutrition experiment, commercially available diets A and B of similar crude composition were used. Acute toxicity of 4-chloroaniline was 60% lower with diet B than with diet A. If compared to diet B, diet A induced a higher specific growth rate and increased hepatocellular volume of endoplasmic reticulum and Golgi fields, whereas glycogen and lipid of the liver as well as body lipid contents were reduced. The toxicity of 4-chloroaniline was correlated with the development of the endoplasmic reticulum, the major site of biotransformation enzymes. A consistent correlation with lipid contents could not be established. Results illustrate not only that assay conditions during the actual test may profoundly interact with results of toxicity studies, but also that maintenance conditions before the test can have significant consequences on results. In order to improve reproducibility of the results of acute toxicity tests, more consideration should be given to the standardization of pretest maintenance conditions of fish.
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PMID:Preexposure temperature acclimation and diet as modifying factors for the tolerance of golden ide (Leuciscus idus melanotus) to short-term exposure to 4-chloroaniline. 138 81

We describe two proteins of 24 kDa and 33 kDa (p24 and p33) which associate with H-2 Kb and H-2 Db molecules, respectively, in human cells transfected with H-2 Kb and H-2 Db genes. This association is particularly clear in the mutant cell line T2, in which association of endogenous peptide with newly synthesized class I molecules may not occur (V. Cerundolo et al., Nature 1990. 345: 449). We show that p33 is the 33-kDa form of the human invariant chain which is resident in the endoplasmic reticulum of T2 cells (P. Cresswell, Cold Spring Harbor Symp. Quant. Biol. 1989. LIV:309). The stability of the invariant chain H-2 Db complex is critically dependent upon occupation of the class I binding site by peptide ligand. In the absence of peptide, the complex is stable at 4 degrees C whereas following exposure to peptide, the invariant chain dissociates rapidly from H-2 Db molecules (half-life of 30 min at 4 degrees C). Although the interaction between the human invariant chain and murine H-2 Db is unlikely to have any functional significance, the peptide-induced dissociation of the invariant chain is consistent with a conformational change in H-2 Db on peptide binding.
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PMID:Association of the human invariant chain with H-2 Db class I molecules. 151 17

In 1925, Wilson listed, in his classic third edition of Cell in Development and Heredity, four theories for the morphological and physiological characteristics of cytoplasm; each theory provided some sort of explanation as to the mechanism(s) of organelle translocations. During the past twenty years, cell biologists have focused their attentions on the cell's cytoskeleton, microtrabecular lattice, and associated mechanochemical motors which drive organelles along cytoskeletal tracks. A number of cell types have been used to study organelle translocations, but chromatophores, pigment cells, from cold-blooded vertebrates have been one of the more popular models. This article reviews some of the research findings during the past twenty years, particularly those involving cytoplasmic elements: i.e, microfilaments, intermediate filaments, microtubules, and mechanochemical motors. In addition, it contrasts the proposed involvement of these elements in organelle translocations with the endoplasmic reticulum, a tubulovesicular organelle, which we recently demonstrated is responsible, through its elongation or retraction, for the translocations of carotenoid droplets in goldfish xanthophores and swordtail fish erythrophores. Here, the carotenoid droplets are not free in the cytoplasm and do not translocate via cytoskeletal tracks, but instead are attached to or are a part of the endoplasmic reticulum. On the other hand, carotenoid droplets of squirrel fish erythrophores are free in the cytoplasm and appear to translocate via microtubules. Finally, the rates of pigmentary organelle translocations are reviewed in light of the participation of the cytoskeletal elements with the endoplasmic reticulum.
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PMID:Does the introduction of a new player, the endoplasmic reticulum, create more or less confusion in understanding the mechanism(s) of pigmentary organelle translocations? 163 Oct 22


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