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Summary At 30 to 60 min after infection of primary rabbit kidney cells with Shope fibroma virus, the majority of virus particles were found within dense granules identified as lysosomes, whereas by 24 h no particles could be observed. The lysosomes appeared to become more fragile as infection proceeded, cellular proteins being progressively released from 7 to 24 h. Extracted lysosomal enzymes had no effect on purified Shope fibroma virus.

1. The centrifuge method was used to determine protoplasmic viscosity in cortex cells (and in some instances in ray and pith cells) of bean petioles and stems which had been daubed with lanolin preparations of indole-3-acetic acid, indole-3n-propionic acid, and α-naphthalene acetic acid. 2. Unilateral applications of the growth substances initially conditioned negative curvatures, in which instances the protoplasmic viscosity was lower in cells on the faster growing sides of the petioles and stems than in cells on the slower growing sides, and likewise lower than in control petioles or stems. When subsequent positive curvatures resulted, the viscosity was decreased about equally on the treated and untreated sides, except in the case of petioles treated with a paste containing 100 mg. of indole-3n-propionic acid per gram of lanolin, in which instance the viscosity was lower on the untreated sides. 3. Applications of indole-3n-propionic acid or α-naphthalene acetic acid to the tops of decapitated plants res...

1. The centrifuge method was used to determine the structural viscosity of protoplasm in leaf cells of Mnium sp. and Bryum sp. which had been dried for periods up to 50 minutes. In other experiments with Mnium, dried plants were placed in water and the viscosity determined after periods varying from 15 to 90 minutes. 2. Incipient drought conditioned a decrease in the structural viscosity as a consequence of protein dissociations. During the recovery period a decrease in viscosity preceded the return to normal. 3. It is suggested that the dissociation of cellular proteins by incipient drought conditions an increased protoplasmic swelling pressure, accelerated rates of respiration and polysaccharide hydrolysis and may at times lead to mitotic abnormalities.

Summary Evidence is presented that in the malignant cell of rat liver tumours a highly specific cellular protein has either been lost or has been modified; this is judged by the cell's control the growth of tissues and organs and, in ordinary circumstances, limit the proliferation of tissue cells. The significance of these observations in human neoplasms is as yet uncertain. However, this is being studied and if the staining technique should prove applicable it will be not only a valuable method of investigating tumours but possibly also important in differentiating tumour-like masses from true neo-plasms.

It has been established (2, 12) that intact tissues of higher plants readily incorporate C14-labeled amino acids into their cellular proteins. In addition, evidence has been presented (11) that an isolated mitochondrial fraction from bean seedlings is capable of incorporating several amino acids. This incorporation into mitochondrial protein is of particular interest as it closely resembles the synthesis of simple peptides (14, 15, 16) in its dependence on the respiratory energy of adenosinetriphosphate (ATP). The ability of such an isolated cellular fraction to incorporate amino acids makes a further study of cell-free systems of interest. The sole purpose of the present investigation has been to study in some detail the incorporation of amino acids into the proteins of cell-free extracts of higher plants. The present communication reports results on the nature of the incorporation process and on the partial purification and properties of a particulate system from pea seedlings that incorporates amino acids at relatively high rates.

It has been known for many years that cultures of bacteria can be cooled to very low temperatures without destroying all the cells present (see, for example, MacFadyen and Rowland 1900). More recently the preservation of bacteria and sera by rapid freezing and drying has come into general use. The fundamental changes accompanying these processes have not so far been investigated in much detail. This paper presents the results of experiments on the effects of cooling and freezing at various temperatures on a number of bacterial species, and an attempt to correlate the observed effects of freezing on viability with the effect of freezing on the cellular proteins of B. pyocyaneus [Pseudomonas aeruginosa] . Hypotheses previously put forward to explain the observed effects of low temperatures on living cells may be briefly summarized under three headings

The oxidized tannin-azo (OTA) method was used to study the location of tannophilic protein in hepatic cells. In this method tannic acid was first attached to the tissue proteins and then oxidized with periodic acid; the oxidized tannin, which was firmly bound to the cellular proteins, was subsequently converted to a highly coloured azo dye by coupling with diazotized o-dianisidine. Preliminary deamination with nitrous acid markedly diminished the capacity of hepatic cells to stain with OTA; this indicates that -NH3 groups in the tissue proteins are the principal loci revealed by the OTA method. Sections of liver, after tanning and oxidation, were also treated with 6-amino-3-dimethylaminophenol; this technique produced intense colouration of the hepatic cells probably owing to the formation of an oxazine dye. The colouration of oxidized tannin by 6-amino-3-dimethylaminophenol confirms the view that bound tannin is oxidized by periodic acid to a 1–2-quinone.

The exchange of phospholipids between chick embryo fibroblasts and their growth medium was studied. It was found that the phospholipids of secondary chick fibroblasts, labeled with 32 PO 4 or 14 C-choline, were continuously released into the growth medium. The release was dependent on the serum concentration of the medium; the greater the serum concentration, the greater was the rate of release. At 4 °C, there was very little release of phospholipid even in the presence of serum. Measurement of the appearance of DNA in the medium indicated that there was little death or disintegration of cells and, therefore, that phospholipids were released from living cells. The released phospholipids appeared to be associated with proteins, and these lipid-protein complexes could be fractionated by gel filtration into two fractions, having estimated molecular weights of 250,000 Daltons and greater than 5,000,000 Daltons. It is suggested that some of the released phospholipids become associated with serum proteins through an exchange process, but also that there is a release and exchange of phospholipids which are associated with cellular proteins. When medium containing released, labeled phospholipids was added to unlabeled cells, the labeled phospholipids were taken up by the cells and an equilibrium between cells and medium was established.

The synthesis of non-histone chromosomal proteins in synchronized HeLa S3 cells was studied in 3 phases of the cell cycle: S, G2 and mitosis. A 70–90% decrease in the rate of synthesis of total cellular protein and of chromatin-associated protein fractions extractable with low salt concentrations or with dilute acid was observed in cells in mitosis. On the contrary, the residual non-histone chromosomal proteins were synthesized during mitosis at a rate which did not differ significantly from that of S and G2 phases. Thus, at variance with the other cellular proteins, acidic chromosomal proteins are synthesized at an undiminished rate even during mitosis, when there is complete cessation of RNA synthesis.

Experiments were carried out on male albino rats which were given 0.25 g of thyroidin per 100 g body weight for 10 days. Vital staining with neutral red was used to study the interaction between the tissues of the different viscera (spleen, lungs, liver, kidneys, heart, testes, brain, small intestine, and skeletal muscle). In the animals receiving thyroidin there was a change in the sorptive property of the tissue of the liver, kidneys, heart, testes, brain, small intestine and skeletal muscle, which was thought to result from denaturation of cellular proteins. The results obtained reflect the nature and specific features of pathological and compensatory reactions occuring in tissues under the influence of thyroidin.

In 1893, Audry1postulated that defective epidermal keratinization or cornification was the essential pathological feature of psoriasis. This hypothesis, based on histological studies, has been amply justified by recent biochemical investigations. However, before entering into a discussion of these recent findings, it would be well to reiterate Flesch's definition of the processes involved in cornification or rather in the maturation of the human epidermis.2He has called the consolidation of fibrous keratin precursorskeratinizationand the decomposition of cellular proteins or the formation of nonkeratinous components, in the horny layer,differentiation. These terms will be used forthwith in this paper. Concerning keratinization, it has been found that, in psoriasis, a fibrous protein can be extracted from the scales, which is similar or identical with tonofibrin, which has previously been isolated from normal cellular epidermis.3This protein appears to be a fibrous, keratin precursor

The use of acute labeling techniques (pulse labeling) has been successful in tracing and locating rapid metabolic pathways in vivo. This procedure was used in the classical experiments of Schoenheimer [1] on labile cellular proteins which gave rise to the concept of the dynamic state of body constituents. The concept described protein turnover as a continual process of synthesis and degradation as evidenced by the active uptake and release of isotopic compounds (see Fig. 1). Turnover represented the occurrence of synthesis which cannot be detected analytically because it was exactly balanced by breakdown [2]. Acute and chronic isotopic studies have demonstrated that the fibrous proteins of muscle and connective tissues have the least active turnover and are considered to be relatively inert metabolically [3, 4]—inert in the sense that the proteins were nonrenewable. However, these studies could not distinguish between essentially non isotopic turnover (nonsynthetic and nondestructive) of macromolecules and absolute inertness.

Journal Article, SCOPUS: ar.j, info:eu-repo/semantics/published

Identification of types of cellular proteins and determination of their patterns of distribution and association with nucleic acids may be regarded as essential to an understanding of the processes involved in duplication of the living cell. A more specific evaluation of these processes with respect to replication of the gene complex requires precise information concerning the organization of the chromosome and the arrangement of its constituent materials during the various phases of mitosis. Inferences concerning the chemical composition of chromosomes derived from the earlier observations of descriptive cytologists have been supplemented in recent years by information provided by a variety of experimental procedures. Descriptions of patterns of linear organization in terms of achromatic and chromatic materials have accordingly been replaced by descriptions in terms of proteins and nucleic acids.

Radial diffusion of protein antigens through gels containing antibodies has been used to quantitate proteins derived from cellular origins. For quantitation, the diameters of radial precipitin zones formed by tissue extracts were compared with zones formed by known concentrations of the standard proteins. The method employs immunological features of specific proteins to measure concentrations within the range of sensitivity usually obtained only with enzymic analyses.

A 30-sec. pulse of tritiated leucine was given to logarithmically growing cells of Escherichia coli during induction with either melibiose or galactose. β-Galactosidase was thereafter isolated, and its specific radioactivity compared to that of the average cellular protein. Melibiose-induced enzyme had one-third and galactose-induced enzyme twice the specific radioactivity of the average cellular protein. These results suggest that β-galactosidase, when melibiose-induced, is more stable than the average cellular proteins, and that alterations in its turnover may be involved in the mechanism of its induction.

SummaryEhrlich ascites cells were incubated in vitro with radioactive amino acids or radioactive ascites proteins prepared biosynthetically. Incubations with free amino acids resulted in accumulation of large amounts of radioactivity in the acid-soluble fraction and in incorporation of radioactivity into the proteins. Incubations with labeled proteins resulted in labeling of cell proteins without significant accumulation of radioactivity in the acid-soluble fraction. Radioactive proteins were isolated from various cell fractions of ascites cells following incubation with labeled free amino acids or proteins. These results suggest that proteins enter ascites cells where they are utilized for synthesis of cellular proteins; free amino acids do not appear to be intermediates in this process.

THE monomer molecular weight distribution in the total proteins of various cell types is unknown. A list has been compiled1 for purified proteins of which the molecular weights of the monomeric subunits are known. Large polypeptides are rare; only about 20 per cent of the listed monomeric proteins are larger than 80,000 daltons. The overall size distribution of cellular proteins may be inferred from such data, but it would never be possible to be sure that these extensively purified proteins represented a truly random sample.

The preparation of highly purified L, M, and S plaque-type variants of Mengo virus is described, and data are presented to show that the purification procedure eliminates at least 99.92% of cellular proteins and nucleates. The nucleotide compositions of the ribonucleates and the amino acid compositions of the proteins isolated from the three virions are strikingly similar. However, surface (charge) differences between the variants do exist, as evidenced by differences in elution profiles obtained from chromatography on hydroxylapatite, and it has been shown that these differences can be exploited to separate L-Mengo from either of the other two variants.

Ethacrynic acid, injected intravenously after surgical removal of one kidney of anesthetized dogs, lowered the concentration of protein-bound sulfhydryl groups in cells of the remaining kidney. Chloride excretion and urinary output of the kidney exposed to the drug increased. These findings indicate that the diuresis produced by ethacrynic acid may be related to its capacity for binding sulfhydryl groups of renal cellular proteins.

A study of the kinetics of sulfur incorporation into the molecule of β-galactosidase during the induced synthesis of this enzyme in E. coli brings proof that the enzyme-protein is synthesized entirely de novo without any appreciable participation of materials coming from other cellular proteins. Furthermore, there is no measurable renewal of β-galactosidase sulfur in growing cells whether or not the enzyme is being synthesized. The induced synthesis of β-galactosidase appears as a virtually irreversible process. The bulk of the other cellular proteins in E. coli are equally stable and do not undergo any appreciable degradation and resynthesis during growth. The apparent contradiction between these results and the generally accepted concepts regarding the dynamic state of intracellular proteins is discussed.

The rates of removal of intravenously injected folate, dihydrofolate and tetrahydrofolate from blood serum of rats have been found to be rapid and similar. Over the wide concentration range examined it was found that the proportions of the injected doses of folate and reduced folate retained in the body varied only between 25 and 50 per cent, the remainder being excreted in the urine. ‘Flushing’ injections of folate or methotrexate were found to be equally effective in removing a small proportion of the retained folate. The suggestion is made that the removal of injected folate from the blood stream into the body is not associated with a specific uptake mechanism nor with folate-utilizing enzymes. It has been found that folate and dihydrofolate are capable of being bound onto serum, but that this binding can be reversed by electrophoresis in a density gradient column. The results could indicate that the removal of folate from the blood is by means of a non-specific binding onto cellular proteins similar to the observed binding to serum.

Ultracentrifugal and electron microscopic data are presented on ribosomes from cells of baker's yeast which were cultured in nutrient and starving media. The sedimentation patterns show that the gamma - or 65S-peak is present only in the growing ribosomes. Some of the ribosomes were irradiated with x rays in an attempt to split some of the components; little or no change occurred in the sedimentation constants. The results are discussed with respect to the theory of ribosomes being the synthetic site for cellular proteins and to the role of the 65S yeast ribosome, and comparative structures and sedimentation rates are given for ribosomes of E. coli and yeast. (D.J.C.)

Chlorpromazine and 16 other phenothiazine derivatives induced up to 11-fold increases in phenylalanine ammonia lyase activity and the de novo synthesis of up to 200 μg pisatin per g of pea pod tissue. The induction of phenylalanine ammonia lyase was dependent on new RNA and protein synthesis and was accompanied by increased synthesis of an array of cellular proteins.

WHEN the replication of density-inhibited cultures of fibroblasts1,2 is stimulated by a change of medium3–5, the rate of nuclear acidic protein synthesis10–13 is immediately increased. We wanted to determine whether the induction of cellular DNA synthesis by an oncogenic virus6–9 is also preceded by nuclear acidic protein synthesis. We report here the effect of SV40 virus infection of a permissive and a non-permissive cell line on their synthesis of total cellular proteins and nuclear acidic proteins in the first hours after infection.

Ever since the careful studies of Vaughan, Novy and others on the intracellular constituents of bacteria, considerable attention has been paid to these substances. Various procedures have been devised for the purpose of putting the endocellular materials into solution or into suspension, and such preparations have been subjected to chemical analysis or to tests of toxicity and antigenic activity, often on the assumption that the fractionated extracts contained compounds existing under natural conditions in the living cell. There would appear to be some doubt concerning the validity of such a blanket assumption, particularly as it applies to cellular proteins, for recent work, especially that of Anson and Mirsky,1 has tended to revise the classic concept of protein denaturation, making of it a much more comprehensible process and one occurring more widely than was previously supposed. In the light of this understanding it is safe to say that many of the processes of cell extraction, utilizing drastic treatment of the cells with heat or chemicals, or both, result in partial or complete denaturation of the cell proteins. The very real role which such factors may play is perhaps best exemplified by the single item of denaturation by heat, for which the temperature coefficient (Qioo) is in the neighborhood of 600. This unique figure, three hundred times greater than that holding for ordinary chemical reactions, indicates that even the very moderate temperatures commonly employed in preparing vaccines result in partial or complete denaturation of the cellular proteins. This, in turn, renders difficult the interpretation of immunization experiments as well as tests of toxicity, since Cutler 2 showed that the immune response to native protein is quite different from that exhibited toward denatured protein, and Vaughan 3 recorded numerous instances in which extremely toxic substances were obtained by the chemical treatment of atoxic cells. Further, the experiments of Anson and Mirsky reveal the remarkable ease with which denaturation may proceed under a variety of chemical conditions.

The work of Vaughan, his associates and others interested in protein poisons has established the relationship of these substances to local and general anaphylactic reactions. Some of the reactions following the injection of bacterial vaccines are undoubtedly due to extraneous medium proteins which have not been removed from the bacterial suspensions in the prevalent process of manufacture. Since in the preparation of bacterial vaccines we are concerned only with the immunizing properties of the cellular proteins, it should be our aim to reduce, so far as possible, the amount of extraneous proteins in the method employed. Most of the commonly employed mediums used for the growth of bacteria contain protein substances. When the bacterial growth is washed or scraped from the surface of an agarslant, or separated by centrifugation from a bouillon culture, the soluble excretory products of the bacteria, as well as soluble medium products are present in considerable