GROWTH AND DIFFERENTIATION OF CYTOPLASMIC MEMBRANES IN THE COURSE OF LIPOPROTEIN GRANULE SYNTHESIS IN THE HEPATIC CELL : I. Elaboration of Elements of the Golgi Complex

The synthesis of "very low" density lipoprotein in liver cells is characterized by the fact that the synthesized products, mostly triglycerides, are processed in the form of discrete, size-limited granules or globules, about 400 A in diameter. The present investigation has been made possible in part by the use of a fixative (OsO4 in bidistilled H2O at pH 6.0, in the absence of electrolytes) particularly effective in preserving cytoplasmic membranes and lipids, and giving them high stainability and differential contrast. Under these technical conditions, the lipoprotein granules retain their morphology and high density to electrons practically unaltered, and may serve as tracers in determining their route of transport from the sites of synthesis, starting at the rough-smooth ER junctions, to the lumen of Golgi concentrating vesicles. From the observations, it may be deduced that, along with lipoprotein granule synthesis and transport, there are also production and transfer of new membranes in the form of tubular extensions of smooth ER network which, by progressive fusion and coalescence, participate in the elaboration of fenestrated plates and solid Golgi sacs. In contradistinction to the entire process of liver lipoprotein granule synthesis, transport, and segregation, as reported in the present paper, appears to constitute a developmental sequence which includes the following communicating compartments, in consecutive order: cisternae of rough ER where proteins and possibly phospholipids are synthesized, smooth ER network where triglycerides are synthesized and transported in the form of dense granules, fusion of smooth ER tubular extensions into Golgi fenestrated plates, and further coalescence into solid Golgi sacs, ending in the segregation of the granules in appended concentrating vesicles, or detached "secretory vesicles." It seems that it is this progressive evolution in growth and configuration of membranes which is reflected in the so called polarity, from forming to mature faces, of the Golgi apparatus

ELECTRON MICROSCOPE STUDIES OF CELLS BY THE METHOD OF REPLICAS

The method of replicas has been applied to the study with the electron microscope of blood cells and bacteria. The results indicate that the method can reveal details of intracellular structures. Nuclei can be perceived, and also cytoplasmic bodies such as mitochondria and vacuoles

SPREADING PROPERTY OF AZOPROTEINS IN THE DERMIS

1. Azoproteins are shown to have the property of spreading when introduced intradermally into the rabbit skin. 2. The aromatic derivative selected for the coupling does not affect specifically the spreading property of the azoprotein. Likewise, the type of protein has no importance, except in quantitative respects. 3. The spreading property conferred upon a protein by coupling appears to derive from the presence of the azo group. 4. The spreading power of an azoprotein preparation seems to be determined by the number of diazo groups which enter the protein molecule, and to vary in direct proportion with the concentration of the solution. 5. Azo compounds of low molecular weight fail to exhibit any significant effect on skin permeability

FRACTIONATION OF MAMMALIAN LIVER CELLS BY DIFFERENTIAL CENTRIFUGATION : I. PROBLEMS, METHODS, AND PREPARATION OF EXTRACT

Page 52, line 36, for 300µ read 300 mµ, and for 150µ read 150 mµ. Page 52, line 40, for 50µ read 50 mµ

THE CONSTITUTION OF MITOCHONDRIA AND MICROSOMES, AND THE DISTRIBUTION OF NUCLEIC ACID IN THE CYTOPLASM OF A LEUKEMIC CELL

1. Rat tumor extracts, containing chiefly the cytoplasmic constituents of leukemic cells, were fractionated into three main portions, the different components separating in the centrifuge according to size. 2. Mitochondria were isolated by centrifugation at relatively low speed. Elementary composition of purified mitochondria was found to correspond to about 11.5 per cent nitrogen, 1.6 per cent phosphorus, and 27 per cent lipids. Phosphorus and nitrogen content of the lipid portion suggests that as much as 75 to 80 per cent of the lipids of mitochondria is represented by phospholipids. Tests for ribose nucleic acid were positive. 3. Microsomes were separated by means of centrifugation at 18,000 x g. A relation between the high phosphorus content of the microsomes and the marked basophilia of the cytoplasm of leukemic cells is suggested. 4. Phosphorus distribution in the tumor extract, and light absorption analysis of the third fraction, seem to demonstrate that nucleic acid was not present either in a free condition, or in the form of nucleoprotein of relatively low molecular weight. The nature of the results suggests that ribose nucleic acid occurs in the cytoplasm of leukemic cells only in association with formed elements of relatively large size, namely microsomes, and mitochondria

THE ENHANCING EFFECT OF AZOPROTEINS ON THE LESIONS PRODUCED BY VACCINE VIRUS, THE SHOPE FIBROMA VIRUS, AND THE AGENT TRANSMITTING CHICKEN TUMOR I

It is known that azoprotein solutions, like testicular extracts, possess the property of causing particles to spread through the dermis. The present work shows that azoproteins exhibit, like testicular extract, the power to increase the size of virus lesions in the skin of rabbits, and the size of tumors in chickens. The results indicate that the extent of the lesion is roughly proportional to the spreading power of the solution. This suggests that the spread of the infective material, over a larger area of skin, is directly responsible for the enhancing effect. The production of extensive lesions by means of spreading agents may have a practical value when large amounts of working material are needed

SPREADING PROPERTIES OF LEECH EXTRACTS AND THE FORMATION OF LYMPH

1. The injection of leech extracts into the skin increases its permeability, as shown both by the spread of fluid and of foreign particles through the dermis. The spread is followed some hours after the injection by more or less edema of the subcutaneous tissue. 2. A preliminary study of the chemical properties of the leech spreading factor indicates a similarity with the spreading factor prepared from testicle. 3. Attempts to separate the leech spreading and anticoagulating factors showed that the two have practically the same distribution in the leech body, extracts from the separated head being the most active. 4. It is undetermined whether two distinct factors are responsible for the spreading and anticoagulating properties of leech extracts. A chemical similarity is suggested by the fact that agents which affect the activity of one factor have a parallel effect on the other. 5. The mechanism of the spread produced by leech extracts and by other spreading agents is discussed

PROPERTIES OF THE CAUSATIVE AGENT OF A CHICKEN TUMOR : X. CHEMICAL PROPERTIES OF CHICKEN TUMOR EXTRACTS

A brief description is given of the main physical and chemical characteristics of active chicken tumor extracts. By special methods constituents have been removed from the active solution: (1) the major part of the tumor-proteins, which are adsorbed on alumina gel and discarded; (2) a carbohydrate, present in large amounts in the tumor extract, is eliminated by precipitation in combination with gelatin. In both cases the tumor principle is not directly affected and largely remains in active form in the solution

FRACTIONATION OF MAMMALIAN LIVER CELLS BY DIFFERENTIAL CENTRIFUGATION : II. EXPERIMENTAL PROCEDURES AND RESULTS

1. A method is described whereby the major components of liver suspensions are segregated according to size into three main fractions: (a) a large granule fraction composed of elements approximately 0.5 to 2 µ in diameter; (b) a microsome fraction composed of submicroscopic elements approximately 80 to 150 mµ in diameter; and, (c) a supernate fraction containing the soluble components of the extract. 2. The nature and origin of the constituents of liver extract is discussed. The large granule fraction is deemed to consist mostly of mitochondria and liver secretory granules, whereas the microsome fraction corresponds to the chromophilic ground substance of the hepatic cell. Phosphorus distribution in the supernate fraction, and ultraviolet absorption of the solution suggests that practically all the ribose nucleoproteins of liver extract are sedimentable, and occur in association with the large granules and microsomes. 3. The method of fractionation of liver suspension by differential centrifugation is being used as a means to investigate the chemical constitution of the morphological constituents of cytoplasm, and the distribution of biochemical activities in the cytoplasm of the hepatic cell. 4. The method of differential centrifugation is found to be applicable not only to the fractionation of cells but also, with the aid of auxiliary techniques, to the fractionation of much smaller elements, such as mitochondria

« Re-connaître » et « Connaître » par les signes

Appliquées au domaine de la communication de masse, les théories du sémioticien américain Charles Sanders Peirce peuventelles rendre compte de l'interprétation des périodiques culturels? Il semble bien que oui, puisque conformément à l'une des définitions triadiques du signe, ce genre de textes commande avant tout la recherche d'une information connue a priori. À cette étape de la «reconnaissance» de l'objet d'une conception succède un apprentissage du réel par l'entremise d'un protocole contrôlé simultanément par l'auteur et le lecteur. Le mode d'inférence abductive, seul responsable de l'acquisition de « connaissances » nouvelles, n'est pas le favori des éditeurs de périodiques; il arrive néanmoins qu'il devienne dominant comme dans le cas du numéro 28 de la revue québécoise Vice -versa.When applied te the realm, of mass communication, can the theories of the American semiotician Charles Sanders Peirce account for the interpretation of cultural periodicals? The answers seems te be affirmative, since according te one of the triadic definitions fo the sign this species of text presupposes above all the search for information known a priori. This phase, of the « recognition » of the conceptual object, is followed by an apprehension of the real mediated by a protocol controlled at the same time by author and reader. The abductive mode of inference which alone can lead te the acquisition of new knowledge is not one favoured particularly by periodical editors, although it can occasionally predominate, as in the case of number 28 of the Québec review Vice-versa