Evaluation of the hepatotoxicological effects of a drug in an in vivo/in vitro model.

Both in vivo and in vitro models have certain disadvantages for the study of the chronic hepatotoxicity of drugs. The aim of this work was to evaluate a new approach based on an in vivo/in vitro model. After chronic in vivo treatment of rats with Vincamine and Vindeburnol (an eburnamenine derivative which exhibits hepatotoxic properties in man) liver cells were isolated, and functional and metabolic disorders (metabolic utilization of fructose and protein biosynthesis) were studied to determine injury. The results showed no modification of blood parameters, but a direct relationship between the dose of Vindeburnol administered in vivo and the metabolic disorders observed in vitro, evidencing the high sensitivity and reliability of this model.     

Hormonal control of Sertoli cell metabolism regulates spermatogenesis

Hormonal regulation is essential to spermatogenesis. Sertoli cells (SCs) have functions that reach far beyond the physical support of germ cells, as they are responsible for creating the adequate ionic and metabolic environment for germ cell development. Thus, much attention has been given to the metabolic functioning of SCs. During spermatogenesis, germ cells are provided with suitable metabolic substrates, in a set of events mediated by SCs. Multiple signaling cascades regulate SC function and several of these signaling pathways are hormone-dependent and cell-specific. Within the seminiferous tubules, only SCs possess receptors for some hormones rendering them major targets for the hormonal signaling that regulates spermatogenesis. Although the mechanisms by which SCs fulfill their own and germ cells metabolic needs are mostly studied in vitro, SC metabolism is unquestionably a regulation point for germ cell development and the hormonal control of these processes is required for a normal spermatogenesis.     

Evaluation of the hepatotoxicological effects of a drug in an in vivo/in vitro model

Both in vivo and in vitro models have certain disadvantages for the study of the chronic hepatotoxicity of drugs. The aim of this work was to evaluate a new approach based on an in vivo/in vitro model. After chronic in vivo treatment of rats with Vincamine and Vindeburnol (an eburnamenine derivative which exhibits hepatotoxic properties in man) liver cells were isolated, and functional and metabolic disorders (metabolic utilization of fructose and protein biosynthesis) were studied to determine injury. The results showed no modification of blood parameters, but a direct relationship between the dose of Vindeburnol administered in vivo and the metabolic disorders observed in vitro, evidencing the high sensitivity and reliability of this model.     

Lack of effect of dihydroergotamine on endothelial and smooth muscle cell proliferation and endothelial cell prostanoid production

The most important effect of dihydroergotamine is venoconstriction, but certain metabolic effects and changes in vessel prostanoid activity have also been suggested. In this study endothelial cell production of 6-keto PGF1 alpha and TxB2 was quantitated in vitro. No evidence of altered prostanoid production was noted after incubation with dihydroergotamine (exposure ranging from 5 x 10(-3) to 5 x 10(-7) g/l). Similarly, no effect of dihydroergotamine on the growth rates of endothelial cells or smooth muscle cells in vitro was documented.     

Electronmicroscopic identification of type C particles in cultured murine neuroblastoma.

Monolayer of murine neuroblastoma were treated with dexamethasone and examined by electronmicroscopy. Most of the treated cells were morphologically differentiated and exhibited type C virus particles which were budding from the cell surface. This in vitro system may be of great value for exploring the oncogenic potential of the virus, and its possible role in cell differentiation.     

Aflatoxin metabolism and absence of cytochrome P-450 in rat colon tissue during vitamin A malnutrition

Summary Homogenized mucosal linings prepared from vitamin A adequate and deficient male rats were used in metabolic studies of aflatoxin B₁ (AFB₁). Cytochrome P-420 was identified in both groups which metabolized AFB₁ to 4 metabolic products in vitro. The implications of this observation are discussed in relation to colon carcinoma.Acknowledgments. This work was supported by USPHS (NIEHS), grant R01 ES 00336 and R01 CA 00270. Hoffman-La Roche Foundation Research Corporation awarded to T. C. C., Research Career Development Awardee of the NIEHS. Present address: Division of Nutritional Sciences, Cornell University, Ithaca, New York, USA.     

Selected decrease of haemocytes of the freshwater snail Planorbarius corneus (L.) (Gastropoda, Pulmonata) after bacteria injection

The decrease of haemolymph phagocytic cells (SH) in Planorbarius corneus after bacterial injection seems to be mediated by humoral factor(s) released into the haemolymph. SH show different adhesiveness in vitro in the presence of bacterial metabolic products.     

In vitro morphological characterization of the bursal reticuloepithelial (REp) cells of chicken.

The REp cells of the bursa follicle medulla of chicken were isolated in vitro. Culture of the REp cells was maintained over a period of 10 days and the cells were observed at 3 and 10 days by means of transmission electron microscopy (TEM) and immunofluorescence. The use of an anticytokeratin monoclonal antibody confirmed their epithelial nature. TEM observations showed the presence of desmosomes and tonofilaments, which are characteristic of epithelial cells. Furthermore, to some extent the cells regenerated in vitro the network they form in vivo. Though the growth rate becomes slower with time, the features of the REp cells do not significantly change.     

Selected decrease of haemocytes of the freshwater snailPlanorbarius corneus (L.) (Gastropoda,Pulmonata) after bacteria injection

Summary The decrease of haemolymph phagocytic cells (SH) inPlanorbarius corneus after bacterial injection seems to be mediated by humoral factor(s) released into the haemolymph. SH show different adhesiveness in vitro in the presence of bacterial metabolic products.     

Thymidine H3 incorporation in the nurse cells of amphigonic and parthenogenetic ovaries ofMegoura viciae (Horn. Aph.)

Conclusions In the amphigonic females ofM. viciae an active nuclear incorporation of thymidine H³ occurs during growth which may be attributed to continuous endomitotic divisions. However, even when the nurse cells are functioning fully, and when the nuclei appear to have achieved maximum development, incorporation of the thymidine H³ continues, and, as was seen in other insects, does not affect all the nuclei. Incorporation would therefore seem to be due not to the continuance of endomitotic divisions but rather to the synthesis of metabolic DNA. On the other hand, even if one supposes that in the nurse cells of the amphigonic ovary endomitotic processes continue right up to the end of vitellogenesis of the amphigonic winter egg, this is quite out of the question so far as the parthenogenetic ovary is concerned. Diploid nurse cells are functioning continuously, since in a parthenogenetic ovary a great many ovocytes reach maturity one after the other, passing through all stages of development to produce the embryos. The nurse cells always retain, in such cases, their characteristic appearance right from the beginning of their differentiation³ and therefore thymidine H³ incorporation cannot be ascribed to continuous endomitotic divisions. It can therefore be assumed that the active synthesis which occurs in the nuclei does not concern genetically stable DNA but a metabolic DNA. The above results thus add new weight to the assumption by former authors that metabolic DNA may be synthesized in the nurse cells of amphigonic insects as well.

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Riassunto Nell'afideMegoura viciae le cellule nutrici diploidi dell'ovario partenogenetico e quelle poliploidi dell'ovario anfigonico si comportano in maniera analoga incorporando timidina H³ durante l'accrescimento ovocitario. Tale incorporazione viene attribuita alla sintesi di DNA metabolico.

     

Aragusterol C: A novel halogenated marine steroid from an Okinawan sponge,Xestospongia sp., possessing potent antitumor activity

A novel chlorinated steroid, aragusterol C, was isolated from an Okinawan marine sponge of the genusXestospongia. The compound strongly inhibited the proliferation of KB cells in vitro, and also showed potent in vivo antitumor activity against L1210 cells in mice. The complete structure of aragusterol C was determined by spectroscopic analysis and X-ray crystallographic analysis.     

Murine type C endogenous virus expression in murine 129 teratocarcinoma cell line]

Murine type C viral information is detectable in the cellular genome of both differentiated and undifferentiated cell lines derived from 129 Mouse teratocarcinoma. Cytoplasmic RNA expression which is negligible in differentiated cells, is significantly higher in multipotential undifferentiated cells. Furthermore it was observed that in vitro differentiation of multipotent cells leads to a decrease of this expression.     

Evidence for changes in cell shape from a 2-dimensional to a 3-dimensional substrate

Summary Chick embryo mesoderm cells were explanted to culture systems in vivo and in vitro and their subsequent movements were correlated with the external morphology as studied by SEM. In vitro cell movements are exaggerations of normal in vivo movements where a 2-dimensional substrate is encountered rather than a 3-dimensional environment.The authors are grateful to Mr J. Smith and Mrs S. Bulman who provided excellent technical assistance and to Mr G. L. C. McTurk who skillfully produced the scanning electron micrographs in the Leicester University Scanning Electron Microscope Unit.     

Evidence for changes in cell shape from a 2-dimensional to a 3-dimensional substrate.

Chick embryo mesoderm cells were explanted to culture systems in vivo and in vitro and their subsequent movements were correlated with the external morphology as studied by SEM. In vitro cell movements are exaggerations of normal in vivo movements where a 2-dimensional substrate is encountered rather than a 3-dimensional environment.     

Histamine binding to H2 receptors stimulates phospholipid methylation in mast cells

Summary Rat peritoneal mast cells incubated in vitro in the presence of L-[methyl-³H] methionine and exposed to histamine undergo a rapid but transient increase in phospholipid methylation. By using specific H₁- and H₂-receptor antagonists, and histamine analogues differing in their H₂-receptor agonist potency, it has been demonstrated that this metabolic event is dependent on histamine binding to H₂-receptors.We are grateful to Smith Kline and French Laboratories for the generous gift of histamine analogues.     

Lack of effect of dihydroergotamine on endothelial and smooth muscle cell proliferation and endothelial cell prostanoid production

Summary The most important effect of dihydroergotamine is venoconstriction, but certain metabolic effects and changes in vessel prostanoid activity have also been suggested. In this study endothelial cell production of 6-keto PGF₁ and TxB₂ was quantitated in vitro. No evidence of altered prostanoid production was noted after incubation with dihydroergotamine (exposure ranging from 5×10^–3 to 5×10^–7 g/l). Similarly, no effect of dihydroergotamine on the growth rates of endothelial cells or smooth muscle cells in vitro was documented.     

Effect of cold exposure on electrophysiological properties of rat heart

Male rats exposed to the cold (4°C) for five or ten days exhibited modifications in their thyroid state, as documented by increases in serum thyroid hormone levels, to which differently graded modifications of heart weight/body weight ratio, heart rate, and resting metabolic rate were associated. The values of the above mentioned thyroid state indicators returned to those of the control when the animals, kept at cold for ten days, were re-exposed to room temperature (24°C) for an additional 10 days. The configuration of action potentials, recorded in vitro at 26°C from fibres of anterior papillary muscles, was different in control rats of different age and was affected by prolonged cold exposure. In fact, the action potential duration (APD) increased after ten days of cold exposure. In the re-exposed group the APD was not different from that of the controls. Such a pattern was not significantly modified when the stimulation frequency increased from 1 Hz to 5 Hz. The above results suggest that in cold exposure, as in experimental hyperthyroidism, thyroid hormone might exert a cardiac chronotropic effect by modifying heart electrophysiological properties. Thus thyroid hormone should play a basic role during the exposure to cold environment, stimulating the body metabolism and increasing heart rate as a response to the requirement for greater tissue perfusion.     

Differences in in vitro incorporation of tritiated deoxycytidine and tritiated thymidine into human lymphocytes.

Human lymphocytes stimulated in vitro by PHA or PWM incorporate 3H-CdR into DNA, but less well than 3H-TdR. More 3H-CdR is incorporated in populations enriched for T cells. No 3H-CdR is used by cells stimulated by lipopolysaccharides under circumstances in which 3H-TdR is incorporated. We conclude that human T cells and B cells differ in their ability to use 3H-CdR.     

A comparative analysis of the cell biology of senescence and aging

Various intracellular organelles, such as lysosomes, mitochondria, nuclei, and cytoskeletons, change during replicative senescence, but the utility of these changes as general markers of senescence and their significance with respect to functional alterations have not been comprehensively reviewed. Furthermore, the relevance of these alterations to cellular and functional changes in aging animals is poorly understood. In this paper, we review the studies that report these senescence-associated changes in various aging cells and their underlying mechanisms. Changes associated with lysosomes and mitochondria are found not only in cells undergoing replicative or induced senescence but also in postmitotic cells isolated from aged organisms. In contrast, other changes occur mainly in cells undergoing in vitro senescence. Comparison of age-related changes and their underlying mechanisms in in vitro senescent cells and aged postmitotic cells would reveal the relevance of replicative senescence to the physiological processes occurring in postmitotic cells as individuals age.