Several data in the literature suggest that an intriguing relationship exists between cell proliferation and cell death. Accordingly, we studied the early expression of different genes in the same cells, i.e. rat thymocytes, undergoing cell proliferation upon stimulation with Concanavalin A or cell death following dexamethasone treatment. We showed that an early accumulation of c-fos, c-jun and c-myc mRNA occurred in both phenomena but with different kinetics. It can be speculated that the early induction of nuclear oncogenes is necessary to allow the later induction of other genes probably regulated at the transcriptional level by the AP-1 complex and/or by Myc protein. The accumulation of the transcript for another gene, i.e. poly(ADP-ribose)polymerase, an enzyme responsible for posttranslational modifications of several nuclear proteins, could instead be related to chromatin modifications occurring in both processes.

Animals↗

PubMed1992

Inhibition of apoptosis by zinc: a reappraisal.

Apoptosis--or programmed cell death--is an active type of cell death, occurring in several pathophysiological conditions. One of the most important characteristics of apoptosis is that cell death is preceded by DNA fragmentation, consequent to the activation of nuclear calcium- and magnesium-dependent endonuclease(s). DNA fragmentation can be inhibited by zinc ions. By using several techniques, such as DNA agarose gel electrophoresis, cytofluorimetric analysis of DNA content and of cell cycle, 3H-thymidine incorporation and trypan blue dye exclusion test, we show that zinc, despite completely inhibiting DNA fragmentation and the consequent loss of nuclear DNA content, does not protect rat thymocytes from spontaneous or dexamethasone-induced death. Our data also suggest that DNA fragmentation, although characteristic, is not a critical event for thymocyte death of apoptotic type.

Animals↗

PubMed1992

Thyroid and other organ-specific autoantibodies in healthy centenarians.

To investigate the prevalence of thyroid autoantibodies in very old subjects, we assayed sera from 34 healthy centenarians (7 men, 27 women; age range 100-108 years) for these antibodies. There was a clear age-dependent increase in prevalence of thyroid autoantibodies in sera from 549 control subjects aged 7-85 years, prevalence in 40 subjects aged 70-85 being significantly greater (p less than 0.001, chi 2) than that in 436 subjects aged less than 50. By contrast, prevalence of thyroid autoantibodies in centenarians was not significantly different from that in controls aged less than 50. Cytofluorimetric analysis of peripheral blood lymphocytes showed a striking age-dependent decrease in total and CD5+B cells (without changes in their ratio), which reached its nadir in centenarians. The age-dependent increase in prevalence of thyroid autoantibodies in the elderly is not seen after the ninth decade of life. What relation this characteristic has to derangement of circulating B cells is unknown.

Adolescent↗

PubMed1992

The effect of some macromolecular ionic complexes on the pharmacokinetics and -dynamics of ocular cyclopentolate in rabbits.

The effect of mucoadhesive polymeric vehicles on the mydriatic efficacy, and on the systemic and ocular absorption of cyclopentolate from eyedrops was studied in albino rabbits. Combining cyclopentolate base to polygalacturonic (CY-PGA) or hyaluronic (CY-HA) acid resulted in an increased mydriatic effect when compared with cyclopentolate hydrochloride (CY-HCl). During the first half an hour, the systemic absorption of cyclopentolate was lower after CY-PGA than after CY-HCl. The ocular penetration of cyclopentolate, based on drug concentrations in aqueous humor 30 minutes after the eyedrop instillation, was increased 3 fold when the polygalacturonate complex was used. CY-PGA, as well as other polymeric salts, might offer a possibility to increase the therapeutic index of cyclopentolate.

Absorption↗

PubMed1992

Apoptosis--programmed cell death: a role in the aging process?

Cells continuously exposed to genotoxic agents, such as oxygen free radicals (OFRs), deeply involved in the aging process use a variety of cellular defense mechanisms. These defense mechanisms include DNA repair enzymes, antioxidants, poly(ADP-ribosyl)polymerase (pADPRP), and stress proteins and they constitute an integrated network. An age-related failure of the efficiency of this network can affect cell proliferation and cell death, two phenomena tightly linked and regulated. Recent data from our laboratory on the role of DNA damage and pADPRP activation and on the type of cell death induced by OFRs in human lymphocytes are reviewed. In vitro and in vivo data on possible strategies to reduce oxidative stress in lymphocytes from normal and Down syndrome subjects, by using natural compounds and trace elements, are presented. They indicate that nicotinamide and L-carnitine protect human cells from OFR-induced damage and suggest that they are possible candidates as antiaging substances.

Aging↗

PubMed1992

Cytotoxicity and cell death: studies on molluscan cells and evolutionary considerations.

In a previous study we demonstrated the presence of NK-like activity in the mollusc Planorbarius corneus. This activity can be ascribed to round hemocytes that have a morphology similar to that of vertebrate lymphocytes. We show here that this NK-like cytotoxicity is evident in serum-free culture medium. Moreover, the type of death induced by molluscan effector cells on their targets is probably similar to that induced by vertebrate effector cells, i.e. apoptosis or programmed cell death, as assessed by the protective effect exerted by 3-aminobenzamide when both types of effector cells were used.

Animals↗

PubMed1991

Studies on the relationship between cell proliferation and cell death: opposite patterns of SGP-2 and ornithine decarboxylase mRNA accumulation in PHA-stimulated human lymphocytes.

To assess the relationship between cell proliferation and cell death, the mRNA accumulation of ornithine decarboxylase (ODC) and sulfated glycoprotein 2 (SGP-2) were measured in human peripheral blood lymphocytes (HPBL) 2-6 hours after stimulation with phytohemagglutinin (PHA). ODC is the rate limiting enzyme of polyamines biosynthesis and its early induction in mitogen-stimulated lymphocytes has been reported. On the other hand, SGP-2, a glycoprotein present in most mammalian tissues, is induced in classical models of apoptosis, such as dexamethasone-treated thymocytes. Indeed, a consistent amount of SGP-2 mRNA in quiescent HPBL, an early and progressive decrease of SGP-2 mRNA and a parallel increase of ODC mRNA accumulation, were observed, in PHA-stimulated HPBL, suggesting that concomitant repression of SGP-2 and induction of ODC genes contribute for the cell entering the cell cycle.

Blotting, Northern↗

PubMed1991

ACTH-like molecules in gastropod molluscs: a possible role in ancestral immune response and stress.

The presence of immunoreactive ACTH molecules on phagocytic cells from the freshwater snails Planorbarius corneus and Lymnaea stagnalis was shown by cytofluorimetric analysis. The role of ACTH in phagocytosis and in the release of biogenic amines, two biological responses that may be taken as ancestral types of immune response and stress, respectively, has also been evaluated. ACTH markedly increased the phagocytosis of Staphylococcus aureus by P. corneus haemocytes and caused the release of biogenic amines from such cells into the serum. These data, as well as tracing the ancestral physiological role of ACTH, favour the hypothesis that immune and neuroendocrine systems share a common evolutionary origin.

Adrenocorticotropic Hormone↗

PubMed1991

Spontaneous and mitomycin-C-induced micronuclei in human lymphocytes exposed to extremely low frequency pulsed magnetic fields.

The cytokinesis block micronucleus method, a very sensitive cytogenetic assay, was used to ascertain the possible genotoxic effects of extremely low frequency pulsed magnetic fields in phytohemagglutinin-stimulated human lymphocytes cultures from 16 healthy donors. Four conditions were studied: i) lymphocytes not exposed to the field (control cultures); ii) lymphocytes exposed to the field; iii) lymphocytes treated with mitomycin-C and not exposed to the field; iv) lymphocytes treated with mitomycin-C and exposed to the field. Mitomycin-C-treated cultures were used as control for the micronucleus method, because it is known that mitomycin-C is a potent genotoxic agent, capable of inducing micronuclei. The frequency of micronuclei in field-exposed cultures was similar to the spontaneous frequency observed in control unexposed-cultures. Moreover, the exposure to pulsed magnetic fields did not affect the frequency of micronuclei induced by mitomycin-C, suggesting that, in the experimental conditions used, this kind of field neither affected the integrity of chromosomes nor interfered with the genotoxic activity of mitomycin-C.

Alkylating Agents↗

PubMed1991

In vivo accumulation of sulfated glycoprotein 2 mRNA in rat thymocytes upon dexamethasone-induced cell death.

Two hours after a single intraperitoneal injection of dexamethasone (20 micrograms/Kg b.w.) into adult male rats, a typical ladder of DNA fragments was detectable upon separation on agarose gels of DNA from thymocytes. This became maximally evident at 4 hours. Accumulation of sulfated glycoprotein-2 (SGP-2) mRNA, whose rate of expression has been associated to the processes of programmed cell death, preceded the appearance of DNA degradation, starting to increase as early as 30 min after steroid injection, and maintained higher than controls until 8 hrs; a different time course was shown by changes in the levels of beta-actin mRNA. In the spleen, under the same conditions, the SGP-2 message also increased at 30 min, prior to DNA fragmentation, but decreased thereafter below the control value.

Animals↗

PubMed1991

Age-related expansion of functionally inefficient cells with markers of natural killer activity in Down's syndrome.

Peripheral blood lymphocyte subsets of two groups of patients affected by Down's syndrome (DS), ie, 28 children and nine adults of relatively advanced age (greater than 34 years), were investigated and compared with those of age- and sex-matched healthy controls (13 children and 20 adults). Particular attention was devoted to cells with markers of natural killer (NK) activity. Double- and triple-color cytofluorimetric analysis was used to better characterize the phenotypic features of the different subsets. Apart from a reduced number of T lymphocytes (CD3+) in DS children and of B lymphocytes (CD19+) in both DS groups, the major alteration we found was a marked age-related increase of the percentage of cells bearing markers associated with NK activity, such as CD16, CD56, and CD57. These DS cells were apparently severely defective as far as their function was concerned, because NK activity was significantly reduced in comparison with age-matched controls, but still capable of responding to cytokines such as interleukin-2, interferon-beta, and interferon-gamma, and to the modulation of lytic activity exerted by the anti-CD16 monoclonal antibody. On the whole, our data stress the importance of studying DS subjects of different ages to fully appreciate the immunologic derangement characteristic of this syndrome.

Adolescent↗

PubMed1991

Cytotoxicity and immunocyte markers in cells from the freshwater snail Planorbarius corneus (L.) (Gastropoda pulmonata): implications for the evolution of natural killer cells.

The hypothesis that natural killer (NK) cells represent an important form of cell recognition and cytotoxicity leads to the prediction that NK-like activity should be preserved throughout phylogenetic development. This was tested in the invertebrate Planorbarius corneus. Two types of cells can be identified and separated from the hemolymph of this mollusc, i.e. glass-adherent macrophage-like spreading hemocytes (SH) and nonadherent round hemocytes (RH). Only RH are able to lyse the K-562 human target cell line in a short-term NK cytotoxicity test. This NK-like activity, severely reduced after 18 h incubation at 24 degrees C, is preserved by human recombinant interleukin 2. A further analysis of P. corneus hemocytes has been performed by using several mouse anti-human monoclonal antibodies and cytofluorimetric analysis. Unexpectedly, both SH and RH react with several monoclonal antibodies, including those directed against epitopes typical of mammalian NK cells and cell adhesion molecules. On the whole, these data support the hypothesis that a primitive NK-like activity appeared early in evolution and is not shared by phagocytic cells.

Animals↗