The G1 period

In previous papers the existence of two cycles of chromosome condensation-decondensation per cell cycle was suggested based on experiments involving nuclear morphometry measurements of Feulgen-stained nuclei. This conclusion can be criticized since its assumption of a relationship between nuclear morphology and chromatin structure is derived from indirect evidence. In this paper, we report simultaneous measurements of nuclear area and nuclear fluorescence intensity on individual cells stained with the intercalating dye, acridine orange (AO). Using cells in various stages of G₁ and synchronized by two different methods, our results demonstrate a linear correlation between nuclear area and fluorescence intensity. They also indicate two cycles of chromatin condensation-decondensation during the G₁ period, as assayed by the number of chromatin primary, intercalating AO binding sites. Finally, they show that the first of these cycles involves a transition in early G₁ from a very small condensed nucleus (immediately after telephase) to a relatively large, dispersed nucleus that occurs abruptly.     

Cell cycle controls in higher eukaryotic cells: Resting state or a prolonged G1 period?

We express the viewpoint that control over cell growth in higher eukaryotes is achieved predominantly by regular transition of cells from proliferation to rest and vice versa as a result of coordinated interrelationship between intracellular growth inhibitors and extracellular growth factors. The resting state is considered as a special physiological state of a cell where the prereplicative reactions necessary for the onset of DNA synthesis are inhibited. Cells pass into a resting state at each successive cell cycle, with regard to the next cycle, once the threshold level of growth inhibitors has been attained. Cellular rest may thus initiate and proceed in parallel with conventional periods of the cell cycle but in a hidden way. Its termination strictly depends on the appropriate concentration of extracellular growth factors. In the absence of growth factors cells, after completing mitosis, pass into an overt state of rest metabolically different from any period of the cell cycle including G1.     

An obligatory role of protein glycosylation in the life cycle of yeast cells

Two water-soluble carbodiimides, differing in molecular dimensions, have been used to characterize the cytochrome c binding site of bovine heart cytochrome c oxidase. Several polypeptide components of the enzyme contain acidic residues which are modified by these reagents. Carboxyl groups present in subunit II, VII and polypeptide c, are protected from modification when cytochrome c, equimolar to oxidase, is added and they can cross-link to the substrate once activated by the carbodiimide. Comparison of the modification patterns suggest that the most reactive residues are located on subunit II and VII, the former being also more exposed. The data obtained indicate that even though subunit II plays the major role in binding cytochrome c, at least two other lower Mr polypeptides contribute to the cytochrome c binding domain.     

The role of serotonin in a bdelloid life cycle

Serotonin is a neurotransmitter present throughout animal kingdom that controls a number of crucial functions in different taxa. In this study we document the role of serotonin in a bdelloid rotifer, Macrotrachela quadricornifera. Following life table experimental protocol, we recorded age-specific fecundity and survival rates of cohorts that received WAY 100135 maleate, a selective antagonist of the serotonin receptor 1A. The antagonist was provided from the age of 4 days (age at first reproduction) until death to one cohort group, and during 15 days to another group. Both groups were cultivated regularly, and their life history traits were recorded. Treated rotifers continued to produce eggs, but most eggs were never oviposited and eventually ruptured the mother’s body wall. The retained eggs, being parthenogenetic began embryogenesis and some could hatch inside the mother’s body cavity (pseudocoel). When WAY was suspended, most treated rotifers oviposited all their eggs. About 75% of these eggs developed, but development was 1–2 days longer than in controls. Most newborns reached sexual maturity, although their maturity was delayed as well. Eggs produced after WAY suspension hatched as much as the controls (~100%). WAY possibly did not affect egg production, but prevented regular oviposition. Nevertheless, viability was reduced and development took longer during WAY treatment. Results suggest that in bdelloid rotifers serotonin is involved in the control of egg laying and development, among other features, as it does in most animals, from nematodes to chordates.     

The missing link in the eukaryotic ribosome cycle

A truly groundbreaking paper by Pisarev et al. (2007), recently published in Cell, has solved a wide gap in our knowledge of eukaryotic mRNA translation, by elucidating how ribosomes are released from mRNA after the termination step.     

Ecdysone-induced accumulation of mosquito cells in the G1 phase of the cell cycle

We have established baseline conditions for investigating the interaction of the insect steroid hormone 20-hydroxyecdysone (20E) with the cell cycle in the C7-10 cell line from the mosquito, Aedes albopictus. As is the case with Drosophila melanogaster cells, treatment of C7-10 cells with 20E inhibits proliferation. In the presence of 10⁻⁶ M 20E, a gradual decline in cell number is typically apparent at 24 h. Media components such as phenol red and the potential presence of endogenous steroids in serum have no effect on the response to 20E. Pre-treating the cells with 10⁻⁸ M 20E, with or without an intervening hormone-free period, did not alter the response to 10⁻⁶ M 20E. However, replenishment of the medium appeared to synchronize the response to 10⁻⁶ M 20E, causing an abrupt and complete cessation of cell division by 48 h. Flow cytometry over a 20 h period showed a decrease in the proportion of cells in S within 4-6 h after exposure to 20E. By 6-10 h, a transient increase in G2 was followed by the accumulation of more than 70% of the cells in G1. These data suggest that after treatment with 20E, cells complete the ongoing cycle before arresting in G1. Consistent with the decrease in the proportion of cells in S and G2, western blots show that levels of cyclin A, which is required during the S phase of the cycle, decreased in 20E-treated cells.     

Involvement of the role of Chk1 in lithium-induced G2/M phase cell cycle arrest in hepatocellular carcinoma cells

Lithium, a therapeutic agent for bipolar disorder, can induce G2/M arrest in various cells, but the mechanism is unclear. In this article, we demonstrated that lithium arrested hepatocellular carcinoma cell SMMC-7721 at G2/M checkpoint by inducing the phosphorylation of cdc2 (Tyr-15). This effect was p53 independent and not concerned with the inhibition of glycogen synthase kinase-3 and inositol monophosphatase, two well-documented targets of lithium. Checkpoint kinase 1 (Chk1), a critical enzyme in DNA damage-induced G2/M arrest, was at least partially responsible for the lithium action. The lithium-induced phosphorylation of cdc2 and G2/M arrest was abrogated largely by SB218078, a potent Chk1 inhibitor, as well as by Chk1 siRNA or the over-expression of kinase dead Chk1. Furthermore, lithium-induced cdc25C phosphorylation in 7721 cells and in vitro kinase assay showed that the activity of Chk1 was enhanced after lithium treatment. Interestingly, the increase of Chk1 activity by lithium may be independent of ataxia telangiectasia mutated (ATM)/ATM and Rad3-related (ATR) kinase. This is because no elevated phosphorylation on Chk1 (Ser-317 and Ser-345) was observed after lithium treatment. Moreover, caffeine, a known ATM/ATR kinase inhibitor, relieved the phosphorylation of cdc2 (Tyr-15) by hydroxyurea, but not that by lithium. Our study's results revealed the role of Chk1 in lithium-induced G2/M arrest. Given that Chk1 has been proposed to be a novel tumor suppressor, we suggest that the effect of lithium on Chk1 and cell cycle is useful in tumor prevention and therapy.     

Smad7 induces G0/G1 cell cycle arrest in mesenchymal cells by inhibiting the expression of G1 cyclins

The major Smad pathways serve in regulating the expression of genes downstream of TGFbeta signals. In this study, we examined the effects of sustained Smad7 expression in cultured cells. Interestingly, Smad7 caused various mesenchymal cells, including NIH3T3 fibroblast and ST2 bone-marrow stromal cells, to undergo a marked morphological alteration into a flattened cell shape, but kept them alive for as long as 60 days. Furthermore, Smad7 arrested the proliferation of the cells even before they reached confluence. These cells became quiescent in G0/G1 phase and accumulated a hypophosphorylated form of retinoblastoma. The cytostatic effect of Smad7 was closely associated with a preceding decrease in the levels of G1 cyclins, such as cyclin D1 and cyclin E. Accordingly, ectopic cyclin E was able to overcome the Smad7-induced arrest of proliferation. These results indicate that Smad7 functions upstream of G1 cyclins and suggest a novel role for Smad7 as an antiproliferative factor. In contrast to the growth of mesenchymal cells, that of epithelial cells was little susceptible to Smad7. The present findings raise the possibility that a link between Smad7 and the G1 to S phase transition may also contribute to the cell cycle control by certain Smad7-inducing stimuli in a cell-type-dependent fashion.     

The role of cell contact in the life cycle of some dinoflagellate species

It is suggested, based on published and experimental data, thatinter- and intra-specific cell contact plays an important rolein the life cycle of some dinoflagellate species.     

The role of flexible packaging in the life cycle of coffee and butter

Background, aim and scope

The evaluation of packaging’s environmental performance usually concentrates on a comparison of different packaging materials or designs. Another important aspect in life cycle assessment (LCA) studies on packaging is the recycling or treatment of packaging wastes. LCA studies of packed food include the packaging with specific focus on the contribution of the packaging to the total results. The consumption behaviour is often assessed only roughly. Packaging is facilitating the distribution of goods to the society. Broader approaches, which focus on the life cycle of packed goods, including the entire supply system and the consumption of goods, are necessary to get an environmental footprint of the system with respect to sustainable production and consumption.

Materials and methods

A full LCA study has been conducted for two food products: coffee and butter packed in flexible packaging systems. The aim was to investigate the environmental performance of packaging with respect to its function within the life cycle of goods. The study looks at the environmental relevance of stages and interdependencies within the life cycle of goods whilst taking consumers’ behaviour and portion sizes into consideration. The impact assessment is based on the following impact categories: non-renewable cumulative energy demand (CED), climate change, ozone layer depletion (ODP), acidification, and eutrophication.

Results

The study shows that the most relevant environmental aspects for a cup of coffee are brewing (i.e. the heating of water) and coffee production. Transport and retail packaging are of minor importance. Brewing and coffee production have an impact share between 40% (ODP, white instant coffee) and 99% (eutrophication, black coffee). Milk added for white coffee is relevant for this type of preparation. The instant coffee in the one-portion stick-pack needs more packaging material per cup of coffee and is prepared by a kettle with lower energy demand, such as a coffee machine, thus leading to higher shares of the retail packaging in all indicators. A one-portion stick-pack can prevent wastage and resources related to coffee production can be saved. The most relevant aspect regarding the life cycle of butter is butter production, dominated by the provision of milk. Over 80% of the burdens in butter production stem from the provision of milk for all indicators discussed. Regarding climate change, methane and dinitrogen monoxide, emissions of milk cows and fodder production are most relevant. Fertilisation during livestock husbandry is responsible for most burdens regarding acidification and eutrophication. The distribution and selling stage influences the indicators CED and ODP distinctly. The reasons are, on the one hand, the relatively energy-intensive storage in supermarkets and, on the other hand, the use of refrigerants for chilled storage and transportation. The storage of butter in a refrigerator for 30 days is responsible for about 10% of the CED.

Discussion

Several aspects have been modelled in a sensitivity analysis. The influence of coffee packaging disposal is very small due to the general low influence of packaging. In contrast, the brewing behaviour is highly relevant for the environmental impact of a cup of coffee. That applies similarly to the type of heating device—i.e. using a kettle or an automatic coffee machine. Wastage leads to a significant increase of all indicators. Under the wastage scenario, the coffee from one-portion stick-packs has a considerable better environmental performance concerning all indicators because, in case of instant coffee wastage of hot water and in case of ground coffee wastage of prepared coffee, has been predicted. Regardless of urban or countryside distances, grocery shopping has a low impact. The storage time of butter is relevant for the results in the indicator non-renewable CED. This is mainly the case when butter is stored as stock in the freezer. The end of life treatment of the packaging system has practically no influence on the results. Grocery shopping is of limited importance no matter which means of transport are used or which distances are regarded. Spoilage or wastage is of great importance: a spoilage/wastage of one third results in about 49% increased impacts compared to the standard case for all indicators calculated.

Conclusions

The most important factors concerning the environmental impact from the whole supply chain of a cup of coffee are the brewing of coffee, its cultivation and production and the milk production in case of white coffee. The study highlights consumer behaviour- and packaging-related measures to reduce the environmental impact of a cup of coffee. The most relevant measures reducing the environmental impacts of butter consumption are the optimisation of the milk and butter production. Another important factor is the consumers’ behaviour, i.e. the reduction of leftovers. The consumer can influence impacts of domestic storage using efficient and size-adequate appliances. The impacts of packaging in the life cycle of butter are not of primary importance.

Recommendations and perspectives

This study shows that, in the case of packaging industry, a reduction of relevant environmental impacts can only be achieved if aspects indirectly influenced by the packaging are also taken into account. Thus, the packaging industry should not only aim to improve the production process of their packages, but also provide packages whose functionality helps to reduce other more relevant environmental impacts in the life cycle such as, for example, losses. Depending on the product, tailor-made packaging may also help to increase overall resource efficiency.

     

Microsatellites or the eukaryotic genome: life cycle concept and neutrality issues

Microsatellite markers have a great discriminating power. Widely exploited in many disciplines such as forensic science, medical genetics, conservation biology and molecular ecology, they are also used in human population genetics to illuminate our origins. However, strikingly, their fundamental evolutionary mechanisms remain obscure, because of the difficulty of disentangling the complex and numerous factors involved. After a brief summary of their basic characteristics, the concept of life cycle size-dependant is explored. The major mechanisms known to explain the four different phases of their life (conception, birth, growing and senescence/renaissance) are discussed. Emerging questions about their neutrality are also investigated, pointing out a real need to improve our understanding of their mutational dynamics.     

The role of GLP-1 in the life and death of pancreatic beta cells.

Glucagon-like peptide-1 (GLP-1), a peptide hormone produce by intestinal cells, has recently been shown to be capable of modulating islet cell mass. Administration of GLP-1 to rodent models of type 2 diabetes ameliorates insulin secretion, induces the replication of islet cells, and promotes islet-cell neogenesis from pancreatic ductal cells susceptible to transdifferentiate in insulin-producing cells. In addition, an anti-apoptotic effect of GLP-1 has been described in hyperglycemic animal models, using freshly isolated human islets or cultured beta cell lines exposed to various pro-apoptotic stimuli. The aim of this article is to review those reports that have emphasized the role of GLP-1 as a regulator of islet cell mass.     

Polycystin-1 induced apoptosis and cell cycle arrest in G0/G1 phase in cancer cells

Studies have shown that polycystin-1, encoded by PKD1, the major ADPKD, may have a central role in regulating both apoptosis and proliferation, which could prevent the malignant transformation of affected cells. However, as a putative tumor suppressor, direct studies on the possibility that polycystin-1 may play a role in cancer cells' biological properties have not yet been reported. We have demonstrated that the apoptosis of cancer cells was induced by overexpression of polycystin-1. After transfection with polycystin-1, three cancer cell lines, HepG2, A549, and SW480, showed significantly increased apoptosis compared with the respective control groups. This was accompanied by cell cycle arrest at G(0)/G(1) phase, whereas cell proliferation was not significantly affected. Overexpression of polycystin-1 induces apoptosis in cancer cells, at least partially, through Wnt and a caspase-dependent pathway.