In most species the cell cycle is arrested in the unfertilized egg. After fertilization the cell cycle is reestablished and a rapid series of cleavages ensues. Preceding the first cleavage in Xenopus the egg undergoes a contraction of its cortex, called the "surface contraction wave," which can be visualized by time-lapse cinematography. This wave of contraction is propagated in a circular manner from the animal pole to the equator. We have found that eggs prevented from cleaving by treatment with antimitotic drugs undergo a sequence of periodic surface contraction waves timed with the cleavage cycle in untreated eggs. In addition, artificially activated eggs, which fail to cleave presumably for lack of a functioning centriole, undergo the same periodic contractions. No nuclear material is required for the periodic waves because a separated egg fragment, produced by constricting a fertilized egg, still undergoes contraction waves with the same period as the cleaving nucleated fragment. These results demonstrate that some expression of the cell cycle persists in the absence of any nuclear material or centrioles, suggesting to us that a biological clock exists in the cytoplasm or cortex of vertebrate eggs, which may be involved in timing the cell cycle.In most species, the cell cycle is arrested in the unfertilized egg and is then reinstated by fertilization. In amphibians, after fertilization there is a somewhat long period leading up to the first cleavage and then cells in the animal, equatorial, and vegetal regions in sequence proceed through a rapid series of 10 or 11 metachronous cleavages until the midblastula stage is reached. During the metachronous cleavage period, the cells within each region divide synchronously. Thereafter, the cell cycle variably lengthens and cleavage becomes totally asynchronous (1-3). Thus, in amphibian development, the cell cycle is acquired in steps after fertilization, beginning with a short rudimentary cycle containing only M and S phases and characterized by little if any transcriptional activity and followed by a longer cell cycle having G1 and G2 phases and active RNA synthesis (4-6). Because the high degree of synchrony at the early stages is preserved when the individual blastomeres are dissociated and separated (ref. 2 and unpublished data), the machinery for timing accurately the alternate waves of DNA synthesis and mitosis must be partitioned to each of the daughter cells. An understanding of the mechanism of timing of the simple cell cycle in the early cleavage period may be useful for understanding the overall control of the cell cycle in somatic cells.Although many cell types have been used for studies of the cell cycle, the amphibian egg offers some special advantages. Its large size permits enucleation and nuclear transplantation, allowing a clear-cut distinction between the contributions of the nucleus and the cytoplasm. In general, the lack of activity of the nucleus in the early cleavage period makes the egg a good system for studying the autonomy of the...

Previously, we have shown that the adipocyte-specific nuclear form of sterol regulatory element-binding protein-1c (nSREBP-1c) transgenic mice spontaneously developed hepatic lesions that are similar to those of human nonalcoholic steatohepatitis (NASH) with a concomitant elevation of plasma TNF-α. In this study, we analyzed the role of TNF-α in the progression of nonalcoholic fatty liver disease (NAFLD). We established a Tnf knockout nSREBP-1c transgenic mouse line. Glucose tolerance and liver histology were examined at the age of 20 weeks. The gene expression and protein levels were assessed by quantitative RT-PCR and Western blot, respectively. The Tnf knockout improved glucose tolerance and significantly reduced the prevalence of hepatic steatosis (20% vs. 100%, p<0.0001) and fibrosis (15% vs. 65%, p=0.0057). The expressions of Acaca, Scd1, Mcp1, Tgfb1, Col1a1, and Timp1 were increased in the liver from the original nSREBP-1c transgenic mice. However, gene upregulation was reduced in the livers from the Tnf(-/-) nSREBP-1c transgenic mice. Furthermore, the hepatic levels of TIMP1 protein were increased in the original nSREBP-1c transgenic mice but not in Tnf(-/-) nSREBP-1c transgenic mice. To assess the direct effect of TNF-α on the expression of the genes, we cultured primary hepatocytes in the presence of TNF-α and found that TNF-α increased the expression of Mcp1, Tgfb1, and Timp1 in hepatocytes. These observations indicate that TNF-α plays a pivotal role in the development of NAFLD and progression to NASH through upregulating key molecules associated with lipid metabolism, inflammatory cytokines, and fibrosis in the liver.

ObjectiveMetformin is known to have a beneficial effect on body weight and body composition, although the precise mechanism has not been elucidated yet. The aim of this study is to investigate the effects of metformin on energy metabolism and anthropometric factors in both human subjects and rats.MethodsIn human studies, metformin (1500mg/day) was administered to 23 healthy subjects and 18 patients with type 2 diabetes for 2 weeks. Metabolic parameters and energy metabolism were measured during a meal tolerance test in the morning before and after the treatment of metformin. In animal studies, 13 weeks old SD rats were fed 25–26 g of standard chow only during 12-hours dark phase with either treated by metformin (2.5mg/ml in drinking water) or not for 2 weeks, and metabolic parameters, anthropometric factors and energy metabolism together with expressions related to fat oxidation and adaptive thermogenesis were measured either in fasting or post-prandial state at 15 weeks old.ResultsPost-prandial plasma lactate concentration was significantly increased after the metformin treatment in both healthy subjects and diabetic patients. Although energy expenditure (EE) did not change, baseline respiratory quotient (RQ) was significantly decreased and post-prandial RQ was significantly increased vice versa following the metformin treatment in both groups. By the administration of metformin to SD rats for 2 weeks, plasma levels of lactate and pyruvate were significantly increased in both fasting and post-prandial states. RQ during a fasting state was significantly decreased in metformin-treated rats compared to controls with no effect on EE. Metformin treatment brought about a significant reduction of visceral fat mass compared to controls accompanied by an up-regulation of fat oxidation-related enzyme in the liver, UCP-1 in the brown adipose tissue and UCP-3 in the skeletal muscle.ConclusionFrom the results obtained, beneficial effects of metformin on visceral fat reduction has been demonstrated probably through a mechanism for a potential shift of fuel resource into fat oxidation and an upregulation of adaptive thermogenesis independent of an anorexigenic effect of this drug.

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Gravitationally induced displacements of the contents of the frog egg can predictably determine the orientation of the subsequent dorsal-ventral axis of the embryo, regardless of the original position of sperm entry or of the grey crescent. In certain conditions, these displacements in the egg can also lead to the formation of a second axis, that is, to twinning. The previously reported ability of grafts of grey crescent cortex to induce secondary axes in recipient eggs is interpreted here as an unrecognized twinning effect of gravity. Our results lead to question the classic interpretation of the grey crescent as a dorsal determinant in amphibian development.

Solvation dynamics of an excited solvatochromic probe molecule in micellar environment has been studied as a function of pressure. In addition to steady-state spectrum, time-dependent fluorescence Stokes shift of coumarin 153 in aqueous solution of typical neutral surfactant Triton X-100 was measured at high pressures using time-correlated single-photon counting techniques with a time-resolution of 20 ps. It was found that polarity of the microenvironment decreases with increasing pressure. The solvation dynamics exhibits bimodal relaxation behavior with two characteristic time constants of 198 ps and 1.63 ns at atmospheric pressure. The solvation time becomes shorter with increasing pressure. The bimodal relaxation and its pressure dependence is considered as closely connected with the pressure effect on the hydrogen bonding of water molecules. And also the model assuming an equilibrium between "bound water" and "free water" within the Stern layer of micelles is discussed.

To determine the effects of the multifunctional iron-binding glycoprotein, lactoferrin (LF) and related compounds on the growth of leukemic cells, human myeloid leukemic cells (HL-60) were exposed to bovine lactoferrin (bLF) and proteolytic hydrolysates of bLF. Pepsin hydrolysates of bLF showed a greater growth suppressive effect than tryptic hydrolysates or mature bLF. Four peptides with proliferation inhibition activity were purified from pepsin hydrolysates by ion-exchange chromatography, reverse-phase HPLC, and gel-filtration. All peptides were from the N-terminal end, in a region where lactoferricin B (Lfcin B), an antibacterial peptide, is located. Among the four peptides, peptide 1 (pep1) was found to exhibit highest activity and corresponded to residues 17 to 38 of bLF, with a molecular weight of 2753.88. The IC50 value of this peptide was 6.3 micrograms/ml. Three other peptides were less active and corresponded to sequences 1 to 16 and 45 to 48, linked by disulfide-bridge (pep2, molecular mass of 2430.13), 1 to 15 and 45 to 46 linked by disulfide bridge (pep3, molecular mass of 2017,92) and from residues 1 to 13 (pep4, molecular mass of 1558.73). Cell proliferation inhibition activity of the peptides was thought to be due to induction of apoptosis, which was evaluated by DNA ladder formation, DNA fragmentation, enhanced expression of phosphatidyl serine, and morphological changes. The IC50 values of the three peptides were confirmed using synthetic peptides and were consistent with those of purified peptides.

The aggregation number of a nonionic surfactant micelle, Triton X 100 (TX100), in aqueous solution was determined as a function of pressure by using the method of steady-state fluorescence quenching. The method of this work uses the fluorescence quenching of a probe (pyrene) by a quencher (coumarin 153), which are solubilized within a micelle. With increasing pressure, the aggregation number of TX100 takes a minimum. Namely, it decreases from 250 at atmospheric pressure down to 80 at around 100−150 MPa and then increases up to 230 at 500 MPa, the highest pressure studied. This behavior is closely related to the turnover phenomenon of critical micelle concentration (cmc) against pressure. By taking the pressure effect on the micellar concentration into account, it is demonstrated that in addition to the equilibrium between dispersed state and micellar state, there are equilibria among different-sized micelles.