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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 585-592 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of metabolic inhibitors on nontransferrin bound iron transport by K562 cells was investigated. Incubation with 1 μM rotenone, 10 μM antimycin, or 0.5 mM 2,4-dinitrophenol effectively reduced ATP levels by ∼50%. Both the rate and extent of Fe+3 uptake were impaired in ATP-depleted cells, which display a reduced Vmax for uptake. K562 cell ferrireductase activity was also lowered by metabolic inhibitors, suggesting that the apparent energy requirements for transport reside in the reduction of Fe+3 to Fe+2. However, ATP depletion was found to inhibit the rate and extent of Fe+2 uptake as well. Thus, the transbilayer passage of Fe+2 and/or Fe+3 appears to be an energy-requiring process. These features possibly reflect properties of the transport mechanism associated with a recently identified K562 cell transport protein, called SFT for “Stimulator of Fe Transport,” since exogenous expression of its activity is also affected by ATP depletion. J Cell Physiol 177:585-592, 1998. © 1998 Wiley-Liss, Inc.
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  • 2
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of the monokines tumor necrosis factor α (TNF) and interleukin 1 (IL 1) on parathyroid hormone (PTH)-responsive adenylate cyclase were examined in clonal rat osteosarcoma cells (UMR-106) with the osteoblast phenotype. Recombinant TNF and IL 1 incubated with UMR-106 cells for 48 hr each produced concentration-dependent inhibition of PTH-sensitive adeylate cyclase, with maximal inhibition of PTH response (40% for TNF. 24% for IL 1) occuring at 10-8 M of either monikine. Both monokines also decreased adenylate cyclase stimulation by the tumor-derived PTH-related Protein (PTHrP). In contrast, TNF and IL 1 had little or no inhibitory effect on receptor-mediated stimulation of adenylate cyclase by isoproterenol and nonreceptors-mediated enzyme activation by cholera toxin forskolin; both monokines increased prostaglandin E2 stimulation of adenylate cyclase. Binding of the radiodinated agonistt mono-[125I]-[Nle3, 18, Tyr34]bPTH-(1-34)NH2 to UMR-106 cells in the presence of increasing concentrations of unlabeled [Nle8,18, Tyr34]bPTH-(1-34)NH2 revealed a decline in PTH receptor density (Bmax) without change in receptor binding affinity (dissociation constant, Kd) after treatment with TNF or IL 1. Pertusis toxin increased PTH-sensitive adenylate cyclase activity but did not attenuate monokine-induced inhibiton of PTH response. In time course studies, brief (1hr) exposure of cells to TNF or IL 1 during early culture was sufficient to decrease PTH response but only after exposed cells were subsequently allowed to grow for prolonged periods. Inhibition of PTH response by monokines was blocked by cycloheximide. The results and indicate that TNF and IL 1 impair responsiveness to PTH (and PTHrP) by a time protein synthesis-dependent down-regulation of PTH receptors linked to adenylate cyclase. © 1992 Wiley-Liss, Inc.
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  • 3
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Retinoids modulate cellular proliferation and mediate gene function through a series of nuclear receptors. The retinoic acid nuclear receptor β (RARβ) plays an important role in the differentiation of a number of cell types. We now demonstrate that RARβ expresion is confined to normal mammary tissue and is not expressed in either immortalized normal or malignant cell lines. Treatment of RARβ-transfected MDA-MB-231 cells with 1 μM all-trans-retinoic acid (RA) significantly inhibited monolayer growth of the cells which express recombinant RARβ. RARβ-expressing MDA-MB-231 cells formed significantly smaller and fewer colonies soft agar than the mock-transfected cells. Addition of 1 μM RA stimulated colony size and number in the RARβ-transfected MDA-MB-231 cells. In contast to the RARβ-expressing cells, colony formation by the RARβ-expressing cells was similar to the mock-transfected controls and the addition of 1 μM RA to the RARα-transfected cells inhibited colony formation. While demonstrating decreased colony formation in agar, RARβ-expressing MDA-MB-231 cells failed to exhibit decreased growth in SCID mice. Our results show that RARβ functions as a negative regulator of growth in breast epithelial cells. In addition, the growth of these cells is differentially regulated by RARα and RARβ which is most likely the result to the modulation of different genes. © 1995 Wiley-Liss Inc.
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  • 4
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of transforming growth factor β (TGFβ) on parathyroid hormone (PTH)-responsive adenylate cyclase were examined in clonal rat osteosarcoma cells (UMR-106) with the osteoblast phenotype. Purified TGFβ incubated with UMR-106 cells for 48 hr produced a concentration-dependent increase in PTH stimulation of adenylate cyclase, with maximal increase in PTH response (37%) occurring at 1 ng/ml TGFβ. TGFβ also enhanced receptor-mediated activation of adenylate cyclase by isoproterenol and prostaglandin E2 (PGE2) and nonreceptormediated enzyme activation by cholera toxin and forskolin. In cells in which PTH-stimulated adenylate cyclase activity was augmented by treatment with pertussis toxin, the incremental increase in PTH response produced by TGFβ was reduced by 33%. However, TGFβ neither mimicked nor altered the ability of pertussis toxin to catalyze the ADP-ribosylation of a 41, 000-Da protein, presumably the α subunit of the inhibitory guanine nucleotide-binding regulatory component (Gi) of adenylate cyclase, in cholate-extracted UMR-106 cell membranes. TGFβ also had no effect on the levels of α or β subunits of Gi, as assessed by immunotransfer blotting. In time course studies, brief (≥ 30 min) exposure of cells to TGFβ during early culture was sufficient to increase PTH response but only after exposed cells were subsquently allowed to grow for prolonged periods. TGFβ enhancement of PTH and isoproterenol responses was blocked by prior treatment of cells with cycloheximide but not indomethacin. The results suggest that TGFβ enhances PTH response in osteoblast-like cells by action(s) exerted at nonreceptor components of adenylate cyclase. The effect of TGFβ may involve Gi, although in a manner unrelated to either pertussis toxin-catalyzed ADP-ribosylation of the α subunit of Gi or changes in levels of Gi subunits. The regulatory action of TGFβ on adenylate cyclase is likely to be mediated by the rapid generation of cellular signals excluding prostaglandins, followed by a prolonged sequence of events involving protein synthesis. These observations suggest a mechanism by which TGFβ may regulate osteoblast responses to systemic hormones.
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  • 5
    ISSN: 1040-452X
    Keywords: Synthetic progestins ; Uteroglobin ; Pregnancy ; Rabbit endometrium ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Norethisterone (NET) has been used as a contragestational postcoital agent. It is biotrans-formed to 5α dihydro-NET (5α-NET) and 3β,5α tetrahydro-NET (3β,5α-NET) in target tissues. The participation of these metabolites in NET effects is unknown. We have examined the antiimplantation and antiprogestational effects of NET and its metabolites, in adult mated female rabbits, by assessing the number of implantation sites and the expression products of the uteroglobin (UTG) gene in the uterus, and by comparing them with those of RU-486 and estradiol. Steroids were daily administered s.c. at several doses for 7 consecutive days, starting 24 hr after coitus. To assure that fertilization occurred in all animals, the presence of early pregnancy factor was determined. The results demonstrated that high doses (5 mg/kg) of NET reduced both implantation and the expression of the UTG gene. On the other hand, lower doses (1.5 mg/kg) of 5α-NET produced an antiimplantation effect and suppressed UTG synthesis and its mRNA. These effects were similar to those of RU-486. At lower doses (1 mg/kg), both estradiol and the estrogenic metabolite 3β,5α-NET were also effective in inhibiting implantation and UTG gene expression. The overall results suggest that NET metabolites exert antiimplantation and antiprogestational effects through their interaction with progesterone and estrogen receptors, and provide an explanation for the molecular mechanisms involved in the postcoital contraceptive action of NET. © 1995 Wiley-Liss, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 20 (1992), S. 34-42 
    ISSN: 1059-910X
    Keywords: Intercellular tracer ; Lanthanum ; Testis ; Galea ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: With the purpose of evaluating a new intercellular tracer, nickel-K ferrocyanide, we compared results yielded by lanthanum with information provided by nickel. This was done in the seminiferous epithelium of Holtzman rats of several postnatal ages and in a wild local seasonal breeder Galea musteloides. Tissues were studied with transmission electron microscopy and freezefracture replications. Nickel tracing proved to delineate cell contours more intensely and less interruptedly than lanthanum. With regard to seasonal variations in adult galea, the limits of the barrier were similar to those described in other mammals: spermatogonia, preleptotene, and leptotene spermatocytes were surrounded by the tracer in the basal compartment. The zygotenepachytenes were contained in the lumenal compartment and tracers were stopped at the inter - Sertoli cell tight junctions. During the inactive spermatogenic phase in winter, the seminiferous epithelium contained Sertoli cells and occasional germ cells, never beyond the spermatocyte stage. The tracer filled intercellular spaces, indicating that the barrier was incompetent. Some resting germ cells showed nuclear hyperchromasia, karyolysis, organelle loss, cell shrinkage, and cell fusion leading to a multinucleated cells. The inter-Sertoli tight junctions were scanty and had randomly oriented and discontinuous junctional strands. Moreover, inter - Sertoli cell gap junctions proliferated. During the active spermatogenic phase in summer, junctions were numerous. Their junctional strands were parallel to each other, and continuous.
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  • 7
    ISSN: 1040-452X
    Keywords: Steroid receptors ; Rabbit endometrium ; Hormone regulation ; Gene expression ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The progesterone receptor (PR) plays a pivotal role in the maturation process of the secretory endometrium, implantation and maintenance of pregnancy in rabbits. To determine the dynamics of PR gene expression and its physiological significance, the endometrial expression of PR and PR mRNA were evaluated and compared with the expression of the progesterone-regulated uteroglobin (UG) gene during 0-5 days post-coitus in rabbits. The results of immunoblot experiments indicated the presence of PR in endometrial cell extracts from days 1-4 of pregnancy with maximum PR immunostaining on day 2, followed by a marked diminution until its complete disappearance on day 5. When endometrial PR mRNA content was assessed by Northern blots, the results were similar to those of PR immunostaining, with maximal concentrations on the second day after mating. However, PR mRNA levels were still high on day 3, despite the concomitant decrease in immunostainable PR. Endometrial UG gene expression, on the other hand, exhibited a different time sequence. Thus, the UG content in uterine flushings progressively increased from day 3 after mating, reaching maximal levels on the fifth day. The endometrial UG mRNA content presented a similar profile, as its maximum concentration occurred on days 4-5. The overall results indicate that endometrial PR is down-regulated at both the mRNA and protein levels, possibly by endogenous progesterone during early pregnancy. The striking observation that maximal expression of endometrial UG gene products occurred when PR and its mRNA are no longer detectable suggests an important role for this progesterone-binding uterine protein during the preimplantation period. © 1993 Wiley-Liss, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 36 (1993), S. 338-345 
    ISSN: 1040-452X
    Keywords: Sperm capacitation ; True acrosome reaction ; Oviductal epithelial cell monolayers ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The effects of different epithelial cells, namely, hamster oviduct, sheep oviduct, and pig kidney epithelial cells (IBRS-2), on the viability, percentage of progressive motility (PPM), and acrosome reactions of ejaculated ram spermatozoa were investigated. Sperm aliquots were cultured on cells, cell-conditioned medium 199, or control medium 199. The PPM of unattached spermatozoa was estimated after 0, 3, 6, 9, 12, and 24 hr of incubation at 37°C under 5% CO2 in air. Viability and the occurrence of true acrosome reactions were assessed using a triple-stain technique. Spermatozoa started to attach within 1 hr of coculture with the hamster or sheep oviductal epithelial cell (OEC) monolayers, and these spermatozoa showed vigorous tail motion. No spermatozoa were found to attach to the IBRS-2 monolayer. The PPM of unattached spermatozoa cocultured with the various types of epithelial cell monolayers for 12 hr was significantly higher than that of spermatozoa incubated in conditioned media or medium 199 alone (54% in hamster OEC vs. 40% in conditioned; 68% in sheep OEC vs. 38% in conditioned; 36% in control medium). On the other hand, after 24 hr of incubation, there were no differences in the PPM of spermatozoa cocultured with epithelial cells or incubated in conditioned media. The percentages of cells undergoing a true acrosome reaction reached maximum values (P 〈 0.05) in spermatozoa incubated for 9 hr in the presence of hamster OEC (22.5%) or for 12 hr on sheep OEC (20.5%) monolayers. IBRS-2, a commercial nonreproductive cell type, had a positive influence on both PPM and sperm viability but no effect on the occurrence of the acrosome reaction. Interactions leading to the acrosome reaction were thus observed only when spermatozoa were cocultured with OEC monolayers. The values of PPM in unattached sperm cells seen after 12 hr of coculture with OEC or IBRS-2 were still at a high level (52-67%) for in vitro fertilization. The coculture with OECs provides an “in vitro” model to study the capacitation processes in a situation that may resemble that occurring in vivo. Moreover, the coculture with hamster OECs may provide a convenient and standardized in vitro system to study mechanisms underlying capacitation and the acrosome reaction. © 1993 Wiley-Liss, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 59 (1995), S. 161-167 
    ISSN: 0730-2312
    Keywords: micrococcal digestion ; chromatin ; DNA replication ; sea urchins ; early development ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: To investigate changes in chromatin organization associated with DNA replication during the first stages of development of the sea urchin Tetrapygus niger, we compared micrococcal nuclease (MNase) digestion patterns of chromatin from zygotes harvested during the first S phase and from unfertilized eggs. We observed that the majority of DNA fragments derived from MNase digested zygote nuclei were similar to or smaller than a mononucleosome, while those derived from unfertilized egg nuclei were larger (1,500 to 410 bp). This result indicates that in zygotes, where active DNA replication is occurring, the major chromatin fraction is represented as unfolded nucleosomes. In contrast, in unfertilized eggs chromatin appears to be organized into polynucleosomes. To determine if the unfolded structure of nucleosomes observed during S phase is related to the level of poly (ADP-ribosylation) of cleavage stage (CS) histone variants, zygotes were treated with 20 mM 3-Amino Benzamide (3 ABA) during the interval between 3 and 30 min post-insemination (p.i.). This treatment with 3 ABA decreases the poly (ADP-ribosylation) of CS histone variants and inhibits the first S phase in zygotes [Imschenetzky et al. (1991): J Cell Biochem 46:234-241; Imschenetzky et al. (1993): J Cell Biochem 51:198-205]. When the MNase digested patterns of chromatin from these 3 ABA treated and control zygotes were compared, we found that the unfolded structure of the nucleosomes remains unaltered by the inhibition of the poly (ADP-ribose) synthetase with 3 ABA. This result indicates that the unfolded nucleosomal structure, particular to the chromatin of S phase zygotes, is not contemporaneous to DNA replication and is independent of the normal level of poly (ADP-ribosylation) of CS histone variants. © 1995 Wiley-Liss, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 141 (1973), S. 293-305 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The gular gland of the bat Tadarida brasiliensis is a specialized sebaceous gland located in the skin of the suprasternal region of adult males. It consists of an aggregation of simple branched tubulo-acinar gland units, the number of which varies seasonally. Each acinus is composed of densely packed sebaceous cells at various stages of differentiation. Acinar basal cells and cells of the epithelium of the ducts can differentiate into sebaceous cells. Two main changes appear in the cytoplasm concurrent with the sebaceous transformation: the differentiation of cytoplasmic organelles and the deposition of lipid material. The appearance of a different type of mitochondrion and the development of large numbers of ribosomes and polyribosomes can be recognized in the cytoplasm at an early stage of differentiation. Concomitant with the deposition of significant numbers of lipid droplets, the cells develop abundant agranular endoplasmic reticulum occurring mainly as scattered tubular cisternae. These at times form whorls surrounding lipid droplets. At later stages, the cisternae of the agranular endoplasmic reticulum often occur in crystalline arrays between secretory oil droplets. The roles of the different cytoplasmic organelles, especially in relation to the production of sebum, are discussed.
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