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  • Life and Medical Sciences  (17)
  • Instrumentation and Photography  (10)
  • Mexico  (10)
  • Sarcoplasmic reticulum
  • 11
    ISSN: 1573-5117
    Keywords: Cladocera ; chydoridae ; taxonomy ; Mexico ; aloninae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spinalona anophtalma n. gen. n. sp. is describedon parthenogenetic and ephippial females andmales from material collected in a temporary lagoonlocated in the Neovolcanic Province from Mexico at analtitude of 2507 m above sea level. It ischaracterized by a strong armature of the antenna,postabdomen and postabdominal claw, no compound eyeor ocellus, the exopod of thoracic limb IIIwith only four setae and that of P5 with only three setae.This new taxon has no relationwith blind Alona from hypogean habitats.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 387-388 (1998), S. 47-54 
    ISSN: 1573-5117
    Keywords: Mexico ; Rotifera ; new record ; taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A survey of rotifers from a small pond (less than 2 ha in area and 3 m deep), located at Kilometer 28 in the federal highway Ixtlahuaca-Jilotepec (19° 49′ 13″ N, 99° 42′ 22″ W) at an altitude of 2503 m above sea level, resulted in a total of 78 species. From these, 20 are new records for Mexico. This study confirms the presence of some of the rotifer species listed only in earlier studies. Comments on some species are made from a zoogeographical point of view.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 287-388 (1998), S. 47-54 
    ISSN: 1573-5117
    Keywords: Mexico ; Rotifera ; new record ; taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A survey of rotifers from a small pond (less than 2 ha in area and 3 m deep), located at Kilometer 28 in the federal highway Ixtlahuaca-Jilotepec (19° 49′ 13″ N, 99° 42′ 22″ W) at an altitude of 2503 m above sea level, resulted in a total of 78 species. From these, 20 are new records for Mexico. This study confirms the presence of some of the rotifer species listed only in earlier studies. Comments on some species are made from a zoogeographical point of view.
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  • 14
    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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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 213 (1992), S. 33-45 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Autogeneic bone marrow was implanted into an artificially created cavity in a segment of rat sciatic nerve, after removal of nerve fascicles, without damaging the epineurium or surrounding microcirculation. Under these conditions, the bone marrow induces capillary growth and forms granulation tissue from surrounding tissues, the behavior of pericytes being studied in the preformed (preexisting) postcapillary venules of the latter. Beginning 20 h after bone marrow implantation, the pericytes of the preexisting postcapillary venules hypertrophy, with shortening of their processes, prominent nucleoli, dispersal of ribosomes into their free form, fragmentation of basal lamina, and increased DNA synthesis. The number of contact surfaces between pericytes and endothelium is noticeably lower than in controls. Many pericytes are in mitosis. Cells with a shape transitional between pericytes and interstitial fibroblast-like cells appear. In some cases, Monastral Blue (MB) was used as a marker of the cells in preexisting venule walls of the graft bed. In the earlier stages of the experiment, the MB labelling is restricted to the cytoplasm of pericytes and endothelial cells of postcapillary venules, and to the macrophages that occur in the space between pericytes and endothelium. Furthermore, the marker continues to be observed, at a later stage, in some of the following cells: pericytes and endothelial cells of the newly formed vessels, macrophages migrating into the interstitium, transitional cells between pericytes and fibroblasts, and typical fibroblasts of the granulation tissue. The present study provides greater evidence that preformed microvasculature pericytes are substantially activated during postnatal angiogenesis and granulation tissue formation, suggesting that they may contribute to the origin of new pericytes and fibroblasts. © 1992 Wiley-Liss, Inc.
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  • 16
    ISSN: 0730-2312
    Keywords: bone morphogenetic protein ; defined media ; in vitro ; development ; stem cell ; ascorbic acid ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: During embryonic development, cartilage formation involves the condensation of mesenchymal stem cells and a series of maturation steps that ultimately results in the mineralized hypertrophic chondrocyte. The embryonic, murine, mesenchymal stem cell line, C3H/10T1/2, is pluripotent; exposure to azacytidine or to bone morphogenetic protein-2 or -4 results in low rates of differentiation to three mesengenic lineages. In contrast to previous studies, we report conditions for 10T1/2 differentiation specifically to the cartilage lineage and at high yields. These conditions include high cell density micromass cultures, a purified mixture of osteoinductive proteins (BP; Intermedics Orthopedics, Denver, CO), a serum substitute, 50 μg/ml ascorbic acid, and 10 mM β-glycerophosphate. The cartilagenous fate was confirmed by 1) histological detection of sulfated proteoglycans, 2) electron microscopic detection of proteoglycan and rounded cells separated by extracellular matrix containing short, disorganized collagen fibrils, 3) morphological detection of a chondrocytes surrounded by a territorial matrix and encompassed within a distinct perichondrium, and 4) immunocytochemical detection of type II collagen and link protein. After 4 weeks in culture, mature although unmineralized cartilage was observed, as indicated by hypertrophic morphology, immunocytochemical detection of osteocalcin, and histological detection of lacunae. These conditions promote overt chondrogenesis for most of the treated cells and preclude lineage determination to the fat, muscle, and bone lineages, as assayed by electron microscopy and histomorphology. The faithful recapitulation of cartilage differentiation that we have established in vitro provides a versatile alternative to the use of chondrocyte and limb bud explant cultures. We propose this as a model system to study the factors that regulate commitment to the chondrogenic lineage, exclusion to related mesengenic pathways, and maturation during chondrogenesis. J. Cell. Biochem. 65:325-339. © 1997 Wiley-Liss, Inc.
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  • 17
    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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  • 18
    ISSN: 0730-2312
    Keywords: chromatin ; pronucleus ; nucleoprotein particles ; sea urchins ; zygotes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: To determine the changes in chromatin organization during male pronucleus remodeling, we have compared the composition of nucleoprotein particles (NP-ps) resulting from digestion with endogenous nuclease (ENase) and with micrococcal nuclease (MNase). Whole nuclei were isolated from sea urchin gametes and zygotes containing a partially decondensed (15 min postinsemination, p.i.) or a fully decondensed (40 min p.i.) male pronucleus and digested with nucleases. The NP-ps generated were analyzed in agarose gels, and their histone composition was determined. Sperm core histones (SpH) and cleavage stage (CS) variants were identified by Western immunoblots revealed with specific antibodies. A single NP-ps was generated after digestion of sperm nucleus with MNase, which migrated in agarose gels between DNA fragments of 1.78-1.26 Kb. Sperm chromatin remained undigested after incubation in ENases activating buffer, indicating that these nuclei do not contain ENases. One type of NP-ps was obtained by digestion of unfertilized egg nuclei, either with ENase or MNase; the NP-ps was located in the region of the agarose gel corresponding to DNA fragments of 3.4-1.95 Kb [Imschenetzky et al. (1989): Exp Cell Res 182:436-444]. When whole nuclei from zygotes containing the female pronucleus and a partially remodeled male pronucleus were digested with ENase, a single NP-ps was generated, which migrated between DNA fragments of 2.5-1.9 Kb. This particle contained only CS histone variants. Alternatively, when these nuclei were digested with MNase, two NP-ps were generated; the slower migrating NP-ps (s) was located in the same position of the agarose gel as those resulting from ENase digestion and the faster migrating NP-ps (f) migrated between DNA fragments of 1.95-1.26 Kb. It was found that Np-ps (s) contained only CS histone variants, whereas NP-ps (f) were formed by a subset of SpH and by CS histone variants. When nuclei from zygotes containing a fully decondensed male pronucleus were digested either with ENase or MNase, a single type of NP-ps was observed, which migrated in the same position as NP-ps (s) in agarose gels. This particle contained only CS histone variants. On the basis of the histone compositions and on electrophoretic similarities, it was concluded that NP-ps (s) originated from the female pronucleus and that NP-ps (f) were generated from the partially remodeled male pronucleus. Consequently, our results indicate that at an intermediate stage of male pronucleus remodeling the chromatin is formed by NP-ps containing a subset of both SpH and of CS histone variants, whereas at final stages of male pronucleus decondensation chromatin organization is similar to that of the female pronucleus. © 1996 Wiley-Liss, Inc.
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  • 19
    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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  • 20
    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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