Sugar-Induced Increase of Calcium-Dependent Protein Kinases Associated with the Plasma Membrane in Leaf Tissues of Tobacco

The sugar-inducible expression of genes for sporamin and [beta]-amylase in leaf explants of sweet potato (Ipomoea batatas) and that of a [beta]-glucuronidase-fusion gene, with the promoter of the gene for [beta]-amylase in leaves of tobacco (Nicotiana tabacum), requires Ca2+ signaling (M. Ohto, K. Hayashi, M. Isobe, K. Nakamura [1995] Plant J 7: 297-307), and it was inhibited by staurosporin and K252a, inhibitors of protein kinases. Autophosphorylation activities of several potential protein kinases in leaves of tobacco were significantly higher in younger leaves than in mature leaves. However, the autophosphorylation activities of these proteins in mature leaves, especially those of the major autophosphorylatable proteins with apparent molecular masses of 56 and 54 kD, increased upon treatment of leaf discs with a 0.3 M solution of sucrose, glucose, or fructose, did not increase with sorbitol or mannitol treatments, and the increase by sucrose was inhibited by cycloheximide. Autophosphorylation of the 56- and 54-kD protein in vitro was dependent on Ca2+ and inhibited by staurosporine, K-252a, and by W-7. These results suggest that they belong to the family of calcium-dependent protein kinases. They were concentrated in the plasma membrane fraction and were released from membrane vesicles by high salt or with sodium carbonate. The possible functions of these sugar-inducible calcium-dependent protein kinases associated with the plasma membrane are discussed.     

Aluminum Induces Rigor within the Actin Network of Soybean Cells

Aluminum is toxic to both plants and animals. Root growth and pollen-tube extension are inhibited after aluminum stress in acidic environments. Incubation of cultured neurons with aluminum results in the formation of neurofibrillar tangles reminiscent of the neural pathology observed in Alzheimer's disease. The present communication demonstrates that aluminum induces a rapid and dramatic increase in the rigidity of the actin network in soybean (Glycine max) root cells. This rigidity can be prevented by either co-incubation with sodium fluoride or magnesium, or pretreatment with cytochalasin D. It is proposed that the growth-inhibitory activity and cytotoxicity of aluminum in plants may be a consequence of a global rigor that is induced within the actin network. This rigor may result from the formation of nonhydrolyzable [Al3+-ADP] or [Al3+-ATP] complexes whose binding to actin/myosin can modify contraction. Additionally, Al3+-mediated interference with the normal kinetics of F-actin filament assembly/disassembly could precipitate subsequent disorganization of associated cytoskeletal structures and promote altered expression of cytoskeletal proteins.     

The Biochemical Response of Electrical Signaling in the Reproductive System of Hibiscus Plants

Stimulation of the stigma of Hibiscus flowers by pollen, wounding (heat), or cold shock (4[deg]C) evokes electrical potential changes in the style, which propagate toward the ovary with a speed of 1.3 to 3.5 cm s-1. Potential changes were measured intracellularly by microelectrodes inserted in the style. The resting potential ranged from -90 to -112 mV (n = 20) in cells of the vascular tissue and from -184 to -220 mV (n = 22) in cells of the pollen-transmitting tissue. The amplitude of the potential changes was between 40 and 150 mV, depending on the kind of stimulus. Self- as well as cross-pollination hyperpolarized the resting potential after 50 to 100 s, followed by a series of 10 to 15 action potentials. In contrast, cooling of the stigma caused a single action potential with a different shape and duration, whereas wounding generated a strong depolarization of the membrane potential with an irregular form and a lower transmission rate. To determine the physiological function of the different signals measured in the style, the gas exchange and metabolite concentrations were measured in the ovary before and 10 min after stimulation of the stigma. Self- and cross-pollination caused a transient increase of the ovarian respiration rate by 12%, which was measured 3 to 5 min after the stigma was stimulated. Simultaneously, the levels of ATP, ADP, and starch increased significantly. In contrast, both cold shock and wounding of the stigma caused a spontaneous decrease of the CO2 content in the measuring chamber, as well as reduced metabolite concentrations in the ovary. Since the transport of labeled auxin from the top to the base of the style lasts at least 45 min, the influence of a chemical substance transmitted within 10 min is unlikely. Thus, our results strongly support the view that different, stimulus-dependent electrical signals cause specific responses of the ovarian metabolism.     

A comparative microscopic and ultrastructural study of perichondrial tissue in cartilage of Octopus vulgaris (Cephalopoda, Mollusca)

The microscopic and submicroscopic structures of perichondrial tissues in the head cartilages of Octopus vulgaris were studied by polarized light and transmission electron microscopy. The orbital cartilages possess a birefringent layer parallel to the surface of the cartilage; ultrastructurally, this layer, which may be considered perichondrial tissue, has the typical organisation of connective tissue but does not possess the stratification of collagen laminae found in vertebrate perichondria. Perichondrial extracellular matrix is clearly distinct from that of cartilage because its collagen fibrils are of a larger diameter than collagen fibrils from cartilage. In addition, perichondrial fibroblasts are characteristically located at the center of collagen fibers. In the cerebral cartilage, the perichondrium is absent or discontinuous in relation to complex interconnections between cartilage and connective fibres, muscle fibres, blood vessels and nerve. Distinctive cartilage-lining cells, rich in electron dense cytoplasmatic granules, are stratified either along the cartilage surface or along vessels and muscle fibres that penetrate within the cartilage. The perichondrium of cephalopod cartilage, whose structure varies according to the location and function of its skeletal segments, mimics that of vertebrate perichondrium, exemplifying the high level of tissue differentiation attained by cephalopods.     

Freemartinism among singleton bovine females born from multiple embryo transfer

Heterosexual chimerism among singleton females produced by multiple nonsexed embryo transfer (MNET singleton females) was investigated using chromosome typing and PCR (polymerase chain reaction)-amplification of male-specific DNA (msDNA). Of the 22 animals tested, 21 were classified as normal by both methods (i.e., showing no male cells among 100 metaphase spreads in chromosome typing and being msDNA negative in PCR). No morphological abnormalities of the genital organs were observed among 19 MNET single females. One MNET singleton female was, however, classified as a freemartin by PCR (male-specific DNA positive), but it was classified as normal cytogenetically. This individual probably had a low degree of heterosexual chimerism, and it seems that the chimerism derived from MNET was difficult to diagnose by chromosome typing, although it was detectable by PCR. The genital organs of this individual (15-mo-old Aberdeen Angus) were normal in form (both external and internal) and size. However, a very small structure, resembling seminiferous tubule, was found in the left ovary. It may be concluded that most MNET singleton females are expected to have normal reproductive function.     

Cryopreservation of wild mouse spermatozoa

Spermatozoa of wild mice from China, Czechoslovakia, Denmark, India, Japan and Switzerland were frozen and stored at -196 degrees C. After thawing, intact oocytes were inseminated in vitro with relatively high motility frozen-thawed mouse spermatozoa from Czechoslovakia, Denmark and India, while oocytes with a partially dissected zona were inseminated with low motility frozen-thawed spermatozoa from China, Japan and Switzerland. Embryos developing to the 2-cell stage from oocytes fertilized with frozen-thawed spermatozoa were transferred to the oviducts of female recipients on the first day of pseudopregnancy (day when a vaginal plug was confirmed). Successful embryo development to the 2-cell stage was 46 to 67%. Offspring resulted from 17 to 51% of these transferred 2-cell embryos.     

Dose-dependent effect of heparin on fertilizing ability of goat spermatozoa

Intact bovine oocytes were used to study the effect of heparin on goat IVF. Oocytes were matured in Medium 199 plus estrous sheep serum. Fresh semen was incubated for 4 h at room temperature, and spermatozoa were then resuspended in medium Talp plus serum and incubated further for 1 h at 39 degrees C in 5% CO(2) in air. Later, spermatozoa were resuspended in Talp plus serum and heparin and were then incubated in microdrops until the oocytes were matured. In Experiment 1, the effect of heparin on spermatozoa from individual males was studied by a dose-response curve. In Experiment 2, the timing of sperm penetration in matured oocytes was studied to assess the stage at which the action of heparin could be expressed in the fertilization process. In Experiment 3, heparin from the same source but at different grades of bioactivity was adjusted for bioactivity and its effect on spermatozoa was compared in terms of penetration rates in order to identify heparin-dependent variations on goat IVF. In Experiment 4, the influence of calcium on the effect of heparin at different levels of bioactivity on the fertilizing ability spermatozoa was assessed as in Experiment 3. In Experiment 5, different batches of heparin from the same source and grade of bioactivity were compared as above. The results suggest that 1) heparin stimulates fertilization rates following a comparable pattern between males; 2) the most probable site of action is at the stage of sperm capacitation; and 3) provided that the source and grade of bioactivity is preserved, heparin maintains the efficiency of sperm penetration into matured oocytes.     

Embryo production and endocrine response in ewes superovulated with PMSG, with or without monoclonal anti-PMSG administered at different times

Mature nonlactating Altamurana ewes (n = 168) were synchronized in the seasonal anestrus period with FGA-impregnated intravaginal pessaries for 12 d. In Experiment 1, 48 ewes were divided into a 3 x 4 factorial design for anti-PMSG monoclonal antibody (AP) bioassay test. Concomitant injections of PMSG (1000, 1500, 2000 IU) and AP (0, 1, 2, 3 microl/IU PMSG) were given, and ovarian response was evaluated by laparoscopy. In Experiment 2, 120 ewes were divided into 8 experimental groups (n = 15 per group). The ewes treated with 1000 or 1500 IU PMSG at -24 h from sponge removal were given AP intravenously at 50 h after pessary withdrawal, 12 or 24 h after the onset of estrus, while the controls did not receive AP. Blood samples were collected from ewes (n = 6) treated with 1500 IU PMSG with or without anti-PMSG. Ovarian response and embryo production were evaluated on Day 7 after sponge removal upon laparotomy. It was found that 1 microl AP was effective in neutralizing 1 IU PMSG. No significant differences in serum concentrations of progesterone were observed among the groups of superovulated ewes. Estradiol-17 beta levels were reduced following AP treatment 12 h after the onset of estrus. At a lower dosage of superovulatory treatment (1000 IU PMSG), AP injected at 12 or 24 h after the onset of estrus significantly lowered large follicles (P < 0.01) and increased the rate of ovulation (P < 0.05). Moreover, embryo production showed a more than two-fold increase (P < 0.01) of viable embryos following AP injection at 12 or 24 h after the onset of estrus (3.2 to 3.3 vs 1.3, with vs without anti-PMSG). It is concluded that superovulatory treatment with 1000 IU PMSG plus AP administered at a fixed time after the onset of estrus may improve ovarian response and the yield of viable embryos in ewes.