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We constructed a new centrifuge microscope of the stroboscopic type, with which the cytoplasmic streaming in Nitella internodal cells under centrifugal acceleration was studied. Under moderate centrifugal acceleration (ca. 50-100× g), the direction of cytoplasmic streaming in an internodal cell of Nitella is parallel to the direction of the subcortical fibrils. The speed of endoplasm flowing contiguous to the subcortical fibrils is neither accelerated nor retarded by moderate centrifugal acceleration. The endoplasmic flow, however, stops suddenly following an electrical stimulus. The endoplasm contiguous to the subcortical fibrils is immobilized transiently at the time of streaming cessation induced by an electrical stimulus under centrifugal acceleration at 50-100× g, even at 900× g. It is suggested that transitory cross bridges between the immobilized endoplasm and the subcortical fibrils are formed at the time of streaming cessation. The bulk endoplasm flows as a whole in the direction parallel to that of the subcortical fibrils and stops promptly upon electrical stimulation. Soon after the stoppage the bulk endoplasm starts to flow passively in the direction parallel to that of the centrifugal acceleration as a result of the centrifugal force. [ABSTRACT FROM AUTHOR]

The photoprotein aequorin was introduced into tonoplast-free Chara cells. Aequorin light emission transiently increased when the cell generated an action potential, which consisted of initial rapid depolarization and a subsequent maintenance of this at a plateau level. The light emission change also consisted of two components. First was a rapid rise followed by a rapid return to nearly the initial level. This rapid component corresponded to the initial rapid depolarization of the action potential and seemed to reflect the Ca release from the plasmalemma. The second component of light emission was a gradual increase of luminescence that continued for the prolonged depolarization phase of the action potential. When the action potential was terminated, the luminescence instantly began to decrease. This component probably reflects the Ca influx through the plasmalemma which may become highly permeable to ions during excitation. Free Ca concentrations of tonoplast-free Chara cells containing 1 m MEGTA are estimated to be about 2 μM at the resting state and about 4 μM at the initial phase of the light emission change. [ABSTRACT FROM AUTHOR]

Isolated characean internodal cells of Nitellopsis obtusa can be stored in artificial pond water for many days, but they cannot survive in 100mol m-3 NaCl solution unless more than several mol m-3 Ca2+ is added. Short-term effects of NaCl stress on the cytosolic concentration of Ca2+ ([Ca2+]c), cytosolic pH (pHc) and vacuolar pH (pHv) were studied in relation to the external concentration of Ca2+ ([Ca2+]c). Changes in [Ca2+]c were measured with light emission from a Ca2+-sensitive photoprotein, semisynthetic fch-aequorin which had been injected into the cytosol. Both pHc and pHv were measured with double-barrelled pH-sensitive microelectrodes. When internodal cells were treated with 100 mol m-3 NaCl (0-1 mol m-3 [Ca2+]0, [Ca2+]c. increased and then recovered to the original level within 60 rain. The time course of the transient change in [Ca2+]c was not influenced by the level of [Ca2+]c (0.1 and l0 mol m-3). In some cases, the transient increase in [Ca2+]c was induced only by increasing external osmotic pressure with sorbitol, in response to treatment with 100 mol m-3 NaCl (0.1 mol m-3 [Ca2+]c), pHc decreased by 0.1-0.2 units after 10 min but recovered after 30--60 min, while pHv increased by 0.4-0.5 units after 2-50 rain and tended to recover after 60 min. The initial changes in both PHc and pHv were suppressed when [Ca2+]c was raised from 0.1 to 10 mol m-3. These results show that the charophyte alga Nitellopsis call regulate [Ca2+]c, pHc and pHv under NaCl stress in the short term and that the protective effect of Ca2+ on salinity stress is apparently unrelated to perturbation of Ca2+ and pH homeostasis. [ABSTRACT FROM AUTHOR]

The behavior of cytoplasmic streaming in plasmodial strand of Physarum polycephalum was studied under centrifugal acceleration using a centrifuge microscope of the stroboscopic type. Cytoplasmic streaming in the plasmodium was greatly affected by changes in the acceleration. The endoplasmic flow in the centrifugal direction was accelerated, while that in the centripetal was retarded, by centrifugal acceleration. The centrifugal acceleration required to stop the endoplasmic flow in the centripetal direction did not cause total cessation of streaming but always induced a bidirectional flow of endoplasm in one and the same strand. Each profile of velocity distribution of the bidirectional flow was both parabola with flattened apex. One possible cause of the bidirectional flow is discussed. [ABSTRACT FROM AUTHOR]

With an attempt to measure the motive force responsible for cytoplasmic streaming in characean internodal cells, the difference between densities of cytoplasm and vacuolar sap was heightened by about 10 times (density of vacuolar sap was made larger than that of cytoplasm) by replacing the natural vacuolar sap of Chara corallina with an artificial one of higher density. Endoplasmic flow contiguous to the peripheral actin cables (peripheral flow of endoplasm) in the centrifugal direction was not influenced at all by the application of centrifugal acceleration up to 1400 g. We thus concluded that the motive force for the peripheral flow should be much larger than 12dyn/cm, a figure more than 10 times larger than that for bulk endop lasmic flow so far reported. [ABSTRACT FROM AUTHOR]

By injuring cells of Valonia ventricosa, one of two survival strategies - wound-healing and protoplast formation - is induced. The present study revealed that turgor pressure, as well as Ca in bathing medium, is involved in the choice between these survival strategies. On the process of wound-healing, turgor pressure is recovered in the presence of both the wound plug, which closes the wound immediately after an injury, and the aggregation of protoplasm around the wound, which serves to protect the inflow of outer medium into the protoplasm layer and also to strengthen the wound plug. When the size of the wound is more than 150 μm in diameter, the protoplasmic aggregate strengthen the wound plug incompletely and, as a result, wound-healing is unsuccessful. In this case, the ejection of vacuolar sap is repeated, due to partial restoration of turgor pressure. In each ejection, the wound plug is blown off, together with the aggregated protoplasm and, after several ejections are repeated, the cell is unable to heal the wound because of a lack of protoplasm around the wound. Continuous depression of turgor pressure, during the repeat of the unsuccessful wound-healing, induces disorganization of the protoplasm layer. Under these conditions, the centrifugal propagation of protoplasmic aggregation, followed by the protoplasts formation, takes place easily. Effects of turgor pressure and Ca in the bathing medium upon the wound healing is discussed and the cytoplasmic behavior for survival of wounded cells is presented schematically. [ABSTRACT FROM AUTHOR]

Taking advantage of prolonged action potential under low temperature, we studied temporal relationship among the action potential, increase of cytoplasmic Ca concentration and cessation of cytoplasmic streaming in Nitella. The Ca concentration began to increase at a very early stage of the action potential and the cessation of streaming followed that increase. [ABSTRACT FROM AUTHOR]

Using a stroboscopic centrifuge microscope, we demonstrated that, when actin cables (=bundles of F-actin) had been previously removed locally from the cell cortex of Nitella internodes, the passively flowing endoplasm found there under centrifugal force did not stop at all upon electrical stimulus, while the actively flowing endoplasm contiguous to the actin cables at the normal cell cortex promptly stopped following the stimulus and was immobilized for several seconds. The results present evidence that, upon electrical stimulus, the presence of actin cables is required to immobilize the endoplasm flowing contiguous to the actin cables in a state that resists displacement by centrifugal force. [ABSTRACT FROM AUTHOR]

When Ca, K or Cl was injected iontophoretically into the cytoplasm of intact Nitella cell, only Ca reversibly inhibited the cytoplasmic streaming. However, when an extremely large current was used, the cytoplasmic streaming was reversibly inhibited irrespective of the ion species. This inhibition may be due to a transient increase of free Ca. [ABSTRACT FROM AUTHOR]

N-acetylchitooligosaccharides (fragments of chitin) elicit the production of phytoalexin in suspension-cultured rice cells. This oligosaccharide elicitor induced rapid and transient membrane depolarization at sub-nanomolar concentrations. Only the oligomers with a certain degree of polymerization were active, while deacetylated chitooligosaccharides caused no effect. Such specificity coincided well with that for the elicitor activity, suggesting possible involvement of this transient change in membrane potential as one of the initial signals in the signal transduction sequence for the activation of defense responses. [ABSTRACT FROM AUTHOR]

The article discusses the case of a female patient with isolated accessory pancreatic duct. The patient had a history of recurrent abdominal pain. An upper abdominal ultrasonography and a computed tomography revealed an atrophic pancreas. An endoscopic pancreatography showed a short pancreatic duct that failed to connect with the main pancreatic duct. The minor papilla was removed by endoscopic resection. Histological evaluation revealed a small adenoma.