Effects of winter flooding on phosphorus dynamics in rice fields

Limnology - Controlling phosphorous (P) loads from rice fields is important for the conservation of aquatic ecosystems, in part because P is relatively concentrated at its sources. Recently, winter...     

Mechanisms of modulation of neuronal nicotinic receptors by substance P and OAG

Substance P is known to modulate neuronal nicotinicacetylcholine receptors (nAChRs) in the sympathetic nervous system.There are two conflicting proposals for the mechanism of this effect, an indirect action mediated by protein kinase C (PKC) and a direct interaction with receptor subunits. We studied the mechanisms of thiseffect in PC-12 cells. Substance P enhanced the decay of thenicotine-induced whole cell current. This effect was fast in its onsetand was not antagonized by guanosine5'-O-(2-thiodiphosphate), a G protein blocker, orstaurosporine, a nonselective PKC blocker. Staurosporine failed toreverse the inhibition by 1-oleoyl-2-acetyl-sn-glycerol (OAG), a synthetic diacylglycerol analog known to activate PKC. Theinhibitory effects of the peptide and OAG were preserved in excisedpatches, but substance P applied to the extra patch membrane wasineffective in the cell-attached patch configuration. We conclude thatsubstance P modulates neuronal nAChRs most likely by direct interactions with the receptors but independently from activation ofPKC or G proteins and that PKC does not participate in modulation by OAG.

     

Age-related differences in muscle activity, stride frequency and heart rate response during walking in water.

This study aimed to examine whether walking in water produces age-related differences in muscle activity, stride frequency (SF), and heart rate (HR) response. Surface electromyography (EMG) was used to evaluate muscle activities in six older and six young subjects while they walked in water immersed to the level of the xiphoid process. The trials in water utilized the Flowmill which consists of a treadmill at the base of a water flume. The measurement of maximal voluntary contraction (MVC) of each muscle was made prior to the gait analysis. The %MVCs, which refer to the surface EMG measures, from the gastrocnemius of the older subjects were significantly lower than those of the young subjects, in every experimental condition (P<0.05). In contrast, the %MVCs from the rectus femoris (P<0.05) and the biceps femoris (P<0.001) of older subjects were significantly greater than those of young subjects in every experimental condition. Moreover, the SFs of older subjects were also significantly greater than those of young subjects (P<0.05), while the HR responses of older and young subjects were similar. In conclusion, the older subjects had increased hip musculature activity and decreased ankle plantar flexor activity while walking in water, compared with the young subjects.     

Low serum reverse T3 levels in patients with primary hyperparathyroidism

Although patients with primary hyperparathyroidism (1 degree HPT) were euthyroid, we measured serum thyroid hormone levels in 16 patients with 1 degree HPT together with 17 patients with hypercalcemia due to malignant diseases (HCM). In patients with 1 degree HPT, serum levels of T3, T4 and T3U were within normal range, but serum rT3 (reverse T3) levels (205 +/- 37 pg/ml, mean +/- SD) were significantly decreased as compared with those in normal controls (276 +/- 44 pg/ml, P less than 0.01). A significant inverse correlation was observed between the serum levels of rT3 and parathyroid hormone (PTH) (r = 0.54, P less than 0.05). After parathyroidectomy, serum rT3 levels were significantly elevated (240 +/- 56 pg/ml) compared to preoperative levels (P less than 0.01). Low levels of serum rT3 seemed to be attributed to the high levels of serum PTH. On the other hand, serum levels of T3 and T4 were low and serum rT3 levels were high in patients with HCM. Low serum rT3 allows for the differentiation of patients with 1 degree HPT from those with HCM.     

Filipin-sterol complexes in golden hamster sperm membranes with special reference to epididymal maturation

Summary The distribution of membrane filipin-sterol complexes (FSCs) was qualitatively surveyed on freeze-fracture replicas of spermatozoa from the male reproductive tract and ejaculates of golden hamster. In the head, the acrosomal plasma membrane showed the strongest filipin labeling on the principal segment, but it was absent in the quilt-like pattern areas. These latter were observed in both caput and corpus epididymal spermatozoa, but were absent in mature spermatozoa. The postacrosomal plasma membrane had few FSCs and both the outer and inner acrosomal membranes were always negative to filipin. The nuclear membrane of the principal segment was constantly filipinpositive. The nuclear membrane of the postacrosomal region had more FSCs than that of the principal segment, particularly in mature spermatozoa. Many linear, rod-like FSCs were observed on the postacrosomal nuclear membrane of mature spermatozoa, especially in the uterine spermatozoan samples. In the neck, the plasma membrane had only a few FSCs. The redundant nuclear membrane was slightly filipin-positive, while the membrane scroll of mature spermatozoa was heavily labeled. In the tail, the plasma membrane of both the middle and principal piece was moderately labeled.     

Immunohistochemical localization of proteoglycans in interstitial elements of human pancreas and biliary system

Summary The immunohistochemical localization of large proteoglycan and small proteoglycan was observed, using antibodies 2B1 and 6B6 (Sobueet al., 1988, 1989a), in fetal and adult pancreas and biliary system as well as in tumour tissues, obtained from 11 autopsies and 74 biopsies. The distribution of chondroitin 4- and 6-sulphate side chains, type I and IV collagen and elastin were also studied. In adult pancreas and all the biliary tracts examined, periductal fibrous tissues consisted mainly of dermatan sulphate small proteoglycan with networks of fibrous elements, which were composed of large proteoglycan, elastin, type I collagen and type IV collagen. In the interstitial components of cystadenoma of pancreas and biliary duct carcinoma, similar small proteoglycan-rich components were relatively abundant, although large proteoglycan was present in much larger amounts than that in non-neoplastic adult tissues. In some cholangiomas, the extra-and intracellular hyaline globules formed by the carcinoma cells were found to contain chondroitin sulphate large proteoglycan, laminin and fibronectin.The distribution of proteoglycans was observed to be different in the arterial walls of the interlobular tissues of the adult and the fetal pancreas. The biological significance of large and small proteoglycans in the interstitial connective tissues was discussed.     

Specific arrangements of cortical microtubules are correlated with the architecture ofmeristems in shoot apices of angiosperms and gymnosperms

Arrangements of corticalmicrotubules (MTs) as seen in median longitudinal cryosections of shoot apices of several angiosperms and gymnosperms were studied by indirect immunofluorescence microscopy.Bryophyllum, Clethra, Helianthus, Houttuynia, Vinca (angiosperms), andPinus, Cedrus, Cedrus andGinkgo (gymnosperms) were examined. In all angiosperm apices collected during the growing season, MTs were mainly arranged anticlinally in the tunica, randomly in the corpus, and transversely in the rib meristem. This pattern of arrangements of MTs was further confirmed by electron microscopy inBryophyllum apices. In the apices of winter shoots MTs in the rib meristem were arranged randomly, indicating a seasonal change with respect to their arrangment. In all examined gymnosperm apices, populations of superficial cells showed both random and anticlinal arrangements of MTs, in contrast to those of angiosperm apices that consistently show anticlinally arranged MTs. In the shoot apices of both angiosperms and gymnosperms, cortical MTs were arranged perpendicularly to the directions of cell expansion. The significance of MTs in the maintrnance of the different architectures of shoot apices in angiosperms and gymnosperms is discussed.     

Uptake of Gibberellin Methyl Esters by Spores and Induction of Dark Germination in Lygodium japonicum

In the fern Lygodium japonicum, the effect of the exogenousapplication of two gibberellin methyl esters, gibberellin A₄methyl ester (GA₄Me) and gibberellin A₂₀ methyl ester (GA₂₀Me)on spore germination in the dark and uptake of GA₄Me and GA₂₀Meby spores was investigated. Tritiated GA₄Me and GA₂₀Me wereprepared and used as radioactive tracers. The activity of GA₄Mewas more than 100-fold that of GA₂₀Me for the induction of sporegermination. When treated for 24 h, the activity for inducingspore germination remained after removal of the gibberellinmethyl esters from the medium. The amount of GA₄Me taken upby spores was more than three times that of GA₂₀Me throughoutthe 24 h time course of treatment. The uptake of both gibberellinmethyl esters was proportional to the external concentrationfor the range of concentrations between 10^–9 M and 10^–6M. When treated with the tritiated gibberellin methyl estersat 10^–6 M and 10^–7 M for 24 h, most of the gibberellinmethyl esters taken up by the spores were not metabolized. Althoughthe uptake of the two gibberellin methyl esters differed by3- to 5- fold, their abilities to induce spore germination differedby more than 100-fold. Therefore, the difference in the activityof the two gibberellin methyl esters regarding the inductionof spore germination could not be explained solely by the differencein their uptake. (Received January 11, 1988; Accepted May 26, 1988)     

In vitro propagation of Glehnia littoralis from shoot-tips

Shoot cultures of Glehnia littoralis F. Schmidt ex Miq. (Umbelliferae) were established by placing shoot tip explants on Linsmaier and Skoog medium with 1 M NAA and 10 M BAP. Shoots were multiplied on the basal medium supplemented with 0.3 M NAA and 3 M BAP and rooted on medium containing either 1 M IBA or 3–10 M IAA. Plantlets survived in pots without any covering. This unique characteristic of the plantlets was ascribed partly to a well-developed cuticle on the surface of the leaf and the small ratio of surface area to fresh weight of a leaf blade in comparison with those of other species whose plantlets needed coverings after potting. The regenerated plantlets were finally transferred to soil.Abbreviations IAA potassium indole-3-acetate - IBA indole-3-butyric acid - IPA indole-3-propionic acid - NAA potassium 1-naphthaleneacetate - 2,4-D sodium 2,4-dichlorophenoxyacetate - BAP 6-benzylaminopurine - 2-iP N⁶-(2-isopentenyl)adenine