Mercurial-sensitive water transport in barley roots

An isolated barley root was partitioned into the apical and basal part across the partition wall of the double-chamber osmometer. Transroot water movement was induced by subjecting the apical part to a sorbitol solution, while the basal part with the cut end was in artificial pond water. The rate of transroot osmosis was first low but enhanced by two means, infilitration of roots by pressurization and repetition of osmosis. Both effects acted additively. The radial hydraulic conductivity (Lp_r) was calculated by dividing the initial flow rate with the surface area of the apical part of the root, to which sorbitol was applied, and the osmotic gradient between the apical and basal part of the root. Lp_r which was first 0.02–0.04 pm s⁻¹ Pa⁻¹ increased up to 0.25–0.4 pm s⁻¹ Pa⁻¹ after enhancement. Enhancement is assumed to be caused by an increase of the area of the plasma membrane which is avallable to osmotic water movement. The increased Lp_r is in the same order of magnitude as the hydraulic conductivity (Lp) of epidermal and cortical cells of barley roots obtained by Steudie and Jeschke (1983). HgCl₂, a potent inhibitor of water channels, suppressed Lp_r of non-infiltrated and infiltrated roots down to 17% and 8% of control values, respectively. A high sensitivity of Lp_r to HgCl₂ suggests that water channels constitute the most conductive pathway for osmotic radial water movement in barley roots.     

Sucrose consumption in mice: Major influence of two genetic Loci affecting peripheral sensory responses

Individual variability in sucrose consumption is prominent in humans and other species. To investigate the genetic contribution to this complex behavior, we conducted behavioral, electrophysiological, and genetic studies, using male progeny of two inbred mouse strains (C57BL/6ByJ [B6] and 129/J [129]) and their F₂ hybrids. Two loci on Chromosome (Chr) 4 were responsible for over 50% of the genetic variability in sucrose intake. These loci apparently modulated intake by altering peripheral neural responses to sucrose. One locus affected the response threshold, whereas the other affected the response magnitude. These findings suggest that the majority of difference in sucrose intake between male B6 and 129 mice is due to polymorphisms of two genes that influence receptor or peripheral nervous system activity. Received: 27 January 1997 / Accepted: 17 March 1997     

In vitro study on release of thyroid hormone in solitary autonomously functioning thyroid nodules using cell culture method

In vitro release of thyroid hormone was investigated under basal and TSH-stimulated conditions in the solitary autonomously functioning thyroid nodules (AFTN). A small portion (0.5 g of wet weight) of the nodules and adjacent thyroid tissues removed surgically from five patients with solitary AFTN were prepared for the dispersed cell culture. In the experiment on non TSH-stimulated (basal) conditions, those culture media which were totally replaced on the 5th day after primary culture were utilized for the determination of thyroxine (T4) and triiodothyronine (T3) by radioimmunoassay. T4 and T3 levels in culture media of the functioning nodules were 1.15 +/- 0.33 microgram/dl (mean +/- SEM) and 2.72 +/- 0.68 ng/ml, contrasted with levels of 0.67 +/- 0.09 microgram/dl and 1.24 +/- 0.22 ng/ml in the paranodular tissues. The mean ratios of T3/T4 of the nodules and paranodular tissues were 0.25 +/- 0.02 and 0.19 +/- 0.02, respectively (p less than 0.05). Meanwhile, in another experiment under TSH stimulatory conditions employing 40 and 80 microU/ml of human TSH, there were no significant differences in T4 and T3 releases when the two groups were compared.     

Presence of adrenocorticotropin-potentiating factors in porcine thyroid glands

An extract of porcine thyroid gland in 0.1 N acetic acid exerted dose-dependent potentiation of ACTH-induced corticosterone production in isolated rat adrenal cells. The extract by itself manifested no steroidogenic activity. Upon gel-filtration of the extract, potentiating activities were demonstrated in three main peaks with molecular weights of about 10,000, 5,000 and 2,000. These findings indicate the presence of heterogeneous forms of ACTH-potentiating factors in the thyroid. Significant enhancement of ACTH-induced steroidogenesis was readily apparent with three gel-filtration fractions at a lower concentration of ACTH (4.75 pM). At this concentration, dose-dependent potentiation was observed with these three fractions. Enhanced corticosterone production responses by cells preincubated with the thyroid extract were observed and the results indicated the existence of potentiating mechanisms other than inhibition of ACTH proteolysis. The lack of T4, T3 and thyroglobulin in this activity suggests that the activity resides in other constituents of the thyroid.     

Adenine-nucleotide levels and metabolism-dependent membrane potential in cells of Nitellopsis obtusa Groves

The relationship between adenine-nucleotide levels and metabolism-dependent membrane potential was studied in cells of Nitellopsis obtusa. Effects of ADP and AMP in the presence of ATP on electrogenic pump activity were measured in the dark, using the continuous perfusion method. Both ADP and AMP acte as competitive inhibitors for ATP, the K_i value for either compound being about 0.4 mM. The role of ADP and AMP as regulating factors for the electrogenic pump was investigated under various metabolic conditions. Application of N₂ gas in the dark caused a significant membrane depolarization amounting to 90 mV, but cytoplasmic streaming and membrane excitability were not affected. Under anoxia, the ATP level decreased from 1.6 to 0.5 mM; ADP increased but only slightly, and AMP increased greatly. However, the time course of changes in the adenine nucleotides was not concurrent with that of the membrane-potential changes, thus, the adenine-nucleotide level changes cannot fully account for the N₂-elicited depolarization. Under light, although the membrane hyperpolarized, no significant changes in the adenine-nucleotide levels were observed. Therefore, the light-induced membrane hyperpolarization cannot be explained solely by changes in adenine-nucleotide levels.Abbreviations APW artificial pond water - E_m membrane potential - R_m membrane resistance     

Sulphides and furanones from steam volatile oils of Allium fistulosum and Allium chinense

The constituents of the steam volatile oils from two kinds of Allium fistulosum, A. fistulosum var. caespitosum and A. chinense, have been investigated by GC and spectral techniques (IR, UV, GC/MS, ¹H NMR and ¹³C NMR). The compounds identified from the neutral fraction of each volatile oil included sulphides, thiolanes, alcohols, aldehydes, ketones, furanones and others. Among the sulphur compounds, dipropyl disulphide comprised ca 28% of A. fistulosum oil, ca 23% of A. fistulosum var. caespitosum oil and ca 30% of A. chinense oil. A. fistulosum oil was characterized by a large quantity of tridecan-2-one (ca 52%) and 2,3-dihydro-2-octyl-5-methylfuran-3-one (ca 16%). Also, a large amount of 2,3-dihydro-2-hexyl-5-methylfuran-3-one (ca 20%) was isolated from A. chinense oil.     

Complement-dependent cytotoxicity of sera obtained from subacute sclerosing panencephalitis patients

Human lymphoid cells (NC-37) persistently infected with either measles virus (Schwarz and TYCSA strains) or subacute sclerosing panencephalitis (SSPE) virus (Halle and Mantooth strains) were destroyed in the presence of complement by anti-measles sera as well as by sera from SSPE patients. The cytotoxic activity was demonstrated in both IgG and IgM fractions of measles convalescent sera, but only in IgG fraction of SSPE sera. Measles convalescent sera completely lost the cytotoxic activity to all the cell lines, when absorbed with any one of the cell lines, indicating that the viral surface antigens of these cell lines infected with measles or SSPE virus are identical. On the other hand, the cytotoxic activity of SSPE sera could not be readily absorbed with these cells. Thus, the affinity of SSPE sera for the viral surface antigens might be lower than that of measles convalescent sera.     

Histochemical studies of mucosubstances in metaplastic epithelium of the stomach,with special reference to the development of intestinal metaplasia

Summary Processes in the development of intestinal metaplasia of the stomach were investigated from the morphological and histochemical approaches using light and electron microscopic techniques. The specimens taken from 38 gastric carcinomas and 15 gastric and/or duodenal ulcers were subjected to this study. Morphological appearances of the intestinal metaplasia observed in routine examination with hematoxylin and eosin staining was able to be divided into complete and incomplete metaplasia by the light and electron microscopic histochemical stainings of the mucosubstances. The columnar cells at the area of the incomplete metaplasia had both the properties of the intestinal epithelia and the gastric foveolar epithelia. The incomplete as well as the complete metaplasia arose from the generative cells at the isthmus of the gland. The generative cells, however, sometimes gradually transformed to produce the complete metaplastic cells. The two processes of the development of the intestinal metaplasia were proposed and discussed.     

Control of membrane potential and excitability ofChara cells with ATP and Mg2+

Summmary Electric characteristics of internodalChara australis cells, from which the tonoplast had been removed by vacuolar perfusion with media containing EGTA, were studied in relation to intracellular concentrations of ATP and Mg²⁺ using the ordinary microelectrode method and the open-vacuole method developed by Tazawa, Kikuyama and Nakagawa (1975.Plant Cell Physiol. 16:611). The concentration of ATP was decreased by introducing hexokinase and glucose into the cell and that of Mg²⁺ by introducing EDTA or CyDTA. The membrane potential decrease and the membrane resistance increase were both significant when the ATP or Mg²⁺ concentration was decreased. An ATP-dependent membrane potential was also found in other species of Characeae,Nitella axillaris andN. pulchella. Excitability of the membrane was also completely lost by reducing the ATP or Mg²⁺ concentration. Both membrane potential and excitability were recovered by introducing ATP or Mg²⁺ into ATP- or Mg²⁺-depleted cells.The time course of membrane potential recovery was followed by the open-vacuole method. Recovery began as soon as intracellular perfusion with medium containing ATP and Mg²⁺ was started. Reversible transition of the membrane potential between polarized and pepolarized levels by controlling the intracellular concentration of ATP or Mg²⁺ could be repeated many times by the open-vacuole method, when the excitability was suppressed by addition of Pb²⁺ to the external medium.The ineffectiveness of an ATP analog, AMP-PNP, and the synergism of ATP and Mg²⁺ in maintaining the membrane potential and excitability strongly suggest that ATP act via its hydrolysis by Mg²⁺-activated ATPase. The passive nature of the membrane, as judged from responses of the membrane potential to changes of the external K⁺ concentration, was not altered by lowering the ATP concentration in the cell. The mechanism of membrane potential generation dependent on ATP is discussed on the basic of an electrogenic ion pump. Involvement of the membrane potential generated by the ion pump in the action potential is also discussed.     

(+)-Arctigenin,a lignan from Wikstroemia indica

A new lignan, (+)-aretigenin has been isolated from the roots of Wikstroemia indica (Nan-Ling-Jao-Hua) and identified as 8(R) 8′(S)-4′-hydroxy-3, 4,3′-trimethoxylignan-olid (9, 9′) on the basis of spectral evidence as well as a direct comparison with its enantiomer, (?)-arctigenin.