Malnutrition impairs alveolar fluid clearance in rat lungs

Inadequate nutrition complicates the clinical course of critically ill patients, and many of these patients develop pulmonary edema. However, little is known about the effect of malnutrition on the mechanisms that resolve alveolar edema. Therefore, we studied the mechanisms responsible for the decrease in alveolar fluid clearance in rats exposed to malnutrition. Rats were allowed access to water, but not to food, for 120 h. Then, the left and right lungs were isolated for the measurement of lung water volume and alveolar fluid clearance, respectively. The rate of alveolar fluid clearance was measured by the progressive increase in the concentration of Evans blue dye that was instilled into the distal air spaces with an isosmolar 5% albumin solution over 1 h. Malnutrition decreased alveolar fluid clearance by 38% compared with controls. Amiloride (10(-3) M) abolished alveolar fluid clearance in malnourished rats. Either refeeding for 120 h following nutritional deprivation for 120 h or an oral supply of sodium glutamate during nutritional deprivation for 120 h restored alveolar fluid clearance to 91 and 86% of normal, respectively. Dibutyryl-cGMP, a cyclic nucleotide-gated cation channel agonist, increased alveolar fluid clearance in malnourished rats supplied with sodium glutamate. Terbutaline, a beta(2)-adrenergic agonist, increased alveolar fluid clearance in rats under all conditions (control, malnutrition, refeeding, and glutamate-treated). These results indicate that malnutrition impairs primarily amiloride-insensitive and dibutyryl-cGMP-sensitive alveolar fluid clearance, but this effect is partially reversible by refeeding, treatment with sodium glutamate, or beta-adrenergic agonist therapy.     

Levels and behavior of 2-phenylbenzotoriazole-type mutagens in the effluent of a sewage treatment plant

We previously reported on the isolation and structural determination of five 2-phenylbenzotriazole (PBTA)-type mutagens (PBTA-1, PBTA-2, PBTA-3, PBTA-4 and PBTA-6) in blue rayon/cotton adsorbed substances collected from surface waters at sites located downstream of sewage treatment plants. We also noted that PBTA-1 and PBTA-2 were discharged from sewage treatment plants and subsequently diluted or decomposed while moving down the Yodo River system. However, it has not been investigated whether they are commonly discharged from sewage treatment plants into rivers. The main purpose of this study was to make a comprehensive survey of levels and behavior of PBTA-type mutagens in effluents discharged from the sewage treatment plant located along the bank of the Uji River, one tributary of the Yodo River system. Water samples were collected at the outlet of the sewage treatment plant for 16 consecutive days in May 1999 and 11 consecutive days in December 1999. Organic constituents were obtained via sorption to blue rayon and subsequent methanol elution. Extract mutagenic activity was measured using Salmonella typhimurium YG1024 with metabolic activation. PBTA-type mutagens (PBTA-1, PBTA-2, PBTA-3, PBTA-4, PBTA-5 and PBTA-6) were quantified by HPLC with electrochemical detection, followed by HPLC purification on reverse-phase columns. The study showed that PBTA-2, PBTA-3, PBTA-4 and PBTA-6 were detected in most samples. The total contribution of these four PBTA-type mutagens to overall extract mutagenicity is on average 33% for the May 1999 sample and 58% for the December 1999 sample. The individual PBTA compounds that had the largest contribution to the overall mutagenicity were PBTA-3 and PBTA-4, accounting for 11 and 16% in May 1999, and 25 and 26% in December 1999. A further comparative study was done in December 1999 using the blue rayon hanging method and the results were similar to those obtained using the blue rayon column method. In conclusion, the present study showed that PBTA-2, PBTA-3, PBTA-4 and PBTA-6 were commonly discharged from a sewage treatment plant into the Uji River, and they accounted for a substantial portion of the effluent mutagenicity.     

Role of ANG II in coronary capillary angiogenesis at the insulin-resistant stage of a NIDDM rat model

With the use of Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of human non-insulin-dependent diabetes mellitus (NIDDM), we assessed whether ANG II is involved in coronary capillary angiogenesis at the insulin-resistant stage of NIDDM (20 wk of age). In OLETF rats, ANG II labeling and angiotensin type 1 (AT(1)) receptor expression in coronary vessels were increased more than in nondiabetic controls. A marked increase in vascular expression of vascular endothelial growth factor (VEGF) at both mRNA and protein levels was found in OLETF rats. The increased expression level of VEGF was associated with accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha) activated by increased advanced glycation end products (AGEs). Morphometric analysis showed a significantly increased total coronary capillary density, which was a result of arterialization of the venular capillary portion in OLETF rats. Treatment of OLETF rats with candesartan, an AT(1) receptor blocker, inhibited vascular expressions of VEGF, HIF-1alpha, and AGEs, and ameliorated the morphometric changes. These results suggest a key role of ANG II in the pathogenesis of the coronary capillary remodeling in this NIDDM model.     

Adaptor protein Shc is an isoform-specific direct activator of the tyrosine kinase c-Src

The activity of c-Src protein-tyrosine kinase is up-regulated under a number of receptor signaling pathways. However, the activation mechanism of c-Src under physiological conditions has remained unclear. We show here that the Shc adaptor protein is a novel direct activator of c-Src in epidermal growth factor receptor signaling in A431 human epidermoid carcinoma cells. Among the three Shc isoforms, P66 and P52, but not P46, were found to interact with and activate c-Src in vitro and in vivo. Activation of c-Src accompanied autophosphorylation of c-Src in the activation segment, but the carboxyl-terminal dephosphorylation was not observed. We have identified the interaction sites between Shc and c-Src and constructed a point mutant of Shc that abolishes the c-Src activation. Using this mutant, we have confirmed that the Shc-mediated c-Src activation triggers Stat-p21/WAF1/Cip1 pathway that has been implicated in the cell cycle arrest and apoptosis of epidermal growth factor-stimulated A431 cells.     

Changes in mutagenicity of herbicide chlornitrofen during biodegradation

We used the Ames assay to investigate changes in the mutagenicity of chlornitrofen during its aerobic biodegradation. Although a mixed culture of bacteria obtained from river water degraded chlornitrofen and reduced its concentration from 39 to 6 microg/l in 21 days, the indirect mutagenicity of the solution to Salmonella strains TA98, YG1021, and YG1026 increased gradually. This finding suggests that mutagenic metabolites were produced during the aerobic biodegradation. The increase in the mutagenicity was, however, much smaller under aerobic than under anaerobic conditions. The differing sensitivities of our test strains to the functional groups on the mutagens showed that the mutagenic metabolites were indirect frameshift-type mutagens that might have neither nitro nor amino groups.     

IL-6 enhances IgE-dependent histamine release from human peripheral blood-derived cultured mast cells

We examined whether interleukin (IL)-6 exerts the stimulatory effects on the secretion of histamine from human mast cells triggered by crosslinking of the high affinity IgE receptor (FcepsilonRI) with IgE and anti-IgE. As target cells, we used peripheral blood-derived cultured mast cells grown with SCF, because they were superior in FcepsilonRIalpha expression to cord blood-derived mast cells. Incubation with SCF+IL-6 for 1 week increased the IgE-dependent release as well as intracellular content of histamine in the cultured mast cells, as compared with the values obtained by incubation with SCF alone. The magnitude of these increases was higher than that for priming with SCF+IL-4. A striking difference was also found in the expression of FcepsilonRIalpha between the two-factor combinations. The addition of IL-6 during FcepsilonRI crosslinking with IgE/anti-IgE in the presence of SCF did not influence histamine secretion. When SCF, IL-6 and IL-4 were used together, a further increase was observed in the anti-IgE-dependent liberation of histamine from the cultured mast cells, compared with the two-factor combinations. These results suggest that IL-6 functions as a secretagogue for the inflammatory mediator of human mast cells in the presence of SCF.     

Differences between maize and rice in N-use efficiency for photosynthesis and protein allocation

The N-use efficiency for photosynthesis was higher in a C(4) plant, maize, than in a C(3) plant, rice, including rbcS antisense rice with optimal ribulose-1,5-bisphosphate carboxylase (Rubisco) content for CO(2)-saturated photosynthesis, even when photosynthesis was measured under saturating CO(2) conditions. The N cost for the C(4) cycle enzymes in maize was not large, and the lower amount of Rubisco allowed a greater N investment in the thylakoid components. This greater content of the thylakoid components as well as the CO(2) concentrating mechanism may support higher N-use efficiency for photosynthesis in maize.     

Enhancement of transpiration by ethylene is responsible for absence of internodal elongation in floating rice at low humidity

Internodal elongation in floating rice (Oryza sativa) is known to be enhanced by treatment with ethylene or gibberellic acid (GA3) at high relative humidity (RH). However, ethylene-induced internodal elongation is inhibited at low RH, while GA3-induced internodal elongation is hardly affected by humidity. We examined the effects of ethylene and GA3 on the rate of transpiration in stem segments incubated at 30% or 100% RH. Ethylene promoted the transpiration of stem segments at 30% RH, but not at 100% RH, while GA3 had little effect on transpiration at either 30% or 100% RH. We propose that the absence of ethylene-induced internodal elongation at low RH is due, at least in part, to ethylene-induced transpiration.     

Acetylcholine increases intracellular Ca2+ in the rat pituitary folliculostellate cells in primary culture

Pituitary folliculostellate cells (FSCs) are thought to partially inhibit pituitary hormone secretion through a paracrine mechanism. In this process, one of the important questions is what factors regulate the function of FSCs. Because ACh is synthesized in and possibly released from the corticotrophs and lactotrophs, we examined whether FSCs respond to ACh by the method of Ca2+ imaging in primary cultured FSCs from male Wistar rats. ACh (30 nM-3 microM) increased intracellular calcium concentration ([Ca2+](i)) of FSCs in a concentration-dependent manner, with an initial rapid rise followed by a relatively sustained increase. The complete block of the response by atropine and pirenzepine suggests involvement of muscarinic receptors. Depletion of the stored Ca2+ by thapsigargin blocked the response completely. Blockers of phospholipase C, U-73122 and neomycin, suppressed significantly the rise of [Ca2+](i). These results suggest that ACh increases [Ca2+](i) in FSCs by activating phospholipase C, presumably through activation of M(1) receptors. The rise in [Ca2+](i) could trigger a variety of Ca2+-dependent cellular processes, including the synthesis and release of bioactive substances, which in turn act on endocrine cells.