Osmotic relations during elongation growth in hypocotyls of Helianthus annum L.

The relationship between growth, change in cell osmotic pressure and accumulation of osmotic solutes was investigated in hypocotyls of sunflower (Helianthus annum L.) seedlings. During growth in darkness the osmotic pressure decreased by 50% between days 2 and 6 after sowing. After irradiation of dark-grown seedlings with continuous white light (WL) an inhibition of hypocotyl growth was measured, but the osmotic pressure of the growing cells was not lower than in the dark-grown control. Growth in darkness and after WL irradiation was accompanied by an increase in the amount of osmotic substances (soluble sugars) which was proportional to the increase in length of the organ. During growth in continuous WL the cell osmotic pressure decreased by 45 % between days 2 and 6 after sowing. The transfer of WL-grown seedlings to darkness (“re-etiolation”) resulted in a rapid acceleration of hypocotyl growth, but the cell osmotic pressure was the same as that of the WL grown control. Growth in continuous WL was accompanied by a corresponding accumulation of osmotic substances (soluble sugars). The transition from WL to darkness resulted in an enhanced accumulation of osmotica and an increase in cell-wall extensibility. The results indicate that the relative maintenance of cell osmotic pressure during rapid hypocotyl growth in darkness is caused by an enhanced accumulation of soluble sugars into the growing cells of the organ.     

Water relations of Picea abies. I. Comparison of water relations parameters of spruce shoots examined at the end of the vegetation period and in winter

Seasonal changes of some water relations parameters of Norway spruce shoots ( Picea abies [L.] Karst.) were studied during two experiments using the pressure-volume analysis. For each experiment only shoots of a single tree were used.
During the first study, the course of the turgor loss point (as bulk osmotic pressure when turgor first reaches zero, πp) of shoots developed in late 1986 vegetation period, were measured in 1987. The turgor loss point decreased temporarily from –2.5 MPa at the beginning of the year to –3.3 MPa at the end of March, but then increased to the original level for the rest of the year.
During the second study, water relations parameters were measured in late summer 1987 and in late winter 1988. Winter shoots at full water saturation contained up to 20% less water than in late summer. Accordingly, the bulk osmotic pressure at full water saturation (π_p) decreased from –1.7 MPa in late summer to –1.9 MPa in winter, π_p decreased also from –2.2 MPa to –2.8 MPa. However, the amount of osmotically active substances (mOsmol, N) remained unchanged. The relative amount of apoplastic water in the total shoot water content appeared to drop insignificantly from 17% to 15%.
The results show that the decrease in π_o and π_p in late winter is not due to an accumulation of osmotically active substances in the vacuoles but is due to a decrease in tissue water content. The temporary reduction of the symplastic volume by deposition of osmotically inert substances seems to be the most probable cause of this phenomenon.     

Effects of drought on nutrient and ABA transport in Ricinus communis

We studied the effects of variations of water flux through the plant, of diurnal variation of water flux, and of variation of vapour pressure deficit at the leaf on compensation pressure in the Passioura-type pressure chamber, the composition of the xylem sap and leaf conductance in Ricinus communis. The diurnal pattern of compensation pressure showed stress relaxation during the night hours, while stress increased during the day, when water limitation increased. Thus compensation pressure was a good measure of the momentary water status of the root throughout the day and during drought. The bulk soil water content at which predawn compensation pressure and abscisic acid concentration in the xylem sap increased and leaf conductance decreased, was high when the water usage of the plant was high. For all xylem sap constituents analysed, variations in concentrations during the day were larger than changes in mean concentrations with drought. Mean concentrations of phosphate and the pH of the xylem sap declined with drought, while nitrate concentration remained constant. When the measurement leaf was exposed to a different VPD from the rest of the plant, leaf conductance declined by 400mmol m^?2 s^?1 when compensation pressure increased by 1 MPa in all treatments. The compensation pressure needed to keep the shoot turgid, leaf conductance and the abscisic acid concentration in the xylem were linearly related. This was also the case when the highly dynamic development of stress was taken into account.     

Fluctuating environments impact thermal tolerance in an invasive insect species Bactrocera dorsalis (Diptera: Tephritidae)

The incidence and severity of environmental stressors associated with global climate change are increasing and insects frequently face variability in temperature and moisture regimes at variable spatio-temporal scales. Coincidental with this, is increased thermal and hydric stress on insects as warming increases vapour pressure deficit (VPD), the drying power of the air. While the effects of mean temperatures on fitness are widely documented, fluctuations in both temperature and relative humidity (RH) are largely unexplored. Here, we investigated the effects of dynamic temperature and RH fluctuations (around the mean [28°C; 65% RH]) on low and high thermal tolerance of laboratory-reared adult invasive Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), measured as critical thermal minima (CT_min), critical thermal maxima (CT_max), chill coma recovery time (CCRT) and heat knockdown time (HKDT). Our results show that increased environmental amplitude significantly influenced low and high temperature responses and varied across traits tested. The highest amplitude (δ12°C; 28% RH) compromised CT_min, CCRT and HKDT traits while enhancing CT_max. Similarly, acclimation to δ3°C; 7% RH compromised both low (CT_min and CCRT) and high (CT_max and HKDT) fitness traits. Variations in fitness reported here indicate significant roles of combined thermal and moisture fluctuations on B. dorsalis fitness suggesting caveats that are worthy considering when predicting species responses to climate change. These results are significant for B. dorsalis population phenology, management, quantifying vulnerability to climate variability and may help modelling future biogeographical patterns.     

Mechanical forces: The missing link between idiopathic pulmonary fibrosis and lung cancer

Patients with idiopathic pulmonary fibrosis (IPF) have a high risk of developing lung cancer compared with the general population. The morbidity of lung cancer in IPF patient ranges from 3% to 22%, and in some cases exceeds 50%, and these patients have a reduced survival time. However, the mechanisms through which IPF increases the morbidity and mortality in lung cancer remain unclear.By carefully analyzing the pathological features of these two diseases, we uncovered that, first, similar to IPF, lung carcinomas are more frequently found in the peripheral area of the lungs and, second, lung cancers tend to develop from the honeycomb areas in IPF. In accordance with the above pathological features, due to the spatial location, the peripheral areas of the lung experience a high stretch force because the average distance between adjacent alveolar cells in this area tends to be larger than that at the central lung when inflated; furthermore, the honeycomb areas, comprised of condensed fibrous tissue, are characterized by increased stiffness. Both of these pathological features of lung cancer and IPF are coincidentally related to abnormal mechanical forces (stretch and tissue stiffness). Therefore, we believe that the aberrant mechanical forces that are generated in the lung with IPF may contribute to the onset and progression of lung cancer.In this review, we discuss the possible effects of mechanical forces that are generated in IPF on the initiation and progression of lung cancer from the perspective of the hallmarks of cancer, including proliferation, metastasis, angiogenesis, cancer stem cells, immunology, epigenetics, and metabolism, so as to advance our understanding of the pathogenesis of IPF-related lung cancer and to harness these concepts for lung cancer mechanotherapies.     

Hydration pressure and phase transitions of phospholipids: I. Piezotropic approach

Dehydration reduces the main phase transition pressure of phospholipids. An analysis based on the Gibbs-Duhem equation shows how the shift of the transition pressure is correlated to the hydration pressure.By using Fourier transform infrared (FT-IR) spectroscopy we determined the hydration-dependent phase transition pressure. The application of our new approach gives hydration pressure values which agree with the values obtained with the osmotic stress method.     

Network organization of interstitial connective tissue cells in the human endolymphatic duct.

The human endolymphatic duct (ED) and sac of the inner ear have been suggested to control endolymph volume and pressure. However, the physiological mechanisms for these processes remain obscure. We investigated the organization of the periductal interstitial connective tissue cells and extracellular matrix (ECM) in four freshly fixed human EDs by transmission electron microscopy and by immunohistochemistry. The unique surgical material allowed a greatly improved structural and epitopic preservation of tissue. Periductal connective tissue cells formed frequent intercellular contacts and focally occurring electron-dense contacts to ECM structures, creating a complex tissue network. The connective tissue cells also formed contacts with the basal lamina of the ED epithelium and the bone matrix, connecting the ED with the surrounding bone of the vestibular aqueduct. The interstitial connective tissue cells were non-endothelial and non-smooth muscle fibroblastoid cells. We suggest that the ED tissue network forms a functional mechanical entity that takes part in the control of inner ear fluid pressure and endolymph resorption.     

Superiority of radiotelemetry over the tail-cuff method in evaluating control and drug-induced data in cardiovascular functions

The aim of the study was to compare an often-used method to measure blood pressure (BP) using a tail-cuff (TC) device, with radiotelemetry (RT) which allows to sample data on heart rate (HR) and BP in freely moving rodents without any restraint in behaviour. Data were collected in male normotensive Wistar-Kyoto rats and in spontaneously hypertensive rats. Experiments were performed under 12:12 h light–dark conditions (lights on at 07:00 h) with simulated dawn and dusk for 45 min. Experiments were performed at 08:00–10:00 h (rest phase) and at 20:00–22:00 h (activity phase) under control conditions and after treatment with the beta-adrenoceptor blocker metoprolol (8 mg/kg). For TC, the Harvard BP Monitoring System (Edenbrigde, England) and for RT radio transmitters (Dataquest IV system, TA11PA-C40, DSI, St. Paul, Minnesota, USA) were used. Rats bearing the TC device were also monitored under RT. The experiments show that TC significantly increased HR and both systolic and diastolic BP in both strains and both at L and D. Metoprolol reduced TC-induced HR but left BP increase uneffected. The study shows that RT is the method of choice to monitor BP and HR in rodents, TC is not suitable.     

Degradation of cholecystokinin octapeptide,related fragments and analogs by human and rat plasma in vitro

The rate of degradation of cholecystokinin octapeptide, related fragments and analogs by human and rat plasma was investigated, using high pressure liquid chromatography for the separation and identification of the degradation products.CCK tetrapeptide showed a half-life of 13 min in human plasma while its cleavage in rat plasma occurred at a very high rate (half-life of less than 1 min).The kinetics of disappearance of both sulphated and unsulphated CCK-8 indicated more than a single rate of degradation; the faster degrading system showed a half-life of 18 min for unsulphated CCK-8 and of 50 min for the sulphated peptide in human plasma as compared respectively with 5 and 17 min in rat plasma. The cleavage of CCK-8 was inhibited by bestatin and puromycin, suggesting that aminopeptidases play a major role in the breakdown of this peptide.CCK-9 analogs were rapidly converted into their corresponding octapeptides (half-life of 2.7 min in human plasma). This conversion was inhibited by puromycin and bestatin, suggesting the participation of aminopeptidase(s) probably specific for basic amino acids.CCK decapeptide exhibited a greater stability than the nonapeptides (half-life of 30 and 45 min in human and rat plasma respectively) and also gave rise to CCK-8 as degradation product. This cleavage was not affected by aminopeptidase inhibitors but was decreased by aprotinin (Trasylol®), suggesting that trypsin-like and/or kallikrein-like enzyme(s) were involved in the plasma metabolism of this peptide.