Online measurement of temperature and relative humidity as marker tools for quality changes in onion bulbs during storage

A long shelf life of onions (Allium cepa L.) is of high importance in the onion industry. Onions are dried and stored in large wooden boxes that are difficult to access. Monitoring temperature and relative humidity during these processes is challenging. Moreover, quality may change in storage without being noticed. Therefore, there is a need to find alternative methods for monitoring and controlling the drying and storage processes of onions and to identify early changes in quality during storage. The potential use of online measurements of temperature and relative humidity (RH) in the vicinity of onions was evaluated during drying and long-term storage of six onion batches (four cultivars and three selections of one of the cultivars) in commercial storage. The batches varied in bulb weight, dry matter content, firmness and disease incidence. The dry matter content and firmness decreased during storage, while the respiration rate and incidences of individual and total disease increased. Two of the batches had low storability with high disease incidences and high average temperatures and variations in the RH. The results showed that tracking the temperature and RH in the vicinity of the onions is a promising tool for improving the drying and storage processes in commercial storage and for identifying onion batches with reduced storability early in storage.

A survey of modelling methods for high-fidelity wind farm simulations using large eddy simulation

Large eddy simulations (LES) of wind farms have the capability to provide valuable and detailed information about the dynamics of wind turbine wakes. For this reason, their use within the wind energy research community is on the rise, spurring the development of new models and methods. This review surveys the most common schemes available to model the rotor, atmospheric conditions and terrain effects within current state-of-the-art LES codes, of which an overview is provided. A summary of the experimental research data available for validation of LES codes within the context of single and multiple wake situations is also supplied. Some typical results for wind turbine and wind farm flows are presented to illustrate best practices for carrying out high-fidelity LES of wind farms under various atmospheric and terrain conditions.This article is part of the themed issue 'Wind energy in complex terrains'.

The lateral intercellular space as osmotic coupling compartment in isotonic transport

Solute-coupled water transport and isotonic transport are basic functions of low- and high-resistance epithelia. These functions are studied with the epithelium bathed on the two sides with physiological saline of similar composition. Hence, at transepithelial equilibrium water enters the epithelial cells from both sides, and with the reflection coefficient of tight junction being larger than that of the interspace basement membrane, all of the water leaves the epithelium through the interspace basement membrane. The common design of transporting epithelia leads to the theory that an osmotic coupling of water absorption to ion flow is energized by lateral Na(+)/K(+) pumps. We show that the theory accounts quantitatively for steady- and time dependent states of solute-coupled fluid uptake by toad skin epithelium. Our experimental results exclude definitively three alternative theories of epithelial solute-water coupling: stoichiometric coupling at the molecular level by transport proteins like SGLT1, electro-osmosis and a 'junctional fluid transfer mechanism'. Convection-diffusion out of the lateral space constitutes the fundamental problem of isotonic transport by making the emerging fluid hypertonic relative to the fluid in the lateral intercellular space. In the Na(+) recirculation theory the 'surplus of solutes' is returned to the lateral space via the cells energized by the lateral Na(+)/K(+) pumps. We show that this theory accounts quantitatively for isotonic and hypotonic transport at transepithelial osmotic equilibrium as observed in toad skin epithelium in vitro. Our conclusions are further developed for discussing their application to solute-solvent coupling in other vertebrate epithelia such as small intestine, proximal tubule of glomerular kidney and gallbladder. Evidence is discussed that the Na(+) recirculation theory is not irreconcilable with the wide range of metabolic cost of Na(+) transport observed in fluid-transporting epithelia.

Fluid transport and ion fluxes in mammalian kidney proximal tubule: a model analysis of isotonic transport

AIM

By mathematical modelling, we analyse conditions for near-isotonic and isotonic transport by mammalian kidney proximal tubule.

METHODS

The model comprises compliant lateral intercellular space (lis) and cells, and infinitely large luminal and peritubular compartments with diffusible species: Na+, K+, Cl- and an intracellular non-diffusible anion. Unknown model variables are solute concentrations, electrical potentials, volumes and hydrostatic pressures in cell and lis, and transepithelial potential. We used data mainly from rat proximal tubule to model epithelial cells and interspace with luminal and peritubular baths of identical composition.

RESULTS

The model of the tubular epithelium with physiological water permeability and paracellular electrical resistance generates solute coupled water uptake with an approx. 3% hypertonic absorbate. This function remains unperturbed following 'blocking' of apical water channels and in 'aquaporin-null' simulation. Reduced rate of volume reabsorption in AQP(-/-) mice would also require decreased apical sodium permeability. Paracellular convection accounts for approx. 36% of the net Na+ absorption, and the model epithelium accomplishes uphill water transport similar to rat proximal tubule. Na+ recirculation is required for truly isotonic transport. The tonicity of the absorbate and the recirculation flux depend critically on ion permeabilities of interspace basement membrane.

CONCLUSION

Our model based on solute-solvent coupling in lateral space simulates major physiological features of proximal tubule, including significantly lower water permeability of the AQP1-null preparation, and a ratio of net sodium uptake and oxygen consumption exceeding that predicted from stoichiometry of the Na+/K+-pump. Physical properties of interspace basement membrane are critical for obtaining near-isotonic and truly isotonic transport.

Biochemical effects of dietary intakes of different broccoli samples. I. Differential modulation of cytochrome P-450 activities in rat liver, kidney, and colon

Modulation of xenobiotic metabolism, including cytochrome P-450 (CYP) enzyme activities, due to dietary intakes of cruciferous vegetables, has been described in animals and humans, and the induction of CYP1A enzymes is suggested mainly to be related to the content of indolyl glucosinolates in these vegetables. The aim of the present study was to evaluate the effects on specific CYP activities of various broccoli samples containing different levels of glucosinolates. Groups of rats were fed 1 of 8 broccoli samples from 2 cultivars grown at different conditions. Thirteen different glucosinolates were quantified. The content of the 4 major glucosinolates, glucoraphanin (GRAP), glucoiberin, glucobrassicin (GB), and neoglucobrassicin (NeoGB) varied 5.6-, 2.7-, 3.2-, and 6.6-fold, respectively, among the broccoli samples. Dietary broccoli induced the CYP1A enzyme activities, 7-ethoxyresorufin-O-deethylase (EROD) and 7-methoxyresorufin-O-demethylase (MROD), in rat liver, weakly in colon, but not in kidney. In concordance, the hepatic metabolism of 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP) to the proximate carcinogen N-OH-PhIP, a CYP1A-related activity, was enhanced by broccoli. The 7-pentoxyresorufin-O-depenthylase (PROD) activity, an assay for CYP2B1/2, was weakly induced in colon and kidney but not in liver by broccoli. The 2 beta-OH- and 6 beta-OH-testosterone hydroxylase activities were induced in liver microsomes, showing that broccoli increased CYP3A activity. The observed modulations of CYP activities depended clearly on the broccoli sample used, and significantly different responses were observed for different cultivars and growth conditions. These results indicate that modulation of CYP metabolism by broccoli may vary significantly in humans as well, as the content of glucosinolates and other active substances also varies between commercially available broccoli samples. The different effects depending on the vegetable sample eaten have to be considered in future experiments and dietary recommendations.

A mathematical model of solute coupled water transport in toad intestine incorporating recirculation of the actively transported solute

A mathematical model of an absorbing leaky epithelium is developed for analysis of solute coupled water transport. The non-charged driving solute diffuses into cells and is pumped from cells into the lateral intercellular space (lis). All membranes contain water channels with the solute passing those of tight junction and interspace basement membrane by convection-diffusion. With solute permeability of paracellular pathway large relative to paracellular water flow, the paracellular flux ratio of the solute (influx/outflux) is small (2-4) in agreement with experiments. The virtual solute concentration of fluid emerging from lis is then significantly larger than the concentration in lis. Thus, in absence of external driving forces the model generates isotonic transport provided a component of the solute flux emerging downstream lis is taken up by cells through the serosal membrane and pumped back into lis, i.e., the solute would have to be recirculated. With input variables from toad intestine (Nedergaard, S., E.H. Larsen, and H.H. Ussing, J. Membr. Biol. 168:241-251), computations predict that 60-80% of the pumped flux stems from serosal bath in agreement with the experimental estimate of the recirculation flux. Robust solutions are obtained with realistic concentrations and pressures of lis, and with the following features. Rate of fluid absorption is governed by the solute permeability of mucosal membrane. Maximum fluid flow is governed by density of pumps on lis-membranes. Energetic efficiency increases with hydraulic conductance of the pathway carrying water from mucosal solution into lis. Uphill water transport is accomplished, but with high hydraulic conductance of cell membranes strength of transport is obscured by water flow through cells. Anomalous solvent drag occurs when back flux of water through cells exceeds inward water flux between cells. Molecules moving along the paracellular pathway are driven by a translateral flow of water, i.e., the model generates pseudo-solvent drag. The associated flux-ratio equation is derived.

Proton pump activity of mitochondria-rich cells. The interpretation of external proton-concentration gradients

We have hypothesized that a major role of the apical H(+)-pump in mitochondria-rich (MR) cells of amphibian skin is to energize active uptake of Cl- via an apical Cl-/HCO3(-)-exchanger. The activity of the H+ pump was studied by monitoring mucosal [H+]-profiles with a pH-sensitive microelectrode. With gluconate as mucosal anion, pH adjacent to the cornified cell layer was 0.98 +/- 0.07 (mean +/- SEM) pH-units below that of the lightly buffered bulk solution (pH = 7.40). The average distance at which the pH-gradient is dissipated was 382 +/- 18 microns, corresponding to an estimated "unstirred layer" thickness of 329 +/- 29 microns. Mucosal acidification was dependent on serosal pCO2, and abolished after depression of cellular energy metabolism, confirming that mucosal acidification results from active transport of H+. The [H+] was practically similar adjacent to all cells and independent of whether the microelectrode tip was positioned near an MR-cell or a principal cell. To evaluate [H+]-profiles created by a multitude of MR-cells, a mathematical model is proposed which assumes that the H+ distribution is governed by steady diffusion from a number of point sources defining a set of particular solutions to Laplace's equation. Model calculations predicted that with a physiological density of MR cells, the [H+] profile would be governed by so many sources that their individual contributions could not be experimentally resolved. The flux equation was integrated to provide a general mathematical expression for an external standing [H+]-gradient in the unstirred layer. This case was treated as free diffusion of protons and proton-loaded buffer molecules carrying away the protons extruded by the pump into the unstirred layer; the expression derived was used for estimating stationary proton-fluxes. The external [H+]-gradient depended on the mucosal anion such as to indicate that base (HCO3-) is excreted in exchange not only for Cl-, but also for Br- and I-, indicating that the active fluxes of these anions can be attributed to mitochondria-rich cells.

Influence of growth conditions on the value of crisphead lettuce. 4. Quality changes during storage

Crisphead lettuce (Lactuca sativa L. var capitata cvs. Marius and Saladin) were grown with a nitrogen supply from 50 to 200 kg N/hectare. Heads were stored for one or two weeks at 1 degree C in cold storage or ice bank cooling. Samples were taken for measurement of dry matter, sugars, vitamin C and nitrate. The content of dry matter, sugars (glucose, fructose) and vitamin C decreased with increasing level of nitrogen, and the content of nitrate increased. Except for nitrate the contents of the other quality attributes decreased at all nitrogen supply levels during storage. No differences were found between the storage systems, and beside fructose no significant differences were found between the two cultivars. The content of dry matter, vitamin C, and nitrate decreased from the outer to the inner head fraction, while the content of sugars increased. Trimming decreased the content of dry matter, vitamin C and nitrate and increased the content of sugars. To obtain heads from storage with a relatively high content of dry matter, sugars and vitamin C, and a relatively low content of nitrate the nitrogen supply must be as low as possible. Except for nitrate where no distinct results were found in this experiment it must also be recommended to store the heads as short time as possible. Possibly the cv. Saladin has some advantage quality attributes after storage compared with the cv. Marius.

Influence of growth conditions on the value of crisphead lettuce. 3. Protein quality and energy density as determined in balance experiments with rats

Crisphead lettuce was cultivated under different growth conditions. Sixteen batches differed in time of planting (early and late), total nitrogen supply (200 kg N/ha, 150 kg N/ha, 100 kg N/ha, 50 kg N/ha) and time of harvest (early and late). Based on chemical analysis and balance studies on rats the nutritive value of each 16 batches was determined. The protein content increased progressively from 16.00 to 19.88% with fertilization level. This increase in protein caused a significant drop in essential amino acids (g/16 g N) demonstrating a lower biological value of this protein. Early planting or early harvest resulted in a higher protein content than in lettuce of late planting or late harvest. Total dietary fibre content was approximately 25% of DM-and this value was not much influenced by the different growth conditions. Soluble dietary fibre was approximately 20-25% of total dietary fibre. Due to the high fibre content, energy digestibility was relatively low. The contents of Cd and Pb were below what is considered as 'acceptable' levels.

Influence of growth conditions on the value of crisphead lettuce. 1. Marketable and nutritional quality as affected by nitrogen supply, cultivar and plant age

The marketable and nutritional quality of crisphead lettuce as affected by nitrogen supply, cultivar, and plant age at harvest was investigated in six plantings during 1989 and 1990. The optimum yield of marketable heads was obtained at a total nitrogen supply of 150 kg N per ha although only small differences were observed to the yield at 100 and 200 kg total N per ha. The total nitrogen supply included the amount of mineral nitrogen within the rhizosphere. The incidence of dry tipburn in older leaves was clearly decreased by an increased nitrogen supply, especially at late planting. The content of nitrate was increased and the content of dry matter and vitamin C decreased with increased nitrogen supply. The vitamin C content was higher for the cultivar 'Marius' than for 'Saladin'. As plants got older, the nutritional quality of crisphead lettuce decreased because the content of nutrients, especially vitamin C, decreased with increased plant age at harvest.

Influence on growth conditions on the value of crisphead lettuce. 2. Weight losses during storage as affected by nitrogen, plant age and cooling system

Storage of crisphead lettuce was carried out at 1 degrees C in an ordinary cold storage room and in an ice bank cooling system. The plants were grown at three plantings at 50, 100, 150 and 200 kg total nitrogen supply per hectare and harvested at two or three different plant ages. The cultivars used were 'Marius' and 'Saladin'. The aim of the experiment was to prolong the storage and to reduce the losses. After 14 days of storage the greatest total weight losses were found at the mid-season planting whereas the least total weight loss was found at the late planting. Ice bank cooling at all plantings reduced the total weight loss in comparison to the cold storage. The effect of nitrogen and cultivar was low. The total weight loss defined as loss due to transpiration and trimming was neither related to the head weight nor the surface area of the heads. A reduced loss with increasing plant age was not a question of increased transpiration due to surface to volume ratio changes, but may be related to other factors. A lower average total weight loss was found in the ice bank cooling system compared to the cold storage. The explanation of this might be the existence of a high relative humidity in the ice bank storage. To reduce the total weight loss harvest must take place at the right plant age. No definite growth stage was defined here, but the plants must have reached marketable quality as the young plants are more susceptible to weight loss during storage. It seems likely that some unknown internal factors in the plant were involved in reduction of the total weight loss.

[Hypertrophic tonsils, upper airway obstruction and cardiac complications. A combined otological, medical and anesthesiological problem]

Hypoventilation in children with hypertrophied tonsils can cause hypoxemia, hypercarbia, acidosis and pulmonary vasoconstriction resulting in cardiac arrhythmias or cor pulmonale. In addition, cerebral symptoms such as day-time hypersomnia or even seizures may be present. Early recognition of hypertrophied tonsils is necessary to avoid development of severe cardiac symptoms. If cardiac incompensation is present, medical treatment is advocated prior to tonsillectomy. Anaesthesia for tonsillectomy in these children is associated with special considerations. Preoperative sedation should be excluded, and inhalational induction with O2 and Halothane is recommended. On induction a difficult intubation should be expected.

Ventricular premature beats on Holter monitoring in patients admitted with chest pain, in whom acute myocardial infarction is not confirmed. The prognostic value and relationship to scars or ischemia on thallium-201 scintigraphy

Ambulatory 24-h Holter monitoring was carried out in 198 patients who had been admitted because of suspected acute myocardial infarction (AMI) due to chest pain, but in whom AMI was not confirmed. During a follow-up period of 12-24 months (median 14 months) 16 cardiac events (i.e., nonfatal AMI or cardiac death) occurred. Ventricular premature beats (VPBs) were found in 65.2% of the patients, complex VPBs in 28.8%. Pairs of VPBs which were seen in 10.0% of the patients were the only important type of VPBs significantly related to an impaired prognosis. Thallium-201 scintigraphy was performed in 144 of the patients. VPBs were significantly related to scar formation (i.e., to permanent defects, but not to ischemia, specifically, to transient defects). It is concluded that ventricular arrhythmias in this patient category indicate presence of chronic ischemic heart disease, and that pairs of VPBs seem to identify patients at risk for cardiac events.

Effects of a thromboxane antagonist (BM 13.177) during endotoxin-induced pulmonary vasoconstriction in sheep

We investigated the effect of a thromboxane antagonist, BM 13.177, during endotoxin-induced pulmonary vasoconstriction in sheep. In control animals intravenous E-coli endotoxin (1 microgram/kg) caused a transient increase of pulmonary artery and airway pressure paralleled by large concentration increases of TXB2: in comparison peak plasma concentrations of 6-keto-PGF1 alpha (a prostacyclin metabolite) were small and delayed in time. Pre-treatment with BM 13.177 (bolus 5 mg/kg), followed by 0.75 mg/kg/min intravenously) abolished the rise of pulmonary artery and airway pressure. Plasma concentrations of TXB2 and 6-keto-PGF1 alpha were similar to controls. These and previous investigations imply that BM 13.177 specifically antagonizes TXA2 on the putative receptor in pulmonary vascular and airway smooth muscle.