Largest Relative Decrease Research Articles

Clouds, shadows or twilight? Mayfly nymphs recognise the difference

Summary1. We examined the relative changes in light intensity that initiate night‐time locomotor activity changes in nymphs of the mayfly, Stenonema modestum (Heptageniidae). Tests were carried out in a laboratory stream to examine the hypothesis that nymphs increase their locomotion in response to the large and sustained reductions in relative light intensity that take place during twilight but not to short‐term daytime light fluctuations or a minimum light intensity threshold. Ambient light intensity was reduced over a range of values representative of evening twilight. Light was reduced over the same range of intensities either continuously or in discrete intervals while at the same time nymph activity on unglazed tile substrata was video recorded.2. Nymphs increased their locomotor activity during darkness in response to large, sustained relative light decreases, but not in response to short‐term, interrupted periods of light decrease. Nymphs did not recognise darkness unless an adequate light stimulus, such as large and sustained relative decrease in light intensity, had taken place.3. We show that nymphs perceive light change over time and respond only after a lengthy period of accumulation of light stimulus. The response is much lengthier than reported for other aquatic organisms and is highly adaptive to heterogeneous stream environments.

Sources, bioavailability, and photoreactivity of dissolved organic carbon in the Sacramento–San Joaquin River Delta

We analyzed bioavailability, photoreactivity, fluorescence, and isotopic composition of dissolved organic carbon (DOC) collected at 13 stations in the Sacramento-San Joaquin River Delta during various seasons to estimate the persistence of DOC from diverse shallow water habitat sources. Prospective large-scale wetland restorations in the Delta may change the amount of DOC available to the food web as well as change the quality of Delta water exported for municipal use.Our study indicates that DOC contributed by Delta sources is relatively refractory and likely mostly the dissolved remnants of vascular plant material from degrading soils and tidal marshes rather than phytoplankton production. Therefore, the prospective conversion of agricultural land into submerged, phytoplankton-dominated habitats may reduce the undesired export of DOC from the Delta to municipal users.A median of 10% of Delta DOC was rapidly utilizable by bacterio- plankton. A moderate dose of simulated solar radiation (286 W m � 2 for 4 h) decreased the DOC bioavailability by an average of 40%, with a larger relative decrease in samples with higher initial DOC bioavailability. Potentially, a DOC-based microbial food web could support £ 0.6 · 10 9 gC of protist production in the Delta annually, compared to � 17 · 10 9 g C phytoplankton primary production. Thus, DOC utilization via the microbial food web is unlikely to play an important role in the nutrition of Delta zooplankton and fish, and the possible decrease in DOC concentration due to wetland restoration is unlikely to have a direct effect on Delta fish productivity.

"Renalism": inappropriately low rates of coronary angiography in elderly individuals with renal insufficiency.

Higher risk patients (including the elderly) receive more conservative therapy for cardiovascular diseases, even though the relative benefits of therapy tend to be greater. The perceived risk of radiocontrast-associated nephrotoxicity may influence the provision of coronary angiography and subsequent revascularization, especially among individuals with chronic kidney disease (CKD). The aim of this study was to determine whether there is excessive variation in the provision of coronary angiography after acute myocardial infarction on the basis of the presence of CKD and whether there is an association between angiography and mortality. Elderly (age 65 to 89 yr) individuals with acute myocardial infarction from the Cooperative Cardiovascular Project were classified by the presence or absence of CKD (defined as a baseline serum creatinine of 1.5 to 5.0 mg/dl). In CKD patients, the propensity to undergo coronary angiography was determined and the effect of coronary angiography on mortality was estimated using multivariable logistic regression and stratification. Mortality was significantly higher with CKD (52.6 versus 26.4%). Fewer patients with CKD underwent coronary angiography (25.2 versus 46.8%) despite the observation that a similar proportion of patients were deemed appropriate for angiography by standard, published criteria. When limiting the analysis to CKD patients who are considered appropriate, the multivariable estimate of the odds of death associated with coronary angiography was 0.58 (95% confidence interval, 0.50 to 0.67). With adjustment using propensity scores, the odds ratio averaged across propensity score quintiles was 0.62 (95% confidence interval, 0.54 to 0.70). Results were qualitatively similar when patients were stratified by CKD stage IV (estimated GFR <30 ml/min per 1.73 m(2)). There is a large relative decrease in utilization of coronary angiography among patients with CKD. Alteration in practice because of an aversion to the risk of radiocontrast-associated nephrotoxicity ("renalism") is inappropriate, even if the true relative benefit of invasive strategies is a fraction of what is estimated here.

Relations among premorbid weight, referral weight, and psychological test scores for patients with anorexia nervosa.

The purpose of this study was to test the hypothesis that, in anorexia nervosa, patients with a low premorbid weight are associated with a low weight at referral and that premorbid weight, referral weight, and weight loss are associated with mood states. The changes of Body Mass Index from premorbid to referral, the duration of illness, and the psychological scores on the Profile of Mood States and the Cornell Medical Index-Health Questionnaire were examined in 49 anorexia nervous patients. Body Mass Index at referral of patients with lower premorbid Body Mass Index was significantly lower than that of patients with higher premorbid level. For patients with a larger relative decrease, scores on depressive mood were lower. These findings suggested that in anorexia nervosa patients, lower premorbid Body Mass Index was associated with lower Body Mass Index at referral, and that the patients with higher relative decrease in Body Mass Index might be satisfied with their weight loss.

Quantitative changes in protein, glycogen and fat content in the eggs of the locusts, Locusta migratoria migratorioides and Schistocerca gregaria (Orthoptera), during embryogenesis

Changes in the content of protein, glycogen, neutral lipids and sterols were investigated in locust eggs from oviposition until larval hatching. The content of all of these nutritional reserves was higher in the eggs of S. gregaria because of their larger size, although relative changes in utilization or synthesis of these materials during embryogenesis showed a more or less parallel course. The amount of protein increased progressively during embryogenesis, while glycogen and neutral lipids were successively metabolized or utilized for development of the embryo. There appeared significant relative differences in the way of utilizing energetic reserves during embryogenesis between the two species. This was especially manifested by a larger relative decrease in the content of neutral lipids (mainly triglyceride) in the eggs of S. gregaria. Conversely, the eggs of L. migratoria showed a larger relative utilization of glycogen reserves. The content of steroids was higher in the eggs of S. gregaria during the initial 6 days of embryonic development. Later on, during advanced stages of pharate larval development, the steroids were rapidly utilized and decreased in both species. The described changes in utilization of the main energetic resources were correlated with periods of tissue growth and differentiation and with the cuticulogenesis of the growing embryo.

Mouse Mastocytoma Cells Synthesize Undersulfated Heparin and Chondroitin Sulfate in the Presence of Brefeldin A

In order to study the subcellular localization and organization of the enzymes involved in the glycosylation of the hybrid proteoglycan serglycin, mouse mastocytoma cells were metabolically labeled with [35S]sulfate or [3H]glucosamine in the absence or presence of brefeldin A. This drug is known to induce a disassembly of the proximal part of the Golgi complex, resulting in a redistribution of cis-, medial-, and trans-Golgi resident enzymes back to the endoplasmic reticulum, and to block the anterograde transport of proteins to the trans-Golgi network. Although the total incorporation of [3H]glucosamine into glycosaminoglycan chains was reduced to about 25% in brefeldin A-treated cells compared to control cells, both control cells and cells treated with brefeldin A synthesized heparin as well as chondroitin sulfate chains. Therefore, enzymes involved in the biosynthesis of both types of glycosaminoglycan chains seem to be present proximal to the trans-Golgi network in these cells. Chondroitin sulfate and heparin synthesized in cells exposed to brefeldin A were undersulfated, as demonstrated by ion-exchange chromatography, compositional analyses of disaccharides, as well as by a lower [35S]sulfate/[3H]glucosamine ratio compared to controls. In heparin biosynthesis, both N- and O-sulfation reactions were impaired, with a larger relative decrease in 2-O-sulfation than in 6-O-sulfation. Despite undersulfation, the heparin chains synthesized in the presence of brefeldin A were larger (30 kDa) than the heparin synthesized by control cells (20 kDa). The reduced [3H]glucosamine incorporation in brefeldin A-treated cells was partly due to decreased number of glycosaminoglycan chains synthesized, but also to the biosynthesis of chondroitin sulfate chains of smaller molecular size (8 versus 15 kDa in control cells). Brefeldin A had no effect on the glycosaminoglycan synthesis when used in a cell-free, microsomal fraction, indicating that brefeldin A does not interfere directly with the enzymes involved in the biosynthesis of glycosaminoglycans.

Photobleaching of fluorescence and the organic carbon concentration in a coastal environment

Abstract In order to investigate the photobleaching potential of estuarine waters from different depths and redox conditions and with varying degree of biological activity, filtered, unfiltered and chloroform-poisoned water samples from the Baltic Sea were exposed to ambient sunlight. Fluorescence, at excitation 350 nm and emission 450 nm, was used as an indication of humic substance concentration. Fluorescence and organic carbon concentration were measured at regular time intervals during light exposure. We found that the decrease in humic substance fluorescence can be fitted to an exponential decay function. The fluorescence half-lives were within the range 0.4 – 4.6 days in different water masses, with fluorescence decreasing to between 20% and 60% of initial concentration, respectively. Results from the curve fitting procedure indicate a rest concentration of humic substance fluorescence, similar among the sampled sites, that is resistant to further photochemical degradation. The largest relative decreases in fluorescence were found in deep waters, but samples from deep waters also had a higher fluorescence rest concentration than samples from surface waters. Biological activity was reduced by filtering the samples through 0.2μm pore size filters or adding chloroform. No statistically significant differences were found after 3 days of irradiation between samples with and without treatment to reduce biological activity. The highest initial fluorescence values and the largest fluorescence decrease were found in the anoxic waters of the Gotland Deep. The organic carbon concentrations decreased 3–7% at all stations. The shortest half-life of humic substance, and the largest decrease in organic carbon concentrations, were found in samples from the northern basins of the Baltic Sea.

Desk set revisited: Reference librarians, reality, & research systems' design

To determine if partial nephrectomy (PN) confers a renal functional benefit compared to radical nephrectomy (RN) for clinical T2 renal masses (T2RM) when adjusting for tumor complexity characterized by the RENAL nephrometry score.A 2-center study of 202 patients with T2RM undergoing RN (122) or PN (80) (median follow-up, 41.5 months). RN and PN cohorts were subanalyzed according to RENAL sum as a categorical variable of <10 or ≥10. Primary outcome was median change in estimated glomerular filtration rate (ΔeGFR) between preoperative to 6 months postoperative. Logistic regression–identified prognostic factors and survival models analyzed association between the RENAL sum and the freedom from de novo chronic kidney disease (CKD; eGFR<60 mL/min/1.73m2).No significant differences existed between PN and RN for RENAL score. ΔeGFR was greater in RN (−19.7) vs PN (−11.9; P = .006). De novo CKD was 40.2% after RN vs 16.3% after PN (P <.001). RENAL score ≥10 (odds ratio, 6.67; P = .025) and RN among patients with RENAL score <10 (odds ratio, 24.8; P <.001) were independently associated with de novo CKD at 6 months by logistic regression. Among patients with RENAL score <10, median CKD-free survival was PN 38 vs RN 16 months (P = .001). Cox proportional hazard demonstrated decreasing risk of CKD for PN vs RN from RENAL 10 (hazard ratio, 0.836) to RENAL 6 (hazard ratio, 0.003; P = .001).RN is independently associated with decreased renal function compared to PN for T2RM with RENAL sum ≤10, but not >10, with larger relative decrease in eGFR for each decrease in RENAL sum. Further investigation is required to determine optimal candidates for PN in T2RM.

Effects of selective type I and II adrenal steroid agonists on immune cell distribution.

Adrenal steroids exert their effects through two distinct adrenal steroid receptor subtypes; the high affinity type I, or mineralocorticoid, receptor and the lower affinity type II, or glucocorticoid, receptor. Adrenal steroids have well known effects on immune cell distribution, and although both type I and II receptors are expressed in immune cells and tissues, few data exist on the relative effects mediated through these two receptor subtypes. Accordingly, we administered selective type I and II adrenal steroid receptor agonists to young adult male Sprague-Dawley rats for 7 days and then measured immune cell distribution in the peripheral blood and spleen. Results were compared with those of similar studies using the naturally occurring glucocorticoid of the rat, corticosterone, which binds both type I and II receptors. The majority of the well characterized effects of adrenal steroids on peripheral blood immune cells (increased neutrophils and decreased lymphocytes and monocytes) were reproduced by the type II receptor agonist, RU28362. RU28362 decreased the numbers of all lymphocyte subsets [T-cells, B-cells, and natural killer (NK) cells] to very low absolute levels. The largest relative decrease (i.e. in percentage) was seen in B-cells, whereas NK cells exhibited the least relative decrease and actually showed a 2-fold increase in relative percentage during RU28362 treatment. Similar to RU28362, the type I receptor agonist, aldosterone, significantly reduced the number of lymphocytes and monocytes. In contrast to RU28362, however, aldosterone significantly decreased the number of neutrophils. Moreover, aldosterone decreased the number of T-helper cells and NK cells, while having no effect on the number of B-cells or T-suppressor/cytotoxic cells. Corticosterone at physiologically relevant concentrations had potent effects on immune cell distribution, which were indistinguishable from those of the type II receptor agonist, RU28362. Taken together, these results indicate that effects of adrenal steroids on immune cell distribution are dependent on the receptor subtype involved as well as the specific cell type targeted. These factors allow for varied and complex effects of adrenal steroids on the immune system under physiological conditions.

Antisense oligonucleotide complementary to endogenous retroviral MCF env gene inhibits both BFU-E and CFU-S colony formation in mice

A possible biologic activity of endogenously expressed env sequence of retroviral mink cell focus-forming virus (MCF) genome for hematopoietic colony formation was studied in mice. Antisense 20-mer complementary to MCF env sequence was used to detect the result of blockage of this gene translation on the potency of marrow cells to form colonies of erythroid (BFU-E), myeloid granulocyte-macrophage (CFU-GM), and stem cell (day 11 CFU-S) hematopoietic compartments. A large relative decrease in BFU-E number was found in bone marrow cell cultures preincubated with antisense oligonucleotide during 4 h, whereas CFU-GM colonies remained unaffected. A marked reduction of CFU-S colony formation was also registered under antisense oligomer influence. Following a decreased proliferation of erythroid progenitors, we suggest the mechanism by which antisense oligonucleotide could cause the loss of colony formation. Taken together, these data allow to propose that the expression of this gene is naturally significant for hematopoietic progenitor activity exerting some property of env gene products to regulate the growth of erythroid and multilineage hematopoietic precursors.

Postischemic blockade of AMPA but not NMDA receptors mitigates neuronal damage in the rat brain following transient severe cerebral ischemia.

Glutamatergic transmission is an important factor in the development of neuronal death following transient cerebral ischemia. In this investigation the effects of N-methyl-D-aspartate (NMDA) and non-NMDA receptor antagonists on neuronal damage were studied in rats exposed to 10 min of transient cerebral ischemia induced by bilateral common carotid occlusion combined with hypotension. The animals were treated with a blocker of the ionotropic quisqualate or alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) receptor, 2.3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX), given postischemia as an intraperitoneal bolus dose of 30 mg kg-1 followed by an intravenous infusion of 75 micrograms min-1 for 6 h, or with the noncompetitive NMDA receptor blocker dizocilpine (MK-801) given 1 mg kg-1 i.p. at recirculation and 3 h postischemia, or with the competitive NMDA receptor antagonist DL-(E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid (CGP 40116), 5 mg kg-1, given intraperitoneally at recirculation. Treatment with NBQX provided a significant reduction of neuronal damage in the hippocampal CA1 area by 44-69%, with the largest relative decrease in the temporal part of the hippocampus. In neocortex a significant decrease in the number of necrotic neurons was also noted. No protection could be seen following postischemic treatment with dizocilpine or CGP 40116. Our data demonstrate that AMPA but not NMDA receptor antagonists decrease neuronal damage following transient severe cerebral ischemia in the rat and that the protection by NBQX may be dependent on the severity of the ischemic insult. We propose that the AMPA receptor-mediated neurotoxicity could be due to ischemia-induced changes in the control mechanisms of AMPA receptor-coupled processes or to changes of AMPA receptor characteristics.

Spectroscopic and Chemical Evidence of Variability across a Pine Litter Layer

AbstractChemical‐composition data and spectroscopic analyses are reported for three layers in a ponderosa pine (Pinus ponderosa Dougl. ex P. Lawson &amp; Lawson) litter sample (O horizon) and for fresh needles sampled from a plantation site. The data were taken to obtain evidence for variability in chemical properties accompanying well‐known changes in the visual characteristics of a litter layer that result from the gradual humification of its organic matter. Composition data for Mg, Al, Si, P, S, Ca, Mn, Fe, Cu, and Pb showed that all but Mg, P, S, and Pb increased in content in the litter relative to the needles, and that the content of Al, S, Mn, and Fe increased, while that of Mg decreased, in passing from the Oi to the Oa layer. The increases for Al and Fe were especially large. Fourier‐transform infrared and electron spin resonance spectra of the litter samples indicated, respectively, the presence of a variety of aromatic and aliphatic structures with carboxyl and hydroxyl functionalities and an increase in organic free‐radical content with depth in the litter layer. The electron spin resonance spectra further indicated that Fe(III) was bound in inner‐sphere complexes uniformly down the litter layer, whereas Mn(II) was bound in outer‐sphere complexes. Aqueous extracts of the litter samples showed increases in pH and decreases in the concentration of organic C, carboxyl groups, and free organic acids with depth, some of the changes being as large as an order of magnitude. Composition data for aqueous extracts of the needle and litter samples showed that the water extractability of Mg, Al, P, Ca, and Mn was greater in the needles than in the litter, and that extractability decreased with increasing depth for all of the elements examined except Si and Pb. The largest relative decrease in water extractability (20‐fold) was for Al. These trends, which require confirmation for other Pinus species litter samples, were interpreted as an effect of the variability in organic structures in the litter that develop from differing degrees of humification, bioassimilation, and leaching/retention processes.

Juvenile specimens ofEusthenopteron foordiWhiteaves, 1881 (osteolepiform rhipidistian, Pisces) from the Late Devonian of Miguasha, Quebec, Canada

ABSTRACT A size series of thirty-five specimens of Eusthenopteron foordi Whiteaves, 1881, shows isometric and allometric changes. As in Recent fishes, the main difference between small (juvenile) and large (adult) specimens is the relative size of the orbit and of the head. The large relative decrease of the orbit diameter from 31% to 12–7% of head length (b = 0.632) explains the positive allometric growth of bones surrounding the orbit, i.e., the change from a palaeoniscoid-like juvenile to a typical rhipidistian with an elongated postorbital region. With the exception of the caudal prolongation, all fin positions remain isometric to standard length.

Influence of severe hypoglycemia on brain extracellular calcium and potassium activities, energy, and phospholipid metabolism.

In the cerebral cortices of rats, during insulin-induced hypoglycemia, changes in the concentrations of labile phosphate compounds [ATP, ADP, AMP, and phosphocreatine (PCr)] and glycolytic metabolites (lactate, pyruvate, and glucose) as well as phospholipids and free fatty acids (FFAs) were studied in relation to extracellular potassium and calcium activities. Changes in extracellular calcium and potassium activities occurred at approximately the onset of isoelectricity . The extracellular calcium activity dropped from 1.17 +/- 0.14 mM to 0.18 +/- 0.28 mM and the potassium activity rose from 3.4 +/- 0.94 mM to 48 +/- 12 mM (means +/- SD). Minutes prior to this ionic change the levels of ATP, PCr, and phospholipids were unchanged while the levels of FFAs remained unchanged or slightly elevated. Following the first ionic change the steady-state levels of ATP decreased by 40%, from 2.42 to 1.56 mumol/g. PCr levels decreased by 75%, from 4.58 to 1.26 mumol/g. Simultaneously, the levels of FFAs increased from 338 to 642 nmol/g, arachidonic acid displaying the largest relative increase, 33 to 130 nmol/g. The first ionic change was followed by a short period of normalization of ionic concentrations followed by a sustained ionic change. This was accompanied by a small additional decrease in ATP (to 1.26 mumol/g). The FFA levels increased to 704 nmol/g. There was a highly significant negative correlation between the levels of FFAs and the energy charge of the tissue. The formation of FFAs was accompanied by a decrease in the phospholipid pool. The largest relative decrease was observed in the inositol phosphoglycerides, followed by serine and ethanolamine phosphoglycerides.(ABSTRACT TRUNCATED AT 250 WORDS)

AN ASSESSMENT OF THE IMPACT OF LARGE SCALE SPRAYING OPERATIONS ON THE REGIONAL DYNAMICS OF SPRUCE BUDWORM (LEPIDOPTERA: TORTRICIDAE) POPULATIONS

AbstractExploratory data analysis was employed to investigate the regional dynamics of managed budworm populations based upon survey data reporting spruce budworm egg-mass densities and damage to balsam fir. The Maine Forest Service collected these data annually from 1975 to 1980 at approximately 1000 different locations each year throughout Maine's spruce–fir forest regions. Although spraying was often associated with ‘better’ conditions in heavily defoliated or infested areas, it was generally associated with somewhat ‘poorer’ conditions in areas which had experienced only light defoliation or infestation in the previous year. The analysis also indicated that while insecticide application may reduce budworm larval populations immediately after application, the largest relative decrease in defoliation rates appeared the year after insecticide application. Insecticide treatments were not as effective as expected. In the year following application, the maximum reduction observed in average defoliation was 20% and in average egg-mass density the maximum reduction was 50%. In many cases the reduction was substantially less. Spraying was not associated with any substantial decline in hazard rating.

Temperature dependence of the vibrational modes of molybdenum

Inelastic neutron scattering techniques have been used to study the temperature dependence of the phonon dispersion curves of bcc Mo. We find that, with increasing temperature, the largest relative decrease in phonon frequencies (\ensuremath{\sim}12%) occurs for the $\mathrm{L}[\ensuremath{\xi}\ensuremath{\xi}\ensuremath{\xi}]$ branch in the vicinity of $\ensuremath{\xi}=\frac{2}{3}$. The phonon frequencies in the vicinity of the $H$ point in the Brillouin zone, on the other hand, increase slightly with increasing temperature. As a result, at high temperatures, the anomalous drop in the phonon frequencies at $H$ decreases in magnitude and the $\mathrm{L}[\ensuremath{\xi}\ensuremath{\xi}\ensuremath{\xi}]$ branch develops a dip at $\ensuremath{\xi}=\frac{2}{3}$. The experimental results also indicate that the phonon anomaly in the vicinity of point $N$ is less pronounced at high temperatures. For the purpose of comparison with the experimental results, we have performed first-principle frozen-phonon calculations for the longitudinal-phonon frequencies of Mo at the ($\frac{2}{3}$,$\frac{2}{3}$,$\frac{2}{3}$) and $H$ points of the Brillouin zone. The results show that thermal expansion and anharmonicity can account for the temperature dependence of the ($\frac{2}{3}$,$\frac{2}{3}$,$\frac{2}{3}$) longitudinal-phonon frequency. For the $H$ phonon, on the other hand, the thermal expansion and anharmonicity terms cannot account for the observed frequency shift and we suggest that the contributions arising from the electron-phonon renormalization and the thermal disorder of the lattice must be included.

Factors affecting the price of watermelons at Los Angeles

Abstract does not appear. First page follows. The Problem As the quantity of any commodity put on the market increases, the value which the consumer places on each unit declines, and hence he will pay less for each unit. It is the purpose of this study to determine for a specific commodity at a specific market (watermelons on the Los Angeles market) how much prices have actually changed during the past six years with the various changes in the supply, and to measure the effect of all other factors on which data are available and which affect the price. It is a matter of general experience that variations in the supply of one commodity may cause large proportional changes in its price, whereas similar variations in the supply of another commodity may cause only small proportional changes in its price. For example, an increase of 20 per cent in the supply of potatoes would cause a large relative decrease in their price.(8) A similar increase in the supply of apples would cause a much smaller proportional decrease in their price.(5) It is possible also that the demand for a commodity may change over a period of time. The price of potatoes seems to change more now for a given change in the supply than it did twenty years ago.(1) Changes of this kind however, usually come about gradually and the trend can be noted before a marked change occurs.