The effect of culture and membrane potential on Goα expression in neonatal rat cardiac myocytes

The effects of culture and membrane potential on G_o39 expression were examined in neonatal rat cardiac myocytes. During six days of culture, the amount of G_o39 in myocytes increased six-fold. The increase in G_o39 appeared to be programmed, since G_o39 of rat hearts also increased in vivo within three days after birth before declining by six days after birth. Furthermore, the age of the rat from which cardiac myocytes were isolated determined the amount of G_o39 that accumulated in cultured cells with myocytes from two day-old rats producing more G_o39 than myocytes from six day-old rats. In addition, agents which alter membrane potential (KCl and bupivacaine) inhibited the accumulation of G_o39 in cultured myocytes. In an attempt to identify the signaling pathway in which cardiac G_o39 is involved, muscarinic receptor-stimulated inositol phosphate production was examined, but was found to be comparable in myocytes that had six-fold differences in G_o39 content. Thus G_o39 does not appear to couple muscarinic receptors to phospholipase C in rat cardiac myocytes.     

The effect of angiotensin II and indomethacin on immunoreactive prostaglandin “A” levels in man

The effect of angiotensin II on peripheral levels of immunoreactive prostaglandin A₂ (IR-PGA) was determined in 17 normal male volunteers. IR-PGA rose from 338 ± 65 (SE) pg/ml to 635 ± 142 in response to pressor infusions of angiotensin II (p <0.05 on paired analysis). This increase was not observed when indomethacin, 75 mg p.o., was given to 8 patients two hours prior to a repeat infusion. Five patients of the original group were placed on a low sodium diet (10–20 mEq). The response to angiotensin was now exaggerated (278 ±52 pg/ml to 916 ± 284). These five patients were kept on a low sodium intake and given indomethacin 50 mg p.o. q 6 hourly for 4 days. There was no significant rise with angiotensin infusion (106 ± 31 pg/ml to 120 ± 70). Pressor infusions of angiotensin II raise peripheral levels of IR-PGA, and this response is exaggerated by a low sodium diet and blocked by either acute or chronic indomethacin administration. This data supports the concept that vasodilatory prostaglandins may be released by endogenous angiotensin and thus provide a dynamic antagonism to the renin angiotensin system in man.     

The effect of learning and search images on predator–prey interactions

In dealing with the spatial and temporal variability of prey species, predators may be able to forage optimally if they have flexible and rapid behavioral plasticity rather than predetermined responses. For predators that learn to focus attention on the cryptic prey type most frequently encountered during recent searching (termed a “search image”), rare prey types may be overlooked because of a focus on more common prey. Search imaging reflects biased searching for one of a number of available prey types, and has been studied widely in birds and mammals. Here we discuss the significant implications of this phenomenon for insect predator–prey systems, particularly with respect to parasitic wasps searching for host species using learned olfactory cues. We (1) review studies about perceptual development through individual ontogeny, (2) define the term “search image” and discuss the cognitive mechanisms involved in search-image formation, (3) discuss the role of search images and frequency-dependent predation as a proximate mechanism in the maintenance of prey diversity, (4) examine data on host–parasitoid olfactory search imaging, and (5) conclude by identifying important research areas for future studies in the field of olfactory search images.     

The possible role of zinc and metallothionein in the liver on the therapeutic effect of IFN-α to hepatitis C patients

We have studied zinc deficiency in hepatitis C patients (complete responder [C,R] 22, nonresponder [NR] 25) with relation to the therapeutic effect of interferon-α (IFN-α). Circadian variations in serum zinc levels were high in the morning (basal level) and then gradually decreased during the day in both chronic hepatitis C patients and healthy controls. Basal zinc levels in serum were significantly lower in chronic hepatitis C patients (73±3 μg/dL,n=12) than in controls (93±5 μg/dL). An injection of 10 MU of IFN-α to hepatitis C patients augmented the serum zinc reductions, up to 40% in 8 h. Serum cortisol levels were significantly elevated 8 h (25.6±2.3 μg/dL) after IFN-α dose. Forty-seven chronic hepatitis C patients were treated with IFN-α for 24 wk, and serum zinc and copper levels were determined 12 and 24 wk during and after the completion of IFN-α therapy. Serum zinc levels and zinc/copper ratio were higher in CRs than in NRs to IFN therapy at each time-point. Hepatic metallothionein staining became prominent after IFN therapy in most of CRs, whereas it diminished NRs. These data suggest that nutritional status of zinc influences the effect of IFN on hepatitis C patients.     

The effect of tumor necrosis factor-α inhibitor soon after hypoxia-ischemia on heart in neonatal rats

AimsPerinatal hypoxic-ischemic insult has acute and long term deleterious effects on many organs including heart. Although tumor necrosis factor alpha (TNF-α) has been reported to increase soon after hypoxia, the inhibition of this mediator has not been documented. The aim of this study was to investigate the effects of a TNF-α inhibitor (etanercept) on contractility and ultrastructure of rat heart muscles exposed to hypoxia-ischemia during neonatal period.Main methodsForty-five seven-day old rats divided into three groups were included in this study. The right carotid arteries of Saline and Etanercept groups of rats were ligated and kept in a hypoxia chamber containing 8% oxygen for 2 h. Immediately after hypoxia, while Etanercept group was administered 10 mg/kg etanercept, Saline group had only saline intraperitoneally. The carotid arteries of rats in Sham group were located without ligation and hypoxia. Mechanical activity of heart was recorded and tissue samples were examined by electron microscopy in the sixteenth week following the hypoxia-ischemia.Key findingsWhile atrial contractile force in Etanercept group was similar to Sham group, there was significant decrease in Saline group (p < 0.001). However, there was only non-significant decrease in ventricular contractility of Saline group comparing to Sham group (p > 0.05). After hypoxia-ischemia, ultrastructural degenerative changes and mitochondrial damage in atriums of Etanercept group were significantly less severe than Saline group.SignificanceThis study demonstrated that neonatal hypoxia-ischemia caused long term cardiac dysfunction and ultrastructural degenerative changes in the heart of rats. TNF-α inhibitor administration soon after hypoxia-ischemia may have heart protective effect.     

The effect of maternal and child health and family planning services on mortality: is prevention enough?

OBJECTIVE--To examine the impact on mortality of a child survival strategy, mostly based on preventive interventions. DESIGN--Cross sectional comparison of cause specific mortality in two communities differing in the type, coverage, and quality of maternal and child health and family planning services. In the intervention area the services were mainly preventive, community based, and home delivered. SUBJECTS--Neonates, infants, children, and mothers in two contiguous areas of rural Bangladesh. INTERVENTIONS--In the intervention area community health workers provided advice on contraception and on feeding and weaning babies; distributed oral rehydration solution, vitamin A tablets for children under 5, and ferrous fumarate and folic acid during pregnancy; immunised children; trained birth attendants in safe delivery and when to refer; treated minor ailments; and referred seriously ill people and malnourished children to a central clinic. MAIN OUTCOME MEASURES--Overall and age and cause specific death rates, obtained by a multiple step "verbal autopsy" process. RESULTS--During the two years covered by the study overall mortality was 17% lower among neonates, 9% lower among infants aged 1-5 months, 30% lower among children aged 6-35 months, and 19% lower among women living in the study area than in those living in the control area. These differences were mainly due to fewer deaths from neonatal tetanus, measles, persistent diarrhoea with severe malnutrition among children, and fewer abortions among women. CONCLUSIONS--The programme was effective in preventing some deaths. In addition to preventive components such as tetanus and measles immunisation, health and nutrition education, and family planning, curative services are needed to reduce mortality further.     

The effect of losartan and carvedilol on renal haemodynamics and altered metabolism in fructose-fed Sprague–Dawley rats

The aim of this study is to assess the effects of losartan and carvedilol on metabolic parameters and renal haemodynamic responses to angiotensin II (Ang II) and adrenergic agonists in the model of fructose-fed rat. Thirty-six Sprague-Dawley rats were fed for 8 weeks either 20% fructose solution (F) or tap water (C) ad libitum. F or C group received either losartan or carvedilol (10 mg/kg p.o.) daily for the last 3 weeks of the study (FL and L) and (FCV and CV), respectively, then in acute studies the renal vasoconstrictor actions of Ang II, noradrenaline (NA), phenylephrine (PE) and methoxamine (ME) were determined. Data, mean±SEM were analysed using ANOVA with significance at P <0.05. Losartan and carvedilol decreased the area under the glucose tolerance curve of the fructose-fed group. The responses (%) to NA, PE, ME and Ang II in F were lower (P <0.05) than C (F vs. C, 17±2 vs. 38±3; 24±2 vs. 48±2; 12±2 vs. 34±2; 17±2 vs. 26±2), respectively. L had higher (P <0.05) responses to NA and PE while CV had blunted (P <0.05) responses to NA, PE and Ang II compared to C (L, CV vs. C, 47±3, 9±2 vs. 38±3; 61±3, 29±3 vs. 48±2; 16±3, 4±3 vs. 26±2), respectively. FL but not FCV group had enhanced (P <0.05) responses to NA, PE and ME compared to F (FL vs. F, 33±3 vs. 17±2; 45±3 vs. 24±2; 26±3 vs. 12±2), respectively. Losartan and carvedilol had an important ameliorating effect on fructose-induced insulin resistance. Losartan treatment could be an effective tool to restore normal vascular reactivity in the renal circulation of the fructose-fed rat.     

The effect of time of day and exercise on platelet functions and platelet–neutrophil aggregates in healthy male subjects

Platelet activation state changes by exercise. The effect of exercise time on platelet activation state and formation of platelet–neutrophil aggregates are not known yet. In this study the effect of exercise and time of day were examined on platelet activity with platelet–neutrophil aggregates. Ten moderately active males aged 27± 1.63 (mean±S.D.) years completed sub-maximal (70% VO_2max) exercise trials for 30 min. Blood pressure (BP) was recorded. Venous blood samples were obtained at rest, immediately post-exercise and after 30 min of recovery. Whole blood was analysed for haematocrit (Hct), haemoglobin (Hb), platelet count (PC), mean platelet count (MPV) and platelet aggregation (PA). Platelet–neutrophil aggregates and beta-thromboglobulin (β-TG) levels were assayed. Platelet count showed significant increase after morning exercise ((236± 32)×10⁹ l⁻¹ versus (202± 34)×10⁹ l⁻¹ baseline, p < 0.05). Exercise resulted in significantly lower MPV after the evening exercise (9.16± 0.5 fl versus 9.65± 0.36 fl, p < 0.05). Platelet aggregation by adenosine diphosphate (ADP) decreased after morning exercise and the recovery aggregation levels were significantly different at two different times of the day (68± 20% a.m. versus 80± 12% p.m., p < 0.05). It was also showed that platelet–neutrophil aggregates increased significantly from baseline after both exercises. Exercise-induced platelet–neutrophil aggregates were higher in the evening (10.7± 1.3% p.m. versus 6.4± 1.8% a.m., p < 0.0001). It is therefore concluded that besides platelet–platelet aggregation, exercise can cause platelet– neutrophil aggregates. In addition, time of day has an effect on platelet activation related events. Circadian variations of physiological parameters may have an effect on thrombus formation by platelet activation. (Mol Cell Biochem xxx: 119–124, 2005)     

The effect of norflurazon on protein composition and chlorophyll organization in pigment–protein complex of Photosystem II

The pyridazinone-type herbicide norflurazon SAN 9789 inhibiting the biosynthesis of long-chain carotenoids results in significant decrease in PS II core complexes and content of light-harvesting complex (LHC) polypeptides in the 29.5–21 kDa region. The Chl a forms at 668, 676, and 690 nm that belong to LHC and antenna part of PS I disappear completely after treatment. The intensity of the Chl b form at 648 nm is sharply decreased in treated seedlings grown under 30 or 100 lx light intensity. The bands of carotenoid absorption at 421, 448 (Chl a), 452, 480, 492, 496 (β-carotene), and 508 nm also disappear. The band shift from 740 to 720 nm and decrease in its intensity relative to the 687 nm emission peak in the low-temperature fluorescence spectrum (77 K) suggests a disturbance of energy transfer from LHC to the Chla form at 710–712 nm.     

The effect of birthplace on heat tolerance and mortality in Milan, Italy, 1980–1989

The temperature–mortality relationship follows a well-known J-V shaped pattern with mortality excesses recorded at cold and hot temperatures, and minimum at some optimal value, referred as Minimum Mortality Temperature (MMT). As the MMT, which is used to measure the population heat-tolerance, is higher for people living in warmer places, it has been argued that populations will adapt to temperature changes. We tested this notion by taking advantage of a huge migratory flow that occurred in Italy during the 1950s, when a large number of unemployed people moved from the southern to the industrializing north-western regions. We have analyzed mortality–temperature relationships in Milan residents, split by groups identified by area of birth. In order to obtain estimates of the temperature-related risks, log-linear models have been used to fit daily death count data as a function of different explanatory variables. Results suggest that mortality risks differ by birthplace, regardless of the place of residence, namely heat tolerance in adult life could be modulated by outdoor temperature experienced early in life. This indicates that no complete adaptation might occur with rising external environmental temperatures.     

The effect of chondroitin sulphate–protein on the formation of collagen fibrils in vitro

1. It was found that the precipitation of collagen fibrils at 37 degrees from mixtures of chondroitin sulphate-protein and tropocollagen at physiological ionic strength and pH takes place in two distinct phases. The first occurs immediately on mixing either at 4 degrees or at 37 degrees , and the second occurs only at 37 degrees and after a lag phase whose magnitude depends on the proportions of components. 2. When the second stage of precipitation was inhibited by mixing the reactants at 4 degrees , the initial precipitate was found to contain ;native-type' collagen fibrils and chondroitin sulphate-protein. 3. On the basis of kinetic experiments it was concluded that aggregates of chondroitin sulphate-protein and tropocollagen form instantaneously and that these act as sites for the second stage of precipitation of fibrils. 4. The gels that result after continued incubation at 37 degrees are fibrous in appearance if formed in the presence of the initial precipitate of chondroitin sulphate-protein and tropocollagen. 5. On the basis of these experiments in vitro the authors propose a sequence of events for collagen fibrogenesis in vivo.     

The effect of cross-links on the mobility of proteins in dodecyl sulphate–polyacrylamide gels

The effect of reduction of intramolecular disulphide bridges on the mobility of proteins in 5% (w/v) polyacrylamide gels in the presence of sodium dodecyl sulphate was investigated. A series of polypeptide polymers, containing up to 68 intramolecular disulphide bridges, was prepared by cross-linking proteins of known structure with glutaraldehyde. These model polypeptides were denatured with heat, sodium dodecyl sulphate and urea, and their mobilities in sodium dodecyl sulphate-polyacrylamide gels compared before and after reduction with dithiothreitol. The mobilities of polypeptides containing no cystine were unaffected by reduction. However, reduction generally decreased the mobilities of polypeptides containing cystine; the extent of this decrease depended on the number of cystine residues originally present in the polypeptide polymer, and on the protein from which the latter was derived. In contrast with their higher oligomers, the monomer of lysozyme and the dimer of ribonuclease increased in mobility after reduction. The reduced polypeptide oligomers formed by reaction with glutaraldehyde were generally found to migrate at a rate significantly faster than was expected from their calculated molecular weights. It was concluded that the use of unreduced proteins and protein aggregates for molecular-weight measurements by the sodium dodecyl sulphate-polyacrylamide-gel method may give erroneous estimates of the molecular weight of any protein being investigated.     

The effect of disturbance on an ant–plant mutualism

Protective ant–plant mutualisms—where plants provide food or shelter to ants and ants protect the plants from herbivores—are a common feature in many ecological communities, but few studies have examined the effect of disturbance on these interactions. Disturbance may affect the relationship between plants and their associated ant mutualists by increasing the plants’ susceptibility to herbivores, changing the amount of reward provided for the ants, and altering the abundance of ants and other predators. Pruning was used to simulate the damage to buttonwood mangrove (Conocarpus erectus) caused by hurricanes. Pruned plants grew faster than unpruned plants, produced lower levels of physical anti-herbivore defenses (trichomes, toughness), and higher levels of chemical defenses (tannins) and extrafloral nectaries. Thus, simulated hurricane damage increased plant growth and the amount of reward provided to ant mutualists, but did not have consistent effects on other anti-herbivore defenses. Both herbivores and ants increased in abundance on pruned plants, indicating that the effects of simulated hurricane damage on plant traits were propagated to higher trophic levels. Ant-exclusion led to higher leaf damage on both pruned and upruned plants. The effect of ant-exclusion did not differ between pruned and unpruned plants, despite the fact that pruned plants had higher ant and herbivore densities, produced more extrafloral nectaries, and had fewer physical defenses. Another common predator, clubionid spiders, increased in abundance on pruned plants from which ants had been excluded. I suggest that compensatory predation by these spiders diminished the effect of ant-exclusion on pruned plants.     

The effect of landscape heterogeneity on host–parasite dynamics

Environmental heterogeneity has been shown to have a profound effect on population dynamics and biological invasions, yet the effect of its spatial structure on the dynamics of disease invasion in a spatial host–parasite system has received little attention. Here we explore the effect of environment heterogeneity using the pair approximation and the stochastic spatially explicit simulation in which the lost patches are clustered in a fragmented landscape. The intensity of fragmentation is defined by the amount and spatial autocorrelation of the lost habitat. More fragmented landscape (high amount of habitat loss, low clustering of lost patches) was shown to be detrimental to the parasitic disease invasion and transmission, which implies that the potential of using artificial disturbances as a disease-control agency in biological conservation and management. Two components of the spatial heterogeneity (the amount and spatial autocorrelation of the lost habitat) formed a trade-off in determining the host–parasite dynamics. An extremely high degree of habitat loss was, counter-intuitively, harmful to the host. These results enrich our understanding of eco-epidemiological, host–parasite systems, and suggest the possibility of using the spatial arrangement of habitat patches as a conservation tool for guarding focal species against parasitic infection and transmission.     

Prostaglandin 15-hydroxy dehydrogenase and Δ13 reductase levels in the lungs of maternal,fetal and neonatal rabbits

The levels of prostaglandin 15-hydroxy dehydrogenase and reductase have been studied in the lungs of maternal, fetal and neonatal rabbits. Fetal lungs obtained at gestational age of 28–30 days (full term 31 days) had the same levels of prostaglandin dehydrogenase as the adults, while the reductase levels in the fetal lungs were only one fourth that in the adults. The lungs of maternal rabbits at near term possessed very high levels of prostaglandin dehydrogenase — approximately twenty-fold higher than in the adult non-pregnant female controls. The Δ¹³ reductase appeared slightly elevated during pregnancy. Neonatal animals at different ages showed the same levels of both enzymes as the near term fetus and/or the non-pregnant adults, which suggests that the development of the ability for prostaglandin metabolism is completed at least several days before birth. The high dehydrogenase levels in the near term maternal lungs indicated the requirement for extra protection against prostaglandin release during late pregnancy.     

The effects of β-glucan on iron levels and lipid peroxidation in intra-abdominal sepsis in rats

Sepsis is defined as a systemic response of organisms to microorganisms and toxins. Sepsis is associated with the enhanced generation of reactive oxygen metabolites, leading to multiple organ dysfunctions. β-glucan is accepted to be one of the most powerful immune response modifiers. The aim of this study was to investigate the putative protective effect of β-glucan on changes of iron and malondialdehyde (MDA) levels in various tissue and blood after experimental sepsis in rats. Sepsis was induced by cecal ligation and perforation (CLP) in 32 male Wistar albino rat. To evaluate this, rats were divided into four groups as sham operated, β-glucan treated sham operated, CLP and β-glucan treated CLP. Sixteen hours after operation, rats were decapitated and MDA and iron levels were measured in the liver, kidney, heart, diaphragm tissues and blood. Also, whole tissue histopathology was evaluated by a light microscope. The results demonstrate that sepsis significantly decreased iron levels of all tissues and blood. The decrease in tissue iron levels and the increase MDA levels demonstrate the role of trace elements and free radicals in sepsis-induced tissue damage. Our results indicate that the given dose of β-glucan was probably insufficient to prevent sepsis-induced organ injury.