Seasonal Diet and Prey Preference of the African Lion in a Waterhole-Driven Semi-Arid Savanna

Large carnivores inhabiting ecosystems with heterogeneously distributed environmental resources with strong seasonal variations frequently employ opportunistic foraging strategies, often typified by seasonal switches in diet. In semi-arid ecosystems, herbivore distribution is generally more homogeneous in the wet season, when surface water is abundant, than in the dry season when only permanent sources remain. Here, we investigate the seasonal contribution of the different herbivore species, prey preference and distribution of kills (i.e. feeding locations) of African lions in Hwange National Park, Zimbabwe, a semi-arid African savanna structured by artificial waterholes. We used data from 245 kills and 74 faecal samples. Buffalo consistently emerged as the most frequently utilised prey in all seasons by both male (56%) and female (33%) lions, contributing the most to lion dietary biomass. Jacobs’ index also revealed that buffalo was the most intensively selected species throughout the year. For female lions, kudu and to a lesser extent the group “medium Bovidae” are the most important secondary prey. This study revealed seasonal patterns in secondary prey consumption by female lions partly based on prey ecology with browsers, such as giraffe and kudu, mainly consumed in the early dry season, and grazers, such as zebra and suids, contributing more to female diet in the late dry season. Further, it revealed the opportunistic hunting behaviour of lions for prey as diverse as elephants and mice, with elephants taken mostly as juveniles at the end of the dry season during droughts. Jacobs’ index finally revealed a very strong preference for kills within 2 km from a waterhole for all prey species, except small antelopes, in all seasons. This suggested that surface-water resources form passive traps and contribute to the structuring of lion foraging behaviour.     

Tetracycline residues and tetracycline resistance genes in groundwater impacted by swine production facilities

Antibiotics are used at therapeutic levels to treat disease; at slightly lower levels as prophylactics; and at low, subtherapeutic levels for growth promotion and improvement of feed efficiency. Over 88% of swine producers in the United States gave antimicrobials to grower/finisher pigs in feed as a growth promoter in 2000. It is estimated that ca. 75% of antibiotics are not absorbed by animals and are excreted in urine and feces. The extensive use of antibiotics in swine production has resulted in antibiotic resistance in many intestinal bacteria, which are also excreted in swine feces, resulting in dissemination of resistance genes into the environment. To assess the impact of manure management on groundwater quality, groundwater samples have been collected near two swine confinement facilities that use lagoons for manure storage and treatment. Several key contaminant indicators - including inorganic ions, antibiotics, and antibiotic resistance genes - were analyzed in groundwater collected from the monitoring wells. Chloride, ammonium, potassium, and sodium were predominant inorganic constituents in the manure samples and served as indicators of groundwater contamination. Based on these analyses, shallow groundwater has been impacted by lagoon seepage at both sites. Liquid chromatography-mass spectroscopy (LC-MS) was used to measure the dissolved concentrations of tetracycline, chlortetracycline, and oxytetracycline in groundwater and manure. Although tetracyclines were regularly used at both facilities, they were infrequently detected in manure samples and then at relatively trace concentrations. Concentrations of all tetracyclines and their breakdown products in the groundwater sampled were generally less than 0.5 microg/L. Bacterial tetracycline resistance genes served as distinct genotypic markers to indicate the dissemination and mobility of antibiotic resistance genes that originated from the lagoons. Applying PCR to genomic DNA extracted from the lagoon and groundwater samples, four commonly occurring tetracycline (tet) resistance genes - tet(M), tet(O), tet(Q), and tet(W) - were detected. The detection frequency of tet genes was much higher in wells located closer to and down-gradient from the lagoons than in wells more distant from the lagoons. These results suggested that in the groundwater underlying both facilities tetracycline resistance genes exist and are somewhat persistent, but that the distribution and potentially the flux for each tet gene varied throughout the study period.     

Dietary Response of Chimpanzees and Cercopithecines to Seasonal Variation in Fruit Abundance. II. Macronutrients

In a continuation of our study of dietary differentiation among frugivorous primates with simple stomachs, we present the first comparison of differences in dietary macronutrient content between chimpanzees and cercopithecine monkeys. Previously we have shown that chimpanzee and monkey diets differ markedly in plant part and species content. We now examine whether this diet diversity is reflected in markedly different dietary macronutrient levels or the different feeding strategies yield the same macronutrient levels in their diets. For each primate group we calculated the total weighted mean dietary content of 4 macronutrients: crude lipid (lipid), crude protein (CP), water-soluble carbohydrates (WSC), and total nonstructural carbohydrates (TNC). We also calculated 4 fiber fractions: neutral-detergent fiber (NDF), which includes the subfractions hemicellulose (HC), cellulose (Cs), and sulfuric acid lignin (Ls). The HC and Cs are potentially fermentable fibers and would contribute to the energy provided by plant food, depending on the hind gut fermenting capacity of the individual primate species. The chimpanzee diet contained higher levels of WSC and TNC because during times of fruit abundance the chimpanzees took special advantage of ripe fruit, while the monkeys did not. The monkey diets contained higher levels of CP because the monkeys consumed a constant amount of leaf throughout the year. All four primate species consumed diets with similar NDF levels. However, the chimpanzees also took advantage of periods of ripe fruit abundance to decrease their Ls levels and to increase their HC levels. Conversely, the monkey diets maintained constant levels of the different fiber fractions thoughout the year. Nevertheless, despite these differences, the diets of the 4 frugivores were surprisingly similar, considering the substantial differences in body size. We conclude that the chimpanzee diet is of higher quality, particularly of lower fiber content, than expected on the basis of their body size.     

The role of dendritic cells in the initiation of immune responses to contact sensitizers. II. Studies in nude mice

Twenty-four hours after skin painting nude mice with picryl chloride, there was an increase in the number of dendritic cells (DC) isolated from the draining lymph nodes. This increased inflow or retention of DC in lymph nodes following skin painting is therefore unlikely to depend on interaction of DC with T cells. The DC obtained initiated primary proliferative responses in vitro in lymph node cells from congenic euthymic mice. Contact sensitivity developed in congenic mice when they received footpad injections of 60,000 DC from the lymph nodes of nude mice skin sensitized 1 day previously with picryl chloride or oxazolone. The initiation of delayed hypersensitivity was therefore independent of T-cell contamination within the donor DC.     

Effect of vascular cannulation on serum concentrations of LH, FSH, prolactin and cortisol in prepubertal gilts

Two experiments were conducted to determine whether cannulation of the jugular vein in gilts alters serum concentrations of LH, FSH, prolactin (PRL) or cortisol (C). In Experiment 1, 12 crossbred prepubertal gilts weighing 95 +/- 1.3 kg were immobilized by snaring, and tygon tubing was threaded into the anterior vena cava through a 12-gauge needle inserted into the jugular vein. Five hours later, blood samples were drawn at 20-min intervals for 4 h (Day 0). Samples were also drawn at 20-min intervals for 4-h periods 24 h (Day 1) and 48 h (Day 2) after cannulation. Serum concentrations of LH were similar (P=0.26) among Day 0 (0.40 ng/ml), Day 1 (0.39 ng/ml) and Day 2 (0.34 ng/ml). Serum PRL was similar (P=0.07) among Day 0 (4.10 ng/ml), Day 1 (3.87 ng/ml) and Day 2 (3.43 ng/ml). Serum concentrations of C were greater (P < 0.001) on Day 0 (8.32 ng/ml) than Day 1 (4.48 ng/ml) or Day 2 (3.54 ng/ml). In Experiment 2, cannulas were placed in 29 prepubertal gilts. Two days after initial cannulation, six blood samples were drawn at 20-min intervals. Gilts were then immobilized by snaring, and a second cannulae was inserted into the contralateral vein. Five blood samples were taken at 2-min intervals during the second cannulation and then six samples were drawn at 20-min intervals. Serum LH and FSH were not altered by cannulation or elevated during the subsequent 2-h sampling period (P>0.05). In contrast, serum concentrations of PRL rose slowly (P<0.05) during cannulation and remained elevated for 60 min before returning to baseline. Serum concentrations of C rose within 6 min of cannulation, remained elevated for 30 min, and then declined over the next 90 min. From these two experiments, it appears that secretory patterns of LH and FSH can be accurately assessed immediately after cannulation in prepubertal gilts. Measurements of serum PRL and C that reflect nonstressed conditions, however, cannot be obtained until at least 2 h or 1 d after cannulation, respectively.     

The platelet microparticle proteome

Platelet-derived microparticles are the most abundant type of microparticle in human blood and contribute to many biologically significant processes. Here, we report the first proteomic analysis of microparticles generated from activated platelets. Using 1D SDS-PAGE and liquid chromatography coupled to a linear ion trap mass spectrometer, the identification of 578 proteins was accomplished using a minimum of 5 MS/MS detections of at least two different peptides for each protein. These microparticles displayed many proteins intrinsic to and well-characterized on platelets. For example, microparticles in these experiments were found to contain membrane surface proteins including GPIIIa, GPIIb, and P-selectin, as well other platelet proteins such as the chemokines CXCL4, CXCL7, and CCL5. In addition, approximately 380 of the proteins identified were not found in two previous studies of the platelet proteome. Since several of the proteins detected here have been previously implicated in microparticle formation and/or pathological function, it is hoped that this study will help fuel future work concerning the possible role of microparticles in various disease states.     

pH, healing rate, and symptom relief in patients with GERD

Gastroesophageal reflux symptoms are common and occur in all of us from time to time. In others, reflux may be associated with ulcerative esophagitis. The symptoms may be aggravated by large meals, coffee, smoking and position. Physiological and pathological reflux can be separated by the frequency and duration of the exposure of the lower esophagus to acid. Pathological reflux results in symptoms and also esophagitis and ulceration in some patients. Although gastroesophageal reflux disease (GERD) is considered to result from a disorder of motility in the esophagus, gastric acid and peptic activity are deemed pivotal to the initiation and continuation of the esophageal damage and the development of symptoms. Acid exposure in the esophagus is normally less than 4 percent of the 24 hours with a pH below 4. An increase over 4 percent of the time with a pH less than 4 is considered pathological. Hence, antisecretory drugs have become the principle approach to the treatment of reflux symptoms and esophagitis since they reduce the acidity, of gastric juice and the activity of pepsin. Importantly, they also reduce the volume of gastric juice available for reflux into the esophagus. There is a clear relationship between the degree and duration of acid suppression and the relief of heartburn and healing of esophagitis. Pharmacodynamic studies with different dose regimens of the H2-receptor antagonists and the proton pump inhibitors show a difference in the degree and duration of the antisecretory effect, and this correlates closely with the results of clinical trials with respect to the healing of esophagitis and the relief of symptoms. Proton pump inhibitors achieve healing rates by week four, which are not achieved by H2-receptor antagonists even after 12 weeks of treatment. The advantage of proton pump inhibitors over H2-receptor antagonists is due to the greater degree, longer duration of effect and more complete inhibition of acid secretion that maintains intragastric pH above 4 for a maximal duration. Although there is no significant difference between proton pump inhibitors with respect to healing of esophagitis, symptom relief occurs earlier with lansoprazole than omeprazole, and this is probably due to the greater oral bioavailability and faster onset of action of lansoprazole when compared to omeprazole.     

Mesozooplankton interactions with the shelf around the sub-Antarctic Prince Edward Islands archipelago

Mesozooplankton surveys were conducted in April/May for fourconsecutive years (1996–1999) in the vicinity of the PrinceEdward Islands (PEIs), Southern Ocean. The PEIs are locatedin the Polar Frontal Zone, directly in the path of the east-flowingAntarctic Circumpolar Current. Zooplankton were collected byoblique tows using a Bongo net fitted with 300 µm mesh.The abundance, biomass and average size of the mesozooplanktonin the upstream (USR), inter-island (IIR) and downstream (DSR)regions indicated that some groups and species were significantlyaffected by their interaction with the shallow shelf watersof the PEIs. Total mesozooplankton abundance and biomass weretypically highest in the DSR, but no consistent pattern wasevident in the USR and IIR. Copepods, euphausiids and fish weregenerally of a low average size in the IIR. This small sizewas largely attributed to the reduced abundance, or completeabsence, of mesopelagic species from the shelf region. Of totalbiomass, the mesopelagic species Euphausia longirostris, Euphausiasimilis, Pleuromamma abdominalis, Paraeuchaeta biloba and Oncaeaantarctica together contributed an average of 16% to the USR,2% to the IIR and 15% to the DSR. Conversely, epipelagic speciesshowed no consistent pattern of abundance and biomass distributionbetween regions. The low incidence of mesopelagic species overthe island shelf was attributed mainly to reduced advectionof deep water into the shelf region (average depth = 200 m),rather than predation, particularly during the through-flowmode between the islands. This resulted in substantial regionaldifferences in euphausiid community structure. The epipelagicspecies Euphausia vallentini and Thysanoessa vicina completelydominated the IIR, comprising on average 89% of total euphausiidbiomass in this region. However, predation may be importantduring the water-trapping mode between the islands. Advectionof zooplankton into the IIR appeared to be affected by the proximityof the Subantarctic Front (SAF). In 1996, when the SAF was farnorth of the PEIs, reduced current velocities resulted in somedegree of water retention over the shelf and an increased predationimpact. Conversely, when the SAF was close to the PEIs in 1999,more large plankton were transported over the island shelf.High current velocities and productivity associated with theSAF appear to increase the biomass and size of allochthonouszooplankton/nekton advected into the IIR, and consequently mayhave increased the availability of prey to land-based predators.The long-term southward movement of the SAF recently observedin the vicinity of the PEIs may therefore have important implicationsfor the ecosystem of these islands.     

Site-Specific Phosphorylation of the DNA Damage Response Mediator Rad9 by Cyclin-Dependent Kinases Regulates Activation of Checkpoint Kinase 1

The mediators of the DNA damage response (DDR) are highly phosphorylated by kinases that control cell proliferation, but little is known about the role of this regulation. Here we show that cell cycle phosphorylation of the prototypical DDR mediator Saccharomyces cerevisiae Rad9 depends on cyclin-dependent kinase (CDK) complexes. We find that a specific G2/M form of Cdc28 can phosphorylate in vitro the N-terminal region of Rad9 on nine consensus CDK phosphorylation sites. We show that the integrity of CDK consensus sites and the activity of Cdc28 are required for both the activation of the Chk1 checkpoint kinase and its interaction with Rad9. We have identified T125 and T143 as important residues in Rad9 for this Rad9/Chk1 interaction. Phosphorylation of T143 is the most important feature promoting Rad9/Chk1 interaction, while the much more abundant phosphorylation of the neighbouring T125 residue impedes the Rad9/Chk1 interaction. We suggest a novel model for Chk1 activation where Cdc28 regulates the constitutive interaction of Rad9 and Chk1. The Rad9/Chk1 complex is then recruited at sites of DNA damage where activation of Chk1 requires additional DDR–specific protein kinases.