Foraging habits of Alouatta palliata mexicana in three forest fragments

The activity patterns and diet of howler monkeys (Alouatta palliata mexicana) were studied in 3 forest fragments in south-eastern Mexico: Playa Escondida (PLA), Agaltepec Island (AGA) and Arroyo Liza (LIZ). Intersite differences offered the opportunity to investigate the foraging adaptations of howler monkeys in response to population and habitat size. In the largest fragment (PLA), the howlers' diet was based on high-quality items (fruit and young leaves). In AGA, where the density of howlers was the highest, their diet was mostly folivorous with a marked exploitation of uncommon food items such as vines, lianas, shrubs and herbs. The dietary differences in AGA were accompanied by more time spent travelling and less time spent resting. Although LIZ was the smallest fragment and had a high howler density, the small group size and the use of energy-minimizing strategies (less time spent travelling and more time spent resting) probably allowed howlers to maintain a frugivorous diet.     

Guard cell-specific inhibition of Arabidopsis MPK3 expression causes abnormal stomatal responses to abscisic acid and hydrogen peroxide

MAP kinases have been linked to guard cell signalling. Arabidopsis thaliana MAP Kinase 3 (MPK3) is known to be activated by abscisic acid (ABA) and hydrogen peroxide (H(2)O(2)), which also control stomatal movements. We therefore studied the possible role of MPK3 in guard cell signalling through guard cell-specific antisense inhibition of MPK3 expression. Such transgenic plants contained reduced levels of MPK3 mRNA in the guard cells and displayed partial insensitivity to ABA in inhibition of stomatal opening, but responded normally to this hormone in stomatal closure. However, ABA-induced stomatal closure was reduced compared with controls when cytoplasmic alkalinization was prevented with sodium butyrate. MPK3 antisense plants were less sensitive to exogenous H(2)O(2), both in inhibition of stomatal opening and in promotion of stomatal closure, thus MPK3 is required for the signalling of this compound. ABA-induced H(2)O(2) synthesis was normal in these plants, indicating that MPK3 probably acts in signalling downstream of H(2)O(2). These results provide clear evidence for the important role of MPK3 in the perception of ABA and H(2)O(2) in guard cells.     

Genetic analysis of hybridization between white-handed (Hylobates lar) and pileated (Hylobates pileatus) gibbons in a contact zone in Khao Yai National Park,Thailand

Primates - Natural hybridization has played various roles in the evolutionary history of primates. Its consequences range from genetic introgression between taxa, formation of hybrid zones, and...     

Alveolar macrophages are necessary for the systemic inflammation of acute alveolar hypoxia.

Alveolar hypoxia (Fi(O(2)) 0.10) rapidly produces inflammation in the microcirculation of skeletal muscle, brain, and mesentery of rats. Dissociation between tissue Po(2) values and inflammation, plus the observation that plasma from hypoxic rats activates mast cells and elicits inflammation in normoxic tissues, suggest that the response to hypoxia is initiated when mast cells are activated by an agent released from a distant site and carried by the circulation. These experiments tested the hypothesis that this agent originates in alveolar macrophages (AM). Male rats were depleted of AM by tracheal instillation of clodronate-containing liposomes. Four days after treatment, AM recovered by bronchoalveolar lavage were <10% of control. Control rats received buffer-containing liposomes. As expected, alveolar hypoxia (Fi(O(2)) 0.10) in control rats increased leukocyte-endothelial adherence, produced degranulation of perivascular mast cells, and increased fluorescent albumin extravasation in the cremaster microcirculation. None of these effects was seen when AM-depleted rats were exposed to hypoxia. Plasma obtained from control rats after 5 min of breathing 10% O(2) elicited inflammation when applied to normoxic cremasters. In contrast, normoxic cremasters did not develop inflammation after application of plasma from hypoxic AM-depleted rats. Supernatant from AM cultured in 10% O(2) produced increased leukocyte-endothelial adherence, vasoconstriction, and albumin extravasation when applied to normoxic cremasters. Normoxic AM supernatant did not produce any of these responses. The effects of hypoxic supernatant were attenuated by pretreatment of the cremaster with the mast cell stabilizer cromolyn. These data support the hypothesis that AM are the source of the agent that initiates hypoxia-induced systemic inflammation by activating mast cells.     

Microbial 7α-Hydroxylation of 3-Ketobisnorcholenol

The transformation of 22-hydroxy-23,24-bisnorchol-4-en-3-one to 7α-22-dihydroxy-23,24-bisnorchol-4-en-3-one by Botryodiploida theobromae, Lasiodiplodia theobromae, and various Botryosphaeria strains is described. Factors affecting the reaction were incubation temperature, sonication of the substrate, and addition of 2,2′-dipyridyl, extra carbohydrate, and Amberlite XAD-7. The enzyme responsible for the reaction appeared to be very specific and was not characteristic of all members of the genera listed above.     

Biochemical composition of particulate organic matter and bacterial dynamics at the sediment–water interface in a Mediterranean seagrass system

The seagrass Posidonia oceanica is the most productive system of theMediterranean Sea. In order to gather information on the temporal andspatial variability of the suspended particulate matter in relation tobacterial dynamics, water samples were collected at 10 cm above thesediments over a period of 13 months in the Prelo Bay (Ligurian Sea, NWMediterranean). Measurements of seston concentration, as well as theelemental (POC and PON) and biochemical composition (lipids, proteins,carbohydrates and nucleic acids) of particulate matter were carried out toassess the origin, composition and bacterial contribution to the foodpotentially available in the seagrass system to consumers. Lipids andproteins were the main biochemical classes of organic compounds, followed bycarbohydrates. Despite the highly refractory composition of the seagrassleaves, particulate organic matter was mostly composed of labile compounds(69.9% of POC). POM temporal patterns were controlled by currentspeed at the sediment–water interface that resuspended only smallparticles largely colonised by bacteria after an intensive process offractionation and aging. In the seagrass system, the POM appears to bedominated by bacteria (density ranging from 0.7 to 2.5×10⁹ cells l^™1, representing more than48.3% of POC and 68.7% of the biopolymeric carbon, as the sumof lipid, protein and carbohydrate carbon). This feature was characteristicof the seagrass system since much lower bacterial densities were foundoutside the Posidonia meadow. Bacteria were negatively correlated with theconcentration of nitrite and nitrate suggesting a selective utilisation ofinorganic nutrients to support their growth. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chemotaxis in Actinoplanes

The chemotactic properties of spores of Actinoplanes brasiliensis were examined. The spores are attracted to chloride and bromide solutions but not to a number of organic compounds that are capable of supporting growth in chemically defined media. Chloride attraction has been tested in several other species of the genus and in a number of Actinoplanes strains isolated from soils. Some are attracted to chloride, but most strains are indifferent to the halide. In dense suspensions, the spores of A. brasiliensis show an apparent microaerophilic behavior. The ecological implications of the chemotactic properties of the A. brasiliensis spores are discussed.Dedicated to Professor R. Y. Stanier on the occasion of his 60th birthday     

Patterns of prostaglandin production in the bovine fetal and maternal vasculature

Prostaglandin (PG) synthesis by the blood vessel wall may contribute to the regulation of vascular tone and prevent deposition of platelets. The pattern of prostaglandin synthesis was investigated in vascular tissues from fetal, maternal and non-pregnant cows. Thin slices of blood vessels were incubated in Krebs' solution to which was added [1-¹⁴C] arachidonic acid. The radioactive products were extracted from the incubation medium, separated by thin-layer chromatography, and quantitated by scintillation counting. In all blood vessels studied the principal prostaglandin recovered from the incubation medium was 6 keto-PGF_1α, the stable hydrolysis product of prostacyclin; the highest yield of radioactive prostaglandins was obtained with fetal tissues. Only the mesenteric arteries obtained from pregnant and non-pregnant cows demonstrated a biosynthetic capacity comparable to those of the fetal vasculature; pulmonary arteries and aortas of adult animals had a much lower capacity to synthesize prostaglandins. Release of prostaglandins by the ductus arteriosus was also measured by mass fragmentography. Again 6 keto-PGF_1α was the predominant product: 6 keto-PGF_1α = 223 versusPGE₂ = 10 and PGF_2α = 15 ng/g of wet weight of tissue. The identity of 6 keto-PGF_1α was confirmed by mass spectroscopy. The high capacity of fetal blood vessels to synthesize PGI₂ may reflect an important role for this substance in the regulation of the fetal circulation.     

Determinants of maximal O(2) uptake in rats selectively bred for endurance running capacity.

O(2) transport during maximal exercise was studied in rats bred for extremes of exercise endurance, to determine whether maximal O(2) uptake (VO(2 max)) was different in high- (HCR) and low-capacity runners (LCR) and, if so, which were the phenotypes responsible for the difference. VO(2 max) was determined in five HCR and six LCR female rats by use of a progressive treadmill exercise protocol at inspired PO(2) of approximately 145 (normoxia) and approximately 70 Torr (hypoxia). Normoxic VO(2 max) (in ml. min(-1). kg(-1)) was 64.4 +/- 0.4 and 57.6 +/- 1.5 (P < 0.05), whereas VO(2 max) in hypoxia was 42.7 +/- 0.8 and 35.3 +/- 1.5 (P < 0.05) in HCR and LCR, respectively. Lack of significant differences between HCR and LCR in alveolar ventilation, alveolar-to-arterial PO(2) difference, or lung O(2) diffusing capacity indicated that neither ventilation nor efficacy of gas exchange contributed to the difference in VO(2 max) between groups. Maximal rate of blood O(2) convection (cardiac output times arterial blood O(2) content) was also similar in both groups. The major difference observed was in capillary-to-tissue O(2) transfer: both the O(2) extraction ratio (0.81 +/- 0.002 in HCR, 0.74 +/- 0.009 in LCR, P < 0.001) and the tissue diffusion capacity (1.18 +/- 0.09 in HCR and 0.92 +/- 0.05 ml. min(-1). kg(-1). Torr(-1) in LCR, P < 0.01) were significantly higher in HCR. The data indicate that selective breeding for exercise endurance resulted in higher VO(2 max) mostly associated with a higher transfer of O(2) at the tissue level.     

Increasing maximal heart rate increases maximal O2 uptake in rats acclimatized to simulated altitude

Gonzalez, Norberto C., Richard L. Clancy, Yoshihiro Moue,and Jean-Paul Richalet. Increasing maximal heart rate increases maximal O₂ uptake in ratsacclimatized to simulated altitude. J. Appl.Physiol. 84(1): 164-168, 1998.Maximal exerciseheart rate (HR_max) is reducedafter acclimatization to hypobaric hypoxia. The lowHR_max contributes to reducemaximal cardiac output(_max) andmay limit maximal O₂ uptake(O_{2 max}). Theobjective of these experiments was to test the hypothesisthat the reduction in_max afteracclimatization to hypoxia, due, in part, to the lowHR_max, limitsO_{2 max}. Ifthis hypothesis is correct, an increase in _max wouldresult in a proportionate increase inO_{2 max}. Rats acclimatized to hypobaric hypoxia [inspiredPO₂(PI_O2) = 69.8 ± 3 Torr for 3 wk] exercised on a treadmill in hypoxic (PI_O2 = 71.7 ± 1.1 Torr) or normoxic conditions(PI_O2 = 142.1 ± 1.1 Torr). Each rat ran twice: in one bout the rat was allowed to reach itsspontaneous HR_max, which was 505 ± 7 and 501 ± 5 beats/min in hypoxic and normoxic exercise,respectively; in the other exercise bout,HR_max was increased by 20% to the preacclimatization value of 600 beats/min by atrial pacing. This resulted in an ~10% increase in_max, since theincrease in HR_max was offset by a10% decrease in stroke volume, probably due to shortening of diastolicfilling time. The increase in_max was accompanied by a proportionate increase in maximal rate of convective O₂ delivery(_max × arterial O₂ content), maximal workrate, and O_{2 max} inhypoxic and normoxic exercise. The data show that increasingHR_max topreacclimatization levels increasesO_{2 max}, supportingthe hypothesis that the lowHR_max tends to limitO_{2 max} after acclimatization to hypoxia.