Coffee agroforestry systems in Central America: II. Development of a simple process-based model and preliminary results

Research on coffee agroforestry systems in Central America has identified various environmental factors, management strategies and plant characteristics that affect growth, yield and the impact of the systems on the environment. Much of this literature is not quantitative, and it remains difficult to optimise growing area selection, shade tree use and management. To assist in this optimisation we developed a simple dynamic model of coffee agroforestry systems. The model includes the physiology of vegetative and reproductive growth of coffee plants, and its response to different growing conditions. This is integrated into a plot-scale model of coffee and shade tree growth which includes competition for light, water and nutrients and allows for management treatments such as spacing, thinning, pruning and fertilising. Because of the limited availability of quantitative information, model parameterisation remains fraught with uncertainty, but model behaviour seems consistent with observations. We show examples of how the model can be used to examine trade-offs between increasing coffee and tree productivity, and between maximising productivity and limiting the impact of the system on the environment.     

Evidence for a potential role of neuropeptide Y in ovine corpus luteum function

Neuropeptide Y (NPY) is a neurohormone that is typically associated with food intake, but it has also been reported to affect the production of progesterone from luteal tissue in vitro. However, NPY has not been previously immunolocalized in the ovine ovary or in the corpus luteum (CL) of any species, and the effects of this neurohormone on luteal function in vivo are not known. Thus, we performed fluorescent immunohistochemistry (IHC) to localize NPY in the ovine ovary and used avidin-biotin immunocytochemistry (ICC) to further define the intracellular localization within follicles and the CL. We then infused NPY directly into the arterial supply of the autotransplanted ovaries of sheep to determine the in vivo effect of exogenous NPY on ovarian blood flow and on the luteal secretion rate of progesterone and oxytocin. Immunohistochemistry revealed that the NPY antigen was localized to cells within the follicles and CL, in the nerve fibers of the ovarian stroma, and in the vessels of the ovarian hilus. In the follicle, the NPY antigen was localized to nerves and vessels within the theca interna layer, and strong staining was observed in the granulosal cells of antral follicles. In the CL, NPY was localized in large luteal cells and in the vascular pericytes and/or endothelial cells of blood vessels, found dispersed throughout the gland and within the luteal capsule. In vivo incremental infusions of NPY at 1, 10, 100, and 1,000 ng/min, each for a 30-min period, into the arterial supply of the transplanted ovary of sheep bearing a CL 11 d of age increased (P ≤ 0.05) ovarian blood flow. The intra-arterial infusions of NPY also increased (P ≤ 0.05) in a dose-dependent manner the secretion rate of oxytocin, which was positively correlated (P ≤ 0.05) with the observed increase in ovarian blood flow. The infusions of NPY had a minimal effect on the secretion rate of progesterone, and similar intra-arterial infusions of NPY into sheep with ovarian transplants bearing a CL over 30 d of age had no significant effect on ovarian blood flow or on the secretion rate of progesterone. These results suggest that NPY acts on the luteal vascular system and the large luteal cells to rapidly stimulate blood flow and the secretion of oxytocin, respectively, which collectively implies a putative role for NPY during the process of luteolysis when increasing amounts of oxytocin are secreted from the ovine CL in response to uterine pulses of prostaglandin F2α.     

Exploring below ground complementarity in agroforestry using sap flow and root fractal techniques

Indices of shallow rootedness and fractal methods of root system study were combined with sapflow monitoring to determine whether these ‘short-cut’ methods could be used to predict tree competition with crops and complementarity of below ground resource use in an agroforestry trial in semi-arid Kenya. These methods were applied to Grevillea robusta Cunn., Gliricidia sepium (Jacq.) Walp., Melia volkensii Gürke and Senna spectabilis syn. Cassia spectabilis aged two and four years which were grown in simultaneous linear agroforestry plots with maize as the crop species. Indices of competition (shallow rootedness) differed substantially according to tree age and did not accurately predict tree:crop competition in plots containing trees aged four years. Predicted competition by trees on crops was improved by multiplying the sum of proximal diameters squared for shallow roots by diameter at breast height², thus taking tree size into account. Fractal methods for the quantification of total length of tree root systems worked well with the permanent structural root system of trees but seriously underestimated the length of fine roots (less than 2 mm diameter). Sap flow measurements of individual roots showed that as expected, deep tap roots provided most of the water used by the trees during the dry season. Following rainfall, substantial water uptake by shallow lateral roots occurred more or less immediately, suggesting that existing roots were functioning in the recently wetted soil and that there was no need for new fine roots to be produced to enable water uptake following rainfall. This revised version was published online in June 2006 with corrections to the Cover Date.     

Differential Diagnosis of Some Conditions of the Canine and Feline Thorax : (First Installment)

Routine clinical examination of the chest is described.

The basic principles of viewing X-ray plates are mentioned.

The conditions of the canine and feline thorax dealt with are mostly those which can be confirmed radiologically during life.

The major points of differential diagnosis of each condition are dealt with within groups determined by some cardinal clinical sign. For convenience each condition is dealt with only under one groupheading, although it may have additional signs of some of the other groups.

The groups and conditions are as follows:

Gross Dyspnoea

Hydrothorax

Pyothorax

Pneumothorax

Diaphragmatic hernia

Pneumonia

Cough

Distemper

Tuberculosis

Secondary lung tumour

Filaroides osleri infestation of the trachea

Kennel cough

Feline influenza

Tiring on exercise

Cardiac valvular disease

Congenital cardiac disease

Difficulty in swallowing

Oesophageal foreign body

Feline oesophageal annular carcinoma

Oesophageal diverticulum

Mega-oesophagus (Achalasia)

Oesophageal dilatation associated with

vascular anomalies of the right aortic arch.

     

Demonstration of a new intracellular antigen in porcine intestinal adenomatosis and hamster proliferative ileitis

In the proliferate enteropathies of the pig, intracellular Campylobacter-like organisms can be demonstrated in the apical cytoplasm of affected cells. A new antigen (omega) can be visualised at the site of bacterial parasitism using certain rabbit sera in a sandwich immunofluorescence test; the rabbit sera tested were largely derived from rabbits immunised with bacterial antigens including Campylobacter spp., but it appeared that the reaction was not related to the immunisation procedure and was also present in at least one "normal" rabbit serum. Rabbits immunised with bacteria extracted from the tissues sero-converted to omega-antigen yet did not react with Campylobacter spp., cultured from pig intestine. The omega-antigen was also present in the lesions of hamster proliferative ileitis.