Histology of lamb epididymal development

To describe the distribution of the histological regions and their morphometry during epididymal development, 10 Corriedale lambs were castrated monthly from 90 to 180 days of age (n = 24), and their testes and epididymides were weighed. All animals were weighed monthly. Epididymides were divided into caput, corpus and cauda, and cut sagitally so that sections included all the length of the organ. The diameter of the epididymal duct, the smooth muscle depth and the epididymal epithelium height were measured. The quantitative histology of the ovine epididymal development was described. Epididymal development advanced from caput to cauda. The distribution of the histological regions varied according to epididymal weight. Transient histological regions were found during epididymal development. The present results indicate a new way of epididymal development in sheep, which courses from caput to cauda with transient histological regions appearing, varying in location and disappearing during ovine epididymis development.     

Spatiotemporal normalized ratio methodology to evaluate the impact of field-scale variable rate application

Precision Agriculture - Wide assimilation of precision agriculture among farmers is currently dependent on the ability to demonstrate its efficiency at the field-scale. Yet, most experiments that...     

Assessment of the removal efficiency of fish farm effluents by grey mullets: a nutritional approach

A field study was carried out to assess the use of the bottom‐feeding grey mullet (Mugil cephalus) within benthic enclosures as a means to reduce the benthic impacts of a net cage fish farm in the Gulf of Aqaba, Red Sea. Five experimental 1‐m³ net‐cage enclosures were stocked with 12 grey mullets each (fish weights 50, 70 or 144 g). The enclosures had no bottom and the mullets had access to the enclosed organically enriched sediments and to particulate matter (PM) falling from the overlying cages. Sediment traps were used to quantify and qualify the PM falling from the fish farm to the sea floor. Simultaneously, a feeding trial was performed with mullets (50 and 70 g) in experimental tanks. In order to estimate the potential growth rate and to quantify energy and protein requirements, the fish were fed a formulated diet with known composition. After approximately 70 days at sea, mullets in the enclosures had used up all the available food in the sediment and gained up to 0.78 g day^?1 fish^?1. Applying the values for energy and protein requirements for maintenance and growth derived from the experimental trial, estimates indicated that the grey mullets effectively removed 4.2 g organic carbon, 0.70 g nitrogen and 7.5 mg phosphorus kg^?1 mullet m^?2 day^?1 from the organically enriched sediment. Thus deployment of grey mullets may be an efficient means to improve the quality of sediments below intensive net‐cage fish farms.     

Urban ragweed populations in vacant lots: An ecological perspective on management

Ragweed (Ambrosia artemisiifolia L.) is one of the most prolific producers of allergenic pollen in North America, and negatively impacts tens of millions of people each year. Recent work shows that local plant populations can be the most important source of allergenic pollen in the urban environment. This research emphasizes that management choices that influence species abundance can determine the burden of allergenic pollen for people living near these plant populations. In Detroit, MI, USA, ragweed populations are predominantly found in vacant lots; the management of these lots could therefore have large impacts on allergenic pollen burdens. The main form of management in these vacant lots is mowing, which occurs at frequencies ranging from monthly mowing to no mowing. We hypothesized that annual or biennial mowing would result in conditions where ragweed populations could thrive. To test this, we conducted a vegetation survey of vacant lots in Detroit, in which we quantified the mowing regime, characteristics of the vegetation, and ragweed presence and stem density. We found that ragweed was significantly more likely to be present in lots that were mowed annually or biennially; unfortunately these are the most common management types, accounting for 51% of vacant lots in Detroit. Ragweed's association with this disturbance regime fits with its early successional status, as it is most competitive in recently disturbed soils where there is reduced competition for resources such as light. We therefore recommend one of two alternative management regimes for reducing ragweed in vacant lots: either mow them frequently (multiple times a growing season) or do not mow them at all. Both approaches will reduce ragweed prevalence in vacant lots and reduce allergenic pollen exposure for people who live near vacant lots.     

Neurotransmitter plasticity at the molecular level

Contrary to long-held assumptions, recent work indicates that neurons may profoundly change transmitter status during development and maturity. For example, sympathetic neurons, classically regarded as exclusively noradrenergic or cholinergic, can also express putative peptide transmitters such as substance P. This neuronal plasticity is directly related to membrane depolarization and sodium ion influx. The same molecular mechanisms and plastic responses occur in mature as well as developing neurons. Further, contrary to traditional teaching, adult primary sensory neurons may express the catecholaminergic phenotype in vivo. Transmitter plasticity is not restricted to the peripheral nervous system: ongoing studies of the brain nucleus locus ceruleus in culture indicate that specific extracellular factors elicit marked transmitter changes. Consequently, neurotransmitter expression and metabolism are dynamic, changing processes, regulated by a variety of defined factors. Transmitter plasticity adds a newly recognized dimension of flexibility to nervous system function.     

Legionnaires' disease: structural characteristics of the organism

The Legionnaires' disease organism was isolated from lung tissue taken from two fatalities of the Legionnaires' disease epidemic that occurred in Philadelphia during 1976. In yolk sac tissue the agent grew as a small coccobacillary microorgansim, which was Gram variable and Giménez positive. Intracellular coccoid and bacillary forms, detected by electron microscopy, within and without vacuoles, underwent multiplication by septate binary fission. Some of the intracellular forms resembled obligate intracellular pathogens. On defined bacteriologic media, the organisms were predominantly bacillary. The organism conforms to the morphologic criteria of a prokaryocyte.     

Sodium- and potassium-activated adenosine triphosphatase of gills: role in adaptation of teleosts to salt water

The activity of adenosine triphosphatase activated by sodium and potassium ions is greatly increased in the gill and pseudobranch of the euryhaline killifish, Fundulus heteroclitus, after its adaptation to seawater. Adenosine triphosphatase activity in gills of fish in salt water is reduced by hypophysectomy. The data suggest that this enzyme is involved in the excretion of sodiumions by the gill and that the adaptive increase which occurs in seawater is influenced by the hypophysis.