Identification and concentration of airborne basidiospores

Although clinical investigations have shown that basidiospores are allergenic, very little information exists on the airborne concentration or identification of these spores. The atmosphere in Tulsa, Oklahoma has been monitored for the presence of basidiospores using Burkard Volumetric Spore Traps. The concentration of total basidiospores shows that they are a significant component of the Tulsa atmosphere during certain periods. Overall spores of 18 genera have been identified from the atmosphere; the morphology of these spores is described. Field studies have shown that fruiting bodies of all these genera are common within the city. In addition other basidiospores present in the atmosphere include those identifiable only to the family level as well as many morphologically indistinct hyaline basidiospores.     

Prevalence of airborne basidiospores in three coastal cities of Saudi Arabia

Seasonal and diurnal variations of airborne basidiomycetous spores concentrations (basidiospores, smuts and rust spores) were studied using Burkard Volumetric Spore Traps in three major coastal cities viz., Dammam, Jeddah and Jizan in Saudi Arabia. The distance between the sites was approximately 1600 km from East to West. In addition to numerous airborne deuteromycetous spores identified at all sites, a considerable concentration of basidiomycetous spores were also recorded. The data revealed that basidiospores constituted a maximum of 17% of the total air spora in Jizan, while the maximum for Dammam and Jeddah was 11% each. Spores from smuts constituted the highest percentages of all basidiosmycetous spores ranging between 9–33% and 12–33% respectively in Dammam and Jizan. In Jeddah, it constituted between 14–26%. In contrast, rusts were less frequent at all sites. Maximum concentration of basidiospores showed that at certain months the level reached between 1000–6000 m⁻³. The data did not exhibit any seasonal pattern in their maximum appearance. Maximum concentration of smuts were much higher compared to basidiospores and the level fluctuated between 500–4000 m⁻³. Rusts were low in concentration (<150 m⁻³). The diurnal pattern of basidiospores concentration for at least one site (Jizan) averaged over the year showed a nocturnal trend consistent with basidiospores active discharge. The other two sites had no such trend. Diel periodicities of smuts and rusts spores did not exhibit any clear pattern. The study suggests that even in coastal regions having the same climatic conditions with a slightly different geography, show variation in basidiospores concentrations.     

Freeze-etch and thin section studies ofNeurospora crassa ascospores

Summary Mature, dormant ascospores derived from crosses of wild type stocks of the fungusNeurospora crassa were studied using both thin section and freeze-etch techniques for electron microscopy. The spore wall is composed of three major layers with, perhaps, a fourth distinct layer covering these layers. The spore contains several nuclei, many discrete mitochondria, lipid bodies, vacuoles and small pieces of endoplasmic reticulum. Freeze-etch fracture faces of several membranes are described in this paper. Included is a diagram illustrating various fracture faces and surfaces seen following freeze-etching. The thin section results are less than satisfactory but serve to generally confirm the freeze-etch observations and suggest that further work could lead to the development of techniques which will result in high quality thin sections of ascospores.     

The need for sublethal studies.

In problems of waste management, the preoccupation of the would-be manager is the means whereby waste may be released to the environment without impairing the health of the biota inhabiting the receiving waters. In such a situation, measurements based upon acute poisoning are unhelpful since they tell nothing of the impact that the much lower concentrations found at some distance from the waste source have upon the ability of the affected organisms to undertake the responses necessary to ensure survival and more particularly to reproduce successfully. Such responses can only be investigated with organisms not at the point of death, i.e. in truly sublethal studies.     

Ultrastructure and evolution of ballistosporic basidiospores

Basidiospores oiCoprinus cinereus were examined before and during spore discharge using light microscopy, and SEM of frozen-hydrated and other preparations. The process of droplet development at the hilar appendix was divided into three stages: pre-droplet, early and late enlargement. The fully expanded droplet was preserved only in frozen-hydrated specimens. Two-step droplet enlargement was also observed with TEM in Boletus rubinellus, and the droplet at the early enlargement stage was enclosed by a trilaminate membrane. The droplet was not observed in Auricularia species, but basidiospore preservation for SEM was optimum in Auricularia auricula with frozen-hydrated preparations. The hilar appendix of Auricularia fuscosuccinea as studied by TEM was simple compared with those of the Homobasidiomycetes. The implications of the data for evolution of the ballistosporic basidiospore and the discharge mechanism are considered.     

Antitussive agents as N-methylaspartate antagonists: further studies

The relative potencies of ketamine and the morphinan derivatives dextrorphan, dextromethorphan, and levorphanol as antagonists of the excitatory actions of N-methylaspartate on rat spinal neurones in vivo were examined, both following their microelectrophoretic administration and, with the exception of levorphanol, after intravenous injection. Applied microelectrophoretically, dextrorphan was a more potent N-methylaspartate antagonist than ketamine, levorphanol, or dextromethorphan. After systemic administration, however, dextrorphan was rather less potent than ketamine in this respect, whereas dextromethorphan remained less potent than either ketamine or dextrorphan. Noscapine, an antitussive that lacks anticonvulsant activity, failed to reduce selectively responses to N-methylaspartate as did papaverine, an isoquinoline structurally related to noscapine, and triprolidine, an antihistamine commonly found in proprietary cough medicines. The results are discussed with particular reference to the potential of the compounds tested as anticonvulsant and neuroprotective agents in vivo.     

Sex determination in hymenoptera: A need for genetic and molecular studies

Sex-determining mechanisms appear to be very diverse in invertebrates. Haplodiploidy is a widespread mode of reproduction in insects: males are haploid and females are diploid. Several models have been proposed for the genetic mechanisms of sex determination in haplodiploid Hymenoptera. Although a one-locus multi-allele model is valid for several species, sex determination in other species cannot be explained by any of the existing models. Evidence for and predictions of two recently proposed models are discussed. Some genetic and molecular approaches are proposed to study sex determination in Hymenoptera.     

Simulation modelling in landscape genetics: on the need to go further

With the emergence of landscape genetics, the basic assumptions and predictions of classical population genetic theories are being re‐evaluated to account for more complex spatial and temporal dynamics. Within the last decade, there has been an exponential increase in such landscape genetic studies ( Holderegger & Wagner 2006 ; Storfer et al. 2010 ), and both methodology and underlying concepts of the field are under rapid and constant development. A number of major innovations and a high level of originality are required to fully merge existing population genetic theory with landscape ecology and to develop novel statistical approaches for measuring and predicting genetic patterns. The importance of simulation studies for this specific research has been emphasized in a number of recent articles (e.g., Balkenhol et al. 2009a ; Epperson et al. 2010 ). Indeed, many of the major questions in landscape genetics require the development and application of sophisticated simulation tools to explore gene flow, genetic drift, mutation and natural selection in landscapes with a wide range of spatial and temporal complexities. In this issue, Jaquiéry et al. (2011) provide an excellent example of such a simulation study for landscape genetics. Using a metapopulation simulation design and a novel ‘scale of phenomena’ approach, Jaquiéry et al. (2011) demonstrate the utility and limitations of genetic distances for inferring landscape effects on effective dispersal.     

Forecasting the airborne spread of Mycosphaerella fijiensis, a cause of black Sigatoka disease on banana: estimations of numbers of perithecia and ascospores

Banana leaves showing different levels of black Sigatoka disease were collected from an unsprayed plantation in Costa Rica during two separate periods representing the wet to dry season transition (October 1993 – February 1994) and the dry to wet season transition (April – September 1995). Laboratory studies were used to investigate the relationship between the release of Mycosphaerella fijiensis ascospores and the amount of inoculum on banana plants showing different levels of infection, as assessed by leaf necrotic area. The number of perithecia present in the necrotic area was used as an indication of potential ascospore loads and was investigated as a series of regression equations. A series of rewetting and incubation regimes was used to investigate spore release under field conditions (21°C and 100% relative humidity in the early morning and 28°C, 60% relative humidity on days when it rained in mid-afternoon). Results suggest that rainfall, combined with a high temperature, may lead to peaks of ascospore release but without necessarily increasing overall numbers released over periods of up to 4 days and that a high level of spore release was less sensitive to changes in temperature once it had been initiated. The exact role of temperature in spore release is still unclear, however, as leaf samples kept at atypically low temperatures also released non-germinating ascospores. An average of 4.5 ascospores was released per perithecium. This does not resolve ambiguities in the literature regarding the number of ascospores present in each perithecium. A linear model relating the average ascospore numbers and necrotic area, using quick estimates of the amounts of necrotic area on the leaves of a random sample of plants across a plantation, is proposed, to give an indication of the relative amount of airborne inoculum potentially available between different plantations.     

Flow dichroism of DNA: a new apparatus and further studies

A new apparatus for the study of flow dichroism of macromolecules is described. The flow is down a long, narrow channel and an unpolarized light beam propagates along the flow direction. For a molecule such as DNA, in which the transition moments of the chromophores are perpendicular to the axis of orientation, an increase of absorbance is observed during flow. The apparatus is best suited for macromolecules which are readily orientable or at high shear gradients so that the extinction angle is close to 0°. The apparatus has the following advantages: dilute macromolecule solutions can be used; high shear gradients are easily obtained; only small volumes of solution are needed. The flow can be stopped rapidly so that relaxation times for disorientation can be studied. The flow dichorism of native, two-stranded DNA has been measured for the molecular weight range of 0.6 × 10⁶ to 125 × 10⁶, and for the shear gradient range (in aqueous solution at 25°C) from 200 sec^?1 to 21000 sec^?1. At a fixed gradient the dichroism increases with molecular weight, but the curve is concave downwards. At a given molecular weight the dichroism increases with increasing shear gradient, but the curve is concave downwards. When the solvent viscosity and temperature are varied, the dichroism is a function of η〈G〉/T showing that the orientation is due to hydro-dynamic shear stress and that the flexibility of DNA in a flow field is not due to local denaturation. The Zimm-Rouse theory with no parameters taken from flow optical data predicts the correct order of magnitude of the dichroism but the experimentally observed shear gradient and molecular weight dependence do not fit the theory. This is an expected result, since the theory is believed to be applicable only at small distortions and extensions of the macromolecule.     

Image analysis of Agaricus basidiospores for use in systematics

Basidiospore characters were measured using computer-based image analysis with greater speed (10 x) and objectivity than possible manually. This technology allowed measurement of additional variables for studies of spores, including area and circularity, as well as length, breadth and elongation. Principal component analysis of basidiospore characters aided definition of species and species groups.     

Cell population kinetics in pig epidermis: further studies

The cell population kinetics of the epidermis were studied in 4-month-old pigs. Mitotic figures were confined to the basal cell (L1) and the first suprabasal cell layer (L2). The mitotic index (MI) was 0.17 +/- 0.04% for L1 and 0.08 +/- 0.03% for L2. Labelled nuclei were distributed throughout the viable epidermis, the majority (79.1 +/- 1.1%) were in L1 with 19.5 +/- 1.2% in L2. The labelling indices (LI) in layers L1 and L2 were 7.1 +/- 0.4% and 3.4 +/- 0.1%, respectively. After labelling with two injections of tritiated thymidine [3H]TdR separated by 90 min, the LI increased to 8.2 +/- 0.3% in L1 and to 4.0 +/- 0.2% in L2. This increased labelling confirmed that cell proliferation occurs in both layers, L1 and L2, of the epidermis. The cell production rate (K) in L1 and L2 had an upper limit of 10.7 +/- 1.0 and 6.2 +/- 1.8 cells per 1000 cells per hour respectively. The cell flow rate per hour (cell flux), into and out of the DNA synthesis phase (S), and the duration of DNA synthesis were determined from double-labelling studies with [3H]TdR and [14C]TdR. The cell flux into and out of S was identical and was calculated as 0.6 +/- 0.1%/hr (L1) and 0.5 +/- 0.1%/hr (L2). Values for tS varied from 8 to 10 hr. The cell turnover times (tT) were in the range 89-129 hr and 180-261 hr for L1 and L2, respectively. Log normal curves were fitted to the fraction labelled mitoses data for L1 and L2. Values for tS for cells in L1 and L2 were 9.8 hr and 11.9 hr, respectively. tG2 + 1/2tM was 7.2 hr in L1 and 9.1 hr in L2.