Periodic droughts and long-term dynamics of alvar grassland vegetation on Öland,Sweden

Dynamics of vegetation was studied on Stora Alvaret in Öland, Sweden, in comparison with precipitation in the May–July part of the growing period. Three data sets representing three main life forms (shrub, dwarf-shrub, and herbs) were collected. species composition eight grassland permanent plots (1969–1993, ass.Veronica spicata-Avenula pratensis), survival and health status ofJuniperus communis (1975–1993), andCalluna vulgaris cover at two permanent plots for the same period. Mortality ofJuniperus andCalluna and proportion of annual species were synchronized and correlated with severe droughts. *** DIRECT SUPPORT *** A02DO006 00003     

Bronchopneumonia and oral health in hospitalized older patients. A pilot study

Aims: To correlate microbial findings obtained by bronchoalveolar lavage in pneumonia patients with the clinical situation of the oral cavity. Method: Quantitative aerobic and anaerobic cultures were carried out in 150 ml samples of bronchoalveolar lavage (BAL) obtained by means of an endoscope (Video Endoscope Pentax®) inserted per as in the infected bronchus. Material: Twenty consecutive patients with a tentative clinical diagnosis of bronchopneumonia in whom BAL was carried out for diagnostic purposes. A clinical evaluation of the oral health status (oral hygiene, caries, periodontal diseases) was subsequently carried out. Results: In seven edentulous subjects wearing complete dentures the culture of anaerobic microorganisms was negative or yielding less than 100 cfu/ml BAL. Two patients yielded high counts of S. aureus and one high counts of P. aeruginosa. In the 13 subjects with natural teeth left one showed high counts of Veillonella spp. (anaerobic)+P. aeruginosa, one high counts of Veillonella spp. +S. aureus, one high counts of P. aeruginosa + S. aureus and one high counts of E. coli. These four subjects showed poor oral hygiene, periodontal pockets and a BAL microflora consistent with periodontal pathology. Conclusion: The results of this pilot study suggest that microorganisms of denture plaque or associated with periodontal diseases may give rise to aspiration pneumonia in susceptible individuals.     

Estimation of the benchmark dose by structural equation models

While epidemiological data typically contain a multivariate response and often also multiple exposure parameters, current methods for safe dose calculations, including the widely used benchmark approach, rely on standard regression techniques. In practice, dose-response modeling and calculation of the exposure limit are often based on the seemingly most sensitive outcome. However, this procedure ignores other available data, is inefficient, and fails to account for multiple testing. Instead, risk assessment could be based on structural equation models, which can accommodate both a multivariate exposure and a multivariate response function. Furthermore, such models will allow for measurement error in the observed variables, which is a requirement for unbiased estimation of the benchmark dose. This methodology is illustrated with the data on neurobehavioral effects in children prenatally exposed to methylmercury, where results based on standard regression models cause an underestimation of the true risk.     

Restoration of alvar vegetation on Öland,Sweden

Abstract. Alvars in the Baltic region, particularly on the Swedish islands of Öland and Gotland and in western Estonia, are well‐known for their plant species richness and extensive populations of rare species. Grasslands make up most of alvar vegetation. The extent of these grasslands decreases because of bush enchroachment which takes place in most alvars when traditional land use practice changes, notably when grazing is ceased. The main threat for the alvar grassland is formed by the rapid expansion of Juniperus communis and Potentilla fruticosa in dry and wet sites, respectively. Applied research has been carried out during several years in order to develop plans for the restoration of alvar grassland. Thus it was shown that species richness in areas with a mixture of grassland and shrubland decreases in relation to the increased cover by shrubs. In the case of Juniperus there is a distinct drop in species number as soon as the cover exceeds 75‐80%, while the decrease is more gradual with increased cover of Potentilla. The seed banks under dense stands of these shrubs only contain ca. 20% of the species found in dry and wet alvar meadows. This was confirmed by clearing experiments. Long‐term recordings have shown that establishment of juniper seedlings takes place mainly in half‐open areas between already existing junipers. Intermediate‐sized junipers expanded faster than old and big shrubs. Potentilla shrubs recover fast from cutting or burning. After 2‐4 yr they have almost attained their former size. This recovery can be prevented when cattle grazing is introduced. In the framework of a local alvar restoration project on Öland, covering 7000 ha, grazing regimes are re‐established, fences erected and large‐scale clearings carried out. Recently established juniper shrubs are being cleared, intermediate sized junipers (30‐50 yr old) are selectively removed while creating a mosaic landscape with high biological diversity. Older dense juniper stands are left alone or are only partly cleared. Potentilla stands in moist areas are cut to create moist meadows which are breeding grounds for waders, and to establish corridors between remaining open areas. Three items are discussed (1) the importance of the Stora Alvar area; (2) re‐introduction of grazing and (3) re‐introduction of species. The outstanding importance of the area regarding species richness and endemism should be recognized through a ‘golden list’ to be used along with red and blue lists.     

Proteome analysis of spermatogonia: identification of a first set of 53 proteins

During spermatogenesis, the various classes of germ cells synthesize proteins necessary for their own functioning and for regulation of the Sertoli cells. However, the nature of these proteins has been little studied, especially in spermatogonia, the germ stem cells. In this study, the electrophoretic patterns of high-resolution, silver-stained, two-dimensional polyacrylamide gels of intracellular spermatogonial protein extracts were studied by computerized gel image analysis. We detected 675 individual spots, some of which we identified by mass spectrometry and database searching. We present here a first set of 53 proteins identified. They include housekeeping proteins never before detected in spermatogonia, ten proteins previously detected in the reproductive tract but not in spermatogonia, including stathmin, a protein previously shown to be involved in cell proliferation and differentiation, and one new testicular protein named translationally controlled tumor protein (TCTP), also known as a growth-related protein. Immunohistochemistry demonstrated that the two latter proteins were indeed highly expressed in spermatogonia in situ, and their possible involvement in spermatogonial division and proliferation is currently under investigation in our laboratory. We conclude that this type of experimental strategy, known as proteomics, is a very powerful way to analyze germ cell proteins comprehensively and should rapidly greatly improve our understanding of spermatogenesis.     

Dark diversity in dry calcareous grasslands is determined by dispersal ability and stress‐tolerance

Temperate calcareous grasslands are characterized by high levels of species richness at small spatial scales. Nevertheless, many species from a habitat‐specific regional species pool may be absent from local communities and represent the ‘dark diversity’ of these sites. Here we investigate dry calcareous grasslands in northern Europe to determine what proportion of the habitat‐specific species pool is realized at small scales (i.e. how the community completeness varies) and which mechanisms may be contributing to the relative sizes of the observed and dark diversity. We test whether the absence of particular species in potentially suitable grassland sites is a consequence of dispersal limitation and/or a low ability to tolerate stress (e.g. drought and grazing). We analysed a total of 1223 vegetation plots (1 × 1 m) from dry calcareous grasslands in Sweden, Estonia and western Russia. The species co‐occurrence approach was used to estimate the dark diversity for each plot. We calculated the maximum dispersal distance for each of the 291 species in our dataset by using simple plant traits (dispersal syndrome, growth form and seed characteristics). Large seed size was used as proxy for small seed number; tall plant height and low S‐strategy type scores were used to characterise low stress‐tolerance. Levels of small‐scale community completeness were relatively low (more species were absent than present) and varied between the grasslands in different geographic areas. Species in the dark diversity were generally characterized by shorter dispersal distances and greater seed weight (fewer seeds) than species in the observed diversity. Species within the dark diversity were generally taller and had a lower tolerance of stressful conditions. We conclude that, even if temperate grasslands have high levels of small‐scale plant diversity, the majority of potentially suitable species in the regional species pool may be absent as a result of dispersal limitation and low stress‐tolerance.     

A method for preparing and staining histological sections containing titanium implants for light microscopy

An improved method for preparing and staining ground tissue-implant sections for light microscopy is presented. Undecalcified tissue blocks with titanium implants were dehydrated in an ascending series of ethanol and stained in toto with basic fuchsin. Specimens were infiltrated and embedded in methyl methacrylate and sections were prepared using a cutting-grinding-system. The polished surface was counterstained with light green or anilin blue. Light polymerizing resin was used as slide mounting medium and for mounting the coverglass. The sections obtained were 10-15 microns thick with tissue architecture which clearly differentiated structures at the tissue-implant interface. The method was very useful for computer assisted morphometric analysis.