Cytopress: automated slide preparation of cytologic material from suspension

This paper describes a new automated system to prepare slides of cytological material from suspension. The system collects material on a filter tape by filtration and transfers it to glass slides by means of pressure-fixation. Using cervical cells as a model, results show that a well-defined cell number is evenly deposited over a standardized area, while a small number of cells is retained on the tape and a negligible number lost in the filtrate. Contamination is very small. Application of the system to other cytological material (fine needle aspirations, monolayer and cell suspension cultures, agar cultures, and isolated nuclei) is shown. In general, more than one slide can be made from one sample. Several histological staining procedures as well as immunofluorescence labeling protocols can be applied to the preparations obtained in this way. This system thus introduces a method that will standardize specimen preparation, is quick, saves operator time, and can be used for both diagnostic and research applications.     

Serum zinc in highly trained adolescent gymnasts

Serum zinc was measured in 20 adolescent gymnasts (9 boys, 11 girls, age 12–15 yr) explored for detecting possible adverse effects of intense training on pubertal maturation and growth. They had low serum zinc (0.599±0.026 mg/L) when compared to matched control sedentary children (n=118 mean 0.81±0.014p<0.001). Girls had lower zinc than boys (0.557±0.023 vs 0.651±0.044p<0.001). Zinc was correlated to isometric adductor strength (r=0.468p<0.05). Children with serum zinc <0.6 mg/L had lower insulin-like growth factor binding protein 3 than others (2.326±0.264 vs 2.699±0.12p<0.01). Thus, zinc is lowered in trained adolescent gymnasts and even lower in females. This reduction could play some role in abnormalities of puberty, growth, or muscular performance.     

Nitrogen supply rate in Scots pine (Pinus sylvestris L.) forests of contrasting slope aspect

We studied Nitrogen (N) transformations in Pinus sylvestris forest stands in the foothills of the SE Pre-Pyrenees (NE Spain). Plots were selected in two contrasting aspects (two plots per aspect) and N supply rate was measured by the resin-core incubation technique once every three months. N leaching through litter layers (L and F horizons) was evaluated by 5 zero-tension lysimeters in each plot. NH₄ ⁺-N, NO₃ ^--N and soluble organic-N were determined in all solutions. N supply rate showed a clear seasonal pattern. Ammonification and nitrification were segregated in space and in time. While ammonification showed a peak in spring, nitrification was higher in summer. There was evidence suggesting that nitrification occurs mostly in A1 horizon. Nitrification rates differed significantly among plots. N supply rate was 12.7–23.5 kg N·ha^-1·yr^-1 but it did not differ between aspects or plots. Inorganic-N leached through litter layers was 14–17 kg N·ha^-1·yr^-1, and represented a high proportion of N supply rate. Organic-N leached through litter layers (27.8–37.0 kg N·ha^-1·yr^-1) was higher than leached inorganic-N. However, in most cases organic-N did not represent a high proportion of changes in soluble organic-N pools in H and A1 horizons (about 240 kg N·ha^-1·yr^-1). This large decrease in soluble organic-N was much greater than the increase in inorganic-N. The possible fate of these large amounts of organic-N is discussed.     

Decreases in the relative concentrations of specific hepatocyte plasma membrane proteins during liver regeneration: down-regulation or dilution?

Antibodies were used to quantify seven domain-specific integral proteins of the rat hepatocyte plasma membrane during rat liver regeneration in response to two-thirds hepatectomy. Quantitative immunoblotting revealed that a subset of the plasma membrane proteins exhibited transient 30-70% decreases in relative concentration during the period of hepatocyte proliferation. The list of affected proteins included at least one representative from each of the plasma membrane domains: the apical protein HA 4, the lateral protein HA 321, and the basolateral receptors for epidermal growth factor and asialoglycoproteins. In contrast, the relative concentrations of three other plasma membrane proteins, the basolateral protein CE 9 and the two apical proteins dipeptidylpeptidase IV and aminopeptidase N, remained unchanged throughout liver regeneration. The decreases in the relative concentrations of the plasma membrane proteins were observed even when the synthesis of hepatocyte DNA was blocked by hydroxyurea, suggesting that the signalling for these two delayed consequences of two-thirds hepatectomy occurred along parallel, dependent pathways. Pulse and pulse-chase metabolic radiolabeling studies revealed that the decreases in the concentrations of the PM proteins were accomplished through protein-selective decreases in the rates of synthesis of the high-mannose precursors of the affected proteins, but not through the accelerated degradation of the mature plasma membrane proteins.     

Intermediate clutches in the Starling (Sturnus vulgaris): replacement clutches, additional clutches of polygynous males or late first clutches?

Summary Literature on the breeding biology of the StarlingSturnus vulgaris refers to a sequence of egg-layings usually termed as first, intermediate and second broods. Egg-laying of first broods is highly synchronous. Accurate data concerning the identity of pairs producing the intermediate clutches, i.e. clutches that are laid in the period between the first and second brood layings, are lacking. These clutches are considered to be mainly replacement clutches of early clutches that failed. In this paper, we analyse the degree of synchronization of first layings during 5 breeding seasons and determine the identity of pairs producing intermediate clutches. The synchronized laying period of the first brood varied from 3 to 9 days. The percentage of intermediate clutches ranged from 14 % to 66 %. Only few intermediate clutches were replacement clutches of early clutches that failed. Most (95 %) were additional clutches of early breeding polygynous males or clutches of males that arrived only during the incubation or nestling period of the early breeding pairs (i.e. pairs being involved in a brood, initiated during the synchronized first brood period). The late arriving males and females may have been birds that migrated further than these being involved in a first brood, and consequently returned later in the season. The arrival of new males and females after the synchronized laying period of the first brood therefore may be a typical phenomenon for Continental Europe where starlings are mainly migratory.

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Zwischenbruten beim Star: Ersatzbruten, zusätzliche Bruten von polygynen Männchen oder späte Erstbruten?

Zusammenfassung In der Literatur zur Brutbiologie des Stars,Sturnus vulgaris, werden oft Erst-, Zwischen- und Zweitbruten unterschieden. Innerhalb einer Kolonie erfolgt die Eiablage bei der Erstbrut sehr synchron. Die Identität der Paare, die Zwischenbruten zeitigen, ist unbekannt. Oft wurde vermutet, Zwischenbruten ersetzten vorwiegend verlorene Erstbruten. Wir analysieren das Ausmaß der Synchronisation bei Erstgelegen aus 5 Brutperioden und bestimmen, welche Paare Zwischenbruten produzieren. Der Zeitraum der synchronen Eiablage zur Erstbrut dauerte 3–9 Tage. 14% bis 66% aller Bruten waren Zwischenbruten. Nur wenige Zwischenbruten ersetzten verlorene Erstbruten. Die meisten (95 %) waren zusätzliche Bruten von frühbrütenden polygynen Männchen oder Bruten von spät ankommenden Männchen. Solche Männchen trafen erst zu einer Zeit in der Kolonie ein, zu der frühbrütende Paare schon ihre Gelege bebrüteten oder Junge fütterten. Die spät ankommenden Männchen und Weibchen könnten Vögel gewesen sein, die weiter gewandert waren und deshalb später zurückkehrten als Vögel, die zur ersten Brut kamen. Es mag für kontinentaleuropäische Stare, die überwiegend Zugvögel sind, typisch sein, daß einige Männchen und Weibchen erst nach der Periode der synchronen Eiablage der Erstbrut ankommen.

     

Effects of landscape structure on the invasive spread of black cherry Prunus serotina in an agricultural landscape in Flanders, Belgium

Analysing invasive spread from a landscape ecological perspective forms an important challenge in plant invasion ecology. The present study examines the effects of landscape structure on the spatial and temporal dynamics of an expanding black cherry Prunus serotina population within a rural landscape in Flanders, Belgium, carrying a dense network of interconnected hedgerows. The study area, 251 ha in size, harboured a total of 2962 P. serotina individuals. The population was characterised by a negative exponential age distribution, a high growth rate and an early and continuous reproduction throughout the species' life cycle. The historical rate of spread of the species through the hedgerow network progressively increased with time, especially during the last decade. Spatial point pattern analysis revealed that the individuals had a significantly clustered distribution pattern and were spatially aggregated around seed sources, hedgerow intersections and roosting trees. Logistic regression analysis confirmed the effect of landscape structure on P. serotina occurrence, suggesting directional long distance dispersal by avian dispersal vectors, resulting in a differential seed pressure throughout the hedgerow network due to the preference of dispersing birds for roosting in structurally rich hedgerow with large trees near hedgerow intersections. Hence, the distribution of P. serotina in agricultural landscapes was strongly mediated by dispersal processes. Furthermore, decreasing spatial aggregation along the species life cycle, with especially seedlings and saplings being significantly aggregated while adult individuals were mostly distributed at random, and a relative outward shift of seedling recruitment curves with time indicate density dependent mortality, probably caused by intraspecific competition.     

Impact of hemiparasitic Rhinanthus angustifolius and R. minor on nitrogen availability in grasslands

Root hemiparasites like Rhinanthus angustifolius C.C. Gmel and R. minor L. have a potential to accelerate the restoration of semi-natural grasslands because they may decrease above-ground biomass of the vegetation. This, in turn, may be beneficial for species diversity. It is known that hemiparasites often accumulate high nutrient concentrations in their above-ground parts, resulting in high quality litter. Because of the short life cycle of many parasitic plants, litter is released early in the season and the main part is not removed from the grassland by hay-making. This has been shown to yield an increased nutrient availability locally. We performed an introduction experiment with R. angustifolius and R. minor in three semi-natural grasslands in Flanders (Belgium). In the second year after sowing, the above-ground nitrogen (N) content of the grasses and of the potential host vegetation (excluding the hemiparasite), was increased in the parasitized plots. The reduction of grass (and legume) above-ground biomass in parasitized plots resulted in a decrease in the total above-ground N uptake of grasses, host and total vegetation (ex- and including the parasite, respectively) of the parasitized plots compared to the control. Furthermore, with a tracer experiment (¹⁵N), we demonstrated that the N from the added tracer was relatively less available in parasitized plots, suggesting larger soil N pools in these treatments. This is probably the consequence of increased mineralization, resulting from the high-quality, parasitic litter. Further experiments should be conducted to investigate the impact of hemiparasitic Rhinanthus spp., e.g. on the availability of other nutrients such as phosphorus.     

[Na] in the subsarcolemmal ‘fuzzy’ space and modulation of [Ca]i and contraction in cardiac myocytes

The strength of the heart beat depends on the amplitude and time course of the transient increase in [Ca²⁺] in the myocytes with each cycle. [Na⁺]_i modulates cardiac contraction through its effect on the Ca²⁺ flux through the Na/Ca exchanger. Cardiac excitation–contraction coupling has been postulated to occur in a microdomain or ‘fuzzy’ space at the junction of the T-tubules and the sarcoplasmic reticulum. This ‘fuzzy’ space is well described for the Ca²⁺ fluxes and the interaction between the L-type Ca²⁺ channel, the Ca²⁺ release channel of the sarcoplasmic reticulum and the Na/Ca exchanger. Co-localization of the Na⁺ transporters, in particular the Na/K pump and the Na⁺ channel, within this ‘fuzzy’ space is not as well established. The functional and morphological characteristics of the ‘fuzzy’ space for Na⁺ and its interaction with the Ca²⁺ handling suggest that this space is not strictly co-inciding with the Ca²⁺ microdomain. In this space [Na⁺] can be several-fold higher or lower than [Na⁺] in the bulk cytosol. This has implications for modulation of [Ca²⁺]_i during a single beat as well as during alterations in Na⁺ fluxes seen in pathological conditions.     

Mitochondrial phylogeny of African wood mice, genus Hylomyscus (Rodentia, Muridae): implications for their taxonomy and biogeography

This paper investigates the usefulness of two mitochondrial genes (16S rRNA and cytochrome b) to solve taxonomical difficulties within the genus Hylomyscus and to infer its evolutionary history. Both genes proved to be suitable molecular markers for diagnosis of Hylomyscus species. Nevertheless the resolving powers of these two genes differ, and with both markers (either analyzed singly or in combination), some nodes remain unresolved. This is probably related to the fact that the species emerged during a rapid diversification event that occurred 2-6 Myr ago (4-5 Myr ago for most divergence events). Our molecular data support the recognition of an "aeta" group, while the "alleni" and "parvus" groups are not fully supported. Based on tree topology and genetic divergence, two taxa generally recognized as subspecies should be elevated at the species level (H. simus and H. cf kaimosae). H. stella populations exhibit ancient haplotype segregation that may represent currently unrecognized allopatric species. The existence of cryptic species within H. parvus is questioned. Finally, three potentially new species may occur in West Central Africa. The Congo and Oubangui Rivers, as well as the Volta and Niger Rivers and/or the Dahomey gap could have formed effective barriers to Hylomyscus species dispersal, favoring their speciation in allopatry. The pronounced shifts in African climate during the late Pliocene and Miocene, which resulted in major changes in the distribution and composition of the vegetation, could have promoted speciation within the genus (refuge theory). Future reports should focus on the geographic distribution of Hylomyscus species in order to get a better understanding of the evolutionary history of the genus.