Biodegradable Gelatin Microcarriers Facilitate Re-Epithelialization of Human Cutaneous Wounds - An In Vitro Study in Human Skin

The possibility to use a suspended tridimensional matrix as scaffolding for re-epithelialization of in vitro cutaneous wounds was investigated with the aid of a human in vitro wound healing model based on viable full thickness skin. Macroporous gelatin microcarriers, CultiSpher-S, were applied to in vitro wounds and cultured for 21 days. Tissue sections showed incorporation of wound edge keratinocytes into the microcarriers and thicker neoepidermis in wounds treated with microcarriers. Thickness of the neoepidermis was measured digitally, using immunohistochemical staining of keratins as epithelial demarcation. Air-lifting of wounds enhanced stratification in control wounds as well as wounds with CultiSpher-S. Immunohistochemical staining revealed expression of keratin 5, keratin 10, and laminin 5 in the neoepidermal component. We conclude that the CultiSpher-S microcarriers can function as tissue guiding scaffold for re-epithelialization of cutaneous wounds.     

Effects of an invertebrate grazer on the spatial arrangement of a benthic microhabitat

We demonstrated the effect of an aquatic herbivore on the spatial arrangement of benthic algal biomass within artificial stream channels. Transects of ceramic tiles were exposed to a gradient of snail (Physella) densities in a 30 d experiment. We observed positive effects of snails on the mean abundance of overstory algae (the filamentous chlorophyte Cladophora and associated epiphytes), an important benthic microhabitat in streams. Snails altered several aspects of the spatial arrangement of overstory algae. Snails reduced the strength of downstream gradients in overstory biomass, as well as residual variability around these gradients. Geostatistical analysis revealed that snails also reduced the strength of spatial dependence, and so reduced spatial heterogeneity of the overstory, at small scales (<40 cm). As a result, organisms inhabiting the overstory might experience a more fragmented habitat landscape at high snail densities. In addition, snails increased the scale of spatial dependence in understory algal biomass (algae remaining on tiles after overstory was removed) from 10 cm to 40 cm. Consumer effects on the spatial arrangement of a microhabitat argue for the inclusion of feedbacks between the biota and the environment in spatially-explicit models.     

Convergent evolution of cysteine residues in sperm protamines of one genus of marsupials, the Planigales

A characteristic feature of the sperm P1 protamines of eutherian mammals is the constant presence of six to nine cysteine residues per molecule. During spermiogenesis these residues become oxidized to form a three-dimensional network of disulfide bridges between, and within, protamine molecules in the sperm chromatin. This covalent cross linking strongly stabilizes eutherian sperm nuclei. In contrast, protamines sequenced from teleost fish, birds, monotremes, and marsupials all lack cysteine residues and their sperm nuclei, without the stabilizing cross links, are easily decondensed in vitro. We have now found that one genus of tiny, shrewlike dasyurid marsupials, the Planigales, possess P1 protamines containing five to six cysteine residues. These residues appear to have evolved since the divergence of Planigales from other members of the family Dasyuridae, such as the marsupial mouse, Sminthopsis crassicaudata. We believe this constitutes a case of convergent evolution in a subfamily of dasyurid marsupials toward the cysteine-rich eutherian form of sperm protamine P1.      

Zooplankton Community Responses during Recovery from Acidification in Little Rock Lake, Wisconsin

Follow-up studies after whole-ecosystem-stress experiments can provide important insights into the recovery process itself and into basic ecosystem properties. We report here on zooplankton community recovery during the first 5 years following the experimental acidification of Little Rock Lake, Wisconsin, U.S.A. Acidity in the lake's treatment basin returned quickly to near pre-manipulation levels. Zooplankton population shifts, however, did not support our hypothesis that species that had increased in abundance with acidification would persist and resist the return of the pre-manipulation community. The three species that had proliferated most dramatically under low pH conditions— Daphnia catawba, Tropocyclops extensus, and Keratella taurocephala , returned close to their originally low, pre-acidification population levels during the early stages of acid recovery. Some species that had been reduced during low pH conditions, such as Diaptomus minutus and Daphnia dubia , did not recover to pre-manipulation levels. Overall, the zooplankton community in the treatment basin exhibits little similarity to that in the reference basin, a condition quite different from that which had occurred prior to the imposition of acid stress.     

Spatial and temporal patterns in the hydrogeochemistry of a poor fen in northern Wisconsin

We studied the factors causing spatial and temporal patterning of interstitial water chemistry in Crystal Bog, a 7 ha northern Wisconsin kettle-hole peatland. Over the course of the snow-free season Crystal Bog exhibited spatial and temporal patterns in chemistry, especially hydrogen-ion, dissolved organic carbon, and specific conductance. The peatland contains a 0.5 ha pond that has water more dilute than the interstitial water of the surrounding peatland. The direction of groundwater flow between the lake and the peatland was seasonally dependent. In the spring and early summer, flow was from the lake into the peatland, especially on the eastern side of the lake. This flow resulted in a plume of relatively dilute surface interstitial water in the peatland. In mid and late summer direction of groundwater flow was from the peatland into the lake and the dilute plume was reduced in areal extent. By fall the direction of water flow was again from the lake to the peatland.The spatial and temporal heterogeneity in water chemistry produced by the seasonal variation in the direction of horizontal water flow was substantial. Minimum and maximum observed concentrations of dissolved organic carbon (DOC) in the interstitial water of the peatland, for example, differed by more than a factor of three, and pH ranged between 3.8 and 5.0. Correlations of DOC with anion deficit and hydrogen ion concentration and experiments of photo-oxidation of water samples showed that organic acids were the primary cause of acidity in the peatland. Specific conductance was highly correlated with DOC, probably because of DOC's correlation with the very conductive hydrogen ion. In Crystal Bog it was possible to use the relatively simple measure of specific conductance to estimate the temporal and spatial distribution of the more difficult to determine DOC.     

R1767, an example of the evolution of resistance plasmids

The Salmonella R-factor system R1767 undergoes frequent rearrangement of its plasmid components. The flux of genetic material within this plasmid system depends on a combination of illegitimate and homologous recombination. The presence of several copies of IS160 and two multiresistance transposons, Tn2410 and Tn2411, are substantial reasons for the observed variations.     

Annual Patterns in Bacterioplankton Community Variability in a Humic Lake

Bacterioplankton community composition (BCC) was monitored in a shallow humic lake in northern Wisconsin, USA, over 3 years using automated ribosomal intergenic spacer analysis (ARISA). Comparison of ARISA profiles of bacterial communities over time indicated that BCC was highly variable on a seasonal and annual scale. Nonmetric multidimensional scaling (MDS) analysis indicated little similarity in BCC from year to year. Nevertheless, annual patterns in bacterioplankton community diversity were observed. Trends in bacterioplankton community diversity were correlated to annual patterns in community succession observed for phytoplankton and zooplankton populations, consistent with the notion that food web interactions affect bacterioplankton community structure in this humic lake. Bacterioplankton communities experience a dramatic drop in richness and abundance each year in early summer, concurrent with an increase in the abundance of both mixotrophic and heterotrophic flagellates. A second drop in richness, but not abundance, is observed each year in late summer, coinciding with an intense bloom of the nonphagotrophic dinoflagellate Peridinium limbatum. A relationship between bacterial community composition, size, and abundance and the population dynamics of Daphnia was also observed. The noted synchrony between these major population and species shifts suggests that linkages across trophic levels play a role in determining the annual time course of events for the microbial and metazoan components of the plankton.     

The ecological organisation of lake districts: general introduction

1. Here we introduce a special issue of Freshwater Biology that focuses on the landscape‐scale spatial and temporal patterns exhibited by multiple lakes within lake districts. We call this patterning, and the processes that lead to it, the ‘ecological organisation of lake districts.’ 2. Papers in this special issue share the common goal of examining landscape‐level processes that lead to spatial and temporal patterns of lake characteristics in individual or multiple lake districts. Several papers focus on the degree to which multiple lakes have synchronous among year variability in various physical, chemical, and biological variables. Others focus on the landscape‐level processes that lead to spatial patterning of lake characteristics. Finally, a few papers examine the relationship between spatial patterning and temporal dynamics. Papers in this special issue present results from 10 lake districts from North America, Europe, and Antarctica.     

Changes in glycosylation of human blood plasma chitotriosidase in patients with type 2 diabetes

Human blood plasma chitotriosidase (CHIT1) is a glycoprotein with chitinolytic activity with not fully elucidated biological function. Its increased level is observed in type 2 diabetes mellitus (T2DM) and is associated with development of diabetic complications. The CHIT1 glycosylation profile and degree is still poorly studied and never investigated in T2DM. Therefore the aim of the present study was to examine the association between glycosylation profile and degree and diabetes with accompanying nephropathy. In blood plasma of 28 patients with T2DM and 11 healthy subjects the CHIT1 concentration and specific activity were examined. The profile and degree of CHIT1 glycosylation were determined by lectin-ELISA using lectins specific to O-glycans (Jacalin, MPL, VVL) and sialo-specific SNA and MAA. We revealed that both concentration and specific activity of CHIT1 significantly increased in T2DM, especially in nephropathy with elevated albuminuria. The relative reactivities with lectins, except Jacalin, decreased progressively with T2DM occurrence and albuminuria progression. The most significant differences were observed between control vs. albuminuric group (Micro and Macro). It is also possible that the observed differences in immunoblotting pattern in molecular masses of CHIT1 bands between T2DM patients and healthy subjects may be caused by the differences in degree of CHIT1 glycosylation. The analysis of CHIT1 glycosylation status and the determination of CHIT1 concentration together with its enzymatic activity in blood plasma might constitute additional valuable diagnosis tools for the evaluation the T2DM patients with accompanying nephropathy. Extension of the lectin panel specific to O-glycans occurs useful for the further research using microarray formats, which are expected to accelerate “lectin-based glycan profiling” of glycoproteins.     

The pig as a model of tachycardia and dilated cardiomyopathy

Chronic Supraventricular Tachycardia (SVT) can produce a dilated cardiomyopathy which has a poorly understood association with ventricular dysfunction in humans and animals. The purpose of this study was to produce a model of chronic SVT and dilated cardiomyopathy using swine, which have a cardiac anatomy similar to man. Eight pigs were implanted with chronic atrial catheters and a pacemaker, with four additional sham-operated pigs serving as controls. We examined ventricular function and morphology at baseline (120 +/- 3 bpm), pacing baseline (240 bpm), and at 1, 2 and 3 weeks of rapid atrial pacing (240 bpm). Ventricular ejection fractions fell significantly from baseline following 1 week (left: 38 +/- 3% vs baseline 61 +/- 1%; right: 31 +/- 5% vs baseline 56 +/- 1%; p less than 0.05) and deteriorated further by 3 weeks of SVT (left: 26 +/- 4%, right: 19 +/- 3%; p less than 0.05). Significant biventricular chamber dilation developed by 2 weeks of SVT (left: 50 +/- 5 cc vs paced baseline 27 +/- 2 cc; right: 67 +/- 6 cc vs paced baseline 28 +/- 3 cc; p less than 0.05) and continued to increase by week 3 of SVT (left: 66 +/- 11 cc; right: 78 +/- 8 cc; p less than 0.05). Five additional paced pigs, without chronic atrial catheters, were followed using echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)