Nonlinear and asymmetric open channel characteristics of an ion-selective porin in planar membranes.

The open channel characteristics of the bacterial porin Omp32 from Comamonas acidovorans were investigated by means of conductance measurements in planar lipid bilayers of the Montal-Mueller type. Particularly at low salt conditions (< or = 30 mM KCl) Omp32 exhibited some unusual asymmetric and nonlinear functional properties. Current-voltage relationship measurements showed that conductance depends on the orientation of porin molecules and is a nonlinear function of the applied membrane potential. Conductance also depends on the salt concentration in a manner not common to porins and the salt concentration modulates the nonlinearity of conductance-voltage relationships. Omp32 is strongly anion-selective. The nonlinear and asymmetric conductance of the open channel is a new observation in porins.     

Cytology and mRNA expression analysis of fine needle aspirates of thyroid nodules in an East German region with borderline iodine deficiency.

Fine needle aspiration cytology (FNAC) is widely recommended as an important tool for pre-operative identification of malignancy in patients with nodular thyroid disease. To assess the diagnostic contribution of FNAC and the potential of quantitative mRNA analysis in fine needle aspirates in daily practice, we conducted a prospective study in thyroid clinics (n=2) and endocrine practices (n=3), respectively in an East German region with borderline iodine deficiency. Two-hundred and forty-four consecutive FNACs were obtained over a period of 2 years (2002-2004) from euthyroid patients presenting for first evaluation of a solitary thyroid nodule. The mean nodule size for FNAC was 27 mm (range: 10-79 mm). In 55% of patients FNAC was performed after scintiscan detection of a cold or normal functioning thyroid nodule (CTN), while in the remainder FNAC was performed as a primary investigation. FNAC outcomes were: 57.8% benign, 22.1% indeterminate, 2.5% suspicious for malignancy, 17.6% non-diagnostic. Messenger RNA levels for a house keeping gene (beta-actin) and a thyroid specific marker (thyroglobulin, Tg) were studied as basic molecular markers using real-time PCR. Both in the IN VIVO and EX VIVO FNA series, beta-actin and Tg mRNA levels were positively correlated with the thyrocyte cell yield/respective FNA smear. However, subgroup analysis showed that FNAC with histologically confirmed follicular thyroid cancer and/or microfollicular adenoma exhibited significantly lower Tg mRNA expression despite high beta-actin levels. Sufficient mRNA quantities were obtained in >90% of FNA specimen to allow quantitative mRNA analysis of at least 5 further genes. In conclusion, quantitative mRNA analysis is feasible in FNA on a routine basis and provides a perspective for a molecular distinction of thyroid nodules, once specific marker genes have been defined for benign and malignant thyroid tumours respectively.     

The Use of Case Studies in Establishing Feasibility for Wetland Restoration

Establishing restoration feasibility is a multifaceted process that requires consideration of the ecological, social, and economic conditions of a given site. Examining completed restoration projects that report successes and failures may enhance this complex decision‐making process. We describe five completed wetland restoration projects and identify commonalities among them to inform the process of establishing feasibility for proposed restoration projects. Most of the case studies identified the need to gather preexisting and historical information, develop scenarios through hydrologic modeling, study the restoration materials, use best professional judgement for unanswered questions, establish multigroup collaboration, gain public support from stakeholders, and monitor postrestoration. We applied these lessons to a study that evaluated the feasibility of restoring Dyke Marsh Preserve, a tidal freshwater marsh in Virginia that the National Park Service is mandated to preserve. We found that the use of case studies substantially increased confidence in the decision‐making process by focusing discussions on the most important ecological, social, and economic aspects of a potential restoration.     

Long-term pancreatic duct occlusion impairs the entero-insular axis in the dog--failure of plasma VIP to respond as "incretin"

The response of VIP to either an oral glucose load (OGT) or intravenous glucose (IV glucose), aimed at reproducing the plasma glucose level after OGT, was studied in trained, conscious, sham-operated (Sham; n = 6) dogs, and dogs having initially (12 months before the glucose experiments) undergone occlusion of the pancreatic duct by the prolamine glue technique (Occ; n = 5). As a result, prior to glucose studies, the exocrine pancreas function was found subtotally reduced, as indirectly evaluated by the para-aminobenzoic acid (PABA) test, but no signs of diabetes were detected. The two studies with glucose administration designed to demonstrate the release of insulin, VIP, somatostatin into plasma as modified by enteric signals (represented by the difference of plasma peptide concentration during OGT minus peptide concentration during IV glucose) revealed the following: (1) basal plasma glucose, insulin, VIP, somatostatin did not differ between Sham and Occ dogs; (2) after OGT in Occ dogs the plasma glucose was elevated, whereas plasma insulin was markedly reduced, and VIP, somatostatin were largely unchanged; (3) the integrated output of insulin only was impaired when considering the so-called entero-insulin axis, while integrated VIP, somatostatin were unaltered. It was concluded (a) the Occ procedure in the dog has the capacity to subtotal destruction of the pancreatic acinar tissue, and of the entero-insular axis of insulin, the latter through yet unknown pathways, (b) the Occ technique may be a useful tool for investigation of the nature of "incretin," (c) VIP and somatostatin do not respond to elevated blood glucose and may have no role in the "incretin" concept of enteric modulation of the B-cell.     

The structure of the gastric mucosa of the llamas (Lama guanocoe and Lama lamae). I. Forestomach]

The mucous membrane of the first and second compartments (ventral regions) as well as of the third compartment of Lama guanacoe and Lama lamae stomach shows tubular glands opening into pits. Below the surface epithelium blood capillaries of the fenestrated type form a regular network, each mesh of which surrounds a gastric pit. From a morphological point of view (thin section and freeze-fracture replicas) the columnar cells of the surface epithelium and those of the pits closest to the capillaries are largely similar to the epithelial cells of the rabbit gallbladder. This similarity suggests that at the level of the columnar cells sodium-dependent water reabsorption occurs. This reabsorption has already been demonstrated in the abovementioned compartments by physiological methods. The surface and foveolae epithelial cells as well as some cells of the tubular glands have a secretory function. Their secretory granules contain mucosubstances, as indicated by light-(PAS- and Alcian blue reactions) and electron microscopic (PA-TCH-Ag-reaction) histochemistry. The secretory granules originate from the Golgi complex which shows a positive histochemical reaction in its innermost sacculi at the electron microscope level. Endocrine cells (s. second part of this investigation) are rare. The mucosal membrane of each muscular lip separating the glandular sacs in the first compartment shows a stratified, not keratinized, squamous epithelium.     

Postmortem diagnostics of renal diseases from semithin sections.

For the light microscopic postmortem study of mostly glomerular renal diseases, in addition to the paraffin technique, 0.5 mu thick (semithin) sections from material fixed in buffered formaldehyde and embedded in methacrylate or Durcupan ACM were used. The method allows for eventual electron microscopic examinations. The semithin sections were stained with methylene blue combined with basic fuchsin, as well as with periodic acid-silver methamine. The method is not a substitution, but the supplementation of the paraffin technique and is suited for the clarification of numerous fine details: in some cases the exact diagnosis was made in this way.     

Fluctuations in the production of specific cellular peptides during the growth of animal cells

Patterns of newly synthesized proteins of Vero cells in different growth states were obtained using two-dimensional gel electrophoresis. The 240 most prevalent peptide spots were then compared. Cells in exponential growth and in the stationary phase were found to have patterns of peptide spots characteristic of their state of growth. The transition between these patterns is progressive, and the cells acquire a pattern characteristic of quiescent cells by the late exponential phase. These observations suggest that a series of modulations in gene expression occurs during the transition of growth states in animal cells that leads to the specific appearance or disappearance of certain cellular peptides.     

STUDY ON THE PROLIFERATIVE STATE OF HAEMOPOIETIC STEM CELLS (CFU)

Hydroxyurea was used to study the proliferation rate of haemopoietic stem cells (CFUJ in normal mice, after irradiation or transplantation into irradiated recipients. It was demonstrated that the proliferation rate of endogenous CFU_S (endo-CFU,) and exogenous CFU_S (exo-CFU_s) are identical. After irradiation (650 R) the surviving endo-CFU_s begin to proliferate immediately. By contrast exo-CFU, transplanted into the irradiated recipient mouse (850 R), begin to proliferate only after about 30 hr. However, injection of isoproterenol (which stimulates adenyl cyclase) or dibutyryl cyclic adenosine 3′,5′-monophosphate shortly after marrow cell graft, triggers the transplanted CFU_S into cell cycle as shown by an almost immediately increased sensitivity to hydroxyurea. Isoproterenol is capable of inducing DNA synthesis also in stem cells of normal mice but it takes about 20 hr before CFU, become to be increasingly sensitive to hydroxyurea.     

Cation-dependent solubilization of rat thymocyte chromatin is closely related to decondensation of the nuclei

The cation-dependent solubilization of rat thymocyte chromatin has been compared with decondensation of the nuclei as a function of sodium phosphate-mediated changes in the concentration of Mg2+ and Na+. After digestion of the nuclei with DNase I or Micrococcus nuclease for a time just sufficient to permit extraction of a maximal amount of chromatin (minimum digestion), solubilization of most of the chromatin was found to occur with the same cation dependency as decondensation of untreated nuclei, while further digestion changed the ionic requirements for solubilization. The cation-dependency of the chromatin solubility and of the nuclear decondensation also exhibited the same variations with temperature. The chromatin in the nuclei became up to 4-times more sensitive to DNase I by decondensation, which also induced a shift in the DNase I cleavage mode from a 200 bp to a 100 bp repeat pattern. In contrast, the sensitivity to Micrococcus nuclease appeared to be nearly unchanged. These results suggest that solubilization of chromatin prepared by a mild endonuclease treatment occurs as a direct consequence of structural changes in the chromatin which take place during decondensation of the nuclei.