Comparative lectin histochemistry on taste buds in foliate, circumvallate and fungiform papillae of the rabbit tongue.

Taste buds (TB) in the foliate, circumvallate and fungiform papillae of the rabbit tongue were examined with lectin histochemistry by means of light (LM) and electron (EM) microscopy. Biotin- and gold-labeled lectins were used for the detection of carbohydrate residues in TB cells and subcutaneous salivary glands. At the LM level, the lectins of soybean (SBA) and peanut (PNA) react with material of the foliate and circumvallate taste pores only after pretreatment of the section with neuraminidase. This indicates that the terminal trisaccharide sequences are as follows: Sialic acid-Gal-GalNAc in O-glycosylated glycoproteins or Sialic acid-Gal-GlcNAc in N-glycosylated glycoproteins. In fungi-form taste buds the lectins of Dolichos biflorus (DBA) and Helix pomatia (HPA), also specific to GalNAc residues, are reactive without preincubation with neuraminidase. Wheat germ agglutinin (WGA), specific to GlcNAc, reacts with TBs of all papillae; and the lectin from Ulex europaeus (UEA I), specific to fucose, binds to individual TB cells. The presence of sialic acid may protect mucus or other glycoproteins in TB cells and inside the taste pore from premature enzymatic degradation. In a post-embedding EM procedure on LR-White-embedded tissue sections, only gold-labeled HPA was found to bind especially on membrane surfaces of the microvilli which protrude into the taste pore; however HPA did not bind to the electron-dense mucus inside the taste pore. The mucus situated in the trough and at the top of the adjacent epithelial cells also is strongly HPA-positive, but is of different origin and composition than that found in the taste pore. These results demonstrate distinct carbohydrate histochemical differences between fungiform and circumvallate/foliate taste buds. The different configuration of galactosyl residues and the occurrence of mannose in circumvallate and foliate TBs leads to the suggestion that the lectin reactivities of TBs are not only due to the presence of mucins, but also to N-linked glycoproteins, possibly with a hormone-like paraneuronal function. A possible relationship to v. Ebner glands in these papillae is discussed.     

Biofilm Formation by Cryptococcus neoformans Under Distinct Environmental Conditions

Cryptococcus neoformans is an opportunistic fungal pathogen with a propensity to infect the central nervous system of immune compromised individuals causing life-threatening meningoencephalitis. Cryptococcal biofilms have been described as a protective niche against microbial predators in nature and shown to enhance resistance against antifungal agents and specific mediators of host immune responses. Based on the potential importance of cryptococcal biofilms to its survival in the human host and in nature, these studies were designed to investigate those factors that mediate biofilm formation by C. neoformans. We observed that C. neoformans preferentially grew as planktonic cells when cultured under specific conditions designed to mimic growth within host tissues (37°C, neutral pH, and ~5% CO₂) or phagocytes (37°C, acidic pH, and ~5% CO₂) and as biofilms when cultured under conditions such as those encountered in the external environment (25–37°C, neutral pH, and ambient CO₂). Altogether, our studies suggest that conditions similar to those observed in its natural habitat may be conducive to biofilm formation by C. neoformans.     

Isolation and complete amino-acid sequence of the small polypeptide from light-harvesting pigment-protein complex I (B870) of Rhodopseudomonas capsulata

The small bacteriochlorophyll-binding polypeptide of the light-harvesting complex B870 was extracted from the intracytoplasmic membrane of the strain A1a+ of Rhodopseudomonas capsulata with chloroform/methanol/ammonium acetate and separated by chromatography on Sephadex LH60 using the same solvent. The polypeptide obtained from the peak fraction III was found to be homogeneous and identical with the small polypeptide isolated from the B870 complex as shown by dodecyl sulfate/polyacrylamide gel electrophoresis, amino acid composition and N-terminal sequence. The complete amino acid sequence is given. The relative molecular mass based on the amino acid sequence is 5341. The polarity of amino acids is 35.42%. The C-terminal part of the peptide chain from residue 29 to 48 is hydrophobic and includes one His residue.     

Prevalence, risk factors and rheological profile of arterial vascular disease; first results of the Aachen study

During a prospective cohort-study of several year's duration the results of a survey regarding prevalence of arterial occlusive disease, as well as classical risk factors and rheological profile of patients suffering from vascular disease were examined. 364 patients out of a total of 2,498 individuals suffered from vascular disease. 168 (6.7%) had cardiovascular, 151 (6.0%) cerebrovascular and 109 (4.4%) peripheral vascular disease. Compared to to healthy individuals, the patients showed a significant accumulation of classical risk factors (elevated cholesterol and triglyceride values, decreased HDL-cholesterol concentration, obesity, smoking, high blood pressure, gout or diabetes mellitus). Only 30.2% of the healthy controls presented two or more risk factors, whereas the angiological patients showed two or more risk factors in 71.9%. Rheological parameters measured in the survey were: Plasma viscosity, erythrocyte and platelet aggregation, erythrocyte rigidity and hematocrit. Only 14.2% of the healthy individuals had two or more rheological parameters exceeding the 1-s range, whereas 56.6% of the patients showed two or more elevated rheological parameters.     

Retrospective monitoring of rangeland vegetation change: ecohistory from deposits of sheep dung associated with shearing sheds

This paper explores the potential of a new method of reconstructing historical vegetation change in the Australian rangelands. Historical monitoring of rangeland vegetation has been so deficient that it is not possible to determine whether a long‐term trend toward degradation has occurred (as is often assumed) or, indeed, if it is continuing to occur. Because long‐term records are unavailable any attempt to monitor vegetation retrospectively must be based on proxy measures rather than direct observation. Where historical data are lacking an integration of palaeoecological, archaeological and ecological methods is required to reconstruct the past. Our research is based on a detailed analysis of sheep faeces deposited near a shearing shed in the semiarid rangelands of south‐west Queensland between the late 1930s and the mid‐1990s. The faeces in these deposits represent the diet of sheep in the days leading up to the property’s annual shearing and as such are a potentially useful index to changes in vegetation. Results indicate significant changes in the diet of sheep since the late 1940s. The potential of this method, and its limitations, are discussed. Long‐term records are critical in understanding issues of sustainability in land management and it is intended that this paper will stimulate further research into historical vegetation change in rangelands.     

Immunohistochemical investigations on the differentiation marker protein E11 in rat calvaria, calvaria cell culture and the osteoblastic cell line ROS 17/2.8

 Until now, many extracellular matrix proteins, e.g. osteopontin and osteonectin, have been used to determine a cell’s osteogenic maturation. The disadvantage in evaluation of these proteins is their relative wide-ranging appearance throughout the osteogenic differentiation process. Thus, the aim of this study was to establish an immunohistochemical setup using E11, a marker that binds selectively to cells of the late osteogenic cell lineage. In addition, the histochemical expression of the bone matrix proteins osteonectin, osteopontin and fibronectin was compared to that of E11 using monoclonal antibodies. For light microscopical detection of osteogenic markers in cultured cells we developed a simple paraffin technique using a fibrin glue as embedding medium. This allows the handling of cultured cells such as a tissue sample and includes the use of stored biological specimens for further immunohistochemical experiments. We used newborn rat calvariae for whole tissue preparations and for isolation and cultivation of bone cells. In addition, we included the rat osteosarcoma cell line ROS 17/2.8 in this study. For the first time, we have localised E11 in osteocytes of rat calvaria preparations at the electron microscopical level. E11 was detected at plasma membranes of osteocytes and their processes, but not at those of osteoblasts. Accompanying experiments with cultured newborn rat calvaria cells and ROS 17/2.8 cells revealed E11 reactivity on a subset of cells. The results obtained confirm the suitability of the differentiation marker E11 as a sensitive instrument for the characterisation of bone cell culture systems. Accepted: 25 August 1998