Formation of tight junctions and desmosomes protects MDCK cells against hyperthermic killing

Cell density is known to modify the survival of mammalian cells exposed to elevated temperatures. We have examined the role that cell–cell contact plays in this phenomenon. The formation of cell–cell contact is carried out by cells' junctional complex, i.e., tight junctions, desmosomes, and gap junctions. Lack of formation of tight junctions and desmosomes, or their opening, could interfere with the functions and structures of cell membrane. Membrane damage is at least partially responsible for cell death at elevated temperatures. MDCK cells with high density plated in low calcium medium form confluent monolayers devoid of the formation of tight junctions and desmosomes but quickly assemble them after Ca²⁺ restoration. We used MDCK cells and the calcium switch technique to investigate effects of cell–cell contact and, independently, of cell density on hyperthermic cell killing. We found that MDCK cells that formed tight junctions and desmosomes were more resistant to hyperthermic treatment than those that did not. Blocking the formation pathway of tight junctions made cells sensitive to heat. Cells growing at lowdensity showed almost the same survival as did cells at high density in the absence of the formation of tight junctions and desmosomes. The results suggest that the formation of tight junctions and desmosomes play a more important role in determining hyperthermic response than does density per se. The formation of tight junctions and desmosomes appears to protect cells modestly against hyperthermic killing. © 1994 Wiley-Liss, Inc.     

Water potentials for developing cladodes and fruits of a succulent plant, including xylem-versus-phloem implications for water movement

Developing cladodes had lower water potentials and developingfruits had higher water potentials than the underlying cladodesof the widely cultivated prickly pear cactus, Opuntia ficus-indica.The 0.06 MPa lower value in 4-week-old daughter cladodes indicateda typical water potential gradient from the underlying clad-odealong the xylem of –0.2 MPa m^–1; the 0.17 MPa highervalue in 4-week-old fruits, which decreased to 0.07 MPa by 10weeks, implicated the phloem as their supplier of water. Thephloem sap of the underlying cladodes had an osmotic pressureof only 0.90 to 0.98 MPa, so the phloem could supply a relativelydilute solution to the photosynthetically dependent fruits (daughtercladodes of O. ficus-indica are photosynthetically independentat 4 weeks). Although the water potentials were similar foradjacent tissues, the osmotic pressures were lower for the water-storagecompared with the photosynthetic tissue; the osmotic pressureswere higher for xylem sap from fruits, for which xylary flowapparently occurred toward the underlying cladodes, than fordaughter cladodes. The relative capacitance (change in relativewater content divided by change in tissue water potential) wasapproximately 0.71 MPa^–1 for the water-storage tissueand the photosynthetic tissue of both daughter cladodes andfruits at 4 weeks of age. When these organs approached maturityat 10 weeks, the relative capacitance increased about 40% fortheir water-storage tissue, but decreased 30% for their photosynthetictissue. As the plant water content decreases during drought,about twice as much water will thus be lost per unit volumeof the water-storage tissue compared with the photosynthetictissue of maturing fruits and cladodes. Key words: Opuntia ficus-indica, phloem, relative water content, water capacitance, water potential     

Postpartum anestrus in French beef cattle: an epidemiological study

Postpartum anestrus of lactating beef cows was studied by means of an epidemiological study carried out on 878 lactating beef cows in 60 French herds. The cows calved between October 1992 and March 1993 and were housed 2 mo after calving, when the anestrus status was determined by progesterone radioimmunoassays. Data analysis was performed using a multiple logistic model in order to adjust for confounding and interaction. Fifty-one percent of the primiparous and 23% of the multiparous cows were found to be in anestrus. Factors significantly related to anestrus were parity (primiparous); breed (Charolais); housing type (tie housing); suckling (compared to weaning at birth); and, among those that were under the control of the farmer, calving conditions (manual exploration of the birth canal); body condition score at calving (3 or less, on a 5-point scale); and loss in body condition score after calving (1 point or more within 2 mo). Previous reproductive performance for multiparous cows such as a long calving interval and induced estrus in the previous year also appeared to be related to anestrus.     

Procedure for whole mount fluorescence in situ hybridization of interphase nuclei on Arabidopsis thaliana

A procedure for whole mount fluorescence in situ hybridization (FISH) on plant tissue is reported. The technique was demonstrated on seedlings and flowers of Arabidopsis thaliana L. with rDNA as a probe, labelled, both for direct and indirect detection. It was found that fixation in 1% formaldehyde yielded the best results with respect to morphology and hybridization efficiency. The combination of whole mount FISH and confocal scanning laser microscopy allowed the nuclear localization of the rDNA loci in all tissues of both seedlings and flowers. Direct labelling yielded the best signal-to-noise ratio, especially in the apical zones of the seedlings. The technique was further illustrated on seedlings of A. thaliana in double labelling experiments with rDNA and a tandemly repeated, 500 bp sequence of A. thaliana. Although nuclei in all tissues in the seedling exhibited both signals, hybridization efficiency for both signals was reduced in the dense, apical zones as compared with single labelling experiments with rDNA.     

Effects of chorda-lingual nerve injury and repair on human taste

Citric acid detection threshold and magnitude response weremeasured on the anterior tongue in 10 patients with unilateralchorda-lingual nerve transections before and after repair. Fungiformtaste buds were analysed by videomicroscopy. Preliminary datasuggests that humans can regenerate fungiform taste buds andrecover some taste sensitivity after repair.     

中国羽枝藻属新资料

1.山西羽枝藻 新种 图1:1—4 Cloniophora shanxiensis Y. J. Ling et S. L. Xie, sp. nov. Species affnis C. spicatae (Schmid.) Islam, sed primariis ramulis irregularibus alternatisvel oppositis, pyrenoidibus solitariis, ramuli cellulis apprime irregularibus differt. Thallo caespitoso, usque ad 5 cm longo; rhizoideis e filamenti cellulis basalibus angustis     

Somatic hybridization between Citrus reticulata and Citropsis gabunensis through electrofusion

Protoplasts from embryogenic calli of Citrus reticulata Blanco cv. Ponkan and Citropsis gabunensis (Engl.) Swing. & M. Kell (Cabon Cherry Orange), were isolated and fused using electric current. Maximum fusion frequency was obtained with AC at 75 kV/cm (1.0 MHz) for 15 s, followed by DC square-wave pulses at 1.25 kV/cm for 40 s. Fusion-treated protoplasts were cultured on MT medium containing no growth regulators, solidified with 0.6% Bacto Difco agar. Protoplast-derived calli were proliferated on MT medium containing 1 mg/l zeatin and 0.9% agar. A total of 31 lines of somatic hybrid calli were obtained by screening on the basis of chromosome count and isozyme analysis. The somatic hybrids were tetraploid (2n=36). Plants were regenerated from the calli via somatic embryogenesis. The somatic hybrid plants exhibited morphological characteristics intermediate to the parental plants.Abbreviations 2,4-D 2, 4-dichlorophenoxyacetic acid - BA 6-benzylaminopurine - MT Murashige and Tucker (1969) - PEG polyethylene glycol - AC alternating current - DC direct current