Chloride cell responses to long-term exposure to distilled and hard water in the gill of the armored catfish, Hypostomus tietensis (Loricariidae)

The morphological changes in the gill chloride cells of the armored catfish, Hypostomus tietensis , were investigated after 15 days' exposure to either distilled or hard water. The thickness of the water–blood barrier in the lamellae increased significantly in fish kept in distilled water due to the high proliferation of chloride cells. The apical surface of about 68% of chloride cells was sharply reduced by the development of an apical crypt with a sponge-like surface, although no change in the chloride cell fractional area was found. In contrast, H. tietensis kept in Na⁺, Cl⁻ and Ca²⁺ rich water displayed no significant changes in the number of chloride cells or in their apical surface morphology compared with the control fish. Chloride cell response to ion challenge in H. tietensis suggested the involvement of different strategies to maintain homeostasis in ion-poor water, which may be related to the life history of species.     

Rapid immunofluorescent determination of cells in the S phase in pea root meristems: An alternative to autoradiography

Photosystem II (PS II) activity and the localization of ribulose-l,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) were studied in primary leaves of young maize plants ( Zea mays L. cv. Fronica) by tetra-nitro-blue-tetrazoliumchloride reduction and immunolocalization, respectively. In tissue of 3-day-old plants all chloroplasts were structurally identical. From day 4 they developed into their typical appearance of mesophyll and bundle sheath chloroplasts. First PS II-activity was present in both types of chloroplasts. From day 4 it disappeared in bundle sheath chloroplasts concomitant with the loss of grana. RuBP carboxylase on the other hand was only present in bundle sheath chloroplasts at all stages of development. Thus, the control of the development of the photosystems and the Calvin cycle enzymes seem to differ.     

Plasmid-encoded ropiness production inLactobacillus casei SSP.casei

Summary Genetic determinants of the Muc⁺ character were investigated in two ropy strains,Lactobacillus delbrueckii ssp.bulgaricus 201 andL. casei ssp.casei NCIB 4114, which secrete a large amount of slime in culture media. Plasmid DNA analysis revealed the presence of two plasmids (4.5 and 2.3 Mdal) inL. casei ssp.casei, whileL. delbrueckii ssp.bulgaricus was plasmid free, suggesting a chromosomal location of Muc⁺ character in this strain. Curing experiments carried out onL. casei ssp.casei NCIB 4114 indicated a correlation between the Muc⁺ phenotype and the 4.5 Mdal plasmid.     

Phenolic and mineral content of leaves influences decomposition in European forest ecosystems

Summary Factors influencing decomposition in European forests growing on different soils were studied in stands dominated by the European beechFagus sylvatica L. Phenolic contents of freshly fallen leaves ofF. sylvatica growing on nutrient-poor soils (acid sandy soil) were higher than those of similar leaves on nutrient-rich soils (calcareous mull soil). Analysis of fallen leaves of different ages showed rapid decay of phenolics during the first winter on the ground. After 1 year the phenolic content of leaves ofF. sylvatica growing on nutrient-poor soils was still twice as high as in similar leaves on nutrient-rich soils. Field and laboratory experiments showed that a major decomposer (Oniscus asellus, Isopoda) preferred leaves from trees on nutrient-rich soils. Mineral contents of leaves ofF. sylvatica growing on different soils differed: on rich soils leaves had higher contents of Ca, Mg, Na, and K. These elements are important nutrients for decomposers. The distribution of major decomposers reflects the mineral content of their diet, which in turn reflects soil type. Different rates of leaf turnover and nutrient turnover in different forest ecosystems (even when the same tree species is dominant) are due to the decomposing system, which is influenced by the phenolic and mineral contents of the leaves.     

Reactions of the fauna on the bark of trees to the frequency of fires in a North American savanna

Summary The arthropod communities living on the bark of the oak species Quercus macrocarpa and Q. ellipsoidalis were investigated in a North American oak savanna. Differences were found in the community structure of the arthropods living on the bark of these two tree species, although they have the same fissured bark type. In the North American oak savanna ecosystem the most important disturbance factor is fire, which maintains species richness. Highest numbers of species and specimens were found at moderately disturbed sites. Three main ecological groups of arthropods living on the bark of trees can be distinguished in relation to the degree of disturbance: (1) Inhabitants of bark of trees restricted to undisturbed sites: they do not occur in fire-disturbed areas; (2) Inhabitants of bark of trees adapted to a moderate degree of disturbance: many species occur in high numbers only in moderately disturbed areas; and (3) Specialist inhabitants of bark of trees in heavily disturbed areas. The number of specimens of these species increases per trunk with the frequency of disturbance.     

Cytometry and flow cytometry of 4',6-diamidino-2-phenylindole (DAPI)-stained suspensions of nuclei released from fresh and fixed tissues of plants

Cytometry and flow cytometry were used to study characteristics of fluorescence of the DNA-DAPI complex in nuclei released from different fresh and formaldehyde-fixed pea ( Pisum sativum L. cv. Lincoln) tissues. The two methods of isolation are compared and discussed as well as their possible use for quantitative analysis of DNA in plant tissues. With fixed tissues it is possible to obtain a number of nuclei sufficient for the flow cytometric analysis, even using small amounts of plant tissue.     

Solitary Song and its inhibition in some Estrildidae

Summary In the species studied song appears to have two functions; an epigamic function = Display Song, and a contact function = Solitary Song. Solitary Song appears to be common to all the species studied. Its utterance indicates that the bird is unpaired or separated from another individual with which it has formed a bond. InUraeginthus bengalus, U. angolensis, andAmandava amandava Solitary Song is also uttered by the hen in similar circumstances. InLonchura punctulata, A. amandava, andEuodice malabarica song is usually but not completely inhibited by the presence of a mate, in whose absence Solitary Song will be uttered even when other individuals of the same species are present. In the species studied of the generaEstrilda, Lagonosticta, andUraeginthus Solitary Song is inhibited by the continued close proximity of another bird even though this may be of the same sex or of a different species and may elicit aggressive or fleeing reactions; but conditions of close association with a bird other than a suitable mate would presumably only occur under captive conditions. There appears to be a distance factor controlling such inhibition. There is evidence of the inhibition of song due to the presence of a mate in other passerine species.