Physiological ecology of a metalimnetic Cryptomonas population: relationships to light, sulfide and nutrients

The possible mechanisms by which Cryptomonas phaseolus maintainsa large metalimnetic population during stratification were studiedin Lake Cisó. The population was shown to always remainat the oxygen-sulfide interface despite the fact that sometimesthe amount of light reaching was <1% of incident light. Thismeant that the amount of light reaching the peak was sometimesmuch lower than the optimum light intensity for photosynthesisof the population, which was     

A highly conserved α-tubulin sequence from Prunus amygdalus

The sequence of an -tubulin from Prunus amygdalus has been obtained by cDNA cloning. When this sequence is compared to that of the Tub1 gene from maize it shows a very high degree of similarity, much higher than any of the -tubulin sequences reported so far from plants. The expression of this gene is high in the stages of seed development where a high divisional activity is present. It is preferentially expressed in the radicular tissues as it is gene Tub1 in maize. Southern analysis indicates that this gene may from a subfamily of -tubulin genes having similar sequence and tissue specificity and existing at least in maize and in Prunus.     

Thermoregulation and roost selection by reproductive female big brown bats (Eptesicus fuscus) roosting in rock crevices

A free-ranging maternity colony of big brown bats Eptesicus fuscus roosting in rock crevices along the South Saskatchewan River in south-eastern Alberta, Canada, was studied to understand better the discrepancy that exists in the literature regarding torpor use by reproductive female bats. Using radio-telemetry, thermoregulatory patterns and roost microclimate were recorded for pregnant, lactating and post-lactating females. Relative torpor use is described in several ways: the proportion of days on which torpor was used, depth, minimum body temperature, time spent in torpor, and a comprehensive torpor unit (degree-min). Pregnant and lactating female E. fuscus used torpor to the same extent overall (degree-min), but pregnant bats used torpor less frequently and with more time in deep torpor. Torpor was used to the greatest extent after weaning (post-lactation). Evidence is presented that the cost:benefit ratio for deep and prolonged periods of torpor may be highest during lactation. Microclimates of rock-crevice roosts mirrored the use of torpor throughout reproduction by bats. Lactation roosts (deeper, larger opening size) were more thermally stable and remained warmer at night compared to the shallow roosts used by pregnant and post-lactating females. It is shown that conclusions about relative use of torpor can differ depending on the units of comparison, necessitating measurement of all aspects of torpor (depth, duration and frequency). Comprehensive measurements, individual-based normothermic temperatures, and a definition of torpor that accounts for all energy savings, allow a more accurate depiction of patterns and facilitates inter-study comparisons.     

The freshwater planarian Dugesia (G.) tigrina contains a great diversity of homeobox genes

To identify potential pattern control and cell determination and/or differentiation genes in the freshwater planarian Dugesial (G.) tigrina, we searched for homeobox genes of different types in the genome of this primitive metazoan. We applied two basic approaches: 1) Screening the cDNA library with degenerate oligonucleotides corresponding to the most conserved amino acid sequence from helix-3 of the homeodomain of each family; and 2) PCR amplification of genomic DNA or cDNA, using two sets of degenerated oligonucleotides corresponding to helices 1 and 3 of the homeodomain or two specific domains of the POU family. Using the first strategy we have identified and characterized two tissue-specific cell determination and/or differentiation NK-type homeobox genes. Using the second strategy we have identified several homeobox genes that belong to the HOM/Hox, paired (prd) or POU families.     

Histochemical study of glycoconjugates in the epididymis of the hamster (Mesocricetus auratus)

Summary The glycoconjugates of hamster epididymis were investigated with conventional and lectin histochemistry. A zone of the caput epididymis, with particular histochemical characteristics, has been differentiated. β-Elimination in combination with lectins was used to establish the presence and distribution of N- and O-linked glycoconjugates. The epithelium, spermatozoa and the intertubular matrix were rich in glycoconjugates. The Golgi apparatus and stereocilia of the principal cells were intensely positive with HPA, PNA and SBA lectins. β-limination indicated that these cells contained abundant O-linked glycoconjugates. Apical and clear cells presented a common lectin affinity; their reactivities towards WGA and UEA-I were very positive. These cells probably contain abundant N-glycoconjugates. The spermatozoa were stained by periodic acid-Schiff (PAS) and by all the lectins (especially in the acrosome), except by those with an affinity for α-l-fucosyl residues; the most intense reaction was found with HPA, WGA, PNA and SBA. Changes in the sperm lectin binding along the ductus were observed: sperm flagellum abruptly acquired WGA and PNA labelling from the posterior caput, and HPA reactivity was negative only in the zone between the caput and the corpus.     

The brief survival of free-ranging baboon infants (Papio cynocephalus) after separation from their mothers

The importance of mother — infant attachment in free-ranging primates is illustrated by events culminating in the deaths of two baboon infants a few days after losing their mothers. These two cases are contrasted with those of a severely injured infant, not separated from its mother, which lived, and an animal which lost and refound its troop. Protective behavior of adult males is described. In captivity, separation sometimes produces infant depression; in nature, such depression may be fatal.     

Effects of the dipolar form of phloretin on potassium conductance in squid giant axons.

The effects of phloretin on membrane ionic conductances have been studied in the giant axon of the squid, Loligo pealei. Phloretin reversibly suppresses the potassium and sodium conductances and modifies their dependence on membrane potential (Em). Its effects on the potassium conductance (GK) are much greater than on the sodium conductance; no effects on sodium inactivation are observed. Internal perfusion of phloretin produces both greater shifts in GK(Em) and greater reductions maximum GK than does external perfusion; the effect of simultaneous internal and external perfusion is little greater than that of internal perfusion alone. Lowering the internal pH, which favors the presence of the neutral species of weakly acidic phloretin (pKa 7.4), potentiates the actions of internally perfused phloretin. Other organic cations with dipole moments similar to phloretin's have little effect on either potassium or sodium conductances in squid axons. These results can be explained by either of two mechanisms; on postulates a phloretin "receptor" near the voltage sensor component of the potassium channel which is accessible to drug molecules applied at either the outer or inner membrane surface and is much more sensitive to the neutral than the negatively charged form of the drug. The other mechanism proposes that neutral phloretin molecules are dispersed in an ordered array in the membrane interior, producing a diffuse dipole field which modifies potassium channel gating. Different experimental results support these two mechanisms, and neither hypothesis can be disproven.     

Bacterial Contamination of Drinking Water Supplies in a Modern Rural Neighborhood

On six occasions during a 15-month period, the private well and spring water supplies in a modern rural neighborhood of 78 households were examined for total coliforms, fecal coliforms, Staphylococcus aureus, and standard plate count bacteria. More than one-third of the water supplies were unsatisfactory on at least one occasion as judged by standard plate counts over 10³/ml and the presence of coliforms, fecal coliforms, and/or S. aureus. Citrobacter freundii, Klebsiella pneumoniae, and Escherichia coli were the most frequently isolated total coliforms. At least 12 other genera of bacteria were identified from standard plate count agar. Coliform contamination was found to be higher after periods of rainfall, and high standard plate counts were more prevalent during warmer weather. These observations probably reflect leakage of surface water into improperly sealed wells or aquifer contamination during winter and the lack of chlorination to control microbial regrowth during the warm season. An inverse correlation was found between the presence of high standard plate counts and incidence of coliforms. Consumer education and at least a twice yearly monitoring of private water supplies (winter and summer) are suggested methods to signal that treatment may be necessary to reduce the risk of waterborne disease.     

Social development of stumptail macaques (Macaca arctoides): Synchrony of changes in mother-infant interactions and individual behaviors during the first 60 days of life

Several categories of social and individual behaviors were recorded during the first 60 days of life for seven stumptail macaques. Mother-infant interactions tended to decelerate in synchrony with increases in infant nonsocial behaviors, such as object manipulation. Several aspects of stumptail social growth during the first two months were similar to those of rhesus and other macaques. Approaching-leaving, which has been used previously as an index of waning of the mother-infant bond, was due more to infants than to mothers during the second month of life     

Mitochondrial DNA evolution in lagomorphs: Origin of systematic heteroplasmy and organization of diversity in European rabbits

Summary A characterization was conducted on mitochondrial DNA (mtDNA) molecules extracted separately from 107 European rabbits (Oryctolagus cuniculus) both wild and domestic, 13 European hares (Lepus capensis), and 1 eastern cottontail (Sylvilagus floridanus). Experimentally this study took into account restriction site polymorphism, overall length variation of the noncoding region, and numbers of repeated sequences. Nucleotide divergences indicate that the mtDNAs from the three species derived from a common ancestor some 6–8 million years (Myr) ago. Every animal appeared heteroplasmic for a set of molecules with various lengths of the noncoding region and variable numbers of repeated sequences that contribute to them. This systematic heteroplasmy, most probably generated by a rate of localized mtDNA rearrangements high enough to counterbalance the cellular segregation of rearranged molecules, is a shared derived character of leporids.The geographic distribution of mtDNA polymorphism among wild rabbit populations over the western European basin shows that two molecular lineages are represented, one in southern Spain, the second over northern Spain, France, and Tunisia. These two lineages derived from a common ancestor some 2 Myr ago. Their present geographical distribution may be correlated to the separation of rabbits into two stocks at the time of Mindel glaciation.Finally the distribution of mtDNA diversity exhibits a mosaic pattern both at inter- and intrapopulation levels.