Skull growth and the presence of auxiliary fontanels in rhinolophoid bats (Microchiroptera)

 Cephalometry was used to detect patterns of cranial growth in fetal bats that have been differentially stained for bone and cartilage. Rhinolophoid bats exhibit elaborate nasal cavities with coincidental distortions of the maxilla. The expansion of these cavities creates paired auxiliary fontanels among the nasal, maxillary, and frontal bones. This distortion of the rostrum is also associated with the loss of the lacrimal bones and the modification of the infraorbital foramen into a shallow canal. The use of the head as an acoustical horn is discussed with reference to the ontogeny of echolocation. Accepted: 12 October 1996     

The importance of macrophyte bed size for cladoceran composition and horizontal migration in a shallow lake

Cladoceran composition and diel horizontal migration were studiedin 2, 10 and 25 m diameter macrophyte exclosures establishedin the littoral zone of shallow Lake Stigsholm, Denmark. Theexclosures were protected from waterfowl grazing, but open tofish. The macrophyte community cornprized Potwnogeton pectinatus,Potamogeton pusillus and Callitriche hemaphroditica. Cladoceranswere sampled randomly every third hour inside and outside themacrophyte exclosures during a 24 h period. In the 2m exclosure,the pelagic species Ceriodaphnia spp. and Bosmina spp. dominatedduring the day, mean density being as high as 3430 indiv. l^–1During the night, density decreased to 10–20% of the daytimedensity thus indicating diel horizontal migration. In the 10and 25 m exciosures, the daytime mean density of Ceriodaphniaspp. was 865 and 202 indiv. l^–1, respectively, and didnot decrease at night. In contrast to the pelagic species, thedensity of macrophyte-associated species tended to be higherin the 10 and 25 m exclosure than in the 2 m exclosure. In thedaytime, Eurycercus lamellatus density in the 2, 10 and 25 rnmacrophyte exclosures was 7, 28 and 16 indiv. l^–1 respectively,while that of Simocephalus vetulus was 11, 171 and 92 mdiv.l^–1, respectively. There was no thy-night difference inthe density of macrophyte-associated species. We conclude thatcladoceran community composition varies with macrophyte bedsize, and that the edge zone between the bed and open wateris an important daytime refuge for potentially migrating pelagiccladocerans.     

Genetic and environmental correlations among serum lipids and apolipoproteins in elderly twins reared together and apart.

Genetic and environmental correlations among five serum-lipid measures were examined in the Swedish Adoption/Twin Study of Aging. The sample included 302 twin pairs; 146 of these twin pairs were separated at an early age and were reared apart. The lipid measures examined include total cholesterol, HDL-cholesterol, triglycerides, and apolipoproteins A-I and B. Genetic and environmental correlations were evaluated for two different age groups, formed by dividing the sample at the median. The younger group included individuals 41.8-65.4 years of age at the midpoint of testing, although only 24 individuals were < 50 years of age. The older group included all those > 65.4 years of age, up to age 87 years of age. Substantial genetic correlations were found within each age group, although there is no evidence for a single genetic factor common to all five lipids. The comparison of twins reared together with twins reared apart allowed estimation of the effects of shared rearing environment; however, shared rearing environment only appears to be a significant mediator of the phenotypic correlation between apolipoprotein B and cholesterol in the older group. Examination of the genetic and environmental covariances suggests that the relative contributions of genetic factors are lower in the older group. Nonshared environmental factors are relatively more important mediators of phenotypic correlations among the serum lipids in individuals > 65.4 years of age than they are for the younger group. Sex differences in the mediation of these serum lipids were not as clear.     

Effect of 4.5S RNA depletion on Escherichia coli protein synthesis and secretion.

We examined the synthesis of individual proteins following depletion of 4.5S RNA by using a strain deficient in the induction of heat shock proteins. We found that initially the synthesis of all proteins was equally affected, and the peptide elongation rate was reduced by approximately 10%. For up to 1 generation time after the onset of inhibition of total protein synthesis, the processing of secreted proteins was unaffected. After further depletion of 4.5S RNA, accumulation of precursors of secreted proteins was observed under some growth conditions.     

Genetic analysis of the minimal replicon of the Lactococcus lactis subsp. lactis biovar diacetylactis citrate plasmid

Using a combination of mutagenesis with the transposon and polymerase chain reaction subcloning, the essential elements of the replication region of the Lactococcus lactis subsp. lactis biovar diacetylactis citrate plasmid have been identified. An open reading frame, coding for a protein with homology to Rep proteins from other Lactococcus plasmids, is essential. This protein is trans-acting and could not be replaced by the Rep protein from another Lactococcus plasmid. A second open reading frame immediately downstream from the first could be removed or inactivated with no apparent effect on plasmid replication. A region containing two 10 by direct repeats and three tandem repeats of a 22 by sequence, immediately upstream of the essential open reading frame, is also essential and probably includes the origin of replication. A 181-bp DNA fragment containing this region was sufficient to allow replication in Lactococcus if the trans-acting protein was provided on another replicon. Single-stranded replication intermediates could not be detected, suggesting that the citrate plasmid uses theta replication rather than rolling-circle replication.     

Short period leaf movements in Oxalis regnellii

Oxalis regnellii Mig. is a trifoliate plant, and the three leaflets usually show synchronized up and down movements with a circadian period of 26–27 h. The three leaflets can also perform desynchronized ultradian oscillations, and we report on such rhythms under different conditions. A study of the occurrence of ultradian leaf movement rhythms as a function of irradiance is presented. At an irradiance of approximately 1 μW cm⁻², the occurrence was maximal and ca 30%. The periods varied from 5 to 15 h. Four other cases of ultradian rhythms in different conditions are also presented. In one case spontaneous ultradian rhythms occurred, and in another, two of the leaflets showed ultradian rhythms when the third leaflet had received a light pulse. In two more cases, the three leaflets on a leaf were separated by physical cuts along the petiole between the pulvini; in both cases the period was approximately 5 h. Possible mechanisms to explain the ultradian rhythms in Oxalis regnelli are discussed.     

Phosphate transport in mitochondria: Past accomplishments,present problems,and future challenges

The requirement of inorganic phosphate (P_i) for oxidative phosphorylation in eukaryotic cells is fulfilled through specific P_i transport systems. The mitochondrial proton/phosphate symporter (P_ic) is a membrane-embedded protein which translocates P_i from the cytosol into the mitochondrial matrix. P_ic is responsible for the very rapid transport of most of the P_i used in ATP synthesis. During the past five years there have been advances on several fronts. Genomic and cDNA clones for yeast, bovine, rat, and human P_ic have been isolated and sequenced. Functional expression of yeast P_ic in yeast strains deficient in P_i transport and expression inEscherichia coli of a chimera protein involving P_ic and ATP synthase subunit have been accomplished. P_ic, in contrast to other members of the family of transporters involved in energy metabolism, was demonstrated to have a presequence, which optimizes the import of the precursor protein into mitochondria. Six transmembrane segments appear to be a structural feature shared between P_ic and other mitochondrial anion carriers, and recent-site directed mutagenesis studies implicate structure-functional relationships to bacteriorhodopsin. These recent advances on P_ic will be assessed in light of a more global interpretation of transport mechanism across the inner mitochondrial membrane.     

Evidence for the Colonization of Lactic Acid Bacteria in the Gastrointestinal Tract of Suckling Mink

Lactic acid bacteria are considered indigenous members of the gastrointestinal microflora in a number of animal species (Savage 1977a). Some intestinal strains of lactobacilli and streptococci are aWe to adhere to stratified squamous epithelium of some animals (Tannock et al. 1987), in the non-secreting part of the stomach of piglets (Barrow et al. 1980, Fuller et al. 1978) and rodents (Tannock et al. 1982), and in the crop of poultry (Fuller 1978). The presence of lactic acid bacteria in the digestive tract is believed to be of beneficial value to the host animal (Fuller 1989). The production of organic acids in the stomach or the crop helps maintaining a low pH which may be important for inhibiting the colonization of potentially pathogenic bacteria, particularly in the newborn animal (Barrow et al 1980, Fuller 1977, Fuller 1978). The adhesion of lactobacilli to squamous epithelium is host specific: strains capable of adhering to the epithelium of piglets are usually not able to adhere in rodents or poultry and vice versa (Fuller 1978, Lin & Savage 1984, Tannock et al 1982). Adhesion of lactic acid bacterial strains to other epithelia than stratified squamous epithelium has been reported. Thus, the attachment of lactobacilli to cells from the secreting epithelium of the murine stomach (Kotarski & Savage 1979), to intestinal cells of humans (Goldin & Gorbach 1987), and to columnar epithelial cells of piglets and calves (Mäyrä-Mäkinen et al 1983) has been demonstrated using in vitro methods. In another study the in vivo attachment of Enterococcus faecium to duodenal epithelium of gnotobi-otic chickens was demonstrated (Fuller et al 1981). Recent research indicated that in adult mink lactic acid bacteria are not indigenous members of the intestinal flora, and they do not attach to epithelium in any part of the gastrointestinal tract (Federsen & Jørgensen 1992). The present paper presents evidence that Gram positive cocci may colonize the gut of suckling mink kits and attach to the gut mucosa.