Effects of fish predation and habitat type on stream benthic communities

The influence of habitat on interactions between a fish predator (brown trout Salmo trutta) and a benthic invertebrate community was studied in nine field enclosures (8 ×3 m) in a creek in southern Sweden. Three habitat treatments were tested, a shallow sandy habitat, a deep habitat containing a mixture of large and small cobbles and a moderately deep habitat with large cobbles. The one month-long experiment showed that there were no major differences in the abundance and biomass of the benthic macroinvertebrate fauna among these habitats as no functional groups of invertebrates and only a few taxa differed between treatments. Invertebrate drift rates decreased over time, which was probably related to seasonal changes in invertebrate life cycles or to effects of predation independent of habitat type, as there was no difference between treatments.     

X-linked progressive mixed deafness: a new microdeletion that involves a more proximal region in Xq21.

We report a large two-generation pedigree with seven affected males segregating for an X-linked mixed conductive sensorineural deafness. The patients present with atypical Mondini-like dysplasia, dilated petrous facial canal, dilatation of the internal auditory meatus fully connected with enlarged cochlear canals, and, in one patient, a wide bulbous posterior labyrinth. Obligatory carrier females are mildly affected. Molecular characterization of this family revealed a deletion of locus DXS169, in Xq21.1. Loci DXS72 and DXS26, which, respectively, flank DXS169 proximally and distally, were intact. Since a gene responsible for X-linked progressive mixed deafness with perilymphatic gusher (DFN3) has previously been assigned by deletion mapping to a slightly more distal interval between DXS26 and DXS121, this study indicates either two different deafness genes or the involvement of a very large region in Xq21.     

A topoisomerase II cleavage site is associated with a novel mitochondrial DNA deletion

Mitochondrial myopathies and encephalopathies can be caused by nucleotide substitutions, deletions or duplications of the mitochondrial DNA (mtDNA). In one such disorder, Kearns-Sayre Syndrome (KSS), large-scale hetero-plasmic mtDNA deletions are often found. We describe a 14-year-old boy with clinical features of KSS, plus some additional features. Analysis of the entire mitochondrial genome by the polymerase chain reaction and Southern blotting revealed a 7864-bp mtDNA deletion, heteroplasmic in its tissue distribution. DNA sequencing established that the deletion was between nucleotides 6238 and 14103, and flanked by a 4-bp (TCCT) direct repeat sequence. Deletions between direct repeats have been hypothesised to occur by a slipped-mismatching or illegitimate recombination event, or following the DNA cleavage action of topoisomerase II. Analysis of the gene sequence in the region surrounding the mtDNA deletion breakpoint in this patient revealed the presence of putative vertebrate topoisomerase II sites. We suggest that direct repeat sequences, together with putative topoisomerase II sites, may predispose certain regions of the mitochondrial genome to deletions.     

New chromosomal translocations correlate with specific immunophenotypes of childhood acute lymphoblastic leukemia

Cytogenetic analysis of leukemic cells obtained at diagnosis from 122 patients with childhood acute lymphoblastic leukemia (ALL) disclosed chromosomal translocations in 36 cases. Two new nonrandom translocations were identified and found to be associated with specific immunophenotypes of the disease. The first, identified in 4 of 16 cases of T-cell ALL positive for sheep erythrocyte receptors (E+), involved the short arm (p) of chromosome 11 and the long arm (q) of chromosome 14 and was designated t(11;14) (p13;q13). The second, found in 7 of 23 cases with a pre-B-cell phenotype, involved the long arm of chromosome 1 and the short arm of chromosome 19; it was designated t(1;19) (q23;p13.3). A third abnormality involving a common breakpoint on chromosome 12 (band p 12) was also identified. These two new differentiation-specific translocations suggest a mechanism for aberrant expression of genes that influence lymphoid cell growth and development, as well as leukemogenesis.     

The passage of orally fed proteins from mother to foetus in the rat

Pregnant rats were orally fed with a mixture of bovine IgG, bovine albumin, ovalbumin and beta-lactoglobulin. Using immunoprecipitation methods, these proteins were detected in the maternal blood serum, urine and uterine fluids, and also in the foetal blood serum and the amniotic fluid. The results imply that a variety of dietary proteins, still immunoprecipitable, are able to cross the materno-foetal barriers to be detected in the foetal circulation, where they may influence the maturation of the immune system of the foetus.     

Construction of Texas coastal foredunes with sea oats (Uniola paniculata) and bitter panicum (Panicum amarum)

Studies were conducted on Padre Island, Texas since 1968 to provide specifications for how to use vegetation to reconstruct destroyed portions of foredunes of Gulf Coast barrier islands. The area has a subtropical, semi-arid climate, moderated by maritime tropical air from the Gulf of Mexico. Annual precipitation averages 670 mm for the island. We established experimental foredunes in broad overwash areas, 1.5 m M.S.L. where foredunes were eroded by hurricanes or destroyed by blowouts and across hurricane overwash channels of lower elevation behind the berm and more susceptible to surges. Most successful establishment of a vegetated dune was by transplanting directly onto the level backbeach to reestablish the original duneline about 125 meters inland. Sea oats and bitter panicum proved best of all species tested. Bitter panicum was the more desirable because of higher transplant survival, a longer planting season, and ease of harvest. Transplant survival was influenced more by soil salinity, soil moisture, and plant vigor, than by planting season as successful plantings occurred during all seasons. December through February plantings were best for sea oats, but survival of bitter panicum transplants different little from November through May. Both species are capable of growth year round during periods of favorable climatic conditions, although little growth occurs from mid-December to mid-February. Transplants placed 0.6 m apart with total planting width of 15 m produced foredunes nearly 6 m high in 6 years. Such plantings trapped sand at the rate of 12.5 m³/m of beach. In hurricane overwash channels, we used 0.6 m high sand fence placed 3 m apart to produce a flat topped dune free of salt for a planting surface. Without this site preparation, no transplants survived due to high soil salinity. Dune width was effectively widened by planting a strip 15 m wide immediately beachward of a previously established 4-year old dune.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, USA.     

Modified procedure for the recovery of naturally accumulated poliovirus from oysters.

Methods were compared for their ability to recover poliovirus from oysters (Crassostrea gigas) which had been allowed to accumulate virus via normal filtration activities. Clarification procedures included glycine-NaCl and polyelectrolyte extraction methods followed by a variety of acid precipitation concentration methods. Polyelectrolyte flocculation followed by a beef extract-supplemented acid precipitation carried out at pH 3.5 yielded the most efficient recoveries. Direct assay of homogenates was found to be an unreliable method for determining the initial virus concentration in "naturally infected" oysters.     

HE TURNOVER RATE OF TUBULIN IN RAT BRAIN

The turnover rate of tubulin in rat brain was determined from the decay in specific radioactivity of the protein after pulse-labeling. When precursors were administered by a parenteral route, the shortest half-life, 9.8 days, was obtained with [¹⁴C]NaHCO₃; the longer half-lives obtained with [U-¹⁴C]glucose or [4,5-³H]leucine suggest significant reutilization of label. Furthermore, with leucine as precursor maximal specific radioactivity of tubulin was not obtained until eight days after administration of label. Labeling and decay kinetics obtained with [4,5-³H]leucine were markedly different when the isotope was administered directly into the lateral ventricle. The difference between the turnover rates of the -α and β subunits of tubulin purified by means of high resolution polyacrylamide gel electrophoresis was not statistically significant. A half-life for tubulin of 6.2 days was measured by continuous intravenous infusion of [U-¹⁴C]tyrosine.     

Fusion of neurohypophyseal membranes in vitro

Freeze cleaving electron microscopy has shown that fusion of isolated secretory vesicles from bovine neurohypophyses was induced by Ca²⁺ in micromolar concentrations. Mg²⁺ and Sr²⁺ were ineffective. Mg²⁺ inhibited Ca²⁺-induced fusion.In suspensions containing secretory vesicles as well as sheets of cell membrane, release of vasopressin parallel to intervesicular fusion of secretory vesicles with sheets of cell membrane was observed after exposure to Ca²⁺. Mg²⁺ and Sr²⁺ were ineffective in replacing Ca²⁺ as trigger for fusion or vasopressin release.Intervesicular fusion and exocytotic profiles were observed when isolated neurohypophyses or neurosecretosome were exposed to cold.