Experimental analysis of the thermal and salinity preferences of glass-eels, Anguilla anguilla (L.), before and during the upstream migration

During their upstream migration European glass-eels, Anguilla anguilla (L.), encounter a series of varying environmental situations. The migration requires a sequence of physiological adaptations determined by the different chemico-physical conditions they meet. Temperature and salinity are two of the most important factors. It is reasonable that glass-eels may utilize them as cues to orientation. Laboratory experiments were designed to elucidate the thermal and salinity preferences of glass-eels. These were assessed by examining the choices of specimens caught either at sea and then kept in salt water (33%), or in the Arno river and then reared in fresh water. Water flows, triggering the rheotactic reaction, prompted glass-eels to choose between two different salinities and/or temperatures. The results confirm the preference of glass-eels for flows whose temperature does not differ from that of acclimation. Specimens tested towards two water flows, both at different temperatures from that of acclimation, preferred the colder. Fresh water was usually preferred to salt water, this preference being not so marked in the case of the glass-eels caught at sea and thus not yet adapted to fresh water. Clear-cut choices were recorded when one of the tested flows presented both the preferred temperature and preferred salinity. When only one of the two parameters reproduced the preferred situation, the choices were differently affected by temperature and salinity at different values of temperature. When the temperature of both flows was below 11–12°C, glass-eels preferred fresh water; at higher temperatures the colder of the two flows was preferred, even if salty.     

cDNA cloning of a calcineurin B homolog in Saccharomyces cerevisiae.

We have isolated a cDNA clone encoding a homolog of mammalian calcineurin B (the regulatory subunit of calmodulin-dependent protein phosphatase) by screening a cDNA expression library of Saccharomyces cerevisiae with antiserum against bovine calcineurin B. The yeast calcineurin B homolog (YCNB) is composed of 175 amino acids with a calculated molecular mass of 19,639 daltons and contains four putative Ca(2+)-binding domains. The amino-acid alignment of YCNB with human calcineurin B demonstrates 53% sequence identity and 82% homology. Southern blot analysis indicates that the gene for YCNB is a single-copy gene. Thus, yeast calmodulin-dependent protein phosphatase apparently has a heterodimeric structure similar to that of the enzyme in mammalians.     

Monoclonal proliferation of Friend murine leukemia virus-transformed myeloblastic cells occurs early in the leukemogenic process.

Integrated Friend murine leukemia virus copies were analyzed by the Southern blotting procedure in myeloblastic cell lines obtained after in vitro infection of long-term mouse bone marrow cultures. Several steps leading to the generation of malignant myeloblastic cells after a long latency period were observed in the evolution of infected cultures. Shortly after infection, a random distribution of integrated provirus copies was observed in the DNA of normally differentiating myeloid cells. In contrast, a distinct pattern of integrated Friend murine leukemia virus copies was evident in the first non-differentiating immature myeloblastic cells appearing in cultures, suggesting a monoclonal origin of these cells. For each cell line, characteristic hybridizing fragments were conserved during the 1-year culture period necessary for the acquisition of tumorigenic properties and were also observed in tumors grafted in vivo. We can conclude that monoclonality is effective very early in the myeloid transformation process, as soon as the precursor cells are blocked in their differentiation.     

Characterization of the smtA gene encoding an S-adenosylmethionine-dependent methyltransferase of Escherichia coli

Abstract The mukB operon is located at 21 min on the Escherichia coli chromosome and seems to consist of four genes, orf30 ( smtA ), mukF , mukE , and mukB . Based on sequence similarity, the promoter-proximal gene, orf30 ( smtA ), could encode an S-adenosylmethionine-dependent methyltransferase. The smtA gene is not essential for cell growth and its expression is positively regulated by H-NS, an Escherichia coli histone-like protein.     

Molecular Characterization of Mycobacterium avium Complex Isolates from Caribbean Patients by DT1/DT6-PCR,Nonradioactive Southern Hybridization,and the Accuprobe System

A genetic fingerprinting analysis of Caribbean isolates of M. avium complex (MAC) from AIDS patients by a Southern blotting technique after Pstl digestion with nonradioactive DNA probes coding for single-copy sequences DT1 and DT6 was performed. In parallel, a selective amplification of a 187-bp fragment within the DT6 sequence with AV6/AV7 primers for Mycobacterium avium and of a 666-bp fragment within the DT1 sequence of M. intracellulare with the IN38/IN41 primers was also performed, and the molecular speciation with these two methods was compared with results obtained with DNA probes of the Accuprobe system. 66 strains investigated comprised 31 international reference isolates of MAC belonging to serovars 1–28 and 42–44, and 35 clinical isolates including 24 strains from Caribbean AIDS patients. 91.43% of the clinical isolates tested gave concordant data with the DT1/DT6 Southern hybridization and PCR as compared with 74.28% for PCR and Accuprobe, and 71.43% for Accuprobe and Southern hybridization. Our results corroborated previous findings showing that the DT1 probe was specific for M. intracellulare, whereas the DT6 probe was specific for M. avium (reference serovars 2 and 3 probed positive both with DT1 and DT6 probes). Contrary to DT1 probe, which did not reveal sufficient polymorphism to discriminate between MAC isolates, DT6 probe showed an interesting polymorphism giving four distinct clusters. Three clusters corresponded to profiles previously reported for reference and/or clinical isolates; however, a fourth cluster was discovered in five Caribbean isolates from four AIDS patients that did not correspond to previously published genetic patterns. When probed with the insertion sequence IS1245, this cluster retained its homogeneity. Received: 9 May 1996 / Accepted: 10 June 1996     

Carboxyl terminal region of the MukB protein in Escherichia coli is essential for DNA binding activity

Abstract The purified MukB protein of Escherichia coli has DNA binding activity and nucleotide binding activity. We have isolated a mutation, mukB1013 , causing a substitution of valine at position 1379 to leucine. This mutant MukB protein was defective for DNA binding, while the ATP binding activity remained unaffected. A truncated MukB protein that is short of 109 amino acids from the C-terminus failed to bind DNA.     

Cytogenetic analysis of a self-fertilizing fish, Rivulus marmoratus: remarkable chromosomal constancy over a vast geographic range.

The aplocheiloid killifish Rivulus marmoratus is the only known self-fertilizing hermaphroditic vertebrate. Most natural populations consist almost entirely of hermaphrodites and comprise arrays of homozygous clones. However, in almost all populations thus far studied, clonal variation, as detected with molecular techniques, is very high. A karyological survey was carried out on specimens from Brazil, the Bahamas, Belize, and Florida (4 locales) by C-banding, silver staining, and fluorescent staining. The chromosome complement of R. marmoratus is surprisingly uniform over its vast geographic range, in terms of both chromosome number and morphology, heterochromatin distribution and composition, and nucleolar organizer region (NOR) distribution. The short arms of chromosome pair 15, where NORs are located, showed the only variation detected in this study: those of pattern A were consistently shorter than those of pattern B; moreover, the latter show positive heteropycnosis with Giemsa staining. The present data demonstrate that chromosomal variation is not a significant part of the clonal divergence in this species, even though its breeding system, by forming homozygotes for new rearrangements almost immediately, should make that variation easier to detect. The high chromosomal homogeneity is discussed in the light of the peculiar natural history of the species.     

Cryptic Caribbean species of Scorpaena (Actinopterygii: Scorpaeniformes) suggested by cytogenetic and molecular data

Cytogenetic and molecular analyses enabled identification of two cytotypes among individuals of the spotted scorpion fish Scorpaena plumieri from Margarita Island, Venezuela. Cytotype 1 was characterized by 48 subtelo‐acrocentric chromosomes and fundamental number (number of chromosome arms; FN) equalled 48, while cytotype 2 was characterized by two metacentric and 46 subtelo‐acrocentric chromosomes and FN was 50. These cytotypes also differed in the location of the ribosomal gene clusters and in the distribution of the constitutive heterochromatin. Moreover, fish from the cytotypes 1 and 2 were found to belong to distinct mitochondrial lineages. The presence of two S. plumieri cytotypes from two lineages separated by high genetic distance suggests that they correspond to sympatric cryptic species.