Impaired phagocytosis by the mononuclear phagocytic system in sapphire mink affected with Aleutian disease

The phagocytic function of the mononuclear phagocytic system (MPS) in normal sapphire mink and in sapphire mink affected with experimental Aleutian disease was compared. Clearance from blood of carbon particles or 125I-labeled microaggregated human serum albumin, and subsequent measurement of radioactivity in phagocytic organs indicated profound MPS blockade in mink affected with advanced Aleutian disease. In contrast, MPS activity in mink in the early stage of the disease was comparable to that of normal mink. It is suggested that the MPS blockade may be responsible for some pathologic changes in Aleutian disease.     

Use of antidepressants among people committing suicide in Sweden.

OBJECTIVE--To analyse the outcome of depression in the Swedish population as reflected by the detection of antidepressants in a national forensic toxicological screening programme of unnatural deaths. DESIGN--Antidepressants detected by the National Laboratory of Forensic Chemistry were related to data on use expressed in person years of exposure. SUBJECTS--All 7000 cases of unnatural death with results from forensic toxicological screening in 1990-1; this included 3400 (85%) of the 4000 cases of suicide in Sweden. MAIN OUTCOME MEASURES--Number of findings of antidepressants in the screening programme and number of findings of different antidepressants in relation to their use. RESULTS--Antidepressants were found in 585 screening tests, corresponding to 542 subjects or less than 16% of the 3400 cases of suicide. Newer, less toxic antidepressants were found more often than the older compounds. Toxic concentrations of antidepressants were found in only 190 cases (5.6%). CONCLUSION--A consistent finding in surveys of suicide is that about half of the patients who commit suicide are depressed. The current data suggest that most depressed patients who commit suicide are not taking antidepressants immediately before death. Therapeutic failure may be a greater problem with antidepressants than toxicity as the results did not indicate any advantage of the newer, less toxic antidepressants. All causes of death should be included in risk analyses, thereby providing an estimate of effectiveness as well as toxicity of antidepressants.     

Localization of a multifunctional chaperonin (GroEL protein) in nitrogen-fixing Anabaena PCC 7120

The occurrence and distribution of a multifunctional chaperonin-60 (cpn60), the GroEL protein, was demonstrated in the cyanobacterium Anabaena PCC 7120 by using a rabbit anti-GroEL (Escherichia coli) antibody. Western-blot analysis showed a distinct cross-reaction with a protein of approx. 65 kilodaltons, analogous to the Mr of the E. coli homologue. Immunocyto-chemical studies of vegetative cells showed that a chaperonin was localized in both vegetative cells and heterocysts. In vegetative cells cpn60 was primarily detected both in the carboxysomes, and in the cytoplasm, though mainly in the thylakoid region of the latter. In heterocysts, specialized cells for nitrogen fixation, the cpn60 label was prominent and was evenly distributed throughout the cell. These results support recent findings that chaperonins are multifunctional proteins, and extend those findings by demonstrating the occurrence of cpn60 in a prokaryotic cyanobacterium and by raising the possibility of the involvement of this chaperonin in the assembly of heterocystous proteins.Abbreviations cpn60 chaperonin-60 - Mr relative molecular mass - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase     

Isolation of nifH and part of nifD by modified capture polymerase chain reaction from a natural population of the marine cyanobacterium Trichodesmium sp.

Abstract A modified capture polymerase chain reaction (CPCR) technique was used to isolate the entire sequence of the nifH gene and its flanking regions from a natural population of Trichodesmium sp. A set of specific CPCR primers derived from a known 72-bp DNA segment of the nifH sequence permitted isolation of both the upstream and the downstream region of Trichodesmium sp. nifH . The 882-bp nifH gene presented here is the first full-length gene isolated from Trichodesmium sp. A sequence similar to a nif -like promoter was found in front of nifH . The nifH open reading frame of Trichodesmium sp. encoded 294 amino acids. Comparative analysis of the Trichodesmium sp. NifH sequence revealed strong similarity with 23 known NifH proteins. Amino acids postulated to be involved in binding of the 4Fe:4S cluster and those subjected to ADP-ribosylation were present. An open reading frame for the nifD gene was identified 189 bp downstream of nifH . A sequence similar to the consensus of the nif -like promoter was also found in front of nifD .     

Characterization of photodamage to escherichia coli in optical traps

Optical tweezers (infrared laser-based optical traps) have emerged as a powerful tool in molecular and cell biology. However, their usefulness has been limited, particularly in vivo, by the potential for damage to specimens resulting from the trapping laser. Relatively little is known about the origin of this phenomenon. Here we employed a wavelength-tunable optical trap in which the microscope objective transmission was fully characterized throughout the near infrared, in conjunction with a sensitive, rotating bacterial cell assay. Single cells of Escherichia coli were tethered to a glass coverslip by means of a single flagellum: such cells rotate at rates proportional to their transmembrane proton potential (. J. Mol. Biol. 138:541-561). Monitoring the rotation rates of cells subjected to laser illumination permits a rapid and quantitative measure of their metabolic state. Employing this assay, we characterized photodamage throughout the near-infrared region favored for optical trapping (790-1064 nm). The action spectrum for photodamage exhibits minima at 830 and 970 nm, and maxima at 870 and 930 nm. Damage was reduced to background levels under anaerobic conditions, implicating oxygen in the photodamage pathway. The intensity dependence for photodamage was linear, supporting a single-photon process. These findings may help guide the selection of lasers and experimental protocols best suited for optical trapping work.     

Active muscle and whole body lactate kinetics after endurance training in men.

We evaluated the hypotheses that endurance training decreases arterial lactate concentration ([lactate](a)) during continuous exercise by decreasing net lactate release () and appearance rates (R(a)) and increasing metabolic clearance rate (MCR). Measurements were made at two intensities before [45 and 65% peak O(2) consumption (VO(2 peak))] and after training [65% pretraining VO(2 peak), same absolute workload (ABT), and 65% posttraining VO(2 peak), same relative intensity (RLT)]. Nine men (27.4 +/- 2.0 yr) trained for 9 wk on a cycle ergometer, 5 times/wk at 75% VO(2 peak). Compared with the 65% VO(2 peak) pretraining condition (4.75 +/- 0.4 mM), [lactate](a) decreased at ABT (41%) and RLT (21%) (P < 0.05). decreased at ABT but not at RLT. Leg lactate uptake and oxidation were unchanged at ABT but increased at RLT. MCR was unchanged at ABT but increased at RLT. We conclude that 1) active skeletal muscle is not solely responsible for elevated [lactate](a); and 2) training increases leg lactate clearance, decreases whole body and leg lactate production at a given moderate-intensity power output, and increases both whole body and leg lactate clearance at a high relative power output.     

CHARACTERIZATION AND COMPARISON OF PROKARYOTIC EPIPHYTES ASSOCIATED WITH THREE EAST AFRICAN SEAGRASSES1

Prokaryotic epiphytes on leaves of three seagrass species, Thalassodendron ciliatum, Thalassia hemprichii, and Cymodocea rotundata, from two Kenyan coastal sites, Nyali (a high‐nutrient site) and Vipingo (a low‐nutrient site), were characterized genetically and morphologically. Denaturing gradient gel electrophoresis (DGGE) and clone libraries of PCR‐amplified 16S rRNA gene fragments were used to study prokaryotes associated with these seagrasses. In general, the epiphytic coverage was greater in the high‐nutrient site, while the microbial diversity was linked to seagrass species rather than the study sites. Cytophaga–Flavobacteria–Bacteroides (CFB) were associated with T. ciliatum and T. hemprichii mainly in the nutrient‐poor site, while α‐, β‐, and γ‐proteobacteria were associated with all three species at the two study sites. Some bacteria phylotypes were closely related to sequences of microorganisms previously recovered from wastewaters or other contaminated sources, indicating the influx of land‐based wastes into these coastal lagoon ecosystems. The abundance of potential nitrogen (N₂)‐fixing cyanobacteria on C.  rotundata, particularly in the low‐nutrient site, suggested that this association may have been acquired to meet N demands. Unicellular cyanobacteria were dominant and associated with C. rotundata and T. hemprichii (with those on T. hemprichii being closely related to cyanobacterial symbiotic species), while T. ciliatum was almost devoid of cyanobacterial associations at the same site (Nyali), which suggests specificity in the cyanobacteria–seagrass associations. The abundance of prokaryotic epiphytes was considered to be linked to water depth and tidal exposure.     

Mapping and cloning of a fla-che region of the Rhizobium meliloti chromosome.

We constructed a genetic map of the fla-che region of the Rhizobium meliloti chromosome using cotransduction with bacteriophage phi M12. Several other chromosomal markers located in the general area are included in the map. We isolated plasmids carrying wild-type DNA inserts that complement the mapped mutations from a genomic library carried in the broad-host-range vector pLAFR1. The complementation data obtained from the clones confirmed the contransduction map and clarified the exact order of several of the behavioral genes. A restriction map of this area was developed by using the cloned DNA. One of the five individual EcoRI fragments subcloned from the original clones complemented two of the behavioral mutations.