Identification of a complex of the three forms of the rat liver asialoglycoprotein receptor

We have generated antibodies against synthetic peptides which represent the carboxyl terminus of either the major, or the two minor, forms of the rat hepatic lectin which recognizes galactose-terminated glycoproteins (asialoglycoproteins). The antibodies were shown to be specific for the form of the lectin containing the immunizing peptide sequence by the following: reaction with purified lectin after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoprecipitation of sodium dodecyl sulfate-denatured lectin, immunoprecipitation of lectin synthesized in vitro. These antibodies, however, precipitated all three rat hepatic lectin forms from nonionic detergent extracts of hepatocytes labeled with 125I via the lactoperoxidase catalyzed technique. A similar result was obtained if antibody was bound to intact cells prior to solubilization with detergent and collection of the immune complexes. We conclude that at least the plasma membrane-associated fraction of the rat hepatic lectin forms exists as a heterotypic complex.     

Round robin investigation of methods for recovering human enteric viruses from sludge

To select a tentative standard method for detection of viruses in sludge the American Society for Testing and Materials D19:24:04:04 Subcommittee Task Group initiated round robin comparative testing of two procedures that, after initial screening of several methodologies, were found to meet the basic criteria considered essential by the task group. Eight task group member laboratories agreed to perform round robin testing of the two candidate methods, namely, The Environmental Protection Agency or low pH-AlCl3 method and the Glass or sonication-extraction method. Five different types of sludge were tested. For each particular type of sludge, a single laboratory was designated to collect the sludge in a single sampling, make samples, and ship it to the participating laboratories. In most cases, participating laboratories completed all the tests within 48 h of sample arrival. To establish the reproducibility of the methods, each laboratory tested each sludge sample in triplicate for the two candidate virus methods. Each processed sludge sample was quantitatively assayed for viruses by the procedures of each individual round robin laboratory. To attain a more uniform standard of comparison, a sample of each processed sample from all laboratories was reassayed with one cell line and passage number by a single laboratory (Environmental Protection Agency Environmental Monitoring and Support Laboratory, Cincinnati, Ohio). When the data were statistically analyzed, the Environmental Protection Agency method was found to yield slightly higher virus recoveries for all sludge types, except the dewatered sludge. The precisions of both methods were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chromatid damage induced by fluorescent light during G2 phase in normal and Gardner syndrome fibroblasts. Interpretation in terms of deficient DNA repair

Skin fibroblasts from Gardner syndrome (GS) compared with those from normal donors showed a significantly higher incidence of chromatid gaps and breaks following exposure to low-intensity, cool-white fluorescent light during G2 phase of the cell cycle. Considerable evidence supports the concept that chromatid gaps and breaks seen directly after exposure to DNA-damaging agents represent unrepaired DNA single- and double-strand breaks respectively. The changes in incidence of chromatid aberrations with time after light exposure are consistent with the sequence of events known to follow DNA damage and repair. Initially, the incidence of light-induced chromatid gaps was equivalent in GS and normal fibroblasts. In the normal cells, the chromatid gaps disappeared by 1 h post-exposure, presumably as a result of efficient repair of DNA single-strand breaks. In contrast, the incidence of gaps increased in GS cells by 0.5 h followed by a decrease at 1 h and concomitant increase in chromatid breaks. It appears from these findings that the increased incidence of chromatid damage in GS fibroblasts results from deficient repair of DNA single-strand breaks which arise from incomplete nucleotide excision of DNA damage during G2 phase.     

Aphanizomenon ovalisporum (Forti) in Lake Kinneret, Israel

The filamentous cyanobacterium Aphanizomenon ovalisporum wasobserved for the first time in Lake Kinneret in August 1994and formed a prominent bloom from September through October.Aphanizomenon ovalisporum reappeared in diminished amounts inthe summer and fall of 1995. These events are the first recordof significant quantities of a potentially toxic nitrogen-fixingcyanobacterium in this lake. No definite provenance of inoculumhas been identified, although A.ovalisporum was also observedin a newly reflooded area (Lake Agmon) in the catchment. Unusuallyhigh water temperatures and low wind inputs were observed priorto and during the A.ovalisporum bloom period. These, togetherwith possibly enhanced availability of phosphorus or other growthfactors, may have contributed to the cyanobacterium growth in1994. Phosphorus limi tation, as indicated by high cellularalkaline phosphatase activity, the onset of stormy conditionsand a fall in water temperatures led to the demise of the 1994bloom. Although the A. ovalisporum bloom in 1994 had no seriousdirect impact on water quality, the continued presence of apotentially toxic cyanobacterium in Lake Kinneret, a major nationalwater supply source, is a cause for serious concern.     

Phosphoenzyme conformational states and nucleotide-binding site hydrophobicity following thiol modification of the Ca2+-ATPase of sarcoplasmic reticulum from skeletal muscle

Enhanced fluorescence of the ATP analogue 2',3'-O-(2,4,6-trinitrocyclohexyldienylidine)adenosine 5'-triphosphate (TNP-ATP), bound to the Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum, is closely related to phosphoenzyme levels (Bishop, J. E., Johnson, J. D., and Berman, M. C. (1984) J. Biol. Chem. 259, 15163-15171) and has an emission maximum consistent with decreased polarity of the TNP-ATP-binding site. The phosphoenzyme conformation responsible for increased nucleotide-binding site hydrophobicity has been studied by redistribution of phosphoenzyme intermediates following specific thiol group modification. N-Ethylmaleimide, in the presence of 50 microM Ca2+, 1 mM adenyl-5'-yl imidodiphosphate, pH 7.0, at 25 degrees C for 30 min, selectively modified the SH group essential for phosphoenzyme decomposition, which resulted in decreased ATPase activity, Ca2+ uptake, and a decrease in ATP-induced TNP-ATP fluorescence. Phosphorylated (Ca2+, Mg2+)-ATPase levels from [gamma-32P] ATP remained relatively unaffected (3.1 nmol/mg), but the ADP-insensitive fraction decreased from 56 to 15%. Phosphoenzyme levels from 32Pi were also decreased to the same extent as turnover, with equivalent loss of Pi-induced TNP-ATP fluorescence. The E1 to E2 transition, as monitored by the change in intrinsic tryptophan fluorescence, was unaffected. Modification of thiol groups of unknown function did not modify turnover-induced TNP-ATP fluorescence. It is concluded that the ADP-insensitive phosphoenzyme, E2-P, is responsible for enhanced TNP-ATP fluorescence. This suggests that the conformational transition, 2Ca2+outE1 approximately P----2Ca2+inE2-P, is associated with altered properties of the noncatalytic, or regulatory, nucleotide-binding site.     

Natural populations of bacteria in Lake Kinneret: Observations with scanning electron and epifluorescence microscopy

The bacterioplankton assemblage in Lake Kinneret, Israel, sampled on 6 occasions representative of different seasonal conditions was studied with scanning electron microscopy (SEM) and epifluorescence microscopy after acridine-orange staining. In near-surface (1–3 m) samples taken in October 1981 and March 1983, several unusual types of budding, appendaged, and filamentous cells were found. During lake stratification, typical large anaerobic forms (including photosynthetic green sulphur bacteria) were observed in samples from the metalimnion and deep (40 m) hypolimnion. Epifluorescence counts indicated that bacteria in the water column ranged from 0.55 to 2.67 × 10⁶ cells ml^–1.     

Phytoplankton assemblages in the deep chlorophyll maximum layers off the Mediterranean coast of Israel

Phytoplankton assemblages in the deep chlorophyll maximum andnear-surface layers were compared at seven stations in the inshoreand offshore waters of the Mediterranean coast of Israel. Thestudy included the entire spectrum of taxonomic categories overa wide size range, comprising the nano/pico phytoplankton componentsdown to 1 µm and the larger phytoplankters consistingprimarily of diatoms and dino-flagellates. The coccolithophorids<20 µm and the monads constituted the most abundantcomponents of the phytoplankton at the deep chlorophyll maximum(DCM) and near surface layer. Certain individual species, mainlypennate diatoms and smaller dinoflagellates, seemed to adaptto the DCM to form a characteristic association.