The inactivation of beta-galactosidase (E. coli) by the carbodiimide reaction

When beta-galactosidase reacted with 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide (EDC), activity was lost. The inhibitor, isopropyl-beta-D-galactopyranoside (IPTG), decreased inactivation. Of 3 nucleophiles tested, incorporation was only decreased in the protected (IPTG added) enzyme when sulfanilic acid was the nucleophile but HPLC profiles of tryptic peptides were identical in protected and unprotected enzyme (except for magnitude). There were also no differences (except for magnitude) of HPLC profiles after 10 and 90 min of reaction and between active (soluble) and inactive (precipitated) enzyme. The data indicate that inactivation is not caused by reaction with a specific active site group. Inactivation probably occurs when a combination of groups are reacted.     

A sequence motif found in a Drosophila heterochromatin protein is conserved in animals and plants.

Modifiers of position-effect-variegation in Drosophila encode proteins that are thought to modify chromatin, rendering it heritably changed in its expressibility. In an attempt to identify similar modifier genes in other species we have utilized a known sequence homology, termed chromo box, between a suppressor of position-effect-variegation, Heterochromatin protein 1 (HP1), and a repressor of homeotic genes, Polycomb (Pc). A PCR generated probe encompassing the HP1 chromo box was used to clone full-length murine cDNAs that contain conserved chromo box motifs. Sequence comparisons, in situ hybridization experiments, and RNA Northern blot analysis suggest that the murine and human sequences presented in this report are homologues of the Drosophila HP1 gene. Chromo box sequences can also be detected in other animal species, and in plants, predicting a strongly conserved structural role for the peptide encoded by this sequence. We propose that epigenetic (yet heritable) changes in gene expressibility, characteristic of chromosomal imprinting phenomena, can largely be explained by the action of such modifier genes. The evolutionary conservation of the chromo box motif now enables the isolation and study of putative modifier genes in those animal and plant species where chromosomal imprinting has been described.     

Selectivity in metabolic cooperation between cultured mammalian cells

Selective communication between cultured mammalian cells was detected as selectivity in metabolic cooperation. Whilst the majority of the cell types examined (human skin fibroblast, PC13, G3, Don, PyY) showed metabolic cooperation at almost all (>95%) of their homotypic cell-to-cell contacts, they did not necessarily show cooperation at such a high proportion of their heterotypic contacts. Less than 10% of G3/human fibroblast contacts, and usually less than 30% of G3/PC13 contacts were observed to be positive for metabolic cooperation. L cells differed from these other cell types in that they formed permeable junctions at a greater proportion of their heterotypic cell-to-cell contacts (contacts between L and PyY cells) than their homotypic contacts. We question why it was that the contacts between any two poorly-compatible cell types were positive for metabolic cooperation in only a small proportion of cases. We could find no indication that this phenomenon was attributable to heterogeneity within the cell stocks. Time course studies upon PC13 and G3 cells showed that the proportion of cooperation-positive contacts was not constant but that it continued to increase over many hours of co-culture. In comparing the homotypic and heterotypic interactions of these cell types, selectivity manifested as a difference in the rate of appearance of permeable junctions. We discuss possible explanations for these findings.     

The differentiation of teratocarcinoma stem cells is marked by the types of collagen which are synthesized.

A cloned line of undifferentiated teratocarcinoma cells (OC15S1) was either maintained as a homogeneous embryonal carcinoma (EC) cell population or was cultured under conditions where the cells differentiated into endoderm-like (END) cells. In this study we examine the synthesis of collagen in both EC and END cells. Cell cultures were incubated with tritiated proline and lysine, and the radioactive collagen secreted into the medium was extracted and purified or immunoprecipitated by antibodies to type IV collagen (Adamson and Ayers, 1979). Radioactive collagens were identified by electrophoretic mobility, by sensitivity to collagenase and to reduction, by insensitivity to pepsin, by cyanogen bromide peptides, and by aminoacid analyses of 3-hydroxyproline, 4-hydroxyproline and proline. OC15S1 EC cells were found to synthesize several collagenous polypeptides, of which 60–70% of the radioactivity was like that of basement membrane (type IV) collagen. Type I-like collagen was the main collagenous product of END cells, but a minor product of EC cells. We concluded that type IV collagen synthesis was suppressed during the differentiation of EC cells to END, while type I-like synthesis was increased. Similarly, other EC cell lines produced mainly type IV-like collagen polypeptides (PC13, F9, PSA1), and following the formation of END cells, two lines produced mainly type I-like collagen polypeptides (PC13, C145b). The type of endoderm formed on embryoid bodies, however, presents an alternate route of differentiation, since immunoperoxidase tests showed that it was synthesizing significant amounts of type IV collagen. We discuss the significance of these findings in relation to a similar change which occurs during normal development.     

Effect of intravenous dextran 70 and pneumatic leg compression on incidence of postoperative pulmonary embolism.

The incidence of pulmonary embolism and deep vein thrombosis was measured in 50 matched pairs of patients undergoing common surgical procedures with preoperative and postoperative ventilation-perfusion lung scans and the fibrinogen uptake test. One patient in each pair was treated with intravenous dextran 70 and pneumatic leggings. The incidence of pulmonary embolism among the treated patients was significantly reduced from 24% to 8%, but the incidence of deep vein thrombosis was not significantly reduced (34% to 24%).     

Role of ultrasonography in diagnosing early rheumatoid arthritis and remission of rheumatoid arthritis - a systematic review of the literature

Introduction

Ultrasonography (US) might have an added value to clinical examination in diagnosing early rheumatoid arthritis (RA) and assessing remission of RA. We aimed to clarify the added value of US in RA in these situations performing a systematic review.

Methods

A systematic literature search was performed for RA, US, diagnosis and remission. Methodological quality was assessed; the wide variability in the design of studies prohibited pooling of results.

Results

Six papers on the added value of US diagnosing early RA were found, in which at least bilateral metacarpophalangeal (MCP), wrists and metatarsophalangeal (MTP) joints were scanned. Compared to clinical examination, US was superior with regard to detecting synovitis and predicting progression to persistent arthritis or RA. Eleven papers on assessing remission were identified, in which at least the wrist and the MCP joints of the dominant hand were scanned. Often US detected inflammation in patients clinically in remission, irrespective of the remission criteria used. Power Doppler signs of synovitis predicted X-ray progression and future flare in patients clinically in remission.

Conclusions

US appears to have added value to clinical examination for diagnosing of RA when scanning at least MCP, wrist and MTP joints, and, when evaluating remission of RA, scanning at least wrist and MCP joints of the dominant hand. For both purposes primarily power Doppler US might be used since its results are less equivocal than those of greyscale US.     

Gastrointestinal torsion in a channel catfish (Ictalurus punctatus)

A case of gastrointestinal torsion with dilatation in a farm-raised channel catfish (Ictalurus punctatus) was examined at the Thad Cochran National Warmwater Aquaculture Center (Stoneville, Mississippi, USA). The affected fish was a gravid female broodfish, which displayed pale gills and a markedly distended abdomen. Internal examination revealed that the gastrointestinal tract and ovaries were rotated around each other four times in a counterclockwise direction as viewed in right lateral recumbency. The catfish had a markedly distended gastrointestinal tract, pale liver, hypoplastic spleen, hypoplastic swim bladder, and high volume of ascitic fluid. Blood analysis indicated multiple abnormalities, including severe anemia and metabolic acidosis. The etiology of the torsion was uncertain; however, the presence of a hypoplastic swim bladder most likely allowed for increased movement of the gastrointestinal tract and ovaries. When examining cases of abdominal distention in fish, gastrointestinal torsion can be considered among the differential diagnoses.