Mouse polyclonal and monoclonal antibody to scrapie-associated fibril proteins.

Antibody response in mice to scrapie-associated fibril proteins (protease-resistant proteins [PrPs]) was generated to different epitopes depending on the source of antigen. Mice responded differently to PrPs isolated from scrapie-infected animals of homologous (mouse) versus heterologous (hamster) species. An enzyme-linked immunosorbent assay established to monitor this antibody response in mice immunized with PrPs was unable to detect such a response in scrapie-infected mice. A monoclonal antibody (MAb), 263K 3F4, derived from a mouse immunized with hamster 263K PrPs reacted with hamster but not mouse PrPs. MAb 263K 3F4 also recognized normal host protein of 33 to 35 kilodaltons in brain tissue from hamsters and humans but not from bovine, mouse, rat, sheep, or rabbit brains. This is the first demonstration of epitope differences on this host protein in different species. The defining of various epitopes on PrP through the use of MAbs will lead to a better understanding of the relationship of PrPs to their host precursor protein and to the infectious scrapie agent.     

Influence of cyclic nucleotides on the processing of the carbohydrate part of the alpha-subunit of human choriogonadotropin by first trimester human placenta tissue

In pulse-chase experiments ([35S]Met as radioactive label) 4 intracellular forms of the alpha-subunit (apparent molecular weights of 11, 16.5, 19.5, and 23.4 kDa) were observed whereas almost no label was incorporated into the beta-subunit. The 23.4 kDa form was secreted as free alpha-subunit, the others were precursors of the alpha-subunit contained in secreted human choriogonadotropin. The rate-limiting step seemed to be the processing of the 19.5 kDa precursor by alpha-mannosidase II. 8-bromo-cAMP increased the total amount of intracellular forms of the alpha-subunit and accelerated significantly the velocity of all glycosylation steps. It seemed to cause a higher efficacy of the alpha-mannosidase II reaction. In the presence of 8-bromo-cAMP intracellular as well as extracellular alpha-subunits showed a higher sialic acid content.     

Feeding postures of suspension-feeding larval black flies: the conflicting demands of drag and food acquisition

Summary We tested whether larval black flies actively control the positioning of their feeding appendages (labral fans), and if so, whether their posture represents a balance between the conflicting demands of drag and feeding. We compared the postures of live larvae with the postures of larvae killed by heat-shock in three different flow regimes in a laboratory experiment; we assumed that the postures of heat-killed larvae approximated a passive response to drag. The average height of the labral fans above the bed declined significantly in faster flows, and was significantly greater in live than dead larvae. There was also a significant interaction effect, since the difference between the fan heights of live and dead larvae was greater in slower flows. Two mechanisms may contribute to this result. Larvae in slower flows have to increase their fan heights more than larvae living in faster flows to achieve comparable increases in velocity and thus particle flux. In addition, muscular strength may limit the feeding postures larvae can assume. The fan heights of live larvae also varied depending on the concentration of food particles: larvae exposed to low food concentrations held their fans higher above the bed than did larvae exposed to high food concentrations in the same flow regime. This change in posture is due neither to an uneven particle concentration in the boundary layer nor to added drag from particles trapped in the labral fans. Collectively, our results indicate that these suspension feeders actively control their feeding posture, and suggest that these varying postures represent a dynamic balance between the conflicting needs of minimizing drag and maximizing feeding.     

Irreversible Activation of the Opiate Receptor of Neuroblastoma × Glioma Hybrid Cells by an Alkylating Benzomorphan Derivative

The benozomorphan derivative (-)-2-[2-(p-bromoacetamidophenyl)ethyl]-5,9 alpha-dimethyl-2'-hydroxy-6,7-benzomorphan (BAB), capable of reacting with nucleophilic groups, acts on neuroblastoma X glioma hybrid cells as a potent, irreversible opiate agonist. Its potency in inhibiting the increase in cellular cyclic AMP, evoked by prostaglandin E1, is comparable to that of Leu-enkephalin. This also applies to its capacity to compete with [3H]D-Ala2-Met-enkephalinamide ([3H]DAEA) in binding on cell membrane preparations. The comparatively lower potency of (-)-2-[2-(p-acetamidophenyl)-ethyl]-5,9 alpha-dimethly-2'-hydroxy-5,7-benzomorphan (AB), which differs from BAB in the substitution of the bromoacetamido group by an acetamido group, is of the same order of magnitude as that of morphine. The covalent interaction of BAB with the opiate receptors is deduced from the observations that (1) it is not possible to wash away this compound from the receptors, (2) the potency of BAB in inhibiting the specific binding of [3H]DAEA increases with prolonged preincubation time, and (3) AB behaves as a reversible agonist.     

EXPERIMENTALLY INDUCED CHROMOSOME ABERRATIONS IN PLANTS : II. THE EFFECT OF CYANIDE AND OTHER HEAVY METAL COMPLEXING AGENTS ON THE PRODUCTION OF CHROMOSOME ABERRATIONS BY X-RAYS

The discovery of Lilly and Thoday, that the presence of potassium cyanide (KCN) increases the production of chromosome aberrations by x-rays in anoxia, but has no effect on the production of chromosome aberrations by x-rays in air, was confirmed. In the presence of cyanide, the effect of a given dose of x-rays in nitrogen was found to be even greater than the effect of the same dose of x-rays in air. The cyanide effect on x-ray breakage in nitrogen was obtained at cyanide concentrations as low as 2 x 10^–5 M. The breakage obtained after the combined x-ray-cyanide treatments was of the x-ray type, as evidenced by the distribution of breaks within and between the chromosomes. A number of other heavy metal complexing agents as well as some other compounds were tested for their ability to increase x-ray breakage in nitrogen and air. Of these compounds only cupferron proved to be effective. The results are discussed and it is concluded that the increased x-ray breakage in the presence of cyanide or cupferron cannot be due to an accumulation of peroxides. Instead it is suggested that the cyanide effect may be due to a complex formation between the active agents and heavy metals, presumably iron, within the chromosomes. The consequences of this hypothesis on the concept of the "oxygen effect," are discussed.     

Separation of the gonadotropic activity of crude choriogonadotropin from the inhibitory effect on lymphocyte transformation.

The effect of choriogonadotropin of different purities on the transformation of peripheral human lymphocytes was studied. Various crude hormone batches inhibited lymphocyte transformation in a dose-dependent manner, both in the mixed lymphocyte reaction and in the phytohemagglutinin-induced stimulation. The inhibitory activity, however, was found not to be correlated with the gonadotropic activity of the crude hormone batches (2660-4300 IU/mg). Choriogonadotropin (13 000 IU/mg), which was purified in 3 steps, showed no inhibitory effect except at high doses (greater than 5000 IU/ml final dilution). More detailed investigations provided evidence that in the first step of the choriogonadotropin purification procedure (batch adsorption of crude choriogonadotropin on SP-Sephadex C-50), the inhibitory activity can be enriched in a fraction (Fract. I) which displays a very low gonadotropic activity (less than 500 IU/mg). A further separation of Fract. I was achieved by isoelectric focusing as well as by chromatography on DEAE-Sephadex A-25. By these means, the inhibitory potency could be enriched more than 100-fold. The substances which display inhibition of DNA synthesis in lymphocytes were proven to act in a nontoxic way. A preliminary characterization of the strongly inhibiting substances which show a dose-dependent suppression of lymphocyte transformation by about 99%, showed that this effect is probably exerted via non-dialysable sialoglycoproteins. By a fourth purification step entailing a chromatography of purified choriogonadotropin (13 000 IU/mg) on SP-Sephadex C-50, a highly purified choriogonadotropin (14000 IU/mg) could be obtained which showed no inhibitory effect on lymphocyte transformation (in both mixed lymphocyte reaction and in phytohemagglutinin-induced stimulation) up to a dose of 43 000 IU/ml. The components which were removed from choriogonadotropin in this step seem to be immunologically identical with the strongly inhibiting substances isolated by isoelectric focusing. These investigations demonstrate that biologically active, highly purified choriogonadotropin is unable to inhibit lymphocyte transformation. The inhibitory activity of crude hormone can be enriched in choriogonadotropin-free fractions. Therefore, it is concluded that the inhibitory activity of crude hormone is not a property of choriogonadotropin itself.     

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.