Skin reactivity of unsensitized monkeys upon challenge with staphylococcal enterotoxin B: a new approach for investigating the site of toxin action.

The correlation between skin tests and emetic responses in unsensitized monkeys was used to elucidate the cellular site of action of staphylococcal enterotoxin B (SEB). Evidence is presented that SEB administered intradermally provoked immediate-type skin reactions associated with mild degranulation of cutaneous mast cells. The cytoplasma showed signs of synthetic and metabolic activity, with formation of vesicles and increased prominence of mitochondria. Carboxymethylation of histidine residues of SEB altered the molecule (cSEB) from more alkaline components to more acidic species with increased microheterogeneity. This modification caused a loss in toxicity and completely abrogated the skin-sensitizing activity without changing the immunological specificity. cSEB, however, could compete with SEB for binding sites on the target cell surface. Previously, compound 48/80-treated skin sites behaved refractively to challenge with SEB, indicating that mediators from cutaneous mast cells are required for SEB-induced skin reactions. Skin reactions as well as emetic responses challenged with SEB were completely inhibited by H2 receptor antagonists and calcium channel blockers but not by H1 antihistamine or competitive antagonists of serotonin. This new approach provides a model for investigating the mechanisms of SEB action.     

Observer variability in the histopathological reporting of abnormal rectal biopsy specimens.

AIMS--To study the consistency of reporting of abnormal rectal biopsy specimens, especially in the differentiation of inflammatory bowel disease from other causes of abnormality. METHODS--Sixty rectal biopsy specimens were identified from patients presenting with bloody diarrhoea. These were then circulated to the 11 consultant pathologists in the study who filled in a proforma with a list of 12 diagnostic categories and 22 features. RESULTS--Forty one of the 60 cases were examples of inflammatory bowel disease. In 33 of these cases nine or more pathologists had made the diagnosis. Further categorisation into ulcerative colitis and Crohn''s disease showed better recognition of ulcerative colitis. In the 19 cases of non-inflammatory bowel disease recognition of pseudomembranous colitis and solitary rectal ulcer syndrome was good, but the results were poorer in the case of infective colitis. CONCLUSION--The findings suggest that a group of consultant pathologists can differentiate between inflammatory bowel disease and other causes of an abnormal rectal biopsy specimen and can also recognise pseudomembranous colitis and solitary rectal ulcer syndrome satisfactorily.     

Impaired renal response to parathyroid hormone in potassium depletion.

In potassium depletion, a possible alteration of the proximal tubular response to parathyroid hormone (PTH) was evaluated in rat kidney. 1) There were impairments of both phosphaturic and urinary cyclic AMP responses to PTH. The site of the impairment was further investigated by studying the PTH-dependent cycle AMP system in renal cortex. 2) There was a lesser increase of cyclic AMP concentration by PTH in potassium-depleted slices, indicating the lesser urinary cyclic AMP was due to the specific impairment of PTH-dependent cyclic AMP in the kidney. 3). The activation of adenylate cyclase by PTH was impaired , but phosphodiesterase activity was not affected by potassium depletion, indicating the impairment of cyclic AMP generation was due to inhibition of adenylate cyclase. 4) The phosphaturic response to dibutyryl cyclic AMP infusion was also significantly less in the potassium-depleted animals, indicating the step subsquent to the cyclic AMP generation is also impaired. All above results indicate that, in potassium depletion, the renal response to PTH is impaired, and the impairment is both within the step of cyclic AMP generation and after the cyclic AMP generation.     

Expression of the Bovine Leukemia Virus Envelope Glycoprotein (gp51) by Recombinant Baculovirus and Its Use in an Enzyme-Linked Immunosorbent Assay

The gene encoding the major envelope glycoprotein (gp51) with its signal sequence, represented by an additional NH₂-terminal 33-residue amino acid sequence of bovine leukemia virus (BLV), was inserted into a baculovirus transfer vector. A recombinant virus expressing a secreted gp51 protein in insect cells was isolated. The recombinant gp51 expressed was characterized by using an anti-BLV monoclonal antibody by both Western blotting analysis and enzyme-linked immunosorbent assay (ELISA). The secreted gp51 was used as an antigen, and an ELISA with recombinant gp51 (rgp51) was developed for the detection of BLV antibodies. This new procedure was compared with a previous ELISA method for the detection of BLV antibodies and an agar gel immunodiffusion test performed with an unpurified BLV antigen preparation. The comparative testing of field samples showed that the ELISA with rgp51 is more specific and also suitable for the testing of pooled sera.     

The influence of killed Mycobacterium leprae and other mycobacteria on opsonized yeast phagocytosis.

The influence of killed mycobacteria on the metabolic burst associated with phagocytosis of opsonized zymosan by normal human polymorphonuclear leucocytes (PMNL) or monocytes was studied by chemiluminescence (CL) measurements. M. leprae reproducibly reduced the peak and total CL of both types of phagocyte to a small, but highly significant extent. Electron microscopy showed that M. leprae were phagocytosed: cells with ingested or adherent M. leprae phagocytosed fewer zymosan particles. M. leprae did not cause aggregation of the phagocytes or quenching of CL. M. lepraemurium did not influence the CL response to zymosan. Addition of M. tuberculosis caused an increased response with PMNL but not with monocytes.     

Food granules elicit heavy drinking in polydipsic rats independently of meal duration.

Excessive drinking, in rats made polydipsic on intermittent delivery of food pellets, is inversely related to the time the rat spends with its head in the feeder, early in the interfood interval. In a sensitization model, this explains why food textures that induce more oral activity, e.g., powder, do not elicit drinking. This hypothesis was examined by coding the behavior of polydipsic rats and varying the duration of the meal delivered in each interval, while holding texture constant. Polydipsic rats were presented with pellets, food granules, or food powder. The food granules were dispensed over periods lasting 1, 14, 21, and 28 s. All food deliveries were of the same mass. The food was delivered periodically at 60-s intervals in each condition. The 14 rats in the experiment served as their own controls by experiencing every condition. The food granule conditions induced the expected increases in feeding early in the interval. However, instead of progressively reducing drinking, the excessive drinking simply occurred later in the interval. By contrast, the powder condition resulted in the immediate elimination of polydipsia. The results suggest that food texture elicits excessive drinking independently of temporal factors and that elicitation of the sensitized drinking response must depend on other factors.     

Antigen-binding peripheral blood lymphocytes in guinea-pigs immunized with human thyroglobulin in BCG

Guinea-pigs were immunized with an emulsion of human thyroglobulin (Tg) and BCG vaccine in Freund's incomplete adjuvant. Peripheral blood lymphocytes binding Tg and purified protein derivative of mammalian tuberculin (PPD) labelled with ¹²⁵I were demonstrated with an autoradiographic technique. The percentage of these cells was compared with the size of the delayed hypersensitivity (DH) skin reactions to Tg and PPD, and Tg antibody titres at intervals up to 35 days after immunization. The individual responses to Tg showed the time course of primary immune reactions although they did not parallel each other closely. By contrast, a depression of cutaneous DH to PPD was observed in spite of the presence of substantial numbers of ¹²⁵I-PPD-binding peripheral blood lymphocytes. In non-immune guinea-pigs, approximately 2·8% of peripheral blood lymphocytes bound ¹²⁵I-PPD whereas <0·1% bound ¹²⁵I-Tg.

The significance of antigen-binding lymphocytes in the immune response is discussed, and it is suggested that the presence of a substantial pool of antigen-binding lymphocytes in unprimed may be of importance in the induction of DH.

     

Bryostatin 1-induced modulation of nucleoside transporters and 2-chlorodeoxyadenosine influx in WSU-CLL cells

WSU-CLL cells, a fludarabine resistant B-cell chronic lymphocytic leukemia cell line, has been shown to exhibit enhanced sensitivity to 2-chlorodeoxyadenosine (2-CdA) following 48-72 h exposure to bryostatin 1. For 2-CdA to manifest its chemotherapeutic activity, it must first enter the cell through one of several specific nucleoside transporter systems. We present data to show that bryostatin 1-induced enhanced influx of 2-CdA is in part the result of bryostatin 1-induced modulation of nucleoside transporters in WSU-CLL cells. The bi-directional equilibrative NBMPR sensitive transporters in WSU-CLL cells were significantly down-regulated 90 min post-exposure to 1-200 nM bryostatin 1. This down-regulation was evident up to 144 h. In contrast, WSU-CLL cells exhibited a transient increase in Na+-dependent concentrative 2-CdA influx from 48 to 96 h after bryostatin 1 exposure which was evident for a longer duration than that accounted for by the increase in deocycytidine kinase activity. These data may, in part, explain the enhanced efficacy of 2-CdA seen in WSU-CLL cells following 48-72 h exposure to bryostatin 1. It may raise questions as to the importance of the bi-directional transporters in determining the resistance or sensitivity of CLL cells to 2-CdA or other nucleoside analogues.