Upregulation of interleukin-1 receptors in mouse AtT-20 pituitary tumor cells following treatment with corticotropin-releasing factor.

Treatment of AtT-20 cell cultures with increasing concentrations of rat/human corticotropin-releasing factor (r/hCRF) for 24 h resulted in a dose-dependent 2-3 fold increase in specific 125I-labelled recombinant human IL-1 alpha (125I-IL-1 alpha) binding that was paralleled by a 70-80% decrease in 125I-Tyro-ovine CRF binding. Saturation analysis of 125I-IL-1 alpha binding in control and CRF-treated cultures indicated that CRF produced an increase in the density (Bmax) of IL-1 receptors without altering their affinity (KD). The CRF-induced upregulation of IL-1 receptors appears to be mediated through specific membrane receptors for CRF since the CRF receptor antagonist, alpha-helical oCRF (9-41), blocked the CRF-induced upregulation of IL-1 receptors without producing any effect on 125I-IL-1 alpha binding by itself. In summary, these data demonstrate complex interactions between CRF and IL-1 at the pituitary level and identify potential novel mechanisms for cytokines to alter neuroendocrine function.     

Modulation of beta-adrenergic receptors in the pituitary gland following adrenalectomy in rats

The effects of adrenalectomy on beta-adrenergic receptors in the rat pituitary were examined using quantitative in vitro autoradiography with 125I-iodocyanopindolol (125ICYP). 125ICYP binding in the anterior, intermediate and posterior lobes of the pituitary gland was significantly increased in chronically adrenalectomized rats. The increase in 125ICYP binding sites in the rat pituitary following adrenalectomy was not reversed by glucocorticoid replacement with dexamethasone. These data indicate that catecholamines of adrenomedullary origin are capable of modulating beta-adrenergic receptors in the pituitary gland and suggest that peripheral epinephrine may be important in regulating pituitary hormone secretion.     

Castor oil increases intestinal formation of platelet-activating factor and acid phosphatase release in the rat.

1. When castor oil was administered by gavage to rats, the duodenum and jejunum but not ileum and colon produced large amounts (5-6 fold greater than control) of platelet activating factor (Paf). 2. Intraluminal release of acid phosphatase (AP) was also markedly increased (5-6 fold greater than control) in the duodenum and jejunum of castor oil-treated rats and there was a correlation between the elevated release of AP and intestinal hyperaemia. 3. These findings support a role for Paf as a mediator of intestinal damage induced by castor oil.     

Endocytosis of gold-labeled proteins and LDL byTrypanosoma cruzi

Endocytosis was studied at the ultrastructural level in different developmental forms ofTrypanosoma cruzi after incubation of the parasites in the presence of gold-labeled proteins (albumin-Au, peroxidase-Au and transferrin-Au) and low-density lipoprotein (LDL-Au). Epimastigote (culture) forms actively ingested LDL and proteins. Initially, gold particles were seen adhering only to the cytostome and inside the flagellar pocket. In parasites incubated at 4°C with transferrin-Au or peroxidase-Au, labeling was found only at these two sites, showing that receptor-mediated endocytosis occurs in both regions. In the cytoplasm, gold particles were seen only inside two different compartments: membrane-bound vesicles and reservosomes. Incubation of epimastigotes with acridine orange followed by fluorescence microscopy revealed intense orange staining, indicating that the reservosomes have an acidic pH. This staining was abolished after incubation of the parasites in the presence of ammonium chloride. These data confirm that this compartment is the site of accumulation of ingested lipids and proteins. Little intracellular labeling with transferrin-Au was found in in vitro — derived amastigotes and trypomastigotes (both lack reservosomes). However, although in amastigotes very few gold particles were seen bound to the cells, in trypomastigotes they were observed bound to the membrane that encloses the cell body, the flagellar pocket, and the flagellum, suggesting that the receptors are more abundant in this form.     

Early gamma interferon responses in lethal and nonlethal murine blood-stage malaria.

This study was undertaken to explore early differences in cytokine production during nonlethal and lethal blood-stage murine malaria infections. Cytokine analysis of spleens during these infections showed that the principal difference between two nonlethal and two lethal Plasmodium species was the production of gamma interferon 24 h after infection with nonlethal parasites. In contrast, no increases in interleukin-4 production were observed in the first 24 h and tumor necrosis factor alpha levels increased equally in both nonlethal and lethal infections. During the later phase of infection with nonlethal parasites, both gamma interferon and interleukin-4 levels increased markedly a few days before parasite clearance. Early increases in gamma interferon production in nonlethal infections of Plasmodium yoelii and Plasmodium chabaudi were dose related and increased significantly with the size of the inoculum. Studies with the nonlethal P. yoelii suggest that the early gamma interferon response is mediated by T cells and natural killer cells, as it was reduced in athymic mice and in mice depleted of their natural killer cells by treatment with specific antiserum. Infecting mice with increasing numbers of lethal P. yoelii and Plasmodium berghei parasites did not increase the amount of gamma interferon, interleukin-4, and tumor necrosis factor alpha produced in a dose-dependent fashion. We conclude that one consequence of the early production of gamma interferon and tumor necrosis factor-alpha, particularly after nonlethal P. yoelii infection, may be to adjust the balance of T-helper cell subset activation, and probably that of other immune responses, so as to enhance the mechanisms that are essential for elimination of the parasites. This suggests that a successful vaccine should contain antigens capable of inducing such responses.     

Clinico-microbiological study of dermatophytoses.

In the present series, 80 cases of dermatophytoses were subjected to mycological examination including microscopy and culture the mycological findings were correlated with clinical presentation of the patients. The isolation rate was 62.5 percent. Fungal culture was successful in 36.25 percent of cases, Trichophyton rubrum being the commonest etiological agent accounting for 55.18 percent of cases.