Gap junction-mediated cell-to-cell communication in bovine and human adrenal cells. A process whereby cells increase their responsiveness to physiological corticotropin concentrations.

We have studied the role of gap junction-mediated intercellular communication on the steroidogenic response of bovine (BAC) and human (HAC) adrenal fasciculo-reticularis cells in culture to corticotropin (ACTH). Indirect immunofluorescence analyses showed that intact human and bovine adreno-cortical tissue as well as HAC and BAC in culture expressed the gap junction protein connexin43 (also termed alpha 1 connexin). Both HAC and BAC were functionally coupled through gap junctions as demonstrated by microinjection of a low molecular mass fluorescent probe, Lucifer yellow. The cell-to-cell transfer of the probe was blocked by 18 alpha-glycyrrhetinic acid (GA), an inhibitor of gap junction-mediated intercellular communication. GA markedly decreased the steroidogenic response (cortisol production) of both HAC and BAC to low (10 pM) but not to high (5 nM) concentrations of ACTH. GA had no inhibitory effect on the steroidogenic response to 8 Br-cAMP (at either low or high concentrations) and did neither modify the binding of 125I-ACTH to its receptor nor the ACTH-induced cAMP production. BAC cultured at high or low cell densities (2.4 x 10(5) vs. 0.24 x 10(5) cells/cm2) exhibited distinct levels of intercellular communication and were differently responsive to sub-maximal ACTH concentrations. The ACTH ED50 values for cortisol production were 8.5 +/- 1.3 and 45 +/- 14 pM (P < 0.02) for BAC cultured at high and low density, respectively. In the presence of GA, there was a shift of the ACTH concentration-response curves in the two culture conditions. The ACTH ED50 of high density and low density cultured BAC increased 25- and 5-fold, respectively, and became similar (220 +/- 90 and 250 +/- 120 pM). These results demonstrate that gap junction-mediated communication between hormone-responsive and nonresponsive cells is one mechanism by which adrenal cells increase their responsiveness to low ACTH concentrations.

Cell-to-cell communication in the anterior pituitary: evidence for gap junction-mediated exchanges between endocrine cells and folliculostellate cells.

The ability of rat anterior pituitary cells to communicate through gap junctions (GJ) was studied using a fluorescent molecule, Lucifer Yellow (LY), which freely passes through GJ channels. The probe was introduced into the cell cytoplasm by using either the cut-end loading method on intact tissue, or cell microinjection on cultured cells. The identification of communicating cells was performed by immunofluorescence labeling of specific hormones in endocrine cells and of S100 protein in folliculostellate (FS) cells. Rat anterior pituitary cells in their physiological organization, i.e. in the intact tissue, exhibited a high level of coupling through GJ. LY-labeled cells were found up to 300-microns apart from its site of introduction. The communicating cells were primarily PRL cells, GH cells, and FS cells. Only a few LH, TSH, and ACTH cells were labeled with LY. Anterior pituitary cells, isolated from the rat tissue by mild protease treatment and cultured for 3 days, reestablished functional GJ as demonstrated by microinjection of LY into individual cells. By immunolabeling of specific hormones and/or S100 protein, we found a GJ coupling between FS cells, and between FS cells and endocrine cells, including PRL cells. The communication between FS cells was by far the most frequent. In conclusion, we demonstrate the presence of functional GJ between anterior pituitary cells of the same type and between anterior pituitary cells having distinct differentiated functions.

[Toxocara canis infection. 2 cases of peripheral granuloma in adults]. / Toxocarose canis. Deux cas de granulome périphérique chez l'adulte.

PURPOSE: We report two cases of toxocariasis peripheral granuloma in adults. METHODS: Diagnostic difficulties linked to parasite serologies, particular to these two cases, are presented. Serology is often poorly contributive, but PCA and/or vitreous study with the ELISA reaction to Toxocara canis homologous antigens in the endocular fluids are the most reliable means of reaching a diagnosis, as evidence in our two observations. In the same way, the presence of eosinophils and of IgE in the aqueous humor and or vitreous is of great importance for orienting the diagnosis. RESULTS: The treatment consisted in systemic steroids and granuloma cryotherapy associated with vitrectomy and for one case indentation due to a traction. Later, retinal membrane peel was performed for the same patient. No treatment with antihelminthic drugs was proposed. The functional and anatomic results were good in both cases (8/10-P2 and 6/10-P2). CONCLUSION: Toxocara canis infection is based on clinical aspects. The ELISA technique is useful for biological diagnosis.

[True or supposed bacterial endophthalmitis. Study of anatomo-functional outcome apropos of 32 cases]. / Endophtalmies bactériennes ou supposées telles. Etude du devenir anatomo-fonctionnel à propos de 32 cas.

PURPOSE: Vision prognostic study depending on the germs and the therapic performed in bacterial endophthalmitis. METHODS: In a retrospective study over a period of 3 years (1991-1993), 32 cases of post surgery bacterian endophthalmitis were detected: 30 cases after cataract surgery (29 cases after extra capsular surgery and one case after intra capsular), one case after trabeculectomy and one case after keratoplasty. RESULTS: A risk factor was evidenced in 15.6% of the cases. Endocular samples were done in 68.75% of the cases. The positive rate was 36.4% showing a Staphylococcus in 5 cases out of 8 (62,5%). In 37.5% of the cases an intraocular antibiotic injection was associated to the anterior chamber punction. 40% of the cases contaminated with Staphylococcus regained a visual acuity of more than 3/10. For the two cases where a Streptococcus was isolated an evisceration was necessary. Our results show that a higher visual acuity was obtained when a posterior vitrectomy was performed. When the posterior vitrectomy was associated with a corticoid therapy, the visual prognostic was better. Thus, 71% of these cases regained a visual acuity of more than 3/10. CONCLUSION: Our results show that performing a posterior vitrectomy associated to a general corticotherapy within 48 hours from the bacterian endophthalmitis diagnosis would allow best vision improvement.

Lack of correlation between the gap junctional communication capacity of human colon cancer cell lines and expression of the DCC gene, a homologue of a cell adhesion molecule (N-CAM).

In many human colorectal cancers, the DCC gene encoding for a homologue of the neural cell adhesion molecule (N-CAM) is found to be deleted. Previous work suggested that gap junctional intercellular communication (GJIC) might play an important role in carcinogenesis and could be regulated by the expression of cell adhesion molecules such as E-cadherin in some epithelial cell systems. In order to examine whether the deletion of the putative cell adhesion molecule DCC is related to the level of GJIC, which might, in turn, be important in human colorectal cancers, we compared levels of expression of the DCC gene with the GJIC capacity of a panel of human colorectal adenocarcinoma cell lines isolated from different stages of tumor progression. While the level of GJIC varied between the cell lines studied, we found no correlation between their communication capacity and DCC expression revealed by a reverse-transcriptase/polymerase chain reaction method. This lack of correlation suggests that DCC is not a crucial regulator of GJIC.

Gap junctions and cell polarity: connexin32 and connexin43 expressed in polarized thyroid epithelial cells assemble into separate gap junctions, which are located in distinct regions of the lateral plasma membrane domain.

Epithelial cells of the thyroid gland present an uncommon connexin expression pattern, they coexpress connexin32 and connexin43. In the present work, we have analyzed the membrane distribution of these two connexins to determine: (i) whether they co-assemble in the same gap junctions or form separate gap junctions; and (ii) whether their location is somehow related to the thyroid cell polarity. Immunofluorescence analyses of the localization of the two connexins in thyroid tissue sections revealed that connexin32 and connexin43 are located in different regions of the plasma membrane. We further analyzed the location of each of the two connexins with regard to that of the tight junction-associated protein, ZO1. Laser scanning confocal microscope observations of connexin32 or connexin43 and ZO1 double-immunolabelled thyroid cells, gave evidence for a separate localization of gap junctions made of each of these two connexins. Connexin32 gap junctions appeared as fluorescent spots scattered over the lateral membrane domain, while connexin43 gap junctions formed a meshed network superimposable with that of tight junctions in the subapical region of the cells. Western blot analyses of the distribution of connexins in thyroid plasma membrane subfractions obtained by ultracentrifugation on a sucrose gradient led to the identification of membrane sub-populations enriched in either connexin32 gap junctions or connexin43 gap junctions. Connexin32 gap junctions and connexin43 gap junctions were found to differ in their resistance to solubilization by N-lauroylsarcosine. Increasing concentrations of this detergent from 0.12% to 0.42% caused a progressive solubilization of connexin43 while connexin32 remained membrane-bound.(ABSTRACT TRUNCATED AT 250 WORDS)