Zinc(II) inhibits the release of thyroid and glucocorticoid receptors from chromatin of cultured GC cells.

The effect of Zn(II) on the association of thyroid and glucocorticoid hormone receptors with chromatin was studied in chromatin from cultured GC cells. Chromatin was incubated at 0-4 degrees C in 20 mM Tris, pH 7.4. When buffers contained 0.15 M NaCl, the release of T3 receptors from chromatin was time-dependent; 50% of T3 receptors were released after 30 min incubation. Receptor release appeared relatively specific since less than 10% of chromatin protein and DNA, and less than 13% of chromatin zinc were released under these conditions. Addition of Zn(II) inhibited receptor release; one-half maximal inhibition occurred at 1 microM ZnCl2. Cd(II) and to a lesser extent Co(II) had similar but smaller effects. Addition of EDTA prevented this effect of Zn(II); EDTA alone enhanced receptor release. Zn(II) also inhibited the release of glucocorticoid receptors from chromatin in similar incubations. Our findings suggest that Zn(II) increases the association of hormone receptors with chromatin and, thereby, may influence receptor function.

Differential effects of sodium butyrate and hyperosmolality on the modulation of alkaline phosphatases of LoVo cells.

LoVo cells produce term-placental and intestinal alkaline phosphatases. Hyperosmolality and sodium butyrate increase the levels of both, but the effect of sodium butyrate is more pronounced on the intestinal enzyme. When applied together, induction of term-placental alkaline phosphatase is additive and that of the intestinal enzyme is synergistic. Induction by either stimulus or by their mixture is independent of cell density. However, whereas the effect of hyperosmolality is readily reversible, induction by sodium butyrate is not. No synergistic increase in intestinal alkaline phosphatase activity occurs when cells are sequentially treated with hyperosmolality and sodium butyrate or vice versa. This indicates that only when applied concurrently does one inducer amplify the effect of the other. Since the normal colonic mucosa produces intestinal alkaline phosphatase, its predominant induction by sodium butyrate in LoVo cells may reflect a more differentiated state.

Modulation of alkaline phosphatases in LoVo, a human colon carcinoma cell line.

LoVo, a continuous cell line derived from a human colon carcinoma produces two alkaline phosphatases: the heat-labile, L-homoarginine-insensitive, intestinal form, characteristic of its tissue of origin and the heat-stable, term-placental form, ectopically produced by a variety of tumors. Under basal conditions the activity levels of both enzymes are similar. Hyperosmolality and sodium butyrate induce increased levels of activity of the two alkaline phosphatases in a disparate fashion; whereas hyperosmolality augments the activity of both to the same extent, the effect of butyrate is more pronounced on the activity of the intestinal enzyme. When the two inducers are combined, induction of term-placental alkaline phosphatase is additive and that of the intestinal enzyme is synergistic. The effect of hyperosmolality is blocked by cycloheximide, and induction by sodium butyrate is inhibited by thymidine, cordycepin and cycloheximide. The known alkaline phosphatase inducer, prednisolone, has no effect on the enzymes of LoVo cells. Our results suggest that in these tumor cells the activity levels of the closely homologous term-placental and intestinal alkaline phosphatases appear to be independently controlled.

Identification of human papillomavirus types in male urethral condylomata acuminata by in situ hybridization.

An in situ hybridization technique was applied under stringent conditions to paraffin sections of urethral condylomata from male patients to determine the presence of DNA sequences of human papillomavirus (HPV) types 6, 11, 16, and 18. The material consisted of 15 classical condylomata acuminata, two flat condylomata, and five recurrent lesions. HPV DNA sequences could be identified in all 15 condylomata acuminata; in 13 lesions, two types of viral DNA were observed (types 6 and 11 in 12, types 6 and 18 in one). In the remaining two condylomata acuminata, only HPV type 11 was present. One of the two flat condylomata was negative with all the probes, and one was borderline-positive for HPV 6. Four of five recurrent lesions contained the same types of viral DNA as the primary lesions, albeit with slight differences in the intensity of viral expression. One lesion was negative with all probes. We conclude that urethral condylomata in males contain the same types of HPV as seen in other anogenital lesions of both sexes and that infection with two viral types is common. In situ hybridization with HPV DNA probes is applicable to archival material and therefore may prove to be of value in future epidemiologic studies comparing lesions in sexual partners. The determination of viral type may have therapeutic implications.

Characterization of human papilloma virus types in condylomata acuminata in children by in situ hybridization.

The presence of human papilloma virus (HPV) DNA sequences of types 6, 11, 16, and 18 was determined by in situ hybridization under stringent conditions on archival paraffin-embedded tissue sections in eight condylomata acuminata observed in children below the age of 12 years. Viral sequences were detected in seven of eight cases: all of them contained HPV 6, four contained also HPV 11, and one contained HPV 16 and 18. Papilloma virus common antigen was detected in only three of eight cases, all of them being positive also by in situ hybridization. We conclude that most condylomata acuminata in children are associated with the same types found in anogenital lesions in adults. Since little is known about the long-term significance of genital condylomas in children the identification of the papilloma virus type may prove to be important as a prognostic tool particularly in patients infected with HPV types 16 and 18, thought to have high oncogenic potential.

Preferential alkaline phosphatase isoenzyme induction by sodium butyrate.

SW-620, a continuous cell line derived from a poorly differentiated human colon carcinoma, produces two alkaline phosphatases. Under basal conditions the heat-stable, term-placental is the major isoenzyme and the heat-labile, liver/bone/kidney form represents a minor component. Exposing SW-620 cells to sodium butyrate causes induction of increased levels of activity accompanied by a striking shift in isoenzyme distribution not observed heretofore. The activity increase is accounted for entirely by augmentation of the liver/bone/kidney isoenzyme, with the term-placental form not being affected. Two other known alkaline phosphatase inducers, prednisolone and hyperosmolality, do not influence specific activity and isoenzyme distribution. The preferential induction of the liver/bone/kidney form of alkaline phosphatase in SW-620 cells may reflect a butyrate-elicited expression of a more differentiated state.

Synergistic induction of alkaline phosphatase in colonic carcinoma cells by sodium butyrate and hyperosmolality.

Exposing HT-29 cells to the combination of two inducers of intestinal alkaline phosphatase, sodium butyrate and hyperosmolality, causes a synergistic (over 1000-fold) increase in specific activity. Evidence is presented showing that enzyme induction is reversible; the half-life of the induced activity is approximately 30 h. Preinduction by butyrate or by hyperosmolality does not prime the cells so as to respond synergistically when subsequently exposed to hyperosmolality or butyrate, respectively. This study demonstrates that when applied in combination, the effect on gene expression by one alkaline phosphatase inducer is amplified by the other.