In-vitro teratogenicity of retinoids

Mid-gestation rat conceptuses were cultured for 48 h in serum containing the retinoids all-trans-retinoic acid (TRA), 13-cis-retinoic acid (13-CRA), etretinate (ETR), etretin or one of six retinamides at concentrations ranging from 0.5 to 400 micrograms/ml. TRA was toxic at a concentration of 0.5 microgram/ml. 13-CRA and etretin caused abnormal development at 1.0 microgram/ml. However, the six retinamides were less toxic and adverse developmental effects were only evident at concentrations of 50 or 100 micrograms/ml. ETR was without effect at 100 micrograms/ml, the highest dose level of this compound tested. In vivo, TRA, 13-CRA and ETR are highly teratogenic. In this culture system, TRA and 13-CRA caused abnormal development at very low concentrations but in contrast, ETR was non-toxic at 100 micrograms/ml. Therefore these findings indicate that in vivo, maternal pharmacokinetics, and bioactivation in particular, play a major role in inducing abnormal development. Cis/trans isomerization was not a major determinant of toxicity. However, there appeared to be a relationship between abnormal development and the actual or estimated pKa values of the 10 retinoids tested.     

Sucrase-isomaltase: a marker associated with the progression of adenomatous polyps to adenocarcinomas.

Adenocarcinomas of the colon arise from adenomatous polyps. We hypothesized that sucrase-isomaltase (SI), a glycoprotein hydrolase, found in normal small intestine, fetal colon, and colon carcinomas is a marker associated with progression of adenomatous polyps with dysplasia to adenocarcinomas. To examine this hypothesis, we performed immunostaining using a polyclonal antihuman SI antibody in 32 adenomatous polyps with varying degrees of dysplasia. In addition, sucrase enzyme activity was determined in three sets of simultaneously harvested polyps, cancer, and adjacent normal mucosa from the same patient. All severely dysplastic polyps (6/6) exhibited SI staining. Most polyps (85%) with 3+ staining (i.e., greater than 10% of polyp positive for SI) had severe dysplasia, whereas those with mild dysplasia had either 1% to 5% staining or no staining in 95% of the cases. These data indicate that the extent of SI immunostaining in polyps correlates with the degree of dysplasia (p = 0.0001). Sucrase-isomaltase activity in the polyps was 18.1 +/- 1.8 mU/mg (mean +/- SD); in adjacent carcinoma SI activity was 29.1 +/- 1.8 mU/mg. Adjacent mucosa showed no activity in all cases. In summary, our results suggest that SI expression correlates with the progression of dysplastic adenomatous polyps to carcinoma. Sucrase-isomaltase expression may be useful as a clinical marker to improve our prognostic capabilities in patients with dysplastic lesions of the colon, that is, inflammatory bowel disease.     

Sialyltransferase activity and hepatic tumor growth in a nude mouse model of colorectal cancer metastases.

Sialyltransferase activity (EC 2.4.99.6) was measured in the microsomal fraction of colorectal cancer cell lines using an assay based on the incorporation of [14C]CMP-sialic acid into asialofetuin. In the poorly differentiated lines MIP101 and Clone A, sialyltransferase activity had a Vmax of 0.36 and 0.31 nmol/mg protein/h, respectively, while the moderately differentiated to well-differentiated cell lines HT-29, CCL188, and CX-1 had Vmaxs of 2.46, 1.05, and 1.24 nmol/mg protein/h, respectively. All cell lines tested had a Km of 15.4 (+/- 0.7)(SD) mumol/liter. The better differentiated cells had higher levels of sialyltransferase activity, which correlated with their higher levels of sialic acid and their enhanced ability to form liver metastases in the nude mouse following intrasplenic injection compared to the poorly differentiated cell lines. Treatment of the cell lines with KI-8110, a CMP-sialic acid derivative which prevents incorporation of sialic acid into glycoconjugates, resulted in reduced formation of hepatic metastases by the colorectal carcinoma cell lines in the nude mouse model. It is suggested that reduced sialylation of adhesion molecules such as carcinoembryonic antigen may change the biology of the tumor cell, one consequence of which is the prevention of implantation of the cells into distant sites, resulting in a reduced incidence of metastases.     

Laminin expression in colorectal carcinomas varying in degree of differentiation

We are studying the ability of colorectal carcinomas, which vary in degree of differentiation, to assemble a basement membrane and the relationship between differences in this ability and perturbations in laminin expression. For these studies, we are using human colorectal carcinoma cells grown both in vitro and in nude mice as well as tumors obtained at surgery. Immunoperoxidase staining of human tumors indicates that laminin is present in a defined basement membrane in moderately to well-differentiated tumors. This staining pattern is absent in poorly differentiated tumors. In these tumors, staining is discontinuous and sometimes observed intracellularly. The laminin synthesized by in vitro cells was immunoprecipitated and analyzed by acrylamide electrophoresis. Neither poorly nor well-differentiated carcinoma cells exhibit marked differences in the rate of synthesis of laminin. Differences are present in the rate at which newly synthesized laminin is secreted. These differences may result from alterations in posttranslational processing. Such alterations may contribute, along with other factors, to the inability of poorly differentiated tumors to make a basement membrane.     

Laparoscopic bowel surgery registry

Laparoscopic surgery has evolved rapidly since 1989. The American Society of Colon and Rectal Surgeons, the Society of American Gastrointestinal Endoscopic Surgeons, and the American College of Surgeons Commission on Cancer jointly sponsored a registry to identify as early as possible the patterns of practice and acute complications of laparoscopic colectomy. METHODS: Cases were voluntarily registered by community and academic surgeons. Information was entered in the EPI-5 database. RESULTS: One thousand fifty-six cases were contributed by 118 surgeons; 763 patients were completed laparoscopically. The most common indication for surgery was cancer in 453 patients. The right colon (n=364) and sigmoid (n=294) were most frequently resected. Respondents felt adequate cancer resections were performed. Although several unique complications were noted, intraoperative complications were similar in type and frequency to open cases. CONCLUSION: Laparoscopic colorectal surgery can be performed with acceptable complications. It remains unclear if this approach is adequate for long-term management of colon and rectal cancer.Read at the meeting of The American Society of Colon and Rectal Surgeons, Orlando, Florida, May 8 to 13, 1994.     

Lifestyle factors in monozygotic and dizygotic twins

In examining genetic influences on biological variables using twins, it may be important to examine the distribution between and within twin pairs of demographic and lifestyle factors that may themselves affect the biological variable being studied. We explored the distribution of demographic and lifestyle factors that may affect blood lipid levels or ischaemic heart disease (IHD) risk among a sample of 106 monozygotic (MZ) and 94 like-sex dizygotic (DZ) twin pairs. In our sample, MZ twins were statistically significantly different from DZ twins only in marital status, cigarette smoking habits, and the ratio of polyunsaturated to saturated fat (P:S ratio) in their dietary intake. The latter variable was among many dietary variables examined (using 4-day weighed food diaries), and the size of the difference in intake was small. When comparisons were made of the similarities within twin pairs, we found members of MZ twin pairs to be statistically significantly closer than DZ twins in educational achievement, occupation, cigarette smoking, and exercise habits, and the number of days a week on which alcohol was consumed. These last three variables were consistently closer among twins with closer contact than among those with a smaller degree of current shared environment. For 12 of the 13 nutrients examined, the within-pair correlations were higher for MZ than for DZ twins, although our test for significant genetic variance showed statistical significance only for intake of complex carbohydrates. We conclude that MZ twins share demographic and lifestyle factors that might influence the risk of IHD and blood lipid levels to a greater degree than do DZ twins, although it is difficult to say if these similarities in lifestyle result from genetic influences or not. Nevertheless, ascribing differences between correlations in MZ and DZ twin pairs for lipid levels as being purely "genetic"--as implicit in conventional measures of heritability--is likely to overestimate the influence of genetic factors.     

Vitamin D3, gamma interferon, and control of proliferation of Mycobacterium tuberculosis by human monocytes.

Previous studies have shown that recombinant interferon gamma (IFN-gamma), crude T cell supernatants, or appropriate T-cell lines can cause total inhibition of the growth of M. tuberculosis inside murine peritoneal macrophages. In similar experiments with human monocytes much smaller effects are seen. This could be due to the relative immaturity of these cells. Because dihydroxy vitamin D3 (1,25-(OH)2 D3) can cause phenotypic differentiation of immature leukemic lines into macrophage-like cells, we have explored the possibility that exposure to cholecalciferol metabolites in vitro might increase the ability of monocytes to control proliferation of M. tuberculosis, or cause monocytes to mature into cells able to respond appropriately to IFN-gamma. Incubation of monocytes with three cholecalciferol metabolites induced anti-tuberculosis activity to an extent that correlated with their binding affinities to the intracellular receptor protein for the derivatives. 1,25-(OH)2 D3 also primed monocytes for phorbol myristate acetate-triggered reduction of nitroblue tetrazolium. The effects were additive rather than synergistic with those of IFN-gamma. Monocytes incubated with IFN-gamma developed 25-OH D3 1-hydroxylase activity, detected by conversion of tritiated 25-(OH) D3 to a more polar metabolite which coeluted with 1,25-(OH)2 D3 on straight and reverse-phase HPLC. The latter is a more active form in vivo. These findings help to explain claims for the efficacy of vitamin D in the treatment of some forms of tuberculosis, and also the occasional finding of raised serum calcium, and disturbed vitamin D metabolism in these patients.     

Leukocyte survival in cerebrospinal fluid.

Delays in the laboratory examination of cerebrospinal fluid are commonly encountered in clinical medicine. The present studies were designed to evaluate changes in cerebrospinal fluid leukocyte counts relative to time elapsed before analysis. Neutrophil counts decreased most rapidly, being 68 +/- 10% (standard error of the mean) and 50 +/- 12% of initial values at 1 and 2 h, respectively. Lymphocyte and monocyte numbers were not significantly altered until 3 h.