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The epidemiological understanding of inflammatory bowel disease has been limited by the referral bases of most inflammatory bowel disease studies. The Colitis-Ileitis Study Group of Rochester, N.Y., developed a community-wide, computerized cumulative registry of all inflammatory bowel disease patients hospitalized at the 8 community hospitals for 1973-86. Clinical data were abstracted from each of the 1651 identified hospital charts. All of these patients resided in Monroe County (city and suburbs) and the 5 contiguous counties (Genesee/Finger Lakes Region, population 1,030,640). Of the 1651 hospital patients identified in the study, 1358 resided in Monroe County (Rochester and its immediate suburbs, population 702,238). Incidence, defined as time of onset of symptoms of inflammatory bowel disease, rose from baseline rates in the 1930s to peak in 1980 (Crohn's disease = 50.29/10(5) per decade, ulcerative colitis = 35.12/10(5) per decade) and declined through 1986. For Crohn's disease, the age-specific incidence rates peaked in the 20-29-yr-old group in each of the 5 decades studied. Ulcerative colitis seems to occur at all ages and may have a bimodal distribution. There was a period effect, with the 1970s having the highest incidence of Crohn's disease and ulcerative colitis for each age group. However, the age-specific incidence rate for Crohn's disease showed a 40% decrease in the 1980s compared with the 1970s in the 10-39-yr-old group (p less than 0.001). The age-specific incidence rate for ulcerative colitis showed a 50% decrease in the 1980s compared with the 1970s in the 10-49-yr-old group (p less than 0.001).

The uptake by rat yolk sacs of native invertase and invertase which was deglycosylated by treatment with endo-beta-N-acetylglucosaminidase was compared. The initial rate of uptake of the deglycosylated enzyme was severalfold greater and its accumulation leveled off much earlier than that of the native enzyme. Uptake rates of the deglycosylated and native forms of the enzyme were proportional to their concentration in the medium in the range employed and were inhibited about 85% by 10(-6) M glucagon in both cases. After preloading of yolk sacs with native invertase, the tissue level of activity remained relatively constant over a subsequent 6-h time period, while with the deglycosylated form, activity declined substantially. Since this difference appears not to be attributable to differences in thermal stability, it is suggested that the deglycosylated form of the protein is more susceptible to intracellular proteolytic digestion. In vitro studies on the digestion of these two forms of invertase by trypsin are consistent with this suggestion.

Swainsonine, an alpha-mannosidase inhibitor found in the Australian plant Swainsona canescens and in spotted locoweed, was tested for its effect on the degradation of endocytosed proteins in rat liver cells. The compound inhibited the release of proteolytically derived breakdown products from endocytosed glycoproteins but not from nonglycoproteins. Fifty per cent inhibition of the degradation of 125I-asialofetuin occurred at a concentration of swainsonine in the medium of 6 X 10(-7) M. In the presence of the inhibitor, there was an increased cellular accumulation of the glycoproteins corresponding quantitatively to the decreased degradation, so that total uptake was the same in the presence or absence of the inhibitor. The excess 125I-labeled material which accumulated within cells under these conditions was found entirely in the lysosomal peak on Percoll density gradient centrifugation and migrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a mobility indistinguishable from that of the original material. Thus, the inhibition of breakdown occurs prior to any conversion of the protein to intermediates of detectably smaller size. In contrast to the results with swainsonine, degradation of both glycoproteins and nonglycoproteins was inhibited by chloroquine and by 3-methyladenine. The findings with 3-methyladenine are in conflict with earlier reports in the literature on the effect of this compound on degradation of endocytosed proteins.

Rates of protein degradation and synthesis were determined in myofibrillar and non-myofibrillar fractions and in myofibrillar subunits of cultured muscle cells from normal and dystrophic chick embryos of genetically closely related lines. Growth characteristics of normal and dystrophic cells were identical as measured by DNA, RNA and protein accumulation. Degradation rates of myofibrillar and non-myofibrillar protein determined from label-chase experiments were the same in normal and dystrophic cultures. In similar experiments in which degradation rates of eight different components of the myofibrillar fraction were measured, a spectrum of degradation rates was obtained indicating that myofibril components turn over individually or in groups, rather than as an intact unit. Myosin heavy chain was the slowest turning over component of those measured, while actin was among the most rapid. No differences were found between normals and dystrophics in the turnover of any of the components. Fractional rates of protein synthesis were also determined for the myofibrillar and non-myofibrillar fractions of cultured cells. The rates obtained with normal and dystrophic cells were indistinguishable and were the same for the myofibrillar and non-myofibrillar fractions. Initial amino acid incorporation rates into 17 separate components of the myofibrillar fractions were compared in normal and dystrophic cells. No significant differences were found.

The effect of swainsonine, an inhibitor of Golgi alpha-mannosidase II and lysosomal alpha-mannosidase, on the synthesis, processing, and turnover of two glycoproteins, lysosomal beta-galactosidase and lysosomal beta-glucuronidase, has been studied in cultured mouse peritoneal macrophages. No effect of the inhibitor on the relative rates of synthesis of the precursor form of either enzyme was observed. On the other hand, carbohydrate processing of beta-galactosidase and beta-glucuronidase was markedly altered by swainsonine, consistent with a blockage by the inhibitor of the removal of the alpha-1,3- and alpha-1,6-linked mannose residues which occurs in normal processing. In homogenates of both normal and swainsonine-treated cells, the precursor forms of the enzymes were found exclusively in the light membrane fraction on Percoll gradients and the mature forms exclusively in the lysosomal fractions indicating that translocation from Golgi to lysosomes and proteolytic processing in the lysosome were not impaired by the presence of abnormal oligosaccharide side chains. There was no detectable effect of swainsonine during a 4-day chase period on the total cellular turnover of these enzymes which involves two processes, secretion and degradation. In the absence of swainsonine, secretion represented about 40% of the total turnover of beta-galactosidase and about 50% with beta-glucuronidase. The presence of swainsonine increased these proportions to about 60 and 70%, respectively.

This report is based on a review of the various investigations attempting to determine the etiology of Crohn's disease. It has paid special attention to three main possible etiologic mechanisms, reported in the literature up to the time of this review; namely, immunologic, unknown transmissible agents or known such as L-forms, protoplasts, or spheroplasts, viral or infectious RNA and/or DNA, and a combination of the preceding causative possibilities. It has discussed the unrewarding immunological mechanisms, the failure to confirm the various investigations suggesting a transmissible agent and/or the speculations concerning the possible combination of factors. It also has included the remarks of Sacchar and Auslander, who stated that four important pieces were missing to allow acceptance of transmissible agent as the cause of Crohn's disease. This review has demonstrated that up to the present time the etiology of Crohn's disease has remained a puzzle and concluded that further investigations are necessary to resolve the etiology of Crohn's disease with the suggestion that evidence for an infectious agent will require experiments that satisfy Koch's postulates.

The uptake of macromolecular markers by fluid pinocytosis in the rat yolk sac was inhibited by glucagon, with half-maximal effect at a hormone concentration of approximately 3 X 10(-8) M. Glucagon had no effect on the cellular distribution of the marker subsequent to its uptake. Rates of uptake promptly returned to normal when the yolk sacs were transferred from a glucagon-containing to a glucagon-free medium. Epinephrine also inhibited, but only at much higher concentrations. The effect of the latter was augmented by theophylline. Insulin (10(-6) M) had no effect when added alone or with an inhibitory level of glucagon (10(-7) M). The presumption that the hormone effect was mediated by cyclic AMP was supported by the findings that the cellular levels of cyclic AMP were elevated in the presence of glucagon and that dibutyryl cyclic AMP could replace glucagon as an effective inhibitor. The conclusion that the hormone effect was on uptake rather than on subsequent regurgitation was based on the linearity of accumulation in both the presence and absence of glucagon and the inability of glucagon to stimulate loss of invertase from preloaded cells. Colchicine and vinblastine also inhibited uptake. This finding and those of others which are discussed suggest the possibility that effects of cyclic nucleotides on certain cell functions may involve their regulation of microtubular status.

Rat liver lysosomes, isolated from metrizamide gradients by the method of Wattiaux et al. (Wattiaux, R., Wattiaux-de Coninck, S., Ronveaux-Dupol, M.F., and Dubois, F. (1978) J. Cell Biol. 78, 349-368) took up from the medium and degraded several marker protein preparations, viz. 125I-asialofetuin, [35S]methionine-labeled hemoglobin, and [3H]leucine-labeled rat liver cytosol proteins. Rates were indistinguishable for all the markers, indicating that uptake was by a nonspecific process analogous to fluid pinocytosis. No effect of added MgATP or K+ was observed. Lysosomal degradation of all the markers was inhibited by 10(-4) M chloroquine. Swainsonine, on the other hand, at 10(-5) M, inhibited the breakdown only of the glycoprotein, 125I-asialofetuin. In the presence of the inhibitors, there was an accumulation of markers in the lysosomes in amount corresponding to the decreased breakdown, indicating that uptake was unaffected. Degradation and inhibition were measured at pH 7.0, 6.0, and 5.0 with both intact lysosomes and with lysosomes disrupted by the addition of 0.2% Triton X-100. Degradation with intact lysosomes was relatively independent of pH. On the other hand, activity with disrupted lysosomes was negligible at pH 7.0 and rose rapidly with decreasing pH. Inhibition by 10(-4) M chloroquine and 10(-5) M swainsonine with intact lysosomes decreased sharply with decreasing pH and did not occur with disrupted lysosomes.

Parenchymal cells isolated from rat liver are capable of taking up free hemoglobin. Uptake was saturable with a concentration for half-maximal velocity of 1.35 mg/ml (1.99 X 10(-5) M) hemoglobin. At a concentration of 0.088 mg/ml, the endocytic index for hemoglobin uptake was 4.5 microliters/h per mg of cell protein. This may be compared with the rate of fluid pinocytosis by these cells of 0.025 microliter/h per mg of cell protein (determined with yeast invertase as the marker). Free beta globin chains were also taken up with an endocytic index of 26.7 microliters/h per mg of cell protein at a beta chain concentration of 0.075 mg/ml. Hemoglobin inhibited the uptake of labeled beta globin. Hemoglobin-haptoglobin complex at a concentration of 0.12 mg/ml (as hemoglobin) was cleared at a rate of 0.89 microliter/h per mg cell protein and its uptake was also inhibited by free hemoglobin. We conclude that haptoglobin serves to conserve the iron of hemoglobin by preventing its renal clearance and not by promoting its hepatic uptake.

A substance has been purified to apparent homogeneity from rat liver which, as previously reported (Dunaway, G. A., Jr., and Segal, H. L. (1974) Biochem. Biophys. Res. Commun. 56, 689-696), specifically stabilizes the major liver isozyme of phosphofructokinase (PFK-L2) against thermal inactivation and whose level in vivo changes in parallel with and in precedence to that of the enzyme. Molecular weight determinations gave values around 3,500. Evidence for the peptide nature of the factor includes its correspondence with ninhydrin-positive material on gel filtration and paper electrophoresis and its susceptibility to pronase. Electrophoretic behavior indicated at least one free amino group and several carboxyl groups. Amino acid analysis of the peptide yielded only glutamate, glycine, and half-cystine, in equimolar amounts. However, neither GSH nor GSSG have PFK-L2-stabilizing activity. No free sulfhydryl groups were present. Chemical analysis for tryptophan was also negative. The ultraviolet spectrum confirmed the absence of aromatic amino acids. The spectrum exhibited a characteristic peptide peak at 190 nm with no absorbance beyond 240 nm. The factor is unstable to storage in the cold except in the presence of glucose or dithiothreitol. Sucrose, fructose, and GSH were ineffective in this regard. It was slowly denatured by heat or reduced pH even in the presence of glucose. The factor was induced in fasted animals specifically by glucose, of the nutrients tested, and in diabetic animals by insulin. Induction by both glucose and insulin was blocked by cycloheximide and actinomycin. The time course of the glucose induction was the more rapid of the two with a marked overshoot to 3 times normal levels at 12 hours. Increased levels of the factor preceded the increased levels of PFK-L2 brought about by glucose or insulin administration. Native PFK-L2 was inactivated by lysosomal extracts, and this inactivation was strongly inhibited by the peptide factor. These results are in accord with the proposal that the peptide plays a role in regulating PFK-L2 turnover in vivo. The factor also activated the phosphofructokinase-catalyzed reaction by promoting fructose-6-P binding. This effect is analogous to that of AMP on the kinetics of the reaction; however, the factor effect was additive to that of AMP, and the factor did not reverse inhibition by excess ATP as does AMP. We postulate that the stabilizing factor affects an equilibrium between PFK-L2 conformers in favor of one more resistant to lysosomal and thermal inactivation and with greater affinity for fructose-6-P.