A specific gastrin receptor site in the rat stomach.

A specific receptor for gastrin I has been demonstrated in the rat stomach fundus. Specific binding of 125I-labelled gastrin I was localised to particles sedimenting between 250--20 000 X g. Saturation of binding sites occurred with a gastrin concentration of 10(-11) M in an assay system containing 0.6--1.7 mg/ml of homogenate protein. Gastrin binding was shown to be reversible, temperature- and pH-dependent, and susceptible to tryptic digestion. Electron microscopic and enzymatic studies showed the binding fraction to contain predominantly mitochondria. Preincubation of the homogenate with 10(-8) M cholecystokinin or secretin inhibited gastrin binding to a greater extent than an equimolar concentration of pentagastrin. Cimetidine, a histamine receptor antagonist, did not affect binding of gastrin to the receptor.

Increased intestinal uptake of cobalamin in pregnancy does not require synthesis of new receptors.

Increased intrinsic factor cobalamin binding to receptors present in ileal mucosa from mice in the late stages of pregnancy is regulated by placental lactogen. In mice at day 18-20 of pregnancy given an intraperitoneal injection of cycloheximide, 0.5 mg/kg, receptor binding was reduced from 0.42 ng/mg protein to 0.18 ng/mg protein 4 h later. Intestinal mucosal protein synthesis was less than 20% of control values after this dose of cycloheximide. Although this result could be interpreted to mean that the increase in receptors in pregnancy was due to new protein synthesis, cycloheximide-treated mice also had reduced concentrations of placental lactogen in serum. Supplementation with the hormone in cycloheximide-treated mice maintained receptor binding at pregnant levels. Analysis of binding data showed receptor number to be 3.1 X 10(11)/mg protein and the binding constant (Ka) to be 0.5 X 10(12) M-1, which were similar to values found in untreated pregnant mice. It is concluded that, because the increase in receptors cannot be explained on the grounds of new protein synthesis, placental lactogen may recruit cryptic intrinsic factor cobalamin receptors.

Tolerance to rat liver allografts. I. Differences between tolerance and rejection are more marked in the B cell compared with the T cell or cytokine response.

Liver allografts in the fully allogenic combination of LEW donor liver to DA recipient (LEW-->DA) are spontaneously tolerated (TOL) with no requirement for immunosuppression, while DA-->LEW allografts are rejected in 12-15 days (REJ). We investigated the mechanism of tolerance induction by identifying differences between TOL and REJ grafts from day 1 to day 9 after transplantation and in normal livers and syngeneic liver graft controls. Infiltrating cell populations were counted after immunohistochemical staining of liver graft sections. There were occasional minor differences between TOL and REJ grafts in the T cell or CD11b/c+ (monocyte/macrophage/granulocyte) infiltrate. In contrast, there was a major difference in B cell infiltrate between TOL and REJ liver grafts. Membrane IgD+ cells were significantly greater in TOL (1796 +/- 225) versus REJ (569 +/- 281) (P = 0.004) portal tracts, as were B220+ cells (1086 +/- 100 vs. 181 +/- 105, P = 0.0004) and CD45RC+ cells (2317 +/- 456 vs. 597 +/- 194, P = 0.004). IgG1, IgG2a, IgM, and IgD deposition in liver allografts, identified by immunohistochemical staining of tissue sections, revealed no IgG or IgD in normal rat liver and low levels of IgM. Deposition of IgG1 was observed in REJ but not in TOL liver on days 7 and 9. IgM was increased in both TOL and REJ liver and appeared to be associated mainly with hepatocytes in REJ and with infiltrate in TOL liver. There was a parallel increase in IgG1-expressing plasma cells in the spleen and lymph nodes of REJ but not TOL animals. Cytokine mRNA was analyzed by reverse transcription and semiquantitative polymerase chain reaction amplification of liver RNA. Increased levels of IL-2, IL-4, IL-6, IL-10, TNF-alpha, transforming growth factor-beta, and IFN-gamma were observed, with similar levels of expression in TOL compared with REJ liver. Cytokine mRNA in syngeneic grafts was not different from normal except for IL-6 and transforming growth factor-beta, which were increased. There is no major difference in the T cell component of the infiltrate or in the extent of upregulation of cytokine mRNA between TOL and REJ grafts. There is a major difference in the B cell compartment, with more B cells in TOL livers and deposition of IgG1 in REJ grafts.

Deletion of spontaneous rat liver allograft acceptance by donor irradiation.

Liver transplants in rodents or pigs are often spontaneously accepted across a complete MHC mismatch. They induce tolerance to grafts of other organs or skin of liver donor strain and can even suppress ongoing rejection of heart grafts. It has not been established whether liver-induced tolerance is due to components of the liver or to passenger leukocytes within the liver. We depleted populations of passenger leukocytes from the transplanted liver by irradiation of the donor with 10 Gy, followed after 7 days by transplantation of the liver. Recipients of livers from irradiated donors had a median survival of 16 days compared with > 100 days for recipients of livers from normal donors. Examination of recipients of irradiated donor livers showed that allograft rejection was the cause of death. Syngeneic transplants of irradiated PVG donor to PVG recipient or of irradiated DA donor to DA recipient survived indefinitely. Parking of livers from irradiated PVG donors in normal PVG animals for 36 hr reconstituted tolerance when the livers were retransplanted to DA recipients. Livers from irradiated donors had greatly reduced passenger leukocyte numbers compared with normal or parked livers, with virtually complete loss of lymphocytes. These results show that spontaneous liver allograft acceptance is associated with populations of passenger leukocytes that are depleted by donor irradiation.

Evaluation of a commercial enzyme radioimmunoassay kit for serum carcinoembryonic antigen.

An enzyme immunoassay kit for carcinoembryonic antigen (CEA) that uses plastic beads coated with guinea-pig anti-CEA as first antibody and goat anti-CEA conjugated with horseradish peroxidase as second antibody has been evaluated. The method does not involve perchloric acid extraction and therefore avoids a dialysis procedure. It is accurate, sensitive, and inexpensive to operate, and provides values comparable to those obtained with the Roche-CEA Z-Gel radioimmunoassay.

An Australian experience of hepatitis B infection, cirrhosis and hepatocellular carcinoma.

A review of 180 patients with either chronic hepatitis or hepatocellular carcinoma (HCC) indicate a significant association. 40 patients with chronic hepatitis were seen between 1975-79. 6/25 of chronic active hepatitis and 7/15 with chronic persistent hepatitis were HBsAg positive (RIA). In the 41 patients with HCC, 15 (37%) were alcoholic, 10 cirrhosis (HBsAg positive), 5 haemochromatosis 5 cryptogenic cirrhosis, 2 probably due to sex steroids and in 4 no aetiological factor was apparent. HBsAg was present in 10/22 (45%) of HCC with cirrhosis, 15/256 (6%) for alcoholic cirrhosis, 5/16 (33%) for haemachromatosis and 5/30 (16%) cryptogenic cirrhosis. 8/80 (10%) who had acute viral hepatitis (B) are antigen positive at 6 months. This report shows that Hepatitis B virus infection is now a significant causes of liver injury in 180 patients studied. The majority of patients who have HBsAg positive cirrhosis do not have a history of acute hepatitis.

Importance of vitamin B12 and folate metabolism in malabsorption.

The risk of developing folate deficiency is greatest in patients who have a poor diet and malabsorption secondary to disease of the jejunal mucosa or drugs which interfere with its metabolism. In contrast to cobalamin deficiency, in which body stores delay the onset of major metabolic complications, folate deficiency may develop in a matter of months. It is frequently possible to predict these deficiencies and always possible to reverse them by supplementation.

In vivo evidence that cobalamin is absorbed by receptor-mediated endocytosis in the mouse.

This study examines the mechanism of cobalamin absorption in the context of receptor-mediated endocytosis. Uptake, the amount of cobalamin that left the intestinal lumen, and transport, the component that was located in organs beyond the intestine, were measured after feeding saturating doses of [57Co]cobalamin to mice. Uptake from a 40-ng dose of [57Co]cobalamin at 1 h was 18.6 +/- 6.3 ng (mean +/- SD; n = 6). When the dose was given 1 h after 40 ng of unlabeled cobalamin, uptake was 18.5 +/- 1.5 ng, n = 6, indicating rapid clearance of the surface receptors. Transport of the initial and of a subsequent dose of cobalamin could not be detected for 2 h but the amounts and rates of transport were similar. Oral chloroquine and intraperitoneal cycloheximide reduced transport at 4 h to 4.3 +/- 1.6 ng, n = 8 and 5.6 +/- 2.4 ng, n = 7, respectively. Control values were 14.3 +/- 1.3 ng, n = 8. These results indicate that the transport of cobalamin involves a series of compartments, one of which may be lysosomal, and that there is a requirement for new protein synthesis.

Malignancy in a 19-year experience of adult celiac disease.

Malignancy has developed in 10 of 93 patients with celiac disease who attended this hospital from 1959 to 1978. Four patients developed lymphoma, 5 a squamous carcinoma of the esophagus, and 1 an adenocarcinoma of the ileum. Because the majority of patients were ingesting varying amounts of gluten at the time of their follow-up no conclusion can be drawn about the possible role of a gluten-free diet in the prevention of malignancy.

Effect of placental lactogen on the number of intrinsic factor receptors in the pregnant mouse.

Experiments were designed to identify the factor in serum which has been shown to result in an increased number of intrinsic factor (IF) receptors in the small intestine of the mouse in late pregnancy. IF receptors for cobalamin (Cbl) were measured by determining the quantity of IF-57CoCbl bound in ileal homogenates. A Scatchard plot of the binding data confirmed that there was an increase in the number of IF receptors and revealed that there was a reduction in their affinity constant (K alpha). The K alpha for pregnant mice was 0.7 x 10(12) M-1 compared with 2.8 x 10(12) M-1 in nonpregnant mice. The number of receptors decreased between 2 and 4 hr after hysterectomy (Hx) in day 19 pregnant mice. Hourly injections of human placental lactogen (PL) maintained IF-Cbl binding at pregnant levels in the Hx mice. Growth hormone but not prolactin produced a similar response. The smallest quantity of PL which was effective was 1 microgram. Placental lactogen did not have an effect on IF-Cbl binding in nonpregnant female mice. Neither hypophysectomy nor ovariectomy affected IF-Cbl. It is proposed that placental lactogen is the serum factor which is responsible for the increased number of IF receptors in the pregnant mouse.

Role of the placenta in intestinal absorption of iron in pregnant rats.

Intestinal uptake (U) and transport (T) of a 40-mug dose of 59Fe from an isolated duodenal loop has been shown to increase from day 15 of pregnancy until term in the rat. U, 60.4 +/- 4.3%, and T, 44.0 +/- 4.6%, were significantly (P less than 0.01) higher than control values, which were 31.6 +/- 3.6% and 18.9 +/- 1.8%, respectively, and resembled those in nonpregnant iron-deficient rats. Eighteen hours before the increase in absorption there was a rapid fall in the t1/2 of 59Fe in maternal serum to 37.2 +/- 3.4 min (control, 72.1 +/- 2.4 min). Hysterectomy at day 20 to 21 of pregnancy resulted in a rise in t1/2 59Fe within 5 hr to 58.0 +/- 4.7%, followed by a fall in U and T to a degree comparable to that in rats studied 18 hr postpartum. Fetectomy had no significant effect on U, 63.8 +/- 2.7%, T, 34.7 +/- 3.4%, or t1/2 59Fe, 27.8 +/- 2.5 min, when compared with corresponding values in day 20 to 21 pregnant rats. The results indicate the importance of placental iron uptake in the control of iron absorption during the 3rd week of pregnancy.