Rapid acidification of endocytic vesicles containing asialoglycoprotein in cells of a human hepatoma line

Acidification of endocytic vesicles has been implicated as a necessary step in various processes including receptor recycling, virus penetration, and the entry of diphtheria toxin into cells. However, there have been few accurate pH measurements in morphologically and biochemically defined endocytic compartments. In this paper, we show that prelysosomal endocytic vesicles in HepG2 human hepatoma cells have an internal pH of approximately 5.4. (We previously reported that similar vesicles in mouse fibroblasts have a pH of 5.0.) The pH values were obtained from the fluorescence excitation profile after internalization of fluorescein labeled asialo-orosomucoid (ASOR). To make fluorescence measurements against the high autofluorescence background, we developed digital image analysis methods for estimating the pH within individual endocytic vesicles or lysosomes. Ultrastructural localization with colloidal gold ASOR demonstrated that the pH measurements were made when ligand was in tubulovesicular structures lacking acid phosphatase activity. Biochemical studies with 125I-ASOR demonstrated that acidification precedes degradation by more than 30 min at 37 degrees C. At 23 degrees C ligand degradation ceases almost entirely, but endocytic vesicle acidification and receptor recycling continue. These results demonstrate that acidification of endocytic vesicles, which causes ligand dissociation, occurs without fusion of endocytic vesicles with lysosomes. Methylamine and monensin raise the pH of endocytic vesicles and cause a ligand-independent loss of receptors. The effects on endocytic vesicle pH are rapidly reversible upon removal of the perturbant, but the effects on cell surface receptors are slowly reversible with methylamine and essentially irreversible with monensin. This suggests that monensin can block receptor recycling at a highly sensitive step beyond the acidification of endocytic vesicles. Taken together with other direct and indirect estimates of endocytic vesicle pH, these studies indicate that endocytic vesicles in many cell types rapidly acidify below pH 5.5, a pH sufficiently acidic to allow receptor-ligand dissociation and the penetration of some toxin chains and enveloped virus nucleocapsids into the cytoplasm.

Intercellular junctions in hepatocellular carcinoma

The freeze-fracture technique has been used to study the organization of intercellular junctions in two cases of hepatocellular carcinoma. A tumor free cirrhotic liver has been included for comparison. Tight junctions were disorganized in the tumor cells of hepatocellular carcinoma. The tight junction networks often were not orientated parallel to the canalicular lumen. In some areas tight junctions comprised 2 to 4 strands, while in other areas they were reduced to a single strand. Discontinuities and local proliferation of tight junctions were also seen. Some tight junctions were composed of intramembrane particles aligned to form a discontinuous network. Gap junctions between the tumor cells were small and infrequent. Gap junctions were found only on the lateral plasma membranes and were not seen within the tight junction networks. These findings have been interpreted to indicate changes in intercellular communication, and an alteration in the ability of hepatocytes to differentiate tight junctions in hepatocellular carcinoma.

Research needs for hepatic injury due to environmental agents

This report presents an overview of the patterns of liver injury produced by presently recognized toxic substances in the environment. Current concepts of the metabolic disposition of these substances in the liver suggest that their toxic effects may be modulated by an interplay between enzymatic pathways for activation or inactivation of foreign compounds. A better understanding of the genetic control of the enzymes involved in these pathways, as well as the mechanisms of cell death or malignancy produced by the products of these pathways, is needed. Although a number of sensitive biochemical tests of liver function are currently available, development of specific, noninvasive screening tests for the earliest manifestations of liver injury are urgently needed.

[Correlation between protein thiols and the doubling time of various rat hepatomas]

The SH content of the soluble proteins (nanomol./mg protein) from five transplantable rat hepatomas and from the DENA-hepatoma were determined with dithionitrobenzoate (Ellman reagent). Both the total number of thiols as well as the number of SH groups that can be blocked by hydroxypentenal (HPE) increase with increasing growth rate of the tumors. In comparison with the protein thiol content of the slowest growing DENA-hepatoma (doubling time 100 days), the total protein thiols of the fastest growing Yoshida hepatoma (doubling time 2,5 days) increase by 100% and the HPE-sensitive protein thiols by 350%. The total protein thiols are significantly correlated with the growth rate (probability of error 5%), the HPE-sensitive thiols are correlated with high significance (probability of error less than 1%). These results are in accordance with the "Molecular Correlation Concept" of G. Weber and might possibly be understood as a consequence of reprogramming of gene expressions.

An evaluation of cellular lineages in the pathogenesis of experimental hepatocellular carcinoma

Analysis of liver from rats exposed to chemical hepatocarcinogens has led to a model that postulates sequential premalignant changes, culminating in hepatoma formation from neoplastic nodules. Several experimental protocols devised during the last quarter century have focused upon this lineage model. But proof that neoplastic nodules are the definitive premalignant lesions has not been achieved. Recent work, using alpha-fetoprotein as a marker for liver cell alterations induced by different carcinogen-feeding regimens, suggests that chemically induced hepatomas may also arise from nonnodular cell populations. Therefore, the extensive biochemical and biological studies of presumed "premalignant" cells may have utilized the wrong cells. Unequivocal identification of the cell population at risk for malignancy is needed to delineate mechanisms by which chemicals cause hepatocellular carcinoma.

Thyroxine binding globulin and thyroid function tests in patients with hepatocellular carcinoma

To determine the prevalence of elevated serum concentrations of thyroxine binding globulin (TBG) in patients with hepatocellular carcinoma (HCC) and the influence of the associated cirrhosis, TBG was measured in 39 patients with HCC, 22 with and 17 without cirrhosis, in 20 patients with cryptogenic macronodular cirrhosis but without HCC, and in 40 matched controls. The mean serum TBG concentration in the patients was 34.5 +/- 17.7 microgram per ml, compared to 21.4 +/- 6.8 microgram pr ml in controls and 20.5 +/- 6.3 microgram per ml in cirrhosis without HCC (p less than 0.01). The presence or absence of cirrhosis in the HCC patients did not significantly influence the frequency with which elevated TBG levels were found; levels were normal in every subject with cirrhosis and no HCC. The mean thyroxine (T4): TBG ratio was 5.58 +/- 1.78 in controls and was reduced in HCC patients with both elevated (3.33 +/- 0.80, p less than 0.001) and normal TBG values (4.39 +/- 1.90, p less than 0.05), and in cirrhotics without HCC (4.29 +/- 1.01, p less than 0.01). T4 and TBG concentrations correlated significantly in controls, in HCC patients with elevated TBG, and in the cirrhotics without HCC. It is concluded that in patients with HCC (i) TBG levels may be elevated both in the presence or absence of cirrhosis; (ii) there is reduced binding of T4 TBG, and (iii) a low T4:TBG ratio excludes the diagnosis of hyperthyroidism in the presence of high T4 levels. TBG levels are normal in patients with cryptogenic macronodular cirrhosis without HCC.

Effect of portal venous blood flow diversion on portal pressure

To anticipate the hepatic vascular response to portacaval anastomosis, we studied portal pressure during diversion of portal blood through a temporary extracorporeal umbilical vein to saphenous vein shunt. The relationship of portal pressure to shunted flow was approximately linear. In five schistosomiasis patients (controls) portal diversion to 1,250 ml/min gave portal pressure-shunted flow curve slopes ranging from 0.13 to 0.57 cm water/100 ml per min (0.31+/-0.18, mean+/-SD). In 17 cirrhotic patients with portal hypertension a continuum of slopes was observed from within mean+/-2 SD of control (type A) to larger slopes (type B) indicating failure of portal pressure regulation. When portal flow was augmented by shunting from saphenous vein to portal vein, cirrhotic patients who had slopes less than mean+/-2 SD of controls during diversion (type A) exhibited a compliant system with small increases in portal pressure, whereas type B patients had significantly greater pressure increases. Selective investigations suggested that changes in portal pressure provoked compensatory changes in hepatic arterial blood flow that tended to maintain portal pressure at a set point. Type B patients demonstrated failure of this mechanism to varying degrees.After end-to-side portacaval shunt, seven type A cirrhotic patients maintained residual intrahepatic venous pressure unchanged from prior portal pressure, whereas six type B patients had a significant decrease. Residual intrahepatic venous pressure was measured after portacaval shunt in 40 cirrhotic patients who were followed for as long as 9 yr (median survival 4.0 yr). The 13 patients who developed chronic encephalopathy had significantly lower pressure (21.1+/-4.4 cm, mean+/-SD) and shorter survival (median 0.6 yr) than the other 27 patients (32.6+/-5.3 cm, 5.0 yr). The preoperative estimation of portal pressure-diverted portal flow curve slope anticipates the hepatic vascular response to portacaval anastomosis and identifies a group of patients in whom loss of portal blood flow results in a low residual intrahepatic venous pressure that is associated with early death and chronic encephalopathy.

Remnant liver function during surgery for extensive hepatic resection

True functional reserve of remnant liver should be determined at the same condition that contemplated hepatectomy has been performed, and this condition can be achieved before resection by temporary clamping of the inflow vessels of hepatic lobes to be removed. Using indocyanine green (ICG), the remnant liver function (RLF) was evaluated whether or not the method can be a useful indicator for or against hepatomy. In the study of healthy dogs, the RLF proved to be a reliable indicator to prospect hepatic failure which may occur after extensive resection of the liver. Then, the method was employed in nine patients who underwent 40 to 70 per cent hepatectomy. The results indicated that the RLF with ICG during surgery, if performed under stable hemodynamics, is a beneficial tool to decide the resectability in equivocal cases.

Role of leucocytes in ascites in the production of factor(s) stimulating differentiation of mouse myeloid leukemia cells

Although the ascitic fluid of animals bearing various tumors and that of mice induced by complete Freund's adjuvant had high activity for inducing differentiation of myeloid leukemic cell line (M1) from an SL mouse to macrophages and granulocyte-like cells, the activity in the ascitic fluid of syngeneic mice bearing the M1 cells was markedly reduced. Macrophages and granulocytes were abundant in the active ascites of animals bearing tumors (8 to 12% of the total ascites cells) while in the ascites of syngeneic mice bearing the M1 cells they were not (0.1 to 0.7% of the total ascites cells). Appearance of lymphocytes in the ascites of both types was not significantly different. Although the conditioned media of the Ehrlich tumor cells, M1 cells, and whole ascites cells with the M1 cells were not active in inducing differentiation of the M1 cells, the conditioned media of all the ascites cells with Ehrlich tumor cells and those of peritoneal macrophages and granulocytes in mice did show a high activity. These results indicate that the peritoneal macrophages and granulocytes in the ascites are responsible for the production of factors stimulating differentiation of the M1 cells.

[Change in the resistance of partially hepatectomized mice to transplanted tumors in the period of liver regeneration completion]

There were two inhibition periods of the growth of ascitic hepatoma 22a when its cells were transplanted intraperitoneally to partially hepatectomized A/he mice 1 to 12 days after the operation. The first inhibition took place when the transplantation was performed one day, and the second--3 to 10 days, after partial hepatectomy. The animals which were most resistant to this tumour (5 to 8 days after the operation) proved to be resistant, although to a lesser extent, to the intraperitoneal transplantation of sarcoma 37 and Ehrlich's adenocarcinoma.

[Rate of progress of the 1st post-stimulation division of the mitotic cycle by cells of ascitic hepatoma 22A of different ages]

A study was made of the progress rate of cells of the ascitic hepatoma 22A of different age during the iirst mitotic cycle after the stimulation of division. The "ageing" (11-day), terminal (14-day), and "delayed" (4 days older than the terminal stage) ascitic fluids were used. The maximal values of the labeled nuclei index was found to be reached by 9--12 hours (it was mainly due to the transtion of the quiescent to the S-period) and the maximal mitotic index--by 18--21 hours after the inoculation, independently of the tumour age. These results suggest that the duration of both the prereplicative (G1) period and of the whole first mitotic cycle after the stimulation were independent of the time during which the cells of the ascitic hepatoma 22A were at the resting stage or at the very prolonged G1-period.

Effect of pyridoxine on the growth of Morris hepatoma No. 7288Ctc and enzyme activity

The effect(s) of lack of dietary pyridoxine (PX) on the growth of Morris hepatoma no. 7288Ctc was studied. Buffalo strain female rats were fed a diet lacking PX. Pair-fed controls were fed the same diet with PX added. Animals were inoculated with no. 7288Ctc hepatoma cells at 21 days and were sacrificed 16 days later. Host livers and tumors were removed, weights recorded and the activity of tyrosine aminotransferase (TAT; L-tyrosine: 2-oxoglutarate aminotransferase, EC 2.6.1.5) was determined in both host liver and hepatoma. The average weight of 30 hepatomas grown in pair-fed control rats was 11.61 +/- 1.5 g while the average weight of the same number of hepatomas grown in animals fed the PX free diet was 4.73 +/- 0.7 g (P less than 0.001). Further TAT specific activity levels were 39% and 32% higher in host livers and tumors from deficient animals, respectively. The results show that availability of dietary pyridoxine stimulates the growth of this hepatoma and, in addition, exercises a type of control over the expression of TAT activity.

Solid tumor models for the assessment of different treatment modalities: I. Radiation-induced changes in growth rate characteristics of a solid tumor model

A computer program has been developed to quantitatively evaluate changes in tumor growth rates of a solid tumor model (hepatoma 3924A) after a series of radiation doses from 375 R to 3750 R. The computer-derived growth curves are simulated from the volumes of the individual tumors rather than from the mean tumor volume at any specific time point after treatment. The ability to generate data from a family of tumor growth curves permits a more precise evaluation of therapeutic effects on tumors than can be obtained with conventional methods. The quantitative determination of equivalent amounts of radiation needed to produce comparable 5-fluorouracil-induced changes in tumor growth rate has been made. The ability to determine quantitatively radiotherapeutic and chemotherapy equivalents on these solid tumor models has direct implications in regard to our effort to improve the treatment of cancer. At present no specific solid tumor or groups of solid tumors have provided all of the necessary information for clinical utilization in therapeutic scheduling of different forms of cancer treatment. Since solid tumors comprise the majority of human cancer, one of the primary objectives of these studies has been the establishment of a solid tumor model that could serve both as a system for devising improved therapeutic scheduling and for a better understanding of solid tumors.

Reticuloendothelial system function test using 131I-labeled aggregated albumin

The reticuloendothelial system function test using 131I-labeled aggregated human albumin (131IAA) as test particle is thought to be one of the best methods for the study of RES function of human beings. This method needs a large amount of 131IAA, but 131IAA has been used as a tracer of liver scintiscanning, and we tired to study RES function by using commercially available 131IAA specially made as tracer of liver scintiscanning. Because the amount of 131IAA used in this study was smaller than the critical dosis, our interest was focussed on the catabolic activity of 131IAA phagocytized by Kupffer's cells. The plasma obtained 60 min after 131IAA injection was fractionated into two distinct peaks by gel column chromatography; ionic 131I and protein-bound 131IAA. The ratio between ionic 131I and bound 131IAA (F/B ratio) was studied in various diseases. The F/B ratios of liver cirrhosis and hepatoma were significantly lower than that of the control. The lowered F/B ratio had no correlation with other liver function tests, data of hepatic scintiscanning, or with clinical findings. The F/B ratio was also not correlated with congo red index as RES function test.

Hepatic dearterialization in 3'-methyl-4-dimethylaminoazo-benzene-induced hepatocellular carcinoma with special reference to circulatory dynamics and mitochondrial functions

This time trend of hemodynamics and mitochondrial functions were studied to determine whether the ligation of the hepatic artery would result in an antitumor effect on 3'-methyl-4-dimethylaminoazobenzene-induced hepatic carcinoma in rats. The studies revealed that the hepatic tumors were nourished predominantly by the artery and less by the portal vein; the size of the vascular beds in the hepatic tumors decreased as compared with those in the non-tumor area; and as the tumors grew larger, the artery became less predominant and the size of vascular beds decreased further. The mitochondria in the tumor were characterized by impaired growth, impaired oxidative phosphorylation, and by the low activity and nucleotide specificity of membrane bound ATPase. Hepatic dearterialization enhanced ischemia in the tumors and was accompanied by intensified impairment of the aerobic energy production, resulting in necrosis of the tumor. The effects of the dearterialization tended to decrease after the 5th day following the operation. In view of the gross findings upon relaparotomy and the recovery of hemodynamics and mitochondrial functions, this tendency appeared to be chiefly attributed to the increasing collateral circulation.

The use of multiple radionuclide imaging to differentiate the focal intrahepatic lesion

Thirty-five patients with various focal intrahepatic lesions were evaluated with multiple radionuclides. Comparison of the blood pool scans with angiography and histology demonstrated an excellent correlation of these studies. Diagnostic accuracy was improved by separating the blood and pool scans into 3 categories. Each category suggested, at most, one further study to provide specific diagnostic information. Thus, by utilizing 3 radiopharmaceuticals, one can be more specific in preoperative diagnoses.

The variable course of primary hepatocellular carcinoma

Analysis of the clinical course in 85 patients with histologically proved primary hepatocellular carcinoma showed that 73 followed the classic pattern of the disease with a rapid onset and a quick demise. Howeoer, in I2 patients the course was longer in that the duration of illness was over 2 years. This was largely accounted for by the duration of symptoms prior to diagnosis. No clinical differences could be discerned between these 12 patients and the other 73, and survival once diagnosis had been made was no different. The frequency of an underlying cirrhosis in the whole series was 58 per cent. The course of these patients differed in no way from those without cirrhosis except that the age hepatocellular carcinoma presented was older. One patient who received no specific therapy lived for 4 years from the time of diagnosis, and in each of the treatment groups there were occasional patients surviving for several years.