The nuclear pattern of the parenchymal cells of the liver after partial hepatectomy

Dose-dependent induction of preneoplastic lesions by the tobacco-specific nitrosamine carcinogen NNK in the in ovo carcinogenicity assessment (IOCA) assay

The potential of the carcinogenic tobacco specific nitrosamine 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-1-butanone (NNK) to induce preneoplastic hepatocellular altered foci (HAF) was tested in the in ovo carcinogenicity assessment (IOCA) assay. Single doses of NNK over a dose range from 0.1 mg to 6 mg were injected into fertilized turkey eggs prior to incubation for 24 days. The livers were investigated by histological, histochemical and morphometric methods. Mortality was increased for eggs exposed to 6 mg. In this group, the whole livers were severely altered, showing pronounced changes of nucleus size and signs of cell death. At the dose of 2 mg various types of foci of altered hepatocytes (HAF) were observed. Basophilic cell foci of the solid or tubular type were most frequent. The NNK-induced HAF were very similar to the preneoplastic lesions that occur in the livers of mammals during hepatocarcinogenesis which are regarded as early indicators of carcinogenesis. The similarity to the HAF in rodents included histochemically detectable alterations like decreased activities of glucose-6-phosphatase, adenosine triphosphatase and glycogen phosphorylase. At doses of 1 mg or below, no HAF were detected. At all dose levels an increased occurrence of enlarged hepatocytes with enlarged nuclei and prominent nucleoli (karyomegalic hepatocytes) were observed. The increase in karyomegalic hepatocytes was also statistically significant at the low dose of 0.1 mg/kg NNK but the dose-effect curve for their induction was clearly non-linear. Induction of HAF and karyomegalic hepatocytes in ovo is a simple (one dose), rapid (24 days) and inexpensive (no animal purchase or housing) experimental approach for studies on chemically induced hepatocarcinogenesis.

Optimum conditions for detecting hepatic micronuclei caused by numerical chromosome aberration inducers in mice

To ascertain an optimum condition for detecting micronuclei in the liver caused by numerical aberration inducers, either carbendazim (125-1000mg/kg, p.o.), colchicine (0.375-1.5mg/kg, i.v.), cytochalasin B (2.5-20mg/kg, i.v.), diazepam (3.13-25mg/kg, i.v.), noscapine (7.8-62.5mg/kg, i.v.), paclitaxel (1-100mg/kg, i.v.) or trichlorfon (18.75-150mg/kg, i.v.) was administered once to male Slc:ddY mice 1 day before or after partial hepatectomy (PH, Day 1). Five days after PH (on Day 6), hepatic micronuclei were determined in conjunction with classifications of the main nuclei and relative liver weights as a proliferative indicator or a dysfunction marker of cell division. Additionally, hepatocyte proliferation index (HPI) was calculated by using mono-, bi- and multinucleated cell counts. Treatment of mice with six compounds, except for colchicine, after PH showed higher incidence of micronucleated hepatocytes (MNH) than that before PH, and also increases in binucleated and multinucleated cells. Especially for carbendazim, diazepam, noscapine and trichlorfon, the dosing after PH was essential for the detecting numerical aberration. Colchicine evidently increased HPI and decreased relative liver weights without MNH induction on Day 6. On Day 8 when HPI and relative liver weights almost returned to the basal range, a significant increase in MNH was noted. This implied that the strong inhibition of colchicine on hepatocyte proliferation may obstruct the induction of MNH on Day 6. In conclusion, to detect the potential numerical aberration, exposure of mice to test chemicals should be performed 1 day after PH, during which enhanced proliferation of hepatocytes was seen, and it would be better to analyze the liver specimens on Day 6 or more post-PH.

Diagnostic and prognostic value of DNA ploidy and cell nuclearity in ultrasound-guided liver biopsies

BACKGROUND

Focal nodule lesions in patients with cirrhotic livers may be visualized by using imaging techniques; however, the diagnostic and prognostic judgment of biopsies from borderline lesions may be difficult using conventional histologic criteria.

METHODS

The diagnostic and prognostic value of DNA ploidy analysis determined by image cytometry of Feulgen-stained isolated hepatocytes was investigated in ultrasound-guided biopsies from 50 nodular lesions found in patients with cirrhotic livers (39 hepatocellular carcinomas [HCCs] and 11 macroregenerative nodules) and from 10 patients with livers affected by viral chronic hepatitis. Of the 11 macroregenerative nodules, 7 presented a subsequent neoplastic behavior. Specimens from the morphologically normal livers of five patients who underwent liver surgery served as control tissues. Image cytometry was performed on Feulgen-stained cytologic preparations, obtained by enzymatic digestion of formalin fixed biopsies. The DNA ploidy of the main stem line and the distribution of mononucleated and binucleated hepatocytes (nuclearity) were compared using histologic diagnosis, Edmondson's grade, tumor size, and patient follow-up.

RESULTS

The main stem line was peridiploid in all benign specimens and in 31 clinically confirmed HCCs, peritetraploid in 11 HCCs, perioctaploid in 1 HCC, and aneuploid in 3 HCCs. The fraction of mononucleated polyploid hepatocytes was found to be the best diagnostic parameter in euploid HCCs and was significantly correlated with the Edmondson grade and the nodular size. Survival information was available for 43 patients, with a median observation period of 350 days. A DNA ploidy value of the main stem line greater than 3c was an important determinant of survival as a single parameter and in association with histologic grade and greatest dimension of tumor.

CONCLUSIONS

This study suggests that the ploidy distribution analysis of mononucleated and binucleated hepatocytes can provide valuable information for making correct diagnoses and for predicting survival outcome for patients with HCCs.

Metabolic zonation of the liver: regulation and implications for liver function

Liver parenchyma shows a remarkable heterogeneity of the hepatocytes along the porto-central axis with respect to ultrastructure and enzyme activities resulting in different cellular functions within different zones of the liver lobuli. According to the concept of metabolic zonation, the spatial organization of the various metabolic pathways and functions forms the basis for the efficient adaptation of liver metabolism to the different nutritional requirements of the whole organism in different metabolic states. The present review summarizes current knowledge about this heterogeneity, its development and determination, as well as about its significance for the understanding of all aspects of liver function and pathology, especially of intermediary metabolism, biotransformation of drugs and zonal toxicity of hepatotoxins.

Immunocytochemical determination of ploidy class-dependent bromodeoxyuridine incorporation in rat liver parenchymal cells after partial hepatectomy

Immunocytochemistry of bromodeoxyuridine (BrdU) incorporated in DNA was performed on cryostat sections of rat liver and on isolated hepatocytes after partial hepatectomy using a two-step labeling technique. The method enabled the detection of S-phase nuclei in both tissue preparations. Quantification of the number of labeled nuclei in sections showed that the number of nuclei in S-phase increased from 0.3% in control liver to about 36% at 24 h after partial hepatectomy. The detection of BrdU in isolated hepatocytes showed the same labeling index of binuclear diploid, mononuclear tetraploid and binuclear tetraploid cells. A special role for mononuclear diploid cells in proliferation did not seem to occur.

Morphometric study of alterations of extrafocal hepatocytes of rat liver treated with N-nitrosomorpholine

Male Sprague-Dawley rats were treated with the hepatocarcinogen N-nitrosomorpholine for 7 weeks and observed for up to 40 weeks after withdrawal of the carcinogen. In addition to the focal preneoplastic lesions described earlier there were also alterations in extrafocal hepatocytes and these changes have been quantified morphometrically. Since the periportal and perivenous hepatocytes were not altered to the same extent, cells of the periportal zone (PPZ) and cells of the perivenous zone (PVZ) were measured separately. Immediately after stopping treatment there was marked enlargement of the hepatocellular cytoplasm and of the nuclei in both the PPZ and the PVZ and a reduction in the number of binuclear hepatocytes. While these alterations were totally reversed during the first 10 weeks after treatment ceased in the PPZ, statistically significant changes in nuclear size, nuclear-cytoplasmic ratio and number of binuclear cells persisted in the PVZ up to 40 weeks after the end of treatment. We suggest that both the foci of altered hepatocytes as well as the persisting changes in extrafocal hepatocytes may be involved in the process of hepatocarcinogenesis.

Detection of metabolic changes in hepatocytes by quantitative cytochemistry

Studies by means of quantitative histochemistry and cytochemistry have greatly contributed to the knowledge of metabolic changes in liver parenchymal cells. In the present paper recent work along this line is reviewed with emphasis on three topics, polyploidy as a source of metabolic heterogeneity, proteolysis in the regulation of hepatocyte cell mass and ischemic injury of hepatocytes. In all three fields, accuracy and precision of information obtained by quantitative histochemical means has been greatly enhanced by a thorough knowledge of the mechanisms of histochemical reactions obtained by fundamental work on matrix chemistry, and well-considered application of optical measuring tools and conditions of measurement. These are the principles put forward by van Duijn since the pioneer period of histochemistry and to whom this review is dedicated.

Flow cytometry of renal oncocytoma: common occurrence of deoxyribonucleic acid polyploidy and aneuploidy

Flow cytometry was performed on 51 typical specimens of renal oncocytoma. Nuclei were extracted from paraffin-embedded archival material and isolated nuclei were stained with propidium iodide. Of the 51 available tissue blocks 86 per cent were evaluable and 50 per cent of these samples showed a deoxyribonucleic acid (DNA) histogram that was approximately the same as normal renal parenchyma. Of the oncocytoma samples 39 per cent showed a marked increase (more than 10 per cent of the nuclei) in the tetraploid DNA peak, while 11 per cent showed a distinct DNA aneuploid peak. Among 21 evaluable grade 2 oncocytic renal tumors 33 per cent showed a normal DNA histogram, 43 per cent showed a marked increase in the DNA tetraploid peak and 24 per cent showed a DNA aneuploid peak. The common presence of polyploid nuclei containing double quantities of chromosomal DNA may correlate with the long-standing pathological observation that oncocytic tumors often contain a distinct population of large nuclei. Indeed, 86 per cent concurrence was seen between the detection of an abnormal DNA content by flow cytometry and the histopathological presence of large abnormal nuclei in these specimens. Since renal oncocytomas (grade 1 oncocytic tumors) rarely, if ever, metastasize and are relatively noninvasive locally, their markedly abnormal flow cytometry patterns are of considerable interest. Moreover, DNA polyploidy has not been identified previously in renal tumors. The biological significance and mechanism of DNA polyploidy, and the relationship of DNA polyploidy and DNA aneuploidy to the pathogenesis of oncocytic renal tumors require further laboratory investigation. The clinical use of flow cytometry to classify and to predict the behavior of renal tumors will be complicated, since renal oncocytomas commonly have polyploid and aneuploid DNA histograms.

Ploidy class-dependent metabolic changes in rat hepatocytes after partial hepatectomy

Glucose-6-phosphate dehydrogenase (G6PDH), succinate dehydrogenase (SDH) activity and the single-stranded RNA (ssRNA) content of isolated hepatocytes of different ploidy classes from adult male rats have been studied after partial hepatectomy using quantitative cytochemical means. The SDH activity and ssRNA content in all classes of hepatocytes are decreased during the first hours after operation followed by an increase above control values. The increase of both SDH activity and ssRNA content is significant only in the mononuclear diploid (MD) cells but not in the hepatocytes of higher ploidy classes and is related with the mitotic wave at 32 h after hepatectomy. After the mitotic wave, the values quickly return to normal levels. The G6PDH activity does not show any significant change in hepatocytes other than MD cells. In MD cells the G6PDH activity is elevated on a highly significant level up to a maximum value of 3.5 times the control value at 48 h after operation. The G6PDH activity in MD cells is returned to normal values within 14 days after operation. It is concluded that: 1. The MD cells show a distinct metabolic behaviour due to their function as stem cells of liver parenchyma and retain at least some of their fetal characteristics. 2. G6PDH activity is not a transformation-linked discriminant for neoplastic metabolism.

Changes in quantitative measures of hepatic function after 90% hepatectomy in rats

Quantitative measures of liver functions were investigated in rats up to 360 h after 90% hepatectomy and related to total hepatic DNA. Galactose elimination capacity (cytosolic phosphorylation of carbohydrate), p-nitro-anisole demethylase activity (endoplasmic drug hydroxylation) and prothrombin index (protein synthesis at rough endoplasmic membranes) were initially reduced as much as the liver weight, but recovered differently. During hepatic regeneration prothrombin index and galactose elimination were back to control values after an interval of 360 h, while p-nitro-anisole demethylase activity was about 0.4 times control value after that interval. The correlation between total hepatic DNA and liver weight, and between total hepatic protein and liver weight was 0.92 in both cases, indicating their close relationship during hepatic regeneration. Compared to earlier studies on 70% hepatectomy the recovery of metabolic functions after 90% hepatectomy is delayed, as compared to regeneration of total hepatic DNA. The compensatory hyperfunction observed after 70% hepatectomy was not found after 90% hepatectomy, indicating a lost ability to hyperfunction when hepatic function is reduced close to the minimal residual function. This is suggested to be important for the sudden onset of hepatic insufficiency.

Nuclear enlargement--an early change produced in mouse epidermis by carcinogenic chemicals applied topically in the presence of a promoter

A series of 27 compounds, including 11 polycyclic hydrocarbons, 8 proximate carcinogens and 8 other compounds, were tested for their ability to induce epidermal nuclear enlargement in mouse skin. The materials were applied topically in methyl ethyl ketone containing 0.1% croton oil, repetitively for 3 days. Nuclear enlargement present on the fourth day was determined with the aid of a Quantiment image-analysing computer. The results obtained indicated a close correlation between the topical carcinogenicity of the test compounds and their ability to induce epidermal nuclear enlargement in the presence of croton oil.

Histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase

Histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase has found many applications in biomedical research. However, up to several years ago, the methods used often appeared to be unreliable because many artefacts occurred during processing and staining of tissue sections or cells. The development of histochemical methods preventing loss or redistribution of the enzyme by using either polyvinyl alcohol as a stabilizer or a semipermeable membrane interposed between tissue section and incubation medium, has lead to progress in the topochemical localization of glucose-6-phosphate dehydrogenase. Optimization of incubation conditions has further increased the precision of histochemical methods. Precise cytochemical methods have been developed either by the use of a polyacrylamide carrier in which individual cells have been incorporated before staining or by including polyvinyl alcohol in the incubation medium. In the present text, these methods for the histochemical and cytochemical localization of glucose-6-phosphate dehydrogenase for light microscopical and electron microscopical purposes are extensively discussed along with immunocytochemical techniques. Moreover, the validity of the staining methods is considered both for the localization of glucose-6-phosphate dehydrogenase activity in cells and tissues and for cytophotometric analysis. Finally, many applications of the methods are reviewed in the fields of functional heterogeneity of tissues, early diagnosis of carcinoma, effects of xenobiotics on cellular metabolism, diagnosis of inherited glucose-6-phosphate dehydrogenase deficiency, analysis of steroid-production in reproductive organs, and quality control of oocytes of mammals. It is concluded that the use of histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase is of highly significant value in the study of diseased tissues. In many cases, the first pathological change is an increase in glucose-6-phosphate dehydrogenase activity and detection of these early changes in a few cells by histochemical means only, enables prediction of other subsequent abnormal metabolic events. Analysis of glucose-6-phosphate dehydrogenase deficiency in erythrocytes has been improved as well by the development of cytochemical tools. Heterozygous deficiency can now be detected in a reliable way. Cell biological studies of development or maturation of various tissues or cells have profited from the use of histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Cytophotometry of liver cells from ethanol-fed rats: ethanol causes increased polyploidization and protein accumulation

Cellular protein and DNA content were determined by Feulgen--Naphthol Yellow S cytophotometry on isolated liver cells from rats fed ethanol for 2--6 months. It was found that parenchymal liver cells after ethanol feeding contained 13% more protein than cells of the same ploidy class from controls; that the average parenchymal cell in ethanol-fed rats contained 16% more protein than in controls due to the increased occurrence of polyploid cells; that the protein accumulation develops over 2 months, does not progress thereafter and disappears after a few days of reduced ethanol intake; that the tendency to form polyploid cells is accentuated during liver regeneration. It is suggested that the effect of alcohol on microtubular function, which is regarded as the cause of the protein accumulation, may also bring about increased polyploidization.

A cytophotometric measurement of DNA in murine hepatocytic nuclei during cytomegalovirus infection

The amount of Feulgen-DNA in the nuclei of normal murine hepatocytes as well as those from livers on the third and fifth day after lethal, cytomegalovirus infection was assessed by scanning cytophotometry. The technique enabled the measurement of the increasing content of DNA in hepatocytic nuclei during the course of the disease. The results suggest that although some of this increase may be due to cellular DNA synthesis, most of it is due to viral DNA replication. Lastly, the megalohepatocytes which characterise this disease reflect viral replication in predominantly diploid hepatocytes.

Analysis of cell cycle compartments of hepatocytes after partial hepatecomy

An analysis of cell kinetic parameters as a function of intralobular localization of hepatocytes was performed using autoradiographic methods to obtain a basis for a quantitative description of cell cycle compartments after partial hepatectomy. The influx into the S compartment revealed a maximum in a lobular zone not immediately adjacent to the portal tract, with a decrease towards the perivenous and periportal area of the lobule. The maximum influx was found in the intermediate zone at 34 hr and a lower one in the perivenous parts of the lobule at 40 hr. The influx pattern at 56 hr was similar to the situation at 18 hr. The fraction of labelled mitoses in the whole liver and in subunits of the lobule disclosed a constant duration of S whereas the duration of G2 + M was prolonged from the periportal to the perivenous zone. A graphical model of kinetic events after partial hepatectomy is proposed, which describes the sizes of the various cell cycle compartments; the model successfully predicted the results of a continuous labelling experiment.

Correlated morphometric and biochemical studies on the liver cell. II. Effects of phenobarbital on rat hepatocytes

The changes occurring in rat hepatocytes during a 5 day period of treatment with phenobarbital were determined by morphometric and biochemical methods, particular attention being paid to the endoplasmic reticulum. The hepatocytic cytoplasm played an overwhelming part in the liver hypertrophy, while the hepatocytic nuclei contributed to only a moderate extent. The endoplasmic reticulum accounted for more than half of the increase in cytoplasmic volume. The increase in the volume and number of hepatocytic nuclei in the course of phenobarbital treatment was associated with changes in the ploidy pattern. Until the 2nd day of treatment both the rough-surfaced endoplasmic reticulum (RER) and the smooth-surfaced endoplasmic reticulum (SER) participated in the increase in volume and surface of the whole endoplasmic reticulum (ER). Subsequently, the values for RER fell again to control levels, whereas those for SER continued to increase, with the result that by the 5th day of treatment the SER constituted the dominant cytoplasmic element. The specific volume of mitochondria and microbodies (peroxisomes) remained constant throughout the duration of the experiment, while that of the dense bodies increased. The specific number of mitochondria and microbodies displayed a significant increase, associated with a decrease in their mean volume. The phenobarbital-induced increase in the phospholipid and cytochrome P-450 content of the microsomes, as well as in the activities of microsomal reduced nicotinamide-adenine dinucleotide phosphate-cytochrome c reductase and N-demethylase, was correlated with the morphometric data on the endoplasmic reticulum.

The fractionation of nuclei from mammalian cells by zonal centrifugation

1. Purified liver nuclei from adult rats separate into two main zones when centrifuged in the slow-speed zonal rotor. One zone contains diploid nuclei, the other tetraploid. 2. The effect of age on the pattern of rat liver ploidy was examined. Tetraploid nuclei are virtually absent from young animals. They increase in proportion steadily with age. Partial hepatectomy disturbs the pattern of ploidy. 3. The zonal centrifuge permits the separation of diploid, tetraploid, octaploid and hexadecaploid nuclei from mouse liver. 4. Rat liver nuclei are isopycnic with sucrose solutions of density 1.35 at 5 degrees .