Cytokeratin 14 expression in rat liver cells in culture and localization in vivo

Rat liver epithelial cells (LECs) are non-parenchymal proliferating cells that readily emerge in primary culture and can be established as cell lines, but their in vivo cell(s) of origin is unclear. We reported recently some evidence indicating that the LEC line, T51B, contains two cytokeratins (CKs) equivalent to human CK8 and CK14 respectively. T51B cells also contain vimentin assembled as a network of intermediate filaments distinct from that of the CKs. In the present study, we examined the expression of CK14 gene in various LEC preparations and a Triton-resistant rat skin cytoskeletal fraction, and then assessed its usefulness as an LEC specific marker in the liver. Northern and Western blot analyses with cDNAs and antibodies for CK8, CK14, CK18 and vimentin confirmed that rat hepatocytes express CK8 and CK18 genes only, whereas T51B cells express CK8, CK14 and vimentin genes in the absence of CK18. CK14 was also present in LECs derived as primary from embryonic-day 12 rat liver and secondary cultures from 4-day-old rat liver. Primary cultures of oval cells isolated from 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) treated rat liver (an enriched source of biliary epithelial cells) contained CK14 mRNAs which were slightly shorter than those in LECs. The analyses of CK5 (the usual partner of CK14) gene expression using specific cDNA and antibody clearly demonstrated its absence in LECs. In situ double immunolocalization analyses by laser scanning confocal microscopy showed that CK14 was not present in hepatocytes (HES6+ cells) and was expressed in some biliary epithelial (BDS7+ cells). CK14-positive cells were also found in the Glisson's capsule. However, CK14-positive cells of the portal region were vimentin negative, whereas those of the Glisson's capsule were vimentin positive. Our results suggest that CK14 gene expression is part of the differentiation program of two types of LECs and that this differential CK14 gene expression can be used as a new means to type LECs in culture and in vivo.

Modulation of cytokeratin and actin gene expression and fibrillar organization in cultured rat hepatocytes

Intermediate filaments of rat hepatocytes are composed of cytokeratins 8 and 18 (CK8 and CK18, respectively). Recent work from our laboratory has indicated a close relationship between the synthesis of these cytokeratins, their organization into intermediate filaments, and the promotion of growth and differentiation of cultured rat hepatocytes by insulin, epidermal growth factor, and dexamethasone. In the present study, we examined the mRNA expression, level of protein synthesis, and fibrillar distribution of cytokeratins 8 and 18 and actin in hepatocytes, isolated from normal and dexamethasone-injected rats and cultured as monolayers or spheroids in the presence of insulin, or from normal rat hepatocytes, cultured as monolayers in the presence of dexamethasone, insulin, and dimethyl sulfoxide. The CK8 mRNA level was lower in hepatocytes isolated from noninjected rats and cultured as either monolayers or spheroids, than in those from dexamethasone-injected rats. However, the CK18 mRNA level varied in a manner that was different from that of CK8 mRNA, showing that the modes of expression of the two genes were independent. The various changes in hepatocyte culture conditions led to variations in albumin mRNA levels that largely followed those observed in CK8 mRNA levels. In the case of actin, the amount of mRNAs varied from relatively high levels in hepatocyte monolayers to extremely low levels in hepatocyte spheroids, even though in both cases the cells were isolated from dexamethasone-injected rats. These changes in mRNA levels did not necessarily correlate with changes in the synthesis of cytokeratins 8 and 18, and actin. Changes in culture conditions induced a major reorganization in the distribution of cytokeratin intermediate filaments and actin filament between the region near the surface membrane and the cytoplasm. The most divergent patterns in cytokeratin intermediate filaments and actin filament distributions were observed between hepatocytes cultured as spheroidal aggregates and as monolayers in the presence of dimethyl sulfoxide. The former condition resulted in patterns of cytokeratin and actin gene expression and fibrillar organization that best matched those in situ. In the latter condition, inappropriate patterns were obtained, in spite of the fact that dimethyl sulfoxide treated hepatocytes are known to exhibit survival and functional activities equivalent to that of hepatocyte spheroids. These results demonstrate for the first time that the survival and functional activity (i.e., albumin production) of rat hepatocytes in vitro is not necessarily correlated with a particular pattern of cytokeratin and actin gene expression and fibrillar arrangement.

Temperature-dependent immunoreactive assay to screen for digoxin-like immunoreactive factor(s)

Endogenous circulating digoxin-like immunoreactive factors (DLIF) are known to cross-react with antibodies to digoxin and to inhibit Na+/K(+)-transporting ATPase (Na+K+ATPase; EC 3.6.1.37). Moreover, increasing the immunoassay temperature from 4 to 37 degrees C markedly decreases DLIF from human cord serum. We tested several compounds, including hormonal steroids, bile salts, lipids, and methionine-enkephalin, for their ability to cross-react with two commercially available 125I digoxin RIAs, to inhibit porcine Na+K+ATPase, and to see whether they present the same incubation temperature dependence as human cord serum. Except for methionine-enkephalin, all compounds were inhibitors of Na+K+ATPase in the range of 1-10 mmol/L. Progesterone exhibited the highest cross-reactivity in the two RIAs. The apparent digoxin immunoreactivity for the majority of the cross-reacting steroids, bile salts, and linoleic acid was markedly decreased by increasing the incubation temperature from 4 to 37 degrees C, whereas estriol, pregnanediol, and nonspecific compounds (e.g., ethanol, human serum albumin) did not appear to be temperature-sensitive. Both lysophosphatidyl lipids gave an increased apparent digoxin concentration with increasing incubation temperature. Our data suggest that numerous weakly cross-reactive compounds can parallel the response of human cord serum. However, the temperature-dependent effect could be an additional criterion for identifying DLIF.

Temperature-dependent immunoreactive assay to screen for digoxin-like immunoreactive factor(s)

Endogenous circulating digoxin-like immunoreactive factors (DLIF) are known to cross-react with antibodies to digoxin and to inhibit Na+/K(+)-transporting ATPase (Na+K+ATPase; EC 3.6.1.37). Moreover, increasing the immunoassay temperature from 4 to 37 degrees C markedly decreases DLIF from human cord serum. We tested several compounds, including hormonal steroids, bile salts, lipids, and methionine-enkephalin, for their ability to cross-react with two commercially available 125I digoxin RIAs, to inhibit porcine Na+K+ATPase, and to see whether they present the same incubation temperature dependence as human cord serum. Except for methionine-enkephalin, all compounds were inhibitors of Na+K+ATPase in the range of 1-10 mmol/L. Progesterone exhibited the highest cross-reactivity in the two RIAs. The apparent digoxin immunoreactivity for the majority of the cross-reacting steroids, bile salts, and linoleic acid was markedly decreased by increasing the incubation temperature from 4 to 37 degrees C, whereas estriol, pregnanediol, and nonspecific compounds (e.g., ethanol, human serum albumin) did not appear to be temperature-sensitive. Both lysophosphatidyl lipids gave an increased apparent digoxin concentration with increasing incubation temperature. Our data suggest that numerous weakly cross-reactive compounds can parallel the response of human cord serum. However, the temperature-dependent effect could be an additional criterion for identifying DLIF.

Fumarylacetoacetase measurement as a mass-screening procedure for hereditary tyrosinemia type I

Fluorometric quantitative tyrosine determination on dried-blood spots is the primary neonatal screening test used for tyrosinemia type I (HT) in the province of Quebec. Succinylacetone determination on these same spots is used as the complementary test when the tyrosine level is higher than a given threshold. This procedure has proved to be less discriminant over the past few years because of changes in newborn feeding and because of early discharge of newborns from the nursery. We have developed an enzyme-linked immunosorbent assay (ELISA) to measure the deficient enzyme in HT in dried-blood spots. Fumarylacetoacetase (FAH) (E.C.3.7.1.2) was measured retrospectively by an ELISA on 25 dried-blood samples from proven patients with HT and prospectively in 72,000 specimens received in the neonatal screening program. In this pilot project, FAH was measured first, and, if necessary, succinylacetone was determined as the complementary test. All 25 samples from proven patients and specimens from four other patients detected in the pilot study have shown almost complete absence of FAH in dried-blood samples. At a cutoff level of 12.5% of normal adult blood spotted on the same type of paper, only 30 other cases disclosed FAH levels low enough to warrant succinylacetone measurement but had no detectable succinylacetone. The false-positive rate is thus 1:2,400 with this primary ELISA. However, blood transfusion in newborns prior to blood collection on filter paper may yield false-negative tests, since FAH is present in erythrocytes of normal donors.(ABSTRACT TRUNCATED AT 250 WORDS)

Oral loading of homogentisic acid in controls and in obligate heterozygotes for hereditary tyrosinemia type I

Homogentisic acid (HGA) (50 mg/kg) was given orally to 22 obligate heterozygotes for hereditary tyrosinemia type 1 (HT) and to 11 controls. After 1 h the mean +/- standard error (SE) plasma level of HGA was 30.42 +/- 1.41 micrograms/ml in carriers and 19.29 +/- 1.62 in controls. Mean +/- SE fasting delta-amino-levulinate dehydratase (delta-ALD) was 40.05 +/- 1.79 m microM/min/g Hb in carriers, much lower than the 60.81 +/- 5.11 found in controls. After 3 h this difference in levels of delta-ALD remained, with mean +/- SE values of 25.70 +/- 2.89 m microM/min/g Hb in carriers, compared with 48.83 +/- 5.37 in controls. Three-hour mean +/- SE excretion of fumarylacetone "equivalent" [FAc] in urine in carriers, 51.597 +/- 5.580 micrograms/mg/creatinine, was significantly higher than the 27.941 +/- 5.916 in controls. Three-hour excretion of succinylacetone "equivalent" [SAc] was also significantly higher in the urine of carriers. FAc in 3-h urine was identified by thin-layer chromatography and confirmed by gas chromatography/mass spectrometry. Multivariate stepwise discriminant analysis showed that the inclusion order of significant variables was as follows: HGA levels at 1 hr, fasting level of delta-ALD, residual level of HGA at 3 h, and 3-h excretion of [FAc]. Non-significant variables were HGA tolerance, levels of delta-ALD at 3 h, sex, and 3-h excretion of [SAc].(ABSTRACT TRUNCATED AT 250 WORDS)

Neurologic crises in hereditary tyrosinemia

Hereditary tyrosinemia results from an inborn error in the final step of tyrosine metabolism. The disease is known to cause acute and chronic liver failure, renal Fanconi's syndrome, and hepatocellular carcinoma. Neurologic manifestations have been reported but not emphasized as a common problem. In this paper, we describe neurologic crises that occurred among children identified as having tyrosinemia on neonatal screening since 1970. Of the 48 children with tyrosinemia, 20 (42 percent) had neurologic crises that began at a mean age of one year and led to 104 hospital admissions. These abrupt episodes of peripheral neuropathy were characterized by severe pain with extensor hypertonia (in 75 percent), vomiting or paralytic ileus (69 percent), muscle weakness (29 percent), and self-mutilation (8 percent). Eight children required mechanical ventilation because of paralysis, and 14 of the 20 children have died. Between crises, most survivors regained normal function. We found no reliable biochemical marker for the crises (those we evaluated included blood levels of tyrosine, succinylacetone, and hepatic aminotransferases). Urinary excretion of delta-aminolevulinic acid, a neurotoxic intermediate of porphyrin biosynthesis, was elevated during crises but also during the asymptomatic periods. Electrophysiologic studies in seven patients and neuromuscular biopsies in three patients showed axonal degeneration and secondary demyelination. We conclude that episodes of acute, severe peripheral neuropathy are common in hereditary tyrosinemia and resemble the crises of the neuropathic porphyrias.

Prospective ascertainment of complete and partial serum biotinidase deficiency in the newborn

We screened 163,000 newborn filter-paper blood samples for serum biotinidase deficiency (McKusick 25326) and found 15 probands: three had complete deficiency (incidence 18.4 cases per million live births, 95% confidence interval 4-54 cases per million); the others had partial deficiency. The positive predictive value of the test for either form of biotinidase deficiency was 9.86%. We found seasonal variation in biotinidase activity in filter-paper blood samples. The cost per test was Can.$0.27 (1987 dollar value) and per case of complete deficiency ascertained, $15,500. Family studies indicated that complete serum biotinidase deficiency is a homozygous phenotype and partial deficiency is the heterozygous form. Homozygous cases were treated with biotin and have shown no clinical manifestations (55 patient-months of observation). None of the heterozygotes (n = 42, age 3 months - 62 years) has clinical manifestations. The number of heterozygotes found by screening was much less than predicted probably because the screening test detects mainly the samples with very low (outlier) biotinidase activity. The variant allele(s) for biotinidase deficiency was more common in French Canadians than in other ethnic groups in Quebec; there was no evidence of regional clustering or founder effect.

Biochemical studies of a patient with hereditary hepatorenal tyrosinemia: evidence of glutathione deficiency

Metabolic and enzymatic studies in a patient with hereditary tyrosinemia demonstrated for the first time a deficiency of erythrocyte and hepatic glutathione. Markedly decreased hepatic fumarylacetoacetate hydrolase activity was demonstrated in this patient. The activities of hepatic enzymes not involved in tyrosine metabolism were also determined. Assay of mixed function oxidase activity demonstrated low levels of aryl hydrocarbon hydroxylase and 7-ethoxycoumarin deethylase, suggesting decreased hepatic detoxification capacity. 5-Aminolevulinic acid dehydratase activity was undetectable. Succinylacetone (4,6-dioxoheptanoic acid), an abnormal metabolic product secondary to fumarylacetoacetate hydrolase deficiency was found in serum and urine. Succinylacetone was demonstrated to inhibit 5-aminolevulinic acid dehydratase in vitro, as did the urine, plasma, and red cell lysates of the patient.

Maternal alphafetoprotein screening by the polypropylene tube immunoradiometric assay on dried blood

The polypropylene tube immunoradiometric assay for alphafetoprotein (AFP) determination was applied to maternal serum along with a radioimmunoassay technique during the second trimester of pregnancy. Blood from pregnant women was collected by finger prick on strips of chromatography paper (Schleicher and Schuell No. 903C) and air dried. A 4.75 mm disc spot was eluted in anti-AFP coated tubes containing 1.0 ml of assay medium. After one hour the medium was vortexed and the tubes washed and counted on a Concept 4tm (Micromedic Systems, Horsham, PA. 19044). The sensitivity of the technique is about 9 micrograms/l (35 ng/l in the assay) by the Rodbard formula. The concordance between the dried blood and the serum RIA tests in normal pregnancies was over 90 per cent at the 95th and 97th percentiles. This assay on dried blood spotted on chromatography paper was tested on 1003 patients and proved to be an ideal alternative to whole serum screening techniques: it minimizes sample manipulations and can easily be integrated into an existing newborn screening programme.

Detection of succinylacetone and the use of its measurement in mass screening for hereditary tyrosinemia

A technique designed to measure quantitatively succinylacetone (4,6-dioxoheptanoic acid) is presented. It essentially involves the inhibition of delta-aminolevulinate dehydratase (EC 4.2.1.24) by succinylacetone. Prior to their use in the assay, the samples are heated at 100 degrees C for 30 min in order to transform all succinylacetoacetate (3,5-dioxooctanedioic acid) to succinylacetone. By this transformation of the first abnormal metabolite specific to hereditary tyrosinemia to the second and last one, which is a powerful inhibitor of delta-aminolevulinate dehydratase, we determine in one sensitive assay the total amount of both. Succinylacetone was measured in sera and urines from 19 patients with hereditary tyrosinemia. All sera and urines contained succinylacetone at concentrations ranging, respectively, from 2 to 100 mumol/l and from 190 to 6000 mumol/g creatinine. The technique was also adapted to dried blood spots on paper and was used as a test complementary to blood tyrosine determination in mass screening for hereditary tyrosinemia. A total of 2412 samples having concentrations of 60 mg/l or more of tyrosine were assayed, and ten showed the presence of succinylacetone. These were all from newborns with hereditary tyrosinemia. The test has proven to virtually eliminate false positives, and, thereby, much clerical work and parental anxiety.

Prenatal diagnosis of hereditary tyrosinaemia: measurement of succinylacetone in amniotic fluid

A method is proposed for prenatal diagnosis in pregnancies at risk of hereditary tryosinaemia. Affected fetuses were detected on the basis of the abnormal presence in the amniotic fluid of succinylacetone, a metabolite previously identified in sera and urines of patients suffering from hereditary tyrosinaemia. Our data show that the forty amniotic control samples had no detectable succinylacetone, while succinylacetone was found in three out of the thirteen cases at risk. Following the parents' decision, these three fetuses were aborted. The ten other mothers who brought their pregnancies to term had normal infants. Enzymatic analysis from two of their aborted fetuses' livers revealed an absence or a low activity of fumarylaceto-acetate hydrolase (EC 3.7.1.2) compared with control fetal livers of the same age.

["Liberated" motricity by holding the head during the first weeks of life (author's transl)]

The instability of the head disturbs neonatal motricity. However, when the head is held during a long period of observation (30 minutes) a motricity called "liberated" motricity, probably cortical in origin can be induced. 246 children, less than 8 weeks of age, have been examined while they were sitting on a bench and while their attention was kept in alert by the examinator who was holding their heads. In 97% of cases, the reflex motricity calms down and the following signs can be observed: (a) a stage of intense communication with the examinator, (b) then, the trunk straights up and the limbs become quiet and make movements which recall those of an older infant (43,5%), at least, there is a real interest for a toy, either looked at without gestures (39%), or touched and taken in an intentional way (19%). The theorical interest of this study is to get a new aspect of the normality of neonatal motricity. The clinical knowledge is still too recent to help detecting brain damage.

Cord-blood tyrosine levels in the full-term phenylketonuric fetus and the "justification hypothesis"

The "justification hypothesis" attributes mental retardation in phenylketonuria (PKU) to an inability of the heterozygous mother to deliver an appropriate amount of tyrosine to the PKU fetus who, in turn, is unable to correct for this deficiency because of its genetic constitution. We tested this hypothesis by measuring concentrations of tyrosine and phenylalanine in cord blood obtained at delivery from nine infants with PKU and five infants with persistent (non-PKU) hyperphenylalaninemia (PHP). For each of these specimens there were four control cord-blood specimens from infants born on the same day and, generally, in the same hospital. PKU and PHP groups were similar with respect to cord-blood tyrosine and phenylalanine values. There was no biologically significant deficiency of tyrosine in cord blood of the pooled PKU and PHP deficiency of tyrosine in cord blood of the pooled PKU and PHP groups (54 +/- 10 microM, mean +/- SD) compared with controls (61 +/- 16 microM, P = 0.13). On the other hand, phenylalanine in cord blood of the pooled PKU and PHP groups was significantly increased (144 +/- 30 microM, mean +/- SD) compared with controls (128 +/- 24, P = 0.004). The mangitude of the differences in cord-blood tyrosine and phenylalanine between control and PKU subjects are so small that it is unlikely that they have any consequences for physical and mental development. The justification hypothesis, as it pertains to blood tyrosine at term, is not upheld.

Toxicity, pharmacokinetics, and cholesterol-inhibitory effect of 7-ketocholesterol

The possible toxic effect of intravenous 7-ketocholesterol (7-KC), a steroid which has been shown to inhibit cholesterol flux in the arterial wall, was investigated in rabbits. The histology, hematology and blood chemistry were compared in 4 control animals, 3 animals receiving high doses (5.50 +/- 0.33 mg/kg/day) and 4 animals injected with lower doses 1.85 +/- 0.28 mg/kg/day) of the oxygenated sterol. Each animal received a total of 16 injections at the rate of 2 injections per day. Pharmacokinetic studies on the disappearance rate of [4-(14)C]7-KC were also carried out. Pathologic changes in the organs of animals injected with 7-KC were few. In one animal exposed to the higher concentration of 7-KC, some granulomatous angiitis in the lung was noticed. Changes in the liver were not significantly different from those observed in the control animals. Inhibition of arterial flux of cholesterol (inhibition of 55%) was noticed with high and low doses of the oxidized sterol. The disappearance curves of [14C]cholesterol in blood and plasma were characteristic of a 2-compartment model. The rate constant determining tissue uptake of 7-KC was higher than tissue efflux and there was no appreciable reflux into red cells. The results indicate that it is possible to reduce cholesterol flux in the arterial wall of rabbits without causing major toxic changes and that both red cells and tissue act as a reservoir for the oxygenated sterol.