Distinct effects of transforming growth factor-beta on EGF receptors and EGF-induced DNA synthesis in primary cultured rat hepatocytes

Previous studies showed that transforming growth factor-beta (TGF-beta, 1 ng/ml) strongly inhibited DNA synthesis induced by epidermal growth factor (EGF) in primary cultures of adult rat hepatocytes. This paper reports that TGF-beta (4 ng/ml) caused marked increase of EGF-binding to cultured rat hepatocytes. The binding increased biphasically with time to a maximum after treatment with TGF-beta for 12 h. Scatchard analysis showed that adult rat hepatocytes had a single class of non-cooperative binding sites with a Kd of 1.5 nM, that there were 1.4 X 10(5) binding sites/cell, and that TGF-beta increased the number of binding sites without changing the Kd value. The increase in EGF binding sites by TGF-beta was dose-dependent and the dose that elicited the maximum increase was about 10 times that which inhibited DNA synthesis stimulated by EGF. These findings suggest that the effect of TGF-beta in modulating the EGF receptor is not directly related to that in inhibiting DNA synthesis in adult rat hepatocytes.     

Micrococcus luteus homolog of theEscherichia coli uvrA gene: Identification of a mutation in the UV-sensitive mutant DB7

Summary Restriction fragments ofMicrococcus luteus DNA containing the gene affected by a mutation in the UV-sensitive mutant DB7 were cloned both from the wild type and from the mutant in anEscherichia coli host-vector system. The wild-type fragment was able to reverse the multiple sensitivity of the mutant to UV, mitomycin C, and 4-nitroquinoline 1-oxide by a one-step transformation. Determination of the nucleotide sequences revealed a potential open reading frame coding for a protein of 992 (tentative) amino acid residues, within which the DB7 mutation was identified as a CG-to-TA transition causing a translation termination. The putative product of the open reading frame shares an extensive amino acid sequence homology with theE. coli UvrA protein comprising 940 residues. The homology extends over the greater part of both polypeptides except for two extra sequences of 31 and 24 amino acid residues located at the amino-terminal and in the interior, respectively, of theM. luteus protein. In the homologous region, 56.7% and 16.7% of the 933 pairs of the aligned amino acids were accounted for by conserved residues and conservative substitutions, respectively. These results indicate that the gene defined by the mutation in DB7 represents a homolog of theE. coli uvrA gene. Hence, it has to be concluded that DB7, known for its deficiency in UV endonuclease (pyrimidine dimer DNA glycosylase/apurinic-apyrimidinic endonuclease) activity, is a double mutant which is also defective in an enzyme complex similar to theE. coli UvrABC excinuclease. Dedicated to the memory of Shunzo Okubo (1930–1978), who considered the possibility of a double-mutant status for the mutant DB7 most seriously     

Accumulation of hepatic collagen following long-term administration of sake to rats

Sake, a rice wine, induced hepatic collagen accumulation in rats. This was noted after 16 weeks of a liquid diet containing 35% ethanol by caloric content. However, under similar experimental conditions, whiskey and ethanol did not produce any changes. Hepatic collagenase activities in sake-fed rats were slightly, but significantly, higher than in the whiskey group. The central and pericellular liver fibrosis in sake-fed rats was caused possibly by either accelerated collagen synthesis or maturation, exceeding the increased collagen degradation. Mechanisms of enhanced fibrogenesis in sake-fed rats were discussed.     

Novel Isoforms of Mouse Myelin Basic Protein Predominantly Expressed in Embryonic Stage

Abstract: Myelin basic protein (MBP), a major protein of myelin, is thought to play an important role in myelination, which occurs postnatally in mouse. Here we report that the MBP gene is expressed from the 12th embryonic day in mouse brain and that most of the predominant embryonic isoforms are not those reported previously. These isoforms have a deletion of a sequence encoded by exon 5 from the well-known isoforms. These isoforms show a unique developmental profile, i.e., they peak in the embryonic stage and decrease thereafter. In jimpy, a dysmyelinating mutant, the level of these isoforms remains high even in the older ages. These results suggest that MBPs have heretofore unknown functions unrelated to myelination before myelinogenesis begins. The possible presence of 18 isoforms of MBP mRNA, which are classified into at least three groups with different developmental profiles, is also reported here.     

Enzymatic synthesis of biopterin from D-erythrodihydroneopterin triphosphate by extracts of kidneys from Syrian golden hamsters.

An enzyme system was found in either crude homogenates of dialyzed extracts of liver, kidney, lung, and brain from Syrian golden hamsters that catalyzed the synthesis of radioactive 6(L-erythro-1',2'-dihydroxypropyl)pterin (biopterin) from [U-14C]6(D-erythro-1',2',3'-trihydroxypropyl)-7,8-dihydropterin triphosphate (D-erythrolH2neopterin-PPP) preparation. The specific radioactivity of biopterin was found to be comparable to that of D-erythroH2neopterin-PPP. The enzyme system from hamster kidney was purified severalfold by fractionation with ammonium sulfate and with an Ultrogel AcA-34 column. It was demonstrated that (a) NADPH or NADAH was essential and that (b) Mg2+ was stimulatory for the enzymatic synthesis of biopterin from D-erythroH2-NEOPTERIN-PPP. Also GTP and nonphosphorylated neopterins were not converted to biopterin. Although 6-lactyl-7,8-dihydropterin (sepiapterin) was converted to biopterin in the presence of NADPH, sepiapterin was not detected from D-erythroH2neopterin-PPP in the absence of NADPH. A preliminary experiment was performed to identify dihydrobiopterin.     

Plasma amino acid imbalance in alcoholic liver cirrhosis

Plasma amino acid concentrations and plasma glucagon and serum insulin levels were studied in male patients with compensated alcoholic and nonalcoholic liver cirrhosis. Age, nutritional status, and liver function tests were similar in both groups; none of the patients presented hepatic encephalopathy. Plasma valine and leucine concentrations were lower, and tyrosine, higher in alcoholic than nonalcoholic liver cirrhosis. As a result, the molar ratios of branched-chain amino acids (BCAA) to aromatic amino acids (AAA) were reduced markedly in this group. Although correlation coefficients comparing BCAA/AAA ratios and KICG in alcoholic and nonalcoholic liver cirrhosis were similar, a steeper regression line was observed in alcoholics. Plasma glucagon and proline levels were significantly higher in alcoholic than nonalcoholic liver cirrhosis, the former correlated with AAA concentrations only in alcoholic liver cirrhosis, but not with BCAA levels. These results indicated that alcoholic liver cirrhosis presented a more deranged plasma amino acid pattern than nonalcoholic, and the amino acid imbalances, except for depressed BCAA and elevated proline, were derived, in part, from the hyperglucagonemia.     

Relationship between the cytologic characteristics of intraperitoneal free cancer cells and the prognosis in patients with gastric cancer

The presence of free cancer cells in the peritoneal cavity of 387 patients with gastric cancer was analyzed using specimens obtained by intraoperative lavage of the pouch of Douglas. If cancer cells were found in the specimen, the case was classified with respect to the number and arrangement (clustered or isolated) of the cancer cells found. Study of the relationship between the histologic type of cancer and the presence of free cancer cells showed that poorly differentiated adenocarcinomas and signet ring-cell carcinomas were associated with a higher incidence of free cancer cells than were other types of cancer. The relationships between the characteristics of the free cancer cells and the postoperative survival rate were also studied. Patients whose free cancer cells were present in clusters were associated with a more favorable prognosis than were those with no such clusters. Patients with small numbers of free cancer cells survived longer than did those with large numbers of free cancer cells.     

Morphological observations in normal primary palate and cleft lip embryos in the Kyoto collection

Normal developmental events during human primary palate formation and alterations associated with cleft lip remain poorly defined. The purpose of this study was to analyze serially sectioned human embryos to identify morphological changes during normal palatal closure and alterations associated with failure of palatal formation. Normal and cleft embryos from the histological collection at the Congenital Anomaly Research Center at the University of Kyoto were studied and photographed for detailed evaluation. Seven serially sectioned cleft lip embryos of stages shortly after primary palate formation (Streeter-O'Rahilly stages 19, 20, and 22) with unilateral or bilateral clefts with varying degrees of clefting were studied. In the normal Kyoto embryos, initial nasal fin (epithelial seam) formation was observed between the medial nasal process and the lateral nasal and maxillary processes at stage 17. During stages 18 and 19, the nasal fin epithelium was replaced by an enlarging mesenchymal bridge, as the maxillary processes united with the medial nasal processes to form the primary palate. The most prominent features observed in the cleft embryos were a reduced thickness of mesenchymal bridging between the medial nasal and maxillary processes, with an excessive amount of epithelium at the junctions between these processes. With ingrowth of the maxillary processes, greater cell dispersion and apparent extracellular matrix accumulation were observed in the medial nasal region. During closure of the primary palate, terminal branches of the maxillary nerve crossed the mesenchymal bridge to the medial nasal region. The partial clefts had reduced maxillary ingrowth and smaller union areas with the medial nasal process. Detailed studies of experimental animal models are required to identify regional growth required for contact between the facial prominences, to clarify the mechanisms of mesenchymal ingrowth and epithelial displacement during palatal formation, and to identify local and/or general factors causing alterations that lead to primary palatal clefting.