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Biomedical subjects

J R Bloomer

Publications and source records attributed to J R Bloomer.

At least 73 records · Page 4Linked to original sources
PubMed1979

Effect of endogenous heme generation on delta-aminolevulinic acid synthase activity in rat liver mitochondria.

This study examined the possibility that generation of heme within mitochondria may provide a local concentration sufficient to inhibit the activity of delta-aminolevulinic acid (ALA) synthase, the enzyme that catalyzes the rate-limiting step in hepatic heme biosynthesis. This was accomplished by simultaneously running ALA synthase and heme synthase activities in intact mitochondria isolated from rat liver. Radiochemical assays were used to measure the enzyme activities. ALA synthase activity did not decrease as the rate of heme formation was increased by varying the concentration of substrates for heme synthase. Even at a rate of heme generation estimated to be at least 75 times the rate occuring in vivo, ALA synthase activity was unchanged. We conclude that end product inhibition of ALA synthase activity by heme is not an important physiological mechanism for regulation of hepatic heme biosynthesis.

5-Aminolevulinate Synthetase↗
PubMed1978

Efficacy and safety of long-term phenobarbital therapy of familial cholestasis.

Two brothers with progressive familial intrahepatic cholestasis were followed during four years of phenobarbital therapy to assess its long-term safety and efficacy. Effects attributable to phenobarbital included sustained relief of pruritus, lowering of serum bilirubin levels, and enhanced hepatic excretion of 131I-rose bengal; serum bile acid levels were only transiently decreased. Two brief interruptions in therapy resulted in symptomatic deterioration. Phenobarbital did not retard growth nor impede the response to vitamin D therapy of concomitant rickets.

Bile Acids and Salts↗
PubMed1977

Heme content of normal and porphyric cultured skin fibroblasts.

Partial deficiencies in enzyme activities of the heme biosynthetic pathway have been demonstrated in cultured skin fibroblasts and other tissues from patients with protoporphyria (PP) and acute intermittent porphyria (AIP). We have quantitatively and qualitatively assessed the heme and free porphyrin content in cultured PP, AIP, VP (variegate porphyria, in which an enzymatic deficiency has not been identified), and normal skin fibroblasts during routine culture conditions in order to assess the overall metabolism of heme in these cells. The total heme concentration was not significantly different between control and porphyric lines; 189 +/- 15 pmoles/mg protein (mean +/- SEM) in controls, 154 +/- 17 in PP, 175 +/- 20 in AIP, and 181 +/- 81 in VP. The hemoprotein difference spectra were similar in all lines. Free porphyrins were not detected in any of the disorders. Despite partial deficiencies in enzyme activities of the heme pathway, porphyric fibroblasts thus maintain normal heme content during routine culture conditions without detectable porphyrin accumulation.

Cells, Cultured↗
PubMed1977

Study of factors causing excess protoporphyrin accumulation in cultured skin fibroblasts from patients with protoporphyria.

The activity of heme synthetase, which catalyzes the chelation of ferrous iron to protoporphyrin to form heme, is deficient in sonicates of skin fibroblasts cultured from patients with protoporphyria. During culture in Eagle's medium supplemented with fetal calf serum, these cells do not accumulate protoporphyrin, however. This may be due to a minimal requirement for heme synthesis, since glycine is incorporated into heme at a low rate which is similar to that in normal fibroblasts. In addition, the activity of delta-aminolevulinic acid (ALA) synthetase, the first and rate-limiting enzyme of heme biosynthesis which catalyzes the formation of ALA from glycine, is normal in lysates of the fibroblasts. Cultured fibroblasts were therefore incubated with ALA in order to bypass the rate-limiting step of heme biosynthesis. In the presence of 25 muM iron, protoporphyrin was detected in protoporphyria cell lines when the concentration of ALA in the medium reached 50 muM, but not in normal lines. As the concentration of ALA was increased above 50 muM, all lines accumulated protoporphyrin. However, the amount was 2-3 times more in cultured fibroblasts from patients with protoporphyria, reflecting their deficiency of heme synthetase activity. When iron was not added to the medium, protoporphyrin accumulated to a similar degree in normal and protoporphyria fibroblasts; this was significantly more than that in the presence of iron. These studies indicate that excessive protoporphyrin accumulation in protoporphyria, which is due principally to deficient heme synthetase activity, may be modified by the rate of ALA formation in heme-producing tissues, and by the availability of iron.

Carbon Radioisotopes↗
PubMed1977

Serum alpha-fetoprotein in patients with massive hepatic necrosis.

Serum concentrations of alpha-fetoprotein (AFP) were measured by radioimmunoassay in 12 patients with massive hepatic necrosis, 11 of whom died. Levels were significantly elevated after the 8th day of illness in 8 of the 9 patients who died between the 10th and 60th day, and in the 1 patient who survived. All 9 patients with increased levels of serum AFP exhibited histological evidence of hepatic regeneration. These findings indicate that the rise in serum AFP in massive hepatic necrosis is related to the duration of survival after the onset of illness, but does not necessarily imply ultimate recovery. Because available evidence suggests that the serum AFP level reflects hepatic regenerative activity, it appears that the onset of regeneration in fulminant hepatitis is delayed until the 2nd week of illness.

Adolescent↗
PubMed1977

Elevations in skin tissue levels of bile acids in human cholestasis: relation to serum levels and topruritus.

To define the relationship of bile acid retention to the pruritus of cholestasis, we quantified individual bile acids in serum, acetone swabs of skin, and skin tissue in 13 patients with cholestasis undergoing laparotomy and in 8 controls. There was no consistent relationship between pruritus and concentrations of either total or individual bile acids in serum. Skin tissue concentrations of bile acids were elevated in patients with cholestasis, were linearly related to serum levels, and did not differentiate between those patients with and those without pruritus. Concentrations of bile acids on the skin surface, which were lower than those reported by others, did not correlate with pruritus, and were decreased by simple soap and water washing. These data indicate that the pruritus of cholestasis is not directly related to the skin tissue concentration of any of the major bile acids, although a relationship to a particular molecular form of bile acids could not be excluded.

Adult↗
PubMed1976

Inheritance in protoporphyria. Comparison of haem synthetase activity in skin fibroblasts with clinical features.

The activity of haem synthetase, the enzyme which chelates iron to protoporphyrin to form haem, was measured in cultured skin fibroblasts of children with protoporphyria and their parents from three families. In each family, one parent had deficient haem synthetase activity (3-0-11-1 pmol protohaem formed/mg protein/h) when compared to values in eight non-porphyric controls (means 24-9, range 13-7-51-5). The level of activity in the three parents was similar to that in their affected children. In two families the parent with deficient activity was also thought to be the carrier of the abnormal gene, as judged from a history of photosensitivity and analysis of erythrocyte protoporphyrin concentrations, but in the third family the pattern of inheritance could not be determined from these criteria. The activity of delta-aminolaevulinic acid synthetase was normal in cultured fibroblasts from the protoporphyric children and their parents, excluding a generalised defect in haem-pathway enzymes. These results support the premise that deficient haem synthetase activity, inherited in an autosomal dominant patter, is the primary defect in protoporphyria.

Adolescent↗
PubMed1976

Serum bile acids in alcoholic liver disease. Comparison with histological features of the disease.

Fasting serum bile acids were measured by gas-liquid chromatography in 64 patients with alcoholic liver disease and compared with histological features in their percutaneous liver biopsy specimens. Total bile acid concentrations were normal (less than 2 mug/ml) or minimally increased in 6 patients in whom fatty infiltration was the only hepatic lesion. In the remaining 58 patients with more severe histological lesions, levels were increased in 93%, whereas serum bilirubins were elevated in only 43%. Chenodeoxycholic acid was usually the predominant serum bile acid, regardless of the degree of necrosis or connective tissue change in the biopsy specimen. Only small amounts of the secondary bile acids, deoxycholic acid and lithocholic acid, were detected. Levels of these secondary bile acids did not correlate with histological features.

Alcoholism↗
PubMed1976

Effect of graded bilirubin loads on bilirubin transport by perfused rat liver.

Features of hepatic bilirubin transport were studied with the isolated perfused rat liver. Male Wistar rats weighing 350-400 g were used as liver donors. When bilirubin was constantly infused into the perfusion medium, which contained sheep erythrocytes and 3.0 g/100 ml bovine serum albumin, the maximal excretion rate for bilirubin was 14.4 +/- 1.2 mug/min per g liver. Over a wide range of constant bilirubin infusion rates which went as high as 25.9 mug/min per g liver, there was no effect on bile flow, bile acid excretion, or the pattern of bilirubin conjugates in bile. The hepatic extraction efficiency for unconjugated bilirubin from the perfusate also remained constant averaging 26%. However, when bolus injections of bilirubin were used to produce higher levels of unconjugated bilirubin in the perfusate than could be attained during constant infusion, the disappearance rate of [14C]bilirubin from the perfusate decreased with increasing bilirubin concentrations. This was consistent with saturation of the hepatic removal of unconjugated bilirubin.

Animals↗
PubMed1976

Inhibitory effects of scillaren and dinitrophenol on bilirubin excretion by the isolated perfused rat liver.

The effects of scillaren and dinitrophenol on bilirubin excretion by the perfused rat liver were studied. Both compounds inhibited bile flow, scillaren by 20 to 40%, and dinitrophenol by 60 to 80%. Bilirubin excretion was also impaired. However, the effect of scillaren on bilirubin excretion was less than that on bile flow, as indicated by an increase in the bile bilirubin concentration, whereas dinitrophenol had a greater effect on bilirubin excretion than on bile flow. Dinitrophenol also inhibited the hepatic removal of unconjugated bilirubin from the perfusate, probably because it impaired the initial uptake and/or storage of unconjugated bilirubin by the perfused liver.

Animals↗
PubMed1976

Serum bile acids in primary biliary cirrhosis.

Fasting serum bile acid levels were measured by gas-liquid chromatography in 56 patients with primary biliary cirrhosis. Of these, 52 (93%) had increased levels (greater than 2mug/ml), including 14 of the 18 with normal serum bilirubin concentrations. The four patients with normal bile acid levels had early lesions as judged by histological and clinical criteria. With progression of the disease, as indicated by the histological features of the lesions, total bile acid levels increased, and the ratio of serum cholic-to-chenodeoxycholic acid decreased. Ratios of serum cholic-to-chenodeoxycholic acid below 1 occurred predominantly in patients with advanced or terminal disease. These studies suggest that serial measurement of serum bile acids may aid in the evaluation of primary biliary cirrhosis.

Adult↗
PubMed1975

alpha-fetoprotein in noneoplastic hepatic disorders.

Serum alpha-fetoprotein levels were measured by radioimmunoassay in 473 patients with biopsy-proved noneoplastic hepatic disorders; 22% had values greater than 40 ng/ml, whereas only 1 of 350 patients with nonhepatic benign diseases had a value greater than this. Levels exceeded 40 ng/ml in more than 30% of patients with various types of hepatitis, and in 0% to 15% with inactive postnecrotic cirrhosis, primary biliary cirrhosis, biliary tract obstruction, and alcoholic liver disease. Values greater than 500 mg/ml were observed solely in viral subacute hepatic necrois. Only one patient had a level exceeding 3,000 ng/ml, the concentration at which alpha-fetoprotein is detectable by agar-gel diffusion. Of 75 patients with hepatoma, serum alpha-fetoprotein levels exceeded 40 ng/ml in 69%, and exceeded 3,000 ng/ml in 48%. These studies indicate that serum alpha-fetoprotein levels are elevated in several nonneoplastic hepatic disorders when a sensitive assay is used; this phenomenon may reflect hepatic regeneration.

Acute Disease↗
PubMed1975

Hepatic disease in erythropoietic protoporphyria.

Two sisters had erythropoietic protoporphyria and a spectrum of liver disease. One (F.B.) died in hepatic failure within 3 months after the development of jaundice. Only 10 months before she died, she had exhibited only bromsulfalein retention and a borderline increase in serum transaminase. Surgical exploration because of the jaundice revealed patency of the bile ducts which was confirmed at autopsy. Wedge biopsy and autopsy specimens of liver showed an active cirrhosis with massive amounts of protoporphyrin in Kupffer cells, portal histiocytes, bile canaliculi and parenchymal cytoplasm. The other sister (L.R.) had never had symptomatic liver disease and only a slight increase in serum transaminase and bromsulfalein retention. On needle biopsy, the liver specimen showed portal inflammation with erosion of limiting plates, occasional bridging between triads and central areas of cell dropout. Protoporphyrin pigment was present in portal histiocytes, areas of central collapse and, more rarely, in parenchymal cytoplasm. These studies demonstrate that significant, progressive hepatic disease may occur insidiously in erythropoietic protoporphyria, and that once jaundice appears it may be followed rapidly by fatal hepatic failure.

Adult↗
PubMed1975

Heme synthetase deficiency in human protoporphyria. Demonstration of the defect in liver and cultured skin fibroblasts.

The final step in heme biosynthesis is chelation of porphyrin with Fe++ catalyzed by the mitochondrial enzyme heme synthetase. We have employed a sensitive radiochemical assay for this enzyme, using 59Fe and deuteroporphyrin or protoporphyrin as substrates. In this method iron is maintained in the ferrous state, oxygen is excluded from the incubation system, and labeled heme product is extracted into ethyl acetate. This assay has been used to measure the activity of heme synthetase in homogenates of liver, obtained by needle biopsy, and in sonicates of human skin fibroblasts, cultured in vitro. In addition, activity of the first enzyme of the heme synthetic pathway, delta-aminolevulinic acid synthetase, has been measured in fibroblast lysates. Lysates of fibroblasts from eight patients with protoporphyria had activities of delta-aminolevulinic acid synthetase which did not differ significantly from those of eight normal fibroblast lines, whereas activity of heme synthetase, with either deuteroporphyrin or protoporphyrin as substrate, was markedly decreased in sonicates of skin fibroblasts from these patients, the mean being 8% of control with deuteroporphyrin and 14% with protoporphyrin as substrate. In homogenates of liver from five patients with protoporphyria, activity of heme synthetase was also significantly less than that found in six patients without prophyria, the mean being 13% of control with protoporphyrin as substrate. These results provide evidence that decreased activity of heme synthetase is the basic defect in the heme synthetic pathway in protoporphyria. This deficiency is probably responsible for protoporphyrin accumulation and hence the biochemical and clinical features observed in protoporphyria.

5-Aminolevulinate Synthetase↗
PubMed1975

Phenobarbital effects in cholestatic liver diseases.

Fifteen patients with cholestatic disorders were treated for 1 to 5 months with phenobarbital. Primary biliary cirrhosis was diagnosed in seven, sclerosing cholangitis in two, intrahepatic biliary hypoplasia in three, and cholestatic hepatitis in three. Except for the patients with cholestatic hepatitis, in whom marked cholestasis was virtually the only abnormality in liver biopsy specimens, serum bilirubin and bile acid concentrations were diminished during therapy, the hepatic clearance of sulfobromophthalein and 131-I-rose bengal was variably enhanced, and there was relief from pruritus. Serum cholesterol concentrations and other measures of hepatic function were not significantly changed during therapy except for serum alkaline phosphatase activity, which rose in twelve patients. Parallel changes occurred in 5'-nucleotidase, suggesting a hepatic origin for the alkaline phosphatase activity. These studies indicate that phenobarbital therapy is associated with improvement in organic anion clearance in some patients with cholestatic disorders and may be beneficial to such patients.

Adult↗
PubMed1975

Relationship of serum alpha-fetoprotein to the severity and duration of illness in patients with viral hepatitis.

Using a radioimmunoassay which detect concentrations of alpha-fetoprotein as low as 5 ng per ml, 38% of 176 patients with viral hepatitis compared with health volunteers and patients with chronic diseases not affecting the liver. When separated into two groups based on histological classification of liver biopsy specimens, differences in the degree and frequency of increased serum alpha-fetoprotein were related to the severity of the hepatic lesion. Of 75 patients with the lesion of viral subacute hepatic necrosis, in which zones of necrosis bridge adjacent portal triads or central veins, 52% had increased values, and 12% had levels ranging from 500 to 3300 ng per ml. In contrast, only 28% of the 101 patients without bridging necrosis had increased values, and none had levels that exceeded 500 ng per ml. In the patients with subacute hepatic necrosis, comparison of alpha-fetoprotein concentrations with the duration of illness indicated that the protein rose to peak levels in serum as the SGOT was declining. This was confirmed by serial observations in 10 patients. Thus, the increase of alpha-fetoprotein in the sera of patients with severe hepatitis occurs as liver necrosis is subsiding. Due to other known features of alpha-fetoprotein, it is intriguing to speculate that the increase in serum levels of this protein in viral hepatitis reflects hepatic regeneration after parenchymal damage.

Adult↗