Bond strength of rebonded orthodontic brackets.

A study was undertaken to determine the bond strength of brackets rebonded with a no-mix resin system or a paste-paste resin system. The efficacy of plastic conditioner and Enhance adhesion booster (Reliance Orthodontic Products, Inc., Itasca, Ill.) as an aid in rebonding was also evaluated. Sixty extracted human premolars were divided into two groups based on the two adhesive systems used. Both groups of 30 were subdivided and (1) initial bond, (2) rebond, and (3) rebond using plastic conditioner and adhesion booster. Samples were stressed to bond failure using an Instron machine. Bond separation occurred in the majority of samples at the enamel/resin interface. Mean bond strengths ranged from 78.8 kg cm-2 for rebonding with a no-mix adhesive and no other conditioners, to 182.7 kg cm-2 for initial bonding using a paste-paste adhesive. Rebonding using a paste-paste adhesive with no other conditioners produced a bond strength statistically indistinguishable from initial bonding with either system. Plastic conditioner and adhesion booster failed to improve rebond strength. The data suggest that, given certain circumstances, rebonding is a viable option when a bracket has been debonded.

Homozygosity for hemochromatosis: clinical manifestations.

We identified 35 homozygotes for hemochromatosis through pedigree studies. Thirteen were asymptomatic. Arthropathy was present in 20, hepatomegaly in 19, transaminasemia in 16, skin pigmentation in 15, splenomegaly in 14, cirrhosis in 14, hypogonadism in six, and diabetes in two. No homozygote was in congestive failure. Only one had the triad of hepatomegaly, hyperpigmentation, and diabetes. Serum iron was increased in 30 of 35, transferrin saturation was increased in all 35, serum ferritin in 23 of 32, urinary iron excretion after deferoxamine in 28 of 33, hepatic parenchymal cell stainable iron in 32 of 33, and hepatic iron in 27 of 27. Iron loading was 2.7 times greater in men than in women. No female had hepatic cirrhosis. Diagnosis of asymptomatic hemochromatosis is important because organ damage may be prevented by early therapy. Clinical diagnosis of early hemochromatosis is difficult. Persons with unexplained elevation of transferrin saturation should be studied for hemochromatosis.

Genetic mapping of the hemochromatosis locus on chromosome six.

The purpose of this paper is to report a pedigree with hereditary hemochromatosis in which a recombination between the HLA-A and B loci occurred. Both the maternal and paternal HLA-A3, B7 haplotypes were carrying an allele for hemochromatosis. The A3, B12 haplotype of the proband was a recombinant of the maternal A3, B7 and A28, B12 haplotypes. The hemochromatosis locus segregated with the HLA-A locus and not with the HLA-B locus. Thus, the hemochromatosis locus maps in close proximity to the HLA-A locus.

Association of HLA-linked hemochromatosis with idiopathic refractory sideroblastic anemia.

Five of seven patients with idiopathic refractory sideroblastic anemia carried an HLA-A3 alloantigen (relative risk, 7.3; P = 0.02). The significance of this association was strengthened by study of two pedigrees. An abnormality in iron metabolism was found in two siblings who had an HLA-A3,B14 haplotype in common with the first proband. A second proband with idiopathic refractory sideroblastic anemia had clinically manifest hemochromatosis. His brother had clinically manifest hemochromatosis but not sideroblastic anemia. This proband and his brother shared only the HLA-A3,B12 haplotype. Our findings infer that patients with idiopathic refractory sideroblastic anemia carry a single allele for hemochromatosis, that this allele accounts for the increased iron loading in this form of anemia, and that clinically manifest hemochromatosis may develop in an occasional patient with only one allele for hemochromatosis in the presence of the sideroblastic factor.

Clinical studies of a large family with Wilson's disease.

We have identified 11 individuals with Wilson's disease, members of five sibships within a larger family which was traced through seven generations. Of 206 other family members evaluated for Wilson's disease, none had abnormally low serum ceruloplasmin or copper levels and none had Wilson's disease. There were two documented instances of consanguinity, associated with two of the five affected sibships and four of the 11 affected individuals. The patterns of occurrence of Wilson's disease within the family is consistent with the hypothesis that the disorder is transmitted as an autosomal recessive characteristic. It is likely that the apparently high frequency of disease within the family can be explained solely by the founder effect.

Hereditary hemochromatosis. Phenotypic expression of the disease.

Previous studies have shown that hemochromatosis is an inherited, autosomal-recessive disease and that the gene is closely linked to the HLA locus on chromosome 6. We obtained a lod score for linkage of +9.8 for a recombination fraction of 0.0 and a gene frequency of 0.056, the frequency estimated in this population. We studied the phenotypic expression of the disease in 261 members of 10 pedigrees. In heterozygotes over 20 years of age, there was an intermediate increase in transferrin saturation and a limited increase in hepatic iron but no clinical manifestations. In male heterozygotes, the average amount of iron in the liver increased from about 0.2 to 1.3 g. Abnormal homozygotes accumulated iron progressively with time, with men accumulating about 18 g in the liver. All measurements of iron status were increased in abnormal homozygotes. Hemochromatosis is inherited as an autosomal-recessive disease, with partial biochemical expression in heterozygotes.

Hereditary hypoceruloplasminemia.

Serum ceruloplasmin values of less than 21.0 mg/100 ml in males or less than 23.0 mg/100 ml in females were observed in 14 out of 156 otherwise healthy members of a pedigree. The hypoceruloplasminemia segregated in a fashion suggesting that the affected individuals are heterozygous for a mutant gene that results in hypoceruloplasminemia. This mutant gene could be a Wilson's disease gene, but excessive copper loading was absent. It is suggested that hereditary hypoceruloplasminemia may be a benign entity distinct from Wilson's disease.

Hereditary hemochromatosis. Diagnosis in siblings and children.

We studied five patients with clinically manifest hemochromatosis and 19 of their siblings and children to define better the diagnostic criteria for stages of the disease. The earliest detectable abnormalities were an increase in hepatic-parenchymal-cell stainable iron, hepatic iron concentration, transferrin saturation and serum iron concentration. In contrast, urinary iron excretion after deferoxamine and serum ferritin concentration were usually normal in early iron loading. In either latent or clinically manifest disease, hepatic-parenchymal-cell stainable iron was Grade 3 or 4; hepatic iron concentration was greater than 250 microng per 100 mg; serum iron was greater than 170 microng per 100 ml; transferrin saturation was greater than 70 per cent; urinary iron excretion exceeded 2.2 mg per 24 hours; and serum ferritin usually exceeded 1000 ng per ml. Estimation of liver iron is the most sensitive method for detecting early disease. Urinary iron excretion and serum ferritin estimate the total body burden of iron in latent and clinically manifest disease.

The anemia of vitamin E deficiency in swine: an experimental model of the human congenital dyserythropoietic anemias.

The ultrastructural and erythrokinetic characteristics of vitamin E deficiency in swine were investigated in an effort to evaluate the suitability of the swine disorder as a model of the human congenital dyserythropoietic anemias. The dominant erythrokinetic abnormality in vitamin E deficient pigs, as in the CDAs, is ineffective erythropoiesis. As in some patients with CDA, the activity of a number of erythrocyte enzymes was increased. Distinctive ultrastructual changes previously described in patients with CDA were found in normoblasts from vitamin E deficient pigs. The morphologic, erythrokinetic, biochemical and ultrastructural similarities between vitamin E deficiency in swine and the CDAs in man appear to justify the study of the animal disorder as a model of the human disease. A complete hematologic response was elicited by the administration not only of vitamin E, but also, as in the previous studies of vitamin E deficiency in monkeys, by hexahydrocoenzyme Q4. The partial hematologic response occurring after deletion of tocopherol stripped corn oil from the diet indicates that factors other than the dietary lack of vitamin E are important in the pathogenesis of this disorder.

Role of copper in mitochondrial iron metabolism.

Heme synthesis by copper-deficient cells was investigated to elucidate the nature of the defect in intracellular iron metabolism. Iron uptake from transferrin by copper-deficient reticulocytes was 52% of normal, and the rate of heme synthesis was 33% of normal. Hepatic mitochondria isolated from copper-deficient animals were deficient in cytochrome oxidase activity and failed to synthesize heme from ferric iron (Fe III) and protoporphyrin at the normal rate. The rate of heme synthesis correlated with the cytochrome oxidase activity. Heme synthesis from Fe(III) and protoporphyrin by normal mitochondria was enhanced by succinate and inhibited by malonate, antimycin A, azide, and cyanide. It is proposed that an intact electron transport system is required for the reduction of Fe(III), thereby providing a pool of ferrous iron (Fe II) for protoheme and heme a synthesis.

The effect of detergent treatment of the gastric mucosa on drug transport.

The effect of detergent treatment of the canine gastric mucosa on transport of drugs from blood to gastric juice was studied using a chamber technique, in vivo. Detergent treatment was found to increase antipyrine and aminopyrine transport. Facilitation of drug transport was associated with disruption of the gastric mucosal barrier and an increase of aminopyrine clearance.

Inhibition by superoxide dismutase of methemoglobin formation from oxyhemoglobin.

The formation of methemoglobin from oxyhemoglobin in a solution containing photoreduced riboflavin and oxygen was inhibited by superoxide dismutase. The rate of the reaction was pH-dependent in the range of 6.8 to 7.8, increasing as the pH was reduced. Inhibition by superoxide dismutase was enhanced as the EDTA concentration increased and was dependent on enzymatic activity. Under conditions in which superoxide dismutase inhibition was incomplete, catalase inhibited the reaction but mannitol had no effect. The data support the mediation of methemoglobin formation by superoxide. The hypothesis is offered that superoxide anion reduced the heme-bound oxygen in oxygemoglobin by one electron, permitting the subsequent dissociation of ferrihemoglobin and peroxide. The ability of superoxide dismutase to inhibit the formation of methemoglobin may represent one of its functions in the mature erythrocyte.

Superoxide dismutase activity in copper-deficient swine.

These experiments demonstrate the dependency of cuprozinc superoxide dismutase activity in red cells and liver on an adequate dietary intake of copper. The superoxide dismutase activity in red cells decreased to 15% of control values and, therefore, these cells may be used as a convenient model for studying the physiologic consequences of free radicals

The prognosis in aplastic anemia.

The biphasic shape of the survival curve of 99 patients with aplastic anemia suggested that there may be at least two subgroups of patients with this disease, one with a very short survival and another with a longer survival. Patients who survived for 4 mo or less after the first clinic visit (group A) were different from the patients who survived longer (group B) with respect to their modes of onset, sex, intervals from the onset of symptoms to first clinic visit, and initial hematologic values. These differences suggested that short survival could be predicted from data available at the first contact with the physician. From these measurements, a prognostic index could be calculated which was useful in identifying the patients in group A. Although this method of prognostication needs further testing, if validated, it may prove useful in selecting patients for therapeutic trials and could explain the divergent results in previous studies of androgen treatment of aplastic anemia. When our androgen-treated subjects were compared with subjects with a similar prognostic index who had not received androgens, a beneficial effect of androgen therapy on survival could not be demonstrated.