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Biomedical subjects

J W Halliday

Publications and source records attributed to J W Halliday.

At least 73 records · Page 4Linked to original sources
PubMed1989

Effects of iron loading on free radical scavenging enzymes and lipid peroxidation in rat liver.

A comparison of the antioxidant protective system and presence of lipid peroxidation was made between rats iron-loaded by two different mechanisms. Superoxide dismutase activity, glutathione peroxidase activity, and reduced glutathione concentrations, together with malondialdehyde production, were measured in the livers of rats chronically iron-overloaded by (a) parenteral iron (primarily Kupffer cell iron deposition) and (b) dietary carbonyl iron (mainly parenchymal iron deposition). In carbonyl iron-treated rats, hepatic superoxide dismutase activity was significantly decreased, whereas hepatocyte lipid peroxidation, as measured by malondialdehyde levels, was significantly increased when compared with control rats at or above iron concentrations of 100 and 185 mumol/g dry wt, respectively. However, no significant decrease in superoxide dismutase activity or significant increase in malondialdehyde levels was observed in iron dextran-treated rats. Glutathione peroxidase activities and reduced glutathione concentrations in rats, iron-loaded by either method, were not significantly different from those of control animals. These results suggest that the deposition of iron in the reticuloendothelial cells of the liver does not lead to lipid peroxidation; however, iron deposited in the parenchymal cells of the liver may lead to an altered free radical antioxidant protective system, resulting in lipid peroxidation in these cells at a similar level of iron loading. We conclude that the cellular site of iron deposition as well as the hepatic iron concentration is important in determining iron-induced liver injury.

Animals↗
PubMed1989

The clinical manifestations of chronic iron overload.

Primary or genetic haemochromatosis is an inherited disease characterized by an inappropriate degree of iron absorption with accumulation of excessive amounts of tissue iron. Parenchymal iron accumulation results in the typical clinical features of the disease including hepatic cirrhosis, diabetes, testicular atrophy and skin pigmentation. The disease is inherited in an autosomal recessive manner. The gene for the disease has not been identified but is tightly linked to the A locus of the histocompatibility complex on chromosome 6. The approximate homozygote frequency in Caucasians is 0.3% with an equal sex ratio. Excessive body iron stores have been described in a number of other conditions, particularly alcoholic liver disease. There is increasing evidence that many of these individuals are in fact also suffering from genetic haemochromatosis. Diagnostic tests including serum iron, transferrin saturation, serum ferritin and liver iron concentration make it possible to detect sufferers of the disease. Screening relatives of affected individuals with these tests allows a diagnosis to be made before permanent tissue damage has occurred. Removal of excess iron stores by repeated phlebotomy is the primary treatment. If iron is removed before significant tissue damage has occurred, the complications and natural course of the disease will be prevented provided reaccumulation of iron does not occur. Excessive iron accumulation with resultant organ damage also occurs in anaemias associated with ineffective erythropoiesis and after excessive parenteral iron administration or repeated blood transfusions. Similar clinical features may be seen. Chelation therapy is the mainstay of treatment in these cases where long-term venesection is not possible.

Bloodletting↗
PubMed1989

Hepatic iron in the control of iron absorption in a rat liver transplantation model.

Rat liver transplantation was utilized to study the effect of hepatic iron on the control of iron absorption. Six iron-loaded and six normal livers were transplanted into normal or iron-loaded animals. Iron absorption was measured pretransplant and 10 days posttransplant by total-body counting (59Fe). The animals were loaded with oral carbonyl iron to produce a predominantly parenchymal hepatic iron distribution and with parenteral iron dextran to produce a predominantly reticuloendothelial iron distribution. The carbonyl iron-loaded livers contained 175 +/- 6.6, the iron dextran livers 180 +/- 41, and the normal livers 6.6 +/- 2.8 mumol FE/g dry wt. Iron absorption was unchanged by the insertion of normal livers into normal animals. The transplantation of carbonyl iron-loaded livers into normal animals caused a marked decrease in iron absorption posttransplant from 7.2 +/- 0.9% to 0.3 +/- 0.4% (P less than .001) posttransplant. Neither the transplantation of iron dextran-loaded livers into normal animals nor the transplantation of normal livers into iron-loaded animals significantly altered iron absorption at 10 days posttransplant. These results are consistent with the hypothesis that hepatocyte iron stores are a major determining factor controlling iron absorption.

Absorption↗
PubMed1989

Inherited iron overload.

Several inherited forms of iron overload have been described. It is now accepted that HC, usually regarded as a disease of adult life, is an inherited disorder, hence all first degree relatives must be presumed to be at increased risk of developing iron overload and the diagnosis is now frequently made in young relatives. The combination of serum iron, transferrin saturation and serum ferritin determination will detect iron overload in an early, precirrhotic stage. Liver biopsy and the determination of hepatic iron concentration provide the definitive proof. Where HC is recognized sufficiently early to permit adequate removal of iron before cirrhosis has developed, the prognosis is excellent. Thus haemochromatosis as a clinical disease should be preventable in a large proportion of patients. Severe iron overload has been described in juveniles and also in neonates. These conditions are familial but whether they are HLA-related has not been determined. Cardiac and endocrine disorders are frequently the presenting manifestations of parenchymal iron overload in the young and, at least in neonates, the condition is usually fatal in early infancy. It is not possible at present, to say whether these rare juvenile and neonatal forms of haemochromatosis are related to the much more common adult form. Identification of the gene for HC may assist in answering this question.

Adolescent↗
PubMed1989

Identification of H- and L-ferritin subunit binding sites on human T and B lymphoid cells.

Monoclonal antibodies to the H and L subunits of ferritin were used in indirect immunofluorescent studies to investigate the subunit specificity of ferritin binding to transformed T and B lymphoid cell lines. Pre-incubation of cells with recombinant H ferritin followed by antibodies to the H subunit produced a labelling pattern in which all cells showed strong fluorescent stippling. Corresponding experiments with liver ferritin and an antibody to the L subunit revealed that most cells were lightly stippled, but 3-5% of the cells were intensely labelled. These two labelling patterns were distinct as assessed by cross-blocking experiments with recombinant H and liver ferritins. These results imply that different binding sites exist for each subunit.

Antibodies, Monoclonal↗
PubMed1989

IL-2 and IL-4 can co-modulate the generation of cytotoxic T cells through CD8- CD4- splenic lymphocytes.

Following activation with concanavalin A (Con A), murine T cells are able to suppress the generation of allospecific cytotoxic T lymphocytes (CTL). We have analysed the phenotype, tissue distribution, and mode of action of these cells in an effort to understand further the regulation of CTL-mediated immunity. The precursors of such cells are rare (1 cell per 70,000 spleen cells being able to suppress the generation of a particular allospecific response), but are much more abundant in the spleen than in the thymus. By the use of cytotoxic antibodies, we have been able to demonstrate that the splenic precursors of such cells are Thy-1.2+, CD4-, CD8- but, following activation with Con A, these cells acquire the CD8 marker. Cellular suppression by these lymphocytes is dramatically increased in the presence of the Th2-derived lymphokine, IL-4, whereas IL-2, the Th1-derived lymphokine, significantly augments the generation of CTL in a mixed lymphocyte culture even though relative suppression is still evident in the presence of Con A-activated lymphocytes. Suppression is not due to overcrowding of a cell culture since adding Con A-activated cells to an A anti-B + C culture often resulted in the suppression of the A anti-B response but not the A anti-C response, or vice versa. Suppression appears to require cellular interaction since supernatants from Con A-activated lymphocytes are unable to mediate suppression. Such cells may play an important intermediate role in homeostasis.

Adjuvants, Immunologic↗
PubMed1989

HLA determinants in an Australian population of hemochromatosis patients and their families.

The frequencies of different HLA-A and -B alleles in 77 Australian patients with hemochromatosis have been compared with frequencies of HLA alleles not associated with hemochromatosis in 63 of their heterozygous relatives and with published population frequencies. As for all other populations reported, an association of HLA-A3 and HLA-B7 with the disease was found. A weak association with HLA-B12 was also detected. No other significant positive or negative associations with HLA alleles were detected. In addition, HLA-A2 and -B12 were in significant linkage disequilibrium in patients but not in controls, which may indicate a new mutation or recent recombination between HLA-A and hemochromatosis either in our patient group or in the founding population. HLA-A1 and -B8 and HLA-A29 and -B12 were in linkage disequilibrium in controls but not in patients, suggesting that this population is not segregating a hemochromatosis allele on either of these haplotypes. Genetic linkage analysis using the program LIPED showed strong linkage in 23/24 families, most of which had additional HLA alleles (other than A3 and B7) associated with hemochromatosis. This provides evidence for a single hemochromatosis locus, possibly with more than one allele.

Alleles↗
PubMed1989

Limit dilution analysis of peripheral blood T lymphocytes specific to periodontopathic bacteria.

Limit dilution analysis (LDA) was used to determine the presence and frequency of periodontopathic-bacteria-specific T cells in the peripheral blood of patients with chronic inflammatory periodontal disease. Twelve adult periodontitis (AP), 13 marginal gingivitis (MG) and 12 healthy control subjects took part in the study. Bacteroides gingivalis and Actinomyces viscosus were used as test organisms, while tetanus toxoid was used as the control antigen. The median PTL-p frequencies to B. gingivalis were 46.33 x 10(-6), 45.33 x 10(-6) and 58.83 x 10(-6) in the control, gingivitis and AP groups respectively, while the median PTL-p frequencies to A. viscosus were 13.8 x 10(-6), 17.33 x 10(-6) and 11.5 x 10(-6), again in the control, gingivitis and AP groups. There were no statistically significant differences between the groups. All subjects displayed 'single-hit' kinetics with the control tetanus toxoid antigen and, with three exceptions, 'single-hit' kinetics was also found with the two test organisms. One control subject displayed a 'saw-tooth' curve with A. viscosus and a 'suppressor' curve with B. gingivalis, while two MG subjects had a 'saw-tooth' curve with B. gingivalis. These complex curves suggest that, in some subjects, more than one limiting cell type may exist in the cultures. Nevertheless, the results of the present study illustrate that lymphocytes specific to periodontopathic bacteria exist in the peripheral blood of both diseased and non-diseased subjects.

Actinomyces↗
PubMed1988

Iron status and cellular immune competence.

There is increasing evidence that both iron overload and iron deficiency are associated with significant abnormalities of immune function. In diseases associated with iron overload there is increased susceptibility to both infection and neoplasia. The precise mechanisms are still being unravelled but iron overload has been shown to impair antigen-specific immune responses and to reduce the number of functional helper precursor cells. Similarly, iron in vitro in concentrations reported to be present in the serum of patients with iron overload impairs the generation of cytotoxic T-cells, enhances suppressor T-cell activity and reduces the proliferative capacity of helper T-cells. The predominant tumor seen in iron overload is primary hepatocellular carcinoma; however other aetiological factors appear to be involved in addition to iron overload, especially hepatic cirrhosis. Nevertheless, primary liver cancer occurs much more frequently in hemochromatosis than in other forms of cirrhosis. Iron deficiency is associated with an altered response to infection but the relationship is again a complex one. The cellular mechanisms involved have yet to be clearly defined, although impaired T and B cell function have been demonstrated.

Animals↗
PubMed1988

Solid phase immunoradiometric assay for porcine serum ferritin.

1. A solid phase immunoradiometric assay using anti-serum coated polystyrene tubes, is described for the assay of porcine serum ferritin. 2. The mean concentration of ferritin in the serum of both male and female pigs (Sus scrofa) was 12.1 micrograms/l +/- 8.7 micrograms (range less than 1-35 micrograms/l) and no sex differences were observed in 40 pigs from 1 day to 4 years old. 3. Serum ferritin increased with increasing body iron stores in iron loaded pigs as assessed by hepatic iron concentration. 4. The assay is sensitive (detecting less than 1 microgram/l), reproducible, specific and it does not cross-react with human or rat ferritin.

Animals↗
PubMed1988

Isolation of a porcine hepatic ferritin receptor.

1. A ferritin receptor has been isolated from porcine liver and has been partially purified using affinity chromatography. 2. A binding assay has been developed which utilizes a hepatic ferritin receptor coupled to a microparticulate support which facilitates the separation of bound and free ligand. 3. An affinity constant of 2.9 x 10(9) mol-1 litre was determined for the purified hepatic ferritin receptor. 4. The molecular weight of the receptor was estimated to be approximately 53,000 by gel electrophoresis. 5. Binding of ferritin to the insolubilized receptor was unaffected by a 100-fold excess of bovine albumin, porcine and human transferrin, and human asialo-orosomucoid. 6. Binding was specific for porcine ferritin with no demonstrable binding of rat or human ferritin.

Animals↗
PubMed1988

The effect of smoking on caffeine elimination: implications for its use as a semiquantitative test of liver function.

1. The effects of caffeine ingestion and cigarette smoking on caffeine and antipyrine pharmacokinetics were studied using normal subjects as their own controls before and after cessation of smoking in an attempt to minimize genetic and other environmental influences. 2. Moderate caffeine ingestion had no inducing effect on caffeine or antipyrine clearance. 3. Cessation of cigarette smoking significantly reduced clearance of caffeine and antipyrine. 4. These results demonstrate that cigarette smoking significantly affects caffeine pharmacokinetics and this may contribute to the variable results for caffeine kinetics found in patients with liver disease.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Association between alcoholism and increased hepatic iron stores.

Although alcoholic liver disease is often associated with some increase in hepatic iron stores, it is now established that when gross iron overload is present, this is due to genetic hemochromatosis. Furthermore, there appears to be a critical iron concentration necessary for the induction of hepatic fibrosis. Lipid peroxidation induced by ethanol and/or iron would appear to play a major role in hepatic damage in both humans and experimental animals. Although the exact mechanism(s) of induction of lipid peroxidation by ethanol and iron remains to be elucidated, both toxins can exert a synergistic effect upon hepatic lipid peroxidation. Iron overload has also been shown to stimulate directly hepatocyte and hepatic procollagen mRNA expression, which is further stimulated by ethanol. The observed synergism between iron and alcohol with respect to both hepatic lipid peroxidation and collagen biosynthesis offers a possible explanation of the apparent early onset of fibrosis and cirrhosis in patients with iron overload who have an excessive alcohol intake.

Hemochromatosis↗
PubMed1988

Is all genetic (hereditary) hemochromatosis HLA-associated.

1. GH in Australia is significantly associated with the HLA-A3 antigen, which is the only independent marker for the disease (B7 in linkage disequilibrium with A3). 2. The haplotype A3, B7, DR2 is the only one with increased prevalence in this disease, presumably due to its being the predominant haplotype among early immigrants. 3. Exceptions to HLA association in GH are rare and can be explained by: (1) incorrect HLA serotyping, (2) chromosomal recombination, or (3) rare homozygous-homozygous mating. 4. These data are consistent with GH being due to a mutant gene or genes in close proximity to HLA-A. 5. Heavy alcohol ingestion does not lead to expression of hemochromatosis in heterozygous subjects.

Alcohol Drinking↗