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L McNamara

Publications and source records attributed to L McNamara.

14 recordsLinked to original sources
PubMed1999

Non-transferrin-bound iron and hepatic dysfunction in African dietary iron overload.

BACKGROUND: Circulating iron is normally bound to transferrin. Non-transferrin-bound iron (NTBI) has been described in most forms of iron overload, but has not been studied in African dietary iron overload. This abnormal iron fraction is probably toxic, but this has not been demonstrated. METHODS: High-pressure liquid chromatography was used to assay serum NTBI in 25 black African subjects with iron overload documented by liver biopsy and in 170 relatives and neighbours. Levels of NTBI were correlated with indirect measures of iron status and conventional liver function tests. RESULTS: Non-transferrin-bound iron (> 2 micromol/L) was present in 43 people, 22 of patients of whom underwent liver biopsy and 21 relatives and neighbours. All but four of these had evidence of iron overload on the basis of either liver biopsy or elevated transferrin and serum ferritin concentrations. Among all 195 subjects, the presence of NTBI in serum was independently related to elevations in alanine and aspartate aminotransferase activity and bilirubin concentration. This relationship between serum NTBI and hepatic dysfunction was confirmed in the subgroup of 25 subjects with iron overload documented by liver biopsy. Non-transferrin-bound iron correlated significantly with elevations in alanine and aspartate aminotransferase activities after adjustment for hepatic iron grades, inflammation and diet. CONCLUSIONS: Non-transferrin-bound iron was found to be commonly present in African patients with dietary iron overload and to correlate with transferrin saturation and serum ferritin concentration. The independent relationship between NTBI and elevated liver function tests suggests that it may be part of a pathway leading to hepatic injury.

Aspartate Aminotransferases↗
PubMed1999

Administration of a nonpeptidyl growth hormone secretagogue, L-163, 255, changes somatostatin pattern, but has no effect on patterns of growth hormone-releasing factor in the hypophyseal-portal circulation of the conscious pig.

The activity of the growth hormone secretagog, L-163,255, on growth hormone (GH), growth hormone-releasing factor (GRF), and somatostatin (SRIF) levels was evaluated in a porcine model of hypophyseal portal blood (HPB) collection. Young, castrated pigs had HPB and jugular blood collected for approximately 300 min. The blood collection was divided into discrete periods: baseline (BL) approximately 180 min; GH response period (RSP) approximately 90 min; and positive control period following a GRF bolus, 30 min. RSP was divided into a dominant response period (DOM) and a tail (TL). The spontaneous relationship between HPB GRF and SRIF and peripheral GH during BL has been reported (Proc Soc Exp Biol Med 217:188-196, 1998). The apex of the GH pulse resulting from L-163,255 administration was nonrandomly associated (P < 0.05) with descending periods of SRIF troughs. Frequency and amplitude of GRF and SRIF pulses, and frequency and depth of SRIF troughs were not different between BL and the beginning of DOM (the 20-30 min of GH increase). GH AUC was significantly greater (P < 0.05) for DOM compared to BL and TL, and for TL compared to BL. GRF AUC tended to be greater (P < 0.1) for RSP compared to BL, but the majority of the increase was in the TL period. There were no significant differences in the SRIF AUCs between the sampling periods. Furthermore, in a separate experiment, fos activity (a marker of neuronal activation) in the hypothalamus of pigs was examined after either L-163,255 (1x or 4x), isotonic saline (control), or hypertonic saline (positive control) administration. There were no differences in fos activity in the GRF, SRIF, or CRH immunopositive neurons between L-163,255 treatment and control. The pituitaries of the L-163,255-treated pigs showed marked fos activation compared to the controls. In conclusion, L-163,255 in pigs has its primary effect at the level of the anterior pituitary.

Animals↗
PubMed1998

Is there a link between African iron overload and the described mutations of the hereditary haemochromatosis gene?

Over 80%, of Caucasian patients with hereditary haemochromatosis are homozygotes for a C282Y mutation in the HFE gene on chromosome 6. Recent evidence suggests that a genetic factor may also be involved in the pathogenesis of African iron overload, although the locus has not been described. PCR analysis of DNA from 25 southern Africans, identified by segregation analysis as having a high probability of carrying the putative African iron-loading gene, failed to identify any subjects with the C282Y mutation. The possible genetic defect in African iron overload appears to be different from that described in most cases of hereditary haemochromatosis in Caucasians.

Adult↗
PubMed1998

Hypophyseal-portal concentrations of growth hormone-releasing factor and somatostatin in conscious pigs: relationship to production of spontaneous growth hormone pulses.

A method of collecting hypophyseal portal blood (HPB) in conscious pigs was used to show the relationship between GRF and somatostatin (SRIF) concentration and peripheral GH response. Six male castrate pigs (approximately 63 kg body weight) had HPB and jugular blood collected individually for an average of 175 min each. Twenty-seven spontaneous GH pulses were detected in the 1050 min of total HPB collection. Of the associations examined, the only significant finding was that GH pulse maxima occurred nonrandomly within periods of SRIF descent (63%; P = 0.005). Although 48% (13/27) of GH pulse maxima were associated with an ascent in portal GRF concentration, these associations were not determined to be nonrandom (P = 0.14). Only 7 of 27 (26%) GH pulse maxima were associated with an ascent in portal GRF concentration and a descent in SRIF concentration occurring simultaneously. A saline infusion given approximately 120 min after beginning blood collection resulted in an increase in SRIF pulse frequency and a decrease in GH-AUC and GRF-AUC. The cause of this saline effect is unknown, but it may have been related to acclimation of the pigs to the blood collection procedure. These data show the complexity of the relationship between SRIF and GRF concentrations and GH secretion and may indicate a close relationship with SRIF in GH pulse generation in the pig. In addition, these data support the hypothesis that, in the pig, mediation of GH release cannot be explained simply by antagonism between GRF and SRIF.

Animals↗
PubMed1993

Malaria pigment and extracellular iron. Possible target for iron chelating agents.

Extracellular iron is necessary for many biochemical reactions involved in Plasmodium falciparum growth and multiplication. The incorporation of radioactive iron taken up by the parasite was found, electrophoretically and via gamma counting, to be mainly associated with the haemozoin only in the presence of the active metabolism of the parasite. The potent antimalarial activity of desferrioxamine, a ferric iron chelating agent, has shown that iron deprivation is inhibitory to the parasite. We propose that the mechanism of action of desferrioxamine in addition to the chelation of iron from the parasitic compartment, chelates iron from the haemozoin crystal resulting in free radical generation and parasite death. The ability of desferrioxamine and not the ferrous iron chelating agent, 2,2'-bipyridyl, to chelate the non-haem iron from the haemozoin structure indicates that the oxidative state of iron associated with the haemozoin structure is ferric in nature.

2,2'-Dipyridyl↗
PubMed1992

Gamma-tubulin is a centrosomal protein required for cell cycle-dependent microtubule nucleation.

gamma-Tubulin is a newly identified member of the tubulin family whose sequence is highly conserved from yeast to man. This minor microtubule protein is localized to the microtubule organizing centres and a mutation in the gene encoding it produces a microtubuleless mitotic arrest in the filamentous fungus Aspergillus nidulans. Here we investigate the in vivo function of gamma-tubulin in mammalian cells using a synthetic peptide to generate a polyclonal antibody that binds to a highly conserved segment of gamma-tubulin. After microinjection into cultured mammalian cells, immunofluorescence localization revealed that this antibody binds to native centrosomes at all phases of the cell cycle. In the presence of the gamma-tubulin antibody, microtubules fail to regrow into cytoplasmic arrays after depolymerization induced by nocodazole or cold. Furthermore, cells injected immediately before or during mitosis fail to assemble a functional spindle. Thus in vivo gamma-tubulin is required for microtubule nucleation throughout the mammalian cell cycle.

3T3 Cells↗
PubMed1989

A systematic evaluation of bathophenanthroline, ferrozine and ferene in an ICSH-based method for the measurement of serum iron.

The chromogenic substrates ferrozine and ferene were compared to bathophenanthroline disulphonic acid for the measurement of iron concentrations in aqueous and serum samples in an assay based on that of the Iron Panel of the International Committee for Standardisation in Haematology. Ferrozine and ferene were more sensitive than bathophenanthroline. Copper at physiological concentrations in plasma caused only minimal positive interference with all three chromogenic substrates when thioglycollic acid was used as the reducing agent, but when ascorbic acid was used significant positive interference occurred with ferrozine and ferene. Interference due to contaminating haem was comparable with all agents. Bilirubin and carotene produced no interference. Profound reductions in colour development were noted with EDTA plasma.

Chromogenic Compounds↗
PubMed1988

A screening test for detecting iron overload in population studies.

A simple, robust, inexpensive and reasonably accurate screening test, which involves colorimetric assessment of the unsaturated iron-binding capacity, was used to detect significant degrees of iron overload in a field setting. It was used in a survey of 152 men aged over 40 years who had previously been identified as having serum ferritin values above 400 micrograms/l and who were therefore potentially homozygous carriers of the HLA-linked iron-loading gene responsible for the clinical disorder idiopathic haemochromatosis (IHC). Such individuals almost always have a raised transferrin saturation and the screening test was compared with a standard method of measurement. The screening test accurately identified 7 out of 10 subjects with transferrin saturations above 62%. It also accurately identified 137 out of 142 subjects with saturation below 62%. There were 5 false-positive results; in all these subjects saturations were at the upper limit of normal or marginally raised. The test thus had a sensitivity of 77%, a specificity of 97%, an accuracy of 95% and a positive predictive accuracy of 67%. The test successfully identified a subgroup of subjects with serum ferritin values above 400 micrograms/l who appeared to have more severe degrees of iron overload. The screening test, which requires only 200 microliter serum and costs only 6.2 c, should not only be of potential value in identifying subjects at risk of developing the clinical manifestations of IHC but may prove even more useful in defining the prevalence of significant iron overload in the rural black population of South Africa.

Adult↗
PubMed1988

Transferrin iron interactions with cultured hepatocellular carcinoma cells (PLC/PRF/5).

Hepatocellular carcinoma cells of the PLC/PRF/5 cell line had 1.9 x 10(5) transferrin receptors per tumor cell with a Kd of 1.5 x 10(-8) M. At high concentrations of transferrin the binding was not saturable. Transferrin internalization by hepatoma cells was shown by time and temperature-dependent binding studies and by pronase experiments. Transferrin recycling was confirmed by the demonstration of a progressive increase in the cellular molar ratios of iron to transferrin and by chase experiments. Ammonium chloride interfered with iron unloading. The vinca alkaloid vincristine inhibited iron and transferrin uptake. The hepatocarcinoma cells appeared to lack asialoglycoprotein receptors and therefore internalized partially desialated transferrin by the regular route. Iron uptake from transferrin was markedly inhibited by the hydrophobic ferrous chelator 2,2' bipyridine but was relatively unaffected by the hydrophilic ferric chelator desferroxamine. The implication that ferrous iron was involved in postendocytic transvesicular membrane iron transport was supported by a study in which hepatoma cells were shown to take up large amounts of ferrous iron suspended in 270 mM sucrose at pH 5.5. The interaction at this pH between surface labeled hepatoma cell extracts and ferrous iron on a Sephacryl S-300 column suggested that the postendocytic transvesicular transport of iron through the membrane was in part protein mediated. The endocytosed iron in hepatoma cells was found in association with ferritin (33%), transferrin (31%) and a low molecular weight fraction (21%).

2,2'-Dipyridyl↗
PubMed1986

Effect of alpha-difluoromethylornithine on L-phenylalanine mustard-induced cytotoxicity and DNA interstrand cross-linking in a human cell line in vitro.

We compared L-phenylalanine mustard (L-PAM)-induced cytotoxicity and DNA cross-linking with and without a 42-h preincubation with the ornithine decarboxylase inhibitor alpha-difluoromethylornithine (DFMO, 1 mM) in a human lymphoma cell line. The combination showed increased toxicity with a Do ratio of 1.6. L-PAM-induced DNA protein cross-linking as measured by alkaline elution was not altered by a DFMO pretreatment. DNA interstrand cross-linking was increased when L-PAM-treated cells were pretreated with DFMO. The differences occurred between 12 and 24 h following the L-PAM treatment. Peak protein cross-linking occurred 6 h following L-PAM removal with or without DFMO pretreatment. While peak interstrand cross-linking occurred 6 h following L-PAM removal, the DFMO-pretreated cells maintained higher cross-link levels longer than did control cells. The increase in interstrand cross-linking seen in DFMO-pretreated cells was maintained at several different L-PAM doses. The increased cytotoxicity could not be accounted for by the increased cross-linking alone. We have postulated that DFMO pretreatment results in a delay in the appearance of a cross-link removal system. The differences seen between results using these human cells and previous reports using rodent cells are discussed.

Cell Cycle↗
PubMed1983

The effect of single-density bovine serum albumin columns on sperm concentration, motility, and morphology.

Experiments were conducted to determine whether single-density albumin columns could be used to improve sperm motility and morphology. Semen samples from 92 men seen at a fertility evaluation clinic were analyzed for count, motility, and morphology and centrifuged. An aliquot of the resuspended sample was then layered on top of 1 ml of a 7.5% solution of bovine serum albumin (BSA). Another aliquot was layered on top of a 10% BSA column. After 60 minutes, the sperm penetrating the bottom two thirds of the albumin layer were isolated and analyzed for count, motility, and morphology. The sperm count after exposure to both 7.5% and 10% BSA columns decreased to approximately 60% of the preisolation counts. Sperm motility was not altered by column separation at either albumin concentration, but sperm morphology significantly improved with both columns. The single-density albumin separation technique therefore improved morphology and had no effect on motility, and a reasonable number of sperm were retained after separation. Albumin separation techniques could be utilized to improve samples with morphology defects before use with artificial insemination or in vitro fertilization. It is uncertain whether this procedure would result in a higher pregnancy rate.

Adult↗
PubMed1975

Psychiatric disturbance with acute onset and offset in a Darwin evacuee.

A case of transient situational disturbance in a Darwin evacuee is presented in order to place on record the nature of and the circumstances associated with a "breakdown" following the patient's evacuation form Darwin as a result of cyclone Tracy. The apparently gross behavioural disturbance was rapidly resolved after the involvement of a number of people willing, and apparently able, to provide help, without resort to hospitalization or medication.

Acute Disease↗
PubMedDate not supplied

Albuquerque Target Cities: preliminary findings.

Overall, there appeared to be a decline in frequency of use in the substance patterns of the 46 cases investigated for this analysis. The rising frequency with which prescription drugs are reported may be explained by the fact that these clients are in treatment, a situation which frequently necessitates the prescription of various medications. Additionally, the rise in methadone use can also be explained by the fact that it is prescribed to individuals who are undergoing treatment for a heroin addiction. Finally, it is probable that polysubstance use is underreported in the intake data, thus explaining the apparent increase reported at follow-up.

Demography↗