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Biomedical subjects

G J Brewer

Publications and source records attributed to G J Brewer.

At least 19 recordsLinked to original sources
PubMed1992

Use of zinc acetate to treat copper toxicosis in dogs.

Zinc acetate was used for the treatment and prophylaxis of hepatic copper toxicosis in 3 Bedlington Terriers and 3 West Highland White Terriers. Two dogs of each breed were treated for 2 years, and 1 of each breed for 1 year. A dosage of 200 mg of elemental zinc per day was required to achieve therapeutic objectives related to copper, which included a doubling of plasma zinc concentration to 200 micrograms/dl and a suppression of oral 64 copper absorption. The dosage was later reduced to 50 to 100 mg/day to avoid an excessive increase in plasma zinc concentration. The preliminary clinical results were good. Three dogs had mild to moderate active liver disease and high liver copper concentrations at the time of initiation of zinc administration. Biopsy of the liver 2 years later revealed a reduction in hepatitis and copper concentrations. One other dog without active hepatitis also had a reduction in hepatic copper concentrations over a 2-year period. All 6 dogs have done well clinically. On the basis of these findings, we believe zinc acetate to be an effective and nontoxic treatment for copper toxicosis in dogs.

Absorption↗
PubMed1992

Polarity decrease at the adhesive junction between two model membranes containing gangliosides.

The increased electrical conductance previously observed between two model membranes containing gangliosides suggests the creation of a new environment in the adhesive junction [Brewer, G. J., & Thomas, P.D. (1984) Biochim. Biophys. Acta 776, 279]. In order to provide a mechanism for this novel finding, we now report an investigation of the micropolarity in the adhesive junction. Emission from the fluorescent probe PRODAN is a sensitive measure of polarity of the probe environment. A bimodal linear relationship correlates the emission wavelength from PRODAN with the inverse of solvent dielectric constant (1/epsilon). A better single linear relationship is obtained using Reichardt's relative polarity measure (RPM). Creation of two macroscopic spherical lipid bilayers from phosphatidylcholine, brain gangliosides, and PRODAN allowed selective excitation and observation of fluorescence from either a single bilayer or the double bilayer in the adhesive junction. The reported PRODAN polarity of -0.57 in a single ganglioside-containing membrane was midway between the polarity of water and n-hexane, suggesting PRODAN localization near the lipid carbonyls. The adhesive junctional region exhibited two new less polar environments of PRODAN fluorescence, RPM = -0.45 and -0.29. These measures are consistent with a relatively dehydrated immobilized phase. These changes were not observed in the adhesion zone between two membranes made with phosphatidylcholine without gangliosides. The changes in molecular structure in the junction that could be responsible for the altered PRODAN emission are discussed. A decrease in the hydrocarbon thickness of junctional membranes or a decrease in the aqueous junctional polarity could be responsible for the polarity decrease reported by PRODAN.

2-Naphthylamine↗
PubMed1992

Congregation of gangliosides at the junction between two model membranes.

The diversity and distribution of gangliosides in vertebrate tissue suggests an important role in cellular recognition. Two types of experiments are reported to test the hypothesis that gangliosides can congregate to form an adhesive junction between two membranes. First, to monitor ganglioside distribution and mobility in different regions of two large spherical bilayer membranes, fluorescent derivatives of natural gangliosides were synthesized. Second, the cation carrier nonactin was used as a conductance probe to measure the membrane surface potential, which would be altered if there were a redistribution of the charged gangliosides. These studies were conducted in large spherical artificial membranes made from egg phosphatidylcholine or oleoylpalmitoylphosphatidylcholine with 0-12 mol % bovine brain gangliosides dissolved in n-decane. The fluorescent gangliosides utilized were lucifer yellow adducts to the sialic acids (LY-gangliosides) or a cis-paranaric acid substitution of the N-acyl moiety in the ceramide portion of gangliosides GM1 and GD1a (paranaryl-GM1 and paranaryl-GD1a). The polarized fluorescence from the adhesive junction between two membranes containing LY-gangliosides or either paranarylganglioside was compared to that in nonadhesive regions. For LY-gangliosides, total fluorescence in the junction decreased with time, possibly due to electrostatic repulsion of this highly charged derivative. For paranarylgangliosides, fluorescence in the junction increased 7-fold with time, suggesting congregation of this ganglioside. In both cases, a measure of rotational mobility, fluorescence anisotropy, increased dramatically, about 2-fold, as expected for restricted mobility of adhesive compounds. Independent evidence for congregation of charge-bearing gangliosides was found with the conductance probe nonactin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adhesiveness↗
PubMed1992

Human serum stimulates Alzheimer markers in cultured hippocampal neurons.

The mechanism for promoting the distinct types of lesions in the Alzheimer disease (AD) brain and other changes outside the brain is unknown. We examined neurons in culture, unprotected by glia or a blood-brain barrier, to determine if exposure to serum from Alzheimer patients would affect markers for Alzheimer brain lesions. Rat hippocampal neurons were first grown for 4 days in a new serum-free culture medium, then exposed for 24 hr to human sera. Sera from 12 AD patients or their spouses increased four molecular markers characteristic of Alzheimer senile plaques and neurofibrillary tangles: Alz-50, beta-amyloid (beta/A4), MAP2, and ubiquitin, each with their expected cytologic distributions. Sera from ten young adults produced significantly less stimulation. By quantitative immunofluorescence, neuronal exposure to the elderly human sera produced 1.8- to 2.5-fold increases in mean fluorescent area/cell for each of these four markers relative to no serum exposure. As controls, an unrelated neuronal marker, enolase, was unaffected and fetal bovine serum did not stimulate immunoreactivity. Neuron viability and somal area were unaffected at 24 hours. The MAP2 increases were dose dependent with negligible effect at 2% serum and maximum effect at 10% serum after 24 hr. The MAP2 increase was greater after 48 hr of exposure than 24 hr and negligible at 2 hr. This stimulation of AD markers by human serum suggests that the genesis of both neuronal plaques and tangles may arise from access of toxic serum factors to susceptible neurons and/or failure to detoxify these factors.

Adult↗
PubMed1992

Wilson disease.

Wilson disease is an inherited disorder of copper metabolism. Progress has been made in establishing the location of the gene on the long arm of chromosome 13, and in finding nearby probes that can be used to identify affected sibs of newly diagnosed patients. However, the gene has not been cloned, and the molecular nature of the defect remains unknown. The cause of the disease is a failure to excrete unneeded and excessive copper in the bile for loss in the stool. This may be due to a failure to excrete copper packaged in ceruloplasmin into the bile. Clinically, patients usually present during the second to fourth decades of life with liver, neurologic, or psychiatric disease, but the diagnosis is often missed or delayed. Once a diagnosis of Wilson disease is considered, reliable studies of copper variables can be carried out. After diagnosis, patients must receive anticopper treatment for the rest of their lives, to reduce copper levels and prevent copper reaccumulation. For life-long maintenance therapy, we recommend zinc acetate because of its complete efficacy and lack of toxicity; it acts by blocking copper absorption. For initial therapy of the acutely ill patient, no currently available therapy has proven to be ideal. A chelator-type drug, either penicillamine or trien, can be used for the initial therapy of patients who present with liver disease; transition to zinc acetate can then be made after a few months. For the initial therapy of acutely ill patients who present with neurologic disease, chelation should be avoided because neurologic worsening frequently occurs, probably due to redistribution of copper which temporarily raises the levels of copper in the brain. For initial treatment, zinc therapy is also not ideal because it is relatively slow-acting. A new experimental drug, tetrathiomolybdate, shows promise in the initial treatment of patients with Wilson disease. The major challenges ahead include closing the remaining therapeutic hiatuses, cloning and expressing the gene to understand its function, and improving clinical diagnosis so that therapy can be instituted as quickly as possible.

Hepatolenticular Degeneration↗
PubMed1992

Treatment of Wilson's disease with zinc: X. Intestinal metallothionein induction.

Oral zinc therapy is effective in controlling copper balance in patients with Wilson's disease and blocks the intestinal absorption of copper, as demonstrated by uptake of copper 64 and copper balance measurements. In this study, 64Cu uptake measurements were concomitantly carried out with intestinal biopsies to investigate the relationship of reduced copper absorption to the levels of intestinal metallothionein in patients with Wilson's disease at different stages of zinc therapy. A pronounced increase in intestinal metallothionein levels and a sharp drop in 64Cu absorption were found 4 to 5 days after the initiation of zinc treatment. Conversely, metallothionein levels decreased and 64Cu uptake increased on the discontinuation of zinc therapy. The data indicate that 64Cu absorption varies as a function of intestinal metallothionein level. Intestinal metallothionein levels were found to correlate linearly with urinary zinc levels, which reflect body zinc status. These findings support our hypothesis that intestinal metallothionein induction mediates decreased copper absorption observed during zinc therapy. The suppressive effect of zinc on copper absorption appears to have a half-life of about 11 days.

Adult↗
PubMed1991

Initial therapy of patients with Wilson's disease with tetrathiomolybdate.

Patients with Wilson's disease who present with acute neurological symptoms often become clinically worse when initially treated with penicillamine. Other available anticopper drug therapies do not appear to offer a solution to this treatment problem. We are developing and evaluating a new drug, ammonium tetrathiomolybdate for this purpose. Theoretically, tetrathiomolybdate has optimal properties, including an immediate blockade of copper absorption and the property of forming complexes with copper in the blood, rendering the copper nontoxic. In this article, we present results from six patients treated with tetrathiomolybdate for up to 8 weeks as initial therapy. None of the five patients who had presented with acute neurological symptoms worsened. Also presented are methods of assay, preliminary stability studies, and methods of evaluating therapeutic end points with respect to copper metabolism.

Adolescent↗
PubMed1991

Compliance of hippocampal neurons to patterned substrate networks.

Neuronal growth can be controlled in vitro by plating cells at low density and by differential adhesion between the cell and substrate. Primary cultures of rat hippocampal neurons were grown in serum-free culture on polylysine-coated glass coverslips patterned by selective laser ablation so as to leave grids of polylysine with varying linewidths (3, 5, and 10 microns), intersection distance (80, 120, and 160 microns), and nodal (intersection) diameter (5, 10, and 20 microns). Not only did somae strongly prefer the unablated polylysine areas, but they also migrated to loci where the local area of unablated polylysine was higher. These loci were the nodes, as opposed to the narrow connecting paths, and larger nodes, as compared with smaller nodes. Maximum migration to nodes of 88% occurred for a combination of 5-microns path width, 20-microns node diameter, and 80-microns path length. Daily observations indicated active migration to larger adhesive areas, which explains the differential compliance.

Animals↗
PubMed1991

The psychiatric presentations of Wilson's disease.

We reviewed the records of 42 patients with Wilson's disease participating in a zinc acetate treatment protocol and interviewed 17 of them. Five of the patients studied were asymptomatic. A significant number of symptomatic patients (64.8%) reported psychiatric symptoms at the time of initial presentation. These symptoms were severe enough to warrant psychiatric intervention in almost half of all symptomatic patients before the diagnosis of Wilson's disease was made. Personality changes, particularly irritability and aggression, were most commonly described (45.9%), followed by depression (27%). Cognitive changes, anxiety, psychosis, and catatonia, while less frequent, also occurred. These data underscore the need to include Wilson's disease in the differential diagnosis of psychiatric disorders.

Acetates↗
PubMed1991

Ecto 5' nucleotidase (5'NT) as a sensitive indicator of human zinc deficiency.

Ecto 5' nucleotidase (5'NT) is an integral plasma membrane enzyme located on most mammalian cells, and it is zinc dependent. We assayed 5'NT activity in the lymphocytes of two groups of subjects. The first group of six subjects had a mild state of zinc deficiency, as measured on the basis of zinc levels in lymphocytes, granulocytes, and platelets, but were otherwise healthy. They received 50 mg zinc as acetate orally for 12 weeks. The second six subjects were normal human volunteers in whom a mild state of zinc deficiency was induced experimentally by dietary techniques (4.2 to 5.6 mg daily zinc intake). For the assay of 5'NT, intact lymphocytes were incubated with 8-14C-labeled inosine monophosphate as substrate. Product and substrate were separated by thin-layer chromatography. Zinc level in cells was measured by flameless atomic absorption technique. In the first group of subjects with zinc deficiency, the decreased activity of 5'NT was corrected and the cellular zinc levels were normalized by oral zinc supplementation (p less than 0.01). In the second group of subjects, the baseline data were compared with those in early zinc depletion (4 to 8 weeks) and late depletion periods (greater than 20 weeks). A decrease in the activity of 5'NT was observed during the early zinc depletion phase. Zinc levels in lymphocytes, granulocytes, and platelets decreased significantly only during the late zinc depletion phase (p less than 0.01). Plasma zinc level did not change even during the late zinc depletion phase. Our studies show that 5'NT activity may be a sensitive and useful indicator of mild deficiency of zinc in human subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

5'-Nucleotidase↗
PubMed1991

Diagnosis and characterization of presymptomatic patients with Wilson's disease and the use of molecular genetics to aid in the diagnosis.

Wilson's disease (WD) is an autosomal recessive disorder of copper accumulation leading to liver and/or brain damage. Although fatal if untreated, the condition can be treated effectively. Autosomal recessive inheritance indicates that siblings of affected patients are at 25% risk of having the disease. If they are diagnosed prior to becoming symptomatic, affected siblings can be kept free of symptoms by prophylactic therapy. In this paper we have examined the utility of copper-related variables, along with other clinical and molecular findings, in identifying those siblings of affected patients who should be further evaluated with a liver biopsy. Data are presented on a series of 13 presymptomatic patients in whom we have made the diagnosis of WD based on liver biopsy findings. Signs of liver disease were present in 12 out of 13 cases. The classic, noninvasive, screening approaches that we evaluated were not adequate to identify all cases of WD in this group of patients. These included positive Kayser-Fleischer (KF) rings, elevated liver serum alanine transferase, elevated urine copper, or elevated plasma nonceruloplasmin copper. We have introduced the use of molecular genetics for screening siblings of affected patients for WD. We show that a probe from the linked retinoblastoma (RB) gene can be very helpful in problem cases. However, at this time, the quantitative determination of liver copper concentration remains as the definitive diagnostic criterion.

Adolescent↗
PubMed1991

Treatment of Wilson's disease with zinc. IX: Response of serum lipids.

Zinc therapy in Wilson's disease is a lifelong treatment to prevent reaccumulation of copper. Previous reports have shown that in normal male subjects, zinc ingestion has reduced high-density lipoprotein cholesterol level. This finding raises the possibility that lifelong zinc therapy could be atherogenic. In the present work, the effects of zinc therapy on serum lipids over a period of years is evaluated in patients with Wilson's disease. Zinc therapy reduces total cholesterol level by about 10% in both sexes and reduces high-density lipoprotein cholesterol level by about 20% in male patients. The mechanisms of these interesting effects of zinc on cholesterol metabolism are unknown. The coronary heart disease risk factor is not changed significantly by zinc therapy in either sex, and further, it remains below average in these patients after zinc therapy. We conclude that zinc therapy in Wilson's disease is not atherogenic.

Cholesterol, HDL↗
PubMed1990

Use of zinc-copper metabolic interactions in the treatment of Wilson's disease.

Zinc acetate is becoming a well-established therapy for the treatment of Wilson's disease. It is excellent for maintenance therapy and for the treatment of the presymptomatic patient. Current evidence suggests that it will also be excellent for the treatment of the pregnant patient. Zinc acts by inducing intestinal cell metallothionein, which binds copper with high affinity, blocking its absorption, and causing its excretion in the stool. We have shown that zinc, even in doses as low as 25 mg daily, negatively affects copper balance. Zinc in doses of 50 mg three times daily, with all doses separated from food, controls the abnormal positive copper balance, blocks uptake of orally administered 64Cu, controls urine and plasma copper, prevents the reaccumulation of hepatic copper, and prevents the development or progression of symptoms of copper toxicosis in Wilson's disease patients. Zinc acetate will probably be licensed in the near future for the treatment of Wilson's disease. We recommend that physicians use urine and plasma copper, and urine zinc, as primary monitoring tools. In contrast to the comfortable situation with maintenance therapy, the initial treatment of acutely ill Wilson's disease patients is not well worked out. Patients with neurological disease often get worse initially on penicillamine, and zinc acts more slowly than is ideal. We have initiated studies of tetrathiomolybdate for this purpose. Studies of biliary secretions of normal subjects suggest that they excrete regulatory (excess) copper packaged in a protease-resistant ceruloplasmin fragment. This fragment is missing in Wilson's disease bile. The gene for Wilson's disease is on chromosome 13, close to the retinoblastoma locus.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1990

Membrane morphogenesis from cloned fragments of bacteriophage PM2 DNA that contain the sp6.6 gene.

The formation of new membrane vesicles normally occurs during eukaryotic organellogenesis and maturation of bacteriophage PM2. This virus was studied as a simple model for membrane morphogenesis. Previous biochemical and genetic studies suggest that a major structural protein of PM2, sp6.6, is an integral membrane protein involved in viral membrane morphogenesis. To establish the necessity of sp6.6 in membrane formation, restriction fragments of PM2 that contained the sp6.6 coding sequence were cloned into several plasmid vectors for expression in Escherichia coli. A construction in pBR322 containing two HindIII fragments of PM2 DNA caused production of intracellular membrane vesicles of the same size as those produced in the course of natural infection of Alteromonas espejiana. Similar results were obtained with a smaller construct of HindIII fragments in the plasmid vector pPL-lambda. Expression of sp6.6 was detected via incorporation of 35S-labeled methionine after SDS-polyacrylamide gel electrophoresis and with a specific rabbit antiserum on immunoblots. Other constructs did not produce recognizable vesicles or sp6.6. These results are the first to suggest that a hydrophobic membrane protein can cause development of new membrane structure.

Bacteriophages↗
PubMed1990

Copper diseases.

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Adult↗
PubMed1990

Pancreaticobiliary secretion of zinc and copper in normal persons and patients with Wilson's disease.

The objectives of this study were (1) to examine basal and cholecystokinin-stimulated pancreaticobiliary secretion of zinc in normal subjects with zinc-adequate and zinc-deficient diets, and (2) to investigate whether basal and stimulated secretion of zinc was abnormal in patients with Wilson's disease before and after zinc therapy. Gastroduodenal intubation was performed in six healthy subjects and five patients with Wilson's disease. After intravenous infusion of octapeptide of cholecystokinin (40 ng/kg/hr) the pancreaticobiliary secretion of zinc increased from a basal rate of 283.1 +/- 75.8 nmol/L/min to a peak of 716.6 +/- 175.3 nmol/L/min in normal subjects. Normal subjects with a zinc-deficient diet had both lower basal (66.8 +/- 15.8 nmol/L/min) and stimulated (559.5 +/- 31 nmol/L/min) pancreaticobiliary secretion of zinc than with a zinc-sufficient diet. In contrast to the markedly reduced pancreaticobiliary secretion of copper, patients with Wilson's disease not treated with zinc had normal basal (226.6 +/- 126 nmol/L/min) and stimulated (728.7 +/- 195.5 nmol/L/min) zinc secretion. These studies indicate that a considerable amount of zinc is being secreted in pancreaticobiliary fluid in healthy subjects and there was no impairment of zinc secretion in patients with Wilson's disease. Our data also indicate that pancreaticobiliary secretion of zinc is dependent on the zinc status of the subjects, suggesting that endogenous secretion of zinc may play a significant role in the homeostasis of zinc.

Acetates↗