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Biomedical subjects

M R Wills

Publications and source records attributed to M R Wills.

At least 19 recordsLinked to original sources
PubMed1992

Antigenic characterization of the live attenuated Japanese encephalitis vaccine virus SA14-14-2: a comparison with isolates of the virus covering a wide geographic area.

In China, a live attenuated Japanese encephalitis (JE) vaccine, based on strain SA14-14-2, has been derived from the wild-type strain SA14 as an alternative to the current inactivated vaccines such as Nakayama-NIH and P-3. SA14-14-2 has been characterized using monoclonal antibodies derived in mice, using HAI and neutralization tests, and compared with other Chinese live vaccine clones and 14 wild-type strains of JE virus. Wild-type strain SA14 was found to be a poor immunogen and antigenically distant from all other viruses examined. The vaccine derivatives SA14-5-3 was more immunogenic than its wild-type parent, while SA14-14-2 (derived from SA14-5-3) was more immunogenic than SA14-5-3 and elicited a cross neutralizing antibody response. Our studies indicated that JE virus strain Nakayama elicited as good a neutralizing antibody response in hyperimmunized mice as the SA14-14-2 vaccine clones grown in either primary hamster kidney (PHK) or primary dog kidney (PDK) cells. A single dose of live SA14-14-2 (PHK) also elicited a good antibody response. Antigenic variation between wild-type and vaccine clones of JE virus were detected but were not considered significant in terms of controlling JE virus infections by vaccination.

Animals↗
PubMed1992

Immunogenicity of experimental live attenuated Japanese encephalitis vaccine viruses and comparison with wild-type strains using monoclonal and polyclonal antibodies.

A total of 105 hybridomas secreting anti-Japanese encephalitis (JE) virus monoclonal antibodies (mAbs) were generated from six fusions against four strains of JE virus: wild-type strains SA14 and G8924 and live attenuated vaccines SA14-5-3 and SA14-14-2 (PDK-9). Most of the mAbs (87%) elicited haemagglutination inhibition activity while only a minority (24%) elicited neutralization. None of the mAbs prepared against SA14-5-3, parent of SA14-14-2, elicited neutralization while the only mAbs prepared against SA14-14-2 that elicited neutralization recognized flavivirus cross-reactive epitopes. In comparison, mAbs raised against wild-type strains showed that a spectrum of epitopes with different specificities, including JE type-specific epitopes, elicited neutralizing activity. Two mAbs, prepared against SA14-5-3 virus, were found to be vaccine-specific and five, prepared against strains SA14 and G8924, were wild-type-specific.

Animals↗
PubMed1992

Variation in the biological function of envelope protein epitopes of yellow fever vaccine viruses detected with monoclonal antibodies.

Three different virus strains (17D-204, 17DD and the French neurotropic vaccine) have been used as live attenuated yellow fever (YF) vaccines and are manufactured in different centres around the world. The envelope proteins of these vaccine viruses were examined and compared using mouse monoclonal antibodies (MAbs) in haemagglutination inhibition (HAI) and neutralization (N) tests. The epitopes eliciting HAI and/or N were found to vary depending on the virus examined. Such variation was also found between vaccine viruses of the same strain manufactured in different centres. These data were confirmed by the use of mouse polyclonal antisera. On the basis of the MAb results in HAI tests a dendrogram of the similarity coefficients between the viruses was constructed and showed that the viruses could be placed into three major groups. Thus, it is concluded that YF vaccines manufactured in different centres are antigenically distinct as recognized by the mouse immune system.

Antibodies, Monoclonal↗
PubMed1992

Identification of envelope protein epitopes that are important in the attenuation process of wild-type yellow fever virus.

Monoclonal antibodies (MAbs) have been prepared against vaccine and wild-type strains of yellow fever (YF) virus, and envelope protein epitopes specific for vaccine (MAbs H5 and H6) and wild-type (MAbs S17, S18, S24, and S56) strains of YF virus have been identified. Wild-type YF virus FVV, Dakar 1279, and B4.1 were each given six passages in HeLa cells. FVV and B4.1 were attenuated for newborn mice following passage in HeLa cells, whereas Dakar 1279 was not. Examination of the envelope proteins of the viruses with 87 MAbs showed that attenuated viruses gained only the vaccine epitope recognized by MAb H5 and lost wild-type epitopes recognized by MAbs S17, S18, and S24 whereas the nonattenuated Dakar 1279 HeLa p6 virus did not gain the vaccine epitope, retained the wild-type epitopes, and showed no other physical epitope alterations. MAb neutralization-resistant (MAbr) escape variants generated by using wild-type-specific MAbs S18 and S24 were found to lose the epitopes recognized by MAbs S18 and S24 and to acquire the epitope recognized by vaccine-specific MAb H5. In addition, the MAbr variants became attenuated for mice. Thus, the data presented in this paper indicate that acquisition of vaccine epitopes and loss of wild-type epitopes on the envelope protein are directly involved in the attenuation process of YF virus and suggest that the envelope protein is one of the genes encoding determinants of YF virus pathogenicity.

Animals↗
PubMed1992

Trace metals: essential nutrients or toxins.

Trace metals play important roles in biological processes, both as essential components and toxins. Monitoring body status of trace metals thus has become an important function of many clinical, industrial, and government laboratories. Deficiencies of some essential trace metals are seen occasionally, but of most importance is the area of metal toxicity resulting from environmental, occupational, accidental, or iatrogenic exposure. Major questions persist about which specimen best reflects body status, and in this regard each metal has different requirements. Blood is used most widely, urine has a few applications, and hair can be used, although external contamination is an ever-present problem. Tissue is by far the best specimen but is not easily obtained. Contamination of specimens during collection and processing must be controlled. Of the instrumental techniques available, atomic absorption spectrometry has been used most widely, particularly with electrothermal and atomization approaches.

Chemistry, Clinical↗
PubMed1991

In vitro homotypic and heterotypic interference by defective interfering particles of West Nile virus.

Defective interfering (DI) particles of the flavivirus West Nile (WN) were generated after as few as two high multiplicity serial passages in Vero and LLC-MK2 cells. Six cell lines (Vero, LLC-MK2, L929, HeLa, BHK-21 and SW13) were used to assay interference by DI particles in a yield reduction assay. Interference was found to vary depending on the cell type used. The highest levels of interference were obtained in LLC-MK2 cells, whereas no detectable effect was observed in BHK-21 and SW13 cells. The ability of DI virus to be propagated varied depending on the cell line used; no detectable propagation of DI virus was observed in SW13 cells. Optimum interference was obtained following co-infection of cells with DI virus and standard virus at a multiplicity of 5. Interference between DI and standard viruses occurred only when they were co-infected or when cells were infected with DI virus 1 h before standard virus. Investigation of heterotypic interference by DI particles of WN virus strains from Sarawak, India and Egypt revealed that interference was dependent on the strain of WN virus or flavivirus used as standard virus. A measure of the similarity between five strains of WN virus and other flaviviruses was made on the basis of interference by DI viruses, and was found to be similar to that based on haemagglutination inhibition tests using a panel of monoclonal antibodies.

Animals↗
PubMed1991

Aluminium maltol-induced neurocytoskeletal changes in fetal rabbit midbrain in matrix culture.

We have developed a neuronal culture system to evaluate the neurotoxic effects of aluminium maltol on fetal rabbit midbrain sections containing the oculomotor nucleus. Cultures were treated with 5, 7, 9, 11, 13 and 15 mumol/l aluminium maltol or 39 and 45 mumol/l maltol (molal equivalents to 13 and 15 mumol/l aluminium maltol). Control cultures were maintained in nutrient medium alone. Silver-positive neuritic swellings and occasional perikaryal neurofibrillary tangles were observed in cultures treated with 11, 13 and 15 mumol/l aluminium maltol. The number of tangles (involved neurons) produced in aluminium maltol treated cultures were counted and compared to (untreated) controls. We observed a total of 3, 7 and 7% of involved neurons following treatment with 11, 13 and 15 mumol/l aluminium maltol respectively, and none in the control group. By immunohistochemistry, neurofibrillary tangles were immunoreactive with MAbs to phosphorylated (SMI-31), non-phosphorylated, phosphorylation dependent (SMI-32) and phosphorylation independent (SMI-33) epitopes of the high (-H) and middle (-M) molecular weight neurofilament subunits (NF-H/M). By contrast these lesions were nonreactive with MAbs recognizing tau, MAP2 or different beta-tubulin isotypes. The perikaryal tangles consisted of focal accumulations of 10 nm straight filaments by electron microscopy. These findings are in agreement with previous data from rabbit in vivo studies after the administration of aluminium maltol intravenously (Bertholf et al., 1989) or intraventricularly (Katsetos et al., 1990). Using this in vitro system, aluminium-induced neurofibrillary tangles can be consistently produced, and changes in the distribution of neurofilament proteins evaluated. These studies may aid in the assessment of the possible role of aluminium in the aetiology of human neurodegenerative disorders.

Aluminum↗
PubMed1990

Determination of chromium in urine by stable isotope dilution gas chromatography/mass spectrometry using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent.

An isotope dilution gas chromatography/mass spectrometry method using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent is described for the determination of chromium in urine. A wet digestion procedure with HNO3-H2O2 is used for oxidizing the organic matter associated with urine samples. The isotope ratios are measured by selected ion monitoring in a general-purpose mass spectrometer using a 10-m fused silica capillary column. Memory effect, in sequential analyses of samples with different isotope ratios, was evaluated by preparing a series of synthetic mixtures and was found to be negligible. The accuracy of the method was verified by quantitation of chromium in the NIST freeze-dried urine reference material, SRM-2670, with a recommended chromium concentration of 13 micrograms/L in the normal level and certified chromium concentration of 85 +/- 6 micrograms/L in the elevated level.

Chelating Agents↗
PubMed1990

Effects of renal failure.

The multiple features of the syndrome of uremia are a result of the retention of a wide variety of metabolic end products. Although a number of metabolites have been incriminated as "the uremic toxin," none of them accounts for all aspects of uremia. It is likely that the uremic syndrome is a result of the pathological effects of many retained substances. Of major current interest is the development of toxicity in brain, bone and other tissues due to accumulation of aluminum. The recognition of aluminum toxicity may have implications not only in patients with impaired renal function but also in other disease states.

Aluminum↗
PubMed1990

Effect of administration of sodium aurothiomalate on the virulence of yellow fever viruses in adult mice.

Administration of sodium aurothiomalate (SATM) to adult mice results in a reduction of their average survival time (AST) following intracerebral challenge with the wild-type strains, Asibi and French viscerotropic virus (FVV), of yellow fever (YF) virus. Most attenuated 17D YF vaccines, derived by passage of the wild-type Asibi strain in chick tissue, showed no reduction in AST following intracerebral challenge and administration of SATM. In contrast, challenge with the majority of live attenuated French neurotropic vaccines, derived by passage of FVV in mouse brain, still resulted in SATM reducing the AST of mice. SATM also changed some YF viruses from non-lethal to lethal following intraperitoneal challenge and negated the ability of a monoclonal antibody to elicit passive protection of mice challenged intracerebrally with YF virus.

Administration, Intranasal↗
PubMed1990

Neuronal cytoskeletal lesions induced in the CNS by intraventricular and intravenous aluminium maltol in rabbits.

The antigenicity of neuronal cytoskeletal lesions was studied immunohistochemically in adult New Zealand white rabbits after intraventricular (subacute) and intravenous (chronic) administration of a water-soluble aluminium compound, aluminium (Al) maltol. After short-term intraventricular administration, rabbits developed widespread neurofibrillary degeneration (NFD) involving pyramidal neurons of the isocortex and allocortex, projection neurons of the diencephalon, and nerve cells of the brain stem and spinal cord. There was a predilection for motor neuron involvement and for the infratentorial portions of the neuraxis. Perikarya and proximal neurites were especially affected. Bundles of 10 nm filaments were frequently present. Three of the animals treated intravenously for 12 weeks or longer displayed NFD in the oculomotor complex and in the pyramidal neurons of the occipital isocortex. Following either mode of administration, the affected neurons exhibited immunostaining with a panel of monoclonal antibodies (MAbs) against phosphorylated (SMI-31), non-phosphorylated/phosphatase-sensitive (SMI-32), and dephosphorylation-independent (SMI-33) epitopes of high and middle molecular weight neurofilament (NF) protein subunits. They were non-reactive with MAbs to microtubule-associated protein 2 and the class III neuron-associated beta-tubulin isotype. Our findings indicate that intraventricular Al maltol produces similar, but more widespread degeneration of projection-type neurons than the less water-soluble Al compounds as reported by others. The NFD lesions are compared with those of senile dementia of the Alzheimer type (SDAT) and motor neuron disease.

Aluminum↗
PubMed1990

Aspects of aluminum toxicity.

Aluminum is the most abundant metal in the earth's crust. The widespread occurrence of aluminum, both in the environment and in foodstuffs, makes it virtually impossible for man to avoid exposure to this metal ion. Attention was first drawn to the potential role of aluminum as a toxic metal over 50 years ago, but was dismissed as a toxic agent as recently as 15 years ago. The accumulation of aluminum, in some patients with chronic renal failure, is associated with the development of toxic phenomena; dialysis encephalopathy, osteomalacic dialysis osteodystrophy, and an anemia. Aluminum accumulation also occurs in patients who are not on dialysis, predominantly infants and children with immature or impaired renal function. Aluminum has also been implicated as a toxic agent in the etiology of Alzheimer's disease, Guamiam amyotrophic lateral sclerosis, and parkinsonism-dementia.

Aluminum↗
PubMed1990

Critical appraisal of two methods for determining aluminum in blood samples.

We report two methods for determining aluminum concentrations in blood. Method 1, proposed for routine monitoring of patients with chronic renal failure, includes a collection procedure that can be adopted by any renal dialysis unit, with a minimum of sample contamination. Plasma samples are diluted fourfold with HNO3/Triton X-100 matrix modifier. Method 2 is proposed for determining aluminum concentrations in patients with normal renal function, e.g., in drug studies and environmental monitoring. Samples are diluted with an equal volume of Mg(NO3)2 matrix modifier and atomized from a L'vov platform. By either method, analytical recovery of aluminum added to serum ranged between 92% and 105% throughout the linear calibration range. The reference interval (mean +/- SD) for aluminum in 22 healthy subjects by method 2 was 0.044 +/- 0.030 mumol/L.

Aluminum↗
PubMed1989

Isotope dilution gas chromatography/mass spectrometry for the determination of nickel in biological materials.

Precise and accurate methods are required to measure nickel in urine and serum samples to identify clinical states of either deficiency or toxicity. This paper presents an isotope dilution gas chromatography/mass spectrometry method for the measurement of nickel in biological samples. The method involves the preparation of a thermally stable and volatile nickel chelate using lithium bis(trifluoroethyl)dithiocarbamate as the chelating agent. Conditions were optimized for the digestion of the sample and quantitative preparation of chelate as well as the precise and accurate measurements of the isotope ratios using a capillary column gas chromatograph with a general purpose mass spectrometer. The memory effect between samples of different isotope ratios was evaluated and was found to be negligible. The quantitative accuracy of isotope dilution was validated by measuring nickel in the NIST freeze-dried urine reference material, SRM 2670, with comparison to the recommended value.

Chelating Agents↗
PubMed1989

A long-term intravenous model of aluminum maltol toxicity in rabbits: tissue distribution, hepatic, renal, and neuronal cytoskeletal changes associated with systemic exposure.

We studied the toxicity of an intravenously injected, water-soluble aluminum complex (aluminum maltol) in 20 young adult male New Zealand white rabbits over a period of 8 to 30 weeks. Sixteen rabbits injected with aluminum-free maltol and 15 untreated rabbits served as controls. Rabbits were injected three times per week with 75 mumol of aluminum maltol per injection, or a molar equivalent amount of maltol alone, through an indwelling jugular catheter. Liver contained the highest concentrations of aluminum among the aluminum maltol-treated rabbits, and aluminum accumulation was correlated with the appearance of periportal multinucleated giant cells in 13 of 20 rabbits. These cells stained positively for aluminum when a fluorescent (Morin) stain was applied to tissue from rabbits with a high concentration of aluminum in the liver. Proximal renal tubular necrosis or atrophy was found in 15 of 20 aluminum maltol-treated rabbits but not in maltol-treated and untreated controls. Renal tubules in rabbits with acute proximal renal necrosis stained positively for aluminum. Neurofibrillary tangles, immunoreactive with a monoclonal antibody to the 200-kDa subunit of neurofibrillary protein, were observed in the oculomotor nucleus of 3 aluminum maltol-treated rabbits (treated for 12, 20, and 29 weeks), but in none of the two groups of controls. These tangles were present in 3 of 10 aluminum-treated rabbits in which the nucleus was located. None of the 17 animals in both control groups in which the nucleus was found demonstrated tangles. A slight increase in brain tissue aluminum concentration was confirmed by an electrothermal atomic absorption spectrophotometric method. There were no specific findings in heart or lung tissue from aluminum-treated rabbits, although the aluminum content of these tissues was 10 to 20 times greater than control values. This model should be useful for investigating the effects of systemic exposure to high concentrations of solubilized aluminum.

Aluminum↗
PubMed1989

Ultrastructural localization of aluminium in liver of aluminium maltol-treated rabbits by laser microprobe mass analysis.

By means of laser microprobe mass analysis (LAMMA), we have studied the ultrastructural localization of aluminium in livers of aluminium maltol-treated rabbits. This animal model was developed to study long-term aluminium toxicity using systemic (intravenous) administration of aluminium. We could only detect aluminium in electron-dense inclusion bodies found in large, sometimes multinucleated cells. These results prove that the actual observation of aluminium deposits in liver with LAMMA gives more information than bulk analysis and can be very useful to explore mechanisms of toxicity.

Aluminum↗
PubMed1989

Aluminum and chronic renal failure: sources, absorption, transport, and toxicity.

In normal subjects the gastrointestinal tract is a relatively impermeable barrier to aluminum with a low fractional absorption rate for this metal ion. Aluminum absorbed from the gastrointestinal tract is normally excreted by the kidneys; in the presence of impaired renal function aluminum is retained and accumulates in body tissues. Aluminum-containing medications are given, by mouth, to patients with chronic renal failure as phosphate-binding agents for the therapeutic control of hyperphosphatemia. Patients with chronic renal failure are also exposed to aluminum in domestic tap-water supplies used either for drinking or, in those on dialysis treatment, in the preparation of their dialysate. In patients with end-stage chronic renal failure, particularly in those on treatment by hemodialysis, the accumulation of aluminum in bone, brain, and other tissues is associated with toxic sequelae. An increased brain content of aluminum appears to be the major etiological factor in the development of a neurological syndrome called either "dialysis encephalopathy" or "dialysis dementia"; an increased bone content causes a specific form of osteomalacia. An excess of aluminum also appears to be an etiological factor in a microcytic, hypochromic anemia that occurs in some patients with chronic renal failure on long-term treatment with hemodialysis. The various mechanisms involved in the toxic phenomena associated with the accumulation of aluminum in body tissues have not been clearly defined but are the subject of extensive investigations.

Aluminum↗