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Biomedical subjects

R A Hall

Publications and source records attributed to R A Hall.

At least 19 recordsLinked to original sources
PubMed1992

Mouse telencephalon exhibits an age-related decrease in glutamate (AMPA) receptors but no change in nerve terminal markers.

The central excitatory amino acid receptor selective for alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) was examined in brain tissue from mice at 3 and 25 months after birth. Antibodies against the rat GluR-A glutamate receptor subunit (selective for kainate and AMPA) labeled a mouse brain component of about M(r) 100,000. Telencephalic tissue from the older group of mice exhibited 31% less immunoreactivity towards this component as compared with that from the young group. Binding of [3H]AMPA also decreased with age in the telencephalon to an extent which was similar to the loss of receptor immunoreactivity. Scatchard analysis revealed that this reduction is due to a decrease in receptor density and not to a change in binding affinity. In contrast, there were only small age-related changes in AMPA receptor immunoreactivity and binding levels in the brain stem and cerebellum. Binding to dopamine, serotonin, or GABA receptors was not significantly reduced in the older mice. Since the nerve terminal markers synaptophysin and the SV2 glycoprotein were not detectably different in the two groups of mice, the age-related reduction in AMPA receptors is not likely to be due to a general decrease in synaptic density. These data suggest that glutamatergic neurotransmission mediated by AMPA-type receptors is selectively impaired with aging in the telencephalon.

Aging↗
PubMed1992

Evidence that high- and low-affinity DL-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) binding sites reflect membrane-dependent states of a single receptor.

Binding of DL-alpha-[3H]amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid ([3H]AMPA) to lysed rat brain membranes in the presence of potassium thiocyanate resulted in curvilinear Scatchard plots that could be resolved by regression analysis into a large low-affinity component and a small high-affinity component. Solubilization with Triton X-100 resulted in solubilized and nonsolubilized fractions that were considerably enriched in the high-affinity component and correspondingly reduced in the low-affinity component. It thus appears that solubilization converts low-affinity AMPA receptors into high-affinity receptors. Also, synaptic plasma membranes were found to be greatly enriched in the low-affinity form and deficient in the high-affinity form of the AMPA receptor. These experiments provide evidence for the hypothesis that the high- and low-affinity components of AMPA binding are interconvertible states of the same receptor rather than separate binding sites and that the conversion of these receptors from their native high-affinity state to the low-affinity state occurs on insertion of the receptors into synapses.

Animals↗
PubMed1992

Functional reconstitution of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors from rat brain.

Glutamate receptors belonging to the subclass specifically activated by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) were solubilized from rat forebrain membranes with Triton X-100 and partially purified through a series of three chromatographic steps. Specific [3H]AMPA binding increased 30-60-fold during the isolation procedure. A protein band recognized by antibodies against specific amino acid sequences of the glutamate receptor-A subunit was enriched with each purification step; the molecular mass of this band (105 kDa) corresponded to that of cloned AMPA receptor subunits. Photoaffinity labeling of forebrain membranes with 6-cyano-7-[3H]nitroquinoxaline-2,3-dione, a specific antagonist of the AMPA receptor, labeled a single band that comigrated with the immunolabeled protein. On reconstitution of the partially purified material into bilayer patches, single-channel current fluctuations were elicited by 300 nM AMPA and blocked by 1 microM 6,7-dinitroquinoxaline-2,3-dione.

Animals↗
PubMed1991

Immunoaffinity purification of the NS1 protein of Murray Valley encephalitis virus: selection of the appropriate ligand and optimal conditions for elution.

A novel approach was used to select the most suitable antiviral monoclonal antibody (mAb) and elution conditions for immunoaffinity purification of the NS1 protein of Murray Valley encephalitis virus (MVE). Crude NS1 protein was subjected to a variety of chemical conditions produced by common elution buffers, and tested with a panel of NS1-specific mAbs by ELISA to determine which buffers denatured antigenic epitopes. Buffers that caused least structural damage to NS1 epitopes were tested by ELISA for dissociation of NS1-mAb complexes adsorbed to the solid phase. For each mAb analysed, the conditions required to break the mAb-NS1 complex on the solid phase were similar to those required to release antigen bound to mAb-sepharose beads. From these results we selected an appropriate antibody for affinity purification of the non-structural viral protein NS1 on CNBr-activated sepharose columns. Elution at pH 11.5 yielded good recoveries of highly pure and antigenically intact NS1 dimer. The results demonstrate that the appropriate ligand and optimal elution conditions can be rapidly determined generally by immunoassay in microtitre plates.

Antibodies, Monoclonal↗
PubMed1991

Monoclonal antibodies to Kunjin and Kokobera viruses.

Five monoclonal antibodies (MoAb) were produced to the envelope (E) protein of Kunjin (KUN) virus. Three of these were specific for the KUN/West Nile complex, and two reacted with epitopes that were common to the flavivirus family. These MoAb defined at least four distinct epitopes on the E protein of KUN virus. Eight MoAb were also produced to unidentified proteins of Kokobera (KOK) virus. Seven were specific for KOK, while the remaining antibody cross-reacted with Stratford virus and an unregistered flavivirus CS946. The application of these MoAb to arboviral surveillance is discussed.

Animals↗
PubMed1990

Epitope analysis of the envelope and non-structural glycoproteins of Murray Valley encephalitis virus.

Previous studies have shown that antibodies produced against strategic flavivirus epitopes play an important role in recovery and immunity. Definition of the conformation and location of these epitopes and the degree of their conservation among flaviviruses is important to understanding the humoral response to flavivirus infection. In this study we have examined epitopes recognized by 14 monoclonal antibodies (MAbs) produced to the envelope (E) and non-structural (NS1) proteins of Murray Valley encephalitis virus (MVE). These antibodies were analysed for specificity, neutralization, haemagglutination inhibition (HI) and competitive binding. We have identified six distinct epitopes on the E protein which are located in four non-overlapping domains. MAbs to epitopes in one domain neutralized virus, were specific for MVE and Japanese encephalitis virus, and reacted with epitopes resistant to reduction. Two other E domains, one specific to MVE and the other shared by all flaviviruses, also contained neutralization sites and were stabilized by disulphide bonds. The fourth domain on E was conserved among the flaviviruses, sensitive to SDS denaturation and did not induce neutralizing antibody. Studies with MVE NS1 MAbs revealed that they were mostly type-specific, unreactive with conserved epitopes, and unreactive in HI and neutralization tests. The six epitopes identified on NS1 did not overlap and represent antigenic domains either resistant or sensitive to reduction. Immunoblotting of viral proteins in MVE-infected C6/36 cells revealed two distinct forms of NS1 and high Mr proteins of 97K and 108K that represented disulphide-linked heterodimers of E and NS1.

Animals↗
PubMed1989

Lipoprotein subfraction composition in non-insulin-dependent diabetes treated by diet, sulphonylurea, and insulin.

Lipoprotein abnormalities may predispose to an increased risk of coronary heart disease in type II (non-insulin-dependent) diabetes mellitus. To investigate the effects of different treatment modalities, the composition and concentrations of fasting plasma lipoproteins were determined in a cross-sectional study of patients with type II diabetes at diagnosis, treated by diet alone, treated by diet + glibenclamide (2.5 to 15 mg/d for 6 to 48 months), and treated by diet + insulin (25 to 65 U/d for 8 to 144 months). Compared with normal subjects matched for sex, age, body mass index, exercise, alcohol consumption and smoking, type II patients at diagnosis showed increased concentrations of nonesterified and esterified cholesterol, triglyceride, phospholipid, and protein in the very low density lipoprotein (VLDL) fraction. However, the only alteration in VLDL composition was a small decrease in the relative proportion of phospholipid. Apolipoprotein-B and low density lipoprotein (LDL) cholesterol concentrations were also raised in type II patients at diagnosis. Plasma concentrations of high density lipoprotein (HDL) nonesterified and esterified cholesterol, phospholipid, and apo-AI were lower in type II patients at diagnosis. This was largely accounted for by reduced concentrations of these components in the HDL2 subfraction, which retained a normal composition. Type II patients treated by diet alone and diet + glibenclamide exhibited similar abnormalities of plasma lipoprotein concentrations, which are associated with premature coronary disease, to the type II patients at diagnosis. However, in type II patients treated with insulin, plasma lipoprotein concentrations and composition were normal, except LDL cholesterol, which was lower than normal in insulin-treated patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoproteins B↗
PubMed1989

Preoperative crossmatch guidelines for total hip arthroplasty.

The use of crossmatch guidelines has become commonplace as a means of guiding surgeons to efficient preoperative blood ordering. To further refine existing guidelines for a major elective procedure, a number of specific characteristics of 175 patients who underwent 189 total hip arthroplasties were correlated with blood use by univariate and multivariate analyses. The findings of this study demonstrate that for patients with no detectable red cell alloantibody, four units of blood should be crossmatched and reserved preoperatively if the patient is undergoing exchange arthroplasty, or undergoing a transtrochanteric procedure. All other patients with no detectable red cell alloantibody should have two units of blood reserved preoperatively. Proper preoperative crossmatch ordering can result in more labor-efficient and thrifty use of transfusion services, as well as increased effectiveness of autologous predeposit programs.

Analysis of Variance↗
PubMed1989

Apolipoprotein assays: methodological considerations and studies in non-insulin-dependent diabetes treated by diet, glibenclamide and insulin.

The effect of sample pre-treatment as a source of variability of apolipoprotein (apo) AI, AII and B assays was demonstrated with lipid dissociating agents. The average mean percentage change ranged from -58 to +133% compared with untreated samples. The apolipoprotein method selected was validated by comparing their concentrations with their corresponding lipoprotein lipid or protein in normal controls and Type 2 (non-insulin-dependent) diabetic patients. The coefficient of variation was maintained below 3.5% for apo AI, AII, B and HDL2-apo AI. The apolipoprotein concentrations of fasting plasma lipoproteins were determined in a cross-sectional study of non-obese (body-mass index less than or equal to 30) patients with Type 2 diabetes mellitus. Compared with normal subjects matched for sex, age, body-mass index, exercise, alcohol consumption and smoking. Type 2 patients at diagnosis showed reduced apo AI and HDL2-apo AI concentrations, lowered apo AI:B ratio and increased concentrations of apo B. Type 2 patients treated by diet alone (for 6-72 months) and diet plus glibenclamide (2.5-15 mg/day for 6-48 months) exhibited similar abnormalities of plasma apolipoprotein concentration to Type 2 patients at diagnosis. However, in Type 2 patients treated with insulin (25-65 U/day for 8-144 months) concentrations of apo AI and HDL2-apo AI, and the apo AI:B ratio were normal. Apo B concentrations were generally lower compared with all groups of non-insulin treated patients. These abnormalities of apolipoprotein metabolism, which are associated with premature coronary disease, are still evident in patients treated by diet and diet plus glibenclamide, but are not seen in Type 2 patients treated with insulin.

Adult↗
PubMed1989

Lipoprotein subfraction composition in non-obese newly diagnosed non-insulin dependent diabetes after treatment with diet and glibenclamide.

The composition and concentrations of fasting plasma lipoproteins were determined in a prospective study of 11 +/- 2 (mean +/- 1 SD) months in 16 non-obese (body mass index less than or equal to 30) patients with Type 2 (non-insulin dependent) diabetes mellitus at diagnosis, treated by diet alone or diet plus glibenclamide (2.5-7.5 mg/day). Compared with normal subjects matched for sex, age, body mass index, exercise, alcohol consumption and smoking, Type 2 patients at diagnosis showed increased concentrations of non-esterified and esterified cholesterol, triglyceride, phospholipid and protein in the very low density lipoprotein (VLDL) fraction. The apolipoprotein (apo) B concentrations was also raised, but low density lipoprotein (LDL) cholesterol concentrations were not significantly altered in Type 2 patients at diagnosis. Plasma concentrations of high density lipoprotein (HDL) non-esterified and esterified cholesterol, HDL phospholipid and apo AI were lower in Type 2 patients at diagnosis. This was largely accounted for by a reduced number of HDL2 molecules of normal composition. After treatment of Type 2 patients with diet alone, there was a marginal increase in plasma HDL cholesterol and phospholipid, and in plasma HDL2 cholesterol, phospholipid, protein and apo AI concentrations, in association with reductions of VLDL component concentrations, body mass index and glycaemia. Type 2 patients treated with diet plus glibenclamide exhibited similar abnormalities of plasma lipoprotein concentrations before and after treatment, except for a small reduction in VLDL component concentrations and a slight increase in the apo AI:B ratio. Institution of diet alone and diet plus glibenclamide generally failed to restore VLDL, HDL and HDL2 component concentrations and the apo AI:B ratio to normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Drinking↗
PubMed1988

Isolation and characterization of dengue viruses serotype 1 from an epidemic in northern Queensland, Australia.

Thirteen strains of dengue type 1 were isolated from the lymphocyte fractions of 69 acute phase blood samples collected at Thursday Island Hospital during 1981 and 1982. One further strain of type 1 was isolated from 7 blood samples despatched by air from Cairns Base Hospital during 1982. Four of these Australian isolates representing the beginning, middle, and end of the epidemic were examined by restriction enzyme mapping and were found to be identical for the nine restriction enzymes used. The maps differed from those derived from two Malaysian dengue type 1 strains isolated during the epidemic of 1981-82 in that country. This suggests reliance on serological typing to establish global circulation patterns of epidemic dengue is insufficient and that more specific methods such as genome mapping are useful.

Adolescent↗
PubMed1988

Type-specific monoclonal antibodies produced to proteins of Murray Valley encephalitis virus.

Two monoclonal antibodies have been produced to the flavivirus, Murray Valley encephalitis (MVE). Immunofluorescent antibody and ELISA tests revealed that one antibody was specific for MVE while the other cross-reacted weakly with Alfuy and Kunjin viruses. These antibodies have neither haemagglutination inhibition nor neutralising activity. One of the monoclonal antibodies reacted with the envelope glycoprotein (E) and a 45,000 MW protein, while the other reacted with a protein of 23,000 daltons. Competitive binding assays confirmed that these antibodies reacted with unrelated epitopes.

Antibodies, Monoclonal↗
PubMed1987

Pharmacology of L-655,240 (3-[1-(4-chlorobenzyl)-5-fluoro-3-methyl-indol-2-yl]2,2-dimethylpro pan oic acid); a potent, selective thromboxane/prostaglandin endoperoxide antagonist.

L-655,240 (3-[1-(4-chlorobenzyl)-5-fluoro-3-methyl-indol-2-yl]2,2-dimethylpropa noic acid) has been studied in vitro on the guinea-pig tracheal chain, pulmonary artery and thoracic aorta ring and shown to be a potent, competitive antagonist of contractions induced by the prostaglandin endoperoxide analogue, U-44069 (pA2 values 8.0, 8.4 and 8.0 respectively). Selectivity on the guinea-pig trachea was indicated by non-competitive antagonism of contractions induced by prostaglandin D2 and minimal activity against contractions induced by leukotriene D4, prostaglandin F2 alpha, serotonin, histamine and acetylcholine. L-655,240 was a potent inhibitor of the aggregation of washed human platelets induced by U-44069 (IC50 value 7 X 10(-9) M) and inhibited aggregation of human platelet rich plasma induced by U-44069, U-46619, thromboxane A2 and collagen but not ADP or platelet activating factor. In vivo i.v. L-655,240 administered to guinea-pigs inhibited bronchoconstriction induced by i.v. U-44069 and arachidonic acid (ED50 values 0.09 and 0.23 mg kg-1) but not histamine, acetylcholine or serotonin. When administered to rhesus monkeys (3 and 10 mg/kg p.o.), L-655,240 inhibited ex vivo platelet aggregation induced by U-44069 but not ADP. It is concluded that L-655,240 is a potent, selective, orally active thromboxane/prostaglandin endoperoxide antagonist.

Animals↗
PubMed1987

An enzyme immunoassay to detect Australian flaviviruses and identify the encephalitic subgroup using monoclonal antibodies.

An antigen-capture enzyme-linked immunosorbent assay (ELISA) has been developed to detect antigens of Australian flaviviruses in mosquito pools, suckling mouse brain and infected cell culture supernatant fluid. A monoclonal antibody reactive to an epitope on the envelope glycoprotein common to all flaviviruses was used as the capture antibody. Purified rabbit IgG, produced against Murray Valley encephalitis (MVE) virus, which reacted with eight Australian flaviviruses in haemagglutination inhibition (HI) and in an indirect fluorescent antibody test, was used as the indicator antibody in direct and indirect antigen-capture ELISA. A monoclonal antibody specific for a subgroup of encephalitic flaviviruses was conjugated to horseradish peroxidase and used as the indicator antibody to distinguish MVE, Kunjin and Alfuy viruses from the remainder tested. This ELISA could detect viral antigen in mosquito cell culture fluids and suckling mouse brain preparations at titres as low as 1000 TCID50/100 microliters. Viral antigen in a single mosquito infected with MVE could be detected in a pool of 500.

Animals↗
PubMed1987

The experimental infection of horses with Murray Valley encephalitis and Ross River viruses.

Eleven weanling horses were inoculated with Murray Valley encephalitis and Ross River viruses either by intravenous injection or by the bite of Culex annulirostris or Aedes vigilax mosquitoes infected orally. Five of the 11 horses circulated trace amounts of MVE virus for 1 to 5d and they infected 7/408 Cx annulirostris which subsequently fed on them. Haemagglutination-inhibiting antibody persisted at detectable levels for the 24-week observation period. With Ross River virus, only one of 11 horses inoculated developed a viraemia detectable by inoculation of suckling mice but 5 horses contained virus sufficient to infect 41/383 Cx annulirostris that fed on them 3 to 4 days after inoculation. On primary inoculation with Ross River virus, only 2 horses developed HI antibody but late responses occurred in 3 horses following probable naturally acquired re-infections. With both viruses, most horses remained normal, some developed mild pyrexia and transient clinical signs. This paper, therefore, indicates that horses are unlikely to be efficient amplifiers of either MVE or RR viruses and does little to incriminate them as important pathogens.

Aedes↗
PubMed1987

L-641,953 (R-8-fluoro-dibenzo[b, f]thiepin-3-carboxylic acid-5-oxide): a novel thromboxane-prostaglandin endoperoxide antagonist.

The effects of L-641,953 (R-8-fluoro-dibenzo[b, f]thiepin-3-carboxylic acid-5-oxide) have been studied on pulmonary and other smooth muscle preparations in vitro and in vivo. When studied in vitro on guinea-pig tracheal chains, L-641,933 produced significant shifts in the dose-response curves to the prostaglandin endoperoxide analogues, U-44069 (pA2 7.06) and U-46619 (pA2 7.14), and prostaglandin (PG) F2 alpha (pA2 6.33) had minimal activity against contractions induced by histamine (pA2 4.38), 5-hydroxytryptamine (pA2 4.63), and acetylcholine (pA2 4.56) and slightly enhanced relaxation induced by PGE2. When tested on the guinea-pig gall bladder strip in vitro, L-641,953 antagonized contractions induced by U-44069 (pA2 7.03) but was less active against those induced by PGF2 alpha (pA2 6.03), PGE1 (pA2 5.62), and histamine (pA2 4.84). When tested in vitro on the guinea-pig pulmonary artery, L-651-953 significantly antagonized contractions induced by U-44069 (pA2 7.04), U-46619 (pA2 7.14), and PGF2 alpha (pA2 7.16) but was less effective against contractions induced by histamine (pA2 4.19). Schild analysis indicated that L-641,953 was fully competitive against contractions of either the guinea-pig tracheal chain induced by U-46619 or the guinea-pig pulmonary artery induced by U-44069 and U-46619. When tested on human platelets in vitro L-641,953 inhibited aggregation induced by U-44069 (IC50 1.3 X 10(-6) M) but not ADP.(ABSTRACT TRUNCATED AT 250 WORDS)

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗