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Biomedical subjects

A Graham

Publications and source records attributed to A Graham.

At least 145 records · Page 8Linked to original sources
PubMed1994

Vehicle crashworthiness ratings in Australia.

The paper reviews the published vehicle safety ratings based on mass crash data from the United States, Sweden, and Great Britain. It then describes the development of vehicle crashworthiness ratings based on injury compensation claims and police accident reports from Victoria and New South Wales, the two most populous states in Australia. Crashworthiness was measured by a combination of injury severity (of injured drivers) and injury risk (of drivers involved in crashes). Injury severity was based on 22,600 drivers injured in crashes in the two states. Injury risk was based on 70,900 drivers in New South Wales involved in crashes after which a vehicle was towed away. Injury risk measured in this way was compared with the "relative injury risk" of particular model cars involved in two car crashes in Victoria (where essentially only casualty crashes are reported), which was based on the method developed by Folksam Insurance in Sweden from Evans' double-pair comparison method. The results include crashworthiness ratings for the makes and models crashing in Australia in sufficient numbers to measure their crash performance adequately. The ratings were normalised for the driver sex and speed limit at the crash location, the two factors found to be strongly related to injury risk and/or severity and to vary substantially across makes and models of Australian crash-involved cars. This allows differences in crashworthiness of individual models to be seen, uncontaminated by major crash exposure differences.

Acceleration↗
PubMed1994

Human (THP-1) macrophages oxidize LDL by a thiol-dependent mechanism.

The oxidative modification of low-density lipoprotein by macrophages may be an important mechanism in the pathogenesis of atherosclerosis. The human monocytic leukaemia cell line THP-1, when stimulated with phorbol ester, shares many properties with human monocyte-derived macrophages. Oxidation of LDL by these cells was characterised by depletion of alpha-tocopherol, increases in thiobarbituric acid reactive substances and increases in electrophoretic mobility. The LDL particles were also converted to a form which increased accumulation of cholesteryl esters within macrophages. The oxidative mechanism appeared to be dependent upon the presence of thiols in the cellular medium. Oxidation of LDL by THP-1 macrophages, and production of thiols by these cells, were dependent upon the presence of L-cystine in the medium. Furthermore, cellular oxidation of LDL could be partially mimicked by the addition of cysteine to Hams F10 medium. Macrophage-independent oxidation of LDL, mediated by the addition of copper ions, was inhibited by cystine and cysteine in phosphate buffered saline, but not in Hams F10 medium. The glutathione content of THP-1 macrophages was also dependent upon the presence of cysteine or cystine in the medium, but inhibition of glutathione synthesis by buthionine sulfoximine did not prevent the production of thiols or the oxidation of LDL by THP-1 macrophages.

Buthionine Sulfoximine↗
PubMed1994

Isolation and characterization of neurokinin A receptor cDNAs from guinea-pig lung and rabbit pulmonary artery.

cDNA clones for NK-2 receptors (NK-2R) were isolated from guinea-pig lung (GPl) and rabbit pulmonary artery (Rpa) using a polymerase chain reaction based methodology. The GPl NK-2R consists of 402 amino acids and encodes a protein with a relative molecular mass of 45,097. The Rpa NK-2R consists of 384 amino acids and encodes a protein with a relative molecular mass of 43,169. The GPl and Rpa NK-2Rs share significant amino acid sequence homology amongst themselves (90.1%), as well as with human, bovine, hamster and rat NK-2 receptors. The two receptors were stably transfected into mouse erythroleukemia cells, high-speed membranes were prepared from induced cells and their pharmacological properties examined utilizing [3H]-NKA in a receptor-binding assay. [3H]NKA bound to both NK-2Rs with high affinity (KD = 2-7 nM) and saturable (Bmax = 633-9000 fmol/mg protein) manner which was inhibited by GTP analogs. Competition experiments with agonists demonstrated identical order of potency in both NK-2Rs; NKA > [Nle10]NKA(4-10) > [beta-Ala8]NKA(4-10) > > Substance P > > > Senktide. Similarly, an identical profile for both receptors was observed with selective NK-2 antagonists: SR48,968 > MEN10,376 > > R396. The rank order of antagonist affinity is consistent with that in cloned human NK-2R and the observations of NK-2 receptor pharmacology in native human, guinea pig and rabbit tissues.

Amino Acid Sequence↗
PubMed1994

Characterization and comparison of ion transport across sheep and human airway epithelium.

This study aimed to assess the suitability of sheep tracheal epithelium as a model for studies of human airway ion transport. Ovine and human airway epithelium were mounted in Ussing chambers under short circuit conditions. Bumetanide (100 microM) reduced short-circuit current (Isc) by a mean of 21.3% +/- SEM 2.0, n = 8, in sheep, and 30.4% +/- 9.7, n = 3, in human airway epithelium. Acetazolamide (100 microM) decreased Isc by 10.6% +/- 1.2, n = 18, in sheep, and 5.8% +/- 2.9, n = 3, in human airways. Phloridzin (200 microM) reduced Isc by 4.7% +/- 0.8, n = 7, and 3.1% +/- 5.1, n = 3 in sheep and human tissue respectively. Amiloride (100 microM) decreased Isc by 42.9% +/- 3.5, n = 12, in sheep airways, whilst bathing the mucosal surface with Na(+)-free solutions reduced Isc by 67.4% +/- 4.2, n = 18. The sequential addition of acetazolamide, bumetanide, phloridzin, amiloride and mucosal Na(+)-free solutions totally inhibited the basal Isc in both sheep and human tissues, suggesting that Cl- and HCO3- secretion, Na(+)-glucose co-transport and amiloride-sensitive and -insensitive Na+ absorption contribute to the Isc. The similarities between the species suggest that sheep tracheal epithelium is a useful model for basal studies of airway ion transport, and may prove a valuable tool for further regulatory studies.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1994

Isolation and pharmacological characterization of a hamster urinary bladder neurokinin A receptor cDNA.

Functional cDNA clones for hamster neurokinin-2 receptor (NK-2R) were isolated from hamster urinary bladder using a polymerase chain reaction-based methodology. The hamster NK-2R consists of 384 amino acids with a relative molecular weight of 43,418. Hamster NK-2R shares significant amino acid sequence homology with other tachykinin receptors, particularly with rat, bovine, and human NK-2R (94.3, 84.4, and 86.5%, respectively). To examine the pharmacology of cloned hamster NK-2R, we transfected mouse erythroleukemia cells with this receptor, prepared high speed membranes, and studied the receptor properties utilizing the ligand [4,5-3H-Leu9]NKA in a receptor-binding assay. For pharmacological comparison, we also transfected the human NK-2R into mouse erythroleukemia cells. [3H]NKA bound to hamster NK-2R receptor in a protein-dependent, high affinity (Kd1 = 4.14 +/- 0.31 nM), saturable (Bmax1 = 679 +/- 26 fmol/mg of protein), and highly specific manner (89 +/- 2%). A smaller population (10% density) of lower affinity receptors (Kd2 = 150 +/- 92 nM), was also observed in competition experiments. [3H]NKA bound to the human receptor with significantly higher affinity and overall greater receptor density (Kd1 = 0.37 +/- 0.11 nM, Bmax1 = 234 +/- 175 fmol/mg of protein; Kd2 = 9.0 +/- 2 nM, Bmax2 = 1989 + 990 fmol/mg of protein). [3H]NKA binding to both hamster and human receptors was enhanced greatly by divalent cations, whereas GTP analogs weakly inhibited binding to hamster receptor, but potently inhibited binding to the human receptor. Competition experiments with agonists demonstrated binding to high and low affinity states of NK-2 receptors, with identical order of potency in hamster or human NK-2R; NKA > [Nle10]NKA(4-10) > [beta-Ala8]NKA(4-10) >> substance P >>> Senktide. However, remarkable differences were observed in studies with selective NK-2 antagonists (hamster, SR48,968 > L659,877 > R396 >> MEN10,376 versus human, SR48,968 > MEN10,376 > L659,877 > R396). The rank order of antagonist affinity is consistent with the observations of NK-2 receptor pharmacology in the native tissues.

Amino Acid Sequence↗
PubMed1993

Inhibition of glutathione synthesis increases the toxicity of oxidized low-density lipoprotein to human monocytes and macrophages.

Macrophages are thought to play an important role in the pathogenesis of atherosclerosis by mediating the oxidation of low-density lipoprotein (LDL). However, it is known that these cells show elevated glutathione levels after exposure to oxidized LDL. Here we demonstrate that this increase in the level of intracellular glutathione is due to synthesis de novo stimulated by oxidized LDL. Furthermore, inhibition of glutathione synthesis renders oxidized LDL cytotoxic to both monocytes and macrophages at a concentration well tolerated by untreated cells. The stimulation of cholesterol esterification in macrophages by low, non-toxic, concentrations of oxidized LDL is enhanced under conditions where glutathione synthesis is inhibited. These results suggest that the glutathione status of macrophages in the artery wall could be important in both controlling foam-cell formation and the detoxification of oxidized LDL.

Antimetabolites↗
PubMed1993

Peroxynitrite modification of low-density lipoprotein leads to recognition by the macrophage scavenger receptor.

Peroxynitrite is an oxidant which could be formed in the vasculature by the reaction of superoxide with nitric oxide. It is capable of modifying amino acid residues and of initiating lipid peroxidation. In the present study we have shown that peroxynitrite converts low density lipoprotein to a form recognized by the macrophage scavenger receptor and that this process is associated with modification of the protein and lipid, and with the oxidation of alpha-tocopherol to alpha-tocopherol quinone.

Cell Line↗
PubMed1993

Human bradykinin B2 receptor: nucleotide sequence analysis and assignment to chromosome 14.

Functional cDNA clones for human bradykinin B2 receptor were isolated from uterus RNA by a polymerase chain reaction (PCR)-based method and by screening a human cosmid library with rat bradykinin B2 receptor probe. We isolated several overlapping clones from the cosmid library, each of which encodes the entire protein coding sequence. The human bradykinin B2 receptor gene codes for a 364-amino-acid protein with a molecular mass of 41,442 Da that is highly homologous to rat bradykinin B2 receptor cDNA (81%). The entire human cDNA sequence was cloned into an expression vector and mRNA was synthesised by in vitro transcription. Applications of bradykinin caused membrane current responses in Xenopus oocytes injected with the in vitro-synthesized mRNA. Preincubation with the potent B2 antagonist, HOE140, prevented this response. The genomic clone is intronless, and we have identified an upstream promoter region and a downstream polyadenylation signal. The human bradykinin B2 receptor gene has been mapped to chromosome 14 using PCR to specifically amplify DNA from somatic cell hybrids.

Amino Acid Sequence↗
PubMed1993

Tin protoporphyrin prolongs the biochemical remission produced by heme arginate in acute hepatic porphyria.

BACKGROUND: In acute porphyria, repletion of intrahepatic heme, with exogenously administered heme, suppresses the overproduction of delta-aminolaevulinic acid (ALA) and porphobilinogen (PBG). The effect of reducing heme breakdown has been assessed by administering tin protoporphyrin, a competitive inhibitor of heme oxygenase. METHODS: The effect of tin protoporphyrin, 1 mumol/kg, and heme arginate, 3 mg/kg, individually and combined was compared with placebo in patients with an acute porphyric crisis. The treatments were given by intravenous infusion on three successive mornings. Thirty-four attacks were studied in 8 patients (9 placebo, 10 heme arginate alone, 4 tin protoporphyrin alone, and 11 combination treatments). RESULTS: Placebo and tin protoporphyrin alone had little effect on ALA and PBG excretion. Following heme arginate alone or combined with tin protoporphyrin, there was a marked and similar suppression of both ALA and PBG excretion (P < 0.005 for each, compared with pretreatment values). However, on the 5th day after discontinuing treatment, the excretion of ALA and PBG were both lower following combination therapy than following heme arginate alone (P < 0.005 and P < 0.01, respectively). CONCLUSIONS: These findings suggest that inhibition of heme oxygenase by tin protoporphyrin prolongs the biochemical remission induced by heme arginate in the porphyric crisis.

Acute Disease↗
PubMed1993

Opioid regulation of parental behavior in juvenile rats.

When exposed to young rats for a period of days, juvenile rats will respond with full parental behavior (FPB: retrieval and grouping of, and crouching over, pups). Because the parental behavior of juveniles is so robust, and because opiates have been shown to be involved in the regulation of parental behavior in adult animals, we examined morphine's ability to disrupt the display of parental behavior in the juvenile animal. In Experiment 1, 25-day-old males and females were administered one of three injection regimens of morphine (MOR), saline (SAL), or naloxone (NAL)--[MOR (5.0 mg/kg) + SAL; MOR + NAL (0.5 mg/kg); or SAL + SAL]--and 1 h later were exposed to three 1- to 6-day-old neonates. Behavior was scored over a 60-min period and animals were considered parental if they responded with FPB for 2 consecutive testing days. Whereas the SAL + SAL and MOR + NAL were not different, MOR + SAL virtually failed to respond to young over a 10-day period. Experiment 2 exposed juveniles to young for a period of days until they displayed 2 consecutive days of FPB. Next, separate groups of juveniles were treated with the same regimen as above. Again, SAL + SAL and MOR + NAL responded rapidly to young, whereas MOR + SAL did not. These data suggest that the display of parental behavior, both its onset (Experiment 1) and maintenance (Experiment 2), appears to be regulated by opiates.

Animals↗
PubMed1993

'Correctable undetected visual acuity deficit' in patients aged 65 and over attending an accident and emergency department.

The rate of occurrence of correctable undetected visual acuity deficit (CUVAD) in a population of patients aged 65 and over was investigated, using a pinhole screening method, to compare the sociodemographic and optical eye care habits of patients with or without a functionally significant CUVAD. Of 136 patients 46 (34%) were found to have a functionally significant CUVAD in one or both eyes which was not significantly associated with optician or general practitioner contact, age, sex, social class, living situation, or number of medications. Half the patients with significant CUVAD had not attended for 2 years mainly because of financial considerations. Three quarters attended of their own volition; only one in seven were prompted by opticians' postal invitations. It was concluded that a significant degree of CUVAD could be detected using a simple procedure which can be carried out by general practitioners as part of their general elderly health screen.

Aged↗
PubMed1993

Even-numbered rhombomeres control the apoptotic elimination of neural crest cells from odd-numbered rhombomeres in the chick hindbrain.

Neural crest cells originate at three discontinuous levels along the rostrocaudal axis of the chick rhombencephalon, centred on rhombomeres 1 and 2, 4 and 6, respectively. These are separated by the odd-numbered rhombomeres r3 and r5 which are depleted of migratory neural crest cells. Here we show elevated levels of apoptosis in the dorsal midline of r3 and r5, immediately following the formation of these rhombomeres at the developmental stage (10-12) when neural crest cells would be expected to emerge at these neuraxial levels. These regions are also marked by their expression of members of the msx family of homeobox genes with msx-2 expression preceding apoptosis in a precisely colocalised pattern. In vitro and in ovo experiments have revealed that r3 and r5 are depleted of neural crest cells by an interaction within the neural epithelium: if isolated or distanced from their normal juxtaposition with even-numbered rhombomeres, both r3 and r5 produce migrating neural crest cells. When r3 or r5 are unconstrained in this way, allowing production of crest, msx-2 expression is concomitantly down regulated. This suggests a correlation between msx-2 and the programming of apoptosis in this system. The hindbrain neural crest is thus produced in discrete streams by mechanisms intrinsic to the neural epithelium. The crest cells that enter the underlying branchial region are organised into streams before they encounter the mesodermal environment lateral to the neural tube. This contrasts sharply with the situation in the trunk where neural crest production is uninterrupted along the neuraxis and the segmental accumulation of neurogenic crest cells is subsequently founded on an alternation of permissive and non-permissive qualities of the local mesodermal environment.

Animals↗
PubMed1993

No added benefit from nebulized amiloride in patients with cystic fibrosis.

In cystic fibrosis (CF) airway epithelial sodium absorption is increased 2-3 fold. Since sodium absorption is inhibited by the sodium channel blocker amiloride, our aim was to assess its therapeutic benefit in cystic fibrosis. A randomized, double-blind, placebo-controlled, cross-over trial of nebulized amiloride was performed in 23 patients with cystic fibrosis. Amiloride or placebo was administered four times daily for two six month periods. Existing treatment was continued, and any infective exacerbations treated in the usual way. Fourteen patients completed the study. No significant changes occurred in forced expiratory volume in one second, forced vital capacity, oxygen saturation, body weight, sputum volume, culture and rheology, serum urea, and electrolytes, white cell count and erythrocyte sedimentation rate during either treatment period. The frequency of infective exacerbations was also not different in either treatment period. We were thus unable to confirm the benefit shown in the only other clinical trial of nebulized amiloride in cystic fibrosis and conclude that, in the presence of established treatment for cystic fibrosis lung disease, nebulized amiloride offers no additional clinical benefit.

Administration, Intranasal↗