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Biomedical subjects

M J Muller

Publications and source records attributed to M J Muller.

72 records · Page 4Linked to original sources
PubMed1985

Experimental infection of Culicoides brevitarsis from south-east Queensland with three serotypes of bluetongue virus.

Laboratory-reared C. brevitarsis (biting midges) were fed on sheep which had been experimentally infected with bluetongue serotype 1 (CSIRO 156), bluetongue serotype 20 (CSIRO 19) or bluetongue serotype 21 (CSIRO 154), or on cattle experimentally infected with bluetongue serotype 20 (CSIRO 19). Approximately 77 000 C. brevitarsis were exposed to sheep and 9000 to cattle. The average percentage feeding on sheep was 54% and on cattle 47%. In attempts to transmit virus by bite 3360 C. brevitarsis which had fed on viraemic sheep were held for 11-15 days before exposure to susceptible sheep. Although 11% of these insects fed, transmission of virus from sheep to sheep was not demonstrated. Estimated infection rates of C. brevitarsis for each serotype from sheep and serotype 20 from cattle were similar at 0.4% or lower. These low infection rates are one of the factors which make it unlikely that C. brevitarsis could be an efficient vector of bluetongue viruses in sheep in the field.

Animals↗
PubMed1985

Mortality of Culicoides brevitarsis fed on cattle treated with ivermectin.

Adult female Culicoides brevitarsis Kieffer, important vectors of arboviruses affecting livestock in Australia, were fed on penned Hereford yearling cattle which had been given a single subcutaneous injection of ivermectin at a dose of 200 mcg/kg. The mean mortality of engorged females 48 hr after feeding on the treated cattle was 99% for 10 days posttreatment and in excess of 40% for 18 days posttreatment. Based on these results, it appears that ivermectin administered subcutaneously could be a useful tool for the control of Culicoides-transmitted diseases and would provide an attractive alternative to "slaughter out" programs in the case of a major exotic disease threat.

Animals↗
PubMed1984

Isolation of arboviruses from insects collected at Beatrice Hill, Northern Territory of Australia, 1974-1976.

Between October 1974 and May 1976, 57 596 mosquitoes, 169 957 Culicoides, 5923 Lasiohelea and 1043 phlebotomines were collected for virus isolation at Beatrice Hill (lat. 12 degrees 39'S.,long. 131 degrees 20'E.) in the Northern Territory of Australia. A total of 94 viruses belonging to 22 different serological groupings was isolated. The following species of insect yielded viruses which were identified and those viruses marked with an asterisk represent a new record of insect host: Culex annulirostris: Ross River, Kokobera, Barmah Forest, Corriparta, Eubenangee*, Wongorr; Anopheles amictus: Mapputta*; An bancroftii: bovine ephemeral fever*; An farauti: Eubenangee*; An annulipes: Mapputta; Culicoides marksi: Barmah Forest*, Belmont, Eubenangee*, Wallal, Warrego, Leanyer*, Parker's Farm*, Humpty Doo*; C. peregrinus: Beatrice Hill*; C. oxystoma: Bunyip Creek*, Marrakai*; C. pallidothorax: Wongorr*; C. histrio: Thimiri*; Lasiohelea spp.: Humpty Doo*. Pools of mixed species of Culicoides yielded bluetongue, Belmont, CSIRO Village, Warrego and Facey's Paddock viruses. Filter-passing agents not yet identified, were isolated from Cx annulirostris and An bancroftii. As well as providing new locality records for all but one of the 22 viruses isolated, the study yielded five new viruses (bluetongue serotype 20, CSIRO Village, Marrakai, Beatrice Hill and Humpty Doo viruses) and a new record for Thimiri virus which had not been recorded previously in Australia nor had it been isolated from an arthropod. Nine of the viruses isolated occur in more than one family of Diptera.

Animals↗
PubMed1983

Relaxant effects of forskolin in smooth muscle. Role of cyclic AMP.

Forskolin was found to cause concentration dependent, reversible relaxations of isolated smooth muscle preparations including rat aorta, bovine coronary artery, canine coronary artery, guinea pig taenia caeci and rabbit small intestine. The relaxant effects of forskolin in guinea pig taenia caeci and rabbit small intestine were potentiated by cyclic nucleotide phosphodiesterase inhibitors Ro 20-1724 and MIX. In rabbit small intestine, Ro 20-1724 also potentiated the relaxant effects of isoproterenol but not those of verapamil or 2-chloroadenosine. However, in bovine coronary arteries the phosphodiesterase inhibitors had to be used at concentrations of 100 nM or below because of relaxant effects and did not alter forskolin-induced relaxations. Forskolin caused a concentration dependent activation of adenylate cyclase in broken cell preparations from guinea pig taenia caeci and rabbit small intestine, exceeding the stimulatory effect of 10 mM NaF. These results indicate that relaxations of smooth muscle by forskolin are mediated by cyclic AMP and, in turn, that cyclic AMP may well serve as an intracellular mediator of physiological relaxant stimuli.

Adenylyl Cyclases↗
PubMed1980

Apamin, a nonspecific antagonist of smooth muscle relaxants.

Apamin, a peptide of bee venom, was shown to inhibit the relaxant responses of guinea-pig taenia caeci to ATP, noradrenaline, adenosine and, less effectively, to stimulation of noradrenergic inhibitory nerves. Thus apamin acts nonspecifically and, contrary to the suggestion of Vladimirova and Shuba (1978), the fact that inhibitory responses due to nerve stimulation and ATP are blocked by the toxin does not allow conclusions as to the possible transmitter role of ATP in these nerves.

Adenosine↗
PubMed1979

Presynaptic inhibitory actions of 2-substituted adenosine derivatives on neurotransmission in rat vas deferens: effects of inhibitors of adenosine uptake and deamination.

In the isolated rat vas deferens, various 2-substituted adenosine derivatives and adenosine inhibited contractions elicited by field stimulation but had little effect on responses to exogenous noradrenaline. 2-Chloroadenosine, 2-bromoadenosine, 2-hydroxyadenosine and 2-fluoroadenosine were all more potent than adenosine. Theophylline antagonized the action of the 2-substituted derivatives. The inhibitory action of adenosine was potentiated by dipyridamole, 2-amino-6-[(2-hydroxy-5-nitro)benzylthio]-9-beta-D-ribofuranosylpurine (HNBTG) or 2'-deoxycoformycin while that of 2-choloroadenosine was not altered by any of these drugs or by phenoxybenzamine, atropine or indomethacin. Pretreatment of the vas deferens with both HNBTG and 2'-deoxycoformycin eliminated the difference in inhibitory potency between adenosine and 2-chloroadenosine. These results indicate that 2-substituted adenosine derivatives, like adenosine, produce inhibition of transmission by acting on a presynaptic site which can be blocked by theophylline. The high apparent potency of 2-chloroadenosine compared to adenosine appears to be due to the former being neither taken up nor deaminated, while the apparent potency of adenosine is masked by uptake and deamination in this tissue.

Adenosine↗
PubMedDate not supplied

Superoxide dismutase and leupeptin prevent delayed reperfusion injury in the rat small intestine during burn shock.

Delayed fluid resuscitation during burn shock is thought to compromise the integrity of gut mucosa and allow enteric bacteria to cross the luminal wall and infect other sterile organ systems. Superoxide dismutase, a free-oxygen radical scavenger; leupeptin, a protease inhibitor; and verapamil, a calcium channel blocker, were studied to evaluate their efficacy in maintaining cellular integrity in the gut of thermally burned rats whose fluid resuscitation had been delayed. Fifty male rats weighting 280 to 320 gm were given a full-thickness scald burn covering 50% total body surface area. Ten received early fluid resuscitation beginning half an hour after burn, and 40 received fluid resuscitation delayed by 6 hours. Those receiving delayed resuscitation were given superoxide dismutase (n = 10), leupeptin (n = 10), verapamil (n = 10), or a placebo of normal saline solution (n = 10) at the time of fluid resuscitation. Ileal mucosa samples were harvested, and adenosine triphosphate, diphosphate, and monophosphate were measured. Adenosine triphosphate, total nucleotides, and energy charge potential were significantly lower in the placebo group without therapy compared with those of the early resuscitation group. Superoxide dismutase and leupeptin therapy prevented this drop in cellular energy. Total water content was significantly increased in the placebo group compared with that of the early resuscitation group; superoxide dismutase was able to prevent this increase. Data indicate that intestinal reperfusion injury in burned rats can be effectively modulated with superoxide dismutase or leupeptin therapy.

Adenosine Diphosphate↗
PubMedDate not supplied

Beneficial wound healing and metabolic effects of clenbuterol in burned and nonburned rats.

Clenbuterol is known to increase muscle mass in nonburned and burn-injured subjects. The effects of clenbuterol on wound healing and the postburn response were examined in both nutritionally matched and free-feeding groups of rats. Rats received either a sham or 30% total body surface area scald burn and then a dorsal incision. Clenbuterol (2 mg/kg/day) was administered subcutaneously via a miniosmotic pump. The burn injury resulted in a sustained non-temperature-dependent hypermetabolism that was not altered by clenbuterol. Clenbuterol induced muscle anabolism and body growth in sham and burned-injured animals. Treated sham animals demonstrated increased wound breaking strength. Matched nutritional intake attenuated the body weight gain, although muscle anabolism was still evident in treated animals. Clenbuterol elevated RNA concentration in the tibialis muscle and reduced it in the liver. There was no statistical difference in wound strength when nutritional intake was matched. Clenbuterol's actions appear to be dependent on substrate availability. Clenbuterol may prove beneficial in patients with severe prolonged catabolic state, such as that associated with burn injury, by promoting protein anabolism and enhancing wound healing.

Adrenergic beta-Agonists↗
PubMedDate not supplied

The reduction of itch during burn wound healing.

The purpose of this study was to find a method to reduce the itch experienced by patients who have sustained burn injuries, by using and comparing the effectiveness of 2 shower and bath oils. One product contained liquid paraffin with 5% colloidal oatmeal and the other contained liquid paraffin. The study was carried out in the Adult Burns Unit, Royal Brisbane Hospital (RBH), Brisbane. It was conducted during a 10-month period from July 1998 until April 1999. Thirty-five acute burns patients participated in an assessor-blind clinical trial. Patients were asked twice daily to rate their discomfort from itch and pain. The amount of antihistamine requested by each patient was totalled daily. Analysis of data supplied by patients showed that the group using the product with colloidal oatmeal reported significantly less itch and requested significantly less antihistamine than those using the oil containing liquid paraffin.

Administration, Cutaneous↗
PubMedDate not supplied

Inflammation, acid and ulcers.

Chronic active type B gastritis is invariably the result of Helicobacter pylori infection and is an important factor in duodenal ulcer disease. The actions of mediators produced (a protein factor, a lipid soluble "pore-forming factor" and urease) or induced (immune/inflammatory cell mediators) by this bacterium on the control of gastric acid secretion are currently being investigated. These studies are reviewed in light of our current knowledge of the physiological control of gastric acid secretion.

Animals↗
PubMedDate not supplied

[The utilization of nutrient substances during wound healing].

The process of wound healing represents a series of complex physicochemical reactions requiring different nutritional microcomponents at each stage. In patients with extremely grave diseases and injuries the course of wound healing is impaired because of a hypermetabolic reaction to stress, leading to protein catabolism. The hypothalamus responds to cytokine stimulation by changes of thermoregulation (increase of heat production) and increased production of stress hormones (catecholamines, hydrocortisone, and glucagon). In turn, stress hormones trigger the thermogenous (unproductive) metabolic cycle and the lipolysis and proteolysis processes. Hyperproduction of glucose at the expense of skeletal muscle tissue degradation leads to the formation of amino acid substrate for liver glyconeogenesis. Additional nutrients are obligatory for wound healing in such patients. Protein catabolism cannot be arrested by amino, acids alone partly because amino acid transport is impaired; it can be normalized by anabolics, such as growth hormone and insulin-like growth factor 1. Treatment with growth hormone yields a dramatic positive effect in severely burned children. Proteins and vitamins, specifically arginine and vitamins A, B, and C provide the optimal nutritive support during wound treatment.

Disease↗