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Biomedical subjects

C Price

Publications and source records attributed to C Price.

At least 181 records · Page 10Linked to original sources
PubMed1986

A method of determining the radiopacity of dental materials and foreign bodies.

The desirability of radiopacity in dental materials and other materials that may become foreign bodies is documented. No simple, reliable methods are available for the determination of radiopacity, and no standard specifications have been devised with regard to the radiopacity of dental materials. A method that enables radiopacity to be determined is described. The theoretical aspects of radiopacity in relation to the method are considered. Possible applications of this method in the development of standards for radiopacity are suggested.

Absorptiometry, Photon↗
PubMed1986

The effects of beam quality and optical density on image quality in dental radiography.

The literature relating to the choice of beam quality in dental radiography is reviewed. Twenty observers were asked to select radiographs of a test object at different beam qualities and densities. The same observers were asked to identify numbers of circular areas of small density differences in zones of high and low density. Subjectively, the observers favored radiographs produced with lower beam energies; 90 kVp aluminum filtration and 3.5 mm was least popular, and 70 kVp with 2.5 mm aluminum was most popular. Objectively, there was little difference in the success of identification between the beams of different energies. Masking of radiographs improved success apart from the low density zones in less exposed radiographs. Little evidence has been found within the range investigated for selecting one beam quality over another, other than subjective preference. However, low beam energies should be avoided because of reduced emulsion sensitivity.

Densitometry↗
PubMed1986

Scattered radiation grids in cephalometric radiography.

Scattered radiation grids are routinely used in medical radiological examinations of the skull, but less commonly in cephalometric radiography. Because the grids involve an increased radiation dose, it is necessary to determine whether the diagnostic quality of cephalometric radiographs is improved by a grid to an extent that justifies this increased dose. This investigation has failed to demonstrate any improvement in the identification of five landmarks. It is thus concluded that there is no justification for the use of scattered radiation grids in cephalometric radiography.

Adult↗
PubMed1986

Facial morphology and obstructive sleep apnea.

In a sample of 25 adult male subjects with moderate to severe obstructive sleep apnea, the interaction among craniofacial, airway, tongue, and hyoid variables was quantified by means of a canonical correlation analysis. One lateral cephalometric radiograph with the teeth in occlusion was obtained for each subject together with overnight polysomnographic measurements before the initiation of therapy. A principal component analysis reduced the data base and one significant canonical correlation (r1 = 0.994) was identified for the 22 variables. Sleep apnea subjects showed a posteriorly positioned maxilla and mandible, a steep occlusal plane, overerupted maxillary and mandibular teeth, proclined incisors, a steep mandibular plane, a large gonial angle, high upper and lower facial heights, and an anterior open bite in association with a long tongue and a posteriorly placed pharyngeal wall. A multivariate statistical analysis extracted clinically significant associations among craniofacial, tongue, and airway variables. Subjects with sleep apnea demonstrated several alterations in craniofacial form that may reduce the upper airway dimensions and subsequently impair upper airway stability.

Adult↗
PubMed1985

The EcoR124 and EcoR124/3 restriction and modification systems: cloning the genes.

The Escherichia coli plasmid R124 codes for a type I restriction and modification system EcoR124 and carries genetic information, most probably in the form of a "silent copy," for the expression of a different R-M specificity R124/3. Characteristic DNA rearrangements have been shown to accompany the switch in specificity from R124 to R124/3 and vice versa. We have cloned a 14.2-kb HindIII fragment from R124 and shown that it contains the hsdR, hsdM, and hsdS genes which code for the EcoR124 R-M system. An equivalent fragment from the plasmid R124/3 following the switch in R-M specificity has also been cloned and shown to contain the genes coding for the EcoR124/3 R-M system. These fragments, however, lack a component present on the wild-type plasmid essential for the switch in specificity. Restriction fragment maps and preliminary heteroduplex analysis indicate the near identity of the genes that encode the two different DNA recognition specificities. Transposon mutagenesis was used to locate the positions of the hsdR, hsdM, and hsdS genes on the cloned fragments in conjunction with complementation tests for gene function. Indirect evidence indicates that hsdR is expressed from its own promoter and that hsdM and hsdS are expressed from a single promoter, unidirectionally.

Cloning, Molecular↗
PubMed1985

A psychophysical analysis of morphine analgesia.

Intravenous administration of 0.04-0.08 mg/kg morphine sulfate reduced both sensory intensity and unpleasantness visual analogue scale (VAS) responses to graded 5 sec nociceptive temperature stimuli (45-51 degrees C) in a dose-dependent manner. The lower doses of morphine (0.04 and 0.06 mg/kg) resulted in statistically reliable reductions in affective but not sensory intensity VAS responses, possibly reflecting supraspinal effects on brain regions involved in affect and motivation. However, the highest dose of morphine tested (0.08 mg/kg) reduced both sensory and affective VAS responses to graded nociceptive stimuli as well as VAS sensory responses to first and second pain evoked by brief heat pulses. Morphine also had an especially potent inhibitory effect on temporal summation of second pain that is known to occur when intense nociceptive stimuli occur at rates greater than 0.3/sec. The results support current hypotheses about neural mechanisms of narcotic analgesia and further clarify the relative effects of morphine on sensory and affective dimensions of experimental pain. The derived morphine dose-analgesic response functions also provide a reference standard for quantitatively comparing magnitudes of different CNS-mediated forms of analgesia.

Adult↗
PubMed1985

Potentiation of systemic morphine analgesia in humans by proglumide, a cholecystokinin antagonist.

Proglumide, a cholecystokinin antagonist, potentiates analgesia produced in rats by morphine and endogenous opiates, and appears to reverse tolerance in rats to opiate analgesia. Therefore, proglumide and other cholecystokinin antagonists may be clinically valuable. We have tested proglumide's possible opiate analgesic potentiating effects by examining, in volunteers, the effects of morphine and proglumide on human pain visual analogue scale responses to 45-51 degrees C skin temperature stimuli. Proglumide (50-100 micrograms intravenously) potentiated both the magnitude and duration of analgesia produced by small doses of morphine. This study provides indirect evidence for a cholecystokinin-opiate interaction in humans. Therefore, cholecystokinin antagonists such as proglumide may serve to potentiate exogenous or endogenous opiate action.

Adult↗
PubMed1984

International migration to and from Australia.

Australia's immigration policies during the past 30 years are reviewed, with a focus on the change "from an earlier emphasis on economic and population growth to an emphasis on humanitarian considerations such as family reunion and refugee resettlement." Socioeconomic and demographic effects of the country's policy of nondiscrimination are considered, and possible future changes in immigration patterns are projected.

Australia↗
PubMed1984

The so-called eruption sequestrum.

The literature relating to so-called eruption sequestra is reviewed. Two cases in which there were calcified fragments adjacent to the crowns of all four first molars are described. Histologic evidence suggests that these calcified fragments consist of a cementum-like substance formed within the follicle, and not sequestrated bone.

Calcinosis↗
PubMed1984

Effect of starvation and elective surgery on hand dynamometry and circulating concentration of various proteins.

The effect of 4 days total starvation (water only) in five normal subjects on the circulating concentrations of various proteins was studied. Changes in plasma albumin and total protein concentrations were compared with those of six patients undergoing elective abdominal surgery with partial starvation and six patients undergoing orthopaedic surgery with adequate feeding - (0.126-0.146 MJ/kg/day and 1.2-1.4 g protein/kg/day). In a companion study hand grip strength was measured daily in ten normal subjects during starvation and in 18 patients undergoing surgery for hernia repair (n = 6), cholecystectomy (n = 6) and major abdominal surgery (n = 6). Starvation produced marked reductions (approximately 30%) in the circulating concentrations of retinol binding protein and prealbumin but did not significantly affect the plasma concentration of immunoglobulins (IgG, IgA, IgM) acute phase reactants (orosomucoid, haptoglobin, alpha(1) antitrypsin), albumin and total protein. On the other hand both types of elective surgery produced significant reductions in plasma albumin and total protein concentrations irrespective of feeding. Grip strength was not significantly altered by four days of starvation but surgery produced a temporary reduction in grip strength, the extent and duration of which was related to the severity of operation. This study helps to separate the effect of surgery and starvation on hand dynamometry and circulating protein concentrations and indicates their limitations as indicators of nutritional state.

Journal Article↗
PubMed1984

Nuclear proteins that become part of the mitotic apparatus: a role in nuclear assembly?

A structure located at the poles of the mitotic spindle is described, which may function as a centre for post-mitotic nuclear assembly. Evidence in support of this function is incomplete, but comes from two different kinds of experiments, which are reviewed here. First, fluorescence microscopy studies show that mitotic chromosomes at telophase or late anaphase are drawn into juxtaposition with this polar structure and second, the structure is made up in part of a non-histone chromosomal protein that in interphase cells can be detected only in the nucleus. Studies of this nuclear-mitotic apparatus protein (NuMA protein) are reported here. Monoclonal antibodies specific for the NuMA protein have been used in immunofluorescence studies to visualize the prenucleus-like polar structure and to identify the NuMA protein by immunoblotting after electrophoretic separation. The NuMA protein is a non-histone chromosomal protein of molecular weight 250000 relative to standard protein molecular weight markers in sodium dodecyl sulphate/polyacrylamide gel electrophoresis. Experiments are described that indicate several difficulties in studying the possible affinity and association of NuMA protein with mitotic chromosomes. Metaphase chromosomes isolated by the polyamine procedure of Lewis and Laemmli have bound NuMA protein detectable by immunofluorescence or by immunoblotting, but measurements made at different stages of chromosome purification show that most of the NuMA protein is separated from the chromosomes using this purification procedure. Chromosomes purified from mixtures of human and Chinese hamster cells (the latter have none of the human form of NuMA recognized by a monoclonal antibody) have human NuMA protein bound to the hamster chromosomes. Results suggest that in cell extracts exchange reactions of NuMA protein can occur, which must be avoided in the study of its natural function.

Animals↗
PubMed1984

The effect of sympathomimetic agents on gastric acid secretion in rats.

Beta-adrenoceptor agonists have been reported to inhibit gastric acid secretion in vivo but their site and mode of action is uncertain. A study of the effects of such agents on acid secretion in the rat has been made using both an in vivo preparation and an in vitro one where possible effects due to neural, hormonal or cardiovascular actions of beta-agonists are avoided. In conscious rats with Heidenhain pouches, isoprenaline (40 micrograms kg-1h-1) inhibited the response to pentagastrin (20 micrograms kg-1h-1). This inhibition was abolished by propranolol (2 mg kg-1) and butoxamine (8 mg kg-1) and partially reversed by practolol (8 mg kg-1). Propranolol alone (2 mg kg-1) significantly increased the response to pentagastrin in the pouch rats but butoxamine and practolol (both at 8 mg kg-1) and the inactive isomer (+)-propranolol were without effect on the pentagastrin response. In the rat isolated stomach preparation isoprenaline, salbutamol, salmefamol , adrenaline and nor-adrenaline all stimulated acid output over the range 2 X 10(-7) to 10(-5)M. These responses were antagonised by propranolol (2 X 10(-5)M), pindolol and timolol (10(-6)M) but only nor-adrenaline stimulated secretion was inhibited by the selective antagonists practolol, atenolol, butoxamine and ICI 118551. In vitro responses to beta-adrenoceptor agonists were not antagonised by atropine (10(-5)M), metiamide (10(-4)M) or prostaglandin E2 (10(-5)M).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

The alternate expression of two restriction and modification systems.

Plasmids R124 and R124/3 carry genes coding for two different R-M systems and normally only one set of genes is expressed. These genes can be translocated to F plasmids that are compatible with the R factors and in strains carrying these F plasmids and an R factor a transacting regulatory mechanism switches off the expression of R-M genes on the introduced plasmid. Additionally the unexpressed genes on the introduced plasmid are expressed. The regulatory mechanism controlling the alternative expression of R124 and R124/3 R-M genes involves a physical rearrangement of DNA sequences.

Coliphages↗