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Biomedical subjects

C J Thomas

Publications and source records attributed to C J Thomas.

At least 73 records · Page 4Linked to original sources
PubMed1996

Fluconazole therapy for histoplasmosis. The National Institute of Allergy and Infectious Diseases Mycoses Study Group.

We assessed the efficacy of oral fluconazole (200-800 mg daily) in the treatment of non-life-threatening acute pulmonary histoplasmosis, chronic pulmonary histoplasmosis, or disseminated histoplasmosis in patients without human immunodeficiency virus infection. Of 27 evaluable patients, two had progressive acute pulmonary histoplasmosis, 11 had chronic pulmonary histoplasmosis, and 14 had disseminated histoplasmosis. Median durations of treatment in each of the three groups were 6 months, 7 months, and 11 months, respectively. Nineteen patients were treated with 400 mg of fluconazole daily (two of these patients received 800 mg daily for a portion of their treatment courses), seven were treated with 200 mg daily, and one was treated with 800 mg daily. Treatment was successful in 17 (63%) of 27 cases. Both of the patients with acute pulmonary infection responded to therapy, as did five (46%) of 11 patients with chronic pulmonary infection and 10 (71%) of 14 patients with disseminated infection. No substantial toxicity was observed. We conclude that fluconazole therapy for histoplasmosis is only moderately effective and should be reserved for patients who cannot take itraconazole.

Female↗
PubMed1996

Effect of multiplicity of infection on Listeria monocytogenes pathogenicity for HeLa and Caco-2 cell lines.

The significance of multiplicity of infection (moi) for invasiveness and intracellular multiplication of Listeria monocytogenes in Caco-2 and HeLa cell monolayers was investigated. A low moi (1:1) resulted in recovery of significantly more L. monocytogenes when these bacteria were used to infect either cell line. At high moi (100:1), the percentage recovery of bacteria was comparatively low, even after extensive invasion and intracellular multiplication. Microscopic analysis of Giemsa- and immunofluorescent-stained infected monolayers revealed extensive cell disruption and exposure of the internalised bacteria to the bactericidal effect of gentamicin. By contrast, a low moi resulted in minimal cytopathic effects and evidence of cell to cell spread by L. monocytogenes was consistently observed in HeLa and J774, but not in Caco-2 cell lines. Nevertheless, the use of HeLa and Caco-2 cell monolayers enabled a clear distinction to be made between invasive (L. monocytogenes) and non-invasive Listeria spp. (L. innocua, L. ivanovii, L. seeligeri, L. grayi, L. welshimeri and L. monocytogenes LLO19). The use of a low moi with HeLa cell monolayers provided a reliable tissue-culture model of infection for L. monocytogenes.

Caco-2 Cells↗
PubMed1996

Evidence for a renomedullary vasodepressor hormone.

1. Recent physiological experiments have established that increasing the perfusion pressure of the kidney causes the release of vasodepressor substance from the renal medulla. 2. The substance is not a platelet activating factor, a prostaglandin or nitric oxide and the vasodepressor response to increased renal perfusion is not due simply to inhibition of renin release. 3. The mechanisms by which the renomedullary vasodepressor substance lowers arterial pressure remain to be determined. Sympathoinhibition may account for part of the response, but the hypotension still occurs in autonomic ganglion blocked animals. 4. The source of substance appears to be the renomedullary interstitial cells, though the control of the production and release of the substance remain to be determined. 5. The substance may be a lipid but it is yet to be fully isolated and identified. 6. The threshold for release of the substance appears to be close to normal resting arterial blood pressure. 7. Despite strong evidence that the renal medulla releases a vasodepressor hormone in response to increased renal perfusion pressure, much is still to be determined regarding the physiology of this hormone and its involvement in the aetiology of hypertension.

Kidney Medulla↗
PubMed1996

Choosing dentistry as a career--a profile of entering students (1992) to the University of Sydney, Australia.

The present study is an investigation of motives students have for wishing to become dentists. The study population comprised 85 first year dental students of the class of 1992 at the University of Sydney. A questionnaire which sought information on student demography, attitudes to dentistry, and motive rankings was administered. Demographic findings indicated that the majority of students came from countries in the Pacific rim and the male/female ratio was 62 to 38 per cent. Responses to the attitude questionnaire showed that Australian student motives for becoming dentists did not differ from those of students in other countries. The most predominant of these motives was to serve others, to become independent, to enjoy job satisfaction, and to acquire financial security. The least important motives were manual and communication skills, science and knowledge, and surprisingly, status and prestige. To attribute meaning and value to these motives, however, reflects inconsistencies which are expressed as contradictions between motive categories, between items within categories, and between motive categories and motive rankings. When one considers the basis upon which career decisions are made, disparity in the findings may be attributable to a decision-making process that rests on subjective rather than objective criteria.

Adolescent↗
PubMed1996

Effect of hypoxia on nitric oxide production in neonatal pig lung.

Nitric oxide (NO) synthase inhibitors potentiate hypoxic vasoconstriction (HV), suggesting that NO production during hypoxia normally acts to attenuate HV. To begin to examine the effect of hypoxia on lung NO production, we studied four groups of isolated neonatal pig lungs. In three groups of lungs, the accumulation of nitrite/nitrate (NOx-) was measured in the recirculating perfusate during ventilation with a control gas mixture (Cont), a hypoxic gas mixture (Hyp), or the control gas mixture with N omega-nitro-L-arginine methyl ester (L-NAME) added to the perfusate. Both hypoxia and L-NAME significantly increased perfusion pressure [pulmonary arterial pressure (Pa)-pulmonary venous pressure (Pv)] compared with control. NOx- accumulated in the perfusate at an average rate of 9.1 +/- 2.3 (SE) nmol/min in Cont, 3.7 +/- 0.8 nmol/min (P < 0.05 vs. control) in Hyp, and 3.7 +/- 0.6 nmol/min (P < 0.05 vs. control) in L-NAME. In the fourth group of lungs, exhaled NO output was measured during ventilation with the control gas mixture, the hypoxic gas mixture, and the control gas mixture with L-NAME added to the perfusate. Pa-Pv increased significantly with both hypoxia and L-NAME in these lungs. The exhaled NO output also decreased significantly with both hypoxia and L-NAME. These results suggest that in this preparation there was continuous production of NO that was decreased by hypoxia or L-NAME. It is not clear how the potentiation of HV by NO inhibitors and inhibition of NO production by hypoxia are linked.

Animals↗
PubMed1996

Alveolar epithelial lining fluid cellularity, protein and endothelin-1 in children with congenital heart disease.

This study applied bronchoalveolar lavage (BAL) to children with congenital heart disease (CHD) prior to elective cardiac catheterization (n = 48), to determine the influence of pulmonary blood flow and viral infection on the alveolar epithelial lining fluid (ELF) concentration of leucocytes, protein and endothelin-1 (ET-1). Lower respiratory tract (LRT) viral infection was defined as either a positive immunofluorescence for virus, or a virus cultured from the bronchoalveolar lavage fluid (BALF). Haemodynamic status was determined at cardiac catheterization. Normative data for BALF, but not ELF parameters, were obtained from 26 asymptomatic, noninfected normal children undergoing elective surgery. In the absence of LRT infection, the BALF macrophage, lymphocyte and neutrophil differential in CHD was not significantly different from the normal controls. In CHD, both increased pulmonary-to-systemic flow ratio (Q'p/Q's) and increased pulmonary artery-to-left ventricular pressure ratio PAP/LVP were associated with a decrease in ELF protein (rs = -0.59; p < 0.0001; and rs = -0.50; p < 0.0001 respectively). A respiratory virus was isolated from the BALF in 8 (17%) of CHD children. Virus isolation was associated with an increased ELF total protein (p < 0.05 vs no infection), a decreased alveolar macrophage differential count (p < 0.01), and an increased neutrophil differential count (p < 0.05). ET-1 was detected in the BALF of 83% of the noninfected CHD children compared to only 23% of the controls (p < 0.001). ELF ET-1 concentrations did not correlate with haemodynamic status in CHD, but were up to 100 times higher than paired plasma levels. We conclude that, in congenital heart disease, both lower respiratory tract viral infection and increased pulmonary blood flow and/or pulmonary vascular pressure influence the alveolar milieu. High alveolar epithelial lining fluid concentrations of endothelin-1 occur in congenital heart disease, but the stimulus for pulmonary endothelin-1 production is unclear.

Bronchoalveolar Lavage Fluid↗
PubMed1996

The effect of thermal deactivation on the properties and processing characteristics of E. coli.

Recombinant microorganisms are often employed to produce proteins of commercial significance. It is important to render such organisms non-viable before culture fluids are released from the fermenter. Thermal deactivation is a superficially attractive option because of its simplicity. The effects of such a thermal deactivation step at the end of a recombinant fermentation are reported in this study. In particular, the consequences of this treatment for down-stream process operations, namely homogenisation and centrifugation, are analysed and discussed. Homogenisation efficiency was adversely affected by a simple treatment whereby cells are raised to 65 degrees C from stationary phase. Cell debris size was also significantly increased. These changes could be partially explained by an increase in fractional peptidoglycan crosslinkage and a decrease in mean cell length. A simple process modification removed these detrimental effects. Specifically, the addition of 15 g of glucose 15 mins prior to thermal deactivation enhances downstream processing. Disruption efficiency is increased above that for stationary-phase cells and the resultant cell debris size is significantly reduced, theoretically aiding inclusion body purification. This novel process modification demonstrates that thermal deactivation may be employed to prevent the release of viable recombinant organisms while providing a broth with desirable processing characteristics. It also emphasises the need to optimise any bioprocess as an interconnected sequence of units.

Bioreactors↗
PubMed1995

Variation in odor thresholds for l-carvone and cineole and correlations with suprathreshold intensity ratings.

Specific anosmias have been reported for l-carvone and cineole, two compounds of importance in food flavor perception. Detection thresholds were assessed in groups of 50+ individuals by ascending forced-choice tests conducted in quadruplicate. Wide individual differences in thresholds were observed. Within the same session, threshold correlations were in the range of +0.8 to +0.9, showing good short-term reliability. Correlations with suprathreshold ratings were moderate (in the range of r = -0.5) after subtraction of false positive ratings for blank samples. However, a cineole mixture experiment failed to show any differences between subgroups that were previously classified as high or low sensitivity on the basis of threshold measurements. Re-testing selected groups after a period of months showed considerable within-individual variation in the thresholds, especially for l-carvone. These results call into question the stability and utility of threshold classification for these two compounds.

Adult↗
PubMed1995

Astringent subqualities in acids.

Astringency, astringent subqualities (drying, roughing and puckering) and sourness were compared among six acids: hydrochloric, lactic, citric, acetic, fumaric and malic acids. The attribute profiles of organic acids were similar to each other but different from hydrochloric acid, the only inorganic acid, which was the most astringent and the least sour. In a second experiment, two inorganic acids (hydrochloric and phosphoric) and two organic acids (citric and malic) were tested at three concentration levels. At approximately equal levels of overall sensory impact, the inorganic acids were alike in astringency and sourness, receiving higher ratings for roughing and drying, and lower ratings for sourness than the organic acids. Interactions with concentration (differences in psychophysical functions) for the subquality of drying were noted, in addition to the differences in the astringent subqualities of roughing and drying seen across acids in both experiments. The higher level of astringency for inorganic acids suggests that the current model for tannin binding to salivary proteins as an explanation of astringency needs to be extended to include a direct pH-dependent effect.

Adult↗
PubMed1995

The effect of sodium hypochlorite on potential pathogenic traits of Candida albicans and other Candida species.

Strains of Candida albicans, Candida krusei, Candida kefyr, Candida tropicalis, Candida parapsilosis and Candida guilliermondii were grown in the presence or absence of concentrations of sodium hypochlorite below the minimal inhibitory concentration and tested for a range of characteristics that may be associated with pathogenicity. Sodium hypochlorite is used routinely in hospitals in Australia for disinfection procedures, and these experiments were designed to assess the efficacy of hypochlorite as a sterilizing agent for acrylic dentures. Candida showed varying abilities to adhere to surfaces that may be present in the oral cavity. Sodium hypochlorite reduced the adhesion of all C. albicans strains and most other Candida species to both polystyrene and buccal epithelial cells. A biofilm of Streptococcus gordonii reduced the adhesion of most C. albicans strains and most other Candida species to polystyrene. However, Candida species were able to coaggregate with S. gordonii in suspension, with one strain of C. albicans, GDH 2346, showing greater coaggregating ability than the other strains or species. Sodium hypochlorite increased coaggregation of all C. albicans strains and most other Candida species. Examination of cell wall proteins from strains of C. albicans and a strain of C. parapsilosis showed that growth in hypochlorite increased the amount of protein in some existing bands and, in one strain of C. albicans, increased the number of detectable protein bands ranging from 56 to 26 kDa. Only 4 strains of C. albicans were able to produce hyphae, and 3 of these same strains and C. parapsilosis were able to produce proteinase. Hypochlorite increased the rate of blastospore to hyphal transition but had no effect on proteinase production or activity. It is concluded that hypochlorite at a concentration below the minimal inhibitory concentration may function as an anti-adhesin for Candida species but may not affect their more pathogenic characteristics.

Acrylic Resins↗
PubMed1995

Nitric oxide inhibition does not prevent the hypotensive response to increased renal perfusion in rabbits.

1. The involvement of nitric oxide (NO) and platelet activating factor (PAF) in the systemic depressor responses to increased renal perfusion pressure (RPP) were investigated. 2. In anaesthetized rabbits, the left kidney was perfused via an extracorporeal circuit which allowed RPP to be increased from 65 mmHg to 125 mmHg. The response of systemic blood pressure (SBP) to increasing RPP was measured in the same rabbits. 3. One group of rabbits (n = 5) was treated with NG-nitro-L-arginine (NOLA) to inhibit NO synthase activity (20 mg/kg i.v. bolus). Another group (n = 5), received 250 mmol/L NaHCO3 (4 mL/kg bolus) as vehicle treatment. 4. Following an increase in RPP to 125 mmHg, SBP fell at a rate of 0.43 +/- 0.06 mmHg/min in the vehicle treated rabbits. After NO synthase inhibition the rate of fall in SBP of 0.34 +/- 0.07 mmHg/min was not significantly different from that in the vehicle group (P = 0.3). 5. Blockade of NO synthesis did not alter the renal blood flow, renal vascular resistance changes and pressure-related natriuresis and diuresis responses to increased RPP to 125 mmHg. 6. PAF receptor blockade, using WEB 2086 (0.5 mg/kg plus 0.5 mg/kg/h), did not alter the systemic, renal haemodynamic or urinary responses to increasing renal perfusion pressure to 125 mmHg. 7. These findings indicate that neither NO nor PAF play an important role in the blood pressure lowering activity, intrarenal haemodynamics and urinary excretory responses observed when RPP was increased to a level within the physiological range.

Animals↗
PubMed1995

Renal medullary antihypertensive mechanisms.

1. Increasing renal perfusion pressure, using an extracorporeal circuit in rabbits and dogs, causes release from the kidney of a vasodepressor substance. 2. The hypotensive response occurs in denervated kidneys, and it is not due to platelet activating factor, nitric oxide, prostanoids or suppression of renin release. 3. In the rabbit, the pressure threshold for release of the hypotensive substance appears to be slightly above normal resting pressures. 4. The source of the hypotensive substance is medullary, since the hypotensive response to increased renal perfusion pressure is abolished in dogs and rabbits whose medullae are damaged by bromoethylamine treatment. 5. The chemical nature of the hypotensive substance remains unknown. 6. Thus the renal medulla appears to possess a hypotensive hormone, released in response to elevation of renal perfusion pressure. Many aspects of the physiology and pathology of the substance and its significance in blood pressure regulation remain to be determined.

Animals↗
PubMed1995

Microwaving of acrylic resin dentures.

Denture hygiene is an important factor in the treatment of denture stomatitis. Sterilization of dentures by microwaves has been recommended, but using specialized equipment not available to the average person. This study tests the effect of microwaving on the dimensional stability of dentures (in an unmodified domestic microwave oven). After microwaving (10 mins at 604 W) some measurements showed significant contraction or expansion but reduced exposure (6 mins at 331 W) caused much smaller changes. The dimensional changes are inexplicable but at lower radiation are considered to be harmless.

Absorption↗
PubMed1995

In search of a suitable denture marker.

The ID-Band (SDI AB, Sweden) has become the standard, internationally and FDI accepted denture marking system. In Australia however the strip is not easily obtainable and is expensive. Two other materials have been trialled as possible alternatives: (1) Titanium foil (9 microns) and (2) Ho Band (matrix) (3 microns) (Lorvic Corp, USA). All three bands were tested for tensile strength and elongation at temperatures: RT, 700 degrees and 900 degrees C. As the ID- and Ho Bands are both 18-8 stainless steel their performance was similar. The 18-8 was stronger, had a higher percentage break point and a higher elongation. The latter meant that it was softer and could be more easily inscribed and was therefore more suitable for denture marking. T1 is becoming increasingly used in dentistry but in spite of its abundance it is not likely to replace stainless steel for denture marking at present. On the other hand the Ho Band is cheaper, more readily available and it could replace ID-Band for use in Australia. An alternative paper based marking system is also presented together with the rationale for its use.

Denture Identification Marking↗
PubMed1995

Denture marking. Clinical and technical aspects.

The frequency of edentulousness has decreased in recent years due to the improvement in oral health. However, there is still a need to address the issue of denture marking for social and legal reasons because the oral status of populations varies in different countries and the wearing of complete dentures will be a fact for the foreseeable future. Given that only one marked denture can tell us the identity of a decreased when all other methods fail makes it a worthwhile exercise. The marking of dentures is not regulated by law in Sweden, but it is recommended by the Swedish Board of Health and Welfare (SOSFS[M]1986), that all patients should be offered the opportunity to have their dentures marked, which they may refuse. In Sweden, the dental laboratories report that they mark all dentures. The Swedish ID-Band has become the international standard and FDI accepted denture marking system, but recent research has indicated that this metal band is not resistant to very high temperatures. Since there is no international consensus regarding the matter we suggest that new materials should be explored.

Denture Identification Marking↗
PubMed1994

Pressure range for release of renomedullary depressor substance in rabbits.

We investigated the relation between renal perfusion pressure and the release of a renal vasodepressor substance in vivo to determine whether this substance was released at physiological pressures. We perfused the left kidneys of anesthetized rabbits using an extracorporeal circuit that allowed renal perfusion pressures to be set at 65 mm Hg (control) and increased to 95, 125, 155, or 185 mm Hg for 30-minute experimental periods. Systemic blood pressure did not change significantly when renal perfusion pressure was maintained at 65 mm Hg throughout. When renal perfusion pressure was increased to 95, 125, 155, or 185 mm Hg, systemic blood pressure fell significantly at rates of 0.17 +/- 0.04, 0.79 +/- 0.31, 0.60 +/- 0.11, and 2.18 +/- 0.79 mm Hg/min, respectively (P < .05). Restoration of renal perfusion pressure to 65 mm Hg abruptly reversed the falls in systemic blood pressure in each group. There was a natriuresis and diuresis that were both pressure related and progressive in the face of each constant level of increased renal perfusion pressure. In summary, there was a continuum of arterial vasodepressor responses across a renal perfusion pressure range from resting pressure to 185 mm Hg. We suggest that the threshold level for the release of significant amounts of a renal medullary depressor substance, probably medullipin, is just above normal arterial blood pressure and that the rate of release increases with increasing arterial pressure.

Animals↗