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Biomedical subjects

R D Davis

Publications and source records attributed to R D Davis.

At least 109 records · Page 6Linked to original sources
PubMed1995

Recurrence of diffuse panbronchiolitis after lung transplantation.

Diffuse panbronchiolitis (DBP) is characterized by chronic inflammation of the upper and lower respiratory tract. DPB has been found almost exclusively in oriental populations. We describe the occurrence of a case of DPB in an African American patient who underwent bilateral sequential lung transplantation. Ten weeks after transplantation, DPB recurred in the lung allograft, with rapid and significant deterioration in graft function. Allograft function improved within a few weeks after beginning treatment with erythromycin. This early recurrence is suggestive of a systemic etiology of DPB. Although recurrence of other systemic diseases has been reported after lung transplantation, no previous patients have been reported with early functional deterioration based solely on disease recurrence.

Adult↗
PubMed1995

Myocardial performance after graft preservation and subsequent cardiac transplantation from brain-dead donors.

BACKGROUND: This study examined the effects of brain death and graft preservation on right and left ventricular function after subsequent cardiac transplantation. METHODS: Seventy-eight dogs underwent 34 orthotopic complete atrioventricular transplantations using a validated brain-dead organ donor model, hypothermic cardiac preservation, and right and left ventricular function analysis (preload-independent recruitable stroke work). Four groups were studied: controls, transplantation from brain-dead organ donors, graft preservation without brain death, and donor brain death and graft preservation before transplantation. RESULTS: Without brain death, cardiac arrest alone as well as the combination of cardiac arrest and preservation did not significantly decrease cardiac function after transplantation. After brain death alone, right ventricular and left ventricular function decreased significantly by 30% and 25%, respectively, but subsequent transplantation did not cause further cardiac dysfunction. Preservation after brain death led to a further significant decrease in right ventricular function after subsequent transplantation, and dopamine hydrochloride was required to wean 4 animals from cardiopulmonary bypass. CONCLUSIONS: Brain death causes a significant loss of right and left ventricular function. These injuries are greater in the right ventricle and may contribute to early right ventricular failure after transplantation. Brain death and cardiac preservation interact significantly to impair right ventricular function further. Future studies of graft preservation should use brain-dead organ donors.

Animals↗
PubMed1994

Synthesis and opioid receptor affinity of a series of aralkyl ethers of 6 alpha- and 6 beta-naltrexol.

A series of 6-O-ethers of 6 beta- and 6 alpha-naltrexol (6 and 7) were prepared to examine the effect of large aralkyl groups on affinity of the ligands for opioid receptors. The affinities of the 6 beta- and 6 alpha-O-ether with benzyl, biphenylmethyl, 1- and 2-naphthylmethyl, and 9-anthracylmethyl groups were determined. Preparation of the ligands was accomplished from suitably 3-O-protected derivatives of 6 and 7 by phase transfer catalyzed alkylation using aralkyl halides, followed by deprotection. Both 3-O-trityl and -benzyl protecting groups were used. In radioligand displacement assays, compounds from the 6 alpha-O ether series had higher affinity than the analogous diastereomers in the 6 beta-O series, with few exceptions. In the 6 alpha-O series, the benzyl ether (29) and the biphenylmethyl ether (30) had the highest affinity, similar to naltrexone. In the 6 beta-O series, the benzyl ether had the highest affinity. The larger aralkyl ethers had slightly less affinity. Large lipophilic 6 beta-O- and 6 alpha- O-aralkyl groups are readily accommodated in the drug-receptor interaction.

Alkylation↗
PubMed1994

Isothiocyanate-substituted kappa-selective opioid receptor ligands derived from N-methyl-N-[(1S)-1-phenyl-2-(1-pyrrolidinyl)ethyl] phenylacetamide.

The synthesis of isothiocyanate-substituted kappa-selective opioid ligands derived from N-methyl-N-[(1S)-1-phenyl-2-(1-pyrrolidinyl)ethyl]ethyl]phenylacetami de (8) and their effects in radioligand displacement assays are reported. Ligands 3-5 with the S-absolute configuration were prepared with the isothiocyanate functionality at the 2-, 3-, and 4-positions in the phenylacetamide aromatic ring. The 2-isothiocyanato-4,5-dichlorophenylacetamide 6 was prepared to evaluate the effect of 4,5-dichloro substitution in the same aromatic ring as the 2-isothiocyanate function. N-Methyl-N-[(1S)-1-(4-isothiocyanatophenyl)-2-(1-pyrrolidinyl) ethyl]-3,4-dichlorophenylacetamide (7), with the 4-isothiocyanate function in the 1-phenyl ring, was prepared for comparison with the other compounds in the series. Of the prepared ligands, 7 and 8 (IC50s congruent to 1.4-1.8 nM) were approximately equal in affinity with 2 (ICI-199,441), followed by 3 and 6. All of these compounds were more kappa-selective than 2, as well. The binding characteristics of 8 show that the previously reported 4,5-dichloro substitution is not required for high affinity and kappa-selectivity. All of the synthesized isothiocyanate-substituted ligands irreversibly inhibited radioligand binding to guinea pig brain membrane preparations, including compound 2 (ICI-199,441) which had no isothiocyanate functionality.

Acetamides↗
PubMed1994

Differences in early results after single-lung transplantation. Washington University Lung Transplant Group.

Single-lung transplantation is an effective treatment for end-stage pulmonary failure caused by a variety of lung diseases. Although single-lung recipients may undergo a similar operative procedure, physiologic differences in the remaining native lung dictate differences in postoperative management and perhaps outcome. To examine these effects on the early results after single-lung transplantation, we retrospectively reviewed the course of 83 patients undergoing single-lung transplantation from September 1988 through July 1993. The cause of the lung disease was obstructive (OLD) in 43, idiopathic pulmonary fibrosis (IPF) in 16, and primary pulmonary hypertension (PPH) in 24 patients. The hospital mortality was 5% in OLD, 13% in IPF, and 8% in PPH. Gas exchange as demonstrated by alveolar-arterial oxygen gradients was worse after transplantation in patients with IPF (349 +/- 159 mm Hg) or PPH (270 +/- 171 mm Hg) compared with patients with OLD (174 +/- 105 mm Hg; p < 0.05). Mean pulmonary artery pressures were higher in patients with IPF (28 +/- 6 mm Hg) and PPH (26 +/- 7 mm Hg) compared with patients with OLD (22 +/- 5 mm Hg; p < 0.05). Peak airway pressures after transplantation were greater in patients with IPF (36 +/- 6 cm H2O) compared with patients with OLD (28 +/- 6 cm H2O; p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

An in vitro comparison of incomplete root fractures associated with three obturation techniques.

This study compared the incidence of incomplete root fractures among five groups of mandibular incisors (20/group). The groups were: (a) no canal preparation, (b) canal preparation, (c) canal preparation and obturation with laterally condensed gutta-percha, (d) canal preparation and obturation with thermoplasticized gutta-percha on a central carrier (Thermafil), and (e) canal preparation and obturation with thermoplasticized injectable gutta-percha (Ultrafil). Following experimental manipulation, all teeth were stained, transversely sectioned, and evaluated for the presence of root fracture. No complete root fractures were noted. The lowest incidence of stained incomplete fracture was found in the no canal preparation group. The canal preparation, lateral condensation, Ultrafil, and Thermafil groups had more incomplete fractures than the no canal preparation group. The incidence of stained fracture in the three obturation groups was not significantly different from the incidence in the group which had only canal preparation.

Humans↗
PubMed1992

Accuracy of second pour casts using dual-arch impressions.

This study compared the accuracy of the second pour of addition silicone impressions made using custom acrylic resin complete-arch trays and two types of dual-arch trays. Thirty impressions were made of a typodont using metal dual-arch, plastic dual-arch and acrylic resin complete-arch custom trays (10 impressions/group). Tooth #30 (first molar) and tooth #32 (third molar) in the typodont were custom metal dies made in the shape of complete crown preparations. On the metal dies were scribed reference marks permitting measurements to be made in the mesial-distal, buccal-lingual and occlusal-gingival dimensions. In addition, an inter-tooth measurement between tooth #30 and #32 was made. Following impression procedures, gypsum casts were poured. The casts were removed from the impression and, 24-hours later, second pours were completed. The distances between reference marks on each cast were measured using a measuring microscope. The measurements from each second pour cast were used to compute a group mean, with values expressed as a percent deviation from the master model. A two way analysis of variance was used to compare the groups. No statistically significant differences were found in accuracy among the three type trays except in the inter-tooth measurement where the metal dual-arch tray was more accurate than the other trays.

Analysis of Variance↗
PubMed1991

Marginal ridge strength in Class II tunnel restorations.

This in vitro study evaluated the compressive fracture resistance of marginal ridges of teeth with Class II tunnel preparations. Tunnel preparations were completed in extracted human bicuspid and molar teeth (bicuspids, bur size: #2, #4, #6; molars, bur size: #4, #6, #8). Control teeth in both the molar and bicuspid groups remained unprepared. Half the preparations in each group were restored with a glass ionomer cermet. After thermocycling, each marginal ridge was loaded in compression in an Instron Universal testing machine. Fracture values were compared with a two-factor ANOVA. A Dunnet post hoc test was used to compare the strength of each group to its control. Results indicated that up to a certain size, tunnel preparations could be completed without diminishing the strength of the undermined marginal ridges. Placement of a glass-ionomer cermet in the tunnel preparations restored the strength of all but the largest preparations (#6 bur in the bicuspid group) to a level which was not statistically significantly different from the controls.

Bicuspid↗
PubMed1991

Dual-arch and custom tray impression accuracy.

This study compared the accuracy in three dimensions of casts made from complete-arch custom acrylic resin trays and two types of dual-arch impression trays. Using addition silicone impression material, 30 impressions (10/group) were made of a typodont. Reference marks on the typodont allowed measurements in the mesiodistal, buccolingual and occlusogingival dimensions. Gypsum casts were made and the distances between the reference marks on each cast were determined with a measuring microscope. The measurements from each cast were compared with one another and expressed as a percent deviation from the typodont measurements. Analysis with a two-way ANOVA and a Tukey B post hoc test established that the dual-arch trays were at least as accurate as the custom tray in every dimension measured.

Analysis of Variance↗
PubMed1991

Predictable seating of the single-unit cast restoration.

Prior to cementation, a cast restoration must be clinically evaluated in a number of critical areas. The proximal contacts and internal surface of the casting, as well as centric and excursive occlusion, require assessment and generally require adjustment before cementation. The time necessary to accomplish these adjustments is not predictable. A technique is presented that permits the majority of these adjustments to be completed in the laboratory, thus minimizing the clinical time required to seat the casting.

Crowns↗
PubMed1989

Screening for learning disabilities: a neuropsychological approach.

The ability of the Trail Making Test (TMT) and Tactual Performance Test (TPT) to discriminate between learning-disabled and normal children was examined. Twenty children aged 9 to 14 years who recently had been classified as learning disabled and 20 matched controls were administered individually the TPT, TMT, and two experimental forms of the TMT (parts X and Y). The data from the two groups were analyzed with a discriminant analysis. An overall accuracy rate of 82.5% was obtained when the measures were used to predict the classification status of individual children. A stepwise discriminant analysis procedure revealed an experimental form of the TMT (part X), Tactual Performance Test total time, and Tactual Performance Test localization to be the most sensitive measures. The use of such measures to screen for learning disabilities is discussed.

Achievement↗
PubMed1988

Distribution of metals in grassland soils following surface applications of sewage sludge.

In order to decide on a suitable sampling depth for grassland soil treated with sewage sludge and to assess implications for grazing animals, a field trial on two soils was designed to estimate the distribution of metals in grassland soil profiles following surface applications of sludge. Thus the sites represented permanent grassland where no form of cultivation had taken place. Soil cores were taken using specialised equipment to 30 cm depth and divided into seven sections. Movement from the soil surface to a depth of 10 cm was observed for all of the seven metals, Cd, Cr, Cu, Mo, Ni, Pb and Zn, but most of the metal (60%-100%, mean 87%) remained in the upper 5 cm of soil. It was concluded that sampling to a depth of 5 or 7.5 cm would be most suitable for monitoring long-term grassland treated with surface applications of sludge.

Journal Article↗
PubMed1987

Primary cysts and neoplasms of the mediastinum: recent changes in clinical presentation, methods of diagnosis, management, and results.

Major changes have recently occurred in the clinical presentation, diagnosis, and management of primary lesions of the mediastinum. New diagnostic techniques and improved therapy have led to more objective preoperative diagnoses as well as better long-term results. These features are clearly demonstrated in a series of 400 consecutive patients with primary lesions of the mediastinum seen at Duke University Medical Center. Of these, 99 (25%) had a primary cystic lesion. The primary tumors included thymic neoplasms (17%), neurogenic tumors (14%), lymphoma (16%), germ cell tumors (11%), and a miscellaneous group. Malignant neoplasms were present in 166 patients (42%). The anterosuperior mediastinum was the most commonly involved site of a primary cyst or neoplasm (54%), followed by the posterior mediastinum (26%) and the middle mediastinum (20%). Symptoms were present in 62% of the patients and included chest pain (30%), dyspnea (16%), fever and chills (20%), and cough (16%). Of the lesions found on routine chest roentgenograms, 83% were benign. In contrast, 57% of the lesions in symptomatic patients were malignant. Prior to 1967, 94% of asymptomatic lesions were benign, but this figure has now decreased to 76%. Fifty percent of symptomatic patients had a malignant neoplasm before 1967 compared with 62% after that year. Newer diagnostic techniques have greatly enhanced the accuracy of the preoperative diagnosis. They include radioisotopic scanning, monoclonal antibodies, hormonal assay, electron microscopy, fine-needle aspiration biopsy, computed tomographic scans, and magnetic resonance imaging. Each has a definite role and is specifically illustrated as being quite important in this series.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiocardiography↗
PubMed1986

Cadmium in sludges used as fertilizer.

In intensively populated countries efficient sewage treatment is essential to protect river quality. An inevitable by-product is sewage sludge which has to be disposed of safely and economically. Utilisation of sludge as a fertilizer of agricultural land is the most economic disposal route for inland sewage-treatment works and also benefits farmers by providing a cheap manure. Much of the cadmium in wastewater is concentrated into sludge which consequently contains higher concentration of cadmium than soil does. It is impracticable to reduce cadmium concentrations in sludge below certain levels. When sludge is used on farmland rates of application must be controlled so that cadmium concentrations in soil never reach levels that could significantly contaminate food crops. Cadmium is a principal factor limiting the use of sludge on land. Nevertheless, it is a local problem since agricultural land in general receives more cadmium from aerial deposition and phosphatic fertilizers. The significance of accumulations of cadmium in soil depends mainly on its availability for crop uptake. Investigations are described which have attempted to identify and to determine the availability of forms of cadmium in soil. There is considerable research interest in cadmium in soil solution which is likely to be directly available for crop uptake. Another area of interest is the apparent disappearance of cadmium from sludge-treated soil. Soil analysis often cannot fully account for the cadmium added in sludge. Apart from the effect of soil conditions, especially pH value, crop uptake varies according to the particular crop examined. Highest concentrations of cadmium occur in tobacco, lettuce, spinach and other leafy vegetables. Using crop uptake data from field trials it is possible to relate potential human dietary intake of cadmium, on which hazard depends, to soil concentrations of cadmium, which can be controlled by regulating applications of sludge. This provides an objective basis for limits for cadmium concentrations in soils receiving sludge. Transfer of cadmium via farm animals to meat and dairy products for human consumption is thought to be minimal, even allowing for some direct ingestion of sludge-treated soil by the animals. Evidence from these and other investigations suggests that a loading rate limit of 5 kg Cd/ha (equivalent to a soil concentration of about 3.5 mg Cd/kg) affords adequate protection to the foodchain where sludge is used on agricultural land. More research work is needed to provide a basis for predicting the long-term availability of cadmium introduced to the soil in sludge.

Cadmium↗
PubMed1986

An inexpensive and portable talking-tactile terminal for the visually handicapped.

The visually handicapped computer user or programmer is faced with a very difficult task in interfacing with computing hardware. The types of equipment currently available for this purpose fall into one of several general categories: expensive, nonportable, and domain-specific. In the current paper, we describe a new terminal device designed specifically for the visually handicapped that answers all of the problems mentioned above. The work is already under way, with a prototype model is currently in use by a visually handicapped programmer on the development team. In the remainder of this paper we will present a report on the current status of our project as well as plans and milestones for future work.

Algorithms↗
PubMed1986

A clinical comparison of three anterior restorative resins at 3 years.

An in vivo comparison was made of three different types of restorative resins: a conventional composite resin, a chemically cured microfilled resin, and a small-particle, glass-filled, visible light-cured composite resin. Twenty-eight sets of three restorations were placed 20 patients and examined using the Ryge rating system. All resins performed well and were not significantly different from one another at 1 year. After 3 years, all materials were considered satisfactory, but the conventional composite resins had significantly more surface roughness than did the other resins. Each of the resin materials also declined in color match after 3 years.

Acrylic Resins↗