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Biomedical subjects

D E Clark

Publications and source records attributed to D E Clark.

At least 19 recordsLinked to original sources
PubMed1992

Radiographic demonstration of oronasal fistulas in patients with cleft palate with the use of barium sulfate contrast.

The purpose of this investigation was to determine the overlapping and unique contributions that radiographic techniques might provide for accurate characterization of hard palate fistulas associated with cleft palate. Five subjects with oronasal fistulas were selected for radiographic imaging, and their informed consent was obtained. Results indicated that radiographs with contrast can provide important supplemental and unique information. Qualitative descriptions of the inferior-superior course and location, and the size of the narrowest aperture could be obtained from the combination of maxillary occlusal, posteroanterior tomographic, and lateral tomographic projections. This information could not be obtained from the common clinical methods in use to describe fistulas. This technique can provide valuable information to all members of a multidisciplinary cleft palate team to document palatal fistulas for both clinical and research purposes.

Barium Sulfate↗
PubMed1992

Pharmacophoric pattern matching in files of three-dimensional chemical structures: use of bounded distance matrices for the representation and searching of conformationally flexible molecules.

This paper discusses the use of bounded distance matrices for the representation of conformationally flexible three-dimensional (3D) molecules. It is shown that pharmacophoric pattern searches of databases of flexible 3D molecules represented in this way can be carried out using screen and geometric searching algorithms that are analogous to those used for searching databases of rigid 3D structures. Molecules matching a query pattern after the geometric search must then undergo a final conformational search to determine whether they can, in fact, adopt a conformation that matches the query. An analysis of this three-stage searching procedure shows that searching databases of flexible 3D molecules is extremely demanding of computational resources.

Algorithms↗
PubMed1992

Collagen concentrations in dissected tissue compartments of rat uterus on days 6, 7 and 8 of pregnancy.

Implantation and non-implantation sites were dissected into myometrial and stromal components; a decidual/embryonic region was obtained on Days 7 and 8 of pregnancy. The concentration of collagen (as a percentage of the dry weight of tissue), measured by hydroxyproline analysis, was significantly lower in the implantation regions than in the non-implant regions in all areas studied. The concentrations in the antimesometrial myometrium and stroma of the implantation region remained the same over the days studied. In contrast, the mesometrial collagen concentration in the implantation region declined from Day 6 to Day 8 of pregnancy. Collagen concentration was low within the decidual/embryonic tissue on Days 7 and 8 of pregnancy. Remodelling of collagen within the embryonic area appears to be an important feature of the uterine response to implantation in rats.

Animals↗
PubMed1991

Effect of x-ray tube motion on dental radiographic resolution.

X-ray tube movement during intraoral radiography is generally discouraged; however, the effects have not been quantified or reported. A portable x-ray tube head was mounted on the horizontal cross-beam of Instron model 1125 universal testing machine. Precise movement from 0 to 25 mm of oscillation was accomplished in increments of 1 mm. Four test objects were imaged during x-, y-, and z-axis movement of the tube head. Pinhole camera and star test pattern images were used to measure focal spot size for each increment of motion. Images of a resolution plate and a section of dry mandible were used to evaluate levels of resolution objectively and subjectively for each increment of motion. Results indicate that the size of the effective focal spot increases predictably with increasing increments of tube motion accompanied by a corresponding loss of resolution. Movement of the tube along the x- and y-axis relative to the plane of the film produced similar losses of resolution and were much greater than loss associated with z-axis movement.

Motion↗
PubMed1991

Pharmacophoric pattern matching in files of three-dimensional chemical structures: use of smoothed bounded distances for incompletely specified query patterns.

This paper describes a technique for increasing the screen-out of pharmacophoric pattern searches in the databases of three-dimensional chemical structures when only some of the interatomic distances in the query pattern are specified. The technique involves the application of a distance bounds-smoothing procedure to the query distances; this smoothing allows the calculation of upper and lower bounds for the unspecified distances. The bounded distances can then be used to set screens additional to those that are set to describe the distances that have been specified by the searcher. Evidence is presented to suggest that use of the technique can lead to increases in the efficiency of substructure searches for partially specified query patterns.

Databases, Factual↗
PubMed1991

Blunt trauma to the carotid arteries.

Blunt carotid artery trauma is an uncommon but potentially dangerous clinical entity. We report eight patients from a 10-year interval who sustained blunt injuries to the carotid arteries. Six of eight patients suffered a hyperextension injury or had a cervical spine fracture or both. Arteriography revealed four arterial dissections and four thrombotic occlusions. Two asymptomatic common carotid artery occlusions and one dissection with transient ischemic attacks had successful arterial reconstructions. Five patients were treated nonoperatively: three internal carotid artery dissections with minor or no neurologic deficit; one asymptomatic thrombosis; and one internal carotid artery thrombosis with a major fixed neurologic deficit that did not improve. No patient died, and seven of eight made a complete neurologic recovery or remained asymptomatic. The diagnosis of blunt carotid artery injuries should be suspected in patients with neck hyperextension injuries or with cervical spine fractures as well as in patients with neurologic deficits not explained by intracranial trauma. Duplex scanning may be a useful noninvasive study. Surgery is indicated for selected patients with accessible lesions who have minor or no neurologic deficits. Asymptomatic patients with small intimal flaps or dissections may be successfully treated nonoperatively.

Adolescent↗
PubMed1991

Orthotic devices for ambulation in children with cerebral palsy and myelomeningocele.

Children with cerebral palsy and children with myelomeningocele frequently require orthotic devices for standing and walking. The purpose of this article is to review the literature on orthotic devices for walking, present principles of lower-extremity orthoses, discuss designs of orthoses, and consider criteria for selecting orthotic devices. Although discussion of the devices is specific to children with myelomeningocele and to children with cerebral palsy, the orthoses can be used with children having other disabilities. The information presented should be of value to clinicians, educators, and researchers interested in reviewing orthotic applications for children with disabilities.

Cerebral Palsy↗
PubMed1990

Blunt hepatic trauma. Nonoperative management in adults.

Fifty-six adults were identified with blunt hepatic trauma. Sixteen patients (29%) were treated successfully with nonoperative management. There were no delayed laparotomies or deaths in the nonoperative group. All patients required close observation. Eight (50%) of 16 patients required transfusion of no more than 3 U of packed red blood cells. There were two significant late complications requiring readmission. Four (25%) of 16 patients had complex fractures, yet were treated successfully without laparotomy. The quantity of fluid in the abdomen, as estimated by computed tomography, did not predict failure of treatment. Nonoperative management of blunt hepatic injuries is a useful alternative in selected patients when the course of therapy is based on the hemodynamic stability of the patient and supported by computed tomographic findings.

Adolescent↗
PubMed1990

Decreased collagen concentration in rat uterine implantation sites compared with non-implantation tissue at days 6-11 of pregnancy.

Collagen concentrations at implantation sites in the rat uterus were found to be significantly decreased compared with concentrations in adjacent non-involved uterine tissue in early pregnancy (75% by Day 11). The decrease in collagen was most marked in primary decidua and was also observed to a lesser extent (20%) in myometrium at the implantation site. There was a decrease of 20% in the concentration of total proteins at Day 7 (as measured by the ninhydrin method) and a slight increase in water content (2%) at Days 6 and 7. The differences in total protein and water content were transient, but the difference in collagen was maintained throughout early pregnancy. The localized changes in collagen content observed in this study, along with previously reported morphological changes in fibrillar and basement-membrane collagens in the uterus, give support to a theory of remodelling in early pregnancy involving simultaneous synthesis and degradation of extracellular proteins during decidualization.

Animals↗
PubMed1990

Evaluation of alveolar bone in relation to nutritional status during pregnancy.

Demand for nutrients necessary for the formation of mineralized tissues increases dramatically during pregnancy to meet fetal requirements. The purpose of this clinical study was to identify short-term effects of pregnancy and dietary intakes of calcium, phosphorus, protein, and vitamin C on radiographic density and alveolar crest morphology of the mandible. Seventy-six subjects between ten and 20 weeks' gestational age were recruited from the Jefferson County, Alabama, Department of Health maternity clinic. Initially, an evaluation of their diet was done, and a single periapical radiograph was taken in the canine-premolar region of the mandible. A final evaluation of the diet and a periapical radiograph of the same teeth were obtained at a time as close to the expected date of delivery as possible. Dietary evaluation consisted of a 24-hour recall history and a food-frequency history at the two visits. Radiographs were made with a bite-block film-holding system with occlusal registration in acrylic for reproduction of projection geometry at the two visits. An aluminum stepwedge was incorporated for densitometric standardization. Measurements of plaque, and bleeding and pocket-depth probing were recorded for control of local effects on alveolar change. Standard statistical procedures of regression determined correlation of 12 nutrients and periodontal variables with bone density change and with alveolar crest morphology change. Vitamin C intakes (24-hour recall) showed a positive correlation (p = 0.033) with bone density change, and calcium intakes (24-hour recall) showed a negative, but not significant, correlation (p = 0.058) with bone density change, contributed particularly by subjects with the highest calcium intakes. The strongest relation with alveolar crest morphology change was the interproximal pocket-depth change (p = 0.086).

Adult↗
PubMed1990

Radiation absorbed from dental implant radiography: a comparison of linear tomography, CT scan, and panoramic and intra-oral techniques.

Absorbed radiation dose in bone marrow, thyroid, salivary gland, eye, and skin entrance was determined by placement of lithium fluoride thermoluminescent dosimeters (TLD's) at selected anatomical sites within and on a human-like x-ray phantom. The phantom was exposed to radiation from linear tomographic and computer-assisted tomographic (CT) simulated dental implant radiographic examinations. The mean dose was determined for each anatomical site. Resulting dose measurements from linear tomography and computer-assisted tomography are compared with reported panoramic and intra-oral doses. CT examination delivered the greatest dose, while linear tomography was generally lowest. Panoramic and intra-oral doses were similar to those of linear tomography.

Dental Implantation, Endosseous↗
PubMed1990

An ultrastructural evaluation of toluene toxicity using cultured mammalian cells.

Animal cells were cultured in media containing toluene and then examined by electron microscopy to determine changes in subcellular architecture. Cellular viability and cloning studies indicated toluene toxicity at concentrations of 50-500 ppm. At all dosage levels, toluene accelerated cell death compared to comparable control cells that had not been exposed to toluene. However, media composition and, particularly, the presence or absence of fetal bovine serum (FBS), markedly affected toluene toxicity. In media without FBS reversible changes in filopodia and cell shape were identified after 15 min of exposure to as little as 50 ppm toluene, and cell death occurred within 5 min at concentrations of 500 ppm toluene. In media with FBS, no filopodial changes were observed at 50 ppm toluene, and cell death, although accelerated, was clearly evident only after 24-48 h of exposure to 200-500 ppm toluene. Except for the cell-surface changes, chronic toluene exposures (50-100 ppm without FBS or 200-500 ppm with FBS in the growth medium) produced no unusual intracellular changes until 24-48 h of toluene exposure. With toluene exposures of 24 h or longer, cellular changes included condensation of heterochromatin in nuclei, formation of bulbous protuberances at the cell surface, loss of polyribosomes (but not ribosomes) and, ultimately, degeneration of organelles. These late changes were irreversible and the prelude to cell death.

Animals↗
PubMed1990

Blunt aortic trauma: signs of high risk.

In the last 10 years, our center has managed 60 cases of aortic rupture from blunt chest trauma. Nineteen patients died (32%), 11 of whom were moribund on admission. Two patients out of ten who had undergone aortography at other institutions arrived at our hospital with massive bleeding in the left chest and died despite immediate operation. Six patients exsanguinated 1 to 2 1/2 hours after admission while aortography was being arranged or performed, and review of these cases to identify clinical signs of high risk revealed that left hemothorax, pseudocoarctation, and/or supraclavicular hematoma were present in five of the six. It appeared that the survival rate of patients suspected of blunt aortic trauma who had any of these clinical signs might be improved if they were taken directly to the operating room. To investigate this possibility we reviewed all cases from the past 10 years (excluding patients moribund on arrival or who had aortography elsewhere) in whom suspicion of aortic trauma led to aortography or surgery. Thirteen of the 17 patients (76%) with one or more signs of high risk had torn the aortic isthmus, compared to 26 of 154 patients (17%) without these signs. Five of the high-risk group (29%) exsanguinated, compared to one (less than 1%) of the others. No patient in this series died from unsuspected aortic trauma, which we attribute to the liberal use of aortography. Except for the patients with exsanguinating hemorrhage preoperatively, there were no operative or postoperative deaths.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Selective nonoperative management of blunt splenic trauma in adults.

The use of selective nonoperative management of blunt splenic trauma in adults is based on the undeniable benefits of this approach in children. Proper patient selection requires hemodynamic stability, lack of generalized peritoneal irritation, and minimal blood transfusion needs. Computed tomography is now used to make the diagnosis, but the decision for laparotomy is based on clinical grounds. Forty-one (87%) of 47 patients selected for nonoperative management were treated successfully without laparotomy, while the remaining 6 patients underwent delayed operations for persistent splenic bleeding. Blood transfusion requirements were significantly less in the observed group than in the operative group for patients with isolated trauma and for patients with polytrauma. There were no known missed intra-abdominal injuries and no deaths with the nonoperative approach. Analysis of our results has confirmed that nonoperative management is a safe and effective alternative to immediate laparotomy in properly selected patients and it can result in splenic salvage without the need for an operation.

Adolescent↗
PubMed1989

Effects of T-2 toxin on saccharin aversion and food consumption in adult rats.

The present experiment used a saccharin aversion paradigm to evaluate the potential aversive action of T-2 toxin, a trichothecene mycotoxin that induces emesis and weight loss. Adult male rats were fed either a control diet or a diet adulterated with 640 ppm lithium chloride (positive control) or with 2.5, 5.0 or 10.0 ppm T-2 toxin and given access to a 0.1% saccharin solution and to tap water during four training days. The rats were then shifted to the control diet during three extinction days. Moderate saccharin aversion induced by the positive control diet and the 5.0 and 10.0 ppm T-2 diets was apparent on the third day of exposure and the aversion to the saccharin solution abated during the extinction trials. Saccharin aversion was evident at levels of T-2 toxin that did not induce obvious tissue pathology.

Animals↗
PubMed1989

Conditioned saccharin taste aversion induced by mycotoxins in rats: lack of effect of ochratoxin A.

The present study examined the putative aversive action of ochratoxin A (OA) using a conditioned saccharin aversion paradigm. Adult male rats consumed a 0.1% saccharin solution then were treated (IP) with either a 5% NaHCO3 vehicle (negative control), 32 mg/kg LiCl (positive control) or 0.75, 1.5 or 3.0 mg/kg OA. Twenty-four hours later, the rats were given a choice between tap water and the 0.1% saccharin solution. Rats treated with the vehicle or any of the doses of OA exhibited a marked preference for the saccharin solution, whereas the rats treated with LiCl exhibited a marked rejection of the saccharin solution. The implications of these data for an understanding of mycotoxicosis are discussed.

Animals↗
PubMed1989

Rehabilitation inpatient screening of early cognitive recovery.

A neuropsychologic bedside screening instrument has been developed for use with recovering, cognitively impaired inpatients. Its purpose is to help clarify the nature and extent of cognitive impairments and to quantify change during recovery. The Barry Rehabilitation Inpatient Screening of Cognition (BRISC) represents an extension downward into the broad range of below-normal functioning. Reliability and validity data, based on 20 head-injured inpatients, and normative data, based on 52 nonpatients are presented. These data indicate that the BRISC is an appropriate instrument for use with its target population.

Adolescent↗