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Biomedical subjects

R C Smith

Publications and source records attributed to R C Smith.

At least 109 records · Page 6Linked to original sources
PubMed1997

Soft-tissue "rim" sign in the diagnosis of ureteral calculi with use of unenhanced helical CT.

PURPOSE: To determine the value of the ureteric soft-tissue "rim" sign for differentiation of ureteral calculi from phleboliths on unenhanced helical computed tomographic (CT) scans and to identify factors that are associated with the presence of the rim sign. MATERIALS AND METHODS: Of 442 patients with ureteral obstruction confirmed at CT, 200 had documented ureteral stone disease; 136 of these patients had ureteral calculi, excluding the ureterovesical or ureteropelvic junctions. Each calculus and phlebolith along the course of the ureter were evaluated retrospectively and blindly for the presence of the rim sign, stone location, and stone size; the duration of symptoms was documented when available. RESULTS: The rim sign was present in 105 of 136 ureteral calculi (77%) and in 20 of 259 phleboliths (8%) and yielded a sensitivity of 77% and a specificity of 92% for distinguishing a calculus from a phlebolith. Calculi associated with the rim sign had a mean size of 4.3 mm, and calculi without a rim sign had a mean size of 6.3 mm (P < .001). There was no difference in duration of symptoms among patients who did or did not exhibit a rim sign. CONCLUSION: In patients with flank pain, the presence of a rim sign is a strong indicator that a calcification along the course of the ureter is a stone. Absence of the rim sign indicates that a calcification remains indeterminate.

Calculi↗
PubMed1997

Detection of choledocholithiasis: comparison of unenhanced helical CT and endoscopic retrograde cholangiopancreatography.

PURPOSE: To compare unenhanced helical computed tomography (CT) and endoscopic retrograde cholangiopancreatography (ERCP) in the detection of common bile duct calculi. MATERIALS AND METHODS: Within 13 months, 51 patients (aged 18-94 years) with clinically suspected choledocholithiasis underwent unenhanced helical CT immediately before undergoing ERCP. CT scans were evaluated for the presence of bile duct stones, ampullary stones, the gallbladder and gallbladder stones, intrahepatic biliary dilatation, and the size of the bile duct at the porta hepatis and in the pancreatic head. ERCP images were evaluated for the presence of bile duct or ampullary stones, as well as for biliary dilatation. RESULTS: Unenhanced helical CT depicted common bile duct stones in 15 of 17 patients found to have stones at ERCP. Three patients had stones impacted at the ampulla, all of which were detected with CT. In addition, there was one false-positive finding at CT. CT had a sensitivity of 88%, a specificity of 97%, and an accuracy of 94% in the diagnosis of common bile duct stones. CONCLUSION: Unenhanced helical CT is useful for evaluating suspected choledocholithiasis.

Adolescent↗
PubMed1997

Ureteral calculi in patients with flank pain: correlation of plain radiography with unenhanced helical CT.

PURPOSE: To determine the sensitivity and specificity of plain radiography for the detection of ureteral calculi with use of unenhanced helical computed tomography (CT) as the standard of reference. MATERIALS AND METHODS: Plain radiographs and helical CT scans of 178 patients with acute flank pain were reviewed retrospectively. Three interpretations of plain radiographs were used: (a) Original reading. This was the report made at the time of the patient's evaluation before the patient underwent CT. (b) Blinded retrospective reading. Each plain radiograph was interpreted without knowledge of the CT findings. (c) Unblinded retrospective reading. The plain radiograph of each patient whose CT scan showed a stone was reviewed with the CT scan. RESULTS: The original reading had a sensitivity of 45% and a specificity of 77% for the detection of ureteral calculi. The blinded retrospective reading had a sensitivity of 59% and a specificity of 71%. The unblinded retrospective reading had a sensitivity of 59% (95% confidence interval: 47%, 70%). CONCLUSION: Plain radiography is of limited value for aiding the diagnosis of ureteral stones. All patients with acute flank pain for whom radiologic imaging is recommended can directly undergo unenhanced helical CT; plain radiographs need not be obtained first.

Acute Disease↗
PubMed1997

Embryonic expression of the Gax homeodomain protein in cardiac, smooth, and skeletal muscle.

Gax is a homeobox-containing gene that has been detected in adult cardiovascular tissues and exhibits a growth arrest-specific pattern of expression in cultured vascular myocytes. To study the regulation of gax during development, we performed immunohistochemistry and in situ hybridization on mouse embryos. Gax was present in mesodermally and, as with other homeobox genes, neuroectodermally derived tissues. Early mesodermal protein expression was limited to the lateral plate and somitic mesoderm. Gax in the cardiac muscle lineage exhibited a biphasic pattern of expression. Expression was prominent in the heart tube of the earliest cardiomyocytes and remained prominent through the looping stage (day 12.5 post coitum [pc]) but fell below the threshold of detection in atria and ventricles by day 13.5 pc. At day 15.5 pc, Gax protein was again detectable but restricted to cells within the compact layer of the ventricular myocardium. Gax expression was also noted in smooth muscle cells as early as day 9.5 pc. In the skeletal muscle lineage, Gax protein was expressed at the onset of somitogenesis before the expression of the myogenic basic helix-loop-helix and MEF2/RSRF family proteins. Subsequently, it was noted at day 9.5 pc in premyogenic cells migrating into head, trunk, and limb buds. Gax was detected in myotomes, premuscle masses, and mature muscle groups. These data suggest an important developmental role for Gax in all muscle lineages.

Animals↗
PubMed1997

Trends in dental care among insured Americans: 1980 to 1995.

This article presents data on the use of a wide range of dental services by insured patients between 1980 and 1995. The patterns of dental care revealed in this study show clear trends that indicate profound improvements in oral health. These improvements are evident in all age groups, and the effect of the caries decline in children that began about 20 years ago has moved well into the adult population. As those born since about 1950 continue to age and represent an ever-increasing proportion of the population, the overall need for restorative care of all types will continue to diminish.

Adolescent↗
PubMed1997

Differentiation of achalasia from pseudoachalasia by computed tomography.

OBJECTIVES: The purpose of this study was to determine the computed tomography (CT) findings in idiopathic achalasia and in the pseudoachalasia of malignancy. METHODS: We identified 12 patients with the manometric diagnosis of achalasia who also had CT scans available for review: eight had idiopathic achalasia, and four had pseudoachalasia. As controls, we selected nine patients with endoscopically obvious esophageal cancer who also had CT scans. The CT scans were blindly reviewed to determine esophageal wall thickness, symmetry of the esophageal wall, presence of esophageal dilation or mass, and a radiological diagnosis. RESULTS: Six of the eight patients with achalasia had a dilated esophagus. Five had symmetric wall thickening >5 mm (range 7-10 mm) at the gastroesophageal junction. One patient with a 10-mm wall thickening was incorrectly diagnosed with a mass. All others were correctly diagnosed with achalasia. Three of the four patients with pseudoachalasia had esophageal dilation. Two had an obvious esophageal mass. The other two were given an indefinite diagnosis: one had asymmetric wall thickening (11 mm) at the gastroesophageal junction, and the other had symmetric thickening of 18 mm. Eight of the nine patients with obvious esophageal cancer had a mass on CT; the other patient had asymmetric wall thickening of 6 mm at the gastroesophageal junction and was given an indefinite diagnosis. CONCLUSIONS: Most achalasia patients have CT findings of esophageal dilation and mild, symmetric wall thickening. Therefore, symmetric esophageal wall thickening (<10 mm) should not dissuade one from the diagnosis of achalasia. Most pseudoachalasia patients have CT findings of esophageal dilation, more marked and/or asymmetric wall thickening, or mass. In this group, asymmetric or marked thickening (>10 mm) indicated pseudoachalasia. Therefore, CT can be helpful in differentiating between achalasia and the pseudoachalasia of malignancy.

Adenocarcinoma↗
PubMed1996

The effect of the rate and route of nutrient delivery on total body and organ composition in rats.

To assess the effects of administering increasing rates of total parenteral nutrition (TPN) on total-body and organ composition, infusion catheters were implanted aseptically into the right jugular vein of Sprague-Dawley rats. Animals received 14 d of either a high (H), medium (M), or low (L) rate of TPN infusion (1.22, 1.49, 1.74 MJ.kg-1BW.d-1 and 1.74, 1.48, 1.22 gN.kg-1BW.d-1, respectively: 1:1 lipid:glucose energy), or the TPN solution orally (O TPN group). Weight-matched (w) chow-fed (c) animals were sacrificed at the same final weight as the L TPN and O TPN groups (190 g, LWC group), or the M and H TPN groups (250 g, HWC group). There were 5 animals in each group. The rates of body weight increase of the M TPN, H TPN, and HWC groups were similar (p > 0.05) and greater than the L TPN and O TPN groups (p < 0.001). The L TPN and O TPN groups who received similar amounts of nutrients had similar rates of weight gain. Total body lipid expressed as a percentage of body weight was significantly greater (P < 0.01) in the L, M, and H TPN groups compared to the orally fed groups. The proportion of water and protein in the fat-free wet weight were similar for all groups (p > 0.05). The lipid content of the liver as a percentage of its weight was greater (P < 0.05) in the orally fed groups. There was no significant difference in the percentage of water or protein of individual organs or the total viscera between any group. These finding indicate that: (a) TPN administration can maintain similar rates of protein and water deposition compared to normal growth-maintaining oral diets; (b) there is an effect of route of TPN administration on lipid deposition in adipose tissues; and (c) infusion of a glucose/lipid TPN regimen at rates in excess of requirements for growth in rats promotes lipid deposition in adipose tissues rather than visceral tissues.

Animals↗
PubMed1996

Extended followup of the influence of wide excision of the neurovascular bundle(s) on prognosis in men with clinically localized prostate cancer and extensive capsular perforation.

PURPOSE: The effect of wide excision of the neurovascular bundles on disease-free survival was determined in men with clinically localized prostate cancer and pathological evidence of extensive capsular perforation in the region of the neurovascular bundle. MATERIALS AND METHODS: We previously analyzed 107 men with clinically localized prostate cancer and pathological evidence of extensive capsular perforation in the region of the neurovascular bundles. Wide excision of the neurovascular bundle on the sides of palpable induration resulted in negative surgical margins in 58% of patients compared to only 45% in whom the neurovascular bundles were left intact (p = 0.03). At a mean followup of 20 months, median interval to disease recurrence as defined by a measurable PSA level was 33 months in patients whose neurovascular bundle(s) were widely excised versus 22 months in those whose neurovascular bundle(s) were left intact (p = 0.03). However, by 43 months 75% of the patients in both groups had a detectable prostate specific antigen and the Kaplan-Meier curves had converged, suggesting that wide excision of the neurovascular bundle(s) did not confer a sustained survival advantage. RESULTS: With an additional followup of 28 months, the probability of having an undetectable prostate specific antigen level at 5 years was 47% in patients with negative versus 6% with positive surgical margins (p < 0.001). CONCLUSIONS: Our extended followup suggests that some patients with extensive capsular perforation can be rendered free of disease with wide excision of the neurovascular bundle(s).

Actuarial Analysis↗
PubMed1996

A seminar/case-based approach to teaching removable partial dentures to predoctoral students.

This article describes a seminar/case-based, instructional model designed to simulate removable partial denture (RPD) problem-solving and decision-making processes encountered in third-year clinic in dental school and in dental general practice. Groups of approximately 20 second-year students (in the 3-year program) meet in a series of six 1-hour seminars during the first days of the course. Following the seminars, students complete an exercise on mouth preparation and multiple clasp and major connector designs on prototype casts. This is followed by survey-design exercises on casts of dentitions representing six variations of RPD requirements. Instructors assist students during the practice phase of each class. Each 2-hour practice session is followed by a 1-hour practical examination. The last day of the course is devoted to a comprehensive final practical examination on both maxillary and mandibular casts, incorporating any of the design features previously studied.

Curriculum↗
PubMed1996

Diagnosis of acute flank pain: value of unenhanced helical CT.

OBJECTIVES: The purpose of our study was to determine the value of unenhanced CT in the diagnosis of acute flank pain. We determined the accuracy of unenhanced Ct for stone detection as well as the detection of abnormalities unrelated to stone disease. MATERIALS AND METHODS: During an 18-month interval, 292 patients with acute flank pain were imaged with unenhanced CT. Confirmation of the CT diagnosis was obtained for 210 patients: One hundred patients were proved to have ureteral stones based on other imaging studies (58 patients), lithotripsy (seven patients), ureteroscopic stone extraction (five patients), and stone recovery (30 patients). One hundred ten patients were proved not to have ureteral stones based on other imaging studies (24 patients), failure to recover a stone (56 patients), or a confirmed diagnosis unrelated to stone disease (30 patients). This latter group of 30 patients included diagnoses of adnexal masses (eight patients), appendicitis (five patients), diverticulitis (four patients), and common bile duct stones (three patients), as well as other diagnoses. RESULTS: Unenhanced CT findings were falsely negative for stone disease in three patients and falsely positive for stone disease in four patients. These data yield a sensitivity of 97%, a specificity of 96%, and an accuracy of 97% for diagnosing ureteral stone disease. Of 31 patients with a CT abnormality unrelated to stone disease, there was one false-negative diagnosis of acute appendicitis. CONCLUSION: Unenhanced CT is a valuable technique for examining patients with acute flank pain in whom a clinical diagnosis is uncertain. It can accurately determine the presence or absence of ureteral stones as well as extraurinary causes of acute flank pain. In most cases, other imaging studies are not required.

Acute Disease↗
PubMed1996

Acute ureteral obstruction: value of secondary signs of helical unenhanced CT.

OBJECTIVE: The purpose of our study was to determine the value of secondary signs of ureteral obstruction on helical unenhanced CT. MATERIALS AND METHODS: Over a 19-month interval, 312 patients with acute flank pain were imaged with helical unenhanced CT. Ureteral stone disease was confirmed to be present in 109 patients and confirmed to be absent in 111 patients Ninety-two remaining patients had no confirmatory imaging studies or surgery and were unable to be contacted for follow-up. For each of the 220 patients with a confirmed diagnosis, we determined the presence or absence of ureteral or collecting system dilatation, perinephric stranding, symmetry of renal size, and renal stones. In all patients with a ureteral stone, we noted the presence or absence of a circumferential rim of soft-tissue attenuation ("tissue-rim" sign) surrounding each stone and each phlebolith. RESULTS: The sensitivity of each secondary sign was ureteral dilatation, 90%; perinephric stranding, 82%; collecting system dilatation, 83%; and renal enlargement, 71%. The specificity of each secondary sign was ureteral dilatation, 93%; perinephric stranding, 93%; collecting system dilatation, 94%; and renal enlargement, 89%. Ureteral dilatation and perinephric stranding were both present or both absent in 181 of the 220 patients with a confirmed diagnosis. In this subgroup, this combination of signs had a positive predictive value of 99% and a negative predictive value of 95%. The odds ratio for the frequency of the tissue-rim sign with stones versus tissue-rim with phleboliths was 31:1. CONCLUSION: When using unenhanced CT to help diagnose acute flank pain, if one does not see a ureteral stone or does see an indeterminate but suspicious calcification, then secondary signs of obstruction are important for diagnosis. The results of this study form the basis of an imaging algorithm that can be used when interpreting unenhanced CT images of patients with acute flank pain.

Acute Disease↗
PubMed1996

Efficacy of risperidone in reducing positive and negative symptoms in medication-refractory schizophrenia: an open prospective study.

BACKGROUND: Although risperidone has been shown to be an effective antipsychotic medication in schizophrenia, the clinical studies performed for the Food and Drug Administration's approval process focused on only a mixed group of schizophrenic patients. Most of these studies did not directly address the efficacy of risperidone in chronic nonresponding schizophrenics. To better evaluate whether risperidone has a substantial degree of efficacy in schizophrenic non-responders, we conducted an open prospective study of risperidone in a sample of chronically hospitalized schizophrenic patients. METHOD: Twenty-five patients who met DSM-III-R criteria for schizophrenia or schizoaffective psychosis, who were chronically hospitalized at a tertiary care state facility, and who had not responded to conventional neuroleptics were evaluated before and during treatment with risperidone by using several standard rating scales and adjunctive assessments. RESULTS: Endpoint analysis showed that 36% (N = 9) of the patients were classified as responders on the basis of at least a 20% decrease in total Brief Psychiatric Rating Scale score at final evaluation. A higher percentage of patients were classified as responders when other rating scale criteria were used. Reductions in psychopathology scores were seen in scales reflecting positive symptoms but not in scores of negative symptoms. High baseline negative symptom scores were correlated with poorer response to risperidone as indicated by the decrease in positive symptom scores. CONCLUSION: This study offers evidence that risperidone may reduce positive symptoms of schizophrenia for a subgroup of chronically hospitalized schizophrenic patients who have not responded to conventional neuroleptics. The comparative evaluation of the efficacy of risperidone versus that of clozapine in these types of patients requires further study.

Adult↗
PubMed1995

Interactions between arachidonic acid and metabotropic glutamate receptors in the induction of synaptic potentiation in the rat hippocampal slice.

Perfusion of neither the metabotropic glutamate receptor agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), nor arachidonic acid caused any long-term enhancement of synaptic transmission in the CA1 region of the rat hippocampal slice. However, co-perfusion of ACPD (50 microM) and arachidonic acid (10 microM) for 5 min induced a rapidly evoked and long-lasting enhancement of synaptic transmission. This enhancement persisted in the presence of D(-)-2-amino-5-phosphonopentanoic acid (40 microM) and is therefore independent of NMDA receptor activation. The potentiation was mimicked by perfusion of the phospholipase A2 activator melittin (10 micrograms/ml) for 5 or 10 min, or exogenous phospholipase A2 (1 microgram/ml) for 5 min, immediately before ACPD application. We propose a role for arachidonic acid in the induction of synaptic potentiation, possibly as a retrograde transmitter substance.

Animals↗