Biomedical subjects

W T Ambrosius

Publications and source records attributed to W T Ambrosius.

35 records · Page 2Linked to original sources

PubMed1999

Levels of mineralocorticoids in whites and blacks.

Blacks appear, on average, to retain more Na than whites. A higher production rate of mineralocorticoids could explain the greater Na retention in blacks. Although production of aldosterone has been shown to be lower in blacks, the level of another mineralocorticoid may be increased. Plasma levels of deoxycorticosterone and cortisol were measured in young whites (n=23; age=16.4+/-3.1[SD] years) and young blacks (n=25; age=13.8+/-1.3 years). Blacks had lower plasma levels of renin activity and aldosterone and lower urinary aldosterone excretion rates; thus, they appeared to be representative of blacks that retain additional Na. Plasma deoxycorticosterone levels were lower in blacks than in whites both at baseline (247+/-161 versus 381+/-270 pmol/L, P=0.048) and after stimulation with adrenocorticotropic hormone (822+/-294 versus 1127+/-628 pmol/L at 30 minutes, P=0.047; 925+/-366 versus 1440+/-834 pmol/L at 60 minutes, P=0.013). Cortisol levels were also lower in blacks at baseline (P=0.014) but were not significantly different from levels in whites after stimulation with adrenocorticotropic hormone. In a larger cohort of 407 whites (age=12.0+/-2.9 years) and 247 blacks (age=12.9+/-3.1 years), 18-hydroxycortisol excretion rates were also lower in blacks (P=0. 021). In conclusion, increased Na retention in blacks does not appear to be secondary to increased production of either aldosterone, deoxycorticosterone, cortisol, or 18-hydroxycortisol. A primary renal mechanism may mediate the increase in Na reabsorption in blacks.

Adolescent↗

PubMed1999

Genetic variants in the epithelial sodium channel in relation to aldosterone and potassium excretion and risk for hypertension.

Renin and aldosterone secretion is often lower in blacks than in whites, characteristics that resemble a milder form of Liddle syndrome in which a mutation in the amiloride-sensitive epithelial sodium channel (ENaC) of the kidney results in enhanced resorption of sodium. In the present study, we looked for evidence that the intrinsic level of ENaC activity is indeed higher in blacks than in whites. In overnight urine samples collected from young people (249 white and 181 black subjects, mean age 13.4 years), the urinary aldosterone/potassium ratio, which is typically very low in Liddle syndrome, was lower in blacks than in whites: 0.421+/-0.024 (mean+/-SE) versus 0.582+/-0.016 nmol/mmol (P<0.0001). In addition, all but 1 of 5 molecular variants in ENaC were much more common in blacks than in whites. G442V in the beta-subunit, present in 16% of the blacks and in only 1 white, was associated with parameters reflective of a greater Na retention and potentially a higher ENaC activity: a lower plasma aldosterone concentration (P=0.070), a lower urinary aldosterone excretion rate (P=0.052), a higher potassium excretion rate (P=0.048), and a lower urinary aldosterone/potassium ratio (P=0.027). In a second cohort consisting of 126 black and 161 white normotensive subjects and 232 black and 188 white hypertensive subjects, betaG442V did not show a significant association with hypertension (P=0.089). On the other hand, a variant that was twice as common in whites, alphaT663A, was associated with being normotensive both in blacks (P=0.018) and in whites (P=0.034). Expression of either betaG442V or alphaT663A in Xenopus oocytes did not result in a change in basal Na current, consistent with the variants being in linkage disequilibrium with alleles at active loci. In conclusion, several lines of evidence are presented to suggest that ENaC activity is higher in blacks than in whites, which could contribute to racial differences in Na retention and the risk for hypertension.

Adolescent↗

PubMed1998

Comparison of treatment of tardive dystonia and idiopathic cervical dystonia with botulinum toxin type A.

To compare clinical parameters of patients treated with botulinum toxin type A (BTX) for treatment of idiopathic cervical dystonia (ICD) and for tardive cervical dystonia (TCD), we studied 156 patients (149 with ICD and 7 with TCD) who were treated with serial injections of BTX over 5 years. We hypothesized that patients with TCD and ICD would demonstrate similar improvement in severity scores after treatment with BTX. The diagnosis, dates, dosages, and frequency of BTX injected and severity assessments were recorded into a computerized database. Nonparametric Wilcoxon rank sum and signed-rank tests were used to assess statistical significance. The change in severity scores between the first treatment and last treatment in both groups was not statistically significant (p = 0.4859), indicating similar improvement. The difference in BTX doses was significant (p = 0.0045). ICD patients (n = 149) received an average of 219.8 +/- 63.5 units and those with TCD (n = 7) were treated with an average dose of 287.4 +/- 60.3 units. The average number of days between treatments for individuals with ICD was 142.9 +/- 85.8, similar to that for persons with TCD (144.7 +/- 64.5) (p = 0.6075). Our analysis provides preliminary evidence that the improvement from the administration of BTX for patients with ICD and TCD is similar.

Adult↗

PubMed1998

Objective measurement of motion in patients undergoing spiral CT examinations.

PURPOSE: To develop and evaluate an objective measurement of patient motion during spiral computed tomography (CT). MATERIALS AND METHODS: An acrylic rod was attached along the length of the torso in 109 patients (56 women, 53 men; age range, 21-79 years; mean age, 51 years) who underwent abdominal spiral CT examinations. Subjective evaluation of motion was graded on a five-point scale by two radiologists. Objective measurements of motion were determined by means of computer reconstruction of the rod in three dimensions and calculation of the deviation of the rod from its estimated position in the motionless state with time. RESULTS: Complete data were available in 98 patients. Subjective and objective measurements of patient motion showed a moderately high Spearman correlation coefficient of .49 (P < .001). The correlation between either observer and objective measurements was similar to the correlation between one observer and the other. CONCLUSION: This objective technique for assessing patient motion correlated well with subjective methods and may be useful in evaluating scanning parameters that may affect patient motion and hence scan quality.

Artifacts↗

PubMed1998

Spiral CT with ionic and nonionic contrast material: evaluation of patient motion and scan quality.

PURPOSE: To assess the effect of rapidly injected ionic or nonionic contrast material on patient motion and scan quality in spiral computed tomography (CT). MATERIALS AND METHODS: One hundred nine patients were prospectively, randomly chosen to receive ionic or nonionic contrast material. An acrylic rod was attached to the anterior abdomen with tape, which allowed an objective measurement of motion. Abdominal spiral CT was performed after intravenous injection of contrast material at a rate of 0.9 g of iodine per second. Scans were evaluated subjectively and objectively for motion and subjectively for quality. Complete data were available in 98 patients (47 in the ionic and 51 in the nonionic group). RESULTS: The acrylic rod moved an average of 0.44 mm per section in the nonionic group and 0.71 mm per section in the ionic group. Both subjective and objective measurements showed a statistically significant difference in patient motion. Use of nonionic contrast material resulted in less patient motion. Scan quality was better with nonionic contrast material. CONCLUSION: Less patient motion occurs and scan quality improves when spiral CT is performed with nonionic contrast material.

Artifacts↗

PubMed1998

Possible pulmonary embolus: evaluation with digital subtraction versus cut-film angiography--prospective study in 80 patients.

PURPOSE: To determine whether intraarterial digital subtraction angiography (DSA) is as accurate as cut-film (film hard-copy) angiography (CFA) in the evaluation of suspected pulmonary embolus. MATERIALS AND METHODS: Under a protocol approved by the institutional review board, CFA and DSA images were obtained in identical posteroanterior and oblique projections in one lung of each patient undergoing pulmonary angiography (n = 80). Diagnoses based on results of blinded review of each study (CFA vs DSA) by three separate reviewers (80 patients x three reviewers = 240 diagnoses for each modality) were compared with the diagnoses made by the physician who performed the procedure on the basis of CFA, DSA, and clinical data and with the consensus diagnoses obtained by means of group review of both studies together if necessary. The reviewers' confidence in their diagnoses was graded from 1 (certain) to 10 (uncertain). RESULTS: Pulmonary emboli were present in 13 (16%) of 80 patients. Two hundred thirty-six (98.3%) of 240 DSA diagnoses and 231 (96.3%) of 240 CFA diagnoses were correct. The sensitivity (correct identification of emboli by all three reviewers) of DSA was 92% and of CFA was 69% (P = .083). The specificities of the modalities were not statistically significantly different. The reviewers' confidence was significantly better in their DSA diagnoses than in their CFA diagnoses (P < .004). CONCLUSION: DSA allows more confident detection of pulmonary embolus than does CFA, with no loss in diagnostic accuracy.

Adult↗

PubMed1998

Tunneled hemodialysis catheters: use of a silver-coated catheter for prevention of infection--a randomized study.

PURPOSE: To determine whether silver-coated tunneled hemodialysis catheters reduce infection and to determine the frequency of central venous thrombosis and stenosis with percutaneous placement of right internal jugular vein dialysis catheters by interventional radiologists. MATERIALS AND METHODS: Ninety-one patients were randomly assigned to a treatment (silver-coated catheter; n = 47) or control (identical catheter without silver coating; n = 44) arm. Baseline venography was performed. Catheter tips were cultured and venography was repeated at catheter removal. RESULTS: Mean duration of catheter placement was 92 days. Infection occurred in 11 patients (five in the treatment group, six in the control group). Tip cultures in 15 patients (eight treatment, seven control) were positive without clinical infection. Infection and colonization rates were slightly but not significantly higher in the treatment group than in the control group. Silver-coated catheters in two (4%) patients were removed due to reaction to the coating. Completion venograms (n = 72) showed new minor abnormalities in four (6%) patients and major abnormalities (stenosis, thrombosis) in three (4%) patients. Permanent venous abnormalities occurred in two (3%) patients. CONCLUSION: Silver coating does not confer a benefit against clinical infection or colonization. Interventional radiologic placement of tunneled dialysis catheters yields a low frequency of permanent central venous thrombosis and stenosis.

Bacteria↗

PubMed1998

Relation of race, age, and sex hormone differences to serum leptin concentrations in children and adolescents.

We explored the effects of race, age, and sex hormones on the serum leptin concentrations in 203 white and 88 black children and adolescents (ages 9.3-20.5 years). A significant sex by race interaction on serum leptin levels (p = 0.0301) was observed with lower serum leptin concentrations, adjusted for subscapular thickness and age, in black boys than in white boys. Girls had serum leptin levels that were on average 2.15 times those of boys (p < 0.0001). There was an age by sex interaction (p < 0.0001) with serum leptin concentrations decreasing in boys but not in girls with age. A strongly inverse relationship of serum testosterone levels with serum leptin levels in boys (p = 0.0067) appeared to explain this effect of age. In conclusion, the serum leptin concentration is slightly lower in black boys. A higher testosterone level in boys appears to account for an age-related decline in serum leptin in boys and the overall lower levels in boys than in girls.

Adolescent↗

PubMed1998

Serum angiotensinogen concentration in relation to gonadal hormones, body size, and genotype in growing young people.

Multiple factors are thought to influence the level of circulating angiotensinogen (AGT). We showed previously that the serum AGT concentration was significantly related to body mass index (BMI) in a cohort of young people. In the present study, we studied whether levels of the gonadal hormones estradiol and testosterone might also predict the AGT level and might contribute to the BMI effect, since both the production of these hormones and BMI increase with age. In boys (n=127; mean+/-SD age, 14.7+/-1.9 years) and girls (n=104; age, 14.8+/-1.9 years) studied as a single group, we found a significant association of AGT level with level of estradiol (P=0.015) after adjustment for haplotype, age, race, testosterone concentration, and BMI. In girls studied alone, the level of AGT showed a significantly positive relation to level of testosterone (P=0.043), possibly a result of peripheral conversion of testosterone to estradiol, after adjustment for haplotype, age, race, estradiol concentration, and BMI. In boys, on the other hand, the level of testosterone was inversely related to AGT concentration (P=0.019), again after making adjustments for the other variables. Finally, in pairs of subjects matched for BMI, age, race, and gender where 1 member of each pair had either 1 or 2 copies of an AGT gene haplotype (T235 and -1074t) and the other member had no copy, the level of AGT was higher in the carrier of a haplotype in 24 of the 34 pairs (P<0.001). In conclusion, gonadal hormones are an additional influence on the circulating level of AGT in growing young people. In addition, with matching for BMI and other covariates, there is a strong association of AGT genotype with the serum level of AGT, emphasizing the importance of AGT gene expression as a determinant of the circulating level of AGT.

Adolescent↗

PubMed1997

Mild renal pelvic dilatation is not predictive of vesicoureteral reflux in children.

OBJECTIVE: To determine if mild renal pelvic dilatation at renal ultrasound (RUS) is a reliable sign of vesicoureteral reflux (VUR) at voiding cystourethrogram (VCUG) in children. MATERIALS AND METHODS: All patients less than 10 years of age who had RUS and VCUG on the same day during a 2-year period were identified in a computerized database. The appearance of the collecting system of each kidney was classified into two groups: group 0 - no dilatation (</= 2-mm anteroposterior diameter of the renal pelvis) and group 1 - 3 to 10-mm AP diameter of the renal pelvis without caliectasis. VUR at VCUG was graded using the International Reflux Study Committee system. RESULTS: Four hundred fifty-five patients (76 boys; 379 girls) with 910 kidneys were included. VUR occurred in 268 kidneys in 174 patients. There were 820 group 0 kidneys and 90 group 1 kidneys. Kidneys classified as group 1 (25.0 % had reflux) were no more likely to have reflux than were kidneys with nondistended (group 0) collecting systems (31.2 % had reflux). There was no statistical difference in the rate of reflux in patients with group 1 renal pelvic distention (39.2 % refluxed) and a normal collecting system (33.3 % refluxed) (P = 0.365). CONCLUSION: The frequency of vesicoureteral reflux in children with mild renal pelvic distention is not significantly different than in children with no distention. Therefore, mild dilatation of the renal pelvis should not be considered an indication for voiding cystourethrography.

Child↗

PubMed1997

Sustained relief of oral aphthous ulcer pain from topical diclofenac in hyaluronan: a randomized, double-blind clinical trial.

OBJECTIVES: The purpose of this study was to test the hypothesis that topically applied 3% diclofenac in 2.5% hyaluronan reduces aphthous ulcer pain. STUDY DESIGN: A randomized, double-blind, single dose study of 60 healthy adults with aphthous ulcers in three treatment groups--3% diclofenac in 2.5% hyaluronan, 2.5% hyaluronan, 3% viscous lidocaine--was undertaken. Visual analogue scale pain scores were obtained before and after gel application and hourly, for up to 8 hours after gel application. Statistical analysis was performed with repeated measures ANOVA with square root transformation and Bonferroni correction. RESULTS: A 48% overall reduction in pain (p < 0.01) was observed 10 minutes after gel application; however, no significant difference was found between the three topical agents. A 35% to 52% pain reduction (p < 0.01) was reported 2 to 6 hours after the application of diclofenac in hyaluronan, whereas hyaluronan gel alone and viscous lidocaine failed to produce significant VAS reductions. CONCLUSIONS: A dose of 3% diclofenac in 2.5% hyaluronan is an effective and novel treatment for this common, painful disorder.

Administration, Topical↗

PubMed1997

Effect of administered potassium on the renin-aldosterone axis in young blacks compared with whites.

BACKGROUND: We had observed previously that the aldosterone excretion rate and plasma aldosterone concentration were lower for black children than they were for white children. We did not know whether this was secondary to a lower intake of potassium or to suppression of the renin-angiotensin system in blacks. OBJECTIVE: To test the hypothesis that the secretion of aldosterone in response to potassium would be different in blacks than in a control group of whites. DESIGN: Black and white subjects were selected on the basis of their having aldosterone excretion rates that were in the lowest quartile for the entire original cohort. Since the blacks typically had lower aldosterone excretion rates than did the whites, the black participants were represented primarily by those with average rates of aldosterone production among blacks, whereas the whites were represented by those with the lowest aldosterone production rates among whites. The protocol consisted of a placebo-controlled, randomized cross-over study design. METHODS: Twelve blacks and 12 whites, aged 14.1 +/- 1.6 (mean +/- SD) and 15.4 +/- 2.1 years, respectively, were allocated randomly to double-blind treatment either with placebo or with 40 mmol/day potassium chloride for 7 days and then the alternate treatment Measurements of the plasma renin activity (PRA), plasma aldosterone concentration, and urinary aldosterone excretion were performed in an inpatient research unit at the end of the treatment. The blood pressure was monitored for 24 h. RESULTS: Treatment with potassium increased the plasma aldosterone concentration (P = 0.0006) and the urinary excretion of aldosterone (P = 0.0002) significantly both for blacks and for whites. There was no significant racial difference in the response to potassium. The PRA was overall 1.605-fold lower in the blacks than it was in the whites (P = 0.0124). The lowest PRA levels, such as those in the blacks when they were supine, tended to be increased with the potassium treatment. The blood pressure did not change significantly with the potassium supplement for either racial group. CONCLUSIONS: After we had supplemented the intake of potassium, aldosterone production increased in the blacks and in the control group of whites to the same extent The potassium treatment appeared to increase lower PRA levels. A lower intake of potassium could at least partially account for the suppression of the renin-aldosterone system in blacks.

Adolescent↗

PubMed1997

Outcome of tunneled hemodialysis catheters placed via the right internal jugular vein by interventional radiologists.

PURPOSE: To assess the outcome of interventional radiologic placement of tunneled hemodialysis catheters via the right internal jugular vein. MATERIALS AND METHODS: In 194 patients, the catheter was placed via the right internal jugular vein unless thrombosis was present. Real-time ultrasound-guided puncture and fluoroscopic guidance were used. Patients were followed up until catheter removal or death. Outcomes evaluated included infection, thrombosis, and catheter malfunction. RESULTS: In 175 patients, 250 consecutive catheters were placed via the right internal jugular vein with 100% success. All catheters functioned immediately after placement. Procedural complications were limited to clinically unimportant air embolus (n = 2). No instances of pneumothorax, hemothorax, or substantial bleeding complications occurred. Follow-up was available in 173 (99%) patients. Mean and median "catheter duration" were 87 and 56 days, respectively. Catheter-related symptomatic venous thrombosis or stenosis was not observed. The rate of infection was 0.08 per 100 catheter days, and the rate of malfunction that necessitated removal was 0.22 per 100 catheter days. Definite or possible catheter thrombosis that necessitated removal occurred at a rate of 0.16 per 100 catheter days. CONCLUSION: Interventional radiologic placement of tunneled hemodialysis catheters via the right internal jugular vein showed equal or better long-term results than those reported for surgical placement. Interventional radiologic placement should be the method of choice.

Catheterization↗

PubMed1997

Association of the angiotensinogen gene to serum angiotensinogen in blacks and whites.

A variant of the angiotensinogen gene (AGT) that encodes for threonine at codon 235 (T235) has been associated with a higher serum angiotensinogen concentration and with hypertension in white subjects. The frequency of T235 is about two times higher in blacks than whites, suggesting that AGT may contribute to the susceptibility to hypertension in blacks more than it does in whites. However, an association of T235 with angiotensinogen level or blood pressure has not been observed in blacks, possibly because the high prevalence of T235 makes it insufficiently informative as a marker. For this reason, we undertook to further differentiate the T235 carrier state by constructing haplotypes with alleles in the 5' upstream region of AGT. One such haplotype, -1074t;T235, showed a significant association with angiotensinogen level in a cohort of black and white children and adolescents (76 blacks, mean age = 12.3 +/- 2.0 [SD] years; 139 whites, mean age = 12.4 +/- 1.8 years). With a linear regression model, the level of serum angiotensinogen was significantly related to body mass index (P = .0017) and the haplotype (P = .0001). Within specific race groups, the haplotype was significantly related to serum angiotensinogen in both the blacks (P = .0277) and whites (P = .0001). The mean level of angiotensinogen was higher in the blacks carrying a single copy of the haplotype than in those without the haplotype (1472.2 +/- 68.4 versus 1274.9 +/- 46.7 nmol angiotensin I/L), a difference that was marginally significant (P = .0609). In the whites, the level of angiotensinogen was also higher in carriers of a single copy than in those with no copy (1527.9 +/- 71.2 versus 1099.2 +/- 20.1 nmol angiotensin I/L) (P = .0003). Serum angiotensinogen level did not increase with two copies of the haplotype, but in each racial group, there were only four individuals who were homozygous. The haplotype showed a marginally significant relation (P = .0757) to the mean of longitudinally determined diastolic pressures adjusted for body mass index, race, sex, and age. In summary, using a haplotype to differentiate further the T235 carrier state, we observed an association of genotype with serum angiotensinogen level and blood pressure in blacks and whites. The findings suggest that AGT may play an important role in blood pressure regulation in both racial groups.

Adolescent↗

PubMedDate not supplied

Abdominal and pelvic needle aspiration biopsies: can we perform them well when using small needles?

BACKGROUND: The aim of this study was to compare abdominal fine-needle aspirations (FNAs) performed with large (>/=20-gauge) or small (</=21-gauge) needles for diagnostic rate, number of samples required for diagnosis, diagnostic accuracy, and complication rates. METHODS: Abdominal and pelvic FNA procedures were retrospectively reviewed. Needle size, imaging guidance used, number of pathology slides created, complications, and cytologic and final diagnoses were obtained by reviewing radiologic, medical, and cytology records. RESULTS: Two hundred ninety procedures were included in the study. Two hundred fifty-seven were performed in patients having only one biopsy during the study interval. Of these, 159 had biopsies using small needles and 98 using large needles. Small needle biopsies had as high a diagnostic rate as did large needle biopsies (97.5% vs. 92. 9%, p = 0.11). Small and large needle biopsies showed high diagnostic accuracy (96.1 and 98.9%, respectively; p = 0.27). Incorrect cytologic diagnoses plus nondiagnostic examinations composed 6.3% of biopsies using small needles and 8.2% of biopsies using larger needles (p = 0.62). Complication rates were low. Average number of needle passes tended to be lower when small needles were used. CONCLUSION: Small needles can be successfully used for abdominal and pelvic FNAs. Small needles require the same or fewer needle passes, have low risk, have the same or improved ability to obtain diagnostic material, and achieve correct diagnoses compared with larger needles.

Abdomen↗

PubMedDate not supplied

Comparison of digital subtraction and cut film arteriography in the evaluation of suspected thoracic aortic injury.

PURPOSE: To determine whether intraarterial digital subtraction arteriography (DSA) is as sensitive and specific as cut film arteriography (CFA) in the evaluation of suspected aortic injury resulting from blunt chest trauma. MATERIALS AND METHODS: Both CFA and DSA images of the thoracic aorta were obtained in the right posterior oblique (RPO) projection in 100 of 103 consecutive patients undergoing arteriography after blunt chest trauma. Diagnoses based on blinded separate review of both studies (CFA vs DSA) by four independent reviewers were compared. Reviewers graded their confidence in their diagnoses from 1 (certain) to 10 (uncertain). RESULTS: Eleven of 100 patients had aortic or great vessel injuries confirmed by operation (n = 10) or transesophageal echocardiography (n = 1). Three hundred eighty-eight of 400 diagnoses based on RPO CFA and 390 of 400 diagnoses based on RPO DSA agreed with the correct diagnoses. The sensitivity, specificity, and diagnostic accuracy of CFA versus DSA were not significantly different. The reviewers' confidence in their diagnoses was equivalent between CFA (average confidence score, 1.373) and DSA (average confidence score, 1.375). CONCLUSION: DSA and CFA yield equivalent sensitivity, specificity, and diagnostic accuracy in the evaluation of blunt chest trauma.

Adolescent↗

PubMedDate not supplied

Rates of change in measures of body size vary by ethnicity and gender.

Obesity, a major risk factor for a variety of diseases, is more common in Blacks than in Whites. In the current study, a cohort of young Blacks and Whites was followed longitudinally to determine rates of change in body mass index (BMI) and subscapular and triceps skinfold thickness from the ages of 5 to 25 years. A significant difference in the rate of change of BMI (P<.0001) between Blacks and Whites was observed with Blacks gaining at a faster rate. The rate of increase of subscapular (P<.0001) and triceps fat (P<.0001) was significantly higher in the girls than in the boys. We also examined for differences by household income and maternal education level. Children from poorer families had more fat (P<.01 for all three outcomes), whereas education level was not related to the amount of body fat. Differences in the prevalence of obesity between Blacks and Whites and between males and females that manifest during adulthood appear to begin in childhood. The results re-emphasize the important need for early intervention in weight control measures.

Adolescent↗