Diffuse idiopathic skeletal hyperostosis as a cause for dysphagia in a patient with ankylosing spondylitis

BACKGROUND

Diffuse idiopathic skeletal hyperostosis (DISH) is characterized by ankylosing spinal alterations which are often asymptomatic but may typically cause back pain and spinal stiffness. Presence of DISH may complicate spinal trauma and lead to unstable fractures requiring surgical intervention. Treatment options include physical activity, symptomatic treatment, local heat application, and optimization of metabolic comorbidities.

CASE

A multimorbid older patient was admitted to the gastroenterological ward for the investigation of progressive dysphagia and weight loss. Gastroscopy revealed a dorsal impression of the esophagus at 25 cm from the incisor. Clinical work-up including computed tomography (CT) and magnetic resonance imaging (MRI) ruled out malignancy but showed ankylosing spondylophytes and non-recent fractures of vertebrae C5-C7, compatible with DISH of the cervicothoracic spine as a cause for the esophageal impression. Notably, imaging diagnostics showed ankylosing spine alterations extending to the lumbar spine and both sacroiliac joints, suggestive of ankylosing spondylitis (AS). Typical imaging characteristics, a history of psoriasis, and positive HLA*B27 status supported the diagnosis of underlying AS in this patient with dysphagia as an unusual primary symptom of DISH. Additionally, pulmonary alterations compatible with a usual interstitial pneumonia (UIP)-like pattern were seen on lung CT.

CONCLUSION

Overlaps among AS, DISH and pulmonary abnormalities including UIP have been described previously; however, they represent unexpected findings in this older patient. This case underlines the importance of interdisciplinary collaboration and consideration of DISH as a differential diagnosis in patients with atypical symptoms.

Abscess penetration of cefpirome: concentrations and simulated pharmacokinetic profiles in pus

PURPOSE

Abscess patients frequently receive antibiotic therapy when incision cannot be performed or in addition to incision. However, antibiotic concentrations in human abscesses are widely unknown.

METHODS

Pharmacokinetics of cefpirome in 12 human abscesses located in different body regions was studied. Cefpirome (2 g) was administered as an intravenous short infusion, and concentrations were measured in plasma over an 8-h period and in abscesses at incision. A pharmacokinetic two-stage model was applied.

RESULTS

At abscess incision performed 158 ± 112 min after the start of the infusion, the cefpirome concentrations in the abscess fluid varied markedly, ranging from ≤0.1 (limit of quantification) to 47 (mean 8.4 ± 14.1 ) mg/L. Cefpirome was detectable in nine of 12 abscesses. Maximum concentrations were calculated to be 183 ± 106 mg/L in plasma and 12 ± 16 mg/L in the abscess. A cefpirome concentration of 2 mg/L, which is the minimum concentration inhibiting growth of 90% of the most relevant bacterial pathogens, was exceeded spontaneously in six of 12 abscesses after a single dose. Cefpirome concentrations in the abscess did not correlate with either the pH or the ratio of surface area to volume of the abscesses, nor with plasma pharmacokinetics.

CONCLUSIONS

Cefpirome may be useful to treat abscess patients because it was detectable in most abscesses after a single dose. However, the penetration of cefpirome into abscesses is extremely variable and cannot be predicted by measuring other available covariates.

Good penetration of moxifloxacin into human abscesses

Abscesses are often treated with antibiotics in addition to incision or when incision is unfeasible, but accurate information about antibiotic abscess penetration in humans is missing. This study aimed at evaluating the penetration of moxifloxacin into human abscesses. After administration of a single dose of 400 mg moxifloxacin, drug concentrations were measured in 10 differently located abscesses at incision, and in plasma over 8 h. At incision performed 0.9-4.8 h after administration, moxifloxacin concentrations in abscesses ranged from ≤0.01 to 9.2 mg/l (1.9 ± 3.4 mg/l), indicating pronounced drug accumulation in some abscesses. The degree of abscess penetration could not be explained by covariates like the ratio of surface area to volume or pH of abscesses, or by moxifloxacin plasma concentrations. Concluding, moxifloxacin was detectable in most abscesses and may be a useful antibiotic for this indication. However, antibiotic abscess penetration was highly variable and unpredictable, suggesting surgical abscess incision whenever possible.

Agreement of duplex ultrasonography vs. computed tomography angiography for evaluation of native and in-stent SFA re-stenosis--findings from a randomized controlled trial

BACKGROUND

Multidetector CT angiography (CTA) is a non-invasive imaging technique for evaluation of peripheral vascular disease. CTA might be particularly useful for assessment of intermediate- and long-term morphological outcome after endovascular treatment. Validation of CTA vs. the current imaging standard, colour Doppler ultrasonography (CDUS), for quantification of native and in-stent re-stenosis in the superficial femoral artery (SFA) is required.

METHODS

Seventy randomized patients who underwent stent implantation (n=47) or balloon angioplasty (n=23) underwent 6-month follow-up with CDUS and CTA. CTA was compared with CDUS in both sub-groups of patients in terms of binary re-stenosis (>50% lumen narrowing) and re-occlusion. Agreement between CTA and CDUS was assessed using Kappa (κ) statistics with 95% confidence intervals, and correlation coefficients.

RESULTS

Binary re-stenosis was detected in 16/70 (22.9%) patients by CTA and 17/70 (24.3%) patients by CDUS (κ=0.88, 95% CI: 0.80-0.96). Re-stenosis rates after balloon angioplasty were 39.1% (9/23) on CTA and CDUS (κ=0.82, 95% CI: 0.66-0.98), and after stent implantation 14.9% (7/47) on CTA and 17.0% (8/47) on CDUS (κ=0.92, 95% CI: 0.84-1.00). Re-occlusions were detected in 3/70 (4.3%) patients by both CTA and CDUS (κ=0.65; 95% CI 0.54-0.76). Significant correlations (r=0.85, p<0.001) were noted between degree of re-stenosis on CTA and peak velocity ratio on CDUS. The correlation coefficient was higher in patients after balloon angioplasty (r=0.94, p<0.001) than in patients after stent implantation (r=0.71, p<0.001).

CONCLUSION

CTA and CDUS show excellent agreement for evaluation of native and in-stent re-stenosis after endovascular treatment of SFA obstructions. CTA is an appropriate non-invasive imaging modality for follow-up after endovascular therapy.

Improved detection of in-stent restenosis by blood pool agent-enhanced, high-resolution, steady-state magnetic resonance angiography

OBJECTIVE

The aim of this study was to assess whether visualisation of in-stent changes can be improved with high-resolution, steady-state, blood pool contrast-enhanced MR angiography compared with first-pass MR angiography. Intra-arterial digital subtraction angiography (DSA) served as the reference standard.

METHODS

Twenty patients after stent placement in the superficial femoral artery (SFA) underwent MRA prior to reintervention. MRA of the SFA includes first-pass MRA as well as 3D high-resolution MRA in the steady state (SS-MRA) after injection of Gadofosveset trisodium. Sensitivity and specificity values for the detection of significant in-stent lesions by means of SS-MRA were calculated at the proximal, middle and distal stent segments in comparison to DSA. Kappa statistics were used to determine agreement between the two techniques.

RESULTS

Sensitivity and specificity values for the detection of significant stenosis with SS-MRA reached 95% in the proximal, 100% in the middle and 100% in the distal stent segment. Kappa coefficients between SS-MRA and DSA were 0.789, 0.797 and 0.859 for the proximal, middle and distal segments, whereas the Kappa coefficients for FP-MRA were 0,211, 0,200 and 0,594 in these segments, respectively.

CONCLUSION

Detection of in stent stenosis is significantly improved using SS MRA, in comparison to state-of-the-art FP-MRA.

Prospective randomized study of doxorubicin-eluting-bead embolization in the treatment of hepatocellular carcinoma: results of the PRECISION V study

Transcatheter arterial chemoembolization (TACE) offers a survival benefit to patients with intermediate hepatocellular carcinoma (HCC). A widely accepted TACE regimen includes administration of doxorubicin-oil emulsion followed by gelatine sponge-conventional TACE. Recently, a drug-eluting bead (DC Bead) has been developed to enhance tumor drug delivery and reduce systemic availability. This randomized trial compares conventional TACE (cTACE) with TACE with DC Bead for the treatment of cirrhotic patients with HCC. Two hundred twelve patients with Child-Pugh A/B cirrhosis and large and/or multinodular, unresectable, N0, M0 HCCs were randomized to receive TACE with DC Bead loaded with doxorubicin or cTACE with doxorubicin. Randomization was stratified according to Child-Pugh status (A/B), performance status (ECOG 0/1), bilobar disease (yes/no), and prior curative treatment (yes/no). The primary endpoint was tumor response (EASL) at 6 months following independent, blinded review of MRI studies. The drug-eluting bead group showed higher rates of complete response, objective response, and disease control compared with the cTACE group (27% vs. 22%, 52% vs. 44%, and 63% vs. 52%, respectively). The hypothesis of superiority was not met (one-sided P = 0.11). However, patients with Child-Pugh B, ECOG 1, bilobar disease, and recurrent disease showed a significant increase in objective response (P = 0.038) compared to cTACE. DC Bead was associated with improved tolerability, with a significant reduction in serious liver toxicity (P < 0.001) and a significantly lower rate of doxorubicin-related side effects (P = 0.0001). TACE with DC Bead and doxorubicin is safe and effective in the treatment of HCC and offers a benefit to patients with more advanced disease.

Prospective randomized study of doxorubicin-eluting-bead embolization in the treatment of hepatocellular carcinoma: results of the PRECISION V study

Transcatheter arterial chemoembolization (TACE) offers a survival benefit to patients with intermediate hepatocellular carcinoma (HCC). A widely accepted TACE regimen includes administration of doxorubicin-oil emulsion followed by gelatine sponge-conventional TACE. Recently, a drug-eluting bead (DC Bead) has been developed to enhance tumor drug delivery and reduce systemic availability. This randomized trial compares conventional TACE (cTACE) with TACE with DC Bead for the treatment of cirrhotic patients with HCC. Two hundred twelve patients with Child-Pugh A/B cirrhosis and large and/or multinodular, unresectable, N0, M0 HCCs were randomized to receive TACE with DC Bead loaded with doxorubicin or cTACE with doxorubicin. Randomization was stratified according to Child-Pugh status (A/B), performance status (ECOG 0/1), bilobar disease (yes/no), and prior curative treatment (yes/no). The primary endpoint was tumor response (EASL) at 6 months following independent, blinded review of MRI studies. The drug-eluting bead group showed higher rates of complete response, objective response, and disease control compared with the cTACE group (27% vs. 22%, 52% vs. 44%, and 63% vs. 52%, respectively). The hypothesis of superiority was not met (one-sided P = 0.11). However, patients with Child-Pugh B, ECOG 1, bilobar disease, and recurrent disease showed a significant increase in objective response (P = 0.038) compared to cTACE. DC Bead was associated with improved tolerability, with a significant reduction in serious liver toxicity (P < 0.001) and a significantly lower rate of doxorubicin-related side effects (P = 0.0001). TACE with DC Bead and doxorubicin is safe and effective in the treatment of HCC and offers a benefit to patients with more advanced disease.

In vitro imaging of coronary artery stents: Are there differences between 16- and 64-slice CT scanners?

PURPOSE

To compare the performance of 64-slice with 16-slice CT scanners for the in vitro evaluation of coronary artery stents.

METHODS AND MATERIALS

Twelve different coronary artery stents were placed in the drillings of a combined heart and chest phantom, which was scanned with a 16- and 64-slice CT scanner. Coronal reformations were evaluated for artificial lumen narrowing, intraluminal attenuation values, and false widening of the outer stent diameter as an indicator of artifacts outside the stent.

RESULTS

Mean artificial lumen narrowing was not significantly different between the 16- and 64-slice CT scanner (44% versus 39%; p=0.408). The differences between the Hounsfield Units (HU) measurements inside and outside the stents were significantly lower (p=0.001) with 64- compared to 16-slice CT. The standard deviation of the HU measurements inside the stents was significantly (p=0.002) lower with 64- than with 16-slice CT. Artifacts outside the stents were not significantly different between the scanners (p=0.866).

CONCLUSION

Visualization of the in-stent lumen is improved with 64-slice CT when compared with 16-slice CT as quantified by significantly lesser intraluminal image noise and less artificial rise in intraluminal HU measurement, which is the most important parameter for the evaluation of stent patency in vivo.

Image Quality, lesion detection, and diagnostic efficacy in digital mammography: Full-field digital mammography versus computed radiography-based mammography using digital storage phosphor plates

OBJECTIVE

To compare image quality, the lesion detection, and the diagnostic efficacy of full-field digital mammography (FFDM) and computed radiography-based mammography using digital storage phosphor plates (DSPM) in the evaluation of breast lesions.

MATERIALS AND METHODS

In this prospective study, 150 patients with suspicious breast lesions underwent FFDM and DSPM. Nine aspects of image quality (brightness, contrast, sharpness, noise, artifacts, and the detection of anatomic structures, i.e., skin, retromamillary space, glandular tissue, and calcifications) were evaluated by five radiologists. In addition, the detection of breast lesions and the diagnostic efficacy, based on the BI-RADS classification, were evaluated with histologic and follow-up correlation.

RESULTS

For contrast, sharpness, and the detection of all anatomic structures, FFDM was rated significantly better (p<0.05). Mass lesions were equally detected, whereas FFDM detected more lesions consisting of calcifications (85 versus 75). DSPM yielded two false-negative results. Both lesions were rated BI-RADS 4 with FFDM, but BI-RADS 2 with DSPM. Both were invasive carcinoma at histology. The sensitivity, specificity, PPV, NPV, and accuracy of FFDM were 1.0, 0.397, 0.636, 1.0, and 0.707, compared to 0.974, 0.397, 0.630, 0.935, and 0.693 of DSPM.

CONCLUSION

Based on image quality parameters, FFDM is, in part, significantly better than DSPM. Furthermore, the detection of breast lesions with calcifications is favorable with FFDM. However, the diagnostic efficacy of FFDM and DSPM was equal. The interpretation of the false-negative results suggests that the perception and characterization of breast lesions is not defined solely by the digital mammography system but is strongly influenced by the radiologist, who is one of the determinants in the interpretation of breast imaging.

Impaired vascular nitric oxide bioactivity in women with previous gestational diabetes

BACKGROUND

Dysfunction of the vascular endothelium, preceding vascular morbidity and type 2 diabetes, is present in women with previous gestational diabetes (GDM). However, it is unknown whether excess weight, insulin resistance, and asymmetric dimethylarginine (ADMA)--an endogenous nitric oxide (NO) synthase inhibitor--also contribute to the vascular changes observed in these patients. The aim of this study was therefore to identify factors other than GDM that impair vascular function.

METHODS

Seven overweight and five non-overweight women with previous GDM were included in this study. Vascular function was assessed from forearm blood-flow responses to the endothelium-dependent vasodilator acetylcholine (ACh), the endothelium-independent vasodilator glyceryltrinitrate, the vasoconstrictor norepinephrine and the NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA). ADMA was measured in venous blood, and insulin resistance was estimated from a modified intravenous glucose tolerance test. Twenty healthy male volunteers served as a historical control group.

RESULTS

Vasodilation of forearm resistance vessels in response to ACh was impaired in overweight women when compared with non-overweight women (P < 0.05); similarly, vasoconstrictor reactivity tended to be smaller in the overweight group. In addition, there was a significant relationship between vascular responsiveness to ACh and L-NMMA, body-mass index, serum ADMA concentrations and stimulated glucose levels (all P < 0.05). ACh responses and ADMA levels in non-overweight women were similar to those of healthy controls.

CONCLUSION

Factors such as obesity, increased ADMA levels and insulin resistance appear to be strong contributors to endothelial dysfunction observed in women with GDM.

Time-resolved analysis of fMRI signal changes using Brain Activation Movies

Conventional fMRI analyses assess the summary of temporal information in terms of the coefficients of temporal basis functions. Based on established finite impulse response (FIR) analysis methodology we show how spatiotemporal statistical parametric maps may be concatenated to form Brain Activation Movies (BAMs), dynamic activation maps representing the temporal evolution of brain activation throughout task performance. These BAMs enable comprehensive assessment of the dynamics in functional topology without restriction to predefined regions and without detailed information on the stimulus paradigm. We apply BAM visualization to two fMRI studies demonstrating the additional spatiotemporal information available compared to standard fMRI result presentation. Here we show that BAMs allow for unbiased data visualization providing dynamic activation maps without assumptions on the neural activity except reproducibility across trials. It may thus be useful in proceeding from static to dynamic brain mapping, widening the range of fMRI in neuroscience. In addition, BAMs might be helpful tools in visualizing the temporal evolution of activation in "real-time" for better and intuitive understanding of temporal processes in the human brain.

Validation of image quality in full-field digital mammography: Is the replacement of wet by dry laser printers justified?

OBJECTIVE

Dry laser printers have replaced wet laser printers to produce hard copies of high-resolution digital images, primarily because of environmental concerns. However, no scientific research data have been published that compare the image quality of dry and wet laser printers in full-field digital mammography (FFDM). This study questions the image quality of these printers.

MATERIALS AND METHODS

Objective image quality parameters of both printers were evaluated using a standardized printer test image, i.e., optical density and detectability of specific image elements (lines, curves, and shapes). Furthermore, mammograms of 129 patients with different breast tissue composition patterns were imaged with both printers. A total of 1806 subjective image quality parameters (brightness, contrast, and detail detection of anatomic structures), the detectability of breast lesions, as well as diagnostic performance according to the BI-RADS classification were evaluated. In addition, the presence of film artifacts was investigated.

RESULTS

Optical density values were equal for the dry and the wet laser printer. Detection of specific image elements on the printer test image was not different. Ratings of subjective image quality parameters were equal, as were the detectability of breast lesions and the diagnostic performance. Dry laser printer images showed more artifacts (164 versus 27). However, these artifacts did not influence image quality.

CONCLUSION

Based on the evidence of objective and subjective parameters, a dry laser printer equals the image quality of a wet laser printer in FFDM. Therefore, not only for reasons of environmental preference, the replacement of wet laser printers by dry laser printers in FFDM is justified.

Antibiotic abscess penetration: fosfomycin levels measured in pus and simulated concentration-time profiles

The present study was performed to evaluate the ability of fosfomycin, a broad-spectrum antibiotic, to penetrate into abscess fluid. Twelve patients scheduled for surgical or computer tomography-guided abscess drainage received a single intravenous dose of 8 g of fosfomycin. The fosfomycin concentrations in plasma over time and in pus upon drainage were determined. A pharmacokinetic model was developed to estimate the concentration-time profile of fosfomycin in pus. Individual fosfomycin concentrations in abscess fluid at drainage varied substantially, ranging from below the limit of detection up to 168 mg/liter. The fosfomycin concentrations in pus of the study population correlated neither with plasma levels nor with the individual ratios of abscess surface area to volume. This finding was attributed to highly variable abscess permeability. The average concentration in pus was calculated to be 182 +/- 64 mg/liter at steady state, exceeding the MIC(50/90)s of several bacterial species which are commonly involved in abscess formation, such as streptococci, staphylococci, and Escherichia coli. Hereby, the exceptionally long mean half-life of fosfomycin of 32 +/- 39 h in abscess fluid may favor its antimicrobial effect because fosfomycin exerts time-dependent killing. After an initial loading dose of 10 to 12 g, fosfomycin should be administered at doses of 8 g three times per day to reach sufficient concentrations in abscess fluid and plasma. Applying this dosing regimen, fosfomycin levels in abscess fluid are expected to be effective after multiple doses in most patients.

Liver metastases of colorectal cancer: US, CT or MR?

In contrast to other extrahepatic malignancies many colorectal cancers can be cured even when there is metastatic spread to the liver. The diagnosis of liver metastases relies totally on imaging to decide which patients may be surgical candidates. The diagnostic value of ultrasound with contrast agents, multidetector CT and MR imaging with non-specific gadolinium chelates and liver-specific contrast agent is discussed. Nowadays MDCT is the mainstay of staging and follow-up of these patients, because it provides good coverage of the liver and the complete abdomen and the chest in one session. MR imaging has been shown to be superior to helical CT in the preoperative assessment of colorectal liver metastases. Large studies are needed to define the role of MDCT vs. MRI staging in patients referred for resection of liver metastases.

Perkutane Leberbiopsie

To classify a liver tumor, image-guided percutaneous biopsy of a liver lesion is indicated. Using ultrasound (US) to guide a biopsy needle into a liver lesion has been proven useful and safe. If a lesion cannot be seen on US or the access to a lesion has been complicated by its position, CT-guided biopsy can be performed. If a lesion cannot be delineated on US or CT, MR-guided biopsy is recommended. Using hepatospecific contrast agents, the time span to delineate tumor tissue can be prolonged. To differentiate diffuse liver disease, transvenous biopsy under fluoroscopic control can be performed if a percutaneous biopsy is contraindicated. In recent years fine-needle aspiration biopsy has been increasingly replaced by coaxial 14-20 G core biopsy, which is a safe and efficient technique to classify liver lesions and has a low complication rate.

Extracorporeal shockwave treatment is effective in calcific tendonitis of the shoulder. A randomized controlled trial

BACKGROUND

Calcific tendonitis of the shoulder is often associated with chronic pain and impairment of function. Extracorporeal shockwave therapy (ESWT) is considered to be a treatment option. We compared the effects of two different ESWT regimens.

METHODS

43 patients (57 shoulders) with symptomatic calcific tendonitis of the shoulder for more than six months were included in a double-blinded study. Thirty-one shoulders were treated at the area of maximum pain with application of 2 x 2000 impulses of 0.28 mJ/mm2 at an interval of two weeks (treatment group) and 26 shoulders with 2 x 2000 impulses of < 0.07 mJ/mm2 at an interval of two weeks (control group), without pretreatment analgesia. Shoulder function (Constant score) and pain (visual analogue scale, VAS) were assessed before treatment and at one week, three months and seven months after treatment. Shoulder X-rays were performed at the 3- and 7-month follow-up visits.

RESULTS

Improvement in Constant score was significantly higher in the treatment group at all follow-up visits (p < 0.05). Seven months post-treatment, calcifications dissolved completely in 19% of the treatment group and 8% of the control group, and a > 50% reduction was observed in 19% and 8% respectively. With regard to reduction of pain, there was significant improvement in the treatment group compared with the control group at the 1-week follow-up (p < 0.05). However, at the 3-month and 7-month visits, no significant between-group difference in pain could be detected.

CONCLUSION

As applied, ESWT with an energy flux density of 0.28 mJ/mm2 led to a significantly greater improvement in shoulder function and a slightly higher, nonsignificant, rate of > 50% disintegration of calcific deposits compared with the control group. However, this did not result in reduction of pain.

Effect of norepinephrine on cefpirome tissue concentrations in healthy subjects

OBJECTIVES

To test whether norepinephrine (NOR) affects tissue microcirculation and impairs plasma-to-tissue equilibration of antimicrobial agents.

MATERIALS AND METHODS

Eight healthy male volunteers were enrolled to an analyst-blinded, randomized, two-period two-sequence crossover study. A single intravenous dose of 2 g of cefpirome was administered simultaneously with starting a continuous infusion of NOR (0.16 microg/kg per min) or placebo (PL) over 180 min. The microdialysis technique was used for the assessment of unbound cefpirome concentrations in skeletal muscle tissue and subcutaneous adipose tissue. Free plasma concentrations were related to corresponding tissue concentrations. Haemodynamics were determined by the measurement of mean arterial blood pressure (MAP), heart rate and forearm blood flow (FBF).

RESULTS

Area under the concentration-time-curve (AUC) values of cefpirome for interstitium and plasma were not significantly different between the PL and NOR groups (P > 0.47). Tissue penetration of cefpirome as described by the ratios of the AUCs from 0 to 180 min for tissue to the AUC values for plasma were 0.81 +/- 0.34 for the PL group and 0.80 +/- 0.26 for the NOR group (P > 0.05). Baseline values of MAP, heart rate and FBF were not significantly different between study days. MAP increased significantly following NOR administration from 73.3 +/- 3.5 mmHg at baseline to 94.0 +/- 5.2 mmHg during infusion (P = 0.017). NOR exerted no significant effects on FBF.

CONCLUSIONS

We have shown that intravenous administration of NOR does not exert a significant effect on peripheral blood flow and tissue penetration of cefpirome in healthy men. This might be attributed to systemic regulatory mechanisms, which probably fully compensate for major changes in blood flow in peripheral tissues.

Bone homogeneity factor: an advanced tool for the assessment of osteoporotic bone structure in high-resolution magnetic resonance images

RATIONALE AND OBJECTIVES

Osteoporosis is characterized by low bone mass and inferior structural competence. In this study we introduce the bone homogeneity factor (BHF) as a quantitative measurement of bone structure, which could be equally important as bone mineral density.

METHODS

BHF represents an advanced texture analysis tool based on the spatial autocorrelation function calculated in 9 different directions. These calculations were performed on high-resolution magnetic resonance images of the calcaneus at 3.0 T and compared with dual-energy x-ray absorptiometry measurements of the femoral neck.

RESULTS

The quality and resolution of the high-resolution magnetic resonance images is sufficient for reliably calculating BHF. The mean BHF of the control group (n = 5, mean BHF = 525,0) with normal bone is significantly (P = 0.009, Mann-Whitney U test) higher than in the osteoporotic group (n = 7, mean BHF = 137,8). The BHF correlates with the DXA measurements of the femoral neck (correlation coefficient = 0.75).

CONCLUSIONS

By calculating the BHF, it was possible to distinguish between osteoporotic and nonosteoporotic bone structure. Hence, BHF could be a possible candidate for noninvasive assessment of osteoporotic bone structure giving additional information to routinely used bone mineral densitometry.

C-peptide has no effect on forearm blood flow during local hyperinsulinaemia in healthy humans

BACKGROUND

C-peptide increases forearm blood flow (FBF) in patients with Type 1 diabetes, probably by interaction with insulin, but not in healthy subjects. It is unclear if the vasodilating effect is sealed at normal fasting insulin concentrations.

METHODS

The effects of C-peptide alone and during local hyperinsulinaemia were studied in healthy young men. Subjects received intra-arterial insulin at 6 pmol min-1 (low dose) or placebo for 60 min with subsequent coinfusion of C-peptide at increasing doses of 2-60 pmol min-1 in a double-blind crossover study (n = 8). In control experiments insulin at 30 pmol min-1 (high dose) was coinfused with C-peptide (n = 3). FBF was measured by strain-gauge plethysmography.

RESULTS

Placebo had no effect on FBF (mean percentage change from baseline at 50 min -3.1%, 95% confidence interval [CI]-14.9, + 8.7). Insulin infusion slightly enhanced FBF by + 10.2% (95% CI -6.8, + 27.2; low dose) and + 17.6% (95% CI -38.8, + 74.0; high dose), respectively. The mean individual difference of the change in FBF between low-dose insulin and placebo was + 13.3% (95% CI -6.0, + 32.7; P = NS). Infusion of C-peptide increased local C-peptide concentrations from 1.8 +/- 0.1 ng ml-1 to 6.1 +/- 2.8 ng ml-1, but had no effect on FBF during placebo or hyperinsulinaemia (mean difference vs low dose insulin -16.0%, 95% CI -38.9, + 6.9).

CONCLUSION

The vasodilating effect of C-peptide seen in Type 1 diabetes is not detectable during fasting or hyperinsulinaemia in the forearm vasculature of healthy subjects. This suggests saturation of its vasodilating potency at insulin concentrations within the normal or in the supraphysiological range.

Transcapillary insulin transfer in human skeletal muscle

BACKGROUND

Transcapillary insulin transfer is considered a rate-limiting step in insulin action at supraphysiological insulin concentrations. However, it remains unclear whether this concept also applies for physiological conditions.

MATERIALS AND METHODS

In the present study we set out to characterize transcapillary insulin transfer by measuring insulin concentrations in plasma and interstitial space fluid of skeletal muscle during an oral glucose tolerance test and euglycaemic hyperinsulinaemic clamp conditions, respectively. For this purpose we employed in vivo microdialysis of skeletal muscle in conjunction with an ultrasensitive insulin assay in eight healthy lean male volunteers (aged 25 +/- 1 years).

RESULTS

Insulin concentrations at baseline were 48 +/- 8 pmol x L(-1) in plasma and 19 +/- 4 pmol x L(-1) in the interstitium (P = 0.002). The mean interstitium to plasma ratio at baseline was 0.48 +/- 0.09 pmol x L(-1). During the oral glucose tolerance test the interstitium to plasma ratio remained unchanged (0.43 +/- 0.12, P = NS vs. baseline), but was significantly reduced during euglycaemic hyperinsulinaemic clamp conditions at steady-state hyperinsulinaemia (0.12 +/- 0.01, P = 0.01 vs. baseline).

CONCLUSION

In summary there is a substantial transcapillary insulin gradient in healthy human skeletal muscle under baseline and glucose-stimulated conditions. Our findings support the hypothesis of a saturable transcapillary insulin transport representing a partly rate-limiting step for insulin action.

On the origin of respiratory artifacts in BOLD-EPI of the human brain

BOLD-based functional MRI (fMRI) can be used to explicitly measure hemodynamic aspects and functions of human neuro-physiology. As fMRI measures changes in regional cerebral blood flow and volume as well as blood oxygenation, rather than neuronal brain activity directly, other processes that may change the above parameters have to be examined closely to assess sensitivity and specificity of fMRI results. Physiological processes that can cause artifacts include cardiac action, breathing and vasomotion. Although there has been substantial research on physiological artifacts and appropriate compensation methods, controversy still remains on the mechanisms that cause the fMRI signal fluctuations. Respiratory-correlated fluctuations may either be induced by changes of the magnetic field homogeneity due to moving organs, intra-thoracic pressure differences, respiration-dependent vasodilation or oxygenation differences. The aim of this study was to characterize the impact of different breathing patterns by varying respiration frequency and/or tidal volume on EPI time courses of the resting human brain. The amount of respiration-related oscillations during three respiration patterns was quantified, and statistically significant differences were obtained in white matter only: p < 0.03 between 6 vs. 12 ml/kg body weight end tidal volume at a respiration frequency of 15/min, p < 0.03 between 12 vs. 6 ml/kg body weight and 15 vs. 10 respiration cycles/min. There was no significant difference between 15 vs. 10 respiration cycles/min at an end tidal volume of 6 ml/kg body weight (p = 0.917). In addition, the respiration-affected brain regions were very similar with EPI readout in the a-p and l-r direction. Based on our results and published literature we hypothesize that venous oxygenation oscillations due to changing intra-thoracic pressure represent a major factor for respiration-related signal fluctuations and increase significantly with increasing end tidal volume in white matter only.

Endothelin ETA receptor-subtype specific antagonism does not mitigate the acute systemic or renal effects of exogenous angiotensin II in humans

BACKGROUND

Angiotensin II (Ang II) is assumed to play a pathophysiological role in a variety of vascular diseases. Animal studies indicate that these effects are partly attributed to stimulation of endothelin-1 (ET-1) release. The aim of the present study was to investigate whether the acute effects of Ang II on systemic and renal haemodynamics in healthy subjects can be influenced by endothelin ET(A)-receptor blockade.

DESIGN

The study design was balanced, randomized, placebo-controlled, double blind, two-way cross-over, in 10 healthy male subjects.

METHODS

Subjects received stepwise increasing intravenous doses of Ang II (0.65, 1.25, 2.5, 5 ng kg(-1) min(-1) for 15 min per dose level) in the presence or absence of BQ-123 (60 microg min(-1)), a specific ETA-receptor antagonist. Renal plasma flow (RPF) and glomerular filtration rate (GFR) were assessed by the para-aminohippurate and inulin plasma clearance method, respectively. Renal vascular resistance (RVR) was calculated from mean arterial pressure (MAP) and renal plasma flow.

RESULTS

Ang II decreased RPF by 34% and GFR by 9% and increased RVR by 94% and MAP by 27% (ANOVA, P < 0.001 vs. baseline, for all parameters). BQ-123 did not alter these renal and systemic haemodynamic responses to a significant degree. In addition, BQ-123 had no significant haemodynamic effect under baseline conditions.

CONCLUSIONS

Short-term increase of circulating Ang II levels causes systemic and renal pressor effects, which are not mitigated by endothelin ETA-receptor blockade. This suggests that the pressor response to Ang II cannot be accounted for by the acute release of vasoactive ET-1.

Adrenoceptor hyporeactivity is responsible for Escherichia coli endotoxin-induced acute vascular dysfunction in humans

Impaired response to catecholamines contributes to the altered hemodynamics in sepsis, which has been attributed to excessive NO formation. We have studied the systemic hemodynamic and local forearm responses and inducible NO synthase (iNOS) expression during experimental endotoxemia in humans. Escherichia coli endotoxin (lipopolysaccharide [LPS]) was administered at doses of 1 or 2 ng/kg to healthy volunteers. In 10 subjects, the systemic pressor effect of phenylephrine was assessed before and after the administration of LPS. In 9 further subjects, forearm blood flow responses to intra-arterial noradrenaline, acetylcholine, glyceryl trinitrate, and N(G)-monomethyl-L-arginine (L-NMMA) were studied at baseline and after LPS administration. Peripheral blood was collected and analyzed for iNOS mRNA and protein. Four hours after LPS, the response of systolic blood pressure (P<0.0005) and heart rate (P<0.05) to phenylephrine was significantly reduced. In the forearm, noradrenaline-induced vasoconstriction was also reduced by approximately 50% (P<0.01), but L-NMMA responsiveness was unchanged. iNOS mRNA or protein was not increased. Marked vascular adrenoceptor hyporeactivity is detectable in the absence of increased NO activity or iNOS expression in endotoxemia, arguing against major involvement of vascular iNOS activity in the acute systemic vasodilation to LPS.

Autocorrelation analysis of bone structure

We propose a method called spatial autocorrelation analysis (SACA) to determine the spatial anisotropy of the trabecular bone in order to investigate osteoporosis. For demonstrating the potential of SACA we first evaluate the method on rectangular, simulated test patterns as a simple model for the anisotropic pore structure of the bone. As a next step towards biomedical application, photographic reference images of human vertebral bone were investigated by SACA. Osteoporotic bone structure could be clearly differentiated from non-osteoporotic sample images. Moreover, for demonstration of the applicability and potential of the method for in vivo characterization of osteoporosis, the microstructure of the human calcaneus was investigated by MR-microimaging on a young healthy male subject and an osteoporotic female. The measurements were performed using a high-field (3T) whole-body MR tomograph equipped with a special, strong head gradient system. The signal was acquired with a surface coil mounted on an in-house-built device for convenient immobilization of the subject's foot. Using a 3D gradient echo sequence a resolution of 0.254 x 0.254 x 2.188 mm3 was achieved in vivo. Selected images were inverted, gradient corrected for the inhomogeneous but sensitive detection by the surface coil, and subsequently analyzed by SACA. The anisotropy of bone structure detected by SACA is a possible candidate for noninvasive determination of the osteoporotic status, potentially complementing standard bone mineral density measurements.

Hypercapnia-induced cerebral and ocular vasodilation is not altered by glibenclamide in humans

Carbon dioxide is an important regulator of vascular tone. Glibenclamide, an inhibitor of ATP-sensitive potassium channel (K(ATP)) activation, significantly blunts vasodilation in response to hypercapnic acidosis in animals. We investigated whether glibenclamide also alters the cerebral and ocular vasodilator response to hypercapnia in humans. Ten healthy male subjects were studied in a controlled, randomized, double-blind two-way crossover study under normoxic and hypercapnic conditions. Glibenclamide (5 mg po) or insulin (0.3 mU. kg(-1). min(-1) iv) were administered with glucose to achieve comparable plasma insulin levels. In control experiments, five healthy volunteers received glibenclamide (5 mg) or nicorandil (40 mg) or glibenclamide and nicorandil in a randomized, three-way crossover study. Mean blood flow velocity and resistive index in the middle cerebral artery (MCA) and in the ophthalmic artery (OA) were measured with Doppler sonography. Pulsatile choroidal blood flow was assessed with laser interferometric measurement of fundus pulsation. Forearm blood flow was measured with venous occlusion plethysmography. Hypercapnia increased ocular fundus pulsation amplitude by +18.2-22.3% (P < 0. 001) and mean flow velocity in the MCA by +27.4-33.3% (P < 0.001), but not in the OA (2.1-6.5%, P = 0.2). Forearm blood flow increased by 78.2% vs. baseline (P = 0.041) after nicorandil administration. Glibenclamide did not alter hypercapnia-induced changes in cerebral or ocular hemodynamics and did not affect systemic hemodynamics or forearm blood flow but significantly increased glucose utilization and blunted the nicorandil-induced vasodilation in the forearm. This suggests that hypercapnia-induced changes in the vascular beds under study are not mediated by activation of K(ATP) channels in humans.