Characterization of MR Imaging-Visible Perivascular Spaces in the White Matter of Healthy Adolescents at 3T

BACKGROUND AND PURPOSE

Perivascular spaces play a role in cerebral waste removal and neuroinflammation. Our aim was to provide data regarding the burden of MR imaging-visible perivascular spaces in white matter in healthy adolescents using an automated segmentation method and to establish relationships between common demographic characteristics and perivascular space burden.

MATERIALS AND METHODS

One hundred eighteen 12- to 21-year-old subjects underwent T1- and T2-weighted 3T MR imaging as part of the National Consortium on Alcohol and Neurodevelopment in Adolescence. Perivascular spaces were identified in WM on T2-weighted imaging using a local heterogeneity approach coupled with morphologic constraints, and their spatial distribution and geometric characteristics were assessed.

RESULTS

MR imaging-visible perivascular spaces were identified in all subjects (range, 16-287). Males had a significantly higher number of perivascular spaces than females: males, mean, 98.4 ± 50.5, versus females, 70.7 ± 36.1, (P < .01). Perivascular space burden was bilaterally symmetric (r > 0.4, P < .01), and perivascular spaces were more common in the frontal and parietal lobes than in the temporal and occipital lobes (P < .01). Age and pubertal status were not significantly associated with perivascular space burden.

CONCLUSIONS

Despite a wide range of burden, perivascular spaces are present in all healthy adolescents. Perivascular space burden is higher in adolescent males than in females, regardless of age and pubertal status. In this population, perivascular spaces are highly symmetric. Although widely reported as a feature of the aging brain, awareness of the presence of perivascular spaces in a cohort of healthy adolescents provides the foundation for further research regarding the role of these structural variants in health and disease.

Effect of low-dose cyclosporine A in the treatment of refractory proteinuria in childhood-onset lupus nephritis

We performed a prospective study to evaluate the efficacy and safety of low-dose cyclosporine A (CSA) treatment in paediatric lupus nephritis refractory to conventional therapy. Seven children with biopsy-proven Class III-IV lupus nephritis were treated with CSA (2-4 mg/kg/day) combined with low-dose prednisone for one year. All patients had failed to achieve sustained proteinuria remission with corticosteroids and cytotoxic drugs. Proteinuria decreased from median value of 2.5 g/24 hours (range, 1.2-4.9) to 0.14 g/24 hours (range, 0.0-0.84) after treatment (P = 0.018). Median values of creatinine clearance and serum creatinine did not change significantly. Median systemic lupus erythematosus disease activity index score decreased from 12 (range, 6-16) to 4 (range, 0-8) at end of treatment (P = 0.027). However, two patients experienced flares of extrarrenal manifestations and complement levels did not improve. Moreover, most patients relapsed with proteinuria within a few months of stopping CSA therapy. Side effects were not significant. In conclusion, low-dose of CSA combined with steroids appears to be useful to reduce proteinuria in paediatric proliferative lupus nephritis refractory to steroids and cytotoxic drugs; however, relapses are common after CSA discontinuation. Further studies are needed to define the precise role of CSA in paediatric lupus nephritis.

The mechanics of corporal veno-occlusion in penile erection: a theory on the effect of stretch-associated luminal constrictability on outflow resistance

In order to further our understanding of the physiology of corporal veno-occlusion, we developed a theory of a possible contribution to corporal venous outflow resistance which occurs as the result of venule stretching with resultant luminal narrowing when penile volume increases during the erection process. We stretched non-biological tubes and rabbit abdominal vena cava segments, performed flow-based and volume-based experiments to calculate the magnitude of N, the newly defined 'stretch-associated luminal constrictability' factor. We solved for (R(s)/R(u)), the ratio of the venule fluid resistance in the stretched state (R(s)) to the unstretched state (R(u)), to quantify the projected increases in fluid resistance as well as Q.R(u) where Q is the subtunical venule flow rate. For a given tube, N was found to be essentially constant for different amounts of stretch. A theory was formulated which predicted R(s) and Q as a function of N, DeltaP (intracavernosal pressure increase); V(E)/V(F) (tunical distensibility); X (cavernosal expandability) and R(u). Based on the magnitude of N=2, this theory predicts that patients with the highest values of both V(E)/V(F) and X would have maximal R(s) values, approaching infinity (complete occlusion) at a low DeltaP near 5 mmHg. In contrast, patients with low values of both V(E)/V(F) (eg Peyronie's disease) and X (eg corporal fibrosis), would be predicted to have minimal R(s) values. For example, a hypothetical patient with the lowest values of V(E)/V(F) and X would yield R(s) values only approaching 7.9 times that of unstretched values at a DeltaP increase of 90 mmHg. We concluded to that stretch-associated venule resistance may occur as a result of decreased sub-tunical venule diameter and increased sub-tunical venule length. In individual patients, stretch-associated venule resistance may either dominate or be a minor component of the overall mechanism of corporal veno-occlusion.

A laser ablation method for the synthesis of crystalline semiconductor nanowires

A method combining laser ablation cluster formation and vapor-liquid-solid (VLS) growth was developed for the synthesis of semiconductor nanowires. In this process, laser ablation was used to prepare nanometer-diameter catalyst clusters that define the size of wires produced by VLS growth. This approach was used to prepare bulk quantities of uniform single-crystal silicon and germanium nanowires with diameters of 6 to 20 and 3 to 9 nanometers, respectively, and lengths ranging from 1 to 30 micrometers. Studies carried out with different conditions and catalyst materials confirmed the central details of the growth mechanism and suggest that well-established phase diagrams can be used to predict rationally catalyst materials and growth conditions for the preparation of nanowires.

Pharmacokinetics, biodistribution and dosimetry of 99mTc-labeled anti-human epidermal growth factor receptor humanized monoclonal antibody R3 in rats

The pharmacokinetics, biodistribution and dosimetry of 99mTc-labeled anti-human epidermal growth factor receptor (anti-hEGF-r) humanized monoclonal antibody (MAb) R3 was investigated following intravenous injection in normal Wistar rats. Serum disappearance curves were best fit by a two-compartment model having a mean distribution half-life (t 1/2alpha) of 0.250 h and a mean elimination (t 1/2beta) of 13.89 h. Among the various organs, a little accumulation of the radiolabeled antibody was found only in kidneys. Biodistribution and dosimetry studies in humans were performed by extrapolation of the animal data to humans. Absorbed dose to normal organs and the remainder of the whole body were estimated using the medical internal radiation dose formula, and dose contributions from radioactivity in transit through the gastrointestinal tract were estimated using a compartment model. Extrapolated values of radiation absorbed dose to normal organs in rads per millicurie administered were whole body, 0.0085; lower large intestine wall, 0.0898; small intestine, 0.0530; upper large intestine wall, 0.0731; and kidneys, 0.0455. The effective dose equivalent predicted was 0.0162 rem/mCi and the effective dose was found to be 0.015 rem/mCi. On the basis of the pharmacokinetics, biodistribution and internal radiation dosimetry information obtained in this study, a diagnostic phase I clinical trial with 99mTc-labeled humanized MAb R3 conjugate in patients should be supported.

Monitoring aminophylline therapy using Jusko's dosage guidelines

Treatment with aminophylline, according to the nomogram published by Jusko and coworkers, was monitored in 13 patients suffering from acute exacerbations of COPD. After 24 h of therapy, the clinical state, the pO2 and the pCO2 values were markedly improved. Theophylline plasma concentrations were maintained within the therapeutic range. A slight but noticeable increase of drug serum levels during therapy could be related to changes in the arterial pH; the implications of this finding are discussed.

Thyroid carcinoma and Cushing's syndrome. A report of two cases with a review of the common features of the "non-endocrine" tumours associated with Cushing's syndrome

Two cases of thyroid carcinoma and Cushing's syndrome are reported. Nine other previously published cases of this association are reviewed: in one the thyroid tumour was described as medullary, in two as papillary, and in the other six as anaplastic, undifferentiated, atypical, or solid carcinoma. Both of our own cases were medullary carcinomas of the thyroid, and on reviewing the histology of five of the other cases all proved to be medullary carcinoma with identifiable amyloid in the stroma. A consideration of the temporal relationships of the development of the carcinoma and of Cushing's syndrome suggested that in the two cases with papillary carcinoma these conditions could have been unrelated, but that in eight of the nine cases with medullary carcinoma there was evidence that thyroid carcinoma was present at the time of diagnosis of Cushing's syndrome. The other main groups of the so-called ;non-endocrine' tumours associated with Cushing's syndrome are briefly reviewed, and evidence that a surprising number of these cases are related to carcinoid tumours is put forward. Medullary carcinoma of the thyroid is also probably related to this group of tumours. It is suggested that the great majority of the tumours associated with Cushing's syndrome are derived from cells of foregut origin which are endocrine in nature. In neoplasms derived from these cells the polypeptide hormone may well be imperfectly formed, and possess an amino-acid sequence in common with ACTH or other biologically active polypeptides.