Progressive multifocal leukoencephalopathy and human immunodeficiency virus-associated white matter lesions in AIDS: magnetization transfer MR imaging

PURPOSE: To determine the magnetization transfer features of progressive multifocal leukoencephalopathy (PML) and human immunodeficiency virus (HIV)-associated white matter lesions (WML) (hereafter, HIV-WML) on magnetic resonance (MR) images obtained in patients with acquired immunodeficiency syndrome (AIDS). MATERIALS AND METHODS: Conventional MR imaging and magnetization transfer MR imaging were performed in 21 AIDS patients with 42 areas of white matter hyperintensity on MR images (13 patients had 25 PML lesions, eight patients had 17 WML). The magnetization transfer ratio was calculated for each lesion. RESULTS: Compared with normal-appearing white matter (magnetization transfer ratio = 47.9%), both PML and HIV-WML showed reduced magnetization transfer ratio. The magnetization transfer ratio was significantly lower in PML lesions (magnetization transfer ratio = 26.1%) than in HIV-WML (magnetization transfer ratio = 38.0%, P < .0001), and there was no overlap in the magnetization transfer ratio between PML lesions and HIV-WML. The separation in magnetization transfer ratio between the two lesion types was valid for lesion as small as 0.5 cm2. CONCLUSION: The larger reduction in magnetization transfer ratio for PML lesions is most likely due to demyelination, whereas the reduction in HIV-WML may be associated primarily with gliosis. PML lesions appear to cause strong reductions in magnetization transfer ratio early in the course of disease. Magnetization transfer MR imaging is a noninvasive tool that improves the differentiation between PML and HIV-WML in patients with AIDS.     

HAART improves prognosis in HIV-associated progressive multifocal leukoencephalopathy

Introduction of highly active antiretroviral therapy (HAART) has been associated with many changes in the complications of human immunodeficiency virus (HIV) infection. A cohort of 25 HIV patients with progressive multifocal leukoencephalopathy (PML) treated with HAART experienced a median survival of >46 weeks. This is an improvement in prognosis compared with recent historic experience and correlated with HIV RNA viral load reductions. We conclude that current HIV therapy is important in improving the outlook of PML in the setting of HIV.     

Pediatric tetracycline-induced pseudotumor cerbri.

BACKGROUND: Tetracyclines have long been recognized as a cause of pseudotumor cerebri in adults, but the role of tetracyclines in the pediatric age group has not been well characterized in the literature and there have been few reported cases. We present 6 cases to better delineate the problem, the patient profile, the response to treatment, and the sequelae. METHODS: We retrospectively analyzed the records of all patients admitted with a diagnosis of pseudotumor cerebri who had documented usage of a tetracycline-class drug immediately before presentation at the Hospital For Sick Children in Toronto, Canada, from January 1, 1986, to March 1, 1996. RESULTS: Six patients (5 female, 1 male) who met all inclusion and exclusion criteria were identified; their ages ranged from 12 to 17 years. All were being treated for acne vulgaris. Duration of use before diagnosis was as short as 2 weeks and as long as 10 months, with a mean of 4.4 months. Duration of symptoms ranged from 0.57 to 4 weeks. Symptoms included headache (6 of 6), nausea (5 of 6), and diplopia (4 of 6). All for whom height and weight data were known (5 of 6) were in the upper quartile for body mass index. Visual acuity was 6/6 in all but 1 eye of one patient (6/9) at diagnosis, and final visual acuity was 6/6 in all patients. All had normal color vision, where this was recorded (5 of 6). The only recorded field defect was enlargement of the blind spot (4 of 6). All patients responded to treatment, with loss of symptoms in 1 day to 4 weeks. CONCLUSIONS: Pseudotumor cerebri as a result of tetracycline-class drugs does occur in the pediatric population. With prompt and appropriate medical treatment, long-term sequelae can almost always be avoided. Physicians who treat patients with tetracyclines need to be aware of the potential complications in children.     

Predicting the time needed to achieve steady state if absorption and elimination constants are equal

A simple table is derived to facilitate the rapid estimation of the number of dose administrations needed to achieve a certain fraction of the steady-state plasma concentration in the case of one-compartment model with uniform multiple oral dosing and equal absorption and elimination constants.     

Serum levels of clomipramine and desmethylclomipramine and clinical improvement in panic disorder

Several placebo-controlled trials have shown the efficacy of clomipramine (CMI) in panic disorder. However, none has investigated the relationship between CMI, and desmethylclomipramine (DCMI) plasma levels, and outcome. In this trial, 41 patients meeting the DSM-III-R criteria for panic disorder with/without agoraphobia received 50-200 mg of CMI daily in a single-blind, flexible dose regimen for 14 weeks. At the end of treatment, 97% of the patients were free of panic attacks. Patients were classified into two groups of improvement according to the panic symptom items of the 'Patient-Rated Anxiety Scale'. A repeated-measures analysis of variance suggested a significant association between outcome and serum DCMI level/daily dose ratio as well as total serum level/daily dose. Patients with intense improvement showed DCMI and total serum levels lower than those with moderate improvement. The results indicate the importance of monitoring clomipramine and desmethylclomipramine serum levels in this disorder.     

Dirac operators coupled to vector potentials

Characteristic classes for the index of the Dirac family [unk]_A are computed in terms of differential forms on the orbit space of vector potentials under gauge transformations. They represent obstructions to the existence of a covariant Dirac propagator. The first obstruction is related to a chiral anomaly.     

Multiple effects of glucocorticoids and hyperosmolality on isoenzyme expression in cultured KB cells

The KB cell line, though indicted as a HeLa-contamined line, is a useful in vitro model for the study of the regulation of isoenzyme expression. KB cells produced three isoenzymic forms of alkaline phosphatase. When KB cells were grown in the presence of prednisolone and/or in hyperosmolar medium, the total enzyme activity was reduced. This change in activity was coupled with specific alterations in the proportion of each isoenzyme. The slow-moving form (identified biochemically and immunologically as the heat-stable, placental, Regan isoenzyme) was substantially increased by the steroid hormone and/or hyperosmolality. The fast-moving form [identified as the intestine-like, amnion (FL) isoenzyme] was strikingly diminished by either treatment. The intermediate form (tentatively referred to as "hybrid," inasmuch as it shared properties of the other two isoenzymes) was decreased only when KB cells were grown in hyperosmolar medium containing prednisolone. These results corroborated the notion that these stimuli cause the induction of increased levels of the heat-stable Regan alkaline phosphatase only. They also point out the necessity of performing isoenzyme analysis when one is investigating the regulation of this enzyme.