Pharmacokinetics and dose recommendations for cyclosporine and tacrolimus when coadministered with ABT-450, ombitasvir, and dasabuvir.

ABT-450, ombitasvir, and dasabuvir are direct-acting antiviral agents (DAAs) that have been developed for combination treatment of chronic hepatitis C virus (HCV) infection. Because these DAAs have metabolic and transporter profiles that overlap with cyclosporine and tacrolimus disposition, there is potential for drug interactions. Two Phase 1 studies assessed effects of ABT-450 (150 mg coadministered with ritonavir 100 mg once daily), ombitasvir (25 mg once daily), and dasabuvir (400 mg twice daily) on the pharmacokinetics, safety, and tolerability of a single dose of cyclosporine (30 mg) or tacrolimus (2 mg) in healthy volunteers (N = 12 per study). In the presence of steady-state concentrations of all 3 DAAs, dose-normalized cyclosporine concentration at 24 hours (C24), and area under the concentration-time curve from time 0 to infinity (AUC(∞)) were 15.8-fold and 5.8-fold, respectively, and dose-normalized tacrolimus C24 and AUC(∞) were 17-fold and 57-fold, respectively, of either agent alone. Cyclosporine and tacrolimus half-lives increased from 7 to 25 h and 32 to 232 h, respectively. There were no major safety or tolerability issues in these studies. The results suggest that cyclosporine and tacrolimus doses and dosing frequency should be reduced in HCV-infected posttransplant patients being treated with this 3-DAA regimen.

El signo de la pata de oso En TC / The bear paw sign on CT scans

The "bear paw sign" is an unusual radiologic finding indicating xantogranulomatous pyelonephritis (XGP). It refers to the replacement of the renal parenchyma by necrotic areas or xanthomatous collections with a pattern mimicking hydronephrotic calyx dilatation, associated with peripheral enhancing of the renal cortex after intravenous contrast administration. This sign can be observed on computed tomography (CT) scannings, where the cross-sectional appearance of the kidney resembles the paw of a bear and necrotic areas mimic the toe-pads of the paw. Depending on the presentation of the disease (i.e., focal or diffuse), a differential diagnosis considering tumor-like renal cell carcinomas or fibrolipomatous replacement of the kidney has to be performed. A proper recognition of the "bear paw sign" on CT scans enables the radiologist to establish the diagnosis of XGP.

El signo de la "pata de oso" es poco habitual de observar en la práctica radiológica. Representa el reemplazo de parénquima renal por áreas necróticas o colecciones xantomatosas, con un patrón que simula dilatación caliciliar hidronefrótica asociado a realce periférico de la corteza renal tras la administración de contraste intravenoso. Este signo se describe en tomografía computada (TC) donde cada cojinete de los dedos representa dichas áreas necróticas y es característico de la pielonefritis xantogranulomatosa (PXG). Según la presentación de la pielonefritis (focal o difusa), es necesario realizar un diagnóstico diferencial con lesiones tumorales como el carcinoma de células renales o el reemplazo fibrolipomatoso del riñón. El reconocer el signo de la "pata de oso" en TC permite al radiólogo establecer el diagnóstico de PXG.

ADF/Cofilin-actin rods in neurodegenerative diseases.

Dephosphorylation (activation) of cofilin, an actin binding protein, is stimulated by initiators of neuronal dysfunction and degeneration including oxidative stress, excitotoxic glutamate, ischemia, and soluble forms of beta-amyloid peptide (Abeta). Hyperactive cofilin forms rod-shaped cofilin-saturated actin filament bundles (rods). Other proteins are recruited to rods but are not necessary for rod formation. Neuronal cytoplasmic rods accumulate within neurites where they disrupt synaptic function and are a likely cause of synaptic loss without neuronal loss, as occurs early in dementias. Different rod-inducing stimuli target distinct neuronal populations within the hippocampus. Rods form rapidly, often in tandem arrays, in response to stress. They accumulate phosphorylated tau that immunostains for epitopes present in "striated neuropil threads," characteristic of tau pathology in Alzheimer disease (AD) brain. Thus, rods might aid in further tau modifications or assembly into paired helical filaments, the major component of neurofibrillary tangles (NFTs). Rods can occlude neurites and block vesicle transport. Some rod-inducing treatments cause an increase in secreted Abeta. Thus rods may mediate the loss of synapses, production of excess Abeta, and formation of NFTs, all of the pathological hallmarks of AD. Cofilin-actin rods also form within the nucleus of heat-shocked neurons and are cleared from cells expressing wild type huntingtin protein but not in cells expressing mutant or silenced huntingtin, suggesting a role for nuclear rods in Huntington disease (HD). As an early event in the neurodegenerative cascade, rod formation is an ideal target for therapeutic intervention that might be useful in treatment of many different neurological diseases.

Ten-year results of a press-fit, porous-coated acetabular component.

We retrospectively reviewed, ten years after surgery, 100 consecutive total hip replacements in which the Duraloc 300 cup had been used. Post-operative radiographs were analysed for placement of the cup and interface gaps and follow-up radiographs for lucent lines, osteolysis, wear and migration. All the components were found to be stable with no evidence of loosening. The mean rate of wear was 0.12 mm/year. Three hips developed acetabular osteolysis at the level of the apex hole. Two have successfully undergone bone grafting without removal of the implants and one patient is awaiting surgery. The Duraloc 300 cup has a survival of 100% at ten years with no aseptic loosening and a low incidence of pelvic osteolysis.

Cutaneous polyarteritis nodosa in patients presenting with atrophie blanche.

BACKGROUND: The term 'atrophie blanche' is used both as a descriptive term denoting ivory-white stellate scars on the lower limbs as well as a diagnostic label synonymous with livedoid vasculitis, an ill-defined entity. Medium-sized vasculitides, such as polyarteritis nodosa (PAN), occasionally present with ulceration resulting in ivory-white stellate scarring on the lower limbs and may potentially be misdiagnosed as livedoid vasculitis. OBJECTIVES: To assess the occurrence, clinical and immunopathological features of medium-sized vasculitis in patients presenting with atrophie blanche without clinical and/or compression duplex ultrasonographic evidence of venous insufficiency. METHODS: We retrospectively evaluated patients presenting with atrophie blanche at the Department of Dermatology of Johns Hopkins Medical Institutions, from April 1996 until April 2002, following the diagnostic guidelines for leg ulcers of the Division of Immunodermatology. Deep and multiple skin biopsies were performed for histology. Investigations for underlying vasculitis, thrombophilia, nerve conduction studies and compression duplex ultrasonography of the lower extremities were performed in all patients. RESULTS: Of 29 consecutive patients presenting with atrophie blanche, six had underlying medium-sized vasculitis consistent with PAN, three of whom had previously been diagnosed to have segmental hyalinizing vasculitis/vasculopathy (livedoid vasculitis/vasculopathy) on superficial biopsies. All six patients with cutaneous PAN were women with a median age of 36.5 years (range 34-46) and with a median duration of the disease prior to diagnosis of 18 years (range 3-30). Of the six cutaneous PAN patients, four had neurological involvement evidenced by clinical symptoms and nerve conduction studies. No evidence of any other extracutaneous involvement was found. Erythrocyte sedimentation rate and tests for vasculitis and thrombophilic were normal in all six patients. None had evidence of venous insufficiency. Immunosuppressive therapy was effective in controlling PAN-associated cutaneous and neurological disease. Of the remaining 23 patients, two had antiphospholipid syndrome and one had homocystineaemia; all three also had evidence of venous insufficiency. One patient had multiple myeloma-associated type I cryoglobulinaemia and 19 patients had venous insufficiency alone. None of the non-PAN patients had abnormalities in the nerve conduction studies. CONCLUSIONS: In patients presenting with atrophie blanche without evidence of venous insufficiency and thrombophilia, PAN should be excluded, particularly in the presence of mononeuritis multiplex. Repeated and deep biopsies are often necessary to reveal the accurate underlying pathology of necrotizing medium-sized vasculitis in the reticular dermis and the subcutis, especially in the setting of atrophie blanche lesions. Immunosuppressive therapy was effective in controlling the PAN-associated clinical manifestations.

Prevalence of complementary and alternative medicine use in cancer patients.

Interest in complementary and alternative medicine (CAM) has grown dramatically over the past several years. Cancer patients are always looking for new hope, and many have turned to nontraditional means. This study was conducted to determine the prevalence of complementary and alternative medicine use in cancer patients and what if any agents are being used. Approximately, 100 adult cancer patients in a private nonprofit South Florida hospital completed a descriptive cross-sectional survey questionnaire. The mean age of participants was 59 years; 42 patients were male and 58, female. According to survey results, 80% of patients reported using some type of CAM; 81% took vitamins, 54% took herbal products, 30% used relaxation techniques, 20% received massages, and 10% used home remedies. Among patients who took vitamins, 65% said they took a multivitamin, 39% took vitamin C, and 31%, vitamin E. The most common herbal remedies used were green tea, echinacea, shark cartilage, grape seed extract, and milk thistle. Meditation and deep breathing were the two most common relaxation techniques practiced. A large majority of cancer patients are using CAM. In light of the growing interest in CAM, health-care professionals need to be educated about the most common therapies used.

A new cervical spine clearance protocol using computed tomography.

OBJECTIVE: The purpose of this study was to assess a cervical spine clearance protocol for blunt trauma patients using helical computed tomographic (CT) scan of the cervical spine (C-spine). METHODS: A protocol using CT scan of the C-spine was implemented and the first 6 months of use reviewed. Patients requiring a CT scan of the head had the C-spine evaluated by lateral C-spine radiography and a helical CT scan. Patients without indication for CT scan of the head had the C-spine evaluated by three-view radiography (anteroposterior, lateral, and odontoid) with selective CT scan of the C-spine for imaging areas not well visualized or those with abnormalities identified by radiography or by clinical examination alone. RESULTS: Three hundred twenty-four patients were admitted to the trauma center after blunt trauma during the first 6 months of protocol implementation. Head CT scans were obtained in 158 patients and lateral cervical spine radiography in conjunction with helical CT scanning evaluated the C-spine. The other 166 patients had the cervical spine cleared by three-view radiography series or by clinical examination alone. For patients in whom a head CT scan was not indicated, CT scanning was used only when plain radiographs failed to adequately visualize the entire C-spine. A total of 15 injuries (4.6% of the group) were detected. Seven injuries were suspected or detected by lateral plain radiographs and confirmed by CT scan. Six patients had an injury not detected by radiography but diagnosed by CT scan, and one patient had a false-positive radiograph. Of the remaining two injuries, one was diagnosed by magnetic resonance imaging and the other by CT scan outside of the protocol. Lateral plain radiographs alone failed to detect 46% (n = 6) of all injuries. CONCLUSION: In our series, the selective use of helical CT scanning with plain radiography increased the accuracy with which cervical spine injury was detected from 54% to 100%. The protocol allowed for more rapid evaluation in many patients as well. We recommend that practice guidelines include the use of helical CT scan of the entire C-spine as the diagnostic procedure for those blunt trauma patients undergoing CT scanning of the head.

A simple provider-based educational intervention to boost infant immunization rates: a controlled trial.

We sought to determine if a simple educational intervention initiated at the first well-child care visit, with reinforcement at subsequent visits, can improve inner-city infant immunization rates. We conducted a controlled trial involving 315 newborn infants and their primary caregivers in 3 inner-city primary care centers. Child health care providers gave caregivers in the intervention group an interactive graphic card with verbal reinforcement. At later visits, stickers were applied to the card when immunizations were given. Routine information was given to controls. After the trial, age-appropriate immunization rates at 7 months were 58% in each group. Intervention infants had 50% fewer missed opportunities to immunize (p=0.01) but cancelled 77% more appointments (p=0.04) than controls. We conclude that a brief educational intervention at the first well-child care visit did not boost 7-month immunization rates, although it was associated with fewer missed opportunities to immunize.

Identification of genotypic changes in human immunodeficiency virus protease that correlate with reduced susceptibility to the protease inhibitor lopinavir among viral isolates from protease inhibitor-experienced patients.

The association of genotypic changes in human immunodeficiency virus (HIV) protease with reduced in vitro susceptibility to the new protease inhibitor lopinavir (previously ABT-378) was explored using a panel of viral isolates from subjects failing therapy with other protease inhibitors. Two statistical tests showed that specific mutations at 11 amino acid positions in protease (L10F/I/R/V, K20M/R, L24I, M46I/L, F53L, I54L/T/V, L63P, A71I/L/T/V, V82A/F/T, I84V, and L90M) were associated with reduced susceptibility. Mutations at positions 82, 54, 10, 63, 71, and 84 were most closely associated with relatively modest (4- and 10-fold) changes in phenotype, while the K20M/R and F53L mutations, in conjunction with multiple other mutations, were associated with >20- and >40-fold-reduced susceptibility, respectively. The median 50% inhibitory concentrations (IC(50)) of lopinavir against isolates with 0 to 3, 4 or 5, 6 or 7, and 8 to 10 of the above 11 mutations were 0.8-, 2.7-, 13.5-, and 44.0-fold higher, respectively, than the IC(50) against wild-type HIV. On average, the IC(50) of lopinavir increased by 1.74-fold per mutation in isolates containing three or more mutations. Each of the 16 viruses that displayed a >20-fold change in susceptibility contained mutations at residues 10, 54, 63, and 82 and/or 84, along with a median of three mutations at residues 20, 24, 46, 53, 71, and 90. The number of protease mutations from the 11 identified in these analyses (the lopinavir mutation score) may be useful for the interpretation of HIV genotypic resistance testing with respect to lopinavir-ritonavir (Kaletra) regimens and may provide insight into the genetic barrier to resistance to lopinavir-ritonavir in both antiretroviral therapy-naive and protease inhibitor-experienced patients.

Safety and efficacy of high dose etanercept in treatment of juvenile rheumatoid arthritis.

OBJECTIVE: To evaluate safety and efficacy of high dose etanercept (> 0.8 mg/kg, maximum 25 mg subcutaneously twice weekly) (Enbrel) in children with juvenile rheumatoid arthritis (JRA) and inadequate prior response to standard dose etanercept. METHODS: Retrospective chart review of 8 children (6 girls, 2 boys, mean age 8.4 yrs, range 5-16 yrs). Five children had systemic onset, polyarticular course JRA; 2 had polyarticular onset; and one had pauciarticular onset, polyarticular course JRA. All children had failed at least 3 mo (mean 9 mo) treatment with standard dose etanercept (0.4 mg/kg SC twice a week). All 8 children had increase in the etanercept dose to at least 0.8 mg/kg (mean 1.1 mg/kg, maximum 25 mg SC twice weekly) for a mean of 7 mo (range 3-10 mo). Efficacy of high dose etanercept was evaluated by changes in joint count, laboratory data, and ability to decrease concomitant medication. RESULTS: Improvements in the joint count and laboratory findings (erythrocyte sedimentation rate, hemoglobin and platelet count) were observed in 2 of 8 (25%) children. In these 2, concomitant prednisone was reduced or discontinued. In contrast, no changes in disease activity or laboratory findings were observed in the other 6 children. Overall, high dose etanercept was well tolerated. No laboratory abnormalities were detected and no child withdrew because of adverse events. CONCLUSION: High dose etanercept is safe and well tolerated in children, but efficacy seems limited. In children with unsatisfactory response to standard dose etanercept, an increased dose or treatment prolongation may not offer any additional benefit.

Etanercept therapy in children with treatment-resistant uveitis.

OBJECTIVE: To evaluate the safety and efficacy of the tumor necrosis factor fusion protein etanercept in children with treatment-resistant uveitis. METHODS: Ten children with chronic active uveitis (7 girls and 3 boys, mean age 7.5 years [range 3-12 years]) were enrolled in this prospective study. In 7 children, uveitis was associated with pauciarticular juvenile rheumatoid arthritis. Five children were antinuclear antibody positive. All patients had failed previous therapy with topical steroids and methotrexate and/or cyclosporine. All were treated with etanercept at a dosage of 0.4 mg/kg twice weekly for the first 3 months, and then, if eyes did not improve, with 25 mg twice weekly (mean 1.1 mg/kg) for at least 3 additional months. RESULTS: At the beginning of the trial, uveitis affected 18 eyes in the 10 children. Within 3 months, 10 of 16 affected eyes (63%; P = 0.017) showed a rapid decrease in anterior chamber cell density, including remission of uveitis in 4 eyes. In children with visual acuity of less than 20/25, 4 of 10 eyes (40%) improved. An exacerbation of uveitis during etanercept therapy occurred in only 1 child (1 of 14 eyes [7%]). Other ocular outcome parameters, such as intraocular pressure, synechia formation, and lens clarity, remained unchanged. Following a dosage increase to an average of 1.1 mg/kg after 3 months in 7 children, no further improvement was noted. CONCLUSION: Our data suggest that etanercept injected subcutaneously twice a week has a beneficial effect on treatment-resistant chronic uveitis in children. Further controlled studies with etanercept in systemic or topical form are necessary to confirm its efficacy and optimal mode of administration.

Primary angiitis of the central nervous system in children: 5 cases.

We describe 5 children who meet criteria for primary angiitis of the central nervous system (PACNS). All patients presented with headache and/or focal neurologic deficits and exhibited clinical and/or radiographic evidence of disease progression. Two patients had disease progression prior to combined treatment with cyclophosphamide and corticosteroids; one progressed while receiving intravenous cyclophosphamide and stabilized after a change to daily oral dosing; one progressed after discontinuing therapy after less than 12 months and improved after retreatment; and one progressed on steroid therapy alone but was lost to followup. Children who have frequent or severe headaches or focal neurologic deficits should be carefully evaluated and those meeting criteria for PACNS should be treated aggressively.

Treatment of collagen induced arthritis in DBA/1 mice with L-asparaginase.

OBJECTIVE: To evaluate the safety and efficacy of L-asparaginase as an immunosuppressive agent in a mouse model of rheumatoid arthritis. METHODS: Male DBA/1 mice with collagen-induced arthritis (CIA) were treated at different intervals with various doses of native and pegylated L-asparaginase from E. coli. The mice were observed for 4 weeks during which time arthritis was scored. Outcome parameters included effect on severity and progression of established arthritis as well as prevention of disease. In addition, X-rays from the affected joints were obtained for comparison. RESULTS: Both native L-asparaginase at a dose of 50 IU/injection intraperitoneally three days a week and pegylated asparaginase (PEG-L-asparaginase) at a dose of 25 IU/injection twice a week, significantly reduced the mean arthritic score (MAS) in mice with established arthritis (p < 0.001 for PEG-L-asparaginase). When native L-asparaginase was administered before the onset of arthritis (days 14-post immunization) the number of mice developing arthritis as well as the number of arthritic paws and the severity of arthritis in the treatment group were significantly decreased (p < 0.0001). Significant differences were found in the X-ray evaluation between treated and control mice. None of the animals died due to drug related events or showed signs of asparaginase induced toxicity. CONCLUSION: Our data provide the first direct evidence that L-asparaginase is a potent antiarthritic agent and may represent an effective second line agent for future treatment studies in juvenile and adult rheumatoid arthritis.

Docetaxel as an alternative to paclitaxel after acute hypersensitivity reactions.

OBJECTIVE: To review the mechanism involved in paclitaxel-induced hypersensitivity reactions and to evaluate the potential use of docetaxel after acute hypersensitivity reactions (HSRs) to paclitaxel. DATA SOURCES: Literature identified through a MEDLINE search (1966-September 2000) and through secondary sources. DATA SYNTHESIS: HSRs to paclitaxel can be life-threatening. The exact etiology involved in paclitaxel-induced HSRs has not been fully elucidated; the reactions may be due to the Cremophor EL vehicle or to paclitaxel itself. Options for treatment following HSRs are limited. A rechallenge attempt can be made, but is not always successful. Docetaxel, a semisynthetic taxane, may have a role in therapy for patients unable to tolerate paclitaxel therapy. This review examines the etiology of paclitaxel-induced HSRs and the potential role of docetaxel following these acute reactions. CONCLUSIONS: Docetaxel may be a viable alternative for patients who experience HSRs to paclitaxel.

Genomewide studies of histone deacetylase function in yeast.

The trichostatin A (TSA)-sensitive histone deacetylase (HDAC) Rpd3p exists in a complex with Sin3p and Sap30p in yeast that is recruited to target promoters by transcription factors including Ume6p. Sir2p is a TSA-resistant HDAC that mediates yeast silencing. The transcription profile of rpd3 is similar to the profiles of sin3, sap30, ume6, and TSA-treated wild-type yeast. A Ume6p-binding site was identified in the promoters of genes up-regulated in the sin3 strain. Two genes appear to participate in feedback loops that modulate HDAC activity: ZRT1 encodes a zinc transporter and is repressed by RPD3 (Rpd3p is zinc-dependent); BNA1 encodes a nicotinamide adenine dinucleotide (NAD)-biosynthesis enzyme and is repressed by SIR2 (Sir2p is NAD-dependent). Although HDACs are transcriptional repressors, deletion of RPD3 down-regulates certain genes. Many of these are down-regulated rapidly by TSA, indicating that Rpd3p may also activate transcription. Deletion of RPD3 previously has been shown to repress ("silence") reporter genes inserted near telomeres. The profiles demonstrate that 40% of endogenous genes located within 20 kb of telomeres are down-regulated by RPD3 deletion. Rpd3p appears to activate telomeric genes sensitive to histone depletion indirectly by repressing transcription of histone genes. Rpd3p also appears to activate telomeric genes repressed by the silent information regulator (SIR) proteins directly, possibly by deacetylating lysine 12 of histone H4. Finally, bioinformatic analyses indicate that the yeast HDACs RPD3, SIR2, and HDA1 play distinct roles in regulating genes involved in cell cycle progression, amino acid biosynthesis, and carbohydrate transport and utilization, respectively.

Intracellular pH modulation of ADF/cofilin proteins.

The ADF/cofilin (AC) proteins are necessary for the high rates of actin filament turnover seen in vivo. Their regulation is complex enough to underlie the precision in filament dynamics needed by stimulated cells. Disassembly of actin by AC proteins is inhibited in vitro by phosphorylation of ser3 and pH<7.1. This study of Swiss 3T3 cells demonstrates that pH also affects AC behavior in vivo: (1) Wounded cells show pH-dependent AC translocation to alkaline-induced ruffling membrane; (2) The Triton extractable (soluble) ADF from Swiss 3T3 cells decreases from 42+/-4% to 23+/-4% when the intracellular pH (pH(i)) is reduced from 7.4 to 6.6; (3) Covariance and colocalization analyses of immunostained endogenous proteins show that ADF partitions more with monomeric actin and less with polymeric actin when pH(i) increases. However, the distribution of cofilin, a less pH-sensitive AC in vitro, does not change with pH; (4) Only the unphosphorylatable AC mutant (A3), when overexpressed as a GFP chimera, uniquely produces aberrant cellular phenotypes and only if the pH is shifted from 7.1 to 6.6 or 7.4. A mechanism is proposed that explains why AC(A3)-GFP and AC(wt)-GFP chimeras generate different phenotypes in response to pH changes. Phospho-AC levels increase with cell density, and in motile cells, phospho-AC increases with alkalization, suggesting a homeostatic mechanism that compensates for increased AC activity and filament turnover. These results show that the behavior of AC proteins with pH-sensitivity in vitro is affected by pH in vivo.

Food stamps are associated with food security and dietary intake of inner-city preschoolers from Hartford, Connecticut.

The goal of the present study was to examine the association of the Food Stamp Program with the food security and dietary intake of low-income children from Hartford, CT, who were enrolled in the Supplemental Food Program for Women, Infants, and Children (WIC). We compared the food and nutrition situation of low-income preschoolers who received food stamps (FS, n = 59) with that of those who did not receive food stamps (NFS, n = 40). Children were an average age of 2.7 +/- 0.6 y, and 95% were receiving WIC benefits at the time of the study. Groups were comparable in demographic characteristics, but the socioeconomic status of the FS group was lower than that of the NFS group (P < 0.05). Food security was assessed with the Radimer/Cornell hunger scale, and dietary intake was assessed with a single 24-h recall and a 14-item food frequency questionnaire. Multivariate analyses within the FS group indicated that a monthly duration of food stamps of <4 wk was a predictor of household food security (odds ratio 0.10, 95% confidence interval 0.02-0.56). Food stamp use was associated with above-median energy-adjusted intakes of vitamin B-6 (3.13, 1.16-8.45), folate (2.92, 1.09-7.81) and iron (3.72, 1.31-10.54). The NFS children were more likely to consume <8 mg iron/d (3.73, 1.09-12.80). These results suggest that the Food Stamp Program is associated with food security and preschoolers' micronutrient intake.

Regulating actin dynamics in neuronal growth cones by ADF/cofilin and rho family GTPases.

Growth cone motility and navigation in response to extracellular signals are regulated by actin dynamics. To better understand actin involvement in these processes we determined how and in what form actin reaches growth cones, and once there, how actin assembly is regulated. A continuous supply of actin is maintained at the axon tip by slow transport, the mobile component consisting of an unassembled form of actin. Actin is co-transported with actin-binding proteins, including ADF and cofilin, structurally related proteins essential for rapid turnover of actin filaments in vivo. ADF and cofilin activity is regulated through phosphorylation by LIM kinases, downstream effectors of the Rho family of GTPases, Cdc42, Rac and Rho. Attractive and repulsive extracellular guidance cues might locally alter actin dynamics by binding specific GTPase-linked receptors, activating LIM kinases, and subsequently modulating the activity of ADF/cofilin. ADF is enriched in growth cones and is required for neurite outgrowth. In addition, signals that influence growth cone behavior alter ADF/cofilin phosphorylation, and overexpression of ADF enhances neurite outgrowth. Growth promoting effects of laminin are mimicked by expression of constitutively active Cdc42 and blocked by expression of the dominant negative Cdc42. Repulsive effects of myelin and sema3D on growth cones are blocked by expression of constitutively active Rac1 and dominant negative Rac1, respectively. Thus a series of complex pathways must exist for regulating effectors of actin dynamics. The bifurcating nature of the ADF/cofilin phosphorylation pathway may provide the integration necessary for this complex regulation.

Drug-induced linear immunoglobulin A bullous disease that clinically mimics toxic epidermal necrolysis.

Drug-induced linear immunoglobulin A bullous disease is a subepidermal blistering disorder that most commonly occurs after exposure to vancomycin. It can clinically mimic toxic epidermolytic necrolysis. We describe an 87-year-old white woman in whom linear immunoglobulin A bullous disease developed while she was taking vancomycin and phenytoin. A few days after the linear immunoglobulin A bullous disease developed, both medications were discontinued. No new bullae developed, and the eruption completely resolved within 2 weeks. The patient was treated with only topical therapy.