Investigation of the peak action wavelength of light-activated gene transduction.

Light-activated gene transduction (LAGT) is an approach to localize gene therapy via preactivation of cells with UV light, which facilitates transduction by recombinant adeno-associated virus vectors. Previous studies demonstrated that UVC induces LAGT secondary to pyrimidine dimer formation, whereas UVA induces LAGT secondary to reactive-oxygen species (ROS) generation. However, the empirical UVB boundary of these UV effects is unknown. Thus, we aimed to define the action spectra for UV-induced LAGT independent of DNA damage and determine an optimal wavelength to maximize safety and efficacy. UV at 288, 311 and 320 nm produced significant dose-dependent LAGT effects, of which the maximum (800-fold) was observed with 4 kJ m⁻² at 311 nm. Consistent with its robust cytotoxicity, 288 nm produced significantly high levels of DNA damage at all doses tested, whereas 311, 320 and 330 nm did not generate pyrimidine dimers and produced low levels of DNA damage detected by comet assay. Although 288 nm failed to induce ROS, the other wavelengths were effective, with the maximum (10-fold) effect observed with 30 kJ m⁻² at 311 nm. An in vivo pilot study assessing 311 nm-induced LAGT of rabbit articular chondrocytes demonstrated a significant 6.6-fold (P<0.05) increase in transduction with insignificant cytotoxicity. In conclusion, 311 nm was found to be the optimal wavelength for LAGT on the basis of its superior efficacy at the peak dose and its broad safety range that is remarkably wider than the other UV wavelengths tested.

Disseminated histoplasmosis in a patient with sarcoidosis: a controversial relationship and a diagnostic dilemma.

The diagnosis of sarcoidosis in patients with disseminated histoplasmosis remains controversial. It has been suggested that the immune abnormalities in sarcoidosis predispose one to disseminated histoplasmosis. Two cases have been reported that indicate a possible relationship between the two diseases. This is a case of sarcoidosis complicated with disseminated histoplasmosis in which the controversial relationship between the two diseases is emphasized and the available medical literature is reviewed.

Case report: transverse colon volvulus in a patient with Clostridium difficile pseudomembranous colitis.

Sixty-eight cases of transverse colon volvulus have been reported in the literature. The authors report the first case of transverse colon volvulus in association with Clostridium difficile pseudomembranous colitis, with a review of the available literature. It is possible that the acute inflammation of the colonic mucosa, which occurred from the pseudomembranous colitis in this patient, contributed to the development of volvulus. Further studies are needed to explore the role of mucosal inflammation in the occurrence of volvulus.

Time course of corticospinal excitability in reaction time and self-paced movements.

We used transcranial magnetic stimulation (TMS) to study the time course of corticospinal excitability before and after brisk thumb abduction movements, either in a simple reaction time (RT) paradigm or self-paced. Premovement increase in corticospinal excitability began about 20 msec earlier for self-paced compared with simple RT movements. For both simple RT and self-paced movements after electromyographic (EMG) offset, there was a first period of increased excitability from 0 to 100 msec, followed by a second period from 100 to 160 msec. Corticospinal excitability was decreased from about 500 to 1,000 msec after EMG offset for both types of movements. Our results show that motor preparation that begins 1.5 to 2 seconds before self-paced movement is not associated with increased corticospinal excitability. The first phase of increased corticospinal excitability after EMG offset may be due to activity of motor cortex neuron subthreshold for activating spinal motor neurons, and the second phase may reflect a subthreshold second agonist burst. The period of decreased corticospinal excitability after movement corresponds to the onset of event-related synchronization (ERS) of electroencephalographic signals in the 20-Hz band, and supports the hypothesis that ERS may be related to an inactive, idling state of the motor cortex.

Mechanisms of cortical reorganization in lower-limb amputees.

The human motor system undergoes reorganization after amputation, but the site of motor reorganization and the mechanisms involved are unknown. We studied the site and mechanisms of motor reorganization in 16 subjects with traumatic lower-limb amputation. Stimulation at different levels in the CNS was used to determine the site of reorganization. The mechanisms involved were evaluated by measuring the thresholds for transcranial magnetic stimulation (TMS) and by testing intracortical inhibition and facilitation. With TMS, the threshold for muscle activation on the amputated side was lower than that of the intact side, but with transcranial electrical stimulation there was no difference in motor threshold between the two sides. TMS at the maximal output of the stimulator activated a higher percentage of the motor neuron pool (%MNP) on the amputated side than on the intact side. The %MNP activated by spinal electrical stimulation was similar on the two sides. Paired TMS study showed significantly less intracortical inhibition on the amputated side. Our findings suggest that motor reorganization after lower-limb amputation occurs predominately at the cortical level. The mechanisms involved are likely to include reduction of GABAergic inhibition.

Dissociation of the pathways mediating ipsilateral and contralateral motor-evoked potentials in human hand and arm muscles.

1. Growing evidence points toward involvement of the human motor cortex in the control of the ipsilateral hand. We used focal transcranial magnetic stimulation (TMS) to examine the pathways of these ipsilateral motor effects. 2. Ipsilateral motor-evoked potentials (MEPs) were obtained in hand and arm muscles of all 10 healthy adult subjects tested. They occurred in the finger and wrist extensors and the biceps, but no response or inhibitory responses were observed in the opponens pollicis, finger and wrist flexors and the triceps. 3. The production of ipsilateral MEPs required contraction of the target muscle. The threshold TMS intensity for ipsilateral MEPs was on average 1.8 times higher, and the onset was 5.7 ms later (in the wrist extensor muscles) compared with size-matched contralateral MEPs. 4. The corticofugal pathways of ipsilateral and contralateral MEPs could be dissociated through differences in cortical map location and preferred stimulating current direction. 5. Both ipsi- and contralateral MEPs in the wrist extensors increased with lateral head rotation toward, and decreased with head rotation away from, the side of the TMS, suggesting a privileged input of the asymmetrical tonic neck reflex to the pathway of the ipsilateral MEP. 6. Large ipsilateral MEPs were obtained in a patient with complete agenesis of the corpus callosum. 7. The dissociation of the pathways for ipsilateral and contralateral MEPs indicates that corticofugal motor fibres other than the fast-conducting crossed corticomotoneuronal system can be activated by TMS. Our data suggest an ipsilateral oligosynaptic pathway, such as a corticoreticulospinal or a corticopropriospinal projection as the route for the ipsilateral MEP. Other pathways, such as branching of corticomotoneuronal axons, a transcallosal projection or a slow-conducting monosynaptic ipsilateral pathway are very unlikely or can be excluded.

Effect of muscle activity immediately after botulinum toxin injection for writer's cramp.

Animal and human studies have shown that nerve stimulation enhances some effects of botulinum toxin (btx A) injection. Voluntary muscle activity might work similarly and would focus the effect of an injection into the active muscles. We studied the effects of exercise immediately after btx A injection in eight patients with writer's cramp with established response to btx A over two injection cycles with a single-blinded, randomized, crossover design. Immediately after the first study injection, they were randomly assigned to write continuously for 30 min or have their hand and forearm immobilized for 30 min. Following the second injection, they were assigned the alternate condition. Patients were assessed just before each injection, and at 2 weeks, 6 weeks, and 3 months post-injection. Assessment included objective strength testing, self-reported rating of benefit and weakness, and blinded evaluation of videotapes and writing samples of the patients writing a standard passage. Strength testing showed that the maximum weakness occurred at 2 weeks post-injection, but the benefit was maximum at 6 weeks post-injection. The "write" condition resulted in greater reduction in strength than the "rest" condition. Btx A treatment led to improvement in self-reported ratings, writer's cramp rating scale scores by blinded raters, and reduction in writing time, but the differences between the "write" and "rest" conditions were not significant. We conclude that voluntary muscle activity immediately after btx A injection leads to greater reduction in muscle strength. Our findings raise the possibility that voluntary muscle activation may allow reduction of btx A doses and favorably alter the balance of benefit and side effects of btx A injections.