Spatial propagation of protein polymerization.

We consider the spatial dependence of filamentous protein self-assembly. Through studying the cases where the spreading of aggregated material is dominated either by diffusion or by growth, we derive analytical results for the spatial evolution of filamentous protein aggregation, which we validate against Monte Carlo simulations. Moreover, we compare the predictions of our theory with experimental measurements of two systems for which we identify the propagation as either growth or diffusion controlled. Our results connect the macroscopic observables that characterize the spatial propagation of protein self-assembly with the underlying microscopic processes and provide physical limits on spatial propagation and prionlike behavior associated with protein aggregation.

Hydrodynamics of hemostasis in sickle-cell disease.

Vaso-occlusion, the stoppage of blood flow in sickle-cell disease, is a complex dynamical process spanning multiple time and length scales. Motivated by recent ex vivo microfluidic measurements of hemostasis using blood from sickle-cell patients, we develop a multiphase model that couples the kinetics and hydrodynamics of a flowing suspension of normal and sickled cells in a fluid. We use the model to derive expressions for the cell velocities and concentrations that quantify the hydrodynamics of hemostasis, and provide simple criteria as well as a phase diagram for occlusion, consistent with our simulations and earlier observations.

The HD mutation causes progressive lethal neurological disease in mice expressing reduced levels of huntingtin.

Huntingtin is an essential protein that with mutant polyglutamine tracts initiates dominant striatal neurodegeneration in Huntington's disease (HD). To assess the consequences of mutant protein when huntingtin is limiting, we have studied three lines of compound heterozygous mice in which both copies of the HD gene homolog (Hdh) were altered, resulting in greatly reduced levels of huntingtin with a normal human polyglutamine length (Q20) and/or an expanded disease-associated segment (Q111): Hdh(neoQ20)/Hdh(neoQ20), Hdh(neoQ20)/Hdh(null) and Hdh(neoQ20)/Hdh(neoQ111). All surviving mice in each of the three lines were small from birth, and had variable movement abnormalities. Magnetic resonance micro-imaging and histological evaluation showed enlarged ventricles in approximately 50% of the Hdh(neoQ20)/Hdh(neoQ111) and Hdh(neoQ20)/Hdh(null) mice, revealing a developmental defect that does not worsen with age. Only Hdh(neoQ20)/Hdh(neoQ111) mice exhibited a rapidly progressive movement disorder that, in the absence of striatal pathology, begins with hind-limb clasping during tail suspension and tail stiffness during walking by 3-4 months of age, and then progresses to paralysis of the limbs and tail, hypokinesis and premature death, usually by 12 months of age. Thus, dramatically reduced huntingtin levels fail to support normal development in mice, resulting in reduced body size, movement abnormalities and a variable increase in ventricle volume. On this sensitized background, mutant huntingtin causes a rapid neurological disease, distinct from the HD-pathogenic process. These results raise the possibility that therapeutic elimination of huntingtin in HD patients could lead to unintended neurological, as well as developmental side-effects.

The natural history and longitudinal study of the surgically corrected clubfoot.

Surgical treatment for clubfoot has been largely directed at finding the best one-stage operation for the resistant clubfoot. Eighteen patients with 27 clubfeet (average follow-up 11 years since first surgery; range, 3.5-24 years) were reviewed. More than one clubfoot operation was required in 56% of cases. Forty-six percent were corrected after one surgery; 33% required a second surgery and 14% required a third operation. One patient with particularly severe feet required a fourth operation on each foot. The mean age at the time of surgery was 1.26 years, 5.12 years, and 8 years for the first, second, and third operations, respectively. The first operation consisted of a soft-tissue release. The second and third operations consisted of more extensive soft-tissue release and various rearfoot and forefoot procedures. Radiographic values revealed an AP talocalcaneal angle of 18 degrees, AP talo-first metatarsal angle of 6 degrees, lateral talocalcaneal angle of 29.6 degrees, lateral talo-first metatarsal angle of 15 degrees, and calcaneo-first metatarsal angle of 143 degrees. At follow-up all patients had adequate function as determined by personal interview and clinical examination. We conclude that correction of resistant congenital clubfoot often requires more than one surgery, not because of a "failed first operation," but due to dynamic muscle imbalances that may not be fully recognized in infancy and early childhood. Thus, the need for a second operation should not be perceived as a failure of the first, but as part of the natural history of congenital clubfoot.

Potential cost savings from pill splitting of newer psychotropic medications.

Many of the newer psychotropic medications have a pricing structure in which there are only small cost differences between pills of different strengths, affording an opportunity for cost saving by splitting pills. Twelve newer psychotropic medications were examined. Although savings varied for each drug, aggregate data indicated that splitting pills can produce an annual savings of up to $1.45 billion, which represents about 10 percent of the retail sales of these drugs. Such savings can benefit individuals, state Medicaid programs, community mental health centers, and managed care companies. The authors propose several strategies for encouraging the use of pill splitting.

Pelvic resection of recurrent rectal cancer: technical considerations and outcomes.

PURPOSE: Pelvic recurrence of rectal cancer is an ominous event for the patient and a formidable challenge to the managing surgeon. We reviewed the results of abdominosacral resection to manage these patients and correlated outcome (survival and recurrence) with known prognostic factors. METHODS: An abdominosacral resection was performed on 61 patients with pelvic recurrence (53 with curative intent and 6 for palliation; 2 had extended pelvic resection). Of the 53 patients (32 males; average age, 59 years) previous resection included abdominoperineal resection in 27 patients, abdominoperineal resection plus hepatic lobectomy in 2 patients, low anterior resection in 19 patients, plus trisegmentectomy in 1 patient, and advanced primary cancers in 4 patients. Initial primary stage was Dukes B (64 percent) and Dukes C (36 percent). All had been irradiated (3,000-6,500 in 50 patients, 8,300 and 11,000 in 2 patients, and unknown dose in 3 patients). Preoperative carcinoembryonic antigen was elevated (>5 ng/ml) in 54 percent. Extent of resection: high sacral resection S-1-S2 was done in 32 patients, midsacrum in 14 patients, and low S-4-S-5 in 6 patients. Twenty-eight patients (60 percent) required partial or complete bladder resection with or without adjacent viscera, and all had internal iliac and obturator node dissection. RESULTS: There were four postoperative (within 60 days) deaths, 8 percent in curative groups (5.4 percent overall). Major complications included prolonged intubation (20 percent), sepsis (34 percent), posterior wound infection or flap separation (38 percent). The survival rate in the curative group (49 postoperative survivors) was 31 percent at five years, with 13 patients surviving beyond five years. Seven of these patients survived from 5 to 21 years, whereas six patients recurred again and died within 5.5 to 7.5 years after abdominosacral resection. Disease-free survival rate at five years was 23 percent. Recent reconstruction with large composite myocutaneous gluteal flaps in 5 patients permitted complete sacral wound coverage, resulting in earlier ambulation and reduced hospital stay. CONCLUSIONS: Abdominosacral resection permits removal of pelvic recurrence of rectal cancer that is fixed to the sacrum and is associated with long-term survival in 31 percent of patients. Recent technical advances have improved the short-term outcome and have made the procedure more feasible for surgical teams familiar with these techniques.

Risk of nodal metastases at laparoscopic pelvic lymphadenectomy using PSA, Gleason score, and clinical stage in men with localized prostate cancer.

Laparoscopic pelvic lymph node dissection (LPLND) is a low-morbidity procedure used to stage prostate cancer accurately prior to definitive local therapy. To better select patients for LPLND, we reviewed the clinical features of 120 patients with clinically localized prostate cancer who underwent LPLND to define significant risk factors for nodal metastases. The age ranged from 43 to 79 years (mean 68). Serum prostate specific antigen (PSA) concentration ranged from 1.3 to 329 ng/mL, Gleason score ranged from 2 to 9, and clinical stage ranged from T1b to T3c. Nodal metastases were discovered in 15 patients (13%). Among men with a Gleason score > or = 7, 21% had nodal metastases (P = 0.004). A serum PSA > 20 ng/mL and clinical stage T1b, T2b, or greater also were statistically significant predictors of lymph node metastases (20% and 19%, respectively). In multivariate analysis, Gleason score significantly predicted nodal metastases when controlling for all other clinical measures. Therefore, LPLND is indicated for any patient with a Gleason score > or = 7, PSA > 20 ng/mL, and advanced clinical T stage, independently or in combination.

Alcohol and benzodiazepines generate anxiety, panic and phobias.

In almost half the patients seeking advice for anxiety, panic and phobias the cause was alcohol or benzodiazepines. In the remainder it was psychological, usually a state of conflict or a traumatic event. When symptoms are persistent following a distressing event it is often the case that alcohol or benzodiazepines are keeping them going. There is a large variation in individual vulnerability and the mechanism responsible for these symptoms is rebound arousal.