Surface shear viscosity as a macroscopic probe of amyloid fibril formation at a fluid interface

Amyloidogenesis of proteins is of wide interest because amyloid structures are associated with many diseases, including Alzheimer's and type II diabetes. Dozens of different proteins of various sizes are known to form amyloid fibrils. While there are numerous studies on the fibrillization of insulin induced by various perturbations, shearing at fluid interfaces has not received as much attention. Here, we present a study of human insulin fibrillization at room temperature using a deep-channel surface viscometer. The hydrodynamics of the bulk flow equilibrates in just over a minute, but the proteins at the air-water interface exhibit a very slow development during which the surface (excess) shear viscosity deduced from a Newtonian surface model increases slightly over a period of a day and a half. Then, there is a very rapid increase in the surface shear viscosity to effectively unbounded levels as the interface becomes immobilized. Atomic force microscopy shows that fibrils appear at the interface after it becomes immobilized. Fibrillization in the bulk does not occur until much later. This has been verified by concurrent atomic force microscopy and circular dichroism spectroscopy of samples from the bulk. The immobilized interface has zero in-plane shear rate, however due to the bulk flow, there is an increase in the strength of the normal component of the shear rate at the interface, implicating this component of shear in the fibrillization process ultimately resulting in a thick weave of fibrils on the interface. Real-time detection of fibrillization via interfacial rheology may find utility in other studies of proteins at sheared interfaces.

Shear-induced amyloid fibrillization: the role of inertia

Agitation of protein is known to induce deleterious effects on protein stability and structure, with extreme agitation sometimes resulting in complete aggregation into amyloid fibrils. Many mechanisms have been proposed to explain how protein becomes unstable when subjected to flow, including alignment of protein species, shear-induced unfolding, simple mixing, or fragmentation of existing fibrils to create new seeds. Here a shearing flow was imposed on a solution of monomeric human insulin via a rotating Couette device with a small hydrophobic fluid interface. The results indicate that even very low levels of shear are capable of accelerating amyloid fibril formation. Simulations of the flow suggest that the shear enhances fibrillization kinetics when flow inertia is non-negligible and the resulting meridional circulation allows for advection of bulk protein to the hydrophobic interface.

The short-term effect of pelvic irradiation for gynecologic malignancies on bladder function

Urinary symptoms and urodynamic studies were evaluated prospectively in 33 women undergoing radiation therapy for cervical cancer. Patients were evaluated during treatment, after one to two months, and after five to six months. Significant reductions in peak urinary flow, volume at first desire to void, cystometric capacity, and bladder compliance were evident during and immediately after therapy. Bladder symptoms and urodynamic alteration did not correlate with age, race, or stage of disease. Bladder compliance was significantly reduced in those patients receiving more than 3000 rads to the entire bladder from external beam irradiation.

The adverse effects of cervical cancer treatment on bladder function

Bladder dysfunction is a recognized complication following radical hysterectomy, however, the effect of radiation alone or in combination with surgery on bladder function has received little attention. Thirty patients who underwent radical hysterectomy with postoperative whole pelvis radiation (RH + RT) were matched for age, stage of disease, and time interval since therapy, with 30 patients who had radical hysterectomy alone (RH) and 30 patients who were treated with pelvic radiotherapy (RT). Bladder function was assessed by symptoms and urodynamic evaluation. Altered bladder sensation and voiding problems were associated with surgery, and were more frequent after RH or RH + RT than RT (P = 0.002). fifty percent of RH patients voided by abdominal straining compared to 10% who had only RT. No greater problem was seen after RH + RT compared to RH. Urinary incontinence was present in 15% of patients prior to therapy. After treatment, incontinence requiring protection developed in 23% of RT patients, 26% of RH patients, and 63% of RH + RT patients. The severity of the incontinence was greater after RH + RT. Bladder neck and urethral function was similar in all groups, however, bladder compliance was reduced in RT patients and significantly (P = 0.0001) reduced after RH + RT compared to RH alone. This reduction was related to the bladder dose of external radiation and was a factor in the etiology of the urinary incontinence seen in RH + RT patients.

Predicting the risk of abdominal disease in Hodgkin's lymphoma. A multifactorial analysis of staging laparotomy results in 255 patients

There were 425 consecutive patients treated for Hodgkin's disease at this Medical Center from 1943 to 1983. Of these, 255 patients underwent a staging laparotomy and had complete preoperative clinical records. Overall, 35% had a change in stage (24% were upstaged, 11% downstaged). Twenty-nine per cent of clinical stage I patients were upstaged; 31% of stage II patients were upstaged, while less than 1% were downstaged; and four per cent of stage III patients were upstaged while 44% were downstaged. The diagnostic laparotomy yielded involvement in the spleen in 71% of patients with abdominal involvement, in the periaortic lymph nodes in 41%, in the liver in 11%, and the bone marrow in seven per cent. Only 12% of the 135 patients with negative laparotomies subsequently relapsed in the abdomen after a mean follow-up of 4.8 years. A multifactorial analysis was performed to identify dominant factors predicting the risk for abdominal disease. The factors best predicting abdominal involvement in stage I and II patients were: antecedent symptoms (greater than or equal to 2, 1, 0; p less than 0.00001), histological type [nodular sclerosing (NS) less than lymphocyte-predominant (LP) less than mixed cellularity (MC) less than lymphocyte-depleted (LD); p = 0.0009], and sex (females less than males, p = 0.01). The clinical stage (I vs. II), the site of lymphoma presentation, and the age and race of the patient did not have significant predictive value for the risk of abdominal disease after the other factors were accounted for. A mathematical model was derived for identifying dominant prognostic factors for predicting the risk of abdominal disease in an individual patient setting. The lowest risk patients were asymptomatic females with NS histology (6%) or LP histology (8%), while the highest risk patients were men with multiple symptoms and either MC histology (85%) or LD histology (93%). This information can be useful in making clinical decisions in Hodgkin's lymphoma patients, especially those at an increased risk for surgery.