Pressure-actuated microfluidic devices for electrophoretic separation of pre-term birth biomarkers.

We have developed microfluidic devices with pressure-driven injection for electrophoretic analysis of amino acids, peptides, and proteins. The novelty of our approach lies in the use of an externally actuated on-chip peristaltic pump and closely spaced pneumatic valves that allow well-defined, small-volume sample plugs to be injected and separated by microchip electrophoresis. We fabricated three-layer poly(dimethylsiloxane) (PDMS) microfluidic devices. The fluidic layer had injection and separation channels, and the control layer had an externally actuated on-chip peristaltic pump and four pneumatic valves around the T-intersection to carry out sample injection. An unpatterned PDMS membrane layer was sandwiched between the fluidic and control layers as the actuated component in pumps and valves. Devices with the same peristaltic pump design but different valve spacings (100, 200, 300, and 400 µm) from the injection intersection were fabricated using soft lithographic techniques. Devices were characterized through fluorescent imaging of captured plugs of a fluorescein-labeled amino acid mixture and through microchip electrophoresis separations. A suitable combination of peak height, separation efficiency, and analysis time was obtained with a peristaltic pump actuation rate of 50 ms, an injection time of 30 s, and a 200-µm valve spacing. We demonstrated the injection of samples in different solutions and were able to achieve a 2.4-fold improvement in peak height and a 2.8-fold increase in separation efficiency though sample stacking. A comparison of pressure-driven injection and electrokinetic injection with the same injection time and separation voltage showed a 3.9-fold increase in peak height in pressure-based injection with comparable separation efficiency. Finally, the microchip systems were used to separate biomarkers implicated in pre-term birth. Although these devices have initially been demonstrated as a stand-alone microfluidic separation tool, they have strong potential to be integrated within more complex systems.

Atypical pericardial cyst location: the value of computed tomography.

A case of pericardial cyst that arose in an unusual location is presented, In this patient, the cystic structure was clearly defined by computed tomography preoperatively, and pathological confirmation was obtained after surgical resection during mediastinoscopy.

Pedicle injury masquerading as renal contusion: a possible urographic pitfall.

Renal vascular pedicle injuries are relatively rare, accounting for 1-5% of renal injuries [1]. Intravenous urography is generally the initial procedure used to assess the severity of renal damage and the need for further evaluation. Non-function of the injured kidney is a characteristic finding of renal pedicle injury on excretory urography [1, 2, 3, 4]. This finding generally necessitates further expeditious evaluation with renal arteriography. Opacification of the pelviureteric system during excretory urography genereally implies that the renal vascular pedicle is intact and a major renal injury does not exist. We report a case of a major renal vascular injury associated with excretion of contrast at urography--findings mimicking the radiographic features of renal contusion.

Portal vein ectasia simulating a vascular lesion in the pancreatic head in an enhanced CT scan.

An ectatic portal vein in a patient with portal hypertension and chronic active hepatitis simulated a vascular lesion in the head of the pancreas in a contrast-enhanced CT scan.

Extramedullary plasmacytoma.

Extramedullary plasmacytoma is a rare form of plasma cell dyscrasia, in which malignant plasma cell tumors arise outside the bone marrow. The tumor may arise in any part of the body but the vast majority occur in the head and neck, primarily in the nasal cavity, paranasal sinuses, or upper airway. Six patients with extramedullary plasmacytoma are presented and the clinical and radiographic findings are reviewed.

Duodeno-duodenal fistula--a manifestation of carcinoma of the colon.

Two cases of duodeno-duodenal fistula complicating carcinoma of the right colon, both presenting with upper gastrointestinal hemorrhage, are presented. The close proximity of the ascending colon and hepatic flexure and their draining lymphatics to the duodenum are discussed.

Osler revisited: an unusual cause of inversion of the diaphragm.

Osler described depression of the left hemidiaphragm and left lobe of the liver as a physical finding in some patients with pericardial effusion. Inversion of the left hemidiaphragm associated with a large pericardial effusion is an unusual, previously unreported complication. It may be a contributory factor in the production of unexplained dyspnea in some patients.