Improved limit of detection and quantitation development and validation procedure for quantification of zinc in Insulin by atomic absorption spectrometry.

A simple and expeditious analytical method for determination of zinc in human insulin isophane suspension by flame atomic absorption spectrophotometer (FAAS) was validated. The method was carried out on atomic absorption spectrometer with 0.4 nm bandwidth, 1.0 filter factor on deuterium (D2) background correction. The integration time was set at 3.0 second with 5.0 mA lamp current. The parameters of method validation showed adequate linearity, efficiency and relative standard deviation values were between 0.64%-1.69% (n=7), 1.31%-1.58% (n=10) for repeatability and intermediate precision respectively. The limit of detection 0.0032 µg/mL, 0.0173 µg/mL, 0.0231 µg/mL and limit of quantitation 0.0107µg/mL, 0.0578 µg/mL, 0.0694 µg/mL based on signal to noise (SN), calibration curve method (CCM) and fortification of blank (FB) were obtained respectively. The percentages of recovery for low, medium and high spiked concentration levels of zinc in human insulin were 99.38 ± 0.04 to 100.3 ± 0.03, 98.45 ± 0.38 to 100.3 ± 0.07 and 99.42 ± 0.03 to 99.42 ± 0.08 respectively. With the use of this method, five samples from each vial of human insulin isophane suspension were analyzed and the zinc content was determined. The zinc content were 22.1 ± 0.025 µg/mL and 24.3 ± 0.028 µg/mL which compliance the British Pharmacopoeia standard.

Postoperative fibrosis after surgical treatment of the porcine spinal cord: a comparison of dural substitutes. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004.

OBJECT: Postoperative adhesion- and fibrosis-induced spinal cord tethering is not uncommon and may be associated with delayed clinical sequelae. Multiple dural substitutes have been used in surgery without a full appreciation of the grafts' adverse effects. The authors conducted a comparative animal experimental study to evaluate the degree of chronic inflammatory reactions, adhesions, and fibrosis caused by the use of four dural substitutes--Surgicel, Durasis, DuraGen, and Preclude. METHODS: Twenty-six pigs weighing 30 to 40 kg underwent a two-level lumbar laminectomy (a midline durotomy, implantation of a 2-cm dural substitute in the subarachnoid space, and watertight dural closure). After 8 weeks the animals were killed, and two independent neuropathologists blinded to the dural substitute group evaluated several sites along the implants, providing descriptions and quantitative scoring of fibrosis, chronic inflammatory reactions, foreign-body reactions, and spinal cord changes. Kruskal-Wallis one-way analysis of variance for ranks corrected for multiple comparisons was used to examine differences among the materials. CONCLUSIONS: The DuraGen dural substitute produced the least amount of inflammation in the subarachnoid space and Preclude generated the most (p < 0.001). Surgicel and DuraGen were completely resorbed on histological sections, but both produced some inflammation, which diminished gradually from the dural implant center. Histological evaluation of the nonresorbed grafts demonstrated that Durasis caused the least degree of inflammatory cell infiltration (p < 0.001). The Preclude dural substitute consistently demonstrated encapsulation and arachnoidal reaction. There was no evidence of implant-related adverse effects on the underlying pia mater and white matter regardless of the substitute type.

Repeat γ knife surgery for incompletely obliterated cerebral arteriovenous malformations.

OBJECTIVE: The causes of failure after an initial Gamma procedure were studied, along with imaging and clinical outcomes, in a series of 140 patients with cerebral arteriovenous malformations (AVMs) treated with repeat Gamma Knife surgery (GKS). METHODS: Causes of initial treatment failure included inaccurate nidus definition in 14 patients, failure to fill part of the nidus as a result of hemodynamic factors in 16, recanalization of embolized AVM compartments in 6, and suboptimal dose (<20 Gy) in 23. Nineteen patients had repeat GKS for subtotal obliteration of AVMs. In 62 patients, the AVM failed to obliterate despite correct target definition and adequate dose. At the time of retreatment, the nidus volume ranged from 0.1 to 6.9 cm3 (mean, 1.4 cm3), and the mean prescription dose was 20.3 Gy. RESULTS: Repeat GKS yielded a total angiographic obliteration in 77 patients (55%) and subtotal obliteration in 9 (6.4%). In 38 patients (27.1%), the AVMs remained patent, and in 16 patients (11.4%), no flow voids were observed on magnetic resonance imaging. Clinically, 126 patients improved or remained stable, and 14 experienced deterioration (8 resulting from a rebleed, 2 caused by persistent arteriovenous shunting, and 4 related to radiation-induced changes). CONCLUSION: By using repeat GKS, we achieved a 55% angiographic cure rate. Although radiation-induced changes as visualized on magnetic resonance imaging occurred in 48 patients (39%), only 4 patients (3.6%) developed permanent neurological deficits. These findings may be useful in deciding the management of AVMs in whom total obliteration after initial GKS was not achieved.