Development of melamine certified reference material in milk using two different isotope dilution mass spectrometry techniques.

A new certified reference material (CRM) of melamine in milk GLHK-11-02 was developed aiming to address the great demand from the testing community after the melamine crises. The material was prepared by adding an appropriate quantity of melamine into the skimmed milk samples and the final product was in the form of fine lyophilized powder. Characterization of the material relied on two newly developed gravimetric isotope dilution mass spectrometry (IDMS) methods, one using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and another gas chromatography-mass spectrometry (GC-MS). Experimental parameters with crucial effects on the performance of the two IDMS methods were thoroughly investigated. These included purity of standard used, equilibration time of isotopes, efficiency of extraction methods as well as possible interferences from the matrix and melamine analogues. Precision was found to be excellent with a coefficient of variation of 2.5% for the LC-IDMS/MS (n=46) and 1.9% for the GC-IDMS (n=30) respectively. Using one-tail Student's t-test at 95% confidence interval, analytical data sets generated from the two methods were found to exhibit no significant difference. Measurement accuracy of the methods was further verified through an Asia Pacific Metrology Program (APMP) pilot study. Analytical results of the present LC-IDMS/MS for the two milk test samples at the concentration level of about 0.45 and 3.5 mg kg(-1) were proven to be very good. There were excellent overlaps between our results and the assigned reference values, and the absolute deviation was less than 3.2%. Both the LC-IDMS/MS and GC-IDMS methods were shown to be sufficiently reliable and accurate for certification of the melamine CRM. Certified value of melamine in dry mass fraction in GLHK-11-02 was 1.14 mg kg(-1). Expanded uncertainty due to sample inhomogeneity, long term and short term stability and variability in the characterization procedure was at 7.1% or 0.08 mg kg(-1). The CRM is primarily used to provide a complete method validation for and to improve the technical competence of melamine analysis to food and chemical testing laboratories.

Triangular fibrocartilage injuries in pediatric and adolescent patients.

This is a retrospective review of 29 posttraumatic pediatric and adolescent patients with surgically documented triangular fibrocartilage complex tears. All patients complained of ulnar wrist pain. Fifteen patients (52%) sustained distal radius fracture at the time of the original injury. Twenty-three (79%) of the triangular fibrocartilage complex tears were Palmer 1B lesions. There were 31A, 11C, and 21D lesions. All 1B, 1C, and 1D tears were repaired. Coexisting pathology was present in 25 patients (86%). This pathology included ulnar styloid nonunion, distal radioulnar joint instability, ulnocarpal impaction, distal radius deformity, and intercarpal ligament tears, which were treated by ulnar styloid nonunion excision, distal radioulnar joint stabilization, ulnar shortening, radius corrective osteotomy, and intercarpal ligament debridement, respectively. The length of the follow-up period averaged 21 months. Three patients were lost to follow-up. Outcomes were graded by a modification of the Mayo wrist score. Twenty-four patients (89%) had excellent results, 3 had good results.

Acute slipped capital femoral epiphysis: the value and safety of urgent manipulative reduction.

A 40-year experience consisting of 91 cases of acute slipped capital femoral epiphysis (SCFE) was reviewed to assess the safety of manipulative reduction and to determine whether urgent reduction has an effect on the development of avascular necrosis (AVN) of the capital femoral epiphysis. All patients had a history of sudden onset of severe hip pain and were documented to have an unstable (acute) slipped epiphysis. Treatment modalities included manipulative reduction under general anesthesia followed by internal fixation (41 hips), epiphysiodesis and internal fixation (15 hips), epiphysiodesis and cast immobilization (31 hips), and cast immobilization alone (three hips). One case was treated with cast immobilization after reduction by skeletal traction. Patient follow-up averaged 44 months, and ranged from 12 to 216 months. Radiographic review identified 13 (14%) cases of AVN in the series of 91 hips. Of 42 hips reduced in <24 h from presentation, AVN developed in three (7%). Of 49 hips reduced in >24 h from presentation, AVN developed in 10 (20%). Manipulative reduction of the acute SCFE may be accomplished without increased risk of AVN. Time to reduction may be an important risk factor for development of AVN after acute SCFE.

Insulin-like growth factor I receptor expression and function in fibroblasts from two patients with deletion of the distal long arm of chromosome 15.

Most patients with deletion of the distal long arm of chromosome 15 have intrauterine growth retardation and postnatal growth deficiency in addition to developmental abnormalities. It has been proposed that the absence of one copy of the insulin-like growth factor I (IGF-I) receptor gene may play a role in the growth deficiency seen in this syndrome. To address this question we examined IGF-I receptor expression and function in fibroblasts from two patients with deletion of the distal long arm of chromosome 15 (15q26.1-->qter). Quantitative Southern blot analysis of the IGF-I receptor gene was performed on HindIII digests of fibroblast DNA. Radioactivity in the 1.7-kilobase receptor fragment in the two patients was 55% and 51% of the values in controls, consistent with the absence of one copy of the IGF-I receptor gene. IGF-I receptor messenger ribonucleic acid levels were quantitated by a solution hybridization/nuclease protection assay. Receptor messenger ribonucleic acid levels in the two patients were 45% and 52% of the values in controls. Northern blotting demonstrated normal size IGF-I receptor transcripts and affinity crosslinking of [125I]IGF-I to Triton X-100-solubilized fibroblasts demonstrated a normal size receptor in the patients. Analysis of placental membranes prepared from one patient revealed no difference in [125I]IGF-I binding. In the patients' fibroblasts, however, binding of [125I]long [R3]-IGF-I to the IGF-I receptor was significantly reduced, as assessed by the amount of radioactivity competed by the monoclonal antibody alpha IR-3 or insulin and Scatchard analysis of binding data. To assess IGF-I receptor function, stimulation of [alpha-1-14C]-methylaminoisobutyric acid transport and stimulation of [methyl-3H]thymidine incorporation into DNA by a full range of IGF-I concentrations was examined in patient and control fibroblasts. There was a significant decrease in the maximal response to IGF-I in both assays for one of the two patients when data were expressed as fold response over the basal value. However, there was no evidence for impairment of response to IGF-I in either patient's fibroblasts when data were expressed as net stimulation (maximal response minus basal). In conclusion, although IGF-I receptor expression was decreased in fibroblasts from two patients with deletion of the distal long arm of chromosome 15, we were unable to provide conclusive evidence for impairment of the biological response to IGF-I.