Determination of tilmicosin residues in chicken, cattle, swine, and sheep tissues by liquid chromatography.

A method was developed and validated for determination and quantitation of tilmicosin residues in swine, cattle, and sheep edible tissues, as well as chicken fat, skin, and muscle over a concentration range of 0.025 microg/g-20 microg/g. For chicken kidney and liver, the method was validated over a range of 0.060 microg/g-20 microg/g. The tissue sample was extracted with methanol and a C18 cartridge was used for solid-phase extraction cleanup. A reversed-phase gradient liquid chromatographic method with detection at 280 nm was used to separate the tilmicosin from matrix components in 30 min run time. The limit of quantitation (LOQ) of the method was 0.025 microg/g for all tested tissues except chicken kidney and liver, for which the LOQ was 0.06 microg/g. Average recoveries for tissue samples ranged from 73 to 98%. Relative standard deviation values ranged from 0.6 to 14.7%.

Determination of tilmicosin residues in cow and sheep milk by liquid chromatography.

This method was developed and validated to detect and quantitate tilmicosin residues in cow milk over a range of 0.010-10 microg/mL, and in sheep milk over a range of 0.025-0.5 microg/mL. The procedure involves extracting the milk sample with acetonitrile and using a C18 cartridge to perform a solid-phase extraction cleanup of the extract. A reversed-phase gradient liquid chromatography method with detection at 280 nm is used to separate the tilmicosin from matrix components in a 30 min run time. The limit of quantitation of the method is 0.010 microg/mL for cow milk, and 0.025 microg/mL for sheep milk. Average percentage recoveries for milk samples ranged from 82 to 94%. Percentage relative standard deviation values ranged from 3.1 to 17.2%.

Cytologic diagnosis of peritoneal fluids. Applicability to the laparoscopic diagnosis of endometriosis.

OBJECTIVE: To determine the accuracy of cytologic examination of laparoscopically obtained peritoneal fluid in the diagnosis of endometriosis. STUDY DESIGN: This investigation analyzed 50 laparoscopic fluid specimens received over a three-year period. Retrospective cytologic findings were correlated with clinical history and laparoscopic diagnoses. Touch preparations were also collected from necropsies to develop cytologic criteria necessary to distinguish endometrial cells from mesothelial cells. RESULTS: The presence of hemosiderin-laden macrophages in peritoneal fluids was more specific but less sensitive than the presence of endometrial cells for the diagnosis of endometriosis. CONCLUSIONS: In women undergoing laparoscopy to detect endometriosis, the identification of endometrial cells alone in peritoneal fluids may not be sufficient to render a definitive diagnosis of endometriosis. However, the presence of hemosiderin-laden macrophages in this population should alert the cytologist to that possibility.

Detection of radionuclides in capillary electrophoresis using a phosphor-imaging detector.

A capillary electrophoresis (CE) postcolumn radionuclide detector has been developed that uses a commercial phosphor-imaging detector and has been optimized for low-energy beta emitters. Eluant from the separation capillary is deposited on a membrane. Emission from radioactive analytes on the membrane is integrated using the phosphor-imaging system for 10-72 h. Results from the phosphor-imaging system are converted to conventional electropherograms. Modifications to a prior postcolumn CE deposition system have been accomplished by adding a buffer makeup capillary; this increases the electrolyte pH range and improves reproducibility. The limit of detection (LOD) for 35S-labeled analytes is 0.13 amol (8.7 pM or 0.007 Bq), while the LOD for 32P-labeled analytes is 4.9 zmol (0.33 pM or 0.002 Bq), with a linear range for 35S-Met from 1.5 amol to 1.5 fmol.

Herpesvirus mimics. A potential pitfall in endocervical brush specimens.

The recent media focus on inadequacies in cervical smear collection and interpretation has resulted in improved collection methods, such as endocervical brushes, as well as closer scrutiny of morphologic criteria. However, endocervical cell artifacts may be associated with these endocervical brushes. Recently in our laboratory a case of reactive-atypical endocervical cells that resembled the cytologic changes associated with Herpes simplex virus (HSV) infection resulted in a false-positive diagnosis of HSV infection. Of 14,622 gynecologic specimens accessioned over 14 months, 459 cases with reactive endocervical cells and 117 with atypical endocervical cells were reported. These cases were reviewed by two independent observers with no knowledge of the prior diagnoses and were evaluated for four cytologic criteria considered diagnostic of HSV infection: multinucleation, margination of nuclear chromatin, ground glass chromatin and intranuclear inclusions. Nineteen cases were diagnostic/suggestive of HSV; 19 additional cases were identified as herpesvirus mimics. The original diagnoses, demographics, clinical data and method of collection were reviewed. In all but three cases an endocervical brush was the method of collection. Of the four criteria studied, only ground glass chromatin had both high sensitivity (95%) and specificity (95%). Intranuclear inclusions, while pathognomonic, had low sensitivity (42%). Altered endocervical cells that mimic herpesvirus are a potential pitfall in the diagnosis of HSV infection. Use of strict criteria, knowledge of the collection method and clinical history will avoid misdiagnosis.