Liquid chromatographic determination of tilmicosin in swine feed at 200-400 mg/kg level: interlaboratory study.

An analytical method for the determination of tilmicosin at 200-400 mg/kg, the intended use concentration range, was evaluated in an interlaboratory study involving 5 laboratories, including the sponsor. The interlaboratory study evaluated the intra- and interlaboratory precision and accuracy of a tilmicosin feed method. The method procedure involved extracting tilmicosin from feed by adding 200 mL extractant to 20 g feed and shaking for 1 h. The extract is filtered and analyzed by gradient liquid chromatography which separates tilmicosin from feed matrix in 30 min. Each laboratory assayed 5 replicates of fortified feed at concentrations of 0, 100, 200, 400, and 600 mg/kg. The mean recovery among fortified samples ranged from 81.4 to 98.8%, with a percent coefficient of variation (%CV) ranging from 0.3 to 4.0%. For all blank control feed samples no significant interferences were observed. In addition, each laboratory assayed 5 replicates of medicated feed samples prepared at 2 levels (200 and 400 mg/kg) with either a horizontal or vertical mixer. Along with the medicated feed samples were included 5 replicates of a blank control feed. The identities of the medicated and blank control feed samples were blinded to the analysts. The results for the medicated feed samples ranged from 95.8 to 106% of label claim, with a %CV ranging from 2.1 to 6.7%.

Liquid chromatographic determination and liquid chromatographic-thermospray mass spectrometric confirmation of nicarbazin in chicken tissues: interlaboratory study.

The U.S. Food and Drug Administration sponsored an interlaboratory study of a liquid chromatographic determination with ultraviolet detection of nicarbazin in chicken liver and muscle tissues. The method determined the 4,4'-dinitrocarbanilide (DNC) portion of nicarbazin. The interlaboratory study of the determinative method was successful for nicarbazin at the 4 ppm level. Results showed good reproducibility for the fortified liver and muscle samples. Mean interlaboratory recoveries and percent coefficients of variation at about 4 ppm were 87.1 and 10.9%, respectively, for muscle and 87.4 and 7.5%, respectively, for liver. The interlaboratory analyses of the dosed liver and muscle tissues produced concentration levels similar to those obtained by the sponsor. The confirmatory procedure, which identified DNC in purified tissue extracts, used liquid chromatography-thermospray/mass spectrometry. The confirmatory procedure was successfully evaluated by one FDA laboratory.

Confirmation of oxytetracycline, tetracycline and chlortetracycline residues in milk by particle beam liquid chromatography/mass spectrometry.

A method using particle beam liquid chromatography/mass spectrometry was developed for the confirmation of oxytetracycline, tetracycline and chlortetracycline residues in bovine milk. This method is one of the first to apply particle beam technology to the confirmation of animal drug residues in food products for regulatory purposes. The milk is centrifuged, using molecular weight cut-off filters to remove components of 25,000 daltons and above from the milk. The filtrate is passed through a C-18 sample preparation cartridge which retains the tetracyclines. After the columns are washed with water, the tetracyclines are eluted with 0.1 M oxalic acid in methanol and concentrated. The compounds are separated on a Novapak C-18 column with a methanol-oxalic acid-acetonitrile mobile phase. Negative chemical ionization with selective ion monitoring is used to identify the tetracyclines. The procedure was used to confirm the presence of each tetracycline at 100 ng ml-1 in fortified and incurred milk samples.

The use of a tissue expander to enlarge a graft for surgical treatment of a pressure ulcer in a quadriplegic. Case report.

This case reports the use of a tissue expander to facilitate the surgical closure of a decubitus ulcer in a spinal cord injured quadriplegic. The patient is a 42-year-old man with chronic nonhealing of a right ischial pressure ulcer. It had required a flap rotation and partial ischiectomy in the remote past that had been problem-free for many years. The patient subsequently required the placement of a new flap, but insufficient tissue was available to close the wound with the hip in 90 degrees of flexion. Closing the wound with the hip in extension merely led to breakdown when the hip was put in the 90 degrees of flexion required for the sitting position. The problem was solved by using a tissue expander to increase the available soft tissue. A tissue expander was inserted and gradually expanded over a period of weeks by injecting it with fluid. It was then removed, and the expanded tissue that had grown over it allowed closure of the wound without tension on the tissues with the hip in flexion. The patient subsequently returned to the sitting position and his work as a computer programmer. Tissue expanders are commonly used in breast reconstruction, but have found many other uses in plastic surgery over the last decade. It is felt that tissue expansion techniques should not be the primary surgery treatment of decubitus ulcers, but can be used in difficult cases like this one to provide additional tissue.

Salvage of chronically exposed Gore-Tex vascular access grafts in the hemodialysis patient.

Exposure and infection of a Gore-Tex vascular access graft often results in removal of the graft. Salvage of the graft is possible, however, with the use of well-vascularized muscle flaps. In 1982, Hodgkinson was the first to use a sublimis muscle flap to cover an exposed vascular access graft. We used the flexor carpi ulnaris and flexor digitorum superficialis to cover exposed Gore-Tex grafts in nine patients. The sublimis was used to cover distal graft exposures, and the longer flexor carpi ulnaris muscle was used to cover more proximal sites. Multiple exposures required both flaps or combinations of muscle flaps and local rotation flaps. Eight of nine chronically exposed grafts were salvaged using these techniques; a graft was removed from one patient because of diffuse unrecognized graft bed infection. Disability is minimized by using only part of the sublimis, and loss of the flexor carpi ulnaris is compensated by local muscles with similar actions. Vascular puncture can be continued during healing.

Orbital rim trauma causing a blowout fracture.

A case report is presented that supports the theory that traumatic deformation of the bony orbital rims, without concomitant orbital soft-tissue injury, can cause an orbital blowout fracture.

Active sugar transport by the small intestine. The effects of sugars, amino acids, hexosamines, sulfhydryl-reacting compounds, and cations on the preferential binding of D-glucose to tris-disrupted brush borders.

Tris-disrupted and intact brush border membrane preparations from mucosa of hamster jejunum were capable of preferentially binding actively transported D-glucose in a similar manner. Density gradient centrifugation of the Tris-disrupted brush borders indicated that D-glucose was bound to a fraction containing the cores or inner material of the microvilli. The properties of this binding were examined with the Tris-disrupted brush border preparation. Actively transported sugars competitively inhibited preferential D-glucose binding, whereas no effect was observed with nonactively transported sugars. Neither actively nor nonactively transported amino acids affected D-glucose binding. D-Glucosamine, which is not actively transported, was inhibitory to preferential D-glucose binding as well as to the active transport of D-glucose by everted sacs of hamster jejunum. No inhibitory effect was observed with the same concentration of D-galactosamine. Preferential D-glucose binding was also inhibited by sulfhydryl-reacting compounds, Ca(2+), and Li(+) ions. On the other hand, Mg(2+) was shown to be stimulatory and Na(+), NH(4) (+), and K(+) had no effect on this phenomenon. The results of these experiments suggest that preferential D-glucose binding to brush borders is related to the initial step in active sugar transport by the small intestine.