Oral reserpine administration in horses results in low plasma concentrations that alter platelet biology.

BACKGROUND: Reserpine is a popular drug in the equine industry for long-term tranquilisation. Clinical observations revealed that blood from horses receiving oral reserpine was hypercoagulable. No studies have documented the pharmacokinetics of orally administered reserpine nor the effects of reserpine on platelets in horses. OBJECTIVES: To evaluate the pharmacokinetics of oral reserpine in horses and the effects of clinically relevant concentrations of reserpine on platelet functionality in vitro. STUDY DESIGN: Experimental controlled study. METHODS: The pharmacokinetics of oral reserpine (2.5 mg/horse, once) were determined in six healthy adult horses. Plasma samples were collected and concentrations of reserpine were determined by UPLC-MS/MS. Using this data, the in vitro effects of reserpine on platelets were examined. Aggregation, adhesion and releasate assays for serotonin and thromboxane B2 were performed on platelets exposed to varying concentrations of reserpine (0.01-10 ng/mL), aspirin (negative control) and saline (unexposed control). RESULTS: Oral reserpine administration demonstrated low plasma concentrations with a Cmax of 0.2 ± 0.06 ng/mL and a prolonged half-life of 23.6 ± 6.24 h. Simulations over a dose range of 2-8 µg/kg predicted Cmax at steady state between 0.06-0.9 ng/mL. Platelets exposed to these reserpine concentrations in vitro displayed increased aggregation and adhesion compared to unexposed or aspirin-exposed platelets as well as compared to higher concentrations of reserpine. These functional changes correlated with lower concentrations of serotonin and higher concentrations of thromboxane B2 in the platelet suspension supernatant. MAIN LIMITATIONS: This study used a small number of horses and only in vitro platelet experiments. CONCLUSIONS: Oral reserpine demonstrates low plasma concentrations and a prolonged half-life in horses. At these concentrations, reserpine causes significant changes in platelet function, most likely due to serotonin release and re-uptake which primes platelets for activation and thromboxane B2 release. These findings suggest that clinicians should harvest blood for biological processing prior to the onset of reserpine administration.

Feline musculoskeletal pain index: responsiveness and testing of criterion validity.

BACKGROUND: Progress in establishing if therapies provide relief to cats with degenerative joint disease (DJD)-associated pain is hampered by a lack of validated owner-administered assessment methods. HYPOTHESIS: That an appropriately developed subjective owner-completed instrument (Feline Musculoskeletal Pain Index-FMPI) to assess DJD-associated impairment would have responsiveness and criterion validity. ANIMALS: Twenty-five client-owned cats with DJD-associated pain. METHODS: FMPI responsiveness (ability to detect the effect of an analgesic treatment) and validity (correlation with an objective measure) were explored through a stratified, randomized, double blinded, placebo-controlled, crossover 10-week clinical study. Meloxicam was administered to effect pain relief. A linear mixed model, backward stepwise regression, and Pearson correlations were used to assess responsiveness and criterion validity with the assumption that the NSAID would increase activity. RESULTS: Positive responses of cats to placebo (P = .0001) and meloxicam treatment (P = .0004) were detected; however, the instrument did not detect any difference between placebo and meloxicam (linear mixed model), even for the high impairment cases. Percent meloxicam target dose administered, temperament, and total baseline FMPI score were covariates that most affected FMPI scores. Controlling for significant covariates, most positive effects were seen for placebo treatment. Positive treatment effects on activity were detected, but only for the cases designated as most highly impaired. CONCLUSIONS AND CLINICAL IMPORTANCE: Neither responsiveness nor criterion validity were detected by the inclusion criteria for cases in this study. The data suggest that further work is indicated to understand factors affecting activity in cats to optimize inclusion criteria.

Ronidazole pharmacokinetics in cats following delivery of a delayed-release guar gum formulation.

Ronidazole (RDZ) is the only known effective treatment for feline diarrhea caused by Tritrichomonas foetus. This study aimed to develop guar gum-coated colon-targeted tablets of RDZ and to determine the pharmacokinetics of this delayed-release formulation in cats. Guar gum-coated tablets were administered orally once to five healthy cats (mean dose 32.3 mg/kg). The tablets were then administered once daily for 5 days to four cats (mean dose 34.5 mg/kg), and absorption studies repeated on day 5. Plasma was collected and analyzed for RDZ concentration, and pharmacokinetic noncompartmental and deconvolution analysis were performed on the data. There was negligible RDZ release until after 6 h, and a delayed peak plasma concentration (mean Cmax 28.9 µg/mL) at approximately 14.5 h, which coincides with colonic arrival in cats. Maximum input rate (mg/kg per hour) occurred between 6 and 16 h. This delayed release of ronidazole from guar gum-coated tablets indicates that release of RDZ may be delayed to deliver the medication to a targeted area of the intestine. Repeated dosing with guar gum tablets to steady-state did not inhibit drug bioavailability or alter the pharmacokinetics. Such targeted RDZ drug delivery may provide improved efficacy and reduce adverse effects in cats.

A gene expression map for Caenorhabditis elegans.

We have assembled data from Caenorhabditis elegans DNA microarray experiments involving many growth conditions, developmental stages, and varieties of mutants. Co-regulated genes were grouped together and visualized in a three-dimensional expression map that displays correlations of gene expression profiles as distances in two dimensions and gene density in the third dimension. The gene expression map can be used as a gene discovery tool to identify genes that are co-regulated with known sets of genes (such as heat shock, growth control genes, germ line genes, and so forth) or to uncover previously unknown genetic functions (such as genomic instability in males and sperm caused by specific transposons).

Glial swelling with eosinophilia in human post-mortem brains: a change indicative of plasma extravasation.

Swollen, intensely eosinophilic glial cells are often observed in the vicinity of hemorrhagic lesions in post-mortem human brains. We sought to determine the nature of this change. Thirty adult human brains removed at autopsy and three surgical specimens were obtained 6h to 60 days following a hemorrhagic event. They were subjected to a battery of histochemical and immunohistochemical stains. The swollen cells, which were observed in the majority of autopsy specimens in which hemorrhage had occurred within the previous 9 days, stained intensely red with Masson stain and were immunoreactive for IgG, IgM, IgA, and fibrinogen. Some were also immunoreactive for glial fibrillary acidic protein, particularly in subpial and subependymal areas, if the lesions were more than 3 days old. In white matter some of the cells were immunoreactive for CNPase. There was no labeling with markers for macrophage/microglial cells. The absence of DNA fragment detection by TUNEL suggests that the cells were not dying. Mild glial cytoplasmic eosinophilia without swelling was observed in surgical specimens. No eosinophilic swollen glia were seen in perfusion-fixed rat brains with experimental intracerebral hemorrhage, although they were seen in rat brains that were not promptly fixed. We conclude that human macroglia, including astrocytes and oligodendrocytes, ingest plasma proteins that have been released into brain parenchyma. This likely represents a homeostatic mechanism that maintains the composition of the extracellular environment. If the tissue is not promptly fixed the cells become more swollen and eosinophilic.

Redox control of RNA synthesis in potato mitochondria.

This study shows that the incorporation of radiolabelled UTP into RNA in Percoll-gadient-purified potato mitochondria is regulated by the redox state of the mitochondrial electron transport chain. An early indication that there might be a redox effect on RNA synthesis was a decrease in UTP incorporation in incubates containing an oxidisable substrate, such as succinate or malate. Subsequent use of a variety of electron transport inhibitors acting at different points in the electron transport chain established that the redox state of the Rieske iron-sulphur protein was the major determinant of UTP incorporation. Inhibitors acting on the substrate side of the Rieske iron-sulphur protein, and causing oxidation of components on the oxygen side of their site of action, increased UTP incorporation into RNA. These included antimycin A, myxothiazole, and undecylhydroxydioxobenzothiazole at 500 nM. Inhibitors acting on the oxygen side of the Rieske iron-sulphur protein, and causing a reduction of components on the substrate side of the block, decreased UTP incorporation. These inhibitors were undecylhydroxydioxobenzothiazole at 25 nM and KCN. When phenazine methosulphate was present as an auto-oxidisable electron sink the effect of KCN was diminished. The conclusion from the inhibitor experiments that the redox state of the Rieske iron-suphur protein was important was supported when RNA synthesis was measured at a range of redox potentials. This gave a measured redox potential for the control of UTP incorporation into RNA of +270 mV and the slope of the curve indicated an n = 1 carrier. This value is close to the reported value of the Rieske iron-suphur protein. UTP incorporation was decreased by some 50% in the presence of low concentrations of okadaic acid (5 nM), an inhibitor of protein phosphatases PP1 and PP2A, and alpha-naphthyl acid phosphate, a broad-spectrum phosphatase inhibitor, indicating that the redox effect on RNA synthesis may be mediated via protein phosphorylation. We did not, however, detect an expected increase in RNA synthesis when protein kinase inhibitors were used, so the involvement of protein phosphorylation in the redox regulation of RNA synthesis is as yet uncertain.

Histologic long-term follow-up after embolization with polyvinyl alcohol particles.

A large facial vascular malformation was embolized with polyvinyl alcohol particles twice in 8 years. Resected tissue enabled long-term examination of this material, confirming its chemical inertness and revealing minimal tissue reaction to it apart from calcification. No particle migration, fragmentation, or absorption occurred. There was some recanalization of occluded vessels. Most vessels containing polyvinyl alcohol particles, and all of the larger vessels, were incompletely occluded, with particles becoming embedded in their walls.

Tuberculous infection of skeletal muscle in a case of dermatomyositis.

A patient with dermatomyositis associated with carcinoma was treated with steroids and antibiotics for possible tuberculosis. Autopsy showed an overwhelming diffuse nongranulomatous infection of Mycobacterium tuberculosis involving only the skeletal muscles and one inguinal lymph node. The rare localization of tuberculosis to skeletal muscle in this case is possibly due to steroid immunosuppression and the humoral immune attack on muscle blood vessels that is a part of dermatomyositis.

Amyloid destructive spondyloarthropathy causing cord compression: related to chronic renal failure and dialysis.

Destructive spondyloarthropathy is a recently recognized disease that has not been reported in the neurosurgical literature. It is associated with spinal amyloid deposition in long-term renal failure and dialysis, and it occurs increasingly as the number of dialysis patients and their survival times increase. Clinically, there is a multisegmental and often rapidly progressive radiculomyelopathy that may require emergency stabilization. The radiological features are disc space narrowing with erosion of vertebral end plates and subarticular cysts. The pathological features include deposition of amyloid, which stains with Congo Red and antibodies to beta-2-microglobulin. We present two cases with clinical, radiological, and pathological features and a review of the literature.

Rapid immunoperoxidase staining of axons for frozen section diagnosis of nerve biopsy specimens.

A new method of freezing and embedding a nerve biopsy specimen and staining it with the immunoperoxidase technique for neurofilaments was developed to overcome the difficulties normally encountered in the assessment of tiny portions of nerve. The method clearly shows the architecture of the nerve, the exact number and size of all axons present, and the degree of fibrosis present. The entire procedure may be accomplished in 20 minutes.

Meningeal tumors of childhood.

Meningeal tumors occurring in a pediatric hospital over a period of 18 years were studied. The incidence of meningeal sarcomas was much lower than has been previously reported. A histologic subtype of meningiomas was found which has not previously been described. In these "sclerosing" tumors only a small portion of the lesion contained viable cells, most of which bore little resemblance to conventional meningothelial cells. The bulk of the lesions consisted of whorling collagen bundles produced by the tumor. All cases in which there was tumor invasion of the brain fell into this category. The prognosis for the sclerosing meningiomas was similar to conventional meningiomas, casting doubt on the value of brain invasion as a marker of malignancy in childhood meningiomas. The recognition of this histologic type may aid diagnosis, guide surgical management, and possibly make postoperative radiotherapy unnecessary.

Sonographic evaluation of spinal cord birth trauma with pathologic correlation.

Birth trauma to the spinal cord is a serious potential complication of delivery. Determining the presence, severity, and extent of injury poses a difficult problem because of the often confusing clinical setting. Myelography has been recommended for assessing spinal cord birth trauma but is invasive and may not be helpful. The role of sonography in evaluating spinal cord birth trauma has not been previously described. We assessed the value of sonography in four patients, three of whom also had CT metrizamide myelography. Autopsy correlation was available in three patients. Sonography was able to easily demonstrate the cord configuration, allowing for multiple assessments over time. Internal cord echogenicity was helpful in a case of hematomyelia and in demonstrating the changes of myelomalacia. Sonography is useful in evaluating neonates with severe spinal cord injury; it obviates the need for myelography and also may allow less severely injured patients to be assessed more frequently.

Delayed myelopathy following lightning strike: a demyelinating process.

Although the clinical findings in over 30 cases of delayed myelopathy after electrical injury have been described, there are scanty reports of the pathology of the spinal cord in such cases. We report a case in which progressive myelopathy presented 1 month after electrical injury by lightning strike and death occurred 4 months after injury. The spinal cord showed widespread demyelination of white matter from the medulla to just above the conus medullaris. This consisted of selective degeneration of myelin sheaths without inflammation or injury to axons, other cord components, or nerve roots. Infarction of more circumscribed segments of the thoracic cord where demyelination was greatest was probably due to edema associated with myelin degeneration, causing cord swelling limited by the pia mater. Raised pressure within the cord then resulted in secondary infarction.