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Biomedical subjects

J R Cook

Publications and source records attributed to J R Cook.

At least 109 records · Page 6Linked to original sources

Cerebrospinal fluid.

It is hoped that we have demonstrated that collection, handling, and limited analysis of CSF samples from the dog and cat are relatively simple. No special equipment or handling is required, and the procedures are within the capabilities of any veterinarian interested in performing them. In addition, although this article was not intended to present a detailed discussion on the interpretation of the analysis of CSF, we have demonstrated some very practical interpretations to the various aspects of a routine CSF analysis. When combined with a signalment, complete history, and thorough general physical and neurologic examination, CSF analysis can prove invaluable in the workup of an animal with a neurologic disorder. Relatively simple laboratory procedures can be helpful in differentiating peripheral blood contamination from true intrathecal hemorrhage, in identifying an active inflammatory process, in potentially characterizing an etiologic agent, and, on rare occasions, in identifying primary or metastatic neoplastic disease involving the CNS. In many cases, the above is not directly possible, because the changes observed in our routine analysis are nonspecific. Yet, documenting and following these "nonspecific" alterations are helpful in determining if there is progression or regression of the disease process. In turn, these changes or lack of changes are helpful in identifying if the proper therapy has been instituted and if additional or different therapy is required.

Animals↗

Fibrocartilaginous embolism.

Fibrocartilaginous embolism (FCE) is an acute myelopathy that affects primarily dogs and human beings, and occasionally other mammalian species. It is frequently associated with trauma or vigorous exercise; in dogs it tends to affect mature non-chondrodystrophoid and giant breeds. Signs are acute and frequently indicate a very lateralized or focal lesion within the spinal cord, with resultant disparities in sensory and motor function. Lower motor neuron disease is common and hyperesthesia is unusual. The primary differential diagnoses are concussive trauma and intervertebral disc herniation, but the acute onset of strongly lateralizing spinal cord deficits without hyperesthesia in a breed at risk is strongly suggestive of the FCE syndrome. Attention must be given to other systemic diseases that might also give rise to emboli in the absence of FCE. Diagnosis is based on history, clinical signs, and elimination of other differential diagnoses. Treatment is largely supportive, although high doses of methylprednisolone may be beneficial early in the course of the disease. Affected patients may make a functional recovery if deep pain sensation is preserved and there are not complete lower motor neuron signs in affected limbs or sphincters.

Animals↗

Methylation of the alpha-fetoprotein gene in isogenic rat hepatoma and liver cell lines.

We have found that DNA methylation is inversely correlated with alpha-fetoprotein (AFP) gene expression in a series of isogenic rat hepatoma cell lines. The 5' end of the gene is extensively demethylated in AFP-producing cells and is highly methylated in cell lines which do not produce AFP. Glucocorticoid affects markedly the synthesis of AFP in the hepatoma cells. However, methylation patterns of cell lines which were treated with dexamethasone were not different from those of control cells, indicating that glucocorticoid action on AFP gene expression does not alter DNA methylation in this region of the gene.

Animals↗

Motor evoked potentials in the dog: effects of global ischemia on spinal cord and peripheral nerve signals.

Motor evoked potentials (MEPs) in cats, rats, and humans have been reported. They appear promising as a test of central nervous system function, and they are sensitive not only to mechanical injury but also to ischemia. In mechanical trauma, the peripheral nerve response is much more sensitive to damage than the cord response, with a lower threshold and an earlier disappearance. We are reporting that the MEP can also be produced in the dog and that, under conditions of cardiac arrest induced by fibrillation, the peripheral nerve response disappears first at about 30 seconds and then the spinal cord response disappears at about 10 to 13 minutes. The late disappearance of the spinal cord response raises serious questions about its role as an adequate injury monitor. The most useful warning feature of the spinal cord response is an increase in amplitude during the critical first 2 minutes of arrest. Latency changes in the cord and peripheral nerve response did not seem as useful as amplitude changes in terms of providing adequate detection of injury. We also evaluated the peripheral nerve signals to determine whether they are partially volume-conducted weak muscle responses, and evidence substantiates their nonmuscle origin.

Animals↗

Monensin toxicosis in swine: potentiation by tiamulin administration and ameliorative effect of treatment with selenium and/or vitamin E.

Modulation of acute monensin toxicosis in swine was evaluated in 2 studies. In study 1, 56 weanling male pigs were allotted to 14 groups of 4 each. Pigs in 7 groups were given tiamulin in the drinking water (to supply 7.7 mg/kg of body weight/day) for 3 days before and for 2 days after monensin administration. Monensin was given as a single oral dose (at 0, 7.5, 15, 25, 50, 75, or 100 mg/kg) to pigs in groups with or without tiamulin exposure. Prominent acute clinical signs of monensin toxicosis (hypermetria, hind limb ataxia, paresis, knuckling of hind limbs, and recumbency) developed by 2 to 6 hours after dosing in pigs given 15 or 25 mg of monensin/kg with tiamulin exposure, but not in pigs given the 15 or 25 mg of monensin/kg without tiamulin exposure. Also, the extent of monensin-induced skeletal muscle damage at 4 days after monensin dosing was enhanced in pigs given 7.5, 15, or 25 mg of monensin/kg and exposed to tiamulin. In study 2, 48 weanling male pigs were allotted to 8 groups of 6 each. Four groups of pigs were given 20 mg of monensin/kg orally, and 4 groups were given 100 mg of monensin/kg orally. For each monensin dose, a group was treated 24 hours before monensin administration with (i) selenium (Se)-vitamin E preparation, 0.25 mg of Se and 68 IU of d-alpha-tocopheryl acetate (vitamin E)/kg, IM; (ii) vitamin E only, 68 IU of d-alpha-tocopheryl acetate/kg; (iii) Se only, 0.25 mg of Se/kg; or (iv) vehicle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Mechanism of the dexamethasone effect on alpha-fetoprotein gene expression in McA-RH8994 rat hepatoma cells.

We have investigated the mechanism by which dexamethasone (DEX) increases alpha-fetoprotein (AFP) secretion by the McA-RH8994 rat hepatoma cell line. In contrast to the 7777 cell line, DEX was found to increase the amount of hybridizable cytoplasmic AFP mRNA in McA-RH8994 cells. This effect was dose-dependent, reversible after removal of DEX, and was partially blocked by progesterone in excess, indicating a receptor-mediated response. In vitro nuclear transcription experiments showed that DEX increased AFP gene transcription in McA-RH8994 cells. Cycloheximide blocked the effect of DEX on AFP mRNA levels in both the McA-RH8994 and 7777 cell lines, showing that ongoing protein synthesis is required for glucocorticoids either to enhance or to suppress AFP gene expression in these cell lines.

Animals↗

Genetic regulation of sn-glycerol-3-phosphate dehydrogenase in brown adipose tissue.

The levels of sn-glycerol-3-phosphate dehydrogenase (GPDH) were determined in the brown adipose tissue (BAT) of different inbred strains of mice. The BAT of the BALB/cJ strain contains twice as much enzyme activity per milligram protein as do other strains. The appearance of this difference is developmentally dependent, since it is not detected in BAT until 25-30 days postpartum. Genetic analysis of this strain difference has shown that the mechanism of inheritance involves at least two genes, one of which is linked to the Gdc-1 structural locus on chromosome 15. Determinations of GPDH synthesis by immunoprecipitation of GPDH protein labeled in vivo with [3H]leucine, and of GPDH mRNA by Northern blot analysis, establish that in BALB/cJ mice higher rates of enzyme synthesis are determined by elevated levels of GPDH mRNA. It was also found that cold stress increases GPDH mRNA levels in all the strains examined.

Adipose Tissue, Brown↗

Clindamycin for treatment of Toxoplasma polymyositis in a dog.

Toxoplasma polymyositis was diagnosed in a dog given repeated injections of glucocorticoids for a skin condition. The dog developed generalized lower motor neuron paralysis, with generalized hyperesthesia, myoglobinuria, and high serum muscle enzyme activities. Diagnosis of toxoplasmosis was confirmed by muscle biopsy and seroconversion. Despite supportive care, the dog's neurologic status deteriorated progressively until parenteral treatment with clindamycin was instituted. The dog made a gradual recovery, with complete return of locomotor function and muscle mass within 2 months.

Animals↗

Physical properties of a plasmid-like DNA from Euglena gracilis.

A small circular extrachromosomal DNA of the flagellate protozoan Euglena gracilis has been characterized as having a contour length of 11.3 kb, with a consistent restriction map. The buoyant density (rho = 1.717) and melting temperature (tm = 89 degrees C) both indicate a base content of 59% G + C. The DNA is found in both wild-type cells and those lacking plastids. The copy number is estimated to be about 1000.

DNA Restriction Enzymes↗

Oncogene expression in rat hepatomas and during hepatocarcinogenesis.

In this study we examined oncogene expression in several Morris hepatomas. We found elevated transcripts for Ha-ras, Ki-ras, and the myc oncogenes, while the src oncogene was not increased. Northern analysis revealed transcript sizes of 1.4 kb for Ha-ras and 2.5 kb for myc. Analysis of primary tumors induced by the carcinogen 3'-methyl-4-dimethylaminoazobenzene (3'-MDAB) showed increasing oncogene transcript production with increasing length of diet. The results show enhanced ras and myc expression in rat hepatocellular carcinomas and during hepatocarcinogenesis.

Animals↗

Effect of sodium butyrate on alpha-fetoprotein gene expression in rat hepatoma cells in vitro.

Sodium butyrate has been reported to induce cellular differentiation and reduce the tumorigenicity of certain tumor cells. We have examined the effects of butyrate on alpha-fetoprotein (AFP) gene expression in 7777 and McA-RH8994 rat hepatoma cells and have found that nontoxic concentrations of the drug decrease AFP mRNA levels in both cell lines. However, McA-RH8994 requires a 10-fold lower concentration (0.5 mM) of butyrate to affect a 50% reduction in AFP mRNA levels within 48 h. At 2 mM, sodium butyrate reduces AFP mRNA levels in McA-RH8994 cells by at least 90% after 48 h, while having little effect on the expression of either the 7S RNA or Harvey-ras genes. Time-course studies show that the effect of butyrate on McA-RH8994 AFP mRNA levels is immediate and is accompanied by an accumulation of cells in the G1/G0 phase of the cell cycle. Sodium butyrate was found to reduce AFP mRNA levels in both dexamethasone-treated 7777 and McA-RH8994 cells; dexamethasone decreases AFP mRNA levels in the former cell line and increases AFP mRNA levels in the latter. Therefore, it is unlikely that butyrate acts simply by reducing the dexamethasone receptor concentration in 7777 cells.

Animals↗

Disseminated protothecosis causing acute blindness and deafness in a dog.

A 3-year-old Collie bitch was euthanatized two weeks after the onset of blindness and deafness. The hearing deficit had been localized by clinical signs, brain stem auditory evoked responses, and impedance audiometry. Protothecosis was diagnosed by cytologic and histologic examinations. The organism was identified as Prototheca zopfii . Organisms and granulomatous lesions were found in kidney, heart, liver, skeletal muscle, thyroid gland, colon, bronchial lymph node, brain, and cochlea.

Acoustic Impedance Tests↗

Assessment of the anti-tumor potential of glutathione.

This study assesses the effect of reduced glutathione (GSH) on regenerating liver, 3'-methyl-4-dimethylaminoazobenzene (3'-MDAB) hepatocarcinogenesis, and normal and transformed hepatocytes in vitro. GSH administered intragastrically caused only a 30% reduction in thymidine incorporation into liver DNA at 24 h after partial hepatectomy; there was no apparent effect on RNA and protein synthesis. Furthermore, in 3'-MDAB induced hepatocarcinogenesis, all GSH-treated animals developed hepatocyte nodules, and serum alpha-fetoprotein (AFP) levels were not reduced. In vitro, GSH was shown to be cytotoxic to both normal and transformed hepatocytes at serum concentrations under 10%. GSH inhibited [3H]thymidine incorporation slightly in 2 transformed hepatocyte lines, but not in normal hepatocytes.

Animals↗

Blood lactate and ammonium ion accumulation during graded exercise in humans.

The purpose of this study was to determine the pattern of blood lactate and ammonium ion (NH+4) accumulation during graded exercise in humans. Six adult volunteers performed a maximum O2 uptake (VO2 max) test on a bicycle ergometer. Blood samples were collected each minute of the test. Both blood lactate (r = 0.92) and NH4+ (r = 0.70) increased exponentially in relation to increased work. However, closer examination of individual curves revealed that both metabolites remained near resting levels during mild exercise (less than 40% VO2 max) and then demonstrated abrupt upward break points at increased work loads (greater than 50% VO2 max). There was a significant linear relationship (r = 0.96) between the work load at which the lactate break point (LBP) and NH4+ break point (ABP) occurred in each subject. In addition, there was a significant linear relationship (r = 0.82) between the blood concentrations of NH4+ and lactate during exercise. The results suggest a connection between NH4+ production and glycolytic energy metabolism during exercise. Several possible explanations are offered; however, further work at the cellular level is needed before the exact relationship between NH4+ and lactate can be determined.

Adult↗