PubMed Health⌕ Search

Biomedical subjects

W E Howell

Publications and source records attributed to W E Howell.

At least 19 recordsLinked to original sources
PubMed2001

Evaluation of i-STAT creatinine assay.

BACKGROUND: We evaluated a new, 2-min blood creatinine method using the hand-held i-STAT analyzer. Good results have already been reported using this analyzer for 10 methods including electrolytes, TCO2, pH, PCO2, bicarbonate, glucose, hemoglobin and urea for uremic blood, hemodialysate and peritoneal effluent. METHODS: Evaluation included study of imprecision and accuracy. RESULTS: Imprecision studies gave excellent results, including those for reproducibility of 6 solutions with a mean of 10 repeats and coefficients of variation (CVs) of 0.4-3.4%, and also the mean of the differences between 33 duplicate blood specimens which was 2.2% of the specimen mean. To assess accuracy, we compared results of 149 tests by i-STAT and Beckman Synchron CX7 methods. The difference between the two means was 2.6% and the mean of all differences was 10.9% with i-STAT results higher, especially when blood creatinine values were < 100 micromol/l (1.1 mg/dl) indicating the need for a slightly higher upper limit of the normal range. The correlation coefficient between the two methods was 0.99, the slope 1.0 and the intercept -5.0 micromol/l (-0.06 mg/dl). We assessed the recommended creatinine correction for variation in PCO2 above and below 40 mm Hg, but our results did not suggest the need for such a correction in our range of 27-64 mm Hg; omission would remove a major method disadvantage. Assays of hemodialysate and peritoneal effluent were also satisfactory. CONCLUSIONS: The i-STAT creatinine method is simple and rapid and our evaluation showed satisfactory accuracy and precision. However, results were on average slightly higher than for the Beckman Synchron CX7 method.

Carbon Dioxide↗
PubMed1999

Differentiation of closely related but biologically distinct cherry isolates of Prunus necrotic ringspot virus by polymerase chain reaction.

Prunus necrotic ringspot ilarvirus (PNRSV) exists as a number of biologically distinct variants which differ in host specificity, serology, and pathology. Previous nucleotide sequence alignment and phylogenetic analysis of cloned reverse transcription-polymerase chain reaction (RT-PCR) products of several biologically distinct sweet cherry isolates revealed correlations between symptom type and the nucleotide and amino acid sequences of the 3a (putative movement protein) and 3b (coat protein) open reading frames. Based upon this analysis, RT-PCR assays have been developed that can identify isolates displaying different symptoms and serotypes. The incorporation of primers in a multiplex PCR protocol permits rapid detection and discrimination among the strains. The results of PCR amplification using type-specific primers that amplify a portion of the coat protein gene demonstrate that the primer-selection procedure developed for PNRSV constitutes a reliable method of viral strain discrimination in cherry for disease control and will also be useful for examining biological diversity within the PNRSV virus group.

DNA Restriction Enzymes↗
PubMed1988

The use of estradiol benzoate to manage lambing period in ewes bred at synchronized estrus.

The induction and management of lambing was studied in a commercial flock of ewes. These ewes were bred at synchronized estrus and managed to lamb three times in 2 yr, with lambings occurring in the sequence of February, September and June. Ewes treated with 2 mg of estradiol benzoate in oil (i.m.) at approximately 17 d prior to term did not lamb in response to treatment. When 2 mg estradiol benzoate was given at 0800 on d 142 of gestation, lambing occurred an average of 37 +/- 5 h later in ewes treated in June or September and at 70 +/- 10 h later in ewes treated in February. The comparable figures for oil-treated ewes (control) were 70 +/- 5 h and 116 +/- 9 h, respectively. Altering the time of day of injection or using two injections 24 h apart did not alter the time for injection to lambing. Increasing the dose of estradiol benzoate to 15 mg decreased the time from injection to lambing (43 +/- 7 h, ewes treated in February) but also increased the incidence of dystocia (50% incidence). The incidence of dystocia averaged 8% for all other treatments and controls. Death loss of lambs to 1 wk of age was 12% and was not affected by treatment. The length of the lambing period was reduced from 9.0 +/- 3.3 d in control ewes to 3.6 +/- 1.1 d in induced ewes. A single injection of 2 mg estradiol benzoate given at 0800 on d 142 of gestation or a double treatment, with injections at 2000 on d 142 and 143, resulted in 53% of ewes lambing between 0800 and 1600 on each day of the lambing period, compared with 33% in control ewes.

Animals↗
PubMed1984

Duration of the breeding season and response to reproductive manipulation in five breeds of sheep under northern prairie conditions.

The breeding season was 157, 154, <126, 210 and 217 days for Rambouillet, Columbia, Suffolk, Rambouillet x Finnish Landrace and Columbia x Finnish Landrace ewes respectively. Treatment of cyclic ewes with pregnant mare serum gonadotropin (PMSG) (500 IU), following a 12-day treatment with progestin-containing intravaginal sponges, did not affect fertility, but did decrease the time from sponge removal to estrus, (control 48.0 +/- 3.1 hr; PMSG 39.4 +/- 1.8 hr) to the preovulatory surge of LH (control 52.7 +/- 2.8 hr; PMSG 39.0 +/- 1.7 hr) and FSH (control 52.3 +/- 2.9 hr; PMSG 42.8 +/- 1.6 hr) and caused an elevation of serum LH levels prior to the preovulatory surge (control 1.25 +/- 0.18 ng/ml; PMSG 2.31 +/- 0.22 ng/ml). Exposure of the purebred ewes to 18 hours of daylight in January, decreasing by 30 minutes a week subsequently, counteracted the seasonal reduction in the number of ewes lambing following induced breeding under natural daylight in May. Prolificacy was greatest in crossbred ewes and their fertility was not affected by season. Gestation period was longer for fall-bred ewes and varied with breed.

Journal Article↗
PubMed1981

Neonatal triethyltin exposure alters adult electrophysiology in rats.

In adults, triethyltin (TET) produces degeneration of white matter, edema, vacuolization on myelin and histotoxic hypoxia. To determine the functional consequences of perinatal exposure to TET, albino rats were administered either 0, 3, 6, or 9 mg/kg TET on postnatal day 5. Upon reaching adulthood, the rats were implanted with electrodes for recording visual evoked potentials (VEPs) and hippocampal afterdischarges (ADs). In addition to these tests, 17 days of kindling trials were administered to the rats followed by testing with pentylenetetrazol and picrotoxin for seizure susceptibility. TET increased latencies of P2, P3, and N3 of the VEP in a dose dependent fashion. TET also decreases N1P2 amplitudes and produced gender-specific alterations in both P1, N1, and N2 latencies and N2P3 amplitudes. TET produced alterations in duration of the AD recorded from cortex during kindling, but did not produce significant alterations in any of the other variables tested. The results support previous studies, since they show that the adult VEP is sensitive to perinatal toxicant exposure.

Analysis of Variance↗
PubMed1980

Arthrogryposis: an inherited defect in newborn calves.

Arthrogryposis, frequently associated with cleft palate, scoliosis and kyphosis, has been investigated in pure and crossbred Charolais calves. During a 3-year study, a total of 76 congenitally malformed arthrogrypotic calves from 41 purebred and commercial Charolais herds was investigated. Investigations of the management, feeds, water and poisonous pasture plants in 6 herds reporting deformed calves did not reveal any factors which could be associated with the appearance of the defect. Analysis of pedigrees and matings which produced arthrogrypotic calves revealed that the arthrogryposis syndrome in the Charolais breed and its crosses in Canada is genetic in origin and caused by an autosomal recessive gene with complete penetrance in the homozygous state.

Animals↗
PubMed1979

Alcohol-induced alterations in hippocampal afterdischarges and afterdischarge thresholds: dose-reponse studies.

The hippocampal afterdischarge (AD) has been suggested as an index of toxicant-induced CNS change [1]. The present experiments report raised AD thresholds, decreased AD durations, shorter post-stimulation latencies to AD onset, decreased numbers of AD spike complexes and increased numbers of spikes/complex following alcohol administration. Results are discussed in light of single-unit data concerning alcohol effects upon hippocampal cells, and the biphasic effects of alcohol upon behavior.

Animals↗
PubMedDate not supplied

Visual system dysfunction following acute trimethyltin exposure in rats.

Trimethyltin (TMT) has been shown to produce damage in the limbic system and several other brain areas. To date, damage to sensory systems has not been reported. The present study investigated the integrity of the visual system following acute exposure to TMT. Rats were chronically implanted with electrodes for recording the evoked response from either the visual cortex or optic tract following photic stimulation. Following recovery, the animals were exposed to either 0 (saline), 4, 5, 6, or 7 mg/kg trimethyltin chloride (TMT). Evoked potentials were averaged the peak-to-peak amplitudes and latencies were determined. The results indicated that exposure to TMT produced alterations in the visual evoked response. The pattern of changes suggested two effects, an alteration in retinal processing and an alteration in arousal. The manifestation of these changes was an increase in early peak latencies recorded from the visual cortex and the optic tract, a decreased amplitude recorded from the visual cortex and optic tract early peaks (all suggestive of retinal changes) and a decreased P3N3 amplitude and N3 latency recorded from the visual cortex (suggestive of increased arousal). The results demonstrate that TMT does produce alterations in sensory systems as well as in the limbic system.

Analysis of Variance↗
PubMedDate not supplied

Somatosensory dysfunction following acute trimethyltin exposure.

A variety of trimethyltin (TMT)-produced sensory and behavioral dysfunctions have been reported. In this study the functional integrity of the somatosensory system was evaluated. Animals were tested using three different measures prior to (day 0) and 1, 4, and 16 days following dosing with either 0 (saline) or 7 mg/kg TMT. The tests employed were: (1) hot-plate pain threshold: (2) dorsal caudal nerve response threshold and conduction velocity; and (3) the somatosensory evoked response (SER). In the hot-plate test, TMT treated animals took longer to lick the hind paws in response to the heat. No effects were seen in the nerve function evaluation (conduction velocity and threshold), although increased N1, P1, and P2 latencies and decreased N1P1 amplitude were seen in SER recordings. The fact that no peripheral nerve function effects were observed suggests that the hot-plate and SER findings were the result of central nervous system dysfunction.

Animals↗
PubMedDate not supplied

Acute triethyltin exposure: effects on the visual evoked potential and hippocampal afterdischarge.

Acute administration of triethyltin (TET) produces a well-described sequence of pathological events characterized by intramyelinic vacuolation, edema, and histotoxic hypoxia. Recent behavioral studies have attempted to characterize the functional consequences of TET exposures. In this study, the effects of exposure on the visual evoked response (VER) and hippocampal afterdischarge (AD) were determined. Rats were administered either 0, 0.188, 0.375, 0.75, or 1.50 mg/kg TET bromide IP each day for 6 consecutive days. TET increased latencies of P1, N1, P2, N2, and N3 peaks of the VER. The increased latencies are consistent with delayed conduction produced by alterations in the myelin of the optic nerve. TET increased the frequency of spikes within ADs, increased the severity of postictal EEG depressions, and prolonged recovery of excitability following ADs. These effects may be partially explained as reflecting a generalized CNS depression.

Animals↗