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Biomedical subjects

F Bartlett

Publications and source records attributed to F Bartlett.

17 recordsLinked to original sources
PubMed1996

Are ruminal bacteria armed with bacteriocins?

The production of toxic compounds or antibiotics is a common component of intermicrobial competitive interactions, and many of these toxins have been adopted and adapted for the control of microbial populations. One class of these toxins, the bacteriocins, is a heterogeneous group of proteinaceous antibiotics that often display a high degree of target specificity, although many have a very wide spectrum of activity. To date, only limited information is available concerning the occurrence of bacteriocins among ruminal isolates or the sensitivity of ruminal microorganisms to exogenous bacteriocins. A survey of 50 strains of Butyrivibrio spp. isolated from a variety of sources (sheep, deer, and cattle) for bacteriocin production indicated a high incidence of bacteriocin-like activity (50%). Many of these inhibitory compounds appear to have a broad spectrum of activity, which suggests that bacteriocins may have a significant impact on both the competitive fitness of individual microbial strains within the rumen and on the overall structure of the microbial population within the rumen. Selected bacteriocins from lactic acid bacteria also were shown to have activity against Butyrivibrio spp. and may have application in ruminant systems. Bacteriocins may provide an alternative group of antibiotics for the manipulation of ruminal microbial populations. Bacteriocins have significant advantages over other antibiotics in target specificity, susceptibility to proteolytic digestion, possibility of genetic transfer and manipulation, and, in the case of some bacteriocins derived from lactic acid bacteria, a long history of safe use.

Animals↗
PubMed1978

Evoked response correlate of symbol and significate.

Changing the source and intensity of the auditory signal to six trained cats responding to meaningful auditory stimuli permits exogenous and endogenous processes in the auditory evoked potential to be separated. For short-latency exogenous processes, latency and amplitude depend on the parameters of the physical stimulus. However, the amplitude and shape of longer-latency endogenous processes are essentially independent of the location and intensity of the signal source and seem to be invariant concomitants of the significance of the signal.

Animals↗
PubMed1977

Neurometrics.

Explore the source record for details and available documents.

Aged↗
PubMed1977

Disposition of pirprofen, a new anti-inflammatory drug.

Plasma and urine concentrations of 2-(3-chloro-4[3-pyrrolinyl]phenyl) propionic acid, pirprofen, a new nonsteroidal anti-inflammatory compound, are described for normal male volunteers receiving one or more doses of the drug. Orally administered pirprofen is rapidly and almost completely absorbed from the gastrointestinal tract, resulting in maximum plasma levels in 1 to 2 hr. Mean peak levels are 23 microng/ml after an oral pirprofen dose of 200 mg; lower doses given proportionally lower levels. Administration 1 hr after a meal slightly delays the peak plasma level, but the extent of absorption is not affected significantly. Administration of pirprofen, 150 mg, 4 times daily, or 200 mg, 3 times daily, results in nearly identical plasma levels at steady-state. Pirprofen has an apparent elimination half-life of about 7 hr. The results obtained from a 200-mg pirprofen-14C dose indicate that excretion of the drug occurs primarily by the renal route in the form of metabolites and is essentially complete within 24 hr. In urine, less than 5% of the administered dose is accounted for as unchanged drug.

Adolescent↗
PubMed1973

Equipotentiality quantified: the anatomical distribution of the engram.

Sensory events and the representation of past experience cause distinctive changes in the electrical activity of widespread regions of the brain. These regions have similar roles in the engram in the sense that they all seem to participate in responses to external events and in subsequent representations of these events. However, the relative contribution of these processes to the activity of different brain regions is quantitatively different, in that some regions are much more strongly affected than others. These results may constitute the basis for reconciliation of localizationist and antilocalizationist views of brain function.

Animals↗
PubMed1969

Neural readout from memory during generalization.

Eight cats with implanted electrodes were trained to obtain food on presentation of one flicker frequency and to avoid shock on presentation of a second flicker frequency. A third flicker frequency, midway between the first and the second, was then presented. Differential generalization ensued, in which either the food response or the avoidance response was performed. Average evoked potentials from generalization trials with different outcomes were significantly different. The wave shape elicited by the stimulus for generalization closely resembled the usual response to the appropriate signal for the behavior which was displayed. This constitutes evidence for release of a neural process representing previous experience. The release of this process begins about 35 milliseconds after stimulation.

Animals↗
PubMed1968

Observation learning in cats.

In two experiments cats acquired a stimulus-controlled approach or avoidance response by observational or conventional shaping procedures. Observer cats acquired the avoidance response (hurdle jumping in response to a buzzer stimulus) significantly faster and made fewer errors than cats that were conventionally trained. Observer cats acquired the approach response (lever pressing for food in response to a light stimulus) with significantly fewer errors than cats that were conventionally trained. In some cases, observer cats committed one or no errors while reaching criterion.

Animals↗
PubMedDate not supplied

Metabolism of methylphenidate in dog and rat.

The urinary metabolites of methylphenidate in the dog and rat were investigated. After oral administration of 14C-labeled methylphenidate, approximately 86% and 63% of the dose was recovered in the urine of the dog and rat, respectively. Less than 1% of the dose was excreted as unchanged drug. Metabolism involved oxidation, hydrolysis, and conjugation processes. The primary hydrolytic product was alpha-phenyl-2-piperidineacetic acid (24%, dog; 35-40%, rat). The primary metabolites of oxidation were methyl 6-oxo-alpha-phenyl-2-piperidineacetate (3%, dog; 1.5%, rat) and the glucuronide of alpha-(p-hydroxyphenyl)-2-piperidineacetic acid (10%, rat). The former also underwent extensive biotransformation, including: 1) hydrolysis to the lactam acid (27%, dog; 7-10%, rat) and subsequent carboxylic acid O-glucuronidation (15%, dog); or 2) hydroxylation at the 5-position (1%, dog; 2%, rat) and subsequent hydrolysis (4%, dog; 15-17%, rat); or 3) 5-O-glucuronidation (12%, dog). Additional minor metabolites from methyl-6-oxo-alpha-phenyl-2-piperidineacetate were the phenolic O-glucuronide of methyl alpha-(p-hydroxyphenyl)-6-oxo-2-piperidineacetate (1%, dog), and the 4-O-glucuronide of methyl 4-hydroxy-6-oxo-alpha-phenyl-2-piperidineacetate (1%, dog), and the taurine amide conjugate of alpha-(p-hydroxyphenyl)-6-oxo-2-piperidineacetic acid (1%, dog). Additional products from methylphenidate conjugation included methyl 1-carbamoyl-alpha-phenyl-2-piperidineacetate (1%, dog or rat) and its carboxylic acid hydrolysis product (1%, rat). The chirality of the major metabolites isolated from dog urine showed that metabolism was partially stereoselective in all investigated cases, except in the formation of alpha-phenyl-2-piperidineacetic acid.

Animals↗
PubMedDate not supplied

Metabolism of aminoglutethimide in the rat.

The metabolism of aminoglutethimide was studied in the rat by use of the 14C-labeled compound. Following oral doses of 5 and 50 mg/kg, the drug was almost completely eliminated within 48 hr into urine and feces, mostly in the form of metabolites. In bile duct-cannulated rats, biliary excretion of radioactivity amounted to about 52% within 24 hr of an orally administered 50 mg/kg dose, with the remainder of the dose being eliminated into urine. The major urinary metabolites resulted from acetylation of the aniline moiety, hydroxylation of the glutarimide ring at positions 3 and 4, and oxidative elimination of the ethyl sidechain. The polar metabolites are accounted for by aromatic hydroxylation with subsequent sulfate conjugation and by a glutarimide ring-opened compound. In addition, a gamma-butyrolactone derivative was also identified.

Aminoglutethimide↗
PubMedDate not supplied

Metabolism of pirprofen in man, monkey, rat, and mouse.

Pirprofen was well absorbed by man, rhesus monkey, rat, and mouse after oral administration of a solution of 14C-labeled compound. The major route of elimination of radioactivity in all four species was renal, mostly in the form of metabolites. Twelve metabolites of pirprofen, accounting for 80% or more of the urinary radioactivity, were identified in the urine of the four species. The metabolic pathways of pirprofen involved oxidation to the pyrrole analogue, and oxidation of the pyrroline double bond to an epoxide, followed by opening of the oxirane ring to a trans-diol derivative. Scission of the pyrroline or pyrrole ring was also observed, leading to the corresponding aniline-type metabolite, part of which underwent subsequent acetylation. Conjugation of the propionic acid functionality with glucuronic acid was found to be extensive in the mouse, rhesus monkey, and man, but not in the rat. Conjugation with taurine was also observed in the rat and mouse.

Adult↗