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Biomedical subjects

C Jensen

Publications and source records attributed to C Jensen.

At least 145 records · Page 8Linked to original sources
PubMed1978

Selected autoimmune diseases in the dog.

In summary, previous attempts to explain the role of inheritance in autoimmune disorders through family studies have been hampered by the variable degree of phenotypic expression. Our evidence utilizing dogs in family studies is consistent with the concept that genetic factors play some role in determining disease susceptibility. Recognizing the complexity of the genetic components involved in these studies, we have proposed a hypothesis of two classes of genes, one that relates to immunoregulation and another that specifies pathologic lesions (and thus the clinical signs). This dual system of interacting genes provides a rational explanation for many of the observations previously encountered in both human and canine studies.

Alleles↗
PubMed1978

Learning performance varies with brain weight in heterogeneous mouse lines.

Three lines of unselected heterogeneous stocks of mice were tested for learning and activity in active avoidance acquisition and extinction, water-maze discrimination learning and reversal learning, operant discrimination, and passive avoidance acquisition tasks. Ambulation in the open field was also measured. Small to moderate correlations (absolute values of .17 to .42) between brain weight and learning measures were obtained for all tasks except passive avoidance. A moderate correlation between brain weight and activity was found only in the open field (r = .39). Partialing out differences in operant level and body weight and learning performance. When ambulation in the open field was partialed out, however, all correlations between brain weight and learning performance decreased. Previous research has suggested a positive relation between brain weight and learning scores across mammalian orders and species. The results reported here extend this relation to within-species variation in brain size. The results also emphasize the limitations of estimating genetic associations between brain and behavior from comparisons between small numbers of inbred strains or selected lines.

Animals↗
PubMed1976

A rapid gas chromatographic method for the determination of chlorophenoxyisobutyric acid in plasma and urine.

A rapid gas chromatographic method is described for the determination of chlorophenoxyisobutyric acid (the active metabolite of clofibrate) in plasma and urine. The assay involves an extraction into toluene and back-extraction of the chlorophenoxyisobutyric acid and the internal standard (2-naphthoic acid) into the methylating reagent (trimethylanilinium hydroxide). Concentrations of 1 mug/ml in plasma and urine can easily be measured; the precision of the method is 3.3 +/- 0.7% for plasma and 2.7 +/- 0.4% for urine. There is no interference from endogenous compounds or from drugs commonly prescribed together with clofibrate.

Chromatography, Gas↗
PubMed1975

Studies of substructure and tightly bound nucleotide in bacterial membrane ATPase.

Highly purified preparations of Streptococcus faecalis ATPase contain a similar but inactive protein detected by prolonged polyacrylamide gel electrophoresis. The inactive protein appears to arise by proteolytic cleavage of the major subunits in the enzyme. By use of a new technique, subunit analysis in SDS gels was performed on the enzyme band and the inactive protein band excised from a polyacrylamide gel after electrophoresis. The results indicated that the ATPase has the composition alpha3beta3gamma in which alpha = 60,000, beta = 55,000, and gamma = 37,000 daltons. The inactive protein appears to have the composition (f)6 in which f = 49,000 daltons. There is also evidence that the enzyme band contains some slightly modified forms of the ATPase, such as alpha3beta2 (f)gamma. The inactive protein lacks the capacity for tight nucleotide binding. Our experiments show that the tight ATPase-nucleotide complex formed in S. faecalis cells (the endogenous complex) behaves differently from the tight complex formed in vitro (the exogenous complex). We prepared a doubly labeled complex containing endogenous 32P-labeled ADP and ATP and exogenous 3H-labeled ADP. We observed that the addition of free nucelotide to the doubly labeled ATPase displaced the exogenous bound ligand from the enzyme but not the endogenous bound nucleotide. We suggest that the displaceable and nondisplaceable forms of the tight ATPase-nucleotide complex correspond to two different conformational states of the enzyme.

Adenosine Diphosphate↗
PubMed1973

Behavioral aftereffects of reinforcement and its omission as a function of reinforcement magnitude.

Rats responded on a multiple fixed-interval fixed-interval schedule of reinforcement. Each complete cycle of the multiple schedule was separated from the next by a relatively long period of timeout from all schedule contingencies. A response at the end of the second component of each cycle was always reinforced with an invariant reinforcement magnitude, while reinforcement magnitude and reinforcement omission were systematically varied in the first component. Response rate in the first component was a monotonic function of reinforcement magnitude in that component. These changes in response rate in the first component did not affect response rate in the second component. When reinforcement was omitted on 50% of occasions in the first component, following reinforcement there was a reduction in response rate in the second component that was monotonically related to reinforcement magnitude. Following reinforcement omission there was an increase in response rate in the second component that was unrelated to reinforcement magnitude. When reinforcement was omitted on 100% of occasions in the first component, behavioral contrast was observed.

Journal Article↗
PubMed1972

Mycoplasma-virus interrelationships in mouse tracheal organ cultures.

The effects produced by single and mixed infections with Mycoplasma pulmonis and influenza A/PR-8 virus were studied in mouse tracheal organ cultures. M. pulmonis multiplied in the tracheal organ cultures, producing inhibition of ciliary activity and histologic tissue damage. The organism grew in close association with the cell membranes but did not appear to attach directly to the membranes or the cilia. Influenza A virus also replicated in tracheal organ cultures, producing ciliary inhibition and more extensive cytopathologic changes. Virus particles were seen by electron microscopy to attach to and cause clumping of the cilia. Simultaneous infection of the organ cultures with mycoplasma and virus resulted in more rapid inactivation of ciliary activity and greater tissue damage than occurred when the cultures were infected with only mycoplasma or virus. Presence of the virus appeared to have no effect on the growth of the mycoplasma; however, the mycoplasma partially interfered with virus replication.

Animals↗