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J Van Houten

Publications and source records attributed to J Van Houten.

At least 19 recordsLinked to original sources
PubMed2000

A study of the fluorescence of some newly synthesized europium complexes with pyrazolone derivatives.

Some europium complexes with pyrazolone derivatives and 1,10-phenanthroline were synthesized and characterized. The europium ion was found to coordinate to O atoms of the pyrazolone derivatives and to N atoms of 1,10-phenanthroline. A strongly ligand-localized UV absorption leads to the europium-centered emissions between 580 and 750 nm which were assigned as the 5D0-->7F0,1,2,3,4 and 5D1-->7F3,4 transitions. A low site symmetry for the Eu3+ ion was confirmed from the observation of 5D0-->7F0 emission and from the splitting of the other bands. In contrast to many Eu complexes that have been investigated a rather weak emission was measured by introduction of a Schiff base to form a ternary complex with the pyrazolone derivative. The long fluorescence lifetimes of these complexes suggest an energy transfer process from ligands to Eu3+ ion through the triplet state of the ligands.

Europium↗
PubMed1994

Computer-assisted dosing of heparin. Management with a pharmacy-based anticoagulation service.

BACKGROUND: Expert consultation by means of established practice guidelines has been shown to lead to improved accuracy of inpatient anticoagulation therapy, with a reduction in the frequency of hemorrhagic complications. We evaluated a different strategy to improve the accuracy of in-hospital anticoagulation: pharmacy-based, computer-assisted dosing of intravenous heparin therapy. METHODS: Patients treated with computer-assisted dosing of heparin (N = 131) were compared with a randomly selected historical cohort (N = 57) in whom heparin therapy was managed by the primary physician. All patients treated by the pharmacy team received a bolus of heparin, 70 U/kg of ideal body weight, except for patients with pulmonary embolism, who received 100 U/kg of ideal body weight. A computer-generated infusion dose was selected (generally 13 to 16 U/kg per hour). The target was an activated partial thromboplastin time (APTT) ratio of 1.8 times the patient's baseline APTT, with a therapeutic range of 1.5 to 2.5 times baseline. Computer-assisted dosage recommendations were generated after each APTT measurement. RESULTS: In the historical control group, 62% of the patients achieved a therapeutic APTT during the first 24 hours; 17% failed to reach a therapeutic level by 48 hours. The median time to reach a therapeutic APTT was 15 hours. Of all 696 APTTs in this group, 42% were below, 43% in, and 15% above the therapeutic range. In the computer-assisted group, 90% achieved a therapeutic APTT within 24 hours (P < .001); 97% had a therapeutic APTT by 48 hours (P < .01). The median time to achieve a therapeutic APTT was 7 hours (P < .001). Of all 880 APTTs in this group, 17% were below, 75% in, and 8% above the therapeutic range (P < .001). CONCLUSIONS: Pharmacy-based, computer-assisted dosing of heparin is feasible and results in faster and more accurate anticoagulant dosing.

Aged↗
PubMed1994

Chemosensory transduction in eukaryotic microorganisms: trends for neuroscience?

It might appear curious to read about yeast, slime molds and protozoa in a journal dedicated to neuroscience. However, despite their distinct lack of synapses, eukaryotic microorganisms hold a wealth of information relevant to the signal-transduction pathways that underly activity in neuronal receptor cells, particularly those subserving the chemical senses. Microorganisms are sensitive to chemical stimuli from their environment and thus have similarities to receptor neurons of the olfactory system and the taste bud. Here, we introduce receptors, second messengers and effectors responsible for chemosensory signal transduction in yeast mating, sea-urchin spermatozoan chemotaxis, slime-mold aggregation and development, and ciliate chemoresponses.

Animals↗
PubMed1994

The effects of low alcohol beverages on alcohol consumption and impairment.

We examined the effects of providing drinks with half the alcohol level on alcohol consumption and blood alcohol concentration (BAC) of 4 patrons of a private club. Alcohol consumption was measured by observers and level of impairment was determined from breath samples obtained by digitalized ALERT (Alcohol Level Evaluation Road Tester) breath testing devices. An alternating treatments design was employed to compare the sessions during which people drank mixed drinks with their usual alcohol concentration with sessions during which they drank mixed drinks with half the alcohol concentration that cost half as much as the regular drinks. All 4 participants consumed less alcohol during sessions when they received drinks with the lower alcohol content. BAC was also less on all but two sessions during the low alcohol condition.

Alcohol Drinking↗
PubMed1993

Ca2+ transport and chemoreception in Paramecium.

Intracellular Ca2+ levels in Paramecium must be tightly controlled, yet little is understood about the mechanisms of control. We describe here indirect evidence that a phosphoenzyme intermediate is the calmodulin-regulated plasma membrane Ca2+ pump and that a Ca(2+)-ATPase activity in pellicles (the complex of cell body surface membranes) is the enzyme correlate of the plasma membrane pump protein. A change in Ca2+ pump activity has been implicated in the chemoresponse of paramecia to some attractant stimuli. Indirect support for this is demonstrated using mutants with different modifications of calmodulin to correlate defects in chemoresponse with altered Ca2+ homeostasis and pump activity.

Animals↗
PubMed1993

Comparative analysis of current US and EC biosafety regulations and their impact on the industry. US National Institutes of Health.

On July 18, 1991, the US National Institutes of Health added a section entitled 'Good Large-Scale Practice' (GLSP) to Appendix K of the Guidelines for Research Involving Recombinant DNA Molecules. Highlights of this section include the requirement for: (i) a health and safety program; (ii) well-trained personnel; (iii) facilities, clothing and practices appropriate to the risk of exposure; (iv) discharges to air, water and soil that must be done in accordance with environmental regulations; (v) aerosol generation that must be kept to a minimum so that employee health is not adversely affected; and (vi) a spill control plan. This complements the blueprint for regulation of biotechnology in the US (Coordinated Framework for Regulation of Biotechnology), in which the jurisdiction of each federal agency is established. Activities in Europe at this time included the adoption of three directives by the European Economic Community: "on the protection of workers from risks related to exposure to biological agents at work", "on the contained use of genetically modified organisms", and "on the deliberate release of genetically modified organisms". The relationship of these new guidelines and regulations to existing practices and their potential impact on future activities are discussed.

Biotechnology↗
PubMed1992

Increasing generalized social interactions in psychotic and mentally retarded residents through peer-mediated therapy.

This study investigated whether withdrawn adults living in a residential center for psychotic and mentally handicapped persons could serve as peer therapists to increase the social interaction of other withdrawn residents. Two pairs of residents served as participants. Treatments were introduced and evaluated within a multiple baseline with reversal design. After baseline, the peer therapist was instructed to increase the social interactions of a target peer through engagement in social interactions. The results demonstrated that the peer therapist increased the social interactions of target peers. However, these increases did not generalize to other residents until the introduction of a multiple peer therapist condition. The percentage of time the peer therapists interacted with other nontarget residents also increased throughout the study. These results were maintained during a 4-month follow-up condition.

Adult↗
PubMed1987

Correlations between cyclic AMP binding and chemoreception in Paramecium.

Paramecium tetraurelia is attracted to cyclic AMP, which probably, as other attractants, signifies the presence of food. Attraction to cyclic AMP was specific, saturable, and, therefore, likely to be receptor-mediated. In these studies, we measured the binding of cyclic [3H]AMP to whole cells and found it to be saturable, reversible, and displaying specificity similar to that of attraction. An HPLC method of separating nucleotides was devised and used to determine that external cyclic AMP was degraded in the absence of IBMX, a phosphodiesterase inhibitor, and that cyclic AMP was taken into the cells in small amounts. Since binding and attraction were subsequently measured in the presence of IMBX, it was cyclic AMP and not a degradation product that served as the attractant stimulus for Paramecium.

1-Methyl-3-isobutylxanthine↗
PubMed1987

Eukaryotic unicells: how useful in studying chemoreception?

The description of the chemoreception pathway in Paramecium is incomplete, but the technical means are available to study these pathways at the molecular level. The hallmark of ciliates is their versatility and their most important attribute is the availability of useful mutants. It is just this versatility and amenability to genetic manipulation that will move the study of Paramecium chemoreception forward and provide useful information for chemoreceptor cell function in general.

Animals↗
PubMed1986

Inbreeding of Wistar-Kyoto rat strain with hyperactivity but without hypertension.

A genetic inbreeding program using Wistar-Kyoto rat strains as progenitors was used to combine the hyperactivity trait of the spontaneously hypertensive rat (SHR) with the normotensive trait of the WKY genetic control strain. From an SHR X WKY cross we produced a gene-assorting F2 population from which selected brother-sister matings were carried out through seven successive inbred populations. This program produced a new strain of hyperactive rats with normotensive mean systolic blood pressure levels, and we have designated the new strain as the Wistar-Kyoto hyperactive (WK/HA) rat. Another behavioral characteristic of the SHR rat, poor habituation in a nonreinforcing novel environment, did not appear as a characteristic trait of the new strain of WK/HA rats, suggesting a separate underlying genetic basis for the two traits that had been apparently fortuitously fixed in the SHR genotype as a result of intensive inbreeding of that strain. The new WK/HA strain, together with the WKY control strain, is considered as more suitable for subjects in studying hyperactivity in rats than the original SHR strain with its concomitant hypertension and poor habituation traits.

Animals↗
PubMed1984

Intracellular localization of photosynthetic membrane growth initiation sites in Rhodopseudomonas sphaeroides.

Putative membrane invagination sites at which intracytoplasmic photosynthetic membrane growth is initiated in Rhodopseudomonas sphaeroides can be isolated in an upper pigmented fraction by rate-zone sedimentation. The intracellular localization of membranes present in the isolated fraction was investigated with the impermeant surface-labeling reagent pyridoxal 5'-phosphate, which has been shown to diffuse into the periplasmic space and to label proteins of both the peripheral cytoplasmic membrane and the mature intracytoplasmic membrane. A comparison of the extent of labeling at 25 and 0 degrees C was consistent with the possibility that membranes present in the upper pigmented fraction arise from sites near the cell periphery. Pronase digestion of the surface-labeled membranes suggested further that the purified upper fraction consisted largely of open membrane fragments and that the majority of the intracytoplasmic membrane is labeled by this procedure. The pigmented membrane growth initiation sites were separated partially from undifferentiated respiratory cytoplasmic membrane also present in the upper fraction.

Bacterial Chromatophores↗
PubMed1982

Mutants of Paramecium defective in chemokinesis to folate.

Ten mutant lines of Paramecium tetraurelia defective in attraction to folate were isolated and examined. All mutants were normal in response to other attractants and repellents tested. One mutant was able to accumulate in folate given sufficient time. All mutations were recessive and behaved as single site Mendelian lesions. Complementation tests indicate that the mutants fall into three complementation groups. Mutants of Group 2 fall into two phenotypic classes and probably represent two alleles of the mutated fol2 gene. Possible sites of the mutants' blocks in chemoresponse are discussed.

Animals↗
PubMed1982

Kinetic analysis of chemokinesis of Paramecium.

Paramecia detect and accumulate in or disperse from some chemicals. Cells do this by changing frequency of turning and speed of swimming. There are at least two mechanisms by which cells respond: one dependent on ability to turn, one dependent on speed modulation. There are also two classes of chemicals: those that require the cells' ability to turn in order to cause accumulation and dispersal (type I), and those that apparently require only speed modulation (type II). Attractants of type I cause qualitatively similar changes in behavior to repellents of type II and the converse; therefore, assays are needed to distinguish between these two classes of chemicals, despite qualitatively similar behavior of some attractants and repellents. We examined two assays of paramecium chemoresponse, T-maze assay and well test, to understand how the T-maze distinguishes between attractants of type I and repellents of type II and why the well test does not.

Animals↗
PubMed1979

Membrane potential changes during chemokinesis in Paramecium.

Intracellular recordings show that (i) paramecia hyperpolarize slightly in attractants and depolarize in repellents that depend on the avoiding reaction (an abrupt change of swimming direction), and (ii) paramecia more strongly hyperpolarize in repellents and more strongly depolarize in attractants that depend on changes of swimming velocity. These membrane potential changes are in agreement with a hypothesis of membrane potential control of chemokinesis in Paramecium.

Animals↗