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Biomedical subjects

A Keller

Publications and source records attributed to A Keller.

At least 253 records · Page 14Linked to original sources
PubMed1975

The impact of organization of family planning clinics on waiting time.

Mathematical simulations and structured observations were used to assess factors in family planning clinic procedures responsible for long waiting times for clients. Principal causes of unnecessarily long waiting times in selected clinics of a Mexican program included: inflexibilty of client's routes within the clinic and of staff functions, late arrival of staff, patterns of client arrival times, and the proportion of clients seen by the doctor.

Appointments and Schedules↗
PubMedDate not supplied

Preparation and in vitro pharmacology of 5-HT4 receptor ligands. Partial agonism and antagonism of metoclopramide analogous benzoic esters.

Alicyclic ester analogues of the gastroprokinetic benzamide metoclopramide (1) and its ester congener SDZ 205557 (2), a 5-HT4 receptor antagonist, were prepared by O-alkylation of 4-amino-5-chloro-2-methoxybenzoate with N-(2-chloroethyl) substituted alicyclic amines. The bromo and iodo analogue of compound 13b (2-(1-piperidinyl)ethyl 4-amino-5-chloro-2-methoxybenzoate) were obtained by halogenation of dechloro-13b with N-halogenated succinimides. The series was evaluated in functional in vitro assays with regard to affinity for serotoninergic 5-HT4, 5-HT3 and muscarinic M3 receptors. The affinities for 5-HT3 and M3 receptors were below 6.0 (pKB or pA2). On 5-HT4 receptors in guinea-pig ileal longitudinal muscle and rat oesophagus, the majority of compounds revealed partial 5-HT4 receptor agonism susceptible to blockade by SDZ 205557, a reference 5-HT4 receptor antagonist (pKB = 7.25-7.73 (guinea-pig ileum) and 7.09-7.43 (rat oesophagus)). The relative agonist potency was in the range of 5-303% (5-HT: 100%). Compound 13b and its bromo analogue 17 were the most potent esters of the series. The enantiomers of 13g ((R)- and (S)-2-(2-methyl-1-piperidinyl)ethyl 4-amino-5-chloro-2-methoxybenzoate) interacted stereoselectively with 5-HT4 receptors and displayed enantiomeric potency ratios (R)/(S) of 4.3-8.7. There was an excellent correlation between (a) antagonist affinity on guinea-pig ileum and rat oesophagus, (b) relative agonist potency on guinea-pig ileum and rat oesophagus, and (c) between antagonist affinity and relative agonist potency within each assay (r2 > 0.91). The new compounds may serve as academic tools in evaluating the functional role of 5-HT4 receptors. The selective partial 5-HT4 receptor agonists presented in this paper may be useful to restore physiological motility and secretion in the gut with reduced or absent propensity to elicit tachycardia and desensitization of the intestinal target receptor.

Animals↗
PubMedDate not supplied

The role of condensation and coagulation in aerosol monitoring.

We derive general-purpose mathematical model for pollution concentration studies. The model is based on the aerosol general dynamic equation (GDE). It accounts for aerosol processes like coagulation and growth by deposition and is therefore suited for suspended-particle monitoring. Our model is validated by controlled experiments done using standard aerosol monitoring devices that measure PM10, particle cross section, particle-bound polycyclic aromatic hydrocarbons (PPAHs) and number concentration, showing an excellent agreement with the experimental data in a 77-m(3) room with a time sequence of cigarettes smoked. As an example of an application, we calculated the mean PPAH emission rate in environmental tobacco smoke (ETS) for a "smolder-smoked" cigarette and found it to be 8 ng/s for a total emission of 5.28 microg per cigarette. The results show that real aerosol dynamics should be taken into account when monitoring suspended particles.

Aerosols↗