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Biomedical subjects

R K Thomas

Publications and source records attributed to R K Thomas.

At least 55 records · Page 3Linked to original sources
PubMed1996

Investigating cognitive abilities in animals: unrealized potential.

Cognitive abilities related to learning ability and intelligence involve 8 levels of fundamental processes. Any and all of such cognitive abilities reduce to these 8 levels or to combinations of them. The 8 levels are hierarchical because lower levels, generally, are prerequisites for higher levels. An animal's general cognitive ability is determined by how many of the fundamental processes it can use. Although the processes are hierarchical, an animal will use all processes available to it in serial or in parallel as the situation requires. A perusal of contemporary journals' contents will show that behavioral neuroscientists, including behavioral pharmacologists, rarely study cognitive abilities that require the use of processes at the highest 4 levels. Yet, all vertebrates may be capable of using level-5 processes, and several avian and mammalian species have been shown to use level-6 processes. The use of level-7 processes has been shown in non-human primates and likely can be shown in non-primate species, too. The present article provides an overview of the basic cognitive processes as well as types of tasks that might be used to investigate the neural correlates or substrates of higher cognitive processes in animals. Unless and until better measures of cognitive ability are used, a vast potential for research will be unrealized.

Animals↗
PubMed1995

Neutron reflection study of bovine beta-casein adsorbed on OTS self-assembled monolayers.

Specular neutron reflection has been used to determine the structure and composition of bovine beta-casein adsorbed on a solid surface from an aqueous phosphate-buffered solution at pH 7. The protein was adsorbed on a hydrophobic monolayer self-assembled from deuterated octadecyltrichlorosilane solution on a silicon (111) surface. A two-layer structure formed consisting of one dense layer of thickness 23 +/- 1 angstroms and a surface coverage of 1.9 milligrams per square meter adjacent to the surface and an external layer protruding into the solution of thickness 35 +/- 1 angstroms and 12 percent protein volume fraction. The structure of the (beta-casein) layer is explained in terms of the charge distribution in the protein.

Adsorption↗
PubMed1993

A note on the early history of electrical stimulation of the human brain.

We address inconsistencies in two areas concerning who was first to electrically stimulate a human's brain. First, Boring (1950) and others attributed priority to Eduard Hitzig based on information mentioned somewhat incidentally in Fritsch and Hitzig's (1870) classic work using dogs. Others cited Fritsch and Hitzig but attributed priority to Roberts Bartholow (1874). Second, our examination of translations of Fritsch and Hitzig, especially of footnote 16 in Hitzig's report (1870) of a human case, revealed errors, omissions, and inconsistencies. To aid our inquiry, we requested and received new translations of footnote 16 and of Hitzig's report.

Brain↗
PubMed1993

Health demography comes of age.

The U.S. health care industry has been hampered in the development of a mature marketing function in part due to characteristics unique to the industry. These characteristics include a lack of market data, poorly developed market research techniques, and a poor understanding of consumer behavior within the industry. Some of the deficiencies are being addressed through the development of an emerging field that is being referred to as "health demography." Health demography and those who have begun to refer to themselves as health demographers are drawing from the fields of demography, epidemiology, biostatistics, and the social sciences to formulate a new discipline uniquely related to the needs of today's health care marketers and planners. Those involved with health demography are developing databases and models for application to concrete problems in health care delivery. The development of this field is contributing to the advancement of the state of marketing in health care and serving to reduce many of the barriers that have retarded the development of a mature marketing function within the health care industry.

Catchment Area, Health↗
PubMed1992

A review of common ophthalmic antibacterial and corticosteroid-antibacterial combination drugs.

The use of antibacterial agents and corticosteroid-antibacterial combinations are essential to the practice of primary care optometry. In this paper we review common antibacterial drugs available for the treatment of ocular infection or prophylaxis, and offer some clinical guidelines for their use. Corticosteroid-antibacterial combination drugs, used primarily to suppress ocular inflammation, are also discussed, and the distinctions between common drugs are described.

Anti-Bacterial Agents↗
PubMed1991

Coupling of spectrin and polylysine to phospholipid monolayers studied by specular reflection of neutrons.

The technique of specular reflection of neutrons is applied for the first time to study the charge-dependent interaction of the protein spectrin and the polypeptide poly-L-lysine with model phospholipid monolayers in the condensed phase state. We first established the structure of a pure monolayer of dimyristolyphosphatidylcholine (DMPC) in both the expanded and condensed fluid phase states without protein in the subphase. The thickness of the hydrocarbon chains increases from 11.4 +/- 1.5 A in the expanded state to 15.8 +/- 1.5 A in the condensed state, whereas the head group region is approximately 10 A thick for both phase states. When spectrin is present in the subphase, the dimensions of DMPC in the condensed state are not significantly affected, but there is approximately 0.09 volume fraction spectrin in the head group region. Lipid-spectrin coupling is enhanced by electrostatic interaction, as the volume fraction of spectrin in the head group region increases to 0.22 in a mixed monolayer of DMPC and negatively charged dimyristolyphosphatidylglycerol in the condensed state. In contrast to spectrin, polylysine does not penetrate the head group region, but forms a layer electrostatically adsorbed to the charged head groups.

Biophysical Phenomena↗
PubMed1991

Structure of an adsorbed dimyristoylphosphatidylcholine bilayer measured with specular reflection of neutrons.

Using specular reflection of neutrons, we investigate for the first time the structure of a single dimyristoylphosphatidylcholine bilayer adsorbed to a planar quartz surface in an aqueous environment. We demonstrate that the bilayer is strongly adsorbed to the quartz surface and is stable to phase state changes as well as exchange of the bulk aqueous phase. Our results show that the main phase transition is between the L alpha phase and the metastable L beta'* phase, with formation of the P beta' ripple phase prevented by lateral stress on the adsorbed bilayer. By performing contrast variation experiments, we are able to elucidate substantial detail in the interfacial structure. We measure a bilayer thickness of 43.0 +/- 1.5 A in the L alpha phase (T = 31 degrees C) and 46.0 +/- 1.5 A in the L beta'* phase (T = 20 degrees C). The polar head group is 8.0 +/- 1.5 A thick in the L alpha phase. The water layer between the quartz and bilayer is 30 +/- 10 A for the lipid in both the L alpha and L'* phase. Our results agree well with those previously reported from experiments using lipid vesicles and monolayers, thus establishing the feasibility of our experimental methods.

Dimyristoylphosphatidylcholine↗
PubMed1991

The importance of internal marketing: the case of geriatric services.

Hospitals seeking to become more aggressive often are tempted to introduce programs prematurely. Using the example of a geriatric services program at a large hospital, the authors illustrate the dangers of neglecting internal marketing and offer recommendations for ensuring internal coordination prior to introduction of a product externally.

Aged↗
PubMed1991

Medical management of anterior uveitis.

Anterior uveitis is frequently caused by systemic disease, and it is appropriate not only to diagnose the iritis but also to determine, if possible, the underlying condition. Although diagnosis of an anterior uveitis is usually straightforward, medical management occasionally is not. Satisfactory treatment may be achieved in many cases with cycloplegics and topical corticosteroid therapy, but the management protocol must be tailored to suit the patient. Frequent assessment of the patient is required during the 2- to 3-week period usually required for resolution of an anterior uveitis.

Administration, Topical↗
PubMed1990

Specular reflection of neutrons at phospholipid monolayers. Changes of monolayer structure and headgroup hydration at the transition from the expanded to the condensed phase state.

The specular neutron reflection technique has been applied for the first time to study the structure and head group hydration of a phospholipid monolayer (dimyristoylphosphatidylcholine containing negatively charged phospholipids) in the condensed and expanded state. By variation of the contrast of the subphase to that of the air it is shown that at the transition from the condensed to the expanded state the carboxyl bonds of the glycerol backbone are hydrated leading to a strong structural change of the headgroup. The total monolayer thickness in the condensed state is 22.5 +/- 1 A (tilt angle 32 +/- 6 degrees) and decreases to 19.5 +/- 1 A in the expanded state. The mean molecular volume increases from 1190 +/- 50 A3 to 1250 +/- 50 A3.

Deuterium↗
PubMed1990

Number-related discrimination and summation by squirrel monkeys (Saimiri sciureus sciureus and S. boliviensus boliviensus) on the basis of the number of sides of polygons.

In Experiment 1, with the number of sides or angles of irregular polygons as cues, programmed training, and a 90% correct criterion (36 of 40), 2 squirrel monkeys' (Saimiri sciureus sciureus and S. boliviensus boliviensus) best performances were to discriminate heptagons from octagons, a 3rd's best was hexagons from heptagons, and a 4th's best was pentagons from heptagons. In Experiment 2, on most trials 2 polygons on one or both discriminanda had to be summed to determine which discrimination had the total fewer sides. Only 1 monkey met criterion (27 of 30) on the 2 tasks, 6 vs. 8 and 7 vs. 8 sides, but the other 3 performed better than chance on the 6 vs. 8 task. We conclude that previous studies of animals' discrimination of polygons in terms of complexity were minimally relevant to this work, and counting and subitizing were rejected in favor of a prototype-matching process to explain our monkeys' performances.

Animals↗