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Biomedical subjects

C George

Publications and source records attributed to C George.

At least 199 records · Page 11Linked to original sources
PubMed1970

Dynamics of systems with large number of degrees of freedom and generalized transformation theory.

A generalized transformation theory which leads to a non-Hamiltonian description of dynamics is introduced. The transformation is such that all averages of observables remain invariant. However, the time evolution of the density matrix can no longer be expressed in terms of a commutator with the Hamiltonian. Therefore such transformations are not canonical in the usual sense. An explicit "two components" representation of the equations of motion is given which has the following properties: (a) each of the components satisfies a separate equation of motion, and (b) one component satisfies a kinetic equation of a generalized Boltzmann type.WE OBTAIN, THEREFORE, THE MOST REMARKABLE RESULT THAT THE RELATION BETWEEN DYNAMICS AND STATISTICAL MECHANICS (OR THERMODYNAMICS) TAKES A SPECIALLY TRANSPARENT AND SIMPLE FORM: thermodynamics appears in a precise sense as the random phase approximation of dynamics.Other problems such as the meaning of diagonalization of the Hamiltonian and definition of excitations will be treated in a forthcoming paper.

Journal Article↗
PubMed1970

Physical particle representation and generalized transformation theory.

The investigation of the recently described generalized transformation theory which leads to a non-Hamiltonian description of dynamics is pursued. The concept of generalized unitary transformations of superoperators is introduced and a specific class of transformations studied. For nondissipative systems it is equivalent to the usual unitary transformations that diagonalize the Hamiltonian. The important point is that this class of transformations remains meaningful for dissipative systems, hence a new representation of dynamics that we shall call the "physical particle" representation. It has the following properties: (a) The energy (or an arbitrary function of the energy) is represented by a diagonal matrix. (b) In the ((0))II space (see these Proceedings, 65, 789 (1970)) corresponding to the coherent processes, the evolution can be described in terms of the changes in population of the physical particles. (c) At thermodynamic equilibrium, the physical particles are uncorrelated and behave as independent entities; the entropy has a purely combinatorial meaning.A full description of dynamics in this representation will be given in a forth-coming paper.

Journal Article↗
PubMedDate not supplied

Conformational analysis and a crystal structure of bupropion, an antidepressant with dopamine reuptake blocking activity.

A conformational analysis has been performed on the antidepressant bupropion using the MM3-92 program. In addition, the structure of the compound in the crystal state was obtained. There is good agreement between the computed global minimum and the structure observed by crystallography. The three-dimensional structure of the preferred conformer of bupropion is consistent with the three-dimensional structures of other dopamine reuptake blockers such as cocaine, CFT, and methylphenidate.

Antidepressive Agents, Second-Generation↗
PubMedDate not supplied

Conformationally restricted nucleosides. The reaction of adenosine deaminase with substrates built on a bicyclo[3.1.0]hexane template.

Adenosine deaminase (ADA) can discriminate between two distinct (North and South), conformationally rigid substrate conformers. (N)-methanocarba-2'dA (4) is deaminated 100 times faster than the antipodal (S)-methanocarba-2'dA (5), whereas a non-rigid analogue, aristeromycin (6), is deaminated at an intermediate rate. These results are in agreement with crystallographic data from ADA-ribonucleoside complexes showing the furanose ring of the bound purine in a C3'-endo (North) conformation. The data presented here suggests that 4 and 5 are useful probes to ascertain conformational preferences by purine metabolizing enzymes.

Adenosine Deaminase↗
PubMedDate not supplied

Magnetic resonance imaging of a brain abscess in a 10-month-old filly.

The purpose of this paper was to correlate the magnetic resonance imaging (MRI) characteristics of a mature brain abscess in a horse with histopathologic alterations of brain tissue. Eight months after the onset of clinical signs, MRI of the brain of a 10-month-old filly was performed. A large space-occupying lesion in the right cerebral hemisphere was identified. This space-occupying lesion was delineated by a thick and well-defined capsule that was isointense to brain parenchyma on the T1-weighted images and with a markedly hypointense on the T2-weighted images. The identification of such a capsule is highly diagnostic of a mature brain abscess. The lesion seen on MR images was confirmed at necropsy where a large abscess of the right hemisphere was observed. Streptococcus zooepidemicus and Pseudomonas aeruginosa were isolated from the abscess. Based on histopathologic examination, the signal characteristics of the capsule on T1-weighted and T2-weighted images were found to be due to the presence of numerous hemosiderin-laden macrophages. These results are in agreement with previous studies on human patients. This report confirms the value of MRI in the diagnosis of equine brain diseases.

Animals↗
PubMedDate not supplied

Fibrodysplasia ossificans progressiva in the cat. A case report.

Clinical, radiographic, electromyographic, and pathologic findings in a cat with fibrodysplasia ossificans progressiva are described. The features of five previously reported cases of this feline disorder are also presented. This disorder affects young adult to middle-aged cats of both sexes. Characteristic clinical features include progressive stiffness of gait, with enlargement of proximal limb musculature. Radiography reveals multiple mineralized densities within the affected musculature. The clinical course is rapid, with development of severe disability within 2 weeks to several months. Electromyographic and pathologic findings suggest that this is a disorder of connective tissue, affecting primarily the epimysium, tendons, and fasciae, and results in marked proliferation of fibrovascular connective tissue, with associated chondroid and osseous metaplasia.

Animals↗
PubMedDate not supplied

Longitudinal analysis of nortriptyline side effects in elderly depressed patients.

Forty-five depressed elderly patients were closely monitored in a research setting during treatment with nortriptyline and interpersonal psychotherapy for 7 consecutive months of acute and continuation treatment. Overall, nortriptyline was efficacious and well tolerated in this group. The frequency of somatic complaints measured by the Rating Scale for Side Effects declined by 50% during the acute phase of treatment, suggesting that many somatic complaints that may be attributed to side effects of nortriptyline are actually somatic symptoms of depression. The authors discuss the implications of these findings and offer practical advice for the treating clinician.

Aged↗
PubMedDate not supplied

Quality assurance: using BS 5750 in health care settings.

This article places the issue of standards within the arena of a quality service. It argues that standards of quality can only be turned into reality if they are developed through the discipline of a quality assurance system, combined with the motivation of a quality culture. A quality assurance system, British Standard (BS) 5750, is briefly outlined and attention is given to examining the mechanisms for defining the specific requirements necessary to develop quality assurance within residential care homes. This is based on the authors' experience of working with Napier House, the first caring enterprise in Europe working directly with patients or residents to obtain the BS 5750.

Health Services↗
PubMedDate not supplied

Acute cerebral ischemia in rabbits: correlation between MR and histopathology.

The histologic description of cerebral ischemia is complex, and within most lesions there are regional variations in degrees of neuronal cell injury, edema, and neuropil disruption. These parameters of tissue injury were analyzed histopathologically in transient and permanent experimental cerebral ischemia in 15 rabbits and the results were spatially correlated with MR images of pre- and postmortem (formalin-fixed) brains. MR was performed at 1.5 T (eight animals) and at 0.38 T (seven animals). Areas of high signal on T2-weighted MR images were closely correlated with histologic signs of cytotoxic glial edema and with disruption of the neuropil (widening of the interstitial spaces in the background matrix of glial and neuronal cellular processes), but MR tended to underestimate the extent of ischemic neuronal injury, especially low-grade histologic changes (mild neuronal shrinkage and nuclear basophilia). Low-grade ischemic neuronal changes were often found in the penumbra zone of ischemic lesions in areas that appeared normal on T2-weighted MR. High-grade neuronal injury was also seen occasionally in areas of normal signal on MR, especially in the striatum. No significant differences were seen on T2-weighted MR between the experimental groups with respect to transient vs permanent occlusion, in vivo vs in vitro MR, and low vs high magnetic field. In the setting of suspected acute cerebral ischemia, an abnormal T2-weighted MR study often underestimates the extent of neuronal ischemic injury, especially potentially reversible injury; and a normal MR study does not completely exclude significant neuronal ischemic injury.

Acute Disease↗
PubMedDate not supplied

Diagnosis of acanthamoeba keratitis--a report of four cases and review of literature.

Acanthamoeba keratitis is not reported often in India. We reported the first case diagnosed in this country a year back. In this communication, four more cases of Acanthamoeba keratitis diagnosed since then are being reported along with a brief review of literature. Diagnosis in all these patients was based on observation of acanthamoeba cysts in 10% KOH wet mount of corneal ulcer scrapings and subsequent culture. The characteristic ring infiltration of cornea was seen in all of them. All cases were treated medically with the available antiamoebic drugs (Miconazole, Neosporin, Ketoconazole and Metronidazole) in different combinations. Only one out of four, responded with complete healing of the ulcer. Acanthamoeba keratitis is probably not as uncommon in India as it is thought to be. With increased awareness and performance of minimal laboratory tests the condition may be diagnosed more often.

Acanthamoeba Keratitis↗