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Biomedical subjects

D Kahn

Publications and source records attributed to D Kahn.

At least 109 records · Page 6Linked to original sources
PubMed1998

To dream or not to dream? Relevant data from new neuroimaging and electrophysiological studies.

The study of sleep and dreams has enjoyed a major breakthrough with recent findings from brain imaging studies in humans. Several independent groups have shown global deactivation of the brain during non rapid eye movement sleep and a regionally selective reactivation during rapid eye movement sleep. These results are complemented by new brain lesion and electrophysiological recording data to give a detailed picture of the brain dynamics of changes in conscious state.

Brain Mapping↗
PubMed1998

Consequences of the combined deficiency in dystrophin and utrophin on the mechanical properties and myosin composition of some limb and respiratory muscles of the mouse.

The mechanical properties and the myosin isoform composition were studied in three isolated muscles (EDL, soleus, diaphragm) of mutant mice lacking both dystrophin and utrophin (dko). They were compared with the corresponding muscles of the normal and the dystrophin-deficient (mdx) and the utrophin-deficient (uko) mice. In comparison with mdx muscles, dko muscles show a significant reduction of the normalized isometric force, confirmed by the reduced muscular activity of the whole animal. Kinetics parameters (twitch time-to-peak and half-relaxation time) were slightly reduced, and the maximal speed of shortening of soleus, Vmax, was reduced by 30%. The maximal power output (muW/mm3) was reduced by 50% in dko soleus. In the three muscles studied, the relative myosin heavy chains (MHC) composition showed a shift towards slower isoforms. dko EDL presented a dramatic decrease of the resistance ot tetanic contraction with forced lengthenings (eccentric contractions), while muscle lacking only utrophin (uko mutants) display a normal resistance to this exacting mechanical challenge. These experiments suggest that lack of both dystrophin and utrophin is very detrimental to the mice and that mechanical properties of the muscles may explain the overall phenotype. Moreover these results bring some support to the idea that the expression of utrophin in mdx muscle compensates, to some extent, for the lack of dystrophin.

Animals↗
PubMed1998

Rebound effect of the allogenic T-cell response to donor and third-party lymphocytes after cyclosporine withdrawal in renal transplant recipients.

Mixed lymphocyte reaction (MLR) assays were performed serially over 24 months in 19 first cadaver renal transplant recipients. Immunosuppression consisted of cyclosporine, methylprednisolone and azathioprine. Cyclosporine was withdrawn at 6 months postoperatively. The MLR reactivity gradually decreased over the first 3 months following transplantation. However, there was a significant increase in MLR reactivity at 12 months postoperatively after the cyclosporine withdrawal. This rebound effect in MLR reactivity following cyclosporine withdrawal could account for the increased incidence of acute rejection episodes.

Adult↗
PubMed1998

Expression of full-length utrophin prevents muscular dystrophy in mdx mice.

Duchenne muscular dystrophy (DMD) is a lethal, progressive muscle wasting disease caused by a loss of sarcolemmal bound dystrophin, which results in the death of the muscle fiber leading to the gradual depletion of skeletal muscle. The molecular structure of dystrophin is very similar to that of the related protein utrophin. Utrophin is found in all tissues and is confined to the neuromuscular and myotendinous junctions in mature muscle. Sarcolemmal localization of a truncated utrophin transgene in the dystrophin-deficient mdx mouse significantly improves the dystrophic muscle phenotype. Therefore, up-regulation of utrophin by drug therapy is a plausible therapeutic approach in the treatment of DMD. Here we demonstrate that expression of full-length utrophin in mdx mice prevents the development of muscular dystrophy. We assessed muscle morphology, fiber regeneration and mechanical properties (force development and resistance to stretch) of mdx and transgenic mdx skeletal and diaphragm muscle. The utrophin levels required in muscle are significantly less than the normal endogenous utrophin levels seen in lung and kidney, and we provide evidence that the pathology depends on the amount of utrophin expression. These results also have important implications for DMD therapies in which utrophin replacement is achieved by delivery using exogenous vectors.

Animals↗
PubMed1998

The economic value of caring.

A heuristic method for monetizing effects of caring is presented. Practitioners' caring behaviors have economic value to health care organizations through effects on patient satisfaction, physiology, self-disclosure, and self-esteem, and subsequent use of medications, laboratory tests, and procedures. These effects are monetized as revenues generated, costs avoided, costs reduced, and externalities.

Caregivers↗
PubMed1998

Radioimmunoscintigraphy with In-111-labeled capromab pendetide predicts prostate cancer response to salvage radiotherapy after failed radical prostatectomy.

PURPOSE: We investigated the ability of In-111-capromab pendetide to separate patients who have failed radical prostatectomy into categories of those who would versus those who would not respond to salvage radiotherapy. METHODS: Prostate-specific antigen (PSA) levels in 32 men with prostate cancer who had failed radical prostatectomy and had undergone a whole-body In-111-capromab pendetide scan were followed-up for 13 months (median) after salvage radiotherapy to the pelvis. A logistic regression model was used to determine whether the scan findings, as well as other clinical variables, were associated with a durable complete response (DCR), a nondurable response (NDR), or no response (NR). RESULTS: Sixteen of 23 (70%) men with a normal scan outside the prostatic fossa achieved a DCR after salvage radiotherapy versus two of nine (22%) who had a positive scan outside the prostate fossa and pelvis (P = .0225, Fisher's exact test). Predicted probability (95% confidence interval [CI]) that a DCR would be obtained with a normal scan was 0.88 (0.55 to 0.98); for men with a positive scan limited to the prostatic fossa it was 0.62 (0.42 to 0.79); and for men with a positive scan outside the pelvis it was 0.27 (0.09 to 0.58). No other variables before radiotherapy showed a significant association with the DCR rate. CONCLUSION: Salvage radiotherapy is statistically more likely to lead to a durable complete PSA response in men with prostate cancer who have failed radical prostatectomy and have a negative In-111-capromab pendetide scan outside the pelvis as compared with those who have a positive scan.

Aged↗
PubMed1998

A new method of developing expert consensus practice guidelines.

To improve the quality of medical care while reducing costs, it is necessary to standardize best practice habits at the most crucial clinical decision points. Because many pertinent questions encountered in everyday practice are not well answered by the available research, expert consensus is a valuable bridge between clinical research and clinical practice. Previous methods of developing expert consensus have been limited by their relative lack of quantification, specificity, representativeness, and implementation. This article describes a new method of developing, documenting, and disseminating expert consensus guidelines that meets these concerns. This method has already been applied to four disorders in psychiatry and could be equally useful for other medical conditions. Leading clinical researchers studying a given disorder complete a survey soliciting their opinions on its most important disease management questions that are not covered well by definitive research. The survey response rates among the experts for the four different psychiatric disorders have each exceeded 85%. The views of the clinical researchers are validated by surveying separately a large group of practicing clinicians to ensure that the guideline recommendations are widely generalizable. All of the suggestions made in the guideline are derived from, and referenced to, the experts' survey responses using criteria that were established a priori for defining first-, second-, and third-line choices. Analysis of survey results suggests that this method of quantifying expert responses achieves a high level of reliability and reproducibility. This survey method is probably the best available means for standardizing practice for decisions points not well covered by research.

Bias↗
PubMed1997

The Rhizobium meliloti PII protein, which controls bacterial nitrogen metabolism, affects alfalfa nodule development.

Symbiotic nitrogen fixation involves the development of specialized organs called nodules within which plant photosynthates are exchanged for combined nitrogen of bacterial origin. To determine the importance of bacterial nitrogen metabolism in symbiosis, we have characterized a key regulator of this metabolism in Rhizobium meliloti, the uridylylatable P(II) protein encoded by glnB. We have constructed both a glnB null mutant and a point mutant making nonuridylylatable P(II). In free-living conditions, P(II) is required for expression of the ntrC-dependent gene glnII and for adenylylation of glutamine synthetase I. P(II) is also required for efficient infection of alfalfa but not for expression of nitrogenase. However alfalfa plants inoculated with either glnB mutant are nitrogen-starved in the absence of added combined nitrogen. We hypothesize that P(II) controls expression or activity of a bacteroid ammonium transporter required for a functional nitrogen-fixing symbiosis. Therefore, the P(II) protein affects both Rhizobium nitrogen metabolism and alfalfa nodule development.

Bacterial Proteins↗
PubMed1997

Consciousness in waking and dreaming: the roles of neuronal oscillation and neuromodulation in determining similarities and differences.

State-dependent aspects of consciousness are explored with particular attention to waking and dreaming. First, those phenomenological differences between waking and dreaming that have been established through subjective reports are reviewed. These differences are robustly expressed in most aspects of consciousness including perception, attention, memory, emotion, orientation, and thought. Next, the roles of high frequency neuronal oscillation and neuromodulation are explored in waking and rapid eye movement sleep, the stage of sleep with which the most intense dreaming is associated. The high frequency neuronal oscillations serve similar functions in the wake and rapid eye movement states sleep but neuromodulation is very different in the two states. The collective high frequency oscillatory activity gives coherence to spatially separate neurons but, because of the different neuromodulation, the binding of sensory input in the wake state is very different from the binding of internally perceived input during rapid eye movement sleep. An explanatory model is presented which states that neuromodulation, as well as input source and brain activation level differentiate states of the brain, while the self-organized collective neuronal oscillations unify consciousness via long range correlations.

Consciousness↗
PubMed1997

Expression of truncated utrophin leads to major functional improvements in dystrophin-deficient muscles of mice.

Dystrophin-deficient mice (mdx) expressing a truncated (trc) utrophin transgene show amelioration of the dystrophic phenotype. Here we report a multifunctional study demonstrating that trcutrophin expression leads to major improvements of the mechanical performance of muscle (that is, force development, mechanical resistance to forced lengthenings and maximal spontaneous activity) and of the maintenance of the intracellular calcium homeostasis. These are two essential functions of muscle fibers, known to be impaired in mdx mouse muscles and Duchenne muscular dystrophy (DMD) patients. Our results bring strong support to the hypothesis that muscle wasting in dystrophin-deficient DMD patients could be prevented by upregulation of utrophin.

Animals↗
PubMed1997

XDOM, a graphical tool to analyse domain arrangements in any set of protein sequences.

MOTIVATION: To extract the maximum possible information from a set of protein sequences, its modular organization must be known and clearly displayed. This is important both for structural and functional analysis. RESULTS: This paper presents an algorithm and a graphical interface called XDOM which performs a systematic analysis of the modular organization of any set of protein sequences. The algorithm is an automatic method to identify putative domains from sequence comparisons. The graphical tool displays the proteins as a set of linked boxes, corresponding to its domains. The method has been tested on a family of bacterial proteins and on whole genomes. It is currently applied to the complete SWISS-PROT database to build the PRODOM database. AVAILABILITY: XDOM is available free of charge by anonymous ftp:¿¿ftp://ftp.toulouse.inra.fr/pub/xdom¿ ¿. The ProDom database can be consulted at ¿¿http://protein.toulouse.inra.fr/prodom.html¿¿.

Algorithms↗
PubMed1997

Kaposi's sarcoma-associated herpesvirus and human herpesvirus 8 (KSHV/HHV8)-associated lymphoma of the bowel. Report of two cases in HIV-positive men with secondary effusion lymphomas.

This report describes two cases of Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8 (KSHV/HHV8)-associated lymphomas that primarily involved the large bowel and that secondarily caused malignant effusions. Involvement of the gastrointestinal tract is of interest because epidemiologic evidence suggests that KSHV/HHV-8 may be transmitted via the fecal-oral route, and KSHV/HHV8 DNA has been detected in rectal samples from HIV-positive patients. This report describes two HIV-positive men who developed primary KSHV/ HHV8-associated lymphomas of the bowel. Despite similar morphology and immunophenotype, these cases differ from most KSHV/HHV8-associated primary effusion lymphomas, which present with malignant effusions in the absence of a solid tumor mass. The spectrum of KSHV/HHV8-associated lymphomas is expanded to include a subset of primary bowel lymphomas in individuals infected with human immunodeficiency virus.

AIDS-Related Opportunistic Infections↗