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Biomedical subjects

C Samuel

Publications and source records attributed to C Samuel.

10 recordsLinked to original sources
PubMed2000

Justification of statistical overlap theory in programmed temperature gas chromatography: thermodynamic origin of random distribution of retention times.

A specific distribution of compounds' standard-state changes of enthalpy and entropy between mobile and stationary phases in programmed temperature gas chromatography (PTGC) is shown to produce the Poisson distribution of retention times often postulated in statistical-overlap theory (SOT). A three-part model is proposed, in which the enthalpy change is Poisson distributed, the average entropy change depends on the enthalpy change, and the actual entropy change varies in a uniformly random manner about the average entropy change. To test the model, the entropy and enthalpy changes of 350 aliphatic and aromatic hydrocarbons in petroleum were calculated with commercial GC software. These changes are shown to follow the three-part model. The model then was used with Monte Carlo methods to mimic the enthalpy and entropy changes. The substitution of the mimicked enthalpy and entropy changes into an equation for the retention temperature in PTGC is shown to produce a Poisson distribution of retention times that is statistically significant. This finding establishes a scientific link between the thermodynamics governing retention in PTGC and the superficially ad hoc assumption of the Poisson retention time distribution in SOT. Similar thermodynamic distributions are found for flavors and fragrances and for tetrachlorodibenzo-p-dioxins and furans, which follow SOT based on the Poisson distribution, but not for polychloronaphthalenes, which do not follow that SOT.

Journal Article↗
PubMed1999

Production of recombinant human type I procollagen homotrimer in the mammary gland of transgenic mice.

The large scale production of recombinant collagen for use in biomaterials requires an efficient expression system capable of processing a large (> 400 Kd) multisubunit protein requiring post-translational modifications. To investigate whether the mammary gland of transgenic animals fulfills these requirements, transgenic mice were generated containing the alpha S1-casein mammary gland-specific promoter operatively linked to 37 Kb of the human alpha 1(I) procollagen structural gene and 3' flanking region. The frequency of transgenic lines established was 12%. High levels of soluble triple helical homotrimeric [(alpha 1)3] type I procollagen were detected (up to 8 mg/ml) exclusively in the milk of six out of 9 lines of lactating transgenic mice. The transgene-derived human procollagen chains underwent efficient assembly into a triple helical structure. Although proline or lysine hydroxylation has never been described for any milk protein, procollagen was detected with these post-translational modifications. The procollagen was stable in milk; minimal degradation was observed. These results show that the mammary gland is capable of expressing a large procollagen gene construct, efficiently assembling the individual polypeptide chains into a stable triple helix, and secreting the intact molecule into the milk.

Amino Acids↗
PubMed1998

Dysprosody after severe closed head injury: an acoustic analysis.

OBJECTIVES: Neurological speech disorders (dysarthria and dysprosody) are known to be frequent sequelae after severe closed head injury. These disorders may dramatically alter communicative intent and accentuate social isolation. The aim was to provide an instrumental evaluation for prosodic production in a group of patients with severe closed head injury and to determine the correlations between prosodic production and neurobehavioural status. METHODS: Fifteen patients, at the subacute stage after severe closed head injury, were studied and compared with 11 controls, matched for age, sex, and duration of education. Each subject was required to read aloud a French sentence "Je m'en vais samedi matin" (I am leaving saturday morning) under six different prosodic intonations (neutral, affirmation, interrogation, happiness, sadness, anger). The recorded sentences were analysed using a sound signal analysis software (Signalyse) allowing the measurement of signal intensity and fundamental frequency. Statistical analyses were carried out using repeated measures analysis of variance (ANOVA). RESULTS: Patients with closed head injury were significantly less able than controls to modulate speech output (pitch and intensity) according to prosodic context. This deficit was particularly pronounced for the intonation feature of anger, question, and statement. No consistent correlations could be found between prosodic production and cognitive or behavioural data. CONCLUSIONS: Acoustic analysis of pitch and intensity may show impairments of prosodic production after severe closed head injury, which may be useful in rehabilitation planning. This impairment does not seem to reflect the eventual cognitive and behavioural deficits of the patients, but rather a specific disorder of modulation of speech output.

Adolescent↗
PubMed1996

Late cognitive and behavioural improvement following treatment of disabling orthopaedic complications of a severe closed head injury.

Interactions of physical, emotional, cognitive and behavioural impairments after severe closed head injury (CHI) remain poorly understood. A 47-year-old man was referred to our department 13 months after a severe CHI. He demonstrated severe left hemiplegia and disabling orthopaedic complications (left hip infectious arthritis, after surgical treatment for heterotopic ossification). His hip was blocked and extremely painful. He was totally dependent for daily-life activities (Functional Independence Measure (FIM) score = 18). Moreover he exhibited severe cognitive and behavioural troubles, which had been stable for many months beforehand, e.g. complete disorientation for time and place, major memory disorders, agitation, anxiety, depression, irritability, disinhibition, aggressiveness and lack of initiative. Pain disappeared within a few weeks after treatment. Progressively, functional improvement occurred (sitting position, transfers, walking between parallel bars). The FIM score increased to 63. Aggressiveness, irritability and agitation disappeared. Surprisingly, neuropsychological assessment demonstrated parallel improvement of cognitive functions, especially in regard to orientation, and to a lesser degree attention and memory. Such an observation should encourage use of active treatment of physical disabilities, even in patients presenting with an apparently poor cognitive prognosis at a late stage of severe CHI.

Cognition Disorders↗
PubMed1987

Affective disorder in the neurological patient.

An index sample of neurological patients diagnosed as clinically depressed (83) was compared with a "major depression" sample (43) and a "neurological sample" (44) who were free from psychiatric disorder. There was no difference in global Hamilton Scores between the index and the major depression sample. The latter, however, more often exhibited family and personal history of psychiatric illness, early awakening, guilt, suicidal ideas, shorter index episodes of depression, and better response to treatment. The three samples were followed up for a period of up to 5 years. The index sample did worse on follow-up than did the depressed and the neurological samples. The disease profiles of both the index and neurological samples were similar, but there were more cases of epilepsy in the former. The index sample responded badly to conventional antidepressant treatment. It is concluded that the presence of chronic affective disorder in the neurological patient has an adverse effect on prognosis.

Age Factors↗
PubMed1985

Psychiatric morbidity following total and partial thyroidectomy.

Thirty subjects were screened for psychiatric morbidity approximately 7 years after they had undergone a thyroid operation. Thirteen were identified as "cases" by the General Health Questionnaire. Total and partial thyroidectomy subjects were compared. The total thyroidectomy patients identified as "cases" showed lower values of plasma calcium and higher values of inorganic phosphate than the partial thyroidectomy "cases", but the difference failed to reach statistical significance. No clinical or biochemical differences were found between cases and non-cases, irrespective of the type of operation.

Adult↗
PubMed1981

Macronuclear chromatin organization in Paramecium primaurelia.

Chromatin organization and transcriptional activity in the macronucleus of the ciliate Paramecium primaurelia have been studied by electron microscopic examination of spread chromatin preparations. Under spreading conditions which inhibit the activity of endogenous nucleases and proteases, various morphologically distinct types of chromatin are seen: (1) Largely condensed chromatin in the form of 30-40 nm supranucleosomal globules which aggregate to form knobbly 40-60 nm fibres and unravel into 12 nm nucleosomal filaments; (2) In rapidly growing cells, extended chromatin arranged groups of 4-8 adjacent nucleofilaments, each bearing numerous and very densely packed lateral fibrils. These fibrils are 20 nm thick, have a smooth outline and extend to lengths of up to 3 micron. Such transcripts are grouped in units along the chromatin axis and are apparently organized in register in adjacent filaments; (3) In starved cells, extended nucleofilaments bearing only occasional RNP fibrils. These various morphological characteristics are discussed in terms of macronuclear transcriptional activity and the polyploid nature of macronuclei.

Animals↗