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Biomedical subjects

B Meyer

Publications and source records attributed to B Meyer.

At least 343 records · Page 19Linked to original sources
PubMed1984

A polychromatic flash photolysis apparatus (PFPA).

A wide variety of biologically relevant chemical intermediates have been identified and characterised by their spectral properties. When rapid kinetics, i.e. rapid changes in these spectral properties are studied, the equipment designed for these studies (flash photolysis-, T-jump apparatus) usually allows only the registration of intensity changes of the monitoring light beam at one particular wavelength. Quite frequently, however, particularly in biological systems, the reactions of interest are too complex to be fully understood using single wavelength techniques. We have therefore designed and built a flash photolysis apparatus which permits the simultaneous recording of absorbance changes at 32 wavelengths, freely selectable between 300 and 1000 nm, as well as changes in fluorescence, luminescence, birefringence and light scattering. The apparatus, which we have called Polychromatic Flash Photolysis Apparatus (PFPA), acquires up to 8000 difference spectra per second with an amplitude resolution of better than 0.0001 absorbance unit. Data acquisition and activation of an actinic xenon flash unit occurs under computer control. The same computer is responsible for data storage, handling and graphic display. This communication describes the PFPA, its performance, and, as a demonstration of its potential usefulness, its application to the measurement of the light driven photocycle of bacterial rhodopsin, the proton pumping protein of Halobacterium halobium.

Photolysis↗
PubMed1984

Treatment of vaginal endometriosis with danazol.

Six infertile patients with vaginal endometriosis were treated with danazol at 600 mg daily for 6 months. Three patients had previously undergone surgery for pelvic endometriosis. After 4 months of danazol treatment there was a clear reduction in the size and number of the lesions in all the patients. At the end of the treatment 4 patients still had small lesions, which showed histological evidence of regressive changes. Four women became pregnant within 6 months of the termination of therapy.

Adult↗
PubMed1984

Surgical procedure and implanted material description.

The 12 intracochlear electrode placement is greatly facilitated by using our electrode-bearer which is introduced through the round window via a posterior tympanotomy approach. However, partial or complete ossification of the cochlea may oblige us to use again our first technique of one-by-one electrode placement, using Silastic pieces through 12 cochlear fenestrations. The microconnectors and the receptor are also described.

Cochlea↗
PubMed1984

Presence of alpha-2-macroglobulin in normal but not in malignant cervical epithelium.

alpha-2-Macroglobulin (alpha 2M) was demonstrated in normal and mildly dysplastic cervical epithelium using immunohistochemical methods. In contrast, staining for alpha 2M diminished gradually with advancing epithelial dysplasia and was totally negative in truly neoplastic lesions. No in vitro synthesis could be detected in cultured ectocervical cells or in a corresponding malignant cell line (HeLa). However, alpha 2M was taken up from added human serum by cultured normal ectocervical cells, whereas HeLa cells remained negative also under these conditions. These and previous results suggest that normal cells may have the capacity to synthesize or endocytose alpha 2M, thus possibly regulating their pericellular proteolysis, while these functions may be defective in malignantly transformed cells.

Cervix Uteri↗
PubMed1984

Topical treatment of flat vaginal condyloma with human leukocyte interferon.

Human leukocyte interferon cream was evaluated in a double blind placebo-controlled trial in 13 patients with widespread vaginal flat condylomatous dysplasia. Patients applied 12 million units of interferon vaginal cream daily into vagina during four two-week treatment courses separated by one-week intervals. Five of eight patients treated with interferon showed clear remissions in colposcopy. Cytologic examinations, however, revealed cells typical of condyloma in all cases. Two responding patients relapsed one and two months after the treatment. Among five patients using placebo, the lesions remained unchanged in three patients and progressed in two. Interferon treatment did not alter the microbiologic or cytologic picture of Papanicolaou smears, but lymphocytic infiltrations in the stroma next to condylomas were seen in histologic samples. No overt side effects were observed during interferon treatment.

Adult↗
PubMed1984

Amadori- and N-nitroso-Amadori compounds and their pyrolysis products. Chemical, analytical and biological aspects.

N-(1-Deoxy-D-fructos-1-yl)-L-amino acids (fructose amino acids), Amadori compounds, are formed by reaction of D-glucose and L-amino acids and Amadori rearrangement. They are detected in heat-processed natural products and various foodstuffs and are key products of the Maillard-Browning reaction. N-Nitroso-N-(1-deoxy-D-fructos-1-yl)-L-amino acids (N-NO-fructose amino acids), N-NO-Amadori compounds, are formed in high yields by reacting fructose amino acids with sodium nitrite in acidic aqueous solution. They constitute a new class of non-volatile, bis-beta-oxidized nitrosamine derivatives with unknown biological (mutagenic and/or carcinogenic) activity. N-NO-Fructose amino acids may be formed in nitrite-containing Maillard systems (e.g., cured-meat products, tobacco) or in the human stomach after ingestion of food containing fructose amino acids and nitrite in food or saliva. Thirteen fructose amino acids and 13 N-NO-fructose amino acids (-gly, -ala, -val, -leu, -ileu, -ser, -thr, -met, -asp, -pheala, -tyr, -his, -trp) were prepared and investigated by high-resolution 1H-nuclear magnetic resonance (NMR) and 13C-NMR spectroscopy. The percentage amounts of the sugar ring forms (beta-pyranose, beta-furanose, alpha-furanose and alpha-pyranose) of these compounds in D2O mutarotation equilibrium were determined by 13C-NMR spectroscopy, together with the amounts (%) of E/Z isomers in the case of N-NO-compounds. The nitrosation products of D-fru-L-tyr, D-fru-L-his and D-fru-L-trp were isolated and identified by spectroscopic methods (NMR, infra-red). The N-NO-fructose amino acids can be separated by reversed-phase, ion-pairing, high-performance liquid chromatography. In some case the E/Z isomers are separated.

Amino Acids↗
PubMed1984

Prognostic evaluation of the multichannel cochlear implant.

Preoperative appreciation of the future clinical results of the multichannel cochlear implant is important to assess in the case of pre- or post-lingual total deafness, in order to improve the patients selection. The psychological status of the future implanted is one of the main concerns because the post-operative reeducation efficacity depends on the patient's motivation. The Round Window electrical stimulation test supplies us with important and measurable data (electrical threshold level, tone decay test). The age of the patient, the age and the etiology of the deafness, the vestibular status and the cochlear tomodensitometry only offer non-decisive informations. The patient's socialisation level is a considerable factor. But per-operative observations are sometimes and surprisingly determinant (electrode impedances, ossified cochlea). Moreover immediate post-operative electrical and psychophysic data must also be considered.

Auditory Perception↗
PubMed1984

Results of the round window electrical stimulation in 460 cases of total deafness.

In order to avoid false and quantitatively unprecise responses the stimulating electrode must be directly placed on the round window membrane. That necessitates a transmeatal approach removing the eardrum, which is commonly achieved under local anesthesia. The positive response is subjectively easy to identify; it may be objectively registered by means of brain stem evoked responses; this registration is indispensable in case of children who need general anesthesia. This positive response signifies that some cochlear nerve fibers are still present, and therefore that the rehabilitation of the cochlear implant is possible. Among the 460 totally deaf, stimulated patients, more than 93% of them presented a positive response. The threshold level voltage value represents a statistically significant representation of the functional value of the electrode nerve interface. The features of the tone decay tests, which may be also subjectively or objectively performed, present important data which may be used to predict the clinical results that can be obtained by the cochlear implant.

Adolescent↗
PubMed1984

Clinical results of the French multichannel cochlear implant.

Clinical assessment and results are described in 66 patients (among them 20 were less than 20 years old). Voice changes may be objectively observed on sonograms. Phonetic discrimination depends on the electrical and nervous status of the implanted deaf cochlea. Discrimination of words and sentences with reference list, but without lipreading, is commonly obtained. Discrimination of unknown words is more difficult and varies from one patient to the other. Discrimination with lipreading progress elicited by the device depends on the pre-operative status and the own possibilities of each patient. Psychoaffective improvement is evident in every case, especially in 3 cases of autistic deaf-mute children. We shall try to summarize the efficacity of the French 12-channel cochlear implant regarding the clinical results we obtained in 66 patients who have been implanted between October 1976 and September 1983. Among them, 39 suffered from pre-lingual deafness and 27 from post-lingual deafness.

Adolescent↗
PubMed1984

Implant material tolerance.

After surgical and antibiotic destruction of guinea pig cochleas non specific lesions appear which seem more due to this destruction than to the electrode implantation or chronic stimulation. Moreover, despite these lesions, the electrical threshold level value necessary to elicit brain stem evoked responses in these implanted animals does not vary in time. The electrical chronic stimulation of the newborn deafened guinea pigs cochlea prevents the cochlear nucleus atrophy observed in the non stimulated animals. In man the implanted material tolerance is perfect provided this material is covered by a Silastic or teflon sheet and is located far from the skin incision. Degradation of isolating material occurred only in case of chronic movements. For this reason device and electrodes must be placed above and behind the ear. The waterproofness of the implanted receptor is indispensable to avoid physiological liquid penetration inside the electronic device. High level voltage stimulation may involve bubble formation responsible for temporary system failure; this drawback is suppressed by enlarging the electrode tip surface allowing low level stimulation. The threshold level and the frequency discrimination of the implanted electrodes did not change for more than 6 years. Post-operative infection occurred especially in case of pre-operative chronic otitis; it may be due also to the large use of "Histoacryl". However, these infections, which never affected the threshold level voltage of the implanted electrodes, are no longer encountered since we use "Tissucol", exclude the middle ear closing the Eustachian tube, and employ our electrode bearer.

Animals↗
PubMed1984

Sound signal processing.

In the CHORIMAC-12, the French device, the whole speech information despite its redundancy is transmitted to the few cochlear nerve fibers that are still present. Only loud speech intensities between 40 db and 100 db are introduced in a filter battery which gives out the frequency information in 12 channels including the 100-6000 Hz. This 60 db intensity scale is transmitted in a compression rate of about 6 db. The time sampling is 3 msec. A 12 electrode bearer or 12 separate electrodes (in case of ossified cochlea) transmit the electrical information. The electrical stimulus is a square wave: its frequency is equal or inferior to 300 Hz; its voltage may vary between 2.5 and 6.5 volts; its duration may vary between 0 and 200 mu sec. The performances of the system is demonstrated by means of a system of computerized psychophysic tests and speech intelligibility tests.

Cochlear Implants↗
PubMed1983

[Bronchiolitis obliterans: technics of exploration and diagnosis].

Bronchiolitis obliterans is an anatomo-clinical entity which may, in young pediatric patients, follow severe viral infections, especially due to measles virus and adenoviruses. After a transient remission, the disease progresses to chronic respiratory failure with dyspneic paroxysms. Diagnosis is based on different investigations which confirm the absence of proximal bronchiolar obstruction and the presence of bronchiolar obliteration. Deficient pulmonary perfusion due to ventilatory defects are demonstrated by pulmonary scintigraphy and even better by digital subtraction pulmonary angiography. Obliteration of non-cartilaginous bronchioli by granulation tissue produces bronchiolar destruction and explains the permenence of alterations. Dissimilarity of the responses of children to acute respiratory viral infection remains unexplained. The degree of the viral load and of the initial immune deficiency as well as the persistence of the virus within the pulmonary tissue probably account for the chronic pulmonary damage.

Adenovirus Infections, Human↗
PubMed1983

[Treatment of total deafness. Indications for and results of the multi-electrode cochlear implant].

Most cases of total deafness are due to destruction of Corti's organ leaving some of the auditory nerve fibres untouched. When these fibres are electrically stimulated the patient may perceive sounds the pitch of which depends upon the location of the stimulated nerve-endings along the cochlea. An intracochlear electronic device with 12 electrodes implanted in different areas and driven from outside by a portable radiofrequency emitter provides the patient with new hearing and some speech intelligibility. After several months' training words and sentences can be recognized without having recourse to lip reading. Performances depend upon a variety of factors, many of which can be determined prior to implantation. The long-term results obtained in 54 totally deaf patients are reported.

Cochlear Implants↗