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Biomedical subjects

J Lavergne

Publications and source records attributed to J Lavergne.

At least 37 records · Page 2Linked to original sources
PubMed1990

[Importance of masseter insertion surface in different mammal groups].

The objective of this study is to compare the strength of the masseter muscle in various mammals by calculating the ratio between insertion area of the masseter and total mandibular surface. We will also determine the factors capable of modifying the insertion area of this masticatory muscle.

Anatomy, Comparative↗
PubMed1989

Mitochondrial responses to intracellular pulses of photosynthetic oxygen.

When submitting anaerobic algal cells to a series of saturating flashes, transient absorption changes of mitochondrial origin were detected, showing the characteristic flash-number dependence of photosynthetic oxygen evolution. The faster kinetic event is the oxidation of heme a(3) of the cytochrome-c oxidase, which reaches a maximum at [unk]3.5 ms before again being reduced within 20 ms. The oxidation of cytochrome c involves an initial submillisecond lag, and its half-time is [unk]3.3 ms. Another component, probably indicating oxidation of heme a, is seen around 607 nm, with a kinetic behavior similar to that of cytochrome c. The fast time scale of these reactions excludes long-range diffusion and supports a direct intracellular trapping of O(2). It is estimated that, under appropriate conditions, the yield of this process is >30%. The linearity of these responses with respect to the amplitude of the oxygen pulse implies that a single turnover of the cytochrome oxidase is involved. These results suggest that the intracellular oxygen pathway may be of physiological importance in green algae. On the other hand, this technique seems promising both as an alternative to polarographic detection of photosynthetic oxygen and as a means of studying the cytochrome oxidase response in vivo to single-turnover oxygen pulses.

Journal Article↗
PubMed1987

Hand movement asymmetry during speech: no effect of speaking topic.

Right-handed subjects were videotaped as they spoke on verbal, spatial and neutral topics and the frequencies of their spontaneous hand movements were analyzed. Although subjects made more free movement gestures during the spatial topics than during the other topics, there was a consistent level of right hand preference for free movements across topics. Self-touching movements showed no hand preference in any topic. The results suggest that free movements are generated by a left-hemisphere motor control system which exerts consistently greater influence over the right than the left hand regardless of the source of processing preceding activation of this system.

Adolescent↗
PubMed1982

Morphogenetic classification of malocclusion as a basis for growth prediction and treatment planning.

This study has shown that the different groups, defined as morphogenetically homogeneous show homogeneity in several aspects. The individuals constituting a given group exhibit a peculiar pattern of craniofacial morphology, they grow alike and they seem to respond alike to a given type of treatment. Within the general frame defined by the group the occlusion seems to play an important role in the future development of the face. In this way the classification presented here is the first in the procedure leading to growth prediction and treatment planning. This classification also permits an analysis of the rotational pattern of the face and consequently allows one to pinpoint the 'failure' in facial growth more accurately. This should allow treatment to be more reliably matched to the growth pattern of the individual.

Adolescent↗
PubMed1979

[Teratogenic effect of dicrotophos on the embryonic chick tibia ; histological and cytological studies (author's transl)].

The organophosphorus insecticide dicrotophos injected at 4 days of incubation into the yolk sac of hen'eggs determined achondroplasia with tibiotarsus deformities. These malformations were studied at different stages of embryogenesis using different histological methods. After injecting 0,5 mg per egg, the size of the hindlimbs was decreased by 50% and the growth was much less (from 20 to 30% of the normal) When giving the toxic et the level of 1 mg per egg. Light and electron microscopical observations showed a reduction or a lack of the proliferative zones and a decrease in the secretory activity of the chondrocytes which may possibly be related to the growth retardation. Using adaptated techniques for mineralized tissue examination and scanning microscope, a disorganized and an asymmetrical deposition of the periosteal osseous lamellae was observed.

Animals↗
PubMed1978

Formation and development of photosynthetic units in repigmenting Rhodopseudomonas sphaeroides wild type and "Phofil" mutant strain.

The formation of the photosynthetic apparatus in the wild type Rhodopseudomonas sphaeroides and in the "Phofil" mutant was investigated by analyzing absorption and fluorescence parameters and the kinetics of fluorescence induction. Repigmentation was induced by transfer of bleached cells to semi-aerobic culture conditions. 1. In the "Phofil" mutant, functional photosynthetic units appear at pigment cellular contents which depend on the physiological state of the inoculum. The unadapted mutant can reach the functional units stage at a cellular pigment level 20 times lower than that of the wild type, although the size and composition of the units are identical in both strains. This rules out the hypothesis of photosynthetic units forming by random integration of pigments into the membrane. Moreover, the fact that units are separate at this stage (as shown by the exponential shape of fluorescence induction kinetics) suggests that the units' formation proceeds from discrete predetermined membrane sites. 2. In repigmentng wild type cells, the multistep assembly of bacteriochlorophyll complexes appears correlated to their organization in photosynthetic units as follows: (i) During a first stage, B-875 is mostly synthesized, while the efficiency of transfer increases, suggesting that the pigments are initially interpersed at comparatively large average distances from each other in the bleached membrane. (ii) After 1.5 h of repigmentation, the transfer and trapping efficiencies reach a maximum. The units (26 B-875 + 11 B-850 per center) are still separate, as shown by exponential fluorescence kinetics. (iii) The increase in the units' size then essentially proceeds through B-850 incorporation. Energy transfer between units occurs at a comparatively late stage, i.e., 5 h repigmentation.

Bacteriochlorophylls↗
PubMed1977

Identification of S2 as the sensitive state to alkaline photoinactivation of photosystem II in chloroplasts.

1. Chloroplasts have been preilluminated by a sequence of n short saturating flashes immediately before alkalinization to pH 9.3, and brought back 2 min later to pH 7.8. The assay of Photosystem II activity through dichlorophenolindophenol photoreduction, oxygen evolution, fluorescence induction, shows that part of the centers is inactivated and that this part depends on the number of preilluminating flashes (maximum inhibition after one flash) in a way which suggests identification of state S2 as the target for alkaline inactivation. 2. As shown by Reimer and Trebst ((1975) Biochem. Physiol. Pflanz. 168, 225-232) the inactivation necessitates the presence of gramicidin, which shows that the sensitive site is on the internal side of the thylakoid membrane. 3. The electron flow through inactivated Photosystem II is restored by artificial donor addition (diphenylcarbazide or hydroxylamine); this suggests that the water-splitting enzyme itself is blocked. The inactivation is accompanied by a solubilization of bound Mn2+ and by the occurence of EPR Signal II "fast". 4. Glutaraldehyde fixation before the treatment does not prevent the inactivation which thus does not seem to involve a protein structural change.

2,6-Dichloroindophenol↗