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Biomedical subjects

M Julian

Publications and source records attributed to M Julian.

At least 19 recordsLinked to original sources
PubMed1997

Protein complexes containing gamma-tubulin are present in mammalian brain microtubule protein preparations.

The presence of gamma-tubulin in microtubule preparations, obtained by disassembly/ assembly cycles at 0degreesC/37degreesC from the brain of several mammals, is demonstrated by immunoblotting with specific antibodies directed against three distinct regions of the protein. In contrast gamma-tubulin was absent from pure tubulin obtained by chromatography on phosphocellulose, but was retained on the column with the other microtubule-associated proteins. A large part of the gamma-tubulin was present in cold stable material remaining after microtubule disassembly at OdegreesC and was partially solubilized using high salt, thus preventing its purification by the usual assembly/disassembly procedure used for alpha/beta-tubulin heterodimers. Brain gamma-tubulin was purified by affinity chromatography with gamma-tubulin antibodies raised against its carboxyl terminal region. Purified gamma-tubulin consisted of at least two polypeptides present in equal quantities and exhibiting a pI of 6.5 and 6.6, respectively. It was associated with the alpha/beta-tubulin heterodimer and with at least five other polypeptides of 75, 105, 130, 195, and 250 kDa. With the exception of the 250 kDa polypeptide, all of these proteins seem to be present in gamma-tubulin complexes isolated from Xenopus eggs. But, in contrast with Xenopus egg complexes, brain complexes exhibited a considerable heterogeneity of their apparent masses and composition in sucrose gradient centrifugation, in agreement with the absence of an homogeneous structure in electron microscopy. Despite this heterogeneity, gamma-tubulin complexes bind quantitatively to microtubule extremities. The possibility to further use mammalian brain gamma-tubulin and some of its associated proteins in biochemical and pharmacological experiments is of interest since brain microtubule protein preparations have been extensively used for studying both microtubule dynamics and the activity of microtubule poisons.

Animals↗
PubMed1996

Transgenic mice expressing the Sh ble bleomycin resistance gene are protected against bleomycin-induced pulmonary fibrosis.

Despite the high efficiency of bleomycin (BLM) as a chemotherapeutic agent against various carcinomas, the potentially lethal and chronic fibrotic response of the lung is a major dose-limiting side effect. Here, we explore the possibility of a direct inhibition of lung tissue injury by in vivo expression of the actinomycetes BLM resistance protein Sh ble. Transgenic mice expressing the Sh ble gene under the control of a composite viral promoter were produced after introduction of the transgene into D3 ES cells. The protein was detected at high level in lungs, spleen, and kidney. We then assessed its ability to modulate the BLM-induced fibrotic response in the transgenic mice in comparison with C57BL/6 and 129/Sv parental mice. Cumulative doses of 300, 400, or 500 mg/kg BLM were administered either by i.p. or s.c. repeated injections in the different strains. Transgenic mice were shown to be clearly less sensitive to BLM toxicity, as assessed by lung histology. The pulmonary hydroxyproline content in the treated transgenic mice was close to its baseline level, whereas it was up to 50% higher than the control level in C57BL/6 and 129/Sv parental mice. These observations are consistent with the hypothesis that a resistance gene specifically expressed in lungs may prevent the BLM-induced inflammation.

Acetyltransferases↗
PubMed1996

A single gamma-tubulin gene and mRNA, but two gamma-tubulin polypeptides differing by their binding to the spindle pole organizing centres.

Cells of eukaryotic organisms exhibit microtubules with various functions during the different developmental stages. The identification of multiple forms of alpha- and beta-tubulins had raised the question of their possible physiological roles. In the myxomycete Physarum polycephalum a complex polymorphism for alpha- and beta-tubulins has been correlated with a specific developmental expression pattern. Here, we have investigated the potential heterogeneity of gamma-tubulin in this organism. A single gene, with 3 introns and 4 exons, and a single mRNA coding for gamma-tubulin were detected. They coded for a polypeptide of 454 amino acids, with a predicted molecular mass of 50,674, which presented 64-76% identity with other gamma-tubulins. However, immunological studies identified two gamma-tubulin polypeptides, both present in the two developmental stages of the organism, uninucleate amoebae and multinucleate plasmodia. The two gamma-tubulins, called gamma s- and gamma f-tubulin for slow and fast electrophoretic mobility, exhibited apparent molecular masses of 52,000 and 50,000, respectively. They were recognized by two antibodies (R70 and JH46) raised against two distinct conserved sequences of gamma-tubulins. They were present both in the preparations of amoebal centrosomes possessing two centrioles and in the preparations of plasmodial nuclear metaphases devoid of structurally distinct polar structures. These two gamma-tubulins exhibited different sedimentation properties as shown by ultracentrifugation and sedimentation in sucrose gradients. Moreover, gamma s-tubulin was tightly bound to microtubule organizing centers (MTOCs) while gamma f-tubulin was loosely associated with these structures. This first demonstration of the presence of two gamma-tubulins with distinct properties in the same MTOC suggests a more complex physiological role than previously assumed.

Amino Acid Sequence↗
PubMed1996

An atypical aortic atherosclerotic lesion in cynomolgus monkeys during hypercholesterolemia: a protection by smooth muscle cells against advanced lesions?

This study focuses on the fortuitous discovery of an atypical atherosclerotic lesion in four of 49 male adult cynomolgus monkeys (macacus fascicularis) which were maintained for a long time at a high level of hypercholesterolemia, and in seven of 19 female cynomolgus monkeys examined from the second to the 24th week of hypercholesterolemic diet: this lesion was in formation or already mature during this period of diet. This atypical lesion was formed by a collagen and elastic network surrounding synthetic smooth muscle cells without fibrofatty or fibrous plaques. Lipids were occasionally seen in the inner intima. The lesion appeared early (from the third week of diet). Once established, its morphology did not change. It became more extensive, but was not complicated by lipid overload in spite of prolonged, permanent hypercholesterolemia. This response to hypercholesterolemia is interesting because the activity of the smooth muscle cells differs from that observed in the classic lesion: they intervene earlier, their replication is very marked and rapid, their elastin secretion is greater and remains constant over time, and their phagocytic properties are reduced. This experimental study examines the installation and the maintenance of this lesion and raises the problem of its origin.

Animals↗
PubMed1994

Recruitment of antigenic gamma-tubulin during mitosis in animal cells: presence of gamma-tubulin in the mitotic spindle.

It has been claimed repeatedly that gamma-tubulin is exclusively localized at the spindle poles in mitotic animal cells, where it plays a role in microtubule nucleation. In addition to this localization, we have observed a gamma-tubulin-specific staining of the mitotic spindle in several animal cells (human, kangaroo rat, mouse, Chinese hamster, Xenopus and Drosophila) using five polyclonal antibodies raised against unique gamma-tubulin sequences and four different fixation protocols. In HeLa and PtK2 cells, gamma-tubulin was detected in the mitotic spindle from late prometaphase to telophase. In contrast, in other cell types, it was detected in metaphase only. In all cases we failed to detect gamma-tubulin in the short aster microtubules at the spindle poles. Electron microscopic observation revealed that at least part of the gamma-tubulin localized on the surface of spindle microtubules with a preferential distribution along kinetochore microtubules. In HeLa cells, the amount of antigenic gamma-tubulin was fairly constant in the spindle poles during mitosis from prometaphase to telophase. In contrast, gamma-tubulin appeared in the mitotic spindles in prometaphase. The amount of gamma-tubulin decreased in telophase, where it relocalized in the interzone. In metaphase cells about 15-25% of the total fluorescence was localized at the spindle poles, while 75-85% of the fluorescence was distributed over the rest of the spindle. These results suggest that the localization and timing of gamma-tubulin during the cell cycle is highly regulated and that is physiological role could be more complex and diverse than initially assumed.

Animals↗
PubMed1993

gamma-Tubulin participates in the formation of the midbody during cytokinesis in mammalian cells.

Animal cells undergoing cytokinesis form an inter-cellular bridge containing two bundles of microtubules interdigitated at their plus ends, which constitute the midbody. Polyclonal antibodies raised against three specific amino acid sequences of gamma-tubulin (EEFATEGGDRKDV, NIIQGEADPTDVHKSL and EYHAATRPDYISWGTQEQ) specifically stained the centrosome in interphase, the spindle poles in all stages of mitosis, and the extremities of the midbody in mammalian cells (Potorous, human, Chinese hamster, mouse). This staining was prevented by the corresponding peptides, by Xenopus gamma-tubulin, but was not modified by purified alpha beta-tubulin heterodimer. An identical staining was obtained with affinity-purified antibodies against the carboxyl-terminal amino acid sequence of human gamma-tubulin. No gamma-tubulin could be detected in the interzone during anaphase and early telophase. Material containing gamma-tubulin first appeared in the two daughter cells on each side of the division plane in late telophase, and accumulated transiently at the minus ends of the two microtubule bundles constituting the midbody for one hour after metaphase. Micro-injection of gamma-tubulin antibodies into anaphase cells prevented the subsequent formation of the microtubule bundles between the two daughter cells. In contrast with previous views, these observations suggest that the microtubules constituting the midbody may be nucleated on special microtubule organizing centres, active during late telophase only, and assembled on each side of the dividing plane between the daughter cells.

Amino Acid Sequence↗
PubMed1992

[Non-atherosclerotic aorta in Cynomolgus after a hypercholesterolemic regimen].

The authors present a study on atherosclerotic and non atherosclerotic lesions of aortas of Cynomolgus (Macaca Fascicularis) on high fat diet (HFD) (6-12-24 months), after regression and after resumption. At 6 months 2 aortic responses are seen: an edema, deep and superficial clumps of foam cells, few synthetic smooth muscle cells (SSMC) few collagenic fibers--an edema, few superficial foam cells, many SSMC, secreting collagen and elastin. At 12-24 months, after regression and resumption, two aortic lesions are observed: a pronounced atheroma (47 animals) and no atheroma (14 animals). In this case, in the inner part of the aortic wall there are a fibrosis and an elastogenesis, SSMC and just some superficial lipids deposits. These aortic responses of SSMC are certainly the consequence of the environment (the diet) but also the possible consequence of the genetic determinism of SSMC since some animals only present this early, constant fibro-elastic response during this experimental follow up even though all the animals have been subjected to the same lipidic stress.

Animals↗
PubMed1989

Self-expanding endovascular stent in experimental atherosclerosis. Work in progress.

To investigate the physiologic and histologic responses induced by the self-expanding endovascular prosthesis, rabbits subjected to a combination of high-cholesterol diet and intravascular trauma underwent stent implantation. The results were compared with those obtained with the placement of stents in the healthy aortas of rabbits. Stents in healthy aortic tissue led to stent intimalization, previously reported in canine studies. For stents placed in animals subjected to a high-cholesterol diet but no intimal trauma, it was found that the stent was not the source of atherogenesis. Stents placed in atheromatous plaque were found to radially compress plaque with time and to stimulate for formation of a fibrotic crust. The results suggest that the self-expanding stent protects against progressive encroachment of the vessel lumen by atherosclerotic tissue.

Animals↗
PubMed1989

[Experimental atherogenesis: early wall changes in the cynomolgus monkey].

The early parietal changes in atherogenesis are characterized by: Increase of endothelial permeability with proteoglycans and L.D.L. storage. Lysis of internal elastic lamellae. Penetration into sub-endothelial space of monocytes macrophages and transformation into foam cells. Parietal fibrosis and proliferating smooth muscle cells play a role in the extension of lipid deposit.

Animals↗
PubMed1988

Bicarbonate and fast-twitch muscle: evidence for a major role in pH regulation.

Internal pH (pHi) was analyzed in rat extensor digitorum longus (Edl) muscle at 30 degrees C with single-barrel liquid ion-selective electrodes. Average pHi in 284 cells was 7.197 +/- 0.006. Increases in CO2 from nominally 0 to 5% produced an acidification from which recovery took place. In different groups of cells, recovery from the 5% CO2 acidification was significantly inhibited by 100 microM 4,4' diisothiocyanatostilbene 2,2' disulfonic acid (DIDS), Cl removal, Na removal and 2 mM amiloride. Prepulsing with 20 mM NH4 in the presence of CO2/HCO3 typically reduced pHi to only about neutral, whereas 50 mM reduced pHi to 6.7-6.8. In the nominal absence of CO2/HCO3, 20 mM NH4 reduced pHi to about 6.7 from which recovery took place at about 58% of the rate seen in different cells in the presence of CO2/HCO3. In the presence of CO2/HCO3, cells prepulsed with 50 mM NH4 had fully recovered to an average pHi of 7.22 +/- 0.04 about 90 min after removal of NH4. However, 90 min after removal of 20 mM NH4 in the absence of CO2/HCO3, average pHi was significantly less (7.05 +/- 0.03). Intrinsic buffering capacity (beta i) was obtained during pulses of CO2, acetic acid or after an NH4 pulse. beta i was significantly reduced in the absence of HCO3, Cl or Na and HCO3. The data provide significant support for an important role of HCO3 in the control of pHi in fast-twitch muscle.

Animals↗
PubMed1988

The elastic tissue of the skin. A comparison of spontaneous and actinic (solar) aging.

In order to separate the changes of actinic damage from those of simple aging, we studied the elastic fibers in low and high sun-exposed skins of normal subjects at different ages. Low sun-exposed skin shows chronologic aging lesions only. These begin at age 30 with a disappearance of oxytalan fibers and with some abnormalities in the reticular and deep dermis; at age 40, aging changes are established: no oxytalan fibers, marked abnormalities, and lysis of elaunic and elastic fibers. In high sun-exposed skin, age-related lesions also occur but are associated with more or less precocious elastotic degeneration in reticular and deep dermis. Both types of aging fibers are revealed by the antielastin antibody HB 8, disappear with elastase, but resist collagenase. Actinic elastosis clearly originates from elastin. The two types of change differ in electron microscopic appearance: with spontaneous aging, elastic fibers are disintegrated (loose and porous fibers); in actinic damage, elastotic fibers are thicker and have accentuated microfibril dense masses. The age-associated lesions could be due to the activity of protease of fibroblastic origin whereas the elastotic degeneration is probably due to the actinic stimulation of fibroblasts.

Adult↗
PubMed1988

Fibroblasts in dermal tissue repair. Electron microscopic and immunohistochemical study.

The cellular dynamics of dermal regeneration were studied in nonsutured cutaneous wounds of female pigs and monkeys with electron microscopy and immunohistochemistry to demonstrate the origin and the development of fibroblasts forming granulation tissue. The results indicate that fibroblasts do not originate from histiocytes but from resting fibroblasts in the wound margins. These resting fibroblasts first become undifferentiated mesenchymal cells termed "X" cells. The "X" cells then multiply, migrate, and invade the wound defect in approximately 3 days, transforming into highly active fibroblasts. The active fibroblasts are endowed with the capacity of further transformation to fibroclasts and myofibroblasts. The latter two cell populations then effectively cause remodeling of newly formed tissue and contraction of wound margins.

Animals↗
PubMed1987

[Repair of the connective tissue in a non-sutured skin wound].

During the healing of a second intention wound, granulation tissue is built up during the inflammatory and detersive phase which commences in the wound edges as soon as the loss of substance is created. Granulation tissue becomes scar tissue via connective and vascular proliferation and epidermization takes place concurrently. The origin of the fibroblasts composing the granulation tissue is debated: monocytes or fibroblasts from the wound edges? Ultrastructural and immunohistochemical data from studies of experimental wounds in the pig and the monkey make it possible to determine their origin and follow their progress. These cells originate from the fibroblasts of the wound edges and become undifferentiated cells which multiply and migrate to reach the loss of substance. There they become activated fibroblasts and contribute to repairing the loss of substance by secreting fibronectin and type I and type III collagen. As differentiated fibroblasts and myofibroblasts, they remodel and contract scar tissue.

Acute-Phase Reaction↗
PubMed1986

Coronary atheroma in the cynomolgus monkey: predictive value of serum and cutaneous lipoprotein measurement.

Hyperlipaemia was induced by a high fat diet in 11 cynomolgus monkeys. Morphological study of coronary arteries was carried out in 5 coronary samples from these 11 monkeys. The degree of arterial involvement was compared with the serum and cutaneous lipoprotein levels. These experimental data confirm that cutaneous apoprotein B measurement is the best marker for evaluation of coronary atheroma.

Animals↗
PubMed1986

A kinase able to phosphorylate exogenous protein synthesis initiation factor eIF-2 alpha is present in lysates of mengovirus-infected L cells.

Infection of mouse L929 cells by mengovirus resulted in the expression of a kinase activity that selectively phosphorylated the small, 38,000-molecular-weight subunit of eucaryotic initiation factor 2 and histone H2. This kinase activity was independent of host cell RNA synthesis and was located in the postribosomal supernatant (S-100 fraction) early after infection (up to 3 h). At later times after infection (5 h), kinase activity was also associated with the polysome fraction. The kinase present in the S-100 fraction bound strongly to DEAE-cellulose, its peak activity eluting at 0.5 M KCl. Kinase activity was independent of the presence of exogenous double-stranded RNA, and KCl at concentrations greater than 0.1 M inhibited eucaryotic initiation factor 2 phosphorylation. The 67,000-molecular-weight phosphoprotein activated in interferon-treated cells by double-stranded RNA was not detected by standard phosphorylation assays in lysates from mengovirus-infected cells. Labeling of this protein in vivo during 5 h of infection was also not detected. The DEAE-cellulose-purified mengovirus kinase inhibited protein synthesis in reticulocyte lysates, and the inhibition was not reversible by high concentrations of poly(I).poly(C).

Animals↗