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Biomedical subjects

M Osman

Publications and source records attributed to M Osman.

At least 19 recordsLinked to original sources
PubMed1992

A homolog of Escherichia coli RecA protein in plastids of higher plants.

Studies of chloroplast DNA variations, and several direct experimental observations, indicate the existence of recombination ability in algal and higher plant plastids. However, no studies have been done of the biochemical pathways involved. Using a part of a cyanobacterial recA gene as a probe in Southern blots, we have found homologous sequences in total DNA from Pisum sativum and Arabidopsis thaliana and in a cDNA library from Arabidopsis. A cDNA was cloned and sequenced, and its predicted amino acid sequence is 60.7% identical to that of the cyanobacterial RecA protein. This finding is consistent with our other results showing both DNA strand transfer activity and the existence of a protein of the predicted molecular mass crossreactive with antibodies to Escherichia coli RecA in the stroma of pea chloroplasts.

Amino Acid Sequence↗
PubMed1991

Bioenergetic consequences of glucoamylase production in carbon-limited chemostat cultures of Aspergillus niger.

Aspergillus niger has been grown in glucose- and maltose-limited continuous cultures to determine the bioenergetic consequences of the production of the extracellular enzyme glucoamylase. Growth yields (g biomass per mol substrate) were high, indicating that growth was very efficient and protein production for biomass was not exceedingly energy consuming. It has been found that the energy costs for the production of this extracellular enzyme is very high. Depending on the efficiency of energy conservation the glucoamylase protein yield on ATP is between 1.3 and 2.6 g protein per mol ATP, which is equal or less than 10% of the theoretical maximum of 25.5. These high energy costs most probably have to be invested in the process of excretion. A comparison between an industrial over-producing strain and the wild type Aspergillus niger showed that this over-producing strain most probably is a regulatory mutant. Two regions of specific growth rates could be determined (one at specific growth rates lower and one at specific growth rates higher than 0.1 h-1), which are characterized by differences in mycelium morphology and a significant deviation from linearity in the linear equation for substrate utilization. Analysis of the region of specific growth rates higher than 0.1 h-1 yielded maintenance requirements of virtual zero. It has been concluded that for a good analysis of the growth behaviour of filamentour fungi the linear equation for substrate utilization is not suitable, since it contains no term for the process of differentiation.

Adenosine Triphosphate↗
PubMed1991

Sweetness-dependent facilitation of sucrose drinking by raclopride is unrelated to calorie content.

Previous studies have reported that dopamine receptor antagonists increase the intake of solid or liquid diets containing high concentrations of sucrose. In Experiment 1, different groups of rats were trained in two-bottle tests (sweet solution vs. water), using three concentrations of either sucrose (0.7, 7 or 34%) or saccharin (0.02, 0.2 or 0.8%). Both sweeteners showed an inverted-U-shaped concentration-intake function. Raclopride increased intake of 34% sucrose, but not of 0.8% saccharin. In Experiment 2, raclopride had similar effects in three-bottle tests (all 3 concentrations available concurrently). However, whereas 34% was the most preferred sucrose solution, 0.2% saccharin was preferred to 0.8%. Thus, 0.8% saccharin differs from 34% sucrose in two ways, being not only noncaloric, but also aversive. In Experiment 3, 34% sucrose was rendered aversive by the addition of 0.08% quinine. Intake of this cocktail was not increased by raclopride. These results suggest that the difference between sucrose and saccharin in the effects of raclopride is related to the aversive properties of a concentrated solution of saccharin, rather than to its lack of calories.

Animals↗
PubMed1991

Early changes in lung tissue hyaluronan (hyaluronic acid) and hyaluronidase in bleomycin-induced alveolitis in hamsters.

Intratracheal instillation of bleomycin in hamsters initiates a series of events that mimic human interstitial pulmonary fibrosis. Because glycosaminoglycans and particularly hyaluronan (hyaluronic acid, HA), may play an important role in the extracellular matrix response to early injury and subsequent fibrosis, this study was undertaken to define the early time course of changes in HA and hyaluronidase. Hamsters were given either 1 unit bleomycin sulfate in 0.2 ml saline or 0.2 ml saline (control), and randomly selected animals from both groups were killed at Days 3, 5, 6, 7, 9, and 17. Glycosaminoglycan fractions prepared from lung tissue of individual animals were analyzed for HA. The maximal HA content was reached 6 days after instillation of bleomycin and was 14.6-fold the normal value. The weight of injured lungs was 2.3-fold the control value. Thus, the increase in HA content was 30-fold. By Day 7 the HA content had dropped sharply. It then declined gradually to approximately double control values at Day 17. The specific activity of lysosomal hyaluronidase was the same in bleomycin-treated lungs and control lungs. Total units of the enzyme were increased in injured lungs, even at the time of maximal HA content, indicating active turnover of HA. The maximal HA content occurs prior to the rise in collagen and elastin biosynthesis. This observation in addition to the magnitude of the increase and its abrupt decline suggest that HA may be an important initiating factor for pathologic changes in lung extracellular matrix components.

Animals↗
PubMed1990

Molecular analysis of the Drosophila nuclear lamin gene.

A complete nucleotide sequence of a 4.2-kb genomic fragment containing the Drosophila lamin gene and flanking sequences is presented. Primer extension experiments and sequence analysis revealed that transcription starts from a single promoter. The lamin maternal 2.8-kb transcript and the 3.0-kb zygotic transcript are generated from two alternative polyadenylation sites. The gene contains four exons. The first intron is 7 bp upstream of the first AUG site. The two other introns are located within the alpha-helical rod domain of the protein: one in coil 1B in the 42-amino-acid domain that is absent in vertebrate cytoplasmic intermediate filament proteins and the other in coil 2 at a position different from intron positions within the vertebrate intermediate filament genes. Together with the sequence homology analysis, the data suggest either that the lamin gene was the ancestral gene of intermediate filament genes or that the lamin gene diverged from other intermediate filament genes early in evolution.

Amino Acid Sequence↗
PubMed1979

Bacteriological criteria for feeding raw breast-milk to babies on neonatal units.

Aerobic cultures of 207 samples of drip breast-milk from seventy mothers in hospital showed that 6 (3%) were sterile and 170 (82%) contained only the commensal organisms coagulase-negative staphylococci and Streptococcus viridans. 25 (15%) grew potential pathogens--Staphylococcus aureus in 13 (6%); enterobacteria in 15 (7%); and group-B streptococci in 3 (2%). It is proposed that milk with commensals in any numbers may be considered for use unheated but not milk containing any potential pathogens.

Aerobiosis↗
PubMed1979

[Role of dental pulp in the histogenesis of the enamel organ].

The histological study of in vitro cultured associations between dental pulps and outer dental epithelium showed that the predontoblasts initiated the histogenesis of the enamel organ and particularly the differentiation of the inner dental epithelium.

Animals↗
PubMed1979

3H-glucosamine electron microscope autoradiography after isolated labeling of the enamel organ or the dental papilla followed by reassociated toothgerm culture.

Electron microscope autoradiography was performed after isolated labeling with 3H-glucosamine of the enamel organ or the dental papilla of Swiss mice followed by reassociated toothgerm culture for 9.30 h and 19 h. After these two time intervals in case of an enamel organ labeling, numerous silver grains were observed in the intercellular spaces of the stellate reticulum indicating a concentrating and storing role of the latter. After dental papilla labeling, an almost complete absence of radioactivity was noted at 19 h. suggesting that 3H-glucosamine is not stored by the dental papilla. A clear labeling of the basement membrane area and of the adjacent aperiodic filamentous material found on the pulpal side was only observed after enamel organ labeling with 3H-glucosamine, suggesting an epithelial origin of the glycosaminoglycans found in these structures.

Animals↗
PubMed1978

Basement membrane reconstitution and cytodifferentiation of odontoblasts in isochronal and heterochronal reassociations of enamel organs and pulps.

The restoration of the basement membrane and the terminal differentiation of odontoblasts were studied in iso- and heterochronal reassociations between dental mesenchyme and enamel organs. It was suggested that the cytodifferentiation of odontoblasts was triggered by the basement membrane secreted by the enamel organ of a specific stage.

Animals↗
PubMed1978

Action of 5-bromodeoxyuridine on tooth germs "in vitro." I. - Effects on cytodifferentiation.

Sixteen or eighteen day old mouse embryonic first lower molars were treated with 5-bromodeoxyuridine (BrdU) in vitro. --In 16-day old tooth germs cytodifferentiation of both odontoblasts and ameloblasts was inhibited. This inhibition was reversible. --In 18-day old tooth germs, the odontoblasts localized at the top of the principal cusps (post-mitotic cells) differentiated normally and secreted predentin. In these conditions ameloblasts localized in front of functional odontoblasts differentiated, although they were able to incorporate BrdU. --In others experiments, control and BrdU-treated tooth germs were dissociated into enamel organs and pulps. Cultivated associations between either control or BrdU treated pulps with either control or BrdU treated enamel organs were analyzed. It appeared that the primary effect of BrdU might result in its incorporation in the preameloblasts which were no longer able to interact normally with the preodontoblasts.

Ameloblasts↗
PubMed1978

Action of 5-bromodeoxyuridine on tooth germs "in vitro". II. - Effects on collagen synthesis.

The first lower molar tooth germs removed from 16-day-old mouse embryos were cultured for 2 days on a standard medium and then for 24 hours on the same medium containing BrdU (treated tooth germs) or not (controls). We attempted to study the effects of 5-Bromodeoxyuridine on the type I and type III collagen synthesis 24 (stage 16 + 4) and 72 (stage 16 + 6) hours after the incorporation of this thymidine analogue. At stage 16 + 4, type I and type III collagen were synthesized both in control and BrdU-treated tooth germs. However BrdU induced quantitative modifications in the type I collagen synthesis which might be explained by modifications in the turnover of this type of collagen. At stage 16 + 6, the BrdU treatment resulted in the inhibition of the terminal differentiation of odontoblasts. Consequently, the normal amplification of collagen type I synthesis could not occur. However, both control and BrdU-treated tooth germs synthesized type I and type III collagen. Quantitatively, the synthesis of type III collagen was slightly affected by BrdU treatment.

Animals↗
PubMed1978

Effect of light quality on the photoinduction of carotenoid synthesis in Verticillim agaricinum.

The action spectrum of photoinduction of carotenoid biosynthesis in Verticillium agaricinum has a high peak in the near-UV region with very small peaks in the blue, yellow and red regions. This suggests that neither a flavoprotein nor a carotenoid could be the photoreceptor, but a new unknown pigment system. Sporulation however is not photoregulated and is unaffected by light in the near-UV region. So, mycochrome cannot be implicated in the sporulation of this fungus. Further, sporulation and carotenogenesis must be under separate regulatory control in this organism, but not necessarily so in other organisms.

Carotenoids↗
PubMed1978

Studies on the near-UV effect on carotenogenesis in Verticillium agaricinum.

Carotenoids identified in Verticillium agaricinum under near-UV were beta-, zeta-, and gamma-carotenes, neurosporene, torulene, neurosporaxanthin and one of its esters. Evidence supports the proposal that gamma-carotene, and not torulene, is the immediate precursor of neurosporaxanthin. It is also suggested that phytochrome may be involved in the high irradiance reactions (HIR) causing carotenoid synthesis in this fungus although there is no knowledge of how this is effected. Spores grown under near-UV conditions varied in size and shape from those grown in the dark. A new pigment (390, 420 nm) is also proposed as the photoreceptor for carotenogenesis in V. agaricinum.

Carotenoids↗
PubMed1977

Reduced uterine response to PGF2alpha under oral contraceptives.

The effect of prostaglandin F2alpha (PGF2alpha) on the nonpregnant human uterus was evaluated in 35 patients. The compound was administered both by intra-uterine and intravenous routes. Two groups of volunteers were studied;fifteen cases who were under oral contraceptives and twenty women with normal ovulatory cycles. The uterus under the influence of oral contraceptives showed a reduced response to local and systemic administration of PGF2alpha at all phases of the menstrual cycle. The implications of these findings in certain physiological and pathological conditions related to reproduction are discussed.

Contraceptives, Oral↗