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Biomedical subjects

R Michel

Publications and source records attributed to R Michel.

At least 91 records · Page 5Linked to original sources
PubMed1987

Ultrastructure of the amoebo-flagellate Protonaegleria westphali.

Investigation of the ultrastructure of Protonaegleria westphali has been carried out by means of scanning electron microscopy (SEM) and transmission electronmicroscopy (TEM). SEM investigation demonstrated much enlarged trophozoites, flagellates and cysts corresponding to those under light microscopical observation. In situ fixation of moving trophozoites revealed attachment to the substratum by many uroidal and lateral filopodia. The typical flagellate stage has four flagella inserted two by two at the anterior pole of the cell. The smooth wall of cysts had prominent pores sealed by a mucous plug. Apart from their greater size, trophozoites and cysts resemble those of the genus Naegleria. Mitochondria are not as elongated as in the case of Naegleria; rather, they are round. The cyst is surrounded by a thick, layered endocyst (0.2-0.5 micron) and a delicate ecotcyst loosely apposed to the endocyst. Both walls join at the region of the prominent pores, forming a characteristically thick collar. This, together with the pore structure (up to 1.0 micron in diameter) places the amoeba in group I of N. gruberi, according to Pussard and Pons (1979). The flagellate state usually has four flagella which are anchored firmly by a prominent flagellar apparatus or mastigont at the anterior pole of the cell, comparable to that of the genus Tetramitus. The flagella show a typical 9 + 2 arrangement of microtubules (MT) and are surrounded by a sheath which is continuous with the cell membrane. Main elements of the mastigont could be demonstrated as typical kinetosomes of 0.75 micron length. Each is closely associated with the cross-striated rhizoplast located perpendicular to it.(ABSTRACT TRUNCATED AT 250 WORDS)

Amoeba↗
PubMed1987

Effect of parental malnutrition on enzyme content of rat pancreas.

The aim of this study was to assess in rat pups the influence of protein diets ingested by their mothers during gestation and lactation on the enzyme content of the pancreas of the offspring. Rat pups born of either well-nourished mothers or of mothers fed a diet moderately restricted in protein (9% casein w/w) were studied. After weaning, the pups were fed on one of three diets: a well-balanced diet, a 5% casein diet (protein restricted), or a well-balanced diet of a similar caloric value as the protein-restricted diet (pair-fed rat pups). The pups were sacrificed after intervals of one to 25 weeks after weaning. The results showed that the enzyme content of the pancreas increased progressively with time in pups born of malnourished mothers, particularly in pups fed the protein-restricted diet. This suggests prolonged maturation of the pancreas. Pups fed the 5% casein diet had a decreased amylase content per milligram of DNA but not of other enzymes. Malnutrition in the mother increased the ratio of enzymes to DNA and the total pancreatic enzyme content at different times after weaning, indicating that maternal malnutrition had a prolonged effect on the pancreatic enzyme content of the pups' pancreas. This mechanism could play a role in the pathogenesis of tropical chronic calcific pancreatitis in man and explain some of the geographic differences in the incidence of the disease.

Amylases↗
PubMed1987

Influence of thyroid status on body weight gain, food intake and serum lipid levels in genetically obese Zucker rats.

Body weight gain, food intake and serum concentrations of total lipids, cholesterol, triglycerides, phospholipids and free fatty acids were measured in genetically obese and lean female Zucker rats after surgical thyroidectomy and treatment with 3,5,3'-triiodothyronine (T3) (3 micrograms/100 g body wt per day) for 4 wk. There were large differences in the major serum lipids between the control obese and lean rats. Obese rats were characterized by high levels of the various categories of lipids, especially of triglycerides. Thyroidectomized rats had higher serum concentrations of total lipids and cholesterol than controls in both obese and lean rats. The serum concentration of triglycerides was higher in the thyroidectomized lean rats than in lean controls but lower in their thyroidectomized obese littermates than in obese controls. The T3 treatment resulted in a marked reduction in serum total lipid, cholesterol, triglyceride and phospholipid levels in both thyroidectomized and control obese rats. The same treatment given to thyroidectomized and control lean rats also produced a lower concentration in serum total lipid, cholesterol and triglyceride levels but had no significant effect on serum phospholipid levels. The serum concentration of free fatty acid was not significantly affected by T3 administration in either obese or lean rats. Thyroidectomy induced a lower body weight gain in both obese and lean rats. The T3 treatment restored the body weight gain in the thyroidectomized lean rats but not in the thyroidectomized obese rats, although the food intake was increased by T3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Increased EMG of rat plantaris during locomotion following surgical removal of its synergists.

A chronic EMG electrode implant system was used to determine recruitment patterns of rat plantaris, during treadmill locomotion, before and after surgical removal of its synergists, gastrocnemius and soleus. Bilateral synergist removal resulted in increased plantaris muscle weight and myofibrillar protein content of 59% and 44%, respectively, by 30 days following surgery. Evidence of increased plantaris EMG during treadmill walking (increases in amplitude and integral of EMG bursts to ca. 200% of pre-excision values) occurred at 15-30 days and decreased to non-significant levels at 35 days postsurgery. No corresponding alterations occurred in sham-operated controls. At 25 and 30 days, EMG of plantaris during locomotion was still submaximal, since burst amplitudes were 53% to 67% of those recorded during a dynamic grid-climbing task. The magnitude and time course of changes in EMG of overloaded plantaris during a standardized locomotor task, which reflect increased recruitment and rate of discharge of motor units, are consistent with the chronology of morphological and metabolic events previously described for this model.

Animals↗
PubMed1986

Comparative effects of 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT) and 3,5-diiodo-3'-isopropylthyroacetic acid (IpTA2) on body weight gain and lipid metabolism in genetically obese Zucker rats.

3,5-Dimethyl-3'-isopropyl-L-thyronine (DIMIT) and 3,5-diiodo-3'-isopropylthyroacetic acid (IpTA2), two thyroid hormone analogs, have been tested in genetically obese Zucker rats and their lean littermates, in comparison with thyroxine (T4) and triiodothyronine (T3) for their thyromimetic activities on body weight gain and lipid levels in serum and liver. The compounds were administered for 9 weeks by orogastric tube to 6- to 8-week-old animals. While body weight gain remained practically unchanged in the lean rats, it decreased significantly in the obese individuals, especially with IpTA2. The serum lipid concentrations were also decreased in the obese rats in comparison with their lean littermates, especially with DIMIT. The connection observed between the structure of DIMIT and IpTA2 on one hand and their effects on the other is in good agreement with previous studies. Our results confirm that the iodine substituents are not necessary for thyromimetic activity and demonstrate that the isopropyl substituent in 3' plays an important role in the serum lipid-lowering effect of the thyroid hormone analogs tested.

Animals↗
PubMed1986

Nonparallel secretion of enzymes by the rabbit pancreas.

Since nonparallel secretion of enzymes by the exocrine pancreas has been demonstrated with several experimental models, we were interested in verifying a recent claim that enzyme secretion remained strictly proportional (parallel) upon stimulation of the in vivo rabbit pancreas. Pancreatic juice was collected by extraduodenal cannulation of the pancreatic duct, in two different protocols. In the first protocol the administration of pentobarbital induces a mild anesthesia. Under this condition, amylase and chymotrypsin secretion remained parallel after cholecystokinin stimulation. In a second protocol, a deeper and constant anesthesia was attained with Fluothane resulting in a lower basal protein output than in the first protocol. Pancreatic secretion was collected under intravenous secretin perfusion (4.5 clinical units X kg-1 X h-1). After stabilization and basal collection periods, pancreatic secretion was stimulated with an i.v. bolus injection of either cholecystokinin (2 Ivy dog units/kg), caerulein (0.1 micrograms/kg), or carbachol (6 micrograms/kg). Upon stimulation of the pancreas, protein output increased an average of 30-fold and there was a concomitant 20-25% decrease in the ratio of the specific activities of amylase to chymotrypsin which resulted from a greater increase in the specific activity of chymotrypsin in pancreatic juice after stimulation of secretion. Thus, under appropriate conditions, nonparallel secretion of enzymes by the exocrine pancreas can be demonstrated in yet another experimental model. Furthermore, the proportion of amylase and chymotrypsin activities in pancreatic juice are once more shown to be dependent, up to a threshold, upon the rate of protein output by this exocrine gland.

Amylases↗
PubMed1985

Ultrastructural changes of Trichomonas vaginalis prior and after cryopreservation.

Fine structural changes of Trichomonas vaginalis are described prior and after the freezing process in liquid nitrogen. Dimethyl sulfoxide (DMSO) used as the cryoprotectant caused distinct alterations of the cytoplasm when trichomonads were equilibrated with 5% DMSO under various experimental conditions. Changes were bubble-like protrusions, fissuration and/or vacuolation of the cytoplasm, doubling and removal or/and rupture of the cell membrane. Apart from these findings cryopreservation caused marked alterations on the hydrogenosomes, such as condensation and flocculence of the usually homogeneous contents; in addition numerous hydrogenosomes fused while loosing membrane at the site of fusion. However, several parasites revealed normal hydrogenosomes after the freezing process. It is assumed that these organisms survived freezing and thawing as demonstrated by successful cultivation of recovered trichomonads.

Animals↗
PubMed1985

[Effect of hypothyroidism on mitochondrial energy metabolism and nuclear synthesis of RNA in the liver of Cynomolgus monkeys].

The effects of hypothyroidism and of replacement therapy with T4 or T3 were studied on the enzymatic activities of liver subcellular fractions isolated from Cynomolgus monkeys. Animals were sacrificed 20 days after thyroidectomy. In mitochondria, thyroidectomy decreased significantly the respiratory chain activity (succinate cytochrome c-reductase), the transfer of cytosolic reducing equivalents (glycerol-3-phosphate dehydrogenase) and the phosphorylating capacity (oligomycin-sensitive ATPase and state 3 respiratory rate). The activity of nucleolar and nucleoplasmic RNA polymerases dropped by about 50% in hypothyroid monkeys. In T4 (2.5 micrograms/kg/d) or T3 (1 microgram/kg/d) treated thyroidectomized animals, the iodothyronine concentrations and the activity of mitochondria and nuclei enzymes were halfway between normal and hypothyroid values. Thus, the mitochondrial effects of thyroidectomy in monkey are, as in rat, at least partly secondary to a decrease in nucleocytoplasmic protein synthesis.

Animals↗
PubMed1984

[Special pathologico-anatomical aspects of AIDS--acquired immune deficiency syndrome].

Data from morphologic and immunologic follow-up studies are presented of ten patients with AIDS. The sequence of morphologic lesions in lymph nodes proceeds from an initial marked hyperplasia of T- and B-zones (follicular hyperplasia with plasmacytosis and diffuse paracortical hyperplasia) to paracortical atrophy with reactive reticulo-histiocytic hyperplasia and to a late irregular B-cell hyperplasia with effacement of lymph node structure. These changes are accompanied immunocytological by a polyclonal increase in B-Lymphocytes while T-helper cells (TH) and T-suppressor cells (TS) initially exhibit a normal 2:1 ratio, an inversion of the TH/TS ratio is observed in advanced stages. Inversion occurs at the time when paracortical atrophy becomes evident in lymph nodes. Pathogenetically, persistent virus infections and a self-sustaining disturbance of immune regulatory mechanisms are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Previous exercise training influences functional sprouting of rat hindlimb motoneurons in response to partial denervation.

Rats had soleus and plantaris muscles of one hindlimb partially denervated by cutting L4 radicular nerve, and functional sprouting of intact L5 motoneurons was estimated physiologically 10 days later. Animals that had undergone daily exercise training (10 weeks) prior to partial denervation showed evidence of enhanced sprouting in plantaris, and reduced sprouting in soleus. Exercise training, known to cause motoneuron changes, enhances short-term sprouting of fast muscle motoneurons. Differences between plantaris and soleus responses probably reflect differing sprouting stimuli, or degree of prior overload.

Animals↗
PubMed1984

Trace element burdening of human tissues due to the corrosion of hip-joint prostheses made of cobalt-chromium alloys.

Using instrumental neutron activation analysis, the concentrations of 18 elements were studied in human articular capsule and fascia lata before and after application of total endoprostheses of the hip joint made of cobalt-chromium alloys. Tissues from the vicinity of the implant showed extreme burdening by corrosion products (Co, Cr, Ni), as well as by Zr, Hf, and Ba from the bone cements. Tissues more distant from the implants exhibited lower, but still significant burdening. Moreover, some essential trace elements not contained in the implant materials were changed in the tissues after implantation. In order to clarify the dissolution of alloy constituents in biological media, the passivation of cobalt-chromium alloy was investigated by tracer techniques using Ringer's solution as a simple model of the body fluids. The passivation process lasted for more than 1 month and was accompanied by a selective dissolution of the alloys constituents in the order Ni greater than Co approximately Fe greater than Mo greater than Cr. A comparison of the tissue analyses with the corrosion experiments demonstrates that the distribution patterns of the corrosion products in the tissues are influenced by both the corrosion process and the biochemical properties of the corrosion products.

Adult↗
PubMed1984

Effects of procaine on the oxidative phosphorylation of brain mitochondria from senescent rats.

Senescence affects cerebral metabolic functions. Various drugs have been tested to counteract the effects of aging on the brain. In this paper, we studied the influence of treatment using procaine, 1 mg per 100 g body weight, injected over a period of 3 days, to both young and old rats, on the phosphorylative oxidation properties of cerebral mitochondria. Respiratory activity decreased significantly in the brain of old rats. This reduction of oxygen consumption measured in the presence of glutamate, reached 31% in state 4, 25% in state 3 and, in the presence of succinate, 23% in state 4 without significant changes in state 3. The injection of procaine into young rats induced a significant increase of oxygen consumption rate with both glutamate and succinate as substrates. The same treatment administered to old rats was followed by a rise in respiratory activity, with values close to those observed in young control rats. Although the mechanism of action of procaine is not yet clear, there is some evidence that it interacts with membrane phospholipid sites. Therefore, it may be concluded that procaine facilitates oxygen transport towards the mitochondrial matrix by modifying the membrane structure in both old and young rats, although, in the latter case, this increase is not intended to improve the energetic properties of the mitochondrion.

Aging↗
PubMed1984

Comparative effects of thyroid hormone analogs on the activities of brain and liver mitochondria and nuclei in thyroidectomized rats.

Several thyroid hormone analogs have been tested for thyromimetic activity on rat brain and liver subcellular organelles. The compounds were administered immediately after thyroidectomy to 90 g male S-D rats for 10 days, by daily s.c. injection. In cerebral cortex and liver we measured the activities of mitochondrial succinate cytochrome c reductase and alpha-GPD, and nuclear RNA polymerase I. Brain mitochondrial enzymes were unchanged in thyroidectomized (Tx) and in Tx-treated rats, whereas the activities of these enzymes in liver mitochondria were partially restored by the treatments. RNA polymerase I activity in brain and liver dropped significantly 10 days after thyroidectomy and daily injection of thyroid hormones or analogs maintained the nuclear activity at a normal level. Correlation between the structure of thyroid hormone analogs and their subcellular effects is in good agreement with previous binding and in vivo studies. Enzyme activities stimulated by T3 were lowered by replacing the T3 side-chain by an acetic acid group or by substituting the bridged oxygen atom by atom by CO. In contrast, the activity was enhanced by substituting iodine with a 3' isopropyl group. Although less active than iodine, the 3,5-dimethyl substituents may be introduced without a complete loss of nuclear activity.

Animals↗
PubMed1984

A comparative study of 14 strains of Naegleria australiensis demonstrates the existence of a highly virulent subspecies: N. australiensis italica n. spp.

Fourteen strains of Naegleria australiensis, including the type strain, were compared for virulence for mice, maximum growth temperature, lectin agglutination, isoenzyme pattern, and total protein banding pattern. Their relation to other species of Naegleria also was compared by immunoelectrophoretic analysis. Strains with high virulence, comparable to that of N. fowleri, were found to be different in concanavalin A agglutination as well as with regard to zymograms and total protein patterns. Although serologically different from N. fowleri and reacting with N. australiensis antiserum in the fluorescent antibody test, these high-virulence strains differed in number of immunoelectrophoretic precipitin bands. Because of these results, the high-virulence strains are considered to be a subspecies of N. australiensis. The low-virulence strains showed minor differences from the type strain. Thus, N. australiensis does not appear to be as homogenous a species as N. fowleri. Pathogenic N. australiensis also seems to be more widespread than previously thought.

Agglutination↗
PubMed1984

[Acanthamoebae, Naegleria and other free-living Amoebae in cooling and rinsing water of dental treatment units].

215 water samples were taken from 49 dental treatment units and investigated for the existence of free-living amoebae. In all water-carrying systems of the dental treatment units it was possible to verify the incidence of one or more amoeba species. In 8.2 per cent of the units Naegleria species was found and in 12.2 per cent Acanthamoeba species was present. Seven Naegleria and six Acanthamoeba strains (2 A. castellanii and 4 A. polyphaga) were isolated. From samples originating from 12 dental treatment units (DTU) another 42 amoeba strains were isolated which consisted of 14 different species within 9 classes. Among them Vannella mira (in 19 per cent of samples) and Hartmannella vermiformis (10.6 per cent) were found to be the most frequent species, followed by H. cantabrigensis (9.5 per cent), V. platypodia, Platyamoeba stenopodia and V. simplex (7.1 per cent each). In 10 per cent of samples monotrichous and bitrichous flagellates such as the Bodo species were found, whereas two samples contained ova, larvae and adult free-living nematodes. Among the isolated Naegleria strains no thermophilic strain was present. Consequently they belong to the N. gruberi complex. Among the Acanthamoebae five of the six strains were thermophilic. All strains were investigated for pathogenic properties by means of the mice inoculation test. Two strains proved pathogenic - it was possible to isolate them from the brain and lung of dead mice. Another two strains proved to have invasive properties because they were isolated from the brain of infected animals; however, they did not give rise to disease or death of the respective animals. Supplementary microbiological tests demonstrated the existence of bacteria and fungi in 84 per cent of dental treatment units. Pseudomonas spec. were detected in 75% of dental units, Serratia marcescens in 2% and fungi in nearly 3%. 58.3% of all water samples contained total germ counts of more than 100/ml.

Amebiasis↗