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Biomedical subjects

M Jacob

Publications and source records attributed to M Jacob.

At least 253 records · Page 14Linked to original sources
PubMed1977

Complexity of the structure of particles containing heterogeneous nuclear RNA as demonstrated by ribonuclease treatment.

Brain ribonucleoprotein particles containing heterogeneous nuclear RNA (hnRNA) and a large number of polypeptides ranging from 23000 to 150000 molecular weight were treated with pancreatic and T1 ribonucleases at low (0.1 or 0.5 microng plus 5 or 25 units/ml), high (2 microng plus 100 units/ml) and very high (20 microng plus 1000 units/ml) concentrations. At low enzyme concentration, a large fraction of the particle material accumulated at 35-45 S. The accumulation was more marked for proteins in the 30000-38000 molecular weight range. Heterogeneous complexes containing a large spectrum of proteins with a characteristic distribution were disclosed between 60 and 200 S. At high ribonuclease concentration the total quantity of proteins at 35-45 S decreased, but the proteins of 30000-38000 molecular weight predominated. Heterogeneous complexes were also present. Finally at very high enzyme concentration, the particles were almost entirely hydrolyzed. Only a small amount of heterogeneous complexes subsisted at 30-190 S. The RNA content of the remaining ribonucleoprotein complexes as well as its size decreased upon ribonuclease treatment as shown by CsCl density determination and electrophoretic analysis. The results suggested that the stability of the complexes depended upon protein-protein as well as RNA-protein interactions. They also showed that sequences up to 200-300 nucleotides were protected by proteins against ribonuclease. The results were compatible with the existence of at least 3 constituents in the particles. The previously defined monoparticle population accumulating at 35-45 S was heterogeneous in respect to ribonuclease sensitivity and protein composition. The 30000-38000 molecular weight proteins accumulating at low ribonuclease and predominating afterwards were assumed to belong to monoparticles alpha. Monoparticles beta contained a larger range of proteins more easily released by the enzymes. The heterogeneous complexes were a third constituent whose relationship with the monoparticles war not established yet. A large fraction of the particle phosphoproteins was associated to these complexes. On the basis of our experiments in vitro it is assumed that monoparticle alpha can be preferentially isolated from the nuclei under conditions where endogeneous ribonuclease is high and (or) not inhibited. This might explain why, in certain cases, only one or a few proteins were described in nuclear particles instead of the complete set present in the native particles.

Animals↗
PubMed1977

Experimental analysis of the origin of the wing musculature in avian embryos.

Interspecific grafts of somites, as well as parts of the somatic plate mesoderm, have been made between quail and chick embryos (stages 12--14 H. H.) at the level of the prospective wing bud in order to examine the relationship between somites and wing bud myogenesis. The stability of the natural quail nuclear labelling makes it possible to follow the developmental fate of grafted mesodermal cells in the host embryo. Embryos examined after subsequent incubation periods of 3--7 days show the following distribution of somatic and somitic cells within the wing bud: as soon as the three zones of different cell density within the mesoderm can be distinguished, cells of somitic origin are limited to the prospective myogenic area which is made up of mixed population of somatic and somitic cells, whereas the prospective chondrogenic area as well as the subectodermal zone only consists of cells originated from the somatic plate mesoderm. After further incubation, single muscle blastema are present which were also seen to be a mixture of somatic and somitic cells. The cells of muscular bundles are of somitic origin, while the muscle connective tissue cells are derived from the somatic plate mesoderm. After grafting into the coelomic cavity or on the chorio-allantoic membrane, fragments of the somatic plate mesoderm previously isolated from quail embryos (stage 14 H.H.) at the level of the prospective wing bud exhibit well developed skeletal elements, but fail to differentiate any musculature. These experimental investigations support previous evidence for a somitic origin of wing bud myogenic cells. Histological and scanning electron microscopic studies of the brachial somites and the adjacent somatic plate mesoderm of chick embryo (stages 13--15 H.H.) reveal that migration of still undifferentiated somitic cells into the brachial somatic plate mesoderm begins to take place in embryos at stage 14.

Animals↗
PubMed1977

Protease activities during preparation and handling of nuclear particles containing hnRNA.

Conditions were devised to avoid protease activity during the preparation and the subsequent handling of nuclear particles containing hnRNA. During all the steps of preparation of rat liver particles, the presence of phenylmethyl sulfonyl fluoride (PMSF) was required for the reproducibility of the results. It probably inhibited the cellular serine proteases before the separation of the particles from the other cellular structures. Protease activity was detected in the rat liver particles. The enzyme(s) preferentially hydrolyzed a few particle polypeptides. It was not inhibited by PMSF, nor by two trypsin and chymotrypsin-like protease inhibitors, nor by iodoacetamide, but was inhibited by sodium bisulfite and para-hydroxymercury benzoate (PHMB). PHMB was preferred above bisulfite because it could be used at lower concentration. It proved useful when particles were to be incubated at 37 degrees C. A protease hydrolysing the same polypeptides as the liver enzyme was also detected in rat brain particles. However, its activity was much lower in this tissue and the presence of protease inhibitors was not absolutely required under the standard conditions of preparation and handling of brain particles.

Animals↗
PubMed1977

Metrizamide dissociates nuclear particles containing heterogeneous nuclear RNA.

Metrizamide gradients were tested for the possible fractionation of the constitutive units of nuclear particles. Material from 35-55 S monoparticles was indeed distributed along the gradient but rerun experiments, CsCl density determinations, formaldehyde fixation prior to centrifugation suggested that the separation was due to dissociation or (and) action of endogeneous ribonucleases rather than to monoparticle fractionation. That dissociation had indeed occured was confirmed by the study of 60-110 S polyparticles. They were dissociated into ribonucleoproteins rich in phosphoproteins and into free proteins. These products were essentially similar to those obtained after NaCl treatment of the particles though the modes of action of metrizamide and NaCl are likely to be different. The loss of proteins from particles reaches 60-70% and we conclude that metrizamide gradients are not utilizable for the fractionation of the units of nuclear particles.

Animals↗
PubMed1977

Eosinophilic leukocytes in diffuse proliferative and exudative glomerulonephritis.

Differential counts of glomerular eosinophils and neutrophils were performed on renal biopsies from 16 patients with diffuse proliferative and exudative glomerulonephritis. The results indicate that eosinophils and neutrophils are present in the glomerular exudate in the same proportion as in the peripheral blood. The eosinophilia present in some of the cases could not be etiologically related to the acute nephritis and probably represented a chance association, showing how a well known histological entity can sometimes be modified in a tropical environment. The functional effects, if any, of this modification require further study.

Adolescent↗
PubMed1976

Size heterogeneity of the structural units of brain nuclear ribonucleoprotein particles.

Nuclear ribonucleoprotein particles were examined by electron microscopy after negative staining. The results confirmed the polymeric nature of the particles. The constitutive units were distributed into 4 size classes (diameters varying from 100 to 300 A, approximately) indicating that the monoparticle population was heterogenous. When examined on ultrathin sections, the particles had a fibrillar appearance.

Animals↗
PubMed1976

Biochemical assessment of the nutritional status of low-income pregnant women of Mexican descent.

Biochemical parameters of nutritional status were investigated in 300 women of Mexican descent during the first and second trimesters of pregnancy. Blood samples were obtained from the women during clinic visits, and measurements were made of serum iron, hemoglobin, hematocrit, serum protein, and transferrin saturation. Additionally, the nutritional status of seven vitamins was determined either by direct assay of the vitamin levels in blood or by measurement of erythrocyte enzyme stimulation. Thiamin and riboflavin were also determined in causal urine samples. Very few women, 8% or less, were classified as being low or deficient in hemoglobin, serum protein, iron, transferrin saturation, vitamin C, carotene, vitamin A, or vitamin B12. Thirty-one percent had low or deficient hematocrit values according to the guidelines used. Folic acid was the most prevalent vitamin deficiency, with 69% of the women having low or deficient serum levels. Based on the erythrocyte enzyme stimulation tests, 22% of the women were low or deficient in thiamin, 29% were low or deficient in riboflavin, and 9% were deficient in pyridoxine. None of the women had a low urinary excretion of thiamin, but 8% had excretion values of riboflavin below the acceptable level. Fewer deficiencies of thiamin and serum folic acid were observed in women taking vitamin and mineral supplements than in those who were not.

Adolescent↗
PubMed1976

Effect of nutrition education on the nutritional status of low-income pregnant women of Mexican descent.

Low-income pregnant women of Mexican descent were studied to determine whether their food habits could be improved by nutrition education. Biochemical indices of nutritional status were also investigated. Twenty-four-hour dietary recalls were obtained at an initial interview and again at a final interview after a nutrition education program, which was offered to a randomly selected treatment group. At the initial interview, the mean nutrient intakes that were most often below two-thirds of the Recommended Dietary Allowance (RDA) were iron, vitamin A, thiamin, and calcium. The mean energy value of the diets was also frequently below the RDA. At the final intakes, although the mean energy values and the calcium and carbohydrate of both the control and treatment groups increased significantly, the following improvements in dietary intakes were seen only within the treatment group: 1) there were significant increases in the mean intake of protein, ascorbic acid, niacin, riboflavin, and thiamin, 2) there were significant decreases in the percentage of intakes below two-thirds of the RDA for ascorbic acid and riboflavin, and 3) there was a significant decrease in the incidence of multiple low nutrient intakes. These dietary improvements, which occurred only in the treatment group, suggest the effectiveness of the nutrition education program. The most common biochemical deficiencies were of folic acid, thiamin, and riboflavin. Except for an improvement in mean serum folate levels, the biochemical indices for the treatment group did not appear to be influenced by the nutrition education. It is possible that the vitamin and mineral supplements which were taken by 80% of the women could have obscured improvements in biochemical indices which may have been due to the education program.

Adult↗
PubMed1976

Incidence of murmurs in the aging heart.

One hundred patients aged 60 or older were studied clinically after excluding those with cardiac enlargement, definite valvular lesions or electrocardiographic (ECG) evidence of left ventricular hypertrophy. In 30 of the the 100 patients a significant systolic murmur was heard on auscultation. Phonocardiograms (PCGs), mitral echograms and pulse tracings were obtained in 28 of these 30 patients (2 had died meanwhile), and the ECGs and chest roentgenograms were reviewed. In 23 PCG patients there was an early or midsystolic murmur, best recorded at the base of the heart and often transmiteed to the apex. Mitral valve echograms and carotid and jugular pulse tracings were normal in all cases. Chest roentgenograms revealed aortic enlargement in 83 percent of the 23 patients. In the elderly with no evidence of organic heart disease, a basal systolic murmur is probably an aortic flow phenomenon caused by either moderate aortic dilatation or minimal fibrotic fusion of one or more commissures of the aortic valve.

Age Factors↗
PubMed1976

[Differention of the neural tube. Experimental study in chick and quail embryos].

In order to study the possible influence of adjacent structures upon differentiation and proliferation of the chick spinal cord, a piece of neural tube of chick embryos incubated for 2 days (stages 12-14 of HAMBURGER and HAMILTON) was extirpated and replaced by an equal graft from a donor embryo of the same age. The grafts were rotated 90 or 180 degrees around their longitudinal axis. The examination of the serial histological sections and the analysis of the distribution of mitotic density in the rotated spinal cord of embryos fixed 2-8 days after the operation led to the following results: the differences in morphogenesis and histogenesis between dorsal and ventral sectors of the spinal cord are already determined in 2-day-old chick embryos. The reversal of the neural tube at this time has no effect either upon the typical differentiation or the characteristic distribution of the mitotic cells in the spinal cord.

Animals↗