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At least 73 records · Page 4Linked to original sources
PubMed1975

Three-dimensional reconstruction of lung perfusion image with positron detection.

Transverse section images of the distribution of pulmonary perfusion in a canine have been obtained using microspheres labeled with the positron-emitting isotope 68Ga and a three-dimensional reconstruction technique. The reconstruction method is more accurate than conventional tomographic procedures and is facilitated by the use of positron detection. The transverse sections presented demonstrate the capacity of the technique to delineate reduction in regional perfusion resulting from occlusion of the artery to the left lower lobe.

Animals↗
PubMed1975

Chemical modification of ribosomes with dimethyl sulfate: a probe to the structural organization of ribosomal proteins and RNA.

Ribosomal proteins from [14-C]dimethyl sulfate treated with 30S and 50S subunits of Escherichia coli ribosomes were separated by two-dimensional polyacrylamide gel electrophoresis and the degree of methylation of each protein was determined. Comparison of the results from this relatively non-specific chemical modification procedure with results from the milerd lysine-specific reductive alkylation procedure reported previously (Moore, G. & Crichton, R.R. (1974) Biochem. J. 143, 607-612) has permitted a topographical classification of ribosomal proteins in terms of 'degree of exposure' in the 30S and 50S subunits. The reaction of dimethyl sulfate with ribosomal RNA, both in intact subunits and after isolation from the subunits, has indicated that approximately half of the RNA in 30S and 50S subunits is exposed on the surface of the ribonucleoprotein complexes, and that no large sections (extended sequences) of 16S RNA are concealed in the 30S subunit. It is proposed that modification of ribosomes with dimethyl sulfate is a potentially useful technique for probing exposed and hidden regions and also exposed single-stranded regions of RNA in ribosomes.

Bacterial Proteins↗
PubMed1978

Altered E2 glycoprotein of Sindbis virus and its use in complementation studies.

We have detected a Sindbis virus variant that contains a smaller-molecular-weight form of the viral glycoprotein E2. The molecular weight of the PE2 precursor and the glycosylation pattern of the smaller E2 are normal, thus indicating that this E2 is formed by an aberrant proteolytic cleavage. The altered E2 was detected in an RNA+ temperature-sensitive mutant that was defective in proteolytic cleavage, but the abnormal PE2-to-E2 reaction could be separated from the ts mutation and is not itself a temperature-sensitive defect. We used the variant E2 as a marker to monitor the complementation reaction between an RNA+ and an RNA- mutant and discovered that complementation was not reciprocal; the RNA defect was corrected by the RNA+ mutant gene products but the RNA+ defect was not complemented by any RNA- gene products. Other studies have shown that the smaller E2 is not preferentially selected during viral maturation and budding. No significant changes have been detected in the biological activity of virions with this altered E2 protein. Comparison of the electrophoretic migration of the E1 and E2 Sindbis viral glycoproteins in a two-dimensional polyacrylamide slab gel system that was first run in the absence of sulfhydryl-reducing reagent and then with beta-mercaptoethanol indicated that the mobility of E1, but not that of E2, was significantly altered by reduction.

Genetic Complementation Test↗
PubMed1975

Conformational studies on modified proteins and peptides. IX. Conformation and immunochemistry of hemoglobin reduced at some carboxyl groups by diborane.

A derivative of apohemoglobin was prepared by reduction with diborane at -10 degrees C for 2 h. Four aspartate and two glutamate side chains were reduced per half molecule to their corresponding alcohols. The modifications were identified as: alpha asp 64, alpha-asp 74, alpha-asp 75 and alpha asp 85;beta-glu 121 and beta-glu 6 (or beta-glu 7). Recombination of reduced apohemoglobin with unmodified ferriheme yielded the corresponding reduced hemoglobin derivative which was electrophoretically homogeneous. Hemoglobin and reduced hemoglobin had different electrophoretic mobilities and showed slight spectral differences. Titration with ferriheme revealed that reduced globin possessed an anomalous heme-binding behavior. The s 20,w of reduced hemoglobin was slightly higher than that of hemoglobin. Agregation of the derivative was also apparent from its behavior in gel filtration. ORD and CD measurements indicated substantial conformational differences between hemoglobin and its derivative. Immunochemical studies showed that the derivative reacted poorly with antisera to hemoglobin and, conversely, hemoglobin showed little reaction with antisera to the derivative. The results are discussed in terms of the three-dimensional structure of hemoglobin in the crystalline state and its relationship to the structure in solution.

Amino Acids↗
PubMedDate not supplied

Resolution and contrast reduction.

Lack of resolution (unsharpness) can reduce contrast in diagnostic radiography if the proper conditions of magnification and unsharpness are met. To describe this phenomenon, a modification of the contrast reduction factor (CRF) was introduced which used the response function of a semi-opaque edge to predict contrast reduction for small bar-shaped objects. To predict CRF, unsharpness is employed as a single-term description of resolution and is obtained experimentally from the edge response function. The unsharpness term is defined as the distance over which the response goes from 16.5% to 83.5% of the maximum. Measured and predicted CRFs were compared and the CRF concept was found to be an excellent predictor of contrast reduction. The individual components of unsharpness were determined experimentally and the sum-of-squares rule predicted adequately their combination. Three methods to measure unsharpness were compared: (a) the ICRU prescription using pinhole radiographs of the focal spot, (b) one-dimensional integration of the focal-spot pinhole radiograph, and (c) the unsharpness term produced by a semi-opaque edge. The latter two were measured using a microdensitometer.

Mathematics↗
PubMed1977

Quantitative coronary arteriography: estimation of dimensions, hemodynamic resistance, and atheroma mass of coronary artery lesions using the arteriogram and digital computation.

More accurate characterization of coronary artery lesions is needed for evaluation of short and long-term interventions in coronary disease. A method of segmental artery analysis has been developed to maximize the information obtained from coronary arteriograms. Coronary lesions are traced from two projected, perpendicular, 35 mm cineangiographic views and transmetted, in digital form, to a PDP 11/45 computer. Magnification and distortion of the image are compensated for in order to determine the actual vessel profiles, using the catheter and its location as a scaling device. The two views are matched; a spatial representation of the vessel centerline is constructed mathematically; and orthogonal vessel diameters are computed at increments along this centerline. Assuming an elliptical lumen, the absolute and percentage reduction in diameter and cross-sectional area in the stenosis are computed. More complex functions (integrated atheroma mass, Poiseuille resistance, and orifice resistance) are then calculated. The accuracy and variability of the different steps involved in lesion analysis have been determined. Dimensional accuracies of +/- 150 microns (SD) are feasible. Examples are given of patients with Prinzmetal's angina and with progressive coronary disease.

Adult↗
PubMed2026

Aging of hair follicle stem cells and their niche: mechanisms and regenerative therapeutic strategies.

Hair follicles (HFs) are vital skin appendages that perform fundamental functions including protection, thermoregulation, and sensation. Orchestrated by hair follicle stem cells (HFSCs), HFs undergo cyclic regeneration throughout the lifespan. However, during chronological aging, this mini-organ experiences progressive physiological decline, clinically characterized by a marked reduction in hair density and hair graying due to pigmentation dysfunction. This aging process involves HFSC exhaustion accompanied by diminished regenerative potential and differentiation capacity, leading to degenerative changes in the bulge architecture. Concurrently, the niche supporting HFSC homeostasis undergoes multi-dimensional and systemic degradation. This niche deterioration disrupts the delicate balance between HFSC quiescence and activation, further impeding hair regeneration. In this review, we delineate the dynamic anatomical changes throughout the hair growth cycle and describe the alterations of HFSCs during aging. We specifically focus on the mechanisms underlying the multi-dimensional degradation of the HFSC niche at tissue, cellular, and molecular levels. Furthermore, we discuss various therapeutic strategies aimed at ameliorating HF aging, offering potential insights for future clinical translation in hair regeneration. Finally, we propose that integrating spatiotemporal high-resolution technologies with genomic data to further decipher the spatiotemporal behaviors of aging HFSCs and niche cells will facilitate the establishment of a robust mechanistic framework for HFSC and niche aging.

Hair Follicle↗
PubMed1978

Reoxidation of reduced hen egg white lysozyme fragment 1-123.

The reactivation of reduced lysozyme, whose 6 COOH-terminal amino acid including cysteine 127 were cut off, was studied. The results show that the disulfide bridge I-VIII as well as the COOH-terminal hexapeptide do not play a decisive role in the acquisition of the native 3-dimensional structure of the enzyme.

Animals↗
PubMed1978

An analysis of alterations in ribosomal conformation using reductive methylation.

Optimal conditions for reductive alkylation of ribosomal proteins in their native and denatured states were examined. The relative accessibility of rat liver ribosomal proteins to reductive alkylation was then examined. Intact ribosomes were firs labeled with [14C]formaldehyde and NaBH4. The proteins were then separated from RNA, denatured in 6 M guanidine, and labeled again using formaldehyde and NaB3H4. The relative accessibility of individual proteins to labeling in the intact state could thus be determined from their 3H/14C ratios following separation by two-dimensional electrophoresis. The results suggest that proteins S6, S11, S26, L3, and L35 are less accessible to labeling while proteins S1, S15, L11, L12, L16, and L24 appear relatively more accessible. The accessibility of individual proteins in ribosomes in different conformational states were then compared. The results indicated that S3, L7, and L36 are likely to be involved in a structural difference when normal polysomes and normal monomers are compared. Also, that S26 and L35, and probably S3, S20, L7, L8, L24, L27, L28 and L34 appear to be involved in a ribosomal conformation change induced by ethionine intoxication.

Animals↗
PubMed1975

Modulation of myosin in right ventricular hypertrophy.

Mild pulmonic stenosis was performed in dogs to evaluate the effect of systolic pressures overloading on the activity and subunits of myosin in the early hypertrophied right ventricle. Three weeks following pulmonary constriction, six hypertrophied dogs were sacrificed and compared to six sham-operated dogs which served as controls. In the right ventricular free wall of hypertrophied right ventricles (HRV), the heart/body weight was 46% greater than that of normal right ventricles (NRV) (p less than 0.01). Myosin ATPase activity (Vmax values) in mumoles phosphate/mg/min, was elevated significantly in the stressed ventricle for both K+ and Ca++ activity in hypertrophied right ventricles. Associated with the increase in myosin activity, there was an increase in proportion of heavy to light chains in myosin from HRV. There were approximately 2 moles of myosin light chains per mole of myosin heavy chains in NRV and approximately 1 mole of myosin light chains per mole of myosin heavy chains in HRV. The proportion of light chain C1 to C2, did not change in myosin from NRV and HRV. Of the C1 light chains, according to two-dimensional gel electrophoresis, there was less C1d as compared to C1c in HRV as compared to NRV. Thus K+- and Ca++- activated myosin is elevated in early canine HRV by pressure overload. It is suggested taht the augmented myosin activity is due to a reduction of light chain inhibition of myosin ATPase activity, which appears to result from the slower turnover rate of myosin light chains relative to heavy chains. Furthermore, when myosin light chains are added to hypertrophied right ventricular myosin, the ATPase activity is lowered.

Adenosine Triphosphatases↗
PubMed1977

The effect of varying the rate of presentation on the information transmission of schizophrenic and control groups.

Groups of subjects were tested on a paced serial reaction-time task in order to study the effect of varying the rate at which information was presented. The groups were: two groups of patients with acute schizophrenia but differentiated on the basis of primary symptoms, a group of institutionalized schizophrenic patients, a group of neurotic patients and a normal group. All groups showed a reduction in efficiency when the presentation rate was increased. The groups most adversely affected were the non-integrated and institutionalized schizophrenic patients. The integrated schizophrenic and the neurotic groups were affected to a lesser degree, the normal groups being least affected. These results favour a dimensional view of personal illness, in which deficits are most marked in patients with non-integrated schizophrenia.

Adult↗
PubMed1976

[Studies on high temperature oxidation of noble metal alloys for dental use. (II) Effects of high temperature oxidation on casting (author's transl)].

The specimens which were cast from commercial alloys were polished metallographically and then oxidized at 800 degrees C for 1 hour in air. The results obtained were as follows: 1. The reduction rate of Cu aginast the original Cu amount in the alloy is given by the following equation: (see article) where S is surface area of the casting, KW is oxidation rate constant, t is time, Wc is weight of the casting, Ccu is weight percent of Cu, and n is between 1 and 2. 2. Owing to decrease of the Cu concentration in the outer layer of the alloy, the age-hardening did not appear in that layer. 3. Reflexibility of the polished surface of alloys became lower than that of the matrix due to precipitation of the oxide particles. 4. Hardness numbers of the internal oxidation zone (oxide particles, ZnO) decreased to 1/2 of the matrix. 5. The surface roughness of specimens after pickling was affected by the shape of oxide particles in the internal oxidation zone and varied with the different commercial alloys. 6. The dimensional change of casting due to oxidation is given by the following equation: (see article) where sigmacu is density of copper, KW is oxidation rate constant, t is time and n is between 1 and 2.

Copper↗
PubMed1977

[Graphical methods in data analysis (author's transl)].

Data analysis is concerned with attentive description and communication of the information contents of a body of data. Background information, conceptual insight and especially graphical methods play a key role in data analysis for developing a feeling for the data both by formal procedures to be applied in the light of specified models and even more by informal inference or methods that are suggestive and conctructive. This paper reviews graphical methods useful for description, screening, analysis, cross-examining, selection, reduction, presentation and summary of data: for uncovering distributional peculiarities and understanding the structure underlying experimental and survey data. Moreover scatter plots, probability plots and residual plots provide insight into the possible inappropriateness of certain assumptions of the statistical model. Some techniques are illustrated by examples: four-dimensional data may be reprented as scatter plot on ordinary graph paper by using a combination of 2 different sets of symbols for at most 7 different levels of the third variable (formula: see text) and of the fourth variable (formula: see text). Comments on the use of tables and graphical methods, a small overview of the latter and of the scope of applications endeavour to pave the way such that structures may be better understandable and unanticipated characteristics may be spotted.

Factor Analysis, Statistical↗
PubMed1976

Knee forces during the activity of getting out of a chair with and without the aid of arms.

This is a preliminary study of the knee forces during the activity of getting out of a chair with and without the aid of arms. The equipment limited the study to the phase of the activity where no contact occurred between the subject and the chair seat. The model of the knee considered was two-dimensional, and quasi-static. Analysis showed that the forces acting in both compartments of the knee were comparable with those occurring during other non-strenuous activities such as level walking. It was also shown that the use of arms to aid rising from a chair causes considerable reduction in both joint and muscle forces.

Arm↗
PubMed1976

Purification and characterization of initiation factor IF-E3 from rabbit reticulocytes.

Initiation factor IF-E3 from rabbit reticulocytes was isolated from a high salf extract of ribosomes prepared according to the procedure of Schreier and Staehelin (J. Mol9 Biol, 73, 329-349, 1973). The factor was highly purified from the crude extract by ammonium sulfate fractionation, sucrose gradient centrifugation, salf gradient elution from DEAE-cellulose and phosphocellulose columns, and glycerol gradient centrifugation. IF-E3 stimulated cell-free protein synthesis dependent on an exogenous globin mRNA fraction 4- to 5-fold. The factor under nondenaturing conditions behaved as a large multipolypeptide complex, but was separated into 11 major protein components by two-dimensional polyacrylamide gel electrophoresis with urea and sodium dodecyl sulfate. The stoichiometry and molecular weights (range: 28,000-140,000) of the IF-E3 proteins were determined. None of the components corresponded to ribosomal proteins found in high salt-washed ribosomes. 14CH3-IF-E3 was prepared by reductive alkylation without detectable loss of its initiation factor activity, and bound stoichiometrically to 40S ribosomal subunits, but not to 60S or 80S ribosomes. 14CH3-IF-E3 isolated from the 40S complex contained only nine of the 11 original protein components.

Animals↗
PubMed1978

Base composition studies on transfer RNA from normal and regenerating rat liver.

The base composition of bulk tRNA isolated from regenerating rat liver, 12, 18, 24 and 30 h after partial hepatectomy, was determined by a 3H derivative method. Only a few minor statistically significant changes (2--11%), as compared to sham-operated liver, were found at 18, 24 and 30 h after hepatectomy. These included a reduction in the amounts of adenosine and 3-(3-amino-3-carboxypropyl)-uridine, and an increase in the amounts of 1-methyl-adenosine, 1-methylguanosine, 3-methylcytidine and pseudouridine. Similarly, when the base composition of tRNA fractions from control and 24-h regenerating rat liver, partially purified by one-dimensional polyacrylamide gel electrophoresis, was determined, no gross differences were observed. These results suggest that the process of liver regeneration is not accompanied by a gross alteration of the modification pattern of tRNA.

Animals↗
PubMed1975

[Effect of thermal expansion on the accuracy of fit of cast crowns].

Extent and direction of dimensional changes in the finished cast crown resulting from the thermic expansion of the wax model are determined as a function of the time the crown was subjected to tempering as a function of tempering temperature. Expansion of the wax model does not come up to the expectation of preventing a reduction of the cast object.

Crowns↗