Biomedical subjects

I Zs-Nagy

Publications and source records attributed to I Zs-Nagy.

At least 37 records · Page 2Linked to original sources

PubMed1989

The lack of age-pigments and the alterations in intracellular monovalent electrolytes in spontaneously hypertensive, stroke-prone (SHRsp) rats as revealed by electron microscopy and X-ray microanalysis.

Male, spontaneously hypertensive, stroke-prone (SHRsp) rats established by Okamoto et al. (1974) were studied. About 80% of the males of this strain have a particularly short life span (33-41 weeks); they display a considerable hypertension (above 220 mmHg) and a tendency for plurifocal brain strokes. Hypertension and strokes can be provoked in an accelerated and synchronized fashion by supplementing 1% NaCl into their drinking water. Symptoms of the appearance of brain strokes can be judged from characteristic signs of motor disorders, and can be established also by pathohistology. Since hypertension and arteriosclerosis are frequently involved in aging, the question we intended to answer was whether these animals may represent a model of the normal aging process or not. Two approaches are described: (1) Accumulation of lipofuscin granules in their brain, liver and myocardium was followed by transmission electron microscopy before and after the appearance of strokes. It has been established that these tissues do not show any typical accumulation of lipofuscin granules, although submicroscopic signs of an enhanced damage of cell organelles (especially of mitochondria in liver and brain cells, but not in myocardium) were encountered. (2) The intracellular monovalent composition in the brain and liver was measured by using bulk-specimen X-ray microanalysis. The intracellular Na-content (mEq/kg water) was significantly higher (170-200%) in both the brain and liver cells, whereas the K-content increased only moderately (118-130%). The results suggest that although the SHRsp rats do not represent a direct model for the normal aging process from the point of view of lipofuscin accumulation, the shifts of the monovalent electrolyte contents in the brain and liver cells observed already in the youngest ages, are similar to those observed in aged normal rats. The theoretical consequences of such a conclusion are discussed.

Aging↗

PubMed1989

Gerontopsychological studies using NAI ('Nürnberger Alters-Inventar') on patients with organic psychosyndrome (DSM III, Category 1) treated with centrophenoxine in a double blind, comparative, randomized clinical trial.

A double blind clinical trial was performed on 50 persons (25 men, 25 women) over the age 60 (average age: 77 years). They suffered from dementias of medium level (DSM III, Category 1, ICD No. 299), and had been residents in an old age home longer than 3 months at the start of the trial. The patients were treated first for 2 weeks by placebo tablets and their initial performance was recorded during this period by using the Nuremberg Gerontopsychological Inventory (NAI). This was then followed by a treatment for 8 weeks with the nootropic drug, centrophenoxine (CPH), the dose of which was 2 g/day distributed in 2 x 2 tablets of Helfergin500 (Promonta, Hamburg, FRG), or with placebo tablets of identical size, then the NAI test was repeated again. Verum or placebo treatment was selected randomly and the code was revealed only after having elaborated all the results of the trial. During the treatment period four drop-outs occurred for intercurrent diseases. Evaluation was based on a semi-quantitative, intra-individual comparison of the performance before and after treatment. The results obtained suggest that CPH treatment may be useful in dementias of medium level in quite old groups of patients, since 48% of the verum group displayed improvements in the memory functions against 28% of the placebo group. CPH seems to be a useful and harmless drug in the treatment and most probably also in prevention of the dementias.

Aged↗

PubMed1989

Effect of centrophenoxine and BCE-001 treatment on lateral diffusion of proteins in the hepatocyte plasma membrane as revealed by fluorescence recovery after photobleaching in rat liver smears.

The average lateral diffusion coefficient of proteins (D) in the cell membrane of hepatocytes has been measured in liver smears by fluorescence recovery after photobleaching (FRAP), based on the so-called peroxide-induced autofluorescence (PIAF) deriving from the oxidation of riboflavin bound to membrane proteins. It has been previously shown that D displays a significant negative linear age correlation. The in vivo effects of two drugs were tested on this parameter. Young (2.7 months) and old (24-26 months) male rats received centrophenoxine (CPH) or a new drug (BCE-001) by either intraperitoneal (i.p.) injection or per os through a gastric tube for 26 to 42 days. D was measured on a double-blind basis in the hepatocyte plasma membrane of treated and control groups. The CPH and BCE-001 treatments did not affect the value of D in the young rats. However, the latter drug increased their growth rate. An increase of D in old animals was induced by treatment with either drug. When the drug effects in old rats were compared, BCE-001 proved to be more efficient than CPH, and at the same time was able to significantly retard the age-dependent loss of body weight characteristic of these animals at the age of approximately 2 years. Our results are in good accord with the predictions of the membrane hypothesis of aging as regards the role of properly placed OH. free radical scavengers in the improvement of membrane and overall cell function.

Aging↗

PubMed1989

Age-dependence of the lateral mobility of proteins in the plasma membrane of hepatocytes of C57BL/6 mice: FRAP studies on liver smears.

Protein lateral diffusion in hepatocyte membranes was measured in 23 male and 16 female C57BL/6 mice in four groups of age 5 to 32 months by means of fluorescence recovery after photobleaching (FRAP). The peroxide-induced autofluorescence (PIAF) in H2O2 treated liver smears is due to the oxidation of flavins bound uniformly to all proteins of the cell membrane, i.e., an average lateral diffusion constant (D) of those proteins can be measured. D showed a negative linear age-correlation in both sexes: D male = (2.81 - 0.016X)10(-10), and D female = (2.67 - 0.020X)10(-10) cm2/sec, (r greater than 0.94), where X is the age in months. Sex differences are significant (p less than .001) in the intercept. Fractional recovery did not prove to be age-dependent; it was, on average, 91% in males and 100% in females. The findings agree well with the previously obtained data on Fischer 344 and Wistar rats, and strengthen the gerontological relevance of D.

Aging↗

PubMed1989

A review on the use of bulk specimen X-ray microanalysis in cancer research.

The freeze-fracture, freeze-drying (FFFD) method of biological bulk specimen preparation combined with quantitative X-ray microanalysis is suitable for the measurement of intracellular concentrations of biologically relevant elements in human biopsy or experimental animal materials. Especially useful information can be obtained regarding the intracellular Na+/K+ ratios being independent of the actual (and unknown) water content of the cytoplasm. The sustained increase of this ratio indicates a sustained depolarization of the cell membrane. These data are of importance from the point of view of the membrane hypothesis of mitogenesis (MHM). It has been revealed that the distribution histograms of the intracellular Na+/K+ ratio display a very significant broadening and an increase of the average values in human urogenital, thyroid and laryngeal tumors, as well as in experimentally induced cell proliferation models. Although MHM has been claimed to be invalid on the basis of some atomic absorption measurements of the intracellular monovalent ion concentrations as well as of some in vitro results obtained with amiloride, this review paper demonstrates that MHM may still be a valid hypothesis for the explanation of mitotic regulation.

Cell Transformation, Neoplastic↗

PubMed1988

Possibilities and limitations of the smearing technique for cellular studies in compact tissues: a transmission electron microscopic analysis of liver smears.

During the last decade a sophisticated biophysical technique called fluorescence recovery after photobleaching (FRAP) has become available for the measurement of lateral diffusion constants of lipids and proteins in the cell membrane. The information obtainable by this method is of great importance; however, the applicability of this method is seriously hindered by the fact that it has been elaborated mostly for isolated, individual cells. On the other hand, the use of freshly prepared cells from compact tissues for such studies is highly desirable. Therefore, a special smearing method was devised (using liver cells) for this purpose. The present paper describes (i) the method of standardization of the smearing technique, (ii) the ultrastructural features of the liver cells when studying the liver smears by means of transmission electron microscopy. The possibilities and limitations of this method are discussed. According to the observations, under well-defined conditions the structural integrity of hepatocytes is maintained in the liver smears to such an extent that they are suitable for FRAP experiments.

Animals↗

PubMed1988

Dysdifferentiation hypothesis of aging and cancer: a comparison with the membrane hypothesis of aging.

Our laboratories have been testing the basic concept that the age-dependent deterioration of the molecular components of living systems may be due in part to the biochemical effects of active oxygen species. The dysdifferentiation hypothesis of aging and cancer (DHAC) as well as the membrane hypothesis of aging (MHA) are discussed and compared to each other. These two hypotheses consider cellular mechanisms through which free radical-induced alterations may lead to the aging process. DHAC emphasizes the importance of the instability of the differentiated state of cells and how active oxygen species may interact with the genetic apparatus of cells, leading to improper gene regulation. The evidence supporting this hypothesis includes an age-dependent increase in the expression of specific genes that normally are expected to be repressed. Such evidence now includes the c-myc oncogene as well as an age-dependent decrease in the average methylation level of the entire genome in liver tissue of mice. The central concept of DHAC is that aging is a result of gene regulatory instability and that lifespan is governed by mechanisms acting to stabilize proper gene regulation. MHA is based on the concept that all cellular components are exposed to free-radical attacks, and that the damaging efficiency of the radicals is density-dependent. Compact structures like membranes are consequently more susceptible to damage than cytosolic components. In addition, the cell plasma membrane is exposed to another damaging effect called residual heat damage, which is due to the depolarization-induced discharge of the membrane during the action potential. MHA predicts that a key process of normal differentiation as well as aging is a continuous, age-dependent loss of the passive permeability of the cell membrane for potassium and probably also for water. This is due to a constant difference between the rates of damage and replacement of the membrane components and results in a gradual dehydration of the intracellular mass from the embryonic state to the aging state. The increasing intracellular density will eventually become rate-limiting for many different cellular functions, resulting in the cessation of growth and the beginning of aging. MHA also predicts an overall decrease of gene expression and protein turnover rate during aging. Pharmacological interventions on the cell membrane have supported the validity of MHA and have indicated specific mechanisms of how aging and dysdifferentiation may occur.

Aging↗

PubMed1988

Effect of enzymic (collagenase) harvesting on the intracellular Na+/K+ ratio of Swiss/3T3 cells as revealed by X-ray microanalysis.

Swiss/3T3 cell cultures were harvested with 0.05% collagenase and after centrifugation the pellet was prepared by the freeze-fracture/freeze-drying (FFFD) method for bulk-specimen X-ray microanalysis. Time-dependent variations in the intracellular monovalent elemental concentrations (Na+, K+ and Cl-) as well as of the Na+/K+ ratio were followed for 120 min subsequent to harvesting. The quantitative measurements revealed a very considerable increase in the intracellular Na+ and Cl- accompanied by a decrease in the K+ concentration as soon as 5 min after harvesting. The Na+/K+ ratio had increased by this time to about 1.5 on average. These changes indicate a sustained depolarization of the cell membrane. During the first 60 min this depolarization tended to normalize as demonstrated by an exponential decrease in the intracellular Na+ and Cl- and an increase in the K+ content involving a decrease in the Na+/K+ ratio. The total intracellular monovalent ion concentration remained almost constant during this post-harvesting period. These results suggest that harvesting represents a serious depolarizing stimulus to the cells, the consequences of which are restored only after 1-2h. These alterations should be taken into consideration during various experimental designs when using anchorage-dependent cell cultures.

Animals↗

PubMed1987

Age-dependent changes in the osmotic behavior of rat brain and liver.

Osmotic potential of liver and brain tissue has been determined by measuring swelling or shrinkage of the tissues in anoxic Ringer solution the osmotic concentration of which was rendered hypo- or hyperosmotic by dilution or addition of polyethylene glycol (PEG 6000), respectively. The percentages of volume change were fitted to an exponential equation permitting the calculation of the initial speed of volume change. The age-dependent increase of the intracellular dry mass content was also taken into consideration. It has been established that initial velocity of the volume change displays an age-dependent decline in all kinds of media tested; however, the slope of this decrease is steeper in the diluted Ringer solution than in the other ones. Calculations show that the colloid osmotic pressure (mmHg) of the intracellular mass decreases between 1 and 26 months of age from 810 to 596 and from 2,477 to 904 in the brain and liver, respectively. The results may be interpreted as consequences of a decreased colloid dispersity which may be related to an oxygen free radical induced intermolecular cross-linking.

Aging↗

PubMed1986

Age-dependent decrease of the lateral diffusion constant of proteins in the plasma membrane of hepatocytes as revealed by fluorescence recovery after photobleaching in tissue smears.

When fresh liver is smeared on slides and incubated in Krebs-Henseleit Ringer solution containing 1 mM H2O2 at 37 degrees C, a yellowish-green autofluorescence develops in the hepatocyte plasma membrane. Indirect evidence shows that this peroxide-induced autofluorescence (PIAF) is due most probably to chemical reactions between proteins and the malondialdehyde produced by the membrane lipid peroxidation. Although the chemical nature of the PIAF has not been clarified yet, it is suitable under certain conditions for the measurement of the average lateral diffusion constant of the membrane proteins by means of the fluorescence recovery after photobleaching (FRAP) technique without the addition of any external fluorescent label. Analysis of four age groups for both sexes of Fischer 344 rats (3-5 rats per group, total 32) from 2 to 31 months of age revealed a significant negative linear correlation of the lateral diffusion constant of proteins with age in both sexes, with the slope of the females being somewhat smaller. Young males showed a diffusion constant about 2.8 X 10(-10) decreasing to 1.7 X 10(-10) cm2 X s-1 by 31 months of age at 37 degrees C, whereas the respective values in females were 2.7 X 10(-10) and 1.9 X 10(-10). The results are consistent with the predictions of the membrane hypothesis of aging, according to which an age-dependent loss of the passive permeability of the cell membrane for potassium (and probably for water) is the crucial point of the cellular aging.

Aging↗

PubMed1986

Age-estimations of rats based on the average lateral diffusion constant of hepatocyte membrane proteins as revealed by fluorescence recovery after photobleaching.

A method has been developed recently for measuring the average lateral diffusion constant of the proteins (D) in the cell membrane of hepatocytes in liver smears by fluorescence recovery after photobleaching (FRAP). A peroxide-induced autofluorescence (PIAF) of the membrane proteins was used as a fluorescent label. It has been established that D displays a significant negative linear correlation with age. The present paper describes age-estimations carried out on 12 male Fischer 344 rats (7-29 months of age) in so-called "blind experiments": the operator knew only the sex of the rat, determined D from a small piece of the freshly removed liver, and estimated the age of the rat from the age-dependent regression line for D established previously on 16 other Fischer 344 male rats of various ages. There was a strong correlation of the estimated age with the actual one (r = 0.92), the slope of the regression line was 0.98 and its intercept differed from 0 by only 0.5 months. These results indicate that D may play a decisive role in the determination of membrane functions as predicted by the membrane hypothesis of aging.

Aging↗

PubMed1985

Superoxide radical scavenging ability of centrophenoxine and its salt dependence in vitro.

The superoxide radical scavenging ability of centrophenoxine (CPH) and its components (dimethylaminoethanol = DMAE, p-chlorophenoxyacetic acid = PCPA) was studied in vitro using the method of pyrogallol autoxidation, cytochrome c reduction and photoxidation of o-dianisidine in salt-free assay media and in the presence of increasing NaCl or KCl concentrations. The CPH proved to be a superoxide radical scavenger in all three systems used, however, the rate constant for this reaction was rather low (1.7 X 10(2) M-1 s-1). This scavenging ability decreased linearly with increasing ionic strength. DMAE and PCPA behaved in a somewhat contradictory manner. The former proved to be a weak superoxide radical generating compound being partially sensitive to the ionic strength. The latter showed either superoxide radical scavenging or generating effects in various assays depending on the actual salt concentrations of the media. On the basis of the results one has to assume that the superoxide radical scavenger ability of CPH may hardly be responsible for the in vivo effects of this compound, therefore, its OH. radical scavenger reactions the rate constant of which is about 10(9) M-1 s-1 may be of much greater importance.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1984

Centrophenoxine increases the rates of total and mRNA synthesis in the brain cortex of old rats: an explanation of its action in terms of the membrane hypothesis of aging.

The rates of total and polyA+ RNA (mRNA) synthesis were measured by radioisotope technique in the brain cortex of female CFY rats. There was practically no significant difference between the young (1.5 months) and adult (13 months) rats; however, the old group (26 months) displayed a considerable decrease of the rates of synthesis of both classes of RNA studied. Centrophenoxine treatment (100 mg per kg body weight per day, for 2 months) reversed this tendency, and increased significantly the synthesis rates of old rats almost to the adult level. The results are interpreted in terms of the membrane hypothesis of aging, attributing a free-radical scavenger function of the dimethylamino-ethanol incorporated into the nerve cell membrane from the centrophenoxine.

Aging↗

PubMed1983

Spin label studies on synaptosomal membranes of rat brain cortex during aging.

Membrane lipids of brain synaptosomes of 2, 12 and 24 months old rats were labeled by stearic acid spin probes with a doxyl group in the C-5 and C-16 position, respectively. We demonstrated that the hydrophobic region of synaptosomal membranes became more rigid during the life span studied, and the region located nearer the surface of membranes displays a significantly decreased fluidity only in the oldest group. Membrane proteins labeled with a nitroxide derivative of maleimide suggest that conformational changes take place during aging.

Aging↗

PubMed1983

In vivo stimulation of nerve cells by phytohemagglutinin. II. Alterations in the rate of total and mRNA synthesis in the brain cortex of old rats.

Bacto-phytohemagglutinin-P (PHA-P) was administered in form of a single intralumbar injection of 2 mg/100 g body weight dose to 24- to 28-mth-old female CGY rats. The accuracy of the injection technique was checked by adding 2% lidocaine to the injection mixture, which resulted in a transient and symmetric paralysis of the posterior limbs when reaching the cerebrospinal fluid. The total RNA content of the liver and brain cortex were measured, and phenolic extraction of RNA was performed the brain cortex. Poly(A) +RNA (mRNA) was separated from the total RNA of the brain cortex by oligo(dT)-cellulose chromatography. Pulse labeling with tritiated uridine was performed 45 min before killing the animals and the incorporation of the radiolabel was measured in the respective RNA classes and corrected for the nucleotide pool size. The rates of total and mRNA synthesis are expressed in percentages of the young untreated rats and compared to old untreated animals. The effects of PHA-P was studied at 4, 10, 20 and 44 h after its injection. A considerable increase of the total RNA content of the brain cortex was measured during the first 10 h of the experiment followed by a slow decrease. However, the RNA content of the brain cortex was still significantly higher at the end of experiment compared to untreated old rats. The rate of total RNA synthesis increased significantly during the first 10 h and remained constantly high until 44 h. The rate of mRNA synthesis increased to a higher extent than that of the total RNA, and also remained high until 44 h.

Aging↗

PubMed1983

The validity of some morphologic methods in the diagnosis of thyroid malignancy.

The diagnostic accuracy of intraoperative frozen section and imprint cytology in thyroid conditions was analyzed along with that of cytofluorimetric nuclear DNA determination. Of 149 frozen sections in a four-year period, 90% gave a correct diagnosis, while four results were false-positive and one was false-negative. The intraoperative accuracy of imprint cytology was 95% in 309 examinations, with 12 false-positive and four false-negative results. The misjudgements with both morphologic methods derived mainly from decisions on benignancy or malignancy of follicular tumor types. Neither atypical adenoma nor encapsulated follicular carcinoma can be conclusively distinguished with these methods. Their routine application nevertheless is of great help to the surgeon, in that they can considerably reduce the need for second (radical) operations and thus the risk of complications. Nuclear DNA determination was unhelpful in the intraoperative situation.

DNA, Neoplasm↗

PubMed1979

Cytofluorimetric measurements on the DNA contents of tumor cells in human thyroid gland.

The relative DNA contents of thyroid cell nuclei were measured in surgically removed thyroid tissue of 50 patients by means of cytofluorimetry. Smears were prepared immediately after removal of the thyroid nodules according to the classical Feulgen technique. The fluorescence intensities were always compared with those of healthy thyroid tissue prepared in the same way. In each case samples were investigated by the usual histology. The observations indicate that differentiated carcinomas of thyroid gland have an increased DNA content of nuclei, at about the tetraploid level. Among them the follicular carcinomas (11 cases) showed an even higher DNA content of about 250% of the diploid level. Frequency distribution of the cell pools studied revealed a widely scattered aneuploidization of the malignant tumor cells. The benign adenomas displayed only a moderate increase of nuclear DNA content reaching only about 130% of the diploid value. Among the 22 adenomas classified histologically as of benign character, two cases showed very highly increased and widely scattered DNA contents. These latter two cases might be in process of malignant transformation. DNA cytofluorimetry may contribute to a more safe differential diagnosis of the "follicular neoplasia" of the thyroid gland.

Adenocarcinoma↗

PubMed1979

The role of membrane structure and function in cellular aging: a review.

A survey of the available theoretical and experimental evidence is given regarding the cell membrane properties, such as the membrane fluidity, potassium permeability, etc., which are involved in the regulation of intracellular ion contents. These properties of the membrane undergo some age-dependent alterations in numerous cells studied so far, resulting in an increase of the intracellular potassium content. This phenomenon has a serious inhibitory effect on the rates of enzymatic catalyses involved in the protein synthesis, and may explain the decreased protein synthetic capacity of the old cells. Data are presented indicating that some changes in the membrane permeability are also involved in the malignant transformation of the cells; however, these are of opposite direction as compared to aging of cells. The "membrane hypothesis" of aging based on these facts seems to be a useful experimental approach to the problem of cellular aging.

Animals↗