Biomedical subjects

P He

Publications and source records attributed to P He.

At least 127 records · Page 7Linked to original sources

PubMed1994

Dietary butylated hydroxytoluene counteracts with paraquat to reduce the rate of hepatic DNA single strand breaks in senescence-accelerated mice.

The present study was designed to assess the age-related changes of DNA single strand breaks (SSB) in the liver of senescence-resistant and senescence-prone mice, SAMR1/Fky and SAMP1@Fky. In the first series of experiments, the animals were fed a commercial diet for 12-18 months. The mice were killed and the livers were excised at 3- or 6-month intervals for the analysis of the rate of DNA SSB by the ethidium bromide fluorescence method. With advancing age, the rate of DNA SSB was increased in both strains of mice but the increase was significantly higher in SAMP1@Fky than in SAMR1/Fky. In the second series of experiments, the mice were fed one of the following diets for 12 weeks: 20% casein diet (basal diet), basal diet with 300 ppm butylated hydroxytoluene (BHT) added, basal diet with 200 ppm paraquat (PQ) added, and basal diet with 200 ppm PQ plus 300 ppm BHT added. Added dietary PQ increased the rate of DNA SSB in both SAMP1@Fky and SAMR1/Fky. The increases were offset by co-administration of BHT. Dietary BHT, therefore, may suppress the oxidative stress developed by paraquat administration.

Aging↗

PubMed1994

Bacteriophage T4 ribonucleoside diphosphate reductase: on the defect causing decreased formation of the beta 93(2) subunit encoded by the nrdB93 mutant gene.

Bacteriophage T4 ribonucleoside diphosphate reductase is composed of two proteins, alpha 2 and beta 2, encoded by the nrdA and nrdB genes, respectively. The expression of nrdB is the limiting factor for the assembly of the enzyme. A recently described mutation, nrdB93, may give new insight into the regulation of synthesis of the beta subunit encoded by nrdB. Infection by T4 nrdB93 produced only low concentrations of the beta 2(93) protein. However, a site-specific mutation of phage T4 gene 39, encoding one of the subunits of T4 DNA topoisomerase, phenotypically suppressed the defect. The present work sought to characterize the nature of this defect. The mutation in nrdB93 was a single-base transition (G-->A) resulting in a Gly253-->Asp change. In vivo and in vitro studies provided no evidence of degradation of the beta 2(93) protein. Furthermore, the decrease in beta 2(93) formation was not caused by a delayed onset of transcription, neither by a decreased rate of mRNA formation from the nrdB promoter, nor by a defective intron splicing of the nrdB gene or in the transcription of the terminal segments of the message. These findings are consistent with the concept that the nrdB93 lesion produces a defect at the level of translation.

Amino Acid Sequence↗

PubMed1994

Endothelial cell hyperpolarization increases [Ca2+]i and venular microvessel permeability.

We tested the hypothesis that Ca2+ influx into endothelial cells forming the walls of intact venular microvessels was increased when the cell membranes were hyperpolarized. Cytoplasmic free Ca2+ concentration ([Ca2+]i) was measured after the endothelial cells forming the microvessel wall were loaded with fura 2, endothelial cell membrane potential was measured with the membrane potential dye bis-oxonol, and hydraulic conductivity (Lp) of the vessels was measured by the modified Landis technique to follow changes in microvessel permeability. When microvessels were exposed to low-K+ (0.1 mM) Ringer solution, the membrane of the endothelial cells was hyperpolarized approximately 27 mV and [Ca2+]i increased from 47 nM to a peak value of 151 +/- 28 nM. Under the same experimental conditions, Lp increased to a peak 6.3 times control. In the presence of ionomycin (5 microM), the initial peak [Ca2+]i measured with low-K+ Ringer solution was 347 +/- 58 nM compared with 252 +/- 58 nM with ionophore and normal Ringer solution. The corresponding initial increases in Lp were 28 times control and 10 times control, respectively. The results conform to the hypothesis that vasoactive substances that hyperpolarize the endothelial cell membrane may initiate and/or potentiate the inflammatory response in venular microvessels.

Animals↗

PubMed1994

[Study of interaction between vitamin D2 and excipients by use of diffuse reflectance spectra].

The interaction of Vit D2 with calcium compounds and excipients commonly used was studied by use of diffuse reflectance spectra (DRS). The results indicated that there was some interaction between Vit D2 and calcium lactate, glucose, and a strong interaction between Vit D2 and magnesium stearate; and that the interaction between Vit D2 calcium gluconate, CaHPO4, sucrose, starch, lactose and mannitol was very weak and could even be neglected.

Drug Interactions↗

PubMed1994

[Effects of high-level-manganese sewage irrigation on children's neurobehavior].

The neurobehavioral status was tested for 92 matched-pair pupils aged 11-13 in an area with high-level-manganese sewage irrigation and a control area. Results showed there was significant difference in manganese contents of drinking water between the area with sewage irrigation and the control area during 1990-1992, ranged 0.241-0.346 mg/L and 0.030-0.040 mg/L, respectively, with P < 0.01. Hair manganese content of children in the area with sewage irrigation (1.252 micrograms/g) was significantly higher than that in the control area (0.961 micrograms/g) with P < 0.01. Scores in digit span, Santa Ana manual dexterity, digit symbol, Benton visual retention test and pursuit aiming test for children in the area with sewage irrigation were significantly lower than those in the control area (P < 0.01). Hair manganese contents of the children in the area with sewage irrigation correlated negatively with most of those scores. It suggested high level of manganese in drinking water of the area with sewage irrigation might be an important factor affecting children's neurobehavioral changes.

Adolescent↗

PubMed1994

Ethnic differences in disposition of antipyrine and acetaminophen between Tibetan and Han healthy volunteers.

The differences in disposition of antipyrine and acetaminophen between Tibetan and Han healthy volunteers were studied in a randomized crossover design. The half-life of antipyrine was found to be 18.8 +/- 4.89 h in 16 Han and 15.0 +/- 3.02 h in 17 Tibetan (P < 0.05) and the clearance was 1.35 +/- 0.37 L.h-1 in Han and 1.71 +/- 0.44 L.h-1 in Tibetan (P < 0.05). The half-life of acetaminophen was 3.1 +/- 0.86 h in Han and 3.2 +/- 1.12 h in Tibetan (P > 0.05). The experimental results indicate that the disposition of antipyrine between Tibetan and Han healthy volunteers significantly differed, the clearance of antipyrine in Tibetan increased by 20%, but the disposition of acetaminophen between the two ethnic groups showed no difference.

Acetaminophen↗

PubMed1994

Transformation of Solanum dulcamara protoplasts and regeneration of transgenic plants.

We have achieved successful transformation of Solanum dulcamara protoplasts by direct DNA uptake and regeneration of transgenic plants. The plasmids pDW2 carrying CAT gene and pCaMVNEO carrying NPTII gene were used. The electroporation voltage was 1500 V, which gave a field strength of 1500 V/cm with a time decay constant of 59.4 sec. The concentration of plasmid was 20 micrograms/2 x 10(6) protoplasts. Under these conditions, a very high transformation efficiency was obtained, with relative transformation frequency being up to 12.4% and absolute transformation frequency 2.4 x 10(-4). The activity of NPTII was detected in 75% of the kanamycin resistant calli and all of the plants regenerated from resistant calli. Southern blot analysis showed that the DNA sequence of NPTII gene derived from pCaMVNEO plasmid existed in the transformed plants of S. dulcamara.

Blotting, Southern↗

PubMed1993

Glycosphingolipids of rabbit, sheep, and pig thymus.

The thymus plays a major role in the immune system and many of the processes that occur in this tissue depend on cell-cell interactions. Glycoconjugates are known to mediate cell-cell interactions and thus to understand more fully the function of this class of compounds in thymus, structural characterization and quantification of the glycosphingolipids in thymus from sheep, rabbit, and pig were performed. Qualitative and quantitative differences were found for each species. Thymus from all three species contained neolacto (Gal beta 1-4GlcNAc) glycosphingolipids; however, significant differences in the types and quantities expressed by each animal were found. An evaluation of other classes of glycosphingolipids and their quantities demonstrate that pig thymus has a much different pattern of glycosphingolipid expression than sheep and rabbit thymus. The major glycosphingolipids in pig thymus are globo-series neutral glycosphingolipids (Gb3 and Gb4) and lactosyl-series gangliosides (GM3 and GD3). In contrast, sheep and rabbit thymus express significant levels of lacto and neolacto neutral glycosphingolipids, and also lacto and neolacto gangliosides, including three previously unidentified compounds. The major difference in glycosphingolipid expression in these two species was the presence of branched-chain gangliosides in sheep thymus.

Animals↗

PubMed1993

Albumin modulation of capillary permeability: role of endothelial cell [Ca2+]i.

Albumin is required in vascular perfusates to maintain the normal permeability of microvessel walls. The most common mechanism proposed for action of albumin involves binding to the endothelial cell surface to increase the resistance to water and solute flows through hydraulic pathways across the capillary wall. The results of the present experiments do not conform to this simple adsorption model. Ringer perfusion increased the hydraulic conductivity (Lp) of the wall of single perfused frog mesenteric microvessels by 4.0 +/- 0.5-fold. The increase in Lp was associated with an increase of cytoplasmic calcium concentration ([Ca2+]i) from 59 +/- 5 nM when albumin was in the perfusate to a transient peak of 181 +/- 13 nM, 1-2 min after Ringer perfusion. [Ca2+]i then fell back to close to 100 nM. Processes that reduced Ca2+ influx into endothelial cells (removal of extracellular Ca2+, membrane depolarization) reduced Ca2+ influx and attenuated the increase in [Ca2+]i. The same processes abolished the increase in Lp after Ringer perfusion and restored Lp to close to control values during Ringer perfusion. Thus Ca2+ entry into endothelial cells is required to initiate and maintain the increased permeability during Ringer perfusion.

Animals↗

PubMed1993

Differential actions of cAMP on endothelial [Ca2+]i and permeability in microvessels exposed to ATP.

We investigated the hypothesis that one of the actions of adenosine 3',5'-cyclic monophosphate (cAMP) to attenuate agonist-induced increase in microvessel permeability is to reduce the initial increase in endothelial cell cytoplasmic Ca2+ concentration ([Ca2+]i). ATP (10 microM) was used to increase hydraulic conductivity (Lp) and [Ca2+]i in venular microvessel in frog mesentery. The cAMP analogue, 8-bromo-cAMP (8-BrcAMP, 2 mM) significantly attenuated the initial increase in Lp (from a peak increase of 7.1 +/- 2.4 times control with ATP alone to 1.2 +/- 0.34 times control with ATP and cAMP). In contrast, cAMP did not significantly change the magnitude or time course of the biphasic increase in [Ca2+]i, which increased from 54 +/- 5 nM to peak of 187 +/- 48 nM with ATP alone, and from 55 +/- 8 nM to 190 +/- 28 nM with ATP and cAMP. Thus the action of cAMP to attenuate microvessel permeability increase in the presence of ATP does not involve modification of the initial Ca2+ transient in endothelial cells. Our results enable alternative hypotheses, such as the suggestion that cAMP might modulate a Ca(2+)-calmodulin-dependent actin-myosin cascade, to be investigated without the added complications of having to account for the modulation of initial changes in [Ca2+]i. Our data also demonstrate, for the first time in the endothelial cells of intact microvessels, that an increase in [Ca2+]i is not always associated with an increase in microvessel permeability.

Adenosine Triphosphate↗

PubMed1993

Microbially detoxified vomitoxin-contaminated corn for young pigs.

A performance trial was conducted to evaluate the effect of microbially detoxified moldy corn in a corn-soybean meal-based starter diet for young pigs. Moldy corn containing 450 ppm of vomitoxin replaced clean corn in a control diet to give a diet containing 5 ppm of vomitoxin. The same amount of moldy corn was microbially detoxified by incubation with the contents of the large intestine of chickens (CLIC) and then incorporated into the control diet to give a "detoxified" vomitoxin diet, which contained 2.1 ppm of vomitoxin. A paired diet was formulated by incorporating the untreated moldy corn into the control diet to give a diet containing the same level of vomitoxin as the "detoxified" vomitoxin diet. Clean corn was also treated with CLIC and replaced corn in the control diet to give a biologically treated control diet. Each diet was fed to six pigs (three gilts and three boars) for 5 d and then all pigs were changed to the control diet for a further 5-d feeding period. During the first 5-d feeding period, no differences were observed in pigs fed either the control diet or the biologically treated control diet. A diet containing 5 ppm of vomitoxin decreased the pigs' daily feed consumption, weight gain, and feed efficiency by 25, 57, and 45%, respectively, compared with the control diet (P < or = .05). Daily feed intake, weight gain, and feed efficiency in pigs fed the "detoxified" vomitoxin diet were 19, 54, and 37% greater, respectively, than for pigs fed the vomitoxin diet (P < or = .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1993

[Cardiac amyloidosis: an analysis of five cases].

Five patients with the diagnosis of cardiac amyloidosis established by autopsy and biopsy of noncardiac tissue were reported. All of the patients had cardiac dysfunction. Echocardiogram showed symmetrical thickness of left ventricle, increase of heart weight and reduction of left ventricular ejection fraction. Only two cases had "granular sparkling" on the ventricular wall. The clinical findings of cardiac amyloidosis are arrhythmias, conduction disturbances and intractable heart failure. Echocardiographic examination may reveal cardiac involvement and severity of pathological involvement and predict prognosis. The "granular sparkling" is not a specific feature for the diagnosis of cardiac amyloidosis. Biopsy of either noncardiac or cardiac tissue is required for correct diagnosis.

Amyloidosis↗

PubMed1992

The role of saccades in the perception of texture patterns.

We studied the perception of texture patterns when observers used saccadic eye movements to scan the display and when the line of sight was maintained in the display center without saccades. Saccades improved the discrimination of the size and the shape of a central randomly-shaped polygon for display durations > 1 sec. Saccades were more important with textures that did not readily segregate into target and background regions than with those that did. Directing saccades to the curvature extrema of the central target figure was more useful than directing them elsewhere. Saccades did not enhance texture segregation, but rather improved the discriminability of individual target and background elements by overcoming lateral interference. To the extent that strong lateral interference is inevitable with poorly-segregating textures, our results show that serial inspection is best carried out by sequences of saccades, not by sequences of attention shifts.

Attention↗

PubMed1992

Characterization of the tet(M) determinant of Tn916: evidence for regulation by transcription attenuation.

The nucleotide sequence of the tetracycline resistance determinant tet(M), located on conjugative transposon Tn916 of Enterococcus faecalis, was determined and found to encode a 72,486-dalton protein exhibiting a high degree of homology with other tet(M) determinants. A short open reading frame corresponding to a 28-amino-acid peptide and containing a number of inverted repeat sequences was noted immediately upstream of tet(M), suggesting that regulation might occur by a mechanism involving transcriptional attenuation. Transcription analyses found this to indeed be the case, showing that the expression of tet(M) resulted from an extension of a small transcript representing the upstream leader region into the resistance determinant. Exposure of cells to tetracycline resulted in a significant increase in the amount of tet(M) transcription; this increase could be explained on the basis of increased transcriptional read-through from the upstream transcript. A model suggesting how transcriptional attenuation might operate in this system is presented.

Amino Acid Sequence↗

PubMed1992

Microbial transformation of deoxynivalenol (vomitoxin).

Microbial inocula from rumen fluid, soil, and contents of the large intestines of chickens (CLIC) and of swine (SLIC) were tested for their ability to transform deoxynivalenol (vomitoxin) in vitro. Microorganisms in (CLIC) completely transformed pure vomitoxin, and this activity was retained through six serial subcultures. No alteration of the toxin by incubation with SLIC was detected, whereas 35% of the vomitoxin was metabolized in the original culture of rumen fluid and 50% was metabolized by the soil sample, though metabolism was decreased in subsequent subcultures of either sample. A single metabolite was isolated and identified as deepoxy vomitoxin. The increase in concentration of deepoxy vomitoxin in the culture medium corresponded with the decrease in vomitoxin concentration. The vomitoxin transformation rate was not affected by either the ratio of CLIC to vomitoxin (5 to 0.2 g of CLIC per mg of vomitoxin) or the initial concentration of vomitoxin (14 to 1,400 ppm) in the medium. Biotransformation of vomitoxin was completely inhibited when the pH in the medium was lowered to 5.20. Sodium azide at a 0.1% (wt/vol) concentration in the medium blocked the transformation of vomitoxin, suggesting that the deepoxidation of vomitoxin is an energy-dependent process. About 50% of the vomitoxin in moldy corn in culture medium was transformed by microorganisms from CLIC. The vomitoxin transformation rate in moldy corn was not affected when the concentration of CLIC changed from 0.2 to 0.8 g/ml of medium. Vomitoxin in the moldy corn was not transformed when CLIC were added to corn without culture medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Tandem cloning of bacteriophage T4 nrdA and nrdB genes and overproduction of ribonucleoside diphosphate reductase (alpha 2 beta 2) and a mutationally altered form (alpha 2 beta 2(93)).

To investigate the role of ribonucleoside diphosphate reductase in the deoxyribonucleoside triphosphate synthetase multienzyme complex induced by bacteriophage T4 infection and to study the expression of the T4 nrdA and nrdB genes, we have constructed separate plasmid expression strains overproducing their respective alpha 2 and beta 2 protein products. Because complementation of the two proteins to form an active alpha 2 beta 2 enzyme presented complications, nrdA and nrdB, each with its own tac promoter, were also cloned in tandem into a single expression vector. The resulting plasmid (pnrdAB) overproduces ribonucleoside diphosphate reductase. Phage T4 nrdB93, described by Wirak et al. (D. O. Wirak, K. S. Cook, and G. R. Greenberg, J. Biol. Chem. 263:6193-6201, 1988) contains a lesion in exon II of the gene. The mutation causes not only a temperature-sensitive inactivation of the catalytic structure of the beta 2(93) protein and of its ability to interact with alpha 2 protein to form the alpha 2 beta 2(93) enzyme but also a profound non-temperature-sensitive decrease in the formation of the beta 2(93) protein. An expression vector overproducing active alpha 2 beta 2(93) was constructed by site-directed mutagenesis of the nrdB gene.

Base Sequence↗

PubMed1992

Effect of ingestion of excess methionine diet on aging of erythrocytes in mice.

Accelerated senescence prone mice and resistant mice (SAM-P/1 and SAM-R/1) were fed 10% casein diet or that supplemented with 2.5% methionine (Met) diet for 4 weeks. Erythrocytes withdrawn from animals of each group were separated by density gradient centrifugation into four fractions of different cell density, that is, different age of erythrocytes, and were analyzed for the activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and the level of oxidized protein. Excess Met decreased the specific activity of GSH-Px in each fraction and the whole population of erythrocytes in SAM-P/1 but not in SAM-R/1. The changes in SOD activities were least significant among the erythrocyte fractions of every dietary group. The oxidized protein level in cell lysate increased with the increase of cell density in both strains of animals. These results were interpreted as indicating that excess Met had a positive effect on the erythrocytes senescence, and suggested that the activity of GSH-Px may be a useful enzymatic marker for the age of erythrocytes.

Animals↗

PubMed1992

[Study on the interaction between water-soluble vitamins by the "three-point-test" of differential scanning calorimetry].

The physico-chemical compatibility of solid-state pharmaceuticals is mainly determined by their interaction. The "Three-point-test" of differential scanning calorimetry in which three samples of different ratios are determined is proposed to study this interaction, and the simplified judging rules are as follows: If there are two or less than two endotherm peaks in DSC thermogram for all 3 ratio samples, we may mainly consider the peaks at lower temperature. If these temperatures are the same, which would be monotectic system or simple eutectic mixture, there will be very weak interaction in their solid state, and these could be compatible. If the temperatures are different, which would be solid solution system or solid complex system, there would be interaction in their solid state. If there is no endotherm peak, or there are exotherm peaks or there are more than two endotherm peaks, they all indicate that there is a stronger interaction in their solid state and they are incompatible. As an example, the interaction between water-soluble vitamins--Vit B1, Vit B2, Vit C and nicotinamide was determined. The results indicated that only Vit C is incompatible with nicotinamide, as there is a stronger interaction, and with Vit B1, there is a weak interaction.

Ascorbic Acid↗