Biomedical subjects

P He

Publications and source records attributed to P He.

At least 19 recordsLinked to original sources

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↗

PubMed1991

The causes and complications of late diagnosis of foreign body aspiration in children. Report of 210 cases.

Late diagnoses of foreign body aspiration were defined as occurring beyond 3 days between the aspiration of the foreign body, or onset of symptoms, and correct diagnosis. We reviewed a total of 210 children with late diagnosis of foreign body aspiration. The causes creating late diagnosis of foreign body aspiration in children were as follows: (1) parental negligence (106/210, 50%); (2) misdiagnosis by the fellow professionals and pediatricians (39/210, 19%); (3) the normal chest roentgenographic findings (29/210, 14%); (4) lack of typical symptoms and signs (26/210, 12%); (5) mismanagement (8/210, 4%); and (6) a negative bronchoscopic finding (2/210, 1%). The most common complications encountered were obstructive emphysema (77/186, 41%), mediastinal shift (63/186, 34%), pneumonia (43/186, 24%), and atelectasis (33/186, 18%) in 186 patients who underwent a chest roentgenographic examination. The incidence of major complications was 64% (48/75) in the children who were diagnosed within 4 to 7 days; however, the complication rate was 70% (39/56) in those with a delay in diagnosis of 15 to 30 days, and 95% (20/21) in the cases with a delay in diagnosis of over 30 days after aspirating the foreign bodies.

Child, Preschool↗

PubMed1991

Nucleotide sequence of the gelatinase gene (gelE) from Enterococcus faecalis subsp. liquefaciens.

The gene coding for gelatinase (also called metalloendopeptidase II; microbial proteinase, EC 3.4.24.4) of Enterococcus faecalis subsp. liquefaciens strain OG1-10 was cloned in an Escherichia coli-Enterococcus shuttle vector, and its nucleotide sequence was determined. The DNA sequence encodes one large open reading frame (ORF) with 509 amino acid residues. The ORF contains a signal sequence in its N-terminal region, whereas the N-terminal amino acid sequence determined from the purified extracellular proteinase starts at residue 192 deduced from the ORF. This implies that the gelatinase is synthesized as a prepropolypeptide or prezymogen. The mature gelatinase contains 318 amino acid residues (molecular weight, 34,582) and has significant homology with neutral proteinases from Bacillus species and elastase from Pseudomonas aeruginosa.

Amino Acid Sequence↗

PubMed1991

Depolarization modulates endothelial cell calcium influx and microvessel permeability.

We investigated the mechanisms whereby high-potassium (57.9 mM) Ringer solutions attenuate the increase in permeability caused when microvessels are exposed to the calcium ionophores ionomycin and A23187 (5 microM). In single perfused microvessels we measured cytoplasmic calcium concentration, [Ca2+]i, in the cells forming the microvessel wall and the hydraulic conductivity, Lp, to follow changes in the permeability of the microvessel walls. In normal Ringer solution, [Ca2+]i was increased to an initial peak value of 226 +/- 12 nM after exposure to calcium ionophores; the corresponding increase in microvessel Lp was 10.3 +/- 2.6 times control. With high-potassium solutions, the peak value of [Ca2+]i was 133 +/- 12 nM and Lp was increased to only 2.5 +/- 0.7 times control. Increasing extracellular calcium from 1.1 to 5 mM with high potassium restored the initial peak value of [Ca2+]i to 303 +/- 38 nM. The increases in both [Ca2+]i and Lp were abolished in calcium-free solutions. If high-potassium solutions depolarize the cells forming the microvessel wall as indicated by the membrane potential-sensitive dye bisoxonol, then the magnitude of the initial increase in [Ca2+]i could be accounted for by changes in the electrochemical driving force through conductive channels for calcium ion. Our results conform to the hypothesis that the permeability properties of microvessels are modulated by changes in the membrane potential of the endothelial cells and/or pericytes forming the microvessel wall.

Animals↗

PubMed1991

Inhalation of foreign bodies in Chinese children: a review of 400 cases.

A retrospective review of 400 Chinese children who had inhaled foreign bodies was undertaken. There has been a yearly increase in the total number of cases of airway foreign bodies removed in our hospital. Fifty-eight percent of the children presenting were from the countryside; 42% were townspeople. Approximately 90% of the patients were under 3 years of age, with the peak incidence of foreign body inhalation occurring between 1 and 2 years of age (57.8%). The male-female ratio was about 1.2:1. About 95% of the removed foreign bodies were organic in origin. The majority of the foreign bodies were found most often in the right bronchial tree (46%). A positive history of foreign body inhalation was obtained in 98% of the cases. Twenty-eight percent of the children presented at the hospital within 24 hours, 71% within 1 week, and 29% more than 1 week after inhaling the foreign body. The most common presenting symptoms of laryngotracheal foreign bodies were cough, wheezing, dyspnea, and hoarseness; those of bronchial foreign bodies were cough, wheezing, decreased air entry, and rhonchi. More than two-thirds of the children with larygotracheal foreign bodies had normal x-ray findings. The most common fluoroscopic findings in those children with bronchial foreign bodies were mediastinal shift (36.8%), obstructive emphysema (35.7%), and normal findings (35%). A total of 348 (87%) bronchial foreign bodies were removed by rigid bronchoscopy (81%), rod-lens bronchoscopy (5%), and spontaneous expulsion (1%); 52 (13%) laryngeal and tracheal foreign bodies were removed by direct laryngoscopy (12%) and tracheotomy (1%). A single endoscopic procedure successfully removed 92.5% of 400 foreign bodies detected in the airways. One child died during bronchoscopy, for a mortality rate of 0.25%.

Adolescent↗

PubMed1990

Regulation of the expression of Gal alpha 1-3Gal beta 1-4GlcNAc glycosphingolipids in kidney.

Previous studies (Galili, U., Clark, M. R., Shohet, S. B., Buehler, J., and Macher, B. A. (1987) Proc. Natl. Acad. Sci. U. S. A. 84, 1369-1373; Galili, U., Shohet, S. B., Korbrin, E., Stults, C. L. M., and Macher, B. A. (1988) J. Biol. Chem. 263, 17755-17762) have established that there is a unique evolutionary distribution of glycoconjugates carrying the Gal alpha 1-3Gal beta 1-4GlcNAc epitope. These glycoconjugates are expressed by cells from New World monkeys and non-primate mammals, but not by cells from humans, Old World monkeys, or apes. The lack of expression of this epitope in the latter species appears to result from the suppression of gene expression for the enzyme UDP-galactose:nLc4Cer alpha 1-3-galactosyltransferase (alpha 1-3GalT) (Joziasse, D. H., Shaper, J. H., Van den Eijnden, D. H., Van Tunen, A. J., and Shaper, N. L. (1989) J. Biol. Chem. 264, 14290-14297). Although many non-primate species are known to express this carbohydrate epitope, the nature (i.e. glycoprotein or glycosphingolipid) of the glycoconjugate carrying this epitope is only known for a few tissues in a few animal species. Furthermore, it is not known whether all animal species express this epitope in the same tissues. We have investigated these questions by analyzing the glycosphingolipids in kidney from several non-primate animal species. Immunostained thin layer chromatograms of glycosphingolipids from sheep, pig, rabbit, cow, and rat kidney with the Gal alpha 1-3Gal beta 1-4GlcNAc glycosphingolipid-specific monoclonal antibody, Gal-13, demonstrated that kidney from all of these species except rat contained Gal alpha 1-3Gal beta 1-4GlcNAc neutral glycosphingolipids. A lack of expression of Gal alpha 1-3Gal beta 1-4GlcNAc glycosphingolipids in rat may be due to the lack of expression of the enzyme (alpha 1-3GalT) which catalyzes the formation of the Gal alpha 1-3Gal nonreducing terminal sequence of these compounds or to the lack of expression of glycosyltransferases which are necessary for the synthesis of the neolacto core structure of these compounds. These possibilities were evaluated in two ways. First, the three enzymes (UDP-N-acetylglucosamine:LacCer beta 1-3-N-acetyl-glucosaminyltransferase, UDP-galactose:Lc3Cer beta 1-4-galactosyltransferase, and alpha 1-3GalT) involved in the synthesis of the Gal alpha 1-3Gal beta 1-4GlcNAc glycosphingolipids were assayed using an enzyme-linked immunosorbent assay-based assay system and carbohydrate sequence-specific monoclonal antibodies. Second, TLC immunostaining was done to determine if the glycosphingolipid precursors (i.e. Lc3Cer and nLc4Cer) are expressed in rat kidney. Interestingly, rat kidney had a relatively high level of alpha 1-3GalT activity compared with the other animals tested.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1990

Radiological diagnosis of aspirated foreign bodies in children: review of 343 cases.

In our series of 400 Chinese children with foreign body aspiration (FBA), 343 cases were evaluated by fluoroscopy and/or plain chest X-rays before endoscopic removal of the foreign bodies. The majority of the foreign bodies (FBs) were organic (378/400, 94.5 per cent). The results showed that mainstem bronchial foreign bodies were diagnosed correctly in 68 per cent of cases compared with 65 per cent correct diagnoses with segmental bronchial foreign bodies, but only 22 per cent correct diagnoses with tracheal, and 0 per cent correct diagnosis in those with laryngeal foreign bodies. Eighty per cent (32/40) of the children with laryngotracheal FBs had normal X-ray findings, whereas 67.7 per cent (205/303) of the children with bronchial FBs had abnormal chest X-ray findings. The most common positive radiological signs in the children with tracheobronchial FBs were obstructive emphysema (131/213, 62 per cent) and mediastinal shift (117/213, 55 per cent). The incidence of major complications was related not only to the size of the foreign body and its location but also the duration since aspiration. The most common types of bronchial obstructions by airway FBs are discussed.

Adolescent↗

PubMed1990

Bacteriophage T4 nrdA and nrdB genes, encoding ribonucleotide reductase, are expressed both separately and coordinately: characterization of the nrdB promoter.

We examined the expression of the bacteriophage T4 nrdA and nrdB genes, which encode the alpha 2 and beta 2 subunits, respectively, of ribonucleoside diphosphate reductase, the first committed enzyme in the pathway of synthesis of the deoxyribonucleoside triphosphates. T4 nrdA, located 700 bp upstream from nrdB, has been shown previously to be transcribed by two major transcripts: a prereplicative, polycistronic message, TU, orginating at an immediate-early promoter, PE, that is 3.5 kb upstream from nrdA, and a postreplicative message commencing from a late promoter in its 5' flank. We have found a third promoter initiating a transcript at 159 nucleotides upstream from the reading frame of nrdB. PnrdB functions only in the presence of the T4 motA gene product, which is required for middle (time) promoters, and therefore the onset of nrdB transcription is delayed more than 2 min after infection. Because of the distance of nrdA from PE, the inception of nrdA transcription (delayed early) coincides closely with that of nrdB. An apparent termination site, tA, occurs about 80 bp downstream from nrdA. Some of the polycistronic mRNA reading through the site after 5 min contributes to nrdB transcription. nrdA and nrdB genes in an uninfected host have been reported to be transcribed only coordinately. In contrast, T4 nrdA and nrdB are initially transcribed separately onto the PE and PnrdB transcripts, respectively, but at about 5 min after infection are transcribed both coordinately and on separate transcripts. Evidence is presented that TU coordinately transcribes a deoxyribonucleotide operon in the order: frd, td, gene 'Y,' nrdA, nrdB. Since the beta 2 subunit is known to be formed after the alpha 2 subunit, the expression of the nrdB gene determines the onset of deoxyribonucleoside triphosphate synthesis and thus of T4 DNA replication.

Base Sequence↗

PubMed1990

Measurement of cytoplasmic calcium in single microvessels with increased permeability.

We investigated the hypothesis that an increase in cytoplasmic calcium ion concentration, [Ca2+]i, is one of the mechanisms responsible for increased microvessel permeability. We loaded the cells forming the walls of individually perfused microvessels in frog mesentery with fura-2 and measured [Ca2+]i in the control state and after adding the Ca2+ ionophore ionomycin to the perfusate. [Ca2+]i in the control state was 65 +/- 6 nM and increased to an initial peak of 285 +/- 29 nM after 1-3 min. After 4, 6, and 10 min, [Ca2+]i was 199 +/- 18, 163 +/- 16, and 129 +/- 9 nM, respectively. [Ca2+]i fell back to 77 +/- 7 nM after ionophore was removed. In similar experiments, hydraulic conductivity (Lp) increased to a peak of 9.5 times control after 1-3 min, then fell to 2.0 times control after 6 min. Lp remained elevated at this level for as long as ionophore was present in the perfusate. [Ca2+]i modulates the initial and sustained phases of the permeability increase. Both processes depend on external Ca2+ influx. Our experiments provide the first direct measurement of [Ca2+]i during a change in the permeability of an intact microvessel.

Animals↗

PubMed1990

Manipulation of porcine carcass composition by ractopamine.

The effect of dietary ractopamine and protein level on growth performance, individual muscle weight and carcass composition of finishing pigs were evaluated in two experiments. Twelve barrows and 12 gilts (Exp. 1) and 32 barrows (Exp. 2) with an average initial weight of 64 kg were penned individually and offered ractopamine at 0 or 20 ppm in diets containing 13 or 17% CP in 2 x 2 factorial experiments for 28 d. In both experiments, dietary ractopamine improved daily gain (P less than .1) and gain-to-feed ratio (P less than .05) at 17% dietary protein level but depressed these response criteria at 13% protein level. Leaf fat was reduced (P less than .05) and longissimus muscle depth was increased (P less than .1) by feeding ractopamine regardless of dietary CP concentration. Longissimus, psoas major, semitendinosus, biceps and quadriceps femoris (P less than .05) and tensor facia latae (P less than .1) muscles were 8 to 22% heavier with ractopamine feeding at 17% dietary CP level. Results from both trials suggest that ractopamine improves growth rate and carcass leanness at the higher dietary protein level but improves only carcass leanness at the lower protein level.

Adipose Tissue↗

PubMed1989

Parameter estimation for nonlinear frequency dependent attenuation in soft tissue.

Most current attenuation estimation methods are based on an assumption that tissue attenuation is linearly frequency dependent. For tissues exhibiting nonlinear attenuation, such methods could produce biased results. This paper describes a new time-domain, amplitude method for estimating two parameters, beta and n, in nonlinear attenuation. In this method, echo signal of each A-line is first filtered in parallel by a bank of narrow-bandpass filters. Attenuation values at filter center frequencies can be calculated from the envelope peaks of each filtered narrowband signal, and beta and n are then estimated from these attenuation values. A quantitative study of the estimation uncertainty indicates that there is a significant increase in the variance of beta estimate when the attenuation model is changed from linear to nonlinear. The analysis yields insights into the tradeoff between estimation accuracy and estimation precision when tissue attenuation is only slightly deviated from linearity.

Connective Tissue↗

PubMed1989

[Serological survey of cytomegalovirus infection in Guizhou].

From August to October 1987, 577 serum samples were examined for the presence of CMV-IgG antibody by using indirect ELISA in Guizhou. The positive rate of CMV antibody varied from 87.5 to 92.4% in three areas and from 80.9-94.9% in various ages groups. It was suggested that the main transmission route of CMV infection in early life might be transmitted from mothers to their infants, but there might be some close contact transmission in population. The results showed that CMV infection was common in Guizhou. It was necessary to study further the correlation between CMV infection and birth defects.

Adolescent↗

PubMed1989

[Kinetics of solid-state decomposition of aspirin].

The kinetics of the solid-state decomposition of aspirin was studied at 85 degrees, 80 degrees, 75 degrees, 70 degrees C and various relative humidities. Decomposition percentage of aspirin (x) and time (t) could be described by the equation: x = ktn where k is a constant which depends on the temperature and relative humidity. The water vapour pressure effected on the solid-state decomposition of aspirin may be presented by the Arrhenius equation: k = A.exp (-E/RT).Ps where T is the absolute temperature, P is water vapour pressure, s is a constant, R is the gas constant, A is another constant, E is the activation energy. From this equation, the activation energy of the decomposition of aspirin is calculated to be 122.17kJ.mol-1 (29.2 kcal.mol-1).

Aspirin↗