Biomedical subjects

Z Yang

Publications and source records attributed to Z Yang.

At least 667 records · Page 37Linked to original sources

PubMed1996

Approximate methods for estimating the pattern of nucleotide substitution and the variation of substitution rates among sites.

We propose two approximate methods (one based on parsimony and one on pairwise sequence comparison) for estimating the pattern of nucleotide substitution and a parsimony-based method for estimating the gamma parameter for variable substitution rates among sites. The matrix of substitution rates that represents the substitution pattern can be recovered through its relationship with the observable matrix of site pattern frequences in pairwise sequence comparisons. In the parsimony approach, the ancestral sequences reconstructed by the parsimony algorithm were used, and the two sequences compared are those at the ends of a branch in the phylogenetic tree. The method for estimating the gamma parameter was based on a reinterpretation of the numbers of changes at sites inferred by parsimony. Three data sets were analyzed to examine the utility of the approximate methods compared with the more reliable likelihood methods. The new methods for estimating the substitution pattern were found to produce estimates quite similar to those obtained from the likelihood analyses. The new method for estimating the gamma parameter was effective in reducing the bias in conventional parsimony estimates, although it also overestimated the parameter. The approximate methods are computationally very fast and appear useful for analyzing large data sets, for which use of the likelihood method requires excessive computation.

Algorithms↗

PubMed1996

Studies on the mechanisms of stress wave propagation in the chest subjected to impact and lung injuries.

To gain some quantitative understanding of the nature and properties of stress wave propagation and the pathological characteristics of lung injuries, pressure values at eight sites in the lungs during an impact period were recorded. The lung injury severity scores in the corresponding regions were determined in 11 dogs, which were subjected to blunt, left lateral impact at a velocity of 16.33 m/sec with a 24.5% compressive response. The results showed that the pressure value at the contact point was the greatest and that pressure decreased significantly from left side to right side. However, at the left hilum a second pressure peak developed. The pressure value at the contact point was 0.68 and 0.50 times greater than those at left lung and left hilum, respectively. The speed at which the pressure at the contact point rose was much faster than the speed at other points. The lung injury scores at different sites corresponded well with the pressure values (p < 0.001). The data indicated that the reflection and refraction of the stress waves result in the accumulation of forces at some points, transferring more energy to the tissues at those points. Therefore, the severity of injury at these points in these tissues was more severe.

Animals↗

PubMed1996

Study on characteristics of blast-fragment combined injury in dogs.

It is known that blast wave and fragments are the primary causes of casualties from explosive weapons. To study the characteristics of blast-fragment combined injuries, functional and morphological changes were investigated in three groups of anesthetized dogs with blast injury, high velocity fragment extremity injury, and combined injuries of both types. The same parameters were also examined in a control group. Several of the functions investigated were systemic pressure, mean pulmonary arterial pressure (PAP), oxygenic partial pressure of arterial blood (Po2), thromboxane B2(TXB2), and 6-keto-prostaglandin F1 alpha (6-keto-PGF alpha). The morphologic study included gross, light microscopic, and transmission electronic microscopic observations. In the blast injury group, Po2 decreased and PAP, levels of blood plasma 6-keto-PGF alpha and level of TXB2 increased after injury, whereas PAP and level of 6-keto-PGF alpha decreased 24 hours after injury. The levels of 6-keto-PGF alpha and TXB2, in lung tissues, lung/body weight index were higher than those of the control group 24 hours after injury. The TXB2/6-keto-PGF alpha level in blood plasma increased slightly after injury, but showed no difference in lung tissue 24 hours after injury compared with the control group. The morphological changes showed that most of the animals sustained moderate lung injury. In the fragment injury group, Po2 decreased slightly and PAP increased slightly after injury; the levels of 6-keto-PGF alpha, TXB2 and TXB2/6-keto-PGF alpha in blood plasma increased after injury and were higher in lung tissue than in the control group 24 hours after injury. The lung/body weight index was nearly equal to that of control group. The morphological changes showed that only a few animals suffered from mild lung injury. In the combined injury group, Po2 and PAP changed in a manner similar to those of the other two injury groups but were more significantly. The level of blood plasma 6-keto-PGF alpha decreased gradually, whereas that of TXB2 increased permanently; thus, the levels of TXB2/6-keto-PGF alpha obviously increased after injury and were much higher than those in the other injury groups. The level of TXB2 in lung tissue was higher than that of the control group 24 hours after injury, but that of 6-keto-PGF alpha showed no change compared with that of the control group, and the level of TXB2/6-keto-PGF alpha was higher than in the other three groups. The morphological changes showed that most of animals sustained severe lung injury. It is concluded that extremity injury from high velocity fragment will aggravate lung blast injury. Changes in the levels of PGI2 and TXA2, can be used to determine the extent of injury in the three kinds of wounds. This may be useful for early diagnoses and rational treatment of the victims of explosion.

Animals↗

PubMed1996

Experimental studies on the hemodynamic changes after thoracic impact injury.

Hemodynamic changes were monitored in eight dogs subjected to blunt impact (velocity = 19m/s) in the cardiac region. There was a transitory cardiac arrest for 1 to 2 seconds in some animals after trauma. The heart rate decreased markedly at 30 minutes after trauma, and recovered at 4 hours. At 15 minutes after trauma, the cardiac index, stroke volume index, left ventricular stroke work index, and mean artery pressure were much lower than that before trauma (p < 0.05 or p < o.o1). However, the mean pulmonary artery pressure, pulmonary capillary wedge pressure, and central venous pressure at 30 minutes after trauma were higher than that before trauma (p < 0.05). The above changes recovered generally at 8 to 16 hours after trauma. The pathological results showed that superficial spotty or flat hemorrhages and ecchymoses were most common in the injured heart. Severe contusion on the anterior wall of the left or right ventricle was also seen.

Animals↗

PubMed1996

Relationship between the dynamic parameters and injury severity of chest subject to impact.

Seventeen dogs were subjected to blunt left lateral impact at velocities from 7.14 m/s to 19.05 m/s. The impacts to the thoracic wall were recorded by accelerometers fixed on the ribs at the impacted point and other areas. From this information the dynamic parameters (compression response, instantaneous deformation velocities, and viscous response) were calculated. The thoracic injury scores were recorded according to the Abbreviated Injury Scale (AIS-85). The results showed that the chest was a viscoelastic structure. The dynamic parameters of the chest wall were correlated with the physical parameters in exponential function or logarithmic function. There was a more significant relationship between viscous criterion and injury score among the various parameters. The relationship curve was sigmoid. The results indicated that the viscous response might be a valid parameter for indicating the severity of injury.

Animals↗

PubMed1996

Pathologic study of thoracic impact injury involving a movable impact pattern.

The left thoracic walls of 28 rabbits were subjected to lateral blunt impact in a movable impact pattern. The impact velocities ranged from 7.95 m/s to 16.13 m/s, and the compression response ranged from 15.69% to 46.14% of the thoracic width. The surviving animals were sacrificed at 6 hours after trauma and were autopsied. Injury scores were assigned according to the hemorrhage area and the injury type (e.g., rupture or rib fracture). When compared with the pathologic characteristics of the thoracic injury involving a relatively static impact pattern, the severity of thoracic injury involving a movable impact pattern was milder. Also there were more significant differences in the severity of injury to lungs and ribs on the left as compared with the right sides. The viscous criterion is still a good parameter reflecting the severity of injury to lungs and heart. The severity of rib injury was mainly related to compression response.

Animals↗

PubMed1996

Biological effects of weak blast waves and safety limits for internal organ injury in the human body.

One hundred and seventeen adult sheep of both sexes, each weighing 15.2-42.4 kg, were used for this study. The purpose of this study was to investigate the relationship of the physical parameters of the waves to internal organ injury by exposing sheep to weak blast waves in TNT (trinitrotoluene) explosions, biological shock tube, and gun muzzle blasts. The results showed that the organ most sensitive to the TNT explosion was the lungs, whereas the upper respiratory tract was most sensitive to muzzle blast waves. The injury thresholds of overpressure were 29.0, 29.5, and 41.2 kPa for upper respiratory tract, lungs, and gastrointestinal tract respectively at a single exposure. Repeated exposure to 60 blasts reduced the injury threshold of the internal organs. The injury thresholds for upper respiratory tract, lungs, and gastrointestinal tract were 21.0, 18.0, and 40.4 kPa, respectively. The duration of overpressure of weak blast waves was 2.4-4.2 milliseconds, which did not significantly affect the severity of injury. The safety limits of weak blast waves to internal organ injury of human body were as follows: Ps = 37-3Ln.Tc.N/4(Tc.N < or = 1000) and Ps = 20.4(Tc.N > 1000). The results suggest that repeated exposures decrease the injury threshold of the internal organs. The safety limits proposed could protect 90% of the exposed population against internal organ injury caused by weak blast waves.

Animals↗

PubMed1996

Pathologic study of thoracic impact injury involving a relatively static impact pattern.

Fifty-five rabbits were subjected to left thoracic wall lateral blunt impact involving a relatively static impact pattern. The impact velocities ranged from 7.92 m/s to 16.33 m/s and the compression response ranged from 14.08% to 45.84% of the thoracic width. The surviving animals were sacrificed 6 hours after trauma and autopsies were performed. The lung was divided into bronchial and alveolar regions. Injury scores were assigned according to the hemorrhage area and the injury type (e.g., rupture or rib fracture). The results showed that the severity of bronchial injury was greater than alveolar injury when the impact velocity was low. However, alveolar injury was much more severe than bronchial injury at all levels of impact displacement when the impact velocity was high. The ratio of left/right lung injury decreased when the product of impact velocity and compression criterion increased. The latter was also well correlated with the severity of lung and heart injuries. In addition, the severity of rib injury was mainly related to compression response.

Animals↗

PubMed1996

Protein farnesyltransferase in plants: molecular characterization and involvement in cell cycle control.

Farnesylation is required for membrane targeting, protein-protein interactions, and the biological activity of key regulatory proteins, such as Ras small GTPases and protein kinases in a wide range of eukaryotes. In this report, we describe the molecular identification of a plant protein farnesyltransferase (FTase) and evidence for its role in the control of the cell cycle in plants. A pea gene encoding a homolog of the FTase beta subunit was previously cloned using a polymerase chain reaction-based strategy. A similar approach was used to clone a pea gene encoding a homolog of the FTase alpha subunit. The biochemical function of the pea FTase homologs was demonstrated by the reconstitution of FTase enzyme activity using FTase fusion proteins coexpressed in Escherichia coll. RNA gel blot analyses showed that levels of FTase mRNAs are generally higher in tissues, such as those of nodules, that are active in cell division. The relationship of FTase to cell division was further analyzed during the growth of suspension-cultured tobacco BY-2 cells. A biphasic fluctuation of FTase enzyme activity preceded corresponding changes in mitotic activity at the early log phase of cell growth. Moreover, manumycin, a specific inhibitor of FTase, was effective in inhibiting mitosis and growth in these cells. Using synchronized BY-2 cells, manumycin completely blocked mitosis when added at the early S phase but not when added at the G2 phase. These data suggest that FTase is required for the plant cell cycle, perhaps by modulating the progression through the S phase and the transition from G1 to the S phase.

Alkyl and Aryl Transferases↗

PubMed1996

Sequence comparison of mitochondrial tRNA genes and origin of light strand replication in Bos taurus and Nellore (Bos indicus) breeds.

Although the complete bovine mitochondrial DNA molecule has been previously sequenced and sequence comparisons of the mitochondrial displacement loop have been performed, detailed sequence information is limited on coding regions of mitochondrial DNA within and among breeds of Bos taurus and Bos indicus. This study analysed polymorphism of the mitochondrial DNA transfer RNA genes for tryptophan, alanine, asparagine, cysteine, tyrosine and the origin of light strand replication among Ayrshire, Canadian, Belgium Blue, Brown Swiss, Hereford, Jersey, Limousine, Piedmontaise, Red Angus, Simmental (Bos taurus) and a Nellore (Bos indicus). Nucleotide sequence analysis of a 420-bp fragment of mitochondrial DNA comprising the five transfer RNA genes showed 100% homology among single individuals of the Bos taurus breeds. The Nellore breed showed guanine to adenine substitutions in the DHU arm of asparagine tRNA and in the origin of light-strand replication. This equates to a 0.5% sequence difference between the Nellore and Bos taurus breeds and may reflect an independent evolutionary origin of the species.

Animals↗

PubMed1996

Evaluation of method for secondary DNA typing of Mycobacterium tuberculosis with pTBN12 in epidemiologic study of tuberculosis.

Secondary fingerprinting of Mycobacterium tuberculosis DNA with a probe containing the polymorphic GC-rich repetitive sequence present in pTBN12 has been found to have greater discriminating power than does fingerprinting with the insertion sequence IS6110 for strains carrying few copies of IS6110. To validate the use of pTBN12 fingerprinting in the molecular epidemiology of tuberculosis, M. tuberculosis isolates from 67 patients in five states in the United States and in Spain were fingerprinted with both IS6110 and pTBN12. Epidemiologic links among the 67 patients were evaluated by patient interview and/or review of medical records. The 67 isolates had 5 IS6110 fingerprint patterns with two to five copies of IS6110 and 18 pTBN12 patterns, of which 10 were shared by more than 1 isolate. Epidemiologic links are consistently found among patients whose isolates had identical pTBN12 patterns, whereas no links were found among patients whose isolates had unique pTBN12 patterns. This suggests that pTBN12 fingerprinting is a useful tool to identify epidemiologically linked tuberculosis patients whose isolates have identical IS6110 fingerprints containing fewer than six fragments.

Bacterial Typing Techniques↗

PubMed1996

Usefulness of the secondary probe pTBN12 in DNA fingerprinting of Mycobacterium tuberculosis.

A comparison was made between DNA fingerprints of Mycobacterium tuberculosis produced with the insertion sequence IS6110 and those produced with the polymorphic GC-rich repetitive sequence contained in the plasmid pTBN12. A total of 302 M. tuberculosis isolates from the prison system in Madrid, Spain, and the Denver Public Health Department (Denver, Colo.) were analyzed with the two probes. Both probes identified the same isolates in the same clusters when the fingerprints had six or more copies of IS6110. Analysis of isolates with unique IS6110 fingerprints demonstrated that they were unique with pTBN12. The pTBN12 probe had greater discriminating power in isolates having five or fewer copies of IS6110. Forty-seven isolates from Denver having fewer than five copies of IS6110 which were grouped in 11 clusters with identical fingerprint patterns were subdivided into 35 different patterns by pTBN12. Isolates with IS6110 fingerprints with more than six copies of IS6110 that differed from one another by only one or two hybridizing bands were analyzed with pTBN12. Most of these sets of isolates demonstrated identical patterns with pTBN12. However, some exceptions were observed, suggesting that those having nearly identical IS6110 patterns should not necessarily be included in the same cluster. Since IS6110 provides more polymorphism in the fingerprint, it is most useful in identifying isolates with unique fingerprint patterns and those in clusters in which the isolates contain six or more copies of the insertion. However, it is necessary to employ a secondary probe, such as pTBN12, to discriminate isolates with five or fewer copies of IS6110 and those with similar but not identical IS6110 patterns.

DNA Fingerprinting↗

PubMed1996

Kashin-Beck disease: radiographic appearance in the hands and wrists.

PURPOSE: To review the radiographic changes of Kashin-Beck disease (KBD) in the hands and wrists and provide a method for the diagnosis, staging, and evaluation of the effectiveness of prevention and treatment of this disease. To perform radiographic-histologic correlation to facilitate an early diagnosis of KBD. MATERIALS AND METHODS: Hand and wrist radiographs in 300 children and five autopsy cases with KBD from an endemic area of China were analyzed for radiographic changes in the epiphyseal plates, bone ends, epiphyses, and carpal bones. Histopathologic sections of the hand and wrist from five autopsies were studied for comparison with corresponding radiographs. RESULTS: The chief histopathologic changes in KBD included chondronecrosis, secondary repair, and remodeling processes. These histopathologic stages occurred in isolation or simultaneously in a patient. The radiographic and histopathologic changes within cartilage were related specifically to the different sites of cartilage. CONCLUSION: Radiographic changes in the hands and wrists in patients with KBD result from atrophy and necrosis of chondrocytes and their subsequent repair processes in the deep layer of growing cartilage.

Carpal Bones↗

PubMed1996

Motor neuron disease in Hong Kong Chinese: epidemiology and clinical picture.

This study documents the clinical features, incidence and prevalence of motor neuron disease (MND) in Hong Kong Chinese. Patients with MND who were alive between 1989 and 1992 were recruited by retrieval of medical records from the four major hospitals in Hong Kong, and by referral of neurologists, neurosurgeons and medical consultants. Mortality statistics was provided by the Census and Statistics Department. A total of 84 cases were identified with a male preponderance of 1.98:1. The average annual period incidence was 0.31/100,000 and the point prevalence on December 31, 1992, was 0.95/100,000. The mean age at onset was 55.5 years (range 19-81) with a peak observed from 55 to 65 years. The clinical features are similar to other reported series of MND. The incidence and mortality of MND in Hong Kong are therefore lower than the worldwide figures of 2.0/100,000 and 1.5/ 100,000, respectively.

Adult↗

PubMed1996

Identification of calcium-dependent phospholipase A2 isoforms in human and rat pancreatic islets and insulin secreting beta-cell lines.

Phospholipase A2 (PLA2) and its end product, arachidonic acid, are thought to be important signaling components in insulin secretion from pancreatic beta-cells. Because there are multiple Ca2+ -dependent and independent PLA2 biochemical activities in beta-cells, we have used a combination of molecular and immunological techniques to identify the isoforms of Ca2+ -dependent PLA2 present in pancreatic beta-cells. Total RNA extracted from the purified rat and human pancreatic islets and from insulin-secreting beta-TC3 and beta-HC6 cells was used as a template for complementary DNA (cDNA) synthesis. The RT-PCR was performed based on the oligonucleotide primers designed for the 14- kDa type II PLA2 and the 85-kDa cytosolic PLA2. The PCR products for both enzymes yielded single bands (375 bp and 910 bp for type II PLA2 and cytosolic PLA2, respectively). The PCR-generated cDNA fragments were confirmed to be identical to the type II and cytosolic PLA2 isoforms expressed in rat tissues, U937 cells, and A9 cells by DNA sequencing of the PCR products. The presence of these two isoforms of PLA2 was further confirmed by immunoblotting of extracts of pancreatic islets and beta-cells using specific antibodies directed toward each type of PLA2. Demonstration of the presence of type II and cytosolic PLA2 isoforms in islets provides the framework for further investigation of the regulation of PLA2 isoforms and their role in insulin secretion.

Animals↗

PubMed1996

Affinity for the insulin-like growth factor-II (IGF-II) receptor inhibits autocrine IGF-II activity in MCF-7 breast cancer cells.

We have investigated the autocrine regulation of insulin-like growth factor-II (IGF-II) signaling by the insulin-like growth factor-I receptor (IGF-IR) and the insulin-like growth factor-II/mannose 6-phosphate receptor (IGF-IIR) in MCF-7 breast cancer cells, employing retroviruses encoding both IGF-I, IGF-II, and IGF-I and II mutants with reductions in affinity for either the IGF-IR or the IGF-IIR. These studies revealed reciprocal roles for IGF-IR and IGF-IIR affinity in the regulation of autocrine IGF-II activity. IGF-IR affinity was required for serum-free proliferation but also for efficient IGF-II secretion. In contrast, cellular proliferation, receptor tyrosine kinase-dependent signaling, and extracellular IGF-II protein accumulation were all reduced in the presence of IGF-IIR affinity. Inhibition of IGF-II signaling appeared to be the sole consequence of IGF-IIR affinity, as no cellular responses attributable to selective IGF-IIR binding by a reduced IGF-IR affinity IGF-II mutant could be detected. By operating as an IGF-II antagonist, the IGF-IIR has tumor suppressor-like properties, a suggestion consistent with reports of loss of heterozygosity at the IGF-IIR locus in a variety of human malignancies.

Amino Acid Sequence↗

PubMed1996

Kallistatin in human ocular tissues: reduced levels in vitreous fluids from patients with diabetic retinopathy.

PURPOSE: Kallistatin is a serine proteinase inhibitor, which binds to tissue kallikrein and inhibits its proteolytic activity. This study is to determine the expression, cellular localization and the potential function of kallistatin in the eye. METHODS: Tissue kallikrein-kallistatin complex formation was performed to detect the kallikrein-binding activity in ocular tissues. Immunoreactive kallistatin was detected and quantified by an enzyme-linked immunosorbent assay using polyclonal antibody specific to human kallistatin. In situ hybridization histochemistry was employed to localize the kallistatin mRNA in human eyes using an antisense riboprobe of kallistatin. RESULTS: We have identified active kallistatin in the cornea, ciliary body, sclera, choroid, optic nerve, retina, vitreous and aqeous fluids. Kallistatin binds to tissue kallikrein and forms an SDS-stable complex. Immunoreactive kallistatin was identified in these tissues. Linear dose-dependent curves of the tissue extracts of the retina and choroid are parallel to that of purified human kallistatin, suggesting their immunological identity. The kallistatin mRNA was identified in the ciliary muscle, lens epithelial cells, all the layers of retina cells, optic nerve, choroid and vascular endothelial cells. These cells were not stained by the sense riboprobe under the same conditions, indicating the specificity of the hybridization. We also compared immunoreactive kallistatin levels in vitreous fluids from 18 patients with diabetic retinopathy and 17 non-diabetic subjects. The results show that diabetic subjects have significantly lower kallistatin levels (233.0 +/- 14.6 ng/mg protein) compared to non-diabetic subjects (334.1 +/- 26.9 ng/mg protein). CONCLUSIONS: Kallistatin is produced endogenously in the eye and the decrease in the vitreous kallistatin levels may be involved in diabetic retinopathy.

Adult↗

PubMed1996

[Effects of frostbite on some factors of blood coagulation system in rats under hypoxia].

The changes of some factors of blood coagulation system in rats following frost-bite of both hind feet under hypoxia were investigated. Male Wistar rats weighed 200 +/- 20g were divided into four groups: normal control (C); frostbite at normoxia (FN); frostbite during acute hypoxia (FAH) and frostbite during hypoxia after altitude acclimation (FHAC). Bleeding time and clotting time, rate of clot-retraction, plasma content of 6-keto-PGF1 alpha and TXB2 were determined following exposure to cold. The results showed that bleeding time and clotting time were shortened, and rate of clot-retraction was decreased, plasma content of 6-keto-PGF1 alpha and TXB2, T/P ratio were increased significantly after exposure to cold in all frostbite groups, but these changes were more prominent in FHAC than those in FN and FAH. The results demonstrated that there were changes in blood coagulation system following cold injury, blood coagulability was increased. These changes were closely related to the degree of frostbite. In addition, the degree of cold injury was aggravated by altitude acclimation and this may play an important role in the pathological process of dysfunction leading to necrosis of local frostbite tissue.

Acclimatization↗