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Z Lou

Publications and source records attributed to Z Lou.

35 records · Page 2Linked to original sources
PubMed1995

Tree-structured prediction for censored survival data and the Cox model.

Prediction trees for the analysis of survival data are discussed. It is shown that trees are useful not only in summarizing the prognostic information contained in a set of covariates (prognostic classification), but also in detecting and displaying treatment-covariates interactions (subgroup analysis). The RECPAM approach to tree-growing is outlined; prognostic classification and subgroup analysis are then formulated within the RECPAM framework and on the basis of the Cox proportional hazards models with a priori strata. Two examples of data analysis are presented. The issue of cross-validation is discussed in relation to computationally cheaper model selection criteria.

Algorithms↗
PubMed1995

[Effects of Chinese herbs on impaired lymphocyte functions after thermal injury in mice].

Four Chinese herbs were chosen for this study. They were Panax pseudoginseng wall (PPW), Loniconica japonica thunb (LJT), Polygonum cuspidatum (PC) and Jilin ginseng (JG). They were given from the 2nd to the 7th postburn day (PBD). The results showed that the response to antigen signal, the proliferative capacity, the interleukin II production function, and the antibody production ability by lymphocytes in control burned mice were more noticeably reduced than that in the normal mice. The PPW, LJT, PC might restore all the impaired functions in different degrees. The JG showed no effect at all.

Animals↗
PubMed1994

An ellipsoid farrowing crate: its ergonomical design and effects on pig productivity.

An ellipsoid farrowing crate was designed and compared to the conventional rectangular crate with regard to its effect on sows' production traits. The main features of this crate are its oval horizontal frame and bowed vertical bars. Thirty-two sows farrowed in each system. Those in the ellipsoid crates raised 318 pigs and those in the rectangular crates raised 304. Stillbirth rate was lower in the ellipsoid crates than in the rectangular crates (P < .05). Among pigs born live, no significant difference due to crate was found on the deaths by crushing, infection, and other causes. The overall pigs' weaning rate from total births was also similar in both crates (P > .05). The daily weight gains of pigs for the 1st wk in the ellipsoid crate did not differ from those of pigs in the rectangular crates (P > .05) but were higher for the period from d 7 to d 21 (P < .05). The ellipsoid crate allowed the sow to turn around and have more freedom to move. However, the increase in sow movement did not cause a higher pig crushing rate than that in the traditional crate (P > .05). Behavioral observations also showed that the ellipsoid farrowing crate permitted easier visual and tactile contact of dams with their pigs and offered pigs better access to the sow's teats.

Animal Welfare↗
PubMed1993

A homozygous deletion within the carbonic anhydrase-like domain of the Ptprg gene in murine L-cells.

Protein tyrosine phosphatases, on purely theoretical grounds, were suggested as possible tumor suppressor genes, and receptor protein tyrosine phosphatase gamma (PTPRG) has been proposed, on the basis of its location at human chromosome region 3p14.2, specifically as a tumor suppressor gene for renal cell carcinoma. We have isolated murine genomic and complementary DNA clones for analysis and mapping of the murine Ptprg locus; interspecific backcross analysis showed that the Ptprg locus maps to the centromeric region of mouse chromosome 14. We also observed a homozygous, intragenic deletion in the Ptprg gene in all clonal derivatives of the original L-cell strain, a methylcholanthrene-treated mouse connective tissue cell line which produces sarcomas in syngeneic mice. The deletion begins in the second intron of the carbonic anhydrase-like domain of the Ptprg gene and ends in the fourth intron of the carbonic anhydrase-like domain. At the genomic level, perhaps several hundred kilobases of DNA are deleted; at the complementary DNA level the 400 base pairs comprising exons 2, 3, and 4 of the carbonic anhydrase-like domain are deleted. By reverse transcription polymerase chain reaction, an amplified fragment is produced from L-cell mRNA which is 400 base pairs shorter than the wild type gene product, suggesting that the deleted gene is transcribed and may produce a protein product. Thus, mouse L-cells have lost one Ptprg allele and sustained an intragenic deletion in the other; such allele loss and mutation frequently occur at tumor suppressor gene loci.

Amino Acid Sequence↗
PubMed1993

Characterization of human bone marrow-derived closed circular DNA clones.

Because of interest in mechanisms of recombination involved in chromosomal deletions in neoplastic disease, and their relation to possible rearrangements in normal tissues, we are studying circular DNA molecules from human tissue with a long-term goal of investigating them as possible by-products of physiologically relevant intrachromosomal recombination events. Covalently closed circular (ccc) DNA from human bone marrow was cloned in bacteriophage vectors, and fourteen clones chosen randomly from the cccDNA-derived library were characterized. Five clones originated from chromosome-specific centromeric alpha-satellite DNA; two clones carried highly repetitive sequences probably derived from interspersed repetitive elements; six clones were derived from single-copy chromosome-specific sequences which detected homologous rodent sequences; and one clone (EPM10) was derived from a small chromosome 11-specific sequence family which localized to chromosome regions 11cen and 11q14. Oligonucleotide primers derived from the cccDNA clones were used in polymerase chain reaction studies to show that (1) the EPM10 clone carried the circular junction, (2) several of the single-copy products could be detected in three different bone marrow cccDNA preparations, and (3) the Alu-PCR profile for bone marrow cccDNA showed distinct bands which were similar in four bone marrow cccDNA preparations.

Acute Disease↗
PubMed1993

A computer simulation of the non-Newtonian blood flow at the aortic bifurcation.

A two-dimensional numerical model was developed to determine the effect of the non-Newtonian behavior of blood on a pulsatile flow at the aortic bifurcation. The blood rheology was described by a weak-form Casson equation. The successive-over-relaxation (SOR) method was used to solve both the vorticity and Poisson equations numerically. It was disclosed that the non-Newtonian property of blood did not drastically change the flow patterns, but caused an appreciable increase in the shear stresses and a slightly higher resistance to both flow separations and the phase shifts between flow layers.

Aorta, Abdominal↗
PubMed1993

A computer simulation of the blood flow at the aortic bifurcation with flexible walls.

To understand the role of fluid dynamics in atherogenesis, especially the effect of the flexibility of arteries, a two-dimensional numerical model for blood flow at the aortic bifurcation with linear viscoelastic walls is developed. The arbitrary Lagrangian-Eulerian method is adopted to deal with the moving boundary problem. The wall expansion induces flow reversals or eddies during the decelerating systole while the wall contraction restricts them during the diastole. A flexible bifurcation experiences the shear stresses about 10 percent lower than those of a rigid one.

Aorta, Abdominal↗
PubMed1992

NHPPREG: a computer program for the analysis of nonhomogeneous Poisson process data with covariates.

A program written in C is described which finds maximum likelihood estimates of regression coefficients and other relevant parameters for a point process with covariates. The data are assumed to come from a Poisson point process and may be modelled, at the user's choice, either totally parametrically or semi-parametrically. Furthermore, extra Poisson variation may be introduced, in both the parametric and semi-parametric approach, by the device of random effects. The work closely follows the theory developed by Lawless (1987).

Humans↗
PubMed1992

[Effect of electro-acupuncture on cortical and hippocampal EEG in adjuvant arthritis rats].

Adjuvant arthritis (AA) rats were used as the chronic pain model. The cortical and hippocampal (HPC) EEG were recorded. The behaviour and local inflammatory reaction were observed. The results showed an arousal response of desynchronization of the ECoG and HPC EEG in the AA rats, the delta waves were decreased and beta waves increased significantly. However, the inhibited effect to the desynchronization were showed could be inhibited by the electro-acupuncture (EA) on bilateral Zusanli points and morphine in the AA rats. The results suggested that the cortex and hippocampus participate in the modulating action of chronic pain, and the EA has an analgesic action.

Acupuncture Analgesia↗
PubMed1992

[Textual study of Chinese drug loulu].

Through a critical study of Loulu in ancient Chinese herbals, it is concluded that the botanical origin of Loulu should be Qizhou Loulu, the dried root of Rhaponticum uniflorum of family Compositae, while the dried root of Echinops latifolius, which is also one of the species specified in Chinese Pharmacopoeia, should not be used as Loulu because of its deficiency of herbal evidences and totally different chemical constituents from those of the former. It is therefore recommended the latter plant be deleted from the Chinese Pharmacopoeia.

Drugs, Chinese Herbal↗
PubMed1992

[A study of the regularity of pain threshold changes after trauma and the effect of electroacupuncture].

Pain threshold of rats was measured by the latent period of tail flick and limb withdrawal elicited by radiant heat. 52 male SD rats were used and trauma was produced by aseptic amputation just beneath the right ankle joint. The effect of nerve block and electroacupuncture (EA) was studied and non-traumatic groups were arranged as control. The pain threshold was reduced right after trauma and the lowest level appeared on the 3rd day and then recovered gradually up to the 7th day after trauma. Nerve block and EA markedly raised the pain threshold. Particularly, EA elevated pain threshold of traumatic rats more marked and long-lasted than the effect of nerve block. This may be resulted by mobilizing the functions of the endogenous analgesic systems.

Acupuncture Analgesia↗
PubMed1992

Biofluid dynamics at arterial bifurcations.

Hemodynamics has long been suspected of being involved in arterial diseases, e.g., atherosclerosis. Seemingly good correlation between the atherosclerosis localization and the flow disturbance around bends and bifurcations in large arteries has prompted many studies of blood flow around those regions. This article reviews and critiques biofluid studies at various arterial bifurcations. Both experimental and theoretical models vary greatly in the major assumptions and parameters. The issues discussed include: possible errors from two-dimensional models, the validity of steady flow studies, the existence and influence of the secondary flow, effects of non-Newtonian blood rheology, influences from arterial wall distensibility, effects of the Reynolds number, effects of the area ratio, effects of the Womersley number, effects of corner curvatures, effects of bifurcation angle, errors in the measurement and calculation of wall shear rate, and the possible existence of turbulence.

Animals↗
PubMed1991

A computer simulation of the blood flow at the aortic bifurcation.

A two-dimensional finite-difference numerical model is developed for the blood flow at the aortic bifurcation to determine the possible role of fluid dynamics in the atherogenesis. Arterial walls are assumed to be rigid, while the fluid is Newtonian. Parametric studies are performed to evaluate the effects of the area ratio, Reynolds number, corner curvatures, Womersley number, bifurcation angle and arterial pulsation on the flow and shear stresses. A high shear stress region exists on the inner wall distal to the vertex, while both high and low shear stress regions coexist along the outer wall. A temporary eddy is found along the outer wall, with more strength in the case of a higher area ratio. The results agree qualitatively with the existing experimental observations.

Aorta↗
PubMed1990

Whole body heat balance during the human thoracic hyperthermia.

A whole-body heat balance model during hyperthermia is developed. In the model, local temperature is calculated using a finite-element model. The perfusion blood, along with its energy, is circulated to the rest of the body, where the heat dissipation is calculated using lumped segments. With this model the effects of the electromagnetic power dosage on the body core temperature and the responses of other body elements are analysed for the human thoracic hyperthermia.

Biophysics↗
PubMedDate not supplied

Errors in the estimation of arterial wall shear rates that result from curve fitting of velocity profiles.

An analysis was performed to determine the error that results from the estimation of the wall shear rates based on linear and quadratic curve-fittings of the measured velocity profiles. For steady, fully developed flow in a straight vessel, the error for the linear method is linearly related to the distance between the probe and the wall, dr1, and the error for the quadratic method is zero. With pulsatile flow, especially a physiological pulsatile flow in a large artery, the thickness of the velocity boundary layer, delta is small, and the error in the estimation of wall shear based on curve fitting is much higher than that with steady flow. In addition, there is a phase lag between the actual shear rate and the measured one. In oscillatory flow, the error increases with the distance ratio dr1/delta and, for a quadratic method, also with the distance ratio dr2/dr1, where dr2 is the distance of the second probe from the wall. The quadratic method has a distinct advantage in accuracy over the linear method when dr1/delta << 1, i.e. when the first velocity point is well within the boundary layer. The use of this analysis in arterial flow involves many simplifications, including Newtonian fluid, rigid walls, and the linear summation of the harmonic components, and can provide more qualitative than quantitative guidance.

Arteries↗