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Biomedical subjects

H D Li

Publications and source records attributed to H D Li.

36 records · Page 2Linked to original sources
PubMed1991

Observation of the phase transition in the growth of a biomineralized calcium carbonate.

Transmission electron microscope studies of the cellular nucleation sites of a biomineralized calcium carbonate(aragonite) in the lamellar nacreous layer of the bivalvia Cristaria plicata (Leach) shell showed that the low density calcium particles were confined within some large vesicles of the bivalve mantle cells on which the crystalline aragonite phases were deposited. These vesicles served as the nucleation sites for the growth of the crystals. The crystalline phases at the first few lamellae were mostly imperfect while the whole nacreous layer acquitted itself into a highly oriented biomineralized aragonite. The structure of the vesicles is addressed in detail.

Animals↗
PubMed1991

[Relation between changes in monoamine transmitters and brain edema after thermal burns in rats].

The HPLC with electro-chemical detector was employed to determine the change in monoamine transmitters and their metabolites murine hypothalamus, brainstem and spinal cord after burn. Also the pathological changes after burn in three brain parts was observed with photomicrograph and electromicrograph. The results show that: the monoamine contents were increased remarkably 5 min after burn, and even 360 min after burn, the monoamine contents were still higher than before the burn. The changes however, were different in the three brain parts. Edema appeared 5 min after burn in the three parts, and it was more evident in the hypothalamus. After icv phentolamine and CPA, edema was decreased. These results suggest that brain edema after thermal burn is related to changes in monoamine transmitters of CNS, mediated by receptor and 5-HT synthesis.

Animals↗
PubMed1991

[Effect of intraventricular injection of somatostatin on pain threshold, and contents of the monoamines, xanthine, hypoxanthine in rats brain].

Using HPLC with electrochemical detection, we found that icv somatostatin (Som) 5 or 10 micrograms increased rat's pain threshold and contents of 5-HT and 5-HIAA in hippocampus, hypothalamus and brainstem, except the 5-HIAA content of brainstem in Som 5 micrograms group. However, the changes of NE among above three areas of brain were different, the NE contents of hypothalamus and brainstem significantly increased while that of hippocampus markedly decreased. After icv Som 20 micrograms, hypoxanthine and xanthine in hippocampus and hypothalamus decreased significantly, but encephaledema occurred. Som 40 micrograms icv caused necrotic changes of neurons in brain.

Animals↗
PubMed1990

Depletion of U14 small nuclear RNA (snR128) disrupts production of 18S rRNA in Saccharomyces cerevisiae.

Repression of an essential nucleolar small nuclear RNA (snRNA) gene of Saccharomyces cerevisiae was shown to result in impaired production of 18S rRNA. The effect, observed for an snRNA species of 128 nucleotides (snR128), was evident within one generation after the onset of SNR128 gene repression and correlated well with depletion of the snRNA. The steady-state mass ratio of 18S RNA to 25S RNA decreased eightfold over the course of the analysis. Results from pulse-chase assays revealed the basis of the imbalance to be underaccumulation of 18S RNA and its 20S precursor. This effect appears to result from impairment of processing of the 35S rRNA transcript at sites that define the 20S species coupled with rapid turnover of unstable intermediates. Possible bases for the effects observed are discussed. A common U14 designation is proposed for the structurally related yeast snRNA and 4.5S hybRNAs from amphibians and mammals.

Base Sequence↗
PubMed1990

[Serotonin of hippocampus and hypothalamus taking part in the analgesic effect of adrenocorticotropic hormone in rats].

The effects of ip intra-PAG injection of ACTH on serotonin (5-HT), norepinephrine (NE) contents of hippocampus and hypothalamus and pain threshold were investigated. The results showed: (1) After ip ACTH, the pain threshold, the contents of 5-HT of the two brain regions and the NE content of hippocampus were markedly elevated. Prior destruction of periaqueductal gray (PAG), the elevation of pain threshold and the increase of the 5-HT contents of two brain regions due to ip ACTH were completely abolished, while the effect of ACTH in elevating NE content of hippocampus still persisted. (2) After intra-PAG injection of ACTH, the pain threshold and the 5-HT contents in hippocampus and hypothalamus were significantly increased, however, the NE levels in hippocampus and hypothalamus showed no significant changes. The analgesic effect of the intra-PAG injection of ACTH was prevented by icv LSD, but not by naloxone, atropine, hexamethonium and phentolamine. (3) After icv ACTH, the pain threshold did not change. These results suggest that the serotoninergic system may be activated by PAG for mediation of ACTH-induced analgesia.

Adrenocorticotropic Hormone↗
PubMed1989

Paraplegia caused by local spinal cord ischemia. An animal spinal cord ischemia model.

Local spinal cord ischemia model was established in 11 adult dogs. The anterior spinal artery, posterior spinal artery and radicular artery were cauterized with bipolar cautery. Ischemia of this segment of spinal cord was thus produced followed by paraplegia. The pathological findings of this spinal cord segment were softening and necrosis. The establishment of this animal model of segmental spinal cord ischemia is beneficial to scientific research in basic medicine and clinical practice.

Animals↗
PubMed1989

[Thoracoscopy using flexible fiberoptic bronchoscopy--a preliminary report of experimental and clinical studies].

The preliminary experience on thoracoscopy with fiberoptic bronchoscope through a trocar designed by the authors for the purpose of studying its diagnostic implication and safety was reported. Structures in the pleural cavity of 8 dogs, being examined for 16 times, could be clearly perceived and taken for biopsy with exact localization. This technique was also carried out in 5 patients suffering from pleural effusion, mediastinal mass and periphery lung disease of unknown cause. After the examination, diagnosis was made as mesothelioma in 2 cases and non-specific pleurisy, malignant lung tumor with mediastinal lymphatic node metastasis and pulmonary benign tumor in the remaining 3 cases respectively. It was observed that its respiratory and circulatory effects were negligible as there were only transient fever in all the cases and local subcutaneous emphysema in one case with prompt recovery without treatment. Thoracoscopy is a technique easy to operate, safe, less traumatic and gives accurate diagnosis in clinical practice.

Adult↗
PubMedDate not supplied

Microstructural investigation of the early external callus after diaphyseal fractures of human long bone.

Microstructures of the early external callus after diaphyseal fractures of human long bone were investigated by using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. It was found that the main structural framework of the human early callus consists of disordered, mineralized collagen fibrils with a small fraction of regions of ordered collagen fibrils. X-ray diffraction analyses show that hydroxyapatite containing some carbonate impurity has been the dominant crystalline phase in the human early callus. In addition, a small amount of brushite phase was detected. Selected area diffraction analyses indicated that hydroxyapatite microcrystals were embedded in microfibrils with a diameter of 4.5 nm and well-banded fibrils, whereas brushite particles of 15-20 nm in an irregular shape were located in the noncollagenous organic matter around the nonmineralized, ordered collagen fibrils. The spatial distribution of the brushite particles in the human early callus was for the first time determined. The brushite particles probably serve as the reservoir of calcium and phosphate ions for subsequent mineralized periods rather than the precursor of hydroxyapatite.

Bony Callus↗
PubMedDate not supplied

Digital mammography: M-channel quadrature mirror filters (QMFs) for microcalcification extraction.

Multiresolution methods are reported for feature extraction in breast cancer screening using digital mammography. The initial application is directed at the detection of microcalcification clusters (MCCs). Quadrature mirror filter (QMF) banks, using both two and three channel are proposed for the first time for both multiresolution decomposition and reconstruction. These filters are specifically tailored for automatic extraction of MCCs. The QMF multiresolution methods are compared to two channel tree structured wavelet transforms (TSWTs) methods previously reported. The QMF filters are preceded by an advanced tree structured nonlinear filter for noise suppression, prior to feature extraction, in order to minimize the false positive (FP) detection rate in digital mammography. The relative performance of these methods were evaluated using both simulated images and fifteen representative digitized mammograms containing biopsy proven microcalcification clusters. Similar high sensitivity (true positive (TP) detection rate (100%) and high specificity (0.6 average false positive (FP) MCC's/image) were observed, substantially better than more traditional approaches using single scale filters. The three channel QMF method, however, demonstrated better detail preservation of MCC's extracted compared to the two channel method. Detail preservation is important for the characterization of MCC's or individual microcalcifications in cancer screening.

Algorithms↗
PubMedDate not supplied

Hyaluronic acid-poly-D-lysine-based three-dimensional hydrogel for traumatic brain injury.

Brain tissue engineering in the postinjury brain represents a promising option for cellular replacement and rescue, providing a cell scaffold for either transplanted or resident cells. In this article, a hyaluronic acid (HA)-poly-D-lysine (PDL) copolymer hydrogel with an open porous structure and viscoelastic properties similar to neural tissue has been developed for brain tissue engineering. The chemicophysical properties of the hydrogel with HA:PDL ratios of 10:1, 5:1, and 4:1 were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectrometry. Neural cells cultured in the hydrogel were studied by phase-contrast microscope and SEM. The incorporation of PDL peptides into the HA-PDL hydrogel allowed for the modulation of neuronal cell adhesion and neural network formation. Macrophages and multinucleated foreign body giant cells found at the site of implantation of the hydrogel in the rat brain within the first weeks postimplantation decreased in numbers after 6 weeks, consistent with the host response to inert implants in numerous tissues. Of importance was the infiltration of the hydrogel by glial fibrillary acidic protein-positive cells-reactive astrocytes-by immunohistochemistry and the contiguity between the hydrogel and the surrounding tissue demonstrated by SEM. These findings indicated the compatibility of this hydrogel with brain tissue. Collectively, the results demonstrate the promise of an HA-PDL hydrogel as a scaffold material for the repair of defects in the brain.

Animals↗