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Biomedical subjects

H K Liu

Publications and source records attributed to H K Liu.

32 records · Page 2Linked to original sources
PubMed2000

Surgical treatment of nonunited fractures of the odontoid process, with special reference to occipitocervical fusion for unreducible atlantoaxial subluxation or instability.

Fifty-seven consecutive patients treated surgically for nonunited fractures of the odontoid process were reviewed. All patients presented late, exhibiting neurological deficits subsequent to nonunion. Delay in presentation was between 6 and 120 months (mean 32 months) after the original injury, due to missed diagnosis or inappropriate management. Seven patients who were reduced in traction underwent a Gallie atlantoaxial fusion. In the remaining 50 patients who were unreducible, an occipitocervical arthrodesis was performed. They were followed up for a minimum of 2 years, except one who died from postoperative respiratory failure. All patients obtained a solid bony union, including two in whom nonunion occurred following atlantoaxial fusion, and occipitocervical fusion was added as a rescue. Thirty-eight patients achieved excellent neurological recovery, nine still had some disability, five retained their neurological deficits and two reported a deterioration. In two patients, a recurrence in a traumatic episode was experienced long after a resolution. Our findings demonstrate that occipitocervical arthrodesis is preferable for unreducible subluxation or instability of atlantoaxial articulation in nonunion of odontoid fractures.

Adolescent↗
PubMed1997

Interlaboratory comparison of autoradiographic DNA profiling measurements. 4. Protocol effects.

The observed total interlaboratory uncertainty in restriction fragment length polymorphism (RFLP) measurements is sufficiently small to be of little significance given current forensic needs. However, as the number of RFLP data increase, further reduction in the total uncertainty could help minimize the resources required to evaluate potential profile matches. The large number of data available enable quantitative estimation of the within-laboratory imprecision and among-laboratory bias contributions to the total uncertainty. Some small but consistent among-laboratory measurement biases can be attributed to specific procedural or materials differences. The bias direction is often fragment-specific and thus unpredictable for unknown samples. Actions that would minimize currently recognized sources of interlaboratory bias include the following: (1) all laboratories should use the same algorithm for data interpolation, (2) all laboratories should use the same sizing ladders, (3) each laboratory should prepare control DNA and sample DNA in the same manner and with the identical reagents, (4) all laboratories should adopt a uniform policy on ethidium bromide use, and (5) all laboratories should adopt the same control DNA sizing acceptability criteria.

Autoradiography↗
PubMed1996

Lumbar disc herniation in patients with developmental spinal stenosis.

Lumbar spinal stenosis and lumbar disc herniation are usually regarded as two pathogenetically different conditions, but in the literature lumbar disc herniation in patients with developmental spinal stenosis has been rarely documented. In a clinical retrospective study, 42 lumbar disc herniations with developmental spinal stenosis were reported and analyzed. Discectomy was performed after laminotomy. The patients were followed-up for an average of 4.4 years (range 2-7 years). The preoperative symptoms disappeared completely in 28 patients, in 13 patients some degree of backache remained although their nerve root pain had been relieved, and in 1 patient intermittent claudication reappeared after 6 years resolution of their preoperative pain. We conclude that when developmental spinal stenosis is combined with disc herniation, discectomy through laminotomy rather than laminectomy is usually sufficient for decompression.

Adult↗
PubMed1995

Interlaboratory comparison of autoradiographic DNA profiling measurements. 2. Measurement uncertainty and its propagation.

Identifying the intrinsic sources of measurement uncertainty greatly facilitates control and further optimization of a measurement system. We have developed a model which quantitatively describes the observed interlaboratory variability of autoradiographic DNA band sizing. The model focuses on optical imaging measurements of band position and the calibration techniques used to convert measured band position to reported band size. The imaging component of measurement variability is described as a 0.05-0.2% standard deviation in determining the relative location of sample and calibration bands on a given film image. While developed solely with optical imaging information, the model is consistent with interlaboratory band sizing measurement variability observed with pristine samples. This interlaboratory variability can be modeled as a 0.2-0.4% standard deviation in the relative positions of sample and calibration bands across different electrophoretic gels. Further band sizing protocol standardization among laboratories would thus be expected to achieve at best a 2-fold reduction in interlaboratory band sizing variability.

Autoradiography↗
PubMed1992

Surgical treatment of cervical spine tumors.

Of 40 patients with cervical spine tumor treated from 1980 to 1990, 24 had a primary tumor and 16 a metastatic tumor. Thirty-four patients were operated on through anterior and 5 through posterior approach. Preoperative neck pain was relieved and muscular strength of shoulder and arm increased after operation. Total excision methylmethacrylate or metal prosthesis replacement was used. Total excision of the lesion was emphasized for preventing the recurrence of the tumor. Indications and aims of the operation are discussed.

Adenoma↗
PubMed1985

Are beta-adrenergic mechanisms involved in ocular hypotensive actions of adrenergic drugs?

Specific beta 1- and beta 2-adrenergic agonists and antagonists were studied for their effects on aqueous humor dynamics in a cat model. Tazolol (beta 1-agonist) reduced formation of aqueous humor more than outflow, while metoprolol (beta 1-antagonist) reduced outflow more than formation. Both salbutamol (beta 2-agonist) and butoxamine (beta 2-antagonist) inhibited aqueous humor formation and aqueous humor outflow to an equal extent. It is concluded that the adrenergic mechanism is functioning only slightly, if at all, in affecting the intraocular pressure. On the other hand, receptor binding experiments on iris-ciliary body showed clearly that there are 40-fold and 281-fold differences in binding affinity of D- and L-isomers of timolol and propranolol, respectively. These results indicate that the adrenergic receptor mechanism does exist in the eye tissues but that it does not control intraocular pressure significantly.

Adrenergic beta-Agonists↗
PubMed1981

Dynamic pupillary response to positive differential of light stimulus.

Under low background illumination, the pupil responds only to an increase in light intensity by a transient constriction when the extent and rate of the increase exceed a certain values. We term this response the dynamic papillary response in order to differentiate it from the much more sluggish and much less pronounced response moiety that governs the static pupil size according to the level of light adaptation. The characteristics of the dynamic response are studied in some detail. This virtually unidirectional rate sensitivity of pupil to light renders it difficult to be subjected to frequency-response analysis even by small signal approximation. Analysis of the experimental results suggests that this transient response is a light-precipitated confluence of few consecutive hippus.

Adaptation, Ocular↗
PubMed1980

Ocular hypotensive effects of timolol in cat eyes.

The effects of timolol on the aqueous humor (AH) formation and AH outflow in cat eyes were simultaneously studied with a continuous infusion method under constant intraocular pressure. The rate of AH formation was reduced 28%, 56%, and 71%, respectively, by 0.005%, 0.025%, and 0.15% of timolol solution infused intracamerally. There was no significant change of AH outflow after the administration of timolol. It was noted that the pupil was dilated by 0.025% and 0.15% timolol solutions. To determine the action mechanism of timolol to inhibit AH formation, experiments of carbonate dehydratase inhibition were performed with various concentrations of timolol. No appreciable enzyme inhibition was noted with timolol at concentrations up to 0.5%. It is thus concluded that the action mechanism of timolol to inhibit AH formation differs from that of carbonate dehydratase inhibitors.

Animals↗
PubMed1977

Display of three-dimensional information in computed tomography.

From a sequence of computed tomograms of two-dimensional transverse slices of a body one can build up a three-dimensional array of numbers containing spatial rather than cross-sectional information. We have developed computer methods to display a slice at arbitrary orientation through the three-dimensional object. The three-dimensional array of numbers can also be used to display what any particular organ would look like if it were removed from the body. This is done by a computer technique that first detects the surface of the organ of interest and then displays this surface on a screen.

Data Display↗
PubMedDate not supplied

Characterization of nanoparticles of LiMn2O4 synthesized by a one-step intermediate-temperature solid-state reaction.

Nanoparticles of lithium manganese oxide (LiMn2O4) with a spinel structure have been synthesized by a one-step intermediate temperature solid-state reaction. The influence of the molar ratio of citric acid to the metal ions on the physicochemical properties of LiMn2O4 powders in air has been analyzed by means of X-ray diffraction and electron microscope techniques. The electrochemical behavior of the material has been examined by charge/discharge tests and cyclic voltammetry. Test results reveal that LiMn2O4 particles with lower molar ratios of citric acid to metal ions (1:2) are highly crystalline and highly electrochemically reversible, with better cycle capabilities when compared with a sample with a higher molar ratio (2:1). The LiMn2O4 powders obtained by this method have a uniform morphology with a narrow size distribution.

Crystallization↗