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Biomedical subjects

J C Liu

Publications and source records attributed to J C Liu.

At least 109 records · Page 6Linked to original sources
PubMed1994

The putative dopamine D3 receptor agonist 7-OH-DPAT: lack of mesolimbic selectivity.

7-Hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT), an agonist with relative selectivity for the dopamine D3 receptor, was examined in several electrophysiological assays to determine whether it exhibits preferential effects in the mesolimbic versus nigrostriatal dopamine systems. Extracellular single unit activities of substantia nigra pars compacta (A9) and ventral tegmental area (A10) dopamine neurons, and caudate-putamen and nucleus accumbens neurons, were recorded in male rats anesthetized with chloral hydrate. Intravenous (+/-)-7-OH-DPAT potently and completely inhibited the firing of both A9 and A10 dopamine neurons (ED50's: 3.5 +/- 0.7 micrograms/kg and 3.9 +/- 0.9 micrograms/kg, respectively). The active enantiomer, (+)-7-OH-DPAT, was 2 to 3 times more potent than the racemic drug (ED50's: 1.2 +/- 0.3 micrograms/kg and 1.7 +/- 0.4 micrograms/kg for A9 and A10 cells, respectively). There were no significant differences in potency for either form in inhibiting A9 and A10 dopamine neurons. In other studies, iontophoretically applied (+)-7-OH-DPAT caused current-dependent inhibitions of spontaneously active or glutamate-driven caudate-putamen and nucleus accumbens neurons (I50 values, 6.5 and 7.9 nA, respectively). Again, no difference in potency between cell populations was noted. Finally, in cell-attached patch-clamp recordings from freshly dissociated rat caudate-putamen neurons, an 85 pS K+ channel known to be activated by dopamine and the "D2-like" agonist quinpirole was also observed with (+/-)-7-OH-DPAT (0.2-1 microM) applied in the patch pipette.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Alpha thalassemia and stroke risk in sickle cell anemia.

In an effort to identify possible risk factors for stroke in Sickle Cell Anemia (Hb SS), we analyzed the distribution of alpha-globin gene deletions in a group of Hb SS patients with and without stroke. The group with stroke consisted of 44 patients, (27 male, 17 female) with a mean of 7.5 years at time of stroke. The control group (non-stroke) had 256 Hb SS patients (126 male, 130 female) with a mean age of 7.7 years. There were 9 patients with heterozygous alpha-thalassemia in the stroke group (20.5%). In the control group, there were 93 patients with heterozygous alpha-thalassemia and 5 with homozygous alpha-thalassemia. The incidence of alpha-thalassemia in Hb SS patients without stroke (38%) was comparable to that reported for the African-American population in general. The incidence in the stroke population (20.5%) was significantly lower (P = 0.02) These results indicate that alpha-thalassemia is associated with a lower risk of stroke in Hb SS. This observation should be confirmed in studies involving larger numbers of patients. Possible protective effects of alpha-thalassemia are unknown but may be related to decreased hemolysis and more favorable rheologic properties of red blood cells.

Adolescent↗
PubMed1994

Activation of neurons in cardiovascular areas of cat brain stem affects spinal reflexes.

In 65 cats anesthetized with chloralose (40 mg/kg) and urethane (400 mg/kg), the effects of electrical stimulation and microinjection of sodium glutamate (0.25 M, 100-200 nl) in the pressor areas in the rostral brain stem on the evoked L5 ventral root response (EVRR) due to intermittent stimulation of sciatic afferents were compared to stimulating the dorsomedial (DM) and ventrolateral (VLM) medulla. In general, stimulating these rostral brain stem pressor areas including the diencephalon (DIC) and rostral pons (RP) produced increases in systemic arterial pressure (SAP). In most of the cases (85%) there were associated changes in the EVRR, predominantly a decrease in EVRR (72%). Stimulation of the midbrain (MB, principally in the periaqueductal grey) produced decreases in SAP and EVRR. Decreases in EVRR was observed in 91% of the DM and VLM stimulations in which an increase in SAP was produced. This EVRR inhibition was essentially unaltered after acute midcollicular decerebration. Increases in EVRR were also observed and occurred more often in the rostral brain stem than in the medulla. Since changes of both EVRR and SAP could be reproduced by microinjection of Glu into the cardiovascular-reactive areas of the brain stem, this suggests that neuronal perikarya in these areas are responsible for both actions. On some occasions, Glu induced changes in EVRR but not in SAP. This effect occurred more frequently in the rostral brain stem than in the medulla. The present data suggest that separate neuron population exist in the brain stem for the integration of SAP and spinal reflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Restoration of dopamine overflow and clearance from the 6-hydroxydopamine lesioned rat striatum reinnervated by fetal mesencephalic grafts.

The purpose of these experiments was to investigate the electrochemical indices of mesencephalic dopaminergic grafts as they function in the rat striatum. Sprague-Dawley rats were injected unilaterally with 6-hydroxydopamine into the medial forebrain bundle, and the effectiveness of these lesions was tested by measuring apomorphine-induced rotation. The unilaterally lesioned rats were later transplanted with fetal ventral mesencephalon. Only animals receiving ventral mesencephalon transplants showed significant decreases in rotation after grafting. High-speed chronoamperometric recording techniques using Nation-coated carbon fiber electrodes were used to evaluate dopamine (DA) overflow in the striatum of urethane-anesthetized rats. We found that 6-hydroxydopamine lesions resulted in a loss of KCl-induced DA overflow and clearance. Ventral mesencephalon grafts restored neurochemical indices. The zone of normalized DA clearance was considerably larger than that of normalized release. Furthermore, histochemical studies using tyrosine hydroxylase immunoreactivity confirmed graft survival and neurite outgrowth from the graft into the lesioned striatum. In conclusion, these findings suggest that the behavioral improvements by grafts of fetal mesencephalic tissue are accompanied by morphological and electrochemical evidence of reinnervation and the restoration of DA input. Measurement of DA clearance may reveal a wider area of reinnervation than that indicated by more traditional immunocytochemical methods.

Animals↗
PubMed1993

Localization of sympathetic postganglionic neurons innervating the femoral-saphenous vein in cats.

Physiological and histochemical studies have suggested that the limb veins are innervated by sympathetic adrenergic fibers. In the present experiment, horseradish peroxidase (HRP) was used as a retrograde tracer to identify and localize the sympathetic postganglionic neurons that innervate the femoral-saphenous vein in cats. In anesthetized cats, HRP was applied perivascularly on a femoral and a saphenous vein segment (4-8 mm in length for each segment) to allow uptake into the nerve endings. The sympathetic chains on both sides were dissected after the animal was sacrificed and fixed 60 h following the HRP application. Histological examination on serial section was done to count the HRP-labeled neurons in each sympathetic ganglion from L1 to S1. In 10 cats, the total number of HRP neurons amounted to 8569. Most neurons arose from L3 (47%) and then L4 (31%). The number of neurons became progressively decreasing towards both ends of the sympathetic chain. Few neurons (less than 2% of the total) were discovered in the contralateral sympathetic ganglia. In each ganglion, the distribution of HRP neurons appeared to be scattering. Our findings provide anatomical evidence to support that the femoral-saphenous vein of the cat was innervated by the sympathetic efferent fibers. The main origins of these neurons are the third and fourth lumbar sympathetic ganglia.

Animals↗
PubMed1993

Topical bupivacaine and proparacaine: a comparison of toxicity, onset of action, and duration of action.

Bupivacaine is a local ocular anesthetic with a long duration of action when administered by retrobulbar injection. To determine the potential for the use of bupivacaine as a topical ocular anesthetic, the onset and duration of action and toxicity of various concentrations of bupivacaine were studied after instillation in rabbit eyes. The onset and duration of action were not significantly different from that of topical 0.5% proparacaine. Increasing the pH of the bupivacaine solution from 5.7 to 6.5 nearly doubled the duration of action, but the increase was not sufficient to be clinically important. Slit lamp biomicroscopic examination and scanning electron microscopy showed that bupivacaine was less toxic to the corneal epithelium than 0.5% proparacaine. Healing after keratectomy was significantly more rapid in eyes treated with 0.75% bupivacaine, compared with eyes treated with 0.5% proparacaine. These results suggest that bupivacaine may be less toxic to the corneal epithelium than proparacaine and could be clinically useful for topical ocular anesthesia, particularly if pharmacologic modifications can increase the duration of anesthesia provided by this drug.

Administration, Topical↗
PubMed1993

The effect of the static magnetic field on the response of radiation survey instruments.

The effects on the response of eight radiation survey instruments in static magnetic fields up to 0.03 T (300 G) have been investigated. The instruments studied are the Xetex 303B Pacer, the Bicron Micro Rem survey meter, the Victoreen 450p survey meter, the Victoreen 440 survey meter, the SLAC orange meter, the Keithley 36150 survey meter, the Anderson-Braun neutron remmeter, and the Victoreen 488 neutron survey meter. The results show that the effect may depend on several factors such as instrument design, alignment of the instrument axis with the magnetic flux lines, whether the instrument is stationary or moving relative to the magnetic field, the direction of the movement relative to the magnetic flux lines, and the magnetic field intensity. Also presented are results of work to enhance magnetic shielding of some of the instruments.

Electromagnetic Fields↗
PubMed1993

Black alpha-thalassemia-1: partial characterization of an approximately 80 kb deletion which includes the zeta- and alpha-globin genes.

A large novel alpha-thalassemia-1 deletion which includes the zeta-, alpha 2-, alpha 1-, and theta 1-globin genes is described in a Black family living in Georgia and Florida. The deletion which was characterized by restriction enzyme analysis, extends 15 to 35 kb 5' and at least 35 kb 3' to the Cap site of the zeta-globin gene. Mental retardation was not observed. The deletion was present in a 35-year-old male with Hb H disease and his mother; the major hemoglobin type in the propositus was Hb G-Philadelphia or alpha (2)68(E12)Asn-->Lys beta 2 because his second chromosome carried the -alpha G(-3.7 kb) alpha-thalassemia-2 deletion.

Adolescent↗
PubMed1993

Dengue in China: a clinical review.

Three etiologically proven outbreaks of dengue fever and one etiologically confirmed epidemic of dengue haemorrhagic fever have occurred in south China since 1978. The first of these, an epidemic of dengue due to virus type 4 took place in Shiwan town, Foshan city, Guangdong Province, in 1978; the epidemic began in May and ended in November. The clinical manifestations of 583 hospitalized patients were observed from August to October. The majority (81.3%) of patients were aged 21-50 years (male:female = 1.2:1). The course of illness was about 1 week in most cases; three patients (0.5%) died. A local outbreak of dengue due to virus type 1 occurred in Shiqi town, Zhongshan County, Guangdong Province, from September to November 1979. The majority of patients were older children and adolescents. There was no marked difference between males and females in terms of the course of the illness, and there were no complications or deaths. A large epidemic of dengue due to virus type 3 occurred on Hainan Island in 1980. The clinical manifestations of 510 hospitalized patients (mostly adolescents and adults) were observed from April to September. Some patients developed rare complications, such as loss of hair, acute intravascular haemolysis, and multiple peripheral paralysis; there were four deaths (0.78%). The first known epidemic of dengue haemorrhagic fever in China occurred among 10-29-year-olds on Hainan Island in 1985 and 1986. There were no essential differences between males and females. Some cases had rare complications such as acute intravascular haemolysis, while others had diffuse intravascular coagulation and altered mental status; 10 patients (6.5%) died.

Adolescent↗
PubMed1992

A new gene deletion involving the alpha 2-, alpha 1-, and theta 1-globin genes in a black family with Hb H disease.

A new deletion of approximately 8.5 kb that includes the alpha 2-, alpha 1-, and theta 1-globin genes was detected in a father and newborn son of a black family from Georgia. In the newborn baby the chromosome with the deletion occurred together with a rightward (-alpha 3.7) deletion chromosome. The resulting Hb H disease was detected at birth by the high level of Hb Bart's; a moderate anemia with severe microcytosis and hypochromia was present at the age of 5 months. A review of cord blood testing results for a period of over 20 years, involving at least 200,000 black newborns, indicated that this baby was the first with a level of Hb Bart's in excess of 10-15%; this underscores the rarity of alpha-thalassemia-1 in this population.

Adult↗
PubMed1992

A proposed four-element neutron-photon-beta thermoluminescence dosimeter.

It is common practice for a worker exposed to a mixed field with neutrons to wear both a photon-beta dosimeter and a neutron dosimeter. In this study, a thermoluminescence dosimeter has been designed and is proposed for use in mixed fields. The maximum applicable ranges of the mixed field can have photons with unknown energy from 20 keV to 2 MeV, betas with unknown energy from 147Pm to 90Sr-Y, and neutrons of known energy from thermal to 15 MeV. This proposed dosimeter (a combination of Harshaw beta-gamma thermoluminescence dosimeter and albedo neutron thermoluminescence dosimeter) has an advantage of using a minimum number of thermoluminescence dosimeter elements (therefore, making it less costly) to measure the dose equivalents in a mixed field of neutron, photon, and beta radiation. The basic dosimeter design consists of four thermoluminescence elements of TLD-600 and TLD-700 with different filtrations. Using the high-temperature peak methodology for TLD-600 and a filtration algorithm, the neutron, photon, and beta dose equivalents in a mixed field can be determined. The design, detection principle, and three dosimetric algorithms for three versions of the basic design of the four-element dosimeter are presented and discussed. The work that is required for the proposed dosimeter to be usable when it is made is also presented.

Algorithms↗
PubMed1992

Combinations of three different forms of alpha-thalassemia in a large Indian family from Durban, South Africa: hematological observations.

We have identified three types of alpha-thalassemia in 28 members of an Indian family from Durban, South Africa. The rare South African (SA) type of alpha-thalassemia-1, which is characterized by an approximately 23-kb deletion involving the psi zeta, psi alpha 2, psi alpha 1, alpha 2, alpha 1, and theta 1 genes, was present in 13 members [6 simple heterozygotes, 5 with Hb H disease of the --(SA)/-alpha(-3.7 kb) type, and 2 with Hb H disease of the --(SA)/-alpha(-4.2 kb) type]. Seven others were heterozygotes for alpha-thalassemia-2 (-3.7 kb), 1 was homozygous for this deletion, and 1 was a compound heterozygote [-alpha(-3.7 kb/-alpha(-4.2 kb)]. Hematological and hemoglobin composition data indicated a moderate anemia in all 7 patients with Hb H disease with severe microcytosis and hypochromia, no elevation of gamma-chain synthesis, low levels of Hb A2 (0.3-0.7%), and low levels of Hb H. The most severe disease was present in 2 teenagers with the --(SA)/-alpha(-4.2 kb) combination.

Adolescent↗
PubMed1992

A new variant, HB Muscat [alpha 2 beta (2)32(B14)Leu----Val] observed in association with HB S in an Arabian family.

The silent Hb Muscat with a Leu----Val replacement at position beta 32 was discovered by reversed phase high performance liquid chromatography in two members of an Arabian family from Oman; in one person Hb Muscat occurred with Hb S and in the other with Hb A. Hb Muscat is slightly unstable but its presence has no apparent adverse effect on the health of its carriers. Additional hemoglobin abnormalities observed in this family were a common alpha-thalassemia-2 (-3.7 kb) and Hb S. The beta S haplotypes in the heterozygous carriers and the two sickle cell anemia patients were #19 (Benin) and #20 (Bantu); the latter likely originated from an East African population.

Adolescent↗
PubMed1992

Localization of the sympathetic postganglionic neurons innervating cardiac coronary artery with horseradish peroxidase in monkeys.

Localization of the sympathetic postganglionic neurons innervating the cardiac coronary arteries in monkeys was investigated by using retrograde axonal transport of horseradish peroxidase (HRP). HRP was applied to the main trunk of the left and right coronary arteries, and to the terminal branches of the ventral and dorsal descending vessels of the left and right coronary arteries, respectively. The animals were sacrificed 84-96 hours later and perfused via the left ventricle. The paravertebral sympathetic ganglia from the superior cervical, middle cervical and stellate ganglia to the T9 ganglia, and nodose ganglia were removed and processed for HRP identification. After HRP was applied into the main trunk of the right coronary artery, and into the main trunk and the terminal branches of the descending vessels of the left coronary artery, the HRP-labeled sympathetic neurons were localized predominantly in the right superior cervical ganglion, and next in the left superior cervical ganglia. However, labeled cells were found in the stellate ganglia bilaterally. After HRP applications to the terminal branches of the dorsal descending vessels of the right coronary artery, HRP-labeled cells were mainly present in the left superior cervical ganglion and next in the right superior cervical ganglion. Some labeled cells were found in the middle cervical and stellate ganglia. No labeled cell was found in ganglia below the second thoracic ganglia on either side in these four groups.

Animals↗
PubMed1992

[Profuse hemorrhage from the axillary artery in electric burn: prevention and treatment].

A total of 53 cases of electric burns were admitted to our unit during the 1977-1985 period. In 19 cases an upper limb was involved, accounting 35.8 percent of the total. In 15 cases disarticulation of the shoulder was done, and in 3 of them a profuse hemorrhage from the axillary artery occurred as a result of infection of the amputation stumps. The second segment of the axillary artery was ligated during the amputations in the other 4 cases, no hemorrhage occurred in them.

Adult↗