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Biomedical subjects

J F Chen

Publications and source records attributed to J F Chen.

At least 73 records · Page 4Linked to original sources
PubMed1994

The Cleveland Clinic-Nimbus total artificial heart. Design and in vitro function.

We describe the design and in vitro testing of the Cleveland Clinic-Nimbus electrohydraulic permanent total artificial heart as it nears completion of development. The total artificial heart uses an electric motor and hydraulic actuator to drive two diaphragm-type blood pumps. The interventricular space contains the pump control electronics and is vented to an air-filled compliance chamber. Pericardial tissue valves and biolized blood-contacting surfaces potentially eliminate the need for anticoagulation. In vitro studies on a mock circulatory circuit demonstrated preload-sensitive control of pump output over the operating range of the blood pump: 70 to 160 beats/min and 5 to 9.6 L/min at right and left atrial pressures of 1.0 to 7.0 mm Hg and 5.0 to 12.0 mm Hg, respectively. The pump output was found to be insensitive to afterload over a range of 15 to 40 mm Hg mean pulmonary artery pressure and 60 to 130 mm Hg mean systemic pressure. The left master alternate control mode balanced the ventricular outputs during simulated bronchial artery shunting of up to 20% of cardiac output. A 10% to 15% right-pump, stroke-volume limiter balanced ventricular outputs during maximum output of 9.6 L/min. In response to a sustained increase in systemic venous return, the pump increased output by 2 L/min (29%) in 35 seconds. Thus the Cleveland Clinic-Nimbus total artificial heart meets the National Heart, Lung, and Blood Institute hemodynamic performance goals for devices being developed for permanent heart replacement. The biolized blood-contacting surfaces should decrease the risk of thromboembolism associated with circulatory assist devices.

Cardiac Output↗
PubMed1993

Irreversible blockade of D2 dopamine receptors by fluphenazine-N-mustard increases glutamic acid decarboxylase mRNA in rat striatum.

The influence of dopaminergic activity on the function of GABAergic neurons in striatum was examined by administering rats the irreversible D2 dopamine receptor antagonist, fluphenazine-N-mustard (FNM), and determining the level of glutamic acid decarboxylase (GAD) mRNA in striatum. Rats were given either an acute single injection or chronic daily injections of FNM (20 mumol/kg, i.p.) for 6 days. The level of GAD mRNA in striatum was determined by in situ hybridization histochemistry. The results showed that acute treatment with FNM failed to significantly change striatal GAD mRNA. However, chronic FNM treatment significantly increased in the level of striatal GAD mRNA. These results demonstrate that irreversible blockade of D2 dopamine receptors increases the expression of GAD mRNA in rat striatum.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1993

Compliance effects on small diameter polyurethane graft patency.

Microporous compliance matched and noncompliant grafts were compared in a dog carotid artery interposition model. We fabricated 4 mm diameter sponge type polyurethane (Biomer) tubes 5 cm in length with a 0.5 mm wall thickness. The luminal surface was covered with a 50 microns coating of cross-linked gelatin. Compliance was measured in vitro and in vivo by volume and vessel diameter changes. Over a mean arterial pressure range of 55-155 mm Hg, the diameter changes of grafts and stump arteries were measured in situ using an ultrasonic Hokanson device. Compliance matched grafts were found to have the same in vitro compliance values as the natural canine carotid at a mean arterial pressure of 100 mm Hg. Compliance matched and noncompliant grafts had values of 10.3 +/- 1.3 and 0.9 +/- 0.1 x 10(-2) mm Hg, respectively. End to end arterial anastomoses were constructed between the graft and the host arteries. The use of synthetic grafts with matched compliance to the adjacent natural vessels has been advocated as the ideal solution to circumvent the problems of graft failure. These studies indicate that compliance values for compliance matched grafts decreased immediately after implantation (from 10.3 to 6.5 x 10(-2) %/mm Hg) and within 6 weeks decreased to 3.6 x 10(-2) %/mm Hg. The compliance values for noncompliant grafts remained constant throughout the test period. At autopsy all grafts showed a tightly adhered tissue capsule. The thickness of the anastomotic hyperplasia at the distal sites of compliance matched grafts was significantly different (P < .05) than that of the adjacent artery. The patency for compliant and noncompliant grafts was 64% and 50%, respectively. Evidence for polyurethane graft degradation was obtained by Fourier transform infrared spectroscopy and gel permeation chromatography analysis of patent explants. Compliance mismatch alone does not contribute to graft failure, however, material degradation, suture technique and/or capsule formation can play a contributory role although these were not tested directly.

Animals↗
PubMed1993

Continuous treatment with the D2 dopamine receptor agonist quinpirole decreases D2 dopamine receptors, D2 dopamine receptor messenger RNA and proenkephalin messenger RNA, and increases mu opioid receptors in mouse striatum.

Dopamine-mediated behaviors and certain biochemical and molecular events associated with these behaviors were examined following continuous infusion of the D1 dopamine agonist SKF38393 or the D2 dopamine agonist quinpirole into mice for six days. SKF38393 produced a transient grooming behavior while quinpirole initially induced stereotypy, which was followed by an increased locomotor behavior. Continuous infusion of quinpirole caused a significant down-regulation of striatal D2 dopamine receptors without significantly changing the density of D1 receptors. This was accompanied by a decrease in the level of D2 receptor messenger RNA in striatum as measured by Northern analysis. The down-regulation of dopamine receptors was selective for D2 dopamine receptors, since treatment with SKF38393 had no significant effects on either D1 or D2 dopamine receptors, nor did it alter the messenger RNAs for the D1 and D2 receptors. Continuous treatment with quinpirole resulted in a significant increase in striatal mu opioid receptor levels without significant changing delta opioid receptors. This treatment also induced a significant decrease in proenkephalin messenger RNA in striatum. Taken together, these results suggest that the down-regulation of D2 dopamine receptor and D2 receptor messenger RNA is the result of the persistent stimulation of D2 receptors and that the up-regulation of mu opioid receptors may be a compensatory response to a decreased biosynthesis of enkephalin. They suggest further that the biochemical and molecular changes that take place in dopaminergic and enkephalinergic systems following continuous treatment with dopamine agonists may underlie the mechanisms by which certain dopamine-mediated behaviors occur.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1993

[Primary hyperparathyroidism with parathyroid adenocarcinoma in a patient with Turner's syndrome complicated with thyrotoxicosis].

We report a rare case of Turner's syndrome coexisting with thyrotoxicosis and parathyroid adenocarcinoma resulting in hyperparathyroidism. This 45-year-old female patient presented with primary amenorrhea and poor development of secondary sexual characteristics. She also experienced repeated bone fractures, and body weight loss. Multiple risk factors of osteoporosis developed simultaneously in this patient. The interesting interactive relationship of hypercalcemia between thyrotoxicosis and primary hyperparathyroidism was noted. The best choice was surgery for both cases. Calcium supplements and various hormone replacements in addition to regular investigative radionuclide scans were required.

Adenocarcinoma↗
PubMed1992

Developmental and age-related changes in the D2 dopamine receptor mRNA subtypes in rat brain.

The influence of ontogeny and aging on the D2 dopamine receptor mRNA in rat brain were examined using in situ hybridization histochemistry and Northern analysis utilizing oligonucleotide probes complementary to the different D2 mRNA subtypes. At birth, there was a high level of D2 dopamine receptor mRNA in corpus striatum relative to that found in the cerebral cortex and other brain areas. The hybridization signal of striatum (using a probe that hybridizes to both the D2A and D2B mRNA) increased during the first two postnatal weeks, reached a peak at day 16, then declined slightly. The D2A mRNA showed a similar distribution and developmental pattern. Intracisternal injection of 6-hydroxydopamine into neonates did not significantly alter the increase of the D2 dopamine receptor mRNAs, suggesting that neuronal input does not influence the ontogenetic development of this mRNA. In striatum, olfactory tubercule and inferior colliculus, the D2A mRNA declined between 3 and 24 months of age. By contrast, there was an age-related increase in the D2A mRNA in the anterior and intermediate lobes of the pituitary. The mRNA for the D2B dopamine receptor showed very low but nevertheless detectable levels in striatum, olfactory tubercule and pituitary. Like with the D2A mRNA, in 24-month-old rats the D2B mRNA declined in striatum and olfactory tubercule and increased in pituitary. These results show that there are differential tissue-related changes in the mRNAs for the D2 dopamine receptor during both development and aging.

Aging↗
PubMed1992

Biodegradable pericardial implants for bladder augmentation: a 2.5-year study in dogs.

Bladder augmentation using biodegradable pericardial tissue was evaluated in canine bladders. Acetic acid and acetic anhydride treated pericardial tissue grafts were stored in 75% ethanol for 18 to 27 months before implant. Ten dogs weighing 20 to 25 kg. were subjected to a 50% partial cystectomy. After careful separation of the mucosa, bladder muscle and adventitial layers a pericardial graft volumetrically equivalent to the portion of the bladder removed was sutured to the bladder remnant in 2 layers. In 1 control dog the bladder was opened, 50% of the bladder was removed and the bladder was closed primarily. In another control dog the excised bladder was replaced with fresh chemically treated patch material that was never subjected to ethanol storage. Excretory urography and cystography were performed on all dogs. Urodynamics with filling pressures and bladder volumes measured before and after the operation at intervals of up to 36 months confirmed that adequate bladder capacity was achieved. There were no operative complications. Postmortem histological evaluations revealed a smooth epithelialized inner surface with no traces of any surface irregularities or suture lines. The bladder apex showed an intact epithelium and the absence of a smooth muscle layer. The biodegradable acetylated tissue provides an intact structural reservoir for urine and serves as a template for epithelial regeneration. This permits volumetric bladder enlargement while the graft is progressively reabsorbed with time.

Animals↗
PubMed1992

Ultracytochemical studies on Trichomonas hominis.

The results of ultracytochemical studies on Trichomonas hominis showed that ACPase and CMPase were mainly located in the mature face sacs of the primary lysosomes, digestive vacuoles, as well as in the parabasal body. TPPase and NADPase were found in the saccules at the mature face and the intermediate saccules of parabasal body respectively. This study revealed that T. hominis had well-developed parabasal bodies. Negative COase and catalase reactions indicated that T. hominis lacked both mitochondria and microbody. Hydrogenosome was stained well with the Ur-Pb-Cu impregnation technique.

Acid Phosphatase↗
PubMed1991

Ontogenetic expression of D2 dopamine receptor mRNA in rat corpus striatum.

The ontogenetic expression of the D2 dopamine receptor (D2R) mRNA has been characterized in rat corpus striatum by in situ hybridization histochemistry and Northern and slot blot analyses using oligonucleotide probes directed toward either the D2R-A subtype of the D2R mRNA or to both the D2R-A and D2R-B subtypes of the D2R mRNA. The results showed that both D2R mRNAs were detected in rat striatum at birth, gradually increased until day 16 postnatally (P16), then declined slightly. At early stages of development, the hybridization signal, when viewed under low magnification, was fairly evenly distributed throughout the striatum. However, later in development (P16) a cluster pattern became manifest. Autoradiographic studies using the mu-opiate receptor as an indication of striatal 'patches' in serial, adjacent sections of striatum indicated that the cluster pattern of the D2R mRNA was not associated solely with the patch or matrix compartments of the striatum. A cellular analysis showed that at early developmental stages the quantity of D2R mRNA per cell was very low in striatum. During the first two postnatal weeks, certain subpopulations of striatal neurons evidenced a marked increase in the expression of D2R mRNA per cell. Administration of 6-hydroxydopamine into neonatal rats failed to significantly change the developmental profile of D2R mRNA in the rat striatum of 16- and 32-day-old animals, although the same treatment caused a marked increase in proenkephalin mRNA. These results suggest that the postnatal development of the D2R mRNA in rat striatum correlates well with the ontogeny of the D2 dopamine receptor, that the developmental expression of the D2R mRNA is highly associated with the maturation and differentiation of striatal neurons, and that the development of the D2R mRNA in rat striatum, unlike that of proenkephalin mRNA, can proceed even with reduced dopaminergic afferent input from the substantia nigra.

Animals↗
PubMed1991

Neuronal localization and modulation of the D2 dopamine receptor mRNA in brain of normal mice and mice lesioned with 6-hydroxydopamine.

A novel oligonucleotide probe was designed, characterized and utilized to study the distribution and modulation of the mRNA encoding the D2 dopamine receptor in the brain of the mouse. Using in situ hybridization histochemistry, the highest levels of the D2 receptor mRNA were found in regions of the brain containing the cell bodies and the terminal projection fields of the nigrostriatal, mesolimbic and mesocortical dopaminergic systems. Particularly high levels of the D2 receptor mRNA were found in substantia nigra pars compacta, ventral tegmental area, caudate-putamen and olfactory tubercle. This distribution generally paralleled that of the D2 dopamine receptor. Some areas, not usually associated with dopaminergic systems, also contained significant levels of the D2 receptor mRNA signal. These areas included the hippocampus, certain thalamic nuclei, the inferior colliculus and the spinal trigeminal nucleus of the medulla and spinal cord. Lesioning the corpus striatum with 6-hydroxydopamine had little effect on the level of the D2 receptor mRNA in the striatum but greatly reduced the hybridization signal in the substantia nigra pars compacta and ventral tegmental area. Similarly, lesioning the substantia nigra, nearly abolished the signal in the pars compacta but failed to substantially alter the D2 receptor mRNA signal in the striatum. These results suggest that the D2 receptor mRNA in the substantia nigra pars compacta was localized largely to dopaminergic cell bodies, the terminal projections of which lie in the striatum and codes for D2 autoreceptors and that the D2 receptor mRNA of the striatum is in non-dopaminergic cell bodies that are intrinsic to the striatum and probably codes for post-synaptic D2 receptors. Further, the evidence that lesions of striatum and substantia nigra induced with 6-hydroxydopamine greatly reduced the D2 receptor mRNA signal in the substantia nigra, without concomitantly increasing the D2 receptor mRNA in the striatum, suggests that the increase in dopamine receptor binding in the striatum that is ipsilateral to the lesion with 6-hydroxydopamine and the enhanced behavioral sensitivity to dopaminergic agonists, cannot be accounted for solely by an increase in D2 receptor mRNA.

Animals↗
PubMed1991

Characterization of rehydrated gelatin gels.

Five percent glutaraldehyde cross-linked gels have shown excellent blood compatibility as coatings for cardiac prostheses. A method was developed for producing thin dehydrated coatings using a proprietary dehydration procedure and ethylene oxide (EO) sterilization. The swollen surfaces of rehydrates versus wet (original) gels were compared. Within 30 min of saline rehydration, dry 30-50-microns films on textured surfaces became smooth, uniform, and comparable to original gelatin gels. Mechanical test results after rehydration showed values for strain remain unchanged (39.3 + 10.0 to 40.0 + 7.8%), but stress increased (2.79 + 1.21 to 4.22 + 1.60 dyne/cm2; p less than 0.01). The contact angle data reported gamma C values of 26.1 and 30.4 dyne/cm for original and rehydrated gels. Using a coulometric titrimeter, the measured water content of original gels was reduced from 85 to 3.4% after drying. Dried and saline rehydrated gels had a 73.2% moisture content. Gels shrank 8.8% of their original length after rehydration; however, the thickness of all pump coatings remained stable. Two-hour incubations with bovine platelet rich plasma showed no differences in platelet reactivity or morphology when compared to original gels. Light microscopy and scanning electron microscopy (SEM) showed no evidence of gel cracking or surface defects after pump endurance testing for 3 and 5 weeks. The process of dehydration eliminates the wet storage and sterility problems of such hydrogels and provides a stable film coating for a variety of blood-contacting substrates.

Biocompatible Materials↗
PubMed1991

[Electron microscopic cytochemistry studies on membrane-bound organelles of Trichomonas hominis].

This paper presents the results of an electron microscopy cytochemistry study on the membrane-bound organelles of Trichomonas hominis. Acid phosphatase (ACP) and cytidine monophosphatase (CMPase) were located in the primary lysosomes, digestive vacuoles, as well as in the parabasal body stacks, being usually in its mature surface sacs. Thiamine pyrophosphatase (TPPase) and nicotinamide adenine dinucleotide phosphatase (NADPase) were found in the saccules, being on the mature surface and in the intermediate saccules of parabasal body stacks, respectively. The reactive products of peroxidase (POase) were seen only in the digestive vacuoles. Cytochrome oxidase (COase) and catalase (Cat) reactions were both negative. It is suggested that T. hominis lacks mitochondrion and microbody but possesses hydrogenosome. The parabasal body, endoplasmic reticulum and hydrogenosome were stained well with the U-Pb-Cu impregnation technique.

Animals↗
PubMed1990

Ontogenetic development of calmodulin mRNA in rat brain using in situ hybridization histochemistry.

An oligonucleotide probe complementary to the area on calmodulin coding for the calcium binding domain II on calmodulin was used to study the ontogenetic development of calmodulin mRNA in rat brain using in situ hybridization histochemistry. The hybridization signal for this probe was saturable, RNAse sensitive and was displaced by excess unlabelled calmodulin probe but was not displaced by an S-100 probe or by another calmodulin probe which was complementary to the mRNA coding for a different portion of calmodulin. At birth, high levels of calmodulin mRNA were found in hippocampus, cerebral cortex, thalamic nuclei and corpus striatum, and relatively low levels were in white matter. The rate at which calmodulin mRNA changed during development in the different brain areas varied with the brain area. At postnatal day one, the highest hybridization signals were in the cortical plate of the cerebral cortex, in thalamus and in the pyramidal cell layers of hippocampus and pyriform cortex. This distribution became more uniform with age. In contrast to most other brain areas, calmodulin mRNA in cerebellum increased markedly between one and 32 days postnatal; the hybridization signal was low at day one and was confined to the external germinal layer, but by day 16 calmodulin mRNA was largely in the granular layer. These results taken together with other findings on the effects of calmodulin on cellular growth differentiation, suggest that calmodulin may play a role in neuronal maturation.

Aging↗
PubMed1990

Image processing by microcomputer on ultrastructure of griseofulvin-resistant fungi in favus.

The ultrastructure of 5 griseofulvin-resistant fungi of favus was studied by image processing with microcomputer. It was found that the cell walls of the fungi consisted of 8 layers, and the inner layer containing cytoplasm was loose. It was also found that all structures within the cytoplasm possessed a 1-3 layers integral envelope with chromatins in the nucleus. These might be contributing factors in the development of resistance to griseofulvin. This multiple-layered, thick cell wall might act as a barrier responsible for the impermeability of the cell to griseofulvin.

Drug Resistance, Microbial↗
PubMed1989

Construction and screening of Plasmodium falciparum cDNA library.

The HAINAN isolate of Plasmodium falciparum FCC1/HN was cultured in vitro in large quantities. The total parasite mRNA was purified and reverse transcribed into cDNA. The cDNA fragments were inserted into lambda gt11 to construct a P. falciparum FCC1/HN erythrocytic stage cDNA library. Inhibitory monoclonal antibodies (McAbs) M26-32, F6-C2, and F6-D3 were used to screen the cDNA library expressed in E. coli. A total of 27 positive clones were found to react with M26-32 alone and 34 clones with both M26-32 and F6-C2. These expressed proteins may be candidates for use in malaria vaccine.

Animals↗