Search PubMed⌕ Search

Biomedical subjects

W Lee

Publications and source records attributed to W Lee.

At least 325 records · Page 18Linked to original sources
PubMed1989

Secretion of activin by interstitial cells in the testis.

Activin, a dimer formed by the beta subunits of inhibin, has an effect that is opposite to that of inhibin in a number of biological systems. Which cell types secrete activin in vivo is not known. TM3 cells, a Leydig-derived cell line, contained messenger RNAs that hybridized with human beta A and beta B complementary DNA probes and were similar in size to the porcine messenger RNA for the beta subunits of inhibin. No hybridization to the inhibin alpha subunit was detectable in the TM3 cells. Conditioned medium from TM3 cells and from primary cultures of rat and porcine interstitial cells stimulated the release of follicle-stimulating hormone in a pituitary cell culture assay. It is likely that, in the testis, the Leydig cells secrete activin and the Sertoli cells produce inhibin, or a combination of both.

Activins↗
PubMed1989

Biodegradable mechanical retinal fixation. A pilot study.

Mechanical retinal fixation is a useful tool in the armamentarium of vitreoretinal surgeons. Unfortunately, the use of metallic retinal tacks on a permanent basic mandates a retained intraocular foreign body that poses some potential for long-range toxic effects. Herein, we report the results of our initial experience with a temporary, biodegradable mechanical retinal fixation device ("biopin") in rabbits. When compared with metallic tacks, the biopins appeared to be well tolerated intraocularly, with minimal damage detectable at the light microscopic level. Disinsertion of the biopins occurred in 46% of the eyes within two weeks and in all eyes by four weeks. Initial signs of degradation of the biopins were observed at six weeks (median) in the ensectomized/vitrectomized eyes and at 12 weeks (median) in the nonvitrectomized eyes. Differences were found in the occurrence of retinal detachment between animals that underwent lensectomy/vitrectomy with insertion of two metallic tacks and animals that underwent insertion of one biopin without vitrectomy. The biopin has a potential as a vehicle for sustained release of pharmacologic agents to inhibit directly the development of vitreoretinal proliferation, thereby retarding or preventing subsequent retinal traction and detachment.

Animals↗
PubMed1989

A caliper-hook for strabismus surgery.

An instrument to assist in resection surgery consists of a telescoping hook within a second hook that can be spread a calibrated distance. Its primary purpose is to maintain a constant tension and an accurate measure of tendon length during suture passage. Additionally, the grooved distal hook supports the needle and protects the globe from needle trauma.

Equipment Design↗
PubMed1989

Maternal hemodynamic effects of uterine contractions by M-mode and pulsed-Doppler echocardiography.

Nineteen normotensive term gravid women were studied by M-mode and pulsed-Doppler echocardiography to noninvasively evaluate the hemodynamic consequences of uterine contractions on maternal left ventricular function. These laboring subjects were placed in the left lateral decubitus position with epidural labor anesthesia. Ejection fraction was not affected by firm contractions, although a small increase in left ventricular end-diastolic measurements was noted. There was a tendency for maternal heart rate to decrease (-5%); however, this trend was not statistically significant. A 16% increase in left ventricular stroke volume (75 +/- 15 to 89 +/- 17 ml) (p less than 0.001) was associated with an overall 11% augmentation of maternal cardiac output (6.31 +/- 1.79 to 7.12 +/- 1.93 L/min) (p less than 0.001). These findings support the hypothesis that uterine contractions increase maternal stroke volume through autotransfusion of uteroplacental blood and cardiac preload augmentation during normal labor.

Cardiac Output↗
PubMed1989

Ultrasonographic guidance for central venous access during pregnancy.

Real-time ultrasonographic imaging of vascular and anatomic neck structures allows easy visualization of the right internal jugular vein and carotid artery. Application of this technology during pregnancy may reduce potential complications encountered with central venous monitoring and will be especially useful in cases of difficult anatomy.

Adult↗
PubMed1989

Central hemodynamic assessment of normal term pregnancy.

Ten carefully screened primiparous patients between 36 and 38 weeks' gestation underwent pulmonary artery catheterization, arterial line placement, and central hemodynamic assessment in the left lateral recumbent position. Studies were repeated in the same patients between 11 and 13 weeks post partum. Compared with the nonpregnant state, there was a significant fall in systemic vascular resistance, pulmonary vascular resistance, colloid oncotic pressure, and colloid oncotic pressure-pulmonary capillary wedge pressure gradient by the late phase of the third trimester (p less than 0.05). Pregnancy was associated with a significant rise in cardiac output and pulse in all patients (p less than 0.05). There was no significant change in pulmonary capillary wedge pressure, central venous pressure, left ventricular stroke work index, or mean arterial pressure. Normally the late phase of the third trimester is not associated with hyperdynamic left ventricular function as assessed by the left ventricular stroke work index/pulmonary capillary wedge pressure ratio.

Adult↗
PubMed1989

Doppler assessment of the fetal and uteroplacental circulation during nifedipine therapy for preterm labor.

To investigate the effects of nifedipine on the human fetal circulation, 11 fetuses whose mothers were treated with nifedipine for treatment of preterm labor were studied. Maximum velocity waveforms were obtained in the middle cerebral artery (n = 8), renal artery (n = 6), ductus arteriosus (n = 8), and umbilical artery (n = 10). Transvalvular maximal velocity waveforms were obtained across the aortic (n = 11) and pulmonary (n = 7) valves. Maternal uterine arteries also were studied (n = 7). Doppler data were collected before and 5 hours after nifedipine therapy. Patients received an oral loading dose of 30 mg of nifedipine followed by a second oral dose of 20 mg 4 hours later. No significant difference in the flow velocity waveforms was found in the vessels studied 5 hours after the initial dose. These results suggest that short-term nifedipine therapy does not influence either fetal or uteroplacental circulation as evaluated with the Doppler technique.

Adolescent↗
PubMed1989

A comparison of immunoblot and DNA restriction patterns in characterising methicillin-resistant isolates of Staphylococcus aureus.

The ability of EcoR1 restriction enzyme fragmentation patterns and of immunoblotting to differentiate methicillin-resistant isolates of Staphylococcus aureus were compared. All isolates examined were typable by both methods and the reproducibility of each was excellent. Immunoblotting differentiated eight types and DNA restriction patterns four. The former technique was of value in characterising methicillin-resistant isolates of S. aureus and controlling an outbreak due to them.

DNA, Bacterial↗
PubMed1989

Regulation of muscarinic receptor subtypes and their responsiveness in rat brain following chronic atropine administration.

Chronic administration of l-atropine to rats caused a dose-dependent increase (30%) in the density of muscarinic receptors, as measured with [3H]quinuclidinyl benzilate ([3H]QNB], in cortex (CTX), dorsal hippocampus (DH), and heart but not the corpus striatum. Serum concentrations of l-atropine reached 80 to 160 nM within 6 hr, whereas densities of binding sites for [3H]QNB did not show a significant increase until after the second day of infusion and receptor densities did not reach new steady state levels until after the fourth day of infusion. The density of binding sites for the M1-selective muscarinic receptor antagonist, [3H]pirenzepine ([3H]PZ) was also measured. As noted previously, the density of binding sites for [3H]PZ (defined as M1) was lower than the density of binding sites for [3H]QNB (defined as M1 plus M2). When the densities of binding sites for [3H]QNB and [3H]PZ in CTX plus DH were determined after 14 days of treatment, [3H]QNB binding sites showed a 28% increase, whereas [3H]PZ binding sites did not show any increase. The difference between the densities of binding sites for [3H]QNB and [3H]PZ, an estimate of the density of M2 sites, doubled. The density of binding sites for [3H]QNB appeared to be stable for at least 64 hr after the withdrawal of the drug. The increase in the density of binding sites for [3H]QNB was not reflected in the binding of [3H]oxotremorine-M ([3H]OXO-M), a muscarinic agonist, which was unchanged by l-atropine administration. Because the binding of [3H]OXO-M is sensitive to GTP, this observation suggests that the "induced" receptors may not be coupled to a guanine nucleotide-binding protein. In spite of the fact that there was a doubling of the density of M2 sites, no significant differences in dose-response curves for carbachol-induced inhibition of [3H]cAMP accumulation were observed in slices of CTX plus DH from control and l-atropine-treated rats. Similarity, acetylcholine-stimulated accumulation of [3H]inositol phosphates in slices of CTX plus DH showed no significant differences between the tissues from control and treated rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Management of septic shock complicating pregnancy.

Septic shock can be a devastating management problem during pregnancy. Current concepts regarding the pathophysiology and clinical impact of this disorder are detailed with emphasis upon the cardiovascular system. A hemodynamic approach for stabilizing such patients is offered.

Critical Care↗
PubMed1989

Cost-analysis of neonatal intensive and special care.

In the present economic climate and with increasing expenditure on neonatal intensive care, there has been a demand for economic evaluation and justification of neonatal intensive care programmes. This study assesses the inhospital costs of neonatal intensive care. Fixed and variable costs were calculated for services and uses of an Intensive/Special Care Nursery for the year 1985 and corrected to 1987 Australian dollar equivalents. Establishing a new neonatal intensive care unit of 43 costs in an existing hospital with available floor space including operating costs for a year were estimated in Australian dollars for 1987 at $6,408,000. Daily costs per baby for each were $1282 ventilator, $481 intensive, $293 transitional and $287 recovery, respectively. The cost per survivor managed in the Intensive/Special Care Nursery in 1985 showed the expected inverse relationship to birthweight being $2400 for greater than 2500 g, $4050 for 2000-2500 g, $9200 for 1500-1999 g, $23,900 for 1000-1499 g and $63,450 for less than 1000 g. Further analysis for extremely low birthweight infants managed in 1986 and 1987 demonstrated costs per survivor of $128,400 for infants less than 800 g birthweight and $43,950 for those 800-999 g. This methodology might serve as a basis for further accounting and cost-evaluation exercises.

Birth Weight↗
PubMed1988

Hypodermic stainless steel tacks and companion inserter designed for peripheral fixation of retina.

Mechanical fixation of the torn or cut edge of retina with 30-gauge hypodermic stainless steel tacks has been performed in 15 patients at the Bascom Palmer Eye Institute, Miami, and Miami Veterans Administration Medical Center with six to 18 months of follow-up. The companion tack inserter allows the surgeon to select an angle for the shaft of the tack in relation to the inserter to allow the tack to be driven perpendicularly into sclera even when the insertion is anterior to the equator. If residual detachment remains following fluid-gas exchange after preliminary placement of the retinal tacks, a given tack may be removed and reinserted to facilitate complete retinal reattachment. This utilitarian feature allows the surgeon to eliminate residual anteroposterior traction following complete membrane peeling by extending relaxing retinotomies and tacking the posterior cut edge of the retina securely between the ora serrata and the equator.

Adult↗
PubMed1988

Antagonistic effect of dibutyryl cyclic GMP on caerulein induced insulin secretion in isolated perifused rat islets.

The effects of caerulein and dibutyryl cyclic GMP on isolated rat islets were studied using the perifusion system. One, 20, 50 and 100 nM caerulein stimulated insulin secretion in the perifused rat islets, in a dose dependent manner. Insulin secretion reached a maximal level in the presence of 50 nM caerulein. Caerulein-induced insulin secretion showed a predominant first and minimal second phase. After cessation of stimulation with 50 nM caerulein, the insulin secretion level did not return to the basal value, but enhanced hormone secretion was sustained to a significant extent (p less than 0.01). The simultaneous administration of 10(-3) M dibutyryl cyclic GMP, a specific membrane antagonist against cholecystokinin (CCK), inhibited the first and second phases of caerulein-induced insulin secretion. Moreover, with this nucleotide, "persistent" insulin secretion induced by 50 nM caerulein was inhibited. These data indicate that caerulein directly stimulates pancreatic B cells and that this peptide causes "persistent" insulin secretion. Dibutyryl cyclic GMP counteracts the effects of caerulein. Thus, both pancreatic B cells and pancreatic acinar cells possibly possess a CCK receptor.

Animals↗