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Biomedical subjects

D Lee

Publications and source records attributed to D Lee.

At least 415 records · Page 23Linked to original sources
PubMed1993

Ascorbic acid enhances forskolin-induced cyclic AMP production and pro-ANF mRNA expression of hypothalamic neurons in culture.

Besides acting as an important cofactor in the biosynthesis of catecholamine, ascorbic acid (AA) also modulates the activity of peptidyl-glycine alpha-amidating monooxygenase for the post-translational modification of neuropeptides such as alpha-MSH and TRH. We report here a novel action of AA in modulating the secretion and mRNA expression of atrial natriuretic factor (ANF) in rat hypothalamic neurons. Primary cultures of hypothalamic neurons from neonatal rats as previously described were employed in the present studies. Six days after plating, cultures were replenished with serum free media and incubated with vehicle or various doses of AA, alone or in the presence of forskolin. Treatment with AA alone significantly increased irANF secretion from the cultures in a time-related and a dose-dependent manner with an ED50 of approximately 3 microM and an Emax of 100 microM. At the concentration of 10 microM, AA augmented irANF release approximately 3 fold that of the controls (55 +/- 7 pg/well; mean +/- SE, n = 3; P < 0.01), but it failed to affect the abundance of pro-ANF mRNA in the cultures. However, 10 microM of AA markedly enhanced forskolin-induced irANF secretion and pro-ANF mRNA abundance of the cultured cells. This potentiating effect of AA on forskolin stimulation showed a good parallelism to the levels of cAMP produced in the hypothalamic cultures. We thus conclude that AA acts alone or in synergism with forskolin to stimulate the secretion and production of ANF in rat hypothalamic neurons; this latter effect may operate at the genomic level and is mediated, at least in part, through the protein kinase A dependent pathway.

Animals↗
PubMed1993

In vitro evidence for atrial natriuretic factor-(5-28) production by macrophages of adult rat thymi.

Although recent evidence suggests the presence of the 15-kilodalton (K) mol wt (Mr) precursor of atrial natriuretic factor (ANF) and pro-ANF mRNA in the thymus of human and rat neonates, the cellular origin of the peptides in the tissues remains to be elucidated. We report here that in adult male rats, the 15K M(r) presumptive precursor for ANF and a smaller 3K M(r), N-terminal truncated congener of the peptide, ANF-(5-28), are localized in a small population of thymic macrophages. The production of ANF in the thymus was further confirmed by demonstrating the presence of a single band of pro-ANF mRNA signal of approximately 0.8 kilobases from the tissue extract, corresponding to that in the heart. To examine the distribution of pro-ANF mRNA at a cellular level, colorimetric in situ hybridization with digoxigenin-labeled 30-mer oligonucleotides complementary to the first 10-amino acid sequence of ANF-(1-28) was employed. Positive staining was found in thymic cells localized mainly in subcapsular areas, with diffuse staining of positive cells in both the cortex and medulla mainly concentrated around the cortico-medullary junction of the tissue. The identity of the ANF-positive cells was further investigated using a double staining technique to costain immunoreactive (ir) ANF and the macrophage markers ED1 and S22 or the T-cell marker OX-19 in both thymic sections and in monolayer cultures of thymic cells. In the latter, approximately 17% of the adherent cells stained positive for irANF after 48 h in culture. Of these cells, more than 95% also stained positive for the macrophage marker ED1, whereas approximately 36% of the ED1-positive cells were colocalized with irANF. In contrast, no irANF-positive cells were colocalised with the pan-T-cell marker OX-19. In tissue sections, irANF was found in cells distributed predominantly around the cortico-medullary junctions and subcapsular areas, with diffuse staining of the cells in the medullary and cortical regions. Sephadex G-50 gel chromatographic profiles of thymic extracts revealed a major peak of immunoreactivity consistent with 15K M(r) and a smaller peak that coeluted with rat ANF-(1-28) of 3K M(r). HPLC analysis of the 3K M(r) species showed a single peak of immunoreactivity, which eluted with a retention time identical to that of synthetic rat ANF-(5-28).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Coexpression of atrial natriuretic factor and beta-endorphin in a subpopulation of rat splenic macrophages: age-related differences.

Separate demonstration of immunoreactive (ir) atrial natriuretic factor (ANF) and ir-beta-endorphin (beta EP) in macrophages of the rat spleen prompted a reexamination of their distribution and cellular localization in addition to their developmental regulation. Double labeling immunohistochemistry was carried out on paraffin-embedded spleen sections of adult male Sprague-Dawley rats. Cells stained positive with antiserum (S118) raised against rat ANF-(99-126) were colocalized in more than 95% of cases with immunofluorescent staining of ir beta EP-(1-31) and distributed sparsely throughout the venous sinusoidal regions of the red pulp. In 1- or 5-day monolayer cultures of adherent splenocytes, 11-16% of the cells stained positive for either irANF or ir beta EP. Under these conditions, more than 95% of irANF- and ir beta EP-positive cells were also fluorescence stained for the histiocyte marker S22 or the rat macrophage marker ED-1. Colorimetric in situ hybridization similarly revealed signals for pro-ANF mRNA in more than 95% of ir beta EP-positive adherent cells. Thus, taken together with previous reports, our present findings suggest that in the rat spleen, both ANF and beta EP are produced by the same population of macrophages. However, the tissue levels and processing of the two peptides over the developmental period of the animal differed markedly in several ways. In splenic extracts of 2-day-old neonatal rats, Northern blot analysis and RIA revealed a greater abundance of pro-ANF mRNA signal and an irANF concentration about 6-fold greater than those in 30-day-old animals. In contrast, the ir beta EP concentration did not vary significantly over the same period, consistent with the level of POMC mRNA. Sephadex G-50 gel chromatography of splenic extracts from 2-day-old animals revealed predominantly higher mol wt forms of irANF and ir beta EP. From days 16-60, a significant proportion of irANF eluted in the same fractions as the mature circulating form, rat ANF-(99-126); the proportion of 3.5-kilodalton ir beta EP increased progressively to become the predominant species in adult tissues. Thus, it appears that although ANF and beta EP are coexpressed by the same population of splenic macrophages, they differ markedly during the developmental period with respect to their constitutive regulation.

Aging↗
PubMed1993

Pitfalls in evaluation of photosensitizing agents: an example with Q-switch II dye.

Photosensitizing agents potentiating laser therapy should have limited toxicity, no mutagenicity, stable spectral characteristics, and acceptable solubility when administered in vivo. Q-Switch II dye (QII) has been shown by others to be an effective chromophore for photodynamic therapy at 1051 nm in fibroblast cell culture. The objective of this study was to determine the spectral stability of QII in biological media and then to localize QII after administration in vivo. Spectral evaluation was performed between 250 and 1100 nm. QII dissolved in dimethyl sulfoxide (DMSO) rapidly lost its spectral characteristics, including its 1051-nm peak, when contacting water, minimal essential medium, human serum, organ surfaces, and intracellular fluid. One minute following intramuscular (IM) injection of 0.1 mg QII in 0.2 mL of DMSO, the dose precipitated as a discrete mass which was excised and reconstituted in DMSO. A new spectral pattern was seen, with no absorption between 850 and 1100 nm. Following intravenous (i.v.), (IM), or intraperitoneal (IP) injection, QII was not detected in any organ. Q-Switch II dye is not a suitable chromophore for in vivo photodynamic therapy at 1051 nm. Previous cell culture reports to the contrary did not account for the QII spectral change caused by biological media. Simple rapid assays are described to avoid this pitfall.

Absorption↗
PubMed1993

The role of thyroidal type-I iodothyronine deiodinase in tri-iodothyronine production by human and sheep thyrocytes in primary culture.

We have studied the origin of tri-iodothyronine (T3) secreted by human and sheep thyrocytes in primary culture and also the expression of type-I thyroidal iodothyronine deiodinase (ID-I) in the thyroid and liver of man and various other animals. Inhibitors of ID-I reduced T3 secretion from human but not sheep thyrocytes. In contrast, inhibitors of de-novo thyroid hormone synthesis reduced both thyroxine (T4) and T3 production in sheep thyrocytes, but had no effect on the T3 secreted by human thyrocytes. Human thyrocytes did not produce T4 under the culture conditions used, although some endogenous T4 was present in the cells following their isolation. Although thyrotrophin (TSH) stimulated T3 production in both human and sheep thyrocytes, iodine in the form of potassium iodide was only essential for T3 and T4 production by the sheep cells. Although 125I from Na125I was incorporated into T3 and T4 in TSH-stimulated sheep thyrocytes, no 125I incorporation into T3 or T4 was detected in TSH-stimulated human thyrocytes. Using activity measurements and affinity labelling, ID-I was present in the livers of all species studied, but ID-I could not be detected in thyroid tissue from cattle, pigs, sheep, goats, rabbits, deer or llamas. In contrast, thyroid tissue from man, mice, guinea-pigs and rats had significant ID-I activity and expressed an affinity-labelled protein with a molecular mass of approximately 28.1 kDa on SDS-PAGE. These data show that under the culture conditions used, sheep thyrocytes produced T3 by de-novo synthesis, whilst human thyrocytes produced T3 by deiodination of endogenous T4. We conclude that thyroidal ID-I shows marked species difference in its expression and that, in those species which express the enzyme (man, mice, guinea-pigs and rats, in this study), it appears that it may make an important contribution to thyroidal T3 production.

Animals↗
PubMed1993

Effect of implementing a cancer chemotherapy order form on prescribing habits for parenteral antineoplastics.

Effect of implementing a cancer chemotherapy order form on prescribing habits for parenteral antineoplastics. The purpose of this study was to determine whether the use of a cancer chemotherapy order form improved prescriber inclusion of necessary prescription information to minimize errors for parenteral antineoplastics when compared to orders written on standard treatment-order forms. Standard treatment order forms and the newly developed chemotherapy order forms were examined for differences in completeness of the following 13 prescription components: diagnosis, height, weight, body surface area, start date and time, dosage (e.g., mg/m2), dose (mg), solution diluent (drips only) and volume (drips only), infusion rate (drips only), route (i.e., IV push or IV drip), frequency of administration, and total number of scheduled doses. The results demonstrate a significant improvement in completeness of necessary prescription information when cancer chemotherapy was ordered by physicians using a chemotherapy order form compared to a standard treatment order form. Importantly, the availability of various prescription components such as height, weight, and dosage may be used by the pharmacist to verify physicians' calculations of body surface area and dose and thereby reduce the chance of serious medication dosage errors. An additional benefit of the new form is a reduction in the time pharmacists spend clarifying orders.

Antineoplastic Agents↗
PubMed1993

Prognosis of mechanically ventilated patients.

In this Department of Veterans Affairs cooperative study, we examined predictors of in-hospital and 1-year mortality of 612 mechanically ventilated patients from 6 medical intensive care units in a retrospective cohort design. The outcome variable was vital status at hospital discharge and after 1 year. The results showed that 97% of patients were men, the mean age was 63 +/- 11 years (SD), and hospital mortality was 64% (95% confidence interval, 60% to 68%). Within the next year, an additional 38% of hospital survivors died, for a total 1-year mortality of 77% (95% confidence interval, 73% to 80%). Hospital and 1-year mortality, respectively, for patients older than 70 years was 76% and 94%, for those with serum albumin levels below 20 grams per liter it was 92% and 96%, for those with an Acute Physiology and Chronic Health Evaluation II (APACHE II) score greater than 35 it was 91% and 98%, and for patients who were being mechanically ventilated after cardiopulmonary resuscitation it was 86% and 90%. The mortality ratio (actual mortality versus APACHE II-predicted mortality) was 1.15. Conclusions are that patient age, APACHE II score, serum albumin levels, or the use of cardiopulmonary resuscitation may identify a subset of mechanically ventilated veterans for whom mechanical ventilation provides little or no benefit.

Aged↗
PubMed1993

A semi-natural habitat for housing small, nonhuman primates.

A semi-natural habitat that was designed to house a social group of squirrel monkeys (Saimiri sciureus sciureus) at Goucher College, in Maryland is described. The design could be readily adapted for use with other small primate species.

Animal Husbandry↗
PubMed1993

Computation of flow fields and shear rates in an aortic bifurcation.

A finite volume method in a boundary-fitted coordinate system together with a zonal grid method is employed to compute the flow fields and shear stresses in a two-dimensional aortic bifurcation. Eddy is found distal to plaques during pulsatile flow, whereas permanent eddies are observed only during steady flow. The computed flow fields are consistent with those visualized experimentally by other authors. It is also found that although the time averaged shear rates in a pulsatile flow are similar to those of a steady flow with mean Reynolds number in most regions, they are different in recirculation zones. This result implies that care should be taken if a steady flow shear rate were to be used in modeling shear-dependent physiological processes. The non-Newtonian viscosity has only a minor effect on the flows.

Aorta, Abdominal↗
PubMed1992

Marked reduction of high density lipoprotein cholesterol in mice genetically modified to lack apolipoprotein A-I.

Atherosclerosis is a major cause of morbidity and mortality in developed countries. In humans the risk of atherosclerosis is inversely correlated with plasma levels of high density lipoprotein (HDL). As a step in determining whether the experimental reduction of plasma HDL level will increase susceptibility to atherosclerosis, we have used gene targeting in embryonic stem cells to produce mice lacking apolipoprotein A-I, the major protein component of HDL particles. Mice homozygous for the disrupted gene have no plasma apolipoprotein A-I detectable by double immunodiffusion; their total plasma cholesterol and HDL-cholesterol levels after overnight fasting are reduced to about one-third and one-fifth of normal levels, and they are grossly deficient in alpha-migrating HDL particles.

Animals↗
PubMed1992

Race/ethnicity and other risk factors for gestational diabetes.

Although gestational diabetes is estimated to complicate between 1% and 5% of pregnancies, there are only limited data on the role of race/ethnicity as well as other risk factors in the development of this disorder. Epidemiologic characteristics of gestational diabetes were assessed in an ethnically diverse cohort of 10,187 women who had undergone standardized screening for glucose intolerance and who delivered a singleton infant at the Mount Sinai Medical Center in New York City between January 1987 and December 1989. The overall prevalence of gestational diabetes was 3.2%. Multiple logistic regression analysis showed excess risks for Oriental women, Hispanics born in Puerto Rico or elsewhere outside the United States, women from the Indian subcontinent and the Middle East, older mothers, heavier women, those with a positive family history of diabetes, women with a history of infertility, and those who delivered on the clinic service. These data suggest that, after controlling for traditional risk factors (maternal age, prepregnancy weight, and a family history of diabetes), Orientals, first generation Hispanics, women from the Indian subcontinent and the Middle East, those with a history of infertility, and low socioeconomic status women are at an increased risk for gestational diabetes.

Academic Medical Centers↗
PubMed1992

Relation of hostility to medication adherence, symptom complaints, and blood pressure reduction in a clinical field trial of antihypertensive medication.

The impact of hostility was examined in relation to the conduct and results of a clinical field trial. Data were derived from a multi-center randomized double-blind study of the comparative effects of antihypertensive therapy (captopril, methyldopa and propranolol) on the quality of life of 620 hypertensive men. Hostility levels were higher in subjects reporting skipping medication dosages compared to those reporting they always complied with the medication schedule. Reporting of symptoms often associated with antihypertensive drug regimens was positively related to hostility scores throughout the study, even during the blinded placebo period. Persons with high hostility scores showed the greatest decline in blood pressure independent of type of antihypertensive medication. However, there was some limited evidence that hostility levels were significantly reduced by one antihypertensive medication. Overall, the present findings suggest that double-blind pharmacologic clinical trials may benefit from using reliable measures of hostility as covariates in the evaluation of symptom reports and amount of blood pressure reduction.

Adult↗
PubMed1992

Inhibition of intimal hyperplasia by photodynamic therapy using photofrin.

Photodynamic therapy using photofrin and light energy inhibits human myofibroblast proliferation in cell culture. The purpose of this study is to evaluate its influence on intimal hyperplasia in vivo. Twenty New Zealand White rabbits underwent a standardized intimal injury to both common carotid arteries with a 2 Fr balloon catheter. One week later, half of the animals received photofrin (5 mg/kg) intravenously. The remaining 10 rabbits received no photofrin. Two days later, all neck incisions were reopened and a 1-cm segment of each of the 40 carotid arteries was exposed for 5 min to 80 mW of 630 nm light energy from a continuous wave tunable dye laser (fluence = 7.6 J/cm2). All vessels were harvested 5 weeks post-laser treatment following in vivo fixation with formalin. From each artery, separate cross-sections taken from both the lasered and non-lasered regions of each vessel were mounted and stained for histologic evaluation. Analyzed segments were then divided into four different treatment groups: group I segments consisted of arterial cross-sections which were taken from vessel regions that were injured but received neither photofrin nor laser treatment (group I, n = 20); group II segments also did not receive photofrin but were exposed to light energy (group II, n = 20); group III segments received photofrin but no light energy (group III, n = 20); and cross-sections in group IV were taken from those segments which received both photofrin and laser treatment. Using planimetry, the ratio of the area of intimal hyperplasia (IH) to the area enclosed by the internal elastic lamina (IEL) was measured for each specimen (IH/IEL).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Percutaneous absorption enhancement of leuprolide.

Chemical enhancers and vehicles were tested for their ability to improve the percutaneous absorption of leuprolide, a nonapeptide (luteinizing hormone releasing hormone analogue; MW 1209.4). In vitro permeabilities in nude mouse, snake, and cadaver skin were evaluated in either Franz diffusion cells or a Bronaugh flow-through system using an HPLC assay. Skin irritation caused by the formulations was evaluated in the rabbit. The chemical enhancer systems investigated strongly enhanced skin penetration of leuprolide. Maximum permeability enhancement of leuprolide acetate can be achieved with a nonirritating formulation containing ethanol, menthol, camphor, methyl salicylate, urea, and hydrogel. The in vitro permeability in nude mouse skin was 10 or 100 times higher than that obtained in cadaver skin, depending on the type of enhancer that was used in the formulation. Snake skin was at least 10 times less permeable than cadaver skin in this study. However, the effects of chemical enhancers on skin permeability were highly dependent on the skin model. Further, the in vitro permeability of leuprolide in the base form was 10 times higher than in the acetate form with the enhancers.

Acetates↗