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Biomedical subjects

M C Lee

Publications and source records attributed to M C Lee.

At least 289 records · Page 16Linked to original sources
PubMed1987

Lectins as markers for eosinophilic leukocytes.

Lectin from Griffonia simplicifolia (GSA-I) and soybean (SBA) are reliable markers for human eosinophils. In this study we have shown that fluorochrome labeled GSA-I and SBA can be used for specific labeling of eosinophils in paraffin embedded tissue sections, in peripheral blood smears and in cell suspensions prepared for flow cytometry. These two lectins are useful diagnostic reagents which could be applied for further characterization of cytoplasmic components selectively found in human eosinophils.

Cell Separation↗
PubMed1987

Biaxial mechanical properties of human pericardium and canine comparisons.

The two-dimensional mechanical properties of human pericardium from seven males undergoing coronary artery bypass surgery were studied. A 25-mm square piece of parietal pericardium overlying the right ventricle was excised. An approximately 8-mm square target was marked at the center, and its dimension was measured electrooptically. When immersed in physiological saline at 37 degrees C, the specimen was subjected to biaxial isotropic loading. Large deformations developed in the beginning of the loading; the pericardium became increasingly stiffer when load was increased, and then became almost inextensible. As in canine pericardium [Lee et al., Am. J. Physiol. 249 (Heart Circ. Physiol. 18): H222-H230, 1985], hysteresis was present and tension-stretch relationship was insensitive to loading frequency during cyclic loading, relaxation of tension was substantial, and creep was insignificant. Unlike canine specimens, however, human pericardium was nearly isotropic and almost three times as thick [mean 0.55 +/- 0.02 mm (SD)]. The human tension-area relation for isotropic loading could be described by an exponential function and was found to shift significantly to the left of the canine. Therefore, human pericardium is less extensible than canine.

Adult↗
PubMed1986

Blood flows in the maxillocarotid anastomoses and internal carotid artery of conscious dogs.

Although the external carotid artery is known to contribute to the cerebral blood flow in anesthetized dogs, quantitative information on the anastomoses and their role in conscious dogs is lacking. This study was carried out to determine blood flows in these anastomoses and the internal carotid artery, and also to examine the functional significance of the anastomoses in conscious dogs. Fifteen-micron radioactive microspheres were injected into common and external carotid arteries of four conscious dogs through chronically implanted catheters. Blood flows were determined by the reference sample method and by comparing microsphere distributions in the brain and the masseter muscle. Blood flows were estimated to be 140 +/- 32, 7.7 +/- 1.4, and 3.3 +/- 1.1 ml/minute (mean +/- SD) in the common carotid artery, internal carotid artery, and anastomoses on each side, respectively. Additional evidence indicated that the anastomotic flow so determined was primarily the flow in the anastomotic artery. Humoral responses to angiotensin II infusions were also studied in conscious dogs. External carotid angiotensin increased plasma 11-hydroxycorticosteroid concentration (used as an index of ACTH secretion) but did not increase plasma vasopressin concentration to the same extent as common carotid infusion. Therefore, the external carotid artery is functionally important in perfusing the brain in conscious dogs.

11-Hydroxycorticosteroids↗
PubMed1986

Lectin binding sites on human endocervix: a comparison with secretory and proliferative endometrium.

Endocervix and corresponding endometrium of women of reproductive age were studied histochemically with 13 fluorescein isothiocyanate-labeled lectins to delineate the differences between the epithelial cells in two anatomical sites. Lectin from Maclura pomifera (MPA), Ulex europaeus (UEA-I), Glycine max (SBA), and Vicia villosa (VVA) bound only to endocervical epithelium and were the only four lectins that distinguished endocervical from endometrial epithelium. These differences were independent of menstrual cyclic changes and blood group antigen secretion. These data show that lectins can be used to histochemically distinguish endocervical from endometrial glands.

Cell Division↗
PubMed1986

A constitutive model for two-dimensional soft tissues and its application to experimental data.

A constitutive relation proposed by Shoemaker (Ph.D. dissertation, 1984) to model the mechanical behavior of membraneous or two-dimensional soft tissues is described. Experiments by Schneider (Ph.D. dissertation, 1982) on human skin and Lee et al. (Am. J. Physiol., 249, H222-H230, 1985) on canine pericardium, and the application of the constitutive model to biaxial stress-strain data from these experiments, are discussed. Some experimental data and predictions of the model obtained by curvefitting are presented for comparison. Values of material parameters are also presented. It is concluded that the constitutive model is well able to fit results of individual tests, and that its generality (judged by consistency of parameters from test to test of the same specimen), though not complete, does compare favorably with some other results presented in the literature.

Animals↗
PubMed1986

Regulation of the yeast metallothionein gene.

To study regulation of the yeast CUP1 gene, we have employed plasmids containing the CUP1 regulatory sequences fused to the Escherichia coli galK gene. A comparison of galK expression from low- and high-copy-number CUP1/galK fusion plasmids demonstrated that both basal and induced levels of galactokinase (GalK) increase proportionately with plasmid copy number. Host strains with an amplified, single or deleted CUP1 locus were compared to look for effects of chromosomal CUP1 gene dosage on expression from the episomal CUP1 promoter. Basal GalK levels are similar in CUP1R and cupls hosts, but can be induced to higher levels in the cup1s than the CUP1R host. In contrast, in a strain deleted for the chromosomal copy of CUP1, synthesis of GalK is constitutive but can be induced to yet higher levels by copper. A hybrid vector, placing the CUP1 coding sequence under the control of a constitutive promoter, was constructed. Introduction of this hybrid CUP1 gene into the deletion host containing the CUP1/galK plasmid restores regulation. Thus, metallothionein, in trans, can effect repression of the CUP1 promoter. The possible roles of metallothionein and free copper in CUP1 regulation are discussed.

Copper↗
PubMed1986

Simplified detection system for neuroreceptor studies in the human brain.

A simple, inexpensive dual-detector system has been developed for measurement of positronemitting receptor-binding drugs in the human brain. This high efficiency coincidence counting system requires that only a few hundred microcuries of labeled drug be administered to the subject, thereby allowing for multiple studies without an excessive radiation dose. Measurement of the binding of [11C]carfentanil, a high affinity synthetic opiate, to opiate receptors in the presence and in the absence of a competitive opiate antagonist indicates the potential utility of this system for estimating different degrees of receptor occupation in the human brain.

Binding, Competitive↗
PubMed1985

Transfer RNA splicing in Saccharomyces cerevisiae. Secondary and tertiary structures of the substrates.

Secondary and tertiary structures of four yeast tRNA precursors that contain introns have been elucidated using limited digestion with a variety of single-strand- and double-strand-specific nucleases. The pre-tRNAs, representing the variety of intron sizes and potential structures, were: pre-tRNALeuCAA, pre-tRNALeuUAG, pre-tRNAIleUAU, and pre-tRNAPro-4UGG. Conventional tRNA cloverleaf structure is maintained in these precursors except that the anticodon loop is interrupted by the intron. The intron contains a sequence which is complementary to a portion of the anticodon loop and allows the formation of a double helix often extending the anticodon stem. The 5' and 3' splicing cleavage sites are located at either end of this helix and are single-stranded. The intron is the most sensitive region to nuclease cleavage, suggesting that it is on the surface of the molecule and available for interaction with the splicing endonuclease. Absence of Mg2+ or spermidine renders the dihydrouridine and T psi C loops of these precursors highly sensitive to nuclease digestion. These ionic effects mimic those observed for tRNAPhe and suggest that the tRNA portion of these precursors has native tRNA structure. We propose consensus secondary and tertiary structures which may be of significance to eventual understanding of the mechanism of yeast tRNA splicing.

Macromolecular Substances↗
PubMed1985

Lectin binding sites on human sperm and spermatogenic cells.

Testes of sexually mature men were studied histochemically with 20 fluorescein isothiocyanate-labeled lectins. Based on their pattern of reactivity with intratesticular spermatogenic cells, lectins were divided into five groups: 1) lectins reacting with all spermatogenic cells (Suc. ConA, WGA, LCA, PHA-E, PHA-L, STA, MPA, and RCA-II); 2) lectin reacting with spermatocytes, spermatids, and spermatozoa, but not with spermatogonia (RCA-I); 3) lectins reacting with spermatids and spermatozoa only (BPA, PNA, SBA, and VVA); 4) lectins reacting only with spermatozoa (HPA, GSA-I, UEA-II, and GSA-II); and 5) lectins with no distinct staining of spermatogenic cells (DBA, LBA, and UEA-I). All lectins from groups 1-4 were reactive with ejaculated spermatozoa. On the basis of the staining patterns of the head region of ejaculated spermatozoa, four lectin reactivity groups were defined: 1) lectins reacting with the plasma membrane of the whole head (BPA, WGA, LCA, STA, RCA-II, PHA-E, PHA-L, RCA-I, UEA-II, and GSA-II); 2) lectin reacting with the acrosomal cap and postacrosomal region of the plasma membrane (Suc. ConA); 3) lectin reacting with the acrosomal cap region of the plasma membrane (PNA); and 4) lectins reacting with the midregion of the sperm head in a bandlike manner (HPA, VVA, SBA, GSA-I, and MPA). These data provide a map of lectin binding sites on human testicular spermatogenic cells and ejaculated spermatozoa and show that the distribution of glycoconjugate domains of spermatogenic cell changes during differentiation and maturation.

Adult↗
PubMed1985

Pregnancy-related changes in the human endometrium revealed by lectin histochemistry.

The binding of 22 fluorescein isothiocyanate (FITC) conjugated lectins to human proliferative phase and pregnant endometrium was studied histochemically. Only the lectin from Bauhinia purpurea (BPA) reacted exclusively with the epithelial cells. All the others reacted to a certain extent with glandular and/or stromal cells. Lectins from soybean (SBA), and Vicia villosa seeds (VVA) reacted with endometrial glands of pregnancy but not with the glands of the proliferative endometrium. In the proliferative endometrium SBA reacted only with cells of the surface endometrium. Lectin from peanuts (PNA) reacted only with some glands in the proliferative endometrium but was unreactive with others. In pregnant endometrium PNA reacted with all glands. Lectins from lentils (LCA) and red kidney beans (PHA-E and PHA-L) reacted with endometrial glands of the proliferative phase but not with the glands from pregnant endometrium. We thus show that FITC labeled lectins define specific carbohydrate moieties selectively expressed on either proliferative phase or pregnant endometrial glands.

Endometrium↗
PubMed1985

Biaxial mechanical properties of the pericardium in normal and volume overload dogs.

The two-dimensional mechanical properties of the pericardium from dogs with a normal or chronically enlarged heart were studied in vitro. A 3.0-cm-square piece of the pericardium overlying the right and/or left ventricle was excised. An approximately 1.0-cm-square target was marked at the center, and its dimension was measured electrooptically. When immersed in physiological saline at 37 degrees C, the specimen was stretched and unloaded sinusoidally in one direction while force in the transverse direction was held constant. The tension-stretch relationship was highly reproducible and was insensitive to strain rate in the range of 0.002-0.1 Hz. Hysteresis was present. The pericardium was mostly anisotropic; however, the direction of maximal compliance varied among dogs. The elastic properties of the pericardium overlying the left and right ventricles were the same in most cases. Substantial stress relaxation was observed; in contrast, insignificant creep developed over 30 min. In five dogs with chronic cardiac dilatation due to an infrarenal aortocaval shunt, the tension-stretch curves were shifted significantly to the right (i.e., greater deformation at the same tension level). However, the pericardial viscoelastic properties and thickness were unchanged. In other words, chronic cardiac dilatation resulted in a more compliant pericardium.

Animals↗
PubMed1985

Lectin histochemistry of classic and spermatocytic seminoma.

Six spermatocytic and 13 classic seminomas were studied histochemically with fluorescein isothiocyanate-labeled lectins. Wheat-germ lectin and succinyl concanavalin A reacted with all 19 tumors, whereas other lectins bound to some, but never to all, tumors in either group. Soybean lectin reacted with seven of 13 classic seminomas but with none of the spermatocytic seminomas. On the other hand, Maclura pomifera lectin reacted with two of six spermatocytic and with none of the classic seminomas. Our data thus illustrate some differences between classic and spermatocytic seminomas, but no diagnostic or pathognomonic pattern of lectin binding could be discerned. Neither classic nor spermatocytic seminomas (with a single exception) reacted with the lectins that do not react with normal spermatogenic cells. Spermatocytic seminomas did not react with eight lectins typically recognizing spermatids and spermatozoa. Thus, our data do not support the earlier contentions that spermatocytic seminomas contain malignant equivalents of cells in advanced stages of spermatogenesis.

Dysgerminoma↗
PubMed1984

Transfer RNA splicing in Saccharomyces cerevisiae: defining the substrates.

The primary sequences of all the tRNA precursors which contain intervening sequences and which accumulate in the Saccharomyces cerevisiae rnal mutant are presented. A combination of DNA and RNA sequence analysis has led to elucidation of the primary sequence of four hitherto uncharacterized precursors. The location of the intervening sequence has in all cases been unambiguously determined by analysis of the intermediates in the splicing reaction. Secondary structures based upon the tRNA cloverleaf are shown for all the tRNA precursors and discussed with respect to common recognition by the yeast splicing endonuclease.

Base Sequence↗
PubMed1984

Spasmodic torticollis and other idiopathic torsion dystonias. Medical management.

The pathophysiologic mechanisms of spasmodic torticollis and other idiopathic torsion dystonias remain unknown. Thus, a variety of drugs have been used alone or in combination on an empirical basis to treat these disorders, but to date none have efficacy that is proven and consistent. The drugs in use include anti-cholinergics, benzodiazepines, dopaminergics , and neuroleptics. The variable responses that have been observed are due in part to the heterogeneous nature of these disorders. Trial of several agents or combinations of agents may be necessary before symptoms are satisfactorily controlled. Only when a patient's symptoms are refractory to all medical treatment should he or she be considered a candidate for neurosurgical procedures.

Adrenergic Agents↗
PubMed1984

Lectin binding sites of the mouse ovary, intraovarian and ovulated ova.

Fluorescein isothiocyanate (FITC) labeled lectins were used to study the distribution of specific binding sites in histologic sections of mouse ovaries as well as ovulated ova. Four distinct patterns of reactivity of the components of the follicle (exclusive of the ovum) and the surrounding ovarian stroma were recognized: uniform staining of granulosa cells, theca cells and surrounding stroma; weak to moderate staining of the granulosa cells and strong staining of the theca cells and stromal cells; no reactivity of the granulosa cells coupled with strong reactivity of the theca and stromal cells; no reactivity with any component of the cumulus oophorus. Three lectins (from Triticum vulgare, Arachis hypogaea and Maclura pomifera) distinctly accentuated the basal lamina of the cumulus oophorus. The reaction of lectins with oocytes and zona pellucida revealed six distinct patterns: no reactivity with either structure; weak reactivity with the cytoplasm of the oocyte and no reactivity with the zona pellucida; very strong reactivity with the cytoplasm of the oocyte and no reactivity with the zona pellucida; moderate reactivity with both the oocyte and the zona pellucida; moderate reactivity with the oocyte and very strong reactivity with the zona pellucida; no reactivity with the oocyte and moderate reactivity with the zona pellucida. The same pattern of reactivity was seen in the ovulated ova in the oviduct except for the lectin from Arachis hypogaea, the reactivity of which changed upon ovulation and/or fertilization of the ovum. These data provide a list of lectin markers for distinct components of the mouse ovary.

Animals↗