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Biomedical subjects

R Guzman

Publications and source records attributed to R Guzman.

88 records · Page 5Linked to original sources
PubMed1978

Antibody-mediated activation of a defective beta-D-galactosidase: dimeric form of the activatable mutant enzyme.

Sedimentation analyses of AMEF, an activatable mutant beta-D-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23), and the products of its reaction with Fab fragments of activating antibody show that this enzyme exists mainly as 10S dimers. Activation of AMEF by purified antibody resulted in formation of 16S tetramers. A unifying hypothesis postulating a dimer--tetramer equilibrium accounts for this observation as the counterpart of inactivation, which was shown to involve the breakdown of tetramers into inactive subunits [Roth, R. A. & Rotman, B. (1975) Biochem. Biophys. Res. Commun. 67, 1382--1390]. Conditions are described under which AMEF loses the specific antigenic determinant(s) responsible for binding activating antibody, allowing its subsequent use as an absorption to obtain immunologically purified activating antibody,

Antibodies↗
PubMed1976

Roles of individual mgl gene products in the beta-methylgalactoside transport system of Escherichia coli K12.

Previous findings showed that galactose-binding protein defective mutants (mgl B-,A+,C+) of Escherichia coli K12 are still capable of growth on methyl-beta-D-galactopyranoside, while mgl A- and mgl C- mutants are not. When assayed by previous methods, none of these mutants exhibited methylgalactoside transport system activity. In this study, we present a modified assay developed for measuring low levels of transport. Using this assay, we found that mgl B-,A+,C+ mutants defective in galactose-binding protein accumulate methyl-beta-D-galactopyranoside up to six times the concentration gradient while mgl A- and mgl C- mutants failed to accumulate this substrate. Similar results were obtained using D-glyceryl-beta-D-galactopyranoside, another substrate of the methylgalactoside transport system. In contrast, all sugars tested which are not substrates of this system were transported equally by all mgl- mutants. The kinetic parameters of transport in mgl B- mutants were compared to those of the isogenic mgl+ strain which accumulates methyl-beta-D-galactopyranoside against a 10,000-fold concentration gradient. The apparent Km of methyl-beta-D-galactopyranoside influx was 1,000 times greater in mgl B- than in mgl+ strains. In contrast, there was no significant difference between these strains in either the Vmax of substrate influx or the rate of substrate exit. D-Galactose competitively inhibited methyl-beta-D-galactopyranoside influx into both mgl B- and mgl+ strains; the Ki of inhibition in mgl B- cells was 2,000-fold greater than that in mgl+ cells.

Biological Transport, Active↗
PubMedDate not supplied

Angiocentric T-cell lymphoma of the nose, paranasal sinuses and hard palate.

Sixty-five cases of malignant lymphoma of the nose, paranasal sinuses and hard palate were retrospectively analysed to identify the presence or absence of angiocentric lesions. We observed that the 23 patients with angiocentric lesions had a worse prognosis with a shorter duration of response and also a shorter duration of survival, compared with 42 cases of malignant lymphoma of the same anatomical region but without angiocentric lesions. Patients with angiocentric lymphoma were associated with other bad prognostic factors such as elevated levels of lactic dehydrogenase and beta 2 microglobulin, local bone destruction and lymphopenia. Immunophenotyping studies showed that most patients with angiocentric lesions had T cell lymphomas (18 of 23, 78 per cent). We believe that patients with angiocentric T cell lymphomas of the nose, paranasal sinuses and hard palate represent a distinctive clinico-pathological entity with different clinical presentation and outcome. Patients with angiocentric T cell lymphomas had frequent relapse at extranodal sites and combined therapy should be considered as the initial therapeutic approach.

Adult↗
PubMedDate not supplied

Development of in vitro performance tests and evaluation of nonabsorbable monofilament sutures for cardiovascular surgery.

There have been reports suggesting that polypropylene (PP) monofilament sutures are associated with mechanical failure. To overcome this problem, a new monofilament suture made from polyvinylidene fluoride, under the trade name of Teflene, has been developed. Few studies have measured the in vitro properties of Teflene sutures, and those that have, have been limited to a few tensile properties of the straight suture such as tensile strength, elongation, and creep behavior. The in vitro performance properties of Teflene sutures were evaluated and compared with those of commercial sutures made from PP such as Prolene and Surgilene in four sizes, 2-0, 3-0, 4-0, and 5-0. The performance properties of sutures included both the physical properties of straight sutures, such as suture diameter, tensile strength, elongation, surface roughness, coefficient of friction, bending stiffness, and tissue drag, and the knot characteristics, such as knot pull strength, knot run-down, and knot security. Existing standard test methods and testing instruments were used if available to measure certain suture properties such as diameter, tensile strength, knot pull strength, and some physical properties. The other novel test methods and unique accessory devices needed to perform the tests for measuring tissue drag, knot run-down, coefficient of friction, and knot security were developed in the authors' laboratories, and the comparative results are reported for the first time. From the test results, Teflene sutures were found in general to possess equivalent characteristics to those of existing PP commercial sutures, but some differences also were observed, such as greater elongation and less knot run-down. These differences may give them a unique feel and handling performance, especially in terms of making a knot, sliding it into position, and causing less damage to adjacent tissue.

Cardiovascular Surgical Procedures↗
PubMedDate not supplied

CT and MRI in acute hemorrhagic stroke.

We report the case of a woman presenting with an acute onset of hemiplegia. MRI was performed and showed a hyperintense mass on diffusion-weighted imaging, with areas of high signal intensity on T2* imaging and T2/PD imaging. T1-weighted imaging showed a more inhomogeneous lesion with a central isointense part corresponding to the acute clot, as well as a peripheral crescent of hypointense plasma; since another mass lesion could not be acutely excluded, computed tomography was performed immediately afterwards, showing a hyperdense hematoma. The patient was taken to the neurosurgical operating theater, where she underwent decompressive craniotomy and evacuation of the hematoma.

Acute Disease↗
PubMedDate not supplied

Estrogen and progesterone receptors can be maintained in normal human breast epithelial cells in primary culture and after transplantation into nude mice.

The estrogen and progesterone receptor expression was determined in breast epithelial cells from reduction mammoplasty specimens. Only a subset of the luminal epithelial cell population was found to be positive for these receptors. When these cells were subsequently cultured in 3-dimensional collagen gel system (in vitro model) or transplanted into nude mice (in vivo model), the cells retained their ability to express both receptors in these experimental systems. The maintenance of primary normal human breast epithelial cells expressing the estrogen and progesterone receptors in experimental systems has not been reported previously.

Animals↗
PubMedDate not supplied

Beware of contaminating mouse cells in human xenografts from nude mice.

Human tumor xenografts in nude mice are widely utilized model system for the transplantation of human surgical specimens and human established cell lines. Gene expression studies are often carried out in these model systems. With an increasing use of PCR based analyses, the extreme sensitivity of this technique poses a serious challenge with regards to the extent of contaminating host mouse cells in the human tumor xenografts. These xenografts are never free of host cell contamination. We detected mouse estrogen receptor expression in several human tumor xenografts using RT-PCR demonstrating that precaution is necessary when utilizing PCR based analyses in human tumor xenografts. A cytologically based methodology which distinguishes human versus mouse cells will be more suitable for ER expression studies using human xenograft models. Both (1) in situ hybridization using human probe and (2) immunocytochemistry using a monoclonal antibody directed against human cytokeratin have been used successfully to distinguish human cells versus host mouse cells in human xenografts in nude mice. Immunostaining of ER can then be utilized to determine the expression pattern of ER in the transplanted human cells.

Animals↗
PubMedDate not supplied

Reconstituted normal human breast in nude mice: estrogen and progesterone receptors regulation.

Actions of estrogen and progesterone on normal human breast are mediated by their respective receptors. Since receptor regulation studies in humans are difficult to perform, we have utilized our model system of reconstituted normal human breast in nude mice to determine expression of estrogen and progesterone receptors in response to exogenous estrogen and progesterone. In normal human breast in situ, only a subset of epithelial cells (about 10%) are positive for estrogen receptor. These cells which remain positive after transplantation into nude mice can be completely downregulated by administration of exogenous estrogen resulting in all transplanted human breast epithelial cells now being negative for estrogen receptor. Exogenous estrogen also upregulates the progesterone receptor in a subset of human breast epithelial cells rather than in all cells. Exogenous progesterone, alone or in combination with estrogen, did not affect the estrogen or progesterone receptors. Double immunofluorescent labelings for a proliferation marker and progesterone receptor in both surgical specimens and nude mice transplants demonstrate that proliferation and progesterone receptor expression do not take place in the same cell. Our in vivo model system enables studies on the biology of primary normal human breast epithelial cells which otherwise are difficult to perform in humans.

Animals↗
PubMedDate not supplied

Fresh venous femoral autografts and allografts as carotid substitutes in matched dogs from the same litter.

Pathological and biochemical investigations were performed on femoral veins used as fresh autografts and allograft substitutes in the carotid arteries of dogs from the same litter and separated in two groups described as compatible and incompatible after a mixed leukocyte culture (MLC). After 5 months of implantation, all the arterial substitutes were patent. The analyses gave the following results: 1. The haematologic parameters were not affected by the grafts. 2. Light microscopy (LM) and scanning electron microscopy (SEM) indicate a thrombotic accumulation and the presence of inflammatory cells in the compatible and the incompatible allografts. The occurrence of pathological changes was more pronounced in the incompatible group. 3. Immunostaining of anti-factor VIII-related antigen reveals a better preservation of the endothelial cell wall on the autograft. 4. The 6-keto-PGF1 alpha/TXB2 ratios of the autografts and the compatible allografts were similar.

6-Ketoprostaglandin F1 alpha↗
PubMedDate not supplied

Craniofacial and intraoral manifestations of congenital hemifacial hyperplasia: report of case.

The craniofacial and intraoral developmental and morphologic characteristics of the rare congenital disorder known as hemifacial hyperplasia are reviewed. The case of a 7.7-year-old Caucasian girl affected by this malformation is presented to corroborate and supplement existing clinical knowledge regarding hemifacial hyperplasia. Suggestions are made regarding the implications of early differential diagnosis and treatment planning of affected individuals. Special emphasis is placed on the advantage of multidisciplinary team management.

Alveolar Process↗