Biomedical subjects

H Molina

Publications and source records attributed to H Molina.

At least 19 recordsLinked to original sources

PubMed1996

Markedly impaired humoral immune response in mice deficient in complement receptors 1 and 2.

Complement receptor 1 (CR1, CD35) and complement receptor 2 (CR2, CD21) have been implicated as regulators of B-cell activation. We explored the role of these receptors in the development of humoral immunity by generating CR1- and CR2-deficient mice using gene-targeting techniques. These mice have normal basal levels of IgM and of IgG isotypes. B- and T-cell development are overtly normal. Nevertheless, B-cell responses to low and high doses of a T-cell-dependent antigen are impaired with decreased titers of antigen-specific IgM and IgG isotypes. This defect is not complete because there is still partial activation of B lymphocytes during the primary immune response, with generation of splenic germinal centers and a detectable, although reduced, secondary antibody response. These data suggest that certain T-dependent antigens manifest an absolute dependence on complement receptors for the initiation of a normally robust immune response.

Animals↗

PubMed1995

Characterization of a complement receptor 2 (CR2, CD21) ligand binding site for C3. An initial model of ligand interaction with two linked short consensus repeat modules.

Human CR2 (CD21, EBV receptor) is an approximately 145-kDa receptor and a member of the regulators of complement activation gene family. Regulators of complement activation proteins are characterized by the presence of repeating motifs of 60 to 70 amino acids that are designated short consensus repeats (SCR). CR2 serves as a receptor for four distinct ligands. Three of these ligands (complement C3, gp350/220 of EBV, and CD23) interact with the amino terminal 2 of 16 SCR (SCR 1 and 2). Previous studies have determined that at least four sites are important in allowing CR2 to efficiently bind EBV. Two of these sites are also important for binding mAb OKB7, a reagent that blocks both EBV and iC3b/C3dg binding to CR2. We have identified and characterized important sites of iC3b ligand binding by utilizing human-mouse CR2 chimeras, a rat anti-mouse CR2 mAb designated 4E3 that blocks receptor binding to C3, and human CR2-derived peptides. In addition to demonstrating an important role for the same sequence in SCR 1 that is part of the mAb OKB7 and EBV binding site, we have identified a new region within SCR 2 that interacts with C3. These results, when compared with a model of a dual SCR solution structure derived from human factor H SCR, predict that two distinct largely surface-exposed sites on CR2 interact with iC3b. A relative twist of 130 degrees about the long axis of the second SCR in this model would be necessary for these sites to form a single patch for iC3b binding on CR2.

Amino Acid Sequence↗

PubMed1995

Mouse complement regulatory protein Crry/p65 uses the specific mechanisms of both human decay-accelerating factor and membrane cofactor protein.

Normal host cells are protected from the destructive action of complement by cell surface complement regulatory proteins. In humans, decay-accelerating factor (DAF) and membrane cofactor protein (MCP) play such a biologic role by inhibiting C3 and C5 convertases. DAF and MCP accomplish this task by specific mechanisms designated decay-accelerating activity and factor I cofactor activity, respectively. In other species, including mice, structural and/or functional homologues of these proteins are not yet well characterized. Previous studies have shown that the mouse protein Crry/p65 has certain characteristics of self-protecting complement regulatory proteins. For example, Crry/p65 is expressed on a wide variety of murine cells, and when expressed on human K562 erythroleukemic cells, it prevents deposition of mouse C3 fragments on the cell surface during activation of either the classical or alternative complement pathway. We have now studied factor I cofactor and decay-accelerating activities of Crry/p65. Recombinant Crry/p65 demonstrates cofactor activity for factor I-mediated cleavage of both mouse C3b and C4b. Surprisingly, Crry/p65 also exhibits decay-accelerating activity for the classical pathway C3 convertase strongly and for the alternative pathway C3 convertase weakly. Therefore, mouse Crry/p65 uses the specific mechanisms of both human MCP and DAF. Although Crry/p65, like MCP and DAF, contains tandem short consensus repeats (SCR) characteristic of C3/C4 binding proteins, Crry/p65 is not considered to be a genetic homologue of either MCP or DAF. Thus, Crry/p65 is an example of evolutionary conservation of two specific activities in a single unique protein in one species that are dispersed to individual proteins in another. We propose that the repeating SCR motif in this family has allowed this unusual process of evolution to occur, perhaps driven by the use of MCP and DAF as receptors by human pathogens such as the measles virus.

Animals↗

PubMed1995

Familial dwarfism and painful muscle spasms.

We report a family with a disorder characterized by limbs and truncal undulating painful muscle spasms, short stature, fine and sparse hair in the scalp, absence of body hair, low implanted ears, big nose, pitched voice, enlarged heart ventricles and increased fasting glucose levels. Symptoms began in childhood and did not progress after the third decade of life. This disorder represents a new clinical phenotype among the several forms of dwarfism associated with neurological manifestations already described in the literature.

Adult↗

PubMed1995

CLECOS_P: clinical evolution control system on Parkinsonian patients undergoing neural transplantation.

The CLECOS_P system was conceived for registering and automating the processing of clinical evaluations performed on patients with Parkinson's disease who undergo functional neurosurgery and/or neural transplant. CLECOS_P represents the first time a computerized system is able to offer--with high precision and considerable time-savings--an integral analysis of the evolutive behavior of the universe in integrated variables at the core assessment program for intracerebral transplantations (CAPIT). CAPIT is used internationally for the evaluation and follow-up of patients with this pathology who have undergone neural transplant. We used the so-called MEDSAC methodology for the preparation of this system. The methodology that was used for the design of an intelligent system aimed at medical decision-making was based on the quantitative analysis of the clinical evolution. At the present moment, there are 20 patients controlled by this system: 11 bilaterally transplanted, 9 unilaterally (registered in ranks of 3 months before operation up to 1, 2, 3, 6, 9, 12, 18, and 24 months after operation). The application of CLECOS_P to these patients permitted the evaluation of 400 clinical variables, where a better evolutive characterization of the patients was obtained, thus getting most favorable results with personalized therapeutic methods aimed at raising their quality of life. CLECOS_P is used in a multi-user environment on a local area network running Novell Netware version 3.11.

Brain Tissue Transplantation↗

PubMed1994

Analysis of C3b/C3d binding sites and factor I cofactor regions within mouse complement receptors 1 and 2.

Human and murine CR1 and CR2 are defined as evolutionary homologues on the basis of their in vitro activities and a shared structural motif known as a short consensus repeat (SCR). To identify additional similarities between the two species, we analyzed the functional domains within the mouse receptors by constructing mouse-human chimeric cDNAs in which the C3 binding site of human CR2 has been replaced by different regions within the first eight SCRs of mouse CR1. Rosette analysis of cells expressing chimeric proteins, with erythrocytes bearing different mouse C3 fragments, coupled with rosette inhibition studies using specific anti-mouse CR1/CR2 mAbs reveal a weak C3b binding site within SCRs 1 and 2 of mouse CR1. There is no independent C3b interacting domain within SCRs 3 to 6, but their presence enhances C3 binding. A molecule that contains only the first six SCRs of mouse CR1 also binds C3b, but with less efficiency. There is no C3d binding area within the first six SCRs, but our data confirms previous studies indicating an additional C3b/C3d binding region within SCRs 7 and 8 of mouse CR1 (SCRs 1-2 of mouse CR2). The presence of SCRs 1 to 4 is required for C3 cofactor activity. 8C12, a mAb which blocks C3b erythrocyte rosette binding and the C3 cofactor activity of mouse CR1, binds only to chimeras containing SCRs 3 to 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Stereotactic retransplantation in Parkinson's disease: clinical, imaging and electrophysiological evidence of adrenal brain graft viability.

In March 1993, a patient with idiopathic Parkinson disease who had received an adrenal brain autograft 6 years before underwent bilateral stereotactic transplantation of a mesencephalic cell suspension into the striatum, in order to prevent further deterioration in his neurological condition. During the CT-guided surgical planning and the transplantation procedures, electrophysiological evidence of the adrenal graft viability was assessed. Based on these findings, we drew the preliminary conclusion that the chromaffin tissue implanted in April 1987 is still functional, which explains the clinical evolution of this patient during the postoperative long-term follow-up.

Adrenal Medulla↗

PubMed1994

CT-oriented microrecording guided selective thalamotomy.

A further trial of CT-oriented microrecording guided stereotactic selective thalamotomy was conducted at the Centro Internacional de Restauración Neurológica, Havana City as treatment of resting tremor in 11 patients with idiopathic Parkinson's disease (PD), and in 3 other patients with intentional tremor associated with multisystemic atrophy and cerebral palsy. Three of the parkinsonian patients had undergone fetal mesencephalic tissue transplantation with significant improvement of the most debilitating symptoms of PD and stabilization of the motor state, but predominantly unilateral tremor had impaired them progressively despite increased levodopa doses. A Leksell frame was used with a novel surgical planning system and electrophysiological recordings to identify the optimal target point inside the ventralis intermedius. In all but 1 case, the tremor was totally arrested. No persistent complications were observed.

Case-Control Studies↗

PubMed1994

Neurotransplantation in Parkinson's disease: from open microsurgery to bilateral stereotactic approach: first clinical trial using microelectrode recording technique.

This paper summarizes the results of three controlled clinical trials related to the transplantation of embryonic ventral mesencephalic tissue into the striatum of 46 idiopathic parkinsonian patients exhibiting motor complications on standard levodopa therapy. From January 1988 to April 1990, 30 subjects with fluctuating Parkinson's disease received fetal dopaminergic tissue implants by the open microsurgical technique. In March 1992 the stereotactic approach was adopted for successive fetal mesencephalic cell suspension transplants (7 unilateral and 9 bilateral) into the caudate and putamen of parkinsonian patients with levodopa-induced complex fluctuations and dyskinesias. The neurological assessment performed 12 months before and 3-18 months after transplantation demonstrated a reduction of both the daily time spent in the 'off' condition and the number of daily 'off' periods, and a significant improvement of the motor scale. The stereotactic selective thalamotomy with microelectrode recording was introduced in January 1993, in order to provide a further potential treatment strategy; i.e., the combination of the two surgical trends in Parkinson's disease, the restorative neurotransplantation technique, and the selective lesional approach. In addition to that, microelectrode recording is also used for implantation site selection and functional characterization.

Adrenal Medulla↗

PubMed1994

Computer-assisted CT-guided stereotactic biopsy and brachytherapy of brain tumors.

From March 1991 to September 1993, 26 patients (aged 4-78 years) with brain tumors (4 glioblastoma multiforme, 10 nonglioblastoma multiforme, 1 mixed oligoastrocytoma, 2 carniopharyngiomas, 2 meningiomas and 7 metastases) were treated with stereotactic techniques at the Centro Internacional de Restauración Neurológica, La Habana, Cuba. A total of 28 stereotactic surgical procedures were performed with no operative mortality; they included biopsies in all cases, 1 stereotactic microsurgical resection and 12 permanent implants of 192Ir, followed by external beam fractionated radiation therapy (40-60 Gy). The present paper shows that the combined use of a stereotactic approach, a comprehensive and reliable stereotactic dosimetric planning system, stereotactic brachytherapy with 192Ir and complementary percutaneous radiation treatment constitutes a promising strategy for brain tumor management.

Adolescent↗

PubMed1993

Mouse Crry/p65. Characterization of monoclonal antibodies and the tissue distribution of a functional homologue of human MCP and DAF.

In previous studies we have demonstrated that mouse Crry/p65 regulates complement component C3 deposition on self membranes, a functional property that both human decay-accelerating factor (DAF) and membrane cofactor protein (MCP) exhibit. We have proposed that Crry/p65 has a similar biologic role in mouse as MCP and perhaps DAF and is the mouse analogue of one or both of these proteins. In order to address this hypothesis and further study Crry/p65, we have prepared rat mAb and a rabbit polyclonal Ab to this protein. Using these reagents we demonstrate that, like human MCP and DAF, the tissue distribution of Crry/p65 is very broad. Most if not all cells of nonneuronal origin express this protein. In addition, by immunohistochemical analysis, Crry/p65 is shown to be more highly expressed in some tissues at potential sites of immune complex deposition and damage, such as the mesangium of the renal glomerulus and the arterial vessel endothelium. By Western blot analysis, protein isoforms can be demonstrated. Unlike human DAF, however, no phosphatidylinositol-specific phospholipase C-sensitive Crry/p65 protein form can be demonstrated on lymphocytes or erythrocytes. Five of six anti-Crry/p65 mAb can partially or completely reverse the capacity of Crry/p65 to block C3 deposition on cell membranes. Analysis of four IgG rat anti-Crry/p65 mAb demonstrates that two major independent epitopes can be detected. Overall, Crry/p65 retains many of the major features of human MCP and DAF, and the use of these reagents should further the understanding of the biologic roles of this class of complement regulatory proteins.

Animals↗

PubMed1993

Mouse Crry/p65 is a regulator of the alternative pathway of complement activation.

Like man, mouse has evolved a unique set of regulatory proteins which provide protection from complement-mediated damage to self membranes. The recently described mouse protein Crry/p65 has been shown to inhibit classical complement pathway C3 deposition on cell membranes in which it is expressed. In two distinct experimental systems, we now further delineate the regulatory activity of Crry/p65 and demonstrate its inhibitory effect on alternative complement pathway C3 activation. First, significant inhibition of mouse alternative pathway C3 deposition was demonstrated on neuraminidase-treated human K562 cells expressing recombinant Crry/p65. Second, using a baculovirus technique, recombinant Crry/p65 was synthesized as a soluble molecule and then purified. This molecule was found to inhibit mouse C3 deposition on the surface of zymosan, a potent alternative complement pathway activator. These studies, combined with our earlier findings, demonstrate that Crry/p65 can regulate both the classical and alternative complement pathways. Crry/p65 must, therefore, exert its effects prior to, or at the level of, the C3 convertases, in a fashion similar to that of human membrane cofactor protein and/or decay-accelerating factor. These studies provide further proof of the hypothesis that Crry/p65 is an evolutionarily unique, complement regulatory protein which has developed in mouse.

Animals↗

PubMed1993

Computer assisted CT-guided stereotactic transplantation of foetal ventral mesencephalon to the caudate nucleus and putamen in Parkinson's disease.

We report our preliminary results related to CT-guided stereotactic transplantation of foetal ventral mesencephalic cell suspension into the striatum of five patients with idiopathic Parkinson's disease. The mean age was 51 years, the evolution time of the disease ranged from 7 to 14 years, and all of them had motor complications associated with chronic L-dopa therapy. The patients were evaluated according to the Core Assessment Program for Intracerebral Transplantations (CAPIT) for one year before and three months after surgery. The postoperative clinical assessment demonstrated significant improvement of neurological symptoms and reduction of daily L-dopa dosage.

Caudate Nucleus↗

PubMed1992

Distinct receptor and regulatory properties of recombinant mouse complement receptor 1 (CR1) and Crry, the two genetic homologues of human CR1.

The relationship between the characterized mouse regulators of complement activation (RCA) genes and the 190-kD mouse complement receptor 1 (MCR1), 155-kD mouse complement receptor 2 (MCR2), and mouse p65 is unclear. One mouse RCA gene, designated MCR2 (or Cr2), encodes alternatively spliced 21 and 15 short consensus repeat (SCR)-containing transcripts that crosshybridize with cDNAs of both human CR2 and CR1, or CR2 alone, respectively. A five SCR-containing transcript derived from a second unique gene, designated Crry, also crosshybridizes with human CR1. We have previously shown that the 155-kD MCR2 is encoded by the 15 SCR-containing transcript. To analyze the protein products of the other transcripts, which are considered the genetic homologues of human CR1, we have expressed the 21 and the 5 SCR-containing cDNAs in the human K562 erythroleukemia cell line. We demonstrate that cells expressing the 21 SCR transcript express the 190-kD MCR1 protein. These cells react with five unique rat anti-MCR1 monoclonal antibodies, including the 8C12 antibody considered to be monospecific for MCR1. In addition, these cells efficiently form rosettes with mouse C3b-bearing sheep erythrocytes. In contrast, cells expressing the five SCR-containing Crry transcript are strongly recognized by an anti-human CR1 antibody that also defines the mouse p65 protein. Using a functional assay that measures the surface deposition of C3 activated via the classical complement pathway, we show that Crry/p65-expressing cells have a markedly decreased amount of C3 deposited on them as compared with control cells expressing the antisense construct or cells expressing MCR1 or MCR2. This suggests that Crry has intrinsic complement regulatory activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

The evolution of mouse and human complement C3-binding proteins: divergence of form but conservation of function.

Despite the fact that the early components of the mouse and human complement cascades are very similar, there are marked differences between the two species in the structure of C3 receptors and the molecules that control homologous lysis. Here, Michael Holers, Taroh Kinoshita and Hector Molina compare and contrast the mouse and human RCA region products and conclude that the receptor and regulatory roles are conserved despite the structural variation.

Animals↗

PubMed1992

T lymphocyte expression of complement receptor 2 (CR2/CD21): a role in adhesive cell-cell interactions and dysregulation in a patient with systemic lupus erythematosus (SLE).

Complement receptor 2 (CR2, CD21), the receptor for both the C3d,g portion of human complement component C3 and the Epstein-Barr virus, has been recently described on peripheral T cells. By using dual stain flow cytometric analysis, we have also observed that a peripheral T lymphocyte subpopulation of normal healthy donors bears CR2 in a range varying from 1.1 to 23.2% (mean 12.6%) of total CD3+ cells. T lymphocytes from nine patients with inactive SLE expressed CR2 in a similar range. Three patients with active SLE were also studied. One of them, having neuropathy and glomerulonephritis, displayed an expansion of the CR2 T cell subpopulation which reached as much as 89% of total CD3+ cells. To examine potential functional roles of T cell CR2, cells from a Jurkat-derived CR2 expressing T cell line were found to bind in vitro to human CR2-, complement-coated K562 cell targets in a CR2- and complement-dependent fashion. Based on these studies, we hypothesize that CR2 might act to increase adherence of T cells to nucleated target cells bearing C3d,g, a function which may be relevant to cytotoxicity or other T cell activities requiring cell-cell interaction.

B-Lymphocytes↗

PubMed1992

Stereotactic technique and pathophysiological mechanisms of neurotransplantation in Huntington's chorea.

In Huntington's chorea, embryonal brain tissue (striatum) was implanted in the caudate nucleus bilaterally, using stereotaxy assisted by CT. A special cannula allowed the placement into the brain of 3 or 4 grafts of embryonal tissue along the determined trajectory by one introduction of the cannula. The pathophysiological mechanism of neurotransplantation in Huntington's chorea is to compensate for the degenerated striatal tissue by embryonal striatum, so it is necessary to supply a quantity of embryonal striatal tissue which enables the whole functional integrity. Therefore, we use material from several embryos.

Brain Tissue Transplantation↗

PubMed1991

Analysis of Epstein-Barr virus-binding sites on complement receptor 2 (CR2/CD21) using human-mouse chimeras and peptides. At least two distinct sites are necessary for ligand-receptor interaction.

The predicted amino acid sequence of human complement receptor 2 (CR2, CD21, C3d,g/Epstein-Barr virus receptor) and its genetic murine homologue are approximately 70% identical. The sequence of each consists of a linear array of 60-70 amino acid repeats designated short consensus repeats (SCRs). Although they share significant sequence identity, a major difference in the activities of these two proteins has been believed to be the ability of human, but not mouse, CR2 to mediate Epstein-Barr virus (EBV) infection of B lymphocytes. In order to formally address this question and to directly compare the activities of the CR2 protein of each species, we have expressed recombinant mouse CR2 (rMCR2) in a human K562 erythroleukemia cell line background. We have found that rMCR2 reacts with two previously described rat anti-MCR2 monoclonal antibodies (mAbs), 7G6 and 7E9, but not mAb 8C12, which recognizes only mouse complement receptor 1. rMCR2 rosettes with erythrocytes bearing mouse and human C3d,g and binds glutaraldehyde cross-linked human C3d,g with a similar Kd as human CR2 (HCR2). rMCR2 does not bind EBV. By using this observation and constructing chimeras bearing portions of MCR2 on a HCR2 background, we have been able to define unique sequences in HCR2 SCRs 1 and 2 important in the interaction with both mAb OKB7, which blocks EBV binding and infection, and with EBV. In addition, by using blocking peptides derived from HCR2 sequence, we have identified a second distinct region in SCR2 important in EBV binding. Therefore, within the first two SCRs of HCR2 are multiple distinct sites of interaction with EBV and with mAb OKB7.

Amino Acid Sequence↗