Biomedical subjects

C M Cabrera

Publications and source records attributed to C M Cabrera.

12 recordsLinked to original sources

PubMed2006

Strategies for preventing immunologic rejection of transplanted human embryonic stem cells.

Human embryonic stem alls (hESC) have an unlimited capacity of proliferation and self-renewal resulting in a promise for future applications in regenerative medicine. One major problem derived from their use in cellular therapy protocols is the immunological rejection due to HLA incompatibility. Currently, there are four strategies to prevent allograft rejection of hESC; the development of a ''universal hESC line'' with lack of HLA class 1 expression; the creation of nuclear transfer hESC line; the development of hESC line banks; and the generation of haemopoietic chimerism.

Embryonic Stem Cells↗

PubMed2005

APC and chromosome instability in colorectal cancer.

Colon cancer is a common disease that can be sporadic or familial. An inactivated adenomatous polyposis coli (APC) suppressor gene is found in over 80% of colorectal tumors, this being an early alteration in the development of adenomatous polyps. APC function is not only critical for tumor initiation and progression, and chromosome instability (CIN) is another characteristic dependent at least partly on APC mutations.

Chromosomal Instability↗

PubMed2004

Promyelocytic leukemia (PML) nuclear bodies are disorganized in colorectal tumors with total loss of major histocompatibility complex class I expression and LMP7 downregulation.

The promyelocytic leukemia (PML) protein is the product of the PML gene that fuses with the retinoic acid receptor-alpha (RARalpha) gene in acute promyelocytic leukemia (APL) and produces disruption of PML bodies. Wild-type PML localizes in the nucleus with a typical speckled pattern. PML bodies accumulate several proteins involved in multiple cellular pathways such as apoptosis, transcriptional regulation, and proteasomal degradation of ubiquitinated proteins. The ubiquitin-proteasome pathway at PML bodies is dependent on proteasome component recruitment. Proteasome components such as low-molecular weight proteins (LMPs) are frequently downregulated in different tumor tissues that present impaired major histocompatibility complex (MHC) class I expression. We have recently documented LMP7 downregulation in colorectal tumors with total loss of MHC class I antigen. An immunohistochemical study of PML protein in these tumors revealed a disrupted pattern of PML bodies in a nuclear diffuse form, as observed in APL cells. Therefore, the disruption of the PML bodies was clearly associated with LMP7 downregulation.

Colorectal Neoplasms↗

PubMed2003

Total loss of MHC class I in colorectal tumors can be explained by two molecular pathways: beta2-microglobulin inactivation in MSI-positive tumors and LMP7/TAP2 downregulation in MSI-negative tumors.

The mechanisms that lead to loss of MHC class I expression in different types of tumors are not yet fully known. Accordingly, we studied colorectal carcinomas to elucidate the specific mechanisms of evasion of the T-cell immune response. We selected tumors with total loss of MHC class I expression and studied 124 colorectal carcinomas with immunohistochemical staining and anti-HLA monoclonal antibodies (mAb). Fourteen of 124 (11%) tumors exhibited a phenotype with HLA class I total loss. Microsatellite instability (MSI) analysis was also carried out in the same tumor samples. The expression of beta2-microglobulin (beta2m), HLA-A, B, and C antigens, transporter associated with antigen processing 1 (TAP1), TAP2, low-molecular-weight protein 2 (LMP2), and LMP7 were analyzed using reverse-transcription polymerase chain reaction (RT-PCR) in microdissected tumor samples. Four of 14 microsatellite instability-positive (MSI+) and W6/32 mAb-negative tumors showed biallelic inactivation of beta2m and accumulation of HLA class I heavy chain in the cytoplasm. MSI-negative (MSI-)/W6/32 mAb-negative tumors presented alterations in the expression of components of the antigen processing machinery (APM). Nine of 10 tumor samples showed LMP7 gene downregulation, and four of 10 presented TAP2 dysregulation. This group apparently expressed normal levels of heavy chain and beta2m mRNA. Two major mechanisms in colorectal cancer appear to be responsible for the total loss of MHC surface expression (beta2m mutations and LMP7/TAP2 downregulation) that may contribute to the failure of T lymphocyte recognition during an immune response. The precise identification of the molecular defects that underlie HLA class I abnormalities will have important implications for patients receiving T-cell-based specific immunotherapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2003

Defective regulation of the protective IgE response against intestinal helminth Ascaris lumbricoides in malnourished children.

It is well established that malnutrition affects the immune response and increases the susceptibility to parasitic infection. In the present study we evaluated some aspects of the cellular and cytokine network that regulate the IgE responses, which are important components of host defence mechanisms against helminthic parasites in children infected with the intestinal helminth Ascaris lumbricoides, and with differing degrees of malnutrition. We found a defective T cell response in malnourished children, as indicated by diminished levels of circulating total (CD3+), helper (CD4+), IL-2-receptor-bearing (CD4+CD25+) and memory helper T cell responses (CD4+CD45RO+) in keeping with the decreased specific IgE levels against Ascaris lumbricoides. In contrast, the proportions of total B cells (CD20+), and those bearing the low-affinity IgE receptor (CD23+) were increased in the moderated malnourished children. Moreover, serum IL-4 levels and total IgE were also increased in these children. We suggest that malnutrition can cause an imbalance in T cell subpopulations that may lead to a defective T cell maturation and a decreased specific anti-Ascaris IgE response thus increasing the susceptibility to such infections. The high levels of total IgE observed may be related to a non-specific stimulation of the proliferation of activated B cells, probably caused by helminthic parasites and other infectious agents that are frequent in malnourished children.

Analysis of Variance↗

PubMed1991

Partial purification and characterization of rhinoceros gonadotropins, growth hormone, and prolactin: comparison with the horse and sheep.

The rhinoceros is an endangered species related to the horse family. Little is known of its reproductive endocrinology. The objectives of this study were to partially purify rhinoceros pituitary hormones, determine which assays could be used for their assessment, and to ascertain whether rhinoceros LH possesses the intrinsic FSH activity of equine LH. A single pituitary each from a White (1.3 g) and a Black (1.2 g) Rhinoceros was homogenized and extracted (pH 9.5), then subjected to pH and salt fractionation, and ion-exchange chromatography (DEAE and Sephadex SP-C50) to yield partially purified fractions of LH, FSH, growth hormone (GH), and prolactin (PRL). LH was readily measured by a rat Leydig cell assay (0.1-1% x equine LH) and an RIA using a monoclonal antibody to bovine LH (6-11% x equine LH). FSH activity detected in the LH by either an FSH RIA or a calf testis radioreceptor assay (RRA) was extremely low. No FSH activity could be detected in the White Rhinoceros pituitary "FSH" fraction, but was readily detected in the Black Rhinoceros fraction (RIA: 0.2% x equine FSH: RRA: 0.8% x equine FSH). The presence of GH and PRL was determined by SDS-PAGE and Western blots. Results showed a single immunoreactive GH band and multiple immunoreactive PRL bands. Adsorption with Concanavalin A-Sepharose indicated that some of the PRL bands are glycosylated.

Animals↗

PubMed1990

Elephant pituitary gonadotropins.

We describe for the first time the purification and some properties of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) isolated from anterior pituitary tissue of the African elephant (Loxodonta africana). Methodology previously applied to equine and donkey pituitaries was used to obtain purified preparations of elephant LH and FSH in yields of 8.8 and 0.48 mg, respectively, per 10 g pituitary powder. The preparations were characterized by HPLC gel filtration and amino acid analysis, both of which showed the elephant LH and FSH to be very similar to ovine LH and FSH. The preparations were also characterized by radioimmunoassays and bioassays for LH and FSH and a radioreceptor assay for FSH. Results showed virtually no cross-contamination of hormonal activities in the elephant LH and FSH preparations. Elephant LH potencies ranged from 50 to 66% of highly purified ovine LH and elephant FSH potencies ranged from 21 to 52% of highly purified ovine FSH in the various assays employed. No evidence was found for any demonstrable intrinsic FSH activity in elephant LH. The assays employed suggest possible usage for making physiological measurements of gonadotropins in the elephant.

Amino Acids↗

PubMed1988

Cushing's syndrome due to bilateral adrenal macronodular hyperplasia with undetectable ACTH: cell culture of adenoma cells on extracellular matrix.

A 59-year-old man developed Cushing's syndrome with massive bilateral adrenal macronodular hyperplasia. Plasma ACTH levels were undetectable both peripherally and in the inferior petrosal sinus. Computed tomography scans of his pituitary were normal. Hypercortisolism was not suppressed by high doses of dexamethasone. His adrenal cells were successfully isolated and grown on bovine corneal extracellular matrix. The cultured cells displayed strikingly rapid growth and hypersecretion of cortisol during incubation with control serum. Addition of the patient's serum to cultured fetal adrenal cells did not accelerate their growth. This was the first experience with our in vitro system in this rare clinical condition. The techniques described here may be used for future in vitro adrenal studies. These in vivo and in vitro data indicate that this patient's bilateral adrenal hyperfunction and growth were independent of ACTH.

Adrenal Glands↗

PubMed1987

Elephant prolactin: isolation and characterization.

Prolactin was isolated from anterior lobes of elephant pituitary glands. It consisted of 199 amino acids with three disulfide bridges and two tryptophan residues as found in prolactin from other species. The sequence of the NH2-terminal 28 amino acids was determined and shown homologous with the ovine hormone. In comparison with ovine prolactin, a marked difference was seen in the methionine content; the elephant hormone possessed only 18-34% lactogenic potency. The conformation of elephant prolactin was examined by zero order, second order and circular dichroism spectroscopy. The alpha helical content was estimated to be about 60%. In comparison with prolactins from other species, the second order spectra of elephant prolactin suggest that the local microenvironment for one or both tryptophan residues is somewhat different.

Amino Acids↗

PubMed1986

Identification of insulin-like growth factor-II in human seminal and follicular fluids.

Antisera raised in rabbits against synthetic insulin-like growth factor-II (IGF-II) were used to develop a specific radioimmunoassay (RIA) for IGF-II. Affinity purified antibodies showed 6% cross-reactivity with IGF-I but failed to recognize insulin even at 10 micrograms/tube. Utilizing this RIA system, immunoreactive IGF-II was identified in the pooled samples of human follicular fluid and seminal plasma. The acid-ethanol precipitates of human seminal and follicular fluids were chromatographed on Sephadex G-50 column and the IGF-II immunoreactive fractions were subjected to reversed-phase high performance liquid chromatography. It was found that immunoactive IGF-II was eluted in the same location as that of synthetic IGF-II. The data indicate for the first time that human seminal plasma and follicular fluid contain significant amounts of IGF-II.

Body Fluids↗

PubMed1985

Human somatotropin: noncovalent interactions of the natural NH2-terminal 1-134 segment with synthetic analogs of the COOH-terminal fragment.

Three analogs of the COOH-terminal fragments of human somatotropin (HGH), namely [Nle170,Ala165,182]-HGH-(150-187), [Nle170,Ala165,182]-HGH-(152-187), and [Nle170,Ala165,182]-HGH-(154-187), have been synthesized by the solid-phase method. The synthetic analogs were complemented with the natural NH2-terminal fragment [Cys(Cam)53]-HGH-(1-134) to form recombinants with HGH activities, as revealed by the rabbit liver membrane receptor binding and the Nb2 lymphoma cell assays.

Amino Acid Sequence↗

PubMed1985

Radioimmunoassay for an inhibin-like peptide from human seminal plasma.

Antisera raised in rabbits to a synthetic peptide consisting of 31 amino acids with a sequence identical to inhibin-like peptide (ILP) isolated from human seminal plasma afford a highly specific and sensitive radioimmunoassay. Synthetic ILP completely displaces antiserum binding of radioiodinated [Tyr4]-ILP, with half maximal displacement at 36 fmoles ILP/tube. ILP, [Tyr4]-ILP and ILP-(9-31) had essentially equal potency, while ILP-(1-25), ILP-(1-23) and ILP-(1-16) had reduced potency. No cross reactivity was found among a variety of peptide hormones and proteins. Human seminal plasma displaces 50% of [125I-Tyr4]-ILP at dilutions equivalent to 50-250 pl/tube, corresponding to immunoreactive ILP concentration of 0.5-2.5 mg/ml.

Amino Acid Sequence↗