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Biomedical subjects

J C Ruiz

Publications and source records attributed to J C Ruiz.

At least 109 records · Page 6Linked to original sources
PubMed1993

Pulsatile-secretion of parathyroid hormone in patients with chronic renal failure.

Peripheral blood concentration of intact PTH is a simple assay very useful in the diagnosis and evolutive control of secondary hyperparathyroidism in patients with chronic renal failure. Episodic secretion of PTH in CRF patients would affect interpretation of single random determinations. To evaluate the secretory pattern of intact PTH we sampled peripheral blood at 6-min intervals for 60 to 90 min from seven normal subjects (group I) and seven patients with chronic renal failure (group II: 4 with normal parathyroid function and 3 with hyperparathyroidism). The resultant time series of serum intact PTH and ionized calcium were assessed by computerized cluster data analysis program. Evaluation of episodic intact PTH pulsatile nature revealed that in group I, 3 out of 7 normal subjects presented 1 maximum and 6 subjects presented at least one minimum. In group II, 3 out of 4 CRF patients with normal parathyroid function presented at least 1 maximum and all four patients at least one minimum. One out of 3 CRF patients with hyperparathyroidism presented 2 maximum and all three at least one minimum. Despite pulsatile character intact PTH levels were maintained all the time within the normal range in control group and in CRF patients with normal parathyroid function. In CRF patients with hyperparathyroidism intact PTH changes were restricted within a level of hyperparathyroidism. Ionized calcium levels in control group remained virtually constant along the period and in CRF group fluctuated widely. Parathyroid hormone is secreted in a pulsatile fashion in normal subjects and in patients with chronic renal failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Use of magnetic resonance in the diagnosis of neuro-cryptococcosis in the acquired immunodeficiency syndrome: study of 4 patients].

Neuro-cryptococcosis is a common opportunistic infection in AIDS or HIV infected patients. From a series of 10 neuro-cryptococcosis the four of them studied by magnetic resonance (MR) are reported. In AIDS patients a high suspicion of opportunistic infection of the CNS is needed as exemplified by two of the four patients who only presented cephalalgia. The other two patients suffered additional symptoms and signs of meningeal and CNS involvement, such as nuchal rigidity, cranial nerve palsies, papilloedema, gait ataxia and dismetria. Diagnosis was achieved (confirmed) by a positive culture, serology or indian ink test in CSF. CT scan did not contribute to the diagnosis and management of the patients. In contrast MR, showed in three of them a peculiar pattern of small, confluent, high-signal lesions, roughly symmetrically placed in the basal ganglia and the internal capsule. They probably correspond to the dilated Virchow-Robin spaces through which torulae migrate from the subarachnoid space.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Interleukin-2 deficit in hemodialysis patients. Role of prostaglandins.

Uremic patients suffer from various immunological alterations, whose pathogenesis is still unknown. Here, we studied 37 hemodialysis patients in order to investigate the role of prostaglandins (PGs) in uremic immunological deficiency, specifically in relation to interleukin-2 (IL-2) synthesis. We confirmed previous published data on deficient response to PHA in chronic renal failure patients (cpm, mean +/- SEM: 15,400 +/- 2,100 in uremics vs. 29,500 +/- 3,380 in controls, p < 0.04) and established a correlation between this deficiency and diminished IL-2 synthesis (r = 0.619, p < 0.05). The direct measurement of PGs in lymphocyte cultures showed greatly increased concentrations in the presence of uremic serum (US). We found that PGs synthesis can be inhibited by up to 80% if cultures are supplemented with indomethacin (IND--a cyclooxigenase inhibitor) or by removal of monocytes (producers of PGs). Both methods situated the uremic proliferative response within the normal range in cultures with FCS, and close to the normal range in cultures with US. We observed a deficit of IL-2 in hemodialysis patients (means +/- SD: 8,940 +/- 6,420 in uremics vs. 16,900 +/- 3,890 in controls). Addition of exogenous IL-2 normalized lymphocyte response even in US cultures, with no additive effect between PGs inhibition and exogenous IL-2 except in US cultures. It is suggested that IL-2 deficit of uremics depends, at least in part, on an increase in PGs synthesis induced by US.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Low level of Hox1.3 gene expression does not preclude the use of promoterless vectors to generate a targeted gene disruption. off.

A variety of experimental approaches have been devised recently to mutate mammalian genes by homologous recombination. In this report, we describe the disruption of the Hox1.3 locus by using two of these approaches, namely, positive-negative selection and activation of a promoterless gene. Interestingly, we observe similarly high frequencies of targeted disruption with both procedures. The high frequency of targeted disruption with a promoterless vector was unexpected given the extremely low level of Hox1.3 expression in the embryonic stem cell line used for these studies. These data indicate that minimal expression of the target gene is required to enrich for homologous recombination events with promoterless vectors and thus enhance the promoterless gene approach as a general strategy to mutate mammalian genes by homologous recombination.

Animals↗
PubMed1990

Chromosomal destabilization during gene amplification.

Acentric extrachromosomal elements, such as submicroscopic autonomously replicating circular molecules (episomes) and double minute chromosomes, are common early, and in some cases initial, intermediates of gene amplification in many drug-resistant and tumor cell lines. In order to gain a more complete understanding of the amplification process, we investigated the molecular mechanisms by which such extrachromosomal elements are generated and we traced the fate of these amplification intermediates over time. The model system consists of a Chinese hamster cell line (L46) created by gene transfer in which the initial amplification product was shown previously to be an unstable extrachromosomal element containing an inverted duplication spanning more than 160 kilobases (J. C. Ruiz and G. M. Wahl, Mol. Cell. Biol. 8:4302-4313, 1988). In this study, we show that these molecules were formed by a process involving chromosomal deletion. Fluorescence in situ hybridization was performed at multiple time points on cells with amplified sequences. These studies reveal that the extrachromosomal molecules rapidly integrate into chromosomes, often near or at telomeres, and once integrated, the amplified sequences are themselves unstable. These data provide a molecular and cytogenetic chronology for gene amplification in this model system; an early event involves deletion to generate extrachromosomal elements, and subsequent integration of these elements precipitates a cascade of chromosome instability.

Animals↗
PubMed1989

Autonomously replicating episomes contain mdr1 genes in a multidrug-resistant human cell line.

Gene amplification in human tumor cells is frequently mediated by extrachromosomal elements (e.g., double minute chromosomes [DMs]). Recent experiments have shown that DMs can be formed from smaller, submicroscopic circular precursors referred to as episomes (S. M. Carroll, M. L. DeRose, P. Gaudray, C. M. Moore, D. R. Needham-Vandevanter, D. D. Von Hoff and G. M. Wahl, Mol. Biol. 8:1525-1533, 1988). To investigate whether episomes are generally involved as intermediates in gene amplification, we determined whether they mediate the amplification of the mdr1 gene, which when overexpressed engenders cross resistance to multiple lipophilic drugs. A variety of methods including electrophoresis of undigested DNAs in high-voltage gradients, NotI digestion, and production of double-strand breaks by gamma irradiation were used to distinguish between mdr1 sequences amplified on submicroscopic circular molecules and those amplified within DMs or chromosomal DNA. The gamma-irradiation procedure provides a new method for detecting and determining the size of circular molecules from 50 kilobases (kb) to greater than 1,000 kb. These methods revealed that some of the amplified mdr1 genes in vinblastine-resistant KB-V1 cells are contained in supercoiled circular molecules of approximately 600 and approximately 750 kb. Analysis of the replication of these molecules by a Meselson-Stahl density shift experiment demonstrated that they replicate approximately once in a cell cycle. The data lend further support to a model for gene amplification in which DMs are generally formed from smaller, autonomously replicating precursors.

DNA Probes↗
PubMed1988

Formation of an inverted duplication can be an initial step in gene amplification.

We have developed a gene transfer approach to facilitate the identification and isolation of chromosomal regions which are prone to high-frequency gene amplification. Such regions are identified by assaying for transformants which show high-frequency resistance to PALA and/or methotrexate by amplification of a vector containing the genes which encode the enzyme targets of these antiproliferative agents. We identified 2 of 47 transformants which displayed high-frequency amplification of the transfected genes, and in this report we describe the analysis of one of them (L46). Molecular analysis of the integration site in transformant L46 revealed that the donated genes were at the center of an inverted duplication which spanned more than 70 kilobase pairs and consisted largely of host DNA. The data suggest that integration of the transfected sequences generates a submicroscopic molecule containing the inverted duplication and at least 750 kilobases of additional sequences. The donated sequences and the host sequences were readily amplified and lost in exponentially growing cultures in the absence of drug selection, which suggests that the extrachromosomal elements are acentric. In contrast to the instability of this region following gene insertion, the preinsertion site was maintained at single copy level under growth conditions which produced copy number heterogeneity in L46. The implications of our results for mechanisms of genetic instability and mammalian gene amplification are discussed.

Animals↗
PubMed1987

Cosmid vectors for rapid genomic walking, restriction mapping, and gene transfer.

We have designed cosmid vectors for rapid genomic "walking" and restriction mapping. These vectors contain the transcription promoters from either bacteriophage SP6, T7, or T3 flanking a unique BamHI cloning site. Mammalian expression modules encoding the dominant marker neomycin phosphotransferase or the amplifiable dihydrofolate reductase gene expressed from SV40 promoters were inserted for use in gene transfer studies. Restriction sites for the enzymes Not I and Sfi I, which cut mammalian DNA very infrequently, have been engineered near the transcriptional promoters to enable the excision of most inserts as single, full-length fragments. Genomic libraries representative of mouse, human, and hamster genomes were constructed by inserting 33- to 44-kilobase-pair (kbp) DNA fragments, generated by partial cleavage of genomic DNA with Mbo I or Sau3A, into the unique BamHI site. Digestion of recombinant cosmids with restriction enzymes that cleave frequently but do not disrupt the transcriptional promoters generates two small DNA templates for the synthesis of end-specific RNA probes to facilitate directional "walking." Cosmid restriction maps can be determined rapidly by one of several methods. The cosmids and methods we describe should have wide utility in determining the functional and structural organization of complex eukaryotic genomes and for physically linking distant genetic loci.

Cloning, Molecular↗