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M D Johnson

Publications and source records attributed to M D Johnson.

At least 37 records · Page 2Linked to original sources
PubMed2001

Evidence for mitogen-associated protein kinase activation and transduction of mitogenic signals by platelet-derived growth factor in human meningioma cells.

OBJECT: Coexpression of platelet-derived growth factor (PDGF)-BB and activated PDGF-beta receptor in meningioma cells indicates that this cytokine may act as an autocrine or paracrine stimulant of meningioma growth. The intracellular events transducing signals from PDGF-beta receptor tyrosine kinases are unknown. In this study the authors evaluated whether or not mitogen-activated protein kinases (MAPKs) are expressed in meningiomas, regulate their growth, and transduce mitogenic signals of PDGF-BB. METHODS: Ten human meningioma tumors as well as cells cultured from two normal leptomeninges and 10 additional human meningiomas were evaluated using Western blot analysis to determine the presence of MAPK and phosphorylated (activated) MAPK. The effects of PD098059, a selective inhibitor of MAPK phosphorylation/activation, on proliferation of meningioma cells stimulated with 10% fetal bovine serum was also evaluated. Last, the authors evaluated whether PDGF-BB stimulation of meningioma cells was associated with activation of MAPK. Western blots of lysates from meningiomas and from cultured leptomeningeal and meningioma cells demonstrated MAPK and phosphorylated MAPK. Treatment with PD098059 produced a 52 to 84% (x = 69.8) loss in [3H]thymidine incorporation, which was associated with a partial or complete loss of phosphorylated MAPK after 3 days of treatment. The PDGF-BB produced a significant increase in [3H]thymidine incorporation and phosphorylation of MAPK at 1 and 3 days. Coadministration of PD098059 completely blocked PDGF-BB's stimulation of [3H]thymidine incorporation and cell proliferation concomitant with reduced MAPK phosphorylation. CONCLUSIONS: The findings indicate that MAPK is constitutively expressed in leptomeningeal and meningioma cells and transduces mitogenic signals of PDGF, contributing to the growth of human meningiomas.

Adolescent↗
PubMed2001

Detection of proliferating S-phase brain tumor cells by in situ DNA replication.

OBJECT: Current methods used to describe the proliferative status of brain tumors rely on labor-intensive, potentially costly procedures. This article provides a description of a rapid, inexpensive, uncomplicated technique used to identify proliferating cells in tissue obtained at the time of resection. METHODS: Touch preparations of 16 fresh astrocytic tumors and four fresh healthy temporal neocortical tissue samples were obtained at the time of surgery. Slides were placed in hypotonic potassium chloride to permeabilize their membranes, incubated in nucleotide precursors, and labeled with bromodeoxyuridine; they were later examined with the aid of a fluorescence microscope. The percentage of tumor cells in the S phase increased in conjunction with the grade of tumor and corresponded with the findings of immunohistochemical staining for the cell-cycle marker MIB-1. These results were confirmed in cell culture by using normal human astrocytes and two glioma cell lines. Slides can be analyzed in as little as 30 minutes after removal of tissue during surgery. CONCLUSIONS: In this study the authors describe a simple method by which cells in the S phase of the cell cycle. which are contained in fresh tumor obtained at the time of surgery, can be labeled. This method may prove a useful adjunct to frozen-section analysis and may permit discrimination of neoplastic tissues from other tissues observed in small specimen samples.

Antigens, Nuclear↗
PubMed2001

December 2000: 6 month old boy with 2 week history of progressive lethargy.

This 6-month-old Caucasian boy presented with a 10-day history of lethargy, obtundation, inability to hold his head up and mild torticollis. MRI and CT scans showed a large solid and cystic mass involving the right temporal, parietal and occipital lobes, pineal, superior pons, mesencephalon and posterior right thalamus. He underwent craniotomy initially for a partial tumor resection with an intraoperative diagnosis of desmoplastic astrocytoma. With immunohistochemistry and special stains the diagnosis of desmoplastic infantile ganglioglioma (DIG) was made. A near total resection was performed a week after initial resection.The patient then was treated with chemotherapy. Two months later an MRI showed tumor growth. Following additional aggressive chemotherapy, an MRI at 5 months post-resection indicated further tumor progression. This case illustrates that some DIGs may behave more aggressively than typical WHO grade I lesions.

Brain↗
PubMed2001

Cytochrome P450 induction in rat hepatocytes assessed by quantitative real-time reverse-transcription polymerase chain reaction and the RNA invasive cleavage assay.

The acceleration of drug discovery due to combinatorial chemistry and high-throughput screening methods has increased the numbers of candidate pharmaceuticals entering the drug development phase, and the capability to accurately predict whether drug candidates will induce various members of the drug-metabolizing cytochrome P450 (CYP) enzyme superfamily is currently of great interest to the pharmaceutical industry. In the present study, we describe the rapid and reliable analysis of CYP induction in a readily obtained model system (cultured rat hepatocytes) using both real-time quantitative reverse transcription-polymerase chain reaction (real-time RT-PCR) and the RNA invasive cleavage assay. The levels of members in the three primary inducible rat CYP subfamilies (CYP1A1, CYP2B1/2, and CYP3A1) were analyzed in untreated and induced (beta-naphthoflavone, phenobarbital, and hydrocortisone) hepatocyte cultures under various media conditions to screen for optimal CYP induction profiles. The fold inductions measured by real-time RT-PCR and the RNA invasive cleavage assay were also compared with enzyme activity measurements in parallel cultures using liquid chromatography/double mass spectrometry-based assays, and the sensitivity and the specificity of the two RNA analysis methods were compared. Using these techniques, various culture conditions were examined for optimizing induction of the three CYP subfamily members. Both real-time RT-PCR and the RNA invasive cleavage assay prove to be effective methods for determining the effects of drugs on specific CYPs in primary rat hepatocytes.

Animals↗
PubMed2001

Carcinoid tumor development in an intramedullary spinal cord mature teratoma.

The case of a 43-year-old woman with a several month history of severe back pain is reported. CT and MR imaging revealed an intramedullary cystic tumor, which was considered a dermoid cyst or teratoma. During surgery, the tumor was found within the base of the filum terminale and completely resected. Microscopic studies revealed a mature teratoma with an intramural carcinoid nodule. Thirteen-month follow-up after surgical resection showed no evidence of tumor recurrence or neoplasms elsewhere.

Adult↗
PubMed2001

Rifampin is a selective, pleiotropic inducer of drug metabolism genes in human hepatocytes: studies with cDNA and oligonucleotide expression arrays.

We used expression microarrays to test the effects of rifampin on the overall pattern of mRNA expression of multiple metabolic enzymes in primary human hepatocytes. Two microarrays were utilized, a cDNA-based array and one that is oligonucleotide-based. The cDNA-based expression arrays showed that rifampin caused a 7.7 +/- 6.6-fold induction in CYP2A6 and a 4.0 +/- 2.0-fold increase in the CYP2C family of enzymes while having little effect on CYP2E1 or CYP2D6. Many non-P450 enzymes were also induced including FMO-4 and -5, UGT-1A, MAO-B, and GST-P1. The oligonucleotide-based array made it possible to detect different levels of induction within the CYP2C family, with rifampin causing a 6.5-fold increase in expression of CYP2C8 and a 3.7-fold increase in CYP2C9 while having no effect on the level of CYP2C18 mRNA. Rifampin also induced other CYP enzymes including CYP2B6 and all three members of the CYP3A family, with CYP3A4 showing the highest level of induction at 55.1-fold. RNase protection assays were used to validate results from the arrays and a comparison of all three methods of mRNA detection showed qualitatively similar results. These data make it clear that rifampin treatment brings about broad changes in the pattern of gene expression, rather than increased expression of a small number of metabolic enzymes. Clinicians and researchers who use and study rifampin and other drugs that induce drug metabolism should be alert to the possibility of multiple effects.

Antibiotics, Antitubercular↗
PubMed2000

Role of the mouse ank gene in control of tissue calcification and arthritis.

Mutation at the mouse progressive ankylosis (ank) locus causes a generalized, progressive form of arthritis accompanied by mineral deposition, formation of bony outgrowths, and joint destruction. Here, we show that the ank locus encodes a multipass transmembrane protein (ANK) that is expressed in joints and other tissues and controls pyrophosphate levels in cultured cells. A highly conserved gene is present in humans and other vertebrates. These results identify ANK-mediated control of pyrophosphate levels as a possible mechanism regulating tissue calcification and susceptibility to arthritis in higher animals.

Animals↗
PubMed2000

Cryptophyte algae are robbed of their organelles by the marine ciliate Mesodinium rubrum.

Mesodinium rubrum (Lohmann 1908) Jankowski 1976 (= Myrionecta rubra) is a common photosynthetic marine planktonic ciliate which can form coastal red-tides. It may represent a 'species complex' and since Darwin's voyage on the Beagle, it has been of great cytological, physiological and evolutionary interest. It is considered to be functionally a phytoplankter because it was thought to have lost the capacity to feed and possesses a highly modified algal endosymbiont. Whether M. rubrum is the result of a permanent endosymbiosis or a transient association between a ciliate and an alga is controversial. We conducted 'feeding' experiments to determine how exposure to a cryptophyte alga affects M. rubrum. Here we show that although M. rubrum lacks a cytostome (oral cavity), it ingests cryptophytes and steals their organelles, and may not maintain a permanent endosymbiont. M. rubrum does not fall into recognized cellular or functional categories, but may be a chimaera partially supported by organelle robbery.

Animals↗
PubMed2000

Dual regulation of proliferation and apoptosis: c-myc in bitransgenic murine mammary tumor models.

Recent progress in the study of c-Myc has convincingly demonstrated that it possesses a dual role in regulating both proliferation and apoptosis; however, the manner in which c-Myc influences these cellular response pathways remains incompletely characterized. Deregulation of c-Myc expression, via many mechanisms, is a common feature of multiple cancers and is an especially prominent feature of many breast cancers. Of significant interest to those who study mammary gland development and neoplasia is the unresolved nature and contribution of apoptosis to breast tumorigenesis. Recently, the use of transgenic mice and gene-knockout mice has allowed investigators to evaluate the pathological mechanisms by which different genes influence tumor development and progression. In this review, we address two distinct c-myc-containing bitransgenic murine mammary tumor models and discuss the contribution and possible future directions for resolution of cancer-relevant molecular pathways influenced by c-Myc.

Animals↗
PubMed2000

Efficient studies of long-distance Bmp5 gene regulation using bacterial artificial chromosomes.

The regulatory regions surrounding many genes may be large and difficult to study using standard transgenic approaches. Here we describe the use of bacterial artificial chromosome clones to rapidly survey hundreds of kilobases of DNA for potential regulatory sequences surrounding the mouse bone morphogenetic protein-5 (Bmp5) gene. Simple coinjection of large insert clones with lacZ reporter constructs recapitulates all of the sites of expression observed previously with numerous small constructs covering a large, complex regulatory region. The coinjection approach has made it possible to rapidly survey other regions of the Bmp5 gene for potential control elements, to confirm the location of several elements predicted from previous expression studies using regulatory mutations at the Bmp5 locus, to test whether Bmp5 control regions act similarly on endogenous and foreign promoters, and to show that Bmp5 control elements are capable of rescuing phenotypic effects of a Bmp5 deficiency. This rapid approach has identified new Bmp5 control regions responsible for controlling the development of specific anatomical structures in the vertebrate skeleton. A similar approach may be useful for studying complex control regions surrounding many other genes important in embryonic development and human disease.

Animals↗
PubMed2000

Use of cultured cerebral capillary endothelial cells in modeling the central nervous system availability of 2',3'-dideoxyinosine.

The biochemical and physiological mechanisms responsible for the limited central nervous system (CNS) uptake of dideoxynucleoside reverse transcriptase inhibitors currently used to treat HIV-1 infection in humans are poorly understood. In vitro models of the blood-brain barrier (BBB) offer an attractive alternative to in vivo or in situ animal studies for understanding the role of the blood-brain barrier in regulating brain tissue concentrations of these agents. In the present study, the kinetics of 2', 3'-dideoxyinosine (ddI) uptake and purine nucleoside phosphorylase (PNP) mediated catabolism in primary cultures of bovine brain microvessel endothelial cells (BBMECs) were determined in order to ascertain the importance of both transport and metabolism governing the CNS availability of this purine dideoxynucleoside. Initial rates of ddI uptake as a function of ddI donor concentration suggest the involvement of both passive diffusion and carrier-mediated processes. These studies confirm earlier in vivo findings that transporters may play a role in regulating the CNS concentration of ddI. Analysis of ddI uptake and metabolite accumulation in BBMECs over longer time intervals (beyond the intial rate region) provide substantial in vitro evidence for an enzymatic BBB for ddI. Simulations of the CNS availability of ddI derived from in vitro estimates of parameters for passive diffusion, carrier-mediation, and metabolism indicate that the fraction of ddI entering the BBB cells which actually reaches the brain parenchyma may be quite low (< 2%) due to metabolism by PNP localized within the BBB, consistent with the low CNS delivery of ddI observed in vivo. Transporters and metabolic enzymes within the BBB may function in coordinated fashion to reduce the CNS concentrations of both rapidly metabolized and poorly metabolized dideoxynucleosides.

Animals↗
PubMed2000

The role of the human thalamus in language and memory: evidence from electrophysiological studies.

The data reviewed here indicate that electrical stimulation of the dominant ventrolateral thalamus can produce deficits in language processing that are not seen after similar stimulation of the nondominant ventrolateral thalamus. The nature of the language deficit produced varies, depending upon the rostrocaudal location of the stimulation site. Stimulation of the anterior left ventrolateral thalamus in right-handed patients resulted in production of a repeated erroneous word, stimulation of the medial ventrolateral thalamus evoked perseveration, and stimulation of the posterior ventrolateral thalamus and anterior pulvinar resulted in misnaming and omissions. Additional studies have examined the effect of electrical thalamic stimulation on verbal and nonverbal short-term memory. Left (but not right) ventrolateral thalamic stimulation during verbal memory input greatly decreased subsequent recall errors, while stimulation during verbal memory retrieval increased recall errors. This finding contrasted with those obtained from studies on nonverbal memory, in which right ventrolateral stimulation during memory input decreased recall errors, while left thalamic stimulation at the same stage increased recall errors. Left pulvinar stimulation disrupted verbal memory processing, while right pulvinar stimulation disrupted nonverbal memory processing. Limited evidence suggests that the effects of thalamic electrical stimulation on verbal memory may persist for several days after the stimulation has ended. The lateralization of thalamic functions also affects the motoric aspects of speech production. Left (but not right) ventrolateral thalamic stimulation disrupted speech articulation and increased the expiratory phase of respiration. The fact that these motor effects were evoked from the same general area of the thalamus that produced the language deficits discussed above raises the possibility that the thalamus is involved in coordinating the cognitive and motoric aspects of language production. A model of thalamic function is discussed in which defined regions of the thalamus operate as a "specific alerting response," increasing the input to memory of category-specific material while simultaneously inhibiting retrieval from memory.

Electrophysiology↗
PubMed2000

Local administration of mu or kappa opioid agonists attenuates capsaicin-induced thermal hyperalgesia via peripheral opioid receptors in rats.

RATIONALE: By acting on peripheral opioid receptors, opioid agonists can attenuate nociceptive responses induced by a variety of agents. OBJECTIVES: This study was conducted to characterize capsaicin-induced thermal hyperalgesia in rats and to evaluate the hypothesis that local administration of either mu or kappa opioid agonists (fentanyl and U50,488, respectively) can attenuate capsaicin-induced nociception. METHODS: Capsaicin was administered s. c. in the tail of rats to evoke a nociceptive response, which was measured by the warm-water tail-withdrawal procedure. Either fentanyl or U50,488 was co-administered with capsaicin in the tail to evaluate local antinociceptive effects. In addition, the local antagonism study was performed to confirm the site of action of both opioid agonists. RESULTS: Capsaicin (0.3-10 microg) dose dependently produced thermal hyperalgesia manifested as reduced tail-withdrawal latencies in 45 degrees C water. Co-administration of either fentanyl (0.32-3.2 microg) or U50,488 (10-100 microg) with capsaicin (3 microg) attenuated capsaicin-induced hyperalgesia in a dose-dependent manner. Furthermore, this local antinociception was antagonized by small doses (10-100 microg) of an opioid antagonist, quadazocine, applied s.c. in the tail. However, the locally effective doses of quadazocine, when applied s.c. in the back (i.e., around the scapular region), did not antagonize either fentanyl or U50,488. CONCLUSIONS: In this experimental pain model, activation of peripheral mu or kappa opioid receptors can attenuate capsaicin-induced thermal hyperalgesia in rats. It supports the notion that peripheral antinociception can be achieved by local administration of analgesics into the injured tissue without producing central side effects.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed2000

Toxicogenomics-based discrimination of toxic mechanism in HepG2 human hepatoma cells.

The rapid discovery of sequence information from the Human Genome Project has exponentially increased the amount of data that can be retrieved from biomedical experiments. Gene expression profiling, through the use of microarray technology, is rapidly contributing to an improved understanding of global, coordinated cellular events in a variety of paradigms. In the field of toxicology, the potential application of toxicogenomics to indicate the toxicity of unknown compounds has been suggested but remains largely unsubstantiated to date. A major supposition of toxicogenomics is that global changes in the expression of individual mRNAs (i.e., the transcriptional responses of cells to toxicants) will be sufficiently distinct, robust, and reproducible to allow discrimination of toxicants from different classes. Definitive demonstration is still lacking for such specific "genetic fingerprints," as opposed to nonspecific general stress responses that may be indistinguishable between compounds and therefore not suitable as probes of toxic mechanisms. The present studies demonstrate a general application of toxicogenomics that distinguishes two mechanistically unrelated classes of toxicants (cytotoxic anti-inflammatory drugs and DNA-damaging agents) based solely upon a cluster-type analysis of genes differentially induced or repressed in cultured cells during exposure to these compounds. Initial comparisons of the expression patterns for 100 toxic compounds, using all approximately 250 genes on a DNA microarray ( approximately 2.5 million data points), failed to discriminate between toxicant classes. A major obstacle encountered in these studies was the lack of reproducible gene responses, presumably due to biological variability and technological limitations. Thus multiple replicate observations for the prototypical DNA damaging agent, cisplatin, and the non-steroidal anti-inflammatory drugs (NSAIDs) diflunisal and flufenamic acid were made, and a subset of genes yielding reproducible inductions/repressions was selected for comparison. Many of the "fingerprint genes" identified in these studies were consistent with previous observations reported in the literature (e. g., the well-characterized induction by cisplatin of p53-regulated transcripts such as p21(waf1/cip1) and PCNA [proliferating cell nuclear antigen]). These gene subsets not only discriminated among the three compounds in the learning set but also showed predictive value for the rest of the database ( approximately 100 compounds of various toxic mechanisms). Further refinement of the clustering strategy, using a computer-based optimization algorithm, yielded even better results and demonstrated that genes that ultimately best discriminated between DNA damage and NSAIDs were involved in such diverse processes as DNA repair, xenobiotic metabolism, transcriptional activation, structural maintenance, cell cycle control, signal transduction, and apoptosis. The determination of genes whose responses appropriately group and dissociate anti-inflammatory versus DNA-damaging agents provides an initial paradigm upon which to build for future, higher throughput-based identification of toxic compounds using gene expression patterns alone.

Algorithms↗
PubMed2000

Primary intracerebral Hodgkin's disease mimicking meningioma: case report.

OBJECTIVE AND IMPORTANCE: A rare case of dura-based primary cerebral Hodgkin's disease clinically and radiographically indistinguishable from a meningioma is described. CLINICAL PRESENTATION: A 55-year-old immunocompetent woman presented with headaches and ataxia. Magnetic resonance images demonstrated a circumscribed diffusely enhancing mass with a dural tail attached to the cerebellar tentorium. INTERVENTION: Operative inspection also suggested a meningioma, but a frozen section of the firm mass revealed an inflammatory lesion. Subsequent pathological analysis demonstrated Hodgkin's disease, nodular sclerosing type. An extensive workup revealed no systemic disease. CONCLUSION: This case illustrates the rare occurrence of primary intracranial Hodgkin's disease and its mimicry of meningioma.

Brain Neoplasms↗
PubMed2000

Phase II evaluation of thalidomide in patients with metastatic breast cancer.

PURPOSE: To determine the efficacy, safety, pharmacokinetics, and effect on serum angiogenic growth factors of two dose levels of thalidomide in patients with metastatic breast cancer. PATIENTS AND METHODS: Twenty-eight patients with progressive metastatic breast cancer were randomized to receive either daily 200 mg of thalidomide or 800 mg to be escalated to 1,200 mg. Fourteen heavily pretreated patients were assigned to each dose level. Each cycle consisted of 8 weeks of treatment. Pharmacokinetics and growth factor serum levels were evaluated. RESULTS: No patient had a true partial or complete response. On the 800-mg arm, 13 patients had progressive disease at or before 8 weeks of treatment and one refused to continue treatment. The dose was reduced because of somnolence to 600 mg for five patients and to 400 mg for two and was increased for one to 1,000 mg and for four to 1,200 mg. On the 200-mg arm, 12 patients had progressive disease at or before 8 weeks and two had stable disease at 8 weeks, of whom one was removed from study at week 11 because of grade 3 neuropathy and the other had progressive disease at week 16. Dose-limiting toxicities included somnolence and neuropathy. Adverse events that did not require dose or schedule modifications included constipation, fatigue, dry mouth, dizziness, nausea, anorexia, arrhythmia, headaches, skin rash, hypotension, and neutropenia. Evaluation of circulating angiogenic factors and pharmacokinetic studies failed to provide insight into the reason for the lack of efficacy. CONCLUSION: Single-agent thalidomide has little or no activity in patients with heavily pretreated breast cancer. Further studies that include different patient populations and/or combinations with other agents might be performed at the lower dose levels.

Adult↗
PubMed2000

The interaction of ferrocytochrome c with long-chain fatty acids and their CoA and carnitine esters.

Non-covalent modification of cytochrome c may have implications for electron transport and energy metabolism. We examined the interaction of various fatty acids (FAs), their coenzyme A and carnitine esters, and fatty alcohols with horse heart ferrocytochrome c. A comparison of FAs indicated a minimum chain length of 14 carbons was required for significant effect on the ferroheme chromophore and major changes in electronic spectra. Coenzyme A and carnitine esters interacted less strongly than FAs whereas long-chain alcohols did not interact with the protein. We found a single, saturable FA binding site with Kd (oleate) of 23.1 microM (by stopped-flow kinetics), 30 microM (by radiochemical binding assay), and 29 microM (by spectrophotometric assay). The binding stoichiometry was 1:1. We present evidence from electronic spectra, and proton NMR (nuclear magnetic resonance) that the S-Fe coordination (methionine 80) was disrupted by ligand binding. From molecular modeling we identify a putative binding channel flanked by lysines 72 and 73.

Acyl Coenzyme A↗