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Biomedical subjects

M D Johnson

Publications and source records attributed to M D Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1999

How to spot illicit drug abuse in your patients.

Illicit drug abuse continues to become more widespread, especially in teenagers. Therefore, it is important for physicians to recognize the signs and symptoms of abuse in their patients. Drug abuse should be considered in differential diagnosis of many physical and nearly all psychiatric complaints. An understanding of the pharmacologic mechanisms and adverse effects of illicit drugs can enhance overall care of patients who abuse drugs. The primary classes of drugs of abuse--cannabinoids, opiates, stimulants, hallucinogens, and inhalants--produce clinically diverse presentations. By recognizing these unique signs and symptoms, physicians can differentiate between drug-induced conditions any psychiatric illness.

Cannabinoids↗
PubMed1999

The effects of the phyllolitorin analogue [desTrp(3), Leu(8)]phyllolitorin on scratching induced by bombesin and related peptides in rats.

Bombesin along with several closely related neuropeptides elicit scratching behavior when administered centrally. The first part of the study was designed to determine the antagonistic effects of a novel phyllolitorin analogue [desTrp(3),Leu(8)]phyllolitorin (DTP) on scratching induced by three peptides (bombesin, neuromedin-C, and [Leu(8)]phyllolitorin). In addition, the binding affinity of each peptide for the bombesin receptor site was determined. DTP (30 microg) inhibited scratching induced by these peptides, but unlike the peptides, DTP had no affinity for the bombesin site, thereby suggesting that DTP is displaying physiological antagonism through an unknown mechanism.

Animals↗
PubMed1999

Cardiovascular effects of acute and chronic cocaine administration in pregnant and nonpregnant rabbits.

The effects of cocaine administration on cardiovascular parameters were studied in anesthetized nonpregnant and pregnant rabbits with no prior exposure to cocaine and in pregnant rabbits repeatedly administered cocaine (4 mg/kg, bid, iv) for 15-20 days prior to the experiment. Rabbits were instrumented to determine the effects of cocaine on blood pressure, heart rate, and organ blood flows. Administration of the 1 and 2 mg/kg doses of cocaine increased blood pressure and decreased heart rate in both pregnant and nonpregnant rabbits. In contrast, the 4 mg/kg dose of cocaine caused reductions in both blood pressure and heart rate. Cocaine (1, 2, and 4 mg/kg, iv) also caused dose-dependent reductions in organ blood flows. Interestingly, cocaine did not affect uterine blood flow in the nonpregnant rabbits, whereas uterine and placental flows were markedly reduced in both groups of pregnant rabbits. Chronic treatment with cocaine caused a significant increase in the basal blood flow to the placenta and spleen, and a more precipitous decrease in blood flow in both organs in response to an acute injection of cocaine. The chronically treated rabbits also had a greater incidence of cardiac arrhythmias in response to an acute injection of cocaine (4 mg/kg, iv). Rabbits that received repeated administrations of cocaine experienced more prolonged reductions in blood flow than rabbits with no prior exposure to cocaine. These studies show that cocaine has marked effects on organ blood flows and that pregnancy and repeated prior administrations of cocaine can enhance these effects.

Animals↗
PubMed1999

Contribution of p53-dependent caspase activation to neuronal cell death declines with neuronal maturation.

Caspases play a pivotal role in neuronal cell death during development and after trophic factor withdrawal. However, the mechanisms regulating caspase activity and the role played by caspase activation in response to neuronal injury is poorly understood. The tumor suppressor gene p53 has been implicated in the loss of neuronal viability caused by excitotoxic and DNA damaging agents. In the present study we determined if p53-mediated neuronal cell death required caspase activation. DNA damage increased caspase activity in both cultured embryonic telencephalic and postnatal cortical neurons in a p53-dependent manner. Caspase inhibitors protected embryonic telencephalic neurons, but not postnatal cortical neurons, from DNA damage-induced cell death as measured by direct cell counting and annexin V staining. In marked contrast to the caspase inhibitors, an inhibitor of the DNA repair enzyme, poly(ADP-ribose) polymerase, conferred significant protection from genotoxic and excitotoxic cell death on postnatal cortical neurons but had no effect on embryonic neurons. Glutamate-mediated excitotoxicity in postnatal neurons was not associated with measurable changes in caspase activity, consistent with the failure of caspase inhibitors to prevent cell death under these conditions. Moreover, adenovirus-mediated overexpression of p53 killed embryonic and postnatal neurons without activating caspases. Thus, p53-mediated neuronal cell death may occur via both caspase-dependent and caspase-independent pathways. These results demonstrate that p53 is required for caspase activation in response to some forms of neuronal injury. However, the relative importance of caspase activation in neurons depends on the developmental status of the cell and the specific nature of the death stimulus.

Adenoviridae↗
PubMed1999

Activation of protein kinase C by phorbol esters modulates alpha2beta1 integrin on MCF-7 breast cancer cells.

Cellular adhesions to other cells and to the extracellular matrix play crucial roles in the malignant progression of cancer. In this study, we investigated the role of protein kinase C (PKC) in the regulation of cell-substratum adhesion by the breast adenocarcinoma cell line MCF-7. A PKC activator, 12-O-tetradecanoylphorbol-l, 3-acetate (TPA), stimulated cell adhesion to laminin and collagen I in a dose-dependent manner over a 1- to 4-h interval. This enhanced adhesion was mediated by alpha2beta1 integrin, since both anti-alpha2 and anti-beta1 blocking antibodies each completely abrogated the TPA-induced adhesion. FACS analysis determined that TPA treatment does not change the cell surface expression of alpha2beta1 integrin over a 4-h time interval. However, alpha2beta1 levels were increased after 24 h of TPA treatment. Thus, the enhanced avidity of alpha2beta1-dependent cellular adhesion preceded the induction of alpha2beta1 cell surface expression. Northern blot analysis revealed that mRNA levels of both alpha2 and beta1 subunits were increased after exposure to TPA for 4 h, indicating that the induction of alpha2beta1 mRNA preceded that of its cell surface expression. This further suggested that the TPA-induced avidity of alpha2beta1 was independent of increased expression of alpha2beta1. Pretreatment of cells with the PKC inhibitor calphostin C partially antagonized the TPA-induced increase in expression of alpha2beta1 integrin expression and of alpha2beta1-mediated cellular adhesion. To identify a possible mechanism by which TPA could be acting to promote the rapid induction of alpha2beta1 adhesion, we treated the cells with the Rho-GTPase inhibitor Clostridium botulinumexotoxin C3. C3 inhibited TPA-induced adhesion to laminin and collagen I in a dose-dependant manner, suggesting a likely role for Rho in TPA-induced adhesion. Together, these results suggest that PKC can modulate the alpha2beta1-dependent adhesion of MCF-7 cells by two distinct mechanisms: altering the gene expression of integrins alpha2 and beta1 and altering the avidity of the alpha2beta1 integrin by a Rho-dependant mechanism.

ADP Ribose Transferases↗
PubMed1999

Contig assembly of bacterial artificial chromosome clones through multiplexed fluorescence-labeled fingerprinting.

A rapid multiplexed fingerprinting method has been developed for bacterial artificial chromosome (BAC) contig assembly. Defined subsets of BAC DNA fragments that result from digestion by three paired restriction endonucleases are labeled with unique fluorescent F-ddATP for each subset. Lists of the labeled fragment size are generated by an ABI 377 DNA sequencer and the GeneScan analysis software and then processed by an assembly program, FPC (Fingerprinted Contigs), to produce contig maps. Data obtained from the multiplexed labeling permit detection of smaller overlaps than is observed when data from a single double-digest are analyzed. The method has been tested on 98 BACs from chromosome 22 regions where large-scale sequencing is under way and also through simulation, using randomly generated BAC clones derived from existing DNA sequence data. In each case, contig assembly results demonstrated the advantages of multiplexed fingerprinting.

Chromosomes, Bacterial↗
PubMed1999

Regulation of motility and protease expression in PKC-mediated induction of MCF-7 breast cancer cell invasiveness.

We investigated a potentially central role of protein kinase C (PKC) in controlling multiple pathways in breast cancer cell invasiveness. To do this we evaluated the ability of pharmacologic agents that alter PKC activity to regulate the behavior of the poorly invasive human breast cancer cell line MCF-7. Treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) produced a dramatic induction of the invasiveness of these cells (18-fold), an effect that concurrent treatment with the PKC inhibitor Bryostatin-1 was able to block. To characterize alterations in the cellular properties that might be responsible for these effects we measured the impact of these two agents on a number of processes thought to be important for invasiveness. The motility of the cells was first examined; it was markedly increased by treatment with TPA (20-fold) and again, Bryostatin-1 inhibited this stimulation. We next examined the expression of MMP-1, 3, 9, 10, and 11 (matrix metalloproteinases), all of which have been shown to be PKC responsive in other systems. We found that the expression and secretion of MMP-9 were increased by at least 100-fold, though all of the enzyme secreted was in the latent form. Finally, the expression of both urokinase plasminogen activator (UPA) and its receptor (UPAR) were induced after TPA treatment by 8- and 7-fold, respectively. In conclusion, we have shown that stimulation of PKC activity markedly increases the invasiveness of MCF-7 cells, and that this change in behavior is correlated with a coordinated set of biochemical and cellular changes which are likely to contribute to this process. These data highlight the possible utility of PKC inhibitors such as Bryostatin-1 as anti-invasive and/or antimetastatic agents. Bryostatin-1 is currently in early clinical trials as an anticancer agent.

Breast Neoplasms↗
PubMed1999

Third-strand in situ hybridization (TISH) to non-denatured metaphase spreads and interphase nuclei.

A methodology has been developed for binding oligodeoxyribonucleotide 'third strands' to duplex DNA targets in fixed but not additionally denatured metaphase spreads and interphase nuclei under conditions found to be optimal in solution. Third-strand in situ hybridization (TISH) at pH 6.0 of a psoralen- and biotin-modified 16-nucleotide homopyrimidine third strand to a unique multicopy target sequence in human chromosome 17 alpha-satellite (D17Z1 locus) is described. UVA-photofixed third strands, rendered fluorescent by fluorescein isothiocyanate-labeled avidin, are reproducibly centromere-specific for chromosome 17, and visible without amplification of the signal in lymphocyte and somatic cell hybrid spreads and interphase nuclei. Two third-strand-specific D17Z1 haplotypes were identified. TISH has potential diagnostic, biochemical, and flow cytometric applicability to native metaphase and interphase chromatin.

Base Sequence↗
PubMed1999

In vitro models of the blood-brain barrier to polar permeants: comparison of transmonolayer flux measurements and cell uptake kinetics using cultured cerebral capillary endothelial cells.

Given that the cerebral microvasculature within the brain constitutes the rate-limiting barrier to drug entry, primary cultures of cerebral capillary endothelial cells would appear to offer a potentially useful model system for predicting drug delivery to the central nervous system. In the present study, the predictive capabilities of two potential models of the in vivo blood-brain barrier (BBB) to the passive diffusion of polar permeants were assessed. A comparison of the logarithms of the in vitro transmonolayer permeability coefficients (Pmonolayer) for several polar permeants varying in lipophilicity (from this study and literature data) with the well-established relationship between the logarithms of the in vivo BBB permeability coefficients (log PBBB) and permeant lipophilicity as measured by the logarithm of the octanol/water partition coefficient (log PCoctanol/water) demonstrated that in vitro permeation across these monolayers is largely insensitive to polar permeant lipophilicity as a result of the predominance of the paracellular component in the transmonolayer flux. Conversely, kinetic studies of uptake of the same compounds into monolayers yielded transfer rate constants (kp) reflecting membrane permeability coefficients ranging over several orders of magnitude, similar to the variation in permeant lipophilicity. Furthermore, a linear relationship could be demonstrated between the logarithms of kp and in vivo BBB log P (slope = 1.42 +/- 0.35; r = 0. 92). In conclusion, this preliminary investigation suggests that monitoring the kinetics of cell uptake into cerebral capillary endothelial cell monolayers may be superior to transmonolayer flux measurements for predicting the passive diffusion of polar permeants across the BBB in vivo.

Acetamides↗
PubMed1999

Clinically significant drug interactions.

Ironically, pharmacotherapy can harm the very patients it is intended to help if clinically significant drug interactions occur. However, knowledge of the role of the hepatic cytochrome P-450 isoenzyme system in drug interactions has expanded greatly with advances in gene-mapping technologies, and an understanding of the system can aid physicians in preventing or minimizing complications from drug interactions mediated through that system. The authors summarize the role of important isoenzymes and drugs that induce and inhibit the P-450 system. They also discuss serious drug interactions mediated through the P-450 system and ways to predict and avoid them. As a special aid, they provide a reference guide which, when used faithfully in prescribing, should result in better drug therapy.

Cytochrome P-450 Enzyme System↗
PubMed1999

Intracisternal nor-binaltorphimine distinguishes central and peripheral kappa-opioid antinociception in rhesus monkeys.

Systemic administration of nor-binaltorphimine (nor-BNI) produces a long-lasting kappa-opioid receptor (kappaOR) antagonism and has kappa(1)-selectivity in nonhuman primates. The aim of this study was to establish the pharmacological basis of central kappaOR antagonism in rhesus monkeys (Macaca mulatta). After intracisternal (i.c.) administration of small doses of nor-BNI, the duration and selectivity of nor-BNI antagonism were evaluated against two kappaOR agonists, (trans)-3, 4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]benzeneacetamide (U50,488) and bremazocine. Thermal antinociception was measured in the warm water (50 degrees C) tail-withdrawal assay and sedation was evaluated by observers blind to treatment conditions. Following i.c. pretreatment with 0.32 mg nor-BNI, a 5- to 10-fold rightward shift of the U50,488 baseline dose-effect curve was observed in antinociception. In contrast, this dose of nor-BNI only produced an insignificant 2-fold shift against bremazocine. Pretreatment with a smaller dose (0.032 mg) of nor-BNI produced a 3-fold shift of U50, 488, which lasted for 7 days, but failed to alter the potency of bremazocine. This differential antagonism profile of i.c. nor-BNI also was observed in sedation ratings. In addition, the centrally effective dose of nor-BNI (0.32 mg), when administered s.c. in the back, did not antagonize either U50,488- or bremazocine-induced antinociception and sedation. After i.c. pretreatment with the same dose, nor-BNI also did not antagonize the peripherally mediated effect of U50,488 against capsaicin-induced thermal nociception in the tail. These results indicate that i.c. nor-BNI produces central kappaOR antagonism and support the notion of two functional kappaOR subtypes in the central nervous system. Moreover, it provides a valuable pharmacological basis for further characterizing different sources of kappaOR-mediated effects, namely, from central or peripheral nervous system receptors.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1998

Evidence for involvement of Bax and p53, but not caspases, in radiation-induced cell death of cultured postnatal hippocampal neurons.

Bax (a death-promoting member of the bcl-2 gene family), the tumor suppressor gene product p53, and the ICE/ced-3-related proteases (caspases) have all been implicated in programmed cell death in a wide variety of cell types. However, their roles in radiation-induced neuronal cell death are poorly understood. In order to further elucidate the molecular mechanisms underlying radiation-induced neuronal cell death, we have examined the ability of ionizing radiation to induce cell death in primary cultured hippocampal neurons obtained from wild-type, p53-deficient and Bax-deficient newborn mice. Survival in neuronal cultures derived from wild-type mice decreased in a dose-dependent manner 24 hr after a single 10 Gy to 30 Gy dose of ionizing radiation. In contrast, neuronal survival in irradiated cultures derived from p53-deficient or Bax-deficient mice was equivalent to that observed in control, nonirradiated cultures. Western blot analyses indicated that neuronal p53 protein levels increased after irradiation in wild-type cells. However, Bax protein levels did not change, indicating that other mechanisms exist for regulating Bax activity. Adenovirus-mediated overexpression of p53 also caused neuronal cell death without increasing Bax protein levels. Irradiation resulted in a significant induction in caspase activity, as measured by increased cleavage of fluorogenic caspase substrates. However, specific inhibitors of caspase activity (zVAD-fmk, zDEVD-fmk and BAF) failed to protect postnatal hippocampal neurons from radiation-induced cell death. Staurosporine (a potent inducer of apoptosis in many cell types) effectively induced neuronal cell death in wild-type, p53-deficient and Bax-deficient hippocampal neurons, indicating that all were competent to undergo programmed cell death. These results demonstrate that both p53 and Bax are necessary for radiation-induced cell death in postnatal cultured hippocampal neurons. The fact that cell death occurred despite caspase inhibition suggests that radiation-induced neuronal cell death may occur in a caspase-independent manner.

Animals↗
PubMed1998

Myc/p53 interactions in transgenic mouse mammary development, tumorigenesis and chromosomal instability.

We have examined defects in mammary development and tumorigenesis in a transgenic model expressing the c-myc gene under the MMTV-LTR promoter. The stochastic tumors which arise from hyperplastic ductal and lobular lesions in this model are characterized by high rates both of apoptosis and of chromosomal instability. Since the p53 gene product is thought to be central in the maintenance of genomic integrity, in part due to its ability to induce apoptosis in cells harboring DNA damage, we examined its expression and possible mutation. Initially, we observed that unmutated p53 is strongly expressed in premalignant mammary glands and in mammary tumors derived from the MMTV-c-myc strain. We then mated the MMTV-myc strain to a p53-deficient strain as a means of examining the effect of this lesion on mammary development and tumorigenesis in the context of c-myc overexpression. A lack of both p53 alleles in the presence of c-myc overexpression resulted in a dramatic hyerplastic alteration in mammary gland development. Specifically, in female bitransgenic MMTV-c-myc/p53 null mice (MMTV-myc/p53(-/-)), lobular hyperplasias were observed at almost every ductal end bud as early as 32 days of age. In contrast, only mild ductal and lobular hyperplasias were seen in MMTV-myc mice that contained both p53 alleles (MMTV-myc/p53(+/+)); an intermediate phenotype occurred in mice with a single intact (MMTV-myc/p53(+/-)) p53 allele. Mammary carcinomas arose with a high frequency in MMTV-myc/p53(+/-) mice; the tumors were comparable in frequency, histology and apoptotic index to the tumors in MMTV-myc/p53(+/+) mice. Also, as previously observed (Elson et al., 1995), lymphomas arose with extremely short latency in MMTV-myc/p53(-/-) mice, precluding study of the fate of their hyperplastic mammary lesions in situ. The frequency of p53 mutations in MMTV-myc/p53(+/+) and MMTV-myc/p53(+/-) mammary tumors and in cell lines derived from these tumors was examined by direct sequencing. No point mutations or deletions in p53 were observed in mammary tumors or cell lines from either genotype. Finally, a detailed chromosomal analysis using multicolor spectral karyotyping (SKY) revealed that there were multiple chromosomal alterations in the c-myc-overexpressing cells that contained either one or two unmutated p53 alleles. Variable ploidy changes, a common translocation of chromosome 11, and other chromosomal aberrations were observed. Our data thus support an interaction between c-Myc and p53 in mammary development, but suggest that loss of p53 is required neither for c-myc-dependent tumorigenesis nor for c-myc-dependent chromosomal instability.

Animals↗
PubMed1998

Genetic risks of intracytoplasmic sperm injection in the treatment of male infertility: recommendations for genetic counseling and screening.

OBJECTIVE: To review the most clinically significant genetic disorders associated with severe oligospermia and azoospermia in males, and to present recommendations for the genetic counseling and screening of infertile males and their partners before undertaking intracytoplasmic sperm injection (ICSI)-assisted reproduction. DESIGN: The literature on genetic disorders associated with severe oligospermia and azoospermia was reviewed, and the most recent outcome data from surveys of ICSI-derived offspring are presented. Studies related to this topic were identified through MEDLINE. RESULT(S): Genetic disorders are not infrequent causes of severe oligospermia and azoospermia in males undergoing ICSI-assisted reproduction. The application of ICSI in the treatment of oligospermic or azoospermic males may result in the transmission or de novo introduction of genetic mutations or chromosomal abnormalities in their offspring. Genetic counseling and appropriate screening of couples with male infertility should be performed before their undertaking ICSI-assisted reproduction. CONCLUSIONS: An understanding of the genetic risks and possible consequences that are inherent when ICSI is used to assist fertilization in couples with male infertility is necessary for clinicians and their patients.

Cytoplasm↗
PubMed1998

Bacteriophage T7 mRNA is polyadenylated.

To determine whether the RNA of bacterial viruses is polyadenylated like bacterial mRNAs, pulse-labelled as well as the steady-state population of bacteriophage T7-specific transcripts were examined for the presence of poly(A) tracts by binding to oligo(dT) cellulose followed by hybridization with specific gene probes. Representatives of all classes of bacteriophage-specific mRNA--early, middle and late--were found to be polyadenylated. This conclusion was confirmed by screening the products of oligo(dT)-dependent cDNA synthesis. A cDNA library was prepared from RNA synthesized after bacteriophage T7 infection and the sequence of bacteriophage-specific clones was determined to define the sites of polyadenylation. About half of the clones were polyadenylated near the end of a protein-coding region, one of them at the site of post-transcriptional processing by RNase III. Other clones were polyadenylated within protein-coding regions. These observations suggest that polyadenylation occurs after the nucleolytic processing of primary transcripts and in some cases also after mRNA degradation has already begun.

Bacteriophage T7↗
PubMed1998

Fatal familial insomnia: clinical and pathologic heterogeneity in genetic half brothers.

We describe clinical and pathologic features of a patient with fatal familial insomnia (FFI) whose prion (PrP) genotype is D178N coupled with methionine at codon 129 on his mutant allele and valine at codon 129 on his normal allele. A cousin (genetic half brother) with identical PrP genotypes exhibited strikingly different clinical and pathologic changes. Comparison of these cousins shows the phenotypic heterogeneity of FFI and suggests that the phenotypic expression of D178N is influenced by multiple factors.

Adult↗
PubMed1998

Troglitazone: review and assessment of its role in the treatment of patients with impaired glucose tolerance and diabetes mellitus.

OBJECTIVE: To introduce troglitazone (CS-045, Rezulin), a new oral antidiabetic agent and discuss its pharmacology, therapeutics, pharmacokinetics, dosing guidelines, adverse effects, drug interactions, and clinical efficacy. DATA SOURCES: A MEDLINE database search was completed to identify relevant articles including reviews, recent studies and abstracts, and data from Parke-Davis. STUDY SELECTION: Due to the small number of published human studies available, some data are derived from animal studies and abstracts of human studies. Studies and abstracts chosen summarize the clinical action of troglitazone in healthy volunteers, in subjects with impaired glucose tolerance, and in patients with diabetes mellitus. Three of the six published human studies used subjects in a placebo-controlled, multicenter, randomized environment (type 2 diabetic patients or obese subjects with insulin resistance). DATA EXTRACTION: All clinical trials available, including unpublished reports, were reviewed. DATA SYNTHESIS: Troglitazone is the first member of a new class of medications, the thiazolidinediones, to be approved for clinical use. Troglitazone increases insulin sensitivity in skeletal muscle and in hepatic and adipose tissue. It has been shown to decrease hepatic glucose output while having no effect on stimulating insulin secretion from the pancreatic beta-cells. Its metabolic effects decrease fasting and postprandial hyperglycemia, insulin concentrations, and triglyceride concentrations, while increasing high-density lipoprotein concentrations. There is some evidence, based on short-term trials, that troglitazone causes only minimal decreases in glycosylated hemoglobin A1C (HbA1C) concentrations. Data suggest that troglitazone decreases impaired glucose tolerance in nondiabetic obese subjects and leads to a reduction in both systolic and diastolic blood pressure in hypertensive type 2 diabetes mellitus patients. Troglitazone has a mild adverse effect profile, with rare instances of abnormal liver function tests. CONCLUSIONS: Troglitazone appears to be a safe, effective, and useful new agent in the treatment of insulin-requiring type 2 diabetes mellitus patients, although its HbA1C-lowering effects have been minimal in short-term trials, and its insulin dosage-reduction activity remains unclear. The Food and Drug Administration has also approved its use as monotherapy and in combination with sulfonylureas for patients with type 2 diabetes. It may have use in the treatment of patients with impaired glucose tolerance, but more clinical experience is needed before definitive conclusions can be made. The role of troglitazone therapy in diabetes mellitus and impaired glucose intolerance will continue to evolve as the results of studies and our clinical experience with this agent become available.

Animals↗