Biomedical subjects

M D Johnson

Publications and source records attributed to M D Johnson.

At least 163 records · Page 9Linked to original sources

PubMed1993

Type I IGF receptor and acquired tamoxifen resistance in oestrogen-responsive human breast cancer cells.

Tamoxifen inhibited the oestrogen-stimulated proliferation of MCF-7 cells but had little effect on the oestrogen-stimulated proliferation of two tamoxifen-resistant variants (RL-3 and AL-1). The lack of oestrogen antagonist activity in the resistant cells was largely a result of an increased oestrogen agonist activity of tamoxifen on cell proliferation. Proliferation of the tamoxifen-resistant cells was also stimulated by 4-hydroxytamoxifen but not by ICI 164,384, a structurally distinct pure anti-oestrogen. Tamoxifen does not have increased oestrogen agonist activity for the induction of a series of oestrogen-regulated RNAs, and this suggests that the increased agonist activity may be restricted to key components involved in the proliferative response. Tamoxifen-stimulated cell proliferation was dependent on insulin-like growth factor I (IGF-1) in the resistant cells, suggesting that tamoxifen stimulates cell proliferation by sensitising cells to the proliferative effects of IGF-1. This may involve induction of the type-I IGF receptor.

Breast Neoplasms↗

PubMed1993

Inhibition of mammary duct development but not alveolar outgrowth during pregnancy in transgenic mice expressing active TGF-beta 1.

The transforming growth factors beta (TGFs-beta) are potent inhibitors of cell proliferation and are usually secreted in a latent form. TGF-beta 1, TGF-beta 2, and TGF-beta 3 are expressed in distinct but overlapping patterns in the developing mouse mammary gland. To study the role of transforming growth factor-beta 1 (TGF-beta 1) in normal mammary development and in mammary neoplasia, we have constructed three transgenic mouse lines that express a simian TGF-beta 1 s223/225 mutated to produce a constitutively active product under the control of the MMTV enhancer/promoter. Expression of the transgene, as confirmed by in situ hybridization, immunohistochemistry, and Northern blot analysis, was associated with marked suppression of the normal pattern of mammary ductal tree development in female transgenics. Reduction in total ductal tree volume was observed at 7 weeks, soon after estrous begins, and was most apparent at 13 weeks, as ductal growth in the normal mammary gland declines. This effect was seen in all three lines. However, during pregnancy, alveolar outgrowths developed from the hypoplastic ductal tree, and lactation occurred, therefore, all transgenic females could feed full litters. Unlike many other transgenic mouse models in which expression of growth factors or oncogenes under control of the MMTV promoter leads to mammary epithelial hyperplasia and increased tumor formation, the MMTV-TGF-beta 1S223/225 transgene causes conditional hypoplasia of the mammary ductal tree and no spontaneous tumors have been detected in the MMTV-TGF-beta 1S223/225 transgenic animals.

Animals↗

PubMed1993

Sucrose does not raise blood pressure in rats maintained on a low salt intake.

Diets high in sucrose or fructose have been shown by others to induce a modest elevation of blood pressure in rats. The present experiments were conducted to determine whether the sucrose-induced increase of blood pressure is dependent on the intake of sodium chloride. Four groups of Sprague-Dawley rats were studied: 1) a group maintained on a low salt diet and distilled water (0.45% sodium chloride, no added sucrose), 2) a low salt-high sucrose group (0.45% sodium chloride diet and 7% sucrose in distilled water), 3) a high salt group (4% sodium chloride diet and distilled water), and 4) a high salt-high sucrose group on a diet adjusted daily to maintain the same high intakes of sodium chloride and sucrose as those of groups 2 and 3. Systolic blood pressures were measured by tail-cuff plethysmography during weeks 1-3 of treatment, and direct mean arterial blood pressures were recorded in conscious animals during week 4. Animals on the high salt diet gained weight more slowly than those on the low salt intake. On the low sodium chloride intake, blood pressures were not affected by high dietary sucrose (group 1 versus 2). In contrast, on the high sodium chloride intake, blood pressures were 10-14 mm Hg higher in sucrose-drinking animals than in water-drinking animals (group 3 versus 4). The increments in blood pressures of the high sodium chloride-high sucrose group were not accompanied by greater increments in body weight compared with the animals on the high sodium chloride intake alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Anti-transforming growth factor (TGF)-beta antibodies inhibit breast cancer cell tumorigenicity and increase mouse spleen natural killer cell activity. Implications for a possible role of tumor cell/host TGF-beta interactions in human breast cancer progression.

TGF-beta effects on angiogenesis, stroma formation, and immune function suggest its possible involvement in tumor progression. This hypothesis was tested using the 2G7 IgG2b, which neutralizes TGF-beta 1, -beta 2, and -beta 3, and the MDA-231 human breast cancer cell line. Inoculation of these cells in athymic mice decreases mouse spleen natural killer (NK) cell activity. Intraperitoneal injections of 2G7 starting 1 d after intraperitoneal inoculation of tumor cells suppressed intraabdominal tumor and lung metastases, whereas the nonneutralizing anti-TGF-beta 12H5 IgG2a had no effect. 2G7 transiently inhibited growth of established MDA-231 subcutaneous tumors. Histologically, both 2G7-treated and control tumors were identical. Intraperitoneal administration of 2G7 resulted in a marked increase in mouse spleen NK cell activity. 2G7 did not inhibit MDA-231 primary tumor or metastases formation, nor did it stimulate NK cell-mediated cytotoxicity in beige NK-deficient nude mice. Finally, serum-free conditioned medium from MDA-231 cells inhibited the NK cell activity of human blood lymphocytes. This inhibition was blocked by the neutralizing anti-TGF-beta 2G7 antibody but not by a nonspecific IgG2. These data support a possible role for tumor cell TGF-beta in the progression of mammary carcinomas by suppressing host immune surveillance.

Animals↗

PubMed1993

Neoplastic meningitis as the presentation of occult primitive neuroectodermal tumors.

Seven children and young adults initially presented with subacute meningitis and/or increased intracranial pressure. The diagnosis of neoplastic meningitis secondary to a primitive neuroectodermal neoplasm was delayed by the absence of an obvious primary tumor. The neuroradiologic appearance was that of a basimeningeal infiltrative process, complicated by communicating hydrocephalus or "pseudotumor cerebri." Myelography was important in the diagnosis of disseminated meningeal malignancy in four cases. Cerebrospinal fluid cytologic diagnosis was insensitive but ultimately confirmed in five cases. All seven patients experienced progressive disease despite neuraxis radiotherapy and intensive chemotherapy; six have died. Systemic dissemination to bone and/or peritoneum occurred in three patients while on therapy. In two, a primary parenchymal brain or spinal cord tumor could not be identified at postmortem examination. The presentation of a primitive neuroectodermal tumor as subacute meningitis without an evident primary tumor heralds an aggressive and refractory neoplasm.

Adolescent↗

PubMed1993

Poor response to oral ciprofloxacin in the treatment of peritonitis in patients on intermittent peritoneal dialysis.

OBJECTIVES: To assess the clinical value of oral ciprofloxacin in the treatment of peritonitis in an intermittent peritoneal dialysis (IPD) population. DESIGN: Open nonrandomized prospective study. SETTING: Nephrology Peritoneal Dialysis Unit in a tertiary care, teaching hospital of the University of Toronto. PATIENTS: Subjects were participants of the IPD program with an acute episode of peritonitis defined as at least two of the following: 1. signs and symptoms of peritonitis, 2. cloudy peritoneal fluid with a white blood cell count of > 100/microL, 3. demonstration of bacteria in peritoneal effluent by gram stain or culture. Ten patients were enrolled in the study, but two were withdrawn because of side effects and growth of a resistant bacteria. INTERVENTIONS: Ciprofloxacin 750 mg po q12h for 2 doses, then 750 mg daily or 500 mg twice daily for 10 days. MAIN OUTCOME MEASURES: Efficacy was determined by clinical and microbiological assessment. Cure was defined as resolution of signs and symptoms with eradication of the causative organism. Peritoneal effluent and blood samples were analyzed for ciprofloxacin concentration. RESULTS: Ciprofloxacin was effective in treating only one of ten episodes of peritonitis. Seven patients were defined as microbiological failures (persistence or relapse of organisms). The signs and symptoms of peritonitis improved in 2 patients, but the remaining 5 failed clinically. Only Gram-positive organisms were cultured. CONCLUSIONS: Ciprofloxacin cannot be recommended for the treatment of intermittent peritoneal dialysis-related Gram-positive bacterial peritonitis.

Acute Disease↗

PubMed1992

In vitro karyotypic and immunophenotypic characterisation of primitive neuroectodermal tumours: similarities to malignant gliomas.

Monoclonal antibody (Mab) mediated immunotherapy of brain tumours requires the identification of tumour-restricted cell surface antigens. We have characterised four primitive neuroectodermal tumours, which included pineoblastoma, medulloblastoma and ependymoblastoma cultures, that demonstrated in vitro evidence of malignant behaviour (anchorage-independent growth and nu/nu xenograft tumour formation). The cytogenetic findings ranged from normal G-banded and Q-banded karyotypes through mixed near-diploid/hyperdiploid. These cultures resembled the cell surface immunophenotypic spectrum of malignant gliomas. They were distinguished from normal glia in vitro by the expression of restricted fetal mesenchymal, neuronal, myoblastic, melanocytic, epidermal, chondrocytic, lymphoid and epithelial antigens. Certain antigens appeared sufficiently represented among central nervous system (CNS) neoplasms to afford potential targets for Mab-mediated immunotherapy.

Adolescent↗

PubMed1992

Growth factors in breast cancer: mitogenesis to transformation.

While endocrine steroid hormones have been known for many years to regulate normal and malignant mammary epithelium, recent studies have led to an appreciation of polypeptide growth factors as locally-acting autocrine and paracrine effectors. In the current article we summarize what is known about growth factor regulation and action in the normal mammary gland and about perturbations of the steroid-growth factor interplay as cancer progresses. A major theme is that oncogenic activation modulates both regulation of production and function of growth factors in the mammary gland.

Animals↗

PubMed1992

Effect of age on potassium- and tyramine-induced release of norepinephrine from cardiac synaptosomes in male F344 rats.

Potassium (K+)-induced norepinephrine (NE) release was examined in preparations of cardiac synaptosomes and sliced atria from 6-, 24-, and 26-mo-old male F344 rats. Cardiac synaptosomes were prepared from rat hearts by collagenase digestion followed by homogenization in 0.32 M sucrose and centrifugation. The synaptosome preparations and the sliced atria were labeled with 3H-NE and then placed in a superfusion system. K(+)-induced net fractional release of NE from synaptosomes prepared from 24- and 26-mo-old rats (4.3% and 3.0%, respectively) was significantly reduced when compared to NE release from synaptosomes from 6-mo-old rats (5.2%). K(+)-induced NE release from sliced atria from 24-mo-old rats (4.7%) was also significantly reduced when compared to NE release from atria from 6-mo-old rats (6.3%). Perfusion of cardiac synaptosomes with buffer prepared without calcium (CA++free, < 5 microM) reduced K(+)-induced release by 50% in all age groups studied. Perfusion with tyramine induced identical rates of NE release from cardiac synaptosomes prepared from 6- and 24-mo-old rats. These results confirm that depolarization-induced NE release from cardiac sympathetic nerves is reduced in the old male F344 rat.

Adrenergic Fibers↗

PubMed1992

Effects of an opiate receptor antagonist on renin release in dogs.

The present experiments were designed to determine whether blockade of endogenous opiate receptors with naloxone would suppress renin release induced by circulating epinephrine or by reductions of renal perfusion pressure. In the first series of experiments, anesthetized dogs were prepared with a flow probe around the left renal artery and a catheter in the left renal vein, permitting measurement of renin secretion before, during, and after 15-min infusions of epinephrine (50 ng.kg-1.min-1 iv). The epinephrine infusions were conducted either before or after blockade of opiate receptors with naloxone (1 mg/kg iv). Naloxone failed to alter the renin secretory response to intravenous epinephrine infusion. In a second series of experiments, anesthetized dogs were uninephrectomized and prepared with a constrictor cuff around the left renal artery and a renal arterial catheter distal to the cuff. After control measurements of renal perfusion pressure and plasma renin activity (PRA), the cuff was constricted at 15-min intervals to produce controlled stepwise reductions of renal perfusion pressure ranging from 15 to 90 mmHg. One-half of the animals was pretreated with naloxone (1 mg/kg iv). Naloxone pretreatment had no effect on the PRA response to reduced renal perfusion pressure at any pressure. The data fail to support the hypothesis that endogenous opioid peptides are modulators in the control of renin release.

Animals↗

PubMed1992

Effect of naloxone on hypertension in Dahl salt-sensitive rats.

Experiments were conducted to test the hypothesis that chronic administration of an opioid receptor antagonist, naloxone, would affect the outcome of the developmental phase of hypertension in Dahl salt-sensitive (S/JR strain) rats. Accordingly, S/JR rats were maintained on either a low-salt (0.45% NaCl) or a high-salt (7% NaCl) diet for 4 wk. Half of the animals of each dietary group were treated with naloxone (100-130 micrograms/h) by osmotic minipump. Food and water intakes of the high-salt animals were measured for the first 25 days, and blood pressure was measured at the end of the 4 wk via an indwelling femoral arterial catheter. Naloxone treatment slightly but significantly reduced the level of hypertension attained in the high-salt animals (158 +/- 2 mmHg in naloxone-treated animals vs. 168 +/- 3 mmHg in control animals; P less than 0.05) and also attenuated food (and hence salt) and water intakes. Naloxone did not affect the blood pressure of the low-salt animals. To determine whether the slight attenuation of hypertension might be secondary to a reduction of salt intake, a group of control S/JR animals were fed a moderately high-salt diet (2% NaCl), and naloxone-treated S/JR animals were salt-intake matched to this group by daily adjustment of the dietary salt content. Blood pressures after 4 wk of treatment were not different between these two groups. Finally, acute administration of 1 and 30 mg/kg of naloxone failed to lower blood pressure of animals with established hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

A PrP gene codon 178 base substitution and a 24-bp interstitial deletion in familial Creutzfeldt-Jakob disease.

Several mutations in the prion protein (PrP) gene are associated with familial Creutzfeldt-Jakob disease (FCJD). We describe a family in which five members in three generations have had FCJD. The proband and some descendants of the affected members carried an abnormal PrP gene allele. This allele contained a 24-bp deletion from the tandem repeat region of the open reading frame and a codon 178 missense substitution. Observations suggest that the codon 178 mutation is involved in the pathogenesis of FCJD in the family described here. The 24-bp deletion may be an uncommon polymorphism.

Adult↗

PubMed1992

Age-related decrease in omega conotoxin binding to rat cardiac synaptosomes.

A cardiac synaptosomal preparation developed by this laboratory was used to study neuronal calcium channels in aging rat heart. Ca2+ channels were quantified by measuring binding of iodinated omega conotoxin, which is reported to specifically block neuronal Ca2+ channels. We determined the binding of [125I]-omega conotoxin GVIA to a synaptosomal preparation from the hearts of 6- and 24-month-old male Fisher 344 rats. The maximum number of binding sites (Bmax +/- SD, fmol/mg protein) is lower in preparations from 24-month (2.2 +/- 0.6) than from 6-month (3.4 +/- 0.7)-old rats. This decrease in number of binding sites suggests an age-related reduction in the number of neuronal calcium channels. Since calcium is essential for exocytotic release of norepinephrine and is made available intracellularly through neuronal calcium channels, the reduction in neuronal calcium channel number may explain, in part, our previous observations of diminished release of norepinephrine in senescent hearts.

Age Factors↗

PubMed1992

Transforming growth factor-beta and transforming growth factor beta-receptor expression in human meningioma cells.

The transforming growth factor-beta (TGF beta) family in mammals includes three closely related peptides that influence proliferation and numerous physiologic processes in most mesenchymal cells. In this study, Northern blots, immunohistochemistry, TGF beta radioreceptor assays, TGF beta receptor affinity labeling and [3H] thymidine incorporation were used to evaluate whether primary cell cultures of human meningiomas synthesize the three TGF beta isoforms, bear TGF beta receptors, and respond to TGF beta. Transcripts for TGF beta 1 and 2 were detected in the three cases analyzed. Transforming growth factor-beta 1 immunoreactivity was detected in three of six cases, and TGF beta 2 and 3 immunoreactivity were detected in each case analyzed. Media conditioned by cells cultured from six meningiomas also contained latent TGF beta-like activity. Transforming growth factor-beta receptor cross-linking studies identified TGF beta binding sites corresponding to the type 1, type 2, and type 3 receptors on meningioma cells. Treatment with active TGF beta 1 produced a statistically significant reduction in [3H] thymidine incorporation after stimulation with 10% fetal calf serum and epidermal growth factor in all six cases studied.

Blotting, Northern↗

PubMed1992

Evidence for transforming growth factor-beta expression in human leptomeningeal cells and transforming growth factor-beta-like activity in human cerebrospinal fluid.

BACKGROUND: Little is known about the factors regulating growth and maintenance of human leptomeningeal cells. The influence of cerebrospinal fluid on these functions is also unknown. Possible mediators include the transforming growth factor-beta (TGF beta) family, three closely related peptides that regulate proliferation and numerous other physiologic processes in most mesenchymal cells. EXPERIMENTAL DESIGN: Expression of both mRNA and protein for TGF beta isoforms TGF beta 1, TGF beta 2, and TGF beta 3 as well as TGF beta-competing activity were evaluated in primary human leptomeningeal cultures by Northern blot analysis, immunohistochemistry, and a radioreceptor assay, respectively. TGF beta 1, TGF beta 2, and TGF beta 3 immunoreactivity was also evaluated in brain sections containing leptomeninges from which these cell cultures were established. An additional study analyzed human cerebrospinal fluid for TGF beta-like activity. RESULTS: Transcripts for TGF beta 1, TGF beta 2 and TGF beta 3 were detected in RNA from each of the eight leptomeningeal cultures. Significant TGF beta 1 immunoreactivity was detected in leptomeningeal tissue from five of eight cases. TGF beta 2 and TGF beta 3 immunostaining was seen in eight and seven of the cases, respectively. Similarly, cells cultured from these meninges exhibited variable TGF beta 1 and extensive TGF beta 2 and TGF beta 3 immunoreactivity. Radioreceptor assays of conditioned media from four cultures demonstrated significant latent TGF beta-like activity. TGF beta radioreceptor competing activity was also detected by radioreceptor assay in normal blood-free cerebrospinal fluid from 32 patients without neurological disease. In addition, pooled cerebrospinal fluid (from six additional patients) exhibited dose dependent TGF beta-like activity in the radioreceptor assay, stimulation of AKR-2B cell growth in soft agar and inhibition of growth in CCL-64 cell assays suggesting that cerebrospinal fluid contains TG beta-like activity. CONCLUSIONS: These findings suggest that the human leptomeninges synthesize TGF beta 1, TGF beta 2 and TGF beta 3 and secrete latent TGF beta s at least in vitro. Human cerebrospinal fluid may also contain TGF beta isoforms. Collectively, these observations raise the possibility that members of the TGF beta family contribute to biologic processes of the leptomeninges.

Agar↗

PubMed1991

Elevated content of the tyrosine kinase substrate phospholipase C-gamma 1 in primary human breast carcinomas.

Phospholipase C-gamma 1 (PLC-gamma 1) is a substrate for several receptor tyrosine kinases and its catalytic activity is increased by tyrosine phosphorylation. However, the biological significance of this molecule in normal or malignant human epithelial cell proliferation is unknown. We determined the relative content of PLC-gamma 1 in primary human mammary carcinomas and in nonmalignant mammary tissues. By Western blot and immunohistochemistry, considerably higher levels of PLC-gamma 1 protein were detectable in the majority of carcinomas and in one of two benign fibroadenomas compared to normal breast tissues. In 18 of 21 carcinomas that contained high levels of PLC-gamma 1, the presence of phosphotyrosine on PLC-gamma 1 could also be detected. All carcinomas in which tyrosine phosphorylated PLC-gamma 1 was present also expressed detectable levels of the epidermal growth factor receptor or erbB-2, two tyrosine kinases known to phosphorylate this enzyme. Thus, a high percentage of mammary carcinomas concomitantly display increased levels of receptor tyrosine kinases and a direct tyrosine phosphorylation substrate, thereby potentially amplifying two successive steps in a signal transduction pathway.

Amino Acid Sequence↗

PubMed1991

Phorbol diester-induced alterations in the expression of protein kinase C isozymes and their mRNAs. Analysis in wild-type and phorbol diester-resistant HL-60 cell clones.

In an HL-60 cell subline (PR-17) which was greater than 100-fold resistant to the differentiating and cytostatic activities of phorbol 12-myristate 13-acetate (PMA), the protein kinase C phenotype was found to be nearly identical to that of wild-type HL-60 cells. A measurable decrease (30%) in the specific activities of crude preparations of PR-17 cell protein kinase C was observed when the enzyme was measured with histone as the phosphate acceptor substrate, but other aspects of the protein kinase C phenotype (intracellular concentrations and binding affinities of phorbol diester receptors, translocation of activated enzyme from cytosolic to particulate subcellular fractions, relative expression of the alpha and beta isozyme proteins) were equivalent in both PMA-resistant PR-17 cells and in wild-type HL-60 cells. Direct analysis of the behavior of the alpha and beta isozymes after the exposure of each cell type to 100 nM PMA for 12 h revealed that the activities and intracellular concentrations of both isozymes were downregulated to an equivalent extent in both wild-type and PMA-resistant cells. These results suggest that the cellular basis for the resistance to the effects of PMA was present "down-stream" from the activation and down-regulation of protein kinase C and was perhaps a nuclear component. Among the genes which were likely to be differentially regulated when each of the two cell lines were treated with PMA were those for the protein kinase C isozymes themselves. In wild-type HL-60 cells, the intracellular concentrations of type HL-60 cells, the intracellular concentrations of mRNA for each of the beta isozymes were increased (up to 5-fold) 48 h after the initiation of PMA treatment; further studies indicate that an activator of protein kinase C could influence the expression of HL-60 cell protein kinase C genes in an isozyme-specific manner. Comparable PMA-induced alterations in mRNA levels were not observed in PMA-resistant cells, even under conditions of significant activation and subsequent down-regulation of protein kinase C protein. Taken together, these data suggest that activation and down-regulation of the isozymes of protein kinase C may not represent absolute determinants of the PMA-induced differentiation of HL-60 cells, but that specific alterations in the levels of the mRNA for the beta isozymes of protein kinase C, or of other genes which may be regulated by the activated kinase isozymes, are important to the induction of leukemia cell differentiation by PMA.

Animals↗

PubMed1991

Effect of age on presynaptic beta2 receptor mediated responses in the rat heart.

Presynaptic alpha2 adrenergic receptor inhibition of norepinephrine (NE) release is diminished in older animals [1]. To determine whether presynaptic beta2 adrenergic receptor facilitation of NE release is also affected by age, the effect of propranolol on neurally-induced NE release was examined in perfused heart preparations isolated from 6- and 24-month-old rats. The heart was isolated with the right cardiac sympathetic nerve and then was stimulated electrically in the absence and presence of propranolol (10(-8)-10(-6) M). NE content in the effluent was measured by an HPLC/EC methodology. The data indicate that there is a greater suppression of NE release by propranolol in preparation isolated from younger animals. For example, in nerve-heart preparations of 6-month-old animals stimulated at 12 Hz, propranolol (10(-6) M) reduced the amount of NE released by 34% whereas in preparations from 24-month-old animals at 12 Hz there was no significant change in the NE overflow. Like the alpha2 receptor mechanism, autoregulation of NE release by presynaptic beta2 receptors is diminished in older animals. Lack of presynaptic autoregulation may explain in part, the reduced capacity of adrenergic influences to control and regulate cardiac function in older animals.

Aging↗