PubMed Health⌕ Search

Biomedical subjects

J A Smith

Publications and source records attributed to J A Smith.

At least 19 recordsLinked to original sources
PubMed1992

Peanut lectin: a mitogen for normal human colonic epithelium and human HT29 colorectal cancer cells.

BACKGROUND: The protein peanut agglutinin (PNA) is a galactose-binding lectin whose receptor, the Thomsen-Friedenreich (TF) blood-group antigen, shows increased expression in hyperplastic and neoplastic colonic epithelium. PURPOSE: Our hypothesis was that, under these conditions, increased lectin receptors could interact with dietary lectins, which would act as tumor promoters by stimulating cell proliferation. This study was designed to confirm whether active PNA is recoverable from feces after ingestion of peanuts and to assess the mitogenic effect of PNA on proliferation of epithelial cells in the colon. METHODS: Peanut lectin was extracted from feces by lactose-agarose affinity chromatography and was assayed for hemagglutinating activity. Cultured explants of histologically normal biopsy specimens of colonic mucosa from 31 patients were examined. Crypt cell production rate and incorporation of [3H]N-acetylglucosamine into mucin were assessed as indicators of proliferative and metabolic responses to PNA. In addition, we evaluated the separate and combined effects of PNA and epidermal growth factor (EGF) on cell proliferation in human HT29 colorectal cancer cells, by using tritiated thymidine incorporation and cell counts. RESULTS: Peanut lectin extracted from feces showed hemagglutinating activity toward desialylated red blood cells similar to that of a lectin preparation extracted from raw peanuts. Evaluation of biopsy specimens of normal colonic mucosa demonstrated that PNA at a concentration of 25 micrograms/mL caused statistically significant increases in crypt cell production (31% [mean] +/- 5% [SD]; P = .00005) and mucus synthesis (77% +/- 12%; P less than .000001). At 7.5-100 micrograms/mL, PNA was mitogenic for the HT29 colorectal cancer cell line. At 25 micrograms/mL, PNA alone produced a statistically significant increase in thymidine incorporation (44% [mean] +/- 3.7% [SD]; P = .002). For PNA in combination with EGF at 100 pg/mL, the increase was significantly greater (222% +/- 11.2%) than that for EGF alone (57% +/- 5%; P = .003). CONCLUSIONS: These results suggest that expression of the PNA receptor, TF antigen, by hyperplastic or neoplastic colonic epithelium may affect cell proliferation. IMPLICATIONS: It is possible that dietary lectins such as PNA, which bind to the TF antigen, promote cell proliferation and thus cancerous growth, while galactose-containing vegetable fiber would inhibit this effect by competing for binding by these lectins.

Arachis↗
PubMed1992

Management of localized prostate cancer.

BACKGROUND: Given the variable natural history of prostate cancer, prognostic parameters are needed to help guide treatment decisions in individual patients. In some series, analysis of DNA ploidy has correlated well with prognosis. This review was performed to determine whether flow cytometry could be used to help guide treatment decisions in patients with localized carcinoma of the prostate. METHODS: Two hundred consecutive patients were observed for a minimum of 10 years after radical prostatectomy. Follow-up information was incomplete in 14 patients, leaving 186 for analysis. Clinically, there were 72% Stage B tumors and 28% Stage A. RESULTS: Sixty percent of patients were alive with a minimum of 10 years of follow-up, and 47% apparently were tumor free. Twenty-two percent died of carcinoma of the prostate and 18% of other causes. The median time until death from prostate cancer was 6.5 years. Seventy-four percent of tumors were diploid on flow cytometry. Fifty-three percent of patients with diploid tumors survived 10 years without recurrence, whereas 20% died of carcinoma of the prostate. Aneuploid tumors were identified in 16% of the total group; 47% of these patients were alive at 10 years, whereas 24% had died of prostate cancer. CONCLUSIONS: Aneuploid tumors have a worse overall prognosis than diploid lesions. However, the correlation is not strong enough to allow treatment decisions on an individual patient basis. Analysis of DNA ploidy was no more accurate than Gleason histologic grading.

DNA, Neoplasm↗
PubMed1992

Immunodominance: intermolecular competition between MHC class II molecules by covalently linked T cell epitopes.

The T cell response to complex protein Ag typically focuses on a few, and frequently a single, immunodominant epitope. Several groups have proposed that the mechanism of immunodominance is determined by the steps of Ag processing and presentation including protein unfolding, the sites of proteolytic cleavage, and the affinity of binding to MHC molecules. Also, the failure of the TCR repertoire to recognize MHC-bound peptides, termed a hole in the repertoire, can prevent recognition of a potentially dominant processed peptide. In the present study, we demonstrate that immunodominance can be determined by intermolecular competition for binding to MHC class II molecules between covalently linked T cell epitopes. In addition, we have analyzed the factors controlling T cell recognition of the covalently linked epitopes. In our system, T cell recognition of the dominant epitope is not altered by Ag processing, and is not simply a function of MHC-binding affinity. We propose that adjacent sequences can subtly alter the conformation of an epitope, creating significant changes in T cell recognition. These observations are discussed in terms of the mechanisms of immunodominance and in terms of the development of synthetic peptide vaccines.

Amino Acid Sequence↗
PubMed1992

Rapid purification and reconstitution of a plant vacuolar ATPase using Triton X-114 fractionation: subunit composition and substrate kinetics of the H(+)-ATPase from the tonoplast of Kalanchoë daigremontiana.

A rapid procedure for the purification and reconstitution into proteoliposomes of the H(+)-translocating ATPase of plant vacuolar membranes is reported. It involves fractionation of the tonoplast with Triton X-114, resolubilization of the ATPase with octyl glucoside in the presence of a mixture of phosphatidylcholine, phosphatidylserine and cholesterol (27:53:20, by weight), and removal of the detergent by gel-filtration. Starting with partially purified vacuolar membranes, the procedure can be accomplished in about 2 hours. It has been applied to the H(+)-ATPase from the crassulacean plant Kalanchoë daigremontiana, from which it yields vesicles with a specific ATPase activity of about 3 mumol/min per mg protein. The purified enzyme contains polypeptides of apparent molecular mass 72, 57, 48, 42, 39, 33 and 16 kDa; these polypeptides also co-sediment on centrifugation of the solubilized ATPase through glycerol gradients. The 16-kDa subunit is labelled with [14C]dicyclohexylcarbodiimide. There is no evidence for a larger ATPase subunit in this preparation. The reconstituted ATPase proteoliposomes undergo ATP-dependent acidification, which can be measured by quenching of the fluorescence of 9-aminoacridine. The initial rate of fluorescence quenching is a measure of the rate of H+ translocation, and is directly proportional to the vesicle protein concentration, so the preparation is suitable for studying the kinetics of the tonoplast H(+)-ATPase. The dependence of the rate of fluorescence quenching on the concentration of MgATP is well fitted by the Michaelis equation, with a Km value about 30 microM. ATP can be replaced by dATP, ITP, GTP, UTP or CTP, and Mg2+ by Mn2+ or Ca2+; kinetic parameters for these substrates are reported. In contrast, hydrolysis of MgATP shows complex kinetics, suggestive either of negative cooperativity between nucleotide-binding sites, or of two non-interacting catalytic sites. Both the hydrolytic and the H(+)-translocating activities of the proteoliposomes are inhibited by nitrate, though not in parallel, the latter activity being the more sensitive. Both activities are inhibited in parallel by bafilomycin A1, which does not produce complete inhibition; the bafilomycin-insensitive component has complex ATPase kinetics similar to those of the uninhibited enzyme.

Adenosine Triphosphate↗
PubMed1992

Molecular cloning, sequencing, deletion, and overexpression of a methionine aminopeptidase gene from Saccharomyces cerevisiae.

A yeast gene for a methionine aminopeptidase, one of the central enzymes in protein synthesis, was cloned and sequenced. The DNA sequence encodes a precursor protein containing 387 amino acid residues. The mature protein, whose NH2-terminal sequence was confirmed by Edman degradation, consists of 377 amino acids. The function of the 10-residue sequence at the NH2 terminus, containing 1 serine and 6 threonine residues, remains to be established. In contrast to the structure of the prokaryotic enzyme, the yeast methionine aminopeptidase consists of two functional domains: a unique NH2-terminal domain containing two motifs resembling zinc fingers, which may allow the protein to interact with ribosomes, and a catalytic COOH-terminal domain resembling other prokaryotic methionine aminopeptidases. Furthermore, unlike the case for the prokaryotic gene, the deletion of the yeast MAP1 gene is not lethal, suggesting for the first time that alternative NH2-terminal processing pathway(s) exist for cleaving methionine from nascent polypeptide chains in eukaryotic cells.

Amino Acid Sequence↗
PubMed1992

Genistein differentially inhibits postreceptor effects of insulin in rat adipocytes without inhibiting the insulin receptor kinase.

Genistein, an isoflavone putative tyrosine kinase inhibitor, was used to investigate the coupling of insulin receptor tyrosine kinase activation to four metabolic effects of insulin in the isolated rat adipocyte. Genistein inhibited insulin-stimulated glucose oxidation in a concentration-dependent manner with an ID50 of 25 micrograms/ml and complete inhibition at 100 micrograms/ml. Genistein also prevented insulin's (10(-9) M) inhibition of isoproterenol-stimulated lipolysis with an ID50 of 15 micrograms/ml and a complete effect at 50 micrograms/ml. The effect of genistein (25 micrograms/ml) was not reversed by supraphysiological (10(-7) M) insulin levels. In contrast, genistein up to 100 micrograms/ml had no effect on insulin's (10(-9) M) stimulation of either pyruvate dehydrogenase or glycogen synthase activity. We determined whether genistein influenced insulin receptor beta-subunit autophosphorylation or tyrosine kinase substrate phosphorylation either in vivo or in vitro by anti-phosphotyrosine immunoblotting. Genistein at 100 micrograms/ml did not inhibit insulin's (10(-7) M) stimulation of insulin receptor tyrosine autophosphorylation or tyrosine phosphorylation of the cellular substrates pp185 and pp60. Also, genistein did not prevent insulin-stimulated autophosphorylation of partially purified human insulin receptors from NIH 3T3/HIR 3.5 cells or the phosphorylation of histones by the activated receptor tyrosine kinase. In control experiments using either NIH 3T3 fibroblasts or partially purified membranes from these cells, genistein did inhibit platelet-derived growth factor's stimulation of its receptor autophosphorylation. These findings indicate the following: (a) Genistein can inhibit certain responses to insulin without blocking insulin's stimulation of its receptor tyrosine autophosphorylation or of the receptor kinase substrate tyrosine phosphorylation. (b) In adipocytes genistein must block the stimulation of glucose oxidation and the antilipolytic effects of insulin at site(s) downstream from the insulin receptor tyrosine kinase. (c) The inhibitory effects of genistein on hormonal signal transduction cannot necessarily be attributed to inhibition of tyrosine kinase activity, unless specifically demonstrated.

Adipose Tissue↗
PubMed1992

Heterogeneity of progesterone receptor content and remodeling by tamoxifen characterize subpopulations of cultured human breast cancer cells: analysis by quantitative dual parameter flow cytometry.

Breast cancers treated with the antiestrogen tamoxifen invariably become resistant. To analyze the behavior of cell subpopulations within a tumor following tamoxifen treatment, we have used a new flow cytometry-based immunoassay and software that simultaneously quantitate PR levels and the DNA indices of ploidy and cell cycle stage in total cell populations or any subset thereof. The human breast cancer cell line T47D and its clonal derivatives were used as models of stage IV breast cancer, and growth and PR were measured as markers of antiestrogen responsiveness. We demonstrate and quantitate a remarkable heterogeneity in PR content and show the existence of distinct subpopulations with large differences in their PR levels and DNA indices, even among T47D sublines that are clonally derived. Following chronic tamoxifen treatment, an overall decrease in PR levels and growth masks an extensive heterogeneity in the response of cell subpopulations. PR levels decrease in some cells but increase in others; populations having a growth advantage expand while others contract. We find little evidence that cells, unaffected by the hormone, gain a growth advantage. Rather than exhibiting autonomy, we propose that under the influence of tamoxifen, tumors become remodeled as selected subpopulations emerge that are stimulated by the hormone, explaining the paradoxical recurrence of disease in patients undergoing endocrine therapy.

Breast Neoplasms↗
PubMed1992

Prodromal symptoms in manic depressive psychosis.

Twenty patients suffering from manic depressive psychosis were interviewed about the prodromes to both manic and depressive episodes. These prodromal periods were compared with a recent control period during which the patient was in remission. It was possible for 85% of patients to identify a depressive prodrome and 75% a manic prodrome. Prodromal periods were characterised by a significant increase in the number and magnitude of symptoms compared with those present during remission. The mean duration of manic prodromes was slightly longer than that of depressive prodromes (28.9 days and 18.8 days respectively). The majority of patients could identify a time sequence to the retainment of insight during their prodromes and could also identify idiosyncratic symptoms.

Adult↗
PubMed1992

Saphenous vein graft pseudoaneurysm formation after postoperative mediastinitis.

Pseudoaneurysm formation involving the body of an aortocoronary saphenous vein graft is a rare event. True aneurysmal dilatation of the graft and anastomotic pseudoaneurysm formation occur more commonly. We present the case of a 73-year-old woman in whom a pseudoaneurysm communicating with the body of a posterior descending coronary artery saphenous vein graft developed, presumably after a postoperative sternal wound infection. The aneurysm was excised and the defect within the saphenous vein graft repaired using hypothermia and circulatory arrest.

Aged↗
PubMed1992

Silencing of immunodominant epitopes by contiguous sequences in complex synthetic peptides.

We have previously shown that the T cell response to the synthetic peptide cI12-26:NP365-380 (covalently linked epitopes of lambda repressor (cI) and influenza A nucleoprotein (NP) polypeptides) requires amino acid sequences located in the junctional region between the cI12-26 and NP365-380 epitopes in the H-2d and H-2k haplotypes. In this study, we show that the dominant epitope of cI12-26:NP365-380 in H-2b mice is also located within the junctional region of the peptide, indicating that the same amino acid sequence is immunodominant in three different H-2 haplotypes. Based on results using fixed APC, there was no qualitative difference in epitope recognition due to antigen processing. In addition, antigen presentation by APC expressing mutant I-A molecules constructed by hemiexon shuffling of regions of the molecule containing primarily beta sheet or alpha helix showed that many different substitutions were permissive for at least one of the T hybridomas. More importantly, however, when the junctional sequences are covalently linked in composite synthetic peptides containing additional previously defined T cell epitopes, antigenicity of the immunodominant junctional region was silenced and a new epitope assumed immunodominance. Thus, immunodominance does not correlate with the primary amino acid sequence of the potential epitope. Instead, the immunodominant epitope is determined by complex interactions among the epitopes, which most likely depend on the structural conformation of the composite peptide.

Amino Acid Sequence↗
PubMed1992

A comparative study of the effects of intranasal triamcinolone acetonide aerosol (ITAA) and prednisone on adrenocortical function.

A comparison of adrenocortical function before and after treatment with either intranasal triamcinolone acetonide aerosol (ITAA), prednisone, or placebo was done. Sixty-two male subjects with allergic rhinitis were treated for 6 weeks with either ITAA (220 or 440 micrograms/day), oral prednisone (10 mg/day), or placebo in double-blind, parallel-group fashion. Adrenocortical function was assessed by 6-hour cosyntropin stimulation before and at the end of the treatment period. The placebo-treated and two ITAA-treated groups produced no changes in adrenocortical function with treatment, and the ITAA-treated groups were not different from the placebo-treated group with mean +/- SEM changes in stimulated plasma cortisol (micrograms per deciliter) as follows: placebo, -2.68 +/- 1.77; ITAA 220 micrograms, -2.69 +/- 1.18; ITAA 440 micrograms, -2.96 +/- 1.81. The prednisone-treated group had a mean reduction in adrenocortical function (mean +/- SEM change in stimulated plasma cortisol of -19.8 +/- 1.77 micrograms/dl) that was significant (p less than 0.0001) compared with that of the placebo-treated group. The results of this study indicate that 6 weeks of treatment with 220 micrograms/day or 440 micrograms/day of ITAA has no effect on adrenocortical function, but prednisone, at a dosage of 10 mg/day for 6 weeks, produces partial adrenocortical suppression.

Administration, Intranasal↗
PubMed1992

The influence of endocardial endothelium on myocardial contraction.

A novel unidentified agent, provisionally named 'endocardin', has been shown to be released from endocardial endothelium. Endocardin has a unique prolonging effect on myocardial contraction. In contrast, endothelium-derived relaxing factor released from endocardial endothelium has the opposite effect of abbreviating contraction. Jerry Smith and colleagues discuss the mechanisms of action of these agents and their possible physiology and pathophysiology.

Animals↗
PubMed1992

A screening study of prostate cancer in high risk families.

In a study of the familial risk of prostate cancer 17 sets of 2 brothers with prostate cancer were identified. A total of 34 first-degree relatives of these probands (sons and brothers, 55 to 80 years old) underwent an intensive screening examination that included prostate specific antigen, digital rectal examination, transrectal ultrasound and systematic as well as clinically directed core needle biopsies. Previously unsuspected and clinically relevant cancers were found in 8 men (24%), compared to the approximately 1 expected (p less than 0.01). Of these cancers 2 were detected by the systematic biopsies. This study emphasizes the importance of thorough screening in first-degree relatives of prostate cancer patients.

Aged↗
PubMed1992

Effects of photodynamic therapy in combination with intravesical drugs in a murine bladder tumor model.

This study was designed to evaluate the interaction of photodynamic therapy (PDT) and intravesical drugs (thiotepa, adriamycin, mitomycin C and BCG) in a murine transitional cell carcinoma (MBT-2) model. C3H/He mice with implanted MBT-2 flank tumors were treated with either thiotepa (TT), adriamycin (ADM), mitomycin C, Bacillus Calmette-Guerin (BCG), photodynamic therapy (PDT) or a combination of the drug and PDT. The MBT-2 tumor showed sensitivity to adriamycin, MMC or PDT compared to control. PDT combined with either adriamycin, MMC or BCG, produced a greater retardation in the growth of the MBT-2 tumor than monotherapy with adriamycin, MMC, BCG or PDT. PDT combined with the anticancer agents currently used in intravesical therapy for bladder cancer is well tolerated. The combination of PDT and intravesical drugs may enhance the tumoricidal effect of either treatment used alone.

Administration, Intravesical↗
PubMed1992

Adriamycin absorption after Nd:YAG laser coagulation compared to electrosurgical resection of the bladder wall.

The toxicity of intravesical drugs used for the treatment of bladder cancer is increased by systemic absorption. Therefore, treatment is often delayed several weeks after transurethral resection until sufficient healing occurs. Since a neodymium:YAG laser causes tissue injury by thermal coagulation, we investigated differences in bladder permeability after laser treatment compared to TUR. Comparable 2.5 cm in diameter areas of tissue injury were created in the bladder of mongrel dogs either by Nd:YAG laser coagulation or transurethral electrocautery resection (TUR). Subsequently, 30 mg. of adriamycin were instilled intravesically. A control group consisted of animals receiving adriamycin alone. Blood was taken at 10, 30, 60, and 120 minutes after instillation and the serum concentration of adriamycin measured quantitatively by high performance liquid chromatography (HPLC) with fluorescence detection. The maximum serum ADM concentration during 120 minutes for the control group was 28.0 +/- 12.9 ng/ml compared to 38.9 +/- 4.8 for the laser group and 102.9 +/- 29.9 for TUR. The area under the curve was 35.1 +/- 10.2 ng x hours/ml for control, 43.5 +/- 3.9 for laser and 127.7 +/- 49.9 for TUR. Using a two-tailed Student's t test, the difference between the TUR and the laser group was significant (p less than 0.01). There was no difference between laser and control. These results suggest that laser treatment has minimal effect on the absorption of drugs from the bladder. The clinical practice of delaying intravesical therapy after TUR is verified but a similar policy may not be necessary after laser treatment.

Administration, Intravesical↗