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Biomedical subjects

R Stein

Publications and source records attributed to R Stein.

At least 91 records · Page 5Linked to original sources
PubMed1998

The intracellular domain of p55 tumor necrosis factor receptor induces apoptosis which requires different caspases in naive and neuronal PC12 cells.

Apoptosis is induced in cells via distinct pathways, which may differ according to various stimuli and different cell types. One apoptotic stimulus is the activation of receptors such as the p55 tumor necrosis factor (TNF) receptor. These receptors transduce their apoptotic signals via a cytoplasmic region termed the death domain. Here we investigated the apoptotic pathway induced by overexpression of the intracellular domain of p55 TNF receptor (p55-IC) in a neuronal model system consisting of PC12 cells. Using the tetracycline-regulated transactivator system, which allows controlled gene expression, we show that overexpression of p55-IC induces apoptosis in both naive and neuronal PC12 cells. The apoptosis-inducing effect of p55-IC is blocked by the expression of bcl-2, suggesting that p55-IC induces apoptosis in PC12 cells via a pathway controlled by bcl-2. The need for caspases in the p55-IC-induced cell death effect in naive and neuronal PC12 cells was studied by examining the effects of broad-spectrum and specific inhibitors of caspases as well as expression of antisense caspase-2 RNA. The broad-spectrum caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl-ketone blocked p55-IC-induced cell death in both naive and neuronal cells, suggesting that caspases are needed for this process in both cell types. Caspase-1-like proteases are most probably not involved in the process since neither expression of crmA nor treatment with the caspase-1-specific peptide inhibitor Ac-Try-Val-Ala-Asp-aldehyde had any protective effect. Interestingly, expression of antisense caspase-2 RNA blocked the p55-IC-induced cell death in naive but not in neuronal PC12 cells, whereas the caspase-3-like specific inhibitor Ac-Asp-Glu-Val-Asp-aldehyde partially inhibited this death in neuronal but not in naive cells. These results suggest that the apoptosis-inducing effect of p55-IC requires different caspases in naive and neuronal PC12 cells.

Animals↗
PubMed1998

Long-term metabolic effects in patients with urinary diversion.

The use of intestinal segments in genitourinary reconstruction could influence vitamin metabolism and affect the skeletal bone and its mineral content in the long term. In 137 patients, serum levels of the vitamins A, B1, B2, B6, B12, D, and E and of folic acid, bile acid, and ammonia as well as levels of intracorpuscular vitamin B12 and folic acid were examined and a red blood cell count was performed. The patients were divided into three groups (< or = 2 years, > 2 to < or = 4 years, and > 4 years after surgery) as well as into children and adults. In addition, bone mineral density (dual-photon absorptiometry) was measured in 25 patients. Of these, 16 patients were approximately 16.8 years s/p rectal reservoir, 6 were approximately 20.5 years s/p colonic conduit, two were 6 and 8 years s/p ileocecal pouch, and one adolescent was 5 years s/p ileal bladder augmentation. In all patients the levels of vitamins A, B1, B2, B6, D, and E and of folic acid, bile acid, and ammonia as well as the red blood cell count were within normal ranges. In children (n = 51) there was no significant drop in vitamin B12 levels after the operation. In adults (n = 86), serum vitamin B12 levels dropped significantly from 402 +/- 182 ng/l during the first 2 years after the operation to 292 +/- 204 ng/l after the 4th year (normal range 240-1,100 ng/l). No significant increase in the intracorpuscular vitamin B12 level was observed during the same period. The bone mineral density was normal in all 25 patients with different types of urinary diversion. In addition to regular examination (sonography, creatinine levels, and base excess), vitamin B12 levels should be determined at 4 years after urinary diversion. It remains unclear whether substitution is necessary. However, substitution is easy to achieve and cheaper than the regular determination of vitamin B12. No decrease in bone mineral content was seen in the long-term follow-up with early correction of the base excess (below -2.5).

Adult↗
PubMed1998

Treatment of interstitial cystitis: comparison of subtrigonal and supratrigonal cystectomy combined with orthotopic bladder substitution.

PURPOSE: We retrospectively evaluate the outcome of interstitial cystitis treated with subtrigonal or supratrigonal cystectomy and orthotopic bladder substitution. MATERIALS AND METHODS: Of 22 women and 1 man a mean of 51 years old with interstitial cystitis refractory to conservative therapy 17 were treated with subtrigonal cystectomy and ureteral reimplantation (group 1), and 6 were treated with supratrigonal cystectomy directly above the ureteral orifices (group 2). Both groups underwent orthotopic bladder substitution with an ileocecal pouch (Mainz pouch I). RESULTS: Postoperatively functional capacity significantly increased from a mean plus or minus standard error of mean 46 +/- 5 to 346 +/- 57 ml. in group 1 and 34 +/- 61 to 319 +/- 29 ml. in group 2 (p < 0.001). Daytime and nighttime urinary frequency significantly decreased from 24 +/- 2 to 8 +/- 1 and 7 +/- 1 to 2 +/- 1 ml., respectively, in group 1 and 28 +/- 2 to 6 +/- 1 and 6 +/- 1 to 1 +/- 1 ml., respectively, in group 2 (p < 0.001). At a mean followup of 93.9 months 14 patients in group 1 (82%) are completely symptom-free, and 1 has tolerable residual urinary urgency and suprapubic pain. At a mean followup of 31.5 months all group 2 patients are symptom-free and void spontaneously, whereas 41% of the group 1 patients require self-catheterization after subtrigonal cystectomy. CONCLUSIONS: For interstitial cystitis refractory to conservative treatment subtotal cystectomy with orthotopic bladder substitution with the ileocecal pouch (Mainz pouch I) is a valid therapeutic option. In this series supratrigonal and subtrigonal cystectomy resulted in similar relief of symptoms but the former appears to provide better functional bladder rehabilitation.

Adult↗
PubMed1998

Neurobiology of cocaine-induced organic brain impairment: contributions from functional neuroimaging.

The present review is directed at imparting the current knowledge regarding functional neuroimaging as a tool for enhancing the understanding of cerebrophysiologic and neurobehavioral consequences of stimulant abuse. Stimulants like cocaine are capable of inducing clinically significant neurocognitive impairment through direct action on the brain, and indirectly through other organs that influence cerebral physiology. Neurochemical dysregulation including profound effects on the serotonergic and dopaminergic systems have substantial physiological and neurobehavioral consequences. Brain hemorrhages, transient ischemic attacks, strokes,and seizures frequently follow cocaine use. The residual cerebropathologic consequences of cocaine are seen only in significant or pronounced brain events when structural neuroimaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI) are employed. However, recent research with newer functional neuroimaging techniques such as single photon emission, positron emission tomography, and quantitative electroencephalography have revealed high rates of significant alteration in brain function among cocaine users, with negative structural imaging studies. These findings are often associated with impairment on neuropsychological evaluation, also in the absence of positive findings on CT and MRI. Both cerebral metabolic and hypoperfusion anomalies are seen, especially in anterior and temporal brain regions. Observed changes can persist for months, and for some patients, may represent a permanent change in brain functioning.

Brain Ischemia↗
PubMed1998

Whole-body potassium and bone mineral density up to 30 years after urinary diversion.

OBJECTIVES: To evaluate the long-term effects of different types of urinary diversion on skeletal bone density and whole-body potassium content in patients with an early correction of base excess (< -2.5). PATIENTS AND METHODS: The early correction of base excess (< -2.5) is one of the principles of the treatment of patients undergoing urinary diversion at our institution. In 27 patients with urinary diversion, bone mineral density (assessed by dual-photon absorptiometry), whole-body potassium, electrolyte and creatinine levels were determined, and capillary blood gas analysed. The mean time since surgery was 16.8 years in 16 patients with a rectal reservoir, 20.5 years in six patients with a colonic conduit, 7.8 years in four patients with an ileocaecal pouch and 5 years in one adolescent with an ileal bladder augmentation. RESULTS: Bone mineral density was normal in 25 of the 27 patients; no exact measurement was possible in the remaining two. The whole-body potassium content was reduced in eight of the 27 patients (three with a conduit, two with a rectal reservoir, two with an ileocaecal pouch and one with ileal augmentation). In four of these eight patients the base excess was < -2.5 (-2.7 to -5). Of the other four, two had no regular testing of their base balance and two were obese. The electrolytes were within the normal ranges. None of the patients had hyperchloraemic metabolic acidosis. CONCLUSION: With early correction of the base excess (< -2.5), there was no decrease in bone mineral density and no hyperchloraemic acidosis. There was no significant difference between the different types of urinary diversion. There seems to be a relationship between low base excess and decreased whole-body potassium.

Adolescent↗
PubMed1998

p300 mediates transcriptional stimulation by the basic helix-loop-helix activators of the insulin gene.

Pancreatic beta-cell-type-specific and glucose-inducible transcription of the insulin gene is mediated by the basic helix-loop-helix factors that bind to and activate expression from an E-box element within its enhancer. The E-box activator is a heteromeric complex composed of a beta-cell-enriched factor, BETA2/NeuroD, and ubiquitously distributed proteins encoded by the E2A and HEB genes. Previously, we demonstrated that the adenovirus type 5 E1A proteins repressed stimulation by the E-box activator in beta cells. In this study, our objective was to determine how E1A repressed activator function. The results indicate that E1A reduces activation by binding to and sequestering the p300 cellular coactivator protein. Thus, we show that expression of p300 in beta cells can relieve inhibition by E1A, as well as potentiate activation by the endogenous insulin E-box transcription factors. p300 stimulated activation from GAL4 (amino acids 1 to 147) fusion constructs of either BETA2/NeuroD or the E2A-encoded E47 protein. The sequences spanning the activation domains of BETA2/NeuroD (amino acids 156 to 355) and E47 (amino acids 1 to 99 and 325 to 432) were required for this response. The same region of BETA2/NeuroD was shown to be important for binding to p300 in vitro. The sequences of p300 involved in E47 and BETA2/NeuroD association resided between amino acids 1 and 1257 and 1945 and 2377, respectively. A mutation in p300 that abolished binding to BETA2/NeuroD also destroyed the ability of p300 to activate insulin E-box-directed transcription in beta cells. Our results indicate that physical and functional interactions between p300 and the E-box activator factors play an important role in insulin gene transcription.

Animals↗
PubMed1998

The poignant, the excessive and the enigmatic in sexuality.

The author offers a contribution to redressing a certain lack of theorization concerning the specific power and meaning of sexuality. This begins with George Klein's suggestion that it is the quality of a specific, poignant sensuality that characterizes sexuality. Bataille's ideas about the violent and excessive aspects of eroticism provide some answers to the question of what makes for this special poignant quality. Bataille captures a profound link between the sacred and the erotic with regard to their both being linked with taboos and their transgression as opposed to habitual 'work mentality' and established order. The excessive dimension highlighted by Bataille is complemented in the work of Laplanche about sexuality as opposed to 'functional', self-preservative ego needs, and the excess of the 'enigmatic message' transmitted by the mother while satisfying the infant's ego needs that establishes the infant's unconscious and sexuality. Losing the nutritive object, a process of fantasizing sets in; the influx of strong sensations that cannot yet be integrated spills over into libidinal excitement. The gap between the other's excess and the child's limited resources can then be sexualized. A picture emerges of non-procreative sexuality as foreign to ordinary experience and as transcending one's limits.

Humans↗
PubMed1998

The enigmatic dimension of sexual experience: the "otherness" of sexuality and primal seduction.

Sexual experience has an "otherness" about it that distinguishes it from daily, habitual modes of experiencing and relating. This paper attempts to use Freud's and Laplanche's theories of primal seduction by the mother, who sends an "enigmatic signifier" or message of her sexuality to the child whom she nurtures. A tension arc is created between bodily sensations and the enigmatic other carrying over into adult life and constituting a bedrock for the sense of enigma and unfathomableness and the sense of the profound revelation that sometimes accompanies sexual experience. The author articulates links with transference and countertransference forms and offers new possibilities of understanding some clinical phenomena.

Adult↗
PubMed1997

Advantage of yttrium-90-labeled over iodine-131-labeled monoclonal antibodies in the treatment of a human lung carcinoma xenograft.

BACKGROUND: The purpose of this investigation was to compare the therapeutic effectiveness of yttrium-90 (90Y)-labeled monoclonal antibodies (MoAbs) with iodine-131 (131I)-labeled MoAbs delivered to human tumor xenografts at their maximum tolerated doses (MTD). METHODS: Nude mice bearing size-matched human lung adenocarcinoma xenografts (Calu-3) with mean tumor dimensions of approximately 0.8 cm received intravenous injections of the MTD of either 90Y- or 131I-labeled MoAbs. The mice received 125 microCi of 90Y-RS11 or 90Y-RS7, or 300 microCi of 131I-RS11 or 131I-RS7. Tumor size was measured weekly. Body weight and blood counts were monitored to measure toxicity. RESULTS: The calculated average radiation doses delivered to tumors in mice treated with 90Y-RS11 and 90Y-RS7 were 3578 and 3787 centigray (cGy), respectively, versus 1264 and 1368 cGy for 131I-RS11 and 131I-RS7, respectively. These values were calculated taking into consideration the tumor size-dependent absorbed fractions for the beta particles of both radioisotopes. The calculated radiation doses absorbed in the tumor correlated with the tumor responses observed. Mean tumor volume decreases at nadir were 66% and 87% after 90Y-RS11 and 90Y-RS7 therapy, respectively, with 15 of 30 mice treated with either MoAb having complete regression of their tumors. In contrast, only mean stable disease was observed with the 131I MoAb treatments. CONCLUSIONS: The results demonstrate the superiority of 90Y-labeled MoAbs over conventionally labeled 131I-labeled MoAbs for therapy in this model. The fact that a substantial percentage of complete remissions was achieved with 90Y-labeled MoAbs suggests a considerable radiosensitivity of the tumor studied, and supports the suitability of choosing this tumor type as an attractive target for future clinical radioimmunotherapy.

Animals↗
PubMed1997

Active site-directed inhibitors of Rhodococcus 20 S proteasome. Kinetics and mechanism.

We have studied the mechanism of inhibition of the recombinant Rhodococcus proteasome by four different chemical classes of active site-directed small molecule inhibitors. Clasto-lactacystin beta-lactone is a time-dependent inhibitor of the Rhodococcus proteasome's ability to hydrolyze Suc-Leu-Leu-Val-Tyr-AMC, a substrate for this proteasome's single type of active site, and proceeds with a kinact/[I] of 1,700 M-1 s-1. Using peptide mapping of tryptic digests, LC/MS, and amino acid sequence analysis, we have established that the Ogamma of the hydroxyl group on the N-terminal threonine of the beta-subunit is the sole modification made by the beta-lactone. Active site titrations of the Rhodococcus proteasome with reversible peptide aldehydes show the expected stoichiometry of one inhibitor molecule per beta-subunit. Prior modification with beta-lactone completely abrogates the binding of peptidyl boronic acid inhibitors, suggesting that these inhibitors also inactivate the enzyme by reacting with the Ogamma moiety on Thr1. High performance liquid chromatography analysis of peptidyl vinyl sulfone-modified intact Rhodococcus proteasome beta-subunit and its tryptic peptides suggests that the peptidyl vinyl sulfone modifies a residue in the N-terminal 20 amino acids. This modification is also blocked by prior treatment with beta-lactone.

Binding Sites↗
PubMed1997

Need for caspases in apoptosis of trophic factor-deprived PC12 cells.

PC12 cells are a useful model system for studying neuronal apoptosis. Like neurons, they undergo apoptosis when deprived of trophic support. Involvement of caspases [interleukin 1beta-converting enzyme (ICE)-related proteases] has been implicated in apoptosis induced by various stimuli in many cell types, including neurons. In the present study we investigated the need for caspases participation in apoptosis induced by growth factor deprivation in naive and neuronal PC12 cells. For this purpose we generated PC12 cell lines that consistently express the viral caspases inhibitor genes p35 or crmA, and analyzed their susceptibility to trophic factor deprivation. We also examined the effects of cell-permeable peptide inhibitors of caspases. Our results showed that broad-spectrum inhibitors of the caspases, namely the baculovirus p35 gene and the peptide benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, effectively inhibit the death of both naive and neuronal PC12 cells. However, caspase-1 (ICE)-specific inhibitors, namely the peptides Ac-Try-Val-Ala-Asp-chloromethylketone and Ac-Try-Val-Ala-Asp-aldehyde, as well as crmA, were much less effective. These findings demonstrate that caspases, but not caspase-1, are needed for apoptosis induced by trophic factor deprivation in both naive and neuronal PC12 cells. Northern and Western blot analyses showed that PC12 cells express caspase-3. We therefore examined the involvement of caspase-3 in the death process of trophic factor-deprived PC12 cells. Our results showed that the pro-caspase-3 and its substrate poly-(ADP-ribose) polymerase are cleaved at similar rates in serum-deprived PC12 cells. Moreover, cell lysates prepared from these cells possess caspase-3-like activity, as determined by their ability to cleave the fluorogenic peptide substrate Ac-Asp-Glu-Val-Asp-7-amino-4-methylcoumarin. These findings strongly suggest that caspase-3 or caspase-3-like proteases are activated in trophic factor-deprived PC12 cells.

Amino Acid Chloromethyl Ketones↗
PubMed1997

Identification of cis- and trans-active factors regulating human islet amyloid polypeptide gene expression in pancreatic beta-cells.

Islet amyloid polypeptide is expressed almost exclusively in pancreatic beta- and delta-cells. Here we report that beta cell-specific expression of the human islet amyloid polypeptide gene is principally regulated by promoter proximal sequences. The sequences that control tissue-specific expression were mapped between nucleotides -2798 and +450 of the human islet amyloid polypeptide (IAPP) gene using transgenic mice. To localize the cis-acting elements involved in this response, we examined the effects of mutations within these sequences using transfected islet amyloid polypeptide promoter expression constructs in pancreatic beta cell lines. The sequences between -222 and +450 bp were found to be necessary for beta cell-specific expression. Linker-scanning mutations of the 5'-promoter proximal region defined several key distinct control elements, including a negative-acting element at -111/-102 base pairs (bp), positive-acting elements like the basic helix-loop-helix-like binding site at -138/-131 bp, and the three A/T-rich, homeobox-like sites at -172/-163, -154/-142, and -91/-84 bp. Mutations within any one of these elements eliminated transcriptional expression by the promoter. Gel mobility shift assays revealed that the PDX-1 homeobox factor, which is required for insulin gene transcription in beta cells, interacted specifically at the -154/-142- and -91/-84-bp sites. Since PDX-1 is highly enriched in beta and delta cells, these results suggest that this factor plays a principal role in defining islet beta cell- and delta cell-specific expression of the IAPP gene.

Amyloid↗