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Biomedical subjects

J Stein

Publications and source records attributed to J Stein.

At least 127 records · Page 7Linked to original sources
PubMed2000

Analysis of low-molecular-weight GTP-binding proteins in two functionally different intestinal epithelial cell lines.

Low molecular weight GTP-binding proteins are molecular switches that are believed to play pivotal roles in cell growth, differentiation, cytoskeletal organization, and vesicular trafficking. In this study, for the first time, members of this family of proteins in two functionally different intestinal epithelial cell lines are identified and characterized. [alpha-32P]GTP blot overlay assays of cytosolic and membranous fractions revealed the presence of specific GTP-binding proteins in the range of 20-30 kDa (small GTPases) in both fractions, with considerably higher amounts in the membranous insoluble fraction. Analysis by two-dimensional electrophoresis, immunoprecipitation using monoclonal and sequence-specific polyclonal antibodies, and C3 exoenzyme-mediated ADP ribosylation demonstrated the presence of Ras, Rap, Rho, Rac, Rab, and several other small GTPases. The pattern of small GTP-binding proteins corresponded to the characteristics of the cell lines. Caco-2 cells showed a Rab5 protein that is known to be involved in endocytosis but was not found in T84 cells. On the contrary Rab3 has been shown to participate in secretory processes. It is highly expressed in T84 cells (sixfold compared to Caco-2 cells).

Caco-2 Cells↗
PubMed2000

Application of the colon-simulation technique for studying the effects of Saccharomyces boulardii on basic parameters of porcine cecal microbial metabolism disturbed by clindamycin.

AIMS: The present study analyzed the effects of Saccharomyces boulardii on the biochemical parameters of microbial hindgut metabolism disturbed by clindamycin. METHODS: The experiments were carried out under in vitro conditions using the semicontinuous colon-simulation technique. This technique is standardized for quantitatively measuring parameters of microbial hindgut metabolism. The fluid and particle phase of pig hindgut contents were used for the in vitro incubations. The 5-day control period was followed by clindamycin exposure alone (312.5 mg/day for 5 days) or by a combined treatment of clindamycin and S. boulardii (400 mg/day for 5 days). RESULTS: Clindamycin resulted in significant decreases in production rates of short-chain fatty acids (SCFAs) which were associated with substantial changes in molar SCFA proportions at the expense of butyrate. These effects could at least partly be compensated for by S. boulardii, in particular by enhancements of acetate and propionate fermentation to control levels. In contrast, butyrate fermentation could not be reconstituted. In a second experiment the potential use of S. boulardii as a substrate for hindgut microbial metabolism was studied by comparing living and autoclaved yeast. Propionate and butyrate fermentation rates were unaffected whereas acetate fermentation tended to be higher in the presence of living yeast. CONCLUSIONS: S. boulardii can be effective to compensate for changes in microbial fermentation in response to antibiotic treatment. Despite the lack of statistical significance it might be concluded that the increase in fermentation end products can only partly be explained by the utilization of the yeast as a substrate for microbial metabolism.

Analysis of Variance↗
PubMed2000

EGF-stimulated polyamine accumulation in the colon carcinoma cell line, Caco-2.

BACKGROUND: Polyamines (putrescine, spermidine and spermine) are ubiquitous molecules indispensable for cell proliferation. In the intestinal lumen they are present in high amounts. Polyamine accumulation in proliferating cells of the intestinal mucosa is high, and it occurs both by enhanced synthesis and by increased uptake from the lumen. AIMS: To study mitogen-induced polyamine accumulation in the gut, we treated proliferating Caco-2 cells with epidermal growth factor (EGF) and measured the activity of ornithine decarboxylase (ODC) and putrescine uptake. Furthermore, we investigated whether EGF-induced changes in the apical membrane could be responsible for the effect of EGF on polyamine uptake in Caco-2 cells. METHODS: Putrescine uptake, ODC activity and intracellular polyamine content were evaluated in the presence of 100 ng/ml EGF. To study the mechanisms of EGF-stimulated polyamine uptake, apical membrane vesicles were isolated, and putrescine uptake into the vesicles measured. Possible enrichment in brush border membrane cytoskeleton proteins (ezrin and villin) was assessed by Western blot. RESULTS: Treatment with EGF induced an increase in ODC activity, which occurred within the first minutes of treatment and reached peak values after 3 h. In contrast, an increase in putrescine uptake was more sustained, with peak levels at 12 h. Both synthesis and uptake contributed to an over 60% increase in intracellular putrescine and spermidine after EGF treatment. There were no detectable changes in apical membrane cytoskeleton (as concluded by the absence of ezrin and villin enrichment in EGF-treated Caco-2 cells). However, in apical membrane vesicles isolated from EGF-pretreated cells, putrescine uptake was enhanced twofold. CONCLUSIONS: EGF stimulates both synthesis and uptake of polyamines in Caco-2 cells. Enhanced synthesis seems to ensure rapid supply with polyamines in the earliest stages of growth, while the uptake is responsible for the maintenance of high polyamine intracellular levels during late growth phases. EGF-stimulated polyamine uptake is apparently not a consequence of structural changes in the apical membrane, but is likely to occur by a distinct EGF-induced alteration of the polyamine transporter itself.

Biological Transport↗
PubMed2000

Substrate and inhibitor specificity of butyrate uptake in apical membrane vesicles of the rat distal colon.

BACKGROUND/AIMS: There is substantial evidence that transcellular flux of short-chain fatty acid (SCFA) absorption, at least in part, is mediated by an anion exchange process with bicarbonate. METHODS: This anion exchange system was further characterized in apical membrane vesicles of the rat distal colon by studying substrate and inhibitor specificities of a variety of substituted monocarboxylic acids as well as of known inhibitors of the recently described monocarboxylate transporter MCT1 and MCT2. RESULTS: SCFA transport was significantly reduced in the presence of branched and unbranched SCFAs and several bromo, chloro and mercapto analogues as well as nicotinic acid and L-lactate. In contrast, known inhibitors of monocarboxylate transporter proteins like stilbene derivatives, phloretin and 2-cyano-4-hydroxycinnamate did not inhibit bicarbonate-gradient stimulated butyrate transport. Kinetic analysis of increasing substrate concentrations of 3-mercaptopropionate, L-lactate and nicotinic acid showed saturation kinetics with apparent K(i) of 6.1, 18.3 and 14.7 mmol/l, respectively. CONCLUSIONS: The data not only confirm earlier results that absorption of SCFAs in apical membranes of the rat distal colon is mediated by a relatively low affinity/high capacity SCFA(-)/HCO(-)(3) exchange mechanism, but also indicate that although this anion transporter shares some functional similarities, is not identical with the recently cloned MCT isoforms.

Animals↗
PubMed2000

Histopathologic study of alternative substances for vocal fold medialization.

This research investigated the histopathologic and migratory properties of injectable alternatives for vocal fold medialization. Thirteen dogs underwent sectioning of the recurrent laryngeal nerve followed by vocal fold injection with 1 of 4 substances: Teflon, autologous fat, silicone suspension, or hydroxyapatite cement. Six months later, the animals were painlessly sacrificed and histopathologic analysis of the larynx and regional lymph nodes was performed. Although regional lymph node migration was noted, Teflon injection resulted in minimal vocal fold inflammatory reaction. Vocal folds injected with autologous fat exhibited persistence of fat at the injection site without significant inflammation or migration. Silicone suspension caused a localized giant cell reaction without regional lymph node migration, and 1 study subject died secondary to acute inflammation with critical respiratory compromise. Hydroxyapatite cement was well tolerated without inflammation or migration. This pilot study indicates that a wide range of possible substances for vocal fold medialization exist. Many of these may produce results superior to those obtained with Teflon and are thus far untested.

Adipose Tissue↗
PubMed2000

Subacute central nervous system degeneration in a child: an unusual manifestation of ifosfamide intoxication.

A 5-year-old child with desmoplastic small round-cell tumor was treated with a protocol of very-high-dose, short-term chemotherapy, containing HD-CAV (cyclophosphamide, doxorubicin, vincristine, and mesna), ifosfamide, and etoposide. Two days after the initiation of ifosfamide, he exhibited new-onset lethal encephalopathy manifested by subacutely progressive cerebellar and then temporal and frontocortical degeneration leading to a vegetative state and eventually to death. A full work-up, including brain biopsy, was negative, excluding infections and metabolic or vascular causes. Ifosfamide is known to be capable of causing acute encephalopathy that can be severe but is generally reversible. This child showed a very atypical progressive, lethal course of ifosfamide toxicity. The possibility of this complication should be considered when high-dose ifosfamide treatment is planned for children.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2000

Methotrexate treatment protocols and the central nervous system: significant cure with significant neurotoxicity.

Methotrexate can influence the central nervous system through several metabolic toxic pathways. These effects can be categorized as immediate, acute to subacute, or chronic neurologic syndromes. The acute to subacute syndrome occurs frequently in acute lymphoblastic leukemia treatment protocols, generally manifesting with focal neurologic signs and changes seen on magnetic resonance imaging and single photon emission computed tomography. While in some patients the neurotoxicity is transient and benign and allows for continuation of chemotherapy, in others it can be quite severe and debilitating, leading to permanent neurologic deficits. The need to modify the treatment protocols when neurotoxicity appears is not fully established. It is also unknown whether the use of sufficient amounts of leucovorin can overcome the toxic effects of the drug.

Adolescent↗
PubMed2000

Two malaria parasites (Apicomplexa: Plasmodiidae) of the Australian skink Egernia stokesii.

The Australian skink Egernia stokesii is parasitized uncommonly by Plasmodium circularis n. sp. and by Plasmodium mackerrasae. Plasmodium circularis is distinguished from all other plasmodiids by immature schizonts that encircle host cell nuclei, forming an unbroken ring from apparent fusion of the attenuated ends. Mature schizonts contract into halteridial or dumbbell-shaped forms 15.6 x 4.3 microm, LW 66.2 microm2, with 19-52 nuclei. Rounded or oval gametocytes are 9.0 x 7.3 microm, LW 66.9 microm2, and L/W 1.24. Gametocyte LW is 2.63 x host erythrocyte nucleus size and 1.79X uninfected erythrocyte nuclei. Plasmodium mackerrasae occurs in high prevalence and often massive parasitemia in E. stokesii. Schizonts, often oblong, elongate, or oval, are 5.1 x 3.7 microm, LW 19.8 microm2, with 7.2 merozoites. Immature gametocytes, elongate with terminal nucleus, may produce multiple infections of 6 or more parasites. Mature gametocytes, usually rounded, are 5.8 x 4.6 microm, LW 26.7 microm2, and L/W 1.29. Gametocyte size is 0.98 x host erythrocyte nucleus size and 1.03 x uninfected erythrocyte nuclei. Phanerozoites, in endothelium or connective tissue of most organs, may appear in large numbers in circulating blood as seemingly intact bodies of regular form, similar to or larger than phanerozoites seen in sections. Previously unreported phenomena for hemosporidian parasites include extremely large, highly irregular exoerythrocytic schizonts, in circulating blood, perhaps torn from endothelial lining of blood vessels and sinuses, and a visible flooding of free merozoites into the blood stream.

Animals↗
PubMed2000

Induction of apoptosis by 2-chloro-2'deoxyadenosine (2-CdA) alone and in combination with other cytotoxic drugs: synergistic effects on normal and neoplastic lymphocytes by addition of doxorubicin and mitoxantrone.

2-CdA is active as a single agent in the treatment of low-grade lymphomas. We analyzed the induction of apoptosis by 2-CdA alone (n=5) and in combination with other drugs in peripheral lymphocytes from 25 patients with leukemic low-grade lymphomas and from 25 healthy volunteers. 2-CdA was tested in 4 escalating concentrations (0.05 microg/ml to 0.4 microg/ml). Linear regressions showed a dose dependent apoptosis rate of 0.29 x microg 2-CdA/ml + 0.11 (r2=0.88, p=0.006) in normal cells and 0.41 x microg 2-CdA/ml + 0.15 (r2=0.88, p=0.005) in leukemic cells. Intracellular metabolization of 2-CdA into 2-CdA-5'mono-, -di- and the active metabolite -triphosphate was analyzed by HPLC and paralleled the dose dependent increase of apoptosis. The combination of 2-CdA with doxorubicin or mitoxantrone had a synergistic effect on the induction of apoptosis (p<0.001) in both normal and neoplastic lymphocytes, whereas 2-CdA plus etoposide or cytosine arabinoside were only additive. Due to the flat slope of the dose response of 2-CdA concentration on apoptosis we assume that higher in vivo dosages of 2-CdA in the treatment of low-grade lymphomas may not result in a higher clinical efficacy. The synergistic lymphocytotoxic effect of 2-CdA combined with doxorubicin or mitoxantrone may be relevant for new treatment approaches.

2-Chloroadenosine↗
PubMed1999

Intensity modulation with the "step and shoot" technique using a commercial MLC: a planning study. Multileaf collimator.

PURPOSE/OBJECTIVE: For complex planning situations where organs at risk (OAR) surrounding the target volume place stringent constraints, intensity-modulated treatments with photons provide a promising solution to improve tumor control and/or reduce side effects. One approach for the clinical implementation of intensity-modulated treatments is the use of a multileaf collimator (MLC) in the "step and shoot" mode, in which multiple subfields are superimposed for each beam direction to generate stratified intensity distributions with a discrete number of intensity levels. In this paper, we examine the interrelation between the number of intensity levels per beam for various numbers of beams, the conformity of the resulting dose distribution, and the treatment time on a commercial accelerator (Siemens Mevatron KD2) with built-in MLC. METHODS AND MATERIALS: Two typical, clinically relevant cases of patients with head and neck tumors were selected for this study. Using the inverse planning technique, optimized treatment plans are generated for 3-25 evenly distributed coplanar beams as well as noncoplanar beams. An iterative gradient method is used to optimize a physical treatment objective that is based on the specified target dose and individual dose constraints assigned to each organ at risk (brain stem, eyes, optic nerves) by the radiation oncologist. The intensity distribution of each beam is discretized within the inverse planning program into three to infinitely many intensity levels or strata. These stratified intensity distributions are converted into MLC leaf position sequences, which can be subsequently transferred via computer link to the linac console, and can be delivered without user intervention. The quality of the plan is determined by comparing the values of the objective function, dose-volume histograms (DVHs), and isodose distributions. RESULTS: Highly conformal dose distributions can be achieved with five intensity levels in each of seven beams. The merit of using more intensity levels or more beams is relatively small. Acceptable results are achievable even with three levels only. On average, the number of subfields per beam is about 2-2.5 times the number of intensity levels. The average treatment time per subfield is about 20 s. The total treatment time for the three-level and seven-beam case with a total of 39 subfields is 13 min. CONCLUSION: Optimizing stratified intensity distributions in the inverse planning process allows us to achieve close to optimum results with a surprisingly small number of intensity levels. This finding may help to facilitate and accelerate the delivery of intensity-modulated treatments with the "step and shoot" technique.

Brain Stem↗
PubMed1999

[Adult-onset Still's disease. Differential diagnosis in recurrent pharyngitis, fever of unknown original and excessive hyperferritinemia].

HISTORY AND PHYSICAL EXAMINATION: Six weeks before admission a 43-year old previously healthy woman got right-sided pharyngitis, accompanied with Herpes labialis and oral candidiasis. Two weeks later she travelled to a holiday in the Caribbean. During the first week of holiday she developed pharyngitis again, this time accompanied with fever and arthralgies. Therapeutic trial with antibiotics, antimalaric drugs and antiamoebics, given at the holiday resort, did not reduce fever. Immediately after return to Germany a therapeutic trial with imipenem was was attempted, without any apparent improvement. At admission, the patient was febrile, had pinky patchy exanthema and arthralgias. EXAMINATIONS: At admission, abnormal findings included anaemia (Hb 8.8 mg/dl), severe leukocytosis (35.3/nl), increased ESR (43/89 mm), CRP (24.2 mg/dl) and ferritin (5751 micrograms/l). Ultrasound examination revealed mild splenomegaly. Computed tomography of the abdomen and chest were without apparent abnormalities. TREATMENT AND CLINICAL COURSE: Infection, autoimmune diseases and neoplasia were ruled out. The diagnosis of adult onset Still's disease was established on the basis of a typical triad of symptoms (fever, exanthema, arthritis). Treatment with 100 mg/d prednisolon (started intravenously) was beneficial for fever and arthralgia, and resulted in the normalisation of laboratory findings. After gradual reduction in the corticosteroid dosage, maintenance treatment with 20 mg/d prednisolon was continued over following months. CONCLUSION: Recurrent prodromal pharyngitis and excessive hyperferritinaemia are, in addition to the triad fever-exanthema-arthritis, further important diagnostic criteria of adult onset Still's disease.

Adult↗
PubMed1999

Cognitive disorders: A question of misattribution.

A recent study indicates that schizophrenia patients are prone to auditory hallucinations because they have difficulty recognising their 'inner speech' as their own, and consequently tend to misattribute it to an external source.

Auditory Perception↗
PubMed1999

Lymphohematopoietic stem cell engraftment.

Traditional dogma has stated that space needs to be opened by cytoxic myeloablative therapy in order for marrow stem cells to engraft. Recent work in murine transplant models, however, indicates that engraftment is determined by the ratio of donor to host stem cells, i.e., stem cell competition. One hundred centigray whole body irradiation is stem cell toxic and nonmyelotoxic, thus allowing for higher donor chimerism in a murine syngeneic transplant setting. This nontoxic stem cell transplantation can be applied to allogeneic transplant with the addition of a tolerizing step; in this case presensitization with donor spleen cells and administration of CD40 ligand antibody to block costimulation. The stem cells that engraft in the nonmyeloablated are in G0, but are rapidly induced (by 12 hours) to enter the S phase after in vivo engraftment. Exposure of murine marrow to cytokines (IL-3, IL-6, IL-11 and steel factor) expands progenitor clones, induces stem cells into cell cycle, and causes a fluctuating engraftment phenotype tied to phase of cell cycle. These data indicate that the concepts of stem cell competition and fluctuation of stem cell phenotype with cell cycle transit should underlie any new stem cell engraftment strategy.

Animals↗
PubMed1999

Chemically defined structured lipids: current status and future directions in gastrointestinal diseases.

Over the past two decades various concepts for the supply of lipids in parenteral and enteral nutrition have been developed. Traditionally, the nutritional dietary management typically includes physical mixtures of medium chain and long-chain triglycerides. Recently, chemically defined structured lipids have been developed that combine the advantages of conventional fats with those of special purposes. The first structured lipids were produced by mixing pure medium-chain triglycerides and long-chain triglycerides, allowing hydrolysis to free fatty acids, followed by random transesterification of the fatty acids into mixed triglyceride molecules. This results in a triglyceride containing combinations of short-, medium-, and long-chain fatty acids on a single glycerol backbone. These have unique chemical, physical, and/or physiological properties which differ from simply blending mixtures from the starting fats. By use of 1,3-specific or 2-specific lipases it is now possible to synthesize 1,3-specific or 2-specific triglycerides containing short- and/or medium-chain acids. For instance, incorporation of linoleic, arachidonic, or eicosapentaenoic acid at the sn-2 position is being evaluated for the specific objective of modulating membrane fatty acid composition and essential fatty acid absorption in models of cancer, burns, and immune dysfunction. This contribution reviews the current status of experimental and clinical studies of chemically defined structured lipid-based fat emulsions, with emphasis on their therapeutic potential for nutritional support in hospitalized patients.

Animals↗