Biomedical subjects

M Rapp

Publications and source records attributed to M Rapp.

At least 19 recordsLinked to original sources

PubMed2002

Simulation code for the interaction of 14 MeV neutrons on cells.

The structure of the survival curve of melanoma cells irradiated by 14 MeV neutrons displays unusual features at very low dose rate where a marked increase in cell killings at 0.05 Gy is followed by a plateau for survival from 0.1 to 0.32 Gy. In parallel a simulation code was constructed for the interaction of 14 MeV neutrons with cellular cultures. The code describes the interaction of the neutrons with the atomic nuclei of the cellular medium and of the external medium (flask culture and culture medium), and is used to compute the deposited energy into the cell volume. It was found that the large energy transfer events associated with heavy charged recoils can occur and that a large part of the energy deposition events are due to recoil protons emitted from the external medium. It is suggested that such events could partially explain the experimental results.

Cell Survival↗

PubMed2001

Circadian rhythm in NO synthase I transcript expression and its photoperiodic regulation in the rat pineal gland.

The photoneural regulation of nitric oxide synthase type I (NOS I) expression in the rat pineal was investigated using semiquantitative RT-PCR. NOS I transcript expression exhibited a daily rhythm with peak values during the night hours. The daily rhythm in NOS I transcript expression persisted under constant dark conditions and was abolished under constant light conditions. The extent of nocturnal NOS I expression was found to be dependent on the photoperiod. It was attenuated under 20 h light and 4 h dark (L:D 20:4) compared with 12 h light and 12 h dark (L:D 12:12). The present findings indicate that, in the rat pineal, NOS I transcript expression exhibits a true circadian rhythm. Further, photoperiod-induced changes in circadian transcript expression appear to be responsible for reported changes in NOS I protein expression.

Animals↗

PubMed2001

Covalent bound sensing layers on surface acoustic wave (SAW) biosensors.

This paper reports on the development of immunosensors based on commercially available surface acoustic wave (SAW) devices working at 380 MHz. Approaches for coating the sensor surface with a sensing layer of receptive biomolecules are presented and discussed. It was found that the sensitivity strongly relates to the immobilization method. Additionally, the sensitivity can be influenced by the density of accessible biomolecules on the active sensing area. Usually, by most of the standard immobilization procedures, two-dimensional layers of receptive biomolecules are obtained. We present a three-dimensional layer, which provides a higher absolute amount of recognition molecules. A dextran layer is photoimmobilized to the sensor surface and the recognition molecules are covalently embedded into the dextran matrix. The feasibility of specific immunosensing is investigated using SAW sensors connected to a fluid handling system.

Acoustics↗

PubMed2001

Interferon alpha extends the survival of human myeloma cells through an upregulation of the Mcl-1 anti-apoptotic molecule.

We have recently reported that Mcl-1, an anti-apoptotic member of the Bcl-2 family, is upregulated by interleukin (IL)-6 in human myeloma cells through the janus kinase/signal transducers and activators of transduction (JAK/STAT) pathway. In the current study, we have explored the effects of interferon (IFN)-alpha, a cytokine which has been shown to increase myeloma cell survival. Our results demonstrate that IFN-alpha potently upregulates Mcl-1 on both myeloma cell lines and purified native myeloma cells. Of note, this upregulation is not due to an induction of an IL-6 autocrine loop. Furthermore, we showed that IL-6 and IFN-alpha had no additive effect on Mcl-1 upregulation, suggesting that both cytokines act through a common mechanism. Finally, the analysis of signalling transduction pathways strongly suggests that Mcl-1 upregulation induced by IFN-alpha depends on STAT3 activation. Altogether, our data show that IFN-alpha has an IL-6-like effect on human myeloma cells and suggest that it could be deleterious in some patients.

Apoptosis↗

PubMed2001

Serine/threonine phosphatase inhibitors decrease adrenergic arylalkylamine n-acetyltransferase induction in the rat pineal gland.

Adrenergic regulation of the pineal enzyme serotonin N-acetyltransferase [arylalkylamine N-acetyltransferase (AA-NAT); EC 2.3.1.87] accounts for the circadian rhythm in melatonin formation. In the present study, the role of protein phosphatases in the adrenergic regulation of rat pineal AA-NAT was investigated using specific inhibitors. In cultured pineals, the serine/threonine phosphatase type 1 and type 2A inhibitors okadaic acid and calyculin A significantly decreased adrenergically or cAMP-induced AA-NAT activity, whereas the serine/threonine phosphatase type 2B inhibitor cypermethrin and tyrosine phosphatase inhibitor dephostatin were ineffective. Reverse transcriptase-polymerase chain reaction (RT-PCR) data indicate that okadaic acid exerts its effect on cAMP-dependent AA-NAT induction by downregulating the amount of AA-NAT transcript. The 'third' messengers, inducible cAMP early repressor (ICER) and Fos-related antigene-2 (Fra-2), are believed to play a negative role in pineal AA-NAT transcription. Okadaic acid increased the cAMP responsiveness of neither ICER mRNA nor Fra-2 mRNA. Therefore, the regulatory role of pineal serine/threonine phosphatases in adrenergically stimulated AA-NAT expression probably does not depend on ICER or Fra-2.

Animals↗

PubMed2001

The Emergency Medical Treatment and Labor Act as a federal health care safety net program.

Despite the greatest economic expansion in history during the 1990s, the number of uninsured U.S. residents surpassed 44 million in 1998. Although this number declined for the first time in recent years in 1999, to 42.6 million, the current economic slow-down threatens once again to increase the ranks of the uninsured. Many uninsured patients use hospital emergency departments as a vital portal of entry into an access-impoverished health care system. In 1986, Congress mandated access to emergency care when it passed the Emergency Medical Treatment and Labor Act (EMTALA). The EMTALA statute has prevented the unethical denial of emergency care based on inability to pay; however, the financial implications of EMTALA have not yet been adequately appreciated or addressed by Congress or the American public. Cuts in payments from public and private payers, as well as increasing demands from a larger uninsured population, have placed unprecedented financial strains on safety net providers. This paper reviews the financial implications of EMTALA, illustrating how the statute has evolved into a federal health care safety net program. Future actions are proposed, including the pressing need for greater public safety net funding and additional actions to preserve health care access for vulnerable populations.

Delivery of Health Care↗

PubMed2000

A differential role of CREB phosphorylation in cAMP-inducible gene expression in the rat pineal.

In the rat pineal gland cAMP mediates nocturnal induction of the enzyme arylalkylamine N-acetyltransferase (AA-NAT) as well as of transcription factors such as inducible cAMP early repressor (ICER), Fos-related antigen-2 (Fra-2) and JunB. Cyclic AMP stimulates the phosphorylation of the DNA binding protein cAMP response element binding protein (CREB). While cAMP-induced CREB phosphorylation appears to be a prerequisite for AA-NAT and ICER gene expression, it is not known whether CREB phosphorylation accounts for the full cAMP response of the two genes. Furthermore, the significance of CREB phosphorylation in cAMP-activated Fra-2 and JunB transcription is unknown. In the present in vitro study we used the serine/threonine protein phosphatase inhibitor okadaic acid (OA) to phosphorylate CREB without altering intrapineal cAMP concentration. It was observed that OA (10(-7) M) was less effective than dibutyryl cAMP (dbcAMP; 10(-3) M) in inducing AA-NAT mRNA and ICER mRNA, respectively. On the basis of this finding, it is concluded that CREB phosphorylation alone is apparently not sufficient for the full cAMP response of the two genes. By contrast, OA and dbcAMP equally stimulated the accumulation of the mRNAs of Fra-2 and JunB. Therefore cAMP may induce Fra-2 and JunB transcripts via CREB phosphorylation. Our observations suggest that CREB phosphorylation plays a critical role in diversification of cAMP-dependent gene induction in the rat pineal.

Animals↗

PubMed2000

Toxicity and/or insufficient analgesia by opioid therapy: risk factors and the impact of changing the opioid. A retrospective analysis of 273 patients observed at a single center.

The charts of 273 cancer patients were retrospectively analyzed in order (1) to evaluate the frequency of opioid change (OCH) when adjuvants (antiemetics/laxatives) were administered on a regular basis and co-analgesic medication as indicated by the specific type of pain, (2) to define risk factors for the request of OCH, and (3) to reveal settings in which OCH may not be recommended as a first-line therapeutic intervention. Opioids used included morphine, fentanyl, 1-methadone, and buprenorphine. Out of 273 patients, 103 changed opioids at least once, with a success rate of 65%. The indications for the OCH were insufficient analgesia in 43%, intolerable side effects in 20%, both in 15%, and other reasons in 22% of patients. The frequency of OCH was not influenced by the routine use of adjuvants or co-analgesics except corticosteroids, which raises queries about the concept of an opioid-sparing effect of co-analgesics. The occurrence of intolerable side effects is thought not to be dose dependent so much as to reflect differences in the individual tolerability of a distinct opioid for whatever reason (genetically fixed or individually acquired pharmacodynamic or kinetic properties). Moreover, there was strong evidence for the existence of an unpredictable and incomplete cross-tolerance between opioids, which meant careful titration of the new opioid was required after OCH. The overall frequency of OCH was similar to that observed in previous studies in spite of the documented addition of adjuvants and co-analgesics. This retrospective study supports the notion that opioid rotation must be retained as an essential therapeutic option even with optimized adjuvant and co-analgesic regimens.

Analgesics, Opioid↗

PubMed2000

Effects of low-dose neutrons applied at reduced dose rate on human melanoma cells.

Human melanoma cells that are resistant to gamma rays were irradiated with 14 MeV neutrons given at low doses ranging from 5 cGy to 1.12 Gy at a very low dose rate of 0.8 mGy min(-1) or a moderate dose rate of 40 mGy min(-1). The biological effects of neutrons were studied by two different methods: a cell survival assay after a 14-day incubation and an analysis of chromosomal aberrations in metaphases collected 20 h after irradiation. Unusual features of the survival curve at very low dose rate were a marked increase in cell killing at 5 cGy followed by a plateau for survival from 10 to 32.5 cGy. The levels of induced chromosomal aberrations showed a similar increase for both dose rates at 7.5 cGy and the existence of a plateau at the very low dose rate from 15 to 30 cGy. The existence of a plateau suggests that a repair process after low-dose neutrons might be induced after a threshold dose of 5-7.5 cGy which compensates for induced damage from doses as high as 32.5 cGy. These findings may be of interest for understanding the relative biological effectiveness of neutrons and the effects of environmental low-dose irradiation.

Cell Survival↗

PubMed2000

Disposition in rats of N-pyridinium-propyl-cyclam, N-triethylammonium-propyl-cyclam, and N-[Triethylammonium]-3-propyl-[15]ane-N5, potential cartilage imaging agents.

Quaternary ammonium compounds are known to highly concentrate in articular cartilages after i.v. administration. This property was used to synthesize new potential radiodiagnostic agents for joint imaging. Pharmacokinetic study was performed in rats for three new compounds: N-pyridinium-propyl-cyclam (NPPC), N-triethylammonium-propyl-cyclam (NTPC), and N-[triethylammonium]-3-propyl-[15]ane-N5 (NTP 15-5). After i.v. administration, [(3)H]NPPC and [(3)H]NTPC highly and rapidly concentrated in articular cartilage, this uptake being followed by a single exponential decrease with half-lives of, respectively, 75 and 82 min. Except cartilage, only the kidney was highly labeled. After complexation of (99m)Tc by NPPC, NTPC, and NTP 15-5, only (99m)Tc-NTP 15-5 exhibited a high affinity for cartilage. On the other hand, the pharmacokinetic behavior of (99m)Tc-NTPC and (99m)Tc-NPPC was very different from those of their (3)H-labeled analogs. Concentration in cartilaginous tissues was strongly diminished, and liver and bone were highly labeled. For all labeled species, the major route of excretion was urine, and HPLC analysis showed that [(3)H]NTPC and [(3)H]NPPC were excreted under their unchanged form. On the other hand, no (99m)Tc-NTPC and (99m)Tc-NPPC were found in the urine, the radioactivity being mainly due to free technetium, contrary to (99m)Tc-NTP 15-5, which was excreted in the urine under the complexed form. These data can explain the striking differences observed between the three (99m)Tc-labeled molecules, the lack of concentration of (99m)Tc-NTPC, and (99m)Tc-NPPC in cartilages in comparison with their (3)H-labeled analogs due to an instability in vivo of these technetiated complexes.

Animals↗

PubMed1999

New quaternary ammonium oxicam derivatives targeted toward cartilage: synthesis, pharmacokinetic studies, and antiinflammatory potency.

Analogues of nonsteroidal antiinflammatory drugs (NSAIDs) oxicams, in which the active group was linked to a quaternary ammonium function [(4-hydroxy-2-methyl-2H-1,2-benzothiazine-1, 1-dioxide-3-carboxamido)2-methylpyridinium iodide or piroxicam-N(+) and [3-(4-hydroxy-2-methyl-2H-1,2-benzothiazine-1, 1-dioxide-3-carboxamido)propyl]trimethylammonium iodide or propoxicam-N(+)] were synthesized. Compounds were labeled with tritium for piroxicam-N(+) and carbon-14 for propoxicam-N(+). Pharmacokinetic studies conducted on rats showed that these molecules were able to highly concentrate in joint cartilages but their bioavailability by the oral way was low. Only propoxicam-N(+) exhibited a sufficient water solubility to be administered intravenously. This molecule was able to restore proteoglycans biosynthesis in cultured articular chondrocytes treated with Interleukin-1beta with an efficiency identical to that of indomethacin. These results suggest that the functionalization of oxicam derivatives by a quaternary ammonium group greatly increases their affinity toward articular cartilage without eliminating their pharmacological activity. New drugs synthesized according to this scheme could be useful to obtain a significant decrease of the efficient administered dose and consequently an attenuation of adverse effects such as digestive toxicity.

Animals↗

PubMed1999

[Ciguatera poisoning. Growing differential diagnostic significance in the age of foreign tourism].

BACKGROUND: In the tropic sea there are carnivore fishes, e.g. the "peak bass", that incorporate toxin producing seaweed and can cause the ciguatera intoxication. Due to the frequent tourism to tropic regions even more cases of ciguatera intoxication can be seen in Europe. The late phase of ciguatera intoxication has hardly been recognized due to its different unspecific symptoms. In some cases ciguatera intoxication can even grow a vital threatening. CASE DESCRIPTION: Four patients from a travel group addressed us 4 and 14 days after breaking off their holidays in the Dominican republic. They presented complex neurological symptoms including paraesthesia, nervousness, inverse temperature perception, muscle cramps, headache and dizziness. The physical and apparative investigation of the patients, whose age ranked between 22 and 31 years, was totally unobtrusive. Essential for the diagnosis of ciguatera intoxication was the clue to the symptom causing dinner at their holiday location existing of "peak bass and lemon sauce". First symptoms in all members of the travel group were diarrhea, sickness and sweating. In this late phase only a symptomatic therapy could be offered. CONCLUSION: The here described cases show the importance of a comprehensive information for tropic travellers as for physicians accounted to in the acute phase of ciguatera intoxication, because recognized early enough (within the first 24 hours) the total symptomatology of ciguatera intoxication can be prevented effectively by intravenous infusions of mannitol.

Adult↗

PubMed1999

New immobilization method for SAW-biosensors: covalent attachment of antibodies via CNBr.

Surface acoustic wave devices (SAWs) based on horizontally polarized shear waves can be used as mass-sensitive immunosensors. If the standard material, aluminium, is used for the interdigital transducers (IDTs) of these devices a pretreatment with a shielding layer of polyimide is necessary to prevent corrosion processes. However, this layer also prevents an easy covalent attachment of the necessary receptive molecules. Therefore, we developed a new activation method of this inert polyimide surface by treating with cyanogenbromide using the established cyano-transfer-technique. With a subsequent covalent attachment of anti-glucose oxidase (anti-GOD) a very sensitive SAW-immunosensor for glucose oxidase (GOD) can be obtained.

Aluminum↗

PubMed1999

Study of implanted biomaterial functionality by diphosphonate molecules labeled with radioactive 99mTc.

An implanted biomaterial can be transformed into young bone after some months, but it has not necessary reached full biofunctionality. Mineral concentration kinetics and crystal-structure studies, still being carried out in our group, are completed here by biofunctionality determinations. A natural coral is implanted in vivo at the cortical level of the femoral diaphyoff++ in rabbits. Diphosphonates molecules labeled with radioactive 99mTc are then injected in rabbits and the fixation of the radioactivity is analyzed in several sites for 8 mo after the implantation. Nuclear instruments and methods are used for the measurements. Four successive cycles of osseous remodeling are determined before reaching a biofunctional phase.

Animals↗

PubMed1999

Focal transcriptional activity of murine cytomegalovirus during latency in the lungs.

Interstitial pneumonia is a frequent and critical manifestation of human cytomegalovirus (CMV) disease in immunocompromised patients, in particular in recipients of bone marrow transplantation. Previous work in the murine CMV infection model has identified the lungs as a major organ site of CMV latency and recurrence. It was open to question whether the viral genome is transcriptionally silent or active during latency. Transcription could be latency associated and thus be part of the latency phenotype. Alternatively, transcriptional activity could reflect episodes of reactivation. We demonstrate here that transcription of the immediate-early (IE) transcription unit ie1-ie3 selectively generates ie1-specific transcripts during latency. Notably, while the latent viral DNA was found to be evenly distributed in the lungs, transcription was focal and randomly distributed. This finding indicates that IE transcription is not a feature inherent to murine CMV latency but rather reflects foci of primordial reactivation. However, this reactivation did not initiate productive infection, since ie3 gene mRNA specifying the essential transactivator IE3 of murine CMV early gene expression was not detectable. Accordingly, transcripts encoding gB were absent during latency. By contrast, during induced virus recurrence, IE-phase transcription switched from focal to generalized and ie3-specific transcripts were generated. These data imply that latency and recurrence are regulated not only at the IE promoter-enhancer and that there exists an additional checkpoint at the level of precursor RNA splicing. We propose that focal transcription reflects random episodes of nonproductive reactivation that get terminated before IE3 is expressed and ignites the productive cycle.

Animals↗

PubMed1998

Covalent photolinker-mediated immobilization of an intermediate dextran layer to polymer-coated surfaces for biosensing applications.

A new method is presented for the covalent binding of dextran as an intermediate layer on surface acoustic wave (SAW) devices. For biosensing applications in aqueous media commercially available SAW devices require surface passivation to prevent corrosion of the aluminum device structures in electrolytes. Thin films of polyimide and parylene revealed exceptional passivation properties. They were used as a base for dextran immobilization. Covalent binding of dextran to polymer-coated surfaces was achieved by photoimmobilization. Aryldiazirine-functionalized bovine serum albumin served as the multifunctional light-activable linking agent (photolinker polymer). Dextran and photolinker polymer were mixed and photobonded to sensor surfaces. Essential photoimmobilization parameters were optimized. The binding of proteins to dextran applying carbodiimide chemistries was exemplified with antiurease antibodies and the feasibility of specific immunosensing was investigated on SAW sensors connected to a fluid handling system.

Acoustics↗

PubMed1998

Recombinant mouse-human chimeric antibodies as calibrators in immunoassays that measure antibodies to Toxoplasma gondii.

In the present study, we examined the feasibility of using recombinant antibodies containing murine variable regions and human constant regions as calibrators or controls in immunoassays. As a model system, we chose the Abbott IMx Toxo immunoglobulin M (IgM) and Toxo IgG assays designed to detect antibodies to Toxoplasma gondii. Two mouse monoclonal antibodies were selected based on their reactivity to the T. gondii antigens P30 and P66. Heavy- and light-chain variable-region genes were cloned from both hybridomas and transferred into immunoglobulin expression vectors containing human kappa and IgG1 or IgM constant regions. The constructs were stably transfected into Sp2/0-Ag14 cells. In the IMx Toxo IgG assay, immunoreactivity of the anti-P30 chimeric IgG1 antibody paralleled that of the positive human plasma-derived assay calibrators. Signal generated with the anti-P66 chimeric IgG1 antibody was observed to plateau below the maximal reactivity observed for the assay calibrator. Examination of the IgM chimeric antibodies in the IMx Toxo IgM assay revealed that both the anti-P30 and anti-P66 antibodies matched the assay index calibrator manufactured with human Toxo IgM-positive plasma. When evaluated with patient samples, the correlation between results obtained with the chimeric antibody calibrators and the positive human plasma calibrators was > or =0.985. These data demonstrate that chimeric mouse-human antibodies are a viable alternative to high-titer positive human plasma for the manufacture of calibrators and controls for diagnostic assays.

Amino Acid Sequence↗

PubMed1998

Disposition and metabolism of a novel antineoplastic agent, 4-tert-butyl-[3-(2-chloroethyl)ureido]benzene, in mice.

1-Aryl-3-(2-chloroethyl)ureas are new agents that have shown promising cytotoxic and antineoplastic activities. In this work, we studied the disposition and metabolism of one of these molecules, 4-tert-butyl-[3-(2-chloroethyl)ureido]benzene (tBCEU). tBCEU was labeled with 14C and 13C in the urea function and in the chloroethyl moiety. After ip administration of the molecule labeled in the urea function, radioactivity was widely distributed in the whole organism, including the brain. HPLC analysis of plasma showed that tBCEU was extensively metabolized, with <20% being found in the plasma as unchanged tBCEU 1 hr after administration. One main metabolite was identified by NMR and MS analysis as N-[4-(2-hydroxy-1, 1-dimethylethyl)phenyl]urea, widely conjugated to glucuronic acid. The same metabolite was found in the urine. After administration of tBCEU labeled in the chloroethyl moiety, the same tissue affinities were observed, but the decrease of total radioactivity in blood and tissues was slower than that observed for the molecule labeled in the urea function. HPLC analysis of urine showed the presence of two main metabolites, identified by MS as thiodiacetic acid and its sulfoxide. From these results, we can deduce that the metabolic pathway of tBCEU involves N-dealkylation of the urea portion of the molecule and hydroxylation of the tert-butyl group. The strong cytochrome P450 reactivity of the carbon adjacent to the urea portion of tBCEU is probably related to particular sensitivity to oxidation at this position, based on the chemical structure of tBCEU. These results can explain the fact that the cytotoxic effect of tBCEU is not due to DNA alkylation, in contrast to that of its parent molecule, chloroethylnitrosourea.

Animals↗