Apomorphine contracts and relaxes circular smooth muscle of guinea-pig stomach via action on adrenoceptor mechanisms

Summary Nanomolar concentrations of apomorphine caused contractions of the circular smooth muscle from the body region of the guinea-pig stomach, the response showing rapid tachyphylaxis. These contractions were antagonised by yohimbine but not by prazosin, haloperidol, propranolol or methysergide. Higher concentrations of apomorphine caused concentration-related relaxations of the stomach body which were not subject to tachyphylaxis. These were antagonised by propranolol but not by prazosin, yohimbine or haloperidol. Dopamine-induced contractions of the circular smooth muscle from the stomach body were antagonised by apomorphine in nanomolar concentration; acetylcholine-induced contractions and isoprenaline-, dopamine- and phenylephrine-induced relaxations were unaffected by apomorphine. Thus, it is concluded that the contraction of circular smooth muscle from the stomach body to apomorphine is mediated via an adrenoceptor with characteristics of the ₂-type, and that a partial agonist-antagonists action prevents subsequent contractile responses to apomorphine and dopamine. Relaxation caused only at higher concentrations of apomorphine is mediated via an adrenoceptor with characteristics of the -type.     

Benzamide action at α2-adrenoceptors modifies catecholamine-induced contraction and relaxation of circular smooth muscle from guinea-pig stomach

Summary Dopamine was shown to act on the circular smooth muscle of the stomach body to cause contraction at a yohimbine-sensitive site (₂) and a relaxation at a prazosin-sensitive site (₁). Metoclopramide and tiapride failed to modify either response, failed to antagonise a relaxation to phenylephrine at 1(₁ sites in the same tissue, and failed to modify the contractions caused by dopamine and phenylephrine at an ₂-adrenoceptor site in the pyloric sphincter. However, (+)- and (–)-sultopride and (+)-sulpiride antagonised the dopamine-induced contractions of the stomach body indicating an ₂-antagonist action. An ability to attenuate the relaxation of this tissue may reflect a displacement of the contraction curve to the right rather than an ₂-antagonist action since the response to phenylephrine was not antagonised either in this tissue or in the pyloric sphincter. Within the central nervous system the (–)-enantiomers of sultopride and sulpiride have a highly selective dopamine receptor blocking action. This cotrasts with the present findings in the stomach musculature of a non-stereospecific antagonism at ₂-type adrenoceptors.     

Aristolochic acids in Aristolochia chilensis

The major components of the acid fraction of the leaves and tender stems of Aristolochia chilensis Miers are aristolochic acids I and Ia. Aristolochic acid Ia has been isolated from plant material for the f?rst time, and its PMR spectrum is discussed.     

Variations in Prkdc and susceptibility to benzene-induced toxicity in mice.

Benzene, a carcinogen that induces chromosomal breaks, is strongly associated with leukemias in humans. Possible genetic determinants of benzene susceptibility include proteins involved in repair of benzene-induced DNA damage. The catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), encoded by Prkdc, is one such protein. DNA-PKcs is involved in the nonhomologous end-joining (NHEJ) pathway of DNA double-strand break (DSB) repair. Here we compared the toxic effects of benzene on mice (C57BL/6 and 129/Sv) homozygous for the wild-type Prkdc allele and mice (129/SvJ) homozygous for a Prkdc functional polymorphism that leads to diminished DNA-PK activity and enhanced apoptosis in response to radiation-induced damage. Male and female mice were exposed to 0, 10, 50, or 100 ppm benzene for 6 h/d, 5 d/week for 2 weeks. Male mice were more susceptible to benzene toxicity compared with females. Hematotoxicity was evident in all male mice but was not seen in female mice. We observed similar, large increases in both micronucleated erythrocyte populations in all male mice. Female mice had smaller but significant increases in micronucleated cells. The p53-dependent response was induced in all strains and genders of mice following benzene exposure, as indicated by an increase in p21 mRNA levels in bone marrow that frequently corresponded with cell cycle arrest in G2/M. Prkdc does not appear to be a significant genetic susceptibility factor for acute benzene toxicity. Moreover, the role of NHEJ, mediated by DNA-PK, in restoring genomic integrity following benzene-induced DSB remains equivocal.     

Adjuvant immunization of HLA-A2-positive melanoma patients with a modified gp100 peptide induces peptide-specific CD8+ T-cell responses.

PURPOSE: To measure the CD8+ T-cell response to a melanoma peptide vaccine and to compare an every-2-weeks with an every-3-weeks vaccination schedule. PATIENTS AND METHODS: Thirty HLA-A2-positive patients with resected stage I to III melanoma were randomly assigned to receive vaccinations every 2 weeks (13 vaccines) or every 3 weeks (nine vaccines) for 6 months. The synthetic, modified gp100 peptide, g209-2M, and a control peptide, HPV16 E7, were mixed in incomplete Freund's adjuvant and injected subcutaneously. Peripheral blood mononuclear cells obtained before and after vaccination by leukapheresis were analyzed using a fluorescence-based HLA/peptide-tetramer binding assay and cytokine flow cytometry. RESULTS: Vaccination induced an increase in peptide-specific T cells in 28 of 29 patients. The median frequency of CD8+ T cells specific for the g209-2M peptide increased markedly from 0.02% before to 0.34% after vaccination (P <.0001). Eight patients (28%) exhibited peptide-specific CD8+ T-cell frequencies greater than 1%, including two patients with frequencies of 4.96% and 8.86%, respectively. Interferon alfa-2b-treated patients also had significant increases in tetramer-binding cells (P <.0001). No difference was observed between the every-2-weeks and the every-3-weeks vaccination schedules (P =.59). CONCLUSION: Flow cytometric analysis of HLA/peptide-tetramer binding cells was a reliable means of quantifying the CD8+ T-cell response to peptide immunization. This assay may be suitable for use in future trials to optimize different vaccination strategies. Concurrent interferon treatment did not inhibit the development of a peptide-specific immune response and vaccination every 2 weeks, and every 3 weeks produced similar results.     

CeReS-18, a novel cell surface sialoglycopeptide, induces cell cycle arrest and apoptosis in a calcium-sensitive manner

Very few growth inhibitors have been identified whichcan inhibit the proliferation of a broad spectrumof human breast cancer cell lines. CeReS-18, anovel cell surface sialoglycopeptide growth inhibitor, can reversiblyinhibit the proliferation of both estrogen receptor positive(MCF-7) and negative (BT-20) human breast cancer celllines. In addition, at concentrations above those requiredfor the reversible inhibition of cell proliferation, CeReS-18can also induce cell death in MCF-7 cells.Changes in nuclear and cytoplasmic morphology, characteristic ofapoptosis, were detected in MCF-7 cells treated witha cytotoxic concentration of CeReS-18, and internucleosomal DNAcleavage was also observed. The sensitivity of MCF-7and BT-20 cells to the biological properties ofCeReS-18 could be influenced by altering the calciumconcentration in the extracellular growth medium, such thatwhen the calcium concentration in the environment wasdecreased, an increased sensitivity to CeReS-18-induced growth inhibitionand cytotoxicity were observed. The addition of thecalcium chelating agent EGTA to MCF-7 cells, culturedin a normal calcium environment, could mimic theincreased sensitivity to the biological effects of CeReS-18observed under reduced calcium conditions.     

The prediction of late rectal complications in patients treated with high dose-rate brachytherapy for carcinoma of the cervix

: The aim of this work is to invetigate an unusually high rate of late rectal complications in a group of 43 patients treated with concomitant irradiation and chemotherapy for carcinoma of the cervix between December 1988 and April 1991, with a view to identifying predictive factors.

: The biologically effective dose received by each patient to the rectal reference point defined by the International Commission of Radiation Units and Measurements, Report 38, were calculated. Radiotherapy consisted of 46 Gy external beam irradiation plus three dose-rate intracavitary treatments of 10 Gy each prescribed to point A. Cisplatin 30 mg/m² was given weekly throughout the duration of the irradiation. The results have been compared to data from 119 patients treated with irradiation alone to assess the cofounding effect of the cisplatin.

: The relationship between the biologically effective dose delivered to the rectal reference point and the development of late complications shows a strong dose-response with a threshold for complications occurring at aproximately the same biologically effective dose threshold as that found for external beam irradiation in the head and neck region. The date from the group of patients treated wihout cisplatin is comparable to the date from the first group of patients in the lower dose ranges; the higher doses were not used and thus are not available for comparison.

: Using the linear quadratic model applied to our clinical results, we have established a threshold for late rectal complications for patients treated with external beam irradiation and high dose-rate brachytherapy for carcinoma of the cervix. This threshold is consistent with similar data for external irradiation in the head and neck region.     

Non beating heart donors as a possible source for liver transplantation

Organ shortage for liver transplantation continues to be a major problem. Non heart beating donors (NHBD) are gaining increasing importance as a potential source of transplantable organs for clinical use, mainly in kidney transplantation. Up to now, the experience in liver transplantation with this type of donors has been limited and has only been considered in donors in whom cardiac arrest (CA) has occurred at a known given time. This is due to the high risk of primary non-function and late complications related to intrahepatic biliary lesions when warm ischemia time (WIT) is not controlled. The method of retrieval of these organs should offer the possibility to stop liver injury, revert histologic lesions appeared after WIT, and to assess the quality of the potential donor liver. Based on the experience of kidney transplantation, total body cooling achieved by extracorporal cardiopulmonary bypass seems to be the best method. Moreover it allows the inclusion of a time for tissue oxygenation at 37 degrees C (Normothermic Recirculation, NR) prior to body cooling which has been shown to improve graft viability, and also allows a time to measure organ quality before transplantation. In our experience, we demonstrated that liver transplantation from NHBD is feasible; NR has beneficial effect on liver viability improving endothelial cell damage, hepatocyte energy charge and histological changes at 5 days. We also showed that time of cardiac arrest is determinant of graft viability; even if hepatocellular function is preserved after 40 minutes of CA using NR, irreversible intrahepatic biliary lesions are always present and burden long-term survival. Moreover, bypass pump and blood flows are directly related to WIT and the achievement of better pump flows may predict survival during NR. In animals with 40 minutes of CA, we also reported the possibility to manipulate the potential graft during NR with L-Arginine, Glycine and S-Adenosyl-Methyonine, which minimize endothelial and hepatocellular damage as well as lesions at 5 days. Further research needs to be done in order to confirm our experimental data.     

Using an immunization registry: effect on practice costs and time.

INTRODUCTION: Immunization registries can consolidate immunization records scattered among different providers, allowing immunization documentation for legal purposes, generation of needed-immunization lists, inventory management, and outreach for underimmunized children. They have been endorsed by the Centers for Disease Control and Prevention and health professionals as a means of sustaining high immunization rates. However, some providers perceive the cost of registry use as a barrier to participation. We sought to determine the effects of registry use on cost and time. METHODS: We used a pre-post design and a cost-accounting approach to measure labor costs and time for immunization-related activities possibly affected by registry use before development of a regional registry in Colorado and after the registry was being fully used. Two rural family practices, 2 rural community health centers (CHCs), 3 urban pediatric practices, and 2 rural public health agencies participated in both periods. RESULTS: Cost per shot increased slightly in the postregistry period for private practices and CHCs ($0.56 per shot in 2001 dollars) and public health agencies ($0.38). Since costs can increase for several reasons, including salary increases above inflation, we analyzed time spent per shot and found that staff time decreased for private practices and CHCs but increased substantially for public health agencies. CONCLUSIONS: The study findings suggest to private practices that registry participation can provide a net benefit by making the vaccination process more efficient and, absent above-average salary increases, less costly. Public health agencies, however, would have to rely exclusively on the registry and eschew the use of paper vaccination records to realize efficiencies seen by other practice types.