A code of ethics for the medical dosimetrist--the American Association of Medical Dosimetrists experience

The Committee on Protocol and Ethics of the American Association of Medical Dosimetrists (AAMD) has developed a Code of Ethics for a radiation oncology society of medical dosimetrists. The purpose of the code of ethics is fourfold: (1) Establish an ideal of professional conduct specific to the medical dosimetry profession; (2) Develop a statement of the moral values and commitment of the AAMD; (3) Recognize professional relationships and obligations; and (4) Define goals to which the medical dosimetrist should aspire. The Code of Ethics was adopted as AAMD policy in October 1995.

Signaling in plant-microbe interactions

Analysis of viral and bacterial pathogenesis has revealed common themes in the ways in which plants and animals respond to pathogenic agents. Pathogenic bacteria use macromolecule delivery systems (types III and IV) to deliver microbial avirulence proteins and transfer DNA-protein complexes directly into plant cells. The molecular events that constitute critical steps of plant-pathogen interactions seem to involve ligand-receptor mechanisms for pathogen recognition and the induction of signal transduction pathways in the plant that lead to defense responses. Unraveling the molecular basis of disease resistance pathways has laid a foundation for the rational design of crop protection strategies.

Treatment of feline otoacariasis with 2 otic preparations not containing miticidal active ingredients

Two otic products not containing miticidal active ingredients were compared for the treatment of otoacariasis in 20 cats. It was concluded that treatment of feline otoacariasis can be achieved using products with an oil/wax base in conjunction with routine ear cleaning and total body parasitacide treatment.

Prevalence of panic disorder in cardiac outpatients

OBJECTIVE

To evaluate outpatients from Toronto-area cardiology clinics for panic disorder (PD) and investigate differences between patients with and without PD.

METHOD

Participants were diagnosed using both standard DSM-IV criteria and an altered formulation that identified a more fearful panic group.

RESULTS

There was a prevalence of panic disorder (12.5%) in cardiac outpatients in keeping with previous studies. Patients with PD did not differ significantly from other patients with regard to the presence of significant heart disease. The higher prevalence of palpitations found in patients who met criteria for PD compared with those who did not reflects previous findings. PD cases did not differ significantly in family history from respondents without the disorder, but the more fearful group did (P < 0.05).

CONCLUSION

PD often presents with cardiac symptoms, especially palpitations, and is often comorbid with heart disease.

Immunization tracking systems: experience of the CDC Vaccine Safety Datalink sites

Recognizing the potential of large databases within HMOs for the evaluation of vaccine safety, the Centers for Disease Control and Prevention (CDC) funded the Vaccine Safety Datalink project, linking outcome and vaccine exposure information at Group Health Cooperative of Puget Sound, Kaiser Permanente Northwest, Kaiser Permanente Medical Care Program Northern California, and Southern California Kaiser Permanente. Integral to the Vaccine Safety Datalink Project was the development of Immunization Tracking Systems at each site; this report describes the effort required to establish these tracking systems. Essential requirements are the methods used to insure data quality and to educate system users. Tracking systems can be a valuable means for assessing vaccine coverage, evaluating barriers to complete immunization, and studying the effectiveness of interventions design to improve immunization coverage. Finally, we report on recent efforts to link HMO Immunization Tracking Systems with developing regional tracking systems.

Electrocardiographic effects of fluoxetine and doxepin in patients with major depressive disorder

Cardiovascular adverse effects are amongst the most serious observed with antidepressant drugs and are often due to effects on cardiac conduction and refractoriness. However, such electrophysiologic effects may not be evident when using conventional electrocardiographic measures. Forty patients with major depressive disorder (according to DSM-III-R criteria) were enrolled in a 6-week double-blind parallel group study of fluoxetine (N = 20) or doxepin (N = 20). Cardiac conduction (QRS duration) and repolarization (corrected QT interval, QTc), were measured using signal-averaged electrocardiograms and 12-lead electrocardiogram at baseline and after 2, 4, and 6 weeks of treatment. Patients taking doxepin (mean daily dosage at 6 weeks 169 +/- 42 mg) were similar to those taking fluoxetine (37 +/- 18 mg) for demographic variables and improvement in depression scores but volunteered more side effects (p = 0.011), especially dry mouth (p < 0.001) and dizziness/lightheadedness (p = 0.005). After 6 weeks, doxepin increased heart rate (69 +/- 12 to 81 +/- 13 beats per minute; p = 0.0003) and prolonged QTc (from 417 +/- 36 to 439 +/- 28 msec; p < 0.03); overall QRS duration was not prolonged but was correlated with serum doxepin concentrations (r = 0.78, p < 0.0001). Fluoxetine had no effect on QTc (428 +/- 24 msec at baseline vs. 430 +/- 24 msec at 6 weeks) or QRS duration (97 +/- 12 msec at baseline vs. 94 +/- 12 msec at 6 weeks). The standard 12-lead electrocardiogram showed no significant change in QRS or QTc for either drug. Using a sensitive measure of electrocardiographic effects, doxepin prolongs repolarization and may slow cardiac conduction. Fluoxetine has no measurable electrocardiographic effects, which suggests an increased safety margin for cardiac adverse effects. The ability of the signal-averaged electrocardiogram to resolve small changes in the electrocardiogram is useful in the assessment of drugs with subtle electrophysiologic effects.

Ds excision from extrachromosomal geminivirus vector DNA is coupled to vector DNA replication in maize

Analysis of transposition products generated after Activator (Ac) excision from the P locus in maize suggest that Ac excises either during or after replication of the P locus. The frequency of excision of the non-autonomous Ac derivative, Dissociation (Ds), from extrachromosomal replicating and nonreplicating vector DNAs in transfected black mexican sweet maize protoplasts was compared to assess directly a role of extrachromosomal vector DNA replication in Ds excision. Replicating (rep+) and nonreplicating (rep-) vector DNAs comprised a Ds element that harbored a geminivirus, wheat dwarf virus (WDV), origin of replication and WDV genes required for viral DNA replication (rep+) or mutant, inactive derivatives of these genes (rep-). Excision of Ds was detected only in those cell nuclei co-transfected with the replicating Ds-vector DNA and a transposase expression vector. Quantitative reconstruction experiments showed that Ds excised at least 3 x 10(5)-fold more frequently from replicating vector DNA as compared with nonreplicating vector DNA. Therefore, these results provide direct evidence for a coupling of Ds excision from extrachromosomal vector DNA to vector DNA replication in maize.

Biochemical characterization of atroxase and nucleotide sequence encoding the fibrinolytic enzyme

Atroxase, isolated from the venom of Crotalus atrox (western diamondback rattlesnake), is a non-hemorrhagic protease which has fibrinolytic activity in vitro and in vivo. Fibrin solubilization occurs primarily from the hydrolysis of alpha-polymer and unpolymerized alpha- and beta-chains. The enzyme also cleaves the A alpha-chain of fibrinogen first, followed by the B beta-chain, and shows no effect on the gamma-chain. Although crude venom induces platelet aggregation, atroxase demonstrated no ability to induce or inhibit aggregation. Intravenous administration of atroxase at a dosage of 6.0 mg/kg resulted in thrombolysis within 1 hr followed by recanalization. The primary structure of atroxase was deduced from the cDNA encoding the atroxase protein. The venom glands of C. atrox were used to prepare a cDNA library. Degenerate oligonucleotides were synthesized based on the partial amino acid sequence of atroxase and were used as primers in the polymerase chain reaction to amplify overlapping cDNA fragments from the C. atrox cDNA library. The resulting cDNA fragments were subcloned, sequenced, and translated. The final nucleotide sequence shows high homology to previously described primary structures of non-hemorrhagic fibrinolytic proteases isolated from snake venom. The base sequence of cDNA obtained from colony hybridization also showed comparable results to the cDNA fragment amplified by PCR.

The N gene of tobacco confers resistance to tobacco mosaic virus in transgenic tomato

It has been proposed that cloned plant disease resistance genes could be transferred from resistant to susceptible plant species to control important crop plant diseases. The recently cloned N gene of tobacco confers resistance to the viral pathogen, tobacco mosaic virus. We generated transgenic tomato plants bearing the N gene and demonstrate that N confers a hypersensitive response and effectively localizes tobacco mosaic virus to sites of inoculation in transgenic tomato, as it does in tobacco. The ability to reconstruct the N-mediated resistance response to tobacco mosaic virus in tomato demonstrates the utility of using isolated resistance genes to protect crop plants from diseases, and it demonstrates that all the components necessary for N-mediated resistance are conserved in tomato.

Serum insulin-like growth factor II levels in normal adolescents and those with insulin dependent diabetes mellitus

OBJECTIVE

Unlike IGF-I and its principal binding proteins, data regarding IGF-II levels have not been well defined in normal subjects and those with insulin-dependent diabetes mellitus (IDDM). We have therefore measured IGF-II, as well as IGF-I, and IGFBP-3, levels in a large cohort of subjects with IDDM and in age/sex matched controls.

PATIENTS

One hundred and fourteen patients with IDDM (57 males, 57 females) and 89 control subjects (49 males, 40 females).

MEASUREMENTS

Random blood samples were obtained from each subject for the measurement of IGF-II, IGF-I and IGFBP-3 levels.

RESULTS

Mean values of IGF-II (+/- SEM) were 630 (+/- 27.8) micrograms/l and 646 (+/- 32.3) micrograms/l in female and male controls, compared to 569 (+/- 23.3) micrograms/l and 623.3 (+/- 28.1) micrograms/l in female and male diabetics respectively. IGF-II levels did not differ significantly between the sexes or show any change with transition through puberty in either control or diabetic groups. In contrast, IGF-I levels increased through puberty peaking at stages 3-5 in controls (P < 0.001) and G4-5 (P = 0.002) in diabetic males but not females. IGF-I levels in all diabetics were generally lower than in controls, differences reaching significance at G4-5 in males (P = 0.002) and B5 in females (P = 0.002). IGFBP-3 levels did not show any variation with puberty stage in diabetics, in contrast to controls where levels increased, peaking at G4-5 in males (P = 0.001) and B3 in females. IGFBP-3 levels were lower in diabetics of both sexes and at all stages compared to controls (P range 0.047 to < 0.001). Multiple regression analysis revealed significant correlations between IGF-II and IGFBP-3 (F = 20.1, P = < 0.001) and reaffirmed previously observed associations for IGF-I and IGFBP-3. The sum of IGF-I and IGF-II (expressed as nmol/l) correlated with IGFBP-3; r = 0.47 in controls and 0.60 in diabetics.

CONCLUSIONS

Insulin-dependent diabetes mellitus is not associated with any significant changes in IGF-II levels during puberty. The binding of IGFBP-3 for both IGF-I and IGF-II is unaltered by insulin-dependent diabetes mellitus.

The effect of growth hormone treatment on the insulin-like growth factor axis in a child with nonislet cell tumor hypoglycemia

We have previously described a case of tumor-associated hypoglycemia secondary to the production of high molecular weight insulin-line growth factor (IGF)-II in a child with congenital neuroblastoma. The child's hypoglycemia resolved with GH therapy and has continued to be well controlled for 1 yr. This represents one of the first cases of nonislet cell tumor hypoglycemia (NICTH) treated successfully with long-term exogenous GH. We now present an in-depth analysis of the IGF axis in this patient, before and after GH treatment. Although IGF-II levels at presentation were in the normal range, they were inappropriate for the patient's low GH state. Furthermore, the percentage of "big" IGF-II was elevated, as was the level of the IGF-IIE peptide, which is normally cleaved in the processing of the mature peptide. On the initial evaluation, GH levels failed to rise in response to hypoglycemia, IGF-I levels were low, IGF binding protein-3 (IGFBP-3) levels were suppressed, and IGFBP-2 levels were elevated. We have shown that baseline IGFBP-3 levels were low by RIA and immunoblotting and have demonstrated that this decrease was not associated with IGFBP protease activity. We have also demonstrated the baseline suppression of the acid labile subunit (ALS) of the 150K ternary complex by a novel immunoblot assay. The ratio of IGFs to IGFBP-3 was dramatically elevated, presumably leading to hypoglycemia. Furthermore, the percentage of serum IGF-I and IGF-II present as part of a binary (50K) complex with IGFBPs was also increased. GH therapy resulted in a normalization of the levels of blood sugars, IGFBP-3, ALS, IGFBP-2, and IGF-I, as well as the IGF/IGFBP-3 ratio. In summary, we have presented evidence that the hypoglycemia in this patient resulted from tumor production of high molecular weight IGF-II, which suppressed GH secretion, leading to the described derangements in the IGF binding proteins. We speculate that as a result of the decreased IGFBP-3 and ALS levels, the IGF population was shifted from the stable 150K complex to lower molecular weight complexes with IGF binding proteins, increasing IGF availability to tissues due to rapid turnover of these low molecular weight complexes. We demonstrated the reversal of the abnormalities in the IGFBP levels with GH treatment, corresponding to the clinical response of euglycemia.