Ferromagnetism and MR imaging: safety of carotid vascular clamps

Metallic extracranial carotid vascular clamps of the Selverstone, Crutchfield, Poppen-Blaylock, Salibi, Kindt, and tantalum varieties have been placed for treatment of large, giant, or inoperable intracranial aneurysms. To ascertain what adverse effect, if any, MR imaging would have on these clamps, magnetic deflection at 1.5 T was measured for various carotid clamps. Marked magnetic deflection (and torque) was displayed by stainless steel Poppen-Blaylock clamps. Relatively mild magnetic deflection was displayed by the stainless steel Selverstone, Salibi, Crutchfield, and Kindt clamps. Three patients with previously placed carotid clamps (two Selverstone, one Salibi) and one patient with a nonferromagnetic tantalum carotid clip had cranial or cervical MR studies at field strengths ranging from 0.35 to 0.60 T. No patient experienced any discomfort or neurologic sequelae as a result of MR imaging. Although the ferromagnetic clamps created severe "black-hole" artifacts and image distortion within the cervical and facial regions, no significant image degradation was apparent during spin-echo imaging of the brain. The tantalum clip created a far smaller MR artifact than did ferromagnetic clamps and allowed effective spin-echo and gradient-echo imaging in the cervical region. Our findings indicate that most patients with carotid vascular clamps (and nonferromagnetic clips) can probably be imaged safely with MR.     

Tumour profile ofN-[2-(dimethylamino)ethyl]acridine-4-carboxamide after intraperitoneal administration in the mouse

N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (AC) is an experimental antitumour agent that is being considered for phase I trials. After i.p. administration of 150 mg/kg [³H]-AC to tumour-bearing mice, AC was absorbed rapidly into the plasma and tissues such as the heart, liver, kidney and brain but more slowly into the s.c. tumour. The maximal AC concentration (86±36 mol/kg) in the tumour occurred at 35–60 min and was 3-fold the maximal plasma concentration, which occurred at 15 min. Although higher maximal concentrations were observed in other tissues, these concentrations fell rapidly in parallel with plasma concentrations. In contrast, AC concentrations in the tumour remained elevated, thet1/2 value (16.3 h) and mean residence time (MRT, 9.5 h) being prolonged in comparison with those in the plasma and other tissues (t1/2 range, 1.0–2.9 h; MRT, 1.2–1.4 h). AC concentrations were not detectable by our high-performance liquid chromatographic (HPLC) method (limit of detection, 0.02 mol/l) in the plasma or other tissues at 24 or 48 h after administration but were measurable in the tumour (1.6±0.8 and 0.6±0.3 mol/kg, respectively). Radioactivity concentrations in the plasma, tissues and tumour were very variable but were greater than the corresponding levels of unchanged parent AC. By 24 h, radioactivity concentrations in the plasma, tissues and tumour had fallen to similar levels with prolonged elimination profiles. Thus, the exposure of the s.c. implanted tumour to a threshold AC concentration for a prolonged time (>24 h) may partly explain the greater efficacy of AC against this tumour, whereas the shorter period of exposure of blood and other tissues may explain its low haematological toxicity.     

Stages of adolescent tobacco-use acquisition

The present study extended the results of previous research in applying the "stages of acquisition" model to the onset of smokeless tobacco as well as cigarette use. Three expert judges classified an initial pool of items as to whether they represented "precontemplation," "contemplation," "action," or "maintenance" stages of smokeless tobacco acquisition. Fifty items with adequate inter-rater reliability were combined with 21 previously developed items pertaining to cigarette smoking acquisition in an overall tobacco acquisition questionnaire, which in turn was administered to 358 junior and senior high public school students. Three distinct components labeled precontemplation, action, and maintenance were delineated through principal component analyses. Coefficient alphas and discriminant analyses according to self-reported use demonstrated adequate reliability and validity for the new smokeless tobacco- and previously developed smoking-acquisition scale.     

The Liposome as a Model Membrane in Correlations of Partitioning with α-Adrenoceptor Agonist Activities

The apparent partition coefficients of a group of imidazoline -adrenoceptor agonists in liposome/buffer systems (K_m) and in the n-octanol/buffer system (P) have been compared in quantitative structure–activity relationships (QSAR) employing biological activities and receptor binding affinities. A parabolic relationship between log K _m and log P was found, and log K _m was greater than log P for all liposome compositions. In liposomes, log K _m decreased in the order, negatively charged > neutral > positively charged. Overall, hyper- and hypotensive activities of these drugs correlated better with log K _m than with log P; however, poor correlations were obtained between partition coefficients and in vitro binding affinities. Linear correlations of log K _m with hypotensive activities were obtained with negatively charged liposomes, whereas correlations with hypertensive activities were obtained using positively charged liposomes. Multiple regressions of biological activities with binding affinities showed positive correlations with hypotensive but not hypertensive activities with or without the inclusion of log K _m or log P. Thus, the liposome represents a more selective model membrane system than a bulk oil phase for predicting the biological activities of imidazoline -adrenoceptor agonists.     

Temporal Bone Histopathology in Connexin 26–Related Hearing Loss

Objective: Mutations in GJB2, a gene that encodes a gap junction protein, Connexin 26 (Cx26), are responsible for approximately one third of sporadic severe‐to‐profound or profound congenital deafness and half of severe‐to‐profound or profound autosomal recessive nonsyndromic hearing loss (ARNSHL). Mouse mutants homozygous for knockouts of this gene are nonviable, precluding histopathologic studies of the associated inner ear pathology in this animal model. Therefore, we studied archival temporal bone sections to identify temporal bone donors with Cx26‐related deafness. Study Design: Temporal bone donors with a history of congenital severe‐to‐profound or profound deafness were identified in the registry of the Temporal Bone Library at the University of Iowa. Histological findings were interpreted in a blinded fashion. DNA extracted from two celloidin‐embedded mid‐modiolar sections from each temporal bone was screened for the 35delG Cx26 mutation. The entire coding region of Cx26 was screened for other deafness‐causing mutations if the 35delG mutation was detected. Results: Of five temporal bone donors with congenital severe‐to‐profound deafness, one donor was found to have Cx26‐related deafness. This individual was a Cx26 compound heterozygote, carrying the 35delG mutation and a noncomplementary Cx26 missense mutation on the opposing allele. Microscopic evaluation of this temporal bone showed no neural degeneration, a good population of spiral ganglion cells, near‐total degeneration of hair cells in the organ of Corti, a detached and rolled‐up tectorial membrane, agenesis of the stria vascularis, and a large cyst in the scala media in the region of the stria vascularis. Conclusion: This study is the first to report the temporal bone histopathology associated with Cx26‐related deafness. Preservation of neurons in the spiral ganglion suggests that long‐term successful habilitation with cochlear implants may be possible in persons with severe‐to‐profound or profound Cx26‐related deafness.     

Conservative Surgery in T3–T4 Pharyngolaryngeal Squamous Cell Carcinoma: An Alternative to Radiation Therapy and to Total Laryngectomy for Good Responders to Induction Chemotherapy

Objective To evaluate the possibility of preservation of the larynx after neoadjuvant chemotherapy by performing a conservative surgery instead of total laryngectomy initially planned, in patients with previously untreated laryngeal and piriform sinus squamous cell carcinoma (SCC). Study Design Retrospective study. Methods A total of 115 patients treated at Tenon Hospital with induction chemotherapy from 1985 to 1995, all with initial indication of radical surgery, were available for the study. The clinical tumor response was evaluated after three cycles of chemotherapy. According to this response, to preserve laryngeal functions, some patients had a modification of the treatment initially planned: radiation therapy essentially for complete responders, and conservative surgery for some partial responders. Results Of 69 patients with laryngeal cancer, 14 were treated by partial laryngectomy and 19 by radiation therapy; of 46 patients with piriform sinus cancer, 8 were treated by partial surgery and 12 by radiation therapy; the other patients were treated as was initially planned (total laryngectomy with partial pharyngectomy). Overall survival rates, estimated by the Kaplan‐Meier method, were not statistically different between the three treatment groups. The laryngeal functions were preserved in 54% of the patients who were alive at 3 years. Conclusion This report is a retrospective study, but these results suggest the possibility of using conservative surgery, instead of initially planned total laryngectomy, for good responders to induction chemotherapy with a small residual tumor.     

Re‐evaluation of normative electronystagmography data in healthy ageing

Previous work by our group questions the validity of existing electronystagmography ( eng ) reference ranges in the elderly. We aim to establish valid reference ranges for eng in people over 65 on the Nicolet Nystar Plus system. Ninety‐six healthy asymptomatic subjects over 65 underwent eng , including spontaneous and positional nystagmus, saccades, smooth pursuit, optokinetic nystagmus and bithermal calorics; 95% reference ranges with confidence intervals were calculated. The newly determined reference ranges were far wider than those provided by the eng equipment manufacturer for eight out of 11 parameters (all P < 0.001). Vestibular function is known to deteriorate and become more variable with age. The failure to reflect this change in currently used reference ranges may have contributed to the high rates of vestibular disease reported in some series of dizzy elderly patients. Clinical interpretation of eng depends on valid reference ranges.     

Work-place screening of mine employees using the alcohol use disorders identification test (AUDIT) and alcohol breathalyzation

Although public health campaigns focusing on alcohol in the work-place are receiving increasing attention, there is little empirical evidence regarding the use of screening. In this work-place study, 152 mining personnel (67% of the work-force) completed a self report screen using the Alcohol Use Disorders Identification Test (AUDIT). One hundred and thirty-three of these (58.5% of the work-force) also consented to be breathalysed and one (0.75%) recorded a BAC just over threshold for detection. Forty-eight males (37.7% of the male work-force) recorded AUDIT scores of eight or more consistent with hazardous alcohol use and one female registered a cumulative score above the female cut-off level for hazardous alcohol use. Eighty males (67% of the work-force), recorded binge drinking at least monthly and 81 males recorded a cumulative AUDIT score of less than eight; however, on item analysis, 64 (83%) of these recorded binge drinking at least sometimes. There is substantial hazardous alcohol use in this sample work group and younger males had higher alcohol consumption, more adverse consequences and higher total AUDIT scores identifying them as particularly at risk. The Cronbach & AUDIT was 0.72, confirming adequate internal consistency.