Immunohistochemistry: a useful adjunct in the evaluation of malignant cutaneous spindle cell tumors

We used immunohistochemistry to evaluate four cytologically malignant cutaneous neoplasms on the face or neck of elderly individuals. All four lesions were composed of a dermal proliferation of spindle and pleomorphic giant cells. Differential diagnosis included spindle cell carcinoma, atypical fibroxanthoma, malignant melanoma, leiomyosarcoma, and angiosarcoma. All four neoplasms were strongly immunoreactive for vimentin and negative for cytokeratin, S100 protein, desmin, and factor-VIII-related antigen. Focal immunoreactivity for lysozyme and/or a1-antichymotrypsin was seen in the giant cells of each lesion. These results supported the diagnosis of atypical fibroxanthoma in each instance. Immunohistochemical staining can provide useful information for distinguishing among malignant cutaneous spindle cell tumors.     

A prototype retractor system designed to minimize ischemic brain retractor injury: initial observations

The authors have developed and patented a neurosurgical retractor system incorporating an infrared emitter and detector that allows detection of cerebral pulsations. Gentle contact with the surface of cat brains shows cerebral pulsations that correlate with arterial pulse as well as mechanical ventilation. The amplitude of cerebral pulsations decreases with higher retraction pressure and disappears at approximately 20 mmHg. The pressure on the surface of the brain decreased 50% in 5 minutes even though the position of the retractor was maintained constant. The authors postulate that monitoring cerebral pulsation may prove useful in clinical neurosurgery with respect to avoiding excessive retraction, which causes brain damage.     

Left internal carotid artery dissection presenting with headache, Collet-Sicard syndrome and sustained hypertension

The baroreflex maintains blood pressure through the glossopharyngeal (IX) cranial nerve. We report a 54-year-old man who developed a left sided headache, hoarseness, dysarthria, dysphagia, and sustained hypertension from a left internal carotid artery dissection. We hypothesise that interruption of the left IX nerve caused hypertension in this patient.     

Shoot First,Draw Later Peroneal Nerve Palsy: A Sonographic Study

A 32–year–old man had an unusual gunshot wound to the leg, causing a peroneal nerve palsy. Sonography provided useful complementary findings to the electrodiagnostic localization of the injury.     

Immunology

A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in immunology.     

Stability of parenteral midazolam in an oral formulation.

Midazolam is increasingly being used for oral sedation in pediatric dentistry. Unfortunately, it is available only as a parenteral formulation in Canada and the United States. Preparation of the parenteral solution for oral use is not uniform and leads the clinician to question the stability of this drug when used in conjunction with these vehicles. Therefore, the purpose of this study was to investigate the chemical stability of parenteral midazolam as an oral formulation to determine its expiry date. This was evaluated using a validated stability-indicating liquid chromatographic method. Midazolam was diluted in orange-flavored syrup to yield concentrations of 0.35, 0.64, and 1.03 mg/ml and then stored at room temperature. Samples were drawn on each of 9 study days (0, 1, 2, 6, 7, 9, 13, 21, and 102) and chromatographed. On each study day, solutions were inspected visually for changes in color, clarity, and appearance of particulate matter. Midazolam concentrations were considered within acceptable limits if they were not less than 90% of the initial concentration. Over the 102-day study period, there was no significant change in concentration in any of the solutions. On day 102, the remaining midazolam was within 7% of the day zero concentration. Therefore, these formulations of midazolam are stable at room temperature for a period of 102 days and would be suitable for clinical use.     

Enhanced cis-platinum ototoxicity in children with brain tumours who have received simultaneous or prior cranial irradiation

We report on four children who received cis-platinum simultaneously with, or in one case 10 months after, cranial irradiation and experienced exaggerated ototoxicity affecting all audible frequencies. The hearing loss was severe, affecting the critical areas for speech perception, and necessitated the provision of bilateral hearing aids. The audiograms of these patients are shown and compared to those of four children who had received cis-platinum as part of their treatment for neuroblastoma but without cranial irradiation. The precipitation of the exaggerated hearing loss with the administration of cis-platinum in one patient 10 months after finishing cranial irradiation suggests that care should be taken in the timing of cis-platinum administration in relation to concurrent or previous cranial irradiation.     

Differential binding kinetics of cholera toxin to intestinal microvillus membrane during development

A complete randomized block design was used to compare the binding kinetics of cholera toxin to developing rat enterocyte microvillus membranes prepared from newborn, 2-week-old, 4-week-old, and adult animals. Saturation-binding isotherms were generated on 16 independent samples (four blocks) under steady-state and reversible conditions. Scatchard analyses suggested positive cooperative binding to a single class of receptors, and the isotherms were analyzed by both the Hill-Waud and Michaelis-Menten functions. Receptor density varied significantly with age (P = 0.013). An abrupt rise in receptor density occurred after the neonatal period and normalized in the adult animal. The half-dissociation constant also varied significantly with age (P = 0.019). Microvillus membranes from suckling animals had a slightly higher apparent affinity than those from weaned animals. Neither receptor concentration nor membrane purity confounded these observations. Whereas age-related changes in apparent affinity correlated with cellular responses, changes in receptor density did not. This study suggests that developmental changes in membrane structure which influence binding affinity but not receptor density may, in part, contribute to the increased sensitivity of suckling rats to cholera toxin exposure.