The Physical Volume Test in impedance audiometry

Impedance audiometry offers a clinically practical method for measuring the physical volume in cc of air space medial to the hermetically sealed probe tip. Knowledge of the air space volume is meaningful when average norms are known, either when the TM is intact or, more significantly, when the TM is perforated. With the latter, the temporally dynamic space changes during external, middle ear and/or mastoid disease, the size of the total air space measured offers objective information when determined over time. The resultant volume can offer an indirect mirror readout of progression or regression of a disease process. Likewise, historically there may be a close relationship between eustachian tube function and the overall air cell space within the petrotympanomastoid bone. In such conditions, the smaller the air cell space, the poorer the eustachian tube function. The PVT offers a more expedient clinical tool over roentgenography for measuring the viable air space of the middle ear and petromastoid air cell system. Since the PVT is used primarily with an open system (i.e. with a perforated TM) electroacoustic volumetric determinations with a 220 Hz acoustic input more reliably represents the actual volume present.     

Effect of cisplatin chemotherapy on extracortical tissue formation in canine diaphyseal segmental replacement

The reconstruction of large bone and joint defects after the resection of malignant tumors remains a major challenge. Chemotherapy has significantly lowered the risk of metastasic disease, but complications associated with reconstructive techniques continue to result in late morbidity. In the present study, biomechanical torsion testing, gait analysis, and histomorphometric and scanning electron microscopic evaluations of 24 dogs were used to examine the effects of preoperative and postoperative administration of cisplatin on the biologic fixation of a porous-coated segmental replacement prosthesis. The chemotherapy consisted of four cycles of cisplatin administered at a dosage of 75 mg/m:² preoperatively or postoperatively. The healing was enhanced by use of an autogenous corticocancellous bone graft. The graft was placed evenly around the prosthesis and the adjacent femoral cortex. Mechanical analyses of torsional stiffness, yield strength, and maximum strength revealed no statistically significant differences between the groups at 12 weeks. Such lack of difference was mainly due to the penetration of highly organized fibrous tissue into the porous surface; this provided strong fixation of the implant to bone even in the absence of bone ingrowth. Although bone ingrowth into the prostheses was not affected, electron microscopic, histomorphometric, and radiologic analyses showed a clear difference in the formation of new bone around the prosthesis. Preoperative chemotherapy did not alter the formation of new bone, but specimens from animals treated postoperatively with cisplatin showed significantly less bone graft resorption and less new bone formation. Hence, the effect of cisplatin administration caused only a temporary delay, not a permanent effect, on extracortical capsule formation. The formation of extracortical bone and soft tissue might prevent debris-incised osteolysis and, therefore, prevent late complications by forming a tight capsule around the bone-prosthetic interface.     

Incidence, investigations and staging of soft-tissue sarcoma

Soft-tissue sarcomas account for only 1% of all malignant lesions. The Canadian Sarcoma Group encourages the investigation and management of these tumours at tertiary institutions, where a multidisciplinary team can handle the complex problems. Staging of these tumours implies accurate anatomic determination of the extent of disease, the histogenesis and grade of the tumours and the presence of regional or distant metastases. Arteriography, computed tomography and magnetic resonance imaging can accurately define the tumour before biopsy. The biopsy should be muscle-splitting to minimize contamination of additional compartments and should allow inclusion of the biopsy site at definitive surgical resection. It should be done at the institution where definitive management will be performed. Regional lymph-node involvement can be detected using magnetic resonance imaging or gallium scanning, whereas for distant metastases, specifically of lung, computed tomography is the method of choice. To date no one staging system for soft-tissue sarcomas has been universally accepted. A hybrid, encompassing the advantages of each system, is being formulated.     

Narcotic reversal in hypercapnic dogs: comparison of naloxone and nalbuphine

Reversal of opioid effects by naloxone (NX) can lead to significant cardiovascular problems. We have reported previously that hypercapnic dogs develop greater increases in blood pressure and plasma catecholamine (CA) levels than hypocapnic ones when reversed with naloxone. We have also demonstrated differences between NX and nalbuphine (NBPH) in producing excitatory adrenergic responses when administered during normocapnia. The present study was designed to investigate possible dissimilarities in cardiovascular and sympathetic events after administration of either NX or NBPH in dogs made hypercapnic following fentanyl administration. After induction of anaesthesia with thiopentone and intubation, two groups of dogs were maintained with controlled ventilation on enflurane in oxygen anaesthesia and given 50 micrograms.kg-1 fentanyl IV. This caused a significant decrease in heart rate (HR) (P less than 0.001), mean arterial blood pressure (MAP) (P less than 0.001), and plasma concentrations of norepinephrine (NE) (P less than 0.002). Then, ventilation was decreased to produce a PaCO2 of 60 mmHg; this was accompanied by a significant elevation in plasma level of both epinephrine (EPI) (P less than 0.02) and NE (P less than 0.001). Administration of 20 micrograms.kg-1 NX to six dogs resulted in immediate increases in HR (P less than 0.01) and MAP (P less than 0.01), and a further rise in CA levels to greater than pre-fentanyl baseline values. In six other dogs, NBPH (0.3 mg.kg-1) caused increases in HR (P less than 0.001) and MAP (P less than 0.001) only, and the MAP rise was significantly less than that seen in the NX group (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Factor VIII assays. Assessment of variables

Factor VIII assays are the most common specific coagulation factor assay performed in the United States. Interlaboratory proficiency studies have documented persistent problems with variation in results between laboratories. The Coagulation Resource Committee of the College of American Pathologists conducted a workshop to analyze variables that may affect performance of the one-stage factor assay. The results indicate that accuracy of the assay can be improved by uniform standardization of reference plasma samples and that reproducibility can be enhanced through appropriate choice of reagents and instruments. Optimizing performance of this assay should lead to more reproducible interlaboratory results.     

Pigmented lesions of the vulva.

Pigmented vulvar lesions, including diffuse hyperpigmentation, are present in 10% to 12% of white women. About 2% of them are nevocellular nevi. In general, nevi on the vulva are identical by morphologic and histopathologic criteria to nevi elsewhere on the body, with the exception of a small subset of nevi in younger women. Nevi in this subset have the unusual features of enlarged junctional nests that are variable in size, shape, and position. The long-term biologic behavior of these nevi has not been determined. Other benign pigmented lesions include lentigines, melanosis, postinflammatory hyperpigmentation, seborrheic keratoses, and warts. Malignant pigmented lesions include some cases of vulvar intraepithelial neoplasia and melanoma. Melanoma of the vulva has a poorer prognosis overall than melanoma on the torso, apparently because of the extent of the disease at the time of diagnosis. Therefore, improving mortality rates depends to some extent on earlier diagnosis. Management of female patients includes careful inspection of the vulva with each full-skin or gynecologic examination, followed by biopsy of any suspicious lesion. The need for excision of benign nevocellular and melanocytic lesions is dependent on the histopathology. Because there are no long-term prospective studies of vulvar melanosis and the group of unusual vulvar nevi, treatment must be individualized.     

Sodium channels accumulate at the tips of injured axons

The axolemmal distribution of voltage-gated sodium channels largely determines the regions of axonal electrical excitability. Using a wellcharacterized anti–sodium channel antibody, we examined peripheral nerve fibers focally injured by exposure to the neurotoxic agent, potassium tellurite (K₂TeO₃). Immunocytochemical and radioimmunoassay data showed a focal accumulation of sodium channels within the tips of injured axons. The major increase in sodium channel concentration occurred between 7 and 11 days after toxin exposure; however, immunocytochemically, excess sodium channels persisted in several axonal endings for a much longer time. The accumulation of sodium channels at injured axonal tips may be responsible, in part, for ectopic axonal excitability and the resulting abnormal sensory phenomena (especially pain and paresthesias) which frequently complicate peripheral nerve injury in humans. © 1994 John Wiley & Sons, Inc.