Biomedical subjects
Publications and source records attributed to J F Hahn.
Cerebral edema may be vasogenic or cytoxic, and its main significance is raised intracranial pressure. Vasogenic edema results from damage to the blood vessel wall. The hallmark of cytotoxic edema is intracellular accumulation of fluid which occurs because of the exposure of the cells of the brain to toxic substances. Few diagnostic tests will document edema; the best is presently the CAT scan.
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A case of mucormycosis presenting with signs of positional nystagmus and obstructive hydrocephalus is described. The authors believe that this presentation of Mucor is unique.
The usefulness and relative safety of the technique of jet injection, mainly used in mass immunization, have been well established. A patient who developed a traumatic ulnar neuroma at the site of jet injection of swine flu vaccine is reported. This unusual and previously unreported complication of this procedure is thought to have occurred because of the patient's extremely small size and small muscles.
Biopsies can be performed directly with computerized tomography (CT) head scanners with some difficulty. The small scanning orifice does not allow enough room for needle placement; therefore, biopsy is difficult. In contrast, the scanning orifice of the CT body scanner is large enough to permit biopsies without hindrance. Over 300 CT-guided abdominal biopsy procedures have been performed at the Cleveland Clinic Foundation. We are reporting the technique and the results of 14 CT-guided brain biopsies. There were no complications in the series and an accurate diagnosis was made for 13 of the 14 patients.
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Described is a unique mixed intracerebral tumor composed of schwannoma, piloid astrocytoma, and angiomatous malformation. Review of conventional staining methods for distinguishing glial from connective tissue fibrils reveals that Mallory's phosphotungstic acid-hematoxylin (PTAH) method is less specific than is generally recognized. Knowledge of these pitfalls, combined with use of hematoxylin and eosin stains, and reticulum impregnations are currently most useful in making the distinction by light microscopy. Criteria for malignancy of schwannoma and other mesenchymal tumors should be based on number of mitotic figures and invasiveness rather than on pleomorphiam of cells. Prior knowledge of the location of the tumor may lead to diagnosing some schwannomas as other types of tumor.
An unusual case of ganglioneuroblastoma containing melanin is presented. Electron microscopy revealed various stages of development of melanosomes in neoplastic cells of Schwann, the first direct demonstration in human material that these cells are malanogenic. The frequent occurrence of neuromelanin in autonomic ganglia and in ganglioneuromas is interpreted as the presence of altered lipofuscin. Review of ultrastructural and other observations indicates a relation between various pigmented tumors, the cell of Schwann, and other cells arising from the neural crest.
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In the saphenous nerve of the barbiturate-anesthetized cat, single-unit recordings were made while stimulating guard-hair of down-hair receptors with sinusoidal or narrow-band "noise" displacements. From the units' frequency responses it was inferred that a significant contribution to their firing rate is made by stimulus displacement as well as by stimulus velocity. The appellation "velocity detector" for these units is only partially correct. The proposed division of guard-hair units into types G1 and G2 was not supported by the results obtained with the stimulus used in this investigation.
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1. In the infraorbital nerve of anaesthetized cat, recordings were made from single units serving the vibrissae. The directional sensitivity of individual units was rather gross, but comparison of the outputs of several units from the same vibrissa could provide information that was more precise about the direction of vibrissa deflexion.2. Many of the units showed ;spontaneous' activity. The majority of rates were less than 1 impulse/sec, so that this activity is not likely to be an important carrier of information.3. When sinusoidal deflexions in the frequency range of 0.5-100 Hz were applied, the frequency responses of about half of the units were those to be expected if they were responding to the velocity of the stimulus; most of the remainder responded to both the velocity and the magnitude of the deflexion. This form of information presentation has been shown to be well suited for compensatory tracking tasks, and it is suggested that the vibrissae are important for such tasks in the animal's life, rather than merely serving as obstacle detectors.4. Greatest deflexion sensitivity typically was at higher frequencies than could be attained in this experiment, but would be greater than the median threshold deflexion angle of 12 min found at 50 Hz. It is suggested that these low thresholds are more appropriate for a tracking system than for an obstacle detector.
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