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Biomedical subjects

G T Schneider

Publications and source records attributed to G T Schneider.

At least 19 recordsLinked to original sources
PubMed1996

Granular cell tumor of the vulva: literature review and case report.

Granular cell tumors are an uncommon neoplasm of neural origin. They occur throughout the body; only about 10% are found in the vulvar region. Granular cell tumors are most frequent in the third and fourth decade of life, the African-American race, and the female. Generally, they appear as small, firm, painless, slow-growing subcutaneous nodules. They are rarely encapsulated and recurrence is common. The malignant granular cell tumor is rare, representing 1% to 2% of cases. This form is highly aggressive, unresponsive to treatment, and ultimately fatal. A third type of granular cell tumor has been described which has benign pathologic characteristics but behaves in a clinically malignant manner. The treatment of choice for all types is wide, local surgical excision. A case is described which typifies the benign type granular cell tumor.

Adult↗
PubMed1991

Studies of stereodynamic interaction of the EEG and auditory potentials of the limbic system and non-auditory frontal cortex.

These studies use 24 cats under non-anesthetic states. Electrodes are implanted, under appropriate anesthetic and stereotoxic procedures in non-auditory neocortical areas, nucleus accumbens, and certain nuclei of the amygdala complex. Auditory stimulation was done using the free field method with periodic tones at 2.0 KHz to 3.0 KHz at 80db. The auditory stimulation and recording was performed with hard wire and telemetry methods. The analog data is collected on FM tape and processed with minicomputer. Digital filtering, cross, coherence, phase, spectral and cycle time analyses are used on the analog data. In these studies, we have looked at the electroencephalogram (EEG) and the auditory evoked potentials (AEP) of cortical and subcortical regions using frequency and time domain methods. The analyses of the interaction of spatially distributed neuronal networks during EEG and AEP activity may give insights to topographical relations in the brain.

Animals↗
PubMed1991

Partial (coherence & correlation) estimates of brain autorhythmicity.

These experiments try to exhibit the interactions of the electrical activity of the microenvironment of a neuronal population spatially distant from the microenvironment of a different neuronal population. These experiments involve 18 cats with chronic electrodes surgically implanted into cerebral cortex, septal nuclei and amygdala. The Fast Fourier Transform (FFT) algorithm is done to process frequency domain data. In order to compare the phase relations between two channels, x(t) and y(T), use is often made of the coherence function. Computing partial coherence implies first eliminating from each two signals, that part which can be considered as being determined by, or predictable, on the basis of a third signal. It is assumed that there are three stochastic signals Y1, Y2, Y3. These variables can be considered as spectral components for a particular frequency. We assume that the correlations can be interpreted as square root of the coherence. For simplicity we use, in the partial correlations analyses.

Animals↗
PubMed1990

A new technique to define and clarify esophageal motor disorders.

Ambulatory 24-hour esophageal manometry was applied to analyze motility in 12 normal subjects and 9 patients with chest pain and dysphagia caused by diffuse esophageal spasm (DES). Pain episodes characterized by nonperistaltic activity occurred in 7 of 9 patients. A score based on 10 variables of the motility pattern differentiated patients from normal subjects and quantitated the severity of the disorder. Ambulatory motility monitoring was prospectively performed in 8 normal subjects and 37 patients: 8 with DES, 13 with hypertensive contractions, and 16 with a nonspecific disorder on standard manometry. The score was positive in 6 of 8 patients with DES and negative in all normal subjects (accuracy 87 percent). Nine of the 13 patients with hypertensive contractions (70 percent) and 6 of 16 with nonspecific disorders (38 percent) had a pathologic score reflecting a dysmotility as severe as DES. Ambulatory esophageal manometry is a more physiologic way to identify a motor disorder than standard manometry and has the potential to improve selection of patients for a surgical myotomy.

Adult↗
PubMed1990

Autoregressive spectral filter studies on the sensorimotor rhythm EEG state variable.

These studies concern the EEG rhythms of the sensory motor cortex in cats. The cat generates a 12H to 16Hz rhythm related to the MU (Rolandic) rhythm in man. The behavioral state required to generate the rhythm in man and the cat requires complete immobility and alertness. The MU rhythm in man centers around 9Hz and in the cat at 12Hz to 16Hz. This rhythm is used in the biofeedback training for the treatment of intractable seizures in man. It has also been used (12 Hz to 16 Hz) experimentally in animals. It is necessary to enhance the MU rhythm and simultaneously depress the seizure activity. Our interest has been to detect and enhance the SMR rhythm (12 H to 16 Hz) in the cat. We found that when it is enhanced it also enhances the amplitude of auditory evoked potentials in other brain regions.

Algorithms↗
PubMed1990

Forty hertz (40Hz) and sensorimotor rhythms (SMR) as EEG state variables and related evoked potentials.

There is evidence that certain brain rhythms may signal the occurrence of different brain states. Support for this hypothesis may be provided by evidence that processing of information is changed during different brain states. The prestimulus period proceeding the auditory evoked potential (AEP) is converted to a power spectral estimate. These power spectra are used to sort for the AEP when certain power values for the (36-42Hz) and the (11-16Hz) are reached in the prestimulus period of the sensory motor cortex, nucleus accumbers and amygdala. Attempts are made to measure the performance of the 40Hz and SMR estimators. These studies are made in the cerebral cortical and subcortical regions in cats. In these studies D and L isomers of amphetamine are used to induce a chemical brain state changes. The AEP are selected in the amphetamine altered states based on the prestimulus auto spectra.

Analog-Digital Conversion↗
PubMed1989

Directionality of neural signals in central nervous system neural networks.

These studies are concerned with neuronal population theory of brain function. Neural networks the cerebral cortex and the limbic systems are investigated. We use coherence, partial coherence, phase and cycle time spectral analysis in these studies. The development of software for phase filtering has permitted us to analyze directionality of neural signal flow following coherence and partial coherence estimates. These estimates give an indication of the interaction between the brain regions studied. These data give further insights of the input and output status and the linear aspects of these interactions. Spontaneous and evoked potential analog data are analyzed to evaluate the physiological parameters of these interrelations.

Amygdala↗
PubMed1985

Voltage sensitive, high-conductance chloride channels in the luminal membrane of cultured pulmonary alveolar (type II) cells.

The properties of ion channels in patches from the luminal membrane of cultured monolayers of type II alveolar epithelial cells from adult rat lung have been studied. In excised patches, prepared as described to yield the "outside-out" configuration (with cesium ions in the bathing solutions to suppress currents arising from potassium channels), we observed anion-selective channels with a conductance of 350-400 pS, and burst lengths lasting seconds. When patches were bathed in solutions with equal chloride concentrations, channels opened and closed spontaneously at membrane voltages close to zero, but tended to close when the potential was shifted by +/- 10 mV, particularly in the negative direction. Other anions could pass through these channels with a permeability sequence of I(1.5) greater than Br(1.02) = greater than Cl(1.00) greater than NO3(0.9) greater than gluconate(0.6) but there was a very low permeability for sodium (PNa/PCl = 0.015 +/- 0.006). Calcium ions reduced channel conductance. The channels probably have a role to play in salt absorption by this epithelium, but insufficient information is available about how sodium crosses it for the role of the anion channels in transport to be defined with confidence.

Animals↗
PubMed1985

Multicentric müllerian squamous neoplasia.

Pure squamous neoplasia of the uterine corpus and uterine tube is explained by two possible mechanisms termed horizontal spread and vertical proliferation. We have reported a case of epidermoid carcinoma in situ of the uterine tube exemplifying the latter.

Carcinoma in Situ↗
PubMed1984

Pelvic arteriography in obstetrics and gynecology: arteriovenous fistulas and embolization.

Pelvic arteriography has become an increasingly useful diagnostic and therapeutic tool in the past decade along with angiography of other areas of the body. A brief historical review of its development in obstetrics and gynecology since 1950 is presented, including placental localization and study of pelvic arterial adequacy. Modern practical uses include (1) diagnosis and therapy of pelvic arteriovenous fistulas, and (2) arterial embolization for intractable recurrent pelvic hemorrhage associated either with malignancy or with trauma or uncontrollable surgical bleeding.

Adolescent↗
PubMed1983

Sexual dimorphism in the fibers of a "clasp" muscle of Xenopus laevis.

When antibodies specific to fast-twitch, slow-twitch, and slow-tonic myosins were used to stain the clasp muscle, m. sternoradialis, of Xenopus laevis, three predominant fiber types were identified in both males and females. Three fiber types can also be distinguished by the diameters and conduction velocities of their motor nerves. Significant differences in the numbers of slow-tonic fibers were identified between the genders and between control and castrated male animals. This finding suggests that these slow-tonic fibers, which probably dominate the clasp reflex during mating, may be under hormonal control.

Animals↗
PubMed1983

Vaginal infections. How to identify and treat them.

Vaginal infection occurs at some time in the majority of women. Most such infections are caused by Candida albicans, Trichomonas vaginalis, and Gardnerella (Hemophilus) vaginalis. Some less common--but in many cases increasingly prevalent--causes include herpes-virus type 2, papillomavirus, Chlamydia trachomatis, Mycoplasma T strains, and toxic shock syndrome.

Adolescent↗