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Biomedical subjects

R A Schmidt

Publications and source records attributed to R A Schmidt.

At least 127 records · Page 7Linked to original sources
PubMed1990

Neuroanatomy of the striated muscular anal continence mechanism. Implications for the use of neurostimulation.

The striated pelvic floor musculature and the striated muscle of the external and sphincter contribute to anal continence by effecting, respectively, the rectoanal angulation of the bowel and an anal high pressure zone. The muscular anatomy of the pelvic floor is generally understood, but the neuroanatomy remains controversial. The authors dissected three male cadavers and traced the sacral nerves from their entrance into the pelvis through the sacral foramina throughout their branching to their final destinations. Deriving from a common source, the sacral nerves S2 to S4, the neural supply of the levator ani was distinct from that of the external anal sphincter: the levator is supplied by direct branches splitting from the sacral nerves proximal to the sacral plexus and running on the inner surface; the external anal sphincter is supplied by nerve fibres travelling with the pudendal nerve on the levator's undersurface. To document the functional relevance of these anatomic findings, stimulation of the pudendal and sacral nerves was performed at different levels in five patients with lower urinary tract dysfunction. Stimulation of the pudendal nerve increased the anal pressure, whereas stimulation of S3 increased it only slightly but caused an impressive decrease of the rectoanal angle; when S3 was stimulated after bilateral pudendal block, anal pressure did not change but the decrease in the rectoanal angulation persisted. The changes in anal pressure could be obtained without fatigue at stimulation frequencies of 10 to 20 Hz.

Adult↗
PubMed1990

Transplantation studies in mice with congenital hemolytic anemia.

Sphha/sphha anemic mice have an abnormality in the erythroid membrane protein, alpha spectrin, and exhibit multiple related clinical abnormalities, including spherocytosis, shortened red cell survival, chronic hemolysis, hemosiderosis, and extramedullary hematopoiesis. In addition, these mutant mice exhibit a granulocytosis and lymphocytosis, lymph node hyperplasia, elevated serum immunoglobulins, membranoproliferative glomerulonephritis, and decreased lifespan--abnormalities that are less clearly attributable to a spectrin defect. In order to further elucidate the mechanisms of disease in these animals, we undertook a series of bone marrow transplantation experiments. Transplantation of anemic marrow into lethally irradiated congenic +/+ mice resulted in chronic spherocytosis, hemolytic anemia, peripheral leukocytosis, and extramedullary hematopoiesis. Additionally, transplant recipients of anemic marrow which had received a higher radiation dose (12 Gy) had increased numbers of peripheral blood CD4+ and CD8+ lymphocytes, a hypocellcular thymus, and a severe pneumonitis characterized by nodular areas of consolidation and edema. Mice receiving congenic +/+ marrow and irradiated with the same radiation dose exhibited minimal pulmonary abnormalities. Anemic mice transplanted with congenic +/+ marrow usually died, but the survivors exhibited reversal of some clinicopathological changes. These results would suggest that the clinical abnormalities of sphha/sphha mice are in part attributable to abnormalities of hematopoietic stem cells but may also involve defects in other cell types. The pathogenesis of the accompanying lymphoid abnormalities observed in this mutant anemic mouse and any correlation with the erythroid spectrin defect are presently unknown. The pulmonary disease that develops in the transplant recipients of anemic marrow needs to be characterized further but may represent a unique model of lung injury.

Anemia, Hemolytic, Congenital↗
PubMed1990

Functional evaluation of sacral nerve root integrity. Report of a technique.

We report our technique of direct stimulation of the sacral roots governing voiding by which the functional and anatomic integrity of these nerve roots can be assessed in patients with voiding dysfunction. The muscular responses to stimulation of each sacral root are described, as are the landmarks and approach used to achieve stimulation.

Humans↗
PubMed1990

Synchronized electrical stimulation of the sympathetic and parasympathetic innervation of the bladder: facilitation of the initiation of micturition in the dog.

To improve the quality of bladder contractions induced by parasympathetic stimulation and to facilitate the initiation of voiding, we investigated the effect of sympathetic stimulation on the parasympathetic innervation of the bladder in 12 dogs. For the sympathetic system, the lumbar sympathetic trunks were electrically stimulated; for the parasympathetic system, either the pelvic nerve or the ventral root of S2 was stimulated. With voltages at or just above the threshold for achieving a measurable effect on bladder pressure, stimulation of the sympathetic system or the pelvic nerve alone did not lead to voiding, and sacral root stimulation alone elicited voiding in only 7.4 per cent of stimulations. However, when the same stimulus parameters were used for synchronous stimulation, the voiding process was facilitated when sympathetic stimulation was begun five to 10 seconds before parasympathetic stimulation. When the pelvic nerve was used, voiding resulted in 77.7 per cent of stimulations and the bladder was emptied by a mean of 68.7 per cent; with S2 ventral root stimulation, voiding resulted in 83.3 per cent of stimulations and the bladder was emptied by 59.7 per cent. The facilitory effect of sympathetic stimulation was not abolished when the sympathetic trunks were cut centrally to the point of stimulation, but was absent when the hypogastric nerves were transected. We feel that sympathetic stimulation modulates the parasympathetic innervation of the bladder.

Animals↗
PubMed1990

Neuroprostheses in the management of incontinence in myelomeningocele patients.

A 16-year-old boy and a 17-year-old girl underwent successful closure of the meningomyelocele defect in childhood but they continued to suffer incontinence of stool and urine. After a 5-day trial with percutaneous electrostimulation of the pudendal nerve both patients received permanent neuroprosthetic implants. They became completely continent of stool and exhibited greater than 90% improvement in urinary control. These patients demonstrate that there is a small subset of meningomyelocele patients who, despite absence of spontaneous reflex tonus in the urinary and bowel sphincters, nevertheless have preserved motor capabilities.

Adolescent↗
PubMed1990

Pathophysiology of urinary incontinence after radical prostatectomy.

To define the origin of urinary incontinence after radical prostatectomy urodynamic studies in 24 incontinent patients were compared to those of 13 continent patients. A statistically significant difference between incontinent and continent patients was found for the mean functional profile length (2.1 versus 3.6 cm., respectively, p less than 0.001), maximal urethral closure pressure (39 versus 74 cm. water, respectively, p less than 0.001) and maximal urethral closure pressure during voluntary contraction of the external sphincter (107 versus 172 cm. water, respectively, p less than 0.002). The differences among maximal detrusor pressure, initial bladder volume at which a detrusor contraction occurs, maximal cystometric capacity and residual urine were not statistically significant between the 2 groups. Urethral instability was present in 1 of the 24 incontinent patients (4.2%) and in none of the 13 continent patients, while detrusor instability was present in 6 (25%) and 3 (23.1%), respectively. Urethral and detrusor instability correlated poorly with incontinence (correlation coefficients 0.123 and 0.021, respectively). The appearance of the bladder outlet on voiding cystourethrography was correlated with urodynamic parameters and the presence or absence of continence. Tubularization above the level of the external sphincter was present in continent but absent in incontinent patients. Continence after radical prostatectomy is dependent upon sphincteric efficiency, which may be influenced by the anatomical configuration of the reconstructed bladder outlet and the integrity of the distal urethral sphincteric mechanism.

Aged↗
PubMed1990

Improvement in radiologists' detection of clustered microcalcifications on mammograms. The potential of computer-aided diagnosis.

Relatively simple, but important, detection tasks in radiology are nearing accessibility to computer-aided diagnostic (CAD) methods. The authors have studied one such task, the detection of clustered microcalcifications on mammograms, to determine whether CAD can improve radiologists' performance under controlled but generally realistic circumstances. The results of their receiver operating characteristic (ROC) study show that CAD, as implemented by their computer code in its present state of development, does significantly improve radiologists' accuracy in detecting clustered microcalcifications under conditions that simulate the rapid interpretation of screening mammograms. The results suggest also that a reduction in the computer's false-positive rate will further improve radiologists' diagnostic accuracy, although the improvement falls short of statistical significance in this study.

Calcinosis↗
PubMed1990

Evaluation of radiographs developed by a new ultrarapid film processing system.

The image quality of radiographs developed by a new ultrarapid processor was evaluated to determine if faster processing causes degradation in the image. The processor used was the Konica Super-Rapid SRX-501 model. Two films designed for this processor (Konica MGH-SR and MGL-SR) were processed in 45 sec and were compared with standard rapid processing in 90 sec of corresponding conventional films (Kodak TMG and OC). Rare-earth screens (Kodak Lanex Regular and Lanex Medium) used with the new and conventional films interleaved during angiographic studies or for phantom images were assessed for image quality. The basic imaging properties of the screen-film systems were examined by measuring (1) Hurter and Driffield curves, (2) modulation transfer functions by using the slit method, and (3) noise Wiener spectra. Subjective clinical assessment showed that the images obtained with ultrarapid processing were acceptable, with increased contrast and graininess. Hurter and Driffield curve measurements confirmed higher gradients. Modulation transfer function measurements were the same as for the conventional films. Noise Wiener spectrum measurements showed a 10% increase in noise for MGH-SR vs TMG film and a 30% increase for MGL-SR vs OC film. We conclude that acceptable image quality can be obtained using ultrarapid processing, with processing time approximately 60% that of conventional rapid processing. Potential applications include all areas in which rapid availability of the radiograph for interpretation is important. Although the processor studied was the first of its kind available, our evaluation indicates that the technology is available for a new class of ultrarapid processors.

Evaluation Studies as Topic↗
PubMed1990

Paraganglioma of the spermatic cord. Report of a case with immunohistochemical and ultrastructural studies.

We describe a case of paraganglioma arising in the spermatic cord, which is an extremely rare location. Immunohistochemical studies characterized two types of cells: (1) polygonal cells expressing neuron-specific enolase, chromogranin A, and synaptophysin and (2) S100 protein-positive sustentacular cells. Electron microscopy revealed that within the cytoplasm of the polygonal cells, there were electron-dense granules whose morphological appearance was consistent with that of neurosecretory granules. Paraganglioma of the spermatic cord may originate from embryonic chromaffin cells that have followed the testis into the scrotum.

Adolescent↗
PubMed1990

[Clinical use of neurostimulation].

Our experience is broad-based and covers a number of difficult conditions that urologists deal with regularly. In patients who have been followed for several years, consistency of stimulation response has been observed. Even after use of the stimulator for several months or years, symptoms often return as soon as the stimulation ceases in cases of a malfunction or electrode movement. Neurostimulation, however, is no panacea. Patients with specific muscular dysfunction, determined urodynamically, must be carefully selected. They must also be willing to cooperate actively in their care. Test stimulation of the sacral nerves has provided invaluable insight into the neuromuscular responses mediated by the S2-4 nerves and has thus helped identify dysfunction that is specifically associated with each of these nerves. It has also helped discern differences between the integrity of pelvic muscles and the capability of the patient to use these muscles. This information allows the urologist to focus on a specific muscular dysfunction and to re-educate the patient to use the pelvic musculature properly or, failing this, to use neurostimulation via an implant to modulate the dysfunction. There must be a strong commitment on the part of the physician. No two patients are alike. Attention to patients' symptoms, the pattern of muscle dysfunction found in the pelvis, the responses to test stimulation, the urodynamic findings with and without stimulation, and the underlying anxieties of patients, which can contribute to symptoms, are all important considerations. Neurostimulation is an exciting and fascinating addition to the urologist's armamentarium. Most important, urologists are now able to test the functional integrity of the pelvic musculature and specifically identify weakness and dysfunction. Therapy can now be based on an assessment of the functional capabilities of the nervous system involved in micturition control.

Electric Stimulation Therapy↗
PubMed1989

Changes in limb dynamics during the practice of rapid arm movements.

In our study we examined Bernstein's hypothesis that practice alters the motor coordination among the muscular and passive joint moments. In particular, we conducted dynamical analyses of a human multisegmental movement during the practice of a task involving the upper extremity. Seven male human volunteers performed maximal-speed, unrestrained vertical arm movements whose upward and downward trajectories between two target endpoints required the hand to round a barrier, resulting in complex shoulder, elbow, and wrist joint movements. These movements were recorded by high-speed ciné film, and myopotentials from selected upper-extremity muscles were recorded. The arm was modeled as interconnected rigid bodies, so that dynamical interactions among the upper arm, forearm, and hand could be calculated. With practice, subjects achieved significantly shorter movement times. As movement times decreased, all joint-moment components (except gravity) increased, and the moment-time and EMG profiles were changed significantly. Particularly during reversals in movement direction, the changes in moment-time and EMG profiles were consistent with Bernstein's hypothesis relating practice effects and intralimb coordination: with practice, motor coordination was altered so that individuals employed reactive phenomena in such a way as to use muscular moments to counterbalance passive-interactive moments created by segment movements.

Action Potentials↗
PubMed1989

Neural stimulation for control of voiding dysfunction: a preliminary report in 22 patients with serious neuropathic voiding disorders.

Our experience with electrode implantation has demonstrated that the most successful combination to achieve continence and promote bladder evacuation is implantation on the ventral component of S3 or S4 and extensive dorsal rhizotomy with selective peripheral neurotomy. Of 22 patients with serious neuropathic voiding disorders treated during the last 6 years results were available for evaluation in 19 (2 were lost to followup and 1 was withdrawn from the protocol because of an infection at the receiver site). In 8 patients (42 per cent) complete success was achieved. These patients have regained reservoir function, are completely dry and void with electrical stimulation. The voiding is synchronous, with low voiding pressure and low residual urine volumes. Ten patients qualify as having partial success. They have regained reservoir function and are dry. One patient voids partially with stimulation, 5 depend on intermittent self-catheterization, 1 regained reservoir function and received an artificial sphincter, and 3 are catheter-dependent (these 3 all had been incontinent preoperatively despite continuous catheter drainage). The remaining patient entered the program long after a cerebrovascular accident and treatment has failed owing to poor selection. The stimulation parameters, once stabilized, did not need to be increased, and neither the surgical manipulation of the sacral roots nor the electrode implantation resulted in further neural loss in any patient.

Adult↗
PubMed1989

Technique of pudendal nerve localization for block or stimulation.

A diagnostic technique is described for study of the pudendal nerve via a dorsal rather than perineal approach. The method offers unique advantages for the urodynamic study of sphincteric function. The patient is placed in the prone position with slight flexion of the hips. The position of the ischial spine is identified topographically using the ischial tuberosities, greater trochanter and lower edge of the ischial-tuberous ligament. Local anesthesia and electrical stimulation then are used to position a needle tip adjacent to the pudendal nerve. This approach allows for specific localization of the nerve for accurate temporary or permanent nerve block. It also permits continuous urodynamic monitoring of pelvic floor behavior with stimulation of the pudendal nerve to assess functional integrity of the nerve and the pelvic floor striated muscles.

Anesthesia, Local↗
PubMed1989

Summary knowledge of results for skill acquisition: support for the guidance hypothesis.

Summary knowledge of results (KR) involves the presentation KR for each of a set of trials (e.g., 10) only after the last trial in the set has been completed. Earlier, Lavery (1962) showed that, relative to providing KR after each trial, a 20-trial summary KR was detrimental to performance in a practice phase with KR present but was beneficial for a no-KR retention test. Using a relatively simple ballistic-timing task, we examined summary lengths of 1 (essentially KR after every trial), 5, 10, and 15 trials, searching for an inverted-U relationship between summary length and retention performance as predicated by a guidance hypothesis for KR. During acquisition when KR was present and being manipulated, all groups showed improvements in performance across practice, while increased summary lengths generally depressed performance. However, in a delayed no-KR retention test, there was an inverse relation between the summary length in acquisition and absolute constant error on the retention test. A guidance hypothesis is favored to explain how, relative to immediate KR, long KR summaries can provide detrimental effects in acquisition while enhancing retention performance.

Adult↗
PubMed1989

Impaired clearance of aerosolized Legionella pneumophila in corticosteroid-treated rats: a model of Legionnaires' disease in the compromised host.

To develop a model of legionnaires' disease in a host with defective cell-mediated immunity, rats were treated with subcutaneous cortisone acetate and exposed to aerosolized Legionella pneumophila. Bacterial clearance, histopathology, cell recovery by bronchoalveolar lavage, serology, and splenocyte blastogenesis to heat-killed L. pneumophila were studied in cortisone-treated rats and normal controls. Corticosteroid administration resulted in a dosage-related defect in the clearance of L. pneumophila. Cortisone-treated animals had a diffuse, progressive pneumonitis, but the influx of neutrophils to the lung, the serum antibody response, and the sensitization of splenocytes to L. pneumophila were not impaired by corticosteroids. The marked lymphocyte depletion observed in cortisone-treated animals may have contributed to defective expression of cell-mediated immunity. This model may be useful in further studies of the pathogenesis and treatment of legionellosis in the compromised host.

Aerosols↗