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Biomedical subjects

R J Nelson

Publications and source records attributed to R J Nelson.

At least 199 records · Page 11Linked to original sources
PubMed1990

Photoperiod affects reproductive responsiveness to 6-methoxy-2-benzoxazolinone in house mice.

House mice (Mus musculus) have traditionally been characterized as nonphotoperiodic because reproductive function is unaffected by day length in the laboratory. In the present study, the reproductive responsiveness of CF1 mice to a naturally occurring plant metabolite was assessed in animals that were maintained in either long (16L:8D) or short (8L:16D) photoperiods from birth until the end of the study. Males and females were implanted i.p. with either an empty Silastic capsule or one containing 6-methoxy-2-benzoxazolinone (6-MBOA) at either 21 or 60 days of age for 3 days. Other 31-day-old mice were implanted with capsules for 8 wk. Three-day exposure to 6-MBOA stimulated uterine growth in short-day, adult females, but did not affect adult females housed in long photoperiods. Short-term treatment with 6-MBOA did not significantly affect reproductive parameters in either long- or short-day peripubertal house mice, or in adult males regardless of photoperiod, nor did exposure to 6-MBOA for 8 wk influence reproduction in males in either photoperiodic condition. However, short-day female mice had significantly reduced ovarian and uterine masses after 8 wk chronic 6-MBOA treatment as compared to long-day animals or mice unexposed to 6-MBOA. Short-day females exposed to 6-MBOA for 8 wk developed a denser pelage compared to long-day mice treated with this compound. Photoperiod-mediated differential responsiveness to 6-MBOA indicates that female house mice can discriminate long from short days, and these results suggest that the physiological mechanisms for photoperiodic responsiveness remain extant in this species previously characterized as nonphotperiodic.

Animals↗
PubMed1990

Interpreting the sounds of swallowing: fluid flow through the cricopharyngeus.

The sounds of swallowing in normal subjects were recorded by means of a miniature accelerometer on the throat, simultaneously with videofluoroscopy of a modified barium swallow. Consistent correspondence was found between a rapid change in the acoustic spectrum of the accelerometer signal (the appearance of a region of energy prominence above 1,000 Hz) and bolus flow through the cricopharyngeus.

Adult↗
PubMed1990

Reaction times for hand movements made in response to visual versus vibratory cues.

Reaction times were determined for monkeys and humans who made wrist flexion and extension movements in response to vibratory and visual cues. Humans initiated movements approximately 50 msec sooner in response to vibratory as compared to visual cues. For monkeys, this difference was approximately 100 msec. Mean daily reaction times for monkeys and humans improved with practice until they reached a steady level of performance. Increased differences between vibratory and visual reaction times were weakly correlated with increased age of humans. The increase in the differences appeared to result from decreased reaction times by older subjects for vibratory-cued movements; reaction times for visually cued movements did not consistently vary across the age range of subjects tested (19-36 years). The results obtained using this novel paradigm suggest that it may be a useful tool for simultaneously testing behavioral performance or neurological function during somatosensorimotor and visuomotor tasks.

Adult↗
PubMed1990

Transcranial Doppler ultrasound studies of cerebral autoregulation and subarachnoid hemorrhage in the rabbit.

The authors describe a method for Doppler ultrasound recording of flow velocity in the basilar artery of normal rabbits and rabbits with experimental subarachnoid hemorrhage (SAH). With this transcranial Doppler (TCD) model, clinical assumptions regarding flow velocity/cerebral blood flow (CBF) relationships, autoregulatory responses, and Doppler spectral waveform analysis can be tested under controlled conditions and compared with established methods of CBF measurement (hydrogen clearance). The time course of changes in flow velocity following SAH (cerebral vasospasm) is successfully demonstrated using the experimental TCD method. There are significant differences in the flow velocity and CBF responses to hypercapnia, hypocapnia, and trimethaphan-induced hypotension which indicate that TCD cannot be considered a simple alternative to CBF measurement for the study of cerebrovascular reactivity and cerebral autoregulation.

Analysis of Variance↗
PubMed1989

Changes in premovement activity in primary somatosensory cortex differ when monkeys make hand movements in response to visual vs vibratory cues.

Rhesus monkeys were taught to make identical wrist flexion and extension movements in response to either a visual cue or to vibratory cues. Changes in firing rates that were not stimulus-associated but preceded the movements were measured for each primary somatosensory cortical neuron recorded under the two stimulus cued conditions. The onset of the premovement activity changes and the magnitude of these changes differed when visually cued trials were compared with vibratory cued trials that resulted in the same behavioral response. In general, the magnitudes of premovement activity changes were less and the onset of these changes occurred earlier for vibratory cued trials than for the corresponding trials triggered by the visual stimulus. These findings support the hypothesis that centrally generated modulatory influences arriving at primary somatosensory cortical neurons prior to movement onset may differ, depending upon the modality of the stimulus which signals that a movement may be initiated.

Animals↗
PubMed1989

The rudimentary first rib. A cause of thoracic outlet syndrome with arterial compromise.

The symptoms of thoracic outlet syndrome are neurologic, not vascular, in more than 95% of cases. Subclavian artery compression is usually related to cervical ribs; however, congenitally abnormal first ribs may also produce vascular compromise. We review our two cases of thoracic outlet syndrome associated with significant subclavian artery compression caused by rudimentary first ribs and the prior literature emphasizing the mechanism of injury, diagnostic features, and treatment. Transaxillary resection of the first and second ribs was curative in both cases. The operative specimens demonstrated fusion of the rudimentary first rib to the second rib, with compression of the subclavian artery by a large first-rib exostosis. Patients with thoracic outlet syndrome and a rudimentary first rib should be examined for substantial vascular compromise, and, if it is found, the abnormal first and second rib complex should be resected early without prolonged conservative measures.

Adult↗
PubMed1989

Detection of multiple cardiac papillary fibroelastomas using transesophageal echocardiography.

Papillary fibroelastomas are rare, benign cardiac tumors that may be associated with embolization, angina, and sudden death. We report a case of multiple papillary fibroelastomas diagnosed during life by transesophageal echocardiography. Surgical resection during mitral valve replacement for rheumatic mitral stenosis prevented the development of any of the life-threatening complications sometimes associated with this tumor.

Echocardiography↗
PubMed1989

Pleuropulmonary actinomycosis associated with a systemic-to-pulmonary artery fistula and contralateral metastatic back mass.

We report a case of systemic-to-pulmonary artery fistula associated with thoracic actinomycosis and with metastatic hematogenous dissemination to the soft tissues of the back. The difficulty in diagnosing thoracic actinomycosis may predispose to the increased incidence of hematogenous spread of this disease. Although resection of pulmonary tissue including the infectious mass was required in previous cases, resection of the pleural mass alone was curative in this patient when combined with penicillin therapy.

Abscess↗
PubMed1989

Prolactin and paternal behavior in the biparental California mouse, Peromyscus californicus.

Relatively little is known about hormonal mechanisms underlying paternal behavior in mammals. Male California mice, Peromyscus californicus, display extensive parental care toward their young. Parental behavior of fathers, expectant fathers (males living with their pregnant partner), and virgin males was assessed in a 10-min test with a 1- to 3-day-old alien pup. Few virgin males acted parental (19%) compared to fathers one day postpartum (80%) and expectant fathers (56%). Plasma prolactin levels were significantly elevated in fathers 2 days postpartum compared to expectant fathers and virgin males. Paternal prolactin levels were similar to those of mothers. There were no differences between groups in levels of plasma testosterone. These data suggest, contrary to other reports, that prolactin is a likely correlate of paternal behavior in rodents.

Animals↗
PubMed1989

Simulated drought influences reproduction in male prairie voles.

The environmental factors that arrest breeding in prairie voles during the middle of the breeding season are unknown. The role of water availability on reproductive function was examined by limiting water intake to 50% of ad lib water consumption for 10 weeks. At autopsy, testicular, epididymal and seminal vesicle masses were reduced in water restricted males as compared to animals with ad lib access to water. Body mass was also reduced in water restricted males. Plasma testosterone levels and the number of testicular and epididymal sperm were significantly reduced in water restricted voles as compared to animals drinking water ad lib, but plasma levels of luteinizing hormone were unaffected. Taken together, these data suggest that reduced water availability can inhibit male prairie vole breeding.

Animals↗
PubMed1989

The rat as a model for the study of penile erection.

A model has been developed for the study of penile erection in the Sprague-Dawley rat. Anatomical dissections demonstrate a bilateral ganglion lateral to the prostate called the major pelvic ganglion. This ganglion receives input from the pelvic and hypogastric nerves and innervates the pelvic viscera. A large fiber from the major pelvic ganglion courses along the urethra and innervates the corpus cavernosum, the cavernous nerve. In 40 animals, electrical stimulation of either the cavernous nerve or the pelvic nerve resulted in reproducible repetitive tumescence of the corpora cavernosum. Following ablation of the cavernous nerve, electrical stimulation failed to produce erections. Standard mating behavior tests of mounting, intromission and ejaculation in 38 rats showed that surgical ablation of the cavernous nerve resulted in a decrease in the rate of intromissions and ejaculations compared with sham operated controls. Present models for the study of erection have been limited to the dog, monkey and cat. The rat model presented here offers several advantages over these existing models: 1) the cavernous nerve is easily identified, 2) electrical stimulation is easily accomplished and reproducible, 3) behavioral and neurophysiological studies are possible, and 4) animal purchase, housing, and maintenance costs are low. These advantages make this model a uniquely useful tool in the further study of penile erection.

Animals↗
PubMed1989

Photoperiod and temperature affect reproductive and nonreproductive functions in male prairie voles (Microtus ochrogaster).

Adult male prairie voles (Microtus ochrogaster) were housed for 10 wk and exposed to long (16L:8D) or short (8L:16D) photoperiods at 21 degrees or 5 degrees C. Maintenance in short day lengths reduced testicular, epididymal, and seminal vesicle mass and also significantly depressed spermatogenic activity. Cold ambient temperature further suppressed gonadal size in voles exposed to short days. Several pelage characteristics were affected by photoperiod, but not by temperature. Increased fur density, fur depth, and length of guard hair and underhair were observed in voles exposed to short days. Intrascapular brown fat and gonadal fat pad mass as well as body mass were significantly less in voles housed in cold temperatures than in voles exposed to warm ambient temperatures; photoperiod did not affect these parameters. Approximately 30% of the male voles exposed to short days maintained their reproductive systems, yet they clearly processed photoperiodic information; all short-day males, regardless of reproductive condition, had comparable winter pelage development. Our results suggest that in prairie voles, photoperiod may be a predictive cue for reproductive function in nature; however, it appears that pelage development is a more obligatory response to photoperiod than is reproduction.

Animals↗
PubMed1989

Pott's disease. A resurgent challenge to the thoracic surgeon.

Nineteen patients were treated at the Los Angeles County Harbor/UCLA Medical Center between 1971 and 1986 for tuberculosis of the spine. Fourteen were immigrants, a high-risk group. A high index of suspicion is required for Pott's disease, which occurs in fewer than 1 percent of patients with tuberculosis, often presents with nonspecific symptoms, and may result in permanent deformity or neurologic impairment. CT scan, the most useful diagnostic test, showed abnormal results in 11 of 11 patients. MRI, a newer modality, may provide even more information. Eight patients required operation in addition to antimicrobial therapy. Four had lesions between T3 and T10, where the spinal canal is narrow, of whom three (75 percent had neurologic involvement. All four underwent anterior approach (thoracotomy) for decompression, debridement, and spinal fusion. Fifteen had lesions between T11 and S2. Three (20 percent) had neurologic involvement but responded to medical treatment alone. Four underwent drainage of abscess or spinal fusion for deformity. Combined surgical and medical treatment gave excellent results in this series.

Adolescent↗
PubMed1989

Predictive risk factors for periannular extension of native valve endocarditis. Clinical and echocardiographic analyses.

The study objective is to identify clinical, microbiologic, and/or echocardiographic risk factors present early in the course of native valve endocarditis that predict subsequent development of periannular extension of infection. A multivariate computer-generated analysis of 21 clinical-microbiologic parameters and 11 two-dimensional echocardiographic parameters in patients with native valve endocarditis was designed. These parameters were statistically compared in operated-on patients with native valve endocarditis with and without periannular extension of infection. The study took place in a 600-bed acute-care, nonreferral, municipal hospital primarily servicing an indigent patient population. Seventy-three documented episodes of native valve endocarditis occurred between the years of 1973 and 1987, including 29 operated-on patients with surgically confirmed periannular extension of infection and 44 operated-on patients without periannular extension of infection. Multivariate logistic-regression analyses of multiple clinical, microbiologic, and echocardiographic parameters which are potentially predictive of eventual periannular extension of native valve endocarditis were carried out. The only two independent parameters that significantly predicted periannular infection among patients with native valve endocarditis were (1) aortic valve involvement and (2) abuse of intravenous (IV) drugs (p less than 0.01; p less than 0.01, respectively, multivariate analysis). The relative risk of developing periannular extension of endocarditis among patients with aortic valve involvement and/or IV drug abuse was increased by approximately 2.5-fold compared with patients without these characteristics. Factors not significantly associated with increased risk of periannular extension of native valve endocarditis included the following: prolonged febrile morbidity; Staphylococcus aureus etiology; or two-dimensional echocardiographic demonstration of vegetations, large vegetations (greater than or equal to 1 cm), multiple vegetations, or enlargement of aortic root or annulus. These data suggest that patients with native aortic valve endocarditis, particularly in the setting of IV drug abuse, should be considered for routine, serial noninvasive evaluation for the early detection of periannular extension of their infection.

Adult↗
PubMed1989

Myocardial contusion in the stable patient: what level of care is appropriate?

To evaluate the significance of myocardial contusion, we evaluated 243 stable patients hospitalized for blunt chest trauma between 1982 and 1986. The groups were identified according to results of radionuclide angiography, mean injury severity score (ISS), and outcome. Group I (n = 71; mean ISS = 12.7) patients were those without myocardial contusion by radionuclide angiography. Two patients with cardiac complications were in this group. The patients with myocardial contusion were divided into two groups. Group II (n = 69; ISS = 19.5) patients had myocardial contusion as an isolated injury, and group III (n = 103; ISS = 30.9) patients had myocardial contusion and injury to at least one other organ system. Three patients from group II had cardiac complications. Eleven patients from group III had cardiac complications. There were no significant differences between the cardiac complication rate in the three groups, and each complication was present when the patient arrived in the emergency department. The predicted mortality rate based on ISS was 10% to 20% for patients with myocardial contusion, whereas the observed mortality rate for the groups (II and III) overall was 0.58%. We conclude that in the stable trauma patient myocardial contusion (1) does not by itself increase the risk of complication, (2) does not necessitate intensive care unit monitoring, (3) should be devalued when computing ISS scores, (4) may account for lengthy and often unnecessary hospitalization, and (5) in patients at risk for complications may be identified by ECG abnormalities on arrival to the emergency department.

Adolescent↗
PubMed1989

The circulatory assist device program at University Medical Center. Clinical training and technical support.

A great deal of preparation and coordination is necessary for participation in the investigational use of temporary circulatory assist devices. The use of engineers for technical support as well as for programs coordination has been very useful in the ongoing evaluation of our device performance. It is hoped that the early studies conducted today will lead to improvements in the devices and the eventual production of permanent, totally implantable circulatory assist devices. As these devices continue to develop, it is expected that the biomedical engineer will be able to continue to participate significantly in the development process.

Academic Medical Centers↗