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Biomedical subjects

R Shannon

Publications and source records attributed to R Shannon.

At least 73 records · Page 4Linked to original sources
PubMed1982

Lumbar spinal nerve lateral entrapment.

In past years, lumbar nerve lateral entrapment seldom has been diagnosed. A presumptive preoperative diagnosis has been made based on clinical findings and radiographs demonstrating disc resorption. The Computed Tomography scan has made it possible to diagnose the lesion with certainty and accuracy. Treatment for patients who do not respond to conservative measures is a bilateral minimal partial laminectomy. The lateral canal is enlarged by removing the medial and anterior parts of the superior articular process. Adhesion formation is prevented by placing a free fat graft posterior to the dura. Instability is diagnosed by examining stress radiographs and, when present, is treated by a one level posterolateral fusion. After operation, marked improvement was obtained in 62% of patients and slight improvement in another 21%; 17% were unimproved. Sixty-two per cent of patients reported no pain or mild pain. Sixty-six per cent resumed their previous occupation.

Adult↗
PubMed1981

Nucleus retroambigualis respiratory neurons: responses to intercostal and abdominal muscle afferents.

Studies were performed on anesthetized (Dial), paralyzed, vagotomized, artificially ventilated cats. Phrenic efferent activity, ventral respiratory group neuron activity in the region of the nucleus retroambigualis and, in some instances, thoracic dorsal root compound action potentials were recorded during electrical stimulation of intercostal nerve afferents (INS). Phrenic activity and inspiratory (I) neurons were inhibited by stimulating external, internal and lateral intercostal nerve afferents. Some expiratory (E)-neurons were also inhibited by these afferents. No I or E-neurons were facilitated with INS. Changes in I and E activity were correlated with muscle proprioceptor and cutaneous receptor afferent fibers. It is concluded that the dominant effect of intercostal and abdominal muscle proprioceptive afferent information on medullary respiratory activity in inhibition of inspiratory activity.

Abdominal Muscles↗
PubMed1980

Intercostal and abdominal muscle afferent influence on medullary dorsal respiratory group neurons.

Studies were performed on anesthetized, paralyzed, artificially ventilated cats. Phrenic (C5) efferent activity, dorsal respiratory group (DRG) neuron activity in the vicinity of the medullary solitary tract complex, and thoracic dorsal root compound action potentials were recorded during electrical stimulation of intercostal and lumbar nerves. DRG neurons were identified by their firing pattern and response to lung inflation. Phrenic activity (PA) was inhibited by stimulating external intercostal nerves T3-T10, internal intercostal nerves T3-T12, lateral branch of the main intercostal nerves T6-T12, or lumbar nerves 1-2. Stimulation of lower (T9-T11) intercostal or lumbar nerves produced a short duration (10-20 msec) facilitation of PA prior to the inhibition. Facilitation and inhibition of PA were correlated with recruitment of afferent fibers from muscle proprioceptors. Inspiratory neurons (I alpha and I beta) in the DRG were inhibited simultaneously with PA regardless of the nerves stimulated. DRG neurons which fired in phase with lung inflation (P cells) were unaffected by nerve stimulation even though PA was inhibited. Lower intercostal nerve (T9-T11) stimulation produced a brief facilitation of medullary neuron activity simultaneous with facilitation of PA. It is concluded that intercostal and abdominal muscle proprioceptor afferents, and perhaps cutaneous afferents, reflexly alter the activity of DRG inspiratory neurons (I alpha, I beta) which drive the phrenic motoneurons. The inhibitory effect is not via P cells but may be via other interneurons in close proximity to the I cells.

Action Potentials↗
PubMed1980

Immunological responses in late syphilis.

Thirty-one serum samples from 18 patients with clinically established late syphilis and 1319 from patients at other stages of the disease were fractionated by density gradient ultracentrifugation and examined for antilipoidal and antitreponemal antibodies of the IgM and IgG classes. Sera from the patients with late syphilis always showed persistent concentrations of antilipoidal IgM and IgG and of antitreponemal IgG but never yielded detectable concentrations of antitreponemal IgM. When treated, these patients' antibody titres did not decline. Patients with secondary or latent syphilis also showed this serological picture after treatment but only transiently; their antibody titres continued to decline in a way which clearly distinguished them from the cases of late syphilis. It is suggested that patients whose sera persist in showing the stable pattern described may develop late symptomatic syphilis.

Adult↗
PubMed1980

Respiratory pattern changes during costovertebral joint movement.

Experiments were conducted to determine if costovertebral joint manipulation (CVJM) could influence the respiratory pattern. Phrenic efferent activity (PA) was monitored in dogs that were anesthetized with Dial-urethane, vagotomized, paralyzed, and artificially ventilated. Ribs 6-10 (bilaterally) were cut and separated from ribs 5-11. Branches of thoracic nerves 5-11 were cut, leaving only the joint nerve supply intact. Manual joint movement in an inspiratory or expiratory direction had an inhibitory effect on PA. Sustained displacement of the ribs could inhibit PA for a duration equal to numerous respiratory cycles. CVJM in synchrony with PA resulted in an increased respiratory rate. The inspiratory inhibitory effect of joint receptor stimulation was elicited with manual chest compression in vagotomized spontaneously breathing dogs, but not with artificial lung inflation or deflation. It is concluded that the effect of CVJM on the respiratory pattern is due to stimulation of joint mechanoreceptors, and that they exert their influence in part via the medullary-pontine rhythm generator.

Animals↗
PubMed1979

Abdominal aortic aneurysm: a review of 12 years surgical experience.

A personal series of 187 consecutive resections for abdominal aortic aneurysm between 1967 and 1979 has been reviewed. The cases are classified as elective, acute or ruptured. Aetiology, presenting symptoms, investigations, management, complications and deaths are discussed. The hospital mortality rate in elective and acute cases was 4.7%, and in ruptured aneurysms was 27.8%.

Acute Kidney Injury↗
PubMed1979

Involvement of thoracic nerve afferents in the respiratory response to chest compression.

Chest compression elicits extravagal neural reflexes which can alter the respiratory pattern. Experiments were conducted to determine the source of the afferents responsible for the respiratory response to chest compression (CC). The effects of CC on VT, f, TI, TE, blood gases, end-tidal CO2, and blood pressure were studied in anesthetized, vagotomized dogs and cats. In dogs, thoracic wall afferents were eliminated by thoracic dorsal rhizotomies (TDR) and/or spinal blocks (SB). There were two different respiratory responses to CC. In one (I), Tt decreased and TE increased, resulting in a decreased f. The second (II) resulted in a decreased TI and TE. The I response was still present, but weaker, in animals after TDR (1--4), TDR (5--9), TDR (1--9, T5 or T10 SB and absent in those with T1SB. The II response was still present after TDR ()--4), TDR (5--9), TDR (1--9), or T10SB and absent after T5SB. The results indicate that: (1) afferents responsible for the I response to CC arise from the upper, middle and lower thoracic wall, (2) afferents responsible for the II response arise from the middle and lower thoracic wall, and (3) the responses are not due to changes in chemical drive, blood pressure or lung receptors.

Afferent Pathways↗
PubMed1978

Lumbar spinal stenosis: a review article.

(1) In discussing the types of lumbar spinal stenosis, emphasis has been placed on the developmental form. (2) The importance of nerve entrapment in the lateral recess has been stressed. (3) An attempt has been made to demonstrate the relationship of developmental stenosis to other lesions affecting the lumbar spine. (4) Our knowledge of the development of the lumbar spine and its patho-anatomy in children is limited. (5) Attention to minor trauma and to preventive measures during childhood will do much to prevent stenosis in later years.

Adolescent↗
PubMed1977

The pattern of immunological responses at various stages of syphilis.

Each of 212 sera, taken from 129 patients with clinically established syphilis, was subjected to seven immunological tests. The tests were designed to detect both anti-lipoidal and anti-treponemal antibodies and to titrate antibody of both IgG and IgM molecular species. It was found that patients of similar clinical history were usually recognisable by the similarity of results obtained in the seven tests, and a progression of these patterns of results was also found in samples of serum taken from individual patients during the course of their disease. It is suggested that this more comprehensive type of serological examination of patients can provide valuable information to the clinician.

Complement Fixation Tests↗
PubMed1977

Effects of thoracic dorsal rhizotomies on the respiratory pattern in anesthetized cats.

Experiments were conducted to determine if thoracic wall proprioceptor afferents are involved in the modulation of respiratory activity during eupnea. The effects of elimination of thoracic wall afferents (thoracic dorsal rhizotomies (TDR) on tidal volume (VT), frequency (f), inspiratory time (ti) and expiratory time (te) were studied in vagotomized cats anesthetized with diallylbarbituric acid (Dial). Dorsal rhizotomies 1-12 resulted primarily in a decreased VT and ti, and an increased f. Further experiments were performed to determine if these changes in respiratory pattern could be correlated with known reflexes from the middle and lower intercostal muscles, or lungs, via thoracic dorsal roots. Afferents from these sources were eliminated by TDR 5-9, 10-13, and 1-4. TDR 1-4 had no significant effect on the respiratory pattern. TDR 5-9 and TDR 10-13 produced changes similar in direction to TDR 1-12. The results indicate that: a) afferents 1-4 from the upper intercostal muscles and lungs (sympathetic afferents) do not contribute significantly to the control of the spontaneous respiratory rhythm, and b) afferents via the middle thoracic roots, 5-9, and the lower thoracic roots, 10-13, contribute significantly to the rhythm. The results do not completely correlate with known intercostal reflexes, but it is suggested that elimination of intercostal muscle proprioceptor afferents is responsible for the observed effects of thoracic dorsal rhizotomies.

Animals↗
PubMed1976

A study of blood coagulation parameters.

The object of this study was to determine the presence or absence of abnormalities in a variety of blood coagulation parameters in women on contraceptive medication. A prospective double-blind study involving a control group with a total study enrollment of 211 women during a 29 month period was established. Although research has not proved that changes in coagulation parameters will cause abnormal clotting in normal patients, a pattern appears to be developing involving antithrombin III determinations. Corresponding patterns do not appear to be developing in the other blood coagulation parameters.

Adolescent↗
PubMed1976

Respiratory frequency control during hypercapnia in vagotomized, anesthetized cats.

There is a small, but significant, increase in frequency during hypercapnia in vagotomized, anesthetized animals, indicating involvement of an extravagal mechanism in the response. The intent of this study was to determine the source of this second mechanism regulating frequency during hypercapnia. Experiments were performed on 22 vagotomized, anesthetized (Dial) cats. Frequency (f), inspiratory time (ti) and expiratory time (te) responses to CO2 were monitored before and after sectioning of afferent nerves from the carotid bodies (carotid sinus nerve section), chest wall (dorsal rhizotomies, T1-T12) and diaphragm (dorsal rhizotomies. C4-C7). Most vagotomized animals responded to 6% CO2 with an increased frequency, decreased ti and no consistent change in te. The responses to CO2 were essentially unaltered following chest wall and diaphragm deafferentation. Sodium cyanide stimulation of the carotid bodies produced similar respiratory pattern changes as CO2; furthermore, the f and ti changes with CO2 were still present following carotid body deafferentiation. The results of this study suggest that: (1) afferents from chest wall and diaphragm mechanoreceptors are not responsible for the vagal-like effects on ti and f during hypercapnia, (2) afferents from lung mechanoreceptors, via the vagus nerves, are the only inputs from respiratory mechanoreceptors causing an increased f during hypercapnia, (3) the extravagal mechanism responsible for the decreased ti and increased f during hypercapnia is inherent to the medullary-pontine rhythm generator, and (4) input from the chemoreceptors can elicit the response.

Animals↗