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.

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.

Two epidemics of pseudobacteremia due to Staphylococcus aureus and Aerococcus viridans

Two epidemics of pseudobacteremia are reported. The first, due to Staphyloccus aureus, was caused by a physician who had active staphylococcal skin infection and nasal colonization. Because the blood culture system in use at the time was open, and used screw cap bottles, we assume that the physician contaminated the bottles at the time of inoculation. The second outbreak, caused by Aerococcus viridans, was traced to contamination of the blood culture bottle tops as they were received from the manufacturer. We assume that there was inadequate disinfection of the bottle tops by the physicians prior to their use.

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.

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.

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%.

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.

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.

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.

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.

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.

Distribution of levels of penicillin resistance among freshly isolated strains of N. gonorrhoeae. Application of a novel sensitivity assay

A novel diffusion zone method of quantitative assay of the antibiotic sensitivity of bacterial strains was tested on freshly isolated gonococci. Smoothly variable estimates of the minimum inhibitory concentration of penicillin for these strains was obtained with sufficient accuracy and precision (coefficient of variation c. 10 per cent.) by means of a simple graphical analysis and without replication. Such estimates were free from the chief sources of error associated with the commonly applied 'incorporation' and 'diffusion' methods. The method revealed that 816 isolates of gonococci obtained in the Bristol area during a 6-month period fell into a large 'sensitive' group (MIC c. 0.02 unit per ml.) and three smaller more resistant groups, and that this pattern occurred in three widely spaced centres within the area. It is suggested that the method is capable of revealing details of distribution that may be masked by the usual techniques and that it is of wide applicability.

Respiratory frequency control during external elastic loading and chest compression

Experiments were conducted to determine if extravagal (i.e. chest wall) respiratory mechanoreceptors are involved in the control of respiratory frequency during steady-state external elastic loading (EEL) and chest compression (CC) in the anesthetized (Dial), vagotomized cat and dog. Frequency versus PaCo2 curves obtained by breathing CO2 mixtures were compared with curves obtained during elastic loading and chest compression. There was no significant difference between the CO2 and EEL curves in cats or dogs indicating there is no extravagal mechanoreceptor information contributing to the control of respiratory frequency during EEL. Comparison of curves obtained with chest compression and CO2 breathing show that dogs respond to chest compression with an extravagal (i.e. involving chest wall mechanoreceptors) neural reflex increase in frequency.

Reversibility of the specific adsorption of colicin E2-P9 to cells of colicin-sensitive strains of Escherichia coli

The adsorption of colicin E2-P9 to its specific receptors on cells of sensitive strains of Escherichia coli is reversible under normal experimental conditions. At temperatures above 20 C, colicin may desorb from one cell and be readsorbed by a second with potentially lethal consequences. However, desorption of colicin seems unable to rescue a cell once it has received a lethal dose. These findings have implications both for the nature and types of specific receptors, and for the assay of colicin by the survivor count (lethal unit) methods.

Kinetics of lethal adsorption of colicin E-2 by Escherichia coli

The kinetics of lethal adsorption of colicin E2 by Escherichia coli C6 were studied by means of survivor plots. These were determined by a method which allowed rapid sampling of the reaction mixture and estimation of approximate confidence limits for the plotted data. The results were consistent with the predictions of a hypothetical model that assumed a single-hit mechanism of colicin action upon a bacterial population whose cells varied in their number of specific (lethal) receptors for colicin. The possibility of nonlethal adsorption is discussed.

Daily penicillin serum concentrations following injection of 2.4 mega-units of "all purpose" penicillin

In order to investigate the reliability with which a given dose of benzathine penicillin will result in predictable ranges of penicillinaemia on any particular day during the week after injection, ambulant adult males were injected with 2 400 000 IU of "all-purpose" penicillin (600 000 IU potassium penicillin G, 600 000 IU procaine penicillin G and 1 200 000 IU of benzathine penicillin). Penicillin serum assays were performed, 24 each day, from the third to the seventh day after injection (120 assays in all).Statistical evaluation of the results showed that the means of the groups of 24 assays fell within narrow ranges, indicating that the long-acting component (benzathine penicillin) gives reliable daily ranges in a high proportion of cases. The results of a previous trial, using half the present dosage (1.2 mega-units of "all-purpose" penicillin) were compared statistically with those of the present trial. A very satisfactory degree of correlation between dosage and resulting daily serum concentration was observed-in general double the dose yielded double the daily concentration. The many factors which affect absorption rate are discussed and it is suggested that preparations which depend on an oily gel to delay absorption add an avoidable factor to the list of variables which may play an important part in producing the significant differences in serum levels commonly reported after the use of PAM preparations. The narrow ranges of penicillinaemia observed after 1.2 mega-units and 2.4 mega-units of benzathine penicillin and the degree of correlation observed in general between dose and resulting serum levels suggest that a large-scale controlled series of parallel trials should be undertaken to compare the relative long-acting qualities of PAM and benzathine penicillin.

Daily penicillin serum concentrations following injection of 1.2 mega-units of "all-purpose" penicillin

In view of evidence suggesting that 1.2 mega-units of "all-purpose" penicillin (300 000 IU potassium penicillin G, 300 000 IU procaine penicillin G and 600 000 IU benzathine penicillin) did not maintain treponemicidal serum concentrations during the week following injection-which if true, might necessitate a reappraisal of prophylactic and treatment schedules in wide use against syphilis-daily assays were performed to determine the penicillinaemia levels in ambulant adult males for one week following intramuscular injection with this dosage of two "all-purpose" products (168 assays in all, 24 each day).Statistical evaluation of the results showed that the mean daily serum concentrations were, in fact, treponemicidal during the whole week after injection. The means of groups of 24 assays fell within narrow daily ranges on each of the seven post-injection days, suggesting that the long-acting component (benzathine penicillin) gives reliable and predictable daily levels in a high proportion of cases. This is in contrast to those penicillins which rely for their long-acting property on the oily gel in which they are suspended. On the other hand, the extremes of penicillinaemia for any individual in a large group were shown to cover a very wide range, demonstrating that a particular patient's failure to respond to standard treatment or prophylaxis can be due to factors quite unrelated to the quality or specificity of the product or to the sensitivity of the organism causing disease.