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Biomedical subjects

A Guz

Publications and source records attributed to A Guz.

At least 163 records · Page 9Linked to original sources
PubMed1984

The role of spinal cord transmission in the ventilatory response to exercise in man.

The ventilatory response to electrically induced exercise was studied in thirteen patients with traumatic spinal cord transection at or about the level of T6. The steady-state and on-transient responses to this exercise were compared with those obtained in eighteen normal subjects (Adams, Garlick, Guz, Murphy & Semple, 1984). Exercise was produced by surface electrode stimulation of the quadriceps and hamstring muscles so as to produce a pushing movement at 1 HZ against a spring load. At rest there was no significant difference between normals and patients, except that the patients had a lower CO2 elimination (VCO2) and end-tidal PCO2 (PET,CO2) and a higher heart rate. On exercise the mean rise in VCO2 for the patients was 172 ml min-1 (S.D. 72), and for the normals was 287 ml min-1 (S.D. 143). The corresponding mean changes in ventilation (VI) were 4.4 l min-1 (S.D. 2.2) and 7.6 l min-1 (S.D. 3.2). However, the ventilatory equivalent for CO2 (delta VI/delta VCO2) in the steady state was not significantly different between patients (26.0, S.D. 5.9) and normals (28.5, S.D. 7.4). In the steady state there was a mean rise in PET,CO2 of 0.9 mmHg (S.D. 1.4) in the normals, and 3.2 mmHg (S.D. 2.7) in the patients, but there was overlap between the two groups. In many experimental runs in both groups, PET,CO2 did not rise, and sometimes fell. Where PCO2 did rise, the ventilatory response to exercise could not be accounted for on the basis of the ventilatory sensitivity to CO2 inhalation. From arterial sampling in three of the patients it was found that when PET,CO2 rose, the corresponding change in Pa,CO2 was less. During the on transient, there was a significant rise in both VCO2 and VI by the second breath in both groups. At the end of the on transient the normal subjects had achieved 84% (S.D. 40) of the steady-state increase in VCO2 and 88% (S.D. 24) of the increase in VI. The corresponding values for the patients were 67% (S.D. 17) and 77% (S.D. 16) respectively; these differences between normals and patients are significant. The increase of VI during the on transient in the patients was achieved almost entirely by an increase in tidal volume whereas in normals, an increase in respiratory rate was a more important component. We conclude therefore that in man, spinal cord transection with a presumed loss of muscle afferents allows a ventilatory response to electrically induced exercise that cannot be explained by classical chemoreception.(ABSTRACT TRUNCATED AT 400 WORDS)

Carbon Dioxide↗
PubMed1983

Acromegaly and hyperprolactinemia in McCune-Albright syndrome. Evidence of hypothalamic dysfunction.

In a 21-year-old woman with McCune-Albright syndrome, acromegaly and hyperprolactinemia with hypopituitarism developed secondary to a large pituitary tumor. Bromocriptine suppressed the secretion of growth hormone and prolactin, with a reduction in tumor size. However, at the age of 8, she already showed evidence of biochemical acromegaly, with a paradoxical rise of growth hormone levels during two glucose tolerance tests, in the presence of a radiologically normal pituitary fossa. These data support the hypothesis that long-standing hypothalamic stimulation may have been responsible for the later development of a pituitary tumor.

Acromegaly↗
PubMed1983

Breathlessness and psychiatric morbidity in chronic bronchitis and emphysema: a study of psychotherapeutic management.

This paper describes a study of the outcome of psychotherapy with patients disabled by chronic obstructive airways disease giving rise to dyspnoea. Forty-three men and 22 women with severe COAD were randomly allocated for 8 weeks to one of three types of psychotherapy or to an untreated control group, and were followed up six months later. The group treated by a medical nurse without training in psychotherapy experienced sustained relief of dyspnoea but tended to undergo less psychodynamic change; psychiatric symptoms were reduced in those receiving supportive, but not analytical, psychotherapy. The psychosomatic mechanisms involved and the implications for medical and nursing practice and for liaison psychotherapy are discussed.

Aged↗
PubMed1983

Patterns of smoking: measurement and variability in asymptomatic smokers.

Measurements of patterns of puffing (cigarette-holder pneumotachograph) and ventilation (plethysmography) were made in ten asymptomatic smokers during the smoking of a cigarette, on four separate occasions. There were marked individual differences and these were consistent over 3-5 weeks. In itself, the pattern of smoking could be responsible for a threefold variation in smoke intake. Puffing but not inhalation became less intense as a cigarette was smoked. It was not possible to predict indices of absorption from smoking patterns. Certain smoking patterns, e.g. small puff volume, low puff frequency, short duration of inhalation and expulsion of volume between puff and inhalation, may be less harmful than others and this may explain why some individuals remain healthy despite a lifetime of smoking.

Adolescent↗
PubMed1983

The Charing Cross-Cassel Focal Psychotherapy Research Project: method of content analysis.

A method of content analysis has been designed for application in brief focal psychotherapy with physically ill patients. The method is being used to study the process of therapy with patients with chronic obstructive airways disease. This paper discusses its reliability and validity in this context and suggests that it may illuminate the relevance of environmental factors to the development of the transference.

Humans↗
PubMed1982

The role of spinal cord transmission in the ventilatory response to electrically induced exercise in the anaesthetized dog.

1. The ventilatory response to electrically induced ;exercise' was studied in six chloralose-anaesthetized dogs. The on-transient and steady-state responses to ;exercise' were compared in the same dogs before and after spinal cord transection at T8/9 (dermatome level T6/7) on fifteen occasions.2. Phasic hind limb ;exercise' was induced for periods of 4 min by passing current (2 Hz modulated 50 Hz sine wave) between two needles inserted through the hamstring muscles. The maximum current used was 30 mA. This was below the level previously found to produce an artifactual stimulation of breathing with the cord intact.3. Cord transection produced no significant change in either the resting values of ventilation ( V(I)) and CO(2) production ( V(CO) (2)) or the ventilatory equivalent for CO(2) during ;exercise' ( big up tri, open V(I)/ big up tri, open V(CO) (2)).4. During the steady state of exercise P(a, CO) (2) was on average significantly lower than at rest with the cord intact (mean big up tri, openP(a, CO) (2), - 2.1 mmHg; range - 5.7 to + 1), and higher, though not significantly, with the cord cut (mean P(a, CO) (2), + 1.2 mmHg; range - 1.5 to + 4.3). However, even in the absence of spinal cord transmission, the ventilatory response to exercise could not be accounted for on the basis of CO(2) sensitivity; the big up tri, open V(I)/ big up tri, openP(a,CO) (2) obtained with exercise (apparent sensitivity) was significantly greater than that obtained with CO(2) inhalation (true sensitivity) both before and after cord section.5. V(I) and V(CO) (2) increased more slowly with the cord cut than with the cord intact. This was thought to be due to a slower increase in venous return in the absence of sympathetic innervation of the lower half of the body following cord transection.6. Similar experiments were performed during muscle paralysis (following gallamine triethiodide). Ventilation was maintained with a respirator controlled by phrenic nerve activity. These experiments showed an increase in ventilation, independent of muscle contraction, which was only present when the cord was intact and which was confined to the on-transient. Only in the absence of spinal cord transmission could there be certainty that the dynamics of the ventilatory response to electrically induced ;exercise' was free of artifact.7. It was concluded that spinal cord transmission is not necessary for the steady-state ventilatory response to electrically induced exercise of the hind limbs.8. The dog with spinal cord transection provides a suitable model for the study of the chemical control of breathing during electrically induced exercise.

Anesthesia, General↗
PubMed1982

The ph oscillations in arterial blood during exercise; a potential signal for the ventilatory response in the dog.

1. The effect of electrically induced ;exercise' on the respiratory oscillation of arterial pH was studied in chloralose-anaesthetized dogs with spinal cord transection at T8/9 (dermatome level T6/7).2. Respiratory oscillations of arterial pH (presumed to be due to oscillations of arterial P(CO2)) were sensed with a fast-responding electrode in one carotid artery. Breath-by-breath estimates of the maximum rate of change of pH of the downstroke of the pH oscillation (dpH/dt downward arrowmax) were obtained by differentiating the pH signal.3. Consistent with the findings of the previous paper (Cross et al. 1982), the ventilatory response to exercise could not be explained on the basis of sensitivity to CO(2); the Delta V(I)/DeltaP(a, CO2) was significantly greater for ;exercise' than for CO(2) inhalation.4. On average, the amplitude of the pH oscillations decreased during ;exercise'. The change in the phase relationship (varphi) between respiratory and pH cycles, although significant from the second breath onwards, was not thought to be responsible for the increased ventilation V(I); the direction of the change was opposite to that previously found to increase V(I).5. Inspiratory duration (t(i)), expiratory duration (t(e)), V(I) and the dpH/dt downward arrowmax changed significantly by the third breath of ;exercise'. A significantly linear relationship was obtained between t(e) and dpH/dt downward arrowmax during the on-transient (first ten breaths) of ;exercise'. This relationship was maintained throughout ;exercise'. V(I) and dpH/dt downward arrowmax were also linearly related during the on-transient, although the same relationship did not hold true throughout ;exercise'.6. The dpH/dt downward arrowmax was related to CO(2) production ( V(CO2)) lending support to the prediction that the slope of the downstroke of the pH oscillation is a function of V(CO2).7. It was concluded that the dpH/dt downward arrowmax (dpCO(2)/dt upward arrowmax) is a potential humoral signal in ;exercise' and could account totally for the shortening of t(e). Since there was a late rise in V(I) (due to an increase in tidal volume V(T)) in the absence of a change in dpH/dt downward arrowmax, it was considered unlikely that the dpH/dt downward arrowmax was the only humoral signal present during ;exercise'.

Animals↗
PubMed1982

Cigarette smoking among secondary schoolchildren 1975-79.

A questionnaire relating to smoking habits, respiratory symptoms, and health attitude was administered to schoolchildren aged between 11 and 17 throughout a defined geographical area in both 1975 and 1979, with a valid response from 10498 and 12002 young people respectively. Each cohort was almost entirely different. The results suggest that although the prevalence of regular smoking has decreased in boys from 16 to 13% it has increased in girls from 13 to 14% and that at all ages more girls smoke more than boys. However despite the fall in the prevalence of regular smoking in boys there has been an overall increase in cigarette consumption. Young people who are regular smokers predominantly smoke middle tar cigarettes while among experimental smokers there is a high incidence of low tar smoking, which might suggest that such cigarettes facilitate the taking up of the habit in children. The previously described relationships between smoking and respiratory symptoms was confirmed. During the 4-year study period young people's knowledge of the associated links between smoking and heart disease and stroke has increased appreciably. It is suggested that specific health education during the years 1975-79 has not been successful, and there is the need for research.

Adolescent↗
PubMed1982

Sympathetic and parasympathetic cardiac control in athletes and nonathletes at rest.

A simple model to characterize sympathetic and parasympathetic effects on heart rate (R) was tested during rest in 10 nonathletes and 8 world-class oarsmen. The model states that R = mnR0, where R0 is the intrinsic cardiac rate, and m and n depend only on sympathetic and parasympathetic activity, respectively. The multipliers, m and n, were determined by dual pharmacological blockade in two sessions under similar conditions, but in one session propranolol and in the other atropine was given first. In agreement with the model, when corrections were made for atropine-induced blood pressure changes, m and n did not depend on which blocking agent was administered first. In athletes the control heart rate [55 +/- 3.3 (SD) beats/min] and R0 (81 +/- 8.3 beats/min) were lower than in nonathletes (62 +/- 6.0, P less than 0.01 and 102 +/- 11, P less than 0.001, respectively). The sympathetic multiplier, m, was similar (1.18 +/- 0.06 vs. 1.20 +/- 0.05, P greater than 0.4) in the two groups, but n, the parasympathetic multiplier, was closer to 1 in the athletes (0.57 +/- 0.03 vs. 0.51 +/- 0.05, P less than 0.01). We conclude that the model is suitable for the quantitative study of sympathetic/parasympathetic heart rate control in humans, and that the lower resting heart rate in oarsmen is solely due to a reduction in intrinsic cardiac rate, and not to an increase in parasympathetic tone.

Adult↗
PubMed1981

The role of histamine receptors in asthma.

1. Eighteen non-asthmatic and 18 asthmatic subjects underwent challenge with increasing doses of histamine from a dosimeter-nebulizer system. Half the subjects in each group were atopic and half non-atopic. Bronchial response was monitored with serial measurements of specific airways conductance (sGaw) and a dose-response curve was constructed for each challenge. In addition, the nine atopic asthmatic patients underwent antigen challenges with a similar technique. In each subject the challenges were repeated, on separate days, after intravenous injections of either sodium chloride solution (150 nmol/l: saline) placebo, chlorpheniramine (an H1-receptor antagonist), cimetidine (an H2-receptor antagonist) or after both antagonists together. Baseline bronchial tone was always comparable within subjects immediately before challenge. 2. Cimetidine had no significant effect on baseline sGaw in any group, whereas chlorpheniramine raised baseline sGaw in the asthmatic subjects. Placebo did not alter the mean dose-response curves for histamine or antigen. However there was a small, but significant, shift of the curves to the right after cimetidine and a much larger shift to the right with chlorpheniramine, whether given alone or with cimetidine. The effect of the histamine antagonists on histamine and antigen responses was very similar and there was no difference in the pattern of response among normal subjects as compared with asthmatics or among atopic as compared with non-atopic subjects. 3. In conclusion, the same pattern of histamine receptors exists in the airways of asthmatic and normal subjects. Histamine-induced bronchoconstriction is mediated predominantly via the H1-receptors, with little, if any, contribution from the H2-receptors. Histamine appears to be an important mediator in the immediate allergic response in airways since this response is blocked by an H1-receptors antagonist.

Airway Resistance↗
PubMed1981

The summation of left and right lung volume information in the control of breathing in dogs.

1. Reflex respiratory responses to unilateral and bilateral changes of lung volume have been studied in anaesthetized paralysed, open-chest dogs.2. The two lungs were separately ventilated by two phrenic-driven respirators via a specially designed double-lumen tube. Respiratory motor output was measured from the phrenic motoneurone activity recorded from the C(5) root. Expiratory lung volumes were set by the use of expiratory threshold loads (e.t.l.s).3. The reflex changes of expiratory time (t(e)) were used to study the summation of left and right expiratory lung volume information. Changes in the peak amplitude of the phrenic ;integral' (Phr) and inspiratory time (t(i)) were used to assess summation of left and right tidal volume information.4. Summation in the reflex responses to bilateral lung volume changes was estimated by comparing the measured responses to these manoeuvres with the sum of the component unilaterally evoked responses. If simple addition were present, response (measured)/response (predicted) would equal 1.0 Mutual facilitation would give a value higher than this; mutual inhibition, a lower value.5. The responses of t(e) to changes of e.t.l. on the right side were always greater than for changes confined to the left, and in each animal the response of t(e) to bilateral changes of e.t.l. were greater than for either of the unilaterally evoked responses. In six out of eight animals this was shown to be due to simple addition of the responses evoked from the two lungs individually. In the remaining two animals, slight mutual inhibition was seen.6. The tidal volume V(T) was changed in one or both lungs. During the bilateral V(T) changes, the volumes were changed simultaneously, either in the same direction (;same' V(T) changes) or in one direction in one lung and in the opposite direction in the other (;opposite' V(T) changes).7. In the bilateral ;same' V(T) changes, mutual facilitation was seen in the response of Phr; Phr (measured)/Phr (predicted) = 1.60 +/- 0.42 (s.d.), n = 8. There was only slight facilitation in the response of t(i); t(i) (measured)/t(i) (predicted) = 1.18 +/- 0.17, n = 8.8. With the bilateral ;opposite' V(T) changes, responses of t(i) and Phr were markedly and significantly reduced compared to those for the bilateral ;same' V(T) changes. During these manoeuvres significant mutual inhibition was seen in the response of t(i), and the predicted responses of Phr in general could not be correlated with the measured response.9. The responses of the phrenic ;integrals' were the same in both right and left phrenic nerves.10. Unilateral vagotomy abolished both the responses of Phr and t(i) to ipsilateral V(T) changes in the range +/- 100% of control V(T), and also the response of t(e) to ipsilateral expiratory volume changes.

Afferent Pathways↗
PubMed1981

Mast cells in the human alveolar wall: an electronmicroscopic study.

Mast cells were identified by electronmicroscopy in the alveolar wall of the lung in 20 subjects (10 normal, 10 abnormal). A quantitative and qualitative study was made of the mast cells. In the normal lung there was an average concentration of 350 mast cells/mm2 of alveolar wall and in the abnormal 523/mm2. Mast cells occupied approximately 1.6-2.1% of the area of the alveolar wall. There was marked variation in the structure of the mast cell granules but no differences between those in the normal and abnormal lungs. There was evidence that constant degranulation of mast cells may be occurring in the lung. The role that alveolar mast cells may play in the vasoconstrictor response to alveolar hypoxia is discussed. It is suggested that the tachypnoea present in asthma may partly be due to release of mediators from sensitised mast cells within the alveolar wall.

Aged↗
PubMed1980

The role of vagal afferent information during inspiration in determining phrenic motoneurone output.

Dogs were anaesthetised, paralysed and artifically ventilated using ramp inflations triggered by the onset of the 'integrated' phrenic signal. VT was initially adjusted to maintain a constant PaCO2 and the duration of inflation (TI(resp)) was adjusted to match the phrenic TI. With these control values of VT and TI(resp) a variety of experimental manoeuvres were performed to alter the pattern of volume information delivered during inspiration. These manoeuvres included: (1) alterations in VT while maintaining a constant TI(resp); (2) alterations in TI(resp) alone, with and without obstruction to expiration; (3) delays in the onset of inflation with and without a simultaneous reduction in TI(resp) and (4) the imposition of two inflations, each with the same reduced TI(resp) within the same inspiration. The results suggest that the pattern of vagally-mediated volume information during inspiration determines both the shape and the duration of phrenic motoneurone output. The importance of volume at inspiratory 'offswitch' as the sole determinant of TI is therefore denied. The rate of inflation was not found to contribute to the responses obtained.

Afferent Pathways↗
PubMed1980

Diazepam in the treatment of dyspnoea in the 'Pink Puffer' syndrome.

Diazepam, in moderate doses, has been used in a placebo controlled, single blind study to treat dyspnoea in four patients severely disabled from chronic airflow obstruction. The subjects had the 'pink puffer syndrome', usually associated with emphysema and were not hypercapnoeic nor severely hypoxic at rest. With diazepam, they experienced a striking reduction in dyspnoea, and an improvement in effort tolerance; in addition the slope of the ventilation/CO2 response curve was reduced. There were no changes in resting blood gases. Psychiatric examination at the end of the study did not reveal prominent anxiety, although three patients were depressed. The use of diazepam to treat dyspnoea in this syndrome is safe in the absence of any acute infection

Aged↗