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Biomedical subjects

D R Jones

Publications and source records attributed to D R Jones.

At least 343 records · Page 19Linked to original sources
PubMed1979

Projections from cortex to tectum in the tree shrew, Tupaia glis.

Sensory neocortex of the tree shrew was divided into three main areas: the visual field, the auditory field, and the somatic field which includes motor cortex. Cortical cells which project to the tectum were identified by injecting HRP into superficial or deep layers of the superior colliculus and into various parts of the inferior colliculus. The main result is that these descending projections are well organized according to their origin in the three main sensory fields of the cortex. (1) Auditory field: labeled cells are found only in the core or auditory koniocortex, after injections of HRP in the pericentral area of the inferior colliculus; labeled cells are found in auditory belt areas after injections in posterior parts of the intermediate and deep layers of the superior colliculus, adjacent to the inferior colliculus. (2) Somatic field: labeled cells are also found in the somatic field after injections in the intermediate and deep layers of the superior colliculus, so that auditory and somatic fields probably overlap to some extent. The results do not exclude the possibility that somatic koniocortex has an exclusive target in the intermediate or deep layers of the superior colliculus. (3) Visual field: labeled cells are found only in the core or striate cortex after injections in the superficial layers of the superior colliculus. Labeled cells are found in the visual belt after injections in the rostral parts of the intermediate layers of the superior colliculus. When these results are related to ascending sensory pathways a picture emerges of a series of circuits or loops which interconnect parallel sensory pathways. These loops eventually reach the deep layers of the superior colliculus which of course have indirect access to motor neurons.

Animals↗
PubMed1979

Computer simulation as a tool for clinical trial design.

Use of a computer simulation technique as a tool for optimising the design of a clinical trial is described. One of several aspects of trial design facilitated by use of the technique is the estimation of the number of patients required in the trial. The simulation tool provides the basis for structured and disciplined discussion of all the issues to be considered in designing a trial. Copies of the simulation program are available from the author.

Clinical Trials as Topic↗
PubMed1979

Pulmonary receptor chemosensitivity and the ventilatory response to inhaled CO2 in the turtle.

Ventilatory responses of unanesthetized turtles to changes in the intrapulmonary CO2 content of a vascularly isolated and an intact lung were measured during spontaneous breathing. The hyperpnea associated with inhalation of CO2 by the vascularly isolated lung was 19% of that associated with inhalation of CO2 by the intact lung. Transection of the vagus nerve supplying the isolated lung abolished this response. We conclude that both inhibition of pulmonary stretch receptor discharge with increasing levels of FICO2 and a functional increase in central inspiratory volume threshold during hypercapnia contribute to tidal volume increases following CO2 inhalation in normal animals. The major component of the ventilatory response of intact turtles to increasing levels of FICO2, however, was an increase in respiratory frequency. When CO2 was inspired only by the vascularly isolated lung the increase in respiratory frequency was only 21% of that recorded when the same levels of CO2 were inspired by the intact lung. Thus the ventilatory response of turtles to increasing levels of FICO2 is primarily dependent upon concomitant hypercapnia.

Animals↗
PubMed1979

Mental health of medical school applicants: the role of the admissions committee.

This study was of the role of admissions committees as it relates to the mental health of applicants. Two-part questionnaires were sent to 115 medical schools. The first part explored the composition of the committee. In most schools the dean selected the members, attempting to obtain equal representation from clinical and basic science departments; most of the schools had one or more psychiatrists on the committee. The second part focused on the policy for applicants with former mental health problems. Over one-third of the committees asked about previous or present mental illness or therapy. Ninety percent of the schools had no policy or guidelines for using such information; instead, most relied on psychiatric interview or outside reports in making admissions decisions. The impact of federal legislation regarding the handicapped on admissions procedures is discussed. Since more students with previous or current psychiatric problems may be admitted, schools must be prepared to respond to their needs as fully as they now respond to other medical problems.

Educational Measurement↗
PubMed1979

The initiation and maintenance of bradycardia in a diving mammal, the muskrat, Ondatra zibethica.

1. The cardiac and respiratory responses shown by muskrats in both unrestrained and restrained dives have been compared with responses elicited by stimulation of a number of cardio-depressant receptor inputs, in an attempt to determine which are most important in initiating and maintaining diving bradycardia. 2. In unrestrained voluntary dives heart rate fell from 310 +/- 3 to 54 +/- 3 beats min-1 in 1 to 2 sec, which was significantly below that seen in dives by restrained unanaesthetized or anaesthetized animals. 3. Pouring water on the external nares during maintained artificial ventilation caused heart rate to decline to 76 +/- 12 beats min-1 after 1 sec. Flowing water through the internal nares caused apnoea, in the expiratory position, and bradycardia within one third of a second. Heart rate fell to 20 +/- 2 beats min-1, 1 sec after the start of water flow. Substituting saline for water reduced both the apnoeic and cardiac responses. Bilateral section of the maxillary branch of V and the inferior laryngeal (X) nerves completely abolished the cardiac and respiratory response to water flow. 4. Artificial ventilation throughout periods of nasal stimulation with water or saline reduced the bradycardia, although even the saline driven response could not be completely abolished. Lung deafferentation eliminated any direct effect of artificial ventilation on heart rate during nasal stimulation. 5. Lung deflation caused bradycardia within 0.97 +/- 0.17 sec, heart rate falling from 268 +/- 7 to 59 +/- 4 beats min-1. Bradycardia also occurred during maintained lung inflation but it was delayed for a period which varied from 6.8 +/- 1.8 sec at an inflation pressure of 0.5 kPa to 35 +/- 7 sec at 1.5 kPa. 6. Bradycardia caused by nasal water flow or lung deflation was unaffected by bilateral section of the sinus nerve. 7. Artificial ventilation of paralysed muskrats with 5% CO2 in N2 caused bradycardia when Pa, O2 reached 8.4 +/- 0.8 kPa and heart rate declined to 76 +/- 7 beats min-1 at 4 kPa. Bilateral section of the sinus nerve delayed bradycardia until Pa, O2 reached 4.5 +/- 0.5 kPa. 8. These results suggest that the cardiac response to submergence could be the expression of input from three groups of receptors, nasal, lung and carotid chemoreceptors, although it is not clear how they interact with one another to generate the cardiac responses displayed by unrestrained animals during submergence.

Animals↗
PubMed1979

Functional characteristics of slowly adapting pulmonary stretch receptors in the turtle (Chrysemys picta).

1. Single nerve fibre discharge has been recorded from slowly adapting pulmonary stretch receptors in single-pithed turtles on artificial ventilation. 2. Receptor discharge during static and dynamic lung inflations showed that lung volume was the major stimulus of these receptors. The rate and degree of change in transpulmonary pressure were without direct effect. 3. The response of these receptors to static and dynamic lung inflation differed only quantitatively from those of bronchopulmonary stretch receptors in mammals. The lower discharge frequencies and sensitivities of the turtle receptors may arise from the low body temperature of these animals. 4. The sensitivity of turtle pulmonary receptors to CO2 was greater than that recorded for bronchopulmonary receptors of mammals although the effects of CO2 on receptor discharge were qualitatively similar. In several instances, receptor discharge was totally inhibited throughout the ventilatory cycle by inflation with 5--10% CO2 in air.

Action Potentials↗
PubMed1979

A method of intrarenal blood flow measurement using xenon-133 in the intact rat.

A method is described for measuring distribution of intrarenal blood flow in anesthetized rats by a xenon-133 washout technique that avoids the trauma of opening the abdominal cavity and manipulating the kidney. Precise delivery of the tracer to the kidney and fine collimation of the radiation reduces the amount of tracer required. Washout curve analysis is achieved by a multifit computer program that accepts only count rates and time as input data.

Animals↗
PubMed1979

Assessment of left ventricular ejection fraction and volumes by real-time, two-dimensional echocardiography. A comparison of cineangiographic and radionuclide techniques.

Five different algorithms for determining left ventricular (LV) ejection fraction (EF) and volumes from two-dimensional echocardiographic examination (TDE) were compared with standard methods for obtaining EF and volume from x-ray cineangiography (cine) and EF from radionuclide ventriculography (RVG) in 35 patients. Although all methods correlated positively, the degree of correlation varied with the algorithm used. For EF determination, TDE algorithms (especially those using multiple planes of section) were superior to unidimensional algorithms commonly used with M-mode echocardiography. The best algorithm (modified Simpson's rule) correlated well enough with cine EF (r = 0.78; SEE 0.097) and RVG EF (r = 0.75; SEE 0.087) to make clinically useful estimates. TDE volumes also correlated meaningfully with cine end-diastolic and end-systole volumes (r = 084; n = 70) but were associated with a large standard error of the estimate (43 ml) and offered less advantage over unidimensional volume estimates. Quantitative application of TDE appears to be a useful noninvasive method of evaluating LVEF, but is not as useful for estimating LV volumes.

Cineangiography↗
PubMed1979

Drugs and prescribing: what the patient thinks.

Two hundred and forty-one patients, 173 females and 68 males, completed questionnaires designed to identify their knowledge of drugs and attitudes to doctors' prescribing behaviour. These results were compared with those of 35 ancillary staff, 277 schoolchildren, 55 student nurses, 69 medical students, and 78 general practitioners. Although over 80 per cent of patients thought that heroin was a drug, only 10 per cent thought that penicillin should be so classified. Only two per cent of patients thought it was safe for doctors to prescribe without first seeing the patient, although 80 per cent of general practitioners thought that this was sometimes acceptable.Seventy per cent of doctors thought that antibiotics, tranquillizers, hypnotics, and antidepressants were over-prescribed and nearly half the patients appeared to agree with them.More patients thought that antibiotics were designed to kill viruses than bacteria, over a quarter thought that these preparations were the best form of treatment for a cold, and almost half expected diarrhoea to be treated with an antibiotic.Doctors need to spend more of their time in simple health education. By doing so they could reduce their future workload and the nation's drug bill.

Attitude↗
PubMed1978

Smoking and risk factors in deep vein thrombosis.

The incidence of deep vein thrombosis (DVT) as diagnosed by the 125I fibrinogen test (125IFT) was determined in a series of 300 newly admitted medical and 201 surgical patients. 6 medical patients died before 125IFT screening could be completed. The incidence of DVT was 14% in medical patients and 18% in surgical patients. Increasing age, a malignant condition and a past history of thromboembolism all increased the risk of DVT. Increasing levels of cigarette smoking were found to be associated with a reduced incidence of DVT. Although statistical significance was achieved at only the 10% level for this finding it is in agreement with the results from studies on patients with myocardial infarction. The protective effect of cigarrette smoking was observed at all ages, and in both medical and surgical patients.

Adult↗
PubMed1978

Blood pressure and vascular resistance in genetically hypertensive rats treated at birth with 6-hydroxydopamine.

Genetically hypertensive (GH) rats of the New Zealand strain and normotensive (N) rats were sympathectomized from birth with 6-hydroxydopamine (100 mg/kg,s.c, on alternate days, seven treatments). In adult treated rats from each strain (GHTr and NTr), blood pressure was lower than normal. Functional tests and electron microscopy showed that denervation was virtually complete in mesenteric and hindlimb arteries; the innervation of the renal artery was little affected. Ganglionic blockade still caused a large fall in blood pressure in treated rats. Vascular resistance was higher in blood-perfused hindlimbs and tails of GH rats than in those of N rats; in contrast, resistance was similar in limbs and tails of GHTr and NTr rats and was greater than that found in untreated N rats. Saline-perfused limb vessels had neither neurogenic nor myogenic tone and resistance was higher in GH limbs (whether these were from treated rats or not) than in untreated N limbs. In saline-perfused NTr limbs, there was a paradoxical structural adaptation (probably luminal narrowing) of the hindlimb blood vessels and resistance was higher than in untreated N rats. The resistance of saline-perfused GH and GHTr limbs was similar. A high peripheral resistance appears to be the main mechanism sustaining genetic hypertension, and the integrity of the vasomotor sympathetic nerves is necessary for the development of this form of experimental hypertension.

Animals↗