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Biomedical subjects

R G Williams

Publications and source records attributed to R G Williams.

At least 163 records · Page 9Linked to original sources
PubMed1980

The hemodynamic effects of dopamine in infants after corrective cardiac surgery.

The hemodynamic effects of dopamine were measured during the immediate postoperative period in five infants with low cardiac output following repair of congenital cardiac defects. Dopamine was administered at doses of 5, 10, 15, 20 and 25 micrograms/kg/minute. Heart rate, systemic arterial pressure, and cardiac index increased significantly at a dose of 15 micrograms/kg/minute or greater. There were no significant changes in right atrial pressure, left atrial pressure, pulmonary artery pressure, pulmonary vascular resistance, systemic vascular resistance, or stroke volume. These data support the hypothesis that inants respond to dopamine in a fashion qualitatively and quantitatively different from that in adults.

Blood Pressure↗
PubMed1980

Low-attenuation lesions in the middle cranial fossa: differential diagnosis.

The reliability of cranial computed tomography (CT) in detecting a broad range of intracerebral disorders has been well established (1) and its complementary role with other neuroradiologic procedures has been documented (2). Some attempts at inferring specific histologic diagnosis from static CT scans have been made (3,4). However, other investigators have demonstrated that it is difficult to separate cystic from noncystic, benign from malignant, and neoplastic from non-neoplastic lesions by absorption coefficients alone (5,6). While initial studies utilizing dynamic CT scanning indicate that patterns of contrast accumulation may be helpful in distinguishing enhancing cerebral lesions (7,16), the differential diagnosis of the low-attenuation lesion remains difficult (17). We present a series of hypodense lesions in the middle cranial fossa that demonstrate a broad range of pathologic entities. Their CT features, differential diagnosis, and pathologic correlation are discussed.

Arachnoid↗
PubMed1980

Medical student use of objectives in basic science and clinical instruction.

The purpose of this study was to investigate the long-term use of objectives by medical students who were experienced with objectives and immersed in a basic science and clinical curriculum referenced to objectives. The investigators examined: the extent to which medical students used objectives, the manner in which they used objectives as they progressed through the curriculum, and the factors that influenced their use of objectives. Questionnaires mailed to two classes of students yielded a 77 percent (n = 103) response rate. Students reported that objectives were essential early in the curriculum, but they became gradually less useful as the curriculum proceeded. The two factors showing most influence on the students' use of objectives were the relation of objectives to testing and the quality of the objectives. Curricular implications and questions to be addressed in future research were discussed.

Curriculum↗
PubMed1980

Antagonism of 5-hydroxytryptamine receptors by quipazine.

1 The antagonist actions of quipazine on 5-hydroxytryptamine (5-HT) receptors have been investigated in the rabbit isolated superior cervical ganglion and on the rat isolated spinal cord and stomach strip. 2 Changes in membrane potential induced by 5-HT or by the nicotinic agonist, 1,1-dimethyl-4-phenyl piperazinium (DMPP), were measured in the ganglion by the sucrose-gap technique. At ganglionic receptors, quipazine had little or no agonist activity, but greatly depressed depolarizations evoked by 5-HT but not depolarizations evoked by DMPP or trimethylammonium (TMA). Injections into the superfusion stream to the ganglion of 2 to 5 mumol quipazine in a small volume of Krebs solution prevented all subsequent responses to 5-HT. Superfusion of the ganglion with quipazine at a concentration of 1 microM produced complete blockade of responses to 5-HT in 3 of 6 ganglia and reduced responses by over 90% in 2 others; responses to DMPP were potentiated in amplitude and duration. Superfusion at a concentration of 0.1 microM depressed responses to 5-HT by 75% on average. The threshold concentration for the blocking action was around 0.01 microM, which depressed responses by 42% on average in 6 experiments (range 0 to 75%). 3 5-HT (1 microM or 100 microM) depressed the amplitude of the dorsal root potentials recorded from the isolated, hemisected cord of the neonate rat by 27 +/- 5% (mean +/- s.e. mean, n = 14) and by 45 +/- 6% (n = 14), respectively. In the presence of quipazine (0.01 microM), 5-HT (1 microM or 100 microM) depressed the amplitude by 6 +/- 2% (n = 15) and by 3 +/- 1% (n = 7), respectively. 4 Concentration-response curves of the contractions induced by 5-HT in the fundus of the rat stomach were obtained in the absence and presence of quipazine. Quipazine (1 microM) shifted the concentration-response curve to the right and depressed the maximum, suggesting a non-competitive mode of antagonism. pI50 values were calculated in order to assess the antagonist activity of quipazine at rat fundus 5-HT receptors; the mean pI50 was 6.91 +/- 0.2 (n = 6). 5 It is concluded that quipazine may be an effective antagonist at 5-HT receptors in various tissues.

Animals↗
PubMed1980

Prospective identification of ventricular septal defects in infancy using subxiphoid two-dimensional echocardiography.

The objective of this study was to establish a dependable technique for imaging the interventricular septum and ventricular septal defects in infants. Subxiphoid two-dimensional echocardiograms were performed on 81 infants who were 1 day to 12 months (median 43 days) old and weighed 1.6-8.6 kg (median 3.4 kg). A short-focus, 5-MHz crystal with a 13-mm active element diameter was used in all studies. The interventricular septum was visualized in 80 of 81 infants. Defects in the membranous, atrioventricular canal, conoventricular and muscular segments of the sentum were identified using three standard transverse subxiphoid projections. All defects in the membranous and atrioventricular canal segments, as well as malalignment type conoventricular communications, were correctly identified when compared with selective angled cineangiocardiography. Only two of the three subpulmonic and four of 11 muscular defects were identified successfully. Limitations in imaging defects in the muscular septum reflected the varied morphology of these interventricular communications and the tangential orientation of the echo beam to the extreme apical and anterior segments of the muscular septum.

Airway Obstruction↗
PubMed1980

Rationing: how it is done with community services for the older disabled.

A number of studies have estimated the prevalence of needs for long-term community services. However, these needs inevitably exceed the services available, and little has been done to show how the supply of services is actually rationed. In 1973, allocations were studied among the patients of a well-provided rural group practice. All those aged 65 and over who had, on a fixed date, been receiving home help, home nursing, meals service, or day care in the previous two months were interviewed (N = 145), together with a comparison group composed by a 1 in 6 random sample of practice patients in the same age group (N = 149). The needs regularly considered by local agents of referral were analysed and ordered by severity. Assuming that a less severe category of cases was not normally accepted in the place of more severe categories known to be waiting, it was possible to show what categories of cases constituted a normal claim on services at this level of resources, together with the numbers of these cases per 1000. The method used is suitable for comparing the rationing process in areas with different levels of resources or needs, and for identifying the categories who suffer as a result of a given difference of resources.

Aged↗
PubMed1979

Normal anatomy and limitations in CT interpretation of lymph node disease.

The CT appearance of normal retroperitoneal lymph nodes has been described. In many instances the structures are too small to be identified. other retroperitoneal structures, such as collapsed bowel loops, vessels, and other perirenal structures, may simulate the presence of nodes. CT is of great benefit in disease with bulky tumors, such as non-Hodgkin's lymphoma, testicular tumors, etc. Its usefulness is much more limited in disease that may have extensive nodal involvement but no significant enlargement of the nodes. The accuracy of CT scanning in Hodgkin's disease and in many instances of genitourinary tumors is questioned, and we submit that further studies are needed to establish the reliability of this mode of examination.

Adult↗
PubMed1979

Subxiphoid two-dimensional imaging of the interatrial septum in infants and neonates with congenital heart disease.

The interatrial septum (IAS) was studied by subxiphoid two-dimensional echocardiography (S2DE) in 88 infants under 12 months of age who weighed 1.2-9.1 kg. The IAS was adequately displayed in 87 of 88 patients. The morphology, presence and localization of defects in the IAS were evaluated by S2DE and retrospectively related to the findings at cardiac catheterization. In seven patients with no interatrial communication at cardiac catheterization, the IAS was straight, with an area of central thinning corresponding to the veil-like cover of the septum primum over the foramen ovale. The morphology of the IAS with a stretched, patent foramen ovale (56 patients) indicated the coexistence of a right or left ventricular volume or pressure overload, and was readily distinguishable from the IAS with a secundum type communication (13 patients). In patients with a stretched, patent foramen ovale and left ventricular overload lesions, the IAS was a nearly homogenous, curvilinear structure bowing into the right atrium, with a small area of septal dropout at the superior rim of the septum primum. In the presence of right ventricular overload lesions, the central defect of the foramen ovale was associated with a redundant flap valve of the septum primum billowing into the left atrium. In secundum type communications, the centrally located defect represented a deficiency rather than a redundancy of the septum primum. Balloon atrial septostomy (BAS) in 17 patients produced a secundum-type defect bordered by the flail remnants of the torn septum primum. Blalock-Hanlon septectomy (two patients) resulted in a large, posterior, sinus venosus-type communication which incorporated the preexisting BAS. Ostium primum defects (seven patients) were distinguished from the secundum lesions by their eccentric position in the IAS adjacent to the atrioventricular ring.

Cardiac Catheterization↗
PubMed1979

Prospective diagnosis of d-transposition of the great arteries in neonates by subxiphoid, two-dimensional echocardiography.

Subxiphoid, two-dimensional echocardiograms (S2DE) were performed and interpreted before diagnostic cardiac catheterization on 59 neonates who weighed 1.3--6.0 kg (median 3.3 kg) and were 1--35 days old (median 4.5 days). The echocardiographic studies were successfully performed on 58 of 59 infants. Using appropriate longitudinal and transverse projections, S2DE permitted simultaneous visualization of the branch pulmonary arteries, proximal thoracic aorta and ventriculoarterial attachments. D-transposition of the great arteries was correctly predicted in all 16 infants with levocardia, situs solitus and atrioventricular concordance. In these patients, the standard left ventricular longitudinal projection demonstrated the bifurcating main pulmonary artery attached to the posterior ventricle; the transverse projection displayed the relationship of the proximal thoracic aorta to the anterior ventricle. The broad acoustical window using the subxiphoid approach in conjunction with a high-frequency focused transducer and a large active-element diameter permitted detailed imaging of intra- and supracardiac structures.

Aorta, Thoracic↗
PubMed1979

Unusual features of pulmonary sling.

Patients with an anomalously placed left pulmonary artery ("pulmonary sling") typically have signs and symptoms of respiratory obstruction in the neonatal period. Experience with four previously unreported patients confirmed this. Typical radiographic features include unilateral air trapping (usually on the right side), an abnormal position of the esophagus, and a soft tissue mass interposed between the trachea and esophagus. Less common findings include a normal esophageal position, left-side air trapping, and delayed egress of neonatal pulmonary fluid. Both typical and atypical features were seen; the more unusual aspects are emphasized.

Apnea↗
PubMed1979

A forced-choice procedure to detect feigned or exaggerated hearing loss.

A forced-choice technique which may be used to confirm the existence of a non-organic hearing loss is described. Evidence is presented which shows that although this technique is not infallible it can in many cases unmask attempts to simulate or exaggerate a hearing loss. Supplementary tests using conventional audiometry demonstrated that persons with normal hearing can consistently feign a bilateral hearing loss.

Hearing Loss↗
PubMed1978

Low attenuation lesions in the midline posterior fossa: differential diagnosis.

A wide variety of cystic appearing or low attenuation lesions in the midline posterior fossa can so closely resemble one another as to render specific histologic diagnosis from CT scans alone fraught with error. Absorption coefficients often overlap and are too nonspecific to infer consistently accurate histologic diagnosis. It is virtually impossible to separate cystic from noncystic, benign from malignant, and neoplastic from non-neoplastic lesions by absorption coefficients alone.

Brain↗