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Biomedical subjects

M A Carpenter

Publications and source records attributed to M A Carpenter.

At least 55 records · Page 3Linked to original sources
PubMed1985

Spatial contrast sensitivity: effects of peripheral field stimulation during monocular and dichoptic viewing.

This report examines whether a radial grating with a blank 2 deg central aperture viewed with one eye can affect contrast sensitivity for foveally-viewed, counterphasing or stationary, sine-wave gratings seen with the other eye. We find that the moving radial grating preferentially raises the threshold for the low spatial frequencies of the counterphasing but not the stationary foveal stimulus. These results closely parallel recent primate electrophysiological work which suggests that visual stimulation of the peripheral field with a moving radial grating can activate inhibitory corticofugal influences on lateral geniculate neurons. The current data are evaluated in terms of a model which suggests that the peripheral stimulus activates corticofugal mechanisms.

Form Perception↗
PubMed1985

Baffle obstruction following the Mustard operation: cause and treatment.

Baffle obstruction developed in 11 patients after they had undergone the Mustard procedure. Eight of them required operative revision. The cause of the baffle obstruction seemed to be related to patient age (less than 1 year) and to the use of Dacron for the baffle but not to the shape of the baffle. A technique of revision that involves widely opening the previously placed baffle and enlarging it and the atriotomy with polytetrafluoroethylene was employed for the last 6 patients. All 5 survivors of this operation had good long-term results without recurrence.

Child, Preschool↗
PubMed1985

Left ventricular hyperkinesia at rest and during exercise in normotensive patients 2 to 27 years after coarctation repair.

The short- and long-term results of effective surgical repair of coarctation of the aorta on left ventricular mass and function in 48 patients were evaluated using echocardiography and stress-gated radionuclide angiography. Thirty-two of the 48 patients who had no additional cardiac problems and had technically adequate radionuclide angiograms form the basis for this report. Among these, three had mild systolic hypertension and none had significant aortic valve dysfunction. Age at the time of study ranged from 6.5 to 59 years (mean 27). Age at the time of surgery ranged from 3 months to 34 years (mean 12 years). Duration from surgery to the time of noninvasive study ranged from 2 to 29 years (mean 15). In the 32 patients, left ventricular mass was 120 +/- 20 g/m2, compared with a control value of 87 +/- 10 g/m2. Mean left ventricular ejection fraction was elevated to 69.2 +/- 1.6% at rest (control 60 +/- 1.3%) and 78.8 +/- 1.3% during exercise (control 70 +/- 1.7%) (p less than 0.01). The systolic ejection rate was significantly increased (p less than 0.01) and end-systolic volume significantly decreased (p less than 0.01) compared with values in control patients. There was no correlation between ejection fraction and either age at the time of surgery or years since surgery. These findings of hyperdynamic left ventricular function and increased left ventricular mass without apparent cause many years after coarctation repair raise important questions as to mechanisms, extension to other forms of afterload stress that have been surgically or medically relieved and long-term outcome.

Adolescent↗
PubMed1984

Ductal origin of the left pulmonary artery in severe tetralogy of Fallot: problems in management.

Cardiac catheterization in a neonate demonstrated tetralogy of Fallot and absence of anatomic origin of the left pulmonary artery from the main pulmonary artery. A central aortopulmonary shunt was performed in order to increase pulmonary blood flow. Because of the concern that the left pulmonary artery was actually being supplied by a ductus arteriosus, repeat catheterization was performed and this revealed closure of the ductus arteriosus with obliteration of arterial supply to the left pulmonary artery. A left Blalock-Taussig shunt was subsequently performed and this reestablished blood supply to the left pulmonary artery. This case report describes problems in management of congenital heart disease with absence of anatomic origin of the left pulmonary artery from the main pulmonary artery.

Blood Vessel Prosthesis↗
PubMed1981

Congenital absence of the pulmonary valve.

Congenital absence of the pulmonary valve (CAPV) is a rare anomaly usually associated with ventricular septal defect or Fallot's tetralogy. CAPV may be rapidly fatal in infancy because of severe disturbance of pulmonary ventilation resulting from bronchial compression by massively dilated pulmonary arteries. Other cases may be relatively benign. Our group of five cases with CAPV ranged from the severe to one case in which there was documented closure of a patent ductus arteriosus and a ventricular septal defect, leaving the CAPV as an apparently isolated, well-tolerated lesion. Plain chest radiographs play a major part in the diagnosis of CAPV since they almost invariably give some indication od the aneurysmal dilatation of the pulmonary arteries. On angiography, dilated main pulmonary arteries are shown giving rise to branches of normal or even diminished caliber.

Angiography↗
PubMed1981

Individual speaker influence on relative intelligibility of esophageal speech and artificial larynx speech.

Comparisons were made of the relative intelligibility of esophageal and artificial larynx speech. Care was taken to minimize the variable effects of individual speaker characteristics. For example, rather than relying solely on data comparisons between groups of different speakers, contrasts were also made between samples from subjects who could use both means of alaryngeal speech. Fifteen proficient male laryngectomized speakers were selected. Five used only esophageal speech, five used only artificial larynx speech, and five produced both forms of speech. Recordings were made while the subjects read 50 PB (Phonetically Balanced) words embedded in a carrier phrase and were transcribed by 30 naive listeners. Differences in intelligibility between esophageal and artificial larynx speech resulted when data comparisons were based on different speaker groups. However, differences were not evident when data from the same speakers were compared. The results were interpreted to highlight the possible influence of individual speaker characteristics, rather than differences between communication methods.

Humans↗
PubMed1980

Maximum duration of sustained /s/ and /z/ in children.

It has been proposed in the clinical literature that a ratio of the maximum duration of /s/ to /z/ may be useful in determining the possible contribution of the respiratory and vocal mechanisms to a disordered voice. The purpose of this study was to obtain preliminary normative data for the maximum phoneme duration (MPD) of /s/ and /z/ and to determine the ratio of /s/ to /z/ in five, seven, and nine year olds. The results indicated that while there were no significant differences in MPD for either /s/ or /z/ between males and females at any one age level, there was a significant increase in the MPD of /s/ and /z/ for both sexes as a function of age. When the ratio of /s/ to /z/ was computed for the subjects, there were no significant differences in these ratios between males and females nor were there significant differences as a function of age.

Age Factors↗
PubMed1978

Ionized calcium and magnesium: the effect of septic shock in the baboon.

Ionized calcium (Ca2+) and ionized magnesium (Mg2+) are important intracellular "second messengers" and control exictation-contraction coupling, excitation-secretion, oxidative phosphorylation, and mitochondrial acid-base balance. The present study examines the effect of septic shock on serum (Ca2+) and (Mg2+). Five adult female baboons were subjected to live E. coli septic shock and then resuscitated. Three baboons served as controls. Ca2+ was measured by the Orion SS-20 flow-through calcium electrode and Mg2+ calculated by the method of Killen. Other measurements included: total calcium, bound calcium, total magnesium, bound magnesium, phosphate, albumin, globulin, hemotocrit, and total protein. This study shows that there are significant disturbances of Ca2+ and Mg2+ during septic shock in the baboon. These disturbances may in part explain cellular dysfunction during shock including: decreased myocardial contractility, inappropriate secretion of endocrine cells, decrease in oxidative phosphorylation, and mitochondrial acidosis.

Animals↗
PubMed1978

Ionized calcium and magnesium in the baboon: hemorrhagic shock and resuscitation.

Ionized calcium (Ca2+) and ionized magnesium (Mg2+) are important intracellular "second messengers" and control excitation-contraction coupling excitation-secretion coupling, oxidative phosphorylation, and mitochondrial acid-base balance. This study examines the effect of hemorrhagic shock on serum Ca2+ and Mg2+. Eight baboons were subjected to severe hemorrhagic shock and then resuscitated. Ca2+ was measured by the Orion SS-20 flowthrough calcium electrode and Mg2+ was calculated by the method of Killen. Other measurements included: total calcium, bound calcium, total magnesium, bound magnesium, albumin, globulin, total protein, phosphate, pH, and hematocrit. This study shows that there are significant disturbances of Ca2+ and Mg2+ during resuscitation from hemorrhagic shock. These disturbances may in part explain cellular dysfunctions during shock, including decreased myocardial contractility, inappropriate secretion of endocrine cells, decrease in oxidative phosphorylation, and mitochondrial acidosis.

Animals↗
PubMed1977

Sepsis in the baboon: factors affecting resuscitation and pulmonary edema in animals resuscitated with Ringer's lactate versus Plasmanate.

Septic shock and the formation of pulmonary edema were studied in 19 baboons. Four animals served as controls. Four were subjected to deep septic shock by infusion of live E. coli and then deliberately killed while in deep shock. Four were subjected to septic shock, resuscitated with Ringer's lactate (RL), and then killed 11/2 hours after resuscitation was started. Seven were subjected to shock and resuscitation attempted with Plasmanate (PL). Resuscitation with RL was successful for 11/2 hours in all four RL-animals. Resuscitation with PL was successful for 11/2 hours in three of the 7 PL-animals. There was an increased tendency for albumin to extravasate into the interstitium of the lungs after resuscitation. The amount of pulmonary edema, measured by both the thermodye technique and by analysis of post-mortem lung composition, was the same in animals resuscitated with RL and PL. Administration of pure colloid offers no protection to the lungs in resuscitating patients from septic shock.

Animals↗
PubMed1976

Monitoring resuscitation of primates from hemorrhagic and septic shock.

Monitoring data in 16 primates subjected to septic or hemorrhagic shock and resuscitated with various solutions is presented. From a paractical standpoint, central venous pressure and urine output appear to be the best indices to use in the emergency department for resuscitation of the shock victim. The sophisticated measurements such as cardiac output, thermodye volumes, pulmonary artery wedge pressure and oxygen consumption should be reserved for the individual with depressed cardiovascular reserves and who needs "fine tuning" of his volume status.

Animals↗