Search PubMed⌕ Search

Biomedical subjects

J R Foster

Publications and source records attributed to J R Foster.

At least 127 records · Page 7Linked to original sources
PubMed1980

Use of the respiratory magnetometer in diagnosis and classification of sleep apnea.

Seventeen patients with sleep apnea were studied with reference to the frequency and duration of apneic episodies, the mechanism of the apnea and the extent to which oxygen saturation was depressed by the apnea. In all patients, esophageal pressure was recorded simultaneously with respiratory magnetometer records of rib cage and abdominal motion. Thermistor records from the nose and mouth indicated the presence of apnea. Nine patients had purely obstructive apnea and eight a mixture of central and obstructive apnea. In all instances the magnetometer records alone permitted distinction between obstructive and central apnea. Inspiratory efforts against an occluded airway produced a very different pattern of motion when compared to unobstructed breathing or to central apnea. We propose that magnetometer monitoring of thoracoabdominal motion indicates upper airway obstruction reliably and provides a noninvasive and thus more acceptable alternative to esophageal pressure recording for detecting upper airway obstructive apnea.

Airway Obstruction↗
PubMed1978

Study of the temporal effects on conduction and refractoriness of the His-Purkinje system in man.

Temporal effects on refractoriness within the His-Purkinje system (HPS) were studied in 14 patients in whom effective refractory period (ERP) of HPS could be determined, using His bundle electrograms, incremental atrial pacing, and atrial extrastimulus method. His-Purkinje conduction times (H-V interval) and relative (R), effective (E), and functional (F) refractory periods (RP) of HPS were measured during the control period and repeat measurements were made after a 30 minute interval. H-V intervals were unchanged from control in all patients. Although changes of the magnitude of 5 to 25 msec. in either direction from control values commonly occurred, on the average, no statistically significant changes were seen in RRP, ERP, or FRP of HPS. The results of the present study confirm the stability of refractoriness of HPS over a 30 minute period and provide baseline data for future investigations of cardiovascular drugs which act primarily on the distal part of the A-V conduction system.

Adult↗
PubMed1978

Additional evidence for re-entry within the bundle branches in man.

A repetitive, non-paced ventricular beat (V3) often occurs during ventricular extrastimulus testing at short coupling intervals when critical retrograde His-Purkinje conduction delay is achieved. Though re-entry within the bundle branches has been proposed as the mechanism for V3, it has been difficult to exclude local re-entry. In the present case, we consistently recorded a right bundle branch potential as well as a bundle of His potential before each V3. The anterograde activation sequence of these potentials provides evidence against local re-entry and supports re-entry involving the bundle branches as the mechanism for V3.

Arrhythmias, Cardiac↗
PubMed1978

Dual echocardiographic determination of atrial contraction sequence in atrial flutter and other related atrial arrhythmias.

We have applied the new technique of dual echocardiography to determine the sequence of atrial contraction as reflected in the simultaneously recorded movements of the tricuspid and mitral valves. The study group included 29 normal subjects and 23 patients with either atrial flutter, coarse atrial fibrillation or atrial tachycardia with block. In normal individuals, right atrial contraction preceded left atrial contraction, with an average interatrial contraction time of 17 +/- 8 msec. In contrast, the atrial contraction sequence was reversed in atrial flutter, with left preceding right atrial contraction and a prolonged interatrial contraction time of 82 +/- 20 msec. In two patients with atrial tachycardia with block, atrial contraction was either simultaneous or left preceded right atrial contraction by a brief interval. The sequence of atrial excitation, as determined by electrode catheter recordings from the right and left atria in one patient with atrial flutter and one patient with normal sinus rhythm, was the same as the contraction sequence. Left atrial pacing reversed both excitation and contraction sequences. After cardioversion of three patients from atrial flutter to normal sinus rhythm, interatrial contraction time was shortened but remained longer than in normal subjects, suggesting an interatrial conduction disturbance in patients with atrial flutter. In coarse atrial fibrillation, the contraction sequence varied. Significant motion of both mitral and tricuspid valves coincident with fibrillary waves occurred frequently, especially when the fibrillary waves were coarse and regular. Dual echocardiography permits the noninvasive determination of the sequence of atrial contraction and excitation, and may be useful in studying the characteristics of atrial arrhythmias.

Atrial Fibrillation↗
PubMed1977

Lithium treatment in the elderly. I. Clinical usage.

Clinical use of lithium salts in manic states in the elderly is reviewed. Special problems with toxicity are discussed. A dose titration method that has been safely used for 10 years is presented and illustrated with case material. Lower blood levels than usually advised are recommended.

Aged↗
PubMed1977

Interaction of aortic pressure and left ventricular end-diastolic pressure in the dog.

Fiber length (preload) is an important determinant of left ventricular performance. Mean aortic blood pressure also influences ventricular performance. The present study was undertaken to examine the influence of mean aortic pressure on the fiber length-ventricular performance relationship. Fifteen anesthetized, adrenergically blocked dogs were studied on right-heart bypass at constant heart rate and coronary blood flow. An increase in mean aortic pressure permitted a greater improvement in performance as evaluated by stroke work for a given increase in left ventricular end-diastolic pressure. A given increase in mean aortic pressure at a constant stroke volume produced a greater rise in stroke work over intermediate ranges of left ventricular end-diastolic pressure than occurred with higher or lower left ventricular end-diastolic pressure. Thus, the degree of afterload-induced performance improvement depended on the magnitude of the preload. External circumference-left ventricular end-diastolic pressure data suggested a possible relationship between isovolumic systolic circumferential expansion and the improvement of ventricular performance at higher mean aortic pressures.

Animals↗
PubMed1976

Interventricular septal motion during preexcitation and normal conduction in Wolff-Parkinson-White syndrome: echocardiographic and electrophysiologic correlation.

Interventricular septal motion was studied by echocardiogram in 20 consecutive patients with documented Wolff-Parkinson-White (WPW) syndrome before and during electrophysiologic evaluation using His bundle recordings and pacing techniques. Characteristic abnormal interventricular septal motion was seen in 8 of 11 patients with type B WPW syndrome (groups I and II). All eight patients had electrocardiographic patterns consistent with an anomalous pathway located in the anterior right ventricular wall (group I). In five of these eight patients normalization of the QRS complex for one or more beats was accomplished and produced normalization of the septal motion in four; whereas in the fifth patient, who had an underlying atrial septal defect, the abnormal septal motion remained abnormal. All nine patients with type A WPW syndrome (groups III to V) had normal septal motion both during total preexcitation and during normalization of the QRS complex. The normalization of the abnormal interventricular septal motion with normalization of the QRS complex in type B WPW syndrome strongly suggests that the abnormal motion is related to an abnormal sequence of ventricular depolarization during preexcitation. Furthermore, persistent abnormal septal motion after normalization of the QRS complex suggests that other factors such as right ventricular volume overload may be responsible. Likewise, when abnormal septal motion occurs in the presence of type A WPW syndrome, an explanation other than preexcitation must be sought.

Adolescent↗
PubMed1976

Congenitally corrected transposition of the great vessels: localization of the site of complete atrioventricular block using his bundle electrograms.

Complete atrioventricular block proximal to the bundle of His in a patient with congenitally corrected transposition of the great vessels was documented using His bundle electrograms. The spontaneous rhythnm probably originated from the bundle of His and was responsive to carotid sinus massage, atropine and isometric and treadmill exercise. These electrophysiologic observations are consistent with recent anatomic studies of congenitally corrected transposition of the great vessels.

Adult↗
PubMed1976

Interaction of interval-force relationship with aortic pressure and stroke volume.

The modification by aortic pressure and stroke volume of the response in cardiac performance to increases in heart rate (interval-force relationship) has not been previously studied. To investigate this interaction, 30 adrenergically blocked anesthetized dogs on right heart bypass were studied. At constant low aortic pressure and stroke volume, increasing heart rate (over the entire range 60-180) is associated with a continuously increasing stroke power, decreasing systolic ejection period, and an unchanging left ventricular end-diastolic pressure and circumference. At increased aortic pressure or stroke volume at low rates (60-120), increases in heart rate were associated with an increased performance. However, at increased aortic pressure or stroke volume at high rates (120-180), increases in heart rate were associated with a leveling or decrease in performance. Thus, an increase in aortic pressure or stroke volume results in an accentuation of the improvement in cardiac performance observed with increases in heart rate, but this response is limited to a low heart rate range. Therefore, the hemodynamic response to given increases in heart rate is critically dependent on aortic pressure and stroke volume.

Animals↗
PubMed1975

To die young, to die old management of terminal illness at age 20 and at age 85: case reports. Death and dying in a 20-year-old woman.

An effort was made to provide emotional support during the terminal phase of leukemia in a 20-year-old woman. Notable were the patient's own ways of coping and the responses of her family and the hospital staff. She first denied and then recognized her own dying. Her anger was prominent, and she withdrew from objects toward the end. The intense stresses in the doctor-patient relationship, transference, countertransference, and reality factors are described.

Adaptation, Psychological↗
PubMed1969

Ageing and the regulation of cell activities during exposure to cold.

The inability to maintain body temperature and a selective pattern of changes in the regulation of cell activities were revealed by briefly exposing ageing C57B1/6J male mice to cold (10 degrees C). The induction of liver tyrosine aminotransferase (TAT) during exposure to cold (a gene-dependent process) was markedly delayed in senescent mice (26 months old) as compared with younger mice (3-16 months old); after the delay, the rate of increase of TAT was similar to that prevailing in younger mice. Direct challenge of the liver with injections of corticosterone or insulin elicited the induction of TAT on an identical time course in young and senescent mice. These experiments provide an example of an age change in a gene-dependent cell process (the delayed induction of TAT in senescent mice during exposure to cold) which is not due to a change in the potential of the genome for responding when exogenous stimulae are supplied (injection of hormones). In contrast to the age-related change in liver cell activities, no significant changes were found in the secretion of corticosterone during exposure to cold. Although the seat of these selective age-related changes in the regulation of cell activities remains unclear, it is argued that generalized damage to the genome of cells throughout the body is not involved. The results of this and other studies showing the selective effect of age on cell activities are considered in terms of the concept that many cellular age changes represent the response of cells to primary age-related changes in humoral factors in the internal environment of the body.

Adrenal Glands↗
PubMedDate not supplied

Effects of p-nonylphenol (NP) and diethylstilboestrol (DES) on the Alderley Park (Alpk) rat: comparison of mammary gland and uterus sensitivity following oral gavage or implanted mini-pumps.

An earlier report by Colerangle and Roy indicated that administration of p-nonylphenol (NP) to Noble rats, via subcutaneously implanted mini-pumps at estimated doses of 53.2 and 0.073 mg kg(-1) day(-1) for 11 days, led to proliferation of the mammary gland. Those results indicated a ca. 600-fold enhancement in assay sensitivity to NP over that of the standard 3-day rat uterotrophic assay. The potential importance of these observations led us to repeat the experiments in the Noble rat, as described earlier. Although our earlier results confirmed the reported effects of diethylstilboestrol (DES) on the mammary gland of Noble rats, we found no effects with NP. The present report extends our investigations of the effects of NP and DES on the mammary gland and uterus of other rat strains using both oral dosing and exposure via mini-pumps. The 3-day oral uterotrophic assay responses to NP were similar for immature Alderly Park (Alpk; Wistar-derived) and immature Sprague-Dawley rats. Likewise, oral administration of NP to ovariectomized Alpk rats for 11 days gave responses of a similar magnitude to those seen in the 3-day immature assays and in earlier 3-and 11-day oral assays conducted using Noble rats. Administration of NP via mini-pumps to ovariectomized Alpk rats, at the implant doses employed by Colerangle and Roy, gave a negative uterotrophic response. The highest achieved dose levels of NP in the implant experiment (27 mg kg(-1) day(-1)) were lower than in the above assays and the negative response was therefore consistent with the previously defined minimum detection level for NP in the uterotrophic assay of ca. 40 mg kg(-1) day(-1) day(-1). It is concluded that the uterotrophic activity of NP is independent of the strain of rat, the duration of dosing and the route of exposure. Two mammary gland studies were conducted on NP and DES in the Alpk rat. In the first study (a repeat of the techniques used in earlier studies with the Noble rat), NP was administered via mini-pumps (achieved doses of 0.052 and 37.4 mg kg(-1) day(-3) NP) and produced no effect on mammary gland development, whereas DES gave the expected trophic response. In the second mammary gland study, NP was administered orally to Alpk rats at 100 mg kg(-1) day(-1) for 11 days (a dose that produced a positive uterotrophic response in ovariectomized rats). In this experiment, DES, and to a lesser extent NP, increased mammary gland differentiation and cell proliferation. The present studies have demonstrated that the rat mammary gland responds predictably to oestrogenic stimulation but does not show increased sensitivity to oestrogens when compared to the rat uterus. It is also concluded that the minimum detection level for oestrogenic responses of NP in rodents, following oral, dietary and implant routes of exposure, is ca. 40 mg kg(-1) day(-1).

Administration, Oral↗
PubMedDate not supplied

Changes in the distribution of histochemically localized mercury in the CNS and in tissue levels of organic and inorganic mercury during the development of intoxication in methylmercury treated rats.

The development of neurotoxicity in rats after exposure to methylmercuric chloride was monitored using behavioural indices. At selected time points the cellular localization of mercury and the relative amounts of organic and inorganic mercury were determined in several regions of the CNS, and in some non-neural tissues. The CNS showed an affinity for organic mercury, the levels of inorganic mercury remaining low throughout symptomatic intoxication. Histopathological changes were not closely related to the regional tissue content of the organic or inorganic forms, nor to mercury localized histochemically at the cellular level. The stained deposits, which had focal cytoplasmic distribution, appeared in glial cells initially then in larger neurones as the intoxication progressed. These observations may represent changes in the mercury content of different cell types or reflect differences in the way that they handle a similar burden of mercury. A transitory accumulation of mercury in glial cells may be a factor contributing to the occurrence of a latent period and sequestration of mercury in cytoplasmic organelles may serve to protect some cell types from injury.

Animals↗