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Biomedical subjects

P Freed

Publications and source records attributed to P Freed.

13 recordsLinked to original sources
PubMed1983

On the uniqueness of cerebral blood flow measured by the in vivo autoradiographic strategy and positron emission tomography.

Factors are examined in this report which govern the uniqueness and sensitivity of regional cerebral blood flow (rCBF), as determined by an in vivo autoradiographic strategy and positron emission tomography (PET), and a series of theorems is derived which specify conditions under which a unique relationship between cumulative cranial activity of the tracer (C) and regional blood flow (f) may be assured. It is demonstrated that, independent of the specific form of the arterial tracer input function, flow is a unique function of C whenever the start time (T1) of the PET scan is coincident with the start of tracer infusion. Other theorems state that, even for nonzero T1S, a unique solution for flow may be expected, as long as the duration of the scan is sufficiently short. The implementation of this theory is illustrated using arterial tracer activity curves obtained in three normal subjects by a multiple arterial sampling procedure following the bolus i.v. infusion of 20-30 microCi of [15O]water. Based on these arterial curves, it is confirmed that the C vs. f relationship resulting from scan parameters T1 = 0 and T2 = 1.5 min (i.e., a PET scan of 90 s commencing with tracer infusion) has an excellent separation of flow values within the range of physiological interest, whereas a 90-s scan beginning at time T1 = 1.7 min results in poorer separation of flow values and loss of the monotonic relationship between C and f at higher flows. The results of this study serve to clarify the in vivo autoradiographic method for measuring rCBF in humans and help to define favorable study parameters for assuring uniqueness and sensitivity of the flow measurement.

Autoradiography↗
PubMed1983

A method for generating obstructive thrombi in the coronary arteries of the conscious dog.

A technique for staging the generation of obstructive thrombi in the coronary arteries of conscious dogs is described. At thoracotomy, electrodes are placed in the lumina of coronary artery branches. When thrombus generation in proximity to the intraluminal electrode tip is desired, anodal current is applied to the exteriorised end of the electrode. In each of nine anaesthetised adult mongrel dogs two to seven intracoronary electrodes were implanted for a total of 35. One to 75 days later, 50 to 800 microA anodal current was applied to 16 electrodes for 30 min to 48 h. Upon autopsy, thrombi in various stages of organisation were found in proximity to the intracoronary portion of 15 electrodes. Six electrodes were found to be damaged or broken. In contrast, only four of the 13 control electrodes were sites of thrombus formation. In seven dogs tissue sections indicated either myocardial ischaemia or infarct in regions whose perfusion was blocked by thrombi. This method may provide for discretionary generation of intracoronary thrombi in the desired quantity, at the preferred site(s), at selected times of onset. Consequently, it offers the possibility of adjusting the onset, severity, and time course of myocardial ischaemia.

Animals↗
PubMed1976

Permanent in-series cardiac assistance with the dynamic aortic patch: Blood-prosthesis interaction in long-term canine experiments.

The blood-prosthesis interaction of the dynamic aortic patch (DAP), an in-series assist device for permanent circulatory support which is implanted in the descending thoracic aorta, was studied in 65 long-term experiments. Periods of postoperative observation with the device inactive or activated ranged from 2 weeks to 22 months. The intravascular surface of the DAP, fabricated of Dacron velour backed by bioelectric polyurethane, displayed various degrees of organization, ranging from a thin fibrin layer to a well organized pseudointima. Activation of the system did not prevent the development of an organized pseudointima. Changes in free-plasma hemoglobin were minimal; platelet count per square millimeter and state of reactivity remained within normal limits. Evidence of renal embolization, attributable to activation of the device, was found in five animals. Frequent lethal complications were aortic rupture and infections of the thoracic cavity originating at the implantation site. Further improvement of the DAP and the techniques of implantation is indicated to insure its efficacy during long-term implantation and activation.

Animals↗
PubMedDate not supplied

Crib sheets or security blankets?

This article describes the sanctioned use of crib sheets as a nursing intervention to decrease test anxiety when the classroom is the practice setting for psychiatric/mental health nursing faculty. The products that the students created offered additional unsuspected benefits. The faculty were convinced that the use of crib sheets can be a sound intervention to reduce students' test-taking anxiety.

Anxiety↗