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Biomedical subjects

A Johnson

Publications and source records attributed to A Johnson.

At least 631 records · Page 35Linked to original sources
PubMed1978

Evaluation of the in vivo function of the Hancock porcine xenograft in the aortic position.

We evaluated the vivo hemodynamic function of the stent-mounted glutaraldehyde-fixed porcine xenograft in 23 patients who had undergone aortic valve replacement from 2 days to 24 months prior to the study. Functional aortic valve orifice areas for the porcine xenograft ranged from 0.58 to 3.0 sq. cm., the average area being 1.36 sq. cm. Six patients had calculated prosthetic valve orifice areas less than 1.0 sq. cm. Valve orifice area did not correlate significantly with valve size or the time interval from surgery to postoperative study. Left ventricular stroke volume showed a significant, positive correlation with calculated xenograft orifice area. Systemic thromboembolism was not encountered. One patient required reoperation for xenograft stenosis caused by dense fibrin deposition on the aortic leaflets. We conclude that use of the stent-mounted glutaraldehyde-fixed porcine xenograft can be associated with significant functional stenosis which may be related to annulus size or inertial properties of the valve. These factors should be taken into consideration when considering use of the stent-mounted glutaraldehyde-fixed porcine xenograft in individual patients.

Adult↗
PubMed1977

Mixed-valence cytochrome oxidase-formate complex. A steady-state intermediate.

At neutral pH, formate binds to the haem a3 component of cytochrome c oxidase to give a complex that reacts differently from the non-liganded enzyme with reducing agents. Addition of sodium dithionite to the formate complex leads directly to the formation of the fully reduced species, whereas reduction with ascorbate/tetramethylenephenylene-diamine can lead to the production of a mixed-valence species. The stability of this mixed-valence form was studied, and the species appears to represent a 'steady-state' situation that is stable only in the presence of an excess of O2 and reducing equivalents. Characterization of the mixed-valence complex by electron paramagnetic resonance and magnetic circular dichroism reveals the presence of reduced low-spin haem a together with reduced detectable copper and high-spin ferric haem a3.

Ascorbic Acid↗
PubMed1977

Recent trends in sex mortality differentials in the United States.

Since 1920, American men, to an increasing degree, have experienced higher levels of mortality than American women for virtually all causes of death at almost every age. Recently, several authors have asserted that there is evidence of a change in these trends, caused primarily by rises in the levels of female mortality. Using age-adjusted death rates and data for the most recent years available (1960-1974). This paper shows that most female death rates are either stable or falling, and that the sex mortality differential for all causes except lung cancer is either stable or increasing.

Accidents↗
PubMed1977

Adaptation of rat pancreatic amylase and chymotrypsinogen to changes in diet.

This study represents an attempt to determine the effect of dietary protein quality and hypophysectomy on the enzymic adaptability of the pancreas in the rat. The specific enzymes studied were amylase, which was purified by immunologic techniques and chymotrypsinogen (activated), which was isolated by affinity column chromatography. Content and synthesis of each enzyme were accurately determined in relation to total pancreatic protein. When rats were fed a 64% sucrose diet (19% casein), there was a two- to three-fold increase in synthesis of amylase. However, if a poor-quality protein (gelatin, gluten, or zein) was substituted for casein, there was no increase in the synthesis of amylase in response to increased carbohydrate. When rats were fed a 19% sucrose diet (64% casein), there was a significant increase in chymotrypsinogen synthesis. Of the poor-quality proteins, gluten was the only one effective in stimulating synthesis of chymotrypsinogen. Peptides, either free or as part of a protein, were necessary for the stimulation of chymotrypsinogen synthesis. Amylase synthesis in hypophysectomized rats was considerably depressed and unresponsibe to increased carbohydrate. This effect could be partially relieved with hydrocortisone, corticosterone, or thyroxin, but not with growth hormone. Hypophysectomy had little effect on synthesis or content of chymotropsinogen.

Amylases↗
PubMed1977

Treatise on aeromedical evacuation: I. Administration and some medical considerations.

Well conceived administrative procedures must be considered the backbone of a good, strong aeromedical evacuation system. These procedures must insure 1) centralized control of patient transportation by aircraft, 2) specialized medical attendants and equipment for inflight medical care, 3) facilities for limited medical care of patients entering, en route in, or leaving the system, and 4) communications with destination and enroute medical facilities concerning patient transportation. There are no absolute contraindications to aeromedical evacuation. However, patients with the following conditions require special consideration. Such conditions are 1) severe anemia, less than 2.5 million RBC/cc or less than 7.0 g hemoglobin/100 ml, 2) respiratory embarrassment, and 3) trapped gas within any of the body cavities. Medical problems in aeromedical evacuation defy resolution only when patient preparation has been improper. When the patient is properly evaluated, then unnecessary, costly, hazardous, and special flights are avoided. Aeromedical evacuation presents no problem so long as one remembers that man is adapted for life at or near sea level and that changes in pressure with increasing altitude affect his physiological processes. This invisible barrier will continue to challenge human ingenuity in the conquest of high altitude.

Adolescent↗
PubMed1977

Treatise on aeromedical evacuation: II. Some surgical considerations.

Preventive medicine is the primary responsibility of every physician. When prevention fails and therapeutic measures are required, the initial approach tends to be along a conservative line. When this approach fails, surgical intervention becomes a necessity. Surgical patients, both pre- and post-surgical, may be moved by aircraft providing that one is aware of the hazards in a hostile atmosphere in which pressure and temperature change with increasing altitude. Air or gas trapped in the body cavities expands in direct proportion to the decrease in pressure. This increased volume becomes significant at 5500 m, where the volume of air or gas in the body is doubled. Quite apart form intense discomfort and actual pain caused in certain types of injury, this expansion of gas at high altitude may constitue a real danger, such as in the probability of rupturing a recently sutured intestine and, in cases of pneumothorax, by disturbance of cardiopulmonary dynamics. Thus, aeromedical evacuation of the surgical patient becomes a challenge to those responsible for the medical care between the originating and destination hospitals.

Aerospace Medicine↗
PubMed1977

Medical waivers: an extension of the pilot's career.

The medical examination has been conducted periodically to determine medical qualifications for the continued performance of military service and as a preventive medicine measure to reveal latent and undiagnosed disease. When an individual fails to meet the medical standards for flying duties, he may be granted a waiver. A waiver means that the individual is considered by the reviewing authority to be capable of effective performance of duty world-wide without compromising health or safety. In 1973, a total of 1218 waivers were granted to 741 rated officers in Headquarters Command. This command is responsible for medical administration of 4057 rated officers. The ages of the officers granted waivers ranged from 27 to 58 years, with a mean age of 46 years. Over 80% of the waivers granted were to pilots. The value of the medical examination schedule followed in the United States Air Force today is often debated. Those who oppose the annual physical examination because of its questionable value speak in an even louder voice because the medical crunch has reduced the availbale grass roots flight surgeons to a bare minimum. These studies, however, point up the need for a continuous, strong, preventive medicine program in Headquarters Command.

Adult↗
PubMed1977

Two years of routine patient movement in the U.S.A. (Jan. 1974-Dec. 1975).

During a 2-year period, Jan. 1974-Dec. 1975, a total of 102,547 routine patients were aeromedically evacuated from an originating medical facility to a destination hospital within the Continental United States (CONUS). It is the policy of the Department of Defense (DOD) that, in both peace and war, the movement of patients of the Armed Forces shall be accomplished by airlift when airlift is available and conditions are suitable for aeromedical evacuation, unless medically contraindicated. The DOD Regulation 4515.13-R states that a routine patient will be delivered to the destination hospital within 72 h after pickup from aerial ports or from the originating CONUS medical facility. During this 2-year period, 66% of all patients moved were delivered to their destination hospital the same-day they were picked up and 93% of all patients were delivered to their destination hospital within the 72-h DOD criteria for routine patients. In order to reach the destination medical facility, many patients had to remain overnight (RON) at an aeromedical staging facility (ASF). Contributing factors were weather, aircraft maintenance problems, expiration of the crew duty day, patients originating overseas, and patients moving out of originating areas and requiring a second mission to reach the destination hospital.

Aviation↗
PubMed1976

Physostigmine: effects on cognition and affect in normal subjects.

Physostigmine was given intravenously to a total dose of 3 mg to 13 subjects; a placebo of 0.25 N saline was given intravenously to 10 other subjects; both groups received 1 mg of methscopolamine bromide subcutaneously preceding the intravenous infusions. A "physostigmine syndrome" consisting of decreased speech, slowed thoughts, mild sedation, expressionless faces, nausea, and decreased spontaneous activity was evident following doses of 1.5 to 2.0 mg of physostigmine. The capacity of short-term memory (STM) as measured by digit span tasks was significantly less for the subjects who received physostigmine than for the subjects who received placebo. No difference was observed between the two groups on tasks of consolidation from STM to long-term memory (LTM). Subjects who received physostigmine did not significantly differ from subjects who received placebo in their mood. However, two subjects in the physostigmine group, and no subjects in the saline group became tearful and depressed.

Adult↗
PubMed1976

Non-steroid skin cream in traumatic dermatoses: A clinical open evaluation.

Attention is drawn to the unwanted side effects of the long-term topical use of steroids on the skin. The topical use of steroids in conditions in which immunological factors are not involved is not necessary. An open clinical evaluation demonstrated that simple protective applications are quite effective in these conditions.

Administration, Topical↗
PubMed1976

Group B streptococcal meningitis associated with otitis media.

A full-term infant of an appropriate size for gestational age was found to have meningitis due to Lancefield group B beta-hemolytic streptococci at 8 weeks of age. On admission, the baby had bulging tympanic membranes Lancefield group B beta-hemolytic streptococci were isolated from aspirate of the middle ear, supporting the importance of otitis media in the pathogenesis of late-onset Lancefield group B beta-hemolytic streptococcal meningitis.

Brain Diseases↗