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Biomedical subjects

M L Johnson

Publications and source records attributed to M L Johnson.

At least 343 records · Page 19Linked to original sources

The initial evaluation of the patient with multiple injuries.

The management of trauma patients requires organization and the cooperation of trained health personnel, beginning at the site of injury and continuing until the patient is discharged from the hospital. Treatment guidelines and priorities must be well outlined in advance to provide optimal care and minimize delay prior to definitive therapy. Resuscitation and treatment must begin immediately and simultaneously following well established principles. These guidelines and the general care of the patient with multiple trauma are discussed in this article.

Abdominal Injuries↗

Ultrasonic evaluation of the pancreas.

With the advent of new gray scale imaging techniques, ultrasound plays a major role in the diagnosis of pancreatic lesions. As a noninvasive, nonionizing, accurate, and inexpensive diagnostic modality that directly images the pancreatic gland, ultrasound can be used as a primary screening tool. It is helpful in confirming the diagnosis of acute pancreatitis and in detecting and following pseudocysts and other complications. Neoplasms can be detected with a high rate of accuracy, and by assessing the presence of ascites or metastatic foci in the liver, ultrasound can aid in the staging of the neoplastic process. Bowel gas and obesity remain serious limitations to adequate examination, and in these patients computed tomography offers a complementary modality.

Acute Disease↗

Subunit association and heterogeneity of Limulus polyphemus hemocyanin.

The molecular weights of the 6S, 24S, 36S, and 60S components of Limulus polyphemus hemocyanin were determined by high speed sedimentation equilibrium to be 69 400, 856 000, 1 690 000, and 3 160 000. The behavior of this hemocyanin appears to be similar to that of other arthropod hemocyanins where the first aggregation step is the formation of a hexamer of the 6S monomer. Here the larger aggregated states (24S, 36S, and 60S) are successive dimers of an unobserved hexamer (16S). The 24S-36S-60S association was found to be heterogeneous, suggesting that 24S components of different composition may be present.

Animals↗

Effects of Hofmeister salts on the self-association of glucagon.

The trimerization constants of glucagon at pH 10.6 in 0.76 M K2HPO4 have been calculated from circular dichroism data between 5 and 50 degrees C. The free energy, enthalpy, and entropy of transfer have been evaluated from the current results and published data in 0.20 M phosphate. The free energies of transfer are derived completely from an increase in the entropy of transfer, since the enthalpy of transfer is less favorable at all temperatures. These parameters are compared with those of various model groups and compounds: CH2, peptide, methane, ethane, and the 1--13 N-terminal fragments of ribonuclease. The effects of fluoride and chloride on the self-association of glucagon have been compared with that of phosphate at 25 degrees C. These effects are consistent with the binding of approximately one molecule of salt to the trimer and a systematic decrease in the number of water molecules bound to the trimer compared to the monomer for the series K2HPO4, KF, and KCl.

Anions↗

Physical, emotional and social adjustments to home dialysis.

Forty home dialysis patients and their families were interviewed by means of a standard questionnaire to determine their physical, emotional, and social adjustment to treatment. The results indicated a reasonable level of health, particularly in patients under the age of 50 years. However, home dialysis produced considerable strain in the family, particularly in the dialysis partners. Home training programmes should provide appropriate learning and technical experience for the dialysis partners and continued support, including integrated medical and paramedical services, domiciliary visiting, and regular holidays. Limited-care dialysis facilities should be provided where home dialysis is impractical or becomes intolerable.

Adaptation, Psychological↗

Self-association of glucagon as measured by the optical properties of rhodamine 6G.

The fluorescence of rhodamine 6G is completely quenched in glucagon solutions in 0.6 M K2HOP4 at pH 10.6. The absorption of rhodamine 6G is red-shifted by the same reaction. A single rhodamine 6G molecule appears to be bound to a hydrophobic patch in the center of the trimer of glucagon. Since the glucagon monomer has almost no organized structure this site exists only in the associated trimer form of glucagon. The self-association of glucagon to the trimer has been determined from the variation in rhodamine 6G fluorescence and absorption measured over a 60-fold range of dye concentration. The self-association constant agrees with values determined by other methods in the absence of dye. The binding isotherms of rhodamine 6G to glucagon shift with glucagon concentration and exhibit negative cooperativity.

Anilino Naphthalenesulfonates↗

Left ventricular outflow obstruction produced by a pedunculated fibroma in a newborn: clinical, angiographic, echocardiographic and surgical observations.

An unusual case of a one-day-old infant with significant left ventricular outflow obstruction produced by a pedunculated fibroma is described. The clinical findings were indistinguishable from severe valvular or subvalvular aortic stenosis. The tumor was difficult to detect by echocardiography. It produced an echo-free widening of the left ventricular outflow tract. Left ventricular cineangiography clearly demonstrated a mobile mass beneath the aortic valve.

Aortic Valve Stenosis↗

Percutaneous nephrostomy: a series and review of the literature.

A series of 53 percutaneous nephrostomies and a literature review of 516 such procedures are presented. The selection of patients with supravesical urinary obstruction, urinary fistulas, and renal calculi is discussed, and the concept is advanced that percutaneous nephrostomy is more than a temporizing preoperative procedure. The available techniques are compared; modified instrumentation for balloon catheter insertion, a combination of fluoroscopic with real-time ultrasound guidance, and some additional principles of subsequent management are introduced. Successful results can be expected in over 90% of percutaneous nephrostomies, with major complications limited to 4% and minor complications to 15%. The limitations of percutaneous nephrostomy and the role of surgical nephrostomy are discussed.

Adolescent↗

Resolvability of Adair constants from oxygenation curves measured at low hemoglobin concentration.

Analyses of low concentration oxygenation curves for apparent Adair constants in which the effects of dimers is ignored have been explored using recently determined values of the overall energy coupling parameters. For high affinity systems and favorable energy distributions, it is found that the errors in estimated binding free energies may be less than one kcal provided the measurement errors are strictly random and of small magnitude. These errors are nevertheless quite substantial as compared with the differences between values for the successive binding steps.

Calorimetry↗

Thermodynamics of the self-association of glucagon.

In water, glucagon exists in an equilibrium between a trimer in which more than half of the peptide groups are in an alpha-helical configuration and a monomer which has a random coil configuration with few alpha-helical residues. The thermodynamics of this self-association have been evaluated by studying the temperature- and concentration-dependence of the mean residue ellipticity at 220 nm. The enthalpy and entropy changes of association were negative at all temperatures between 5 degrees and 50 degrees and had large negative temperature dependencies. Usually an association that involves nonpolar groups is considered to be driven by a positive entropy term. Such an explanation is not tenable in the case of glucagon. However, if the effects of nonpolar groups on the coil-to-helix transition of a polypeptide are included into the thermodynamic considerations of hydrophobic interactions, then the negative parameters observed for glucagon association can be readily understood. The hydrophobic interaction is therefore not necessarily controlled by the entropy change because, if there are significant conformational changes, the reaction may be controlled by the enthalpy change. Consequently, the more important parameter characteristic of all hydrophobic reactions is the heat capacity change.

Glucagon↗

Two-dimensional echocardiographic assessment of vegetative endocarditis.

Real-time, two-dimensional echocardiography was used to document the presence and assess the size and location of vegetative lesions of the cardiac valves and chambers in seven patients with bacterial endocarditis. Anatomic correlation (surgical or autopsy) was accurate in all patients. Two-dimensional echocardiography was shown to be of particular value in determining morphologic characteristics of the lesions since this technique provides spatial information concerning moving cardiac structures. The results of two-dimensional echocardiography were most helpful in determining selected aspects of the clinical care provided for each patient. These data demonstrate that real-time, two-dimensional echocardiography, in combination with M-mode imaging techniques, may be of great potential value in the detection of vegetative endocarditis. Furthermore, reliable assessment of lesion size and location may, in time, become a valuable method for following the morphologic changes that occur in vegetative lesions, and thus determine the efficacy of antibiotic therapy. This information may also provide a means for evaluating certain patients for surgical intervention.

Adolescent↗

Utilization of physician services for dermatologic complaints. The United States, 1974.

The National Ambulatory Medical Care Survey provides data on the "who," "for what complaint," and "to whom" for office visits to office-based physicians. In 1974, complaints referable to the skin accounted for 44 million physicians visits. This represents 7% of the 634 million visits to physician offices made during this period. Dermatologists accounted for 34% of all visits for skin complaints. General and family practitioners accounted for 40% of such encounters. Office visits prompted by dermatologic complaints were frequently less than 16 minutes long. Each office-based dermatologist accounted for an average of 5,600 patient visit per year. According to the dermatologist's diagnosis, 31% of these visits were prompted by acne; warts accounted for an additional 8%.

Acne Vulgaris↗

New health practitioners and dermatology manpower planning.

To assess the need for dermatologists in the United States, the potential role of new health practitioners in this specialty is considered. Available data on physician extenders in general and informed opinion on dermatologist extenders in particular suggest that specially trained, nonphysician personnel could substantially augment the supply of dermatological services. At present, however, widespread adoption of new staffing patterns appears unlikely. A long-run trend toward greater use of all categories of ancillary personnel in this specialty is expected, and the profession is urged to play an early and active role in this trend's development.

Allied Health Personnel↗