Biomedical subjects
Publications and source records attributed to J R Morgan.
The activity of netilmicin against a variety of bacteria was similar to that of gentamicin, sisomicin, and tobramycin, but it was less active than these three drugs against Pseudomonas aeruginosa. Synergy with penicillin G against enterococci was demonstrated.
The Autobac 1 system was compared to the disk diffusion and agar dilution methods. Overall, there was good correlation; however, certain antibiotic/bacterial combinations gave unreliable results. In particular, unreliable results were obtained against staphylococci with penicillins, aerobic gram-negative rods with cephalothin, and enterococci with cephalothin and clindamycin.
A comparison was made of the performance of a newly established anaerobic section of a clinical laboratory and the routine diagnostic section in terms of isolation and identification of anaerobic bacteria. Both sections attempted to isolate obligate anaerobes from the same clinical specimens which were not transported in anaerobic containers. Anaerobic and diagnostic sections isolated anaerobes from 35% and 6% respectively of clinical specimens. The use of antibiograms greatly improved the identification of anaerobic organisms.
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A semi-micromethod is described for characterizing anaerobic bacteria by substrate utilization. Small volumes of individual substrates were placed in the wells of plastic microtiter trays. When heavy inocula and a colorimetric indicator were used, complete results were available after 30 h of incubation. Microtiter trays containing a range of substrates can be stored at -20 degrees C. The method is accurate, economical, and convenient for use in a hospital microbiology laboratory.
Relative regional ventilation and perfusion were measured with xenon-133 in 16 seated patients with pure or predominant mitral stenosis (group 1) and in 12 patients with chronic pulmonary congestion due to left-sided heart disease without mitral stenosis (group 2). The apex-base perfusion gradient was abnormally reduced and often reversed in group 1 patients. There was a significant negative correlation between perfusion gradient and mean pulmonary capillary pressure in both groups, but for a given elevation of pulmonary capillary pressure the perfusion gradient tended to be greater (i.e., less abnormal) in group 2. The regression line of perfusion gradient on pulmonary capillary pressure indicated that perfusion gradient had a value of zero (indicating reversal of the perfusion gradient) at a mean pulmonary capillary pressure of 26 mm Hg in group 2 but at only 18 mm Hg in group 1. Relative lower zone ventilation was abnormally reduced in group 1 and there was a significant negative correlation between ventilation gradient and pulmonary capillary pressure in group 1 but not group 2 patients. Comparison of the distribution of slowly inhaled small volume boluses, large volume boluses, and inspiratory capacity breaths of 133Xe suggested that the lower zone hypoventilation was due mainly to closure of peripheral airways but that selectively increased resistance and reduced compliance in the lower zones may contribute in some patients. Both ventilation and perfusion were reduced at the lung bases in group 1 patients, and between regions nonuniformity of relative ventilation/perfusion was significantly less than normal. Although ventilation distribution was relatively normal in group 2 patients, they also had significantly less regional ventilation/perfusion nonuniformity than normal subjects.
The formation of cysts has been studied in kidneys removed from day-15 and day-18 rat fetuses and cultured in a mixture of medium 199 (Morgan et al., '50) for periods of up to 15 days. Gas phases of 95% O2 and 5% CO2, and 95% air and 5% CO2, were employed, the latter being considered more satisfactory. In day-15 kidneys cysts formed from the ampullary portions of the collecting tubules after 2 days whereas cysts derived from nephrons were not seen until 9 days of culturing. The latter arose from developing juxtamedullary nephrons. In day-18 kidneys cysts from collecting tubules and nephrons were both present after 3 days of culturing. The latter, in this instance, originated mostly in immature midcortical nephrons, the juxtamedullary mephrons having undergone rapid degeneration. The tubular portion of the nephron seemed to be the primary site of dilatation. Under culture conditions cysts of nephrons thus formed from immature actively developing nephrons and not from those that were mature. Cysts associated with collecting tubules arose from the ampullary (terminal) portions of the latter in both day-15 and day-18 cultured kidneys. The study of cultured mammalian fetal kidneys can provide information on the nature and genesis of renal cysts. It is possible that the same technique also may be helpful for examining the effects of teratogens directly on the kidney.
Interpretation of irregularities of the left heart border on routine posterior-anterior and lateral roentgenograms may be quite challenging. Partial absence of the left pericardium provides a characteristic abnormality of the left heart border. Described is a case of a thymoma which mimicked partial absence of the left pericardium on routine roentgenography. The importance of including both partial absence of the left pericardium and thymoma in the differential diagnosis of irregularities of the left heart border is discussed.
The in vitro inactivation of gentamicin by carbenicillin and a new semisynthetic penicillin, ticarcillin (BRL 2288), has been demonstrated. Gentamicin half-lives have been studied in eight patients with end-stage renal failure, and a 25 to 74% reduction in half-life has resulted from the concomitant administration of therapeutic doses of carbenicillin and ticarcillin.
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