Search PubMed⌕ Search

Biomedical subjects

M K Johnson

Publications and source records attributed to M K Johnson.

At least 289 records · Page 16Linked to original sources
PubMed1968

Effects of salts on the halophilic alga Dunaliella viridis.

Determinations of the salt sensitivity of enzymes extracted from the halophilic alga Dunaliella viridis revealed that pentose phosphate isomerase, ribulose diphosphate carboxylase, glucose-6-phosphate dehydrogenase, and phosphohexose isomerase were inhibited by NaCl concentrations far lower than that in the growth medium (3.75 m). The inhibition was reversible and was not prevented by preparing the extracts in the presence of salt. Potassium, lithium, and cesium chlorides were equally inhibitory. In contrast, whole cells require rather high levels of NaCl for optimal growth, whereas growth is inhibited by low levels of the other cations. The results suggest a specific mechanism for the exclusion of sodium from the interior of the cell.

Carbon Dioxide↗
PubMed1966

Metabolism of iodomethane in the rat.

1. The LD(50) of iodomethane orally administered to rats is 76mg./kg. body wt. but repeated daily doses of 30-50mg./kg. body wt. are without effect. 2. Oral doses of iodomethane to rats are rapidly converted into S-methylglutathione in the liver, and S-methylglutathione is excreted in the bile. 3. The conjugation process has been reproduced in vitro and shown to be enzymically catalysed. 4. S-Methylglutathione is degraded to S-methylcysteine by kidney homogenates. 5. Only a small proportion of a dose of iodomethane or of S-methylcysteine is excreted as compounds related to methylmercapturic acid. 6. Paper chromatography of extracts of livers from normal and dosed rats supports the view that GSH is the predominant non-protein thiol present.

Animals↗
PubMed1966

Studies on glutathione S-alkyltransferase of the rat.

1. A rat-liver enzyme catalysing the S-alkylation of glutathione by iodomethane and various other alkyl compounds has been identified and partially purified; its stability, specificity and response to inhibitors and activators and to changes in reaction pH have been studied. 2. The enzyme is distinct from glutathione S-aryltransferase, but both enzymes respond similarly to various inhibitors. 3. A similar enzyme has been found in the kidney and adrenal of rat and in the liver and kidney of numerous species. 4. The identity and the physiological role of the enzyme are discussed.

Adrenal Glands↗
PubMedDate not supplied

Lengthening of the humerus for upper extremity limb length discrepancy.

We present a case of humeral lengthening for a limb length discrepancy of 7.7 cm due to proximal humeral growth arrest in a 12-year-old boy. Lengthening of 69 mm was achieved using the Wagner technique. Bone grafting was not required. Humeral lengthening may be performed for upper extremity limb length discrepancy with good results. Objectives of treatment must include protection of the radial nerve from traction injury and from entrapment in the osteotomy site. Elbow extension may be lost during lengthening, but in the adolescent age group, full return of elbow motion can be expected.

Bone Diseases↗
PubMedDate not supplied

Response of leukopenic rabbits to pneumococcal toxin.

Pneumolysin, a cytolytic toxin from Streptococcus pneumoniae, has previously(1) been shown to interact in vitro with polymorphonuclear leukocytes in a variety of ways behaving as a chemotactic, lethal or lytic agent, depending on its concentration. In this study we examined the effect of leukopenia induced by administration of nitrogen mustard on the response of the rabbit to conjunctival instillation and intracorneal injection of pneumolysin. Control animals responded to instillation of crude and pure toxin with intense erythema and chemosis, and production of a thick discharge. No discharge and only traces of erythema and chemosis were noted in leukopenic animals. Leukopenic rabbits also showed a decreased capacity to respond to intracorneal injection of the toxin, particularly striking in the first 48 hours following pneumolysin injection, when opacification, discharge formation, chemosis, and erythema were found to be markedly less than in control animals. We conclude that the polymorphonuclear leukocyte plays a key role in the response of the rabbit eye to pneumococcal toxin. This system appears to be a good model for study of the inflammatory response to microbial products.

Animals↗
PubMedDate not supplied

True prophylactic gentamicin application in experimental Pseudomonas keratitis.

In an experimental model of Pseudomonas keratitis, 50 rabbit eyes were treated with gentamicin sulfate (3 mg/mL) prophylactically on four different treatment regimens. One group (13 eyes) received one drop of gentamicin sulfate every hour to a total of four drops, the last drop 25 minutes before inoculation. A second group (13 eyes) was given one drop of gentamicin sulfate one hour before inoculation. A third group (12 eyes) received one drop of gentamicin sulfate per minute to a total of 4 drops, the last drop 25 minutes prior to inoculation. A fourth group (12 eyes) received one drop of antibiotic 25 minutes before inoculation. Twelve control eyes received saline solution. Subsequently, a superficial corneal scratch was inflicted and each eye received one drop (0.05 mL) of a solution containing Pseudomonas aeruginosa. The infection rate in all four experimental groups was low, whereas all control eyes became infected. These results demonstrate the effectiveness of prophylactic antibiotic application in the prevention of Pseudomonas keratitis prior to superficial ocular trauma.

Animals↗
PubMedDate not supplied

Complications of triple arthrodesis with comparison to select rearfoot fusions.

Triple arthrodesis is valuable in the stabilization and correction of foot deformity resulting from postcalcaneal fracture, talipes equinovarus, and neurological deficits. This manuscript summarizes the literature related to the complications of delayed union, hypermobility, and arthrosis following triple arthrodesis. A comparison of the outcome of specific rearfoot fusions is also presented.

Adolescent↗
PubMedDate not supplied

Hallux amputation for diabetic osteomyelitis.

Digital amputation for infection in the diabetic patient requires accurate assessment of wound healing potential as a function of clinical and noninvasive studies of cutaneous blood flow. The diabetic propensity for staphylococcal infection, microangiopathy, and delayed wound healing may be questionable in light of recent literature. X-rays, xeroradiographs, and bone scans are useful guides to osseous infection involvement. Amputation technical planning is mandatory. Proper assessment results in a dynamic functional amputation stump with little impact on gait.

Adult↗
PubMedDate not supplied

The orally active renin inhibitor A-74273. In vivo and in vitro morpholine ring metabolism in rats, dogs, and humans.

The metabolism and disposition of [14C]A-74273--a potent, orally active renin inhibitor--were investigated in beagle dogs and Sprague-Dawley rats. Two male and two female dogs received a single 10 mg/kg oral or 1 mg/kg intravenous dose in a cross-over experiment and urine and feces were collected for 5 days. After both intravenous and oral dosing, > 92% of the dose was recovered in the feces and < 3% was recovered in the urine. The predominance of hepatobiliary elimination in the clearance of A-74273 was verified in a bile-exteriorized dog, where 79.8% of a 1 mg/kg intravenous dose was excreted in the bile within 6 hr after administration. Similarly, administration of a 1 mg/kg intravenous dose to a bile-exteriorized rat resulted in biliary excretion of 60.5% of the dose within 6 hr. Radio-HPLC analysis of bile and feces from both species indicated extensive metabolism of A-74273 to three major morpholine ring-opened metabolites; the ethanolamine A-78242, the amine A-78030, and the carboxylic acid A-81307. These three metabolites each contributed 12.0-20.2% of the biliary radioactivity after intravenous dosing, while unchanged A-74273 contributed 5-17%. Incubation of [14C]A-74273 with rat, dog, and human liver microsomes afforded nearly equal amounts of the three in vivo metabolites for all three species, suggesting that the in vitro system was representative of A-74273 in vivo metabolism and that humans should also convert A-74273 to the morpholine ring-opened metabolites in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗