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Biomedical subjects

R M Johnson

Publications and source records attributed to R M Johnson.

At least 145 records · Page 8Linked to original sources
PubMed1980

Reported lactose tolerance of members of various racial/ethnic groups in Hawaii and Asia.

Subjects from various racial/ethnic groups in Hawaii and homeland Chinese, Japanese, and Koreans reported on their milk drinking in childhood and adulthood, as well as on whether or not milk drinking produced symptoms of intolerance. Intolerance was comparatively infrequent in all groups, although significant differences existed between groups in the frequency with which they manifested symptoms and in discomfort scores. Differences between Hawaiian subjects of Asian ancestry and homeland Asians in the frequency of reported symptoms, in mean discomfort scores, and in amount of milk needed to produce symptoms, as well as the high proportion of symptomatology among Hapa-Haoles (persons of Caucasian and Oriental ancestry) and other data reported herein, are not supportive of the usual genetic explanation of lactose tolerance and are supportive of the belief that dietary practice influences tolerance.

Adult↗
PubMed1980

The site of VX2 tumor transplantation affects the development of hypercalcemia in rabbits.

The relationship between plasma levels of 15-keto-13, 14-dihydroprostaglandin E2 (15K-H2-PGE2) and serum calcium levels was studied in nontumor-bearing rabbits and in rabbits bearing the VX2 carcinoma intramuscularly and intra-abdominally. The plasma levels of 15K-H2-PGE2 in the two groups of tumor-bearing animals did not vary significantly but was several fold greater than in nontumor-bearing rabbits. Rabbits bearing the VS2 carcinoma intramuscularly developed hypercalcemia between the second and third week after implantation of neoplastic tissue and remained hypercalcemic until they expired. The serum calcium levels in rabbits bearing the VX2 carcinoma intra-abdominally did not vary significantly from those of nontumor-bearing rabbits. The differences in the serum calcium levels in rabbits bearing the VX2 carcinoma at intramuscular and intra-abdominal implant sites may be related to different extents of metabolism by the lung and by the liver of prostaglandin E2 or other cyclooxygense of polyenoic fatty acids produced by the tumor.

Animals↗
PubMed1980

Shape and volume changes in erythrocyte ghosts and spectrin-actin networks.

In response to changes in electrolyte concentration and pH, erythrocyte ghosts can exhibit some of the characteristic shapes seen in the intact erythrocyte. These shape changes are accompanied by volume changes; both are reversible, not energy dependent, and not inhibited by sulfhydryl reagents. The volume reduction can also be seen in isolated Triton-free spectrin-actin lattices, showing that this network is capable of reversible contraction. The results suggest that reversible changes in size of the underlying cytoskeleton of the erythrocyte membrane can control cell shape.

Actins↗
PubMed1979

The effect of nucleosides and deoxycoformycin on adenosine and deoxyadenosine inhibition of human lymphocyte activation.

Micromolar deoxyadenosine inhibits leucine uptake during the 1st day of proliferation in mitogen-stimulated lymphocytes if adenosine deaminase is inhibited. This inhibition occurs before DNA synthesis begins, suggesting that deoxyadenosine can affect mitogenesis by mechanisms that do not involve ribonucleotide reductase inhibition. If deoxyadenosine addition to mitogen-stimulated lymphocytes is delayed to the 2nd or 3rd day post-stimulation, inhibition of proliferation is markedly reduced. Although the time dependence of deoxyadenosine toxicity resembles that of adenosine, these compounds appear to inhibit early protein synthesis by different mechanisms: 1) deoxycoformycin markedly potentiates deoxyadenosine but not adenosine; 2) deoxycytidine and thymidine reverse deoxyadenosine toxicity but do not alter adenosine toxicity.

Adenosine↗
PubMed1978

Loss of resealing ability in erythrocyte membranes. Effect of divalent cations and spectrin release.

Washed human erythrocyte membranes can recover impermeability to macromolecules upon warming in solutions of sufficient ionic strength. This ability is rapidly lost from most ghost preparations in dilute salt solution at temperatures of 15 degrees C of higher. Divalent cations both reseal ghosts in the absence of high ionic strength and prevent loss of resealing ability. The effective concentrations are 40 micron for Ca2+ and 200 micron for Mg2+. The loss of resealing ability is associated with the release of spectrin polypeptides from the inner surface of the membrane. In ghost preparations that have not become irreversibly leaky, or in the presence of Ca2+, loss of spectrin does not occur. These results suggest that an intact spectrin netwoek is required for resealing to macromolecules, and divalent cations stabilize this network. In light of this information, the effect of temperature on resealing kinetics is described.

Calcium↗
PubMed1978

Review of cervical orthoses.

Six commonly prescribed cervical orthoses are presented for a qualitative review of their structural properties and their clinical applicability. A quantitative review of each brace has previously been reported. The characteristics of 1) structure, 2) ease of donning, 3) ease of adjusting, 4) comfort, and 5) general clinical applicability are summarized for each brace. Generally, as the orthosis becomes more restrictive, it also becomes more cumbersome and more difficult to don. Ease of adjustment and comfort are compromised. The one exception was the Somi orthosis which was comfortable, easy to don and adjust, and which still provided good stability in forward flexion. The information presented in this paper in conjunction with information on the quantitative qualities of each brace and the services available at most health care facilities may be used as a guide for selecting specific cervical orthoses.

Braces↗
PubMed1978

The yale cervical orthosis: an evaluation of its effectiveness in restricting cervical motion in normal subjects and a comparison with other cervical orthoses.

The Yale cervical orthosis is a lightweight polyethylene foam Philadelphia collar with molded fiberglass extensions over the thorax. This orthosis was studied on 17 normal subjects in the extremes of the ranges of flexion, extension, rotation, and lateral bending using roentgenograms and axial photographs to assess how effectively it limited motion of the neck. Overall, it satisfactorily controlled cervical motion and was similar to the most effective rigid cervical orthoses. Flexion and extension ranges were compared at different segmental levels of the spine. The Yale orthosis was most successful in restricting flexion in the area of the middle and lower cervical spine and was acceptable in controlling extension range. The orthosis was least effective in controlling motion in the upper spine, particularly at the atlantoaxial articulation. The Yale orthosis is recommended for postsurgical protection of the middle and lower cervical spine and in select situations of spinal instability, but it is not recommended for control of odontoid fractures or atlantoaxial subluxation.

Adult↗
PubMed1977

Cervical facet fusion for control of instability following laminectomy.

Cervical laminectomy may compromise the stability of the spine. Posterolateral facet fusion can be used to stabilize the spine after laminectomy and prevent progressive deformity. The procedure includes passing wires through drill holes in the articular processes and binding two longitudinal struts of bone to the posterior columns of the articular processes. Sixty-three p atients with cervical laminectomy and facet fusion were reviewed, and fifty-two of them were followed for one to seventeen years. The reasons for fusion were to control overt spinal instability and deformity or to eliminate motion which may contribute to spondylosis. Solid fusion occurred in fifty of fifty-two patients at a mean of 6.5 months and provided continuing stability without progressive deformity. Although facet fusion is a complex procedure, it provides secure stabilization, does not interfere with decompression, and permits early mobilization of the patient.

Adolescent↗
PubMed1977

Cervical orthoses. A study comparing their effectiveness in restricting cervical motion in normal subjects.

The effectiveness of five cervical orthoses in restricting cervical motion was evaluated quantitatively in normal subjects using roentgenograms and overhead photographs made at the extremes of three planes of motion, while the effectiveness of the halo with a plastic body-vest was studied in seven patients with cervical fractures or local fusions. Flexion and extension were measured at each cervical intervertebral joint and combined cervical motion was measured for rotation and lateral bending. The best conventional braces restricted only 45 per cent of flexion-extension at the atlanto-axial joint; the halo restricted 75 per cent. The conventional braces were more effective in the middle and lower portions of the cervical spine. The results may prove to be useful guidelines for the selection of an appropriate orthosis to control motion in different planes and at different levels of the spine.

Adult↗
PubMed1976

Flammability of disposable surgical drapes.

We discuss the high degree of flammability of disposable surgical drapes. The results of two separate tests and corresponding photographs are presented to verify the flammability. We stress the importance of the flame spread rate.

Disposable Equipment↗