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D R Johnson

Publications and source records attributed to D R Johnson.

At least 181 records · Page 10Linked to original sources
PubMed1990

Rearrangement and expression of T-cell receptor genes in marmoset lymphoid cell lines with natural killer activity.

To study the role of the T-3/T-cell receptor complex in mediating natural killer activity, we have examined T-cell receptor gene configuration and expression in five transformed marmoset cell lines with natural killer activity. All lines showed rearrangement of the beta chain of the T-cell receptor and expressed full size beta chain transcripts as well as full size delta chain transcripts. Only three lines contained full size T-cell receptor alpha chain transcripts. Of the three lines which had potential for encoding functional T-3/T-cell receptor complex, those which possessed natural killer activity also expressed T-gamma transcripts. In addition, one clone with high natural killer activity which did express high levels of T-gamma mRNA was unable to produce functional T-3/T-cell receptor complex due to truncated T-cell receptor alpha chain message. The results in this paper provide strong evidence that natural killer activity is dependent upon expression of the T-cell receptor gamma chain.

Animals↗
PubMed1990

Clinical application of the metabolic cart to the delivery of total parenteral nutrition.

In critically ill patients, the inaccuracy of predictive formulas for nutritional assessment often leads to inappropriate and potentially detrimental feeding regimens. This study evaluates the clinical utility of the metabolic cart in an urban university hospital setting. Twenty-six studies were performed on each of 26 patients (18 surgical, 8 medical) using an MMC Horizon metabolic cart. Although 58% of patients were overweight, 42% were still shown to have a kwashiorkorlike pattern of malnutrition. Three patients demonstrated a marasmic-like pattern. Fifteen percent of studies showed patients to be hypometabolic and 62% hypermetabolic. Harris-Benedict resting energy expenditure, based on actual or ideal body weight, underestimated needs; however, addition of a metabolic activity factor overestimated needs. Only 32% of patients were fed appropriately; 41% were underfed, and 27% were overfed. Urine area nitrogen correlated poorly with energy expenditure. Measured RQ appropriately reflected substrate utilization in 77% of studies; multiple factors may have caused differences between measured and predicted RQ in 23%. Use of the metabolic cart determines precisely the metabolic state, identifies problems with substrate utilization, and enables the physician to design the most efficacious nutritional regimen.

Adolescent↗
PubMed1990

The effect of diet on bone shape in the mouse.

The effects of four deficient diets (oats, barley, wheat, buckwheat) on the shape of first and second cervical vertebrae and scapulae in C57BL mice have been measured using Fourier analysis. Bone shape was found to be robust, and only minimally affected by dietary change. The significance of this lack of change is discussed in the light of changes induced by diet in non-metrical variants in the skeleton. The study further emphasises the dangers of using certain non-metrical characters in taxonomic studies and indicates that the shapes of mouse bones are affected to a lesser degree by dietary influences than are the incidences of certain non-metrical character states.

Animals↗
PubMed1990

Kinetic parameters in the growth plate of normal and achondroplastic (cn/cn) mice.

We have reinvestigated the overall size, zone size, mitotic rate and growth rate in the tibial epiphysis of normal and achondroplastic (cn/cn) mice aged 7-55 days. Our present sample did not contain the two phenotypes characteristic of some stocks carrying the gene: cn/cn mice showed smaller zone sizes within the growth plates, smaller cells, decreased mitotic indices and growth rates.

Achondroplasia↗
PubMed1989

Catalytic hydrolysis of vasoactive intestinal peptide by human autoantibody.

Vasoactive intestinal peptide (VIP) labeled with 125I, [Tyr10-125I]VIP, can be hydrolyzed by immunoglobulin G (IgG) purified from a human subject, as judged by trichloroacetic acid precipitation and reversed-phase high-performance liquid chromatography (HPLC). The hydrolytic activity was precipitated by antibody to human IgG, it was bound by immobilized protein G and showed a molecular mass close to 150 kilodaltons by gel filtration chromatography, properties similar to those of authentic IgG. The Fab fragment, prepared from IgG by papain treatment, retained the VIP hydrolytic activity of the IgG. Peptide fragments produced by treatment of VIP with the antibody fraction were purified by reversed-phase HPLC and identified by fast atom bombardment-mass spectrometry and peptide sequencing. The scissile bond in VIP deduced from these experiments was Gln16-Met17. The antibody concentration (73.4 fmol per milligram of IgG) and the Kd (0.4 nM) were computed from analysis of VIP binding under conditions that did not result in peptide hydrolysis. Analysis of the antibody-mediated VIP hydrolysis at varying concentrations of substrate suggested conformity with Michaelis-Menton kinetics (Km). The values for Km (37.9 X 10(-9) M) and the turnover number kcat (15.6 min-1) suggested relatively tight VIP binding and a moderate catalytic efficiency of the antibody.

Amino Acid Sequence↗
PubMed1989

Conformational changes of type II regulatory subunit of cAMP-dependent protein kinase on cAMP binding.

The effect of cAMP on the conformation of the regulatory subunit of type II cAMP-dependent protein kinase (RII) from bovine heart was investigated by UV-difference and circular dichroism (CD) spectroscopy. The UV-difference spectrum of RII with and without cAMP showed a positive band around 278 nm and a negative band at 256 nm. Similarly, cAMP enhanced the ellipticity of RII in the region between 280 and 300 nm and decreased that between 250 and 280 nm. In addition, cAMP transformed the far-UV CD spectrum of RII from that of a negative band minimally at 209 nm with a shoulder at 223 nm to one with two minima at 222 and 211 nm. These data show that cAMP induces conformational changes of RII upon binding. Such structural changes may be the basis of activation of cAMP-dependent protein kinases by cAMP.

Animals↗
PubMed1989

Secondary osteoporosis and the microanatomy of trabecular bone.

Osteoporosis is a generic term implying a decrease in bone mass which increases the risk of fracture. It is now becoming appreciated that decreases in bone mass alone are not the sole factor in increasing the risk of osteoporotic fracture, and that other skeletal and extraskeletal factors also contribute significantly to this risk. Extraskeletal factors include the propensity to falls and responses to falls, whereas additional skeletal factors include bone turnover, the ability to repair fatigue damage and the tertiary structure of bone, particularly trabecular tissue. There are a large number of causes of secondary osteoporosis each with their own specific pathophysiological mechanisms. It is therefore not surprising that they have heterogeneous effects on the skeleton. A good example is provided in corticosteroid osteoporosis which is characterised by thinning of trabecular elements, whereas postmenopausal osteoporosis is characterised less by thinning and more by destruction of trabecular elements which derange trabecular continuity. A variety of techniques are now being developed to address the heterogeneity of trabecular osteoporosis. These include direct histomorphometric techniques to assess trabecular continuity, and indirect techniques such as the attenuation of ultrasound. These different pathophysiological mechanisms in osteoporosis have important therapeutic implications, particularly with agents that affect bone remodelling. Since bone remodelling is a surface-based phenomenon, if trabecular surfaces are destroyed, the augmentation of bone mass may thicken remnant structures without restoring trabecular continuity. Since most treatments for osteoporosis affect bone remodelling they are likely to have a greater effect in restoring structural integrity of the skeleton in corticosteroid than in postmenopausal osteoporosis.

Adrenal Cortex Hormones↗
PubMed1989

Topical anesthesia of the eye as a diagnostic test.

We investigated whether ocular response to topical anesthetic could assist the physician in distinguishing between patients with simple corneal injury and those with iritis, conjunctivitis, or other causes of acute eye pain. Seventy-one patients who presented to the emergency department filled out visual analog pain scores (range, 0 to 10) before and after use of topical anesthetic (proparacaine 0.5%). Mean initial pain scores were higher (6.3 +/- 3.0 vs 4.8 +/- 2.8, P less than .05), final pain scores were lower (1.1 +/- 1.7 vs 3.5 +/- 2.5, P less than .001), and changes in scores were greater (5.2 +/- 3.0 vs 1.3 +/- 1.3, P less than .001) in patients who had simple corneal injury compared with those who had other causes of acute eye pain. By defining response to topical anesthetic as a reduction in pain score by more than 5 (on a scale of 1 to 10) or as a final pain score of less than 1, we found the sensitivity of this test for simple corneal injury to be 80% and the specificity to be 86%. This information is useful to physicians, either with or without a slitlamp, attempting to diagnose the cause of acute eye pain.

Acute Disease↗
PubMed1989

Rapid antigen detection in the diagnosis of group A streptococcal pyoderma: influence of a "learning curve effect" on sensitivity and specificity.

To evaluate the efficacy of rapid antigen detection for diagnosis of Group A streptococcal pyoderma, lesions on 129 children were swabbed for culture and for rapid antigen detection testing. Duplicate cultures and duplicate rapid antigen tests were performed in two laboratories. The sensitivity and the specificity of the test were high, supporting the validity of this technique in diagnosing streptococcal pyoderma. Of importance, however, was the documentation of a learning curve effect on the sensitivity and specificity. There was a significant difference between the early samples and the later samples in one laboratory which had less previous experience with the rapid antigen detection test. By the time the later samples were collected, the proficiency of the first laboratory was equal to that of the second laboratory for both sensitivity and specificity. Although a learning curve effect on sensitivity and specificity of rapid antigen detection tests for Group A streptococci has been suspected, this is the first documentation of such an effect. This finding has important clinical implications for using rapid antigen detection tests for Group A streptococcal infections.

Antigens, Bacterial↗
PubMed1989

The effect of the gene undulated (un) on the shape of cervical and upper thoracic vertebrae in the house mouse (Mus musculus).

Videodigitised outlines of C6, C7, T1 and T2 vertebrae from 23 mice carrying the mutant gene undulated (un/un) and normal littermates (+/un) have been examined by Fourier analysis. There were large differences in shape between C6 vertebrae, smaller but significant differences in C7 and insignificant differences between T1s. The situation in T2 was complicated by the effects of the genetic background, but the effect of undulated was still significant. We conclude that the undulated gene shows significant pleiotropy in its effects even over this short length of the vertebral column.

Animals↗
PubMed1989

The relationship between age, size and shape of mouse thoracic vertebrae: a scanning electron microscopic study.

Scanning electron microscopic studies of replicas of the first and second thoracic vertebrae of mice aged 25-60 days allow us to differentiate areas of bone deposition and resorption, the sites of areas of calcified cartilage and the attachments of ligaments. The main site of resorption throughout the period is beneath the neural arch, with other local areas of resorption occurring around the developing vertebral processes. The spinous process increases in size over the period, especially in T2. Results obtained in this way correlate well with an earlier morphometric study of the same bones.

Aging↗
PubMed1988

Enzyme activity and sulfhydryl status in rat renal cortex following mercuric chloride and dithiothreitol administration.

Previous experiments indicated that the partial reversal of mercuric chloride-induced renal dysfunction in rats by subsequent dithiothreitol (DTT) administration was not related to increased mercury excretion, decreased renal mercury concentration, a change in renal cortical subcellular mercury distribution, or the formation of a Hg-DTT complex. The present studies investigated whether DTT, a sulfhydryl reducing agent, protected renal cortical sulfhydryl status in general, or the activity of various renal enzymes (Mg- and Na,K-ATPases, alkaline phosphatase, and glutathione peroxidase) in particular. Additionally, the occurrence of conjugated dienes was used to assess the degree of lipid peroxidation. HgCl2 produced significant decreases in renal cortical protein-bound sulfhydryl concentration, alkaline phosphatase activity, and ATPase activity within 2.5 h of administration, with no effect observed on glutathione peroxidase activity or the levels of conjugated dienes in rat renal cortex. Administration of DTT 60 min after mercury neither provided protection from inhibition nor promoted restoration of the affected enzymes or sulfhydryl status. It is concluded that the partial protection of renal function offered by DTT in the early stages of mercury toxicity does not result from maintaining the integrity of renal cortical sulfhydryl status or the activity of the enzymes investigated. Furthermore, the early stages of mercury toxicity did not appear to be related to lipid peroxidation.

Alkaline Phosphatase↗
PubMed1988

Regulation of human natural cytotoxicity by enkephalins and selective opiate agonists.

This study reports a bidirectional effect of the enkephalins and selective opiate receptor agonists on human natural killer (NK) cell activity. Peripheral blood mononuclear cells (PBMC) were obtained from healthy donors and enriched for T lymphocytes and large granular lymphocytes (LGL) by passage over nylon wool columns. Nylon wool nonadherent cell populations were preincubated for 18 h in the presence of fetal bovine serum with and without methionine-enkephalin, leucine-enkephalin, dynorphin (fragment 1-13), [D-Ser2]-leucine-enkephalin-Thr (DSLET), and [D-Ala2,N Me-Phe4, Gly-ol5]-enkephalin (DAGO). NK activity was measured by a standard 51Cr release assay with radiolabeled K562 cells. The cytolytic capacity of low NK responder populations was enhanced by the endogenous opioids while the NK activity of high responder populations was suppressed. These results suggest an immunoregulatory action of opioid peptides on NK activity. This possibility was confirmed using a serum-free system in conjunction with recombinant interferon-alpha. In addition, the classic opioid receptor antagonist naloxone displayed both antagonist and direct immunomodulatory properties, which may indicate the presence of lymphocyte derived opioid peptides in the culture system.

Adult↗