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Biomedical subjects

D L Johnson

Publications and source records attributed to D L Johnson.

At least 127 records · Page 7Linked to original sources
PubMed1996

Discovery of the hemifumarate and (alpha-L-alanyloxy)methyl ether as prodrugs of an antirheumatic oxindole: prodrugs for the enolic OH group.

Ether, ester, and carbonate derivatives of the antirheumatic oxindole 1 were prepared and screened as potential prodrugs of 1. This effort led to the discovery of the (alpha-L-alanyloxy)-methyl ether and hemifumarate derivatives of 1 which deliver the drug efficiently into the circulation of test animals, are stable in the solid state, and possess good stability in solution at low pH as required to ensure gastric stability. Success in achieving acceptable bioavailabilities of 1 across species (rats, dogs, and monkeys) followed the inclusion of ionizable functionality within the promoiety to compensate for masking the polar enolic OH group of the free drug. However, the introduction of ionizable functionality was often associated with decreased stability, as demonstrated by the hemisuccinate, hemiadipate, hemisuberate, and alpha-amino ester derivatives of 1 which could not be isolated. A clear exception was the hemifumarate derivative of 1 which was not only isolable but actually more stable at neutral pH than the nonionizable ester analogues. The solution and solid state stability of the hemifumarate, together with its activity as a prodrug of 1, suggests that hemifumarate be considered as an alternative to hemisuccinate as a prodrug derivative for alcohols, particularly in situations where solution state stability is an issue.

Animals↗
PubMed1996

Effects of spaceflight on rat peripheral blood leukocytes and bone marrow progenitor cells.

The white blood cell (WBC) elements and the bone marrow myeloid progenitor cell populations were analyzed to ascertain adaptation to micro-gravity and subsequent readaptation to 1 G in rats flown on the 14-day Spacelab Life Sciences-2 (SLS-2) mission. Bone marrow cells were harvested from one group of rats killed inflight (FD13) and blood was drawn from three other groups at various times. The WBC level was normal on FD14 with the exception of neutrophilia. On FD13, numbers of colony-forming units-granulocyte (CFU-G), CFU-GM, and CFU-M from flight animals were decreased compared with ground controls when incubated with recombinant rat interleukin-3 (rrIL-3) alone or in combination with recombinant human erythropoietin (rhEpo). On recovery (R + 0), flight rats had decreased numbers of total leukocytes and absolute numbers of lymphocytes and monocytes with elevated neutrophils compared with control rats. They had lower numbers of CD4, CD8, CD2, CD3, and B cells in the peripheral blood but no differences in spleen lymphocytes.

Animals↗
PubMed1996

Refolding, purification, and characterization of human erythropoietin binding protein produced in Escherichia coli.

The extracellular domain of the human erythropoietin receptor (EPO binding protein (EBP)) has been expressed and overproduced in Escherichia coli. Regardless of the presence ofpelB or ompT signal sequences the recombinant protein produced in this fashion appears, as with many other recombinant eukaryotic proteins produced in E. coli as an insoluble product in laboratory scale fermentations. The induction product of the pelB protein expression system appears as two protein forms with slightly different molecular weights. Based on N-terminal sequence analysis of recovered protein, these forms represent two variants, one with the signal sequence properly processed to yield the expected "native" amino terminus and another which retains the signal sequence. Both forms appear as insoluble fermentation products. Control of oxygen levels and pH during high density fermentation allows the production of only the protein variant with the native amino terminus. Methods reported here permit the efficient recovery of purified EBP which quantitatively binds EPO in solution as determined by high performance size exclusion chromatography. A long-lived refolding intermediate was observed which penultimately collapses into an active conformation. The active purified protein competes with membrane associated EPO receptor for binding [125I]EPO and neutralizes EPO-dependent stimulation in a cell based proliferation assay. Further, the radioligand equilibrium binding constant for this interaction has been determined by immobilizing EBP on agarose gel via a free cysteine. The production of EBP by these methods should facilitate the structural determination of the protein by NMR or crystallography and may serve as a guide for the refolding of other hematopoietic receptors.

Amino Acid Sequence↗
PubMed1996

The dimpling phenomenon: articular cartilage injury overlying an occult osteochondral lesion at the time of anterior cruciate ligament reconstruction.

The authors report the arthroscopic finding of articular cartilage "dimpling" when a probe is placed onto the discrete chondral area involved over the geographic bone bruise incurred during traumatic anterior cruciate ligament disruption. As we develop an understanding of the pathology and sequelae of this osteochondral injury, this finding may be useful to document injury extent and possibly guide treatment including weight-bearing status and rehabilitation.

Anterior Cruciate Ligament↗
PubMed1996

Occupational exposure of nonsmoking nightclub musicians to environmental tobacco smoke.

This study assessed environmental tobacco smoke (ETS) exposures of nonsmoking musicians in nightclub environments using total suspended particulate (TSP), the ultraviolet absorbing fraction of TSP (UVPM), gaseous nicotine, saliva nicotine, saliva cotinine, and perceived smokiness as exposure/dose indicators. Measured exposures were as high or higher than those of other occupational groups studied. TSP ranged from 110 to 1714 micrograms/m3 (mean 502, SD 390 micrograms/m3). UVPM (mean 221, SD 95 micrograms/m3) was associated with gaseous and saliva nicotine concentrations. Paired-sample variation was much higher for TSP than for UVPM. Correlation of TSP with UVPM, gaseous nicotine, and saliva nicotine was poor. Paired-sample gaseous nicotine results were similar, with exposures of 28.0 to 50.0 micrograms/m3 (mean 37.1, SD 6.9 micrograms/m3), and were high compared with previous studies. These results suggested that nightclub musicians may be exposed to higher concentrations of ETS than some other occupational groups. Saliva nicotine results were consistent with those previously reported with regard to the range of values, large variation observed, and increase in saliva nicotine levels observable after only a few hours of exposure. Saliva nicotine results could not be correlated with other measures of exposure and did not appear to be a reliable biological indicator of absorbed dose. Saliva cotinine levels were comparable to other occupational groups studied, but were lower than previous findings for bartenders and waitresses. Levels ranged from 1.7 to 5.0 ng/mL (mean 3.4, SD 0.9 ng/mL), and increased with number of exposures during the workweek, but did not correlate with other ETS indicators.

Adult↗
PubMed1996

Quantitative analysis of In-111 satumomab pendetide immunoscintigraphy. An aid to visual interpretation of images in patients with suspected carcinomatosis.

The diagnosis of the diffuse intrapertioneal spread of ovarian or colorectal carcinoma (carcinomatosis) can be difficult when based on visual interpretation of immunoscintigraphic images alone. Twenty-nine patients with either colorectal or ovarian cancer were retrospectively evaluated by three technologists for carcinomatosis employing a quantitative analysis technique that compares uptake of In-111 satumomab pendetide (Oncoscint CR/ OV, Cytogen Corp., Princeton, NJ) in a region of interest in the femoral vascular bundle to the uptake in two regions of interest in the lower abdomen, resulting in an uptake ratio (UR). All 29 patients underwent laparotomy after immunoscintigraphy. Of the 29 patients evaluated, 7 had histologically proven carcinomatosis obtained from the laparotomy. Using quantitative analysis, patients who did not have carcinomatosis had a mean uptake ratio of 1.12, and patients with carcinomatosis had a mean uptake ratio of 2.12. The differences between the means of these two groups of patients was statistically significant for all three technologists (P < .05). The results of this study indicate that there is a significant difference in uptake ratios between patients with carcinomatosis and those without it, and that quantitative analysis can be a useful adjunct to visual interpretation.

Abdomen↗
PubMed1996

Revision anterior cruciate ligament surgery: experience from Pittsburgh.

Twenty-five patients who underwent revision anterior cruciate ligament reconstruction after failure of a previous intraarticular reconstruction were retrospectively reviewed. Before revision, all patients reported functional instability with sports or activities of daily living and exhibited increased anterior patholaxity on physical examination. Fresh frozen irradiated allograft tissue was used for all revisions. A comprehensive knee analysis using a subjective and objective system was done for all patients preoperatively and at the time of final followup. The mean age at revision surgery was 25 years and average time from primary to revision surgery was 30 months. Average length of followup was 28 months. The anteroposterior displacement was improved in all patients. Sixty-four percent of patients had less than 5 mm side to side difference on arthrometric testing. Eighty percent had either a Grade 0 or Grade 1 pivot shift. The average modified Cincinnati Knee Score was 68 with the results of 88% of patients rated abnormal by International Knee Documentation Committee guidelines. Seventy-six percent of patients were satisfied with their results and would elect to have revision surgery again. These results show that patients having revision anterior cruciate ligament reconstruction for a failed intraarticular reconstruction had improvement in their functional status compared with prerevision; however, they did not achieve the same level of satisfactory results as primary anterior cruciate ligament reconstruction.

Activities of Daily Living↗
PubMed1996

TATA-binding protein is limiting for both TATA-containing and TATA-lacking RNA polymerase III promoters in Drosophila cells.

We have investigated the role of the TATA-binding protein (TBP) in modulating RNA polymerase (Pol) III gene activity. Epitope-tagged TBP (e-TBP) was both transiently and stably transfected in Drosophila Schneider S-2 cells to increase the total cellular level of TBP. Analysis of the transcripts synthesized from cotransfected tRNA and U6 RNA genes revealed that both types of RNA Pol III promoters were substantially stimulated by an increase in e-TBP in a dose-dependent manner. Furthermore, a TBP-dependent increase in the levels of endogenous tRNA transcripts was produced in the stable line induced to express the e-TBP. We further determined whether the ability of increased TBP to induce RNA Pol III gene expression was due to a direct effect of increased TBP complexes on RNA Pol III gene promoters or an indirect consequence of enhanced expression of RNA Pol II genes. A TBP expression plasmid (e-TBP332), containing a mutation within the highly conserved carboxy-terminal domain, was both transiently and stably transfected into S-2 cells. e-TBP332 augmented the transcription from two RNA Pol II gene promoters indistinguishably from that observed when e-TBP was expressed. In contrast, e-TBP332 was completely defective in its ability to stimulate either the tRNA or U6 RNA gene promoters. In addition, increasing levels of a truncated TBP protein containing only the carboxy-terminal region failed to induce either the tRNA or U6 RNA gene promoter, whereas it retained its ability to stimulate an RNA Pol II promoter. Thus, the TBP-dependent increase in RNA Pol II gene activity is not sufficient for enhanced RNA Pol III gene transcription; rather, a direct effect on RNA Pol III promoters is required. Furthermore, these results provide the first direct evidence that the amino-terminal region of TBP is important for the formation or function of TBP-containing complexes utilized by TATA-less and TATA-containing RNA Pol III promoters. Together, these studies demonstrate that TBP is limiting for the expression of both classes of RNA Pol III promoters in Drosophila cells and implicate an important role for TBP in regulating RNA Pol III gene expression.

Animals↗
PubMed1996

Transcriptional activation of RNA polymerase III-dependent genes by the human T-cell leukemia virus type 1 tax protein.

The human T-cell leukemia virus-encoded tax protein is a potent activator of many viral and cellular genes transcribed by RNA polymerase II. We find that both chromatin and cell extracts derived from human T-cell leukemia virus type 1-infected human T lymphocytes support higher levels of 5S rRNA and tRNA gene transcription than chromatin or extracts from uninfected T lymphocytes. The viral protein Tax was likely responsible for this higher level of class II gene transcription, as purified Tax was found to stimulate both genes when added to the uninfected cell extract or in reconstituted systems. Both limiting-component transcription assays and DNA binding assays identified the class III gene transcription factor TFIIIB as the principle target of Tax activity. Surprisingly, we find that Tax increases the effective concentration of active TFIIIB molecules. These data suggest that Tax stimulates RNA polymerase III-dependent gene expression by accelerating the rate and/or extent of transcription initiation complex assembly.

Base Sequence↗
PubMed1996

Fluid flow stimulates rapid and continuous release of nitric oxide in osteoblasts.

Interstitial fluid flow may mediate skeletal remodeling in response to mechanical loading. Because nitric oxide (NO) has been shown to be an osteoblast mitogen and inhibitor of osteoclastic resorption, we investigated and characterized the role of fluid shear on the release of NO in osteoblasts. Rat calvarial cells in a stationary culture produced undetectable levels of NO. Fluid shear stress (6 dyn/cm2) rapidly increased NO release rate to 9.8 nmol.h-1.mg protein-1 and sustained this production for 12 h of exposure to flow. Cytokine treatment also induced NO synthesis after a 12-h lag phase of zero production, followed by a production rate of 0.6 nmol.h-1.mg protein-1. Flow-induced NO production was blocked by the NO synthase (NOS) inhibitor NG-amino-L-arginine, but not by dexamethasone, which suggests that the flow stimulated a constitutive NOS isoform. This is the first time that a functional constitutively present NOS isoform has been identified in osteoblasts. Moreover, fluid flow represents the most potent stimulus of NO release in osteoblasts reported to date. Fluid flow-induced NO production may therefore play a primary role in bone maintenance and remodeling.

Animals↗
PubMed1996

Effects of spaceflight on rat erythroid parameters.

Hematologic studies were performed on 21 ground control rats and 21 rats flown during the Spacelab Life Sciences-2 14-day mission. Group A (n = 5) was used to collect blood in flight and 9 days postflight, group B (n = 5) was injected with recombinant human erythropoietin (rhEpo), group C (n = 5) received saline as a control, and group D (n = 6) was killed in flight and tissues were collected. Results indicated no significant changes in peripheral blood erythroid elements between flight and ground control rats. The nonadherent bone marrow on flight day 13 showed a lower number of recombinant rat interleukin-3 (rrIL-3)-responsive and rrIL-3 + rhEpo-responsive blast-forming unit erythroid (BFU-e) colonies in flight rats compared with ground control rats. On landing day, a slight increase in the number of rhEpo + rrIL-3-responsive BFU-e colonies of flight animals compared with ground control rats was evident. Nine days postflight, bone marrow from flight rats stimulated with rhEpo alone or with rhEpo + rrIL-3 showed an increase in the number of colony-forming unit erythroid colonies and a decrease in BFU-e colonies compared with ground control rats. This is the first time that animals were injected with rhEpo and subsequently blood and tissues were collected during the spaceflight to study the regulation of erythropoiesis in microgravity.

Animals↗
PubMed1996

Lymphatic tissue changes in rats flown on Spacelab Life Sciences-2.

Thymus, spleen, inguinal lymph node, and bone marrow specimens from rats flown on the 14-day Spacelab Life Sciences-2 mission were examined after staining of tissue sections. The primary observation was a transient retrogressive change in lymphatic tissues in the rats within a few hours after landing. There was a diffuse increase in tingible body-containing macrophages in the cortex of the thymus, thymus-dependent areas of the splenic white pulp, and inguinal lymph node. This was not observed 9 days after recovery. The in situ labeling of fragmented DNA strands catalyzed by exogenous terminal deoxynucleotidyltransferase (TdT) with ApopTag reagents (Oncor, Gaithersburg, MD) inside the tingible body-containing macrophages indicated that the process was one of apoptosis. No increase in tingible body macrophage activity was noted in thymus and spleen tissue obtained from rats in flight on flight day 13. The reaction to gravitational stress from readaptation to 1 G is the most likely explanation of the transient retrogressive change in lymphatic tissues.

Adaptation, Physiological↗
PubMed1996

Epileptic seizure as a sign of cerebrospinal fluid shunt malfunction.

Epilepsy was evident in 308 of 817 (38%) children with shunted hydrocephalus. The first seizure occurred after shunting in 181 of 817 (22%), a median of 1.6 years after the original shunt procedure. The incidence of seizures was not statistically different in the parietooccipital, parietotemporal, or frontal region. Over a 15-year period, 16 of 544 (2.9%) visits to the emergency room for seizures culminated in shunt revision, and 16 of 1,831 (0.9%) shunt revisions were associated with a seizure. Although seizures in shunted patients are not uncommon, a seizure is seldom an indication of shunt malfunction.

Brain↗
PubMed1996

Send severely head-injured children to a pediatric trauma center.

Between 1985 and 1988, a total of 1,320 head-injured children were seen by the neurosurgical service at the Children's Hospital in Washington, D.C. (CHOW). This included 1,095 minor injuries, 127 moderate injuries, and 98 severe injuries. Children brought from the scene of an accident were considered direct transports, whereas those taken to another hospital prior to transfer to CHOW were indirect. Of the children that suffered severe head injuries, 56 were admitted directly to the hospital and 42 indirectly. The indirect group had a higher percentage of children with lower coma scores and abused children. The trauma score was significantly higher in the direct group (9 vs. 7). The mortality rate for severe injuries referred directly from the scene of the accident was 26.8%, and the mortality rate for children referred indirectly was 50.0%. The higher number of abused children in the indirect group did not account for the increase in mortality rate (p = 0.021) in this group. This is the first study to show that children brought directly from the scene of an accident to a well-established pediatric trauma center have a significantly better chance of survival than children transported first to the nearest available hospital.

Adolescent↗
PubMed1996

Brachioradialis transfer for wrist extension in tetraplegic patients who have fifth-cervical-level neurological function.

The brachioradialis tendon was transferred to the extensor carpi radialis longus and brevis tendons to restore active extension of the wrist in nine patients who had traumatic tetraplegia. The classification of neurological function was the fifth cervical level for all patients. The average time from the injury to the operation was six years (range, one to twenty years), and the average duration of follow-up was ten years (range, two to fifteen years). The evaluation of the patient included a determination of the preoperative and postoperative ranges of motion of the wrist, manual muscle-testing of the strength of the brachioradialis and the wrist extensors, a functional assessment of the ability to perform activities of daily living (eating, grooming, dressing, personal hygiene, and desktop activities [writing, typing, using a telephone, and so on]), and an assessment of functional independence. In addition, the result of the operation was evaluated subjectively by the patient. No patient had active extension of the wrist against gravity preoperatively. The strength of the wrist extensors improved postoperatively to a grade of good in six patients and to a grade of fair-plus in three. Function of the hand improved markedly in seven patients, and no patient had a loss of function. The patients had improvement in the ability to pick up objects, to feed and groom themselves, to tend to personal hygiene, to write and type, and to use a telephone.

Activities of Daily Living↗
PubMed1996

Participation in multicomponent hypnosis treatment programs for women's weight loss with and without overt aversion.

Studies of hypnotic, covert and overt aversive techniques have yielded equivocal results when each has been examined for a singular effect on weight lost. Some have advocated study of effective combinations of techniques before investing in other applications. Two programs of hypnosis, imagery, diet, tape, behavior management and support but differing in the overt use of aversion (electric shock, disgusting tastes smells) were examined. A total of 172 overweight adult women were treated, 86 in a hypnosis only and 86 in an overt aversion and hypnosis program. Both programs achieved significant weight losses. Although subjects who received overt aversion attained somewhat more desired goals and lost more weight than subjects recovering only hypnosis, the differences were not significant.

Adult↗
PubMed1996

Breast feeding and children's intelligence.

Breast feeding was reported in 1992 by Lucas, et al. to provide advantages for the development of intelligence in children of low birth weight, possibly through nutrients or other biological factors found in human breast milk but not cow's milk. Research on breast feeding and intelligence in children of normal birth weight has yielded mixed results, probably because measurement of environmental influences has not been thorough and the range of intelligence components measured has been limited. Our research with 204 3-year-old children of normal birth weight included control measures for the environment and maternal intelligence (Hollings-head socioeconomic status, Home Observation for the Measured Environment, Shipley) and two measures of childhood intelligence (Stanford-Binet Fourth Edition and Peabody Picture Vocabulary Test-Revised). Controlling for environmental variables and maternal intelligence, initiation of breast feeding predicted scores on intelligence tests at age three. Breast feeding was associated with 4.6-point higher mean in children's intelligence.

Breast Feeding↗