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Biomedical subjects

D L Johnson

Publications and source records attributed to D L Johnson.

At least 163 records · Page 9Linked to original sources
PubMed1995

Role of apnea in nonaccidental head injury.

We hypothesize that apnea induced by shaking or by shaking combined with impact plays a major role in the pathophysiology of nonaccidental head trauma and accounts for the poor outcome in this subgroup of patients. In a retrospective study of 28 children who suffered significant nonaccidental head injury, 57% had a history of apnea prior to hospitalization, 82% were intubated upon admission, and 71% had early seizures. For further evidence of ischemia and hypoxia, the first recorded blood pressure was < 80 in 50% and the arterial pH < 7.3 in 54%. Seventy-one percent had diffuse brain swelling which is characteristic of cerebral hypoxia and/or ischemia on the first CT scan. None of the children who had clinical evidence of cerebral hypoxia or ischemia had a good outcome. We conclude that trauma-induced apnea causes cerebral hypoxia and/or ischemia which is more fundamental to outcome than the mechanism of injury (shaken vs. shaken with impact), subdural hemorrhage, subarachnoid hemorrhage, diffuse axonal injury, parenchymal shear, or brain contusion.

Apnea↗
PubMed1995

Intracranial complications of sinusitis in childhood.

Complications of sinusitis in children, such as intracranial abscess formation, are uncommon and are often clinically unremarkable in comparison to similar disease processes in adults. Between 1983 and 1991, 443 children were admitted to Children's National Medical Center in Washington, DC, for treatment of sinusitis. Fourteen of these children presented with intracranial extension of the infection and abscess formation. A retrospective review of these patients revealed that the risk of developing an intracranial abscess secondary to sinusitis was 3%. The management of these patients included surgical drainage of the infected sinuses and intracranial surgical exploration. Cranialization and exenteration of the frontal sinus proved to be effective single-stage procedures. While not indicated in all patients, these procedures eliminated the sinus as a source of continued or potential infection and obviated the need for a second obliterative procedure. Combined antimicrobial therapy and surgical drainage should be the management protocol.

Adolescent↗
PubMed1995

Combined sagittal and lateral sinus dural fistulae occlusion.

The clinical course of three patients who had combined sagittal and lateral sinus dural fistulae is described. One patient, with impending blindness and a short life span, underwent right lateral sinus thrombosis in one stage. The second patient underwent sagittal and right lateral sinus thrombosis in four stages, and her remaining lateral sinus spontaneously occluded. A small untreated fistula persists in the right lower sigmoid. The third patient underwent sagittal sinus, left lateral sinus, and left parietal sinus thrombosis in six stages. A small untreated far-anterior fistula persists. All "satellite" fistulae have spontaneously disappeared. The small asymptomatic untreated residual fistulae have no demonstrable retrograde venous drainage and, therefore, require no treatment at this time.

Adult↗
PubMed1994

The rat vault RNA gene contains a unique RNA polymerase III promoter composed of both external and internal elements that function synergistically.

A novel gene transcribed by RNA polymerase (pol) III has been recently identified that produces an RNA component of a large cytoplasmic ribonucleoprotein complex (Kickhoefer, V. A., Searles, R. P., Kedersha, N. L., Garber, M. E., Johnson, D. L., and Rome, L. H. (1993) J. Biol. Chem. 268, 7868-7873). Since sequence analysis revealed that this gene contains promoter elements from two different classes of RNA pol III gene promoters, we examined the function of the 5'-flanking type-3 and internal type-2 sequences on transcription activity and the production of stable transcription complexes. We find that the vRNA gene contains a novel RNA pol III promoter, where both the external and internal sequences are essential for template activity and for the productive interaction of TFIIIC with the internal elements. Thus, the vRNA gene represents the first example of a template that requires both type-2 and type-3 promoter elements that appear to function synergistically in the formation of productive transcription complexes. We have further examined the function of the unique arrangement of an internal A box and two B box elements. We find that at least one B element is required for template activity. In the absence of the 5'-flanking sequence the presence of both B elements inhibits transcription and the binding of TFIIIC. The formation of active complexes is restored when either the B2 element is inactivated or the distance separating the two B elements is increased. Therefore, the B2 element appears to negatively regulate template activity in the absence of the upstream sequences. This unique RNA pol III promoter arrangement may provide a novel mechanism for the regulation of vRNA gene activity.

Animals↗
PubMed1994

The effects of lesions of the entorhinal cortex and the horizontal nucleus of the diagonal band of broca upon performance of a spatial location recognition task.

The effects of lesions of the horizontal nucleus of the diagonal band of Broca (HNDB) and the entorhinal cortex (ENTO) upon performance of a spatial location recognition task were assessed. Two hypotheses of entorhinal cortex function were considered in interpretation of the data. The first hypothesis assumes that the anatomical proximity and interconnections between the hippocampus and the entorhinal cortex are indicative of a functional similarity. The second hypothesis recognizes the interconnections of the hippocampus and the entorhinal cortex, but posits that the two structures have distinct functions. The hippocampus receives input primarily from the medial septum (MS), whereas the entorhinal cortex receives input from the HNDB and the MS. The study attempted to assess the function of the ENTO and the HNDB in a spatial location recognition task with the intent of comparing the findings to previous research of the hippocampus and MS. Performance of animals with HNDB lesions and the ENTO lesions was at chance levels for all serial positions. Results indicated that there are functional differences between the HNDB and other basal forebrain structures. Further, the performance deficit of the ENTO group does not differ from that observed following lesions of the hippocampus.

Animals↗
PubMed1994

Tubular atrophy in the end-stage kidney: a lectin and immunohistochemical study.

Atrophic tubules in end-stage renal disease (ESRD) may have various morphologic appearances: some show microscopic features of "classic" atrophic tubules (thick, wrinkled tubular basement membrane and simplified epithelium), others show "thyroidization" (round tubules with simplified epithelium and casts), and many have the appearance of "endocrine" tubules (small tubules with narrow lumina, clear cells, and relatively thin basement membranes). Other tubules in ESRD may be enlarged and dilated with hypertrophic cells ("super" tubules). The exact segment of the nephron from which these tubules arise in ESRD has not been well studied. We examined paraffin sections of 28 end-stage kidneys with a panel of nephron-segment-specific renal epithelial markers (proximal nephron markers: Tetragonolobus purpureas and Phaseolus vulgaris erythroagglutinin lectins; distal nephron markers: antibodies to epithelial membrane antigen, low molecular weight cytokeratin [AE1/AE3], the lectin Arachis hypogaea, and an antibody to Tamm-Horsfall protein labeling the thick ascending limb of Henle). In addition, an antibody to proliferating cell nuclear antigen was applied to determine the proliferation index (proliferating cell nuclear antigen-positive nuclei/all counted nuclei x 100, ie, the percentage of proliferating cell nuclear antigen-positive nuclei) of the various atrophic and "super" tubules in ESRD. Classic atrophic tubules and the "super" tubules showed primarily a proximal phenotype. Tubules showing thyroidization were consistently positive with markers of the distal tubular epithelium. "Endocrine" tubules stained primarily with distal tubular markers; however, some proximal staining also was noted. The widened renal interstitium contained single cells or loosely organized small cell clusters positive with both the AE1/AE3 and the epithelial membrane antigen antibodies. Serial sectioning showed that the majority of these single cells were not forming tubules. The proliferation index of the "classic" atrophic tubules was the highest (3.08%), followed by the "super" tubules (2.39%), the "endocrine" tubules (1.58%), and the "thyroid" tubules (1.09%). These indexes are all considerably higher than the proliferation index of the normal renal tubular epithelium. Our findings suggest that different types of tubular atrophy may arise from different segments of the nephron, and that the renal interstitium in ESRD may harbor isolated cells with epithelial characteristics. Furthermore, the end-stage kidney is not a resting organ; on the contrary, it shows a high proliferative activity, particularly in the epithelium of the "classic" atrophic and the "super" tubules.

Adult↗
PubMed1994

Use of intravenous alfentanil-midazolam anesthesia for sedation during brief endourologic procedures.

Traditionally, general or regional anesthesia has been employed during endourologic procedures. The success of sedative-analgesic sedation during SWL prompted an investigation into its use in minor endourologic procedures. We compared intravenous alfentanil-midazolam anesthesia (n = 30) with spinal anesthesia (n = 35) during procedures such as ureteroscopy and stent placement using physiologic measures and patient and anesthetist ratings. The former series was prospective; the latter was retrospective. Physiologic measures remained stable and oxygen saturation was above 90% in all patients in both groups during the procedures. The average anesthesia and recovery room times were significantly shorter for patients given alfentanilmidazolam: 23.3 v 36.1 minutes and 85.5 v 179.6 minutes, respectively (P < 0.001; t-test), and this difference reduced the anesthesia cost an average of 46%. The anesthetists rated the intravenous regimen satisfactory in 92% of the patients, and 94% of the patients rated the procedure as comfortable. All 18 of the patients who had previously had spinal anesthesia considered alfentanil-midazolam superior. Intravenous alfentanil-midazolam sedation anesthesia can provide adequate analgesia for many minor endourologic procedures while shortening the anesthesia recovery time.

Alfentanil↗
PubMed1994

Induction of Drosophila RNA polymerase III gene expression by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) is mediated by transcription factor IIIB.

We have previously found that the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) induces specific transcription of tRNA and 5S RNA genes in Drosophila Schneider S-2 cells (M. Garber, S. Panchanathan, R. F. Fan, and D. L. Johnson, J. Biol. Chem. 266:20598-20601, 1991). Having derived cellular extracts from TPA-treated cells, that are capable of reproducing this stimulation in vitro, we have examined the mechanism for this regulatory event. Using conditions that limit reinitiation and produce single rounds of transcription from active gene complexes, we find that the number of functional transcription complexes is increased in extracts prepared from TPA-induced cells. We have analyzed the activities of the transcription factors TFIIIB and TFIIIC derived from extracts prepared from TPA-induced and noninduced cells. Examination of the relative activities of TFIIIC showed that both its ability to reconstitute transcription with TFIIIB and RNA polymerase III and its ability to stably bind to the DNA template are unchanged. However, the activity of TFIIIB derived from the TPA-induced cells is substantially increased compared with that derived from the noninduced cells. The differences in TFIIIB activity account for the differences in the overall transcriptional activities observed in the unfractionated extracts. Western blot analysis of the TATA-binding protein subunit of TFIIIB revealed that there is an increase in the amount of this polypeptide present in the induced cell extracts and TFIIIB fraction. Together, these results indicate that the TPA response in Drosophila cells stimulates specific transcription of RNA polymerase III genes by increasing the activity of the limiting transcription component, TFIIIB, and thereby increasing the number of functional transcription complexes.

Animals↗
PubMed1994

Parosteal lipoma: MR imaging characteristics.

OBJECTIVE: The purpose of this study was to determine the characteristics of parosteal lipomas on MR imaging. MATERIALS AND METHODS: We retrospectively reviewed the images and medical records of eight patients with surgically and pathologically confirmed parosteal lipomas. Radiologic studies performed included conventional radiography and MR imaging (n = 8), CT (n = 7), conventional tomography (n = 2), and scintigraphy (n = 5). RESULTS: Osseous reaction was present in all cases, manifesting as either mild cortical thickening best seen on magnification radiographs or larger osseous excrescences seen on all radiologic images. These osseous reactions were surrounded by the lipomatous component of the neoplasm and created a firm attachment of the neoplasm to the underlying bone. The lipomatous component showed typical features of adipose tissue on all images and was usually seen on radiographs (n = 7). However, CT or MR imaging was needed to determine the anatomic location and relationship to surrounding structures before surgery. MR imaging was considered superior to CT for preoperative assessment, primarily because of its multiplanar imaging capability. In addition, cartilage and fibrous tissue (n = 3) were identified adjacent to larger osseous excrescences. Associated muscle atrophy in three cases was caused by nerve impingement. These manifestations of parosteal lipoma were also better assessed with MR images because of improved contrast resolution. The distribution of muscle atrophy could be used to determine the site of nerve involvement preoperatively. CONCLUSION: We conclude that MR imaging is the most useful adjunct to conventional radiography in the presurgical evaluation of parosteal lipomas because of its multiplanar imaging capabilities and improved contrast resolution for detecting muscle atrophy and site of nerve involvement when present. These factors are important for preoperative assessment to help guide surgical intervention.

Adolescent↗
PubMed1994

Performance by gender in a stop-smoking program combining hypnosis and aversion.

Increased rates of smoking initiation and smoking-related illness among women have narrowed the gender gap in smoking behavior. Past studies of performance by gender in prevention and treatment programs have reported reduced success with women and have suggested a need for stronger interventions having greater effects on both genders' smoking cessation. A field study of 93 male and 93 female CMHC outpatients examined the facilitation of smoking cessation by combining hypnosis and aversion treatments. After the 2-wk. program, 92% or 86 of the men and 90% or 84 of the women reported abstinence, and at 3-mo. follow-up, 86% or 80 of the men and 87% or 81 of the women reported continued abstinence. Although this field study in a clinical setting lacked rigorous measurement and experimental controls, the program suggested greater efficacy of smoking cessation by both sexes for combined hypnosis and aversion techniques.

Aversive Therapy↗
PubMed1994

Quality of long-term survival in young children with medulloblastoma.

The reported success of treatment for children with medulloblastoma must be balanced against the effect that treatment has on the quality of life of long-term survivors. The outcome of long-term survivors reported in previous studies has been conflicting. The authors evaluate the mental and behavioral skills of a group of medulloblastoma survivors from their institution, all of whom had survived for more than 5 years postdiagnosis. A review of the institutional records yielded 32 patients. Twenty-three families were interviewed by telephone and, of these, 13 subjects came to the hospital for detailed neuropsychological and neurological evaluations. Intelligence quotient (IQ) was less than 90 for all participants tested, and patients diagnosed before the age of 3 years had lower IQ scores on average than those diagnosed later. Mean IQ and achievement test scores in reading, spelling, and mathematics were all higher in survivors who had undergone shunting. Achievement test results were often not in accord with intellectual potential, and individual intellectual skills varied widely. Perceptual-motor task performance was below average in more than 50% of the participants, but motor dexterity was more severely affected than perception. Problems in learning and a delay in both physical growth and development were seen in a majority of participants. This study directs attention to the serious difficulties faced by long-term survivors of medulloblastoma and their families, and underscores the importance of routine neuropsychological testing. Moreover, the study provides further impetus to seek alternatives to irradiation in the treatment of malignant brain tumors.

Adolescent↗
PubMed1994

The origin of the long head of the biceps from the scapula and glenoid labrum. An anatomical study of 100 shoulders.

We dissected 105 cadaveric shoulders to study the origin of the tendon of the long head of biceps, and examined histologically the interrelationship between the tendon, the supraglenoid tubercle and the superior labrum of the glenoid. In all specimens approximately 50% of the biceps tendon arose directly from the superior glenoid labrum with the remainder attached to the supraglenoid tubercle. The main labral origin was from the posterior labrum in more than half of the specimens, and in a quarter this was the only labral attachment. On the basis of the biceps attachment to the anterior or posterior labrum, we distinguished four types of origin. These normal anatomical variations are significant for arthroscopic diagnosis and may help to explain the various patterns of injury seen in partial or complete detachment of the tendon, the labrum or both.

Cadaver↗
PubMed1994

Ultrastructure and mineral composition of urinary calculi from horses.

Urinary calculi from 17 horses with urolithiasis were examined to study their mineral content and ultrastructure. Among the analytic methods used were X-ray diffractometry, scanning electron microscopy, and electron microprobe analysis. The calculi initially were observed by use of a stereoscopic dissecting microscope and generally were found to have nodular surfaces surrounding a banded or granular-to-chalky interior. Observation by scanning electron microscopy revealed an intricate pattern of irregularly concentric, fine bands and spherules. These had a round, finely banded, globular texture formed by precipitation of ultrafine-grained radiating crystals. The original pore spaces (ie, between spherules, between bands and spherules, or between crystal generations) could be observed as primary porosity. Precipitation and dissolution of these urinary calculi were observed to be spontaneous processes, which can occur simultaneously within an individual calculus. Another prominent feature of the ultrastructure was secondary porosity (spontaneous dissolution) which, in its incipient stages, appeared to be site-selective (ie, some bands appeared to be more susceptible to development of pinpoint porosity). Textures indicative of dissolution were observed not only on the calculus surface, but within the calculus interior as well. Areas that had more advanced stages of dissolution, resulting in increased secondary porosity, also were observed. All 17 samples of the study were found to be composed of calcium carbonate in the form of the mineral calcite, although minor quantities of 2 other polymorphs of calcium carbonate, minerals vaterite and aragonite, also were encountered. Vaterite was observed in 5 of the samples, whereas aragonite was found in 1 sample. Strontium and sulfur were observed as trace elements in 3 of the calculi, whereas magnesium was present in all calculi. Magnesium was observed to substitute for calcium within the calcite crystal lattice in larger quantities than those of strontium or sulfur. Magnesium K alpha X-ray dot maps generated by use of an electron microprobe analyzer indicated that the distribution pattern of magnesium appeared to closely follow layer-by-layer growth of the calculus. Magnesium distribution also appeared to be related to porosity development. In samples where preferential dissolution was observed, the more porous areas had higher magnesium content. Quantitative chemical analyses, using the electron microprobe analyzer, confirmed these observations. Association of the magnesium distribution pattern to the primary growth texture of the calculus indicated that magnesium content of the calculus varied during the formation process. This also indicated that changes in urine chemical analytes may be reflected in composition of the calculi formed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗