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Biomedical subjects

D L Johnson

Publications and source records attributed to D L Johnson.

At least 37 records · Page 2Linked to original sources
PubMed2001

Excretion of miserotoxin and detoxification of the aglycone by grasshoppers (Orthoptera: Acrididae).

Two species of grasshoppers (Melanoplus bivittatus and M. sanguinipes) tolerated high levels of miserotoxin (3-nitro-1-propyl-beta-D-glucopyranoside) in their diet. Miserotoxin is a causative agent in cattle poisoning when timber milkvetch (Astragalus miser) is consumed. Toxic effects were averted by grasshoppers in part by excretion of the intact glycoside. When the aglycone was administered, detoxification was achieved by two routes: by oxidation of the aglycone to 3-nitropropionic acid which was then conjugated with glycine, and by glucosylation of the aglycone to miserotoxin, in each case followed by excretion.

Animals↗
PubMed2001

Split biceps femoris tendon reconstruction for proximal tibiofibular joint instability.

Recurrent instability of the proximal tibiofibular joint is an infrequently diagnosed abnormality. We present a new technique for reconstructing the joint using a split biceps femoris tendon passed through a bone tunnel in both the proximal tibial metaphysis and fibular head. The case report is also presented. The procedure offers an anatomic reconstruction and firm stabilization. It allows normal motion of the proximal tibiofibular joint and preserves the normal mechanics of the ankle. This procedure is an excellent alternative to resection of the fibular head, transarticular arthrodesis, or pseudoarthrosis focus at the fibular head.

Adult↗
PubMed2001

What is "powder free"? Characterisation of powder aerosol produced during simulated use of powdered and powder free latex gloves.

OBJECTIVES: To characterise the distribution of particle size and mass of glove powder aerosol released from powdered and powder free non-sterile latex gloves under controlled conditions. METHODS: Gravimetric sampling and aerodynamic particle size analysis were performed during simulated use of gloves on a prosthetic hand in a chamber designed to minimise background particle concentrations. RESULTS: Aerosol was detectable for both powdered and powder free gloves under both aggressive and non-aggressive handling conditions. Most of the particles detected had aerodynamic diameter less than 10 microm. CONCLUSION: Powder free gloves were not entirely free of powder aerosol. Particles from both powdered and powder free gloves are sufficiently fine to penetrate into the thoracic region of the respiratory tract.

Air Pollutants, Occupational↗
PubMed2001

Biological control of locusts and grasshoppers.

Control of grasshoppers and locusts has traditionally relied on synthetic insecticides, and for emergency situations this is unlikely to change. However, a growing awareness of the environmental issues associated with acridid control as well as the high costs of emergency control are expanding the demand for biological control. In particular, preventive, integrated control strategies with early interventions will reduce the financial and environmental costs associated with large-scale plague treatments. The recent development of effective oil formulations of Metarhizium anisopliae spores in Africa, Australia, and Brazil opens new possibilities for environmentally safe control operations. Metarhizium biopesticide kills 70%-90% of treated locusts within 14-20 days, with no measurable impact on nontarget organisms. An integrated pest management strategy, with an emphasis on the use of Metarhizium, that incorporates rational use of chemical pesticides with biological options such as the microsporidian Nosema locustae and the hymenopteran egg parasitoids Scelio spp., has become a realistic option.

Animals↗
PubMed2001

Ultrastructure of selected calcium oxalate-containing urinary calculi from dogs.

OBJECTIVE: To elucidate the ultrastructural details of calcium oxalate-containing urinary calculi from dogs. Sample Population-38 specimens selected from a collection of 8,297 oxalate-containing urinary calculi from dogs: 22 specimens composed of calcium oxalate (calcium oxalate monohydrate [COM], calcium oxalate dihydrate [COD], or COM and COD) and 16 specimens composed of calcium oxalate with amorphous calcium phosphate. PROCEDURE: Analyses of specimens included use of plain, reflected, and polarized light microscopy, X-ray diffractometry, scanning electron microscopy (SEM) with backscattered electron (BSE) imagery, and electron microprobe analysis. RESULTS: Four texture types were observed in calcium oxalate calculi; 4 texture types of calcium oxalate-calcium phosphate-mixed calculi were recognized. Texture types were delineated through differences in calcium oxalate crystal sizes, which were affected by urine supersaturation and abundance of crystal nucleation sites. Segregation of calcium oxalate from calcium phosphate indicated they do not precipitate under the same conditions. Deposition of calcium phosphate between calcium oxalate crystals decreased the volume of pore spaces within calculi. Porosity was observed along boundaries between COM and COD. Minute pores increased the surface area of calculi exposed to urine, and this increase in liquid-solid interface promotes interaction of crystals with the surrounding urine. CONCLUSIONS AND CLINICAL RELEVANCE: Calcium oxalate urolithiasis is of major concern, because it is often a recurrent disease among dogs, principally treated by surgical removal of calculi, with few effective dissolution strategies. Understanding the ultrastructure and mineralogic content of calcium oxalate and its association with amorphous calcium phosphate is a step toward the solution of this increasingly important medical problem.

Animals↗
PubMed2001

Efficacy of a new premilking teat disinfectant containing a phenolic combination for the prevention of mastitis.

A teat disinfectant containing a phenolic combination was evaluated in a natural exposure study in two dairy research herds. Premilking teat disinfection was compared with a negative control using a split-udder experimental design. In both herds, premilking and postmilking teat disinfections with the phenolic combination were significantly more effective in preventing new intramammary infection (IMI) than was postmilking teat disinfection only. Clinical mastitis and new IMI by Streptococcus uberis, Streptococcus dysgalactiae, Gram-negative pathogens, and coagulase-negative Staphylococcus species were significantly lower in quarters of cows with teats predipped and postdipped than in quarters with teats postdipped only. No chapping or teat skin irritation was observed. Premilking teat disinfection with the phenolic combination in association with good udder preparation and postmilking teat disinfection can further reduce the occurrence of new IMI by numerous mastitis pathogens during lactation.

Animals↗
PubMed2001

The meniscus: review of basic principles with application to surgery and rehabilitation.

OBJECTIVE: To review basic meniscal anatomy, histology, and biomechanical principles as they apply to surgery and rehabilitation. DATA SOURCES: We searched MEDLINE and CINAHL for the years 1960-1999 using the terms meniscus,surgery,rehabilitation,meniscal repair, and arthroscopy. DATA SYNTHESIS: Injuries to a healthy meniscus are usually produced by a compressive force coupled with transverse-plane tibiofemoral rotation as the knee moves from flexion to extension during rapid cutting or pivoting. The goal of meniscal surgery is to restore a functional meniscus to prevent the development of degenerative osteoarthritis in the involved knee. The goal of rehabilitation is to restore patient function based on individual needs, considering the type of surgical procedure, which meniscus was repaired, the presence of coexisting knee pathology (particularly ligamentous laxity or articular cartilage degeneration), the type of meniscal tear, the patient's age, preoperative knee status (including time between injury and surgery), decreased range of motion or strength, and the patient's athletic expectations and motivations. Progressive weight bearing and joint stress are necessary to enhance the functionality of the meniscal repair; however, excessive shear forces may be disruptive. Prolonged knee immobilization after surgery can result in the rapid development of muscular atrophy and greater delays in functional recovery. CONCLUSIONS/RECOMMENDATIONS: Accelerated joint mobility and weight-bearing components of rehabilitation protocols represent the confidence placed in innovative surgical fixation methods. After wound healing, an aquatic therapy environment may be ideal during all phases of rehabilitation after meniscal surgery (regardless of the exact procedure), providing the advantages of controlled weight bearing and mobility progressions. Well-designed, controlled, longitudinal outcome studies for patients who have undergone meniscectomy, meniscal repair, or meniscal reconstruction are lacking.

Journal Article↗
PubMed2000

Synthesis and erythropoietin receptor binding affinities of N,N-disubstituted amino acids.

N,N-Dicinnamyl, N-benzyl-N-cinnamyl, and N,N-dibenzyl amino acids were prepared and evaluated in an EPO binding assay. Several derivatives of aspartic acid, glutamic acid, and lysine exhibited moderate (10-50 microM) affinity for EBP; 'dimerization' of the most potent analogues by coupling with linear diamines led to EPO competitors having 1-2 microM binding affinities.

Amino Acids↗
PubMed2000

On giving up on the mental health system.

This chapter describes how the author, who at the time was a practicing psychologist, became personally involved in advocacy for persons with mental illness. He also gives an overview of the activities of several organizations that are, or should be, advocating for this vulnerable population. He describes several specific programs that he sees as exemplary. Finally, the author argues for an approach for improving care, which he feels family and consumer advocates can be particularly effective in implementing.

Humans↗
PubMed2000

The epidemiology of knee dislocations.

The traumatically dislocated knee can be a devastating injury; fortunately, it is uncommon. More attention is being given to the treatment of knee dislocations as the capability of ligamentous reconstruction increases. Great treatment advances are anticipated as this interest grows and outcomes are evaluated. Nonetheless, the complications of this injury, including loss of limb, still occur from the missed diagnosis of a knee dislocation. MR imaging and other technological advances do not relieve the clinician of the responsibility for performing a thorough physical examination. Suspicion of an associated neurovascular injury must always be high. To a certain degree, prevention of this injury may be possible in the high-velocity accidents that occur with motor vehicles and in industry. Advancement in vehicular designs, with specific attention to airbags, dashboards, and firewalls, needs to be made to reduce the incidence and magnitude of lower extremity trauma in motor vehicle accidents. Seat belts remain the most effective restraint in the prevention of lower extremity trauma in the motor vehicle.

Accidents, Traffic↗
PubMed2000

Biomechanical comparison of quadriceps tendon fixation with patellar tendon bone plug interference fixation in cruciate ligament reconstruction.

PURPOSE: The purpose of this study was to use current fixation techniques and compare the stiffness and ultimate tensile failure of the tendinous end of the quadriceps tendon (QT) with the bone plug end of the bone-patellar tendon-bone (BPTB) graft using current techniques of fixation. TYPE OF STUDY: Randomized trial of elderly cadaver knees. MATERIALS AND METHODS: Tibial and femoral biodegradable interference fixation and femoral EndoButton (Smith & Nephew, Acufex, Mansfield, MA) fixation in bone tunnels with the QT and the BPTB graft were compared by using 10 pairs of elderly cadavers and biomechanical testing. Two groups, fixation at time zero (simulating fixation in the operating room) and testing after 1, 000 loading cycles (simulating patient rehabilitation exercises), were used. RESULTS: At time zero fixation, stiffness of the soft tissue QT tibial tunnel interference fixation was 59% less stiff than the stiffness of the interference fixation of a BPTB plug in a femoral tunnel (P =.11). The EndoButton femoral fixation resulted in a decrease in stiffness at time zero compared with femoral tunnel interference fixation of the soft tissue QT (P =.03). All groups improved stiffness with cycling the construct to 1,000 cycles. CONCLUSIONS: Placement of the QT tendinous end of the graft in the femoral bone tunnel when using a interference fixation will approximate the stiffness of a bone plug in the tibial bone tunnel with interference fixation. The EndoButton fixation is not as stiff as either of the femoral interference fixation options. The addition of more than 20 loading cycles could remove laxity from the graft fixation-graft cruciate ligament complex and improve its stiffness.

Anterior Cruciate Ligament↗
PubMed2000

The effect of fluorine-18 fluorodeoxyglucose positron emission tomography on the management of cutaneous malignant melanoma.

PURPOSE: To assess the effect of positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) on the treatment of patients with cutaneous malignant melanoma. MATERIALS AND METHODS: We retrospectively reviewed the medical records of 38 patients with newly diagnosed (n = 25) and recurrent (n = 13) cutaneous melanoma who were referred for evaluation with FDG PET imaging at our institution. We compared the PET findings with computed tomography (CT), which was available in 21 (55%) patients, and tabulated the changes in the diagnostic evaluation and therapeutic management that were prompted by PET during a follow-up period of 10 to 36 months. RESULTS: Compared with PET, the extent of disease was underestimated by CT in 5 (13%) patients. Planned surgical resection of metastases was canceled in two of these patients. In another patient, surveillance PET detected an unsuspected hypermetabolic abdominal mass that was noted on a subsequent CT to arise from the small bowel. The mass was found to be jejunal metastatic melanoma at the time of resection. Overall, PET influenced surgical management in 3 (8%) patients, but it did not affect the wait-and-watch strategy or decision to initiate immunotherapy in the others. CONCLUSIONS: FDG PET contributes important information not provided by CT and has a substantial effect on the clinical management of patients with malignant melanoma.

Adult↗
PubMed2000

Transcriptional regulation of the TATA-binding protein by Ras cellular signaling.

Our previous studies have demonstrated that the level of the central transcription factor TATA-binding protein (TBP) is increased in cells expressing the hepatitis B virus (HBV) X protein through the activation of the Ras signaling pathway, which serves to enhance both RNA polymerase I and III promoter activities. To understand the mechanism by which TBP is regulated, we have investigated whether enhanced expression is modulated at the transcriptional level. Nuclear run-on assays revealed that the HBV X protein increases the number of active transcription complexes on the TBP gene. In transient-transfection assays with both transformed and primary hepatocytes, the human TBP promoter was shown to be induced by expression of the HBV X protein in a Ras-dependent manner, requiring both Ral guanine nucleotide dissociation stimulator (RalGDS) and Raf signaling. Transient overexpression of TBP did not affect TBP promoter activity. To further delineate the downstream Ras-mediated events contributing to TBP promoter regulation in primary rat hepatocytes, the best-characterized Ras effectors, Raf, phosphoinositide 3-kinase (PI-3 kinase), and RalGDS, were examined. Activation of either Raf or RalGDS, but not that of PI-3 kinase, was sufficient to induce TBP promoter activity. Both Raf- and RalGDS-mediated induction required the activation of mitogen-activated protein kinase kinase (MEK). In addition, another distinct Ras-activated pathway, which does not require MEK activation, appears to induce TBP promoter activity. Analysis of the DNA sequence requirement within the TBP promoter responsible for these regulatory events defined three distinct regions that modulate the abilities of Raf, RalGDS, and the Ras-dependent, MEK-independent pathways to regulate human TBP promoter activity. Together, these results provide new evidence that TBP can be regulated at the transcriptional level and identify three distinct Ras-activated pathways that modulate this central eukaryotic transcription factor.

Animals↗
PubMed2000

RNA-Dependent replication and transcription of hepatitis delta virus RNA involve distinct cellular RNA polymerases.

Cellular DNA-dependent RNA polymerase II (pol II) has been postulated to carry out RNA-dependent RNA replication and transcription of hepatitis delta virus (HDV) RNA, generating a full-length (1.7-kb) RNA genome and a subgenomic-length (0.8-kb) mRNA. However, the supporting evidence for this hypothesis was ambiguous because the previous experiments relied on DNA-templated transcription to initiate HDV RNA synthesis. Furthermore, there is no evidence that the same cellular enzyme is involved in the synthesis of both RNA species. In this study, we used a novel HDV RNA-based transfection approach, devoid of any artificial HDV cDNA intermediates, to determine the enzymatic and metabolic requirements for the synthesis of these two RNA species. We showed that HDV subgenomic mRNA transcription was inhibited by a low concentration of alpha-amanitin (<3 microgram/ml) and could be partially restored by an alpha-amanitin-resistant mutant pol II; however, surprisingly, the synthesis of the full-length (1.7-kb) antigenomic RNA was not affected by alpha-amanitin to a concentration higher than 25 microgram/ml. By several other criteria, such as the differing requirement for the de novo-synthesized hepatitis delta antigen and temperature dependence, we further showed that the metabolic requirements of subgenomic HDV mRNA synthesis are different from those for the synthesis of genomic-length HDV RNA and cellular pol II transcripts. The synthesis of the two HDV RNA species could also be uncoupled under several different conditions. These findings provide strong evidence that pol II, or proteins derived from pol II transcripts, is involved in mRNA transcription from the HDV RNA template. In contrast, the synthesis of the 1.7-kb HDV antigenomic RNA appears not to be dependent on pol II. These results reveal that there are distinct molecular mechanisms for the synthesis of these two RNA species.

Animals↗
PubMed2000

Intrathecal baclofen for management of spastic cerebral palsy: multicenter trial.

Intrathecal baclofen infusion has demonstrated effectiveness in decreasing spasticity of spinal origin. Oral antispasticity medication is minimally effective or not well tolerated in cerebral palsy. This study assessed the effectiveness of intrathecal baclofen in reducing spasticity in cerebral palsy. Candidates were screened by randomized, double-blind, intrathecal injections of baclofen and placebo. Responders were defined as those who experienced an average reduction of 1.0 in the lower extremities on the Ashworth Scale for spasticity. Responders received intrathecal baclofen via the SynchroMed System and were followed for up to 43 months. Fifty-one patients completed screening and 44 entered open-label trials. Lower-extremity spasticity decreased from an average baseline score of 3.64 to 1.90 at 39 months. A decrease in upper extremity spasticity was evidenced over the same study period. Forty-two patients reported adverse events. Most common reports were hypotonia, seizures (no new onset), somnolence, and nausea or vomiting. Fifty-nine percent of the patients experienced procedural or system-related events. Spasticity in patients with cerebral palsy can be treated effectively by continuous intrathecal baclofen. Adverse events, although common, were manageable.

Adolescent↗