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Biomedical subjects

K D Johnson

Publications and source records attributed to K D Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1986

Oligosaccharide Side Chains of Glycoproteins that Remain in the High-Mannose Form Are Not Accessible to Glycosidases.

Glycoproteins present in the soluble and organelle fractions of developing bean (Phaseolus vulgaris) cotyledons were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, affinoblotting, fractionation on immobilized concanavalin A (ConA), and digestion of the oligosaccharide side chains with specific glycosidases before and after protein denaturation. These studies led to the following observations. (a) Bean cotyledons contain a large variety of glycoproteins that bind to ConA. Binding to ConA can be eliminated by prior digestion of denatured proteins with alpha-mannosidase or endoglycosidase H, indicating that binding to ConA is mediated by high-mannose oligosaccharide side chains. (b) Bean cotyledons contain a large variety of fucosylated glycoproteins which bind to ConA. Because fucose-containing oligosaccharide side chains do not bind to ConA, such proteins must have both high-mannose and modified oligosaccharides. (c) For all the glycoproteins examined except one, the high-mannose oligosaccharides on the undenatured proteins are accessible to ConA and partially accessible to jack bean alpha-mannosidase. (d) Treatment of the native proteins with alpha-mannosidase removes only 1 or 2 mannose residues from the high-mannose oligosaccharides. Similar treatments of sodium dodecyl sulfate-denatured or pronase-digested glycoproteins removes all alpha-mannose residues. The results support the following conclusions: certain side chains remain unmodified as high-mannose oligosaccharides even though the proteins to which they are attached pass through the Golgi apparatus, where other oligosaccharide chains are modified. The chains remain unmodified because they are not accessible to processing enzymes such as the Golgilocalized alpha-mannosidase.

Journal Article↗
PubMed1986

Biomechanical performance of locked intramedullary nail systems in comminuted femoral shaft fractures.

The biomechanical properties of commercially available locked nail systems designed for use in comminuted femoral shaft fractures were compared and evaluated. Ender nails as well as three forms of interlocking nails, Brooker-Wills (B-W), Klenm-Schellman (K-S), and Grosse-Kempf (G-K), were implanted in cadaver femora. The femora were tested in torsion, bending, and axial loading to failure. Two fracture models were tested--a 3 cm subtrochanteric defect and an 8 cm midshaft defect. Results of the testing revealed the three interlocking nails to be comparable to each other and superior to Ender nails in bending and torsion. However, the distally bolted locked nails (K-S, G-K) resisted significantly higher loads than either the distally bladed locked nail (B-W) or Ender nails when tested to failure by axial loading.

Adult↗
PubMed1986

Treatment of tibial fractures by reaming and intramedullary nailing.

We treated 112 fractures of the tibia by manipulative reduction, reaming of the medullary canal, and fixation of the fracture fragments with an intramedullary nail. Seventy-six of the fractures were acute, and eight of these were second or third-degree open fractures. The other thirty-six fractures had a non-union, osteotomy for malunion, or failure of other types of treatment. Follow-up of 100 fractures showed union in all but one, which was in a drug abuser who had an amputation due to infection. The main complication was infection, which was successfully treated in six of seven fractures. The method of treatment, employing either closed or open technique and recently making use of interlocking bolts to stabilize one or both principal fracture fragments on the nail, is an excellent one for unstable acute fractures and for secondary procedures in fractures that are not associated with infection. The infection rate was increased with the open surgical technique. The few contraindications to its use are described.

Adolescent↗
PubMed1986

Orthopedic experience with methicillin-resistant Staphylococcus aureus during a hospital epidemic.

Thirty-eight orthopedic patients with proven methicillin-resistant Staphylococcus aureus (MRSA) infections were assessed as to the effectiveness of treatment. All patients were admitted between June 1981 and September 1983 and were among the 508 patients who had positive cultures for MRSA during that period. The average age of the patients was 32.5 years. Thirty-two patients had fractures. In 70% of the patients the injury was due to a motor vehicle accident. Sixty percent of the patients had Grade III open fractures with severe soft tissue injury or associated vascular injury. All patients were given antibiotics within 30 days of a positive culture, with 97% getting a first-generation cephalosporin. There were an average of 5.5 surgical procedures per patient (range, one to 16). Nine patients (24%) required amputation and eight (21%) lost joints either by excision or fusion. Only 14 patients (37%) healed without drainage. Four patients (10%) healed the original fracture or surgery with chronic drainage. There were three nonunions, two of which continue to drain. The antibiotic cost for Vancomycin alone increased 300%, from $2,000 in 1982 to approximately $680,000 in 1983. Methicillin-resistant in 1983. Methicillin-resistant S. aureus (MRSA) has significant epidemic potential. Infection with this organism carries a high-morbidity in order to control the organism. Any reported case of MRSA should be isolated quickly and thoroughly investigated epidemiologically in an attempt to prevent an epidemic. Vancomycin is the antibiotic of choice. Emphasis should be placed on the interruption of transmission of MRSA within and among hospitals. Serious consideration must be given to the long-term effects of prophylactic antibiotics.

Adolescent↗
PubMed1985

Incidence of adult respiratory distress syndrome in patients with multiple musculoskeletal injuries: effect of early operative stabilization of fractures.

Records of 132 consecutive patients with multiple musculoskeletal injuries were examined for the purpose of assessing the relationship between the length of time from injury to the operative stabilization of major fractures and the incidence of adult respiratory distress syndrome (ARDS). To be included in the study patients had to have had at least two major long-bone fractures and a Hospital Trauma Index-Injury Severity Score (ISS) of 18 or higher. Early operative fracture stabilization (STAB) is defined as an operation in the first 24 hours postinjury at which the majority of fractures were stabilized without leaving a spine, pelvis, or femur fracture unstable. A stepwise logistic regression was performed on the data. The dependent variable was the presence or absence of ARDS. The independent variables were age, sex, number of injuries, days to first surgery, early operative fracture stabilization (STAB), units of blood the first week, and ISS and its major components: RESP, ABD, CV, EXT, NS, and SSQ. The two independent variables selected as significant by this procedure were STAB and ISS. For the overall data set, a delay in orthopedic surgery (greater than 24 hours) is associated with a five-fold increase in the incidence of ARDS (p less than 0.001). For the more severely injured patients (ISS greater than 40), the comparable rates are 17% with early surgery and 75% with delayed surgery (p less than 0.001). A Chi-square test for association between ARDS and STAB adjusting for changes due to ISS grouping is significant (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Biomechanical factors affecting fracture stability and femoral bursting in closed intramedullary rod fixation of femur fractures.

Intramedullary rodding of femur fractures, although a safe and rapidly performed procedure, can result in several complications. If the rod fit is too loose, fracture instability, rod migration, and delayed union may result. If the rod fit is too tight, cracking of the femur may occur during rod insertion. These complications were investigated in terms of geometric and mechanical parameters of the bone-implant system. Results showed that rods of the same nominal size from different manufacturers showed more than twofold difference in flexural rigidity and a threefold difference in torsional modulus. These differences appear to be due to differences in cross sectional shape and wall thickness of the rods. Measurements of pushout force and hoop stress in cadaver femora showed a large difference in pushout force with different rods, and significantly lower forces in distal than in proximal femoral fracture components. Pushout force decreased with fracture component length proximally and dropped to zero in distal components less than 170 mm long. An increase in ream diameter in the distal components of just 1 mm was found to decrease the mean pushout force from 740N to 90N. The most significant variable was found to be anterior offset of the starting hole more than 6 mm from the centerline of the medullary canal which resulted in consistent lifting of the anterior cortex during insertion of the rod.

Adult↗
PubMed1984

The conserved 5 S rRNA complement to tRNA is not required for translation of natural mRNA.

We have tested a putative base-paired interaction between the conserved GT psi C sequence of tRNA and the conserved GAAC47 sequence of 5 S ribosomal RNA by in vitro protein synthesis using ribosomes containing deletions in this region of 5 S rRNA. Ribosomes reconstituted with 5 S rRNA possessing a single break between residues 41 and 42, deletion of residues 42-46, or deletion of residues 42-52 were tested for their ability to translate phage MS2 RNA. Initiator tRNA binding, aminoacyl-tRNA binding, ppGpp synthesis, and miscoding were also tested. All of the measured functions could be carried out by ribosomes carrying the deleted 5 S rRNAs. The sizes and relative amounts of the polypeptides synthesized by MS2 RNA-programmed ribosomes were identical whether or not the 5 S RNA contained deletions. Aminoacyl-tRNA binding and miscoding were essentially unaffected. Significant reduction in ApUpG (but not poly(A,U,G) or MS2 RNA)-directed fMet-tRNA binding and ppGpp synthesis were observed, particularly in the case of the larger (residues 42-52) deletion. We conclude that if tRNA and 5 S rRNA interact in this fashion, it is not an obligatory step in protein synthesis.

Base Composition↗
PubMed1984

Development of a variable stiffness external fixation system for stabilization of segmental defects of the tibia.

The mechanical properties of a variable stiffness external fixation system were explored. Initial testing of a unilateral fixator configuration demonstrated that system rigidity could be increased by maximizing pin separation distance in the fracture component and the number of pins used while minimizing pin separation distance across the fracture site and the sidebar offset distance from bone. A triangulated system composed of half pin frames mounted anteriorly and medially on the tibial aspects and linked by crossbars was devised. Progressive disassembly of the frame was shown to result in progressive decreases in fixator rigidity in all planes.

Biomechanical Phenomena↗
PubMed1984

A biomechanical comparison of various methods of stabilization of subtrochanteric fractures of the femur.

Subtrochanteric femoral fractures with and without bony contact were simulated in cadaver specimens, fixed with one of seven different types of intramedullary or plate implants, and tested biomechanically. The implants used were Enders pins, Zickel nail, compression hip screw, AO angled blade plate, and intramedullary locked nail systems of the Klemm-Schellman, Brooker-Wills, and Grosse-Kempf types. Femur-implant constructs using intramedullary devices were a maximum of 5% as stiff in torsion as intact cadaveric femora tested in the same manner, while plate-fixed fractures were nearly 50% as stiff. In bending, all devices except the Enders pins were approximately 80% as stiff as intact femora. Loss of bony contact at the fracture site had little effect on stiffness except in the case of the keyless compression hip screw, where the screw rotated freely in the barrel. In combined bending and compression to failure, a test to simulate forces due to body weight, the intramedullary locked rods were found to support between 300 and 400% of body weight while the plate systems failed at loads between 100 and 200% of body weight.

Biomechanical Phenomena↗
PubMed1984

Immediate internal fixation of open ankle fractures. Report of thirty-eight cases treated with a standard protocol.

We reviewed thirty-eight cases of open ankle fractures that had been treated with a standard protocol: alignment and splinting of the fracture at the scene of injury if possible, antibiotics administered in the emergency room and continued for forty-eight hours, admission of the patient to the operating room as quickly as possible, copious irrigation and thorough débridement of the wound, immediate rigid anatomical internal fixation, and delayed primary closure at five days. All of the fractures united, but three patients required subsequent ankle fusion because of cartilage damage noted at the initial operation. Of the thirty-five ankles with complete follow-up, the functional result was excellent in twenty-six and fair or poor in nine.

Adolescent↗
PubMed1984

Comminuted femoral-shaft fractures: treatment by roller traction, cerclage wires and an intramedullary nail, or an interlocking intramedullary nail.

In a retrospective study, we attempted to assess progress in the treatment of comminuted fractures of the femoral shaft at Parkland Memorial Hospital from 1978 to 1983. Seventy-nine comminuted femoral-shaft fractures were available for follow-up: thirty-two treated by roller traction, twenty-three treated by cerclage wires and an intramedullary nail, and twenty-four treated by an interlocking intramedullary nail. Using the classification of Winquist and Hansen, Grade-III and IV comminuted fractures accounted for 69 per cent of those treated by roller traction, 68 per cent of those treated by nailing and cerclage wires, and 96 per cent of those treated by an interlocking nail. The frequency of multiple injuries was 38 per cent in the patients treated by roller traction, 39 per cent in those treated by nailing and cerclage wires, and 58 per cent in those treated by an interlocking nail. The average hospitalization times were thirty-one days for roller traction, sixteen days for cerclage wires and an intramedullary nail, and 19.5 days for an interlocking nail. The average length of follow-up was 132 weeks after roller traction, 115 weeks after cerclage wiring and an intramedullary nail, and sixty weeks after insertion of an interlocking nail. All fractures were followed until after union; the average times to union were 18.4 weeks after roller traction, thirty-four weeks after open reduction and intramedullary nailing with cerclage wires, and 13.8 weeks after insertion of an interlocking nail. For the purposes of this study, treatment was assumed to have failed if a change in treatment was necessary, an unplanned reoperation was performed, femoral shortening exceeded 2.5 centimeters, angulation was more than 15 degrees, non-union or a deep infection developed, motion of the knee was less than 70 degrees of flexion, or a refracture occurred. By these criteria, the frequency of failure after roller traction was 66 per cent (secondary to malalignment and shortening); after insertion of an intramedullary nail with cerclage wires, 39 per cent (secondary to unplanned surgery, non-union, shortening, and infection); and after use of an interlocking nail, 4 per cent (secondary to shortening). Currently, at our institution, an interlocking intramedullary nail is the treatment of choice for comminuted femoral-shaft fractures because it encourages early union with maintenance of length and alignment and the results are predictable.

Adolescent↗
PubMed1982

Enzymatic and chemical structure mapping of mouse 28S ribosomal ribonucleic acid contacts in 5.8S ribosomal ribonucleic acid.

Secondary structure mapping experiments using S1 nuclease, RNase T1, and diethyl pyrocarbonate as conformational probes have identified those regions in mouse 5.8S rRNA containing major sites of interaction with 28S rRNA. One site encompasses the 3'-terminal 20 nucleotides and corresponds to the region identified previously as a component of an RNase-resistant 5.8S/28S rRNA junction complex. A second site, located at the 5' terminus, has not been defined precisely but is believed to involve approximately 20--30 nucleotides. The existence of these sites of interaction is supported by comparing sequences of eukaryotic 5.8S and 28S rRNA with those of the prokaryotic 23S rRNA. Evidence for the occurrence of at least three helical regions in the central portion of the mouse 5.8S rRNA molecule is also presented.

Animals↗
PubMed1982

Conserved 5S rRNA complement to tRNA is not required for protein synthesis.

The notion that tRNA and 5S rRNA interact through evolutionarily conserved complementary sequences has been tested by nucleolytic modification of the 5S rRNA, using the modified rRNA to reconstitute the large ribosomal subunit, and assaying for poly(uridylic acid)-directed polyphenylalanine synthesis. The 5S rRNA sequence C-G-A-A (residues 43-46) and several residues surrounding it are not essential for protein synthesis.

Base Sequence↗