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Biomedical subjects

K D Johnson

Publications and source records attributed to K D Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1990

Digestibility and feeding value of pearl millet as influenced by the brown-midrib, low-lignin trait.

Our objectives were to determine the intake and digestibility of pearl millet as influenced by the brown-midrib (BMR), low-lignin trait and to determine the relative acceptability of BMR pearl millet in relation to its normal counterpart. Two field replicates of brown-midrib pearl millet and its normal counterpart were harvested as hay at the boot to heading stage twice during the growing season (2 genotypes x 2 cuttings x 2 field replicates). Twenty-four wethers had ad libitum access to a total forage diet (pearl millet forage), water and trace mineralized salt. The experimental period was 21 d (14 d for adjustment and 7 d for sample collection). Lignin was 23% lower (P less than or equal to .01) and in vitro DM digestibility (IVDMD) was 4% higher (P less than or equal to .01) in BMR vs normal genotype forages. Wethers preferred first-cutting millet to second-cutting millet, as evidenced by 62% higher (P less than or equal to .01) DMI for first-cutting forages. Dry matter intake of second-cutting forages was higher (P less than or equal to .10) for BMR pearl millet forage than for normal pearl millet (2.0 vs 1.5% of BW), but first-cutting forages were similar in DMI (2.9% of BW). In an acceptability trial of pearl millet regrowth (4 wk), grazing lambs with access to both genotypes displayed a marked preference (P less than .01) for the BMR genotype, spending an average of 2.6 min on plots containing the brown-midrib pearl millet for every minute spent on the normal genotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1990

Mechanics of intramedullary nails for femoral fractures.

Biomechanical studies were carried out to assess the function and performance of intramedullary (IM) nails for femoral fractures. An appropriately sized femoral IM nail with a radius of curvature of about 109 cm would most closely match the anterior bow of most human femora. A number of parameters can interact to result in bursting of the femur during insertion of the nail. These include mismatch in curvature of the nail and femur, high stiffness in bending, and poor location of the starting hole. An anatomic starting position for the IM nail is just medial to the greater trochanter and anterior to the pyriformis recess. Moving anterior to the midline of the femur significantly increases the potential for bursting the femur during insertion of the nail. Other factors can decrease the force of insertion of the IM nail in the femur. These include overreaming, shortening the axial length of the fracture component, and use of a nail of lower bending rigidity. IM-nail-fixed femoral shaft fractures with locking bolts can be expected to have about 75% the rigidity of the intact femur in bending and can support about 400% of normal body weight (= 70 kg). Slotted IM nail/femur constructs have only about 3% the rigidity of the intact femur in torsion, while an unslotted (closed) section implant produces constructs with about 50% the rigidity. The distal locking bolts increase the torsional rigidity and maximum axial load capacity of the construct, and reduce the potential for shortening and the residual deformation upon release of a torsional load. Two distal bolts reduce the toggle of the nail in the femoral shaft.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗
PubMed1989

A review of reduction and internal fixation of adult femoral neck fractures in a county hospital.

Treatment of femoral neck fractures at a county hospital, Parkland Memorial Hospital, Dallas, Texas, from 1978 to 1983 was reviewed. A study of the use of the quadratus femoris muscle-pedicle graft (MPG) as adjunctive treatment to open reduction and internal fixation (ORIF) was in effect during that time. Patients who had primary prosthetic replacement of their femoral head were not included in the study. Two groups of patients were identified, one group that had ORIF without a muscle-pedicle graft (no-MPG) and another group that had ORIF with a muscle-pedicle graft (MPG). There were a similar number of patients in each group (MPG = 25 patients, no-MPG = 24 patients). Although the groups were not exactly similar, the overall outcome was unexpected. The no-MPG group had 76% good-to-excellent results whereas the MPG group had only 24%. A poor result or outright failure of the technique occurred in 68% of the MPG group and in only 16% of the no-MPG group. No accurate assessment of the incidence of avascular necrosis of the femoral head could be made.

Adolescent↗
PubMed1989

Characterization of a xylose-specific antiserum that reacts with the complex asparagine-linked glycans of extracellular and vacuolar glycoproteins.

Antibodies were raised against carrot (Daucus carota) cell wall beta-fructosidase that was either in a native configuration (this serum is called anti-betaF(1)) or chemically deglycosylated (anti-betaF(2)). The two antisera had completely different specificities when tested by immunoblotting. The anti-betaF(1) serum reacted with beta-fructosidase and many other carrot cell wall proteins as well as with many proteins in extracts of bean (Phaseolus vulgaris) cotyledons and tobacco (Nicotiana tabacum) seeds. It did not react with chemically deglycosylated beta-fructosidase. The anti-betaF(1) serum also reacted with the bean vacuolar protein, phytohemagglutinin, but not with deglycosylated phytohemagglutinin. The anti-betaF(2) serum reacted with both normal and deglycosylated beta-fructosidase but not with other proteins. These results indicate that the betaF(2) antibodies recognize the beta-fructosidase polypeptide, while the betaF(1) antibodies recognize glycan sidechains common to many glycoproteins. We used immunoadsorption on glycoprotein-Sepharose columns and hapten inhibition of immunoblot reactions to characterize the nature of the antigenic site. Antibody binding activity was found to be associated with Man(3)(Xyl)(GIcNAc)(2)Fuc, Man(3)(Xyl)(GIcNAc)(2), and Man(Xyl) (GIcNAc)(2) glycans, but not with Man(3)(GIcNAc)(2). Treatment of phytohemagglutinin, a glycoprotein with a Man(3)(Xyl)(GIcNAc)(2)Fuc glycan, with Charonia lampas beta-xylosidase (after treatment with jack-bean alpha-mannosidase) greatly diminished the binding between the antibodies and phytohemagglutinin. We conclude, therefore, that the antibodies bind primarily to the xylosebeta, 1--> 2mannose structure commonly found in the complex glycans of plant glycoproteins.

Journal Article↗
PubMed1989

An abundant, highly conserved tonoplast protein in seeds.

We have isolated the membranes of the protein storage vacuoles (protein bodies) from Phaseolus vulgaris cotyledons and purified an integral membrane protein with M(r) 25,000 (TP 25). Antiserum to TP 25 recognizes an abundant polypeptide in the total cell extracts of many different seeds (monocots, dicots, and a gymnosperm), and specifically labels the vacuolar membranes of thin-sectioned soybean embryonic axes and cotyledons. TP 25 was not found in the starchy endosperm of barley and wheat or the seed coats of bean but was present in all seed parts examined that consist of living cells at seed maturity. The abundance of TP 25 was not correlated with the amount of storage protein in seed tissue, and the protein was not found in leaves that accumulate leaf storage protein. On the basis of its abundance, evolutionary conservation, and distribution in the plant, we propose that TP 25 may play a role in maintaining the integrity of the tonoplast during the dehydration/rehydration sequence of seeds.

Journal Article↗
PubMed1989

Intramedullary nailing with reaming to treat non-union of the tibia.

The records of fifty-one patients who were treated by intramedullary nailing with reaming for non-union of the tibia were retrospectively reviewed. The fractures had been treated initially by closed reduction and immobilization in a cast, external fixation followed by immobilization in a cast, fixation by pins incorporated in a plaster cast, minimum internal fixation and immobilization in a cast, dynamic compression plating, or intramedullary nailing with or without reaming. After the initial treatment had failed, intramedullary nailing with reaming was done to gain union. Although closed nailing of the tibia was preferred, in thirty-three patients, the site of the non-union was opened to improve alignment by performing an osteotomy or to remove failed hardware. Bone grafts from the iliac crest were used in ten patients, and a fibular ostectomy or osteotomy was done in thirty-three. Of thirty-four open fractures (fourteen grade I, seven grade II, and thirteen grade III), eight were infected at the time of intramedullary nailing. The average time of the diagnosis of a non-union was 9.6 months; the average length of follow-up after nailing was twenty months. In forty-nine (96 per cent) of the fifty-one patients, tibial union occurred at an average of seven months postoperatively. Complications included persistent infection (three patients), acquired infection after intramedullary nailing with reaming (three patients), fracture of the nail that necessitated an additional operation (two patients), shortening of more than one centimeter (two patients), malrotation of more than 15 degrees (one patient), peroneal palsy (one patient), and amputation (one patient). When used to treat non-union of the tibia, intramedullary nailing with reaming can produce union as effectively as other alternatives, while enabling the patient to function more normally without external immobilization or walking aids.

Adolescent↗
PubMed1989

Early versus delayed stabilization of femoral fractures. A prospective randomized study.

A prospective randomized study comparing the results of early with delayed reduction and stabilization of acute femoral fractures in adults was performed over a two-year period in 178 patients. Only patients who were more than sixty-five years old and had a fracture of the hip were excluded. Arterial blood gases, injury-severity score at the time of admission, pulmonary function, days in the hospital, days in the intensive-care unit, and hospital costs were recorded for all patients. The patients were divided into two groups: those who had an isolated fracture of the femur and those who had multiple injuries. When stabilization of the fracture was delayed in the patients who had multiple injuries, the incidence of pulmonary complications (adult respiratory-distress syndrome, fat embolism, and pneumonia) was higher, the hospital stay was longer, and the number of days in the intensive-care unit was increased. The cost of hospital care showed a statistically significant increase for all patients who had delayed treatment of the fracture compared with those who had early stabilization.

Adolescent↗
PubMed1988

Severe open tibial fractures: a study protocol.

A prospective randomized study of severe open tibial fractures (Type II and III) was performed. Individual fractures were randomized to treatment groups according to initial antibiotic therapy: One consisted of a first-generation cephalosporin, and the other consisted of a third-generation cephalosporin. Initial antibiotic therapy was given in all patients for 48 h and then specific antibiotic treatment was used as indicated by culture. The purpose of this study was to determine whether or not additional gram-negative coverage had an effect on the overall infection rate or the type of infection in severe open tibial fractures. Additional factors, such as the timing of bone grafts and soft tissue coverage, were evaluated in this study as well. Although there was no statistical difference in the rate of infection with the use of a first- versus a third-generation cephalosporin, there was a trend toward a decreased infection rate as well as toward less morbid infections with the use of a third-generation cephalosporin. The study also confirms that early bone graft should not be performed prior to 6 weeks post injury or after successful soft tissue coverage has been achieved. On the other hand, soft tissue coverage procedures should be performed at the earliest possible date to decrease the overall infection rate.

Adolescent↗
PubMed1987

Biomechanical factors affecting fracture stability and femoral bursting in closed intramedullary nailing of femoral shaft fractures, with illustrative case presentations.

Closed intramedullary nailing is an accepted method of treatment for femoral shaft fractures. Technical complications of the procedure include fracture instability, which may result in proximal nail migration, malrotation, delayed union, and occasionally femoral bursting during insertion of the nail, sometimes leading to fracture instability as well as shortening. This study defines the effect of starting hole position, fracture component length, reamed diameter, and nail type on the potential for femoral bursting and fracture instability. The most significant factor in the proximal femoral component was found to be the position of the starting hole. Anterior displacement by greater than 6 mm from the neutral axis of the medullary canal consistently caused high hoop stresses at the level of the fracture, which resulted in bursting of the proximal femoral component by lifting off the anterior cortex. Hoop stresses at the level of the fracture were less sensitive to lateral or medial placement of the starting hole. Distally, fracture stability was governed by femoral component length and reamed diameter. In the proximal and distal components, fracture stability and the potential for bursting were influenced by the particular nail used. This was due to significant differences in mechanical geometric properties between nails of different manufacturers. Case reports are presented to illustrate these biomechanical principles as they apply to clinical situations.

Adult↗
PubMed1987

Treatment of unstable femoral shaft fractures with closed interlocking intramedullary nailing.

From 1979 to 1982, 64 femoral shaft fractures in 62 patients were treated by closed interlocking nailing at Harborview Medical Center, Seattle, WA, U.S.A., and Parkland Memorial Hospital, Dallas, TX, U.S.A. Twenty-nine patients sustained multiple system injuries and 29 of the involved extremities (45%) had at least one additional injury. There were 17 (26%) open fractures. Static mode nailing was used to treat 52 fractures; dynamic mode nailing was performed for 12 fractures. Patient follow-up averaged 17 months (range 7-41 months). The average time to union was 13.5 weeks. Normal femoral length within 1 cm was achieved in 97% of cases. Knee range of motion averaged 127 degrees. Complications (9%) included two delayed unions, one nonunion, two cases of shortening or lengthening of more than 1 cm, and one case of malunion with angulation or more than 10 degrees. The delayed unions and nonunions healed after one additional procedure. This study shows that closed interlocking nailing is a safe, effective technique that provides stable fixation in most unstable femoral shaft fractures. This technique represents a major advance in the treatment of difficult femoral shaft fractures that would be poorly suited for standard closed nailing.

Adolescent↗
PubMed1987

Substrate Specificities of N-Acetylglucosaminyl-, Fucosyl-, and Xylosyltransferases that Modify Glycoproteins in the Golgi Apparatus of Bean Cotyledons.

As part of their posttranslational maturation process, newly synthesized glycoproteins that contain N-linked oligosaccharide side chains pass through the Golgi apparatus, where some of their oligosaccharides become modified by carbohydrate processing reactions. In this paper, we report the presence of Golgi-localized enzymes in plant cells (Phaseolus vulgaris cotyledons) that transfer GlcNAc, fucosyl, and xylosyl residues to the oligosaccharide side chains of glycoproteins. All three enzyme activities are involved in the transformation of high mannose side chains into complex glycans. As judged by acceptor specificity studies, at least two GlcNAc residues can be added to the nonreducing side of high mannose oligosaccharides, which have been trimmed by alpha-mannosidase(s). A Man(5)(GlcNAc)(2)-peptide serves as the acceptor for the first GlcNAc added. The second GlcNAc can be added only after the prior removal of two additional mannose residues, ultimately yielding (GlcNAc)(2)Man(3)(GlcNAc)(2)-peptide. Fucosyltransferase can transfer fucose to GlcNAcMan(5)(GlcNAc)(2)Asn, GlcNAcMan(3)(GlcNAc)(2)Asn, and (GlcNAc)(2)Man(3)(GlcNAc)(2)Asn; xylosyltransferase exhibits significant activity toward the latter two substrates only. These results suggest an overlapping sequence of oligosaccharide modification in the Golgi apparatus that, in regard to GlcNAc and fucose additions, is analogous to pathways of oligosaccharide processing reported for animal cells. To our knowledge, this is the first report characterizing a xylosyltransferase involved in N-linked oligosaccharide modification, an activity that is apparently absent in most animal cells.

Journal Article↗
PubMed1987

Subcellular localization of glycosidases and glycosyltransferases involved in the processing of N-linked oligosaccharides.

Using isopycnic sucrose gradients, we have ascertained the subcellular location of several enzymes involved in the processing of the N-linked oligosaccharides of glycoproteins in developing cotyledons of the common bean, Phaseolus vulgaris. All are localized in the endoplasmic reticulum (ER) or Golgi complex as determined by co-sedimentation with the ER marker, NADH-cytochrome c reductase, or the Golgi marker, glucan synthase I. Glucosidase activity, which removes glucose residues from Glc(3)Man(9)(GlcNAc)(2), was found exclusively in the ER. All other processing enzymes, which act subsequent to the glucose trimming steps, are associated with the Golgi. These include mannosidase I (removes 1-2 mannose residues from Man(6-9)[GlcNAc](2)), mannosidase II (removes mannose residues from GlcNAcMan(5)[GlcNAc](2)), and fucosyltransferase (transfers a fucose residue to the Asn-linked GlcNAc of appropriate glycans). We have previously reported the localization of two other glycan modifying enzymes (GlcNAc-transferase and xylosyltransferase activities) in the Golgi complex. Attempts at subfractionation of the Golgi fraction on shallow sucrose gradients yielded similar patterns of distribution for all the Golgi processing enzymes. Subfractionation on Percoll gradients resulted in two peaks of the Golgi marker enzyme inosine diphosphatase, whereas the glycan processing enzymes were all enriched in the peak of lower density. These results do not lend support to the hypothesis that N-linked oligosaccharide processing enzymes are associated with Golgi cisternae of different densities.

Journal Article↗
PubMed1987

Management of malunion and nonunion of the tibia.

When treating acute tibial shaft fractures, every attempt should be made to prevent malunion or nonunion of the tibia. When these complications occur, tibial osteotomy and intramedullary nailing is a functional treatment alternative when infection is not present. Treatment of an infected nonunion usually requires staged protocol using several surgical procedures to effect an acceptable outcome.

Bone Lengthening↗
PubMed1987

Distal femoral fractures.

Distal femoral fractures may be treated by operative or nonoperative methods. There is no single surgical implant that can be used for all distal femoral fractures. Implant selection is determined by fracture pattern, patient age, bone density, and other injuries that the patient may have sustained. Rewarding results may be obtained with operative fracture intervention when appropriate patient and implant selection is made and the surgeon demonstrates meticulous skill and sound judgment.

Bone Plates↗
PubMed1987

Comminuted femoral shaft fractures.

Comminuted femoral shaft fractures are often grouped with more simple femoral fractures for study. Although union always occurs, shortening and angulation can result from closed treatment using traction and cast bracing. Operative intervention using locked intramedullary nails can lead to a consistently excellent outcome when the performance of the procedure is technically correct. The surgical procedure can eliminate a difficult management problem in multiply-injured patients.

Bone Nails↗