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Biomedical subjects

J A Shaw

Publications and source records attributed to J A Shaw.

At least 19 recordsLinked to original sources
PubMed1992

Angled bearing inserts in total knee arthroplasty. A brief technical note.

Malalignment of total knee prosthetic components may lead to premature wear, loosening of components, or patellar instability. Unfortunately, removal of securely cemented or ingrown components is difficult and may be extremely destructive to the available bone stock. Angled bearing inserts provide a means to compensate for malpositioned components and should be considered an alternative to component removal in certain cases.

Aged↗
PubMed1992

Chitinase and chitin synthase 1: counterbalancing activities in cell separation of Saccharomyces cerevisiae.

Previous results [E. Cabib, A. Sburlati, B. Bowers & S. J. Silverman (1989) Journal of Cell Biology 108, 1665-1672] strongly suggested that the lysis observed in daughter cells of Saccharomyces cerevisiae defective in chitin synthase 1 (Chs1) was caused by a chitinase that partially degrades the chitin septum in the process of cell separation. Consequently, it was proposed that in wild-type cells, Chs1 acts as a repair enzyme by replenishing chitin during cytokinesis. The chitinase requirement for lysis has been confirmed in two different ways: (a) demethylallosamidin, a more powerful chitinase inhibitor than the previously used allosamidin, is also a much better protector against lysis and (b) disruption of the chitinase gene in chs1 cells eliminates lysis. Reintroduction of a normal chitinase gene, by transformation of those cells with a suitable plasmid, restores lysis. The percentage of lysed cells in strains lacking Chs1 was not increased by elevating the chitinase level with high-copy-number plasmids carrying the hydrolase gene. Furthermore, the degree of lysis varied in different chs1 strains; lysis was abolished in chs1 mutants containing the scs1 suppressor. These results indicate that, in addition to chitinase, lysis requires other gene products that may become limiting.

Cell Division↗
PubMed1992

Linkage analysis of glucokinase gene with NIDDM in Caucasian pedigrees.

NIDDM has a strong genetic component, as evidenced by the high level of concordance between identical twins. The nature of the genetic predisposition has remained largely unknown. Recently, the glucokinase gene locus on chromosome 7p has been shown to be linked to a subtype of NIDDM known as MODY in French and British pedigrees, and glucokinase mutations have been identified. To study the relationship between the glucokinase gene and NIDDM, we performed a linkage analysis in 12 Caucasian pedigrees ascertained through a proband with classical NIDDM. The LINKAGE program was used under four models, including autosomal dominant and recessive, with individuals with glucose intolerance counted as either affected or of unknown status. Linkage was significantly rejected with the dominant models (LOD scores -4.65, -4.25), and was unlikely with the recessive model when glucose intolerance was considered as affected (LOD score -1.38). These findings suggest that mutations in or near the glucokinase gene are unlikely to be the major cause of the inherited predisposition to NIDDM in Caucasian pedigrees, but do not exclude a role for this locus with a polygenic model, or a major role in some pedigrees.

Adult↗
PubMed1992

The influence of age, sex, and initial fit on bony ingrowth stabilization with the AML femoral component in primary THA.

A radiographic review of 178 consecutive primary total hip arthroplasties using the AML femoral component with a mean follow up of 40.1 months identified 92.3% to be stabilized by bony ingrowth and 7.7% by fibrous tissue. None were classified as loose. The quality of fit in the isthmus and calcar regions was identified as an important factor in achieving bony ingrowth stabilization. Bony ingrowth was achieved in all age groups with equal frequency. No relationship between sex and the type of stabilization was identified. A clinical correlation utilizing a subset of patients with identical prosthetic components identified equivalent clinical results across all age groups. Thirty-four percent of patients experienced some residual thigh pain. No statistically significant relationship between the presence of thigh pain and the type of femoral component stabilization (bony vs fibrous) could be identified. Ninety-eight percent of patients expressed unconditional satisfaction with their hip replacements.

Adult↗
PubMed1991

Proteinase B is, indeed, not required for chitin synthetase 1 function in Saccharomyces cerevisiae.

Previous genetic evidence led to the conclusion that proteinase B of yeast was not involved in the function of chitin synthetase 1 (Chs1), based on the demonstration of normal septum formation, cell division and chitin deposition in mutants devoid of the proteinase (Zubenko, G.S., Mitchell, A.P., and Jones, E.W. (1979) Proc. Natl. Acad. Sci. USA 76, 2395-2399). Later, however, it was found that the essential enzyme for septum formation is chitin synthetase 2, whereas Chs1 acts as an auxiliary enzyme, whose absence results in daughter cell lysis under acidic conditions (Cabib, E., Sburlati, A., Bowers, B. and Silverman, S.J. (1989) J. Cell Biol. 108, 1665-1672). By using the lytic behavior as a criterion, we have now found that prb1 strains are not defective in Chs1 function. Certain strains contain a recessive suppressor of lysis which could mask the Chs1 defect. However, appropriate crosses and transformation experiments showed that the prb1 mutants do not harbor the suppressor. It may now be concluded with confidence that proteinase B is not required for chitin synthetase 1 function.

Base Sequence↗
PubMed1991

Biomechanical comparison of cannulated small bone screws: a brief follow-up study.

The compressive forces generated by the ASIF and Herbert small bone cannulated screws were measured in the laboratory with the use of simulated bones and a custom-designed load washer as a means of quantifying their fixation capabilities. Comparative data were also generated for the Herbert scaphoid bone screw and the ASIF 4 mm cancellous screw. The cannulated Herbert bone screw and the ASIF 4 mm cancellous screw were found to have nearly identical compression capabilities. Both generated compression forces approximately five times those of the Herbert scaphoid bone screw. The ASIF small cannulated screw demonstrated a compressive capacity 2 1/2 times that of the Herbert screw.

Biomechanical Phenomena↗
PubMed1991

Experience with a modified posterior approach to the hip joint. A technical note.

A modified posterior approach to the hip joint is described with particular applicability to revision or complex primary hip arthroplasty. The procedure involves osteotomy of the posterior one-third of the greater trochanter with posterior reflection of a full-thickness flap, consisting of the posterior trochanteric fragment, short external rotators, joint capsule, and posterior portion of the gluteus medius. The approach allows for excellent exposure of the acetabulum and femoral canal, with minimal disruption of the gluteal muscle insertions. The majority of the greater trochanter is left intact, enhancing femoral component stability. Closure is accomplished by suture of soft tissues and reattachment of the posterior trochanteric fragment with bone screws. An intact soft tissue envelope is thereby restored around the prosthetic components. A limited clinic series has identified no problem referable to this exposure. No loss of reduction or nonunion has been encountered.

Acetabulum↗
PubMed1991

CAL1, a gene required for activity of chitin synthase 3 in Saccharomyces cerevisiae.

The CAL1 gene was cloned by complementation of the defect in Calcofluor-resistant calR1 mutants of Saccharomyces cerevisiae. Transformation of the mutants with a plasmid carrying the appropriate insert restored Calcofluor sensitivity, wild-type chitin levels and normal spore maturation. Southern blots using the DNA fragment as a probe showed hybridization to a single locus. Allelic tests indicated that the cloned gene corresponded to the calR1 locus. The DNA insert contains a single open-reading frame encoding a protein of 1,099 amino acids with a molecular mass of 124 kD. The predicted amino acid sequence shows several regions of homology with those of chitin synthases 1 and 2 from S. cerevisiae and chitin synthase 1 from Candida albicans. calR1 mutants have been found to be defective in chitin synthase 3, a trypsin-independent synthase. Transformation of the mutants with a plasmid carrying CAL1 restored chitin synthase 3 activity; however, overexpression of the enzyme was not achieved even with a high copy number plasmid. Since Calcofluor-resistance mutations different from calR1 also result in reduced levels of chitin synthase 3, it is postulated that the products of some of these CAL genes may be limiting for expression of the enzymatic activity. Disruption of the CAL1 gene was not lethal, indicating that chitin synthase 3 is not an essential enzyme for S. cerevisiae.

Amino Acid Sequence↗
PubMed1991

The function of chitin synthases 2 and 3 in the Saccharomyces cerevisiae cell cycle.

The morphology of three Saccharomyces cerevisiae strains, all lacking chitin synthase 1 (Chs1) and two of them deficient in either Chs3 (calR1 mutation) or Chs2 was observed by light and electron microscopy. Cells deficient in Chs2 showed clumpy growth and aberrant shape and size. Their septa were very thick; the primary septum was absent. Staining with WGA-gold complexes revealed a diffuse distribution of chitin in the septum, whereas chitin was normally located at the neck between mother cell and bud and in the wall of mother cells. Strains deficient in Chs3 exhibited minor abnormalities in budding pattern and shape. Their septa were thin and trilaminar. Staining for chitin revealed a thin line of the polysaccharide along the primary septum; no chitin was present elsewhere in the wall. Therefore, Chs2 is specific for primary septum formation, whereas Chs3 is responsible for chitin in the ring at bud emergence and in the cell wall. Chs3 is also required for chitin synthesized in the presence of alpha-pheromone or deposited in the cell wall of cdc mutants at nonpermissive temperature, and for chitosan in spore walls. Genetic evidence indicated that a mutant lacking all three chitin synthases was inviable; this was confirmed by constructing a triple mutant rescued by a plasmid carrying a CHS2 gene under control of a GAL1 promoter. Transfer of the mutant from galactose to glucose resulted in cell division arrest followed by cell death. We conclude that some chitin synthesis is essential for viability of yeast cells.

Cell Division↗
PubMed1991

Computer-aided design of two-dimensional electric-type hyperthermia applicators using the finite-difference time-domain method.

A hyperthermia applicator design tool consisting of a finite-difference time-domain (FDTD) technique in combination with a graphical display of electric fields and normalized linear temperature rise is described. This technique calculates, rather than assumes, antenna current distributions; it includes mutual interactions between the body and the applicator, and it calculates driving-point impedance and power delivered to the applicator. Results show that the fundamental limitation of 2-D electric-type applicators is overheating of the fat by normal components of the electric field, which exist because of near fields and capacitive coupling with the muscle. Two factors which contribute to the capacitance are the muscle conductivity and the small antenna size in air. Two examples of applicators designed to avoid fat overheating are described: a 27-MHz segmented dipole for heating large tumors to 7 cm depth, and a 100-MHz dipole for small tumors to 5 cm depth. The first uses a water bolus, and the second uses a water bolus with low-permittivity strips to reduce normal fields at the antenna ends. The results of this study describe fundamental limitations of electric field applicators, and illustrate the use of a powerful applicator design tool that allows rapid evaluation of a wide range of ideas for applicators which would require months and years to test experimentally.

Algorithms↗
PubMed1990

Tetanus toxin-induced seizures cause microglial activation in rat hippocampus.

Tetanus toxin (about 20 mouse LD50) injected into the ventral hippocampus of rats leads to brief seizures occurring intermittently over a period of weeks. Toxin injection leads to the appearance of activated microglia (detected with OX42 immunohistochemistry) in the hippocampus. After 7-14 days, many activated microglia are visible in CA1 area of dorsal hippocampus aligned with the pyramidal cell dendrites and having the morphology characteristic of 'rod cells'. Extensive cell loss is found in dorsal CA1, but not at the injection site, in about one third of injected rats.

Animals↗
PubMed1990

Ulnar styloid fixation in the treatment of posttraumatic instability of the radioulnar joint: a biomechanical study with clinical correlation.

Biomechanical displacement testing was done on nine fresh human upper extremities to define the stabilizing influence of the triangular fibrocartilage on the radioulnar joint and the efficacy of triangular fibrocartilage-ulnar styloid avulsion fracture repair in restoring lost stability. Test data confirmed that the triangular fibrocartilage is a major stabilizer of the radioulnar joint and internal fixation of triangular fibrocartilage-ulnar styloid avulsion fractures can restore preavulsion stability in all positions of forearm rotation. On the basis of this data and a successful clinical experience, primary repair of displaced ulnar styloid avulsion fractures is advised as a means of stabilizing the radioulnar joint and preventing the disability associated with chronic radioulnar joint instability.

Biomechanical Phenomena↗
PubMed1990

Threaded acetabular components for primary and revision total hip arthroplasty.

A clinical and radiographic review of 48 total hip arthroplasty patients with threaded acetabular components was undertaken at 24-44 months of follow-up study. Twenty-five patients had primary hip arthroplasties and 23 had revision procedures. Clinical scores revealed good to excellent results in 60% of primary and 30% of revision procedures. Radiographic analysis revealed stable acetabular components in 88% of primary and 61% of revision procedures. Potentially loose acetabular components were noted in 8% of primary and 4.3% of revision procedures and loose acetabular components in 4% of primary and 34.7% of revision procedures. The rate of acetabular component loosening was considered unacceptably high in revision cases and an area of concern in primary cases. Discretionary use of these components is advised.

Acetabulum↗
PubMed1990

Islet cell neoplasms. A fine-needle aspiration cytology study with immunocytochemical correlations.

Islet cell neoplasms (ICNs) are uncommon tumors that may present with bizarre endocrine manifestations. Only rarely have their fine-needle aspiration (FNA) cytomorphologic characteristics been reported. The authors have studied FNAs of ICNs in ten patients, including immunocytochemistry (ICC) directly on the aspirates. FNA yielded moderately to markedly cellular specimens with numerous individual cells and large aggregates. Although moderate pleomorphism was present in three cases, striking uniformity in nuclear size and contour and in delicate nuclear membranes was evident. Typically the round nuclei were eccentric, imparting a plasmacytoid appearance. Cytoplasmic granularity was noted in only a minority of tumor cells. Five of the ICNs were positive for chromogranin (CG). In comparison, seven ICNs were positive for CG in tissue sections. None of the cytologic material showed immunoreactivity with insulin, glucagon, somatostatin, or gastrin. Histologic material showed positivity for these hormones in 33% (three of nine), 22% (two of nine), 22% (two of nine), and 11% (one of nine), respectively. Although CG is the most useful immunocytochemical marker for ICNs, and thus is helpful in confirming a diagnosis of ICN in FNA material, it is negative in half of the cases and may be negative when the histologic material is positive.

Adenoma, Islet Cell↗
PubMed1989

Characterization of the inverted duplication in the mitochondrial DNA of Candida albicans.

The mitochondrial DNA (mtDNA) of Candida albicans contains a large inverted duplication. As is the case with most chloroplast DNAs and one other mtDNA, the nonduplicated regions of the molecule occur in two orientations with respect to each other, indicating that internal recombination occurs. Like some other mtDNAs, the C. albicans mtDNA contains a single SalI restriction site located near one end of the large rRNA gene. In contrast to other cases, however, the inverted duplication does not appear to contain any sequences coding for rRNA.

Candida albicans↗
PubMed1989

Total knee arthroplasty using the kinematic rotating hinge prosthesis.

Patients receiving a Kinematic Rotating Hinge total knee prosthesis with a 25-month minimum follow up were reviewed. A total of 46 patients and 54 knees were included in the study. A detailed clinical assessment was available on 38 knees. Twenty of these knees had primary arthroplasties performed with the Kinematic Rotating Hinge prosthesis and 18 knees had revision arthroplasty. Ninety-five percent of primary knees and 83% of revision knees caused no or mild pain postoperatively. Using the Brigham and Women's Hospital and Harvard Medical School knee rating system, 80% of primary knees and 61% of revision knees were rated as good to excellent. Using the criteria defined in this article, 90% of primary knees and 83% of revision knees were labeled as having a satisfactory result. Forty-five percent of primary components and 52% of revision components demonstrated lucent lines on radiographic review. Seven percent of primary knees and 20% of revision knees showed evidence of aseptic lucency progression in one or more zones. No radiographic evidence of aseptic loosening was noted in this review. Documented sepsis occurred in one primary knee and two revision knees. Patellar instability occurred in 21% of primary knees and 36% of revision knees, representing the major complication. The Kinematic Rotating Hinge prosthesis is intended for use in arthroplasty cases where there is functional absence of collateral ligament stability. This review suggests that a high percentage of satisfactory clinical results can be achieved with this prosthesis with long-term radiographic stability.

Activities of Daily Living↗
PubMed1988

Childhood depression.

The spectrum of depressive disorders found in children and adolescents presents diagnostic and treatment challenges for the physician. The increasing scientific rigor of child and adolescent mental disorder research has explicated the importance of clinical diagnoses. Distinctions have to be made between depressive symptoms that are transient and situational specific and the constellation of depressive symptoms that represent clinical disorders such as bipolar disorder, cyclothymia, major depressive disorder, or dysthymia. The clinically sensitive physician attuned to the diagnostic criteria of these disorders has the opportunity to promote effective treatment and to reduce the morbidity associated with these conditions. The established severity and persistence of these disorders over time suggests the need for definitive medical management of these conditions. The recognition of childhood depression as a medical entity of varying severity, persistence, and prognosis represents the first step in effective treatment.

Adjustment Disorders↗