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Biomedical subjects

J P Jackson

Publications and source records attributed to J P Jackson.

At least 19 recordsLinked to original sources
PubMed2001

CmC(A/T)GG DNA methylation in mature B cell lymphoma gene silencing.

DNA methylation has been linked to gene silencing in cancer. Primary effusion lymphoma (PEL) and myeloma are lymphoid malignancies that arise from terminally differentiated B cells. Interestingly, PEL do not express immunoglobulins or most B lineage-specific genes. The B cell-specific B29 (Igbeta/CD79b) gene is silenced in PEL and some myelomas but is expressed in other normal and malignant B cells. B29 expression was reactivated in PEL by demethylating and histone deacetylase inhibiting treatments. Bisulfite sequencing revealed two types of DNA methylation in silenced B29 promoters: at conventional CpG and at CC(A/T)GG B29 promoter sites. The pattern of methylated CpG ((m)CpG) and C(m)C(A/T)GG B29 promoter methylation observed was similar to that recently reported for epigenetic silencing of an integrated retrovirus. Methylation of C(m)C(A/T)GG sites in the B29 promoter significantly repressed in vivo transcriptional activity. Also, methylation of a central conserved C(m)CTGG B29 promoter site blocked the binding of early B cell factor. This methylated motif formed DNA-protein complexes with nuclear extracts from all cell types examined. Therefore, C(m)C(A/T)GG methylation may represent an important type of epigenetic marker on mammalian DNA that impacts transcription by altering DNA-protein complex formation.

Antigens, CD↗
PubMed2001

Requirement of CHROMOMETHYLASE3 for maintenance of CpXpG methylation.

Epigenetic silenced alleles of the Arabidopsis SUPERMAN locus (the clark kent alleles) are associated with dense hypermethylation at noncanonical cytosines (CpXpG and asymmetric sites, where X = A, T, C, or G). A genetic screen for suppressors of a hypermethylated clark kent mutant identified nine loss-of-function alleles of CHROMOMETHYLASE3 (CMT3), a novel cytosine methyltransferase homolog. These cmt3 mutants display a wild-type morphology but exhibit decreased CpXpG methylation of the SUP gene and of other sequences throughout the genome. They also show reactivated expression of endogenous retrotransposon sequences. These results show that a non-CpG DNA methyltransferase is responsible for maintaining epigenetic gene silencing.

Alleles↗
PubMed2000

The late flowering phenotype of fwa mutants is caused by gain-of-function epigenetic alleles of a homeodomain gene.

The transition to flowering in Arabidopsis thaliana is delayed in fwa mutant plants. FWA was identified by loss-of-function mutations in normally flowering revertants of the fwa mutant, and it encodes a homeodomain-containing transcription factor. The DNA sequence of wild-type and fwa mutant alleles was identical in the genomic region of FWA. Furthermore, the FWA gene is ectopically expressed in fwa mutants and silenced in mature wild-type plants. This silencing is associated with extensive methylation of two direct repeats in the 5' region of the gene. The late flowering phenotype, ectopic FWA expression, and hypomethylation of the repeats were also induced in the ddm1 hypomethylated background. Mechanisms for establishment and maintenance of the epigenetic mark on FWA are discussed.

Alleles↗
PubMed2000

The triumph of the segregationists? A historiographical inquiry into psychology and the Brown litigation.

Psychologists testified at the trials of Brown v. Board of Education and helped write briefs that were submitted to the Supreme Court on appeal. Psychologists were once proud of what they did in Brown but are now seen as liberal reformers who masked their political wishes in the guise of social science. The argument that psychologists involved with Brown were social reformers rather than objective scientists dates to the segregationist critique of Brown. The author traces the history of the critique of the Brown psychologists from its segregationist origins to its acceptance by mainstream social scientific and historical scholars. The author concludes that the critique is based on a misreading of what the Brown psychologists did during the litigation.

Black or African American↗
PubMed1996

Bridle transfer for paresis of the anterior and lateral compartment musculature.

In the Riordan (bridle) transfer, the posterior tibialis muscle as motor is routed through the interosseous membrane and anastomosed into a "bridle" formed by the distal tibialis anterior and peroneus longus muscles. In theory, the bridle provides inversion/eversion balance even if the transfer effects only tenodesis. However, the procedure has been criticized because its insertion is not into bone. This review analyzes the use of bridle transfer in flaccid paresis involving musculature innervated by the peroneal nerve. Surgery was performed 1 to 3 years after injury for patients with traumatic etiology. Ten patients are reviewed at 61 months' mean follow-up. Eight patients had traumatic peroneal nerve loss. Two had neuromuscular etiology. Evaluation included review of records, telephone interviews, and physical examinations. Data on functional status included walking barefoot running, need for bracing, return to duty, and patient satisfaction. Physical examination recorded ankle position and motions, gait findings, and results of static electromyograms. All patients were able to walk barefoot, but 6 of 10 had a mild to moderate limp. Five patients returned to running initially; only two were able to keep running. Nine patients were brace-free initially (polio sequela required bracing initially), and four others returned to bracing. Of these, two experienced an acute "tearing" and dorsiflexion loss, one sustained a prolonged gradual loss of dorsiflexion, and one sustained a contralateral cerebrovascular accident. Only three of seven patients returned to active duty, and one is on jump status. All patients were satisfied with their initial result. Only two patients had no detectable swing phase problems (both returned to active duty). Five patients had peroneal nerve exploration with repair or neurolysis; two of them sustained complete transections. Postoperative electromyograms showed insignificant, if any, nerve return. The Riordan transfer works well for neuromuscular flaccid paresis and in patients with peroneal nerve injuries with low demands. It may stretch out over time to the point of acute failure in patients with high demands. Concurrent peroneal nerve exploration and repair did not seem to be beneficial in this small study.

Adolescent↗
PubMed1988

Controlled motion rehabilitation after flexor tendon repair and grafting. A multi-centre study.

We present a system for treatment by controlled motion after repair of flexor tendons in the hand. This Washington regimen incorporates both controlled active extension against passive flexion by rubber band and the use of controlled passive extension and flexion. We utilise the Brooke Army Hospital modification of the rubber band passive flexion splint; this provides for maximal excursion of the tendon with full passive flexion of the finger. The 66 patients (78 fingers) who form the basis of this study all sustained complete laceration of the flexor profundus and superficialis tendons in "no man's land". Results were evaluated by the Strickland formula of total active motion (TAM) of the proximal and distal interphalangeal joints. Sixty-two fingers (80%) were rated "excellent", 14 fingers (18%) were "good", two fingers (2%) were "fair", none was rated "poor". Our regimen of controlled motion rehabilitation has also been applied with equal success to cases of flexor tendon grafting.

Adolescent↗
PubMed1986

Cast-brace treatment of ankle sprains.

Forty-two severely sprained ankles treated by a cast-brace have been reviewed. This method was devised to avoid the disadvantages of immobilization. Diagnosis was based on the history and clinical signs. Strain films were taken in 31 patients but it is submitted that this investigation may be misleading unless general anaesthesia is used. The results of the treatment by cast-brace compare favourably with those by other methods and it is considered that patients were able to return to sport in a shorter time.

Ankle Injuries↗
PubMed1982

Injuries to the lateral ligament of the ankle: assessment and treatment.

Initial assessment of severity of injury to the lateral ligament of the ankle is by clinical examination. If it is thought that there is a possibility of either lateral or anterior instability, patients are investigated radiologically by anterior and inversion stress films. If instability is demonstrated a peroneal tenogram is carried out to exclude damage to the calcaneo-fibular ligament. Treatment is by means of a cast brace if instability is present. The advantages of this are preservation of calf power and improved joint function. The early results are reported in relation to the improvement in stability and early return to sporting activity.

Ankle Injuries↗
PubMed1981

Tibial intercondylar fractures in children: a review of the classification and the treatment of mal-union.

Forced flexion with internal rotation of the knee in a child can result in an avulsion fracture of the tibial intercondylar area by the anterior cruciate ligament. Accurate radiological assessment of the size of the fragment is difficult. Conservative treatment with plaster immobilization in 30-50 degrees of flexion is recommended for Type I fractures. Operative reduction is suggested for all Type III and some Type II fractures. Correction of mal-union can be achieved by excision of a wedge of tibial bone and reattachment of the origin of the anterior cruciate ligament.

Child↗
PubMed1977

Investigation of shoulder disability by arthrography.

Fifty patients with pain and limitation of movement at the shoulder joint were investigated by arthrography. Normal findings using a double contrast technique are described. The main arthrographic patterns encountered were found in complete and incomplete tears of the rotator cuff, and capsulitis. Abnormalities of the bicipital tendon sheath were non-filling and leakage of contrast medium from the sheath. Extravasation of contrast medium from the bicipital tendon sheath and subscapularis bursa was considered to be due to over-distension of a joint with a reduced capacity. The accuracy of the procedure and the reasons for false negative arthrograms and surgical exploration are discussed.

Adolescent↗
PubMed1976

Bucket-handle tear of the medial meniscus. A case for conservative surgery.

To compare the results of two methods of treatment for bucket-handle tears of the medial meniscus eighty-seven knees were studied, thirty-seven treated by excision of the bucket-handle tear alone and fifty by total meniscectomy. A postoperative history suggestive of locking was given by one patient in each treatment group. Anteroposterior laxity was found in 72% of knees treated by excision of the bucket-handle tear alone as compared with 68% of the knees treated by total meniscectomy, but in all other respects the results showed a marginal preference in favor of the simpler operation. Although the numbers are too small to prove that results are better following excision of the bucket-handle tear alone, it is suggested, in the absence of evidence that total meniscectomy is more advantageous, that the simpler operation of excision of just the bucket-handle tear is the treatment of choice in bucket-handle tears of the medial meniscus.

Adolescent↗