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B J Jenkins

Publications and source records attributed to B J Jenkins.

At least 19 recordsLinked to original sources
PubMed1998

Saturation mutagenesis of the beta subunit of the human granulocyte-macrophage colony-stimulating factor receptor shows clustering of constitutive mutations, activation of ERK MAP kinase and STAT pathways, and differential beta subunit tyrosine phosphorylation.

The high-affinity receptors for human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 are heterodimeric complexes consisting of cytokine-specific alpha subunits and a common signal-transducing beta subunit (hbetac). We have previously demonstrated the oncogenic potential of this group of receptors by identifying constitutively activating point mutations in the extracellular and transmembrane domains of hbetac. We report here a comprehensive screen of the entire hbetac molecule that has led to the identification of additional constitutive point mutations by virtue of their ability to confer factor independence on murine FDC-P1 cells. These mutations were clustered exclusively in a central region of hbetac that encompasses the extracellular membrane-proximal domain, transmembrane domain, and membrane-proximal region of the cytoplasmic domain. Interestingly, most hbetac mutants exhibited cell type-specific constitutive activity, with only two transmembrane domain mutants able to confer factor independence on both murine FDC-P1 and BAF-B03 cells. Examination of the biochemical properties of these mutants in FDC-P1 cells indicated that MAP kinase (ERK1/2), STAT, and JAK2 signaling molecules were constitutively activated. In contrast, only some of the mutant beta subunits were constitutively tyrosine phosphorylated. Taken together, these results highlight key regions involved in hbetac activation, dissociate hbetac tyrosine phosphorylation from MAP kinase and STAT activation, and suggest the involvement of distinct mechanisms by which proliferative signals can be generated by hbetac.

Animals↗
PubMed1997

A family of cytokine-inducible inhibitors of signalling.

Cytokines are secreted proteins that regulate important cellular responses such as proliferation and differentiation. Key events in cytokine signal transduction are well defined: cytokines induce receptor aggregation, leading to activation of members of the JAK family of cytoplasmic tyrosine kinases. In turn, members of the STAT family of transcription factors are phosphorylated, dimerize and increase the transcription of genes with STAT recognition sites in their promoters. Less is known of how cytokine signal transduction is switched off. We have cloned a complementary DNA encoding a protein SOCS-1, containing an SH2-domain, by its ability to inhibit the macrophage differentiation of M1 cells in response to interleukin-6. Expression of SOCS-1 inhibited both interleukin-6-induced receptor phosphorylation and STAT activation. We have also cloned two relatives of SOCS-1, named SOCS-2 and SOCS-3, which together with the previously described CIS form a new family of proteins. Transcription of all four SOCS genes is increased rapidly in response to interleukin-6, in vitro and in vivo, suggesting they may act in a classic negative feedback loop to regulate cytokine signal transduction.

Amino Acid Sequence↗
PubMed1996

Interacting residues in the extracellular region of the common beta subunit of the human granulocyte-macrophage colony-stimulating factor, interleukin (IL)-3, and IL-5 receptors involved in constitutive activation.

A previous study using random mutagenesis identified an activating mutation in the common beta subunit (hbetac) of the human granulocyte-macrophage colony-stimulating factor, interleukin-3, and interleukin-5 receptors in which an isoleucine residue (Ile374) in the extracellular region of hbetac is replaced by asparagine (Jenkins, B. J., D'Andrea, R., and Gonda, T. J. (1995) EMBO J 14, 4276-4287). To investigate the mechanism by which this mutation (I374N) acts, we employed site-directed mutagenesis to explore predictions based on a structural model of hbetac. We focused on possible interactions between Ile374 and other hydrophobic residues in its vicinity and found that replacement of two such residues, Leu356 and Trp358, with asparagine resulted in constitutive activation of hbetac. Hydrophilic substitutions at both of these positions and at position 374 resulted in the greatest degree of activation, as measured by the growth rate of factor-independent cells, while hydrophobic substitutions had lesser or no effects. Moreover, these "weak" substitutions appeared to synergize, since factor-independent cells expressing the double mutants I374F/W358F and I374F/L356A showed substantially higher growth rates than the single mutants. Taken together, these results suggest that Ile374 normally interacts with Leu356 and Trp358, and that disruption of these interactions results in a conformational change in hbetac that leads to constitutive activity. A model relating this notion to the predicted structure and to ligand- and alpha subunit-dependent activation of hbetac is proposed.

Amino Acid Sequence↗
PubMed1995

Activating point mutations in the common beta subunit of the human GM-CSF, IL-3 and IL-5 receptors suggest the involvement of beta subunit dimerization and cell type-specific molecules in signalling.

We have combined retroviral expression cloning with random mutagenesis to identify two activating point mutations in the common signal-transducing subunit (h beta c) of the receptors for human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-3 and IL-5 by virtue of their ability to confer factor independence on the haemopoietic cell line, FDC-P1. One mutation (V449E) is located within the transmembrane domain and, by analogy with a similar mutation in the neu oncogene, may act by inducing dimerization of h beta c. The other mutation (I374N) lies in the extracellular, membrane-proximal portion of h beta c. Neither of these mutants, nor a previously described mutant of h beta c (FI delta, which has a small duplication in the extracellular region), was capable of inducing factor independence in CTLL-2 cells, while only V449E could induce factor independence in BAF-B03 cells. These results imply that the extracellular and transmembrane mutations act by different mechanisms. Furthermore, they imply that the mutants, and hence also wild-type h beta c, interact with cell type-specific signalling molecules. Models are presented which illustrate how these mutations may act and predict some of the characteristics of the putative receptor-associated signalling molecules.

Amino Acid Sequence↗
PubMed1995

Non-invasive estimation of venous admixture: validation of a new formula.

We have developed a computer program that estimates venous admixture (intra-pulmonary shunt) from four measurements: haemoglobin concentration, end-tidal carbon dioxide tension (PE'CO2), fractional inspired oxygen concentration (FIO2) and pulse oximetry (SpO2). The formula was tested on patients in an intensive therapy unit by using it to estimate shunt while it was measured simultaneously by a standard, invasive method. A total of 101 measurements were made in 29 patients. After correcting the systematic errors in the assumed differences between PE'CO2 and arterial PCO2, and between SpO2 and co-oximetrically measured SaO2, and correcting for a trend in the arteriovenous oxygen concentration difference (C(a-v))2) with shunt, the bias of the non-invasive minus invasive shunt differences was negligible, with no significant dependence on shunt. The limits of agreement were then +/- 16% shunt overall (+/- 13% within patients). When SaO2 was used instead of SpO2, the limits were +/- 11% (+/- 8% within patients).

Carbon Dioxide↗
PubMed1995

Substitution cystoplasty for intractable interstitial cystitis.

OBJECTIVE: To assess the results of substitution cystoplasty for the treatment of intractable interstitial cystitis (IC). PATIENTS AND METHODS: Thirty-two patients (29 women and three men; mean age 58 years, range 24-74) with intractable IC resistant to conservative therapy who had undergone substitution cystoplasty between 1983 and 1992 were reviewed. Their bladder capacities were measured pre-operatively and related to the outcome of treatment. RESULTS: All but two of the 22 women with a bladder capacity of < 250 mL under anaesthetic were improved (five) or cured (15) of their symptoms. The results in women with larger bladder capacities were much less reliable, with only two of seven being cured of their symptoms. The three men all had a good result. Those who had undergone supratrigonal cystectomy were more likely to void spontaneously, but four patients developed pyelonephritis from associated reflux. Subtotal cystectomy reduced the likelihood of reflux and, although there were too few patients for statistical significance, probably increased the chance of cure at the expense of increasing the need for intermittent self-catheterization (ISC). CONCLUSIONS: Pre-operative bladder capacity under anaesthetic is the most reliable predictor of outcome of substitution cystoplasty for treating intractable IC in women. It is contra-indicated if bladder capacity is > 250 mL. Supratrigonal cystectomy is a quick and easy operation and is preferable in the older patient. Subtotal cystectomy with reimplantation of the ureters is preferable in the younger patient, even though it may increase the need for ISC.

Adult↗
PubMed1994

Differential expression of genes encoding a cysteine-rich keratin family in the hair cuticle.

In the hair follicle the cuticle develops as a thin layer of cells between the hair shaft cortex and the inner root sheath. Once the cuticle cells begin to differentiate they accumulate cysteine-rich granules in their cytoplasm but the identity of their constituent proteins has remained largely an enigma. In this report we show differential expression of a family of genes encoding cysteine-rich, glycine-rich keratins in the cuticle. Two clones of the sheep KAP5 gene family were isolated: the KAP5.4 cDNA encodes a protein of 190 amino acids (M(r) = 16,936) containing 32 mol% cysteine, 26 mol% glycine and the partial KAP5.5 cDNA encodes a protein of at least 197 amino acids (M(r) > or = 17,474) containing 29 mol% cysteine, 28 mol% glycine. The predicted amino acid sequences of the KAP5 family show extensive sequence conservation and all the proteins are composed almost entirely of cysteine-rich and glycine-rich repeats. Each KAP5 gene produces an approximately 1.5-kb mRNA species but the KAP5.4 and KAP5.5 mRNA levels appear to be severalfold greater than the KAP5.1 mRNA. Comparative tissue in situ hybridizations reveal a positive correlation between the onset of expression and follicle depth. For a given KAP5 gene two widely different cuticle expression patterns were noted amongst the follicle populations, and on the basis of follicle bulb cell kinetics they are consistent with expression in either sheep primary or secondary follicle types.

Amino Acid Sequence↗
PubMed1994

The accuracy of conventional and three-dimensional thallium-technetium scans in patients with hyperparathyroidism resulting from multiglandular hyperplasia.

25 patients with hyperparathyroidism resulting from multiglandular hyperplasia were studied prior to cervical exploration. 43% of abnormal glands were correctly localized by preoperative thallium-technetium scintigraphy. In the 11 patients who underwent three-dimensional scanning, all glands already identified by scintigraphy were also localized in a third plane. In one patient an additional gland, not detected by the conventional scan, was visible.

Adult↗
PubMed1994

Junior doctors' hours: what do they really think?

Junior doctors' hours are one of the most controversial topics under debate in the health service today. We undertook a detailed postal questionnaire of hospital doctors in training within a major teaching unit in order to assess the awareness and perceived implications of the incipient changes and to elucidate how it was felt these changes would affect both the doctors and patients. The questionnaire focused specifically on the effect of the changes on quality and continuity of patient care, junior training and socio-economic factors relating to the medical staff. The questionnaire was entirely anonymous and carried only the first author name but provision was made to determine current grade, specialty, age, sex and career plans of the respondents. Importantly, space was included at the end for pertinent comments. All junior staff in training in all specialties in the Cardiff area were circulated. Three hundred and twenty-six questionnaires were sent out and 202 were returned of which 192 were properly completed (59%). Almost everyone was au fait with the proposed changes. There was a surprisingly high level of support for changes among non-surgical trainees, and half felt that quality of care would improve, though the more senior the trainee, the less enthusiastic they were in all aspects. Many felt that far too little consultation with junior staff had taken place and there was generalized criticism of general practitioner trainees by their specializing counterparts, partly because of a perceived lack of commitment and partly because of blame of this group for the inception of the changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Partial orchidectomy for second testicular tumour.

This report describes a patient who underwent a partial orchidectomy for testicular cancer, having already had a radical orchidectomy of the contra lateral side. He subsequently fathered two children. This policy may have a role in the management of men with an early germ cell tumour in a solitary testis who have not completed their family.

Adult↗
PubMed1992

Ethics, logistics and a trial of transurethral versus open prostatectomy.

An increased long-term morbidity rate after transurethral compared with open prostatectomy has recently been claimed on the basis of retrospective studies of operations done up to 20 years ago. These studies have led to a demand for a prospective trial. Most reports show that peri-operative mortality following prostatectomy is virtually confined to unfit men over 80 years old. Before agreeing to participate in a trial we examined our operative mortality in this group of patients. Between 1981 and 1987, 123 octogenarians underwent transurethral prostatectomy: 64 operations were elective and 59 were performed for retention. There were 2 operative deaths (1.6%), both from gram-negative septicaemia despite prophylactic antibiotics. There were no additional deaths in the first 12 months following surgery. Few of these patients would have been considered fit to undergo an open prostatectomy. Any proposed randomised trial would have to exclude such high risk patients until it can be shown that open prostatectomy is equally safe.

Aged↗
PubMed1992

Long-term results of treatment of urethral injuries in males caused by external trauma.

Of 134 males with traumatic rupture of the urethra seen between 1967 and 1989, 10 have been lost to follow-up and 124 have been followed up for 1 to 22 years (mean 8); 100 patients had a pelvic fracture (3 with associated rectal injury) and 24 had perineal injuries. Prior to referral 31 patients (25%) had undergone treatment in addition to suprapubic cystostomy. Wherever possible, strictures were managed by optical urethrotomy (33) or intermittent dilatation (4). In 2 patients only a suprapubic cystostomy was possible. Skin inlay urethroplasty in 1 or 2 stages was performed in 75 cases, an end-to-end anastomosis with or without resection of the symphysis pubis in 7 and a scrotal tube pull-through in 3. The immediate and long-term results depended on the severity of the original injury. With minimal displacement the management was simple and the long-term prognosis good, a single urethrotomy being sufficient in 22 patients. Where there was considerable displacement the initial management was more difficult and there was a high incidence of long-term complications: of 73 patients treated by urethroplasty or end-to-end anastomosis, significant post-operative infection occurred in 11 (15%) and restenosis in 15 (20%), of whom 7 required a revision urethroplasty. Data in respect of potency were recorded in 80 patients: 28 of these were impotent, 20 of the 28 having sustained an injury with considerable displacement.

Adolescent↗
PubMed1992

Isolation and characterization of a sheep cysteine-rich cuticle keratin pseudogene.

The cysteine-rich keratin proteins of the hair cuticle are derived from a multigene family that has been highly conserved during mammalian evolution. We have recently characterized one cuticle keratin gene isolated from a sheep lambda library, and Southern blot analysis of that clone suggested the presence of a second related gene. In the present paper sequencing of the second gene has now indicated that it is a pseudogene, a finding supported by a lack of expression in vivo. The pseudogene appears to have arisen by gene duplication, possibly from the adjacent functional gene. Key mutations seem to have occurred in the promoter and processing signals of this gene to render it non-functional and two in-frame termination codons are present in the coding region. A possible recombination point between sequences encoding glycine-rich repeats was identified that could have lead to the creation of the in-frame termination codons.

Amino Acid Sequence↗
PubMed1992

The quality of life after radical radiotherapy for bladder cancer.

The quality of life in 72 patients who had shown a complete response to radiotherapy, using a modified bladder symptom score and the Nottingham health profile, was compared with the quality of life in a similar control group matched for age and sex. There was no significant difference in either group. The records of 69 patients who had undergone post-radiation salvage cystectomy were reviewed, looking specifically at surgical complications. There were 3 post-operative deaths (5%), 3 pulmonary emboli and 3 fistulae--with some overlap of complications. Five patients who underwent cystectomy for intractable symptoms in the apparent absence of recurrent tumour were found to have residual cancer in the excised specimens.

Adult↗