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Biomedical subjects

C J Watson

Publications and source records attributed to C J Watson.

At least 73 records · Page 4Linked to original sources
PubMed1998

Efficient BLG-Cre mediated gene deletion in the mammary gland.

Using the phage P1-derived Cre/loxP recombination system, we have developed a strategy for efficient mammary tissue specific inactivation of floxed genes. Transgenic mice were generated which express Cre DNA-recombinase under the control of the mammary gland specific promoter of the ovine beta-lactoglobulin (BLG) gene. To test the specificity of Cre mediated recombination, we crossed these mice to animals harbouring a floxed DNA ligase I allele. We show that the BLG-Cre construct specifies mammary specific gene deletion, and furthermore that it is temporally regulated, predominantly occurring during lactation. We fully characterised the extent of gene deletion in one line (line 74). In this strain the virgin gland is characterised by low levels (7%) of Cre mediated deletion, whereas 70-80% of cells within the lactating mammary gland have undergone recombination. Immunohistochemistry and indirect in situ PCR were used respectively to demonstrate that both Cre protein and Cre activity were evenly distributed throughout the population of secretory epithelial cells. The level of background recombination in non-mammary tissues was found to be < or = 1.1%, irrespective of mammary gland developmental status. Crossing the transgenic BLG-Cre strain described here to mice harbouring other floxed alleles will facilitate the functional analysis of those genes during differentiation and development of the mammary gland.

Animals↗
PubMed1998

Vascular endothelial growth factor (VEGF) is released from platelets during blood clotting: implications for measurement of circulating VEGF levels in clinical disease.

1. Dysregulated vascular endothelial growth factor (VEGF) expression has been reported in several pathological states based upon evidence of elevated serum VEGF levels. Using two immunoassays for VEGF, this study determines normal plasma and serum VEGF ranges, determines which are more likely to reflect circulating VEGF levels and investigates a potential contribution of VEGF from platelets to VEGF levels detected in serum. 2. The presence of soluble VEGF receptor, sflt-1, at a molar excess of 7:1 significantly reduced measured VEGF levels in both assays. Serum VEGF levels were higher than plasma levels in children [(mean +/- S.E.M.) 306.1 +/- 39.4 versus 107.4 +/- 24.9 pg/ml, P < 0.0001] and adults (249.4 +/- 46.4 versus 76.1 +/- 10.7 pg/ml, P < 0.0001). Serum VEGF increased with clotting time (P = 0.0005 t0 compared with 2 h samples); plasma VEGF levels were not affected by time between sampling and centrifugation. 3. Calcium-induced clotting of platelet-rich but not platelet-poor plasma induced VEGF release with a proportional response between platelet count and VEGF level and isolated platelets released significant quantities of VEGF upon incubation with thrombin. Reverse transcriptase-PCR studies confirmed that platelets express VEGF121 and VEGF165 mRNA. 4. These data suggest that plasma is the preferred medium to measure VEGF levels; a significant and highly variable platelet-mediated secretion of VEGF during the clotting process invalidates the use of serum as an indicator of circulating VEGF levels in disease states.

Adult↗
PubMed1998

Updated measurements from CREAM & CREDO & implications for environment & shielding models.

Flight data obtained between 1995 and 1997 from the Cosmic Radiation Environment Monitors CREAM & CREDO carried on UoSat-3, Space Shuttle, STRV-1a (Space Technology Research Vehicle) and APEX (Advanced Photovoltaic and Electronics Experiment Spacecraft) have been added to the dataset affording coverage since 1990. The modulation of cosmic rays and evolution of the South Atlantic Anomaly are observed, the former comprising a factor three increase at high latitudes and the latter a general increase accompanied by a westward drift. Comparison of particle fluxes and linear energy transfer spectra is made with improved environment & radiation transport calculations which account for shield distributions and secondary particles. While there is an encouraging convergence between predictions and observations, significant improvements are still required, particularly in the treatrnent of locally produced secondary particles.

Atlantic Ocean↗
PubMed1997

What is the long-term outcome for patients with very small abdominal aortic aneurysms?

OBJECTIVE: To determine the long-term outcome for patients with abdominal aortic aneurysms (AAA) less than 4 cm in AP diameter (very small AAA). DESIGN: Population-based screening study. MATERIALS AND METHODS: One hundred and forty-two patients who had AAA less than 4 cm at presentation were assessed by ultrasound at intervals of 6-12 months. The records of these patients were reviewed. RESULTS: During the period of follow-up the median annual growth rate for aneurysms while under 3.0 cm was 1 mm, rising to 2 mm when between 3.0 and 3.9 cm, and 3 mm when between 4.0 and 4.9 cm in diameter. Elective aneurysm repair was undertaken when aneurysms exceeded the threshold value, which itself increased from 4 cm to 5.5 cm in the 9 years of follow-up. More patients died with their aneurysm (n = 35) then underwent surgery (n = 23). There was one perioperative death, and three unrelated late deaths after resection. One aneurysm ruptured in a patient who had refused follow-up 5 years previously. CONCLUSIONS: This study suggests that aneurysms less than 4.0 cm diameter are relatively benign, and questions the appropriateness of early intervention.

Adult↗
PubMed1997

Claudication distance is poorly estimated and inappropriately measured.

BACKGROUND: Claudication distance is the commonest measure of the disability caused by lower-limb occlusive arterial disease. The accuracy of claudication distance as a surrogate for handicap has been assessed. METHODS: Seventy patients who attended a specialist vascular clinic with intermittent claudication were studied prospectively. Patients were asked to estimate their claudication distance and maximum walking distance before undergoing both a patient-controlled corridor walk and a fixed-speed treadmill walk. RESULTS: The claudication distance reported by patients bore little relation to the distance recorded in the medical correspondence. There was no correlation between the estimated distance and the actual distance walked on either a patient-controlled corridor walk or a fixed-speed treadmill walk. Most patients were able to walk substantially further at their own speed on the corridor than on the treadmill at a slower speed. CONCLUSION: Claudication distance is spuriously estimated, inaccurately reported, falsely recorded, inappropriately measured and usually misinterpreted. It is of little value in judging the need for treatment. Objective measures of the handicap caused by the disability of reduced walking distance are required if rational management decisions are to be made.

Adult↗
PubMed1996

Differential activation of STATs 3 and 5 during mammary gland development.

We have investigated the activity of STAT family members throughout a mammary developmental cycle. Transcripts for Stat 5 were upregulated during pregnancy whilst STAT1 and STAT3 mRNAs were expressed at constant levels. DNA binding complexes containing both STAT5a and 5b showed differing affinities for two naturally occurring STAT5 binding sites. In the involuting mammary gland STAT5 activity decreased whereas STAT3 was specifically activated. These observations reveal a complex pattern of activation of STAT factors during mammary growth, differentiation and remodelling and provide the first evidence for the involvement of STAT3 in development of the mammary gland.

Animals↗
PubMed1996

Regulation of surface and soluble TNF receptor expression on human monocytes and synovial fluid macrophages by IL-4 and IL-10.

By regulating monocyte and macrophage production of IL-1, its receptor, and its receptor antagonist, IL-4 and IL-10 may exert significant anti-inflammatory activity. We determined whether a similar multicomponent process controlling TNF activity was regulated by IL-4 and IL-10 in nonadherent monocytes and synovial fluid macrophages. Previous studies differed in their conclusions. For both the p75 and p55 TNF receptors, mRNA levels, surface receptor expression, and soluble receptor levels were measured for blood monocytes incubated in vitro for 17, 40, or 64 h with IL-4 or IL-10. The predominant TNF receptor on monocytes, the p75 receptor, was down-regulated by IL-4 at the mRNA level. In turn, both surface and soluble receptor levels on LPS-stimulated cells were reduced and the inhibitory effects were maintained for at least 64 h. In contrast, IL-10 increased surface and soluble p75 TNF receptor levels on monocytes for approximately 40 h, which reflected an increase in receptor mRNA. These studies suggest that IL-4 and IL-10 do not directly regulate the cleavage of TNF receptors from monocytes and macrophages. Addition of an Ab to IL-10 suggested that the stimulatory effects of LPS on p75 TNF receptor expression were due, at least in part, to LPS stimulation of IL-10 production and that IL-4 acted, in part, by decreasing IL-10 production. IL-4 was down-regulatory and IL-10 stimulatory for TNF receptor expression by synovial fluid macrophages. By increasing surface receptor levels, IL-10 enhanced the activities of TNF on monocytes for IL-1beta production. By increasing soluble TNF receptor levels, IL-10 may limit only temporarily the activity of other TNF-responsive cells. This study questions the benefit of IL-10 to resolving TNF-associated inflammation.

Arthritis, Rheumatoid↗
PubMed1996

Involvement of microtubules in prothoracicotropic hormone-stimulated ecdysteroidogenesis by insect (Manduca sexta) prothoracic glands.

Secretion of ecdysteroid molting hormones by insect prothoracic glands is stimulated by neuropeptide prothoracicotropic hormones (PTTH). Studies reported here were conducted to assess the effects of microfilament and microtubule inhibitors on in vitro ecdysteroidogenesis by prothoracic glands of Manduca sexta. Microfilament inhibitors (cytochalasins B and D) had no effect on basal or big PTTH-stimulated ecdysteroidogenesis. Microtubule inhibitors (colchicine, podophyllotoxin, nocodazole) had no effect on basal ecdysteroid secretion, but suppressed PTTH-stimulated secretion in a concentration-dependent manner. The effect of nocodazole was partially reversible, suggesting it was not due to nonspecific toxicity. Colchicine had no effect on glandular ecdysteroid levels, indicating that inhibition was not due solely to blockage of secretion. The combined results are consistent with the hypothesis that microtubule-mediated transport of ecdysteroid precursors plays a critical role in stimulation of ecdysteroidogenesis by PTTH.

Actin Cytoskeleton↗
PubMed1996

Radionuclide studies in intestinal transplantation. Diagnosis of rejection and assessment of permeability.

Three patients who received intestinal allografts were studied using two distinct radionuclide investigations. In the first, 111In or 99mTc-labeled leukocyte scanning was performed to assist in the diagnosis of rejection. It was able to demonstrate the occurrence of rejection in the transplanted intestine, and the response to antirejection therapy. In 1 case, the abnormality on the scan preceded the histological confirmation of rejection. The second technique studied mucosal integrity by serial 51Cr-EDTA/14C-mannitol permeability tests. These studies demonstrated the initial marked impairment and the slow return to normal function of the intestinal mucosal barrier. In 1 patient, this occurred by 91 days; in another, it took 232 days. A single assay performed in the third patient at the time of allograft rejection was also abnormal. Both radionuclide tests were helpful in the care of these complicated cases.

Adult↗
PubMed1996

Successful use of size-mismatched liver allografts in children by delayed primary closure of the abdominal wall.

Children who are too ill to await a liver graft of suitable size may be transplanted with a relatively oversized graft by leaving the abdominal wound partially open, the defect reduced being bridged with polypropylene mesh and the mesh reduced in stages until it can be removed and the wound directly closed. This technique has been used in seven children who received nine grafts (five reduced and four full size). Their mean age was 7.3 (range 0.5-11) months and mean weight 5.8 (range 2.3-7.2) kg. Progressive reduction in the size of the transplanted liver made primary closure possible in survivors in up to four stages. Over a follow-up period of 3 to 58 months, five of the nine grafts and five of the seven patients survived. No significant complications attributable to the technique were encountered. The technique of delayed primary abdominal wall closure may be of benefit in children at risk of graft failure because of a size-mismatched graft.

Female↗
PubMed1996

Prolactin signal transduction mechanisms in the mammary gland: the role of the Jak/Stat pathway.

Prolactin signal transduction in mammary epithelial cells is mediated by a novel, direct signalling system that links the activation of the prolactin receptor at the cell surface to changes in gene transcription in the nucleus. This recently identified pathway is a variant of the Jak/Stat (for Janus kinase/signal transducer and activator of transcription) pathway used by many other growth factors and cytokines. Current data suggest that the key intracellular components of the prolactin signalling pathway are the kinase Jak2 and the transcription factor Stat5. This discovery has exciting implications for the interaction between prolactin and other extracellular signals in both the mammary gland and other tissues. Here we review work that began with attempts to understand the regulation of milk protein gene expression and ultimately demonstrated the central role of the Jak/Stat pathway in prolactin signal transduction in the mammary gland.

Animals↗
PubMed1995

Stat5 as a target for regulation by extracellular matrix.

Transcription of tissue-specific genes in mammary gland requires signals from both prolactin and basement membrane. Here we address the mechanism by which this specialized extracellular matrix regulates transcription. Using mammary cell cultures derived from transgenic mice harboring the ovine beta-lactoglobulin gene, we show that either a basement membrane extract, or purified laminin-1, induced high levels of beta-lactoglobulin synthesis. It is known that prolactin signals through Stat5 (signal transducer and activator of transcription). This transcription factor interacts with gamma-interferon activation site-related motifs within the beta-lactoglobulin promoter, which we show are required for matrix dependence of beta-lactoglobulin expression. The DNA binding activity of Stat5 was present only in extracts of mammary cells cultured on basement membrane, indicating that the activation state of Stat5 is regulated by the type of substratum the cell encounters. Thus, basement membrane controls transcription of milk protein genes through the Stat5-mediated prolactin signaling pathway, providing a molecular explanation for previous studies implicating extracellular matrix in the control of mammary differentiation.

Animals↗
PubMed1995

CsA levels in the early posttransplant period--predictive of chronic rejection in liver transplantation?

The increasing success of clinical liver transplantation has brought rejection to the forefront as a cause of morbidity and graft loss. The relationship of immunosuppressive drug doses and levels to acute and chronic rejection remains a matter of debate. The effect of blood CsA levels and drug doses on the incidence of acute and chronic rejection and the impact of acute rejection episodes on the occurrence of chronic rejection were studied in 146 grafts in 132 patients. These patients were transplanted in the 4-year period from June 1989 using CsA-based immunosuppression (CsA, azathioprine, prednisolone). Liver grafts in patients maintained on median CsA levels (whole blood, trough level) of > or = 175 micrograms/L in the first 28 days posttransplant had a significantly lower incidence of chronic rejection (2 out of 49 vs. 22 out of 97; P = 0.002). There was no significant difference in incidence of graft loss due to fatal sepsis (6% vs. 5%) or nephrotoxicity between the high and low CsA level groups. The overall graft loss rate was lower in the higher CsA level group (22% vs. 37%). The total doses of the individual drugs did not correlate with the incidence of acute or chronic rejection. Although the occurrence of acute rejection itself did not determine later chronic rejection, late occurrence (P < 0.00001) and multiple episodes (two or more; P = 0.0002) of acute rejection were significant risk factors for the occurrence of chronic rejection. We conclude that to minimize graft loss to rejection, CsA levels should be maintained at greater than 175 micrograms/L in the early posttransplant period, and late and recurrent episodes of acute rejection should be prevented.

Adult↗
PubMed1995

Liver transplantation in patients with situs inversus.

Seven patients with situs inversus abdominis and one with situs inversus totalis underwent liver transplantation; all are alive at follow-up of between 7 months and 5 years. Two patients required retransplantation within the first 3 weeks (for primary non-function and thrombotic infarction). Seven had additional abnormalities associated with the polysplenia-biliary atresia syndrome. Liver transplantation in these patients involved selection of relatively small donor organs or use of reduced-size grafts. Delayed abdominal wall closure was necessary in two patients and all required a modification of the 'piggy-back' technique of suprahepatic vena caval anastomosis to overcome recipient venous anomalies. Biliary drainage by Roux-en-Y choledochojejunostomy was the preferred technique. Although technically challenging, situs inversus is not a contraindication to liver transplantation and patients should expect full recovery.

Anastomosis, Roux-en-Y↗