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Biomedical subjects

D G Lowe

Publications and source records attributed to D G Lowe.

At least 73 records · Page 4Linked to original sources
PubMed1994

Unilateral testicular obstruction: orchidectomy or reconstruction?

Unilateral testicular obstruction can cause infertility in man by reducing sperm output, or by stimulating antisperm antibody production. Amongst 125 subfertile men with unilateral blocks, the causes were defined as post-infective (n = 72), post-traumatic (n = 41) or congenital (n = 12) by surgical exploration. Of these, 50 had severe oligozoospermia or azoospermia, and another 30 had oligozoospermia; 67 had significantly raised serum antisperm antibody titres. The outflow tracts were reconstructed in 87 men, while in 24 the obstructed testis was removed and replaced with a prosthesis. Follow-up information is available in 104 men. Reconstruction produced significant improvement in sperm concentration in the ejaculate but little change in antisperm antibody titres. Orchidectomy lowered seminal plasma antibody titres and had no effect on sperm output. Orchidectomy plus prednisolone was most effective in terms of pregnancies produced in the female partners. Testicular biopsies showed that spermatogenesis was normal on the side of the block in 90% of cases, whereas it was impaired in the contralateral testis in 40% of men. Although sperm output can be improved by reconstruction, the stimulus to antibody production is more reliably eliminated by orchidectomy. Sperm concentration, antisperm antibody titres and bilateral testicular biopsy results should be taken into account before making a final therapeutic recommendation in men with unilateral testicular obstruction.

Adult↗
PubMed1994

Expression of c-erbB-2, c-myc, and c-ras oncoproteins, insulin-like growth factor receptor I, and epidermal growth factor receptor in ovarian carcinoma.

AIMS: To assess whether the overexpression of five dominant oncogene encoded proteins is crucial to the pathogenesis of ovarian carcinoma and whether this provides any useful prognostic information. METHODS: The expression of the insulin-like growth factor 1 receptor (ILGFR 1), epidermal growth factor receptor (EGFR), and the c-erbB-2, c-ras, and c-myc products was studied by multiparameter flow cytometry in 80 patients with epithelial ovarian cancer for whom long term follow up was available. RESULTS: Overexpression of ILGFR 1, EGFR, c-erbB-2, c-ras and c-myc was found in, respectively, nine of 80 (11%), 10 of 80 (12%), 19 of 80 (24%), 16 of 80 (20%) and 28 of 80 (35%) ovarian carcinomas. The levels of expression of ILGFR 1, EGFR, c-erbB-2 and c-ras were significantly higher in the tumours of patients with recurrent or persistent disease after chemotherapy than in the tumours of patients at initial presentation (p < 0.02). Multivariate analysis showed that residual tumour (p < 0.001), FIGO stage (p = 0.002), EGFR overexpression (p = 0.030) and previous chemotherapy (p = 0.034) were independent variables for predicting survival. CONCLUSIONS: Overexpression of these oncoproteins only occurs in a small proportion of ovarian carcinomas but may have an important role in the progression of the disease.

Carcinoma↗
PubMed1994

Serum placental-type alkaline phosphatase activity in women with squamous and glandular malignancies of the reproductive tract.

AIM: To investigate serum placental-type alkaline phosphatase (PLAP-type) activities in women with squamous and glandular malignancies of the reproductive tract using an immunoradiometric assay. METHODS: PLAP-type immunoreactivity was measured in 180 women with non-ovarian malignancies of the reproductive tract and the values were compared with those from 334 controls. The cases comprised 18 vulval, nine vaginal, 103 cervical, 46 endometrial, and five fallopian tube cancers. RESULTS: Serum PLAP-type activities were no different from controls in patients with squamous cell tumours. Women with adenocarcinoma of the cervix, endometrium, and fallopian tube had increased values: women with endometrial cancer had a median value nearly four times greater than that of controls. There was no direct correlation between PLAP-type activities and stage of disease in patients with endometrial cancer, but values reverted to normal after treatment. CONCLUSIONS: Serum PLAP-type measurements are of no value in the management of patients with squamous cell tumours of the female reproductive tract. Raised activities can, however, be found in glandular tumours, in particular endometrial cancer where serum PLAP-type measurements may be of value in predicting remission.

Adenocarcinoma↗
PubMed1994

R-Ras induces malignant, but not morphologic, transformation of NIH3T3 cells.

Although previous studies have not identified transforming properties of the Ras-related protein R-Ras, two recent observations have prompted our further evaluation of R-Ras function. First, we observed that mutant forms of the closely related R-Ras2/TC21 protein (approximately 70% identity) exhibited the same potent transforming activity as oncogenic Ras proteins. Second, R-Ras association with Bcl-2 suggested a possible role for R-Ras in apoptotic growth control. Therefore, we have performed a detailed analysis of R-Ras transforming potential in NIH3T3 cells. Whereas expression of a mutant R-Ras protein (38V; analogous to the 12V activating Ras mutation) did not induce morphologic transformation of NIH3T3 cells, R-Ras(38V)-expressing cells proliferated in low serum, formed colonies in soft agar, and formed progressive tumors in nude mice. Like Ras-transformed cells, R-Ras(38V)-transformed cells exhibited constitutively activated mitogen activated protein kinases. Furthermore, R-Ras(38V) stimulated transcriptional activation of Ras-responsive promoter elements, and this activity (and transformation) was blocked by Raf dominant negative proteins. Finally, whereas co-expression of Bcl-2 did not cause significant alteration in wild type or mutant R-Ras transforming activity, coexpression of v-Myc and R-Ras(38V) induced a striking morphologic transformation of NIH3T3 cells. Taken together, these observations suggest that aberrant R-Ras function may stimulate malignant transformation, in the absence of morphologic transformation, via up-regulation of part of the Ras signal transduction pathway.

3T3 Cells↗
PubMed1994

Bilateral phaeochromocytomas in von Hippel-Lindau disease: diagnosis by adrenal vein sampling and catecholamine assay.

Three unrelated patients with von Hippel-Lindau disease had phaeochromocytomas diagnosed as a result of screening in their third decade. All had raised 24-h urinary noradrenaline levels and obvious unilateral adrenal tumours on ultrasound scanning and computed tomography. The contralateral adrenal appeared either normal or equivocally abnormal using the same imaging techniques. Radiolabelled meta-iodo-benzylguanidine uptake and enhanced T2-weighted magnetic resonance signals confirmed the ipsilateral lesion, but showed no abnormality in the contralateral adrenal. Nevertheless, venous sampling demonstrated abnormally elevated noradrenaline:adrenaline ratios (normal < 1) in blood draining both adrenals in all three patients. All underwent bilateral adrenalectomy: histological examination confirmed bilateral phaeochromocytomas in all three patients, with the smaller adrenal showing tumours between 3 and 11 mm in diameter. A fourth patient with von Hippel-Lindau disease was also evaluated because of a left 'suprarenal' mass discovered by ultrasound scanning. Urinary and plasma catecholamines were normal. Computed tomography showed a normal right adrenal, with a left para-aortic mass lying superior to the left adrenal. Magnetic resonance scanning showed an enhanced T2 signal from the mass, which also showed positive uptake with radiolabelled mIBG. At operation, a non-secretory left para-aortic paraganglioma was found. Venous sampling suggested that the left adrenal was normal, and this was confirmed on histology. Venous sampling for catecholamine assays is effective in locating small bilateral phaeochromocytomas and defining a normal adrenal gland, and can be useful in preventing unnecessary or repeat operations in patients with non Hippel-Lindau disease.

Adrenal Gland Neoplasms↗
PubMed1993

Hormonal induction of low affinity receptor guanylyl cyclase.

We describe a unique transient binding phenomenon for atrial natriuretic peptide (ANP) binding to the natriuretic peptide receptor-A (NPR-A) guanylyl cyclase stably expressed in 293 cells. The time course of ANP binding to intact cells peaked at 15 min followed by a subsequent decrease. Reduced binding was a consequence of an ANP induced low affinity state of NPR-A, and required the receptors' kinase homology domain. In a particulate fraction, ANP-stimulated cGMP production was dependent on ATP as a cofactor, and ATP promoted a lower affinity state. Our findings suggest that the kinase homology domain of NPR-A mediates the regulatory action of ATP, not only for signal transduction, but in the modulation of NPR-A hormone affinity.

Adenosine Triphosphate↗
PubMed1993

Radioimmunoscintigraphy with technetium-99m-labelled monoclonal antibody, SM3, in gynaecological cancer.

Radioimmunoscintigraphy (RIS) with technetium-99m labelled SM3, a monoclonal antibody reacting with a polymorphic epithelial mucin glycoprotein core antigen, is evaluated. No adverse effects or thyroid uptake were observed. Studies in 45 patients (one twice) had a sensitivity for gynaecological malignancy of 100% (35/35) and a specificity of 73% (8/11), giving an overall accuracy of 93% (43/46). These results have led to the routine adoption of 99mTc RIS in the management of patients suspected of or having primary or recurrent gynaecological cancer.

Adult↗
PubMed1993

Malignant prolactinoma with extracranial metastases: a report of three cases.

OBJECTIVE: Prolactin-secreting tumours of the pituitary almost never metastasize extracranially. However, we have recently seen three such patients, whose presentation, clinical course and response to treatment are reviewed in order to determine whether they possess unique clinical features, and to assess optimum therapy. DESIGN AND PATIENTS: Three patients with extracranial metastases from prolactinomas have been retrospectively reviewed. MEASUREMENTS: Clinical courses, biochemical parameters and imaging modalities (CT, MR and radiolabelled somatostatin analogue scanning) and histopathology were assessed before and during different therapeutic regimens. RESULTS: All three patients' presentations were initially unremarkable, but later each had persistent and relentlessly increasing serum prolactin concentrations and evidence of distant spread of their tumours. The first patient presented aged 32 and was treated with repeated transsphenoidal resections of the tumour, pituitary radiotherapy, high dose bromocriptine therapy, the somatostatin analogue octreotide and chemotherapy. Nine years after the original diagnosis a liver biopsy revealed carcinoma cells positively immunostaining for prolactin. At autopsy further microscopically similar metastases were seen in both lungs and the left hilar lymph nodes. The second patient presented aged 48 and was treated with external beam pituitary radiotherapy, bromocriptine, transsphenoidal hypophysectomy and chemotherapy. Fifteen years after the original diagnosis bone biopsy revealed carcinoma cells positively immunostaining for prolactin; the patient developed interstitial nephritis and died in renal failure. The third patient presented aged 48 with hypogonadism and bitemporal hemianopia due to a macroadenoma. This was removed transfrontally and followed by external beam radiotherapy. After recurrence, further surgery and radiotherapy were undertaken, but the tumour continued to grow and the patient died suddenly of a pulmonary embolus. At autopsy, tumour was found in thoracic lymph nodes and lung capillaries. CONCLUSIONS: These three patients may be added to the previous two reported cases of malignant prolactinoma with extracranial spread. Several different therapies were tried but were of limited value in controlling the progression of the disease, although chemotherapy is an important modality to be considered. No particular factor or combination of factors at presentation differentiated these patients from more typical patients whose disease is much less aggressive.

Adult↗
PubMed1993

Transsphenoidal resection in Cushing's disease: undetectable serum cortisol as the definition of successful treatment.

OBJECTIVE: We tested the hypothesis that in Cushing's disease, ACTH secretion from the normal pituitary surrounding an ACTH-secreting adenoma is inhibited and hence removal of the entire adenoma should result in an undetectable serum cortisol in the immediate post-operative period. DESIGN: A retrospective study of patients undergoing transsphenoidal selective adenomectomy, hemi-hypophysectomy or total hypophysectomy for Cushing's disease at St Bartholomew's Hospital between 1985 and 1990. PATIENTS: Forty-eight consecutive patients (33 women, mean age 43, range 7-69 years) undergoing transsphenoidal hypophysectomy for Cushing's disease. Ten patients who underwent a second operation were re-evaluated; the patients were followed for a median time of 40 months after operation (range 15-70). MEASUREMENTS: Post-operatively, serum cortisol was measured daily at 0900 h. Serum TSH, T4, prolactin, LH, FSH, testosterone or oestradiol plus plasma and urine osmolality were measured. RESULTS: After initial surgery, post-operative serum cortisol was undetectable (< 50 nmol/l) in 20 out of 48 patients (42%) and < 300 nmol/l in 32 out of 48 patients (67%). Re-exploration of the pituitary fossa in 10 patients found undetectable cortisol levels in 25 (52%) and levels < 300 nmol/l in 39 (81%) patients. Cushing's syndrome has not recurred, clinically or biochemically, in any patient in whom the post-operative cortisol was < 50 nmol/l. Post-operatively, hypothyroidism was present in 40% of patients and hypogonadism in 53% of men and 30% of premenopausal women. Diabetes insipidus, persisting for at least six months, occurred in 46% of patients. CONCLUSIONS: Cushing's disease has not recurred in any patient with an undetectable serum cortisol (< 50 nmol/l) post-operatively. Serum cortisol should be regarded as a tumour marker in Cushing's disease and the aim of transsphenoidal hypophysectomy for Cushing's disease should be to render the immediate post-operative serum cortisol undetectable.

Adenoma↗
PubMed1993

Paraneoplastic syndromes in patients with ovarian neoplasia.

The prevalence of several paraneoplastic syndromes associated with ovarian cancer was determined from a clinicopathological study of 908 patients with primary ovarian malignancy in the North East Thames Region. The diversity and rarity of these manifestations are great and the explanation for them is difficult. Circumstantial evidence suggests that in some cases an autoimmune phenomenon is the most plausible cause.

Arthritis, Rheumatoid↗
PubMed1993

Early vulval cancer: the place of conservative management.

There is a trend towards conservative surgery for early vulval cancer, which is increasingly being diagnosed in younger women. In this series there were 21 patients who had lesions which had invaded to a depth of 3 mm or less. Nine patients were treated by wide local excision without any form of lymphadenectomy, and eight patients had wide local excision with ipsilateral groin dissection. In the remaining four patients, radical surgery was carried out, consisting of radical vulvectomy and bilateral lymphadenectomy. None of the 12 patients who had some form of lymphadenectomy was shown to have nodal involvement. None of the patients suffered from local recurrence or recurrence in the groin nodes. No patient died from vulval cancer, and all but one of the patients are still alive with a mean follow-up period of 54.8 months. Though there is as yet no universal agreement on the criteria for early vulval cancer, with superficial invasion there is a place for individualized treatment, when patients will benefit from less than radical surgery.

Adult↗
PubMed1992

Human natriuretic peptide receptor-A guanylyl cyclase is self-associated prior to hormone binding.

The human natriuretic peptide receptor-A (NPR-A) guanylyl cyclase is specifically activated to synthesize cGMP by binding of atrial natriuretic peptide (ANP) to the receptor's extracellular domain. In this report, NPR-A monoclonal and polyclonal antibodies were used to assess the aggregation status of wild-type NPR-A and a truncation mutant lacking most of the NPR-A cytoplasmic domain. On intact human embryonic kidney 293 cells, in the absence of ANP, recombinant human NPR-A is self-aggregated through disulfide bonds in an M(r) > 500,000, possibly tetrameric, complex. Under nonreducing conditions, truncated NPR-A was a monomer, indicating that the cytoplasmic domain is necessary for NPR-A self-association. In the presence of the homobifunctional cross-linker dithiobis(succinimidyl propionate), or disuccimidyl suberate, truncated NPR-A could be cross-linked as a dimer and trimer only in the presence of ANP. Wild-type NPR-A was cross-linked with disuccinimidyl suberate to an M(r) > 500,000 species in the absence of ANP, and with ANP, a smaller, M(r) approximately 400,000 receptor trimer cross-linking product was observed, together with the larger, possibly tetrameric complex. When whole cell stimulation of cGMP production by ANP was tested on the low level of endogenous 293 cell NPR-A, maximal stimulation was observed regardless of truncated NPR-A overexpression. The absence of a dominant negative effect by the truncated NPR-A, together with the cross-linking data, demonstrates that preassociated NPR-A is the functionally relevant form of this receptor.

Atrial Natriuretic Factor↗
PubMed1992

Human natriuretic peptide receptor-A guanylyl cyclase. Hormone cross-linking and antibody reactivity distinguish receptor glycoforms.

Most of the physiological actions of atrial natriuretic peptide (ANP) may be attributed to activation of the natriuretic peptide receptor-A (NPR-A) guanylyl cyclase. We report here that truncation of the NPR-A cytoplasmic domain results in increased expression of cell surface ANP binding sites. The truncated receptor exhibited a hyperbolic time course for ANP binding and had a high affinity for [125I]hANP, Kd = 8 pM. Cells expressing truncated NPR-A were used as an immunogen to obtain monoclonal antibodies against the native conformation of the extracellular domain. These antibodies were used to select for high levels of stable NPR-A expression in 293 cells, by fluorescence-activated cell sorting. Disuccinimidyl suberate cross-linked [125I]ANP to 135-kDa NPR-A on intact cells. Monoclonal antibody immunoprecipitation of 35S-labeled proteins revealed NPR-A size heterogeneity, with 135- and 125-kDa species. A synthetic peptide antibody directed against the extracellular domain immunoprecipitated 125-kDa NPR-A, but recognized both sizes of receptor by Western blotting. The 125-kDa NPR-A did not bind to or cross-link ANP. NPR-A size variants were expressed on the cell surface, and heterogeneity was removed by deglycosylation with protein:N-glycosidase F. Our results suggest that the degree of N-linked glycosylation of the NPR-A extracellular domain influences the ability to bind ANP.

Antibodies, Monoclonal↗