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Biomedical subjects

A Howell

Publications and source records attributed to A Howell.

At least 19 recordsLinked to original sources
PubMed2001

YkdA and YvtA, HtrA-like serine proteases in Bacillus subtilis, engage in negative autoregulation and reciprocal cross-regulation of ykdA and yvtA gene expression.

HtrA-type serine proteases participate in folding and degradation of aberrant proteins and in processing and maturation of native proteins. Mutation of the corresponding genes often confers a pleiotropic phenotype that can include temperature sensitivity, sensitivity to osmotic and oxidative stress, and attenuated virulence. There are three HtrA-type serine proteases, YkdA, YvtA, and YycK, encoded in the Bacillus subtilis genome. In this report we show that YkdA and YvtA display many similarities: their expression profiles during the growth cycle in wild-type and mutant backgrounds are very alike, with expression being directed by very similar promoters. Both are induced by temperature upshift and by heterologous amylases at the transition phase of the growth cycle. These characteristics are quite different for YycK, suggesting that it has a cellular function distinct from that of the other two proteases or that it performs the same function but under different conditions. We also show that inactivation of either ykdA or yvtA results in compensating overexpression of the other gene, especially during stress conditions, with a concomitant increase in resistance to heat and hydrogen peroxide stresses. Mutation of both ykdA and yvtA leads to growth defects and to thermosensitivity. The fact that their expression increases dramatically at the transition phase of the growth cycle under certain conditions suggests that the YkdA and YvtA proteases may function in the processing, maturation, or secretion of extracellular enzymes in B. subtilis.

Amylases↗
PubMed2000

Serum soluble vascular cell adhesion molecule-1: role as a surrogate marker of angiogenesis.

BACKGROUND: Angiogenesis, the development of new blood vessels from pre-existing vasculature, is a prerequisite for tumor growth and metastasis. Surrogate markers for angiogenesis would be useful for studying the effectiveness of antiangiogenesis drugs. We examined the potential of three serum glycoproteins-vascular cell adhesion molecule-1 (VCAM-1), endothelial selectin (E-selectin), and von Willebrand factor (VWF)-to serve as markers for angiogenesis. METHODS: Preoperative serum levels of VCAM-1, E-selectin, and VWF were measured by enzyme-linked immunosorbent assay in 93 women with early breast cancer and were compared with microvessel density in each tumor, histologic features, and recurrence after surgery. Serum samples were taken from 55 women with advanced breast cancer who were commencing hormonal therapy, both immediately before therapy and 3 months later. Changes in serum levels of VCAM-1, E-selectin, and VWF were compared with the response of the disease to hormonal therapy assessed 6 months after the start of hormone therapy or at disease progression. All P: values are two-sided. RESULTS: In women with early breast cancer, serum levels of VCAM-1 (but not of E-selectin or VWF) correlated closely with microvessel density in tumors (r =.65; P:<.001), and women who developed early recurrence had higher preoperative levels of serum VCAM-1 than those who remained disease free (P: =.01). Serum VCAM-1 levels rose in women with advanced breast cancer whose disease progressed (P:<.001) but remained unchanged or fell in women with advanced breast cancer whose disease remained stable or showed a partial response to hormonal therapy. CONCLUSION: Serum VCAM-1 appears to be a surrogate marker of angiogenesis in breast cancer. Its measurement may, therefore, help in the assessment of antiangiogenesis drugs currently in phase II trials.

Adult↗
PubMed2000

ICI 182,780 (Faslodex): development of a novel, "pure" antiestrogen.

BACKGROUND: The nonsteroidal antiestrogen tamoxifen is well established as an effective treatment for patients with breast carcinoma, both for the treatment of metastatic disease and as an adjuvant to surgery for patients with primary breast carcinoma. In addition to exerting antagonistic effects on the estrogen receptor, tamoxifen and its derivatives act as partial agonists on certain tissues. These agonistic effects, for example, endometrial stimulation and stimulation of tumor growth after previous response to tamoxifen, may limit their clinical efficacy. ICI 182,780 (Faslodex) from AstraZeneca (Cheshire, United Kingdom) is a novel, steroidal estrogen antagonist that was designed to be devoid of estrogen agonist activity in preclinical models. METHODS: ICI 182,780 was tested in a large number of in vitro and in vivo preclinical models, and its value was assessed clinically when administered before surgery for breast carcinoma and hysterectomy for benign conditions and after failure of tamoxifen in patients with advanced breast carcinoma. RESULTS: All data indicated that ICI 182,780 is devoid of agonist activity in preclinical models and in clinical trials. It inhibits growth of the breast and endometrium. In animal models, it does not cross the blood-brain barrier and appears to be neutral with respect to lipids and bone. ICI 182,780 down-regulates the estrogen receptor and is active in tamoxifen-resistant breast carcinoma. In a small, Phase II study, durable responses were seen: Phase III clinical trials are in progress comparing ICI 182,780 with anastrozole and tamoxifen in the treatment of patients with advanced breast carcinoma. CONCLUSIONS: ICI 182,780 specifically down-regulates the estrogen receptor and, thus, represents the first of a new class of therapeutic agents. In this report, the authors present the current evidence that distinguishes ICI 182,780 from tamoxifen and related nonsteroidal compounds and establishes ICI 182,780 as the first in a new class of therapeutic agents.

Animals↗
PubMed2000

Antiparkinson potential of delta-opioid receptor agonists.

delta-Opioid receptors, present in very high concentrations in striatum and overlying cortex, are thought to be involved in a number of processes, including analgesia, mood, reward, modulation of neuronal excitability, and alterations in neurotransmitter release. Given the localization of the receptors in motor circuits in brain, we thought it of interest to study the antiparkinson potential of delta-opioid receptor agonists. Rats were given unilateral 6-hydroxydopamine lesions of the nigrostriatal tract, and following recovery, were tested for rotational activity. Tonazocine mesylate is a nonpeptide, partial delta-opioid receptor agonist with mu-receptor antagonist properties. Tonazocine (0.1-10 mg/kg) evoked a dose-related, ipsilateral rotation, consistent with augmentation of dopaminergic function on the unlesioned side. The rotation evoked by tonazocine was blocked by the selective delta-opioid receptor antagonist naltrindole, suggesting that the effect was mediated by delta-opioid receptors. The full delta-opioid receptor agonist (+)-4-¿9-alpha-R)-alpha-(2S,5RO-4-allyl-2, 5-dimethyl-1-piperaziny l)-3-methoxybenzyl-N,N-diethylbenzamide (SNC-80) produced both contralateral and ipsilateral rotation. Tonazocine additionally augmented the effects of L-3,4 dihydroxyphenylalanine (L-DOPA) on reserpine-induced suppression of motor activity. Binding affinities and efficacies of tonazocine and SNC-80 against mu-, kappa-, and delta-opioid receptors were also confirmed and compared to standards. These data suggest therapeutic potential of agents interacting with delta-opioid receptors, and indicate some differences in the activities of tonazocine and SNC-80.

Animals↗
PubMed2000

Long-term functional end points following middle cerebral artery occlusion in the rat.

The purpose of the present study was to assess the magnitude and stability of a number of functional deficits in rats subjected to occlusion of the middle cerebral artery (MCAO). Three groups of rats, treated with 90-min, 120-min, or sham occlusion were used in functional studies for 22 weeks following surgery. The following tests were used: methamphetamine-induced rotation, the staircase test, acquisition of operant responding, running-wheel behavior, and performance of operant differential reinforcement of a low-rate responding (DRL) schedule of reinforcement. Histology performed at 23 weeks following infarct showed on average modest damage of a 19% reduction in hemispheric volume. Of the behavioral tests conducted, rotation, the staircase test, and the operant DRL were sensitive to ischemic damage, and were under some circumstances related to lesion size. These data show that long-term functional deficits following MCAO are demonstrable, and hence, assessment of long-term neuroprotection is feasible.

Animals↗
PubMed2000

Disruption of acquisition and performance of operant response-duration differentiation by unilateral nigrostriatal lesions.

Response duration differentiation (RDD), an operant schedule requiring fine motor timing and control, was assessed as a possible baseline for study of the long-term consequences of nigrostriatal lesions and as a possible baseline to test the therapeutic efficacy of candidate palliative, neuroprotective and neurorestorative drugs. Rats were subjected to unilateral 6-hydroxydopamine (6-OHDA) lesions of striatum, medial forebrain bundle (mfb), or were sham lesioned, and their ability to acquire the operant task was studied in a single overnight session. In a second set of studies, rats that had been well trained in the RDD task were sham lesioned or were given unilateral 6-OHDA lesions of the mfb, and behavior under this baseline was studied for more than 30 weeks. Lesions of both striatum and of mfb resulted in impaired acquisition of RDD responding, with the relatively greater effect by the mfb lesion. In rats previously trained under the RDD schedule, mfb lesions produced marked disruptions in RDD performance, which did not fully recover. L-DOPA administration decreased the variability of the response durations, primarily by decreasing the proportion of short-duration lever presses.

Amphetamine↗
PubMed2000

P27(KIP1) expression indicates that steroid receptor-positive cells are a non-proliferating, differentiated subpopulation of the normal human breast epithelium.

To test the hypothesis that steroid receptor-expressing cells are derived from the proliferative population, we examined expression of the p27(KIP1) inhibitor of cyclin-dependent kinase activity (a differentiation marker) while tracking the fate of proliferating cells in normal human breast tissue implanted into athymic nude mice using tritiated thymidine [3H]-dT. We identified a small number of cells that appeared to have divided just once before switching on p27(KIP1) expression. p27(KIP1)+ve cells also expressed steroid receptors, but not the Ki67 proliferation-associated antigen. These data support the hypothesis that steroid receptor-expressing cells are a differentiated population within the normal human breast epithelium.

Animals↗
PubMed2000

Faslodex (ICI 182780). an oestrogen receptor downregulator.

Anti-oestrogen therapy, tamoxifen in particular, has revolutionised the treatment of breast cancer. However, the partial agonist activity of tamoxifen is associated with an increased risk of endometrial cancer and the acquisition by patients of tamoxifen-resistance. In an attempt overcome these negative aspects of tamoxifen therapy, 'pure' anti-oestrogens have been developed and are currently being investigated for the treatment of breast cancer.

Antineoplastic Agents↗
PubMed2000

Idarubicin and cyclophosphamide--an active oral chemotherapy regimen for advanced breast cancer.

UNLABELLED: Between October 1993 and September 1994, 33 women with metastatic breast cancer aged between 29 and 74 years with a median age of 58 were entered into a study of oral chemotherapy from three UK centres. Patients by definition had metastatic disease and were fit and well with performance status 0 or 1 in 23 cases, 2 in seven cases and 3 in two cases (one missing). Five patients had received prior adjuvant CMF chemotherapy, nine first line non-anthracycline containing chemotherapy for relapse, eight patients second line non-anthracycline containing chemotherapy and all patients had had hormone therapy either as adjuvant or for relapsed disease. Adjuvant radiotherapy had been given to 17 and palliative radiotherapy to 12 patients. In nine patients there was one site of disease at start of therapy, in 10 two sites, in 11 three sites and in three patients four or more sites. The regimen comprised oral idarubicin 15 mg/m2 on day 1, 10 mg/m2 on days 2 and 3 and oral cyclophosphamide 250 mg/m2 (maximum 400 mg) on days 1, 2 and 3. Treatment was continued until disease progression or toxicity. RESULTS: Overall 25% of 32 evaluable patients responded objectively including one complete response; 50% of patients had stable disease and 25% of patients progression. Among patients who had had no prior chemotherapy the objective response rate was 37.5%; 45% of patients had symptomatic improvement. The most common severe toxicity was granulocytopenia WHO grade 3 or more in 69.7% of patients. Thrombocytopenia grade 3 or 4 was seen in four patients. Six patients had documented infections and all but four patients had alopecia. All patients complained of mild or moderate fatigue. Nausea and vomiting occurred in 75% of patients but only four individuals had grade 3 toxicity. Two patients stopped therapy after myocardial infarction and one after impaired cardiac function was noted. The median time to progression was 2.7 months (1-11.5 months) and median survival time 8.8 months (1-13+ months). CONCLUSION: The combination chemotherapy is active in heavily treated patients with manageable toxicity but there are problems in heavily pre-treated patients. There was good compliance in taking medication and at the doses chosen the drugs appear to be suitable for younger fitter patients.

Administration, Oral↗
PubMed2000

Phase II study of docetaxel in patients with liver metastases from breast cancer. UK study group.

BACKGROUND: Previous phase II studies of docetaxel have indicated that hepatic metastases from breast cancer respond well to first-line treatment with docetaxel. The objective of this prospective, open label phase II study therefore was specifically to evaluate the activity and safety of docetaxel in this indication. PATIENTS AND METHODS: The study recruited 47 women (mean age 50 years, range 33-66 years) with hepatic metastases from breast cancer who fulfilled the eligibility criteria. After premedication with steroids, patients received a one-hour intravenous infusion of docetaxel 100 mg/m2 at three-weekly intervals for up to eight cycles. Response to treatment during medication was assessed after three, six and where appropriate, eight cycles and every three month follow-up thereafter, until disease progression or death. RESULTS: The best overall response rate (ORR) for evaluable patients was 64.3% (95% CI: 48.0-78.5%). In terms of the primary efficacy parameters, the ORR at the sixth cycle of treatment was 62% (95% CI: 45%-80%) with 17% complete responses. The median duration of response was 139 days (95% CI: 111-216 days) and the median survival duration calculated on an intent-to-treat basis was 335 days (227-568 days, 95% CI). One (2%) toxic death was reported. CONCLUSIONS: Docetaxel is a highly effective cytotoxic agent in the treatment of patients with liver metastases from breast cancer.

Adult↗
PubMed2000

A radiation-controlled molecular switch for use in gene therapy of cancer.

Ionising radiation induces the expression of a number of radiation-responsive genes and there is current interest in exploiting this to regulate the expression of exogenous therapeutic genes in gene therapy strategies for cancer. However, the radiation-responsive promoters used in these approaches are often associated with low and transient levels of therapeutic gene expression. We describe here a novel radiation-triggered molecular switching device based on promoter elements from the radiation-responsive Egr-1 gene and the cre-LoxP site-specific recombination system of the P1 bacteriophage. Using this system, a single, minimally toxic dose of radiation induced cre-mediated excision of a lox-P flanked stop cassette in a silenced expression vector and this resulted in amplified levels of CMV-promoter-driven expression of the exogenous tumour-sensitising gene, HSV-tk. This strategy could be used in combination with targeted delivery and tumour-specific promoters to elicit the tumour-targeted and prolonged expression of a variety of tumour-sensitising genes and provide an unprecedented level of control and tumour selectivity.

Antiviral Agents↗
PubMed2000

A protocol for preventative mastectomy in women with an increased lifetime risk of breast cancer.

This paper describes a protocol for women at high risk of breast cancer wishing to undergo preventative mastectomy. The protocol described is a holistic approach to each woman involving the use of a multidisciplinary team. The protocol takes a number of months from initiation to surgery. A time delay is deliberate to allow women to fully address the issues involved with a decision for surgery. Early evidence suggests that this prepares the women emotionally and physically for their surgery.

Adult↗
PubMed2000

Hormonally-regulated proteins in breast secretions are markers of target organ sensitivity.

Anti-oestrogen therapy is being used in an attempt to prevent breast cancer but no intermediate end points of the effect of tamoxifen on the normal breast are available. Therefore, the purpose of this study was to develop a physiological measure of oestrogen action on the breast. We measured oestrogen-stimulated and -inhibited proteins in breast secretions from women on and off anti-oestrogen therapy. Two oestrogen-stimulated proteins (pS2 and cathepsin D) and oestrogen-inhibited proteins (CP15, gross cystic disease fluid protein 15; Apo,: apolipoprotein D) were measured. Premenopausal women had significantly higher pS2 and cathepsin D in association with lower Apo D and CP15 secretion levels compared to post-menopausal women. Sequential nipple aspirates from women treated with the luteinizing hormone releasing hormone agonist goserelin (n = 9), tamoxifen (n = 9) and hormone replacement therapy (HRT) (n = 26) were measured. Following treatment with goserelin, median nipple secretion levels of pS2 fell (P < 0.02) and Apo D and CP15 rose significantly (P < 0.03 and P < 0.05 respectively). Similar changes were seen on tamoxifen therapy but not in untreated control women. Treatment with HRT resulted in a rise of pS2 (P < 0.001) and a fall in Apo D (P < 0.05). Measurement of pS2 and Apo D in nipple aspirates may prove useful intermediate end point of breast responsiveness to anti-oestrogens.

Adult↗
PubMed2000

Expression of ykdA, encoding a Bacillus subtilis homologue of HtrA, is heat shock inducible and negatively autoregulated.

There are three members of the HtrA family of serine proteases, YkdA, YvtA, and YyxA, encoded in the chromosome of Bacillus subtilis. In this study, we report on the promoter structure and regulation of ykdA expression. The ykdA gene is heat inducible, exhibiting a biphasic pattern of expression during a 60-min interval after heat shock. Increased expression after heat shock occurs at the transcriptional level. The heat-shock-inducible promoter has a single mismatch with a SigA-type -10 motif, but does not exhibit similarity to a SigA -35 region. There are six octamer repeats with a consensus TTTTCACA positioned at, and upstream of, the normal position of a -35 region. While repeats V and VI appear dispensable, repeat IV is essential for normal thermoinducible expression. This promoter structure is also found in the control region of yvtA, encoding a second member of this family of proteases. Expression of ykdA is negatively autoregulated both during the growth cycle and during heat shock. Our evidence suggests that YkdA protease activity is not required for this form of regulation. Null mutants of ykdA display increased tolerance to heat and are 80-fold more resistant to 10 mM hydrogen peroxide than wild-type cells. However, ykdA expression is not induced by hydrogen peroxide. These results indicate that the regulon to which YkdA belongs is linked to the oxidative stress response in B. subtilis.

Bacillus subtilis↗