Studies on the molecular pharmacology of GR63178A. A novel pentacyclic pyrolloquinone anticancer drug.

GR63178A (NSC D611615) is the second pentacyclic pyrolloquinone to be evaluated clinically as an anticancer drug. Its mechanism of action is unknown but may be related either to its quinone group or planar ring system. In this report we have investigated the ability of GR63178A to bind non-covalently to DNA, inhibit topoisomerase II and undergo reduction to reactive free radical species. Using two DNA duplexes, a 12-mer oligonucleotide which is a preferred sequence for minor groove binders and a hexamer which is a preferred sequence for intercalators, no evidence of significant binding with GR63178A was found. Neither GR63178A nor GR54374X (its 9-hydroxy metabolite) inhibited purified human topoisomerase II in a decatenation assay. Free radical chemistry was studied by both pulse radiolysis and ESR spectroscopy as well as by in vitro drug incubations with NADPH-fortified rat liver microsomes and purified cytochrome P450 reductase. The one-electron reduction potential of GR63178A was -207 mV +/- 10 which is much more positive than other quinone-containing anticancer drugs such as doxorubicin, mitomycin C and mitozantrone. GR63178A underwent enzyme-catalysed quinone reduction more readily than doxorubicin but produced significantly fewer reactive oxygen species. No evidence was detected of drug-induced, radical-mediated DNA damage in vitro using pBR322 plasmid DNA. Disproportionation of the GR63178A semi-quinone free radical proceeded with a rate constant of 1 x 10(9) M-1 sec-1 under anaerobic conditions, one order of magnitude faster than doxorubicin. The preferential disproportionation of the semi-quinone may explain our inability to detect a free radical signal by ESR. The hydroquinone of GR63178A was stable and exhibited strong visible absorption with a bathochromic shift of 120 nm over the parent drug. These unusual properties may be due to the hydroquinone undergoing a form of keto-enol tautomerization. Thus, GR63178A free radical formation does not appear to result in significant drug activation. In conclusion, GR63178A is unlikely to mediate its antitumour activity by DNA binding, topoisomerase II inhibition or free radical formation in direct contrast to similar anthracycline- and anthraquinone-based anticancer drugs.     

The potentiation of adrenaline-induced in vitro platelet aggregation by ADP, collagen and serotonin and its inhibition by naftopidil and doxazosin in normal human subjects.

1. Aggregation in platelet-rich plasma from normotensive men was induced by adrenaline (0.25-16 microM), ADP (0.25-16 microM), collagen (0.25-8 micrograms ml-1) or serotonin (10 microM) alone, or by previously sub-threshold concentrations of adrenaline (0.03-1 microM) in combination with sub-threshold concentrations of serotonin (2.5 microM), ADP (0.5 microM) or collagen (0.125 micrograms ml-1). The effects of the alpha 1-adrenoceptor blockers naftopidil and doxazosin on platelet aggregation were investigated. 2. The dose-response curves for collagen and ADP were unaffected by either drug. However, naftopidil (40 microM) inhibited serotonin-induced platelet aggregation (23.9%, 95% confidence interval (CI) 10.7 to 37.1%; P < 0.01) and caused a slight shift to the right of the adrenaline dose-response curve with a mean increase in the EC50 value of 0.5 microM (95% CI 0.07 to 0.93 microM; P < 0.05). Doxazosin had no effect on serotonin or adrenaline-induced aggregation. 3. A marked potentiation of the aggregation induced by subthreshold concentrations of adrenaline resulted from the prior addition of low concentrations of ADP, collagen or serotonin. 4. These potentiated responses were inhibited in a dose-dependent manner by naftopidil and to a lesser extent doxazosin. The maximum inhibitions (%) produced by naftopidil (40 microM) on the responses of adrenaline potentiated by ADP were 58.3% (95% CI 36.8 to 79.8%; P < 0.001), serotonin 58.9% (95% CI 40.0 to 77.8%; P < 0.001), and collagen 70.9% (95% CI 52.5 to 89.3%; P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Feasibility of monitoring patient based health outcomes in a routine hospital setting.

OBJECTIVE--To assess the feasibility of monitoring health outcomes in a routine hospital setting and the value of feedback of outcomes data to clinicians by using the SF 36 health survey questionnaire. DESIGN--Administration of the questionnaire at baseline and three months, with analysis and interpretation of health status data after adjustments for sociodemographic variables and in conjunction with clinical data. Exploration of usefulness of outcomes data to clinicians through feedback discussion sessions and by an evaluation questionnaire. SETTING--One gastroenterology outpatient department in Aberdeen Royal Hospitals Trust, Scotland. PATIENTS--All (573) patients attending the department during one month (April 1993). MAIN MEASURES--Ability to obtain patient based outcomes data and requisite clinical information and feed it back to the clinicians in a useful and accessible form. RESULTS--Questionnaires were completed by 542 (95%) patients at baseline and 450 (87%) patients at follow up. Baseline health status data and health outcomes data for the eight different aspects of health were analysed for individual patients, key groups of patients, and the total recruited patient population. Significant differences were shown between patients and the general population and between different groups of patients, and in health status over time. After adjustment for differences in sociodemography and main diagnosis patients with particularly poor scores were identified and discussed. Clinicians judged that this type of assessment could be useful for individual patients if the results were available at the time of consultation or for a well defined group of patients if used as part of a clinical trial. CONCLUSIONS--Monitoring routine outcomes is feasible and instruments to achieve this, such as the SF 36 questionnaire, have potential value in an outpatient setting. IMPLICATIONS--If data on outcomes are to provide a basis for clinical and managerial decision making, information systems will be required to collect, analyse, interpret, and feed it back regularly and in good time.     

Interaction of active and passive slow eye movement systems

Summary Independent target and background motions have been used to generate conflicting activity within the pursuit and optokinetic systems. Subjects were required to pursue a small target against a structured background which moved independently. Selective enhancement of the response to the target generated high-gain active pursuit which dominated the eye movements. Passive eye movements induced during relative target and background motion are not normally directly quantifiable due to their low gain. By reducing the gain of the active pursuit optokinetically induced eye movements were enhanced and quantified. Three techniques are described for degrading active pursuit: tachistoscopic, eccentric and pseudorandom methods of target presentation. Our results demonstrate the synchronous input of active and passive eye movement drives to the oculomotor system and illustrate their interaction.     

LIMITATIONS OF RADIOTHERAPY IN THE DEFINITIVE TREATMENT OF SQUAMOUS CARCINOMA OF THE TONSILLAR FOSSA

Between 1970 and 1990, 104 patients with squamous cell carcinoma (SCC) of the tonsil were treated. The median age was 58 years and 80% of patients were males. Distribution among clinical stages was: stage I, 19 patients; stage II, 12 patients; stage III, 23 patients; and stage IV, 48 patients. More than 70% of patients had initial radiotherapy as definitive treatment irrespective of stage, reflecting the treatment philosophy over much of this period. The overall survival rate was 26% at 5 years, with survival being significantly affected by T stage, clinical stage and age. Clinical node status did not significantly affect survival rates. Good local control of T₁N₀ cancers was achieved with radiotherapy alone, but patients with more advanced cancers did poorly. We have now moved away from a non-selective policy and use initial surgery combined with postoperative radiotherapy in most patients, reserving radiotherapy alone for mainly early tonsil cancers.     

Selective Embolization of Glomus Jugulare Tumors

Four patients with grade C or D₁ glomus jugulare tumors who underwent preoperative highly selective embolization followed by infratemporal fossa removal of their tumors were compared to three patients undergoing surgery alone with respect to intraoperative blood loss, operative time, cranial nerve palsy, length of hospitalization, and perioperative complications. Embolized patients demonstrated a marked reduction in blood loss (650 vs 1375 cc) compared with the nonembolized group. Operative time was shortened (by 51 minutes). Facial nerve function did not appear related to embolization but was directly related to intraoperative nerve manipulation. Hospital stay, perioperative complications, and lower cranial nerve palsies were not related to embolization.     

CT visualization of medullary sponge kidney

Recognizing the changes of medullary sponge kidney (MSK) on computed tomographic (CT) scans may be of value in both diagnosis and in differentiating this from other disease states. The appearance on CT of MSK has not previously been well described. A case is reported that demonstrates ectatic renal collecting tubules visualized by CT, and techniques are suggested to optimize visualization of these changes.     

Retinal vasculitis

Evidence is now accumulating on both clinical and experimental grounds that the retina is an a priori source of inflammatory activity. Reactive inflammation in the retina may produce many of the clinical signs previously ascribed to uveal inflammation. Autoimmune mechanisms are probably responsible for the majority of cases of retinal vasculitis. Autoimmune retinal vasculitis occurs without other classical signs of inflammatory response in any other parts of the body. When associated systemic manifestations occur they may reflect different underlying immunopathogenic abnormalities. Thus in diseases with predominantly arterial involvement (e.g. systemic lupus erythematosus, polyarteritis nodosa) the retinal arteries bear the brunt of this disease. In Behçet''s disease the systemic involvement is usually venous and ocular involvement produces diffuse capillary and venous inflammation with areas of retinal necrosis and major vascular occlusion. The retinal appearances differ from sarcoidosis in which a granulomatous response produces characteristic periphlebitis. Finally, autoimmune retinal vasculitis produces diffuse capillary and venous damage, without any systemic signs. In the next decade the search will be for the identification of the specific antigens initiating these disparate retinal features. Retinal S antigen is a potent antigen, but rhodopsin, interphotoreceptor binding protein, and transducin all need further experimental investigation. Precise documentation will herald the dawn of new therapeutic measures based on a sound immunological fabric.