Hippocampal circuit dysfunction in the Tc1 mouse model of Down syndrome.

Hippocampal pathology is likely to contribute to cognitive disability in Down syndrome, yet the neural network basis of this pathology and its contributions to different facets of cognitive impairment remain unclear. Here we report dysfunctional connectivity between dentate gyrus and CA3 networks in the transchromosomic Tc1 mouse model of Down syndrome, demonstrating that ultrastructural abnormalities and impaired short-term plasticity at dentate gyrus-CA3 excitatory synapses culminate in impaired coding of new spatial information in CA3 and CA1 and disrupted behavior in vivo. These results highlight the vulnerability of dentate gyrus-CA3 networks to aberrant human chromosome 21 gene expression and delineate hippocampal circuit abnormalities likely to contribute to distinct cognitive phenotypes in Down syndrome.

Aortic aneurysm morphology in Asians: features affecting stent-graft application and design.

PURPOSE: To determine the morphological features of abdominal aortic aneurysms (AAA) in an Asian cohort in order to identify unique features relevant to stent-graft planning and application. METHODS: Spiral computed tomography (CT) and angiographic assessment of AAA morphology was performed on 65 ethnic Chinese (58 men; mean age 74 years, range 50-87) who underwent endovascular AAA repair. Morphological parameters were compared with published data from American and European patients. The eligibility and potential concerns referable to 4 current stent-graft designs were addressed. RESULTS: Both common iliac arteries (CIA) measured significantly shorter in Asians, particularly on the right side. The mean RCIA and LCIA lengths were 29.9 mm and 34.2 mm, respectively (25.7 and 34.1 mm for CIAs <20 mm in diameter), compared to >50-mm in Caucasians (p<0.001). The distance between the lowest renal artery and the CIA bifurcation averaged 20 mm shorter in Asians: 148 mm on the right side and 153 mm for the left. The CIAs were also wider, averaging 20.2 mm for the right and 17.9 mm for the left. Other linear measurements did not show a population difference. The AAAs in this series were slightly larger (p<0.001), with a shorter neck (mean 23 mm, p<0.001). No correlation was found between the morphological parameters and body build. Internal iliac artery coverage with or without embolization was necessary in 51% of endovascular repairs due to short or aneurysmal CIAs. CONCLUSIONS: These differences in AAA morphology pose unique challenges for endovascular repair in Asians. Preoperative angiography is more often necessary. The need for an accurate landing in a short CIA and insufficient length for maneuvering placed constraints on 2-piece graft designs with long main body lengths. A 3-piece endograft with wider aortic and iliac diameters is currently the most attractive option.

Paclitaxel and doxorubicin, a highly active combination in the treatment of metastatic breast cancer.

The activity of single-agent paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) has been documented in untreated and previously treated metastatic breast cancer, including both patients with anthracycline-resistant disease and those with extensive pretreatment. Such activity has prompted investigations of the optimal doses and schedules of paclitaxel/doxorubicin combinations. With one exception, paclitaxel has been administered as either a 24- or a 3-hour infusion, while the administration times for doxorubicin vary from bolus injection to 72-hour infusion. Results of these completed phase I and II trials are reviewed. Also reported are two European trials that have achieved promising results. In Milan, a phase I/II trial has shown a preliminary response rate exceeding 90% in 32 chemotherapy-naive patients treated with an alternating schedule of paclitaxel given over 3 hours and intravenous bolus doxorubicin. At doses of paclitaxel 200 mg/m2 and doxorubicin 60 mg/m2, the dose-limiting toxicities were neutropenia, oral mucositis, myalgias, and peripheral neuropathy. Congestive heart failure occurred in six patients. A phase I/II study of a 30-minute doxorubicin infusion preceding a 3-hour paclitaxel infusion every 3 weeks in minimally pretreated patients also is reported. Of 29 patients evaluable for response, 17 have achieved partial responses and seven complete responses, for an overall response rate of 83% (95% confidence interval, 79% to 99%). Toxicities observed were grades 3 to 4 neutropenia and moderate paresthesias, nausea/vomiting, alopecia, myalgia, and mucositis. Cardiotoxicity also occurred, as 15 patients had a significant decrease in left ventricular ejection fraction measured by isotope cardiography. Six of these developed congestive heart failure. This effect has been observed only in studies using short infusions of both drugs, and it is now being investigated whether lowering the peak doxorubicin concentration will preclude it.

Treatment of metastatic breast cancer with paclitaxel and doxorubicin.

The activity of single-agent paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) against untreated and previously treated metastatic breast cancer (documented in anthracycline-resistant disease and in extensively pretreated patients as well) has prompted investigations of the optimal doses and schedules of paclitaxel/doxorubicin combinations. With one exception, paclitaxel has been administered in either a 24- or a 3-hour infusion, while the administration times for doxorubicin vary from bolus injection to a 72-hour infusion. Results of these completed phase I and II trials are reviewed. Also reported are two ongoing European trials that have achieved promising preliminary results. In Milan, a phase I trial has achieved a preliminary response rate exceeding 90% in 30 chemotherapy-naive patients treated with an alternating schedule of paclitaxel over 3 hours and intravenous bolus doxorubicin. At doses of paclitaxel 200 mg/m2 and doxorubicin 60 mg/m2, the dose-limiting toxicity is leukopenia and mucositis. Furthermore, congestive heart failure has occurred in six patients. We are conducting a phase I/II study in minimally pretreated patients, with a 30-minute doxorubicin infusion preceding a 3-hour paclitaxel infusion every 3 weeks. Of 24 patients evaluable for response, five have achieved partial responses and three complete responses. (Another five partial and two complete responses need confirmation.) Of the two dose levels now given, all responses occurred at the higher paclitaxel/doxorubicin level, 175 and 60 mg/m2, respectively. Despite grades 3 and 4 neutropenia in 31% and 60% of courses, respectively, only six patients have been hospitalized for febrile neutropenia. Of concern, the left ventricular ejection fraction has decreased to below normal in six patients and two have developed symptomatic congestive heart failure. Whether lowering the peak doxorubicin concentration will preclude this effect, which has been observed only in the studies using short infusions of both drugs, is under investigation.

Ondansetron plus metopimazine compared with ondansetron alone in patients receiving moderately emetogenic chemotherapy.

BACKGROUND AND METHODS: The serotonin (5-hydroxytryptamine3) antagonists have improved the treatment of acute chemotherapy-induced nausea and vomiting, but their ability to prevent delayed nausea and vomiting seems less pronounced. The results of a preliminary open trial suggested that the addition of a selective dopamine D2 antagonist could improve the antiemetic efficacy of the serotonin antagonists. In a randomized, double-blind, crossover trial, we compared oral treatment with ondansetron (8 mg twice a day) and the dopamine D2 antagonist metopimazine (30 mg four times a day) with treatment with ondansetron alone for three days in 30 patients who had vomited during the previous cycle of chemotherapy. All the patients received moderately emetogenic chemotherapy. RESULTS: Combination treatment with ondansetron and metopimazine significantly reduced the incidence of acute (P = 0.006) and delayed (P = 0.02) nausea and acute (P = 0.02) and delayed (P = 0.006) vomiting, as compared with treatment with ondansetron alone. Patients had significantly fewer days of nausea (P = 0.03) and vomiting (P = 0.003) if they received combination therapy. Sixty-seven percent of the patients preferred ondansetron and metopimazine, and 33 percent favored ondansetron alone (P = 0.10). Adverse reactions were mild with both regimens. With the exception of constipation, which was reported more frequently with combination therapy (P = 0.03), there were no significant differences in adverse reactions. CONCLUSIONS: Ondansetron plus metopimazine is a highly effective and safe antiemetic regimen that is markedly superior to treatment with ondansetron alone in patients receiving moderately emetogenic chemotherapy.