Model selection tests for nonlinear dynamic models

This paper generalizes 73 asymptotically normal tests for model selection in several important directions. First, it allows for incompletely parametrized models such as econometric models defined by moment conditions. Second, it allows for a broad class of estimation methods that includes most estimators currently used in practice. Third, it considers model selection criteria other than the models’ likelihoods such as the mean squared errors of prediction. Fourth, the proposed tests are applicable to possibly misspecified nonlinear dynamic models with weakly dependent heterogeneous data. Cases where the estimation methods optimize the model selection criteria are distinguished from cases where they do not. We also consider the estimation of the asymptotic variance of the difference between the competing models’ selection criteria, which is necessary to our tests. Finally, we discuss conditions under which our tests are valid. It is seen that the competing models must be essentially nonnested.     

Posttraumatic false aneurysm of the superficial temporal artery. Apropos of a case report and review of the medical literature

Traumatic false aneurysm of superficial temporal artery is infrequent. About 21 cases were published during these last fifty-three years (1932-1985) in medical literature. The authors report a case of traumatic false aneurysm in a 50 y. o. woman, having had a frontal trauma one month before. They discuss the physiopathologic mechanism of this rare lesion. False aneurysm is always secondary to an arterial wall rupture. This rupture may be complete in arterial wound or partial with disruption of intima and media in simple contusion. It depends not only on the nature and the intensity of the trauma but also on the particular topography of the artery which is prone to such a complication.     

Alternating chemotherapy and radiotherapy combination for bulky stage I and II intermediate and high grade non-Hodgkin lymphoma: an update

In 1980, based on experimental and clinical data, a protocol was developed at the Institut Gustave-Roussy (IGR), alternating eight monthly courses of chemotherapy (CHVP) and two, then three, radiotherapy sequences (15 Gy in 6 fractions and 10 days to the initially involved areas), for early stage unfavourable histology non-Hodgkin lymphomas (NHL). The results are updated for 55 selected patients presenting with bulky stage I and II NHL, intermediate and high grade according to the Working Formulation. Five-year overall survival rate was 69% and freedom from progression was 68%. Early haematologic and digestive tolerance was satisfactory, probably because a 10-15-day interval was respected between chemotherapy and radiotherapy and vice versa. No late toxicity was detected in 39 patients who presented with head and neck localizations; xerostomia was found to be only mild and transient. All patients given mediastinal irradiation experienced radiological mediastinitis, but functional impairment was usually moderate. One of the 4 patients who received 3 x 15 Gy radiotherapy courses to part of the abdomen, died of small bowel obstruction and perforation. The study demonstrated the feasibility of an alternated schedule of chemotherapy and radiotherapy, with satisfactory results in terms of long-term survival. However, the few late complications which were detected after irradiation of the abdomen or of the thorax led to an alteration of the initial scheme when these volumes are to be treated.     

Secondary alveolar echinococcosis in lymphotoxin-α and tumour necrosis factor-α deficient mice: exacerbation of Echinococcus multilocularis larval growth is associated with cellular changes in the periparasitic granuloma

The availability of mice carrying a deletion of LT-alpha and tumour necrosis factor (TNF)-alpha genes enabled us to investigate the role of the TNF during alveolar echinococcosis. We compared the growth rate of Echinococcus multilocularis in LT-alphaTNF-alpha +/+ mice to that of mice having either no or only one LT-alphaTNF-alpha functionnal allele. LT-alphaTNF-alpha -/- mice harboured a significantly higher parasite burden than did the other two populations at 5, 10, and 15 weeks of infection, and they did not survive thereafter. Liver metacestodes removed from these mice were alive and the dehydrogenase activities of peritoneal metacestodes were decreased. Liver lesions regressed in most wild-type mice. Indeed, dead parasites were cordoned by granulomas containing numerous macrophages and lymphocytes leading to focal liver fibrosis at an early stage of infection. In contrast, most of LT-alphaTNF-alpha -/- mice harboured metacestodes interspersed with leucocytes, realising purulent abscesses with secondary extensive irregular fibrosis at a late stage of infection. Heterozygous mice had behavioural characteristics intermediate between homozygous mutants and wild-type mice. Levels of E. multilocularis-specific delayed-type hypersensitivity and serum antibodies were slightly decreased in LT-alphaTNF-alpha -/- mice. This study shows that TNF-alpha and/or LT-alpha genes play an essential role in the immune protection mechanisms against E. multilocularis at the site of infection.     

2 trichostrongyloid nematode parasites in an African murid. IV. Migration in the vertebrate

For the species both oral and skin penetrations are possible. The ingested infective larvae pass through the excretory pore of a stomachal gland, leave the bottom of the gland through a blood capillary at H8, cross the liver (portal vein, sinusoids, sus-hepatic vein), the right heart and reach the lung around H12; they dwell in the pulmonary alveoli from H12 to D3, in the bronchi from D3 to D4, ascend the trachea, are swallowed by the host and reach the intestine on D4 and 5.     

Vanishing white matter: a leukodystrophy due to astrocytic dysfunction

VWM is one of the most prevalent leukodystrophies with unique clinical, pathological and molecular features. It mostly affects children, but may develop at all ages, from birth to senescence. It is dominated by cerebellar ataxia and susceptible to stresses that act as factors provoking disease onset or episodes of rapid neurological deterioration possibly leading to death. VWM is caused by mutations in any of the genes encoding the five subunits of the eukaryotic translation initiation factor 2B (eIF2B). Although eIF2B is ubiquitously expressed, VWM primarily manifests as a leukodystrophy with increasing white matter rarefaction and cystic degeneration, meager astrogliosis with no glial scarring and dysmorphic immature astrocytes and increased numbers of oligodendrocyte progenitor cells that are restrained from maturing into myelin‐forming cells. Recent findings point to a central role for astrocytes in driving the brain pathology, with secondary effects on both oligodendroglia and axons. In this, VWM belongs to the growing group of astrocytopathies, in which loss of essential astrocytic functions and gain of detrimental functions drive degeneration of the white matter. Additional disease mechanisms include activation of the unfolded protein response with constitutive predisposition to cellular stress, failure of astrocyte‐microglia crosstalk and possibly secondary effects on the oxidative phosphorylation. VWM involves a translation initiation factor. The group of leukodystrophies due to defects in mRNA translation is also growing, suggesting that this may be a common disease mechanism. The combination of all these features makes VWM an intriguing natural model to understand the biology and pathology of the white matter.     

Ramipril for the prevention and treatment of cardiovascular disease

OBJECTIVE: To evaluate the effectiveness of ramipril in the prevention and treatment of cardiovascular disease and determine its need for inclusion on a formulary. DATA SOURCES: A MEDLINE and PubMed database search was conducted (1987-May 2002). Only journals written in the English language were selected for review. DATA EXTRACTION AND STUDY SELECTION: Articles reporting the use of ramipril in humans were evaluated. Emphasis was placed on randomized, controlled trials assessing efficacy. DATA SYNTHESIS: Ramipril is an angiotensin-converting enzyme (ACE) inhibitor that exerts its effects through inhibition of the renin-angiotensin-aldosterone system. It exhibits a safety profile that is similar to that of other ACE inhibitors and is comparable in cost to the majority of the available agents. Clinical trials have proven the effectiveness of ACE inhibitors in the treatment of hypertension, heart failure, and nephropathy. Ramipril, however, is the only ACE inhibitor currently approved for the prevention of cardiovascular events in high-risk patients without evidence of left-ventricular dysfunction or heart failure, based on the results of the HOPE (Heart Outcomes Prevention Evaluation) trial. Whether this effect is specific to ramipril has yet to be proven. This article emphasizes the major trials involving ramipril including the AIRE (Acute Infarction Ramipril Efficacy), REIN (Ramipril Efficacy in Nephropathy), and HOPE trials. CONCLUSIONS: Although similar to other ACE inhibitors in many aspects, it cannot be assumed that the benefits shown with ramipril in the HOPE trial are a class effect. Ongoing trials should help to clarify this matter. Until this time, current evidence justifies the inclusion of ramipril on a formulary.