步入DirectX的圣殿（上）

本文讲解TDirectX的基本概念，并介绍了托管DirectX类库的构成。此外还介绍了3D编程中的一些基本概念，进而对前一篇文章给出的示例代码进行了充实。     

Apoptosis in a neonatal rat model of cerebral hypoxia-ischemia

BACKGROUND and PURPOSE: The mechanisms of excitotoxic cell death in cerebral ischemia are poorly understood. In addition to necrosis, apoptotic cell death may occur. The purpose of this study was to determine whether an established model of cerebral hypoxia-ischemia in the neonatal rat demonstrates any features of apoptosis. METHODS: Seven-day-old neonatal rats underwent bilateral, permanent carotid ligation followed by 1 hour of hypoxia, and their brains were examined 1, 3, and 4 days after hypoxia-ischemia. The severity of ischemic damage was assessed in the dentate gyrus and frontotemporal cortex by light microscopy. Immunocytochemistry was performed to detect the cleavage of actin by caspases, a family of enzymes activated in apoptosis. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) reactivity was examined in the cortical infarction bed and dentate gyrus. Neonatal rat brain DNA was run on agarose gel electrophoresis to detect DNA fragmentation. Ethidium bromide-staining and electron microscopy were used to determine whether apoptotic bodies, 1 of the hallmarks of apoptosis, were present. RESULTS: The frontotemporal cortex displayed evidence of infarction, and in most rats the dentate gyrus showed selective, delayed neuronal death. Immunocytochemistry demonstrated caspase-related cleavage of actin. TUNEL and DNA electrophoresis provided evidence of DNA fragmentation. Ethidium bromide-staining and electron microscopy confirmed the presence of chromatin condensation and apoptotic bodies. CONCLUSIONS: Features of apoptosis are present in the described model of cerebral hypoxia-ischemia. Apoptosis may represent a mode of ischemic cell death that could be the target of novel treatments that could potentially expand the therapeutic window for stroke.     

Ambulatory health care visits by children: principal diagnosis and place of visit

OBJECTIVES: This report presents national estimates of ambulatory health care use by children under 15 years of age according to principal diagnosis, place of visit (physician office, hospital outpatient department, and hospital emergency department), and patient characteristics (age, sex, and race). METHODS: Data were from the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey. Data were from 1993-95. RESULTS: In 1993-95 children under 15 years of age made 165.3 million visits per year (289 visits per 100 children). Visit rates were highest among infants and varied inversely with age. Visit rates were 43 percent higher among white children than black children. Three-quarters of ambulatory visits occurred in physician offices, 8 percent in hospital outpatient departments, and 14 percent in hospital emergency departments. Visits by white children were more likely to occur in physician offices than visits by black children (81 percent and 54 percent). Conversely, visits by black children were more likely to occur in hospital outpatient departments (19 percent and 7 percent) and hospital emergency departments (28 percent and 12 percent) than visits by white children. The following principal diagnoses accounted for almost 40 percent of visits: well-child visit, 15 percent; middle ear infection, 12 percent; and injury, 10 percent. Rates for well-child visits were almost 80 percent higher among white infants than black infants. Continued monitoring of these differences in use of ambulatory care among children are needed, particularly in view of the possible impact of changes in the health care system on these differences.     

Grafting of vinyl acetate onto low density polyethylene—starch biodegradable films for printing and packaging applications

Starch‐based biodegradable low‐density polyethylene (LDPE) films were used for graft copolymerization of vinyl acetate with ceric ammonium nitrate (CAN) in aqueous acidic medium as redox initiator with nitric acid. The extent of grafting was examined by Fourier‐transform infrared (FTIR) spectroscopy, attenuated total reflectance (ATR) spectroscopy, X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The objective behind the grafting of vinyl acetate onto the LDPE–starch biodegradable films is to make these suitable for printing and packaging applications without affecting the biodegradability of the original films. Copyright © 2004 Society of Chemical Industry     

An image-processing system for qualitative and quantitative volumetric analysis of brain images

In this work, we developed, implemented, and validated an image-processing system for qualitative and quantitative volumetric analysis of brain images. This system allows the visualization and quantitation of global and regional brain volumes. Global volumes were obtained via an automated adaptive Bayesian segmentation technique that labels the brain into white matter, gray matter, and cerebrospinal fluid. Absolute volumetric errors for these compartments ranged between 1 and 3% as indicated by phantom studies. Quantitation of regional brain volumes was performed through normalization and tessellation of segmented brain images into the Talairach space with a 3D elastic warping model. Retest reliability of regional volumes measured in Talairach space indicated errors of < 1.5% for the frontal, parietal, temporal, and occipital brain regions. Additional regional analysis was performed with an automated hybrid method combining a region-of-interest approach and voxel-based analysis, named Regional Analysis of Volumes Examined in Normalized Space (RAVENS). RAVENS analysis for several subcortical structures showed good agreement with operator-defined volumes. This system has sufficient accuracy for longitudinal imaging data and is currently being used in the analysis of neuroimaging data of the Baltimore Longitudinal Study of Aging.     

The effect of rate of administration on brain concentrations of propofol in sheep

Lipopolysaccharide (LPS) and interleukin (IL)-1beta have been reported to induce airway hyperresponsiveness in several animal models. This study investigated the effect of LPS or IL-1beta on bradykinin-induced human isolated bronchi contraction. LPS (100 ng x mL(-1) for 3-6 h) and IL-1beta (3x10(-10) and 3x10(-9) M for 20 min to 3 h) time-dependently potentiated bradykinin-induced contraction. This contraction was abolished, as in control experiments, by indomethacin (10(-6) M) or by the thromboxane (Tx) receptor antagonist GR 32191 but not by the cyclo-oxygenase-2 inhibitor, CGP28238. In contrast, the Tx mimetic U46619-induced contraction of human bronchi was not enhanced IL-1beta pretreatment. In the presence of GR 32191 (10(-6) M), bradykinin induced a prostanoid dependent relaxation that was not significantly modified by IL-1beta pretreatment. Determination of prostanoids in the organ bath fluid showed that bradykinin induced TxB2, the stable metabolite of TxA2, and 6-keto prostaglandin F1alpha, the stable metabolite of PGI2, release. Only TxA2 release was potentiated by IL-1beta. Taken together our results suggest that interleukin-1beta (1-3 h)-induced potentiation of the effect of bradykinin is linked to an increased activity of thromboxane synthase and, in turn, to increased thromboxane synthesis.     

The public and private problem of euthanasia. A comparison of The Netherlands and the United States

We present a 24 case-study of intact ossicular chain cholesteatomas among 158 first-look procedures performed between august 93 and april 96 (15%). The eradication of the disease was achieved via canal wall up technique without disrupting the ossicular chain in 20 cases (84%). Technical procedures are described. This new surgical attitude has enabled us to achieve better functional results. Second look procedures have not been necessary in all cases and occurrence of residuals has not been increased on a 14 months follow up period (2 cases out of 24 patients: 8%). Therefore, a longer follow up period is necessary to validate the results obtained using this recent concept.     

Diagnostic and therapeutic challenges

A laparoscopic cholecystectomy on a 63-year-old woman was uneventful. Twenty-one months after the operation she complained of dull right flank pain, loss of appetite, weight loss, and cough. CT of the abdomen showed an 8.5 cm mass adjacent to the posterior aspect of the upper pole of the right kidney. CT also demonstrated a small calcification (5 mm diameter) posterior to the upper pole of the right kidney. The patient underwent exploratory laparotomy 2 months after the presentation with flank pain. Examination of the mass showed a thick abscess wall and 250 mL of pus. The patient's symptoms improved after the abscess was drained.     

Craniocerebral magnetic resonance imaging measurement and findings in Lesch-Nyhan syndrome

OBJECTIVE: To provide the first comprehensive magnetic resonance imaging (MRI) assessment of brain in a series of patients with Lesch-Nyhan syndrome (LNS), with emphasis on basal ganglia measurements. DESIGN: Routine readings of MRI studies, repeated reading in random order blinded to subject diagnosis, and 3-dimensional volumetric measures of basal ganglia regions. SETTING: The Johns Hopkins Hospital, Baltimore, Md. PATIENTS: Seven patients with LNS who have hypoxanthine guanine phosphoribosyltransferase levels less than 1.6% and characteristic clinical features of the disorder, which include hyperuricemia, cognitive impairment, and dystonic movement disorder, were compared with 7 age-matched control subjects. Five of the 7 patients demonstrated self-injurious behavior. MRI studies were performed using general anesthesia because of the severity of the movement disorder. MAIN OUTCOME MEASURES: Measurement of brain regions from MRI-obtained images. RESULTS: Routine readings described mild cerebral atrophy in 2 of 7 patients, but no caudate or putamen abnormalities were reported. However, on the directed blinded rereading, small caudates were suspected in 5 of 7 cases, and abnormalities in cerebral size and cranium were identified. Volumetric studies of the patients with LNS confirmed a 34% decrease in caudate volume (P<.001), a 17% decrease in total cerebral volume (P<.03), and a 12% decrease in putamen volume (P=.19). CONCLUSIONS: To our knowledge, this is the first demonstration of consistent neuroanatomic abnormalities in LNS. The findings of reduced basal ganglia volume are consistent with the dystonic movement disorder.