Post-mortem computed tomography ventilation; simulating breath holding.

Whilst the literature continues to report on advances in the use of post-mortem computed tomography (PMCT), particularly in relation to post-mortem angiography, there are few papers published that address the diagnostic problems related to post-mortem changes in the lungs and ventilation. We present a development of previous methods to achieve ventilated PMCT (VPMCT). We successfully introduced a supraglottic airway in 17/18 cases without causing overt damage, despite rigor mortis. Using a clinical portable ventilator, we delivered continuous positive airway pressure to mimic clinical breath-hold inspiratory scans. This caused significant lung expansion and a reduction in lung density and visible normal post-mortem changes. All thoracic pathology identified at autopsy, including pneumonia, was diagnosed on VPMCT in this small series. This technique provides a rapid form of VPMCT, which can be used in both permanent and temporary mortuaries, allowing for the post-mortem radiological comparison of pre-ventilation and post-ventilation images mimicking expiratory and inspiratory phases. We believe that it will enhance the diagnostic ability of PMCT in relation to lung pathology.

Accuracy of targeted post-mortem computed tomography coronary angiography compared to assessment of serial histological sections.

Post-mortem computed tomography with coronary angiography (PMCTA) could have a role in the investigation of sudden natural death. This study assesses the accuracy of targeted coronary PMCTA, using both air and iodinated contrast media, to provide sensitivity and specificity for critical stenosis (CS) on a segmental basis, based on a gold standard of 3-5 mm serial sections of the coronary arteries using macroscopic and histological techniques. Assessment of stenosis at 1 mm intervals on PMCTA was compared with the data from pathological analysis. Stenosis was defined as "critical" when the stenotic region reaches ≥75 %. Regions were defined every 20 mm or by a clear change in stenosis. Discrepancies were defined as significant if only one test showed CS. Five cases with 25 vessels with 124 regions were assessed. PMCTA was unable to identify plaque hemorrhage or dissection (but this was normally associated with CS). Eighteen segments had significant discrepancies, giving a sensitivity and specificity of 50 and 91.5 %. When an alternative gold standard was constructed by excluding regions beyond a CS (five cases), taking PMCTA as correct where a heavily calcified vessel opens under contrast injection (four cases), and correcting for misregistration of distance (one case), the sensitivity rose to 85.7 %. There was complete agreement when the right or left coronary arteries are assessed as a whole. This study shows that PMCTA is not a perfect replacement for histological examination of coronary vessels, but may have a role in routine post-mortem investigation.

The evolutionary convergence of hearing in a parasitoid fly and its cricket host.

Parasitism is a widespread and diverse life strategy that connects species throughout the animal kingdom. Female parasitoid flies of the genus Ormia must find a specific cricket host on which to deposit their parasitic maggots. To reproduce, female flies must perform the same task as female crickets: find a singing male cricket. These flies have evolved a unique hearing organ that allows them to detect and locate singing male crickets. Through evolutionary convergence, these flies possess a hearing organ that much more resembles a cricket's ear than a typical fly's ear, allowing these parasitoids to take advantage of the sensory ecological niche of their host.

Identification of Tay-Sachs by hexosaminidase analysis of urine and tear samples.

1. Two readily obtainable biological fluids, i.e., urine and tears, were investigated as possible substitutes for serum and leukocytes for the detection of Tay-Sachs disease (TSD) heterozygotes based on Quantitative hexosaminidase A (Hex A) determinations. 2. Hexosaminidase isoenzyme patterns were determined, by means of an automated DEAE-cellulose microcolumn procedure, for serum, urine and tear samples from normals, TSD carriers, normal pregnancies, carrier-pregnancies and TSD children. 3. Normal pregnancy and TSD carrier sera gave almost identical hexosaminidase patterns with multiple intermediate peaks. Whereas, urine and tear samples from normal pregnant women showed hexosaminidase isoenzyme patterns resembling those of normal controls. These results suggested that use of these fluids might eliminate the effect of pregnancy of the Hex A ratio which occurs when serum is used as the test fluid. In addition these fluids are most economical and simpler to obtain than a blood sample. 4. About 200 urine samples, from the various categories listed above, were analyzed for Hex A with both the heat denaturation and pH inactivation methods and the results compared with serum and leukocyte levels from many of the same individuals. With either method, the wide overlap between the urinary Hex A normal and heterozygote ranges would require retesting with leukocytes of about 30% of the subjects. These results would preclude the use of urines as a suitable fluid for the mass screening of the Ashkenazic Jewish population for TSD heterozygotes.

Automated differentiation and measurement of hexosaminidase isoenzymes in biological fluids and its application to pre- and postnatal detection of Tay-Sachs disease.

Three hexosaminidase (EC 3.2. 1.52) isoenzymes other than isoenzymes A and B in body fluids have been separated by chromatography on diethylaminoethyl cellulose. By inserting a microcolumn into a continuous-flow system for automated, fluorometric hexosaminidase analysis [Clin. Chem. 20, 538 (1974)], samples eluted with buffered-NaCl gradients can be continuously monitored. Isoenzyme patterns were obtained for fluids from normal individuals, pregnant women, Tay-Sachs disease carriers, pregnant carriers, and patients with the disease. These chromatograms revealed a hitherto undetected isoenzyme (I-3) in serum. An increase in serum hexosaminidase isoenzyme I-2 (or P) during pregnancy is characteristic of a carrier pattern. Our data show that serum and urinary hexosaminidase isoenzyme patterns may be used in addition to leukocyte analysis, to distinguish a pregnant carrier from a normal pregnant woman. All fluids tested demonstrated no isoenzyme A activity and above-normal activity of isoenzymes B and (or) I-2 in homozygotes. Urine is preferred fluid for postnatal and amniotic fluid for the prenatal diagnosis of the disease. Quantitative data on isoenzyme A obtained with the procedure described here agree well with those obtained by heat-and pH-inactivation methods.