Limitations of computerized tomography in the localization of intraocular foreign bodies

Computerized tomography (CT) scanning was used to evaluate nine patients with intraocular foreign bodies. We found that significant limitations of this method still exist, even with high resolution scanners, in the localization of extremely small, multiple or relatively radiolucent foreign bodies and those located near the ocular wall.     

Digital radiography of the gastrointestinal tract

The gastrointestinal tract lends itself quite well to digital imaging. Since fluoroscopy is already employed, the images can easily be obtained in digital format and several manufacturers have now developed systems for commercial use. Because of the type of pathology as well as the inherent subject contrast, it would appear the resolution requirements for digital imaging of the gastrointestinal tract are less than in other organ systems. The necessary resolution level is already technically available and feasible without significant cost. Digital imaging also holds promise of at least a modest reduction in radiation dose to the patient, as well as a reduction in costs, although these factors are operator dependent. However, digital imaging provides a latitude in performing the examination that is not available with screenfilm systems. Finally, there is promise that by acquiring gastrointestinal images in digital format, manipulation of the images may help increase diagnostic accuracy by improving both technical and perceptive components of diagnosis. Not only will simple image manipulation be helpful but there is even potential for computer-assisted evaluation of gastrointestinal images.     

Effect of gamma irradiation on the B vitamins of pork chops and chicken breasts

A study was made of the effect of low-dose gamma irradiation on the content of thiamine (B1), riboflavin (B2), niacin, pyridoxine (B6) and cobalamin (B12) in pork chops, and thiamine, riboflavin and niacin in chicken breasts. Gamma irradiation from a caesium-137 source was used to irradiate the samples in a range of 0.49 to 6.65 kGy from -20 to +20 degrees C. Over the range of dose and temperature studied it was possible to derive a mathematical expression for predicting the losses. A calculation was made of the effect of the loss of thiamine, riboflavin and niacin due to irradiation on the overall loss of these vitamins in the American diet. The losses of riboflavin and niacin were of the order of a fraction of a per cent. Pork is an important source of thiamine, but the calculated loss at 1.0 kGy of this vitamin in cooked pork was only 1.5 per cent. There were initial increases with radiation doses up to 2-4 kGy in the measured concentrations of riboflavin and niacin in both pork and chicken. The increases were highly significant, and are of concern both to the study of radiation effects and the chemical method of the determination of these two vitamins.     

The response of right ventricular size,function, and pressure to supine exercise: A comparison of patients with chronic obstructive lung disease and normal subjects

The response of right ventricular ejection fraction (RVEF) and right ventricular end-diastolic volume (RVEDV) to exercise was studied in 11 patients with severe (FEF_25%–75%=0.32±0.13, mean ±SD) chronic obstructive pulmonary disease (COPD). Using gated radionuclide cardiac blood pool imaging techniques, the response of the patients with COPD was compared with that of 15 control subjects. Arterial blood gases, pulmonary arterial pressures, wedge pressure, and right ventricular pressures also were monitored in patients with COPD. The resting R VEF was lower and the resting RVEDV was higher in patients with COPD than in normals (both,P<0.01). Two of the 11 COPD patients had a RVEF during rest that was below lower limits, while 10 of 11 patients had RV dilation. Right ventricular end-diastolic pressure, measured during rest in patients with COPD, was normal (6.1±2.1 mm Hg) and cardiac index was within normal limits (3.55±0.82 l/min/m²). With exercise this cardiac index rose to 5.52±1.7/min/m² (P<0.01) due to the increase in heart rate (83±18 to 125±25 beats/min;P<0.01) while stroke volume did not significantly change. During exercise, normal subjects showed and increase in RVEF while RVEDV did not change; in patients with COPD, the RVEF fell and the RVEDV increased. In the patients with COPD, mild resting arterial hypoxemia and hypercapnia were both exaggerated during exercise; and mild resting pulmonary arterial hypertension (PAm=24.3±7.6 mm Hg) also worsened with exercise (PAm=41±19 mm Hg,P<0.01). Correlation between change in RVEF and PAm was-0.58, and between change in RVEDV and PAm was 0.63. We conclude that patients with severe COPD often have right ventricular dilation at rest and commonly respond to supine exercise with a fall in LV ejection fraction and further dilation of the right ventricle.Supported in part by the Research Service of the Veterans Administration Hospital     

Intragenic suppression of trafficking-defective KCNH2 channels associated with long QT syndrome

Mutations in the KCNH2 or human ether-a-go-go-related gene-encoded K(+) channel reduce functional KCNH2 current (I(KCNH2)) to cause long QT syndrome (LQT2) by multiple mechanisms, including defects in intracellular transport (trafficking). Trafficking-deficient, or class 2, LQT2 mutations reduce the Golgi processing and surface membrane expression of KCNH2 channel proteins. Drugs that associate with pore-S6 intracellular drug binding domain of KCNH2 channel proteins to cause high-affinity block of I(KCNH2) also can increase the processing of class 2 LQT2 channel proteins through the secretory pathway. We used a strategy of intragenic suppression to test the hypothesis that amino acid substitutions in the putative drug binding domain at residue Y652 could compensate for protein folding abnormalities caused by class 2 LQT2 mutations. We found that the Y652C substitution, and to lesser extent the Y652S substitution, resulted in intragenic suppression of the class 2 LQT2 G601S phenotype; these substitutions increased Golgi processing of G601S channel proteins. The Y652C substitution also caused intragenic suppression of the class 2 LQT2 V612L and F640V phenotypes but not the LQT2 N470D or F805C phenotypes. These are the first findings to demonstrate that a single amino acid substitution in the putative KCNH2 drug binding domain can cause intragenic suppression of several LQT2 mutations.