The enhancement of creep by irradiation

Three new processes are proposed for the enhancement of creep by irradiation. They all depend on the assumption that the rate controlling process in steady-state creep is the annihilation of edge dislocation dipoles in sub-grain boundaries by climb. The relaxation or misfit volume strain is much greater for an interstitial than for a vacancy and leads to a preferential loss of interstitials at isolated edge dislocations in irradiated materials. This biassed loss of interstitials constitutes the first process and causes edge dislocations of opposite sign present in a boundary to climb in opposite directions and thereby increases the rate at which they collide with each other and annihilate. The resulting creep rate increases with stress less rapidly than does the corresponding creep process in the absence of irradiation. In the second process the positive relaxation volume strain of an interstitial ensures that it will be attracted into regions where the tensile fields of adjacent dislocations overlap and reinforce each other. This dislocation dipole size effect interaction always favours climb in a direction which leads to dislocation annihilation. In addition to the size effect interaction the tetragonal interaction associated with the dumb-bell configuration of interstitials. has been evaluated for both these processes. It is shown in the appendix that if the interstitial has a very small effective shear modulus, which is also a consequence of the dumb-bell configuration, the tetragonal interaction also becomes insignificant. In the third process, the overlapping shear stress fields of two neighbouring dislocations of opposite sign attract interstitials by the inhomogeneity interaction. This arises because a dumb-bell interstitial has a very low effective shear modulus compared to the surrounding material. The increased concentration of interstitials also leads to dislocation climb which is preponderantly in the direction which favours annihilation. This process is a second order effect which is always much less than the size effect which controls the first two processes. In a fourth process, the energy barriers which impede the absorption of interstitials (usually at jogs) on dislocation of different systems are affected differently by an applied stress, and this leads to a rate of creep which, like the established mechanism of stressinduced preferential absorption, is to a first approximation linear in both the rate of irradiation and the applied stress.     

Contrast enhancement and distributed encoding by bipolar cells in the retina

Responses of bipolar cells, cone photoreceptors, and horizontal cells were recorded intracellularly in superfused eyecup preparations of the tiger salamander (Ambystoma tigrinum). Contrast flashes of positive and negative polarity were applied at the center of the receptive field while the entire retina was light adapted to a background field of 20 cd/m2. For small contrasts, many bipolar cells showed remarkably high contrast gain: up to 15-20% of the bipolar response was evoked by a contrast step of 1%. There was considerable variation from cell to cell but, on average, no striking differences in contrast gain were found between the depolarizing (Bd) and hyperpolarizing (Bh) bipolar cells. Quantitative comparisons of contrast/response measurements for cone photoreceptors and cone-driven bipolars suggest that the high contrast gain of bipolars is the consequence of a 5-10 x amplification of small signals across the cone-->bipolar synapse. Bipolar cells had a very restricted linear range of response and tended to saturate at stimulus levels that were within the linear range of the cone response. The contrast/response of horizontal cells was similar to that of cones and differed markedly from that of Bh cells. For steps of equal contrast, the latency of the Bh cells was approximately 20 ms shorter than that of the Bd cells regardless of the contrast magnitude. For both bipolar cells and cones, the effect of contrast polarity on latency seems largely due to the absolute value of the light step, delta L. In the large signal domain, properties of the contrast responses of bipolar cells varied appreciably, both within and between the Bd and Bh classes. Cells of either class could be positive- or negative-contrast dominant. These and additional results show that in the light-adapted retina, the bipolar population is functionally diverse and has the potential to provide a rich substrate for distributed encoding of visual images.     

Contrast enhancement using the triggered imaging

Cancer risk in patients with cirrhosis could be modified by factors such as changes in hormonal levels, impaired metabolism of carcinogens, or alteration of immunological status. We investigated the risk of liver and various forms of cancer in patients with cirrhosis in a follow-up study. We identified 11,605 1-year survivors of cirrhosis from the files of the Danish National Registry of Patients (NRP) from 1977 to 1989. Occurrence of cancer through 1993 was determined by linkage to the Danish Cancer Registry. For comparison, the expected number of cancer cases was estimated from national age-, sex-, and site-specific incidence rates. Overall, 1,447 cancers were diagnosed among the study subjects, as compared with 708.1 expected, to yield a standardized incidence ratio (SIR) of 2.0 (95% CI: 1.9 to 2.2). In all diagnostic subgroups of cirrhosis, the risk of primary liver cancer, mainly hepatocellular carcinoma, was markedly elevated, with 245 observed cases and an overall 36-fold elevated risk (59.9-fold elevated for hepatocellular carcinoma and 10-fold for cholangiocarcinoma). Substantial and persistent excesses during follow-up were seen for all types of cancer associated with tobacco and alcohol habits (cancer of the lung, larynx, buccal cavity, pharynx, pancreas, urinary bladder, and kidney), while moderate excesses were seen for cancers of the colon and breast. The latter, however, were not complemented by any decrease in the risk of prostate cancer (SIR: 1.0; 95% CI: 0.7 to 1. 3). A slightly increased risk was seen for testis cancer, but disappeared after 10 years. We found evidence of an increased risk for liver and several extrahepatic cancers in patients with cirrhosis. Although part of this increase is likely attributable to alcohol and tobacco consumption, our study opens up the possibility that cirrhosis plays a role in the carcinogenesis of types of cancer other than liver cancer.     

Symptomatic vessel narrowing caused by spontaneous rupture of craniopharyngioma cyst--case report

A 36-year-old female presented with cerebral infarction due to severe vessel stenosis after spontaneous rupture of a craniopharyngioma, manifesting as aphasia and drowsiness. Neuroimaging showed the suprasellar cystic tumor with wall enhancement and cerebral infarction in the left temporoparietal region, and also enhancement of the left sylvian fissure and prepontine cistern. Angiography showed severe narrowing at the C1 portion of the left internal carotid artery (ICA) and the M1 portion of the left middle cerebral artery (MCA). The tumor was subtotally removed via a bifrontal craniotomy. There was accumulated milky-white debris around the left ICA and MCA. She became alert within a few days postoperatively. Repeat angiography 1 month after surgery demonstrated slight improvement of vessel narrowing. The neuroimaging and intraoperative findings suggested that the stenosis was due to vasospasm induced by chemical meningitis resulting from cyst rupture.     

Pulmonary cyst caused by septic emboli in the preterm infant

Serologic assays could be useful for determining circulating subtypes in different geographic regions. A total of 175 serum samples from the same number of Argentinian HIV-infected patients from Buenos Aires and Rosario were tested against a panel of peptides representing V3 consensus subtypes A through H. A V3 peptide enzyme immunoassay was used for screening the sera. Most sera were reactive with peptides representing subtypes B (58.28%), F (13.14%), and A (8.57%). Cross-reactivity between the remainder of the peptides was observed. Genotypes of eight patients from Rosario were determined and compared with serotyping. Results showed that seven of eight genotyped patients reacted with their respective consensus B peptide and one reacted with consensus B and F. V3 peptide serology proved to be useful for determining HIV-1 clades circulating in Argentina.     

Management of colitis caused by irradiation

Radiation therapy has assumed a role of primary importance in the management of gynecologic and other malignant growths. To be effective, the treatment dosage must be adequate. However, with higher dosages for curative radiation therapy, damage from the treatment may promote prolonged morbidity and even death. The effects of this treatment may be intensified by predisposing conditions within the patient, but the damage seems to be related to the insertion of radium. Prior to therapy, each patient must be individualized, and any predisposing factors should be kept in mind during treatment to recognize and treat these complications early. Once complications have arisen, the most conservative modality of dealing with the irradiated tissue is best, since these areas of intestinal injury do not heal. This requires early diversion or resection as conservative therapy, because fistulas and bleeding will become recurrent and intractable. If diversion fails to control bleeding, resection is necessary, even if it involves an abdominoperineal resection. Therefore, conservative can become radical for this supposedly benign illness.     

Contrast enhancement in primary tumors of the brain and spinal cord

The patterns of contrast enhancement by CT and MR imaging for most intramedullary primary tumors of the brain and spinal cord are discussed. Contrast administration allows for the separation of tumor from normal neighboring tissues in most cases. Although most of the published data refer to contrast-enhanced CT scanning, gadolinium-enhanced MR imaging has become the modality of choice in the evaluation of primary central nervous system tumors.     

Acute abdominal aorta embolism caused by primary cardiac echinococcus cyst

Embolism of the abdominal aorta by an echinococcus cyst is extremely rare and is due to rupture of an intracardiac hydatid cyst. We report a case of abdominal aortic embolism by a primary intracardiac echinococcus cyst which was treated successfully with bilateral femoral embolectomy followed by direct aortotomy. We found only 16 previous cases reported and only one caused by a primary cyst.     

Hemoperitoneum caused by spontaneous rupture of a true splenic cyst

A 34 year-old man presented with hemoperitoneum from a spontaneously ruptured spleen. At laparotomy, a 5-cm diameter splenic cyst was found to be ruptured. Histological examination confirmed the diagnosis of a true splenic cyst of the mesothelial type. Spontaneous rupture with hemoperitoneum is a rare but potentially lethal complication of a true splenic cyst.     

Preoperative diagnosis of hypernephroma in a renal cyst wall by selective renal angiography

Presented is a case in which preoperative diagnosis of a hypernephroma in the wall of a renal cyst was made by selective renal arteriography. Reviewed are the incidence and possible causative relationship between the two lesions and the potential and limitations of presently available diagnostic procedures for this entity.     

Laryngeal obstruction caused by lingual thyroglossal duct cyst presenting at birth

The complete nucleotide sequence of Biomphalaria glabrata actin has been cloned by PCR amplification and screening of a cDNA library of Biomphalaria glabrata. The comparison of the deduced amino acid sequence with other actins suggests that a cytoskeletal form of the protein has been cloned.     

Effect of ATP on radiation damage to DNA caused by prolonged irradiation

The influence of bradykinin and kallikrein on the action of norepinephrine, epinephrine, isoprenaline, phentolamine, propranolol, aminophylline and theophylline on blood pressure was studied. The kinins potentiated the hypertensive action of norepinephrine and epinephrine, weakened the hypotensive action of isoprenaline, potentiated the hypotensive action of propranolol, and had no effect on the action of phentolamine, aminophylline and theophylline.     

Histologic studies on pancreas changes, caused by experimental fractionated local roentgen irradiation

After exposition to a total dose of 8000 R delivered with 16 fractions, the pancreatic parenchymal changes in rats were investigated by the author using histological and histochemical techniques. The observations were performed from the first to the 150th day following the last fraction. During the period of acute changes (1st to 15th day), the most part of the acini is morphologically intact, many smaller or greater necrotic foci, however, are to be seen. This is partly due to the enzymes with cytolytic effects coming from the damaged smaller ducts and from glandular acini. The formation of the other part of the necrobiotic foci originates not only from direct radiation injury, but also from the capillary lesion by radiation. The injury to the wall of greater ducts induces edema, inflammations, dilatation of efferent ductules and stasis, all this leading consequently to an atrophy of the acini associated with the efferent ducts. During the period of chronical changes (50th to 150th day), the number of capillaries diminishes, the necrobiotic foci are multiplied especially in places where no capillaries are visible. This clearly emphasizes the role of the pathological reasons for capillary lesions. The regenerative phenomena occur only to a lesser extent, being confirmed to the efferent ducts. The extension of the necrotic zones together with the insignificant regeneration leads to a gradual destruction of the tissular substance. All this draws attention to the fact, that the radiation sensitivity of the organ can only be determined, if its acute and chronical changes are known.     

A phaeohyphomycotic cyst and peritonitis caused by Phialemonium species and a reevaluation of its taxonomy

Two cases of human fungal infections caused by members of the genus Phialemonium, a genus proposed by Gams and McGinnis (1983) for fungi intermediate between the genera Acremonium and Phialophora, are presented. The first case was a phaeohyphomycotic cyst on the foot of a renal transplant recipient. The fungus was detected by direct examination and histopathology and was recovered by several procedures over 4 months. It was flat, glabrous, and white becoming yellow with the production of a diffusible yellow pigment; it had conidiophores that were mostly solitary and lateral and terminal phialides and adelophialides with distinct collarettes producing cylindrical to curved conidia. The isolate resembled both Phialemonium dimorphosporum and Phialemonium curvatum, although its characteristics were more consistent with those of the latter. The second case was peritonitis in a renal transplant recipient. The fungus was white-to-cream colored and yeast like, but later became black with a green diffusible pigment, and produced obovoid conidia; it was easily identified as Phialemonium obovatum. Difficulties encountered in the identification and taxonomy of members of this genus highlight the need for standardized conditions, e.g., potato dextrose agar culture incubated at 24 to 25 degrees C for morphologic comparisons, to control significant variations due to culture conditions.     

Increased CA-19-9 caused by a splenic cyst: a rare differential diagnosis

Adenocarcinoma of the gastrointestinal tract, particularly primary adenocarcinoma of the pancreas lead to elevation of serum carbohydrate 19-9 (CA19-9) levels. Some benign disorders, like inflammatory diseases also cause CA19-9 tumor marker elevation. An extremely rare entity are benign splenic cysts which express this tumormarker as reported here.