[Light and electron microscopic studies of the histopathogenicity of Macracanthorhynchus hirudinaceus (Archiacanthocephala) in experimentally infected domestic swine]

One and 12 weeks after infection the lesions in the small intestine of two domestic pigs caused by Macracanthorhynchus hirudinaceus were studied by means of light and electron microscopy. Worms of 7 d.p.i. were found to have penetrated with their presoma into the tunica propria and partly into the tunica muscularis where they had caused local mechanic destructions and heavy eosinophilic-like and hemorrhagic reactions. Most eosinophilic-like granulocytes were attracted to the proboscis hooks, at the base of which an osmiophilic substance apparently was excreted. Worms of 84 d.p.i. had penetrated with their proboscis deeply into the tunica muscularis. The presoma had become encapsulated by a solid capsule of necrotic/inflammatory tissue in its inner part and by filamentous connective tissue in its outer part. The predominant leucocytes in the inflammatory tissue now were plasma cells indicating a progressive immune reaction. No worms were found to have perforated the entire intestinal wall as was described from human patients in China.

Magnetic resonance imaging of flow dynamics in the circle of Willis

Magnetic resonance angiography was applied to the study of blood flow dynamics in the circle of Willis in nine patients with cerebrovascular disease and two normal volunteers. In conjunction with two-dimensional or three-dimensional gradient-echo acquisitions, selective presaturation of individual vessels was used to determine the direction of blood flow and the origin of the vascular supply. Presaturation causes signal loss within the territory supplied by the presaturated artery, without affecting vessels not crossing the presaturation slab. The results were correlated with those from transcranial Doppler sonography and conventional angiography. Magnetic resonance angiography was able to demonstrate the direction of blood flow, the presence or absence of collateral blood flow, and the blood supply to the pericallosal arteries, as well as the presence of a fetal posterior circulation. Magnetic resonance angiography is a noninvasive means for imaging the blood supply of the major intracranial arteries.

Intracerebral arteriovenous malformations: evaluation with selective MR angiography and venography

Magnetic resonance (MR) angiography and spin-echo methods were used to evaluate intracerebral arteriovenous malformations (AVMs) in 10 patients. Spin-echo images obtained with flow presaturation demonstrated the nidus of the AVM in all cases, but it was difficult to determine feeding vessels. These vessels were directly visualized with three-dimensional MR angiography; their presence could be indirectly determined by means of selective presaturation of individual vessels, which resulted in a marked decrease in signal within the portion of the AVM supplied by that vessel. Vascular supplies from the internal carotid artery and anterior, middle, or posterior cerebral arteries were detected in all cases, but in three large malformations it was not possible to demonstrate small feeding vessels. MR angiograms were also helpful for further defining the nidus. The combination of MR angiographic and spin-echo methods provides information useful for therapeutic planning not provided by either technique alone.

MR angiography and dynamic flow evaluation of the portal venous system

We studied the value of MR angiographic techniques in imaging the portal venous system. Projection angiograms were created by postprocessing a series of two-dimensional, flow-compensated gradient-echo images. Flow velocity was determined by a bolus-tracking method with radiofrequency tagging and multiple data readout periods. Each image was acquired during a breath-hold. MR angiography was applied to six normal subjects and four patients with abnormal hemodynamics in the portal venous system. Flow velocity determined by MR was correlated with the results of duplex sonography. The main portal vein and intrahepatic branches were shown in all cases. Portosystemic collaterals were identified in all patients with portal hypertension. In normal subjects, peak flow velocities (17.9 +/- 2.8 cm/sec) on MR correlated well with values determined by duplex sonography (17.5 +/- 2.2 cm/sec) (r = .846, p less than .04). Reversed portal blood flow was shown in two patients. One patient with portal vein thrombosis had no evidence of flow by MR angiography. Our results indicate that MR angiography can provide a three-dimensional display of normal and abnormal vascular anatomy as well as functional information in the portal venous system.

Projection arteriography and venography: initial clinical results with MR

Motion currently limits the applications of magnetic resonance (MR) angiography in certain regions of the body. To overcome this problem, a series of breath-hold, two-dimensional, flow-compensated gradient-echo images were acquired. These images were then processed by means of the maximum intensity projection algorithm to produce projection angiograms. The method was evaluated in 10 healthy subjects and in 12 patients and validated by comparing conventional angiograms, contrast material-enhanced computed tomographic scans, and duplex sonograms with MR projection arteriograms and venograms of the chest, abdomen, and pelvis. The aorta and pulmonary arteries and their branches were demonstrated, as was detailed anatomy of the hepatic and portal venous systems and inferior vena cava. Renal arteries and veins could be studied in both native and transplanted kidneys. The method permits determination of flow direction and differentiation of arteries and veins and is superior to three-dimensional acquisition techniques for imaging slow blood flow. Initial results suggest that the method may have clinical applications for a variety of vascular disorders.

Electron microscopic observation on infected hairs of kerion caused by Microsporum nanum

Microsporum nanum can afflict human hair, although pigs are the usual focus of infection. Although this dermatophyte was thought to invade hair as an endothrix, electron microscopic studies show it to cause ectothrix infection due to its keratinolytic activities.

Cloning full-length dengue type 4 viral DNA sequences: analysis of genes coding for structural proteins

DNA sequences (approximately 11,000 nucleotides) representing the full-length genome of the dengue virus type 4 were cloned. The sequence of the first 2,429 nucleotides at the 5' terminus which includes the coding region for the structural proteins is presented. The virion structural proteins are encoded in one long open reading frame specifying a polyprotein precursor which is apparently proteolytically cleaved by a mechanism resembling that proposed for expression of structural proteins of other flaviviruses such as yellow fever (YF) and West Nile (WN) viruses. The N terminus for each of the dengue virus structural proteins was tentatively assigned by homology alignment to the corresponding sequence of YF or WN virus. Comparison of sequence homology of structural proteins suggests that dengue virus is more closely related to WN virus than to YF virus or Murray Valley encephalitis virus. Finally, analysis of the extreme 5'- and 3'-terminal nucleotides of the dengue virus genome revealed sequences that may be involved in transcription, replication, and packaging of viral RNA.

Cytochemical and ultrastructural studies of the Langerhans' cells. Sequential observations in experimental contact allergic reaction

In the guinea pig, experimental allergic contact dermatitis (ACD) and primary irritant contact dermatitis (PICD) were induced with different concentrations of dinitrochlorobenzene (DNCB). The epidermal Langerhans' cells (LCs) were observed sequentially by both adenosine triphosphatase (ATPase) and electron microscopy. Light microscopically, in ACD, the density and dendritic processes of LC decreased markedly within 12 h after antigen challenge. Almost no recognization LCs could be seen within 2 to 5 days. Later, LCs began to repopulate in the epidermis. Within 14 days, the density and shape of the LCs returned to normal. On the contrary, LCs changed more rapidly in PICD. The dendritic processes of LC decreased within 2 h and cell density decreased dramatically within 6 h after DNCB application. LCs also repopulated more rapidly in the epidermis. Electron microscopically, in ACD, we observed that lymphocyte-like cells apposed to LCs; LCs were activated and damaged; however, in PICD, we found neither the apposition of lymphocyte-like cells to LCs, nor the activation of LCs. LCs play an important role in the convalescence phase as well as in the early and later phases of contact allergic reaction.