Protection of sheep by vaccination against experimental challenge with Leptospira borgpetersenii serovar Hardjo and L. interrogans serovar Pomona.

AIMS: To evaluate a multivalent leptospiral and clostridial vaccine for prevention of renal colonisation and urinary shedding in sheep, following experimental challenge with New Zealand strains of Leptospira borgpetersenii serovar Hardjo type Hardjobovis and L. interrogans serovar Pomona. METHODS: Two separate but similarly designed studies were conducted. In both studies, Romney-cross lambs, aged 9-11 weeks, were randomly allocated to a vaccinated group and a control group. Vaccinated lambs each received two 1.5-mL S/C doses of a multivalent leptospiral and clostridial vaccine, 4 weeks apart, and animals in the control groups received the same dose of saline. Groups of 12 vaccinated and 12 control lambs were randomly selected in each study for challenge with serovars Hardjo or Pomona. Challenge was initiated 16 weeks following the second vaccination with three daily doses of live leptospires by intranasal and conjunctival routes. Following challenge, urine samples were collected weekly for 6 weeks, for dark field microscopy and leptospiral culture; 6 weeks after challenge the lambs were slaughtered and kidneys collected for leptospiral culture. RESULTS: In lambs challenged with serovar Hardjo, 8/12 unvaccinated lambs had ≥1 urine or kidney sample that was positive for leptospires following culture, compared with 0/12 lambs in the vaccinated group (p=0.001). In lambs challenged with serovar Pomona, 9/12 unvaccinated lambs had ≥1 urine or kidney sample that was positive following culture, compared with 0/12 lambs in the vaccinated group (p<0.001). Prevention of renal colonisation and urinary shedding, expressed as the prevented fraction, was 100 (95% CI=61.7-100)% and 100 (95% CI=68.3-100)% against challenge with serovars Hardjo and Pomona, respectively, at 4 months after vaccination. CONCLUSIONS AND CLINICAL RELEVANCE: Use of a multivalent leptospiral and clostridial vaccine demonstrated protection against challenge from New Zealand strains of serovars of Hardjo and Pomona 4 months after vaccination in lambs first vaccinated at 9-11 weeks of age. Further studies are required to assess the duration of immunity against challenge in sheep.

Prevention of fetal infection in heifers challenged with bovine viral diarrhoea virus type 1a by vaccination with a type 1c or type 1a vaccine.

AIMS: To evaluate a vaccine containing type 1c bovine viral diarrhoea (BVD) virus for prevention of fetal infection in pregnant heifers when challenged with New Zealand BVD virus type 1a 6 months after vaccination, compared to unvaccinated heifers and heifers vaccinated with a vaccine containing type 1a BVD virus. METHODS: Fifty five crossbred Friesian heifers, free from BVD virus and antibody, were randomly allocated to three groups. Twenty five heifers were vaccinated twice with a vaccine containing type 1c BVD virus (T1c group), and 10 heifers with a vaccine containing type 1a BVD virus (T1a group), and 20 heifers were unvaccinated (NC group). After oestrus synchronisation the heifers were bred by artificial insemination followed by natural bull mating. Six months after booster vaccination 15 heifers from the T1c group, eight from the T1a group, and 15 from the NC group, were exposed to four calves that were persistently infected with type 1a BVD virus, for 4 weeks. At the beginning of the challenge phase 36/38 heifers were 72-74 days pregnant and 2/38 heifers were approximately 53 days pregnant. Approximately 52 days after the start of the challenge the heifers were subjected to euthanasia and fetal tissues were collected for the detection of BVD virus by ELISA in fetal heart blood and PCR in fetal tissues. RESULTS: Based on PCR results, BVD virus was detected in 15/15 fetuses in the NC group, compared to 4/14 fetuses in the T1c group and 3/8 fetuses in the T1a group. The proportion of BVD virus-positive fetuses was lower in both vaccinated groups compared to the NC group (p<0.002), but there was no difference in proportions between the vaccinated groups (p=1.00). Fetal protection, expressed as the prevented fraction, was 71.4 (95% CI=41.9-91.6)% and 62.5 (95% CI=24.5-91.5)% for the T1c and T1a groups, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The vaccines containing killed type 1c and type 1a BVD viruses significantly reduced fetal infection following challenge with a New Zealand type 1a BVD virus. Prevention of fetal infection by vaccination may not be 100%, and the risk of persistently infected calves being born to some vaccinated cattle should be acknowledged and managed as part of a BVD control programme.

High-resolution tensor MR elastography for breast tumour detection.

MR elastography is a novel imaging technique for the visualization of elastic properties of tissue. It is expected that this method will have diagnostic value for the clarification of suspicious breast lesions. Low-frequency mechanical waves are coupled into the tissue and visualized via an MR sequence which is phase-locked to the mechanical excitation. Commonly, elasticity is assumed to be isotropic and reconstruction is performed in only two dimensions. The technique is extended to three dimensions such that the entire symmetric elasticity tensor is assessed. This is achieved by measuring different phases of the mechanical wave during one oscillatory cycle. Thereby it is possible to provide information about the anisotropy of the elasticity tensor. Finite-element simulations as well as phantom experiments are performed to demonstrate the feasibility of the method. Initial clinical results of a breast carcinoma are presented. The analysis of the eigenvalues of the elasticity tensor support the hypothesis that breast carcinoma might exhibit an anisotropic elasticity distribution. The surrounding benign tissue appears isotropic. Thereby new and additional diagnostic information is provided which might help in distinguishing between benign and malignant breast diseases.

MR fluoroscopy using projection reconstruction multi-gradient-echo (prMGE) MRI.

A projection reconstruction multi-gradient-echo (prMGE) technique is presented. The introduced technique is an extension of a standard projection reconstruction steady-state gradient-echo technique allowing for the acquisition of several gradient echoes after each excitation of the spin system. Each echo train is used for acquiring data of a certain angular segment of k-space. By use of echo trains consisting of up to four echoes, the overall acquisition time for a 128(2) image can be reduced to 150 ms without sacrificing image quality. Results are presented for cardiac fluoroscopy, for the visualization of swallowing, and for the visualization of joint motion. For all investigated applications promising results have been obtained. Especially in parts of the body where motion on an even shorter time scale than the acquisition process or significant in-plane or through-plane flow are within the field of view, the introduced technique appears to be a promising technique for MR fluoroscopy. Magn Reson Med 42:324-334, 1999.

Catheter tracking using continuous radial MRI.

The guidance of minimally invasive procedures may become a very important future application of MRI. The guidance of interventions requires images of the anatomy as well as the information of the position of invasive devices used. This paper introduces continuous radial MRI for the simultaneous acquisition of the anatomic MR image and the position of one or more small RF-coils (mu-coils), which can be mounted on invasive devices such as catheters or biopsy needles. This approach allows the in-plane tracking of an invasive device without any prolongation of the overall acquisition time. The extension to three-dimensional position tracking is described. Phantom studies are presented demonstrating the capability of this technique for real-time automatic adjustment of the slice position to the current catheter position with a temporal resolution of 100 ms. Simultaneously the in-plane catheter position is depicted in the actually acquired MR image during continuous scanning.

Continuous radial data acquisition for dynamic MRI.

Since image acquisition times in MRI have been reduced considerably over recent years, several new important application areas of MRI have appeared. In addition to pure static anatomic information, the evolution of a dynamic process may be visualized by a sequence of temporal snapshots of the process acquired within a short time period. This makes applications like interactive or interventional MRI as well as the acquisition of additional functional information feasible. For high temporal resolution, all these applications require a quasi real-time image acquisition during the time the interaction or dynamic process evolves. We present an approach to real-time imaging using a continuous radial acquisition scheme. The intrinsic advantages of radial or projection reconstruction (PR) techniques are used to minimize motion-related image distortions. Modifications of the acquisition scheme as well as dedicated reconstruction techniques are used to further reduce the temporal blurring due to the finite acquisition time of one entire data set in our approach. So far we have used this technique for the visualization of active joint motion.

Radial turbo spin echo imaging.

Fast MR imaging methods should provide a familiar contrast behavior at a reduced scan time. The multi-spin echo approach (TSE) is one of the most promising techniques satisfying this condition. Although the data acquisition time is significantly reduced, image quality may still suffer from artifacts due to patient motion and flow. The radial turbo spin echo (rTSE) approach combines TSE methods and projection reconstruction (PR) techniques. In PR images, artifacts induced by patient motion or flow are known to have a different appearance with lower level of intensity. The contrast and artifact behavior of the rTSE approach has been investigated. The new technique has been applied to abdominal imaging with acquisition times shorter than 30 s and to heart imaging in combination with cardiac triggering.

[New therapeutic approach in the celiac trunk compression syndrome]. / Nouvelle approche thérapeutique dans le syndrome de compression du tronc coeliaque.

Etiology and treatment of the coeliac compression syndrome remains controversial. The external compression, near the origin of the truncus coeliacus and the poststenotic dilatation is well demonstrated by angiography on a lateral projection. The development of collaterals like the pancreaticoduodenal and gastroduodenal artery can be assessed on a frontal view. The grading of the stenosis as well as the direction of the flow in these artery can be measured with the duplex sonography. These investigations show a steal syndrome: blood coming from the mesenteric artery irrigate the common hepatic artery through the collaterals. The flow in the common hepatic artery is therefore retrograde. We used an original technique to correct this flow pattern in the case of a 52-year-old patient: after dividing the arcuate ligament, we reduced the vascular territory of the truncus coeliacus with the proximal ligation of the splenic artery. The duplex sonography shows postoperatively the suppression of the steal syndrome with a normal flow pattern in the hepatic artery despite minimal change in the stenosis of the truncus coeliacus. The patient remained asymptomatic since the operation. We concluded that an angioplasty or reimplantation of the truncus coeliacus is unnecessary to correct the steal syndrome. A normal flow can be provided by a stenotic truncus coeliacus once the splenic artery has been ligated.

Automatic shimming for localized spectroscopy.

Localized in vivo nuclear magnetic resonance studies often require a high spectral resolution not achievable with the basic shim of a whole-body magnetic resonance magnet. Therefore, the magnetic field homogeneity needs to be optimized in the selected volume of interest within a reasonable time. For this purpose, a method of automatic shimming was developed and tested on phantoms and volunteers. The volume selection is performed by means of a surface coil or by using a localization method which generates a stimulated echo from the volume of interest. The optimization procedure uses the time integral over the magnitude of the free induction decay or echo signal as homogeneity criterion. A complete shimming process generally requires only 80 transients. Test experiments were conducted on various volume sizes ranging from 2 X 2 X 2 cm3 to 15 X 15 X 15 cm3 inside a large phantom. The resulting linewidth in small volumes at the magnet center compared well with the natural linewidth determined by means of the Carr-Purcell-Meiboom-Gill sequence. As expected, shimming in selected volumes at off center positions led to somewhat broader lines. Results obtained on volunteers demonstrate the practical value of this rapid, automatic shimming method for in vivo studies.

The importance of SH-containing substances for red blood cells in acute myeloic leukemia.

Electron spin resonance (ESR) spectra of lyophilized erythrocytes obtained from patients with acute myeloid leukemia (AML) show, in comparison to controls, a characteristic change especially in the low-field region of the spectrum concomitant with a reduction of the spin concentration. This effect can be simulated by addition of SH-containing substances (e.g. reduced glutathione or cysteine) to healthy erythrocytes. S-S containing compounds exhibit no effect. Since SH-containing substances can hardly permeate plasma membranes, the membrane surface seems to be defective in the case of "AML" erythrocytes. Furthermore, it can be concluded that the concentration of SH-containing substances, such as cysteine, is increased in the plasma of AML-patients, which could be confirmed by HPLC-measurements. In the case of a successful treatment of the patients with alexan, daunoblastin, and thioguanine the spin concentration increased again and the resulting ESR spectrum is very similar to the control spectrum. It should be pointed out, that the ascorbic acid concentration is very low in both plasma and erythrocytes of AML patients.

Influence of metal ions on the transport of ascorbate across membranes.

The effect of Fe2+, Cu2+, Ca2+, and Mg2+ on the permeation of ascorbate across membranes of dipalmitoyllecithin (DPPC) vesicles was investigated. As in previous experiments, the spin label I (1,14) was used for monitoring this transport. While Mg2+ and Ca2+ exerted a small effect only, Fe2+ and Cu2+ increased considerably the reduction of the spin label. In the case of Fe2+, this is not only due to a higher permeation rate of ascorbate but is also caused by a permeation of Fe2+. As a matter of fact, the largest reduction of the spin label was obtained if Fe2+ alone was added to the spin labelled DPPC solution. The reduction of the spin label seems to depend on the redox potentials of the constituents.

Structure of ascorbic acid and its biological function. I. ESR determination of the ascorbyl radical in biological samples and in model systems.

ESR investigations on lyophilized systems have shown that the signal at g = 2.005 can be explained by an interaction between Na+ or K+ and the anionic ascorbyl radical. The unpaired electron is probably localized near the C(4) region and is produced by a cleavage of an H atom belonging to a water molecule bound tightly to C(4). Experiments on aqueous samples revealed that ascorbic acid in its radical configuration and in its highest concentration exists only at physiological pH and temperature. An additional splitting is obtained by the ring formation between C(3) and C(6)-OH. The coupling constants of the triplets produced by the CH2-6 protons differ between ascorbic acid and isoascorbic acid. Thus, the ESR technique can be applied for an easy distinction between these two epimers.

On the origin of the non-haemic iron transferrin ESR signal: ESR investigations on histidine-iron-citric acid systems.

The nature of the high spin ferric iron complex located at g = 4.3 has been investigated by means of electron spin resonance spectroscopy and polarography. It could be shown that two complexes each exist in the acid and alkaline pH region, and that the iron is bound to two histidines, three citric acids, and probably to one bicarbonate. These results agree well with previous findings according to which the ligand field of iron should be composed mainly of oxygen and nitrogen atoms. Another low-field signal located at g = 3.6 appears in the pH range from 2 to 7 only and exhibits its maximum where the g = 4.3 signal has its minimum. Its exact nature is still unknown but it seems to represent some intermediate state of the ternary Fe3+-histidine-citric acid complex. When citric acid is used, the spin concentration seems to be always larger than in the case of ascorbic acid. Since the effect obtained with ascorbic acid and citric acid seems to be similar, it may be concluded that the biological function of both of the acids might be somehow related to each other.

The effect of alcohol oxidase on the ascorbic acid-erythrocyte interaction: ESR investigations.

Addition of alcohol oxidase to erythrocytes treated with ascorbic acid reverses the vitamin C effect, as expressed by the appearance of the semidehydroascorbate signal, and the increase in spin concentration. The original erythrocyte electron spin resonance (ESR) signal is, however, never restored completely, as it is in the case if ascorbate oxidase is used. Additional interaction between the enzyme alcohol oxidase and haemoglobin iron must occur, since both of the iron ESR signals at g = 4.3 and g = 6 disappear and the erythrocyte ESR spectrum at g approximately equal to 2 is changed characteristically. The spin concentration of the latter spectrum increases again above a certain concentration of alcohol oxidase.

ESR investigations on the modification of the ascorbic acid-erythrocyte interaction by ferrous ions.

An ascorbic acid-erythrocyte interaction results in the formation of the semidehydroascorbate (SDA) radical and an increase in spin concentration. Addition of a more than ten-fold concentration of Fe2+ (as FeSO4) to such a system compensates the effect produced by ascorbic acid, that is the electron spin resonance spectrum obtained resembles very closely that of erythrocytes only. With the disappearance of the SDA radical a high spin ferric ion signal appears concomitantly at g = 4.3.

On the origin of the non-haemic iron transferrin ESR signal: ESR investigations on histidine-iron-ascorbic acid systems.

The nature of the ferric high spin iron complex located at g = 4.3 has been investigated by means of electron spin resonance spectroscopy. It could be shown that the iron is bound to two histidines, three ascorbic acids, and one bicarbonate. This agrees well with previous findings according to which the ligand field of iron is composed mainly of oxygen and nitrogen atoms. Another low-field signal located at g = 9.5 appears always concomitantly with the g = 4.3 signal. It should be due, therefore, to a transition between the two sublevels of the low-lying Kramers doublet in one principal direction.