Benchmarking passive transfer of immunity and growth in dairy calves.

Poor health and growth in young dairy calves can have lasting effects on their development and future production. This study benchmarked calf-rearing outcomes in a cohort of Canadian dairy farms, reported these findings back to producers and their veterinarians, and documented the results. A total of 18 Holstein dairy farms were recruited, all in British Columbia. Blood samples were collected from calves aged 1 to 7 d. We estimated serum total protein levels using digital refractometry, and failure of passive transfer (FPT) was defined as values below 5.2 g/dL. We estimated average daily gain (ADG) for preweaned heifers (1 to 70 d old) using heart-girth tape measurements, and analyzed early (≤35 d) and late (>35 d) growth separately. At first assessment, the average farm FPT rate was 16%. Overall, ADG was 0.68 kg/d, with early and late growth rates of 0.51 and 0.90 kg/d, respectively. Following delivery of the benchmark reports, all participants volunteered to undergo a second assessment. The majority (83%) made at least 1 change in their colostrum-management or milk-feeding practices, including increased colostrum at first feeding, reduced time to first colostrum, and increased initial and maximum daily milk allowances. The farms that made these changes experienced improved outcomes. On the 11 farms that made changes to improve colostrum feeding, the rate of FPT declined from 21 ± 10% before benchmarking to 11 ± 10% after making the changes. On the 10 farms that made changes to improve calf growth, ADG improved from 0.66 ± 0.09 kg/d before benchmarking to 0.72 ± 0.08 kg/d after making the management changes. Increases in ADG were greatest in the early milk-feeding period, averaging 0.13 kg/d higher than pre-benchmarking values for calves ≤35 d of age. Benchmarking specific outcomes associated with calf rearing can motivate producer engagement in calf care, leading to improved outcomes for calves on farms that apply relevant management changes.

Efficacy of liposome-encapsulated ciprofloxacin in a murine model of Q fever.

Encapsulation of antibiotics may improve treatment of intracellular infections by prolonging antibiotic release and improving antibiotic uptake into cells. In this study, liposome-encapsulated ciprofloxacin for inhalation (CFI) was evaluated as a postexposure therapeutic for the treatment of Coxiella burnetii, the causative agent of Q fever. Intranasal treatment of male A/Jola (A/J) mice with CFI (50 mg/kg of body weight) once daily for 7 days protected mice against weight loss and clinical signs following an aerosol challenge with C. burnetii. In comparison, mice treated twice daily with oral ciprofloxacin or doxycycline (50 mg/kg) or phosphate-buffered saline (PBS) lost 15 to 20% body weight and exhibited ruffled fur, arched backs, and dehydration. Mice were culled at day 14 postchallenge. The weights and bacterial burdens of organs were determined. Mice treated with CFI exhibited reduced splenomegaly and reduced bacterial numbers in the lungs and spleen compared to mice treated with oral ciprofloxacin or doxycycline. When a single dose of CFI was administered, it provided better protection against body weight loss than 7 days of treatment with oral doxycycline, the current antibiotic of choice to treat Q fever. These data suggest that CFI has potential as a superior antibiotic to treat Q fever.

An amoeba phagocytosis model reveals a novel developmental switch in the insect pathogen Bacillus thuringiensis.

The Bacillus cereus group bacteria contain pathogens of economic and medical importance. From security and health perspectives, the lethal mammalian pathogen Bacillus anthracis remains a serious threat. In addition the potent insect pathogen Bacillus thuringiensis is extensively used as a biological control agent for insect pests. This relies upon the industrial scale induction of bacterial spore formation with the associated production of orally toxic Cry-toxins. Understanding the ecology and potential alternative developmental fates of these bacteria is therefore important. Here we describe the use of an amoeba host model to investigate the influence of environmental bactivorous protists on both spores and vegetative cells of these pathogens. We demonstrate that the bacteria can respond to different densities of amoeba by adopting different behaviours and developmental fates. We show that spores will germinate in response to factors excreted by the amoeba, and that the bacteria can grow and reproduce on these factors. We show that in low densities of amoeba, that the bacteria will seek to colonise the surface of the amoeba as micro-colonies, resisting phagocytosis. At high amoeba densities, the bacteria change morphology into long filaments and macroscopic rope-like structures which cannot be ingested due to size exclusion. We suggest these developmental fates are likely to be important both in the ecology of these bacteria and also during animal host colonisation and immune evasion.

Direct comparison of visual cortex activation in human and non-human primates using functional magnetic resonance imaging.

We report a technique for functional magnetic resonance imaging (fMRI) in an awake, co-operative, rhesus macaque (Macaca mulatta) in a conventional 1.5T clinical MR scanner, thus accomplishing the first direct comparison of activation in visual cortex between humans and non-human primates with fMRI. Activation was seen in multiple areas of striate and extra-striate visual cortex and in areas for motion, object and face recognition in the monkey and in homologous visual areas in a human volunteer. This article describes T1, T2 and T2* values for macaque cortex, suitable MR imaging sequences, a training schedule, stimulus delivery apparatus and restraining hardware for monkey fMRI using a conventional 19 cm knee coil. Much of our understanding of the functional organization of the primate brain comes from physiological studies in monkeys. Direct comparison between species using fMRI such as those described here will help us to relate the wealth of existing knowledge on the functional organization of the non-human primate brain to human fMRI.

Functional magnetic resonance imaging in macaque cortex.

The ability to use fMRI in a monkey model would bridge the gap between the fMRI demonstration of cerebral activation in humans and the cumulative wealth of monkey data on the functional organization of the brain from single electrode mapping, radioisotope and histology studies. We report a new technique for fMRI in an awake co-operative rhesus macaque (Macaca mulatta) in a conventional clinical 1.5T MR scanner and present the first fMRI images from a macaque. Good resolution, signal-to-noise ratio and BOLD response (2.6-4.6%) have been achieved using the manufacturer's standard volume knee coil. T1 values of macaque gray and white matter (1490 ms, 1010 ms respectively) are higher than human brain, whereas T2 values are lower (55 ms, 48 ms respectively). An MR-compatible design for restraining the monkey is also described, along with a suitable EPI sequence for BOLD images, optimized for monkey T2, with voxel sizes from 29 to 61 microl, and MPRAGE sequence for anatomical studies with 0.8 mm isotropic resolution, optimized for monkey T1.

First pass MRA of the abdomen: ultrafast, non-breath-hold time-of-flight imaging using Gd-DTPA bolus.

The authors describe a new fast imaging sequence that can produce projection angiograms of the abdominal vessels at a rate of 2 to 3 frames per second. The result is a versatile imaging technique that can track the arrival of a bolus of contrast in major vessels. With very fast data acquisition, gross patient motion is not a problem, and routine vascular projection studies may be performed without the need for breath-holding. This method is compatible with later high-resolution three-dimensional gradient echo studies using contrast agents and may, in fact, be used as an accurate timing protocol to gauge the arrival time of contrast in various segments of the abdominal vessels. Compared with echo planar imaging, this method has the advantages of avoiding susceptibility artifacts and depicting retroperitoneum and other abdominal fat-containing landmarks and does not require extensive hardware modifications for a clinical system.

Entorhinal axons perforate hippocampal field CA3 in organotypic slice culture.

In growing towards their hippocampal targets, incoming afferent axons from the entorhinal cortex arrive at the subicular pole of the hippocampus and normally turn pialwards from the alvear path, crossing (perforating) the subiculum and field CA1, but never the more distally situated field CA3. To address the question of whether a specific repulsive characteristic of field CA3 might explain this behaviour, artificial confrontation were set up in vitro. Embryonic entorhinal explants were placed in restricted contact with 8-day-old rat hippocampal slices, orientated so that outgrowing axons could only grow into either the dentate gyrus, the subiculum/field CA1, or field CA3. Anterograde biotin-dextran labelling of projections after 2 weeks in culture showed that entorhinal axons perforated the stratum oriens, pyramidal cell layer, and stratum radiatum of CA3 just as readily as they did along their normal trajectory across CA1/subiculum. It is therefore concluded that spatiotemporal cues are more likely than specific chemorepulsive molecules to be involved in setting up this part of the entorhinal pathway.

The N-glycan of the SCR 2 region is essential for membrane cofactor protein (CD46) to function as a measles virus receptor.

Membrane cofactor protein (MCP) (CD46), a complement-regulatory protein, serves as a cellular receptor for measles virus. Its amino-terminal portion is composed of four short consensus repeats (SCR), three of which (SCR1, SCR2, and SCR4) carry an N-linked oligosaccharide. In order to determine the importance of the three N-glycans for the function of MCP as a measles virus receptor, we established Chinese hamster ovary (CHO) cell lines that stably express mutant MCPs lacking one of the three motifs for N glycosylation (NQ1, NQ2, and NQ4). In an additional mutant (NQ1-2), two glycosylation motifs were altered, allowing the addition of an N-linked oligosaccharide only in SCR4. The abilities of the mutant MCPs to function as measles virus receptors were analyzed with three different assays: (i) binding of measles virus hemagglutinin to MCP immobilized on nitrocellulose; (ii) binding of measles virus to CHO cells expressing wild-type or mutant MCP; and (iii) infection of the transfected CHO cells by measles virus. In all three assays, the abilities of the NQ2 and NQ1-2 mutants to serve as measles virus receptors were drastically impaired. The NQ1 and NQ4 mutants were recognized by measles virus almost as efficiently as the wild-type protein. These results indicate that the N-glycan attached to SCR2 is essential for MCP to serve as a measles virus receptor, while the oligosaccharides attached to SCR1 and SCR4 are of only minor importance.

Regeneration of entorhino-dentate projections in organotypic slice cultures: mode of axonal regrowth and effects of growth factors.

Explants of Embryonic Day 18 (E18) rat entorhinal cortex were cocultured with Postnatal Day 6 mouse hippocampal slices to study CNS regeneration in vitro. The present report describes a double-labeling paradigm for quantitative analysis of the type of new growth seen in immature cultures. Entorhinal projection neurons in living static cocultures were retrogradely labeled with DiI or Texas red-dextran at 6 days in vitro and with dextran-FITC at 13 days. An intervening lesion to the entorhinodentate pathway was made at 8 days by replacing the hippocampal slices with fresh ones. About one-third of the new efferent entorhinal projections labeled with the second tracer could be characterized as true regeneration of axons from previously projecting entorhinal neurons by virtue of their being double labeled. The remaining two-thirds comprised new, late-arriving axons from previously nonprojecting cells. Earlier studies have shown that rat entorhinal axons will reinnervate hippocampal slices only if the lesions are made before 2-3 weeks in culture, equivalent to a postnatal age of 11-18 days. In a second series of experiments we tested whether treatment with trophic factors could overcome this age-related failure of regeneration characteristic of mature preparations. E18 explants were lesioned after 4 weeks in vitro and grown for a further 2 weeks in medium supplemented with either Schwann cell conditioned medium or acidic fibroblast growth factor plus heparin. A significant increase in outgrowth was seen in both cases, although the effects of each factor were not additive when they were applied in combination. These results show that our model of CNS lesions in vitro can be used to assess the effectiveness of growth factors in ameliorating the decline in regenerative ability with increasing developmental age.

Normal-pressure hydrocephalus: evaluation with cerebrospinal fluid flow measurements at MR imaging.

PURPOSE: To evaluate magnetic resonance (MR) imaging-based quantitative phase-contrast cerebrospinal fluid (CSF) velocity imaging for prediction of successful shunting in patients with normal-pressure hydrocephalus (NPH). MATERIALS AND METHODS: Eighteen patients (mean age, 73 years) with NPH underwent routine MR imaging and CSF velocity MR imaging before ventriculoperitoneal (VP) shunting. The calculated CSF stroke volume and the aqueductal CSF flow void score were compared with the surgical results. RESULTS: All 12 patients with CSF stroke volumes greater than 42 microL responded favorably to CSF shunting. Of the six patients with stroke volumes of 42 microL or less, three improved with shunting while three did not. The relationship between CSF stroke volume greater than 42 microL and favorable response to VP shunting was statistically significant (P < .05). There was no statistically significant relationship between aqueductal CSF flow void score and responsiveness to shunting. CONCLUSION: CSF velocity MR imaging is useful in the selection of patients with NPH to undergo shunt formation.

Rapid decline in the ability of entorhinal axons to innervate the dentate gyrus with increasing time in organotypic co-culture.

We have used the species-specific monoclonal antibodies OM1 and OM4 to identify the histiotypic pattern of projection from late embryonic rat entorhinal explants to the outer molecular layer of the dentate gyrus in organotypic cultures of 6-day postnatal mouse hippocampal slices. The presence of this entorhinal projection was detectable with the rat-specific OM1 and OM4 markers after 3-7 days in co-culture, and confirmed by use of the later-forming rat neuron-specific marker THy-1.1, which appeared during the second week. Hippocampal slices confronted with control explants of superior colliculus for 4 weeks in culture showed only sparse, non-specific growth of axons with no histiotypic pattern in the dentate gyrus. In order to assess whether the formation of specific entorhino-dentate projections in vitro is age-dependent, embryonic rat entorhinal cortical explants were cultured alone for periods of 1-5 weeks before cutting across the halo of axons radiating into the collagen matrix and presenting each with 6-day-old mouse hippocampal slices as targets to innervate. After allowing a 2 week period for fibre growth to take place, the density of immunostained axonal outgrowth was scored on a five-point scale for each weekly interval. The amount of new axon growth when the cuts were made after 1 week was slightly reduced compared to undamaged control cultures. However, outgrowth was greatly diminished when the cuts were made after 2 or 3 weeks, and essentially abolished if the interval was extended to > or = 4 weeks. Thus we demonstrate that, although hippocampal slices can survive in organotypic co-culture with entorhinal explants and maintain previously formed connections, the explants show an age-related failure in the ability to form new connections. Such a system provides a possible in vitro model for study of the factors influencing the failure of regeneration in the adult central nervous system.

Three-dimensional MR imaging and display of intracranial disease: improvements with the MP-RAGE sequence and gadolinium.

Three-dimensional (3D) image rendering was performed in 14 patients who had undergone magnetic resonance (MR) imaging for focal brain lesions. The MR study included the magnetization-prepared rapid gradient-echo (MP-RAGE) sequence with 64 or 128 partitions. Resultant contiguous sections 2.5 or 1.25 mm thick, respectively, were obtained. Images were acquired before and after administration of gadopentetate dimeglumine. Resultant 3D data sets were processed on a commercially available workstation. Correlative surgical observation was performed in four cases. All data sets were successfully processed into 3D images. The precontrast images proved superior to gadolinium-enhanced images for brain surface rendering. Postcontrast images proved superior for reconstruction of tumors and vascular structures. The 64-partition data set proved sufficient for all postprocessing. Coronal orientation was preferred to sagittal orientation for surface rendering because it provided optimal orthogonal orientation of sulcal and gyral brain surface features. Three-dimensional rendition allowed easy superposition of lesion, brain, vessels, and scalp features--all useful for surgical planning. The central sulcus was easily recognized in the midline partitions and traced mediolaterally for projection on the cortical surface. MP-RAGE provides a 3D data set that can be obtained in just over 3 minutes, from which clinically useful 3D renderings are possible. The rapidity of acquisition and capability for 3D rendering provides additional clinical utility.

Assessment of intracardiac shunts with gadolinium-enhanced ultrafast MR imaging.

Dye dilutional techniques are widely accepted for the assessment of intracardiac shunts, but current techniques require arterial access or radioisotope injection. Ultrafast (less than 500 msec) magnetic resonance (MR) imaging is ideally suited for the evaluation of an indicator during passage through the heart. Twenty patients were studied, including 13 with shunts. Four-chamber, T1-weighted images were obtained during bolus injection of gadopentetate dimeglumine. A single image was obtained in 420 msec, with repetitive images acquired after each QRS complex. After the contrast material was injected, there was pronounced signal intensity enhancement in the right atrium, followed by the right ventricular cavity, left atrium, left ventricular cavity, and descending aorta. Patients with substantial intracardiac shunts demonstrated early recirculation. First-pass contrast material-enhanced MR imaging is a promising new technique for the rapid assessment of intracardiac shunts. Combined with anatomic and functional MR imaging techniques, it can help provide a comprehensive noninvasive evaluation of suspected intracardiac shunts or provide follow-up in patients with known shunts.

[Cerebral angiography using proton spin tomography]. / Zerebrale Angiographie mittels Kernspintomographie.

In only a few years magnetic resonance angiography has evolved to a clinically useful tool. In many situations it can resolve questions which used to be addressed by conventional contrast angiography, such as carotid stenoses, aneurysms, arteriovenous malformations, and venous and sinus disorders. In addition, selective magnetic resonance angiography provides information on direction and origin of flow and circulation in vessels serving as collaterals.

Monoclonal antibodies reveal molecular differences between terminal fields in the rat dentate gyrus.

We have derived a number of monoclonal antibodies which detect molecular differences correlating with the afferent inputs to the molecular layer of the adult rat hippocampal dentate gyrus. One group, dubbed OM-1 to OM-4, strongly stain the outer zone of the molecular layer, which receives its major innervation from the ipsilateral entorhinal cortex. A second group, IM-1 and IM-2, show a complementary pattern and preferentially stain the inner molecular layer, which receives inputs from the ipsilateral and contralateral hippocampus. These antigens are not, however, restricted to these layers, being found outside the hippocampus in several other areas of neuropil in the adult brain. In the developing brain the IM-1 antigen appears ubiquitously from the earliest age studied, embryonic day 12. Within the dentate gyrus, its restriction to the inner terminal field of the molecular layer only occurs during the second postnatal week. In contrast, OM staining appears only sparsely and late in the prenatal brain, appearing in developing cortical white matter between embryonic days 18 and 20. The outer dentate molecular layer becomes OM-positive from birth onwards, corresponding to the time of arrival of entorhinal axons during the first postnatal week. These two groups of monoclonal antibodies recognize a number of different glycoproteins. Ultrastructural immunohistochemistry shows they are cell surface molecules, and as such may be involved in the recognition events required for the establishment of specific patterns of neuronal connectivity.

Middle cerebral artery: determination of flow velocities with MR angiography.

A magnetic resonance (MR) angiographic technique for noninvasive measurement of flow velocities in the intracranial cerebral arteries was studied. Velocity measurements were made in a phantom and in the middle cerebral artery of six volunteers. Velocities were assessed in the volunteers before, during, and after finger movement. Average values for mean maximal velocities determined with MR angiography were 69.8 cm/sec before, 77.2 cm/sec during, and 69.6 cm/sec after finger movement. Correlations between values obtained with MR angiography and transcranial Doppler (TCD) sonography were r = .86 and P = .0001 for values obtained at rest and r = .84 and P = .0001 for values obtained during finger movement. The velocity increase during finger movement compared with that at rest was 11% for MR angiography and 11.3% for TCD sonography. Values measured with TCD sonography, however, were less than those measured with MR angiography (P = .001). The results show the feasibility of measuring flow velocities in intracranial arteries with MR angiography.

First-pass nuclear magnetic resonance imaging studies using gadolinium-DTPA in patients with coronary artery disease.

Nuclear magnetic resonance (NMR) imaging has been shown to accurately portray cardiac anatomy and function. To investigate the potential of NMR imaging for the assessment of coronary stenosis in patients with chest pain, ultrafast NMR imaging in conjunction with a T1 (longitudinal relaxation time) contrast agent was performed in 17 patients with chest pain who had undergone cardiac catheterization. These included 12 patients with significant coronary artery stenoses and 4 who underwent repeat NMR study after myocardial revascularization. Cardiac images at rest were obtained during rapid intravenous injection of gadolinium-DTPA (0.04 mM/kg). Electrocardiographic-gated images were acquired over 380 ms, with repetitive images obtained every 3 to 4 s. After contrast injection, there was pronounced signal enhancement in the right ventricular cavity, followed by enhancement in the left ventricular cavity and myocardium. Regional myocardium perfused by a diseased vessel demonstrated a lower peak signal intensity (p = 0.001) and lower rate of signal increase (p = 0.001) than did myocardium perfused by coronary arteries without stenosis. Repeat NMR study after revascularization showed an increase in peak signal intensity (p less than 0.002). These results demonstrate the clinical potential of dynamic gadolinium-DTPA-enhanced NMR imaging for the assessment of coronary artery disease in patients with chest pain. In combination with anatomic and functional NMR imaging, this technique has the potential to provide a comprehensive noninvasive cardiac evaluation of patients with suspected coronary artery disease.

Evaluation of the extracranial carotid arteries: correlation of magnetic resonance angiography, duplex ultrasonography, and conventional angiography.

We compared duplex scanning, "bright blood" and "black blood" magnetic resonance angiography, and conventional angiography for evaluation of the extracranial carotid arteries. All three methods were applied to 39 vessels in 20 patients. Duplex scanning was inaccurate when compared to conventional angiography in six instances. In three instances the degree of stenosis was overgraded by the scanner, and in three cases the stenosis was undergraded. Magnetic resonance angiography was inaccurate when compared to conventional angiography in three instances. In all cases magnetic resonance angiography overgraded the degree of stenosis. By use of a greater than 70% stenosis as a positive study, the sensitivity of magnetic resonance angiography was 100% and the specificity 92%. With use of the same criteria, the sensitivity of duplex scanning was 86%, and specificity was 84%. In those evaluations where the results of the magnetic resonance angiography and duplex scanning were in agreement, the correlation with conventional angiography was 100%. We conclude that magnetic resonance angiography is an alternative means to duplex scanning for noninvasive carotid imaging. A combination of bright and black blood magnetic resonance angiography is precise in delineating lesions of the extracranial carotid artery and may ultimately eliminate the need for conventional angiography in the evaluation of carotid stenosis.

Fast time-of-flight MR angiography with improved background suppression.

A new technique for improving contrast in time-of-flight magnetic resonance (MR) angiography is described. A selective 180 degrees radio-frequency pulse was applied before data acquisition to suppress the signal intensity of stationary tissues. Vascular images were obtained in 1 second or less by using a single-shot, rapid gradient-echo sequence in conjunction with a very short echo time to minimize flow-related dephasing. Alternatively, the data acquisition could be divided into several segments that were combined to create an image. Because of the short imaging times, abdominal single-shot images were relatively insensitive to motion. The major drawback was decreased spatial resolution and limited signal-to-noise ratio. Spatial resolution of segmented flow images was comparable with that of standard gradient-echo images, but there was a marked reduction in the signal intensity of stationary tissues. For high-resolution MR angiography, the effective background suppression obtained by means of the segmented approach can improve the quality and reliability of images created by the maximum intensity projection algorithm.

Cineangiography of the heart in a single breath hold with a segmented turboFLASH sequence.

Six healthy volunteers and three patients with cardiac anomalies were studied in a comparison of segmented turboFLASH (fast low-angle shot) cine, a method of magnetic resonance imaging that permits an entire series of high-resolution cine images to be obtained in one breath hold, with standard cine. Segmented turboFLASH uses a gradient-echo sequence designed for short imaging times in combination with a segmented data acquisition method. Presaturation pulses were applied to eliminate the blood pool signal; the signal-to-noise ratio was assessed with a phantom. Standard hardware and image reconstruction methods were used. The breath-hold images consistently showed reduced ghosting and blurring from respiration. Because a very short echo time was used, segmented turboFLASH was relatively insensitive to dephasing caused by local field disturbances or flow. The authors conclude that, by reducing imaging times and eliminating respiratory artifact, segmented turboFLASH can be useful for performing cine studies of the heart and great vessels.