Experimental Campylobacter jejuni infection in the chicken: an animal model of axonal Guillain-Barré syndrome

OBJECTIVE

To develop and characterise an animal model of paralytic neuropathy after Campylobacter jejuni infection. Campylobacter infection precedes development of many cases of Guillain-Barré syndrome and is particularly associated with cases having prominent axonal degeneration. Understanding the pathogenesis of Guillain-Barré syndrome after C jejuni infection has been slowed by the lack of animal models.

METHODS

A spontaneous paralytic neuropathy is described that developed in chickens from the farms of four patients with Guillain-Barré syndrome. The production of paralytic neuropathy in chickens experimentally fed Campylobacter jejuni isolated from one of these patients is reported. The sciatic nerves of the spontaneously paralysed chickens were examined pathologically in teased fibres, in plastic embedded sections, and by electron microscopy. Two large groups of chickens were then fed cultures of a C jejuni (Penner type O:19) isolated from one of these patients.

RESULTS

The chickens with spontaneous paralysis had pathologically noninflammatory neuropathy. Pathology in the sciatic nerves ranged from no detectable changes to severe Wallerian-like degeneration. In the experimentally inoculated groups, an average of 33% of the chickens became paralysed. The median time after inoculation to paralysis was 12 days. The lesions found in the first few days of paralysis included nodal lengthening and paranodal demyelination. In those animals that survived for several days after onset of weakness, the pathology was dominated by extensive Wallerian-like degeneration. Animals that survived for weeks with no clinically apparent neuropathy had paranodal remyelination in some teased nerve fibres, reflecting earlier paranodal demyelination.

CONCLUSION

Experimental inoculation with C jejuni may provide a new model for understanding some forms of Guillain-Barré syndrome.

Early nodal changes in the acute motor axonal neuropathy pattern of the Guillain-Barré syndrome

The axonal patterns of Guillain-Barré syndrome, associated in many cases with antecedent Campylobacter jejuni infection, are now recognized as frequent causes of acute flaccid paralysis in some regions of the world. This study examined ultrastructurally the PNS of seven cases of the acute motor axonal neuropathy form of Guillain-Barré syndrome. In this disorder previous studies of advanced cases have found Wallerian-like degeneration of motor fibres in the spinal roots and peripheral nerves, with little lymphocytic inflammation or demyelination. The present study was focused on identifying early changes and establishing the sequence of changes. By electron microscopy the earliest and mildest changes consisted of lengthening of the node of Ranvier with distortion of the paranodal myelin, and in some instances with breakdown of the outermost myelin terminal loops. At this stage many nodes had overlying macrophages which extended their processes through the Schwann cell basal lamina covering the node and apposed the axolemma. Macrophage processes then extended beneath the myelin terminal loops, and the whole macrophage entered the periaxonal space at the paranode. Macrophage processes dissected the axon from the adaxonal Schwann cell plasmalemma and the macrophages advanced into the internodal periaxonal space, where they typically surrounded a condensed-appearing axon. At this stage the adaxonal Schwann cell cytoplasm regularly degenerated and disappeared, so that the periaxonal space was bounded by the innermost myelin lamella, and the axolemma of many fibres could not be seen. The internodal myelin sheath and the abaxonal Schwann cell cytoplasm remained normal. This arrangement appeared to be stable for some time, but in many fibres the axon subsequently underwent Wallerian-like degeneration. By interfering with impulse conduction, these nodal and periaxonal changes may explain paralysis in some pathologically mild cases. In addition, at early stages, these changes may be reversible, thus explaining the rapid recovery of some patients who become paralysed with acute motor axonal neuropathy. These observations, taken together with previous studies, suggest that acute motor axonal neuropathy is an antibody- and complement-mediated disorder in which the relevant epitopes are present on the nodal and internodal axolemma.

Pathology of the motor-sensory axonal Guillain-Barré syndrome

The concept of a severe motor-sensory neuropathy of acute onset caused by an immune attack on the axon ("axonal" Guillain-Barré syndrome) has been advanced primarily based on electrodiagnostic and limited pathological data, but remains controversial. At autopsy some cases demonstrate unusually severe inflammatory demyelinating neuropathy. There are conflicting data about whether antecedent Campylobacter jejuni infection is associated with "axonal" Guillain-Barré syndrome. We report 4 individuals from Hebei Province, China, who died 7, 7, 18, and 60 days after onset of a syndrome diagnosed clinically as Guillain-Barré syndrome. High titers of antibodies recognizing C. jejuni, consistent with recent infection, were found in the 2 patients tested. At autopsy the 3 with early disease had ongoing wallerian-like degeneration of fibers in the ventral and dorsal roots and in the peripheral nerves, with only minimal demyelination or lymphocytic infiltration. All 3 had numerous macrophages in the periaxonal space of myelinated internodes, and rare intraaxonal macrophages as well. Examination of the patient having the syndrome for 60 days confirmed the extensive loss of large fibers in the spinal roots and nerves, and the paucity of demyelination and remyelination. These observations confirm predictions that some patients with severe motor-sensory Guillain-Barré syndrome, as defined clinically, have predominantly axonal lesions of both motor and sensory fibers, even in the early stages of the disease, and that axonal Guillain-Barré syndrome can follow C. jejuni infection. The pathology supports the possibility that such cases of motor-sensory axonal Guillain-Barré syndrome represent the most severe end of a spectrum of immune attack directed toward epitopes on the axon.

Guillain-Barré syndrome in northern China. The spectrum of neuropathological changes in clinically defined cases

The pathology of the Guillain-Barré syndrome remains controversial, and autopsied cases available for study by contemporary techniques are uncommon. Large numbers of cases clinically diagnosed as Guillain-Barré syndrome occur in northern China. In this study we examined the neuropathological changes in 12 autopsied cases from Hebei Province, China. Eleven died early in the course of their disease. In all cases tissue was specially handled and fixed for electron microscopy and for immunocytochemistry. Three of these 12 cases had typical acute inflammatory demyelinating polyneuropathy (AIDP) with lymphocytic infiltration and macrophage-mediated demyelination, reproducing the pathological picture most often reported in Guillain-Barré syndrome in North America, Europe, and Australia. Six cases had predominantly axonal involvement, characterized by Wallerian-like degeneration of nerve fibres, with only minimal demyelination and with minimal inflammation in five. Three cases, even though paralysed at the time of death, had only very mild changes in the spinal roots and sciatic nerves. Within the group of six predominantly axonal cases, there were important differences both in the severity of the abnormalities and in the classes of fibres involved. Three cases had extensive Wallerian-like degeneration of sensory as well as motor fibres [acute motor-sensory axonal neuropathy (AMSAN)], while in the other three cases the fibre degeneration affected the motor nerve fibres almost exclusively. These latter cases establish a structural basis for the clinical and electrophysiological picture termed the acute motor axonal neuropathy (AMAN) pattern. In both the AMAN and the AMSAN patterns, a prominent feature was the presence of macrophages within the periaxonal space, surrounding or displacing the axon, and surrounded by an intact myelin sheath. These studies show that the early pathological changes in cases clinically diagnosed as the Guillain-Barré syndrome are diverse and not restricted to the well-known pattern of AIDP, and that the predominant pathological patterns may differ in different parts of the world. The differences in pathological findings between acute inflammatory demyelinating polyneuropathy and the axonal patterns are likely to reflect differences in the pathogenetic mechanisms. The periaxonal macrophages in the axonal patterns suggest that an important epitope may be localized to the axolemma or periaxonal space. The mild cases indicate that severe paralysis can occur early in Guillain-Barré syndrome without prominent structural changes along the nerve, suggesting that physiological block or nerve terminal changes may be implicated.

Perception of fluoroscopy last-image hold

Last-image hold (LIH) is used in x-ray fluoroscopy systems as a convenience and dose savings feature. In the case of an image sequence, temporal filtering in the human visual system (HVS) reduces perceived noise. In the case of a constant, single image frame, this phenomenon is not present: the image looks noisier, and low-contrast objects disappear. Using low-contrast, stationary cylinder and disk phantoms in noise, perception of single frames are compared with that of conventional 30 acq/s continuous fluoroscopy (continuous). The dose of continuous is fixed at Q/acq, and the dose of single-frame presentations is varied in order to determine an "equivalent-perception dose" for a paired-comparison task. The equivalent-perception dose depends upon the shape and size of an object. As cylinder diameter increases from 1 to 21 pixels, the equivalent-perception dose decreases from 4.6 to 2.8 Q/acq. At equal equivalent-perception dose values, the relationship between cylinder and disk diameters are determined; a cylinder diameter of 10 pixels is roughly equivalent to a disk diameter of 20 pixels. For interventional angiography, an average equivalent-perception dose of approximately 3.5 Q/acq for a single-frame presentation is predicted. Thus processing by the HVS effectively reduces noise variance by a factor of 3.5, corresponding to an effective averaging time of 3.5 frames or 120 ms. Several variance reduction techniques are suggested to create an LIH frame having perception equal to the fluoroscopy sequence.

Model for perception of pulsed fluoroscopy image sequences

Pulsed fluoroscopy at reduced frame rates can be used to lower x-ray dose with equivalent detection (hereafter called equivalent perception) of low-contrast, stationary objects. Experimentally average dose savings of 22%, 38%, and 49%, for pulsed fluoroscopy at 15, 10, and 7.5 acquisitions per second, respectively, are documented. Dose savings depend on object size, with fewer savings for smaller objects. To explain these data, we extend the framework of an ideal observer with three models for the spatiotemporal response of the human visual system (HVS). They are model 1, separable; model 2, nonseparable; and model 3, nonseparable with internal observer noise. With no free parameters, model 1 predicts the average dose savings within a 3% difference but does not describe the effect of object size. Models 2 and 3 explain the influence of size, and model 3, with a single free parameter, fits the measurements best. Perception of pulsed fluoroscopy is thus well described in terms of spatiotemporal processing by the HVS.

Perceptual comparison of pulsed and continuous fluoroscopy

Pulsed fluoroscopy (hereafter called pulsed) at reduced acquisition rates, typically 15 acq/s (pulsed-15), is proposed to reduce x-ray dose in interventional procedures. However, since the human visual system (HVS) acts as a temporal low-pass filter that interacts with such acquisitions, the proper dose for pulsed must be obtained in perception experiments. We determine the dose for low-frame-rate pulsed that gives visualization equivalent to that of conventional 30 acq/s fluoroscopy, hereafter called continuous. Computer-generated phantoms are used. They consist of stationary, low-contrast disks on a flat background containing Poisson noise that mimics quantum noise in fluoroscopy. Image sequences are displayed on the video tachistoscope, a device with considerable display flexibility. Three experimental paradigms are used. (1) In a paired-comparison study, pulsed and continuous are displayed side-by-side on the same monitor, and the visibility of a contrast detail phantom is compared. (2) Using this same display, subjects record the minimally detectable disk contrast (the min-contrast measurement). (3) In a four-alternative forced-choice experiment, a disk is placed in one of four positions, and the subject determines the position of the disk. The methods are complementary--the forced-choice experiment properly eliminates the subjectivity of the observer threshold while the paired-comparison study is much more time efficient. With regard to pulsed and continuous comparisons, remarkable similarity is found between the supra-threshold experiments (1 and 2) and the detectability experiment (3); i.e., the average absolute differences in the equivalent-perception dose as determined by the three measures is approximately 3%. No difference is found between interlaced and noninterlaced display. A relatively small dependence of dose savings on disk size is found with larger disks giving increased dose savings. Average dose savings of 22%, 38%, and 49% are found for pulsed-15, pulsed-10, and pulsed-7.5, respectively.

[Impact on lymphocyte transformation with BCG different strains vaccination]

The authors compared the influence of BCG produced strains D1 and D2 vaccination on lymphocyte transformation of spleen lymphocytes from guinea pigs. The guinea pigs were divided into D1 strain vaccinated group, D2 strain vaccinated group and nonvaccinated group. The response of lymphocyte transformation of spleen lymphocytes from the three groups to the stimulation of PHA, ConA and PPD were compared at 3, 4, and 5 weeks following vaccination. It was shown that the lymphocyte proliferation of D2 strain vaccinated guinea pigs to the stimulation of PHA, ConA and PPD was higher than that of D1 strain vaccinated. The most sensitivity of immunized lymphocytes to PHA and ConA was at 4 weeks following vaccination. Lymphocytes proliferation to PPD at 5 weeks following vaccination was higher than that at 4 weeks. This study showed that the ability of D2 strain to elicit the CMI was more than that of D1 strain.

Antisense oligonucleotide blocks progesterone-induced lordosis behavior in ovariectomized rats

Antisense oligonucleotides were utilized to interfere with the synthesis of progesterone receptor. A specific aODN was shown to decrease significantly the levels of PR in the T47D cell line known to express the PR gene. The molecule described was proved to be effective in hindering the effect of progesterone on target gene expression in T47D cells. The aODN was then utilized in an in vivo study to test its efficacy on the female rat sex behavior. Its injection in the ventromedial hypothalamus significantly inhibited the estrous responsiveness induced by progesterone. This study provides a clear demonstration of the full involvement of PR in the manifestation of lordosis behavior and demonstrates the activity of an aODN as antiprogestative.

A stability study of an opacity standard

Three procedures were adopted to increase the stability of the Chinese National Opacity Standard so that the change in opacity was within a range of +/- 5%.

Microsurgical reversal of female sterilization. Long-term follow-up of 117 cases

A prospective study of 117 consecutive microsurgical reversals of female sterilization from April 1981 to December 1984 was carried out to determine which factors affected the pregnancy outcome. Nylon sutures, 8-0, were placed through the muscularis and mucosal layers. A short abdominal incision was made. The patients were followed for 3.5 to 7.0 years. The term delivery, intra-uterine pregnancy, spontaneous abortion and ectopic pregnancy rates were 81.2%, 83.8%, 1.7% and 1.7%, respectively; two ectopic pregnancies occurred 14 and 24 months after the reversal procedures. We found that the time interval between sterilization and reversal and the methods of sterilization affected the pregnancy outcome. The success rate with intervals of less than five years was much higher than with intervals of more than five years; Pomeroy cases were more reversible than Uchida cases. We did not observe any influence of the anastomosis site on the pregnancy results. The term delivery rates for isthmus-isthmus, isthmus-ampulla and ampulla-ampulla anastomoses were 78.8%, 80.0% and 84.6%, respectively. Patients should be followed for two years at least to determine the pregnancy outcome as well as the occurrence of ectopic pregnancy.