Biomedical subjects
Publications and source records attributed to M Shibayama.
The structure factor of weakly charged polymer gels under external mechanical strain is calculated considering both thermal and frozen concentration fluctuations as well as the screening of ionic interactions. The butterfly patterns are discussed based on our result.
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To determine whether embryonic spinal cord transplants retained the ability to prevent retrograde death of Clarke's nucleus (CN) neurons if supplied after a delay, we hemisected adult rats at the T8 spinal cord segment and placed transplants of fetal tissue into the hemisection cavity immediately or up to 14 days later. Transplants provided in the first 7 days after injury prevented virtually all of the 30% loss of CN neurons at L1 ipsilateral to hemisection that occurs without a transplant. Transplants supplied at 14 days post-hemisection were ineffective. Because prevention of retrograde neuron death is one mechanism by which transplants may contribute to locomotor recovery after spinal cord injury, this window of effectiveness should be considered in the design of clinical trials.
In the present investigation, we studied whether neurotrophin-3 (NT-3) contributes to the rescue of axotomized Clarke's nucleus (CN) neurons in adult rats. A significant (24%) loss of CN neurons occurred at L-1 ipsilateral to T-8 hemisection by 14 days, which reached 31% at 2 months and then stabilized. Axotomized CN neurons had also atrophied by 14 days, but mean cell size did not decrease further. Animals that received gelfoam soaked in nerve growth factor, brain derived neurotrophic factor, or ciliary neurotrophic factor at the lesion site also showed a 30% neuron loss at 2 months, and a 40% reduction in average cell area. Rats receiving NT-3 showed a 15% neuron loss, which was not improved by additional neurotrophins in combination with NT-3. None of the treatments prevented neuron atrophy. Bioassay of the gelfoam showed that NT-3 bioactivity remained at 5 days after surgery but not at 14 days. Additional rats with hemisections that received NT-3 continuously via mini-pump for 2 months showed a 15% neuron loss, the same as with NT-3 given via gelfoam. These results indicate that even limited exposure of axotomized CN neurons to NT-3 produces permanent rescue of 50% of the neurons. The virtually complete rescue that we had previously observed with transplants of fetal central nervous system (CNS) tissues may, therefore, be due at least in part to NT-3, but the exogenous administration of a single neurotrophic factor or a combination of neurotrophic factors is less effective than transplants in producing long-term survival of axotomized CNS neurons.
Intraperitoneal inoculation of axenically cultured Entamoeba histolytica trophozoites constitutes an easy to perform, highly reproducible procedure for inducing amebic liver abscesses in hamsters. Efficiency in abscess production (95% of infected animals after 1 week) was similar to data reported using direct intrahepatic or intraportal inoculation. The morphological sequence of infection shows that amebas in the peritoneal cavity initially produce a large exudate constituted mainly of acute inflammatory cells. These cells form a rim of polymorphonuclear leukocytes surrounding the amebas, which adhere to the trophozoite and can sometimes be observed polarized to one end of the parasite, suggesting capping of surface receptors. Early stages are also characterized by the production of distant inflammatory reactions in the hepatic portal spaces. At 6 h postintraperitoneal inoculation, larger foci of inflammatory reactions surrounding amebas are developed in the peritoneum, extending to and damaging the liver surface membranes as well as the serosa of other internal organs. Thereafter, tissue damage progresses deeper into the liver parenchyma, and a few days later, coalescing granulomas and large necrotic areas are observed in the liver tissue. Based on the present morphological time-sequence study, we suggest that inflammatory cells associated with E. histolytica trophozoites play an important role in commencing the damage of liver sheaths and producing the subsequent parenchymal lesions. The simplicity and reliability of this model are important factors to consider when large numbers of experimentally induced amebic liver abscesses are needed.
Fetal transplants rescue axial muscle representations in M1 cortex of neonatally transected rats that develop weight support. J. Neurophysiol. 80: 3021-3030, 1998. Intraspinal transplants of fetal spinal tissue partly alleviate motor deficits caused by spinal cord injury. How transplants modify body representation and muscle recruitment by motor cortex is currently largely unknown. We compared electromyographic responses from motor cortex stimulation in normal adult rats, adult rats that received complete spinal cord transection at the T8-T10 segmental level as neonates (TX rats), and similarly transected rats receiving transplants of embryonic spinal cord (TP rats). Rats were also compared among treatments for level of weight support and motor performance. Sixty percent of TP rats showed unassisted weight-supported locomotion as adults, whereas approximately 30% of TX rats with no intervention showed unassisted weight-supported locomotion. In the weight-supporting animals we found that the transplants enabled motor responses to be evoked by microstimulation of areas of motor cortex that normally represent the lumbar axial muscles in rats. These same regions were silent in all TX rats with transections but no transplants, even those exhibiting locomotion with weight support. In weight-supporting TX rats low axial muscles could be recruited from the rostral cortical axial representation, which normally represents the neck and upper trunk. No operated animal, even those with well-integrated transplants and good weight-supported locomotion, had a hindlimb motor representation in cortex. The data demonstrate that spinal transplants allow the development of some functional interactions between areas of motor cortex and spinal cord that are not available to the rat lacking the intervention. The data also suggest that operated rats that achieve weight support may primarily use the axial muscles to steer the pelvis and hindlimbs indirectly rather than use explicit hindlimb control during weight-supported locomotion.
The purpose of the study was to evaluate the influence of hyperoxia and hypercapnia on respiration and metabolism during a steady-state exercise. Thirteen healthy subjects were examined during bicycle-ergometer rides at approximately 50% VO2max under four different breathing gas conditions: 1) room air (control); 2) 40% oxygen; 3) 3% carbon dioxide; 4) 40% oxygen and 3% carbon dioxide. Hyperoxia, with or without hypercapnia, decreased respiratory ventilation and carbon dioxide elimination significantly. On the other hand, oxygen uptake in hyperoxia was not significantly different from that of normoxia. Hypercapnia increased respiratory ventilation more than 30% compared to normocapnia, but it did not change oxygen uptake and carbon dioxide elimination significantly.
A 43-year-old patient with rice-induced bronchial asthma was first admitted to our hospital for developing bronchial asthma induced by mite and house dust. At that time, there was no sign of allergic response to rice. Two years later, he was readmitted in an emergency state, with a severe attack of bronchial asthma. This time, however, the result of immunoglobulin E (IgE)-radioallergosorbent test (RAST) for rice was positive, with those to mite and house dust were unexpectedly negative. The causative factors and pathological mechanisms of various kinds of food allergies still remain unknown. The patient is now followed up in an ambulatory setting, and has been eating hypoallergenic rice with no bronchial asthma-induced attack. The present case, being an adult patient with severe grain-induced bronchial asthma previously allergic to mite and house dust, seems to be rather rare in the literature.
We encountered a patient with neuroblastoma showing remarkably high total LD activity (12,585 IU/l). His liver and heart function was normal. In the serum LD isoenzyme pattern, LD1 was increased, and LD2 extra band (LD2 ex) was observed on the negative pole side of LD2. However, LD2 ex was absent in erythrocytes of the patient, which demonstrates the exclusion of genetic factors. Neither the enzyme counter current method or immunofixation showed immune complexes, excluding anomalies. The LD isoenzyme in a metastatic lymphnode lesion before treatment showed increased LD1. The LD isoenzymes in the tissue, removed after 5 courses of chemotherapy, showed predominance of LD3 and absence of LD2 ex. Rapid decreases in the serum total LD activity and LD1 fraction and the disappearance of LD2 ex after chemotherapy suggest that these changes in the two LD fractions are associated with production of abnormal LD (LD2 ex) by the tumor.
To evaluate the effect of glycerol, thirty-two patients with brain tumor were directed to the study, including 17 gliomas and 15 meningiomas. Blood flow before and after the administration of glycerol were measured with Xe CT. Glioma was significantly hypo-perfused. The peritumoral edema of glioma and meningioma were also hypo-perfused. On the other hand, Meningioma was significantly hyper-perfused. After the administration of glycerol, blood flows were increased except for glioma. We suggested that, vascular responses to glycerol was different in the two tumor types. The steal phenomena of blood flow might occur in glioma.
Our study was performed to find out cerebrovascular reactivity post acetazolamide administration in patients with peritumoral edema. Adult patients (n = 9) underwent CBF measurement by 99mTc-HMPAO SPECT pre and post 1 gram i.v. acetazolamide. In all patients, this procedure was repeated once again within 10 days of performing tumor removal. Five of these patients also underwent CBF measurement pre and post 1 gram i.v. acetazolamide post surgery only using oxygen-15 labeled H2O PET. Asymmetry index (AI) was calculated as ratio of ROI counts in the peritumoral edematous area and symmetrical ROI on the contralateral normal hemisphere. The AI increased after acetazolamide in edematous gray matter post operatively though the resting AI remained almost same post operatively. AI in edematous white matter showed non-significant increase post operatively both at rest and after acetazolamide. Good linear correlation of AI between PET and SPECT was observed both in gray and white matter. The improvement of vascular reactivity in edematous gray matter after tumor removal suggests that mass effect not only reduces CBF but also suppresses vascular reactivity. White matter vascular reactivity in early post operative period is little improved, possibly due to factors other than mass effect i.e. excess water accumulation in white matter perivascular space.
Matrix metalloproteinases (MMPs) are important in various pathophysiological processes related with the tissue remodeling. We planned the experiments to determine whether MMPs participate in disruption and repair of the tissue following brain injury. We have studied induction of MMP-9, a 92 kilodalton (kDa) gelatinase, in traumatic brain tissue, which may be produced by brain residual cells. We speculate that MMP-9 plays a role in post-traumatic brain edema formation.
We assessed the cerebral blood flow (CBF) response to electrical stimulation of the contralateral forearm over the primary somatosensory cortex (S-I) in anesthetized cats. CBF was monitored continuously using laser-Doppler flowmetry (LDF). In the first set of experiments, the effects of varying stimulus frequency and intensity were examined. During stimulation, CBF in S-I was increased significantly. At high stimulus intensity, response reached a near-plateau level. In the second set of experiments, the CBF response after introduction of an intracerebral mass was investigated using a mechanical microballoon model to simulate an intracerebral hematoma. A microballoon was inserted into the ventral posterolateral nucleus of the thalamus (VPL). Following gradual balloon inflation, there was a rapid reduction in CBF response. We conclude that CBF regulation to neuronal activation is affected by stimulation parameters, and is impaired by an intracerebral mass obstructing the afferent sensory pathway.
One of the main drawbacks of experimental amebiasis is the lack of an adequate animal model for invasive intestinal lesions. Mongolian gerbils are useful because both intestinal and hepatic amebiasis can be produced experimentally with Entamoeba histolytica trophozoites. In this paper we show results obtained with in vivo and in vitro models of intestinal amebiasis in gerbils. We inoculated gerbils intracecally with monoxenic cultures of a highly virulent E. histolytica HM1:IMSS substrain. In the in vivo model an increase in mucus production was observed during the first 6 h of interaction. Microulcerative mucosal lesions appeared at 24-72 h postinoculation. Inflammatory infiltrate and edema of the lamina propria were associated with superficial foci of necrosis. At 96 h the cecal mucosa had an almost normal appearance and live amebas were no longer detected. In the in vitro model, early damage was detected in cecal strips mounted in Ussing chambers as a rapid fall in potential difference, short-circuit current, and transepithelial resistance that correlated with the extent of the microscopic lesions produced. The latter consisted of cellular edema and the appearance of small, translucent vacuoles at the base of epithelial cells. Further damage led to loss of intercellular junctions, destruction of interglandular epithelial cells, and edema of the lamina propria. The present results demonstrate that the gerbil is useful as an experimental model for the analysis of early stages of invasive intestinal amebiasis both in vivo and in vitro.
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A 47-year-old female with localized fibrous pleural mesothelioma arising from the visceral pleura of S2 of rt-upper lobe is reported. We demonstrated an indirect radiographic sign of pedunculation which was the change in position of the mass with the change in patient's position. The tumor was completely extirpated with a partial resection of the adjacent lung tissues through thoracotomy. Histopathologically, the tumor consisted of collagen fibers and small amount of fibroblast. Localized fibrous mesothelioma was recognized as benign with good prognosis. However, a few cases showing recurrence after resection were reported among them. So it was considered that this patient should be followed up carefully.
We measured serum 1,5 anhydroglucitol (1,5AG) levels by HPLC in 32 patients with liver cirrhosis, 32 with diabetes mellitus and 61 normal subjects. Serum 1,5AG was significantly lower in patients with diabetes mellitus and liver cirrhosis compared with that in normal subjects. Serum levels of type IV collagen were higher in patients with liver cirrhosis than in those without liver cirrhosis. A negative correlation was observed between serum 1,5AG and type IV collagen in patients with liver cirrhosis (r = -0.37, p < 0.05), but not in patients with diabetes mellitus. These data suggest that serum 1,5AG levels reflect the degree of liver cirrhosis.