Imre Repa

Hexose phosphorylation and the putative calcium channel component Mid1p are required for the hexose-induced transient elevation of cytosolic calcium response in Saccharomyces cerevisiae

Saccharomyces cerevisiae responds to environ‐mental stimuli such as an exposure to pheromone or to hexoses after carbon source limitation with a transient elevation of cytosolic calcium (TECC) response. In this study, we examined whether hexose transport and phosphorylation are necessary for the TECC response. We found that a mutant strain lacking most of the known hexose transporters was unable to carry out the TECC response when exposed to glucose. A mutant strain that lacked the ability to phosphorylate glucose was unable to respond to glucose addition, but displayed a normal TECC response after the addition of galactose. These results indicate that hexose uptake and phosphorylation are required to trigger the hexose‐induced TECC response. We also found that the TECC response was significantly smaller than normal when the level of environmental calcium was reduced, and was abolished in a mid1 mutant that lacked a subunit of the high‐affinity calcium channel of the yeast plasma membrane. These results indicate that most or all of the TECC response is mediated by an influx of calcium from the extracellular space. Our results indicate that this transient increase in plasma membrane calcium permeability may be linked to the accumulation of Glc‐1‐P (or a related glucose metabolite) in yeast.

A Review on Radiogenic Lhermitte's Sign *

Radiation myelopathy is a rare, but extremely serious side-effect of radiotherapy. Recovery from radiation-induced motor sequelae is rare, whereas, the regeneration of sensory losses is relatively frequent. Among the sensory radiogenic injuries of the spinal cord, Lhermitte’s sign (LS) is most frequent. This review describes the clinical picture and diagnostic imaging signs of radiogenic LS. There have been only a few studies on large patient groups with radiogenic LS, demonstrating a rate of occurrence of 3.6–13%, relating mainly to mantle irradiation or the radiotherapy of head and neck tumors. These cases typically manifest themselves 3 months following radiotherapy and gradually disappear within 6 months. Only 3 LS cases have been described in the English literature with extraordinarily severe symptoms lasting for more than 1 year. MRI, a sensitive tool in the detection of demyelination, failed to reveal any pathological sign accompanying radiogenic LS. However, positron emission tomography demonstrated increased [18F]fluorodeoxyglucose accumulation and [15O]butanol perfusion, but a negligible [11C]methionine uptake in the irradiated spinal cord segments in patients with long-standing LS. These imaging data are suggestive of a close direct relationship between the regional perfusion and metabolism of the spinal cord, very much like the situation in the brain. We postulate that an altered, energy-demanding conduction along the demyelinated axons of patients with chronic radiogenic LS may explain the increased metabolism and perfusion.

Angiography effectively supports the diagnosis of hepatic metastases in medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) belongs in the group of neuroendocrine tumors with early lymphatic and hepatic dissemination. A high rate of undetectable metastases is hypothesized to be responsible for the frequent mismatch between the apparent relatively small tumor burden and the elevated plasma tumor marker level.

Lung Water and Proton Magnetic Resonance Relaxation in Preterm and Term Rabbit Pups: Their Relation to Tissue Hyaluronan

The present study was performed to investigate simultaneously total lung water, T1 and T2 relaxation times, and hyaluronan (HA) in preterm and term rabbits. Attempts were also made to establish the relationship of HA to total lung water and to T2-derived motionally distinct water fractions. Experiments were performed in fetal Pannon white rabbit pups at gestational ages of 25, 27, 29, and 31 d and at a postnatal age of 4 d. Lung tissue water content (desiccation method), T1 and T2 relaxation times (H1-NMR method), and HA concentration (radioassay) were measured, and free and bound water fractions were calculated by using multicomponent fits of the T2 relaxation curves. Lung water content and T1 and T2 relaxation times were highest at a gestational age of 27 d and then declined steadily during the whole study period. Similar trends and time courses were seen for the fast and slow components of the T2 relaxation curve. The T2-derived free water fraction remained unchanged at a gestational age of 25–29 d (∼67%), but increased progressively to a value of 78.5 ± 7.9% at 31 d (p < 0.001) and to 83.4 ± 9.4% at the postnatal age of 4 d (p < 0.01). Opposite changes occurred in the bound water fraction. Lung HA concentration decreased with advancing gestation from 870.8 ± 205.2 μg/g dry weight at 25 d to 162.6 ± 32.4 μg/g dry weight at 31 d (p < 0.001), but it was increased 2-fold postnatally. HA correlated positively with total lung water (r = 0.39;p < 0.001) but not with the bound water fraction. It is suggested that the physiologic lung dehydration is associated with macromolecule-related reorganization of lung water and that the role of HA in this process needs to be further investigated.

PET identifies transitional metabolic change in the spinal cord following a subthreshold dose of irradiation.

Positron emission tomographic (PET) investigations were performed to obtainin vivo information on symptomless radiation-induced pathological changes in the human spinal cord. PET investigations were carried out prior to radiotherapy and during the regular follow-up in an early hypopharyngeal cancer patient (the spinal cord was irradiated with a biologically effective dose of 80 Gy2), with [18F]fluorodeoxyglucose (FDG), [11C]methionine and [15O]butanol as tracers; radiosensitivity and electroneuronographic (ENG) studies were also performed. A very low background FDG accumulation (mean standardized uptake values, i.e. SUV: 0.84) was observed in the spinal cord before the initiation of radiotherapy. An increased FDG uptake was measured 2 months after the completion of radiotherapy (mean SUV: 1.69), followed by a fall-off, as measured 7 months later (mean SUV: 1.21). By 44 months after completion of irradiation, the FDG accumulation in the irradiated segments of the spinal cord had decreased to a level very close to the initial value (mean SUV: 1.11). The simultaneous [15O]butanol uptake results demonstrated a set of perfusion changes similar to those observed in connection with the FDG accumulation. The patient exhibited an extremely low [11C]methionine uptake within the irradiated and the nonirradiated spinal cord during the clinical course. She has not had any neurological symptoms, and the results of central ENG measurements before radiotherapy and 2 months following its completion proved normal. Radiobiological investigations did not reveal unequivocal signs of an increased radiosensitivity. A transitory increased spinal cord FDG uptake following radiotherapy may be related to the posttherapeutic mild inflammatory and regenerative processes. The normal [11C]methionine accumulation observed is strong evidence against intensive cell proliferation. The high degree of normalization of the temporarily increased FDG uptake of the irradiated spinal cord segments by 44 months is in good agreement with the results of monkey studies, which demonstrated a nearly complete recovery from radiation-induced spinal cord injury.

Investigations into the time- and dose-dependent effect of fumonisin B1 in order to determine tolerable limit values in pigs

Fumonisin B1 (FB1), a metabolite of Fusarium moniliforme, is known to cause oesophageal cancer in humans (carcinogen class 2B in the IARC classification), pulmonary oedema in pigs, and encephalomalacia in horses [Riley et al., Nat. Toxins 4 (1996) 3–15]. Experiments were carried out with weaned piglets, in order to study the dose- and time-dependent effect of FB1. Fungal culture of Fusarium moniliforme was added to the diet so that the FB1 exposure was 0, 10, 20 and 40 mg/kg feed (ppm) for 4 weeks; 0, 1, 5 and 10 ppm for 8 weeks; and finally 0, 1, 5, and 10 ppm for 20 weeks. None of the toxin concentrations and the periods examined had any significant effect on feed consumption, body weight gain, and feed conversion of weaned pigs. The haematological parameters proved to be within the range of the physiological limit values. When applying higher doses (20 and 40 ppm), there was a time- and dose-dependent increase in the AST activities. In case of lower doses (1 and 5 ppm) some of the blood parameters (AST, ALT, ALKP, CREA) of the animals that developed toxin-related gross and histopathological changes were outside the physiological range. One ppm dietary FB1 concentration was the lowest one that failed to increase the SA/SO ratio significantly. Ten to 40 ppm FB1 fed for 4 weeks caused mild or severe pulmonary oedema, while even lower doses (1–10 ppm) fed for 2–20 weeks caused irreversible fibrosis in the lung (detected by CT examination, dissection, and histopathology).

Brain Adaptation to Water Loading in Rabbits as Assessed by NMR Relaxometry

The present study was undertaken to investigate the cerebral adaptation to hypoosmolar stress in adult Pannon white rabbits by applying proton nuclear magnetic resonance relaxometry. Progressive hyponatremia was induced by combined administration of hypotonic dextrose in water and 8-deamino-arginine vasopressin over a hydration period of 3, 24, and 48 h. Each group comprised five animals. After completing the hydration protocols, blood was taken to determine plasma osmolality (freezing point depression) and sodium concentration (ion-selective electrode) and, at about the same time, T2-weighted images were made. After the in vivo measurements, the animals were killed and brain tissue samples were obtained to measure water content (desiccation method) and T1 and T2 relaxation times (proton nuclear magnetic resonance method). Free and bound water fractions were calculated by using multicomponent fits of the T2 relaxation curves. It was shown that brain water content and T1 relaxation time remained unchanged despite the progressing hyponatremia. By contrast, T2 relaxation time increased steadily from the control value of 100.2 ± 7.7 ms to attain its maximum of 107.5 ± 8.5 ms (p< 0.05) after 48 h of hydration. Using biexponential analysis, fast and slow components of the T2 relaxation curve could be distinguished that corresponded to the bound (T21) and free (T22) water fractions. In response to hyponatremia, the bound water fraction was markedly depressed from 6.5 ± 3.0% to 3.6 ± 0.9% (3 h, p< 0.05) and 3.9 ± 0.8% (24 h, p< 0.05); then it approached the initial value of 5.3 ± 2.5% by the end of the hydration period of 48 h. It is concluded that restructuring of brain water is a contributory factor to the successful adaptation to hypotonic environment.

Use of Computed Tomography and Histopathologic Review for Lung Lesions Produced by the Interaction Between Mycoplasma hyopneumoniae and Fumonisin Mycotoxins in Pigs

Mycoplasma hyopneumoniae has a primary role in the porcine respiratory disease complex (PRDC). The objective of this study was to determine whether fumonisin mycotoxins influence the character and/or the severity of pathological processes induced in the lungs of pigs by Mycoplasma hyopneumoniae. Four groups of pigs (n = 7/group) were used, one fed 20 ppm fumonisin B1 (FB1) from 16 days of age (group F), one only infected with M. hyopneumoniae on study day 30 (group M), and a group fed FB1 and infected with M. hyopneumoniae (group MF), along with an untreated control group (group C). Computed tomography (CT) scans of infected pigs (M and MF) on study day 44 demonstrated lesions extending to the cranial and middle or in the cranial third of the caudal lobe of the lungs. The CT images obtained on study day 58 showed similar but milder lesions in 5 animals from group M, whereas lungs from 2 pigs in group MF appeared progressively worse. The evolution of average pulmonary density calculated from combined pixel frequency values, as measured by quantitative CT, was significantly influenced by the treatment and the age of the animals. The most characteristic histopathologic lesion in FB1-treated pigs was pulmonary edema, whereas the pathomorphological changes in Mycoplasma-infected pigs were consistent with catarrhal bronchointerstitial pneumonia. FB1 aggravated the progression of infection, as demonstrated by severe illness requiring euthanasia observed in 1 pig and evidence of progressive pathology in 2 pigs (group MF) between study days 44 and 58.

Water content and proton magnetic resonance relaxation times of the brain in newborn rabbits

The present study, using proton nuclear magnetic resonance relaxation(H1 NMR) measurements, was undertaken to quantitate water fractions with different mobility in the brain tissue obtained from New Zealand White rabbit pups. Serial studies were carried out at the postnatal age of 0-1, 24, 48, 72, and 96 h in pups nursed with their mothers and suckling ad libitum (group I) and in those pups separated from their mothers and completely withheld from suckling (group II). Tissue water content(desiccation method) and T1 and T2 relaxation times (H1 NMR method) were measured. Free, loosely bound, and tightly bound water fractions were calculated by applying multicomponent fits of the T2 relaxation curves. It was demonstrated that brain water content and T1 and T2 relaxation times did not change with age in the suckling pups. In pups withheld from suckling brain water decreased from 89.4 ± 0.5% at birth to 87.7 ± 0.1% at the age of 96 h (p < 0.05), T1 remained unchanged, and there was a significant fall in T2 by the age of 72 h (188 ± 12 versus 178 ± 4 ms,p < 0.05) and 96 h (171 ± 6 ms, p < 0.01). Partition of brain water into bound and free fractions as derived from biexponential fits of T2 decay curve showed that the percent contribution of bound water fraction in pups of group I fell progressively from 61% at birth to 3% at the age of 72-96 h (p < 0.05). This fall was accelerated by the complete deprival of fluid intake, and the level of about 4% could be attained as early as the age of 24 h. Triexponential analysis of T2 relaxation curves revealed that the loosely bound fraction (middle component) predominated over the free (slow component) and the tightly bound (fast component) water fractions. In response to withholding fluid intake, the free water fraction increased 4-fold at the expense of tightly bound brain water. It is concluded that the majority of neonatal brain water is motion-constrained. The free, the loosely bound, and the tightly bound water fractions appear to be interrelated; from the brain water store water can be released to supply free water for volume regulation.

Overview of large animal myocardial infarction models (review).

There are several experimental models for the in vivo investigation of myocardial infarction (MI) in small (mouse, rat) and large animals (dog, pig, sheep and baboons). The application of large animal models raises ethical concerns, the design of experiments needs longer follow-up times, requiring proper breeding and housing conditions, therefore resulting in higher cost, than in vitro or small animal studies. On the other hand, the relevance of large animal models is very important, since they mostly resemble to human physiological and pathophysiological processes. The first main difference among MI models is the method of induction (open or closed chest, e.g. surgical or catheter based); the second main difference is the presence or absence of reperfusion. The former (i.e. reperfused MI) allows the investigation of reperfusion injury and new catheter based techniques during percutaneous coronary interventions, while the latter (i.e. nonreperfused MI) serves as a traditional coronary occlusion model, to test the effects of new pharmacological agents and biological therapies, as cell therapy. The reperfused and nonreperfused myocardial infarction has different outcomes, regarding left ventricular function, remodelling, subsequent heart failure, aneurysm formation and mortality. Our aim was to review the literature and report our findings regarding experimental MI models, regarding the differences among species, methods, reproducibility and interpretation.