Integrins α2ß1 and α11ß1 regulate the survival of mesenchymal stem cells on collagen I.

Although mesenchymal stem cells (MSCs) are the natural source for bone regeneration, the exact mechanisms governing MSC crosstalk with collagen I have not yet been uncovered. Cell adhesion to collagen I is mostly mediated by three integrin receptors - α1ß1, α2ß1 and α11ß1. Using human MSC (hMSC), we show that α11 subunit exhibited the highest basal expression levels but on osteogenic stimulation, both α2 and α11 integrins were significantly upregulated. To elucidate the possible roles of collagen-binding integrins, we applied short hairpin RNA (shRNA)-mediated knockdown in hMSC and found that α2 or α11 deficiency, but not α1, results in a tremendous reduction of hMSC numbers owing to mitochondrial leakage accompanied by Bcl-2-associated X protein upregulation. In order to clarify the signaling conveyed by the collagen-binding integrins in hMSC, we analyzed the activation of focal adhesion kinase, extracellular signal-regulated protein kinase and serine/threonine protein kinase B (PKB/Akt) kinases and detected significantly reduced Akt phosphorylation only in α2- and α11-shRNA hMSC. Finally, experiments with hMSC from osteoporotic patients revealed a significant downregulation of α2 integrin concomitant with an augmented mitochondrial permeability. In conclusion, our study describes for the first time that disturbance of α2ß1- or α11ß1-mediated interactions to collagen I results in the cell death of MSCs and urges for further investigations examining the impact of MSCs in bone conditions with abnormal collagen I.

Establishment of immortalized periodontal ligament progenitor cell line and its behavioural analysis on smooth and rough titanium surface.

Periodontal ligament (PDL) can be obtained from patients undergoing orthodontic treatment. PDL contains progenitor cells that can be expanded and differentiated towards several mesenchymal lineages in vitro. Furthermore, PDL-derived cells have been shown to generate bone- and PDL-like structures in vivo. Thus, PDL cells, combined with suitable biomaterials, represent a promising tool for periodontitis-related research and PDL engineering. Here, a new PDL cell line using lentiviral gene transfer of human telomerase reverse transcriptase (hTERT) was created. HTERT-expressing PDL cells showed similar morphology and population doubling time but an extended lifespan compared to the primary cells. In addition, PDL-hTERT cells expressed several characteristic genes and upon osteogenic stimulation produced a calcified matrix in vitro. When cultivated on two topographically different titanium scaffolds (MA and SLA), PDL-hTERT cells exhibited augmented spreading, survival and differentiation on smooth (MA) compared to rough (SLA) surfaces. These findings differ from previously reported osteoblast behaviour, but they are in agreement with the behaviour of chondrocytes and gingival fibroblasts, suggesting a very cell type-specific response to different surface textures. In summary, we report the testing of titanium biomaterials using a new PDL-hTERT cell line and propose this cell line as a useful model system for periodontitis research and development of novel strategies for PDL engineering.

Malignant lymphoma of the cranial vault in an HIV-positive patient: imaging findings.

We describe the CT and MR imaging findings in an HIV-positive patient with malignant non-Hodgkin's lymphoma of the cranial vault, a rare site for lymphoma involvement. Autopsy revealed lymphomatous bone lesions, lymphoma in the epidural space, and a large necrotic lymphoma in the soft tissue of the skull.

Initial and follow-up MR imaging findings in AIDS-related progressive multifocal leukoencephalopathy treated with highly active antiretroviral therapy.

BACKGROUND AND PURPOSE: Recent studies have shown the beneficial effect of highly active antiretroviral therapy (HAART) in AIDS-related progressive multifocal leukoencephalopathy (PML). The purpose of our study was to evaluate the initial and follow-up imaging findings and survival in patients with PML who were treated with HAART. METHODS: The clinical course and MR imaging findings on initial and follow-up MR studies in four consecutive AIDS patients with PML who were treated with HAART are described. RESULTS: Two patients were short-term survivors and died after 3 months. Two patients are still alive, with a survival time of 22 and 43 months, respectively. On initial MR studies, more extensive white matter changes were seen in the short-term survivors. Development of a mass effect and temporary enhancement (in one patient) was observed in two HAART responders on follow-up MR studies. Increased hypointensity on T1-weighted images with concomitant low signal on fluid-attenuated inversion-recovery fast spin-echo (FLAIR-FSE) images was seen in two responders, representing leukomalacia. Atrophic changes of the involved areas of the brain, consistent with burnt out PML lesions, were seen in two long-term survivors. In the short-term survivors, increased hypointensity was present on T1-weighted images with increased high signal on FLAIR-FSE images, representing progressive destructive disease. CONCLUSION: Our results suggest that a clinical and radiologic response can be seen in some patients with AIDS-associated PML on HAART while in others there may be no beneficial response. Development of a mass effect and temporary enhancement on MR images in the early phase of treatment might represent positive predictive factors for prolonged survival.

Primary central nervous system lymphoma in AIDS: a wider spectrum of CT and MRI findings.

Diagnosis of primary central nervous system lymphoma (PCNSL) in patients with AIDS based on radiological findings is still a challenging problem. Our purpose was to review the CT and MRI findings in PCNSL in our patients with AIDS and compare them with those reported in the literature. CT and MRI of 28 patients with AIDS and pathologically confirmed PCNSL were analysed retrospectively for the number of lesions, their site, size, density, signal intensity, contrast enhancement, oedema and mass effect. We found 82 lesions. On CT 45 lesions were found in 22 patients, whereas MRI revealed 66 in 20 patients. The lymphoma was solitary in 20 patients (29 %) and multiple in 20 (71%). Spontaneous haemorrhage was seen in 7 patients. Contrast-enhanced MRI showed no enhancement in 27.3 % (18/66) of the lesions. In one patient diffuse signal abnormalities in the white matter were seen on T2-weighted images. Our findings suggest that the previously described spectrum imaging characteristics of PCNSL has widened. Neuroradiologists should be aware of the variable appearance in patients with AIDS. Spontaneous haemorrhage, a non-enhancing lesion, or diffuse white matter changes do not exclude lymphoma in an immunocompromised patient.

Highly active antiretroviral therapy for patients with AIDS dementia complex: effect on MR imaging findings and clinical course.

BACKGROUND AND PURPOSE: Recent studies have reported the clinical improvement in patients with AIDS treated with a combination of antiretroviral regimens. The purpose of our study was to describe the effects of highly active antiretroviral therapy on MR images in patients with HIV encephalopathy and to compare the clinical course with follow-up neuroimaging studies. METHODS: Initial and follow-up MR imaging findings are described in four patients with AIDS dementia complex at baseline and after antiretroviral therapy, and correlated with clinical and immunologic findings. RESULTS: Initial MR imaging revealed white matter signal abnormalities on long-TR images without mass effect and without enhancement on postcontrast images, consistent with HIV encephalopathy. Lesions were located in the basal ganglia and posterior fossa in two patients. All four patients showed progression of white matter disease on the first follow-up MR scan (mean, 6 months). On subsequent scans, regression was seen in three patients and stabilization of white matter disease was observed in one patient. Increases in CD4+ count and decreases in viral load below the limit of quantification were present in all patients. CONCLUSION: Although our patient population was small, the results suggest that disease regression in patients with AIDS dementia complex after treatment with highly active antiretroviral therapy can be characterized and monitored by MR imaging.

Effect of heavy metal salts on the activity of rat liver and kidney catalase and lysosomal hydrolases.

The effects of Cu, Fe, Pb and Zn as well as of a Pb + Zn combination on the total, available and nonsedimentable (NS) activities of lysosomal and peroxisomal enzymes were examined. An activating influence on the total activities of liver acid phosphatase (AP) and cathepsin D was shown for Cu. In the kidney the heavy metals induced changes in the total activity only of catalase. The effect of Cu was inhibiting, while that of Pb and of the Pb + Zn combination was activating. Copper produced an increase of NS protease and AP activities in liver homogenates accompanied by a rapid release of latent AP from liver large-granule fractions. According to these data and to generally accepted criteria for assessment of the integrity of lysosomes, Cu can be regarded as a powerful labilizer of lysosomal membranes. This heavy metal induced such an effect on liver peroxisomes as well, a statement which is based on the enhancement of NS catalase activity. In the kidney, Pb and the Pb + Zn combination were shown to produce a significant lowering of NS catalase activity, indicating a stabilization of peroxisomes.

Effect of weightlessness on posture and movement control during a whole body reaching task.

Here are reported preliminary results of the "Synergy" experiment performed aboard the Russian orbital station "MIR" in July 1993 (Altair Mission). The experiment was carried out before, during, and after the space flight of two astronauts (S1 and S2). The duration of the flight was 21 days for S1 and 6 month for S2. The subjects were tested during preflight, inflight and postflight. The astronaut subjects were fixed on the ground by the feet. They were asked to pick up a box in front of them on the ground. Two velocities of movement and two distances of the target to be reached were tested. The movement of several small markers placed on the body was recorded on video tape. Results show that the shape of head and hand trajectories in the sagittal plane remains roughly the same during the flight in spite of the modification of mechanical constraints. Trajectory invariance does not result in joint angular displacement invariance. These data indicate that the planning of the movement takes place in terms of head and hand trajectories rather than joint rotations as it was previously suggested for simple arm reaching movement.

Effect of different factors modifying the activity of some enzyme systems of the endoplasmic reticulum on the sensitivity of cell organelles against the damaging action of chemical agents. II. Studies with chlorpromazine, 2,4-dinitrophenol, phenobarbital and DDT.

Further investigations on the effect of different stress factors on the stability of intracellular membranes were carried out. Large granule fractions derived from livers of sleep-deprived and dehydrated rats and subjected to preincubation at 37 degrees and pH 5 were shown to release latent acid phosphatase with a delayed rate indicating an increased lysosomal stability towards acid media conditioning. Lysosomes of such animals, however, were found to be more sensitive to mechanical treatments (homogenization procedure in this case) than that of controls, a conclusion made on the basis of enhanced "free" and nonsedimentable phosphatase activities in liver homogenates. The stress factors which previously were included in the group of modifiers of the activity of the endoplasmic reticulum-located enzymes caused some changes in the action of certain chemicals on membranes. Earlier such changes were elicited for carbon tetrachloride and only on low-temperature-conditioned rats for chlorpromazine. The present results show that stress factors studied result in deviations (different in extent and in direction) from the usual effects of chlorpromazine, 2,4-dinitrophenol, phenobarbital and DDT on liver lysosomes and peroxisomes.

On the metabolic characteristics of Shigella flexneri X Escherichia coli, devoid of ability for intracellular multiplication in epithelial cells. III. Oxygen uptake and dehydrogenase activity.

The oxygen uptake and dehydrogenase activity of avirulent xyl+ and xyl- str hybrids (KCP-), obtained from virulent strains Sh. flexneri (Sh. flexneri 222 5 a and Sh. flexneri M42-432a) and donor strain E. coli AB 313, devoid of ability for intracellular multiplication in epithelial cells are studied. Some tricarboxylic acid intermediates, hexoses and pentoses were used as substrates. A definite tendency has been established, indicating a decreased rate of oxygen consumption and dehydrogenase activity of the hybrids, compared to the respiratory activity of the virulent recipient strains tsh. flexneri in all substrates used.

Effect of different factors modifying the activity of some enzyme systems of the endoplastic reticulum on the sensitivity of cell organelles against the damaging action of chemical agents. I: Interrelations between the activity of some enzyme systems located in endoplasmic reticulum and hepatotoxicity of carbon tetrachloride.

An increased stability of liver lysosomes and mitochondria of burned, dehydrated and tumour-bearing rats has been found in the present investigations. Using biochemical criteria we were able to show that the membranes of liver subcellular particles of these animals become more resistent to the labilizing action of CCl4. The latter effect was confirmed by electron microscopic data. The tumour growth, dehydration and burning of rats as well as sleep deprivation, overheating, lanthanum and ruthenium red have been shown to cause changes in the activity of some enzyme-systems located in endoplasmic reticulum. The protective action of these chemical, pathological and stress factors against CCl4 produced damage to the cell organelles studied is discussed in relation to the activity of the drug metabolizing pathways; biochemical (modifying of some enzyme activity) as well as pharmacological (duration of hexobarbital sleep) data were used as criteria for the activity of these pathways.

On the metabolic characteristic of hybrids Shigella flexneri x Escherichia coli devoid of their ability for intracellular multiplication in the epithelial cells. I. Glycolysis.

The glycolysis (aerobic and in the presence of KCN) of avirulent xyl+ and xyl-str hybrids Sh. flexneri x E. coli, devoid of their ability to multiply intracellularly in the epithelial cells, is studied. It is established that their glycolytic activity is considerably higher than the activity of the donor strain E. coli, and deviate significantly compared with shown activity of the virulent recipient strains Sh. flexneri. Xyl-str hybrids are showing high values of glycolysis in aerobic conditions and in the presence of KCN, while in xyl+ hybrids very active glycolysis is observed only in the presence of KCN - probably completely sufficient for the persistence of bacteria in the host-cell at anaerobic conditions.

Studies on the energetic metabolism of Shigella flexneri x Escherichia coli hybrids devoid of penetration ability. III. Catalase and phosphatase activity.

The catalase and phosphatase activity of avirulent by keratoconjunctival test of guinea pigs lac+, kcp- hybrids that have lost their ability of penetrating in the epithelium, received from virulent strains Shigella flexneri (Sh. flexneri 222 5a and Sh. flexneri M42-43) and donor strains Escherichia coli (E. coli K-12, P4x and E. coli H) was investigated. It was established that there is no any dependence between the lost of virulence of the hybrids and the level of the catalase activity. During the study of the phosphatase activity it was established, that in comparison with the recipient virulent shigella strains, the investigated avirulent lac+-hybrids revealed higher values of the enzyme activity.

Studies on the energetic metabolism of Shigella flexneri and Escherichia coli hybrids devoid of penetration ability. II. Oxygen uptake and dehydrogenase activity.

Oxygen uptake and dehydrogenase activity are studied with lac+ kcpminus hybrids of Shigella flexneri, being avirulent to the eyes of guinea pigs, because of having lost ability for penetration in epithelial cells. These strains were obtained by hybridization of the virulent strain Shigella flexneri 222 5 a with the Hfr strain Escherichia coli K-12 P4x. It is established that lac+ kcp minus hybrids are characterized by significant decrease of respiratory activity. This decrease is outlined as a tendency studying O2 uptake and is extremely well expressed studying the dehydrogenase activity. The tests being performed with these hybrids show that the loss of virulence and connected with it the loss of the ability for penetration is related to a decrease of the respiratory activity of these bacteria which supply a part of the energy needed for their viability.

Studies on the energetic metabolism of Shigella flexneri times Escherichia coli hybrids devoid of penetration ability I. Glycolysis.

The aerobic and anaerobic (in presence of KCN) glycolysis is studied of avirulent hybrids of Shigella flexneri according to the keratoconjunctivitis test of Sereny with genetic characteristics lac-+kcp-minus devoid of penetration ability. It is established that lac-+kcp-minus hybrids which have lost their ability to penetrate the cells due to replacement of KCP-gene of the chromosome of donor strain E. coli K-12 P4 times, are characterized with a steep decrease of their glycolitic activity in both aerobic and anaerobic conditions. The data shows that the loss of penetrate ability of the Shigella flexneri hybrids correlates with the decrease of their glycolitic ability.