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At least 127 records · Page 7Linked to original sources
PubMed2006

Microvascular engineering in perfusion culture: immunohistochemistry and CLSM findings.

BACKGROUND: One of the most challenging problems in tissue engineering is the establishment of vascular supply. A possible approach might be the engineering of microvasculature in vitro and the supply by engineered feeder vessels. METHODS: An in vitro model for a small-diameter vessel was developed and made from adipose tissue stromal cells and human umbilical vein endothelial cells in a tube-like gelatine scaffold. The number of "branches" emerging from the central lumen and the morphology of the central lumen of the vessel equivalent were assessed after 16 days of either pulsatile perfusion culture or culture in rotating containers by evaluation of immunohistochemically stained sections (n = 6 pairs of cultures). Intramural capillary network formation was demonstrated in five experiments with confocal laser scanning microscopy. RESULTS: Perfused specimens showed a round or oval lumen lined by a single layer of endothelial cells, whereas following rotation culture the lumen tended to collapse. Confocal laser scanning microscopy showed more extended network formation in perfused specimens as compared to specimens after rotation culture. Partially highly interconnected capillary-like networks were imaged which showed orientation around the central lumen. Perfused specimens exhibited significantly more branches emerging from the central lumen. There were, however, hardly any capillary branches crossing the whole vessel wall. CONCLUSION: Pulsatile perfusion supports the development of vascular networks with physiological appearance. Advances in reactor development, acquisition of functional data and imaging procedures are however necessary in order to attain the ultimate goal of a fully functional engineered supplying vessel.

Adipose Tissue↗
PubMed1995

Temperature sensitivity of the keratin cytoskeleton and delayed spreading of keratinocyte lines derived from EBS patients.

Point mutations in the keratin intermediate filament genes for keratin 5 or keratin 14 are known to cause hereditary skin blistering disorders such as epidermolysis bullosa simplex, in which epidermal keratinocytes are extremely fragile and the skin blisters on mild trauma. We show that in 2 phenotypically diverse cases of epidermolysis bullosa simplex, the keratin mutations result in a thermoinstability of the intermediate filament cytoskeleton which can be reproducibly demonstrated even in the presence of tissue culture-induced keratins and in conditions where filament fragility is not otherwise obvious. SV40-T antigen and HPV16 (E6--E7) immortalised keratinocyte cell lines were examined, established from control and epidermolysis bullosa simplex-affected individuals with either severe (Dowling-Meara) or mild (Weber-Cockayne) forms of the disease. In standard tissue culture conditions no significant and consistent abnormality of the keratin cytoskeleton could be demonstrated. However after thermal stress a reduced stability of the keratin filaments was demonstrable in the epidermolysis bullosa simplex cell lines, with filaments breaking into aggregates similar to those seen in skin from EBS patients. These aggregates were maximal at 15 minutes after heat shock and the filament network structure was substantially reversed by 60 minutes. Differences were also seen in the cells during respreading after replating: cells containing mutant keratins were slower to respread than controls and fine aggregates were seen at the cell margins in the Dowling-Meara derived cell line. Such delays in restoring the normal intermediate filament network after physiological processes involving cytoskeleton remodelling may render the cells vulnerable to cytolysis in vivo if physically challenged during this time window. The steady reduction in the mitotic index of the epidermis during the first few years of life could then explain the clinical improvement which is frequently observed in growing children.

Cell Line↗
PubMed2003

Brain repair and neuroprotection by serum insulin-like growth factor I.

The existence of protective mechanisms in the adult brain is gradually being recognized as an important aspect of brain function. For many years, self-repair processes in the post-embryonic brain were considered of minor consequence or nonexistent. This notion dominated the study of neurotrophism. Thus, although the possibility that neurotrophic factors participate in brain function in adult life was prudently maintained, the majority of the studies on the role of trophic factors in the brain were focused on developmental aspects. With the recent recognition that the adult brain keeps a capacity for cell renewal, although limited, a new interest in the regenerative properties of brain tissue has emerged. New findings on the role of insulin-like growth factor I (IGF-I), a potent neurotrophic peptide present at high levels in serum, may illustrate this current trend. Circulating IGF-I is an important determinant of proper brain function in the adult. Its pleiotropic effects range from classical trophic actions on neurons such as housekeeping or anti-apoptotic/ pro-survival effects to modulation of brain-barrier permeability, neuronal excitability, or new neuron formation. More recent findings indicate that IGF-I participates in physiologically relevant neuroprotective mechanisms such as those triggered by physical exercise. The increasing number of neurotrophic features displayed by serum IGF-I reinforces the view of a physiological neuroprotective network formed by IGF-I, and possibly other still uncharacterized signals. Future studies with IGF-I, and hopefully other neurotrophic factors, will surely reveal and teach us how to potentiate the self-reparative properties of the adult brain.

Animals↗
PubMed2005

The zebrafish shocked gene encodes a glycine transporter and is essential for the function of early neural circuits in the CNS.

shocked (sho) is a zebrafish mutation that causes motor deficits attributable to CNS defects during the first2dof development. Mutant embryos display reduced spontaneous coiling of the trunk, diminished escape responses when touched, and an absence of swimming. A missense mutation in the slc6a9 gene that encodes a glycine transporter (GlyT1) was identified as the cause of the sho phenotype. Antisense knock-down of GlyT1 in wild-type embryos phenocopies sho, and injection of wild-type GlyT1 mRNA into mutants rescues them. A comparison of glycine-evoked inward currents in Xenopus oocytes expressing either the wild-type or mutant protein found that the missense mutation results in a nonfunctional transporter. glyt1 and the related glyt2 mRNAs are expressed in the hindbrain and spinal cord in nonoverlapping patterns. The fact that these regions are known to be required for generation of early locomotory behaviors suggests that the regulation of extracellular glycine levels in the CNS is important for proper function of neural networks. Furthermore, physiological analysis after manipulation of glycinergic activity in wild-type and sho embryos suggests that the mutant phenotype is attributable to elevated extracellular glycine within the CNS.

Animals↗
PubMed1997

Rete mirabile in humans--case report.

Carotid rete mirabile is a physiological vascular network between the external carotid and internal carotid systems present in some vertebrate species, but rarely observed in humans. We describe a 17-year-old girl with rete mirabile who presented with subarachnoid hemorrhage. Angiography disclosed the bilateral internal carotid arteries (ICAs) ended at the cavernous portion, and abnormal arterial networks visualized via the ICAs and the external carotid arteries in the paracavernous region. The distal ICAs were visualized via the abnormal arterial networks. After 18 years of follow-up she is leading a normal life without neurological problems. Rete mirabile in humans may present with hemorrhage or ischemic symptoms, but the prognosis appears to be good.

Adolescent↗
PubMed1989

Transforming growth factor type beta (TGF-beta) and adipogenesis in pigs.

The present study was performed on s.c. adipose tissue of fetal pigs at 35 to 110 d of gestation to examine the distribution of TGF-beta-positive cells, to localize TGF-beta immunoreactivity at the cellular level using electron microscopy (EM), and to determine the effect of TGF-beta on primary cultures of pig adipose tissue cells. Tissues for EM were fixed and embedded in LR white resin. Sections then were incubated with a polyclonal antibody specific for TGF-beta and TGF-beta was located using 20 nm colloidal gold conjugated second antibody. Tissues were fixed and embedded in paraffin for localization of TGF-beta at the light microscope (LM) level. Tissues were incubated with anti-TGF-beta followed by localization using biotinylated second antibody. Using LM, only a few cells stained positively for TGF-beta within developing blood vessels at 35 d. By 50 d, more TGF-beta-positive cells were associated with forming capillary networks. Between 70 d and 110 d, positively stained adipocytes usually were clustered around blood vessels. Cells surrounding hair follicles stained positive for TGF-beta between 90 to 110 d. Electron microscopy revealed TGF-beta labeling within fat cells. Fibroblasts and endothelial cells did not exhibit TGF-beta immunoreactivity. The addition of TGF-beta to primary cultures of s.c. adipose tissue cells from newborn pigs prevented lipid filling in fat cells. This effect was dose-dependent, with half-maximal inhibition occurring at 3 pM maximum inhibition occurred at 40 pM. These results indicate that TGF-beta may regulate angiogenic activity and lipid filling in s.c. adipose tissue of fetal pigs. Although TGF-beta was present in adipocytes and in cells associated with developing capillary networks, the physiological role of TGF-beta during early adipose tissue development is not known.

Adipose Tissue↗
PubMed2000

Positive modulation of AMPA receptors increases neurotrophin expression by hippocampal and cortical neurons.

This study investigated whether positive modulators of AMPA-type glutamate receptors influence neurotrophin expression by forebrain neurons. Treatments with the ampakine CX614 markedly and reversibly increased brain-derived neurotrophic factor (BDNF) mRNA and protein levels in cultured rat entorhinal/hippocampal slices. Acute effects of CX614 were dose dependent over the range in which the drug increased synchronous neuronal discharges; threshold concentrations for acute responses had large effects on mRNA content when applied for 3 d. Comparable results were obtained with a second, structurally distinct ampakine CX546. Ampakine-induced upregulation was broadly suppressed by AMPA, but not NMDA, receptor antagonists and by reducing transmitter release. Antagonism of L-type voltage-sensitive calcium channels blocked induction in entorhinal cortex but not hippocampus. Prolonged infusions of suprathreshold ampakine concentrations produced peak BDNF mRNA levels at 12 hr and a return to baseline levels by 48 hr. In contrast, BDNF protein remained elevated throughout a 48 hr incubation with the drug. Nerve growth factor mRNA levels also were increased by ampakines but with a much more rapid return to control levels during chronic administration. Finally, intraperitoneal injections of CX546 increased hippocampal BDNF mRNA levels in aged rats and middle-aged mice. The present results provide evidence of regional differences in mechanisms via which activity regulates neurotrophin expression. Moreover, these data establish that changes in synaptic potency produce sufficient network level physiological effects for inducing neurotrophin genes, indicate that the response becomes refractory during prolonged ampakine exposure, and raise the possibility of using positive AMPA modulators to regulate neurotrophin levels in aged brain.

Aging↗
PubMed1981

Single unit responses of substantia nigra and globus pallidus neurons to GABA agonist and antagonist drugs.

The studies reported here shed some new light upon the role of GABA within the basal ganglia. Although the proposed inhibitory interaction between the striatonigral GABA pathway and nigral dopamine neurons has, over the years, received the greatest attention, it now appears that this interaction may constitute only one part of a more extensive and perhaps more physiologically significant network of GABA-mediated effects upon populations of non-dopaminergic neurons. Specifically, evidence has been presented which indicates that the substantia nigra pars reticulata and the globus pallidus, two regions known to receive striatal GABAergic fibers, each contain groups of cells with a more marked ability to be affected by GABA and GABAmimetic drugs than the nigrostriatal dopamine neurons. Since reticulata and pallidal neurons seem at least as likely as dopamine neurons to be targets of this striatal GABAergic pathway, a much more expanded role for GABA within the basal ganglia might now be explored. Given their marked sensitivities to GABA, if reticulata and pallidal cells do lie postsynaptic to GABA terminals then function in several motor-related areas to which these cells project might be greatly affected by striatal and pallidal GABAergic efferents. Future studies aimed at elucidating the nature and importance of these GABA-mediated interactions may ultimately provide new clues about how the basal ganglia influence motor function.

Animals↗
PubMed1993

[Long-term treatment with i.v. immunoglobulin in the therapy of systemic lupus erythematosus].

BACKGROUND: Treatment of several autoimmune diseases with intravenous gammaglobulins (IvIg) has been demonstrated to be safe and effective in determining clinical improvement and decreasing autoantibody titer. We tested the hypothesis that IvIg would be effective in patients with Systemic Lupus Erythematosus (SLE). METHODS: We conducted an open trial involving 12 patients with SLE refractory to conventional treatments with monthly infusion of IvIg at a dosage of 400 mg/kg/day for 5 consecutive days. The duration of the therapy with the same dose every 4 weeks was from 16 to 24 months. RESULTS: A progressive clinical improvement was observed in 11 patients during IvIg therapy, and it persisted during the all period of treatment. The clinical improvement was associated with an increase of haemoglobin, albumin levels, total serum complement and C3 and C4 components, platelets count in 2 thrombocytopenic patients, and a progressive reduction of ESR, plasma immunocomplexes and antinuclear antibodies. A marked improvement in serum urea, creatinine clearance and proteinuria was also observed in the patients with renal involvement. We have not observed any adverse effects with the long-term use of this treatment. Several mechanisms have been postulated to explain the effect of IVIg in the treatment of autoimmune diseases. Many experimental and clinical data support the interesting hypothesis that IVIg may be effective in some autoimmune diseases by restoring a normal function or the physiological immune network through the same regulatory mechanisms leading to a suppression of autoimmune disorders in normal individuals. The presence of a wide spectrum of anti-idiotypic antibodies in IVIg could regulate T and B-cell activities preventing the emergence of B-cell clones with specificity for autoantigens epitopes and down-regulating autoantibodies production. CONCLUSION: The results obtained suggest that IvIg therapy seems to be a promising and beneficial approach in the treatment of SLE. However, double-blind studies are necessary to confirm the results obtained particularly to ascertain the optimal dosage, the schedule of infusion and the duration of maintenance therapy with IVIg, and to determine their long-term effectiveness, the reduction in late morbidity and mortality and the effect on the quality of life of patients with SLE. Moreover, because of the high cost of IVIg, their use seems to be especially indicated for patients non responders to conventional treatments and for these with infectious complications.

Acute Disease↗
PubMed1988

Collation of student results in practical class experiments in physiology, using a BBC ECONET computer network.

Funding was provided to Queen's University by the Department of Education and by the Industrial Development Board for Northern Ireland to provide microcomputers for undergraduate use. An allocation from the grant to the Department of Physiology enabled the purchase of 20 BBC Master 128 microcomputers with monitors used as student work-stations connected together by an ECONET network with a file server using a dual floppy disc drive, two printer servers and two demonstrator stations. A BASIC program was written to analyse the students' practical class measurements which they entered manually at their work-station keyboards. Class results were presented to the students in the form of frequency distribution histograms or X/Y graphs. Program modifications to suit different practicals can be made relatively easily. The time taken to analyse data has been shortened. It is easy for the students to get immediate comparison of their own results with those of the rest of the class--particularly advantageous if the student's own experiment did not work. The class can be divided into groups to study different variations of the experiment and provide the data from each group to the whole class. The students' opinions on whether the equipment had (1) improved the teaching of physiology and (2) provided helpful preparation for the use of computers in medical practice were assessed by a questionnaire which showed that a clear majority felt these aims had been fulfilled.

Computer-Assisted Instruction↗
PubMed1991

Studies on fibrin network structure: the effect of some plasma proteins.

Significant differences were found between characteristics of networks developed in plasma and those developed in pure fibrinogen solution. Networks in plasma have thicker fibres, are more permeable and have lower tensile strength. In this investigation determinants of network structure under physiological conditions of clotting have been examined in an attempt to account for the differences in network structure in plasma and fibrinogen solution. Effect of antithrombin III and of physiological concentrations of fibronectin, albumin and gamma-globulin on fibrin network structure was examined using mass-length ratio (microT) from turbidity, bulk permeability of networks (tau) and kinetics of network development. At physiological concentrations effect of ATIII was too pronounced to allow this method to quantify changes in network characteristics. Whilst fibronectin and gamma-globulins increased fibrin fibre thickness and network permeability, albumin caused opposite effects. It is concluded that the final network structure is determined by kinetics of fibrin fibre growth and is highly responsive to the presence of plasma proteins.

Antithrombin III↗
PubMedDate not supplied

[Study of giant depolarizing activity in the neonatal hippocampal neurones].

Spontaneous oscillatory activity is a general feature of developing neural networks. Early in postnatal development, spontaneous network-driven events, termed giant depolarizing potentials (GDPs), occur synchronously over the entire hippocampus. By performing simulation of hippocampal network with using physiology parameters of the neurons and its network from the present experiments and literature dates, we investigated the participation of the different components of network in the generation of GDPs. Comparing the results of the model and in vitro experiments we conclude that are necessary for the GDP generation involvement the activation of GABAergic, glutamatergic inputs and perhaps gap junction.

Animals↗
PubMed1996

A neural network simulation of the vestibular system: implications on the role of intervestibular nuclear coupling during vestibular compensation.

Previous neural network simulations of the vestibular system have been based loosely on known physiology. This research involved the use of a strongly physiologically based neural network model which was used to investigate the role of the vestibular commissure in restoring the bilateral symmetry of the resting rates of the vestibular nuclei during vestibular compensation following unilateral labyrinthectomy. It was found the readjustments in the gain of the vestibular commissure were not primarily responsible for vestibular compensation, as has previously been suggested, but rather that it was modifications in extralabyrinthine sources of tone which mediated the restoration of the central symmetry between the two nuclei.

Animals↗
PubMed2001

Coding specificity in cortical microcircuits: a multiple-electrode analysis of primate prefrontal cortex.

Neurons with directional specificities are active in the prefrontal cortex (PFC) during tasks that require spatial working memory. Although the coordination of neuronal activity in PFC is thought to be maintained by a network of recurrent connections, direct physiological evidence regarding such networks is sparse. To gain insight into the functional organization of the working memory system in vivo, we recorded simultaneously from multiple neurons spaced 0.2-1 mm apart in monkeys performing an oculomotor delayed response task. We used cross-correlation analysis and characterized the effective connectivity between neurons in relation to their spatial and temporal response properties. The majority of narrow (<5 msec) cross-correlation peaks indicated common input and were most often observed between pairs of neurons within 0.3 mm of each other. Neurons recorded at these distances represented the full range of spatial locations, suggesting that the entire visual hemifield is represented in modules of corresponding dimensions. Nearby neurons could be activated in any epoch of the behavioral task (stimulus presentation, delay, response). The incidence and strength of cross-correlation, however, was highest among cells sharing similar spatial tuning and similar temporal profiles of activation across task epochs. The dependence of correlated discharge on the functional properties of neurons was observed both when we analyzed firing from the task period as well as from baseline fixation. Our results suggest that the coding specificity of individual neurons extends to the local circuits of which they are part.

Action Potentials↗
PubMed2003

Self-organizing neural network model of motion processing in the visual cortex during smooth pursuit.

A physiologically based neural network model was constructed to study cortical motion processing during pursuit eye movements. The model consists of three layers of computational units, simulating information processing by direction selective neurons in the primary visual cortex (V1), motion selective neurons in the middle-temporal area, and pursuit selective neurons in the middle-superior-temporal (MST) area. MST units integrate visual and eye-movement related information, and their connections develop during an unsupervised training process. The resulting MST units represent a transition from retinal to real-world reference frame. By analyzing the model connectivity, mechanisms underlying the functions performed by the network are studied.

Brain Mapping↗
PubMed2003

Effect of physiological temperature on the mechanical properties and network structure of biodegradable poly(propylene fumarate)-based networks.

Poly(propylene fumarate) (PPF)-based networks have exhibited increases in mechanical properties during their initial stages of degradation. This study was designed to investigate whether physiological temperatures are the source of this reinforcing behavior by influencing the formation of additional crosslinks within the network. Utilizing a model PPF network formed with the crosslinking agent poly(propylene fumarate)-diacrylate (PPF-DA), cylindrical specimens were stored in an inert environment and conditioned at -20 and 37 degrees C while their mechanical properties and network structure were monitored over a six week period. The PPF/PPF-DA specimens exposed to physiological temperatures showed an increase in compressive modulus from 1674 +/- 88 to 2059 +/- 75 MPa. The double bond conversion improved as well, from 64 +/- 1 to 70 +/- 1%, indicating that crosslinks were being formed in the network. The additional reactivity occurred exclusively with unreacted fumarate bonds. PPF/PPF-DA networks stored at -20 degrees C showed no changes in mechanical properties; however, they increased when subsequently conditioned at 37 degrees C. The results were used to explain that PPF-based networks undergo a biphasic degradation behavior due to the competing hydrolytic degradation and thermal induced crosslinking. In addition, heat treating the networks at higher temperatures can be utilized as a means to further reinforce PPF-based materials.

Biocompatible Materials↗