The Physical Mechanism for Retinal Discrete Dark Noise: Thermal Activation or Cellular Ultraweak Photon Emission?

For several decades the physical mechanism underlying discrete dark noise of photoreceptors in the eye has remained highly controversial and poorly understood. It is known that the Arrhenius equation, which is based on the Boltzmann distribution for thermal activation, can model only a part (e.g. half of the activation energy) of the retinal dark noise experimentally observed for vertebrate rod and cone pigments. Using the Hinshelwood distribution instead of the Boltzmann distribution in the Arrhenius equation has been proposed as a solution to the problem. Here, we show that the using the Hinshelwood distribution does not solve the problem completely. As the discrete components of noise are indistinguishable in shape and duration from those produced by real photon induced photo-isomerization, the retinal discrete dark noise is most likely due to ‘internal photons’ inside cells and not due to thermal activation of visual pigments. Indeed, all living cells exhibit spontaneous ultraweak photon emission (UPE), mainly in the optical wavelength range, i.e., 350–700 nm. We show here that the retinal discrete dark noise has a similar rate as UPE and therefore dark noise is most likely due to spontaneous cellular UPE and not due to thermal activation.     

A new role for PGRP-S (Tag7) in immune defense: lymphocyte migration is induced by a chemoattractant complex of Tag7 with Mts1

PGRP-S (Tag7) is an innate immunity protein involved in the antimicrobial defense systems, both in insects and in mammals. We have previously shown that Tag7 specifically interacts with several proteins, including Hsp70 and the calcium binding protein S100A4 (Mts1), providing a number of novel cellular functions. Here we show that Tag7–Mts1 complex causes chemotactic migration of lymphocytes, with NK cells being a preferred target. Cells of either innate immunity (neutrophils and monocytes) or acquired immunity (CD4⁺ and CD8⁺ lymphocytes) can produce this complex, which confirms the close connection between components of the 2 branches of immune response.     

Distinction between glycoprotein IIIa and the 100-kDa membrane protein (aggregin) mediating ADP-induced platelet activation

Previous studies from our laboratories showed that 5'-p-fluorosulfonylbenzoyl adenosine (FSBA) inhibits ADP-induced platelet shape change, aggregation, and exposure of fibrinogen sites while covalently binding to 100-kDa platelet membrane protein (aggregin) on the intact platelet. Chymotrypsin digests aggregin to a fragment of 70 kDa, abolishing the inhibition, and also cleaves platelet glycoprotein IIIa (GPIIIa) (100 kDa) to a 70-kDa fragment containing the P1A1 epitope. We questioned whether these platelet membrane proteins were distinct. Both 5'-p-[3H]sulfonylbenzoyl adenosine (SBA)-labeled aggregin and 125I-GPIIIa were precipitated by polyclonal antibodies to a 100-kDa fraction of platelet membranes, but aggregin was not precipitated by a monospecific antibody to P1A1 which precipitates GPIIIa. Further a monospecific polyclonal antibody to immunopurified GPIIIa coupled to protein A-Sepharose adsorbed GPIIIa but not aggregin. Similarly, both aggregin and GPIIIa were precipitated by a polyclonal antibody to an isolated 70-kDa component of platelet membrane but only GPIIIa was precipitated by the monoclonal antibody to GPIIIa, (SSA6). Two patients with Glanzman's thrombasthenia whose platelet membranes contained less than 5% GPIIIa as assayed by monoclonal antibody binding (A2A6), incorporated [3H]SBA to the same extent as normal individuals. Furthermore, FSBA inhibited ADP-induced shape change with a similar concentration dependence for both thrombasthenic and normal platelets. Finally, mobility of GPIIIa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was decreased following reduction with dithiothreitol whereas that of [3H]SBA-labeled MP 100 was not altered. We conclude that GPIIIa and aggregin are distinct platelet membrane proteins.     

Association of fibronectin with the platelet cytoskeleton

Triton-insoluble cytoskeletons prepared from either normal or thrombasthenic platelets were found to contain approximately 1.3 micrograms of fibronectin/10(9) platelets as measured by a radioimmunoassay. Total endogenous platelet fibronectin was quantitatively retained on the platelet cytoskeleton, whereas 70% of exogenously added fibronectin that bound the surface of thrombin-activated platelets was recovered with the Triton-insoluble cytoskeleton. The exogenously added fibronectin specifically bound platelets and cytoskeletons with the same affinity giving an apparent binding constant of 1.47 X 10(-7) M. The possibility that fibrin associated with the platelet cytoskeleton could serve as the fibronectin receptor was investigated by measuring the binding constant of fibronectin for polymerizing fibrin and by measuring the amount of fibronectin associated with cytoskeletons of thrombasthenic platelets which contain 4-fold less fibrin than controls. The binding constant of fibronectin for polymerizing fibrin was 14-fold lower than that for cytoskeletons and cytoskeletons prepared from thrombasthenic platelets contained approximately the same amount of fibronectin as controls. Therefore, it is unlikely that fibrin is the platelet fibronectin receptor. These results support the hypothesis that platelet fibronectin is released from platelet alpha granules upon thrombin stimulation and becomes bound to the platelet surface and cytoskeleton either directly or through some intermediate protein that spans the membrane and interacts both with fibronectin and the internal cell cytoskeleton.     

Production of DON-related trichothecenes byFusarium graminearum Schw from Krasnodarski krai of the USSR

34Fusarium graminearum Schw isolates produced 4-deoxynivalenol to form significant amounts of 4, 7 — dideoxynivalenol and lesser amounts of 4 — deoxynivalenol monoacetates on grain substratesin vitro. This is the first report on the capability a large group of naturally occurring isolates to produce 4,7-dideoxynivalenol. The average levels of 4,7-dideoxynivalenol on rice, corn, barley, and wheat as a substrate were respectively 26.8, 14.0, 12.8, and 10.5% of the level of 4-deoxynivalenol. 4, 7 — dideoxynivalenol was present in all examined naturally contaminated wheat kernel samples at levels of 1.7 to 7.9% of the level of 4-deoxynivalenol. These findings suggest that more attention should be given to the occurrence of 4,7-dideoxynivalenol in cereals.     

Retroviral vectors

The majority of clinical trials for gene therapy currently employ retroviral-mediated gene delivery. This is because the life cycle of the retrovirus is well understood and can be effectively manipulated to generate vectors that can be efficiently and safely packaged. Here, we review the molecular technology behind the generation of recombinant retroviral vectors. We also highlight the problems associated with the use of these viruses as gene therapy vehicles and discuss future developments that will be necessary to maintain retroviral vectors at the forefront of gene transfer technology.     

Biological activities of peptides and peptide analogues derived from common sequences present in thrombospondin, properdin, and malarial proteins

Thrombospondin (TSP), a major platelet-secreted protein, has recently been shown to have activity in tumor cell metastasis, cell adhesion, and platelet aggregation. The type 1 repeats of TSP contain two copies of CSVTCG and one copy of CSTSCG, per each of the three polypeptide chains of TSP and show homology with peptide sequences found in a number of other proteins including properdin, malarial circumsporozoite, and a blood-stage antigen of Plasmodium falciparum. To investigate whether these common sequences functioned as a cell adhesive domain in TSP, we assessed the effect of peptides corresponding to these sequences and an antibody raised against one of these sequences, CSTSCG, in three biological assays which depend, in part, on the cell adhesive activity of TSP. These assays were TSP-dependent cell adhesion, platelet aggregation, and tumor cell metastasis. We found that a number of peptides homologous to CSVTCG promoted the adhesion of a variety of cells including mouse B16-F10 melanoma cells, inhibited platelet aggregation and tumor cell metastasis, whereas control peptides had no effect. Anti-CSTSCG, which specifically recognized TSP, inhibited TSP-dependent cell adhesion, platelet aggregation, and tumor cell metastasis, whereas control IgG had no effect. These results suggest that CSVTCG and CSTSCG present in the type I repeats function in the adhesive interactions of TSP that mediate cell adhesion, platelet aggregation, and tumor cell metastasis. Peptides, based on the structure of these repeats, may find wide application in the treatment of thrombosis and in the prevention of cancer spread.     

Low-density Lipoprotein Receptor-related Protein 1 (LRP1)-dependent Cell Signaling Promotes Axonal Regeneration

Low-density lipoprotein receptors (LRPs) are present extensively on cells outside of the nervous system and classically exert roles in lipoprotein metabolism. It has been reported recently that LRP1 activation could phosphorylate the neurotrophin receptor TrkA in PC12 cells and increase neurite outgrowth from developing cerebellar granule cells. These intriguing findings led us to explore the hypothesis that LRP1 activation would activate canonical neurotrophic factor signaling in adult neurons and promote axonal regeneration after spinal cord injury. We now find that treatment of adult rat dorsal root ganglion neurons in vitro with LRP1 agonists (the receptor binding domain of α-2-macroglobulin or the hemopexin domain of matrix metalloproteinase 9) induces TrkC, Akt, and ERK activation; significantly increases neurite outgrowth (p < 0.01); and overcomes myelin inhibition (p < 0.05). These effects require Src family kinase activation, a classic LRP1-mediated Trk transactivator. Moreover, intrathecal infusions of LRP1 agonists significantly enhance sensory axonal sprouting and regeneration after spinal cord injury in rats compared with control-infused animals (p < 0.05). A significant role is established for lipoprotein receptors in sprouting and regeneration after CNS injury, identifying a novel class of therapeutic targets to explore for traumatic neurological disorders.     

Somatoform disorders among patients attending walk-in clinics in Trinidad: prevalence and association with depression and anxiety

Objectives Somatoform disorders are common in international primary care settings, but have been little studied in the developing world. The objective of this study was to determine the prevalence of severe undifferentiated somatoform disorder, and its relationship to depression and anxiety, among patients attending walk-in clinics in Trinidad.Methods The study participants, who were all aged 18 years or older and attending walk-in clinics at 16 randomly selected health centres, were surveyed between May and August 2007 using the PRIME-MD questionnaire.Results There were 594 participants (the response rate was 92%), of whom 72.7% were female. Their ages ranged from 18 to 93 years, and 54.5% were over 50 years of age. In total, 37.2% were married and 25.9% were single. Indo-Trinidadians represented 43.1% and Afro-Trinidadians represented 36% of the study sample; 56.5% of the participants reported that their income was less than US$ 400 per month, and 65.7% were unemployed. At walk-in clinics in Trinidad, the estimated prevalence of severe undifferentiated somatoform disorder was 10.3% (95% CI: 7.86–12.74), that of hypochondriasis was 28.5% (95% CI: 24.9–32.1), and that of body dysmorphic disorder was 15.8% (95% CI: 11.9–18.7). Severe undifferentiated somatoform disorder was statistically significantly associated with gender and ethnicity but not with age, level of education, employment status or income. Chi-square testing found significant associations between the presence of severe undifferentiated somatoform disorder and both depression and anxiety (P < 0.05), between hypochondriasis and both anxiety and depression (P < 0.05), and between body dysmorphic disorder and depression (P < 0.05) but not anxiety. Regression analysis suggested that the demographic features that predicted severe undifferentiated somatoform disorder were being female or Indo-Trinidadian.Conclusions Walk-in clinics in Trinidad that serve older patients on a lower income have a high proportion of patients with somatoform disorders as measured by the PRIME-MD scale. These patients exhibit many features of anxiety and depression. These findings have implications for medical training and service delivery.