Pressure ulcers and deep tissue injury: a bioengineering perspective

Wheelchair users are highly susceptible to deep tissue injury. Interface pressures are unlikely to predict this, and an alternative assessment approach is needed that can easily monitor internal mechanical stresses and deformations.     

Metabolic stress reversibly activates the Drosophila light-sensitive channels TRP and TRPL in vivo.

Drosophila transient receptor potential (TRP) is a prototypical member of a novel family of channel proteins underlying phosphoinositide-mediated Ca(2+) entry. Although the initial stages of this signaling cascade are well known, downstream events leading to the opening of the TRP channels are still obscure. In the present study we applied patch-clamp whole-cell recordings and measurements of Ca(2+) concentration by ion-selective microelectrodes in eyes of normal and mutant Drosophila to isolate the TRP and TRP-like (TRPL)-dependent currents. We report that anoxia rapidly and reversibly depolarizes the photoreceptors and induces Ca(2+) influx into these cells in the dark. We further show that openings of the light-sensitive channels, which mediate these effects, can be obtained by mitochondrial uncouplers or by depletion of ATP in photoreceptor cells, whereas the effects of illumination and all forms of metabolic stress were additive. Effects similar to those found in wild-type flies were also found in mutants with strong defects in rhodopsin, Gq-protein, or phospholipase C, thus indicating that the metabolic stress operates at a late stage of the phototransduction cascade. Genetic elimination of both TRP and TRPL channels prevented the effects of anoxia, mitochondrial uncouplers, and depletion of ATP, thus demonstrating that the TRP and TRPL channels are specific targets of metabolic stress. These results shed new light on the properties of the TRP and TRPL channels by showing that a constitutive ATP-dependent process is required to keep these channels closed in the dark, a requirement that would make them sensitive to metabolic stress.     

Valproate decreases inositol biosynthesis.

BACKGROUND: Lithium and valproate (VPA) are used for treating bipolar disorder. The mechanism of mood stabilization has not been elucidated, but the role of inositol has gained substantial support. Lithium inhibition of inositol monophosphatase, an enzyme required for inositol recycling and de novo synthesis, suggested the hypothesis that lithium depletes brain inositol and attenuates phosphoinositide signaling. Valproate also depletes inositol in yeast, Dictyostelium, and rat neurons. This raised the possibility that the effect is the result of myo-inositol-1-phosphate (MIP) synthase inhibition. METHODS: Inositol was measured by gas chromatography. Human prefrontal cortex MIP synthase activity was assayed in crude homogenate. INO1 was assessed by Northern blotting. Growth cones morphology was evaluated in cultured rat neurons. RESULTS: We found a 20% in vivo reduction of inositol in mouse frontal cortex after acute VPA administration. As hypothesized, inositol reduction resulted from decreased MIP synthase activity: .21-.28 mmol/LVPA reduced the activity by 50%. Among psychotropic drugs, the effect is specific to VPA. Accordingly, only VPA upregulates the yeast INO1 gene coding for MIP synthase. The VPA derivative N-methyl-2,2,3,3,-tetramethyl-cyclopropane carboxamide reduces MIP synthase activity and has an affect similar to that of VPA on rat neurons, whereas another VPA derivative, valpromide, poorly affects the activity and has no affect on neurons. CONCLUSIONS: The rate-limiting step of inositol biosynthesis, catalyzed by MIP synthase, is inhibited by VPA; inositol depletion is a first event shown to be common to lithium and VPA.     

Effect of hemin and Protoporphyrin IX on the protein-synthesizing activity of human granulocytes, lymphocytes and platelets.

The hemin effect on protein synthesis of human granulocytes, lymphocytes and platelets was examined. Hemin added to culture media without serum caused a dose-dependent inhibition of protein synthesis in all three cell types. A cell-specific enhancement of protein-synthesizing capability was observed in 24-hour cultures in the presence of hemin and serum. A marked increase of protein synthesis was found in granulocytes, unchanged in lymphocytes and decreased in platelets. Lymphocytes from patients with chronic lymphatic leukemia (CLL) were moderately inhibited by hemin when incubated in media containing serum, the effect being more pronounced in the presence of freshly disolved doses of hemin. Addition of protoporphyrin IX to cells cultures resulted in a marked suppression of protein synthesis by the three cell types, in all experiments. These results confirm the importance of serum proteins in preventing the inhibitory effects of free hemin and protoporphyrin IX on blood cell protein synthesis. On the other hand, they show a cell-specific enhancement of the protein-synthesizing capacity mediated by hemin.     

Myo-inositol-1-phosphate (MIP) synthase: a possible new target for antibipolar drugs

Agam G, Shamir A, Shaltiel G, Greenberg ML. Myo -inositol-1-phosphate (MIP) synthase: a possible new target for antibipolar drugs. Bipolar Disord 2002: 4(Suppl. 1): 15–20. © Blackwell Munksgaard, 2002
Inositol metabolism is well characterized in yeast at a molecular level, and yeast is the only eukaryote in which genetic, molecular and functional genomic approaches to identify lithium, valproate and inositol targets may be combined readily. It has been shown that lithium inhibits yeast inositol monophosphatase (encoded by INM1 and INM2 ), and both valproate and lithium reduce intracellularinositol. Unlike lithium, valproate causes a decrease in intracellular inositol-1-phosphate as well, suggesting that myo -inositol-1-P (MIP) synthase is a site of valproate action in the yeast PI cycle. MIP synthase is the rate-limiting step in inositol biosynthesis and is highly regulated in response to inositol. Yeast genes that are affected by both lithium and valproate in the phosphoinositide pathways ( INO1 increased over 10-fold, INO2 increased twofold and INM1 decreased about twofold) have been identified. It has also been reported previously that both lithium and inositol mildly up-regulate IMPA1 (encoding mammalian inositol monophosphatase) expression in human cells. These findings indicate that IMPA is regulated only mildly by lithium, and therefore may not be the major target in the inositol pathway. Given the substantial evidence for the role of inositol in the mechanism of action of lithium and valproate,the opposing and mild effects of lithium on the genes encoding inositol monophosphatase in yeast and human cells, but the powerful effect of lithium and valproate on INO1 in yeast, it is hypothesized that human hINO1 is a factor in the psychopharmacology of mood stabilizers.     

In Vitro Screening Methods To Assess the Potential of In Vivo Precipitation of Injectable Formulations upon Intravenous Administration

In vivo precipitation of injectable formulations upon intravenous administration is a major concern in formulation development. In this work, two in vitro screening tools, static dilution and dynamic injection, are developed to assess the potential of in vivo precipitation of active pharmaceutical ingredients from injectable formulations upon intravenous administration. Nine model injectable formulations are studied. These include marketed formulations as well as formulations from Merck programs. Results from these models are compared with reports of precipitation from product labels, the Physicians Desk Reference, and literature reports. Good correlation is observed between results from the static dilution and dynamic injection models. The in vitro data correlates well with precipitation reported during clinical evaluations and animal experiments. The importance of protein in dilution medium, prototype formulations for screening studies, and optical microscopy for studying phase behavior is demonstrated. This work demonstrates the utility of using these models as a valuable screen during injectable formulation development. LAY ABSTRACT: In vivo precipitation of injectable formulations upon intravenous administration is a major concern in formulation development. Although animal models are routinely used for this purpose, they require strict protocol and are expensive. Furthermore, their results are far from ideal. This work describes the development of two in vitro screening tools, static dilution and dynamic injection, to assess the potential of in vivo precipitation of active pharmaceutical ingredients from injectable formulations upon intravenous administration. The utility of using these models as a valuable screen during injectable formulation development is demonstrated through the use of several model compounds.     

The possible involvement of glycogen synthase kinase-3 (GSK-3) in diabetes, cancer and central nervous system diseases

Glycogen synthase kinase (GSK-3) is a key enzyme in multiple cell processes. Since many pharmacological compounds that have effects on common metabolic pathways may have uses in many different diseases, we review here the possible involvement of glycogen synthase kinase 3 in diabetes, cancer and CNS diseases. Moreover, diabetes has recently been strongly linked to CNS diseases such as schizophrenia and bipolar illness. GSK-3 is both directly and indirectly inhibited by lithium, a key compound for treatment of bipolar disorder. Several antipsychotic drugs also affect the GSK-3 mediated pathways and postmortem study of brain in schizophrenia led to reports of alterations of GSK-3 activity or mRNA message. However, other reports are contradictory. Development of GSK-3 inhibitors for CNS diseases is complicated by the importance of GSK-3 in glucose metabolism and pancreas function and the possible effect of GSK-3 inhibition to be oncogenic. Further development of GSK-3 inhibitors for clinical trials should be approached with caution.     

Assesment of polyunsaturated fatty acids in cord blood of infants of diabetic mothers

Objective：To assess whether infants of diabetic mothers [ pre pregnancy diabetics （PPD） and gestational diabetics mellitus （GDM） ] have compromised arachidonic and docosahexaenoic acids in their plasma and the relationship with deficiency of the same compounds in their mothers. Methods： This study was conducted on 30 diabetic mothers （ both PPD and GDM） and their infants. Twenty healthy infants and their mothers with age and sex matched were included as controls. All infant （ of diabetic and non diabetic mothers） were subjected to assessment of APGAR Scoring, thorough history taking and anthropometric measures. Lipid profile components as well as polyunsaturated fatty acids（PUFA） were assessed in diabetic GDM and PPD and non diabetic mothers as well as in their babies. Results ： High-density lipoproteir（HDL） level was found to be significantly lower in diabetic mothers （specially those with PPD） compared to non diabetic ones, whereas no significant difference was found between babies of the two groups. Also, the current study revealed that diabetic mothers （ GDM and PPD） and their babies had significantly higher levels of PUFA precursors linoleic acids （LA） and alpha linoleic acids（ALA）. PUFA arachidonic acid（AA） and docosahexaenoic acids（DHA） were found to be significantly lower in diabetic mothers （GDM and PPD） compared to non diabetic mothers, and same results were found in the babies of the two groups. Conclusion： Neonates with diabetic mothers （both GDM and PPD） have highly compromised plasma levels of AA and DHA PUFA, which affects the child well being by far, and produces hazardous muhi-system complications on the long run.     

Perinatal Oxygen Restriction Does Not Result in Reduced Rat Frontal Cortex Synaptophysin Protein Levels at Adulthood as Opposed to Postmortem Findings in Schizophrenia

Synaptophysin, a synaptic vesicle protein and a marker for synaptic density has been found to be reduced in postmortem prefrontal cortex of schizophrenia patients, consistent with evidence for synaptic deficits in schizophrenia. The contribution of both genetic and environmental factors to the etiology of schizophrenia is well established, and obstetric complications have been suggested as a non-genetic risk factor of schizophrenia. As there is only scarce evidence for a genetic linkage between synaptophysin’s chromosomal locus (Xp11.22) and schizophrenia, we hypothesized that early neonatal exposure of rat pups to oxygen restriction would result in reduced frontal cortex synaptophysin protein levels at adulthood. We studied the effects of anoxia or hypoxia on 7-day-old rats frontal cortex synaptophysin protein levels assessed by Western blotting 4 and 7 weeks following the exposure. In hypoxia- or anoxia-exposed rats, synaptophysin protein levels were elevated both 4 and 7 weeks after the exposure. Two-way ANOVA followed by post hoc LSD analysis showed that the effect was predominantly at 4 weeks after exposure and that only anoxia-exposed rats differed significantly from control rats (p = 0.019). These results are in contrast to postmortem findings in schizophrenia and suggest that reduced synaptophysin protein levels in schizophrenia patients’ postmortem brain do not result from perinatal oxygen deprivation.