A REGIONAL STUDY OF SOME OSMOTIC, IONIC AND AGE FACTORS AFFECTING THE STABILITY OF CEREBRAL LYSOSOMES 1

An examination was made of the effect of changes in the osmolarity and the ionic composition of the homogenizing medium on the partition of lysosomal arylsulphatase and N -acetylglucosaminidase of cerebral cortex, hypothalamus and thalamus of the rat. Sulphatase appeared to be more sensitive to hypotonicity than glucosaminidase, since a higher proportion of the sulphatase was released from the lysosomes into the soluble fraction of the cells from all three neuroanatomical areas examined. In the presence of 250 mM-sucrose, supplementation with 10 mM-Mg led to clumping of the lysosomes and their translocation into the heavy-particulate fraction; no such effect of 10 mM-Mg was noted in the absence of 250 mM-sucrose. The intracellular distribution of bound N -acetylneuraminic acid (bound-NANA) was also examined. The shifts observed in its intracellular localization as a result of changes in the ionic composition of the homogenizing medium rule out bound-NANA as a structural component of the membrane of the cortical lysosome. However regional differences in the response of bound-NANA to ionic factors were observed. Lysosomes from cerebral cortex of adult and 12-day-old rats were also compared. Differences in the pattern of distribution of lysosomes in linear sucrose gradients and in response to ionic factors were uncovered. The results support the previously enunciated concept (Sellinger and Hiatt, 1968) of a regional microheterogeneity of lysosomes and add a new, age-related dimension to it.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65807/1/j.1471-4159.1969.tb05969.x.pd

Kinetics of Carboxylmethylation of the Charge Isoforms of Myelin Basic Protein by Protein Methyltransferase II

The charge isoforms (C1-C5) of bovine myelin basic protein (MBP) were used as substrates for the rat brain enzyme protein carboxylmethyltransferase (PM II). The objective of these experiments was to ascertain whether the kinetic behavior of the MBP isoforms reflected differences in the structures of this molecular family. Initial velocity plots as a function of the MBP-isoform concentration showed significnt differences ( p > 0.05) among the assayed isoforms except for isoforms C2 and C4. Under the conditions of our experiment all the curves exhibited a consistent sigmoidicity. The kinetic data were best fitted by a model, previously described for the enzyme D-Β-hydroxybutyrate dehydrogenase, in which two independent sites must be randomly occupied before any catalytic activity can occur. This mechanism is substantially different from that proposed by other investigators for similar PM II enzymes and other substrates. The differences in the rates of isoform carboxylmethylation are largely accounted for by the different apparent dissociation constants K s and is explained on the basis of inherent structural differences among the charge isoforms.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65821/1/j.1471-4159.1989.tb09257.x.pd

Doping Strategies for Small Molecule Organic Hole-transport Materials: Impacts on Perovskite Solar Cell Performance and Stability

Hybrid organic/inorganic perovskite solar cells (PSCs) have dramatically changed the landscape of the solar research community over the past decade, but \u3e25 year stability is likely required if they are to make the same impact in commercial photovoltaics and power generation more broadly. While every layer of a PSC has been shown to impact its durability in power output, the hole-transport layer (HTL) is critical for several reasons: (1) it is in direct contact with the perovskite layer, (2) it often contains mobile ions, like Li+ – which in this case are hygroscopic, and (3) it usually has the lowest thermal stability of all layers in the stack. Therefore, HTL engineering is one method with a high return on investment for PSC stability and lifetime. Research has progressed in understanding design rules for small organic molecule hole-transport materials, yet, when implemented into devices, the same dopants, bis(trifluoromethane)sulfonimide lithium salt (LiTFSI) and tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III) tri[bis(trifluoromethane)sulfonimide] (FK209), are nearly always required for improved charge-transport properties (e.g., increased hole mobility and conductivity). The dopants are notable because they too have been shown to negatively impact PSC stability and lifetime. In response, new research has targeted alternative dopants to bypass these negative effects and provide greater functionality. In this review, we focus on dopant fundamentals, alternative doping strategies for organic small molecule HTL in PSC, and imminent research needs with regard to dopant development for the realization of reliable, long-lasting electricity generation via PSCs

Cerebral microsomes. IV. On the attachment of ribosomes to the microsomal membranes of rat cerebral cortex

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33278/1/0000670.pd

A STUDY OF THE NASCENT POLYPEPTIDES SYNTHESIZED ON THE FREE POLYRIBOSOMES OF RAT BRAIN IN VIVO 1

The free polyribosomes of the cerebral cortex of the immature rat (12-14 days old) were exposed to very low concentrations of trypsin at 0°C and for very brief periods of time and the conditions under which their breakdown to smaller aggregates occurs were determined. Trypsin also caused the release of nascent, radioactive polypeptides from polyribosomes prelabelled with [ 14 C]amino acids in vivo. An examination of the kinetics of release of the nascent chains by trypsin revealed that it was dependent on the concentration of trypsin as well as on the duration of incubation in the presence of trypsin. The influence of the nature of the [ 14 C]amino acid used as precursor of the nascent polypeptides and of the duration of the radioactive pulse in vivo was also determined. The radioactivity associated with polyribosomes as a result of the brief radioactive pulses administered (2 to 10 minutes) was incompletely removed even after the ribosomes were dissociated into subunits by EDTA. These findings suggest that the assembly of the cerebral ribosome in vivo must be a very rapid process, particularly in the immature animal. The nature of the nascent, radioactive polypeptides was studied by disc gel and high voltage electrophoresis and by thin-layer and column chromatography. Evidence was obtained that a rather limited number of qualitatively different molecules resides on the polyribosomes at any given moment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65454/1/j.1471-4159.1971.tb00223.x.pd

CEREBROSIDE GALACTOSIDASE: A METHOD FOR DETERMINATION AND A COMPARISON WITH OTHER LYSOSOMAL ENZYMES IN DEVELOPING RAT BRAIN 1

(1) A method is described for assaying brain for cerebroside galactosidase activity. The enzyme was liberated by sonication and addition of sodium taurocholate, then by digestion with pancreatic enzymes. It was further purified by precipitation at pH 3. The enzyme was then incubated with an emulsion of galactose-labelled cerebroside in taurocholate and oleate at pH 4·5, and the liberated galactose was determined by scintillation counting. (2) The content of cerebroside galactosidase in rat brain at various ages has been determined. The enzyme was present before cerebroside appears in noticeable amounts (4 days) and the amount rose considerably during the period of active cerebroside deposition and myelination. The amount then remained at a high concentration even in the adult. (3) Comparison with other lysosomal brain enzymes was made in the age study. Nitrophenyl galactoside hydrolase also increased during myelination but levelled off earlier; its activity paralleled the amount of ganglioside. Nitrophenyl glucoside hydrolase started at a lower level and decreased with age. Sulphatase activity rose during myelination, then decreased somewhat after 15 days. Ceramidase followed a pattern similar to that of nitrophenyl galactoside hydrolase; it is suggested that both of these enzymes reflect ganglioside metabolism. (4) The relative amounts of brain enzymes in different states were determined as a function of age in the case of cerebrosidase, nitrophenyl galactoside hydrolase and sulphatase. The proportion found in the high speed supernatant fraction was low but increased after myelination. The proportion that could be ‘solubilized’ by sonication decreased after myelination but the values differed greatly for the three enzymes. This treatment solubilized one-seventh of the cerebrosidase, half the nitrophenyl galactosidase and three-quarters of the sulphatase.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66425/1/j.1471-4159.1969.tb06849.x.pd

Cerebral lysosomes. VI. The in vivo uptake of Triton-WR-1339 by the lysosomes of the immature cerebral cortex and cerebellum

The detergent Triton-WR-1339 was injected intrathecally into immature rats and its uptake by the lysosomes of the cerebral cortex and the cerebellum was demonstrated. Uptake was assessed in vitro by examining the shift of the lysosomes centrifugal fractions sedimenting at lower speeds than those commonly yielding these granules from control brains. This shift was maximal after 3 daily injections of Triton when arylsulfatase and , the two lysosomal hydrolases studied, exhibited peaks of relative specific activity (RSA) in fractions known to contain myelin fragments and nerve endings rather than in the heavier fraction known to concentrate lysosomes. A significant proportion of the cortical and cerebellar lysosomes failed to take up the detergent even after 3 days of continued administration.The apparent irreversibility of the uptake process was suggested by the finding that the RSA values for the two hydrolases were still highest in the myelin and light nerve ending fractions 4 days after the administration of Triton-WR-1339 had been discontinued. Sedimentation in linear density gradients of sucrose readily separated the populations of Triton-filled and Triton-devoid lysosomes.The results demonstrate the ability of cerebral lysosomes to perform a functional task characteristic of their extracerebral counterparts. It has not been established whether the uptake of Triton-WR-1339 was selective into the lysosomes of neuronal or glial cells or wether it proceeded uniformly into both cell types.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33687/1/0000199.pd

The action of trypsin and neuraminidase on the synaptic membranes of brain cortex

The population of intracellular membranes of rat cerebral cortex which exhibited the highest relative specific concentration of bound N-acetylneuraminic acid (NANA) and the highest relative specific activity of acetylcholinesterase (EC 3.1.1.7) (synaptic membranes) was incubated with bacterial neuraminidase and with trypsin under a number of experimental conditions. The electrokinetic profile displayed by the membrane preparation upon zonal density gradient electrophoresis changed as a result of the removal of bound NANA by neuraminidase, while its acetylcholinesterase activity remained unaffected; conversely, the action of trypsin led to the inactivation of acetylcholinesterase before any significant alterations of the electrophoretic mobility of the membranes became apparent. Prolonged incubation alone or in the presence of either neuraminidase or trypsin, resulted in the loss of membrane electrophoretic homogeneity, a circumstance which, most likely, reflects a disaggregation of the structural matrix of the membrane.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33001/1/0000385.pd

Pain Care in the Department of Veterans Affairs: Understanding How a Cultural Shift in Pain Care Impacts Provider Decisions and Collaboration

OBJECTIVE: Over the past decade, the Department of Veterans Affairs (VA) has experienced a sizeable shift in its approach to pain. The VA\u27s 2009 Pain Management Directive introduced the Stepped Care Model, which emphasizes an interdisciplinary approach to pain management involving pain referrals and management from primary to specialty care providers. Additionally, the Opioid Safety Initiative and 2017 VA/Department of Defense (DoD) clinical guidelines on opioid prescribing set a new standard for reducing opioid use in the VA. These shifts in pain care have led to new pain management strategies that rely on multidisciplinary teams and nonpharmacologic pain treatments. The goal of this study was to examine how the cultural transformation of pain care has impacted providers, the degree to which VA providers are aware of pain care services at their facilities, and their perceptions of multidisciplinary care and collaboration across VA disciplines. METHODS: We conducted semistructured phone interviews with 39 VA clinicians in primary care, mental health, pharmacy, and physical therapy/rehabilitation at eight Veterans Integrated Service Network medical centers in New England. RESULTS: We identified four major themes concerning interdisciplinary pain management approaches: 1) the culture of VA pain care has changed dramatically, with a greater focus on nonpharmacologic approaches to pain, though many old school providers continue to prefer medication options; 2) most facilities in this sample have no clear roadmap about which pain treatment pathway to follow, with many providers unaware of what treatment to recommend when; 3) despite multiple options for pain treatment, VA multidisciplinary teams generally work together to ensure that veterans receive coordinated pain care; and 4) veteran preferences for care may not align with existing pain care pathways. CONCLUSIONS: The VA has shifted its practices regarding pain management, with a greater emphasis on nonpharmacologic pain options. The proliferation of nonpharmacologic pain management strategies requires stakeholders to know how to choose among alternative treatments