Early transition metal-catalyzed C–H alkylation: hydroaminoalkylation for Csp3–Csp3 bond formation in the synthesis of selectively substituted amines

Protecting group, directing group, and external oxidant free synthesis of structurally diverse amines.

The atmospheric chemistry of trace gases and particulate matter emitted by different land uses in Borneo

We report measurements of atmospheric composition over a tropical rainforest and over a nearby oil palm plantation in Sabah, Borneo. The primary vegetation in each of the two landscapes emits very different amounts and kinds of volatile organic compounds (VOCs), resulting in distinctive VOC fingerprints in the atmospheric boundary layer for both landscapes. VOCs over the Borneo rainforest are dominated by isoprene and its oxidation products, with a significant additional contribution from monoterpenes. Rather than consuming the main atmospheric oxidant, OH, these high concentrations of VOCs appear to maintain OH, as has been observed previously over Amazonia. The boundary-layer characteristics and mixing ratios of VOCs observed over the Borneo rainforest are different to those measured previously over Amazonia. Compared with the Bornean rainforest, air over the oil palm plantation contains much more isoprene, monoterpenes are relatively less important, and the flower scent, estragole, is prominent. Concentrations of nitrogen oxides are greater above the agro-industrial oil palm landscape than over the rainforest, and this leads to changes in some secondary pollutant mixing ratios (but not, currently, differences in ozone). Secondary organic aerosol over both landscapes shows a significant contribution from isoprene. Primary biological aerosol dominates the super-micrometre aerosol over the rainforest and is likely to be sensitive to land-use change, since the fungal source of the bioaerosol is closely linked to above-ground biodiversity.

Pharmacological evidence for the involvement of endogenous alpha-MSH-like peptides in peripheral nerve regeneration

The possible involvement of alpha-MSH-like peptides in the regenerative response of peripheral nerves was investigated with a competitive antagonist of alpha-MSH, the synthetic hexapeptide [D-Trp7,Ala8,D-Phe10)alpha-MSH(6-11)-amide. Subcutaneous administration of the alpha-MSH antagonist during the first 10 days following sciatic nerve crush significantly decreased functional recovery as measured by the foot flick withdrawal test and the walking pattern analysis. Hypophysectomy delayed both the initial sprouting response and the outgrowth rate after major caudal nerve crush. When hypophysectomized rats were treated with the alpha-MSH antagonist, a further delay in initial sprouting was observed, whereas the outgrowth rate of nerve fibers was not affected. These results suggest that 1) endogenous alpha-MSH-like peptides stimulate nerve outgrowth following peripheral nerve injury and 2) alpha-MSH-like peptides derived from a source other than the pituitary may contribute to the physiological stimulus leading to sprouting.

The neurotrophic peptide Org 2766 does not influence the expression of the immediate early gene c-fos following sciatic nerve crush in the rat

The neurotrophic peptide Org 2766 accelerates the regeneration of peripheral nerves. Although the mechanism of action of this neuropeptide is not yet understood, functional, pharmacological, and morphological evidence has demonstrated that Org 2766 exerts its beneficial effect during the early stages of nerve regeneration. The induction of some members of the Immediate Early Gene (IEG) family such as c-jun and c-fos is one of the first molecular events following peripheral nerve damage. The Fos and Jun proteins act as a transcription factor and may stimulate the expression of a number of genes implicated in nerve regeneration. We examined whether Org 2766 stimulates nerve regeneration by enhancing or prolonging the expression of c-fos mRNA. Following a crush lesion of the sciatic nerve, the expression of c-fos mRNA was induced in the spinal cord and in the damaged nerve at 30 min following injury in untreated animals as demonstrated with Northern blot. No effect of the crush lesion was observed in dorsal root ganglia (DRG). The induction of c-fos mRNA in the damaged nerve was more robust as compared to the relatively small induction observed in the spinal cord. With in situ hybridization an increase in c-fos mRNA expression both in the dorsal and in the ventral horn of the spinal cord was demonstrated at 30 min post-lesion. In the distal sciatic nerve portion the expression of c-fos mRNA was predominantly localized around Schwann cell nuclei at 30 min after nerve crush. The effect of Org 2766 treatment on the expression of c-fos mRNA was investigated using semiquantitative dot blots.(ABSTRACT TRUNCATED AT 250 WORDS)

Langenskiöld classification of tibia vara: an assessment of interobserver variability

Six pediatric orthopaedic specialists and six senior orthopaedic residents independently classified 60 radiographs of infantile tibia vara according to the six-stage Langenskiöld classification. Correlation coefficients and percentage agreement were similar in both groups. Interobserver agreement was good for early and late stages, but was poor for intermediate stages. We caution clinicians that small but frequent discrepancies in radiographic staging impart a dubious prognostic value to the Langenskiöld classification.

The expression of B-50/GAP-43 in Schwann cells is upregulated in degenerating peripheral nerve stumps following nerve injury

We have detected mRNA for B-50 (GAP-43, pp46, F1, neuromodulin), which was originally believed to be a neuron-specific protein, in non-neuronal cells in the rat sciatic nerve. In control rats, the level of B-50 mRNA in sciatic nerve tissue was much lower than in dorsal root ganglia. Following nerve crush or transection, the expression of B-50 mRNA in the distal nerve stump increased dramatically between 1 and 2 days post-injury. The B-50 mRNA levels in the distal stump of crushed nerves remained elevated for up to 4 weeks and subsequently returned to control levels after 7 weeks. In contrast, after nerve transection B-50 mRNA levels in the distal nerve portion continued to increase up to 7 weeks post-lesion. No changes in the levels of the B-50 transcript were observed in the proximal portion of either crush-lesioned or transected sciatic nerves. In situ hybridization demonstrated B-50 mRNA associated with Schwann cells in the distal nerve stump. The observation that Schwann cells are capable of producing B-50 mRNA was confirmed by Northern blot analysis of total RNA isolated from primary Schwann cell cultures. Taken together, these data show the expression of B-50 mRNA by Schwann cells and the up-regulation of B-50 mRNA in reactive Schwann cells upon loss of axonal contact.

Expression of the pro-opiomelanocortin gene in dorsal root ganglia, spinal cord and sciatic nerve after sciatic nerve crush in the rat

Neuropeptides related to alpha-melanocyte-stimulating hormone (alpha-MSH) stimulate nerve outgrowth following peripheral nerve injury and may play an important physiological role in peripheral nerve regeneration. The mechanism of action underlying the neurotrophic effect of pharmacologically administered alpha-MSH is unknown. Here we investigate the hypothesis that reexpression of the proopiomelanocortin (POMC) gene, the prohormone of alpha-MSH/adrenocorticotropic hormone (ACTH)-like peptides, is part of the endogenous repertoire of peripheral nerve responses following injury. The effect of sciatic nerve crush on the expression of POMC mRNA between 0.5 h and 14 days after crush was investigated using polymerase chain reaction (PCR) and Northern blot analysis. The presence of a POMC transcript in dorsal root ganglia (DRG), spinal cord and in the sciatic nerve at the crush site could be demonstrated in both control and lesioned animals by PCR using primers located in exon 1 and 3 of the POMC gene. Minute quantities of two POMC transcripts (1200 nt and 800 nt) could be detected by Northern blot analysis of total RNA prepared from DRG, spinal cord and the sciatic nerve of control animals and of animals subjected to nerve crush. POMC mRNA expression was, however, not increased following nerve crush. Probes specific for exons 1 and 2 or specific for exon 3 of the POMC gene were employed to demonstrate that the 800 nt transcript represents the truncated POMC mRNA previously shown to be present in extra-pituitary tissue. The larger 1200 nt transcript comigrates with the full length POMC mRNA expressed in the pituitary gland. The present results demonstrate the expression of small amounts of POMC mRNA in all compartments of the sciatic nerve. The absence of an induction of POMC expression in response to nerve crush suggests that the stimulating effect of exogenously applied alpha-MSH does not mimic a POMC derived neurotrophic peptide induced in the nerve following nerve injury.

Peripheral pain fiber function is relatively insensitive to the neurotoxic actions of acrylamide in the rat

Acrylamide causes degeneration of sensory nerve axons in a range of experimental animals and in humans. Evidence of selective vulnerability of large diameter fibers has been derived largely from histological and electrophysiological measurements. We have examined the effect of repeated doses of acrylamide on the function of small diameter peripheral pain fibers in rats by measuring the intensity of neurogenic edema initiated by chemosensitive nerve endings and assessing the sensitivity of the hind paws to a noxious stimulus. These effects have been compared to the impaired sensorimotor performance (landing foot spread) resulting from acrylamide treatment and the change in functional integrity of the pain fibers following surgical lesioning of the sciatic nerves. Our results show that the selective vulnerability of large over small diameter sensory fibers previously reported in the literature is reflected in the differential impairment of proprioceptive and pain-related functions in the rat.

Neurotoxic acrylamide and neurotrophic melanocortin peptides--can contrasting actions provide clues about modes of action?

Experimental acrylamide neuropathy has been studied as a model of degenerative neurological disorders of the 'dying-back' type for over 30 years. Functional, histological, ultrastructural, electrophysiological and biochemical aspects of acrylamide neuropathy have been described and several hypotheses concerning the mode of action proposed. However, the mechanism whereby acrylamide causes axonal degeneration and inhibits nerve sprouting remains unknown. By analogy with agonist/antagonist comparisons used by the pharmacologist, we have reconsidered the acrylamide problem in the light of the opposite effects summarized in Table 1, of neurotrophic peptides related to ACTH/MSH (collectively termed melanocortins). The contrasting effects on sprouting and the eventual quality of repair of mechanically lesioned nerves have suggested a mechanism whereby sprouting may regulate perikaryal adjustments to injury. We have also posed the question as to whether a common biochemical mechanism, namely selective proteolysis of neurofilament protein may underlie the opposing effects of acrylamide and melanocortins on nerve sprouting. This possibility implies a hitherto unknown role for neurofilament protein turnover in neuronal maintenance and repair, a suggestion that may provoke further research and discussion.

A simple method for reducing autotomy in rats after peripheral nerve lesions

Experiments using peripheral nerve lesions (crush or transection) in rats to study repair processes are hampered by the tendency for the animals to attack the limb in which the peripheral nerves are damaged (autotomy). In this paper we describe a simple method which significantly reduces the incidence of autotomy after peripheral nerve lesions. The method consists of painting the hind paws of operated rats with a commercially available non-toxic lotion, which is used to discourage nail-biting and thumb-sucking in humans. Although the method is not absolute, it was extremely beneficial in our experiments, since the number of animals that had to be taken out of the experiment due to severe autotomy was greatly reduced. We believe that this method may prove to be as beneficial to other investigators who are using experimental peripheral nerve lesions to study the regenerative aspects of the nervous system.

An ACTH-(4-9) analogue, Org 2766, improves recovery from acrylamide neuropathy in rats

Org 2766 is one of a series of melanocortins (ACTH and related peptides) that exert trophic influences on the central and peripheral nervous system of the rat. We used acrylamide neuropathy in rats as an experimental model of peripheral neuropathies of the dying-back type in order to assess the potential therapeutic efficacy of Org 2766 in this type of nerve damage. The peptide reversed the delayed persistent deficit in sensory conduction velocity without preventing the initial loss of motor coordination. The recovery of apparently normal coordination was unaffected by the peptide, but resistance to a second toxic challenge suggested that recovery was more complete in the peptide-treated rats. The finding that Org 2766 improved the quality of the repair following acrylamide neuropathy, together with previous studies showing beneficial effects in neuropathies caused by cisplatin or diabetes and after mechanical trauma, strongly suggests that Org 2766 may be beneficial in the treatment of various conditions in which the nervous system has sustained damage.

Immunological and structural features of the protein core of human polymorphic epithelial mucin

The protein core of high mol. wt polymorphic epithelial mucin (PEM--approximately 400 kDa glycoprotein) which is associated with breast carcinomas, consists of a repeating 20 amino acid peptide motif [Gendler et al. (1988) J. biol. Chem. 263, 12,820-12,823]. Monoclonal antibodies C595 (anti-urinary mucin) and NCRC-11 (anti-breast carcinoma cells), and other antibodies against human milk fat globule membranes, were found to recognize determinants present within this 20 amino acid peptide. A model of the peptide was developed based on hydropathicity and structure prediction calculations and these indicated that the repeated structure is dominated by a hydrophilic domain of seven amino acids, extending into two flanking beta turns. NMR analysis of the 20 amino acid peptide was undertaken to probe the secondary structure. Epitope mapping experiments involving solid phase synthesis of overlapping heptapeptides in the repeat unit identified the minimum structures for antibody binding as Arg-Pro-Ala-Pro and Arg-Pro-Ala for the C595 and NCRC-11 antibodies, respectively. These determinants were found within the predicted hydrophilic turn region domain of the peptide. The epitopes for six other PEM-reactive monoclonal antibodies were also determined to reside within the predicted hydrophilic turn domain. This evidence is in accord with the disposition of this region of the PEM peptide core being at the exterior of the glycoprotein where it would be accessible to antibody recognition and binding events.

Colchicine effect on B-50/GAP43 phosphoprotein localization in rat dorsal root ganglion explants

In rat embryonic dorsal root ganglion explants stimulated by nerve growth factor, the neuron-specific phosphoprotein B-50 (GAP43) is primarily localized in the distal portion of outgrowing neurites. Addition of colchicine leads to a decrease in total amount of B-50 and a marked redistribution in the neurons. The data underscore the role of axonal transport in the concentration of B-50 in growth cones of growing neurites.

Light- and electron-microscopical study of phosphoprotein B-50 following denervation and reinnervation of the rat soleus muscle

The neuron-specific phosphoprotein B-50 was originally identified as a phosphoprotein in synaptic plasma membranes isolated from adult brain tissue. In this paper we study the reinnervation of the soleus muscle, a target muscle of sciatic nerve axons, using affinity-purified anti-B-50 antibodies. Light-microscopical evaluation of the reinnervation process revealed that the period of muscle fiber reinnervation corresponds closely with the time in which high B-50 immunoreactivity was observed in the nerve fibers that invade the muscle and in the newly formed neuromuscular junctions. Upon completion of reinnervation, B-50 immunoreactivity decreased. In the newly innervating terminals, B-50 was associated with presynaptic vesicular structures and with the presynaptic plasma membrane. In intact mature neuromuscular junctions, virtually no B-50 immunoreactivity could be detected with either light- or electron-microscopic procedures. These observations corroborate the association of high levels of B-50/GAP43 during axon outgrowth and support the concept that B-50 may be a key molecule in the reconstruction of axonal structures. We also observed an unexpected transient increase in B-50 immunoreactivity in the degenerating neuromuscular junctions. This observation cannot be explained in terms of increased neuronal synthesis of B-50, since the degenerating axon processes have been completely disconnected from their cell bodies. Thus, our evidence implies that a rise of B-50 immunoreactivity can be associated with stages of neuronal degeneration as well as with those of neuronal differentiation and axon outgrowth.

Damaged rat peripheral nerves do not contain detectable amounts of alpha-MSH

Peptides related to alpha-MSH (collectively termed melanocortins) stimulate nerve growth following injury and may play a physiological role in the repair process. Melanocortins are not normally present in mature peripheral nerves but MSH-like bioactivity has been observed in extracts of injured nerves. alpha-MSH could derive from reexpression of the POMC prohormone in injured nerves or from proteolysis of the intermediate-size neurofilament protein that bears antigenic similarities to melanocortins. Using a radioimmunoassay that will distinguish between alpha-MSH and neurofilament-derived fragments, we have shown that alpha-MSH is not present (detection limit 74 pg alpha-MSH/mg protein) in damaged rat sciatic nerves.

Pharmacological aspects of the influence of melanocortins on the formation of regenerative peripheral nerve sprouts

Adrenocorticotropin (ACTH) and alpha-melanocyte-stimulating hormone (alpha-MSH) stimulate the initial sprouting response in the crushed rat sciatic nerve. In this report a detailed analysis of the neurotrophic action of Org.2766 [a degradation resistant ACTH(4-9) analog] and alpha-MSH is described. Org.2766 treatment results in enhanced numbers of outgrowing sprouts in the damaged nerve. The growth velocity of the sprouts is not affected. The peptide effect is dose-dependent. A single peptide injection administered immediately following the crush stimulates the formation of sprouts significantly. Continued high blood levels of Org.2766 are probably not critical for the neurotrophic effect of these peptides, since a more moderate dosing protocol (injections given every 48 hr) was more effective than more frequent injections (injections given every 12 hr). The present results further the understanding of the mode of action of ACTH/alpha-MSH-like peptides and underscore the necessity to test a wide range of doses and injection protocols to avoid false negative results in clinical work being planned to start in the near future.

Early effect of an ACTH4-9 analog (Org.2766) on regenerative sprouting demonstrated by the use of neurofilament-binding antibodies isolated from a serum raised by alpha-MSH immunization

Antibodies binding to the 150 kDa neurofilament protein NF150 have been purified from a serum raised by immunizing a rabbit with alpha-MSH. The NF150-binding antibodies were purified by affinity chromatography on a column of cytoskeletal proteins coupled to CNBr-activated Sepharose-4B. Immunocytochemical application of these antibodies, followed by a FITC-coupled second antibody, labels axons in intact and regenerating nerves and provides a means of identifying and counting small regenerating sprouts from 48 h after nerve crush. We have been able to demonstrate that treatment with the neurotrophic melanocortin analog, Org.2766, increases the number of regenerating axons present in the nerve as early as 72 h after nerve crush.

The kinase C substrate protein B-50 and axonal regeneration

As reported previously the prominent protein kinase C substrate protein B-50 is present in growth cones isolated from fetal rat brain and in outgrowing hippocampal neurites. These findings suggest that B-50 plays a role in axonal growth during development of the nervous system. In the present paper the fate of B-50 is investigated in regenerating rat sciatic nerve. Using affinity-purified anti-B-50 antibodies B-50 levels have been compared in crushed and contralateral intact nerves by means of immunoblotting and radioimmunoassay. B-50 levels in the crushed nerve increased 5.3-fold as compared to non-crushed controls. Furthermore, the cellular localization of B-50 has been assessed by immunohistochemistry. Virtually no B-50 immunoreactivity was seen in control nerves, but bright immunofluorescence appeared in regenerating sprouts. Our data are in line with current evidence from several laboratories that B-50 is a member of a small family of growth-associated proteins and support the hypothesis that B-50 is involved in axonal growth.

Recovery from peripheral nerve transection is accelerated by local application of alpha-MSH by means of microporous Accurel polypropylene tubes

The peptide hormone alpha-melanocyte stimulating hormone (alpha-MSH), accelerates the return of sensitivity to the rat hindpaw after nerve transection. A marked reduction in the recovery time is observed when alpha-MSH is applied locally to the repair site by means of the microporous Accurel polypropylene tube delivery system. The tubes alone have a significant but smaller beneficial effect. These results have implications for the mode of action of neurotrophic melanocortins and suggest a potential means of improving the outcome of surgical nerve repair in the clinic.

Alpha-melanocyte-stimulating hormone stimulates the outgrowth of myelinated nerve fibers after peripheral nerve crush

The effect of alpha-melanocyte-stimulating hormone on peripheral nerve regeneration was studied by monitoring functional recovery and quantifying histologic changes that follow crush lesion of the rat sciatic nerve. The results showed that such treatment of rats with a crushed sciatic nerve resulted in a reduction of the recovery period and in an increase in the number of regenerating nerve fibers.

Characterization of epitopes shared by alpha-melanocyte-stimulating hormone (alpha-MSH) and the 150-kD neurofilament protein (NF150): relationship to neurotrophic sequences

Immunoblot techniques and immunohistochemistry have been used to investigate epitopes shared by alpha-melanocyte-stimulating hormone (alpha-MSH) and the 150-kD neurofilament protein (NF150). Three anti-alpha-MSH antisera (namely 31H2T, 4394, and M5) from a total of 12 sera were found to react with NF150. The three crossreacting sera are different in their binding properties to peptide fragments related to alpha-MSH, suggesting that at least two distinct epitopes are shared by NF150 and alpha-MSH. The only known sequence common to NF150 and alpha-MSH, the N-terminal Ac-S-Y residues, appears to be essential for binding of sera 31H2T and 4394. However, the binding of antiserum M5 involves other, currently unknown, similarities between NF150 and alpha-MSH. This is shown by the binding of M5 to peptides such as ACTH(4-10), which do not contain the N-terminal Ac-S-Y sequence. Binding of M5 to tobacco mosaic virus coat protein (TMV-coat protein), which is homologous with alpha-MSH and NF150 in its Ac-S-Y residues, was negligible. The peptide structures that are recognized by M5 have previously been shown to exert neurotrophic activity. The data are discussed in the light of the hypothesis that similarity between NF150 and alpha-MSH, as illustrated by binding to M5, may be significant in the neurotrophic activity of MSH-related peptides.

The effect of ACTH4-10 on protein synthesis, actin and tubulin during regeneration

The effects of ACTH4-10, a peptide fragment of corticotropin, on rat dorsal root ganglia (DRG), spinal cord and sciatic nerve were studied following a crush lesion of the sciatic nerve. The in vitro total protein synthesis rate of DRG L4, L5 and L6, measured one and three days after ipsilateral nerve crush, were not altered by various ACTH4-10 treatment regimes. Likewise, neither ACTH4-10 treatment of sham-operated rats nor in vitro exposure of control ganglia to peptide, resulted in changes in synthesis rate. Four days after crush lesion, the amounts of actin and tubulin in the ventral horn L2-L5 region of the spinal cord and of actin in DRG L5 were estimated following 2-dimensional separation. No significant effect of ACTH treatment was found. Degeneration-associated changes in the protein profiles of segments of sciatic nerve were not altered by ACTH4-10 treatment. The data are discussed in relation to the possible site of action of neurotrophic ACTH-like peptides.

Multiple phosphorylation of pp30, a rat brain polyribosomal protein, sensitive to polyamines and corticotropin

A rat brain polyribosomal protein with an apparent Mr of 30 000, designated pp30, was further characterized. The protein was identified by its phosphorylation by an endogenous protein kinase sensitive to both corticotropin and spermine. Two-dimensional separation of a polyribosomal fraction was applied, combining non-equilibrium pH-gradient-gel electrophoresis in the first and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis in the second dimension. In this system, pp30 was separated into at least five defined phosphoprotein spots. Pulse-labelling with [gamma-32P]ATP followed by a chase for various time periods with excess unlabelled ATP resulted in a shift of the distribution of radioactivity and protein staining along the spots towards the anode. This suggests that the various spots of pp30 may represent multiple phosphorylation states. Limited proteolysis of the five spots with three different proteinases resulted in the same one-dimensional peptide maps with a given proteinase, indicating that all five spots represent different forms of a single phosphoprotein. Inhibition of the overall phosphorylation of pp30 by corticotropin or spermine was accompanied by a shift in the recovery of labelled phosphate towards spots nearer the cathode. Immunoblotting with monoclonal antibodies directed against ribosomal protein S6 stained only one band, a protein that had an apparent Mr of 34 000 and was clearly distinct from pp30.

Modulation of phosphorylation of a 30-kD polyribosomal protein (pp30) by ACTH and spermine: comparison with modulation of brain protein synthesis

Gel electrophoretic separation of proteins phosphorylated in a postmitochondrial supernatant fraction of brain in the presence of spermine or adrenocorticotropin (ACTH) indicated modulation in only one region (30 kD) of the gel. The 30-kD (pp30) protein together with enzyme activity catalyzing its phosphorylation and sensitivity of the phosphorylation to spermine and ACTH were retained in a free polyribosomal fraction of this extract. ACTH(11-24) inhibited phosphorylation at all the spermine or Mg2+ concentrations tested. Structure-activity studies revealed that the inhibitory activity within ACTH(1-24) resides in the sequences ACTH(11-24), (5-18, 17Lys, 18Lys)-NH2, (15-24), (7-16)-NH2, and (1-16)-NH2 and can also be found in certain polylysine fragments. Phosphorylation under conditions suitable for measuring protein synthesis revealed only one phosphoprotein (pp30), sensitive to both ACTH(15-24) and spermine. The possibility of a relationship between modulation of pp30 phosphorylation and modulation of brain cell-free protein synthesis is discussed in relation to the effects of ACTH, spermine, and Mg2+.

Cyclic nucleotide- and calcium-independent phosphorylation of proteins in rat brain polyribosome: effects of ACTH, spermine, and hemin

The incorporation of [gamma-32P]ATP into proteins of rat brain polyribosomes was studied in vitro. The effects of cyclic nucleotides, calcium, hemin, ACTH, GTP, and spermine were examined. The incorporation of phosphate into proteins increased with time and phosphatase activity was very low; thus, the extent of phosphorylation was predominantly a reflection of protein kinase activity. Phosphorylation of proteins was not sensitive to Ca2+ in the presence or absence of either calmodulin or phosphatidylserine. Phosphorylation was also unaffected by cyclic nucleotides in the absence of exogenous enzymes. However, addition of a cAMP-dependent protein kinase together with cAMP resulted in a stimulation of the incorporation of phosphate into 4 phosphoproteins (pp70, pp58, pp43, and pp32); phosphorylation of pp32 was completely dependent on the addition of the kinase. ACTH (1-24), (11-24), and spermine inhibited the endogenous phosphorylation of one protein band (pp30). The phosphorylation of this 30 kD band was also selectively increased by hemin (5 microM). Higher concentrations of hemin exerted an inhibitory effect on the majority of the phosphoproteins. Protein phosphatase activity was not influenced by ACTH or spermine. The specific inhibition of pp30 phosphorylation by ACTH or spermine is most probably explained by an interaction with a cyclic nucleotide- and Ca2+ -independent protein kinase.

Evidence that the neurotrophic actions of alpha-MSH may derive from its ability to mimick the actions of a peptide formed in degenerating nerve stumps

The ability of alpha-MSH to facilitate the recovery of sensorimotor nerve function following crush lesion is restricted to a critical period following such a lesion. This period coincided with the initiation of sprouting and the disappearance of the 150 kD neurofilament protein from the degenerating distal stump of the nerve. Degenerating nerve contains a factor that is active in a bioassay system for MSH. This factor could not be detected in control nerves. The hypothesis is forwarded that a neurotrophic factor known to be present in degenerating nerve stumps is an alpha-MSH-like peptide formed by the breakdown of the 150 kD neurofilament protein.

Modulation of protein synthesis in a cell-free system derived from rat brain by corticotropin (ACTH), magnesium, and spermine

Modulation of protein synthesis by fragments of the ACTH molecule has been studied in a cell-free system obtained from subcortical brain tissue of rats. Both the activity of the protein-synthesizing system and its sensitivity to ACTH-like peptides appeared to be highly dependent on the Mg2+ and spermine concentrations. At optimal Mg2+ concentrations (4 mM) the peptide sequences ACTH(1-24) and (11-24) were both inhibitory, the latter being the more active. The inhibitory effect was reduced or abolished at higher (suboptimal) concMg2+ concentrations. Spermine, like ACTH, inhibited protein synthesis at the optimal Mg2+ concentration. However, at lower Mg2+ concentrations spermine had a stimulatory effect and maximal activity was obtained at 0.75-1.0 mM Mg2+. In the presence of spermine (60 microM) and Mg2+ (0.75 mM), a half-maximal inhibition of protein synthesis was obtained with a peptide concentration of 5 microM. A structure-activity study showed that the peptides ACTH(7-16)-NH2, (11-24), (5-18, 17Lys 18Lys)-NH2 and (15-24) were active in inhibiting protein synthesis, whereas the fragments ACTH(1-16)-NH2 and (17-24) were inactive. The results are discussed in terms of an interaction between ACTH, Mg2+, and spermine, and intracellular processes involved in protein synthesis.

The glutathione-linked metabolism of 2-allyl-2-isopropy-lacetamide in rats. Further evidence for the formation of a reactive metabolite

2-Allyl-2-isopropylacetamide (AIA) causes a depletion of liver glutathione in rats only if the animals have been pretreated with phenobarbitone. Phenobarbitone stimulates the excretion in bile of a component derived from AIA and glutathione which is apparently not the same as the conjugate formed by reaction of the two components in simple solutions. The significance of these findings are considered in relation to the suggestion that AIA is metabolised to an epoxide by the microsomal enzyme system; in addition several differences between AIA and the non-porphyrogenic compound, acrylamide, are discussed.