Age- and species-dependent maturation of synaptic transmission in the superficial superior colliculus

Both neonatal maturity and postnatal maturation are known to be species dependent. For instance, guinea pigs are born with their eyes open, while eye opening takes place 2 weeks after birth in rats. Moreover, several abnormalities have been observed in albino compared to pigmented species. The pigment melanin is proposed to play a protective role and its absence is thought to contribute to neuronal deficits. In the present study, we aimed to investigate functional differences in synaptic transmission in the visual, superficial layers of the superior colliculus (SC) of albino and pigmented rats and pigmented guinea pigs, at eye opening and 1 month after birth. This was achieved by analysing evoked field excitatory postsynaptic potentials (fEPSPs) in vitro, and by investigating the ability of these responses to express gamma-aminobutyric acid (GABA)-induced long-term potentiation (LTPG), an enduring increase in synaptic efficacy resulting from bath application of GABA. Guinea pigs did not show any obvious differences with respect to overall fEPSP characteristics and synaptic plasticity at both ages studied, indicating that maturation must have occurred prenatally. Rats, however, underwent synaptic maturation and refinement to produce stronger fEPSPs and a more robust level of synaptic plasticity 1 month after birth compared to the conditions at eye opening. The state of pigmentation was found to have a crucial influence, with albino rats showing less enhancement of the strength of synaptic transmission in the SC. It can therefore be concluded that profound developmental differences in pre- and postnatal maturation of the superficial SC exist between guinea pigs and rats, and that the state of pigmentation is a crucial factor in this process.

Binge pattern ethanol exposure in adolescent and adult rats: differential impact on subsequent responsiveness to ethanol

BACKGROUND

Recent evidence indicates that adolescent animals are more sensitive than adults to the disruptive effects of acute ethanol exposure on spatial learning. It is not yet known whether adolescent animals are also more sensitive than adults to the enduring neurobehavioral effects of repeated ethanol exposure. In this study, animals were exposed to ethanol in a binge-pattern during either adolescence or adulthood. At a time when all subjects were adults, spatial working memory was examined in the absence and presence of an acute ethanol challenge.

METHODS

Rats were exposed to ethanol (5.0 g/kg intraperitoneally) or isovolumetric saline at 48 hr intervals over 20 days. Exposure began on either postnatal day 30 (adolescent group) or 70 (adult group). Twenty days after the final injection, a time at which all animals were adults, the subjects were tested on an elevated plus maze and then were trained to perform a spatial working memory task on an eight-arm radial maze. At the beginning of each session of training on the working memory task, subjects retrieved food rewards on four of the eight arms. After a delay, subjects were placed on the maze and allowed to retrieve food from the remaining four arms.

RESULTS

Prior exposure to ethanol did not influence behavior on the plus maze. Performance of the groups did not differ during acquisition of the spatial working memory task with a 5 min delay or during subsequent testing with a 1 hr delay. However, animals treated with ethanol during adolescence exhibited larger working memory impairments during an ethanol challenge (1.5 g/kg intraperitoneally) than subjects in the other three groups.

CONCLUSIONS

The findings indicate that binge pattern exposure to ethanol during adolescence enhances responsiveness to the memory-impairing effects of ethanol in adulthood.

Islet hormones from the African bullfrog Pyxicephalus adspersus (Anura:Ranidae): structural characterization and phylogenetic implications

The African bullfrog Pyxicephalus adspersus is generally classified along with frogs of the genus Rana in the subfamily Raninae of the family Ranidae but precise phylogenetic relationships between species are unclear. Pancreatic polypeptide (PP), insulin, and glucagon-like peptide (GLP-1) were isolated from an extract of P. adspersus pancreas and characterized structurally. A comparison of the amino acid sequence of Pyxicephalus PP (APSEPQHPGG(10)QATPEQLAQY(20)YSDLYQYITF(30)ITRPRF++ +. NH(2)) with those of the known amphibian PP molecules in a maximum parsimony analysis generates a single phylogenetic tree in which Pyxicephalus is the sister to the clade comprising the members of the genus Rana. The three orders of living amphibians form discrete clades with the representative of the Gymnophiona appearing as sister to the Caudata-Anura. In contrast, Pyxicephalus insulin (A chain, GIVEQCCHSA(10)CSLYDLENYC(20)N; B-chain, LANQHLCGSH(10)LVEALYMVCG(20)ERGFFYYPKS(30)) and and GLP-1 (HAEGTFTSDM(10)TSYLEEKAAK(20)EFVDWLIKGR(30)PK) resemble more closely the corresponding peptides from the cane toad Bufo marinus than the peptides from any species of Rana. Cladistic analysis based upon the amino acid sequences of insulin produced a polyphyletic assemblage with the Gymnophiona nesting within an unresolved clade containing the non-ranid frogs. The data support the assertion that the amino acid sequence of PP, but not those of the other islet hormones, is of value as a molecular marker for inferring phylogenetic relationships between early tetrapod species.

Ethanol, memory, and hippocampal function: a review of recent findings

For well over a century, ethanol was believed to exert its effects on cognition and behavior by producing a ubiquitous depression of central nervous system activity. A general disruption in brain function was consistent with the belief that ethanol's effects on cognition and behavior were also quite general. Substantial evidence now indicates that ethanol produces a host of selective effects on neural activity, resulting in regional differences in ethanol's effects in the brain. Consistent with such evidence, recent research suggests that ethanol's effects on cognition and behavior are not as global as previously assumed. The present paper discusses evidence that many of ethanol's effects on learning and memory stem from altered cellular activity in the hippocampus and related structures. Potential mechanisms for ethanol's disruption of hippocampal function are reviewed. Evidence suggests that ethanol disrupts activity in the hippocampus by interacting directly with hippocampal neurons and by interacting with critical hippocampal afferents.

Acute ethanol administration impairs spatial performance while facilitating nonspatial performance in rats

Acute ethanol administration produces learning and memory impairments similar to those found following lesions to the hippocampal system in rats. For example, both ethanol and hippocampal lesions impair performance on spatial learning and memory tasks while sparing performance on many nonspatial learning and memory tasks. Lesions to the hippocampal system can also alter the nature of the information that the animal uses to guide its behavior, from using spatial information to using individual cues. In the present experiment, rats were trained, while sober, to navigate on an eight-arm radial arm maze to a specific arm for food reward. During training, the rewarded arm was always in the same specific location and contained well-defined cues. After the rat learned the task, a memory test was conducted under different doses of ethanol (0.0 g/kg [saline control], 1.0, 1.5, or 2.0 g/kg, intraperitoneal). On the test day the maze was rotated so that the cued arm was 90 degrees to the right of its original position. During testing, intact rats showed a significant bias to approach the place where they had been previously rewarded, even though the cue was no longer located there. Acute ethanol administration dose dependently reduced approaches to the rewarded place. However, ethanol administration did not result in increases in random choices; rather, it resulted in a dose-dependent increase in approaches to the cued arm, now in a new location. These results extend previous research showing that acute ethanol administration and lesions to the hippocampal system produce similar effects on learning and memory in rats.

Placing hippocampal single-unit studies in a historical context

A profound increase in the study of the role of the hippocampus in behavior and cognitive processing resulted from the startling discovery by O'Keefe and Dostrovsky in 1971 that hippocampal neurons fire selectively in different regions or "place fields" of an environment. That discovery spawned a comprehensive theory of hippocampal function that was elucidated in the publication, The Hippocampus as a Cognitive Map by O'Keefe and Nadel in 1978. According to the theory, the hippocampus serves as the neural substrate for maps of allocentric space. The goal of this paper is to revisit the historical background for the development of the cognitive map theory and to examine the context in which the theory and the phenomenon of place field activity began to gain acceptance by the scientific community. While subsequent research has led some to question if the theory can adequately account for all consequences of hippocampal lesions and all the correlates of hippocampal cellular activity, it is clear the theory has stood the test of time and has been successful in generating an enormous amount of fruitful research.

Insulin and proglucagon-derived peptides from the horned frog, Ceratophrys ornata (Anura:Leptodactylidae)

Insulin and peptides derived from the processing of proglucagon have been isolated from an extract of the pancreas of the South American horned frog, Ceratophrys ornata (Leptodactylidae). Ceratophrys insulin is identical to the insulin previously isolated from the toad, Bufo marinus (Bufonidae). Ceratophrys glucagon was isolated in two molecular forms with 29- and 36-amino acid residues in approximately equal amounts. Glucagon-29 is identical to glucagon from B. marinus and from the bullfrog, Rana catesbeiana (Ranidae) and contains only 1 amino acid substitution (Thr29 --> Ser) compared with glucagon from Xenopus laevis (Pipidae). Glucagon-36 comprises glucagon-29 extended from its C-terminus by Lys-Arg-Ser-Gly-Gly-Met-Ser. This extension is structurally dissimilar to the C-terminal octapeptide of mammalian oxyntomodulin and resembles more closely that found in C-terminally extended glucagons isolated from fish pancreata. Ceratophrys glucagon-like peptide-1 (GLP-1) (His-Ala-Asp-Gly-Thr-Tyr-Gln-Asn-Asp-Val10-Gln-Gln-Phe-Leu-Glu- Glu-Lys-Ala-Ala-Lys20-Glu-Phe-Ile-Asp-Trp-Leu-Ile-Lys-Gly- Lys30-Pro-Lys-Lys-Gln-Arg-Leu-Ser) contains 3 amino acid substitutions compared with the corresponding peptide from B. marinus, 8 substitutions compared with GLP-1 from R. catesbeiana, and between 4 and 11 substitutions compared with the three GLP-1 peptides identified in X. laevis proglucagon. GLP-2 was not identified in the extract of Ceratophrys pancreas. The data indicate that, despite its importance in the regulation of glucose metabolism, the primary structure of GLP-1 has been very poorly conserved during evolution, even among a single order such as the Anura.

Anti-inflammatory actions of interleukin-13: suppression of tumor necrosis factor-alpha and antigen-induced leukocyte accumulation in the guinea pig lung

The Th2 cytokine interleukin (IL)-13 is believed to play an important role in the development of allergy, although it has also been ascribed anti-inflammatory roles in several experimental models. In this study, we have examined the effects of human recombinant IL-13 on eosinophilic lung inflammation in the guinea pig. IL-13 (1 to 100 ng, given by intratracheal instillation) did not elicit airway eosinophil recruitment. A pronounced accumulation of eosinophils, as well as monocyte/macrophages, was elicited by intratracheal instillation of guinea pig tumor necrosis factor alpha (gpTNF-alpha). Intratracheal administration of IL-13 (1 to 100 ng) given immediately prior to exposure to gpTNF-alpha resulted in a dose-related suppression of eosinophil and monocyte/macrophage accumulation in the airways, as assessed by bronchoalveolar lavage (BAL) and eosinophil peroxidase activity in whole-lung homogenates. IL-13 treatment also reduced BAL fluid (BALF) leukocyte accumulation induced by subsequent aerosol antigen challenge of sensitized guinea pigs. Antigen challenge also resulted in elevated levels of immunoreactive eotaxin and eosinophil-stimulating activity in BALF, although only the latter was reduced significantly by IL-13 instillation prior to challenge. In contrast to the suppressive effects of IL-13, instillation of human recombinant IL-4 (100 ng) alone elicited an increase in BALF monocyte/macrophage numbers, and IL-4 was unable to inhibit gpTNF-alpha-induced leukocyte accumulation. Hence, IL-13 (but not human IL-4) exhibits an anti-inflammatory action in the airways of gpTNF-alpha- or antigen-challenged guinea pigs, by mechanisms that may involve the decreased generation of eosinophil-stimulating activity in the airways.

Transient behavior of infrared photoconductors: application of a numerical model

A numerical model for the transient response of extrinsic photoconductors is applied to the behavior of Ge:Ga and GaAs:Te detectors. Photoconductors display a two-component response to changes in illumination. The characteristic time and magnitude for the slow component have been studied as a function of background flux, applied field, temperature, device length, and signal size. For large-signal applications, the background flux affects the transient response even when the signal is orders of magnitude greater than the background. Experimental results are presented to support key predictions of the modeling. Because the ratio of fast to slow components is independent of both background and signal size, we propose the operation of detectors in such a way that final signal levels are derived from the fast component.

Spatial performance is more sensitive to ethanol than nonspatial performance regardless of cue proximity

In rodents, ethanol produces a greater impact on the ability to perform spatial reference memory tasks than nonspatial reference memory tasks. Such evidence may reflect a selective disruption in the use of previously acquired spatial information. However, a nonmnemonic explanation has yet to be ruled out Tasks used to study ethanol's effects on spatial memory commonly require subjects to utilize distal, or extramaze, cues to respond correctly. In contrast, many previously used nonspatial tasks could be solved using cues located on the maze itself. Because ethanol has been shown to disrupt sensory processing, it is possible that previously observed differences in the effects of ethanol on spatial and nonspatial performance were actually due to differences in the proximity of relevant cues in the spatial and nonspatial tasks and not to a selective disruption in spatial memory. The present study compares the effects of ethanol on the performance of spatial and nonspatial reference memory tasks that require subjects to discriminate among extramaze cues for correct responding. Subjects were trained while sober to navigate to a goal arm on a 12-arm maze. In the spatial task, the goal arm was defined by its location with respect to a number of extramaze cues. In the nonspatial task, the goal arm was defined by the presence of a single extramaze cue located directly beyond the end of the arm. Subjects were tested under 1 of 4 doses of ethanol (0.0, 0.7, 1.4, and 2.1 g/kg). Performance on the nonspatial task was more resistant to the effects of ethanol than performance on the spatial task. The results suggest that differences in the effects of ethanol on spatial and nonspatial performance are not due to differences in the proximity of relevant cues in previously used spatial and nonspatial tasks.

The effects of MK-801 on spatial working memory and within-session spatial learning

The present study investigated the effects of the NMDA channel blocker MK-801 (0.05, 0.10, and 0.15 mg/kg) on a task that allows for the assessment of both spatial working memory and within-session spatial learning. During the first trial of each day, subjects were shown the spatial location of a food reward on a six-arm radial-arm maze. During nine subsequent free-choice trials, subjects were reinforced for returning to that same spatial location. The location of the food reward varied across days. Thus, choosing correctly on any given trial required subjects to remember where food had been received during the previous trials of that day. The effects of MK-801 on working memory were assessed by analyzing the overall number of errors committed during the nine free-choice trials of each day. The effects of MK-801 on within-session learning were assessed by comparing the number of errors committed during the first three trials of each day to the number of errors committed during the last three trials of each day. Only the highest dose of MK-801 tested (0.15 mg/kg) impaired spatial working memory. No dose of MK-801 impaired the ability of subjects to acquire spatial information within a given session. The failure of MK-801 to impair within-session spatial learning stands in contrast to the well-known effects of MK-801 on spatial learning measured across days. Thus, when coupled with previous research, the findings of the present study further suggest that the NMDA receptor plays a role in the long-term, but not short-term, storage of spatial information.

Comparison between the effects of ethanol and diazepam on spatial working memory in the rat

The present study compared the effects of ethanol and diazepam on a task that allows for the assessment of both spatial working memory and the acquisition of spatial information within each day. During the first trial of each day, subjects were shown the spatial location of a food reward on a six-arm radial-arm maze. During nine subsequent free-choice trials, subjects were reinforced for returning to that same spatial location. The location of the food reward varied across days. Thus, choosing correctly on any given trial required subjects to remember where food had been received during the previous trials of that day. The effects of ethanol and diazepam on working memory were assessed by analyzing the overall number of errors committed during the nine free-choice trials of each day. The effects of ethanol and diazepam on within-day acquisition were assessed by comparing the number of errors committed during the first three trials of each day to the number of errors committed during the last three trials of each day. Ethanol and diazepam both produced dose-dependent increases in working memory errors, and both did so without impairing within-day acquisition. The results of the present study provide further evidence of the similarities between the effects of ethanol and benzodiazepine receptor agonists on learning and memory, and are consistent with the hypothesis that ethanol's potentiation of GABA at GABAA receptors contributes to the learning and memory impairments produced by ethanol.

Large scale identification of genes involved in cell surface biosynthesis and architecture in Saccharomyces cerevisiae

The sequenced yeast genome offers a unique resource for the analysis of eukaryotic cell function and enables genome-wide screens for genes involved in cellular processes. We have identified genes involved in cell surface assembly by screening transposon-mutagenized cells for altered sensitivity to calcofluor white, followed by supplementary screens to further characterize mutant phenotypes. The mutated genes were directly retrieved from genomic DNA and then matched uniquely to a gene in the yeast genome database. Eighty-two genes with apparent perturbation of the cell surface were identified, with mutations in 65 of them displaying at least one further cell surface phenotype in addition to their modified sensitivity to calcofluor. Fifty of these genes were previously known, 17 encoded proteins whose function could be anticipated through sequence homology or previously recognized phenotypes and 15 genes had no previously known phenotype.

Airway inflammation induced by recombinant guinea pig tumor necrosis factor-alpha

We have cloned and expressed recombinant guinea pig tumor necrosis factor-alpha (gpTNF-alpha) and examined its inflammatory activities after tracheal instillation in guinea pigs. A 1,071-bp cDNA, including the region encoding the full-length 234-amino acid gpTNF-alpha protein, was cloned from concanavalin A-stimulated guinea pig splenocytes. The 154-amino acid protein corresponding to secreted gpTNF-alpha was expressed as a fusion protein in Escherichia coli, purified by affinity chromatography, and cleaved to yield a 17-kDa protein. gpTNF-alpha had a cytotoxic effect on WEHI 164 cells and was detected by goat anti-murine tumor necrosis factor-alpha (TNF-alpha) antibody in Western blots. Intratracheal instillation of gpTNF-alpha (50-150 ng) caused pronounced and dose-dependent airway eosinophilia. Incubation of gpTNF-alpha with rabbit anti-murine TNF-alpha sera or heating the gpTNF-alpha before instillation reduced bronchoalveolar lavage (BAL) eosinophils to near control levels. Maximum BAL eosinophilia was observed at 24 h, but eosinophil numbers remained significantly above vehicle-treated animals for 72 h. Hence, gpTNF-alpha elicits a pronounced and protracted eosinophil accumulation in the guinea pig lung.

Recombinant guinea pig and human RANTES activate macrophages but not eosinophils in the guinea pig

To characterize the biologic activities of potential mediators of allergic inflammation, we have cloned, expressed, and purified guinea pig RANTES (gpRANTES). cDNA for gpRANTES was cloned from Con A-stimulated guinea pig spleen cells. A high level of gpRANTES expression in Escherichia coli was achieved by mutation of a human RANTES (hRANTES) expression construct to obtain a 68-amino acid protein identical with the predicted guinea pig amino acid sequence, assuming an equivalent amino terminus as the human protein. Purified gpRANTES was an effective stimulus of human eosinophils as assessed by increases in intracellular free calcium in fura-2-loaded cells and chemotactic responses in vitro. gpRANTES exhibits similar potency and efficacy to hRANTES. In marked contrast, neither gpRANTES nor hRANTES was able to activate guinea pig peritoneal eosinophils in these assays, even in the presence of IL-5. However, gpRANTES was found to be a potent stimulator of guinea pig peritoneal macrophages. Following tracheal instillation of gpRANTES, a dose-dependent increase in macrophages, but not eosinophils, was observed in gpBAL. Macrophage accumulation was detectable by 6 h and sustained for at least 48 h. These results indicate that RANTES in the guinea pig may have a different cellular selectivity than that described in the human, which may be important in the use of animal models in the analysis of allergic disorders. These selectivities do not appear to be accounted for by differences in guinea pig and human RANTES sequences.

Recombinant guinea pig and human RANTES activate macrophages but not eosinophils in the guinea pig

To characterize the biologic activities of potential mediators of allergic inflammation, we have cloned, expressed, and purified guinea pig RANTES (gpRANTES). cDNA for gpRANTES was cloned from Con A-stimulated guinea pig spleen cells. A high level of gpRANTES expression in Escherichia coli was achieved by mutation of a human RANTES (hRANTES) expression construct to obtain a 68-amino acid protein identical with the predicted guinea pig amino acid sequence, assuming an equivalent amino terminus as the human protein. Purified gpRANTES was an effective stimulus of human eosinophils as assessed by increases in intracellular free calcium in fura-2-loaded cells and chemotactic responses in vitro. gpRANTES exhibits similar potency and efficacy to hRANTES. In marked contrast, neither gpRANTES nor hRANTES was able to activate guinea pig peritoneal eosinophils in these assays, even in the presence of IL-5. However, gpRANTES was found to be a potent stimulator of guinea pig peritoneal macrophages. Following tracheal instillation of gpRANTES, a dose-dependent increase in macrophages, but not eosinophils, was observed in gpBAL. Macrophage accumulation was detectable by 6 h and sustained for at least 48 h. These results indicate that RANTES in the guinea pig may have a different cellular selectivity than that described in the human, which may be important in the use of animal models in the analysis of allergic disorders. These selectivities do not appear to be accounted for by differences in guinea pig and human RANTES sequences.

Nitric oxide-induced mobilization of intracellular calcium via the cyclic ADP-ribose signaling pathway

Cyclic adenosine diphosphate ribose (cADPR) is a potent endogenous calcium-mobilizing agent synthesized from beta-NAD+ by ADP-ribosyl cyclases in sea urchin eggs and in several mammalian cells (Galione, A., and White, A. (1994) Trends Cell Biol. 4, 431 436). Pharmacological studies suggest that cADPR is an endogenous modulator of Ca2+-induced Ca2+ release mediated by ryanodine-sensitive Ca2+ release channels. An unresolved question is whether cADPR can act as a Ca2+-mobilizing intracellular messenger. We show that exogenous application of nitric oxide (NO) mobilizes Ca2+ from intracellular stores in intact sea urchin eggs and that it releases Ca2+ and elevates cADPR levels in egg homogenates. 8-Amino-cADPR, a selective competitive antagonist of cADPR-mediated Ca2+ release, and nicotinamide, an inhibitor of ADP-ribosyl cyclase, inhibit the Ca2+-mobilizing actions of NO, while, heparin, a competitive antagonist of the inositol 1,4,5-trisphosphate receptor, did not affect NO-induced Ca2+ release. Since the Ca2+-mobilizing effects of NO can be mimicked by cGMP, are inhibited by the cGMP-dependent-protein kinase inhibitor, Rp-8-pCPT-cGMPS, and in egg homogenates show a requirement for the guanylyl cyclase substrate, GTP, we suggest a novel action of NO in mobilizing intracellular calcium from microsomal stores via a signaling pathway involving cGMP and cADPR. These results suggest that cADPR has the capacity to act as a Ca2+-mobilizing intracellular messenger.

Reliability of the peabody developmental gross motor scale in children with cerebral palsy

The test/retest, intrarater, and interrater reliability of the Peabody Development Gross Motor Scale (PDGMS) was assessed in 12 children with mild or moderate cerebral palsy. A baseline test was administered, scored, and videotaped by one rater and rescored from the videotape by a second independent rater. In order to minimize the effect of developmental maturation, test/retest correlation coefficients of the tests were performed two weeks apart. The intraclass correlation coefficients ranged from 0.82 to 0.98. For interrater reliability, testing following the same protocol was repeated at 2 weeks, 3 and 6 months. Interrater correlation coefficients (r) ranged from 0.89 to 0.98. Interrater correlation coefficients (ICC) from scoring and later rescoring ten videotapes with the closest and furthest interrater agreement ranged from 0.88 to 0.99. The balance and locomotor skill categories were most responsive for assessing gross motor function in this population. These data support the use of the PDGMS as an assessment tool for children with cerebral palsy and the reliability of videotaping assessments.

Parental concerns following a child's discharge from a bone marrow transplant unit

The purpose of this descriptive study was to explore the concerns of parents following a child's discharge from a bone marrow transplant unit. A qualitative approach which included components of grounded theory was used to explore the posttransplant experience from the parents' perspective. Seven parents of five children who were transplanted for a variety of malignancies at a number of out-of-state centers were interviewed about their experiences. Chart analysis and participant observation provided additional sources of data. Initial coding of audio-taped interviews revealed 32 topics of concern voiced by the parents. Use of the constant comparative analysis technique resulted in the emergence of six major themes of the posttransplant experience. The Return Home, Changing Relationships, Working with This, Learning the Rules, The New Norm, and The Uncertain Future were components of this transitional period for each family. Similarities were found between the experiences of study parents and the parents of chronically ill children and parents or spouses of organ transplant recipients. Awareness of posttransplant concerns may facilitate the efforts of both transplant and referral center staff to educate, support, and care for these children and their families.

Cyclic ADP-ribose-induced Ca2+ release from rat brain microsomes

Cyclic ADP-ribose (cADPR), an endogenous NAD+ metabolite in many mammalian and invertebrate tissues, is a potent mediator of calcium mobilization in sea urchin eggs. Our results show that cADPR also stimulates calcium release from rat brain microsomes, marked release occurring over the concentration range 10-250 nM. This is not inhibited by concentrations of heparin which completely abolish inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release. Ryanodine (100 microM) inhibits the cADPR response. Our results are consistent with cADPR being an endogenous messenger mediating Ca2+ release from ryanodine-sensitive pools in brain.

Comparison of Ins(1,4,5)P3 receptors from rat cerebellum and bovine adrenal cortex

Ins(1,4,5)P3 receptors in adrenal cortical and cerebellar membranes can be distinguished by their affinities for Ins(1,4,5)P3 as well as the potencies with which heparin and Mg2+ inhibit binding. We have found that the differences in Ins(1,4,5)P3 affinity and heparin inhibition are maintained upon receptor solubilization and purification. In contrast to this, heparin-agarose affinity purification of solubilized cerebellar receptors reduces the potency of Mg2+ inhibition to that in adrenal cortex. These results suggest that Ins(1,4,5)P3 receptors in adrenal cortex are structurally distinct from those in cerebellum. Monoclonal antibodies raised against C- and N-terminal regions of mouse cerebellar Ins(1,4,5)P3 receptors recognize 250-300-kDa proteins in both rat cerebellum and bovine adrenal cortex.

Two tRNA gene clusters associated with rRNA operons rrnD and rrnE in Bacillus subtilis

Sequence analysis of cloned rescued DNA fragments from a Bacillus subtilis strain with an inserted recombinant plasmid in ribosomal operon rrnE revealed the presence of two tRNA genes for Met and Asp at the 3' end of the operon. Probing chromosomal DNA from a strain carrying a plasmid inserted in rrnD with a fragment containing the genetically unassigned cluster of 16 tRNA genes revealed that the cluster is located immediately following the rrnD operon. Our findings show that all 10 rrn operons in B. subtilis are associated with tRNA gene clusters.