Formation of Titanium Nitride/Silicide Bilayers by Rapid Thermal Anneal in Nitrogen

Sputter deposited Ti films on Si and SiO2 substrates have been rapid thermal annealed in N2 at temperatures of 400–1100°C, and the reaction followed using AES, TEM, electron diffraction and sheet resistance measurements. The Ti initially becomes contaminated with oxygen before being nitrided at the surface and silicided at the interface. The oxygen is expelled from the siuicide and a TiNxO1−x/TiSix bilayer eventually results. With Si substrates, TiNxO1−x is much the thinner layer whereas the reverse is true on SiO2. Extended annealing in N2 completely converts the TiSi2 layer on Si into TiN.

Characteristics of children referred for evaluation of school difficulties who have adequate academic achievement scores

Forty children (7 to 11 years old) referred for evaluation of learning problems, who had scores within the normal range on standardized measures of academic achievement, were compared to 81 similarly referred children who had scored low (< 90) on at least one measure of academic achievement. We tested the hypothesis that children with normal achievement scores who are referred for evaluation of learning problems show neuropsychological profiles comparable to those of children with low achievement. Referral problems, school history, IQ, academic achievement, and neuropsychological function were evaluated. Referred children with normal achievement scores came from more advantaged backgrounds and had less intensive academic interventions, higher IQs, and better decoding skills. Nonetheless, the two groups showed similar neuropsychological profiles. Vulnerability to complexity and decreased automaticity were prominent. Normal-range achievement test scores among children referred for evaluation should not be regarded as indicating absence of neurodevelopmental vulnerability.

Implication of the GABA(B) receptor in gamma vinyl-GABA's inhibition of cocaine-induced increases in nucleus accumbens dopamine

Previously, we demonstrated that gamma vinyl-GABA (GVG, Vigabatrin) dose-dependently inhibits cocaine-induced increases in dopamine (DA) concentrations in both the rodent and primate brain. Furthermore, it abolishes cocaine self-administration and conditioned place preference, while having no effect on locomotor activity or drug delivery to the brain. In an effort to better understand the mechanisms underlying this inhibition, we examined the effect of the selective GABA(B) receptor antagonist SCH 50911 on the GVG-induced decrease in cocaine's elevation of extracellular DA concentrations in the nucleus accumbens (NACC). Cocaine administration alone (20 mg/kg i.p.) produced a 480% increase in extracellular NACC DA levels. GVG (300 mg/kg i.p.) significantly reduced this increase by 25% (P<0.01). In sharp contrast, extracellular DA levels increased to 550% after the sequential administration of SCH 50911 (3 mg/kg i.p.), GVG, and cocaine. This increase is significantly different than GVG and cocaine (P<0.05) but similar to cocaine alone. These results demonstrate that the GABA(B) antagonist SCH 50911 was able to completely abolish GVG's inhibition of cocaine-induced increases in DA in the NACC and implicates the GABA(B) receptor in the mechanism underlying this inhibition.

A novel strategy for the treatment of cocaine addiction

Cocaine's addictive liability has been linked to its pharmacologic actions on mesotelencephalic dopamine (DA) reinforcement/reward pathways in the central nervous system (CNS). Dopaminergic transmission within these pathways is modulated by gamma-aminobutyric acid (GABA). With this knowledge, we examined the utility of gamma vinylGABA (GVG), a selective and irreversible inhibitor of GABA-transaminase (GABA-T) known to potentiate GABAergic inhibition, to alter cocaine's biochemical effects as well as its effects on behaviors associated with these biochemical changes. GVG significantly attenuated cocaine-induced increases in neostriatal synaptic DA in the non-human primate (baboon) brain as assessed by positron emission tomography (PET) and abolished both the expression and acquisition of cocaine-induced conditioned place preference (CPP). It had no effect on CPP for a food reward, the delivery of cocaine to the brain or locomotor activity. These findings suggest the possible therapeutic utility in cocaine addiction of a pharmacologic strategy targeted at the GABAergic neurotransmitter system, a system distinct from but functionally linked to the DA mesotelencephalic reward/reinforcement system. However, rather than targeting the GABA receptor complex with a direct GABA agonist, this novel approach with GVG takes advantage of the prolonged effects of an irreversible enzyme inhibitor that raises endogenous GABA levels without the addictive liability associated with GABA agonists acting directly at the receptor itself. Human trials with GVG are currently being developed to directly examine the utility of this novel strategy for the treatment of cocaine addiction.

What are we measuring with PET?

Positron emission tomography is a medical imaging technique that provides unique information concerning many biochemical mechanisms underlying normal physiologic function. With respect to the central nervous system (CNS), selective radiolabeled compounds targeted at specific neurotransmitter receptor systems reveal information not only concerning receptor distribution and enzymatic activity but neurotransmitter concentrations as well. Recent advances in our understanding of these systems may be utilized to further understand changes in brain biochemistry that either result from or produce symptomatology associated with many CNS disease states. The ability to measure interactions between neurotransmitter systems in the human brain may also add to our knowledge of drug side effects and disease progression. While many CNS diseases have been defined as "neurotransmitter-specific" in nature, scientific data now suggests that changes in multiple neurotransmitter systems are evident in the brains of patients suffering from these classically described diseases. PET is a powerful tool that can be used to examine many of these changes in the living human brain.

Dyslexia, neurolinguistic ability, and anatomical variation of the planum temporale

This article addresses the relationship between patterns of planum temporale symmetry/asymmetry and dyslexia and neurolinguistic abilities. Considerable research indicates that dyslexic individuals typically do not display the predominant pattern of leftward planum temporale asymmetry. Variable findings on the structural basis of symmetry are due partially to measurement issues, which are examined in some detail in this critical review. The physiological basis of symmetry may be reduced neuronal elimination in the right planum, although other alternatives are offered. Theories are offered to explain how symmetrical plana are related to dyslexia, and it is evident that symmetrical plana are not sufficient to produce dyslexia. However, some evidence suggests that nonleftward plana asymmetry is associated with deficits in verbal comprehension, phonological decoding, and expressive language. It is concluded that nonleftward asymmetry is associated with linguistic deficits, but that explanatory theories need to be further developed. Among the many issues that need to be addressed, future research needs to determine whether the relationship between patterns of planum temporale symmetry/asymmetry and linguistic ability is specific to dyslexia or if asymmetry covaries lawfully with linguistic abilities in nondyslexic populations.

Effects of pharmacologic increases in brain GABA levels on cocaine-induced changes in extracellular dopamine

Cocaine-induced increases in extracellular dopamine (DA) concentrations were measured using in vivo microdialysis techniques in the nucleus accumbens (NACC) of freely moving rats. In control animals, cocaine increased extracellular DA concentrations approximately 482% 60 min following administration, returning to baseline values 200 min later. When administered 2 h following an acute dose of gamma-vinyl-GABA (GVG, Vigabatrin), cocaine-induced increases in extracellular DA were reduced to approximately 365% of baseline values. Chronic GVG administration further dose-dependently attenuated the effects of cocaine but did not alter the rate of increase or the rate of return to baseline values. These results indicate that GVG, a drug that increases brain GABA concentrations, is effective in attenuating the effect of cocaine on NACC DA. Taken with our earlier findings, these results support the targeting of brain GABAergic systems as a potentially effective pharmacologic treatment strategy for cocaine addiction.

Direct approach for attenuating cocaine's effects on extracellular dopamine: targeting the dopamine transporter

Using in vivo microdialysis techniques, the effects of RTI-55 and/or cocaine on extracellular dopamine (DA) concentrations were measured in the nucleus accumbens (NACC) of freely moving rats. In control animals, cocaine (20 mg/kg) increased NACC DA approximately 458% 60 minutes following administration, returning to baseline values within 200 minutes. Similarly, RTI-55 administration (0.25 mg/kg) increased NACC DA levels approximately 347%. When combined, however, cocaine further increased NACC DA to 705% of baseline values when given 4 hours following RTI-55. This increase was significantly larger than cocaine alone (P < 0.05). In addition, chronic RTI-55 administration (5 days) further potentiated cocaine's ability to increase NACC DA (783%) but this did not reach statistical significance (P > 0.1) compared to acute RTI55/cocaine animals. These findings indicate that RTI-55, a drug that binds directly to the dopamine transporter (DAT) with higher affinity than cocaine, does not appear to be effective in attenuating cocaine's effects on NACC dopamine levels. In fact, acute RTI-55 potentiates cocaine's effects on NACC DA.

Involvement of capsaicin-sensitive nerves in regulating the hormone and glucose metabolic response to endotoxin

This study investigated the role that sensory nerves play in mediating the hormone and glucose metabolic response to endotoxin [lipopolysaccharide (LPS)]. Adult rats were pretreated subcutaneously with capsaicin to selectively destroy primary sensory afferent nerve fibers. Ten days later, [3-3H]glucose was infused intravenously to assess whole body glucose flux before and after the intravenous injection of Escherichia coli LPS (100 micrograms/100 g body wt). Control animals responded to LPS with characteristic increases in the plasma concentration of glucose (91%) and lactate (threefold) and elevations in the rates of glucose appearance and disappearance (77%). In capsaicin-treated rats, the maximal LPS-induced increase in these parameters was attenuated by 50-60%. In addition, these animals were hypoglycemic at the conclusion of the experiment. Control animals demonstrated early and sustained elevations in circulating levels of corticosterone, glucagon, and catecholamines. In contrast, the early LPS-induced elevation in epinephrine and norepinephrine, and to a lesser extent glucagon, was completely absent or greatly impaired by capsaicin pretreatment. In a separate study, the epinephrine-induced increase in glucose flux was blunted by 75% in capsaicin-treated rats. These data indicate that sensory afferent neurons play a critical role in the early secretory response of glucagon and catecholamines, the maintenance of tissue catecholamine responsiveness, and the stimulation of glucose production after LPS.

Repeated administration of 3,4-methylenedioxymethamphetamine augments cocaine's action on dopamine in the nucleus accumbens: a microdialysis study

In this study, we examined the ability of a single injection of cocaine (20 mg/kg, i.p.) to augment extracellular dopamine levels in the nucleus accumbens two weeks after pretreating rats with either saline (1 ml/kg, i.p.) or the serotonin neurotoxin 3,4-methylenedioxymethamphetamine (20 mg/kg, s.c., twice daily for 4 days). The level of dopamine in the nucleus accumbens was measured using in vivo microdialysis. Cocaine produced a 400% increase in extracellular nucleus accumbens dopamine levels in control rats, whereas in 3,4-methylenedioxymethamphetamine treated rats the increase produced by cocaine was 800%, which was significantly different from controls. This suggests that 3,4-methylenedioxymethamphetamine, a relatively common drug of abuse, may alter subsequent vulnerability to cocaine dependence and abuse.

Validity of DSM-IV ADHD predominantly inattentive and combined types: relationship to previous DSM diagnoses/subtype differences

Since 1980, three different diagnostic nomenclatures have been published regarding attention-deficit hyperactivity disorder (ADHD). These changing conceptualizations and diagnostic criteria have generated considerable confusion.

OBJECTIVE

To examine the multidimensional DSM-IV ADHD criteria in relation to how children and adolescents with a previous DSM-III ADD diagnosis or a DSM-III-R ADHD diagnosis are diagnosed according to DSM-IV criteria.

METHOD

Children whose original diagnoses were according to DSM-III and DSM-III-R criteria received retrospective diagnoses according to DSM-IV criteria.

RESULTS

Predominantly inattentive (n = 30) and combined types (n = 26) were compared on their previous DSM-III and DSM-III-R diagnoses and on demographic, behavioral, cognitive, and comorbidity variables. Predominantly inattentive and combined type diagnoses corresponded with DSM-III ADD/WO and ADD/H diagnoses, respectively. The DSM-III-R ADHD diagnosis did not correspond with either DSM-IV subtype. Children with the combined type diagnosis had more externalizing codiagnoses, and their parents reported more externalizing, delinquent, and aggressive behaviors. Children with the predominantly inattentive type had more math learning disability codiagnoses.

CONCLUSION

Results support a multidimensional conceptualization of ADHD. There exists close correspondence between the DSM-III ADD/WO type and the DSM-IV predominantly inattentive type and between the DSM-III ADD/H type and the DSM-IV combined type.

Assessment of pain and patterns of analgesic use in hospice patients

The purpose of this study is to describe patterns of pain, analgesic use, barriers to pain control, and various aspects of lifestyle affected by pain in hospice patients. Seventy-six charts of deceased patients were randomly selected of patients who had received care from Hospice of Wake County between August 1990 and August 1991. All patient's charts were reviewed from date of entry into hospice until death. Pain assessments were routinely performed at entry into hospice, then at one month intervals, and, thereafter, whenever a change in pain status occurred. The average number of pain assessments performed per patient was 2.7 (range 18). Pain intensity score increased as the number of pain assessments increased. Pain was described as occasional (25.2 percent), frequent (26.6 percent) or constant (24.1 percent). Most common analgesic medications were long-acting morphine sulphate (25.4 percent), acetaminophen and hydroxy/oxycodone combinations (20.1 percent) and NSAIDS (17.1 percent). Approximately 40 percent of all pain assessments reflected use of greater than one analgesic agent and prn and scheduled medications simultaneously. Eighty percent of all pain assessments prompted a recommendation to change the analgesic regimen and 62.5 percent of regimen changes were associated with improvement in pain status. Barriers to pain control and lifestyle alterations due to pain were identified. The positive findings in this report, compared to previous similar investigations, supports the use of the pain assessment document and guidelines for cancer pain management in use at the Hospice of Wake County.

Characterization and molecular cloning of a proenzyme form of a ribosome-inactivating protein from maize. Novel mechanism of proenzyme activation by proteolytic removal of a 2.8-kilodalton internal peptide segment

Ribosome-inactivating proteins (RIPs) are a widely distributed family of plant enzymes that are remarkably potent catalytic inactivators of eukaryotic protein synthesis. All RIPs described to date, including the A-chain of the plant cytotoxin ricin, are polypeptides of 25-32 kDa and share significant amino acid sequence homologies. We have characterized and cloned an RIP from maize (Zea mays). In contrast to previously described RIPs, we have found that maize RIP is synthesized and stored in the kernel as a 34-kDa inactive precursor (isoelectric point = 6.5). During germination, this neutral precursor is converted into a basic, active form (isoelectric point greater than 9) by limited proteolysis, which removes 25 amino acids (2.8 kDa) of net charge -6 from the center of the polypeptide chain. Additional processing also occurs at the amino and carboxyl termini of the polypeptide. The sequence of the internal processed region is unique and it is equivalent to an insertion centered around Thr-156 in the amino acid sequence of ricin toxin A-chain, i.e. in the center of the enzymatically active domain. The generation of an active enzyme by removal of a large amino acid segment from the middle of a precursor polypeptide chain represents a novel mechanism of proenzyme activation that is distinct from more conventional activation mechanisms involving NH2-terminal proteolytic processing. A two-chain active RIP (comprised of 16.5- and 8.5-kDa fragments that remain tightly associated) is produced from this processing event.