Interleukin-18 (interferon-gamma-inducing factor) is produced by osteoblasts and acts via granulocyte/macrophage colony-stimulating factor and not via interferon-gamma to inhibit osteoclast formation

We have established by differential display polymerase chain reaction of mRNA that interleukin (IL)-18 is expressed by osteoblastic stromal cells. The stromal cell populations used for comparison differed in their ability to promote osteoclast-like multinucleated cell (OCL) formation. mRNA for IL-18 was found to be expressed in greater abundance in lines that were unable to support OCL formation than in supportive cells. Recombinant IL-18 was found to inhibit OCL formation in cocultures of osteoblasts and hemopoietic cells of spleen or bone marrow origin. IL-18 inhibited OCL formation in the presence of osteoclastogenic agents including 1alpha,25-dihydroxyvitamin D3, prostaglandin E2, parathyroid hormone, IL-1, and IL-11. The inhibitory effect of IL-18 was limited to the early phase of the cocultures, which coincides with proliferation of hemopoietic precursors. IL-18 has been reported to induce interferon-gamma (IFN-gamma) and granulocyte/macrophage colony-stimulating factor (GM-CSF) production in T cells, and both agents also inhibit OCL formation in vitro. Neutralizing antibodies to GM-CSF were able to rescue IL-18 inhibition of OCL formation, whereas neutralizing antibodies to IFN-gamma did not. In cocultures with osteoblasts and spleen cells from IFN-gamma receptor type II-deficient mice, IL-18 was found to inhibit OCL formation, indicating that IL-18 acted independently of IFN-gamma production: IFN-gamma had no effect in these cocultures. Additionally, in cocultures in which spleen cells were derived from receptor-deficient mice and osteoblasts were from wild-type mice and vice versa, we identified that the target cells for IFN-gamma inhibition of OCL formation were the hemopoietic cells. The work provides evidence that IL-18 is expressed by osteoblasts and inhibits OCL formation via GM-CSF production and not via IFN-gamma production.

Television-viewing habits and sleep disturbance in school children

OBJECTIVE

To investigate the relationship between specific television-viewing habits and both sleep habits and sleep disturbances in school children.

METHODS

The parents of 495 children in grades kindergarten through fourth grade in three public elementary schools completed two retrospective survey questionnaires, one assessing their children's sleep behaviors and the other examining television-viewing habits of both the child and the family. Sleep domains assessed included bedtime resistance, sleep onset delay, sleep duration, anxiety around sleep, parasomnias, night wakings, and daytime sleepiness. Teachers from all three schools also completed daytime sleepiness questionnaires (N = 402) for the sample.

RESULTS

Most of the television-viewing practices examined in this study were associated with at least one type of sleep disturbance. Despite overall close monitoring of television-viewing habits, one quarter of the parents reported the presence of a television set in the child's bedroom. The television-viewing habits associated most significantly with sleep disturbance were increased daily television viewing amounts and increased television viewing at bedtime, especially in the context of having a television set in the child's bedroom. The sleep domains that appeared to be affected most consistently by television were bedtime resistance, sleep onset delay, and anxiety around sleep, followed by shortened sleep duration. The parent's threshold for defining "problem sleep behavior" in their child was also important in determining the significance of the association between sleep disturbance and television-viewing habits.

CONCLUSION

Health care practitioners should be aware of the potential negative impact of television viewing at bedtime. Parents should be questioned about their children's television-viewing habits as part of general screening for sleep disturbances and as part of anticipatory guidance in regards to healthy sleep habits in children. In particular, the presence of a television set in the child's bedroom may be a relatively underrecognized, but important, contributor to sleep problems in school children.

Mechanism of the t(14;18) chromosomal translocation: structural analysis of both derivative 14 and 18 reciprocal partners

To elucidate the mechanism of the t(14;18)(q32;q21) chromosomal translocation found in follicular lymphoma, we examined the structure of both derivative (der) chromosomal breakpoints as well as their germ-line predecessors. We noted that chromosome segment 18q21 was juxtaposed with immunoglobulin heavy (H) chain gene diversity (DH) regions on all five der(18) chromosomes we examined, and we confirmed the juncture with immunoglobulin H-chain gene joining (JH) regions on the der(14) chromosome. However, the t(14;18) was not fully reciprocal in that chromosome 14 DNA between the DH and JH regions was deleted. Furthermore, extra nucleotides, reminiscent of "N" segments, were present at the der(14) and possibly der(18) junctions. This indicates that despite the mature B-cell phenotype of follicular lymphoma, the t(14;18) occurs during attempted DH-JH joining, the earliest event in immunoglobulin rearrangement in a pre-B-cell. Our detailed analysis of the germ-line 18q21 region indicated that most breakpoints clustered within a 150-base-pair major breakpoint region. However, we found no evidence for evolutionarily conserved immunoglobulin-like recombinational signals at 18q21, arguing against a role for immunoglobulin recombinase in chromosome 18 breakage. Instead, a direct repeat duplication of chromosome 18 sequences was discovered at both chromosomal junctures, typical of the repair of a naturally occurring staggered double-stranded DNA break. These results prompt a translocation model with illegitimate pairing of a staggered double-stranded DNA break at 18q21 and an immunoglobulin endonuclease-mediated break at 14q32 and with N-segment addition, repair, and ligation to generate der(14) and der(18) chromosomes.

A critical incident study of nurses' responses to the spiritual needs of their patients

AIMS OF STUDY

The aims of the study were to carry out a critical incident study to: (1) Describe what nurses consider to be spiritual needs; (2) Explore how nurses respond to the spiritual needs of their patients; (3) Typify nurses' involvement in spiritual dimensions of care; (4) Describe the effect of nurses' intervention related to spiritual care.

BACKGROUND

In the caring professions a focus on individuals as bio-psychological-spiritual beings is gaining recognition and this notion is based on the premise that there should be a balance of mind, body and spirit for the maintenance of health in a person (Stoll 1979). Emerging research highlights the importance of spiritual care in nursing and suggests that there is scope for improving this dimension of care in order to improve the quality of life for many patients. However, there is very little evidence about how nurses respond to the spiritual needs of their patients. Therefore the purpose of this study was to map by critical incident techniques how nurses construct and respond to patients' spiritual needs in a variety of clinical settings.

METHODS

Critical incidents were obtained from 115 nurses. The data from these incidents were subjected to content analysis and categories were developed and described. The emerging categories were subjected to peer reviews to ensure reliability and validity of findings.

FINDINGS

The findings suggest that there is confusion over the notion of spirituality and the nurse's role related to spiritual care. A variety of approaches to spiritual care emerged in this study from the critical incidents derived from nurse respondents. These were categorized as 'personal', 'procedural', 'culturalisit' or 'evangelical'. There was an overwhelming consensus that patients' faith and trust in nurses produces a positive effect on patients and families, and nurses themselves derived satisfaction from the experience of giving spiritual care. In this respect, spiritual care interventions promote a sense of well-being in nurses as well as being a valuable part of total patient care.

CONCLUSION

The study concluded that there is scope for developing an ideal model of spiritual care using the critical incident data from this study.

Sleep and daytime behavior in children with obstructive sleep apnea and behavioral sleep disorders

OBJECTIVE

The purpose of this study was: 1) to examine both bedtime sleep behaviors and daytime behaviors associated with daytime sleepiness in a group of children with a primary medical sleep disorder (obstructive sleep apnea syndrome [OSAS]) compared with a group of children with a primary behavioral sleep disorder (BSD) (limit setting sleep disorder or sleep onset association disorder); and 2) to investigate the impact of a comorbid BSD on sleep and daytime behavioral consequences of OSAS.

METHODS

Children referred to a pediatric sleep disorders clinic during a 3-year period with a primary diagnosis of either polysomnographically-confirmed OSAS (n = 100) or a BSD (n = 52) were compared on several parent report measures assessing the following domains: symptoms of sleep disordered breathing, other sleep behaviors (primarily parasomnias), bedtime behaviors, and externalizing daytime behavior problems. The OSAS sample was then divided into a pure OSAS group (n = 78) and an OSAS plus a behavioral sleep diagnosis group (n = 22) based on the presence or absence of delayed sleep onset and/or prolonged nightwakings and compared on the parent-report symptom domains.

RESULTS

Almost one-quarter of the OSAS group had clinically significant behavioral sleep problems, primarily bedtime resistance, in addition to OSAS. Bedtime resistance was associated with a significantly shortened sleep duration in both the BSD and OSAS-BSD groups. Although the OSAS-BSD group had less severe disease, as defined by polysomnographic variables, than the pure OSAS group, they were rated by their parents as having more daytime externalizing behavior problems associated with daytime sleepiness.

CONCLUSIONS

The results of this study suggest that evaluation for comorbid BSD should be done in all children presenting with symptoms of OSAS. The coexistence of such BSDs may contribute significantly to sleep deprivation, and thus to behavioral manifestations of daytime sleepiness in these children.

Nicotinic acetylcholine receptor distribution in Alzheimer's disease, dementia with Lewy bodies, Parkinson's disease, and vascular dementia: in vitro binding study using 5-[(125)i]-a-85380

Nicotinic acetylcholine receptors (nAChRs) have been implicated in a number of neurological disorders. 5-Iodo-3-[2(S)-2-azetidinylmethoxy]pyridine (5-I-A-85380) is a novel nAChR marker, binding predominantly to the alpha4beta2 subtype. This in vitro autoradiography study describes the distribution of 5-[(125)I]-A-85380 binding in post-mortem brain tissue from normal elderly individuals and from cases with age-associated dementias of both neurodegenerative and vascular types. The binding distribution of 5-[(125)I]-A-85380 in normal brain tissue was found to be consistent with the reported distribution of other high-affinity nicotinic ligands. In addition to high thalamic and moderate striatal and temporal cortex density, moderate 5-[(125)I]-A-85380 binding was also seen in white matter tracts in cingulate, occipital, and temporal areas, indicating the presence of nAChRs along nerve fiber tracts, which has not been reported in other high-affinity nicotinic agonist distribution studies. In Parkinson's disease (PD), loss of striatal 5-[(125)I]-A-85380 binding closely parallels the loss of nigrostriatal dopaminergic markers previously observed. In dementia with Lewy bodies (DLB) reduced striatal 5-[(125)I]-A-85380 binding density, comparable to that in PD, may be a marker of early degeneration in nigrostriatal inputs, while in Alzheimer's disease (AD) reduced striatal 5-[(125)I]-A-85380 binding could be related to reduced cortical inputs. The reductions of nAChRs seen in AD, DLB, and PD were not apparent in vascular dementia (VaD). In conclusion, 5-I-A-85380 is clearly a useful ligand for both in vitro and in vivo single photon emission tomography human studies investigating disease symptoms and progression, response to acetylcholinesterase-inhibiting drugs and in differentiating primary degenerative dementia from VaD.

An exploration of the preceptor role: preceptors' perceptions of benefits, rewards, supports and commitment to the preceptor role

This Australian study, a replication of Canadian research by Dibert & Goldenberg, was undertaken to explore the relationship between preceptors' perceptions of benefits, rewards and support, and their commitment to the preceptor role. A convenience sample of 134 nurse preceptors involved in an undergraduate nursing course were invited to complete a four-part questionnaire consisting of the Preceptor's Perception of Benefits and Rewards Scale, the Preceptor's Perception of Support Scale, the Commitment to the Preceptor Role Scale, and demographic details. The results, in the main, parallel those of the original research, with differences reflecting the distinct nature and the more recent use of preceptorship in Australia. The results indicate a clear commitment to the preceptor role and a perception that both material and non-material benefits are derived from acting in the role. Additionally, support from the institution and coworkers was considered vital for participation in the role. This not only has implications for nursing educators, administrators and potential preceptors, but also for those being preceptored.

Wild-type p53 transgenic mice exhibit altered differentiation of the ureteric bud and possess small kidneys

Transgenic mice expressing wild-type murine p53 under the control of the mouse mammary tumor virus long terminal repeat (MMTV LTR) undergo progressive renal failure due to abnormal kidney development. Similar phenotypes are observed in two transgenic lines that express wild-type p53 within the ureteric bud but not in transgenic animals expressing a dominant-negative p53 mutant allele. Defective differentiation of the ureteric bud, as evidenced by altered marker expression during development, accompanies expression of the p53 transgene. At E17.5-18.5, metanephric mesenchymal cells undergo high rates of apoptosis, and fewer cells than normal are converted to tubular epithelium. As a result, p53 transgenic kidneys grow to only half of their expected size and contain about half of the normal number of nephrons, with compensatory hypertrophy of the glomeruli. In this setting, rather than arrest the cell cycle or induce apoptosis directly, abnormally high levels of wild-type p53 appear to alter cellular differentiation in embryonic ureteric buds and cause secondary effects (apoptosis and inefficient conversion to epithelium) in the adjacent undifferentiated mesenchyme.

Macrophage colony stimulating factor (M-CSF) is essential for osteoclast formation in vitro

The op/op mouse, in which the M-CSF gene is mutated, has greatly reduced numbers of macrophages and osteoclasts. We assessed the ability of M-CSF to induce osteoclast and macrophage formation in op/op hemopoietic cells in vitro. Osteoclast production was undetectable in op/op cell cultures, but was restored by M-CSF at concentrations approximately an order of magnitude higher than those that induced macrophages. In normal hemopoietic tissue M-CSF similarly increased macrophage numbers, but inhibited osteoclast formation. Despite cure of the macrophage defect, neither interleukin 3 nor granulocyte-macrophage CSF were able to induce osteoclastic differentiation in op/op cells. The results suggest that M-CSF induces osteoclastic differentiation but that macrophages, which are also induced by M-CSF, suppress osteoclast differentiation. Macrophages induced by other cytokines seem unable to contribute to osteoclast-formation.

Structure of varicella-zoster virus DNA

Varicella-zoster virus (VZV) DNA was prepared from nucleocapsids and from enveloped virions of a laboratory strain (Ellen) and directly from the vesicle fluids of patients with zoster infections. VZV Ellen nucleocapsid DNA was cleaved with 11 different restriction endonucleases and electrophoresed in agarose gels. The restriction profiles of the nucleocapsid DNA were identical to those of the DNA recovered from purified virions, but differed from those of another VZV strain (KM). In vitro-labeled VZV K.M. DNA purified directly from vesicle fluid yielded a distinct restriction pattern which appeared to be unchanged after several tissue culture passages of the isolate from that fluid. Restriction endonuclease analysis (EcoRI or BglII) of VZV DNA revealed the presence of four cleavage fragments with a molar ratio of approximately 0.5. No individual fragments with molar ratios of 0.25 were noted. This observation suggests that the VZV genome may contain one invertible segment. Comparison of the electrophoretic migrations of VZV DNA fragments relative to those of DNAs of known size permitted calculation of the VZV genome size to be 72 X 10(6) to 80 X 10(6) daltons. These results were confirmed by electron microscopy which demonstrated a genome size of about 76 X 10(6) daltons for passaged and unpassaged VZV DNA. Electron microscopy also revealed that some of the DNA molecules recovered from nucleocapsids or directly from vesicle fluids were superhelical circles.

Cocaine-induced wide complex dysrhythmia

Cocaine is a local anesthetic with the potential to induce dysrhythmia due to direct myocardial sodium channel antagonism similar to class I antidysrhythmic drugs. The hallmark of myocardial sodium channel poisoning is wide complex dysrhythmia, and the current accepted treatment is intravenous bicarbonate. Wide complex dysrhythmio due to cocaine in the absence of myocardial infarction is rare, and optimum management is undefined. We report three cases of acute cocaine intoxicating during which patients developed wide complex dysrhythmia consistent with sodium channel poisoning. In one case, wide complex tachycardia resolved without direct treatment. In the other cases, wide complex dysrhythmia resolved following intravenous bicarbonate therapy directed at reversing sodium channel blockade.

Ethnic differences in self-poisoning: a comparison of Asian and white groups

The characteristics of Asian patients admitted to a Birmingham hospital following deliberate self-poisoning were compared with those of British-born white self-poisoners. Asian patients were more likely to be young, female, and married. They were less likely to have previously self-poisoned, received previous psychiatric treatment, be diagnosed psychiatrically ill, or suffer from a personality disorder. Culture conflict was common among the Asian patients and was present in the majority of unmarried Asian females. The rate of self-poisoning for Asian females was higher than for white females, but for Asian males was lower than for white males.

Intraoperative radiation therapy of pancreatic carcinoma: a report of RTOG-8505. Radiation Therapy Oncology Group

The Radiation Therapy Oncology Group in 1985 began a study of IORT plus external beam radiation therapy for patients with locally unresected, non-metastatic pancreatic cancer. Patients were treated with a combination of 2000 cGy of IORT and postoperative external beam radiation therapy to 5040 cGy in combination with IV 5-FU (500 mg/m2/day on the first 3 days of the external beam treatment). As patients were registered on study prior to exploration, it was expected that a number of patients would be excluded from further analysis at the time of surgery. Eighty-six patients were entered on study through 6/1/88 and analyzed through 4/90. Fifty-one patients were fully analyzable. Median survival time of the 51 patients was 9 months with an 18-month actuarial survival rate of 9%. Local control could not be adequately evaluated in this multi-institutional study. Major postoperative complications were not excessive and occurred in 12% of patients. Two patients had major late morbidity leading to death, one from duodenal bleeding and the second from biliary obstruction. Although this study does demonstrate the feasibility of IORT in a multi-institutional setting, it does not demonstrate any advantage of IORT over conventional therapy for this disease.

'Too withdrawn' or 'too friendly': considering social vulnerability in two neuro-developmental disorders

In some neuro-developmental disorders, the combined effect of intellectual disability and atypicalities of social cognition may put individuals at increased vulnerability in their social environment. The neuro-developmental disorders Williams syndrome, characterised by 'hypersociability', and autism spectrum disorders, characterised by 'social withdrawal', are at two extremes of atypical social functioning in humans. In this article, we use Williams syndrome and autism spectrum disorders as exemplars to demonstrate how atypicalities of social cognition may contribute to social vulnerability in these populations. The lives of individuals with both these disorders are marred by an increased risk of social isolation, bullying, unsteady relationships, employment difficulties and abuse. While different behavioural interventions have been tried to improve social functioning in these populations, there has been great variability in their success. Finally, we discuss different issues regarding social independence of these individuals; including employment, safety and decision making.

Placental control of fetal growth

The placenta exerts its effects on the growth of the fetus from the beginning of pregnancy via metabolic and endocrine mechanisms. To achieve this, the placenta exchanges a wide array of nutrients, endocrine signals, cytokines and growth factors with the mother and the fetus. These exchanges modulate or programme fetal growth and development. This review concentrates on the function and structure of the placenta in humans and in animals, and the effects of experimental perturbation of placental size and function on fetal growth. The consequences for fetal growth of varying the abundance of peptides or, by deleting genes, insulin-like growth factors or cytokines, are also described. Maternal nutritional and hormonal state from as early as the first few days after fertilization, can influence the growth rate of the placenta and the fetus and also the length of gestation. Influences on placental development and their consequences will clearly have an impact on the placental control of fetal growth. Variations in the maternal environment and consequent perturbation of the metabolic and endocrine environment of the placenta and fetus are implicated as being responsible for the associations between prenatal growth of the placenta and its fetus and the subsequent risk of adult disease. The next challenge will be to determine the dominant influences at each stage of fetal and placental growth.

Genome differences among varicella-zoster virus isolates

The DNAs of 17 isolates of varicella-zoster virus (VZV) were analysed by restriction endonuclease cleavage and agarose gel electrophoresis. By comparing gel patterns of DNAs cleaved with only a few enzymes, all epidemiologically distinct isolates were shown to be unique. Two isolates recovered from members of a family infected in a common-source outbreak were identical to each other (4/4 enzymes) but distinct from the other strains. In addition, three isolates recovered at different times during the course of a single episode of zoster in another individual were identical by endonuclease analysis (4/4 enzymes) but once again were distinct from all other isolates. The differences that have been recognized in cleavage profiles of all VZV strains reported thus far map into four regions of the viral genome. Two of these variable regions lie within the long unique sequences while the other differences appear to map in each of the inverted repeat sequences.

Energetics of coupled Na+ and Cl- entry into epithelial cells of bullfrog small intestine

Na+, K+ and Cl- concentrations (cij) and activities (aij), and mucosal membrane potentials (Em) were measured in epithelial cells of isolated bullfrog (Rana catesbeiana) small intestine. Segments of intestine were stripped of their external muscle layers, and bathed (at 25 degrees C and pH 7.2) in oxygenated Ringer solutions containing 105 mM Na+ and Cl- and 5.4 mM K+. Na+ and K+ concentrations were determined by atomic absorption spectrometry and Cl- concentrations by conductometric titration following extraction of the dried tissue with 0.1 M HNO3. 14C-labelled inulin was used to determine extracellular volume. Em was measured with conventional open tip microelectrodes, aiCl with solid-state Cl-selective silver microelectrodes and aiNa and aiK with Na+ and K+-selective liquid ion-exchanger microelectrodes. The average Em recorded was -34mV. ciNa, ciK and ciCl were 51, 105 and 52 mM. The corresponding values for aiNa, aiK and aiCl were 18, 80 and 33 mM. These results suggest that a large fraction of the cytoplasmic Na+ is 'bound' or sequestered in an osmotically inactive form, that all, or virtually all the cytoplasmic K+ behaves as if in free solution, and that there is probably some binding of cytoplasmic Cl-. aiCl significantly exceeds the level corresponding to electrochemical equilibrium across the mucosal and baso-lateral cell membranes. Earlier studies showed that coupled mucosal entry of Na+ and Cl- is implicated in intracellular Cl- accumulation in this tissue. This study permitted estimation of the steady-state transapical Na+ and Cl- electrochemical potential differences (deltamuNa and deltamuCl). deltamuNa (-7000 J . mol-1; cell minus mucosal medium) was energetically more than sufficient to account for deltamuCl (1000--2000 J . mol-1).

Transluminal coronary angioplasty complicated by coronary artery perforation

Transluminal coronary angioplasty may be associated with complications resulting from the dilatation catheter and inflation of the balloon. The most common complications are dissection, occlusion, and coronary spasm. We report an unusual complication of coronary artery perforation by the dilatation catheter resulting in acute pericardial tamponade. The complication was immediately recognized and confirmed by dye injection and hemodynamic measurements. Pericardiocentesis was performed, followed by successful coronary bypass surgery. The reasons for the perforation are unclear. We postulate that the acute angle of the perforated vessel was an important factor for this complication. The importance of a standby cardiac surgeon and operating room is emphasized.

Age and attempted suicide

Clinical and demographic factors associated with suicide attempts admitted to the West Midlands Poisons Unit over a 2-year period were compared by age group. Risk factors for future suicide (living alone, physical illness, psychiatric illness and high suicidal intent in the attempt) were significantly more common among elderly patients (65 years and over) than middle-aged patients (35-64 years) and significantly less common among young patients (under 35 years) than middle-aged patients. Elderly patients that attempted suicide resemble elderly patients that completed suicide and should be considered at high risk of future suicide.

Molecular cloning and physical mapping of varicella-zoster virus DNA

Varicella-zoster virus (VZV) DNA was cleaved with restriction endonuclease EcoRI, and most of the resulting fragments were successfully cloned in the phage vector lambda gtWES . lambda B. Double digestions of cloned fragments with EcoRI and BamHI and hybridizations to blot-transferred BamHI digests of VZV DNA were used to construct a physical map of the genome. The molecular termini of the DNA were identified by restriction enzyme analysis after exonuclease III digestion. The data indicate that VZV DNA exists in two isomeric forms that differ by inversion of one short terminal genome segment. Electron microscopic studies revealed that the short genome segment consists of a terminal revealed that the short genome segment consists of a terminal sequence of about 3.4 X 10(6) daltons that is separated from an internal inverted repeat of itself by a 5.8 X 10(60)-dalton unique DNA segment.

The effect of hepatocyte growth factor on the behaviour of osteoclasts

Hepatocyte growth factor (HGF) stimulates the growth, motility and morphogenesis of a variety of cell types, including hemopoietic progenitors. We found that HGF is a potent inhibitor of bone resorption by isolated rat osteoclasts. However, in the presence of the osteoblastic cell line UMR 106, it stimulated osteoclastic resorption. HGF also increased osteoclastic motility and spread area, over a similar concentration range. We detected no effect on osteoclast formation or survival. Our data suggest that HGF may be involved in the recruitment of osteoclasts to sites of bone resorption, but that during migration resorptive functions are suppressed. Once on resorptive sites, the osteoclast response to HGF is modulated by osteoblastic cells and the bone resorptive activity of osteoclasts may be stimulated accordingly.

Alpha-(trifluoromethyl)amine derivatives via nucleophilic trifluoromethylation of nitrones

(Trifluoromethyl)trimethylsilane (TMSCF(3)) reacts with nitrones to afford alpha-(trifluoromethyl)hydroxylamines protected as O-trimethylsilyl ethers. Potassium t-butoxide initiates the nucleophilic trifluoromethylation. The reaction works best with alpha,N-diaryl nitrones, and the conditions are compatible with a range of substituents on the aryl groups. Acidic deprotection of the nitrone/TMSCF(3) adducts generates alpha-(trifluoromethyl)hydroxylamines. Catalytic hydrogenation of the adducts produces alpha-(trifluoromethyl)amines. Nitrone/TMSCF(3) adducts with strong electron-withdrawing groups on the alpha-aryl ring or heterocyclic alpha-aryl groups undergo an elimination/addition sequence to generate alpha,alpha-bis(trifluoromethyl)amines. Nitrones with alkyl groups bound directly to the 1,3-dipolar moiety fail to react with TMSCF(3), but trifluoromethylation of beta,gamma-unsaturated nitrones followed by reduction of the double bond can circumvent this limitation.

Multiple conductance classes of mouse nicotinic acetylcholine receptors expressed in Xenopus oocytes

Acetylcholine receptor (AcChoR) subunit mRNAs transcribed from mouse BC3H-1 cDNAs were injected into Xenopus oocytes and the expressed AcChoR channels were examined by single channel recording. Injection of alpha-, beta-, gamma-, and delta-subunit mRNAs produced two predominant channel classes with conductances of approximately 50 and approximately 12 pS, while infrequent openings of approximately 25-pS channels were also observed. Injection of alpha-, beta-, and gamma-subunit mRNAs produced a single class of approximately 12-pS AcChoR channels, which resembled the smallest conductance channels present in alpha beta gamma omega-injected oocytes. Assembly of delta-less channels may thus explain the lowest conductance AcChoR channels in alpha beta gamma delta-injected oocytes and might also account for similar channels that have been observed in vertebrate skeletal muscle.