The FDA-approved compound, pramipexole and the clinical-stage investigational drug, dexpramipexole, reverse chronic allodynia from sciatic nerve damage in mice, and alter IL-1β and IL-10 expression from immune cell culture

During the onset of neuropathic pain from a variety of etiologies, nociceptors become hypersensitized, releasing neurotransmitters and other factors from centrally-projecting nerve terminals within the dorsal spinal cord. Consequently, glial cells (astrocytes and microglia) in the spinal cord are activated and mediate the release of proinflammatory cytokines that act to enhance pain transmission and sensitize mechanical non-nociceptive fibers which ultimately results in light touch hypersensitivity, clinically observed as allodynia. Pramipexole, a D2/D3 preferring agonist, is FDA-approved for the treatment of Parkinson's disease and demonstrates efficacy in animal models of inflammatory pain. The clinical-stage investigational drug, R(+) enantiomer of pramipexole, dexpramipexole, is virtually devoid of D2/D3 agonist actions and is efficacious in animal models of inflammatory and neuropathic pain. The current experiments focus on the application of a mouse model of sciatic nerve neuropathy, chronic constriction injury (CCI), that leads to allodynia and is previously characterized to generate spinal glial activation with consequent release IL-1β. We hypothesized that both pramipexole and dexpramipexole reverse CCI-induced chronic neuropathy in mice, and in human monocyte cell culture studies (THP-1 cells), pramipexole prevents IL-1β production. Additionally, we hypothesized that in rat primary splenocyte culture, dexpramixole increases mRNA for the anti-inflammatory and pleiotropic cytokine, interleukin-10 (IL-10). Results show that following intravenous pramipexole or dexpramipexole, a profound decrease in allodynia was observed by 1 hr, with allodynia returning 24 hr post-injection. Pramipexole significantly blunted IL-1β protein production from stimulated human monocytes and dexpramipexole induced elevated IL-10 mRNA expression from rat splenocytes. The data support that clinically-approved compounds like pramipexole and dexpramipexole support their application as anti-inflammatory agents to mitigate chronic neuropathy, and provide a blueprint for future, multifaceted approaches for opioid-independent neuropathic pain treatment.

[Considering the influence of age-related factors on the strategy and satisfaction of refractive surgery]

With the rapid development of materials, equipment and technology related to refractive surgery, the number of people who choose refractive surgery to take off glasses keeps increasing. People at different ages have different needs for refractive surgery with varying effects. How to improve the long-term postoperative satisfaction of patients at different ages should be the focus of refractive surgeons. Age-related factors are not only among the key considerations in the preoperative design of refractive surgery, but also the focus of preoperative communication and education and postoperative follow-up. By analyzing and discussing the influence of age-related factors on the strategy of refractive surgery, this article emphasizes that it is important to pay attention to age-related factors and strengthen perioperative education in ametropic patients, so as to obtain long-term ideal postoperative visual quality and improve patient satisfaction throughout the life cycle.

[Research advances in corneal and scleral collagen cross-linking with ultraviolet A and riboflavin]

In recent years, the use of collagen cross-linking with ultraviolet A and riboflavin is being developed universally due to its significance in the improvement of the mechanical strength of collagen fibers in clinical and basic research. It has been used in treating some corneal diseases including keratoconus, keratectasia and keratohelcosis. Thus, it might become a new treatment to prevent progressive myopia by strengthening scleral tissue. This article focuses on the effectiveness and safety of ultraviolet A-riboflavin cross-linking, and discusses the application prospect, focal points and problems related to cross-linking therapy. (Chin J Ophthalmol, 2018, 54:948-953).

[Advantages and disadvantages of femtosecond laser assisted LASIK and SMILE]

With the development of excimer laser and femtosecond laser equipment, application of diversified and customized surgical decision in modern corneal refractive surgery has been an inevitable trend. However, how to make a personalized decision with an accurate surgical design to achieve better visual quality becomes the main focus in clinical applications. Small-incision lenticule extraction (SMILE) and femtosecond assisted laser in situ keratomileusis (FS-LASIK) have been commonly acknowledged as the mainstream of corneal refractive surgery for ametropia correction nowadays. Both methods have been verified by clinical practice for many years. This article compares and elaborates the different characteristics with advantages and disadvantages of the two methods so as to provide some reasonable treatment options for refractive surgery. (Chin J Ophthalmol, 2018, 54: 7-10).

[Changes of ocular biological parameters and Lumican expression in the monocularly deprivation myopic model of mutant Lumican transgenic mice]

Objective: To investigate ocular changes in the monocularly deprivation myopic model of mutant Lumican transgenic mice. Comparing influences on biological parameters and sclera development between Lumican transgenic and form deprivation mice, and to prepare for further study of pathogenesis of pathological myopia (PM). Methods: Experimental research. Lumican transgenic mice and wild mice were monocularly lid-sutured at ten days after birth. All eyes were divided into 6 groups, group A(32 eyes): control eyes in transgenic mice; group B(34 eyes): sutured eyes in transgenic mice; group C(34 eyes): fellow eyes in transgenic mice; group D(28 eyes): control eyes in wild mice; group E(32 eyes): sutured eyes in wild mice; group F(32 eyes): fellow eyes in wild mice. Refraction was measured by streak retinoscopye and axial length was measured by vernier caliper at 8 weeks (56 days) after birth. Lumican expression was detected by quantitative real-time PCR in all groups. Results: The refraction in group B and group E were (-0.38±1.10) D and (0.14±1.26)D respectively, which were significantly different compared with contralateral groups and normal control groups (F=9.525, 10.067; P<0.01). The mean axial length were also increased in group B ((3.28 ± 0.07)mm and group E (3.24 ± 0.09)mm, (F=7.183, 6.671; P<0.05). Expression level of Lumican mRNA in sclera was increased in group B, which was significantly different from group A and group C (F= 6.262; P<0.05). The expression of Lumican mRNA was increased in group B and C when compared with group E and F (t=4.772, 2.218, P<0.05). Conclusions: Form-deprivation in mutant Lumican transgenic mice causes myopic changes in deprived eyes. The gene expression level of Lumican in sclera of transgenic mice is significantly increased compared with contralateral eyes or that of wild group. Lumican mutation may effect the development of PM, and the interaction of genetic and environmental factors may lead to development of PM. (Chin J Ophthalmol, 2016, 52: 850-855).

Efficient intranasal immunization of newborn mice with recombinant adenovirus expressing rotavirus protein VP4 against oral rotavirus infection

Efficacy of passive protection of newborn mice against rotavirus infection by the rotavirus VP4 protein expressed by an adenoviral vector in mice was studied. The VP4 gene was inserted into the E1 region of adenoviral vector pJM17. Recombinant adenovirus Ad5N/VP4 was grown in 293 cells. Intramuscular (i.m.), oral or intranasal (i.n.) immunization of newborn mice with Ad5/VP4 resulted in appearance of VP4-specific antibodies. Specific IgG antibodies were detected in the serum and intestine specimens of i.m. vaccinated mice. Oral immunization elicited serum IgG antibodies and intestinal IgG and IgA antibodies. Compared with i.m. and oral applications, i.n. immunization led to higher levels of serum IgG and intestinal IgG and IgA antibodies. Pups were challenged twice with simian rotavirus SA11 strain orally at the days 7 and 8 after birth. Pups born to i.n. immunized dams achieved 100% protection from rotavirus-induced diarrhea after both challenges. The protection of pups born to orally immunized dams was 80%, while only 30% of pups born to i.m. immunized dams were protected after both challenges. I.n. immunization was most efficient in inducing rotavirus VP4-specific serum, intestinal and milk IgG or IgA in mice that protected newborn mice completely.

Tyrosinaemia type I and apoptosis of hepatocytes and renal tubular cells

Hereditary tyrosinaemia type I (HT 1) (McKusick 276700) is caused by a deficiency of fumarylacetoacetate hydrolase (FAH) activity, the last enzyme in the tyrosine catabolic pathway. Homozygous disruption of the gene encoding FAH in mice (Fah) causes neonatal lethality (i.e. lethal Albino deletion c14CoS mice), which limits the use of this animal as a model for HT I. We developed a new mouse model that carries two genetic defects, Fah and 4-hydroxyphenylpyruvate dioxygenase (Hpd). The double mutant Fah -/- Hpd -/- mice grew normally without evidence of liver and renal disease, showing a phenotype similar to Hpd -/- mice. Complete blockage of the tyrosine catabolic pathway at the, step of HPD prevents development of clinical phenotypes. Administration of homogentisate resulted in rapid apoptosis of hepatocytes and renal tubular epithelial cells, a central feature of visceral injury in patients with HT I. Simultaneously, renal tubular function was impaired, resulting in Fanconi syndrome. Apoptosis of hepatocyte and renal tubular cells is prevented by the caspase inhibitors YVAD or DEVD. However, these inhibitors do not prevent the release of cytochrome c or the development of renal tubular dysfunction. Apoptosis of hepatocytes and of renal tubular epithelial cells are characteristic features of this disease and the apoptotic signal in this disease seems to be initiated by fumarylacetoacetate.

[Propagation of hepatitis E virus in several cell lines including human embryo lung diploid cell KMB17]

OBJECTIVE

To investigate the hepatitis E virus (HEV) sensitive cells and its tissue culture conditions.

METHODS

The HEV from dejecta supernatant of patients with acute hepatitis E was amplified and activated by passaged in Rhesus. Then, the positive dejecta samples of infected monkeys were dealt with super-centrifugation and virus for culture was obtained. Various human-derived (including KMB17, A549, BEL7402, and Hela) and non-human primates derived cells (Vero) were inoculated with HEV. Sensitivity of cells to HEV was measured by CPE (cytopathic effect), RT-PCR and immunofluorescence.

RESULTS

CPE in KMB17, A549 and BEL7402 cells appeared during 7-9 days, meanwhile, cells shelled during 11-13 days on the first filial generation. The existence of HEV genome +RNA and replicated -RNA was still detectable by RT-PCR after the tenth filial generation. Neither CPE nor amplification of HEV genome RNA could be detected in Hela and Vero cells after the second to fourth filial generation. HEV could also be detected from inoculated KMB17 cells by immunofluorescence and RT-PCR.

CONCLUSIONS

It indicates that KMB17, A549 and BEL7402 cells are sensitive to HEV under the experimental culture conditions, while Hela and Vero cells are insensitive. Tissue culture system of HEV in certain filial generation is established.

[Construction and expression of huGM-CSF (9-127)-IL-6(29-184) fusion protein gene]

OBJECTIVE

To construct and express huGM-CSF(9-127)-IL-6(29-184) fusion protein with high purity and both huGM-CSF and huIL-6 biologic activities.

METHODS

The novel gene coding for the fusion protein of huGM-CSF(9-127)-IL-6(29-184) was constructed by strategy of step by step cloning in pBV220 expression vector. The amino acids 1-8 of huGM-CSF and the amino acids 1-28 of huIL-6 were deleted by PCR technique. The mutant huGM-CSF (9-127) and huIL-6 (29-184) cDNAs were linked via a linker sequence coding 15 amino acid residues (G-G-S-G-S)3. Fusion protein was expressed in E.coli host strain DH5 alpha. To obtain the fusion protein, Q Sepharose H.P. ion exchange chromatography and Sephacryl S-200 gel filtration were performed. The biologic activities were detected by MTT method.

RESULTS

Fusion protein was expressed in E.coli host strain DH5 alpha in the form of inclusion body. The expression level was more than 25% of the total cell lysate. Through Q Sepharose H.P. ion exchange chromatography and Sephacryl S-200 gel filtration, huGM-CSF(9-127)-IL-6(29-184) fusion protein with high purity was obtained. The protein showed both huGM-CSF and huIL-6 biologic activities. The specific activity of huGM-CSF was 1.08 x 10(8) U/mg, and for huIL-6, it reached 1.95 x 10(7) U/mg.

CONCLUSION

huGM-CSF(9-127)-IL-6(29-184) fusion protein with high purity and both huGM-CSF and huIL-6 biologic activities was obtained.

[Purification and immunological characterization of hepatitis E virus recombinant chimeric antigen encoded by ORF2 fragments and ORF3]

OBJECTIVE

To study immunological characteristics of recombinant chimeric HEV antigen.

METHODS

Constructed recombinant plasmids pThioHisORF(2.1 + 2.2 + 3), which contains three HEV antigen gene fragments (ORF2.1:6287-6403nt, ORF2.2:6743-7126nt, ORF3), was transformed into E. coli and induced with IPTG. Expressed product P(2.1 + 2.2 + 3) existed in inclusion bodies, was purified by denature SP Sepharose FF cation exchange chromatography. Rabbits and rats were immunized with renatured P(2.1 + 2.2 + 3). The level of IgG in sera from experimental animals and clinical patients were examined with P(2.1 + 2.2 + 3) by ELISA. The characteristics of IgG of immunized animals interacted with recombinant antigen expressed by baculovirus system as well as recombinant chimeric antigen interacted with clinical patients sera were evaluated by Western-blotting.

RESULTS

High titer of IgG antibodies, 1:25,600 in rabbits and 1:12,800 in rats, were detected after immunized with P(2.1 + 2.2 + 3). Furthermore, recombinant antigen expressed by baculovirus system was specifically recognized by IgG of experimental animal immunized with P(2.1 + 2.2 + 3), and the purified recombinant chimeric antigen P(2.1 + 2.2 + 3) was specifically reacted with the IgG of clinical patients.

CONCLUSIONS

Recombinant chimeric antigen appears a promising strategy for detection of and prevention from HEV infection.

[Expression of hepatitis E virus ORF3 gene fragment in baculovirus system and its immunological character]

OBJECTIVE

To express hepatitis E virus (HEV) ORF3 protein by baculovirus system and provide basis for immunological character research.

METHODS

Hepatitis E Virus ORF3 gene fragment was obtained by RT-PCR, ligated with vector pThioHisA for sequencing and then inserted into transfected vector pVL1393 to construct recombinant plasmid. Mediated by Lipofectin Reagent, the recombinant vector and baculovirus linearized DNA (BaculoGold) co-transfected insect cell Sf9 to make recombinant baculovirus. Expressed ORF3 was analyzed for its immunological character by Western blotting, and immunized Kunming Mice.

RESULTS

Recombinant ORF3 protein could be recognized by the known positive serum and promoted organism to produce HEV-specific antibody.

CONCLUSIONS

Recombinant baculovirus can express effectively HEV ORF3, which has HEV specific immunogenic character.

[Expression in Escherichia coli and immunogenicity of rotavirus VP7]

Rotaviruses are the single most important cause of severe diarrhea in young children all over the world. VP7 is the major outer capsid and is a primary candidate for inclusion in a subunit or recombinant vaccine. Part of the VP7 gene containing all the three antigenic regions was expressed as a chimeric protein with glutathione S-transferase (GST) in E. coli. The chimeric protein, representing about 30% of the total protein of the recombinant-plasmid-carrying bacteria, reacted with polyclonal antibodies raised against whole virus. Immunization of sero-negative rabbits and mice with purified fusion-protein generated both virus-binding and neutralizing antibodies.

Urgent endoscopic nasobiliary drainage without fluoroscopic guidance: A useful treatment for critically ill patients with biliary obstruction

BACKGROUND

Endoscopic nasobiliary drainage (ENBD) is routinely performed under fluoroscopic control. This is a report of our experience with urgent ENBD without fluoroscopic guidance in critically ill patients.

METHODS

Twenty-six critically ill patients who underwent urgent ENBD for biliary obstruction were analyzed. ENBD was performed without fluoroscopic control because of high risk of transportation or inaccessibility of the x-ray facilities. A pig-tailed nasobiliary catheter was inserted into the bile duct with the help of a guidewire under endoscopic control to bypass the site of obstruction. Successful placement was confirmed by free flow of bile on aspiration via the nasobiliary catheter.

RESULTS

A nasobiliary catheter was successfully placed in 23 patients (88%). Adequate bile drainage was achieved in 20 patients with an overall success rate of 77%. There were no procedure-related complications. The mortality rate for patients with successful biliary drainage was 10% (2 of 20), in contrast to 83% (5 of 6) for the group in which drainage was unsuccessful.

CONCLUSIONS

Urgent ENBD is effective for patients with biliary obstruction. With experience, this procedure may be successfully performed in critically ill patients without fluoroscopic guidance at primary care hospitals or intensive care units where fluoroscopic facilities are not readily available.

Combined spinal-epidural anesthesia for cesarean section in a patient with Takayasu's disease

We describe a successful episode of anesthesia management in a parturient affected with Takayasu's disease who underwent elective cesarean section under combined spinal-epidural anesthesia. Takayasu's disease is characterized by chronic occlusive inflammation of the arteries (panarteritis) of unknown origin that usually involves the aorta and its main branches. Progression of the disease may be marked by aneurysmal dilation of the affected arteries and may lead to a fatal outcome, usually from cerebral ischemia or heart failure. The impact of pregnancy on Takayasu's disease is unclear, but worsening of ischemic symptoms, cardiac failure, aggravation of hypertension and cerebral hemorrhage have been reported in sufferers who are in the later stages of pregnancy. Nonetheless, anesthesia management of a parturient with advanced Takayasu's disease presents a challenge to anesthetists.

The optimal effective concentration of lidocaine to reduce pain on injection of propofol

STUDY OBJECTIVE

To determine the optimal concentration of lidocaine that reduces pain on injection of a propofol-lidocaine mixture.

DESIGN

Prospective, randomized, double-blinded, clinical investigation.

SETTING

Medical center, university teaching hospital.

PATIENTS

240 ASA physical status I and II female outpatients, aged 21 to 65 years, undergoing dilation and curettage with propofol for anesthesia induction.

INTERVENTIONS

Patients were randomized to one of four groups in double-blinded fashion. In Group A (control), patients were given propofol containing normal saline; in Group B, Group C, and Group D, patients received propofol containing 0.05% lidocaine (Group B), propofol containing 0.1% lidocaine (Group C), and propofol containing 0.2% lidocaine (Group D) for induction.

MEASUREMENTS AND MAIN RESULTS

The incidence of pain on injection of propofol was significantly decreased in Group C and Group D (8.3% and 10.0%, respectively) in comparison to the control group (91.7%) (p < 0.001). Although the result in Group B (76.7%) was better than that in the control group, the difference was not statistically significant. No significant difference was seen between Group C and Group D.

CONCLUSIONS

The optimal effective concentration of lidocaine, which decreased the incidence of pain caused by propofol injection, was 0.1% in the currently studied population.

Fatal pulmonary embolism in a child undergoing extra-ventricular drainage surgery--a case report

Thromboembolism is rather common in neurological patients and patients with brain tumor, who are bed-ridden or with partial immobile limb. In serious instances morbidity and mortality are inevitable. We present a case report on a fatal pulmonary embolism in a 2-year-old girl who underwent extra-ventricular drainage procedure under general anesthesia for occipital subdural effusion, a sequela of the former surgery undertaken to remove the choroid plexus papilloma 13 days ago. Sudden cardiac arrest occurred during induction of anesthesia and she finally succumbed in spite of vigorous cardiopulmonary resuscitation. Transthoracic and transesophageal echocardiography performed in the course of resuscitation disclosed thrombi of various sizes scattering in right atrium, the right ventricle, main pulmonary trunk, and the left pulmonary artery. The cause of death was thought to be severe obstruction of right ventricular outflow tract by large thrombi. The etiological factors which possibly led to the thrombosis were discussed, and the methods of diagnosis and treatment were also explored.

Right ventricular dysfunction after tetralogy repair in a pediatric patient with successful ECMO support--a case report

Right ventricular dysfunction after surgical repair of tetralogy is a serious life threatening complication. Although pulmonary vasodilators and inotropes can be used for cardiac support in tetralogy repair, these drugs may be ineffective in some patients. To date extracorporeal membrane oxygenation (ECMO) support may be used effectively in these patients when medical therapy fails. We report a case with successful ECMO support in right ventricular dysfunction and pulmonary hypertension after total surgical correction of Fallot's tetralogy. ECMO circuit was instituted in the operating room due to difficulty in weaning from cardiopulmonary bypass in spite of aggressive medical therapy. We reviewed and discussed the indications, contraindications of application of ECMO and patient survival with treatment of ECMO. At the same time we wish to share our limited experience we gained in our first attempt of ECMO support.

Anesthetic management in parturients with uterine rupture preoperatively--report of two cases

Uterine rupture is a rare obstetric emergency, and the diagnosis of rupture is not always obvious. High surgical delivery rate today which tends to increase the incidence of the disaster urged us to present this report. Two cases of spontaneous rupture of uterus are described. Case 1 concerns spontaneous rupture of a previously intact uterus; case 2 is a rupture due to placenta percreta. A review relevant to its incidence, risk factors, clinical characteristics, and anesthetic managements is given.

[Effects of three kinds of inorganic dusts on lipid peroxidation of erythrocytes]

This paper reports on the effects of erythrocytes when incubated with three kinds of inorganic dusts, i.e. quartz (free SiO2 content 97%), alpha-Al2O3 and TiO2. Malonaldehyde as a product of lipid peroxidation was determined as it reacted with thiobarbituric acid, and haemolytic activity was analysed spectrophotometrically. The results showed that quartz presented a stronger stimulative effect on lipid peroxidation of erythrocyte at doses of 1-8 mg than the control (P less than 0.01). No change was observed with alpha-Al2O3 and TiO2 at doses of 1-9 mg. The results suggest that the effects of dusts on lipid peroxidation of erythrocyte are similar to hemolytic reaction, directly reflecting the degree of their damage to the cell membrane. Therefore lipid peroxidation on cell membrane caused by dusts was one of the parameters of cytotoxic effects, and could be considered as one of the measures used in the assessment of cytotoxicity of dusts.

Nonparasitic hepatic cysts detected in ultrasonographic examination: analysis of 95 cases

Ultrasonography has gained wide use in the diagnosis of hepatic cystic diseases. Ninety cases with nonparasitic hepatic cysts were detected in 4,615 patients who underwent routine abdominal ultrasonography. In this series, hepatic cysts were mostly discovered in men (62.1%), in the age range of 51-70 years (63.1%) and located in the right lobe of the liver (62.1%). Hepatomegaly, abdominal mass, abdominal pain, and jaundice were the common clinical manifestations in patients with symptomatic hepatic cysts (13.7%), especially in cases with larger or multiple cysts. Only 4 patients received invasive management; 2 with ultrasonographic guide aspiration alone, 1 with external drainage, and 1 with alcohol instillation. Complications in this series of liver cysts were noted in 3 patients (3.16%) including infection, portal hypertension and jaundice.

First report of an epidemic of diarrhoea in human neonates involving the new rotavirus and biological characteristics of the epidemic virus strain (KMB/R85)

An outbreak of diarrhoea in neonates occurred at the nurseries of the Department of Obstetrics of Zhao Tong Regional Hospital, Yunnan Province, from the middle of August to the end of November, 1985. Fifty-one percent of children were affected 2-8 days after birth. The clinical symptoms were mild; patients mainly had diarrhoea and did not vomit. Rotaviruses were detected in 66.7% by RNA PAGE and in 72.7% by EM. The virus strain designated as KMB/R85 had a typical morphology, which was indistinguishable from that of infantile rotaviruses by EM. The viral RNA genome was composed of 11 segments. The buoyant density in CsCl was 1.377 g/cm3. The KMB/R85 strain possessed a hemagglutinin for rhesus monkey erythrocytes. By ELISA, IEM, and HAI, it was found that KMB/R85 strain did not possess the common group antigen shared by group A rotaviruses and was antigenically similar to the Chinese adult diarrhoea rotavirus (serogroup B).

Rapid diagnosis of parainfluenza virus infection in children

The indirect immunofluorescent-antibody (IFA) assay for detection of parainfluenza virus antigen was performed on samples of nasopharyngeal secretions obtained from infants and children with various respiratory illnesses to determine the usefulness of the IFA assay for rapid diagnosis of parainfluenza virus infection. Ninety-four samples of nasopharyngeal secretions were obtained from 78 children during a community outbreak of parainfluenza virus infection. Application of the IFA assay revealed the presence of parainfluenza antigen in 67 of the 94 samples. When these same specimens were inoculated into tissue culture, the presence of parainfluenza virus was confirmed in 62 (93%) of the 67 IFA-positive specimens by hemadsorption on tissue culture monolayers (31 cases), presence of parainfluenza hemagglutinin in infected tissue culture fluids (23 cases), or by other methods (8 cases). Only four IFA-negative specimens were subsequently shown to be positive for parainfluenza virus by tissue culture infectivity. The IFA assay provided a more rapid and more accurate method for diagnosis of parainfluenza infection in children than did routine tissue culture methods employed currently.

INDO–MO Calculations and Proton Isotropic Shifts of Methyl-Substituted Pyridine Ligands in Ni(II) Complexes

Relative p.m.r. isotropic shifts for the ligands in the complexes NiL4(NO3)2 (L = 4-picoline and 3,5-lutidine), NiL3(NO3)2 (L = 3-picoline and 3,4-lutidine), and NiL2(NO3)2 (L = 2-picoline, 2,3-lutidine, 2,4-lutidine, and 2,5-lutidine) were determined in CDCl3. Proton hyperfine coupling constants for corresponding pyridine cations and analogous phenyl radicals were calculated by the INDO–MO method. Analysis of the p.m.r. shifts and subsequent correlation with the INDO data revealed that the spin transfer process between metal and ligand was dominated by a σ-mechanism, as indicated by ring protons at the α- and β-positions. The γ-ring proton and methyl protons at all positions indicated a π-mechanism was also operative through σ–π spin polarization at the nitrogen atom. The INDO calculations based on spin densities of the hydrogen Is orbitals, however, predicted that all ring protons would be dominated by a σ-mechanism, and that methyl protons at the α- and γ-positions should manifest a π-mechanism. Both mechanisms should be operative for the β-CH3 protons, with 50–60% σ-contribution in the pyridine cations and 30–50% σ-contribution in the phenyl radicals. The pattern of spin polarization (i.e., negative at α-C and γ-C, positive at β-C) is not altered by a small excess of α or β spin in the π-system. However, the π-spin density ratios, especially at the α- and γ-positions, are affected, as is the magnitude of the π-spin densities on each carbon. A comparison of the observed isotropic shifts for the methyl protons and for the γ-ring proton with the INDO calculated π-spin densities allows a determination of the spin delocalization in the ligand π-system.

The Nickel(II)–γ-Picoline–Perchlorate Complex System

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The Nickel(II)–γ-Picoline–Perchlorate Complex System

Three compounds have been isolated; viz., NiL4(ClO4)2, NiL4(H2O)2(ClO4)2 and NiL6(H2O)2(ClO4)2 (L = γ-picoline), and their spectral, magnetic, and other properties compared. Some tentative suggestions as to the possible structure of the last complex are offered; the first two compounds were reported previously (1).

Erratum: Comparative formation constants for complexes of copper, nickel, and silver with some substituted pyridines

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Comparative formation constants for complexes of copper, nickel, and silver with some substituted pyridines

Formation constants for metal complexes of Cu(II), Ni(II), and Ag(I) with some substituted pyridine ligands were determined in a nitrate salt solution of the ligand (0.5 F KNO3 + 0.1 F HL) at 25 °C by pH measurement. The linear relationship shown by a logarithmic plot of the formation constant versus the basicity of the ligands characterizes qualitatively the dΠ → pπ-bonding capacity for each metal ion. The 2-substituents, such as —CH3 and —NH2, on these pyridine ligands have a very profound steric effect upon the stabilities of Cu(II) and Ni(II) complexes, but have no such effect upon that of Ag(I) complexes. An explanation is given which may be useful in selecting analytical reagents.