Changing demographics and immunity to vaccine preventable diseases in people with HIV in Ireland

BACKGROUND

HIV infection is associated with an increased risk of morbidity and mortality from vaccine preventable infections. This research describes, in the context of changing patient demographics, the seroprevalence of vaccine preventable viral infections among attendees of the largest centre for HIV positive patients in Ireland.

METHODS

Baseline serum IgG results for measles, mumps, rubella, varicella zoster virus (VZV) & hepatitis A, as well as hepatitis B sAg, cAb and sAb results, were retrieved for 2534 clinic attendees attending in 2018. Results were available for between 990 and 2363 attendees (39-93%), depending on the test, and were compared with 2013 clinic data.

RESULTS

There was a 35% increase in attendees in 2018 when compared to 2013. The largest increase was in attendees of South American origin. In 2018, males accounted for 73% of the entire cohort and the HIV acquisition risk for 48% of attendees was MSM. 47% of attendees were originally from Ireland. Among those tested, 33% were susceptible to at least one component of the MMR vaccine. 5% were VZV non-immune (significantly associated with younger age and the acquisition risk status of injection drug use). 21% were hepatitis A non-immune (significantly associated with younger age and being of European or South American origin). 32% were hepatitis B cAb seropositive (significantly associated with older age, injection drug use status and being originally from Africa). 3% demonstrated hepatitis B sAg positivity. 64% had hepatitis B sAb ≥ 10mIU.

CONCLUSION

In a cohort of attendees to an HIV clinic in a large urban setting, the susceptibility to several common vaccine preventable viral infections, in particular MMR and hepatitis A and B, was high. These results highlight the importance of proactive screening and immunisation to help protect this high risk patient group against vaccine preventable diseases.

Justifying quarantine in preventing the spread of COVID-19 in healthcare

Background

The first COVID-19-positive patient was identified in Ireland on 29 February 2020 (Department of Health, Government of Ireland; https://www.gov.ie/en/pressrelease/2f75fd-statement-from-the-national-public-healthemergency-team-sat-29-feb/). Healthcare worker (HCW) quarantining became a core intervention for those identified as ‘close contacts’ to reduce onward transmission within the workplace to patients and colleagues. Whether a quarantining strategy could be justified at a time when there was an increased demand for the services of HCWs remained unknown.

Aims

To establish whether quarantining staff away from a healthcare setting during a pandemic is justified.

Methods

This retrospective study examined close contacts of COVID-19-positive index cases (both residents and HCWs) in a community hospital over a 4-week period from 1 to 28 April 2020. Close contacts were identified in accordance with national guidelines. Zones of the hospital were examined to determine the number of COVID-positive index cases and their close contacts. A cumulative result for the hospital was recorded.

Results

While outcomes varied over time, per zone and per HCW category, the overall conversion rate from close contact to an index case was 30%.

Conclusions

This study vindicates the policy of quarantining close contact HCWs from their workplaces as they pose a significant threat to both their patients and fellow workers.

Co-crystal polymorphic control by nanodroplet and electrical confinement

The polymorphic control of the co-crystal carbamazepine–saccharin (CBZ–SAC) metastable form II was achieved by nano-droplet confinement in tandem with droplet surface charging induced by electrospraying the precursor solution.

Electrospun API-loaded mixed matrix membranes for controlled release

The development of biocompatible membrane materials capable of delivering active pharmaceutical ingredients (APIs) over a fixed time period offers significant advantages to the pharmaceutical and biomedical industries alike.

Caffeine and alcohol intakes have no association with risk of multiple sclerosis

BACKGROUND

The association between alcohol and caffeine intakes and risk of multiple sclerosis (MS) is unclear; no prospective studies have examined this relationship.

OBJECTIVE

We examined intakes of alcohol and caffeine in relation to risk of multiple sclerosis.

METHODS

Intakes of alcohol and caffeine were examined in relation to the risk of MS in two large cohorts of women, the Nurses' Health Study (NHS; 92,275 women followed from 1980 to 2004) and Nurses' Health Study II (NHS II; 95,051 women followed from 1991 to 2005). Their diet was assessed at baseline and every four years thereafter. During the follow-up, 282 cases of MS were confirmed with onset of symptoms after baseline. Twenty-four cases were missing information on alcohol intake, leaving a total of 258 cases for the alcohol analyses.

RESULTS

Neither total alcohol consumption, nor consumption of beer, wine, or liquor was related to MS risk. The multivariable-adjusted pooled relative risk (RR) found by comparing categories of alcohol intake to 0 gm/day was 1.07 (95% CI: 0.32-1.99) for 0.1-4.9 gm/day, 1.01 (0.32-1.99) for 5.0-14.9 gm/day, 1.21 (0.69-2.15) for 15.0-29.9 gm/day, and 0.80 (0.32-1.99) for 30+ gm/day; (p for trend=0.89). Caffeine intake was also not significantly associated with MS risk. The multivariable adjusted pooled RR comparing highest to lowest quintile of caffeine intake was 1.14; 95% CI: 0.79-1.66; p for trend=0.71. Consideration of caffeinated and decaffeinated coffee separately also yielded null results.

CONCLUSION

These results do not support an association between alcohol and caffeine intakes and MS risk.

Anti-Epstein-Barr virus antibodies as serological markers of multiple sclerosis: a prospective study among United States military personnel

BACKGROUND

Elevated Epstein-Barr virus (EBV) antibody titers are risk factors for multiple sclerosis (MS), but the strength and consistency of this association are not well characterized.

OBJECTIVES

The objectives of this study were to determine whether this association is confounded by vitamin D or modified by gender or race, and the usefulness of EBV nuclear antigen (EBNA) antibodies as a marker for MS.

METHODS

We conducted a prospective study among US military personnel. Antibody titers against EBV antigens were measured in serum samples from 222 individuals who developed MS and 444 age, sex, and race/ethnicity matched controls. Conditional logistic regression was used to estimate relative risks.

RESULTS

MS risk increased with increasing titers of anti-EBNA complex (p < 10(-9)) and anti-EBNA-1 (p = 5.8 × 10(-9)) titers. MS risk was 36-fold higher among individuals with anti-EBNA complex IgG titers ≥320 than among those with titers <20 (95% confidence interval [CI] 9.6-136), and 8-fold higher among those with anti-EBNA-1 ≥320 than among those with anti-EBNA-1 <20 (95% CI 2.6-23). These associations were consistent across gender and race/ethnicity groups and independent from 25-hydroxyvitamin D levels. Areas under the receiver operating characteristic (ROC) curves were 0.67 for EBNA complex and 0.65 for EBNA-1.

CONCLUSIONS

Serum titers of pre-onset anti-EBNA antibodies are strong, robust markers of MS risk and could be useful in an MS risk score.

Persistent organochlorine pesticides in serum and risk of Parkinson disease

BACKGROUND

Pesticides have been implicated as likely environmental risk factors for Parkinson disease (PD), but assessment of past exposure to pesticides can be difficult. No prior studies of pesticide exposure and PD used biomarkers of exposure collected before the onset of PD. Our investigation examined the association between prospective serum biomarkers of organochlorine pesticides and PD.

METHODS

We conducted a nested case-control study within the Finnish Mobile Clinic Health Examination Survey, with serum samples collected during 1968-1972, and analyzed in 2005-2007 for organochlorine pesticides. Incident PD cases were identified through the Social Insurance Institution's nationwide registry and were confirmed by review of medical records (n = 101). Controls (n = 349) were matched for age, sex, municipality, and vital status. Adjusted odds ratios (ORs) of PD were estimated using logistic regression.

RESULTS

Little association emerged with a summary score of the 5 organochlorine pesticides found at high levels, and only increasing dieldrin concentrations trended toward a higher risk of PD (OR per interquartile range [IQR] 1.28, 95% confidence interval [CI] 0.97-1.69, p = 0.08). Because of possible strong confounding by cigarette smoking among smokers, we ran additional analyses restricted to never smokers (n = 68 cases, 183 controls). In these analyses, increasing dieldrin concentrations were associated with increased odds of PD (OR per IQR 1.95, 95% CI 1.26-3.02, p = 0.003). None of the other organochlorine pesticides were associated with PD in these analyses.

CONCLUSIONS

These results provide some support for an increased risk of Parkinson disease with exposure to dieldrin, but chance or exposure correlation with other less persistent pesticides could contribute to our findings.

Prospective study of chemical exposures and amyotrophic lateral sclerosis

BACKGROUND

Although environmental toxins, including pesticides, are suspected of contributing to the risk of amyotrophic lateral sclerosis (ALS), no data exist from large prospective investigations. This study assessed the association between exposure to chemicals and risk of ALS in a prospective cohort study.

METHODS

The relation between self-report of regular exposure to 11 different chemical classes or x rays and ALS mortality among over 1 million participants in the American Cancer Society's Cancer Prevention Study II was prospectively assessed. Follow-up from 1989 through 2004 identified 617 deaths from ALS among men and 539 among women. Adjusted rate ratios (RR) were calculated using Cox proportional hazards.

RESULTS

The RR for ALS mortality among individuals exposed to pesticides/herbicides compared with that among unexposed individuals was 1.07 (95% CI 0.79 to 1.44), but somewhat higher after excluding those with missing duration of pesticides exposure (RR 1.44; 95% CI 0.89 to 2.31; p = 0.14). A non-significant increase in ALS mortality was found among individuals who reported exposure to formaldehyde (RR 1.34; 95% CI 0.93 to 1.92). Excluding those with a missing duration of formaldehyde exposure, the RR was 2.47 (95% CI 1.58 to 3.86), and there was a strongly significant dose-response relation with increasing years of exposure (p trend = 0.0004).

CONCLUSIONS

There was little evidence for any association between pesticides/herbicide exposure and ALS. In contrast, evidence was found, suggesting an increased risk of ALS with formaldehyde exposure. Because of the longitudinal design, this result is unlikely to be due to bias, but it should nevertheless be interpreted cautiously and needs to be verified independently.

Serum titers of IgG antibodies against tetanus and diphtheria toxoids and risk of multiple sclerosis

We conducted a prospective nested case-control study among military service members to investigate whether antibodies against tetanus or diphtheria predict multiple sclerosis (MS) risk. Paired T-tests were used to compare means of anti-tetanus and diphtheria toxoids among 56 MS cases and 112 matched controls. Conditional logistic regression was used to estimate odds ratios (OR). There were no differences between the mean serum IgG antibodies against tetanus (p-value 0.28) or diphtheria (p-value 0.45) in the baseline samples. The OR of MS associated with 1 standard deviation difference in antibody titers was 0.76 (95% CI: 0.48-1.21) for tetanus (SD=4.71) and 1.03 (0.73-1.45) for diphtheria (SD=0.87). Results of this study suggest serum IgG antibodies against tetanus or diphtheria are not predictors of MS risk.

Human endogenous retrovirus-K18 Env as a risk factor in multiple sclerosis

BackgroundThe human endogenous retrovirus (HERV)-K18 Env is an Epstein-Barr virus (EBV)-associated superantigen. Given the evidence for a role of EBV in the etiology of multiple sclerosis (MS), HERV-K18 Env is a plausible candidate for association with MS.ObjectiveTo assess whether variation in HERV-K18 Env is a risk factor for MS.MethodsWe developed a single nucleotide polymorphism-based genotyping method to determine the distribution of the three alleles of HERV-K18 env. We then conducted a nested case-control study including 207 MS cases and 403 matched controls. Analyses were replicated in an independent series of 909 MS cases and 339 controls.ResultsOverall, there was a significant association between HERV-K18 env genotype and MS risk (chi2 P = 0.03). As compared with K18.2/K18.2 individuals, risk of MS was three fold higher among K18.3/K18.3 individuals (P = 0.03). An increase in MS risk among carriers of the K18.3 allele was also observed in the replication study, but did not reach statistical significance. In pooled analyses, K18.3/K18.3 individuals had a significantly increased risk of MS (relative risks [RR] comparing K18.3/K18.3 vs K18.2/K18.2 = 2.7; 95% confidence interval: 1.1-6.4).ConclusionVariation in EBV-associated superantigen HERV-K18 Env could influence the genetic susceptibility to MS.

Plasma Titers of Antibodies against Epstein-Barr Virus BZLF1 and Risk of Multiple Sclerosis

BACKGROUND/AIMS

Results of recently conducted prospective studies have demonstrated that the presence of high titers of anti-EBNA-1 or anti-EBNA complex IgG antibodies in healthy individuals is a strong risk factor for multiple sclerosis (MS). Antibodies to BZLF1, the product of the homonymous early lytic gene, have been found to be related to risk of nasopharyngeal carcinoma, but have not been previously measured in MS studies.

METHODS

We examined whether high levels of anti-BZLF1 IgG antibodies also predict MS risk in a nested case-control study among women in the Nurses Health Study and Nurses Health Study II cohorts.

RESULTS

Results of this prospective study suggest that antibody titers to EBNAs are the strongest predictor of MS risk.

CONCLUSION

Little further contribution may be provided by measuring anti-BZLF1 antibodies in regard to MS risk.

Temporal relationship between cigarette smoking and risk of Parkinson disease

OBJECTIVE

To characterize further the relationship between smoking history and Parkinson disease (PD) risk by considering temporal and qualitative features of smoking exposure, including duration, average intensity, and recentness, as well as the relative importance of smoking during different periods of life.

METHODS

We prospectively assessed incident PD from 1992 to 2001 among 79,977 women and 63,348 men participating in the Cancer Prevention Study II Nutrition Cohort, according to their cigarette smoking status and lifetime smoking histories.

RESULTS

During follow-up, 413 participants had definite or probable PD confirmed by their treating neurologists or medical record review. Compared with never smokers, former smokers had a relative risk (RR) of 0.78 (95% CI 0.64 to 0.95) and current smokers had an RR of 0.27 (95% CI 0.13 to 0.56). On average, participants with more years smoked, more cigarettes per day, older age at quitting smoking, and fewer years since quitting smoking had lower PD risk. The relative risks and trends did not vary significantly by sex. The cumulative incidence of PD was lowest among participants who quit smoking at later ages. A 30% to 60% decreased risk of PD was apparent for smoking as early as 15 to 24 years before symptom onset, but not for smoking 25 or more years before onset.

CONCLUSIONS

The lower risk of Parkinson disease among current and former smokers varied with smoking duration, intensity, and recentness. The dependence of this association on the timing of smoking during life is consistent with a biologic effect.

Prospective study of military service and mortality from ALS

BACKGROUND

Two recent studies suggest that the risk of ALS is increased among Gulf War veterans. It is not known whether military service outside of the Gulf War is associated with increased risk of ALS.

METHODS

The authors prospectively assessed the relation between service in the military and ALS mortality among participants in the Cancer Prevention Study II cohort of the American Cancer Society, a cohort that includes over 500,000 men from the 50 states, Washington, DC, and Puerto Rico. Participant follow-up was conducted from 1989 through 1998 for ALS mortality. There were a total of 280 deaths from ALS among 126,414 men who did not serve in the military and 281,874 who did. Adjusted relative risks (RRs) were calculated using Mantel-Haenszel weights and Cox proportional hazards.

RESULTS

Men who served in the military had an increased death rate from ALS (RR = 1.53; 95% CI: 1.12 to 2.09; p = 0.007) compared with those who did not serve. The increase in ALS mortality was observed among men who served in the Army or National Guard (RR = 1.54), Navy (RR = 1.87), Air Force (RR = 1.54), and Coast Guard (RR = 2.24); no increase in risk was found in men who served in the Marine Corps, although there were only 13,670 men in this group. The risk of ALS among men who served was elevated in every 5-year birth cohort from 1915 through 1939.

CONCLUSIONS

Military personnel have an increased risk of ALS. This increase appeared to be largely independent of the branch of service and the time period served.

The simpliRED D dimer test: a novel assay for the detection of crosslinked fibrin degradation products in whole blood

A new system for the detection of fibrin degradation products in whole blood has been developed. The test provides a clearly visible agglutination of the patient's red blood cells in the presence of elevated levels of the crosslinked fibrin derivative, D dimer. The test, which uses a bispecific reagent prepared from Fab' fragments of monoclonal antibodies, gives a positive result in 1-2 minutes. One monoclonal antibody (RAT-1C3/86) was raised against human red blood cells, and the second (DD-3B6/22) was specific to the crosslinked fibrin derivative, D dimer. Addition of the bispecific reagent to a drop of patient's whole blood resulted in red blood cell agglutination when elevated levels of D dimer were present in the sample. Clinical trials showed sensitivity equivalent to that of current commercial tests. Samples from patients with thrombotic disease states as well as normals were examined. The test was compared with commercial latex agglutination and enzyme immunoassay systems and showed good correlation with the presence of elevated levels of crosslinked fibrin degradation products. This technology represents an advance which allows rapid "on the spot" whole blood analysis, for the diagnosis of thrombotic disorders.

A rapid whole-blood immunoassay system

A new immunoassay system has been developed which allows the detection of circulating antigens, antibodies or drugs in whole blood without specialized personnel or equipment. This is achieved by the use of bispecific reagents, which comprise specific antibodies or antigens that are coupled to a non-agglutinating antierythrocyte antibody. Within two minutes, these reagents cause specific agglutination of a patient's own red cells in samples that contain the relevant analyte. Levels of low molecular weight haptens also can be measured by the use of an indirect, agglutination-inhibition assay. This simple immunoassay method would fulfil the needs of many physicians and Third-World countries and also has mass-screening and veterinary applications.

Divalent Metal Complexes of 2-Formylphenoxyacetic Acid: The Crystal Structures of 2-Formylphenoxyacetic Acid, and the Isomorphous Cobalt(II) and Zinc(II) 2-Formylphenoxyacetates

The crystal structures of 2-formylphenoxyacetic acid ( ofpaH ), tetraaquabis (2-formylphenoxyacetato)-cobalt(II) (1) and tetraaquabis (2- formylphenoxyacetato )zinc(II) (2) have been determined by X-ray diffraction and refined to residuals R 0.039, 0.058 and 0.045 for 1197, 1178 and 1230 observed reflections respectively. 2-Formylphenoxyacetic acid crystallizes in a monoclinic cell, space group P21/n with a 8.066(2), b 7.375(1), c 14.206(2) Ǻ, β 98.12(1)° and Z 4. The planar molecules form unusual hydrogen-bonded chain polymers (O…O 2.694(3)Ǻ] linked through the carboxyl groups. The complexes (1) and (2) are isomorphous, the comparative cells being a 5.036(1), b 13.463(3), c 15.083(4) Ǻ, β 96.88(2)° for (1), and a 5.044(1), b 13.481(3), c 15.055(4) Ǻ, β 96.95(2)° for (2), with Z 2 and space group P21. The complexes have four waters and two trans-related carboxyl oxygens [mean M-O distances 2.129(5) and 2.117(3) Ǻ respectively] completing almost regular octahedral stereochemistries . The nickel(II) complex [Ni( ofpa )(H2O)4] is probably not isostructural with (1) and (2), and the copper(II) complex is also different, with formula [Cu( ofpa )2(H2O)2].

Metal complexes of dicamba. II. The crystal structure of catena-m-[Diaquabis-(3,6-dichloro-2-methoxybenzoato(O,O')]-calcium(II)

The crystal structure of a calcium complex of the herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid) has been determined by single-crystal X-ray diffraction and refined by least squares to a final residual of 0.045. [Ca(dicamba)2(H2O)2]n is orthorhombic, space group Pbcn, Z 4, with a cell a 15.844(3), b 16.833(2), c 7.751(1) �. The MO8 coordination polyhedron about the calcium ion is a distorted Archimedes antiprism which has twofold rotational symmetry. There are two waters [Ca-O, 2.414(3) �] and six carboxylate oxygens from two bidentate chelate groups [Ca-O, 2.516, 2.517(3) �] and two bridging carboxyls [2.372(3) �]. This results in an infinite linear polymer structure.

Metal complexes of dicamba: the crystal and molecular structures of dicamba(3,6-Dichloro-2-methoxybenzoic acid) and catena-μ-Aqua-diaquabis(3,6-dichloro-2-methoxybenzoato)zinc(II) dihydrate

The crystal structures of the herbicide, dicamba (3,6-dichloro-2-methoxybenzoic acid) and the zinc(II) complex of this acid, {[Zn(dicamba)2(H2O)3].2H2O}}n (1), have been determined from X-ray diffraction data and refined by least squares to final residuals of 0.034 and 0.043 respectively. Dicamba is triclinic, space group P1, Z 2 with a cell a 7.232(1), b 7.971(1), c 9.050(3) �, α 102.76(3), β 91.33(3), γ 110.38(1)�, while (1) is monoclinic, space group P21/n, Z 4 with a cell a 10.467(1), b 8.135(3), c 28.079(2) �, β 96.497(7)�. Dicamba forms hydrogen-bonded cyclic dimers [O---O, 2.655(7) �] with the carboxyl and the methoxy groups synclinal to the benzene ring. The dicamba ligands retain their conformation in the ZnII complex and are cis-related and unidentate [Zn-0,2.083,2.095(4) �]. Three of the waters are coordinated [Zn-0, 2.036, 2.055, 2.099(4) �] with one of these also acting as a bridging ligand between the octahedral zinc centres [Zn-0, 2.326(4) �], giving a 'linear' polymer structure [Zn-0-Zn bridge angle, 133.6(3)�]. The MnII and CoII complexes of dicamba [(2) and (3)] have been confirmed as isomorphous and isostructural with the ZnII analogue.

Copper complexes of Picloram: The crystal and molecular structures of Bis(4-amino-3,5,6-trichloropyridine-2-carboxylato)aquacopper(II) dihydrate and Bis(4-amino-3,5,6-trichloropyridine-2-carboxylato)bis(pyrimidin-2-amine)copper(II)

The crystal structures of two copper(II) complexes of the herbicide Picloram (4-amino-3,5,6-trichloro- pyridine-2-carboxylic acid) have been determined by single-crystal X-ray diffractometry. Bis(4-amino- 3,5,6-trichloropyridine-2-carboxylato)aquacopper(II) dihydrate (1) is monoclinic, space group C2/c, with Z 4 in a cell of dimensions a 15.593(6), b 7.940(6), c 16.983(6) �, β 107.58(3)�. The structure was refined to a residual R 0.046 for 905 'observed' reflections. Complex (1) is trigonal bipyramidal with the trigonal plane consisting of oxygens from two picolinate ligands [Cu-O 1.995(5) �] and a water molecule [Cu-O 2.080(5) �]. The apical positions are occupied by pyridine ring nitrogens from the Picloram ligands [Cu-N 2.021(5) �]. Bis(4-amino-3,5,6-trichloropyridine- 2-carboxylato)bis(pyrimidin-2-amine)copper(II) (2) is monoclinic, space group P2,/c, with Z 4 in a cell of dimensions a 12.3 11(5), b 15.435(5), c 15.320(6) �, β 115.95(3)�, and gave a final R 0.059 for 2429 'observed' reflections. In complex (2), the copper(II) atom has a tetragonally distorted octahedral stereochemistry with the Picloram ring nitrogens once again occupying the two axial positions [Cu-N 2.586(7) and 2.611(7) �]. The square plane consists of two carboxylato oxygens [Cu-O 1.941(6) and 1.960(7) �] and two hetero-nitrogens from pyrimidin-2-amine ligands [Cu-N 2.048(6) and 2.054(6) �].

Crystal and molecular structure of Bis(4-amino-3,5,6-trichloropicolinato)-manganese(II) dihydrate

The manganese(II) complex [Mn(picl)2,2H2O]n of the herbicide picloram has been prepared and the crystal and molecular structure determined from three-dimensional X-ray data collected by counter methods. The crystals of the complex are monoclinic, space group 12/a with two complex units in a cell of dimensions a 23·052(5), b 13·840(2), c 6·441(1) �, β 98·20(1)�. The structure was solved by direct methods and refined by full matrix least squares to unweighted and weighted Rfactors of 0·035 and 0·038 respectively for 887 'observed' reflections. The polymer is best described as having a centrosymmetric two-molecule unit [Mn-O, 2·162(3), 2·246(3) �] with two oxo bridges between manganese centres through two single carboxylate oxygens of the four substituted picolinate ligands. The two molecules are related by a twofold axis. The units form infinite one-dimensional polymer chains in the c direction through oxo bridges involving one oxygen from the other two picolinate ligands [Mn-Mn 3·636(1)�]. The bis(bidentate)picolinate bites are completed by the pyridlne nitrogens [Mn-N, 2·313(4) �] giving a very distorted octahedral MnO4N2 coordination sphere about each manganese [N-Mn-N', 97.0(3)�; O-Mn-O range, 68·9-168.2(3)�; O-Mn-Nrange, 69·9-138·5(3)�]. The lattice waters are involved in hydrogen-bonding interactions which link the polymer in the a crystallographic direction with the uncoordinated carboxylate oxygen ( O···O,2·824, 2·936 �) and the 4-amino groups from the adjacent picolinate ligand (N· ··0, 2·852, 3·030�).

Coordination Compounds of Substituted 1,10-Phenanthrolines and Related Dipyridyls. I. Synthesis of 2,9-Dimethyl-1,10-phenanthroline

A direct synthesis of 2,9-dimethyl-1,10-phenanthroline has been developed. The method involves a Skraup type of reaction between o-phenylenediamine, crotonaldehyde, and either arsenic(V) oxide or sodium m-nitrobenzenesulphonate. Some derivatives of 2,9-dimethyl-1,10-phenanthroline have been characterized.