Structures and Spin States of Iron(II) Complexes of Isomeric 2,6-Di(1,2,3-triazolyl)pyridine Ligands

Iron(II) complex salts of 2,6-di(1,2,3-triazol-1-yl)pyridine (L¹) are unexpectedly unstable in undried solvent. This is explained by the isolation of [Fe(L¹)₄(H₂O)₂][ClO₄]₂ and [Fe(NCS)₂(L¹)₂(H₂O)₂]·L¹, containing L¹ bound as a monodentate ligand rather than in the expected tridentate fashion. These complexes associate into 4⁴ grid structures through O-H···N hydrogen bonding; a solvate of a related 4⁴ coordination framework, catena-[Cu(μ-L¹)₂(H₂O)₂][BF₄]₂, is also presented. The isomeric ligands 2,6-di(1,2,3-triazol-2-yl)pyridine (L²) and 2,6-di(1H-1,2,3-triazol-4-yl)pyridine (L³) bind to iron(II) in a more typical tridentate fashion. Solvates of [Fe(L³)₂][ClO₄]₂ are low-spin and diamagnetic in the solid state and in solution, while [Fe(L²)₂][ClO₄]₂ and [Co(L³)₂][BF₄]₂ are fully high-spin. Treatment of L³ with methyl iodide affords 2,6-di(2-methyl-1,2,3-triazol-4-yl)pyridine (L⁴) and 2-(1-methyl-1,2,3-triazol-4-yl)-6-(2-methyl-1,2,3-triazol-4-yl)pyridine (L⁵). While salts of [Fe(L⁵)₂]²⁺ are low-spin in the solid state, [Fe(L⁴)₂][ClO₄]₂·H₂O is high-spin, and [Fe(L⁴)₂][ClO₄]₂·3MeNO₂ exhibits a hysteretic spin transition to 50% completeness at T_1/2 = 128 K (ΔT_1/2 = 6 K). This transition proceeds via a symmetry-breaking phase transition to an unusual low-temperature phase containing three unique cation sites with high-spin, low-spin, and 1:1 mixed-spin populations. The unusual distribution of the spin states in the low-temperature phase reflects "spin-state frustration" of the mixed-spin cation site by an equal number of high-spin and low-spin nearest neighbors. Gas-phase density functional theory calculations reproduce the spin-state preferences of these and some related complexes. These highlight the interplay between the σ-basicity and π-acidity of the heterocyclic donors in this ligand type, which have opposing influences on the molecular ligand field. The Brønsted basicities of L¹-L³ are very sensitive to the linkage isomerism of their triazolyl donors, which explains why their iron complex spin states show more variation than the better-known iron(II)/2,6-dipyrazolylpyridine system.

Potential risk-factors affecting Salmonella sp. and Escherichia coli occurrence and distribution in Midwestern United States swine feed mills

AIM

This study aimed to evaluate the patterns and potential risk factors associated with the occurrence of Salmonella sp. and Escherichia coli in selected United States swine feed mills.

METHODS AND RESULTS

A total of 405 samples were collected during fall 2018, spring and summer 2019 from selected sites including floors, equipment, shoes and feed in six feed mills in the US Midwest region. Each sample was analysed for the presence of Salmonella and E. coli with culture methods and confirmed by PCR. A survey regarding production volumes, hygiene practices and microbial testing capabilities was conducted in each facility All mills had at least one sampling site positive for either Salmonella or E. coli. Of the 405 samples, 4·7, and 14·1% were positive for Salmonella sp., and E. coli respectively. Sites with higher percentages of positive samples were the receiving, manufacturing, and control area floors. The survey responses indicated that the age of the mill might be a risk factor for bacterial contamination: the older the facility, the higher the number of positive samples. Other risk factors evaluated, such as the production capacity, did not appear to relate to bacterial prevalence.

CONCLUSION

The data documents the presence of E. coli and Salmonella in selected US swine feed mills, and an association between E. coli occurrence and number of ingredient suppliers to feed mill.

SIGNIFICANCE AND IMPACT OF THE STUDY

This information could be used to understand risk factors affecting the occurrence of Salmonella sp. and E. coli in feed mills and help implement monitoring and mitigation strategies for public health.

Effect of plasma exchange in accelerating natalizumab clearance and restoring leukocyte function

BACKGROUND

Accelerating the clearance of therapeutic monoclonal antibodies (mAbs) from the body may be useful to address uncommon but serious complications from treatment, such as progressive multifocal leukoencephalopathy (PML). Treatment of PML requires immune reconstitution. Plasma exchange (PLEX) may accelerate mAb clearance, restoring the function of inhibited proteins and increasing the number or function of leukocytes entering the CNS. We evaluated the efficacy of PLEX in accelerating natalizumab (a therapy for multiple sclerosis [MS] and Crohn disease) clearance and alpha4-integrin desaturation. Restoration of leukocyte transmigratory capacity was evaluated using an in vitro blood-brain barrier (ivBBB).

METHODS

Twelve patients with MS receiving natalizumab underwent three 1.5-volume PLEX sessions over 5 or 8 days. Natalizumab concentrations and alpha4-integrin saturation were assessed daily throughout PLEX and three times over the subsequent 2 weeks, comparing results with the same patients the previous month. Peripheral blood mononuclear cell (PBMC) migration (induced by the chemokine CCL2) across an ivBBB was assessed in a subset of six patients with and without PLEX.

RESULTS

Serum natalizumab concentrations were reduced by a mean of 92% from baseline to 1 week after three PLEX sessions (p < 0.001). Although average alpha4-integrin saturation was not reduced after PLEX, it was reduced to less than 50% when natalizumab concentrations were below 1 mug/mL. PBMC transmigratory capacity increased 2.2-fold after PLEX (p < 0.006).

CONCLUSIONS

Plasma exchange (PLEX) accelerated clearance of natalizumab, and at natalizumab concentrations below 1 mug/mL, desaturation of alpha4-integrin was observed. Also, CCL2-induced leukocyte transmigration across an in vitro blood-brain barrier was increased after PLEX. Therefore, PLEX may be effective in restoring immune effector function in natalizumab-treated patients.

A 75% insulin lispro/25% NPL mixture provides a longer duration of insulin activity compared with insulin lispro alone in patients with Type 1 diabetes

AIMS

To compare a new insulin formulation, high mix (HM) [75% lispro (LP) and 25% neutral protamine lispro (NPL)], to regular human insulin (HR) and LP with respect to glucose response and pharmacokinetics following a test meal in patients with Type 1 diabetes.

METHODS

After fasting overnight, patients received an intravenous insulin infusion to standardize blood glucose (BG) to 7.5 mmol/l (135 mg/dl). In a randomised, three-way crossover study, HR was injected 30 min before, and LP or HM was injected immediately before the test meal on three separate occasions. For each patient, LP and HR were administered at identical doses; the HM dose was one and one third times that of HR and LP to maintain the same dose of short or rapid-acting insulin. The insulin infusion was stopped 15 min after the insulin injection. Free insulin and BG concentrations were measured frequently for 7 h following the test meal.

RESULTS

HM and LP resulted in better glycaemic control than HR during the observation period. BG concentrations during the first 4-5 h did not differ between HM and LP. However, HM exhibited prolonged insulin activity relative to LP beyond 5 h, extending the duration of action by approximately 1 h, and resulting in lower overall BG concentrations when the 0-6- and 0-7-h intervals were considered.

CONCLUSIONS

Compared with LP, HM provided similar glycaemic control for up to 5 h and superior glycaemic control from 5 to 7 h following a standard test meal.

Time-action profiles of novel premixed preparations of insulin lispro and NPL insulin

OBJECTIVE

To study the pharmacodynamic properties of three premixed formulations of the rapid-acting insulin analog insulin lispro and its protamine-retarded preparation, neutral protamine lispro (NPL) insulin.

RESEARCH DESIGN AND METHODS

In this open, single-center, euglycemic glucose clamp study, 30 healthy volunteers (12 women, 18 men) aged 27 +/- 2 years (mean +/- SD), whose BMI was 23.0 +/- 2.3 kg/m2, received subcutaneous injections of 0.3 U/kg body wt of insulin mixture (high-mixture 75/25, mid-mixture 50/50, or low-mixture 25/75 insulin lispro/NPL insulin), insulin lispro, or NPL insulin on one of the five study days in randomized order. Glucose infusion rates were determined over a period of 24 h after administration.

RESULTS

Maximal metabolic activity decreased after subcutaneous injection of the mixtures with lower insulin lispro content; however, the time point of maximal and of early half-maximal metabolic activity was comparable among the three mixtures. Higher proportions of insulin lispro resulted in higher values for area under the curve within the first 360 min after injection and a more rapid decline to late half-maximal activity. Serum insulin concentrations showed a similar pattern.

CONCLUSIONS

This study shows that the pharmacodynamic and pharmacokinetic properties of insulin lispro are preserved in stable mixtures with NPL insulin.

A pilot clinical/pharmacological study of the protein kinase C-specific inhibitor safingol alone and in combination with doxorubicin

We performed a pilot clinical trial with safingol (L-threo-dihydrosphingosine), a protein kinase C-specific inhibitor that potentiates the effect of doxorubicin (DOX) in tumor-bearing animals. Safingol was initially administered as a 1-h infusion at escalating doses. Fourteen days later, patients received the same dose of safingol in combination with a fixed dose of DOX. The combination was repeated at 3-week intervals. Safingol dose levels ranged from 15 to 120 mg/m2. The plasma levels achieved at the final dose level were comparable to those associated with potentiation of DOX in animals. The mean Cmax and area under the curve for safingol at the 120 mg/m2 dose level were 1040 +/- 196 ng/ml and 1251 +/- 317 mg x h/ml, respectively. The mean plasma half-life for safingol was 3.97 +/- 2.51 h, the mean estimated clearance was 3140 +/- 765 ml/min, and the mean volume of distribution was of 995 +/- 421 liters. Coadministration of a fixed dose of DOX did not significantly change the pharmacokinetics of safingol, nor did increasing doses of safingol significantly affect the pharmacokinetics of DOX. Minor responses were observed in three patients with pancreatic cancer and one patient with angiosarcoma of the scalp. This pilot Phase I study indicates that the protein kinase C inhibitor safingol can be given safely with 45 mg/m2 of DOX at a dose that is potentially pharmacologically active without dose-limiting toxicity.

Effect of food on oral availability of apresoline and controlled release hydralazine in hypertensive patients

Hydralazine is a vasodilator antihypertensive drug that has been in use for many years. Efficacy after oral administration correlates well with the levels of the drug in blood. Factors such as food ingestion that affect blood levels of hydralazine may therefore be of importance. There is dispute regarding the effect of food intake on blood levels of hydralazine and on the antihypertensive response. This randomized cross-over study examined the effect of food (642 K calories, 25 g protein, 43 g fat, 40 g carbohydrates, 32 mEq sodium, 17 mEq potassium) ingested immediately before hydralazine (taken as Apresoline, Ciba Geigy, or as slow-release hydralazine, SRH, Pennwalt Corporation) on the blood levels of hydralazine in 16 essential hypertensive patients who were slow acetylators currently taking at least 100 mg Apresoline daily. Peak blood hydralazine levels were reduced by food after both Apresoline and SRH, by 69 and 66%, respectively. Time to peak blood hydralazine concentration was delayed significantly with SRH. We could detect a statistically significant food-related reduction of area under blood hydralazine concentration versus time curves (AUC) only with Apresoline (by 44%). The AUC for SRH was decreased only 29% by food. Hydralazine should be taken at a consistent time with respect to meals.

Cadmium uptake and distribution in sticklebacks related to the concentration and method of exposure

The uptake of cadmium by sticklebacks and its distribution between the body tissues was compared following two methods of exposure, i.e., natural exposure to the heavy metal in water and direct intraperitoneal injection. In both cases, the greatest concentration of cadmium was detected in the liver. In naturally exposed fish high concentrations were also found in the gut and gills while in injected fish high levels were demonstrated in the gall bladder and kidney.

The production of cadmium-binding protein in three species of freshwater fish

Cadmium-binding protein (Cd-BP) was detected in the liver and kidney of stoneloach, Noemacheilus barbatulus, roach, Rutilus rutilus and rainbow trout, Salmo gairdneri which had been dosed i.p. with 1 mg cadmium (Cd)/kg body weight 168 h previously. The cadmium content (microgram Cd/g wet weight tissue) was much lower in the liver and kidney of trout than in stoneloach and roach, but there was no clear relationship between the amount of Cd-BP detected and the reported sensitivity of each species to cadmium.

Radioimmunoassay for phencyclidine (PCP) in serum

This accurate, sensitive radioimmunoassay for determining phencyclidine concentrations in serum specimens involves the use of anti-phencyclidine sera, 0.1 mL of serum specimen, an iodinated tracer, and a solid-phase separation. Phencyclidine metabolites do not show significant cross reactivity, but several phencyclidine analogs do cross react. Within-run coefficients of variation for human and dog serum ranged from 2.5 to 13% for concentrations from 2.0 to 500 micrograms/L. Day-to-day coefficients of variation for human and dog serum ranged from 4.3 to 16.7% for concentrations ranging from 2.0 to 90.0 micrograms/L. The sensitivity of the radioimmunoassay is less than 0.5 micrograms/L. Thirty serum specimens from two dogs given 1 mg of phencyclidine per kilogram body weight were analyzed by radioimmunoassay and a gas-chromatographic method. Nonparametric statistical comparison and linear regression showed that results from the two procedures correlate well (r2 = 0.952). Concentration-time data from the two dogs are presented to illustrate the utility of the radioimmunoassay for examining phencyclidine disposition.

The effects of joint stress on sticklebacks

The effects on the three-spined stickleback, (Gasterosteus aculeatus L.), of various combinations of stresses due to parasitism by Schistocephalus solidus, dietary restriction, and exposure to cadmium (0.032 mg 1-1) were investigated. Sticklebacks exposed to a combination of all three stressors died first with a median period of survival significantly shorter than that for fish subjected to fewer stressors. Compared with fish on a restricted diet alone, parasitism plus dietary restriction also reduced survival; however, the combination of cadmium exposure and restricted diet did not. A possible explanation for this finding is proposed.