Synthesis and hormonal activity of [Tyr 22] glucagon and [desHis 1, Tyr 22] glucagon

[Tyr²²] glucagon and [desHis¹, Tyr²²] glucagon were synthesized by an improved solid phase procedure on a Pam-resin. The course of the synthesis was monitored by quantitative ninhydrin analysis and preview sequencing. Following cleavage by the low/high HF method the peptides were purified by ion exchange chromatography and reverse phase HPLC. The overall yield of homogeneous isolated peptide from the first amino acid was 41%. Circular dichroism measurements on dilute solutions in mixed aqueous organic solvents at pH 2, 6.9 and 9.2 showed increased β-sheet structure relative to glucagon. [Tyr²²]glucagon was a full agonist with 20–30% activity in the rabbit blood glucose assay and 10% activity in the rat liver membrane adenyl cyclase assay. [desHis¹, Tyr²²] glucagon had only a trace of activity in the adenyl cyclase assay (>0.002%) but bound to membranes in a competitive [¹²⁵I] glucagon assay 1.0% as well as glucagon. The analog completely inhibited formation of cAMP by natural glucagon, with 50% inhibition at a ratio of 83:1 and pA₂ = 6.7. The data are discussed in terms of models of glucagon structure in dilute solution.     

PEG-coated Poly(lactic acid) Nanoparticles for the Delivery of Hexadecafluoro Zinc Phthalocyanine to EMT-6 Mouse Mammary Tumours

Hexadecafluoro zinc phthalocyanine (ZnPcF₁₆), a second generation sensitizer for the photodynamic therapy of cancer, was incorporated in three vehicles: poly(d,l -lactic acid) (PLA) nanoparticles, polyethylene glycol (PEG)-coated nanoparticles and a Cremophor EL (CRM) oil-water emulsion. Nanoparticles were prepared by the salting-out procedure. Biodistribution of the dye was assessed by fluorescence in EMT-6 mammary tumour bearing mice after intravenous injection of 1 μmol kg^?1 ZnPcF₁₆. Plain nanoparticles were rapidly retained by the reticuloendothelial system (RES) as reflected by the low area under the blood concentration-time curve (AUC_0–168, 57 μg h g^?1). Little tumour uptake of the dye was observed with this formulation. In contrast, PEG-coated nanoparticles displayed a reduced RES uptake, leading to significantly higher blood levels over an extended period (t1/2 30 h; AUC_0–168 227 μg h g^?1) and enhanced tumour uptake. At 48 h post injection, tumour to skin and tumour to muscle concentration ratios reached 3·5 and 10·8, respectively. Blood levels of ZnPcF₁₆ after administration as a CRM emulsion decreased faster than with PEG-coated nanoparticles (t1/2 12 h), but since no early liver uptake was observed, the AUC_0–168 and the tumour uptake were only slightly lower. However, with the CRM formulation, a late liver uptake was observed, reaching 51% of the injected dose after 7 days.     

Comorbidity and metabolic context are crucial factors determining neurological sequelae of hypoglycaemia

Aim To determine risk factors for neurological sequelae following hypoglycemia. Method We analysed the neurological outcome in 164 patients (mean age 10y 10mo, SD 5.9) following hypoglycemia due to three diseases with various metabolic contexts, different ages at onset, and combinations with comorbidity (fever/infection, hypoxia/ischemia): glycogen storage disease type I (GSDI) (21 patients, mean age at first hypoglycemic episode 3.8mo, SD 3.5); fatty acid β‐oxidation defects (FAOD) (29 patients, mean age at first hypoglycemic episode 14.8mo, SD 12.6); and hyperinsulinism (HIns) (114 patients, mean age at first hypoglycemic episode 2.3mo, SD 4.7). Results Risk factors of poor neurological outcome were aetiology (p<0.006), comorbidity (p<0.001), and prolonged convulsions (p<0.001). Ordinal logistic regression showed that comorbidity (p<0.001) and status epilepticus (p=0.002) were the main determinants of sequelae. Asymptomatic hypoglycemia did not lead to sequelae, whatever the aetiology. Age was not correlated to sequelae, whatever the aetiology. The highest prevalence of hypoglycemic sequelae was found in FAOD and HIns combined with comorbidity, the lowest in GSDI (p<0.001) in which hypoglycemia is often asymptomatic, associated with increased plasma lactate, and rarely combined with comorbidity. Interpretation Hypoglycemia is severely deleterious for the brain in the context of fever/infection and/or hypoxia/ischemia, and status epilepticus. The metabolic context providing alternative fuels may improve neurological outcome.     

Topography of brain damage in metabolic hypoglycaemia is determined by age at which hypoglycaemia occurred

Aim Having previously shown that comorbidity is a major determinant of neurological sequelae in hypoglycaemia, our aim was to describe the neuroimaging patterns of brain damage in different hypoglycaemic situations and to elucidate the factors that determine lesion topography. Method We reviewed 50 patients (31 females, 19 males) with symptomatic hypoglycaemia (<2.8mmol/L) occurring between 1 day and 5 years of age (median 4d) who had undergone magnetic resonance imaging (MRI; at least axial T2‐weighted, sagittal T1‐weighted, and coronal fluid‐attenuated inversion recovery [FLAIR]‐weighted imaging). MRI was performed during the follow‐up examination at least 1 month after the occurrence of symptomatic hypoglycaemia, i.e. between 1 month and 5 years of age (median 3mo). Hypoglycaemia resulted from three inborn errors of metabolism: congenital hyperinsulinism (33 patients), fatty acid β‐oxidation disorders (13 patients), or glycogen storage disease type I (four patients). We selected the patients with clear MRI abnormalities and analysed their topography according to aetiology and age at occurrence of the lesion. Results The topography of the brain lesions depended on age: from the neonatal period to 6 months of age, lesions predominantly involved the posterior white matter; between 6 and 22 months the basal ganglia, and after 22 months the parietotemporal cortex (p=0.04). Interpretation The relationship between brain lesions and age could reflect the maturation sequence of the brain.     

Autonomic Tone in Patients with Supraventricular Arrhythmia Associated with Mitral Valve Prolapse in Young Men

TERECHTCHENKO, L., et al .: Autonomic Tone in Patients with Supraventricular Arrhythmia Associated with Mitral Valve Prolapse in Young Men. This study examined the relation between autonomic tone and the frequency and duration of supraventricular arrhythmias (SVA) in 44 men (mean age   17 ± 5   years) with mitral valve prolapse (MVP), confirmed by echocardiography. Ambulatory and short-term electrocardiograms (ECG) were recorded, and transesophageal pacing was performed. Frequency domain heart rate variability (HRV) indices were obtained from short-term ECG recordings at rest and during postural stress. Results: In 14 patients, the index of parasympathetic activity was significantly higher (   2.1 ± 0,01   vs   -1.5 ± 0.01, P < 0.01   ), and associated with a high incidence of vagally-mediated SVA. The frequency of SV premature beats in patients with parasympathetic prevalence was   58 ± 86/hour   versus   10 ± 27/hour   in patients with sympathetic prevalence  ( P < 0.05 )  . In 30 patients with high sympathetic activity, the index of sympathetic tone was significantly higher (   3.1 ± 0.01   vs   0.5 ± 0.01   ) and the high frequency/low frequency ratio significantly lower (   0.294 ± 0.03   vs   0.581 ± 0.02, P < 0.05   ), though the incidence of SVA was significantly lower and duration shorter. The algorithm allowed the noninvasive quantitative assessment of autonomic activity and mechanism behind the development of SVA, which may help in the choice of treatment. (PACE 2003; 26[Pt. II]:444–446)