The radioimmunoassay of tricyclic antidepressants

An antiserum to nortriptyline has been produced in a sheep against a nortriptyline-bovine serum albumin conjugate. The conjugate was prepared using the reagent N-(4-bromobutyl) phthalimide followed by a carbodiimide reaction to link the hapten to the carrier protein. The antibodies produced were shown to be specific for the tricyclic group of drugs. The sensitivity of the radioimmunoassay developed is currently limited by the lack of a high specific activity label. The possibilities of developing a radioimmunoassay for nortriptyline in plasma are discussed.

A comprehensive review of oral glucosamine use and effects on glucose metabolism in normal and diabetic individuals

Glucosamine (GlcN) is a widely utilized dietary supplement that is used to promote joint health. Reports that oral GlcN supplementation at usual doses adversely affects glucose metabolism in subjects with impaired glucose tolerance have raised concerns that GlcN should be contraindicated in individuals with diabetes and those at risk for developing it. This review addresses its potential, when used at typical doses, to affect glucose metabolism and insulin sensitivity in healthy individuals and those with diabetes or 'pre-diabetes'. Publicly available scientific information and data on GlcN were systematically compiled using the electronic search tool, Dialog , and reviewed with special emphasis on human studies. In long-term clinical trials, including those containing subjects with type 2 diabetes or 'pre-diabetes', GlcN produced a non-significant lowering of fasting blood glucose concentrations in all groups of subjects treated for periods of up to 3 years. Owing to limitations in study design, conclusions based on studies that report adverse affects of GlcN on insulin sensitivity and glucose tolerance in pre-diabetic subjects are suspect. However, no definitive long-term studies of GlcN use for individuals with pre-diabetes are available. Nevertheless, based on available evidence, we conclude that GlcN has no effect on fasting blood glucose levels, glucose metabolism, or insulin sensitivity at any oral dose level in healthy subjects, individuals with diabetes, or those with impaired glucose tolerance.

Some effects of melatonin and the control of its secretion in humans

Whether or not the pineal gland has a significant physiological role in humans is not known. There has nevertheless been speculation about the potential therapeutic use of melatonin (in view of its hypnotic and possible zeitgeber properties) in conditions such as insomnia and jet lag, and in shift-workers. Our work concerns the effects of melatonin administration in humans and the interactions between melatonin and other circadian variables. Chronic (one month), timed (1700 h), low-dose (2 mg daily) melatonin administration to normal subjects without environmental control consistently increased evening fatigue and slightly modified the 24 h prolactin rhythm without effect on cortisol, growth hormone, luteinizing hormone, thyroxine, testosterone or self-rated mood. In five out of 11 subjects the endogenous melatonin rhythm was advanced by one to three hours. During fractional desynchronization of circadian rhythms by increasing imposed 'day' length (26-29 h, 24 days, 500 lux), 5 mg melatonin per os at lights-out in two subjects resulted in better entrainment of the fatigue rhythm to the zeitgeber than in five out of six control subjects, without major consistent effects on other measured circadian variables. Using a new radioimmunoassay for 6-hydroxymelatonin sulphate (aMT6s), the major melatonin metabolite, we have shown that the urinary aMT6s rhythm is closely correlated to that of melatonin in plasma and is completely suppressed by an acute dose of atenolol (100 mg per os), a peripheral beta-adrenergic antagonist. During fractional desynchronization by increasing imposed 'day' length in one subject and decreasing imposed 'day' length in two subjects, the urinary aMT6s rhythm behaved similarly to that of core temperature. The results suggest that fatigue (or alertness) may be entrained by melatonin, but whether critical performance rhythms can be suitably manipulated remains to be clarified. It is likely that melatonin production is linked to the so-called 'strong' circadian oscillator.

Structures of pahayokolides A and B, cyclic peptides from a Lyngbya sp

The isolation and structure elucidation of two cyclic peptides, pahayokolides A (1) and B (2), is described. Structural features determined for these compounds include a pendent N-acetyl-N-methyl leucine, both E- and Z-dehydrobutyrines, a homophenylalanine, and an unusual polyhydroxy amino acid that is most likely of mixed polyketide synthase/nonribosomal peptide synthase origin. These peptides were purified from a new species of cyanobacteria of the genus Lyngbya, which was isolated from a periphyton mat from the Florida Everglades.

1,3-dipolar cycloadditions of trimethylsilyldiazomethane revisited: steric demand of the dipolarophile and the influence on product distribution

The 1,3-dipolar cycloaddition of trimethylsilyldiazomethane with alpha,beta-unsaturated esters was examined. The resulting 1-pyrazolines isomerize to regioisomeric 2-pyrazolines (a or b) or undergo desilylation (c). Acrylates yield only b or c. beta-Substituted dipolarophiles may yield all three types of products. This work demonstrates that the distribution of 2-pyrazoline products is highly dependent on the relative configuration of the substituents on the 1-pyrazoline intermediate.

Novel Carboxylated Pyrrole- and Carbazole-Based Monomers. Synthesis and Electro-Oxidation Features

Carboxylated pyrrole (Pyr, a index)- and carbazole (Cbz, b index)-containing monomers 6-7a/b and 9a/b have been readily synthesized from the monobenzyl ester of L-glutamic acid and triamine 2 using Clauson-Kaas and amide coupling reactions. In contrast to Pyr-containing compounds 6-7a, and 9a, the three Cbz-containing monomers 6-7b, and 9b have been found electroactive and were successfully electropolymerized on a Pt electrode resulting in the deposition of corresponding insoluble electroconducting polyCOOH polyCbz-films poly(6-7b) and poly(9b).

Dynamic and static conformational analysis of acylated tetrahydrobenzazepines

A detailed high-field NMR analysis of several acylated tetrahydrobenzazepines, supported by molecular mechanics calculations, indicates that the heterocyclic ring in these compounds exists in a chair conformation, with the carbonyl oriented anti to the aryl moiety in the dominant rotamer. Surprisingly, ring methylenes are typically diastereotopic at room temperature, as the barriers for the process of enantiomerization of the seven-membered ring are much higher than expected. It is shown that ring inversion is correlated (but not concerted) with rotation of the amide moiety, as the carbonyl is forced out of conjugation with the nitrogen in the transition state.

Best practice No 173: clinical and laboratory investigation of adult spontaneous hypoglycaemia

Adult spontaneous hypoglycaemia is not a diagnosis per se but a manifestation of a disease. Although rare, it is important to identify spontaneous hypoglycaemia and its causes because treatment may be preventative or curative. Hypoglycaemia can occur as an epiphenomenon in many serious diseases. It is sufficient to recognise the disease's association with hypoglycaemia and then take appropriate action to prevent the recurrence of hypoglycaemia. In investigating apparently healthy individuals, common pitfalls to avoid are: failure to recognise subacute neuroglycopenia clinically; failure to document hypoglycaemia adequately during symptoms; failure to measure pancreatic hormones, counter-regulatory hormones, and ketones in hypoglycaemic samples; failure to recognise pre-analytical and analytical limitations of laboratory assays; and failure to abandon obsolete and inappropriate investigations. Providing these caveats are met, appropriate laboratory and radiological investigations will almost always uncover the cause of spontaneous hypoglycaemia.

Crystal structure and rotational barrier of octakis(bromomethyl)naphthalene

Octakis(bromomethyl)naphthalene (4) adopts in the crystal a chiral conformation with a helical central naphthalene core and the bromomethyl groups disposed in an alternate up-down "in" arrangement. According to MM3 calculations, this conformation is less stable than the corresponding all alternated "out" form, while B3LYP/LANL2DZ calculations suggest the opposite stability order. The topomerization barrier (16.0 kcal mol(-1)) is ascribed to an enantiomerization process requiring 180 degrees rotation of all the bromomethyl groups and reversal of the helical sense of the naphthalene core.

Polyethylated triptycene derivatives

The octaethyl triptycenes 7 and 8 were synthesized by Diels-Alder reaction of the octaethylanthracene 4with the corresponding benzynes. Low-temperature NMR spectra of 7 and 8 are consistent with the presence of the fully alternated conformation "a" of C(2) symmetry. However, in the determined crystal structures, the compounds adopt a higher energy conformation with a pair of vicinal ethyls oriented in the same direction.

The biochemical investigation of cases of hypoglycaemia: an assessment of the clinical effectiveness of analytical services

AIM

To assess the extent to which biochemical analytical services contribute to the diagnosis and management of clinical cases of hypoglycaemia.

METHODS

All cases of confirmed hypoglycaemia, referred during a six month period, were included in the survey. Questionnaires were sent to each referring laboratory requesting information on the clinical progress and current status of the patient.

RESULTS

The level of influence exerted by analytical data was assigned in each case and those with similar outcomes combined. Identifiable case groups were: (1) Results not recorded in the patients' notes (15.7%). (2) Inappropriate requesting of insulin and C peptide measurements in cases of diabetes (11.4%). (3) Patient died soon after investigation (20.0%). (4) Patient recovered spontaneously (17.1%). (5) Patient received effective medical or surgical treatment (12.9%). (6) Patient awaiting or not requiring pathology based treatment (31.4%). (7) Inconclusive outcome prompting further investigation (5.7%).

CONCLUSIONS

Within the timescale of the survey (approximately 12 months), positive progress had been made towards diagnosis and subsequent treatment in only 10% of cases. Another 30% were either awaiting some form of treatment or further diagnostic tests. The remaining 60% did not appear to benefit in any way from the biochemical investigations.

Polyethylated aromatic rings: conformation and rotational barriers of 1,2,3,4,5,6,7,8-octaethylanthracene, 1,2,3,4,6,7,8-heptaethylfluorene, and 1,2,3,4,5,6,7,8-octaethylfluorene

1,2,3,4,5,6,7,8-Octaethylanthracene (5), 1,2,3,4,6,7,8-heptaethylfluorene (7), and 1,2,3,4,5,6,7,8-octaethylfluorene (8) were synthesized by Friedel-Crafts ethylations of 9,10-dihydroanthracene and fluorene. MM3 calculations indicate that the two ethylated six-membered rings of 5 and 7 are conformationally independent. According to the calculations, two low-energy conformers of each compound are possible with the ethyl groups attached to the external aryl rings arranged in an alternated "up-down" orientation. MM3 calculations indicate that in the lowest energy conformation the central fluorene core of 8 adopts a twisted conformation to avoid repulsive steric interactions between the ethyls at the bay region. Two fully alternated up-down conformations are possible for 8, differing in the orientation ("in" or "out") of the ethyls in the bay region. MM3 calculations predict that the lowest energy conformer is the fully alternated "out" form of C(2)() symmetry. The rotational barriers of 5, 7, and 8 are in the 8.7-11.3 kcal mol(-1) range, the largest barrier corresponding to the more crowded octaethylfluorene 8. Anthracene 5 adopts in the crystal a conformation of approximate C(2)(h) symmetry with pairs of peri groups on the same edge of the molecule oriented syn. The conformations adopted in the crystal by 7 and 8 do not correspond to the calculated lowest energy form. In the conformation of 7 in the crystal the ethyl groups on the trisubstituted ring adopt the unusual all syn arrangement. Octaethylfluorene 8 adopts a conformation with a twisted central fluorene core but with a syn arrangement of a pair of vicinal ethyl groups.

Hypoglycemic disorders

Hypoglycemia occurs as an epiphenomenon in many serious diseases and further investigation may be unnecessary. In other, often seemingly healthy individuals, it is responsible for their presenting symptoms. In them preliminary diagnosis depends on demonstrating a low blood glucose concentration during spontaneous symptoms by ambulatory self-collection of capillary blood and its analysis for glucose in the laboratory. Subsequent investigation requires appropriate plasma hormone analysis on blood collected while the patient is hypoglycemic.

Preparation and conformation of octaethylbiphenylene

Dimerization of tetraethylbenzyne (generated by reaction of 1, 2-dibromo-3,4,5,6-tetraethylbenzene (8) with 1 equiv of BuLi) afforded in low yield octaethylbiphenylene (3), together with a major product which was characterized as 2,3,4,5,3',4', 5'-heptaethyl-2'-vinylbiphenyl (9). X-ray diffraction indicates that biphenylene 3 adopts in the crystal a conformation of approximate C(2)(h )()symmetry with the ethyl groups within each phenylene ring arranged in an alternated up-down fashion. Notably, pairs of vicinal ethyl groups located at peri positions are oriented in a syn arrangement in the crystal. Low temperature NMR spectroscopy is consistent with the presence in solution of either the crystal conformation or a fully alternated conformation lacking any syn interaction. Molecular mechanics (MM3), semiempirical (AM1, PM3), and ab initio calculations indicate that the crystal conformation is a high energy form, and that the lowest energy conformation is the fully alternated form. The topomerization barrier of the methylene protons of the ethyl groups of 3 is 9.4 +/- 0.1 kcal mol(-)(1), which is between the rotational barriers of 8 and 1,2,3, 4-tetraethylbenzene 7 (9.9 +/- 0.1 and 8.2 +/- 0.1 kcal mol(-)(1), respectively). The similarity in rotational barriers suggests that a given tetraethylphenylene subunit does not markedly affect the rotational barrier of the ethyl groups of the other subunit.