The zebrafish IgH locus contains multiple transcriptional regulatory regions.

Many fish have, in addition to IgM and IgD, a third isotype called IgZ or IgT. The ζ-chain locus is embedded among the Ig heavy chain V-, D- and J-elements in a manner reminiscent of the TcR δ/α locus. Isotype selection thus occurs during VDJ recombination, a process that is facilitated by intralocus transcription. Using in silico analyses and enhancer reporter vectors we identified 3 new regions within the zebrafish IgH locus through which transcription can be activated in catfish B-cell lines. Two of these, termed Eζi (Jζ to Cζ1 intronic) and Eζ3' regions flank the ζ-chain constant domain exons. A third region, Eδ3', resides downstream of the δ-chain exons. All regions contain predicted binding sites for transcription factors that contribute to B-cell specific transcription in fish and mammals. Each region also has proximal matrix attachment regions, which may further contribute to transcriptional activation and chromatin remodeling. We discuss possible roles for these regions during VDJ recombination.

The cause of neuronal degeneration in Alzheimer's disease.

Alzheimer's disease is associated with a specific pattern of pathological changes in the brain that result in neurodegeneration and the progressive development of dementia. Pathological hallmarks common to the disease include beta-amyloid plaques, dystrophic neurites associated with plaques and neurofibrillary tangles within nerve cell bodies. The exact relationship between these pathological features has been elusive, although it is clear that beta-amyloid plaques precede neurofibrillary tangles in neocortical areas. Examination of the brains of individuals in the preclinical stage of the disease have shown that the earliest form of neuronal pathology associated with beta-amyloid plaques resembles the cellular changes that follow structural injury to axons. Thus, the development of beta-amyloid plaques in the brain may cause physical damage to axons, and the abnormally prolonged stimulation of the neuronal response to this kind of injury ultimately results in the profound cytoskeletal alterations that underlie neurofibrillary pathology and neurodegeneration. Therapeutically, inhibition of the neuronal reaction to physical trauma may be a useful neuroprotective strategy in the earliest stages of Alzheimer's disease.

Relationship between apolipoprotein E and the amyloid deposits and dystrophic neurites of Alzheimer's disease.

Although the inheritance of certain apolipoprotein E (ApoE) alleles has been recognized as a genetic risk factor for Alzheimer's disease, the role of ApoE in the pathology underlying this disease is unclear. Several reports have emphasized the association of ApoE with either beta-amyloid plaque formation or the development of neurofibrillary pathology. Utilization of multiple label immunohistochemical methods enabled us to examine directly the localization of ApoE immunoreactivity relative to beta-amyloid plaques, dystrophic neurites and neurofibrillary tangles. In Alzheimer's disease cases, beta-amyloid plaques showing high ApoE immunoreactivity were localized to layers II, III and V of the neocortex. In layer I, beta-amyloid plaques were unlabelled for ApoE relative to beta-amyloid. Dense core plaques labelled for beta-amyloid often had only the central portions labelled for ApoE. Conversely, ApoE labelled spherical structures within some plaques were not immunoreactive for beta-amyloid or dystrophic neurite markers. Unlike beta-amyloid labelled plaques, all ApoE immunoreactive plaques were associated with dystrophic neurites. In preclinical Alzheimer's disease cases, most plaques were double labelled for beta-amyloid and ApoE. ApoE did not label dystrophic neurites or the early stages of neurofibrillary tangle formation, indicating that ApoE may not be directly involved in neurofibrillary pathology. The specific presence of ApoE in plaques associated with dystrophic neurites in demented patients suggests that ApoE may contribute toward a higher degree of beta-amyloid fibrillogenesis, enhancing the ability of certain plaques to cause damage to surrounding axons.

Synthesis and hypoglycemic activity of pyridyl alcohols.

The potent hypoglycemic activity of 3-(3-methyl-2-pyridyl)propan-1-ol (1) prompted us to synthesize and study related structures. Some of the variables studied were the position of the methyl and alcohol side chains, the distance between the heterocyclic ring and the hydroxyl group, the effect of additional nuclear substitution, and the effects of branching and substitution on the alcohol side chain. The compounds were tested in 48-h fasted rats, usually at a dose of 150 mg/kg po. 1, the corresponding propionic acid 12, the acetate and methyl ether of 1 (22 and 23), and the 5-methyl analogue of 1 (29) were of comparable hypoglycemic potency. However, these compounds all caused a concomitant elevation of hepatic triglycerides and/or death in the test animals when observations were continued for 4--24 h.

The central effects of a novel dopamine agonist.

A new peripheral dopamine agonist which causes dopaminergic renal vasodilation, was tested for central dopaminergic activity. SK & F 38393 stimulated the dopamine-sensitive adenylate cyclase in homogenates of rat caudate, as a partial agonist, and caused contralateral rotation in rats with unilateral 6-OHDA lesions of substantia nigra. Rotation was shown to be due to a direct effect on supersensitive dopamine receptors. Stimulation of cAMP formation and rotation were blocked by dopamine antagonists. In contrast to other dopamine agonists, SK & F 38393 did not cause stereotypy, emesis or inhibition of prolactin release, nor did SK & F 38393 affect dopamine turnover. The results suggest that SK & F 38393 may selectively stimulate supersensitive central dopamine receptors in vivo or may activate only a certain subclass of dopamine receptors including the receptor in the renal vasculature and the adenylate cyclase coupled postsynaptic receptor in the caudate.

Synthesis and hypoglycemic activity of some substituted 2-arylthiazolo[3,2-a]pyridinium salts.

A series of substituted 2-arylthiazolo[3,2-a]pyridinium salts (1a-q) was prepared by known methods and tested for hypoglycemic activity in 48-h fasted rats. Two compounds, 2-phenylthiazolo- and 8-methyl-2-phenythiazolo[3,2-a]pyridinium perchlorate (1a and 1q), showed consistent hypoglycemic activity in this screen, demonstrating that a high degree of structural specificity was required for hypoglycemic activity. At higher doses the hypoglycemic activity of 1a and 1q was associated with elevated levels of hepatic triglycerides.

Synthesis and hypoglycemic activity of 4-substituted 3-mercaptopicolinic acids.

3-Mercapto-4-methylpicolinic acid one of very few compounds derived from 3-mercaptopicolinic acid (3-MPA) to have hypoglycemic activity. In an effort to find compounds with greater potency than 3-MPA, several 4-substituted 3-mercaptopicolinic acids (4-OMe, OC6H5, SMe, SH, Cl, NH2, Et; 1-7) were prepared and tested in 48-h fasted rats. None was hypoglycemic in this test system after oral dosing of 150 mg/kg.

Mercapto heterocyclic carboxylic acids, analogues of 3-mercaptopicolinic acid.

3-Mercaptopicolinic acid (3-MPA), a potent hypoglycemic agent in fasted rats, provided the impetus for substituting this compound with a 5-mercapto group (1), a 6-carboxyl group (2), and a 5-mercapto and 6-carboxyl group (3) and for replacing the pyridine ring with other heterocycles: quinoline (4), thiazole (5), pyrazine (6), isoquinoline (7), and indole (8). The methyl sulfoxide (9) and sulfone (10) of 3-MPA were also prepared. The new compounds 1-10, with the exception of 8, did not lower blood glucose levels in 48-h fasted rats. 8 was toxic at doses which were hypoglycemic.

Synthesis and hypoglycemic activity of S-acyl derivatives of 3-mercaptopicolinic acid.

A series of S-alkanoyl and benzoyl derivatives of 3-mercaptopicolinic acid (3-MPA) was prepared and studied for hypoglycemic activity. Three alkanoyl derivatives (propionyl, pivaloyl, and 1-adamantanecarbonyl, 19-21) were prepared with increasing bulk around the thio ester bond. The benzoyl derivatives contained aromatic substituents chosen from a sigma-pi cluster chart so that the esters prepared had a wide range of electronic and solubility properties. In general, compounds with substituents which increased lipid solubility [p-chlorobenzoyl (4), p-trifluoromethylbenzoyl (6), and pivaloyl (20)] had the greatest potency at a dose of 300 mg/kg. Hydrolysis rates, measured at pH 6 and 8, indicated that in vivo breakdown to 3-MPA probably did not account for the observed hypoglycemic activity of the esters. 4, 6, and 20 were less potent than 3-MPA in comparative dose range studies.

Studies on the mechanism of tachyphylaxis to disodium cromoglycate.

The tachyphylaxis to disodium cromoglycate's (DSCG) inhibition of antigen-induced histamine release is readily demonstrable utilizing passively sensitized rat lung fragments. This tachyphylaxis to DSCG is evident whether or not calcium is present during drug preincubation. An attempt to relate the mechanism of tachyphylaxis to the DSCG-induced release of an endogenous cellular inhibitory material was unsuccessful insofar as could be demonstrated by an effect on mediator release.

Further studies on the tachyphylaxis to DSCG. The effects of concentration and temperature.

The tachyphylaxis to DSCG's inhibition of anaphylactic histamine release has been demonstrated in passively sensitized rat lung fragments. The induction of tachyphylaxis appears to depend on the concentration of the drug and the length of pretreatment. Tachyphylaxis is relatively independent of the concentration of the second exposure to DSCG. The development of tachyphylaxis is highly temperature dependent; it can be prevented by cooling the tissues to 2-4 degrees C after a brief (30 sec) preincubation with DSCG. It is suggested that DSCG inhibits histamine release by binding to 'receptor' site(s). Once the site is occupied by DSCG, it is modified by a temperature-dependent process, thus losing the ability as a 'receptor' for inhibition of histamine release. The tachyphylaxis is the result of such a modification.

Species-specific hypoglycemic activity of triphenylphosphoranylideneacetophenones.

The species-specific hypoglycemic activity of two 2-triphenylphosphoranylideneacetophenones is described. 2-Triphenylphosphoranylideneacetophenone (SK&F 45359) and 2-triphenylphosphoranylidene-m-trifluoromethyl-acetophenone (SK&F 62775) were hypoglycemic in various rat models, but failed to exhibit hypoglycemic activity in other species.

Synthesis and hypoglycemic activity of phenacyltriphenylphosphoranes and phosphonium salts.

Phenacyl-riphenylphosphorane (1a) and several analogs substituted in the meta position of the phenacyl group lowered blood glucose levels in 48-hr fasted rats. The corresponding phosphonium salts had comparable hypoglycemic activity. Two compounds (1a and 1b) were also hypoglycemic in fed rats, but hypoglycemia could not be elicited in another species.

3-mercaptopicolinic acid, an inhibitor of gluconeogenesis.

1. 3-Mercaptopicolinic acid (SK&F 34288) inhibited gluconeogenesis in vitro, with lactate as substrate, in rat kidney-cortex and liver slices. 2. In perfused rat livers, gluconeogenesis was inhibited when lactate, pyruvate or alanine served as substrate, but not with fructose, suggesting pyruvate carboxylase or phosphoenolpyruvate carboxylase as the site of inhibition. No significant effects were evident in O(2) consumption, hepatic glycogen, urea production, or [lactate]/[pyruvate] ratios. 3. A hypoglycaemic effect was evident in vivo in starved and alloxan-diabetic rats, starved guinea pigs and starved mice, but not in 4h-post-absorptive rats. 4. In the starved rat the hypoglycaemia was accompanied by an increase in blood lactate. 5. A trace dose of [(14)C]lactate in vivo was initially oxidized to a lesser extent in inhibitor-treated rats, but during 90min the total CO(2) evolved was slightly greater. The total amount of the tracer oxidized was not significantly different from that in the controls.