Chordate origins of the vertebrate central nervous system.

Fine structural, computerized three-dimensional (3D) mapping of cell connectivity in the amphioxus nervous system and comparative molecular genetic studies of amphioxus and tunicates have provided recent insights into the phylogenetic origin of the vertebrate nervous system. The results suggest that several of the genetic mechanisms for establishing and patterning the vertebrate nervous system already operated in the ancestral chordate and that the nerve cord of the proximate invertebrate ancestor of the vertebrates included a diencephalon, midbrain, hindbrain, and spinal cord. In contrast, the telencephalon, a midbrain-hindbrain boundary region with organizer properties, and the definitive neural crest appear to be vertebrate innovations.     

Complex history of a chromosomal paralogy region: insights from amphioxus aromatic amino acid hydroxylase genes and insulin-related genes

Aromatic amino acid hydroxylase (AAAH) genes and insulin-like genes form part of an extensive paralogy region shared by human chromosomes 11 and 12, thought to have arisen by tetraploidy in early vertebrate evolution. Cloning of a complementary DNA (cDNA) for an amphioxus (Branchiostoma floridae) hydroxylase gene (AmphiPAH) allowed us to investigate the ancestry of the human chromosome 11/12 paralogy region. Molecular phylogenetic evidence reveals that AmphiPAH is orthologous to vertebrate phenylalanine (PAH) genes; the implication is that all three vertebrate AAAH genes arose early in metazoan evolution, predating vertebrates. In contrast, our phylogenetic analysis of amphioxus and vertebrate insulin-related gene sequences is consistent with duplication of these genes during early chordate ancestry. The conclusion is that two tightly linked gene families on human chromosomes 11 and 12 were not duplicated coincidentally. We rationalize this paradox by invoking gene loss in the AAAH gene family and conclude that paralogous genes shared by paralogous chromosomes need not have identical evolutionary histories.     

Stress‐responsive accumulation of plastid chaperonin 60 during seedling development

Plastid chaperonin 60 (cpn60) is a chloroplast protein, presumed to assist in assembly and folding of plastid proteins. Although molecular chaperones often accumulate significantly in response to stress, this has never been demonstrated for cpn60. In this study, the accumulation of cpn60 in Nicotiana seedlings during their development was followed under different stress conditions. It was found that cpn60 accumulates markedly in developing seedlings in response to tentoxin and several other (but not all) stresses. Cpn60 accumulates only during a narrow period of seedling development. It is proposed that cpn60 accumulation under stress is developmentally regulated.     

Simple high-performance liquid chromatography method for the simultaneous determination of serum caffeine and paraxanthine following rapid sample preparation

A simple reversed-phase high-performance liquid chromatography (HPLC) method for the simultaneous determination of caffeine and paraxanthine in human serum is described. Serum proteins are precipitated with perchloric acid and the resulting supernatant neutralized for direct injection onto an HPLC column. The method uses a phosphate–methanol mobile phase (85:15, v/v) at pH 4.9 with a flow-rate of 1.75 ml/min and quantitation is by UV absorbance at 274 nm. Elution times are approximately 18 min for caffeine and 8 min for paraxanthine. Theobromine and theophylline have elution times of 5.4 and 9.4 min and do not interfere in the assay. The intra-assay and between-assay means for precision and accuracy for both drugs are: 4.5% C.V. and 3.3% deviation. The sensitivity of the method is 50 ng/ml for each drug.     

Doubletten von Vogel-Eiern

Ohne Zusammenfassung     

Mineralocorticoid radioreceptor assay: application to adrenal-regeneration hypertension.

Identification of unknown hormones has traditionally involved utilizing a bioassay to initially detect the hormone and to follow its purification. However, radioreceptor assays may be more useful for this purpose by offering greater sensitivity and precision. A mineralocorticoid radioreceptor assay has been developed for use in conjunction with chromatographic separation of a urinary extract to detect the presence of unknown urinary mineralocorticoids. This assay utilizes competition of the unknown steroid and aldosterone for rat renal cytoplasmic mineralocorticoid receptors to enable mineralocorticoid quantitation in aldosterone equivalents. This assay provides 100 fold increase in sensitivity and a significant increase in precision over the commonly used adrenalectomized rat bioassay. The mineralocorticoid radioreceptor assay has been utilized to assay mineralocorticoid activity in chromatographic fractions of a urinary extract from rats with regenerating adrenals. A large area of mineralocorticoid radioreceptor activity has been identified which possibly represents an unknown mineralocorticoid contributing to the etiology of adrenal regeneration hypertension. This assay is applicable to other syndromes of postulated unknown mineralocorticoid excess, such as human low renin essential hypertension. In addition, similar radioreceptor assays are applicable for the initial detection of any type of hormone activity and for the subsequent purification and identification of this hormone.     

Evidence for the specific association of the chromosomal origin with outer membrane fractions isolated from Escherichia coli.

DNA-envelope complexes isolated from osmotically lysed spheroplasts of Escherichia coli contained 0.2 to 1% of the total cellular DNA after labeling with [3H]thymidine. Molecular weight determinations indicated that the amount of bound DNA was equivalent in most cases to a maximum of three binding sites per chromosome. Bound DNA from E. coli B/r was distributed approximately equally between inner and outer membrane components when envelopes were fractionated on sucrose equilibrium gradients. Outer membrane-DNA complexes, in particular, fraction H1, with a density of 1.24 g/cm3, were quite stable against shearing and against Sarkosyl NL97. In the case of E. coli B/r, H1-DNA was also relatively resistant to deoxyribonuclease. Inner membrane-DNA complexes, in contrast, were quite labile and readily dissociated to release free DNA. The outer membrane fractions did not appear to contain replication fork DNA, but small amounts may have been present in the inner membrane complexes. A two- to eightfold enrichment for chromosomal origin DNA in the envelope was obtained when cultures of E. coli K-12, synchronized for DNA replication, were pulse labeled at different times in the replication cycle. This enrichment was found invariably in the outer membrane fractions. However, the data do not exclude the possibility that this DNA is bound to regions of adhesion between inner and outer membranes which sediment with a density indistinguishable from that of the outer membrane.     

Lateral hermaphroditism in a C3H mouse.

A spontaneous case of true lateral hermaphroditism was observed in one of approximately 1000 necropsies of 12-wk-old female C3Hf-Wg mice (a substrain of C3H/He). Both the right ovary and abdominal left testis were functional as evidenced by the presence of oocytes in graffian follicles and spermatocytes maturing on sertoli cells. Both gonads communicated, the ovary via an oviduct and normal right uterine horn and the testis via an epididymus and vas deferens, with a vagina which ended in a blind pouch and was filled with squamous debris.     

A procedure for the rapid, quantitative N-acetylation of amino sugar methyl glycosides.

A rapid and quantitative procedure is described for the re-N-acetylation of amino sugar methyl glycosides prior to their analysis by gas-liquid chromatography. Two equivalents of pyridine are added to acidic methanolysates containing amino sugars, serving both to neutralize the acid and to act as a catalyst for the subsequent N-acetylation reaction with acetic anhydride. The N-acetylation is quantitative and complete within 10 min at ambient temperature. Excess acetic anhydride is destroyed by solvolysis with the methanolic solvent. The procedure has been used effectively for methanolysates containing 0.01–2.0 mg/ml glucosamine. The procedures utilizing ion-exchange columns and insoluble salts are thus circumvented and all reaction byproducts are volatile. The procedure is therefore ideally suited for the simultaneous workup of numerous samples for analytical procedures such as gas-liquid chromatography.