Effects of stimulation on the ultrastructure and Na, K, Cl composition of the fundus of the rat plantar sweat gland

Initial stimulation of the rat plantar sweat gland with pilocarpine caused a variable degree of distension of the apical membrane of the secretory cell. This appeared to be a process of filtration of secretory cell cytoplasm through the apical terminal web. Further stimulation resulted in luminal dilatation, cytoplasmic depletion, and morbidity of some cells. These morphological changes in the footpad gland, which thus can no longer be considered as eccrine, were accompanied by a fall in potassium and a rise in sodium concentration within the secretory cells. The mode of secretion induced by pharmacological stimulation was fundamentally the same as that in the glands of species responsive to thermal stimulation.     

The Drosophila ets-2 gene: molecular structure, chromosomal localization, and developmental expression

The cellular homologs of the ets gene from the avian erythroblastosis retrovirus E26 have been studied in chickens, humans, mice, and cats. In this report a further evolutionary step is taken by isolating and characterizing a Drosophila ets-related genomic clone. Sequence analysis of this clone has shown it to contain the 3' end of the v-ets gene, called ets-2, corresponding to the last two exons of chicken ets. The predicted amino acid sequence was found to have over 90% homology when compared to that of v-ets. This is the highest level of conservation observed for any previously characterized Drosophila oncogene homolog. Expression of the ets-2 gene occurs throughout development, but is highest during the embryonic and pupal stages. By in situ hybridization, the ets-2 chromosomal position was determined to be 58A/B which corresponds to no known phenotypic mutant. As this is a highly conserved gene, the Drosophila model system should prove useful for the determination of the ets gene function.     

Wheat germ phosphoglycerate mutase: evidence for a metalloenzyme

Wheat germ phosphoglycerate mutase, exposed to 3.4 M guanidinium chloride at 22 degrees C and pH 7.8, slowly undergoes time-dependent inactivation which can be fully reversed by adding excess Co2+ or Mn2+ to a 50-fold dilution of the denaturing medium. Titration of the denatured enzyme with either Co2+ or Mn2+ shows that wheat germ mutase preferentially binds Co2+. Assuming 1:1 complexation between metal atom and protein, the apparent dissociation constants (Kd) for E Co2+ and E Mn2+ at 22 degrees C and pH 8.7 are approximately 1.06 and 1.84, respectively. Other metal atoms (e.g., Cr2+, Cu2+, Fe2+, Fe3+, Mg2+, and Ni2+) have no effect in restoring the apoenzyme's catalytic activity. At low concentrations (0.11-0.23 mM) Zn2+ partially restores activity, but promotes protein precipitation at elevated concentrations. Evidence suggests that all bisphosphoglycerate-independent phosphoglycerate mutases require either an intra- or an extramolecular metal atom in order to function. Attempts to characterize wheat germ mutase as a glycoprotein have yielded negative results.     

Phylogenetic diversification of immunoglobulin genes and the antibody repertoire

Immunoglobulins are encoded by a large multigene system that undergoes somatic rearrangement and additional genetic change during the development of immunoglobulin-producing cells. Inducible antibody and antibody-like responses are found in all vertebrates. However, immunoglobulin possessing disulfide-bonded heavy and light chains and domain-type organization has been described only in representatives of the jawed vertebrates. High degrees of nucleotide and predicted amino acid sequence identity are evident when the segmental elements that constitute the immunoglobulin gene loci in phylogenetically divergent vertebrates are compared. However, the organization of gene loci and the manner in which the independent elements recombine (and diversify) vary markedly among different taxa. One striking pattern of gene organization is the "cluster type" that appears to be restricted to the chondrichthyes (cartilaginous fishes) and limits segmental rearrangement to closely linked elements. This type of gene organization is associated with both heavy- and light-chain gene loci. In some cases, the clusters are "joined" or "partially joined" in the germ line, in effect predetermining or partially predetermining, respectively, the encoded specificities (the assumption being that these are expressed) of the individual loci. By relating the sequences of transcribed gene products to their respective germ-line genes, it is evident that, in some cases, joined-type genes are expressed. This raises a question about the existence and/or nature of allelic exclusion in these species. The extensive variation in gene organization found throughout the vertebrate species may relate directly to the role of intersegmental (V<==>D<==>J) distances in the commitment of the individual antibody-producing cell to a particular genetic specificity. Thus, the evolution of this locus, perhaps more so than that of others, may reflect the interrelationships between genetic organization and function.      

Water quality during egg incubation influences yolk-sac fry sodium kinetics in Atlantic salmon, Salmo salar L.: a possible mechanism of adaptation to acid waters

Atlantic salmon ( Salmo salar L.) fry hatched from eggs transferred from high-Na to low-Na water during the eyed stage of development had a significantly higher V_max and lower K_m (P <0.01) of the sodium uptake mechanism than fry hatched from eggs incubated entirely in low-Na or high-Na water.
Fry hatched from eggs transferred to acid, high aluminium water during the eyed stage of development had a similar V_max and K_m to fry hatched from eggs incubated entirely in high- or low-Na water. Eggs incubated continuously in acid, high aluminium (low-Na) water produced fry with significantly lower K_m and V_max values than fry hatched from eggs incubated continuously in low-Na water. Eggs and fry in acid, high aluminium water continually lost sodium and mortality was 100% at 5 5 M O degree-days (2–3 weeks after hatching).
The results are discussed with respect to the influence of perivitelline fluid ion activities in eggs in acid, high aluminium water on the kinetic characteristics of sodium uptake in yolk-sac fry. A possible mechanism for the long-term adaptation of teleosts in acidified natural waters is also proposed.     

Kinetic characteristics of the sodium uptake mechanism during the development of embryos and fry of Atlantic salmon, Salmo salar L., in an improved water quality

The kinetics of active sodium uptake in dechorionated embryos, yolk-sac fry and start-feed fry of Atlantic salmon were compared in two groups reared either in low conductivity, untreated, river water (conductivity ∼ 46 μS cm⁻¹, pH 5.75), or in 'improved' river water buffered with sea water (conductivity ∼2200 μS cm ¹, pH 6.56), the latter treatment often being used in commercial hatcheries to avoid problems associated with periodic acidification.
Maximal transport rate ( V _max) increased during development in both groups but was always significantly higher in embryos and fry maintained in untreated river water. Values for K _m were not seen to vary during development up to 12 weeks after hatching and were not significantly different between groups, or from values reported for adult Atlantic salmon in fresh water.
The results are discussed with respect to the influence of Na⁺ concentrations in the perivitelline fluid of developing eggs and in the external medium surrounding fry on V _max and K _m. The ability of fry reared entirely in buffered river water to maintain sodium balance following transfer to untreated river water is also considered.     

A single gonadotropin alpha-subunit gene in normal tissue and tumor-derived cell lines

The structure of gene sequences coding for the mRNA of human chorionic gonadotropin (hCG) alpha-subunit was investigated by Southern blot analysis of genomic DNAs using a cloned, full length cDNA probe. While four hormones, lutropin, follitropin, thyrotropin, and choriogonadotropin, have homologous alpha-subunits, only one gene that bears hCG-alpha sequences could be detected per haploid complement. The structure of this single gonadotropin alpha-subunit gene, which contains intervening sequences, is the same in DNA from first trimester and term placentae. However polymorphism was observed for the presence of a HindIII site and of an Eco RI site in the gene's 3' flanking sequences. The organization of hCG-alpha sequences in several trophoblastic and nontrophoblastic tumor cell lines, which produce hCG subunits, was also examined. In each, the same gene copy number and structure were seen as in normal tissue. Thus, the characteristics of ectopic alpha-subunit expression in these cells seem not to be determined by DNA rearrangements.