Sequence homologies within the 5'' end region of the estrogen-controlled vitellogenin gene in Xenopus and chicken.

In oviparous vertebrates vitellogenin, the precursor of the major yolk proteins, is synthesized in the liver of mature females under the control of estrogen. We have established the organization and primary structure of the 5' end region of the Xenopus laevis vitellogenin A2 gene and of the major chicken vitellogenin gene. The first three homologous exons have exactly the same length in both species, namely 53, 21 and 152 nucleotides, and present an overall sequence homology of 60%. In both species, the 5'-non-coding region of the vitellogenin mRNA measures only 13 nucleotides, nine of which are conserved. In contrast, the corresponding introns of the Xenopus and the chicken vitellogenin gene show no significant sequence homology. Within the 500 nucleotides preceding the 5' end of the genes, at least six blocks with sequence homologies of greater than 70% were detected. It remains to be demonstrated which of these conserved sequences, if any, are involved in the hormone-regulated expression of the vitellogenin genes.     

Elemental composition of the perivitelline fluid in early Drosophila embryos

Samples of the perivitelline fluid in the polar pockets of preblastoderm Drosophila embryos were analyzed with an electron microprobe, and the results compared with analyses of adult hemolymph. The concentrations of sodium, magnesium, calcium, chlorine, and phosphorus are about the same in these two fluids; but potassium and sulfur are three to four times higher in perivitelline fluid. Moreover, the concentrations of these elements in the anterior and posterior pockets of the same embryos were compared. The former five elements seem to be about 10% more concentrated in the anterior pocket; but the latter two show no significant difference between pockets.     

The effect of tri-iodothyronine administration on protein synthesis in the diabetic rat.

In young male rats diabetes caused decreases in circulating free tri-iodothyronine and RNA concentration in liver and muscle, and in the rate of protein synthesis per unit of RNA (RNA activity) in muscle. Tri-iodothyronine treatment significantly increased RNA concentrations, but not RNA activity, in these tissues. Thus: (1) impaired thyroid status is a component of the diabetic condition; (2) tri-iodothyronine cannot stimulate the translational phase of protein synthesis in the diabetic rat.     

Similarities in the heavy and light chains of tetanus toxin suggested by their amino acid compositions

Quantitative comparison of the amino acid compositions of the heavy and light chains of tetanus toxin by the method of Cornish-Bowden [(1983) Methods Enzymol. 91, 60-75)] suggests strongly that there is sequence homology between the two chains and that the heavy chain has two similar halves. Examination (by electrophoresis in polyacrylamide gels in the presence of sodium dodecyl sulphate) of peptides produced from the chains by proteolytic cleavage supports this idea.     

Structural diversity and domain composition of a unique collagenous fragment (intima collagen) obtained from human placenta.

Intima collagen was obtained from pepsin digests of human placenta in two forms, which differ to some extent in the size of their constituent polypeptide chains (Mr 50 000-70 000). These chains are connected by disulphide bonds to large aggregates. The aggregates are arranged in a triple-helical conformation with a remarkably high thermal stability (Tm 41-62 degrees C) and are resistant to further proteolytic digestion. Reduction of as little as 5% of the disulphide bonds produces mainly monomeric triple helices (Mr about 160 000) with Tm 32 degrees C. Partially reduced material can be separated into triple-helical and non-collagenous domains by proteolysis. Pepsin releases a collagenous component with chains of Mr 38 000. Bacterial collagenase liberates two non-collagenous segments (Mr 15 000-30 000) rich in cystine. Treatment with collagenase before reduction separates intima collagen into a large fragment composed of collagenous (Tm 41 degrees C) and non-collagenous structures and a single non-collagenous segment. The data support the electron-microscopical model of intima collagen [Furthmayr, Wiedemann, Timpl, Odermatt & Engel (1983) Biochem. J. 211, 303-311], indicating that the basic unit of the fragment consists of a continuous triple helix joining two globular domains.     

Immunohistochemistry of tonin in rat submandibular gland during development, lactation and secretion

Tonin is a serine protease found in high concentrations in the submandibular gland (SMG) of the adult rat where it has been localized by immunohistochemistry in the granular ducts. The present study examined the development of tonin in the SMG, the effect of lactation and of stimulation of tonin release, using the peroxidase-antiperoxidase technique and antitonin. Tonin-like immunoreactivity first appeared in the primitive striated duct of the SMG on day 19 foetal and increased in intensity as the ducts developed into granular ducts. Reaction product in granules was seen on day 17 postpartum. Its localization within granules was established by immunochemistry of Sepharose beads to which had been coupled the contents of granules isolated from adult rats. The granular ducts of female rats, which are less developed than in the male, showed a marked increase in tonin-immunoreactivity during lactation. Stimulation of tonin secretion by isoprenaline caused massive discharge of tonin-like immunoreactivity into the lumen of the granular ducts during in vitro incubation. However, within one hour complete regranulation was apparent. The secretion was prevented by propranolol. The results indicate that tonin or a tonin-like substance appears in the rat submandibular gland late in gestation in ducts that presumably develop into granular ducts where it is found in abundance in granules in the adult, that the amount in females is increased during lactation, and that most of the granules are discharged during stimulation, only to be rapidly replaced.     

Vasopressin-immunoreactive cells in the dorsomedial hypothalamic region,medial amygdaloid nucleus and locus coeruleus of the rat

Summary Recently, the existence of a vasopressin-immunoreactive cell group was described in the bed nucleus of the stria terminalis (van Leeuwen and Caffé 1983). In the present investigation additional nuclei containing vasopressin-immunoreactive cells were found, after colchicine pretreatment, in the dorsomedial hypothalamus, medial amygdaloid nucleus and the locus coeruleus.Vasopressin-immunoreactive cells in the dorsomedial hypothalamus and medial amygdaloid nucleus are small (8–14 m and 10–14 m, respectively), while those in the locus coeruleus are medium-sized (20–25 m). Incubation with anti-bovine neurophysin II and anti-rat neurophysin revealed staining of the same cell group in the above-mentioned areas. None of these cell groups show stained cells after incubation with anti-oxytocin and anti-bovine neurophysin I. When sections of the homozygous Brattleboro rat, which shows a deficiency in vasopressin synthesis, are incubated with anti-vasopressin, anti-bovine neurophysin II, or anti-rat neurophysin, no immunoreactivity can be observed in these brain regions.The above-mentioned cell groups may contribute to the vasopressinergic innervation of brain sites that have been reported to persist after lesioning of the suprachiasmatic, paraventricular and bed nuclei of the stria terminalis.     

Ontogenetic development of the pineal organ,parapineal organ,and retina of the three-spined stickleback,Gasterosteus aculeatus L. (Teleostei)

The ontogenetic developments of the pineal organ, parapineal organ, and retina were studied by the use of light and electron microscopy in embryos and fry of the teleost, Gasterosteus aculeatus, from 60 to 168 h after fertilization. Sixty to 66 h after fertilization, the primordium of the pineal complex is discernible in the diencephalic roofplate; the parapineal anlage is located rostral to the pineal anlage. Photoreceptor cells endowed with outer segments are present in the embryonic pineal organ already after 72 h, whereas outer segments of retinal photoreceptors could not be demonstrated before 144 h (hatching occurs between 120-144 h). Furthermore, neuropil formations with synaptic specializations are present in the rostral part of the pineal organ 108 h after fertilization. At 72 h, the embryonic parapineal parenchyma is already differentiated into parapinealocytes, which give rise to the parapineal tract, and glia-resembling elements. Although parapinealocytes carry cilia (9 X 2 + 0), only a single outer segment of the photoreceptor type could be demonstrated in the parapineal organ of one adult stickleback. Photoreceptors present in the pineal organ of unhatched embryos are hardly involved in visual functions, but may already at this early developmental stage serve as photoneuroendocrine transducers.     

Cerebrospinal fluid-contacting neurons of the central canal and terminal ventricle in various vertebrates

Cell and Tissue Research - Cerebrospinal fluid (CSF)-contacting neurons were studied by means of electron microscopy in the spinal cord and/or terminal ventricle of the ray, Raja clavata...     

Studies on dissimilatory sulfate-reducing bacteria that decompose fatty acids

Gliding motility, ultrastructure and nutrition of two newly isolated filamentous sulfate-reducing bacteria, strains 5ac10 and 4be13, were investigated. The filaments were always attached to surfaces. Growth was supported by addition of insoluble aluminium phosphate or agar as substrata for gliding movement. Electron microscopy of ultrathin sections revealed cell walls characteristic of Gramnegative bacteria; the undulated structure of the outer membrane may pertain to the translocation mechanism. Intracytoplasmic membranes were present. Acetate, higher fatty acids, succinate or fumarate served as electron donors and carbon sources. Strain 5ac10 grew also with lactate, but not with benzoate that was used only by strain 4be13. Strain 5ac10 was able to grow slowly on H₂ plus CO₂ or formate in the presence of sulfate without additional organic carbon source. The capacity of complete oxidation was shown by stoichiometric measurements with acetate plus sulfate. Both strains contained b- and c-type cytochromes. Desulfoviridin was detected only in strain 5ac10. The two filamentous gliding sulfate reducers are described as new species of a new genus, Desulfonema limicola and Desulfonema magnum.