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Biomedical subjects

C Walther

Publications and source records attributed to C Walther.

At least 55 records · Page 3Linked to original sources
PubMed1990

Pax8, a murine paired box gene expressed in the developing excretory system and thyroid gland.

Several mouse genes designated 'Pax genes' contain a highly conserved DNA sequence homologous to the paired box of Drosophila. Here we describe the isolation of Pax8, a novel paired box containing clone from an 8.5 day p.c. mouse embryo cDNA library. An open reading frame of 457 amino acids (aa) contains the 128 aa paired domain near the amino terminus. Another conserved region present in some other paired box genes, the octapeptide Tyr-Ser-Ile-Asn-Gly-Leu-Leu-Gly, is located 43 aa C-terminal to the paired domain. Using an interspecies backcross system, we have mapped the Pax8 gene within the proximal portion of mouse chromosome 2 in a close linkage to the surf locus. Several developmental mutations are located in this region. In situ hybridization was used to determine the pattern of Pax8 expression during mouse embryogenesis. Pax8 is expressed transiently between 11.5 and 12.5 days of gestation along the rostrocaudal axis extending from the myelencephalon throughout the length of the neural tube, predominantly in two parallel regions on either side of the basal plate. We also detected Pax8 expression in the developing thyroid gland beginning at 10.5 days of gestation, during the thyroid evagination. In the mesonephros and metanephros the expression of Pax8 was localized to the mesenchymal condensations, which are induced by the nephric duct and ureter, respectively. These condensations develop to functional units, the nephrons, of the kidney. These data are consistent with a role for Pax8 in the induction of kidney epithelium. The embryonic expression pattern of Pax8 is compared with that of Pax2, another recently described paired box gene expressed in the developing excretory system.

Amino Acid Sequence↗
PubMed1988

ADP-ribosylation is involved in the integration of foreign DNA into the mammalian cell genome.

The most commonly used DNA transfection method, which employs the calcium phosphate co-precipitation of the donor DNA, involves several discrete steps (1,2). These include the uptake of the donor DNA by the recipient cells, the transport of the DNA to the nucleus, transient expression prior to integration into the host cell genome, concatenation and integration of the transfected DNA into the host cell genome and finally the stable expression of the integrated genes (2,3). Both the concatenation and the integration of the donor DNA into the host genome involve the formation and ligation of DNA strand-breaks. In the present study we demonstrate that the nuclear enzyme, adenosine diphosphoribosyl transferase (ADPRT, E.C. 2.4.2.30), which is dependent on the presence of DNA strand breaks for its activity (4,5) and necessary for the efficient ligation of DNA strand-breaks in eukaryotic cells (4,6), is required for the integration of donor DNA into the host genome. However, ADPRT activity does not influence the uptake of DNA into the cell, its episomal maintenance or replication, nor its expression either before or after integration into the host genome. These observations strongly suggest the involvement of ADPRT activity in eukaryotic DNA recombination events.

Animals↗
PubMed1988

FMRFamide-like immunoreactivity in the metathoracic ganglion of the locust (Schistocerca gregaria).

The distribution of FMRFamide-like immunoreactivity in the metathoracic ganglion of the locust, Schistocerca gregaria, has been investigated in serial semithin transverse sections with the use of the peroxidase-antiperoxidase (PAP) technique. The topographical distribution of approximately 120 immunopositive neurons was established. Antiserum against bovine pancreatic polypeptide (BPP) stains the same ganglionic cells as FMRFamide-antiserum, yet this staining is largely blocked after preabsorption to FMRFamide. A comparison of these results with those from other studies suggests that there may be more than one type of endogenous RFamide-like peptide.

Animals↗
PubMed1987

Phencyclidine depresses transmitter release at the neuromuscular synapse of the locust.

The presynaptic effects of phencyclidine (PCP) were studied in the locust extensor tibiae muscle. The neurally evoked transmitter release is diminished in the presence of 5 x 10(-6) to 5 x 10(-5) M PCP. This is indicated (1) by an increased coefficient of variation of the excitatory junction potentials; (2) by an increased rate of failures (a) with nerve stimulation in low [Ca2+]saline and (b) with focal extracellular stimulation in normal [Ca2+]saline. The rate of spontaneous transmitter release is not affected.

Animals↗
PubMed1987

FMRF-NH2-like factor from neurohaemal organ modulates neuromuscular transmission in the locust.

YGGFMRFamide, FMRFamide and related peptides potentiate transmission at locust slow motor synapses. Since immunohistochemical evidence points to neurohaemal organs (NHO) as potential sources for endogenous RFamide-like peptides we have applied extracts from the metathoracic NHO, equivalent to 1/3 NHO, to the metathoracic extensor tibiae muscle. NHO-extract depolarizes the muscle fibre and increases its membrane resistance; enhances transmitter release; and increases the amplitude of contraction and the rate of relaxation. These effects are in good qualitative and quantitative agreement with those of YGGFMRFamide (5 X 10(-8) to 10(-7) M). Octopamine which partly acts like YGGFMRFamide cannot account for the NHO-effects.

Animals↗
PubMed1987

[Sodium content of liquid antacid preparations].

The sodium content of 13 liquid antacids was determined using two independent analytical methods (flame photometry). With a neutralisation buffering capacity of 564 mmol/d (pH 3.5) the possible body sodium load was calculated by evaluating the sodium content in the supernatant of the antacid suspensions, ranging from 0.56 to 568 mmol/d (method A) and from 0.42 to 468 mmol/d (method B). Therefore, in patients who are on a sodium restriction of 50 mmol/d this critical intake may be easily exceeded by the intake of certain antacids.

Antacids↗
PubMed1984

Synaptic and non-synaptic effects of molluscan cardioexcitatory neuropeptides on locust skeletal muscle.

Neurally evoked contractions of the locust jumping muscle are potentiated by the molluscan cardioexcitatory peptide (FMRFamide) and related peptides. This effect is due to a synaptic and a non-synaptic action of the peptides: (1) excitatory synaptic potentials are increased; (2) excitation-contraction coupling becomes more efficient, as indicated by an increased strength of potassium contractures. Octopus heptapeptide (YGGFMRFamide), which contains the entire enkephalin structure (YGGFM), is 100 times more potent than FMRFamide. Structure-activity studies indicate that the observed actions are not mediated by opioid receptors but are dependent on the C-terminal structure of the peptides.

Animals↗
PubMed1984

[Refractive errors, amblyopia and strabismus in congenital ptosis].

Fifty-four consecutive surgical cases of congenital ptosis were carefully evaluated to determine the incidence of refractive errors, strabismus and amblyopia. Of these patients, 70% had a refractive error, 43% had an astigmatism of more than 1.0, 55% had anisometropia, 27.5% had concomitant squint and 50% amblyopia.

Amblyopia↗
PubMed1984

[Cyclic esotropia in an adult].

The authors describe a 46-year-old man who suddenly developed a typical cyclic esotropia. The most unusual aspects of this case were the late onset of the condition and the unilateral high myopia associated with a severe amblyopia of the squinting eye. The 24-hour-periods of deviation were accompanied by a very disagreeable flicker in the esotropic eye. The onset of this extremely unusual disorder and rare form of esotropia usually occurs at 2 to 4 years of age. To the best of our knowledge only 2 cases of cyclic esotropia have been described in adults hitherto.

Esotropia↗
PubMed1983

Block of synaptic vesicle exocytosis without block of Ca2+-influx. An ultrastructural analysis of the paralysing action of Habrobracon venom on locust motor nerve terminals.

The venom of the wasp Habrobracon hebetor presynaptically blocks excitatory but not inhibitory neuromuscular transmission at locust skeletal muscle. Its mode of action on excitatory motor nerve terminals has been studied at the retractor unguis muscle of Schistocerca by means of ultrastructural stereology. paralysed and unparalysed preparations, either resting or stimulated for 7 min at 20 Hz, were compared. Paralysis does not cause structural damage to the nerve terminals but prevents the depletion of vesicles occurring upon nerve stimulation in the controls. Prolonged paralysis leads to an increase in the number and the size of vesicles resulting in an increase of total membrane per terminal cross-section by about 33% after 2 days. Stimulation causes swelling of mitochondria both in controls and in paralysed preparations, resulting from a rise of intraterminal [Ca2+] as is indicated by the absence of the swelling if extracellular Ca2+ is replaced by Mg2+. In addition, stimulation leads to a reduction of vesicle size, an increase in the area of axolemma and in the number of cisternae and of profiles of the smooth endoplasmic reticulum in controls but not in paralysed preparations. However, neither in controls nor in paralysed preparations is the total amount of membrane per terminal cross-section affected by stimulation. Under paralysis, vesicles tend to stick to the presynaptic membrane. It is concluded that Habrobracon venom does not block the depolarizing-dependent Ca2+-influx into the nerve terminal and that it is unlikely to interfere with some transmitter-related process. Rather, the venom seems to block vesicle exocytosis itself. The results lend further support to the view that in insect neuromuscular synapses exocytosis is the mechanism whereby transmitter quanta are released.

Animals↗
PubMed1983

[The chemistry of antacids].

Antacids are relative simply assembled salts and salt-like compounds which neutralize acids. This neutralization reactions lead to several products (other salts, water, and possibly carbondioxid), resulting in steps, like hydrolysis and precipitations of insoluble compounds. When antacids containing aluminum are neutralized in the presence of organic acids, peptones, and polypeptides, there is a marked loss in their neutralizing capacity and neutralization rate.

Aluminum Hydroxide↗
PubMed1982

Sub-miniature junction potentials in excitatory neuromuscular synapses of the locust.

By recording miniature excitatory junction potentials (mejps) intracellularly at two points from a multiterminally innervated muscle fibre it is possible to select mejps whose amplitudes are not substantially affected by electrotonic decay. Many amplitude histograms of such selected mejps from untreated locust jumping muscle show a bimodal distribution with a high proportion of small-amplitude mejps (sub-mejps). Most amplitudes of excitatory junction potentials (ejps) resulting from the release of a single transmitter quantum correspond to the large-mode mejps. Tetanic nerve stimulation, in high [Mg2+]o without Ca2+, greatly reduces the proportion of sub-mejps. It is concluded that there are two modes of spontaneous transmitter release from the motor nerve endings.

Animals↗