Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LEECHES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,549 records · Page 86Linked to original sources
PubMed1972

Leech and vrach.

Explore the source record for details and available documents.

Leeches↗
PubMedDate not supplied

Medicinal leeches: ancient therapy is a source of biotech drugs.

Hirudin analogs have been shown to be inhibitors of thrombin with many potential uses. These agents appear to have advantages over conventional anticoagulant agents such as heparin. The hirudin compounds do not require a cofactor to work, have consistent dose-dependent effects, act directly on thrombin, are highly specific, and have little to no toxicity.

Animals↗
PubMed1995

Core domain of hirudin from the leech Hirudinaria manillensis: chemical synthesis, purification, and characterization of a Trp3 analog of fragment 1-47.

Hirudin is a small (approximately 7 kDa) disulfide-cross-linked polypeptide known as the most potent and specific thrombin inhibitor. We have previously shown that the N-terminal proteolytic fragment 1-47 of hirudin HM2 from Hirudinaria manillensis maintains inhibitory action toward thrombin [Vindigni, A., et al. (1994) Eur. J. Biochem. 226, 323-333]. Here we report the solid-phase chemical synthesis of an analog of fragment 1-47 bearing a Tyr3-->Trp exchange (Y3W analog). The crude, reduced peptide was purified by reverse-phase HPLC and subjected to oxidative folding to the disulfide-cross-linked species. The folding process of the Y3W analog was slower than that of the natural fragment 1-47, but nevertheless still occurred almost quantitatively as the natural species. The overall final yield of the synthetic product was approximately 35%, and its identity and homogeneity was established by a number of analytical techniques, including electrospray mass spectometry. The unique alignment of the three disulfide bridges of the Y3W analog was established by peptide mapping as Cys6-Cys14, Cys16-Cys28, and Cys22-Cys37 and shown to be identical to that of the natural fragment. The results of far- and near-ultraviolet circular dichroism and fluorescence emission measurements provided evidence that the Y3W analog retains the structural features of the natural species. The thermodynamic quantities (delta GD, delta Hm, delta Sm, and delta Cp) characterizing the reversible and cooperative thermal unfolding processes of the Y3W analog (Tm = 60.5 degrees C) and the natural fragment species (Tm = 62.5 degrees C) were evaluated. Despite the relatively high Tm values, the stability of both fragment species at 37 degrees C was only approximately 10 kJ mol-1, well below the average 50 kJ mol-1 typical of single-domain globular proteins. The synthetic Y3W species was found to be approximately 5-fold more active (KI = 30 +/- 5 nM) than the natural fragment 1-47 (KI = 150 +/- 20 nM) in inhibiting thrombin. Of interest was that the difference in the free energies of binding to thrombin at 37 degrees C, delta delta Gb, between the Y3W analog and natural species (4.2 kJ mol-1) was that expected for the difference in hydrophobicity between the two polypeptides resulting from the Tyr-->Trp exchange. The results of this study indicate that solid-phase chemical synthesis represents a convenient and high-yield procedure to prepare analogs of the biologically active, N-terminal core domain of hirudin with improved functional properties.

Amino Acid Sequence↗
PubMed2004

Analysis of the effects of antibodies to gangliosides on the electrical activity of Retzius neurons in the leech and on the functional activity of influx sodium current channels.

The effects of anti-ganglioside antibodies on the functional states of two types of influx Na+ current channels were studied. Experiments used 20% anti-ganglioside antiserum prepared by standard methods by immunizing rabbits with total bovine brain gangliosides. These experiments showed that incubation of neurons in physiological saline containing antiserum induced discordance in the operation of the two types of influx current Na+ channels responsible for spike generation. This reaction was found to be associated with the slowed rate of activation of TTX-sensitive Na+ channels. Synaptic stimulation of cells in the presence of antiserum induced blockade of TTX-insensitive influx Na+ current channels. High-frequency synaptic activation of cells (10 Hz) showed that apart from blockade of TTX-insensitive Na+ channels, anti-ganglioside antibodies prevented plastic rearrangements in the gate system of TTX-sensitive Na+ channels. This resulted in impairment of the development of the acclimation process - the response of the neuron to high-frequency stimulation seen in normal conditions.

Animals↗
PubMed1985

Habituation of the shortening reflex in the medicinal leech.

The shortening reflex was elicited in food-sated Hirudo medicinalis by light flashes delivered at 20-s intervals over a 40-trial session. The reflex was enhanced if animals were stored at 5-7 degrees C rather than 20 degrees C. Short-term, that is, within-sessions, habituation was readily observed. Dishabituation could be produced by a single electric shock at Trial 30. However, the shock also enhanced responding when delivered before Trial 1 (sensitization). No long-term, that is, between-sessions, habituation occurred over 6 consecutive days of testing; on the contrary, responding gradually increased.

Animals↗