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J Malecha

Publications and source records attributed to J Malecha.

34 records · Page 2Linked to original sources
PubMed1992

Ovohemerythrin, a major 14-kDa yolk protein distinct from vitellogenin in leech.

A 14-kDa protein was identified as a major component of mature oocytes of the leech Theromyzon tessulatum. This protein was, like vitellin, detected in the content of yolk granules and was purified by gel-permeation and ion-exchange chromatography. The yolk protein corresponded to an iron-binding protein which exists in a monomeric unglycosylated form and had no similarities to vitellin. However, a strong resemblance between this protein and sipunculid hemerythrin, a non-heme iron-binding protein, was observed on the basis of its characteristics including molecular mass, iron content, ultraviolet/visible spectrum, amino acid composition and N-terminal sequence. These similarities with hemerythrin and the accumulation of the protein in the oocyte justify the name ovohemerythrin given to the molecule. A coelomic-fluid protein immunologically related to ovohemerythrin was detected in vitellogenic animals. The protein was purified with the chromatographic procedure used to isolate ovohemerythrin from oocytes and was found to be similar to the oocyte protein. This circulating ovohemerythrin was present in large amounts in the coelomic fluid while gametogenesis is in progress, i.e. after the third and last blood meal of the animal (stage 3), except at the time of oocyte enlargement when its concentration decreases dramatically. However, in contrast to vitellogenin, which is detected specifically in the coelomic fluid of leeches at stage 3, circulating ovohemerythrin is also observed after the first (stage 1) and second (stage 2) blood meal. This observation suggests a more complex function for ovohemerythrin than being merely a yolk nutrient for the embryo.

Amino Acid Sequence↗
PubMed1992

Evidence for angiotensin-like molecules in the central nervous system of the leech Theromyzon tessulatum (O.F.M.). A possible diuretic effect.

1. Cells in the central nervous system of the leech Theromyzon tessulatum were revealed with an antiserum against angiotensin II. Among these cells, a group of 4-5 pairs of neurons, called beta giant cells, and located in the posterior compartments of the supraesophageal ganglion was particularly investigated. 2. The amount of angiotensin II-like substance(s) in the brain increased notably in the days immediately following the third meal. 3. Injections of angiotensin II, fragments 1-4 or 5-8 or angiotensin II and of angiotensin III into stage 3 leeches showed that fragment 5-8 of angiotensin II was the most effective: it provokes a loss of mass of the leeches, which could express a diuretic effect.

Angiotensin II↗
PubMed1991

Yolk protein in leech. Identification, purification and characterization of vitellin and vitellogenin.

Theromyzon tessulatum vitellin was identified as a lipoglycoprotein of 490 kDa. The insolubility of this molecule in low-ionic-strength media was used to extract it from the ovaries. Antiserum prepared against vitellin was shown to react with a coelomic fluid component of 520 kDa. This vitellin precursor, or vitellogenin, was purified by gel permeation and ion-exchange column chromatography. These two lipoglycoproteins were characterized by amino acid, carbohydrate and lipid analysis and subunit composition. In spite of differences in terms of native molecular mass, solubility and isoelectric point, the lipoglycoproteins isolated from the coelomic fluid and the ovary were similar in their subunit components (a single polypeptide of 165 kDa) and in their amino acid and carbohydrate compositions. However, vitellogenin was found to be more highly lipidated (31.8% by mass) than vitellin (24% by mass) and lipid analysis indicated a higher amount of sterols and phospholipids in vitellogenin. From these data, we conclude that vitellogenin and vitellin are probably dimers of two identical subunit polypeptides plus lipid and that, after vitellogenin is sequestered in the oocyte, part of its lipid component is stripped from the molecule to give vitellin. Furthermore, electrophoretic analysis seems to indicate that vitellogenin synthesis and secretion is initiated following the third and last blood meal of the animal but that vitellogenin significantly accumulates in the coelomic fluid before being incorporated in the oocytes suggesting a complex mode of vitellogenesis regulation.

Amino Acids↗
PubMed1987

[Characterization of immunoreactive neurons in the central nervous system of the leech Theromyzon tessulatum using monoclonal antibodies].

Two mouse hybridomas producing monoclonal antibodies Tt9 and Tt 159 directed against antigens of supraesophageal ganglia of the leech T. tessulatum were selected to study the neuroendocrine control of osmoregulation in this species. One, Tt 159 reacted with an antigenic determinant of cells recognized by an anti-angiotensin antibody, the other, Tt 9, with neurons immunoreactive to the anti-vasopressin.

Angiotensin II↗
PubMed1986

[Evidence of apparent vasopressin and oxytocin peptides in the brain of the leech Rhynchobdelle Theromyzon tessulatum (O.F.M.)].

Vasopressin- and oxytocin-immunoreactive cells have been demonstrated in the brain of the leech Theromyzon tessulatum. A mapping of their localization in the different compartments of the brain has been undertaken. The cells immunohistochemically identified have been compared to previously described cell types defined by classical staining methods for neurosecretory material. Preliminary results obtained with high performance liquid chromatography confirm the presence in brain homogenates of substances with chromatographic properties similar to that of vertebrate nonapeptides. The possible role of these vasopressin- and oxytocin-like substances in osmoregulation is discussed.

Animals↗
PubMed1983

[Osmoregulation in Hirudinea Rhynchobdellida Theromyzon tessulatum (O.F.M.). Experimental localization of the secretory zone of a regulation factor of water balance].

The body water content of Theromyzon tessulatum changes considerably during the life cycle. Water content is low and undergoes little change during the first stages, but it strongly and regularly increases during the last stage prior to reproduction. It is controlled by a water balance factor (FRBH) released by the brain. With selective removals of nervous follicles, the site of production of this hormone has been localized in the posterior paramedial follicles (follicles 4).

Animals↗