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Biomedical subjects

B T Walther

Publications and source records attributed to B T Walther.

16 recordsLinked to original sources
PubMed1993

Development of hatchability in halibut (Hippoglossus hippoglossus) embryos.

Halibut (Hippoglossus hippoglossus) eggs raised in darkness hatched between days 14.5 and 16 after fertilization. Eggs incubated in white light (3.2 microE/sr1/m2) remained unhatched, so that time of intra ovo development could be doubled. Photo-arrest of hatching was non-diapausal since embryonic growth continued. Transfer of photo-arrested eggs to darkness induced rapid and synchronous hatching. This procedure allowed analysis of development of hatchability. Hatching was not observed prior to day 14. Nonsynchronous hatching over three days was seen when eggs were induced on day 14 + 1 h, or on day 14 + 9 h. However, darkness-induction on day 14 + 22 h produced synchronous hatching within 140 min. This high rate of inducibility persisted until day 18, before declining slowly. Hatching-induction was not observed beyond day 22. Low hatchability in long-term photo-arrested embryos apparently reflects a loss of the anatomical prerequisites for the rim-hatching mechanism. Altered hatchability and morphogenesis after prolonged intra ovo development indicate that hatching in halibut is possible only at an early, defined ontogenetic stage.

Animals↗
PubMed1992

Pancreatic bile salt dependent lipase from cod (Gadus morhua): purification and properties.

The enzymatic basis for cod digestive lipolysis has been investigated. Lipase activity was found in aqueous extracts from pyloric caeca as well as in pancreatic tissue surrounding the caeca and the bile duct. A bile salt-dependent lipase (BSDL) was purified from either defatted powder of cod pyloric caeca or aqueous pancreatic extracts by combined affinity chromatography on cholate-Sepharose and gel filtration on Sephacryl S-200 HR. By SDS-PAGE analysis the molecular weight of purified cod BSDL was estimated to 60 kDa. The enzyme was totally dependent on bile salts for hydrolysis of insoluble fatty acid esters. Antiserum raised against purified cod BSDL reacted specifically with selected mammalian pancreatic BSDLs by Western blot analysis. Results presented in this paper strongly suggest that the bile salt-dependent lipase is the only pancreatic enzyme involved in lipid digestion in cod. The enzyme has been characterized and compared to human pancreatic BSDL with respect to substrate specificity, temperature- and pH-dependence and inhibitors. Both soluble and insoluble fatty acid esters were hydrolysed and the enzyme was 1,3-specific in hydrolysis of triolein. The enzyme was inhibited by di-isopropyl fluorophosphate and phenyl boronic acid, but not significantly by phenyl methyl sulfonyl fluoride. The cod BSDL is probably homologous to mammalian pancreatic BSDLs.

Amino Acids↗
PubMed1992

Zona radiata proteins are synthesized by rainbow trout (Oncorhynchus mykiss) hepatocytes in response to oestradiol-17 beta.

The present study delineates the origin of the three major proteins constituting the rainbow trout (Oncorhynchus mykiss) zona radiata. Intraperitoneal administration of oestradiol-17 beta induced the appearance in the blood from juvenile fish (both sexes) of proteins immunoreactive to rabbit antisera against zona radiata proteins (zr proteins). These proteins had similar molecular weights to the zr proteins (alpha, 60 kDa; beta, 55 kDa; and gamma, 50 kDa). Primary hepatocyte cultures from fish treated with oestradiol-17 beta incorporated radioactive [35S] methionine into four major proteins with molecular weights of 160, 60, 55 and 50 kDa. Only the latter three proteins were specifically immunoprecipitated with antibodies to zr proteins. Furthermore, our data demonstrate that in such cultures the biosynthetic mole ratios of these secreted proteins (60, 55 and 50 kDa) are close to one. Control cultures from fish that had not been treated with oestradiol-17 beta failed to produce immunoreactive proteins. The data support the hypothesis that zr proteins are synthesized in a concerted manner in the liver during teleostean oogenesis and transported by the blood for deposition in ovarian follicles.

Animals↗
PubMed1992

Eggshell zona radiata-proteins from cod (Gadus morhua): extra-ovarian origin and induction by estradiol-17 beta.

Using Atlantic cod (Gadus morhua) as a model organism, the aim of this report was to delineate whether teleostean eggshell zona radiata proteins have their origin, i.e., site of synthesis, in gonadal or somatic tissues. Estradiol-17 beta was administered intraperitoneally to one-year-old cod (Gadus morhua) with either undeveloped gonads or with differentiated gonads. By immunoblotting procedures estradiol-dependent protein induction was investigated using specific rabbit antisera directed against cod eggshell proteins and brown trout vitellogenin. No immunological cross-reactions were observed between the two antisera, and eggshell proteins and vitellogenin were detected in blood plasma and somatic tissues only in estradiol-treated cod. Three plasma-components were immunoreactive to antiserum directed against eggshell proteins, and these proteins possessed molecular weights of 78, 54 and 47 kDa, identical to the molecular weights of the cod eggshell alpha, beta and gamma zona radiata-proteins. These three immunoreactive plasma-components were observed after administration of estradiol-17 beta to both sexes, also in males having reached spermiation, and in juveniles of either sex without developed gonads. The data are interpreted to signify that cod eggshell zona radiata-proteins originate in an extra-ovarian tissue and are transported in the blood for deposition in the ovaries. We propose that oogenesis involves estradiol-17 beta regulation of both eggshell zona radiata-proteins and vitellogenin synthesis.

Animals↗
PubMed1991

Oestradiol-17 beta induces the major vitelline envelope proteins in both sexes in teleosts.

During growth of the ovarian follicle, the teleost oocyte becomes surrounded by an acellular coat, the vitelline envelope. The nature, origin and number of the vitelline envelope proteins in fish appear to vary with species. In this work, polyclonal antibodies directed against vitelline envelope proteins from rainbow trout, brown trout and turbot were used to show that oestradiol-17 beta induces the major vitelline envelope proteins in juveniles, both males and females, from different species. The fact that males can synthesize vitelline envelope constituents shows that the origin of these proteins is not confined to the ovary. The vitelline envelope of rainbow trout eggs consists of three major proteins, designated alpha (60 kDa), beta (55 kDa) and gamma (50 kDa). The amino acid composition of each of the three proteins indicated that the three proteins are alike and the suggestion that these proteins represent a separate class of structural proteins is sustained.

Amino Acids↗
PubMed1991

The hatching mechanism in Atlantic halibut (Hippoglossus hippoglossus).

In general fish larvae emerge from the protective egg after secreting a hatching enzyme (HE) from diffusely located hatching gland cells (HGCs). This proteolytic enzyme is distributed over the entire inner part of the eggshell (zona radiata). In a marine flatfish halibut, (Hippoglossus hippoglossus), we have found a more specialized hatching process. A strategic location of the HGCs in a narrow belt on the anterior part of the yolk sac leads to restricted degradation of the eggshell resulting in cleavage of the eggshell into two distinct rigid parts. This hatching process--termed "rim-hatching"--results in an empty eggshell with a lid approximately 1/4 the size of the bottom shell. During the hatching process the yolk sac is reshaped. The posterior part of the yolk sac contracts and the yolk mass is squeezed forward before hatching. This mechanism ensures close contact between the HGCs and the eggshell during the release of the hatching enzyme, which is a prerequisite for restricted degradation of the eggshell.

Animals↗
PubMed1990

Paradoxical DSP-4 effects: protection against gastric erosions and depletion of mucosal glycoproteins.

We have previously reported that rats pretreated with the central noradrenergic neurotoxin DSP-4 are protected against 23 h restraint-induced gastric erosions. To elucidate the peripheral mechanisms of this protection, we undertook direct biochemical analyses of the gastric mucosa in terms of glycoproteins and proteins. A simple method for preparation of gastric mucosa devoid of the muscular stomach wall tissue is described. A restraint-induced decrease in gastric mucosal wet weight and mucosal glycoprotein content was revealed. Restraint had no effect on mucosal protein content, and no changes were found in gastric wall glycoprotein or protein content. Despite showing protection against restraint-induced gastric erosions, unrestrained DSP-4-treated animals exhibited reduced mucosal wet weight and mucosal glycoprotein content when compared to unrestrained controls. After the stress period, no significant differences on mucosal weight or glycoproteins could be detected between control and DSP-4-treated animals. The results indicate that the protective effect of DSP-4 in this paradigm is not due to enhanced gastric mucosal protection against erosive factors. We suggest that an additional effect of central nervous NA depletion by DSP-4 may be elimination of aggressive factors which precipitate overt ulcers.

Animals↗
PubMed1990

The major structural proteins of cod (Gadus morhua) eggshells and protein crosslinking during teleost egg hardening.

The highly hydrophobic protein aggregate which constitutes the fish eggshell has for the first time been quantitatively solubilized. This study shows that the nonactivated eggshell from cod is composed primarily of only three protein monomers, designated alpha (74 kDa) beta (54 kDa) and gamma (47 kDa). Protein extraction studies of the eggshells before and after egg activation demonstrate that egg hardening is accompanied by a 10-fold decline in total protein solubility, which is due to nonextraction of the alpha, beta, and gamma chains. When present during the egg activation process monodansylcadaverine (MDC-a fluorescent lysine analog) inhibits eggshell hardening and at the same time becomes covalently incorporated into the eggshell. This MDC incorporation is calcium-dependent and suggests the induction of a perivitelline transglutaminase activity after egg activation. (Transglutaminases catalyze the formation of an amide bond (isopeptide bond) between the gamma-carbonyl group of glutamine and the epsilon-amino group of lysine with release of ammonia. Crosslinks between proteins are generated when the two amino acid residues are located on different proteins.) Protein solubilization studies and NaDodSO4 gel analysis of the eggshell proteins from eggs subjected to 5 mM MDC during egg activation, reveal that when eggshell hardening is blocked by MDC, the three main eggshell proteins remain extractable even after egg activation. Simultaneously we observed a covalent incorporation of MDC into the gamma protein.

Amino Acids↗
PubMed1989

Isolation and characterization of growth hormone from Atlantic cod (Gadus morhua).

Growth hormone was purified from cod pituitary extract by a simple two-step procedure involving gel filtration and reversed-phase high-performance liquid chromatography (rpHPLC). At each stage of purification, fractions were monitored by rpHPLC, SDS-polyacrylamide gel electrophoresis, and immunoblotting using anti-chum salmon growth hormone (GH) antiserum. The yield of purified hormone was 1.3 mg/g pituitary. Cod GH was found to exist in two monomeric forms (Mr = 20K and 22K) and dimeric forms (Mr = 40K and 42K). The two monomeric forms have a pI of 5.8, an identical amino acid composition, histidine as the N-terminal residue, and an identical lysyl endopeptidase peptide map. Staining with concanavalin A was observed on the 20K component only, but analysis for total reducing sugar did not confirm these results. Cod GH was found to be a potent stimulator of growth in juvenile rainbow trout which received intraperitoneal injections of the hormone. The partial amino acid sequence has been determined.

Amino Acid Sequence↗
PubMed1989

Purification and characterization of chymotrypsin, trypsin and elastase like proteinases from cod (Gadus morhua L.).

1. Chymotrypsin, trypsin and elastase have been purified from the pyloric caeca of cod. 2. The enzymes were separated by affinity/hydrophobic chromatography on phenyl-butyl-amine (PBA) substituted sepharose. Chymotrypsin eluted in two separate isozyme fractions whereas trypsin and elastase eluted in separate fractions consisting of two closely-related polypeptide chains as revealed by SDS-polyacrylamide electrophoresis and isoelectric focusing. 3. The cod enzymes consist of single polypeptide chains with apparent molecular weights of about 27,000 Da as shown by denaturing polyacrylamide gel electrophoresis. 4. The cod proteinases were retarded on gel filtration media. The retardation increased with increasing pressure. 5. Isoelectric focusing analysis shows that the cod enzymes have isoelectric points in the range between 5 and 7. 6. The cod proteinases are rapidly inactivated when stored at low pH's.

Animals↗
PubMed1973

A quantitative assay for intercellular adhesion.

Intercellular adhesion is measured by a new method based on determination of the rates of attachment of single cells to confluent cell monolayers. The procedure is simple, rapid, and reproducible. Specific and nonspecific intercellular adhesions can be quantitated and distinguished from each other, and from the adhesion to glass (or plastic). The rate of adhesion of single cells to the monolayer is characteristic of more than 80% of the single-cell population. This method, therefore, provides a means for study of the molecular basis of intercellular adhesion.

Animals↗
PubMed1970

The development of the dorsal and ventral mammalian pancreas in vivo and in vitro.

The origin, morphogenesis, and biochemical differentiation of the dorsal and ventral pancreas of the rat embryo have been investigated in order to ascertain the similarities and dissimilarities between the two lobes. We have utilized a culture system in which the primitive gut gives rise to a number of differentiated organs, including the dorsal and ventral pancreas. The two pancreases do not undergo fusion in these cultures, thus allowing independent analyses of the two lobes for comparison with in vivo results. The dorsal pancreas first appeared at the 23-25 somite stage while the ventral pancreas appeared approximately 12 hr later at the 29-30 somite stage. Guts from embryos as young as 12 somites were capable of developing both pancreases in vitro. In spite of the 12 hr difference between the times of their appearance, the dorsal and ventral pancreases exhibited identical patterns of morphological and biochemical differentiation. The two lobes contained the same exocrine enzymes and hormones, at similar levels, differing only in their glucagon content, the dorsal pancreas possessing a fivefold higher glucagon specific activity. The implications of these results are discussed.

Amylases↗
PubMedDate not supplied

Brief uncontrollable stress and psychological parameters influence human plasma concentrations of IgM and complement component C3.

Thirty-eight men participated in a study of immunological, hormonal, and psychological parameters before and after acute stress situations. A brief but acute stress was repeated daily for 4 days. This exposure caused the plasma levels of IgM and C3 to increase from Basal Day to Experimental Day 4. Significant correlations between endocrine and immunological parameters, and also between psychological measures and immunological parameters, were found. Use of psychological defense was related both to endocrine and immunological changes. The authors concluded that psychological stress may influence immunological functions both indirectly, by hormonal changes, and directly, by nervous regulation during brief but acute stress periods.

Adult↗