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Biomedical subjects

A Zweers

Publications and source records attributed to A Zweers.

At least 19 recordsLinked to original sources
PubMed1990

Correlation between peripheral CA-125 levels and ovarian activity.

Serum CA-125 concentrations were measured at three different times in normal cycles, pill-suppressed cycles, and cycles stimulated for intrauterine insemination (IUI) or oocyte retrieval, i.e., (1) during the first half of the cycle, (2) at midcycle or at the moment of oocyte retrieval, and (3) the second half of the cycle. Significant variations of serum CA-125 concentrations were not seen during the cycle in normally cycling women or in women taking oral contraceptives: mean +/- SD 28.9 +/- 13.3 U/mL and 26.9 +/- 11.3 U/mL, respectively. In patients stimulated for in vitro fertilization, luteal phase CA-125 levels (60.6 +/- 38 U/mL) were significantly higher than during stimulation (21.5 +/- 5.9 U/mL) or at oocyte retrieval (19.6 +/- 6.4 U/mL). In stimulated cycles for IUI, without laparoscopy or follicular puncture, a comparable rise of CA-125 was observed in the luteal phase (49.6 +/- 37.8 U/mL). However, in patients undergoing laparoscopic sterilization, serum CA-125 concentrations before and after laparoscopy were not significantly different (22.8 +/- 6.3 U/mL and 25 +/- 4.2 U/mL, respectively).

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1988

Dogfish alpha-crystallin sequences. Comparison with small heat shock proteins and Schistosoma egg antigen.

The amino acid sequences of the alpha-crystallin A and B chains of the dogfish, Squalus acanthias, have been determined. Comparison with alpha-crystallins from other species reveals that charged amino acid replacements have been strongly avoided in the evolution of this lens protein. The homology of alpha-crystallins with the small heat shock proteins is pronounced throughout the major part of the proteins, starting from the position of the first intron in the alpha-crystallin genes, but is also detectable in the amino-terminal sequences of human, Xenopus, and Drosophila small heat shock proteins. In addition, a remarkable short sequence similarity is present only in the amino termini of dogfish alpha B and Drosophila HSP22. The Schistosoma egg antigen p40 turns out to have a tandemly repeated region of homology with the common sequence domain of alpha-crystallins and small heat shock proteins. Comparison of hydropathy profiles indicates the conservation of conformation of the common domains in these three families of proteins. Construction of phylogenetic trees suggests that the alpha A and alpha B genes apparently originated from a single ancestral small heat shock protein gene and indicates that introns have been lost during the evolution of the heat shock protein genes.

Amino Acid Sequence↗
PubMed1985

epsilon-Crystallin, a novel avian and reptilian eye lens protein.

Gel filtration of Peking duck eye lens proteins reveals a component eluting just behind delta-crystallin and comprising approximately 10% of the total soluble protein. The native Mr of this additional component is estimated to be 120000; it appears to be composed of three identical chains of Mr 38000 and pI 7.5. Circular dichroic spectroscopy showed a relatively high alpha-helical content. No immunological cross-reactivity is found with alpha-, beta-, gamma- or delta-crystallins, and partial amino acid sequence determinations likewise failed to reveal any similarity with other known crystallins. We conclude that this protein represents another and novel family of eye lens proteins, for which we propose the designation epsilon-crystallin. epsilon-Crystallin is translated from a 1450-base mRNA, which has been partially purified. epsilon-Crystallin is found scattered among avian and reptilian taxa, but not in other vertebrates. Its rate of evolutionary change seems to be as slow as that of alpha- and beta-crystallins.

Alligators and Crocodiles↗
PubMed1985

alpha-Crystallin A sequences of Alligator mississippiensis and the lizard Tupinambis teguixin: molecular evolution and reptilian phylogeny.

The amino acid sequences of the eye lens protein alpha-crystallin A from many mammalian and avian species, two frog species, and a dogfish have provided detailed information about the molecular evolution of this protein and allowed some useful inferences about phylogenetic relationships among these species. We now have isolated and sequenced the alpha-crystallins of the American alligator and the common tegu lizard. The reptilian alpha A chains appear to have evolved as slowly as those of other vertebrates, i.e., at two to three amino acid replacements per 100 residues in 100 Myr. The lack of charged replacements and the general types and distribution of replacements also are similar to those in other vertebrate alpha A chains. Maximum-parsimony analyses of the total data set of 67 vertebrate alpha A sequences support the monophyletic origin of alligator, tegu, and birds and favor the grouping of crocodilians and birds as surviving sister groups in the subclass Archosauria.

Alligators and Crocodiles↗
PubMed1984

Primary structures of the alpha-crystallin A chains of twenty-eight mammalian species, chicken and frog.

The amino acid sequences of the alpha-crystallin A chains of 28 mammalian species, representing 14 different orders, have been analyzed, mainly on the basis of amino acid compositions of the composing peptides. The alpha A sequences of chicken and a frog have been completely determined by Edman degradation. A method is described to transport eye lenses, to be used for protein sequence studies, at ambient temperature in a solution of guanidine . HCl. The number of cysteine residues in different alpha A chains could be determined by alkaline urea gel electrophoresis after aminoethylation . In some cases the alpha A chains have been isolated from total lens extracts in a single ion-exchange chromatographic step. The average rate of substitutions in the evolution of the alpha A chains is moderately slow, approximately 3 amino acid substitutions per 100 residues in 100 million years, but varies considerably in different lineages. Substitutions involving changes in charge are strongly underrepresented; the alpha A chains tend to keep their net charge constant throughout evolution. Analysis of the types of substitutions suggests a directional trend leading to an increase in functional density of alpha A in the course of evolution.

Amino Acid Sequence↗
PubMed1968

Structural aspects of eye lens polyribosomes.

Epithelial cells and the outer cortex from lenses of 1-day-old calves contain polyribosomes occurring in clusters of five to ten monomers. The structure of these clusters is not affected by trypsin treatment up to 10mug./ml. of ribosomal suspension. When the whole lens is used as starting material the polyribosomal preparations are strongly contaminated with non-ribosomal material, which gives rise to ribosomal aggregates having the appearance of giant polyribosomes. These structures are sensitive to trypsin treatment but resist ribonuclease treatment. The electrophoretic pattern of the contaminating material resembles that of water-soluble lens protein.

Animals↗