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G Weber

Publications and source records attributed to G Weber.

At least 595 records · Page 33Linked to original sources
PubMed1980

Nanosecond segmental mobilities of tryptophan residues in proteins observed by lifetime-resolved fluorescence anisotropies.

Steady-state and lifetime-resolved fluorescence anisotropy measurements of protein fluorescence were used to investigate the depolarizing motions of tryptophan residues in proteins. Lifetime resolution was achieved by oxygen quenching. The proteins investigated were carbonic anhydrase, carboxypeptidase A, alpha-chymotrypsin, trypsin, pepsin, and bovine and human serum albumin. When corrected for overall protein rotation, the steady state anisotropies indicate that, on the average, the tryptophan residues in these proteins rotate 29 degrees +/- 6 degrees during the unquenched excited state lifetimes of these proteins, which range from 1.7 to 6.1 ns. The lifetime-resolved anisotropies reveal correlation times for these displacements ranging from 1 to 12 ns. On the average these correlation times are tenfold shorter than that expected for overall protein rotation. We conclude that the tryptophan residues in these proteins display remarkable freedom of motion within the protein matrix, which implies that these matrices are highly flexible on the nanosecond time scale.

Animals↗
PubMed1980

[Ultrastructure and cytochemistry of the pellicle and apical complexes of the kinete of Babesia bigemina and Babesia ovis in the hemolymph and oavry of the tick].

The term kinete is used in this paper for the cigar-shaped, motile development stages (VERMICULE") OF Babesia occurring intra- and extracellularly in hemolymph and overy (including oocytes) of vectors, hard ticks (Ixodoidea). The structure of, and cytochemical activities of hydrolases (acid phosphatase, nonspecific esterase) in the pellicle and the apical complex was studied at the fine-structural level in kinetes of Babesia bigemina Smith & Kilborne, in hemolympho of female Boophilus microplus Canestrini. The cytochemistry of acid hydrolases was studied also in kinetes of Babesia ovis (Babès) Starcovici, in hemolymph and ovary of Rhipicephalus bursa Canestrini & Fanzago. The pellicle of the B. bigemina kinetes is composted of 3 membranes (pellicular complex): an outer membrane, approximately 8 nm thick (the plasmalemma) and 2 innder ones, each approximately nm thick, lying closely together. The outer membrane appears to be covered by a structureless coat, 3 nm thick. The space between the inner double membrane and the plasmalemma is 7.5 nm. The whole pellicular complex is 30 nm in diameter. The 2 inner pellicular membranes appear to be derived from the endoplasmic reticulum (ER) for the following reasons: (a) a layer of hydrolase-active material is enclosed by these membranes; (b) in the spheroid parasite stages which transform from kinetes inside hemocytes, the inner double membrane is apparently replaced by an ER cisterna; (c) the thickness of each of the inner pellicular membranes is approximately the same as that of the ER membrane. There are circular openings in the pellicular double membrane with average diameters of 100 nm; despite some similarity to micropores, they have a specific structure. The term Intrapellikularfenster (IPF) (intrapellicular windows) or pseudomicropores is proposed for these pellicular differentiations. The margin of an IPF is formed by the 2 inner membranes folding into each other; cytoplasmic, electron-dense material is accumulated alongside this edge. Unlike that of micropores, the plasmalemma of the IPF is not invaginated. The IPF appears as a single, dark ring in tangential sections. At times, rhoptry-like bodies are associated with the openings. The function of the IPF is not known. An intrapellicular opening similar to the IPF, although wider, is present at the apex of the parasite. Its margin coincides with the inners edge of the apical ring. Typical subpellicular microtubuli were not observed in the Babesia kinetes. The apical complex of the B. bigemina kinetes consists of an Apikalschirm (apical umbrella), a crown of microtubuli beneath it, and rhoptries: micronemes are also present in large numbers. The Apikalschirm is located beneath the pellicle of the apical pole of the parasite. It is a wheel-like structure composed of spokes radiating from a wide, hub=like central ring (apical ring). It should be stressed that the apical ring is not identical with the polar ring described as an integral part of the pellicular complex in other Apicomplexa...

Acid Phosphatase↗
PubMed1980

Recent advances in the design of anticancer chemotherapy.

Recent advances in the rational design of anticancer chemotherapy in this laboratory have been based on strategic differences between normal and cancer cells. On the basis of our identification of quantitative biochemical markers and characteristic enzymic and metabolic programs of neoplastic cells, we have designed single and combination drug treatments. This chemotherapeutic approach aims at specific enzymic targets in cancer cells that are closely linked with transformation and progression. With the identification of markedly increased concentrations of CTP, dATP, dGTP, dCTP and dTTP in neoplasms, there should be an operational advantage in directing chemotherapy to depress the concentration of these metabolites elevated in cancer cells, because a drug-imposed curtailment of these metabolites might destroy cancer cells that depend more stringently on the increased concentrations of these nucleotides. Experiments in tissue culture and in solid tumors utilizing treatment schedules with pyrazofurin in combination with galactosamine, and the use of adriamycin, succeeded in achieving profound alterations in the nucleotide concentrations of cancer cells.

Amides↗
PubMed1980

Key enzymes and tumor cell heterogeneity.

Tumor heterogeneity is reflected in many aspects of cancer cells, including morphology, biology, drug responsiveness and biochemistry. The basis of the transformation- and progression-linked biochemical imbalance in cancer cells was revealed to be due to an imbalance in the activity, amount and isozyme pattern of key enzymes. The key enzymes, particularly those in the biosynthetic pathways of purine and pyrimidine metabolism, were identified as sensitive targets of experimental and clinical anticancer drugs. The concept of key enzymes as regulatory elements and targets of chemotherapy led to the design of enzyme-pattern-targeted anticancer chemotherapy approaches.

Adenylosuccinate Lyase↗
PubMed1980

Hereditary factors in sleepwalking and night terrors.

The families of 25 probands with sleepwalking and 27 probands with night terrors were studied. Eighty per cent of the sleepwalking pedigrees and 96 per cent of the night terror pedigrees included one or more individuals, other than the proband, who were affected by sleepwalking, night terrors, or both. Our data appear to fit a 'two threshold' multifactorial mode of inheritance. This finding supports the hypothesis that sleepwalking and night terrors share a common genetic predisposition, with sleepwalking being a more prevalent and less severe manifestation of the same substrate that underlies night terrors. Heritable factors predispose an individual to develop sleepwalking and/or night terrors, but expression of the trait may be influenced by environmental factors.

Female↗
PubMed1980

Ultrastructural demonstration of succinic dehydrogenase and cytochrome oxidase activity in sporozoites of Babesia ovis and Theileria annulata (Apicomplexa: Piroplasmea) in salivary glands of tick vectors (Rhipicephalus bursa, Hyalomma anatolicum excavatum).

Salivary gland stages ("sporozoites") of Babesia ovis and Theileria annulata (Apicomplexa: Piroplasmea) in female ixodid ticks were studied for ultracytochemical activity of the respiratory enzymes, succinic dehydrogenase (SDH), and cytochrome oxidase. Both SDH and cytochrome oxidase were demonstrated in the sporozoites and the mitochondria in these stages. Identified in this way the final reaction product of SDH was located mainly at the inner side of the mitochondrial boundary, though it was also visible in the internal space of the organelle. Cytochrome oxidase activity always was confined to the wall of mitochondria. This enzyme was demonstrated also in the erythrocyte stage of B. ovis. The cytochemical results indicate respiratory potential of the piroplasmean stages studied. Cristate or typical protozoan mitochondria have not been observed in sporozoites of Babesia or Theileria. This report is the first demonstration of mitochondria, or mitochondrialike activity in Babesia.

Animals↗