Geometric optics of trilobite eyes: a theoretical study of the shape of the aspherical interface in the cornea of schizochroal eyes of phacopid trilobites

A general method is given to determine theoretically the shape of the aspherical interface that eliminates spherical aberration in an optionally shaped thick lens. The theory is applied to trilobite eyes. On the basis of the geometric optical method presented, the refractive indices and focal length of the original corneal lenses of trilobites can be determined. The shape of the aspherical interface in the cornea of some phacopid trilobites with schizochroal eyes is investigated. The theoretical aspherical interfaces agree well with the real ones.     

Histochemical localization of carbonic anhydrase in the testis and epididymis of the rabbit.

The distribution of carbonic anhydrase (CA) was studied in the testis and epididymis of mature, male rabbits using a cobalt precipitation method. CA was found only in the endothelium of the capillaries in the testis. The epididymal duct was divided into initial, middle and terminal segments. Strong cytoplasmic CA was present in the apical cells in the initial and middle segments. Vacuoles with CA staining in the membranes were found in the principal cells in the middle segment. Intensely stained basal cells were present in the terminal segment. In the last part of the terminal segment and the first of the ductus deferens the basolateral cell membranes were also stained. The function of the enzyme is discussed especially in relation to acidification of the epididymal fluid and facilitation of CO2 diffusion.     

Characteristics of NADPH-dependent thymidylate synthetase purified from Streptomyces aureofaciens.

NADPH-dependent thymidylate synthetase from Streptomyces aureofaciens has been purified to homogenity by a two-step chromatographic procedure including anion-exchange chromatography and affinity chromatography on methotrexate-Sepharose 4B. The enzyme was purified 1025-fold with a 34% yield. Basic characteristics of the enzyme were determined: molecular weight of the enzyme subunit (28,000), pH and temperature optimum, effect of cations, dependency on reducing agents, Km values for dUMP, mTHF, and NADPH (3.78, 21.1, and 38.9 microM, respectively), and inhibition effect of 5-FdUMP. Binding studies revealed the enzyme mechanism to be ordered sequential: dUMP bound before mTHF. S. aureofaciens thymidylate synthetase exhibits an absolute requirement for NADPH for the enzyme activity--a unique feature not displayed by any of the thymidylate synthetases isolated so far. NADPH is not consumed during enzyme reaction, indicating its regulatory role. The properties of S. aureofaciens thymidylate synthetase show that it is a monofunctional bacterial enzyme.     

Activity of cat cerebellar neurons in penicillin epilepsy and amphetamine treatment.

The discharge pattern of cerebellar Purkinje cells and fastigial neurons was studied after acute amphetamine treatment in immobilized cats, as well as during generalized penicillin-induced epilepsy. There was a marked reversible decrease in spontaneous firing rate of Purkinje cells and an increase in spontaneous firing rate of fastigial neurons after acute d-1 amphetamine administration (5 mg/kg, s.c.). The discharge pattern of Purkinje cells showed tendency towards inhibition, while the fastigial neurons showed less clear tendency towards disinhibition in the course of epilepsy induced by parenteral administration of penicillin (400.000-500.000 I.U./kg, i.m.). Moreover, acute amphetamine treatment (5 mg/kg, s.c.) performed after the development of penicillin-induced epileptic episodes elicited a prominent suppression of Purkinje cell discharges associated with a parallel increase in discharges of fastigial neurons. These results suggest that the changes in discharge rate of cerebellar corticonuclear neurons induced by amphetamine contribute to suppression of seizural activity in the feline model of generalized epilepsy.     

Site-specific endonucleases LplI and AagI

New site-specific endonucleases LplI and AagI have been isolated from the Lactobacillus plantarum and Achromobacter agile cells, respectively. The enzymes' purification stages included treatment of cell-free extracts with polyethylenimine, fractionation in two-phase system by Albertsson's method, chromatography on blue Sepharose and DEAE-cellulose. The results of cleavage of a 5'-32P-labelled oligodeoxynucleotide duplex by restriction endonucleases LplI and AagI indicate that these enzymes recognize and cut the sequence AT decreases CGAT, being therefore true isoschizomers of the ClaI restriction endonuclease from Caryophanon latum. The L. plantarum strain has 400 fold endonuclease productivity as compared with the ClaI producent and is perspective for preparative isolation of LplI.     

Role of Staphylococcus saprophyticus in human infection.

Biological properties of Staphylococcus saprophyticus strains isolated from urinary tract infection and respiratory tract secretions were investigated. The majority of S. saprophyticus strains exhibit moderate surface hydrophobic properties, as measured by Hydrophobic Interaction Chromatography. There was no significant difference between two groups of isolates in respect to electrostatic charge. It was found that the ability to form a diffuse type of growth is characteristic for most of S. saprophyticus strains despite of source of isolation. Five carbohydrates on the surface of 25% of S. saprophyticus strains were shown by means of specific lectin agglutination. Some of the tested strains were capable to bind labelled fibrinogen.     

Effect of cooling rate,cryoprotectant and holding time at different transfer temperatures on the survival of cryopreserved cell suspension culture (Puccinellia distans (L.) Parl.)

Reflexed saltmarsh-grass suspension cultures produced by seed callus were frozen to the liquid nitrogen temperature. Cooling rates, cryoprotectants and holding times were taken as a function of transfer temperatures. The highest survival of cells (45%) was found at a freezing rate of 1°C min^-1, without cryoprotectant treatments. The cryoprotectants (proline, dimethyl sulphoxide, glycerol), used at different concentrations and transfer temperatures, increased the survival rate. The maximum value was 78% at 12.5% (w/v) of proline with –30°C transfer temperature. Considerable improvement of viability (from 0% to 95%) among the 12.5 and 15.0% (v/v) dimethyl sulphoxide cryopreserved cells was achieved by holding them at – 20°C for 10–30 min before plunging into the liquid nitrogen. A 20 min holding time at 15.0% (v/v) glycerol level and – 30°C transfer temperature significantly enhanced the viability of the explants from 42% to 92%. Plants were successfully regenerated from cells cryopreserved with proline (w/v) and dimethyl sulfoxide (v/v) levels of 12.5 and 15.0%, respectively.     

Thymopentin antagonizes stress-induced changes of GABA/benzodiazepine receptor complex

Intraperitoneal administration of thymopentin, a thymopentin II-derived pentapeptide, had no stable and evident effect in the two anxiety models (elevated plus-maze and licking-conflict test) studied. However, in the elevated plus-maze test thymopentin antagonized the behavioral effects of DMCM, a beta-carboline derivative with anxiogenic properties. Further, it was demonstrated that the licking-conflict test procedure itself produced a significant elevation of plasma corticosterone levels, increased the number of [3H]flunitrazepam and decreased the number of [3H]muscimol binding sites in rat hippocampus. The forced-swimming stress similarly to the licking-conflict test also caused an increase in hippocampal [3H]flunitrazepam binding sites. Although ineffective behaviorally in the tests for anxiety, thymopentin pretreatment effectively reversed the changes in corticosterone levels caused by the licking-conflict test. Moreover, it normalized the changed number of benzodiazepine and GABA receptors after stressful stimuli. It is well known that not all anxiolytic drugs (i.e. buspirone) are equally active in behavioral tests for anxiety. According to our data we propose that thymopentin has stress-protective activity. As in vivo and in vitro thymopentin did not change [3H]-flunitrazepam and [3H]muscimol binding, the direct effect of this peptide on the GABA-benzodiazepine-Cl- ionophore receptor complex is unlikely. The action of this peptide on GABA release and/or metabolism can be suggested.     

Studies on the total synthesis of an A7,B7-dicarbainsulin. III. Assembly of segments and generation of biological activity

As a further contribution to the synthesis of an insulin analogue with a stable A7-B7 interchain bond, the synthesis of A(8-21) by solution methods, and of B(9-25) as well as [7-(2,7-diaminosuberic acid)]B(1-8) by solid phase methods is described. In the latter compound, the amino group of the diaminosuberic acid residue was acylated with A(1-6), and the resulting "U-peptide" sequentially elongated with the C-terminal A- and finally B-chain sequences. The conversion of the product into the disulfide moiety gave a mixture which could not be resolved by currently available methods. However, the low biological activity of the crude product indicates that the A7-B7 disulfide bond is not crucially important for the activity of insulin.