Polygalacturonase Isozymes and Pectin Depolymerization in Transgenic rin Tomato Fruit

We have previously described the construction and expression of a chimeric gene that allows developmentally regulated expression of tomato (Lycopersicon esculentum) polygalacturonase in ripening-impaired, mutant (rin) tomato fruit (JJ Giovannoni, D DellaPenna, AB Bennett, RL Fischer [1989] The Plant Cell 1: 53-63). We now show that expression of the chimeric polygalacturonase gene in rin tomato fruit resulted in the accumulation of all three polygalacturonase isozymes (PG1, PG2A, and PG2B). Polyuronide solubilization and polyuronide depolymerization both reached their maximal levels in transgenic rin fruit prior to the appearance of PG2 isozymes. These results demonstrate that PG1, PG2A, and PG2B all arise by differential processing of a single gene product and further suggest that the PG1 isozyme is sufficient to carry out both polyuronide solubilization and depolymerization in vivo.     

Influence of dietary fish on eicosanoid metabolism in man

Two groups of 40 volunteers were given a dietary supplement consisting of 135 g of mackerel or meat (control) paste per day for 6 weeks. Compliance was about 80% in both groups and the daily intake of 20:5(n-3) and 22:6(n-3) from the mackerel supplement was about 1.3 and 2.3 g, respectively. In collagen-activated platelet rich plasma, the potency of blood platelet to produce HHT from arachidonic acid (AA) clearly reduced in the mackerel group, whereas the formation of HHTE from timnodonic acid (TA) increased slightly. Changes in the formation of HHT and HHTE, measured by HPLC, correlated significantly with those of TxB2 and TxB3, respectively, measured by GC/MS. Changes in the formation of the lipoxygenase products HETE (ex AA) and HEPE (ex TA) were qualitatively similar to that seen for the cyclo-oxygenase products, but quantitatively the responses were smaller. Formation of ir TxB2 in clotting blood significantly reduced in the mackerel group. In collagen-activated, citrated whole blood, TxB2 formation tended to be reduced in the mackerel-supplemented volunteers. Mackerel consumption was associated with the formation of considerable amounts of PGI3, as judged from the appearance of 2,3-dinor-delta 17-6-keto-PGF1 alpha in urine. The amount of the major metabolite of PGI2, 2,3-dinor-6-keto-PGF1 alpha was not reduced, or even increased. The daily amount of tetranor prostaglandin metabolites in the urine did not change significantly, which indicates that mackerel supplementation did not alter the formation of prostaglandins E and F.     

Light and scanning electron microscopy of fallow deer (Dama dama) spermatozoa

No basic differences in size (mean +/- s.d. for at least 300 spermatozoa), shape and ultrastructure of the spermatozoa of fallow deer were detected (1) in comparison to other artiodactyls, (2) between different fallow bucks, and (3) between different months of the fertile season. The total length of the normal spermatozoon was 67.2 +/- 1.2 microns. The flat, paddle-shaped head was 8.2 +/- 0.3 microns long, 4.4 +/- 0.2 microns for the greatest width, 1.9 +/- 0.2 microns for basal width and, approximately 0.7 microns in thickness. The tail measurements were 13.7 +/- 0.3 microns for the midpiece, 0.5 +/- 0.1 microns for the diameter of the midpiece, 42.6 +/- 0.9 microns for the principal piece, and 2.7 +/- 0.6 microns for the endpiece. Spermatozoa with abnormalities such as cytoplasmic remnants and droplets, bent and coiled tails, as well as microcephalic forms were observed.     

Neurofibromatosis type 2 appears to be a genetically homogeneous disease

Neurofibromatosis type 2 (NF2) is an autosomal dominant syndrome characterized by the development of vestibular schwannomas and other tumors of the nervous system, including cranial and spinal meningiomas, schwannomas, and ependymomas. The presence of bilateral vestibular schwannomas is sufficient for the diagnosis. Skin manifestations are less common than in neurofibromatosis type 1 (NF1; von Recklinghausen disease). The apparent clinical distinction between NF1 and NF2 has been confirmed at the level of the gene locus by linkage studies; the gene for NF1 maps to chromosome 17, whereas the gene for NF2 has been assigned (in a single family) to chromosome 22. To increase the precision of the genetic mapping of NF2 and to determine whether additional susceptibility loci exist, we have performed linkage analysis on 12 families with NF2 by using four polymorphic markers from chromosome 22 and a marker at the NF1 locus on chromosome 17. Our results confirm the assignment of the gene for NF2 to chromosome 22 and do not support the hypothesis of genetic heterogeneity. We believe that chromosome 22 markers can now be used for presymptomatic diagnosis in selected families. The NF2 gene is tightly linked to the D22S32 locus (maximum lod score 4.12; recombination fraction 0). A CA-repeat polymorphism at the CRYB2 locus was the most informative marker in our families (lod score 5.99), but because the observed recombination fraction between NF2 and CRYB2 was 10 cM, predictions using this marker will need to be interpreted with caution.     

Analysis of catalytic properties of hen egg white lysozyme during renaturation from denatured and reduced material.

Catalytic properties of hen egg white lysozyme were analyzed during the renaturation of the enzyme from completely reduced and denatured material. The formation of intermediate folding products and the generation of native lysozyme was monitored by acetic acid/urea electrophoresis. The results showed that during the beginning of renaturation almost all reduced and denatured lysozyme is converted to forms possessing lower compactness than native lysozyme, probably as a result of formation of only one or two disulfide bonds. Kinetic analysis of lysozyme during renaturation showed that the generation of lysozyme with four disulfide bonds was not necessarily equivalent to the formation lysozyme with native-like catalytic properties. It appeared that the formation rate of the structures of the structures of the substrate binding site and of the catalytic site were limited by the generation of four disulfide bonds containing lysozyme. The catalytic properties of intermediate folding products made it evident that the final structures of the substrate binding site and of the catalytic site were formed after the generation of all disulfide bonds.     

Dissociation of cAMP accumulation and phosphate uptake in opossum kidney (OK) cells with parathyroid hormone (PTH) and parathyroid hormone related protein (PTHrP)

Bovine parathyroid hormone (PTH) 1-34 [bPTH(1-34)] and human PTH related protein [hPTHrP(1-34)] stimulated cAMP accumulation in opossum kidney (OK) cells with Km of 5 x 10(-9) M, but inhibition of phosphate uptake was obtained with 17-fold lower Km of 3 x 10(-10) M. Phosphate uptake was partially inhibited with [Nle8.18Tyr34]bPTH(3-34)NH2 without concomitant cAMP stimulation. With hPTHrP(7-34)NH2, cAMP accumulation was increased in parallel to inhibition of phosphate uptake. [D-Trp12Tyr34]bPTH(7-34)NH2 and [Tyr34]hPTH(7-34)NH2 had no agonist activity on cellular cAMP and inhibition of phosphate uptake. bPTH(1-34)-stimulated cAMP accumulation was antagonized by [Nle8.18Tyr34]bPTH(3-34)NH2, [D-Trp12Tyr34]bPTH(7-34)NH2, hPTHrP(7-34)NH2 and [Tyr34]hPTH(7-34)NH2 with Ki of 1.4 x 10(-7), 2 x 10(-7), 4.7 x 10(-7) and 3.7 x 10(-6) M, respectively. But [Nle8.18Tyr34]bPTH(3-34)NH2 and [D-Trp12Tyr34]bPTH(7-34)NH2 reversed the inhibition of phosphate uptake only marginally, and hPTHrP(7-34)NH2 and [Tyr34]hPTH(7-34)NH2 were inactive. With hPTHrP(1-34) the Ki for cAMP accumulation of [Nle8,18Tyr34]bPTH(3-34)NH2 and hPTHrP(7-34)NH2 were 1.9 x 10(-7) and 7.2 x 10(-7) M, and inhibition of phosphate uptake was partially reversed with [Nle8,18Tyr34]bPTH(3-34)NH2, but not with hPTHrP(7-34)NH2. The present results indicate that truncated hPTHrP(7-34)NH2, unlike [Tyr34]hPTH(7-34)NH2 and [D-Trp12Tyr34]bPTH(7-34)NH2, elevates cellular cAMP and inhibits phosphate uptake. bPTH(1-34)- and hPTHrP(1-34)-evoked cAMP accumulation is suppressed by PTH and PTHrP fragments while inhibition of phosphate uptake remains largely unaltered.     

The photocycle and the structure of iron containing bacteriorhodopsin —a kinetic and Mössbauer spectroscopy investigation

Bacteriorhodopsin (bR), converted by deionization to the blue form was reconstituted to the active purple membrane by the addition of Fe²⁺ or Fe³⁺ ions. ⁵⁷Fe Mossbauer spectra of these samples were measured at different pH values (pH 3.9, pH 5.0 and pH 7.0) and at temperatures ranging from 4 K to 300 K. The hyperfine parameters reveal two iron environments with oxygen atoms in the neighbourhood of iron. Iron type 1 is in the 3⁺ high spin state. It is bound to acid side chains of the protein and/or the phosphate groups of the lipids. Iron type 2 is in the 2⁺ high spin state and is linked to carboxy groups of the protein in a rather unspecific way. Dynamics as measured by Mossbauer spectroscopy show that the purple membrane becomes flexible only above 220 K. At the interface between membrane and bulk water the mobility is comparable to that of proteins with hydrophilic surfaces. The photocycle of Fe ³⁺-bR is slowed down compared to native bR. 3–5 Fe³⁺/bR are sufficient to inhibit the photocycle turnover by one order of magnitude. This specific effect is also found with Cr³⁺, though it is less pronounced. Mössbauer spectra of Fe³⁺-bR at 4 K reveal that iron nuclei are spin-coupled, indicating their close spatial proximity. It is proposed that iron trinuclear clusters interact with the proton uptake site of bR. Offprint requests to: M. Engelhard