Accurate mapping of the “acid meat” RN gene on genetic and physical maps of pig Chromosome 15

It has been shown that a major gene, called RN, is responsible for the RTN technological yield, a meat quality porcine trait. Experimental families informative for the segregation of RN gene were constituted from animals belonging to the Laconie composite line. We have previously mapped the RN gene to Chromosome (Chr) 15 (Milan et al. Genet. Sel. Evol. 27, 195–199, 1995). A Chr 15 map was established with 16 markers. The RN gene was found to be located between markers Sw120 and Sw936, at 2 cM from Sw936 (LOD = 38.1). In addition, by localizing Sw936 at 15q21–22 using DISC-PCR, we also located RN on the physical map. Received: 25 April 1995 / Accepted:     

Cardiac and skeletal muscle troponin I isoforms are encoded by a dispersed gene family on mouse Chromosomes 1 and 7

We mapped the locations of the genes encoding the slow skeletal muscle, fast skeletal muscle, and cardiac isoforms of troponin I (Tnni) in the mouse genome by interspecific hybrid backcross analysis of species-specific (C57BL/6 vs Mus spretus) restriction fragment length polymorphisms (RFLPs). The slow skeletal muscle troponin I locus (Tnni1) mapped to Chromosome (Chr) 1. The fast skeletal muscle troponin I locus (Tnni2), mapped to Chr 7, approximately 70 cM from the centromere. The cardiac troponin I locus (Tnni3) also mapped to Chr 7, approximately 5–10 cM from the centromere and unlinked to the fast skeletal muscle troponin I locus. Thus, the troponin I gene family is dispersed in the mouse genome. Received: 10 May 1995 / Accepted: 1 September 1995     

A rat homolog of the mouse deafness mutant jerker (je)

An autosomal recessive deafness mutant was discovered in our colony of Zucker (ZUC) rats. These mutants behave like shaker-waltzer deafness mutants, and their inner ear pathology classifies them among neuroepithelial degeneration type of deafness mutants. To determine whether this rat deafness mutation (−) defines a unique locus or one that has been previously described, we mapped its chromosomal location. F₂ progeny of (Pbrc:ZUC × BN/Crl) A/a B/b H/h+/− F₁ rats were scored for coat color and behavioral phenotypes. Segregation analysis indicated that the deafness locus might be loosely linked with B on rat Chromosome (Chr) 5 (RNO5). Therefore, 40 −/− rats were scored for BN and ZUC alleles at four additional loci, D5Mit11, D5Mit13, Oprd1, and Gnb1, known to map to RNO5 or its homolog, mouse Chr 4 (MMU4). Linkage analysis established the gene order (cM distance) as D5Mit11–(19.3)–B–(17.9)–D5Mit13–(19.2)–Oprd1–(21.5) − (1.2) Gnb1, placing the deafness locus on distal RNO5. The position of the deafness locus on RNO5 is similar to that ofjerker (je) on MMU4; the phenotypes and patterns of inheritance of the deafness mutation and je are also similar. It seems likely that the mutation affects the rat homolog of je. The rat deafness locus should, therefore, be named jerker and assigned the gene symbol Je. Received: 13 June 1995 / Accepted: 4 January 1996     

Microsatellite mapping of the bovine roan locus: A major determinant of White Heifer Disease

In the Belgian Blue Cattle breed, coat color variation is mainly under the influence of a single autosomal locus, the roan locus, characterized by a pair of codominant alleles: r ⁺ (black) and R (white). Heterozygous r ⁺ R animals have intermingled black and white hairs, yielding the ``blue' phenotype typical of the breed. Major interest for the roan locus stems from its pleiotropic effect on fertility, owing to the critical role of the R allele in the determinism of White Heifer Disease. We describe the linkage mapping of the roan locus to bovine Chromosome (Chr) 5, in the interval between microsatellite markers BPI and AGLA293, with an associated lodscore of 11.2. Moreover, we map a candidate gene, the Steel locus coding for the mast cell growth factor, to bovine Chr 5. Received: 30 May 1995 / Accepted: 6 September 1995     

RAPD linkage mapping of the shell thickness locus in oil palm (Elaeis guineensis Jacq.)

Shell thickness is an important trait in oil palm breeding programs and is the basis for the classification of the varieties of oil palm into the types dura, tenera and pisifera. This trait seems to be controlled by a single locus, with two alleles (sh ⁺ and sh ⁻) showing codominant expression. Two single-tree linkage maps were constructed for a maternal tenera (sh ⁺ sh ⁻) palm and for a paternal pisifera (sh ⁻ sh ⁻) palm using the pseudo-testcross mapping strategy in combination with RAPD markers through the analysis of an F₁ tenera×pisifera progeny. A total of 308 arbitrary primers were screened in a sample of eight F₁ plants and 121 markers were detected in a testcross configuration. An average of 1.66 polymorphic marker per selected primer were identified in this cross. At LOD 5.0 (with some few exceptions) and θ=0.25 the maternal tenera map included a total of 48 markers distributed in 12 linkage groups or pairs of markers (449.3 cM) while the paternal pisifera map included 42 markers distributed in 15 linkage groups or pairs of markers (399.7 cM). We used RAPD and bulked segregant analysis (BSA) to identify markers more tightly linked to the sh ⁺ locus. A total of 174 new primers not previously used in the linkage analysis were screened using bulks of DNA extracted from plants selected for the contrasting shell-thickness phenotypes. Two RAPD markers (R11–1282 and T19–1046) were identified to be linked on both sides of the sh ⁺ locus on linkage group 4. The estimated map distances from sh ⁺ to R11–1282 and to T19–1046 were 17.5 cM and 23.9 cM, respectively. The results demonstrate the usefulness of RAPD markers and the pseudo-testcross mapping strategy for developing genetic linkage information, and constitute an important step towards early marker-assisted selection for shell thickness in oil palm. Received: 21 February 1999 / Accepted: 29 April 1999     

Single-Channel Analysis of a Delayed Rectifier K+ Channel in Xenopus Myelinated Nerve

Single-channel properties of a delayed rectifier voltage-gated K⁺ channel (I-type) were investigated in peripheral myelinated axons from Xenopus laevis. Channels activated between −60 and −40 mV with a potential of half-maximal activation, E₅₀, at −47.5 mV. Averaged single-channel currents activated with a time delay at all membrane potentials tested. Time to half-maximal activation decreased from 80 to 1.6 msec between −60 and +40 mV. The channel inactivated monoexponentially with a time constant of 10.9 sec at −40 mV. The time constant of deactivation was 126 msec at −80 mV and 16.9 msec at −110 mV. In symmetrical 105 mm K⁺, the single-channel conductance (γ) was 22 and 13 pS at negative and positive membrane potentials, respectively, at 13–15°C. In Na⁺-rich solution with 2.5 mm extracellular K⁺γ was 7 pS and the reversal potential was negative to −80 mV, indicating a high selectivity for K⁺ over Na⁺. γ depended on extracellular K⁺ concentration (K _D = 19.6 mm) and temperature (Q ₁₀= 1.45). External tetraethylammonium (TEA) reduced the apparent single-channel current amplitude at all potentials tested with a half-maximal inhibiting concentration (IC₅₀) of 0.6 mm. Open probability of the channel, but not single-channel current amplitude was decreased by extracellular dendrotoxin (DTX, IC₅₀= 6.8 nm) and mast cell degranulating peptide (MCDP, IC₅₀= 41.9 nm). In Ringer solution the membrane potential of macroscopic I-channel patches was about −65 mV and depolarized under TEA and DTX. It is concluded that besides their activation during action potentials, I-channels may also stabilize the resting membrane potential. Received: 2 June 1995/Revised: 13 October 1995     

High-resolution mapping of a linkage group on mouse chromosome 8 conserved on human chromosome 16Q

We have performed a high-resolution linkage analysis for the conserved segment on distal mouse Chromosome (Chr) 8 that is homologous to human Chr 16q. The interspecific backcross used involved M. m. molossinus and an M. m. domesticus line congenic for an M. spretus segment from Chr 8 flanked by phenotypic markers Os (oligosyndactyly) and e, a coat colormarker. From a total of 682 N₂ progeny, the 191 animals revealing a recombination event between these phenotypic markers were typed for 23 internal loci. The following locus order with distances in cM was obtained: (centromere)–Os–4.1–Mmp2–0.2–Ces1,Es1, Es22–1.2–Mt1,D8Mit15–2.2–Got2, D8Mit11–3.7–Es30–0.3–Es2, Es7–0.9–Ctra1,Lcat–0.3–Cdh1, Cadp, Nmor1, D8Mit12–0.2–Mov34–2.5–Hp,Tat–0.2–Zfp4–1.6–Zfp1,Ctrb–10.9–e. In a separate interspecific cross involving 62 meioses, Dpep1 was mapped together with Aprt and Cdh3 at 12.9 cM distal to Hp, Tat, to the vicinity of e. Our data give locus order for markers not previously resolved, add Mmp2 and Dpep1 as new markers on mouse Chr 8, and indicate that Ctra1 is the mouse homolog for human CTRL. Comparison of the order of 17 mouse loci with that of their human homologs reveals that locus order is well conserved and that the conserved segment in the human apparently spans the whole long arm of Chr 16. Received: 30 July 1996 / Accepted: 15 November 1996     

Cloning and functional characterization of a cation–chloride cotransporter gene <Emphasis Type="Italic">OsCCC1</Emphasis>

Potassium (K⁺) and chloride (Cl⁻) are two essential elements for plant growth and development. While it is known that plants possess specific membrane transporters for transporting K⁺ and Cl⁻, it remains unclear if they actively use K⁺-coupled Cl⁻ cotransporters (KCC), as used in animals, to transport K⁺ and Cl⁻. We have cloned an Oryza sativa cDNA encoding for a member of the cation–Cl⁻ cotransporter (CCC) family. Phylogenetic analysis revealed that plant CCC proteins are highly conserved and that they have greater sequence similarity to the sub-family of animal K⁺–Cl⁻ cotransporters than to other cation–Cl⁻ cotransporters. Real-time PCR revealed that the O. sativa cDNA, which was named OsCCC1, can be induced by KCl in the shoot and root and that the expression level was higher in the leaf and root tips than in any other part of the rice plant. The OsCCC1 protein was located not only in onion plasma membrane but also in O. sativa plasma membrane. The OsCCC1 gene-silenced plants grow more slowly than wild-type (WT) plants, especially under the KCl treatment regime. After 1 month of KCl treatment, the leaf tips of the gene-silenced lines were necrosed. In addition, seed germination, root length, and fresh and dry weight were distinctly lower in the gene-silenced lines than in WT plants, especially after KCl treatment. Analysis of Na⁺, K⁺, and Cl⁻ contents of the gene-silenced lines and WT plants grown under the NaCl and KCl treatment regimes revealed that the former accumulated relatively less K⁺ and Cl⁻ than the latter but that they did not differ in terms of Na⁺ contents, suggesting OsCCC1 may be involved in K⁺ and Cl⁻ transport. Results from different tests indicated that the OsCCC1 plays a significant role in K⁺ and Cl⁻ homeostasis and rice plant development.     

Comparison between the three porcine RN genotypes for growth,carcass composition and meat quality traits

A three-step experimental design has been carried out to add evidence about the existence of the RN gene, with two segregating alleles RN^- and rn⁺, having major effects on meat quality in pigs, to estimate its effects on production traits and to map the RN locus. In the present article, the experimental population and sampling procedures are described and discussed, and effects of the three RN genotypes on growth and carcass traits are presented. The RN genotype had no major effect on growth performance and killing out percentage. Variables pertaining to carcass tissue composition showed that the RN^- allele is associated with leaner carcasses (about 1 s.d. effect without dominance for back fat thickness, 0.5 s.d. effect with dominance for weights of joints). Muscle glycolytic potential (GP) was considerably higher in RN^- carriers, with a maximum of a 6.85 s.d. effect for the live longissimus muscle GP. Physico-chemical characteristics of meat were also influenced by the RN genotype in a dominant way, ultimate pH differing by about 2 s.d. between homozygous genotypes and meat colour by about 1 s.d. Technological quality was also affected, with a 1 s.d. decrease in technological yield for RN^- carriers. The RN genotype had a more limited effect on eating quality. On the whole, the identity between the acid meat condition and the RN^- allele effect is clearly demonstrated (higher muscle GP, lower ultimate pH, paler meat and lower protein content), and the unfavourable relationship between GP and carcass lean to fat ratio is confirmed.     

The effect of thidiazuron level on in vitro regeneration type and peroxidase profile in <Emphasis Type="Italic">Eucalyptus microtheca</Emphasis> F. Muell

The green twigs of 1-year-old Eucalyptus microtheca F. Muell seedlings were cultured on modified MS medium, supplemented with α-naphthalene acetic acid (NAA) and kinetin (Kin) hormones at 12 different concentrations. After 4 weeks, the combination of 1 mg l⁻¹ NAA + 1 mg l⁻¹ Kin induced the highest number of axillary shoots. Meanwhile, embryogenic calli were observed in media containing 4 mg l⁻¹ NAA + 0.5 mg l⁻¹ Kin, without any regeneration. The hormone treatments were followed by subculturing the twigs in different levels of thidiazuron (TDZ). The combination of 1 mg l⁻¹ NAA + 1 mg l⁻¹ Kin together with 0.01 mg l⁻¹ TDZ resulted in an increase of direct shoot, while higher amounts of TDZ led to adventitious shoot induction. Somatic embryogenesis was observed in the treatment containing 0.01 mg l⁻¹ TDZ + 4 mg l⁻¹ NAA + 0.5 mg l⁻¹Kin. The peroxidase (POD) band patterns in regenerated plantlets were investigated in order to determine the effect of different levels of TDZ on loci synthesis. A dimer locus, a tetramer locus and two epigenetic bands (a new band for NAA + Kin and the other for TDZ) were observed in the POD profiles. In case of low (0.01 mg l⁻¹ and 0.1 mg l⁻¹) levels of TDZ, one heterozygote allele was disappeared from dimer locus, while at higher TDZ levels, the dimer locus lost its stability and tetramer locus showed a high activity. Thus, POD allele patterns seems to be a feasible marker for different types of regeneration.     

Osmoregulation in juvenile and adult white sturgeon,Acipenser transmontanus

Synopsis Blood samples from cannulated young adult (2.5–15 kg) white sturgeon, acclimated to San Francisco Bay water (24 ppt) had plasma values of 248.8 ± 13.5 mOsm kg⁻¹ H₂O, [Na⁺] = 125 ± 8.0 mEq 1⁻¹, [K⁺] = 2.6 ± 0.8 mEq 1⁻¹ and [CL⁻] = 122 ± 3.0 mEq 1⁻¹. Freshwater acclimated sturgeon had an osmolality of 236 ± 7, [Na⁺] = 131.6 + 4.4, [K⁺] = 2.5 ± 0.7 and [CL⁻] = 110.6 ± 3.6. Freshwater acclimated fish gradually exposed to sea water (increase of 5 ppt h⁻¹) had higher plasma osmolalities than did the bay water acclimated fish. These young adult sturgeon are able to tolerate transfer from fresh water to sea water as well as gradual transfer from sea water to fresh water. Plasma electrolytes in transferred fish are regulated, but tend to differ from long term acclimated fish at the same salinities. There is a gradual increase in the upper salinity tolerance (abrupt transfer) of juvenile white sturgeon with weight: 5–10 ppt for 0.4–0.9 g fish, 10–15 ppt for 0.7–1.8 g fish, and 15 ppt for 4.9–50.0 g fish. The ability of juveniles to regulate plasma osmolality is limited. The young adult fish are able to tolerate higher salinities (35 ppt) than juvenile sturgeon but probably are also characterized by low activity of the necessary ion exchange mechanisms in the gills which permit rapid adjustment of blood electrolytes with graduate change in external salinity.     

Effects of 3 days of carbohydrate supplementation on muscle glycogen content and utilisation during a 1-h cycling performance

This study compared the effects of supplementing the normal diets of six trained cyclists [maximal oxygen uptake O_2max) 4.5 (0.36)l · min⁻¹; values are mean (SD)] with additional carbohydrate (CHO) on muscle glycogen utilisation during a 1-h cycle time-trial (TT). Using a randomised crossover design, subjects consumed either their normal diet (NORM) for 3 days, which consisted of 426 (137) g · day⁻¹ CHO [5.9 (1.4) g · kg⁻¹ body mass (BM)], or additional CHO (SUPP) to increase their intake to 661 (76) g · day⁻¹ [9.3 (0.7) g · kg⁻¹ BM]. The SUPP diet elevated muscle glycogen content from 459 (83) to 565 (62) mmol · kg⁻¹ dry weight (d.w.) (P < 0.05). However, despite the increased pre-exercise muscle glycogen stores, there was no difference in the distance cycled during the TT [40.41 (1.44) vs 40.18 (1.76) km for NORM and SUPP, respectively]. With NORM, muscle glycogen declined from 459 (83) to 175 (64) mmol · kg⁻¹ d.w., whereas with SUPP the corresponding values were 565 (62) and 292 (113) mmol · kg⁻¹ d.w. Accordingly, both muscle glycogen utilisation [277 (64) vs 273 (114) mmol · kg⁻¹ d.w.] and total CHO oxidation [169 (20) vs 165 (30) g · h⁻¹ for NORM and SUPP, respectively] were similar. Neither were there any differences in plasma glucose or lactate concentrations during the two experimental trials. Plasma glucose concentration averaged 5.5 (0.5) and 5.6 (0.6) mmol · l⁻¹, while plasma lactate concentration averaged 4.4 (1.9) and 4.4 (2.3) mmol · l⁻¹ for NORM and SUPP, respectively. The results of this study show that when well-trained subjects increase the CHO content of their diet for 3 days from 6 to 9 g · kg⁻¹ BM there is only a modest increase in muscle glycogen content. Since supplementary CHO did not improve TT performance, we conclude that additional CHO provides no benefit to performance for athletes who compete in intense, continuous events lasting 1 h. Furthermore, the substantial muscle CHO reserves observed at the termination of exercise indicate that whole-muscle glycogen depletion does not determine fatigue at this exercise intensity and duration. Accepted: 25 November 1996     

The pea ( Pisum sativum L.) genes sym33 and sym40 control infection thread formation and root nodule function

Two novel non-allelic mutants that were unable to fix nitrogen (Fix⁻) were obtained after EMS (ethyl methyl sulfonate) mutagenesis of pea (Pisum sativum L.). Both mutants, SGEFix⁻–1 and SGEFix⁻–2, form two types of nodules: SGEFix⁻–1 forms numerous white and some pink nodules, while mutant SGEFix⁻–2 forms white nodules with a dark pit at the distal end and also some pinkish nodules. Both mutations are monogenic and recessive. In both lines the manifestation of the mutant phenotype is associated with the root genotype. White nodules of SGEFix⁻–1 are characterised by hypertrophied infection threads and infection droplets, mass endocytosis of bacteria, abnormal morphological differentiation of bacteroids, and premature degradation of nodule symbiotic structures. The structure of the pink nodules of SGEFix⁻–1 does not differ from that of the parental line, SGE. White nodules of SGEFix⁻–2 are characterised by “locked” infection threads surrounded with abnormally thick plant cell walls. In these nodules there is no endocytosis of bacteria into host-cell cytoplasm. The pinkish nodules of SGEFix⁻–2 are characterised by virtually undifferentiated bacteroids and premature degradation of nodule tissues. Thus, the novel pea symbiotic genes, sym40 and sym33, identified after complementation analysis in SGEFix⁻–1 and SGEFix⁻–2 lines, respectively, control early nodule developmental stages connected with infection thread formation and function. Received: 12 June 1998 / Accepted: 25 June 1998     

Evaluation of ammonium and phosphate release from intertidal and subtidal sediments of a shallow coastal lagoon (Ria Formosa – Portugal): a modelling approach

During an annual cycle, overlying water and sediment cores were collected simultaneously at three sites (Tavira, Culatra and Ramalhete) of Ria Formosa’s intertidal muddy and subtidal sandy sediments to determine ammonium, nitrates plus nitrites and phosphate. Organic carbon, nitrogen and phosphorus were also determined in superficial sediments. Ammonium and phosphate dissolved in porewater were positively correlated with temperature (P < 0.01) in muddy and sandy sediments, while the nitrogen-oxidized forms had a negative correlation (P < 0.02) in muddy sediments probably because mineralization and nitrification/denitrification processes vary seasonally. Porewater ammonium profiles evidenced a peak in the top-most muddy sediment (380 μM) suggesting higher mineralization rate when oxygen is more available, while maximum phosphate concentration (113 μM) occurred in the sub-oxic layer probably due to phosphorus desorption under reduced conditions. In organically poor subtidal sandy sediments, nutrient porewater concentrations were always lower than in intertidal muddy sediments, ranging annually from 20 μM to 100 μM for ammonium and from 0.05 μM to 16 μM for phosphate. Nutrient diffusive fluxes predicted by a mathematical model were higher during summer, in both muddy (104 nmol cm⁻² d⁻¹––NH₄⁺; 8 nmol cm⁻² d⁻¹––HPO₄⁻²) and sandy sediments (26 nmol cm⁻² d⁻¹––NH₄⁺; 1 nmol cm⁻² d⁻¹––HPO₄⁻²), while during lower temperature periods these fluxes were 3–4 times lower. Based on simulated nutrient effluxes, the estimated annual amount of ammonium and phosphate exported from intertidal areas was three times higher than that released from subtidal areas (22 ton year⁻¹––NH₄⁺; 2 ton year⁻¹––HPO₄⁻²), emphasizing the importance of tidal flats to maintain the high productivity of the lagoon. Global warming scenarios simulated with the model, revealed that an increase in lagoon water temperature only produces significant variations (P < 0.05) for NH₄⁺ in porewater and consequent diffusive fluxes, what will probably affect the system productivity due to a N/P ratio unbalance.     

Components of depolarization-induced transmembrane ion current in isolated smooth muscle cells of the guinea pigtaenia coli

Transmembrane ion currents in isolated single smooth muscle cells (SMC) from the guinea pigtaenia coli were investigated using a whole-cell mode of the patch-clamp technique. Currents induced by depolarizing shifts in the membrane potential from its holding level of −60 mV contained an initial inward phase (Ca²⁺ current), which in 30–40 msec was followed by an outward phase. It was shown that outward current was carried by K ions and consisted at least of three components: one Ca²⁺-independent K⁺ current of delayed rectifier (KV) and two Ca²⁺-dependent K⁺ currents. The latter can be further divided into the apamin-sensitive (SK) and charybdotoxin-sensitive (BK) currents. It was found that relative contributions of these three components in total outward current at 0 mV were 35–45%, 5–15%, and 45–55% for KV, SK, and BK currents, respectively. A potential-dependent current carried by Ci ions was also found. This Cl⁻ current had inward direction within the range of potentials below the chloride equilibrium potential (E _Cl) and outward direction above theE _Cl. The magnitude of Cl⁻ current was significantly lower than the magnitude of total K⁺ current.     

Role of MMP-2 in PKCδ-mediated inhibition of Na+ dependent Ca2+ uptake in microsomes of pulmonary smooth muscle: Involvement of a pertussis toxin sensitive protein

Treatment of bovine pulmonary artery smooth muscle with the O₂^•− generating system hypoxanthine plus xanthine oxidase stimulated MMP-2 activity and PKC activity; and inhibited Na⁺ dependent Ca²⁺ uptake in the microsomes. Pretreatment of the smooth muscle with SOD (the O₂^•− scavenger) and TIMP-2 (MMP-2 inhibitor) prevented the increase in MMP-2 activity and PKC activity, and reversed the inhibition of Na⁺ dependent Ca²⁺ uptake in the microsomes. Pretreatment with calphostin C (a general PKC inhibitor) and rottlerin (a PKCδ inhibitor) prevented the increase in PKC activity and reversed O₂^•− caused inhibition of Na⁺ dependent Ca²⁺ uptake without causing any change in MMP-2 activity in the microsomes of the smooth muscle. Treatment of the smooth muscle with the O₂^•− generating system revealed, respectively, 36 kDa RACK-1 and 78 kDa PKCδ immunoreactive protein profile along with an additional 38 kDa immunoreactive fragment in the microsomes. The 38 kDa band appeared to be the proteolytic fragment of the 78 kDa PKCδ since pretreatment with TIMP-2 abolished the increase in the 38 kDa immunoreactive fragment. Co-immunoprecipitation of PKCδ and RACK-1 demonstrated O₂^•− dependent increase in PKCδ-RACK-1 interaction in the microsomes. Immunoblot assay elicited an immunoreactive band of 41 kDa G_iα in the microsomes. Treatment of the smooth muscle tissue with the O₂^•− generating system causes phosphorylation of G_iα in the microsomes and pretreatment with TIMP-2 and rottlerin prevented the phosphorylation. Pretreatment of the smooth muscle tissue with pertussis toxin reversed O₂^•− caused inhibition of Na⁺ dependent Ca²⁺ uptake without affecting the protease activity and PKC activity in the microsomes. We suggest the existence of a pertussis toxin sensitive G protein mediated mechanism for inhibition of Na⁺ dependent Ca²⁺ uptake in microsomes of bovine pulmonary artery smooth muscle under O₂^•− triggered condition, which is regulated by PKCδ dependent phosphorylation and sensitive to TIMP-2 for its inhibition. (Mol Cell Biochem xxx: 107–117, 2005)     

Use of Acadian marine plant extract powder from Ascophyllum nodosum in tissue culture of Kappaphycus varieties

Three varieties of Kappaphycus alvarezii (Kapilaran, KAP), Tambalang purple (PUR), Adik-adik (AA), and one variety of Kappaphycus striatum var. sacol (green sacol (GS) were used to determine the efficiency of Acadian marine plant extract powder (AMPEP) as a culture medium at different concentrations, for the regeneration of young plants of Kappaphycus varieties, using tissue culture techniques for the production of seed stock for nursery and outplanting purposes for the commercial cultivation of carrageenophytes. A shorter duration for shoot formation was observed when the explant was treated with AMPEP + Plant Growth Regulator (PGR = PAA + zeatin at 1 mg L⁻¹) compared to AMPEP when used singly. However, four explants responded differently to the number of days required for shoot formation. The KAP variety took 46 days to form shoots at 3–4 mg L⁻¹ AMPEP + PGR; while PUR required 21 days at 3–5 mg L⁻¹ AMPEP and 3–4 mg L⁻¹ AMPEP + PGR. AA required 17 days at 3–5 mg L⁻¹ AMPEP and AMPEP + PGR; and GS 25 days at 1 mg L⁻¹ AMPEP + PGR. It was observed that among the four explants used, PUR and AA initiated shoot formation with the use of AMPEP only at higher concentrations (3–5 mg L⁻¹) after a shorter period. Only PUR responded positively to ESS/2 for shoot initiation. The use of AMPEP alone and/or in combination with PGR as a culture medium in the propagation of microplantlets using tissue culture technique is highly encouraging.     

Hillslope Nutrient Dynamics Following Upland Riparian Vegetation Disturbance

We investigated the effects of removing near-stream Rhododendron and of the natural blowdown of canopy trees on nutrient export to streams in the southern Appalachians. Transects were instrumented on adjacent hillslopes in a first-order watershed at the Coweeta Hydrologic Laboratory (35°03′N, 83°25′W). Dissolved organic carbon (DOC), K⁺, Na⁺, Ca²⁺, Mg²⁺, NO₃ ⁻-N, NH₄ ⁺-N, PO₄ ³⁻-P, and SO₄ ²⁻ were measured for 2 years prior to disturbance. In August 1995, riparian Rhododendron on one hillslope was cut, removing 30% of total woody biomass. In October 1995, Hurricane Opal uprooted nine canopy trees on the other hillslope, downing 81% of the total woody biomass. Over the 3 years following the disturbance, soilwater concentrations of NO₃ ⁻-N tripled on the cut hillslope. There were also small changes in soilwater DOC, SO₄ ²⁻, Ca²⁺, and Mg²⁺. However, no significant changes occurred in groundwater nutrient concentrations following Rhododendron removal. In contrast, soilwater NO₃ ⁻-N on the storm-affected hillslope showed persistent 500-fold increases, groundwater NO₃ ⁻-N increased four fold, and streamwater NO₃ ⁻-N doubled. Significant changes also occurred in soilwater pH, DOC, SO₄ ²⁻, Ca²⁺, and Mg²⁺. There were no significant changes in microbial immobilization of soil nutrients or water outflow on the storm-affected hillslope. Our results suggest that Rhododendron thickets play a relatively minor role in controlling nutrient export to headwater streams. They further suggest that nutrient uptake by canopy trees is a key control on NO₃ ⁻-N export in upland riparian zones, and that disruption of the root–soil connection in canopy trees via uprooting promotes significant nutrient loss to streams. Received 30 January 2001; accepted 25 July 2002.     

The charge-transfer complex between protochlorophyllide and NADPH: an intermediate in protochlorophyllide photoreduction

A hypothesis describing the mechanism of photoactive protochlorophyllide (P) photoreduction in vivo, relating mainly to the molecular nature of the intermediates, is proposed. The hypothesis is compatible with currently published experimental data. After illumination of etiolated barley leaves at 143 to 153 K, the absorption of P remains essentially unchanged, but a new absorption band at 690 nm is observed. Appearance of this new intermediate enables to distinguish between light and dark stages of the photoconversion reaction. When returned to the higher temperature in the dark, the treated leaves begin accumulating chlorophyllide (Chlide), concomitant with the disappearance of the 690-nm band. The decay time of the excited P (P^*) is estimated at 300 ps, which approximates the time constant of photoinduced electron transfer (ET). It is suggested that the charge-transfer complex (CTC) in its ground state (GS) (ground state of CTC formed by the partial (δ) electron transfer), i.e. (P^δ−•••H–D^δ+), between P and NADPH – the electron and proton donor (H–D) – accumulates in the following sequence: P^* + H–D → (P^*•••H–D)→[(P^*•••H–D)←(P⁻•••H–D⁺)] → ¹(P⁻•••H–D⁺)] → ³(P⁻•••H–D⁺) → (P^δ−•••H–D ^δ+), where an equilibrium state (ES) – [(P^*•••H–D)←(P⁻•••H–D⁺)] – with a lifetime of about 1 to 2 ns, exists between the local excited (LE) and ET states. The existence of a triplet ET state – ³(P⁻•••H–D⁺) – is proposed because the time interval between recording of the ES and appearance of the CTC GS (35–250 ns) does not fit the lifetime of the singlet excited complex (exciplex). It is feasible that apart from NADPH, other intermediate proton carriers are contemporaneously involved in the dark reaction (P^δ−•••H–D^δ+) → Chlide, because proton binding to the C₇–C₈ bond in vivo takes place in the trans-configuration. The hydride ion may approach the C₇–C₈ bond from one side by heterolytic fission and an additional proton, donated by the protein group, may be simultaneously added to this bond from the opposite side of the porphyrin nucleus surface. This revised version was published online in June 2006 with corrections to the Cover Date.