Insulin-like growth factor-I-mediated amplification of follicle-stimulating hormone-supported progesterone accumulation by cultured rat granulosa cells: enhancement of steroidogenic enzyme activity and expression

A body of information now supports the existence of an ovarian intrafollicular insulin-like growth factor (IGF)-I system concerned with the amplification of FSH action at the level of the rat granulosa cell. In this study we examined the ability of IGF-I to modulate the basal and FSH-supported activity and expression of key steroidogenic enzymes concerned with progesterone generation and metabolism in cultured granulosa cells from immature rats. The provision of IGF-I stimulated FSH-supported (20 ng/ml) accumulation of progesterone in a dose-dependent manner, reaching a plateau at an IGF-I dose of 50 ng/ml. This dose of IGF-I substantially enhanced FSH action over a broad range of FSH concentrations, reaching a maximum at an FSH dose of 20 ng/ml. Pulse labeling of FSH-pretreated cells with [3H]pregnenolone revealed relatively rapid (< 5 h) transformation to [3H]progesterone and other distal products that was accelerated by the concurrent addition of IGF-I. These changes in progesterone metabolism were associated with IGF-I-mediated enhancement of the activities and expression of key steroidogenic enzymes. Specifically, treatment with IGF-I produced significant augmentation of the FSH-stimulated activities of cholesterol side-chain cleavage (P450scc) and 3 beta-hydroxysteroid dehydrogenase/ isomerase (3 beta-HSD) enzymes (2.4- and 1.8-fold, respectively). Similarly, P450scc and type I 3 beta-HSD transcripts were elevated by FSH in a dose-dependent manner, the concurrent addition of IGF-I further increasing expression (up to an additional 3-fold) in the range of 1-5 ng/ml (but not at the maximally stimulating dose of 20 ng/ml FSH). The addition of IGF-I also increased basal levels of type I 3 beta-HSD transcripts (3.8-fold). IGF-I enhanced FSH-stimulated 20 alpha-HSD activity and transcripts (2.3-fold and 1.8-fold, respectively) and increased the basal levels of 20 alpha-HSD transcripts (3-fold). Basal levels of 5 alpha-reductase were slightly elevated (1.3-fold) by IGF-I, but the FSH-attenuated activity was unchanged. Taken together, these findings suggest that IGF-I enhances the FSH-supported accumulation of progesterone in cultured granulosa cells through up-regulation of the expression and activity of key enzymes in the steroidogenic pathway. The acceleration of progesterone accumulation reflects a newly established steady state, favoring the activities of progesterone-forming over progesterone-metabolizing enzymes.

Activin-attenuated expression of transcripts encoding granulosa cell-derived insulin-like growth factor binding proteins 4 and 5 in the rat: a putative antiatretic effect

Given the suggestion that intraovarian insulin-like growth factor (IGF)-binding proteins (IGFBPs) may constitute markers of follicular atresia, we investigated the possibility that activin, a putative antiatretic principle, may modulate granulosa cell-derived IGFBPs. Untreated granulosa cells cultured for 72 h exhibited a progressive increase in the steady-state levels of transcripts corresponding to IGFBP-4 and IGFBP-5 (1.5-fold and 12-fold, respectively). Transcript levels corresponding to IGFBP-5 were consistently higher than their IGFBP-4 counterparts. Treatment with activin-A (50 ng/ml) for 72 h produced significant (p < 0.05) decrements in the steady-state levels of IGFBP-4 and IGFBP-5 transcripts (46% and 79%, respectively) as compared to controls. Thus, treatment with activin-A appears to be capable of blocking the spontaneous increase in IGFBP-4 and IGFBP-5 transcripts exhibited by untreated cultured granulosa cells. Consistent activin-A-induced decrements were also observed in the accumulation of the IGFBP-5 (but not the IGFBP-4) protein. Dose-response analysis revealed monophasic dose dependence (half maximal inhibitory doses of 16.2 and 7.8 ng/ml for IGFBP-5 and IGFBP-4 transcripts, respectively). The addition of increasing concentrations of the putative activin-binding protein, follistatin, produced dose-dependent reversal of the activin-A effect on IGFBP transcripts (IGFBP-5 > IGFBP-4). Activin-B was as effective as activin-A in reducing IGFBP-4 transcripts (31% decrement, p < 0.05) whereas it had little or no effect on IGFBP-5 transcripts (21% decrement, p > 0.1). No apparent effect was observed for the corresponding proteins. Activin-A action was specific in that treatment with transforming growth factor (TGF)-beta1, inhibin-A, or Müllerian-inhibiting substance (MIS)--all related peptides--failed to produce statistically significant alterations in the steady-state levels of IGFBP-4 and IGFBP-5 transcripts. Taken together, these observations reveal that activin-A exerts a substantial, relatively rapid, follistatin-neutralizable, dose- and time-dependent inhibitory effect on granulosa cell-derived IGFBP transcripts (IGFBP-5 > IGFBP-4). Other members of the TGFbeta superfamily (e.g., inhibin-A, TGFbeta1, and MIS) were without significant effect on the expression of IGFBP-4 and IGFBP-5. To the extent that the inhibition of IGFBP-4 and IGFBP-5 expression is associated with, and possibly causally related to, the promotion of follicular health, the present observations are in keeping with the proposition that activin may play an antiatretic role in the dynamic process of follicular selection.

Erythropoietin: physico- and biochemical analysis

A hormone, erythropoietin, mainly produced in adult kidneys and fetal livers, acts on bone marrow erythroid progenitor cells to regulate the production of erythrocyte in mammals. As a result, the oxygen carrying capacity of blood increases and the increased oxygen supply raises the cardiac function and physiological working capacity. Erythropoietin is possibly misused by athletes in sports for the purpose of improving performance. Presently there is no discernible and specific method to identify erythropoietin administration for doping control. To address this practical problem, this paper presents a summary of the applications of analytical biotechnology, especially the structural characterization of erythropoietin.

Traumatic cerebrospinal fluid leakage: risk factors and the use of prophylactic antibiotics

Cerebrospinal fluid (CSF) leakage following head trauma is often difficult to diagnose, but is of considerable importance in view of the possibility of fistula formation and meningitis. It is unclear whether specific clinical or radiological signs point to an increased risk of CSF leakage. Previous studies have been largely anecdotal and uncontrolled, leading us to perform a retrospective control study comparing the clinical and radiological features of patients with overt CSF leakage, and those without. Of the 293 patients studied, 115 had clinical CSF leakage and 170 did not, with incomplete documentation in eight patients. The group with CSF rhinorrhoea had significantly greater incidence of periorbital haematoma (chi square = 8.642). This suggests that patients with head injuries and features of periorbital haematoma are at greater risk of unobserved dural tear and delayed CSF leakage. Frontal and ethmoid fractures in particular were also associated with CSF leakage (chi square = 5.46). The use of prophylactic antibiotics was studied. There was a significantly greater incidence of meningitis in the group which received prophylactic antibiotics (p = 0.024). There was no significant difference in the incidence of meningitis in those patients with CSF fistulae treated by surgical or conservative methods.

The anticonvulsant activities of functionalized N-benzyl 2-acetamidoacetamides. The importance of the 2-acetamido substituent

Recent studies have demonstrated that substituted N-benzyl 2-acetamidoacetamides provide significant protection against maximal electroshock (MES)-induced seizures in mice and rats. In this study, we investigated whether the 2-acetamido moiety was necessary for anticonvulsant activity. Ten derivatives of the known anticonvulsant, N-benzyl 2-acetamido-2-phenyl-acetamide were prepared in which the 2-acetamido group was replaced by hydrogen, methyl, oxygen, and halogen substituents. Evaluation of these compounds in the MES-induced seizure test demonstrated that both the hydroxy and the methexy compounds provided full protection against MES-induced seizures in mice given ip at 100 mg/kg. Moreover, evaluation of the individual stereoisomers for the hydroxy compound showed that the principal activity resided in the (R)-isomer. These findings demonstrated that the 2-acetamido substituent is important but not obligatory for the prevention of MES-induced seizures. Further supporting evidence was provided by comparing the pharmacological activities of N-benzyl 2,3-dimethoxypropionamide with N-benzyl 2-acetamido-3-methoxypropionamide. The ED50 value for the former in the MES test was 30 mg/kg (i.p.), which compared favorably with phenobarbital (ED50 = 22 mg/kg), but the ED50 value for N-benzyl 2-acetamido-3-methoxypropionamide was 8.3 mg/kg.

Molecular cloning of a metallothionein-like gene from Nicotiana glutinosa L. and its induction by wounding and tobacco mosaic virus infection

The cloning and characterization of genes expressed in plant disease resistance could be an initial step toward understanding the molecular mechanisms of disease resistance. A metallothionein-like gene that is inducible by tobacco mosaic virus and by wounding was cloned in the process of subtractive cloning of disease resistance-response genes in Nicotiana glutinosa. One 530-bp cDNA clone (KC9-10) containing an open reading frame of 81 amino acids was characterized. Genomic Southern blot hybridization with the cDNA probe revealed that tobacco metallothionein-like genes are present in few or in one copy per diploid genome. Northern blot hybridization detected strong induction of a 0.5-kb mRNA by wounding and tobacco mosaic virus infection, but only mild induction was detected when copper was tested as an inducer. Methyl jasmonate, salicylic acid, and ethylene were also tested as possible inducers of this gene, but they had no effect on its expression. The possible role of this gene in wounded and pathogen-stressed plants is discussed.

The serpin-enzyme complex receptor recognizes soluble, nontoxic amyloid-beta peptide but not aggregated, cytotoxic amyloid-beta peptide

There is now extensive evidence that amyloid-beta peptide is toxic to neurons and that its cytotoxic effects can be attributed to a domain corresponding to amyloid-beta 25-35, GSNKGAIIGLM. We have shown recently that the serine proteinase inhibitor (serpin)-enzyme complex receptor (SEC-R), a receptor initially identified for binding of alpha1-antitrypsin (alpha1-AT) and other serine protease inhibitors, also recognizes the amyloid-beta 25-35 domain. In fact, by recognizing the amyloid-beta 25-35 domain, SEC-R mediates cell surface binding, internalization, and degradation of soluble amyloid-beta peptide. In this study, we examined the possibility that SEC-R mediates the neurotoxic effect of amyloid-beta peptide. A series of peptides based on the sequences of amyloid-beta peptide and alpha1-AT was prepared soluble in dimethyl sulfoxide or insoluble in water and examined in assays for SEC-R binding, for cytotoxicity in neuronal PC12 cells and murine cortical neurons in primary culture, and for aggregation in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The results show that amyloid-beta peptide 25-35 and amyloid-beta peptide 1-40 prepared soluble in dimethyl sulfoxide compete for binding to SEC-R, are nontoxic, and migrate as monomers in SDS-PAGE analysis. In contrast, the same peptides aged in water did not compete for binding to SEC-R but were toxic and migrated as aggregates in SDS-PAGE. An all-D-amyloid-beta 25-35 peptide was not recognized at all by SEC-R but retained full toxic/aggregating properties. Using a series of deleted, substituted, and chimeric ambeta/alpha1-AT peptides, toxicity correlated well with aggregation but poorly with SEC-R recognition. In a subclone of PC12 cells which developed resistance to the toxic effect of aggregated amyloid-beta 25-35 there was a 2.5-3-fold increase in the number of SEC-R molecules/cell compared with the parent PC12 cell line. These data show that SEC-R does not mediate the cytotoxic effect of aggregated amyloid-beta peptide. Rather, SEC-R could play a protective role by mediating clearance and catabolism of soluble, monomeric amyloid-beta peptide, if soluble amyloid-beta peptide proves to be an in vivo precursor of the insoluble, toxic peptide.

Spinal cord diameters in cadaveric specimens and magnetic resonance scans, to assess embalming artefacts

It would be valuable to use cadaveric models of cervical vertebrae and spinal cord to assess how varying degrees of traumatic subluxation would relate to neurological damage. However, before such a study may be undertaken, it would be important to assess the degree of shrinkage of expansion of the spinal cord that occurs during the embalming process. This is achieved in this study by comparing diameters of cadaveric spinal cord to that of sagittal magnetic resonance scans of living subjects. The geometric measurements of radiographs in living subjects has been assessed but no direct model for spinal cord injury has been described [1]. If embalmed spinal cord diameters were a good estimator of living spinal cord diameters then cadaveric cervical spines could be used as a model. By reproducing various degrees of fracture and dislocation the extent of corresponding cord compression could be assessed. Our study shows that spinal cord dimensions increase after embalming using the Cambridge procedure [4].

Characterization and hormonal regulation of granulosa cell-derived insulin-like growth factor binding protein-4

OBJECTIVE

Because of the potential importance of insulin-like growth factor binding protein-4 (IGFBP-4) to ovarian physiology and the obvious limitations imposed by in vivo-exclusive experimental paradigms, we set out to delineate the characteristics and hormonal regulation of granulosa cell-derived IGFBP-4 under in vitro circumstances.

METHODS

Granulosa cells obtained by follicular puncture of the ovaries from diethylstilbestrol-primed intact immature rats were subjected to culture for up to 72 hours. Insulin-like growth factor binding protein-4 mRNA extracted from culture was subjected to Northern blot hybridization. Data normalization was assured by reprobing with the hamster Chinese hamster ovary B (CHOB) cDNA, and the IGFBP-4/CHOB ratio was calculated. Conditioned culture media were subjected to Western ligand blot before and after immunoprecipitation with a rat IGFBP-4-directed polyclonal antiserum (alpha-B104).

RESULTS

Immunoprecipitation studies revealed granulosa cell-derived IGFBP-4 to be composed of a major 24-kDa species as well as a relatively minor 27-kDa moiety. Given cultures of untreated granulosa cells from immature estrogen-treated rats, transcripts corresponding to IGFBP-4 displayed an initial temporary decline culminating in a 6-hour nadir (a decrease of 67%; P < .05) followed by relatively prompt recovery (within 24 hours) to levels comparable to those noted at the outset of the culture (time 0). However, additional (albeit statistically insignificant) increments were noted at the 48-hour (but not 72-hour) time point. Treatment of granulosa cells with increasing concentration of FSH resulted in decrements of up to 30% (P < .05) in the steady-state levels of IGFBP-4 transcripts. A modest, biphasic, time-dependent response was noted for IGFBP-4 transcripts after treatment with high-dose FSH (100 ng/mL), an effect characterized by 24- and 48-hour increments (51% [P < .05] and 26% [P = .052] over untrated controls, respectively) and a 72-hour decrement (25%; P = .16). The concurrent provision of the C19 aromatase substrate androstenedione (10(-7) mol/L) to the culture medium from 72 hours enhanced the inhibitory effect of FSH (100 ng/mL) for a maximal decrement in IGFBP-4 transcripts of 49% (P < .05). Treatment with insulin-like growth factor (IGF)-I produced limited inhibition (up to 26%) of the steady-state levels of IGFBP-4 transcripts (P < .05).

CONCLUSION

Findings indicate the existence of heterogeneously-sized IGFBP-4 species, of which the 27-kDa (as distinct from the 24-kDa) IGFBP-4 moiety constitutes a relatively minor component. The steady-state levels of granulosa cell-derived IGFBP-4 transcripts display relatively limited regulation in response to treatment with either FSH or IGF-I.

Synthesis and anticonvulsant activities of N-Benzyl-2-acetamidopropionamide derivatives

Studies have demonstrated that 2-substituted N-benzyl-2-acetamidoacetamides (2) are potent anticonvulsants. A recent investigation has led to the hypothesis that an important structural feature in 2 for maximal anticonvulsant activity is the placement of a small, substituted heteroatom moiety one atom from the C(2) site. This paper validates this hypothesis. Twelve derivatives of N-benzyl-2-acetamidopropionamide have been prepared in which six different heteroatom substituents (chloro, bromo, iodo, oxygen, nitrogen, and sulfur) were incorporated at the C(3) site. Highly potent activities were observed for the two oxygen-substituted derivatives, N-benzyl-2-acetamido-3-methoxypropionamide (18) and N-benzyl-2-acetamido-3-ethoxypropionamide (19). The ED50 values in mice following intraperitoneal (i.p.) dosing for the maximal electroshock-induced seizure test for 18 and 19 were 8.3 and 17.3 mg/kg, respectively. These values compared favorably to the ED50 value found for phenytoin (ED50 = 6.5 mg/kg). Comparable activities were observed for 18 and 19 upon oral (p.o.) administration to rats (18, ED50 = 3.9 mg/kg; 19, ED50 = 19 mg/kg; phenytoin, ED50 = 23 mg/kg). Evaluation of the individual stereoisomers for 18 demonstrated that the principal anticonvulsant activity resided in the (R)-stereoisomer. The ED50 value for (R)-18 was 4.5 mg/kg, and the ED50 for (S)-18 exceeded 100 mg/kg. This difference in activity for the two stereochemical isomers surpassed comparable values for other members within this class of compounds. The protective indices (PI = TD50/ED50) (where TD50 represents a neurotoxic dose impairing rotorod performance) for (R)-18 in mice (i.p.) and in rats (p.o.) were 6.0 and > 130, respectively.

CT of the bronchus intermedius: frequency and cause of a nodule in the posterior wall on normal scans

OBJECTIVE

A focal nodule in the posterior wall of the bronchus intermedius is occasionally observed on normal CT scans. The purpose of this study was to determine the frequency and the anatomic cause of this finding.

MATERIALS AND METHODS

We prospectively analyzed helical CT scans (10-mm collimation and 10-mm/sec table speed) for evaluating nodules in the posterior wall of the bronchus intermedius from 280 consecutive subjects. A focal round elevation in the posterior wall of the bronchus intermedius was considered a nodule. Frequency of visualization of the nodule was recorded. In patients showing such nodularity, additional enhanced CT scans with thinner slices (5-mm collimation and 5-mm/sec table speed) were obtained to elucidate the nature of the nodularity.

RESULTS

Nodularity in the posterior wall of the bronchus intermedius was observed in 14/280 total subjects (5%) on 10-mm collimation CT scans. On thin-section CT scans, the nodularity was caused by a branch of the vein from the posterior segment of the right upper lobe (10/14, 71%) or by a branch of the vein from the superior segment of the right lower lobe (4/14, 29%). The vein from the upper lobe that caused nodularity in the posterior wall of the bronchus intermedius drained into either the inferior pulmonary vein (7/10) or the superior pulmonary vein (3/10). In all patients whose nodularity was caused by the vein from the superior segment of the right lower lobe, the vein drained into the inferior pulmonary vein.

CONCLUSION

Focal nodularity in the posterior wall of the bronchus intermedius was caused by the draining pulmonary vein, and it was observed in 5% of normal subjects. This nodularity should be differentiated from uniform or lobular thickening associated with abnormality in the bronchus intermedius.

In vivo hormonal regulation of insulin-like growth factor binding protein-5 mRNA in the immature rat ovary

OBJECTIVE

Despite the potential importance of insulin-like growth factor binding protein-5 (IGFBP-5) to follicular development, the hormonal regulation of this antigonadotropic IGFBP has not been investigated. Therefore, it was the objective of this study to eludicate the role of gonadotropins and estrogen in the in vivo regulation of IGFBP-5 mRNA expression.

METHODS

Two models of follicular development in immature rats were used. Specifically, rats were hypophysectomized and treated with FSH and/or diethylstilbestrol (DES). Alternatively, terminal follicular development was induced in intact immature rats by pregnant mare serum gonadotropin (PMSG) and hCG. The IGFBP-5 mRNA in whole ovarian RNA was assayed by Northern blot hybridization. Localization of expression in PMSG and hCG-stimulated ovaries was further assessed by in situ hybridization.

RESULTS

Expression of IGFBP-5 mRNA was increased in ovaries from hypophysectomized rats. Treatment with FSH and/or DES did not alter the abundance of this mRNA. Treatment with PMSG induced a transient increase in IGFBP-5 expression that was localized in a subset of alpha-inhibin-negative follicles. At later times after PMSG, IGFBP-5 expression persisted in the surface epithelium but was not detected in large preovulatory follicles. In vitro studies affirmed the antigonadotropic action of IGFBP-5.

CONCLUSION

In vivo expression of IGFBP-5 in the rat ovary is moderated by hormonal treatment both in terms of total expression and follicular localization.

SMI-32 antibody against non-phosphorylated neurofilaments identifies a subpopulation of cultured cortical neurons hypersensitive to kainate toxicity

SMI-32, an antibody against a non-phosphorylated neurofilament epitope identifies a subpopulation of human cortical neurons preferentially lost in Alzheimer's or Huntington's disease. In murine cortical cultures SMI-32 labeled a small subset of neurons exhibiting enhanced vulnerability to kainate toxicity. Most SMI-32(+) neurons were GABAergic and exhibited kainate-activated Co2+ uptake. Thus expression of Ca2+ permeable AMPA or kainate receptor-gated channels likely underlies the heightened vulnerability of SMI-32(+) cortical neurons to kainate.

Structural requirements for mitomycin C DNA bonding

Information of the specific structure of the activated mitomycin species leading to selective DNA bonding has been secured by determining the bonding sequence selectivities of modified mitomycins in which the identity, spatial orientation, and state of unsaturation of the C-9 and C-9a substituents in the mitomycin were varied. Both mitomycin-9a-sulfonate (8) and mitomycin D (9) gave DNA bonding profiles comparable to those obtained for mitomycin C (1) under reductive conditions, indicating that neither the stereochemistry of the C-9 and C-9a substituents nor the identity of the leaving group at C-9a influenced the site(s) of DNA bonding. These results indicated that aromatization of the dihydropyrrole ring in mitomycin C precedes DNA binding and mitomycin C-1 bonding.

Transposon tagging of tobacco mosaic virus resistance gene N: its possible role in the TMV-N-mediated signal transduction pathway

Plants can recognize and resist invading pathogens by signaling the induction of rapid defense responses. Often these responses are mediated by single dominant resistance genes (R genes). The products of R genes have been postulated to recognize the pathogen and trigger rapid host defense responses. Here we describe isolation of the classical resistance gene N of tobacco that mediates resistance to the well-characterized pathogen tobacco mosaic virus (TMV). The N gene was isolated by transposon tagging using the maize Activator (Ac) transposon. We confirmed isolation of the N gene by complementation of the TMV-sensitive phenotype with a genomic DNA fragment. Sequence analysis of the N gene shows that it encodes a protein with an amino-terminal domain similar to that of the cytoplasmic domains of the Drosophila Toll protein and the interleukin 1 receptor in mammals, a putative nucleotide-binding site and 14 imperfect leucine-rich repeats. The presence of these functional domains in the predicted N gene product is consistent with the hypothesis that the N resistance gene functions in a signal transduction pathway. Similarities of N to Toll and the interleukin 1 receptor suggest a similar signaling mechanism leading to rapid gene induction and TMV resistance.

Glutamine reduces bacterial translocation after small bowel transplantation in cyclosporine-treated rats

Bacterial translocation (BT) of enteric organisms is a major cause of sepsis in patients undergoing small bowel transplantation (SBT). Cyclosporine (CsA) may be toxic to intestinal epithelium and increase the risk of BT. Glutamine (Gln) is the preferred enterocyte fuel and maintains graft epithelial integrity in experimental SBT. This study determined the effects of CsA on mucosal structure and function of transplanted intestinal isograft and examined whether Gln-enriched diet reversed CsA-induced intestinal toxicity. Thirty-three adult Lewis rats underwent resection of the distal 60% of small bowel and received an orthotopic jejunal isograft. Rats received either elemental diet with 2% Gln or the same diet with balanced nonessential amino acids (non-Gln) by gastrostomy for 10 days. CsA (15 mg/kg, im) or olive oil was injected daily. Rats were assigned to four groups: non-Gln with vehicle, non-Gln with CsA, Gln with vehicle, and Gln with CsA. Mucosal villous height, surface area, crypt depth, 14C glucose absorption, BT to mesenteric lymph nodes (MLN), and body weight change were evaluated. The non-Gln with CsA group had the highest incidence of BT (P < 0.001). Gln groups had significantly decreased BT (P < 0.01) and increased crypt depth and villous surface area (P < 0.01) when compared to non-Gln groups. Body weight significantly decreased in CsA groups when compared to non-CsA groups (P < 0.01). These results indicate at CsA significantly decreased body weight and increased BT without decreasing mucosal structure and glucose absorption of intestinal isografts.(ABSTRACT TRUNCATED AT 250 WORDS)

The product of the tobacco mosaic virus resistance gene N: similarity to toll and the interleukin-1 receptor

The products of plant disease resistance genes are postulated to recognize invading pathogens and rapidly trigger host defense responses. Here we describe isolation of the resistance gene N of tobacco that mediates resistance to the viral pathogen tobacco mosaic virus (TMV). The N gene was isolated by transposon tagging using the maize Activator transposon. A genomic DNA fragment containing the N gene conferred TMV resistance to TMV susceptible tobacco. Sequence analysis of the N gene shows that it encodes a protein of 131.4 kDa with an amino-terminal domain similar to that of the cytoplasmic domain of the Drosophila Toll protein and the interleukin-1 receptor (IL-1R) in mammals, a nucleotide-binding site (NBS), and 14 [corrected] imperfect leucine-rich repeats (LRR). The sequence similarity of N, Toll, and IL-1R suggests that N mediates rapid gene induction and TMV resistance through a Toll-IL-1-like pathway.

Effect of passive and active recovery on the resynthesis of muscle glycogen

The purpose of this investigation was to determine the effect of passive and active recovery on the resynthesis of muscle glycogen after high-intensity cycle ergometer exercise in untrained subjects. In a cross-over design, six college-aged males performed three, 1-min exercise bouts at approximately 130% VO2max with a 4-min rest period between each work bout. The exercise protocol for each trial was identical, while the recovery following exercise was either active (30 min at 40-50% VO2max, 30-min seated rest) or passive (60-min seated rest). Initial muscle glycogen values averaged 144.2 +/- 3.8 mmol.kg-1 w.w. for the active trial and 158.7 +/- 8.0 mmol.kg-1 w.w. for the passive trial. Corresponding immediate postexercise glycogen contents were 97.7 +/- 5.4 and 106.8 +/- 4.7 mmol.kg-1 w.w., respectively. These differences between treatments were not significant. However, mean muscle glycogen after 60 min of passive recovery increased 15.0 +/- 4.9 mmol.kg-1 w.w., whereas it decreased 6.3 +/- 3.7 mmol.kg-1 w.w. following the 60 min active recovery protocol (P < 0.05). Also, the decrease in blood lactate concentration during active recovery was greater than during passive recovery and significantly different at 10 and 30 min of the recovery period (P < 0.05). These data suggest that the use of passive recovery following intense exercise results in a greater amount of muscle glycogen resynthesis than active recovery over the same duration.

Involvement of de Novo Protein Synthesis, Protein Kinase, Extracellular Ca2+, and Lipoxygenase in Arachidonic Acid Induction of 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Genes and Isoprenoid Accumulation in Potato (Solanum tuberosum L.)

A series of inhibitors were tested to determine the participation of de novo protein synthesis, protein kinase activity, extracellular Ca2+, and lipoxygenase activity in arachidonic acid elicitation of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) gene expression and sesquiterpene phytoalexin biosynthesis in potato (Solanum tuberosum L. cv Kennebec). Gene-specific probes were used to discriminate effects on the expression of two HMGR genes (hmg1 and hmg2) that respond differentially in tuber tissue following wounding or elicitor treatment. Inhibition of protein synthesis with cycloheximide completely blocked arachidonate-induced hypersensitive necrosis and browning, including HMGR gene induction and phytoalexin accumulation. This suggests that proteins necessary for coupling arachidonic acid reception to HMGR mRNA accumulation are either rapidly turned over or not present constitutively and are induced following elicitor treatment. Staurosporin, a potent inhibitor of protein kinases, and ethyleneglycol-bis([beta]-aminoethyl ether)-N,N[prime]-tetraacetic acid, a Ca2+ chelator, inhibited arachidonate-induction of hmg2 gene expression and phytoalexin accumulation but did not inhibit the wound-induced expression of hmg1. However, staurosporin inhibited arachidonate's suppression of hmg1 gene expression. Eicosatetraynoic acid, a lipoxygenase inhibitor that suppresses elicitor-induced phytoalexin accumulation, also inhibited arachidonate's suppression of hmg1 and induction of hmg2. The results indicate that arachidonate's suppression of hmg1 and activation of hmg2 depend on a common intermediate or set of intermediates whose generation is sensitive to the inhibitors tested.

Lipid-derived signals that discriminate wound- and pathogen-responsive isoprenoid pathways in plants: methyl jasmonate and the fungal elicitor arachidonic acid induce different 3-hydroxy-3-methylglutaryl-coenzyme A reductase genes and antimicrobial isoprenoids in Solanum tuberosum L

Induction of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR; EC 1.1.1.34) is essential for the synthesis of steroid derivatives and sesquiterpenoid phytoalexins in solanaceous plants following mechanical injury or pathogen infection. Gene-specific probes corresponding to different HMGR genes (hmg1 and hmg2) were used to study HMGR expression in potato tissue following treatment with methyl jasmonate, a lipoxygenase product of linolenic acid, or arachidonic acid, an elicitor present in the lipids of the potato late blight fungus Phytophthora infestans. Treatment of potato discs (2.2 cm in diameter) with low concentrations (0.45-45 nmol per disc surface) of methyl jasmonate nearly doubled the wound-induced accumulation of hmg1 transcripts and steroid-glycoalkaloid (SGA) accumulation, reduced the abundance of hmg2 transcripts, and did not induce phytoalexins. High concentrations of methyl jasmonate (2-4.5 mol per disc surface) suppressed hmg1 mRNA and SGA accumulation but did not affect hmg2 mRNA abundance or induce phytoalexins. In contrast, arachidonate treatment strongly suppressed hmg1 and strongly induced hmg2 mRNA in a concentration-dependent manner. There was a corresponding suppression of SGA accumulation and an induction of sesquiterpene phytoalexin accumulation by this elicitor. Lipoxygenase inhibitors reduced the wound-induced accumulation of hmg1 transcripts and suppressed SGA levels, effects that were overcome by exogenous methyl jasmonate (45 nmol per disc surface). The results (i) suggest that methyl jasmonate can function as a signal for hmg1 expression and SGA induction following wounding and (ii) indicate that the arachidonate- and jasmonate-response pathways are distinct in relation to HMGR gene expression and isoprenoid product accumulation. The results also are consistent with placement of the HMGR activities encoded by hmg1 and hmg2 within discrete steroid and sesquiterpenoid biosynthetic channels.