[The Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome: clinical description and genetics]

The Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is characterized by congenital aplasia of the uterus and the upper part (two-third) of the vagina. It may be isolated (type I) or associated with other malformations (type II or MURCS association). These latter involve the upper urinary tract, the skeleton and, to a lesser extent, the otologic sphere or the heart. The incidence of MRKH syndrome has been estimated as 1 in 4500 women. The prime feature is a primary amenorrhea in women presenting otherwise with normal development of secondary sexual characteristics and normal external genitalia. However, the vagina is reduced to a vaginal dimple with variable depth. The ovaries are normal and functional as well as the endocrine status. Karyotype is 46,XX, with no visible chromosome modification. The phenotypic manifestations of MRKH syndrome overlap with various other syndromes or malformations and thus require accurate delineation as well as differential diagnosis. For a long time, the syndrome has been considered as a sporadic anomaly, but increasing familial cases now support the hypothesis of a genetic cause currently under investigation. The syndrome appears to be transmitted as an autosomal dominant trait with incomplete penetrance and variable expressivity.

Evaluation of adipose tissue distribution in obese fa/fa Zucker rats by in vivo MR imaging: effects of peroxisome proliferator-activated receptor agonists

High-resolution MRI of obese (fa/fa) Zucker rats was investigated to characterize and assess in vivo adipose tissue distribution. Thirty animals were gavaged with a placebo, a PPARgamma activator (pioglitazone), or a dual PPARalphagamma activator (LM 4156). At day 15, T1-weighted images were acquired in vivo using a 2TMRI system with a high in-plane spatial resolution (254 microm). Fat volumes of selected territories were measured by image segmentation, and the retroperitoneal fat was weighed post-mortem. Body-weight gain was significant with pioglitazone (101.8+/-5.9 g, p<0.01 vs. placebo). The good quality of MR images allowed the delimitation and quantification of different fat territories. In response to pioglitazone, the retroperitoneal fat was more important compared to placebo (+23%, p<0.01) while subcutaneous fat was not different. No significant effects were observed with LM 4156. In vivo measurements of fat volumes were strongly correlated with ex vivo tissue weights (r=0.91). High-resolution MRI provides an in vivo measurement of adipose tissue distribution in obese Zucker rats. Specific fat depots of regions that were particularly involved in drug response were determined in vivo. Fat remodeling was observed with pioglitazone but not with a dual PPARalphagamma activator (LM 4156).

An expressed GNRP-like gene shares a bi-directional promoter with SF3A2 (SAP62) immediately upstream of AMH

A region of homology, containing the contiguous SF3A2 (formerly called SAP62) and AMH genes, exists between human chromosome 19 (HSA19p) and mouse chromosome 10 (MMU10). In a previous study it was shown that SF3A2/Sf3a2 is very highly conserved between the two species and that AMH/Amh is somewhat less conserved although both human and mouse genes encode a protein (AMH) playing the same critical role during early male sex differentiation. The close association between SF3a2/Sf3a2 and AMH/Amh was thought to maintain open chromatin in the AMH/Amh promoter region, thus facilitating the necessary precise timing of AMH/Amh expression following that of SRY/Sry at the onset of testis differentiation. Further investigation of DNA upstream of Amh has revealed that there is another gene, in close association (about 400 bp) with Sf3a2, which has significant similarities to the N-terminus of a known guanine nucleotide releasing protein (GNRP) and consequently is provisionally named GNRPx/Gnrpx. The Gnrpx-Sf3a2-Amh (GSA) locus of the mouse (MMU10) is conserved in the human (HSA19p). Mapping the Sf3a2 transcription start site eventually led us to locate and characterize its promoter. We found that Sf3a2 and Gnrpx share a bi-directional promoter, with the latter being transcribed in an antisense direction. It has now been shown by RT-PCR analysis that both Sf3a2 and Gnrpx are widely expressed and therefore are likely to be 'housekeeping' genes. GNRPx/Gnrpx messenger RNA codes for a C-terminally truncated protein (149/164 aa), which contains an as yet uncharacterized domain common to GNRPs (and related proteins) and which may therefore act as a specific antagonist of a complete GNRP protein (>1200 aa) involved in the regulation of the GTPase (G-protein/Ras) cycle.

In vivo analysis of the regulation of the anti-Müllerian hormone, as a marker of Sertoli cell differentiation during testicular development, reveals a multi-step process

Anti-Müllerian hormone (AMH) is a member of the TGF-beta family which elicits its main action during male sex differentiation. This hormone is probably the most convenient marker of Sertoli cell differentiation and maturation throughout testicular development. Studying AMH gene regulation may thus be one way of identifying effectors of Sertoli cell differentiation. To this end we first tried to locate and then to characterise DNA elements responsible for in vivo transcriptional control of AMH expression. We obtained transgenic mice expressing a reporter gene (LacZ), under control of various putative AMH regulatory sequences. Analysis of transgenic animals revealed that activation of the AMH gene probably requires a two-step regulatory process. The first step corresponds to the initial activation of the AMH gene occurring at around 12.0 dpc. It requires the presence of regulatory DNA encompassed within a maximum of 370 bp upstream of the translation start site of the gene, delimited by the presence of an upstream housekeeping gene (SAP-62). Following this initial transient phase, a second phase seems to account for the persistence of AMH gene expression until the onset of puberty. As the 370 bp regulatory region is not sufficient on its own to allow the triggering of this second phase, it seems possible that additional control elements are required for normal AMH expression throughout testicular development. The complete array of regulatory elements remains to be located. Mol. Reprod. Dev. 59:256-264, 2001.

The ABI1 and ABI2 protein phosphatases 2C act in a negative feedback regulatory loop of the abscisic acid signalling pathway

The Arabidopsis ABI1 and ABI2 genes encode two protein serine/threonine phosphatases 2C (PP2C). These genes have been originally identified by the dominant mutations abi1--1 and abi2--1, which reduce the plant's responsiveness to the hormone abscisic acid (ABA). However, recessive mutants of ABI1 were recently shown to be supersensitive to ABA, which demonstrated that the ABI1 phosphatase is a negative regulator of ABA signalling. We report here the isolation and characterisation of the first reduction-of-function allele of ABI2, abi2--1R1. The in vitro phosphatase activity of the abi2--1R1 protein is approximately 100-fold lower than that of the wild-type ABI2 protein. Abi2--1R1 plants displayed a wild-type ABA sensitivity. However, doubly mutant plants combining the abi2--1R1 allele and a loss-of-function allele at the ABI1 locus were more responsive to ABA than each of the parental single mutants. These data indicate that the wild-type ABI2 phosphatase is a negative regulator of ABA signalling, and that the ABI1 and ABI2 phosphatases have overlapping roles in controlling ABA action. Measurements of PP2C activity in plant extracts showed that the phosphatase activity of ABI1 and ABI2 increases in response to ABA. These results suggest that ABI1 and ABI2 act in a negative feedback regulatory loop of the ABA signalling pathway.

The ABI1 and ABI2 protein phosphatases 2C act in a negative feedback regulatory loop of the abscisic acid signalling pathway

The Arabidopsis ABI1 and ABI2 genes encode two protein serine/threonine phosphatases 2C (PP2C). These genes have been originally identified by the dominant mutations abi1--1 and abi2--1, which reduce the plant's responsiveness to the hormone abscisic acid (ABA). However, recessive mutants of ABI1 were recently shown to be supersensitive to ABA, which demonstrated that the ABI1 phosphatase is a negative regulator of ABA signalling. We report here the isolation and characterisation of the first reduction-of-function allele of ABI2, abi2--1R1. The in vitro phosphatase activity of the abi2--1R1 protein is approximately 100-fold lower than that of the wild-type ABI2 protein. Abi2--1R1 plants displayed a wild-type ABA sensitivity. However, doubly mutant plants combining the abi2--1R1 allele and a loss-of-function allele at the ABI1 locus were more responsive to ABA than each of the parental single mutants. These data indicate that the wild-type ABI2 phosphatase is a negative regulator of ABA signalling, and that the ABI1 and ABI2 phosphatases have overlapping roles in controlling ABA action. Measurements of PP2C activity in plant extracts showed that the phosphatase activity of ABI1 and ABI2 increases in response to ABA. These results suggest that ABI1 and ABI2 act in a negative feedback regulatory loop of the ABA signalling pathway.

GATA-1 is a potential repressor of anti-Müllerian hormone expression during the establishment of puberty in the mouse

Anti-Müllerian hormone (AMH), also known as Müllerian inhibiting substance (MIS), is one of the earliest and best-known markers of Sertoli cell differentiation and is expressed until around puberty. The present study is aimed at the better understanding of the molecular pathways involved in testicular development and establishment of adult functions with regards to AMH regulation. We found, within the mouse AMH promoter, putative GATA motifs (A/T)GATA(A/G), known to be specifically bound by members of the GATA transcription factor family. We then carried out RNase protection assays and immunohistochemical techniques aimed at comparing precisely the chronological expression patterns of AMH and GATA-1, this latter being expressed in the testis after birth. Using both approaches we found an inverse and close relationship between AMH and GATA-1 mRNA and protein expression during the pre-pubertal period. These results allowed us to define a transitory 4-5-day period, starting from 3 dpp when both proteins are heterogeneously expressed in Sertoli cells and showed that the appearance of GATA-1 is associated with the decrease of AMH expression in these cells. Furthermore DNA-protein interaction in in vitro studies showed first that GATA-1 binds with various affinities on sites found in the AMH promoter and second that the proximity of the two strongest affinity sites leads to a synergistic binding effect. Altogether, the present study suggests that GATA-1 participates in AMH gene repression during the pre-pubertal period.

Cloning and characterisation of MEK1, an Arabidopsis gene encoding a homologue of MAP kinase kinase

We report the cloning of a cDNA for MEK1, an Arabidopsis thaliana gene encoding a homologue of MAP kinase kinase (MEK). The predicted protein sequence shows 41% identity over 270 amino acids to vertebrate MEK proteins, and contains conserved features characteristic of MEK. Analysis of transcript levels show that expression of the gene is regulated by developmental processes (etiolation/de-etiolation) and by wounding. However in contrast to the rapid wound induction of MAP kinase transcripts in other plant species, MEK1 transcripts first accumulated 6-12 h after wounding.

Further progress towards a catalogue of all Arabidopsis genes: analysis of a set of 5000 non-redundant ESTs

Nearly 7000 Arabidopsis thaliana-expressed sequence tags (ESTs) from 10 cDNA libraries have been sequenced, of which almost 5000 non-redundant tags have been submitted to the EMBL data bank. The quality of the cDNA libraries used is analysed. Similarity searches in international protein data banks have allowed the detection of significant similarities to a wide range of proteins from many organisms. Alignment with ESTs from the rice systematic sequencing project has allowed the detection of amino acid motifs which are conserved between the two organisms, thus identifying tags to genes encoding highly conserved proteins. These genes are candidates for a common framework in genome mapping projects in different plants.

The genes for a spliceosome protein (SAP62) and the anti-Müllerian hormone (AMH) are contiguous

During an investigation of the regulatory potential of a region 5' of the mouse anti-müllerian hormone (Amh) gene, we identified a region of homology with the known cDNA sequence of a human spliceosome gene (SAP62). In mouse, the Sap62 termination codon (TGA) is just 434 bp 5' of the Amh start of translation (ATG); in the human the equivalent distance is 789 bp. RNase protection analysis shows the majority of Sap62 transcripts use an uncommon polyadenylation signal (ATTAAA) lying in the intragenic region, 87 bp 3' of the TGA. This analysis also shows that Sap62 is transcribed in all tissues examined, whereas specific Amh transcription initiating 10 bp 5' of the ATG is limited to the developing testis of the fetus from 11.5 days post coitum and in the ovary from 3 days post partum. However, in all tissues a significant number of Sap62 transcripts fail to polyadenylate in the intragenic region and continue through the Amh locus. This implies that the Amh locus is in an open chromatin state in all tissues despite a requirement for precise regulation. Human SAP62 can now be mapped to HSA19p and mouse Sap62 to MMU10.

Antiaggregant and antivasospastic properties of the new thromboxane A2 receptor antagonist sodium 4-[[1-[[[(4-chlorophenyl)sulfonyl]amino]methyl]cyclopentyl] methyl]benzeneacetate

LCB 2853 (sodium 4-[[1-[[[(4-chlorophenyl)sulfonyl]amino]methyl]cyclopentyl] methyl]benzeneacetate, CAS 141335-11-7) was demonstrated to be a potent thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptor antagonist in in vitro, ex vivo and in vivo experiments. The specific mechanism of action was studied in [3H]SQ 29548 receptor binding studies (pKi = 7.93) and was shown to be of competitive nature in U 46619-induced platelet aggregation (pA2 = 6.82). TXA2-dependent platelet rich plasma (PRP) aggregation (U 46619, arachidonic acid (AA), collagen, ADP or serotonin second phase) was inhibited in vitro in humans (IC50:0.037-0.65 mumol/l) and different animal species, as well as ex vivo i.v. rat and p.o. guinea-pig AA-induced aggregation (ED50 = 48 and 57 micrograms/kg). The U 46619-induced contractions of aorta, caudal artery and trachea were inhibited in a dose-dependent way (IC50 = 0.07, 0.02 and 0.5 mumol/l respectively). In vivo, both against platelet aggregation and vasoconstriction, LCB 2853 showed an ED50 lower than 1 mg/kg i.v. in rat AA-induced thrombocytopenia or U 46619-induced hypertension (ED50 = 0.25 and 0.16 mg/kg) as well as in AA-induced sudden death in the mouse (ED50 = 0.44 mg/kg). The U 46619-induced bronchoconstriction was blocked after i.v. administration of LCB 2853 (ED50 = 18.4 micrograms/kg). The duration of action observed in different models was 6 h by oral route and between 3 and 5 h by intravenous route. These properties in TXA2-dependent models led to further investigations of the antithrombotic activity of this novel TXA2 antagonist.

Pharmacodynamics and antithrombotic effects after intravenous administration of the new thromboxane A2 receptor antagonist sodium 4-[[1-[[[(4-chlorophenyl)sulfonyl]amino]methyl]cyclopentyl] methyl]benzeneacetate

The antiplatelet and antithrombotic activities of LCB 2853 (sodium 4-[[1-[[[(4-chlorophenyl)sulfonyl]amino]methyl]cyclopentyl] methyl]benzeneacetate, CAS 141335-11-7) a novel thromboxane A2 (TXA2) receptor antagonist were examined after intravenous administration. The correlation between LCB 2853 plasma concentration and ex vivo inhibition of arachidonic acid-induced aggregation was observed in rats, for 4 h, as long as LCB 2853 was detected in plasma by HPLC analysis. Pharmacokinetic parameters were determined. The antithrombotic activity was tested in arterial and venous thrombosis models. In dog coronary stenosis, LCB 2853 shown a very high efficacy (ED50 = 7.2 micrograms/kg), whereas acetylsalicylic acid (ASA) was only active at 3.2 mg/kg and ticlopidine was ineffective at 12.8 mg/kg. In rat venous thrombosis induced by combination of venous injury and blood stasis, perfused LCB 2853 decreased the weight of thrombi in a dose related manner (ED50 = 220 micrograms/kg/min). In a comparative study, at 250 micrograms/kg/min, ticlopidine was less potent and ASA failed to show any protection. The potent immediate efficacy of LCB 2853 and the advantageous comparisons with ASA (which was ineffective in some models) or ticlopidine (which needs metabolization lag time) observed in many models suggest that this compound may have beneficial effects in patients with TXA2-associated disturbances.

Arabidopsis ABA response gene ABI1: features of a calcium-modulated protein phosphatase

The Arabidopsis ABI1 locus is essential for a wide spectrum of abscisic acid (ABA) responses throughout plant development. Here, ABI1 was shown to regulate stomatal aperture in leaves and mitotic activity in root meristems. The ABI1 gene was cloned and predicted to encode a signaling protein. Although its carboxyl-terminal domain is related to serine-threonine phosphatase 2C, the ABI1 protein has a unique amino-terminal extension containing an EF hand calcium-binding site. These results suggest that the ABI1 protein is a Ca(2+)-modulated phosphatase and functions to integrate ABA and Ca2+ signals with phosphorylation-dependent response pathways.

Two sites of action for LCB29 (idrocilamide) in depressing mechanical tension of rat soleus muscle fibers?

The effects of 50 microM LCB29 (idrocilamide) were tested on depolarization-induced and caffeine contractures of rat soleus muscle fibers. When applied intracellularly by free diffusion in cut-end voltage-clamped fibers, LCB29 decreased tension amplitude by about 25%. The same amount of inhibition by LCB29 was observed on contractures induced by 6 mM caffeine. The drug did not affect the repriming of caffeine contractures, indicating that internal recycling of calcium was not affected. The voltage-dependent inactivation of tension was facilitated by external application of LCB29. This effect was calcium dependent, so that the greater the external calcium concentration, the greater the drug effectiveness. The spontaneous relaxation of K+ contractures was also accelerated by LCB29. It is concluded that LCB29 acts intracellularly by decreasing sarcoplasmic reticulum calcium release and externally by facilitating the voltage-dependent inactivation of the voltage sensor for excitation-contraction coupling.

Anti-Müllerian hormone Bruxelles: a nonsense mutation associated with the persistent Müllerian duct syndrome

The persistent Müllerian duct syndrome (PMDS) is characterized by the persistence of Müllerian derivatives, uterus and tubes, in otherwise normally virilized males. In a previous study, we showed that this syndrome is heterogeneous, with lack of production of anti-Müllerian hormone (AMH) by testicular tissue accounting for only some, AMH-negative, cases of this disorder. We have characterized the point mutation responsible for an AMH-negative PMDS in three siblings: a guanine to thymine transversion at position 2096 in the fifth exon changes a GAA triplet, coding for glutamic acid, to a TAA stop codon. The mutation could also be recognized, using the polymerase chain reaction, on RNA produced in trace amounts by a lymphoblastic cell line. The translation product, although undetectable in testicular tissue, could be visualized in culture medium of cells transfected with the mutant gene.

The direct depressant effect of LCB29 (idrocilamide) on mechanical tension of rat soleus muscle fibers

The effect of LCB29 was tested on twitch characteristics, tetanic tension, and K+ and voltage-clamp contractures of rat soleus muscle fibers. In concentrations ranging from 10(-6) to 5 x 10(-4) M, LCB29 simultaneously inhibited the twitch amplitude, the maximum rate of tension development, and the maximum rate of relaxation. In concentrations ranging from 10(-5) to 10(-4) M, tetanic tension (100 Hz, 1 s) was inhibited by the same amount. The effect of 5 x 10(-5) M LCB29 was studied on K+ contractures and contractures induced, under voltage-clamp conditions, by long-lasting depolarizations. Its effect was significantly stronger than those on twitch and tetanic tension. In addition, LCB29 had a dual effect on strength--duration curves for mechanical threshold. It increased both the rheobasic potential and the steepness of the curve. It is concluded that LCB29 exerts a direct myorelaxant effect on rat soleus muscle; two sites of action are probably involved.

Expression of the gene for anti-Müllerian hormone

The expression of anti-Müllerian hormone, also called Müllerian-inhibiting substance or factor, is limited to immature Sertoli and post-natal granulosa cells. To gain information on the genetic mechanisms of this tissue- and development-specific regulation, a human genomic clone containing 3.6 kilobases of 5' flanking sequences has been isolated and sequenced. Transcription initiation sites include a major site, at the same position as in the bovine gene, and 3 minor sites, accounting together for 12% of transcripts. Sequences of potential interest include an Sp1 binding site, minisatellite-like regions, and a 13-base pair palindrome, nearly identical to the oestrogen response element of the vitellogenin genes. This palindrome binds to the human oestrogen receptor in vitro and activates transcription of a hybrid gene when several copies are inserted 5' of a thymidine kinase promoter. Further studies are needed to determine whether this palindrome is implicated in a feed-back loop regulating oestrogen synthesis in granulosa cells.

Response of primary tumour, spontaneous metastases and recurrence of Lewis lung carcinoma (3LL) to flavone acetic acid (FAA, LM975)

B6D2F1 mice bearing 3LL were more sensitive to FAA than control mice, the LD50 being 180 x 2 and 336 x 2 mg/kg respectively. At a dosage of 140 mg/kg, injected i.p. at day 4 and 11, FAA significantly decreased the primary tumour growth, the occurrence and the growth of spontaneous pulmonary metastases. The effect of two injections was dose-dependent on the primary tumour and metastases; the survival time was also dose-related. Combined with primary tumour ablation, FAA administered before any dissemination (at day 3) was more efficient against metastases than when it was injected after the end of the dissemination (i.e. after primary tumour ablation). When all treatment schedules were pooled, the number of mice without metastasis was significantly higher in treated than in control groups. The effect of FAA on recurrences was also notable.

The persistent Müllerian duct syndrome: a molecular approach

A rare form of male pseudohermaphroditism is characterized by the persistence of Müllerian derivatives in phenotypic males. To determine the etiology of this syndrome, we studied the expression of anti-Müllerian hormone (AMH) in six boys, including three brothers, with the persistent Müllerian duct syndrome. All except one presented with an inguinal hernia containing the Müllerian derivatives, and in two boys the hernial sac contained the contralateral testis. AMH was normally expressed in the testicular tissue of two patients, as shown by bioassay of anti-Müllerian activity and immunocytochemistry. The testicular tissue of the other patients had no detectable bioactive or immunoreactive AMH, yet they expressed AMH mRNA with a normal transcription initiation site and in the amount expected for their age. These results prove the heterogeneity of the persistent Müllerian duct syndrome and suggest that it may sometimes involve peripheral insensitivity to AMH.

Characterization of carbon metabolism in Opuntia ficus-indica Mill. exhibiting the idling mode of Crassulacean acid metabolism

Upon transfer from well-watered conditions to total drought, long-day-grown cladodes of Opuntia ficus-indica Mill. shift from full Crassulacean acid metabolism (CAM) to CAM-idling. Experiments using (14)C-tracers were conducted in order to characterize the carbon-flow pattern in cladodes under both physiological situations. Tracer was applied by (14)CO2 fumigations and NaH(14)CO3 injections during the day-night cycle. The results showed that behind the closed stomata, mesophyll cells of CAM-idling plants retained their full capacity to metabolize CO2 in light and in darkness. Upon the induction of CAM-idling the level of the capacity of phosphoenolpyruvate carboxylase (EC 4.1.1.31) was maintained. By contrast, malate pools decreased, displaying finally only a small or no day-night oscillation. The capacity of NADP-malic enzyme (EC 1.1.1.40) decreased in parallel with the reduction in malate pools. Differences in the labelling patterns, as influenced by the mode of tracer application, are discussed.

Mapping of the gene for anti-müllerian hormone to the short arm of human chromosome 19

The gene coding for human anti-Müllerian hormone (AMH) was localized to subbands p13.2----p13.3 on chromosome 19, using in situ hybridization and Southern blot analysis of a panel of man-mouse and man-hamster somatic cell hybrids.

Cloning and expression of cDNA for anti-müllerian hormone

Messenger RNA, prepared from fetal bovine testicular tissue, was used to construct a cDNA library in lambda gt11 phage. The library was screened with an antibody probe directed against bovine anti-Müllerian hormone and three positive clones were isolated. Cross-hybridizing cDNA inserts carried by clones 4 and 5 (1.2 and 0.08 kilobases long, respectively) code for a fragment of authentic anti-Müllerian hormone, as shown by the ability of the anti-epitope antibodies eluted from fusion protein 4 to bind strongly to anti-Müllerian hormone on immunoblots and by the capacity of anti-epitope antibodies 4 and 5 to precipitate radioiodinated bovine anti-Müllerian hormone. A probe prepared from insert 4 hybridizes with an mRNA present only in tissues that are known producers of anti-Müllerian hormone, such as the fetal testis and adult ovarian follicles. The amount of specific mRNA in tissues of males and females is related to the rate of their anti-Müllerian hormone production. The 2.1-kilobase size of this mRNA species is large enough to code for the Mr 62,000 anti-Müllerian hormone polypeptide chain. Insert 4 also hybridizes with an mRNA of similar size in human and rat fetal testicular tissue. The third isolated clone, clone 8, which does not cross-hybridize with the others, carries a cDNA insert coding for a ubiquitous protein, smaller than anti-Müllerian hormone, with which it apparently shares an epitope.

Photoperiodism and Crassulacean acid metabolism : II. Relations between leaf aging and photoperiod in Crassulacean acid metabolism induction

Measurements of net CO2 exchange, malate accumulation, properties and capacity of phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) in leaves of different ages of two short-day dependent Crassulacean acid metabolism (CAM) plants (Kalanchoe blossfeldiana v. Poelln. Tom thumb and K. velutina Welw.) show that, in both species: a) young leaves from plants grown under long days display a CO2 exchange pattern typical of C3 plants; b) leaf aging promotes CAM under long-day conditions; c) short-day treatment induces CAM in young leaves to a higher degree than aging under long days; d) at least in K. blossfeldiana, the PEPC form developed with leaf aging under long days and the enzyme form synthetized de novo in young leaves grown under short days were shown to have similar properties. Short days also promote CAM in older leaves though at a lesser extent than in young leaves: The result is that this photoperiodic treatment increases the general level of CAM performance by the whole plant. The physiological meaning of the control of PEPC capacity by photoperiodism could be to afford a precisely timed seasonal increase in CAM potentiality, enabling the plant to immediately optimize its response to the onset of drought periods.

Changes in the isozymic pattern of phosphoenolpyruvate : An early step in photoperiodic control of crassulacean acid metabolism level

Two major isofunctional forms of phosphoenolpyruvate carboxylase (EC 4.1.1.31) have been separated from the leaves of Kalanchoe blossfeldiana Poelln. Tom Thumb by acrylamide gel electrophoresis and diethylaminoethyl cellulose techniques: one of the forms prevails under long-day treatment (low crassulacean acid metabolism level), the other develops under short-day treatment (high Crassulacean acid metabolism level). Molecular weights are significantly different: 175·10(3) and 186·10(3), respectively. These results indicate that two populations of phosphoenolyruvate carboxylase are present in the plant, one of which is responsible for Crassulacean acid metabolism activity under the control of photoperiod.The Crassulacean acid metabolism appears to depend on the same endogenous clock that governs other photoperiodically controlled events (e.g. flowering). The metabolic and energetic significance of this feature is discussed. It is suggested that modification in isozymic composition could be an early step in the response to photoperiodism at the metabolic level.

[Effect of sampling conditions on the concentration of corticosterone in rat brown fat]

Corticosterone is more concentrated in the white and brown fat of the Rats killed after ether and nembutal anesthesia, than by decapitation. Corticosterone in the plasma increases in the same manner. There results show that adipose tissue is a pool of dilution in balance with the circulating corticosterone.

[Assay of cortisol and corticosterone in the plasma and adrenal glands of the golden hamster (Mesocricetus auratus)]

Corticosterone and cortisol are assayed by fluorometry after separation of the corticoids by chromatography on silica gel in the plasma and in the adrenals of golden Hamster brought up in the laboratory. The ratio cortisol : corticosterone is 2.7 in the plasma and 2.8 in the adrenals.

[Influence of the pituitary-adrenal axis on the brown fat tissue of the rat and golden hamster]

The suppression or reduction of the adrenal secretion in the Rat and in the golden Hamster results in a reduction of the weight of brown adipose tissue and of the volume of intra cytoplasmic vacuoles. When corticotropin is given to normal and hypophysectomized animals, the intra cytoplasmic vacuolar system and the corticosterone concentration of brown fat increase. After sham hypophysectomy and short ether intake, a considerable lipidic depletion and a high level of corticosterone are observed. The authors speculate that the by adrenaline. The morphologic responses are much more intense and rapid lipid content of brown adipose tissue is increased by corticotropin and reduced by adrenaline. The morphologic responses are much more intense and rapid in brown adipose tissue than in white adipose tissue.

Photoperiodism and enzyme rhythms: Kinetic characteristics of the photoperiodic induction of Crassulacean acid metabolism

The effect of photoperiod on Crassulacean acid metabolism (CAM) in Kalanchoe blossfeldiana Poellniz, cv. Tom Thumb, has characteristics similar to its effect on flowering in this plant (although these two phenomena are not causally related). The photoperiodic control of CAM is based on (a) dependance on phytochrome, (b) an endogenous circadian rhythm of sensitivity to photoperiodic signals, (c) a balance between specific positive (increase in enzyme capacity) and negative (inhibitory substances) effects of the photoperiod. Variations in malate content, capacity of phosphoenolpyruvate (PEP) carboxylase, and capacity of CAM inhibitors in young leaves were measured under photoperiodic conditions noninductive for CAM and after transfer into photoperiodic conditions inductive for CAM. Essential characteristics of the photoperiodic induction of CAM are: 1) lag time for malate accumulation; 2) after-effect of the inductive photoperiod on the malate accumulation, on the increase in PEP carboxylase capacity, and on the decrease in the level of long-day produced inhibitors; final levels of malate, enzyme capacity and inhibitor are proportional to the number of inductive day-night cycles; 3) cireadian rhythm in PEP carboxylase capacity with a fixed phase under noninductive photoperiods and a continuously shifting phase under inductive photoperiods, after complex advancing and delaying transients. Kinetic similarities indicate that photoperiodic control of different physiological functions, namely, CAM and flowering, may be achieved through similar mechanisms. Preliminary results with species of Bryophyllum and Sedum support this hypothesis. Phase relationships suggest different degrees of coupling between endogenous enzymic rhythm and photoperiod, depending on whether the plants are under long days or short days.