4260Loss of Pnn in cardiomyocytes results in impairment of intercalated discs and arrhythmogenic cardiomyopathy in mice

Background

Pnn, a multiple functional protein that localizes within nucleus and in the cytoplasmic region of desmosome. Although recent studies have characterized the physiological role of nuclear Pnn in regulating pre-mRNA alternative splicing and gene transcription, the function of Pnn in desmosome, particularly in cardiomyocytes, remains unidentified.

Purpose and methods

In the present study, we applied an inducible cardiomyocyte-specific Pnn depletion mouse model (Myh6-CreERT2, Pnnflox/flox) to observe the impact of loss of Pnn on cardiac structure and function in adult mice.

Results

Six weeks after tamoxifen injection to induce cardiac Pnn depletion, the electrocardiographic abnormalities and decrease of left ventricular ejection fraction (LVEF) were observed. Histopathological examination showed that the proliferation of cardiac fibroblasts and expression of α-smooth muscle actin were increased with Pnn depletion, while the cell-cell connection among cardiomyocytes were impaired. In addition, cellular hypertrophy and decrease of capillary density were also found. Results from Immunofluorescent staining further showed that the distribution pattern of desmosomal proteins and adherent junctional proteins, including desmoglein, desmocollin, plakoglobin, plakophllin, desmoplakin and β-catenin were altered in the cardiomyocytes with Pnn depletion. Both desmosomal and adherent junctional proteins were translocated form cell-cell junction to cytoplasm, indicating the disruption of intercalated discs in Pnn-depleted cardiomyocytes. Microarray data also indicated that loss of cardiac Pnn regulated the mRNA expression of genes responsible for extracellular matrix-receptor interaction, ribosome, and integrin. In addition, expression levels of oxidative stress-associated proteins were significantly regulated by Pnn depletion.

Impairment of intercalated disc

Conclusion

Results from present study indicated that Pnn plays an essential role in the maintenance of intercalated disc integrity of cardiomyocytes, while cardiomyocyte-specific loss of Pnn leads to arrhythmogenic cardiomyopathy in mice.

Acknowledgement/Funding

Ministry of Science and Technology Taiwan, MOST-106-2320-B-182A-010-MY3

Intestinal IMINO transporter SIT1 is not expressed in human newborns

The expression of amino acid transporters in small intestine epithelia of human newborns has not been studied yet. It is further not known whether the maturation of imino acid (proline) transport is delayed as in the kidney proximal tubule. The possibility to obtain small intestinal tissue from patients undergoing surgery for jejunal or ileal atresia during their first days after birth was used to address these questions. As control, adult terminal ileum tissue was sampled during routine endoscopies. Gene expression of luminal imino and amino acid transporter SIT1 (SLC6A20) was approximately threefold lower in newborns versus adults. mRNA levels of all other luminal and basolateral amino acid transporters and accessory proteins tested were similar in newborn mucosa compared with adults. At the protein level, the major luminal neutral amino acid transporter B⁰AT1 (SLC6A19) and its accessory protein angiotensin-converting enzyme 2 were shown by immunofluorescence to be expressed similarly in newborns and in adults. SIT1 protein was not detectable in the small intestine of human newborns, in contrast to adults. The morphology of newborn intestinal mucosa proximal and distal to the obstruction was generally normal, but a decreased proliferation rate was visualized distally of the atresia by lower levels of the mitosis marker K_i-67. The mRNA level of the 13 tested amino acid transporters and accessory proteins was nonetheless similar, suggesting that the intestinal obstruction and interruption of amniotic fluid passage through the small intestinal lumen did not affect amino acid transporter expression. NEW & NOTEWORTHY System IMINO transporter SIT1 is not expressed in the small intestine of human newborns. This new finding resembles the situation in the proximal kidney tubule leading to iminoglycinuria. Lack of amniotic fluid passage in small intestinal atresia does not affect amino acid transporter expression distal to intestinal occlusion.

Cast wedging: a systematic review of the present evidence

PURPOSE

The objective of this systematic review was to summarise the outcome after cast wedging due to loss of angulation in conservative fracture treatment of children's fractures.

METHODS

Electronic searches were performed using MEDLINE, PubMed, OVID, CENTRAL and EMBASE without language restrictions.

RESULTS

Three studies comprising 316 patients (210 radius, 52 forearm/both bone forearm fractures and 54 tibia fractures) were included in the present analysis. Cast wedge failures occurred in 14 of 316 (4.4%) patients. Three patients (0.9%) needed surgical fixation and 11 patients (3.4%) ended up with a healed deformity. Furthermore, eight of 316 (1.8%) patients needed remanipulation and cast change.

CONCLUSION

Cast wedging reflects a reliable treatment option for secondary displaced long-bone paediatric fractures.

High salt exacerbates programmed hypertension in maternal fructose-fed male offspring

BACKGROUND AND AIMS

Consumption of food and drinks containing high fructose (HF), which is associated with hypertension, is increasing steeply. Moreover, increased salt intake significantly increases hypertension risk. We examined whether maternal HF and postnatal high salt (HS) intake had synergistic effects on blood pressure (BP) elevation in adult offspring and determined the underlying mechanisms.

METHODS AND RESULTS

Pregnant Sprague-Dawley rats received regular chow or chow supplemented with 60% fructose during the entire pregnancy and lactation periods. Half of the male offspring received 1% NaCl in drinking water from weaning to 3 months of age. Male offspring were assigned to 4 groups (control, HF, HS, and HF + HS) and were sacrificed at 12 weeks of age. Offspring in HF and HS groups developed hypertension, indicating that HF and HS synergistically increased BP. Postnatal HS intake increased Ace expression and decreased Agtr1b and Mas1 expression in the kidneys. Renal mRNA levels of Ace and Agtr1a were significantly higher in HF + HS group than in control group. Renal levels of Na-K-2Cl cotransporter, type 3 sodium hydrogen exchanger, and Na(+)/Cl(-) cotransporter were higher in HS and HF + HS groups than in control group.

CONCLUSION

Postnatal HS intake exacerbated prenatal HF-induced programmed hypertension. HF and HS induced programmed hypertension by differentially inducing renin-angiotensin system and sodium transporters in the kidneys. Better understanding of the effect of the relationship between HF and HS on hypertension development will help prevent hypertension in mothers and children exposed to HF and HS.

Reliability and application variability of a commercially available infrared videonystagmography unit

PURPOSE

Nystagmus is a condition of involuntary eye movement. The causes for nystagmus may be congenital, idiopathic, or acquired. Considerable debate exists on the therapeutic potential of various surgical techniques. Currently, there are neither standardized protocols nor devices to record quantitative data on patients with clinical nystagmus undergoing various procedures at multiple centers to facilitate randomized prospective clinical trials.

METHODS

The authors evaluated the reliability and variability of a commercially available infrared videonystagmography unit by recording eye movement waveforms elicited from normal volunteers (n = 117, 13 patients, 9 trials) by different examiners (A, B, and C). Five movement characteristics were examined, including saccadic latency, velocity and precision, and pursuit gain and velocity.

RESULTS

The overall test/retest variability was low, where the median coefficient of variation of the three testers for all five eye movement categories was less than 15%, and less than 10% of the coefficients of variation calculated were more than 20%. However, there was a significant difference in interobserver variability for all outcomes, except saccade latency.

CONCLUSIONS

The between-tester analysis was found to have greater variability than the test/retest reliability analysis. Future studies at multiple sites using videonystagmography measurements should aim to have each patient repeatedly tested by the same tester. In anticipation of multicenter, randomized, prospective clinical trials of surgical procedures for nystagmus, standardized protocols for nystagmographic data collection and analysis must be validated both within and among participating centers.

Nonviolent elaborate behaviors may also occur in REM sleep behavior disorder

OBJECTIVE

To document unusual, nonviolent behaviors during REM sleep behavior disorder (RBD) and evaluate their frequency in Parkinson disease (PD).

BACKGROUND

Most behaviors previously described during RBD mimic attacks, suggesting they proceed from archaic defense generators in the brainstem. Feeding, drinking, sexual behaviors, urination, and defecation have not been documented yet in RBD.

METHODS

We collected 24 cases of nonviolent behaviors during idiopathic and symptomatic RBD (narcolepsy, dementia with Lewy bodies, PD), reported or observed in videopolysomnography. The frequency of violent and nonviolent behaviors during RBD was evaluated by face to face interview of patients and their cosleepers in a prospective series of 100 patients with PD.

RESULTS

Incidental cases of nonviolent behaviors during RBD included masturbating-like behavior and coitus-like pelvic thrusting, mimicking eating and drinking, urinating and defecating, displaying pleasant behaviors (laughing, singing, dancing, whistling, smoking a fictive cigarette, clapping and gesturing "thumbs up"), greeting, flying, building a stair, dealing textiles, inspecting the army, searching a treasure, and giving lessons. Speeches were mumbled or contained logical sentences with normal prosody. In PD with RBD (n = 60), 18% of patients displayed nonviolent behaviors. In this series (but not in incidental cases), all RBD patients with nonviolent behaviors also showed violent behaviors.

CONCLUSIONS

Although they are less frequent than violent behaviors, nonviolent behaviors during REM sleep behavior disorder (RBD) fill a large spectrum including learned speeches and culture-specific behaviors, suggesting they proceed from the cortex activation. Sexual behaviors during RBD may expose patients and cosleepers to forensic consequences.

Na+-H+ exchanger 3 (NHE3) is present in lipid rafts in the rabbit ileal brush border: a role for rafts in trafficking and rapid stimulation of NHE3

1. Rabbit ileal Na+-absorbing cell Na+-H+ exchanger 3 (NHE3) was shown to exist in three pools in the brush border (BB), including a population in lipid rafts. Approximately 50% of BB NHE3 was associated with Triton X-100-soluble fractions and the other approximately 50% with Triton X-100-insoluble fractions; approximately 33% of the detergent-insoluble NHE3 was present in cholesterol-enriched lipid microdomains (rafts). 2. The raft pool of NHE3 was involved in the stimulation of BB NHE3 activity with epidermal growth factor (EGF). Both EGF and clonidine treatments were associated with a rapid increase in the total amount of BB NHE3. This EGF- and clonidine-induced increase of BB NHE3 was associated with an increase in the raft pool of NHE3 and to a smaller extent with an increase in the total detergent-insoluble fraction, but there was no change in the detergent-soluble pool. In agreement with the rapid increase in the amount of NHE3 in the BB, EGF also caused a rapid stimulation of BB Na+-H+ exchange activity. 3. Disrupting rafts by removal of cholesterol with methyl-beta-cyclodextrin (MbetaCD) or destabilizing the actin cytoskeleton with cytochalasin D decreased the amount of NHE3 in early endosomes isolated by OptiPrep gradient fractionation. Specifically, NHE3 was shown to associate with endosomal vesicles immunoisolated by anti-EEA1 (early endosomal autoantigen 1) antibody-coated magnetic beads and the endosome-associated NHE3 was decreased by cytochalasin D and MbetaCD treatment. 4. We conclude that: (i) a pool of ileal BB NHE3 exists in lipid rafts; (ii) EGF and clonidine increase the amount of BB NHE3; (iii) lipid rafts and to a lesser extent, the cytoskeleton, but not the detergent-soluble NHE3 pool, are involved in the EGF- and clonidine-induced acute increase in amount of BB NHE3; (iv) lipid rafts and the actin cytoskeleton play important roles in the basal endocytosis of BB NHE3.

Extraordinary features in the Chlamydomonas reinhardtii chloroplast genome: (1). rps2 as part of a large open reading frame; (2). A C. reinhardtii specific repeat sequence

We have determined the DNA sequence of the 3574-bp chloroplast DNA fragment of Chlamydomonas reinhardtii formed by the overlap of BamHI fragment 3 and EcoRI fragment 5. This sequence encodes most of rps18 and orf570, an unidentified open reading frame that contains a 150 amino acid domain with high homology to the N-terminal part of 30 S ribosomal protein S2 of other chloroplast, cyanobacterial and bacterial genomes. Between these two sequences lies a highly repetitive sequence element of 500 bp, that is composed of multiple direct and inverted repeat sequences that occur in rearranged, but highly conserved form in at least 36 locations in the C. reinhardtii chloroplast genome. Among the conserved repeat sequences in the C. reinhardtii chloroplast genome we identified the borders of the inverted repeats near atpB and rps4. This might indicate that the conserved sequence elements are remainders of gene rearrangements in the chloroplast genome that occurred by relocations of the inverted repeats.

The C. reinhardtii CF1 with the mutation betaT168S has high ATPase activity

We have generated the mutation T168S in the beta subunit of the chloroplast ATP synthase complex of Chlamydomonas reinhardtii by site directed mutagenesis and chloroplast transformation. CF1 and the alpha3beta3gamma complex of this mutant strain were isolated and their enzymatic activities were characterized and compared to those of the corresponding wild type complexes. Without activation the mutant CF1 exhibits MgATPase activity with at least 10 times higher rates than the wild type enzyme. The MgATPase activity could be stimulated to some extent by methanol, but less by ethanol and octylglucoside. The alpha3beta3gamma complex had an even higher MgATPase activity, which was only slightly enhanced by ethanol or methanol. The ATPase activities of the mutant complexes, like those of the wild type complexes, displayed a sharp concentration optimum for Mg2+. Free ADP inhibited neither the mutant nor the wild type ATPase significantly. Azide, which strongly inhibited the ATPase activity of the wild type enzyme, inhibited the mutant enzyme only at an about 30 times higher concentration suggesting that the mutation T168S prevents trapping of a tightly bound MgADP by a catalytic site that regulates chloroplast ATPase activity. The mutant cells grew photoautotrophically at a growth rate of about 50%. Similar to the wild type the cells survived on minimal medium in the dark. Under heterotrophic conditions with acetate as energy and carbon source the mutant cells grew much faster than the wild type cells, but the chlorophyll content per cell decreased dramatically.

Catalytic properties and sensitivity to tentoxin of Chlamydomonas reinhardtii ATP synthases changed in codon 83 of atpB by site-directed mutagenesis

The participation of the amino acid beta83 in determining the sensitivity of chloroplast ATP synthases to tentoxin was reported previously. We have changed codon 83 of the Chlamydomonas reinhardtii atpB gene by site-directed mutagenesis to further examine the role of this amino acid in the response of the ATP synthase to tentoxin and in the mechanism of ATP synthesis and hydrolysis. Amino acid beta83 was changed from Glu to Asp (betaE83D) and to Lys (betaE83K), and the highly conserved tetrapeptide betaT82-E83-G84-L85 (DeltaTEGL) was deleted. Mutant strains were produced by particle gun transformation of atpB deletion mutants cw15DeltaatpB and FUD50 with the mutated atpB genes. The transformants containing the betaE83D and betaE83K mutant genes grew well photoautotrophically. The DeltaTEGL transformant did not grow photoautotrophically, and no CF1 subunits were detected by immunostaining of Western blots using CF1 specific antibodies. The rates of ATP synthesis at clamped DeltapH with thylakoids isolated from cw15 and the two mutants, betaE83D and betaE83K, were similar. However, only the phosphorylation activity of the mutant betaE83D was inhibited by tentoxin with 50% inhibition attained at 4 microM. These results confirm that amino acid beta83 is critical in determining the response of ATP synthase to tentoxin. The rates of the latent Mg-ATPase activity of the CF1s isolated from cw15, betaE83D, and betaE83K were similar and could be enhanced by heat, alcohols, and octylglucoside. As in the case of the membrane-bound enzyme, only CF1 from the betaE83D mutant was sensitive to tentoxin. A lower alcohol concentration was required for optimal stimulation of the ATPase of the betaE83K-CF1 than that of CF1 from the other two strains. Moreover, the optimal activity of the betaE83K-CF1 was also lower. These results suggest that introduction of an amino acid with a positively charged side chain in position 83 in the "crown" domain affects the active conformation of the CF1-ATPase.

A large open reading frame (orf1995) in the chloroplast DNA of Chlamydomonas reinhardtii encodes an essential protein

An open reading frame potentially encoding a protein of 1995 amino acids (orf1995) has been found in the chloroplast genome of the green alga Chlamydomonas reinhardtii. Besides having a short hydrophobic N-terminal domain with five putative transmembrane helices, the predicted orf1995 product is highly basic. orf1995 might be a homologue of the ycf1 gene in land plants, whose function has not yet been determined. Mutants of C. reinhardtii transformed with a disruption of orf1995 remain heteroplasmic for the wild-type and disrupted alleles of this gene, indicating that the orf1995 product is essential for cell survival.

Isolation of CF0CF1 from Chlamydomonas reinhardtii cw15 and the N-terminal amino acid sequences of the CF0CF1 subunits

CF0CF1 was isolated from chloroplasts of the cell wall-deficient Chlamydomonas reinhardtii strain cw15. The subunit pattern was analyzed by SDS-gel electrophoresis and the N-terminal amino acid sequences of all nine subunits were determined by microsequencing. The amino acid sequences of subunits alpha, beta, gamma and epsilon match with those derived from the corresponding Chlamydomonas DNA sequences. In variance with the previously assumed N-terminus of beta; however, it was found that the first 11 amino acids are lacking. The subunits delta, I, II, III and IV were identified by comparison with known sequences of homologous polypeptides of higher plant chloroplasts and cyanobacteria, respectively.

Abdominal tuberculosis--a retrospective analysis of 121 cases

From 1960 to 1989, a total of 121 patients with abdominal tuberculosis were treated at this hospital. Ages, at the time of diagnosis, ranged from 14 years to 81 years with a mean of 44 years. There were 86 males and 35 females. No clinical feature was diagnostic, but the leading presenting complaints were abdominal pain (79%) and fever (53%). Chest x-ray showed that 80 patients (69%) had coexisting evidence of pulmonary tuberculosis. Lesions were most commonly located at the ileocecal region (40%). The diagnosis was bacteriologically established in only 39 patients (32%). It was difficult to obtain the definitive diagnosis, most of our patients (91 cases) were diagnosed while undergoing laparotomy with tissue biopsy. Although the principal treatment of abdominal tuberculosis was chemotherapy and operation should be reserved until complications occurred, there were still 96 patients (79%) who underwent surgical procedures. The reasons of high operative rate were the difficulty of early diagnosis and the delay of proper treatment. The common complications of abdominal tuberculosis and the related managements were discussed and the findings in our cases which were helpful in diagnosing abdominal tuberculosis were also presented. Sixteen severely ill patients who died tended to be older, poor nutrition and associated with underlying medical diseases. Abdominal tuberculosis is still persistent in Taiwan, and it must be included in the differential diagnosis of obscure abdominal conditions to avoid diagnostic delay and unnecessary illness and death.

Transcription and translation of the chloroplast atpB-gene and assembly of ATP synthase subunit beta

In vitro transcription and subsequent translation of the cloned Chlamydomonas chloroplast atpB gene was used to study assembly of ATP synthase. Translation in the presence of thylakoids resulted in association of the beta subunit with the membrane. The in vitro synthesized polypeptide bound to the membrane copurified with CF1 on sucrose gradients. This provides more evidence for the self-assembly of CF1.

Cell cycle-dependent transcriptional and post-transcriptional regulation of chloroplast gene expression in Chlamydomonas reinhardtii

The regulated expression of five chloroplast genes in Chlamydomonas reinhardtii during a 24 hour cell cycle (12 hours light, 12 hours dark) was analyzed. Transcription rates of the genes encoding the two reaction center proteins of Photosystem I (psaA, psaB), the subunits alpha and beta (atpA, atpB) of chloroplast ATP synthase and for chloroplast elongation factor tu (EF-tu) were measured during the cell cycle. All genes are maximally transcribed at the beginning of the light period. Transcription was induced before the onset of illumination by a light-independent mechanism. Transcript abundance of the same genes during the cell cycle was determined by quantification of Northern blots hybridized with gene-specific probes. The atpA, atpB and psaB mRNAs were most abundant in the first 6 hours of the light period and decreased to about 15% of maximum in the dark. The abundance of psaA mRNA showed less variation and was maximal around the middle of the cell cycle. The EF-tu mRNA showed a maximum early in the light period, but decreased to almost undetectable levels in the second half of the light period. Because of the similar transcriptional patterns observed, the differential steady state levels of these chloroplast transcripts appeared to be regulated at the post-transcriptional level.

Synthesis of EF-Tu and distribution of its mRNA between stroma and thylakoids during the cell cycle of Chlamydomonas reinhardii

In Chlamydomonas reinhardii the elongation factor EF-Tu is encoded in the chloroplast DNA. We identified EF-Tu in the electrophoretic product pattern of chloroplast-made proteins and showed that this protein is only synthesized in the first half of the light period in synchronized cells. The newly synthesized EF-Tu contributed little to the almost invariable content of EF-Tu in chloroplasts during the light period of the cell cycle. However, increasing cell volume and the lack of EF-Tu synthesis in the second half of the light period led to a decrease in the concentration of EF-Tu in chloroplasts. At different times in the vegetative cell cycle, the RNA was extracted from whole chloroplasts and from free and thylakoid-bound chloroplast polysomes. The content of mRNA of EF-Tu in chloroplasts and the distribution between stroma and thylakoids were determined. During the light period, the content of the mRNA for EF-Tu varied in parallel to the rate of EF-Tu synthesis. However, in the dark, some mRNA was present even in the absence of EF-Tu synthesis. Most of the mRNA was bound to thylakoids during the whole cell cycle. This suggests that synthesis of EF-Tu is associated with thylakoid membranes.

In-vitro translation of different mRNA-containing fractions of Chlamydomonas chloroplasts

Starting from isolated chloroplasts of the Chlamydomonas reinhardii cw 15 mutant, several mRNA-containing chloroplast subfractions, i.e. thylakoid-bound polysomes, detached polysomes or isolated RNA, were prepared and incubated in homologous and heterologous translation systems. In the reticulocyte lysate these fractions gave rise to strikingly different product patterns. A most prominent difference concerned the in-vivo rapidly labelled 32,000-dalton thylakoid polypeptide. Neither this membrane protein nor its 34,000-dalton precursor was formed when membrane-containing or free polysomes were translated, while the 34,000-dalton precursor was a main product of the RNA isolated from the same membranes. The influence of thylakoid membranes during translation was also observed in homologous translation systems with lysed chloroplasts supplemented with ATP. Membrane and soluble fractions, when translated separately, yielded product patterns which differed from each other, although the RNAs extracted from the respective fractions gave the same product patterns when translated in reticulocyte lysate; the latter included a soluble protein, the large subunit of ribulose-1,5-bisphosphate carboxylase, and a membrane protein, the 34,000-dalton precursor of the 32,000-dalton membrane protein, as major labelled translation products. These results point to a regulatory role of thylakoid membranes in the expression of chloroplast mRNA and argue against compartmentation of the chloroplast mRNAs between the soluble and membrane fractions.