A Toxoplasma palmitoyl acyl transferase and the palmitoylated armadillo repeat protein TgARO govern apical rhoptry tethering and reveal a critical role for the rhoptries in host cell invasion but not egress

Apicomplexans are obligate intracellular parasites that actively penetrate their host cells to create an intracellular niche for replication. Commitment to invasion is thought to be mediated by the rhoptries, specialized apical secretory organelles that inject a protein complex into the host cell to form a tight-junction for parasite entry. Little is known about the molecular factors that govern rhoptry biogenesis, their subcellular organization at the apical end of the parasite and subsequent release of this organelle during invasion. We have identified a Toxoplasma palmitoyl acyltransferase, TgDHHC7, which localizes to the rhoptries. Strikingly, conditional knockdown of TgDHHC7 results in dispersed rhoptries that fail to organize at the apical end of the parasite and are instead scattered throughout the cell. While the morphology and content of these rhoptries appears normal, failure to tether at the apex results in a complete block in host cell invasion. In contrast, attachment and egress are unaffected in the knockdown, demonstrating that the rhoptries are not required for these processes. We show that rhoptry targeting of TgDHHC7 requires a short, highly conserved C-terminal region while a large, divergent N-terminal domain is dispensable for both targeting and function. Additionally, a point mutant lacking a key residue predicted to be critical for enzyme activity fails to rescue apical rhoptry tethering, strongly suggesting that tethering of the organelle is dependent upon TgDHHC7 palmitoylation activity. We tie the importance of this activity to the palmitoylated Armadillo Repeats-Only (TgARO) rhoptry protein by showing that conditional knockdown of TgARO recapitulates the dispersed rhoptry phenotype of TgDHHC7 knockdown. The unexpected finding that apicomplexans have exploited protein palmitoylation for apical organelle tethering yields new insight into the biogenesis and function of rhoptries and may provide new avenues for therapeutic intervention against Toxoplasma and related apicomplexan parasites.

Apicomplexans possess a highly polarized secretory pathway that is critical for their ability to invade host cells and cause disease. This unique cellular organization enables delivery of protein cargo to specialized secretory organelles called micronemes and rhoptries that drive forward penetration into the host cell. The rhoptries are tethered in a bundle at the apex of the parasite, but how these organelles are organized in this manner is unknown. In this work, we identify a rhoptry-localized palmitoyl acyl transferase (named TgDHHC7) that functions to properly affix the rhoptries at the apical end of the parasite. Conditional disruption of TgDHHC7 results in a failure to tether the rhoptries at the cell apex and a corresponding loss of rhoptry function. We exploit this mutant to clearly demonstrate a critical role for the rhoptries in host invasion but not attachment or egress. Additionally, we find that mutation of a key residue predicted to be required for catalytic activity renders TgDHHC7 non-functional and that knockdown of the candidate substrate TgARO produces an identical phenotype to loss of TgDHHC7. The finding that Toxoplasma employs protein palmitoylation to position the rhoptries at the cell apex provides new insight into the molecular mechanisms that underlie apicomplexan cell polarity, host invasion and pathogenesis.

Availability and night-time use of electronic entertainment and communication devices are associated with short sleep duration and obesity among Canadian children

What is already known about this subject Short sleep duration is a risk factor for obesity. Television (TV) in the bedroom has been shown to be associated with excess body weight in children. Children increasingly use other electronic entertainment and communication devices (EECDs) such as video games, computers, and smart phones. What this study adds Access to and night-time use of EECDs are associated with shortened sleep duration, excess body weight, poorer diet quality, and lower physical activity levels. Our findings reinforce existing recommendations pertaining to TV and Internet access by the American Academy of Pediatrics and suggest to have these expanded to restricted availability of video games and smart phones in children's bedrooms.

BACKGROUND

While the prevalence of childhood obesity and access to and use of electronic entertainment and communication devices (EECDs) have increased in the past decades, no earlier study has examined their interrelationship.

OBJECTIVE

To examine whether night-time access to and use of EECDs are associated with sleep duration, body weights, diet quality, and physical activity of Canadian children.

METHODS

A representative sample of 3398 grade 5 children in Alberta, Canada, was surveyed. The survey included questions on children's lifestyles and health behaviours, the Harvard Youth/Adolescent Food Frequency questionnaire, a validated questionnaire on physical activity, and measurements of heights and weights. Random effect models were used to assess the associations of night-time access to and use of EECDs with sleep, diet quality, physical activity, and body weights.

RESULTS

Sixty-four percent of parents reported that their child had access to one or more EECDs in their bedroom. Access to and night-time use of EECDs were associated with shortened sleep duration, excess body weight, poorer diet quality, and lower physical activity levels in a statistically significant manner.

CONCLUSIONS

Limiting the availability of EECDs in children's bedrooms and discouraging their night-time use may be considered as a strategy to promote sleep and reduce childhood obesity.

Toxoplasma ISP4 is a central IMC sub-compartment protein whose localization depends on palmitoylation but not myristoylation

Apicomplexan parasites utilize a peripheral membrane system called the inner membrane complex (IMC) to facilitate host cell invasion and parasite replication. We recently identified a novel family of Toxoplasma IMC Sub-compartment Proteins (ISP1/2/3) that localize to sub-domains of the IMC using a targeting mechanism that is dependent on coordinated myristoylation and palmitoylation of a series of residues in the N-terminus of the protein. While the precise functions of the ISPs are unknown, deletion of ISP2 results in replication defects, suggesting that this family of proteins plays a role in daughter cell formation. Here we have characterized a fourth ISP family member (ISP4) and discovered that this protein localizes to the central IMC sub-compartment, similar to ISP2. Like ISP1/3, ISP4 is dispensable for the tachyzoite lytic cycle as the disruption of ISP4 does not produce any gross replication or growth defects. Surprisingly, targeting of ISP4 to the IMC membranes is dependent on residues predicted for palmitoylation but not myristoylation, setting its trafficking apart from the other ISP proteins and demonstrating distinct mechanisms of protein localization to the IMC membranes, even within a family of highly related proteins.

Breast cancer immunohistochemistry can be useful in triage of some HNPCC families

Immunohistochemistry of tumour samples is increasingly used in the triage of families where hereditary non-polyposis colorectal cancer (HNPCC) due to mismatch repair defects is suspected. Usually, this is undertaken in tumours that are a recognised part of the spectrum of HNPCC-related cancers e.g. colon or endometrial cancers. Although breast cancers are not classed as part of this spectrum, this study examined the extent to which some breast tumours do arise by the mismatch repair pathway in these families. This may have clinical utility in families where an individual with a 'classic HNPPC-related' tumour is not available for evaluation. Immunohistochemistry of a breast tumour may identify an individual in whom germline mutation testing is worthwhile.

Curable hypertension

Hypertension due to a reninoma (suspected on the basis of biochemical and clinical features, and exquisite sensitivity of hypertension to angiotensin-converting enzyme [ACE] inhibition, but not visible on imaging) was cured by laparoscopic nephrectomy. Treatment was followed by an uneventful pregnancy.

Assessment of coronary heart disease risk in testicular cancer survivors

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Background: Testicular cancer survivors (TCS) who receive cisplatin-based chemotherapy (CBCT) are reported to have an increased risk of coronary heart disease (CHD) compared to chemo-naive TCS (J Clin Oncol 21:1513–1523, 2003). We hypothesized that TCS treated with CBCT would demonstrate abnormal objective measures of future CHD risk compared to chemo-naive TCS. Methods: TCS ≥ 2 years from diagnosis underwent evaluation using established objective measures predictive of future CHD risk: body mass index (BMI), Framingham relative risk (RR), flow-mediated endothelium-dependent vasodilation of the brachial artery (FMD), carotid artery intima-media thickness (IMT), serum intercellular adhesion molecule-1 (ICAM-1), and high sensitivity C-reactive protein (hs-CRP). Data were analyzed using parametric and non-parametric statistics as appropriate. Results: 30 TCS who received CBCT and 20 chemo-naive TCS were recruited. The mean age and time from diagnosis were similar between the 2 groups. Both groups demonstrated elevated BMI, increased Framingham RR, and impaired FMD, consistent with an increased risk of CHD. However, there were no statistically significant differences in these measures between the two groups. Carotid IMT, ICAM-1, and hs-CRP were not significantly abnormal and these measures also did not differ between the two groups. Conclusions: TCS demonstrate abnormal objective measures of CHD risk in both CBCT-treated and chemo-naive groups. These data suggest that behavioral interventions to modify CHD risk should target all TCS independent of chemotherapy status. All values reported are mean ± standard deviation

[Table: see text]

No significant financial relationships to disclose.

Neuron numbers in sensory cortices of five delphinids compared to a physeterid, the pygmy sperm whale

With its large mass and enormous gyrification, the neocortex of whales and dolphins has always been a challenge to neurobiologists. Here we analyse the relationship between neuron number per cortical unit in three different sensory areas and brain mass in six different toothed whale species, five delphinids and one physeterid. Cortex samples, including primary cortical areas of the auditory, visual, and somatosensory systems were taken from both hemispheres of brains fixed in 10% buffered formalin. The samples were embedded in paraffin, sectioned at 25 microm thickness and stained with cresyl violet. Because cortical thickness varies among toothed whale species, cell counts were done in cortical units measuring 150mum in width, 25 microm in thickness, and extending from the pial surface to the white matter. By arranging the delphinid brains according to their total mass, 834-6052 g, we found decreasing neuron numbers in the investigated areas with increasing brain mass. The pigmy sperm whale (Kogia breviceps), a physeterid with an adult brain weight of 1000 g had a distinctly lower neuron number per cortical unit. As had been expected, an increase in adult brain weight in delphinid cetaceans (family Delphinidae) is not correlated with an increase in neuron number per cortical unit.

Relationship of neonatal body composition to maternal glucose control in women with gestational diabetes mellitus

OBJECTIVE

To determine whether neonatal fat mass, which may be a better estimate of fetal overgrowth, is correlated with maternal fasting, preprandial and/or postprandial glucose values in women with gestational diabetes mellitus (GDM).

STUDY DESIGN

Women with GDM and no other medical or obstetric problems, and their infants, were the subjects of this study. Portable reflectance meters were used by all participants for self-monitoring of blood glucose levels. Average fasting, preprandial, 2-h postprandial and bedtime glucose values were determined for each subject. Neonatal body composition was obtained by total body electric conductivity and/or anthropometric measurements within 48 h after delivery.

RESULTS

Eighteen women with their infants participated in this study. The age (mean +/- SD) of the mothers was 28.0 +/- 5.7 years. Nine were treated with diet and nine with diet and insulin. An average of 40 fasting (84 +/- 13 mg/dl), 50 preprandial (87 +/- 14 mg/dl), 80 2-h postprandial (106 +/- 19 mg/dl) and 17 bedtime (104 +/- 19 mg/dl) glucose values were obtained from each subject. The average gestational age of the infants at birth was 38.3 +/- 1.3 weeks with a mean weight of 3,356 +/- 526 g. Three infants were > 4 kg and seven infants were > 90th centile for gestational age. The strongest correlation with neonatal fat mass was maternal fasting glucose level (r = 0.71, p < 0.01). Neonatal fat mass was not found to be significantly correlated with any other mean glucose value. Additionally, the infant's per cent body fat (r = 0.71, p < 0.01), sum of skinfold thicknesses (r = 0.70, p < 0.01), fat-free mass (r = 0.50, p < 0.05), and weight (r = 0.61, p < 0.01) were also found to be correlated with maternal fasting glucose level. No other maternal glucose measurements were correlated with either birth weight or estimates of fat free mass.

CONCLUSION

Maternal fasting glucose levels correlated best with neonatal fat mass and other estimates of neonatal body composition.

A long-term randomized, cross-over comparison of auto-titrating and standard nasal continuous airway pressure

This study is a 12-week randomized, cross-over, single-blind comparison of the tolerance, compliance, and symptomatic improvement obtained with standard nasal continuous positive airway pressure (CPAP) vs. an auto-titrating, self-adjusting device (APAP). Sixty newly diagnosed patients, 53 with obstructive sleep apnea (OSA) and seven with upper airway resistance syndrome were studied. Thirty-nine patients (65%) completed the 24-week protocol. Data were complete in 33. In these 33 patients CPAP and APAP reduced the Epworth Sleepiness score from 15+/-1 (+/-SEM) to 8+/-1 and 9+/-1 respectively (both <0.0001 from baseline but NS between modes). The APAP average pressure was lower than the CPAP pressure, 6.4+/-0.4 and 10.6+/-0.4 cm H20, respectively. The average daily machine use was greater with APAP, 6.0+/-0.3 hrs. versus 5.5+/-0.3 hrs. with CPAP (P < 0.04). The number of days of machine use, and the pattern of use were not different between CPAP and APAP. A higher proportion of patients who did not complete the study was randomized to CPAP for their initial treatment period. This study showed that: 1) CPAP and APAP produced an equivalent improvement in daytime sleepiness, 2) APAP pressure was lower than CPAP pressure, 3) patients wore the APAP device longer during nights they used the pressure support system, and 4) patients who began the study with APAP were more prone to continue treatment. We conclude that APAP was better tolerated and used a greater number of hours than CPAP, but the extent of improvement in excessive daytime sleepiness was similar between the two modes of therapy.

Bizarre leiomyoma of the vagina: report of a case

Smooth muscle tumors are the most common mesenchymal tumors of the adult vagina, but no case of bizarre (also referred to as atypical, symplastic, or pleomorphic) leiomyoma has been described at this site. We present such a case in a 44-year-old woman.

The role of community mental health nurses in educating clients and families about schizophrenia

The aim of the study was to investigate the role of community mental health nurses in educating clients and families about schizophrenia. A random sample of community mental health nurses was surveyed using a postal questionnaire. Results showed that most nurses did not use a specific approach for education. Families were educated when clients were admitted to hospital and clients were included when they regained the ability to process information. All nurses provided practical advice to families coping with clients' unpredictable behaviours. The client's home was mostly used for education. Clients and families were often in denial of the illness. Time constraints restricted the nurses' role of providing education. Nurses reported that psycho-educational theories or models were not incorporated into their basic professional education. Nurses require the necessary knowledge, skills and confidence to competently perform this role.

Parent management training in a Chinese population: application and outcome

OBJECTIVE

To examine the applicability and outcome of parent management training in a group of Chinese children referred for aggressive and defiant behaviors.

METHOD

Twenty-five children (aged 4-10 years) were assigned to a standardized 8 to 12 sessions of parent management training. Trained child and adolescent psychiatric nurses conducted the treatment. Measures taken at pretreatment, posttreatment, and 4-month follow-up period included the Child Behavior Checklist, direct observation of parent-child interactions, and a parent perception inventory.

RESULTS

Significant therapeutic gains occurred in parent-child interactions, externalizing behaviors, and parents' perception of their parenting behaviors. These were maintained at 4-month follow-up. Fifty-two percent of cases improved to a level below clinical cutoffs. Poor parent-child interactions had stronger correlation with externalizing disturbances than internalizing disturbances. The changes in parent-child interactions had low correlation with the changes in the symptom profiles.

CONCLUSIONS

The data provide preliminary evidence for the efficacy of parent management training for Chinese children with conduct problems. The rationale for its success and modifications to improve its cultural sensitivity are discussed.

Does postoperative irradiation play a role in the adjuvant therapy of stage T4 colon cancer?

PURPOSE

This study analyzes the long-term outcome of patients with stage T4 colon cancer who receive postoperative irradiation. The purpose of the study is to define the potential role of this modality with current systemic therapies.

PATIENTS AND METHODS

A retrospective analysis was performed of 152 patients undergoing resection of T4 colon cancer followed by moderate- to high-dose postoperative tumor bed irradiation with and without 5-fluorouracil-based chemotherapy. Of the 152 patients, 110 patients (T4N0 or T4N+) were treated adjuvantly, whereas 42 patients received irradiation for the control of gross or microscopic residual local tumor.

RESULTS

For 79 adjuvantly treated patients with stage T4N0 or T4N+ cancer with one lymph node metastasis, the 10-year actuarial rates of local control and recurrence-free survival were 88% and 58%, respectively. Results were less satisfactory for patients with more extensive nodal involvement. The 10-year actuarial rates of local control and recurrence-free survival of 39 patients with T4 tumors complicated by perforation or fistulas were 81% and 53%, respectively. For 42 patients with incompletely resected tumors, the 10-year actuarial recurrence-free survival was 19%.

CONCLUSIONS

In comparison with historical controls, postoperative tumor bed irradiation improves local control for some subsets of patients. In addition to standard 5-fluorouracil-based chemotherapy, adjuvant tumor bed irradiation should be considered when colon cancers invade adjoining structures, when they are complicated by perforation or fistulas, or when they are incompletely excised at the primary site.