Deep Learning-Based Identification of Intraocular Pressure-Associated Genes Influencing Trabecular Meshwork Cell Morphology

Purpose

Genome-wide association studies have recently uncovered many loci associated with variation in intraocular pressure (IOP). Artificial intelligence (AI) can be used to interrogate the effect of specific genetic knockouts on the morphology of trabecular meshwork cells (TMCs) and thus, IOP regulation.

Design

Experimental study.

Subjects

Primary TMCs collected from human donors.

Methods

Sixty-two genes at 55 loci associated with IOP variation were knocked out in primary TMC lines. All cells underwent high-throughput microscopy imaging after being stained with a 5-channel fluorescent cell staining protocol. A convolutional neural network was trained to distinguish between gene knockout and normal control cell images. The area under the receiver operator curve (AUC) metric was used to quantify morphological variation in gene knockouts to identify potential pathological perturbations.

Main Outcome Measures

Degree of morphological variation as measured by deep learning algorithm accuracy of differentiation from normal controls.

Results

Cells where LTBP2 or BCAS3 had been perturbed demonstrated the greatest morphological variation from normal TMCs (AUC 0.851, standard deviation [SD] 0.030; and AUC 0.845, SD 0.020, respectively). Of 7 multigene loci, 5 had statistically significant differences in AUC (P < 0.05) between genes, allowing for pathological gene prioritization. The mitochondrial channel most frequently showed the greatest degree of morphological variation (33.9% of cell lines).

Conclusions

We demonstrate a robust method for functionally interrogating genome-wide association signals using high-throughput microscopy and AI. Genetic variations inducing marked morphological variation can be readily identified, allowing for the gene-based dissection of loci associated with complex traits.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

High throughput functional profiling of genes at intraocular pressure loci reveals distinct networks for glaucoma

INTRODUCTION

Primary open angle glaucoma (POAG) is a leading cause of blindness globally. Characterized by progressive retinal ganglion cell degeneration, the precise pathogenesis remains unknown. Genome-wide association studies (GWAS) have uncovered many genetic variants associated with elevated intraocular pressure (IOP), one of the key risk factors for POAG. We aimed to identify genetic and morphological variation that can be attributed to trabecular meshwork cell (TMC) dysfunction and raised IOP in POAG.

METHODS

62 genes across 55 loci were knocked-out in a primary human TMC line. Each knockout group, including five non-targeting control groups, underwent single-cell RNA-sequencing (scRNA-seq) for differentially-expressed gene (DEG) analysis. Multiplexed fluorescence coupled with CellProfiler image analysis allowed for single-cell morphological profiling.

RESULTS

Many gene knockouts invoked DEGs relating to matrix metalloproteinases and interferon-induced proteins. We have prioritized genes at four loci of interest to identify gene knockouts that may contribute to the pathogenesis of POAG, including ANGPTL2, LMX1B, CAV1, and KREMEN1. Three genetic networks of gene knockouts with similar transcriptomic profiles were identified, suggesting a synergistic function in trabecular meshwork cell physiology. TEK knockout caused significant upregulation of nuclear granularity on morphological analysis, while knockout of TRIOBP, TMCO1 and PLEKHA7 increased granularity and intensity of actin and the cell-membrane.

CONCLUSION

High-throughput analysis of cellular structure and function through multiplex fluorescent single-cell analysis and scRNA-seq assays enabled the direct study of genetic perturbations at the single-cell resolution. This work provides a framework for investigating the role of genes in the pathogenesis of glaucoma and heterogenous diseases with a strong genetic basis.

The molecular characteristics of non-small cell lung cancer in the Northern Territory's Top End

AIM

Indigenous Australians with lung cancer have poorer survival than non-Indigenous Australians. The reasons for the disparity are not fully understood and this study hypothesized that there may be a difference in the molecular profiles of tumors. The aim of this study, therefore, was to describe and compare the characteristics of non-small cell lung cancer (NSCLC) in the Northern Territory's Top End, between Indigenous and non-Indigenous patients, and describe the molecular profile of tumors in the two groups.

METHODS

A retrospective review was conducted of all adults with a new diagnosis of NSCLC in the Top End from 2017 to 2019. Patient characteristics assessed were Indigenous status, age, sex, smoking status, disease stage, and performance status. Molecular characteristics assessed were epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), v-raf murine sarcoma viral oncogene homolog B (BRAF), ROS proto-oncogene 1 (ROS1), Kirsten rat sarcoma viral oncogene homolog (KRAS), mesenchymal-epithelial transition (MET), human epidermal growth factor receptor 2 (HER2), and programmed death-ligand 1 (PD-L1). Student's t-test and Fisher's Exact Test were used in the statistical analysis.

RESULTS

There were 152 patients diagnosed with NSCLC in the Top End from 2017-2019. Thirty (19.7%) were Indigenous and 122 (80.3%) were non-Indigenous. Indigenous patients compared to non-Indigenous patients were younger at diagnosis (median age 60.7 years versus 67.1 years, p = 0.00036) but were otherwise similar in demographics. PD-L1 expression was similar between Indigenous and non-Indigenous patients (p = 0.91). The only mutations identified among stage IV non-squamous NSCLC patients were EGFR and KRAS but testing rates and overall numbers were too small to draw conclusions about differences in prevalence between Indigenous and non-Indigenous patients.

CONCLUSION

This is the first study to investigate the molecular characteristics of NSCLC in the Top End.

Single-cell eQTL mapping identifies cell type-specific genetic control of autoimmune disease

The human immune system displays substantial variation between individuals, leading to differences in susceptibility to autoimmune disease. We present single-cell RNA sequencing (scRNA-seq) data from 1,267,758 peripheral blood mononuclear cells from 982 healthy human subjects. For 14 cell types, we identified 26,597 independent cis-expression quantitative trait loci (eQTLs) and 990 trans-eQTLs, with most showing cell type-specific effects on gene expression. We subsequently show how eQTLs have dynamic allelic effects in B cells that are transitioning from naïve to memory states and demonstrate how commonly segregating alleles lead to interindividual variation in immune function. Finally, using a Mendelian randomization approach, we identify the causal route by which 305 risk loci contribute to autoimmune disease at the cellular level. This work brings together genetic epidemiology with scRNA-seq to uncover drivers of interindividual variation in the immune system.

Use of CRISPR/Cas ribonucleoproteins for high throughput gene editing of induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) have become widely used for disease modelling, particularly with regard to predisposing genetic risk factors and causal gene variants. Alongside this, technologies such as the CRISPR/Cas system have been adapted to enable programmable gene editing in human cells. When combined, CRISPR/Cas gene editing of donor-specific iPSC to generate isogenic cell lines that differ only at specific gene variants provides a powerful model with which to investigate genetic variants associated with diseases affecting many organs, including the brain and eye. Here we describe our optimized protocol for using CRISPR/Cas ribonucleoproteins to edit disease causing gene variants in human iPSCs. We discuss design of crRNAs and homology-directed repair templates, assembly of CRISPR/Cas ribonucleoproteins, optimization of delivery via nucleofection, and strategies for single cell cloning, efficient clone cryopreservation and genotyping for identifying iPSC clones for further characterization.

Comparison of CRISPR/Cas Endonucleases for in vivo Retinal Gene Editing

CRISPR/Cas has opened the prospect of direct gene correction therapy for some inherited retinal diseases. Previous work has demonstrated the utility of adeno-associated virus (AAV) mediated delivery to retinal cells in vivo; however, with the expanding repertoire of CRISPR/Cas endonucleases, it is not clear which of these are most efficacious for retinal editing in vivo. We sought to compare CRISPR/Cas endonuclease activity using both single and dual AAV delivery strategies for gene editing in retinal cells. Plasmids of a dual vector system with SpCas9, SaCas9, Cas12a, CjCas9 and a sgRNA targeting YFP, as well as a single vector system with SaCas9/YFP sgRNA were generated and validated in YFP-expressing HEK293A cell by flow cytometry and the T7E1 assay. Paired CRISPR/Cas endonuclease and its best performing sgRNA was then packaged into an AAV2 capsid derivative, AAV7m8, and injected intravitreally into CMV-Cre:Rosa26-YFP mice. SpCas9 and Cas12a achieved better knockout efficiency than SaCas9 and CjCas9. Moreover, no significant difference in YFP gene editing was found between single and dual CRISPR/SaCas9 vector systems. With a marked reduction of YFP-positive retinal cells, AAV7m8 delivered SpCas9 was found to have the highest knockout efficacy among all investigated endonucleases. We demonstrate that the AAV7m8-mediated delivery of CRISPR/SpCas9 construct achieves the most efficient gene modification in neurosensory retinal cells in vivo.

Comparative performance of the BGI and Illumina sequencing technology for single-cell RNA-sequencing

The libraries generated by high-throughput single cell RNA-sequencing (scRNA-seq) platforms such as the Chromium from 10× Genomics require considerable amounts of sequencing, typically due to the large number of cells. The ability to use these data to address biological questions is directly impacted by the quality of the sequence data. Here we have compared the performance of the Illumina NextSeq 500 and NovaSeq 6000 against the BGI MGISEQ-2000 platform using identical Single Cell 3′ libraries consisting of over 70 000 cells generated on the 10× Genomics Chromium platform. Our results demonstrate a highly comparable performance between the NovaSeq 6000 and MGISEQ-2000 in sequencing quality, and the detection of genes, cell barcodes, Unique Molecular Identifiers. The performance of the NextSeq 500 was also similarly comparable to the MGISEQ-2000 based on the same metrics. Data generated by both sequencing platforms yielded similar analytical outcomes for general single-cell analysis. The performance of the NextSeq 500 and MGISEQ-2000 were also comparable for the deconvolution of multiplexed cell pools via variant calling, and detection of guide RNA (gRNA) from a pooled CRISPR single-cell screen. Our study provides a benchmark for high-capacity sequencing platforms applied to high-throughput scRNA-seq libraries.

International consensus definition of low anterior resection syndrome

AIM

Low anterior resection syndrome (LARS) is pragmatically defined as disordered bowel function after rectal resection leading to a detriment in quality of life. This broad characterization does not allow for precise estimates of prevalence. The LARS score was designed as a simple tool for clinical evaluation of LARS. Although the LARS score has good clinical utility, it may not capture all important aspects that patients may experience. The aim of this collaboration was to develop an international consensus definition of LARS that encompasses all aspects of the condition and is informed by all stakeholders.

METHOD

This international patient-provider initiative used an online Delphi survey, regional patient consultation meetings, and an international consensus meeting. Three expert groups participated: patients, surgeons and other health professionals from five regions (Australasia, Denmark, Spain, Great Britain and Ireland, and North America) and in three languages (English, Spanish, and Danish). The primary outcome measured was the priorities for the definition of LARS.

RESULTS

Three hundred twenty-five participants (156 patients) registered. The response rates for successive rounds of the Delphi survey were 86%, 96% and 99%. Eighteen priorities emerged from the Delphi survey. Patient consultation and consensus meetings refined these priorities to eight symptoms and eight consequences that capture essential aspects of the syndrome. Sampling bias may have been present, in particular, in the patient panel because social media was used extensively in recruitment. There was also dominance of the surgical panel at the final consensus meeting despite attempts to mitigate this.

CONCLUSION

This is the first definition of LARS developed with direct input from a large international patient panel. The involvement of patients in all phases has ensured that the definition presented encompasses the vital aspects of the patient experience of LARS. The novel separation of symptoms and consequences may enable greater sensitivity to detect changes in LARS over time and with intervention.

Utility of Self-Destructing CRISPR/Cas Constructs for Targeted Gene Editing in the Retina

Safe delivery of CRISPR/Cas endonucleases remains one of the major barriers to the widespread application of in vivo genome editing. We previously reported the utility of adeno-associated virus (AAV)-mediated CRISPR/Cas genome editing in the retina; however, with this type of viral delivery system, active endonucleases will remain in the retina for an extended period, making genotoxicity a significant consideration in clinical applications. To address this issue, we have designed a self-destructing "kamikaze" CRISPR/Cas system that disrupts the Cas enzyme itself following expression. Four guide RNAs (sgRNAs) were initially designed to target Streptococcus pyogenes Cas9 (SpCas9) and after in situ validation, the selected sgRNAs were cloned into a dual AAV vector. One construct was used to deliver SpCas9 and the other delivered sgRNAs directed against SpCas9 and the target locus (yellow fluorescent protein [YFP]), in the presence of mCherry. Both constructs were packaged into AAV2 vectors and intravitreally administered in C57BL/6 and Thy1-YFP transgenic mice. After 8 weeks, the expression of SpCas9 and the efficacy of YFP gene disruption were quantified. A reduction of SpCas9 mRNA was found in retinas treated with AAV2-mediated YFP/SpCas9 targeting CRISPR/Cas compared with those treated with YFP targeting CRISPR/Cas alone. We also show that AAV2-mediated delivery of YFP/SpCas9 targeting CRISPR/Cas significantly reduced the number of YFP fluorescent cells among mCherry-expressing cells (∼85.5% reduction compared with LacZ/SpCas9 targeting CRISPR/Cas) in the transfected retina of Thy1-YFP transgenic mice. In conclusion, our data suggest that a self-destructive "kamikaze" CRISPR/Cas system can be used as a robust tool for genome editing in the retina, without compromising on-target efficiency.

Building a national eye-care service in post-conflict Timor-Leste

Problem

Violent conflict left Timor-Leste with a dismantled health-care workforce and infrastructure after 2001. The absence of existing health and tertiary education sectors compounded the challenges of instituting a national eye-care system.

Approach

From 2001, the East Timor Eye Program coordinated donations and initially provided eye care through visiting teams. From 2005, the programme reoriented to undertake concerted workforce and infrastructure development. In 2008 full-time surgical services started in a purpose-built facility in the capital city. In 2014 we developed a clinical training pipeline for local medical graduates to become ophthalmic surgeons, comprising a local postgraduate diploma, with donor funding supporting master's degree studies abroad.

Local setting

In the population of 1.26 million, an estimated 35 300 Timorese are blind and an additional 123 500 have moderate to severe visual impairment, overwhelmingly due to cataract and uncorrected refractive error.

Relevant changes

By April 2018, six Timorese doctors had completed the domestic postgraduate diploma, three of whom had enrolled in master's degree programmes. Currently, one consultant ophthalmologist, seven ophthalmic registrars, two optometrists, three refractionists and four nursing staff form a tertiary resident ophthalmic workforce, supported by an international advisor ophthalmologist and secondary eye-care workers. A recorded 12 282 ophthalmic operations and 117 590 consultations have been completed since 2001.

Lessons learnt

International organizations played a pivotal role in supporting the Timorese eye health system, in an initially vulnerable setting. We highlight how transition to domestic funding can be achieved through the creation of a domestic training pipeline and integration with national institutions.

Risk in the "Red Zone": Outcomes for Children Admitted to Ebola Holding Units in Sierra Leone Without Ebola Virus Disease

We collected data on 1054 children admitted to Ebola Holding Units in Sierra Leone and describe outcomes of 697/1054 children testing negative for Ebola virus disease (EVD) and accompanying caregivers. Case-fatality was 9%; 3/630 (0.5%) children discharged testing negative were readmitted EVD-positive. Nosocomial EVD transmission risk may be lower than feared.

Awareness of periconceptional folic acid supplementation among Nepalese women of childbearing age: a cross-sectional study

OBJECTIVE

Maternal folate deficiency is associated with neural tube defects (NTDs), the most common congenital birth defect at Maternity Hospital, Kathmandu, Nepal. NTDs can be prevented with periconceptional folic acid supplementation (FAS). This study was performed to assess the awareness of FAS among women of reproductive age in Kathmandu.

METHODS

A semi-structured questionnaire was administered to 400 randomly selected patients aged 15 to 45 years visiting Kathmandu Model Hospital from May to July 2011, seeking any awareness of FAS, knowledge of its impact on fetal development and knowledge of the appropriate time of supplementation.

RESULTS

Forty percent (95% CI 35.1-45.0) of women had heard about FAS, 16.3% (95% CI 12.8-20.2) knew that folate affects fetal health and 5.0% (95% CI 3.1-7.6) knew that it should be taken pre-pregnancy. Level of education was strongly associated with awareness (multivariate Odds Ratio for lowest vs. highest level of education: 0.29, 95% CI 0.15-0.56).

CONCLUSIONS

Knowledge of FAS is very low among women of childbearing age in Kathmandu. Inclusion of FAS information in health awareness programs is recommended.

65Zn turnover in short-term alloxan diabetic rats

65Zn was injected subcutaneously in eleven rats with alloxan diabetes of five days duration and in nine control rats. Fifty hours after the injection of 65Zn the animals were killed with an overdose of ether. In the alloxan diabetic rats signs of an altered zinc metabolism were found with an increased excretion of zinc in urine and possibly also faeces and an elevated zinc concentration in the liver compared to controls. The results also indicate an altered distribution of serum zinc in alloxan treated rats. Future studies will be necessary to demonstrate whether changes in zinc metabolism are secondary to the onset of diabetes or a primary effect of alloxan treatment.

CD4+CD25+-regulatory T cells from mouse to man

Immunological tolerance is one of the fundamental concepts of the immune system. During the past decade, CD4+CD25+-regulatory T cells have emerged as key players in the development of tolerance to autoantigens as well as to foreign antigens. Still many questions remain illusive regarding the basic properties of CD4+CD25+-regulatory T cells. This review aims to recapitulate some of the current understandings about the phenotype, function and clinical relevance of murine and human CD4+CD25+-regulatory T cells.

Defective suppression of Th2 cytokines by CD4+CD25+ regulatory T cells in birch allergics during birch pollen season

BACKGROUND

CD4(+)CD25+ regulatory T cells suppress proliferation and cytokine production by human T cells both to self-antigens and exogenous antigens. Absence of these cells in human newborns leads to multiple autoimmune and inflammatory disorders together with elevated IgE levels. However, their role in human allergic disease is still unclear.

OBJECTIVE

This study aimed to evaluate the capacity of CD4(+)CD25+ regulatory T cells to suppress proliferation and cytokine production outside and during birch-pollen season in birch-allergic patients relative to non-allergic controls.

METHODS

CD4+ cells were obtained from blood of 13 birch-allergic patients and six non-allergic controls outside pollen season and from 10 birch-allergic patients and 10 non-allergic controls during birch-pollen season. CD25+ and CD25- fractions were purified with magnetic beads and cell fractions, alone or together in various ratios, were cultured with antigen-presenting cells and birch-pollen extract or anti-CD3 antibody. Proliferation and levels of IFN-gamma, IL-13, IL-5 and IL-10 were measured by thymidin incorporation and ELISA, respectively. Numbers of CD25+ cells were analysed by flow cytometry.

RESULTS

CD4(+)CD25+ regulatory T cells from both allergics and non-allergics potently suppressed T cell proliferation to birch allergen both outside and during birch-pollen season. However, during season CD4(+)CD25+ regulatory T cells from allergic patients but not from non-allergic controls were defective in down-regulating birch pollen induced IL-13 and IL-5 production, while their capacity to suppress IFN-gamma production was retained. In contrast, outside pollen season the regulatory cells of both allergics and non-allergic controls were able to inhibit T-helper 2 cytokine production.

CONCLUSION

This is the first study to show differential suppression of Th1 and Th2 cytokines, with CD4(+)CD25+ regulatory T cells from birch-pollen-allergic patients being unable to down-regulate Th2, but not Th1 responses during birch-pollen season.

Effect of neurofeedback on motor recovery of a patient with brain injury: a case study and its implications for stroke rehabilitation

This case study showed the effect of neurofeedback (NFB) training in a patient with a brain tumor and co-existing traumatic brain injury. The patient received 40 sessions of NFB intervention. Tests and videotaped recordings evaluated pre- and post-NFB intervention. This study demonstrated minimal to significant improvements in several functional tasks. The conclusion is that the use of NFB for a person with a head injury and brain tumor can be generalized to be used with stroke survivors.

A recombinant trimeric surfactant protein D carbohydrate recognition domain inhibits respiratory syncytial virus infection in vitro and in vivo

The pulmonary collectin, lung surfactant protein D (SP-D), plays a role in host defense mediated by the interaction of surface carbohydrates of inhaled pathogens with the lectin domains of SP-D. Respiratory syncytial virus (RSV), the most important viral pathogen of neonates and infants, encodes a highly glycosylated attachment protein, G. Binding studies were performed with G protein from RSV (human, A2 strain) and both native and recombinant human SP-D. The effect of recombinant trimeric SP-D lectin domains (rSP-D) on the interaction between RSV and host cells was determined by two methods: an infectivity study with monolayers of Hep-2C cells and in vivo infections in BALB/c mice. These studies show that full-length and recombinant SP-D bind to RSV G protein in a concentration-dependent manner. Both EDTA and mannan inhibited binding of full-length SP-D. These results indicate that binding occurs via the carbohydrate recognition domain of the SP-D. The recombinant SP-D inhibited RSV infectivity in cell culture in a dose-dependent manner, giving 100% inhibition of replication. Intranasal administration of recombinant SP-D to RSV-infected mice inhibited replication of the virus in the lungs, reducing levels of lung virus by 80%. These results suggest that SP-D plays a major role in clearing RSV from the lungs.

A comparison of iron absorption from single meals and daily diets using radioFe (55Fe, 59Fe)

The purpose of the present study was to compare two measures of Fe absorption, one from single meals and the other from daily diets. Ten ileostomy subjects were given the same low-fibre composite diet for all three meals each day for five consecutive days. After 3 weeks the experiment was repeated with a high-fibre diet. The morning meal constituted one-seventh of the total daily diet intake, the mid-day meal two-sevenths and the evening meal four-sevenths of the total daily diet intake. On days 4 and 5 of each diet period the morning meal was labelled with 55Fe and all three meals were labelled with 59Fe. The activities retained in the subjects 19 d later showed the Fe absorption from the low-fibre diet measured from the morning meals to be almost 80% greater than the average Fe absorption measured from all meals during the same 2 d. With the high-fibre diet the absorption from the morning meals was less than 50% greater than the average for all meals but the difference was not significant. We suggest that all meals of the day should be labelled with radioFe in order to avoid inflating the measures of Fe absorption.

Effect of milk and fermented milk on iron absorption in ileostomy subjects

This study was undertaken to determine whether milk with its high calcium content adversely affects the absorption of nonheme iron from the diet as greatly as single-meal studies indicate. Nine ileostomy subjects ate a low-fiber, low-phytate diet for 8 consecutive weeks. During the first and eight weeks they drank a 250-mL soft drink with three main meals and an evening snack each day (0.16 g Ca/d). During the two intervening 3-wk periods, they drank the same amount of low-fat milk or fermented low-fat milk (Verum; Hälsofil, Norrmejerier, Umeä, Sweden) according to a formally randomized crossover design (1.4 g Ca/d). During the last 2 d in each of the four periods, apparent iron absorption (balance) from a test diet together with that period's beverage was measured and the plasma ferritin concentration was determined. There was no decrease in apparent iron absorption during the milk diet periods.

Sens-A-Ray. A new system for direct digital intraoral radiography

A new system for direct digital intraoral radiography, Sens-A-Ray, is presented. This system is based on a detector with a charge-coupled device that was designed especially for direct exposure to x-ray radiation. The system also includes interface electronics and an IBM AT-compatible personal computer with a digital I/O with frame memory, a super VGA graphics board, a high-resolution monitor, and software for the exposure, capture, storage, and enhancement of images. An external optical mass storage device is used for permanent storage of images in digital format. A video printer may be used to create hard copies. The system produces radiographic images at a significantly lower exposure than required for E-speed intraoral film. Applications of the system are exemplified, and its basic properties are discussed.

A comparative study in rats of measures of the availability of dietary zinc and iron

The purpose of this study was to compare three measures of the availability of dietary Zn and Fe in order to test their validity. Thirty-six 5-wk-old rats were fed deionized water and wheat crispbread made from endosperm flour, whole-grain flour, or endosperm flour supplemented with Zn and Fe to the whole-grain levels ad libitum for 14 d. The retention of 65Zn and 59Fe from test meals of the same breads after 1 wk and the sum of the excretion of endogenous Zn and Fe (injected 65Zn and 59Fe) with the Zn and Fe balances, respectively, were used as independent measures of Zn and Fe absorption. Measurements of Zn absorption, Zn balance, and serum Zn concentration gave quite different results with regard to the availability of Zn in the three breads, presumably because of the homeostatic regulation of the absorption and excretion of Zn when the Zn in the diet is in excess of the body's needs. Measurements of Fe absorption, Fe balance, and Fe concentrations in liver and serum were consistent in demonstrating overloading of Fe in the group given wheat-endosperm crispbread supplemented with Zn and Fe, but there was evidence that the isotope retention method overestimated iron absorption.

The relation of the accumulation of cadmium in human placenta to the intake of high-fibre grains and maternal iron status

Exposure to cadmium via the diet is known to depend to a large extent on the intake of cereal grains, particularly the high-fibre fractions of wheat. Subjects with low iron status absorb more cadmium than those with better iron status. The purpose of the present study was to determine to what extent cadmium accumulation in human placenta is affected by the intake of grain fibre and maternal iron status during pregnancy. Thirty-nine pregnant women participated in the study. In each trimester the women were requested to complete a dietary history and to allow blood samples to be taken for haemoglobin, serum ferritin and serum thiocyanate determinations, the latter as a marker for smoking. At delivery the whole placenta was taken for the determination of the cadmium concentration. The 32 women who had serum thiocyanate levels less than 70 mumol/l, who had completed at least one dietary history and from whom a blood sample was obtained in the third trimester, were included in the final statistical analyses. In the group of women who consumed less than the median intake of grain fibre and had more than 15 micrograms ferritin/l serum in the third trimester, the placenta cadmium concentration was nearly half that in the placentae of women who had consumed more grain fibre or had lower iron status in late pregnancy.

Factors affecting the long-term results of endodontic treatment

The influence of various factors that may affect the outcome of root canal therapy was evaluated in 356 patients 8 to 10 yr after the treatment. The results of treatment were directly dependent on the preoperative status of the pulp and periapical tissues. The rate of success for cases with vital or nonvital pulps but having no periapical radiolucency exceeded 96%, whereas only 86% of the cases with pulp necrosis and periapical radiolucency showed apical healing. The possibility of instrumenting the root canal to its full length and the level of root filling significantly affected the outcome of treatment. Of all of the periapical lesions present on previously root-filled teeth, only 62% healed after retreatment. The predictability from clinical and radiographic signs of the treatment-outcome in individual cases with preoperative periapical lesions cases was found to be low. Thus, factors which were not measured or identified may be critical to the outcome of endodontic treatment.

The extent of coprophagy in rats with differing iron status and its effect on iron absorption

The purpose of this study was to determine the prevalence of coprophagy in rats with differing iron status and its effect on the measurement of iron absorption from test meals with and without bran. Two experiments were performed using radioisotope-labelled microspheres added as a non-digestible marker for the ingested faeces and the diet and 59Fe added as a marker for the nonhaem iron in the test meal. In this study, coprophagy occurred at group mean rates of between 5 and 22% and was independent of the iron status of the rats or the presence or absence of bran in the diet. The relative absorption of iron, measured as the retention of 59Fe from a single meal, was affected to the same extent in groups with the same iron status, if it was affected at all. Thus comparisons of iron absorption from diets with and without bran should not be affected by coprophagy.

The importance of the body's need for zinc in determining Zn availability in food: a principle demonstrated in the rat

1. The hypothesis that the availability of zinc in a food is limited by factors in the food was tested against the hypothesis that Zn absorption is homeostatically regulated by the body according to its need for Zn. 2. The experimental model used was the short-term administration to rats of a parenteral nutrition solution with no added Zn in an attempt to increase their need for Zn in an anabolic phase. 3. The absorption and retention of 65Zn from a piece of endosperm-wheat crisp-bread in rats injected intraperitoneally with the parenteral nutrition solution was more than 40% higher than that in a control group injected with physiological saline (9 g sodium chloride/l). 4. The results indicate that the availability of Zn in the bread is not fixed but variable and dependent on the body's need for Zn.

Development of gingivitis around different types of composite resin

Earlier studies have demonstrated signs of gingivitis around conventional composite resin restorations. Newly developed resin types differ considerably in composition and surface characteristics. The purpose of this study was to compare the initiation of gingival inflammation around aged restorations of 3 types of composite resins and around enamel, during a 7-day period of experimental gingivitis. Plaque index, gingival index and crevicular exudate were registered at days 0 and 7. There was significantly less exudate around the intact enamel surfaces than around the composite fillings at both registration times. The plaque and gingival indices showed no significant differences among the composite resins and enamel. The results indicate that differences among the resins with regard to surface roughness and composition did not result in clinically measurable differences in the development of plaque and gingivitis.

The effect of different types of composite resin fillings on marginal gingiva

Earlier studies of plaque accumulation on and gingival response around conventional composite resin fillings have produced conflicting results. No studies have been found in which the gingival reaction around newer types of resin fillings had been recorded. The aim of this study was to measure plaque retention and gingival conditions around in vivo, aged, subgingivally located, composite fillings of conventional, hybrid and microfiller types. This study was performed in 2 groups of patients. In the 1st group, there were 108 1-year-old class-III restorations of the 3 composite types and in the 2nd group, 228 3- or 4-year-old class-III or class-IV fillings. Plaque and gingival index scores and the amount of crevicular fluid were recorded. In the group with 1-year-old fillings, the composite resins did not adversely affect the health of the gingival tissues. The amount of plaque on and the degree of gingivitis around the composite fillings were not significantly higher than those for the enamel surfaces. Significant differences in the amount of crevicular fluid were found between both the conventional and hybrid composites and the enamel. In the groups with 3-4 year-old fillings, the indices for each material were significantly higher than those for the enamel surfaces and the fillings showed greater amounts of plaque and a higher degree of gingivitis than the 1-year-old fillings. Differences among the 3 types of composite resins were minimal in both groups and not statistically significant.

Bone mineral content in the proximal tibia measured by computer tomography

With a slight modification of the EMI MK1 scanner a sensitive method for examination of the bone mineral content in the proximal tibia was achieved. The method allows an estimation of the amount of trabecular and cortical bone as well as their mineral content. The anatomic structure of the bone substance is demonstrated, differing in osteoporosis and osteomalacia. The reproducibility is acceptable.