Design and Implementation of a Didactic Curriculum in a Large Neonatal-Perinatal Medicine Fellowship Program: A Single-center Experience

OBJECTIVE

 Although the Accreditation Council for Graduate Medical Education and American Board of Pediatrics (ABP) provide regulations and guidance on fellowship didactic education, each program establishes their own didactic schedules to address these learning needs. Wide variation exists in content, educators, amount of protected educational time, and the format for didactic lectures. This inconsistency can contribute to fellow dissatisfaction, a perceived poor learning experience, and poor attendance. Our objective was to create a Neonatal-Perinatal Medicine (NPM) fellow curriculum based on adult learning theory utilizing fellow input to improve the perceived fellow experience.

STUDY DESIGN

 A needs assessment of current NPM fellows at Cincinnati Children's Hospital was conducted to guide the development of a new curriculum. Fellow perception of educational experience and board preparedness before and after introduction of the new curriculum was collected. Study period was from October 2018 to July 2021.

RESULTS

 One hundred percent of the fellows responded to the needs assessment survey. A response rate of 100 and 87.5% were noted on mid-curriculum survey and postcurriculum survey, respectively. Key themes identified and incorporated into the curriculum included schedule structure, content, and delivery mode. A new didactic curriculum implementing a consistent schedule of shorter lectures grouped by organ system targeting ABP core content was created. After curriculum implementation, fellows had higher self-perception of board preparedness, and overall improved satisfaction.

CONCLUSION

 Our positive experience in implementing this curriculum provides a framework for individual programs to implement similar curricula, and could be utilized to aid in development of national NPM curricula.

KEY POINTS

· Fellowship didactic education varies significantly resulting in learner dissatisfaction and poor attendance.. · Widespread need to restructure didactic curricula exists.. · Our study provides a framework for future curricula..

Frequent hypoxemia found in infants with bronchopulmonary dysplasia after weaning home oxygen

OBJECTIVE

Parental reports and brief clinical examinations are the primary information used to assist clinicians in weaning home supplemental oxygen in infants with bronchopulmonary dysplasia (BPD). Recorded nocturnal oximetry provides an objective assessment of hypoxemia; however, it is unknown if it identifies clinically undetected hypoxemia in the home setting. Our objective was to determine if nocturnal oximetry can identify unreported hypoxemia in infants with BPD who appear ready to wean from supplemental oxygen.

STUDY DESIGN

We conducted a retrospective chart review of infants born <32 weeks gestation with BPD who were discharged to home receiving supplemental oxygen and completed recorded nocturnal oximetry in room air during an 18-month period. Abnormal oximetry was defined as >5 min with SpO₂  < 90% and/or an oxyhemoglobin desaturation index (ODI4) >5. Comparative analysis of patients with normal and abnormal overnight oximetry was performed using Fisher Exact and Wilcoxon signed-rank test.

RESULTS

Thirty-five former premature infants completed nocturnal oximetry at 5.8 (3.4-8.3) months corrected age. Nocturnal oximetry was abnormal as defined in 67% of the cohort (n = 21). Five percent of patients were hypoxemic, 52% had frequent desaturation events, and 43% had both. No significant differences existed in neonatal characteristics between patients with normal and abnormal studies.

CONCLUSIONS

Nocturnal oximetry was abnormal in the majority of infants with BPD who were otherwise clinically ready to wean from oxygen support, suggesting that recorded home oximetry could be a feasible and useful tool to evaluate for otherwise clinically unapparent nocturnal hypoxemia in patients with BPD.

Tracheostomy prediction model in neonatal bronchopulmonary dysplasia via lung and airway MRI

RATIONALE

Clinical management of neonatal bronchopulmonary dysplasia (BPD) is often imprecise and can vary widely between different institutions and providers, due to limited objective measurements of disease pathology severity. There is critical need to improve guidance on the application and timing of interventional treatments, such as tracheostomy.

OBJECTIVES

To generate an imaging-based clinical tool for early identification of those patients with BPD who are likely to require later tracheostomy and long-term mechanical ventilation.

METHODS

We conducted a prospective cohort study of n = 61 infants (55 BPD, 6 preterm non-BPD). Magnetic resonance imaging (MRI) scores of lung parenchymal disease were used to create a binomial logistic regression model for predicting tracheostomy requirement. This model was further investigated using clinical variables and MRI-quantified tracheomalacia (TM).

MEASUREMENTS AND MAIN RESULTS

A model for predicting tracheostomy requirement was created using MRI parenchymal score. This model had 89% accuracy, 100% positive predictive value (PPV), and 85% negative predictive value (NPV), compared with 84%, 60%, and 83%, respectively, when using only relevant clinical variables. In a subset of patients with airway MRI (n = 36), a model including lung and TM measurements had 83% accuracy, 92% PPV, and 78% NPV.

CONCLUSIONS

MRI-based measurements of parenchymal disease and TM can be used to predict need for tracheostomy in infants with BPD, more accurately than clinical factors alone. This prediction model has strong potential as a clinical tool for physicians and families for early determination of tracheostomy requirement.

Milestone Level Changes From Residency to Fellowship: A Multicenter Cohort Study

BACKGROUND

A vital element of the Next Accreditation System is measuring and reporting educational Milestones. Little is known about changes in Milestones levels during the transition from residency to fellowship training.

OBJECTIVE

Evaluate the Accreditation Council for Graduate Medical Education (ACGME) Milestones' ability to provide a linear trajectory of professional development from general pediatrics residency to neonatal-perinatal medicine (NPM) fellowship training.

METHODS

We identified 11 subcompetencies that were the same for general pediatrics residency and NPM fellowship. We then extracted the last residency Milestone level and the first fellowship Milestone level for each subcompetency from the ACGME's Accreditation Data System on 89 subjects who started fellowship training between 2014 and 2018 at 6 NPM fellowship programs. Mixed-effects models were used to examine the intra-individual changes in Milestone scores between residency and fellowship after adjusting for the effects of the individual programs.

RESULTS

A total of 1905 subcompetency Milestone levels were analyzed. The average first fellowship Milestone levels were significantly lower than the last residency Milestone levels (residency, mean 3.99 [SD = 0.48] vs fellowship 2.51 [SD = 0.56]; P < .001). Milestone levels decreased by an average of -1.49 (SD = 0.65) from the last residency to the first fellowship evaluation. Significant differences in Milestone levels were seen in both context-dependent subcompetencies (patient care and medical knowledge) and context-independent subcompetencies (professionalism).

CONCLUSIONS

Contrary to providing a linear trajectory of professional development, we found that Milestone levels were reset when trainees transitioned from general pediatrics residency to NPM fellowship.

Timing of Referral to Early Intervention Services in Infants With Severe Bronchopulmonary Dysplasia

This study is a secondary analysis of an observational prospective case series of 50 infants with severe bronchopulmonary dysplasia that describes patient factors associated with the time between initial hospital discharge and referral to early intervention (EI) services. It also evaluates associations between (1) timing of EI referral and reception of EI services and (2) early referral to EI and developmental outcomes at 18 to 36 months corrected age. The results demonstrated that a referral from a neonatologist versus a pediatrician was associated with fewer days between discharge and EI referral. Earlier EI referrals were associated with a shorter time to intake evaluation and service initiation. The Bayley-III (Bayley Scales of Infant and Toddler Development, 3rd Edition) scores at 24 months corrected age (n = 28) were not associated with timing of EI referral. In conclusion, an early referral to EI promoted earlier evaluation and initiation of EI services and should be standard for high-risk infants.

Living with Severe Bronchopulmonary Dysplasia-Parental Views of Their Child's Quality of Life

OBJECTIVE

To assess parents' views of their children's health-related quality of life (HRQoL) and the association between neonatal morbidities and HRQoL in children with severe bronchopulmonary dysplasia (BPD) who survived to 18-36 months of corrected age.

STUDY DESIGN

Study population included infants born <32 weeks of gestational age with severe BPD. At 18-36 months of corrected age, parents of children with severe BPD completed age appropriate validated Pediatric Quality of Life Inventory assessing parental views of their child's physical (PHY-QoL) and psychosocial HRQoL (PS-QoL). Ten neonatal morbidities provided a composite morbidity score between 0 and 10. Linear regression evaluated associations between PHY-QoL and PS-QoL with composite morbidity score, adjusting for gestational age, sex, corrected age at assessment.

RESULTS

Seventy children (67% male, gestational age 26.1 ± 2.0 weeks, and birth weight 797 ± 318g) were enrolled at 27.1 ± 5.8 months of corrected age. Mean PHY-QoL and PS-QoL were 78.0 ± 21.9 and 75.3 ± 17.9, respectively, both significantly lower than reported means for term and preterm cohorts, with the exception of emotional QoL. Adjusted postnatal composite morbidity score was cumulatively associated with poorer PHY-QoL (P = .002) and poorer PS-QoL (P = .015). Presence of each additional neonatal morbidity was associated with a 4.4-point decrease in PHY-QoL and 2.8-point decrease in PS-QoL.

CONCLUSIONS

In this cohort, parental perceived HRQoL for their child with severe BPD was lower than expected for term and preterm populations. Neonatal morbidities had an additive association with poorer parental assessment of PHY-QoL and PS-QoL. These findings may aid in care of children with severe BPD and their families, both in the intensive care nursery and postdischarge.

Why do children with severe bronchopulmonary dysplasia not attend neonatal follow-up care? Parental views of barriers

AIM

To assess in children with severe bronchopulmonary dysplasia at a corrected age of 18-36 months: (i) Neonatal follow-up clinic attendance rates; (ii) Parent-identified reasons for difficulty attending neonatal follow-up.

METHODS

Mixed methods study utilising semi-structured phone interviews with parents of infants eligible for follow-up with severe bronchopulmonary dysplasia (defined as gestational age <32 weeks and requiring ≥30% FiO₂ and/or >2 L nasal cannula at 36 weeks post-menstrual age) at 18-36 months corrected age. Questions addressed barriers to neonatal follow-up attendance. Enrolment continued to saturation (no new themes emerging).

RESULTS

A total of 58 infants (69% male) were enrolled. Infants were 26 ± 2.1 weeks gestational age and birth weight 794 ± 262 g. At 28 ± 5.8 months corrected age, 26% had never attended neonatal follow-up clinic, 16% stopped attending before discharge, 5% were discharged, and 53% were still followed. Longer travel distance from home to follow-up clinic was associated with poorer attendance. Parent-generated items related to neonatal follow-up barriers were coded into four themes: Logistics, Time, Perceptions and Emotional Stress.

CONCLUSION

Despite high risk of developmental delay in infants with severe bronchopulmonary dysplasia, neonatal follow-up rates are suboptimal. Careful review of parent-identified barriers could be utilised to develop targeted strategies to improve neonatal follow-up attendance in this high-risk population.

Virulence genes and genotypic associations in nasal carriage, community-associated methicillin-susceptible and methicillin-resistant USA400 Staphylococcus aureus isolates

It is not well understood why strains of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), a major cause of skin and soft tissue infections, became successful so quickly, overtaking the place of methicillin-sensitive S. aureus (MSSA) in many communities. To evaluate the genetic basis of differences in their virulence traits, 293 S. aureus isolates consisting of three cohorts, genotypically defined clinical CA-MRSA (n = 77), clinical MSSA (n = 103), and nasal carriage MSSA (n = 113), collected over a 19-year period in two Midwestern states in the United States, were (i) extensively genotyped and (ii) screened for 40 known virulence genes which included those for enterotoxins, leukocidins, hemolysins, and surface proteins and several newly identified putative toxin genes from the USA400 lineage of CA-MRSA. Genotypically, nasal carriage and clinical MSSA isolates were much more diverse than was the CA-MRSA group, which was found to be of USA400 lineage only. Virulence gene profiles of the three groups showed that CA-MRSA strains harbored significantly higher percentages (≥95%; P value, <0.05) of the sea, sec, sec4, seg2, seh, sek, sel, sel2, ear, ssl1, lpl10, lukSF-PV, lukD, lukE, and clfA genes than did the carriage and the clinical MSSA group (range, 0% to 58%). Genes of the enterotoxin gene cluster, seg, sei, sem, sen, and seo, were present in the clinical and carriage isolates but not in the CA-MRSA group. These results suggest that the presence of additional virulence factors in USA400 CA-MRSA strains compared to the nasal carriage and clinical MSSA strains probably contributed to their enhanced virulence.

Sporadic "transitional" community-associated methicillin-resistant Staphylococcus aureus strains from health care facilities in the United States

We describe phenotypic and genotypic traits of a group of methicillin-resistant Staphylococcus aureus (MRSA) clones that are either remnants of unsuccessful community-associated MRSA (CA-MRSA) clones or represent a transitional state with some yet-to-be-acquired characteristics of CA-MRSA. These rare strains (n = 20) were identified during a 10-year period (1990-1999) from 13 unrelated health care facilities in Wisconsin. The isolates were recovered from patients in nosocomial or long-term chronic care facilities (60%) and outpatient settings (40%). Sixty percent (n = 12) of the isolates were recovered from skin and soft tissue infections, whereas the remaining isolates (n = 8) were from invasive infections. Ninety percent of isolates were susceptible to all antibiotic classes tested or resistant to erythromycin and clindamycin. Pulsed-field gel electrophoresis, multilocus sequence typing, and spa typing clustered these isolates into 8, 8, and 14 clonal groups, respectively. Eight plasmid profiles were represented in these strains. All four agr types were represented, with type IV being predominant (40%). All strains harbored subtypes of type IV staphylococcal cassette chromosome mec but lacked genes for the virulence factor Panton-Valentine leukocidin (PVL). The strains harbored one or more of the following toxin genes: sea, seb, sec, sed, see, seh, sej, sek, sel, seg, sei, sem, sen, and seo. Individual clonal groups maintained the same set of enterotoxin genes even though they were isolated over extended time periods, suggesting significant genomic stability. The potential role of PVL-carrying phages and plasmids in the success of CA-MRSA clones has been discussed.

Shift in Staphylococcus aureus clone linked to an infected tattoo

A retrospective investigation of skin and soft tissue infections caused by community-associated methicillin-resistant Staphylococcus aureus (MRSA) strains among inmates in a Wisconsin correctional facility suggested a shift in MRSA genotype. Case timeline indicated a displacement of USA400 clone by USA300 clone. The USA300 index case was associated with an infected new tattoo.

Necrotizing fasciitis due to a methicillin-sensitive Staphylococcus aureus isolate harboring an enterotoxin gene cluster

Benign papular eruption on the left leg of a 72-year-old diabetic man developed into rapidly spreading necrotizing fasciitis despite antimicrobial therapy and surgical debridements. This led to eventual amputation to control the infection. The etiological agent was a Staphylococcus aureus isolate harboring the enterotoxin gene cluster seg, sei, sem, sen, and seo but lacked all common toxin genes, including Panton-Valentine leukocidin.

Removal of FMRI environment artifacts from EEG data using optimal basis sets

The combination of functional magnetic resonance imaging (FMRI) and electroencephalography (EEG) has received much recent attention, since it potentially offers a new tool for neuroscientists that makes simultaneous use of the strengths of the two modalities. However, EEG data collected in such experiments suffer from two kinds of artifact. First, gradient artifacts are caused by the switching of magnetic gradients during FMRI. Second, ballistocardiographic (BCG) artifacts related to cardiac activities further contaminate the EEG data. Here we present new methods to remove both kinds of artifact. The methods are based primarily on the idea that temporal variations in the artifacts can be captured by performing temporal principal component analysis (PCA), which leads to the identification of a set of basis functions which describe the temporal variations in the artifacts. These basis functions are then fitted to, and subtracted from, EEG data to produce artifact-free results. In addition, we also describe a robust algorithm for the accurate detection of heart beat peaks from poor quality electrocardiographic (ECG) data that are collected for the purpose of BCG artifact removal. The methods are tested and are shown to give superior results to existing methods. The methods also demonstrate the feasibility of simultaneous EEG/FMRI experiments using the relatively low EEG sampling frequency of 2048 Hz.

Digital mammography: a world without film?

OBJECTIVES

eDiaMoND is a next generation Internet ("Grid") multidisciplinary research project funded by the UK e-Science Programme with the following objectives; the development of a next generation Internet enabled prototype to demonstrate the potential benefits of a national infrastructure to support digital mammography; the exploration of potential benefits for digital mammography systems, with particular emphasis being placed on selected applications, namely, screening, training, computer-aided detection and appropriate support for epidemiological studies.

METHODS

EDiaMoND has worked in conjunction with selected clinical partners to enable the collection of valuable mammography information and the design of applications based upon extensive requirements gathering exercises. The clinical partners validated both the immediate needs and assisted with defining future needs of such an architecture to support the UK Health Service.

RESULTS

The project has succeeded in invoking the interest of clinical partners and representatives of the UK NHS Breast Screening Programme in our vision of a world without film, albeit a long way off. The project has also succeeded in identifying the barriers to adopting this approach with the current limitations within the NHS, and has developed a blueprint for working towards this strategy.

CONCLUSIONS

A UK national digital mammography archive has the potential to provide major benefits for the UK. For example, such an archive could: ensure that previous mammograms are always available, and could link up seamlessly the screening, assessment and symptomatic clinics; it could provide a huge teaching and training resource; it could be a huge resource for epidemiological studies.

Fusion of contrast-enhanced breast MR and mammographic imaging data

Increasing use is being made of Gd-DTPA contrast-enhanced MRI (CE-MRI) for breast cancer assessment since it provides three-dimensional (3D) functional information via pharmacokinetic interaction between contrast agent and tumour vascularity, and because it is applicable to women of all ages as well as patients with post-operative scarring. CE-MRI is complementary to conventional X-ray mammography, since it is a relatively low-resolution functional counterpart of a comparatively high-resolution 2D structural representation. However, despite the additional information provided by MRI, mammography is still an extremely important diagnostic imaging modality, particularly for several common conditions such as ductal carcinoma in situ (DCIS) where it has been shown that there is a strong correlation between microcalcification clusters and malignancy. Pathological indicators such as calcifications and fine spiculations are not visible in CE-MRI and therefore there is clinical and diagnostic value in fusing the high-resolution structural information available from mammography with the functional data acquired from MRI. This article is a clinical overview of the results of a technique to transform the coordinates of regions of interest (ROIs) from the 2D mammograms to the spatial reference frame of the contrast-enhanced MRI volume. An evaluation of the fusion framework is demonstrated with a series of clinical cases and a total of 14 patient examples.

Changes in connectivity profiles define functionally distinct regions in human medial frontal cortex

A fundamental issue in neuroscience is the relation between structure and function. However, gross landmarks do not correspond well to microstructural borders and cytoarchitecture cannot be visualized in a living brain used for functional studies. Here, we used diffusion-weighted and functional MRI to test structure-function relations directly. Distinct neocortical regions were defined as volumes having similar connectivity profiles and borders identified where connectivity changed. Without using prior information, we found an abrupt profile change where the border between supplementary motor area (SMA) and pre-SMA is expected. Consistent with this anatomical assignment, putative SMA and pre-SMA connected to motor and prefrontal regions, respectively. Excellent spatial correlations were found between volumes defined by using connectivity alone and volumes activated during tasks designed to involve SMA or pre-SMA selectively. This finding demonstrates a strong relationship between structure and function in medial frontal cortex and offers a strategy for testing such correspondences elsewhere in the brain.

Characterization and propagation of uncertainty in diffusion-weighted MR imaging

A fully probabilistic framework is presented for estimating local probability density functions on parameters of interest in a model of diffusion. This technique is applied to the estimation of parameters in the diffusion tensor model, and also to a simple partial volume model of diffusion. In both cases the parameters of interest include parameters defining local fiber direction. A technique is then presented for using these density functions to estimate global connectivity (i.e., the probability of the existence of a connection through the data field, between any two distant points), allowing for the quantification of belief in tractography results. This technique is then applied to the estimation of the cortical connectivity of the human thalamus. The resulting connectivity distributions correspond well with predictions from invasive tracer methods in nonhuman primate.

Non-invasive mapping of connections between human thalamus and cortex using diffusion imaging

Evidence concerning anatomical connectivities in the human brain is sparse and based largely on limited post-mortem observations. Diffusion tensor imaging has previously been used to define large white-matter tracts in the living human brain, but this technique has had limited success in tracing pathways into gray matter. Here we identified specific connections between human thalamus and cortex using a novel probabilistic tractography algorithm with diffusion imaging data. Classification of thalamic gray matter based on cortical connectivity patterns revealed distinct subregions whose locations correspond to nuclei described previously in histological studies. The connections that we found between thalamus and cortex were similar to those reported for non-human primates and were reproducible between individuals. Our results provide the first quantitative demonstration of reliable inference of anatomical connectivity between human gray matter structures using diffusion data and the first connectivity-based segmentation of gray matter.

Detecting the brain surface in sparse MRI using boundary models

We introduce a framework for the detection of the brain boundary (arachnoid) within sparse MRI. We use the term sparse to describe volumetric images in which the sampling resolution within the imaging plane is far higher than that of the perpendicular direction. Generic boundary detection schemes do not provide good results for such data. In the scheme we propose, the boundary is extracted using a constrained mesh surface which iteratively approximates a 3D point set consisting of detected boundary points. Boundary detection is based on a database of piecewise constant models, which represent the idealised MR intensity profile of the underlying boundary anatomy. A non-linear matching scheme is introduced to estimate the location of the boundary points using only the intensity data within each image plane. Results are shown for a number of images and are discussed in detail.

Estimation of compressed breast thickness during mammography

To estimate radiation dose during mammography the breast thickness must be known. We present a new method for estimating the thickness of a compressed breast using only the breast image as projected onto a mammogram, calibration data such as the mAs value and image processing techniques. The method proves to be of high accuracy (+/- 0.2 cm for craniocaudal mammograms) and has the advantage over other methods of allowing retrospective estimation of thickness.

Mammographic image analysis

We describe our recent progress aimed at computer analysis of mammograms. The overall aim is to provide the clinician with reliable quantitative information. We summarise a representation we have developed of the 'interesting' (non-adipose) tissue in a breast, then put the representation to work in three ways: (i) to propose a new quantitative measure to aid in diagnosing masses; (ii) to explore the possibility of reducing by half the radiation dose required for a mammogram; and (iii) recalling some of the results that can be provided by differential compression mammography, in which mammograms are taken at two slightly different compressions.

Detecting approximal dental caries with transillumination: a clinical evaluation

Independent examinations of 300 patients were conducted to evaluate fiber optic transillumination's performance in caries detection. FOTI was used as an adjunct to clinical and radiographic examinations for caries, restoration or secondary caries of approximal surfaces in maxillary anterior permanent teeth. Clinical and radiographic examinations were significantly more effective.

Computing the scatter component of mammographic images

The authors build upon a technical report (Tech. Report OUEL 2009/93, Engng. Sci., Oxford Uni., Oxford, UK, 1993) in which they proposed a model of the mammographic imaging process for which scattered radiation is a key degrading factor. Here, the authors propose a way of estimating the scatter component of the signal at any pixel within a mammographic image, and they use this estimate for model-based image enhancement. The first step is to extend the authors' previous model to divide breast tissue into "interesting" (fibrous/glandular/cancerous) tissue and fat. The scatter model is then based on the idea that the amount of scattered radiation reaching a point is related to the energy imparted to the surrounding neighbourhood. This complex relationship is approximated using published empirical data, and it varies with the size of the breast being imaged. The approximation is further complicated by needing to take account of extra-focal radiation and breast edge effects. The approximation takes the form of a weighting mask which is convolved with the total signal (primary and scatter) to give a value which is input to a "scatter function", approximated using three reference cases, and which returns a scatter estimate. Given a scatter estimate, the more important primary component can be calculated and used to create an image recognizable by a radiologist. The images resulting from this process are clearly enhanced, and model verification tests based on an estimate of the thickness of interesting tissue present proved to be very successful. A good scatter model opens the was for further processing to remove the effects of other degrading factors, such as beam hardening.

Evolution of the rat kallikrein gene family: gene conversion leads to functional diversity

Kallikrein-like simple serine proteases are encoded by closely related members of a gene family in several mammalian species. Molecular cloning and genomic Southern blot analysis after conventional and pulsed-field gel electrophoresis indicate that the rat kallikrein gene family comprises 15-20 members, probably closely linked at a single locus. Determination of the nucleotide sequences of the rGK-3, -4, and -6 genes here completes sequence data for a total of nine rat kallikrein family members. Comparison of the rat gene sequences to each other and to those of human and mouse kallikrein family genes reveals patterns of relatedness indicative of concerted evolution. Analysis of nucleotide sequence variants in kallikrein family members shows that most sequence variants are shared by multiple family members; the patterns of shared variants are complex and indicate multiple short gene conversions between family members. Sequence exchanges between family members generate novel assortments of variants in amino acid coding regions that may affect substrate specificity and thereby contribute to the diversity of enzyme activity. Furthermore, small sequence exchanges also may play a role in generating the diverse patterns of tissue-specific expression of rat family members. These analyses indicate an important role for gene conversion in the evolution of the functional diversity of these duplicated genes.

The expression of two kallikrein gene family members in the rat kidney

The mRNAs for two kallikrein gene family members expressed in the rat kidney have been characterized. One mRNA (PS) has previously been found in the pancreas and submaxillary gland and encodes true kallikrein. The second mRNA (K1) encodes a novel kallikrein-like enzyme expressed in the kidney and submaxillary gland that retains many of the key amino acid residues for the characteristic enzymatic cleavage specificity of kallikrein. Two oligonucleotide hybridization probes specific for the K1 mRNA demonstrate that the K1 mRNA is expressed in the kidney and submaxillary gland, but in none of the other eight tissues known to express one or more members of the rat kallikrein gene family. The K1 mRNA is the dominant kallikrein-related mRNA of the kidney, expressed at roughly 10 times the level of the true kallikrein (PS) mRNA. In the submaxillary gland the K1 mRNA is expressed at roughly one-fourth the level of true kallikrein mRNA.

Expression of two kallikrein gene family members in the rat prostate

We have characterized two kallikrein gene family members expressed in the prostate and submaxillary glands of rats. One mRNA (S3) is identical with the previously characterized submaxillary gland S3 mRNA that encodes an enzyme closely related to tonin. The second mRNA (P1) encodes a novel kallikrein-like enzyme that retains key amino acid residues responsible for the characteristic enzymatic cleavage specificity of kallikrein. Two P1-specific oligonucleotide probes derived from the P1 mRNA sequence were used to demonstrate the presence of P1 mRNA in the prostate and submaxillary glands and its absence in eight other rat tissues known to express one or more members of the kallikrein family. The P1-coding gene (rGK-8) was identified among genomic clones containing kallikrein family members by hybridization with a P1-specific oligonucleotide probe. The identification of the P1 gene was verified by nucleotide sequencing; the exon sequences of rGK-8 match the P1 mRNA sequence. The upstream region of rGK-8, where transcriptional regulatory elements likely reside, is very similar to that of other rat kallikrein family genes which are expressed in distinct tissue-specific patterns.

Organization and expression of the rat kallikrein gene family

We have cloned and characterized eight members of the kallikrein gene family from rat genomic DNA. Three of the cloned genes correspond to the previously characterized kallikrein family mRNAs PS, S2, and P1, which encode true kallikrein, tonin, and a novel kallikrein-like enzyme, respectively. In two cases, two kallikrein family genes are located on single genomic clones, suggesting close linkage of this family in the rat genome. Based on the total number of cloned genes and mRNAs, the minimum size of the rat family is 11 genes. Comparisons between the rat genes demonstrate a high degree of nucleotide sequence identity (greater than 80%) in exonic, intronic, and nearby flanking regions. This extensive sequence conservation not limited to clearly functional domains suggests that concerted evolution of this gene family has occurred. Despite the high overall sequence conservation among the rat family members, several discrete regions of high variability exist in the coding regions. We have defined the tissue-specific expression of the PS (true kallikrein), S2 (tonin), and S3 mRNAs with gene-specific oligonucleotide probes derived from these variant regions. PS is expressed in a wide range of tissues, while S2 mRNA is restricted to the submaxillary gland and S3 mRNA to the submaxillary and prostate glands. The high sequence conservation within the upstream flanking regions of these genes suggests that a small number of nucleotide differences determines the disparate transcriptional specificity of individual family members.

Scanning microscopy of resin infiltration patterns in acid-etched incisor enamel

Previous studies have described the surface morphologic characteristics of acid-etched enamel. The purpose of this investigation was to examine the patterns of resin infiltration into the etched enamel. Fourteen, human, incisor teeth, extracted because of advanced periodontal disease, were etched on the labial surfaces for 60 seconds with 37% phosphoric acid, washed in tap water, and then air-dried. A self-cured enamel resin was applied to the etched labial surface and supported with epoxy. The teeth were dissolved in formic acid. The resin remnants were cleaned in water, dried, mounted on specimen stubs, coated with sputtered gold, and examined in a Scanning electron microscope (SEM). Resin infiltration patterns were photographed in the SEM at a magnification of 400 in 0.125-mm2 areas of the incisal, middle, and gingival thirds of each labial surface. Resin infiltration patterns were scored according to the correspondence with the rod-core, rod-periphery, and irregular acid-etch patterns seen in enamel. The distribution of resin infiltration patterns was as follows: rod-core, 9.7%; rod-periphery, 40.5%; and irregular, 49.7%. The values were averaged over all the surface areas. Infiltration patterns into the etched enamel exhibited deep interperikymata resin penetration. Subsurface channeling of resin was responsible for the pattern seen in irregular etch and was the most common form of infiltration in the gingival region. Subsurface channeling may be related to the development of micropores observed in incipient carious lesions. Deep monomer penetration and channeling may be important factors in mechanical attachment.

Scanning electron microscopy of submandibular sialoliths: a preliminary report

This report compares the scanning electron microscopic appearances of the structures in two sialoliths, one surgically removed, the other naturally exfoliated. The first exhibited the typical structure of a lamellated outer layer with an amorphous core. The core contained a large number of structures resembling calcified filamentous organisms. The second consisted of a similar outer lamella but the core contained crystal-lined spaces, amorphous matrix and an heterogeneous array of crystal shapes: there were no structures resembling organisms.

Androgen dependence of specific kallikrein gene family members expressed in rat prostate

We have used oligonucleotide probes specific for members of the rat kallikrein/tonin gene family (PS, S1, S2, S3, K1, and P1) to establish which arginyl esteropeptidase (kallikrein-like) genes are expressed in the prostate. We have also compared the expression and androgen dependence of these genes in prostate, submaxillary gland (SMG) and kidney. Only S3 (tonin-like) and P1 (kallikrein-like) are expressed in the prostate, with S3 very much more abundant. Prostatic S3 mRNA disappears after 8 days castration and is restored to intact levels by dihydrotestosterone (DHT) but not estradiol benzoate (EB) for 8 days. Prostate P1 mRNA levels were similarly but not identically affected. All six genes are expressed in the SMG, with PS (true kallikrein) the most abundant. Levels of PS mRNA in SMG are unaffected by castration, DHT, or EB treatment, although mRNA levels of other kallikrein-like (S1, K1, and P1), tonin (S2), and tonin-like (S3) genes fall 40-60% after castration, and are unaffected or partially restored by DHT and/or EB administration. Only PS and K1 are expressed in the kidney, at much lower levels than in the SMG and unaffected by castration or steroids. These studies thus confirm and extend the concept of tissue specificity of arginyl esteropeptidase gene expression, and further demonstrate that the same gene(s) is differentially regulated by androgens in the rat prostate, SMG, and kidney.

Considering the psychosocial aspects of AIDS

People with AIDS have great needs--not only physical due to the effects of the disease on their bodies, but psychological as well. In addition, fear and repugnance of the disease and its victims has started another epidemic dubbed AFRAIDS.

Osteogenesis imperfecta lethal in infancy: case report and scanning electron microscopic studies of the deciduous teeth

Radiologic evaluation of the skeleton and scanning electron microscopic studies of the teeth were performed on an infant boy with a lethal osteogenesis imperfecta (OI) syndrome who died at 10 mo of pneumonia. The skeletal findings included ribs that were focally expanded by fracture calluses, flat vertebral bodies, and wide limb bones. On fractured tooth surfaces, the enamel and dentin were normal as was the dentin calcification front. Although microscopic abnormalities have been noted in teeth from previously reported infants with lethal OI, a few studies also report infants with normal teeth. These differences in dental findings may indicate heterogeneity in OI lethal in infancy. Results of our study indicate that, until the primary biochemical defects in the OI syndromes are elucidated, examination of teeth from other infants with lethal OI and detailed evaluation of other clinical and skeletal features will aid in delineating heterogeneity and variation in expression in lethal OI.

Light microscopy, scanning electron microscopy, and microprobe analysis of bone response to zinc and nonzinc amalgam implants

Freshly mixed, unset zinc-free and zinc-containing analgam was implanted in the right tibia of 32 rats. Half of the specimens were examined by the light microscope and the other half by the scanning electron microscope and x-ray microprobe analysis. It was found that amalgam is well tolerated by the rat osseous tissue, and there were no histologic reaction differences between zinc and zinc free amalgam. The surfaces of the implants were covered by an organic film at 3 weeks and with bone at later intervals. Very little corrosion products containing sulfur were observed on the amalgam surface at all intervals. Bone adjacent to the amalgam contained tin and sulfur irrespective of the presence of zinc in the alloy, indicating outward migration of specific components of the alloy.

Scanning electron microscopy of teeth in dominant osteogenesis imperfecta: support for genetic heterogeneity

Scanning electron microscopic studies were performed on 25 deciduous and permanent teeth from members of 7 kindreds with dominant nonlethal osteogenesis imperfects (OI). Two families had normal teeth on clinical and radiological examination; five families had blue or brown opalescent teeth with specific radiologic findings. Enamel surfaces and prism organization were normal on all teeth. On fractured surfaces, the dentin tubules of normal teeth from patients with OI were evenly distributed and coursed regularly to the dentin-enamel junction. Opalescent teeth had few tubules and those present were short, narrow, and tortuous. Dentin calcification fronts of normal teeth were composed of many nodules with regularly spaced openings on their surfaces. Calcification fronts of opalescent teeth were composed of irregularly spaced, small nodules, which varied greatly in size and the nodules lacked tubule openings on their surfaces. The results of this study support the concept that at least two dominant forms of OI exist--one in which all individuals with IO have normal teeth, and the other in which all with OI have blue or brown opalescent teeth with characteristic changes on SEM.

Periodontosis: a case report with scanning electron microscopic observations

A tooth and associated periodontal tissues from a patient with the diagnosis of periodontosis was subjected to scanning electron microscopic evaluation after reflection of the soft tissue portion of the lingual defect. The cemental surface of the apical portion of the lesion was found to be populated by markedly similar rod-shaped organisms. The microorganisms were observed to be continuously present in a coronal-apical direction as the transition from cementum to the attached soft tissues at the base of the defect were examined. These findings provide additional evidence that the lesion of periodontosis is characterized by a rather distinct microbial population of rod-shaped organisms located predominately at the base of the defect.

Sealing quality of a temporary filling material

Endodontic access cavities were prepared in forty extracted human teeth. The access cavities were obturated with Cavit and tested for leakage with methylene blue. The data suggested that at least a 3.5 mm. thickness of Cavit should be used in order to prevent leakage. Examination under the scanning electron microscope showed areas in which the constituents of Cavit were improperly mixed, which may lead to increased penetration.

Evaluation of débridement techniques for endodontic instruments

Files, reamers, and Hedström files were used to instrument both wet and dry canals and then cleansed by a chairside technique. Statistical analysis of the various cleansing techniques showed that 2 by 2 inch gauze wipes, either wet or dry, cleansed the instruments of debris better than any other means tested.

Degradation rates of oral resorbable implants (polylactates and polyglycolates): rate modification with changes in PLA/PGA copolymer ratios

This study determined the difference in rate of degradation between pure polymers of lactic acid (pla), glycolic acid (PGA), and various ratios of copolymers of these two substances. Fast-cured and slow-cured polyglycolide was compared with copolymers of glycolide/lactide intermixed in ratios of 75:25, 50:50, and 25:75, as well as pure polylactide. A total of 420 rats were implanted with carbon-14 and tritium-labeled polymers in bone and soft tissue. At intervals of 1, 2, 3, 5, 7, 9, and 11 months, groups of five animals with the implants in bone and five with the implants in the abdominal wall were sacrificed. The implant area as well as tissue from the liver, spleen, kidney, lung and some muscle tissue was analyzed for radioactivity along with the urine and feces collected throughout the experiment. Half-lives of the different polymers and copolymers were calculated from the radioactivity present in the implant area for each time interval. Half-life of the polymers and copolymers decreased from 5 months for 100% PGA to 1 week with 50:50 PGA:PLA copolymer and rapidly increased to 6.1 months for 100% PLA. Fast-cured PGA had a half-life in tissue of 0.85 months. No difference in rate of degradation was seen in soft tissue or bone. No significant radioactivity was detected in urine, feces, or tissue samples. From this study, it is concluded that control of degradation rate of the implant could best be attained by varying the composition of PLA and PGA between 75% and 100% PLA along with a corresponding 25% to 0% PGA. This would provide a half-life range of the implant of from 2 weeks to 6 months.

Evaluation of endodontic instruments as received from the manufacturer: the demand for quality control

Two hundred seventy new files, reamers, and Hedström files from three different manufacturers were evaluated for debris and defects. Statistical analysis of the new instruments showed that one company's instruments were cleaner than the other two but still contained defects. A standard for quality is proposed.