Health and disease in context: a community-based social medicine curriculum.

Despite the increasing attention paid to the role of social forces in determining health, most physicians finish their training ill-prepared to address these issues. The authors describe their efforts to fill that training gap for internal medicine residents at Oregon Health and Science University through a community-based social medicine curriculum, designed in 2006 in conjunction with community partners at Central City Concern (CCC), an organization addressing homelessness, poverty, and addiction in downtown Portland, Oregon. The challenge was to develop a curriculum that would (1) fit within the scheduling constraints of an established categorical internal medicine residency program, (2) give all internal medicine residents a chance to better understand how social forces affect health, and (3) help show how they, as health professionals, might intervene to improve health and health care. The authors maintain that by developing this curriculum with community partners--who took the lead in deciding what residents should learn about their community and how they should learn it--the residency program is providing a relatively brief but extremely rich opportunity for residents to engage the personal, social, and health-related issues experienced by clients served by CCC.The authors first provide a brief overview of the curriculum and describe how the principles and practices of community-based participatory research were used in its development. They then discuss the challenges involved in teaching medical residents about social determinants of health, how their academic-community partnership approaches those challenges, and the recently established methods of evaluating the curriculum.     

A novel regulation mechanism of DNA repair by damage-induced and RAD23-dependent stabilization of xeroderma pigmentosum group C protein

Primary DNA damage sensing in mammalian global genome nucleotide excision repair (GG-NER) is performed by the xeroderma pigmentosum group C (XPC)/HR23B protein complex. HR23B and HR23A are human homologs of the yeast ubiquitin-domain repair factor RAD23, the function of which is unknown. Knockout mice revealed that mHR23A and mHR23B have a fully redundant role in NER, and a partially redundant function in embryonic development. Inactivation of both genes causes embryonic lethality, but appeared still compatible with cellular viability. Analysis of mHR23A/B double-mutant cells showed that HR23 proteins function in NER by governing XPC stability via partial protection against proteasomal degradation. Interestingly, NER-type DNA damage further stabilizes XPC and thereby enhances repair. These findings resolve the primary function of RAD23 in repair and reveal a novel DNA-damage-dependent regulation mechanism of DNA repair in eukaryotes, which may be part of a more global damage-response circuitry.     

Paternal mosaicism for a novel PBX1 mutation associated with recurrent perinatal death: Phenotypic expansion of the PBX1‐related syndrome

Autosomal dominant (de novo) mutations in PBX1 are known to cause congenital abnormalities of the kidney and urinary tract (CAKUT), with or without extra‐renal abnormalities. Using trio exome sequencing, we identified a PBX1 p.(Arg107Trp) mutation in a deceased one‐day‐old neonate presenting with CAKUT, asplenia, and severe bilateral diaphragmatic thinning and eventration. Further investigation by droplet digital PCR revealed that the mutation had occurred post‐zygotically in the father, with different variant allele frequencies of the mosaic PBX1 mutation in blood (10%) and sperm (20%). Interestingly, the father had subclinical hydronephrosis in childhood. With an expected recurrence risk of one in five, chorionic villus sampling and prenatal diagnosis for the PBX1 mutation identified recurrence in a subsequent pregnancy. The family opted to continue the pregnancy and the second affected sibling was stillborn at 35 weeks, presenting with similar severe bilateral diaphragmatic eventration, microsplenia, and complete sex reversal (46, XY female). This study highlights the importance of follow‐up studies for presumed de novo and low‐level mosaic variants and broadens the phenotypic spectrum of developmental abnormalities caused by PBX1 mutations.     

Muscular fatigue during repeated isokinetic shoulder forward flexions in young females

Summary Peak torque, work, mean power and electromyographic (EMG) activity were recorded for each of 150 repeated isokinetic maximal shoulder flexions (45°–90°) in 23 healthy females. From the EMG signals of trapezius, deltoid, infraspinatus and biceps brachii the mean power frequency and the signal amplitude were determined in real time. The mechanical output showed a steep decrease during the first 40 contractions, followed by a plateau maintained until the end. In all muscles, except the biceps brachii, significant decreases in mean power frequency occurred during the first 40 contractions, showing a tendency to stabilize around the same absolute frequency value. Signal amplitude increased in the trapezius, the deltoid and the infraspinatus, but was constant in the biceps brachii. For some individuals rather high EMG activity was recorded in the muscles during the time the arm was supposed to be passively extended to the starting position, and this was found to be associated with lower strength and endurance levels. Longitudinal analyses showed that the mean power frequencies correlated better than the signal amplitudes with the three mechanical variables. The results suggest that the initial steep decrease in mechanical performance and mean power frequency is caused by fatiguing of type 2 motor units.     

Neuronal degeneration in hippocampus and cerebellum of mutant spastic Han-Wistar rats

The neuropathology of the brain of mutant spastic Han-Wistar rats (Han-Wist SPA/SPA) was investigated using histological techniques. A surprising result was the detection of neuronal degeneration in the hippocampus and cerebellum of mutant spastic rat brains, whereas other regions, e.g. neocortex, isocortex, basal ganglia and thalamus, were overall normal. The CA3 sector in the septal third of the hippocampus including the cell band reaching into the hilus ('CA3c') showed a severe neuronal degeneration, whereas the granule cells of the dentate gyrus, several hilar neurons ('CA4') and the pyramidal cells in CA1 were found normal. In the cerebellum, a variable patchy degeneration of Purkinje cells was detected while the general layering was normal and granule cells and Golgi cells appeared preserved.     

Recovery, survival and functional evaluation by transplantation of frozen-thawed mouse germ cells

BACKGROUND: Establishing a successful method for testicular stem cell transplantation of frozen-thawed testicular cells would be of immense benefit to boys with childhood cancer undergoing a sterilizing treatment. In this study, we evaluated different cryopreservation protocols in a mouse model by means of testicular germ cell transplantation (TGCT), in order to establish an optimal freezing protocol. METHODS AND RESULTS: In a first series of experiments, we compared an uncontrolled protocol with 1.5 mol/l dimethyl sulphoxide (DMSO) versus a controlled long protocol (cooling to -80 degrees C) and observed a better viability with the latter protocol (36% versus 48%, P < 0.05). We then compared survival after two thawing methods (37 degrees C water versus ice water) in either a DMSO- or an ethylene glycol (EG)-based protocol, and found no difference. In order to evaluate the functional capacity of the cryopreserved testicular suspension, TGCT was performed with both fresh and frozen-thawed suspensions. In 90% of the successfully injected testes, spermatogenesis was reinitiated using fresh suspensions. In contrast, this figure was only 12.5 and 22.7% after cryopreservation, for the short controlled EG protocol and the uncontrolled DMSO protocol, respectively. CONCLUSION: Reinitiation of spermatogenesis is possible after cryopreservation of testicular germ cell suspensions. Although cell survival was acceptable, our results after TGCT show that our protocols need further improvement.     

Optimization of peptide linker length in production of MHC class II/peptide tetrameric complexes increases yield and stability,and allows identification of antigen-specific CD4+T cells in peripheral blood mononuclear cells

Reliable, efficient systems for producing soluble HLA-DR molecules, suitable for multimerization and use as staining reagents, have proved elusive. We found that the addition of a flexible linker between peptide and N terminus of the DRB1*0101-chain (Crawford, F., Kozono, H., White, J., Marrack, P. and Kappler, J., Immunity 1998. 8: 675-682.), results in greater in vitro folding efficiency of Escherichia coli-expressed alpha- and beta-chains, and increases both the yield and stability of the DRA1*0101/DRB1*0101/peptide complexes. Although a 10-amino acid linker functioned efficiently for a 20mer epitope from HIV p24, a longer linker was required to produce a DR1 MHC class II tetramer with the influenza hemagglutinin epitope (HA(306-318)). The DR1-HA tetramer was able to stain positively over 98% of a specific clone (HA 1.7) with only a brief 30-min incubation. The tetrameric complexes detected clone cells diluted into PBMC, with high sensitivity, coupled with low background staining in CD4(+) cells. It was possible to detect antigen-specific CD4(+) T cells within a population of PBMC stimulated with the HA peptide. This demonstrates the potential to monitor CD4(+) T cell responses in peripheral blood in a number of clinical scenarios.