Organotypic slice cultures from transgenic mice as disease model systems

Organotypic slice cultures have been prepared from the brains of transgenic mice with Alzheimer’s disease-type pathology. Cell types within the slice undergo differentiation and slices can be maintained in culture for up to 6 mo when prepared from young neonates. Slices have been prepared from mice overexpressing genes of relevance to Alzheimer’s disease, including mutant or wild-type tau. Neurons in these slices develop neurons that are immunoreactive for a number of markers of abnormal tau. Organotypic slice models are currently being used to test the impact of tangle enhancers or inhibitors as a prescreen for efficacy before testing drugs in vivo.     

Nontuberculous mycobacterial infection: CT scan findings, genotype, and treatment responsiveness

STUDY OBJECTIVE: The purpose of this study was to compare the imaging findings of nontuberculous mycobacterial (NTM) infection in patients with normal and abnormal cystic fibrosis (CF) genotypes, and normal and abnormal alpha1-antitrypsin (AAT) phenotypes. DESIGN: A retrospective review of medical records and chest CT scans from 85 patients with microbiologically proven NTM infection was performed. All patients had undergone genotype analysis for CF mutations, and phenotypic evaluation for AAT status. Patients with homozygous CF or AAT were not included. Two independent observers assessed the patterns and distribution of disease, according to a standardized score sheet. In 52 patients, follow-up CT scans were obtained 1 to 46 months (mean duration, 8 months) following the initial CT scan. The CT scan findings on the follow-up scan were visually compared with those on the initial CT scan for progression or regression of abnormalities. Statistical analysis was performed to evaluate the relationship between the dominant CT scan pattern and CF/AAT status, and between CT scan pattern and radiologic change on follow-up. RESULTS: Fifteen patients (18%) were found to carry a single CF mutation, and an abnormal AAT phenotype was seen in 13 patients (15%). Three patients (3%) were found to have both a heterozygous CF mutation and a heterozygous AAT phenotype. On the initial CT scans, bronchiectasis and nodules were the most frequent findings of NTM infection in all three groups (p > 0.05). The prevalence of nodules was slightly lower in the CF group, and the prevalence of linear scarring was greater in the AAT group than in the normal group (p < 0.05). Among the 52 patients who had a follow-up CT scan, 8 (15%) had a CF mutation and 6 (12%) had an abnormal AAT phenotype. The extent and pattern of abnormality seen on the initial CT scan did not predict change on follow-up evaluation. After treatment, 40 patients (56%) with a normal CF genotype had decrease in disease extent, compared with 4 patients (25%) with a CF mutation (p < 0.05). Bronchiectasis was improved in approximately 35% of those with normal genotype, but in none of those with a CF mutation. CONCLUSION: In patients with NTM infection, the CT scan findings show only minor differences according to phenotype and genotype. Initial CT scan findings do not predict change on follow-up CT scan evaluation. However, on follow-up CT scan, patients with CF mutations are less likely to improve, while those with AAT phenotype appear to have a radiographic outcome similar to those with normal phenotype.     

Rethinking the Importance of the Individual within a Community of Data

The Covid-19 crisis has underscored the importance of the collection and analysis of clinical and research data and specimens for ongoing work. The federal government recently completed a related revision of the human subjects research regulations, founded in the traditional principles of research ethics, but in this commentary, we argue that the analysis underpinning this revision overemphasized the importance of informed consent, given the low risks of secondary research. Governing the interests of a community is different from governing the interests of individuals, and here we suggest that, moving forward, the analyses of the risks of secondary research protocols be assessed from the perspective of the former.     

Elevated cannabinoid receptor 1 and G protein‐coupled receptor 55 expression in proximal tubule cells and whole kidney exposed to diabetic conditions

Hyperglycaemia increases the risk of developing diabetic nephropathy, with primary targets in the glomerulus and proximal tubule. Importantly, glomerular damage in the kidney leads to elevated albumin levels in the filtrate, which contributes to tubular structural modifications that lead to dysfunction. Diabetes alters the endocannabinoid system in a number of target organs, with previous research characterizing tissue‐specific changes in the expression of the cannabinoid receptor 1 (CB₁) and G protein‐coupled receptor 55 (GPR55), a putative cannabinoid receptor, in diabetes. Although these receptors have a functional role in the cannabinoid system in the kidney, there has been little investigation into changes in the expression of CB₁ and GPR55 in the proximal tubule under diabetic conditions. In this study, CB₁ and GPR55 messenger RNA and protein levels were quantified in cultured human kidney cells and then treated with either elevated glucose, elevated albumin, or a combination of glucose and albumin for 4, 6, 18, or 24 h. In addition, CB₁ and GPR55 protein expression was characterized in whole‐kidney lysate from streptozotocin‐induced diabetic Sprague‐Dawley rats. In vitro exposure to elevated glucose and albumin increased CB₁ and GPR55 messenger RNA and protein expression in proximal tubule cells in a time‐dependant manner. In whole kidney of streptozotocin‐induced diabetic rats, CB₁ protein was upregulated, whereas GPR55 protein concentration was not altered. Thus, expression of CB₁ and GPR55 in proximal tubules is altered in response to elevated levels of glucose and albumin. Further investigations should determine if these receptors are effective physiological targets for the treatment and prevention of diabetic nephropathy.     

Stemming the Standard‐of‐Care Sprawl

The “best interests of the patient” standard—a complex balance between the principles of beneficence and autonomy—is the driving force of ethical clinical care. Clinicians’ fear of litigation is a challenge to that ethical paradigm. But is it ever ethically appropriate for clinicians to undertake a procedure with the primary goal of protecting themselves from potential legal action? Complicating that question is the fact that tort liability is adjudicated based on what most clinicians are doing, not the scientific basis of whether they should be doing it in the first place. In a court of law, clinicians are generally judged based on the “reasonably prudent” standard: what a reasonably prudent practitioner in a similar situation would do. But this legal standard can have the effect of shifting the medical standard of care—enabling a standard‐of‐care sprawl where actions undertaken for the primary purpose of avoiding liability reset the standard of care against which clinicians will be adjudicated. While this problem has been recognized in the legal literature, neither current ethical models of care nor legal theory offer workable solutions . One of the best examples of the conflict between evidence‐based medicine and common clinical practice is the use of electronic fetal monitoring. Despite strong evidence and professional guidelines that argue against the use of EFM for healthy pregnancies, the practice persists. One of the main reasons for this is often assumed to be physicians’ concerns about liability .