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UC San Diego Previously Published Works

Cover page of Peptides rapidly transport antibiotic across the intact tympanic membrane to treat a middle ear infection

Peptides rapidly transport antibiotic across the intact tympanic membrane to treat a middle ear infection

(2025)

The tympanic membrane (TM) forms an impenetrable barrier to medical therapies for middle ear (ME) diseases like otitis media. By screening a phage-displayed peptide library, we have previously discovered rare peptides that mediate the active transport of cargo across the intact membrane of animals and humans. Since the M13 filamentous bacteriophage on which the peptides are expressed are large (nearly 1 µm in length), this offers the possibility of noninvasively delivering drugs, large drug packages, or gene therapy to the ME. To evaluate this possibility, EDC chemistry was employed to covalently attach amoxicillin, or neomycin molecules to phage bearing a trans-TM peptide, as a model for large drug packages. Eight hours after application of antibiotic-phage to the TM of infected rats, ME bacterial titers were substantially reduced compared to untreated animals. As a control, antibiotic was linked to wild-type phage, not bearing any peptide, and application to the TM did not affect ME bacteria. The results support the ability of rare peptides to actively deliver pharmacologically relevant amounts of drugs through the intact TM and into the ME. Moreover, since bacteriophage engineered to express peptides are viral vectors, the trans-TM peptides could also transport other viral vectors into the ME.

Cover page of Gut microbiota and derived metabolites mediate obstructive sleep apnea induced atherosclerosis.

Gut microbiota and derived metabolites mediate obstructive sleep apnea induced atherosclerosis.

(2025)

Obstructive sleep apnea (OSA) is characterized by intermittent hypoxia/hypercapnia (IHC), affects predominantly obese individuals, and increases atherosclerosis risk. Since we and others have implicated gut microbiota and metabolites in atherogenesis, we dissected their contributions to OSA-induced atherosclerosis. Atherosclerotic lesions were compared between conventionally-reared specific pathogen free (SPF) and germ-free (GF) Apoe-/- mice following a high fat high cholesterol diet (HFHC), with and without IHC conditions. The fecal microbiota and metabolome were profiled using 16S rRNA gene amplicon sequencing and untargeted tandem mass spectrometry (LC-MS/MS) respectively. Phenotypic data showed that HFHC significantly increased atherosclerosis as compared to regular chow (RC) in both aorta and pulmonary artery (PA) of SPF mice. IHC exacerbated lesions in addition to HFHC. Differential abundance analysis of gut microbiota identified an enrichment of Akkermansiaceae and a depletion of Muribaculaceae (formerly S24-7) family members in the HFHC-IHC group. LC-MS/MS showed a dysregulation of bile acid profiles with taurocholic acid, taurodeoxycholic acid, and 12-ketodeoxycholic acid enriched in the HFHC-IHC group, long-chain N-acyl amides, and phosphatidylcholines. Interestingly, GF Apoe-/- mice markedly reduced atherosclerotic formation relative to SPF Apoe-/- mice in the aorta under HFHC/IHC conditions. In contrast, microbial colonization did not show a significant impact on the atherosclerotic progression in PA. In summary, this research demonstrated that (1) IHC acts cooperatively with HFHC to induce atherosclerosis; (2) gut microbiota modulate atherogenesis, induced by HFHC/IHC, in the aorta not in PA; (3) different analytical methods suggest that a specific imbalance between Akkermansiaceae and Muribaculaceae bacterial families mediate OSA-induced atherosclerosis; and (4) derived bile acids, such as deoxycholic acid and lithocholic acid, regulate atherosclerosis in OSA. The knowledge obtained provides novel insights into the potential therapeutic approaches to prevent and treat OSA-induced atherosclerosis.

Cover page of Lessons Learned From the Liver About the Undergraduate to Graduate Medical Education Transition.

Lessons Learned From the Liver About the Undergraduate to Graduate Medical Education Transition.

(2025)

The burden of cirrhosis and chronic liver disease is growing, yet there is a projected worsening deficit in hepatology providers. As such, cirrhosis and liver disease have been important inclusions within the core curricula of Internal Medicine. Formal assessments of provider preparedness resulting from the curriculum are lacking though. Prior studies have demonstrated that exposure to cirrhosis in undergraduate medical education is insufficient, as are learner comfort and self-reported knowledge levels. These findings are further corroborated by a multicenter survey of incoming Internal Medicine interns showing that subjective comfort with and objective knowledge of various liver disease topics are lacking compared to other common Internal Medicine topics. This paper also demonstrates how similar surveys may be used to identify additional topics that may require adjustments for curricular improvement.

Cover page of Testing Assumptions for Stable Isotope Analysis of Marine Mammal Dentin Growth Layer Groups.

Testing Assumptions for Stable Isotope Analysis of Marine Mammal Dentin Growth Layer Groups.

(2025)

RATIONALE: Stable isotope analysis of growth layer groups (GLGs) in mammal dentin is an increasingly prevalent and noninvasive approach to study animal foraging ecology. However, empirical evidence to support assumed proper methodologies for sampling GLGs is lacking. Here, we examine the effects of intratooth and intertooth variations with respect to targeted GLGs, as well as the effects of common pretreatments (e.g., formic acid and graphite) to enhance GLG visibility, on stable isotope values (δ13C and δ15N) from dentin. METHODS: We measured the δ13C and δ15N values of killer whale (Orcinus orca) dentin. We used dentin from 37 teeth to compare stable carbon (δ13C) and nitrogen (δ15N) isotope values from multiple locations within a GLG (intratooth variation), from corresponding GLGs among teeth of an individual (intertooth variation), and from treated and untreated teeth. RESULTS: We observed no significant differences in the δ13C or δ15N values when sampling a single GLG from multiple locations (intratooth variation) or when comparing the same GLG across duplicate teeth of individuals (intertooth variation). One tooth in a triplicate set showed a significantly different but likely biologically inconsequential δ13C value. Lastly, formic acid and graphite highlighting to accentuate GLGs did not significantly influence measured stable isotope values. CONCLUSIONS: We validate several previous assumptions in this field of study. First, dentin samples for stable isotope analysis can be sampled from different locations across a GLG. Second, researchers can compare stable isotope values from the same GLGs of different teeth collected from the same individual in most cases, as the δ13C and δ15N values did not vary with the sampled tooth. Third, a common protocol of formic acid and graphite treatment to enhance GLG visibility does not bias the δ13C and δ15N values from dentin. We also describe factors to consider and cautions associated with these conclusions.

Cover page of Testing Assumptions for Stable Isotope Analysis of Marine Mammal Dentin Growth Layer Groups

Testing Assumptions for Stable Isotope Analysis of Marine Mammal Dentin Growth Layer Groups

(2025)

Rationale

Stable isotope analysis of growth layer groups (GLGs) in mammal dentin is an increasingly prevalent and noninvasive approach to study animal foraging ecology. However, empirical evidence to support assumed proper methodologies for sampling GLGs is lacking. Here, we examine the effects of intratooth and intertooth variations with respect to targeted GLGs, as well as the effects of common pretreatments (e.g., formic acid and graphite) to enhance GLG visibility, on stable isotope values (δ13C and δ15N) from dentin.

Methods

We measured the δ13C and δ15N values of killer whale (Orcinus orca) dentin. We used dentin from 37 teeth to compare stable carbon (δ13C) and nitrogen (δ15N) isotope values from multiple locations within a GLG (intratooth variation), from corresponding GLGs among teeth of an individual (intertooth variation), and from treated and untreated teeth.

Results

We observed no significant differences in the δ13C or δ15N values when sampling a single GLG from multiple locations (intratooth variation) or when comparing the same GLG across duplicate teeth of individuals (intertooth variation). One tooth in a triplicate set showed a significantly different but likely biologically inconsequential δ13C value. Lastly, formic acid and graphite highlighting to accentuate GLGs did not significantly influence measured stable isotope values.

Conclusions

We validate several previous assumptions in this field of study. First, dentin samples for stable isotope analysis can be sampled from different locations across a GLG. Second, researchers can compare stable isotope values from the same GLGs of different teeth collected from the same individual in most cases, as the δ13C and δ15N values did not vary with the sampled tooth. Third, a common protocol of formic acid and graphite treatment to enhance GLG visibility does not bias the δ13C and δ15N values from dentin. We also describe factors to consider and cautions associated with these conclusions.

Cover page of Cytoplasmic ribosomes on mitochondria alter the local membrane environment for protein import.

Cytoplasmic ribosomes on mitochondria alter the local membrane environment for protein import.

(2025)

Most of the mitochondria proteome is nuclear-encoded, synthesized by cytoplasmic ribosomes, and targeted to the mitochondria posttranslationally. However, a subset of mitochondrial-targeted proteins is imported co-translationally, although the molecular mechanisms governing this process remain unclear. We employ cellular cryo-electron tomography to visualize interactions between cytoplasmic ribosomes and mitochondria in Saccharomyces cerevisiae. We use surface morphometrics tools to identify a subset of ribosomes optimally oriented on mitochondrial membranes for protein import. This allows us to establish the first subtomogram average structure of a cytoplasmic ribosome at the mitochondrial surface in the native cellular context, which showed three distinct connections with the outer mitochondrial membrane surrounding the peptide exit tunnel. Further, this analysis demonstrated that cytoplasmic ribosomes primed for mitochondrial protein import cluster on the outer mitochondrial membrane at sites of local constrictions of the outer and inner mitochondrial membranes. Overall, our study reveals the architecture and the spatial organization of cytoplasmic ribosomes at the mitochondrial surface, providing a native cellular context to define the mechanisms that mediate efficient mitochondrial co-translational protein import.

Cover page of “Todes” and “Todxs”, linguistic innovations or grammatical gender violations?

“Todes” and “Todxs”, linguistic innovations or grammatical gender violations?

(2025)

This study compared the processing of non-binary morphemes in Spanish (e.g., todxs, todes) with the processing of canonical grammatical gender violations in Spanish pronouns (e.g., Los maestros… todas…). Using self-paced reading, the study examined how individual differences in working memory and gender/sex diversity beliefs affected language processing at three regions of interest (ROI): the pronoun, the pronoun +1, and the pronoun +2. Seventy-eight Spanish-English bilinguals completed two self-paced reading tasks, one with non-binary pronouns and another with grammatical gender violations, as well as a working memory task, a language dominance questionnaire, and a gender/sex diversity beliefs questionnaire. Processing costs were operationalized as longer reaction times (RTs) or inaccurate responses. Results showed overall processing costs for non-binary morphemes at all 3 ROIs, but no processing costs were observed in terms of accuracy or response times to the comprehension question. The results suggest that processing non-binary pronouns results in a small processing cost that does not affect overall sentence comprehension. The small observed processing cost was moderated by gender/sex diversity beliefs, with gender normative beliefs increasing RTs at the pronoun and affirmation of diverse gender identities beliefs reducing the RTs at the second spillover region. In contrast, grammatical gender violations only showed a processing cost at the first spillover region and were not moderated by working memory nor gender/sex diversity beliefs. Taken together, the results suggest that non-binary pronouns are processed differently than grammatical gender violations and that the small processing cost they impose can lead to good enough comprehension.