Perspectives of Certified Nurse-Midwives and Physicians on the Structural and Institutional Barriers that Contribute to the Reproductive Inequities of Black Birthing People in the San Francisco Bay Area

INTRODUCTION

Black birthing people in the United States disproportionately endure inequitable experiences and outcomes during pregnancy and childbirth via structural, interpersonal, and obstetric racism. In this study, the researchers explore provider perspectives of how racism is perpetuated in institutional perinatal and reproductive health care.

METHODS

Critical Race Theory, Reproductive Justice, and midwifery theory were operationalized through secondary thematic analysis of existing qualitative data from the Community Racial Equity and Training Interventions and Evaluation of Current and Future Healthcare Clinicians Study. Twenty-four perinatal providers (certified nurse-midwives [n = 7] and physicians [n = 17]) voluntarily participated in interviews. A comparative approach was used to determine how professional identity and model of care influence physicians' and certified nurse-midwives' perceptions of equity.

RESULTS

Thematic analysis produced 5 themes: racism as a comorbidity, health care systems' inability to address the needs of Black birthing people, health care systems prioritizing providers over patients are failed systems, patients are the experts in the optimal health care model, and benefits of interprofessional teams grounded in Reproductive Justice. Additionally, both physicians and midwives expressed a need for a new care model.

DISCUSSION

With these findings, our team proposes a modification of the midwifery model for application by all provider types that could radically shift the experience and outcomes of perinatal and reproductive health care and reduce mortality. Using a human rights approach to care, a Reproductive Justice-Public Health Critical Race praxis-informed midwifery model may be operationalized by all perinatal and reproductive health care providers. This novel model reflects an iterative process that may offer institutions and providers methods to build on past research supporting midwifery-centered care for improving outcomes for all patients by specifically focusing on improving care of Black birthing people. The implications of this work offer broad application in current clinical practice, quality improvement, research, technology, and patient resources.

Association of Transgender or Gender Non-Binary Identity on Disease Characteristics and Survival Outcomes in Prostate Cancer

PURPOSE/OBJECTIVE(S)

While it is becoming increasingly common for people to identify as transgender or gender-non-binary, our understanding of the influence of gender identity on disease severity of hormone-sensitive malignancies, including prostate cancer (PC) is limited. The goal of this study is to compare the aggressiveness of disease and survival outcomes between transgender or gender non-binary (TG) and cis-gender (CG) patients with PC.

MATERIALS/METHODS

The cohort included patients diagnosed with PC between 1999 and 2022 within the Veterans Health Administration (VHA) Database. TG patients were identified with an ICD 9 or 10 diagnosis code that occurred prior to PC diagnosis. Treatment information and baseline disease characteristics were ascertained through the VHA electronic health records. Multivariable logistic regressions were performed to estimate the association between TG status and presenting with Gleason > = 8, PSA > 20 ng/mL, and metastatic disease at diagnosis. Covariates in these models included age at diagnosis, race, ethnicity, marital status, and smoking status. Metastases were identified through natural language processing from cancer or radiology documents. Time to metastases was defined as the time from PC diagnosis to metastases, with other causes of death considered as competing risks. The association between TG identity status and metastatic disease was calculated with a Cox regression model. The difference in overall survival was assessed with the Kaplan-Meier method and log-rank test.

RESULTS

The final cohort was composed of 282,264 individuals, 219 (0.08%) of which were identified as TG. TG patients have similar odds of presenting with presenting with Gleason Score ≥8 (Odds Ratio (OR) 1.18, p = 0.31), PSA >20 ng/mL (OR 0.78, p = 0.59), and metastasis at diagnosis (OR 0.47, p = 0.29). There were 34,918 patients who develop metastatic disease at any time, 24 of which were TG. The 10-year cumulative incidence of metastases for TG and CG individuals was 11.5% (95% Confidence Interval (CI): 6.6-16.1%) and 13.9% (CI: 13.7-14.0%), respectively. There was no significant difference between TG status and risk of developing metastases (Hazard Ratio (HR) 0.93, p = 0.71). The 10-year overall survival for TG and CG was 73.4% (CI: 66.5-80.9%) and 65.0% (CI: 64.8-65.2%), respectively. There was no significant difference between TG status and overall survival (Hazard Ratio (HR) 0.83, p = 0.13).

CONCLUSION

TG individuals do not appear to have a difference in disease characteristics at diagnosis or survival compared to CG individuals. Future research should be done to determine the effect of gender affirming treatment on these outcomes. Furthermore, it is unclear if diagnosis codes are accurately identifying TG individuals.

Effectiveness of Cisplatin in P16+ Oropharyngeal Cancer According to Relative Risk for Cancer Events: Ancillary Analysis of RTOG 1016

PURPOSE/OBJECTIVE(S)

To test the hypothesis that the effectiveness of cisplatin in p16+ oropharyngeal squamous cell carcinoma (OPSCC) increases with patients' relative risk for cancer events.

MATERIALS/METHODS

Ancillary analysis of 805 patients enrolled on RTOG 1016 accessed via Project DataSphere. Eligible patients had p16+ OPSCC, AJCC 7th T1-T2 N2a-N3 or T3-T4 N0-N3 M0, ECOG PS 0-1. Patients were randomized to RT with concurrent cisplatin vs. cetuximab. Relative risk for competing events was quantified using the Head and Neck Cancer Intergroup predictive classifier (omega score). Higher scores indicate higher relative risk for cancer events (LRF or distant metastasis) vs. competing mortality. We compared this to favorable, unfavorable/low, and unfavorable/intermediate risk groups using standard criteria: NRG HN005 eligible/low RTOG risk (Ang et al.), HN005 ineligible/low RTOG risk, and intermediate RTOG risk. Omega score cutoffs were selected to match numbers in standard risk strata. HRs for the effect of cisplatin vs. cetuximab on PFS and OS were compared for standard vs. relative risk strata. 1-tailed interaction tests were used to test whether cisplatin effectiveness increased within risk strata.

RESULTS

There were 354, 219, and 232 patients in standard favorable, unfavorable/low, and unfavorable/intermediate risk groups. Omega score cutoffs were 0.80 and 0.84 to define low, intermediate, and high relative risk groups. Discordant standard vs. relative risk classifications occurred in 559 patients (69.4%). Increasing omega score was associated with significantly higher relative HR (rHR) for cancer events (3.40, 95% CI: 1.66-6.96) and increasing effectiveness of cisplatin vs. cetuximab (Table), but standard risk grouping was not (rHR 0.80, 95% CI: 0.49-1.32). The effect of cisplatin on PFS significantly increased with higher omega score (interaction -0.30, p = .046), but decreased with increasing standard risk strata (interaction +0.27, p = NS).

CONCLUSION

The effectiveness of cisplatin in p16+ OPSCC increased with higher omega score but not with standard risk group. Relative risk for cancer events should be taken into account when designing deintensification strategies.

Comparison of Standard vs. Relative Risk Models to Define Candidates for Deintensification in Locoregionally Advanced P16+ Oropharyngeal Cancer

PURPOSE/OBJECTIVE(S)

Various methods to identify candidates for treatment deintensification with p16+ oropharyngeal squamous cell carcinoma (OPSCC) have been used, but the optimal approach is unknown.

MATERIALS/METHODS

Multi-institutional cohort study of 385 patients with previously untreated p16+ OPSCC undergoing definitive radiotherapy (RT) with or without systemic therapy between 2009-2020. Chemotherapy intensity was categorized as high (bolus cisplatin and/or induction chemotherapy), medium (weekly cisplatin), or low (non-cisplatin or RT alone). Standard favorable vs. unfavorable risk was defined using NRG HN005 eligibility criteria. High vs. low relative risk (RR) group was defined using the HNCIG omega score (≥ 0.80 vs. < 0.80), which quantifies the proportion of a patient's overall event risk due to cancer. We used multivariable ordinal logistic regression to estimate effects of age (yrs), sex, performance status (PS), Charlson comorbidity index (CCI), T/N (AJCC 8th), current smoking, and pack-years (> 10 vs. ≤ 10) on treatment allocation. Effects on relative event hazards were estimated using generalized competing event regression.

RESULTS

Median follow-up time was 44.2 months. Chemotherapy intensity was high in 206 (54%), medium in 108 (28%), and low in 71 (18%). 280 patients (73%) were unfavorable risk and 197 (51%) were high RR. 178 patients (46%) had discordant risk classification. On univariable analysis, significant predictors of higher intensity chemotherapy (normalized odds ratio (OR)) were CCI 0-1 (OR 1.49, 95% CI: 1.23-1.79), high omega score (OR 1.46; 1.20-1.77), decreased age (OR 1.43; 1.18-1.74), and PS 0 (OR 1.22; 1.01-1.48). Controlling for CCI, higher omega score was associated with significantly higher odds of intensive chemotherapy (OR 1.35; 1.10-1.65, but unfavorable risk (HN005 ineligibility) was not (OR 1.19; 0.98-1.44). Higher omega score was also associated with significantly higher RR for cancer recurrence (Rec) vs. competing mortality (CM) events (relative HR (rHR) 1.76; 1.12-2.75), but unfavorable risk was not (rHR 1.05; 0.63-1.75). Among patients receiving cisplatin, 50 favorable risk patients (58%) had high RR; all of their event risk was due to cancer recurrence (Table). The 110 unfavorable risk patients (48%) with low omega score had significantly lower RR for cancer events compared to the high omega score group (rHR 0.49; 0.29-0.84).

CONCLUSION

Many patients with favorable risk p16+ OPSCC have high relative risk for cancer events, which correlates with a benefit of intensive treatment. The HNCIG omega score is a strong predictor of allocation to intensive chemotherapy and may help identify candidates for deintensification.

Association between National Area Deprivation Index Rank on Disease Characteristics in Prostate Cancer

PURPOSE/OBJECTIVE(S)

Social determinants of health (SDH) play a large role in an individual's health; in recent years, there has been a push to examine the impact of one's neighborhood or "place." Previous studies have showed that living in a disadvantage neighborhood is associated with worth health outcomes. We hypothesize that equal access care will diminish the effects of living in a disadvantaged neighborhood.

MATERIALS/METHODS

We identified non-Hispanic African American (AA) and White (NHW) men diagnosed with PC between 2012 and 2015 in the Veterans Health Administration (VHA). Patient SDH was measured using census tract level 2015 Area Deprivation Index (ADI) information. The ADI is a composite measure that includes factor such as housing quality, income, health care access etc. We measured both National and State ADI rank as a continuous variable from 1 to 10 with 10 being highest deprivation. Patient information was gathered at the census tract level while ADI is assigned at the census block group. In order to get all information on the same geographic level, we averaged the ADI to its corresponding census tract. Associations between ADI and disease characteristics at diagnosis were measured using multivariable logistic regression models including age, race, and marital status as covariates.

RESULTS

The final cohort was composed of 25,222 men (8,384 AA and 16,838 NHW.) At the national level, there was no significant association between ADI and Gleason Score ≥8 (Odds Rations (OR) 0.99 [95% Confidence Interval (CI):0.98 - 1.00]), PSA >20 ng/mL (OR 0.99 [95% CI: 0.98 - 1.01]), and metastasis at diagnosis (OR 1.01 [CI: 0.98-1.04]).

CONCLUSION

Our results are consistent with our hypothesis that equal access care diminishes the impacts of living within a disadvantaged neighborhood. Future research should investigate the interaction between health care access and social and demographic factors.

Pharmacological Modulation of Calcium Homeostasis in Familial Dilated Cardiomyopathy: An In Vitro Analysis From an RBM20 Patient-Derived iPSC Model

For inherited cardiomyopathies, abnormal sensitivity to intracellular calcium (Ca(2+) ), incurred from genetic mutations, initiates subsequent molecular events leading to pathological remodeling. Here, we characterized the effect of β-adrenergic stress in familial dilated cardiomyopathy (DCM) using human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs) from a patient with RBM20 DCM. Our findings suggest that β-adrenergic stimulation accelerated defective Ca(2+) homeostasis, apoptotic changes, and sarcomeric disarray in familial DCM hiPSC-CMs. Furthermore, pharmacological modulation of abnormal Ca(2+) handling by pretreatment with β-blocker, carvedilol, or Ca(2+) -channel blocker, verapamil, significantly decreased the area under curve, reduced percentage of disorganized cells, and decreased terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL)-positive apoptotic loci in familial DCM hiPSC-CMs after β-adrenergic stimulation. These translational data provide patient-based in vitro analysis of β-adrenergic stress in RBM20-deficient familial DCM hiPSC-CMs and evaluation of therapeutic interventions to modify heart disease progression, which may be personalized, but more importantly generalized in the clinic.

Induced pluripotent stem cells: an emerging theranostics platform

Nuclear reprogramming generates induced pluripotent stem (iPS) cells endowed with the unlimited potential to reconstruct genetically identical tissues. This biomedical tool offers unprecedented opportunities to develop scalable yet personalized cell-based reagents. The emerging platform of regenerative theranostics provides a unique approach to expose mechanisms of disease etiology in the context of dysfunctional cell biology. Resolved molecular dynamics that define and regulate the regenerative capacity of individual stem cells will enable next-generation, patient-specific diagnostic and therapeutic applications.

Indolactam V/GLP-1-mediated differentiation of human iPS cells into glucose-responsive insulin-secreting progeny

Nuclear reprogramming of somatic tissue enables derivation of induced pluripotent stem (iPS) cells from an autologous, non-embryonic origin. The purpose of the current study was to establish efficient protocols for lineage-specification of human iPS cells into functional glucose-responsive, insulin-producing progeny. We generated human iPS cells, which were then guided with recombinant growth factors that mimic the essential signaling for pancreatic development. Reprogrammed with four stemness factors, human fibroblasts were here converted into authentic iPS cells. Under feeder-free conditions, fate-specification was initiated with activin A and Wnt3a that triggered engagement into definitive endoderm, followed by priming with FGF10 and KAAD-cyclopamine. Addition of retinoic acid, boosted by the pancreatic endoderm inducer indolactam V (ILV), yielded pancreatic progenitors expressing PDX1, NGN3 and NEUROD1 markers. Further guidance, under IGF-1, HGF and DAPT, was enhanced by glucagon like peptide-1 (GLP-1) to generate islet-like cells that expressed pancreas-specific markers including insulin and glucagon. Derived progeny demonstrated sustained expression of PDX1, and functional responsiveness to glucose challenge secreting up to 230 pM of C-peptide. A pancreatogenic cocktail enriched with ILV/GLP-1 offers a proficient means to specify human iPS cells into glucose-responsive hormone-producing progeny, refining the development of a personalized platform for islet-like cell generation.

Neuroprotective versus tumorigenic protein kinase C activators

Protein kinase C (PKC) activators possess potent neurotrophic and neuroprotective activity, thus indicating potential applications in treating neurodegenerative diseases, stroke and traumatic brain injury. Although some activators, such as bryostatin and gnidimacrin, have been tested as antitumor agents, others, such as phorbol esters, are potent tumor promoters. All PKC activators downregulate PKC at high concentrations and long application times. However, tumorigenic activators downregulate certain PKC isozymes, especially PKCdelta, more strongly. Tumorigenic activators possess unique structural features that could account for this difference. At concentrations that minimize PKC downregulation, PKC activators can improve long-term memory, reduce beta-amyloid levels, induce synaptogenesis, promote neuronal repair and inhibit cell proliferation. Intermittent, low concentrations of structurally specific, non-tumorigenic PKC activators, therefore, could offer therapeutic benefit for a variety of neurologic disorders.

Nuclear transport: target for therapy

Drugs directed at plasma membrane receptors target environment-cell interactions and are the mainstay of clinical pharmacology. Decoding mechanisms that govern intracellular signaling has recently opened new therapeutic avenues for interventions at cytosol-organellar interfaces. The nuclear envelope and nuclear transport machinery have emerged central in the discovery and development of experimental therapeutics capable of modulating cellular genetic programs. Insight into nucleocytoplasmic exchange has unmasked promising anticancer, antiviral, and anti-inflammatory strategies.

Bryostatin enhancement of memory in Hermissenda

Bryostatin, a potent agonist of protein kinase C (PKC), when administered to Hermissenda was found to affect acquisition of an associative learning paradigm. Low bryostatin concentrations (0.1 to 0.5 ng/ml) enhanced memory acquisition, while concentrations higher than 1.0 ng/ml down-regulated the pathway and no recall of the associative training was exhibited. The extent of enhancement depended upon the conditioning regime used and the memory stage normally fostered by that regime. The effects of two training events (TEs) with paired conditioned and unconditioned stimuli, which standardly evoked only short-term memory (STM) lasting 7 min, were--when bryostatin was added concurrently--enhanced to a long-term memory (LTM) that lasted about 20 h. The effects of both 4- and 6-paired TEs (which by themselves did not generate LTM), were also enhanced by bryostatin to induce a consolidated memory (CM) that lasted at least 5 days. The standard positive 9-TE regime typically produced a CM lasting at least 6 days. Low concentrations of bryostatin (<0.5 ng/ml) elicited no demonstrable enhancement of CM from 9-TEs. However, animals exposed to bryostatin concentrations higher than 1.0 ng/ml exhibited no behavioral learning. Sharp-electrode intracellular recordings of type-B photoreceptors in the eyes from animals conditioned in vivo with bryostatin revealed changes in input resistance and an enhanced long-lasting depolarization (LLD) in response to light. Likewise, quantitative immunocytochemical measurements using an antibody specific for the PKC-activated Ca2+/GTP-binding protein calexcitin showed enhanced antibody labeling with bryostatin. Animals exposed to the PKC inhibitor bisindolylmaleimide-XI (Ro-32-0432) administered by immersion prior to 9-TE conditioning showed no training-induced changes with or without bryostatin exposure. However, if animals received bryostatin before Ro-32, the enhanced acquisition and demonstrated recall still occurred. Therefore, pathways responsible for the enhancement effects induced by bryostatin were putatively mediated by PKC. Overall, the data indicated that PKC activation occurred and calexcitin levels were raised during the acquisition phases of associative conditioning and memory initiation, and subsequently returned to baseline levels within 24 and 48 h, respectively. Therefore, the protracted recall measured by the testing regime used was probably due to bryostatin-induced changes during the acquisition and facilitated storage of memory, and not necessarily to enhanced recall of the stored memory when tested many days after training.

Insulin and cholesterol pathways in neuronal function, memory and neurodegeneration

Insulin and cholesterol play important roles in basic metabolic processes in peripheral tissues. Both insulin and cholesterol can also act as signalling molecules in the central nervous system that participate in neuronal function, memory and neurodegenerative diseases. A high-cholesterol diet improves spatial memory in experimental animals. beta-Amyloid, the toxic peptide in neurons of AD (Alzheimer's disease) patients, binds cholesterol and catalyses its oxidation to 7beta-hydroxycholesterol, a highly toxic oxysterol that is a potent inhibitor of alpha-PKC (alpha-protein kinase C), an enzyme critical in memory consolidation and synaptic plasticity and implicated in AD. Oxidized cholesterol also can act as a second messenger for insulin. Oxidized low-density lipoprotein inhibits insulin-dependent phosphorylation of the signalling kinases ERK (extracellular-signal-regulated kinase) and PKB/Akt. In sporadic AD patients, insulin levels are decreased, suggesting links between AD and diabetes. Insulin signalling is also important in synaptic plasticity. Insulin receptors are up-regulated and undergo translocation after spatial learning. Insulin modulates the activity of excitatory and inhibitory receptors including the glutamate and gamma-aminobutyric acid receptors and activates two biochemical pathways: the shc-ras-mitogen-activated protein kinase pathway and the PI3K (phosphoinositide 3-kinase)/PKC pathway, both of which are involved in memory processing. These findings point to a convergence at the biochemical level between pathways involved in AD and those important for normal memory.

Workplace protection factors--supplied air hood

Several organizations list assigned protection factors. For supplied air hoods, the value of the assigned protection factors varies from <10 to 2,000 depending on the organization. Workplace protection factors (WPFs) of a supplied air hood were measured during aircraft sanding and painting operations on several types of aircraft to evaluate whether the American National Standard Z88.2 (1992) assigned protection factor of 1,000 was realistic. The primary contaminant during these activities is strontium chromate. Samples collected inside the hood show that employees during sanding and painting operations were not exposed to strontium. The respirator performed adequately. This study is consistent with other simulated and WPF studies in that the ANSI Z88.2 WPF of 1,000 is supported.

Theta rhythm of hippocampal CA1 neuron activity: gating by GABAergic synaptic depolarization

Information processing and memory consolidation during exploratory behavior require synchronized activity known as hippocampal theta (theta) rhythm. While it is well established that the theta activity depends on cholinergic inputs from the medial septum/vertical limb of the diagonal band nucleus (MS/DBv) and theta discharges of GABAergic interneurons, and can be induced with cholinergic receptor agonists, it is not clear how the increased excitation of pyramidal cells could occur with increased discharges of GABAergic interneurons during theta waves. Here, we show that the characteristic theta activity in adult rat hippocampal CA1 pyramidal cells is associated with GABAergic postsynaptic depolarization and a shift of the reversal potential from Cl(-) toward HCO(3)(-) (whose ionic gradient is regulated by carbonic anhydrase). The theta activity was abolished by GABA(A) receptor antagonists and carbonic anhydrase inhibitors, but largely unaffected by blocking glutamate receptors. Carbonic anhydrase inhibition also impaired spatial learning in a water maze without affecting other sensory/locomotor behaviors. Thus HCO(3)(-)-mediated signaling, as regulated by carbonic anhydrase, through reversed polarity of GABAergic postsynaptic responses is implicated in both theta and memory consolidation in rat spatial maze learning. We suggest that this mechanism may be important for the phase forward shift of the place cell discharges for each theta cycle during the animal's traversal of the place field for that cell.

Functional switching of GABAergic synapses by ryanodine receptor activation

The role of the ryanodine receptor (RyR) in modifiability of synapses made by the basket interneurons onto the hippocampal CA1 pyramidal cells was examined in rats. Associating single-cell RyR activation with postsynaptic depolarization increased intracellular free Ca(2+) concentrations and reversed the basket interneuron-CA1 inhibitory postsynaptic potential into an excitatory postsynaptic potential. This synaptic transformation was accompanied by a shift of the reversal potential from that of chloride toward that of bicarbonate. This inhibitory postsynaptic potential-excitatory postsynaptic potential transformation was prevented by blocking RyR or carbonic anhydrase. Associated postsynaptic depolarization and RyR activation, therefore, changes GABAergic synapses from excitation filters to amplifier and, thereby, shapes information flow through the hippocampal network.

Susceptibility of Vespula vulgaris (Hymenoptera: vespidae) to generalist entomopathogenic fungi and their potential for wasp control

The pathogenicity of Vespula vulgaris wasp workers and larvae to a range of fungi was determined. All fungi were isolated in New Zealand and included isolates from Vespula, known generalist insect pathogens, and isolates generally nonpathogenic to insects. Workers and larvae were highly susceptible to pathogenic isolates at high spore concentrations (>1.75 x 10(5) cfu/individual). Eight isolates, two of Metarhizium anisopliae, five of Beauveria bassiana, and one of Aspergillus flavus were pathogenic while a single isolate of M. flavouiride var. novazealandicum, Cladosporium sp., and Paecilomyces sp. were not. The transfer of spores between workers, and between workers and larvae, was also investigated using several different application methods. Transfer of spores occurred between treated and untreated individuals, and for some of the application methods sufficient spores were transferred to cause mortality of the nontreated individuals. These findings are related to the potential of fungi for the control of wasps.

How protective are respirator assigned protection factors: an uncertainty analysis

This investigation evaluated the risk of overexposure for a selected assigned protection factor by performing Monte Carlo simulations. A model was constructed to assess respirator performance by calculating the concentration inside the respirator. Estimates of the factors that affect respirator performance were described as distributions. The distributions used a worst case estimate for concentration in the workplace, the worst case for respirator performance (the fifth percentile person), and the worst case for exhalation valve leakage. A Monte Carlo analysis then provided estimates of the percentage of time that concentration inside the respirator exceeded the occupational exposure limit (OEL). For a half-facepiece respirator with an APF of 10, the calculations indicated a low risk of being exposed above an OEL, with mean exposures being controlled well below an OEL.

The effect of inhalation resistance on facepiece leakage

Air purifying respirators use filters to remove particulate air contaminants. Resistance to airflow generally increases as the filter loads and a "filter cake" is formed. It has been recommended by ANSI and the Occupational Safety and Health Administration that filters should be replaced when the wearer notices they are hard to breathe through. Repeated faceseal leak rate measurements were made during respiratory wear over a range of simulated breathing resistances from 5.6 to 19.6 mm (0.22 to 0.77 inches) of water. The measured faceseal leak rates increased as the breathing resistance increased and varied depending on the initial leak rate at the 5.6 mm pressure. The increase in faceseal leak rate from 5.6 to 19.6 mm breathing resistance was as high as a factor of 4. Theoretically, a person with an initial respirator penetration of 2.5% could have that value increase to 10% as filter loading increased breathing resistance by 14 mm. Some research has shown that breathing resistances between 60 and 140 mm of water would be "noticeable but well tolerated." It is not known if workers would be able to detect an increase in breathing resistance that would lead to a significant increase in faceseal leakage. These data suggest a need to establish a replacement schedule for all filters used in the workplace. How often a filter should be replaced is difficult to determine. Breathing resistance would vary depending on the individual filter and aerosol loading characteristics, the concentration of the aerosol in the workplace, and breathing rates.

Enhanced BK-induced calcium responsiveness in PC12 cells expressing the C100 fragment of the amyloid precursor protein

Several lines of evidence have implicated the amyloid precursor protein (APP) and its metabolic products as key players in Alzheimer's disease (AD) pathophysiology. The approximately 100 amino acid C-terminal fragment (C100) of APP has been shown to accumulate intracellularly in neurons expressing familial AD (FAD) mutants of APP and to cause neurodegeneration when expressed in transfected neuronal cells. Transgenic animals expressing this fragment in the brain also exhibit some neuropathological and behavioral AD-like deficits. Here, we present evidence that PC12 cells expressing the C100 fragment either via stable transfections or herpes simplex virus-mediated infections show alterations in calcium handling that are similar to those previously shown in fibroblasts from AD patients. This alteration in calcium homeostasis may contribute to the deleterious effects of C100 in PC12 cells. Our data also lend support for a pathophysiological role for C100 since it induces an alteration thought to play an important role in AD pathology.

Calexcitin interaction with neuronal ryanodine receptors

Calexcitin (CE), a Ca2+- and GTP-binding protein, which is phosphorylated during memory consolidation, is shown here to co-purify with ryanodine receptors (RyRs) and bind to RyRs in a calcium-dependent manner. Nanomolar concentrations of CE released up to 46% of the 45Ca label from microsomes preloaded with 45CaCl2. This release was Ca2+-dependent and was blocked by antibodies against the RyR or CE, by the RyR inhibitor dantrolene, and by a seven-amino-acid peptide fragment corresponding to positions 4689-4697 of the RyR, but not by heparin, an Ins(1,4,5)P3-receptor antagonist. Anti-CE antibodies, in the absence of added CE, also blocked Ca2+ release elicited by ryanodine, suggesting that the CE and ryanodine binding sites were in relative proximity. Calcium imaging with bis-fura-2 after loading CE into hippocampal CA1 pyramidal cells in hippocampal slices revealed slow, local calcium transients independent of membrane depolarization. Calexcitin also released Ca2+ from liposomes into which purified RyR had been incorporated, indicating that CE binding can be a proximate cause of Ca2+ release. These results indicated that CE bound to RyRs and suggest that CE may be an endogenous modulator of the neuronal RyR.

Calexcitin transformation of GABAergic synapses: from excitation filter to amplifier

Encoding an experience into a lasting memory is thought to involve an altered operation of relevant synapses and a variety of other subcellular processes, including changed activity of specific proteins. Here, we report direct evidence that co-applying (associating) membrane depolarization of rat hippocampal CA1 pyramidal cells with intracellular microinjections of calexcitin (CE), a memory-related signaling protein, induces a long-term transformation of inhibitory postsynaptic potentials from basket interneurons (BAS) into excitatory postsynaptic potentials. This synaptic transformation changes the function of the synaptic inputs from excitation filter to amplifier, is accompanied by a shift of the reversal potential of BAS-CA1 postsynaptic potentials, and is blocked by inhibiting carbonic anhydrase or antagonizing ryanodine receptors. Effects in the opposite direction are produced when anti-CE antibody is introduced into the cells, whereas heat-inactivated CE and antibodies are ineffective. These data suggest that CE is actively involved in shaping BAS-CA1 synaptic plasticity and controlling information processing through the hippocampal networks.

Time domains of neuronal Ca2+ signaling and associative memory: steps through a calexcitin, ryanodine receptor, K+ channel cascade

Synaptic changes that underlie associative learning and memory begin with temporally related activity of two or more independent synaptic inputs to common postsynaptic targets. In turn, temporally related molecular events regulate cytosolic Ca2+ during progressively longer-lasting time domains. Associative learning behaviors of living animals have been correlated with changes of neuronal voltage-dependent K+ currents, protein kinase C-mediated phosphorylation and synthesis of the Ca2+ and GTP-binding protein, calexcitin (CE),and increased expression of the Ca2+-releasing ryanodine receptor (type II). These molecular events, some of which have been found to be dysfunctional in Alzheimer's disease, provide means of altering dendritic excitability and thus synaptic efficacy during induction, consolidation and storage of associative memory. Apparently, such stages of behavioral learning correspond to sequential differences of Ca2+ signaling that could occur in spatially segregated dendritic compartments distributed across brain structures, such as the hippocampus.

Alzheimer's-specific effects of soluble beta-amyloid on protein kinase C-alpha and -gamma degradation in human fibroblasts

Alzheimer's disease (AD) is a multifactorial disease in which beta-amyloid peptide (betaAP) plays a critical role. We report here that the soluble fraction 1-40 of betaAP differentially degrades protein kinase C-alpha and -gamma (PKCalpha and PKCgamma) isoenzymes in normal (age-matched controls, AC) and AD fibroblasts most likely through proteolytic cascades. Treatment with nanomolar concentrations of betaAP(1-40) induced a 75% decrease in PKCalpha, but not PKCgamma, immunoreactivity in AC fibroblasts. In the AD fibroblasts, a 70% reduction of the PKCgamma, but not PKCalpha, immunoreactivity was observed after betaAP treatment. Preincubation of AC or AD fibroblasts with 50 microM lactacystine, a selective proteasome inhibitor, prevented beta-AP(1-40)-mediated degradation of PKCalpha in the AC cells, and PKCgamma in the AD fibroblasts. The effects of betaAP(1-40) on PKCalpha in AC fibroblasts were prevented by inhibition of protein synthesis and reversed by PKC activation. A 3-hr treatment with 100 nM phorbol 12-myristate 13-acetate restored the PKCalpha signal in treated AC cells but it did not reverse the effects of betaAP(1-40) on PKCgamma in the AD fibroblasts. Pretreatment with the protein synthesis inhibitor, cycloheximide (CHX, 100 microM), inhibited the effects of betaAP(1-40) on PKCalpha and blocked the rescue effect of phorbol 12-myristate 13-acetate in AC fibroblasts but did not modify PKCgamma immunoreactivity in AD cells. These results suggest that betaAP(1-40) differentially affects PKC regulation in AC and AD cells via proteolytic degradation and that PKC activation exerts a protective role via de novo protein synthesis in normal but not AD cells.

0.9% sodium chloride injection with and without heparin for maintaining peripheral indwelling intermittent-infusion devices in infants

The use of 0.9% sodium chloride injection with and without heparin sodium for maintaining peripheral indwelling intermittent-infusion devices (PIIIDs) in infants was studied. In this double-blind study, children up to one year of age who had a 24-gauge PIIID through which a continuous i.v. infusion was no longer running were randomly assigned to have their PIIID capped with 0.9% sodium chloride injection with or without heparin sodium 10 units/mL. PIIIDs were capped every eight hours if no medications were administered; otherwise, they were capped after each dose of an i.v. drug. The heparin group had 26 patients with 28 evaluable PIIIDs, and the 0.9% sodium chloride injection group had 32 patients with 46 evaluable PIIIDs. The two groups did not differ significantly in variables assessing the duration of PIIID use, reasons for removal of PIIIDs, mean number of cappings, irritant potential of administered drugs, or severity of medication-related irritation. There was no significant difference between 0.9% sodium chloride injection with and without heparin sodium 10 units/mL in maintaining 24-gauge PIIIDs in children younger than one year.

Secondary structure and Ca2+-induced conformational change of calexcitin, a learning-associated protein

Calexcitin/cp20 is a low molecular weight GTP- and Ca2+-binding protein, which is phosphorylated by protein kinase C during associative learning, and reproduces many of the cellular effects of learning, such as the reduction of potassium currents in neurons. Here, the secondary structure of cloned squid calexcitin was determined by circular dichroism in aqueous solution and by Fourier transform infrared spectroscopy both in solution and on dried films. The results obtained with the two techniques are in agreement with each other and coincide with the secondary structure computed from the amino acid sequence. In solution, calexcitin is one-third in alpha-helix and one-fifth in beta-sheet. The conformation of the protein in solid state depends on the concentration of the starting solution, suggesting the occurrence of surface aggregation. The secondary structure also depends on the binding of calcium, which causes an increase in alpha-helix and a decrease in beta-sheet, as estimated by circular dichroism. The conformation of calexcitin is independent of ionic strength, and the calcium-induced structural transition is slightly inhibited by Mg2+ and low pH, while favored by high pH. The switch of calexcitin's secondary structure upon calcium binding, which was confirmed by intrinsic fluorescence spectroscopy and nondenaturing gel electrophoresis, is reversible and occurs in a physiologically meaningful range of Ca2+ concentration. The calcium-bound form is more globular than the apoprotein. Unlike other EF-hand proteins, calexcitin's overall lipophilicity is not affected by calcium binding, as assessed by hydrophobic liquid chromatography. Preliminary results from patch-clamp experiments indicated that calcium is necessary for calexcitin to inhibit potassium channels and thus to increase membrane excitability. Therefore the calcium-dependent conformational equilibrium of calexcitin could serve as a molecular switch for the short term modulation of neuronal activity following associative conditioning.

Case-control study of cancer risk in tetraethyl lead manufacturing

A case-control study was conducted to investigate the relative risk of cancer detection among Du Pont employees who worked in a tetraethyl lead (TEL) manufacturing area. The study's objective was to determine whether the employees' risk of developing or dying from cancer was associated with occupational exposure to TEL. All malignant neoplasms detected in the active and pensioned employee population during the period 1956-1987 were studied. TEL exposure was estimated by the following measures: ever employed in the TEL area, years of employment in TEL, TEL exposure rank, and the TEL cumulative exposure index. TEL manufacturing exposed employees to both organic and inorganic lead compounds. Because the underlying data did not permit the exposure assessment to distinguish between organic and inorganic lead, the TEL exposure measures reflect exposure to the TEL manufacturing process itself. The effects of latency, cigarette smoking habits, and exposures to other known or suspected carcinogens at the plant were also assessed. A strong association was observed between exposure to the TEL manufacturing process and rectal cancer (the odds ratio was 3.7 with 90% confidence limits of 1.3-10.2 for the analysis of ever/never exposed to TEL). An exposure-response relationship was noted with a fourfold elevation in the odds ratio at the high-very high cumulative exposure level. These patterns were even more pronounced after assuming a 10 year latency. Similar results were obtained for cancers of the sigmoid colon. These findings suggest that exposure to the TEL manufacturing process may have played a causal role in the colorectal cancer experience at the plant. This position is supported by the graded exposure-response relationships, the consistency of the results across exposure measures, the specificity of the health outcome (i.e., colorectal cancer), and the strength of the association. However, the evidence for causality is not compelling. This is the first report of an association between TEL manufacturing and colorectal cancer, and the evidence is compatible with a wide range of causal (i.e., indirect vs. direct acting; initiating vs. promoting) and noncausal (i.e., statistical and methodological bias; coincidence) interpretations.

Calexcitin: a signaling protein that binds calcium and GTP, inhibits potassium channels, and enhances membrane excitability

A previously uncharacterized 22-kDa Ca(2+)-binding protein that also binds guanosine nucleotides was characterized, cloned, and analyzed by electrophysiological techniques. The cloned protein, calexcitin, contains two EF-hands and also has homology with GTP-binding proteins in the ADP ribosylation factor family. In addition to binding two molecules of Ca2+, calexcitin bound GTP and possessed GTPase activity. Calexictin is also a high affinity substrate for protein kinase C. Application of calexcitin to the inner surface of inside-out patches of human fibroblast membranes, in the presence of Ca2+ and the absence of endogenous Ca2+/calmodulin kinase type II or protein kinase C activity, reduced the mean open time and mean open probability of 115 +/- 6 pS K+ channels. Calexcitin thus appears to directly regulate K+ channels. When microinjected into molluscan neurons or rabbit cerebellar Purkinje cell dendrites, calexcitin was highly effective in enhancing membrane excitability. Because calexcitin translocates to the cell membrane after phosphorylation, calexcitin could serve as a Ca(2+)-activated signaling molecule that increases cellular excitability, which would in turn increase Ca2+ influx through the membrane. This is also the first known instance of a GTP-binding protein that binds Ca2+.

The assigned protection factor according to ANSI

The American National Standards Institute (ANSI) standard for respiratory protection (ANSI Z88.2 1992) lists assigned protection factors (APFs) for various respirators. The committee that developed the APFs based its decisions on a review of available studies of respirator performance. If workplace studies were available, these formed the basis for the number assigned. If no such studies were available, then laboratory studies, design analogies, and other information were used to decide what value to assign. For half-mask air purifying respirators, four workplace protection factor studies were consulted to arrive at an APF. For loose-fitting facepiece powered air purifying respirators (PAPRs), five workplace studies and two laboratory studies were reviewed. For full-face air purifying, helmet/hooded PAPRs, and most supplied air respirators no workplace studies were available. The APF was based on laboratory studies or decided by analogy to other equipment. For the remaining respirators only single workplace protection factor studies were available, and these were used by the committee to assign an APF. The database available to the ANSI committee was limited. Most of the studies available for review were not published. The committee in a sense was required to perform peer review on the information to use the data. Studies completed after the ANSI committee finished its deliberations, when added to the data used, continue to support the APFs assigned by ANSI.

Phosphorylation of the conditioning-associated GTP-binding protein cp20 by protein kinase C

The phosphorylation state of cp20, a low molecular weight membrane-associated GTP-binding protein, was previously shown to increase two- to threefold 24 h after associative conditioning. Here, cp20 is shown to be phosphorylated by protein kinase C (PKC) in vitro. Pronounced differences in activity were observed with the three major isoforms of PKC, whereas casein kinase, calcium/calmodulin-dependent protein kinase II, and cyclic AMP-dependent protein kinase produced no detectable phosphorylation of cp20. Phosphorylation of cp20 had no effect on its GTPase or GTP-binding activity but caused a translocation of cp20 from cytosol to the nuclei/mitochondrial particulate fraction. These results suggest that the increase in phosphorylation of cp20 after conditioning may be due to PKC.

The assigned protection factor of 10 for half-mask respirators

A number of researchers have published or presented papers on workplace protection factor (WPF) studies involving halfmask respirators. Individually, each study contains a relatively small amount of data, generally less than 25 data points for any single respirator. Because of the small amount of data, any attempt to quantify the result statistically does not provide useful information on the low end of the distribution of WPFs. Several studies on half-mask respirators were combined to yield a data set with 390 observations. Of these WPF data, 1.5% were less than 10, the best estimate of the 5th percentile was 13, with a 95% confidence interval of 10 to 18. Differences between the mean WPF based on the type of filter were found, but no difference was found between the mean performance of elastomeric and disposable respirators equipped with dust/mist and dust/fume/mist filters.

Alzheimer and beta-amyloid-treated fibroblasts demonstrate a decrease in a memory-associated GTP-binding protein, Cp20

The two proteins most consistently identified in the brains of patients with Alzheimer disease (AD) have been beta-amyloid and tau, whose roles in the physiology or pathophysiology of brain cells are not fully understood. To identify other protein(s) involved in AD that have been implicated in physiological contexts, we undertook to analyze a specific memory-associated protein, Cp20, in fibroblasts from AD and control donors. Cp20, a GTP-binding protein that is a member of the ADP-ribosylation factor family, was significantly decreased in fibroblasts from AD patients. Normal control fibroblasts exposed to 10 nM beta-amyloid, the same concentration that induced AD-like K+ changes in control fibroblasts, showed a similar decrease in Cp20. Since it has been previously demonstrated that Cp20 is a potent regulator of K+ channels, these findings suggest that changes in this memory-associated protein may explain previously observed differences in AD K+ channels and suggest a pathophysiologic involvement linked to soluble beta-amyloid metabolism that could contribute to the characteristic memory loss of AD.

Characterization of a GTP-binding protein implicated in both memory storage and interorganelle vesicle transport

The phosphorylation state of cp20, a low molecular weight GTP-binding protein that is a high-affinity substrate for protein kinase C, was previously shown to change after associative conditioning of molluscs and mammals and to induce many of the biophysical and structural modifications that accompany memory retention. Here, cp20 was purified from squid optic lobes and biochemically characterized. A monoclonal antibody prepared against squid cp20 reacted with Hermissenda cp20 and a 20-kDa protein in rabbit hippocampus, while a polyclonal antibody also cross-reacted with Sar1p and ADP-ribosylation factor (ARF). A partial peptide sequence of squid cp20 was 50% identical (23/46 amino acids) with Sar1p, a yeast GTP-binding protein involved in vesicle transport, indicating that cp20 is probably a new member of the ARF family. This classification is consistent with our recent demonstration that cp20 affects retrograde movement of intraaxonal organelles or particles and suggests a possible role for particle traffic between intraneuronal organelles in memory acquisition.

Internal Ca2+ mobilization is altered in fibroblasts from patients with Alzheimer disease

The recent demonstration of K+ channel dysfunction in fibroblasts from Alzheimer disease (AD) patients and past observations of Ca(2+)-mediated K+ channel modulation during memory storage suggested that AD, which is characterized by memory loss and other cognitive deficits, might also involve dysfunction of intracellular Ca2+ mobilization. Bombesin-induced Ca2+ release, which is inositol trisphosphate-mediated, is shown here to be greatly enhanced in AD fibroblasts compared with fibroblasts from control groups. Bradykinin, another activator of phospholipase C, elicits similar enhancement of Ca2+ signaling in AD fibroblasts. By contrast, thapsigargin, an agent that releases Ca2+ by direct action on the endoplasmic reticulum, produced no differences in Ca2+ increase between AD and control fibroblasts. Depolarization-induced Ca2+ influx data previously demonstrated the absence of between-group differences of Ca2+ pumping and/or buffering. There was no correlation between the number of passages in tissue culture and the observed Ca2+ responses. Furthermore, cells of all groups were seeded and analyzed at the same densities. Radioligand binding experiments indicated that the number and affinity of bombesin receptors cannot explain the observed differences. These and previous observations suggest that the differences in bombesin and bradykinin responses in fibroblasts and perhaps other cell types are likely to be due to alteration of inositol trisphosphate-mediated release of intracellular Ca2+.

Destaining of nitrocellulose blots after staining with silver or colloidal gold

A new method for destaining blots stained with colloidal gold is described. After destaining and restaining, artifacts and discolorations caused by the colloidal gold can often be removed. The silver produced by silver enhancement can also be selectively removed without affecting the gold stain.

GABA-mediated synaptic interaction between the visual and vestibular pathways of Hermissenda

The synaptic convergence of the eyes and the vestibular hair cells in the nudibranch mollusc Hermissenda has been shown previously to mediate the learning of simple visual-vestibular associations. The neurotransmitter mediating this interaction between the visual and vestibular organs was characterized. HPLC chromatography, confirmed by mass spectroscopic analysis, demonstrated endogenous GABA in the statocysts, in a concentration approximately 150 times greater than in the whole CNS. Additional confirmation was provided by immunocytochemical localization of GABA in hair cell axons and branches that converge with photoreceptor terminal branches. Depolarization of the hair cells in the caudal region of the statocyst in response to positive current injection or vibratory stimulation caused a hyperpolarization and a cessation of the type B photoreceptor impulse activity. The inhibition of the B cell was unaffected by addition to the artificial sea water bath of the adrenergic antagonist yohimbine (250 microM), the cholinergic antagonist atropine (250 microM), and the serotonergic antagonist imipramine (50 microM). In contrast, the GABAA antagonist bicuculline (250 microM) significantly reduced the inhibitory interaction. Moreover, the GABA reuptake inhibitor guvisine (250 microM) increased the hyperpolarization. Pressure microapplication of GABA (12.5 or 25 microM) onto the terminal branches of the B cell resulted in a concentration-dependent hyperpolarization and cessation of spikes in the B cell. Depolarization of the caudal hair cell, or direct GABA application, decreased input resistance across the B cell soma membrane. Moreover, removal of chloride from the extracellular solution reduced inhibition of the B cell induced by GABA application or hair cell stimulation. Furthermore, application of the GABAB agonist baclofen hyperpolarized the type B cell and reduced or eliminated spontaneous impulse activity at the resting membrane potential. The reversal potentials for inhibition induced in all three procedures ranged from -70 to -80 mV and were consistent with mixed Cl- and K+ conductances. These results implicate GABA as the endogenous neurotransmitter mediating visual-vestibular interactions in this animal, and suggest a possible role of GABA in visual-vestibular associative learning.

G-protein effects on retrograde axonal transport

Movements of medium and large sized membranous organelles (0.5-1 microns in diameter) were visualized within segments of the crab walking leg nerve with Nomarski differential interference contrast optics and subjected to video contrast enhancement. Accessibility to the axoplasm was demonstrated by intra-axonal fluorescence following addition of rhodamine conjugated to 40 kDa dextran to the external medium. Perfusion of the axons with a 1 microM solution of the 20 kDa G-protein, cp20, but not control solutions, reduced the number of organelles moving in the retrograde direction per unit time, but not the number of organelles moving in the anterograde direction. Such alteration of organelle movement may contribute to memory-specific changes of neuronal morphology.

Rapid isoelectric focusing of proteins in hydrolytically stable capillaries

Three new types of capillary coatings for capillary isoelectric focusing that avoid siloxane chemistry, resulting in hydrolytically stable coatings, are described and tested: phenyl-silica, acrylamide-reacted vinyl-silica, and pure PTFE. Capillaries of these three types were compared using standard proteins and a biological mixture of proteins similar to what might be encountered in actual use. Of these, the acrylamide-coated capillary produced the highest-quality results. In contrast to capillaries prepared using siloxane reactions, the capillaries described herein exhibited greatly enhanced stability at high pH.

Deconvolution method for accurate determination of overlapping peak areas in chromatograms

A method is described for deconvoluting chromatograms which contain overlapping peaks. Parameters can be selected to ensure that attenuation of peak areas is uniform over any desired range of peak widths. A simple extension of the method greatly reduces the negative overshoot frequently encountered with deconvolutions. The deconvoluted chromatograms are suitable for integration by conventional methods.

Classical conditioning-induced changes in low-molecular-weight GTP-binding proteins in rabbit hippocampus

Classical conditioning of Hermissenda, involving paired light-rotation events, results in a 30-35% decrease in the levels of a 20-kDa G protein (cp20). To test whether a similar protein exists in vertebrates, rabbits were trained to associate a tone with periorbital electrical stimulation and G proteins were analyzed by photoaffinity labeling with [alpha-32P]GTP-azidoanilide. A 20-kDa G protein similar to cp20 decreased by 36% in the hippocampus of rabbits subjected to paired tone and electrical stimulation, but not in unpaired controls. Learning-specific decreases were also found in the amount of ras protein.

GTP-binding proteins and potassium channels involved in synaptic plasticity and learning

Inhibition of potassium channels is possibly the first step in the sequence of biochemical events leading to memory formation. These channels appear to be regulated directly or indirectly by GTP-binding proteins (G proteins), which may themselves be affected by phosphorylation and dephosphorylation in response to elevated calcium levels or other phenomena resulting from the blockage of the potassium channels. A wide variety of cellular phenomena, from transcriptional changes to axonal transport, are thus capable of being initiated by these events.

GYN implant orthogonal film holder

An orthogonal film holder has been developed for the use of implants in the O.R. This film holder provides both AP and lateral films that are truly 90 degrees apart from each other. Placement of the GYN applicators must be checked before completion of the procedure. Traditionally, orthogonal films have been used for positioning and for the dose calculations. Therefore it is critical to have good quality radiographs. The AP film holder is placed beneath the patient and the lateral film holder slides into the side of the AP film holder, providing accurate placement and reproducibility in relation to each other. After the films have been approved, the lateral film holder bolts on top of the AP film holder. The system then looks like a briefcase and has a carrying handle for easy transportation and storage. This newly designed system has been used successfully and has proved its ease of use and accuracy.

Specificity of molecular changes in neurons involved in memory storage

Evidence implicating molecular steps in memory storage is discussed, particularly with reference to molecular specificity and uniqueness and the possible relevance of these steps to other types of long-lasting transformations such as those of development, regeneration, and tumorigenesis. The role of protein kinase C-mediated phosphorylation of identified protein subtrates, such as a 20,000-dalton GTP-binding protein, is described for associative memory of the snail Hermissenda, associative conditioning of the rabbit, and long-term potentiation. Cyclic AMP-mediated phosphorylation during sensitization of the snail Aplysia is also examined.

Isolation of a G protein that is modified by learning and reduces potassium currents in Hermissenda

In Hermissenda crassicornis conditioned to associate light and rotation, type B photoreceptor neurons exhibit pairing-specific decreases in the potassium currents IA and IK-Ca, which account for many of the behavioral changes elicited by associative conditioning. To determine which proteins are involved in storage of this memory, high-performance liquid chromatography was used to examine proteins from Hermissenda eyes. Conditioning-specific changes in four phosphoproteins were observed 24 hours after conditioning. One of these proteins, cp20, was purified to apparent homogeneity and found to be a G protein. When injected back into Hermissenda type B cells, cp20 reduced IK and IK-Ca in a manner indistinguishable from the reduction caused by conditioning, suggesting that this protein may play a crucial role in memory acquisition or retention.

Isolation of a G protein that is modified by learning and reduces potassium currents in Hermissenda

In Hermissenda crassicornis conditioned to associate light and rotation, type B photoreceptor neurons exhibit pairing-specific decreases in the potassium currents IA and IK-Ca, which account for many of the behavioral changes elicited by associative conditioning. To determine which proteins are involved in storage of this memory, high-performance liquid chromatography was used to examine proteins from Hermissenda eyes. Conditioning-specific changes in four phosphoproteins were observed 24 hours after conditioning. One of these proteins, cp20, was purified to apparent homogeneity and found to be a G protein. When injected back into Hermissenda type B cells, cp20 reduced IK and IK-Ca in a manner indistinguishable from the reduction caused by conditioning, suggesting that this protein may play a crucial role in memory acquisition or retention.

Specific high molecular weight mRNAs induced by associative learning in Hermissenda

Associative conditioning of Hermissenda crassicornis has been demonstrated to result in long-term changes in the potassium currents IA and ICa2(+)-K+ in photoreceptor neurons in the eye and to increase mRNA levels in the eye 2- to 3-fold. mRNA isolated from Hermissenda trained with paired light and rotation stimuli was labeled with [3H]acetic anhydride, while mRNA from naive animals or from animals subjected to random light and rotation stimuli was labeled with [14C]acetic anhydride. The labeled RNA was combined and separated by agarose gel electrophoresis. The overall size distribution of labeled mRNA was shifted to longer chain lengths in the paired group. In addition, the 3H/14C ratios were markedly increased for 21 distinct size bands, indicating increased mRNA of specific chain lengths in the paired group. Increases in the same size bands were also observed with mRNA labeled in vivo with 32Pi. This indicates that associative learning in Hermissenda results in a specific induction of a distinct set of at least 21 mRNAs, rather than in a generalized increase in synthesis of all mRNA, thus resembling in some respects a differentiation-like response.