Computational and experimental approaches for investigating nanoparticle-based drug delivery systems.

Most therapeutic agents suffer from poor solubility, rapid clearance from the blood stream, a lack of targeting, and often poor translocation ability across cell membranes. Drug/gene delivery systems (DDSs) are capable of overcoming some of these barriers to enhance delivery of drugs to their right place of action, e.g. inside cancer cells. In this review, we focus on nanoparticles as DDSs. Complementary experimental and computational studies have enhanced our understanding of the mechanism of action of nanocarriers and their underlying interactions with drugs, biomembranes and other biological molecules. We review key biophysical aspects of DDSs and discuss how computer modeling can assist in rational design of DDSs with improved and optimized properties. We summarize commonly used experimental techniques for the study of DDSs. Then we review computational studies for several major categories of nanocarriers, including dendrimers and dendrons, polymer-, peptide-, nucleic acid-, lipid-, and carbon-based DDSs, and gold nanoparticles. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov.

First report of chronic implant-related septic arthritis and osteomyelitis due to Kytococcus schroeteri and a review of human K. schroeteri infections.

We report the first case of Kytococcus schroeteri implant-related septic arthritis and osteomyelitis, identified by phenotypic tests and 16S rRNA sequencing, which responded to implant removal and doxycycline. 16S rRNA sequencing was useful for the accurate and rapid identification of the organism as it exhibited three different colonial morphologies in vitro.

Service learning in medical and nursing training: a randomized controlled trial.

The purpose of this study was to explore the long term effect of a service learning project on medical and nursing students' knowledge in aging and their attitudes toward older adults. A total of 124 students were recruited and then randomized to intervention group (IG) and control group (CG). A pre-and-post-intervention design measured students' knowledge in aging (using modified Palmore's Fact on Aging Quiz) and attitudes toward older adults (using Kogan's Old People Scale). A total of 103 students completed all the activities and questionnaires. After the intervention, there were significant differences between the IG and CG on Palmore's mental health (MH) (P = .04), Palmore's total score (P = .02) and Kogan's negative attitudes toward older adults (P = .001). All students increased their positive attitude toward older adults after the intervention. However, both the IG and CG showed a decrease in positive attitudes 1 month after the interventon, and such decrease varied, depending on the programme which students attended. The current study showed that the 10-week service learning activities significantly increased medical and nursing students' overall knowledge of aging and their understanding of mental health needs in old age, and reduced their negative attitudes toward older adults. However, the effect is not long-lasting. On the other hand, its effect on positive attitudes toward older adults cannot be concluded. Periodic contacts with older adults via service learning activities may be needed to sustain attitude change toward older adults.

Air dispersal of meticillin-resistant Staphylococcus aureus in residential care homes for the elderly: implications for transmission during the COVID-19 pandemic.

BACKGROUND: Meticillin-resistant Staphylococcus aureus (MRSA) infections are rampant in hospitals and residential care homes for the elderly (RCHEs). AIM: To analyse the prevalence of MRSA colonization among residents and staff, and degree of environmental contamination and air dispersal of MRSA in RCHEs. METHODS: Epidemiological and genetic analysis by whole-genome sequencing (WGS) in 12 RCHEs in Hong Kong. FINDINGS: During the COVID-19 pandemic (from September to October 2021), 48.7% (380/781) of RCHE residents were found to harbour MRSA at any body site, and 8.5% (8/213) of staff were nasal MRSA carriers. Among 239 environmental samples, MRSA was found in 39.0% (16/41) of randomly selected resident rooms and 31.3% (62/198) of common areas. The common areas accessible by residents had significantly higher MRSA contamination rates than those that were not accessible by residents (37.2%, 46/121 vs. 22.1%, 17/177, P=0.028). Of 124 air samples, nine (7.3%) were MRSA-positive from four RCHEs. Air dispersal of MRSA was significantly associated with operating indoor fans in RCHEs (100%, 4/4 vs. 0%, 0/8, P=0.002). WGS of MRSA isolates collected from residents, staff and environmental and air samples showed that ST 1047 (CC1) lineage 1 constituted 43.1% (66/153) of all MRSA isolates. A distinctive predominant genetic lineage of MRSA in each RCHE was observed, suggestive of intra-RCHE transmission rather than clonal acquisition from the catchment hospital. CONCLUSION: MRSA control in RCHEs is no less important than in hospitals. Air dispersal of MRSA may be an important mechanism of dissemination in RCHEs with operating indoor fans.

Primary infective spondylodiscitis caused by Lactococcus garvieae and a review of human L. garvieae infections.

We report the first case of primary infective spondylodiscitis due to Lactococcus garvieae, confirmed by 16S rRNA gene sequencing, in the absence of concomitant endocarditis in a patient with long-standing gastritis on famotidine. He responded to a 6-week course of ampicillin. The gastrointestinal tract is probably the source of infection.

Depression literacy among Chinese stroke survivors.

OBJECTIVES: Mental health literacy is fundamental to the pursuit of health. Little is known about patients' literacy levels regarding depression even though it is common among elderly stroke survivors. This paper will report the level of mental health literacy and thematic constructs of depression interpreted by a group of stroke survivors. METHOD: Qualitative data on patients' understanding of 'depression' in Chinese were translated and analyzed by an academic and a researcher separately to identify emerging constructs using a thematic approach. Out of 214 ischemic stroke older adults, aged 50+, 85 were able to explain the term in their own words after their first stroke attack. RESULTS: The majority of stroke patients (60%, 129 out of 214) had never heard of depression and only four referred to it as a medical disease. Only a third would like to learn more about depression. Older Chinese adults depicted depression mainly by using words in the cognitive and affective domains, but the descriptors used were mostly non-specific and might not match the diagnostic criteria for depression or the commonly used screening tools. CONCLUSION: Low mental health literacy among older patients indicated that much more work needs to be done in health promotion and education on depression literacy.

Short- and medium-term outcomes of accelerated infant growth in a Hong Kong Chinese birth cohort.

1. In a large, population representative,Chinese birth cohort, higher birth weight and rapid growth, particularly at 0-3 months, were associated with higher body mass index (BMI) at 7 years. 2. Boys born heavy who had grown fast had the highest BMI, but rapid growth had the largest impact in lighter-born boys. 3. Rapid growth at 0-3 months or 3-12 months was not associated with a compensatory lower risk of serious infectious morbidity. 4. The ability to grow fast may be an embodiment of good health status, rather than fast growth being causally protective.

Ionizable amino lipid interactions with POPC: implications for lipid nanoparticle function.

Lipid nanoparticles (LNPs) composed of ionizable cationic lipids are currently the leading systems for siRNA delivery in liver disease, with the major limitation of low siRNA release efficacy into the cytoplasm. Ionizable cationic lipids are known to be of critical importance in LNP structure and stability, siRNA entrapment, and endosomal disruption. However, their distribution inside the LNPs and their exact role in cytoplasmic delivery remain unclear. A recent study [Kulkarni et al., On the formation and morphology of lipid nanoparticles containing ionizable cationic lipids and siRNA, ACS Nano, 2018, 12(5), 4787-4795] on LNP-siRNA systems containing the ionizable lipid DLin-KC2-DMA (also known as KC2 with an apparent pKa of ca. 6.7) suggested that neutral KC2 segregates from other components and forms an amorphous oil droplet in the core of LNPs. In this paper, we present evidence supporting the model proposed by Kulkarni et al. We studied KC2 segregation in the presence of POPC using molecular dynamics simulation, deuterium NMR, SAXS, and cryo-TEM experiments, and found that neutral KC2 has a high tendency to separate from POPC dispersions. KC2 confinement, upon raising the pH during the formulation process, could result in rearrangement of the internal structure of LNPs. As interactions between cationic KC2 and anionic endosomal lipids are thought to be a key factor in cargo release, KC2 confinement inside the LNP may be responsible for the observed low release efficacy.

A theoretical study of S(N)2' reactions of allylic halides: role of ion pairs.

Various disparate experimental results are explained by the hypothesis that reactions of anionic nucleophiles with allylic halides are generally S(N)2. The S(N)2' reactions that do occur proceed generally with anti stereochemistry. Reactions with ion pair nucleophiles occur preferentially as S(N)2' reactions with syn stereochemistry. This hypothesis is consistent with a variety of computations at the HF, B3LYP, mPW1PW91 and MP2 levels with the 6-31+G(d) basis set of reactions of Li and Na fluoride and chloride with allyl halides and 4-halo-2-pentenes. Solvation is considered by a combination of coordination of dimethyl ether to the lithium and sodium cations and "dielectric solvation" with a polarized continuum model.

Early life second-hand smoke exposure and serious infectious morbidity during the first 8 years: evidence from Hong Kong's "Children of 1997" birth cohort.

BACKGROUND: Second-hand smoke (SHS) exposure is a modifiable cause of ill health. Despite the smoking ban in public places introduced in Hong Kong in 2007, infants and children continue to be exposed within the home. AIMS: To determine the critical windows of SHS exposure and the duration of its impact on serious infectious morbidity in the first 8 years of life. METHODS: The Hong Kong "Children of 1997" birth cohort is a prospective, population-based study of 8327 children comprising 88% of all births in April and May 1997, of whom 7402 (89%) were followed up until their eighth birthday in 2005. We used multivariable Cox regression to assess the relation between postnatal SHS exposure and risk of first admission to public hospitals (together accounting for >95% total bed-days overall) for respiratory, other and all infections from birth to 8 years of age, for all individuals and for vulnerable subgroups. RESULTS: Overall, household SHS exposure within 3 metres in early life was associated with a higher risk of admission for infectious illness up until 8 years of age (hazard ratio 1.14, 95% CI 1.00 to 1.31), after adjustment for sex, birthweight, gestational age, feeding method, maternal age, highest parental education and proxies of preferred service sector. The association was strongest in the first 6 months of life (HR 1.45, 95% CI 1.15 to 1.83). In vulnerable subgroups such as premature babies, the association held through to 8 years of age (HR 2.00, 95% CI 1.08 to 3.72). Infants exposed to SHS in the first 3 months of life were most vulnerable to infectious causes of hospitalisation. CONCLUSION: Household SHS exposure in early infancy increases severe infectious morbidity requiring hospital admission. Reducing SHS exposure in infants and particularly in more vulnerable infants will lower the bed-days burden due to infectious causes.

RNA editing in Trypanosoma brucei: characterization of gRNA U-tail interactions with partially edited mRNA substrates.

Guide RNAs (gRNAs), key components of the RNA editing reaction in Trypanosoma brucei, direct the insertion and deletion of uridylate (U) residues. Analyses of gRNAs reveal three functional elements. The 5'-end of the gRNA contains the anchor, which is responsible for selection and binding to the pre-edited mRNA. The second element (the guiding region) provides the information required for editing. At the 3'-end of the gRNA is a non-encoded U-tail, whose function remains unclear. However, the cleavage-ligation model for editing proposes that the U-tail binds to purine-rich regions upstream of editing sites, thereby strengthening the interaction and holding onto the 5' cleavage product. Our previous studies demonstrated that the U-tail interacts with upstream sequences and may play roles in both stabilization and tethering. These studies also indicated that the U-tail interactions involved mRNA regions that were to be subsequently edited. This raised the question of what happens to the mRNA-U-tail interaction as editing proceeds in the 3'-->5' direction. We examined gCYb-558 and its U-tail interaction with 5'CYbUT and two partially edited 5'CYb substrates. Our results indicate that the 3'-end of the U-tail interacts with the same sequence in all three mRNAs. Predicted secondary structures using crosslinking data suggest that a similar structure is maintained as editing proceeds. These results indicate that the role of the U-tail may also involve maintenance of important secondary structure motifs.

Bone mineral density and calcium metabolism of Hong Kong Chinese postpartum women--a 1-y longitudinal study.

OBJECTIVE: This paper reports longitudinal changes in bone mineral density (BMD), calcium homeostasis and dietary calcium intake in a group of Hong Kong breastfeeding women during the first year postpartum. DESIGN AND SUBJECTS: Nine mothers who breastfed exclusively or almost exclusively for at least 3 months and 14 formula feeding mothers aged 20-40 y were interviewed after delivery, 2 and 6 weeks, 3, 6 and 12 months postpartum. BMD at L2-L4 lumbar spine (LS), trochanter (Tro) and femoral neck (FN), serum intact parathyroid hormone (iPTH), serum bone-specific alkaline phosphatase (b-ALP), urinary deoxypyridinoline (Dpd), serum and urinary calcium (Ca) and phosphorus (P) and dietary intake of macronutrients were assessed. RESULTS: Compared to the formula feeding group, BMD assessed at LS, Tro and FN decreased significantly in the breastfeeding group over the first 6 months, with rebound to approximate baseline values at 12 months for the latter two sites. Serum iPTH increased in both groups, whereas serum b-ALP was consistently higher in the breastfeeders. Urinary Ca and P excretion decreased early postpartum in both groups, but the breastfeeders had higher excretion at 3 and 6 months. Breastfeeding mothers consumed significantly more Ca than the formula feeding mothers in the early postpartum. CONCLUSIONS: Increased calcium requirement during early lactation is affected through mobilisation of bone and renal calcium conservation. Bone mineral loss during lactation is temporary. Further studies are warranted to investigate the effects of diet and other hormonal factors on the calcium homeostasis during lactation.

Epidemiology of IDDM in southern Chinese children in Hong Kong.

OBJECTIVE: To provide reliable data on the incidence of IDDM in southern Chinese children in Hong Kong. RESEARCH DESIGN AND METHODS: A registry was established in 1991 to collect childhood IDDM cases retrospectively and prospectively from four districts in Hong Kong. The study included all newly diagnosed cases of IDDM with onset < 15 yr of age from 1 January 1986 to 31 December 1990. Primary ascertainment was based on review of medical records at a regional hospital serving the four districts. An independent school survey validated registry data. RESULTS: The completeness of ascertainment was 93.8%. The age-standardized incidence of IDDM was 2.0/100,000/yr with the 95% confidence interval of 1.2-3.0/100,000/yr for children < 15 yr of age during the study period. The incidence rates/100,000/yr for the three age-groups were: < or = 4 yr, 0.8; 5-9 yr, 2.2; 10-14 yr, 2.8. The incidence for males was 1.5/100,000/yr (95% confidence interval 0.7-2.9/100,000/yr) and for females, 2.4/100,000/yr (95% confidence interval 1.3-4.0/100,000/yr). CONCLUSIONS: This study documents a very low incidence rate of childhood IDDM in southern Chinese in Hong Kong.

Modulation of the digestive-lysosomal system in Paramecium caudatum. I. Effects of temperature.

The heterophagic pathway of the digestive-lysosomal system in axenically grown Paramecium caudatum is divisible into vacuole formation, vacuole acidification-condensation, lysosomal fusion-digestion and defecation. These four processes can be separated in time, thus permitting the study of the effects of temperature on each process. The optimal growth temperature for this cell was 27 degrees C. The rate of digestive vacuole (DV) formation at varying temperatures was represented by a skewed bell-shaped curve having an optimum between 28 and 30 degrees C. The time course for the acidification-condensation step was lengthened below 26 degrees C, but was not accelerated above this temperature. The rate but not the extent of vacuole condensation was decreased at 19 and 22 degrees C. Temperature increase above 22 degrees C shortened, slightly, the duration of the lysosomal fusion-digestion process, whereas below 22 degrees C small temperature decreases greatly extended this period. Within a given experiment the rates of defecation were proportional to temperatures above 17 degrees C. However, these rates varied widely among different experiments. Interestingly, the activation energies for both the formation and defecation processes averaged 19 kcal/mol. Furthermore, Paramecium appeared to readily adapt to environmental temperature changes, since the length of the processing periods and the rates of defecation were similar in cells with or without a 24 h acclimation. These results indicated that the four processes in the digestive cycle in P. caudatum are distinct but each is energy-dependent.

Modulation of the digestive lysosomal system in Paramecium caudatum. II. Physiological effects of cytochalasin B, colchicine and trifluoperazine.

The heterophagic pathway of the digestive lysosomal system in Paramecium caudatum includes at least four steps: digestive vacuole (DV) formation, acidification-condensation, lysosomal fusion-digestion, and defecation. The second and the third require about 20 min, during which DVs are not egested. Because these steps occur at predictable intervals, the mechanism for each can be explored by exposing labeled DVs to different drugs prior to each step. In this study the effects of cytochalasin B (CB), colchicine and the calmodulin antagonist, trifluoperazine (TFP), were studied. All three drugs inhibited DV formation in a dose-dependent manner when cells were pulsed with latex beads and a drug simultaneously. TFP was cytotoxic above 5 microM. Vacuole formation was completely shut down when cells were pre-exposed to 5 microM TFP for 13 min. At this level, the duration of the acidification step was lengthened, and the rate of defecation decreased with increasing exposure. These results suggest that these inhibitory effects may be more related to TFP's cytotoxicity than to its action on calmodulin-mediated process. Colchicine at 1 mM had no effect on the third or fourth step, but inhibited the acidification step so that DVs were egested later and at a slower rate. Exerting a differential effect on all four steps, CB inhibited DV release from the cytopharynx, egestion of defecation-competent DVs at the cytoproct and lengthened the duration but did not block the lysosomal fusion-digestion step of the acidic DVs; it was most potent in blocking acidification, which prevented both lysosomal fusion with the labeled DVs as well as DV egestion, the latter for more than 50 min.(ABSTRACT TRUNCATED AT 250 WORDS)

A follow-up study on the effects of calcium-supplement withdrawal and puberty on bone acquisition of children.

Recent calcium supplementation trials in children have confirmed a positive but moderate effect of calcium intake on bone mineral accretion. However, the lasting effect of a higher bone mineral mass after calcium-supplement withdrawal is not known. This is an 18-mo follow-up study conducted after an 18-mo controlled calcium supplementation trial to study the persistent effect of higher bone mineral mass in children. Radial bone mineral mass was determined by single-photon absorptiometry; lumbar spine and femoral neck bone mineral mass were evaluated by dual-energy X-ray absorptiometry in 84 healthy Hong Kong children at age 8.5 y and these evaluations were repeated at age 10 y. Pubertal status was determined by Tanner staging. At the end of the follow-up, the differences in percentage gains in lumbar spine bone mineral content (12.1 +/- 8.2% compared with 14.9 +/- 10.05%, P = 0.24) and lumbar spine area (8.6 +/- 5.1% compared with 9.4 +/- 5.5%, P = 0.47) between the study and control groups disappeared. Dietary calcium intakes during follow-up were similar for the two groups (555 and 640 mg/d, P = 0.23). In multiple-regression analyses, pubertal status was the strongest correlate of bone acquisition and linear growth in the study period. In conclusion, higher percentage gains in bone mineral mass in childhood by calcium supplementation for 18 mo were reversible. Our study showed that the benefits of calcium supplementation disappear after treatment is withdrawn. Longer-term calcium trials are necessary to determine whether peak bone mass can be modified through sustained supplementation so that appropriate calcium intakes can be determined.

Double-blind, controlled calcium supplementation and bone mineral accretion in children accustomed to a low-calcium diet.

A randomized, double-blind, controlled calcium supplementation trial was conducted for 18 mo to determine its effects on bone acquisition and height increment in 162 7-y-old Chinese children (87 boys and 75 girls) with habitually low calcium intakes (280 mg/d). Distal one-third radial bone mineral content (BMC), area bone density (BMC/bone width), and height were evaluated every 6 mo. Baseline dietary intakes, serum 25-hydroxycholecalciferol, and physical activity were determined. The study group received 300 mg Ca/d as calcium carbonate; control subjects received placebo tablets. After 18 mo the study group had significantly greater gains in BMC (16.5% vs 13.97%; P = 0.02) and BMC/bone width (9.45% vs 6.31%; P = 0.0008) than the control subjects. The findings confirm a positive effect of calcium intake on bone acquisition but no effect on height increment. Whether a higher bone mass attained at age 8-9 y would be maintained and beneficial to future peak bone mass requires longitudinal investigation. Further study is warranted to determine calcium requirements for Chinese children.

Fat intake in Hong Kong Chinese children.

The people of Hong Kong are experiencing a transition in dietary practices and lifestyle that can be observed in the fat intakes of Hong Kong children as compared with those of their counterparts on mainland China. The studies described here include 1) a longitudinal and observational dietary survey beginning with a cohort of 174 newborns and concluding with 124 children at age 7 y; 2) a biochemical study of serum lipids in relation to dietary fat intake at age 7 y; 3) a chemical fatty acid analysis and comparison of duplicate meals collected from 20 Hong Kong and 20 mainland Chinese children at age 7 y; 4) a dietary assessment of 52 lactoovovegetarian children aged 4-14 y; and 5) a comparison of the growth of all subjects with US National Center for Health Statistics standards. About 30% of the total daily energy intake of Hong Kong Chinese children aged 1-7 y was contributed by fat-much more than that in the traditional Chinese diet. Growth of the children was not impaired, including that of children on the mainland and of those lactoovovegetarians in Hong Kong whose fat intakes were lower. Mean serum cholesterol of Hong Kong Chinese children at age 7 y was 4.59 mmol/L, significantly higher than that of their counterparts on the mainland, 4.16 mmol/L. Foods consumed in Hong Kong had a significantly lower ratio of 18:2 to 14:0. Nutritional deficiency was uncommon. Chinese children in Hong Kong had a dietary fat intake that was both quantitatively and qualitatively different from the traditional Chinese diet.

Role of aggregates in Claisen acylation reactions of imidazole, pyrazole, and thioesters with lithium enolates in THF.

[formula: see text] Although phenyl esters react with both monomers and dimers or tetramers of two lithium enolates in THF, the reactions of phenyl thiobenzoates are relatively much faster with the monomers. Similarly, imidazole esters react primarily with the monomers but pyrazole esters react with monomers and aggregates. The results are rationalized by a mechanism in which coordination with two lithium cations within an enolate aggregate is required for the reaction of aggregates to compete with monomers.