Magnitude and frequency variations of vector-borne infection outbreaks using the Ross-Macdonald model: explaining and predicting outbreaks of dengue fever.

The classical Ross-Macdonald model is often utilized to model vector-borne infections; however, this model fails on several fronts. First, using measured (or estimated) parameters, which values are accepted from the literature, the model predicts a much greater number of cases than what is usually observed. Second, the model predicts a single large outbreak that is followed by decades of much smaller outbreaks, which is not consistent with what is observed. Usually towns or cities report a number of recurrences for many years, even when environmental changes cannot explain the disappearance of the infection between the peaks. In this paper, we continue to examine the pitfalls in modelling this class of infections, and explain that, if properly used, the Ross-Macdonald model works and can be used to understand the patterns of epidemics and even, to some extent, be used to make predictions. We model several outbreaks of dengue fever and show that the variable pattern of yearly recurrence (or its absence) can be understood and explained by a simple Ross-Macdonald model modified to take into account human movement across a range of neighbourhoods within a city. In addition, we analyse the effect of seasonal variations in the parameters that determine the number, longevity and biting behaviour of mosquitoes. Based on the size of the first outbreak, we show that it is possible to estimate the proportion of the remaining susceptible individuals and to predict the likelihood and magnitude of the eventual subsequent outbreaks. This approach is described based on actual dengue outbreaks with different recurrence patterns from some Brazilian regions.

Outpatient Follow Up and Reconstructive Surgery Rates in Massive Burn Survivors: Investigating the Social Determinants.

Burn care continues to improve and larger total body surface area (TBSA) burn survival is increasing. These survivors require more extensive care than smaller burns and are at higher risk for wound/scar related complications. Prior work has shown low rates of follow up for burn survivors linked to socioeconomic factors such as housing insecurity and substance use. There are limited studies that evaluate socioeconomic factors that contribute to follow up and reconstructive surgery rates in massively burned patients. Patients that survived to discharge with >50% TBSA burns and planned return to treating institution were included in the study. Univariate and multivariate analyses were performed on the data collected. Sixty-Five patients were included with an average TBSA of 63.1%. Fifty-three patients (81.5%) attended at least one follow up appointment with median of four follow-up appointments. Younger patients (33±9 vs 44±11; p=0.0006), patients with larger TBSA burns (65±13 vs 55±5%; p=0.02), those with private insurance and those without housing insecurity (1.8% vs 45.4%; p=0.003) were more likely to follow up. On multivariate regression analysis, patients with housing insecurity were independently associated with lack of follow up (OR: 0.009 CI: 0.00001-0.57). Thirty-five patients had at least one reconstructive surgery and 31 patients had reconstructive surgery after discharge. No patients with housing insecurity underwent reconstructive surgery. Follow up rates in massive burns were higher than reported for smaller TBSA burns and more than half received reconstructive surgery. Housing insecure patients should be targeted for improved follow up and access to reconstructive surgery.

A time since onset of injection model for hepatitis C spread amongst injecting drug users.

Studies of hepatitis C virus (HCV) infection amongst injecting drug users (IDUs) have suggested that this population can be separated into two risk groups (naive and experienced) with different injecting risk behaviours. Understanding the differences between these two groups and how they interact could lead to a better allocation of prevention measures designed to reduce the burden of HCV in this population. In this paper we develop a deterministic, compartmental mathematical model for the spread of HCV in an IDU population that has been separated into two groups (naive and experienced) by time since onset of injection. We will first describe the model. After deriving the system of governing equations, we will examine the basic reproductive number R0, the existence and uniqueness of equilibrium solutions and the global stability of the disease free equilibrium (DFE) solution. The model behaviour is determined by the basic reproductive number, with R0 = 1 a critical threshold for endemic HCV prevalence. We will show that when R0 ≤ 1, and HCV is initially present in the population, the system will tend towards the globally asymptotically stable DFE where HCV has been eliminated from the population. We also show that when R0 > 1 there exists a unique non-zero equilibrium solution. Then we estimate the value of R0 from epidemiological data for Glasgow and verify our theoretical results using simulations with realistic parameter values. The numerical results suggest that if R0 > 1 and the disease is initially present then the system will tend to the unique endemic equilibrium.

Massive Burn Injuries: Characteristics and Outcomes From a Single Institution.

Massive burn injuries are a unique patient population with unique treatment paradigms. Data from 155 adult patients, admitted from 2009 to 2019, with >50% total body surface area burns (TBSA) were collected and analyzed. Average burn size was 70% TBSA and 63% had a concomitant inhalation injury. Approximately 30% of patients (46/155) transitioned to comfort care-only measures within 24 hours of admission. Standard treatment patients were younger (37 ± 13 vs 60 ± 19 years; p < .00001), male (94% vs 28%; p = .001) and had smaller TBSA (66 ± 13 vs 80 ± 16; p < .00001). Of the standard treatment group, 72 (66%) survived to discharge. Survivors had smaller TBSA (64 ± 13 vs 71 ± 13; p = .003), less third-degree TBSA (48 ± 25 vs 71 ± 13; p = .003) and lower incidence of renal failure requiring dialysis (22% vs 73%, p < .00001). Multivariate regression analysis showed that age (OR 1.05; p = .025), total TBSA (OR 1.07; p = .005), and renal failure (OR 10.2; p = .00005) were independently associated with mortality. Inhalation injury was not significantly associated with mortality. About 23% (35/155) of patients had a psychiatric condition on admission and 19% (30/155) of patients were burned attempting suicide. Patients with psychiatric conditions spent more time in the hospital (62 vs 30 days; p = .004), more time on ventilator (31 vs 12 days; p = .046), underwent more surgery (4 vs 2 operations, p = .03), and were less likely to die (34% vs 59%; p = .02). In summary, age, burn size, and renal failure were independently associated with mortality, with renal failure being the strongest factor. Psychiatric conditions are prevalent pre-injury and tend to require more inpatient care.

Mutations in the rod domains of keratins 1 and 10 in epidermolytic hyperkeratosis.

Epidermolytic hyperkeratosis is a hereditary skin disorder characterized by blistering and a marked thickening of the stratum corneum. In one family, affected individuals exhibited a mutation in the highly conserved carboxyl terminal of the rod domain of keratin 1. In two other families, affected individuals had mutations in the highly conserved amino terminal of the rod domain of keratin 10. Structural analysis of these mutations predicts that heterodimer formation would be unaffected, although filament assembly and elongation would be severely compromised. These data imply that an intact keratin intermediate filament network is required for the maintenance of both cellular and tissue integrity.

Modelling the Effect of a Novel Autodissemination Trap on the Spread of Dengue in Shah Alam and Malaysia.

In this paper, we will start off by introducing the classical Ross-Macdonald model for vector-borne diseases which we use to describe the transmission of dengue between humans and Aedes mosquitoes in Shah Alam, which is a city and the state capital of Selangor, Malaysia. We will focus on analysing the effect of using the Mosquito Home System (MHS), which is an example of an autodissemination trap, in reducing the number of dengue cases by changing the Ross-Macdonald model. By using the national dengue data from Malaysia, we are able to estimate λ, which represents the initial growth rate of the dengue epidemic, and this allows us to estimate the number of mosquitoes in Malaysia. A mathematical expression is also constructed which allows us to estimate the potential number of breeding sites of Aedes mosquitoes. By using the data available from the MHS trial carried out in Section 15 of Shah Alam, we included the potential effect of the MHS into the dengue model and thus modelled the impact MHS has on the spread of dengue within the trial area. We then extended our results to analyse the effect of the MHSs on reducing the number of dengue cases in the whole of Malaysia. A new model was constructed with a basic reproduction number, R 0,Mala MHS, which allows us to identify the required MHSs coverage needed to achieve extinction in Malaysia. Numerical simulations and tables of results were also produced to illustrate our results.

Sedation during ophthalmic surgery.

Sedation is frequently used during ophthalmic regional anaesthesia. There is no 'ideal' drug for sedation or analgesia. Various drugs either alone or in combination have been used with different methods of administration. This review includes the roles of sedation, the pharmacology of drugs and the safety of sedation in patients undergoing ophthalmic surgery.

ROCK2/rasHa co-operation induces malignant conversion via p53 loss, elevated NF-κB and tenascin C-associated rigidity, but p21 inhibits ROCK2/NF-κB-mediated progression.

To study ROCK2 activation in carcinogenesis, mice expressing 4-hydroxytamoxifen (4HT)-activated ROCK2 (K14.ROCKer) were crossed with mice expressing epidermal-activated rasHa (HK1.ras1205). At 8 weeks, 4HT-treated K14.ROCKer/HK1.ras1205 cohorts exhibited papillomas similar to HK1.ras1205 controls; however, K14.ROCKer/HK1.ras1205 histotypes comprised a mixed papilloma/well-differentiated squamous cell carcinoma (wdSCC), exhibiting p53 loss, increased proliferation and novel NF-κB expression. By 12 weeks, K14.ROCKer/HK1.ras1205 wdSCCs exhibited increased NF-κB and novel tenascin C, indicative of elevated rigidity; yet despite continued ROCK2 activities/p-Mypt1 inactivation, progression to SCC required loss of compensatory p21 expression. K14.ROCKer/HK1.ras1205 papillomatogenesis also required a wound promotion stimulus, confirmed by breeding K14.ROCKer into promotion-insensitive HK1.ras1276 mice, suggesting a permissive K14.ROCKer/HK1.ras1205 papilloma context (wound-promoted/NF-κB+/p53-/p21+) preceded K14.ROCKer-mediated (p-Mypt1/tenascin C/rigidity) malignant conversion. Malignancy depended on ROCKer/p-Mypt1 expression, as cessation of 4HT treatment induced disorganized tissue architecture and p21-associated differentiation in wdSCCs; yet tenascin C retention in connective tissue extracellular matrix suggests the rigidity laid down for conversion persists. Novel papilloma outgrowths appeared expressing intense, basal layer p21 that confined endogenous ROCK2/p-Mypt1/NF-κB to supra-basal layers, and was paralleled by restored basal layer p53. In later SCCs, 4HT cessation became irrelevant as endogenous ROCK2 expression increased, driving progression via p21 loss, elevated NF-κB expression and tenascin C-associated rigidity, with p-Mypt1 inactivation/actinomyosin-mediated contractility to facilitate invasion. However, p21-associated inhibition of early-stage malignant progression and the intense expression in papilloma outgrowths, identifies a novel, significant antagonism between p21 and rasHa/ROCK2/NF-κB signalling in skin carcinogenesis. Collectively, these data show that ROCK2 activation induces malignancy in rasHa-initiated/promoted papillomas in the context of p53 loss and novel NF-κB expression, whereas increased tissue rigidity and cell motility/contractility help mediate tumour progression.

Paradoxical tumor inhibitory effect of p53 loss in transgenic mice expressing epidermal-targeted v-rasHa, v-fos, or human transforming growth factor alpha.

To investigate the effect of p53 tumor suppressor gene loss in the mouse skin model of multistage carcinogenesis, p53 knockout mice, generated by gene targeting (p53 -/-), were mated to transgenic mice expressing v-rasHa (HK1.ras), v-fos (HK1.fos), or human transforming growth factor alpha+HK1.TGFalpha) exclusively in the epidermis, by means of a keratin K1-based targeting vector (HK1). HK1-p53 transgenic progeny expressing wild-type p53 alleles (p53 +/+) or hemizygous for the p53 knockout allele (p53+/-) were identical to parental HK1 lines and exhibited neonatal epidermal hyperplasia or wound-associated hyperplasia in adults, together with spontaneous or 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced benign papillomas. Mating to p53-/- did not lead to the expected tumorigenesis in adults. Instead, whereas HK1.ras or HK1.TGFalpha transgenic mice null for p53 (HK1.ras-p53-/- and HK1.TGFalpha-p53-/-, respectively) retained the neonatal epidermal hyperplasia phenotype, in adults, spontaneous and TPA-promoted papilloma formation was blocked. Similarly, wound-associated epidermal hyperplasia/hyperkeratosis, a hallmark of adult HK1.fos phenotypes, was completely absent in HK1.fos-p53 -/- mice. Histological, immunofluorescence, and bromodeoxyuridine labeling analysis of neonatal or adult epidermis in HK1-p53 transgenic genotypes +/+, +/-, and -/- for p53 revealed no obvious differences in morphology, expression of keratinocyte differentiation markers, or mitotic index attributed to p53 loss. To determine whether the paradoxical absence of papillomas centered on up-regulation of p53 target genes, WAF1/CIP1/p21 RNA expression levels were examined in TPA promotion experiments. WAF1/CIP1/p21 expression increased in response to TPA promotion in all HK1-p53 transgenic genotypes regardless of p53 status. However, in HK1-p53 null genotypes, although TPA-induced, p53-independent WAF1/CIP1/p21 expression was observed, no large increase in expression was associated with the observed paradoxical tumorigenesis block. These data suggest that epidermis is somewhat resistant to the neoplastic effects of p53 loss, possibly possessing several compensatory systems. Alternatively, there may be a requirement forp53 expression in response to TPA or a wound-promotion stimulus in mouse epidermis.

Development of an in vitro model to study carcinogen-induced neoplastic progression of initiated mouse epidermal cells.

Initiation and promotion in mouse skin carcinogenesis produce multiple benign tumors, squamous papillomas, but only a few squamous cell carcinomas. The spontaneous conversion from the benign to the malignant phenotype occurs over many months and in stages, but induced malignant conversion can be accomplished more rapidly by exposure of papilloma-bearing mice to mutagens or by transfection of papilloma cell lines with specific oncogenes. The analysis of genetic targets responsible for carcinogen-induced neoplastic progression would be facilitated by the development of in vitro models where the process is rapid, focal, and quantitative. To this end, primary newborn mouse keratinocytes were initiated in vitro by the introduction of the v-rasHa oncogene via a defective retrovirus. Recipient cells produce squamous papillomas and have a high proliferation rate in culture medium with 0.05 mM Ca2+, but fail to grow in medium with 0.5 mM Ca2+ which is permissive for growth of malignant keratinocytes. When v-rasHa-keratinocytes were exposed to mutagens in vitro, proliferative foci emerged after culture in 0.5 mM Ca2+ for 4 weeks. These foci stained intensely red with rhodamine stain, could be easily quantitated, and readily incorporated bromodeoxyuridine. Dose-response studies with several mutagens indicated that the number of foci increased with concentration to the point where excessive cytotoxicity developed. Mutagens varied in potency for producing foci in the following order: cis-diamminedichloroplatinum greater than or equal to benzo(a)pyrene diolexpoxide I greater than N-methyl-N'-nitro-N-nitrosoguanidine greater than or equal to 4-nitroquinoline-N-oxide greater than N-acetoxy-acetyl- aminofluorene. The tumor promoter 12-O-tetradecanoylphorbol-13-acetate was inactive in the assay. A subset of cell lines derived from foci produced malignant tumors in vivo, while others were not tumorigenic. Analysis of DNA from cell lines and tumors revealed that most tumorigenic cell lines maintained the v-rasHa genome, whereas the viral sequences were deleted in nontumorigenic cell lines. Immunohistochemical analysis indicated that proliferative foci and quiescent v-rasHa keratinocytes expressed keratin 8, a marker of v-rasHa expression in cultured keratinocytes. Cells in foci, but not v-rasHa control cells, expressed keratin 13, a marker which is strongly associated with the malignant progression of skin tumors in vivo. This in vitro assay provides a quantitative model to study chemically induced focal neoplastic progression at the cellular level and to identify agents which may be selective for enhancing malignant conversion.

Cooperation between v-fos and v-rasHA induces autonomous papillomas in transgenic epidermis but not malignant conversion.

Transgenic mice have been previously established that express v-rasHa or v-fos exclusively in the epidermis by means of a targeting vector based on the human keratin 1 gene (HK1). Epidermal expression of v-rasHa (HK1.ras) or v-fos (HK1.fos) resulted in hyperplasia, hyperkeratosis, and later, in benign tumors. To assess the potential for oncogene cooperation in vivo mating experiments were performed. Resultant HK1.fos/ras mice exhibited an obvious increase in the severity of neonatal and juvenile preneoplastic phenotypes, together with the immediate onset of tumorigenesis as compared to single oncogene sibling controls. The HK1.fos/ras tumors grew aggressively and often compromised the animals by 10-12 weeks. However, tumors remained benign as determined by histotype and specific keratin markers. These data indicate that v-fos can cooperate with an initiating v-rasHa phenotype to generate autonomous papillomas, but additional events are required for malignant conversion.

Development of murine epidermal cell lines which contain an activated rasHa oncogene and form papillomas in skin grafts on athymic nude mouse hosts.

We have developed four murine epidermal cell lines which form squamous papillomas when grafted to athymic nude mice in a reconstituted skin. Two of the lines, SP-1 and BP-4, were derived from pools of papillomas produced on SENCAR and BALB/c mouse skin, respectively, by initiation with 7,12-dimethylbenz(a)anthracene and promotion with 12-O-tetradecanoylphorbol-13-acetate. Line 308 was derived from BALB/c mouse skin initiated in vivo with 7,12-dimethylbenz(a)anthracene, culture of the epidermal cells, and selection of cells resistant to Ca2+-induced terminal differentiation. Line LC14 was derived from untreated, cultured newborn BALB/c mouse primary epidermal cells which spontaneously developed resistance to Ca2+-induced terminal differentiation. Each line has an activated rasHa gene with a mutation within codon 61. Cells from all four lines, in contrast to normal primary epidermal cells, survive in medium with Ca2+ levels greater than 0.1 mM. Clonal growth studies in culture showed a unique growth pattern for each of the four lines in medium with 1.4 mM and 0.05 mM Ca2+, with or without 12-O-tetradecanoylphorbol-13-acetate. Early passage cells of these lines should provide a valuable resource for detecting genes or genetic alterations which complement an activated ras gene to cause malignant conversion and for studying the biology of tumor promotion.

TGF alpha and v-fos cooperation in transgenic mouse epidermis induces aberrant keratinocyte differentiation and stable, autonomous papillomas.

To assess the synergistic effect of growth and transcription factor deregulation on carcinogenesis in vivo, mating experiments were performed between transgenic mice expressing human TGF alpha or v-fos exclusively in the epidermis by means of a human keratin K1-based targeting vector (HK1.fos, HK1.TGF alpha and HK1.fos/alpha). While HK1.TGF alpha mice exhibited mild epidermal hyperplasia resulting in a wrinkled appearance, this hyperplasia was significantly increased in HK1.fos/alpha mice which also exhibited a novel opalescent and peeling skin phenotype. HK1.fos/alpha keratinocyte differentiation was considerably deregulated with cornified cells appearing in the granular layer, granular cells in the spinous layer and a sixfold increase in BrdU labeling over normal. In addition, hyperplastic HK1.fos/alpha epidermis exhibited aberrant loricrin, filaggrin and novel K13 expression associated with v-fos expression. Unlike adult HK1.TGF alpha controls, hyperplasia persisted in HK1.fos/alpha adults which also rapidly developed autonomous squamous cell papillomas. These results demonstrate that v-fos and TGF alpha over-expression can cooperate to reprogram keratinocyte differentiation and elicit the early stages of neoplasia. Moreover, TGF alpha over-expression appeared to play an early, initiating role in HK1.fos/alpha papilloma etiology, and a promotion role in the accelerated appearance of v-fos wound-associated preneoplastic phenotypes. However, the stable persistence of HK1.fos/alpha papillomas for up to 12 months, suggests that additional events are required for malignant conversion.

Human keratin-1.bcl-2 transgenic mice aberrantly express keratin 6, exhibit reduced sensitivity to keratinocyte cell death induction, and are susceptible to skin tumor formation.

Nonmelanoma skin cancers (NMSC) are among the most common malignancies in the world. Typically, these neoplasms grow slowly and are comparatively indolent in their clinical behavior. The most frequent molecular alterations implicated in the pathogenesis of these neoplasms involve genes known to be regulators of cell death including p53, Ha-ras and bcl-2. In order to evaluate the significance cell death deregulation during skin carcinogenesis, we generated a transgenic mouse model (HK1.bcl-2) using the human keratin 1 promoter to target the expression of a human bcl-2 minigene to the epidermis. Transgenic HK1.bcl-2 protein was expressed at high levels specifically in the epidermis extending from the stratum basale through the stratum granulosum. The epidermis of HK1.bcl-2 mice exhibited multifocal hyperplasia without associated hyperkeratosis and aberrant expression of keratin 6. The rate of proliferation was similar in HK1.bcl-2 and control epidermis although suprabasal BrdUrd incorporating cells were present only in HK1.bcl-2 skin. Keratinocytes from the HK1.bcl-2 mice were significantly more resistant to cell death induction by U.V.-B, DMBA, and TPA, compared to control keratinocytes. Furthermore, papillomas developed at a significantly greater frequency and shorter latency in the HK1.bcl-2 mice compared to control littermates following initiation with DMBA and promotion with TPA. Together these results support a role for bcl-2 in the pathogenesis of NMSC.

Expression of a p53 mutant in the epidermis of transgenic mice accelerates chemical carcinogenesis.

To develop an in vivo model for studying the role of the p53 tumor suppressor in skin carcinogenesis, a murine p53(172H) mutant (equivalent to human p53(175H)) was expressed in the epidermis of transgenic mice, utilizing a targeting vector based on the human keratin 1 gene (HK1.p53m). HK1.p53m mice developed normally and did not exhibit an obvious epidermal phenotype or develop spontaneous tumors. However, these mice demonstrated an increased susceptibility to a two-stage chemical carcinogenesis protocol, with the rate of formation and number of papillomas being dramatically increased as compared to non-transgenic controls. The majority of papillomas in control mice regressed after termination of 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment, whereas p53m papillomas progressed to carcinomas and metastases. In addition, more advanced malignancy, i.e., undifferentiated spindle cell carcinomas, were exclusively observed in p53m mice. Increased bromodeoxyuridine (BrdU) labeling, accompanied by decreased expression of p21, was observed in HK1.p53m papillomas. In situ examination of centrosomes in HK1.p53m papillomas also revealed marked abnormalities, with 75% of the cells containing > or = 3 centrosomes/cell, whereas centrosome numbers in papillomas from control animals remained normal. These data suggest that the accelerated tumorigenesis observed in chemically-treated p53m mice is most likely due to increased genomic instability resulting from an inhibition of G1 arrest and abnormal amplification of centrosomes.

Hyperplasia, hyperkeratosis and benign tumor production in transgenic mice by a targeted v-fos oncogene suggest a role for fos in epidermal differentiation and neoplasia.

A vector, derived from the human K1 keratin gene, has been employed to target v-fos expression exclusively in the epidermis of transgenic mice. Adult transgenic mice expressors (3-4 months) displayed hyperplasia and hyperkeratosis, initially in wounded (tagged) ears, which later became bilateral. This phenotype appeared at other epidermal sites, most notably in the axilla and inguinal areas. This indicates that a second promoting event, such as wounding or friction, is required to elicit these pathological changes. Highly keratotic benign ear lesions and benign squamous papillomas appeared after long latency at sites of phenotypic epidermis. These data suggest that v-fos may be interfering with c-fos function in normal keratinocyte differentiation, but by itself is insufficient to elicit overt benign lesions.

Delayed wound healing in immunodeficient TGF-beta 1 knockout mice.

Previous studies showed that full-thickness wounds in transforming growth factor-beta1-deficient mice initially heal normally. Unfortunately, transforming growth factor-beta1 deficiency leads to a multifocal inflammatory disease affecting most organs of the body, which ultimately interferes with later stages of wound healing in these mice. As this inflammatory disease is eliminated in transforming growth factor-beta1-deficient mice lacking T and B cells (Tgfb1-/- Scid-/- mice), we hypothesized that wound repair in the latter would proceed normally, even at later stages of healing. Unexpectedly, Tgfb1-/- Scid-/- mice demonstrate a major delay of approximately 1 wk in each of the major phases of wound healing: inflammation, proliferation, and maturation. Immuno- deficient Scid-/- mice that have the wild-type Tgfb1 allele do not experience this delay in wound healing. One interpretation of these findings is that lymphocytes and transforming growth factor-beta1 affect compensatory pathways in wound healing. An alternative interpretation is that the delayed expression of Tgfb2 and Tgfb3 that occurs in the absence of transforming growth factor-beta1 results in the delayed wound healing, suggesting that transforming growth factor-beta2 and/or transforming growth factor-beta3 play important parts in wound healing.