Composite mesh design for delivery of autologous mesenchymal stem cells influences mesh integration, exposure and biocompatibility in an ovine model of pelvic organ prolapse

The widespread use of synthetic transvaginal polypropylene mesh for treating Pelvic Organ Prolapse (POP) has been curtailed due to serious adverse effects highlighted in 2008 and 2011 FDA warnings and subsequent legal action. We are developing new synthetic mesh to deliver endometrial mesenchymal stem cells (eMSC) to improve mesh biocompatibility and restore strength to prolapsed vaginal tissue. Here we evaluated knitted polyamide (PA) mesh in an ovine multiparous model using transvaginal implantation and matched for the degree of POP. Polyamide mesh dip-coated in gelatin and stabilised with 0.5% glutaraldehyde (PA/G) were used either alone or seeded with autologous ovine eMSC (eMSC/PA/G), which resulted in substantial mesh folding, poor tissue integration and 42% mesh exposure in the ovine model. In contrast, a two-step insertion protocol, whereby the uncoated PA mesh was inserted transvaginally followed by application of autologous eMSC in a gelatin hydrogel onto the mesh and crosslinked with blue light (PA + eMSC/G), integrated well with little folding and no mesh exposure. The autologous ovine eMSC survived 30 days in vivo but had no effect on mesh integration. The stiff PA/G constructs provoked greater myofibroblast and inflammatory responses in the vaginal wall, disrupted the muscularis layer and reduced elastin fibres compared to PA + eMSC/G constructs. This study identified the superiority of a two-step protocol for implanting synthetic mesh in cellular compatible composite constructs and simpler surgical application, providing additional translational value.

Effectiveness of the extended parallel process model in promoting colorectal cancer screening

OBJECTIVE

Relatives of colorectal cancer (CRC) patients are at increased risk for the disease, yet screening rates still remain low. Guided by the Extended Parallel Process Model, we examined the impact of a personalized, remote risk communication intervention on behavioral intention and colonoscopy uptake in relatives of CRC patients, assessing the original additive model and an alternative model in which each theoretical construct contributes uniquely.

METHODS

We collected intention-to-screen and medical record-verified colonoscopy information on 218 individuals who received the personalized intervention.

RESULTS

Structural equation modeling showed poor main model fit (root mean square error of approximation (RMSEA) = 0.109; standardized root mean residual (SRMR) = 0.134; comparative fit index (CFI) = 0.797; Akaike information criterion (AIC) = 11,601; Bayesian information criterion (BIC) = 11,884). However, the alternative model (RMSEA = 0.070; SRMR = 0.105; CFI = 0.918; AIC = 11,186; BIC = 11,498) showed good fit. Cancer susceptibility (B = 0.319, p < 0.001) and colonoscopy self-efficacy (B = 0.364, p < 0.001) perceptions predicted intention to screen, which was significantly associated with colonoscopy uptake (B = 0.539, p < 0.001).

CONCLUSIONS

Our findings provide support of the utility of Extended Parallel Process Model for designing effective interventions to motivate CRC screening in persons at increased risk when individual elements of the model are considered. Copyright © 2015 John Wiley & Sons, Ltd.

A bruise-like patch in a 4-year-old girl

Dermatofibrosarcoma protuberans (DFSP), a rare medium grade sarcoma, occasionally occurs in childhood and is even more rarely present at birth. In children, the clinical appearance may be mistaken for a vascular malformation and so delayed diagnosis is not uncommon. Dermatofibrosarcoma protuberans is locally invasive and notorious for its high recurrence rate even after attempted wide local excision owing to extensive subclinical and asymmetrical extensions. In adult DFSP, Mohs Micrographic Surgery (MMS) is the treatment of choice because it offers a higher clearance rate compared to wide local excision. However, MMS may result in extended operating times owing to tissue processing and multiple stages. In children, this means a prolonged period under general anesthetic, which may be undesirable. We describe an interesting case of a 4- year-old girl diagnosed with DFSP. She underwent a modified MMS procedure in which she had two short general anesthetics. The advantage of MMS technique in which the full peripheral and deep margin of the specimen was examined.

Molecular identification of Na(+)-H(+) exchanger isoforms (NHE2) in the gills of the euryhaline teleost Fundulus heteroclitus

In the current study, reverse-transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) PCR were used to clone full-length putative Na(+)-H(+) exchanger isoforms (NHE2a) cDNA from the gills of Fundulus heteroclitus. The 2480 bp cDNA includes a coding region for a protein that shows a 57% amino acid homology to rabbit NHE2. These sequences allowed data mining of available fish genome data, which revealed at least three NHE2 subtypes in some teleost species.

Carbamazepine-Induced Hypersensitivity Syndrome Occurring in a Photodistributed Pattern

A 76- year- old man was commenced on carbamazepine for partial seizures. This was followed by the development of a rash in an apparently photodistributed pattern, fever, lymphadenopathy, eosinophilia, abnormal liver function tests and atypical lymphocytosis fulfilling the criteria for drug-induced hypersensitivity syndrome. Discontinuation of carbamazepine and application of topical steroid resulted in clearance of the rash, normalization of liver function tests and improvement in eosinophilia. The photodistributed pattern in this case of carbamazepine-induced hypersensitivity syndrome is of interest.

Annual incidence and mortality of bullous pemphigoid in the Grampian Region of North-east Scotland

BACKGROUND

Data on the annual incidence of bullous pemphigoid (BP) in the U.K. are scarce.

OBJECTIVES

To estimate the annual incidence of BP in Grampian Region (North-east Scotland) and to assess the causes of mortality in this cohort of patients.

METHODS

Details were obtained of all patients with a diagnosis of BP recorded in the database of the Pathology Department, Aberdeen Royal Infirmary between January 1991 and December 2001. Community Health Index population data were obtained from the Grampian Health Board and the annual incidence and age- and sex-specific incidence were calculated. Mortality data were obtained from the Patient Administration System and causes of death obtained from the Office of the Registrar for Births and Deaths for Scotland.

RESULTS

Eighty-three patients met criteria for diagnosis of BP. The annual incidence of BP in Grampian region was estimated to be 14 cases per million per year. There was a clear and marked rise in the incidence in patients over the age of 80 years. Forty-eight per cent of patients with BP died within 2 years of diagnosis. The all-cause age-standardized mortality ratio was 576%. When compared with cause-specific mortality in the Grampian population over 60 years of age, respiratory disease accounted for a higher than expected number of deaths in our cohort of patients with BP (odds ratio 5.3, 95% confidence interval 3.0-9.4).

CONCLUSIONS

North-east Scotland appears to have a relatively high incidence of BP when compared with incidence rates in continental Europe. The mortality rate in patients with BP is considerable, especially within the first 2 years of diagnosis.

Kaposiform haemangioendothelioma: case report and review of the literature

Kaposiform haemangioendothelioma (KHE) is a rare vascular tumour, predominantly of infancy and early childhood, that has a close association with Kasabach-Merritt syndrome. Despite benign histology, this tumour frequently behaves aggressively, causing significant morbidity and mortality as a result of the compression and invasion of surrounding structures as well as from associated haematological and lymphoproliferative syndromes. There is a need for a high index of suspicion when presented with large, enlarging or abnormal vascular lesions in infancy and, less commonly, in adulthood. An early diagnosis of KHE can lead to prompt treatment, which may be life saving. To date, there have been only four reported cases of KHE occurring in patients over the age of 18 years. We report an otherwise well 26-year-old woman who presented with a KHE of the left thigh, and briefly review the literature. We believe this to be the second reported case of KHE in the UK and the first in an adult patient.

Immunolocalisation of sodium/proton exchanger-like proteins in the gills of elasmobranchs

Na+/H+ exchangers are integral membrane proteins that exchange Na+ and H+ across cell membranes. The Na+/H+ exchangers 2 and 3 are epithelial isoforms in mammals and contribute to acid-base homeostasis. The gills of fishes, including elasmobranchs, are also associated with acid/base balance, and are probably the primary acid/base regulatory organ. This study examines the presence of Na+/H+ exchangers 2 and 3 using immunohistochemistry and immunoblotting in the gills of four species of elasmobranchs, the banjo ray (Trygonorrhina fasciata), southern eagle ray (Myliobatis australis), the gummy shark (Mustelus antarcticus) and the Australian angel shark (Squatina australis) using heterologous antibodies. Na+/H+ exchanger 2-like immunoreactivity was observed in the gills of the banjo ray, eagle ray and angel shark. In the banjo and eagle rays, this Na+/H+ exchanger-like immunoreactivity co-localised with immunoreactivity to Na+ /K+ -ATPase, a marker for the mitochondrial-rich cells of fishes. Na+/H+ exchanger 3-like immunoreactivity was only observed in the gills of the angel and gummy sharks, some Na+/H+ exchanger 3-like cells also showed Na+ /K+ -ATPase immunoreactivity. However, immunoblotting of banjo and eagle ray gill membranes demonstrated Na+/H+ exchanger 3-like immunoreactivity, which was not consistent with the immunohistochemical results. These data demonstrate the presence of epithelial Na+/H+ exchangers 2 and 3 in the gills of elasmobranchs and a link with acid/base regulation is suggested.

Cervical range of motion discriminates between asymptomatic persons and those with whiplash

STUDY DESIGN

A comparative study of cervical range of motion in asymptomatic persons and those with whiplash.

OBJECTIVES

To compare the primary and conjunct ranges of motion of the cervical spine in asymptomatic persons and those with persistent whiplash-associated disorders, and to investigate the ability of these measures of range of motion to discriminate between the groups.

SUMMARY OF BACKGROUND

Evidence that range of motion is an effective indicator of physical impairment in the cervical spine is not conclusive. Few studies have evaluated the ability to discriminate between asymptomatic persons and those with whiplash on the basis of range of motion or compared three-dimensional in vivo measures of range of motion in asymptomatic persons and those with whiplash-associated disorders.

METHODS

The study participants were 89 asymptomatic volunteers (41 men, 48 women; mean age 39.2 years) and 114 patients with persistent whiplash-associated disorders (22 men, 93 women; mean age 37.2 years) referred to a whiplash research unit for assessment of their cervical region. Range of cervical motion was measured in three dimensions with a computerized, electromagnetic, motion-tracking device. The movements assessed were flexion, extension, left and right lateral flexion, and left and right rotation.

RESULTS

Range of motion was reduced in all primary movements in patients with persistent whiplash-associated disorder. Sagittal plane movements were proportionally the most affected. On the basis of primary and conjunct range of motion, age, and gender, 90.3% of study participants could be correctly categorized as asymptomatic or as having whiplash (sensitivity 86.2%, specificity 95.3%).

CONCLUSIONS

Range of motion was capable of discriminating between asymptomatic persons and those with persistent whiplash-associated disorders.

Expression of Na(+) / H(+) exchanger mRNA in the gills of the Atlantic hagfish (Myxine glutinosa) in response to metabolic acidosis

Sodium/proton exchangers (NHE) are transmembrane proteins that facilitate the exchange of a Na(+) ion for a H(+) ion across cellular membranes. The NHE are present in the gills of fishes and are believed to function in acid-base regulation by driving the extrusion of protons across the branchial epithelium in exchange for Na(+) in the water. In this study, we have used reverse transcriptase-polymerase chain reaction (RT-PCR) to detect the presence of a branchial NHE in the gills of the Atlantic hagfish, Myxine glutinosa. The subsequent partial cDNA sequence shares homology with other vertebrate and invertebrate NHE isoforms. In addition, using semi-quantitative, multiplex RT-PCR we demonstrate that mRNA expression of hagfish gill NHE is upregulated following an induced metabolic acidosis. Expression was increased to 4.4 times basal levels at 2-h post-infusion and had decreased to 1.6 times basal by 6 h. Expression had returned to basal levels by 24-h post-infusion. The inference from this study is that a gill NHE which is potentially important in acid-base regulation has been present in the vertebrate lineage since before the divergence of the hagfishes from the main vertebrate line.

Using the Glasgow Coma Scale: analysis and limitations

This article addresses the gap between the literature and practice in relation to the use of the Glasgow Coma Scale (GCS). It will explore level of consciousness and the GCS. The instigation of both central and peripheral painful stimuli is analyzed in an effort to prevent ritualistic practice. Attention is also given to the importance of including vital signs when using the GCS, as these can tell a lot, if not more, about the patient's neurological condition. Finally, the limitations of the GCS are examined to assist in a more accurate and consistent assessment tool for neurologically impaired patients.

Associations between family history of cancer and genes coding for metabolizing enzymes (United States)

OBJECTIVE

Family history of cancer has been a useful tool to identify highly penetrant genes. However, the association between family history and low-penetrance genes that are prevalent in the population, is less well understood. While epidemiologists have studied low-penetrance genes in association studies at the population level, geneticists have often favored family studies to identify low-penetrance genes in the same manner that these families have been used to identify high-penetrance genes. In this study, we evaluated the association between family history of cancer and molecular variants of three genes: N-acetyltransferases (NAT2), glutathione-S-transferases (GSTM-1), and methylenetetrahydrofolate reductase (MTHFR). These genes were examined because of their plausible functional significance and their association with cancer risk in some studies.

METHODS

In a large multi-centered study of colon cancer, reported family history of cancer in first-degree relatives was used to classify cases and controls separately as having a family history of colorectal cancer, hormone-related cancers, smoking-related cancers, prostate cancer, and any cancer.

RESULTS

With three weak exceptions, we did not observe significant associations between any of these genes and family history of cancer. The ability of family history to positively predict the presence of variants of low-penetrance genes that may carry an elevated risk ranged from 41% to 60%; low-penetrance variants accurately predicted a family history of cancer 9 to 17% of the time. Assessment of the likelihood of having a family history of cancer given the combination of genetic and environmental factors, showed that those who smoked 20 or more cigarettes per day were more likely to have a family history of a smoking-related cancer irrespective of genotype.

CONCLUSIONS

People with a family history of cancer are not more likely to have a variant of low-penetrance genes than those without a family history of cancer. Family studies may not be efficient methods to study low-penetrance genes.

Preoperative histological classification of primary lung cancer: accuracy of diagnosis and use of the non-small cell category

AIMS

To compare the preoperative classification of lung carcinoma made on cytological and histological specimens with the postoperative classification made on the resected specimen. In addition, to find out how often the term "non-small cell lung cancer, not otherwise specified" (NSCLC) was used, and in such cases to note the final diagnosis.

METHODS

Between 1991 and 1995, 303 patients had a lung resection in Aberdeen for primary carcinoma. For each patient, the departmental records were examined for preoperative specimens (cytological and histological). A note was made of whether each specimen was positive or negative for malignancy and, if positive, what the cell type was. Where patients had more than one sample submitted, the most specific result was taken.

RESULTS

Fifty four per cent of patients had a correct specific preoperative diagnosis of malignancy, whereas 34% were labelled as NSCLC. Patients with squamous carcinoma were more likely to have a diagnosis of malignancy (88%) that was specifically correct (75%). Patients who had adenocarcinoma were less likely to have a preoperative diagnosis of malignancy (64%) that was specifically correct (35%). For those in whom a diagnosis of NSCLC was made, 55% turned out to have adenocarcinoma whereas 24% had squamous carcinoma.

CONCLUSIONS

By adhering strictly to criteria, a high accuracy of diagnosis can be achieved for squamous carcinoma, but the diagnosis of adenocarcinoma seems to be more of a challenge. NSCLC is a useful and appropriate classification, the use of which reduces the rate of inaccurate specific diagnosis. There are occasions when pathologists can provide a more accurate diagnosis by being less precise.

Colon cancer screening, lifestyle, and risk of colon cancer

OBJECTIVES

Sigmoidoscopy screening and fecal occult blood (FOB) tests have been demonstrated as effective ways to reduce mortality from colorectal cancer. However, most studies of colorectal cancer screening and cancer mortality have not taken into consideration lifestyle factors that could account for the observed associations. The purpose of this study was to determine the association between screening and incidence of colon cancer, taking into consideration important lifestyle factors.

METHODS

We estimated the association between screening and colon cancer after taking into consideration health and lifestyle factors using data obtained as part of population-based case-control study of incident colon cancers.

RESULTS

Sigmoidoscopy screening, especially as part of a checkup, was protective against incident colon cancer in both men (OR 0.56, 95% CI 0.44-0.77) and women (OR 0.53, 95% CI 0.33-0.77) after adjusting for other risk factors for colon cancer. For men, associations were stronger for distal tumors (OR 0.48, 95% CI 0.31-0.71) than for proximal tumors (OR 0.67, 95% CI 0.45-1.11). We did not observe significant associations between FOB test and colon cancer. Differences in characteristics between those who were screened and not screened were also observed. Men were more likely to report having a sigmoidoscopy as part of a checkup than were women, as were people with higher levels of education. People who reported having a sigmoidoscopy as part of a checkup also reported eating diets lower in fat and higher in fiber, folate, and vegetables. Men were more likely to report higher levels of physical activity, and women were more likely to report taking hormone replacement therapy (HRT) if they also reported a sigmoidoscopy. Both men and women who reported a sigmoidoscopy for screening purposes were more likely to have a family history of colorectal cancer.

CONCLUSIONS

These data provide additional support for the benefits of having a screening sigmoidoscopy. The associations between screening sigmoidoscopy and colon cancer do not appear to be the result of lifestyle factors.

Problematic pigmented lesions: approach to diagnosis

A number of pigmented lesions are difficult to classify and raise the possibility of a melanoma diagnosis. Care should be exercised to exclude non-melanocytic lesions, and benign melanocytic entities, both of which can mimic melanoma histologically. In addition, the possibility of the lesion being a melanoma variant or epidermotropic metastasis should be considered. There will still be some cases that are difficult to resolve. These usually fall into one of three categories: atypical junctional melanocytic lesion versus early melanoma; naevus versus naevoid melanoma; and atypical Spitz, cellular blue, and deep penetrating naevi versus thick melanoma. These will pose problems even for experts. The atypical Spitz lesions are perhaps the most important category because they tend to be from younger individuals, the differential diagnosis is thick melanoma, and there is no single discriminating histological feature.

Fluid overload and monitoring indices

Undetected fluid overload can cause serious complications, such as circulatory failure and/or cardiogenic shock. Rather than relying on a single test, a combination of procedures and observations should be used to identify the problem. Early intervention is vital to prevent distress, pain and long hospital stays.

Use of archival tissue in epidemiologic studies: collection procedures and assessment of potential sources of bias

Collection and analyses of archival tumor tissue as a means to increase our understanding of disease pathways is becoming an important avenue of epidemiologic research. In this paper, we present methods of collection and processing of archival tissue and assess the population characteristics of those for whom we were able to and unable to obtain tumor DNA. Cases of colon cancer diagnosed between September, 1991 and October, 1994 living in Utah, Northern California, or the Twin Cities Metropolitan area of Minnesota were targeted for this study. Of the 2477 people for whom we had permission to obtain tumor blocks, we were able to collect blocks and extract DNA for 2117 (85.5%). There were no differences in age, tumor site, or diet and lifestyle characteristics between those with and without DNA extracted. However, we were less likely to be able to extract DNA if the case was diagnosed at a more advanced disease stage or at the earliest disease. Potential bias from exclusion of those with the most advanced disease stage is discussed.

Lifestyle and colon cancer: an assessment of factors associated with risk

Studies of the etiology of colon cancer indicate that it is strongly associated with diet and lifestyle factors. The authors use data from a population-based study conducted in northern California, Utah, and Minnesota in 1991-1995 to determine lifestyle patterns and their association with colon cancer. Data obtained from 1,993 cases and 2,410 controls were grouped by using factor analyses to describe various aspects of lifestyle patterns. The first five lifestyle patterns for both men and women loaded heavily on dietary variables and were labeled: "Western," "moderation," "calcium/low-fat dairy;" "meat and mutagens," and "nibblers, smoking, and coffee." Other important lifestyle patterns that emerged were labeled "body size," "medication and supplementation," "alcohol," and "physical activity." Among both men and women, the lifestyle characterized by high levels of physical activity was the most marked lifestyle associated with colon cancer (odds ratios = 0.42, 95% confidence interval: 0.32, 0.55 and odds ratio = 0.52, 95% confidence interval: 0.39, 0.69, for men and women, respectively) followed by medication and supplementation (odds ratio = 1.68, 95% confidence interval: 1.29, 2.18 and odds ratio = 1.63, 95% CI 1.23, 2.16, respectively). Other lifestyles that were associated with colon cancer were the Western lifestyle, the lifestyle characterized by large body size, and the one characterized by calcium and low-fat dairy. Different lifestyle patterns appear to have age- and tumor site-specific associations.

Chemically distinct preganglionic inputs to iris-projecting postganglionic neurons in the rat: A light and electron microscopic study

Individual autonomic postganglionic neurons are surrounded by pericellular baskets of preganglionic terminals that are easily identifiable with the light microscope. It has been assumed that the target cell of a pericellular basket of preganglionic terminals is the neuron at the centre of the basket. This assumption has enabled the connectivity of preganglionic neurons to be determined at the light microscopic level. However, if the preganglionic terminals in a pericellular basket make synapses with the dendrites of nearby, but functionally different, postganglionic neurons, then the conclusions of light microscopic studies are far less certain. We have used a serial section ultrastructural study to determine the target of the preganglionic pericellular basket in a situation where the apparent target cell is surrounded by neurons of dissimilar function. In the rat superior cervical ganglion, postganglionic neurons projecting to the iris were identified, using retrograde tracers, as single neurons (i.e., not in clusters). We have used immunohistochemistry to show that iris-projecting neurons are surrounded by preganglionic nerve terminals containing calcitonin gene-related peptide (CGRP). We have demonstrated that the pericellular basket of CGRP-immunoreactive preganglionic terminals provides inputs only to the soma at the centre of the basket and not to the dendrites of surrounding neurons. This suggests that, in autonomic ganglia, light microscopic identification of the preganglionic terminal baskets is likely to be a reliable method for identifying the targets of subclasses of preganglionic neurons.

Hormone replacement therapy and improved survival among postmenopausal women diagnosed with colon cancer (USA)

OBJECTIVES

Hormone replacement therapy (HRT) has been inversely associated with colon cancer incidence in several epidemiologic studies. In this study we used data from a population-based incident case-control study of colon cancer to evaluate the role of HRT use in survival after diagnosis with colon cancer.

METHODS

Data from 815 postmenopausal women living in Utah, California, and Minnesota diagnosed between 1 September 1991 and 30 September 1994 were used to examine associations between HRT and survival.

RESULTS

After adjusting for age at time of diagnosis, stage of disease at time of diagnosis, study center, and body mass index (BMI), we observed that women who had ever used HRT had a 30% lesser probability of dying of any cause and a 40% lower probability of dying from colon cancer specifically during the follow-up period. Further evaluation by years of HRT use showed that those who had used HRT for 4 or more years had the lowest risk of dying of colon cancer (hazard rate ratio 0.5, 95% confidence interval 0.3-0.9). Evaluation of other lifestyle variables with HRT use did not show significant confounding or effect modification.

CONCLUSIONS

These findings suggest that HRT use may improve short-term survival after diagnosis with colon cancer; there is no suggestion that HRT use is detrimental to survival.

Uses of therapeutic hypothermia

Therapeutic hypothermia is used to preserve body function during major surgery. While it is a valuable therapeutic process, serious physiological harm can result if it is allowed to continue into the postoperative phase.

Risk of colon cancer associated with a family history of cancer or colorectal polyps: the diet, activity, and reproduction in colon cancer study

The Diet, Activity, and Reproduction in Colon Cancer (DARCC) study is a large, multi-center case-control study of colon cancer. We examined family histories of cancer among first-degree relatives obtained by computer-assisted in-person interviews from the DARCC to study the impact of family histories of several cancers and colorectal polyps on colon cancer risk. We examined familial cancer risks both by treating a family history of polyps or cancer as a covariate in a logistic regression model, and by comparing cancer or polyp incidence among relatives of cases to incidence among relatives of controls in a proportional hazards model. There were few differences between the odds ratios (OR) or confidence intervals (CI) generated from logistic regression models and the hazard rate ratios (HRR) generated from the proportional hazards models. Overall, the OR of colon cancer among subjects with a family history of colorectal cancer was 1.77. There were only minor differences in risk by sex, age and subsite. A family history of colorectal polyps also increased risk by about the same amount as a family history of colorectal cancer. The increased risk associated with a family history of polyps did not appear to decrease with age.

Malnutrition in hospital patients: where does it come from?

This article provides a comprehensive overview of malnutrition in hospital patients. It explores the issues surrounding nutrition and investigates factors that contribute to the malnutrition seen in patients within the community and to the malnutrition that develops while patients are in hospital. It proposes that although patients are at risk of malnutrition in the community, malnutrition can develop while the patient is in hospital, as the result of changes in diet, nutrition not being seen as a high priority, common hospital practices, and lack of knowledge of patients' previous nutritional state.

Vitamin E and colon cancer: is there an association?

The role of vitamin E in the etiology and prevention of colon cancer is not clear. It is possible that various forms of vitamin E may act differently in colon tissue and may be effective chemopreventive agents. Previous reports of vitamin E and colon cancer have focused on alpha-tocopherol and have not considered other dietary forms of vitamin E. Data from a study of 1,993 cases and 2,410 controls were used to evaluate the associations between the four most common forms of dietary vitamin E and supplemental vitamin E and colon cancer. After adjusting for other health and life-style factors, we did not observe a statistically significant association between dietary tocopherols and colon cancer. There were, however, suggestions of an inverse association between total alpha-tocopherol equivalents and colon cancer among women diagnosed with colon cancer before the median age of the control population, 67 years [odds ratio (OR) = 0.66, 95% confidence interval (CI) = 0.36-1.22] and a direct association between gamma-tocopherol and colon cancer among these women (OR = 1.44, 95% CI = 0.92-1.93). Women diagnosed with colon cancer when > or = 67 years of age appeared to have some protection from use of vitamin E supplements (OR = 0.80, 95% CI = 0.56-1.15). These data offer only limited support for a protective effect of vitamin E and colon cancer after adjustment for other health and life-style factors.

Stage of colon cancer at diagnosis: implications for risk factor associations?

BACKGROUND

A potential source of bias in epidemiological studies comes from studying people at different stages of disease progression. This can result in biased selection of cases or in errors of measurement of exposures.

METHODS

We use stage of disease at the time of diagnosis to evaluate how inclusion of people at different stages in the disease process can influence associations between environmental exposures and colon cancer. Data used were generated from a large case-control study of colon cancer.

RESULTS

For most environmental exposures evaluated, including physical activity, body size, use of aspirin and of non-steroidal anti-inflammatory drugs, and dietary intake of folate and fibre, we did not observe differences in patterns of association by stage of disease at diagnosis. However, for total energy and red meat intake (men only), alcohol consumption, cigarette smoking, and family history of colorectal cancer among first degree relatives, patterns of associations were stronger when colon cancer was detected at an earlier stage of disease progression than when it was detected at a more advanced stage.

CONCLUSIONS

Most exposures did not differ by stage of disease, thus selectively excluding cases at different disease stages should not influence associations between these exposures and colon cancer. Associations for other factors, such as alcohol consumption and cigarette smoking, may be biased from asking cases with advanced disease to recall a non-disease-free time period. Associations with family history may also be biased if those with a family history of colorectal cancer are detected at an earlier stage and therefore more likely to participate in epidemiological studies.

Measurement errors stemming from nonrespondents present at in-person interviews

PURPOSE

Data are frequently collected from in-person interviews in epidemiologic studies. Despite the advantages of this mode of data collection, the presence of a third party during the interview can contribute to measurement error, especially if third-party presence is related to case status.

METHODS

Using data obtained from a case-control study of colon cancer, we evaluated the frequency of third-party presence during in-person interviews, and how having someone else present during the interview influences reporting of exposure data.

RESULTS

Interviews were conducted in the presence of a third party for 28% of cases and 22% of controls who lived in a household of two or more individuals. Men with a third party present reported significantly lower age-adjusted mean levels of alcohol consumption (P < 0.01). Associations, as indicated by odds ratios, between colon cancer and alcohol intake were not statistically different among those with a third party present and those without a third party present. Although not statistically significant, energy intake was more strongly associated with colon cancer among those without a third party present during the interview.

CONCLUSIONS

These results emphasize the need to review questions to be asked and decide whether privacy should be emphasized before data collection begins. If privacy is required, interviewers need to be given better skills to ensure privacy during interview.

Critical thinking and analysis: a model for written assignments

The purpose of this article is to propose a model for critical analysis which can be incorporated into nurse education to enhance nurses' understanding of the concepts and to assist students in undertaking academic assignments. It provides a definition and conceptualization of critical thinking and critical analysis, and highlights the differences, similarities and interrelationships between them. The model suggests that there are 10 components of critical analysis. This provides the first step for developing further research on the content of the model, i.e. certain components are accepted and those which are unsuitable are rejected. The model assists the development of educational strategies to promote critical analysis skills, which are an essential element of the autonomous, critical thinking nurse practitioner.

Measuring temperature

The mouth, axilla, rectum and tympanic membrane are commonly used sites for temperature measurement, although readings may vary at different sites. Despite viable alternatives, glass-mercury thermometers remain in common use.

Dietary sugar and colon cancer

It has been hypothesized that levels of triglycerides, glucose, and insulin are associated with risk of colon cancer and that diets high in simple sugars increase risk of colon cancer because of their impact on these factors. Limited epidemiological evidence supports the association between simple carbohydrates and risk of colon cancer. Using data from a population-based case-control study (n = 1993 cases and 2410 controls), we examined the associations between dietary sugars, foods containing high level of sugars, and dietary glycemic index (GI) and colon cancer. A dietary GI was developed to estimate metabolic response to a diet that may increase plasma glucose levels. Dietary data were obtained using a validated diet history questionnaire. High levels of sucrose intake were associated with increased risk of colon cancer among younger men [odds ratio (OR) for highest quintile relative to lowest, 1.59; 95% confidence interval (CI), 1.07-2.37]. There was also a trend of increasing colon cancer risk associated with a higher sucrose:dietary ratio for proximal tumors in both men and women. Individuals with proximal tumors who consumed a diet ranked as having a high GI were at increased risk (for men, comparing highest quintile to lowest quintile: OR, 1.58; 95% CI, 1.06-2.36; P trend 0.04; for women: OR, 1.72; 95% CI, 1.11-2.67; P trend 0.04). Those at greatest risk from a high dietary GI were those who were sedentary (for men, relative to those who were most active and had a low-GI diet: OR, 3.46; 95% CI, 1.78-6.70; for women: OR, 2.00; 95% CI, 0.98-4.07). We also observed that people who had a high sucrose: dietary fiber ration and who also were sedentary and had a large body mass index were at increased risk (OR, 4.58; 95% CI, 2.33-8.98) relative to those who had a low sucrose:dietary fiber ratio, were active, and had low body mass indices. These findings support previous reports that dietary sugars, especially diet high in simple carbohydrates relative to complex carbohydrates, increase risk of colon cancer, possibly through their impact on plasma glucose levels.

Physical activity and colon cancer: a public health perspective

PURPOSE

It has been suggested that performing physical activity for at least 30 min on most days of the week will improve health. The purpose of this study was to assess the association between physical activity and colon cancer as it relates to this public health recommendation.

METHODS

A large population-based case-control study of colon cancer was conducted. Study participants came from three areas of the United States: Northern California, Utah, and the Twin Cities Metropolitan Area in Minnesota.

RESULTS

Long-term involvement in high levels of activity, equivalent to > or = 60 min of vigorous activity per session, was associated with decreased risk (odds ration [OR], 0.68; 95% confidence interval [CI] 0.52-0.87). The amount of time involved in the activity appeared to have a greater impact than the number of days per week that activities were performed. Those reporting the highest level of activity, as defined by both duration and vigorous intensity, were at the lowest risk (OR, 0.62; 95% CI, 0.52-0.75) relative to those who were sedentary; associations did not differ by age at diagnosis, site of the tumor within the colon, or sex. The inverse association between colon cancer and long-term vigorous leisure-time activity was slightly stronger among those without a family history of colorectal cancer than among those with a family history of colorectal cancer. From these data we estimate that 13% of colon cancer could be attributed to lack of vigorous leisure-time activity in the population; we estimate that 4.3 cases of colon cancer/100,000 population are prevented each year because people are involved in vigorous leisure-time physical activity.

CONCLUSIONS

Data from this study suggest that a high level of vigorous leisure-time activity performed over the past 20 years was important in reducing colon cancer risk; the greatest inverse association was observed when activities were performed for longer periods of time per session for the past 20 years. These and other data indicate that it is important to identify ways to facilitate an increase in leisure-time physical activity within the population.

Dietary energy sources and colon cancer risk

Because energy-contributing nutrients are highly correlated with total energy, the association with colon cancer from energy versus other components of energy-providing nutrients is often not clear. Dietary data from a population-based case-control study of colon cancer were analyzed in subjects from California, Utah, and Minnesota in 1991-1994 to assess the colon cancer risk associated with consumption of energy, fat, protein, and carbohydrate. After adjustment for long-term physical activity, total energy intake increased risk of colon cancer in men (odds ratio = 1.74, 95% confidence interval 1.14-2.67 for highest vs. lowest quartile) and in women (odds ratio = 1.70, 95% confidence interval 1.07-2.70). Various methods of analysis suggested that intakes of individual sources of energy (dietary fat, protein, and carbohydrate) were not associated with colon cancer risk after total energy intake was taken into account. People who consumed a high-calorie diet that was dense in fiber and calcium appeared to be at lower risk than people with the same caloric intake who consumed smaller amounts of dietary fiber and calcium. Individuals with a first-degree relative with colorectal cancer, especially those diagnosed at a younger age, were at a greater risk from a diet high in energy than were individuals without a family history of colorectal cancer.

Are dietary factors involved in DNA methylation associated with colon cancer?

Disturbances in DNA methylation have been hypothesized as being involved in carcinogenesis. It has been proposed that dietary factors such as folate, alcohol, and methionine may be associated with colon cancer because of their involvement in DNA methylation processes. Data from a large retrospective population-based case-control study of incident colon cancer were used to evaluate whether intake of alcohol and other dietary factors involved in DNA methylation are associated with colon cancer. Dietary data were obtained using a detailed diet history questionnaire. We did not observe strong independent associations between folate, vitamin B6, vitamin B12, methionine, or alcohol and risk of colon cancer after adjusting for body size, physical activity, cigarette smoking patterns, energy intake, and dietary intake of fiber and calcium. However, when assessing the associations between colon cancer and a composite dietary profile based on alcohol intake, methionine, folate, vitamin B12, and vitamin B6, we observed a trend of increasing risk as one moved from a low- to a high-risk group. This trend was modest and most marked in those diagnosed at a younger age [odds ratio (OR) for men = 1.3, 95% confidence interval (CI) = 0.9-1.9; OR for women = 1.6, 95% CI = 1.0-2.6]. We observed that associations with this high-risk dietary profile were greater among those who took aspirin or nonsteroidal anti-inflammatory drugs on a regular basis and were younger at the time of diagnosis (men OR = 1.7, 95% CI = 1.0-3.2; women OR = 2.2, 95% CI = 1.0-4.8) and for distal tumors (men OR = 1.4, 95% CI = 0.9-2.3; women OR = 2.0, 95% CI = 1.0-3.8). Findings from this study provide only limited support for previously reported associations between dietary factors involved in DNA methylation and risk of colon cancer.

Distinct preganglionic neurons innervate noradrenaline and adrenaline cells in the cat adrenal medulla

Calretinin immunoreactivity was present in a subset of preganglionic neurons retrogradely labelled from the cat adrenal gland. Overall, one-third of adrenal preganglionic neurons showed calretinin immunoreactivity, and their proportion increased in the more caudal spinal cord segments. Calretinin-immunoreactive nerve terminals were prominent within the adrenal gland, but were found only in areas of noradrenergic chromaffin cells (approximately one-third of the area of the adrenal medulla). Synaptophysin immunoreactivity was used to label terminals with and without calretinin immunoreactivity. Nerve terminals lacking calretinin immunoreactivity were present among the adrenergic chromaffin-cells and also comprised 20% of the nerve terminals innervating noradrenergic chromaffin cells. Calretinin immunoreactivity thus labels a subpopulation of cat adrenal preganglionic neurons that innervate the noradrenergic chromaffin cells.

Nitric oxide synthase and chemical coding in cat sympathetic postganglionic neurons

Nitric oxide synthase-like immunoreactivity was found in a subpopulation of sympathetic postganglionic neurons in the cat stellate and lower lumbar ganglia. In the ganglia of other segments such cells were rare. Double staining for tyrosine hydroxylase-like immunoreactivity and nitric oxide synthase-like immunoreactivity or the reduced nicotinamide adenine dinucleotide phosphate diaphorase reaction indicated that nitric oxide synthase-like immunoreactivity and reduced nicotinamide adenine dinucleotide phosphate diaphorase reactivity was always co-localized and was confined to tyrosine hydroxylase-negative (presumably cholinergic) ganglion cells, and was present in most of them. The occurrence of nitric oxide synthase in two subpopulations of cholinergic postganglionic neurons was investigated in triple staining experiments. Presumptive sudomotor neurons have been previously defined as scattered cells containing calcitonin gene-related peptide-like immunoreactivity, usually accompanied by vasoactive intestinal peptide-like immunoreactivity: 99% of these contained nitric oxide synthase. Presumptive muscle vasodilator neurons have been previously identified as clumped cells with strong vasoactive intestinal peptide-like immunoreactivity but no calcitonin gene-related peptide-like immunoreactivity: 70% of these contained nitric oxide synthase. Sweat glands were found in the paw pad skin surrounded by varicose fibres showing calcitonin gene-related peptide-like immunoreactivity and vasoactive intestinal peptide-like immunoreactivity, confirming previous work. Such fibres also stained for nitric oxide synthase-like immunoreactivity and reduced nicotinamide adenine dinucleotide phosphate diaphorase reactivity, although their staining was relatively weaker than in the corresponding cell bodies. Varicose fibres with the same chemical coding were also found around all large and most medium and small arteries in the paw skin as well as around arteriovenous anastomoses. Fibres with the muscle vasodilator coding (vasoactive intestinal peptide-like immunoreactivity without calcitonin gene-related peptide-like immunoreactivity) were not seen in paw skin. These results suggest that nitric oxide may act as a co-transmitter (with acetylcholine, substance P, vasoactive intestinal peptide and calcitonin gene-related peptide) in sudomotor neurons and (with acetylcholine and vasoactive intestinal peptide) in vasodilator neurons. Collateral branches of sudomotor neurons may innervate skin vessels, and release vasodilator transmitters including nitric oxide to cause the vasodilatation which provides the fluid supply for sweat formation. Alternatively, separate vasodilator neurons to skin may share the same chemical code as sudomotor neurons.

Response rates among control subjects in case-control studies

Response rates are an important component of epidemiologic research. The purposes of this study are (a) to evaluate how response rates are defined and calculated for control subjects in epidemiologic case-control studies, and (b) to explore factors that may impact response in epidemiologic studies. Our results show that the method of control subject selection has an impact on study response. Gender of respondent does not appear to impact response rates. However, response rates are generally worse for individuals less than 45 years old. Methods used to calculate response have a great impact on "response rate"; therefore, it is important for researchers to define exactly what the reported response rates represent and how they are derived so that data can be interpreted appropriately.

Characterisation of neurons with nitric oxide synthase immunoreactivity that project to prevertebral ganglia

Retrograde dye tracing was combined with immunohistochemistry to determine the distributions of nitric oxide synthase (NOS) immunoreactive nerve cells that project to prevertebral ganglia from the gastrointestinal tract and spinal cord of the guinea pig. An antiserum was raised against the neuronal form of NOS by selecting an amino-acid sequence specific to this form as immunogen. The antiserum recognised a single band at 150 kDa on Western blots of rat brain extract. Enteric nerve cells that were labelled by Fast Blue injected into the coeliac ganglion were not NOS immunoreactive in the small intestine, whereas 40-70% were reactive in the large intestine. Retrograde dye injected into the inferior mesenteric ganglion labels cells in the colon and rectum; 60-70% were immunoreactive for NOS. The NOS-immunoreactive nerve fibres arising in the intestine appear to end selectively around somatostatin-immunoreactive nerve cells in the coeliac and inferior mesenteric ganglia. Preganglionic nerve cell bodies in the intermediolateral column and dorsal commissural nucleus from T12 to L2 were labelled from the inferior mesenteric ganglion. Nearly 70% of neurons at each level were NOS immunoreactive. Thus, two sources of NOS terminals in prevertebral ganglia have been identified, intestinofugal neurons of the large, but not the small intestine, and sympathetic preganglionic neurons.

Spectroscopic evidence for a common electron transfer pathway for two tryptophan tryptophylquinone enzymes

Aromatic amine dehydrogenase (AADH) and methylamine dehydrogenase (MADH) are the only two enzymes known to use the cofactor tryptophan tryptophylquinone (TTQ). Each catalyzes oxidative deamination of a distinct class of primary amines. A detailed comparison of their circular dichroic spectra indicates that both proteins share a similar fold with their TTQ cofactors residing in similar environments and that this may be a useful diagnostic probe for TTQ enzymes. Alcaligenes faecalis cells induced to express AADH also express a large amount of the blue copper protein, azurin. Oxidized azurin is rapidly reduced by a catalytic amount of AADH in the presence of the substrate, tyramine. Three A. faecalis cytochromes-c and three other cytochromes-c were tested for electron transfer activity with AADH. Azurin markedly facilitated electron transfer from AADH to each cytochrome. This suggests that AADH and azurin may form an electron transfer complex with a c-type cytochrome, analogous to the crystallographically determined MADH-amicyanin-cytochrome c-551i complex (Chen, L., Durley, R. C. E., Matthews, F. S., and Davidson, V. L. (1994) Science 264, 86-90). The similarities of MADH and AADH plus the demonstration of azurin and multiple cytochromes as functional electron-transfer partners suggest that both TTQ-bearing enzymes share common mechanisms for oxidative deamination and subsequent electron transfer.

Intraperitoneal injections of Fluorogold reliably labels all sympathetic preganglionic neurons in the rat

The ability of intraperitoneal injections of a retrograde neuronal tracer, Fluorogold, to label the entire population of sympathetic preganglionic neurones was tested with a double-labelling strategy. Animals were injected intraperitoneally (i.p.) with Fluorogold, while Fast Blue or subunit B of cholera toxin were injected into a peripheral autonomic ganglion or into the adrenal gland. Sympathetic preganglionic neurones were then examined for retrogradely transported tracers. In all cases, preganglionic neurones labelled with Fast Blue or cholera toxin also contained Fluorogold, indicating that i.p. injections of Fluorogold do reliably label the entire population of sympathetic preganglionic neurones.

Aromatic amine dehydrogenase, a second tryptophan tryptophylquinone enzyme

Aromatic amine dehydrogenase (AADH) catalyzes the oxidative deamination of aromatic amines including tyramine and dopamine. AADH is structurally similar to methylamine dehydrogenase (MADH) and possesses the same tryptophan tryptophylquinone (TTQ) prosthetic group. AADH exhibits an alpha 2 beta 2 structure with subunit molecular weights of 39,000 and 18,000 and with a quinone covalently attached to each beta subunit. Neither subunit cross-reacted immunologically with antibodies to the corresponding subunits of MADH, and the N-terminal amino acid sequence of the beta subunit of AADH exhibited no homology with the highly conserved beta subunits of MADH. The absorption spectra for the oxidized, semiquinone, and reduced forms of AADH have been characterized, and extinction coefficients for the absorption maxima of each redox form have been determined. These spectra are very similar to those for MADH, indicating the likelihood of a TTQ cofactor. This was verified by the near identity of the vibrational frequencies and intensities in the resonance Raman spectra for the oxidized forms of AADH and MADH. A stable semiquinone of AADH could be observed during a reductive titration with dithionite, whereas titration with tyramine proceeded directly from the oxidized to the reduced form. AADH was very stable against denaturation by heat and exposure to guanidine. The individual subunits could be separated by gel filtration after incubation in guanidine hydrochloride, and partial reconstitution of activity was observed on recombination of the subunits. Steady-state kinetic analysis of AADH yielded a Vmax of 17 mumol/min/mg and a Km for tyramine of 5.4 microM. Substrate inhibition by tyramine was observed. AADH was irreversibly inhibited by hydrazine, phenylhydrazine, hydroxylamine, semicarbazide, and aminoguanidine. Isonicotinic acid hydrazide (isoniazid) and isonicotinic acid 2-isopropyl hydrazide (iproniazid) were reversible noncompetitive inhibitors of AADH and exhibited K(i) values of 8 and 186 microM, respectively. The similarities and differences between AADH and other amine oxidizing enzymes are also discussed.

Laue diffraction study on the structure of cytochrome c peroxidase compound I

BACKGROUND

Cytochrome c peroxidase from yeast is a soluble haem-containing protein found in the mitochondrial electron transport chain where it probably protects against toxic peroxides. The aim of this study was to obtain a reliable structure for the doubly oxidized transient intermediate (termed compound I) in the reaction of cytochrome c peroxidase with hydrogen peroxide. This intermediate contains a semistable free radical on Trp191, and an oxyferryl haem group.

RESULTS

Compound I was produced in crystals of yeast cytochrome c peroxidase by reacting the crystalline enzyme with hydrogen peroxide in a flow cell. The reaction was monitored by microspectrophotometry and Laue crystallography in separate experiments. A nearly complete conversion to compound I was achieved within two minutes of the addition of hydrogen peroxide, and the concentration of the intermediate remained at similar levels for an additional half an hour. The structure of the intermediate was determined by Laue diffraction. The refined Laue structure for compound I shows clear structural changes at the peroxide-binding site but no significant changes at the radical site. The photographs were processed with a new software package (LEAP), overcoming many of the former problems encountered in extracting structural information from Laue exposures.

CONCLUSIONS

The geometry of the haem environment in this protein allows structural changes to be extremely small, similar in magnitude to those observed for the Fe2+/Fe3+ transition in cytochrome c. The results suggest that these molecules have evolved to transfer electrons with a minimal need for structural adjustment.

The driver's license list as a population-based sampling frame in Iowa

Driver's license lists are infrequently used for population-based sampling, presumably because of suspicions of poor population coverage. The 1990 Iowa driver's license list was compared with the 1990 census to evaluate coverage by 5-year age group, sex, resident county, and urbanicity. Coverage exceeded 90% among 15- to 74-year-old men and 15- to 64-year-old women, with uniform coverage by county and county urbanicity group in these age ranges. In Iowa, these lists are convenient and cost-effective and appear to be representative for 25- to 64-year-olds. The representativeness of driver lists in regard to other factors and in other geographic regions deserves further evaluation.

Subunit b of cholera toxin labels interstitial cells of Cajal in the gut of rat and mouse

Cholera toxin subunit b was found in vivo and in vitro to label interstitial cells of Cajal in the intestine of rat and mouse. Cholera toxin-labelled interstitial cells were present in the subserosa, the myenteric plexus and the deep muscular plexus of mouse small intestine, and the deep muscular plexus only of the rat small intestine. In the large intestine of the mouse, interstitial cells were present in the subserosa and in a plexus associated with the inner surface of the circular muscle, while in the rat they were only present in the latter location. Macrophages, which were present in many of the same locations as interstitial cells, were also labelled by cholera toxin but could be distinguished from interstitial cells by their ability to take-up fluorescein isothiocyanate-labelled dextran. Labelling with subunit b of cholera toxin is a simple way of labelling interstitial cells of Cajal and which is compatible with a range of physiological and histological procedures.

The distribution of nitric oxide synthase-containing autonomic preganglionic terminals in the rat

Nitric oxide synthase (NOS)-immunoreactivity was co-localised with NADPH diaphorase activity in preganglionic sympathetic neurons and in their terminals in pre- and paravertebral sympathetic ganglia. The density of NOS-containing terminals varied between ganglia. Reactive terminals were densest in the superior cervical, stellate and inferior mesenteric ganglia, where the majority of the neurons were surrounded by reactive fibres, and the coeliac and superior mesenteric ganglia, where about half the postganglionic somata were surrounded by reactive terminals. Fibres were least abundant in the pelvic ganglia and thoracic and lumbar sympathetic chain ganglia. NOS reactivity did not coincide with the distribution of calcitonin gene related peptide immunoreactivity, a marker for the terminals of NOS-containing sensory neurons in the rat. The distribution of nerve cells and terminals suggests that NOS is present in more than one functional subpopulation of sympathetic preganglionic neurons.

Crystallographic refinement of lignin peroxidase at 2 A

The crystal structure of the major lignin peroxidase isozyme from Phanerocheate chrysosporium has been refined to an R = 0.15 for data between 8 A and 2.03 A. The refined model consists of 2 lignin peroxidase molecules in the asymmetric unit, 2 calcium ions per monomer, 1 glucosamine per monomer N-linked to Asn-257, and 476 water molecules per asymmetric unit. The model exhibits excellent geometry with a root mean square deviation from ideality in bond distances and angles of 0.014 A and 2.9 degrees, respectively. Molecule 1 consists of all 343 residues, while molecule 2 consists of residues 1-341. The overall root mean square deviation in backbone atoms between the 2 molecules in the asymmetric unit is 0.36 A. The refinement at 2.0 A confirms our conclusions based on the partially refined 2.6-A structure (Edwards, S. L., Raag, R., Wariishi, H., Gold, M. H., and Poulos, T. L. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 750-754). The overall fold of lignin peroxidase closely resembles that of cytochrome c peroxidase. A superimposition of alpha-carbons gives a root mean square deviation of 2.65 A between the two peroxidases and 1.66 A for the helices. The active sites also are similar since both contain a proximal histidine heme ligand hydrogen-bonded to a buried aspartate residue and both contain histidine and arginine residues in the distal peroxide binding pocket. The most obvious difference in the active site is that whereas cytochrome c peroxidase has tryptophan residues located in the proximal and distal heme pockets, lignin peroxidase has phenylalanines. There are four other especially noteworthy differences in the two structures. First, although the heme in cytochrome c peroxidase is recessed about 10 A from the molecular surface, the heme pocket is open to solvent. The analogous opening in lignin peroxidase is smaller which can explain in part the differences in reactivity of the two hemes. This same opening may provide the site for binding small aromatic substrates. Second, lignin peroxidase has a carboxylate-carboxylate hydrogen bond important for heme binding that is not present in cytochrome c peroxidase. Third, lignin peroxidase contains 2 structural calcium ions while cytochrome c peroxidase contains no calcium. The calciums in lignin peroxidase coordinate to residues near the C-terminal ends of the distal and proximal helices and hence are probably important for maintaining the integrity of the active site. Fourth, the extra 49 residues in lignin peroxidase not present in cytochrome c peroxidase constitutes the C-terminal end of the molecule with the C terminus situated at the "front" end of the molecule between the two heme propionates.

Crystal structure of lignin peroxidase

The crystal structure of lignin peroxidase (LiP) from the basidiomycete Phanerochaete chrysosporium has been determined to 2.6 A resolution by usine multiple isomorphous replacement methods and simulated annealing refinement. Of the 343 residues, residues 3-335 have been accounted for in the electron density map, including four disulfide bonds. The overall three-dimensional structure is very similar to the only other peroxidase in this group for which a high-resolution crystal structure is available, cytochrome c peroxidase, despite the fact that the sequence identity is only approximately 20%, LiP has four disulfide bonds, while cytochrome c peroxidase has none, and LiP is larger (343 vs. 294 residues). The basic helical fold and connectivity defined by 11 helical segments with the heme sandwiched between the distal and proximal helices found in cytochrome c peroxidase is maintained in LiP. Both enzymes have a histidine as a proximal heme ligand, which is hydrogen bonded to a buried aspartic acid side chain. The distal or peroxide binding pocket also is similar, including the distal arginine and histidine. The most striking difference is that, whereas cytochrome c peroxidase has tryptophans contacting the distal and proximal heme surfaces, LiP has phenylalanines. This in part explains why, in the reaction with peroxides, cytochrome c peroxidase forms an amino acid-centered free radical, whereas LiP forms a porphyrin pi cation radical.

Using the Mead model as a framework for nursing care

A model of nursing has no valid purpose unless it serves nurses to help make their nursing better (Fawcett, 1989). The Mead model formed the basis for nursing care of Jason, a young patient who sustained a head injury, a puncture wound and lacerations to his face, in the study presented here. Examination of the Mead Model of nursing is followed by an account of why this model was used in preference to others as a framework for Jason's care. Three components of his nursing care--wound care, communication, involvement of relatives--are discussed in relation to both the model and current knowledge. It was concluded that as a structured way of planning and giving care, the Mead model lacks adequate guidelines. A less experienced nurse using the Mead model may overlook certain aspects of care, an experienced nurse may use his/her knowledge to give high standard care using research-based information. However, models need to be tested so they may be rejected or modified as guidelines for care in this case in the United Kingdom, within a welfare-orientated society.