Antibióticos e a falta de controle

Há algum tempo atrás, falei sobre as premissas que estão implícitas em uma

hipótese científica. Agora, vamos ver a importância de se ter um

controle nos experimentos.

Teste de inibição por antibióticos. Cada pastilha branca contém uma concentração de determinado antibiótico que pode impedir a bactéria de crescer, formando os anéis mais transparentes.Imaginem que eu resolvi partir para a

ciência Globo Repórter (alterna entre saúde/alimentação, ambiente e emprego) e quero desenvolver drogas que combatem o câncer

- como se câncer fosse uma coisa só. Eis que, após um processo árduo de

triagem de compostos, eu encontro uma molécula promissora. Vamos

chamá-la de fator X.Melhor não, fator X tem conotação de droga que

causa mutações em todo filme. Vamos chamá-la de poção Gummy.Em

testes com células tumorais em cultura, eu percebo que minha poção

Gummy consegue matar 99% das mesmas. Prêmio Nobel a caminho! Consegui

matar 99% das células tumorais com uma pequena dose de poção Gummy! Vou

publicar um artigo relatando minha descoberta no grande periódico

Tibiriçá News and Chemical Agents. Mas, um dos revisores me pergunta

qual a letalidade da minha poção Gummy em células normais, não

tumorais. Humm, interessante, esqueci este detalhe...

Ao jogar a poção em um frasco com células normais, descubro que ela

mata 100%. Ok, adiem o Nobel. Patentear água sanitária como

quimioterápico não deu certo.O que me faltou em meu

experimento? - Além de noção e vergonha na cara? - Me faltou o

controle. Experimentos científicos precisam de algo que os MythBusters

nunca fazem, os controles positivos e/ou negativos. Eles são experimentos muito parecidos com o

que se quer testar e servem para garantir que o efeito observado é causado

pelo proposto, e não por qualquer outra coisa. Controle

negativo é aquele onde você vai repetir quase tudo o que fez, mas sem o

"princípio ativo" do seu experimento. No meu caso, seria

testar as células tumorais com a água que dissolvi minha poção

meu hipoclorito para ver se apenas a água já não interfere nos

resultados que obtive. Também precisaria testar meu princípio ativo em

outro tipo de célula, normal, para garantir que os efeitos que estou

observando acontecem apenas em células tumorais, e não no corpo todo.

Não que isso seja 100% garantido, quimioterápicos comuns costumam ter

efeito sobre células normais, mas muito mais severos em células

tumorais, de forma que cumprem o seu papel.E acontece esse tipo de coisa em artigos? Opa, claro:Resistência

a antibióticos por bactérias é uma das maiores preocupações da medicina

moderna. Bactérias capazes de sobreviver ao tratamento são um problema

crescente, principalmente em hospitais, pois em alguns casos droga

nenhuma é capaz de ajudar o paciente e pouco se pode fazer além disso.

Em um estudo sobre a prevalência de resistência a antibióticos na

China, pesquisadores resolveram buscar o gene da ß-lactamase, uma enzima que degrada antibióticos como a penicilina..

Normalmente, o que se faz é coletar uma amostra - com aquele cotonete

que o povo do CSI usa - e cultivar as bactérias em um ambiente que

contém antibiótico. Assim, quem crescer é resistente. Mas há algumas

desvantagens neste método: só se pode fazer isso com bactérias

cultiváveis, as que não crescem em meio de cultura escapam do teste e,

organismos que tenham crescimento lento podem demorar semanas para

crescer e dar o resultado. Daí a idéia de se detectar o gene de

resistência.

Detectar um gene conhecido é uma tarefa relativamente simples. Basta

sintetizar um pedacinho da sequência do gene conhecido como primer. O

primer vai servir de "semente" para a sequência de DNA que se quer

detectar. Se ela estiver presente na amostra, o primer vai se ligar a

ela e uma polimerase de DNA - enzima que faz a cópia de moléculas de

DNA - vai extender aquela região, que vai ser detectada depois.A bactéria escolhida foi a Streptococcus pneumoniae,

bem comum em nosso sistema respiratório, mas com potencial para graves

problemas de saúde como pneumonia, meningite e infecções em vários

outros órgãos. Os pesquisadores detectaram uma frequência assustadora

do gene em 91% dos isolados. Assustadora não só pelo grande número,

este gene de resistência nunca havia sido encontrado neste tipo de

bactéria. Os genes foram sequenciados e depositados no GenBank (aliás, ainda estão lá).

Acontece que os pesquisadores esqueceram de um pequeno detalhe. Eles

não realizaram o controle negativo de utilizar uma amostra sem

bactérias para testar se encontravam o gene lá também. Para amplificar

o DNA colhido, eles utilizaram uma enzima chamada Taq polimerase, uma polimerase de DNA de bactéria termófila (Thermus aquaticus, que sobrevive em temperaturas de até 70°C) capaz de aguentar as variações de temperatura utilizadas no procedimento PCR. E ela traz alguns poréns.

Os fabricantes de Taq não utilizam a T. aquaticus para fazer mais enzima, eles inserem o gene da enzima em outra bactéria, a E. coli, muito mais fácil de cultivar. E como eles sabem que a E. coli

possui este gene que inseriram? Junto da Taq, colocam um gene de

resistência a penicilina e adicionam penicilina ao meio de cultura para

impedir outros microrganismos de crescerem. O mesmo gene que foi

detectado em Streptococcus pneumoniae. Exatamente o mesmo. O gene de resistência que encontraram na verdade era um contaminante.

Se eles tivessem utilizado um controle sem bactérias no experimento,

veriam que ainda ocorre a detecção do gene de resistência. Justamente

porque a Taq estava contaminada com ele. E todos os resultados

que tiveram foram decorrentes disso. Agora eu pergunto, quantos outros

não encontraram genes de resistência por pura e simples contaminação, simplesmente por que não fazem o controle negativo?Fonte:

Koncan, R., Valverde, A., Morosini, M., Garcia-Castillo, M., Canton, R., Cornaglia, G., Baquero, F., & del Campo, R. (2007). Learning from mistakes: Taq polymerase contaminated with -lactamase sequences results in false emergence of Streptococcus pneumoniae containing TEM Journal of Antimicrobial Chemotherapy, 60 (3), 702-703 DOI: 10.1093/jac/dkm239 Read the comments on this post......

Koncan, R., Valverde, A., Morosini, M., Garcia-Castillo, M., Canton, R., Cornaglia, G., Baquero, F., & del Campo, R. (2007) Learning from mistakes: Taq polymerase contaminated with  -lactamase sequences results in false emergence of Streptococcus pneumoniae containing TEM. Journal of Antimicrobial Chemotherapy, 60(3), 702-703. DOI: 10.1093/jac/dkm239  Learning from mistakes: Taq polymerase contaminated with  -lactamase sequences results in false emergence of Streptococcus pneumoniae containing TEM


See original: Research Blogging - All Topics - Portuguese Antibióticos e a falta de controle

@slominski Personalized search will put a hurting on the SEOers, but I won't be shedding any tears.

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Prehistoric Pygmy Sea Cow Discovered in Madagascar

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The fossil "water bushpig"—as the locals call it—fills in a gap between primitive land-dwelling mammals to today's aquatic sea cows, a new study says.





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See original: National Geographic News Prehistoric Pygmy Sea Cow Discovered in Madagascar

Testing the reliability and validity of computer-mediated social support measures among older adults: a pilot study.

Comput Inform Nurs. 2004 Jul-Aug; 22(4): 211-9
Nahm ES, Resnick B, Gaines J

With the increasing number of older adult online users, the Internet and e-mail are becoming a new source of social support for older adults. To assess this computer-mediated social support, two traditional social support measures were modified: (1) the Lubben Social Network Scale and (2) the Medical Outcomes Study Social Support Survey. The purpose of this pilot study was to test the reliability and validity of these modified measures. This study was a single group descriptive study with two data collection points. Data were collected using Web surveys. A total of 38 older adult participants completed the first survey; 35, the second survey. The findings of this preliminary study provided evidence for the reliability, content validity, and, to a limited extent, construct validity, of the modified measures. Additional studies with a larger representative sample are needed to further examine the psychometric aspects of these measures.

See original: HubMed - "social network" online Testing the reliability and validity of computer-mediated social support measures among older adults: a pilot study.

Cancer and the computerized family: towards a clinical ethics of "indirect" Internet use.

Med Health Care Philos. 2008 Sep; 11(3): 337-41
Simon C, Schramm S

The normative dimensions of Internet use among patients and their families have not been studied in much depth in the field of clinical ethics. This study considers cancer-related Internet use among families and friends of cancer patients, and how that use of the Internet may affect patients and patient care. Interviews were conducted with 120 cancer patients, most of whom (76%) reported that family, friends, and others in their social network used the Internet in some way related to the patient's cancer. Many patients (73%) did not request this online help from their social networks, yet found it helpful and comforting nonetheless. Other patients were less positive about the helpfulness of the online efforts of friends and relatives. A significant proportion of patients (39%) also felt that the online information they received was prescreened or edited in some way. Very few patients recalled that their clinicians ever discussed these and other issues with them. The study illustrates that indirect Internet use is a central feature of the cancer experience. In contrast to other literature in this area, the study suggests that indirect Internet use may have normatively positive and negative implications for patients. These implications point towards the importance of studying and understanding indirect Internet use-and Internet use in general-in the field of clinical ethics.

See original: HubMed - "social network" online Cancer and the computerized family: towards a clinical ethics of "indirect" Internet use.

Evaluation of an online discussion forum for emergency practitioners.

Health Informatics J. 2007 Dec; 13(4): 255-66
Curran JA, Abidi SS

Knowledge is a critical element in the delivery of quality healthcare. In a busy emergency department (ED) clinicians attempting clinically relevant discussion with their peers face multiple interruptions and a lack of sustained meaningful interactions. Information and communication technologies such as online discussion forums enable practitioners to share practice knowledge at times that fit into their daily workflow. We conducted an experiment in which we provided emergency clinicians with access to an asynchronous discussion forum as a medium to support development of an online social network for information exchange. The outcomes were evaluated using a social network perspective to better understand the knowledge seeking and sharing behaviors among rural and urban emergency practitioners participating in the online discussion forum. The online discussion forum created an opportunity for emergency practitioners from multiple ED sites to engage in dialogue around topics that were relevant to their practice learning needs.

See original: HubMed - "social network" online Evaluation of an online discussion forum for emergency practitioners.

[Self-help from the cyberspace?--An analysis of self-help forums for patients with bipolar affective disorders]

Psychiatr Prax. 2008 Jan; 35(1): 28-32
Schielein T, Schmid R, Dobmeier M, Spiessl H

OBJECTIVE: The study aimed to evaluate if and how online self-help forums are used by patients with bipolar affective disorders. METHODS: Within a six-months period 1200 postings of 135 users in two German language forums were analysed with respect to fields of interest and self-help mechanisms. RESULTS: The topics most discussed were social network of the patients, symptoms of the illness, and medication. Disclosure, online-group cohesion as well as empathy and support were the main self-help mechanisms. CONCLUSIONS: Our study reveals that the social network is very important for patients coping with bipolar affective disorders. We infer that the main interest in participating in online forums for bipolar affective disorders is to share emotions. Attention to those aspects should be given also in psychoeducative programs.

See original: HubMed - "social network" online [Self-help from the cyberspace?--An analysis of self-help forums for patients with bipolar affective disorders]

'Mind control' experiences on the internet: implications for the psychiatric diagnosis of delusions.

Psychopathology. 2006; 39(2): 87-91
Bell V, Maiden C, Muñoz-Solomando A, Reddy V

BACKGROUND: The DSM criteria for a delusion indicate that it should not include any beliefs held by a person's 'culture or subculture'. The internet has many examples of people reporting 'mind control experiences' (MCEs) on self-published web pages, many of which suggest a community based around such beliefs and experiences. It was hypothesized that some of these reports are likely to reflect delusional beliefs and the hyperlinks between web reports were likely to show evidence of social structure, demonstrating the 'culture or subculture' exemption to be increasingly redundant in light of new technology. SAMPLING AND METHODS: Texts from web sites reporting MCEs (n = 10), experience of cancer (n = 10), depression (n = 10) and being stalked (n = 10) were identified, and were blind-rated by three independent psychiatrists for the presence of delusions. Hyperlinks from web sites reporting MCEs were used to create a network structure; this was compared with a size-matched, randomly generated network and known social networks from the literature using social network analysis. CONCLUSIONS: The sampled web-published accounts of MCEs are highly likely to be influenced by delusional beliefs. Social network analysis suggests there is significant evidence of an online community based around these beliefs. The fact that individuals can form a community based on the content of a potentially delusional belief presents a paradox for the DSM diagnostic criteria for a delusion, and suggests the need to revise and revisit the original operational definition in the light of these new technological developments.

See original: HubMed - "social network" online 'Mind control' experiences on the internet: implications for the psychiatric diagnosis of delusions.

Gender, cancer experience and internet use: a comparative keyword analysis of interviews and online cancer support groups.

Soc Sci Med. 2006 May; 62(10): 2577-90
Seale C, Ziebland S, Charteris-Black J

A new method, comparative keyword analysis, is used to compare the language of men and women with cancer in 97 research interviews and two popular internet based support groups for people with cancer. The method is suited to the conjoint qualitative and quantitative analysis of differences between large bodies of text, an alternative to the 'code and retrieval' approach used in much thematic analysis of qualitative materials. Web forums are a rich source of data about illness experience and gender differences. Marked differences in the performance of gender are evident. These differences follow linguistic and other behavioural patterns (such as social network differences) established in other contexts. Men with prostate cancer indicate in research interviews that they are more likely to seek information on the internet; women with breast cancer that they are more likely to seek social and emotional support. Men's concerns cluster around treatment information, medical personnel and procedures. Their experience of disease is more localised on particular areas of the body, while women's experience is more holistic. Women's forum postings orientate much more towards the exchange of emotional support, including concern with the impact of illness on a wide range of other people. Women's use of superlatives as well as words referring to feelings indicate their enactment of greater emotional expressivity. Web forums are platforms for an intensification of men's knowledge gathering activities. Web forums, though actually quite publicly visible, appear to be subjectively experienced by both sexes as relatively private places for the exchange of intimate personal information. The 'privacy' of the breast cancer forum facilitated interactions found in other studies to be characteristic of women's friendship groups.

See original: HubMed - "social network" online Gender, cancer experience and internet use: a comparative keyword analysis of interviews and online cancer support groups.