Hi, Monica.  As Ruth pointed out, truncating a term will turn off the
MeSH mapping feature in the PubMed database.  So, a search with cancer*
will search for cancer and all its variations (cancers, cancerous, etc)
and not include the official MeSH term, Neoplasms.  Also, truncation
will turn off the automatic exploding of MeSH terms (in the PubMed
database).  So if you search with neoplasm*, it will search for neoplasm
and all its variations, but it will not include all the narrower MeSH
terms in the Tree.  Lung Neoplasm* gets fewer hits than (Lung Neoplasms
OR Lung Neoplasm*) because truncating the MeSH term turns off the
automatic exploding, and therefore one wouldn't get the narrower MeSH
terms in the Tree, such as Pulmonary Blastoma.

To see what PubMed is doing with your search term from the PubMed main
page, click on the Details tab (under the search box).  

To get the most hits, we tell our EBM students to search their MeSH
terms in natural language order & without the MeSH brackets and OR it
with its truncated version (if applicable) and OR it with its Entry
Terms (& any other relevant keyword synonyms one can think of).  

For example...
Basic Search (9 hits):
"Common Cold"[Mesh] AND "Ascorbic Acid"[Mesh] AND "Zinc"[Mesh]
 
Intermediate Search (13 hits): 
Common Cold AND Ascorbic Acid AND Zinc
 
Advanced Search (23 hits):
(Common Cold OR cold* OR acute coryza) AND (Ascorbic Acid OR L-Ascorbic
Acid OR L Ascorbic Acid OR Vitamin C OR Ferrous Ascorbate OR Hybrin OR
Magnesium Ascorbicum OR Magnorbin OR Sodium Ascorbate) AND Zinc 
 
Again, this basic PubMed MEDLINE search with just MeSH terms gets 506
results...
"Diabetes Mellitus, Type 2"[Mesh] AND "Metformin"[Mesh] AND
"Insulin"[Mesh]
 
....removing the MeSH brackets (intermediate search) gets 1392 hits:
Type 2 Diabetes Mellitus AND Metformin AND Insulin
 
...and this advanced PubMed MEDLINE search with MeSH terms in natural
language order and without the MeSH brackets and with a few synonyms not
in the Entry Terms list got nearly 3 times the hits (1601) hits as the
basic search:
(Type 2 Diabetes Mellitus OR Adult-Onset Diabetes Mellitus OR
Ketosis-Resistant Diabetes Mellitus OR Non-Insulin-Dependent Diabetes
Mellitus OR Slow-Onset Diabetes Mellitus OR Stable Diabetes Mellitus OR
Maturity-Onset Diabetes Mellitus OR Maturity Onset Diabetes Mellitus OR
MODY OR NIDDM OR Type II Diabetes Mellitus OR Type two Diabetes Mellitus
OR Type 2 Diabet* OR Type II Diabet* OR Type two Diabet*) AND (Metformin
OR Dimethylbiguanidine OR Dimethylguanylguanidine OR Glucophage) AND
(Insulin OR Novolin OR Humulin OR Iletin OR Velosulin)

Take care,

Tanya

Tanya Feddern-Bekcan, MLIS, AHIP, MOT, OTR/L
http://www.geocities.com/nqiya/libraryarticles.html  formerly Tanya
Feddern
305.243.6648 - [log in to unmask] - 305.325.9670 (fax)
EBM Theme Co-Director & Reference and Education Librarian
Louis Calder Memorial Library - University of Miami Miller School of
Medicine


"A library without a librarian is a reading room."-- Jenny Garcia of the
University of Wyoming, MLS, AHIP

-----Original Message-----
From: UK medical/ health care library community / information workers
[mailto:[log in to unmask]] On Behalf Of Ruth Muscat
Sent: Tuesday, February 12, 2008 10:47 AM
To: [log in to unmask]
Subject: Re: Pubmed truncation

Hi Monica,

It's probably because using the truncation symbol in Pubmed turns off
the
MeSH mapping function. So maggot* only looks for textword variants but
misses all the stuff indexed under the MESH term 'Larva'.

Best wishes,

Ruth

____________________________________________________________

Ruth Muscat
Clinical Information Support Librarian
The Friends of the Children of Great Ormond Street Library
Institute of Child Health
30 Guilford Street
London WC1N 1EH
Tel: 020 7405 9200 x 5175
Fax: +44 (0) 20 7831 0488
____________________________________________________________