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Searching for Chemicals in MEDLARS® DatabasesThe publication Medical Subject Headings -Supplementary Chemical Records has been discontinued. This tool contained the listings for chemicals which are not MeSH headings and have been mentioned in a significant way in journals indexed in MEDLINE. These chemical names may be found online in the Name of Substance (NM) field. The NM field is searchable. However, the NM exists only in the dictionary files, MEDLINE, the MEDLINE Backfiles, and the MEDLINE-derived portions of the following composite files: AIDSLINE, CANCERLIT, HealthSTAR and in the MEDLINE-derived portion and DART subfile in TOXLINE. MeSH, ChemID, and CHEMLINEChemicals are listed in three dictionary files online: MeSH, ChemID, and CHEMLINE. The MeSH file is updated several times each week, throughout the year. It is the most current of all the online files listing chemicals. ChemID and CHEMLINE are updated several times a year and therefore may not have an entry for a chemical that does have a record in MeSH (which means that there are citations present in MEDLINE and/or the MEDLINE Backfiles). See Figure 1 for an example of locating the same chemical in the MeSH, ChemID and CHEMLINE files. Note that File MeSH does not indicate which MEDLINE files contain postings for any chemical. Files ChemID and CHEMLINE both contain a Locator (LO) field which indicates the files in which a particular chemical appears. Keep in mind that these Locator listings may be several months out-of-date, depending on when you are conducting your search. Also note that searching MeSH and ChemID are roughly comparable in price; for example, it costs about $0.11 to find and download the information for fluoromethane. It costs $1.79 to retrieve this same information in CHEMLINE (a file containing Chemical Abstracts Service (CAS®) royalty data). Which Chemical Dictionary File Should You Use?You might want to consider restricting your search for a chemical to MeSH if you were only interested in citations appearing in MEDLINE or the MEDLINE Backfiles and you wanted the most current information available. You would use ChemID in place of or in addition to MeSH, when you were interested in citations from the full range of MEDLARS files (including TOXNET files) and you want the convenience of seeing the Locator files (realizing that they are not completely current). You would use CHEMLINE last, in addition to or in place of MeSH and ChemID, if you couldn't find a chemical in the first two files. There are chemicals which are only listed in CHEMLINE; generally, the citations for these chemicals appear only in TOXLIT and the TOXLIT backfile which are also CAS royalty files. Searching the non-Dictionary Databases for non-MeSH ChemicalsOnce you have found your chemical in MeSH, ChemID or CHEMLINE, in most MEDLARS files it is easiest to retrieve citations about that chemical by searching on the Registry Number. The Registry Number may be entered in all MEDLARS files (including TOXNET files) qualified by (rn) or without qualification. In MEDLINE, MEDLINE Backfiles, and MEDLINE-derived files, you may choose to substitute the Name of Substance qualified by (nm) for the Registry Number. In TOXNET files, searching on the registry number is easiest and yields consistent results because all records contain an RN field. In the composite file TOXLINE, not all records contain a Registry Number, so it is best to search on the Registry Number ORed together with the chemical name as a Text Word. To display the Name of Substance field (in those files where it exists), you need to print the Registry Number (RN) field. If you give the command PRINT NM, you will see the following response online: 'NM' IS NOT A VALID PRINT PARAMETER. COMMAND IGNORED. This situation is analogous to the one for displaying subheadings. You can search on the subheading field, but you cannot give the command PRT SH; subheadings display only as part of the MeSH heading field. Similarly NMs display only as part of the Registry Number field. See Figure 2 for an example of retrieving on the registry number for fluoromethane in MEDLINE and displaying the Registry Number field containing the Name of Substance. See Figure 3 for an example of retrieving information on fluoromethane in TOXLINE.
Figure 1 - Searching for a chemical Name in MeSH, ChemID, and CHEMLINE
SS 1 /C?
USER:
file mesh
PROG:
YOU ARE NOW CONNECTED TO THE MESH VOCABULARY (1997) FILE.
SS 1 /C?
USER:
fluoromethane (nm)
PROG:
SS (1) PSTG (1)
SS 2 /C?
USER:
prt dl
PROG:
1
NM - fluoromethane
RN - 593-53-3
RR - 59122-96-2 (ion(1+))
RR - 20666-44-8 (13C-labeled cpd)
RR - 3832-44-8 (18F-labeled cpd)
RR - 20666-45-9 (14C-labeled cpd)
SY - methyl fluoride
HM - *HYDROCARBONS, FLUORINATED
DA - 810626
MR - 830801
RO - O:RLS
RO - C:NLM
RO - M:ACS
SO - Arch Phys Med Rehabil 1981;62(3):100
TH - Merck Index, 9th ed, #4060
FR - 24
* Indicates the frequency of
postings in MEDLINE and the
Backfiles, but not the
specific file locations.
NO - RN given refers to parent cpd
RY - C
UI - C029999
SS 2 /C?
USER:
show cost
PROG:
THE ESTIMATED TOTAL ONLINE COST FOR THIS 0 MINUTE MESH VOCABULARY
SESSION IS $ 0.11.
SS 1 /C?
USER:
file chemid
PROG:
YOU ARE NOW CONNECTED TO THE CHEMID (NON-ROYALTY) FILE.
SS 1 /C?
USER:
fluoromethane (nm)
PROG:
SS (1) PSTG (1)
SS 2 /C?
USER:
prt dl
PROG:
1
RN - 593-53-3
MF - C-H3-F [EINECS:TSCAINV]
N1 - Fluoromethane [EINECS]
N1 - Methane, fluoro- (8CI)(9CI) [TSCAINV]
NM - Fluoromethane [MESH]
NM - [LIST] Methyl fluoride [UN2454] [Flammable gas] [DOT]
NM - [LIST] UN2454 [DOT]
SY - EINECS 209-796-6 [EINECS]
SY - Fluoromethane [NLM]
SY - Fluorure de methyle [French] [NLM]
SY - Fluoruro de metilo [Spanish] [NLM]
LLO - DOT
LO - CANCERLIT ; EINECS ; HSTAR ;
* Shows the files where
citations on fluoromethane
can be found.
MEDLINE ; MED80 ;MED85 ; MED90 ;
MESH ; TOXLINE ; TOXLINE65 ;
TOXLIT ; TOXLIT65 ; TSCAINV ;
SUPERLIST
EM - 9701
SS 2 /C?
USER:
show cost
PROG:
THE ESTIMATED TOTAL ONLINE COST FOR THIS 0 MINUTE CHEMID
SESSION IS $ 0.11.
SS 1 /C?
USER:
file chemline
PROG:
YOU ARE NOW CONNECTED TO THE CHEMLINE (ROYALTY) FILE.
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USER:
fluoromethane (nm)
PROG:
SS (1) PSTG (1)
SS 2 /C?
USER:
prt dl
PROG:
1
RN - 593-53-3
MF - C-H3-F
N1 - Methane, fluoro- (8CI)(9CI)
NM - Fluoromethane [MESH]
SY - Fluoromethane [NLM]
SY - Fluorure de methyle [French] [NLM]
SY - Fluoruro de metilo [Spanish] [NLM]
SY - Methyl fluoride [CAS:MESH]
LO - CANCERLIT
* Shows the files where
citations on fluoromethane
can be found.
LO - EINECS
LO - HSTAR
LO - MEDLINE
LO - MED80
LO - MED85
LO - MED90
LO - MESH
LO - TOXLINE
LO - TOXLINE65
LO - TOXLIT
LO - TOXLIT65
LO - TSCAINV
EM - 9502
SS 2 /C?
USER:
show cost
PROG:
THE ESTIMATED TOTAL ONLINE COST FOR THIS 0 MINUTE
CHEMLINE SESSION IS $1.79.
Figure 2 - Retrieving on RN and Displaying the Name of Substance in MEDLINE
YOU ARE NOW CONNECTED TO THE MEDLINE (1994 - 97) FILE.
SS 1 /C?
USER:
593-53-3
* The Registry Number for
fluoromethane.
PROG:
SS (1) PSTG (1)
SS 2 /C?
USER:
prt include nm
* PRINT commands may not be
used with NM.
PROG:
'NM' IS NOT A VALID PRINT PARAMETER. COMMAND IGNORED.
SS 2 /C?
USER:
prt include rn
* The NM will display in the RN
field in MEDLINE, MEDLINE Backfiles,
MEDLINE-derived files, and the DART
subfile in TOXLINE.
PROG:
1
UI - 94368117
AU - Hyman MR
AU - Page CL
AU - Arp DJ
TI - Oxidation of methyl fluoride and dimethyl ether
by ammoniamonooxygenase in Nitrosomonas europaea.
RN - EC 1. (Oxidoreductases)
RN - EC 1.7.3.- (ammonia monooxygenase)
RN - 0 (Hydrocarbons, Fluorinated)
RN - 0 (Methyl Ethers)
RN - 115-10-6 (dimethyl ether)
RN - 50-00-0 (Formaldehyde)
RN - 593-53-3 (fluoromethane)
* The NM is displayed here.
RN - 67-56-1 (Alcohol, Methyl)
SO - Appl Environ Microbiol 1994 Aug;60(8):3033-5
Figure 3 - Retrieving on RN and Displaying the RN field in TOXLINE
file toxline
PROG:
YOU ARE NOW CONNECTED TO THE TOXLINE (1981 FORWARD,
NON-ROYALTY) FILE.
SS 1 /C?
USER:
593-53-3 * RN for fluoromethane.
PROG:
SS (1) PSTG (16)
SS 2 /C?
USER:
1 or fluoromethane (tw)
PROG:
SS (2) PSTG (18)
SS 3 /C?
USER:
1 and fluoromethane (nm)
PROG:
SS (3) PSTG (1)
* Only one of the eighteen citations
retrieved contains fluoromethane
in the Name of Substance (NM) field.
SS 4 /C?
USER:
prt include rn
PROG:
1
AU - Green T
TI - The metabolic activation of dichloromethane and
chlorofluoromethane in a bacterial mutation assay
using Salmonella typhimurium.
SI - TOXBIB/84/013878
* TOXBIB is the MEDLINE-derived
subfile in TOXLINE.
SO - Mutat Res; VOL 118, ISS 4, 1983, P277-88
RN - 0 (Hydrocarbons, Chlorinated)
RN - 0 (Hydrocarbons, Fluorinated)
RN - 0 (Hydrocarbons, Halogenated)
RN - 0 (Mutagens)
RN - 593-53-3 (fluoromethane)
* The NM is displayed in
the RN field.
RN - 593-70-4 (chlorofluoromethane)
RN - 75-09-2 (Methylene Chloride)
SS 4 /C?
USER:
2 and not 3
PROG:
SS (4) PSTG (17)
SS 5 /C?
USER:
prt 1 include rn
* In TOXLINE, only MEDLINE-derived records
and DART subfile records have a Name of
Substance (NM) field.
PROG:
1
CN - UNIV COLLEGE DUBLIN
TI - KINETICS AND MECHANISMS FOR THE REACTIONS OF
HALOGENATED ORGANIC COMPOUNDS IN THE TROPOSPHERE -
STEP-HALOCSIDE/AFEAS WORKSHOP, WITH COVER LETTER
DATED 032494
SI - TSCATS/442284
* This record comes from the TSCATS
subfile of TOXLINE.
SO - EPA/OTS; Doc #86940000219
RN - 56-23-5; 71-55-6; 74-84-0; 74-98-6; 75-10-5;
75-28-5; 75-37-6; 75-43-4; 75-44-5; 75-45-6;
75-46-7; 75-68-3; 75-73-0; 75-87-6; 75-89-8;
76-02-8; 76-05-1; 100-42-5; 110-83-8; 306-83-2;
334-99-6; 353-36-6; 353-49-1;353-50-4; 354-32-5;
354-33-6; 354-34-7; 359-35-3; 377-36-6; 421-14-7;
422-56-0; 425-82-1; 431-89-0; 507-55-1; 556-82-1;
593-53-3;
* RN for fluoromethane without NM.
TSCATS records do not have NMs.
593-70-4; 679-86-7; 690-22-2; 763-32-6; 811-97-2;
927-84-4; 1493-02-3; 1674-10-8; 1691-17-4;
1717-00-6; 1885-48-9; 2551-62-4; 2837-89-0;
3822-68-2; 6117-91-5; 6185-26-8; 7631-99-4;
7722-84-1; 7727-37-9; 7732-18-5; 7782-44-7;
7782-50-5; 10028-15-6; 10102-43-9; 10102-44-0;
16413-86-8; 21811-29-0; 69884-58-8; 70490-95-8;
73761-32-7; 108083-11-0; 118986-32-6; 119437-62-6;
119437-63-7; 134469-96-8; 134469-97-9;
134469-98-0; 134469-99-1; 138495-42-8;
139702-33-3; 143645-30-1; 144109-03-5;
145252-03-5; 147703-38-6; 147703-39-7
SS 5 /C?
USER:
prt si
* This displays the Secondary Source
ID (SI) fields, indicating the
subfile sources for the other
records retrieved in a search on
the RN associated with fluromethane.
PROG:
1
SI - TSCATS/442284
.
.
.
16
SI - BIOSIS/89/05815
17
SI - HEEP/83/04303
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Searching for Chemicals