Personal sampling in parallel with open-face filter cassettes and IOM samplers for inhalable dust--implications for occupational exposure limits.

Parallel personal sampling was carried out with the open-face filter cassette and the IOM sampler for inhalable dust for nine types of organic dust. Parallel samples numbering 749 were obtained from 152 plants. Extremely large values and outliers were disregarded, and the remaining data for each type of dust were divided into subsets according to type of product or work task, and analyzed with the aid of linear regression. The coefficient of regression for each subset ranged between 0.2 and 0.7. Hypothetical occupational exposure limits (OELs) for inhalable dust were calculated based on the linear relation obtained between the dust concentrations measured with the open-face filter cassette and the IOM sampler. The fraction of person days with time-weighted average (TWA) concentrations exceeding the calculated hypothetical OELs for inhalable dust was obtained from the distribution of measured TWA inhalable dust concentrations. Based on the results of this study and the difference in sampling efficiency for large particles between the two samplers, it was concluded that the numerical value of the OEL for inhalable dust may be set at approximately twice the numerical value of the corresponding limit value for "total dust." Additional consideration of recently discovered health effects, and technical and economical factors may result in other numerical values of future OELs for inhalable dust.

Studies of the synthesis of sugar phosphonates related to 3-deoxy-D-manno-2-octulosonic acid (Kdo).

In attempting to synthesize the analogue of beta-Kdo (2R)-2-carboxy-6-(1',2'-dihydroxyethyl)-4,5-dihydroxy-D-manno-1,2 lambda 5-oxaphosphorinan-2-one (6) as an inhibitor of the enzyme CMP-Kdo synthetase, which is involved in the biosynthesis of the lipopolysaccharide component of the outer membrane of Gram-negative bacteria, (2R)-6-(1',2'-dihydroxyethyl)-2-ethoxy-3,4,5-trihydroxy-4,5:1', 2'-di-O-isopropylidene-D-glycero-D-talo-1,2 lambda 5-oxaphosphorinan-2-one (8) was converted into (2S)-6-(1',2'-dihydroxyethyl)-4,5-dihydroxy-4,5:1',2'-di-O-isop rop ylidene-2-vinyl-D-manno-1,2 lambda 5-oxaphosphorinan-2-one (16), but alkene cleavage to give the target carboxyphosphonate failed. Reduction-oxidation-Arbuzov reaction on the intermediate (2R)-6-(1',2'-dihydroxyethyl)-2-ethoxy-4,5-dihydroxy-4,5:1', 2'-di-O-isopropylidene-D-manno-1,2 lambda 5-oxaphosphorinan-2-one (11) gave the 2S isomer of the protected target compound, but removal of the protecting groups gave the acyclic product dilithium (D-manno-2,3,4,5,6-pentahydroxyhexyl)phosphinatoformate (24). N.m.r. studies of the intermediates allowed assignment of stereochemistry at P for all compounds via 2JP,H coupling constants.

Synthesis of esters of phosphonoformic acid and their antiherpes activity.

Aliphatic and aromatic mono-, di-, and triesters of phosphonoformic acid (foscarnet) were synthesized. The triesters were prepared by the Michaelis-Arbuzov reaction and were hydrolyzed to di- and monoesters. The compounds were tested for antiviral activity on isolated herpes simplex virus type 1 (HSV-1) DNA polymerase, in a HSV-1 plaque reduction assay, and on a cutaneous HSV-1 infection in guinea pigs. None of the esters inhibited the activity of isolated HSV-1 polymerases. Monoesters with a free carboxylic group and diesters with an aromatic carboxylic ester function were active against the cutaneous herpes infection. Mono- and diesters with an aromatic phosphonic ester group also showed activity in the plaque-reduction assay. However, mono- and diesters with an aromatic phosphonic ester group also showed activity in the plaque-reduction assay. However, mono- and diesters with aliphatic carboxylic ester groups were inactive in all test systems. The results show that all three acidic groups of phosphonoformic acid must be free in order to get antiviral activity at the enzyme level. However, certain esters of this acid may be biotransformed to the acid itself to give antiherpes activity.

Trisodium phosphonoformate, a new antiviral compound.

Trisodium phosphonoformate selectively inhibits cell-free DNA polymerase activity induced by herpesvirus. The new inhibitor has an antiviral effect on herpes simplex virus types 1 and 2, pseudorables virus, and infectious bovine rhinotracheitis virus in cell culture. It has a good therapeutic activity against cutaneous herpes simplex virus infection in guinea pigs.

Inhibition of influenza virus ribonucleic acid polymerase by ribavirin triphosphate.

Ribavirin 5'-triphosphate (RTP), derived from the broad-spectrum antiviral compound ribavirin (Virazole), can selectively inhibit influenza virus ribonucleic acid polymerase in a cell-free assay. Ribavirin and its 5'-monophosphate have no effect on the polymerase. The inhibition is competitive with respect to adenosine 5'-triphosphate and guanosine 5'-triphosphate. RTP also inhibits ApG- and GpC-stimulated influenza virus ribonucleic acid polymerase. Since ribavirin is phosphorylated in the cell, the inhibition of influenza multiplication in the cell may also be caused by RTP.