Mechanical ventilation: simplifying the terminology.

There is presently considerable ambiguity and confusion relating to ventilator terminology. This can be eliminated using a simple approach, visualising mechanical ventilation as an inspiratory pump, and defining trigger, limit, and cycling in this context. The trigger is the signal that starts a breath by opening the inspiratory valve, the limit is the factor which controls the way gas flows into the lung, and the cycle is the signal that stops the breath by closing the inspiratory valve and opening the expiratory valve. By identifying these three basic parameters, one can precisely dissect and interpret any of the vast ventilatory terminology.     

Invasive Streptomyces infections: six cases and literature review

Streptomyces are saprophytic soil organisms rarely known to cause invasive infections other than mycetoma. We report 6 cases of invasive Streptomyces infections and review 13 previously reported cases. Our series included 2 cases of lung abscess or pneumonitis, 3 cases of central venous catheter-related bloodstream infection, and I case of possible hypersensitivity pneumonitis. Most previous cases also included lung infections and bloodstream infections. Preexisting conditions, such as cancer, AIDS or HIV infection, presence of a central venous catheter, and prosthetic heart valve, were present in all cases since 1985. Diverse Streptomyces species were involved, consistent with the highly opportunistic nature of the infections. Clinical management depended on the clinical situation of individual cases without consensus. Available susceptibility data showed that Streptomyces organisms were consistently susceptible to amikacin; frequently susceptible to imipenem, clarithromycin or erythromycin, minocycline, and trimethoprim-sulfamethoxazole; and infrequently susceptible to ciprofloxacin and ampicillin. The diagnosis of Streptomyces infection required microbiologic and pathologic correlation to rule out contamination.     

Evidence for involvement of cyclic nucleotides in intrinsic factor secretion by isolated rabbit gastric mucosa.

Secretion of intrinsic factor (IF) has previously been demonstrated in isolated rabbit fundic mucosa maintained in organ culture. We have now investigated the possibility that cyclic nucleotides may play a role in IF secretion. A phosphodiesterase inhibitor, 3-isobutyl methylxanthine (IBMX), stimulated IF secretion nearly fourfold while increasing tissue levels of both cyclic AMP (cAMP) and cyclic GMP (cGMP). Peak IF secretion in response to IBMX was not reached until after tissue cAMP levels were maximal. Dibutyryl cAMP and 8-Br-cAMP increased secretion by the same order of magnitude as did IBMX, whereas corresponding analogues of cGMP had no such effect. Histamine increased secretion of IF. In the presence of 40 microM IBMX, histamine elevated tissue levels of cAMP, but not of cGMP, and the stimulating effect of 10 microM histamine on IF secretion was potentiated. An H2 receptor antagonist, cimetidine, blocked the increases in IF secretion and tissue cAMP levels due to histamine, and the increase in IF secretion due to IBMX. These observations are consistent with a role for cAMP in the secretion of IF by isolated gastric mucosa.