Mechanisms of platelet aggregation by viridans group streptococci

The direct aggregation of platelets is thought to be an important event in the pathogenesis of viridans streptococcal endocarditis, but the mechanisms for platelet activation are unknown. We evaluated the processes by which two endocarditis-producing strains of viridans group streptococci activated human platelets in vitro, as measured by platelet cyclooxygenase activity, secretion, and aggregation. Addition of either streptococcal strain to platelets suspended in whole plasma resulted in a mean lag phase of 15.3 min, followed by platelet secretion and brisk aggregation. The lag phase duration was dependent on the platelet donor and appeared to be a function of direct platelet-bacterial interaction. Aggregation was partially inhibited by 20 muM [corrected] indomethacin and blocked completely by 1 mg of apyrase, an extracellular ADP hydrolase, per ml. Neither strain aggregated washed platelets suspended in Tyrode solution alone. However, both strains produced maximal aggregation when the platelet suspension was supplemented with 10% (final concentration) normal plasma. Studies with factor-deficient plasmas demonstrated that exogenous fibrinogen was required for aggregation. One or more additional plasma components were needed, which eluted with a molecular weight of 67,000 to 130,000 on gel permeation chromatography. These cofactors have not been described for other platelet agonists, which suggests that viridans streptococci may aggregate human platelets by a novel mechanism.

Ganciclovir for the treatment and suppression of serious infections caused by cytomegalovirus

Ganciclovir is a congener of acyclovir with in vitro activity against cytomegalovirus. Ninety-seven patients with the acquired immune deficiency syndrome (AIDS) and a serious cytomegalovirus infection received ganciclovir, 3.0 to 15 mg/kg per day. Viremia cleared during drug therapy in 88 percent of patients. Viral shedding from urine and throat ceased or became inapparent during treatment in 78 percent and 68 percent of patients, respectively. Among patients with cytomegalovirus retinitis, 87 percent of evaluable patients had improvement in (30 of 60) or stabilization (22 of 60) of their disease. However, when the drug was discontinued, progression or recurrence of disease always occurred. Long-term suppressive therapy with ganciclovir, 5.0 mg/kg five to seven times weekly, prevented the recurrence of cytomegalovirus disease (p less than 0.001). The drug was eliminated by renal excretion, and in patients without renal impairment (creatinine clearance rates of more than 60 ml/minute/1.73 m2), ganciclovir has a mean half-life of 4.2 hours. Significant neutropenia and leukopenia occurred in 55 percent and 32 percent of patients, respectively.

Prevention and treatment of experimental herpes simplex virus encephalitis with human immune serum globulin

Pooled human immunoglobulin suitable for intravenous administration (IGIV) was evaluated in the prophylaxis and treatment of herpes simplex virus (HSV) type 1 encephalitis in a murine model. Four-week-old BALB/c mice received a single intraperitoneal injection of IGIV or saline 24 h before or up to 24 h after intranasal infection with 10(4.6) PFU of HSV type 1. Treatment with IGIV was protective against death, and the protective effects were dose and time dependent. Treatment with IGIV blocked the production of HSV antibody by infected mice and reduced the number of trigeminal ganglia containing latent virus. Removal of neutralizing antibody from the IGIV pool did not eliminate the protective effect, whereas F(ab)2 fragments of IGIV, which had virus-neutralizing activity that was identical to that of native IGIV, conferred no protection against death. Pooled human IGIV was effective for the prevention and treatment of HSV encephalitis in mice. Antibody-mediated protection required the Fc portion of the immunoglobulin molecule but did not require the direct neutralization of virus.

Comparison of the effects of histamine H1- and H2-receptor agonists on large and small airways in normal and asthmatic subjects

It is accepted that histamine H1-receptors are present on human bronchial smooth muscle and that they mediate bronchoconstriction. However, the role of the histamine H2-receptor in the airways of man is less certain. In ten non-asthmatic and five asthmatic subjects we have compared the effects of inhalation of a specific H1-receptor agonist, betahistine, a specific H2-receptor agonist, impromidine and the combined H1- and H2-receptor agonist, histamine, on specific airways conductance and measurements from partial expiratory flow-volume curves. Both histamine and betahistine induced reproducible dose-dependent bronchoconstriction in all subjects, as assessed by all measurements made. Impromidine had no effect on measurements of airways function in either group of subjects. These results confirm the presence of bronchoconstricting H1-receptors, and the absence of significant numbers of H2-receptors on human bronchial smooth muscle. There is no difference in the distribution of these receptors in normal and asthmatic subjects.

Effect of combinations of difluoromethylornithine (DFMO) and 9[(1,3-dihydroxy-2-propoxy) methyl]guanine (DHPG) on human cytomegalovirus

Both the nucleoside analog 9[(1,3-dihydroxy-2-propoxy)methyl]guanine (ganciclovir; DHPG) and the polyamine synthesis inhibitor difluoromethylornithine (DFMO) have been reported to inhibit replication of cytomegalovirus (CMV) in vitro. In these studies, DHPG inhibited human CMV replication at concentrations of 0.1 microM or greater, while DFMO was active (and then only inconsistently) at 5 mM or greater. (DFMO was added to cells 3 days before virus to maximize polyamine depletion.) However, DHPG combined with DFMO synergistically inhibited the replication of CMV strain AD169 and one wild-type CMV strain in human foreskin fibroblasts; the effect was evident on both virus yield and plaque formation. The synergistic effect of these two drugs on CMV replication could potentially be exploited clinically to limit drug toxicity or increase efficacy.

Effect of hypoglycin A on insulin release

Thirty experimental and fifteen control Wistar rats were studied to determine whether hypoglycin A influences insulin levels in the body to contribute to the state of hypoglycemia usually observed in Jamaican vomiting sickness, a condition arising after ingestion of unripe ackees. This fruit also grows in other Caribbean islands, as well as North and Central America. Hypoglycin A is one of the toxic compounds found in unripe ackees and is capable of inducing hypoglycemia. A fall in blood glucose occurred after administration of hypoglycin A. The lowest level of 42.60 +/- 4.84 mg/dl was attained 3 hr after administration of the drug. This alteration of blood glucose from the fasting level of 80.31 +/- 5.20 mg/dl was significant (P less than 0.01). The blood glucose level in the control rats showed no significant change from the fasting level. The insulin level in portal and peripheral blood showed no significant change. Results showed that, although hypoglycin A induced severe hypoglycemia after intravenous application, there was no significant change in insulin levels. This observation suggests that hypoglycin A has a mechanism of action other than an alteration in insulin levels to induce hypoglycemia.

Quantitative immunocytofluorographic analysis of CD4 surface antigen expression and HIV infection of human peripheral blood monocyte/macrophages

HIV infection of CD4-bearing lymphocytes alone does not fully explain the immune dysfunction of AIDS. Monocyte/macrophages infected with HIV may serve as a reservoir of HIV, may function abnormally and may transmit infection to other susceptible cells, thus playing a central role in the development of the immunodeficiency of AIDS. Quantitative analysis of surface antigens and measurement of HIV antigens in infected cells have been difficult using the conventional approach of immunofluorescent staining of cells on slides. We have developed a system that maintains monocyte/macrophages in suspension culture for at least four months. Through immunocytofluorographic single cell analysis we have shown that CD4 antigen is present on monocytes, and that a tenfold increase in expression occurs during the first two weeks in culture. In contrast, LeuM3 antigens decreased to background levels in the course of long-term culture. Using anti-HIV p24 antibody, we have demonstrated that monocyte/macrophages can be infected with HIV. Up to 70% of cells from individual donors could be infected. The techniques herein described allow in vitro quantitation of some of the mechanisms by which HIV infection of monocyte/macrophages may contribute to the immunodeficiency states associated with AIDS.

Recurrent herpes labialis in skiers. Clinical observations and effect of sunscreen

Recurrent orofacial herpes infection may be triggered by high altitude skiing, presumably because of solar ultraviolet radiation exposure. Six (12%) of a group of 51 subjects with a history of skiing-triggered herpes observed during 1 week of high altitude skiing experienced reactivations of orofacial herpes a median of 3 1/2 days after exposure. Within this group, application of a sunscreen with a sun protection factor (SPF) of 15 failed to influence the reactivation rate as compared with a placebo. Reactivation of herpes triggered by skiing is common. As application of a sunscreen with an SPF of 15 did not appear to influence the reactivation rate, alternate approaches to the control of recurrent orofacial herpes are needed.

Decompression sickness incidence over 63 months of hypobaric chamber operation

U.S. Army hypobaric chamber operations over a 63-month period were retrospectively reviewed, and incidence rates for decompression sickness were calculated. The overall incidence rate was 1.38/1000 exposures. The rate for interior technicians monitoring chamber operations was 6.16/1000 exposures. The rate for students was 0.64/1000 exposures. The increased incidence of decompression sickness for technicians was especially pronounced for the 10,668-m and 13,106-m flight profiles. Rapid decompression after the 7,620-m flight profile did not appear to increase the incidence of decompression sickness.

Pneumocystis carinii and Toxoplasma gondii infections in patients with AIDS

Pneumocystis carinii and Toxoplasma gondii are the commonest protozoans causing infections in patients with acquired immunodeficiency syndrome (AIDS). P. carinii is almost exclusively a pulmonary pathogen and caused the commonest serious infection experienced by AIDS patients. The clinical findings are those of progressive pneumonia. Diagnosis requires microscopic examination of lower respiratory secretions or lung tissue. Pentamidine or combinations of trimethoprim and sulfamethoxazole are equally effective (85% recovery), but about one-half of patients thus treated experience severe toxicity. T. gondii infections occur primarily in the brain; patients present with focal seizures or neurologic deficit and have focal abnormalities as assessed by computed tomography. Serologic tests for toxoplasmosis are rarely diagnostic in AIDS patients, and most patients are treated empirically with a combination of pyrimethamine and sulfonamide. Less invasive diagnostic tests and better chemotherapeutic agents are required for both pneumocystosis and toxoplasmosis.

Interferon therapy for condylomata acuminata

Current therapy for condylomata acuminata (genital warts) is not consistently effective. Therefore, we conducted a randomized, double-blind trial to compare interferon alpha-2b with placebo in the treatment of this disorder. Our rationale was that interferon has both antiproliferative and antiviral properties. The placebo or interferon (1 X 10(6) IU) was injected directly into one to three warts three times weekly for three weeks. The injections were well tolerated by both groups of patients. The side effects of fever, chills, myalgia, headache, fatigue, and leukopenia occurred more commonly in the interferon group than in the placebo group, but such effects rarely disrupted daily routines. Only 13 of 296 patients (4 percent) discontinued therapy because of side effects (11 in the interferon group and 2 in the placebo group). Twenty-six other patients were excluded from analysis because of a loss to follow-up or other deviations from protocol, thus leaving 257 patients in the final evaluation. At one week after the completion of therapy, interferon had produced a large and significantly greater reduction in mean wart area (a 62.4 percent decrease), as compared with placebo (a 1.2 percent increase in mean area) (P less than 0.001). At the conclusion of the study (13 weeks after the completion of therapy), the mean wart area was still decreased 39.9 percent below the initial size in the interferon group, whereas it had increased by 46 percent over base-line measurements in the placebo group (P less than 0.001). At the same time, all treated warts had completely cleared in 36 percent of the interferon recipients and in 17 percent of the placebo recipients (P less than 0.001), whereas treated warts progressed in 13 percent of the interferon recipients and in 50 percent of the placebo recipients (P less than 0.001). We conclude that injection of interferon alpha-2b directly into genital warts appears to be an effective and fairly well-tolerated form of therapy.

Nuclear cardiology: a comparison of equilibrium gated blood pool and gamma camera first-pass measurements for the assessment of left-ventricular regional wall motion

There are two major problems remaining for the successful assessment of left-ventricular regional wall motion (RWM) using nuclear cardiology. These are as follows. Which technique should be used: first pass or equilibrium? Secondly, which views should be used to give full information about the RWM of the left ventricle? This paper specifically considers each of these questions and concludes that equilibrium blood pool imaging in both the right anterior oblique and left anterior oblique projections is currently the best option.

Keeping track of needs in communal and exchange relationships

Keeping track of needs in communal and exchange relationships was investigated in two experiments. In both, subjects could check to see if another person needed help. The first experiment tested the hypotheses that When there is no opportunity for the other to reciprocate in kind, keeping track of the other's needs will be greater if the person desires a communal relationship with the other than if the person desires an exchange relationship with the other. If the person desires an exchange relationship with the other, keeping track of the other's needs will be greater when an opportunity for the other to reciprocate in kind exists than when it does not. If a communal relationship is desired, the existence of an opportunity for the other to reciprocate in kind will not influence keeping track of the other's needs. The results of the first experiment supported all three hypotheses. The second experiment tested and found support for the hypothesis that even when nothing can be done to help the other, keeping track of the other's needs will be greater if a communal relationship is desired with the other than if an exchange relationship is desired.

Cefuroxime axetil for treatment of uncomplicated gonorrhea

Oral cefuroxime axetil (1 g) plus probenecid cured 29 of 30 urethral and 6 of 6 rectal gonococcal infections in men; alone the drug cured 22 of 23 urethral and 4 of 6 rectal infections. No toxicity was observed. Cefuroxime axetil alone is effective for urethral gonorrhea in males; rectal gonorrhea probably requires additional probenecid.

Passive immunotherapy for encephalitis caused by herpes simplex virus

Passive administration of antiviral antibody has been assessed in animal models as a potential form of treatment for infections due to herpes simplex virus (HSV). Previous investigative work has demonstrated the beneficial effect of immune serum administered either before or after HSV infection of mice. In some studies the protective effect of antibody was abrogated in the absence of T lymphocytes, an observation suggesting that cellular effector mechanisms may be necessary for antibody efficacy. In the present study of a mouse model of encephalitis caused by HSV type 2, a 0.5-ml dose of human immunoglobulin (1,250 mg of immunoglobulin G/kg of body weight) prepared at pH 4.25 for intravenous administration reduced mortality and prolonged survival when administered by intraperitoneal injection 24 hr before or up to 8 hr after intranasal viral challenge. The serum titer of HSV-neutralizing antibody and the response to therapy were dose dependent. Clinical trials of passive immunotherapy for severe HSV infections may be warranted.

Dapsone-trimethoprim for Pneumocystis carinii pneumonia in the acquired immunodeficiency syndrome

All patients with the acquired immunodeficiency syndrome and a first episode of Pneumocystis carinii pneumonia seen at the San Francisco General Hospital between November 1984 and April 1985 were evaluated for oral treatment with dapsone (100 mg/d) plus trimethoprim (20 mg/kg body weight X d). All 15 patients who met the entry criteria improved clinically and radiographically within 3 to 10 days after starting treatment. Repeat pulmonary function tests and gallium lung scans after 3 weeks of therapy also showed improvement. Although side effects occurred in 14 patients, in only 2 were they severe enough to require stopping therapy. Both of these patients had worsening skin rash, and dapsone-trimethoprim therapy was stopped after 10 days. When compared with trimethoprim-sulfamethoxazole or pentamidine used to treat P. carinii pneumonia in similar patients, oral dapsone-trimethoprim is at least as effective, seems to be better tolerated, and may have a lower frequency of serious side effects.

Paromomycin therapy of endemic amebiasis in homosexual men

A prospective evaluation was made of the therapeutic efficacy of paromomycin, an orally administered, nonabsorbable aminoglycoside, in 114 homosexual men with mild-to-moderate (nondysenteric) intestinal amebiasis. All patients received 25-35 mg/kg daily in three divided doses for seven days. Of the 80 patients with gastrointestinal complaints at the onset of therapy, 55 (80%) of 69 were asymptomatic within four to six weeks after completion of treatment; 11 patients were lost to follow-up. Paromomycin produced long-term eradication of intestinal Entameba histolytica infection in 92% of all men evaluated. The rate of microbiologic cure among patients with symptoms at the onset of therapy was comparable to that among asymptomatic individuals. Paromomycin was well tolerated, with mild diarrhea during therapy the only frequent adverse effect (67% of patients). Thus, paromomycin is an effective alternative to conventional multi-drug therapy for intestinal amebiasis, and it has the advantages of low toxicity, brief duration of therapy, and a high rate of patient compliance.

Treatment of gonorrhea with first- and second-generation cephalosporins and other new beta-lactam antibiotics

Aqueous procaine penicillin, ampicillin, and amoxicillin have been used successfully in treatment of gonococcal infections for many years. Many of the new beta-lactam antimicrobial agents subsequently have proved effective for treating these infections as well. First-generation cephalosporins are less active (by weight) than second-generation cephalosporins, which, in turn, are less active than third-generation drugs. Single-dose therapy of uncomplicated mucosal gonococcal infections with first-generation cephalosporins has resulted in generally unacceptably low cure rates of less than 90% in most studies, whereas parenterally and orally administered second-generation cephalosporins show good clinical efficacy. Both second- and third-generation cephalosporins are active against beta-lactamase-producing Neisseria gonorrhoeae. The extended-spectrum and ureido-penicillins are active in vitro against non-beta-lactamase-producing N. gonorrhoeae and have parallel activity in vivo. Single doses of aztreonam, the first monobactam studied in humans, have also shown excellent clinical efficacy.