THE RELATIONSHIP OF YELLOW FEVER OF THE WESTERN HEMISPHERE TO THAT OF AFRICA AND TO LEPTOSPIRAL JAUNDICE

1. The yellow fever now in South America, the present yellow fever of Africa and the historic yellow fever of Panama and other American countries are the same disease. This conclusion is based on cross immunity tests in monkeys with strains of yellow fever virus from Africa and Brazil and on tests of sera from 25 persons, who had recovered from yellow fever in various places and at various times, for the power to protect monkeys against African or Brazilian virus strains. 2. Cases of leptospiral jaundice (Weil's disease) were present among those diagnosed as yellow fever in the recent epidemic in Rio de Janeiro. This is shown by the isolation of cultures of leptospirae from the blood of two patients by H. R. Muller and E. B. Tilden of The Rockefeller Institute, and by the demonstration by us of protective power against leptospirae and absence of protective power against yellow fever virus in the sera from two persons after recovery. The isolation of leptospirae by Noguchi and other investigators from the blood of occasional patients in past epidemics of yellow fever in a number of American countries indicates that leptospiral jaundice was present then as well and was diagnosed clinically as yellow fever. 3. The absence of protective power against leptospirae shown by the Brazilian sera which protected against yellow fever virus and the absence of protective power against yellow fever virus in the sera that protected against leptospirae point to the probability that American yellow fever is not the combined effect of leptospirae and yellow fever virus. The position of L. icteroides, isolated by Noguchi during yellow fever epidemics, now appears to be not that of a secondary invading microorganism in cases of virus yellow fever, but that of the incitant of a form of infectious jaundice, sometimes fatal, often coincident in its appearance with typical yellow fever and apparently indistinguishable from it clinically. This leptospiral disease has not hitherto been separated from true yellow fever. Noguchi's discoveries become; therefore, of the greatest significance in respect to the epidemiology and causation of yellow fever and of infectious jaundice, previously confused one with the other. In all outbreaks of supposed yellow fever hereafter the existence of the two kinds of jaundice, one due to yellow fever virus and the other to leptospirae will have to be taken into account. Only the former probably is spread by mosquitoes and requires anti-mosquito measures for its control. 4. The only difference observed by us between the American and African strains of yellow fever virus was a pronounced difference in virulence for monkeys. The virulence of the two African strains studied was very high while that of the one American strain was highly variable and usually low.

THE TRANSMISSION OF NEUROTROPIC YELLOW FEVER VIRUS BY STEGOMYIA MOSQUITOES

1. By the bites of stegomyia mosquitoes carrying neurotropic yellow fever virus, encephalitis has been produced both in white mice and in rhesus monkeys. 2. The fixed neurotropic strain of virus cannot be maintained in the mosquito host as well as can the viscerotropic strains. This is doubtless attributable in part to a smaller amount of virus ingested, because of paucity in the blood stream of the mammalian host. 3. These experiments furnish additional evidence that the long established neurotropic yellow fever virus has changed fundamentally from the parent French strain.

VACCINATION AGAINST YELLOW FEVER WITH IMMUNE SERUM AND VIRUS FIXED FOR MICE

1. After preliminary experiments in monkeys, 15 persons were actively immunized by a single injection of a dried mixture of living yellow fever virus, fixed for mice, and human immune serum, with separate injections of enough additional serum to make up the amount required for protection. 2. One person was similarly immunized by injecting immune serum and dried virus separately. 3. By titration of the sera of vaccinated persons in mice, it was shown that the immunity rose in a few weeks to a height comparable to that reached after an attack of yellow fever, and remained there throughout an observation period of 6 months. 4. Yellow fever virus could not be recovered from the blood of vaccinated persons or monkeys, except when the latter had received less than the minimal effective amount of immune serum. 5. Neutralization of yellow fever virus by immune serum took place very slowly in vitro at room temperature in our experiments, and could not have been an appreciable factor in vaccination with the serum virus mixtures. 6. A mixture of fixed virus and immune serum retained its immunizing power for 8 months when dried in the frozen state and sealed in glass. 7. It appears that the immunizing reaction after yellow fever vaccination was a part of a true infectious process, as was also the observed leucopenia.

THE USE OF MICE IN TESTS OF IMMUNITY AGAINST YELLOW FEVER

1. A method of testing sera for protective power against yellow fever is described and designated as the intraperitoneal protection test in mice. 2. The test consists essentially of the inoculation of mice intra-peritoneally with yellow fever virus, fixed for mice, together with the serum to be tested, and the simultaneous injection of starch solution into the brain to localize the virus. If the serum lacks protective power the mice die of yellow fever encephalitis. 3. The test is highly sensitive. Consequently it is useful in epidemiological studies to determine whether individuals have ever had yellow fever and in tests to find whether vaccinated persons or animals have in reality been immunized. 4. When mice were given large intraperitoneal injections of yellow fever virus fixed for mice, the virus could be recovered from the blood for 4 days although encephalitis did not occur. If the brain was mildly injured at the time of the intraperitoneal injection, the symptoms of yellow fever encephalitis appeared 6 days later, but the virus was then absent from the blood. 5. Strains of white mice vary greatly in their susceptibility to yellow fever.

THE TITRATION OF YELLOW FEVER VIRUS IN STEGOMYIA MOSQUITOES

Titrations were made of yellow fever virus in stegomyia mosquitoes, using rhesus monkeys as test animals. It was found that: (a) The average mosquito immediately after engorging on highly infectious blood contained between 1 and 2 million lethal doses of virus. The titer of freshly ingested blood was as high as 1 billion lethal doses of virus per cubic centimeter. (b) During the fortnight succeeding a meal on infectious blood there occurred a reduction of titratable virus to not more than 1 per cent of that present in the freshly fed insects. (c) The titer was somewhat higher at later periods. This rise in titer signified possibly not a multiplication, but merely an increase of extracellular virus and of that easily freed by grinding to a titratable form. (d) At no later stage did the quantity of titratable virus equal that demonstrable in freshly fed insects.

Optimized architecture for nutrition in the avascular retina of Megachiroptera

Investigations were undertaken to evaluate the unique choroidal vascular system of the Megachiroptera (fruit bats) and its possible significance for retinal nutrition. Fluorescein angiography was performed and documented on Pteropus poliocephalus. Vascular casts were made of the eye of Pteropus scapulatus. Histologic evaluation was performed on P. scapulatus. Results confirmed that each papilla has a vascular core, and a unique vascular system emanating from the optic disc. The histological appearance of the choroid and retina of P. scapulatus confirmed a vascular core to the papillae with a thin, but definite Bruch's membrane. Megachiroptera have a unique vascular system to supply nutrition to the retina consisting of capillary loops within a dense, uniform mosaic of choroidal projections or papillae, which permit the diffusion of metabolites to the retina and a heretofore undescribed vascular tuft emanating from the optic disc. We suggest that this vascular system provides nutrition by diffusion to a thick avascular retina, without any shadowing by vessels, and allows for nocturnal visual acuity and light-gathering capabilities.

A study of aspirin and clopidogrel in idiopathic pulmonary arterial hypertension

Idiopathic pulmonary arterial hypertension (IPAH) is characterised by in situ thrombosis and increased thromboxane (Tx) A2 synthesis; however, there are no studies of antiplatelet therapy in IPAH. The aim of the current study was to determine the biochemical effects of aspirin (ASA) and clopidogrel on platelet function and eicosanoid metabolism in patients with IPAH. A randomised, double-blind, placebo-controlled crossover study of ASA 81 mg once daily and clopidogrel 75 mg once daily was performed. Plasma P-selectin levels and aggregometry were measured after exposure to adenosine diphosphate, arachidonic acid and collagen. Serum levels of TxB2 and urinary metabolites of TxA2 and prostaglandin I2 (Tx-M and PGI-M, respectively) were assessed. A total of 19 IPAH patients were enrolled, of whom nine were being treated with continuous intravenous epoprostenol. ASA and clopidogrel significantly reduced platelet aggregation to arachidonic acid and adenosine diphosphate, respectively. ASA significantly decreased serum TxB2, urinary Tx-M levels and the Tx-M/PGI-M ratio, whereas clopidogrel had no effect on eicosanoid levels. Neither drug significantly lowered plasma P-selectin levels. Epoprostenol use did not affect the results. In conclusion, aspirin and clopidogrel inhibited platelet aggregation, and aspirin reduced thromboxane metabolite production without affecting prostaglandin I2 metabolite synthesis. Further clinical trials of aspirin in patients with idiopathic pulmonary arterial hypertension should be performed.

TraT: a powerful carrier molecule for the stimulation of immune responses to protein and peptide antigens

A number of integral membrane proteins (Imps) isolated from Escherichia coli have been examined for their ability to generate serum antibody responses in the absence of adjuvant. These proteins were found to stimulate high titers of serum antibody when injected into rabbits or mice in saline. The antibody titers elicited were not significantly increased by the addition of a powerful adjuvant such as IFA. Covalent conjugation of BSA, of the DNP group, and of a peptide Ag from Plasmodium falciparum to these protein carriers resulted in a significant enhancement of the immune response to the conjugated material in comparison with the response elicited when the immunogen was injected without adjuvant or was not conjugated to Imps. The antibody response to these conjugates could not be significantly increased by the addition of IFA. Thus, the Imps of E. coli represent powerful carrier molecules which, when injected into mice and rabbits, are not only capable of generating high titers of antibody to themselves, but also to molecules conjugated to them. Immunization with immunogens coupled to these proteins results in the production of high titers of antibody without the need for oil-based adjuvants, thereby avoiding the unwanted side effects of such adjuvants.

TraT: a powerful carrier molecule for the stimulation of immune responses to protein and peptide antigens

A number of integral membrane proteins (Imps) isolated from Escherichia coli have been examined for their ability to generate serum antibody responses in the absence of adjuvant. These proteins were found to stimulate high titers of serum antibody when injected into rabbits or mice in saline. The antibody titers elicited were not significantly increased by the addition of a powerful adjuvant such as IFA. Covalent conjugation of BSA, of the DNP group, and of a peptide Ag from Plasmodium falciparum to these protein carriers resulted in a significant enhancement of the immune response to the conjugated material in comparison with the response elicited when the immunogen was injected without adjuvant or was not conjugated to Imps. The antibody response to these conjugates could not be significantly increased by the addition of IFA. Thus, the Imps of E. coli represent powerful carrier molecules which, when injected into mice and rabbits, are not only capable of generating high titers of antibody to themselves, but also to molecules conjugated to them. Immunization with immunogens coupled to these proteins results in the production of high titers of antibody without the need for oil-based adjuvants, thereby avoiding the unwanted side effects of such adjuvants.

Actions of growth factors on plasma calcium. Epidermal growth factor and human transforming growth factor-alpha cause elevation of plasma calcium in mice

Specific humoral substances produced and secreted by human tumors that cause hypercalcemia have not been identified. Certain growth factors (such as epidermal growth factor, platelet-derived growth factor, and transforming growth factors-alpha and -beta) have been shown to stimulate the resorption of bone in organ culture by both prostaglandin-dependent and prostaglandin-independent pathways. In this report we demonstrate that epidermal growth factor and recombinant human transforming growth factor-alpha induce a significant rise in plasma calcium concentration when administered repeatedly to intact mice for periods ranging from 24 h to 16 d. The elevation of plasma calcium is not dependent on dietary calcium and is not invariably accompanied by an increase in systemic levels of the prostaglandin E2 metabolite 13,14-dihydro-15-keto-prostaglandin E2. The in vivo calcium-mobilizing activity of epidermal growth factor and transforming growth factor-alpha indicate that these or related growth factors need be considered as potential mediators of tumor-induced hypercalcemia.

Immune complexes, complement, and anti-DNA in exacerbations of systemic lupus erythematosus (SLE)

The usefulness of serological parameters in assessing clinical exacerbations of SLE was examined. Patients with active renal disease tend to have lower levels of CH50 and C3 and highest levels of immune complexes detected by C1qBA than those patients with extrarenal manifestations only. Patients with a combination of both active extrarenal and renal disease are more likely to demonstrate the lowest levels of CH50, C4, and C3. However, immune complex levels are not higher than levels detected in patients with only active nephritis. A normal C3 level argues against active nephritis. Low complement levels without appreciably elevated levels of C1qBA suggest that significant renal disease is unlikely. The serial measurements that best reflect evolving clinical activity and which may serve as markers of impending exacerbation are, in decreasing order of usefulness: C4, CH50, C1qBA, C4, C3 and ADA. However, a combination of CH50, C4, C3 and C1qBA appeared to be the most useful. Given various serologic changes, guidelines for following patients are offered.

Effects of a bone resorptive factor from human cancer ascites fluid on rat bone cell calcium and cyclic AMP

The effects of a bone resorptive protein isolated from human cancer ascites fluid on bone cell calcium and cyclic AMP were studied with fetal rat cells. The osteoclast-activating factor increased bone cell calcium uptake at 37 degrees C and 4 degrees C with no direct effects on calcium efflux. Concentrations of the resorptive factor that increased in vitro bone resorption and cell calcium uptake had no effect on cyclic AMP. The effects of the protein on calcium uptake were not specific for bone cells, and large increases were also observed in isolated fetal rat skin cells. These studies suggest that increases in the permeability of the cell membrane to calcium are involved in the mechanism of action of the ascites fluid resorptive protein.

Stimulation of bone resorption in organ culture by salt-free extracts of Solanum glaucophyllum

Addition of a desalted aqueous extract made from dried leaves of Solanum glaucophyllum produced a marked stimulation of bone resorption in a culture system in vitro. This result indicates that, like the biologically active forms of vitamin D, the active material in the plant not only stimulates intestinal calcium absorption but increases bone mobilization as well.