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P G Janssens

Publications and source records attributed to P G Janssens.

At least 19 recordsLinked to original sources
PubMed1998

[Ronald Ross: a century of the transfer of malaria by mosquitoes].

Ronald Ross is a brilliant and polyvalent mind. When orientated towards medicine he took the training amateurishly and ended up with a limited qualification. After 2 years as a ship doctor, he attended the compulsory complementary training in order to be admissible in the IMS, the garrison life left him with plenty of time to engage in his hobby's: painting for a short while, writing, poetry and mathematics. By the end of his first term he questioned the sense of his medical activities and decided, with a view to his career, to acquire a Public Health diploma and some complementary bacteriology. During his second term the malaria problem drew his attention. As he was unable to detect the parasite of Laveran in the blood of patients with malarial fevers he concluded that the parasite had been some lucky microscopic finding without any value and turned this parasite into ridicule. During his leave in 1894 he met Manson, who showed him the technique to put the parasite in evidence and convinced him to search for its vector which, to his opinion, should be a mosquito. Ross decided to follow this lead. With his minimal parasitological knowledge and an entomological background limited to the external appearance of mosquitoes he endeavoured to establish the life cycle of the malarial parasites. Notwithstanding some service bounded transfers, he followed the fate of the filaments of the crescents and discovered the parasite on the stomachwall of dapled-winged mosquitoes. During his special mission in Calcutta and in the absence of suitable malaria infections in man he shifted to bird proteosoma (now P. relictum) with a grey mosquito (culex) as vector. He demonstrated the complete life-cycle ending in the salivary glands of the mosquitoes and succeeded in transmitting this infection by mosquito-bites in healthy birds. This climax in his research was crowned by the attribution in 1902 of the Nobel Prize for Medicine. In the mean time he resigned from the IMS and was appointed as "Lecturer on Tropical Diseases" at the Liverpool School. He reoriented his activities to the prevention of malaria by control of the vector in its aquatic larval stage, which he tried out and promoted during his journeys to the West African Coast and other countries. His current were variegated but without salient details. Through the survey of the parasite index and the assessment of the spleen rate in children he founded the malariometry as a epidemiological tool, focussed attention on the relation of malaria and the community and on the complexity of the transmission dynamics. By handing in his resignation at the Liverpool School and moving to London he hampered further his scientific productivity. The tardy foundation of the Ross Institute did not stimulate a new impetus. He suffered a stroke which left him partially crippled an he died in his Institute.

Animals↗
PubMed1995

[Louis Pasteur (1822-1895). A century later].

An overview of the amazing series of successive and diverse items worked on by the chemist and physicist Pasteur starts with the asymmetry of paratartrates, switches over to the fermentations and ends in the fight against diseases of invertebrates and vertebrates, including man. It is the wonderful story of an exceptional contribution to the advancement of knowledge, which was made possible by his keen observation skill, his rigorous and innovative methods and his careful judgement. A retrospective analysis of the inner man may impair somewhat the fame of Pasteur. He was a lonely man, in need of solitude to be able to make full use of his thinking capacity, foreboding secretiveness and shrewdness , which are contradictory to his careful writing down day after day of all the details of his thinking and research in his notebooks by now available to the scientific community. He was furthermore selfish, domineering, inflexible, impulsive and inclined to engage in endless controversies. But on the contrary his motivation to accept new assignments was subordinate to their public welfare value and as a rule he endeavoured to work on the problems in the field and in association with those concerned. He was courageous when struck by a cerebral hemorrhage at middle age, so that its aftermath hardly hampered his research activities. The dimness cast on his personality is not up to his pioneer role within a general conservative climate among the medical and even scientific profession, antagonistic to innovation. Pasteur has been a founder of stereochemistry, microbiology and its applications, immunology, bacterial vaccines, pasteurisation and a promotor of prevention and hygiene. These overwhelming achievements justify to keep alive the recognition of the outstanding stature of Pasteur.

Chemistry↗
PubMed1994

[Plague in Zaire].

Two endemic foci of plague have been discovered in Zaïre, the first in the Ituri in 1928, the other in North-Kivu in 1938. They are situated in the region of the great East-African Rift and are adjacent to the Ugandan focus, identified in 1877. A strict surveillance of these endemic foci makes it possible to state that, between 1928 and 1959, 632 cases of plague have been diagnosed in the Ituri, or 20 a year, and 190 in the N-Kivu, or 8 a year. Since then several flare ups have been notified. This situation is very remote from the "black death" concept. Yersinia pestis presents, besides its bipolar staining, many other characteristics such as the indispensable presence of iron to produce virulence, or the fermentation of glycerine and reduction of nitrates as parameters for the identification of 3 biovars, corresponding with a specific geographic distribution: antiqua, medievalis, orientalis or maritima. The antigenic structure has been discussed and also the role of plasmids. Plague is a disease of rats, a variegated gathering of rodents with different degrees of tolerance and sensitiveness to Y.pestis, living in a frail equilibrium. The multimammate houserat was in the Ituri the principal agent until the black rat Rattus rattus invaded the region and a new balance came into being. The frequent changes in taxonomy of Mastomys caused uncertainties. The transmission is due to fleas subject to a blocking of their ventriculum by Y.pestis. Fleas play an active part in the process. Man is only a casual intruder. The pathogenicity is related to its invasiveness and its intracellular localization in macrophages and other R.E. cells, in which Y.pestis can survive. The bubo is characteristic of the disease. In Zaïre a septicaemic tendency has been observed, with a possible involvement of the C.N.S. and of the lungs. The latter may produce among the surrounding relatives primary pneumonic plague. The clinical diagnosis ought to be confirmed by bacteriologic investigation of the puncture fluid of the bubo, the blood, and when necessary the C.S.F. or the sputum by culture and/or animal inoculation. The treatment became very efficient since the availability of sulfamides and later antibiotics: aminoglycosides, chloramphenicol, tetracyclines. A timely administration ensures practically recovery. As soon as Y.pestis was identified vaccination was put into practice and in the first place by killed germs (Haffkine's lymph) to day with formalized F1, for mass vaccination live attenuated strains were used: Tjiwidej (Otten), E.V. (Girard), K120 (Grasset).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

[Seroepidemiological study of malaria in the Algerian Sahara].

On the basis of geoclimatic characteristics, the Saharan region of Algeria (area, 2 million km2) is made up of several subregions; analysis of the historical data on malaria in this region seems to show that the epidemiological situation is closely linked to climatic and hydrographic conditions. A longitudinal sero-epidemiological study was conducted in this vast region from September 1983 to April 1985. The general findings do not appear to support the existence of active foci of transmission, but analysis of the data for certain oases and localities leads to a quite different assessment of the epidemiological situation. At Ouargla, for example, the serological results obtained by indirect immunofluorescence show prevalence of under 5% in the four successive surveys, whereas in Heïha oasis over 50% of subjects over 30 years of age were found to be seropositive. The results of the longitudinal seroepidemiological surveys conducted in a number of localities and oases in the Saharan region reflect the diversity of epidemiological settings and provide evidence that there is low-level malaria transmission in some oases such as Heïha, Yakou, Ihérir and probably in In-Salah. These surveys confirm that malaria transmission has been halted in the former foci such as Ouargla and Timimoune. Finally, the longitudinal sero-epidemiological study shows there are movements of potential parasite carriers from countries south of the Sahara and therefore that oases associated with trans-Saharan trade are vulnerable.

Adolescent↗
PubMed1991

[Fever. A guideline in the development of medical thinking].

Fever being one of the best known symptoms, and appearing so frequently that it is often assimilated to "illness", has brought us to try and find out what "fever" means in a general way; in other words, we examined its medical and scientific concept throughout the centuries. In the course of primitive and archaic periods, fever, as well as diseases, was placed in the supernatural sphere and was reserved to magico-religious practices. Hippocrates will change this method by devoting himself to meticulous clinical observation, considering fever as a sign of illness, and by characterizing the different types of fever. When considering the mechanisms of its appearance, he will stick to the theory of "body-humors" and the "theories of numbers." Galenos will adapt that theory to Aristotle's philosophy and, doing so, he made it last for several centuries. The Renaissance will place critical thinking higher than slavish acceptance of theories, but it will not start any revolution in the appreciation of fevers. The possibility of contagion is mentioned, but the latter will only be well established by Pasteur and Koch. The breakthrough of microscopy into pathology will have to wait for Virchow. Thermometry will have to wait two centuries between Santorio and Wunderlich. The fever-concept will stay vague until experimental physiology and medicine will acquire their vested rights owing to Magendie and Bernard. They will moreover be followed by the microbiological era. The breakthrough will be the consequence of experimental proofs of the existence of a temperature-centre located in the hypothalamus and the pre-optic area. The discovery of endogenous as well as exogenous pyrogens has contributed to the creation of rational models which cover nearly completely the problem of body-temperature and fever. This long way did not progress as a regularly favourable evolution but, now and again, appeared figureheads who allowed us to approach the truth nearer and nearer.

Fever↗
PubMed1989

[Charles Ledger and the Cinchona].

Reading "The life of Charles Ledger", the book written by Gabriele Grammiccia, one notices immediately, what an extraordinary personality Ledger was. He was typically British and belonged to that generation for which, as he wrote himself, "the fact of being a British subject is in itself a reason of pride, including as such a definite obligation to serve the country." This blinding patriotism of even modest British people all over the world, gave the City, as well as the British Empire, a remarkable place in the world trade. The history of Ledger's life, derived from the most authorized sources, is a real adventure novel. At the age of eighteen, he goes to Lima (Peru), in order to find a job. It takes him but a few years to build up his own import-export business. In Tacna, in the very South of Peru, near the Chilean and Bolivian borders (the region where he lived), alpaca wool and quinquina bark are some of the most traded goods. These two products will determine his further life. The principles of his commercial policy were as follows: to buy first quality products, and pack the goods in such a way that they reach the British or European customers in perfect condition, thereby always giving a preferential treatment to the Commonwealth. The quinquina bark trade is hampered by the fact that there is a very great quantity of varieties, each having a different concentration of alkaloids in its bark. To buy the best species, Cinchona calisaya, one needs a perfect knowledge of these trees. The expertise is only to be obtained by visiting the regions where the quinquina tree grows and finding one's way with the help of willing "cascarilleros", the Indians collecting the quinquina bark. During one of his exploration trips, Ledger was fortunate enough to enjoy the service of a Bolivian called Manuel, who faithfully assisted him and his family for years. Together they ranged, at great pains, across every possible region, even the most remote ones; they succeeded in identifying the richest collections of quinquina trees and signing buying contracts on the spot. The most beautiful trees are usually unsuitable for any form of exploitation. In order to understand the special atmosphere that made the solving of the quinquina problems so arduous in the course of time, it seems best to place them in a historical perspective.(ABSTRACT TRUNCATED AT 400 WORDS)

Cinchona↗