- Email: [email protected]
Levels of urinary-chloride excretion in a hot climate
294
LABORATORY MEETING
T h e degree of " resistance " shown is much less than that observed in natural resistant populations of anophelines e . g . A , stephensi in Saudi Arabia and d. sundaicus in Java and adults of the induced " resistant " strain continue to be knocked down and irritated by the insecticide. It is concluded that such " resistance " as has been induced is not of the real pe~'Tnanent genetic type but is rather a result of increased " vigour tolerance " i.e. the selection of some factor or factors, other than a gone or genes of resistance, which enable the mosquitoes to withstand higher dosages of insecticide. A comparison of mortalities among 4th stage larvae of the twentieth selected generation of the larval exposure series and of the parent unexposed stock at two dosages of D D T - i n alcohol-water solution was demonstrated. V.
THE EFFECT OF D D T AND BHC-SELECTION OF ADULTS OF TWO DIELDRIN-BHC-RESlSTANT STRAINS OF A. gambiae, (MR. G. DAVIDSON, MISS C. E. JACKSON AND MISS J. CHALKLEY). Adults of two strains of dieldrin-BHC-resistant A. gambiae from Northern Nigeria have been exposed in successive generations to sublethal dosages of D D T and of BH C and the survivors reared from. With both strains and with both insecticides a marked initial fall in susceptibility was noticeable, but a limit in selection dosage was soon reached at a level indicative not of real resistance but of increased " vigour tolerance." Mortalities at two different dosages of each insecticide among mosquitoes of the parent stock strains and the third selected generations were demonstrated. T h e inability to change significantly the susceptibility to D D T or the degree of resistance to B H C of dieldrin-BHC-resistant A. gambiae by selection with these insecticides is further proof of the permanent genetic nature of this resistance. THE CHROMOSOMES OF Anopheles gambiae. (Miss C. E. JACI~ON). T h e salivary glands of 4th-stage larvae of A. gambiae dissected out by gently pulling off the head and squeezing out the contents of the thorax, are fixed in 33 per cent. acetic acid, stained with aeetocarmine and deeolourized with 45 per cent. acetic acid. T h e preparation is squashed to spread the chromosomes and examined under phase contrast at a magnification of 400 x. Larvae are reared at a lower temperature than is customary in order to retard their growth. Preparations of the hybrid larvae resulting from the cross of the Kano strain (insecticide resistant) with the Lagos strain (susceptible) show the chromosomal differences between the two strains. These may be due only to the fact that the two parental strains are geographically separated populations, but due consideration must also be given to the fact that one is resistant to insecticides while the others not. It is hoped to continue the comparisons of the chromosomal complements of the strains kept at the Ross Institute to ascertain whether there is any chromosomal rearrangement associated with resistance. VI.
A MUTANT IN Anopheles gambiae. (Miss C. E. JACKSON). In order to obtain mutants with a view to establishing linkage groups in A. gambiae, about 275 males were exposed to a dose of 1,000r X-rays. This was done with the co-operation of the Radiotherapy Department of University College Hospital, using 140 Kv, mA5 for 10 mins. 18 secs. These males were mated with unexposed, unfertilized females from the same colony, and the F1 and F, females examined. Several females were found with four distinct bands on the palps as compared with the normal wild type 3-banded palp. An examination of 200 females of the parent colony showed no such 4banded females. Taxonomically this 4-banding is characteristic of the variety A. gambiae melas. VII.
LIVERPOOL SCHOOL OF TROPICAL MEDICINE DEPARTMENT
OF TROPICAL MEDICINE
Dr. C. S. a n d Mrs. L. A. L e i t h e a d : Levels of urinary-chloride excretion in a hot climate.* Histograms displayed estimations of the sodium-chloride content of random samples of urine * A survey carried out at the invitation of the Kuwait Oil Company, with the co-operation of Kuwait State Medical Service.
295
LABORATORY M E E T I N G
from 2,043 men exposed to a high environmental temperature, analysed according to nationality and to the apparent state of health of the individuals concerned. Most of the examinations were performed by the Fantus method on urine samples obtained from Kuwait Oil C~mpany employees who, for widely diverse reasons, attended the general out-patients department at the Ahmadi Clinic in Kuwait during the years 1951-56. Smaller numbers of Volhard estimations were made on urine samples obtained in the summer months of f956 from apparently healthy British and Arab employees of the same Company. For comparison, the results were shown of 49 estimations (42 by the Volhard, seven by the Fantus technique) of sodium-chloride in urine from overt cases of heat illness in the European crews of oil-tankers in the Persian Gulf in the hot season of 1956. T h e histograms showed : i. A wide range of urinary salt excretion in the four larger groups, with a raised lower limit in each of the two " apparently healthy " groups. ii. Mean values for all the groups (except that of heat illness) equal to, if not greater than, the mean values usually quoted for Europeans in cool climates. This finding in urines obtained from locaI Kuwaiti and Bedouin Arabs is of particular interest. iii. Strikingly low urinary salt excretion in marine cases of heat illness (heat syncope or collapse ; anhidrotie heat exhaustion ; salt and water deficiency heat exhaustion ; heat hyperpyrexia and heat stroke).
DEPARTMENT OF ENTOMOLOGY AND PARASITOLOGY
Dr. W. A. F. Webber, Dr. G. Crisp, Mr. A. I. Wright and Mr. P. Williams : Records of Onchocerca f o u n d at postmortem examination of Welsh cattle. T h e records of Onchocerca were obtained by examining tissues collected postmortem from cattle slaughtered at Wrexham abattoir. Adult worms were found in the gastro-splenic omentum and the connective tissue round the nucha! ligament, which were the only tissues examined ; and microfilariae were found in skin taken from the base of the ear and the sternal, inguinal and pastern regions. Most of the Cattle came from areas in Wales and Cheshire, but some records have been obtained of Irish beasts. MicrofiIariae or adult worms or both forms have been found in about 25 per cent. of the Irish cattle and 60 per cent. of the Welsh and Cheshire cattle. Adult worms have been recovered from the gastro-splenic omentum of 31 of the 263 animals examined ( = 12 per cent.), from the nuchal connective tissue of 44 out of 249 animals ( = 18 per cent.), and microfilariae have been found in the skin of 53 out of 164 animals examined ( = 32 per cent).
Dr. M. M. J. Lavoipierre and Mr. W. N. Beesley : A n e w record of Stasisia rodhaini (Diptera. Calliphoridae) causing myiasis in man.
T h e third instar larva of S. rodhaini shown in this demonstration was expressed from the calf of a young male African at K u m b a in the British Cameroons. T h e specimen was preserved in alcohol and upon arrival in Liverpool was treated with a 10 per cent. solution of hot potassium hydroxide. T h e posterior spiracles were dissected from the larva and were mounted separately. Larvae of S. rodhaini have only twice previously been reported as causing myiasis in man in West Africa (LAvoIPIERRE and BRUcE-CHwATT, 1955,) SO that it is of some interest to record the present case. Following a cursory examination, the specimen which was demonstrated was at first identified as Cordylobfa anthropophaga and it was only later, when the posterior spiracles were carefully examined that it was recognized to be the larva of S. rodhaini. We feel that confusion between these two ealliphorid larvae may not be an unusual occurrence and that a proportion of West African cases of myiasis regarded as being caused by C. anthropophaga may be found to be due to S. rodhaini, if the larvae expressed from skin lesions are critically examined. REFERENCE :
LAVOIPIERRE,M. M. J. & BRUcE-CHWATT, L. J. (1955). 49, 461.
Ann. trop. Med. Parasit.,
LABORATORY MEETING
T h e degree of " resistance " shown is much less than that observed in natural resistant populations of anophelines e . g . A , stephensi in Saudi Arabia and d. sundaicus in Java and adults of the induced " resistant " strain continue to be knocked down and irritated by the insecticide. It is concluded that such " resistance " as has been induced is not of the real pe~'Tnanent genetic type but is rather a result of increased " vigour tolerance " i.e. the selection of some factor or factors, other than a gone or genes of resistance, which enable the mosquitoes to withstand higher dosages of insecticide. A comparison of mortalities among 4th stage larvae of the twentieth selected generation of the larval exposure series and of the parent unexposed stock at two dosages of D D T - i n alcohol-water solution was demonstrated. V.
THE EFFECT OF D D T AND BHC-SELECTION OF ADULTS OF TWO DIELDRIN-BHC-RESlSTANT STRAINS OF A. gambiae, (MR. G. DAVIDSON, MISS C. E. JACKSON AND MISS J. CHALKLEY). Adults of two strains of dieldrin-BHC-resistant A. gambiae from Northern Nigeria have been exposed in successive generations to sublethal dosages of D D T and of BH C and the survivors reared from. With both strains and with both insecticides a marked initial fall in susceptibility was noticeable, but a limit in selection dosage was soon reached at a level indicative not of real resistance but of increased " vigour tolerance." Mortalities at two different dosages of each insecticide among mosquitoes of the parent stock strains and the third selected generations were demonstrated. T h e inability to change significantly the susceptibility to D D T or the degree of resistance to B H C of dieldrin-BHC-resistant A. gambiae by selection with these insecticides is further proof of the permanent genetic nature of this resistance. THE CHROMOSOMES OF Anopheles gambiae. (Miss C. E. JACI~ON). T h e salivary glands of 4th-stage larvae of A. gambiae dissected out by gently pulling off the head and squeezing out the contents of the thorax, are fixed in 33 per cent. acetic acid, stained with aeetocarmine and deeolourized with 45 per cent. acetic acid. T h e preparation is squashed to spread the chromosomes and examined under phase contrast at a magnification of 400 x. Larvae are reared at a lower temperature than is customary in order to retard their growth. Preparations of the hybrid larvae resulting from the cross of the Kano strain (insecticide resistant) with the Lagos strain (susceptible) show the chromosomal differences between the two strains. These may be due only to the fact that the two parental strains are geographically separated populations, but due consideration must also be given to the fact that one is resistant to insecticides while the others not. It is hoped to continue the comparisons of the chromosomal complements of the strains kept at the Ross Institute to ascertain whether there is any chromosomal rearrangement associated with resistance. VI.
A MUTANT IN Anopheles gambiae. (Miss C. E. JACKSON). In order to obtain mutants with a view to establishing linkage groups in A. gambiae, about 275 males were exposed to a dose of 1,000r X-rays. This was done with the co-operation of the Radiotherapy Department of University College Hospital, using 140 Kv, mA5 for 10 mins. 18 secs. These males were mated with unexposed, unfertilized females from the same colony, and the F1 and F, females examined. Several females were found with four distinct bands on the palps as compared with the normal wild type 3-banded palp. An examination of 200 females of the parent colony showed no such 4banded females. Taxonomically this 4-banding is characteristic of the variety A. gambiae melas. VII.
LIVERPOOL SCHOOL OF TROPICAL MEDICINE DEPARTMENT
OF TROPICAL MEDICINE
Dr. C. S. a n d Mrs. L. A. L e i t h e a d : Levels of urinary-chloride excretion in a hot climate.* Histograms displayed estimations of the sodium-chloride content of random samples of urine * A survey carried out at the invitation of the Kuwait Oil Company, with the co-operation of Kuwait State Medical Service.
295
LABORATORY M E E T I N G
from 2,043 men exposed to a high environmental temperature, analysed according to nationality and to the apparent state of health of the individuals concerned. Most of the examinations were performed by the Fantus method on urine samples obtained from Kuwait Oil C~mpany employees who, for widely diverse reasons, attended the general out-patients department at the Ahmadi Clinic in Kuwait during the years 1951-56. Smaller numbers of Volhard estimations were made on urine samples obtained in the summer months of f956 from apparently healthy British and Arab employees of the same Company. For comparison, the results were shown of 49 estimations (42 by the Volhard, seven by the Fantus technique) of sodium-chloride in urine from overt cases of heat illness in the European crews of oil-tankers in the Persian Gulf in the hot season of 1956. T h e histograms showed : i. A wide range of urinary salt excretion in the four larger groups, with a raised lower limit in each of the two " apparently healthy " groups. ii. Mean values for all the groups (except that of heat illness) equal to, if not greater than, the mean values usually quoted for Europeans in cool climates. This finding in urines obtained from locaI Kuwaiti and Bedouin Arabs is of particular interest. iii. Strikingly low urinary salt excretion in marine cases of heat illness (heat syncope or collapse ; anhidrotie heat exhaustion ; salt and water deficiency heat exhaustion ; heat hyperpyrexia and heat stroke).
DEPARTMENT OF ENTOMOLOGY AND PARASITOLOGY
Dr. W. A. F. Webber, Dr. G. Crisp, Mr. A. I. Wright and Mr. P. Williams : Records of Onchocerca f o u n d at postmortem examination of Welsh cattle. T h e records of Onchocerca were obtained by examining tissues collected postmortem from cattle slaughtered at Wrexham abattoir. Adult worms were found in the gastro-splenic omentum and the connective tissue round the nucha! ligament, which were the only tissues examined ; and microfilariae were found in skin taken from the base of the ear and the sternal, inguinal and pastern regions. Most of the Cattle came from areas in Wales and Cheshire, but some records have been obtained of Irish beasts. MicrofiIariae or adult worms or both forms have been found in about 25 per cent. of the Irish cattle and 60 per cent. of the Welsh and Cheshire cattle. Adult worms have been recovered from the gastro-splenic omentum of 31 of the 263 animals examined ( = 12 per cent.), from the nuchal connective tissue of 44 out of 249 animals ( = 18 per cent.), and microfilariae have been found in the skin of 53 out of 164 animals examined ( = 32 per cent).
Dr. M. M. J. Lavoipierre and Mr. W. N. Beesley : A n e w record of Stasisia rodhaini (Diptera. Calliphoridae) causing myiasis in man.
T h e third instar larva of S. rodhaini shown in this demonstration was expressed from the calf of a young male African at K u m b a in the British Cameroons. T h e specimen was preserved in alcohol and upon arrival in Liverpool was treated with a 10 per cent. solution of hot potassium hydroxide. T h e posterior spiracles were dissected from the larva and were mounted separately. Larvae of S. rodhaini have only twice previously been reported as causing myiasis in man in West Africa (LAvoIPIERRE and BRUcE-CHwATT, 1955,) SO that it is of some interest to record the present case. Following a cursory examination, the specimen which was demonstrated was at first identified as Cordylobfa anthropophaga and it was only later, when the posterior spiracles were carefully examined that it was recognized to be the larva of S. rodhaini. We feel that confusion between these two ealliphorid larvae may not be an unusual occurrence and that a proportion of West African cases of myiasis regarded as being caused by C. anthropophaga may be found to be due to S. rodhaini, if the larvae expressed from skin lesions are critically examined. REFERENCE :
LAVOIPIERRE,M. M. J. & BRUcE-CHWATT, L. J. (1955). 49, 461.
Ann. trop. Med. Parasit.,