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Egg-white lysozyme in doses sufficient to eliminate the intracellular bacterial symbionts of the cockroach is toxic to the insect. It induces an increase in blood volume that is correlated with reduced cellularity, increased coagulation time, and ease and volume of bleeding. The increase in blood volume is derived equally from the outflow of tissue water into the haemolymph and the intake of water through the intestinal wall. It attains a maximum in 2 to 3 weeks and evidently results from the injury and increased permeability of tissue cells. Although this injury, which involves organised tissue, such as the gonads, as well as the mycetocytes, may be partly due to products of disintegration of the symbiotic bacteria, experimental evidence points to the direct action of lysozyme, indicating the presence of reactive sites on the tissue cells. The effects of lysozyme in the cockroach resemble certain characteristics of inflammation. The toxicity of lysozyme and its action on the gonads preclude any assurance at the present time of the extent, if any, to which growth and reproduction are under the control of the symbionts.

Injection of egg-white lysozyme into adult male cockroaches induces significant changes in the protein and non-protein nitrogen of the blood, but not in uric acid. Analysis of sixteen amino acids showed that twelve increased 50 to 300 per cent, and one decreased 50 per cent. The inorganic ion content increased and the Na + K + ratio was appreciably higher in the lysozyme-treated insects. Injection of NaCl solution is better tolerated by larvae than adults. Larvae have a higher blood protein and uric acid content than adults.

(1957). Studies on Filariasis in Malaya: Notes on the Breeding of Mansonia (Mansonioides) Mosquitoes in the Laboratory. Annals of Tropical Medicine & Parasitology: Vol. 51, No. 3, pp. 297-300.

Isolated cockroach larvae grow more slowly than larvae in groups, but the resultant adults are larger than those from groups of larvae. When single larvae are grown with adults, they grow as rapidly as larvae in groups, and the resultant adults are as large as those from isolates. The following possible growth factors or conditions were examined: the effect of food, shelter, vision, asepsis, secretion from the tergites and cuticular exudates, the presence of a possible contact or air-borne pheromone, and physical contact as observed in ritualistic behaviour, which is here described for the first time; and certain other considerations. Neither air-borne nor contact growth pheromones could be demonstrated, nor could any significant effect by the exudates be shown. Food intake/unit weight of the isolated and grouped larvae did not differ significantly between the two categories. Physical contact with other larvae or with adults was the critical exteroceptive stimulus which promoted the rate of larval growth, but not the ultimate size. The greater size of adults derived from isolated larvae or from larvae reared with adults, as compared with those from grouped larvae, is attributed to ecdysone. Ecdysone, more concentrated in isolated than in grouped larvae, could also have a part in retarding the rate of growth of the isolated insect by reducing its locomotor activity and hence inducing a relatively lower metabolic rate.

Nine temperature-sensitive (Ts) mutants of Neisseria gonorrhoeae strain 49191 were isolated. They were proven to be different from each other by results of transformation experiments. None of the Ts mutations appeared to be linked to antibiotic resistance genes from strain 24392. However, Ts-9 demonstrated 8% linkage with a nalidixic acid resistance marker from strain RW-2.

Stromatolites are organosedimentary structures produced by microorganisms which have been used extensively in the interpretation of Precambrian and, to a lesser extent, Phanerozoic history1–5. Modern stromatolites are generally restricted to hot springs or warm, hypersaline and/or alkaline aquatic environments3. Recently, however, we documented6 the presence of modern stromatolites in several cold, perennially ice-covered Antarctic dry valley lakes. Here, we report a finding in Lake Fryxell, Antarctica, of biogenic calcite structures not observed in our previous study of other Antarctic lakes. These structures were laminated, indurate, unbranched, and had either a vertical or horizontal orientation. We infer that these calcite structures are biogenic in origin, and hence stromatolitic based on the following evidence: (1) the presence of an actively metabolizing algal mat on their surface; and (2) an internal composition of filamentous blue-green algal cell wall fragments, diatom frustules and calcite crystals.

The susceptibility of a standard reference strain of the cattle tick Boophilus microplus, to a group of synthetic pyrethroids, has been compared with that of a DDT-resistant strain. Cross resistance has been demonstrated in laboratory and field tests.

Breeding for resistance to the cattle tick Boophilus microplus was undertaken in a herd of Australian Illawarra Shorthorn (AIS) cattle from 1961 to 1978 and in a herd of Braham x AIS cattle from 1970 to 1979. Breeder cows and their progeny were assessed for tick resistance during October to January. Resistance levels were determined as the average percentage mortality of female ticks from two artificial infestations with cohorts of c 20,000 larvae. Resistance increased from 89.2% to 99% in the AIS breeding herd, as a result of the yearly introductions of more resistant individuals and culling of less resistant ones. Concurrently resistance in the AIS progeny increased from 93.7% to 97.7%, thus demonstrating that the selection and breeding of the cows and bulls resulted in genetic improvement in the resistance of the progeny. Milk production tests on heifers from the selected AIS herd during 1975 to 79 indicated that selection for tick resistance did not select against milk production. Resistance of the Brahman x AIS increased from 98.4% to 99.3% in the breeding herd and from 97.6% to 99.6% in the progeny. Female calves of both breeds were more resistant than males.

Cryoconite holes are water-filled depressions on the surface of glaciers. They contain microbial communities and may contribute to glacial wastage and biological colonization of ice-free areas.

The combinations of imipenem plus ciprofloxacin and imipenem plus amikacin were investigated for their activity against Pseudomonas aeruginosa and other bacterial pathogens. For imipenem-susceptible P. aeruginosa, synergy of imipenem plus ciprofloxacin and imipenem plus amikacin was observed against 36 and 45% of the strains, respectively. The incidence of synergy against imipenem-resistant isolates of P. aeruginosa was 10% for both combinations. Antagonism was not observed with either combination.

SYNERGISM studies with the cattle tick Boophilus microplus have been effected by enclosing larvae in packets impregnated with olive oil solutions of the test chemicals and recording mortality after 48 h1,2. In these conditions larvae exposed continuously to 0.4% piperonyl butoxide were apparently unaffected. Subsequently, in studies to determine the sensitivities of the mixed function oxidase systems in organophosphorus (and carbamate) resistant and susceptible strains of B. microplus, larvae were immersed in aqueous colloids3 of piperonyl butoxide. Concentrations greater than 0.02 % proved to be toxic and an LC50 of 0.044% at 24 h after treatment was determined. This unexpected result aroused interest in the acaricidal potential of piperonyl butoxide. Although it is generally regarded as a nontoxic synergist4, some workers have claimed it is toxic to houseflies at fairly high dosage5 but others found it to be nontoxic6; toxicity to the mite Acarus siro (formerly Tyroglyphus farinae) has been recorded7,8.

The developmental toxicity of trace, subanesthetic, and anesthetic exposure to methoxyflurane was examined in Swiss/ICR mice. No adverse effects on reproduction or fetal development were demonstrated following exposure to trace (2 ppm) and subanesthetic (60 ppm) concentrations of methoxyflurane for 4 hours daily on days 6 through 15 of pregnancy. Exposure to an anesthetic concentration (2000 ppm; 0.2%) for the same period resulted in decreased fetal weight, decreased ossification, and delayed renal maturation. Additionally, the incidence of minor skeletal anomalies was increased. It is concluded that gestational exposure of mice to trace of subanesthetic concentrations of methoxyflurane does not result in reproductive loss or morphologic abnormalities in their offspring.

A bulk O2 budget for Lake Hoare, Antarctica, is presented. Five years of seasonal data show the lake to be persistently supersaturated with O2. Oxygen is carried into the lake in glacial meltstreams and is left behind when this water is removed as ice by ablation and sublimation. A diffusive loss of O2 from the lake through the summer moat is suggested. Measured values of the total O2 in the water column indicate that the time scale of O2 turnover is much longer than a year. Based on these results we suggest that the amount of O2 in the water does not change significantly throughout the year and that the lake is also supersaturated with N2.

Man, with his domestic animals, has intruded into many complex host-parasite relationships involving ticks. Indeed, with the exception of the form of Ornithodorus porcinus which feeds almost exclusively on man in the Kenya Highlands (Walton 1962), all of man’s and many of his domestic animals’ contacts with ticks are casual in that wildlife are the preferred hosts and the source of the disease organisms which ticks transmit. This interaction creates difficult control problems since it means that the habitat and the wild life hosts must be manipulated if control of the arthropod is to be achieved. In these situations, there are obvious difficulties which are technical, cultural and emotional. Area control by residual insecticides, or any insecticide, will become increasingly unpopular, and the destruction of wildlife will be equally distasteful to a world quite rightly concerned with environmental conservation. The following examples illustrate the problems: (1) In the Ozark region of Oklahoma, U.S.A., recreational areas are flooded with the lone star tick Amblyomma americanum which feeds very readily on man and cattle and many other hosts including the white-tailed deer Odocoileus virginianus (Hair and Howell 1970). Control of this tick will ultimately involve the control of the deer or its habitat, yet deer protection at this stage has led to such vast populations of the lone star tick that the tick itself has become a major mechanism in the regulation of deer populations (Bolte, Hair and Fletcher, 1970).

Swiss/ICR mice were tested to determine whether the volatile ether anesthetic, enflurane, causes induction of anesthetic defluorination and organ toxicity. Mice were exposed in utero and postnatally to 0.01, 0.1 and 1.0 volumes percent enflurane vapor. Body weight was measured at frequent intervals throughout the experiment. Animals were sacrificed at 73 days of age and liver microsomal cytochrome P-450 content and the rate of defluorination of enflurane, isoflurane, methoxyflurane ans sevoflurane were determined. In addition, the liver, kidney and testis were weighed and examined histologically for drug induced damage. The maximum tolerated dose of enflurane delivered over a twelve week period was determined to be 0.5 volumes percent for four hours a day, five days a week. Even at this high dose there was no evidence in either sex of liver, kidney or testicular damage. Following enflurane exposure, neither the liver microsomal cytochrome P-450 content nor the rate of anesthetic defluorination was increased. The rate of in vitro inorganic fluoride production per unit time was greatest for methoxyflurane, and approximately equal for enflurane, isoflurane and sevoflurane. Since there was no evidence of enzyme induction or specific organ toxicity, it was concluded that enflurane is a comparatively nontoxic volatile anesthetic under conditions of this study.

The mutagenicity of halothane was tested in an in-vitro microbial assay system employing two histidine-dependent mutants of Salmonella typhimurium, TA98 and TA100, Halothane in concentrations ranging from 0.1 to 30 per cent was incubated with bacteria in the presence or absence of a metabolic activation system prepared from either rat liver treated with Aroclor 1254 or human liver. Trifluoroacetic acid, a major metabolite of halothane, and urine from patients anesthetized with halothane also were tested. Halothane, trifluoroacetic acid, and patients' urines were not mutagenic.

1. (1) The successful transmission of Wuchereria malayi from man to the domestic cat by direct inoculation of infective larvae is described. 2. (2) The pre-patent periods in the five cats infected were 80, 81, 81, 82 and 96 days. 3. (3) The microfilariae were apparently indistinguishable from those of the human donors, and they developed normally in the vector mosquitoes. 4. (4) Adult worms corresponding to the description of W. malayi were recovered from two of the cats. 5. (5) The possible implications are discussed.

1. 1) An attempt was made to transmit back to man a strain of Brugia malayi originally obtained from man and transmitted through a macaque monkey and thence to a cat. Two volunteers were inoculated with infective larvae of this strain which had developed in Mansonia longipalpis. Neither of these volunteers subsequently developed microfilariae. 2. 2) An attempt was also made to transmit to man a strain of B. pahangi, a species hitherto only known as an infection of animals. Two volunteers were inoculated with infective larvae from Armigeres obturbans which had fed on a cat carrying a strain of B. pahangi originally obtained from a naturally infected civet cat. 3. 3) One of the volunteers inoculated with B. pahangi developed microfilariae 84 days later, and these persisted in small numbers for a further 56 days. The microfilariae resembled B. pahangi morphologically, and the identification was confirmed by mosquito-feeding experiments and by experimental transmission to a cat from which an adult male B. pahangi was later recovered. The other volunteer did not develop microfilariae. 4. 4) All four volunteers suffered from episodes of lymphangitis, lymphadenitis, and oedema in the inoculated limb, starting in each instance about one month after the inoculation. 5. 5) Although there was no true leucocytosis, all four volunteers developed a relative increase in eosinophils with maxima ranging from 18 to 32 per cent. occurring 12 to 13 weeks after the inoculation. 6. 6) All volunteers showed positive complement-fixation tests and skin tests (to Dirofilaria antigen) about 12 weeks after the inoculation. 7. 7) One volunteer from each pair developed subcutaneous nodules in the inoculated arm about 4 months afterwards. 8. 8) The significance of these findings is discussed. B. pahangi must now be regarded as potentially infective to man. The clinical episodes are considered to be reactions to the immature developing worms, whereas the eosinophilia is more probably a response to some product of the adult worms. Subcutaneous nodules do not seem to have been described previously in association with filarial infection.

OBSERVATIONS by Bertram and Samawickrema1 have shown that it is possible to determine the number of times that Mansonioides mosquitoes have laid eggs by examination of the ovaries for corpora lutea, a technique developed by Russian workers using Anopheles maculipennis 2. Knowing this, and the time taken from feeding to maturation of eggs it has been suggested that a precise estimate of the age of individual mosquitoes should be possible. Examination of the ovaries of laboratory-bred M. uniformis which had laid one to four times confirmed that, with practice, it was possible to count the number of corpora lutea, and the technique was then tried with wild M. longipalpis, M. annulata and M. uniformis. The first two species are typically swamp-forest mosquitoes and the major vectors of filariasis due to Wuchereria malayi in several parts of Malaya, while M. uniformis breeds mainly in open swamps and is also a vector.

MUIRHEAD-THOMSON1 has reported on the use of an experimental hut with a light-trap fitted into the window, as a method of assessing the efficiency of the residual insecticides D.D.T. and ‘Gammexane’ against Anopheles gambiae in Africa. Similar experiments have recently been conducted against A. maculatus, the principal vector of malaria in Malaya. Unlike gambiae, maculatus normally leaves houses at or before dawn to rest out of doors by day, and nearly all those captured in an untreated experimental hut were found in the light-trap in the morning.

The mortality rate of larvae of Periplaneta americana increases with increasing population density. The mortality curve is not linear but cascading and, like growth, mortality alternates with ecdysis. Three major phases of mortality are recognized: the first, with a high mortality rate during the first to the sixth week; the second, of brief duration and low mortality, during the sixth to the ninth week; and the third, of moderately high mortality which persists until development is completed. The mortality phases are dependent respectively on (1) a maximal increase in the instantaneous percentage rate of growth and a high frequency of ecdysis, which expose the larvae to injury and high mortality when in groups, (2) a slowing down of the growth rate, and (3) sexual development and continuing growth in the last instar associated with the metamorphosis of the larva to the adult. The data support the concept of a homology between the last larval instar of the hemimetabolous insect and the pupal stage of the holometabolous species. Isolation retards development of larvae and exerts its retarding influence at all stages of growth. In the present experiments the optimal density for growth of larvae is about 25. The average weight of adult insects tends to decrease with an increase in the population density of the larvae. On the other hand, the weight-time curve of emergent adults varies with density of the group. The results indicate the presence of a factor(s) which affects the rate of maturation of the insect throughout its development, which is a function of group size and is sex-dependent in that males are more sensitive to its influence. Cannibalism among larvae is observed chiefly with the young and is considered to be sanitary rather than predatory in character.

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(1960). Studies on Filariasis in Malaya: Field and Laboratory Investigations of the Vectors of a Rural Strain of Wuchereria Bancrofti. Annals of Tropical Medicine & Parasitology: Vol. 54, No. 1, pp. 78-91.