On the mechanism of renal potassium wasting in renal tubular acidosis associated with the Fanconi syndrome (type 2 RTA)

The mechanism of renal potassium wasting in renal tubular acidosis associated with the Fanconi syndrome (type 2 RTA) was investigated in 10 patients, each of whom had impaired proximal renal tubular reabsorption of bicarbonate as judged from a greater than 15-20% reduction of renal tubular bicarbonate reabsorption (THCO(3) (-)) at normal plasma bicarbonate concentrations. When the plasma bicarbonate concentration ([HCO(3) (-)]p) was experimentally increased to normal levels in three patients with a fractional potassium excretion (C(K)/C(in)) of less than 1.0 during acidosis, C(K)/C(in) and urinary potassium excretion (U(K)V/C(in)) increased strikingly and concurrently with a striking increase in urinary sodium (U(Na)V/C(in)) and bicarbonate (U(HCO3-)V/C(in)) excretion. When [HCO(3) (-)]p was increased to normal levels in two patients with a C(K)/C(in) of greater than 1.0 during acidosis and in whom U(Na)V/C(in) and U(HCO3-)V/C(in) were already markedly increased, C(K)/C(in) did not increase further. When [HCO(3) (-)]p was decreased to subnormal levels in a patient given ammonium chloride, U(K)V/C(in), C(K)/C(in), and U(HCO3-)V/C(in) decreased concurrently. In the six patients in whom [HCO(3) (-)]p was maintained at normal levels (oral alkali therapy) for 2 months or longer, C(K)/C(in) was directly related to the urinary excretion rates of sodium and bicarbonate, hence was directly related to the magnitude of reduction of THCO(3) (-) at normal [HCO(3) (-)]p; C(K)/C(in) was greater than 0.55 in all six patients and greater than 1.0 in four. In eight patients with classic RTA (type 1 RTA), proximal renal tubular reabsorption of bicarbonate was largely intact as judged from a trivial reduction of THCO(3) (-) at normal [HCO(3) (-)]p. When [HCO(3) (-)]p was either increased from subnormal to normal levels, or decreased from normal to subnormal levels, U(HCO3-)V/C(in) remained essentially constant, and U(K)V/C(in) did not change significantly. When correction of acidosis was sustained, U(HCO3-)V/C(in) remained a trivial fraction of that filtered, and C(K)/C(in) was consistently less than 0.55. These results provide evidence that renal potassium wasting in type 2 RTA is physiologically separable from that in type 1 RTA and in part the result of a reduction in the rate at which the proximal tubule reabsorbs bicarbonate and the distal delivery of supernormal amounts of sodium bicarbonate. With an increased stimulus to distal sodium reabsorption, indicated by the finding of hyperaldosteronism, delivery to the distal nephron of supernormal amounts of sodium with the relatively impermeant bicarbonate anion would be expected to increase intraluminal negativity in the distal nephron, and as a consequence, increase potassium secretion and promote renal potassium wasting.

Modulation of experimental renal dysfunction of hereditary fructose intolerance by circulating parathyroid hormone

In a woman with hereditary fructose intolerance and intact parathyroid function, the experimental administration of fructose at different dosage schedules invariably induced the dose-dependent, complex dysfunction of the proximal renal tubule now recognized as characteristic. But in a woman with hereditary fructose intolerance and hypoparathyroidism given similar amounts of fructose, the experimental dysfunction was strikingly attenuated or nondemonstrable unless or until fructose and parathyroid hormone were administered in sustained combination. Thereupon, a renal dysfunction of characteristic type and severity occurred invariably and almost immediately. Thus, the concentration of circulating parathyroid hormone can modulate the functional expression of the experimental renal disorder. This effect of parathyroid hormone, which appears to involve more than simple physiologic summation, may have important clinical implications.

The duration of egg, larval and pupal stages of Culex pipiens fatigans in Rangoon, Burma

Laboratory experiments to determine the duration of the immature stages of Culex pipiens fatigans were carried out because such information is important from the point of view of control by larvicides. At a temperature of 25.1 degrees C+/-0.7 degrees C the mean incubation period is 27.11+/-0.57 hours. Females spend a longer time in the pupal stage than males (34.16+/-0.74 hours and 32.95+/-0.75 hours, respectively, at 28.6 degrees C+/-0.8 degrees C; there is no 24-hour pupating or emerging rhythm. The duration of larval life is longer for the female (135.3+/-4.4 hours) than for the male (118.4+/-2.4 hours). Larvae that take a long time to pupate also take a long time to emerge. Withholding of food for a few hours from first-stage larvae increases the duration of larval life but does not affect that of pupal life. These observations on the differences between the sexes in the duration of larval and pupal life are in agreement with observations made on Aedes aegypti in Uganda.

Outdoor resting of Culex pipiens fatigans in Rangoon, Burma

The sites occupied by resting adult mosquitos are of importance, since they may be accessible to treatment with insecticide. It has usually been assumed that Culex pipiens fatigans feeds and rests indoors, thus making itself vulnerable to indoor spraying. However, work in the Kemmendine Experimental Area of Rangoon, Burma, has now shown that many C. p. fatigans rest out of doors in a variety of shelters. The lower parous rate in outside catches as compared with indoor catches tends to confirm the view that newly hatched C. p. fatigans rest out of doors for some time before setting off to feed. The percentage of infected mosquitos is remarkably constant from site to site and from month to month and does not differ significantly from that obtained in indoor resting catches or on bait out of doors. It appears that the possibility of acquiring infection out of doors will have to be seriously considered in any anti-filariasis campaign.

Cane-sugar feeding in Culex pipiens fatigans

The relatively poor results that have been obtained in controlling or eradicating Culex pipiens fatigans, the urban vector of Wuchereria bancrofti, have made it necessary to obtain as much information as possible about its biology. In this paper the unexpected finding of the influence of cane sugar in delaying oviposition in the gravid female is reported. This is an important finding for those who are investigating the biology of this mosquito in the laboratory and who make use of the age-old practice of keeping adult mosquitos alive by feeding them cane sugar. It is also reported that under certain conditions extensive cane-sugar feeding takes place in nature and it seems possible that this habit may have unsuspected repercussions on behaviour and physiology beyond the confines of the laboratory. One possible development would be the isolation of the attractant present in unrefined sugars and its use in traps in order to assess mosquito populations in the field.

Time of arrival of gravid Culex pipiens fatigans at an oviposition site, the oviposition cycle and the relationship between time of feeding and time of oviposition

One of the most important activities in a female mosquito's life is the flight to the breeding place and the subsequent deposition of eggs. During this phase, motivated by endogenous and exogenous stimuli, the female is particularly exposed and susceptible to attack. It is therefore important to investigate these episodes in the gravid female's life.The work reported in this paper shows that gravid Culex pipiens fatigans females are easily trapped over breeding-water; there are two peaks in the arrival at a breeding site, one just after sunset and the other at sunrise. The oviposition cycle is biphasic, the two peaks coinciding, in calm weather, with the two arrival peaks; wind and rain cause marked disturbances in the oviposition cycle.The mean duration of the gonotrophic cycle depends on the time of feeding; this finding is of practical importance since the length of the cycle is often used to calculate the daily survival rate of adult mosquitos. It appears that oviposition is stimulated by a change in light: from light to dark for mosquitos ovipositing in the evening and from dark to light for those ovipositing in the morning.Apart from revealing some hitherto unknown behaviour patterns, the techniques evolved could also be used in the assessment of mosquito populations and hence the effects of control measures.

Evaluation of Wuchereria bancrofti infection in Culex pipiens fatigans in Rangoon, Burma

In the past, several indices have been proposed to evaluate the threat of vectors to the community. Such indices, if accurately determined, could serve to assess the effectiveness of vector control campaigns. In this paper, a "risk of infection" index is introduced for the case of urban filariasis transmitted by Culex pipiens fatigans in Rangoon, Burma. This index is directly proportional to the three principal parameters that determine the extent of transmission-namely, the biting density of the vector, the proportion parous to total biting, and the proportion infective to total parous; all these parameters are easily determined from biting catches. Examples of the use of the index are given and it is noted that, in areas where conditions are not favourable to the vector throughout the year, or where the speed of development of the parasite in the vector may not be constant, these variables must be taken into account in calculating the index.

Experiments on the mating of Culex pipiens fatigans in the laboratory

Few studies have been conducted into the mating and insemination of C. p. fatigans, despite the importance of this behavioural aspect for the production of fertile eggs and their development after a blood meal. Moreover, detailed knowledge of the behaviour of male mosquitos is required before the potentialities of genetic manipulation and sterile male techniques for the control and eradication of mosquitos can be fully investigated.The laboratory studies described in this paper show that high percentages of successful matings and insemination can be obtained in relatively small cages in the laboratory and suggest that the classical swarming of males, which takes place in the open, is not essential to mating.

Examination of the stomach contents of Culex pipiens fatigans in Rangoon, Burma, to determine the origin of the blood-meal

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Qualitative and quantitative characteristics adult Culex pipiens fatigans populations according to time, site and place of capture

The composition of a vector population is largely influenced by the pressures and modifying effects of the environment. Changes in the latter, whether natural or induced (e.g., by insecticides) will be reflected in the former. Thus if the existing characteristics of a vector population are determined, the parameters can subsequently be used to assess the effect of control measures.The effect of environmental conditions on the density and parity of Culex pipiens fatigans in catches in Burma is illustrated by a comparison of results obtained in Kemmendine, which is served by a bucket system for the removal of night-soil, with those from South Okkalapa, which has pit latrines; in the latter area there is a large preponderance of young mosquitos in the monsoon period, in contrast to the situation in Kemmendine.In Kemmendine, the inside-biting catch is reduced by about one-half if an inside-resting catch is made simultaneously. This suggests that C. p. fatigans rests indoors before biting indoors and that an efficient insecticide for inside application would markedly reduce the mosquito population. When a correction is made for the inside-resting catch it is shown that there is little to choose between inside- and outside-biting catches as measures of the activity of C. p. fatigans. The chances of acquiring infection are at least as great out of doors as indoors and this may account for differences in infectivity among different ethnic groups, according to the extent that they sleep out of doors.Differences in parity and in the state of infection of mosquitos according to the type of catch and the time of catching are discussed. Finally, it is noted that, although most male mosquitos are obtained in inside-resting catches, a considerable number, surprisingly, are taken on bait; the reason for this is not yet known.

Infection and reinfection of Culex pipiens fatigans with Wuchereria bancrofti and the loss of mature larvae in blood-feeding

Although previous workers had found no evidence of resistance to superinfection in vectors of filariasis, it was considered desirable to reinvestigate the subject because of the epidemiological implications, since a mosquito that can incubate to maturity successive broods of filarial larvae will obviously be a more efficient vector than one that cannot. The results obtained indicate that a Culex pipiens fatigans mosquito that picks up an infection early in its life can, by taking subsequent infecting feeds, remain infective for the rest of its life.The movement of mature larvae in the vector and losses of larvae during feeding are of interest since from this information one can estimate the probable number of larvae deposited on the host at each feed and the period of infectivity of the vector. In the present experiment there were, on average, 6.1 larvae per infective mosquito before a second blood-meal; after the meal the figure was 3.6. Thus, 41% of the original infective larvae were lost; not all would be inoculated into the host, as some would die on the surface of his skin. The release of infective larvae through blood-feeding results from a combination of the passive pressure of the engorged blood in the abdomen and the active movement of the larva itself.

Positive geotaxis in gravid Culex pipiens fatigans

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