A low-cost mesocosm for the study of behaviour and reproductive potential in Afrotropical mosquito (Diptera: Culicidae) vectors of malaria.

A large-scale mesocosm was constructed and tested for its effectiveness for use in experiments on behaviour, reproduction and adult survivorship in the Afrotropical malaria vector Anopheles gambiae s.s. Giles (Diptera: Culicidae) in temperate climates. The large space (82.69 m(3) ) allowed for semi-natural experiments that increased demand on a mosquito's energetic reserves in an environment of widely distributed resources. A one-piece prefabricated enclosure, made with white netting and vinyl, prevented the ingress of predators and the egress of mosquitoes. Daylight and white materials prompted the mosquitoes to seclude themselves in restricted daytime resting sites and allowed the easy collection of dead bodies so that daily mortality could be assessed accurately using a method that accounts for the loss of a proportion of bodies. Here, daily, age-dependent mortality rates of males and females were estimated using Bayesian Markov chain Monte Carlo simulation. In overnight experiments, mosquitoes successfully located plants and took sugar meals. A 3-week survival trial with a single cohort demonstrated successful mating, blood feeding, oviposition and long life. The relatively low cost of the mesocosm and the performance of the mosquitoes in it make it a viable option for any behavioural or ecological study of tropical mosquitoes in which space and seasonal cold are constraining factors.

Quantitative relations of fetal and maternal pitiutary-adrenal systems.

Even though certain aspects of the fetal pituitary-adrenal system have been extensively studied, much remains to be learned of its basic development and function. In the present work, the effect of maternal hypophysectomy upon quantitative pituitary-adrenal relations in mother and fetus was investigated in pregnant beagle dogs. At 57 days gestation in each of seven normal animals and seven animals 3 wk posthypophysectomy, a cannula for collection of adrenal effluent was placed in a single fetus in utero under halothane anesthesia. A timed fetal adrenal sample was obtained; ACTH (10 mU) was injected into the fetus; 3 min thereafter a second fetal adrenal sample was collected and fetal and maternal peripheral arterial samples were drawn. All fetuses and their adrenal glands were weighed. Concentrations of cortisol and corticosterone were determined by a modification of the double-isotope dilution derivative method of Kliman and Peterson. Mean peripheral cortisol concentrations in mother and fetus were 92 and 94 ng/ml, respectively (ratio 1.0), in normal pregnancies and 11 and 54 ng/ml, respectively (ratio 0.2), in maternal hypophysectomy pregnancies. Weights of fetal adrenal gland pairs of 32 and 44 mg, respectively, in normal and hypophysectomy pregnancies indicate increased fetal ACTH secretion in response to lowered circulating cortisol in the fetus secondary to maternal hypophysectomy. These data demonstrate the presence of an active pituitary-adrenal feedback mechanism in the dog fetus which is partly influenced by maternal pituitary-adrenal function. The shift in the maternal-fetal ratio of peripheral cortisol concentrations from 1.0 to 0.2 occasioned by maternal hypophysectomy neither supports nor rules out the presence of specific placental mechanisms affecting relative concentrations of cortisol in mother and fetus. It does suggest, however, that the relative steroid input into maternal and fetal compartments is one of the factors which influences such concentration ratios. Concentrations of cortisol were significantly higher in fetal adrenal effluent (pre-ACTH) than in fetal peripheral plasma in normal pregnancies, which demonstrates secretion of cortisol by the fetus and shows that corticosteroid of maternal origin does not lead to complete suppression of fetal pituitary-adrenal function. Cortisol secretion rates in response to exogenous ACTH were essentially the same in fetuses in normal and hypophysectomy pregnancies (132 and 128 ng/min, respectively). Thus, fetal adrenal responsiveness to ACTH, i.e., maximum secretory capacity, is not enhanced by increased ACTH stimulation sufficient to induce adrenal hypertrophy in the same fetuses.

Fetal bile salt metabolism. The intestinal absorption of bile salt.

The intestinal absorption of sodium taurocholate was studied in the near-term fetal and neonatal dog. Absorption rates were measured in vivo in isolated loops of fetal jejunum and ileum. Absorption was also measured in vitro in everted sacs and rings of fetal and neonatal jejunum and ileum. The maximal rates of taurocholate absorption observed after instillation of 1 micronmol taurocholate into closed segments of fetal jejunum and ileum with intact blood supply were not significantly different (P less than 0.2), and equalled 0.282+/-0.026 (mean+/-SEM) and 0.347+/-0.051 micronmol/h per 10-cm segment length jejunum and ileum, respectively. Similarly, the rates of absorption from open segments of jejunum and ileum perfused with 0.4 and 1.0 mM taurocholate were nearly identical (0.232+/-0.040 and 0.255+/-0.039, respectively at 0.4 mM, and 0.470+/-0.065 and 0.431+/-0.013, respectively at 1.0 mm) (P greater than 0.2). At perfusate concentrations of 4.0 mM, moreoever, jejunal absorption exceeded ileal absorption (1.490+/-0.140 and 0.922+/-0.200, respectively (P less than 0.05). As expected, concentration of taurocholate by the mucosa was readily demonstrated in adult ileal, but not in adult jejunal everted rings. In contrast, there were no significant differences in mucosal uptake of taurocholate by fetal jejunal and ileal rings. Fetal ileal mucosal concentrations were not significantly above those in the incubation medium after 1-h exposure of the mucosa to 0.003, 0.03, and 0.3 mM taurocholate. Uptake was proportional to incubation medium concentration over the full range of values. This was also true of tissues from 1-wk-old neonates. However, by 2 wk of age, ileal mucosal concentration of taurocholate was evident and adult levels were attained by 5 wk of age. It is concluded that taurocholate is absorbed by the fetal gut and that ileal absorption is no more efficient than jejunal absorption. Although active glucose transport was demonstrable in both jejunum and ileum, it was not possible to demonstrate an ileal mechanism for active transport of taurocholate in the fetus. Active ileal transport was not demonstrable in the newborn until at least 2 wk after birth.

Fetal bile salt metabolism. I. The metabolism of sodium cholate-14C in the fetal dog.

Cholate metabolism was studied in fetal dogs 1 wk before term and was compared with cholate metabolism in adult dogs. Tracer amounts of sodium cholate-(14)C were administered to the fetus in utero by intravenous infusion over 6 hr. Fetal plasma disappearance, biliary excretion, tissue distribution, and placental transfer of cholate were measured over 10 hr. Infused cholate-(14)C was cleared rapidly from fetal plasma principally by the fetal liver and to a minor extent by placental transfer to the mother. The taurine conjugate was formed in the fetal liver and was excreted into the proximal small intestine via the biliary tree. Indirect evidence for the functioning enterohepatic circulation of bile salt in the fetus was obtained. Comparison with the results of similar experiments in adult dogs showed that the fetal liver was almost as efficient as the adult liver in the uptake, conjugation, and excretion of tracer amounts of cholate-(14)C. The maximal rate of excretion of radiolabel attained by the fetus was somewhat slower than in the adult (82.8 +/-1.4% and 96.1 +/-4.0% [mean +/-SE] of the infusion rate, respectively), and the proportion of the total dose excreted by the fetal liver during 10 hr was smaller (81.4 +/-1.3% vs. 96.6 +/-4.4%). This difference could be only partly accounted for by placental transfer (2.8 +/-0.6% of the fetal dose). Labeled cholate and taurocholate were excreted by the fetus at similar rates, which suggests that, under the conditions of study, conjugation had little influence on the rate of transfer of cholate across the liver cell. It is concluded that the fetal dog, 1 wk before birth, has a remarkably mature and efficient mechanism for the uptake and excretion of cholate.

Fetal bile salt metabolism. II. Hepatic excretion of endogenous bile salt and of a taurocholate load.

Bile salt metabolism was studied in fetal dogs 1 wk before term. The size and distribution of the fetal bile salt pool were measured, and individual bile salts were identified. The hepatic excretion of endogenous bile salts was studied in bile fistula fetuses, and the capacity of this excretory mechanism was investigated by the i.v. infusion of a load of sodium taurocholate-(14)C up to 20 times the endogenous pool size. The total fetal bile salt pool was 30.9+/-2.7 mumoles, of which two-thirds was in the fetal gallbladder. Expressed on a body weight basis, this was equal to approximately one-half the estimated pool size in the adult dog (119.2+/-11.3 vs. 247.5+/-33.1 mumoles/kg body wt). Measurable quantities of bile salt were found in small bowel (6.0+/-1.8 mumoles), large bowel (1.1+/-0.3 mumoles), liver (1.2+/-0.5 mumoles), and plasma (0.1+/-0.03 mumoles). Plasma bile salt levels were significantly greater in fetal than in maternal plasma (1.01+/-0.24 mug/ml vs. 0.36+/-0.06 mug/ml; P < 0.05). Fetal hepatic bile salt excretion showed a fall over the period of study from 2.04+/-0.34 to 0.30+/-0.07 mumoles/hr. The maximal endogenous bile salt concentration in fetal hepatic bile was 18.7+/-1.5 mumoles/ml. The concentration in fetal gallbladder bile was 73.9+/-8.6 mumoles/ml; and, in those studies in which hepatic and gallbladder bile could be compared directly, the gallbladder appeared to concentrate bile four- to fivefold.Taurocholate, taurochenodeoxycholate, and taurodeoxycholate were present in fetal bile, but no free bile salts were identified. The presence of deoxycholate was confirmed by thin-layer chromatography and gas liquid chromatography, and the absence of microorganisms in fetal gut suggests that it was probably transferred from the maternal circulation. After infusion of a taurocholate load, fetal hepatic bile salt excretion increased 30-fold, so that 85-95% of the dose was excreted by the fetal liver during the period of observation. Placental transfer accounted for less than 5% of the dose. Fetal bile volume increased 15-fold on average, while bile salt concentrations increased two- to threefold. It is concluded that bile salt is taken up, conjugated, and excreted by the fetal liver with remarkable efficiency. The excreted material is either stored and concentrated in the fetal gallbladder or released into the intestine and reabsorbed to be reexcreted in bile.

Bilirubin metabolism in the fetus.

Bilirubin metabolism was studied in dog and monkey fetuses. Bilirubin-(3)H was administered to fetal animals in utero by prolonged intravenous infusion. Fetal plasma disappearance, hepatic uptake, biliary excretion, and placental transfer of bilirubin-(3)H were measured.Bilirubin metabolism and excretion in the fetus was much less efficient than in the adult. Fetal plasma levels of tritium were elevated for prolonged periods, and the combined rate of placental and fetal hepatic excretion was lower than normal values for adult hepatic excretion. Species differences were noted. Hepatic conjugation and excretion appeared to be the primary mechanism of fetal metabolism in the dog. In contrast, the amounts of conjugated bilirubin-(3)H excreted in fetal monkey bile were negligible. Small amounts of (3)H-labeled bilirubin derivatives were excreted in fetal bile, but 10 times as much of the administered material was transferred intact across the placenta and excreted by the maternal liver. The relationship of this functional difference to known anatomic and biochemical species differences is discussed. Preliminary observations on alternate routes of fetal bilirubin metabolism were obtained.

Investigations of the simian ontogenic switch from fetal to adult hemoglobin at the progenitor cell level.

The ontogenic switch from fetal to adult hemoglobin could result from discontinuous events, such as replacement of fetal erythroid progenitor cells by adult ones, or gradual modulation of the hemoglobin program of a single progenitor cell pool. The former would result in progenitors at midswitch with skewed fractional beta-globin synthesis programs, the latter in a Gaussian distribution. For these studies, we obtained bone marrow from rhesus monkey fetuses at 141-153 d (midswitch). Mononuclear cells were cultured in methyl cellulose with erythropoietin, and single BFU-E-derived colonies were removed and incubated with [3H]leucine. Globin synthesis was examined by gel electrophoresis and fluorography. The beta-globin synthesis pattern of single fetal colonies was skewed, and did not fit a normal distribution. The fetal pattern resembled the pattern of an artificial mixture of fetal and adult progenitors, suggesting that the fetal progenitor pool could contain populations with different beta-globin programs. This non-Gaussian distribution in the progenitors of midswitch fetuses is consistent with a discontinuous model for hemoglobin switching during ontogeny.

Control of the simian fetal hemoglobin switch at the progenitor cell level.

This investigation was designed to define the cellular level at which the gamma to beta globin switch is established in the developing simian fetus in order to determine whether the switch is controlled by environmental influences within differentiating erythroid precursors or predetermined by the genetic program of erythroid progenitors. Samples of marrow and liver were obtained from rhesus fetuses throughout the switch period, and marrow was obtained from adult rhesus monkeys. Globin chain synthesis was then measured in differentiated erythroblasts and in erythroid progenitor-derived colonies grown in semisolid media. The relative rates of synthesis of gamma and beta chains were determined by the uptake of [(3)H]leucine into the respective chains separated by Triton gel electrophoresis and in some cases by urea carboxymethyl cellulose chromatography. Four periods of the switch were defined during fetal development. In the preswitch period both erythroblasts and progenitor-derived colonies produced <5% beta globin. In the early switch erythroblasts produced 5-15% beta globin, while progenitor-derived colonies produced 10-35% beta globin. In mid-switch erythroblasts synthesized 50% beta globin, whereas progenitor-derived colonies produced only 15-35% beta. At the completion of the switch erythroblasts produced 100% beta globin, while progenitor-derived colonies produced as little as 40% beta chains. We conclude that the program of globin synthesis that characterizes the fetal switch is established at the level of erythroid progenitors. Fetal erythroid burst-forming units (BFU-E) dominate the marrow prior to the switch. The early switch period is heralded by the appearances of adult erythroid burst-forming units programmed to express increasing beta chain synthesis in colonies. By mid-switch a second class of adult erythroid progenitors capable of giving rise to fetal and adult hemoglobin synthesis in in vitro colonies becomes apparent. These shifting populations of erythroid progenitors with unique globin synthesis programs give rise to the erythroblasts that create the sigmoid pattern of the fetal to adult hemoglobin switch in the developing simian fetus.

Abundance and bionomics of Ochlerotatus j. japonicus in two counties in southwestern Virginia.

Movement of Ochlerotatus japonicus japonicus into virus-endemic areas in the USA has raised concern about its vector potential and prompted monitoring of its spread. The abundance and seasonal distribution of Oc. japonicus in southwestern Virginia was measured in 2003 and 2004 using gravid traps. In 2003, collections were made over 192 trap-nights from June to August yielding 5,879 mosquitoes of which only 24 were Oc. japonicus. In 2004, 12,151 mosquitoes were trapped from June to September over 160 trap-nights. Ochlerotatus japonicus was the second most abundant mosquito species and the dominant Ochlerotatus species collected in gravid traps. Ochlerotatus japonicus was collected in low numbers in June, but the abundance increased significantly in July and remained consistent throughout the rest of the season. Of the other major mosquito species collected in this study, only Aedes albopictus exhibited a similar seasonal pattern as Oc. japonicus. Other biological similarities of Oc. japonicus and Ae. albopictus are discussed.

Hypoxia-induced sympathetic inhibition of the fetal plasma insulin response to hyperglycemia.

Large-for-delivery date babies, considered characteristic of diabetic pregnancy, are believed to result from fetal hyperinsulinemia. Paradoxically, infant birth weights tend to be low-for-delivery date in mothers with more severe diabetes. We tested the hypothesis that hypoxemia in such fetuses leads to sympathoadrenal stimulation and inhibition of insulin secretion; and, thus, produces a net reduction in the growth-promoting effects. Fetal sheep were prepared with chronic peripheral and adrenal cannulas. Fetal blood gases, lactate, norepinephrine, and epinephrine secretion rates; and plasma norepinephrine, glucose, and immunoreactive insulin concentrations were determined at 30-min intervals during a 2-h baseline period and a 4-h period of hyperglycemia divided into 2-h segments of hypoxemia (with and without alpha-blockade) and hyperoxia. Hypoxemia-hyperoxia sequences were varied randomly. Well-oxygenated fetuses responded to a threefold increase in glucose with a sixfold increase in plasma immunoreactive insulin. With hypoxemia, norepinephrine and epinephrine secretion were elevated and the insulin response was blocked. With hypoxemia and phentolamine blockade, the insulin response was enhanced with a 10-fold increase above baseline. In severe maternal diabetes with vascular disease or with poor control and very high glucose levels, the fetus is likely to be relatively hypoxemic. Our experiments suggest that in this situation, the fetal insulin response to hyperglycemia will be attenuated; this effect is mediated, at least partly, through sympathoadrenal stimulation.

Adrenal secretion of glucocorticoids during hypoxemia in fetal sheep.

This work was undertaken to investigate the fetal adrenal corticoid secretory response to hypoxic stress in late gestation. Experiments were performed in two groups of fetal sheep of different gestational ages, group I, 129-132 (mean, 130) days and group II, 135-139 (mean, 136) days. Fetuses were prepared with chronic adrenal cannulas as well as peripheral arterial and venous catheters. With the fetus at rest and after 7, 9, 11 and, in some instances, 30 and 60 min of hypoxia (maternal FIO2 10%), precisely timed (2 min) samples of adrenal effluent were collected for determination of cortisol (F) and corticosterone (B) secretion rates. Peripheral samples were obtained intermittently for blood gas and lactate determinations. Resting corticoid secretory rates were highly variable, suggesting an episodic secretory pattern. Corticoid secretory responses to hypoxemia were significantly elevated at 7-11 min, peaked at 30 min, and remained stable at 60 min. Specifically, in group I, F secretion increased from a baseline value of 37 +/- 19 ng/min to a peak hypoxemic response of 376 +/- 80 ng/min; B secretion increased from 6 +/- 4 to 170 +/- 32 ng/min. In group II, F secretion increased from 99 +/- 20 to 653 +/- 107 ng/min; B secretion increased from 12 +/- 5 to 200 +/- 28 ng/min. When related to adrenal gland weight, there was no difference between F secretory responses in groups I and II, whereas relative B secretory responses were lower in group II than in group I at 9 and 11 min of hypoxemia. We conclude that the 129-139 day sheep fetal adrenal cortex is highly sensitive to hypoxic stress with the effect presumably mediated by elevated levels of endogenous ACTH. The B stress response decreases as gestational age advances from the 129-132 day range to 135-139 days.

Adrenal secretion of catecholamines during hypoxemia in fetal lambs.

A new method for quantifying adrenal secretory function in chronically catheterized fetal lambs was developed. This preparation included insertion of a catheter distally into the fetal left renal vein and placement of a remotely operated, hydraulically controlled choker around the renal vein at its junction with the vena cava. With the choker open, adrenal venous blood flowed into the renal vein and then into the vena cava. With the choker closed, adrenal blood flowed into the catheter so that timed samples of adrenal venous effluent could be obtained. With this technique, left adrenal secretory rates of norepinephrine and epinephrine were determined across a spectrum of oxygen concentrations in five near-term fetal lambs. There was a rapid rise in norepinephrine secretion after induction of hypoxemia. Maximum secretory rates occurred at about 5 min, concomitantly with the lowest attained fetal arterial partial pressure of oxygen (PO2s). There was an inverse exponential relation between these catecholamine secretion rates and fetal arterial PO2 (P less than 0.001). Norepinephrine secretion appeared to increase in response to lesser degrees of hypoxemia than did epinephrine, although a longer time delay between stimulation and epinephrine response may have been a factor. Overall, norepinephrine secretion was greater than that of epinephrine. The ratios of norepinephrine to epinephrine in individual adrenal samples varied considerably and in some instances were less than one. These ratios did not correlate significantly with the degree of hypoxemia. During 25 min of a relatively steady state of hypoxemia, norepinephrine secretion declined markedly after about 5 min, although it remained above control levels throughout. Epinephrine secretion rose more gradually but then was relatively stable during the remaining period of hypoxemia.

A study of placental transfer mechanisms in nonhuman primates using [14C]phenylalanine.

Placental transfer mechanisms were investigated in pregnant Macaca Fascicularis and Macaca mulatta during the gestational age of 120 to 130 days. These primates underwent an operative procedure that allowed continuous fetal blood sampling. The administration of [14C]phenylalanine into the maternal circulation revealed a significant increase of radioactive material in the fetal circulation, indicating an active placental transport mechanism unidirectional to the fetus. When [14C]phenylalanine was injected into the fetus, radioactive aromatic amino acids in the maternal circulation increased only slightly over time, resembling a simple diffusion process.

Surgery in the United Kingdom.

Surgery in the United Kingdom has been practiced for nearly 2000 years. It has evolved as a result of the experiences of warfare and the introduction of the scientific basis of surgery. The influence of the 4 surgical royal colleges in setting standards for training and examinations has ensured that new surgeons are equipped for independent practice as consultants. Responsibility for the National Health Service rests with the government, which determines the number of trainee surgeons in the various surgical specialties. Conflicts between service provision and training are highlighted, as are the pressures on academic institutions to meet the demands of clinical surgery. The government's National Health Service plan for England promises a major expansion in undergraduate places and an increase of 7500 consultants in all specialties by 2004. Time will tell if these changes lead to an improvement in surgical services and a reduction in waiting times.

Bile duct varices.

The diagnosis of biliary duct varices and portal vein occlusion should be considered when nodular or notched defects in the wall of the biliary duct system are shown by cholangiography or when pedunculated vascular structures in the bile ducts are seen at surgery. We present two cases of common hepatic and common bile duct varices due to portal vein occlusion.

Fetomaternal placental transfer mechanisms of aromatic amino acids in Macaca mulatta.

We investigated aromatic amino acid transfer mechanisms from fetus to mother in third-trimester pregnancies in rhesus monkeys after the administration of radioactive phenylalanine to the fetal circulation. The results indicated that fetomaternal transfer takes place mainly by facilitated diffusion via specific membrane carriers. This mechanism might participate in regulating amino acid concentrations in the fetus.

Amyloid tumour of the rectum.

Systemic amyloidosis results in diffuse deposition of amyloid proteins in various organs. Localized deposits in the form of nodules also occur but are rare in the gastrointestinal tract. A localized amyloid deposit in the rectum that was clinically indistinguishable from carcinoma of the rectum or prostate is described.