Changes in the lipid composition of blood serum in girls with different somatotypes after a meal

Changes in the neutral lipid and phospholipid composition of blood serum in response to meals were analyzed in girls with different somatotypes. After meals, a statistically significant decrease in the content of free fatty acids was observed in all subjects, irrespective of the somatotype. Statistically significant increases in the contents of readily oxidized phospholipid fractions were observed in girls of subathletic and athletic somatotypes. These data show the changes in the relationship between variable components of the lipid spectrum of lipoproteins. The main structural constituents of membrane lipoproteins, such as stable phospholipid fractions and free cholesterol, did not change in response to meals in girls of any somatotype. These data demonstrate a stability of membrane lipoprotein complexes in response to this physiological stimulus.     

Changes in the hemolymph of the stable fly,Stomoxys calcitrans,after a blood meal

The stable fly hemolymph was analyzed after a blood meal. The hemolymph volume increased to approximately three times the pre-feeding level 3–6 h after a blood meal and gradually returned to normal 18 h after the blood meal. The osmotic pressure decreased approximately 10% following a blood meal and gradually returned to normal with a pattern that was a mirror-image of that of the hemolymph volume. Concentrations of cations and anions are not directly affected by the ingested blood, indicating a possible selective excretory mechanism.     

Changes in blood lipids and blood pressure during adolescence.

A total of 625 adolescents from three general practices participated in a cross-sectional study of cardiovascular disease risk factors. The girls had higher serum total and high density lipoprotein (HDL) cholesterol concentrations than the boys, while the boys had higher serum triglyceride concentrations. Smoking (equally prevalent in both sexes) was associated with lower HDL cholesterol concentrations, particularly in boys, while in girls use of oral contraceptives was associated with higher total cholesterol and lower HDL cholesterol concentrations showed striking associations with age, height, and sexual maturation in boys, but not in girls. Triglyceride concentrations were associated with age in boys. Systolic blood pressure and serum urate concentrations were higher in boys and rose steeply with age, but no age association was seen for urate concentrations or systolic blood pressure in girls or for diastolic pressures in either sex. Girls, however, had higher diastolic pressures. There was a strong association between urate concentration and the other cardiovascular disease risk factors, especially HDL cholesterol. Adolescence is associated with considerable changes in cardiovascular disease risk factors, and there are striking sex differences in these changes.     

Molecular forms of cholecystokinin in plasma from normal and gastrectomized human subjects following a fat meal

The present study was undertaken to characterize molecular forms of cholecystokinin (CCK) in human fat-stimulated plasma by Sephadex G50 column chromatography followed by radioimmunoassays employing 3 different region-specific antibodies. CCK was extracted and concentrated from plasma of healthy subjects by adsorption to SEP-PAK C18 cartridges and from plasma of gastrectomized patients by addition of 96% ethanol. Antibody 1703 binds to carboxy-terminal CCK-peptides containing at least 14 amino acid residues, antibody T204 to sulfated carboxy-terminal CCK-peptides and antibody 5135 to carboxy-terminal forms of CCK and gastrin. Four molecular forms of CCK were consistently demonstrated; peak I eluted in the void volume and comprised 1.8-10.2% of CCK-immunoreactivity, peak II eluted between the void volume and the CCK-33/39 standard and comprised 9.8-21.6%, peak III eluted at the position of the CCK-33/39 standard and comprised 42.4-55.4%, and peak IV eluted between the CCK-33/39 and CCK-14 standards and comprised 25.4-40.1% of CCK immunoreactivity. Since these 4 molecular forms reacted to all 3 CCK-antibodies it is likely that they contain the sulfated tyrosyl and carboxy-terminal regions of CCK and, therefore, possess biological activity.     

Excretion of proteolytic enzymes by Aedes aegypti after a blood meal.

Excretion of active proteolytic enzymes during the period of blood digestion in a mosquito has been demonstrated for the first time. The rate of excretion has been determined for both proteases and uric acid; each appears in a distinct peak. During the first half of the digestion period, when protease activity in the midgut is increasing, uric acid excretion predominates. During the second half of the digestion period, after the protease has reached its maximum in the midgut, there is considerable excretion of active protease, mainly trypsin.By sealing the anus after feeding (blood enema), it has been demonstrated that secretion of the proteolytic enzymes in the midgut actually stops when maximum activity is reached. Sealing the anus did not interfere with egg development.A model for protease secretion is suggested in which the proteolytic enzymes are induced by their substrate (globular proteins), and secretion stops when 80 per cent of the protein is digested, or the inducer is removed.     

Development of responsiveness to hormones after a blood meal in the mosquito Aedes aegypti

The effects of exogenous hormones on oocyte development in isolated abdomens from blood-fed female Aedes aegypti were examined. Abdomens were prepared immediately after a blood meal. Single applications of hormones were administered immediately after ligation or 18 hr after the blood meal. Double applications were done at both times. Oocyte development was assayed by measuring the amount of yolk in oocytes 66 hr after the blood meal. Topical application of maximum doses of methoprene immediately after ligation caused oocytes to mature in 60% of the abdomens; a half-maximum response was obtained with 300 pg. Injection of 700 ng of 20-hydroxyecdysone (20-HE) was necessary to cause an equivalent response. Delaying the injection of 20-HE until 18 hr after feeding reduced the amount necessary to obtain a half-maximum response to 150 ng. Treating the abdomens twice dramatically reduced the amount of 20-HE needed for the second dose: pretreatment of abdomens immediately after ligation with 50 pg of 20-HE reduced the amount of 20-HE needed in the second injection to 30 ng. Pretreatment with a topical application of 50 pg of methoprene had a similar effect. These data indicate that the sensitivity of the mosquito to exogenous hormones changes after a blood meal, and that either 20-HE or methoprene can promote a further increase in sensitivity.     

Actin redistribution in mosquito malpighian tubules after a blood meal and cyclic AMP stimulation

Fluid secretion by mosquito Malpighian tubules is critical to maintaining fluid and electrolyte balance after a blood meal. Endogenous cAMP levels increase in Malpighian tubules after a blood meal. Here, we determined if corresponding changes in intracellular actin distribution occur after a blood meal or dibutyryl-cAMP (db-cAMP) stimulation and whether altering actin turnover inhibits secretion. In untreated Malpighian tubules, beta-actin immunostaining was more intense in the apical region of adult Malpighian tubules than in the cytoplasm. Stimulation by a blood meal or db-cAMP significantly decreased beta-actin immunostaining in the non-apical region of the cell. Db-cAMP had similar effects in larvae and pupae Malpighian tubules. In contrast, no detectable shift in F-actin distribution was detected; however, F-actin bundles within the cytoplasm increased in size after treatment with db-cAMP. Pretreatment of Malpighian tubules with agents perturbing actin fiber assembly and disassembly decreased basal secretion rates and inhibited the stimulatory effects of db-cAMP. Our results show (1) beta-actin redistributes toward the apical membrane after a blood meal and this correlates temporally with increase urine flow rate and intracellular cAMP levels, (2) Malpighian tubules from all developmental stages exhibit this same response to db-cAMP-stimulation, and (3) dynamic assembly and disassembly of beta-actin is required for db-cAMP-stimulated secretion.     

Evidence for hormonal control of diuresis after a blood meal in the mosquito Aedes aegypti

In previous studies we have presented evidence for the role of peptides, isolated from heads of the mosquito Aedes aegypti, in stimulating fluid secretion by isolated Malpighian tubules. In the present study we conducted experiments to investigate whether these peptides are involved in hormone-mediated diuresis after a blood meal. In vivo experiments showed that the head was required to maintain diuresis after the blood meal. Whereas feeding on blood triggered a prompt diuresis in the intact mosquito, subsequent decapitation caused a gradual, not an abrupt, decline in urine excretion rate. Hemolymph collected from mosquitoes fed blood significantly stimulated fluid secretion in vitro by isolated Malpighian tubules, whereas hemolymph from unfed or blood-fed decapitated mosquitoes did not. These results indicate that a diuretic factor was released into the hemolymph after a blood meal. This factor was not present in the hemolymph of decapitated females. We identified the head as a source of diuretic factors. Peptides isolated from a head extract by high-performance liquid chromatography, when injected into the hemocoel of blood-fed decapitated mosquitoes, triggered diuresis in vivo and also stimulated fluid secretion in isolated Malpighian tubules. These studies support the hypothesis that the head is a storage site for diuretic peptides that may be released after a blood meal to control diuresis.