Shock-tube study of the decomposition of tetramethylsilane using gas chromatography and high-repetition-rate time-of-flight mass spectrometry.

The decomposition of tetramethylsilane was studied in shock-tube experiments in a temperature range of 1270-1580 K and pressures ranging from 1.5 to 2.3 bar behind reflected shock waves combining gas chromatography/mass spectrometry (GC/MS) and high-repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS). The main observed products were methane (CH4), ethylene (C2H4), ethane (C2H6), and acetylene (C2H2). In addition, the formation of a solid deposit was observed, which was identified to consist of silicon- and carbon-containing nanoparticles. A kinetics sub-mechanism with 13 silicon species and 20 silicon-containing reactions was developed. It was combined with the USC_MechII mechanism for hydrocarbons, which was able to simulate the experimental observations. The main decomposition channel of TMS is the Si-C bond scission forming methyl (CH3) and trimethylsilyl radicals (Si(CH3)3). The rate constant for TMS decomposition is represented by the Arrhenius expression ktotal[TMS → products] = 5.9 × 1012 exp(-267 kJ mol-1/RT) s-1.

A single-pulse shock tube coupled with high-repetition-rate time-of-flight mass spectrometry and gas chromatography for high-temperature gas-phase kinetics studies.

Shock tubes are frequently used to investigate the kinetics of chemical reactions in the gas phase at high temperatures. Conventionally, two complementary arrangements are used where either time-resolved intermediate species measurements are conducted after the initiation of the reaction or where the product composition is determined after rapid initiation and quenching of the reaction through gas-dynamic processes. This paper presents a facility that combines both approaches to determine comprehensive information. A single-pulse shock tube is combined with high-sensitivity gas chromatography/mass spectrometry for product composition and concentration measurement as well as high-repetition-rate time-of-flight mass spectrometry for time-dependent intermediate concentration determination with 10 µs time resolution. Both methods can be applied simultaneously. The arrangement is validated with investigations of the well-documented thermal unimolecular decomposition of cyclohexene towards ethylene and 1,3-butadiene at temperatures between 1000 and 1500 K and pressures ranging from 0.8 to 2.4 bars. The comparison shows that the experimental results for both detections are in very good agreement with each other and with literature data.

Adult offspring long-term effects of high salt and water intake during pregnancy.

Offspring from dams subjected to hypereninemia, hyperdipsia, and natriophilia by partial aortic ligation (PAL) showed a long-term modification of their ingestive behavior. These rats, upon reaching adulthood, showed an increased appetite for low-concentration saline solutions (0.1 M) when compared to control rats. They also presented a high intake of a medium concentration NaCl solution (0.45 M) after having been offered a very aversive highly concentrated NaCl solution (1.0 M) along with water for 2 days. An increase was also observed in their salt/water intake ratio following two different thirst challenges, 24-h fluid deprivation or sodium depletion by furosemide treatment. The demonstration of the long-term effect of pregnancy history on salt preference in adult offspring draws attention to the possible physiopathological aspects that may be of relevance, considering the well-established relationship between salt intake and hypertension, a disease most commonly occurring in the adult and aged population.

Effect of castration and gonadal hormones on insulin-induced drinking.

Female Wistar rats in any of the estrual phases have been shown to drink significantly more water than males (p < 0.05), after a single I.P. insulin injection (5 U/kg b.wt.). Sexual differences in insulin-induced drinking persisted after castration when it was made in adult rats (4.6 +/- 1.2 ml/2 h, males = 8; vs. 13.0 +/- 3.1 ml/2 h, females = 8; p < 0.05). On the other hand, when animals were castrated before puberty or when newborn, sexual differences in insulin-induced drinking disappeared. Hence, insulin-induced drinking seems to be a sex-dependent phenomenon that differentiates just before or during puberty since it is abolished by castration prior to sexual maturation. Sex hormone administration in male and female rats castrated at different ages showed a variety of actions on insulin-induced drinking. A pattern emerged showing that androgenized (testosterone treated) rats drank usually less in response to insulin than estrogen-treated rats (independent of their genetic sex). According to the above results, we can conclude that insulin-induced drinking is a phenomenon sensible to gonadal hormones, both by conditioning the differentiation of some physiological structure or mechanisms that underlay drinking behavior in that paradigm and by a direct action on these or other related mechanisms.

Increased salt preference in adult offspring raised by mother rats consuming excessive amounts of salt and water.

This study was designed to evaluate the effects of an early high-salt environment on the maternal and the young offspring physiology and on the adult offspring sodium appetite. Twenty-five-adult female Wistar rats were pseudorandomly divided into two groups. Twelve animals underwent a partial ligature of their abdominal aorta (PAL). Once polydipsia and sodium appetite (tested by measuring water and a 2.7% NaCl intakes) developed, they were mated. The other 13 rats (SHAM) were sham-operated and also mated. Throughout pregnancy and lactation, water and salt intake of PAL rats was consistently and significantly higher than that of the Sham. On gestation day 20, amniotic fluid and maternal plasma sodium concentration of PAL and Sham rats did not differ. Sodium concentration in the milk of the lactating PAL group was elevated (P < 0.05) on day 20 after delivery. At 0, 10 and 21 days of age, plasma sodium concentration of PAL offspring (PAL-O) and Sham offspring (Sh-O) were not significantly different. At 90 days of age, the salt preference of PAL-O rats was greater than that of Sh-O rats after 7 days of sodium deprivation (P < 0.01).

Changes of blood pressure responsiveness in rats exposed in utero and perinatally to a high-salt environment.

We tested the hypothesis that the pressor responses to angiotensin II could be influenced by an early salt exposure. Twenty-five adult female rats were pseudorandomly divided in two groups. Twelve animals underwent a partial ligature of their abdominal aorta (PAL). Once polydipsia and sodium appetite developed, these rats were mated. The other group (13 rats) was sham-operated (Sham) and mated. Throughout pregnancy and lactation, water and 2.7% NaCl solution intakes differed between the two groups of mother rats. PAL offspring (PAL-O; n = 14), and Sham-operated offspring (Sh-O; n = 10), were maintained on a solid diet containing 1% NaCl, tap water and a 2.7% NaCl solution. At 90 days of age, pressor responsiveness to intravenous angiotensin II (50, 100 and 200 ng) was assessed in anesthetized rats. The pressor responses to 50 and 200 ng angiotensin II were significantly greater in PAL-O rats than in Sh-O rats. These results support the hypothesis of a modulation of cardiovascular responsiveness or its underlying mechanisms by an early high salt environment.

Attenuation of insulin-induced drinking by beta-adrenoceptor antagonists.

Insulin-induced drinking (IID) in male Wistar rats, evoked by administering 5 U/kg of crystalline porcine insulin i.p., was significantly decreased by propranolol (0.1 and 0.5 mg/kg s.c.) after 1 and 2 h. The blood glucose of rats treated with a much higher dose of propranolol (10 mg/kg body weight) and insulin did not differ from that of rats treated solely with insulin after 30 and 120 min. Atenolol (0.5 mg/kg s.c.) caused a reduction in IID after 1 and 2h. Butoxamine (1 mg/kg s.c.) also reduced IID after 1 and 2h, and at 0.5 mg/kg after 1h. The alpha-blocker, phenoxybenzamine (10 mg/kg s.c.), had the opposite effect, stimulating IID after 2h. There is no direct evidence that insulin activated the sympathetic system at the doses used in these experiments. Nevertheless, the results reported here seem to be compatible with the involvement of the sympathetic system in IID, possible through the renin-angiotensin system.

Psychological aspects of insulin-induced thirst.

Fifteen normal volunteers received one insulin injection or saline in two nonconsecutive days. At 0', 30', 60' and 90' water intake was measured. Simultaneously subjective thirst and hunger were recorded by running a set of psychological tests. Water intake was higher after insulin than saline at 60' and 90'. Insulin increases thirst sensation even before the sensation of hunger.

Insulin stimulation of water intake in humans.

Drinking response to the intravenous administration of insulin (0.1 U/kg) was studied in 15 volunteers (eight males and seven females). Water intake was significantly higher after insulin than after saline administration during the 90-min period studied. Plasma glucose decreased significantly in individuals receiving insulin and the time of the maximum decrease (30 min) was concurrent with the beginning of water intake. Haematocrit values in the insulin-treated group were also significantly higher at that time. Plasma renin activity (PRA) after insulin administration was higher than under basal conditions or after saline injection. On the other hand, psychological responses indicated that insulin probably elicits thirst prior to the hunger which appears with hypoglycaemia. A possible role of endogenous insulin in meal-related thirst is hypothesized.

Effects of inhibitors of the renin-angiotensin system on water intake after insulin administration.

Male wistar rats drank in a dose-related manner, in response to 1 to 40 U/kg of i.p. insulin. Maximum intakes took place during the first 30 min after i.p. insulin administration, coinciding with the period of maximal drop of blood glucose. Plasma renin activity (PRA) in rats treated with i.p. insulin was higher than in basal conditions or after saline injection. Nephrectomy and adrenalectomy did not abolish insulin-induced drinking. A low dose of captopril (0.1 mg/kg s.c.) did not modify insulin-induced drinking, but a higher dose (10 mg/kg s.c.), or enalapril (0.5 mg/microgram s.c.), significantly increased insulin-induced drinking. Enhancement of insulin-induced drinking by s.c. captopril was not secondary to an increased diuresis. Captopril (50 micrograms i.c.v.) significantly reduced the cumulative water intake after i.p. insulin (20 U/kg i.p.) plus s.c. captopril (10 mg/kg). The blockade of central receptors for angiotensin II with sarile-AII (5 micrograms) significantly diminished insulin-induced drinking. It appears that the peripheral renin angiotensin system is not necessary for insulin-induced drinking but central angiotensin II plays an important role.

Effect of insulin administration on water drinking in children.

The effect of insulin administration on water intake, was studied in children submitted to standard protocols for stimulation of secretion of hypophyseal hormones by i.v. treatment with several different drugs: insulin, insulin plus TRH and LH-RH; and propranolol, clonidine or LH-RH. Drinking was measured from 0 to 90 min after drug administration; from blood samples taken at 60 min for hypophyseal hormones analysis, microhaematocrit values were measured, as well as plasma renin activity (PRA) and glycaemia. Water intake was significantly higher in both groups of patients receiving insulin than in the control group (no insulin). Haematocrit values did not change after 60 min. There was a significant correlation of glycaemia of individuals from all three groups and water intake at 60 min. PRA was significantly higher in insulin treated individuals.

Congenital dysgranulopoietic neutropenia in two siblings: clinical, ultrastructural, and in vitro bone marrow culture studies.

Two siblings with congenital neutropenia are reported. The first patient, female, died after Pseudomonas sepsis. The second patient male, suffered from recurrent pyogenic infections, with a more benign course. Bone Marrow (BM) and Peripheral Blood (PB) analysis in the second patient revealed a reduced number of granules and myelin bodies in the PB neutrophils, suggesting a developmental defect of primary and secondary granules. BM promyelocytes were almost normal, but the myelocytes and metamyelocytes showed defective granulogenesis. The BM in vitro granulocyte-macrophage-colony-forming cell (GM-CFC) growth and the PB white blood cells (WBC) granulocyte-macrophage-colony-stimulating factor (GM-CSF) production, which were analyzed in the second patient, showed normal numbers of GM-CFC, with differentiation mostly toward monocytes and a defect in the GM-CSF production capacity. The second patient's PB mononuclear cells or serum did not inhibit normal GM-CFC when added to control BM cells. We suggest that in this specific form of congenital neutropenia, which is probably an autosomal recessive disorder, the abnormal neutrophil granule production and the defective provision of GM-CSF by PB WBC are unique pathognomonic characteristics, possibly associated with the overt neutropenia.

Ovarian hyperstimulation in rats.

Induction of a mild hyperstimulation syndrome in the female rat, and the possible effect of the induction on prolactin, were studied using light and electron microscopy as well as radioimmunoassay. Five days of human menopausal gonadotropin (HMG) treatment were followed by human chorionic gonadotropin (HCG) administration. Ovarian hyperstimulation was observed in all treated rats, as attested to by the weight increase and by histological studies. Ovaries were enlarged 3-4 times as compared with controls, and consisted mostly of corpora lutea follicular cysts and hemorrhagic cysts. Other visceral organs remained unaffected, except for slight edematous changes observed in the lungs of the treated rats. Electron microscopic examination of the hypophysis of the treated group tends to indicate increased synthesis and secretory activity of the prolactin cells. However, serum prolactin levels of treated and non-treated groups were not different. Augmented doses of the gonadotropins did not change the findings, and only mild grade 2 ovarian hyperstimulation, according to Schenker and Weinstein (1978), could be produced in the mature rat. Thus, the rat experimental model does not seem to be comparable with the situation in the human, and cannot be used to study the pathogenesis of the disorder in the human.