Effects of erythropoietin therapy on iron absorption in chronic renal failure.

The effect of erythropoietin administration on the absorption of dietary and therapeutic iron was examined in patients with anemia of chronic renal failure on maintenance hemodialysis. Absorption from test meals tagged extrinsically with iron 55, iron 59, or both was determined 2 weeks later by using incorporated red blood cell radioactivity and whole body counting. In an initial study of food iron absorption, the effect of initiating erythropoietin therapy was determined by measuring the absorption of heme and nonheme iron before and 2 weeks after the administration of 64 U/kg body weight erythropoietin (range, 46-85 U/kg body weight) three times weekly. Absorption of heme iron increased 1.6-fold from 18.6% to 30.1% (P < .05), and nonheme iron increased 3.7-fold from 1.3% to 4.9% (P < .01) after erythropoietin therapy. In a second study therapeutic iron absorption was evaluated at baseline and after erythropoietin administration (63 U/kg body weight (range, 48-74 U/kg body weight) three times weekly). The absorption of 50 mg of iron as ferrous sulfate increased 2.4-fold from 3.8% to 9.4% (P < .05) when given without food and 4.2-fold from 1.4% to 5.9% (P < .05) when given with food after erythropoietin administration. After adjusting for changes in iron stores with serum ferritin after erythropoietin therapy, the enhanced erythropoiesis associated with erythropoietin therapy increased absorption about 2-fold, which was similar to the response observed previously in normal subjects. In a final study we examined the absorption of therapeutic iron during the steadystate phase of erythropoietin therapy after an erythroid response to erythropoietin had occurred. The absorption of 50 mg of iron was lower than that occurring with the initiation of erythropoietin therapy at 2.2% when given alone and 1.3% when taken with food. We conclude that iron absorption with or without erythropoietin stimulation is unimpaired in patients with chronic renal failure.

In vitro uterine contractions in the viviparous lizard Tiliqua rugosa: effects of gestation and steroid pretreatment in vivo.

Uterine contractility was investigated in the viviparous lizard Tiliqua rugosa. Arginine vasotocin (AVT) induces rhythmic contractions in vitro in strips of uterine tissue from ovariectomized female T. rugosa. The strength of these contractions was related to the dosage of AVT and reduced by pretreatment in vivo with both progesterone and estradiol-17 beta. The frequency of spontaneous and AVT-induced contractions was enhanced by estradiol-17 beta pretreatment. The strength of AVT-induced contractions in pregnant females was not significantly different from that recorded in nonpregnant females. Spontaneous rhythmic contractions were present only in pregnant females. Ovariectomy did not affect either spontaneous or AVT-induced contractions in pregnant females. The data indicate that ovarian steroids modulate uterine contractility in T. rugosa. It is suggested that, following a decline in plasma progesterone levels, estrogen may be involved in the onset of parturition.

Plasma arginine vasotocin, progesterone, and luteal development during pregnancy in the viviparous lizard Tiliqua rugosa.

The relationship between plasma levels of arginine vasotocin (AVT), progesterone, and corpus luteum formation and degeneration was studied in the viviparous lizard Tiliqua rugosa. Hormone levels were monitored in free-ranging, pregnant females which were located for sampling by means of attached radio transmitters. There was an increase in plasma AVT levels in the 30 days immediately prior to parturition. Concurrent with this event was a decline in plasma progesterone levels from relatively high levels in mid-term to basal levels prior to parturition. This is associated with degenerative changes in the corpus luteum which include pyknosis of the nuclei of the cells of the cell mass and increasing prevalence of intercellular spaces, while the thecal layer became increasingly compacted. Ovariectomy experiments indicate that the major source of progesterone during pregnancy in T. rugosa is ovarian.

AIDS prevention for intravenous drug users in the community: street-based education and risk behavior.

Conducted a study of behavior change associated with a street-based AIDS education project targeted to intravenous (IV) drug users in San Francisco. Two cross-sections were sampled from drug detoxification clinics and street locations in 1986 (n = 438) and 1987 (n = 623). Significant increases were reported in the percentage of IV drug users who used bleach to decontaminate syringes, who did not share needles in past year, and in condom use. A significant reduction in an index of the number of needle-sharing partners was reported. Respondents ranked treatment program as most important source of AIDS information prior to implementation of the program, and ranked outreach workers as most important after implementation. Findings suggest that this community-based outreach program had at least some impact on knowledge about AIDS and may have led to reductions in behaviors known to transmit HIV.

Effect of available surface water on levels of antidiuretic hormone (lysine vasopressin) and water and electrolyte metabolism of the Rottnest Island quokka (Setonix brachyurus).

A sensitive radioimmunoassay was developed to measure circulating levels of the neurohypophysial peptide lysine vasopressin (LVP) in the marsupial quokka (Setonix brachyurus), which is abundant on Rottnest Island off the coast of Western Australia. Animals from locations on the island where free water is completely absent were compared in midsummer with animals from sites where brackish water is available and utilized by the quokkas. In the animals from West End, where free water is absent, circulating levels of LVP averaged 89.2 +/- 19.6 pg/ml, which was significantly higher than the mean level of 35.6 +/- 15.8 pg/ml measured in individuals collected from the Lakes site with access to brackish drinking water. Rates of water and sodium turnover, measured with isotopes, were significantly greater in Lakes than West End animals, as were renal clearances of sodium, chloride, urea, and total osmolytes. Despite an obvious osmotic diuresis resulting from the ingestion of salty water, the Lakes animals were in better physical condition at the end of summer than the West End animals which lack free water, and these latter individuals showed signs of slight dehydration with elevated plasma and urinary electrolyte concentrations and osmolalities.

Metabolism in lizards: low lactate turnover and advantages of heterothermy.

The bobtail lizard (Tiliqua rugosa) encounters environmental temperatures that range from 7 to 40 degrees C. We have studied the effects of temperature on the whole-body turnover of glucose, lactate, and fatty acid. At 35 degrees C turnover rates of glucose and fatty acid account for the majority of O2 uptake and reflect the low metabolic rate of the bobtail compared with that of a mammal of equivalent mass. Lactate turnover at rest is very low. The low rates of lactate production correlate with a lack, or relative lack, of those tissues that normally produce most of the lactate in a resting mammal, such as nonnucleated red blood cells, renal medulla, and smooth muscle associated with blood vessels. Q10 (change in rate with a 10 degrees C change in temperature) values for turnover rates of glucose and fatty acid increase as temperature decreases. It is concluded that there is an inverse temperature effect that minimizes fuel usage during torpor.

Hormonal control of femoral gland secretion in the lizard, Amphibolurus ornatus.

Castration of the male lizard Amphibolurus ornatus results in atrophy of the femoral glands. The amount of secretion collected from glands decreased from (mean +/- SE) 136.6 +/- 13.0 micrograms/g body wt prior to castration to 102.7 +/- 14.6 micrograms/g body wt 28 days after castration (P less than 0.001). Over the same period the secretion from a group of intact males increased. Biosynthesis of steroids by testicular tissue from A. ornatus was studied in vitro using [4-14C]progesterone as substrate. A single androgen, probably testosterone, was isolated. Daily injections for 28 days of 1 microgram/g body wt of testosterone propionate (TP) and 5 alpha-dihydrotestosterone (DHT) stimulated femoral gland secretion in castrated males (TP, 201.8 +/- 21.5 micrograms/g body wt; DHT, 142.8 +/- 16.0 micrograms/g body wt). The glands of animals receiving injection medium only remained atrophic. Identical regimes of TP and DHT also stimulated femoral gland secretion in intact females from which no exudate could initially be collected. These data are consistent with the hypothesis that lizard femoral glands are androgen-dependent secondary sex characters.