Anaerobic threshold estimation by statistical modelling.

Anaerobic threshold (AT) is usually estimated as a change point problem by visual analysis of the cardiorespiratory response to incremental dynamic exercise. In this study, two phase linear (TPL) models of the linear-linear and linear-quadratic type were used for the estimation of AT. The correlation coefficient between the classical and statistical approaches was 0.88, and 0.89 after outlier exclusion. The TPL models provide a simple method for estimating AT that can be easily implemented using a digital computer for the automatic pattern recognition of AT.

Rabbit antibody responses to experimental infestation with Dermatobia hominis.

The three larval stages of Dermatobia hominis (Linnaeus) have been evaluated for their immunogenicity by ELISA and immunodiffusion (ID) using sera from experimentally infested rabbits. During a primary infestation, first instar D. hominis were found to cause most reaction and allowed the earliest diagnosis by ELISA. An inhibition of the antibody response against second and third instars was observed. The inhibition disappeared after departure of the larvae from the host. In experimentally immunized hosts the antibody response, following challenge, was highest against second and third instar antigens. Antibody remained elevated during the infestation but fell immediately after the larvae had left the host.

Pancreas damage and intratracheal NiCl2 administration. Effects of nickel chloride.

Changes in activities of Cu-Zn superoxide dismutase (SOD- E.C.1.15.1.1.) and lactate dehydrogenase (LDH- E.C.1.1.1.27.) and levels of copper, total protein, triglycerides, phospholipids and total lipids were investigated in pancreas of rats after intratracheal administration of NiCl2 (8.4 mumol/kg). Nickel chloride induced increased SOD activity in pancreas and erythrocytes. This elevation was related to increased copper and decreased phospholipid content in pancreas of these animals. In conclusion, the ability of an animal to tolerate nickel chloride induced damage was governed by a delicate balance between the generation of cytotoxic agents and the various pancreas defense capabilities.

Two thermal methods to measure the energy fluence of a brief exposure of diagnostic x rays

This paper describes two simple thermal methods for measuring the energy fluence in J/cm 2 from a diagnostic x-ray exposure. Both detectors absorb essentially 100% of the radiation and give a signal that is directly proportional to the energy fluence of the x-ray beam. One detector measures the thermal effect when a pulse of x rays is totally absorbed in the pyroelectric detector of lead-zirconium-titanate (PZT). The other detector measures the expansion of a gas surrounding a lead disk detector in a photoacoustic chamber. The increased pressure of the gas is transmitted through a 1-mm duct to a sensitive microphone. Both detectors have previously been used to measure the energy fluence rate of continuous x-ray beams in the same energy region using a chopped beam and a lock-in amplifier. Measurement of the energy fluence of a pulse of radiation eliminates the need for the beam chopper and lock-in amplifier and results in a simple, rugged, and inexpensive dosimeter. Either method can be combined with the area of the beam to give an estimate of the imparted energy to the patient from a diagnostic x-ray exposure.

Infection and apparent invasion of Vero cells by Paracoccidioides brasiliensis

Paracoccidioides brasiliensis probably uses many different mechanisms to establish itself in the host and cause disease. In this work, we assess an in vitro model system which uses cultured mammalian cells to investigate the virulence factors of P. brasiliensis. We were able to demonstrate an invasion process of the yeast form of this fungus in Vero cell cultures. We deduced that the overall invasive process involved three steps: adhesion, followed by invasion of individual epithelial cells and spread to adjacent cells.

Different effects on rat arterial pressure and heart rate when losartan is injected into the third or fourth ventricle

Cardiovascular responses to central losartan (LOS), a non-peptide angiotensin II (ANG II) receptor antagonist, were investigated by comparing the effects of LOS injection into the 3rd and 4th cerebral ventricles (3rdV, 4thV) on mean arterial pressure (MAP) and heart rate (HR). Adult male Holtzman rats were used (N=6 animals per group). Average basal MAP and HR were 114±3 mmHg and 343±9 bpm (N=23), respectively. LOS (50, 100 or 200 nmol/2 μl) injected into the 3rdV induced pressor (peak of 25±3 mmHg) and tachycardic (peak of 60±25 bpm) responses. LOS injected into the 4thV had no effect on MAP, but it induced bradycardia (peak of -35±15 bpm). KCl (200 nmol/2 μl) injected into the 3rdV or into the 4thV had no effect on either MAP or HR compared to 0.9% saline injection. The results indicate that LOS injected into the third ventricle acts on forebrain structures to induce its pressor and tachycardic effects and that bradycardia, likely dependent on hindbrain structures, is obtained when LOS is injected into the fourth ventricle.

On a possible dual role for central noradrenaline in the control of hydromineral fluid intake

Noradrenaline (NOR) is a neurotransmitter presenl in the central nervous system which is related to the control of ingestive behavior of food and fluids. We describe here the relationship between NOR and intake of water and NaCl solution, fluids that are essential for a normal body fluid electrolytic balance. Central NOR has an inhibitory effect on fluid intake, but it either induces or not alterations in food intake. Several ways of inducing water intake, such as water deprivation, meal-associated water intake, administration of angiotensinergic, cholinergic or beta-adrenergic agonists, or administration of hyperosmotic solutions, are inhibited by alpha-adrenergic agonists. Need-induced sodium intake by sodium-depleted animals is also inhibited by alpha-adrenergic agonists. NOR can also facilitate fluid intake. Water intake is elicited by NOR and the integrity of central noradrenergic systems is necessary for a normal expression of water or salt intake in dehydrated animals. The angiotensinergic component of either behavior apparently depends on a central noradrenergic system. NOR probably facililates fluid intake by acting on postsynaptic receptors, but we do not know how it inhibits fluid infake. The inhibitory and facilitatory effects of NOR on ingestive behavior suggest a dual role for this neurotransmitter in the control of hydromineral fluid intake.

Hyaluronidase and chondroitin sulphatase production by different species of Candida

The production of hyaluronidase and chondroitin sulphatase by Candida albicans, Candida tropicalis, Candida parapsilosis, Candida guilliermondii and Candida krusei was investigated using a complex culture medium (Sabouraud glucose agar) and a chemically defined medium. Among the 63 C. albicans isolates tested, 61 (97.8%) were found to be hyaluronidase and chondroitin sulphatase producers; one isolate produced only chondroitin sulphatase and one other was unable to produce either enzyme. The second major hyaluronidase and chondroitin sulphatase producing species was C. tropicalis followed by C. guilliermondii, C. parapsilosis and C. krusei. Among the C. albicans isolates tested no relation between the source of isolation and the amount of hyaluronidase and chondroitin sulphatase produced was found.

Effects of protein malnutrition on glucose tolerance in rats with alloxan-induced diabetes

Protein-calorie malnutrition produces glucose intolerance and reduced insulin release in response to glucose. Rats adapted to low- or high-protein diets show an increased resistance to the diabetogenic action of a single dose of streptozotocin or alloxan. To determine the effects of dietary protein level on pancreatic function, we measured serum glucose levels under basal conditions and during the oral glucose tolerance test (GTT) performed before and after a single dose of alloxan administered to rats fed a 25% or a 6% protein diet for a period of 8 weeks. The incidence of mild hyperglycemia (serum glucose > 250 mg/dl) was greater among the rats fed the 25% protein diet (81%) than among those fed the 6% protein diet (42%). During the GTT performed before alloxan administration the serum glucose levels of the rats fed the 6% protein diet were not found to be significantly different from those of rats fed the 25% protein diet. During the GTT performed after alloxan injection all rats showed intolerance to the substrate (serum glucose > 160 mg/dl 120 min after glucose administration) regardless of whether basal serum glucose was normal or high. In summary, alloxan was less effective in producing basal hyperglycemia in the rats fed the 6% protein diet than in those fed the 25% protein diet but caused glucose intolerance during the oral GTT in both groups. Thus, it seems that feeding a 6% protein diet to rats offers only partial protection against the toxic effects of alloxan.

The effect of serum on in vitro maturation, in vitro fertilization and steroidogenesis of bovine oocytes co-cultured with granulosa cells.

The influence of fetal calf serum alone (FCS) or associated with proestrous (FCS+PCS), estrous (FCS+ECS) or metaestrous (FCS+MCS) cow serum added to the culture medium and of the steroids produced by co-cultured granulosa cells were evaluated in terms of the in vitro maturation (IVM) and fertilization (IVF) of bovine oocytes. Supplementation of the medium with FCS+ECS and FCS+MCS resulted in higher proportions of oocytes that reached metaphase II (96.0% and 93.3%, respectively) and in higher proportions of embryos that reached the four- and eight-cell/morula stages (51.9% and 65.6%, respectively), whereas the supplementation with FCS and FCS+PCS resulted in only 79.2% and 67.5%, respectively, of matured oocytes and 26.7% and 34.3%, respectively, of cleaved embryos. These findings show that the best IVM and IVF were obtained at lower concentrations of estradiol produced by co-cultured granulosa cells (supplementation with FCS+ECS: 10.3 ng/ml and FCS+MCS: 2.1 ng/ml), whereas the worst results in IVM and IVF occurred at higher concentrations of estradiol that were obtained with FCS (33.1 ng/ml) and FCS+PCS (19.9 ng/ml) supplementation. These data suggest an inhibitory effect of estradiol on resumption of oocyte meiosis in vitro.

Glucose Tolerance and Insulin Action in Monosodium Glutamate (MSG) Obese Exercise-trained Rats

The present study was designed to evaluate the effects of chronic aerobic exercise (swimming, 1h/day, 5 days/week, with an overload of 5% body weight) on glucose metabolism in obese male Wistar rats. Hypothalamic obesity was induced through administration of monosodium glutamate (MSG) at 4 mg/g of body weight every other day from birth to 14 days old. Fourteen weeks after drug administration, the rats were separated into two groups: MSG-S (sedentary) and MSG-T (swimming for 10 weeks). Rats of the same age and strain, receiving saline in place of MSG, were used as control (C), and subdivided into two groups: C-S and C-T. At the end of the experimental period, an oral glucose tolerance test was performed and serum glucose (AG) and insulin (AI) were evaluated. A constant for serum glucose decrease (Kitt) in response to exogenous insulin was calculated. Soleus muscle strips and adipose tissue samples were incubated and insulin stimulated glucose uptake determined. No differences were observed in AG among the 4 groups. MSG-S rats showed higher AI (418%) and lower Kitt (92.3%) than C-S rats. T-rats showed higher glucose uptake by muscle (224.0%) and adipose tissues (94.1%) than S-rats. Among trained rats, glucose uptake by muscle was higher in MSG-T (5.4%) than in C-T. while the opposite was observed in adipose tissue (39% higher in C-T). Chronic aerobic exercise was able to improve glucose tolerance and reduce insulin resistance in MSG-obese rats. These effects were associated to an increase in glucose uptake by muscle and adipose tissue in response to insulin.