Effects of cranial cervical ganglionectomy and castration of male lambs. III. Hormonal responses following administration to gonadotrophin releasing hormone (GnRH)

Entire and castrate male lambs, which were cranial cervical ganglionectomized (GX) or untreated, were utilized in a study of responses to intravenous GnRH; 24 animals were treated at both 101 and 277 days of age. GX caused a reduction in basal LH concentrations of both wethers and rams at the first sampling, but increased pre-injection levels of this hormone in 277 day old wethers. Basal LH levels of castrates were substantially higher than those of entires, but GX had no significant influence on pretreatment testosterone secretion in rams. GnRH treatment elevated plasma LH levels in all animals, while in entires increases in testosterone concentrations also occurred. Castration significantly increased peak LH levels together with total LH output. At neither age were the LH or testosterone reponses influenced significantly by GX, nor was the interaction of castration and GX significant for LH response data. The major effect of age at GnRH treatment was that markedly higher testosterone responses were recorded from the older rams.     

Acclimation responses to high light by Guazuma ulmifolia Lam. (Malvaceae) leaves at different stages of development

• The re‐composition of deforested environments requires the prior acclimation of seedlings to full sun in nurseries. Seedlings can overcome excess light either through the acclimation of pre‐existing fully expanded leaves or through the development of new leaves that are acclimated to the new light environment. Here, we compared the acclimation capacity of mature (MatL, fully expanded at the time of transfer) and newly expanded (NewL, expanded after the light shift) leaves of Guazuma ulmifolia Lam. (Malvaceae) seedlings to high light.
• The seedlings were initially grown under shade and then transferred to full sunlight. MatL and NewL were used for chlorophyll fluorescence and gas exchange analyses, pigment extraction and morpho‐anatomical measurements.
• After the transfer of seedlings to full sun, the MatL persisted and acclimated to some extent to the new light condition, since they underwent alterations in some morpho‐physiological traits and maintained a functional electron transport chain and positive net photosynthesis rate. However, long‐term exposure to high light led to chronic photoinhibition in MatL, which could be related to the limited plasticity of leaf morpho‐anatomical attributes. However, the NewL showed a high capacity to use the absorbed energy in photochemistry and dissipate excess energy harmlessly, attributes that were favoured by the high structural plasticity exhibited by these leaves.
• Both the maintenance of mature, photosynthetically active leaves and the production of new leaves with a high capacity to cope with excess energy were important for acclimation of G. ulmifolia seedlings.

     

Different aggregation properties of sea urchin embryonic cells at different developmental stages. II. Stage specific response to fibronectin and collagen

Fibronectin and collagen were added to cells dissociated from embryos at the blastula and at the 16 cell stages. Both molecules stimulate aggregation of cells dissociated from blastula but they do not affect aggregation of blastomeres dissociated from the 16 cell stage. The stage-specific response to fibronectin and collagen appears to be related to the onset of new functional role(s) of the two molecules at the blastula stage.     

Anatomical and functional responses of Calendula officinalis L. to SO2 stress as observed at different stages of plant development

Growth responses of field-grown marigold (Calendula officinalis L.) plants to SO₂ (0.5, 1.0 and 2.0 ppm) stress were studied at pre-flowering, flowering and post-flowering stages. Low concentrations of SO₂ did not cause any noticeable difference in shoot length, flowers and fruits per plant, and in seeds per fruit, but enhanced leaf number, leaf area and root length. With higher concentrations, however, all these parameters declined. Compared with controls, dry mass of leaves and roots was higher with 0.5 ppm SO₂ but significantly lower with higher doses at each stage. With a high SO₂ dose stomatal pore size increased on adaxial epidermis but decreased on abaxial epidermis. The net photosynthetic rate significantly increased, whereas stomatal conductance and intercellular CO₂ concentration decreased with 0.5 ppm SO₂ treatment, the reverse being the case with higher concentrations. The photosynthetic pigments declined significantly under high SO₂ stress at each stage of plant development, although 0.5 ppm concentration had a stimulatory effect. SO₂ stress delayed the development of interfascicular cambium and altered the proportion of the component tissues in the plant axis. The areas of cortex and vasculature in stems and roots decreased, while pith area increased in the treated plants. The length of fibres and vessel elements increased in the stem and decreased in the root, compared with the control. Vessel density and diameter declined in large vascular bundles and increased in small vascular bundles of the stem. In roots, both the parameters gained under heavy SO₂ stress.     

Plasma immunoreactive N-terminal parathyroid hormone and cyclic AMP and cyclic GMP urinary levels in man after I. M. administration of two different doses of porcine calcitonin

The effects of acute porcine calcitonin (pCT) administration were studied in 11 healthy volunteers with no metabolic disease. Each subject was given, intramuscularly, 1 MRC unit of pCT in glycine vehicle, 160 units of pCT in gelatine vehicle, and placebo, according to a crossover design. The following parameters were studied: blood calcium, phosphorus and immunoreactive parathyroid hormone (iPTH); urine calcium, phosphorus, cyclic AMP and GMP. Both the pCT preparations produced, at the same time after administration, a hypocalcemic effect (P less than 0.01) which was not dose related, without any modification of urinary calcium excretion, implying that both doses are able to inhibit completely bone destruction. Despite the blood calcium decrease, no significant modifications in plasma iPTH levels were observed. pCT administration did not modify the urinary excretion of cyclic AMP, while it increased the urinary levels of cyclic GMP, particularly at the higher dose employed. Blood phosphorus decrease and urinary phosphate excretion increase were observed only after the administration of 160 MRC units of pCT. These observations suggest that the effects on urinary cyclic GMP and on blood and urine phosphorus are not mediated by PTH but could be the result of a direct action of calcitonin seen only when high doses are employed. In conclusion, one MRC unit of pCT is sufficient to inhibit bone resorption.     

Contribution of amino acid substitutions at two different interior positions to the conformational stability of human lysozyme.

To elucidate correlative relationships between structural change and thermodynamic stability in proteins, a series of mutant human lysozymes modified at two buried positions (Ile56 and Ile59) were examined. Their thermodynamic parameters of denaturation and crystal structures were studied by calorimetry and X-ray crystallography. The mutants at positions 56 and 59 exhibited different responses to a series of amino acid substitutions. The changes in stability due to substitutions showed a linear correlation with changes in hydrophobicity of substituted residues, having different slopes at each mutation site. However, the stability of each mutant was found to be represented by a unique equation involving physical properties calculated from mutant structures. By fitting present and previous stability data for mutant human lysozymes substituted at various positions to the equation, the magnitudes of the hydrophobicity of a carbon atom and the hydrophobicity of nitrogen and neutral oxygen atoms were found to be 0.178 and -0.013 kJ/mol.A(2), respectively. It was also found that the contribution of a hydrogen bond with a length of 3.0 A to protein stability was 5.1 kJ/mol and the entropy loss of newly introduction of a water molecules was 7.8 kJ/mol.     

Some life history responses of the cladoceran Ceriodaphnia cf. dubia to variations in population density at two different food concentrations

Atrazine is the most commonly used agricultural herbicide in the midwestern cornbelt of the U.S.A. This project investigated atrazine bioconcentration in Cladophora glomerata (L.) Kütz, the dominant algae by biomass in nutrient enriched rivers. C. glomerata concentrates many organic and inorganic materials from solution, and by considering the partitioning coefficient of atrazine (Log K _ow=2.56), the uptake of atrazine by this green algae was expected. The bioconcentration factor of C. glomerata ranged from 29 to 5223 over a one year sampling period, and bioconcentration was found to be a function of maximum biomass increase (due to high nutrients) and discharge. Uptake increased at low discharges as a result of increased contact time between cells and water. We found that C. glomerata was able to bioconcentrate a yearly average of 54% of the available atrazine from the water. Efficiency of uptake increased during the summer growing season of the algae (81%) and was 34% during the winter months. This field study demonstrates the ability of C. glomerata to bioconcentrate atrazine to a high degree and suggests an alternative and quicker biological removal of atrazine from agriculturally polluted rivers.     

Recognition of two forms of the estrogen receptor in the guinea-pig uterus at different stages of development by a monoclonal antibody to the human estrogen receptor. Dynamics of the translocation of these two forms to the nucleus

Two forms of the estrogen receptor were recognised in the cytosol fraction of fetal uterus of guinea pig by a monoclonal antibody (D547Spγ) to the human estrogen receptor. It was observed that 60–65% of the total cytosol estrogen receptor (the α form) was bound to the antibody, increasing its sedimentation coefficient in a high ionic strength sucrose gradient (10–30% w/v sucrose, 0.4 M KCl) from 4.5 S to 7.4 S. The remaining fraction (the β form) has the classical sedimentation coefficient of 4.5 S. Dynamic studies of the translocation in vitro of the cytosol receptor to the nucleus as a function of time have shown that the a form decreases sharply while the β form is slightly affected when the cytosol was incubated with the nuclei. In contrast only one form, which is bound totally to the antibody, was found in the nuclear fraction. In addition, the presence of these two forms of the cytosol estrogen receptor was also demonstrated in newborn and immature animals.     

Ventilatory responses to carbon dioxide at low and high levels of oxygen are elevated after episodic hypoxia in men compared with women.

We hypothesized that the acute ventilatory response to carbon dioxide in the presence of low and high levels of oxygen would increase to a greater extent in men compared with women after exposure to episodic hypoxia. Eleven healthy men and women of similar race, age, and body mass index completed a series of rebreathing trials before and after exposure to eight 4-min episodes of hypoxia. During the rebreathing trials, subjects initially hyperventilated to reduce the end-tidal partial pressure of carbon dioxide (PetCO2) below 25 Torr. Subjects then rebreathed from a bag containing a normocapnic (42 Torr), low (50 Torr), or high oxygen gas mixture (150 Torr). During the trials, PetCO2 increased while the selected level of oxygen was maintained. The point at which minute ventilation began to rise in a linear fashion as PetCO2 increased was considered to be the carbon dioxide set point. The ventilatory response below and above this point was determined. The results showed that the ventilatory response to carbon dioxide above the set point was increased in men compared with women before exposure to episodic hypoxia, independent of the oxygen level that was maintained during the rebreathing trials (50 Torr: men, 5.19 +/- 0.82 vs. women, 4.70 +/- 0.77 l x min(-1) x Torr(-1); 150 Torr: men, 4.33 +/- 1.15 vs. women, 3.21 +/- 0.58 l x min(-1) x Torr(-1)). Moreover, relative to baseline measures, the ventilatory response to carbon dioxide in the presence of low and high oxygen levels increased to a greater extent in men compared with women after exposure to episodic hypoxia (50 Torr: men, 9.52 +/- 1.40 vs. women, 5.97 +/- 0.71 l x min(-1) x Torr(-1); 150 Torr: men, 5.73 +/- 0.81 vs. women, 3.83 +/- 0.56 l x min(-1) x Torr(-1)). Thus we conclude that enhancement of the acute ventilatory response to carbon dioxide after episodic hypoxia is sex dependent.     

Suppression of cytotoxic response to histoincompatible cells. I. Evidence for two types of T lymphocyte-derived suppressors acting at different stages in the induction of a cytotoxic response.

Spleen and thymus cell populations from normal or allograft tolerant mice have been cultured for 5 days with specific alloantigens and examined for their reactivity in three assay systems. No consistent correlation was observed between the production of cytotoxic T cells (CTL) in these cultures and the ability of such cultured cells to inhibit specifically a CML response from fresh normal spleen cells directed to the priming alloantigens. Furthermore, suppressor cells measured in this latter assay were apparently distinct from those able to inhibit the production of cytotoxic lymphocyte precursors (CTLp) from bone marrow stem cells in lethally irradiated bone marrow protected mice. Velocity sedimentation experiments confirmed that both the precursor and effector cells for the two suppressor systems were physically separable, and were distinct from CTLp or CTL, respectively. Precursor cells for the two suppressor systems investigated belong to the short-lived cortical thymus cell population.     

Biological phenotype of human immunodeficiency virus type 1 clones at different stages of infection: progression of disease is associated with a shift from monocytotropic to T-cell-tropic virus population.

The composition of human immunodeficiency virus type 1 (HIV-1) clonal populations at different stages of infection and in different compartments was analyzed. Biological HIV-1 clones were obtained by primary isolation from patient peripheral blood mononuclear cells under limiting dilution conditions, with either blood donor peripheral blood lymphocytes or monocyte-derived macrophages (MDM) as target cells, and the biological phenotype of the clones was analyzed. In asymptomatic individuals, low frequencies of HIV-1 clones were observed. These clones were non-syncytium inducing and preferentially monocytotropic. In individuals progressing to disease, a 100-fold increase in frequencies of productively HIV-1-infected cells was observed as a result of a selective expansion of nonmonocytotropic clones. In a person progressing to AIDS within 19 months after infection, only syncytium-inducing clones were detected, shifting from MDM-tropic to non-MDM-tropic over time. From his virus donor, a patient with wasting syndrome, only syncytium-inducing clones, mostly non-MDM-tropic, were recovered. Parallel clonal analysis of HIV-1 populations in cells present in bronchoalveolar lavage fluid and peripheral blood from an AIDS patient revealed a qualitatively and quantitatively more monocytotropic virus population in the lung compartment than in peripheral blood at the same time point. These findings indicate that monocytotropic HIV-1 clones, probably generated in the tissues, are responsible for the persistence of HIV-1 infection and that progression of HIV-1 infection is associated with a selective increase of T-cell-tropic, nonmonocytotropic HIV-1 variants in peripheral blood.     

Frequency of chromosome aberrations induced in human peripheral lymphocytes by in vitro 60Co gamma quanta at doses of 1 to 5 Gr. in an analysis of the 1st-division cells at different fixation times

The quantitative analysis of chromosomal aberrations in the first division cells of 50-, 54-, 58-, 52- and 66-hour peripheral blood lymphocytes cultures of healthy donors was performed after irradiation in vitro with 60Co gamma-quantums at doses 1--5 Gy. Cells of the first division were identified by a differential staining of sister chromatid method using 5-bromdeoxyuridine. No significant differences in frequencies of aberrant cells and aberrations of chromosomal type were found between cultures fixed at different times. The distribution of dicentrics in cells did not differ from the Poisson distribution regardless of fixation times and doses. On the basis of these findings it is concluded that chromosomes of human peripheral blood lymphocytes passing the cell cycle at different rates have approximately equal radiosensitivity.     

Growth hormone secretion during sleep. I. Comparison with GH responses to conventional pharmacologic stimuli in pubertal and early pubertal short subjects. Effects of treatment with human GH in patients with discrepant measurements of GH secretion

Growth hormone (GH) was measured in 215 short children (147 males and 68 females, 123 prepubertal, 92 at early pubertal stages), comparing GH responses to classical pharmacologic stimulation tests and spontaneous GH secretion during sleep. GH secretion during sleep, but not GH responses to stimuli, was higher in early pubertal than in prepubertal subjects. The patients were classified into five groups, according to the agreement between GH responses to stimuli and GH secretion during sleep: group I, normal GH-secreting children; group II, completely GH-deficient; group III, partially GH-deficient; group IV, with normal secretion during sleep and low responses to stimuli; group V, with the reverse situation. 30% of the patients were in groups IV and V, both at prepubertal and early pubertal stages. 46 patients of groups II-V were treated with extracted human GH(hGH). The growth rate was enhanced in groups IV and V, to the same extent as in groups II and III. Four points can be concluded: (1) the rise of GH secretion during sleep is an early event at the onset of puberty; (2) the discrepancy between the GH responses to classical stimuli and GH secretion during sleep are of pathological significance; (3) disturbances of GH secretion might be diagnosed by measuring GH secretion during sleep rather than by using conventional stimulation tests; (4) a trial course of hGH treatment could be proposed in patients with both kinds of discrepancies between GH responses to stimuli and GH secretion during sleep.