Transient Photoresponses of a Phototactic Microorganism, Haematococcus Pluvialis, Revealed by Light Scattering

A new method, using incoherent light scattering, has been developed to measure the flagellar beating frequency of swimming microorganisms. By means of this method, transient changes of flagellar beating frequency in response to white light flashes have been revealed in samples of a phototactic microorganism, Haematococcus pluvialis. An increase of flagellar beating frequency occurs when the flash dose (flash intensity × flash duration) is sufficient. Reciprocity between light intensity and flash duration holds for durations not exceeding 60-80 ms. For lower doses a bimodal distribution of flagellar beating frequency is revealed. No effect is observed for very low flashes or for red stimuli, whereas green light is effective. A detailed analysis of experimental results has allowed us to determine the characteristic time of the effect and follow its evolution. The correlation of this effect with visually observed behavior is discussed and a possible underlying mechanism is suggested.     

Further evidence for the presence of specific binding sites for prolactin in the rabbit brain. Preferential distribution in the hypothalamus and substantia nigra

In the present research we have extended our work on the presence of binding sites for prolactin in the rabbit brain focusing our attention on the brain areas with high dopamine cell bodies density. Among these areas the hypothalamus showed the highest specific binding of labeled ovine prolactin (oPRL). Clearly detectible specific binding was observed also in substantia nigra, whereas in other brain regions the specific binding was very small, except for the striatum where a low but not negligible binding was found in female rabbits. The binding of 125I-oPRL showed a hormonal specificity and Scatchard analysis of the binding showed no clear difference in dissociation constant (Kd) between hypothalamus, nigra and striatum.     

Reduced mechanical activity of perfused rat heart following morphine or enkephalin peptides administration

In the isolated and perfused rat heart, the addition of morphine, methionine-enkephalin or leucine-enkephalin to the coronary perfusate, significantly reduces the mechanical activity by negatively affecting both the heart rate and the developed tension. These effects are dose dependent and maximally evident with leucine-enkephalin. Furthermore all the opioids strongly reduce the activity of isoproterenol-stimulated hearts. The suggestion is made that opioid peptides directly influence the cardiac mechanical activity possibly by interacting with membrane-receptor systems.     

Modulation of natural killer activity by thymosin alpha 1 and interferon

Summary A single injection of -interferon (-IFN) (30 000 units/mouse), a major biological modifier of natural killer (NK) cytolytic activity, strongly stimulated NK activity in normal mice, as expected, while the same treatment did not statistically alter the NK response in cyclophosphamide (CY)-suppressed animals.We investigated the possibility of thymosin ₁ cooperating with -IFN in boosting NK activity in CY-suppressed animals.The results show that treatment with thymosin ₁ (200 g/kg) for 4 days, followed by a single injection of -IFN 24 h before testing, strongly restored NK activity in CY-suppressed mice. Thymosin ₁ was, moreover, able to accelerate the recovery rate of NK activity in bone marrow reconstituted murine chimeras.Taken together the data support the concept that the synergic effect between thymosin ₁ and -IFN could be the result of effects on differentiation of the NK lineage at different levels.     

Growth hormone releasing effect of hpGRF-40 in rats at different time intervals following ablation of the mediobasal hypothalamus

We have investigated the effect of hypothalamo-pituitary disconnection in the rat on the growth hormone (GH) responsiveness to human pancreatic GH-releasing factor (hpGRF). Adult female rats, sham-operated (sham-op) or bearing a complete mechanical ablation of the mediobasal hypothalamus (MBH-A) were challenged, while under urethane anesthesia, with hpGRF-40 (20,100,500 ng/rat i.v.) at different time intervals after surgery. In sham-op rats only 500 ng/rat of hpGRF-40 stimulated GH release, while in 1-and 7-day MBH-A rats the stimulation also occurred with the lower hpGRF doses and the rise in plasma GH was greater than in sham-op controls. Twenty-one and 42 days after the placing of the lesions the GH response to hpGRF-40 was still present at the 500 ng/rat dose, though it was smaller than in sham-op controls. Evaluation of pituitary GH content demonstrated a progressive and rapid decline starting the first day after the placing of the lesions. These data indicate that GH responsiveness to hpGRF is: 1) enhanced in the anterior pituitary shortly after hypothalamo-pituitary disconnection and, 2) despite a striking reduction of the pituitary GH stores, it is maintained after these lesions.The physiologic growth hormone (GH) releaser in the rat is GH-releasing factor and, recently, a group of peptides has been characterized from human pancreatic tumors (hpGRFs) (1,2) which are potent and specific GH-releasers in both animals (3) and man (4). The availability of these peptides, which show a high degree of homology with the physiologic rat hypothalamic GRF (5), offers the unique opportunity to assess somatotrope responsiveness to GRF molecules in rats with hypothalamo-pituitary disconnection.In this study we have first evaluated the GH pituitary responsiveness to increasing doses of hpGRF-40 in rats following mechanical ablation of the mediobasal hypothalamus (6). These rats, by definition, lack the effect of both central nervous system (CNS) inhibitory (e.g. somatostatin) and stimulatory (e.g. GRF) influences to GH release. With the aim to ascertain how the lack of these two opposing inputs reflects on the secretory capacity of the somatotropes, we also investigated the GH response to hpGRF-40 at different time intervals after the lesioning. In a study in rats with electrolytic lesions of the ventromedial-arcuate region of the hypothalamus Tannenbaum et al (7) had shown persistence of the GH response to huge doses of a hpGRF analog.     

6β-Hydroxyipolamiide,an iridoid glucoside from Stachytarpheta mutabilis

A new iridoid glucoside has been isolated from Stachytarpheta mutabilis and assigned the structure and configuration of 6β-hydroxyipolamiide on the basis of ¹H NMR and ¹³C NMR evidence. The conversion of this compound into penta- acetyllamiol proved the above assignment.     

Effects of CO2 rebreathing on pulmonary mechanics in premature infants

The effects of hypercapnia produced by CO2 rebreathing on total pulmonary, supraglottic, and lower airway (larynx and lungs) resistance were determined in eight premature infants [gestational age at birth 32 +/- 3 (SE) wk, weight at study 1,950 +/- 150 g]. Nasal airflow was measured with a mask pneumotachograph, and pressures in the esophagus and oropharynx were measured with a fluid-filled or 5-Fr Millar pressure catheter. Trials of hyperoxic (40% inspired O2 fraction) CO2 rebreathing were performed during quiet sleep. Total pulmonary resistance decreased progressively as end-tidal PCO2 (PETCO2) increased from 63 +/- 23 to 23 +/- 15 cmH2O.l-1.s in inspiration and from 115 +/- 82 to 42 +/- 27 cmH2O.l-1.s in expiration between room air (PETCO2 37 Torr) and PETCO2 of 55 Torr (P less than 0.05). Lower airway resistance (larynx and lungs) also decreased from 52 +/- 22 to 18 +/- 14 cmH2O.l-1.s in inspiration and from 88 +/- 45 to 30 +/- 22 cmH2O.l-1.s in expiration between PETCO2 of 37 and 55 Torr, respectively (P less than 0.05). Resistance of the supraglottic airway also decreased during inspiration from 7.2 +/- 2.5 to 3.6 +/- 2.5 cmH2O.l-1.s and in expiration from 7.6 +/- 3.3 to 5.3 +/- 4.7 cmH2O.l-1.s at PETCO2 of 37 and 55 Torr (P less than 0.05). The decrease in resistance that occurs within the airway in response to inhaled CO2 may permit greater airflow at any level of respiratory drive, thereby improving the infant's response to CO2.     

Characteristics of the volume- and chloride-dependent K transport in human erythrocytes homozygous for hemoglobin C

Summary In human red cells homozygous for hemoglobin C (CC), cell swelling and acid pH increase K efflux and net K loss in the presence of ouabain (0.1mm) and bumetanide. We report herein, that K influx is also dependent on cell volume in CC cells: cell swelling induces a marked increase in the maximal rate (from 6 to 18 mmol/liter cell × hr) and in the affinity for external K (from 77±16mm to 28±3mm) of K influx. When the external K concentration is varied from 0 to 140mm, K efflux from CC and normal control cells is unaffected. Thus, K/K exchange is not a major component of this K movement. K transport through the pathway of CC cells is dependent on the presence of chloride or bromide; substitution with nitrate, acetate or thiocyanate inhibits the volume- and pH-dependent K efflux. When CC cells are separated according to density, a sizable volume-dependent component of K efflux can be identified in all the fractions and is the most active in the least dense fraction. N-ethylmaleimide (NEM) markedly stimulates K efflux from CC cells in chloride but not in nitrate media, and this effect is present in all the fractions of CC cells separated according to density. The persistence of this transport system in denser CC cells suggests that not only cell age, but also the presence of the positively charged C hemoglobin is an important determinant of the activity of this system. These data also indicate that the K transport pathway of CC cells is not an electrodiffusional process and is coupled to chloride.