Effect of Lincocin Treatment on the Greening Process in Bean (Phaseolus vulgaris) Leaves

The effect of lincocin (a plastid protein synthesis inhibitor) treatment on the greening process of bean (Phaseolus vulgaris L.) leaves have been studied. In comparison with control leaves treated ones had a decreased rate of chloroplast development. They had a marked chlorophyll deficiency and a decreased chlorophyll a/b ratio. Some long and short wavelength forms of chlorophyll a were lacking as evidenced from the absorption spectra at 25°C and the fluorescence spectra at 77°K. The –¹⁴CO₂ fixation was inhibited by 80–90% in treated leaves. The fluorescence induced by the measuring light was greater in the treated leaves than in the control ones, and the kinetics of the decline of the relative fluorescence intensity were also different. Electron microscopic studies showed macrogranum-like structures and incomplete membrane vesicles in the treated plastids. After longer treatment a destruction of membranes was observed. The results indicate some structural and functional membrane deficiencies and instability of the membranes.     

Lecithotrophic development and metamorphosis in the Indo-West Pacific brittle star Ophiomastix venosa (Echinodermata: Ophiuroidea)

Summary

The larval development of the ophiocomid ophiuroid Ophiomastix venosais described using SEM. The gastrula transforms into a uniformly ciliated early larva which progressively changes into a lecithotrophic late premetamorphic larva with a continuous bilateral ciliated band. This stage is short-lived and equivalent to a highly reduced ophiopluteus. Comparisons between O. venosa and other ophiuroid species whose development has been investigated suggest that, whatever the developmental mode (lecithotrophic or planktotrophic), a pluteus stage always occurs in ophiuroids with planktonic development. Two metamorphic stages were identified, the late metamorphic larva differing from the early one by the closure of the larval mouth. The appearance of the permanent mouth marks the end of the metamorphosis. The postlarva still possesses remnants of larval features. The transformation of the reduced ophiopluteus into a barrel-shaped metamorphic larva with transverse ciliated bands, a vitellaria larva, is followed. The possible occurrence of a unique type of metamorphic larva in non-brooding ophiuroids is discussed. Verification of this, however, needs further SEM investigations on metamorphic larva from species having “regular” planktotrophic development.     

Phosphate deposition during and after hypokinesia in phosphate supplemented and unsupplemented rats

The objective of this study was to show that prolonged restriction of motor activity (hypokinesia) could reduce phosphate (P) deposition and contribute to P loss with tissue P depletion. To this end, measurements were made of tissue P content, P absorption, plasma P levels, urinary and fecal P excretion of rats during and after hypokinesia (HK) and daily phosphate supplementation. Studies were conducted on male Wistar rats during a pre-hypokinetic period, a hypokinetic period and a post-hypokinetic period. All rats were equally divided into four groups: unsupplemented vivarium control rats (UVCR), unsupplemented hypokinetic rats (UHKR), supplemented vivarium control rats (SVCR) and supplemented hypokinetic rats (SHKR). Bone and muscle P content, plasma intact parathyroid hormone (iPTH) levels, P absorption, plasma P levels and urinary and fecal P excretion did not change in SVCR and UVCR compared with their pre-HK values. During HK, plasma P levels, urinary and fecal P excretion increased significantly (p<0.05) while muscle and bone P content, P absorption and plasma iPTH levels decreased significantly (p<0.05) in SHKR and UHKR compared with their pre-HK values and the values in their respective vivarium controls (SVCR and UVCR). During the initial 9-days of post-HK, plasma, urinary and fecal P levels decreased significantly (p<0.05), and plasma iPTH levels, muscle and bone P levels remained significantly (p<0.05) depressed in hypokinetic rats compared with their pre-HK values and the values in their respective vivarium control rats. By the 15th day, these values approached the control values. During HK and post-HK, changes in P absorption, plasma iPTH levels, and P levels in muscle, bone, plasma, urine and feces were significantly (p<0.05) greater in SHKR than in UHKR. Decreased tissue P content with increased P loss in animals receiving and not receiving P supplementation demonstrates decreased P deposition during HK. Higher P excretion with lower tissue content in SHKR and UHKR demonstrates that P deposition is decreased more with P supplementation than without. Because SHKR with a lower tissue P content showed higher P excretion than UHKR it was concluded that the risk of decreased P deposition with greater tissue P depletion is inversely related to P intake, that is, the higher the P intake the greater the risk for decreased P deposition and the greater tissue P depletion. It was shown that P (regardless of the intensity of its tissue depletion) is lost during HK unless factors contributing to the decreased P deposition are partially or totally reversed. It was concluded that dissociation between (decreased) tissue P content and (increased) P uptake indicates decreased P (absorption and) deposition as the main mechanisms of tissue P depletion during prolonged HK.     

Urinary and serum electrolyte changes in athletes during periodic and continuous hypokinetic and ambulatory conditions

Hypokinesia (HK) (diminished movement) induces significant electrolyte changes, but little is known about the effect of periodic hypokinesia (PHK) on minerals. The aim of this study was to measure the effect of PHK and continuous hypokinesia (CHK) on urinary and serum electrolytes. Studies were done during a 30-d period of prehypokinesia (HK) and during 364 d of PHK and CHK periods. Thirty male athletes aged 24.6±7.7 yr were chosen as subjects. They were equally divided into three groups: unrestricted ambulatory control subjects (UACS), continuously hypokinetic subjects (CHKS), and periodically hypokinetic subjects (PHKS). The UACS group experienced no changes in the daily activities and regular training and they were maintained under an average running distance of 11.7 km/d. The CHKS group was limited to an average walking distance of 0.7 km/d; and the PHKS group was limited to an average walking distance of 0.7 and running distance of 11.7 km/d for 5 d and 2 d/wk, respectively, for a period of 364 d. Urinary and serum phosphate (P), calcium (Ca), sodium (Na) and potassium (K), serum intact parathyroid hormone (iPTH), calcitonin (CT), plasma renin activity (PRA) and aldosterone (PA) levels, food and water intakes, and physical characteristics were measured. Urinary P, Ca, Na, and K loss, serum Ca, P, Na, and K, and PRA and PA values increased significantly (p≤0.01), whereas serum iPTH and CT levels decreased significantly (p≤0.01) in the PHKS and CHKS groups when compared with the UACS group. However, significant (p≤0.01) differences were observed between PHKS and CHKS groups regarding urinary and serum electrolytes, serum and plasma hormones. Food and water intakes, body weight, body fat, and peak oxygen uptake decreased significantly (p ≤ 0.01) in the CHKS group when compared with PHKS and UACS groups. Food and fluid intakes, body fat, and body weight increased significantly (p≤0.01), whereas peak oxygen uptake remained significantly (p≤0.01) higher in the PHKS group when compared with the CHKS group. Serum and urinary minerals, serum hormones, food and fluid intakes, and physical characteristics did not change significantly (p>0.01) in the UACS group when compared with their baseline control values. It was shown that both PHK and CHK induce significant serum and urinary electrolyte changes. However, urinary and serum electrolyte changes were significantly (p≤0.01) greater during PHK than CHK. It was concluded that the greater the stability of muscular activity, the smaller the serum and urinary electrolyte changes during prolonged HK.     

Muscle Potassium and Potassium Losses During Hypokinesia in Healthy Subjects

Hypokinesia (HK) induces electrolyte losses in electrolyte-deficient tissue, yet the mechanisms of electrolyte losses in electrolyte-deficient tissue remain unknown. Mechanisms of electrolyte deposition could be involved. To determine the effect of prolonged HK on potassium (K⁺) deposition were measured muscle K⁺ content and K⁺ losses. Studies were conducted on 20 physically healthy male volunteers during 30 days pre-experimental period and 364 days experimental period. Subjects were equally divided into two groups: control subjects (CS) and experimental subjects (ES). The CS group was run average distances of 9.8 ± 1.7 km day⁻¹ and the ES group was walked average distances of 2.7 ± 0.6 km day⁻¹. Muscle K⁺ content decreased (p < 0.05) and plasma K⁺ concentration, and K⁺ losses in urine and feces increased (p < 0.05) in the ES group compared to their pre-experimental level and the values in their respective CS group. Muscle K⁺ content, plasma K⁺ level, and urine and fecal K⁺ losses did not show any changes in the CS group compared to their pre-experimental values. The conclusion was that K⁺ losses in K⁺-deficient muscle of healthy subjects could have been attributable to the less efficient K⁺ deposition inherently to prolonged HK.