Meloidogyne incognita-Induced Changes in Cell Permeability of Galled Roots

Electrolyte leakage of Meloidogyne incognita-infected and healthy tomato roots was compared by conductivity measurements, and by compartmental analysis using ⁸⁶Rb. Conductivity measurements suggested difference in electrolyte loss from healthy and galled roots. On a percentage basis, a greater rate of efflux occurred for healthy plants, but galled roots contain more electrolytes and may show a larger net loss. Compartmental analysis indicated that: (i) the longer half-time for ⁸⁶Rb loss from vacuoles of galled root cells could indicate either a greater vacuolar content or decreased tonoplast permeability, (ii) the shorter half-time for loss ⁸⁶Rb from the cytoplasm of galled root cells could reflect either a reduced cytoplasmic content or an increased plasma membrane permeability, and (iii) in split-root plants, the permeability of the tonoplast and the plasma membrane of cells in nongalled roots is increased by nematode infection on the other half of the root system. Thus, a mechanism for mobilizing minerals to the infection site is proposed.     

A new method for the noninvasive determination of abdominal muscle feedforward activity based on tissue velocity information from tissue Doppler imaging.

Rapid arm movements elicit anticipatory activation of the deep-lying abdominal muscles; this appears modified in back pain, but the invasive technique used for its assessment [fine-wire electromyography (EMG)] has precluded its widespread investigation. We examined whether tissue-velocity changes recorded with ultrasound (M-mode) tissue Doppler imaging (TDI) provided a viable noninvasive alternative. Fourteen healthy subjects rapidly flexed, extended, and abducted the shoulder; recordings were made of medial deltoid (MD) surface EMG and of fine-wire EMG and TDI tissue-velocity changes of the contralateral transversus abdominis, obliquus internus, and obliquus externus. Muscle onsets were determined by blinded visual analysis of EMG and TDI data. TDI could not distinguish between the relative activation of the three muscles, so in subsequent analyses only the onset of the earliest abdominal muscle activity was used. The latter occurred <50 ms after the onset of medial deltoid EMG (i.e., was feedforward) and correlated with the corresponding EMG onsets (r = 0.47, P < 0.0001). The mean difference between methods was 20 ms and was likely explained by electromechanical delay; limits of agreement were wide (-40 to +80 ms) but no greater than those typical of repeated measurements using either technique. The between-day standard error of measurement of the TDI onsets (examined in 16 further subjects) was 16 ms. TDI yielded reliable and valid measures of the earliest onset of feedforward activity within the anterolateral abdominal muscle group. The method can be used to assess muscle dysfunction in large groups of back-pain patients and may also be suitable for the noninvasive analysis of other deep-lying or small/thin muscles.     

Longitudinal study of growth status and airport noise exposure

A study of children living adjacent to an international airport was conducted to learn whether noise exposure affected physical growth. Prenatal and postnatal noise exposures were estimated for each subject based on noise levels at their residences during jetplane takeoffs. Subjects' birthweights were standardized for sex and parity, and their postnatal heights and weights were standardized for sex and age (range 6-11 years). The difference between standardized birthweight score and postnatal height score, and between birthweight score and postnatal weight score, represent a change in growth status of a more or less permanent nature, respectively. After adjusting for confounding factors, children from the exposed community (n = 103) had a significantly smaller mean of status change by height (p less than 0.05), and a somewhat smaller mean of status change by weight (0.10 less than p less than 0.05) in comparison to children from an unexposed community (n = 94). A dose-response curve was then expected in the exposed community. However, in multiple regression analyses of the exposed children, noise exposure was not related to either change in growth status variable. This second result is inconsistent with the differences between communities and suggest that they are a result of factors other than noise exposure. We conclude that the moderate to severe noise levels of the areas surrounding most subjects' homes did not adversely affect postnatal growth. Further studies of noise and growth should concentrate observations on people exposed to even more severe noise levels than those experienced by most subjects in this study.     

THE DEVELOPMENT AND POTENTIAL ROLES OF CELL‐WALL TRABECULAE IN CAULERPA MEXICANA (CHLOROPHYTA)1

Siphonous plants represent an alternate scheme to the way most macroscopic plants are constructed. They are single, often large (1–2 m), sometimes morphologically complex, multinucleate (coenocytic) cells where the whole of the cytoplasm is a continuum. Caulerpa mexicana Sond. ex Kütz. is a siphonous tropical marine green alga characterized by four morphologically distinct regions and, as with other members of the genus, by the presence of a dense network of anastomosing cylindrical cell wall in growths called trabeculae. Based on the results of this study, we propose several roles for trabeculae: (i) They are structural components, which likely add some small amount of support in compression but add considerable strength in tension. (ii) As extensions of the cell wall and plasma membrane, they act as diffusion channels from the cell exterior to the interior cytoplasm. It is possible that trabeculae also play a role in determining cell shape through developmental positioning and placement patterns, thus facilitating the diverse shapes found in the morphologically distinct regions of Caulerpa sp.     

Photorespiratory serine hydroxymethyltransferase 1 activity impacts abiotic stress tolerance and stomatal closure

The photorespiratory cycle is a crucial pathway in photosynthetic organisms because it removes toxic 2‐phosphoglycolate made by the oxygenase activity of ribulose‐1,5‐bisphosphate carboxylase/oxygenase and retrieves its carbon as 3‐phosphoglycerate. Mitochondrial serine hydroxymethyltransferase 1 (SHMT1) is an essential photorespiratory enzyme converting glycine to serine. SHMT1 regulation remains poorly understood although it could involve the phosphorylation of serine 31. Here, we report the complementation of Arabidopsis thaliana shm1‐1 by SHMT1 wild‐type, phosphorylation‐mimetic (S31D) or nonphophorylatable (S31A) forms. All SHMT1 forms could almost fully complement the photorespiratory growth phenotype of shm1‐1; however, each transgenic line had only 50% of normal SHMT activity. In response to either a salt or drought stress, Compl‐S31D lines showed a more severe growth deficiency compared with the other transgenic lines. This sensitivity to salt appeared to reflect reduced SHMT1‐S31D protein amounts and a lower activity that impacted leaf metabolism leading to proline underaccumulation and overaccumulation of polyamines. The S31D mutation in SHMT1 also led to a reduction in salt‐induced and ABA‐induced stomatal closure. Taken together, our results highlight the importance of maintaining photorespiratory SHMT1 activity in salt and drought stress conditions and indicate that SHMT1 S31 phosphorylation could be involved in modulating SHMT1 protein stability.     

Hormonal and behavioural detection of oestrus in blackbuck, Antilope cervicapra, and successful artificial insemination with fresh and frozen semen

Hormonal detection of urinary pregnanediol-3 alpha-glucuronide proved an effective method of monitoring the progress of oestrous cycles in the blackbuck; observation of sexual behaviour in a vasectomized male was, however, a more practical procedure. Good correlation was observed between the occurrence of minimal pregnanediol concentrations in females and the maximal behavioural response by the male. On the basis of intervals between periods of behaviourally detected oestrus, a mean cycle length of 16.9 days (+/- 0.62, s.e.m.) was derived from 12 cycles (4 animals). Eleven females were inseminated in this study, 8 with freshly collected semen and 3 with frozen semen; 6 calves were obtained, 1 after the use of frozen semen. Pregnancy was monitored by measurements of pregnanediol-3 alpha-glucuronide excretion and by ultrasound scanning. The mean interval between insemination and parturition was 183.3 days inclusive, ranging from 182 to 186 days.     

Cobra cardiotoxins. Purification, effects on skeletal muscle and structure/activity relationships [published errtum appears in Eur J Biochem 1988 Feb 1;171(3):727

A new preparative method for isolating homogeneous cardiotoxins from cobra venoms is described. The technique, based on reverse-phase high-pressure liquid chromatography, was used to isolate eight cardiotoxins of known sequence from four different venoms. In each case the method was found to be particularly efficient at removing trace quantities of contaminating phospholipase. Cardiotoxins isolated in this manner were found to retain their full biological activity. Without exception the purified cardiotoxins lacked powerful haemolytic activity at concentrations up to 0.01 mM (about 100 micrograms ml-1), although some lysis of human erythrocytes was induced at higher concentrations. The cardiotoxins displayed a wide range of depolarizing activity on cultured skeletal muscle, the lowest activity being associated with the highest LD50 value. Correlating variations in amino acid sequence and variations in depolarization potency revealed the importance of residues in the second and third loops, especially lysine-46, serine-48 and lysine-52, together with a number of hydrophobic residues. Further modifications of pharmacological activity were associated with the presence of additional basic residues in the first and second loops and to minor differences in secondary structure.     

Artificial insemination in the Giant panda (Ailuropoda melanoleaca)

Artificial insemination was carried out on three adult captive Giant pandas (Ailuropoda melanoleuca). Oestrus in these animals was detected by behavioural observations and by the rise in urinary oestrogen metabolites. Semen was collected from a mature male by electroejaculation. Changes in the quality of semen and the size of the testes indicated a seasonal fluctuation in sperm production. Spermatozoa were capable of penetrating zona-free hamster oocytes and remained viable for up to five days at 15–20°C in a modified Tyrode's medium. After freezing and thawing in a cryopreserving diluent, approximately 50% of spermatozoa recovered progressive motility and displayed a similar velocity to spermatozoa prior to freezing. Unusual protrusions of the acrosome of the panda spermatozoon were noted.
Following insemination, one female conceived and gave birth, after a gestation of 159 days, to two cubs, one of which subsequently died. Another female exhibited a rise in circulating progesterone but pregnancy was not confirmed.