Leucine uptake by tomato leaf tissue under low temperature: Preincubation dependence of uptake reduction

The uptake of ³H-leucine by leaf fragments of Lycopersicon esculentum Mill. cv. Rutgers and L. hirsutum Humb. & Bonpl., a wild tomato, was studied. Two altitudinal races of L. hirsutum were used which differed in chilling tolerance. The temperature dependence of uptake was initially similar for all plant varieties. However, at temperatures below about 11°C, uptake progressively decreased in the more chilling-sensitive varieties ( L. esculentum , Low-altitude L. hirsutum ), but not in the more chilling-tolerant (high-altitude L. hirsutum ) with increasing preincubation time. More than 60 min preincubation was required for this effect, and it was greatest at the lower temperatures. When leaf fragments, chilled for short periods of time (>22 h), were returned to 22°C, initial rates of uptake were recovered within 2 h. The relationship between membrane lipid changes and membrane protein activity under chill stress is discussed.     

Abnormalities in the fine structure of the spermatids of rats injected with cadmium

The degenerative changes in the spermatids as measured by changes in fine structure abnormalities increased with time following injection of Cd²⁺ into rat testis. The spermatids in the twelve hours group appear as peculiarly club shaped and elongated structures with one or two small but perceptible vacuoles. The subacrosomal area and the space between the nucleus and the middle piece are seen abnormally dilated. In the 30 day group, the central filaments are the most susceptible unit of 9+2 axoneme complex. The plasma membrane, the cytoplasmic matrix, the mitochondria of the middle piece and the fibrous sheath appear shrunken, discontinuous and degenerative.     

Studies on the damage to Escherichia coli cell membrane caused by different rates of freeze-thawing

Freeze-thawing of Escherichia coli cells caused a release of cell membrane components such as protein, phospholipids and lipopolysaccharides. A greater amount of release and a lesser extent of cell survival were seen in slow freeze-thawing than in rapid freeze-thawing. Several dehydrogenases in the cells were also freed. The mode of release was also dependent on the rate of freeze-thawing.The materials released by slow freeze-thawing were found to be mostly composed of outer membrane components, whereas the materials released by rapid freeze-thawing contained cytoplasmic as well as outer membrane components. The chemical composition of these fragments differed significantly from that of the original membranes. The relative content of cytoplasmic membrane-bound enzymes in these fragments also differed from that of the cytoplasmic membrane.The fragmentation was assumed to have resulted mainly from the crystallization of external water. In slow freeze-thawing, it was considered that the phase separation of the membrane phospholipid bilayer increased the possibility of outer membrane fragmentation. Rapid freeze-thawing caused cytoplasmic membrane damage to the cells as well as to the outer membrane. In rapid freeze-thawing, the effect of phase separation appeared to be small because of rapid passage through the transition temperatures.The presence of 10% glycerol completely inhibited the release of cellular materials and enzymes. Cell survival was maintained at a high level in the glycerol-treated samples whether freeze-thawed slowly or rapidly.     

Gynandromorphs of the pycnogonid Anoplodactylus portus

A large sample of the pycriogonid Anoplodactylus portus , collected from the Pacific side of the Panama Canal Zone, contains a high percentage of gynandromorphs. The literature on aquatic arthropod gynandromorphs is outlined. The nature and variations of the sexual mosaic population are described and discussed. The several morphological differences between normal and mosaic members of the population are illustrated, and the possible origin of these gynandromorphs is discussed.     

Neuropeptides in spinal cord injury: Comparative experimental models

The possible role of endogenous opioids in the pathophysiology of spinal cord injury was evaluated utilizing a variety of experimental models and species. In the cat, we have shown that β-endorphin-like immunoreactivity was increased in plasma following traumatic spinal injury; such injury was associated with a decrease in spinal cord blood flow (SCBF) which was reversed by the opiate receptor antagonist naloxone. Naloxone treatment also significantly improved functional neurological recovery after severe injury. Thyrotropin-releasing hormone (TRH), possibly through its “anti-endorphin” actions, was even more effective than naloxone in improving functional recovery in the cat. In a rat model, utilizing a similar trauma method, TRH proved superior to naloxone in improving SCBF after injury. In addition, naloxone at high doses attenuated the hindlimb paralysis produced by temporary aortic occlusion in the rabbit. The high doses of naloxone required to improve neurological function after spinal injury suggest that naloxone's actions, if opiate receptor mediated, may be mediated by non-μ receptors. Dynorphin, an endogenous opioid with a high affinity for the κ receptor, produced hindlimb paralysis following intrathecal administration in rats. Taken together, these findings suggest that endogenous opioids, possibly acting at κ receptors in the spinal cord, may serve as pathophysiological factors in spinal cord injury.     

烧伤肠球菌肠源性感染

肠球菌是宿主肠道中正常G~ 球菌,目前已成为医源性感染的重要致病菌。临床上有30％肠球菌感染患者感染源不明,拟肠道来源可能性最大。本文给小鼠肌注灭滴灵3日,造成动物肠系膜淋巴结(MLN)肠球菌的感染率为40％;肌注灭滴灵加口服链霉素,MLN的感染率上升为90％,肝脾内脏中的感染率为83％;联合使用上述抗生素合并25％体表面积烧伤,动物发生致死性肠球菌性肠源性感染,动物诸内脏中肠球菌感染的检出率均高达100％。本研究证明肠球菌感染可以是肠源性的。     

Preparation of spermatogenic cell populations at specific stages of differentiation in the human.

Studying biochemical events in human spermatogenesis requires separated populations of spermatogenic cells. Dissociation of these cells was performed by a Trypsin-DNAse method adapted from the technique used for rodents. Cell separation was performed by centrifugal elutriation. Seven populations were collected, one further purified by Percoll gradient centrifugation, giving nine different cell populations. The efficiency of the cell separation was evaluated by phase contrast microscopy, flow cytometric DNA analysis, and electron microscopy. Five populations were enriched in spermatids: two in round spermatids (87% and 73%), another in round (52%) and elongating (44%) spermatids, another constituted by 80% elongating spermatids, and the last by 90% elongated spermatids. Two of the four remaining populations were enriched in primary spermatocytes (74% and 54%); another population was the upper part of the Percoll gradient and constituted cytoplasmic lobes and residual bodies (89%); the last population was made up of various cells, with no specific enrichment. Electron microscopic observations revealed good preservation of the separated cells; only the flagella from elongated spermatids were lost. Furthermore, an unusual pattern of nucleoplasm distribution during stages 2-4 of spermatid differentiation was observed and its signification is discussed with regard to the shape of the human spermatozoon.