Loss Of Total Protein Research Articles

Increasing peritoneal contact area during dialysis improves mass transfer.

Previous studies in mice demonstrated that relatively large volumes in the peritoneal cavity made contact with only 40% of the anatomic peritoneum and that this contact area (A(contact)) could be increased with use of a surfactant, dioctyl sodium sulfosuccinate (DSS). To investigate the hypothesis that mass transfer rates during peritoneal dialysis are dependent on the area of peritoneum in contact with the dialysis solution, rats were dialyzed for 2 h with a solution that contained (14)C-mannitol, with or without 0.02% DSS. The mass transfer-area coefficients (MTAC) were determined to be (mean +/- SEM, ml/min): no DSS, 0.163 +/- 0.008; with DSS, 0.247 +/- 0.006 (P < 0.002). DSS also caused an increase in total protein loss over 2 h (mean +/- SEM, mg): no DSS, 83.8 +/- 15.8; DSS, 159.5 +/- 6.3 (P < 0.001). In a separate set of animals, the ratio (R) of A(contact) to anatomic area in each plane was measured as in the previous study R(mean) (mean +/- SEM) and equaled 0.466 +/- 0.075, no DSS; 0.837 +/- 0.074, with DSS. The ratio of MTAC (1.52) and protein loss (1.90) approximate the ratio of R(mean(S)) (1.78). Because MTAC = mass transfer coefficient (MTC) x A(contact), small peritoneal transport chambers were used to determine MTC for (14)C-mannitol and fluorescein isothiocyanate-albumin. MTC(mannitol) did not change significantly with the addition of DSS. MTC(albumin) (cm/min x 10(4), mean +/- SEM) equaled 1.47 +/- 0.45 without DSS and 1.78 +/- 0.52 with DSS (P < 0.04). It was concluded that DSS increases the mass transfer rates of mannitol and protein by increasing A(contact), whereas protein transport is further augmented by an apparent increase in the barrier permeability to protein.

Microtubule depolymerization in rat seminiferous epithelium is associated with diminished tyrosination of alpha-tubulin.

In the testis, microtubule-disrupting agents cause breakdown of the Sertoli cell cytoskeleton and sloughing of germ cells with associated Sertoli cell fragments, although the mechanism underlying this event is not understood. In this study, we investigated the effects of carbendazim and colchicine on microtubule polymerization status and posttranslational modifications of tubulin in freshly isolated rat seminiferous tubules. Soluble and polymerized tubulin pools were separated and tubulin was quantified using a competitive ELISA. Carbendazim and colchicine caused extensive microtubule depolymerization, shifting the ratio of soluble to polymerized tubulin from 40%:60% to 78%:22%, and to 84%:16%, respectively. Total tubulin levels remained relatively constant after carbendazim treatment but decreased twofold after colchicine treatment. To determine if modifications to tubulin may be associated with polymerization status, tubulin pools were analyzed by immunoblotting. Acetylated alpha-tubulin and betaIII-tubulin distribution in tubulin pools was not affected by treatment. Tyrosinated alpha-tubulin (52 kDa) was localized in both tubulin pools and had decreased tyrosination in the microtubule pool after carbendazim treatment. A 47-kDa protein immunoreactive with both tyrosinated alpha-tubulin and general alpha-tubulin antibodies was found only in the microtubule pool. The 47-kDa protein (potentially an alpha-tubulin isoform) lost tyrosination, yet was still present in the microtubule pool based on detection with the general alpha-tubulin antibody, after carbendazim treatment. Similar effects were seen with colchicine, although loss of total tubulin protein was measured. Thus, decreased tyrosination of the microtubule pool of tubulin appears to be associated with depolymerization of microtubules.

Serum Albumin and Other Serum Protein Fractions in Stable Patients on Peritoneal Dialysis

Hypoalbuminemia is common in peritoneal dialysis (PD) patients; but the reduction in serum albumin levels (SAlb) that should be expected in stable PD patients is less clear. To determine prospectively, in a group of stable PD patients without comorbid conditions, the changes in SAlb concentration and in the concentrations of the other serum protein fractions. To investigate the best determinants of a significant decrease in SAlb levels. Prospective observational study. Seventeen PD patients in stable clinical condition, with no signs of systemic inflammatory response, were included in the study. SAlb and the electrophoretic pattern of serum proteins were determined immediately before PD start, and after 6, 9, 12, 15, 18, 21, and 24 months on PD. In each study period, clinical characteristics, adequacy parameters, protein catabolic rate (PNPNA: protein equivalent of non protein nitrogen appearance), and protein losses were determined. Patients were divided into two subgroups according to whether SAlb decreased less than 10%, or 10% or more, from baseline values after 24 months on PD. The main differences between the subgroups were investigated. Mean SAlb did not decrease significantly after 24 months on PD (from baseline 3.99 +/- 0.46 g/dL to 3.80 +/- 0.54 g/dL), though percentage SAlb values did (58.36% +/- 5.58% vs 55.15% +/- 5.42%, p < 0.01). A weak increase in alpha2-globulin was observed after 18 months on PD (from 10.62% +/- 2.53% to 12.96% +/- 2.51%, p = 0.001). Alpha-globulin showed a sustained increase from a mean baseline value of 3.51% +/- 1.09% to 6.83% +/- 2.13% after 24 months (p < 0.0001). Seven patients had a reduction in SAlb greater than 10% after 24 months on PD. Kt/V urea and residual renal function tended to be lower in patients whose SAlb decreased. Mean PNPNA was significantly lower in patients who had a reduction in SAlb (0.76 +/- 0.12 g/kg/day vs 0.96 +/- 0.12 g/kg/day, p < 0.0001). However, total protein loss was even greater in patients who had no SAlb reduction. After 24 months on PD, a mean reduction in SAlb of 10%-15% from baseline values should be expected only in those stable patients whose PNPNA is low.

Effects of ultraviolet radiation on photosynthesis and related enzyme reactions of marine macroalgae.

Changes in physiological parameters related to photosynthesis were studied in five macroalgal species from Spitsbergen (Monostroma arcticum, Laminaria solidungula, Alaria esculenta, Palmaria palmata, Phycodrys rubens) during a 72-h exposure to UV radiation. Maximal quantum yield of photochemistry (Fv/Fm) and maximal electron transport rate (ETRmax) were measured with a pulse-amplitude-modulated fluorometer; the activity of the Calvin cycle enzymes ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and glyceraldehyde-3-phosphate dehydrogenase (G3PDH) were estimated using a photometric test. Proteins of crude extracts were separated by SDS gel electrophoresis and changes in cellular concentrations of Rubisco were determined. Moreover, the concentration of chlorophyll a (Ch1 a), and protein content, were measured photometrically. In all species, Ch1 a content, maximal quantum yield as well as ETRmax decreased during the UV treatment. Changes in ETRmax were related to the changes in the overall activity of Rubisco. Analysis of SDS gels showed that in P. rubens, L. solidungula, M. arcticum and A. esculenta decreasing Rubisco activity partly resulted from a degradation of the enzyme. However, in A. esculenta, the formation of a high-molecular-weight polypeptide was observed. In all species, the activity of Rubisco was more strongly impaired than that of G3PDH. Exposure to UV resulted in loss of total protein only in the deepwater species L. solidungula and P. rubens. The different sensitivities to UV exposure of the species tested reflect their zonation pattern in the field.

Differential action of nerve growth factor and phorbol ester TPA on rat synaptosomal PKC isoenzymes

The subcellular redistribution of protein kinase C family members (α, β, γ, δ, ε and ζ isoforms) was examined in response to treatment with 12- O-tetradecanoyl-phorbol-13 acetate (TPA) or nerve growth factor (NGF) in a synaptosomal-enriched P 2 fraction from rat brain. Treatment with TPA affected members of the classical-PKC family (α, β and γ), resulting in a final loss of total protein of each isoenzyme. The kinetics of changes of members of the novel-PKC family are different, the δ isoform being translocated, but not down-regulated, while the ε isoform showing only a slight diminishing of immunoreactivity in the soluble and particulate fractions. The atypical-PKC ζ isoform was not translocated in response to TPA. Incubation with NGF induced a loss of immunoreactivity of the cytosolic α, β and ε isoforms, but the membrane fractions of these isoforms were not appreciably affected. In contrast, a marked translocation from cytosol to membrane was observed in the case of the γ and δ isoforms. The ζ isoform presented a slight translocation from the particulate fraction to the soluble fraction. Thus, the results show that the effects of TPA and NGF on PKC isoforms are not coincident in synaptosomes, the δ isoform being activated and not down-regulated by both treatments, whereas the γ isoform is only down-regulated in the case of TPA, but presents sustained translocation with NGF, indicating that PKC isoform-specific degradation pathways exist in synaptic terminals. The effects of NGF on PKC isoforms coexist with an increase in NGF-induced polyphosphoinositide hydrolysis, suggesting the participation of phospholipases.

Tidal peritoneal dialysis for home-treated patients: should it be preferred?

Tidal peritoneal dialysis (TPD) was introduced to increase the efficacy of peritoneal dialysis. We measured peritoneal clearances of small solutes and beta2-microglobulin, peritoneal protein loss, and efficacy of ultrafiltration in 30 patients during TPD and intermittent peritoneal dialysis (IPD) with low-dialysate flow (1.7 L/h) and, in addition, in 17 of these patients using a high-dialysate flow (3 L/h). Using a low-dialysate flow, patients with low/low average peritoneal transport rates showed significantly better peritoneal creatinine and urea nitrogen clearances during IPD compared with TPD, whereas there was no difference between these two treatment modalities in high/high average transporters. With high-dialysate flow, peritoneal clearances of creatinine and urea nitrogen were similar between TPD and IPD independent of peritoneal transport type. Clearances of phosphate and beta2-microglobulin were similar between TPD and IPD independent of dialysate flow or peritoneal transport type. Increasing the dialysate flow rate led to a significant increase in small-solute clearances, but not beta2-microglobulin clearances, in both peritoneal transport types. Total peritoneal protein and albumin losses were similar between TPD and IPD only with low-dialysate flow. However, using a high-dialysate flow, total protein losses tended to increase in both transport types during IPD compared with TPD. In conclusion, up to a dialysate flow of 3 L/h, TPD did not provide better small-solute or middle-molecule clearances compared with IPD. Moreover, using a low-dialysate flow, IPD was superior to TPD in low/low average transporters.

Longitudinal lipid profiles on CAPD: their relationship to weight gain, comorbidity, and dialysis factors.

The dyslipidemia of chronic renal failure may worsen after the commencement of continuous ambulatory peritoneal dialysis (CAPD). The purpose of this study was to relate baseline and longitudinal changes in the lipid profile to anthropometrics (weight, mid-arm circumference), aspects of treatment (albumin, total protein losses, peritoneal solute transport [dialysate:plasma ratio of creatinine], dialysate caloric load), total calorie intake (cal/kg), preexisting cardiovascular comorbidity, and survival. Lipid profiles (triglycerides [TG], total cholesterol [TC], and HDL) were measured, along with the above factors, every 6 mo in an unselected prospective cohort of 124 patients who were not treated with lipid-lowering drugs, commencing CAPD between 1990 and 1993, until 1995. On univariate analysis, age, plasma albumin, cardiovascular disease, baseline TG, and TC:HDL ratio predicted survival. Simultaneous multiple Cox regression including all of the significant predictors demonstrated that either high TG or TC: HDL still predicted death, both in patients with and without clinically overt cardiovascular disease. Between 6 and 36 mo of treatment, TC, TG, and TC:HDL were elevated when compared with the baseline, more so in patients with preexisting cardiovascular disease (P < 0.05). Throughout this period, weight and mid-arm circumference correlated positively with TG and negatively with HDL. There were positive correlations between TC and albumin levels for 12 mo after commencement of treatment, but otherwise there were no significant or consistent relationships between lipid profiles and total protein losses, dialysate calorie load, or total cal/kg or solute transport. The worsening dyslipidemia associated with CAPD was not associated with aspects of treatment such as glucose load or protein losses. The strongest predictors of worsening lipid profiles were weight gain and preexisting cardiovascular comorbidity.

Optimal protein requirements during the first 2 weeks after the onset of critical illness.

To obtain optimal protein requirements in critically ill sepsis or trauma patients during the first 2 wks after admission to the intensive care unit. Retrospective study. Department of critical care medicine at a teaching hospital. Immediate posttrauma patients or severely septic patients. In vivo neutron activation analysis was used to measure changes in total body protein over a 10-day period which began as soon as the patients were hemodynamically stable. The patients (trauma, n=18; sepsis, n=5) were divided into three groups according to the average daily protein intakes. Because the patients were overhydrated (approximately 10 L) and had variable amounts of body fat, the protein intakes were indexed to normally hydrated (corrected) fat-free mass (FFMc): Groups A, B, and C received an average of 1.1, 1.5, and 1.9 g/kg FFMc/day protein, respectively. Overall, the average loss of total body protein was 1.2=0.7 (SD) kg. Changes in total body protein were significantly (p=.011) different between the three groups. The loss of body protein was significantly more in group A compared with groups B (p=.013) and C (p=.023). When the protein intake was increased from 1.1 g/kg FFMc/day to 1.5 g/kg FFMc/day, protein loss was halved. Further increase in protein intake up to 1.9 g/kg FFMc/day resulted in no further improvement. An intake of 1.5 g/kg FFMc/day was equivalent to 1.0 g/day/kg of body weight measured at the beginning of the study. Current recommended protein requirements of 1.2 to 2.0 g/kg of body weight/day are excessive if they are indexed to the body weight measured soon after the onset of critical illness. Because individual patients have varying degrees of overhydration early in the illness onset, we suggest that the intensivist should obtain information on preillness body weight and prescribe 1.2g of protein/kg body weight/day. If information is not available, 1.0g of protein/day/kg of measured body weight will give a fair approximation to optimal protein requirements.

Skeletal muscle myocytes undergo protein loss and reactive oxygen-mediated NF-κB activation in response to tumor necrosis factor α

Skeletal muscle atrophy and weakness are thought to be stimulated by tumor necrosis factor alpha (TNF-alpha) in a variety of chronic diseases. However, little is known about the direct effects of TNF-alpha on differentiated skeletal muscle cells or the signaling mechanisms involved. We have tested the effects of TNF-alpha on the mouse-derived C2C12 muscle cell line and on primary cultures from rat skeletal muscle. TNF-alpha treatment of differentiated myotubes stimulated time- and concentration-dependent reductions in total protein content and loss of adult myosin heavy chain (MHCf) content; these changes were evident at low TNF-alpha concentrations (1-3 ng/ml) that did not alter muscle DNA content and were not associated with a decrease in MHCf synthesis. TNF-alpha activated binding of nuclear factor kappaB (NF-kappaB) to its targeted DNA sequence and stimulated degradation of I-kappaBalpha, an NF-kappaB inhibitory protein. TNF-alpha stimulated total ubiquitin conjugation whereas a 26S proteasome inhibitor (MG132 10-40 microM) blocked TNF-alpha activation of NF-kappaB. Catalase 1 kU/ml inhibited NF-kappaB activation by TNF-alpha; exogenous hydrogen peroxide 200 microM activated NF-kappaB and stimulated I-kappaBalpha degradation. These data demonstrate that TNF-alpha directly induces skeletal muscle protein loss, that NF-kappaB is rapidly activated by TNF-alpha in differentiated skeletal muscle cells, and that TNF-alpha/NF-kappaB signaling in skeletal muscle is regulated by endogenous reactive oxygen species.

Replacement of Amino Acid and Protein Losses with 1.1% Amino Acid Peritoneal Dialysis Solution

Losses of nutrients into dialysate may contribute to malnutrition. Peritoneal dialysis (PD) patients are reported to lose 3-4 g/day of amino acids (AAs) and 4-15 g/day of proteins. The extent to which one exchange with a 1.1% AA dialysis solution (Nutrineal, Baxter, Deerfield, IL, U.S.A.) offsets these losses was investigated in a 3-day inpatient study in 20 PD patients. Simple, open-label, cross-over study on consecutive days in a clinical research unit. On day 1 all patients were given a peritoneal equilibration test (PET). On day 2 they received 1.5% dextrose Dianeal (Baxter) as the first exchange of the day and their usual regimen thereafter. On day 3, the first exchange of the day was the 1.1% AA solution in place of 1.5% Dianeal and the usual PD regimen thereafter. On days 2 and 3 all dialysate effluent was collected and analyzed for AAs and proteins. Patients were maintained on a constant diet. Losses of AAs and total proteins on day 2 were 3.4 +/- 0.9 g and 5.8 +/- 2.4 g, respectively, totaling 9.2 +/- 2.7 g. The net uptake of AAs on day 3 was 17.6 +/- 2.6 g (80 +/- 12% of the 22 g infused). Mean gains of AAs on day 3 exceeded losses of proteins and AAs on day 2, p < 0.001. Losses of total proteins, but not losses of AAs, and the net absorption of AAs from the dialysis solution were correlated directly with peritoneal membrane transport characteristics, obtained from the PET. Daily losses of AAs and proteins into dialysate are more than offset by gains of AAs absorbed from one exchange with 1.1% AA-based dialysis solution. Net gains of AAs exceeded losses of proteins and AAs in all patients studied. The difference was relatively constant across a wide range of membrane transport types. Net AA gains were approximately two times the total AA and protein losses.

Biology of cachexia.

About half of all cancer patients show a syndrome of cachexia, characterized by loss of adipose tissue and skeletal muscle mass. Such patients have a decreased survival time, compared with the survival time among patients without weight loss, and loss of total body protein leads to substantial impairment of respiratory muscle function. These changes cannot be fully explained by the accompanying anorexia, and nutritional supplementation alone is unable to reverse the wasting process. Despite a falling caloric intake, patients with cachexia frequently show an elevated resting energy expenditure as a result of increases in Cori cycle (i.e., catalytic conversion of lactic acid to glucose) activity, glucose and triglyceride-fatty acid cycling, and gluconeogenesis. A number of cytokines, including tumor necrosis factor-apha, interleukins 1 and 6, interferon gamma, and leukemia-inhibitory factor, have been proposed as mediators of the cachectic process. However, the results of a number of clinical and laboratory studies suggest that the action of the cytokines alone is unable to explain the complex mechanism of wasting in cancer cachexia. In addition, cachexia has been observed in some xenograft models even without a cytokine involvement, suggesting that other factors may be involved. These probably include catabolic factors, which act directly on skeletal muscle and adipose tissue and the presence of which has been associated with the clinical development of cachexia. A polyunsaturated fatty acid, eicosapentaenoic acid, attenuates the action of such catabolic factors and has been shown to stabilize the process of wasting and resting energy expenditure in patients with pancreatic cancer. Such a pharmacologic approach may provide new insights into the treatment of cachexia.

Lysosomal proteolysis in distally or proximally denervated rat soleus muscle.

We examined the mechanism of accelerated proteolysis in denervated rat soleus muscles. The soleus was denervated by severing either the tibial nerve (proximal, short stump) or sciatic nerve (distal, long stump) at 24, 48, 72, or 96 h before excision. Twenty-four hours after denervation, the extent of atrophy was similar for proximal and distal denervation, although lysosomal latency declined in both groups. After 48 and 72 h, denervation resulted in a decline in protein content, an increase in in vitro protein degradation, and a decline in lysosomal latency, all of which were greater in proximally denervated than in contralateral distally denervated muscles. These differences between acute responses of proximally and distally denervated muscles suggest the retention of some factor in the longer nerve stump that attenuates atrophy. After 96 h, total protein loss, protein degradation, and lysosomal latency were similar for proximal and distal denervation, suggesting the loss of axoplasmic flow from the long nerve stump.

Temperature influenced lipid peroxidation and deterioration in broccoli buds during postharvest storage

Abstract The effect of temperature on lipid peroxidation (LP) and deterioration of broccoli flower buds was investigated during postharvest storage. Fresh broccoli florets were packaged in microperforated polymeric film bags and stored under different temperatures (2, 13, and 23 °C) over 144 h. LP was determined by measuring polyunsaturated fatty acids (PUFA). thiobarbituric acid-reactive substances (TBA-RS) and lipoxygenase (LOX) activity. Changes in chlorophyll (Chl) levels, moisture and total soluble protein were used to assess broccoli deterioration. Increased temperature significantly accelerated total Chl (TChl) and soluble protein losses without reduction in moisture content. Temperature abuse at 13 and 23 °C also resulted in reduced PUFA and LOX activity with increased TBA-RS values compared to those in the 2 °C-treated buds over storage. By the end of storage, TChl, proteins. PUFA and LOX activity decreased by >70% in broccoli buds stored at 23 °C. TBA-RS values increased 10-fold. Treatment of samples at 2 °C maintained quality and prevented changes in deterioration and LP parameters. The current investigation shows that increases in temperature accelerate the deterioration and LP of broccoli buds and further demonstrates that there is a relationship between LP and deterioration during postharvest storage of broccoli.

Cytochrome c mRNA in skeletal muscles of immobilized limbs.

Even though immobilization of a slow skeletal muscle in a lengthened position prevents muscle atrophy, it is unknown whether this treatment would prevent a decrease in mitochondrial quantity. We found that, regardless of muscle length in immobilized limbs, the mRNA of a marker for mitochondrial quantity, cytochrome c, decreased. Cytochrome c mRNA per milligram of muscle was 62 and 72% less 1 wk after fixation of the soleus muscle in shortened and lengthened positions, respectively, than age-matched controls. Cytochrome c mRNA per milligram wet weight was 36 and 32% less in the tibialis anterior muscle fixed for 1 wk in the shortened and lengthened positions, respectively, compared with age-matched controls. Recently, in the 3'-untranslated region of cytochrome c mRNA a novel RNA-protein interaction that decreases in chronically stimulated rat skeletal muscle was identified. [Z. Yan, S. Salmons, Y. L. Dang, M. T. Hamilton, and F. W. Booth. Am. J. Physiol. 271 (Cell Physiol. 40): C1157-C1166, 1996]. The RNA-protein interaction in the 3'-untranslated region of cytochrome c mRNA in soleus and tibialis anterior muscles was unaffected by fixation in either shortened or lengthened position. We conclude that, whereas lengthening muscle during limb fixation abates the loss of total muscle protein, the percentage decrease in cytochrome c mRNA is proportionally greater than total protein. This suggests that the design of countermeasures to muscle atrophy should include different exercises to maintain total protein and mitochondria.

Gene expression in leaves ofArabidopsis thalianainduced to senesce by nutrient deprivation

Senescence was induced in leaves of Arabidopsis thaliana by transferring rosettes from a nutrient-sufficient medium to water. A visible gradient of yellowing along the shoot axis became apparent within 5 d. Leaves were grouped into four age-classes, representing fully green (nodes 17-20) through about one-third (nodes 13-16) and one-half (9-12) to more than 80% yellow (5-8). The decrease in chlorophyll and carotenoid content with increasing tissue senescence was accompanied by a loss of total protein and of specific polypeptides identified by electrophoresis and Western blotting. Heterogeneity in the rates at which photosynthetic proteins decreased during senescence could be related to differences in susceptibility to proteolysis conferred by location (soluble proteins are more labile than membrane components) and association with stabilizing components such as pigments. The abundance of senescence-related mRNAs was determined by Northern analysis using heterologous DNA probes and also cDNAs isolated from Arabidopsis by differential library screening. Expression of the plastid gene psbA increased until the most extreme stage of senescence, in contrast to the pattern of the protein it encodes, D1, which was almost undetectable in all but mature green tissue. Transcripts corresponding to two senescence-enhanced cDNAs from Brassica napus, LSC54 and LSC94, were strongly up-regulated in senescing Arabidopsis leaves. Two Arabidopsis cDNAs, LdeVA8 and LdeVA32, detected mRNAs of increasing abundance up to mid-senescence and decreasing thereafter. Another homologous clone, LdeVA43, hybridized with a transcript showing some enhancement in early senescence. Partial base sequences of LdeVA8 and LdeVA32 revealed homologies with genes encoding a metallothienin-like protein and catalase, respectively. LSC54 also encodes a putative metallothionein. The possible significance of the patterns of gene expression in senescing rosette leaves of A. thaliana is discussed.

Dynamic responses of photosystem II and phycobilisomes to changing light in the cyanobacterium Synechococcus sp. PCC 7942

We have examined the molecular and photosynthetic responses of a planktonic cyanobacterium to shifts in light intensity over periods up to one generation (7 h). Synechococcus sp. PCC 7942 possesses two functionally distinct forms of the D1 protein, D1∶1 and D1∶2. Photosystem II (PSII) centers containing D1∶1 are less efficient and more susceptible to photoinhibition than are centers containing D 1∶2. Under 50 μmol photons· m−2·s−1, PSII centers contain D1∶1, but upon shifts to higher light (200 to 1000 μmol photons·m−2·s−1), D1∶1 is rapidly replaced by D 1∶2, with the rate of interchange dependent on the magnitude of the light shift. This interchange is readily reversed when cells are returned to 50 μmol photons·m−2·s−1. If, however, incubation under 200 μmol photons·m−2·s−1 is extended, D1∶1 content recovers and by 3 h after the light shift D1∶1 once again predominates. Oxygen evolution and chlorophyll (Chl) fluorescence measurements spanning the light shift and D1 interchanges showed an initial inhibition of photosynthesis at 200 μmol photons·m−2·s−1, which correlates with a proportional loss of total D1 protein and a cessation of growth. This was followed by recovery in photosynthesis and growth as the maximum level of D 1∶2 is reached after 2 h at 200 μmol photons·m−2·s−1. Thereafter, photosynthesis steadily declines with the loss of D1∶2 and the return of the less-efficient D1∶1. During the D1∶1/D1∶2 interchanges, no significant change occurs in the level of phycocyanin (PC) and Chl a, nor of the phycobilisome rod linkers. Nevertheless, the initial PC/Chl a ratio strongly influences the magnitude of photo inhibition and recovery during the light shifts. In Synechococcus sp. PCC 7942, the PC/Chl a ratio responds only slowly to light intensity or quality, while the rapid but transient interchange between D1∶1 and D 1∶2 modulates PSII activity to limit damage upon exposure to excess light.

Dialysate protein losses with bleach processed polysulphone dialyzers

We measured dialysate protein losses from polysulphone dialyzers undergoing repetitive processing with bleach and formaldehyde. The entire dialysate was collected during the first, fifth and tenth use of F-80 dialyzers. Dialysate protein concentration was 1.5 +/- 0.4 mg/dl N = 11 +/- SEM) during the first use, 2.1 +/- 0.3 mg/dl during the fifth use and 3.6 +/- 0.5 mg/dl (N = 10) during the tenth use. In a follow-up study, dialyzers were evaluated for up to 25 uses. After 12 to 15 uses dialysate protein was 7.9 +/- 0.8 mg/dl (N = 13), after 16 to 20 uses; 12.0 +/- 1.2 mg/dl (N = 13) and after 23 to 25 uses; 19.9 +/- 2.1 mg/dl (N = 5). Mean dialysate volume was 83.9 +/- 1.1 liters (N = 63) yielding total protein losses of up to 20.7 grams per treatment. Dialysate albumin losses, which were unmeasurable during the first use of the dialyzers, revealed a similar increase with reuse resulting in a mean value of 14.4 +/- 3.2 mg/dl after 23 to 25 reuses (N = 5). Dialysate beta-2 microglobulin (beta 2m) levels were 1.05 +/- 0.13 mg/l for dialyzers bleached < 10 times (N = 32) versus 1.54 +/- 0.15 mg/liter for dialyzers bleached > 10 times (N = 31, P < 0.02 vs. < 10 reuses). A random sampling of dialyzers processed without bleach for 8, 14, 15, 24 and 25 reuses revealed minimal protein losses, ranging from 1.4 to 2.7 mg/dl with no relation to reuse number and no measureable albumin.(ABSTRACT TRUNCATED AT 250 WORDS)

The senescence of oat leaf segments is promoted under simulated microgravity condition on a three-dimensional clinostat.

Plants have evolved on the earth, indicating the morphology, growth and development, and life cycle of plants are highly influenced by gravity as well as other environmental stimuli. Indeed, simulated microgravity on a clinostat or hypergravity on a centrifuge has recently been reported to change the growth and development of plants (Hoson et al. 1992, 1993, 1995, Rasmussen et al. 1994, Kasahara et al. 1995). Senescence is a final drastic phenomenon in life cycle of plants, which is characterized by the loss of total chlorophyll and protein, and/or the formation of the abscission (Osborne 1973, Thimann 1977, Addicott 1982). Many environmental stimuli as well as the qualitative and quantitative changes of plant hormones have been reported to affect plant senescence. Among those stimuli, light is the most important factor to regulate plant senescence (Leopold 1964). Dark condition promotes leaf senescence due to the decrease in endogenous level of cytokinin and/or the increase in that of abscisic acid or ethylene (Tetley and Thimann 1974, Gepstein and Thimann 1980). However, there are few reports concerning the effect of gravity on leaf senescence. Strenuous effort to learn leaf senescence under microgravity condition has been done using a three-dimensional (3-D) clinostat. In this paper, we report that simulated microgravity condition on a 3-D clinostat promoted the senescence of oat leaf segments in the dark. A possible mechanism of microgravity condition on promoting the senescence is also discussed.

Integral proteins of the extracellular matrix fibrils of Myxococcus xanthus.

The extracellular matrix fibrils of Myxococcus xanthus are mediators of cell-cell cohesion and as such are required for the maintenance of the social lifestyle characteristic of these prokaryotes. The fibrils have also been implicated as factors involved in contact-mediated cell interactions and in signal exchange. The fibrils are extracellular carbohydrate structures with associated proteins. All of the major proteins associated with the fibrils react with monoclonal antibody 2105 and can be removed from the fibrils only by boiling with sodium dodecyl sulfate (SDS) and beta-mercaptoethanol. For consistency with their integral association with the fibrils, we have designated this class of proteins as integral fibrillar proteins class 1 (IFP-1). IFP-1 comprises five major proteins whose molecular sizes range from 66 to 14 kDa. All of the proteins in IFP-1 have been purified from isolated fibrils by electroelution after size separation on SDS-PAGE gels. Analysis of the purified proteins suggested that the forms with different molecular sizes result from the aggregation of a single small-molecular-size subunit. Fingerprint analysis and amino acid composition profiles confirmed the identity among the different members of IFP-1. The sequence of the 31 amino-terminal amino acids of the 31-kDa form of IFP-1 (IFP-1:31) was determined. There was no significant homology to other known protein sequences. During development there is a dramatic shift in the banding pattern of IFP-1 proteins without any apparent overall loss of total protein.

Changes in residual dextrose and amount of total protein loss in the effluent during the clinical course of continuous ambulatory peritoneal dialysis-related peritonitis

Solute permeability of the peritoneum accelerates considerably in continuous ambulatory peritoneal dialysis (CAPD)-related peritonitis. Residual dextrose (RD) (g/bag) and the amount of total protein loss (LP) (g/bag) in the effluent of dialysate were measured during the clinical course of 21 cases of CAPD-related peritonitis as markers of deranged peritoneal permeability. The following were the results obtained: 1) In 15 cases of intraluminal infection (simple peritonitis by microorganism contamination through the lumen of a peritoneal catheter), RD decreased on day 1 (p < 0.001) and day 3 (p < 0.001) after the onset of peritonitis, and LP increased on day 1 (p < 0.001) and day 3 (p < 0.01), compared to the values of the non-infected phase. Both parameters were restored on day 7 and day 14 by adequate therapeutic maneuver. 2) In 6 cases of periluminal infection (peritonitis caused by an organic lesion of infection along the peritoneal catheter), RD and LP persisted even on day 7 (p < 0.01), and recovered 10 days after surgical removal of the peritoneal catheter with simultaneous catheter replacement. It is concluded that both RD and LP are valuable markers in the evaluation of the clinical course of CAPD-related peritonitis, and are useful in deciding on therapeutic intervention.