Transient Increase In Concentration Research Articles

Feeding Strategies During Natural Calamities

India is one of worst disaster prone countries of the world. Out of 36 states and union territories in the country, 25 of them are disaster prone. Disasters continue to occur without warning and are on an increase in their magnitude, complexity, frequency and economic impact. The natural calamities in the form of floods, tsunamis, famines, cyclones, earthquakes and avalanches are considered mainly due to global warming. The major effects are acute shortages of food, feed and fodder and drinking water which adversely affect human and livestock health and nutrition. Severe malnutrition due to natural calamities may depress growth, productive and reproductive performance. Therefore, while developing the feeding strategies during natural calamities, the first priority should be to save the animals from starvation, diverting feedstuffs from lactating animals and then to sustain productivity of the animals that survived to the extent possible. The water requirement of lactating cattle is in the range of 2.5–4.5 L/kg DM intake. During water scarcity, the watering frequencies in large ruminants should be decreased to once in 2–3 days which increase the retention time and in turn digestibility of nutrients. All affected animals should be shifted to restricted feeding which will reduce the volume and metabolic activity of the viscera and other tissues and in turn basal metabolism. Feed restriction increases the extent of negative energy balance and causes transient increases in concentrations of non-esterified fatty acids, acetate and s-hydroxybutyrate in plasma due to the mobilization of nutrients from body reserves. The restricted feeding may cause loss in body weight and milk yield in lactating animals but ensures animals survivability. The strategies such as 1) restricted feeding; 2) conserved fodders in transportable silage bags; 3) fodder produced in low-cost hydroponic systems; 4) unconventional feed resources including propagation of thornless cactus; 5) urea molasses multinutrient blocks; 6) hay bales, 7) densified complete feed blocks or pellets containing untreated or urea-treated straws/stovers, tree leaves and grasses, mushroom harvested spent straw with and without feed additives could help prevent livestock mortality and morbidity in emergency situations. Once the availability of quality feed and fodder improves, the animals should be given compensatory feeding. The animals will recoup the loss in body weight completely and partly the production performance suffered during natural calamities.

Aphid induction of phytohormones in Medicago truncatula is dependent upon time post-infestation, aphid density and the genotypes of both plant and insect

This study examined the induction of the defence-related hormones jasmonic acid (JA), salicylic acid (SA) and abscisic acid (ABA) and the phytoalexin medicarpin in Medicago truncatula when challenged by the pea aphid Acyrthosiphon pisum. There was some induction of hormones in the compatible interaction between A. pisum clone N116 and M. truncatula cultivar DZA315, whereas JA, SA and medicarpin exhibited more significant increases in foliage concentration during the incompatible interaction between A. pisum clone PS01 and M. truncatula cultivar Jemalong A17. Foliar concentration of JA, SA and medicarpin exhibited a positive relationship with aphid density after 3-day feeding, whereas ABA was not affected by the presence of aphids. When aphids were restricted to a single leaf using plastic tubes, JA, SA and medicarpin displayed strong local induction, whereas there were no significant systemic increases in uninfested leaves. Medicarpin and SA appeared to increase with duration of aphid feeding, whereas JA showed a more transient increase in concentration 24 h after challenge commenced. Results suggest that increases in JA, SA and medicarpin are associated with M. truncatula resistance to particular clones of A. pisum. The variation in concentration of the defence-related compounds recorded with regard to aphid density, duration of challenge, genotypes of plant and aphids, and between locally challenged and distant leaves reinforces the need for consideration of these experimental factors when generalizing about the plant defence processes that occur during aphid–plant interactions.

Defective secretion of Prostaglandin F2α during development of idiopathic persistent corpus luteum in mares

Five mares that developed idiopathic persistent corpus luteum (PCL) were compared with 5 mares with apparently normal interovulatory intervals (IOIs). Progesterone (P4) and a metabolite of prostaglandin F2α (PGFM) were assayed daily beginning on the day of ovulation (Day 0). Transition between the end of an initial progressive P4 increase and the beginning of a gradual decrease in P4 occurred on mean Day 6. The gradual decrease in P4 between Days 6 and 12 was less (approached significance, P < 0.06) in the PCL group than in the IOI group. The P4 concentration on Day 12 (before luteolysis in IOI group) was greater (P < 0.05) in the PCL group than in the IOI group. In a post hoc comparison, an interaction (P < 0.04) of group by day for Days 4 to 7 indicated that the end of the progressive increase in P4 was temporally associated with a transient increase in concentration of PGFM in IOI mares but not in PCL mares. Complete luteolysis (P4 < 1 ng/mL) occurred in the IOI mares on Days 13 to 15. Partial luteolysis (mean P4 decrease, 62%) occurred in 3 of the 5 PCL mares. Normalization to the day at the end of the most pronounced P4 decrease in the IOI mares and in the 3 PCL mares with partial luteolysis resulted in a day-by-group interaction (P < 0.05) for PGFM concentration. The interaction was partly from lower PGFM concentration on the day at the end of the pronounced P4 decrease in the 3 PCL mares than in the IOI mares. The peak of a transient PGFM increase and the day at the end of the most pronounced decrease in P4 were synchronized in each IOI mare but not in any of the 3 PCL mares. In the other 2 PCL mares, partial luteolysis did not occur, and a transient increase in PGFM was not apparent. Results tentatively indicated that the relationship between P4 and PGFM may be altered as early as Day 6 in PCL mares and supported the hypothesis that prostaglandin F2α secretion is defective in mares with idiopathic PCL.

Exposure Controls for Nanomaterials at Three Manufacturing Sites

Because nanomaterials are thought to be more biologically active than their larger parent compounds, careful control of exposures to nanomaterials is recommended. Field studies were conducted at three sites to develop information about the effectiveness of control measures including process changes, a downflow room, a ventilated enclosure, and an enclosed reactor. Aerosol mass and number concentrations were measured during specific operations with a photometer and an electrical mobility particle sizer to provide concentration measurements across a broad range of sizes (from 5.6 nm to 30 μm). At site A, the dust exposure and during product harvesting was eliminated by implementing a wait time of 30 -min following process completion. And, the dust exposure attributed to process tank cleaning was reduced from 0.7 to 0.2 mg/m3 by operating the available process ventilation during this task. At site B, a ventilated enclosure was used to control dust generated by the manual weigh-out and manipulation of powdered nanomaterials inside of a downflow room. Dust exposures were at room background (under 0.04 mg/m3 and 500 particles/cm3) during these tasks however, manipulations conducted outside of the enclosure were correlated with a transient increase in concentration measured at the source. At site C, a digitally controlled reactor was used to produce aligned carbon nanotubes. This reactor was a closed system and the ventilation functioned as a redundant control measure. Process emissions were well controlled by this system with the exception of increased concentrations measured during the unloading of the product. However, this emission source could be easily controlled through increasing cabinet ventilation. The identification and adoption of effective control technologies is an important first step in reducing the risk associated with worker exposure to engineered nanoparticles. Properly designing and evaluating the effectiveness of these controls is a key component in a comprehensive health and safety program.

Blood cell-derived nanovesicles as biomarkers of homeostasis in gastrointestinal cancer.

152 Background: Nanovesicles (NVs) are membrane-enclosed fragments of cell interior which are pinched off from membranes of cells of all types (including cancer) in the last stage of the budding process. They are involved in cell-cell communication and can promote tumor growth and invasion. Interactions of tumor-derived NVs with blood cells, especially platelets are hypothetically reflected in vesiculability of platelets by means of concentration of NVs in blood isolates. Also we hypothesized that in patients whose plasma mediates stronger attractive interaction between membranes the concentration of NVs in blood isolates would be lower. Methods: NVs were isolated from 2.7 ml samples of blood of 29 patients with gastrointestinal cancer, 44 patients with other gastrointestinal diseases, additional 13 patients who were treated by imatinib due to gastrointestinal stromal tumor (GIST) and 50 healthy volunteers, by repeated centrifugation and washing, and counted by flow cytometry. We followed patients with GIST for 32 months. Ability of blood plasma to mediate attractive interaction between membranes was assessed by the angle of contact between giant phospholipid vesicles prepared by electroformation, which adhered due to addition of plasma to the suspension of NVs. Results: The concentration of NVs was considerably (44%, p = 0.0005) higher in the blood isolates of patients with gastrointestinal cancer than in the population of healthy volunteers and considerably (34%, p = 0.025) higher in patients with gastrointestinal cancer than in patients with other gastrointestinal diseases. We observed a considerable (average 13 fold peak) but transient (about one month within 32 montth follow up interval) increase of concentration of NVs in blood isolates due to treatment with imatinib.We found a negative correlation between the concentration of NVs and the average contact angle between adhered giant phospholipid vesicles (r = –0.50, p = 0.031). Conclusions: Concentration of NVs is increased while the ability of plasma to mediate attractive interaction between membranes is decreased in patients with gastrointestinal cancer. Treatment with imatinib caused transient increase of concentration of NVs in isolates from blood.

Endogenous Cytokinin Oscillations Control Cell Cycle Progression of Tobacco BY‐2 Cells

The significance of cytokinins for the progression of the cell cycle is well known. Cytokinins contribute to the control of the expression of D-cyclins and other cell cycle genes, but knowledge as to how they affect the progression of the cell cycle is still limited. Highly synchronized tobacco BY-2 cells with clearly defined cell cycle stages were employed to determine cytokinin patterns in detail throughout the entire cycle. Concentrations of trans-zeatin, and of some other cytokinins, oscillated during the course of the cell cycle, increasing substantially at all four phase transitions and decreasing again to a minimum value during the course of each subsequent phase. Addition of exogenous cytokinins or inhibition of cytokinin biosynthesis promoted the progression of the cell cycle when the effects of these manipulations intensified the endogenous fluctuations, whereas the progression of the cycle was retarded when the amplitude of the fluctuations was decreased. The results show that the attainment of low concentrations of cytokinins is as important as the transient increases in concentration for a controlled progression from one phase of the cell cycle to the next. Cytokinin oxidase/dehydrogenase activity also showed fluctuations during the course of the cell cycle, the timing of which could at least partly explain oscillations of cytokinin levels. The activities of the enzyme were sufficient to account for the rates of cytokinin disappearance observed subsequent to a phase transition.

Expression of interleukin-6 and monocyte chemoattractant protein-1 by peritoneal sub-mesothelial cells during abdominal operations.

Cytokines and chemokines including interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) are secreted in response to major abdominal operations. The aim of this study was to identify the peritoneal cells that produce IL-6 and MCP-1. Samples of peritoneal tissue were taken from patients at the beginning and end of major abdominal operations. The samples were incubated in culture medium on microtitre plates for 5 h. The concentrations of IL-6 and MCP-1 were measured in culture supernatants by enzyme-linked immunosorbent assay (ELISA). In paraffin sections, cells that expressed IL-6 or MCP-1 were identified by combined in situ hybridization and immunohistochemistry. Antibodies against CD68, CD34, actin, and calretinin were included in these experiments. The median production of IL-6 increased significantly from 6256 pg/ml at the start of the operation to 20,000 pg/ml at the end. Production of MCP-1 rose from 7700 pg/ml to 11,820 pg/ml. IL-6 mRNA was mainly confined to endothelial cells. MCP-1 was expressed by a broader range of cells, consisting of actin-positive smooth muscle cells and endothelial cells, fibroblast-like cells, as well as occasional macrophages and mesothelial cells. Peritoneal endothelial cells contribute to the transient increase in concentrations of IL-6 in the circulation after surgical trauma. Recruitment of monocytes to the site of the trauma seems to be mainly effected by actin-positive smooth muscle cells and endothelial cells.

Elemental Sulfur and Thiol Accumulation in Tomato and Defense against a Fungal Vascular Pathogen

The occurrence of fungicidal, elemental S is well documented in certain specialized prokaryotes, but has rarely been detected in eukaryotes. Elemental S was first identified in this laboratory as a novel phytoalexin in the xylem of resistant genotypes of Theobroma cacao, after infection by the vascular, fungal pathogen Verticillium dahliae. In the current work, this phenomenon is demonstrated in a resistant line of tomato, Lycopersicon esculentum, in response to V. dahliae. A novel gas chromatography-mass spectroscopy method using isotope dilution analysis with 34S internal standard was developed to identify unambiguously and quantify 32S in samples of excised xylem. Accumulation of S in vascular tissue was more rapid and much greater in the disease-resistant than in the disease-susceptible line. Levels of S detected in the resistant variety (approximately 10 microg g-1 fresh weight excised xylem) were fungitoxic to V. dahliae (spore germination was inhibited >90% at approximately 3 microg mL-1). Scanning electron microscopy-energy dispersive x-ray microanalysis confirmed accumulation of S in vascular but not in pith cells and in greater amounts and frequency in the Verticillium spp.-resistant genotype. More intensive localizations of S were occasionally detected in xylem parenchyma cells, vessel walls, vascular gels, and tyloses, structures in potential contact with and linked with defense to V. dahliae. Transient increases in concentrations of sulfate, glutathione, and Cys of vascular tissues from resistant but not susceptible lines after infection may indicate a perturbation of S metabolism induced by elemental S formation; this is discussed in terms of possible S biogenesis.

Lactate metabolism during exercise: analysis by an integrative systems model.

To provide a framework for quantitative analysis of metabolic and transport processes associated with ATP production during exercise, we adapted a recently developed model that links cellular metabolism and its control to whole body responses at rest. The enhanced model is based on dynamic mass balances for glycogen, glucose, pyruvate (PY), lactate (LA), O(2), and CO(2) and is solved numerically to simulate responses to acute (<20 min), moderate exercise (i.e., below the LA threshold, less than approximately 60% maximal rate of O(2) uptake). Simulations of responses to a step change in muscle ATP turnover predict substrate changes in muscle, splanchnic, and other tissues compartments, as well as changes in other metabolites (e.g., NADH, ADP) whose reactions are coupled to the main reactions. Even a significant (64%) decrease in muscle O(2) concentration (C(m, O(2))) did not affect muscle O(2) consumption. Model simulations of moderate exercise show that 1) muscle oxygenation is sufficient (C(m, O(2)) >2 mM) even during the transient state; 2) transient increases in concentration of muscle LA and arterial concentration of LA are associated with increases in glycolysis from increases in ADP/ATP and in LA production associated with a rise in NADH/NAD; 3) muscle ADP/ATP reaches a higher steady state that stimulates glycolysis, glycogenolysis, and oxidative phosphorylation to match the ATP demand; and 4) muscle NADH/NAD reaches a lower steady state that stimulates LA oxidation. It is suggested that the continuous stimulation of ATP synthesis processes during moderate exercise is mainly due to a higher ADP/ATP, not to a higher NADH/NAD. Critical measurements needed to quantify metabolic control mechanisms are identified.

Effects of Water Stress on Fruit Quality Attributes of Kiwifruit

Four-year-old kiwifruit vines (Actinidia deliciosa(A. Chev.) C. F. Liang et A. R. Ferguson var.deliciosacv. Hayward) were studied to determine response of the plant and effects on fruit quality when irrigation water was withheld either early or late in the growing season. The greatest effect on fruit growth occurred when water was withheld early in the season. Harvest weight of fruit from early-stressed vines was approx. 25% less than the weight of fruit on control vines. Early season water stress resulted in a transient increase in concentrations of soluble carbohydrates in both leaves and fruit. This was accompanied by a reduction in stomatal conductance of the leaves. Starch levels in leaves but not fruit were reduced by both stress treatments. Concentrations of sucrose at harvest in fruit from vines stressed late in the season were markedly higher than in other fruit, and softness of the fruit was unaffected. These differences were maintained through the 12 weeks in cool storage after harvest. Withholding irrigation water to kiwifruit vines late in the season may prove a useful management tool to manipulate some quality attributes of the fruit.

Pharmacokinetics of a 7‐Day 17β‐Estradiol Transdermal Delivery System: Effect of Application Site and Repeated Applications on Serum Concentrations of Estradiol and Estrone

FemPatch (Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, Ann Arbor, MI), a new 7-day 17 beta-estradiol transdermal delivery system (TDS), has been developed for treatment of menopausal vasomotor symptoms. This two-period crossover study was conducted to determine the effects of TDS application site (buttocks versus abdomen) and early TDS replacement on estradiol and estrone concentrations, and to quantify intersubject and intrasubject pharmacokinetic variability. Eighteen healthy, postmenopausal female volunteers received a single 7-day TDS application to the abdomen and repeated TDS applications to the buttocks (regular replacement on days 7 and 14, intentional early replacement on day 17, and removal on day 21). Serial serum samples were assayed for estradiol and estrone by validated radioimmunoassay methods. The 7-day TDS delivers estradiol at a constant, near zero-order rate for the duration of application, independent of application site. Mean serum estradiol concentrations were higher after application to the buttocks than after application to the abdomen (19 and 15 pg/mL above baseline, respectively), making the buttocks the preferred site for TDS application. Mean serum concentration of estradiol was slightly higher (23 pg/mL above baseline) for the treatment week with early TDS replacement due to the transient increase in concentration over the first 24 hours after replacement. Parallel but smaller increases in concentrations of estrone were observed. Serum estradiol and estrone concentrations are reproducible within an individual from application to application (coefficient of variation, 25%). Variability between individuals was higher (coefficient of variation, 40-50%).

Turgor regulation in a brackish water charophyte,Lamprothamnium succinctum

Internodal cells of a brackish water charophyte,Lamprothamnium succinctum (A. Br. in Ash.) R.D.W. regulate the turgor pressure in response to changes in both the cellular and the external osmotic pressures. During turgor regulation upon hypotonic treatment, net effluxes of K+ and Cl− from the vacuole, membrane depolarization, a transient increase in the electrical membrane conductance and a transient increase in concentration of cytoplasmic Ca2+ are induced. Activation of the plasmalemma Ca2+ channels and the Ca2+-controlled passive effluxes of K+ and Cl− through the plasmalemma ion channels are postulated.

The dechlorination and degradation of Aroclor 1242

Titanocene dichloride, in conjunction with sodium borohydride and pyridine, was shown to dechlorinate Aroclor 1242 to give biphenyl. This was observed as a shift in the congener profile from more heavily chlorinated congeners to the lower chlorinated congeners over the time course of the reaction. The dechlorination process resulted in a transient increase in concentration of the monochlorinated biphenyls, particularly 3-chlorobiphenyl. Dechlorination in the presence of alternative amines or in PCB-contaminated soils proceeded at reduced rates and yielded mono- and dichlorobiphenyls in the final product. Since three hybrid bacteria had previously been produced for the mineralisation of biphenyl and lower chlorinated biphenyls, chemical dechlorination of the PCB mixture (Aroclor 1242) or of contaminated soils produces a potential feed for an aerobic microbial process for complete chlorobiphenyl mineralisation.

Transient Morphological and Biochemical Alterations of Arterial Proteoglycan during Early Wound Healing

Proteoglycan alterations in the carotid arteries of normolipemic rabbits during the first 14 days after injury were evaluated by morphometric analysis of ruthenium red-stained sections using transmission electron microscopy and by incorporation of 35S-sulfate. Two types of de-endothelializing injury were compared, air-drying and balloon catheter. Three days after either injury, a transient increase in concentration of 35S-labeled glycosaminoglycans, changes in distribution of 35S-sulfate among glycosaminoglycans, and a two- to threefold increase in 35S-sulfate content (measured as 35S/μg glycosaminoglycan) were observed. Morphometric analysis revealed an alteration in medial proteoglycan distribution and morphology at 3 days after injury, which was more evident after air-drying than balloon injury. In response to either injury, metabolically activated smooth muscle cells were associated with very large proteoglycan granules (diameter: >60 nm) which possibly contained glycosaminoglycans with longer chains and/or altered charge densities. By 14 days after either injury, the distribution of medial proteoglycan returned to normal and a neointima formed. The neointima was thicker following balloon injury, but irrespective of the nature of the injury proteoglycan concentration was higher in the re-endothelialized than in non-reendothelialized areas. The alterations in extracellular proteoglycan of the intima-medial layers induced by these two forms of injury may influence the pattern of wound healing but are not associated with lipid deposition within the time frame examined.

Metabolic Changes in Blood and Liver of Dairy Cows During Either Feed Restriction or Administration of 1,3-Butanediol

Previous research has shown that a combination of feed restriction and dietary 1,3-butanediol starting at 14 d post-partum resulted in fatty liver and ketosis. Sixteen multiparous Holstein cows were used to determine effects of feed restriction or 1,3-butanediol as separate treatments. Treatments during d 14 to 42 postpartum were 1) control (ad libitum intake), 2) 20% feed restriction, or 3) control plus dietary 1,3-butanediol (5.5% of DM). From d 43 to 56, cows assigned to treatments 2 and 3 received a combination of feed restriction and butanediol. One cow on treatment 2 developed ketosis, but not fatty liver, after only 4 d of feed restriction. No other cows developed fatty liver or ketosis. Both treatments decreased milk production compared with controls. Feed restriction increased the extent of negative energy balance and caused transient increases in concentrations of NEFA, acetate, and ß-hydroxybutyrate in plasma. Concentrations of ß-hydroxybutyrate and insulin in plasma were increased by butanediol, which is a potent ketone body precursor. Concentration of glycogen in liver was less in feed-restricted cows, whereas glycogen and total lipid were greater in cows given butanediol separately. Gluconeogenic capacity of liver slices was not different among groups. Addition of 1,3-butanediol to in vitro incubation media decreased oxidation of propionate to CO2. Neither feed restriction nor dietary 1,3-butanediol as separate treatments induced the fatty liver and ketosis observed in earlier experiments in which the two treatments were given together.

The rise in concentration of free Ca2+ and of pH provides sequential, synergistic signals for secretion in antigen-stimulated rat basophilic leukemia (RBL-2H3) cells.

Ag stimulation of rat basophilic leukemia (RBL-2H3) cells results in hydrolysis of inositol phospholipids, a transient increase in concentration of cytosol Ca2+ [( Ca2+]i), a gradual increase in cytosolic pH (pHi) and the activation of protein kinase C. To determine whether all these changes serve as signals for secretion, studies were conducted with cells permeabilized with streptolysin O in which pHi and [Ca2+]i could be varied independently of each other and enzyme activities could be manipulated. At resting pHi (approximately 7.0) and [Ca2+]i (0.1 microM), the permeabilized cells showed little secretory response to Ag. At resting pHi, elevated levels of Ca2+ (0.33 microM) were required for maximal secretory response to Ag. At a pHi of 7.4, however, 0.1 microM [Ca2+]i was sufficient to sustain near maximal responses to Ag. Therefore, a small increase of [Ca2+]i to 0.33 microM was required to initiate secretion, but once the pHi was elevated secretion could be sustained at near basal levels of [Ca2+]i. Since elevating the [Ca2+]i and pHi, by themselves promoted little secretion, another potentiating signal must have been generated by antigen stimulation. This signal was possibly transduced via hydrolysis of inositol phospholipids and protein kinase C. Even with an elevated [Ca2+]i (0.33 microM) the hydrolysis of the phospholipids and secretion stimulated by Ag were inhibited by guanosine 5'(2-O-thio)diphosphate and neomycin. Furthermore, both protein-kinase C and the secretory response to Ag were lost after permeabilized cells were washed but both were retained if cells were exposed to PMA before permeabilization.

An in vitro model of ischemia: metabolic and electrical alterations in the hippocampal slice

The transverse guinea pig hippocampal slice preparation was used to model the metabolic changes which occur in vivo during ischemia and recovery. Perfusing brain slices with medium devoid of glucose and oxygen elicits rapid decreases in phosphocreatine, ATP, intracellular pH, and in the evoked field potential recorded in the dentate gyrus. AMP and creatine rise during this period, while ADP and lactate levels remain unchanged. Cyclic AMP exhibits a transient increase in concentration. With the exception of ADP and lactate, these responses are very similar to those observed during in vivo ischemia. The return of glucose and oxygen to the incubation medium reverses these metabolic and electrophysiological effects and also leads to pronounced elevations in cyclic nucleotide concentrations. Metabolite concentrations approach, but do not reach, in vitro steady state levels during the first 30 min of recovery. Total adenylate and creatine steady state levels are approximately 50% of in vivo concentrations. The results suggest that, although hippocampal slices differ metabolically from in vivo tissue, they exhibit a similar pattern of metabolic responses to ischemic and reflow conditions.

A specific assay of vitamin D-3 in human serum

A specific mass fragmentographic method for determination of free vitamin D-3 in biological fluids has been developed. The method involves addition of vitamin D-2 to the sample, followed by freeze-drying and extraction with Chloroform/methanol. The amount of vitamin D-2 added should be more than a hundred-fold the amount of vitamin D-3 expected in the sample. The vitamin D and previtamin D present in the extract are heat-equilibrated with each other and then subjected to thin-layer chromatography. Under the Chromatographie conditions employed, there is an only partial separation between vitamin D-2 and vitamin D-3. The material in the appropriate Chromatographie zone is converted into trimethylsilyl ether and analyzed by gas chromatography-mass spectrometry with use of a multiple ion detector. The amount of vitamin D-3 is determined from the ratio between the recordings at m/e 325 and m/e 337. The two ions used correspond to the M — 131 peak in the mass spectrum of trimethylsilyl ether of vitamin D-3 and vitamin D-2, respectively. The method was applied to the determination of vitamin D-3 in human serum and the accuracy of this application was ascertained by different recovery experiments. Considerably lower concentration of vitamin D-3 in serum was found with the present technique than with previous techniques. Thus analysis of serum from 19 healthy men and women gave values ranging from 0 to 6.3 ng/ml (mean about 2 ng/ml). There was little or no increase in concentration after shortterm irradiation of part of body area with UV light. Psoriatic patients subjected to treatment with UV light for 3–5 weeks, however, had considerably higher serum level of vitamin D-3 than normal. Administration of vitamin D-3 per os to one subject gave a transient increase in concentration of vitamin D-3 in serum with a peak value about 4 h after the administration.

MIGRATION OF MAJOR CONSTITUENTS FROM LAKE SEDIMENTS INTO LAKE WATER AND ITS BEARING ON LAKE WATER COMPOSITION

Differences in concentrations of major ions and silica between interstitial and lake water suggest that some fraction of the total chemical budget of a lake may be supported by diffusional flux of dissolved constituents from sediment into lake water. Estimates of flux from the lake floor give a mean rate of dissolution of sediment or the rate of subaqueous weathering. In the case of two lakes on the Precambrian shield near Kenora, Ontario, flux from the lake floor contributes 15–30%, or less, of the four major cations (Ca, Mg, Na, K) in the lakes. Flux of this magnitude corresponds to dissolution of 0.02–0.04 cm yr‒1 of bulk (solids + water) sediment. The rate of dissolution is less than the typical rates of deposition in postglacial lakes. For such events as lasting changes in the concentrations of dissolved constituents in inflow, new steady‐state concentrations in lake water are attained faster in the presence of flux from the sediment. Mixing of a thin layer of lake floor sediment with lake water may produce transient increases in concentration in lake water comparable in magnitude to the contribution of flux from sediments.