Phosphate Replacement Research Articles

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Introduction: National drug shortages result in numerous challenges for clinicians, including the need to make practice changes to limit or conserve supply. With the ongoing shortage of all intravenous phosphate products, our institution had to change practice by revising the CRRT phosphorus replacement protocol. Once sodium phosphate became unavailable, potassium phosphate was used for replacement and the serum phosphorus level threshold for when phosphate is replaced was changed. Previously, the replacement threshold was levels less than 2.9 mg/dL. The revised protocol has a replacement threshold for levels less than 1.6 mg/dL (severe hypophosphatemia). Methods: Single center, retrospective chart review in which phosphate replacement was analyzed in 26 patients, age 18 years and older, who received CRRT during a six week period. Data collection included patient demographics, serum potassium and phosphorus levels before and after phosphate replacement, adverse effects from hypophosphatemia, and all sources of potassium and phosphorus administered. Results: Of the 26 patients on CRRT, 6 (31%) required phosphorus replacement for severe hypophosphatemia. A total of 156 episodes of hypophosphatemia, defined as serum phosphorus less than 2.9 mg/dL, noted in all CRRT patients. Of these 156 episodes, 21 were severe (less than 1.6 mg/dL) meeting the criteria for replacement with the revised protocol. Average increase in serum phosphorous level was 0.67 mg/dL after replacement, with 100% of levels correcting to a moderate hypophosphatemia (1.6-2.2mg/dL). None of the patients experienced hyperkalemia after receiving a replacement dose. There were no documented adverse events in this patient population. Conclusions: Potassium phosphate was able to effectively replace sodium phosphate for use in our CRRT population without causing any incidents of hyperkalemia. It was also determined that supplies of intravenous phosphate could safely be conserved by lowering the threshold for treatment of hypophosphatemia to 1.6 mg/dL. We also determined that changing the threshold for replacement did not result in any adverse events.

Characterization of Complexes of Nucleoside-5′-Phosphorothioate Analogues with Zinc Ions

On the basis of the high affinity of Zn(2+) to sulfur and imidazole, we targeted nucleotides such as GDP-β-S, ADP-β-S, and AP3(β-S)A, as potential biocompatible Zn(2+)-chelators. The thiophosphate moiety enhanced the stability of the Zn(2+)-nucleotide complex by about 0.7 log units. ATP-α,β-CH2-γ-S formed the most stable Zn(2+)-complex studied here, log K 6.50, being ~0.8 and ~1.1 log units more stable than ATP-γ-S-Zn(2+) and ATP-Zn(2+) complexes, and was the major species, 84%, under physiological pH. Guanine nucleotides Zn(2+) complexes were more stable by 0.3-0.4 log units than the corresponding adenine nucleotide complexes. Likewise, AP3(β-S)A-zinc complex was ~0.5 log units more stable than AP3A complex. (1)H- and (31)P NMR monitored Zn(2+) titration showed that Zn(2+) coordinates with the purine nucleotide N7-nitrogen atom, the terminal phosphate, and the adjacent phosphate. In conclusion, replacement of a terminal phosphate by a thiophosphate group resulted in decrease of the acidity of the phosphate moiety by approximately one log unit, and increase of stability of Zn(2+)-complexes of the latter analogues by up to 0.7 log units. A terminal phosphorothioate contributed more to the stability of nucleotide-Zn(2+) complexes than a bridging phosphorothioate.

Is Parenteral Phosphate Replacement in the Intensive Care Unit Safe?

Hypophosphatemia is well recognized in the intensive care setting, associated with refeeding and continuous forms of renal replacement therapy (CCRT). However, it is unclear as to when and how to administer intravenous phosphate supplementation in the general intensive care setting. There have been recent concerns regarding phosphate administration and development of acute kidney injury. We therefore audited our practice of parenteral phosphate administration. We prospectively audited parenteral phosphate administration (20 mmol) in 58 adult patients in a general intensive care unit in a University tertiary referral center. Fifty-eight patients were audited; mean age 57.2 ± 2.0 years, 70.7% male. The median duration of the infusion was 310 min (228-417), and 50% of the patients were on CRRT. 63.8% of patients were hypophosphatemic (<0.87 mmol/L) prior to the phosphate infusion, and serum phosphate increased from 0.79 ± 0.02 to 1.07 ± 0.03 mmol/L, P < 0.001. Two patients became hyperphosphatemic (>1.45 mmol/L). There was no correlation between the change in serum phosphate and the pre-infusion phosphate. Although there were no significant changes in serum urea, creatinine or other electrolytes, arterial ionized calcium fell from 1.15 ± 0.01 to 1.13 ± 0.01 mmol/L, P < 0.01. Although infusion of 20 mmol phosphate did not appear to adversely affect renal function and corrected hypophosphatemia in 67.7% of cases, we found that around 33% of patients who were given parenteral phosphate were not hypophosphatemic, and that the fall in ionized calcium raises the possibility of the formation of calcium-phosphate complexes and potential for soft tissue calcium deposition.

Arsenic Binding to Proteins

Arsenic is a trace element found in the earth’s crust at an average concentration of ∼5 μg/g (ppm). Although its relative abundance in the earth’s crust is about 54th, arsenic can become concentrated in some parts of the world because of natural mineralization. Arsenic is a component of 245 minerals, associated most frequently with other metals such as copper, gold, lead, and zinc in sulfidic ores.1−3 When disturbed by natural processes, such as weathering, biological activity, and volcanic eruption, arsenic may be released into the environment. Anthropogenic activities, such as combustion of fossil fuels, mining, ore smelting, and well drilling, also mobilize and introduce arsenic into the environment. Chronic exposure to arsenic from groundwater has been recognized to cause the largest environmental health disaster in the world, putting more than 100 million people at risk of cancer and other arsenic-related diseases.4,5 Because of its prevalence in the environment, potential for human exposure, and the magnitude and severity of health problems it causes, the United States Agency for Toxic Substances and Disease Registry (ATSDR) has ranked arsenic as No. 1 on its Priority List of Hazardous Substances for many years. The recent priority list, posted in 2011 (http://www.atsdr.cdc.gov/SPL/index.html), shows arsenic as No. 1, ahead of lead, mercury, and polychlorinated biphenyls (PCBs). Epidemiological studies of populations exposed to high levels of arsenic due to ingestion from water, including those from Taiwan,6−8 Argentina,9,10 Chile,11,12 West Bengal, India,13,14 Bangladesh,15−17 and Inner Mongolia, China,18,19 have repeatedly shown strong associations between the exposure to high concentrations of arsenic and the prevalence of several cancers,20−23 most severely bladder, lung, and skin cancers. Arsenic is classified as a human carcinogen by the International Agency for Research on Cancer (IARC) and the U.S. Environmental Protection Agency (EPA). Chronic exposure to elevated concentrations of arsenic has also been associated with the increased risk of a number of noncancerous effects.24−27 Although the adverse health effects arising from exposure to arsenic have been well-recognized, the mechanism(s) of action responsible for the diverse range of health effects are complicated and poorly understood.26−30 It is believed that inorganic arsenate (HAsO42-), which is a molecular analogue of phosphate (HPO42-), can compete for phosphate anion transporters and replace phosphate in some biochemical reactions.28 For example, generation of adenosine-5′-triphosphate (ATP) during oxidative phosphorylation can be inhibited by the replacement of phosphate with arsenate. Depletion of ATP by arsenate has been observed in cellular systems.28 However, the replacement of phosphate in DNA by arsenic is not firmly established.31−35 The toxicity of trivalent arsenicals likely occurs through the interaction of trivalent arsenic species with sulfhydryl groups in proteins. Arsenic binding to a specific protein could alter the conformation and function of the protein as well as its recruitment of and interaction with other functional proteins. Therefore, there has been much emphasis on studies of arsenic binding to proteins, for the purpose of understanding arsenic toxicity and developing arsenic-based therapeutics. This review summarizes various aspects of arsenic binding to proteins. It discusses the chemical basis and biological implications and consequences of arsenic binding to proteins. It also describes analytical techniques and the characterization of arsenic binding, including the binding affinity, kinetics, and speciation.

Hypophosphatemia on the intensive care unit: Individualized phosphate replacement based on serum levels and distribution volume

BackgroundHypophosphatemia occurs in about 25% of patients admitted to the intensive care unit. To date, a safe and validated phosphate replacement protocol is not available. ObjectiveTo evaluate an individualized phosphate replacement regimen. DesignFifty consecutive intensive care unit patients with a serum phosphate level <0.6 mmol/L were treated with sodium-potassium-phosphate intravenously at a rate of 10 mmol/h. The dose was calculated according to the following equation: Phosphate dose in mmol = 0.5 × Body Weight × (1.25 – [serum Phosphate]). Phosphate levels were measured immediately upon completion of the infusion, as well as the next morning at 8 am. ResultsPost-infusion phosphate levels were >0.6 mmol/L in 98% of the patients. Hyperphosphatemia, hyperkalemia or a decrease in serum calcium were not observed. In about a third of patients serum phosphate decreased to <0.6 mmol/L within the next 24 hours after infusion. The phosphate distribution volume calculated from the results of infusion and corrected for renal phosphate loss during the infusion period was 0.51 L/kg (95% CI 0.42–0.61 L/kg). ConclusionThis study shows that phosphate replacement with dose calculation based on serum phosphate levels and a Vd of 0.5 L/kg is effective and safe.

Indispensable or toxic? The phosphate versus arsenate debate

Indispensable or toxic? The phosphate versus arsenate debate

Central pontine and extrapontine myelinolysis secondary to fast correction of severe hyponatremia and hypokalemia in an alcoholic patient

A 59-year-old white alcoholic female was transferred to ER by ambulance at 04:52 a.m. for lethargy, disorientation, weakness, falls, and headache for few days. She was only drinking alcohol for few days but not eating. She had history of hypertension, and she was taking Lorazepam 2 mg thrice daily, Ramipril 2.5 mg once daily and Hydrochlorothiazide 12.5 mg once daily. Her initial vital signs by paramedics revealed BP of 124/56 mmHg, pulse of 75 bpm, and temperature of 36.7 C. Her weight was 60 kg, and her height was 161 cm. Her Glasgow Coma Scale was 13/15. On examination, the patient was confused, only oriented to place and had slurred speech and multiple bruises of different ages. Her pupils were 5 mm, equal and reactive to light. No other significant findings were found. Initial laboratory results are shown in Table 1. Intravenous fluids were started as first line of 1 L of Normal Saline with 40 mEq of KCl at 100 mL/h and second line of 250 mL of Normal Saline with 40 mEq of KCl at 50 mL/h. Head CT scan was negative for acute hemorrhage, infarct, or edema. Thiamine 100 mg IVP was given, and third IV line was then initiated with 1 L of Saline with 40 mEq of KCl at 100 mL/h. Her blood pressure suddenly dropped to 82/44 mmHg, so a bolus of Normal Saline 500 mL was given, and her blood pressure improved to 152/87 mmHg within 15 min. She was transferred to ICU where she additionally received IV magnesium sulfate, oral potassium chloride, and oral sodium phosphate replacements. Serial blood chemistry tests were done, and IV fluid types and rates were adjusted accordingly. During the first day, she excreted a large amount of diluted urine which could be secondary to a quick decrease in serum vasopressin level when her A. G. Tarakji Aleppo University, Aleppo, Syria

Partial replacement of monocalcium phosphate with neutral phytase in diets for grass carp, Ctenopharyngodon idellus

Summary A 9-week experiment was designed to study the effects of partial replacement of monocalcium phosphate (MCP) with neutral phytase on growth, body compositions, serum biochemical statuses and intestinal digestive enzyme activities of grass carp, Ctenopharyngodon idellus. The control diet (designated as P2.0) was prepared with 2.0% MCP but without phytase. The three other diets (designated as PP1.5, PP1.0 and PP0.5, respectively) were supplemented with 1.5, 1.0 and 0.5% MCP, respectively, along with 500 FTU of neutral phytase kg−1 diet in each. After a 9-week feeding trial, fish (initial body weight: 43.44 ± 2.37 g) fed with PP1.5 and PP1.0 had no significant change in weight gain (WG), specific growth rate (SGR), protein efficiency rate (PER) or feed conversion ratio (FCR) compared with the control (P > 0.05) whereas fish fed with PP0.5 showed significantly lower growth performance in the above parameters. The crude lipid content in whole body or muscle of the fish fed with PP1.5 was significantly lower than the control while significantly higher in fish fed with PP0.5 (P < 0.05), whereas no obvious change was observed in the fish fed with PP1.0. For serum indices, higher serum alkaline phosphatase (Alkp), phosphorus (P) and calcium (Ca) contents were observed in fish fed with phytase-supplemented diets in comparison with the control. In addition, dietary phytase supplementation increased amylase activity and decreased lipase activity in both foregut and hindgut. The present study suggests that dietary MCP can be reduced when neutral phytase is added to the grass carp diet, and that the maximum MCP reduction level can be up to 1% when neutral phytase is supplemented at 500 FTU kg−1 diet.

Approach to Treatment of Hypophosphatemia

Hypophosphatemia can be acute or chronic. Acute hypophosphatemia with phosphate depletion is common in the hospital setting and results in significant morbidity and mortality. Chronic hypophosphatemia, often associated with genetic or acquired renal phosphate-wasting disorders, usually produces abnormal growth and rickets in children and osteomalacia in adults. Acute hypophosphatemia may be mild (phosphorus level, 2-2.5 mg/dL), moderate (1-1.9 mg/dL), or severe (<1 mg/dL) and commonly occurs in clinical settings such as refeeding, alcoholism, diabetic ketoacidosis, malnutrition/starvation, and after surgery (particularly after partial hepatectomy) and in the intensive care unit. Phosphate replacement can be given either orally, intravenously, intradialytically, or in total parenteral nutrition solutions. The rate and amount of replacement are empirically determined, and several algorithms are available. Treatment is tailored to symptoms, severity, anticipated duration of illness, and presence of comorbid conditions, such as kidney failure, volume overload, hypo- or hypercalcemia, hypo- or hyperkalemia, and acid-base status. Mild/moderate acute hypophosphatemia usually can be corrected with increased dietary phosphate or oral supplementation, but intravenous replacement generally is needed when significant comorbid conditions or severe hypophosphatemia with phosphate depletion exist. In chronic hypophosphatemia, standard treatment includes oral phosphate supplementation and active vitamin D. Future treatment for specific disorders associated with chronic hypophosphatemia may include cinacalcet, calcitonin, or dypyrimadole.

Synthesis and evaluation of malonate-based inhibitors of phosphosugar-metabolizing enzymes: Class II fructose-1,6-bis-phosphate aldolases, type I phosphomannose isomerase, and phosphoglucose isomerase

In the design of inhibitors of phosphosugar metabolizing enzymes and receptors with therapeutic interest, malonate has been reported in a number of cases as a good and hydrolytically-stable surrogate of the phosphate group, since both functions are dianionic at physiological pH and of comparable size. We have investigated a series of malonate-based mimics of the best known phosphate inhibitors of class II (zinc) fructose-1,6-bis-phosphate aldolases (FBAs) (e.g., from Mycobacterium tuberculosis), type I (zinc) phosphomannose isomerase (PMI) from Escherichia coli, and phosphoglucose isomerase (PGI) from yeast. In the case of FBAs, replacement of one phosphate by one malonate on a bis-phosphorylated inhibitor (1) led to a new compound (4) still showing a strong inhibition (Ki in the nM range) and class II versus class I selectivity (up to 8×104). Replacement of the other phosphate however strongly affected binding efficiency and selectivity. In the case of PGI and PMI, 5-deoxy-5-malonate-d-arabinonohydroxamic acid (8) yielded a strong decrease in binding affinities when compared to its phosphorylated parent compound 5-phospho-d-arabinonohydroxamic acid (2). Analysis of the deposited 3D structures of the kinetically evaluated enzymes complexed to the phosphate-based inhibitors indicate that malonate could be a good phosphate surrogate only if phosphate is not tightly bound at the enzyme active site, such as in position 7 of compound 1 for FBAs. These observations are of importance for further design of inhibitors of phosphorylated-compounds metabolizing enzymes with therapeutic interest.

Refractory rickets due to Fanconi′s Syndrome secondary to Wilson′s disease

Renal tubular disorders are an important cause of refractory rickets. Wilson's disease, an inherited disorder of copper metabolism has varied presentations. We present a case of refractory rickets due to Fanconi's syndrome attributable to Wilson's disease. An adolescent girl presented with pain in the hip and knee joints and a knock-knee deformity since six years. She had received multiple doses of cholecalciferol with little improvement. There was no history of seizures, polyuria, jaundice, intake of drugs, or similar complaints in the family. Examination revealed a severely short stature with widening of the wrist joint and genu valgum. Examination of the central nervous system (CNS) was normal. Skeletal radiographs showed features suggestive of rickets at the hip and knee joints. Routine biochemistry was normal, 25-hydroxyvitamin D [25(OH)D] was adequate (57.1 ng/dL), with normal corrected calcium (9.24 mg/dL), low phosphate (2.76 mg/dL), elevated bone-specific alkaline phosphatase, and normal renal functions. Twenty-four-hour urine revealed phosphaturia, kaliuresis, and glucosuria with normal blood sugars and aminoaciduria. Blood gas analysis revealed normal anion gap metabolic acidosis with a urine pH of 7. Ammonium chloride (NH4CL) challenge test revealed proximal tubular acidosis. A search for causes revealed Kayser-Fleischer rings. The diagnosis of Wilson's disease was confirmed by low serum ceruloplasmin levels (6.5 mg/dL; normal: 18–35 mg/dL) with high 24-hour urine copper levels (433 mcg; normal: 20–50 mcg). She was started on a replacement of alkali, phosphate, calcium, and vitamin D, with zinc acetate for Wilson's disease. Rickets as a presenting feature of Wilson's disease has been reported rarely. Recognition of this entity is important, as treatment of the primary condition may improve tubular function as well.

Treatment of Addison Disease and Subsequent Hypophosphatemic Respiratory Failure

A 38-year-old man was found unresponsive with hypoglycemia by emergency medical service (EMS) personnel. He was intubated in the emergency department after reports of seizure activity. With supportive care and empiric steroids, the patient was extubated the next day. He reported a diagnosis of Addison disease and noncompliance with his steroid replacement therapy. Within 12 hours, respiratory failure and altered mental status required reintubation. Laboratory studies revealed rhabdomyolysis and hypophosphatemia. The replacement of glucose likely stimulated glycolysis, formation of phosphorylated glucose compounds, and an intracellular shift of phosphorus. This patient required phosphate replacement and was extubated on hospital day 5. We report a unique case of hypoglycemia due to Addison disease, leading to hypophosphatemic respiratory failure.

Effect of partial replacement of dietary monocalcium phosphate with neutral phytase on growth performance and phosphorus digestibility in gibel carp, Carassius auratus gibelio (Bloch)

A feeding trial was conducted to study the effect of partial replacement of dietary monocalcium phosphate (MCP) with neutral phytase on growth performance and phosphorus digestibility in gibel carp, Carassius auratus gibelio (Bloch). Control diet was prepared with 2% MCP but without phytase (P0). Other three experimental diets were prepared by replacement of MCP by 25%, 50% and 75% respectively in comparison with control with supplementation of neutral phytase at 500 U kg−1 diet in each and designated as P25, P50 and P75 respectively. Gibel carp (initial body weight of 30.22 ± 1.98 g) were reared in twelve 300-L cylindrical fibreglass tanks provided with filtered flow-through tap water at 26–28°C. After 8-week experiment, gibel carp fed with P50 had no obvious differences from the control group on weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency rate (PER) and survival rate. Phytase supplementation did not affect body compositions or muscle compositions. Crude protein and phosphorus (P) contents in the faeces of fish fed with the phytase-supplemented diets were significantly lower than those of the control group. The apparent digestibility coefficients (ADCs) of crude protein and P in gibel carp were increased when fish fed with the diets in which MCP was replaced by neutral phytase. This study suggested that partial replacement of dietary MCP at 50% with neutral phytase was considered as a recommended dietary supplemental level and increased dietary P and protein availability.

Phosphate Bonded Monolithic Refractory Materials with Improved Hot Strengths as a Potential Replacement for Phosphate Bonded Bricks

The phosphate bond generally provides a lower modulus of elasticity compared to more brittle conventional cement and ceramic bonded materials. The flexible bonding mechanism results in higher impact resistance. Moreover, phosphate bonded materials show excellent resistance to aluminium metal penetration and corundum growth. In addition, phosphate bonded bricks with low alkali content possess high hot strengths at elevated temperatures which can significantly increase their performance against mechanical abuse. Based on this information a project was started to develop phosphate bonded monolithic materials with similar or better physical and chemical properties than phosphate bonded bricks but with the advantage of installation characteristics of conventional cement bonded materials. Additional goals were to use a water based system and minimize restrictions on installations techniques. Flow and working time should be similar to conventional monolithic materials, making this material as versatile as possible. In order to achieve these goals extensive tests were carried out in collaboration with independent research laboratories and as a secondary step, some of the new formulations were installed in severe environment applications with high mechanical abuse and chemical attack. The development process and the physical and chemical properties of a new phosphate bonded monolithic material will be shown in context with available literature and in comparison with test data of phosphate bonded bricks and conventional cement bonded materials. The results of field tests and potential new applications will also be presented.

Management of diabetic ketoacidosis

Although the mortality of diabetic ketoacidosis (DKA) has decreased substantially in the developed world, high mortality rates still prevail in South Africa, thus making this an important condition to recognise early and manage well. This review discusses the treatment of DKA, with emphasis on the controversial aspect of initial fluid replacement therapy. Current guidelines recommend the use of normal saline. The concern is that normal saline, when used in large volumes, leads to the development of a hyperchloraemic metabolic acidosis which is of uncertain clinical significance. This hyperchloraemic acidosis is better quantified using Stewart’s model, as opposed to the “traditional” Henderson-Hasselbalch equation. Ringer’s lactate is an alternative choice for initial fluid resuscitation, but may exacerbate the high lactate to pyruvate ratio in patients in DKA, and may cause hyperkaleamia. Insulin therapy, prevention of electrolyte abnormalities, and the replacement of bicarbonate and phosphate, are other important considerations in the management of the patient with DKA.

Retail Display Evaluation of Steaks from Select Beef Strip Loins Injected with a Brine Containing 1% Ammonium Hydroxide. Part 2: Cook Yield, Tenderness, and Sensory Attributes

The impact of 2 different brines on the palatability and tenderness of select beef strip loin steaks was evaluated. Brines were differentiated by the type of alkaline agent, 4.5% sodium-based phosphate (control brine; CON) or 1% ammonium hydroxide (ammonium hydroxide treatment; AHT), incorporated into the formula. Injected steaks were placed in high oxygen (80% O(2)/20% CO(2)) MAP, stored 4 d at 4 °C in dark storage to simulate transportation, and then placed in retail display. Steaks were selected randomly on day 0, 7, and 14 retail display to measure pH, cook loss, shear force, and sensory characteristics. The pH for AHT steaks (pH 5.96) was slightly higher than CON steaks (pH 5.86; P < 0.05). Cook loss was lower (21%) for CON than AHT steaks (23%). There was neither a treatment nor day effect on tenderness as measured by Warner-Braztler shear force (P > 0.05). Sensory evaluation indicated that on day 0, retail display the initial juiciness, sustained juiciness, tenderness 1st impression, tenderness overall impression, and connective tissue in AHT steaks was not different from CON steaks (P > 0.05). A day effect (decrease) for those sensory parameters was observed only for sustained juiciness (P < 0.05). AHT steaks were rated higher in cooked beef flavor while CON steaks were higher in peppery and salty flavor. There was no difference in soapy and ammonia intensity between treatments. Results indicated that despite lower performance in cook loss the replacement of 4.5% sodium-based phosphate in a meat injection brine with 1% ammonium hydroxide produced a beef loin steak with comparable tenderness and palatability. Practical Application: The research in this study compares steaks that have been injected with a commercial brine formulated with sodium phosphates to steaks that have been injected with a brine where the sodium phosphate in the formulation was replaced with 1% ammonium hydroxide. Ammonium hydroxide is an USDA-FSIS approved ingredient in brines injected into fresh meats. Successful replacement of sodium phosphate with ammonium hydroxide would allow processors to significantly reduce the sodium content of injected fresh meat.

Retail Display Evaluation of Steaks from Select Beef Strip Loins Injected with a Brine Containing 1% Ammonium Hydroxide. Part 1: Fluid Loss, Oxidation, Color, and Microbial Plate Counts

Select beef loin pairs (n = 10) were injected (10% pump) with brine containing either 4.5% sodium-based phosphates, (CON), or 1% ammonium hydroxide treatment (AHT). Both brines also contained 3.6% NaCl and 1% Rosemary Herbalox. Steaks cut from loins were high oxygen (80% O(2)/20% CO(2)) modified atmosphere packaged, stored 4 d at 4 °C in the dark to simulate transportation, and then placed in retail display for 14 d (4 °C). On day 0, 7, and 14 of retail display steak properties were measured. Purge from AHT steaks was higher than CON (P < 0.05). Panelists were not able to visually discriminate between AHT and CON steaks through the first 6 d of retail display. After day 6, panelists rated AHT steaks higher for muscle color, percent discoloration, and overall color. Steaks from both treatments started at day 0 retail display with similar total plate counts (P > 0.05). Microbial counts increased more rapidly for AHT steaks than CON steaks (P < 0.05). AHT and CON steaks were not different in terms of lipid oxidation through day 7 retail display. By day 14 retail display CON steaks were above the threshold for consumer perception of oxidized flavors in fresh meat. However, results also indicated the AHT and CON steaks were no longer acceptable by day 14 in terms of color, were questionable in terms of microbial load, and likely were beyond their reasonable shelf life. Based on retail display properties, results indicated 1% AHT could successfully replace 4.5% SP in a meat injection brine. Practical Application: The research in this report compares steaks that have been injected with a commercial brine formulated with SP to steaks that have been injected with a brine, where the SP in the formulation are replaced with 1% AHT. Ammonium hydroxide is an USDA-FSIS approved ingredient in brines injected into fresh meats. Successful replacement of sodium phosphate with ammonium hydroxide would allow processors to significantly reduce the sodium content of injected fresh meat.

Replacement of dicalcium phosphate by rock phosphate in cattle diets: nutrients digestibility, plasma parameters, ruminal fermentation and microbial synthesis efficiency

This study was conducted in order to evaluate the effects of replacing dicalcium phosphate by rock phosphate in diets of growing steers. It was determined the following aspects: apparent digestibility of diets; phosphorus (P), calcium and fluorine apparent absorption; ruminal pH; ruminal ammonia concentration; microbial efficiency and plasma P. Five rumen fistulated Holstein steers weighting 275 - 283 kg were used. Experimental design was a 5 × 5 Latin square and diets consisted of 0, 25, 50, 75 and 100% of dicalcium phosphate replacement by rock phosphate in the mineral supplement. Addition of rock phosphate in the diets produced a linear increase on intake, rumen outflow and fecal output and total disappearance of fluorine. Diets did not differ to apparent absorption of calcium as well as dry matter, organic matter, crude protein, neutral detergent fiber and non-fiber carbohydrates intake, excretion, digestion and partial and total apparent digestibility. Plasma phosphorus was not influenced by diets and the average was 5.93 mg/dL. There was no difference for ruminal pH and ruminal ammonia concentration. Dicalcium phosphate replacement did not affect apparent and true protein microbial synthesis. Total replacement of dicalcium phosphate by rock phosphate in growing steer mineral supplement did not affect ruminal environment and protein synthesis in rumen. Considering this, dicalcium phosphate replacement in growing steer diets decreases P absorption and depending on its requirements it should be carefully seen.

Insights from the structure of a smallpox virus topoisomerase-DNA transition state mimic.

Poxviruses encode their own type IB topoisomerases (TopIBs), which release superhelical tension generated by replication and transcription of their genomes. To investigate the reaction catalyzed by viral TopIBs, we have determined the structure of a variola virus topoisomerase-DNA complex trapped as a vanadate transition state mimic. The structure reveals how the viral TopIB enzymes are likely to position the DNA duplex for ligation following relaxation of supercoils and identifies the sources of friction observed in single-molecule experiments that argue against free rotation. The structure also identifies a conformational change in the leaving group sugar that must occur prior to cleavage and reveals a mechanism for promoting ligation following relaxation of supercoils that involves an Asp-minor groove interaction. Overall, the new structural data support a common catalytic mechanism for the TopIB superfamily but indicate distinct methods for controlling duplex rotation in the small versus large enzyme subfamilies.

Hypophosphatemia-Induced Seizure in a Child With Diabetic Ketoacidosis

We report an unusual case of hypophosphatemia-related seizure in a child with diabetic ketoacidosis (DKA). A 1-year-old type 1 diabetic boy with hyperglycemia, ketoacidosis, and dehydration was admitted to the pediatric intensive care unit. After having received fluid replacement using isotonic solution with added potassium and continuous intravenous insulin administration according to the protocol for DKA, the patient was conscious, awake, and fed with breast milk. After 20 hours of pediatric intensive care unit stay, he presented 2 tonic-clonic seizures followed by apnea. One hour later, he had cardiorespiratory arrest, requiring cardiovascular support and mechanical ventilation. Serum phosphorus concentration was 1.0 mg/dL, and severe hypophosphatemia was diagnosed. Subsequent to intravenous phosphate replacement, he showed improved neurological and hemodynamic statuses. No other cause of cerebral complication was found. He had no neurologic lesions and was discharged. Although hypophosphatemia is a common complication of DKA treatment, phosphate supplementation has not been routinely recommended in the treatment of DKA. Early recognition and treatment of severe hypophosphatemia in the treatment of DKA are important to reduce the risk of neurological complications.