Evaluation of the reticuloendothelial system function by the vascular clearance of chondroitin sulfate iron colloid

Vascular clearance of chondroitin sulfate iron colloid (CSFe) was evaluated as a test for the reticuloendothelial system (RES) in rabbits. Injected CS59Fe was taken up by the RES in the liver (49%) and bone marrow (41%) after 60 min, suggesting its application for the RES function test. The clearance rate (K-value) of CSFe from the blood was calculated by measuring serum Fe concentrations after releasing iron from CSFe at certain intervals after injection. Depending upon different injected doses, K-values were varied and the phagocytic velocity, computed by multiplying K-values by corresponding injected doses, reached a plateau at high doses, indicating the phagocytosis of CSFe by the RES takes a saturation process. Double-reciprocal plotting of the dose and the phagocytic velocity showed a linear relationship, which provided the data on the maximum phagocytic velocity (Vmax), 0.122 mg/kg/min, and the CSFe concentration producing 1/2 Vmax (Kp), 0.426 mg/kg. Thus, this CSFe clearance test can be used for the evaluation of the RES function.     

Inhibition of cancer growth by resveratrol is related to its low bioavailability

The relationship between resveratrol (RES) bioavalability and its effect on tumor growth was investigated. Tissue levels of RES were studied after i.v. and oral administration of trans-resveratrol (t-RES) to rabbits, rats, and mice. Half-life of RES in plasma, after i.v. administration of 20 mg t-RES/kg b.wt., was very short (e.g., 14.4 min in rabbits). The highest concentration of RES in plasma, either after i.v. or oral administration (e.g., 2.6 +/- 1.0 microM in mice 2.5 min after receiving 20 mg t-RES/kg orally), was reached within the first 5 min in all animals studied. Extravascular levels (brain, lung, liver, and kidney) of RES, which paralleled those in plasma, were always < 1 nmol/g fresh tissue. RES measured in plasma or tissues was in the trans form (at least 99%). Hepatocytes metabolized t-RES in a dose-dependent fashion (e.g., 43 nmol of t-RES/g x min in the presence of 20 microM tRES), which means that the liver can remove circulating RES very rapidly. In vitro B16 melanoma (B16M) cell proliferation and generation of reactive oxygen species (ROS) was inhibited by t-RES in a concentration-dependent fashion (100% inhibition of tumor growth was found in the presence of 5 microM t-RES). Addition of 10 microM H(2)O(2) to B16M cells, cultured in the presence of 5 microM t-RES, reactivated cell growth. Oral administration of t-RES (20 mg/kg twice per day; or included in the drinking water at 23 mg/l) did not inhibit growth of B16M inoculated into the footpad of mice (solid growth). However, oral administration of t-RES (as above) decreased hepatic metastatic invasion of B16M cells inoculated intrasplenically. The antimetastatic mechanism involves a t-RES (1 microM)-induced inhibition of vascular adhesion molecule 1 (VCAM-1) expression in the hepatic sinusoidal endothelium (HSE), which consequently decreased in vitro B16M cell adhesion to the endothelium via very late activation antigen 4 (VLA-4).     

Determination of synthesis, recycling and body mass of glucose in rats and rabbits in vivo with 3H- and 14C-labelled glucose

1. Glucose labelled with (3)H in position 2 and uniformly with (14)C was administered simultaneously to rabbits and rats either as a single injection or by continuous infusion. Plasma glucose specific radioactivity and the yield of (3)H in the plasma water were monitored. 2. The rates of synthesis, recycling of carbon and total body mass of glucose were calculated, without assuming a multicompartmental model and without fitting data by exponential expressions. 3. The rate of synthesis of glucose in starved-overnight rabbits was 4mg/min per kg (range 3-4.5mg/min per kg) and 25-35% of the glucose carbon was recycled. The mass of total body glucose in starved rabbits was 290mg/kg (range 220-390mg/kg). About one-third of the total body glucose equilibrates nearly instantaneously with plasma glucose. 4. In rats starved overnight, glucose synthesis was about 10mg/min per kg and recycling of carbon ranged from 30-40%. Total body mass (per kg body weight) is similar to that in rabbits. 5. The activity in plasma water after injection of [2-(3)H]glucose was determined. The initial rate of (3)H(2)O formation is rapid, indicating that the major site of glucose catabolism is in the rapidly mixing pool. The curve of total body glucose radioactivity was obtained from the (3)H(2)O yield, and total mass of glucose was calculated. This agrees with that obtained from the (3)H specific-radioactivity curve.     

Nephrotoxicity of tiletamine in New Zealand white rabbits.

Tiletamine and zolazepam, the two constituents of Telazol, were evaluated independently to determine which agent was responsible for the nephrotoxicity caused by Telazol in New Zealand White rabbits. Five rabbits were injected i.m. with 32 mg/kg of tiletamine, four animals received 7.5 mg/kg of tiletamine, and five rabbits received 32 mg/kg of zolazepam. Urinalysis was performed and blood urea nitrogen and serum creatinine were monitored for 7 days postinjection. In all five rabbits injected with the high dose of tiletamine, blood urea nitrogen and creatinine rose by 3 days postinjection and increased steadily throughout the week. By 4 days postinjection, urine protein and glucose were elevated and cellular and protein casts were present. No serum chemistry or urine abnormalities were detected in rabbits receiving low doses of tiletamine, zolazepam, or in the four control rabbits. All animals were euthanized and necropsied at 7 days postinjection. Histopathology showed severe renal tubular necrosis in all five rabbits injected with 32 mg/kg tiletamine. Mild nephrosis was present in three of four rabbits injected with 7.5 mg/kg of tiletamine. No lesions were present in the zolazepam-injected or control rabbits. The results of this study show that tiletamine is the constituent responsible for the nephrotoxicity of Telazol in rabbits. They further demonstrate that doses commonly used for anesthetic induction or restraint can produce renal lesions in rabbits.     

Myocardial damage induced by doxorubicins: hydroperoxide-initiated chemiluminescence and morphology

Doxorubicin (1.2 mg/kg body weight) or 4'-epidoxorubicin (1.7 mg/kg body weight) was injected intravenously to rabbits twice a week during 7 to 8 weeks. Total doses were 17.9 +/- 0.2 mg and 24.4 +/- 0.3 mg, respectively. Heart, liver, muscle, and brain homogenates from treated and control animals were supplemented with 3 mM tert-butyl hydroperoxide and hydroperoxide-initiated chemiluminescence was measured. Heart homogenates from doxorubicin-treated rabbits showed an increased hydroperoxide-initiated chemiluminescence (77.2 +/- 3.9; expressed as cpm/mg protein X 10(-3]; whereas 4'-epidoxorubicin-treated rabbits did not exhibit changes (40.7 +/- 4.6) when both were compared with the untreated animals (41.3 +/- 3.0). Liver, muscle, and brain homogenates from doxorubicin and 4'-epidoxorubicin-treated animals showed a hydroperoxide-initiated chemiluminescence that was similar to the one from control animals. Microscopically, the total extent of the myocardial damage (as percentage of damaged myocytes) was markedly higher in the doxorubicin-treated rabbits (63.0 +/- 8.6) than in the 4'-epidoxorubicin-treated group (34.6 +/- 5.0); being both values higher than the one corresponding to control animals (8.0 +/- 1.1). The subendocardial areas of the septum and of the left ventricle were highly sensitive to doxorubicin damage. Hydroperoxide-initiated chemiluminescence of whole heart homogenate correlated statistically with the microscopic tissue damage in the subendocardial and intramural areas of the right ventricle. It is concluded that chronic administration of doxorubicins lead to oxidative stress of the myocardium and that 4'-epidoxorubicin produces less severe oxidative stress and less extensive myocardial damage than those provoked by lower doses of doxorubicin.     

Reticuloendothelial system function and humoral factor deficiency following acute hemorrhage.

The present study has shown that following acute hemorrhage (equivalent to 3% body weight withdrawn over 20 min) in the rat, there is a large reduction (56% of control) in circulating alpha-2-glycoprotein opsonic activity. The reduction in this plasma opsonic activity was near maximal by the completion of blood withdrawal and was maintained throughout a 2-h hypotension period. There was no trend toward recovery of the opsonic activity when evaluated 15 min following reinfusion of shed blood in animals that were hypotensive for 0, 30, and 120 min. Reticuloendothelial system (RES) phagocytic function, as assessed from the carbon clearance rate (phagocytic index) following reinfusion of the shed blood, was depressed in animals that were hypotensive for 0, 30, and 120 min. Thus, phagocytic index followed a time course similar to the depression of opsonic activity. The observed close temporal relationship between alpha-2-glycoprotein opsonic deficiency and depression of RES clearance further supports the possible role of a humoral opsonic deficiency in mediating the RES phagocytic depression during circulatory shock.     

Relationship between the phagocytic inhibition of the rat reticuloendothelial system and the anticholinesterasic effect of an insecticide, Carbaryl (author's transl)]

Phagocytic activity of the reticuloendothelial system (RES) and blood cholinesterase activity were determined in male rats after veinous administrations of carbaryl and 1-naphthol, a carbaryl metabolite. The various parameters were measured 1, 24, 48 and 72 hours after administration of the following four doses per 100 g body weight : 1.875, 3.75, 7.5 and 15 mumol. 1. Results showed an inhibition of the RES phagocytic activity (clearance of colloidal carbon) after carbaryl administration; although 1.875 mumol/100 g had no effect, the other doses inhibited RES activity, blockade time being a function of the dose given. The phagocytic function had returned to normal 72 hr after carbaryl administration. 2. Reductions in spleen weight and protein content were observed together with the RES blockade. 3. At all four doses, the anticholinesterase effect was already apparent one hour after carbaryl administration. 4. 1-naphthol, one of carbaryl's chief metabolites, had no effect either on the RES or on the different parameters studied. These results show a relationship between the phagocytic inhibition of the reticuloendothelial system and the anticholinesterasic effect by carbaryl. They suggest an inhibition of some esterases of macrophages interfering with the phagocytosis.     

Enzymatic properties of the heavy meromyosin subfragment of cardiac myosin from normal and thyrotoxic rabbits.

Myosin from the hearts of thyrotoxic animals (myosin-T) exhibits elevated Ca2+-ATPase activity. To clarify the physiological significance of this increased activity, we have investigated the steady state kinetics of the interaction of actin and MgATP with the double-headed heavy meromyosin subfragment of cardiac myosin from thyrotoxic rabbits (HMM-T). The enhanced Ca2+-ATPase activity of myosin-T was completely retained in HMM-T. The Vmax for actin-activated MgATP hydrolysis by HMM-T (1.08 +/- 0.10 mumol of Pi/mg/min). Under physiological ionic conditions, the Vmax was 0.14 +/- 0.02 mumol of Pi/mg/min as compared with the normal value of 0.08 +/- 0.01 mumol of Pi/mg/min. Furthermore, the salt dependence of Vmax and Kapp for the actin-activated ATPase of HMM-T differed markedly from normal and resembled that usually associated with the single-headed (S1) cleavage product of myosin. These results suggest that the changes in enzymatic properties of myosin-T are responsible for the increased speed of contraction observed in the hearts of thyrotoxic animals. Also, the alteration in the interaction of HMM-T with actin suggests that a loss of cooperativity between the myosin heads may occur.     

Capture and medetomidine-ketamine anesthesia of free-ranging wolverines (Gulo gulo)

Capture and anesthesia with medetomidine-ketamine were evaluated in free-ranging wolverines (Gulo gulo) immobilized for marking with radiocollars or intraperitoneal radiotransmitters in Norrbotten, Sweden, during early June 2004 and 2005. Twelve juvenile wolverines were captured by hand and injected with 0.14 +/- 0.03 mg/kg (mean +/- SD) medetomidine and 7.5 +/- 2.0 mg/kg ketamine. Twelve adult wolverines were darted from a helicopter or the ground, or captured by hand. Adults received 0.37 +/- 0.06 mg/kg medetomidine and 9.4 +/- 1.4 mg/kg ketamine. Arterial blood samples were collected between 15 min and 30 min and between 45 min and 60 min after drug administration and immediately analyzed for selected hematologic and plasma variables. Hyperthermia was recorded initially in one juvenile wolverine and 11 adults. Rectal temperature, heart rate, and lactate decreased significantly during anesthesia, whereas hemoglobin oxygen saturation, pH, partial pressure of arterial carbon dioxide, and base excess increased. Adult wolverines darted from a helicopter had a significantly higher rectal temperature, higher glucose and hematocrit values, and a lower heart rate than juveniles captured by hand. Impaired arterial oxygenation was evident in all wolverines. This study provides baseline data on physiologic variables in adult and juvenile wolverines captured with different methods and anesthetized with medetomidine-ketamine.     

Opioid action on luteinizing hormone secretion in newborn pigs: paradoxical effect of naloxone

German Landrace piglets, 6-7 days of age, received either saline (9 males, 8 females), 0.5 mg naloxone/kg body weight (7 males, 7 females), 2.0 mg naloxone/kg (7 males, 8 females) or 0.5 mg DADLE (potent leu-enkephalin analog)/kg (7 males, 7 females) through a catheter inserted into the jugular vein 2-4 days previously. Male or female piglets were allocated randomly, within litter, to the different experimental groups. Blood samples were withdrawn for a period of 240 min at 10-min intervals for the first 60 min following injection and at 20-min intervals for the rest of the test period. Piglets were separated from their mother via a detachable wall and were allowed to suckle every 50 min. DADLE failed to alter plasma levels of LH in both males and females. Naloxone induced a significant (P less than 0.01) decrease in LH concentrations in females 10 to 60 min after injection (saline: 2.3 +/- 0.2 ng/ml plasma (SEM); 0.5 mg naloxone/kg: 1.0 +/- 0.2 ng/ml plasma and 2 mg naloxone/kg 1.2 +/- 0.4 ng/ml plasma). In males low doses of naloxone reduced plasma LH levels 10 to 40 min after injection (saline: 2.0 +/- 0.3 ng/ml plasma and 0.5 ng naloxone/kg: 1.1 +/- 0.3 ng/ml), whereas a decrease in plasma LH levels occurred 80 to 140 min after injection of high doses of naloxone (saline: 2.1 +/- 0.2 ng/ml and 2 mg naloxone/kg: 1.0 +/- 0.2 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)     

Immobilization of gray wolves (Canis lupus) with sufentanil citrate

Gray wolves (Canis lupus) were immobilized with 0.5 mg/kg xylazine plus 7.5 micrograms/kg of either sufentanil (n = 8), etorphine (n = 8), or carfentanil (n = 2). Drug doses used in this study were selected to provide consistency for comparison and are not recommended doses for effective immobilization of wolves. Induction times were similar among groups (11.9 +/- 1.0 min). Thirty min after induction, wolves were given either 0.5 mg/kg naloxone hydrochloride plus 0.15 mg/kg yohimbine hydrochloride or saline only intravenously. Arousal times for wolves given naloxone and yohimbine (1.2 +/- 0.1 min) were shorter than wolves given saline (35.5 +/- 6.4 min). Respiratory rates were similar among the three drug groups (6.9 +/- 1.0 breaths/min). One animal given sufentanil then saline was found dead 108 min after induction. Presumptive diagnosis was renarcotization and hypothermia. Results indicated that sufentanil is an effective opioid immobilizing agent for gray wolves.     

Dose-dependent hyperlipidemia in rabbits following administration of poloxamer 407 gel

Poloxamer 407 (P-407) is a tri-block polymer that exhibits concentration-dependent reverse thermal gelation, a characteristic potentially useful for developing sustained release injectable drugs. While some reports suggest that P-407 is 'non-toxic', rodent studies demonstrate that P-407 induces hyperlipidemia, an action that makes this polymer a questionable drug delivery vehicle. Unfortunately, the majority of earlier studies employed supra-physiologic doses of P-407. The present study examined if lower, clinically useful, doses of gel-forming concentrations of P-407 induced hyperlipidemia in rabbits. Male and female rabbits were injected with 5.5 mg/kg (0.025 mL/kg), 27.5 mg/kg (0.125 mL/kg), or 137.5 mg/kg (0.625 mL/kg) of 22% P-407 and the actions of this polymer on blood chemistry were assessed at 6 h, 1 d, 2 d, 7 d, and 14 d following injection. Control rabbits received no injection. The highest dose of P-407 (137.5 mg/kg) significantly increased serum triglycerides and cholesterol in both male and female rabbits with the maximum increase observed at 2 d after injection. Male rabbits were more sensitive to P-407 than females following injection of 137.5 mg/kg P-407. The lower doses of P-407 did not alter serum triglycerides or cholesterol. In all groups, serum triglycerides and cholesterol were at baseline levels by 14 d. P-407 did not affect other blood chemistry parameters. Although P-407 induces a dose-dependent hyperlipidemia in rabbits, low doses of this polymer may be used in controlled release drug delivery applications without the untoward hyperlipidemic effect.     

Cardioprotective effect of prostacyclin and 7-oxo-PGI2 in rats against chronic isoproterenol damage

Isoproterenol (ISO) was injected in 5 mg/kg i.p. doses to rats, daily for two weeks. We evaluated the developed myocardial hypoxia and necrosis quantitatively by histological methods. To follow the time course of cardioprotection prostacyclin or 7-oxo-PGI2 were injected daily, i.p. 5, 30 min and 1, 2, 3, 4 hours before or after the ISO to groups of ten rats, respectively. Cardioprotection was defined as the reduction of necrotized areas and was expressed as percentage change compared to the control (saline treated) group. 1 microgram/kg PGI2 and 50 micrograms/kg 7-oxo-PGI2+ showed nearly equipotent cardioprotection (37.3-7.9% and 38.3-6.8%, respectively). The peak effect of both compounds appeared when injected prior to ISO in the 120. min but the action of 7-oxo-PGI2 was more prolonged. The different doses of prostacyclin analogs given after the ISO injection were ineffective with the exception of 50 micrograms/kg 7-oxo-PGI2 (29.75 +/- 5.2%).     

Evaluation of medetomidine/ketamine for short-term immobilization of variable flying foxes (Pteropus hypomelanus)

Four medetomidine/ketamine (M/K) doses (30 microg/kg/3 mg/kg; 40/4; 50/5; 60/6), administered by intramuscular injection, were evaluated for short-term immobilization of adult male variable flying foxes (Pteropus hypomelanus). The highest dose (60 microg/kg/6 mg/kg) produced a significantly faster induction (31 +/- 46 sec) than the lowest dose (30/3) (125 +/- 62 sec). The highest dose levels (50/5, 60/6) produced significantly longer immobilization times (52.5 +/- 25.7 min and 60.6 +/- 20.8 min, respectively) than did the lower doses (30/3, 40/4) (18.8 +/- 8.7 min and 31.0 +/- 14.3 min, respectively). The dose at which 50% of the bats were immobilized for > or = 30 min (ED(50)) was approximately 40 microg/kg/4 mg/kg. This dose produced a mean immobilization time of 31 +/- 14 min, bradypnea and bradycardia. In conclusion, a M/K dose of 50 microg/kg/5 mg/kg is recommended for greater than 30 min of relaxed immobilization in free-living variable flying foxes and is sufficient for safe collection of samples.     

Anesthesia of boma-captured Lichtenstein's hartebeest (Sigmoceros lichtensteinii) with a combination of thiafentanil,medetomidine, and ketamine

A dose range was determined for anesthesia of recently boma-captured Lichtenstein's hartebeest (Sigmoceros lichtensteinii) (n = 13) with the synthetic opiate thiafentanil (THIA) (formerly called A3080) combined with medetomidine (MED) and ketamine (KET) in the Kasungu National Park, Malawi on 4 to 5 September 1999. The dose range of 11-29 micrograms/kg THIA (mean +/- SD = 21 +/- 4 micrograms/kg) combined with 5-10 mg/kg MED (8 +/- 1 micrograms/kg) plus 0.7-1.4 mg/kg KET (1.1 +/- 0.2 mg/kg) was found to be safe and effective for the field conditions associated with this study. The anesthesia produced by this drug combination was very predictable and characterized by a short induction time (3:34 +/- 1:20 min:sec), good muscle relaxation, and acceptable physiologic parameters for anesthesia periods ranging from 22:30-35:00 min:sec (31:14 +/- 2:50). Within the range of doses used in this study, times to onset of initial effects and recumbency were not dependent on THAI, MED, or KET doses. Anesthesia was rapidly and completely reversed by intravenous injections of naltrexone at 30 times the THAI dosage (0.69 +/- 0.19 mg/kg) and atipamezole at about four times the MED dosage (38 +/- 14 micrograms/kg). There was no residual effect from ketamine noted following reversal of THIA and MED and no mortality or morbidity was associated with this anesthetic regimen.     

Hepatic organic anion transport kinetics and bile flow during short-term total parenteral nutrition in the rabbit

Plasma disappearance of sulfobromophthalein (BSP) after an intravenous bolus (5 mg/kg) was determined in six lab chow-fed (LCF) rabbits and in six rabbits maintained on total parenteral nutrition (TPN) for 5 days. A common bile duct cannula enabled measurements of bile flow and biliary BSP excretion. Compartmental analysis of the biexponential plasma disappearance curve yielded three fractional transfer rates, plasma to liver (hepatic uptake), liver to plasma (reflux), and liver to bile (canalicular excretion). The transfer rates for hepatic uptake were 0.253 +/- 0.061/min for LCF and 0.147 +/- 0.040/min for TPN (P less than 0.01) and for the canalicular excretion of BSP were 0.038 +/- 0.019/min for LCF and 0.019 +/- 0.002/min for TPN (P less than 0.05). Model-computed rates for BSP excretion in bile over 60 min were lower with TPN (61%) than with LCF (80%); the measured excretory rates were 53% for TPN rabbits and 75% of injected dose for LCF animals. Basal biliary flow was reduced by 50% in the TPN group. With a two-compartmental model, assuming two pools and three transfer rates, we have demonstrated for the first time significant decreases in hepatic uptake and canalicular excretion of the organic anion BSP during TPN. A decrease in hepatic blood flow due to the enteral fast of TPN could have contributed in part to the decreased hepatic uptake. But, because the second exponent of the biexponential curve is independent of hepatic blood flow, the decrease in liver to bile transfer rate is a true approximation of a diminished canalicular excretory capacity during TPN. It is concluded that the movement of organic anions along the hepatic BSP/bilirubin transport system is impaired early during TPN.     

Field immobilization of raccoons (Procyon lotor) with Telazol and xylazine

The effectiveness of tiletamine plus zolazepam (Telazol) and xylazine was evaluated as an immobilizing combination for raccoons (Procyon lotor). Fifteen raccoons were injected intramuscularly with a 3:2 mixture of Telazol (3.2+/-0.6 mg/kg [mean+/-SD]) and xylazine (2.1+/-0.4 mg/kg) at Pictured Rocks National Lakeshore, Michigan, USA, during May-October, 2001-03. Mean induction time was 4.8+/-3.8 min; mean recovery time was 128.5+/-48.4 min. No linear relationships were found between the amount (mg/kg) of Telazol-xylazine injected and induction (r2 = 0.06, P = 0.40) or recovery times (r2 = 0.01, P = 0.78). Mean heart rate, respiratory rate, and body temperature declined through 20 min after induction (P< 0.05). No mortality occurred and no short-term adverse effects were observed in recaptured individuals. I conclude that a 3:2 mixture of Telazol-xylazine is a safe and effective immobilizing agent for raccoons when conducting nonsurgical field procedures. Immobilizing raccoons with Telazol at 3 mg/kg and xylazine at 2 mg/kg should provide up to 60 min of handling time and usually allow full recovery in about 120 min.     

A role for membrane transport in modulation of intramuscular free glutamine turnover in streptozotocin diabetic rats.

We wished to examine the effects of diabetes on muscle glutamine kinetics. Accordingly, female Wistar rats (200 g) were made diabetic by a single injection of streptozotocin (85 mg/kg) and studied 4 days later; control rats received saline. In diabetic rats, glutamine concentration of gastrocnemius muscle was 33% less than in control rats: 2.60 +/- 0.06 mumol/g vs. 3.84 +/- 0.13 mumol/g (P < 0.001). In gastrocnemius muscle, glutamine synthetase activity (Vmax) was unaltered by diabetes (approx. 235 nmol/min per g) but glutaminase Vmax increased from 146 +/- 29 to 401 +/- 94 nmol/min per g; substrate Km values of neither enzyme were affected by diabetes. Net glutamine efflux (A-V concentration difference x blood flow) from hindlimbs of diabetic rats in vivo was greater than control values (-30.0 +/- 3.2 vs. -1.9 +/- 2.6 nmol/min per g (P < 0.001)) and hindlimb NH3 uptake was concomitantly greater (about 27 nmol/min per g). The glutamine transport capacity (Vmax) of the Na-dependent System Nm in perfused hindlimb muscle was 29% lower in diabetic rats than in controls (820 +/- 50 vs. 1160 +/- 80 nmol/min per g (P < 0.01)), but transporter Km was the same in both groups (9.2 +/- 0.5 mM). The difference between inward and net glutamine fluxes indicated that glutamine efflux in perfused hindlimbs was stimulated in diabetes at physiological perfusate glutamine (0.5 mM); ammonia (1 mM in perfusate) had little effect on net glutamine flux in control and diabetic muscles. Intramuscular Na+ was 26% greater in diabetic (13.2 mumol/g) than control muscle, but muscle K+ (100 mumol/g) was similar. The accelerated rate of glutamine release from skeletal muscle and the lower muscle free glutamine concentration observed in diabetes may result from a combination of: (i), a diminished Na+ electrochemical gradient (i.e., the net driving force for glutamine accrual in muscle falls); (ii), a faster turnover of glutamine in muscle and (iii), an increased Vmax/Km for sarcolemmal glutamine efflux.     

Assessment of hydroxypropyl methylcellulose, propylene glycol, polysorbate 80, and hydroxypropyl-β-cyclodextrin for use in developmental and reproductive toxicology studies

BACKGROUND: A series of studies were conducted to assess Polysorbate 80 (PS80), Propylene Glycol (PG), and Hydroxypropyl‐β‐Cyclodextrin (HPβCD), when compared with Hydroxypropyl Methylcellulose (MC) in developmental and reproductive toxicology (DART) studies. METHODS: In the rat fertility study, 20 mg/kg MC, 10 mg/kg PS80, 1,000 mg/kg PG, 500 mg/kg HPβCD or 1,000 mg/kg HPβCD were administered orally before/during mating, and on gestation Day (GD) 0–7, followed by an assessment of embryonic development on GD 14. In the rat and rabbit teratology studies, the doses of MC, PS80, PG, and HPβCD were the same as those in the fertility study. In these teratology studies, pregnant females were dosed during the period of organogenesis, followed by an assessment of fetal external, visceral, and skeletal development. RESULTS: In the rat fertility and rat teratology studies, PS80, PG, and HPβCD did not exhibit toxicity, when compared with MC. Similarly, in the rabbit teratology study, there was no PS80 or PG‐related toxicity, when compared with MC. However, individual rabbits in the 500 and 1,000 mg/kg HPβCD groups exhibited maternal toxicity, which included stool findings, decreased food consumption, and body weight gain. Furthermore, one rabbit each in the 500 and 1,000 mg/kg HPβCD groups exhibited evidence of abortion, which was considered secondary to maternal toxicity. CONCLUSIONS: Although HPβCD was not well tolerated in rabbits at doses of 500 and 1,000 mg/kg, PS80 and PG were comparable to MC and should be considered for use in developmental and reproductive toxicology studies. Birth Defects Res (Part B) 89:504–516,2010. © 2010 Wiley‐Liss, Inc.     

Effect of intravenous papain on tracheal pressure-volume curves in rabbits

To investigate the effects of airway cartilage softening on tracheal mechanics, pressure-volume (PV) curves of excised tracheas were studied in 12 rabbits treated with 100 mg/kg iv papain, whereas 14 control animals received no pretreatment. The animals were killed 24 h after the injection and the excised specimens studied 24 h later. Treated tracheas exhibited decreased ability to withstand negative transmural pressures, reflected in increased collapse compliance: 6.2 +/- 2.1 vs. 2.0 +/- 0.5% peak volume (Vmax)/cmH2O means +/- SD, P less than 0.001, (Vmax = extrapolated maximal tracheal volume), increased kc (exponential constant that reflects the shape of collapse limb of the PV curve): 0.244 +/- 0.077 vs. 0.065 +/- 0.015 (P less than 0.001). The distension limb of the PV curve greater than 2.5 cmH2O transmural pressure (Ptm) was no different. Compliance between 0 and 2.5 cmH2O Ptm was increased in papain-treated rabbits: 4.97 +/- 1.73 vs. 2.30 +/- 0.31% Vmax/cmH2O (P less than 0.001). Tracheal volume, and therefore mean diameter, was decreased at 0 Ptm: 2.7 +/- 0.26 vs. 3.2 +/- 0.27 mm (P less than 0.001). We conclude that airway cartilage softening increases the compliance of the trachea at pressures less than 2.5 cmH2O Ptm.