Biomedical subjects

T R Waters

Publications and source records attributed to T R Waters.

29 records · Page 2Linked to original sources

PubMed1992

Continuous spectrophotometric assay for restriction endonucleases using synthetic oligodeoxynucleotides and based on the hyperchromic effect.

A continuous spectrophotometric assay for the EcoRV restriction endonuclease has been developed. The synthetic self-complementary oligonucleotide d(GACGATATCGTC) (which is double stranded under the assay conditions) is used as the substrate. The EcoRV endonuclease recognizes d(GATATC) sequences cutting between the central T and dA bases. Thus d(GACGATATCGTC) is converted to d(GACGAT) and d(pATCGTC) during catalysis. Both of the hexameric products are single stranded under the assay conditions. The conversion of the dodecameric substrate to the two hexameric products and the concomitant change from double- to single-stranded DNA is associated with an increase in absorbance at 254 nm due to the hyperchromic effect. This change can be used to monitor column effluents for endonuclease activity and also for Km and kcat determination under steady-state kinetic conditions.

Base Sequence↗

PubMed1992

Understanding and evaluating manual handling injuries: NIOSH research studies.

This paper presents an overview of NIOSH research aimed at characterizing and identifying intervention strategies for reducing musculoskeletal injuries during manual handling activities. Surveillance and evaluative research projects are reviewed. Future research directions of the Institute are also discussed.

Accidents, Occupational↗

PubMed1988

Pretreatment with alpha tocopherol enhances neurologic recovery after experimental spinal cord compression injury.

Lipid hydrolysis with subsequent production of eicosanoids and lipid peroxidation are two of the earliest potentially pathochemical events induced in spinal cord tissue by mechanical trauma. Although these membrane lipid disturbances are thought to contribute to the paralysis that occur subsequent to spinal cord injury, such a correlation has not been demonstrated directly. Consequently, the purpose of this study was to test the capacity of alpha tocopherol, the major lipid antioxidant in cellular membranes and a compound that limits the injury-induced lipid hydrolysis and peroxidation in spinal cord tissue, to promote functional recovery in a static loading model of spinal cord injury. After laminectomy, the L2 spinal cord of cats was compressed with 180 g for 5 min. For 5 days before injury and for 5 days postinjury, treated cats received orally 1000 IUD-alpha tocopherol acetate daily. Control cats were similarly injured but untreated. All cats were blindly evaluated weekly for 4 weeks for their neurologic recovery based on an 11 point behavioral scale that assessed walking, running, and stair climbing. By the second postinjury week, alpha tocopherol-pretreated cats demonstrated significantly better recovery than untreated controls. By 4 weeks, treated cats had recovered 72% of their preinjury function as compared with 20% for untreated controls, i.e., a 3.5-fold difference. These results strongly suggest that lipid peroxidation and/or hydrolysis is primarily involved in the genesis of posttraumatic paralysis and that alpha tocopherol exerts its protection of injured spinal cord tissue, at least in part, by its antioxidant and/or antilipolytic activity.

Animals↗

PubMed1988

Effects of treatment with U-74006F on neurological outcome following experimental spinal cord injury.

The compound U-74006F is one of a series of 21-aminosteroids that lack glucocorticoid or mineralocorticoid activity. These potent inhibitors of lipid peroxidation have been specifically developed for the acute treatment of central nervous system trauma and ischemia. This study evaluated the dose-response characteristics and capability of U-74006F to promote functional recovery in cats subjected to compression trauma of the upper lumbar (L-2) spinal cord. Thirty minutes following injury, randomized and investigator-blinded treatment was initiated with the intravenous administration of either vehicle (citrate-buffered saline) or one of eight doses of U-74006F. Initial doses of U-74006F ranged from 0.01 to 30 mg/kg. Subsequent doses consisted of intravenous bolus injections followed by a continuous 42-hour intravenous infusion. Over the 48-hour treatment period, cats received total U-74006F doses ranging from 0.048 to 160 mg/kg. The animals were evaluated weekly for neurological recovery based upon an 11-point behavioral scale. With the exception of two cats in one group, the animals receiving accumulated doses of U-74006F (ranging from 1.6 to 160.0 mg/kg/48 hrs) exhibited nearly 75% of normal neurological function by 4 weeks after injury. Lower total doses of 0.16 and 0.48 mg/kg/48 hrs were associated with approximately 50% return of normal function, which was not significantly better than the recovery in the vehicle-treated control group. The lowest total dose tested (0.048 mg/kg/48 hrs) gave results indistinguishable from those in vehicle-treated cats, which had recovered only 20% of their preinjury neurological function by 4 weeks. These findings demonstrate that over a 100-fold range of doses, U-74006F has a remarkable capacity to promote functional recovery in spinal cord-injured cats.

Animals↗

PubMed1987

Evaluation of an intensive methylprednisolone sodium succinate dosing regimen in experimental spinal cord injury.

Beginning 30 minutes after compression trauma of the upper lumbar (L-2) spinal cord, cats were treated with either a high-dose regimen of methylprednisolone (MP) administered as the sodium salt of the 21-succinate ester (Solu-Medrol sterile powder) or the MP vehicle. Animals were randomly assigned to either treatment group (10 cats per group), and all personnel were blind as to which animals received vehicle or drug. The intensive 48-hour dosing regimen was designed to maintain therapeutic tissue levels of MP and consisted of an initial 30 mg/kg intravenous bolus of MP; 2 and 6 hours later additional 15 mg/kg MP doses were administered by intravenous bolus. Immediately following the bolus given at 6 hours, a continuous MP infusion of 2.5 mg/kg/hr was started. The infusion was stopped abruptly at 48 hours with no dose tapering. Animals in the vehicle group received an equivalent volume of MP vehicle. The total MP dose administered over 48 hours was 165 mg/kg. Animals were evaluated weekly for neurological recovery based upon a 12-point functional scale which assessed general mobility, running, and stair-climbing. Mean recovery scores at 1 month after injury (+/- standard error of the mean) were: vehicle group (seven cats) 3.7 +/- 0.9, and MP group (10 cats) 8.7 +/- 0.2; (p less than 0.001). Histological evaluation of the spinal cords revealed a strong negative correlation between neurological recovery and size of the spinal cord cavity at 1 month (r = -0.88). Three of 10 animals in the vehicle group became ill and had to be dropped from the study, whereas all of the 10 MP-treated animals survived in excellent health. The results demonstrate the therapeutic effectiveness and low incidence of side effects associated with an intensive MP dose regimen for treatment of experimental spinal cord injury.

Animals↗

PubMed1983

Susceptibility of feline spinal cord energy metabolism to severe incomplete ischemia.

Feline spinal cords were subjected to 10 to 30 minutes of severe incomplete ischemia (average reduction in blood flow of 92%) with and without 90 minutes of recirculation, and the L-2 segment was analyzed for high-energy phosphates and certain glycolytic metabolites. Spinal cord tissue lactic acid levels were stepwise elevated, and adenosine triphosphate (ATP), phosphocreatine (P-creatine), and glucose were progressively consumed by increasing durations of ischemia. However, upon restoration of blood flow, there was extensive recovery of energy metabolites and normalized lactic acid, demonstrating resumption of mitochondrial oxidative metabolism. These data indicate that the spinal cord can tolerate at least 30 minutes of severely reduced blood flow before recovery of energy metabolism is significantly impaired upon restitution of blood flow.

Adenosine Triphosphate↗

PubMed1982

Microvascular perfusion and metabolism in injured spinal cord after methylprednisolone treatment.

The purpose of this study was to determine the effect of treatment with the synthetic glucocorticoid, methylprednisolone, on the microvasulature and metabolism of the traumatized spinal cord. Spinal cords of cats were compressed with a 170-gm weight for 5 minutes and were treated with either high-dose methylprednisolone (HDMP, 15 mg/kg/24 hrs) or megadose methylprednisolone (MDMP,60 mg/kg/24 hrs). Animals were sacrificed at 2, 8, or 24 hours following injury. Treatment with HDMP resulted in substantial preservation of injured spinal cord microvascular perfusion at 8 hours as compared with injured untreated cats. Compression trauma caused a partial derangement of energy metabolism and a shift toward anaerobic glycolysis in both treated and untreated groups for the entire 24-hour postinjury period. Tissue levels of adenosine triphosphate, phosphocreatine, and total adenylates in the HDMP-treated cats sacrificed at 8 hours after trauma were significantly elevated over untreated controls, but those in the 2- and 24-hour groups were not. Concentration of energy intermediates in MDMP-treated cat were either equal to or below those of injured untreated animals al all three postinjury time period. The postinjury metabolite pattern and concentrations seen in this study possibly result from differing levels of blood flow and neuronal activity in the injured untreated, HDMP-, and MDMP-treated spinal cords. Better tissue perfusion in the HDMP-treated cats might be expected to result in an improved tissue energy state in these animals. However, intensive high-dose glucocorticoid treatment has been demonstrated to augment spinal cord monosynaptic and polysynaptic reflex transmission and primary afferent excitability. Furthermore, acute single intravenous dose studies have shown this direct neuronal action to be dose-related. Thus, additional high-energy phosphate molecules that may be reformed as a result of HDMP treatment were perhaps used as the energy source for any increased neuronal activity caused by steroid administration. The beneficial effects of glucocorticoid treatment in experimental spinal cord trauma might derive from preserved cellular structural integrity. This could result in increased levels of neuronal activity, energy utilization, and production in treated as compared with untreated tissue.

Animals↗

PubMed1981

Effect of methylprednisolone in compression trauma to the feline spinal cord.

The purpose of this study was to determine the effect of methylprednisolone sodium succinate on clincal recovery and tissue preservation following compression trauma of feline spinal cord. Cats were anesthetized with pentobarbital and injured by placing a 170-gm weight on the spinal cord for 5 minutes. One hour after injury, the animals were given intravenous steroid (15 mg/kg/day) for 2 days in three devided doses, 15 mg/kg/day for 1 day intramuscularly, 7.5 mg/kg/day intramuscularly for 3 days, and 3.75 mg/kg/day intramuscularly for 3 days, for a total of 9 days. In a control group, the animals were injured but untreated. At 60 days after injury, the animals were sacrifieced by perfusion fixation with 10% formalin. The spinal cord was removed and evaluated for a number of morphometric parameters, including percentage of spinal cord cross-sectional area containing the cavity (%area) and percentage of spinal cord volume occupied by the cavity (%volume). A clinical recovery score (recovery index) was devised to evaluate neurological recovery. Steroid-treated cats showed significantly greater recovery than the untreated controls (p less than 0.001). Moreover, the spinal cord of treated cats displayed greater tissue preservation as measured by %area (p leass than 0.005) and %volume (p less than 0.004). Correlation coefficients comparing the recovery index with morphometric parameters revealed a negative correlation between cavity size and recovery. These data provide evidence for a beneficial effect of methylprednisolone in promoting recovery and preserving spinal cord tissue following blunt injury to the feline spinal cord.

Animals↗

PubMed1980

Spinal cord energy metabolism in normal and postlaminectomy cats.

The purpose of this study was to determine 1) normal concentrations of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), phosphocreatine (P-creatine), glucose, lactate, and pyruvate in upper (L-2) and lower (L-5) feline lumbar spinal cord, and 2) whether previously reported laminectomy-induced reduction in spinal cord blood flow (SCBF) resulted in disturbance of spinal cord energy metabolism. Concentrations of ATP, P-creatine, pyruvate, and glucose were significantly higher at L-5 than at L-2, probably as the result of larger amounts of gray matter at L-5 than L-2. Significant increases in ADP and AMP levels were the only metabolite changes noted 15 minutes following laminectomy. The authors speculate that the increase in ADP and AMP is due to a laminectomy-induced stimulation of ATP utilization. However, lack of change in other metabolites implies an efficient energy homeostasis. These results indicate that although laminectomy can reduce SCBF, the degree of this reduction is insufficient to adversely affect spinal cord energy metabolism. Thus, tissue from beneath or near the laminectomy site is viable and essentially normal.

Adenosine Diphosphate↗

PubMed1980

Spinal cord energy metabolism following compression trauma to the feline spinal cord.

The purpose of this study was to determine the spinal cord metabolic state for 24 hours after compression trauma to the feline spinal cord. Cats were anesthetized with pentobarbital and injured by placing a 190-gm weight on the spinal cord for 5 minutes. Biochemical analysis of the injured segment revealed a significant depletion in the levels of adenosine triphosphate (ATP), phosphocreatine (P-creatine), and total adenylates for the entire 24-hour recovery period. Glucose levels initially declined, but by 1 hour had normalized, and at 8 and 24 hours were significantly supranormal. The lactate/pyruvate ratio and tissue lactate concentrations increased four and five and half times, respectively, for the first 4 hours after injury. Between 8 and 24 hours, lactate levels remained elevated, whereas the lactate/pyruvate ratio declined to contol levels as the result of a significant rise in the tissue pyruvate concentration. This sequence of metabolic changes suggested that metabolism was probably not homogeneous throughout the injured segment, and that tissue metabolic rate was depressed for the initial 4 hours after trauma then increased in metabolically active tissue for the remainder of the 24-hour recovery period. This model of spinal cord trauma results in a severe, prolonged ischemia and metabolic injury to the affected tissue. Whether these metabolic changes results from or cause the tissue damage and irreversible paraplegia associated with this type of spinal cord injury remains to be determined.

Adenosine Monophosphate↗

PubMedDate not supplied

Quantification of back motion during asymmetric lifting.

The objective of this study was to determine how trunk motion characteristics (in all three planes of the trunk) change as a free dynamic lifting task becomes more asymmetric. Trunk motion characteristics included range of motion, velocity (peak and average), and acceleration. Previous studies have shown that trunk motion characteristics affect trunk strength as well as the action of the trunk musculature. These trunk motion characteristics were quantified as a function of seven task asymmetries and three task weights. The experimental task required the subject to lift materials in positions commonly seen in the workplace. The range of motion, peak velocity, average velocity, and peak acceleration in each plane of the body were documented during the tasks. Generally, trunk motion characteristics in all three planes increased with an increase in task asymmetry. However, with an increase in task weight all the sagittal plane parameters and one transverse plane parameter decreased. Models were constructed to predict trunk motion characteristics given a task asymmetry and weight. When these motion components were compared to dynamic strength estimates from previous studies it was found that dynamic asymmetric lifts could reduce available strength up to 21% of maximum static strength. The results provide new insight into factors associated with the risk of developing low back disorders.

Adult↗