Effects of skeleton photoperiods on melatonin secretion in the rainbow trout, Oncorhynchus mykiss (Walbaum)

Abstract Plasma melatonin levels were measured at hourly intervals in rainbow trout, Oncorhynchus mykiss (Walbaum), maitained under three different skeleton photoperiods: 8L:2D:2L:12D;8L:7D:2L:7D; and 8L:12D:2L:2D. Blood samples were taken before, during and after the 2-h light pulses. Melatonin levels increased rapidly to mean scotophase (dark period) values of 261 ± 7 pg/ml after the first light-dark transition and had returned to mean photophase (light period) values of 51 ± 2 pg/ml 30min after the end of the scotophase. Light pulses during the early, mid- and late scotophase elicited similar reductions in melatonin levels, followed by rapid increases after the light pulse, reaching previous scotophase values within 90 min. The inability of any of the light pulses to modulate or truncate melatonin secretion under a LD 8:16 photoperiod provides further support for the hypothesis that melatonin secretion in the rainbow trout is a direct response to darkness, and is not under endogenous circadian control as in other vertebrates examined.     

Changes in chemical properties of organic matter with intensified rice cropping in tropical lowland soil

Rice systems in Asia have intensified rapidly in the past 30 years, and significant areas of irrigated lowland rice are now supporting two or three rice crops per year. Our objective was to compare the chemical composition of soil organic matter (SOM) from four fields with different histories of rice cropping intensity and soil submergence: (i) a single-crop rainfed, dryland rice system without soil submergence, (ii) an irrigated rice and soybean rotation, and irrigated (iii) double- or (iv) triple-crop rice systems in which soil remains submerged during much of the year. In all four soils, extracted mobile humic acid (MHA) and calcium humate (CaHA) fractions were of modern age by ¹⁴C-dating, and represented about 20% of total N and organic C. The MHA was enriched in N and hydrolysable amino acids (AA) compared with CaHA in all soils. With increased frequency of irrigated rice cropping, however, there was a large increase in phenolic content of SOM. We speculate that slower lignin decomposition caused by deficiency of O₂ in submerged soil leads to incorporation of phenolic moieties into young SOM fractions. The increased phenolic character of these fractions may influence N cycling and the N supplying capacity of lowland soils supporting two or three annual crops of irrigated rice.     

13C NMR studies of organic matter in whole soils: I. Quantitation possibilities

A detailed discussion of the quantitative nature of ¹³C CPMAS NMR spectra as applied to solid samples, such as soil, is given. In particular, the influence of the cross-polarization (CP) time constant (T_CH), the relaxation time constant of protons in the rotating frame (T_1pH) and the contact time (t_c) in the CPMAS experiment are considered. Three distinct quantitation regimes are numerically identified according to sample parameters t_CH and T_1PH > and the experimental choice of t_c: (i) quantitation obtainable from a single CPMAS spectrum; (ii) quantitation obtainable from a series of CPMAS spectra; and (iii) quantitation not possible using CPMAS. Strategies for the measurement of sample parameters T_CH and Ti_pH are reviewed. When quantitation is not possible using CPMAS it is necessary to regress to the direct polarization (DP) of ¹³C nuclei. The sensitivity problems of DPMAS are discussed, as too are general factors that affect the quantitation of ¹³C data such as spinning sidebands. More specifically in relation to soil samples, the effects on quantitation arising from the presence of paramagnetics and the actual methods for the measurement of signal intensities are covered.     

Cardiovascular Function and Serum Catecholamine Concentrations after Anesthesia and Surgery in the Dog

Peripheral vasoconstriction and plasma catecholamine concentrations were studied in 37 dogs after cervical disc fenestration and salivary gland excision, laparotomy for intestinal anastomoses and cystotomy, or laparotomy for repair of diaphragmatic rupture, gastrotomy, and pyloromyotomy. Meperidine (4.4 mg/kg) was administered before extubation of 12 dogs undergoing laparotomy. Heart rate, respiratory frequency, indirect blood pressure, rectal temperature, toe web temperature, and plasma concentrations of epinephrine and norepinephrine were determined before induction of anesthesia, after intubation, after extubation, at sternal recumbency, and at standing. All dogs were hypothermic during surgery. After surgery, peripheral hypothermia (large rectal-toe web temperature gradients) increased from a mean of 4.6 degrees C after intubation to a mean of 10.4 degrees C when the dogs initially stood. Heart and respiratory rates and blood pressures during recovery were similar to those before anesthesia. Mean plasma catecholamine concentrations were neither significantly higher during recovery than before surgery nor were they increased in any surgical group, including the dogs not treated with meperidine. After anesthesia, 15% of the epinephrine and 12% of the norepinephrine samples were more than two standard deviations above the mean of the preanesthetic concentrations of all dogs. The ratio of all dogs with an epinephrine concentration more than two standard deviations above the mean of baseline epinephrine concentrations was greater at sternal recumbency than before anesthesia and the ratio of dogs with an increased epinephrine concentration at sternal recumbency was greater in the laparotomy dogs (9 of 24) than in the cervical surgery dogs (0 of 12).(ABSTRACT TRUNCATED AT 250 WORDS)     

Mandibular Fractures in the Cat A Retrospective Study

A retrospective study was made of 75 mandibular fractures in 62 cats. Mandibular fractures comprised 14.5% of all fractures seen in 517 cats. Automobile trauma was the cause of injury in more than 50% of the cases. The mean age of patients was 29.5 months. Symphyseal fractures were most common (73.3%), followed by fractures of the body (16%), condyle (6.7%), and coronoid process (4%). Sixty-seven percent of the fractures were stabilized. Cerclage and interfragmentary wiring were the most common forms of fixation. Antibiotics were administered to 73.6% of the patients. Complications were reported in 24.5% of the cats. Malocclusion and soft tissue infections were the most frequent complications. Complications developed more commonly in cats with multiple or open fractures. Clinical union occurred by an average of 6 weeks (range, 3-12 weeks) for symphyseal fractures, 10 weeks (range, 8-16 weeks) for body fractures, 6 weeks for coronoid fractures, and 6 weeks (range, 4-8 weeks) for condylar fractures.     

EFFECTS OF PELVIC POSITIONING AND SIMULATED DORSAL ACETABULAR RIM REMODELING ON THE RADIOGRAPHIC SHAPE OF THE DORSAL ACETABULAR EDGE

A radiographic study was conducted to evaluate the effect of pelvic rotation and of simulated dorsal acetabular rim (DAR) remodeling on the radiographic appearance of the dorsal acetabular edge (DAE). The DAE is the line connecting the cranial and caudal rims of the acetabulum when viewing a pelvic radiograph made with the dog in the ventrodorsal position with the hind limbs extended. In this study, it was hypothesized that the DAE would change with pelvic rotation and simulated DAR damage. Ventrodorsal radiographs of eight canine pelves were made at 0 degrees, 5 degrees, and 10 degrees of left and right pelvic rotation over its longitudinal axis. These radiographs were repeated following removal of 2, 4, and then 6 mm of bone from the right DAR of each pelvis. The ratio of acetabular width to maximum depth of the DAE was calculated. The area between the DAE and a straight line connecting the cranial and caudal acetabular rims was measured digitally. The DAE depth and area changed with pelvic rotation, and with increasing simulated DAR damage. A linear relationship between the obturator foramina width ratio and pelvic rotation allowed estimation of the degree and direction of pelvic rotation. Equations were developed from the data to assist with the estimation of the amount of DAR remodeling on a clinical radiograph.     

Regional Innovation Clusters: A Critical Review

In this paper, we present a critical assessment of recent economic development policy directions centered on the concept of regional innovation clusters. We begin by investigating the rationale underlying the Obama administration's promotion of regional innovation clusters (RICs) and their introduction to the policy arena in its Strategy for American Innovation. The connections among RICs and existing research and policies in industry and occupational clusters, regional innovation systems and regional economic development are identified and analyzed to highlight those most critical challenges to conceptualizing and theorizing RICs. While we applaud the long overdue focus of economic development policies on sub‐national regions, we identify several major conceptual shortcomings and programmatic difficulties associated with RICs as a centerpiece for economic development strategies.