The caudal lumbar and lumbosacral spine of 13 dogs with pain or neurologic deficits were evaluated using magnetic resonance imaging (MRI). Spin echo T1, proton density, and T2 weighted and gradient echo T2* imaging sequences were utilized. MRI permitted direct, multiplanar, tomographic visualization of the spine facilitating evaluation of all components of degenerative caudal lumbar and lumbosacral stenosis. Abnormalities detected included intervertebral disc degeneration, intervertebral disc protrusion involving both the vertebral canal and intervertebral foramina, articular process osteophytosis, articular process fracture, nerve root impingement by spondylosis deformans, and the presence of low signal material within the vertebral canal of 2 dogs with recurrent pain following previous spinal surgery. In all 7 dogs treated surgically, MRI findings were consistent with surgical findings.

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Unilateral triple pelvic osteotomy was performed with three variations in technique on canine cadaver pelves. The following variables were studied: the angle of the ilial osteotomy (perpendicular to the long axis of the ilium and 10 degrees, 20 degrees, and 30 degrees off perpendicular); the degree of axial rotation (20 degrees, 30 degrees, and 45 degrees); and the type of fixation (canine pelvic osteotomy plate [CPOP] or a 2.7-mm dynamic compression plate [DCP]). Structural changes measured were the pelvic inlet and acetabular area, interischiatic tuberosity distance, and degree of acetabular version. Means and standard error of the means were determined for all pelvic measurements and were analyzed by three-way analysis of variance (P < .05). As the axial rotation increased from 20 degrees to 45 degrees an ilial osteotomy angled 10 degrees, 20 degrees, or 30 degrees resulted in a significantly greater decrease in the pelvic inlet area and significantly less deviation of the interischiatic tuberosity distance and degree of acetabular version from normal than an osteotomy directed perpendicular to the long axis of the ilium. Compared with the CPOP, as the axial rotation increased from 20 degrees to 45 degrees, the DCP resulted in a significantly greater decrease in the pelvic inlet area, an increase in the interischiatic tuberosity distance and degree of acetabular version, and less of an increase in the acetabular area. The results of this study suggest that to maximize dorsal acetabular coverage, while minimizing disruption of normal pelvic architecture, a CPOP and an ilial osteotomy angled 10 degrees to 30 degrees are preferred for all degrees of axial rotation.

Treatment of severe cervical tracheal collapse with commercially-available extraluminal ring placement leads to an overall improvement in quality of life and good long-term results, with about one-third of dogs requiring continued medical management. Most dogs do not have clinical signs consistent with disease progression after surgery.

The synthesis of Mg-protoporphyrin-IX from exogenous protoporphyrin-IX, in a crude plastid pellet extracted from greening cucumber cotyledons was found to require L-glutamate as a cofactor. It has now been shown that glutamate acts in the presence of contaminating mitochondria to provide an ATP regenerating system. With purified plastids, Mg chelatase is not stimulated by glutamate; instead, it requires a high concentration of ATP and is greatly stimulated by added phosphoenolpyruvate and pyruvate kinase. GTP, UTP, CTP, and ITP will not substitute for ATP. ADP in the absence of an ATP generating system is completely ineffective, whereas it is slightly inhibitory in the presence of 10 mM ATP. AMP is strongly inhibitory in the reaction; 50% inhibition is obtained at approximately 3.5 mM AMP in the presence of 10 mM ATP.In our previous communications (1, 2) we reported the synthesis of Mg-Proto3 in chloroplast preparations isolated from greening cucumber cotyledons. These particles could utilize exogenous Proto as the substrate for Mg chelatase, but could also synthesize Proto from ALA or Glu. Regardless of the substrate added to the incubation, Mg-Proto synthesis required ATP and Glu. We concluded that Glu had a double role in Mg-Proto biosynthesis: (a) it was a precursor of ALA and, therefore, of Proto; and (b) it played a more specific role in Mg chelation. The nature of the latter role was completely unknown at the time of our last contribution. Our research has now progressed further, and the role of Glu in Mg chelation is no longer a mystery: Glu interacts with the mitochondria present in the crude plastid preparation to constitute an ATP regenerating system. In the absence of Glu, Mg chelatase activity can still be seen in the presence of high ATP concentrations. A preliminary account of these findings has appeared elsewhere (3). The experimental evidence for the identity of the reaction product as a mixture of Mg-Proto and Mg-Proto-Me was presented previously (2). Germination and Incubation Conditions. Cucumber seeds were germinated in the dark at approximately 25 C for 5.5 days as previously described (8). The co71edons were harvested after greening for 4-5 h under 83 ,IE m s , at room temperature (22-26 C). Routine incubations contained in I ml: 500 ,umol sucrose, 1 ,umol MgCl2, 1 ,umol EDTA, 20 ,tmol Tes,10 ,umol Hepes, 4.0 ,umol GSH, 0.6 ,tmol NAD, 2.0 mg BSA, varying amounts of ATP and Proto, and 3.3-11 mg plastid protein as determined by the biuret method. Incubations were for 1 or 2 h, at 28 or 30 C, under ordinary laboratory illumination (15-30 ,IE m-2 S 1 of white fluorescent light) and were terminated by freezing. Modifications and additions to this standard protocol are given in table and figure legends.Routine Extraction and Determination of Porphyrins. Porphyrins and metalloporphyrins were extracted into ether by a previously described procedure (2). The ether extract was read in a Perkin-Elmer MPF 44-A fluorescence spectrophotometer with the excitation set at 410 ± 10 nm. Emissi...