Specific reduction of chloroplast glyceraldehyde-3-phosphate dehydrogenase activity by antisense RNA reduces CO2 assimilation via a reduction in ribulose bisphosphate regeneration in transgenic tobacco plants

The reduction of 3-phosphoglycerate (PGA) to triose phosphate is a key step in photosynthesis linking the photochemical events of the thylakoid membranes with the carbon metabolism of the photosynthetic carbon-reduction (PCR) cycle in the stroma. Glyceraldehyde-3-phosphate dehydrogenase: NADP oxidoreductase (GAPDH) is one of the two chloroplast enzymes which catalyse this reversible conversion. We report on the engineering of an antisense RNA construct directed against the tobacco (Nicotiana tabacum L.) chloroplast-located GAPDH (A subunit). The construct was integrated into the tobacco genome by Agrobacterium-mediated transformation of leaf discs. Of the resulting transformants, five plants were recovered with reduced GAPDH activities ranging from 11 to 24% of wild-type (WT) activities. Segregation analysis of the kanamycin-resistance character in self-pollinated T1 seed from each of the five transformants revealed that one plant (GAP-R) had two active DNA inserts and the others had one insert. T1 progeny from GAP-R was used to generate plants with GAPDH activities ranging from WT levels to around 7% of WT levels. These were used to study the effect of variable GAPDH activities on metabolite pools for ribulose-1,5-bisphosphate (RuBP) and PGA, and the accompanying effects on the rate of CO2 assimilation and other gas-exchange parameters. The RuBP pool size was linearly related to GAPDH activity once GAPDH activity dropped below the range for WT plants, but the rate of CO2 assimilation was not affected until RuBP levels dropped to 30-40% of WT levels. That is, the CO2 assimilation rate fell when RuBP per ribulose-1,5-biphosphate carboxylase-oxygenase (Rubisco) site fell below 2 mol.(mol site)-1 while the ratio for WT plants was 4-5 mol.m(mol site)-1. Leaf conductance was not reduced in leaves with reduced GAPDH activities, resulting in an increase in the ratio of intercellular to ambient CO2 partial pressure. Conductance in plants with reduced GAPDH activities was still sensitive to CO2 and showed a normal decline with increases in CO2 partial pressure. Although PGA levels did not fluctuate greatly, the effect of reduced GAPDH activity on RuBP-pool size and assimilation rate can be interpreted as being due to a blockage in the regeneration of RuBP. Concomitant gas-exchange and chlorophyll alpha fluorescence measurements indicated that photosynthesis changed from being Rubisco-limited to being RuBP-regeneration-limited at a lower CO2 partial pressure in the antisense plants than in WT plants.(ABSTRACT TRUNCATED AT 400 WORDS)

Third place winner of the Conrad Jobst Award in the gold medal paper competition. Prevention of spinal cord dysfunction in a new model of spinal cord ischemia

Paraplegia or paraparesis caused by temporary cross-clamping of the aorta is a devastating sequela in patients after surgery of the thoracoabdominal aorta. No effective clinical method is available to protect the spinal cord from ischemic reperfusion injury. A small animal (rat) model of spinal cord ischemia is established to better understand the pathophysiological events and to evaluate potential treatments. Eighty-one male Sprague-Dawley rats weighing 300 g to 350 g were used for model development (45) and treatment evaluation (36). The heparinized and anesthetized rat was supported by a respirator following tracheostomy. The thoracic aorta was cannulated via the left carotid artery for post-clamping intra-aortic treatment solution administration. After thoracotomy, the aorta was freed and temporarily clamped just distal to the left subclavian artery and just proximal to the diaphragm for different time intervals: 0, 5, 10, 15, 20, 25, 30, 35, and 40 minutes (five animals per group). The motor function of the lower extremities postoperatively showed consistent impairment after 30 minutes clamping (5/5 rats were paralyzed), and this time interval was used for treatment evaluation. For each treatment, six animals per group were used, and direct local intra-aortic infusion of physiologic solution (2 mL) at different temperatures with or without buffer substances was given immediately after double cross-clamp to protect the ischemic spinal cord. Arterial blood (2 mL) was infused in the control group. The data indicate that the addition of HCO3-(20 mM) to the hypothermic (15 degrees C) solution offered complete protection of the spinal cord from ischemic injury.(ABSTRACT TRUNCATED AT 250 WORDS)

The African Caribbean Eye Survey: risk factors for glaucoma in a sample of African Caribbean people living in London

The purpose of the study was to estimate the prevalence of and risk factors for chronic glaucoma in a sample of African Caribbean people over 35 years of age living in the London Borough of Haringey. A cross-sectional voluntary sample of persons were subjected to detailed ophthalmic assessment including automated tangent screen suprathreshold visual field testing, applanation tonometry and stereoscopic disc evaluation in 50 community-based survey clinics over an 8 month period. Cases and suspects were referred to Moorfields Eye Hospital for more detailed assessment and confirmation of the diagnosis. Of 873 eligible persons examined (out of a total of 1022), 32 definite cases of glaucoma were identified, a prevalence of 3.9%; 42% of these had been previously diagnosed. Approximately 10% of the sample required further assessment and follow-up when ocular hypertensives and glaucoma suspects were included. An age-standardised comparison with the findings of the Roscommon survey revealed a relative risk for glaucoma for Haringey blacks compared with Irish whites of 3.7. Significant risk factors for glaucoma included age, African birthplace and darker skin colour. Neither diabetes nor hypertension reached significance. Despite the lack of a population base, this study provides strong evidence that the 4 times greater risk of glaucoma estimated for American blacks compared with whites applies equally to the United Kingdom population. Community-based facilities are required to raise awareness of the risk among this ethnic minority in this country and case-finding resources should be provided to meet local needs.

Reduction of ribulose biphosphate carboxylase activase levels in tobacco (Nicotiana tabacum) by antisense RNA reduces ribulose biphosphate carboxylase carbamylation and impairs photosynthesis

The in vivo activity of ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) is modulated in response to light intensity by carbamylation of the active site and by the binding of sugar phosphate inhibitors such as 2'-carboxyarabinitol-1-phosphate (CA 1P). These changes are influenced by the regulatory protein Rubisco activase, which facilitates the release of sugar phosphates from Rubisco's catalytic site. Activase levels in Nicotiana tabacum were reduced by transformation with an antisense gene directed against the mRNA for Rubisco activase. Activase-deficient plants were photosynthetically impaired, and their Rubisco carbamylation levels declined upon illumination. Such plants needed high CO2 concentrations to sustain reasonable growth rates, but the level of carbamylation was not increased by high CO2. The antisense plants had, on average, approximately twice as much Rubisco as the control plants. The maximum catalytic turnover rate (k cat) of Rubisco decreases in darkened tobacco leaves because of the binding of CA 1P. The dark-to-light increase in k cat that accompanies CA 1P release occurred to similar extents in antisense and control plants, indicating that normal levels of activase were not essential for CA 1P release from Rubisco in the antisense plants. However, CA 1P was released in the antisense plants at less than one-quarter of the rate that it was released in the control plants, indicating a role for activase in accelerating the release of CA 1P.

Sustained release of salmon calcitonin in vivo from lactide: glycolide copolymer depots

Studies were carried out to determine whether monolithic depot formulations, prepared using lactide:glycolide copolymers, could be used to administer salmon calcitonin (sCT) to rats in vivo. Formulations containing 2, 5, or 10% (w/w) sCT were administered subcutaneously to female Wistar strain rats. Release of sCT was determined by measurement of peptide in plasma using a specific radioimmunoassay and by measurement of residual sCT in the depots after recovery at postmortem. Plasma calcium concentrations and cumulative weight gain of the animals were used to measure pharmacological effects of the released sCT. Release of sCT from the depots was controlled by the copolymer and was sustained for periods up to 10 days. However, the release of sCT from the depots did not significantly alter plasma calcium concentrations, and effects on cumulative weight gain were small and transient. Peptide loading of the formulations was shown to modify sCT release. Maximal release of sCT from depots containing 10% peptide occurred over a 7 to 14-day period postadministration, with 5% sCT release occurred between days 11 and 14, and with 2% sCT, the period of maximal release was between days 11 and 18. Release of peptide from the depots was essentially complete by 21 days postadministration irrespective of the peptide loading. These data suggest that lactide:glycolide copolymer depots may have application for the convenient clinical administration of sCT in metabolic bone diseases.

Epidemiological function of BD8 certification

The quality of information collected during certification for blindness and partial sight was assessed using a combination of review of the literature on registration and analysis of 17,695 BD8 certificates received by the Office of Population Censuses and Surveys (OPCS) between June and November 1990. Three problems were identified which affect the epidemiological function of these data: interpretation of the definitions of blindness and partial sight has changed over time; the degree of under-certification is unknown (although it could be as high as 64% for blind and 77% for partially sighted people); and the cause of visual disability recorded by the ophthalmologist may not always be adequately transmitted into the statistical analyses. Guidelines for completion of part 5 of the BD8 form need to be developed. Strategies for improving the quality of these data are discussed.

Reduction of ribulose-1,5-bisphosphate carboxylase/oxygenase content by antisense RNA reduces photosynthesis in transgenic tobacco plants

A complementary DNA for the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was cloned from tobacco (Nicotiana tabacum) and fused in the antisense orientation to the cauliflower mosaic virus 35S promoter. This antisense gene was introduced into the tobacco genome, and the resulting transgenic plants were analyzed to assess the effect of the antisense RNA on Rubisco activity and photosynthesis. The mean content of extractable Rubisco activity from the leaves of 10 antisense plants was 18% of the mean level of activity of control plants. The soluble protein content of the leaves of anti-small subunit plants was reduced by the amount equivalent to the reduction in Rubisco. There was little change in phosphoribulokinase activity, electron transport, and chlorophyll content, indicating that the loss of Rubisco did not affect these other components of photosynthesis. However, there was a significant reduction in carbonic anhydrase activity. The rate of CO(2) assimilation measured at 1000 micromoles quanta per square meter per second, 350 microbars CO(2), and 25 degrees C was reduced by 63% (mean value) in the antisense plants and was limited by Rubisco activity over a wide range of intercellular CO(2) partial pressures (p(i)). In control leaves, Rubisco activity only limited the rate of CO(2) assimilation below a p(i) of 400 microbars. Despite the decrease in photosynthesis, there was no reduction in stomatal conductance in the antisense plants, and the stomata still responded to changes in p(i). The unchanged conductance and lower CO(2) assimilation resulted in a higher p(i), which was reflected in greater carbon isotope discrimination in the leaves of the antisense plants. These results suggest that stomatal function is independent of total leaf Rubisco activity.

Left flank retroperitoneal exposure: a technical aid to complex aortic reconstruction

Over the last 5 years an extended left flank retroperitoneal approach was used in 85 of 531 (16%) aortic reconstructions deemed technically complex. Abdominal aortic aneurysm repair was performed in 70 patients (82%), bypass of aortoiliac occlusive disease was performed in 11 (13%), and aortic endarterectomy for mesenteric and/or renovascular disease was performed in 4 (5%). Indications for use of this approach included a "hostile" abdomen (43 patients), juxta/suprarenal abdominal aortic aneurysm (35), large (greater than 10 cm) abdominal aortic aneurysm (12), extreme obesity (10), associated renal and/or visceral artery stenosis requiring endarterectomy (9), inflammatory abdominal aortic aneurysm (2), and horseshoe kidney (2). Suprarenal or supraceliac aortic clamping, averaging 31 minutes, was required in 43 patients (50%). Postoperative recovery was rapid (average length of stay, 10.2 days), and morbidity was minimal despite the complex nature of these reconstructions. The perioperative mortality rate in elective operations was 1.2%. This approach facilitated proximal abdominal aortic exposure and anastomosis, especially in large, pararenal aneurysms or in situations unfavorable to a transabdominal approach. Whereas a left flank retroperitoneal approach can be used in most aortic reconstructions, it seems especially suited to those that pose significant technical challenges.

Management of infected aortoiliac aneurysms

A 30-year retrospective review identified 13 patients treated for infected aneurysms of the abdominal aorta or iliac arteries, for an overall incidence of 0.65%. A constellation of clinical findings led to the correct preoperative diagnosis in 11 (85%) of 13 patients. Treatment methods included resection and in situ replacement grafting in seven patients, resection and extra-anatomic bypass in five patients, and resection-ligation in one patient. Four (31%) of 13 patients died within 30 days of operation, three of whom died of rupture. Overall, good results were achieved in five patients (38%), while poor results were noted in the remaining eight patients (62%). The determinants of outcome were aneurysm location or rupture, the presence of established infection, and the virulence of the infecting organism. In 10 (77%) of the 13 aneurysms, Salmonella species, Bacteroides fragilis, Staphylococcus aureus, and Pseudomonas aeruginosa accounted for all deaths, ruptures, and suprarenal aneurysm infections. These data suggest that patients with primary infections of the abdominal aorta or iliac arteries continue to present with advanced infections or aneurysm rupture that result in a high mortality.

Discriminant functions in differential diagnosis of hypercalcemic patients

Using readily available biochemical assays of plasma and urine constituents, we have defined discriminant functions useful as a guide to the differential diagnosis of patients with hypercalcemia. The decreasing rank order of contribution of the variables to the discriminant functions was as follows: plasma albumin, plasma phosphate, plasma chloride, log10 (calcium excretion per liter of glomerular filtrate), and log10 (plasma gamma-glutamyltransferase). Discriminant functions have been defined for patients with values for plasma creatinine above and below 185 mumol/L, and for practical conditions in which plasma and urine samples, or plasma samples only, are available.

Hyponatremia in patients admitted to a coronary care unit

Calculation of osmolal gap in plasma and urine samples from patients after acute myocardial infarction was carried out to see whether changes in these variables support the concept of a "sick-cell" mechanism being responsible for the hyponatremia associated with acute myocardial infarction. Some supportive evidence was found on the first day after admission but, overall, the evidence was not convincing.

The use of routine referral data in the development of clinical audit and management in North Lincolnshire

As part of the national waiting list initiative, a retrospective survey of routine referrals in seven specialties to Lincoln County Hospital by general practitioners within its catchment area, during the months of January to March 1987 inclusive, was carried out, using data from the hospital's Patient Administration System and the Lincolnshire Family Practitioner Committee. These specialties were identified by managers and clinicians as those in which a significant problem of waiting times and waiting lists existed, both as perceived locally and in comparison with other districts. The total referral rate for all GPs in the study was 9.6 referrals/100 patients on their list/year, which is very close to the average of other studies published elsewhere in the country on this topic. However, the range of referral rates between practices was very wide, varying from 2.8 to 17.6. There were also wide variations within individual practices. It is therefore concluded that, taken overall, 'over-referral' by general practitioners is not the cause of any problem at Lincoln County Hospital. However, the wide variation of referral patterns has been of great interest to the general practitioners themselves. They have requested that referral rates be fed back to them routinely, in the manner of the Prescription Pricing Authority, and this will commence shortly. In addition, a working group of orthopaedic surgeons and general practitioner representatives has met to discuss the implications of the study, and the drawing up of mutually agreed referral protocols, the operation of which would be monitored jointly. The setting up of similar groups in the other specialties is under active consideration.

Discriminant functions in differential diagnosis of hypercalcemic patients

Using readily available biochemical assays of plasma and urine constituents, we have defined discriminant functions useful as a guide to the differential diagnosis of patients with hypercalcemia. The decreasing rank order of contribution of the variables to the discriminant functions was as follows: plasma albumin, plasma phosphate, plasma chloride, log10 (calcium excretion per liter of glomerular filtrate), and log10 (plasma gamma-glutamyltransferase). Discriminant functions have been defined for patients with values for plasma creatinine above and below 185 mumol/L, and for practical conditions in which plasma and urine samples, or plasma samples only, are available.

Ureteral complications and aortoiliac reconstruction

A 33-year experience with 58 ureteral complications in 50 of 3580 patients undergoing aortoiliac reconstruction was analyzed. Ureteral obstruction was treated before or in conjunction with aneurysm repair in six patients with aneurysmal disease. The remaining 44 patients had 46 ureteral complications after aortic reconstruction; complications included hydronephrosis (42), ureteral leak (3), and ureteral necrosis (1). A high incidence of associated graft complications was noted. Graft thrombosis developed in one of the six patients undergoing prior or simultaneous ureteral procedures, and graft infection developed in another. Thirty-six graft complications developed in 24 (55%) of the 44 patients with postoperative ureteral complications. The complications included 19 anastomotic aneurysms, eight graft limb thromboses, six graft infections, and three aortoenteric fistulas. Twenty-nine of the 44 patients with postoperative ureteral complications underwent ureteral or graft operations or both. These included five patients having ureteral operations alone, seven with a ureteral procedure and subsequent graft operation, eight requiring simultaneous ureteral and graft procedures, and nine undergoing a graft operation with ureteral observation. Six of these 29 patients (21%) died after operation, all from graft complications including aortoenteric fistulas (three), ruptured anastomotic aneurysms (two), and graft infection (one). Graft complications affected 55% of 44 patients with postoperative ureteral complications, compared to 12% of 3536 patients without ureteral complications (p less than 0.0001). Patients with postoperative ureteral complications were 4.4 times as likely to have graft complications compared to those without ureteral complications (p less than 0.0001). These data suggest that such urologic complications may be markers for recognition of or harbingers for graft complications.

Inorganic sulfate metabolism in the very low birthweight infant

The effect of vitamin D supplementation on inorganic sulfate metabolism was examined in very low birth weight (less than 1,500 g) infants at biweekly intervals after birth until 6 weeks of postnatal age. Baseline serum sulfate concentrations were significantly higher in all infants (471 +/- 24 mumol/l, n = 80) than in adults (299 +/- 25 mumol/l, n = 17). In controls, the levels did not change significantly over the ensuing 6 weeks, although serum creatinine declined. Urinary sulfate excretion rose significantly to near adult levels by 2 weeks. Both urine and serum sulfate were correlated with weight gain but not with estimated glomerular filtration rate, suggesting that factors other than renal clearance have a preponderant influence on serum sulfate in these infants. At 6 weeks, the mean serum sulfate in the high-dose group (receiving 2,170 +/- 23 U/day of vitamin D, n = 41) was significantly higher than in controls (receiving 360 +/- 22 U/day, n = 40). In all infants, there was a significant correlation (r = 0.36, p less than 0.001) between serum sulfate and 25(OH)-vitamin D concentrations, but not other analytes or clinical variables, suggesting that vitamin D may be one of the factors modulating sulfate metabolism in the newborn period.

Mandibulotomy: a surgical approach to oral and pharyngeal lesions

The history of mandibulotomy is reviewed. The surgical steps involved and the variations of techniques are discussed. Two illustrative cases are reported and the clinical applications of the approach are discussed. It is concluded that mandibulotomy has a place in the management of malignancies as well as awkwardly situated benign lesions as well as malignancies.

Effect of high-dose vitamin D supplementation on radiographically detectable bone disease of very low birth weight infants

To test the hypothesis that high-dose vitamin D2 supplementation would result in a lower incidence of radiographically detectable bone disease, we randomly assigned 40 very low birth weight infants to a control group who received vitamin D2 in a dosage of 400 IU/day and 41 to an experimental group who received a dosage of 2000 IU/day. After 6 weeks, radiographs from all infants were scored blindly for degree of radiographic bone disease, and serum osteocalcin and 25-hydroxyvitamin D levels were measured. Mean vitamin D intake was 360 +/- 141 (SD) IU/day in the control group and 2170 +/- 144 (SD) IU/day in the experimental group. Median 6-week serum 25-hydroxyvitamin D levels were 24 ng/ml (range 3 to 60 ng/ml) in the control group and 68 ng/ml (range 9 to 150 ng/ml) in the experimental group (p less than 0.001). Overall, 20% of the infants had evidence of moderate radiographic bone disease and only 2% were severely affected. The radiographic bone score (median = 2.5) and serum osteocalcin concentration (mean = 21.7 +/- 8.7 ng/ml) in the control subjects did not differ significantly from those in the experimental group (median bone score = 2.0; mean osteocalcin level = 24.1 +/- 7.9 ng/ml). Although there may be a subset of very low birth weight infants who would benefit from high doses of vitamin D, we conclude that no generalized clinical improvement can be attributed to this regimen alone.

Drug errors and incidents in a neonatal intensive care unit. A quality assurance activity

We prospectively examined the causes of medication errors and incidents in a level 3 neonatal intensive care unit for a 2-year period. There were 313 incidents in 23,307 patient days (13.4 incidents per 1000 patient days). The relative risk of incidents was greater in more intensive levels of care. The two most common causes of incidents were neglecting to give a medication on schedule (n = 52) and nonregulation of an intravenous infusion (n = 32). Twenty percent of orders made by physicians that were in error resulted in serious incidents compared with only 6% of all other causes.

Pharmacokinetics of iothalamate in endstage renal disease

Some nephrologists make alterations in routine peritoneal and hemodialysis schedules after diagnostic studies that use radiographic contrast agents. A study to determine the pharmacokinetics of one contrast agent, iothalamate, is reported. The plasma (total body) clearance of iothalamate was measured in seven patients who had endstage renal disease (ESRD) and who received maintenance hemodialysis. During an interdialytic period, plasma clearance of iothalamate varied from 0.7 to 5.2 mL/min (3.1 +/- 1.8 mL/min, mean +/- SD) with an elimination rate constant (beta) of 0.0164 +/- 0.01 hr-1, a terminal half-life of 61 +/- 42 hours, and an estimated distribution volume of 11 +/- 3.9 L. Hemodialysis clearance of iothalamate was 104 +/- 54 mL/min. With the assumption that iothalamate is mainly distributed in the extracellular fluid (ECF) compartment, the theoretical fluid shift from the intracellular fluid (ICF) compartment to the ECF compartment was 323 mL after administration of the largest dose (2.1 mL/kg or 1.6 mmol/kg of body weight) of 60% meglumine iothalamate solution. The average maximum serum osmolarity change was less than expected, suggesting some type of internal buffering of meglumine iothalamate. In the first few hours after radiocontrast administration in four patients, the average change in serum osmolarity was 5 mmol/L; the average change in serum sodium concentration during this same time was a decrease of 0.5 mmol/L. The minor increase in ECF volume induced by hyperosmolar contrast agents does not require immediate dialysis in most patients. When needed, however, for contrast-related adverse effects, hemodialysis is efficient in rapidly removing iothalamate.

Effect of timing of cerebral ultrasonography on the prediction of later neurodevelopmental outcome in high-risk preterm infants

To determine the predictive value of cranial ultrasonographic examination in high-risk preterm infants at different postnatal ages, we scanned 110 infants less than or equal to 32 weeks gestational age at 1, 2, 3, and 6 weeks postnatal ages and at 40 weeks postconceptional age (PCA). Cranial abnormalities detected by ultrasonography at each postnatal age of examination were classified as minor (periventricular superolateral echogenicity with or without intraventricular hemorrhage, grades 1 to 3) or major (cystic periventricular leukomalacia with or without intraventricular hemorrhage, grade 4) and correlated with neurodevelopmental outcome determined by 1 year of age. Major abnormalities detected by ultrasonography were present in four infants at 1 week, four at 2 weeks, eight at 3 weeks, and 11 infants at 6 weeks and 40 weeks PCA, respectively. Nineteen infants (17%) had moderate to severe functional handicaps defined as cerebral palsy, cognitive or visual deficit, or deafness. The positive and negative predictive values of ultrasound examinations, with regard to later neurodevelopmental outcome, improved with increasing postnatal age at examination and was best at 40 weeks PCA. Negative results of ultrasound study at 40 weeks PCA most correctly predicted satisfactory outcome. Although only 58% of moderately to severely handicapped infants were correctly identified by ultrasound examination at 40 weeks PCA, all infants with major ultrasonographic abnormalities at 40 weeks PCA had moderate or severe handicap. Our data demonstrate that the timing of cerebral ultrasonography is important in the prediction of later neurodevelopmental outcome in high-risk preterm infants.