Cloning, mapping and mutational analysis of the S-adenosylmethionine decarboxylase gene in Drosophila melanogaster

S-adenosylmethionine decarboxylase is a key enzyme in the synthesis of polyamines. These small cationic molecules are required for growth and development in all organisms. A wealth of biological processes, including synthesis of DNA and protein and condensation of chromatin, involve polyamines. Inhibition of polyamine synthesis has been proposed for treatment of cancer but this requires more knowledge about the in vivo function of polyamines. We report here the cloning of the S-adenosylmethionine decarboxylase gene from Drosophila melanogaster and the analysis of corresponding mutants. The mutant phenotypes are similar to those previously described for ribosomal protein genes (Minutes) and rRNA genes (bobbed). This work elucidates the in vivo consequences of impaired polyamine synthesis with respect to the development of a whole animal.

Chronic low dose islet amyloid polypeptide infusion reduces food intake, but does not influence glucose metabolism, in unrestrained conscious rats: studies using a novel aortic catheterization technique

Islet amyloid polypeptide (IAPP) is a 37-amino acid polypeptide coproduced with insulin in the beta-cells of the pancreatic islets. The physiological effects of IAPP have not been established. Although effects on glucose metabolism are seen only at pharmacological doses both in vitro and in vivo, effects on food intake have been shown at near-physiological concentrations. The aim of the present study was to investigate the effects of similar elevations of circulating plasma IAPP levels on glucose metabolism in rats and to evaluate the function of a novel aortic catheterization technique. In a cross-over design, two sets of experiments in which conscious unrestrained rats received chronic IAPP infusions at 0 and 2 or 0 and 7 pmol/kg min were performed. Peripheral glucose disposal was determined by means of the hyperinsulinemic euglycemic clamp technique. Chronic elevations of circulating IAPP at concentrations that reduced food intake [43.5 +/- 6.2 g (control) vs. 35.7 +/- 8.2 g (IAPP; P < 0.01) and 34.0 +/- 2.2 g (control) vs. 28.8 +/- 1.4 g (IAPP; P = 0.07) for the 7 and 2 pmol/kg x min experiments, respectively] had no effect on the glucose metabolic rate [GMR; 18.5 +/- 0.6 mmol/kg x h (control) vs. 18.7 +/- 0.9 mmol/kg x h (IAPP) and 14.4 +/- 0.7 mmol/kg x h (control) vs. 15.6 +/- 0.7 mmol/kg x h (IAPP) for the 7 and 2 pmol/kg x min experiments, respectively]. Thus, effects on glucose metabolism are unlikely to explain the anorectic effect of IAPP.

Activated protein C resistance in patients with central retinal vein occlusion

AIM/BACKGROUND

A new defect in the anticoagulant system has recently been discovered--activated protein C resistance. The frequency of this disorder has been shown to be increased in young patients (< 50 years of age) with central retinal vein occlusion. This study was carried out to determine if there was any overrepresentation of activated protein C resistance in patients > 50 years of age with central retinal vein occlusion.

METHODS

Blood samples were obtained from 83 patients > 50 years of age and with a history of central retinal vein occlusion. The blood samples were analysed for activated protein C resistance with standard clinical laboratory methods.

RESULTS

In this material 11% of the patients were resistant to activated protein C. The normal incidence of activated protein C resistance in the same geographical area is 10-11%.

CONCLUSION

Activated protein C resistance does not seem to be a cause of central retinal vein occlusion in people older than 50 years.

Ultrafast x-ray diffraction using a streak-camera detector in averaging mode

We demonstrate an apparatus for measuring time-dependent x-ray diffraction. X-ray pulses from a synchrotron are diffracted by a pair of Si(111) crystals and detected with an x-ray streak camera that has single-shot resolution of better than 1 ps. The streak camera is driven by a photoconductive switch, which is triggered by 100-fs laser pulses at a repetition rate of 1 kHz. The laser and the streak camera are synchronized with the synchrotron pulses. In the averaging mode, trigger jitter results in 2-ps temporal resolution. We measured the duration of 5-keV pulses from the Advanced Light Source synchrotron to be 70ps.

Islet hormone secretion in pancreatic cancer patients with diabetes

The diabetes or impaired glucose tolerance that occurs in most patients with pancreatic cancer is characterized by profound insulin resistance. Recent evidence suggests that the diabetes may result from the presence of the tumor rather than being a predisposing factor to development of the malignancy. Some islet hormones have been shown to exhibit diabetogenic effects. To investigate the potential role of these hormones in the diabetic state associated with pancreatic cancer, we measured islet hormones during fasting in pancreatic cancer patients (n = 30), patients with other malignancies (n = 43), and healthy controls (n = 25). Preoperative pancreatic cancer patients were classified as normal glucose tolerance (NGTT), impaired glucose tolerance (IGTT), non-insulin-requiring diabetes (NIRD), and insulin-requiring diabetes (IRD). Nine pancreatic cancer patients were studied after tumor removal by subtotal pancreatectomy. Some preoperative pancreatic cancer patients (n = 19), postoperative patients (n = 9), and controls (n = 8) were also studied during hyperglycemia and following glucagon injection. Fasting plasma C-peptide was elevated in NIRD pancreatic cancer patients compared to controls. Fasting levels of islet amyloid polypeptide (IAPP), glucagon, and somatostatin were elevated in NIRD and IRD patients. IAPP and glucagon, but not somatostatin, normalized following subtotal pancreatectomy. During hyperglycemia, increases in C-peptide and IAPP were seen only in controls and in NGTT and postoperative pancreatic cancer patients. After glucagon infusion, IAPP levels increased in controls and nondiabetic cancer patients; C-peptide levels increased in controls, nondiabetic patients, and NIRD. Responses of C-peptide and IAPP to glucagon normalized after pancreatectomy. During hyperglycemia, glucagon levels fell in all groups except IGTT patients and a decrease in somatostatin concentrations was seen in controls.

Effects of environmental stress on tissue survival and neutrophil recruitment in surgical skin flaps in relation to plasma corticosterone levels in the rat

OBJECTIVE

Because glucocorticoid treatment can improve the survival of surgical skin flaps, we examined the influence of environmental stress on skin flap survival in the rat.

MATERIAL

Female Sprague-Dawley rats.

TREATMENT

Dexamethasone (1 mg/kg i.p.).

METHODS

A standardized dorsal skin flap was raised and sutured back into position, and six days latter the percentage of flap survival was assessed. Corticosterone in rat plasma was measured using radioimmuno assay, and skin flap myeloperoxidase accumulation (reflecting neutrophil recruitment) was determined spectrophotometrically.

RESULTS

Skin flap survival decreased gradually during a 10 day acclimatization period after transportation of the animals from the supplier, and plasma corticosterone levels were increased during the first 5 days of acclimatization compared to day 7 and 10. Dexamethasone treatment of rats accustomed to their new environment for 10 days increased flap survival to a level close to that observed in animals operated at day 1 after arrival. Flap surgery induced pronounced neutrophil recruitment into flap tissue, and this cell accumulation was greatly reduced in both the dexamethasone treated rats and in rats with elevated corticosterone levels.

CONCLUSIONS

Skin flap survival in rats exposed to environmental stress may be significantly increased as compared to animals accustomed to their new environment for one week, possibly as a consequence of anti-inflammatory actions exerted by stress-induced elevations in plasma corticosterone. These findings emphasize the importance of strictly controlling environmental stress factors in studies of inflammation and tissue damage after surgical skin trauma.

Improved wound healing in transtibial amputees receiving supplementary nutrition

The objective of this prospective study of matched controls was to find out whether supplementary nutrition would improve wound healing and decrease mortality in patients undergoing transtibial amputation for occlusive arterial disease. The nutritional status of 32 consecutive transtibial amputees was assessed and 28 were classified as malnourished. Supplementary nutrition was given reaching an average intake of 2098 kcal/day for a total of 11 days. In 24 patients, at least 5 days of preoperative supplementary nutrition were given, followed by postoperative treatment for a total of 11 days. Four patients who had an immediate operation were given only postoperative treatment, and 4 were excluded. The controls were 32 amputees in another hospital and matching procedures were carried out with corrections for diabetes, sex, age, smoking habits, previous vascular surgery and living conditions before amputation. Healing, including those healed before death in both groups, occurred in 26 of the nutrition group compared to 13 in the control group, which was statistically significant. Nine patients died within 6 months in the nutrition group compared to 14 of the controls (not significant). Malnutrition was present in nearly 90% of transtibial amputees and supplementary nutrition improved healing, but not mortality.

Dissociated secretion of islet amyloid polypeptide and insulin in serum-free culture media conditioned by human pancreatic adenocarcinoma cell lines

CONCLUSION

The cosecretion of insulin and islet amyloid polypeptide (IAPP) is altered when isolated rat pancreatic islets are incubated in culture media conditioned by human pancreatic cancer cells.

BACKGROUND

Pancreatic cancer is usually associated with impaired glucose tolerance. This study investigates the tumor-derived influence on beta-cell secretion of pancreatic islets.

METHODS

Four conditioned media were prepared from two human pancreatic cancer cell lines (Panc-1 and HPAF), a hamster pancreatic cancer cell line (PC-1), and a fibroblast cell line (Ag1523). Isolated rat pancreatic islets were incubated first in the conditioned media or nonconditioned control medium for 24 h, then in the same kind of media containing 100 microM carbamylcholine for 90 min. Insulin and IAPP secretion were measured by radioimmunoassay.

RESULTS

Islets in media conditioned by Panc-1 and HPAF cells demonstrated dissociation of insulin and IAPP secretion. During 24-h incubation, the dissociation was expressed as selectively decreased insulin secretion. With addition of 100 microM carbamylcholine, the dissociation was expressed as normal secretion of insulin and hypersecretion of IAPP. As a result, the IAPP/insulin molar ratios were increased in both groups during both time periods. The islets in PC-1 and Ag1523 media did not show any significant changes in insulin and IAPP secretion.

Trophic effects by epidermal growth factor on duodenal mucosa and exocrine pancreas in rats

Epidermal growth factor (EGF) is a potent growth factor with possible implications on the regulation of pancreatic secretion and duodenal absorption but also on pancreatic tumor growth. In the present study the growth effect on duodenal mucosa and pancreas by a 14-day continuous infusion of three different doses of EGF (4, 30 and 60 micrograms EGF/kg/24 h) was studied in rats. The EGF content in duodenal mucosa and pancreatic tissue was significantly increased by 30 and 60 micrograms/kg/24 h of EGF while plasma levels were only marginally increased. Neither duodenal mucosal nor pancreatic weights were changed but DNA content in both tissues was increased with the higher EGF doses. Long-term EGF infusion has moderate trophic effect on duodenal mucosa and the pancreas. There is a high tissue uptake of EGF, specially in duodenal mucosa. The hyperplasia seems to be related to tissue levels of EGF but not to plasma levels.

Chronic infusion of islet amyloid polypeptide causes anorexia in rats

Islet amyloid polypeptide (IAPP) is a hormonal peptide that at high doses has been shown to reduce food intake. In the present study, the dose-response effects of subcutaneous infusion of IAPP (0, 2, 7, and 25 pmol.kg-1.min-1) for 8 days on food intake and meal patterns in rats were investigated. At the end of the experiment, plasma was obtained and levels of IAPP were measured by radioimmunoassay. IAPP dose-dependently and transiently inhibited food intake. The minimal effective dose (2 pmol.kg-1.min-1) caused a small but significant (up to 14%, P < 0.01) inhibition of food intake that lasted 5 days. The highest dose administered (25 pmol.kg-1.min-1) had the greatest effect (up to 44%, P < 0.001), which lasted throughout the 8-day period. Reductions in feeding during light and dark phases occurred through a decrease in number of meals consumed rather than meal size or meal duration. IAPP also decreased body weight gain and water intake dose dependently. IAPP infusion of 2, 7, and 25 pmol.kg-1.min-1 increased plasma IAPP concentrations from a basal level of 10.3 +/- 0.7 pM to 35.1 +/- 5.4, 78.1 +/- 11.2, and 236.6 +/- 23.6 pM, respectively, values that are likely to be close to physiological and within the pathophysiological ranges. Thus IAPP may play an important physiological or pathophysiological role in control of food intake.

Two different areas within the primary motor cortex of man

The primary motor area (M1) of mammals has long been considered to be structurally and functionally homogeneous. This area corresponds to Brodmann's cytoarchitectural area 4. A few reports showing that arm and hand are doubly represented in M1 of macaque monkeys and perhaps man, and that each subarea has separate connections from somatosensory areas, have, with a few exceptions, gone largely unnoticed. Here we show that area 4 in man can be subdivided into areas '4 anterior' (4a) and '4 posterior' (4p) on the basis of both quantitative cytoarchitecture and quantitative distributions of transmitter-binding sites. We also show by positron emission tomography that two representations of the fingers exist, one in area 4a and one in area 4p. Roughness discrimination activated area 4p significantly more than a control condition of self-generated movements. We therefore suggest that the primary motor area is subdivided on the basis of anatomy, neurochemistry and function.

Rehabilitation and follow-up of children with severe traumatic brain injury

We studied the outcome of 25 patients [12 girls and 13 boys; mean age 13.7 (SD 3.9 years)] with severe traumatic brain injury (TBI). The Glasgow Coma Scale (GCS) score 6 h after the injury was (mean) 4.5 (SD 2.7), and the mean duration of unconsciousness was 15.8 (SD 10.6) days. Being the most severely brain-injured children in the health care region, they were all referred to its only regional pediatric rehabilitation center during 1986-1990. At discharge, 1 patient was healthy, 1 was in a vegetative state and 18 had multiple impairments. Motor problems were present in 22, epilepsy in 7 and speech impairment in 14. It was not possible to assess cognition in 3 of the children, and 15 of the remaining 22 fell in the normal range. At follow up 2-6 years after trauma, all 23 survivors reported at least one sequela, and 21 had multiple sequelae. As many as two-thirds had normal I.Q. and only 3 were non-ambulatory, but behavioral and personality disturbances were so disabling that none of the patients in this group had been able to readjust to a normal life in society after the trauma.

Mutations in the Drosophila melanogaster gene encoding S-adenosylmethionine synthetase [corrected] suppress position-effect variegation

In Drosophila melanogaster, the study of trans-acting modifier mutations of position-effect variegation and Polycomb group (Pc-G) genes have been useful tools to investigate genes involved in chromatin structure. We have cloned a modifier gene, Suppressor of zeste 5 (Su(z)5), which encodes S-adenosylmethionine synthetase, and we present here molecular results and data concerning its expression in mutants and genetic interactions. The mutant alleles Su(z)5, l(2)R23 and l(2)M6 show suppression of wm4 and also of two white mutants induced by roo element insertions in the regulatory region i.e., wis (in combination with z1) and wsp1. Two of the Su(z)5 alleles, as well as a deletion of the gene, also act as enhancers of Polycomb by increasing the size of sex combs on midleg. The results suggest that Su(z)5 is connected with regulation of chromatin structure. The enzyme S-adenosylmethionine synthetase is involved in the synthesis of S-adenosylmethionine, a methyl group donor and also, after decarboxylation, a propylamino group donor in the bio-synthesis of polyamines. Our results from HPLC analysis show that in ovaries from heterozygous Su(z)5 mutants the content of spermine is significantly reduced. Results presented here suggest that polyamines are an important molecule class in the regulation of chromatin structure.

No differences in mucosal adaptive growth one week after intestinal resection in rats given enteral glutamine supplementation or deprived of glutamine

OBJECTIVE

To evaluate the effects of intraluminal glutamine on the adaptation of intestinal mucosa after resection compared with transsection and un-operated on control animals.

DESIGN

Open, controlled, experimental study.

SETTING

University hospital, Sweden.

SUBJECTS

123 Sprague-Dawley rats.

INTERVENTION

Daily isonitrogenous oral diet was given either free of glutamine or supplemented with 4% glutamine for 2 or 7 days to rats subjected to intestinal resection, transection or no operation.

MAIN OUTCOME MEASURES

Body weight and protein content, DNA content, and thymidine incorporation in jejunal and ileal mucosa.

RESULTS

Resection resulted in a significant growth stimulation evaluated by weight/body weight, protein, and DNA content (p < 0.05-0.001). Glutamine supplementation did not significantly influence this growth response. Thymidine incorporation in jejunum was stimulated by glutamine on day 3 (p < 0.05-0.001).

CONCLUSION

The glutamine fortified diet had no growth stimulating effects compared with a glutamine free diet one week after 60% intestinal resection. An early increase in thymidine incorporation indicated that glutamine had a transient proliferative effect.

Hyperbaric oxygen reduces ischemia-induced skeletal muscle injury

The effect of hyperbaric oxygen treatment on skeletal muscle submitted to 3 or 4 hours of ischemia was studied in a rat hindlimb model after 48 hours of reperfusion. Forty-eight male Sprague-Dawley rats were allocated to four groups. In the two treatment groups, hyperbaric oxygen was given for 45 minutes at 2.2 atm immediately and 4,8,16,24,32, and 40 hours after release of the ischemia-inducing tourniquet. The injury to skeletal muscle was quantified from the uptake of 99mtechnetium-pyrophosphate (injected intravenously after 45 hours of reperfusion) in anterior tibial muscle harvested 3 hours later. The uptake was significantly lower in hyperbaric oxygen-treated rats than in untreated rats with 3 or 4 hours of ischemia (p < 0.01 and P < 0.05). After 4 hours of ischemia, the changes in levels of the intracellular muscle compounds adenosine triphosphate, phosphocreatine, and lactate were less in the hyperbaric oxygen-treated rats than in the untreated animals.

Activated protein C resistance in young adults with central retinal vein occlusion

BACKGROUND

Central retinal vein occlusion is a disease that is most common in old people. While the disease in old people often is associated with atherosclerosis, hypertension, diabetes, or glaucoma, this is much less evident in young people. However, a new defect in the anticoagulant system has recently been discovered, activated protein C resistance. This hereditary defect may well be associated with central retinal vein occlusion, and so this factor was analysed in patients younger than 50 years with a history of central retinal vein occlusion.

METHODS

Blood samples were obtained from 31 patients younger than 50 years with a history of central retinal vein occlusion, and analysed for activated protein C resistance with standard clinical laboratory methods.

RESULTS

In this material 26% of all the patients and 36% of the patients younger than 45 years were resistant to activated protein C. The normal incidence of activated protein C resistance is 2-7%.

CONCLUSION

Activated protein C resistance seems to be the most common known cause of central retinal vein occlusion in young people.

Cortical representation of self-paced finger movement

We compared the cortical fields activated by simple, self-paced index-finger flexions with those activated during visually triggered movement and rest using PET. Of 12 fields detected during self-paced movement compared to rest, three were located in the classically defined motor areas: primary motor area (M1), premotor cortex (PM) and supplementary motor area (SMA). The latter extended into the cingulate motor area (CMA). Four corresponding clusters were also found when triggered movement was subtracted from self-paced movement. The change in regional cerebral blood flow (rCBF) was greater in SMA than in PM during self-paced movement compared with either control. We conclude that repetitive, self-paced index-finger flexions can activate SMA, PM and CMA, and that this movement activates SMA more strongly than PM.

Activation by attention of the human reticular formation and thalamic intralaminar nuclei

It has been known for over 45 years that electrical stimulation of the midbrain reticular formation and of the thalamic intralaminar nuclei of the brain alerts animals. However, lesions of these sectors fail to impair arousal and vigilance in some cases, making the role of the ascending activating reticular system controversial. Here, a positron emission tomographic study showed activation of the midbrain reticular formation and of thalamic intralaminar nuclei when human participants went from a relaxed awake state to an attention-demanding reaction-time task. These results confirm the role of these areas of the brain and brainstem in arousal and vigilance.

Effects of acute and chronic infusion of islet amyloid polypeptide on food intake in rats

BACKGROUND

Islet amyloid polypeptide (IAPP), also called amylin, is a hormonal peptide produced by the islet beta-cells of the pancreas. Because the peptide is co-stored and co-released with insulin, attention has been focused on IAPP's ability to interfere with glucose metabolism. However, IAPP also has other effects, such as a reduction of food intake.

METHODS

In this study we investigated the dose-response effect of acute systemic administration of rat and human IAPP on food intake, and the cumulative effect of chronically increased circulating IAPP concentrations on food intake and body weight in the rat.

RESULTS

All doses of rat IAPP investigated acutely inhibited food intake. The lowest infusion rate of 8 pmol/kg/min caused an 28% inhibition of the food intake at 2 h (p < 0.05). No effect of human IAPP was observed. Chronic administration of rat IAPP via an osmotic minipump during a 6-day period caused prolonged inhibitory effects on food intake and reduced body weight. During the first 3 days of infusion the food intake of the IAPP group was only 44% of the food intake of the control group (p < 0.001). The body weight of the IAPP group had fallen 18.6 +/- 2.7 g by day 3, in contrast to a small increase in the control group (4.0 +/- 3.1 g; p < 0.001). The reduction in food intake was sustained throughout the last 3 days of study (IAPP, 16.7 +/- 1.1 g/day; control, 20.6 +/- 1.5; p < 0.05). Similarly, the body weight still differed at the end of day 6 and, compared with day 0, was -8.7 +/- 3.7 g for the IAPP group and +10.9 +/- 4.8 for the control group (p < 0.01).

CONCLUSIONS

These findings show that chronic increase of circulating IAPP levels can cause a marked reduction in both food intake and body weight and, together with the reduced food intake seen after acute administration of the peptide, indicates the possibility of IAPP functioning as a satiety factor.

Interrater variability and validity in subjective nutritional assessment of elderly patients

The subjective Global Assessment technique was evaluated with regard to its reliability and validity in a Swedish elderly population. Ninety patients, 70 years of age or older, and newly admitted to the geriatric clinic, participated in the study. The nutritional state was assessed subjectively by two independent observers using the Subjective Global Assessment form, and objectively, using a combination of anthropometry and serum-protein analysis. The subjectively assessed malnutrition rate was about 20% higher than that assessed objectively. The agreement level between the two observers was 77.8%, Kappa 0.56 (< 0.001), and the levels between the subjective and objective assessments were 57.8% (Kappa = 0.17) and 73.3% (Kappa = 0.46), respectively. The experienced observer identified 85.2% of those who were defined as malnourished using the objective criteria and the less experienced observer, 66.6%. Furthermore, a regression analysis indicated weight index as the main significant objective factor influencing the subjective assessment. The subjective technique could be regarded as reliable from a clinical and preventive perspective since the agreement between the two rates was just under 80%. It seems also to be valid since the subnormalities in the selected criteria showed a similar pattern. The necessity of being well trained in order to manage nutritional status assessment, for both clinical and research purposes, is obvious.

The use of perfluorocarbon liquids in vitreoretinal surgery

Two perfluorocarbon liquids (perfluoro-n-octane and perfluorodecaline) were evaluated as technical aids in vitreoretinal surgery in 42 patients. Perfluorocarbon liquids were found to stabilize the retina and simplify removal of repiretinal membranes, which in many cases permitted the subsequent use of an expanding gas instead of silicone oil at the conclusion of the operation. The infusion of a perfluorocarbon liquids allowed the drainage of subretinal fluid through peripheral retinal breaks obviating the need for a retinotomy in most cases. No difference could be observed between the two types of perfluorocarbon liquids, and there were no adverse effects associated with their use. The retina was centrally attached in 32 eyes (76%) at 3-10 months follow-up.

Amantadine treatment of a patient with anoxic brain injury

An 18-year-old boy with anoxic brain injury, suffering from severe psychomotor inhibition, tetrarigidity and dystonia, was treated with amantadine in order to ameliorate his symptoms. Neuropsychological tests showed improvement in motor and cognitive functions.