Abstracts of the contributed papers

Abstracts of the contributed papers     

INVOLVEMENT OF NON-NMDA AND NMDA RECEPTORS IN GLUTAMATE-INDUCED PRESSOR OR DEPRESSOR RESPONSES OF THE PONS AND MEDULLA

1. Fifty-five intact and six baroreceptor denervated and vagotomized cats of either sex were anaesthetized intraperito-neally with urethane (400 mg/kg) and a-chloralose (40 mg/kg). Responses of the systemic arterial pressure (SAP), mean SAP (MSAP) and sympathetic vertebral nerve (VNA) and renal nerve activities (RNA) were recorded. 2. In intact animals, monosodium L-glutamate (Glu, 0.1 mol/L, 50 nL) was microinjected into pressor areas of the locus coeruleus (LC), gigantocellular tegmental field (GTF), rostral ventrolateral medulla (RVLM) and dorsomedial medulla (DM), and the depressor areas of caudal ventrolateral medulla (CVLM). The induced actions were compared before and after microinjection of either glutamate antagonists, glutamate diethylester (GDEE, 0.5 mol/L, 50–100nL), a competitive AMPA receptor blocker, or 2-amino-5-phosphonovaleric acid (D-AP5, 0.025 mol/L, 50–100 nL), a competitive N-methyl-D-aspartate (NMDA) receptor blocker. GDEE completely blocked the increases of SAP and VNA elicited from all pressor areas. D-AP5 only partially blocked the pressor but slightly blocked VNA and RNA responses from LC, GTF and DM, particularly those from RVLM. Neither GDEE nor D-AP5 blocked the depressor responses of SAP and two nerve activities elicited from CVLM. 3. In baroreceptor denervated animals, NMDA (2 mmol/L, 50–100 nL) and AMPA (0.2 mmol/L, 50–100 nL) were micro-injected into the same pressor areas of GTF, RVLM and DM and the depressor area of CVLM responsive to Glu activation (0.1 mol/L, 30 nL). In RVLM, DM and CVLM, the results of either NMDA or AMPA were similar to those induced by Glu. However, in GTF, microinjection of either NMDA or AMPA did not induce similar responses to Glu. This suggests that the nature of GTF may differ from RVLM and DM. 4. The above results suggest that the Glu-induced pressor responses from LC, GTF, DM and especially RVLM, are primarily mediated through AMPA receptors. The Glu-induced depressor responses from CVLM may not be predominantly mediated by either AMPA or NMDA receptors. 5. In both baroreceptor-intact and -denervated cats stimulation of the pressor areas often produced an increase of VNA and a decrease of RNA, while in the depressor CVLM decreased both VNA and RNA. The VNA, but not RNA were positively correlated with the pressor responses, while both VNA and RNA were positively correlated with the depressor responses. This may suggest that neurons of the sympathetic vertebral and renal nerves are topographically organized in the brain.     

Evaluation of trophoblast HLA-G antigen with a specific monoclonal antibody

A monoclonal antibody to HLA-G has been generated by immunizing HLA-A2.1/human β²-microglobulin (β²m) double transgenic mice with murine L cells transfected with both human β²m and HLA-G. This monoclonal antibody, designated as G233, has been found not to cross-react with other HLA class I antigens when tested on numerous cell lines by flow cytometry. With immunohistology, all populations of extravillous trophoblast (cell columns, interstitial trophoblast, endovascular trophoblast, placental bed giant cells) were stained. An extensive range of adult and fetal tissues was also tested but none reacted with monoclonal antibody G233, including those previously reported to express HLA-G mRNA, indicating that the protein has a highly restricted distribution. Failure to detect HLA-G in the fetal thymus raises the question as to how T-cell tolerance to this antigen is induced. Immunoprecipitation of trophoblast surface proteins with monoclonal antibody G233 revealed a heavy chain of 39 kDa and a light chain of 12 kDa, indicating that HLA-G expressed on the surface of trophoblast is complexed with p2m. However, sequential immunoprecipitation with monoclonal antibody W6/32 followed by monoclonal antibody G233 continued to detect a residual band of 39 kDa, suggesting that trophoblast surface HLA-G may also occur as free heavy chains not associated with p2m. Immunoprecipitation followed by two dimensional gel electrophoresis showed that monoclonal antibody G233 recognizes several iso-forms of HLA-G from trophoblast similar to the characteristic spot array previously described for HLA-G. This monoclonal antibody G233 will be highly useful in future experiments to elucidate the function of HLA-G.     

Differences in leisure-time physical activity levels between blacks and whites in population-based samples: The Minnesota heart survey

Energy expenditure in leisure-time physical activity (LTPA) was measured using the Minnesota LTPA Questionnaire in 35- to 74-year-old black and white residents of Minneapolis-St. Paul, Minnesota. Estimates of the geometric mean LTPA energy expenditure were 129 and 204 kcal per day for black and white men (p<.05) and 91 and 123 kcal per day for black and white women (p<.05). The percentage of individuals expending 2000 kcal or more per week in LTPA was significantly lower in black men than white men (25 vs. 35%; p=.01) but was not different in black versus white women (18 vs. 17%). Although black men and women reported greater occupational physical activity than their white counterparts, LTPA and job activity were unrelated in all race and sex groups. In both races, LTPA energy expenditure declined with age. LTPA increased with level of formal education, and the largest LTPA difference between blacks and whites was observed in those who had a high-school diploma or less. Blacks had lower participation rates than whites in most of the individually assessed physical activities. Additional research is needed on the determinants and promoters of LTPA in population subgroups.The research was funded by National Heart, Lung, and Blood Institute Research Grant R01 HL 23727 and National Research Award T32 HL 07328-10.     

Thoraskopische Koronarchirurgie

Thorascopic coronary surgery has achieved great progress in the past few years. After computer-directed instrument systems were introduced, which enabled high precision and expanded mobility in close quarters, the limitations of conventional endoscopic instruments were largely overcome. Employing modern surgical telemanipulators and endoscopic stabilizers, entirely endoscopic myocardial revascularization of the anterior wall is being successfully performed during off-pump surgery. Longer operating times and conversion rates in about one-fifth of the patients due to technical and anatomical limitations still restrict the use of these new surgical techniques compared to conventional surgery. Development of further technologies and integration of video-assisted navigation systems will broaden the application of computer-assisted instrument systems in the near future.     

In-vitro fertilization and the ovarian hyperstimulation syndrome.

Eight patients who developed severe ovarian hyperstimulation syndrome (OHSS) were identified among 1302 patients undergoing in-vitro fertilization (IVF) over a 1 year period (prevalence of 0.6%); 63% had ultrasonically diagnosed polycystic ovaries (PCO) and 75% were undergoing their first attempt at IVF. Pretreatment with a superactive luteinizing hormone-releasing hormone (LHRH) analogue significantly increased the prevalence of severe OHSS (1.1% versus 0.2%, P less than 0.05) compared with ovarian stimulation with clomiphene citrate and human menopausal gonadotrophin (HMG). The mean serum oestradiol concentration on the day of human chorionic gonadotrophin (HCG) administration was 8200 +/- 2300 pmol/l. A mean of 19.6 +/- 6.8 follicles had been aspirated and 13.1 +/- 7.7 oocytes recovered at transvaginal ultrasound-directed oocyte recovery. All patients had an embryo transfer and luteal support in the form of HCG. The clinical pregnancy rate was 88%, multiple pregnancy rate 71% and implantation rate 63.5 +/- 41.3%. In a group of seven patients who were hospitalized for moderate OHSS during the same period, peak oestradiol levels were significantly lower than in those with severe OHSS (P less than 0.05). Of the group with moderate OHSS, 57% had PCO, the clinical pregnancy rate was 100% and multiple pregnancy rate 43%. Patients with ultrasound-diagnosed PCO have an increased risk of developing OHSS and the dose of HMG administered to them should be minimized. In patients at risk of developing OHSS, progesterone instead of HCG should be used for luteal support. Transfer of a maximum of two embryos or freezing all embryos for transfer in a subsequent cycle may reduce the likelihood of multiple pregnancy.     

Entrapment of platelets in the penis during and after erection

Because of the development of hypercoagulability and the deposition of fibrin in the penis during erection a study of the possible role of platelets in this process was undertaken. Platelet response was studied in 9 adult chacma baboons (Papio ursinus) using autologous in vitro indium-111-labelled platelets and sequential scintigraphy of the penis during erection. The blood pooling pattern was obtained using in vivo technetium-99m-labelled red cells in a similar investigation. A statistically significant retention of platelets occurred during and after erection, which could not be attributed to blood pooling (P less than 0,05). Entrapment of platelets could lead to enhanced activity and activation, and might play a significant role in hypercoagulability and fibrin deposition during erection. Therefore platelets could be an important factor in the pathogenesis of ageing impotence.     

The clinical utility of provocative radionuclide oesophageal transit in the evaluation of non-cardiac chest pain.

We combined edrophonium provocative testing with the technique of radionuclide oesophageal transit (RET) in 30 consecutive patients with non-cardiac chest pain (NCCP) and 12 controls. The oesophageal transit time of aqueous technetium-99m sulfur colloid was determined before and after intravenous infusion of 80 micrograms/kg edrophonium chloride (ED). Patient symptoms during provocative RET (P-RET) were recorded. Thirteen (43%) of the patients had abnormal study results, whereas all control subjects had normal results. Three groups considered abnormal were observed: (a) in two patients (6%), the pain was reproduced and transit pre- and post-ED administration was prolonged (greater than 15 s); (b) in six patients (20%), the pain was reproduced, but transit was normal pre- and post-ED; (c) in five patients (17%), transit pre- and post-ED was prolonged, but no pain was reproduced. In five patients (17%), ED prolonged the transit time greater than 15 s without pain, but the baseline transit was normal. Transit time was measurable in 23 patients. Mean pre-ED transit time was 10.2 +/- 7.4 s (mean +/- SD) and post-ED, 12.4 +/- 8.0 s (P = 0.3). We conclude that ED has no significant effect on transit time, and the pain induced by ED rarely correlates with an abnormal transit; P-RET provides additional information to baseline RET, increasing sensitivity, and may be a useful screening method in the evaluation of patients with NCCP.     

Quantitative effects of cerebral infarction on spatial learning in rats.

Outcome following stroke is difficult to measure because the behavioral response to infarction is variable. We hypothesized that cognitive function, such as spatial learning, may be a reproducible and sensitive outcome variable. We developed an animal model of multifocal cerebral ischemia in order to study the effects of infarction on learning. To cause ischemia, several hundred microspheres were injected into the internal carotid arteries of rats. After ischemia, behavior was measured using a global rating and a Morris water maze. Postmortem serial brain sections were stained and the size of the infarctions was measured. We found that intracerebral microspheres caused cortical infarction and an impairment of spatial learning. This impairment was not due to occlusion of the internal carotid artery and was not found in animals who received a sham injection of saline. The degree of learning impairment was not correlated with the volume density of the infarctions or with the volume density of the remaining cerebral hemisphere. The learning impairment clearly differentiated normal from lesioned animals, and the impairment was probably due to a delay in acquisition of spatial information rather than a defect in retention or retrieval. Measurement of learning deficit after cerebral ischemia is an efficient and sensitive method for evaluating new stroke treatments and possibly for exploring structure function relationships.     

Management of refractory peritonitis to maintain the peritoneum for subsequent dialysis.

Peritonitis and its sequelae remain major clinical problems in treating peritoneal dialysis (PD) patients. One of these sequelae is the formation of intra-abdominal adhesions, preventing a patient from returning to peritoneal dialysis after a Tenckhoff catheter is removed for refractory peritonitis. We have recently applied a technique that appears to reduce the incidence of this severe complication. When it is determined that a catheter will be removed for refractory peritonitis, hourly peritoneal dialysis exchanges are performed for 12 hr prior to surgery. Postoperatively, the abdomen is rested for 48 hr, after which a temporary peritoneal dialysis catheter is placed at the bedside and hourly exchanges (with antibiotics) are performed for 2-3 days or until the dialysis fluid white blood cell count improves. Then the temporary catheter is removed and the abdomen is rested until the Tenckhoff catheter is replaced in 10-14 days. We treated 5 consecutive patients with refractory peritonitis (2 Pseudomonas, 1 Proteus, 1 Candida, 1 S. aureus) with this technique. All 5 patients were able to return successfully to peritoneal dialysis. At our institution over the past five years, 9 patients with refractory peritonitis due to the same organisms have had their catheters removed. Only 5 (56%) were able to return to PD. Although preliminary, our technique holds promise for those patients wishing to return to peritoneal dialysis after having a catheter removed for refractory peritonitis.