Carbon dioxide induced vasorelaxation in rat mesenteric small arteries precontracted with noradrenaline is endothelium dependent and mediated by nitric oxide

Hypercapnia induces initial constriction and prolonged relaxation of rat small mesenteric arteries. The mechanism of the relaxation is unknown, but has been attributed to lowering of pHi in the vascular smooth muscle. In this study we have investigated the response to raised PCO2 at constant pHo, in mesenteric small arteries precontracted with noradrenaline. 10% CO2 led to a fall in pHi associated with acute potentiation of tension, and subsequent relaxation. The relaxation did not occur in arteries in which the endothelium had been removed, nor in arteries pretreated with the nitric oxide synthase inhibitor, L-NAME (10(-4)M, NG-nitro-L-arginine methyl ester). The D-enantiomer, D-NAME, was without effect. We conclude that hypercapnic-induced vasodilatation in this circulation occurs via endothelium derived nitric oxide production.

Detection of metabolites of polycyclic aromatic hydrocarbons in human urine

A non-invasive assay has been developed for the recovery of r-7,t-8,t-9,c-10-tetrahydroxy-7,8,9,10-tetrahydrobenzo[alpha]-pyrene (BP-7,10/8,9-tetrol) from human urine. This tetrol is excreted as a metabolite of benzo[alpha]pyrene (BP) in a process catalyzed by cytochrome P450 enzymes and epoxide hydrolases. Urine was hydrolysed to release activated benzo[alpha]-pyrene-diol-epoxides covalently bound to macromolecular species or conjugated tetrols. The relatively non-polar organic molecules from urine hydrolysates were collected on octadecasilane chromatography columns (Sep-Paks). Materials eluted in solvent (80% CH3OH), were further purified on immunoaffinity columns with antibodies raised against anti-N2-[10(7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo [alpha]pyrenyl)]-guanosine. HPLC was then used to isolate BP-7,10/8,9-tetrol, which was quantitated by synchronous fluorescence spectroscopy (SFS). This assay detected 0.24-3.12 pmol BP-7,10/8,9-tetrol per ml urine (limit of detection 0.01 pmol/ml, given 10 ml urine), in four study subjects. Reproducibility was assessed by adding tritium labeled BP-7,10/8,9-tetrol (1500 fmol) to a urine sample previously identified to contain the tetrol at levels below the limit of detection of the fluorescence assay; a recovery of > 30% of the added radioactivity was achieved (510 +/- 64 fmol, mean +/- SD, n = 3). Because HPLC alone was not sufficient to isolate materials for quantitation by SFS directly from human urine, immunoaffinity chromatography was found to be a necessary preparatory step in BP-7,10/8,9-tetrol isolation. These data demonstrate the presence of tetrahydrotetrol metabolites of BP in human urine and suggest that measurement of BP-7,10/8,9-tetrol and other polycyclic aromatic hydrocarbon-tetrols may prove to be valuable dosimeters of human internal exposure to polycyclic aromatic hydrocarbons.

Human lymphocyte sodium-hydrogen exchange. The influences of lipids, membrane fluidity, and insulin

The relation between serum lipids, membrane fluidity, insulin, and the activity of the sodium-hydrogen exchanger was investigated in human lymphocytes from 83 subjects. Subjects had a wide range of serum lipids and no concurrent disease. Lymphocyte membrane anisotropy (inversely related to membrane fluidity) was measured with a fluorescence polarization method. Sodium-hydrogen exchange maximal proton efflux rate, affinity for external sodium, and resting pH were determined with the intracellular pH-sensitive fluorochrome 2',5'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Sodium-hydrogen exchange maximal proton efflux rate was negatively correlated with the age of the subject (p = 0.03). Membrane anisotropy correlated with serum triglyceride (p = 0.04). Multiple regression analysis demonstrated that the maximal proton efflux rate in human lymphocytes was significantly related to age (p = 0.005), systolic blood pressure (p = 0.04), membrane anisotropy (p = 0.03), and serum cholesterol (p = 0.03). Incubation of lymphocytes with insulin failed to affect sodium-hydrogen exchange kinetics, intracellular buffering power, or resting intracellular pH. These results suggest that membrane-bound transport proteins may be influenced by serum lipids and the fluidity of the lipid membrane in which they are bound, but they are unlikely to be affected by insulin.

Choices of training programs and career paths by women in internal medicine

PURPOSE

To examine the choices of career paths of women in internal medicine, specifically to determine (1) whether women continue to prefer primary care practice more often than men do and (2) whether differences in career paths between men and women result from differences in the natures of the training programs they complete.

METHOD

A database containing demographic, training, and clinical-practice information on 19,151 physicians (3,569 women and 15,582 men) who had been trained in internal medicine was constructed by merging data from the National Resident Matching Program matches in internal medicine for 1977-1982 with data from the 1985 American Medical Association Physician Masterfile, which contains physician practice profiles.

RESULTS

Similar percentages of the men and the women chose primary care residencies (8% versus 9%, ns) and trained in the 100 major medical centers (49% versus 50%, ns). The women more frequently trained in programs affiliated with medical schools in the top prestige quartile (38% versus 33%, p < .05). The attrition rates of residents who left their training for careers in other medical fields were the same for the men and the women (14%). Fewer women obtained board certification (74% versus 80%, p < .01). The women chose to practice general internal medicine more frequently than did the men (52% versus 45%, p < .0001), regardless of the training program completed (primary care or traditional).

CONCLUSION

The women pursued primary-care-oriented internal medicine to a significantly greater degree than did the men, regardless of the type of training program completed (primary care or traditional).

Abnormal nondefect zone myocardial thallium washout ratio in patients with reversible thallium defects and normal coronary arteriograms

Thallium myocardial defects in patients with no angiographic coronary artery stenosis have been attributed to attenuation effects and other artifacts. Of 323 patients having thallium myocardial imaging following dipyridamole infusion, 10 of 159 patients with a segmental perfusion abnormality were found to have no luminal diameter stenosis greater than 20% on coronary angiography and no electrocardiographic (ECG) evidence of myocardial infarction or left bundle branch block. A time-standardized regional thallium washout ratio was calculated as thallium myocardial counts with dipyridamole to counts without dipyridamole. In comparison to 10 age-matched control patients with no evidence of cardiac disease and no myocardial thallium defect, study patients had a lower regional myocardial thallium washout ratio from both the defect and nondefect (1.57 +/- 0.40 versus 2.27 +/- 0.92, p = 0.041) zones. Nine of the 10 study patients had independent evidence of noncoronary heart disease, including echocardiographic or ECG evidence of left ventricular hypertrophy in six patients. In patients with thallium defects and normal coronary arteriograms, a time-standardized regional thallium myocardial washout ratio for the nondefect zone may aid in the differentiation of patients with noncoronary heart disease from those with soft tissue artifacts.

Research, academic rank, and compensation of women and men faculty in academic general internal medicine

OBJECTIVE

To evaluate the status of men and women faculty in academic general internal medicine, including their professional training, faculty responsibilities, research performance, academic rank, and compensation, to determine whether systematic differences exist by gender.

DESIGN/SETTING

The authors analyzed responses to a 55-part questionnaire sent to all full-time general internal medicine faculty at the major teaching hospitals in the United States. Unadjusted means were generated for men versus women faculty in demographics, training background, hours of work, professional time allocations, institutional support, professional self-assessment, research performance, academic rank, and compensation. Means were recalculated after adjusting for other variables using multivariate methods.

RESULTS

The authors found no significant difference in the frequency of fellowship training between men and women faculty. Women and men perform similar professional activities, but even after multivariate adjustment, women devote less time to research and perceive less research skill and institutional support for their research, but have similar numbers of grants, abstracts, and publications in refereed journals and have similar academic ranks. Women faculty, however, receive lower compensation than do men faculty, even after adjustment.

CONCLUSION

While the characteristics of men and women faculty are quite similar, including those defining their academic productivity, important differences exist in research time, perceived institutional support, and compensation. These differences cannot be explained by such obvious factors as age differentials, academic rank, or hours of work per week.

Laser angioplasty for superficial femoral and proximal popliteal artery occlusion

A prospective study of percutaneous laser assisted thermal angioplasty for superficial femoral and proximal popliteal artery occlusions was performed on 93 consecutive patients with a mean length of occluded segment of 7.6 cm. Technical success was achieved in 78 patients (84%). Subsequent patency or occlusion has been confirmed by duplex ultrasound scanning or arteriography. The crude patency rate for successfully recanalised vessels was 48% during a mean follow-up period of 18 months. Subsequent femoropopliteal bypass or amputation was required in 20% of these patients. Factors predictive of reocclusion were a length of occluded segment greater than 8 cm (p = 0.05) and less than two patent vessels below the knee (p = 0.005).

The role of bipedal lymphangiography in testicular seminoma

Determining the extent of intra-abdominal spread of testicular seminoma by radiographic studies is an essential step in planning rational treatment following orchidectomy. CT scanning is generally accepted as being superior to lymphangiography in assessing the retroperitoneal space. We reviewed the relative contribution of these two procedures in a retrospective analysis of 73 consecutive patients with testicular seminoma managed at Westmead Hospital between January 1980 and September 1987. Abdominal CT scans and bipedal lymphangiography (LAG) were carried out in 72 and 51 patients respectively, 50 patients undergoing both procedures. We found concordance between the two techniques to be 88%. Upstaging occurred in 5 patients using CT (10%), 7 patients using LAG (14%), and in 8 patients (16%) when both tests were utilised. Four patients were upstaged by both techniques while the remaining 4 patients were upstaged using one technique alone. Serum beta-HCG was not a reliable screen for residual disease. Residual disease in the few patients with an elevated serum beta-HCG was easily detected by CT scanning. We conclude that there is a continuing role for LAG in assessing patients with clinical Stage I seminoma when the abdominal CT scan is equivocal or normal.

Injury surveillance in agriculture

Information on agricultural trauma is limited and difficult to find. Planning for effective prevention strategies and evaluation is compromised by lack of a good surveillance system. Several agencies and organizations have provided some data. Although their summation is at best an approximation of the real situation, a critical review of current data bases is presented. The literature is also reviewed attempting to characterize agricultural trauma. This characterization was classified into: 1) case descriptions, 2) reviews of general articles on the hazards of farming, and 3) descriptive surveys of agricultural injuries. A summary of the available literature still leaves a rather superficial understanding of the entire injury picture. A new approach to surveillance is necessary to overcome past deficiencies. A combined modality approach is suggested, utilizing on-site survey, mail survey, telephone interviewing, and medical record verification. Trial applications of two such systems in Minnesota are described.

Effects of protracted hypothyroidism on pituitary function and structure in endemic cretinism

Pituitary function and structure were assessed in 69 endemic cretins from western China. In hypothyroid cretins (TSH greater than 10 mIU/l), CT imaging of the pituitary revealed adenoma in five of 20 (25%) and partially empty sella (PES) in a further eight of 20 (40%). The majority of tumours were microadenomas and showed a relation with higher levels of serum TSH but not with duration of hypothyroidism. Dynamic pituitary testing with TRH and GnRH in four patients with adenoma on CT gave a flat TSH response but significant rises in serum PRL, GH, LH and FSH concentrations. Hyperprolactinaemia (greater than 350 mIU/l) was present in hypothyroid cretins only (13 of 26; 50%) and serum PRL showed a curvilinear relation with serum TSH levels (r = 0.7, P less than 0.0001). Hypogonadism was seen in approximately half the cretins with high PRL levels. Our data suggest that severe protracted thyroid hormone deficiency may result in thyrotrophin adenomas of the pituitary gland. Disturbances of growth, puberty, and sexual function in endemic cretins are explained by the secondary effects of thyroid hormone deficiency on pituitary function.

The effects of sponsorship on PPO performance

In trying to build a "better health care mousetrap," hospitals, physicians, insurers, employers and other are sponsoring PPOs. Two Mercer-Meidinger-Hansen consultants who specialize in evaluating managed care plans discuss what prompts various sponsors to establish a PPO and how purchasers can discern the effects of these motivations on the plan's objectives, operational components and outcomes.

Lisinopril in elderly patients with hypertension

The antihypertensive efficacy and safety of lisinopril, a long-acting angiotensin-converting enzyme inhibitor, were assessed in 40 elderly patients (aged 65 years or over) with mild to moderate systolic/diastolic or isolated systolic hypertension, in an open study of 12 weeks' duration. Lisinopril was given orally in single daily doses. The starting dose was 5 mg in patients with glomerular filtration rate (GFR) of 30-60 ml/min and 10 mg in patients with GFR greater than 60 ml/min. The dose of lisinopril could be titrated upwards to a maximum of 40 mg daily according to blood pressure response. A thiazide diuretic was then added if blood pressure was not controlled. Thirty-six patients completed the study. Mean sitting blood pressure was significantly reduced by lisinopril treatment. There was no significant alteration in the heart rate, and postural hypotension did not occur. The median dose of lisinopril given was 20 mg daily (range 5-40 mg daily), and only two patients had a diuretic added to the lisinopril. One patient was withdrawn from the study because of unstable angina, and another was discontinued from lisinopril treatment because of anorexia and facial flushing. One patient was withdrawn after 8 weeks because of interruption of lisinopril therapy for a transurethral resection of the prostate, and one patient was lost to follow-up. No clinically significant haematological or biochemical changes were observed. The mean glomerular filtration rate was unchanged during the study. Proteinuria did not occur de novo, nor did established proteinuria increase. Thus lisinopril was well-tolerated and effective therapy in a group of elderly hypertensive patients.