Strong interactions in supported-metal catalysts.

Many commercially important catalysts consist of small metal particles dispersed on inorganic oxide surfaces. Although in most cases there is no significant interaction between the metal and the support, strong bonding can be demonstrated in a recently discovered class of supported-metal catalysts. These cases typically involve group VIII metals dispersed on transition metal oxides whose surfaces can be reduced to form cations with lower valences. Spectroscopic measurements indicate that an electron is transferred from the cation (such as Ti(3+) or Nb(4+)) to the metal particle. This, in turn, leads to profound changes in the catalytic and chemisorption properties and the morphology of the metal particles.

Isotope selectivity of infrared laser-driven unimolecular dissociation of a volatile uranyl compound.

Isotope-selective photodissociation of the volatile complex uranyl hexafluoroacetylacetonate . tetrahydrofuran [UO(2)(hfacac)(2) . THF] has been achieved with both a continuous-wave and a pulsed carbon dioxide laser. The photodissociation was carried out in a low-density molecular beam under collisionless conditions. Transitions of the laser are in resonance with the asymmetric O-U-O stretch of the uranyl moiety, a vibrational mode whose frequency is sensitive to the masses of the uranium and oxygen isotopes. Unimolecular dissociation is observed mass spectrometrically at an extremely low energy fluence, with no evidence of an energy fluence or intensity threshold. The dissociation yield increases nearly linearly with increasing energy fluence. At constant fluence the dissociation yield is independent of contact time between the radiation field and the molecule, indicating that the decomposition is driven by laser energy fluence and not laser intensity. The oxygen and uranium isotope selectivities measured in these experiments are nearly those predicted by the ratio of the linear absorption cross sections for the respective isotopes. Thus, essentially complete selectivity is observed for oxygen isotopes, while a selectivity of only about 1.25 is measured for the uranium isotopes. A model presented to describe these results is based on rapid intramolecular vibrational energy flow from the pumped mode into a limited number of closely coupled modes.

Hyperacute lung rejection in a pig-to-human transplant model: the role of anti-pig antibody and complement.

BACKGROUND: The physiology of hyperacute rejection of pig lung by human blood and the role of antispecies antibody and complement in this phenomenon have not previously been characterized. METHODS: Human blood was perfused through an ex vivo pig heart-lung preparation. In the treatment groups, blood was either unmodified or modified to deplete alternative pathway complement (heat treatment), anti-pig antibody, or both. Control experiments were performed with unmodified and heat-treated pig blood. Physiologic parameters, organ survival, and immunohistology were the primary outcome measures assessed. RESULTS: Pig lung was consistently damaged by human blood within 45 min (median 20 min), as evidenced by elevated pulmonary vascular resistance and parenchymal injury. Immunohistologic studies of perfused lungs showed prominent deposition of IgM and classical pathway component, C4, and weaker deposition of alternative pathway component, properdin. Heat treatment did not impede the rise in pulmonary vascular resistance or significantly prolong survival. Depletion of anti-pig antibody prolonged survival (median 90 min) and attenuated the rise in pulmonary vascular resistance. Antibody absorption, combined with heat treatment of plasma, prevented the elevation in pulmonary vascular resistance and yielded median graft survival (210 min) similar to pig blood perfusion (approximately 240 min). CONCLUSIONS: These results show that elevated pulmonary vascular resistance and pulmonary parenchymal injury are mediated at least in part by antispecies antibody and heat-sensitive pathways. They are consistent with the hypothesis that complement activation contributes significantly to acute lung damage in the pig-to-human species combination.

The effect of methacholine inhalation challenge on regional residual volume in patients with subclinical asthma.

Regional residual volume to total lung capacity (RVr/TLCr) was measured with xenon 133 before and after methacholine challenge in 26 nonsmoking subjects (mean age 34 years). Eleven were normal control subjects and 15 were patients referred for methacholine challenge because of previous asthma-like symptoms. All had normal pulmonary function and normal RVr/TLCr distribution. Following methacholine challenge, RVr/TLCr increased in two control subjects and ten patients who also had decreases in FEV1 of greater than 20 percent. The RVr/TLCr changes were patchy, suggesting that the degree of bronchospasm varied between individual lung regions. The other 14 subjects did not have a 20 percent decrease in FEV1, but two controls and four patients had generalized increases in RVr/TLCr, while seven controls and one patient had no significant changes in RVr/TLCr. In all subjects, FEV1 and RVr/TLCr returned to the baseline level after salbutamol administration. The results indicate that methacholine can cause localized or diffuse effects on lung emptying and that bronchodilator completely reverses the bronchoconstriction induced by methacholine.

Histopathology of cardiac xenograft rejection in the pig-to-baboon model.

BACKGROUND: The use of pig organs transgenic for human decay accelerating factor (hDAF) has largely overcome the problems of hyperacute rejection. With improved immunosuppressive protocols, life supporting grafts are showing greater survival times bringing the possibility of clinical xenotransplantation closer. Examination of the histopathology of the rejection process provides insight into the underlying mechanism and may suggest ways in which new immunosuppressive strategies should be directed. METHODS: 44 baboons (Papio anubis) underwent heart transplants of which 39 were from transgenic donors. The transplanted organs were examined histologically and stained for evidence of immunoglobulin and complement deposition as well as cellular infiltrates. RESULTS: In the transgenic animals survival times were 2 to 99 days (mean 23.5) and the heterotopic group and 1 to 39 days (mean 11.7) in the orthotopic group. There were 3 cases of hyperacute rejection between the 2 groups. Rejected organs showed areas of old and recent myocardial infarction associated with vascular thrombosis. There was widespread deposition within vessels of immunoglobulins IgM and IgG together with complement fractions C3 and C5b to 9 in those organs that were rejected. The amount of complement positive in the longer surviving organs was less than those rejecting early. Cellular infiltate was predominantly macrophage with some later appearing T or natural killer cells. CONCLUSIONS: The histopathological changes support the importance of immunoglobulin and complement in delayed xenograft or acute vascular rejection. With time there is an increase in cellular infiltrate predominantly macrophages and these findings suggest an increasingly important role for the cells and the rejection process. The presence of areas of infarction and underlying vascular thrombosis is in keeping with endothelial activation and the establishment of procoagulant phenotype which may be due to immunoglobulin, complement, secreted cytokines and direct cellular effects.

Measuring and managing quality of surgery. Statistical vs incidental approaches.

New rules for quality assurance provoked a comparison of effects of two approaches used concurrently for 14 years. In an incidental approach, a multidisciplinary conference reviewed all postoperative complications as they occurred and attributed each to one of six causes. Remedies were instituted and data were filed. In a statistical approach, death and complication rates were computed annually and compared with previous years' rates and with rates reported to Congress as national norms. Statistics suggested acceptable quality in each specialty but calculations were tedious and differences achieved significance too rarely or too slowly to identify problems, protect patients, and improve care. The incidental approach was popular and produced immediate improvements in patient care. Conferees attributed one half of complications to errors. Frequent acknowledgment of susceptibility to error may contribute to the safety and quality shown by our statistics.

Chemotherapy as an adjuvant to surgery for colorectal cancer. A follow-up report.

An adjuvant program of fluorouracil for patients undergoing "curative" resection for adenocarcinoma of the colon and rectum was initiated as a randomized clinical trial in January 1968. Patients were randomly assigned to an intraluminal fluorouracil or intraluminal control (saline) group and were so treated at the time of surgical resection if findings at operation indicated that all gross neoplastic disease could be resected. Those patients receiving intraluminal fluorouracil (30 mg/kg) received intravenous fluorouracil (10 mg/kg) on each of the first two postoperative days and five subsequent postoperative courses of oral fluorouracil (90 mg/kg) in each 18-day course over a one-year period. By July 1, 1975, there were 203 patients undergoing curative resection entered into the study. Survival and disease-free data, as of Dec 31, 1976, revealed no benefit from this adjuvant course of fluorouracil. These data support the need for continued randomized clinical trials of new and innovative adjuvant therapy compared with an untreated control group.

Efficacy of oral and systemic antibiotic prophylaxis in colorectal operations.

A cooperative Veterans Administration study of the septic complication rate during large-bowel surgery was undertaken in two groups of patients. The first group received oral neomycin and erythromycin base plus parenteral placebo; the second, the oral antibiotics plus parenteral cephalothin sodium. During a five-year period, 1,128 patients were studied. The overall septic complication rate was 7.8% in patients receiving only oral antibiotics, and 5.7% in patients receiving both oral and parenteral antibiotics. This difference was not significant. The only significant finding was a greater incidence of fever of unknown origin in patients receiving only oral antibiotics. None of those patients were treated with additional antibiotics, and all fevers cleared spontaneously. There seems to be no discernible benefit from adding parenteral antibiotic prophylaxis when performing elective colon surgery if appropriate mechanical cleansing and oral neomycin and erythromycin therapy are employed.

Surgical management of epidermoid carcinoma of the anus.

An analysis of twenty-six cases of epidermoid carcinoma of the anus from the University of Virginia Medical Center and 1,060 cases from the surgical literature has been presented. We believe this review justifies the following conclusions. (1) Considerable delay in diagnosis frequently occurs, adversely affecting the prognosis of patients with this disease. (2) Abdominoperineal resection remains the treatment of choice. Wide local excision is inadequate for most lesions, and should be reserved for lesions of the anal verge less than 2 cm in diameter with favorable histology, that is, low grade of malignancy. (3) Large lesions and those with a high grade of malignancy are associated with a poor prognosis, but even these patients may sometimes be cured with aggressive surgical excision. (4) Synchronous inguinal node metastases are associated with a poor prognosis, but an occasional patient may be cured by iliofemoral node dissection. (5) Iliofemoral node dissection is indicated for metachronous inguinal node metastases in the absence of distant spread. (6) Iliofemoral node dissection should not be performed if these nodes are not clinically involved with metastases. Approximately 70 per cent of these patients will not need this procedure and would therefore have this resection and its attendant morbidity unnecessarily.

A comparative appraisal of emphysematous cholecystitis.

There is ample evidence from this retrospective comparison to indicate that emphysematous cholecystitis does merit clinical distinction apart from acute cholecystitis. It is an acute infection of the gallbladder caused by a specific group of bacteria that may be aided by some aspect of local ischemia. Cholelithiasis does not seem to be a major factor in the pathogenesis of emphysematous cholecystitis, and this, in association with some dependence upon ischemia, may account for the predominance of this disease in males rather than females. Gangrene is a common feature of the pathologic process, and thus it is not surprising that the diagnosis of emphysematous cholecystitis implies a risk of gallbladder perforation that is five times that expected from ordinary acute cholecystitis. The key to identifying this disease is the plain abdominal roentgenogram which in most instances will make the diagnosis and provide an impetus for early operative intervention.

Pancreatic and periampullary carcinoma. Experience with 200 patients over a 12 year period.

The operative management of 200 patients with pancreatic and periampullary cancer was reviewed. Patients with metastatic disease and biliary obstruction are best treated by the nonoperative techniques of biopsy and internal biliary drainage if technically feasible. For patients who undergo exploration and are found to be candidates for a bypass procedure, both biliary and gastroduodenal bypass should be performed. Lymph node involvement and age of the patient were found to be significant variables in determining the candidates suitable for curative resection. A definite incidence of multicentricity was found in patients undergoing total pancreatectomy for ductal carcinoma of the pancreas; however, significant problems with diabetic management arose from this procedure. The primary site of the lesion as well as the intelligence and socioeconomic background of the patient should dictate the type of resection employed. Pancreatoduodenectomy (Whipple procedure) is recommended for periampullary cancers other than pancreatic carcinoma, while total pancreatectomy may be appropriate in selected patients. However, there has been no evidence thus far in this early trial with total pancreatectomy that more complete resection of the pancreas leads to longer survival.

Treatment of biliary obstruction caused by metastatic cancer.

Over an 8-year period, among 41 patients with obstructive jaundice caused by metastases to the liver or lymph nodes adjacent to the porta hepatis, palliative biliary decompression was established surgically in 11, by percutaneous transhepatic biliary drainage (PTBD) in 25, and by both methods in 2. Three patients had no drainage procedure performed. Early mortality after drainage occurred in 6 of 38 patients, and the median survivals (actuarial) for the remaining 32 patients were 4.5 months for the surgical group (range 2 to 21 months) and 4 months for the PTBD group (range 2 to 14 months). Although there were trends toward more frequent hospital readmissions and episodes of cholangitis in the PTBD group, the only statistically significant difference was in the number of catheter manipulations required. We concluded that when patients develop obstructive jaundice as a manifestation of metastatic cancer, useful palliation can be achieved by either surgical or percutaneous decompression.

Bronchial submucosal needle aspiration performed through the fiberoptic bronchoscope.

Retrospective review of 251 bronchial submucosal needle aspirations obtained from 171 patients with unsuspected pulmonary malignancy showed that adequate cytologic material was obtained in 87.6% of the aspirations. Eighty-one patients were found to have primary bronchogenic carcinomas (with a visible endobronchial tumor in 39), and 21 had secondary pulmonary metastases. The overall diagnostic accuracy of bronchial submucosal aspiration was 81%, with only four definite false-negative and no false-positive results. The diagnostic accuracy was 82% for bronchial brushing, 71% for forceps biopsy, 67% for postbronchoscopy sputum cytology and 46% for bronchial washing. The major advantage of the submucosal aspiration technique was in evaluating mural mucosal lesions, especially those covered with intact mucosa, that were not readily accessible to forceps biopsy or successful brush sampling. Negative results from a needle aspiration must be interpreted with caution because of the small area a single sample represents. Multiple sequential submucosal aspirations may be helpful in assessing the resectability of bronchial neoplasms. No complications have been encountered with this technique.

Abortion and nursing: a legal update.

PIP: Almost 2 decades after the Supreme Court's landmark decision in Roe v. Wade, nurses' refusal to assist in abortions is still in question. There are about 1.6 million abortions a year. If Congress passes the Freedom of Choice Act, American women will be guaranteed continued access to abortion. But the effect of new regulations on 2 million nurses is the issue. Title VI of the Civil Rights Act of 1964 protects those who refuse to participate in abortions because of their religious beliefs. Several states have also enacted laws giving the right to health care workers to refuse to participate on ethical grounds. In Florida a staffer at an ambulatory care center was demoted after refusing to assist in an abortion. The appeals court ruled in the nurse's favor, stating that she should have been given a different assignment. Nurses who oppose abortion are advised by attorneys not to accept jobs where they are likely to be expected to assist in them. A New York City nurse refused to assist in an abortion and was reassigned to an administrative position, which she contested. The arbitrator restored her to her original position indicating that if the Freedom of Choice Act is passed it will not eliminate a nurse's right not to assist. In 1988 the so-called gag rule was issued barring caregivers at 4000 federally funded family planning clinics serving nearly 5 million women/year from recommending abortion to patients.^ieng