Ampicillin-sulbactam susceptibility testing criteria

In vitro studies in five different medical centers documented the susceptibility of 2,440 consecutive isolates of theEnterobacteriaceae against ampicillin-sulbactam disks of different potencies. For determination of MICs, both 2:1 or 1:1 ratios were used as long as the concentrations of sulbactam at the breakpoints remained the same, i.e. MIC 16/8.0 µg/ml or 8.0/8.0 µg/ml for the susceptible category. Disks containing 10 µg of ampicillin and 10 µg of sulbactam are still to be preferred with interpretive criteria of 15 mm for susceptible and 11 mm for resistant (MIC 64/32 µg/ml or 32/32 µg/ml). The reliability of the disk test actually diminished when the amount of sulbactam in the disk was increased.     

Mechanism of toxin secretion by Vibrio cholerae investigated in strains harboring plasmids that encode heat-labile enterotoxins of Escherichia coli.

A genetically engineered Vibrio cholerae strain from which the cholera toxin genes had previously been deleted was used as a host in which to study the expression and secretion of related toxins and their subunits. Recombinant plasmids encoding heat-labile enterotoxins (LTs) from Escherichia coli of human and porcine origin were expressed in the V. cholerae host, and this resulted in the secretion of the LTs into the extracellular milieu. The secreted LTs were isolated and it was found that the A subunits of human and porcine LT were "unnicked" polypeptides, which indicates that nicking is not obligatory for toxin secretion. V. cholerae strains were also constructed that harbored plasmids encoding either the A or the B subunits of human LT (A+B-, or A-B+). Approximately 90% of the B subunits were secreted from the A-B+ strain, while all of the A subunits expressed by the A+B- strain remained cell associated. This implies that strains synthesizing both subunits assemble the A and B subunits prior to their secretion. We propose that the entry of the toxin into the secretory step of the export pathway is mediated by a secretory apparatus that recognizes structural domains within the B subunit of LT.     

Lung carcinoma: survey of 2286 cases with emphasis on small cell type.

Lung carcinoma is the commonest major malignancy in men in the United States and its incidence is increasing rapidly in women. It is estimated that there will have been 117,000 new cases and 101,300 deaths in 1980. The 2286 patients with lung carcinoma admitted to the Hospital of the University of Mississippi from 1955 to 1980 were reviewed by decades of chronology and of life, with respect to age, cell type, sex and racial incidence. The greatest age incidence was in the sixth and seventh decades; cell types overall were epidermoid (45% of the patients), adenocarcinoma (12% of the patients), small (oat) cell (21% of the patients), and others (22% of the patients). There was a steady increase in the incidence of disease in females, adjusted for total hospital admissions, and a less certain increase among black patients. Twenty-eight per cent of 250 patients with small cell carcinoma so studied exhibited some feature of the paraneoplastic or paraendocrine syndromes. In 41 patients with small cell carcinoma treated with multiple drug chemotherapy, there was an overall response rate of 50% and an additional "stable disease" rate of 28%. Mean survival period in this group was 52 weeks, compared with 12 weeks in patients whose diseases went untreated. Clearly, definite progress is being made, not only in our knowledge of the biology of lung carcinoma, in general, but in the treatment of small cell carcinoma in particular.     

Heavy-ion-induced cataractogenesis.

Cataract formation following heavy ion exposure (O+8) was noted in three rhesus monkeys secondary to a study of retinal effects. The pathogenesis of these lens changes follows many, but not all, of the characteristics for "radiation cataracts." The ring-shaped opacity was not noted to occur. Posterior capsular changes were noted initially and followed through the formation of a mature cataract.     

Malignant transformation of aneurysmal bone cyst, with an analysis of the literature

An 11-year-old girl had a lytic, benign-appearing, expansive lesion of the distal tibia radiologically interpreted as an aneurysmal bone cyst (ABC). Tissue from two extensive curettage procedures was also histologically diagnosed as ABC. Approximately 50 months after the onset of symptoms, and 28 months after her last curettage, a highly pleomorphic osteosarcoma developed. The patient had not received prior radiation therapy. The cases in the literature of possible malignant transformation of ABC are reviewed. The authors separate their case from telangiectatic osteosarcoma, and from "aneurysmal bone cyst-like osteosarcoma."     

The stability of ascorbic acid in TPN mixtures stored in a multilayered bag

Because of the susceptibility of some vitamins to oxidation, they are not normally added to TPN mixtures until shortly before addministration. Vitamin C (ascorbic acid) is oxidised rapidly, especially in the presence of trace elements. The aim of this study was to investigate the stability of ascorbic acid in complete TPN mixtures in Ultrastab multilayer bags, which are designed to reduce oxygen transmission and thus oxidation, in comparison with standard EVA bags. Ascorbic acid content was determined in two typical TPN mixtures providing 16 g nitrogen, 2000 kilocalories, electrolytes, trace elements and multivitamins, with and without fat emulsion, during storage at 5 degrees C for up to 3 months. In EVA bags ascorbic acid degraded by more than 75% during 24 h and was undetectable in 2-3 days. In contrast, there was a comparatively small initial loss of 15-30% ascorbic acid in mixtures stored in multilayer bags, with little further loss during 1-3 months. Bags containing fat emulsion retained higher concentrations of ascorbic acid after storage compared to those without fat emulsion, but all mixtures in multilayer bags maintained 60-80% ascorbic acid activity after 3 months. Since ascorbic acid is the most oxygen-sensitive vitamin, complete TPN mixtures with vitamins could be compounded in multilayer bags for an extended shelf life, rather than admixing just prior to administration.     

The standardized mortality ratio and life expectancy.

This paper develops a theoretical relation between the standardized mortality ratio (SMR) and the expected years of life and establishes a regression equation for easy conversion between these two statistics. The mathematical expression of the derived relation is an approximation, requiring an assumption of constant age-specific mortality ratios. It underestimates the "true" value calculated based on life table technique when the age-specific mortality ratios increase with age. This equation provides a conservative method to estimate the expected years of life for cohort mortality studies and facilitates an assessment of the impact of work-related factors on the length of life of the worker. It also allows one to convert the SMR to life expectancy in smaller studies whose sole objective is to determine the SMR in a working population. A 1% decrease (or increase) in the standardized mortality ratio will result in 0.1373 years increased (or decreased) life expectancy based on white male data for the US population. Furthermore, with data from 14 large oil refinery and chemical worker cohorts of white males, the "derived" expected years of life based on the regression equation closely predicts the corresponding value calculated using a standard life table technique. This statistical equation is expected to have practical applications when used in conjunction with the SMR to provide an approximate measure of life expectancy, a term and statistic familiar to most lay people.     

The Sequoia circular fixator for limb lengthening

With the Sequoia fixator, lengthenings can be achieved based on the clinical facts of the case. The device is a modular apparatus that can perform corrections in several planes, and, if necessary, in a septic environment. In our opinion, a "lengthener surgeon" is one who can foresee problems and take appropriate steps to prevent them. Likewise, the surgeon must act as the coordinator of an entire team. A successful lengthening is 5% surgery and 95% postoperative nursing and physiotherapy care. In the future, a number of changes will simplify postoperative management: 1. Composite carbon rings will make the frames radiolucent and one third lighter than those made of stainless steel. Automatic tensioners will help maintain steady tension on the wires. 2. Digital analysis of the callus will provide norms of consolidation, allowing faster fixator removal and conversion to an orthosis. 3. Incorporating the foot in the frame to overcome equinus will eliminate the need for tenotomy. We believe that monolateral and ring fixators can work together in certain locations. That is why we proposed, at the 18th Societé Internationale de Chirurgie Orthopédique et Traumatologique meeting, a combined monolateral-ring construct that can be used for lengthening throughout the proximal femoral metaphysis.     

A developmental switch in B lymphopoiesis.

B and T lymphocytes are generated from hematopoietic stem cells during both fetal and adult life. A critical unresolved issue is whether the differentiation pathways in lymphopoiesis are the same in fetal and adult animals or whether they differ, similar to the hemoglobin switch in erythropoiesis. We report here that a developmental switch occurs in B lymphopoiesis. We isolated "pro-B" cells (i.e., cells that have initiated, but not completed, heavy-chain gene rearrangement) from fetal and adult sources and investigated their B-cell progeny generated both in vitro and in vivo. Most of the cells from fetal liver, but few from adult bone marrow, expressed CD5. Further, fetal pro-B cells failed to generate cells expressing high levels of IgD in severe combined immunodeficiency mice, whereas adult pro-B cells gave rise to CD5-B cells bearing IgD at levels comparable to the bulk of cells in the spleen of adult mice. Thus, all committed B progenitors in fetal liver of day 16 gestation mice give rise to phenotypically distinct progeny when compared to cells at a comparable differentiation stage in the bone marrow of adult animals. We conclude that the cohort of B-lineage progenitors in early fetal development is committed to a differentiation pathway distinct from that seen in the adult.