Heary metals and lipofuscinogenesis. A study on myocardial cells cultured under varying oxidative stress

The aim of this study was to examine the influence on lipofuscinogenesis of a number of transition and non-transition heavy metals in cultured post-mitotic cells (neonatal rat myocytes) at varying oxidative stress. The effects of Al, Cd, Cr, Cu, Hg, Pb and Zn, added to the medium as chlorides, were examined after 14 days in culture under 5, 20 and 40% ambient oxygen. Lipofuscin was quantified by microspectrofluorometry of individual cells. The addition of Al (40 microM), Cd (40 nM), Hg (30 microM) and Pb (40 microM) to the culture growth medium markedly increased the amount of intracellular lipofuscin, whereas Cr (40 microM), Cu (40 microM) and Zn (40 microM) had the opposite effect. Transmission electron microscopic examination of the myocytes showed greatly increased numbers of autophagic vacuoles in cells exposed to those heavy metals that increased lipofuscin formation. This effect was most pronounced when cells were grown at high (40%) oxygen tension. Possible explanations for the metal augmented pigment formation may be (i) inhibition of lysosomal enzymes, (ii) catalytic interference with peroxidative reactions, or (iii) general toxicity with unspecifically increased autophagocytosis. The decreased pigment accumulation after the addition of Zn, Cr and Cu may, at least partly, be related to the replacement of iron, which has catalytic activity in Fenton reactions.

A novel hypothesis of lipofuscinogenesis and cellular aging based on interactions between oxidative stress and autophagocytosis

Based on a series of experiments, using cultured postmitotic neonatal rat cardiac myocytes as a model system, we present a novel hypothesis of lipofuscin formation. This hypothesis proposes that lipofuscin is formed within secondary lysosomes due to an interplay of two processes, the production of partially reduced oxygen species by mitochondria and the autophagocytotic degradation within secondary lysosomes. Specifically, it is proposed that H2O2 generated by mitochondria and other organelles permeates into the lumen of secondary lysosomes, which contain iron derived from cellular structures undergoing intralysosomal degradation. The interaction between reactive ferrous iron and H2O2 results, via Fenton-type mechanisms, in the generation of hydroxyl free radicals (OH), inducing lipid peroxidation and eventually leading to intermolecular cross-linking and lipofuscin formation. Additionally, mitochondria undergoing intralysosomal decomposition might continue for a certain period to produce superoxide anion radicals (O2-) and thus also H2O2. This model of lipofuscinogenesis could satisfactorily explain the variations observed in the rates of lipofuscinogenesis among different postmitotic cell types in various species. Such variations might arise from a variety of factors including differences in the efficiency of the 'anti-oxidative shield', rate of H2O2 generation, amount of chain-breaking antioxidants, mode of intralysosomal iron chelation, rate of autophagocytosis as well as degree of efficiency of the intralysosomal hydrolytic enzymes.

Calculating and updating nursing turnover costs

A detailed study allowed FY 1988 nursing turnover costs to be calculated at four southeastern hospitals. These turnover costs were later updated using a procedure incorporating Consumer Price Index information. This procedure allows nurse administrators to determine and update turnover costs, to accurately evaluate the impact of nursing turnover, and to facilitate resource allocation.

A combined intra- and extra-articular reconstruction using a carbon-dacron composite prosthesis for chronic anterior cruciate instability. A two to six-year follow-up study

Fifty patients with chronic symptomatic anterior cruciate insufficiency underwent ligamentous reconstruction using the "Westminster Composite Prosthesis" which consists of a central core of carbon fibre with an external weave of polyester. In 42 patients, the prosthesis was used as an augmentation within a tube of ilio-tibial tract, combined with a MacIntosh's extraarticular reconstruction. The prosthetic replacement alone was used in eight patients where there had been a previous extraarticular reconstruction and was associated with only fair results. The average age of the patients at operation was 28.5 years (range 18 to 50 years); instability of the knee had been present for a mean of 5.3 years and the average follow-up was 3.8 years (range 2 to 6 years). Assessment included subjective functional rating (Lysholm knee score) and clinical examination for instability. Thirty-seven patients (74%) had a good or excellent result, 11 (22%) had a fair result and two (4%) had a poor result. The Lachman test was grade I or less in 35 patients and the pivot shift sign was eliminated in 37 patients. Clinical signs of instability correlated well with the Lysholm knee score (p less than 0.001). Twenty-two unselected patients (44%) underwent an arthroscopic assessment and biopsy of the "neoligament" at an average of 10.4 months post-operatively. The prosthesis was found to be stable and well covered by a thick fibrous sheath ("neoligament") in 19 patients. The prosthesis was partially ruptured in two patients and completely disrupted in one. Thirty-two patients (64%) returned to their previous sports and 13 of them (26%) achieved their pre-injury level of performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive face mask mechanical ventilation in patients with acute hypercapnic respiratory failure

Mechanically assisted intermittent positive-pressure ventilation effectively provides ventilatory support in patients with respiratory failure but it requires placing an artificial airway. We have previously reported our successful experience delivering mechanical ventilation via a face mask (FMMV) rather than with an endotracheal tube in a pilot study of patients with acute respiratory failure. The present investigation evaluated an additional 18 patients with hypercapnic respiratory failure to determine the efficacy of FMMV in a more homogeneous group and to determine factors predicting its success. FMMV was successful in avoiding intubation in 13 of the 18 patients. A significant initial improvement in PCO2 (greater than 16 percent decrease) and in pH (from less than 7.30 to greater than 7.30) predicted success. The five patients who failed on FMMV required endotracheal intubation because of inability to improve gas exchange (three patients), apnea due to sedatives (one patient), and management of secretions (one patient). FMMV was generally well accepted with only two patients withdrawn because of intolerance of the mask. The mean duration of FMMV was 25 h. Complications were seen in only two patients (11 percent): aspiration (one patient) and mild skin necrosis (one patient). Seven patients entered the study by meeting entrance criteria after an unsuccessful extubation attempt and therefore received both forms of mechanical ventilation. All but one patient avoided reintubation, and the face mask proved to be as effective as the endotracheal tube as a conduit for delivering the mechanical tidal volume and improving gas exchange. Our findings indicate that FMMV is a viable option for short-term (one to four days) ventilatory support of patients with hypercapnic respiratory failure and insufficiency.

Staff nurse turnover costs: Part II, Measurements and results

This study demonstrated that the costs of nursing turnover can be high (over +10,000 per RN turnover), and that the potential for adverse impact on the nursing department, the hospital environment, and the healthcare environment exists. The results of this study are important, particularly in the midst of a national nursing shortage, for several reasons. CNEs are responsible for obtaining, allocating, and managing nursing department resources; knowledge of nursing turnover costs will allow them to make more informed decisions about how best to allocate scarce resources. The findings of this study are also important to hospital administrators because they demonstrate the financial impact of high rates of nursing turnover on healthcare delivery. Finally, these findings provide nurse researchers direction for future research into the costs and benefits of nursing turnover and retention activities, so that cost-effective methods of minimizing organizational costs can be determined.

Staff nurse turnover costs: Part I, A conceptual model

The impact of turnover is a major concern for the chief nurse executive. This study provides nurse administrators with information necessary to more fully understand the impact of turnover and assists them in developing and defending retention strategies. Part 1 addresses the conceptual model used to guide the study; Part 2 (May 1990) will discuss the application of the methodology to measure nursing turnover costs and the study's findings.

Epiphyseal distraction monitored by strain gauges. Results in seven children

Ten epiphyses in seven children underwent fixed-rate distraction of 0.25 mm twice daily in an attempt to achieve percutaneous leg lengthening by chondrodiatasis. The forces generated across the growth plate were recorded by means of strain gauges incorporated into the distractors. All epiphyses fractured before 33 days of lengthening. An average gain of 6.75 cm was achieved. Epiphyseal distraction at the lower femur produced many complications, but at the upper tibial epiphysis planned lengthening was achieved, with excellent bone production and few complications.

Prosthetic anterior cruciate ligaments in the rabbit. A comparison of four types of replacement

Four types of prosthetic replacement for the anterior cruciate ligament (carbon fibre, carbon fibre and Dacron composite, Dacron alone and bovine xenograft) were assessed at three, six and 12 months after implantation in the knees of New Zealand white rabbits. The synovium and both intra-articular and intra-osseous portions of the ligaments were examined macroscopically, by light microscopy and by scanning electron microscopy. All the knees showed mild synovitis, and there was no significant growth into the intra-articular part of any ligament. Carbon fibre and xenograft did not appear to be suitable materials in this animal model. The composite ligament showed short-term ingrowth of fibrous tissue only into the periphery of the sheath in its intra-osseous portion, whereas the Dacron ligament showed progressive fibrous tissue ingrowth with some bony incorporation of its outer fibres.

Tumours of the cauda equina. The problem of differential diagnosis

A retrospective study of 32 patients with primary tumours of the cauda equina is presented. Most of the patients were initially diagnosed as having prolapsed intervertebral discs and treated accordingly. The correct diagnosis was eventually made, usually after a long delay, and confirmed by myelography. Treatment consisted of laminectomy and excision of the tumour. Only one tumour was frankly malignant; all the remaining patients were relieved of their pain and the majority recovered completely. The exceptions were those patients with long-standing neurological deficits; this highlights the importance of early diagnosis and correct treatment before irreparable damage occurs.

Duffy (white) genes in a black Baltimore population

Testing of 722 black hospital patients in Baltimore for the Duffy antigens found in whites demonstrated that 36.28 percent of the patients possessed these blood proteins. This group is the largest cluster of black individuals so examined in the United States. The results may provide a genetic benchmark for the Baltimore black population and offer a comparison with blacks in other areas.

Gall-stones and oral contraceptives

An investigation into oral contraceptive use in female patients with gallstones has been undertaken. Comparison between a group of 50 young women aged 20-45 years with gall-stones and a group of young women of similar age and parity without gall-stones, shows a significantly higher incidence of contraceptive use in the gall-stone patients (p > 0·001). It is suggested that oral contraceptives may predispose pre-menopausal women to gall-stone formation and this is discussed in relationship to the physical and chemical alterations in biliary secretion produced by hormonal changes.

Preoperative diagnosis of intrahepatic mycotic aneurysm

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Skin replication procedure for the scanning electron microscope

Ani improved method for preparing polyethylene replicas of skin from silicone rubber molds was developed for examination in the scanning electron microscope. Electro micrographs of the replicas compare favorably to those of fixed tissues from the same animal. Because of the great depth of field of the scanning electron microscope, both loosely attached epidermal cells and the background epidermal surface can be seen simultaneously in sharp focus, thus providing, a more complete picture of the topography of skin.

Liver transplantation in man after an extended period of preservation by a simple technique

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