Limitations of the reporter green fluorescent protein under simulated tumor conditions.

This paper reports a detailed analysis of the effect of low oxygen conditions (hypoxia) on the reporter green fluorescent protein (GFP). It questions the feasibility of using GFP for gene expression studies under tumor conditions. Hypoxia is a characteristic of both experimental and clinical tumors. Several important factors are pointed out which need to be considered when using GFP as reporter gene. GFP fluorescence is the final product of a long and complex pathway involving transcription, translation, and posttranslational modifications. All of these steps may be affected by the availability of oxygen. We show specifically that cellular GFP fluorescence decreased with reduced oxygenation, anoxia virtually eliminated fluorescence and protein levels, and fluorescence recovery after anoxia required 5-10 h of reoxygenation. In conclusion, GFP appears to be a good marker gene to study location or movement of proteins or cells but should be used with great caution as a reporter of gene expression under tumor conditions.

Gene delivery to hypoxic cells in vitro.

Hypoxia in solid tumours has been correlated with poor prognosis and resistance to radiation and chemotherapy. Hypoxia is also a strong stimulus for gene expression. We previously proposed a gene therapy approach which exploits the presence of severe hypoxia in tumours for the induction of therapeutic genes. Hypoxic cells are known to have a reduced metabolic rate, transcription and translation. These facts may prevent gene transfer and therefore warranted further investigation. In this paper the feasibility of gene delivery in vitro under tumour conditions was demonstrated. DNA was delivered in vitro using a peptide-mediated non-viral system. Across a range of oxygen tensions and mammalian cell lines (including human tumour and endothelial cells) it was shown that hypoxic cells could be transfected. Transfection efficiencies varied depending on the level of hypoxia, cell characteristics and gene promoters used. An in vitro model of hypoxia/reoxygenation, designed to mimic the variable nature of tumour hypoxia, showed that hypoxic preconditioning and reoxygenation alone did not reduce transfection efficiency significantly; only chronic anoxia reduced transfection. The fact that neither intermediate hypoxia nor intermittent anoxia significantly reduced transfection is promising for future hypoxia-targeted gene therapy strategies.

Sex steroids and bone density in premenopausal and perimenopausal women.

Bone density begins to decline in women before menopause, and the degree of bone loss is variable. We performed a cross-sectional analysis on the entry data of a 5-yr prospective study of risk factors for osteoporosis to determine the correlation of bone density with serum sex steroid concentrations and body weight. We studied 292 healthy white women, aged 35-50 yr, who were menstruating regularly or had had menses in the past 12 months. Blood samples were drawn in the early follicular phase for estradiol (E2), testosterone (T), dehydroepiandrosterone sulfate, and sex hormone-binding globulin (SHBG). Free levels of E2 (FE2) and T (FT) were calculated based on total T and E2, SHBG, and albumin levels. Women were classified as premenopausal (FSH, less than 12 U/L) and perimenopausal (FSH greater than or equal to 12 U/L; n = 46; 16%). Bone density was measured by dual photon absorptiometry of the lumbar spine (L2-L4) and hip and by single photon absorptiometry of the wrist. Perimenopausal women were older than premenopausal women (45.5 +/- 3.5 and 41.0 +/- 3.9 yr, respectively), but did not differ in height or weight. While bone density did not correlate with age in each group, perimenopausal women had significantly lower bone density at the L2-L4 and femoral neck (L2-L4, 1.18 +/- 0.14 in perimenopausal and 1.24 +/- 0.12 g/cm2 in premenopausal women; femur, 0.84 +/- 0.11 in perimenopausal and 0.90 +/- 0.11 g/cm2 in premenopausal women; P less than 0.005). Body weight showed the strongest positive correlation with bone density. Log FT, percent FT, and FE2 percent correlated positively with bone density, even after controlling for weight. Log SHBG was negatively correlated with bone density in premenopausal women at the hip and wrist after controlling for weight. FSH was inversely correlated with bone density, and E2 and T were lower in perimenopausal than premenopausal women. These data suggest that women who are still menstruating may have relative deficiencies in both E2 and T, with reduced bone densities as a consequence.

Effective case presentations--an important clinical skill for nurse practitioners.

Effective case presentations are an important component of the nurse practitioner's skills, yet very little literature exists to guide the development of this skill, and frequently little priority is given to teaching this skill during the education of the nurse practitioner. This report discusses the importance of effective case presentations, describes the organization of the presentation, and outlines the appropriate information to be included. The main components of a case presentation--introduction, history of the present illness, physical examination, diagnostic studies, differential diagnosis, management, and summary of the case--are discussed in detail. Examples of a formal and an informal case presentation are presented and used to illustrate key points in the text.

Osteoporosis: significance, risk factors and treatment.

Osteoporosis is a serious metabolic bone disorder that results in fractures of the wrist, hip and vertebrae. These fractures frequently occur with little or no trauma. Osteoporosis is seen more frequently in women than men. While the pathogenesis of osteoporosis is incompletely understood at this time, certain risk factors are emerging as important. Among the more important of these are family history, low calcium intake, early menopause and sedentary lifestyle. Other suggested risk factors include high intakes of protein, alcohol and caffeine; low body weight; exercise-induced amenorrhea; and cigarette smoking. No single therapy or combination of therapies for osteoporosis has proven to be uniformly successful. Indeed, once fractures occur, full restoration of the skeleton may not be possible. Currently, calcium, exercise and estrogen form the treatment for osteoporosis. When these conservative measures are ineffective or inadequate, treatment with fluoride, calcitonin, vitamin D or anabolic steroids may be attempted. Research to clearly identify and quantify risk factors and find an effective treatment for osteoporosis continues.

Promoting health in international travel.

As international travel becomes more frequent, consumers are expressing a need for current, comprehensive information about disease prevention abroad. Many health care providers lack the knowledge to respond to this need. This article provides information on general preventive measures for commonly encountered infectious diseases and discusses the use of vaccines and chemoprophylaxis. Legal requirements for the quarantinable diseases are reviewed. Readers are directed to authoritative references, and considerations to be addressed in the pretravel visit are outlined. Disease prevention in international travel is an important aspect of health promotion, particularly in our mobile society. With development of the necessary skills and knowledge, nurse practitioners can and should play a significant role in this area.