Sample preparation for scanning electron microscopy of plant surfaces--horses for courses.

Plant tissues must be dehydrated for observation in most electron microscopes. Although a number of sample processing techniques have been developed for preserving plant tissues in their original form and structure, none of them are guaranteed artefact-free. The current paper reviews common scanning electron microscopy techniques and the sample preparation methods employed for visualisation of leaves under specific types of electron microscopes. Common artefacts introduced by specific techniques on different leaf types are discussed. Comparative examples are depicted from our lab using similar techniques; the pros and cons for specific techniques are discussed. New promising techniques and microscopes, which can alleviate some of the problems encountered in conventional methods of leaf sample processing and visualisation, are also discussed. It is concluded that the choice of technique for a specific leaf sample is dictated by the surface features that need to be preserved (such as trichomes, epidermal cells or wax microstructure), the resolution to be achieved, availability of the appropriate processing equipment and the technical capabilities of the available electron microscope.

G6PD deficiency: its role in the high prevalence of hypertension and diabetes mellitus.

Hypertension and diabetes mellitus represent increasing threats to the health of many populations. For reasons not completely understood, the prevalence of these diseases is higher in some ethnic groups than in others. The key to this puzzle may rest with the interplay of a defect of an enzyme-mediated process and the environment. Oxidative stress and impairment of synthesis or release of nitric oxide (NO) are being regarded as causative factors in the pathogenesis of hypertension, diabetes mellitus and atherosclerosis, among other conditions. Glucose-6-phosphate dehydrogenase (G6PD) deficiency has been overlooked as a cause of both oxidative stress and a decrease in the generation of nitric oxide (NO). G6PD generates nicotinamide adenine dinucleotide phosphate (NADPH), a co-factor in the synthesis of nitric oxide. There is impairment of the production of nitric oxide superoxide and hydrogen peroxide in G6PD-deficient granulocytes. In the polyol pathway, G6PD deficiency causes hyperglycemia, making more glucose available for the non-enzymatic production of advanced glycosylation end products (AGE's), which also causes an increase in superoxide anions and a quenching of nitric oxide. Currently, there are 200 million people worldwide with red cell x-linked chromosome defects who, with the persistent ingestion of refined carbohydrates, are at greater risk of developing hypertension or diabetes mellitus than those racial groups without the defect.

Diet, diabetes, hypertension and blacks.

The prevalence of non insulin dependent diabetes mellitus (NIDDM) is increasing in all populations. This increment has been correlated with changes in lifestyle, particularly in eating behavior. Migration studies strongly suggest that NIDDM becomes more common when lifestyle factors interact with genetic susceptibility. Blacks have a higher prevalence of NIDDM than whites. In this study, it is suggested that persistent hyperglycemia mediated through the main carbohydrate of the Western diet-wheat, as white flour and whole wheat-in combination with partial or complete glucose 6-phosphate dehydrogenase deficiency are possible factors for the higher prevalence of NIDDM in blacks.

Community-acquired methicillin-resistant Staphylococcus aureus in children with no identified predisposing risk.

CONTEXT: Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections in children have occurred primarily in individuals with recognized predisposing risks. Community-acquired MRSA infections in the absence of identified risk factors have been reported infrequently. OBJECTIVES: To determine whether community-acquired MRSA infections in children with no identified predisposing risks are increasing and to define the spectrum of disease associated with MRSA isolation. DESIGN: Retrospective review of medical records. PATIENTS: Hospitalized children with S aureus isolated between August 1988 and July 1990 (1988-1990) and between August 1993 and July 1995 (1993-1995). SETTING: The University of Chicago Children's Hospital. MAIN OUTCOME MEASURES: Prevalence of community-acquired MRSA over time, infecting vs colonizing isolates, and risk factors for disease. RESULTS: The number of children hospitalized with community-acquired MRSA disease increased from 8 in 1988-1990 to 35 in 1993-1995. Moreover, the prevalence of community-acquired MRSA without identified risk increased from 10 per 100000 admissions in 1988-1990 to 259 per 100000 admissions in 1993-1995 (P<.001), and a greater proportion of isolates produced clinical infection. The clinical syndromes associated with MRSA in children without identified risk were similar to those associated with community-acquired methicillin-susceptible S aureus. Notably, 7 (70%) of 10 community-acquired MRSA isolates obtained from children with an identified risk were nonsusceptible to at least 2 drugs, compared with only 6 (24%) of 25 isolates obtained from children without an identified risk (P=.02). CONCLUSIONS: These findings demonstrate that the prevalence of community-acquired MRSA among children without identified risk factors is increasing.

Barnett continent intestinal reservoir. Multicenter experience with an alternative to the Brooke ileostomy.

PURPOSE: Since 1988, surgeons at five hospitals have been performing the Barnett continent intestinal reservoir (BCIR). The BCIR includes modifications to the original Kock pouch, designed to reduce the incidence of valve slippage and fistula formation. Principle modifications include an intestinal collar, an isoperistaltic valve, and a lateral pouch design. METHOD: This unique collaborative study includes 510 ulcerative colitis or familial polyposis patients, with a follow-up time from one to five years postoperatively. RESULTS: Ninety-two percent still have functioning reservoirs. Six and one-half percent have had their pouches removed and replaced with conventional Brooke ileostomies. Reoperation rate for major pouch-related complications (other than pouch removal) was 12.8 percent. These complications included slipped valve (6.3 percent), valve fistulas (4.5 percent), and pouch fistulas (6.3 percent). Several questions were administered to patients whose responses revealed a significant improvement in general quality of life, state of mind, and overall health. CONCLUSIONS: The BCIR represents a successful alternative to patients with a conventional Brooke ileostomy or those who are not candidates for the ileal pouch-anal anastomosis.

Supporting evidence for the use of cassava (Manihot esculeta): products instead of Wheat flour products in the diet of the diabetic

The extent of blood glucose increase produced by products of cassava and wheat flour were compared in experiments performed in cars and rats. In normal anaesthetized cats, a meal of 500 mg grated cassava preparations produced a mean maximum blood glucose increase which is 200% less than the mean maximum blood glucose increase produced bu a meal of 500 mg wheat flour preparation. In diabetic rats, a 20 gm homogenous mixture, consisting of 50% cassava bammy and 50%rat chow that was eaten within a 24-hour period, produced a mean blood glucose increase produced by a 20 gm homogeneous mixture, consisting of 50% wheat flour bread and 50% rat chow and eaten over a similar period of time. The lower glucaemic responses of the cassava preparations therefore represent significant advantages over wheat flour preparations, for its (cassava preparation) inclusion in the diet of the diabetic

Secretagogue-produced duodenal ulcers in the rat.

Duodenal ulcers were produced in rats by the subcutaneous infusion for 6-48 hours of two gastric secretagogues in combination: pentagastrin (2 or 4 microgram kg-1 min-1) and carbachol (0-4 or 0-8 microgram kg-1 min-1). With increasing duration of infusion and higher doses there were increases in the incidence, severity, number and perforation rate of duodenal ulcers, their caudad distribution and mortality from peritonitis. This method of producing duodenal ulcers may sufficiently resemble the clinical situation to provide a model for the study of anti-ulcer drugs and the natural history of duodenal ulcers.

Gastrin, antral g cells, and gastric acid in secretagogue-induced and antihistamine-inhibited duodenal ulcers.

In fasting control rats there was continuous basal gastric acid secretion, with a low plasma gastrin and antral G-cells full or immunofluroescent gastrin. After subcutaneous infusion of the gastric secretagogues, pentagastrin + carbachol, there was a six-hour period of gastric hypersecretion, but no change in plasma and G-cell gastrin. Pretreatment with the antihistamine derivative, Pfizer UK-9040, decreased both basal and stimulated acid secretion, whereas plasma gastrin levels increased and the antral G-cells were emptied of gastrin. These results suggest that this antihistamine derivative decreases gastric acid secretion by a direct action on the parietal cells and not by reducing gastrin release from the G-cells. The increased release of gastrin from the G-cells may be secondary to decreased gastric acid production, or more probably by a direct stimulation of the antral G-cells.

Prevention of secretagogue-induced ulcers in the rat.

An inhibitor of gastric secretion, Pfizer UK -9040, a derivative of the antihistamine triprolidine, was given orally 50 to 100 mg per kg 1 hr before and at various times during a 24-hr subcutanwous infusion of ulcerogenic secretagogues. The higher the dose and the more frequent the dosage, the lower was the incidence, severity, number, and perforations of duodenal ulcers. The mechanisms by which UK -9040 prevents these ulcers is probably inhibition of gastric secretion.

Natural history and morphology of secretagogue-induced duodenal ulcers in rats.

Morphologically typical ulcers were produced in the first part of the duodenum in 300 male Wistar rats by subcutaneous infusion for 24 hr of pentagastrin (4 mug per kg-min) and carbachol (0.8 mug per kg-min). Groups of animals were killed daily for 14 days, and their stomachs and duodenums were examined. Lesions were graded on a seven-point scale: 0, normal; 1, inflammation; 2, petechiae; 3, erosions; 4, definite ulcer crater; 5, penetrating ulcer; and 6, perforated ulcer. Every animal developed one or more definite ulcers (grades 4 to 6). Within the first 48 hr 34% of the animals died with grade 6 ulcers. Ulcer healing began on the 1st postinfusion day when 3 of 46 rats had erosions (grade 3) but no definite ulcer craters. By the following day some animals were found with normal mucosa. After the 5th postinfusion day the few remaining grade 5 or 6 ulcers were those which had perforated and sealed spontaneously. These long-standing ulcers had several features similar to human chronic duodenal ulcers. By the 12th postinfusion day definite ulcers were no longer seen. In this study duodenal ulcers have not only been produced in rats by secretagogues, but have also been observed to heal. This model can be used to compare the efficacy of various antiulcer regimens on ulcer healing.

Pneumonectomy by "en masse" stapling of hilar vessels.

Since the development of automatic surgical stapling instruments in the Soviet Union in the 1950s and their description in the American literature in 1961, American surgeons have used them for a variety of pulmonary resections. However, there is no account of their use in this country for pneumonectomy by "en masse" stapling of the hilar structures. We have used this whenever it was applicable in 41 consecutive pneumonectomies since 1967. There were 2 postoperative deaths, 1 due to pulmonary embolism and the other to myocardial infarction. There were no complications attributable to the operative technique used. The only empyema developed nine months postoperatively and was not accompanied by bronchial fistula. Cancer-free survival was 43% at two and one-half years and 33% at five years. The technique of en masse stapling of hilar vessels renders pneumonectomy easier, safer, and faster than the technique of individual ligation.