Origin and environmental setting of ancient agriculture in the lowlands of Mesoamerica.

Archaeological research in the Gulf Coast of Tabasco reveals the earliest record of maize cultivation in Mexico. The first farmers settled along beach ridges and lagoons of the Grijalva River delta. Pollen from cultivated Zea appears with evidence of forest clearing about 5100 calendar years B.C. (yr B.C.) [6200 (14)C years before the present (yr B.P.)]. Large Zea sp. pollen, typical of domesticated maize (Zea mays), appears about 5000 calendar yr B.C. (6000 yr B.P.). A Manihot sp. pollen grain dated to 4600 calendar yr B.C. (5800 yr B.P.) may be from domesticated manioc. About 2500 calendar yr B.C. (4000 yr B.P.), domesticated sunflower seeds and cotton pollen appear as farming expanded.

New antifungal agents that inhibit the growth of Candida species: dichlorinated 8-quinolinols.

Five dichlorinated 8-quinolinols (2,5- 5,6-, 3,5-, 3,7-, and 4,5-dichloro-8-quinolinol) were tested against Candida albicans and C. tropicalis in Sabouraud dextrose broth with and without bovine serum. The 5,6-, 3,5-, and 3,7-dichloro-8-quinolinols proved to be more effective than the control, 5-fluorocytosine. In cytotoxicity tests employing baby hamster kidney (BHK) cells, all test agents proved to be more cytotoxic than the control. However, the minimum inhibitory concentration (MIC) of 3,5-dichloro-8-quinolinol to both fungi was only one tenth the cytotoxic dose, suggesting that the compound may be useful as a topical or systemic antifungal agent.

Antimicrobial properties of Honduran medicinal plants.

Ninety-two plants used in the traditional pharmacopoeia of the Pech and neighboring Mestizo peoples of central Honduras are reported. The results of in vitro antimicrobial screens showed that 19 of the extracts from medicinal plants revealed signs of antifungal activity while 22 demonstrated a measurable inhibitory effect on one or more bacterial cultures. Bioassay-guided fractionation of extracts from Mikania micrantha, Neurolaena lobata and Piper aduncum produced weak to moderately active isolates. The broad spectrum of activity of the extracts helps to explain the widespread use of these plants for wound healing and other applications.

Recovery from disuse osteopenia coincident to restoration of muscle strength in mdx mice.

The objective of this study was to compare the tibial structure and the strength of the tibia during muscle weakness and after recovery in mdx mice (which demonstrate X-linked muscular dystrophy and subsequent muscle regeneration) and age-matched control mice. The extent of disuse atrophy produced by muscle weakness and recovery following restoration of normal muscle strength could then be determined. The tibiae adjacent to weakened tibialis anterior muscles of 4-week-old mdx mice had significantly reduced radiographic density (p < 0.05) and cortical thickness (p < 0.001), and increased porosity (p < 0.001) compared to age-matched controls, suggesting development of disuse osteopenia. Significantly less force was required to break mdx tibiae than age-matched control tibiae (p < 0.05). In addition, Sharpey's fiber density was reduced (p < 0.001), suggesting a weakened attachment of the tibialis anterior muscle to bone. At 12 weeks, during the period of muscle regeneration, mdx tibial cortical thickness (p < 0.001) and porosity (p < 0.01) remained significantly lower, but percent calcium and Sharpey's fiber and radiographic densities were significantly greater (p < 0.001) than in age-matched controls, suggesting that bone mineralization and muscle attachment strength had increased to above normal levels in parallel with recovery of strength by the attached muscle. By 18 weeks, mdx tibial cross-sectional area, cortical thickness, and porosity remained significantly less (p < 0.001) than normal. Although Sharpey's fiber density was greater than in age-matched controls (p < 0.001) by 18 weeks, mdx tibial percent calcium (p < 0.005) and Sharpey's fiber density (p < 0.001) were significantly reduced from levels in 12-week-old mdx animals. There was significantly less deformation of the tibia prior to fracture in mdx than control tibiae at 18 weeks of age, suggesting tibial brittleness. Thus, at the site of attachment of mdx muscle to osteopenic bone, the remodelling which accompanies recovery of muscle strength is atypical, and produces an attachment of greater strength than function appears to require. These observations suggest that data are needed regarding bone mass and muscle-bone attachments in humans with disuse osteopenia, DMD, and other neuromuscular diseases.

An electron microscopic comparison of bristle end-rounding of three commercial toothbrushes.

The results from three separate examinations using SEM photomicrographs and shape factor (SF) measurements show that Oral-B P-35 brushes have a highly significant difference in bristle end-rounding when compared to Colgate Precision and Crest Complete toothbrushes. The proportion of Oral-B P-35 bristles with highly rounded ends was substantially greater than that for Colgate Precision and Crest Complete toothbrushes. Oral-B also had fewer bristles in the very sharp-edged category than both Complete and Precision toothbrushes. Each toothbrush sample in these studies was purchased from geographically dispersed retail outlets throughout the United States. Scanning electron micrographs were made from a representative random sample of bristles, then digitized and evaluated using image analysis software. The comparisons were made on the basis of the number and distribution of bristles having varying degrees of roundness as determined by shape-factor analysis. Previous studies asserted that low shape-factor values indicate sharp bristle edges that are less conducive to good oral hygiene than end-rounded bristles with high SF values. In separate studies, Oral-B P-35 had a significantly higher number of highly end-rounded bristles than did either the Colgate Precision or Crest Complete toothbrushes. The averages for end-roundness fall in the order of Oral-B P-35 > Complete > Precision. Thus we conclude that the potential for harming dental tissues is less for the Oral-B P-35 toothbrush than for either the Colgate Precision or Crest Complete toothbrushes.

Comparison of marginal adaptation between direct and indirect composites.

The evaluation of composite resin as a posterior restorative material has been slow and attended by several problems. Gap formation has been considered a serious problem by many researchers. The purpose of this in vitro study is to compare the marginal adaptation of posterior composite resins placed by a direct method with those placed by an indirect method utilizing flexible dyes. Conclusions drawn from the results of this study are that both techniques produced marginal gaps. Also there were no differences in the width of marginal gaps in the composite resin restorations placed by our direct or indirect methods, and no marginal gap differences were observed as a result of anatomical location.

Shear bond strengths of prosthodontic adhesive systems to a nickel-chromium-beryllium alloy.

Panavia, a composite resin luting agent containing phosphate monomers, bonds chemically to air-abraded base metal alloys and is particularly suited for cementing resin-bonded retainers. Another adhesive methodology (Silicoater system) incorporates a pyrolytically applied silica layer to metal substrates to promote bonding of a resin adhesive. The object of this study was to compare prosthodontic adhesive systems that incorporated the Silicoater system and/or Panavia. The results showed that the surface treatment that provided significantly higher shear bond strengths was the Silicoater system and a layer of unfilled resin. A second test evaluated use of Panavia as a metal opaquing material beneath laboratory light-curing resins. Results showed that Panavia Opaque material was displaced peripherally during placement of overlying laboratory composite resin veneers. This resulted in an uneven intermediate layer of Panavia.

Toothbrush abrasion caused by different dentifrices.

The purpose of this study was to evaluate the abrasive effect on toothbrush bristles caused by three brands of commercially distributed dentifrices: Colgate regular flavor, Crest tartar-control formula, and Caffree gel. New brushes and brushes tested in distilled water served as controls. Scanning electron micrographs were taken of all test samples, randomly labeled, then presented to independent evaluators. Each bristle evaluated was assigned to one of seven wear categories adapted from previous studies. Crest and Caffree produced the most bristle wear and were not significantly different from each other. Colgate and water resulted in less wear, and new brushes the least wear. These results demonstrate that the effective life of a toothbrush will vary with the type of dentifrice used.

Effects of drug-induced pulmonary phospholipidosis on lung mechanics in rats.

Chronic administration of amphiphilic drugs to rats induces pulmonary phospholipidosis (P), a disease characterized by accumulation of phospholipids and large foamy macrophages in alveolar spaces. We investigated whether P induced by chlorphentermine (CPH) causes changes in lung volumes and mechanics in this species. Groups of rats were fed CPH (50 mg.kg-1.day-1) for 1, 2, 3, 5, 9, and 14 wk. After each treatment period, lung volumes and mechanics were studied in the anesthetized, paralyzed, supine rat. Partial pressure-volume (PV) curves were developed at 3 and 6 ml above functional residual capacity (FRC; PV3, PV6), followed by maximal [up to total lung capacity (TLC)] PV curves. FRC was determined by saline displacement. Lungs were then fixed for histopathological examination. A subgroup of animals was allowed a recovery period of 6 wk, after the 9 wk of CPH administration. Pair-fed rats served as controls (CTR) at each time point. Lung weight increased in CPH-treated (CPH-T) rats from 1.5 +/- 0.2 (SD) g at week 1 to 5.8 +/- 1.4 g at week 14, reflecting the development of P. TLC, FRC, transpulmonary pressure at FRC, the shape of maximal PV curves, and static expiratory lung compliance computed from maximal PV data points did not change in CPH-T rats. However, partial PV curves of CPH-T lungs (particularly PV3) were shifted downward and to the right of those of CTR at 2, 3, 5, and 9 wk, indicating increased recoil pressure in phospholipidotic lungs at these time points.(ABSTRACT TRUNCATED AT 250 WORDS)

Analyses of dental pulp in restored teeth.

Restored teeth were extracted from test animals at four time intervals (1 hour, 1 day, 1 week, and 3 months) following amalgam insertion. Extracted teeth were frozen in liquid nitrogen, cryo-fractured so as to expose the pulps and then freeze-dried. Pulps were analyzed for mercury content by energy dispersive spectrometry (EDS) and atomic absorption spectrophotometry (AAS). Mercury levels appeared below the detection limits of EDS but could be detected by AAS which showed the highest readings seven days after amalgam insertion.

Surface characteristics of glass-ionomer cements when treated with cavity varnish.

Two glass-ionomer cements were evaluated. Sixty molds were prepared, 20 with a lining cement, 20 with a base cement, and 20 with a control cement. The samples were tested for hardness; the glass-ionomer materials proved to be significantly harder than the control.