Micromachining in plastics using X-ray lithography for the fabrication of microelectrophoresis devices

Micromachining was performed in polymethylmethacrylate (PMMA) using X-ray lithography for the fabrication of miniaturized devices (microchips) for potential applications in chemical and genetic analyses. The devices were fabricated using two different techniques: transfer mask technology and a Kapton mask. For both processes, the channel topography was transferred (1:1) to the appropriate substrate via the use of an optical mask. In the case of the transfer mask technique, the PMMA substrate was coated with a positive photoresist and a thin Au/Cr plating base. Following UV exposure, the resist was developed and a thick overlayer (approximately 3 microns) of Au electroplated onto the PMMA substrate only where the resist was removed, which acted as an absorber of the X-rays. In the other technique, a Kapton film was used as the X-ray mask. In this case, the Kapton film was UV exposed using the optical mask to define the channel topography and following development of the resist, a thick Au overlayer (8 microns) was electrodeposited onto the Kapton sheet. The PMMA wafer during X-ray exposure was situated directly underneath the Kapton mask. In both cases, the PMMA wafer was exposed to soft X-rays and developed to remove the exposed PMMA. The resulting channels were found to be 20 microns in width (determined by optical mask) with channel depths of approximately 50 microns (determined by x-ray exposure time). In order to demonstrate the utility of this micromachining process, several components were fabricated in PMMA including capillary/chip connectors, injectors for fixed-volume sample introduction, separation channels for electrophoresis and integrated fiber optic fluorescence detectors. These components could be integrated into a single device to assemble a system appropriate for the rapid analysis of various targets.     

Prostaglandin E2 binding sites in porcine oxyntic mucosa: effects of salicylates

These studies were designed to examine the changes in the characteristics of prostaglandin E2 (PGE2) binding to porcine oxyntic mucosa in the response to oral ingestion of salicylates. Either acetylsalicylic acid (ASA) or salicylic acid (SA) was administered to conscious pigs (100 mg/kg in 30 mL of an equimolar concentration of NaHCO3) once a day for 1, 3, 10, or 20 days. In control experiments a similar volume of 0.3 M NaHCO3 was administered for similar durations. Mucosal ulceration and the characteristics of the binding of [3H]PGE2 to a 30 000 X g membrane preparation of oxyntic mucosa were examined. Generation of mucosal PGE2 was measured by radioimmunoassay. ASA treatment resulted in an increase in the number and severity of mucosal ulcers and a decrease in PGE2 levels within the first treatment day. By day 20 the degree of ulceration had decreased in spite of a persistent reduction of mucosal PGE2 generation. A variable degree of ulceration was observed in SA-treated animals. In control animals only a single class of binding sites for [3H]PGE2 was evident. After 3 days of ASA treatment a second class of binding sites with a high affinity dissociation constant appeared. There was a decrease in the high affinity binding of [3H]PGE2 after 20 days of ASA ingestion. Low affinity binding was not altered. ASA treatment resulted in a significant increase in specific binding capacities for both families of binding sites. SA treatment did not consistently alter PGE2 binding characteristics from control at any time period studied.(ABSTRACT TRUNCATED AT 250 WORDS)     

Biological indicators for low temperature steam formaldehyde sterilization: effect of defined media on sporulation, germination index and moist heat resistance at 110 degrees C of Bacillus strains

Choice of a biological indicator depends upon selecting a strain with the optimum balance of desirable properties. Screening 20 strains of Bacillus spp. for sporulation on three defined media has shown the wide variation that occurs in requirements for sporulation and properties of the resultant spores. Comparison of germination index and moist heat resistance of resultant spores suggest that a combination of high germination index, high heat resistance and linear inactivation may not be possible.     

Solubility of phosphorus added to four Manitoba soils with different calcium and magnesium contents

Summary The solubility of phosphorus was found to approximate that of dicalcium phosphate dihydrate and/or dimagnesium phosphate trihydrate when KH₂-PO₄, H₃PO₄ and K₂HPO₄ were added to four Manitoba soils. Eighty to one hundred, seventy to ninety and sixty to eighty per cent of the phosphorus added remained in solution when H₃PO₄, KH₂PO₄ and K₂HPO₄ were added, respectively. The solubility of the added phosphorus was high in all samples and relatively soluble compounds, dicalcium phosphate dihydrate and dimagnesium phosphate trihydrate, were most likely formed in the samples indicating that phosphorus added to these soils would be readily available to plants. Associate Professor and Professor respectively.     

Sister-chromatid exchanges in association with occupational exposure to ethylene oxide

Sister-chromatid exchange (SCE) frequencies in employees potentially exposed to ethylene oxide (ETO) were compared with those in unexposed control groups. Three worksites where the previous environmental control of ETO was known to have differed were chosen. Within these worksites, subjects were categorized into high potential exposed, low potential exposed and control groups. An additional community control group was obtained. Blood samples for chromosome studies of peripheral lymphocytes were drawn at several time points over a period of 24 months. The effects on SCE of age, sex, smoking habits and reader variation were considered. Worksites I, II and III, respectively, represented increasing levels of exposure. At Worksite III large differences among groups persisted over 24 months. At Worksite II, the SCEs in the high potential exposed workers were higher than those in the other groups. At no time was the low potential exposed group at Worksite II statistically significantly higher in mean SCE than the worksite controls. No consistent differences among groups were noted in Worksite I.     

Definitive Evidence for the existence of tight junctions in invertebrates

Extensive and unequivocal tight junctions are here reported between the lateral borders of the cellular layer that circumscribes the arachnid (spider) central nervous system. This account details the features of these structures, which form a beltlike reticulum that is more complex than the simple linear tight junctions hitherto found in invertebrate tissues and which bear many of the characteristics of vertebrate zonulae occludentes. We also provide evidence that these junctions form the basis of a permeability barrier to exogenous compounds. In thin sections, the tight junctions are identifiable as punctate points of membrane apposition; they are seen to exclude the stain and appear as election- lucent moniliform strands along the lines of membrane fusion in en face views of uranyl-calcium-treated tissues. In freeze-fracture replicas, the regions of close membrane apposition exhibit P-face (PF) ridges and complementary E-face (EF) furrows that are coincident across face transitions, although slightly offset with respect to one another. The free inward diffusion of both ionic and colloidal lanthanum is inhibited by these punctate tight junctions so that they appear to form the basis of a circumferential blood-brain barrier. These results support the contention that tight junctions exist in the tissues of the invertebrata in spite of earlier suggestions that (a) they are unique to vertebrates and (b) septate junctions are the equivalent invertebrate occluding structure. The component tight junctional 8- to 10-nm-particulate PF ridges are intimately intercalated with, but clearly distinct from, inverted gap junctions possessing the 13-nm EF particles typical of arthropods. Hence, no confusion can occur as to which particles belong to each of the two junctional types, as commonly happens with vertebrate tissues, especially in the analysis of developing junctions. Indeed, their coexistance in this way supports the idea, over which there has been some controversy, that the intramembrane particles making up these two junctional types must be quite distinct entities rather than products of a common precursor.     

Entomophthora bullata as a pathogen of Sarcophaga aldrichi

Adults of Sarcophaga aldrichi killed by Entomophthora bullata were found in the field 7 days after emergence. Resting spores were not found until 6 days later, although conidia were formed from the first incidence of mortality. It is suggested that the life cycle of the fungus involves alternating generations of conidia and thick-walled overwintering resting spores.     

Effect of sialoadenectomy on ethanol-induced gastric mucosal damage in the rat: role of neutrophils

We have observed that removal of the salivary glands is associated with an increase in the susceptibility to gastric mucosal damage in the rat. In the present study, we have examined the effect of sialoadenectomy on ethanol-induced mucosal hemorrhagic damage and myeloperoxidase (MPO) activity. Hemorrhagic damage and MPO activity in response to intragastric 50% w/v ethanol were greater in sialoadenectomized rats when compared with sham-operated animals. Pretreatment with 16,16-dimethylprostaglandin E2 (0.3 micrograms/kg s.c.) reduced damage and MPO activity in both sialoadenectomized and sham control rats receiving 50% ethanol. The reduction in these parameters was greater in control than in sialoadenectomized rats. Pretreatment with epidermal growth factor (5 micrograms/kg s.c.) significantly reduced MPO activity but did not significantly affect the extent of damage. These data suggest that sialoadenectomy is associated with an increase in mucosal inflammation in animals given ethanol. However, in some situations tissue inflammation (as indicated by MPO activity) was reduced, while the proportion of gastric mucosa exhibiting hemorrhagic damage was not changed.