Sampling tissue

The analyst (farmer, veterinarian, laboratory scientist, or any other user) saturates a cotton tipped swab with sample tissue fluids, serum, urine, or feed extract. He then firmly places the saturated cotton swab on the surface of the appropriate growth medium previously surface streaked with the working dilution of the appropriate susceptible test organism. The test is then incubated at the proper temperature overnight and observed the next day for antimicrobial activity. If there is a zone of inhibition (no growth of the test organism) around the sample swab, the test is positive no inhibition indicates that antimicrobials are absent or below detectable levels in the sample tested. 

Form for recording the blood samples/tissue samples for special analysis (perhaps stored in fridge/freezer before dispatch)... 

Dermal absorption was also studied in rats. [ C]Diethanolamine was applied to 19.5 cm of the dorsal skin (20 mg/cm, 1500 mg/kg bw) and covered for 48 h (no washing) or for 6 h before it was removed by washing. Absorbed [ Qdiethanolamine was determined in 48-h urine and faeces and from sampled tissues. FInwashed rats absorbed 1.4% and washed animals 0.64% of the dose, while the majority of [ C]diethanolamine was recovered in the occlusive wrappings (80%) and in skin of the dose site (3.6%). The radioactivity was found in carcass, liver or kidneys but very little in urine (0.11%), faeces or blood (Waechter etal., 1995, cited by Knaak etal, 1997). 

Brain samples tissue were properly mixed and centrifuged at 5000 rpm for 5 min After that samples were frozen at temperature of -50 °C... 

Very few methods have appeared in the literature with respect to the extraction, cleanup, and subsequent determination of corticosteroids in food samples (Table 29.17). Milk analysis usually requires a pretreatment step for fat elimination (527). Centrifugation for 20 min at about 7000 g at 4 C is the usually applied procedure for making the fat floating on the top of the sample. Tissue analysis also requires a pretreatment step for matrix break-up that can be accomplished by means of a mincing and/or a homogenizing apparatus. 

Analyte Sample Tissue Sensor Linear range (moll 1) Limit of Response Lifetime Ref. 

Figure 6-27 Raman spectra of (a) normal, (b) cirrhotic (benign), and (c) malignant liver tissues in the 900 to 1,300-cm-1 region. The spectra in the 2,800 to 3,200-cm-1 region were identical in each case. Average of (a) 10, (b) 13, and (c) 10 fifteen-minute acquisitions at different points on the sample tissue. The background was subtracted, and the spectra are normalized to the 1,450-cm-1 band. (Reproduced with permission from Ref. 43.)...

Currently, there is no doubt that the most widely used method for extraction of tissue lipids is that of Bligh and Dyer (1959). Basically, this is a modification of the Folch method and employs a careful calculation of the amount of sample (tissue) water such that the overall mixture will have a final composition of chloroform-methanol-water of 1 2 0.8 (v/v). Thus, a singlephase extract can be obtained and extraction completed very rapidly, even within minutes. Recovery of the lipid in a chloroform-rich phase can be achieved by addition of equal volumes of chloroform (under certain conditions) and water to produce a two-phase system. The lower (CHC13) phase is subsequently washed with a methanol-water (1 0.9, v/v) mixture to allow removal of a substantial amount of the nonlipid contaminant with little or no problems with interfacial fluff formation or emulsions. However, even though this is a highly efficient method, it is still advisable that one take steps... 

The reason why Hg has MLs established for fish only is, of course, that this is the only food in which it is normally found. In other foodstuffs Hg levels are usually so low that the analysis is worth trying only if specific questions need an answer. Systems for CV-AAS are generally available as ancillary to FAAS instruments. MW digestion is probably the most suitable way to get the sample tissue into solution. Contamination by Hg is, in most laboratories, very low and is seldom a problem. 

As previously discussed, electron, light, and confocal microscopy techniques may be used to visualize the position of electron-dense precipitates, radioactive substances, and fluorescent probes, respectively, in the sample tissue. However, none of these techniques possess the capability both to visualize and to selectively measure the flux of a molecule across the skin. SECM, however, permits the measurement and subsequent imaging of the local flux of an electroactive species across biological membranes. Scott et al. [3] used SECM to investigate the effect of pretreatment of the penetration enhancer sodium dodecyl sulfate (SDS), on the ion transport rate and transport pathways of Fe(CN) across hairless mouse skin. Increasing the time of SDS exposure from 10 min to 30 min increased the overall (porous and nonporous) transport of Fe(CN) by 17-fold. More specifically, the SDS-induced increase in Fe(CN)g transport was found to be associated with nonporous (i.e., intercellular) transport routes, while transport via porous routes was significantly reduced. The fraction of Fe(CN)g transport through pores, as measured by... 

Direct determination of trace elements is made in many types of specimens including whole blood, blood plasma or serum, leukocytes, urine, saliva, cerebrospinal fluid (CSF), breast milk, and sweat. Tissue samples may be obtained by needle biopsy (liver, bone,) or following an autopsy. Hair and nail samples offer a noninvasive means of sampling tissue and are used to assess toxic metal exposure. Measurements of hair and nails for essential elements may be of value on a group basis during studies of severely depleted populations but are of Umited value in the investigation of individual hospital patients. Problems of external contamination from environmental pollution, cosmetics, shampoos, and other sources are difficult to control. ... 

---