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Biomedical subjects

M J Allen

Publications and source records attributed to M J Allen.

198 records · Page 11Linked to original sources
PubMedDate not supplied

The natural subcellular surface structure of the bovine sperm cell.

We used atomic force microscopy (AFM), which utilizes a novel 3D image-contrast mechanism, to obtain nanometer-resolved, topographic data images of the natural surface structures of untreated bovine sperm cells. Freshly ejaculated, thawed, sonicated, and demembranated bovine sperm were adsorbed passively or by motility from suspension onto a coverglass substrate and directly imaged in normal air and saline environments without damaging the cells. Our AFM images of the surface structures of unfixed sperm imaged in normal air were consistent with previous electron microscope results on frozen or fixed sperm, demonstrating that the accurate preservation of small cellular structures is achievable using greatly simplified AFM sample preparation and imaging environments. Our AFM results also indicate that imaging sperm in physiologic buffer provides more native views of sperm due to the retention of cytoplasmic structures easily disrupted by drying forces. In addition, the AFM images show that numerous nanometersized subcellular structures of the sperm head and tail regions could be clearly visualized on rapidly prepared, unfixed, intact cells. Consequently, AFM should be considered a new tool for studying sperm structure abnormalities and monitoring the specific effects of, or damage caused by, various chemical reactants or other treatments on the structures of metabolically active or partially demembranated sperm. AFM is now emerging as an important new structural technique for imaging hydrated cells and organelles and, in addition, has the capabilities to physically "interrogate" them with the local probe.

Acrosome↗
PubMedDate not supplied

Neoplastic transformation of cells by soluble but not particulate forms of metals used in orthopaedic implants.

Recent developments in cell culture techniques have made it possible to study the cellular mechanisms involved in carcinogenesis and to apply these methods as screening tools in vitro. This study investigated and compared the ability of the metals most commonly used in orthopedic implants to induce toxicity and neoplastic transformation in the C3H10T1/2 mouse fibroblast cell line. Eight metals (cobalt, chromium, nickel, iron, molybdenum, aluminium, vanadium and titanium) and their alloys (stainless steel, cobalt-chrome alloy and titanium alloy) were tested, both as soluble salts and as solid particles. There were marked differences between the various metals in terms of both toxicity and transforming ability. Significant increases in the incidence of cell transformation were seen with soluble forms of cobalt, chromium, nickel and molybdenum but not with iron, aluminium, vanadium or titanium. For most of the metals. transforming ability was directly related to toxicity, although this correlation did not hold for either molybdenum or vanadium. The physical form of the metal was critically important in determining its effects, and transformation occurred only with soluble metal salts.

Alloys↗
PubMedDate not supplied

The surgical anatomy of the stifle joint in sheep.

OBJECTIVE: To provide a detailed description of the surgical anatomy of the stifle joint in sheep. STUDY DESIGN: The results from analysis of cadaveric dissections (14 stifle joints) and stifle radiographs (8 sets of mediolateral and craniocaudal radiographs) are presented. ANIMALS: Skeletally mature ewes of mixed breeds. CONCLUSIONS: Although the anatomy of the ovine stifle joint is similar to that of the human knee joint, a number of unique features were identified. These included the presence of the tendon of the m. extensor digitorum longus on the craniolateral aspect of the stifle joint, the absence of a cranial meniscofemoral ligament (ligament of Humphrey) in the caudal joint space, and attachment of the patellar tendon to the cranial pole of the patella (rather than to the distal pole, as in humans). The implications of these differences are discussed with reference to the suitability of the ovine stifle as a surgical model for the human knee joint.

Animals↗
PubMedDate not supplied

Defined substrate technology method for rapid and specific simultaneous enumeration of total coliforms and Escherichia coli from water: collaborative study.

The defined substrate technology (DST) method is a reagent system designed to enumerate specific target microbes(s) from a mixture of bacteria. The system simultaneously enumerates total coliforms and Escherichia coli directly from a water sample. The reagent contains o-nitrophenyl-beta-D-galactopyranoside (ONPG), which is hydrolyzed by total coliforms to produce a yellow chromogen, and 4-methylumbeilliferyl-beta-D-glucuronide (MUG), which is hydrolyzed and fluoresces when E. coli organisms grow. Noncoliform bacteria are suppressed and cannot metabolize the indicator nutrients. Nine laboratories participated in a field evaluation of the method, which covered a wide range of surface and subsurface water sources and water-processing modalities, including the examination of natural samples. The DST system was compared to multiple-tube fermentation (MTF) (quantitative) and presence-absence (P-A) (qualitative) Standard Methods formats. Comparison of water samples from natural sources by using the most probable number (MPN) procedure showed that the DST test was equivalent to the currently used MTF test. Results from the DST and the qualitative P-A procedure showed that these tests agreed with each other in 94% of the water samples analyzed. Specificity of the DST method was established by subculturing a species consistent with a total coliform or E. coli from each positive tube. Eight laboratories participated in a collaborative study of the method. Each laboratory received 3 concentrations of E. coli (organisms/100 mL); 10 (low); 60 (medium); and 120 (high). The DST test was inoculated from a split sample of each bacterial density in parallel with Standard Methods brilliant green lactose broth.(ABSTRACT TRUNCATED AT 250 WORDS)

Escherichia coli↗