Influence of femoral stem surface finish on the apparent static shear strength at the stem-cement interface.

The stem-cement interface has long been implicated in failure of cemented total hip replacement. Much research has been performed to study the factors affecting the bond strength between the femoral stem and the bone cement. The present study aims to further investigate the influence of femoral stem surface finish on the apparent static shear strength at the stem-cement interface through a series of pull out tests, where stainless steel rods are employed to represent the femoral stem. The results demonstrated that there was a general tendency for the apparent static shear strength to be increased with the rise of surface roughness. The polished and glass bead-blasted rods illustrated a slip-stick-slip failure whereas the shot-blasted and grit-blasted rods displayed gross interface failure. Following pull out test, cement transfer films were detected on the polished rods, and there was cement debris adhered to the surface of the grit-blasted rods. Micropores, typically 120 mum in diameter, were prevalent in the cement surface interfaced with the polished rods, and the cement surfaces in contact with the shot-blasted and grit-blasted rods were greatly damaged. There was also evidence of metal debris embedding within the cement mantle originating from the tests of the grit-blasted rods, indicating an extremely strong mechanical interlocking at the interface. In summary, this present research demonstrated that the grit-blasted rods with the highest surface roughness were the best in terms of apparent static shear strength. However, it seemed to be most applicable only to the stem designs in which mechanical interlocking of the stem in the initial fixed position was essential.

Copper-induced inhibition of growth of Desulfovibrio desulfuricans G20: assessment of its toxicity and correlation with those of zinc and lead.

The toxicity of copper [Cu(II)] to sulfate-reducing bacteria (SRB) was studied by using Desulfovibrio desulfuricans G20 in a medium (MTM) developed specifically to test metal toxicity to SRB (R. K. Sani, G. Geesey, and B. M. Peyton, Adv. Environ. Res. 5:269-276, 2001). The effects of Cu(II) toxicity were observed in terms of inhibition in total cell protein, longer lag times, lower specific growth rates, and in some cases no measurable growth. At only 6 microM, Cu(II) reduced the maximum specific growth rate by 25% and the final cell protein concentration by 18% compared to the copper-free control. Inhibition by Cu(II) of cell yield and maximum specific growth rate increased with increasing concentrations. The Cu(II) concentration causing 50% inhibition in final cell protein was evaluated to be 16 microM. A Cu(II) concentration of 13.3 microM showed 50% inhibition in maximum specific growth rate. These results clearly show significant Cu(II) toxicity to SRB at concentrations that are 100 times lower than previously reported. No measurable growth was observed at 30 microM Cu(II) even after a prolonged incubation of 384 h. In contrast, Zn(II) and Pb(II), at 16 and 5 microM, increased lag times by 48 and 72 h, respectively, but yielded final cell protein concentrations equivalent to those of the zinc- and lead-free controls. Live/dead staining, based on membrane integrity, indicated that while Cu(II), Zn(II), and Pb(II) inhibited growth, these metals did not cause a loss of D. desulfuricans membrane integrity. The results show that D. desulfuricans in the presence of Cu(II) follows a growth pattern clearly different from the pattern followed in the presence of Zn(II) or Pb(II). It is therefore likely that Cu(II) toxicity proceeds by a mechanism different from that of Zn(II) or Pb(II) toxicity.

Identification of a novel PTEN intronic deletion in Li-Fraumeni syndrome and its effect on RNA processing.

Germline mutations of the TP53 tumor suppressor gene account for the predisposition to cancer observed in many Li-Fraumeni syndrome (LFS) families. A causative genetic factor in the remaining families that harbor no TP53 mutations remains to be elucidated. The PTEN phosphatase tumor suppressor gene is mutated in human cancers observed in LFS. There also exists some phenotypic overlap in the occurrence of cancers in LFS and Cowden's disease (CD), for which germline PTEN mutations are believed to be responsible. We hypothesized that PTEN may be altered in some TP53-wild-type LFS families. We examined LFS primary patient lymphocytes for PTEN alterations using SSCP and sequence analysis. A novel intronic deletion was found in two unrelated individuals, adjacent to the splice acceptor site of PTEN exon 4. Based on an in vitro mRNA processing assay this alteration is predicted to be a polymorphism. The in vivo effects of this proximal splice site deletion are unknown and a genetic cause for the cancers in these families remains to be elucidated. Germline mutations of PTEN were not detected in other families, suggesting that alterations of this tumor suppressor gene do not account for the cancers observed in the subset of LFS individuals with wild-type germline TP53.

Intentional injury--homicide as a public health problem.

This article is an epidemiological analysis of Baltimore homicides between 1986 and 1990. The main findings were that young African-American males between 15 and 34 years of age are at greatest risk of homicide victimization. Homicidal events primarily occurred with handguns, in drug-related circumstances, between acquaintances, and in the western police district area. Questions are raised concerning the expansion of the public health professional's role and the use of epidemiologic data for injury prevention programs. This article is the result of a grant from the Centers for Disease Control and Prevention, Division of Injury Control, to the state of Maryland, Department of Health and Mental Hygiene, and the Baltimore City Health Department.

Do videotapes improve knowledge and attitudes about AIDS?

Three popular videotapes were assessed for their effectiveness in improving knowledge and attitudes about acquired immune deficiency syndrome (AIDS). One hundred forty-four university students completed knowledge and attitude questionnaires and then watched either an AIDS or a control tape. Half the students completed posttest questionnaires immediately after seeing the tape, and half were tested 1 month later. Students who viewed an AIDS tape showed increased knowledge at immediate and 1-month posttesting (p less than .01); the amount of increase declined over the month, however (p = .012). Students who saw two of the AIDS tapes showed an increase in compassion toward people with AIDS when tested immediately after the tape (p less than .01); but 1 month later, only those students who had viewed a third AIDS tape showed an increase in compassion (p less than .01). The AIDS tapes failed to bring about improvements in attitudes toward preventive behavior. The authors concluded that tapes about AIDS can lead to modest changes in knowledge and perhaps in attitudes; more significant changes, however, probably depend on multimedia interventions that include guided discussions as well as audiovisual and other components.

Hypoxaemia during postoperative recovery using continuous pulse oximetry.

Continuous pulse oximetry monitoring was used to determine the incidence of hypoxaemia (arterial oxygen saturation less than or equal to 90%) occurring in the first hour of postoperative recovery. Of 107 patients studied, hypoxaemia was recorded in 80%. Twenty-eight (26%) of these patients had saturations below 80%. The average frequency (i.e., the number of desaturations per patient) and the total duration of these desaturations was 7.7 desaturations and 182 seconds respectively. Intermittent measurements taken preoperatively and at 5 and 30 minutes postoperatively revealed hypoxaemia in 2%, 4% and 6% of patients respectively. In 39 patients who received oxygen therapy throughout the monitoring period, 64% experienced hypoxaemia within the first 15 minutes of recovery as opposed to only 18% in the final 15 minutes monitoring period. Of the factors assessed, only patients with a body mass index greater than 25 had an increased risk of hypoxaemia (P less than 0.01). Four patients required active intervention and ventilatory assistance. We conclude that postoperative hypoxaemia is a particularly common occurrence even in patients otherwise considered healthy. Hence, pulse oximetry should be employed routinely during recovery. Where possible, monitoring should be performed continuously for at least 45 minutes.

Quantitation of vitamin B6 in biological samples by isotope dilution mass spectrometry.

Methods have been developed for the simultaneous quantitative analysis of vitamin B6 forms in biological samples by isotope dilution mass spectrometry using deuterated forms of pyridoxine, pyridoxal, pyridoxamine, and pyridoxic acid. The biological fluid or tissue sample was homogenized and then treated with a cocktail containing appropriate amounts of each deuterated vitamer, as well as the deuterated, phosphorylated vitamer forms. The individual vitamers were isolated from the homogenate by a complex high-performance liquid chromatographic procedure that provided separate fractions for each of the six vitamers found in biological samples. Aldehydic B6 vitamers were reduced to the alcohol form prior to acetylation and analysis by gas chromatography/mass spectrometry (GC/MS). The three resulting vitamers were analyzed by electron ionization GC/MS using a silicone capillary column. The methods have been applied to analysis of vitamin B6 in liver, milk, urine, and feces at levels as low as 0.02 nmol/ml.

Microbial fermentative preparation of L-[15N2]lysine and its tracer: application to serum amino acid kinetic studies.

The microorganism Brevibacterium flavum 21129 has been used to produce multigram batches of L-[15N2]lysine of high purity and isotopic enrichment by supplementation of the growth medium with (15NH4)2SO4 of 98.0 atom% excess. The doubly 15N-labeled lysine can be detected at dilutions 10 times greater than singly labeled lysine when isotope dilution curves are analyzed by gas chromatography-mass spectrometry. This enhanced sensitivity permits kinetic measurements of plasma free-lysine isotope content over a 300-fold dilution during 6 h following a single oral bolus of 5 mg/kg body wt. This inexpensive preparation method lends itself to the production of highly useful biochemical compounds for kinetic studies of human nutrition.

Methadone disposition following oral versus parenteral dose administration in rats during chronic treatment.

A single radiolabeled dose of dl-methadone was administered by the oral, subcutaneous and intravenous routes to rats that had been chronically treated with dl-methadone. Radiolabeled compound (methadone and metabolites) was found in all organs at all time points studied after 30 minutes to 24 hours. Thin-layer chromatographic analysis showed that approximately 30-40 per cent of this compound is unchanged methadone at the 1-hour time point in the liver of rats receiving an oral or intravenous dose and in the brain of rats receiving an oral dose. Ninety-four per cent of compounds in brain is unchanged methadone at 1 hour after intravenous dose administration. Twenty-four hours following dose administration, levels of methadone within any organ are found to be similar irrespective of route of administration. The liver was found to contain the largest amounts of methadone in all animals studied with whole blood, lungs, and kidneys also containing large total amounts of methadone and metabolites. The liver and adrenals contained the highest concentration of radiolabeled compounds.

Cognitive maps of environmental knowledge and preference in nursing home patients.

Two studies examined cognitive maps of environmental knowledge and preference shown by nursing home patients. In study I, knowledge of the nursing home environment was investigated. Age was found to be negatively related to accuracy in identifying the locations of slide-depicted scenes. Also, patients who had lived several years in the nursing home were less able to identify the locations than were students who received a five-minute exposure to each area. Variable identification performance across areas was determined to be the result of relative visual distinctiveness rather than differential familiarity. Study II examined preference structures for different areas of the nursing home. Patients indicated a marked preference for their own room relative to common areas. Two different models of nursing design were suggested: 1) a social facilitation model emphasizing the allocation of a large proportion of space to common areas, and 2) an ethological model emphasizing preferences of patients for more private space.