The effects of muscimol inactivation of small regions of motor and somatosensory cortex on independent finger movements and force control in the precision grip

This study investigated the effects of inactivating small regions of the primary somatosensory (SI) and motor (MI) cortex on the control of finger forces in a precision grip. A monkey was trained to grasp and lift a computer-controlled object between the thumb and index finger and to hold it stationary within a narrow position window for 2 s. The grip force applied perpendicular to the object surface, the lifting or load force applied tangentially in the vertical direction, and the vertical displacement were sampled at 100 Hz. Also, the ability of the monkey to extract small pieces of food from narrow wells of a Klüver board was analyzed from video-tape. Preliminary single-unit recordings and microstimulation studies were used to map the extent of the thumb and index-finger representation within SI and MI. Two local injections of 1 microl each (5 microg/microl) of the GABA(A)-agonist muscimol were used to inactivate the thumb and index region of either the pre- or post-central gyrus. The precision grip was differently affected by muscimol injection into either SI or MI. MI injections produced a deficit in the monkey's ability to perform independent finger movements and a general weakness in the finger muscles. Whole-hand grasping movements were inappropriately performed in an attempt to grasp either the instrumented object or morsels of food. Although the effect seemed strongest on intrinsic hand muscles, a clear deficit in digit extension was also noted. As a result, the monkey was unable to lift and maintain the object within the position window for the required 2 s, and, over time, the grip force decreased progressively until the animal stopped working. Following SI injections, the most obvious effect was a loss of finger coordination. In grasping, the placement of the fingers on the object was often abnormal and the monkey seemed unable to control the application of prehensile and lifting forces. However, the detailed analysis of forces revealed that a substantial increase in the grip force occurred well before any deficit in the coordination of finger movements was noted. This observation suggests that cutaneous feedback to SI is essential for the fine control of grip forces.

The relationship between the rate of starch synthesis, the adenosine 5'-diphosphoglucose concentration and the amylose content of starch in developing pea embryos

Mutations that reduced the rate of starch synthesis in pea (Pisum sativum L.) embryos through effects on enzymes on the pathway from sucrose to adenosine 5'-diphosphoglucose (ADPglucose) also led to a reduction in the amylose content of the starch of developing embryos. Evidence is presented that this relationship between rate of synthesis and the composition of starch is due to the fact that amylopectin-synthesising isoforms of starch synthase have higher affinities for ADPglucose than the amylose-synthesising isoform. First, developing mutant embryos (rb, rug3 and rug4 mutants) displayed both reduced amylose contents in their starches and reduced ADPglucose contents relative to wild-type embryos. Second, incubation of detached, wild-type embryos for 6 h at high and low glucose concentrations resulted in differences in both ADPglucose content and the relative rates of amylose and amylopectin synthesis. At 0.25 M glucose both ADPglucose content and the proportion of synthesised starch that was amylose were about twice as great as at 25 &mgr;M glucose. Third, S(0.5) values for soluble (amylopectin-synthesising) starch synthases in developing embryos were several-fold lower than that for granule-bound (amylose synthesising) starch synthase. Estimates of the expected amylose contents of the starch of the mutant embryos, based on the reduction in their ADPglucose contents and on the S(0.5) values of the starch synthases, were very similar to the measured amylose contents. The implications of these results for the determination of starch composition are discussed.

Personal and social factors influencing age at first sexual intercourse

Early initiation of sexual activity is a concern, in part because of increased risk of sexually transmitted diseases, including HIV, and unwanted pregnancies among young people. In this study, 241 high schoolers were administered a questionnaire to establish the relationships between age at first sexual intercourse and personal qualities (sexual style, attractiveness, physical maturity, restraint, autonomy expectations, and attitudes to gender roles), smoking and drug use, and aspects of the social context (social activities, media impact, peer norms). There were few effects of sex of respondent and none in which respondents' sex impacted on age of initiation. Overall (and among the male sample), perceptions of greater physical maturity, greater use of uncommon (mostly illicit) drugs, and expectations of earlier autonomy significantly differentiated between early and later initiators. This group of factors tends to confirm the view that early experience of sexual intercourse is correlated with problem behaviors and a press toward "adult" behaviors. For girls, this pattern was even clearer, with use of uncommon drugs being replaced as a significant contributor to early sexual experience by relative lack of restraint. We conclude that the desire to achieve the transition to adulthood at an earlier age than their peers constitutes a powerful incentive for young people to become sexually active.

Conflicting advice? Australian adolescents' use of condoms or the pill

CONTEXT

Teenagers are exposed to two potentially conflicting sexual health messages, one emphasizing the prevention of sexually transmitted diseases (STDs) and the other stressing pregnancy prevention. To protect teenagers from both STDs and unwanted pregnancy, it is important to know what method choices they make and why.

METHODS

Data from a 1997 national survey of 3,550 Australian secondary school students were used to examine teenagers' method choice and patterns of advice-seeking about contraception and STD prevention. Logistic regression analyses were conducted to identify factors associated with the exclusive use of condoms or the pill.

RESULTS

Virtually all 961 currently sexually active students were using at least one contraceptive method--primarily condoms (78%) or the pill (45%). Some 31% were using condoms exclusively, and 10% were using the pill exclusively. Older students and those who had sought contraceptive advice had elevated odds of using the pill rather than condoms exclusively (odds ratios, 4.4 and 2.6, respectively), while those who had had only casual partners in the last year had a reduced likelihood of exclusive pill rather than condom use (0.1). Furthermore, the more students believed that their peers used condoms, the less likely they were to report exclusive pill use (0.4). Parents were the most frequent source of advice about contraception, followed by physicians and teachers. The most common sources of advice about HIV and other STDs were parents, teachers and then physicians.

CONCLUSIONS

Young people must be educated about the distinction between safer sex and contraception, and about how to prevent both STDs and pregnancy. Providing parents with current sexual health information may help to improve young people's sexual health.

The diverse role of selenium within selenoproteins: a review

Selenium functions within mammalian systems primarily in the form of selenoproteins. Selenoproteins contain selenium as selenocysteine and perform a variety of physiological roles. Eleven selenoproteins have been identified: cellular or classical glutathione peroxidase; plasma (or extracellular) glutathione peroxidase; phospholipid hydroperoxide glutathione peroxidase; gastrointestinal glutathione peroxidase; selenoprotein P; types 1, 2, and 3 iodothyronine deiodinase; selenoprotein W; thioredoxin reductase; and selenophosphate synthetase. Of these, cellular and plasma glutathione peroxidase are the functional parameters used for the assessment of selenium status. Glutathione peroxidases catalyze the reduction of peroxides that can cause cellular damage. Thioredoxin reductase provides reducing power for several biochemical processes and defends against oxidative stress. Selenoprotein P appears to play a role in oxidant defense. Selenoprotein W may play a role in oxidant defense and be involved with muscle metabolism. Thyroid deiodinases function in the formation and regulation of active thyroid hormone. Selenophosphate synthetase is an enzyme required for the incorporation of selenocysteine into selenoproteins. In addition, a protein in the sperm mitochondrial capsule, which is vital to the integrity of sperm flagella, may be a unique selenoprotein. Recommended intakes, food sources, and status assessment of selenium, as well as selenium's role in health and disease processes, are reviewed.

Mapping the literature of dietetics

Research on the literature of dietetics, apart from the broader field of nutrition, has not been reported in the literature. The purpose of this bibliometric study was to identify the core journals of dietetics and to determine the extent of indexing coverage for these journals. The study was conducted as part of a larger project, the Project for Mapping the Literature of Allied Health, sponsored by the Nursing and Allied Health Resources Section of the Medical Library Association. Citations appearing in three journals between 1995 and 1997 were analyzed by the methodology common to studies in the project. Results revealed that dietetic literature relies heavily on journal literature and on those journals that are from associated health sciences fields. Of the indexing services examined, EMBASE/Excerpta Medica and MEDLINE provided the most complete coverage of the literature. The study's findings have implications for those involved with the literature of dietetics.

MR imaging of hypervascular liver tumors: timing optimization during the arterial phase

To analyze the optimal timing strategy for the detection of hypervascular liver tumors during the arterial phase of magnetic resonance (MR) imaging, a test examination after injection of 2 mL of gadopentetate dimeglumine was performed in 47 patients. The time course of the tumor-to-liver contrast-to-noise ratio (CNR) for all studies together was determined relative to the start of injection, the time of peak aortic enhancement, and the time of peak enhancement in the tumor. All studies were grouped together and the highest CNR was transiently observed at the time of peak tumor enhancement. This CNR was significantly higher than those observed at fixed delays after peak aortic enhancement. However, the CNRs at peak tumor enhancement+/-1.5 seconds did not differ significantly from those obtained after peak aortic enhancement. Finally, the CNRs obtained at fixed delays after the start of injection remained significantly lower. In hypervascular liver tumors, a higher CNR can be obtained during the arterial phase when the MR imaging delay is determined relative to the time of peak enhancement in the tumor or the aorta rather than being fixed after the start of contrast material injection. Timing based on the enhancement profile in the tumor rather than in the aorta should be performed only if rapid MR imaging is available with a time resolution of about 1.5 seconds to image the whole liver.

Neural pathways involved in the processing of concrete and abstract words

The purpose of this study was to delineate the neural pathways involved in processing concrete and abstract words using functional magnetic resonance imaging (fMRI). Word and pseudoword stimuli were presented visually, one at a time, and the participant was required to make a lexical decision. Lexical decision epochs alternated with a resting baseline. In each lexical decision epoch, the stimuli were either concrete words and pseudowords, or abstract words and pseudowords. Behavioral data indicated that, as with previous research, concrete word stimuli were processed more efficiently than abstract word stimuli. Analysis of the fMRI data indicated that processing of word stimuli, compared to the baseline condition, was associated with neural activation in the bilateral fusiform gyrus, anterior cingulate, left middle temporal gyrus, right posterior superior temporal gyrus, and left and right inferior frontal gyrus. A direct comparison between the abstract and concrete stimuli epochs yielded a significant area of activation in the right anterior temporal cortex. The results are consistent with recent positron emission tomography work showing right hemisphere activation during processing of abstract representations of language. The results are interpreted as support for a right hemisphere neural pathway in the processing of abstract word representations.

Making starch

Improvements in understanding the structure of the starch granule and the nature and roles of starch-synthesising enzymes have allowed detailed mechanisms of the synthesis of the amylopectin and amylose components of the granule to be suggested. However, none of these proposed mechanisms has yet been shown to operate in vivo. Several critical aspects of granule synthesis, including granule initiation and the formation of the growth rings, remain a mystery.

Impact of the surface slipperiness of grasped objects on their subsequent acceleration

Seven subjects were asked to reach and grasp an object between the thumb and index finger, lift it about 30 cm high and 25 cm forward from one table to another, at their preferred speed. The perpendicular grip force and the tangential load force applied to the contact surface were digitized at 500 Hz and stored on a laboratory computer. The trajectory of the wrist and of the object was recorded using four infrared cameras tracking the movement of reflective markers attached to the distal styloid process of the radius and on the top of the object. The aim of this study was to demonstrate the influence of low friction (i.e. surface slipperiness) on the acceleration of the wrist. Friction was reduced by coating the smooth brass grasping surface with talc. The seven subjects had skin to surface coefficients of friction which ranged from 0.52-1.18 for dry brass and 0.24 0.34 for talc-coated brass. Two weights (418 and 1070 g) were used with each surface. The results indicated that with the slippery surface the necessary higher grip force/load force ratio was produced by an increase in the grip force and by a decrease in the wrist acceleration and a consequent reduction in the load force. This strategy was observed for both weights over a range of grip strengths between 21-98% of the individual's maximum voluntary contraction (MVC). This implies that even with adequate grip force reserves the reduction in acceleration is an acceptable and probable alternative solution to the force control problem. Our results also suggested that the loading rate and the object acceleration were planned and controlled together which emphasizes the role played by a predictive mechanism in organizing the kinematics of movements involving hand-held objects. This study shows that friction of the grasping surface not only affects the prehensile force dynamics, but it also influences the kinematics of the entire upper limb.

Granule-bound starch synthase I in isolated starch granules elongates malto-oligosaccharides processively

Isoforms of starch synthase belonging to the granule-bound starch synthase I (GBSSI) class synthesize the amylose component of starch in plants. Other granule-bound isoforms of starch synthase, such as starch synthase II (SSII), are unable to synthesize amylose. The kinetic properties of GBSSI and SSII that are responsible for these functional differences have been investigated using starch granules from embryos of wild-type peas and rug5 and lam mutant peas, which contain, respectively, both GBSSI and SSII, GBSSI but not SSII and SSII but not GBSSI. We show that GBSSI in isolated granules elongates malto-oligosaccharides processively, adding more than one glucose molecule for each enzyme-glucan encounter. Granule-bound SSII can elongate malto-oligosaccharides, but has a lower affinity for these than GBSSI and does not elongate processively. As a result of these properties GBSSI synthesizes longer malto-oligosaccharides than SSII. The significance of these results with respect to the roles of GBSSI and SSII in vivo is discussed.

Granule-bound starch synthase I in isolated starch granules elongates malto-oligosaccharides processively

Isoforms of starch synthase belonging to the granule-bound starch synthase I (GBSSI) class synthesize the amylose component of starch in plants. Other granule-bound isoforms of starch synthase, such as starch synthase II (SSII), are unable to synthesize amylose. The kinetic properties of GBSSI and SSII that are responsible for these functional differences have been investigated using starch granules from embryos of wild-type peas and rug5 and lam mutant peas, which contain, respectively, both GBSSI and SSII, GBSSI but not SSII and SSII but not GBSSI. We show that GBSSI in isolated granules elongates malto-oligosaccharides processively, adding more than one glucose molecule for each enzyme-glucan encounter. Granule-bound SSII can elongate malto-oligosaccharides, but has a lower affinity for these than GBSSI and does not elongate processively. As a result of these properties GBSSI synthesizes longer malto-oligosaccharides than SSII. The significance of these results with respect to the roles of GBSSI and SSII in vivo is discussed.

Investigation of low frequency drift in fMRI signal

Low frequency drift (0.0-0.015 Hz) has often been reported in time series fMRI data. This drift has often been attributed to physiological noise or subject motion, but no studies have been done to test this assumption. Time series T*2-weighted volumes were acquired on two clinical 1.5 T MRI systems using spiral and EPI readout gradients from cadavers, a normal volunteer, and nonhomogeneous and homogeneous phantoms. The data were tested for significant differences (P = 0.001) from Gaussian noise in the frequency range 0.0-0.015 Hz. The percentage of voxels that were significant in data from the cadaver, normal volunteer, nonhomogeneous and homogeneous phantoms were 13.7-49.0%, 22.1-61.9%, 46.4-68.0%, and 1.10%, respectively. Low frequency drift was more pronounced in regions with high spatial intensity gradients. Significant drifting was present in data acquired from cadavers and nonhomogeneous phantoms and all pulse sequences tested, implying that scanner instabilities and not motion or physiological noise may be the major cause of the drift.

Fast FLAIR sequence for detecting major vascular abnormalities during the hyperacute phase of stroke: a comparison with MR angiography

In the hyperacute phase of stroke, occluded vessels can be seen as high signal on fast-FLAIR images or as absence of flow-related enhancement in maximum-intensity projection (MIP) MR angiography (MRA). To compare these techniques, we examined 53 patients within 6 h of a stroke, using a standardised MRI protocol including fast-FLAIR and 3D time-of-flight TOF MR to detect vessel occlusion or reduced flow corresponding to the suspected ischaemic territory. Brain infarcts were confirmed on MRI after 1-5 days in 41 cases (77%). The overall accuracy of 3D-TOF MRA was 68% and sensitivity, specificity, positive and negative predictive values were 67%, 71%, 87%, and 43% respectively. Values for the fast-FLAIR sequence were: 65%, 85%, 93% and 44%, with an overall accuracy of 70%. The fast-FLAIR sequence was thus able to show occluded vessels or reduced flow with about the same accuracy as 3D-TOF MRA and enabled better prediction of the ischaemic area.

A comparison of an anti-gastrin antibody and cytotoxic drugs in the therapy of human gastric ascites in SCID mice

The therapeutic effect of antibodies raised by the immunogen Gastrimmune was compared with both a CCKB/gastrin receptor antagonist, CI-988, and 5-Fluorouracil/leucovorin in a gastric cancer model. The human gastric ascites cell line, MGLVA1asc, produced and secreted progastrin and glycine-extended gastrin as determined by radioimmunoassay and immunocytochemistry. Cells were also stained with an antiserum directed against the human CCKB/gastrin receptor. MGLVAI asc cells were injected i.p. into SCID mice. Antibodies raised by Gastrimmune immunization of rabbits (affinity for G17 of 0.15 nM and GlyG17 of 0.47 nM) were passively infused i.p. and significantly enhanced survival by up to 5 days (p=0.0024 from vehicle controls). The enhancement in survival was not significantly different from that achieved by treatment with 5-Fluorouracil and leucovorin. A CCKB/gastrin receptor antagonist, CI-988, did not affect survival with cells injected at 7.5 x 10(5) cells/mouse but significantly increased the survival of mice injected with a lower cell innoculum of 5 x 10(5) cells/mouse from 30 to 35 days (p=0.0186). At this lower innoculum antibodies raised by Gastrimmune induced complete survival in 2 animals with the remaining dead by day 36 (p=0.0022). Thus, both endocrine and autocrine pathways mediated by precursor and mature gastrin molecules may be jointly operational in the gastric cancer scenario and may be important targets for therapeutic agents.

Cloning, expression, and properties of a nonneuronal secreted acetylcholinesterase from the parasitic nematode Nippostrongylus brasiliensis

We have isolated a full-length cDNA encoding an acetylcholinesterase secreted by the nematode parasite Nippostrongylus brasiliensis. The predicted protein is truncated in comparison with acetylcholinesterases from other organisms such that the carboxyl terminus aligns closely to the end of the catalytic domain of the vertebrate enzymes. The residues in the catalytic triad are conserved, as are the six cysteines which form the three intramolecular disulfide bonds. Three of the fourteen aromatic residues which line the active site gorge in the Torpedo enzyme are substituted by nonaromatic residues, corresponding to Tyr-70 (Thr), Trp-279 (Asn), and Phe-288 (Met). High level expression was obtained via secretion from Pichia pastoris. The purified enzyme behaved as a monomeric hydrophilic species. Although of invertebrate origin and possessing the above substitutions in the active site gorge residues, the enzyme efficiently hydrolyzed acetylthiocholine and showed minimal activity against butyrylthiocholine. It displayed excess substrate inhibition with acetylthiocholine at concentrations over 2. 5 mM and was highly sensitive to both active site and "peripheral" site inhibitors. Northern blot analysis indicated a progressive increase in mRNA for AChE B in parasites isolated from 6 days postinfection.

Factors affecting men's liking of condoms they have used

The objective of this study was to assess the impact on men's liking for the condoms they use of a range of factors including demographic variables and variables that describe men's experience of using particular condoms. One hundred and ninety-four men used 3765 condoms for which they provided a liking rating. The condoms were manufactured to one of 2 published standards and the study employed a double-blind crossover design. Sixty-one per cent of condoms were rated favourably, 31% were rated neutrally and the remainder (8%) unfavourably. Men rated condoms less favourably if they were experienced as too loose, too tight, too short, if difficulty was experienced applying the condom, if the condom slipped partially or completely down the penis or if the condom broke. Men rated more highly condoms which were experienced as well lubricated throughout use. Men with larger penises rated condoms less favourably and, of all the variables considered, ejaculating in the condom was the variable which had the largest positive impact. Men's liking for the condoms they use is influenced by a range of factors. However, given that most of the factors associated with men liking condoms less are those that can be addressed through better condom design and manufacture, the opportunity exists to enhance men's experience of condom use and hence help reduce resistance to the adoption of consistent condom use.

A longitudinal examination of athletes' emotional and cognitive responses to anterior cruciate ligament injury

OBJECTIVE

To determine the emotional and cognitive impact of injury and surgery on physical recovery in injured athletes.

DESIGN

A prospective longitudinal study comparing the psychosocial and physical recovery of competitive and recreational athletes.

SETTING

Tertiary-care sports medicine center.

PARTICIPANTS

Twenty-seven athletes (15 men and 12 women) who required anterior cruciate ligament (ACL) reconstruction surgery.

INTERVENTIONS

A repeated-measures design used to compare the psychosocial and physical changes for 6 months after ACL surgery.

MAIN OUTCOME MEASURES

Emotional (mood) and cognitive (coping) functions and physical recovery (range of motion, physician-rated level of recovery, and physician permission to return to sport).

RESULTS

There was a significant time-effect difference in mood, with a greater mood disturbance and recovery rate for competitive athletes than recreational athletes. Differences in mood and pain coping were significant at 2 weeks and 2 months after surgery.

CONCLUSION

Athletes experience significant mood changes throughout rehabilitation, which may hinder rehabilitation early in the process. Longer-term rehabilitation was not impacted by mood or pain coping. Future studies might focus on examining the process over a longer time period (1-2 years after surgery). Physicians should be aware of these findings and appropriately counsel and motivate athletes toward more favorable positive psychological and physical outcomes.

Endoscopic release of the carpal tunnel: a technical note

The Agee technique is a standard approach for the endoscopic release of the carpal tunnel. We describe a modification of the technique. This involves dilatation of the path for the blade assembly with urethral dilators. This permits a graded dilatation of the path. We believe it creates a track of more uniform width. It also provides more accurate information about the tightness of the carpal tunnel. Its adoption may reduce the chance of nerve injury.

MR imaging of hypervascular liver tumors: timing optimization during the arterial phase

To analyze the optimal timing strategy for the detection of hypervascular liver tumors during the arterial phase of magnetic resonance (MR) imaging, a test examination after injection of 2 mL of gadopentetate dimeglumine was performed in 47 patients. The time course of the tumor-to-liver contrast-to-noise ratio (CNR) for all studies together was determined relative to the start of injection, the time of peak aortic enhancement, and the time of peak enhancement in the tumor. All studies were grouped together and the highest CNR was transiently observed at the time of peak tumor enhancement. This CNR was significantly higher than those observed at fixed delays after peak aortic enhancement. However, the CNRs at peak tumor enhancement+/-1.5 seconds did not differ significantly from those obtained after peak aortic enhancement. Finally, the CNRs obtained at fixed delays after the start of injection remained significantly lower. In hypervascular liver tumors, a higher CNR can be obtained during the arterial phase when the MR imaging delay is determined relative to the time of peak enhancement in the tumor or the aorta rather than being fixed after the start of contrast material injection. Timing based on the enhancement profile in the tumor rather than in the aorta should be performed only if rapid MR imaging is available with a time resolution of about 1.5 seconds to image the whole liver.

Uncertain knowledge: a national survey of high school students' knowledge and beliefs about hepatitis C

OBJECTIVE

Hepatitis C (HCV) has recently emerged as an important public health issue. This study documents young people's hepatitis C (HCV) knowledge, risk perceptions and sources of information.

METHOD

Australia, 1997; nationally representative survey; sample of students in Years 10 and 12 in government secondary schools (n = 3,550).

RESULTS

Students' knowledge about HCV was found to be extremely poor. Of the seven questions on hepatitis, only one was answered correctly by more than half the students. Few could differentiate between hepatitis A, hepatitis B and hepatitis C. Only a small number (12%) perceived themselves to be at risk of hepatitis and fewer than half (41%) had sought advice about hepatitis.

CONCLUSION

There is a need for more HCV education and health promotion for secondary school students.

IMPLICATIONS

Some lessons from HIV education can be readily transferred to this new epidemic but others cannot. There is a danger that HIV and HCV will be conflated in education programs.

Introduction to adult posttraumatic osteomyelitis of the tibia

The tibia is the most frequent site of an open fracture, and treatment of adult posttraumatic osteomyelitis of the tibia represents a significant clinical problem that has been recognized for centuries. Ancient modalities such as immobilization and debridement are still mainstays of therapy, and recent developments such as the use of antibiotics and muscle transfer have helped to improve outcome. Osteomyelitis is classified based on the Cierny-Mader system to provide prognostic and therapeutic information. Open fractures can be classified by the Gustilo system, again providing prognostic and therapeutic data. Gustilo Type III fractures have a high likelihood of having infection develop. Treatment principles include immobilization, thorough debridement, control of infection through antibiotic use, control of dead space, and soft tissue coverage.

Application of pbp1A PCR in identification of penicillin-resistant Streptococcus pneumoniae

A seminested PCR assay, based on the amplification of the pneumococcal pbp1A gene, was developed for the detection of penicillin resistance in clinical isolates of Streptococcus pneumoniae. The assay was able to differentiate between intermediate (MICs = 0.25 to 0.5 microgram/ml) and higher-level (MICs = >/=1 microgram/ml) resistance. Two species-specific primers, 1A-1 and 1A-2, which amplified a 1,043-bp region of the pbp1A penicillin-binding region, were used for pneumococcal detection. Two resistance primers, 1A-R1 and 1A-R2, were designed to bind to altered areas of the pbp1A gene which, together with the downstream primer 1A-2, amplify DNA from isolates with penicillin MICs of >/=0.25 and >/=1 microgram/ml, respectively. A total of 183 clinical isolates were tested with the pbp1A assay. For 98.3% (180 of 183) of these isolates, the PCR results obtained were in agreement with the MIC data. The positive and negative predictive values of the assay were 100 and 91%, respectively, for detecting strains for which the MICs were >/=0.25 microgram/ml and were both 100% for strains for which the MICs were >/=1 microgram/ml.

Neuronal activity in somatosensory cortex of monkeys using a precision grip. II. Responses To object texture and weights

Three monkeys were trained to lift and hold a test object within a 12- to 25-mm position window for 1 s. The activity of single neurons was recorded during performance of the task in which both the weight and surface texture of the object were systematically varied. Whenever possible, each cell was tested with three weights (15, 65, and 115 g) and three textures (smooth metal, fine 200 grit sandpaper, and rough 60 grit sandpaper). Of 386 cells recorded in 3 monkeys, 45 cells had cutaneous receptive fields on the index or thumb or part of the thenar eminence and were held long enough to be tested in all 9 combinations of texture and weight. Recordings were made for the entire anterior-posterior extent of the thumb and index finger areas in somatosensory cortex including area 7b. However, the statistical analysis required a selection of only those cells for which nine complete recording conditions were available limiting the sample to cells in areas 2, 5, and 7b. Significant differences in the grip force accompanied 98% of the changes in texture and 78% of the changes in weight. Increasing the object weight also increased the force tangential to the skin surface as measured by the load or lifting force. The peak discharge during lifting was judged to be the most sensitive index of cell activity and was analyzed with a two-way analysis of variance (ANOVA). In addition, peak cell discharge was normalized to allow comparisons among different combinations of texture and weight as well as comparisons among different neurons. Overall, the peak firing frequency of 87% of the cells was significantly modulated by changes in object texture, but changes in object weight affected the peak activity of only 58% of the cells. Almost all (17/18, 94%) of the static cells were influenced by the object texture, and 81% of the dynamic cells that were active only briefly at grip and lift onset were modulated by texture. For some cells, surface texture had a significant effect on neuronal discharge that was independent of the object weight. In contrast, weight-related responses were never simple main effects of the weight alone and appeared instead as significant interactions between texture and weight. Four neurons either increased or decreased activity in a graded fashion with surface structure (roughness) regardless of the object weight (P < 0.05). Ten other neurons showed increases or decreases in response to one or two textures, which might represent either a graded response or a tuning preference for a specific texture. The firing frequency of the majority (31/45) of neurons reflected an interaction of both texture and weight. The cells with texture-related but weight-independent activities were thought to encode surface characteristics that are largely independent of the grip and lifting forces used to manipulate the object. Such constancies could be used to construct internal representations or mental models for planning and controlling object manipulation.

Peritoneal dialysis-associated peritonitis caused by Propionibacteria species

There are an increasing number of reports about unusual causes of peritonitis in peritoneal dialysis (PD) patients. The Propionibacteria species is a microorganism that is a normal skin flora. Under the presence of certain risk factors, it may produce serious infections. Patients at risk of having Propionibacteria sp infections have malignancy, diabetes mellitus, foreign bodies, or immunodeficiency. We describe a PD-associated peritonitis in a 51-year-old woman that was caused by Propionibacteria sp. This patient's risk factors for developing Propionibacteria sp peritonitis include a history of CREST syndrome, malignancy of the breast, and recent catheter surgery. To our knowledge, this is the first case of a PD-associated peritonitis caused by Propionibacteria sp reported in the literature.

Differences in the Composition of Adhesive and Non-Adhesive Mucus From the Limpet Lottia limatula

The mucus used by the limpet Lottia limatula to form glue-like attachments was compared biochemically to the slippery mucus produced during other activities, such as suction adhesion. Colorimetric assays revealed the protein content of the adhesive mucus to be 2.1 times greater than that of the non-adhesive form, and the carbohydrate content to be 1.9 times greater. Both forms of mucus contained roughly six times as much protein as carbohydrate, and there was no difference in their inorganic elemental compositions. Quantitative analysis of the protein content by SDS-PAGE and a scanning densitometer revealed a similar protein composition in both forms of mucus; but three notable differences emerged. First, the overall difference in protein concentration was confirmed. In addition, there was a 118 kD protein that was common only in the adhesive mucus, and a 68 kD protein that occurred only in the non-adhesive mucus.

Neuronal activity in somatosensory cortex of monkeys using a precision grip. III. Responses to altered friction perturbations

The purpose of this investigation was to examine the activity changes in single units of the somatosensory cortex in response to lubricating and adhesive coatings applied to a hand-held object. Three monkeys were trained to grasp an object between the thumb and index fingers and to lift and hold it stationary within a narrow position window for 1 s before release. Grip forces normal to the skin surface, load forces tangential to the skin surface, and the displacement of the object were measured on each trial. Adhesive (rosin) and lubricant (petroleum jelly) coatings were applied to the smooth metal surface of the object to alter the friction against the skin. In addition, neuronal activity evoked by force pulse-perturbations generating shear forces and slip on the skin were compared with the patterns of activity elicited by grasping and lifting the coated surfaces. Following changes in surface coatings, both monkeys modulated the rate at which grip forces normal to the skin surface and load forces tangential to the skin surface were applied during the lifting phase of the task. As a result, the ratio of the rates of change of the two forces was proportionately scaled to the surface coating properties with the more slippery surfaces, having higher ratios. This precise control of normal and tangential forces enabled the monkeys to generate adequate grip forces and prevent slip of the object. From a total of 386 single neurons recorded in the hand area of the somatosensory cortex, 92 were tested with at least 1 coating. Cell discharge changed significantly with changes in surface coating in 62 (67%) of these cells. Of these coating-related cells, 51 were tested with both an adhesive and lubricating coating, and 45 showed significant differences in activity between the untreated metal surface and either the lubricant or the adhesive coating. These cells were divided into three main groups on the basis of their response patterns. In the first group (group A), the peak discharge increased significantly when the grasped surface was covered with lubricant. These cells appeared to be selectively sensitive to slip of the object on the skin. The second group (group B) was less activated by the adhesive surface compared with either the untreated metal or the lubricated surface, and they responded mainly to variations in the force normal to the skin surface. These cells provide useful feedback for the control of grip force. The third group (group C) responded to both slips and to changes in forces tangential to the skin. Most of these cells responded with a biphasic pattern reflecting the bidirectional changes in load force as the object was first accelerated and then decelerated. One hundred sixty-eight of the 386 isolated neurons were tested with brief perturbations during the task. Of these, 147 (88%) responded to the perturbation with a significant change in activity. In most of the cells, the response to the perturbation was shorter than 100 ms with a mean latency of 44.1 +/- 16.3 (SD) ms. For each of the cell groups, the activity patterns triggered by the perturbations were consistent with the activity patterns generated during the grasping and lifting of the coated object.

Surveillance for Barrett's oesophagus in the UK

BACKGROUND

Endoscopic screening for Barrett's oesophagus is being offered without evidence of efficacy Barrett's oesophagus is not an ideal candidate for a screening programme, as the natural history is unclear, uncertainties surround the indication for intervention and the treatment is associated with high morbidity and mortality rates.

METHODS

To determine the practices that clinicians employ in the management of Barrett's oesophagus in the UK, postal questionnaires were sent in May 1997 to 297 randomly selected members of the British Society of Gastroenterology asking for details of their current practice.

RESULTS

Of 152 respondents, 106 (70 per cent) performed surveillance for Barrett's oesophagus; 46 (30 per cent) did not carry out screening. There was no difference in the practices carried out by physicians or surgeons, teaching or acute general hospital clinicians, or those with an upper gastrointestinal interest. There was a wide disparity in screening interval: just over half (52 per cent) screen at yearly intervals. Only nine (8 per cent) took four quadrant biopsies per 2 cm of Barrett's oesophagus. Nearly half (49 per cent) manage mild dysplasia by increasing the frequency of endoscopy; only seven (7 per cent) prescribed patients a proton pump inhibiting agent. Faced with severe dysplasia, 33 (31 per cent) offered surgery immediately; 22 (21 per cent) simply followed the patient by endoscopy. Those not choosing to perform screening most frequently cited lack of evidence of efficacy as the reason behind their decision.

CONCLUSION

There is wide variation in surveillance practices for Barrett's oesophagus. Some methods are ineffectual. The recommendations made by the Barrett's Oesophagus Working Party in 1991 are not followed, possibly because they are not practical. New workable guidelines based on available evidence and a consensus of expert opinion should be established; this was suggested by 38 per cent of respondents who performed screening.

Neuronal activity in somatosensory cortex of monkeys using a precision grip. I. Receptive fields and discharge patterns

Three adolescent Macaca fascicularis monkeys weighing between 3.5 and 4 kg were trained to use a precision grip to grasp a metal tab mounted on a low friction vertical track and to lift and hold it in a 12- to 25-mm position window for 1 s. The surface texture of the metal tab in contact with the fingers and the weight of the object could be varied. The activity of 386 single cells with cutaneous receptive fields contacting the metal tab were recorded in Brodmann's areas 3b, 1, 2, 5, and 7 of the somatosensory cortex. In this first of a series of papers, we describe three types of discharge pattern, the receptive-field properties, and the anatomic distribution of the neurons. The majority of the receptive fields were cutaneous and covered less than one digit, and a chi2 test did not reveal any significant differences in the Brodmann's areas representing the thumb and index finger. Two broad categories of discharge pattern cells were identified. The first category, dynamic cells, showed a brief increase in activity beginning near grip onset, which quickly subsided despite continued pressure applied to the receptive field. Some of the dynamic neurons responded to both skin indentation and release. The second category, static cells, had higher activity during the stationary holding phase of the task. These static neurons demonstrated varying degrees of sensitivity to rates of pressure change on the skin. The percentage of dynamic versus static cells was about equal for areas 3b, 2, 5, and 7. Only area 1 had a higher proportion of dynamic cells (76%). A third category was identified that contained cells with significant pregrip activity and included cortical cells with both dynamic or static discharge patterns. Cells in this category showed activity increases before movement in the absence of receptive-field stimulation, suggesting that, in addition to peripheral cutaneous input, these cells also receive strong excitation from movement-related regions of the brain.

Efficient presentation of house dust mite allergen Der p 2 by monocyte-derived dendritic cells and the role of beta 2 integrins

Monocyte-derived dendritic cells (MDDC) are potent antigen-presenting cells (APC). The APC functions of MDDC in allergy were examined. MDDC presentation of the major house dust mite allergen Der p 2 resulted in 4-12-fold higher T-cell proliferation and markedly higher IFN-gamma and IL-5 production than PBMC cultures. Comparable T-cell proliferation was obtained with 10-fold fewer MDDC than purified monocytes. MDDC cultured from adherent cells, or CD14+, CD11b+ or Percoll-purified monocytes were comparable in presenting soluble Ag, and in stimulating allogeneic MLR. Importantly, MDDC presentation of Der p 2 resulted in both Th1 and Th2 stimulation, although MDDC are known to produce high levels of IL-12 and stimulate biased Th1 responses. The basis for the potent APC function of MDDC was further examined. MDDC were found to be highly phagocytic. Immunoprecipitation studies showed markedly elevated ICAM-1 expression but > 10-fold reduction in LFA-1 expression on MDDC compared with monocytes. Monoclonal antibody (MoAb)-blocking experiments showed that ICAM-LFA-1 interaction was essential for MDDC stimulation of Der p 2-specific T-cell proliferative responses. These results show that the use of MDDC as APC provides a simple, sensitive and versatile method for detecting T-cell responses to allergens and that the strong phagocytic capability and the increased ICAM-1 expression of MDDC contribute significantly to their Ag presentation potency.

Neural pathways involved in the processing of concrete and abstract words

The purpose of this study was to delineate the neural pathways involved in processing concrete and abstract words using functional magnetic resonance imaging (fMRI). Word and pseudoword stimuli were presented visually, one at a time, and the participant was required to make a lexical decision. Lexical decision epochs alternated with a resting baseline. In each lexical decision epoch, the stimuli were either concrete words and pseudowords, or abstract words and pseudowords. Behavioral data indicated that, as with previous research, concrete word stimuli were processed more efficiently than abstract word stimuli. Analysis of the fMRI data indicated that processing of word stimuli, compared to the baseline condition, was associated with neural activation in the bilateral fusiform gyrus, anterior cingulate, left middle temporal gyrus, right posterior superior temporal gyrus, and left and right inferior frontal gyrus. A direct comparison between the abstract and concrete stimuli epochs yielded a significant area of activation in the right anterior temporal cortex. The results are consistent with recent positron emission tomography work showing right hemisphere activation during processing of abstract representations of language. The results are interpreted as support for a right hemisphere neural pathway in the processing of abstract word representations.

AIDS is ... reflections on the Australian research response to the HIV and AIDS epidemics

Drawing on institutional history, biography, and interviews with key informants from the range of academic disciplines that have contributed to the Australian response to the HIV and AIDS epidemics, this article provides critical insights into the factors that have shaped the Australian research response. The author demonstrates conflicts between disciplines that are rooted in epistemological differences. While the conflicts and tensions are often expressed in terms of access to resources, the disputes are grounded in the relative power of academic disciplines, most particularly the preeminence of biomedicine, and are related to the weight attributed to the various knowledge claims of those disciplines.

Regulation of tubulin polypeptides and microtubule function: Luv1p [correction of Rki1p] interacts with the beta-tubulin binding protein Rbl2p

Genetic analysis of microtubule functions in the yeast Saccharomyces cerevisiae suggests that cells manage the levels and activities of the tubulin polypeptides. These reactions may be involved in protein folding, formation of the heterodimer, and maintenance of the appropriate balance between alpha- and beta-tubulin. One protein involved in these functions is Rbl2p, which forms a complex with beta-tubulin. Here we describe the identification of a novel yeast gene, LUV1 [corrected], that interacts genetically with RBL2. Deletion of rki1 causes conditional defects in microtubule assembly and cell growth. Luv1p [corrected] can be isolated in a complex containing Rbl2p. The results support the existence of cellular mechanisms for regulating microtubule function through the tubulin polypeptides.

Functional magnetic resonance imaging: the basics of blood-oxygen-level dependent (BOLD) imaging

There are 2 principal techniques of functional MRI (fMRI): the blood-oxygen-level dependent (BOLD) technique, which is the favoured method because no intravenous contrast medium is required, and the dynamic or exogenous technique. The BOLD technique takes advantage of the fact that the change from diamagnetic oxyhemoglobin to paramagnetic deoxyhemoglobin that takes place with brain activation results in decreased signal intensity on MRI. Commercially available scanners can be used to conduct single-slice BOLD fMRI experiments, but echo-planar hardware is needed for multislice wholebrain experiments. Sequence choices in BOLD fMRI include spin-echo and gradient-echo sequences, to which rapid acquisition with relaxation enhancement and echoplanar techniques may be applied. Optimal imaging parameters (echo time, slice thickness, field of view and flip angle) are important in maximizing signal-to-noise ratios. Various statistical techniques and software programs have been developed to interpret the large amounts of data gathered from BOLD fMRI experiments, which presents one of the biggest challenges in performing this technique with clinical MR units. Controversy exists regarding the effects of draining veins on cortical mapping, of inflow of blood into the imaging slice or volume, and of motion artifact. BOLD fMRI has demonstrated good correlation with positron emission tomography, magneto-encephalography and electrocorticographic recordings of motor responses. It has been used to study cortical activity of visual, motor, auditory and speech tasks as well as brain centres for smell, motor imagery, complex motion and memory. As such, it holds promise for the study of brain function, but must be subjected to larger studies comparing it with the gold standard of electrocorticographic mapping.

A mutant of Arabidopsis lacking a chloroplastic isoamylase accumulates both starch and phytoglycogen

In this study, our goal was to evaluate the role of starch debranching enzymes in the determination of the structure of amylopectin. We screened mutant populations of Arabidopsis for plants with alterations in the structure of leaf starch by using iodine staining. The leaves of two mutant lines stained reddish brown, whereas wild-type leaves stained brownish black, indicating that a more highly branched polyglucan than amylopectin was present. The mutants were allelic, and the mutation mapped to position 18.8 on chromosome 1. One mutant line lacked the transcript for a gene with sequence similarity to higher plant debranching enzymes, and both mutants lacked a chloroplastic starch-hydrolyzing enzyme. This enzyme was identified as a debranching enzyme of the isoamylase type. The loss of this isoamylase resulted in a 90% reduction in the accumulation of starch in this mutant line when compared with the wild type and in the accumulation of the highly branched water-soluble polysaccharide phytoglycogen. Both normal starch and phytoglycogen accumulated simultaneously in the same chloroplasts in the mutant lines, suggesting that isoamylase has an indirect rather than a direct role in determining amylopectin structure.

Characterization of starch-debranching enzymes in pea embryos

Two distinct types of debranching enzymes have been identified in developing pea (Pisum sativum L.) embryos using native gel analysis and tests of substrate preference on purified or partially purified activities. An isoamylase-like activity capable of hydrolyzing amylopectin and glycogen but not pullulan is present throughout development and is largely or entirely confined to the plastid. Activities capable of hydrolyzing pullulan are present both inside and outside of the plastid, and extraplastidial activity increases relative to the plastidial activity during development. Both types of debranching enzyme are also present in germinating embryos. We argue that debranching enzymes are likely to have a role in starch metabolism in the plastid of the developing embryo and in starch degradation during germination.

Sir proteins, Rif proteins, and Cdc13p bind Saccharomyces telomeres in vivo

Although a surprisingly large number of genes affect yeast telomeres, in most cases it is not known if their products act directly or indirectly. We describe a one-hybrid assay for telomere binding proteins and use it to establish that six proteins that affect telomere structure or function but which had not been shown previously to bind telomeres in vivo are indeed telomere binding proteins. A promoter-defective allele of HIS3 was placed adjacent to a chromosomal telomere. Candidate proteins fused to a transcriptional activation domain were tested for the ability to activate transcription of the telomere-linked HIS3 gene. Using this system, Rif1p, Rif2p, Sir2p, Sir3p, Sir4p, and Cdc13p were found to be in vivo telomere binding proteins. None of the proteins activated the same reporter gene when it was at an internal site on the chromosome. Moreover, Cdc13p did not activate the reporter gene when it was adjacent to an internal tract of telomeric sequence, indicating that Cdc13p binding was telomere limited in vivo. The amino-terminal 20% of Cdc13p was sufficient to target Cdc13p to a telomere, suggesting that its DNA binding domain was within this portion of the protein. Rap1p, Rif1p, Rif2p, Sir4p, and Cdc13p activated the telomeric reporter gene in a strain lacking Sir3p, which is essential for telomere position effect (TPE). Thus, the telomeric association of these proteins did not require any of the chromatin features necessary for TPE. The data support models in which the telomere acts as an initiation site for TPE by recruiting silencing proteins to the chromosome end.

The relationship between caregiver burden and TBI survivors' cognition and functional ability after discharge

This exploratory correlational clinical study examines the relationship between reported caregiver burden (as measured by the Burden Interview) and cognition and functional ability (as measured by the Functional Independence Measure instrument) of people who had experienced traumatic brain injury (TBI). The purpose of the research was to explore the impact of cognition and functional ability in adults with TBI on perceived caregiver burden. Forty-two subjects with TBI and their caregivers were studied during the follow-up clinic appointment 3 months after discharge from a 31-bed inpatient rehabilitation unit. Demographic data and relationships to previous studies were explored. Pearson correlation matrixes and a simple single regression model were used to examine the relationships. Functional ability and cognition both negatively affected reported caregiver burden, although the relationship was not statistically significant.

Focal seizure-induced premature myelination: speculation from serial MRI

Local changes in the white matter underlying a focus of cortical thickening were monitored using MRI in an epileptic 2-month-old boy. We hypothesise that these changes reflected seizure-induced premature myelination.

Gastric carcinoid expresses the gastrin autocrine pathway

BACKGROUND

In gastric adenocarcinoma the gastrin autocrine-paracrine pathway is activated. As enterochromaffin-like (ECL) cells originate from the same stem as epithelial cells, the aim of this study was to determine if the gastrin autocrine pathway is present in gastric carcinoid.

METHODS

Samples from ten patients with gastric carcinoid were assessed by immunocytochemistry using primary antibodies directed against gastrin precursors and the gastrin/cholecystokinin B receptor and detected using the avidin-biotin immunoperoxidase system.

RESULTS

A high level of expression of precursor and mature gastrin peptides, together with the gastrin receptor, was seen in all carcinoids screened.

CONCLUSION

In common with the glandular epithelium of the stomach the gastrin gene is activated during the neoplastic process in ECL cells. This finding may explain why some carcinoids do not regress after surgical procedures that lower serum gastrin. Antigastrin agents may be a useful treatment for carcinoid either in their own right or as an adjunct to surgery.

Expression of CCKB/gastrin receptor isoforms in gastro-intestinal tumour cells

Anti-serum raised against the human cholecystokinin B (CCKB)/gastrin receptor was used in Western blotting to differentiate the cellular locations of receptor isoforms expressed by human gastro-intestinal (GI) tumour cell lines. Using anti-serum directed against the amino-terminal extracellular tail of the CCKB/gastrin receptor, 8/9 cell lines were shown to express immunoreactive proteins of either m.w. 70 or 40 kDa, or both. Both isoforms were found to be associated with intracellular, non-nuclear membranes, whereas only the 70 kDa protein was expressed in the plasma membrane. Receptor expression was related to gastrin production and secretion. Both progastrin and glycine-extended gastrin-17 were produced and secreted by the tumour cell lines; however, carboxy amidated gastrin was not detected by radioimmunoassay. A CCKB/gastrin receptor transfectant NIH3T3 cell line did not produce detectable gastrin and showed exclusive expression of the 70 kDa receptor on the plasma membrane. One cell line had <50 pg/ml cell-associated progastrin and no detectable receptor form. Cell lines expressing 50-150 pg/ml had both 40 and 70 kDa receptor forms. Those expressing >150 pg/ml progastrin had only the 40 kDa isoform, which was shown to be exclusively expressed on intracellular, non-nuclear membranes, in one of the cell lines. Of the 4 cell lines exclusively expressing the lower m.w. receptor, 3 had gastrin present within the cell, which was not secreted. Thus, if cell-associated gastrin induces a proliferative effect, it may be by an intracrine pathway. Our study has identified the presence of CCKB/gastrin receptor isoforms in different cellular locations and may help toward understanding the complex autocrine and intracrine pathways mediated by gastrin peptides.

A starch-accumulating mutant of Arabidopsis thaliana deficient in a chloroplastic starch-hydrolysing enzyme

The aim of this work was to identify enzymes that participate in the degradation of transitory starch in Arabidopsis. A mutant line was isolated by screening leaves at the end of the night for the presence of starch. The mutant had a higher starch content than the wild-type throughout the diurnal cycle. This accumulation was due to a reduction in starch breakdown, leading to an imbalance between the rates of synthesis and degradation. No reduction in the activity of endo-amylase (alpha-amylase), beta-amylase, starch phosphorylase, maltase, pullulanase or D-enzyme could be detected in crude extracts of leaves of the mutant. However, native PAGE in gels containing amylopectin revealed that a starch-hydrolysing activity, putatively identified as an endo-amylase and present in wild-type chloroplasts, was absent or appreciably reduced in the mutant. This is the first time that a specific enzyme required for starch degradation has been identified in leaves.

Revisiting sexual styles: patterns of adolescents' self-perceptions

Recently, Buzwell and Rosenthal proposed that sexual styles were a useful way of understanding young people's constructions of a sexual identity. In this work we replicated with a sample of 522 15- to 16-yr.-olds in broad terms, the five styles identified by Buzwell and Rosenthal.

Does penis size influence condom slippage and breakage?

This study examined the effect of penis dimensions on the probability of complete condom slippage and condom breakage in actual use. Men were recruited through advertising, used the condoms supplied and completed a diary sheet for each condom used. A total of 3658 condoms were used by 184 men of which 1.34% broke and 2.05% slipped off. No significant effect was demonstrated for penile dimensions on the probability of complete condom slippage. However, condom breakage was strongly associated with penile circumference. These findings suggest that condom manufacturers may need to increase the range of condom sizes available, or some aspects of their performance, in order to ensure that condoms meet the needs of all men without unduly exposing them to risk.

Quantitation of regional cerebral blood flow increases in prefrontal cortex during a working memory task: a steady-state arterial spin-tagging study

Steady-state arterial spin-tagging MRI approaches were used to quantitate regional cerebral blood flow increases in prefrontal cortex during a working memory ("two-back") task in six normal subjects. Statistically significant increases in cerebral blood flow in prefrontal cortex were observed in all six subjects: the average increase in cerebral blood flow in activated prefrontal cortex regions was 22 +/- 5 cc/100 g/min (23 +/- 7%). The results demonstrate that spin-tagging approaches can be used to follow focal activation in prefrontal cortex during cognitive tasks.

Australian and South African undergraduates' HIV-related knowledge, attitudes, and behaviors

To understand safe sex behavior in two countries which have been differentially affected by the HIV/AIDS epidemic, the present study compared the AIDS-related knowledge, attitudes, and behaviors of 920 heterosexual undergraduate students in Australia and 228 heterosexual undergraduate students in South Africa. South African students were found to have significantly less knowledge about HIV/AIDS, and significantly less favorable attitudes toward safe sex behavior than their Australian counterparts. They were also more likely to report that they have avoided various groups of people for fear of contracting AIDS. Experience from Australia over the period 1986-1995 suggests that significant improvements in the AIDS-related knowledge, attitudes, and behaviors of South African undergraduates are achievable.

Does additional lubrication affect condom slippage and breakage?

The risk of condom slippage (1.94%) and breakage (0.89%) among 3607 condoms was analysed with respect to the use of additional lubricant. Whether or not lubricant was used, the site at which it was applied and the type of lubricant used were all found to vary significantly with the type of sexual act(s) for which the condoms were used. Little evidence was found for differing effects of type of additional lubricant (water-based, saliva or other) or site of lubricant use (on penis/inside condom, on condom, in vagina/anus). The use of lubricant more than doubles the risk of slippage for vaginal sex. While anal sex is associated with much higher risks of slippage the use of lubricant for this practice actually reduces the risk of slippage to that similar for vaginal sex where lubricant is used. No significant effect of additional lubricant on condom breakage was observed. It is recommended that education messages concerning the use of additional lubricant may need to change to take into account the varied nature of lubricant use practices and the differential effects of lubricant with respect to sexual practices. Specifically, if the use of additional lubricant has little or no impact on condom breakage but increases condom slippage then encouraging its use may be counterproductive if condom users consider slippage to be a reason not to use condoms.