Serial transmission in rodents of neurodegeneration from transgenic mice expressing mutant prion protein

Two lines of transgenic (Tg) mice expressing high (H) levels of the mutant P101L prion protein (PrP) developed a neurologic illness and central nervous system pathology indistinguishable from experimental murine scrapie; these mice were designated Tg(MoPrP-P101L)H. Brain homogenates from Tg(MoPrP-P101L)H mice were inoculated intracerebrally into CD-1 Swiss mice, Syrian hamsters, and Tg196 mice, Tg mice expressing the MoPrP-P101L transgene at low levels. None of the CD-1 mice developed central nervous system dysfunction, whereas approximately 10% of hamsters and approximately 40% of the Tg196 mice manifested neurologic signs between 117 and 639 days after inoculation. Serial transmission of neurodegeneration in Tg196 mice and Syrian hamsters was initiated with brain extracts, producing incubation times of approximately 400 and approximately 75 days, respectively. Although the Tg(MoPrP-P101L)H mice appear to accumulate only low levels of infections prions in their brains, the serial transmission of disease to inoculated recipients argues that prion formation occurs de novo in the brains of these uninoculated animals. These Tg mouse studies, taken together with similar findings in humans dying of inherited prion diseases, provide additional evidence that prions lack a foreign nucleic acid.

Social Identity versus Personal Identity: An Investigation into the Interaction of group and Personal Status with Collective Self-Esteem on Ingroup Favouritism

In this study the authors investigated the effects of three independent variables, personal status (high, low, neutral), group status (high, low, neutral) and private collective self-esteem (CSE), on three dependent variables: ingroup favouritism, self-favouritism, and the difference between these two measures — ‘self versus ingroup favouritism’. Personal and group status were manipulated by providing bogus test feedback to 225 school children aged between 13–15 years. It was found that subjects with high CSE showed greater ingroup relative to self-favouritism (‘self vs ingroup favouritism’) than subjects with low CSE but only when group status was neutral or high. When group status was low there was little difference between high and low CSE subjects. A second study on the validity of private collective self-esteem found that it was moderately correlated with Jewish identification, and not correlated with subtle racism.

Results of cancer information assessment of high school students in West Virginia

The "Just Say KNOW To Cancer" education program was implemented in public high schools in Kanawha County, W.Va., to assess students' knowledge of cancer risk factors and to provide an educational program about cancer prevention. An anonymous questionnaire was completed in two urban and six suburban schools by 1,235 students in their classrooms. The responses revealed that only 35% and 10% of students were able to identify two or more risk factors and one American Cancer Society warning sign, respectively. Tobacco was the most commonly identified risk factor, being listed by 64% of urban students, compared to 50% of suburban respondents (p < .001). Although 84% of all students correctly answered the question regarding the medical complications of smokeless tobacco, only 39% correctly answered the question relating second-hand smoke as a cancer risk factor. The results of this study indicate the need for cancer education in the high school health curriculum.

Complementary DNA cloning and kinetic characterization of a novel intracellular serine proteinase inhibitor: mechanism of action with trypsin and factor Xa as model proteinases

The full-length cDNA encoding a novel human intracellular serine proteinase inhibitor has been sequenced and found to encode a 376 amino acid protein (M(r) approximately 42.5K) that we designate as cytoplasmic antiproteinase. Analysis of the primary structure revealed that the cytoplasmic antiproteinase has the majority of structural motifs conserved among the greater superfamily of serine proteinase inhibitors, or serpins. On the basis of several criteria such as amino acid identity and the absence of a classical N-terminal signal peptide, the cytoplasmic antiproteinase represents a new member of the intracellular serpin family. Further inspection of the cytoplasmic antiproteinase amino acid sequence identified three potential N-glycosylation sites and Arg341-Cys342 as the reactive site P1-P1' residues, respectively. We have also employed the slow binding kinetic approach to detail the mechanism of bovine trypsin and human factor Xa inhibition by the novel cytoplasmic antiproteinase. Inhibition of trypsin by the cytoplasmic antiproteinase was preceded by a two-step mechanism corresponding to the formation of an initial loose complex, followed by an isomerization step to a more stable, tight complex. The binding of the cytoplasmic antiproteinase to trypsin occurred with a second-order association rate constant of 2.8 x 10(6) M-1 s-1 and an overall equilibrium constant of 22.5 pM, demonstrating that the factor is a potent inhibitor of this proteinase. Under the appropriate conditions, the tight complex between trypsin and the cytoplasmic inhibitor was reversible, indicated by an exponential regeneration of proteinase amidolytic activity from the preformed complex. Therefore, the tight complex appears to be stabilized predominantly by reversible bonds that form between trypsin and the cytoplasmic inhibitor. In contrast to the inhibition of trypsin, the inhibition of factor Xa amidolytic activity by the cytoplasmic antiproteinase followed a single-step binding mechanism. The apparent first-order rate constant for factor Xa inhibition was found to increase as a linear function of the inhibitor concentration range studied. Formation of the inhibitory complex between factor Xa and the cytoplasmic antiproteinase occurred with a second-order association rate constant of approximately 1.3 x 10(5) M-1 s-1 and a equilibrium constant of 3.7 nM. These findings suggests that the cytoplasmic inhibitor may initially encounter significant energy barriers for proper alignment with the substrate binding cleft of factor Xa. However, once aligned, the reaction proceeds rapidly to a tight factor Xa.inhibitor complex that dissociates at a slow rate.

Degeneration of skeletal muscle, peripheral nerves, and the central nervous system in transgenic mice overexpressing wild-type prion proteins

Prion diseases of humans and animals are known to be caused by infection with prions containing PrPSc or mutation of the prion protein (PrP) gene. During transgenetic studies, we discovered that uninoculated older mice harboring high copy numbers of wild-type (wt) PrP transgenes derived from Syrian hamsters (SHa), sheep (She), and PrP-B mice developed truncal ataxia, hindlimb paralysis, and tremors. These transgenic (Tg) mice exhibited a profound necrotizing myopathy involving skeletal muscle, a demyelinating polyneuropathy, and focal vacuolation of the central nervous system. Development of disease was dependent on transgene dosage. For example, half of all Tg(SHaPrP+/+)7 mice homozygous for the SHaPrP transgene array developed disease by approximately 460 days of age, while no hemizygous Tg(SHaPrP+/o)7 mice became ill before 650 days. The novel neurologic syndrome found in older Tg(wtPrP) mice implies that overexpression of wtPrPC is pathogenic and widens the spectrum of prion diseases.

Return to arc welding following defibrillator implantation

A male arc welder who was fitted with an implantable defibrillator wished to return to his former employment. Device testing and ambient magnetic field measurements were performed at his place of work. During welding, artifacts were seen on the intracardiac electrogram but there was no resulting disturbance of sensing function. Measured field strengths were too low to result in device inactivation. The patient resumed his work without incident. This appears to be the first reported case of a patient with an implantable defibrillator returning to this "electrically hostile" environment following thorough screening.

Ablation of the prion protein (PrP) gene in mice prevents scrapie and facilitates production of anti-PrP antibodies

Mice, homozygous for prion protein (PrP) gene ablation (Prn-p0/0), develop normally and remain well > 500 days after inoculation with murine scrapie prions. In contrast, wild-type mice developed scrapie < 165 days after inoculation and most Prn-p0/+ mice, heterozygous for disruption of the PrP gene, exhibited signs of central nervous system dysfunction between 400 and 465 days after inoculation. In situ immunoblots showed widespread deposition of scrapie PrP (PrPSc) in the brains of both wild-type Prn-p+/+ and Prn-p0/+ mice, while neither cellular PrP (PrPC) nor PrPSc was detected in the brains of Prn-p0/0 mice. In contrast to Prn-p+/+ and Prn-p0/+ mice, Prn-p0/0 mice failed to propagate prion infectivity as measured by bioassays. Syrian hamster (SHa) PrP transgenes rendered Prn-p0/0 mice susceptible to prions containing SHaPrPSc. Immunization of Prn-p0/0 mice with purified, infectious mouse or SHa prions dispersed in Freund's adjuvant produced antisera that bound mouse, SHa, and human PrP on Western blots. Presumably, the lack of PrPC expression in Prn-p0/0 mice prevents them from becoming tolerant to the immunogen. The resistance of Prn-p0/0 mice to developing scrapie after inoculation with murine prions supports the hypothesis that PrPSc is essential for both transmission and pathogenesis of the prion diseases.

Disc degeneration and the young fast bowler in cricket

Twenty-four male fast bowlers of mean age 13.7 years, who bowled competitively at a school and club level were selected from five Western Australian schools. At the time of the testing all bowlers, who were bowling completely freely, underwent magnetic resonance imaging to detect the presence of intervertebral disc abnormalities. While these radiological data were being analysed, the players were filmed both laterally (200 Hz) and from directly above (100 Hz) as their front foot impacted a force platform during the delivery stride of the fast bowling action. In addition these bowlers performed selected physical capacity tests. The occurrence of abnormal radiological data were then used to group the bowlers (group 1, no abnormal features; group 2, disc degeneration and/or bulging on scan). A Mann-Whitney U rank test was then used to identify any significant differences (P < 0.1) between the groups for all dependent variables. Five of the subjects recorded abnormal magnetic resonance imaging scans of the lumbar spine, while nineteen recorded normal intervertebral discs, normal alignment of the lumbar spine, and no sign of spondylolisthesis. Bowlers who rotated the trunk to realign the shoulders to a more side-on position between back foot impact and front foot impact in the delivery stride were more likely to record abnormal intervertebral disc features.

Mapping of glutamic acid decarboxylase (GAD) genes

Glutamic acid decarboxylase (GAD) catalyzes the synthesis of gamma-aminobutyric acid (GABA), which is known as a major inhibitory neurotransmitter in the central nervous system (CNS), but is also present outside the CNS. Recent studies showed that GAD is the major target of autoantibodies associated with the development of insulin-dependent diabetes mellitus and of the rare stiff man syndrome. Studies of GAD expression have demonstrated multiple transcripts, suggesting several isoforms of GAD. In this study, three different genes were mapped by in situ hybridization to both human and mouse chromosomes. The GAD1 gene was mapped to human chromosome 2q31 and to mouse chromosome 2D in a known region of conservation between human and mouse. GAD2, previously mapped to human chromosome 10p11.2-p12, was mapped to mouse chromosome 2A2-B, which identifies a new region of conservation between human and mouse chromosomes. A potential GAD3 transcript was mapped to human chromosome 22q13 and to mouse chromosome 15E in a known region of conservation between human and mouse. It is concluded that the GAD genes may form a family with as many as three related members.

Propagation of prions with artificial properties in transgenic mice expressing chimeric PrP genes

Transgenic mice expressing chimeric prion protein (PrP) genes derived from Syrian hamster (SHa) and mouse (Mo) PrP genes were constructed. One SHa/MoPrP gene, designated MH2M PrP, contains five amino acid substitutions encoded by SHaPrP, while another construct, designated MHM2 PrP, has two substitutions. Transgenic (Tg) (MH2M PrP) mice were susceptible to both Syrian hamster and mouse prions, whereas three lines expressing MHM2 PrP were resistant to Syrian hamster prions. The brains of Tg(MH2M PrP) mice dying of scrapie contained chimeric PrPSc and prions with an artificial host range favoring propagation in mice that express the corresponding chimeric PrP and were also transmissible, at reduced efficiency, to nontransgenic mice and hamsters. Our findings provide genetic evidence for homophilic interactions between PrPSc in the inoculum and PrPc synthesized by the host.

Production of a severe cystic fibrosis mutation in mice by gene targeting

We have used gene targeting in embryonic stem cells to introduce an HPRT mini-gene into the coding sequence of the murine cystic fibrosis gene (cftr). This insertion introduces a termination codon in frame with the cftr coding sequence to terminate prematurely the CFTR protein within the first nucleotide binding domain. Animals homozygous for the cftr disruption fail to thrive and display a range of symptoms including meconium ileus, distal intestinal obstructions, gastrointestinal mucus accumulation and blockage of pancreatic ducts. The animals also show lacrimal gland pathology. Tracheal and caecal transepithelial current measurements demonstrate the lack of a cAMP activatable Cl- channel. These animals will prove useful for the evaluation of new therapeutic drugs and gene therapy strategies.

Identification of a calcium binding site in the protease domain of human blood coagulation factor VII: evidence for its role in factor VII-tissue factor interaction

Previous studies have identified a putative calcium binding site involving two glutamic acid residues located in the protease domain of coagulation factor IX. Amino acid sequence homology considerations suggest that factor VII (FVII) possesses a similar site involving glutamic acid residues 210 and 220. In the present study, we have constructed site-specific mutants of human factor VII in which Glu-220 has been replaced with either a lysine (E220K FVII) or an alanine (E220A FVII). These mutants were indistinguishable from wild-type factor VII by SDS-PAGE but only possessed 0.1% the coagulant activity of factor VII. Incubation of E220K/E220A FVII with factor Xa resulted in a slower than normal activation rate which eventually yielded a two-chain factor VIIa molecule possessing a coagulant activity of approximately 10% that of wild-type rFVIIa. Amidolytic activity measurements indicated that E220K/E220A FVIIa, unlike wild-type factor VIIa, possessed no measurable amidolytic activity toward the chromogenic substrate S-2288, even at high CaCl2 concentrations. Addition of tissue factor apoprotein, however, induced the amidolytic activity of the mutant molecule to a level 30% of that observed for wild-type factor VIIa. This tissue factor dependent enhancement of E220K/E220A FVIIa amidolytic activity was calcium dependent and required a CaCl2 concentration in excess of 5 mM for maximal rate enhancement. This was in sharp contrast to wild-type factor VIIa which required CaCl2 levels of 0.5 mM for maximal enhancement of tissue factor dependent amidolytic activity. Competition binding experiments suggest that the decrease in amidolytic and coagulant activity observed in the factor VII mutants is a direct result of impaired tissue factor binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Job-sharing: an innovative approach for administration

A job-sharing arrangement for the Assistant Directors of Physiotherapy at the Royal Jubilee Hospital proved to be an innovative and successful experience demonstrating the feasibility of job-sharing at administrative levels in rehabilitation. Physiotherapy is traditionally a female dominated profession. By the time therapists are most highly skilled and clinically experienced, they have arrived at prime marriage and child-bearing years. Many valuable members are lost to the profession each year as therapists leave the work force to take care of their families, continue their education and participate in recreational activities. Alternative employment opportunities are needed to retain and return therapists to the work force. Convenience of work time is often important. Financial expectations may become a secondary consideration. A search of the literature revealed that while job-sharing has much to recommend it, it is not yet generally accepted in most health professional situations. A few anecdotal references described job-sharing in nursing. An industry-wide literature search revealed few references to the application of job-sharing at administrative levels.

Chimeric prion protein expression in cultured cells and transgenic mice

The efficient expression of exogenous prion protein (PrP) molecules in mouse neuroblastoma cells that are chronically infected with murine scrapie prions (ScN2a cells; Butler, D.A., et al., 1988, J. Virol. 62, 1558-1564) and in transgenic mice is described. This technology allows investigation of the PrP molecule for structural regions involved in determining species specificity, as well as ablation experiments designed to address the functionality of particular regions of the PrP molecule. Previous reports demonstrated that the PrP gene specifies the host range for susceptibility of transgenic animals to prions (Scott, M., et al., 1989, Cell 59, 847-857; Prusiner, S.B., et al., 1990, Cell 63, 673-686). Consistent with these results, we showed that Syrian hamster (SHa) PrP is ineligible for efficient conversion to PrPSc in ScN2a cells. By constructing a series of chimeric mouse (Mo)/SHaPrP genes, we developed an epitopically tagged functional variant of the MoPrP gene, which can efficiently form protease-resistant PrP molecules upon expression in ScN2a cells. The presence of a defined epitope for an SHa-specific monoclonal antibody allows the products of this chimeric gene to be discriminated from endogenous MoPrP and creates a useful reagent for exploring structure/function relationships via targeted mutagenesis. In addition, we developed a transgenic mouse expression vector by manipulation of an SHaPrP cosmid clone. This vector permits the efficient expression of foreign PrP genes in the brains of transgenic animals, enabling pathological consequences of in vitro mutagenesis to be studied.

‘Race’ and Racism in South African Psychology

In this paper the author sketches how the issues of ‘race’ and racism have been taken up on the psychological terrain in South Africa over the past century. Racism manifested as both segregation and inequality in mental health provisions, and was actively promoted by leading psychologists. Psychologists on the other side of a political divide however turned attention to analysis of race relations mainly through the study of prejudice. Three areas of research are reviewed. While some useful findings have emerged, certain criticisms may be directed against this liberal framework of ‘race’ as prejudice.

Spontaneous neurodegeneration in transgenic mice with prion protein codon 101 proline----leucine substitution

Gerstmann-Sträussler-Scheinker syndrome (GSS) is an autosomal, dominantly inherited, human neurodegenerative disease that can sometimes be transmitted to non-human primates and rodents through intracerebral inoculation of brain homogenates from patients. Recent studies of GSS demonstrated significant genetic linkage between GSS and a leucine substitution at codon 102 of the human prion protein (PrP) gene. Transgenic mice were created to test the biologic activity of this mutation. Spontaneous neurologic disease with spongiform degeneration developed in one of three lines of transgenic mice containing murine PrP genes with a leucine substitution at codon 101 (homologous to codon 102 in humans). Transmission studies of brain homogenates from affected mice are in progress. These results indicate that some of the clinical and pathologic features of GSS can be reproduced in a transgenic mouse paradigm; this represents the first time a dominantly inherited, neurodegenerative process similar to a human disease has been genetically modeled in an experimental animal (Hsiao and Prusiner 1990).

Cloning and primary structure of a human islet isoform of glutamic acid decarboxylase from chromosome 10

Glutamic acid decarboxylase (GAD; glutamate decarboxylase, L-glutamate 1-carboxy-lyase, EC 4.1.1.15), which catalyzes formation of gamma-aminobutyric acid from L-glutamic acid, is detectable in different isoforms with distinct electrophoretic and kinetic characteristics. GAD has also been implicated as an autoantigen in the vastly differing autoimmune disease stiff-man syndrome and insulin-dependent diabetes mellitus. Despite the differing GAD isoforms, only one type of GAD cDNA (GAD-1), localized to a syntenic region of chromosome 2, has been isolated from rat, mouse, and cat. Using sequence information from GAD-1 to screen a human pancreatic islet cDNA library, we describe the isolation of an additional GAD cDNA (GAD-2), which was mapped to the short arm of human chromosome 10. Genomic Southern blotting with GAD-2 demonstrated a hybridization pattern different from that detected by GAD-1. GAD-2 recognizes a 5.6-kilobase transcript in both islets and brain, in contrast to GAD-1, which detects a 3.7-kilobase transcript in brain only. The deduced 585-amino acid sequence coded for by GAD-2 shows less than 65% identity to previously published, highly conserved GAD-1 brain sequences, which show greater than 96% deduced amino acid sequence homology among the three species. The function of this additional islet GAD isoform and its importance as an autoantigen in insulin-dependent diabetes remain to be determined.

Effect of 12 and 20 weeks of resistance training on lumbar extension torque production

This study compared the effect of varied training frequencies on the development of isometric lumbar extension torque (strength) over 12- and 20-week training periods. Fifty-six subjects were randomly assigned to training once every other week (training group 1, n = 10), once per week (training group 2, n = 12), twice per week (training group 3, n = 12), or three times per week (training group 4, n = 7) or to a nontraining control group (n = 15). Training consisted of one set of 8 to 12 variable-resistance lumbar extensions to volitional muscular fatigue. Prior to and following 12 and 20 weeks of training, subjects were given a test that evaluated isolated isometric lumbar extension torque in a seated position at seven positions (angles) through a 72-degree range of motion. The control group showed no change in isometric torque. All training groups showed significant increases in lumbar extension torque at 12 and 20 weeks of training, whereas no significant differences were found among the groups with respect to the magnitude of torque gained. Pooled training showed a significant time x angle interaction at 12 weeks and a continuing trend at 20 weeks, indicating that the shape of the isometric torque-angle curve changed as a result of training. This effect was due to greater increases in isometric torque at the fully extended position than at the fully flexed position at 12 weeks (92% versus 16%, respectively) and at 20 weeks (123% versus 17%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma of the small intestine in Crohn's disease: a unique finding

Development of adenocarcinoma of the small bowel is rare. We present this report of a patient with a long-standing history of Crohn's disease who was found to have the 95th reported case of adenocarcinoma developed in the presence of Crohn's. The unique feature of this case is the finding of two distinctly separate carcinomas in the same surgical specimen. With report of this case and a review of the literature, certain characteristics are presented in hopes of raising suspicions sufficiently to detect this malady at an earlier stage.

Paradoxical shortening of scrapie incubation times by expression of prion protein transgenes derived from long incubation period mice

Prolonged incubation times for experimental scrapie in I/LnJ mice are dictated by a dominant gene linked to the prion protein gene (Prn-p). Transgenic mice were analyzed to discriminate between an effect of the I/LnJ Prn-pb allele and a distinct incubation time locus designated Prn-i. Paradoxically, 4 independent Prn-pb transgenic mouse lines had scrapie incubation times shorter than nontransgenic controls, instead of the anticipated prolonged incubation periods. Aberrant or overexpression of the Prn-pb transgenes may dictate abbreviated incubation times, masking genuine Prn-p/Prn-i congruence; alternatively, a discrete Prn-i gene lies adjacent to Prn-p.

X chromosome inactivation in fibroblasts of mentally retarded female carriers of the fragile site Xq27.3: application of the probe M27 beta to evaluate X inactivation status

Over 30% of female carriers of the fragile X [fra(X)] syndrome are clinically affected. A nonrandom X chromosome inactivation in these cases could be a plausible explanation. A review of previous studies addressing this question showed inconclusive results; thus, we analysed the X inactivation pattern in fibroblasts of 4 unrelated, mentally retarded fra(X) carriers with a high expression of the fragile site Xq27.3. Using Southern analysis with a highly polymorphic probe M27 beta that recognizes methylation differences between the active and inactive X chromosome we found a 50/50 inactivation pattern in 2 cases and skewed patterns in the other 2. As biased patterns were also observed in control females we conclude that at present no evidence exists for a nonrandom X chromosome inactivation in the fra(X) syndrome in females.

Acute upper gastrointestinal haemorrhage in a district general hospital: audit of an agreed management policy

All patients from an unselected population admitted with acute upper gastrointestinal (GI) haemorrhage to a District General Hospital (DGH) were studied prospectively over one year. Before the study period a management policy was agreed between physicians and surgeons. One-hundred-and-nine patients were admitted. Sixty-eight per cent were over 60 and 17% over 80 years of age. Sixty patients bled from peptic ulcers and seven patients rebled. Endoscopic stigmata (visible vessel, adherent clot, and oozing) were useful in identifying those at increased risk of rebleeding but not as an indication for surgery. Six patients underwent surgery for peptic ulceration with one postoperative death. There were four deaths among the other patient groups giving an overall mortality of 4.6%. This audit shows a low mortality after acute upper GI haemorrhage can be achieved even in an elderly population in a DGH without the establishment of a specialist unit but with an agreed policy of management.

Spontaneous neurodegeneration in transgenic mice with mutant prion protein

Transgenic mice were created to assess genetic linkage between Gerstmann-Sträussler-Scheinker syndrome and a leucine substitution at codon 102 of the human prion protein gene. Spontaneous neurologic disease with spongiform degeneration and gliosis similar to that in mouse scrapie developed at a mean age of 166 days in 35 mice expressing mouse prion protein with the leucine substitution. Thus, many of the clinical and pathological features of Gerstmann-Sträussler-Scheinker syndrome are reproduced in transgenic mice containing a prion protein with a single amino acid substitution, illustrating that a neurodegenerative process similar to a human disease can be genetically modeled in animals.

Transgenetic studies implicate interactions between homologous PrP isoforms in scrapie prion replication

Transgenic (Tg) mice expressing both Syrian hamster (Ha) and mouse (Mo) prion protein (PrP) genes were used to probe the mechanism of scrapie prion replication. Four Tg lines expressing HaPrP exhibited distinct incubation times ranging from 48 to 277 days, which correlated inversely with HaPrP mRNA and HaPrPC. Bioassays of Tg brain extracts showed that the prion inoculum dictates which prions are synthesized de novo. Tg mice inoculated with Ha prions had approximately 10(9) ID50 units of Ha prions per gram of brain and less than 10 units of Mo prions. Conversely, Tg mice inoculated with Mo prions synthesized Mo prions but not Ha prions. Similarly, Tg mice inoculated with Ha prions exhibited neuropathologic changes characteristic of hamsters with scrapie, while Mo prions produced changes similar to those in non-Tg mice. Our results argue that species specificity of scrapie prions resides in the PrP sequence and prion synthesis is initiated by a species-specific interaction between PrPSc in the inoculum and homologous PrPC.

Regulation of testicular function by insulin and transforming growth factor-beta

Hyperinsulinism is associated with disorders of androgen production in humans. We have studied the effects of insulin and insulin-like growth factor-1 on androgen production in vitro using a crude preparation of mouse Leydig cells incubated with luteinizing hormone in a serum-free medium. We found a positive correlation between testosterone production and the luteinizing hormone dose over 3 hours. Exposure of the cells for 1 hour to insulin (1 micrograms/ml) prior to the addition of luteinizing hormone significantly augmented the amount of testosterone produced in response to the gonadotropin when added after this preincubation. In contrast, prior exposure of the cells to proinsulin (30 micrograms/ml), insulin-like growth factor-1 (30 ng/ml), or epidermal growth factor-1 (1 micrograms/ml) did not influence the testosterone response to luteinizing hormone. Transforming growth factor-beta reduced the testosterone response to luteinizing hormone. Transforming growth factor-beta (1,000 pg/ml) blocked the insulin augmentation of luteinizing hormone-stimulated testosterone production. We conclude that insulin has an endocrine effect on testosterone production by mouse Leydig cells in vitro. Furthermore, the Leydig cell response to insulin is itself sensitive to interaction with transforming growth factor-beta which may operate as part of the paracrine control of Leydig cell function.

Effect of training frequency and specificity on isometric lumbar extension strength

To investigate the effects of training frequency and specificity of training on isolated lumbar extension strength, 72 men (age = 31 +/- 9 years) and 42 women (age = 28 +/- 9 years) were tested before and after 12 weeks of training. Each test involved the measurement of maximum voluntary isometric torque at 72 degrees, 60 degrees, 48 degrees, 36 degrees, 24 degrees, 12 degrees, and 0 degrees of lumbar flexion. After the pretraining tests, subjects were randomly stratified to groups that trained with variable resistance dynamic exercise every other week (1X/2 weeks, n = 19), once per week (1X/week, n = 22), twice per week (2X/week, n = 23) or three times per week (3X/week, n = 21); a group that trained isometrically once per week (n = 14); or a control group that did not train (n = 15). Analysis of covariance showed that all training groups improved their ability to generate isometric torque at each angle measured when compared with controls (P less than 0.05). There was no statistical difference in adjusted posttraining isometric torques among the groups that trained (P greater than 0.05), but dynamic training weight increased to a lesser extent (P less than 0.08) for the 1X/2 weeks group (26.6%) than for the groups that trained 1X/week, 2X/week, and 3X/week (37.2 to 41.4%). These data indicate that a training frequency as low as 1X/week provides an effective training stimulus for the development of lumbar extension strength. Improvements in strength noted after isometric training suggest that isometric exercise provides an effective alternative for developing lumbar strength.

Quenching of the amidolytic activity of one-chain tissue-type plasminogen activator by mutation of lysine-416

In contrast to most other serine proteases, tissue-type plasminogen activator (t-PA) possesses enzymatic activity as the one-chain zymogen form. The hypothesis that lysine residues 277 or 416 may be involved in stabilization of an active conformation of one-chain t-PA via salt-bridge formation with aspartic acid residue 477 was tested by site-directed mutagenesis. Four recombinant t-PA mutants were constructed. The amidolytic activities of these analogues were compared to that of authentic t-PA. Substitution of arginine-275 provided an analogue [( R275G]t-PA) resistant to plasmin cleavage. The amidolytic activity of [R275G]t-PA was comparable to that of authentic one-chain t-PA, and so was the activity of [R275L,K277L]t-PA, in which additional substitution of lysine residue 277 was carried out. This suggested that its presence was nonessential for obtaining one-chain t-PA activity. In contrast, substitution of lysine residue 416 to obtain [K416S]t-PA and [K416S,H417T]t-PA resulted in substantial quenching of amidolytic one-chain activity. As expected, the amidolytic activities of the two-chain forms were less affected by the substitution. Involvement of lysine residue 416 in one-chain t-PA activity was also indicated by decreased activities of [K416S]t-PA and [K416S,H417T]t-PA with plasminogen as the substrate. The one-chain activity of the lysine residue 416 substitution analogues was partially restored in the presence of fibrin. This could indicate that strong ligands such as fibrin might provide an alternative stabilization of the active conformation of one-chain t-PA.

Transgenic mice expressing hamster prion protein produce species-specific scrapie infectivity and amyloid plaques

Three transgenic mouse lines designated Tg 69, 71, and 81 were produced harboring a Syrian hamster (Ha) prion protein (PrP) gene; all expressed the cellular HaPrP isoform in their brains. Inoculation of Tg 81 mice or hamsters with Ha prions caused scrapie in integral of 75 days; nontransgenic control mice failed to develop scrapie after greater than 500 days. Tg 71 mice inoculated with Ha prions developed scrapie in integral of 170 days. Both Tg 71 and Tg 81 mice exhibited spongiform degeneration and reactive astrocytic gliosis, and they produced the scrapie HaPrP isoform in their brains. Tg 81 brains also showed HaPrP amyloid plaques characteristic of Ha scrapie and contained integral of 10(9) ID50 units of Ha prions based on Ha bioassays. Our findings argue that the PrP gene modulates scrapie susceptibility, incubation times, and neuropathology; furthermore, they demonstrate synthesis of infectious scrapie prions programmed by a recombinant DNA molecule.

Back injuries to fast bowlers in cricket: a prospective study

Eighty-two high performance young male fast bowlers (mean age 16.8 years) were tested immediately prior to the season for selected kinanthropometric and physiological data. Subjects were also filmed both laterally (200 Hz) and from above (100 Hz) while bowling so that their front foot impacted a force platform during the delivery stride. The players then completed a log book over the ensuing season that detailed their training and playing programmes. All cricket related injuries over this season were assessed by a sports physician who used computerized tomography to assist in the diagnosis of spinal injuries. At the completion of this season the players were grouped according to their injury status (Group 1--bony injury to a vertebra; Group 2--soft tissue injury to the back that caused the player to miss at least one game, and Group 3--no injuries). A one-way analysis of variance was used to identify if any variables were significantly (P less than 0.05) different between the three groups, and a Scheffe post hoc comparison was used to determine which groups were significantly different. Eleven per cent of the players sustained a stress fracture to a vertebra(e) (L4 to S1), while 27 per cent sustained a soft tissue injury to the back. Bowlers with a low longitudinal foot arch were more likely to develop a stress fracture than those with a high arch. Shoulder depression and horizontal flexion strength for the preferred limb and quadriceps power in the non-preferred limb were also significantly related to back injuries. Results suggest that bowlers with the above physical characteristics, who bowl with these biomechanical techniques for extended periods, are predisposed to back injuries.

Phorbol ester and calcium ionophore are sufficient to promote cell replication in cultures of quiescent human B lymphocytes

Highly purified, resting B cells could be induced to grow for up to 10 days by culturing in the presence of a synergistic combination of a tumour-promoting phorbol ester and the calcium ionophore ionomycin. In spite of evident cell death occurring, four to five times as many viable B lymphocytes could be harvested at the end of culture than were initially plated. Soluble factors derived from T cells (interleukin-2, commercial B-cell growth factor) or monocytes (interleukin-1) failed to augment further the growth-promotion observed. Evidence is presented to suggest that an autocrine component might be necessary for maintenance of the cell-cycle and growth initiated by the phorbol ester and calcium ionophore combination. The significance of these findings to B-cell physiology are discussed.

Health hazards of farming

The U.S. farm work force numbers approximately 6.5 million. The health risks connected with their farm tasks are many and varied. Accidents and illnesses are caused by tractors, specialized farming equipment, chemicals, zoonoses, fungi, sensitizers, and the environment of confinement buildings. The scattered nature of the work force makes preventive measures difficult to implement.

The effect of polymerised fibrin on the catalytic activities of one-chain tissue-type plasminogen activator as revealed by an analogue resistant to plasmin cleavage

A one-chain recombinant tissue-type plasminogen activator (EC 2.4.31.-) (tPA) analogue was constructed in which Arg-275 of the activation site was changed to Gly by site-directed mutagenesis. This analogue, tPA-Gly275, was very resistant to plasmin (EC 2.4.21.5) cleavage. It has been used to gain information about the activity of the uncleaved one-chain tPA form, also when plasmin is generated as a result of a plasminogen activation reaction. The amidolytic activity of tPA-Gly275 with less than Glu-Gly-Arg-pNA was investigated and compared to that of one-chain and two-chain wild-type recombinant tPA. A small but significant intrinsic amidolytic activity was observed with the analogue as well as the wild-type one-chain tPA form. However, it was much lower than that of two-chain tPA. Polymerised fibrin enhanced the amidolytic activity of both one-chain tPA forms but not of two-chain tPA. Measurements of the plasminogen activation kinetics in the absence of fibrin revealed that tPA-Gly275 possessed a significant intrinsic activity. However, it was 30-fold lower than that of two-chain tPA. Addition of polymerised fibrin profoundly enhanced the plasminogen activation rate of both tPA-Gly275 and wild-type one- and two-chain tPA to approximately the same maximal level. The results were interpreted to mean that fibrin binding can induce an activated state of the intact tPA one-chain form.

Sports injuries at the 1985 Junior Olympics. An epidemiologic analysis

The XIX Junior Olympic Games, hosted in Iowa City, Iowa, in August of 1985, involved 3,028 athletes who participated for 7 days in 13 different sports at 8 separate sites. Medical coverage for the Games was provided by the University of Iowa Sports Medicine Service. Staffing for the events involved approximately 75 physicians, 60 athletic trainers, and other health care personnel. A triage protocol was established prior to the Games whereby the athletic trainer would make first contact with the injured athlete and would evaluate and treat the injury based on standing orders. If in the judgment of the trainer, the athlete needed to be referred to a physician, one would be available, either on site or on call. During the Games, 1,113 medical encounters were recorded, 121 of those being deemed serious enough to withhold an athlete from competition pending further evaluation and treatment. The 121 significant injuries and illnesses involved 116 athletes (66% male, 34% female). Thirty-four percent of the significant injuries only required treatment by the trainer, while 46% were referred to an on site physician and 20% needed a specialty consultant. Seventeen percent of the significant injuries resulted in the athlete being medically disqualified for the remainder of the event. The most common injuries/illnesses were contusions (26%), sprains (21%), heat (17%), strains (9%), and other illnesses (12%). According to body region, 44% of the 121 injuries were to the lower extremity, 26% to the head, neck, and trunk, and 12% to the upper extremity.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective intraarterial DSA of the parathyroid glands in patients with hyperparathyroidism after parathyroidectomy

Eighteen patients with recurrent hyperparathyroidism after parathyroidectomy were prospectively examined with selective intraarterial digital subtraction angiography (DSA) of the brachiocephalic arteries. The results were compared with findings at reoperation. Seventeen of the 21 remaining abnormal parathyroid glands were correctly detected by selective DSA (sensitivity = 81%). In the neck and mediastinum, sensitivities were 73% (8/11) and 90% (9/10), respectively. All patients with histopathologic confirmation of primary hyperparathyroidism (17/18) became normocalcemic postoperatively. We conclude that selective intraarterial DSA is indicated in patients with recurrent hypercalcemia after parathyroidectomy when the results of noninvasive imaging techniques are uncertain.