The limb deformity mutation disrupts the SHH/FGF-4 feedback loop and regulation of 5′ HoxD genes during limb pattern formation

Mutations in the murine limb deformity (ld) gene disrupt differentiation of the Apical Ectodermal Ridge (AER) and patterning of distal limb structures. However, initial outgrowth of the limb bud is not affected, suggesting that early and late functions of the AER are uncoupled. Similarly, activation of the 5′ members of the HoxD gene cluster (Hoxd-11 to Hoxd-13) is not affected in ld mutant posterior limb bud mesenchyme, but the subsequent anteriorization of 5′ HoxD domains is delayed by about 12 hours and is associated with reduced levels of polarising activity. These results indicate that the ld gene products act upstream of 5′ HoxD genes during patterning of the autopod. Expression of the signalling molecule Sonic hedgehog (Shh) in the posterior limb bud mesenchyme is initiated normally, but ceases prematurely indicating a defect in maintenance of Shh by the ld mutant AER. Furthermore, no Fgf-4 transcripts are detected in the ld mutant AER, whereas Fgf-8 transcripts remain expressed. However, Shh expression can be rescued by heterospecific grafting of ld mutant posterior mesenchyme under a wild-type chicken AER. These studies show that the AER defect in ld homozygous limb buds causes disruption of the FGF-4/SHH feedback loop and support the proposed essential role for FGF-4 in maintaining Shh expression during limb pattern formation.

Cardiac allograft failure: successful use of biventricular assist device

Nonspecific primary allograft dysfunction is an important cause of perioperative death in cardiac transplant recipients. We report a case of severe nonspecific allograft dysfunction that was ultimately reversible after 18 days of biventricular mechanical circulatory support. Allograft recovery was echocardiographically recognized by a positive inotropic response to isoproterenol and milrinone. This case illustrates the potential for recovery of even extreme allograft dysfunction.

Quantitative Doppler assessment of acute scrotal inflammation

PURPOSE

To establish quantitative Doppler criteria for acute unilateral epididymitis and/or orchitis.

MATERIALS AND METHODS

Triplex ultrasonography (US) was used to prospectively evaluate 31 patients with acute hemiscrotal pain and 15 asymptomatic control subjects. Morphology and perfusion were assessed, and peak systolic velocities (PSVs) were recorded. Ratios of PSV were calculated by using values from the right and left sides.

RESULTS

PSVs in control subjects differed significantly from those in patients (P < .0001). A PSV > or = 15 cm/sec produced diagnostic accuracy of 90% for orchitis and 93% for epididymitis: Five of six false-negative findings were in patients younger than age 15 years. Epididymal PSV ratios > or = 1.7 or testicular ratios > or = 1.9 were diagnostic of acute inflammation (P < .0001). In three cases, morphologic and color Doppler findings were normal and only the PSV ratios were diagnostic.

CONCLUSION

PSV and PSV ratios provide diagnostic criteria for acute unilateral epididymitis and/or orchitis that are more accurate than morphologic evaluation and color flow imaging either alone or in combination.

Chemotherapeutic tumour targeting using clostridial spores

The toxicity associated with conventional cancer chemotherapy is primarily due to a lack of specificity for tumour cells. In contrast, intravenously injected clostridial spores exhibit a remarkable specificity for tumours. This is because, following their administration, clostridial spores become exclusively localised to, and germinate in, the hypoxic/necrotic tissue of tumours. This unique property could be exploited to deliver therapeutic agents to tumours. In particular, genetic engineering could be used to endow a suitable clostridial host with the capacity to produce an enzyme within the tumour which can metabolise a systemically introduced, non-toxic prodrug into a toxic metabolite. The feasibility of this strategy (clostridial-directed enzyme prodrug therapy, CDEPT) has been demonstrated by cloning the Escherichia coli B gene encoding nitroreductase (an enzyme which converts the prodrug CB1954 to a highly toxic bifunctional alkylating agent) into a clostridial expression vector and introducing the resultant plasmid into Clostridium beijerinckii (formerly C. acetobutylicum) NCIMB 8052. The gene was efficiently expressed, with recombinant nitroreductase representing 8% of the cell soluble protein. Following the intravenous injection of the recombinant spores into mice, tumour lysates have been shown, by Western blots, to contain the E. coli-derived enzyme.

The effect of nearby luminance contrast polarity on color boundary localization

The study measured the shift in apparent position of a color-defined target boundary as a function of the distance, luminance polarity and amount of contrast of a nearby luminance-defined flanking boundary. In general, the position of the target boundary shifted towards the flank with the attraction being somewhat greater for negative than positive polarity flanks, and for high compared to low contrast flanks. High contrast, negative polarity flanks resulted in greater attraction at 3.69 min arc separation. For low contrast flanks, the apparent shift in position of the target boundary depended on the polarity and position of the flank relative to the target. For example, for small separations ( < 3 min arc) flank polarity had little influence, while for larger separations ( > or = 3.69 min arc), negative polarity flanks exhibited attraction while positive polarity flanks began to show repulsion. The results support the notion that luminance and color processing may share a common representation for the localization of boundaries. Position judgments based on this representation appear to be influenced by the amount of luminance contrast in a nearby boundary.

Molecular characterization of plasminogen activators in human gingival crevicular fluid

Plasminogen activators (PAs), a family of serine proteases, and their inhibitors (PAIs) are important in fibrinolysis, wound healing and tissue remodelling. Previous studies revealed differences in the localization of PA activity between healthy and diseased gingival tissues, suggesting that PAs and PAIs could play a part in periodontal homeostasis and disease. PAs and PAIs are synthesized by most of the cells types making up the periodontium and can be identified in gingival crevicular fluid (GCF). These studies sought to characterize the molecular species of PAs and their inhibitors in GCF collected from clinically healthy sites. PA enzymatic activity in GCF samples demonstrated by fibrin zymography revealed the presence of only tissue-type PA (tPA) activity. No urokinase-type PA (uPA) enzymatic activity was detected. tPA enzymatic activity appeared predominantly as an uncomplexed 70-kDa species, although some samples contained enzyme-inhibitor complexes. Quantitation of total tPA by enzyme immunoassay showed a mean concentration of 1.6 ng/microl. Analysis of GCF samples for uPA by immunoblotting and enzyme immunoassay disclosed the presence of small amounts of uPA (0.2 ng/microl), which were present predominantly in activator-inhibitor complexes. Immunoblotting showed specific PAI-2 immunoreactivity bands in high molecular-weight complexes and low molecular-weight degradation products, but less than nanogram amounts of free PAI-2 molecules. Enzyme immunoassay revealed that PAI-2 was present in an at least a seven times greater amount than PAI-1. These observations support the hypothesis that PA-generated proteolysis and its regulation by endogenous inhibitors has a role in the diverse biochemical mechanisms underlying periodontal physiology and pathology including host-microbial interaction, polymorphonuclear leucocyte infiltration, turnover and migration of epithelial cells, connective tissue degradation and remodelling, fibrinolysis and wound healing.

Potential gene therapy strategies in the treatment of cardiovascular disease

Gene therapy is the introduction of new genetic material into somatic cells to synthesize missing or defective proteins. Efficient methods for the introduction of genetic material into cells are available, both in vitro and in vivo. These strategies involve chemical, physical, and viral-mediated mechanisms of gene transfer. Application of these gene transfer techniques has led to the development of potential gene-based treatment strategies that could combat vascular and myocardial disease. Gene therapy in the treatment of cardiovascular disease promises to alter atherosclerotic risk factors, prevent vascular thrombotic disease, retard progression of disease in the peripheral vasculature, provide drug delivery systems, and prevent myocardial infarction in patients with coronary artery disease. This exciting technology will eventually become the ultimate intervention in the treatment of cardiovascular disease.

Selectable insertion and deletion mutagenesis of the human cytomegalovirus genome using the Escherichia coli guanosine phosphoribosyl transferase (gpt) gene

We describe the mutagenesis of the IRSI-US5 region of the human cytomegalovirus genome, demonstrating the potential of the E. coli guanosine phosphoribosyl transferase (gpt) gene as a selectable marker for insertion and deletion mutagenesis of high passage (AD169, Towne) as well as low passage (Toledo) strains of virus. Despite evidence suggesting that the US3 gene product may play a regulatory role, disruption of this gene with a gpt insert had no effect on growth of any of these strains of virus in resting or dividing human fibroblasts, or in human thymus plus liver implants in SCID-hu mice. Transcripts of the gpt gene, under control of the herpes simplex virus thymidine kinase promoter adjacent to the US3 enhancer in the viral genome, accumulated with delayed early (beta) kinetics. Mutants with deletions in the IRS1 and US3-US5 regions were isolated by back-selection against gpt with the drug 6-thioguanine by growing virus in human Lesch-Nyhan (hypoxanthine-guanine phosphoribosyl transferase deficient) skin fibroblasts immortalized with human papillomavirus oncogenes. Thus, we demonstrate a dependable method for insertion and deletion mutagenesis that can be applied to any region of the viral genome.

Functional differentiation within latissimus dorsi

"Functional differentiation" within skeletal muscle refers to the ability of the Central Nervous System (CNS) to control, with a degree of independence, individual subunits of a muscle during a particular muscle contraction. Essentially, the concept of functional differentiation within skeletal muscle suggests an ability of the CNS to selectively activate those segments of a muscle which have the most appropriate line of action for the task as a means of ensuring the muscles efficient utilisation. The present study was undertaken to determine whether functional differentiation was present within the radiate muscle, Latissimus Dorsi, during a series of isometric muscle contractions. Six surface electrode pairs were placed along the origin of the muscle and electromyographic (EMG) potentials were recorded during isometric contractions in various planes and levels of contraction intensity. The EMG waveforms were integrated (IEMG) and then normalised. The normalised EMG waveforms (nIEMG) were then statistically compared to determine if muscle fibres within the detection area of each electrode pair had varied their contribution to the total activity of the muscle, from one isometric contraction to another. Alterations in the contribution of each site were taken to be indicative of functional differentiation. The results of this study indicated that functional differentiation did occur within Latissimus Dorsi. In essence, the most caudal fibres were utilised preferentially when subjects performed adduction from an abducted position of the shoulder joint. Conversely, activity was distributed over the entire muscle when subjects attempted adduction from the anatomical position. A similar situation was observed when subjects performed horizontal extension from either a flexed or abducted position.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of immature myocardial tolerance to ischemia: phenotypic differences in antioxidants, stress proteins, and oxidases

BACKGROUND

Previous work has suggested tolerance to ischemic injury in newborn myocardium. Although various mechanisms for this protection have been proposed, a link between oxidant-antioxidant factors, stress protein expression, and protection from cardiac ischemia/reperfusion (I/R) injury has not been made in newborn myocardium. We hypothesized total newborn myocardial resistance to I/R is related to decreased oxygen radical producing potential, increased free radical scavenging capacity and augmented stress protein expression. The purposes of the study were to examine in newborn and adult rat hearts (1) functional recovery from I/R, (2) catalase and xanthine oxidase (XO) activities, and (3) heat shock protein 72 (HSP 72) expression.

METHODS

Isolated rat hearts (7 to 10 days versus 60 days) were perfused on a nonworking Langendorff apparatus at 60 mm Hg (Krebs-Henseleit buffer, pH 7.4, 37 degrees C) and subjected to 20 minutes of global ischemia and 40 minutes of reperfusion. Left ventricular developed pressure was recorded by using a left ventricular catheter. Catalase and XO were measured by means of standard assays, and HSP 72 was assessed with in situ immunohistochemistry.

RESULTS

Newborn rat hearts had greater percentage functional recovery of left ventricular developed pressure after I/R (66.0% +/- 4.2% versus 44.3% +/- 3.5%; p < 0.05). The newborn myocardium also had increased catalase activity (1027.9 +/- 20.6 units/gm versus 707.3 +/- 38.7 units/gm; p < 0.05), whereas the activity of XO was decreased relative to the adult (0.23 +/- 0.01 mU/gm versus 7.6 +/- 1.4 mU/gm; p < 0.05). Furthermore, the expression of HSP 72 was greater in the newborn than the adult control.

CONCLUSIONS

Relative to adult hearts, newborn rat hearts are more tolerant to a global ischemic insult followed by reperfusion. This improved functional recovery is associated with decreased oxidant production potential (XO), increased scavenging capacity (catalase), and augmented stress protein expression (HSP 72).

Serpentine cAMP receptors may act through a G protein-independent pathway to induce postaggregative development in Dictyostelium

The transcription factor G box-binding factor (GBF) is required for the developmental switch between aggregative and postaggregative gene expression, cell-type differentiation, and morphogenesis. We show that constitutive expression of GBF allows ectopic expression of postaggregative genes, but only in response to exogenous cAMP. GBF activation requires the serpentine cAMP receptors required for aggregation, but not the coupled G alpha 2 or the G beta subunit, suggesting a novel signaling pathway. In response to high cAMP, g alpha 2-null cells can bypass the aggregation stage, expressing cell type-specific genes and forming fruiting bodies. Our results demonstrate that the same receptors regulate aggregation and cell-type differentiation, but via distinct pathways depending upon whether the receptor perceives a pulsatile or sustained signal.

Dramatic interstrain differences in the replication of human cytomegalovirus in SCID-hu mice

The ability of a low-passage strain (Toledo) and laboratory strains (AD169 and Towne) of human cytomegalovirus to replicate in SCID-hu (thymus plus liver) mice were compared. At a time of peak replication, 14 days after inoculation, the Toledo strain grew 2-3 orders of magnitude better than any laboratory strain, a difference reflecting the number of infected thymic stromal cells in the implants. The growth property of the Toledo strain was stable through serial passage and plaque purification. The AD169-ATCC strain failed to grow at all, while an independently maintained stock of this strain obtained from the United Kingdom replicated to low levels, suggesting that divergence had occurred during propagation in different locations. This work predicts the existence of viral genetic determinant(s) for growth in tissues that are lost during propagation in culture.

New Nocardia taxon among isolates of Nocardia brasiliensis associated with invasive disease

Nocardia brasiliensis, the second most frequently isolated aerobic actinomycete in the clinical laboratory, is usually associated with localized cutaneous infections. However, 22% of 238 N. brasiliensis isolates from the United States and 12% of 66 isolates from Queensland, Australia, which had been collected over a 17-year period, were associated with extracutaneous and/or disseminated diseases. Of the 62 invasive isolates, 37 (60%) were susceptible to ciprofloxacin and/or were susceptible to clarithromycin and resistant to minocycline, compared with only 6 (3%) of 242 localized cutaneous isolates. The 43 isolates with this susceptibility pattern appeared to define a new taxon. They were similar to Nocardia asteroides complex isolates clinically in proportions from persons with pulmonary (70%), central nervous system (23%), and/or disseminated diseases (37%) in the setting of corticosteroids (74%) or AIDS (14%). This putative new taxon differed from N. brasiliensis in the hydrolysis of adenine (92 versus 4%), beta-lactamase patterns on isoelectric focusing, and the presence of two early mycolic acid-ester peaks by high-performance liquid chromatography. Restriction analysis of a 439-bp fragment of the 65-kDa heat shock protein gene revealed that N. brasiliensis and the new taxon had different restriction patterns with 8 of the 11 enzymes tested. Screening of invasive isolates of N. brasiliensis for susceptibility to ciprofloxacin will identify most isolates of the new taxon, which likely represents a new Nocardia species.

Polyurethane and silicone: myths and misconceptions

Silicone elastomer has been the standard by which other catheter materials have been judged. In the past ten years, technical advances in polymer research have provided the medical manufacturer with a wide variety of new materials for catheter manufacture. Thermoplastic polyurethane has shown great promise as an alternative to silicone for vascular catheters. This article examines the basic properties of the two materials and describes the findings in the literature that show comparable biocompatibility properties for both materials.

Heart transplantation in children and young adults: early and intermediate-term results

The purpose of this article is to report our short- and intermediate-term follow-up of cardiac transplantation for congenital heart disease and cardiomyopathy in children (age greater than 6 months), adolescents, and young adults. Thirty patients (ages 8 months to 24 years) with end-stage heart failure have undergone cardiac transplantation in our program: 12 (40%) for postoperative end-stage heart failure, 9 (30%) as primary treatment for congenital heart disease, 5 (17%) for dilated cardiomyopathy, and 4 (13%) for restrictive/hypertrophic cardiomyopathy. Nineteen patients (63%) had undergone prior operations; 4 patients received transplants for failed Fontan procedures. Induction therapy with antithymocyte therapy was used routinely, and long-term immunosuppression was by cyclosporine and azathioprine alone. Rejection surveillance/diagnosis was based on echocardiographic criteria. Posttransplantation follow-up ranges from 3 to 78 months. Operative mortality was 3.3% (1/30). No patients have been diagnosed with either accelerated allograft atherosclerosis or posttransplantation lymphoproliferative disease. We conclude that cardiac transplantation may be performed with excellent early and intermediate-term results.

DNA-dependent kinase (p350) as a candidate gene for the murine SCID defect

Severe combined immunodeficient (SCID) mice are deficient in a recombination process utilized in both DNA double-strand break repair and in V(D)J recombination. The phenotype of these mice involves both cellular hypersensitivity to ionizing radiation and a lack of B and T cell immunity. The catalytic subunit of DNA-dependent protein kinase, p350, was identified as a strong candidate for the murine gene SCID. Both p350 and a gene complementing the SCID defect colocalize to human chromosome 8q11. Chromosomal fragments expressing p350 complement the SCID phenotype, and p350 protein levels are greatly reduced in cells derived from SCID mice compared to cells from wild-type mice.

Climatic stress in the workplace: its effect on thermoregulatory responses and muscle fatigue in female workers

The present study was designed to determine the differences in thermoregulatory responses and the levels of muscle fatigue in the seated worker, performing a task involving a light metabolic load (typing), versus the standing worker, undertaking a task of a heavier metabolic load (lifting), in different climatic conditions (neutral and hot, humid). The results showed that environmental heat significantly influenced the cardiovascular and thermoregulatory systems in workers performing both light and heavy work tasks. In addition, environmental heat was shown to influence the magnitude of the frequency shift during the fatiguing muscle contraction in the typists rather than the lifters. These results suggest that: (1) performance of even sedentary workers performing a light manual task may be deleteriously affected by environmental heat; and (2) environmental heat may be of secondary importance to the nature of the task investigated on the level of muscle fatigue.

Effects of normative feedback on consumption among heavy drinking college students

College students, particularly those who drink heavily, tend to overestimate the prevalence of heavy drinking among their peers. A self-regulation model predicts that feedback of undesirable deviation from normative standards would result in correction of behavior toward perceived norms. From a screening of 568 college students, sixty-four heavy drinkers were identified and offered the opportunity to participate in a survey study of drinking. Of these, twenty-six accepted and returned questionnaires with detailed information regarding their drinking practices. These were randomized to receive or not receive, by return mail, personal feedback of their drinking relative to population norms. At an independent follow-up interview, feedback subjects showed greater reduction in weekly consumption and typical intoxication levels, relative to controls. This simple feedback intervention, requiring no personal contact, may be a cost-effective strategy for reducing risky drinking.

Preconditioning of isolated rat heart is mediated by protein kinase C

Catecholamines have been implicated in the phenomenon of ischemic preconditioning. We have previously demonstrated that ischemic preconditioning against postischemic mechanical dysfunction in the isolated rat heart is mediated by the alpha 1-adrenergic receptor. The purpose of this study was to delineate the signal transduction of preconditioning distal to the alpha 1-adrenergic receptor. Our results suggest that (1) transient ischemia and alpha 1-adrenergic receptor-induced preconditioning is inhibited by protein kinase C (PKC) antagonists, (2) functional protection against global ischemia/reperfusion injury can be induced by infusion of diacylglycerol, the second messenger of the alpha 1-adrenergic pathway, and (3) transient ischemia and alpha 1-adrenergic preconditioning are both characterized by similar translocation of PKC-delta to the sarcolemma of myocardium. These findings suggest that PKC is an effector of preconditioning in the isolated rat heart.

Prediction of human cell radiosensitivity: comparison of clonogenic assay with chromosome aberrations scored using premature chromosome condensation with fluorescence in situ hybridization

PURPOSE

The purpose of the present investigation was to determine whether chromosome aberrations scored by premature chromosome condensation (PCC) and fluorescence in situ hybridization (FISH) can predict the radiosensitivity of human cell lines, thereby providing a possible means of assessing the in situ radiosensitivity of normal tissues and the radiocurability of individual human cancers.

METHODS AND MATERIALS

We used four cells lines of different radiosensitivity: normal human fibroblasts (AG1522), ataxia-telangiectasia fibroblasts (AT2052), a human fibrosarcoma cell line (HT1080), and a human melanoma cell line (melanoma 903). These were irradiated in plateau phase with a range of doses and assessed both for clonogenic cell survival and for aberrations in a single chromosome (number 4) immediately after, and 24 h after irradiation.

RESULTS

The initial number of breaks in chromosome 4 was proportional to irradiation dose and was identical for all the different human cell lines, irrespective of radiosensitivity. On the other hand, the number of chromosome 4 breaks remaining 24 h after irradiation reflected the radiosensitivity of the cells such that the relationship between residual chromosome aberrations and cell survival was the same for the different cell lines.

CONCLUSIONS

These results suggest that the scoring of chromosome aberrations in interphase using FISH with PCC holds considerable promise for predicting the radiosensitivity of normal and tumor tissues in situ.

Technique to stent the open sternum after cardiac operations

Extreme myocardial edema may preclude sternal closure after a cardiac operation. We describe a technique to stent the sternum open to optimize cardiac function.

Influence of muscle activation dynamics on reaction time in the elderly

The aim of this investigation was to determine whether age-related changes in the dynamics of muscle activation were, in part, responsible for longer reaction times (RT) in the elderly. A group of 12 young (mean age, 20.6 years) and 12 elderly (mean age, 64.3 years) women performed a series of ballistic forearm supination movements in response to an auditory stimulus while using a simple reaction time test. Surface electromyographic waveforms from biceps brachii (agonist) and pronator teres (antagonist) muscles were recorded, together with the angle-time curves representing the motion of the forearm, on to an IBM compatible microcomputer. The results showed that an age-related increase (P < 0.05) in motor reaction time (MRT) contributed to longer RT in the elderly. In addition, the longer (P < 0.05) MRTs in the elderly were associated with a significantly slower rate (P < 0.05) of biceps brachii muscle activation and a significantly increased proportion (P < 0.05) of the initial biceps brachii muscle burst required to initiate the movement. This data suggested that an important part of the slowing of motor behaviour, commonly observed with increasing age, may be due to either decreases in the ability of aged skeletal muscle to rapidly generate tension or to a reduction in motor drive.