Ligation of the T cell co-stimulatory receptor CD28 activates the serine-threonine protein kinase protein kinase B

The intracellular signaling pathways activated upon ligation of the co-stimulatory receptor CD28 remain relatively ill-defined, although CD28 ligation does result in the strong association with, and activation of, phosphatidylinositol (PI) 3-kinase. The downstream effector targets of the CD28-activated PI 3-kinase-dependent signaling pathway remain poorly defined, but recent evidence from other systems has shown that Akt/protein kinase B (PKB) is a major target of PI 3-kinase and have indicated that a major function of PKB is the regulation of cell survival events. Given the strong coupling of CD28 to PI 3-kinase and the known protective effects of both CD28 and PI 3-kinase against apoptosis in different cell models, we investigated the effects of CD28 on PKB activation. We demonstrate that ligation of CD28 by either anti-CD28 monoclonal antibodies or the natural ligand B7.1, results in the marked activation of PKB in both the leukemic T cell line Jurkat and freshly isolated human peripheral blood-derived normal T lymphocytes. Our data suggest therefore, that PKB may be an important intracellular signal involved in CD28 signal transduction and demonstrate CD28 coupling to downstream elements of a signaling cascade known to promote cell survival.     

Histochemical and immunohistochemical studies on the origin of the blue marlin heater cell phenotype

The superior rectus muscle fibers of marlins, swordfish, sailfish and spearfish are modified for heat production at the expense of contractile ability. Although 'heater cells' are a muscle derivative (Block, 1986, 1991), the myoblast origin and developmental pathway of these thermogenic cells is unknown. To gain insight into heater cell origins, we characterized blue marlin superior rectus muscle and its heater tissue derivative with histochemical and immunological techniques. We specifically employed myosin ATPase and succinate dehydrogenase histochemical assays, and myosin heavy chain immunohistochemistry. Results revealed that marlin superior rectus muscles contain at least six distinct fiber types, and suggested the presence of both twitch and tonic fibers. Immunological results indicate that myosin is present within the thermogenic cells but not in myofibrillar lattices. The antibodies that recognized myosin in heater cells also labeled myosin in the twitch fibers of swimming muscle. In contrast, antibodies that labeled histologically defined tonic fibers did not label heater cells. These results suggest that heater cells and twitch fibers express the same myosin isoform, and establish a phenotypic connection between heater cells and twitch fibers. This conclusion is discussed in the context of the muscle-to-heater trajectory and the muscle fiber-type origin of heater cells.     

Discounting costs and effects: a reconsideration

Using a simple societal utility function--giving equal weight to current and future generations-it is concluded that costs need to be discounted on the basis of the expected increase in income and the marginal utility of consumption, and that effects need to be discounted on the basis of the expected increase in health and the marginal utility of health. It is derived that both rates need to be equal when assuming a kind of perfect market, where growth rates are determined by the societal utility function. It is argued that this is an extremely heroic assumption and that different discount rates may be needed. Additionally, the traditional 'inconsistency arguments' of Weinstein and Stason and of Keeler and Cretin are reconsidered. Within the context presented earlier, the first inconsistency only emerges when a growth equilibrium is assumed, reinforcing the arguments put forward before. The Keeler and Cretin paradox is reconsidered by showing that absolutely no paradox emerges when programs are not supposed to stop after a year but are supposed to continue indefinitely. The conclusion is drawn that non-believers in market mechanisms assuring an optimal social policy, need to reconsider the use of their discount rates.     

Gross deletions of the neurofibromatosis type 1 (NF1) gene are predominantly of maternal origin and commonly associated with a learning disability, dysmorphic features and developmental delay

The adherence of either cholera toxin or the heat-labile enterotoxin of Escherichia coli to monosialoganglioside gal(beta1-3)galNAc(beta1-4)[sialic acid (alpha2-3)]gal(beta1-4)glc(beta)1-ceramide (GM1) present on the surface of epithelial cells lining the intestine is the first step of a series that results in the induction of a watery diarrhea. While cholera is more severe, both can lead to death as a result of dehydration. To determine the potential of defined multivalent oligosaccharides, synthesized by the covalent attachment of multiple phenylisothiocyanate (PITC) derivatives of gal(beta1-3)galNAc(beta1-4)[sialic acid(alpha2-3)]gal(beta1-4)glc (oligo-GM1) to the arms of a poly(propylene imine) dendrimer, as therapeutic agents for these diseases, their ability to inhibit adherence of the toxins to cell surface-associated GM1 was determined. They not only inhibited choleragenoid (binding subunit of cholera toxin) binding to GM1-treated NCTC-2071 cells (chemically transformed murine fibroblasts) at 5 degrees, but also inhibited adherence of the choleragenoid, cholera toxin, and heat-labile enterotoxin of E. coli to GM1-treated NCTC-2071 cells at 37 degrees. Inhibition was observed whether the toxin was preincubated with the oligo-GM1-PITC-derivatized dendrimer prior to addition to cells or given just after the addition of the derivatized dendrimer to cells. The derivatized dendrimer had no effect on cell viability, as monitored by trypan blue exclusion. Blue-shifts in tryptophan fluorescence emission spectra maxima induced by adherence of either choleragenoid, cholera holotoxin, or the heat-labile enterotoxin of E. coli to oligo-GM1-PITC-derivatized dendrimers were similar to those induced by adherence to GM1 or oligo-GM1. Comparable shifts were not observed when the toxins were incubated with gangliosides that fail to function as receptors.     

Basal cell carcinoma of the eyelid. Risk of recurrence according to adequacy of surgical margins

PURPOSE: To examine all basal cell carcinomas of the eyelid diagnosed in Iceland during a 25-year period, paying special attention to the surgical margins of excision in relation to recurrence. Based on the results a simple, clinically relevant method of classifying the surgical margin is proposed. METHODS: All histologically proven basal cell cancer specimens from eyelids were reviewed retrospectively. The surgical excision margins were classified as radical, marginal or intralesional. RESULTS: Recurrence risk was low when the tumor had a surgical margin described as radical or marginal. The recurrence rate was 38% when the margin was intralesional. CONCLUSION: By assessing the surgical margins by this method, which is easy to apply, better understanding between the pathologist and the surgeon may be achieved.     

Relation between coronary artery disease, aortic stiffness, and left ventricular structure in a population sample

With the use of the degenerated nucleotides that contain the conserved sequence of G protein-coupled receptor, we have identified a 648-bp clone (HDGRC02) from human genomic DNA with significant sequence homology to human neurotransmitter receptors. HDGRC02 was then used as a probe for the screening of full length gene. From human Lambda DASH II genomic library, a 1.6 Kb clone encoded a full length gene was isolated and named putative neurotransmitter receptor (PNR). PNR has a single open reading frame which predicts a 38.3 KD protein of 338 amino acids with seven transmembrane domain topography. The amino acid sequence of PNR exhibits considerable homology to the rat 5-HR1D receptor with 35% amino acid identity and 56% amino acid similarity. PNR also shows significant sequence homology to the 5-HT1D receptor from Japanese puffer fish fugu, to the 5-HT4L receptor from mouse, to the alpha-2 adrenergic receptor and to the D2 dopamine receptor. Northern blot analysis indicates that PNR is expressed in skeletal muscle and selected areas of the brain. A chromosome mapping study located the PNR gene with human chromosome band of 6q23. The findings in the present study demonstrate that PNR is a putative neurotransmitter receptor.     

Survival and disability at 7-8 years of age in New Zealand infants less than 28 weeks gestation

AIMS: To determine the survival and disability rates at 7-8 years in infants of less than 28 weeks gestation born in New Zealand in 1986 and admitted to a neonatal unit. METHODS: In 1986, all infants with birthweight less than 1500 g and admitted to neonatal units were enrolled in a prospective audit of retinopathy of prematurity. Surviving infants, including the subset born at less than 28 weeks gestation, have been assessed at a home visit. Parents completed a comprehensive questionnaire and children underwent a visual assessment and were tested on the Wechsler Intelligence Scale for Children. RESULTS: Of 126 liveborn infants less than 28 weeks gestation, 80 (64%) survived to 7-8 years. Sixty eight children (97% survivors resident in New Zealand) were assessed: 72% had no, and 86% no or only mild disability, 77% had some visual problem, with close to one-third having myopia, strabismus or requiring spectacles and 32% received Ministry of Education funded special needs assistance. CONCLUSIONS: There have been few long-term follow-up studies of infants of less than 28 weeks gestation born in a defined geographical area. The outcome for New Zealand infants is comparable with that in other published data.     

Testing the gonadal regression-cytoprotection hypothesis

Germinal damage is an almost universal accompaniment of cancer treatment as the result of bystander damage to the testis from cytotoxic drugs and/or irradiation. Cancer treatment for the most common cancers of the reproductive age group in men has improved such that most are now treated with curative intent, and many others are treated with likelihood of prolonged survival, so that the preservation of fertility is an important component of posttreatment quality of life. This has led to the consideration of developing adjuvant treatments that may reduce the gonadal toxicity of cancer therapy. One dominant hypothesis has been based on the supposition that the immature testis was resistant to cytotoxin damage. Hence, if hormonal treatment were able to cause spermatogenic regression to an immature state via an effective withdrawal of gonadotrophin secretion, the testis might be maintained temporarily in a protected state during cytotoxin exposure. However, clinical studies have been disappointing but have also been unable to test the hypothesis definitively thus far, due to the inability to completely suppress gonadotrophin secretion. Similarly, experimental models have also given conflicting results and, at best, a modest cytoprotection. To definitively test this hypothesis experimentally, we used the fact that the functionally hpg mouse has complete gonadotrophin deficiency but can undergo the induction of full spermatogenesis by testosterone. Thus, if complete gonadotrophin deficiency were an advantage during cytotoxin exposure, then the hpg mouse should exhibit some degree of germinal protection against cytotoxin-induced damage. We therefore administered three different cytotoxins (200 mg/kg procarbazine, 9 mg/kg doxorubicin, 8 Gy of X irradiation) to produce a range of severity in testicular damage and mechanism of action to either phenotypically normal or hpg mice. Testis weight and homogenization-resistant spermatid numbers were measured to evaluate the potential protective effects on spermatogenesis. Although the three cytotoxins produced a range of severity of spermatogenic damage, there was no evidence of cytoprotection in the hpg mice that were completely gonadotrophin deficient at the time of treatment. These findings cast doubt on the validity of the hypothesis that spermatogenic regression via gonadotrophin withdrawal can protect the mouse testis against cytotoxin-mediated spermatogenic damage.     

Recovery of the human compound action potential following prior stimulation

The recovery from prior stimulation of the compound action potential (CAP) was measured using a forward masking stimulus paradigm in four normal-hearing, human subjects. The CAP was recorded using a wick electrode placed on the tympanic membrane. The effects of a 4000-Hz, 97-dB SPL conditioning stimulus on CAP amplitude in response to a 4000-Hz probe were measured as a function of conditioner-probe interval for three probe levels. The normalized probe response amplitude was completely recovered to the control values at an average conditioner-probe interval of 1359 ms, similar to that observed in chinchilla (Relkin, E.M., Doucet, J.R., Sterns, A., 1995. Recovery of the compound action potential following prior stimulation: evidence for a slow component that reflects recovery of low spontaneous-rate auditory neurons, Hear. Res. 83, 183-189). The present results are interpreted as a consequence of the slow recovery of low spontaneous-rate (SR), high threshold neurons from prior stimulation (Relkin, E.M., Doucet, J.R., 1991. Recovery from prior stimulation. I: Relationship to spontaneous firing rates of primary auditory neurons. Hear. Res. 55, 215-222) and may provide indirect physiological evidence for the existence of a class of low-SR auditory neurons in humans.     

DNA repair: getting past a lesion - at a cost

Bacteria survive many types of synthesis-blocking DNA lesion by inducing a number of proteins that enable their polymerases to synthesize past a lesion, albeit at the cost of an increased mutation rate. This process has now been convincingly achieved in vitro, opening the way to a fuller understanding of the mechanism.