Elevated blood pressure and enhanced myocardial contractility in mice with severe IGF-1 deficiency.

To circumvent the embryonic lethality of a complete deficiency in insulin-like growth factor 1 (IGF-1), we generated mice homozygous for a site-specific insertional event that created a mutant IGF-1 allele (igf1m). These mice have IGF-1 levels 30% of wild type yet survive to adulthood, thereby allowing physiological analysis of the phenotype. Miniaturized catheterization technology revealed elevated conscious blood pressure in IGF-1(m/m) mice, and measurements of left ventricular contractility were increased. Adenylyl cyclase activity was enhanced in IGF-1(m/m) hearts, without an increase in beta-adrenergic receptor density, suggesting that crosstalk between IGF-1 and beta-adrenergic signaling pathways may mediate the increased contractility. The hypertrophic response of the left ventricular myocardium in response to aortic constriction, however, was preserved in IGF-1(m/m) mice. We conclude that chronic alterations in IGF-1 levels can selectively modulate blood pressure and left ventricular function, while not affecting adaptive myocardial hypertrophy in vivo.

Functional dissection of the human Bcl2 protein: sequence requirements for inhibition of apoptosis.

Overexpression of the cytoplasmic oncoprotein Bcl2 blocks programmed cell death (apoptosis) in many cellular systems. To map the sequences in Bcl2 that are necessary for its activity, we created a library of deletion-scanning mutants of this 239-amino-acid protein and tested their abilities to block staurosporine-induced fibroblast apoptosis, using a novel transient-transfection assay. Phenotypes of informative mutants were then confirmed by assaying for inhibition of steroid-induced apoptosis in stably transfected T-lymphoid cells. In accordance with earlier results, we found that Bcl2 activity was only partially reduced after deletion of the hydrophobic tail that normally anchors it in cytoplasmic membranes. Essential sequences were found in the remainder of the protein and appeared to be organized in at least two discrete functional domains. The larger, more C-terminal region (within residues 90 to 203) encompassed, but extended beyond, two oligopeptide motifs called BH1 and BH2, which are known to mediate dimerization of Bcl2 and related proteins. The second, more N-terminal regions (within residues 6 to 31) was not required for protein dimerization in vivo, but its deletion imparted a dominant negative phenotype, yielding mutants that promoted rather than inhibited apoptotic death. Residues 30 to 91 were not absolutely required for function; by deleting most of this region along with the hydrophobic tail, we derived a 155-residue mini-Bcl2 that retains significant ability to inhibit apoptosis.

Characterization of the nuclear export signal of human T-cell lymphotropic virus type 1 Rex reveals that nuclear export is mediated by position-variable hydrophobic interactions.

We previously determined that amino acids 64 to 120 of human T-cell lymphotropic virus type 1 (HTLV-1) Rex can restore the function of an effector domain mutant of human immunodeficiency virus type 1 (HIV-1) Rev (T. J. Hope, B. L. Bond, D. McDonald, N. P. Klein, and T. G. Parslow, J. Virol. 65:6001-6007, 1991). In this report, we (i) identify and characterize a position-independent 17-amino-acid region of HTLV-1 Rex that fully complements HIV-1 Rev effector domain mutants and (ii) show that this 17-amino-acid region and specific hydrophobic substitutions can serve as nuclear export signals. Mutagenesis studies revealed that four leucines within the minimal region were essential for function. Alignment of the minimal Rex region with the HIV-1 Rev effector domain suggested that the position of some of the conserved leucines is flexible. We found two of the leucines could each occupy one of two positions within the context of the full-length HTLV-1 Rex protein and maintain function. The idea of flexibility within the Rex effector domain was confirmed and extended by identifying functional substitutions by screening a library of effector domain mutants in which the two regions of flexibility were randomized. Secondly, the functional roles of the minimal Rex effector domain and hydrophobic substitutions were independently confirmed by demonstrating that these effector domains could serve as nuclear export signals when conjugated with bovine serum albumin. Nuclear export of the wild-type Rex conjugates was temperature dependent and sensitive to wheat germ agglutinin and was blocked by a 20-fold excess of unlabeled conjugates. Together, these studies reveal that position-variable hydrophobic interactions within the HTLV-1 Rex effector domain mediate nuclear export function.

Targeting gene expression to specific cardiovascular cell types in transgenic mice.

Transgenic techniques, which allow the introduction of exogenous genes into the genome of experimental animals, promise to bridge the gap between the in vitro observations made by molecular and cellular biologists on cardiac and vascular cells in tissue culture and the physiology and pathology of the whole organ system. One such application of these techniques is tissue targeting: by genetic manipulation to direct expression of a protein--such as a signaling peptide, a growth factor receptor, or an oncogene involved in cell growth--to a tissue where it normally would not be expressed (or where expression is tightly controlled) by fusing it to the transcriptional control sequences of another gene normally expressed in that tissue. In the cardiovascular system, regulatory sequences for cardiomyocyte-specific proteins, vascular endothelium-specific proteins, and smooth muscle-specific proteins can be used to target heterologous genes to their respective tissues in transgenic animals. The effects that such perturbations have on organ physiology and intracellular and intercellular communication can be observed by applying established physiological and molecular approaches. In this review, we highlight some tissue-specific genes from cardiac and vascular cell types whose regulatory sequences may be used to target heterologous proteins; we discuss neutral "reporter" proteins and signal transduction components as paradigms for the application of this technique; and we briefly touch on the potentials and pitfalls of transgenic approaches to molecular physiology.

Loss of adrenergic control of the force-frequency relation in heart failure secondary to idiopathic or ischemic cardiomyopathy.

This study was designed to determine whether the force-frequency effect on myocardial contractility, known to be importantly regulated by the adrenergic nervous system in experimental animals, can be enhanced by beta-adrenergic receptor stimulation in patients with heart failure. Animal experiments have demonstrated that the positive force-frequency relation in most mammals is subject to enhancement by beta-adrenergic receptor stimulation during exercise or infusion of a beta-receptor agonist. In animal models of heart failure, this regulatory mechanism generally is lost. The response to progressive increases in heart rate to 150 to 160 beats/min by right atrial pacing before and during dobutamine infusion was studied in 3 relatively normal subjects and in 5 patients with severe dilated cardiomyopathy. Left ventricular (LV) pressure and its first derivative (LV dP/dt(max)) were measured with a micromanometer, and the time constant of LV relaxation was assessed. The slopes of the relations between heart rate and LV dP/dt(max) in control subjects were positive at baseline and the mean slope increased substantially and significantly during dobutamine infusion. In patients with heart failure, the heart rate versus LV dP/dt(max) relations were depressed and flattened without a descending limb. Dobutamine infusion shifted this relation upward slightly, without increase in mean slope, indicating lack of amplification. The rate of isovolumic relaxation significantly decreased as heart rate increased at baseline and was further shortened by dobutamine. In patients with heart failure, a depressed and flattened relation between heart rate and LV dP/dt(max) (force-frequency effect) did not show the amplification of myocardial contractility by beta-adrenergic stimulation observed in the normal heart. This abnormality in control of the force-frequency relation undoubtedly plays an important role in the impairment of cardiac function during exercise in heart failure.

Detection of massive pulmonary embolus-in-transit by transesophageal echocardiography.

Pulmonary embolus-in-transit represents an important cause of morbidity and mortality in the critically ill patient. Unexplained shock and acute pulmonary hypertension were evaluated with echocardiography. Standard transthoracic echocardiography failed to identify a large embolism-in-transit that was easily visualized by transesophageal imaging. A review of the literature involving emboli-in-transit suggests that early intervention in these patients may be beneficial.

Using attachment theory to understand illness behavior.

This article examines a model of illness as a stressor that activates an individual's characteristic attachment behaviors. These behaviors are the result of the attachment system, a mammalian trait that exists in order to maximize the odds of survival of an infant born without the necessary maturation for immediate independence. Attachment concepts, such as attachment style, coherence, and reflective functioning, are briefly explained, followed by examples of their application to the psychological management of patients with medical or surgical illness. Attachment theory provides a unique, simple, and pragmatically useful model for understanding the particular ways that individuals can feel and react when stressed by illness, and how the professional may help manage that distress.

X-ray diffraction study of some normal alkyl esters of long-chain acids.

X-ray powder diffraction data are reported for 15 normal long-chain esters. The compounds represent all combinations of acid and alcohol where the acid portion is n-tetradecanoic, n-hexadecanoic, or n-octadecanoic acid, and the alcohol portion is n-tetradecanol, n-pentadecanol, n-hexadecanol, n-heptadecanol, or n-octadecanol. The individual compounds can be identified and distinguished by the diffraction data. Several of the esters have long spacings that are a linear function of the number of carbon atoms in the molecule and are consistent with a similar function for ethyl esters of long-chain acids. The remainder of the compounds crystallize in other polymorphic forms and therefore do not follow this function.

Gastric volvulus: two cases and a review of the literature.

We report two cases of gastric volvulus. A discussion of the epidemiology, pathophysiology, clinical presentation, diagnosis, and treatment of this rare entity is presented.

Human factor assessment of the legibility of five numeric visual displays.

Experiments have been carried out designed to find on human factor considerations alone, which of five available displays would be most suitable for the next generation of Post Office telephone exchange switchboard.

Psychiatric problems in chronic facial pain.

Facial pain patients have been known to describe their life as "a living hell." By employing a biopsychosocial approach, the dental surgeon can often markedly reduce suffering and diminish the negative impact of chronic pain on the patient's day-to-day life, and enhance his or her capacity to deal long-term with this often complex clinical presentation.

Relationship between social support and autonomic function during a stress protocol in ulcerative colitis patients in remission.

BACKGROUND: The relationship of psychological stress to relapse in ulcerative colitis (UC) is inconsistent. This may be due to a failure to identify patient characteristics, such as social support, which moderate the transduction of stress from the central nervous system to the immune system. In this study we tested the hypothesis that social support enhances parasympathetic modulation of heart rate in UC. METHODS: An indirect measure of autonomic function (heart rate variability; HRV) was measured in 108 patients with UC in remission during a standard protocol involving periods of stress, paced breathing, and relaxation. Social support was measured with the Social Support Questionnaire. RESULTS: After controlling for age, which is strongly related to HRV, both satisfaction with social support (F = 5.7, significance = 0.002) and its interaction with age (F = 7.8, significance <0.001) were associated with high-frequency HRV, which measures parasympathetic modulation of heart rate. Social support was associated with higher levels of high-frequency HRV at almost all points in the stress protocol. Neither age nor social support was associated with differences in the LF/HF ratio, which measures sympathetic modulation of heart rate. CONCLUSIONS: Social support is related to parasympathetic activity in UC. Given previous evidence of an antiinflammatory role for the parasympathetic nervous system, this suggests that autonomic function could serve as a mediating link between social support and reduced inflammatory activity.

Imaging retinal mosaics in the living eye.

Adaptive optics imaging of cone photoreceptors has provided unique insight into the structure and function of the human visual system and has become an important tool for both basic scientists and clinicians. Recent advances in adaptive optics retinal imaging instrumentation and methodology have allowed us to expand beyond cone imaging. Multi-wavelength and fluorescence imaging methods with adaptive optics have allowed multiple retinal cell types to be imaged simultaneously. These new methods have recently revealed rod photoreceptors, retinal pigment epithelium (RPE) cells, and the smallest retinal blood vessels. Fluorescence imaging coupled with adaptive optics has been used to examine ganglion cells in living primates. Two-photon imaging combined with adaptive optics can evaluate photoreceptor function non-invasively in the living primate retina.

Attachment and psychosomatic medicine: developmental contributions to stress and disease.

OBJECTIVE: The object of this study was to evaluate the evidence linking attachment insecurity to illness. Attachment theory describes lifelong patterns of response to threat that are learned in the interaction between an infant and his or her primary caregiver. Despite its biopsychosocial domain, attachment theory has only recently been applied to psychosomatic medicine. METHOD: MEDLINE and PsychInfo databases were searched from 1966 to 2000 for English language papers with key words "attachment" and "object relations." Papers and their cited references were reviewed if they were directly related to physical illness, symptoms, or physiology. A hypothetical causal model was developed. RESULTS: Direct and indirect evidence from survey studies supports an association between attachment insecurity and disease. Animal studies and human experiments suggest that attachment contributes to individual differences in physiological stress response. There is also less robust support for insecure attachment leading to symptom reporting and to more frequent health risk behaviors, especially substance use and treatment nonadherence. Evidence supports the prediction from attachment theory that the benefits of social support derive more from attachment relationships than nonattachment relationships. CONCLUSIONS: Although the available data are suggestive rather than conclusive, the data can be organized into a model that describe attachment insecurity leading to disease risk through three mechanisms. These are increased susceptibility to stress, increased use of external regulators of affect, and altered help-seeking behavior. This model warrants further prospective investigation.

A peptide sequence from Bax that converts Bcl-2 into an activator of apoptosis.

Bcl-2 and Bax are members of a family of cytoplasmic proteins that regulate apoptosis. The two proteins have highly similar amino acid sequences but are functionally opposed: Bcl-2 acts to inhibit apoptosis, whereas Bax counteracts this effect. The antagonism appears to depend upon dimerization between Bcl-2 and Bax, but its mechanism is otherwise unknown. Here we report that overexpressing Bax induces apoptosis in a mammalian fibroblast cell line, and we identify a novel, short "suicide domain" in Bax that is required for this effect. Inserting this domain in place of the corresponding, divergent sequence in Bcl-2 converts Bcl-2 from an inhibitor into an activator of cell death. These findings imply that a specific region in Bax confers an active propensity for apoptosis in mammalian cells and support the view that Bcl-2 may block death primarily by suppressing Bax activity.

Role of abortive retroviral infection of neurons in spongiform CNS degeneration.

Retroviruses are involved in several human neurological diseases with varying pathological features. Whether these diseases are due to a direct effect of the virus on nervous system cells is unknown. To gain insight into the pathogenesis of one retroviral neurological disease, we are studying the murine neurotropic retrovirus, Cas-Br-E, which causes lower motor neuron disease associated with spongiform degenerative changes in brain and spinal cord. Central nervous system (CNS) injury seems to be due to direct viral action, but the precise target cells of the virus are uncertain. After blood-borne virus enters the CNS it is found in capillary endothelial cells. No microscopic evidence for virus within glia or neurons has been found in some studies, whereas virus or incomplete particles have been observed in CNS cells in other studies. Here we identify the neuron as a major target for Cas-Br-E in the CNS, suggesting that this disease may be a direct result of viral infection of neurons. We also show that envelope protein (Env, encoded by the env gene), a major determinant of neurovirulence, cannot be detected in neurons but is present in non-neuronal cells, although spliced env messenger RNA is synthesized in CNS tissue. This suggests that a post-transcriptional step in Cas-Br-E Env protein synthesis is impaired and that the neurological disease may be a consequence of abortive replication of virus in neurons. This may explain the failure to find neuronal infection in other neurological diseases by conventional methods of virus detection.