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L Davis

Publications and source records attributed to L Davis.

At least 163 records · Page 9Linked to original sources
PubMed1991

Suppressor effects in the relations of psychological variables to resting blood pressure.

The role of suppressor effects in obscuring the relation of psychological variables and blood pressure was studied. Forty-five nonmedicated patients in a family practice rated themselves relative to their peers on a series of characteristics. Two of these, trapped and lonely, exhibited marked suppressor effects in their relationship with each other and resting blood pressure. Self-ratings of lonely exhibited a moderately strong positive association with ratings of trapped (r = .63) while only ratings of lonely showed a significant correlation with resting systolic blood pressure (r = .31). Yet when the suppressor effects of the ratings on feeling lonely were removed in the regression analyses, the ratings on feeling trapped showed a significant positive association with resting systolic pressure (r = .42). Similarly, while neither ratings on feeling lonely or on feeling trapped showed separately a significant association with resting diastolic pressure, when suppressor effects were removed in the regression analyses, the ratings of trapped were significantly associated with diastolic pressure in a positive direction (r = .34) and ratings of lonely were significantly associated in a negative direction (r = .33). The significance of this specific suppressor effect and the implications of suppression for psychosomatic research are discussed.

Adult↗
PubMed1991

Programmed cell death as a new target for prostatic cancer therapy.

To increase survival of men with metastatic prostatic cancer, a modality that can effectively eliminate androgen independent cancer cells is desperately needed. By combining such an effective modality with androgen ablation, all of the heterogeneous populations of tumour cells within a prostatic cancer patient can be affected, thus optimizing the chances of cure. Unfortunately, such effective therapy for the androgen independent prostatic cancer cell is not yet available. This therapy will probably require two types of agents, one having antiproliferative activity affecting the small number of dividing androgen independent cells, and the other able to increase the low rate of cell death among the majority of non-proliferating (ie interphase) androgen independent prostatic cancer cells present. Androgen dependent prostatic epithelial cells can be made to undergo programmed death by means of androgen ablation, even if the cells are not in the proliferative cell cycle. Androgen independent prostatic cancer cells retain the major portion of this programmed cell death pathway, only there is a defect in the pathway such that it is no longer activated by androgen ablation. If the intracellular free Ca2+ is sustained at an elevated level for a sufficient time, androgen independent cells can be induced to undergo programmed death. The long term goal is therefore to develop some type of non-androgen ablative method that can be used in vivo to induce a sustained elevation in Ca2+ in androgen independent prostatic cancer cells. To accomplish this task, a more complete understanding of the biochemical pathways involved in programmed cell death is urgently needed. At present, studies are focusing on the mechanism involved in the Ca2+ elevation in the normal and malignant androgen dependent cell induced following androgen ablation and the role of the TRPM-2 protein in this process.

Adenocarcinoma↗
PubMed1991

Axotomy-induced changes in rabbit hindlimb nerves and the effects of chronic electrical stimulation.

Chronic electrical stimulation and extracellular recording combined with morphological examination of nerves in this study provided a detailed description of the time course and extent of fiber atrophy when the trophic influence of the target was removed by ligation of axotomized nerves and neural activity was replaced by chronic stimulation. The major findings are that decline in amplitude of compound action potentials (CAPs) and fiber diameters is rapid after axotomy and is not reversed or prevented by chronic electrical stimulation, as would be predicted if neural activity played an essential role in maintaining normal fiber caliber. Chronic stimulation had a small short-term sparing effect in the first month after axotomy but was counterproductive over long periods. Comparison of the time course of the decline in CAP amplitude and reduction of fiber diameters with described alterations in mRNA expression of neurofilament protein indicates that the early atrophy is too rapid to be accounted for by reduced synthesis and transport of neurofilaments. It is more likely to result from modification of axonal proteins after axotomy. Replacement of neural activity with stimulation may reduce the initial atrophy but, over longer periods, exacerbates the atrophy, possibly by affecting the synthesis and transport of cytoskeletal proteins. These studies show that the trophic control of nerve fiber size is mediated primarily by functional contacts with peripheral targets and that neural activity plays a relatively small role. Without functional contacts, nerve fibers decline in diameter to stable but lower values. The atrophy was exacerbated by imposing neural activity on the relatively quiescent axotomized neurons.

Action Potentials↗
PubMed1990

Primary central nervous system lymphoma in a pediatric patient with acquired immune deficiency syndrome. Treatment with radiation therapy.

Primary central nervous system (CNS) lymphoma, an otherwise rare pediatric tumor, has been reported with increasing frequency in children with acquired immune deficiency syndrome (AIDS). With current therapy, the outcome of this disease is invariably fatal. The authors present a case of primary CNS lymphoma in a 3.5-year-old girl with AIDS who received treatment with total brain irradiation. After treatment, the patient's mental status improved, the seizures resolved, and she had no further progression of her neurologic symptoms until she died of pneumonia 6 months later. The autopsy revealed a necrotic mass at the site of the original tumor. The brain stem and spinal cord, unirradiated, contained lymphomatous lesions. The patient had extensive fibrinoid necrosis and leukoencephalopathy that were consistent with radiation-induced CNS damage. Coexisting AIDS encephalopathy also contributed to the patient's CNS injury. Effective palliation of CNS lymphoma in children with AIDS may be obtained with cranial irradiation. Pediatric AIDS patients may show more severe tissue effects from irradiation than unaffected children.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Cutaneous T-cell lymphoma in a patient infected with human immunodeficiency virus type 1. Use of radiation therapy.

A patient with cutaneous T-cell lymphoma (CTCL) and acquired immune deficiency syndrome (AIDS) is presented. The patient had a localized lesion on his scalp. Evaluation for systemic lymphoma was negative. A biopsy specimen showed superficial and deep dermal infiltrates of pleomorphic lymphocytes. Immunohistochemistry was consistent with T-cell lymphoma. The patient was treated successfully with local irradiation. He remained free of further systemic and cutaneous recurrences of the lymphoma until he died 8 months after treatment of pneumonia. This case is the first to our knowledge to describe a localized CTCL in a patient infected with human immunodeficiency virus type 1 (HIV-1).

Acquired Immunodeficiency Syndrome↗
PubMed1990

Developmental expression of regionally specific cell surface antigens in the Xenopus gastrula.

Molecular markers for specific cell lineages would be useful in studies of cellular differentiation. To isolate such markers monoclonal antibodies (MoABs) were raised against plasma membranes isolated from gastrulating Xenopus embryos. Those antibodies that recognized subsets of cells within the embryo were selected by indirect immunofluorescence. The analysis of eight such MoAbs is presented. Western blot analysis showed that all but one MoAb recognized a complex pattern of glycoconjugates associated with glycoproteins. All the antigens recognized by the MoAbs were maternal in origin and displayed similar spatial patterns of pregastrular expression. This pattern of immunoreactivity at the apical surface was inherited passively during cleavage by the resulting superficial blastomeres suggesting that ectodermal specific markers of maternal origin are pre-localized to the cortical ooplasm in mature oocytes. We suggest that these maternal components may be specific glycosyl transferases. Three different patterns of expression were observed during gastrulation as exemplified by MoAbs 1F10C1, 3A4D1, and 6F10B6. MoAb 6F10B6 was specific for both neural and non-neural epithelium. MoAb 3A4D1 was specific for non-neural epidermis. MoAb 1F10C1 appeared to recognize a protein epitope on an extracellular component expressed by the superficial and involuting epithelial cells. The pattern of expression for the 1F10C1 antigen suggests that it may play a role in facilitating the movement of the involuting cells during gastrulation.

Animals↗
PubMed1990

Topographical EEG differences between schizophrenic patients and controls during neuropsychological functional activation.

Ten DSM III schizophrenic patients belonging to an Active syndrome were compared with 10 age- and sex-matched normal controls on neuropsychological tests with concurrent monitoring of topographical EEG using a brain imager with a 28-electrode array. In line with predictions, abnormalities in patients were found in tests involving right hemispheric functions. Deficits were found in recognition memory for faces as distinct from a verbal recognition memory task. Right temporo-parietal involvement in the faces task was confirmed by an absence of beta II amplitude reduction in patients compared with controls in the right temporo-parietal region. A similar anomaly occurred in patients in a left- but not right-hand finger-thumb apposition test in left anterior and right posterior regions, and also in a passive visual fixation task where it was located bilaterally in the occipito-parietal region. Functional activation with neuropsychological tests holds promise as one approach to the validation of topographical mapping of brain electrical activity.

Adult↗
PubMed1990

Acne keloidalis.

Explore the source record for details and available documents.

Acne Keloid↗
PubMed1990

Structuring and anxiety reduction prior to myelography.

A form of structuring (providing specific procedural and sensory information, in combination) was effective in lessening anxiety of medical patients scheduled to undergo myelography. Myelography is a complex diagnostic x-ray procedure used to assess nerve damage of the spinal cord which may be serious enough to warrant surgery. Not only was structuring shown to be therapeutically significant, but it was suggested that structuring may provide an additional means of adequately meeting the informed consent requirement prior to medical intervention.

Adult↗
PubMed1990

Dendritic transport: quantitative analysis of the time course of somatodendritic transport of recently synthesized RNA.

We have previously reported that recently synthesized RNA is selectively transported into the dendrites of hippocampal neurons grown in culture (Davis et al., 1987). The present study provides further details about this transport process, focusing especially on the velocity of transport, by comparing the velocity of dendritic transport of RNA in neurons of different ages and in the branched and unbranched dendrites of individual neurons. In our previous study, we recognized that calculations of transport velocity could be compromised because transport was being evaluated in a population of dendrites of varying lengths. The present study uses a mathematical modeling approach to determine how the morphology of the population of dendrites would affect the analysis of transport velocity. Focusing first on a simple model, we compared the distribution of transported material at various times when all dendrites were of the same length and when the population included dendrites of different lengths. We found that the distance of labeling increased linearly over time when all dendrites were of the same length, but increased with a negatively accelerating curve when dendrites were of different lengths. We then determined the actual distribution of dendritic lengths in cultured hippocampal neurons, based on immunostaining with an antibody directed against the selective dendritic marker, microtubule-associated protein 2 (MAP2). Using a computer model, we calculated the mean distance of transport as a function of time in this population of dendrites, assuming different velocities of transport. The velocity that best fit the measured distances of RNA transport in both 7- and 15-d-old neurons was 11 microns/hr (0.26 mm/d). However, for the dendrites exhibiting the longest distance of labeling, the best-fitting curve assumed a velocity of 21 microns/hr in both 7- and 15-d-old neurons (0.50 mm/d). Comparisons of transport in branched and unbranched dendrites revealed that the distance of labeling over branched dendrites was consistently longer than over unbranched dendrites of individual neurons. However, neurons with a larger proportion of branched dendrites did not exhibit a greater mean distance of transport. The density of silver grains was higher over branched than over unbranched dendrites, suggesting that a greater amount of recently synthesized RNA may be transported into branched dendrites. Taken together, these results suggest that RNA transport into dendrites is regulated differentially in the dendrites of individual neurons.

Animals↗
PubMed1989

Mapping the ankyrin-binding site of the human erythrocyte anion exchanger.

This report describes initial efforts to map the ankyrin-binding site of the cytoplasmic domain of the human erythrocyte anion exchanger. The conclusions are that this site is likely to involve a fairly extended sequence in the midregion of the cytoplasmic domain and requires interactions that are not provided by isolated peptides. The region of the sequence involving residues 174-186 is likely to participate in the ankyrin-binding site based on several experiments. Limited tryptic cleavage in the midregion of the cytoplasmic domain (residues 174 and/or 181) nearly abolished the ability of the cytoplasmic domain to inhibit binding of ankyrin to the anion exchanger. Ankyrin protected the cytoplasmic domain from tryptic digestion. Finally, peptide-specific antibodies against the sequence encompassing the site(s) of tryptic cleavage (residues 174-186) blocked binding of ankyrin to the anion exchanger. However, the sequence comprising the tryptic site is not sufficient for high affinity binding of ankyrin. A 39-amino acid peptide (residues 161-200) that includes the tryptic cleavage site(s) was inactive in inhibiting binding of ankyrin to the anion exchanger. Further evidence for a complex ankyrin-binding site is that peptide-specific antibodies against two different, noncontiguous regions (residues 118-162 and 174-186) both inhibited binding of ankyrin to the anion exchanger and were only 10-20% as effective as antibody against the entire cytoplasmic domain. Finally, the ankyrin-binding site of the anion exchanger did not renature following sodium dodecyl sulfate electrophoresis and transfer to nitrocellulose paper even though spectrin did recover ability to bind ankyrin under the same conditions. Thus, the ankyrin-binding site is not defined by a short continuous sequence. A simple consensus sequence for ankyrin-binding regions in other proteins is not likely.

Amino Acid Sequence↗
PubMed1989

Diversity in membrane binding sites of ankyrins. Brain ankyrin, erythrocyte ankyrin, and processed erythrocyte ankyrin associate with distinct sites in kidney microsomes.

This report presents evidence for diversity in membrane binding sites between three forms of ankyrin: brain ankyrin, erythrocyte ankyrin, and a variant of erythrocyte ankyrin (protein 2.2) present in circulating human erythrocytes that is missing a regulatory domain. These ankyrins were compared with respect to binding to kidney microsomes and exhibited the following behavior. 1) Brain and erythrocyte ankyrin each bind to distinct sites. 2) Protein 2.2 is an activated ankyrin that binds to all of the sites accessible to both brain and erythrocyte ankyrin and, in addition, associates with its own specialized sites. 3) The specificity of these membrane sites for various ankyrins is not absolute but reflects 2.5-10-fold differences in relative affinities. Further evidence that binding sites of different ankyrins share some common features is that the cytoplasmic domain of the erythrocyte anion transporter associates with all three ankyrins and displaces binding of the ankyrin variants to kidney membranes. The differences between erythrocyte and brain ankyrins in association with kidney membranes are likely to have physiological relevance to kidney because immunologically related isoforms of ankyrin are expressed in this tissue: erythroid ankyrin which is restricted to the basolateral domains of two cell types and a brain-related ankyrin expressed in all cells and present on apical as well as basolateral membrane surfaces. An unanticipated observation was the discovery of a membrane-associated ankyrin protease in kidney that is specific for erythrocyte ankyrin and may selectively activate the erythroid isoform of ankyrin. The variety of binding sites within this group of ankyrin proteins supports the idea that ankyrins are capable of linking a number of different membrane proteins to the spectrin-actin skeleton.

Animals↗
PubMed1989

Relationship of expressed anger to forearm muscle vascular resistance.

The relationship of style of anger expression to physiological reactivity was examined in 45 nonmedicated subjects during their performance of three tasks with contrasting response demands. The primary physiological focus was on forearm muscle vascular resistance (FMVR) with forearm muscle blood flow (FMBF), digital pulse volume (DPV), digital vascular resistance (DVR), heart rate (HR), diastolic blood pressure (DBP), systolic blood pressure (SBP), and electrodermal frequency (EF) monitored. Family Expressed Anger, i.e. the overtness of anger expression in the subject's family of origin, was related to FMVR such that the more anger was expressed in the family of origin, the greater the vasoconstriction during Mental Arithmetic and the less the vasoconstriction during Anger Imagery. Self Expressed Anger, i.e. the degree to which others were aware when the subject was feeling angry, was related to SBP and DBP during Vigilance with a lesser degree of anger expression going with greater blood pressure increases. The meaning of these findings in relation to task appraisal and task demand is discussed.

Adult↗
PubMed1989

Fast neutron teletherapy in advanced epidermoid head and neck cancer. A review.

An extensive review of clinical studies employing fast neutron teletherapy for advanced epidermoid carcinomas of the head and neck is presented. Head and neck tumors have represented an excellent study site because of their accessibility to physical examination for measurement of tumor response, and because early neutron beams have had poor depth dose characteristics, making the treatment of more deeply seated tumors technically difficult. A summary of the major trials comparing neutron and mixed-beam (combination neutron and photon) therapy with conventional therapy indicates no conclusive evidence of improvement in local control or survival rates for the experimental arms. Exceptions to this are the Hammersmith experience and the slightly higher lymph node control rates seen in two studies. An evaluation of toxicity indicates that with the new generation of cyclotrons, complication rates may approach parity with those of photon linear accelerators.

Carcinoma, Squamous Cell↗
PubMed1989

Fast neutron radiation for inoperable and recurrent salivary gland cancers.

The current standard treatment of salivary gland cancers consists of surgical resection, with or without postoperative low linear energy transfer (LET) radiation, resulting in high locoregional control rates. However, tumor control prognosis is poor when conventional radiation is used alone for advanced, inoperable cases. An extensive review of the world's literature on fast neutron irradiation for inoperable, unresectable, or recurrent malignant salivary gland neoplasms is presented and compared with the experience using conventional low LET radiotherapy. The pooled data indicate a locoregional control rate of 67% for fast neutrons versus 25% for photons and/or electrons in the treatment of such advanced disease. The radiobiological rationale supporting this observed increase in tumor control is discussed. The overall significant late complication rate is 19%, but several suboptimal treatment factors were present that contributed substantially to the reported toxicity. With the modern machines and treatment techniques now available, the evidence overwhelmingly supports the role of fast neutron radiation as the treatment of choice for inoperable and recurrent salivary gland cancers.

Energy Transfer↗
PubMed1989

Transverse images of the human thoracic trachea during forced expiration.

The thoracic trachea and the proximal portion of the major bronchi were imaged in five normal volunteers during a forced expiration maneuver using a cine-computer-tomography system. Sixteen images of two contiguous slices were obtained in less than 1 is while expiratory flow was recorded at the mouth. The area of the thoracic trachea decreased rapidly as flow rate rose to its maximum and the wave of collapse propagated distally. The compressive narrowing of both the pars membranacea and the ventrolateral wall was asymmetric. A contact area appeared between the posterior and the left lateral walls. In one subject the trachea was imaged during the entire maneuver with a lower scan frequency. By 725 ms after the beginning of the forced expiration, the area had first decreased to 15% of its initial value and then reincreased to 46% of its initial value. It stayed constant for the remainder of the maneuver. The measured maximum air velocity was greater than the estimated local wave velocity.

Adult↗