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Biomedical subjects

J Lewis

Publications and source records attributed to J Lewis.

At least 271 records · Page 15Linked to original sources
PubMed1992

Reversibility of left ventricular hypertrophy by differing types of antihypertensive therapy.

Left ventricular hypertrophy (LVH), as assessed by ECG or echocardiography, is a powerful independent coronary risk factor. The present overview of 104 studies sets out to compare the ability of various forms of antihypertensive therapy to reverse LVH as assessed by echocardiography. Most observations involved four classes of treatment--combination therapy, ACE inhibitors, beta-blockers and calcium antagonists (mainly dihydropyridines). The former two therapies were significantly more effective than the latter two in reversing LV mass, independently of length of time on treatment and degree of fall in blood pressure. Possible reasons for these differences are discussed. The clinical significance of these results is unclear although preliminary data indicate that regressing LVH is associated with fewer cardiovascular events.

Antihypertensive Agents↗
PubMed1992

Retroperitoneal hematoma after blunt trauma.

We reviewed retrospectively 233 consecutive patients with retroperitoneal hematoma (RPH) resulting from blunt trauma. This study group represented 2.9 per cent of all admissions for blunt trauma and 13 per cent of all admissions for blunt abdominal trauma. Motor vehicle accidents predominated as the cause of injury. Fifty-five per cent of the patients had fractures of the pelvis. Laparotomy was the primary method used in diagnosing RPH (73 per cent). The RPH was located in zone I in 14 per cent of patients, zone II in 37 per cent, zone III in 46 per cent and zone IV in 3 per cent. The RPH was explored in 35 per cent of all patients. Major vessels were the most common organ system injured (21 per cent) in patients with zone I RPH. The kidney was the most commonly injured organ (27 per cent) in patients with zone II RPH. Injury of either the pancreas or duodenum in 14 per cent of patients with right-sided zone II RPH indicates the need for careful evaluation of those organs at operation. Patients with zone III RPH associated with fractures of the pelvis should be explored only rarely--when main iliac vascular injury is suspected (4.6 per cent in this series). Otherwise, a systematic approach using external fixator devices and angiographic embolization should be used. The over-all morbidity and mortality rates of 59 and 39 per cent, respectively, emphasize the need for aggressive resuscitation, rapid control of hemorrhage and a multidisciplinary approach to the management of these patients.

Abdominal Injuries↗
PubMed1991

DNA methylation and chromatin structure.

Studies of the whole genome by molecular and cytogenetic methods have implicated DNA methylation in the formation of 'inactive chromatin'. This has been confirmed by analysis of specific endogenous sequences, and has been mimicked by introducing methylated and non-methylated sequences into cells. As well as affecting chromatin structure. DNA methylation also represses transcription. A protein (MeCP) which binds specifically to methylated DNA has been identified. The properties of MeCP could account for the effects of DNA methylation on both chromatin and transcription.

5-Methylcytosine↗
PubMed1991

Characterization of the opposite-strand genes from the mouse bidirectionally transcribed HTF9 locus.

The mouse HTF9 locus contains two genes that are bidirectionally transcribed with opposite polarity from a shared CpG-rich island. Both genes were previously shown to be expressed in a housekeeping fashion in mouse. We have now determined the molecular organization of the genes over 12 kb surrounding the island. In addition, we show that the HTF9 locus resides in the proximal region of mouse chromosome 16. We have sequenced the cDNAs corresponding to both divergent transcripts. Both genes appear to code for novel proteins that are structurally unrelated to each other. Finally, we show that both genes are highly conserved and efficiently expressed in human cells.

Amino Acid Sequence↗
PubMed1991

Murine epidermal gamma/delta T cells express Fc gamma receptor II encoded by the Fc gamma R alpha gene.

Short-term bulk cultures and some long-term clones and lines of murine T cell receptor (TcR) gamma/delta-bearing epidermal T cells (dEC) were found to express an Fc gamma receptor II (Fc gamma RII), as revealed by reactivity with the monoclonal antibody 2.4G2. Northern blot analysis showed that the Fc gamma RII expressed on dEC is encoded solely by the Fc gamma R alpha gene. While all the various cultured dEC cell populations analyzed exhibit lectin-dependent cellular cytotoxicity, only those which expressed Fc gamma R alpha were also capable of mediating antibody-dependent cellular cytotoxicity (ADCC). These results in combination with the previous demonstration of Fc gamma R alpha on mouse natural killer cells support an essential role for Fc gamma R alpha in ADCC and extend an analogy with surface CD16 (Fc gamma RIII) expression and ADCC in human natural killer cells and peripheral TcR gamma/delta T cells.

Animals↗
PubMed1991

Effect of cost on the self-administration and efficacy of nicotine gum: a preliminary study.

METHODS. One hundred six smokers seen in a family practice received brief physician advice and a prescription for nicotine gum. Smokers were randomly assigned to pay $20, $6, or $0/box of nicotine gum and followed for 6 months. RESULTS. Decreased cost increased the incidence of obtaining gum, the amount of gum used, and the incidence of long-term use (P less than 0.05). Decreased cost also increased cessation attempts and 1-week cessation (P less than 0.05) and appeared to increase abstinence at 6-month follow-up (19% vs 6% vs 8%, P less than 0.10). Cost-benefit estimates suggest that an insurance plan, HMO, etc., would recoup any costs in subsidizing nicotine gum and perhaps incur a net financial gain.

Adult↗
PubMed1991

Monte Carlo simulation of the water in a channel with charges.

A Monte Carlo simulation of water in a channel with charges suggests the existence of water in immobile, high density, essentially glasslike form near the charges. The channel model has a conical section with an opening through which water molecules can pass, at the narrow end of the cone, and a cylindrical section at the other end. When the charges are placed near the narrow section of the model, the "glass" effectively blocks the channel; with the charges removed, the channel opens. The effect can be determined from the rate of passage of the water molecules through the pore, from the average orientation of the water molecule, and from distortion of the distribution of molecules. In the simulations carried out to date, no external ions have been considered. In addition to the energy, the Helmholtz free energy has been calculated.

Ion Channels↗
PubMed1991

Corticosteroid and thyrotropin-releasing hormone effects on preterm sheep lung function.

Four groups of twin sheep fetuses were catheterized at 121 days of gestational age and intravenously infused with saline, 0.75 mg.kg-1.h-1 cortisol for 60 h, five intermittent bolus injections of 5 micrograms/kg thyrotropin-releasing hormone (TRH) at 12-h intervals, or both hormones before delivery at 128 days. At birth, the lambs were randomized to receive surfactant or no treatment. Surfactant treatment improved lung function of all the groups. Corticosteroids alone and in combination with TRH improved compliance and gas exchange as well as pressure-volume curves. Corticosteroids alone dramatically decreased the recovery of intravenously administered radiolabeled albumin in the lung tissue and air space and improved the pulmonary response to surfactant treatment. There were no additional effects of TRH when given with corticosteroids on lung function or albumin leak. There were no changes in alveolar surfactant-saturated phosphatidylcholine pool sizes after any hormone treatment. The single significant effect of combined corticosteroid and TRH treatment was a fivefold increase in surfactant protein A in alveolar lavage fluid relative to all other groups.

Animals↗
PubMed1991

Nebulized vs. instilled exogenous surfactant in an adult lung injury model.

Three days after subcutaneous injection of N-nitroso-N-methylurethane (NNNMU) to induce lung injury, adult rabbits were mechanically ventilated and lung function was evaluated. Each animal then received either nebulized Survanta (Neb Surv), nebulized saline (Neb Saline), nebulized gas alone (Neb Gas), or tracheally instilled Survanta (Inst Surv). The ventilation efficiency index (VEI) value increased significantly compared with pretreatment values (P less than 0.01) over a 3-h treatment period for the Neb Surv animals, whereas VEI values for the other three groups decreased after treatment (P less than 0.05). Arterial PO2-to-fraction of inspired O2 ratios and dynamic compliance values significantly decreased after treatment for the Inst Surv group (P less than 0.05). Pressure-volume curves demonstrated a significantly greater volume at maximal pressure for the Neb Surv group compared with each of the other groups studied (P less than 0.01). The calculated quantity of surfactant recovered in lung tissue for the Neb Surv group was only 4.9 +/- 1.0 mg lipid/kg compared with 100 mg lipid/kg delivered to the Inst Surv group. Surfactant administered as an aerosol resulted in modest physiological improvements in this model of lung injury and was superior to the tracheal instillation technique.

Aerosols↗
PubMed1991

Rules for the production of sensory cells.

During development and regeneration, cells divide, move, change their internal state, respond to environmental signals and die according to rules specified by their genome. These rules of cell behaviour are fundamental to any explanation of how sensory tissues are generated or repaired. An attempt is made to summarize and compare the rules underlying the development of four different sensory tissues: mammalian retina, avian auditory epithelium, mechanosensory bristle fields in Drosophila and, very briefly, Drosophila retina. There are parallels in cell lineage, in the timing of developmental decisions, in the postponement of the choice of differentiated state until the final cell division cycle, in the role of short-range lateral inhibition, and in the involvement of genes such as Notch and achaete/scute. These similarities may reflect the conservation of some basic mechanisms of sensory development that originated early in the evolution of multicellular animals. If so, studies in Drosophila, with its advantages for molecular genetics, may give important clues to the mechanisms of sensory development and regeneration in vertebrates.

Animals↗
PubMed1990

The effects of superior laryngeal nerve stimulation on the respiratory rhythm: phase-resetting and aftereffects.

The effect of brief superior laryngeal nerve stimulation on the respiratory rhythm was investigated in midcollicular decerebrate, unanesthetized, artificially ventilated, paralysed, vagotomized and debuffered cats. Stimulus trains (50 ms, 200 Hz) delivered during inspiration (I) with intensities exceeding a threshold value, that was inversely related to the phase of the cycle, terminated I and shortened the following expiration (E) (irreversible I termination). Stimulus trains given during I with intensities just below this threshold value produced a transient suppression of I followed by resumption of activity, resulting in a slight prolongation of both I and the following E (reversible I termination). Stimulation during E produced a phase-dependent prolongation of E, but did not affect the next I. Phase-resetting curves were constructed by measuring the changes in respiratory cycle duration produced by stimuli given at phases throughout the cycle. A single stimulus produced aftereffects that lasted several cycles. The aftereffects were investigated by delivering stimuli at a fixed delay from cycle onset every n cycles (n is an integer). Certain combinations of delay, stimulus intensity, and n, resulted in (1) a variable combination of reversible and irreversible I terminations, rather than a consistent response, and (2) an increase in cycle duration. The stimulus aftereffects, that can last up to 9 cycles, may account for previously described unpredictability in the response of the respiratory oscillator to a given stimulus.

Animals↗