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Biomedical subjects

A Taylor

Publications and source records attributed to A Taylor.

At least 559 records · Page 31Linked to original sources
PubMed1989

Regression of left ventricular hypertrophy in hypertension. Effects of prazosin therapy.

Left ventricular hypertrophy is a common consequence of chronic hypertension. Although the hypertrophic response can be considered an adaptive mechanism in the initial stages, its progression is associated with increased cardiovascular morbidity and mortality rates. Therefore, reversal of left ventricular hypertrophy may provide considerable clinical benefits to hypertensive patients. Although treatment of hypertension per se is important, blood pressure alone may not explain the course of the hypertrophic process. Not all antihypertensive drugs cause a reversal of hypertrophy, though they may produce equal effects on blood pressure. Factors other than the severity of blood pressure may play a role in the genesis of left ventricular hypertrophy. Adrenergic inhibitors cause its regression, whereas direct vasodilators may promote progression. In this study, therapy with the alpha-adrenergic inhibitor prazosin resulted in significant regression of left ventricular hypertrophy in a group of patients with moderate-to-severe hypertension. This study utilized a new technique--[123I]phenylpentadecanoic acid myocardioscintigraphy--to measure the left ventricular mass. In this study, it was shown that monotherapy with prazosin produced significant relative reductions in systolic and diastolic blood pressure, along with significant reductions in left ventricular mass.

Blood Pressure↗
PubMed1989

The value of CT scanning in the management of patients with gynecologic malignancies.

The management of gynecologic malignancies is exceedingly complex, requiring thoughtful coordination of surgery, radiation therapy and chemotherapy. Despite the fact that the natural history and clinical course of these cancers are generally well understood, the scarring caused by surgery and/or radiation, and the marked limitations of pelvic examination make clinical staging and evaluation of limited value and known inaccuracy in following women with ovarian, cervical, uterine, vulvar and vaginal cancers. Understandably, the development of computerized axial tomography (CT), and its ability to visualize the abdomen and pelvis, lead to rapid acceptance of CT scans in defining extent of cancer and following patient response to various therapeutic interventions (Chen et al. 1980; Feigen et al. 1987; Photopoulos et al. 1977). Authors have compared the accuracy of CT findings with physical examination, surgical findings, lymphography, conventional radiography or ultrasound (Clarke-Pearson et al. 1986; Vercamb et al. 1987; Amendola 1981; Kerr-Wilson et al. 1984). However, little has been written on the effect of CT scanning on patient management. If we define and accept the accuracy of CT scanning in detecting pelvic and abdominal disease, can we show a benefit in patient management? Or, does CT scanning provide us with expensive information, or misinformation, which fails to translate into better patient care. Do complex imaging modalities compliment thorough examination and experienced clinical judgement, or only duplicate findings and provide extraneous information? To answer these questions, eighty-one months experience in using CT scanning in managing patients with gynecologic malignancies was reviewed.

Biopsy↗
PubMed1989

Central mechanisms of selective fusimotor control.

Experiments on anaesthetized cats have confirmed the existence of regions of the midbrain from which dynamic fusimotor effects can be produced by electrical stimulation. Simultaneous recording from hindlimb and jaw muscle spindles has shown that both of these widely different muscle groups are affected from identical or closely related regions. The anatomical structure common to many of the pathways, which are likely to be involved at the sites of effective stimulation is the fasciculus retroflexus and it is suggested that this indicates that the habenulo-interpeduncular system may be involved in generating "dynamic fusimotor set" at the onset of movements, as a possible function of its place as an output pathway for the limbic system. The results are discussed in relation to the other well known source of dynamic control of spindles, namely the MesADC.

Animals↗
PubMed1989

DNA bending is induced by a transcription factor that interacts with the human c-FOS and alpha-actin promoters.

Conserved sequence elements in the human cardiac and skeletal alpha-actin promoters that contain the CC(A + T-rich)6GG motif have been shown to regulate transcription of these genes. A similar sequence is found in the serum response element of the human c-FOS gene. In this study, we demonstrate that indistinguishable proteins bind to each of five CC(A + T-rich)6GG elements examined in the human cardiac and skeletal alpha-actin promoters and the c-FOS serum response element. Using electrophoretic techniques, we show that these factors induce a stable bend in the DNA upon binding, and the bend center is shown to coincide with the CC(A + T-rich)6GG element. In addition, the ability to bend DNA is retained by a small proteolytic fragment of the protein, suggesting that the DNA-binding domain of the protein is resistant to proteases and is sufficient to bend DNA.

Actins↗
PubMed1989

Relationship between dietary intake and tissue levels of reduced and total vitamin C in the nonscorbutic guinea pig.

The objective of this study was to determine the effect of a broad range of dietary intake levels of ascorbate on the distribution of both total and reduced ascorbate in guinea pig tissues. Young male Hartley guinea pigs were fed for 2 mo a modified Reid-Briggs purified diet containing five different levels of total ascorbate that provided 0.8-52 mg ascorbate/d. We also fed aged guinea pigs two different levels of ascorbic acid (1.5 or 60 mg/d) for 2 mo. Reduced and total ascorbate was measured in eye lens and aqueous humor, liver, kidney and plasma. The data indicate that it is possible to markedly enhance the level of ascorbate in tissues above that obtained by feeding a diet that contains only enough ascorbate to prevent scurvy. In all tissues, as the level of total ascorbate present in the tissue increased, so did the proportion present in the reduced form. In old guinea pigs, the eye lens was the only tissue in which both reduced and total ascorbate were significantly lower than in the young guinea pigs at both high and low intake levels.

Animals↗
PubMed1989

Moderate caloric restriction delays cataract formation in the Emory mouse.

Eye lens senile cataract is a major cause of blindness, affecting the elderly in particular. The etiology of the disorder has been elusive, and attempts to delay the onset of senile cataracts have been unsuccessful. The need for more information is underscored by epidemiologists who estimate that the ability to delay cataract formation in humans by only 10 years would eliminate the need for 50% of the cataract extractions performed annually in the United States. The Emory mouse provides the best model for human senile cataracts. Feeding Emory mice a diet that was restricted in calories by approximately 21% delayed the onset of cataracts. This is the first study that demonstrates in vivo the delay of senile-type cataracts. In these animals, aging and cataracts are associated with diverse changes in the proportion of various proteins (particularly 21, 22, 31-34 kDa) and with transformation of proteins from a soluble to an insoluble state. In advanced cataracts, there is a loss of total protein. Within a cataract grade, there is no difference between restricted and nonrestricted animals in relative proportion of specific lens proteins or in amounts of total or soluble proteins. The transition from a clear to cataractous lens appears when the soluble-to-total protein ratio falls below about 0.58. The exclusive use of gamma-crystallin as an indicator of lens viability is questioned. To the extent that cataract formation is due to lens protein oxidation and/or an inability to proteolytically remove damaged protein, it would appear that caloric restriction results in enhanced protection against lens oxidative stress or in prolonged proteolytic function.

Aging↗
PubMed1989

Gibberellic Acid stimulation of cucumber hypocotyl elongation : effects on growth, turgor, osmotic pressure, and cell wall properties.

Recently developed techniques have been used to reinvestigate the mechanism by which gibberellic acid (GA(3)) stimulates elongation of light-grown cucumber (Cucumis sativus L.) seedlings. Osmotic pressure and turgor pressure were slightly reduced in GA(3)-treated seedlings, which elongated 3.5 times faster than control seedlings. This indicated that GA(3) enhancement of growth was not controlled by changes in the osmotic properties of the tissues. Stress/strain (Instron) analysis revealed that plastic extension of the cell walls of GA(3)-treated seedlings increased by up to 35% above the control values. Stress-relaxation measurements on frozen-thawed tissue showed that T(0) the minimum relaxation time, was reduced following application of GA(3). In vivo wall relaxation (measured by the pressure block technique) showed that the wall yield coefficient was increased, and the yield threshold was slightly reduced. Thus GA(3) affected both the mechanical (viscoelastic) and biochemical (chemorheological) properties of the cell walls of light-grown cucumber. The previous hypothesis, that GA(3) stimulates cucumber hypocotyl growth by increasing osmotic pressure and cell turgor, is contradicted by our results.

Journal Article↗
PubMed1989

Some endocrinological events associated with early pregnancy failure.

Serial measurements of serum progesterone, oestradiol, human chorionic gonadotrophin (hCG) and human placental lactogen (hPL) have been determined in 33 women experiencing early pregnancy failure and compared with the values of the same hormones in 72 healthy women having uncomplicated pregnancies. Steroid production by the corpus luteum seemed similar in both groups up to 6 weeks gestation but thereafter placental steroidogenesis was not evident in those women in whom spontaneous pregnancy losses occurred. Placental production of the two protein hormones, hCG and hPL, did take place, and whereas the circulating levels were not as high as in normal pregnancies, levels did usually increase before clinical evidence of miscarriage occurred. hCG was not a sensitive discriminator of subsequent failure. In these women there were no significant hormone differences between those with evidence of a fetus and those without.

Abortion, Spontaneous↗
PubMed1989

Associations between nutrition and cataract.

Blindness due to opacification of the lens, or cataract, afflicts 50 million persons worldwide. In the United States over 541,000 cataract extractions are done annually at a cost of over $3.8 billion. Conservative estimates indicate that the prevalences of cataracts in Americans aged 65-75 and 75-85 years are 18% and 46%, respectively. Cataracts are even more prevalent in some other populations. It is estimated that the need for cataract extractions would be diminished by half if onset of cataract could be delayed by only ten years. Hypotheses regarding the etiology of cataract include oxidative perturbations of protein metabolism, diverse pathologic conditions, and perhaps glycation of lens proteins. Epidemiologic data indicate that elevated plasma levels of specific nutrients (i.e., carotenoids, ascorbate, tocopherol, and taurine) are associated with diminished incidence of certain types of cataract. Biochemical evidence suggests that each of these compounds can delay photooxidative damage to lens proteins. Roles in lens metabolism for selenium and tryptophan have been suggested. Elucidation of mechanisms by which caloric restriction delays cataract development is a promising area of current research.

Cataract↗
PubMed1989

Effect of nocodazole on the water permeability response to vasopressin in rabbit collecting tubules perfused in vitro.

1. The effect of the microtubule-disruptive agent, nocodazole (methyl [5-(2-thienylcarbonyl)-1H-benzimidazol-2-yl] carbamate), on the water permeability response to vasopressin or the synthetic cyclic AMP analogue, 8-parachlorophenylthio-cyclic AMP (8-CPT-cAMP), has been investigated in isolated cortical collecting tubules from rabbit kidneys, perfused in vitro. 2. Pre-treatment with nocodazole, 1-4 micrograms ml-1, had no significant effect on basal water permeability, but inhibited the increase in hydraulic conductivity elicited by vasopressin, 50 microU ml-1, in a dose-dependent manner. Inhibition of the response to the hormone averaged 65 +/- 6% (n = 8, P less than 0.001) at a nocodazole concentration of 4 micrograms ml-1. 3. Nocodazole, 1-4 micrograms ml-1, had no effect on the increase in lumen-negative potential difference (PD) induced by the hormone. 4. Pre-treatment with nocodazole, 4 micrograms ml-1, inhibited the development of the water permeability response to 8-CPT-cAMP, 1.8 x 10(-5) M, by 45 +/- 7% (n = 7, P less than 0.001). 5. When collecting tubules were exposed to nocodazole, 4 micrograms ml-1, after the hydrosmotic response to vasopressin had been fully established, the drug had no inhibitory effect on the maintenance of a high water permeability. 6. The results are consistent with the view that cytoplasmic microtubules play a role in the initiation of the water permeability response to vasopressin in the mammalian cortical collecting tubule at a cellular site beyond the generation of cyclic AMP.

Animals↗
PubMed1989

Use of robotics to dispense culture media.

Liquid and agar-containing media can be aseptically dispensed by a laboratory robot. Five errors occurred during the filling of 700 tubes with medium; four of these were due to imperfections of the screw-threaded caps of the culture tubes. The mean volume dispensed was 14.8 ml (standard deviation, 0.5; n = 50) when the system was set to deliver 15 ml.

Journal Article↗
PubMed1989

Clinical comparison of I-131 orthoiodohippurate and the kit formulation of Tc-99m mercaptoacetyltriglycine.

Previous studies in animals and humans have shown that technetium-99m mercaptoacetyltriglycine (MAG3) purified by high-performance liquid chromatography is a renal tubular agent with characteristics similar to those of iodine-131 orthoiodohippurate (OIH). A kit formulation for Tc-99m MAG3 has been developed and compared with I-131 OIH in 17 patients with suspected renal dysfunction and three potential kidney donors. There were no adverse reactions. Tc-99m MAG3 images were of good quality and consistently better than I-131 OIH images. There was no significant difference in the relative renal uptake of Tc-99m MAG3 and I-131 OIH. The 30-minute urinary excretion of Tc-99m MAG3 was 36.4%, versus 40.4% for I-131 OIH. The average plasma clearance of Tc-99m MAG3 (138 mL/min +/- 117) was less than that of I-131 OIH (272 mL/min +/- 205) (P less than .001); however, there was good correlation between the Tc-99m MAG3 and I-131 OIH clearances (r = .87). The volume of distribution of Tc-99m MAG3 (5.96 L +/- 1.94) was less than that of I-131 OIH (9.41 L +/- 3.73) (P less than .001). These characteristics and the advantages of a simple kit formulation should lead to widespread clinical use.

Adult↗
PubMed1989

Role of lung injury in the pathogenesis of hyaline membrane disease in premature baboons.

To test the hypothesis that hyaline membrane disease (HMD) has a multifactorial etiology in which barotrauma plays a major role, we compared the immediate institution of high-frequency oscillatory ventilation (HFOV; 15 Hz, n = 5) with positive-pressure ventilation with positive end-expiratory pressure (PPV; n = 7) in premature baboons (140-days gestation) with HMD. Measurements of ventilation settings and physiological parameters were obtained and arterial-to-alveolar O2 (PaO2-to-PAO2) ratio and oxygenation index [(PaO2/PAO2)-to-mean airway pressure ratio (IO2)] were calculated. At death (24 h), static pressure-volume (PV) curves were performed, and phospholipids (PL) and platelet-activating factor (PAF) were measured in lung lavage fluid. Morphological inflation patterns were analyzed using a panel of standards. By design, mean airway pressure was initially higher (19 vs. 13 cmH2O) in the HFOV animals. PaO2-to-PAO2 ratio and IO2 progressively deteriorated in the PPV animals and then stabilized at significantly lower levels than with HFOV. PV curves from HFOV animals had significant increases in lung volume at maximum distending pressure, deflation volume at 10 cmH2O, and hysteresis area compared with PPV, which showed no hysteresis. Seven of seven PPV and only one of five HFOV animals had morphological findings of HMD. PL amount and composition in both groups were consistent with immaturity, even though the quantity was significantly greater in the PPV group. PAF was present (greater than or equal to 0.10 pmol) in six of seven PPV and in the only HFOV animal with HMD. We conclude that HFOV protected PL-deficient premature baboons from changes in gas exchange, lung mechanics, and morphology typical of HMD in this model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

The network trilogy project: linking aging, mental health and health agencies.

There is a striking disparity between the estimated need for mental health care by 18-25% of the nation's elderly, and the minimal utilization of private and publicly funded services by this age cohort. Recognition that the elderly are not well served by existing systems led a trilogy of major Philadelphia aging, mental health, and health organizations to form a partnership for the purpose of improving, expanding, and integrating service delivery for a segment of the population which has been overlooked. A training model was devised to overcome the organizational isolation of agencies serving mutual clients with interrelated problems. For training purposes, the city was divided into five sections. Consultants were recruited to organize staff development groups from the health, mental health and senior centers in the geographic areas to which they were assigned. This paper describes the interagency training experience, the receptivity of the participants, and discusses the issues which must be addressed to improve coordination of elderly services by the aging, health, and mental health systems.

Aged↗
PubMed1989

Estimation of technetium-99m-MAG3 plasma clearance in adults from one or two blood samples.

Technetium-99m mercaptoacetyltriglycine (MAG3) clearance is strongly correlated with effective renal plasma flow and can be used directly as a measure of renal function. For these reasons, formulas were developed for estimation of [99mTc]MAG3 clearance based on one or two plasma samples. A two-exponential model provided an excellent fit for 8-point plasma clearance curves obtained from 35 patients having a wide range of renal function. The 8-point [99mTc]MAG3 clearance could be estimated from a single point at 43 min with an error of 19 ml/min (residual s.d.) or from two samples at 12 and 94 min with an error of 7 ml/min. The relative errors with MAG3 are thus comparable to those reported for similar techniques used with [131I]orthoiodohippurate, [99mTc]diethylenetriaminepentraacetic acid and [51Cr]ethylenediaminetetraacetic acid.

Adult↗