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Biomedical subjects

D Parker

Publications and source records attributed to D Parker.

At least 181 records · Page 10Linked to original sources
PubMed1991

Obesity, blood pressure, and the sympathetic nervous system.

Obesity has long been recognized as a major risk factor for the development of hypertension. Recently, insulin level has been shown to correlate with blood pressure in clinical and population-based studies. Since insulin is a major signal in the relationship between dietary intake and sympathetic nervous system activity, the possibility that insulin-mediated sympathetic stimulation is involved in the pathogenesis of hypertension in the obese has been raised. This hypothesis, developed on the basis of studies in laboratory rodents and normal human subjects, is currently being tested in the Normative Aging Study in Boston. Utilizing epidemiologic techniques applied to this defined population, evidence in support of this hypothesis has been accumulated. The preliminary results indicate that in this population, the abdominal form of obesity is associated with higher insulin levels and increased 24-hour urinary norepinephrine excretion (an index of sympathetic activity).

Animals↗
PubMed1991

Comparative performance of 14-crown-4 derivatives as lithium-selective electrodes.

A series of neutral ionophore-based lithium-selective liquid-membrane electrodes have been prepared and the electrode performance compared with similar electrodes based on the lithium ionophores ETH 1810-ortho-nitrophenyl octyl ether (oNPOE) and ETH 2137-bis(1-butylpentyl) adipate (BBPA). By using a diamide substituted 14-crown-4 macrocycle, selectivities for Li+ in the presence of Na+ of log kpotLi,Na = -3.25 and -2.92 were obtained for diisobutylamide-oNPOE and di-n-butylamide-oNPOE derivatives. The di-n-butylamide-oNPOE based electrode functioned satisfactorily in serum, exhibiting a fast response time (10-15 s), an acceptable lifetime of 50 d and minimal protein interference.

Autoanalysis↗
PubMed1991

Alternative fat-restricted diets for hypercholesterolemia and combined hyperlipidemia: feasibility, design, subject recruitment, and baseline characteristics of the dietary alternatives study.

UNLABELLED: Dietary recommendations for the treatment of hypercholesterolemia (HC) emphasize stepwise reductions in fat intake, but there is no agreement on what lower limit is desirable or achievable. These recommendations have applied broadly to persons with HC alone, as well as to those with a combined elevation in triglyceride (TG) and cholesterol, even though they may differ in pathophysiological mechanisms and response. In this paper, we describe the design and feasibility of recruiting and randomizing subjects with HC or combined hyperlipidemia (CHL) to an outpatient dietary intervention study of progressively fat-restricted diets. Diets were designed to contain 30, 26, 22, and 18% of calories from fat; 300, 200, 100, and 100 mg cholesterol/day; and a polyunsaturated/saturated fat ratio of approximately 1.0. Triglyceride and low-density-lipoprotein cholesterol (LDL-C) cutpoints were based on the age-specific 75th percentile value. Over 18 months, 8372 men were screened, yielding 320 HC subjects randomized to the four diets and 211 CHL subjects randomized to the first three diets (because of fewer CHL subjects). At baseline, HC and CHL subjects were similar in age, education, lifestyle, dietary intake, and LDL-C, but CHL subjects were heavier, more hyperglycemic, hyperinsulinemic, and hypertensive. CONCLUSIONS: Recruiting a large cohort of HC and CHL subjects from an industrial workforce is feasible in a restricted time frame. CHL subjects demonstrate features of the insulin resistance/hypertension syndrome, differing from HC subjects. CHL is sufficiently common relative to HC (2:3) to permit a comparison of dietary responses between the two conditions. Finally, the randomization of HC and CHL subjects to the diets yielded statistically indistinguishable groups, permitting a test of the efficacy of the alternative diets within each hyperlipidemic (HL) category.

Adult↗
PubMed1991

In vitro activity of loracarbef (LY163892), a new oral carbacephem antimicrobial agent, against respiratory isolates of Haemophilus influenzae and Moraxella catarrhalis.

The in vitro activity of a new orally administered carbacephem analog of cefaclor, loracarbef (LY163892), was compared with those of cefaclor and several other oral antimicrobial agents against recent clinical isolates of Haemophilus influenzae and Moraxella catarrhalis. Loracarbef was found to be slightly more active than cefaclor against H. influenzae and had activity essentially equivalent to that of cefaclor for M. catarrhalis. Resistance to loracarbef was uncommon and was noted only with rare beta-lactamase-producing strains of H. influenzae. On the basis of these observations, loracarbef may be of utility in the management of localized, non-life-threatening infections caused by H. influenzae and M. catarrhalis.

Anti-Bacterial Agents↗
PubMed1990

Detection of hepatitis C viral sequences in blood donations by "nested" polymerase chain reaction and prediction of infectivity.

Of 1100 blood donations tested during a prospective study of post-transfusion non-A, non-B hepatitis (NANBH), 6 (0.55%) were repeatedly reactive in a commercial assay for antibodies to the C100 protein of hepatitis C virus. Only 1 of the 6 donations (17%) transmitted NANBH to a recipient. Hepatitis C virus RNA sequences were detected in the serum of the transmitting donor by an assay which used the polymerase chain reaction (PCR) and non-radioisotopic detection. No such sequences were detected in the other 5 donors positive for anti-C100. Stored serum samples from blood donors who had been involved in three episodes of post-transfusion NANBH in 1981 also contained hepatitis C viral sequences. Although the PCR assay in its present form is not suitable for mass donor screening, the presence of hepatitis C viral sequences detected by PCR in blood donations seems a better predictor of infectivity than the presence of anti-C100 alone.

Antigens, Viral↗
PubMed1990

Further data on the selective expression of Ly-5 isoforms.

Ly-5 (CD45) glycoproteins of the mouse, expressed by all or most hematopoietic cell lineages and specified by a single Ly-5 gene, range in size from isoform T200 of T cells (the smallest), in which exons 4, 5, and 6 are not represented, to isoform B220 of B cells (the largest), in which all three of these optional exons are represented. The main purpose of the present study, utilizing the polymerase chain reaction (PCR), was to ascertain whether known isoforms of intermediate size are generated by single or dual usage of optional exons 4, 5, and 6. Transcripts representing all eight isoforms predictable from varied use of three exons were observed among a diverse panel of nine B-cell tumors in culture, but there was no evident concordance with known contrasting differential features that distinguish members of the B-cell tumor panel. No two B tumors exhibited the same variety of transcripts and the relative quantities of transcripts expressed varied greatly from tumor to tumor. Cloning of B-cell tumors did not alter their distinctive transcript patterns. Separation methods (sodium dodecyl sulfate polyacrylamide gel electrophoresis; SDS-PAGE) did not suffice to segregate all corresponding expressed isoforms but did establish that transcripts representing usage of a single optional exon and of two optional exons were actually translated, which supports a provisional inference that all eight isoforms exist. The considerable diversity of B-cell transcript phenotypes was not seen among seven T-cell leukemias, two cytolytic T-cell lines, and three Th 1 helper T-cell lines, all of which displayed a uniform phenotype comprising major expression of the T200 transcript (no optional exon) and minor expression of a transcript employing exon 5. However, a panel of five cloned Th2 T-cell lines, which represent a second and functionally different branch of the helper/inducer T-cell category, exhibited a characteristic transcript pattern which distinguished them from a panel of three Th1 T-cell lines. The major transcript in the Th2 lines was also T200, but the Th2 lines showed higher representation of transcripts containing optional exons. A single Th2 clone expressed an unusual transcript suggesting a potential isoform not compounded simply by varied inclusion of the three identified optional exons. After activation of the helper T-cell lines with concanavalin A (Con A), expression of transcripts containing optional exons appeared to decrease.

Animals↗
PubMed1990

Relationship of spectral noise levels to psychophysical scaling of vowel roughness.

Direct magnitude estimation (DME) and equal-appearing interval (EAI) ratings of perceived roughness and spectral noise level (SNL) measurements of isolated sustained vowel samples (/a/ and /i/) were obtained. The linear and curvilinear relationships between the resulting roughness ratings and SNL were then examined. In the present study, the comparison between the two models resulted in conflicting evidence regarding the model that best described the relationship between roughness ratings and SNL measurements. In all comparisons, however, a significant linear component was indicated. Additionally, when a significant curvilinear component was indicated, the difference between the lines and curves that were fit to the data was minimal. The present findings suggest, therefore, that a high degree of linearity exists between both DME and EAI roughness ratings and SNL.

Adult↗
PubMed1990

Safety of late acetylcysteine treatment in paracetamol poisoning.

Twenty patients who had taken overdoses of paracetamol were treated with acetylcysteine between 12 and 24 hours after the incident. Although 19 patients had plasma paracetamol concentrations greater than those associated with a 90% risk of moderate to severe liver damage, this complication occurred in only seven (35%) individuals. No patient developed hepatic encephalopathy or acute renal failure and all recovered without sequelae. We conclude that acetylcysteine administration up to 24 hours following paracetamol overdose is not dangerous and may prevent further liver damage.

Acetaminophen↗
PubMed1990

Lithium clearance in healthy humans: effects of sodium intake and diuretics.

In summary, our experiments clearly demonstrate that lithium reabsorption occurs by frusemide- and bumetanide-sensitive reabsorption, but we have failed to identify the mechanism(s) responsible for the lower CLi and FELi in salt-depletion. It is possible that some, as yet unknown, factor increases the activity of the Na, K, 2Cl cotransporter and, hence, increases lithium reabsorption in the thick ascending limb in salt-depleted subjects. However, it is equally possible that a fraction of proximal tubular reabsorption is inhibited by frusemide and bumetanide. If this is correct, CLi in humans are reasonable markers of proximal tubular function even in conditions of avid salt retention and in salt depletion, when fractional reabsorption of salt and water in the proximal tubules is enhanced.

Amiloride↗
PubMed1989

Treatment of small cell lung cancer by eight weeks chemotherapy.

Eighty-two patients with small cell lung cancer (SCLC), 32 with limited disease, were treated with alternating chemotherapy. Eight courses were administered at weekly intervals, and responding patients received radiotherapy to sites of bulk disease. Overall response rate was 76.8%. Overall median survival was 265 days, 408 days in patients with limited disease. The median symptom free period after chemotherapy was completed was 123 days. These results are comparable with those in reports of chemotherapy of longer duration and warrant the further investigation of short duration treatment in this disease.

Adult↗
PubMed1989

A topical metabolic inhibitor to improve transcutaneous estimation of arterial oxygen tension in adults.

The use of Eugenol as a contact medium in the measurement of transcutaneous oxygen (tcPO2) partially inhibits the metabolism in the underlying tissue, thereby reducing oxygen consumption and increasing tcPO2. Oxygen consumption in the tissue can be estimated from the rate at which tcPO2 falls when blood flow is occluded, and blood flow in the tissue can be estimated from the rate at which tcPO2 increases when the subject changes from breathing air to pure oxygen. Both these measurements have been made with Eugenol and distilled water as contact media. From these measurements it has proved possible to estimate the arterial oxygen tension (aPO2) of healthy adults at a relatively low sensor temperature (43 degrees C).

Administration, Cutaneous↗
PubMed1989

Biological effect of bright light.

1. Five minute bright light exposures reduced plasma levels of melatonin in eight normal subjects. 2. No significant change in ACTH levels occurred. 3. These results raise the possibility that short intense light exposures can synchronize circadian rhythms as well as benefit patients with seasonal affective disorder. They also indicate that short pulses of bright light do not affect pituitary ACTH production.

Adrenocorticotropic Hormone↗