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Biomedical subjects

A Davis

Publications and source records attributed to A Davis.

At least 289 records · Page 16Linked to original sources
PubMed1989

Enamelins and amelogenins share the same amino-terminal sequence.

Previous results from our laboratory indicated that rabbit enamel high molecular weight proteins have the same amino-terminal sequence that amelogenins, thus suggesting the possibility that this domain is shared by both, enamelins and amelogenins. To determine if this is true for other species, enamel proteins and mRNA were extracted from rabbit and hamster developing teeth and analyzed using probes targeted towards the N-terminal sequence of the amelogenins. Our results strongly suggest that both, enamelins and amelogenins share the same amino-terminal amino acid sequence.

Amelogenin↗
PubMed1989

A randomised comparative trial of nicardipine versus amiloride and hydrochlorothiazide in mild to moderate hypertension. A report from the General Practitioner Hypertension Study Group.

In 1984 the General Practitioner Hypertension Study Group undertook a rescreening of their patient population, looking for patients who still had untreated mild to moderate essential hypertension. Suitable patients were entered into a clinical trial comparing the safety and efficacy of nicardipine (a calcium antagonist) and amiloride + hydrochlorothiazide (HCTZ) (moduretic). The study included one year of long-term follow-up. Both drugs significantly lowered BP in both the short and long term. Numbers and percentages of patients from each group reporting adverse experiences were similar in the short term, but in the long term the frequency of adverse event reporting was much lower with nicardipine treatment than with amiloride + HCTZ treatment (2/10 versus 9/17). Treatment with amiloride + HCTZ led to elevations in serum levels of cholesterol, uric acid and urea, which were maintained at one year, whilst no abnormalities in blood biochemistry were seen in patients treated with nicardipine. In conclusion we have found that nicardipine compares very favourably with amiloride + HCTZ in the treatment of mild to moderate hypertensive patients.

Adolescent↗
PubMed1989

Operations research in schistosomiasis control.

The term "operations research" is used in several different senses but the simplest concept is one of any activity and associated evaluation which will lead us to a better understanding of how to do things in the most competent and effective way. Operations research should attempt to bring all the subsets of variables together within one framework embracing strictly technical matters, organizational and administrative aspects, population cooperation and behavioural constraints or complications, costs and resources required, cost-efficacy and the construction of a system for continued monitoring and subsequent remedial interventions, where necessary. The problems involved in operations research are outlined and the practical points of importance are emphasized. The principles of schistosomiasis control are listed, the use of population based chemotherapy is stressed, the constraints are tabulated and specific suggestions made for worth-while studies in the "operational research" context.

Animals↗
PubMed1989

A diagnostic algorithm for osteonecrosis of the femoral head.

For patients considered at risk for osteonecrosis (ON) of the femoral head, an algorithm for the efficient and appropriate use of diagnostic tests can be developed. Such an algorithm requires a clear idea of the evolution of the disease process and an understanding of the limitations of each of the modalities by which the disease process can be identified. The role of each of the diagnostic tests available for the diagnosis of ON and the results of prospective evaluations to assess their sensitivity, specificity, and predictive values are reviewed. No single diagnostic test is 100% accurate in the diagnosis of the disease. Thus, one must consider an algorithm that accounts for the variable nature of the disease presentation. The goal of such an algorithm is the accurate identification and staging of the disease. For disease not roentgenographically apparent, an approach using magnetic resonance imaging and bone scanning is recommended. For disease that is apparent roentgenographically, tomography is used to define the extent of the disease and the presence or absence of subchondral fracture. The accuracy of diagnosis is critical to understanding the role of the various treatment modalities prescribed for ON. For this purpose, it is necessary to reach a consensus as to what constitutes a successful outcome of treatment. Once diagnosis of the disease is accepted, clinical success of treatment outcomes should be reported in three ways: by a standard hip rating system, by ability to prevent roentgenographic deterioration, and by survival of the femoral head (the absence of further treatment intervention).(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1989

Multicentre clinical trials of benzimidazole-carbamates in human cystic echinococcosis (phase 2).

A multicentre study which constituted the second phase of trials of the efficacy of albendazole and mebendazole in human cystic echinococcosis was coordinated by WHO. A total of 112 patients from four clinical centres in Beirut, Paris, Rome and Sofia completed standardized dosage of regimens of each drug and 68 patients were followed up for at least 12 months after treatment. Albendazole was more effective than mebendazole and adverse reactions were comparable with both treatment regimens. At least 12 months is needed after treatment for an objective evaluation of the efficacy of benzimidazoles. At present, treatment with albendazole or mebendazole should be reserved for inoperable cases of cystic echinococcosis (under strict medical supervision) and individualized according to the patient's response and the occurrence and severity of adverse reactions.

Adolescent↗
PubMed1989

Operational studies on the control of Taenia solium taeniasis/cysticercosis in Ecuador.

A large-scale study in Loja and El Oro Provinces, Ecuador, demonstrated that population-based treatment of human taeniasis with a low dose of praziquantel is feasible and effective for the short-term control of transmission of Taenia solium in hyperendemic areas. Chemotherapeutic intervention also effectively promoted local preventive measures and contributed greatly to the elaboration of a long-term control programme.

Adolescent↗
PubMed1988

Forces in molecular recognition: comparison of experimental data and molecular mechanics calculations.

NMR studies of the rotation barrier of the disaccharide of the glycopeptide antibiotic vancomycin have been used to test the performance of computer simulation techniques using molecular mechanics. In the absence of any solvated water, no correlation could be found between experiment and calculation. By introducing solvent water molecules into the binding region of the antibiotic, the NMR results could be simulated both qualitatively and quantitatively within experimental error without using massive computational resources.

Binding Sites↗
PubMed1988

Decreased platelet 3H-imipramine binding in Down's syndrome.

Platelet 3H-imipramine binding in 12 subjects with Down's syndrome showed a significantly lower maximal number of binding sites (Bmax) as compared to both unrelated normal and parental controls. No difference in the affinity constant (Kd) was observed. The results support the value of the platelet 3H-imipramine binding assay in the investigation of defects in serotonin metabolism in humans.

Adolescent↗
PubMed1988

The status of anencephalic babies: should their bodies be used as donor banks?

In recent months there has been considerable discussion on the ethics of using organs from anencephalic babies for transplantation purposes. The heart of an anencephalic in Ireland was so used, but the recipient died very soon after the operation. Since this case came to light the Royal College of Physicians has imposed a ban on the use of these babies as donors while a working party investigates the issues involved.* This article attempts to examine the problem and reaches the conclusion that in practice it is not ethical to use the organs of anencephalics for transplants.

Anencephaly↗
PubMed1988

Atrial natriuretic factor in the pediatric intensive care unit.

ANF is a newly discovered peptide hormone that has significant implications for critical care physicians. This hormone, released from the heart, is especially responsive to fluid challenges as well as to many of the drugs commonly used in the ICU, including pressor and anesthetic agents. It has potent arterial vasodilating effects in pharmacologic doses and may be an important natural vasodilating agent, especially in the renal vascular bed. In patients on dopamine, it may potentiate the renal vasodilating effect and may provide an effective therapy for developing acute renal failure. Children with congenital heart disease and patients with CHF have elevated levels that clearly alter the aldosterone-angiotensin II system and may help us to understand and treat these conditions more effectively. Additionally, ANF may be a marker for adequacy of treatment in these disease states. The potential uses for ANF include diuresis in patients with fluid overload and diuretic resistance, treatment of CHF, and as a short-acting vasodilator. In the ICU, many therapies affect cardiac pressures and volume regulation. Positive-pressure ventilation may decrease the release of ANF by decreasing venous return and thus contribute to water retention. Drugs used in the ICU may directly affect ANF levels and markedly affect the homeostasis of fluid and electrolyte balance. This hormone system interacts intimately with renin, angiotensin II, and aldosterone. These interactions may play a significant role in the development of essential hypertension. Although not addressed in this article, the treatment and understanding of essential hypertension may be significantly advanced by understanding these relationships. It is clear that ANF acts as a hormone with complex interactions between the heart, volume status, electrolyte balance, renin-angiotensin II-aldosterone, vasopressin, and vascular tone. Although currently no definitive picture exists for these complex interactions, this is an exciting new hormone with significant implications for patient management in the ICU. As research continues, the picture will become clearer and our understanding of this new hormone more precise.

Animals↗
PubMed1987

Strategic approaches to drug design. I. An integrated software framework for molecular modelling.

An integrated molecular graphics and computational chemistry framework is described which has been designed primarily to handle small molecules of up to 300 atoms. The system provides a means of integrating software from any source into a single framework. It is split into two functional subsystems. The first subsystem, called COSMIC, runs on low-cost, serial-linked colour graphics terminals and allows the user to prepare and examine structural data and to submit them for extensive computational chemistry. Links also allow access to databases, other modelling systems and user-written modules. Much of the output from COSMIC cannot be examined with low level graphics. A second subsystem, called ASTRAL, has been developed for the high-resolution Evans & Sutherland PS300 colour graphics terminal and is designed to manipulate complex display structures. The COSMIC minimisers, geometry investigators, molecular orbital displays, electrostatic isopotential generators and various interfaces and utilities are described.

Computer Graphics↗
PubMed1987

Evaluation of the genetic and embryotoxic effects of bis(tri-n-butyltin)oxide (TBTO), a broad-spectrum pesticide, in multiple in vivo and in vitro short-term tests.

The genetic and embryotoxic effects of bis(tri-n-butyltin)oxide (TBTO) were evaluated in multiple in vivo and in vitro short-term tests preparatory to its potential wide use as a molluscicide in control of schistosomiasis. When tested in the rec assay in Bacillus subtilis, TBTO was not mutagenic and it did not induce reverse mutations in Klebsiella pneumoniae. Neither in the presence nor in the absecne of rat liver activation system did TBTO produce point mutations in Salmonella typhimurium strains TA1530, TA1535, TA1538, TA97, TA98 or TA100. TBTO was matagenic in strain TA100 in a fluctuation test, but only in the presence of rat liver S9 (Aroclor-induced). TBTO did not induce gene mutations in the yeast Schizosaccharomyces pombe, mitotic gene conversions in the yeast Saccharomyces cerevisiae, nor sister-chromatid exchange in Chinese hamster ovary cells in the presence or absence of rat or mouse liver S9. In the latter cells, structural chromosomal aberrations, endoreduplicated and polyploid cells were induced. TBTO did not induce gene mutations in V79 Chinese hamster cells (to 8-azaguanine-, ouabain- or 6-thioguanine-resistance) in the presence of a rat liver postmitochondrial fraction or in cell (hamster embryo cells and human and mouse epidermal keratinocyte)-mediated assays. In mouse lymphoma cells, TBTO did not induce 6-thioguanine- or BUdR-resistant mutations. As many tumour promoters inhibit metabolic cooperation between V79 Chinese hamster 6-thioguanine-resistant/-sensitive cells, TBTO was tested but showed no such activity. TBTO was examined for the induction of recessive lethal mutations in adult Berlin K male Drosophila melanogaster, either by feeding or by injection. Doses of 0.37 or 0.74 mM did not increase the number of X-linked recessive lethal mutations. An increased number of micronuclei was observed in the polychromatic erythrocytes of male BALB/c mice 48 h after a single oral dose of TBTO (60 mg/kg bw), while a lower dose (30 mg/kg bw) was ineffective. Neither of the two doses had induced micronuclei 30 h after treatment. The reproductive toxicity of TBTO was studied in NMRI mice. In a 10-day toxicity study, the LD50 and LD10 were 74 and 34 mg/kg bw, respectively. An increased frequency of cleft palates was seen in the fetuses of mice (compared with controls, 0.7%) treated orally during pregnancy with 11.7 mg/kg TBTO (7%), 23.4 mg/kg (24%) or 35 mg/kg (48%).(ABSTRACT TRUNCATED AT 400 WORDS)

Abnormalities, Drug-Induced↗
PubMed1987

An evaluation of microextraction/capillary column gas chromatography for monitoring industrial outfalls.

Microextraction and capillary-column gas chromatography techniques are applied to plant discharge streams for repetitive wastewater discharge permit analyses. This combination allows the analyst to reduce sample preparation since microextraction replaces both purge-and-trap for volatiles and microextraction for semi-volatiles. An additional advantage is the elimination of a concentration step, which is often a major contributor to low method recoveries. The overall procedure is shown to be more precise than purge-and-trap but slightly less precise than conventional extraction. The results of each method are shown to be equivalent.

Chromatography, Gas↗
PubMed1987

Hair cell distributions in the normal human cochlea. A report of a European working group.

Cochlear hair cell counts from individuals who had clinically normal hearing prior to their death have been plotted for various age bands as a function of the number of hair cells per millimetre against their position in the cochlea. Position has been expressed as the distance of that observation of hair cell density from the base of the cochlea, divided by the total length of the cochlea, thereby giving a proportional representation of the cochlea in the range of 0.0 to 1.0 with 20 subdivisions of 0.05. There is an age-related decrease in the number of hair cells in the normal population, and this is more marked for the outer hair cells.

Adolescent↗
PubMed1987

Reimbursement by Medicare.

Medicare part B reimbursement for PA services is six months old. The present legislation represents only a partial victory for PAs, since coverage is restricted to surgical assisting, hospitals, skilled nursing facilities, and intermediate care facilities. All PAs should understand the full implications of Medicare reimbursement so that they can help patients secure payment. As a member of the American Academy of Physician Assistants' Legislative and Governmental Affairs Committee, the author suggests that the new coverage is at least partially successful despite predictable implementation problems. It is especially important for state chapters to contact local carriers, and for PAs to continue lobbying for full coverage.

Fees, Medical↗