PubMed Health⌕ Search

Biomedical subjects

P Andrews

Publications and source records attributed to P Andrews.

At least 19 recordsLinked to original sources
PubMed1992

Evolution and environment in the Hominoidea.

Between 10 and 20 million years ago, a variety of hominoid primates lived in Africa, Europe and Asia. The question of which of these, if any, lie closest to the ancestries of humans and modern apes remains a lively source of debate. Recent fossil discoveries, though, shed light on the environments in which the various groups of hominoid emerged and, it is hoped, on their evolution. But the lack of a hominid fossil record before about 5 million years ago--and any fossil record for the African apes--is still a frustrating barrier.

Animals↗
PubMed1992

Advances in the treatment of acquired and developmental defects of hard dental tissues.

With the decline in dental caries, the dental profession and the general public have become sensitized to the "new" specialty of cosmetic dentistry. As a consequence, research in the field of dental materials for the ideal, most natural restorative materials and techniques has become a primary focus and has had a profound influence on dental education and practice. This brief article will highlight some of these newer concepts.

Composite Resins↗
PubMed1992

Smoking does not contribute to duodenal ulcer relapse after Helicobacter pylori eradication.

Cigarette smoking is believed to be one of the major factors influencing duodenal ulcer (DU) recurrence. However, the influence of cigarette smoking on DU recurrence after the eradication of Helicobacter pylori has not been separately addressed. The aim of this study was to investigate DU relapse rate in smokers and nonsmokers, both with confirmed eradication of H. pylori. Patients with H. pylori eradication, demonstrated at endoscopy 4 wk post-treatment, were included in the study. Smoking history was obtained with a standard questionnaire, and patients were followed endoscopically, both yearly and at symptomatic recurrence, to detect anatomical DU recurrence. Of the 197 (121M:76F) patients enrolled in the study and followed for 1-6 yr, 80 (41%) were smokers, smoking 5-40 cigarettes/day. The 117 (59%) nonsmokers included 31 (26%) patients who had ceased smoking 4-20 yr ago. Another seven (9%) smokers ceased smoking during the follow-up period. In the 197 patients with eradicated H. pylori and cured DU, there has been no recurrence of ulcer, regardless of smoking status. We conclude that in patients with DU in whom H. pylori infection is eradicated, ulcer disease does not recur, as observed for up to 6 yr. Furthermore, cigarette smoking is not a risk factor for DU recurrence, provided H. pylori is eradicated.

Anti-Ulcer Agents↗
PubMed1992

Helicobacter pylori-negative gastric ulcer.

Causes of Helicobacter pylori (HP)-negative gastric ulcers (GUs) have not previously been systematically studied. In this study we examined possible causes of HP-negative GUs. Among 115 consecutive patients with endoscopic diagnoses of GU, 71 (62%) had HP infection, and 44 (38%) were found to be HP-negative. Of the 71 HP-positive patients, 47 (66%) had no other detectable causal factors, 21 (30%) were regularly taking nonsteroidal antiinflammatory drugs (NSAIDs), and three (4%) had malignant GU. Of the 44 HP-negative patients, 29 (66%) were taking NSAIDs, two (5%) had a malignant GU, whereas 13/44 (30%) (11% of total 115) patients had no identifiable cause. These patients were classified as having "idiopathic GU." Some 38/115 (33%) GUs occurred on the lesser curve, and these were more often (p = 0.012) HP-positive (76%) than prepyloric GUs (60/115 (52%)). We conclude that although most patients have an identifiable cause of GU, around 11% will have no apparent contributing factor. HP-positive GUs are more frequently located on the lesser curve. It is now important to identify the cause of GU, because this may dictate choice of management.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1992

Radial keratotomy. II. Role of the myofibroblast in corneal wound contraction.

The cellular mechanism of corneal wound contraction after radial keratotomy (RK) was studied in a feline eye model. A total of 10 cat eyes were evaluated at various times from 0-30 days after surgery. Changes in the distribution of intracellular filamentous actin, nonmuscle myosin, alpha-actinin, surface membrane alpha 5 beta 1 integrin, and extracellular fibronectin were studied using immunofluorescence and laser confocal and electron microscopy. From day 3-7, staining for fibronectin increased along the wound margin. By day 7, keratocytes adjacent to the wound margin showed increased f-actin staining with intense staining for fibronectin compared with normal keratocytes. Myosin and alpha 5 beta 1 integrin expression was very weak at this time; alpha-actinin was not found. By day 14, fibroblasts within the wound formed f-actin microfilament bundles (stress fibers) which colocalized with fibronectin. Wound-healing fibroblasts also stained positively for alpha 5 beta 1 integrin, myosin, and alpha-actinin (the latter two were colocalized). The presence of myosin and alpha-actinin in the wound fibroblasts and the re-organization of f-actin into stress fibers by day 14 correlated with the development of wound contraction. A comparison of the cellular distribution of actin, myosin, and alpha-actinin with alpha 5 beta 1 integrin 14 days after injury suggested that integrin was localized along stress fiber bundles during wound contraction. The data from this study suggest that modulation of wound gape during healing of RK wounds may involve transformation of the corneal keratocyte to a myofibroblast-like cell and the subsequent formation of intracellular stress fibers composed of f-actin, nonmuscle myosin, and alpha-actinin. Based on the colocalization of fibronectin filaments and f-actin filaments and the unique distribution of alpha 5 beta 1 integrin, these findings support the hypothesis that the tension within the wound is generated by the formation of intracellular stress fibers and the interactions between stress fibers and the extracellular matrix, mediated by specific membrane receptor molecules.

Animals↗
PubMed1979

Hydrophobic esters of cellulose: properties and applications in biochemical technology.

We have investigated the utility for enzyme immobilization of several hydrophobic cellulose esters, as a function of solvent composition, extent of esterification, and enzyme. Phenoxyacetyl cellulose was also used for immobilization of rat liver microsomes, hydrophobic chromatography of proteins, and removal of Triton X-100 from protein solutions. Phenoxyacetyl groups esterified to cellulose were much less subject to enzymatic hydrolysis than soluble phenoxyacetyl esters.

Binding Sites↗
PubMed1979

The effect of praziquantel on Hymenolepis diminuta in vitro.

Qualitative observations were made on Hymenolepis diminuta, H. microstoma, H. nana and pre-adult Echinococcus multilocularis in vitro. A dose as low as 0.0001 microgram praziquantel/ml affects the tapeworms, while concentrations of 0.01 - 0.1 and 1-10 microgram/ml cause contraction and paralysis in the contracted state within 10 min and 10-30 s, respectively. The in vitro effects of praziquantel on Hymenolepis diminuta have been studied using anaerobic and aerobic incubations and media containing or lacking glucose. Praziquantel inhibits glucose up-take by half at a concentration of 0.1 microgram/ml, both under anaerobic and aerobic conditions. The stimulation of lactate release was most marked in the absence of glucose. A doubling of the amount of lactate released during anaerobic incubation in the presence of glucose was achieved in 0.1 microgram/ml, while 0.01 microgram/ml had the same effect in the absence of glucose. Under aerobic conditions and in the absence of glucose, 0.1 microgram/ml doubled the amount of lactate released while 3 and 10 microgram/ml were without effect in the presence of glucose. Praziquantel increases the total amount of excreted acidic metabolites only in the absence of glucose. The oxygen consumption of H. diminuta was unaffected by praziquantel at a concentration of 10 microgram/ml. Worms treated in their host and then incubated display the same changes as worms treated in vitro. Praziquantel causes an efflux of glucose and alpha-amino-N from the worm into the medium. This impairment of tegumental integrity and the inhibition of glucose up-take and the stimulation of lactate release are reversible after a 15 min incubation in praziquantel solution. Discussion of pharmacokinetic data indicates, that in the in vivo situation, effective concentrations of praziquantel prevail for much longer. Mechanisms that might explain the observed effects are discussed.

Aerobiosis↗
PubMed1979

Amidantel, a potent anthelminthic from a new chemical class.

N-(4-[(1-(Dimethylamino)-ethylidene)-amino]-phenyl)-2 methoxyacetamide hydrochloride (amidantel, BAY d 8815) is a new aminophenylamidine with an interesting anthelminthic spectrum. In rodents the compound is active against nematodes, filariae and cestodes. Of special interest is the high efficacy in dogs against hookworms and large roundworms. Amidantel was well tolerated by all animals tested and did not show teratogenic effects.

Animals↗
PubMed1978

Effect of praziquantel on the free living stages of Schistosoma mansoni.

The effect of the new schistosomicide praziquantel (2-cyclohexyl-carbonyl-1,2,3,6,7,11 b-hexahydro-2H-pyrazino[2,1a]isoquinolin-4-one) on the miracidia and cercariae of Schistosoma mansoni was investigated. In vivo praziquantel inhibits hatching of miracidia for 24 h after administration of 500 mg/kg to infected mice. In vitro a concentration of 10 microgram/ml inhibits subsequent hatching in drug-free water. Free swimming miracidia are rapidly killed by 1 microgram/ml. Even 0.01 microgram/ml is still partially effective. In a solution of 0.03 microgram/ml cercariae lose their ability to swim within 10 min. This effect is reversible in drug-free water. Morphological damage to cercariae incubated in 0.1 microgram/ml is clearly evident. However, cercariae are fully infective when given subcutaneously to mice after a 3-h incubation period. Incubation in 1 microgram/ml reduces the infection rate by 80%. A 2-h incubation in 0.1 microgram/ml almost completely inhibits the percutaneous infection through the abdominal skin. The number of cercariae that develop to schistosomules is reduced by more than 90%. After a 2-h incubation in a concentration of 0.01 microgram/ml the swimming ability of cercariae is impaired in such a way that the number of cercariae penetrating in the tail immersion test and developing to schistosomules is reduced by half. Praziquantel is a more potent protective agent than the molluscicides copper sulphate, sodium pentachlorophenate and Bayluscide or cadmium and zinc ions.

Animals↗
PubMed1978

Restoration of the holotype of Proconsul nyanzae.

The crushed palate and lower face of the holotype of Proconsul nyanzae has been prepared using the acetic acid technique. The prepared and conserved fragments have been restored to their natural positions using a synthetic cement and polyethylene glycol wax (Carbowax 4000) to fill the gaps. Preparation revealed the inferior margin of the right orbit, the inferior border of the nasal bones, and a posterior divergence of the palate which has now been corrected. The restored face of P. nyanzae shows the orbits to have been wider apart than those of Proconsul major, both absolutely and relatively, and that it had a long narrow nose and palate. It differs from Proconsul africanus, which has the shortest and broadest face of all Proconsul species, and from P. major which has a much longer narrower face.

Animals↗
PubMed1977

New Miocene locality in Turkey with evidence on the origin of Ramapithecus and Sivapithecus.

Collections in early Middle Miocene deposits at Pasalar in Turkey have yielded a very rich fauna. Included in this are two hominoid species referred here to Sivapithecus darwini (Abel) 1902 and Ramapithecus wickeri (Leakey) 1962. These are both more primitive morphologically and earlier in time than other species of these genera, and they provide evdence that Sivapithecus and Ramapithecus are closely related and that their early diversification may have occurred not in Africa but in Eurasia.

Animals↗
PubMed1977

Praziquantel, a new board-spectrum antischistosomal agent.

Praziquantel, (2-cyclohexylcarbonyl)-1,2,3,6,7,11b-hexa-hydro-2H pyrazino[2,1a]isoquinolin-4-one, belongs to a new series of antischistosomal compounds. The results of a detailed study of the efficacy of praziquantel on Schistosoma mansoni in mice, Mastomys and Syrian hamsters are described. Praziquantel is effective after oral and all parenteral routes of administration tested. The amount of praziquantel required to achieve parasite reductions of at least 95% depends on the host species and on the routes and schedules of administration. Total doses range from 200--1,000 mg/kg in mice and from 100--500 mg/kg for Mastomys and hamsters. In all three species, splitting of the total dose into 3 or more fractional doses given within 1 day approximately doubles the efficacy over that achieved after a single oral administration of the same total dose. A single subcutaneous dose is only slightly more effective, whilst a single intramuscular injection in olive oil is about twice as effective as a single oral administration. Praziquantel is very effective against the invading stages and slightly less against schistosomules up to an age of 7 days. It is less effective against 2- to 4-week-old juveniles, but is effective again against 5-week-old and older schistosomes. Praziquantel is equally effective against both sexes of S. mansoni. It is less effective against unpaired and therefore juvenile female worms, but fully effective against single male worms. The efficacy of praziquantel on S. mansoni in mice is not influenced by the strain or the sex of the host, the worm burden or the age of the infection. Considering all data available, praziquantel promises to be a very potent antischistosomal drug.

Animals↗
PubMed1977

A new Arican miocene gibbon-like genus, Dendropithecus (hominoidea, primates) with distinctive postcranial adaptations: its significance to origin of hylobatidae.

The small, common apes of the Miocene deposits of East Africa previously assigned to two species of one genus, Limnopithecus, have been shown to differ at the generic level in both dental and postcranial features. The prior and smaller of the two species (the genotype of Limnopithecus) somewhat resembles in dental morphology African dryopithecines of subgenus Proconsul, while the larger and later described species more nearly resembles European Pliopithecus in dental details but is strikingly different from the latter in comparable postcranial bones. A new genus, Dendropithecus, is here proposed for Limnopithecus macinnesi Clark and Leakey, 1950. Numerous associated postcranial bones and dentitions of Dendropithecus macinnesi were found in a block of red limestone by L.S.B. Leakey in 1948 on Rusinga Island, Lake Victoria, Kenya. These bones make it one of the best known Miocene apes and show clearly that it had advanced away from other Miocene apes in its higher degree of development of suspensory or arm swinging postcranial adaptations. Thus, among known Miocene ape species it has the greatest demonstrated potential to be near the line of ancestry of the modern gibbon and siamang.

Africa, Eastern↗
PubMed1976

A controlled trial of phenothiazine withdrawal in chronic schizophrenic patients.

Phenothiazine drugs were withdrawn from 17 chronic schizophrenic in-patients, with a control group of 14 patients remaining on active medication. The trial was conducted under double blind conditions over a period of 42 weeks with weekly assessment of the patients by ward nurses. Of the placebo group 35% relapsed, relapse being related to the level of previous active medication.

Administration, Oral↗
PubMed1976

Development of fluorescent antibodies directed against larval stages, eggs, and adults of Schistosoma mansoni in mice harbouring unisexual or bisexual infections.

The development of antibodies corresponding to the different developmental phases of Schistosoma mansoni was studied in mice subjected to experimental unisexual and bisexual infections. Blood samples were taken at weekly intervals for up to 5 months and tested by indirect immunofluorescence against frozen sections of male and female worms (collected from animals with unisexual infections), of liver of infected hamsters (containing schistosome eggs) and of the hepatopancreas of infected snails (containing schistosome larval stages). Antibodies appeared around the 10th day. The earlier appearance of antilarval antibodies observed previously could not be confirmed. The study of unisexual infections demonstrated that anti-egg antibodies can be differentiated from antilarval and anti-adult worm antibodies. With all four antigens a stronger serological reaction was obtained in bisexual than in unisexual infections. The anti-male antibodies were always present at higher concentrations than the anti-female antibodies.

Animals↗