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Biomedical subjects

P M Davidson

Publications and source records attributed to P M Davidson.

At least 37 records · Page 2Linked to original sources
PubMed1998

High hydrostatic pressure come-up time and yeast viability.

The effects of the come-up time at selected pressures (50 to 689 MPa) on Saccharomyces cerevisiae and Zygosaccharomyces bailii viability were evaluated at 21 degrees C. For Z. bailii the effects of the water activity (a(w)) of the suspension media and the stage of the growth cycle were also investigated. Pressure come-up times exerted an important effect on the yeast survival fraction, decreasing counts as pressure increased. An increased sensitivity to pressure treatments was observed with yeast cells from the exponential growth phase. Lethality increased as a(w) of the suspension media increased. For an a(w) of 0.98 and cells from the stationary growth phase, pressure treatments at less than 200 MPa had no effect on Z. bailii viability; however, no survivors (< 10 CFU/ml) were observed in treatments applied only for the time needed to reach pressures greater than 517 MPa. Yeast survivor curves showed an excellent fit (r > 0.996) when described by a phenomenological model based on the Fermi equation, S(P) = 1/¿1 + exp[(P - Pc)/k]¿, where S(P) is the survival fraction, P is the pressure, Pc is a critical pressure corresponding to 50% survival, and k is a constant representing the steepness of the curve.

Colony Count, Microbial↗
PubMed1997

Thromboembolic risks of left atrial thrombus detected by transesophageal echocardiogram.

Patients with left atrial thrombus are considered at high risk for thromboembolic events. The actual prognosis of these patients and the features most predictive of future events are unclear. We performed transesophageal echocardiograms in 2,894 patients over a 6 1/2-year period; 94 (age 69 +/- 11 years, 59 men, 83 in atrial fibrillation) were found to have left atrial thrombus. The thrombi were considered mobile in 45 patients and 33 patients had thrombus with a maximum dimension > or = 1.5 cm. Seven of the 94 patients with prosthetic valves were excluded from follow-up analysis. Over a follow-up period of 25.3 +/- 19.2 months, 17 patients had suffered a stroke or embolic event (event rate 10.4% per year) and 27 had died (mortality 15.8% per year). Cox proportional hazard regression analysis identified a maximum thrombus dimension > or = 1.5 cm (RR 19, p = 0.002), history of thromboembolism (RR 4.2, p = 0.038), and mobile thrombus (RR 5.3, p = 0.02) as predictors of subsequent thromboembolism. Moderate or severe left ventricular dysfunction was the only significant predictor of death (RR 2.9, p = 0.04). Gender, age, warfarin therapy at follow-up, atrial fibrillation, location (cavity vs appendage) of thrombus, and spontaneous echocardiographic contrast were not significant. Aggressive antithrombotic therapy may be indicated in these high-risk patients.

Adult↗
PubMed1997

Isolation and identification of antimicrobial furocoumarins from parsley.

Photoactive furocoumarins extracted from four varieties of fresh and freeze-dried parsley leaves inhibited a DNA repair-deficient Escherichia coli in a photobiological assay. Using media-modified assays, the human pathogens E. coli O157:H7 and Listeria monocytogenes, the spoilage microorganism Erwinia carotovora, and Listeria innocua were also inhibited. Pseudomonas fragi was not inhibited. Minimum concentrations of Forest Green parsley powder in agar which showed inhibition ranged from 0.12% to 8.0% depending on the microorganism. Ultraviolet light (UV) at 365 nm for 60 min used to photoactivate the furocoumarins in the bioassay had little effect on L. monocytogenes and L. innocua. A slight UV inhibitory effect was detected with E. carotovora. Furocoumarins, psoralen, 8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP), oxypeucedanin and isopimpinellin were identified using gas chromatography-mass spectrometry. Psoralen, 8-MOP, and 5-MOP were quantified. A difference in relative furocoumarin concentration (weight of furocoumarin per weight of dry parsley leaves) for all varieties of parsley was revealed. The concentration of 5-MOP was significantly greater than 8-MOP (P < 0.05), but not significantly greater than psoralen. Psoralen and 8-MOP were not significantly different in concentration.

5-Methoxypsoralen↗
PubMed1995

How to avoid complications during percutaneous endoscopic gastrostomy.

Percutaneous endoscopic gastrostomy (PEG) has advantages over open gastrostomy, and is an accepted technique for children. However, a number of technical problems may be encountered during insertion. This report identifies those problems and proposes precautions that can be taken to reduce their likelihood. Recognized major complications include esophageal injury, colonic perforation, wound infection, gastric erosion by the gastrostomy tube, and later symptomatic gastroesophageal reflux requiring correction by fundoplication.

Adolescent↗
PubMed1995

Technique and complications of percutaneous endoscopic gastrostomy in children.

Percutaneous endoscopic gastrostomy (PEG) is now a well-established technique in children. In this study of 63 children (mean age 7.8 years, youngest 2.4 months), technical problems associated with insertion of the gastrostomy tube, and complications related to the procedure, were analysed. Complications included wound infection, oesophageal injury (probably sustained during extraction of the guide wire) and symptomatic gastro-oesophageal reflux (GOR) occurring after PEG insertion. Many of these complications can be avoided or reduced in likelihood by refinements to the technique of insertion.

Adolescent↗
PubMed1993

Lymphocyte production of gamma-interferon as a test for non-tuberculous mycobacterial lymphadenitis in childhood.

Infection with Mycobacterium avium, M. intracellulare and M. scrofulaceum (MAIS) organisms in normal children may result in cervical lymphadenopathy. There is a poor response to anti-tuberculous therapy and surgical excision of infected nodes is necessary. The diagnosis therefore requires consideration in children with cervical lymphadenopathy. A simple in vitro assay is described which may be useful for diagnosis prior to excision. Whole blood is cultured with M. avium purified protein derivative. After 24 h the plasma is removed and the concentration of gamma interferon (IFN-gamma) quantified by a radioimmunometric assay. In a prospective study of 38 children with neck lesions, 16 showed MAIS organisms isolated from cultures of excised tissue. The level of IFN-gamma produced by peripheral blood lymphocytes from children in the MAIS group was significantly greater when compared with children having operations for neck lesions that were not due to MAIS organisms (P < 0.001).

Adolescent↗
PubMed1993

Homophobic attitudes and AIDS risk behavior of adolescents.

Adolescents in the United States are increasingly knowledgeable about acquired immunodeficiency syndrome (AIDS), yet they are notoriously resistant to behavioral changes that would reduce their personal risk, such as practicing abstinence, using condoms, or careful selection of sexual partners. For the present study, we asked 80 heterosexual adolescents about their sexual behavior and intentions to avoid risky behavior, in conjunction with assessing their knowledge and attitudes concerning AIDS and AIDS-related issues. The results suggest that many adolescents do not feel vulnerable to AIDS because they still see AIDS as a Gay disease. Those who are most prejudiced against Gays are, on average, five times more willing to engage in indiscriminant sex as are the least prejudiced group; among males, this effect is even greater. In addition, highly prejudiced adolescents are twice as willing to have sex without using a condom. This study indicates the importance of dealing with homophobic attitudes in the context of AIDS education.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Psychological morbidity in the first year after breast surgery.

In this prospective study, the psychological morbidity associated with the treatment of breast cancer was assessed. The study population comprised all patients referred to one centre with a recently diagnosed breast lump, who were to undergo surgery. Psychological morbidity was assessed preoperatively and at 6 and 12 months postoperatively by modified Rotterdam Symptom Checklist. Three hundred and twenty patients completed all three questionnaires: 93 women undergoing mastectomy, 73 women having conservation therapy for breast cancer and 156 women having biopsy for benign breast disease. Patients with a breast malignancy smaller than 4 cm in diameter were treated by lumpectomy and radiotherapy, anti-oestrogen therapy or chemotherapy alone or in combination. Psychological morbidity among patients with malignant disease was significantly greater than that seen in the group with benign disease. Among cancer patients, a significant decrease in anxiety and depression occurred during the year following surgery. The study failed to demonstrate any psychological advantage associated with breast conservation.

Adaptation, Psychological↗
PubMed1990

Growth after gut resection for Crohn's disease.

Seventeen children underwent 19 bowel resections as part of their management of Crohn's disease. Thirteen children had evidence of retardation of linear growth preoperatively, of whom 12 exhibited catch up growth, crossing at least one centile band, after resection. Seven of the 12 showed early signs of puberty at the time of resection and one child was regarded as being fully pubertal. All children were symptomatic before their surgery; at one year 11 were asymptomatic and three others were substantially improved. Surgical resection of localised Crohn's disease, followed by adequate nutritional support has lead to catch up growth and a prolonged symptom free period in most of our patients and this was not limited by their age or stage of puberty.

Adolescent↗
PubMed1989

Non-tuberculous mycobacterial lymphadenitis in children.

Eighty-six children (44 males, 42 females) were identified as having non-tuberculous mycobacterial lymphadenitis. The diagnostic criteria were either culture of the organism from the affected lymph node (n = 68), or, when culture was negative, a positive skin test with non-tuberculous mycobacterial antigens and negative skin test responses to tuberculin purified protein derivative (PPD) in association with typical histological features (n = 18). All children had histopathological findings of granulomatous inflammation with caseation and/or acid-fast bacilli. Eighty-two percent of the children were under 5 years of age at presentation and 30% were less than 2 years old. Most (79%) were city dwellers. Lymph node enlargement had been present for less than 6 months in almost all children (97.5%) and was almost exclusively in the face and neck region (97%). Disease was confined to the involved lymph nodes in 56% but had extended beyond the confines of the infected node to form a collar stud abscess in 38% and 6% presented with a skin sinus. Extranodal extension did not show any statistically significant association with the duration of lymphadenopathy. The duration of lymphadenopathy had been greater in those children in whom an organism was not isolated on culture resected tissue (chi 2 = 10.07, P less than 0.01). All children were treated surgically, and recurrence occurred in five patients. This study describes the clinical and demographic characteristics of non-tuberculous mycobacterial lymphadenopathy in children in a population in which tuberculous adenitis is rare. Recognition of these features may allow earlier diagnosis and appropriate surgical therapy.

Child↗
PubMed1989

Pancreatic beta cell proliferation in rabbits demonstrated by bromodeoxyuridine labeling.

The purpose of the present study was to quantify beta cell proliferation in rabbits that had undergone subtotal beta cell ablation by labeling cell nuclei undergoing DNA synthesis with bromodeoxyuridine (BUdR). Ten New Zealand white rabbits were compared with five sham-operated controls. The beta cells in the head of the pancreas were destroyed by intravenous alloxan (200 mg/kg) while the tail of the pancreas was temporarily isolated from the systemic circulation by vascular occlusion clamps. On day 7, BUdR (70 mg/kg) was infused prior to killing to label newly synthesised DNA. Immunoperoxidase staining with anti-insulin sera and an anti-islet cell monoclonal antibody confirmed the absence of insulin-producing cells in the head of the pancreas. Beta cell proliferation within the islets of the tail of the pancreas was suggested by the appearance of cells undergoing mitosis and confirmed by BUdR labeling of cell nuclei detected with anti-BUdR monoclonal antibody. The mitotic index was significantly increased compared to control rabbits (p = 0.0235, Mann-Whitney U nonparametric test). This study demonstrates that the BUdR labeling can be used to document beta cell proliferation in vivo in the rabbit model after subtotal beta cell ablation.

Animals↗
PubMed1988

Haemolytic-uraemic syndrome after treatment with metronidazole.

This paper describes the clinical features of six children who developed the haemolytic-uraemic syndrome after treatment with metronidazole. These children were older and were more likely to have undergone recent bowel surgery than are other children with this condition. While the involvement of metronidazole in the aetiology of the haemolytic-uraemic syndrome is not established firmly, the action of this drug in sensitizing tissues to oxidation injury and the reported evidence of oxidation changes in the haemolytic-uraemic syndrome suggest a possible link between metronidazole treatment and some cases of the haemolytic-uraemic syndrome.

Adolescent↗
PubMed1987

Sacrococcygeal teratoma: has chemotherapy improved survival?

Case records of 57 patients (50 female, 7 male) with sacrococcygeal teratoma who were treated at the Royal Children's Hospital in Melbourne between 1948 and 1986 were reviewed. There were 40 benign and 19 malignant tumors; two patients had malignant recurrence following excision of a benign tumor. The majority of the benign lesions were readily excised; 80% of these patients presented under the age of 6 months. In contrast, 16 of the 19 patients with malignant disease presented after 6 months of age and 12 of these died. Before 1975, malignant lesions were treated with surgery or irradiation, and in a few patients, single-agent chemotherapy. No patients survived. In 1970, intensive multiagent chemotherapy was introduced, with planned delayed surgical resection, with or without postoperative irradiation. Three of five patients treated between 1976 and 1980 survive disease-free and are almost certainly cured. Modern therapy is with cisplatin-containing regimens, and while initial responses in six patients with extensive disease are impressive, it is too early to evaluate the impact of these newer programs on cure.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1987

The partially diabetic pancreas: a histological study of a new animal model.

An animal model in which part of the pancreas was made diabetic due to almost total loss of insulin-secreting B cells, while the remainder of the gland remained normal, is described. In rabbits, a vascular clamp was placed across the junction of the body and tail of the pancreas, thus occluding the circulation to the tail. Alloxan (200 mg/kg) was injected i.v., and 4 min later dextrose (0.5 g/kg) was given by the same route. After a further 2 min the clamp was removed. Thirty-four animals were studied, 17 of which died in the first postoperative week of surgical complications or of alloxan-induced toxicity to the liver and kidneys. The survivors were killed between 4 and 12 weeks after surgery and were not metabolically diabetic. They had a virtually complete absence of B cells but a normal population of A, D, and PP cells in the head and body of the pancreas. The islets in the tail of the pancreas appeared entirely normal. This model appears suitable for studying the effects of locally produced insulin on pancreatic exocrine function in metabolically normal animals.

Alloxan↗
PubMed1987

The role of the nurse-practitioner in breast care.

Why have a nurse-practitioner in a breast center? This question is appropriate, although it may generate controversy. A hospital-based or freestanding breast diagnostic center that hires a nurse-practitioner is functioning outside the norm. It is unusual to find a nurse-practitioner providing services to women in a breast diagnostic center and representing that center in the community. Until recently, breast diagnostic centers have focused primarily on imaging. However, a breast center wishing to expand services to its patients and referring healthcare providers, as well as market its services to the surrounding community could employ such a nurse. Two issues need to be addressed when discussing the nurse-practitioner in the breast diagnostic center: defining a role for this nurse, which this article discusses, and supporting this role once it is in place.

Breast Neoplasms↗
PubMed1987

Early function concepts: their development and relation to certain mathematical and logical abilities.

Cognition of functions (i.e., y = f(x)) has been identified as an achievement of early childhood. To investigate the development of function concepts and their relation to mathematical and logical abilities typically acquired during the age period of 5-7 years, 72 children in this age range were tested on nonnumerical function tasks (functions as exchange of properties, functions as displacement of positions, and functions as preservation of structure), numerical tasks (number conservation and arithmetic problems), and aspects of logical reasoning (class inclusion, class vicariance, and seriation). Orderly developmental trends were found in function task performance, with younger children manifesting limited success through trial-and-error strategies and older children achieving substantial success with anticipatory strategies. Moreover, certain function abilities were associated with the numerical domain, whereas others were associated with the logical domain. The findings are consistent with the developmental model of Piaget et al. according to which cognition of functions lays the groundwork for reversible operations, but also suggest that this development occurs through parallel processes within separate conceptual domains.

Child↗
PubMed1986

Growth characteristics of selected fungi on polyvinyl chloride film.

The objective of this study was to determine if plasticized polyvinyl chloride film would support the growth of any of nine species of fungi. The film was suspended in distilled water with no nutrients or with glucose or ammonium sulfate. Spores of each of the test species were inoculated into the suspension medium, and the mixture was incubated at 30 degrees C for up to 18 weeks. Most species were found to be capable of utilizing the film for carbon or nitrogen when the other nutrient was supplied. Only two species, Aspergillus fischeri and Paecilomyces sp., were found to be capable of utilizing components of the film without added nutrients. Components of the polyvinyl chloride film were then incorporated into mineral salts medium to determine if these components could serve as carbon sources in the presence of ammonium nitrate. The only component found to be utilized by all the fungi as a carbon source was epoxidized oil, a plasticizer-stabilizer. Calcium-zinc stearate was an available carbon source for all except the Penicillium and Verticillium strains. The only other component utilized was a stearamide, which was metabolized solely by the Aspergillus sp. Only the stearamide contained enough nitrogen to serve as a primary source in the film. The compound, however, did not support growth of fungi in the presence of glucose. It was theorized that either the nitrogen of the stearamide was more readily available to the fungi in the whole film due to the presence of trace nutrients or the nitrogen was supplied by exogenous sources.

Aspergillus↗