Biomedical subjects
C D Allen
Publications and source records attributed to C D Allen.
Drought-induced shift of a forest-woodland ecotone: rapid landscape response to climate variation.
In coming decades, global climate changes are expected to produce large shifts in vegetation distributions at unprecedented rates. These shifts are expected to be most rapid and extreme at ecotones, the boundaries between ecosystems, particularly those in semiarid landscapes. However, current models do not adequately provide for such rapid effects-particularly those caused by mortality-largely because of the lack of data from field studies. Here we report the most rapid landscape-scale shift of a woody ecotone ever documented: in northern New Mexico in the 1950s, the ecotone between semiarid ponderosa pine forest and pinon-juniper woodland shifted extensively (2 km or more) and rapidly (<5 years) through mortality of ponderosa pines in response to a severe drought. This shift has persisted for 40 years. Forest patches within the shift zone became much more fragmented, and soil erosion greatly accelerated. The rapidity and the complex dynamics of the persistent shift point to the need to represent more accurately these dynamics, especially the mortality factor, in assessments of the effects of climate change.
The relationship of broiler breast color to meat quality and shelf-life.
A total of three experiments were conducted to compare physical and microbiological properties of raw and marinated broiler breast fillets selected as being either lighter or darker than normal. Visibly light- and dark-colored breast fillets were divided into marinated and control groups, and vacuum-tumbled for 20 min at 4 C under 80 kPa pressure. Breast fillets from the four treatment groups were evaluated for shear values, raw and cooked meat pH, drip-loss, cook-loss, water-holding capacity, and 7 d psychrotrophic count. The light-colored fillets were significantly lighter, less red, and more yellow than the dark fillets. Lightness values increased when fillets were marinated. Moreover, the light fillets had a lower pH than dark fillets. The pH values of raw and cooked breast meat were related to meat color but not marination. Dark-colored fillets had significantly higher marination pick-up and a higher fraction of bound moisture and significantly lower drip and cook-loss. No differences were observed in shear values between color or marination treatments. There were no significant differences in psychrotrophic plate counts (PPC) or capacitance detection times (CDT) due to color or treatment at Day 1. After 7 d of storage at 4 C, PPC was significantly lower for marinated samples. No correlations were observed between pH and PPC, CDT, or odor. Based on these differences in physical and microbiological properties, further processors may consider separating breast fillets according to color.
The relationship of broiler breast meat color and pH to shelf-life and odor development.
Experiments were conducted to compare the shelf-life of dark-colored and light-colored broiler breast meat. In each of three trials, 100 breast fillets were obtained from a commercial processing plant and subjectively categorized as "dark" or "light". The 100 fillets were then objectively evaluated for C.I.E. color values (lightness, redness, and yellowness). The fillets were separated into five storage groups, with each group containing 10 dark and 10 light fillets, and the fillets were held at 3 C for 0, 3, 6, 9, and 12 d. On each sampling day, fillets were evaluated in duplicate for psychrotrophic plate count (PPC), capacitance detection time (CDT), pH, and subjective odor evaluation. Dark fillets had significantly (P < 0.05) lower lightness values (L*), higher redness values (a*), lower yellowness values (b*), and higher pH values. Regression coefficients for odor scores resulted in darker fillets having significantly (P < 0.05) higher slopes than lighter-colored fillets even though intercept values were similar. Significant correlations existed between pH and color as well as odor, CDT, and PPC. These data suggest that darker broiler breast meat fillets have a shorter shelf-life than lighter breast fillets; the shorter shelf-life may be due to differences in pH.
Prospective study of diarrhoeal outbreaks in child long-daycare centres in western Sydney.
OBJECTIVE: To investigate outbreaks of diarrhoeal illness in children attending long-daycare centres (LDCs), to characterise parasitic, bacterial and viral isolates from the children's faeces and to identify individual and LDC risk factors for diarrhoea. DESIGN: Eleven-month prospective case-control study of diarrhoeal outbreaks among children in LDCs. SUBJECTS: 2368 children attending 35 LDCs in the western Sydney area. MAIN OUTCOME MEASURES: Frequency of diarrhoeal outbreaks, rate of attack and spread to family members; pathogens isolated from stools; and individual and LDC risk factors. RESULTS: The overall incidence of diarrhoeal disease was low (0.28 outbreaks per centre per year and 0.056 outbreak-associated cases per child-year). Attack rates during outbreaks varied widely (4%-55%; mean, 15%), as did secondary spread rates to family members (1%-15%; mean, 9%). Pathogens were isolated from 7% of symptomatic children and 7% of controls; no outbreak was shown to be caused by a recognised pathogen. Children with outbreak-associated diarrhoeal illness were more likely to have suffered vomiting, poor appetite, lack of energy, fever and to have taken antibiotics in the previous week than other children. Hygiene practices varied widely among centres. CONCLUSIONS: We found low incidence and morbidity from diarrhoeal illness in Australian urban LDCs. Diarrhoea in children in LDCs may be caused predominantly by non-infectious factors such as diet and antibiotic exposure. Current hygiene measures in LDCs seem adequate to prevent and contain outbreaks of infectious diarrhoea.
A comparison of chemical dipsticks read visually or by photometry in the routine screening of urine specimens in the clinical microbiology laboratory.
Two different commercially available urine dipsticks were evaluated to determine their usefulness as a screening test for the detection of non-infected urine specimens. The reactions of both dipstick strips were read visually and, in addition, one was read by semi-automated reflectance photometry. 2928 consecutive routine urine specimens received by the microbiology laboratory during normal working hours underwent testing by the conventional method of microscopy and culture and the results were compared with those obtained by dipstick testing. There were poor correlations between microscopy for red and white blood cells and dipstick results for blood and leucocyte esterase respectively. The dipsticks had a low positive predictive value (PPV) in identifying infected urines. In contrast, dipsticks had a very high negative predictive value (NPV) of 98.6-99.5% and correctly identified a significant proportion (about 1/3) of non-infected urines as reported by the conventional method. Introduction of dipstick testing of urine specimens in our hospital has led to significant time saving as dipstick-negative urines are not processed further (except for specific clinical indications) and there has also been a significant decrease (25%) in the number of specimens submitted to the laboratory. Further efficiencies may be obtainable with increased automation.
Technetium thiodiglycollic acid (99mTc-TDG). A new radiopharmaceutical with the potential for the assessment of renal function.
A mixture of hydrophilic complexes is formed on the reduction (employing tin metal as a reductant) of sodium pertechnetate 99mTc in the presence of the ligand thiodiglycollic acid (TDG). When administered to rats, the mixture demonstrated a renal clearance rate marginally greater than Glomerular filtration rate (GFR). HPLC analysis indicated the formation of two technetium complexes of TDG. After isolation of the complexes and their administration to rats, one (complex 1) showed renal clearance similar to that of 99mTc Diethylenetriamine pentaacetic acid (DTPA), while the other (complex 2) demonstrated renal clearance similar to that of 125I o-iodo hippuric acid. On heating the mixture of complexes, the proportion of the faster-clearing 99mTc TDG complex increased to 92% of the total activity, and the biodistribution of the material following heat rearrangement was equivalent to that of isolated complex 2.
Smoking, alcohol, and dietary practices during pregnancy: comparison before and after prenatal education.
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Caries experience in 11-year-old school girls between 1962 and 1981. A radiological study.
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Depth electrode recording in patients undergoing corpus callosotomy for intractable epilepsy.
6 patients undergoing anterior corpus callosotomy for intractable epilepsy have been studied with depth electroencephalography (EEG). Recording before, during and after surgery has confirmed the ability of depth EEG to demonstrate and identify lateralized, focal and often multifocal disturbances. Callosal section has an immediate and lasting effect on clinical seizures and is accompanied by EEG changes with loss of generalization and synchrony following commissurotomy. Depth electrodes within the corpus callosal radiations variably reflect preoperative epileptiform activity recorded from the temporal and frontal regions and postoperatively confirm loss of a potential route of propagation through the commissure.
Brain stem and cerebellar dysfunction with Legionnaires' disease.
A 37-year-old man under treatment for manic-depressive illness developed pneumonia identified as Legionnaires' disease accompanied by a severe neurological disorder with profound dysarthria, ataxia, gaze paralysis, and downbeat nystagmus. At review six months later, he has made only a partial recovery with persisting limb and gait ataxia. Difficulties in diagnosing neurological complications of Legionnaires' disease in a patient with a psychiatric disorder requiring psychotropic medication are discussed.
Factors influencing the lipogenic rate in swine adipose tissue.
Measurements of the lipogenic rate in adipose tissue samples obtained sequentially by biopsy from the same pig may be useful for many nutritional experiments. The average lipogenic rate over a short period (several days to 2 weeks) appears to be relatively stable if the pigs weigh about 20 kg initially and if approximately 10 animals are allotted to each experimental group. The lipogenic rate is readily influenced by the feeding regimen (amount and timing). It is easily lowered by less than ad libitum dietary intakes and is influenced especially by the intake pattern for several days preceding the rate determination. In two different experiments, the lipogenic rate obtained at either 20 or 50 kg body weight was not effective as a predictor of backfat thickness or loineye area measured 13 or 6 weeks later, respectively.
Effect of age, weaning and diet on swine adipose tissue and liver lipogenesis.
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Folate and vitamin B12 in epilepsy.
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Brain folate and diphenylhydantoin (DPH) concentrations in ataxic cats receiving DPH.
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Brain folate concentration in folate-deficient rats receiving diphenylhydantoin.
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Omental transposition to brain of stroke patients.
The intact omentum was transposed to the surface of the brain in three aphasic patients who had stabilized following a dominant hemisphere ischemic stroke. The procedure was found to be safe, causing little physical disfigurement. Subjective and objective improvement in these patients, who are on a strict experimental protocol, has provided encouragement to continue this study in a deliberate and critical manner.