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Biomedical subjects

T W Roberts

Publications and source records attributed to T W Roberts.

At least 19 recordsLinked to original sources
PubMed1999

Automated measurement of oxygen consumption by the yellow fever mosquito, Aedes aegypti.

Oxygen consumption of single mosquitoes was measured using a differential pressure transducer (DPT) connected to two small chambers. A mosquito was placed in the experimental chamber (P1) and was separated from NaOH by 4 cm2 of marquisette mesh. The reference chamber (P2) contained the same amount of NaOH and the marquisette mesh but without a mosquito. When these two chambers were sealed, removed O2 from P1 resulted in a pressure decrease with respect to P2. This pressure differential was transduced into an output voltage that was directly proportional to the amount of O2 consumed by the mosquito. An array of eight DPTs was interfaced with an IBM 486 PC using an ADAC 5500MF analog to digital converter and software from ADAC (Direct View) to automate the recording procedure. We determined that our apparatus was sensitive enough to detect subtle differences in O2 consumption in mosquitoes subjected to different physiologic conditions.

Aedes↗
PubMed1996

Taste in chimpanzee: I. The summated response to sweeteners and the effect of gymnemic acid.

The purpose of this study was to investigate further with electrophysiological and behavioral techniques the similarity between the sense of taste of humans and chimpanzees, especially with regard to the effects of gymnemic acid. Gymnemic acid (GA) is a powerful suppressor of sweet taste in humans but lacks this ability in nonprimates and lower primates. The summated taste responses from the chorda tympani nerve were recorded in nine adult chimpanzees, Pan troglodytes. The results show that all tested compounds that taste to humans elicited nerve responses in chimpanzees. GA suppressed or abolished the response to all sweeteners, but had no effects on the responses to the nonsweet compounds. The suppression varied from complete abolishment (aspartame, saccharin), to about 50% reduction (xylitol). When the effect of GA was tested on concentration series, 20% remained of the response to sucrose, whereas the responses to aspartame and saccharin were basically abolished. Higher concentrations of GA suppressed more. The effects of GA developed also in the presence of saccharin, but seemed less pronounced. The behavioral results were obtained with a one-bottle preference technique before and after GA. The results demonstrated that after exposure of the tongue to GA, the animals' liking for sweet diminished. These results parallel psychophysical and electrophysiological findings in humans. The way GA suppressed sweet taste in chimpanzees added one more characteristic to those that set chimpanzees apart from monkeys and close to humans.

Animals↗
PubMed1994

Sweet taste in the calf: III. Behavioral responses to sweeteners.

The hedonic response to the sweeteners acesulfame-K, aspartame, fructose, galactose, glucose, glycine, lactose, maltose, Na-saccharine, sucrose, and xylitol was recorded in five groups of 4-16-week-old calves. The compounds were presented to the calves for 12 or 24 h in two-bottle preference tests with tap water as one choice. Glycine (10 mM and higher), sucrose (20 mM and higher), and fructose concentrations were most preferred. Sodium-saccharine was highly preferred at and above 4 mM concentration, fructose and lactose were preferred above 40 mM, galactose was preferred moderately, acesulfame-K and maltose were preferred inconsistently, and aspartame and xylitol were not preferred at any concentration. The change of preference during the tests was also studied. Three types of consumption changes were observed. 1) Increased preference of the tastant during consumption, seen during sucrose and, to lesser a extent, fructose consumption. 2) Initial high preference for the tastants, diminishing during the test period, observed with fructose, galactose, glucose, glycine, lactose, and maltose. 3) Initial large fluctuations in consumption from the two bottles, but no change in overall preference. This pattern was seen with xylitol and aspartame. This technique seems to offer a method to assess the long-term preference for a compound within one relatively short two-bottle preference session.

Age Factors↗
PubMed1993

Evaluation of peri-implant sulcular temperature.

Sulcular temperatures were measured on 35 clinically stable and restored osseointegrated dental implants and compared to 50 remaining natural teeth in 9 partially-edentulous adults using the PerioTemp temperature probe (ABIO-DENT, Inc., Danvers, MA USA). Replicate peri-implant sulcular measurements showed a mean difference of 0.1 +/- 0.15 (SD) degrees C. Implant temperatures varied from 0.41 to 3.9 degrees C below sublingual temperatures measured on each patient, and maxillary implants were significantly cooler than mandibular implants (p < 0.001, t-test). A posterior-to-anterior temperature gradient was found in both the maxilla and mandible, with anterior implants significantly cooler than posterior fixtures. No significant differences were found in sulcular temperatures of osseointegrated dental implants and natural teeth located in anatomically-equivalent oral sites. Similarly to natural teeth, sulcular temperature may serve as a valuable diagnostic tool in evaluating dental implant status.

Aged↗
PubMed1980

A general method for determining the replicative age of normal animal cell cultures.

The percentage of cells capable of forming colonies of at least a given size has been found to provide a reliable estimate of the remaining doubling potential of several human diploid fibroblast cell lines and for chick embryo fibroblasts. In five independently derived cell lines of human diploid fibroblasts we have found the same linear relationship between population doublings remaining and the percentage of cells able to form colonies of at least 16 cells. For chick embryo fibroblasts there is a linear relationship between the percentage of cells forming colonies of 64 or more cells and remaining proliferative potential. When human diploid fibroblasts were grown in medium containing hydrocortisone at 5 microgram/ml the increased in vitro lifespan was reflected in the colony size distribution long before the end of the in vitro lifespan.

Cell Count↗
PubMed1980

The proliferative potential of chick embryo fibroblasts: population doublings vs. time in culture.

Chick embryo fibroblasts were maintained in a non-proliferating state up to 150 days in medium containing reduced concentrations of fetal bovine serum. Under these conditions the total time in culture was increased from 50 to 200 days while the total proliferative potential decreased only slightly. From these experiments we conclude that the ability of chick embryo fibroblasts to proliferate in vitro is much more dependent on the number of previous in vitro doublings than on the duration of the time in the culture.

Animals↗
PubMed1977

Pathology and natural history of urethral tumors in females: review of 65 cases.

Cancer of the female urethra, although uncommon, is important because unless recognized early and treated adequately, death will ensue, preceded by much morbidity. The authors present a series of 62 patients with 70 primary tumors, and 3 patients with secondary tumors. A comprehensive classification of neoplasms of the female urethra is also included.

Adenocarcinoma↗
PubMed1976

Intraoral papillary cystadenoma lymphomatosum.

The literature related to intraoral papillary cystadenoma lymphomatosum is critically reviewed and the reported cases analyzed to determine the average age, sex, and race of patients, and the site distribution of this curious lesion. Two new cases are reported. The histogenesis and differential diagnosis from cystadenocarcinoma are briefly discussed.

Adenolymphoma↗