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Biomedical subjects

C Davis

Publications and source records attributed to C Davis.

At least 271 records · Page 15Linked to original sources
PubMed1989

The psychological and behavioral considerations of orthognathic surgery on identical (monozygotic) twins.

The psychologic and behavioral changes that may occur with the impact of orthognathic surgery on the physical appearance of an identical twin set have been addressed. This unique situation has not been discussed in the literature with respect to reconstructive or cosmetic facial surgery. A report on elective orthognathic surgery performed on identical twins and the subsequent impact on the twin relationship due to alterations of "self-image phenomenon" is given. Such an impact was a consideration in this case. Further collective study in this area is needed but is difficult to obtain because of the rarity of occurrence of this type of case.

Adolescent↗
PubMed1989

Adhesion formation in experimental chronic radiation enteropathy.

We have studied the late changes associated with radiation enteropathy in mice over a period of 224 days following single or split doses of gamma radiation delivered to the total abdomen (TAI). We focused on the importance of adhesion formation as a cause of strictures and gut-associated deaths following TAI. Gut-associated peritoneal adhesions were found in mice 2-7 months after receiving 13.5-17.5 Gy TAI and appeared to constitute the most consistent serious late effect of irradiation. There was a good correlation between adhesion formation and death for both the single and split-doses of radiation. Adhesions primarily involved the large gut, normally near the cecum. They appeared to result from serosal breakdown and were the major cause of partial gut obstruction. Submucosal fibrosis was present but seemed to be a comparatively minor cause of strictures. Local lymphoid hyperreactivity was also seen following TAI and may have contributed to the late sequelae. The complexity of the pathogenesis of chronic radiation enteropathy was indicated by finding three successive waves of non-scheduled deaths following TAI. The first wave (28-70 days) was not related to adhesion formation and may have been due to localized failure of mucosa to regenerate after irradiation with consequent ulceration. The second wave (98-140 days) occurred over the period when adhesion formation and fibrosis were most marked. In the third wave (168-224 days), the additional complication of fluid exudation was seen. Further experimentation is obviously needed to better define the complex pathogenesis of radiation enteropathy with dose and time after radiation but our data strongly support a multifactorial causation with an important role for adhesion formation in the disease complex.

Animals↗
PubMed1989

Some sources of variance in skin conductance.

An attempt was made to identity some of the factors that might contribute to the variance associated with skin conductance. Results confirmed earlier findings that Blacks have lower levels of skin conductance than Caucasians. The precise role of skin albedo is difficult to determine because within these groups there appears to be a negative relationship between skin reflectance and skin conductance. Possibly peripheral blood flow differences are responsible. There were no differences in heart rate or in self-report measures of arousal between the groups, and the contribution of personality variables to skin conductance variance was, in part, anomalous.

Acoustic Stimulation↗
PubMed1989

Circadian rhythms: charting oral temperatures to spot abnormalities.

1. A normal daily variation in body temperature is found in the elderly. Normal oral temperature in an older person is lower than in a younger person, and the temperature peaks in the early afternoon and is lowest in the early morning hours before awakening. 2. Elderly subjects may be more prone to hypothermia in the early morning hours when their body temperature is naturally lower. Bathing may cause the body temperature to drop up to 1 degree C and add to this risk. 3. Many factors should be considered when analyzing temperature data for the determination of fever. Time of day, as well as symptoms of infection, should be considered. 4. Disturbances in circadian temperature rhythms accompany central nervous system dysfunction and may be an early indicator of other illnesses.

Aged↗
PubMed1989

Of mice and men: anatomy of the amelogenin gene.

Mammalian enamel matrix is composed of two principal proteins, the enamelins and amelogenin. Recombinant complementary DNA (cDNA) molecules for the predominant mouse amelogenin have been identified, characterized by direct determination of the DNA sequence, and used as a specific hybridization probe. The spatial- and temporal-restricted pattern for amelogenin gene expression within developing mouse molars has been traced at the level of a single cell using in situ hybridization. The mouse genome has been shown to contain only one copy of the amelogenin (AMEL) gene which is not amplified or rearranged during ameloblast determination. In contrast, the human genome contains two copies of the AMEL gene, one residing on the X chromosome and one upon the Y chromosome. These observations, the availability of specific enamel gene probes coupled with the application of new techniques in molecular biology now afford unique opportunities for the analysis of the molecular basis of inherited defects of human enamel such as amelogenesis imperfecta. Recent advances towards obtaining a physical map and the complete nucleotide sequence for the human genome, as well as the documented developmental biology, defined genetics and transgenic capability of the mouse, suggest that mouse and man are the most relevant and potentially informative models for analysis of normal and abnormal enamel biomineralization.

Amelogenesis Imperfecta↗
PubMed1989

Research values of occupational and physical therapists.

A national survey was conducted to determine occupational and physical therapists' values toward research. While members of both professions were found to have similar research-related values, therapists identified as researchers held somewhat more positive views of research than did clinicians. The primary differences between clinicians and researchers related to values regarding the relationship between research and professional status, and to the relationship between research and clinical practice.

Adult↗
PubMed1988

Bacterial agglutinin activity in the saliva of human identical and fraternal twins.

The major factor in human saliva responsible for the specific aggregation of oral streptococci is a high molecular-weight glycoprotein (agglutinin). To determine if the level of this glycoprotein in whole and parotid saliva was genetically determined, agglutinin activity for Streptococcus sanguis and Streptococcus mutans in saliva obtained from identical and fraternal twins was compared. Evidence for the heritability of agglutinin activity and also parotid flow rate and total protein was obtained. There was no evidence for a significant genetic contribution to salivary sodium concentration.

Adolescent↗
PubMed1988

Mode of action of calcium antagonists on responses to spasmogens and antigen challenge in human airway smooth muscle.

Calcium antagonists have been shown to inhibit exercise-induced asthma. The mechanism of inhibition is unclear, but may involve inhibition of mediator release and/or blockade of the mediator effects. We studied the effects of methoxyverapamil (D600) on human airway responses to spasmogens as well as on histamine release from passively sensitized human lung challenged with ragweed antigen. The concentrations of D600 required to inhibit 50% of the spasmogen responses (IC50) were calculated from the concentration-response relationships and were: histamine 4 x 10(-6) M; KCl 7 x 10(-7) M; leukotriene C4 4 x 10(-5) M; electrical field stimulation 5 x 10(-5) M; and for ragweed antigen in passively sensitized muscle 2 x 10(-6) M. Histamine release by antigen challenge from sensitized lung fragments was not blocked by D600, up to a concentration of 10(-5) M. The data suggest that the contractile effects of agonists are mediated through voltage- and receptor-operated calcium channels. The differential inhibitory effects of D600 on antigen-induced mediator release vs the smooth muscle effects of the various agonists may suggest multiple mechanisms of release or sources of mediators in human airway anaphylaxis.

Allergens↗
PubMed1988

Reliability of psychophysiological assessment within temperament-groups.

Four groups of 16 people selected for their relatively extreme scores (greater or equal to 1 S.D. from the mean) on both the E and N scales of the Eysenck Personality Inventory visited the laboratory for four separate but identical testing sessions. Three physiological indices were recorded at each session: heart rate (HR), basal skin conductance level (SCL), and the number of spontaneous skin conductance responses (SCR). Test-retest correlation coefficients were calculated within E x N groups across days. HR and SCR showed moderate to good reliabilities across all groups. The most interesting finding was that SCL was a consistently reliable index for extraverts but not for introverts. Correlations between days were statistically significant for extraverts but not for introverts. A speculative explanation for these results is that SCL is affected by cognitive activity rather than autonomic arousal per se. This study suggests that there are systematic effects of temperament on physiological measures that are important and should not be relegated to error variance.

Arousal↗
PubMed1988

The impact of DRGs on the cost and quality of health care in the United States.

The prospective Payment System (PPS) represents a fundamental change in the way the United States government reimburses hospitals for medical services covered under Medicare, a federal health care insurance program for the elderly and disabled. PPS replaced the retrospective cost-based system of payment for Medicare services with a prospective payment system. Under PPS, a predetermined specific rate for each discharge dictates payment according to the diagnosis related group (DRG) in which the discharge is classified. The PPS was intended to create financial incentives that encourage hospitals to restrain the use of resources while providing high-quality inpatient care. Both objectives appear to have been met under PPS. Hospital utilization has declined, average length of stay has fallen, and the locus of care has shifted from the inpatient setting to less costly outpatient settings. The growth in inpatient hospital benefits has slowed and the impending insolvency of the Medicare trust fund has been forestalled. Studies have found no deterioration in the quality of care rendered to Medicare beneficiaries. Neither the mortality rate nor the rate of re-admission (presumably related to premature discharge) increased under PPS. Indeed, PPS appears to have enhanced the quality of inpatient care by discouraging unnecessary and potentially harmful procedures, and by encouraging the concentration of complex procedures in facilities in which the high frequency of these procedures promotes efficiency. Incentive-based reimbursement also appears to have contributed to the growth in alternative delivery systems, such as HMOs and PPOs, which contain costs by maintaining a high volume of a limited range of services. The success of the PPS/DRG system in controlling costs and promoting quality in this country suggests its application in other countries, either as a method of reimbursement or as a product line management tool.

Diagnosis-Related Groups↗