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Biomedical subjects

A B Davis

Publications and source records attributed to A B Davis.

At least 19 recordsLinked to original sources
PubMed1997

Absence of parasympathetic control of heart rate after human orthotopic cardiac transplantation.

BACKGROUND: Partial reinnervation of cardiac sympathetic nerves has been observed after heart transplantation; we hypothesized that parasympathetic control to the heart after transplantation may return as well. To test this hypothesis, we examined heart rate responses produced by two cardiovascular reflexes whose efferent limbs are subserved by vagal fibers to the heart: (1) trigeminal reflex (simulated diving reflex) and (2) arterial baroreflex with phenylephrine injection. METHODS AND RESULTS: An "early" group (n=31, <24 months after transplantation) and a "late group" (n=27, >45 months after transplantation) were studied and compared with a control group with intact cardiac innervation (n=32) and a renal transplant group with similar transplant immunosuppressive regimen (n=11). For trigeminal reflex testing, responses of the donor sinus node (DSN) (sinus node controlling heart rate) and recipient sinus node (RSN) in the innervated remnant right atrium in cardiac transplant patients were compared with heart rate responses in the control groups. For arterial baroreflex testing, baroreflex gains for the DSN and RSN in the cardiac transplant groups were compared with those of the control group. With engagement of the trigeminal reflex, the DSN rate of both transplant groups changed minimally (early, 1.2+/-1.2 bpm; late, 1.8+/-2.5 bpm) compared with the expected decrease in control subjects (-19.8+/-3.0 bpm) and renal transplant patients (-23.9+/-4.9 bpm) (P<.001 versus cardiac transplants). Changes in the RSN rate of both cardiac transplant groups (early, -13.0+/-4.0 bpm; late, -10.0+/-3.7 bpm) were similar to the control groups. Arterial baroreflex gains for the DSN were also depressed (early, 0.1+/-0.2 ms/mm Hg; late, 0.2+/-0.2 ms/mm Hg) compared with control (14.9+/-1.8 ms/mm Hg) and RSN (early, 9.9+/-1.3 ms/mm Hg; late, 10.9+/-1.3 ms/mm Hg; P<.001 versus DSN transplant). CONCLUSIONS: These data suggest that parasympathetic influences on donor heart rate are absent in the majority of patients up to 96 months after cardiac transplantation.

Adult↗
PubMed1997

Deafferentation of the olfactory bulbs of male rats reduces erection to remote cues from females.

If male rats are paired with a receptive, soliciting female rat in a setting that prevents physical contact, but permits auditory, visual, and olfactory contact, some will have erections of the penis--noncontact erections (NCE). Surgical deafferentation of the olfactory bulbs from all the known chemosensory systems of the nasal septum renders rats anosmic, decreases sexual performance in copulation tests with females, and substantially reduces the frequency of NCE. Thus, NCE appear to be primarily regulated though the olfactory perception of volatile chemosensory cues from receptive females.

Animals↗
PubMed1996

Laparoscopic hernia repair in the community hospital setting.

Eighty-three patients (108 repairs) with inguinal hernias underwent laparoscopic transabdominal preperitoneal repair in the community hospital setting. The patients included 82 men and one woman, ranging in age from 15 to 82 years. Concomitant procedures included umbilical hernia repairs, lysis of adhesions, and varicocoelectomy. Ninety-four percent of these patients were discharged the same day, with only one patient requiring more than an overnight stay. Postoperative complications included five cases of urinary retention requiring overnight catherization (4.6%) and one case each of labile hypertension (0.9%), vasovagal reaction (0.9%), dizziness (0.9%), and ileus (0.9%); there were 12 cases of groin swelling with ecchymosis (11%). With follow-up of almost 2 years, there has been one known recurrence (0.9%). This study demonstrates that laparoscopic hernia repair can be performed safely and successfully in the community hospital setting and can be a sound alternative to the standard open hernia repair.

Adolescent↗
PubMed1995

Evidence against reinnervation of cardiac vagal afferents after human orthotopic cardiac transplantation.

BACKGROUND: Orthotopic cardiac transplantation results in total cardiac denervation. Recent studies in humans suggest that reinnervation of cardiac sympathetic nerves (cardiac efferents) may occur after cardiac transplantation. We hypothesized that reinnervation of cardiac afferents may occur as well. To test this hypothesis, we investigated reflex responses produced by stimulation of ventricular chemosensory endings subserved by vagal afferents (cardiac depressor reflex). METHODS AND RESULTS: Two cardiac transplant groups were studied: an "early" group (n = 18, < 24 months after transplant) and a "late" group (n = 18, > 43 months after transplant); these groups were compared with a control group with intact innervation (n = 18). The reflex response of the recipient sinus node (RSN) in the remnant right atrium, which remains innervated after transplantation, was observed during selective right coronary artery (RCA) and left coronary artery (LCA) injection of the radiographic contrast agent meglumine diatrizoate, which is known to stimulate ventricular chemosensory endings. A decrease in the rate of the RSN was expected if reinnervation of chemosensory endings had occurred and the afferent limb of the cardiac depressor reflex was intact. With injection, the RSN rate of both transplant groups did not decrease but increased (early: LCA, 7.2 +/- 1.4 beats per minute; RCA, 6.3 +/- 1.3 beats per minute; late: LCA, 5.9 +/- 1.0 beats per minute; RCA, 6.0 +/- 0.9 beats per minute) compared with the expected decrease in control patients (LCA, -20.8 +/- 2.5 beats per minute; RCA, -18.0 +/- 4.0 beats per minute; P < .001 versus transplants). Decreases in mean arterial pressure in the transplant groups (early: LCA, -11.3 +/- 1.4 mm Hg; RCA, -10.0 +/- 1.6 mm Hg; late: LCA, -13.0 +/- 1.6 mm Hg; RCA, -9.1 +/- 1.5 mm Hg) were less than those observed in the control group (LCA, -19.8 +/- 2.2 mm Hg; RCA, -18.7 +/- 4.0 mm Hg; P < .05 versus transplants). CONCLUSIONS: The results suggest that reinnervation of ventricular chemosensory endings subserved by vagal afferents in cardiac transplant patients does not occur up to 74 months after transplantation.

Aorta↗
PubMed1994

[Not Available].

Although deriving new insights from knowledge of the scientific aspects of nutrition, a key component of health and the ability to resist disease, the cultural, social and economic factors are equally significant, but were emphasized by the mechanistic-scientific physician. Practical advice, such as counseling patients about the effect of specific foods on their health, was transferred by the mechanistic physicians to nutrition specialists or public health authorities. A variety of intrinsic and extrinsic factors contributed to the development of "high tech" medicine that minimizes or ignores the multi-dimensional dietary component of health and disease, some of which are explored here. The physician will discover that interventions made before disease strikes, especially at an age when health care costs are rising beyond society's ability to pay for them, are as important before than after the body is challenged by illness, particularly in the development of chronic diseases.

History, Modern 1601-↗
PubMed1993

Power of testing proportions in small two-sample studies when sample sizes are equal.

In planning experiments having two groups of equal but small size, investigators face the uncertainty of power calculations that rely on asymptotic methods. This paper presents a method for determining power for two-sided tests. I compare two randomization tests, Fisher's exact test (FET), and the mid-P (MID), with the uncorrected chi-square test (CHI). Results show power as a function of relative risk for these methods, and assesses their relative power and type I error rates. MID is shown to have intermediate power between CHI, which is the most powerful, and FET, the least powerful. Situations are shown in which CHI and MID occasionally exceed the nominal level of alpha.

Data Interpretation, Statistical↗
PubMed1993

The statistical power of family practice research.

To determine the statistical power of family practice research, we conducted a survey of all family practice studies published in 3 major family practice journals in 1988. Only 5 of 86 studies calculated statistical power, although 67 (78%) reported statistically nonsignificant results. Calculations of statistical power revealed that more than 80% of family practice studies had sufficient statistical power to detect medium to large effect sizes, but not small effect sizes, which some readers might deem clinically important. We conclude that the authors of family practice research studies do not pay enough attention to the issue of statistical power when reporting statistically nonsignificant results, leaving their readers in doubt as to whether a clinically significant effect could have been detected.

Data Interpretation, Statistical↗
PubMed1992

[Not Available].

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Academies and Institutes↗
PubMed1992

Recurrent bacterial vaginosis: association with vaginal sponge use.

A hypothesis-generation study was conducted to examine risk factors for bacterial vaginosis recurrences among women participating in a randomized controlled trial of male sexual partner treatment. Of the 140 women enrolled in the trial, 72 had a normal vaginal gram-stained slide at the first follow-up visit and were included in this analysis. Nineteen of the 72 (26.2%) women developed a bacterial vaginosis recurrence documented by a vaginal gram-stained slide during the 6-week follow-up period. Of the 19 women, 4 of 6 sponge users (66%) developed a bacterial vaginosis recurrence (RR 2.93, 95% CI: 1.43-6.02). Logistic regression analysis supported the association between sponge use and bacterial vaginosis recurrences (adjusted RR 2.71, 95% CI: 1.06-6.99) but revealed that an apparent protective effect of diaphragm use was due to the confounding effect of sexual partner treatment. Our hypothesis is that bacterial vaginosis recurrences may be due to factors other than sexual transmission, such as sponge use. Further studies are needed to examine risk factors for bacterial vaginosis recurrences. In the interim, physicians might suggest another form of contraception to their sponge-using patient with frequent bacterial vaginosis infections.

Adolescent↗
PubMed1991

Dental machines then and now.

The earliest dentists brought instruments and techniques from Europe as well as tools used by mechanics, watch makers, jewelers and artists. This historical journey through machinery history is a study in contrast to the machines of the present.

Dental Equipment↗
PubMed1991

Prevalence of gastroesophageal reflux in elderly patients in a primary care setting.

Despite the aging of our population, there remains a paucity of information about gastroesophageal reflux (GER) in the elderly. To assess the prevalence and characteristics of GER within this patient population, questionnaires evaluating symptoms associated with GER were administered to 313 consecutive patients 62 yr old or older from a primary care setting. Fourteen percent of these patients reported having at least weekly heartburn. Ambulatory 24-h esophageal pH monitoring was accomplished in 54 of the 313 patients surveyed. Twenty percent (11/54) of this subgroup exhibited increased acid contact time (pH less than 4 for more than 6% of the monitoring period). Twenty-two percent (12/54) complained of heartburn, yet only six individuals (11%) exhibited both symptomatic and objective indications of acid reflux. Surprisingly, 31% (17/54) of the patients studied exhibited significant alkalinity within the distal esophagus (pH greater than 8 for greater than 1.5% of the monitoring period). Whereas 29% of these patients (5/17) reported heartburn, 40% of those reporting heartburn (2/5) had acid GER as well as excessive alkalinity. In contrast to patients with acid GER--none of whom reported pulmonary symptoms--24% (4/17) of these patients with esophageal alkalinity reported wheezing, nocturnal cough, or paroxysmal nocturnal dyspnea. Of the four patients with significant distal esophageal exposure to both acid and alkali, two reported heartburn and a third reported dysphagia. In addition to the somewhat higher prevalence of acid reflux than anticipated, a surprisingly high prevalence of esophageal alkalinity was observed.

Aged↗