Biomedical subjects

D L McKay

Publications and source records attributed to D L McKay.

11 recordsLinked to original sources

PubMed2000

The effects of a multivitamin/mineral supplement on micronutrient status, antioxidant capacity and cytokine production in healthy older adults consuming a fortified diet.

BACKGROUND: Inadequate micronutrient intake among older adults is common despite the increased prevalence of fortified/enriched foods in the American diet. Although many older adults take multivitamin supplements in an effort to compensate, studies examining the benefits of this behavior are absent. OBJECTIVE: To determine whether a daily multivitamin/mineral supplement can improve micronutrient status, plasma antioxidant capacity and cytokine production in healthy, free-living older adults already consuming a fortified diet. METHODS: An eight-week double-blind, placebo-controlled clinical trial among 80 adults aged 50 to 87 years (mean = 66.5 +/- 8.6 years). RESULTS: Multivitamin treatment significantly increased (p<0.01, compared to placebo) plasma concentrations of vitamins D (77 to 100 nmol/L), E (27 to 32 micromol/L), pyridoxal phosphate (55.1 to 75.2 nmol/L), folate (23 to 33 nmol/L), B12 (286 to 326 pmol/L)), C (55 to 71 micromol/L), and improved the riboflavin activity coefficient (1.23 to 1.15), but not vitamins A and thiamin. The multivitamin reduced the prevalence of suboptimal plasma levels of vitamins E (p=0.003), B12 (p=0.004), and C (p=0.08). Neither glutathione peroxidase activity nor antioxidant capacity (ORAC) were affected. No changes were observed in interleukin-2, -6 or -10 and prostaglandin E2, proxy measures of immune responses. CONCLUSIONS: Supplementation with a multivitamin formulated at about 100% Daily Value can decrease the prevalence of suboptimal vitamin status in older adults and improve their micronutrient status to levels associated with reduced risk for several chronic diseases.

Aged↗

PubMed2000

Multivitamin/mineral supplementation improves plasma B-vitamin status and homocysteine concentration in healthy older adults consuming a folate-fortified diet.

Elevated homocysteine has been identified as an independent risk factor for cardiovascular and cerebrovascular disease. Although multivitamin use has been associated with low plasma homocysteine concentrations in several observational studies, no clinical trials have been conducted using multivitamin/mineral supplements to lower homocysteine. We determined whether a multivitamin/mineral supplement formulated at about 100% Daily Value will further lower homocysteine concentration and improve B-vitamin status in healthy older adults already consuming a diet fortified with folic acid. In this randomized, double-blind, placebo-controlled trial, 80 free-living men and women aged 50-87 y with total plasma homocysteine concentrations of > or =8 micromol/L received either a multivitamin/mineral supplement or placebo for 56 d while consuming their usual diet. After the 8-wk treatment, subjects taking the supplement had significantly higher B-vitamin status and lower homocysteine concentration than controls (P: < 0.01). Plasma folate, pyridoxal phosphate (PLP) and vitamin B-12 concentrations were increased 41.6, 36.5 and 13.8%, respectively, in the supplemented group, whereas no changes were observed in the placebo group. The mean homocysteine concentration decreased 9.6% in the supplemented group (P: < 0.001) and was unaffected in the placebo group. There were no significant changes in dietary intake during the intervention. Multivitamin/mineral supplementation can improve B-vitamin status and reduce plasma homocysteine concentration in older adults already consuming a folate-fortified diet.

Aged↗

PubMed1996

Methamphetamine effects on cognitive processing during extended wakefulness.

We examined the effects of both 5- and 10-mg/7O kg body weight of d-methamphetamine HCl on high event rate vigilance and tracking performance in a 13.5-hr sustained-performance session during one night of sleep loss. At 0116 hours participants were administered either a 5 mg/70 kg oral dose of d-methamphetamine (n=10), 10 mg/70 kg d-methamphetamine (n=10), or a placebo (n=10) using standard double-blind procedures. Performance on all measures degraded markedly during the night in the placebo group. Both the 5- and 10-mg methamphetamines treatment reversed an initial decline in d', and reversed increases in nonresponses (lapses) and tracking error within approximately 3 hr of administration. No evidence that amphetamine treatment increased impulsive responding (fast guesses) was observed. The magnitude of the performance effects of the methamphetamine treatments was similar at 3 hr postadministration. However, the effects of the 5-mg dose were shorter-lived, disappearing by the last testing session (6.5 hr postadministration), whereas effects of the 10-mg dose tended to remain throughout testing. Both amphetamine treatments decreased subjective sleepiness during the night and tended to increase subjective sleep latencies during a post-testing sleep period.

Adult↗

PubMed1995

The effects of tyrosine on cognitive performance during extended wakefulness.

Tyrosine, a large neutral amino acid found in dietary proteins, has received recent attention as a potential treatment for stress. The behavioral effects of tyrosine were examined during an episode of continuous nighttime work involving one night's sleep loss. Subjects performed nine iterations of a battery of performance tasks and mood scales for approximately 13 h, beginning at 1930 and ending at 0820. They remained awake throughout the day on which the experiment began and were awake for more than 24 h by the end of testing. Six hours after the experiment began, one-half of the subjects received 150 mg.kg-1 tyrosine in a split dose while the other half received cornstarch placebo in a double-blind procedure. Tyrosine administration was associated with a significant amelioration of the usual performance decline on a psychomotor task and a significant reduction in lapse probability on a high-event-rate vigilance task. The improvements lasted on the order of 3 h. The results of this study also suggest that tyrosine is a relatively benign treatment at this dose. After further testing with other doses and timing of administration, tyrosine may prove useful in counteracting performance decrements during episodes of sustained work coupled with sleep loss.

Adult↗

PubMed1993

Evaluation of erectile dysfunction by dynamic infusion cavernosometry and cavernosography (DICC). Multi-institutional study.

In a cooperative, private practice, multi-institutional impotence study, dynamic infusion cavernosometry and cavernosography (DICC) was performed on 743 patients to make an accurate diagnosis and/or identify candidates for penile revascularization. Maximum equilibrium intracorporeal pressure achieved following papaverine and phentolamine injection (Phase I) averaged 29.42 +/- 0.76 mm Hg, approximately one third of normal erection pressure. Corporeal pressure fall from 150 mm Hg over thirty seconds (cavernosometry) averaged 82.38 +/- 1.33 mm Hg (Phase II). The gradient between systolic and cavernosal artery pressure averaged 42.84 +/- 1.12 mm Hg on the right and 43.33 +/- 1.13 mm Hg on the left (Phase III). Cavernosography at 90 mm Hg erection pressure was performed in Phase IV. Of the 124 patients from one center who were reviewed in greater detail, pure cavernosal artery insufficiency (CAI) was found in 25 (20.2%), corporeal veno-occlusive dysfunction (CVOD) in 26 (21.0%), and 73 patients (58.9%) demonstrated combined CAI and CVOD. Diabetics (n = 69) achieved lower equilibrium intracorporeal pressures than nondiabetics, had similar CVOD, and worse CAI. Smokers (n = 365) and patients with Peyronie's disease (n = 32) had erectile dysfunction similar to those without these conditions. Patients impotent after trauma (n = 124) were younger, achieved higher intracorporeal pressures, and showed better corporeal veno-occlusive function than those without trauma. Complications of DICC were minimal and infrequent. After DICC, 169 patients underwent internal pudendal arteriography, 105 had arterial bypass surgery with or without penile venous ligation procedures, and 45 had venous surgery alone. Dynamic infusion cavernosometry and cavernosography is a useful erectile function study to evaluate impotence and can be performed easily in a private practice setting.

Blood Pressure↗

PubMed1993

Early experience with the first pre-connected 3-piece inflatable penile prosthesis: the Mentor Alpha-1.

The aim of this clinical investigation was to obtain preliminary treatment outcome data concerning the Mentor Alpha-1, the first 3-piece inflatable penile prosthesis with pre-connected tubing between the pump and the penile cylinders. The study was designed to be the first multi-institutional treatment outcome report for any clinically available penile prosthesis with data analysis to be independent of the participating surgeons. A total of 12 board-certified urologists of mixed surgical training backgrounds and practices implanted the Alpha-1 device in 112 consecutive patients. With a mean of 27 +/- 5 months of followup the surgical complication rate included a 4% mechanical malfunction, 2% infection rate and 9% reoperation rate. Patient experience with the implanted device was computed from information on 96 of the 112 patients who returned a questionnaire. Of the patients 82% stated that the device fulfilled expectations as a treatment for impotence and 83% had improved sexual intercourse by 8 weeks after implantation. Patient satisfaction was computed on a scale of 12 equally weighted interrelated variables. Of the patients 77% recorded 9 or more cumulative satisfaction points. Patient and physician questionnaire data were analyzed for their relation to the cumulative prosthesis satisfaction score. A significant difference in cumulative scores was found for physician reported long-term postoperative problems (mean satisfaction score 8.1 for patients with problems versus 10.2 for patients without problems, p = 0.018). The Alpha-1, with its feature of pre-connected tubing, is a reliable 3-piece inflatable penile prosthesis associated with a high level of patient satisfaction.

Data Collection↗

PubMed1993

Congenital hypertrophy of the retinal pigment epithelium and familial adenomatous polyposis.

Congenital hypertrophy of the retinal pigment epithelium is a common eye sign in patients with familial adenomatous polyposis (FAP). FAP has autosomal dominant inheritance with virtually 100% risk of colonic malignancy in adult life. There may be other associated systemic abnormalities including extracolonic malignancy. Early detection of disease is desirable, but has in the past been reliant on regular endoscopic examination. The nature of congenital hypertrophy of the retinal pigment epithelium and its usefulness as a predictive marker of the disease are discussed.

Adenomatous Polyposis Coli↗

PubMed1991

Cloning, nucleotide sequence, and engineered expression of Thermus thermophilus DNA ligase, a homolog of Escherichia coli DNA ligase.

We have cloned and sequenced the gene for DNA ligase from Thermus thermophilus. A comparison of this sequence and those of other ligases reveals significant homology only with that of Escherichia coli. The overall amino acid composition of the thermophilic ligase and the pattern of amino acid substitutions between the two proteins are consistent with compositional biases in other thermophilic enzymes. We have engineered the expression of the T. thermophilus gene in Escherichia coli, and we show that E. coli proteins may be substantially removed from the thermostable ligase by a simple heat precipitation step.

Amino Acid Sequence↗

PubMed1982

Urine monitoring of textile workers exposed to dichlorobenzidine-derived pigments.

Urine samples from 36 workers exposed to dichlorobenzidine (DCB)-derived pigments and 12 controls were screened for aromatic amines by a nonspecific colorimetric method and then further analyzed by GC/MS specifically for DCB and monoacetyldichlorobenzidine. Of the samples screened for aromatic amines, six (17%) of the exposed population and one (7%) of the control population registered positive (1.0 part per billion [ppb] or greater). One of the positive samples (5.6 ppb) reflected medication, and the remainder (1.1 to 1.8 ppb) were due to high urinary background. The specific analyses were negative (less than 0.2 ppb) for DCB or monoacetyldichlorobenzidine in all samples.

3,3'-Dichlorobenzidine↗

PubMed1977

Hydrocolpos, vaginal atresia, and urethrovaginal fistula in a neonate: abdomino-perineal-vaginal pull-through.

The combination of high maternal estrogenic stimulation of the secretory glands of the reproductive tract of the newborn female and vaginal obstruction results in an abdominal mass due to vaginal distention (hydrocolpos). Prior experience with two infants with hydrocolpos (LG) led us to perform abdomino-perineal-vaginal pull-through, as advocated by Ramenofsky and Raffensperger, in the newborn period. So far as we can ascertain this is only the second infant so reported in the literature.

Abdomen↗

PubMed1975

Balanitis xerotica obliterans in children.

Balanitis xerotica obiterans is a chronic inflammatory process in male subjects, resulting in sclerotic epithelial changes of the glans penis, prepuce and urethral meatus individually or collectively. Four pediatric cases are presented, including the first case of balanitis xerotica obiterans invloving the glans penis and urethral meatus in a child. This lesion may be misdiagnosed or ignored in the young boy. The suggested method of treatment is surgical extirpation of the lesion when possible, wedge meatotomy when needed and sublesional corticosteroids if the lesion cannot be completely excised.

Balanitis↗