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Biomedical subjects

J A Greenberg

Publications and source records attributed to J A Greenberg.

At least 19 recordsLinked to original sources
PubMed2001

Biases in the mortality risk versus body mass index relationship in the NHANES-1 Epidemiologic Follow-Up Study.

BACKGROUND: Conflicting research findings have created uncertainty as to the ideal body weight. OBJECTIVE: To test whether average-adulthood BMI (body mass index, weight in kilograms per height in meters squared) is a more reliable predictor of mortality risk than the one-time baseline BMI measurement which has been used in previous studies. DESIGN: Prospective cohort study with a 20 y follow-up period, the First National Health and Examination Survey (NHANES 1) Epidemiologic Follow-up Study (NHEFS). SUBJECTS: A random probability sample of 14,407 adults aged 25-74 y in the 1971-1975 NHANES 1. MEASUREMENTS: Body-weight data were derived from measurements in the 1971-1975 and 1982-1984 NHEFS surveys, and current and recalled estimates by subjects in the 1971-1975, 1982-1984, 1986 and 1987 surveys. Height was measured in the 1971-1975 survey. Socio-economic and lifestyle covariates were derived from questionnaires administered in all four surveys. Almost all deaths were verified by death certificates. RESULTS: The shape of the morality risk vs baseline BMI curve varied due to a bias (late-life bias) caused by a steep decrease in BMI among the elderly toward the end of the lifespan. In a particular analysis, the portion of subjects at baseline who were deceased elderly with lower BMI than age-matched censored subjects indicated the size of the bias, and appeared to be the proximate cause. Strong evidence was found to support the proximate cause being the actual cause. Excluding deaths during early follow-up was only able to remove the late-life bias in limited circumstances. Using average-adulthood BMI as mortality predictor and baseline BMI as covariate was very effective in removing the late-life bias. It also appeared to remove the reverse-causation and regression-dilution biases, and yielded robustly positive mortality risk vs average-adulthood BMI curves in all analyses in which it was tested. CONCLUSIONS: Average-adulthood BMI appears to be an appropriate predictor of mortality risk, provided baseline BMI is used as a covariate. Among non-elderly persons, being leaner meant a lower mortality risk, down to the lowest category of leanness in the study-<20 kg/m(2). Future survival analyses of the mortality-BMI relationship should account for the effects of the regression-dilution, reverse-causation and late-life biases.

Adult↗
PubMed2000

Whole-body metabolic rate appears to determine the rate of DNA oxidative damage and glycation involved in aging.

While aging has been found to be a multifactorial process, it seems logical that different aging parameters which reflect the deleterious effects of normal basal metabolism should be directly related. Three such putative aging parameters were therefore measured in adult male Fischer 344 rats on three different long-term diets which have been shown to yield different lifespans. It was found that the daily caloric intake per unit organ weight, a measure of whole-body metabolic rate, was directly proportional to: (1) the level of 8-hydroxydeoxyguanosine in skin dermal cells, used as a measure of the rate of DNA oxidative damage; (2) the proportion of hemoglobin that was glycated, used as a measure of the rate of glycation. This appears to be the first evidence suggesting that whole-body metabolic rate plays a role in determining both the rate of DNA oxidative damage and the rate of glycation involved in aging, because whole-body metabolic rate was the only one of these three variables manipulated in the study. The study also found that there were no significant between-group differences in brain, kidney and liver 8-hydroxydeoxyguanosine, suggesting that DNA oxidative damage in non-mitotic and slow-dividing cells is not a reliable linear biomarker of aging.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2000

Metabolic mass, metabolic rate, caloric restriction, and aging in male Fischer 344 rats.

Previous investigators have found the metabolic rate to be the same in calorically-restricted and ad-libitum fed rodents, and hence concluded that the Rate of Living Theory does not help explain the longer lifespan of the calorically-restricted (CR) animal. However, these previous instigators may not have used reliable estimates of metabolic mass in their calculations of metabolic rate. Hence the present study investigated the reliability of ten different estimates of metabolic mass (MM) in 21-month-old male Fischer 344 rats fed three different diets to yield a wide range of body compositions. Two criteria were used to rank each estimate of metabolic mass: strong correlation with daily caloric intake (DCI); and zero Y-intercept on the regression curve of DCI versus the MM. The combined weight of the heart, liver, kidneys and brain (OW) was found to be the best estimate of MM. Statistical analysis of the differences in metabolic rate in the three groups of rats showed that the significance of these differences depended on the estimate of MM used. OW yielded different results than did fat-free mass (FFM), body weight (BW), BW(0.75), and BW(0.67). Therefore, because previous investigators used FFM, BW, BW(0.75), or BW(0.67), rather than a more reliable estimate such as OW, their finding that metabolic rate was not different in the CR and ad-lib groups, and their conclusion that the Rate of Living Theory does not help explain the longer lifespan of the CR animal, are called into question.

Aging↗
PubMed1999

Adjusted and unadjusted energy usage rates both determine body fat and plasma leptin in male Fischer 344 rats.

Previous studies of the relationship between plasma leptin and energy usage have yielded contradictory findings. The present study was therefore conducted to clearly distinguish and measure the energy usage rate and the energy usage rate adjusted for a surrogate of metabolically active tissue mass. We investigated the simultaneous relationships between these two measures of energy usage, leptin, and body fat in 21-month-old adult male Fischer 344 rats on three different long-term dietary regimens: (1) continuous ad libitum feeding (Ad-lib); (2) ad libitum feeding until early adulthood, and then continuous 60% caloric restriction (CR); and (3) ad libitum feeding until early adulthood, then 60% caloric restriction until 16 months, and then ad libitum feeding for 5 months (CR/Ad-lib). Two versions of the daily usage rate were measured: daily dietary caloric intake (DCI), and daily energy expenditure (EE) based on indirect calorimetry. Two versions of the metabolically active tissue mass were also measured: fat-free mass (FFM), and the sum of the weight of the heart, brain, liver, and kidneys. Energy usage rates were adjusted for these measures of metabolically active tissue mass to yield measures of the energy metabolic rate. Correlation, regression, and path analyses showed that both the energy usage rate and adjusted energy usage rate played important independent roles in determining body fat and plasma leptin, but only after multivariate techniques were used to account for the simultaneous interactions between variables. Increases in the energy usage rate were associated with increases in body fat and the adjusted energy usage rate. Increases in the adjusted energy usage rate were associated with decreases in body fat and plasma leptin. These findings suggest that differences in subjects adjusted energy usage rate could explain some of the apparently contradictory findings concerning the relationship between energy usage and plasma leptin in previously published studies. In conclusion, this appears to be the first study to clearly separate and quantify the effects of the energy usage rate and adjusted energy usage rate on body fat and plasma leptin. The findings suggest that under conditions of long-term stable body weight, both of these measures of energy usage play independent simultaneous roles in determining body fat and plasma leptin.

Adipose Tissue↗
PubMed1999

The anconeus muscle flap: its anatomy and clinical application.

The arterial anatomy, coverage area, and potential donor site morbidity of the anconeus muscle flap are described. Using 17 cadaveric upper extremities, we investigated the muscle's arterial anatomy in 12 specimens and defined the coverage area of the anconeus flap in 5 specimens. We also reviewed the records of 9 patients who underwent a pedicle anconeus muscle flap for elbow coverage to assess clinical results of the procedure. The anconeus muscle is supplied from 3 arterial pedicles: the recurrent posterior interosseus artery, the medial collateral artery, and the posterior branch of the radial collateral artery. The recurrent posterior interosseus artery and the medial collateral artery were present in all dissected cadavers and consistently anastomosed with each other underneath the anconeus muscle. By harvesting the muscle on the medial collateral artery, the anconeus muscle flap can be expected to cover a 7.3 cm2 defect over the radiocapitellar joint, a 6.1 cm2 defect over the distal triceps tendon, and a 7.2 cm2 defect over the olecranon. In this series, none of the patients experienced loss of elbow motion, stability, or extension strength. The results of this study indicate that the anconeus can be harvested with minimal risk of morbidity and provides effective coverage for soft tissue defects of the elbow.

Adult↗
PubMed1999

Organ metabolic rates and aging: two hypotheses.

There is currently no satisfactory explanation for caloric restriction's (CR's) well-established ability to reduce the rate of aging. Pearl's rate of living theory postulates a direct relationship between metabolic rates and the rate of aging, but CR, exercise and cold-exposure studies have shown that this theory is not valid in rodents with respect to whole-body energy metabolism. The present paper describes a crude analysis of previously published data from rat CR, wheel running and cold exposure studies, which reached two main conclusions. The first is that there appears to be a direct relationship between organ metabolic rates and the rate of aging. The second is that organ basal metabolic rates (BMRs) decrease by about one-quarter during adulthood in the rat. On the basis of these findings, the following two hypotheses are proposed: (1) the rate of living theory is valid in mammalian organ; (2) organ BMRs decrease by about one-quarter in adulthood in mammals. This hypothesized decrease, if confirmed in humans, would be a major component of the well-established age-related decrease in whole-body resting metabolic rate in humans.

Aging↗
PubMed1999

The leptin-fat ratio is constant, and leptin may be part of two feedback mechanisms for maintaining the body fat set point in non-obese male Fischer 344 rats.

While plasma leptin and adiposity have been found to be strongly related, the specific nature of this relationship has yet to be clarified. Hence, plasma leptin and three indicators of adiposity were measured in adult male Fischer 344 rats on three different long-term diets: continuous ad libitum feeding; ad libitum feeding until early adulthood, then continuous 60% caloric restriction; and ad libitum feeding until early adulthood, then 60% caloric restriction until 16 months, then ad libitum feeding for 5 months. Body fat was found to be a good linear correlate of plasma leptin, with a zero Y-intercept, and a constant plasma leptin-body fat ratio. The number of adipocytes per rat and % body fat were strong quadratic correlates of plasma leptin. This study is the first to find a zero Y-intercept and constant plasma leptin-body fat ratio, probably because it is the first to simultaneously measure both plasma leptin and body fat accurately, and to account for confounders such as gender, genetic background, age, physical activity, and possibly obesity. The study also explored the effect of switching calorically-restricted rats to ad libitum feeding. This led to a rapid rise, and then synchronized up-down cycles in average daily food intake and body weight, with a steady upward trend toward a new stable body-weight set point. It is hypothesized that this pattern resulted from two simultaneous feedback mechanisms, possibly involving leptin. In conclusion, this study suggests that, under controlled conditions, the plasma leptin-body fat ratio is a constant for a particular mammalian strain, independent of dietary history.

Adipose Tissue↗
PubMed1999

Recovery characteristics of sevoflurane and halothane in preschool-aged children undergoing bilateral myringotomy and pressure equalization tube insertion.

UNLABELLED: This double-blinded study was undertaken to prospectively evaluate the role of halothane and sevoflurane and the use of IV ketorolac on the anesthetic emergence in a group of children undergoing bilateral myringotomy with pressure equalization tube procedures. Two-hundred ASA physical status I and II patients were premedicated with nasal midazolam (0.2 mg/kg) and randomized to one of four groups (Group 1 - halothane and ketorolac; Group 2 - halothane and placebo; Group 3 - sevoflurane and ketorolac; Group 4 - sevoflurane and placebo). A blinded nurse observer characterized the quality of the anesthetic emergence and recorded the incidence of emesis and the use of pain medications in the recovery room. There were no differences in age, weight, previous anesthetic experience, or duration of anesthesia among the four groups. There was no difference in the incidence of emergence agitation for patients anesthetized with sevoflurane compared with halothane, regardless of whether they received ketorolac or placebo. Regardless of the anesthetic, the incidence of emergence agitation was significantly less in patients who received ketorolac compared with patients who received placebo. The incidence of emesis in the recovery room, the total 24-h incidence of emesis, and the use of at-home pain medications were similar in all four groups. IMPLICATIONS: We conclude that the incidence of emergence agitation in children undergoing ultrashort anesthetic procedures is similar for sevoflurane and halothane and that ketorolac markedly diminishes emergence agitation and/or pain behavior.

Analgesia↗
PubMed1997

Birth weight as a predictor of brachial plexus injury.

OBJECTIVE: To examine the relationship between birth weight and brachial plexus injury and estimate the number of cesareans needed to reduce such injuries. METHODS: All 80 neonatal records coded for brachial plexus injury from October 1985 to September 1993 at the Brigham and Women's Hospital in Boston, Massachusetts, were studied along with linked maternal files. Birth weight, method of delivery, presence or absence of shoulder dystocia, and any diagnosis of maternal gestational or nongestational diabetes were abstracted. Data for the group with brachial plexus injury were compared with data for live-born infants without this injury during the same period. The sensitivity and specificity of birth weight as a predictor of brachial plexus injury were calculated. Further, the number of cesarean deliveries necessary to prevent a single brachial plexus injury was estimated using various weight cutoffs (4000, 4500, and 5000 g) for elective cesarean delivery. RESULTS: Among 77,616 consecutive deliveries, there were 80 brachial plexus injuries identified, for an incidence of 1.03 per 1000 live births. The incidence of brachial plexus injury increased with increasing birth weight, operative vaginal delivery, and the presence of glucose intolerance. In the group of women without diabetes, between 19 and 162 cesarean deliveries would have been necessary to prevent a single immediate brachial plexus injury. Among women with diabetes, between five and 48 additional cesareans would have been required. CONCLUSION: Although birth weight is a predictor of brachial plexus injury, the number of cesarean deliveries necessary to prevent a single injury is high at most birth weights. Because of the large number of cesarean deliveries needed to prevent a single brachial plexus injury in infants born to women without diabetes, it is difficult to recommend routine cesarean delivery for suspected macrosomia in these women.

Birth Injuries↗
PubMed1997

Vaginal delivery after cloacal malformation repair.

BACKGROUND: Patients with cloacal malformations at birth usually require multiple surgical procedures to correct their anatomic defects. Those who conceive after repairs invariably have had cesarean deliveries on the assumption that vaginal delivery would be difficult and/or dangerous. However, because they usually have undergone multiple previous abdominal procedures, cesarean delivery also may carry greater risks than in the general population. CASE: A 27-year-old nulligravida was delivered vaginally at 34 1/2 weeks' gestation, with a good maternal and neonatal outcome. CONCLUSION: Judiciously treated, pregnant patients with previously repaired cloacal malformations may be candidates for vaginal delivery.

Abnormalities, Multiple↗
PubMed1997

X-ray changes after expanded polytetrafluoroethylene (Gore-Tex) interpositional arthroplasty.

Thirty-one patients with degenerative osteoarthritis at the trapeziometacarpal joint underwent 34 expanded polytetrafluoroethylene interpositional arthroplasties. The average follow-up period for the group of patients was 41 months (range, 15-82 months). Subjective results and objective measurements for the patients at the time of review were favorable. X-ray analysis, however, revealed a high incidence of osteolytic lesions associated with microparticulate degeneration consistent with reactive particulate synovitis. Owing to the unacceptably high rate of secondary osteolysis, the authors recommend that use of this material for trapeziometacarpal or pantrapezial arthroplasty be abandoned.

Adult↗
PubMed1996

High plasma cholesterol, but low triglycerides and plaque-free arteries, in Mexican free-tailed bats.

Female mammals typically become hyperphagic from mid- to late pregnancy and during lactation. Mexican free-tailed bats, Tadarida brasiliensis mexicana, double their nightly food intake from late pregnancy to peak lactation and consume an insect diet that is exceptionally high in fat. During late pregnancy and throughout lactation, fasting plasma levels of cholesterol in this insectivorous bat are high (215 +/- 8 mg/dl) and are nearly 10-fold higher than in three species of Old World frugivorous bats. Fasting triglycerides were unexpectedly low in T. brasiliensis (25 +/- 2 mg/dl), despite evidence of high fat intake during nightly feeding bouts (postprandial cholesterol and triglycerides, 268 +/- 18 and 122 +/- 20 mg/dl, respectively). High-density lipoprotein (HDL) cholesterol levels were extraordinarily high (124 +/- 5 mg/dl) and unaffected by feeding. Low-density lipoprotein cholesterol levels were correspondingly low (86 +/- 7 mg/dl). This unusual plasma lipid profile was not associated with coronary or aortic atherosclerosis, nor was there evidence of hyperglycemia or hyperinsulinemia. A high-fat diet and high levels of cholesterol in T. brasiliensis are not correlated with cardiovascular disease or (possibly) insulin resistance. Among several possible factors that might account for these observations, nightly bouts of powered flight (commuting and foraging for food) may contribute to elevated HDL cholesterol, which may protect this species from developing atherosclerosis.

Animals↗
PubMed1996

Decreased reproductive effects from snakeweed (Gutierrezia microcephala) in Sprague-Dawley rats with increased dietary snakeweed consumption.

Sprague-Dawley rats have been used to study the pathogenesis and toxicokinetics of snakeweed (Gutierrezia microcephala and G sarothrae) toxicosis. Diets containing as little as 10% snakeweed (SW) will induce early embryonic toxicosis and abortion in Sprague-Dawley rats. The sc administration of safflower oil to inseminated female rats will provide protection/tolerance against SW embryotoxins. Two studies evaluated this embryotoxin protection. In the first study, an increase in daily consumption of SW resulted in increased embryo-fetal survival in the SW-containing diet+saline group from 0% in previous studies to 35%. In the second study, once again an increase in diet consumption was associated with 40% of the females in the SW-containing diet+saline group carrying litters to term.

Abortion, Induced↗
PubMed1995

Salvage of the failed Darrach procedure.

Six patients (5 post-traumatic, 1 rheumatoid) underwent a three-component reconstruction for correction of dorsal instability and radioulnar impingement following failure of a Darrach resection of the entire distal end of the ulna. The technique was devised to prevent simultaneous coronal and sagittal instability. The procedure used longitudinal intramedullary tenodesis of the extensor carpi ulnaris tendon, dorsal transfer of the pronator quadratus through the interosseous space, and temporary percutaneous pinning to maintain corrected distal radioulnar relationship. The were evaluated for 11 to 39 months (average, 20 months) following reconstruction. The preoperative wrist extension-flexion arc was preserved following surgery; there was a minimal loss of radial and ulnar deviation. The arc of forearm rotation increased 24 degrees to a range equal to 95% of the rotational arc of the opposite, unoperated wrist. Postoperative grip strength improved to an average value of 65 lb., two and one half times the preoperative value, representing 80% of the value for the opposite extremity. Four patients were able to return to their previous employment. All patients achieved pain-free forearm rotation and relief of their preoperative complaints of painful mechanical popping, clicking, and catching.

Adult↗
PubMed1995

Effects on reproduction in female offspring from Sprague-Dawley rats fed 10% snakeweed (Gutierrezia microcephala) throughout pregnancy and concurrent treatment with safflower oil.

Previous studies determined that safflower oil administration provided protection against the embryotoxicity seen following ingestion of 10% snakeweed (Gutierrezia microcephala) throughout pregnancy. Sixty-two young primiparous female rats born in those studies were paired with adult male Sprague-Dawley rats. After 4 d they were removed and carried their litters to term. Observations were made of the presence and extent of reproductive effects attributable to the 10% snakeweed exposure and differences in fecundity that were attributable to dosing with safflower oil or normal saline during the snakeweed exposure. Of the 62 rats, 50 carried litters to term and approximated the reproductive efficiency of normal primiparous Sprague-Dawley rats. There was no significant difference between the fecundity of females born to rats fed the 10% snakeweed and dosed with safflower oil, those born of rats fed snakeweed dosed with normal saline, or those fed a snakeweed-free diet and dosed with normal saline. Regardless of the diet or treatment administered, dams carrying their litters to parturition gave birth to healthy, normo-reproductive offspring. While the toxic principles in Gutierrezia species plants may act as estrogenic or anti-estrogenic compounds, they did not impair fertility in the female offspring of dosed rats.

Animals↗
PubMed1992

Subperiosteal osteoid osteoma of the hamate: a case report.

Osteoid osteoma is uncommon in the hand. The lesion can arise from either cortical or cancellous bone or subperiosteally. The latter localization is extremely rare in the hand, with only 4 reported cases in the English-language literature. Furthermore, characteristic radiographic findings of a central lucency surrounded by reactive sclerosis often emerge only late in the process, or not at all. Consequently, the diagnosis of osteoid osteoma of the hand can be delayed. We report a case of a subperiosteal osteoid osteoma of the hamate in which the diagnosis was delayed 2 years.

Adult↗