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Biomedical subjects

K Tucker

Publications and source records attributed to K Tucker.

At least 55 records · Page 3Linked to original sources
PubMed1998

Effect of storage temperature on sperm cryopreservation.

OBJECTIVE: To evaluate the influence of cryopreservation temperature on human sperm motility and morphology. DESIGN: Controlled study, investigator was blinded to the type of cryopreservation. SETTING: University-based andrology laboratory. PATIENT(S): Sixteen semen samples with normal motility and sperm count from men after a fertility work up. INTERVENTION(S): Semen aliquots were either stored in a mechanical freezer at -70 degrees C or in liquid nitrogen at -196 degrees C for 7 days or 3 months. Test yolk buffer was used as a cryoprotectant. With use of a programmable freezing unit, all samples were cooled at a controlled rate. MAIN OUTCOME MEASURE(S): Sperm motility and morphology. RESULT(S): After 7 days of cryopreservation, there was a greater decrease in sperm motility among specimens maintained at -70 degrees C than among those maintained at -196 degrees C (47% versus 39% decrease). The difference in sperm motility was even greater after 3 months of cryopreservation (72% versus 39% decrease). No difference in postthaw sperm morphology was detected among sperm preserved at -70 degrees C versus -196 degrees C. CONCLUSION(S): Sperm cryopreservation at -196 degrees C is superior to cryopreservation at -70 degrees C. Sperm can be stored at -70 degrees C for a short period of time with a relatively modest loss of motility.

Cryopreservation↗
PubMed1998

Human enamel as a substrate for in vitro acid dissolution studies: influence of tooth surface and morphology.

The variation in susceptibility of enamel to acid dissolution has been quantitatively assessed in vitro by examination of different surfaces of both maxillary and mandibular teeth of different morphology obtained from a pool of sound human teeth. The lingual/palatal surfaces of all teeth showed greater susceptibility to acid dissolution than the corresponding labial/buccal surfaces. The palatal surface of the maxillary teeth appeared more susceptible to acid than the lingual surface of the corresponding teeth in the mandible. The palatal surfaces of the maxillary teeth showed least variation in acid susceptibility, whilst the lingual surfaces of mandibular teeth and buccal/labial surfaces of teeth from both jaws showed much more variation between teeth of different morphology. These differences in susceptibility to acid dissolution probably reflect both developmental differences and post-eruptive changes in enamel and may contribute to the clinical presentation of dental disease. Importantly, the data indicates that careful selection of teeth for in vitro study of enamel dissolution processes is essential to minimise inter-sample variation. For such purposes, the palatal surface of the maxillary teeth appears to be most suitable.

Adult↗
PubMed1997

Cancer in the family. Guidelines for general practice.

In the past 2 years the major genes for inherited breast-ovarian cancer, bowel cancer and melanoma have been identified. Relatives of cancer patients frequently perceive themselves to be at high risk of cancer. Appropriate assessment of the family history permits the identification of those at particularly high risk who may benefit from special programs of prevention, screening and surveillance. In certain cases, genetic testing and prophylactic surgery may be indicated. This article looks at the general issues involved. A follow-up article next month will look at specific diseases.

Genetic Testing↗
PubMed1996

Relations of vitamin B-12, vitamin B-6, folate, and homocysteine to cognitive performance in the Normative Aging Study.

We investigated the relations between plasma concentrations of homocysteine and vitamins B-12 and B-6 and folate, and scores from a battery of cognitive tests for 70 male subjects, aged 54-81 y, in the Normative Aging Study. Lower concentrations of vitamin B-12 (P=0.04) and folate (P=0.003) and higher concentrations of homocysteine (P=0.0009 ) were associated with poorer spatial copying skills. Plasma homocysteine was a stronger predictor of spatial copying performance than either vitamin B-12 or folate. The association of homocysteine with spatial copying performance was not explained by clinical diagnoses of vascular disease. Higher concentrations of vitamin B-6 were related to better performance on two measures of memory (P=0.03 and P=0.05). The results suggest that vitamins (and homocysteine) may have differential effects on cognitive abilities. Individual vitamins and homocysteine should be explored further as determinants of patterns of cognitive impairment.

Aged↗
PubMed1996

Evaluation of four methods for determining energy intake in young and older women: comparison with doubly labeled water measurements of total energy expenditure.

The accuracy and precision of four different food intake assessment methods were evaluated in young and older women by comparing reported energy intakes with doubly labeled water measurements total energy expenditure (TEE). A study lasting 8 d was conducted in 10 young women aged 25.2+/-1.1 y (-x+/-SEM) and in 10 older women aged 74.0+/-1.4 y. Free-living TEE was measured over 7 d and food consumption was determined from weighed food intake data (7 d), a 24-h food recall (in duplicate), and two different food-frequency questionnaires [Fred Hutchinson Cancer Research Center (FHCRC)/Block and Willett, both in duplicate]. In addition, body composition was determined by using hydrodensitometry, and strenuous physical activity and the extent of dietary restraint were determined by questionnaire. In young women, 24-h recall gave mean energy intakes that were closest to measures of TEE (-0.34+/-3.71 MJ/d compared with TEE, P=0.178), and energy intakes by food-frequency questionnaires were the only intake data that correlated significantly with individual values for TEE (P<0.05). In older women, food-frequency questionnaires gave mean energy intakes that were closest to measured TEE (+0.53+/-2.95 MJ/d with the Willett questionnaire and -1.19+/-3.02 MJ/d with FHCRC/Block questionnaire). No energy intake data from this group correlated significantly with values for TEE. The 7-d weighed dietary intakes were significantly lower than measured TEE in both young and older women (-2.0 MJ/d in young and older women combined, P<0.001), and did not correlate significantly with values for TEE, although they did most closely mirror the mean difference in TEE between the young and older women (2.30 MJ/d for TEE and 2.11 MJ/d for 7-d weighed intake). These data suggest that none of the methods studied gave accurate estimates of the usual energy requirements of individual subjects. In addition, the results suggest that for some types of studies, simple methods for assessing group mean dietary intake may actually give more accurate information than weighed dietary intakes.

Adult↗
PubMed1996

The use of epidemiologic approaches and meta-analysis to determine mineral element requirements.

With a new focus on long-term health effects of nutrient intake as well as the traditional concerns of preventing deficiency and maintaining tissue saturation, epidemiologic studies which identify diet and health relationships have become important to debates on defining nutrient requirements. Epidemiologic studies include descriptive surveys, case-control studies, cohort studies, and intervention studies. National dietary intake survey data have always played a role in defining intake amounts which are feasible and which are associated with no clearly apparent health problem. A growing number of large epidemiologic cohort studies have provided new evidence of preventive effects of specific nutrients on chronic diseases. The question of how that information should be used in setting requirements is still unresolved. Because one epidemiologic study alone cannot prove a causal relationship, and because small studies often lack sufficient power to clearly establish statistical significance, meta-analysis is sometimes used to combine results from many studies to obtain an overall quantitative result. It has been most effectively used with sets of clinical trials. Meta-analysis of multiple observational studies is usually difficult because of variations in design, methodology of data collection and form of the variables; its use has been seriously challenged. Careful review of the totality of epidemiologic studies completed on specific nutrient and health or functional outcome is important to defining future research priorities and designs, and can inform the definition of nutrient requirements when used carefully and in conjunction with the wider body of scientific evidence.

Diet↗
PubMed1996

Overweight and leanness in adulthood: prospective study of male participants in the Normative Aging Study.

OBJECTIVE: Our objective was to examine the stability of body habitus over 15 years in Boston area adult males enrolled in the Normative Aging Study (NAS) and to examine stability as a function of initial leanness or obesity, age and reported body habitus at age 18. DESIGN: Prospective observational study of anthropometric/clinical measures initiated in 1961-1970, follow-up examinations at regular three and five year intervals. Subjects with complete data at entry, 5, 10 and 15 years. SUBJECTS: The 2280 Boston area subjects were aged 21-80 years (mean = 42 y) at entry. A subset (n = 350) with complete data for weight (WT) and height (HT) at four points over 15 years provided estimates of body habitus continuity. The prevalence of obesity and age of those studied were comparable to the complete sample of enrolled men (n = 1403) with any missing follow-up measures. MEASUREMENTS: Obesity was defined as body mass index (BMI) (weight in kg/height in m2) > or = 27.8 and leanness as BMI < 24.0. Three age categories at baseline (young = 25-39 y; middle = 40-49 y and old = 50-74 y) were used to examine secular and longitudinal changes. Obesity prevalence rates during late adolescence, based on self-reported weights at age 18, were compared with measured prevalence rates at entry and follow-up. Individual changes in BMI over time for each subject were estimated by linear regression and were combined to measure change in age and BMI groups. RESULTS: Weights and BMI at entry were highly correlated with 18 year values and 15 year follow-up values. New cases of obesity, defined on the basis of BMI, increased over time while the numbers of subjects classified as lean and intermediate decreased. Among oldest subjects both the lean and obese had slight but significant decreases in mean BMI. Among the lean, only the young showed consistent increments. DISCUSSION: Our results suggest consistency in body habitus among young and middle-aged obese subjects. There was little evidence of long-term reduction. In agreement with previous observations, the current findings of long-term duration in obesity suggest that preventive efforts should be focused on early years.

Adult↗
PubMed1995

Body habitus changes among adult males from the normative aging study: relations to aging, smoking history and alcohol intake.

The Normative Aging Study (NAS) recruited 2280 Boston area healthy males aged 21 to 80 in 1961 through 1970. Clinical exams have continued at 3- to 5-year intervals. Obesity was not an exclusion criterion. Stability in weight and body habitus among 867 adult participants in the NAS was evaluated at 5- and 15-year follow-ups. At study entry, age was linearly related to central adiposity [abdominal circumference (AC) and ratio of AC/Hip Breadth (HB)] throughout the entire age range (30 to 78 years) and linearly and quadratically related to weight (WT) and Body Mass Index (BMI) (kg/m2) with maximal values at age 50. Over 15 years, changes in adiposity were strongly related to age; the greatest increases were among those initially 30 to 44 years of age with decrements in several adiposity measures (BMI, AC) only among the oldest subjects (60+ at entry); significant quadratic effects of age for BMI (p < .001), WT (p < .02) and AC (p < .01). There were major secular differences; men born later were heavier and fatter at the same ages as men born earlier. Men who gained (> 1 BMI) were younger while men who lost (> 1 BMI) had greater initial central adiposity than others. Smoking cessation was independently associated with increments in both central and peripheral adiposity. Moderate alcohol intake was associated with lower gains in AC/HB ratios at 15 years compared with little or high consumption. In general, aging was associated with trends towards central adiposity which tended to plateau or decrease at the oldest ages.

Adult↗
PubMed1995

Segmental analysis of resting echocardiographic function and stress scintigraphic perfusion: implications for myocardial viability.

In 73 patients with coronary artery disease, we performed segmental analysis of resting two-dimensional echocardiography and stress thallium-201 single photon emission computed tomographic scintigraphy with 24-hour delayed imaging to test the hypotheses that (1) combined analysis of stress thallium-201 scintigraphy (with 24-hour redistribution) and echocardiography provides an evaluation of the viability of most myocardial segments; and (2) the severity of the scintigraphic perfusion abnormality in a given segment is equivalent to the severity of its echocardiographically determined functional impairment. Scintigraphy showed 14% of the 1168 segments analyzed to have fixed severe defects. Echocardiography showed 11% of the 1070 segments analyzed to be akinetic or dyskinetic. However, with combined analysis, only 62 (5%) segments showed no evidence of viability by either imaging technique. We conclude that in this group of patients, 95% of segments have evidence of viability by one of these two conventional imaging techniques.

Aged↗
PubMed1995

Assessment of dietary phylloquinone intake and vitamin K status in postmenopausal women.

OBJECTIVE: To examine the relationship between dietary phylloquinone intake and vitamin K status of postmenopausal Caucasian women. DESIGN: Cross-sectional study, in which dietary intake was estimated using weighed record techniques and vitamin K status was measured by a single plasma phylloquinone concentration and 24-h urinary gamma-carboxyglutamic acid (Gla) excretion. SETTING: The metabolic research unit at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA. SUBJECTS: 402 healthy postmenopausal Caucasian women who were participating in a randomized trial to determine the effect of calcium supplementation on bone loss. Of the original group, 362 had complete weighed diet records, 358 had corresponding plasma phylloquinone concentrations, and 346 had corresponding urinary Gla measurements. RESULTS: There was a significant correlation (r = 0.13, P = 0.01) between total dietary intake of phylloquinone (geometric mean = 89 micrograms/day) and plasma phylloquinone levels (mean = 1.12 nmol/l). Dietary intake was neither correlated with urinary Gla excretion (mean = 4.0 mumol/mmol creatinine) nor did it vary by season. The ratio of intra- to interindividual variance in phylloquinone intake was 2.6, from which it was estimated that 5 days of independent recording is necessary to estimate true usual dietary intake, assuming a correlation of 0.8. CONCLUSIONS: A weighed record has the potential to be a reliable method for estimating dietary intakes of vitamin K which relate to plasma phylloquinone levels used as an indicator of vitamin K status in postmenopausal Caucasian women.

1-Carboxyglutamic Acid↗
PubMed1994

Eradication of minimal disease in severe combined immunodeficient mice with disseminated Daudi lymphoma using chemotherapy and an immunotoxin cocktail.

Severe combined immunodeficient (SCID) mice injected intravenously with a human Burkitt's lymphoma cell line (Daudi) develop disseminated lymphoma (SCID/Daudi), which is fatal in 100% of the mice. Early treatment of these mice with either an immunotoxin (IT) cocktail (consisting of anti-CD19-ricin A chain plus anti-CD22-ricin A chain) or chemotherapy significantly prolonged survival but was not curative. Combination therapy with the IT cocktail and any one of three chemotherapeutic drugs (doxorubicin, cytoxan, or camptothecin) cured the mice. Cure was demonstrated by both histopathologic examination of treated mice and, more importantly, by adoptive transfer of cells from organs of the cured mice to naive SCID mice where 100 tumor cells would have caused disease in the recipients. These results provide a strong rationale for combining IT therapy with conventional chemotherapy in the treatment of B-cell neoplasia.

Animals↗
PubMed1994

Anti-CD19 inhibits the growth of human B-cell tumor lines in vitro and of Daudi cells in SCID mice by inducing cell cycle arrest.

In this report, we extend our previous findings that IgG or F(ab')2 fragments of HD37 anti-CD19 antibody (Ab) in combination with the immunotoxin (IT), RFB4-anti-CD22-deglycosylated ricin A chain (dgA) (but neither reagent alone), prolonged the survival of SCID mice with disseminated human Daudi lymphoma (SCID/Daudi mice) to 1 year at which time they still remained tumor-free. We explored the mechanisms by which the HD37 Ab exerts antitumor activity in vivo by studying its activity in vitro. We found that it has antiproliferative activity (IC50 = 5.2 - 9.8 x 10(-7) mol/L) on three CD19+ Burkitt's lymphoma cell lines (Daudi, Raji, and Namalwa) but not on a weakly CD19-positive (CD19lo) pre-B cell tumor (Nalm-6). The inhibitory effect was manifested by cell cycle arrest, but not apoptosis. Results using three additional anti-CD19 Abs, suggest that the affinity of the antibody and possibly the epitope which it recognizes may effect its capacity to transmit a signal that induces cell cycle arrest. Hence, therapeutically useful Abs may exert anti-tumor activity by a variety of mechanisms, each of which should be evaluated before undertaking clinical trials in humans.

Animals↗
PubMed1994

Household headship and child nutrition: a case study in western Kenya.

The effect of female household headship on child nutrition has been hypothesized by some to be negative, based on the assumption that mothers alone will be poorer and will have greater demands on their time and resources. On the other hand, there is some evidence in Kenya that the nutritional status of children of female heads may be better than that of children of male heads, suggesting that when women have more control over resources, more goes to the children. In Kenya, de facto female headship is common due to male labor migration. This study examines the relationship between child nutrition and de facto female vs male household headship in western Kenya through the examination of family income and decision making patterns. Women in male-headed households had greater financial responsibility for household maintenance. Female heads assumed more farming responsibilities and had higher remittances from husbands. Husbands of female heads purchased food and other goods in the city for use by the household. Male headed households produced more food crops and used a larger proportion of them for home consumption. In this study, children of female heads consumed a greater variety of foods. Despite a greater prevalence of stunting, there was a lower prevalence of low weight for age among children of female heads. However, in statistical analyses, headship did not relate significantly to nutritional intake or status. In attempting to understand the possible factors influencing the relationship between headship and nutritional status, we found trade-offs in the ways families were coping, which appeared to balance some of the negative and positive effects of each situation.

Child Nutritional Physiological Phenomena↗
PubMed1993

Food shortages and an epidemic of optic and peripheral neuropathy in Cuba.

From late 1991 to mid-1993, cases of optic neuropathy of unknown etiology, which first appeared in unusual numbers in a western province of Cuba, spread and multiplied throughout the island. The dominant symptoms changed, becoming increasingly those of peripheral neuropathy. Incidence rates peaked in April 1993. An estimated 50,000 cases were reported. The majority were adult men and women (aged about 25-65), with comparatively few children or elderly people being affected. The cause has yet to be delineated. However, food shortages and radical changes in diet resulting from the longstanding US trade embargo and the recent loss of Eastern Europe as Cuba's trading partner have compromised nutritional status, especially B-vitamin sufficiency, and appear to be related to the neuropathic illnesses. In April 1993, the Cuban government began distributing vitamin supplements to every citizen. Causal hypotheses include tobacco-alcohol or "nutritional" amblyopia; cyanide toxicity from cassava; toxic legumes introduced as supplements to scarce flour; other toxins, for example pesticides, or a "blue mold" on tobacco; enterovirus; and a hereditary enzyme deficiency in affected persons. None of these factors appears to be present in all cases, but it is generally believed that an interaction of some toxin or toxins, in combination with nutritional deficiency, is likely to be the major cause.

Adult↗
PubMed1993

Intragastric glucose but not fructose conditions robust flavor preferences in rats.

Prior work indicates that glucose and fructose differ in their postingestive reinforcing effects. The present study investigated this phenomenon by training rats to associate the intake of flavored water with intragastric (IG) infusions of 16% sugar solutions. In experiment 1, rats had one flavor [conditional stimulus (CS)] paired with IG sugar infusions (CS+; e.g., cherry) and another flavor paired with IG water (CS-; e.g., grape) 23 h/day; Chow was available ad libitum. In subsequent choice tests, rats infused with glucose displayed a strong preference (89%) for the CS+ flavor, whereas rats infused with fructose showed only a small and nonreliable CS+ flavor preference (62%). When next trained to associate one flavor (e.g., orange) with IG glucose and another flavor (e.g., strawberry) with IG fructose, rats in both groups developed a significant preference (81%) for the glucose-paired flavor. In experiment 2, food-deprived rats were trained 2 h/day to associate a CS+ flavor with IG sugar and a CS- flavor with IG water infusions. The glucose-reinforced rats displayed a near-total preference (95%) for the CS+ flavor, whereas fructose-reinforced rats showed a much smaller CS+ preference (67%). The preference findings indicate that the postingestive consequences of glucose are much more reinforcing than those of fructose. It appears that food conditioning is mediated by chemospecific actions of nutrients rather than their general satiating or energy repleting effects.

Animals↗
PubMed1993

Transesophageal echocardiography during cardiopulmonary resuscitation.

Transesophageal echocardiography is ideally suited for imaging during CPR because high-quality images can be obtained immediately and continuously without interruption of cardiac compression and ventilation. Use of TEE during CPR is increasing to help monitor resuscitative efforts, for diagnosis, to assist in understanding the physiology of blood flow, and for evaluation of new methods of CPR.

Cardiopulmonary Resuscitation↗