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Biomedical subjects

S S Block

Publications and source records attributed to S S Block.

15 recordsLinked to original sources
PubMed2005

Enhanced photocatalytic inactivation of bacterial spores on surfaces in air.

TiO(2) photocatalysis with ultraviolet (UV-A) light has proven to be a highly effective process for complete inactivation of airborne microbes. However, the overall efficiency of the technology needs to be improved to make it more attractive as a defense against bio-terrorism. The present research investigates the enhancement in the rate of destruction of bacterial spores on metal (aluminum) and fabric (polyester) substrates with metal (silver)-doped titanium dioxide and compares it to conventional photocatalysis (TiO(2) P25/+UV-A) and UV-A photolysis. Bacillus cereus bacterial spores were used as an index to demonstrate the enhanced disinfection efficiency. The results indicate complete inactivation of B. cereus spores with the enhanced photocatalyst. The enhanced spore destruction rate may be attributed to the highly oxidizing radicals generated by the doped TiO(2).

Air↗
PubMed2003

Nutritional and developmental regulation of plasma leptin in dairy cattle.

Leptin is thought to play a critical role in regulating energy metabolism throughout mammalian life. In growing dairy cattle, plasma leptin has been proposed as a partial mediator of the effects of nutrition on reproductive and mammary development. However, the developmental stage at which the plane of nutrition increases plasma leptin has not been well defined. Further, it is unknown whether the onset of puberty is affected by plasma leptin concentration in dairy cattle. To investigate these questions, two studies were performed. In the first study, neonatal calves were fed a milk replacer at levels supporting an average daily gain of 570 g/d (L) or 1210 g/d (H). Weekly blood samples were obtained until slaughter at 105 kg of body weight. Plasma leptin and adiposity remained constant in the L calves, but started to increase by the third week of age in the H calves. In the second study, 3- to 5-mo-old heifers were fed a total mixed ration supplemented with either calcium salts of palm fat or conjugated linoleic acids at levels sustaining an average daily gain of approximately 1.0 kg/d. Blood samples were obtained until the third postpubertal luteal phase. The fat source had no effects on growth parameters, body composition, age at puberty, or plasma leptin. Therefore, plasma leptin was reanalyzed as a function of age from start of treatment until slaughter. The plasma concentration of leptin remained nearly constant at 2.3 ng/ml until 1 yr of age, when a rise in plasma leptin became obvious. Puberty occurred with equal frequency either around 1 yr of age when plasma leptin was nearly constant or later when leptin was rising rapidly. We conclude that plasma leptin is regulated by nutrition in early postnatal life, but that a sudden increase in plasma leptin is not required for the onset of puberty in dairy cattle.

Aging↗
PubMed2003

Demonstration of a role for insulin in the regulation of leptin in lactating dairy cows.

In lactating dairy cows, the onset of negative net energy balance (EB) at parturition causes a reduction in plasma leptin and is also associated with increased concentration of growth hormone (GH) and decreased concentration of insulin. These observations raise the possibility that opposite changes in plasma insulin and GH are partly responsible for reduced plasma leptin. To test this hypothesis, we first examined the effects of undernutrition without the confounding influence of parturition by using late lactating dairy cows fed 120% of their nutrient requirements or restricted to 33% of maintenance requirements. Plasma leptin was reduced within 24 h of feed restriction, and was associated with increased plasma GH and decreased plasma insulin. Complete food deprivation for 48 h caused similar changes in the plasma concentration of leptin. To determine if an elevation in GH is responsible for the fall in plasma leptin, dairy cows were treated with excipient or bovine somatotropin in early lactation or in late lactation. Growth hormone treatment had no significant effect on plasma leptin irrespective of stage of lactation. Finally, the effects of insulin were studied by performing euglycemic hyperinsulinemic clamps in mid-lactating dairy cows. After 96 h of hyperinsulinemia, plasma leptin was increased significantly. These data indicate that insulin regulates plasma leptin in lactating dairy cows. They also suggest that, in undernourished lactating dairy cows, reduced plasma insulin could account for a portion of the decline in plasma leptin but that elevated plasma GH is unlikely to have a major effect.

Animal Nutritional Physiological Phenomena↗
PubMed2001

Decreased concentration of plasma leptin in periparturient dairy cows is caused by negative energy balance.

Dairy cows suffer from an intense energy deficit at parturition due to the onset of copious milk synthesis and depressed appetite. Despite this deficit, maternal metabolism is almost completely devoted to the support of mammary metabolism. Evidence from rodents suggests that, during periods of nutritional insufficiency, a reduction in plasma leptin serves to co-ordinate energy metabolism. As an initial step to determine if leptin plays this role in periparturient dairy cows, changes in the plasma concentration of leptin were measured during the period from 35 days before to 56 days after parturition. The plasma concentration of leptin was reduced by approximately 50% after parturition and remained depressed during lactation despite a gradual improvement in energy balance; corresponding changes occurred in the abundance of leptin mRNA in white adipose tissue. To determine whether negative energy balance caused this reduction in circulating leptin, cows were either milked or not milked after parturition. Absence of milk removal eliminated the energy deficit of early lactation, and doubled the plasma concentration of leptin. The plasma concentration of leptin was positively correlated with plasma concentrations of insulin and glucose, and negatively correlated with plasma concentrations of growth hormone and non-esterified fatty acids. In conclusion, the energy deficit of periparturient cows causes a sustained reduction in plasma leptin. This reduction could benefit early lactating dairy cows by promoting a faster increase in feed intake and by diverting energy from non-vital functions such as reproduction.

Adipose Tissue↗
PubMed2000

Cognitive and visual processing skills and their relationship to mutation size in full and premutation female fragile X carriers.

BACKGROUND: The fragile X gene contains an unstable trinucleotide (CGG) repeat that expands as it is passed from female carriers to the affected offspring. Obligate female carriers may have a premutation or full mutation genotype. METHODS: In this study, fragile X premutation and full mutation female carriers were compared on three tasks of visual processing and cognitive skills. RESULTS: In each case, there were significant differences between premutation and full mutation carriers on a number of the subtests or the full test scores. Specifically, full mutation female carriers performed more poorly in visual-motor processing and analysis-synthesis on the Woodcock-Johnson Psycho-Educational Battery-Revised, The Developmental Test of Visual Motor Integration, and on five of the seven subtests of the Test of Visual-Perceptual Skills. Regression analyses revealed significant negative correlations between mutation size and cognitive ability. CONCLUSIONS: These findings have implications in educational planning decisions for full mutation carriers who may present with specific cognitive deficits.

Adult↗
PubMed1999

Hand-eye dominance in a population with mental handicaps: prevalence and a comparison of methods.

BACKGROUND: The primary purpose of this study was to investigate hand-eye dominance in a population with mental handicaps and how the distribution compared with the general population. In addition, this study investigated the correlation between two methods of hand-eye dominance testing. METHODS: Two methods were used to determine eye dominance: the hole-in-the-hand method and the eye dominance wand. Hand dominance was determined by the subject's choice of accepting hand. The sample was comprised of a population of 421 athletes participating in the 1997 Special Olympic Games in Toronto. All subjects unable to give a dominant hand or unable to perform either of the ocular dominance tests were eliminated from analysis. Athletes who demonstrated strabismus or a difference in visual acuity between the two eyes of greater than 1 line were separated in the analysis, reducing the sample population to 191. RESULTS: The hole-in-the-hand method of eye dominance showed that 40.3% of this population exhibited crossed dominance. The eye dominance wand found crossed dominance in 36.6% of this population. The eye dominance wand demonstrated moderate agreement with the hole-in-the-hand method; however, there was some crossover of eye dominance between tests, when the tests were compared on a case-by-case basis. CONCLUSIONS: The prevalence rate of this population of persons with mental handicaps agrees with the prevalence rates found by Robison et al., in which 41% of a general nonhandicapped population demonstrated crossed dominance. The results suggest that persons with mental handicaps have prevalence rates of crossed dominance similar to those found in the general population.

Adolescent↗
PubMed1999

Testability of a color vision screening test in a population with mental retardation.

PURPOSE: The purpose of this study was to determine the testability of the "Co or Vision Testing Made Easy" color vision test, marketed as a screening test for young children, in a population of individuals with mental retardation. The test uses simple geometric figures that are easily identified. Previously, the test has demonstrated validity as a measure of color deficiency. METHODS: The test was presented to Special Olympic athletes, who are individuals with mental retardation or significant developmental delay, at four sites: the 1997 World Winter Games in Toronto, Canada; the Texas Summer Games in Houston, Texas; the Massachusetts Summer Games in Boston, Massachusetts; and Regional European Swim Competition in Seville, Spain. The criteria for passing was 8 correct responses on the first trial or 9 of 9 on the second attempt. RESULTS: Testability in Toronto, Canada; Houston, Texas; and Seville, Spain was high--95.5%, 98.7%, and 95.7%, respectively. Testability, however, dropped to 78.8% during the Boston, Massachusetts screening. There was no apparent difference in the testing environment that would account for the difference. The overall rate of testability was 93.2% for the 1078 athletes screened. The frequency of males identified as color deficient was similar to that expected in the general population; only two females (in Spain) failed the color vision screening. CONCLUSIONS: The "Color Vision Testing Made Easy" color vision test was successfully completed by a very high percentage of Special Olympics athletes. These results suggest that this test is useful in screening this population for color deficiencies, and that the prevalence of color vision deficiencies is approximately the same in individuals with mental retardation as in the general population.

Adolescent↗
PubMed1998

All-trans beta-carotene is absorbed preferentially to 9-cis beta-carotene, but the latter accumulates in the tissues of domestic ferrets (Mustela putorius puro).

The algae Dunaliella bardawil and Dunaliella salina naturally contain large concentrations of all-trans and 9-cis beta-carotene (betaC). The purpose of this study was to compare the relative serum and tissue accumulation of all-trans and 9-cis betaC in ferrets fed different ratios of all-trans/9-cis betaC derived from two commercial sources, D. bardawil or D. salina (Betatene). Male ferrets (7 wk old) were fed carotene-free, pelleted diets for 27 d. Beginning on d 18, groups of ferrets (n = 6 or 7) received daily, one of six oral supplements varying in ratios of 9-cis and all-trans betaC mixed with approximately 1.0mL of Ensure. Four supplements containing 5.2-8.3 micromol total betaC were prepared from a 20% Betatene preparation, D. bardawil, a high-cis Betatene preparation, and Betatene further enriched in 9-cis betaC with all-trans betaC/9-cis betaC ratios of 2.2, 1.5, 0.6 and 0.4, respectively. Two control supplements, high and low betaC, were prepared from commercial betaC beadlets. The high control supplement had an all-trans/9-cis ratio of 19.0, whereas 9-cis betaC was not detected in the low supplement. On d 27, serum and tissues were obtained for HPLC analysis of betaC and its isomers. Analysis of livers showed that all-trans betaC was the primary isomer present, but 9-cis and other isomers were also detected in all groups. The hepatic all-trans/9-cis ratios were 5.9, 4.9, 2.5, 1.4, 52.2 and47.5, respectively, for the groups listed above. Lower amounts of all-trans and 9-cis betaC were found in kidneys compared with the liver, but ratios of all-trans/9-cis were not different among groups. Only trace amounts of 9-cis betaC were found in serum. These results demonstrate that the algae D. bardawil and D. salina provide a bioavailable source of betaC isomers, but, as in humans, absorption of 9-cis betaC is poor and any 9-cis betaC absorbed is apparently cleared by the liver.

Absorption↗
PubMed1997

Visual anomalies in young children exposed to cocaine.

PURPOSE: The number of children exposed to cocaine in utero each year is increasing. Recent reports suggest significant visual anomalies in infants prenatally exposed to cocaine. The purpose of this retrospective study was to determine if children exposed prenatally to cocaine were at a greater risk for visual abnormalities, such as strabismus and significant refractive errors. METHODS: This pilot study was conducted at two sites, an outpatient clinic and a hospital-based practice. Consecutive files from January to July, 1993, of 79 children (aged 4 months to 94 months); who were identified by case history or meconium analysis information as being exposed to cocaine in utero, were reviewed. Fifty-five children met the inclusion criteria for the study. In addition, a control group of 100 pediatric patients were randomly selected from the pediatric patients seen at the outpatient clinical site. RESULTS: Of the 30 children from the Illinois Eye Institute (IEI) and the 25 children from The Children's Hospital (TCH), spherical refractive errors in the right eye ranged from +6.50 to -12.50 D. The median refractive errors were +0.75 and +0.50 D, respectively. No statistical difference was found in spherical refractive error, astigmatism, or anisometropia between the cocaine-exposed cohorts and the control group (N = 100). Strabismus was found in 15/55 (27%) of the children in the cocaine-exposed group. There was a statistically significant difference in the prevalence of strabismus between the cocaine-exposed group and the control group. Further analysis revealed that full birthweight (> 2500 g) children prenatally exposed to cocaine were at a greater risk for strabismus as compared to the full birthweight control group. Ocular abnormalities were rare, but included optic nerve atrophy and retinopathy of prematurity. CONCLUSIONS: These data suggest cocaine exposure during pregnancy may place a child at risk for conditions that may negatively impact the visual system, specifically strabismus.

Abnormalities, Drug-Induced↗
PubMed1997

Vision profile of the athletes of the 1995 Special Olympics World Summer Games.

BACKGROUND: Special Olympics were organized in 1968 by Eunice Shriver as a program of physical fitness for individuals with mental handicaps. Numerous epidemiologic studies report an increase in visual problems in this population. METHODS: A comprehensive vision screening was conducted at the 1995 Special Olympic World Summer Games to identify the prevalence of visual anomalies in this select group. Testing included visual acuity, refractive error, ocular motor skills, stereopsis, color vision, contrast sensitivity, eye-hand coordination, eye-foot coordination, and an ocular health evaluation. RESULTS: Nine hundred five special athletes, ranging in age from 8 to 58 years, participated in the screening. More than 65% of the participants had not received eye care for more than 3 years. The most commonly reported symptom was difficulty in seeing. Other ocular health problems included refractive errors, poor distance monocular acuity, and strabismus. CONCLUSION: The results of the study indicate that Special Olympians have a high prevalence of vision anomalies that may go undetected. This population demonstrates a high prevalence of refractive errors, decreased visual acuity, ocular health problems, and strabismus. In addition, based on the number of individuals who have not received eye care within the last year, there is a need to increase the availability of vision care to these and other people with mental retardation.

Adolescent↗
PubMed1996

Analysis of child abuse and neglect.

Child abuse and neglect is a problem that has existed for many years. Federal guidelines and state laws make it necessary for the optometrist to be aware of the definitions that describe abuse and neglect. In addition, it is necessary to review the characteristics of the child and caregiver to ascertain who may be at risk. Physical signs, such as specific types of fractures, burns, scalds, and bruises, should act as a key to suspected abuse. The most frequent ocular sign of abuse is intraocular hemorrhage. Other ocular manifestations include periorbital edema, ecchymosis, and retinal detachment, to name a few. Sexual abuse is also of concern. If a sexually transmitted disease is present in a young child, abuse should not be ruled out. It is the responsibility of the health care provider to report any suspected episodes of child abuse and neglect.

Child↗
PubMed1990

Normative contrast sensitivity data for young children.

Contrast sensitivity (CS) was measured in children ages 3 to 7 years using the Vistech Contrast Sensitivity distance chart (VCTS 6500). The purpose of the study was to determine how effectively the technique could be used with young children and to establish normative data for this age group. Of 286 children participating in a vision screening, the contrast sensitivity function (CSF) was measurable on 241 (84%) under binocular conditions and 229 (80%) under both binocular and monocular conditions. The 219 binocular CSF's and 208 monocular CSF's obtained from visually normal children were used to establish normative data and then compared to similar data from 50 visually normal young adults. The results indicated that there is an effect of age between 3 and 7 years, children are significantly less sensitive than adults, and adult-like levels of CS are not yet reached at 7 years of age. In addition, although the children's mean contrast thresholds fell within the norms provided with the VCTS 6500, the variability in the children's CSF's precludes using the Vistech data for diagnostic purposes in the young. The normative data are presented to assist the clinician in evaluating CS in young children when using the VCTS 6500.

Adult↗