Biomedical subjects

S Hendricks

Publications and source records attributed to S Hendricks.

At least 19 recordsLinked to original sources

PubMed2004

Bone conduction auditory brainstem responses in infants.

The contribution of air conduction auditory brainstem response (AC-ABR) testing in the paediatric population is widely accepted in clinical audiology. However, this does not allow for differentiation between conductive and sensorineural hearing loss. The purpose of this paper is to review the role of bone conduction auditory brainstem responses (BC-ABR). It is argued that despite such technical difficulties as a narrow dynamic range, masking dilemmas, stimulus artifact and low frequency underestimation of hearing loss, considerable evidence exists to suggest that BC-ABR testing provides an important contribution in the accurate assessment of hearing loss in infants. Modification of the BC-ABR protocol is discussed and the technical difficulties that may arise are addressed, permitting BC-ABR to be used as a tool in the differential diagnosis between conductive and sensorineural hearing. Two relevant case studies are presented to highlight the growing importance of appropriate management in early identification of hearing loss. It can be concluded that BC-ABR should be adopted as a routine clinical diagnostic tool.

Bone Conduction↗

PubMed2000

Occupational injuries in the mining industry and their association with statewide cold ambient temperatures in the USA.

BACKGROUND: Relatively few occupational epidemiological studies have been conducted concerning the association between cold ambient temperatures and cold exposure injuries, and fewer still of traumatic occupational injuries and cold ambient temperatures. METHODS: The association of ambient temperature and wind data from the National Climatic Data Center with injury data from mines reported to the Mine Safety and Health Administration (MSHA) was evaluated over a 6 year period from 1985-1990; 72,716 injuries from the seven states with the most numerous injuries were included. Temperature and wind data from each state's metropolitan weather stations were averaged for each day of the 6 year period. A weighted linear regression tested the relationship of ungrouped daily temperature and injury rate for all injury classes. For cold exposure injuries and fall injuries, relative incidence rates for grouped temperature data were fit with Poisson regression. RESULTS: As temperatures decreased, injury rates increased for both cold exposure injuries and slip and fall injuries. The association of slip and fall injuries with temperature was inverse but not strictly linear. The strongest association appeared with temperatures 29 degrees F and below. The injury rates for other accident categories increased with increasing ambient temperatures. CONCLUSIONS: This study suggests that statewide average ambient temperature reflects the expected association between the thermal environment and cold exposure injuries for workers, but more importantly, documents an association between ambient temperatures and occupational slip and fall injuries.

Accidental Falls↗

PubMed2000

Short-wavelength automated perimetry and capillary density in early diabetic maculopathy.

PURPOSE: To correlate short-wavelength cone-mediated sensitivity (SWS) assessed by blue-on-yellow perimetry with alterations of the perifoveal vascular bed in early diabetic maculopathy. METHODS: Thirty-one patients (21 M, 10 F; mean age, 35 +/- 12 years; no lens opacities) with no clinically significant macular edema were included in this study. All patients underwent short-wavelength automated perimetry (SWAP) and conventional white-on-white perimetry (Humphrey, 10-2). In digitized video fluorescein angiograms (Scanning Laser Ophthalmoscope), the size of the foveal avascular zone (FAZ) and the mean perifoveal intercapillary area (PIA) as a measure of capillary density were quantified interactively. RESULTS: Mean thresholds of SWAP were significantly correlated with increasing size of FAZ (r = -0.51, P = 0.003) and PIA (r = -0.47, P = 0.01), whereas visual acuity expressed by log MAR (FAZ: r = 0.15, P = 0.41; PIA: r = 0.06, P = 0.76) and mean thresholds assessed with white-on-white perimetry (FAZ: r = -0.25, P = 0.20; PIA: r = -0.31, P = 0.14) were unrelated to diabetic changes of the perifoveal capillary network. CONCLUSIONS: The alterations of the perifoveal network are related to selective disturbances of visual function as measured by blue-on-yellow-perimetry. SWAP may act as an early detector of visual function loss in early diabetic maculopathy and serve as a helpful technique to predict early ischemic damage of the macula and to monitor therapy.

Adult↗

PubMed1999

Design of infection-resistant antibiotic-releasing polymers: I. Fabrication and formulation.

Biomaterials-related infections are often observed with prosthetic implants and in many cases result in the failure of the devices. To design a biomedically useful polymer that is intrinsically infection-resistant, we have developed a ciprofloxacin-loaded polyurethane (PU) matrix that releases antibiotic locally at the implant surface, thereby minimizing bacterial accumulation. We report here the methods of fabrication and formulation for making such antibiotic-loaded devices, as well as evidence of their bactericidal properties. Specifically, various pore-forming agents and drug loadings were examined. An optimum formulation consisting of BIOSPAN PU, poly(ethylene glycol) and ciprofloxacin offered the longest effective period of sustained release (5 days). The bactericidal efficacy of the released ciprofloxacin against Pseudomonas aeruginosa (PA) was four times that of the control PU without antibiotics. This bactericidal efficiency was due to an increase in the PA detachment from the surface. These observations suggested that the released ciprofloxacin was biologically active in preventing the bacteria from permanently adhering to the substratum, and thus decreasing the possibility of biofilm-related infection.

Anti-Infective Agents↗

PubMed1999

The maturation of sperm motility in the epididymis and vas deferens of the vervet monkey, Cercopithecus aethiops.

Among the diverse facets of sperm maturation, changes in motility are conspicuous and hence studies of sperm kinematics might provide good indices for sperm maturation. Accordingly, the maturation of sperm motility in the epididymis and vas deferens of the vervet monkey, Cercopithecus aethiops, was assessed using a computer-aided sperm motility analysis system. The results revealed clear trends in the development of both sperm motility per se and in the movement characteristics of motile spermatozoa from different regions of the epididymis, the vas deferens and the ejaculate, reflecting maturational changes associated with the attainment of functional motility and fertility. Motion of spermatozoa from the caput epididymis was sluggish and irregular. As the spermatozoa moved through the corpus epididymis, motility increased sharply, and continued to improve through the cauda epididymis and vas deferens. Despite the high proportion of motile cells, full maturation of motion capabilities was not completed in spermatozoa from the corpus epididymis. Only once spermatozoa had reached the cauda epididymis and vas deferens did they attain their full vigour, and swam rapidly (greater VCL, VSL and VAP) with straightline trajectories (greater LIN, WOB and STR; lower ALH, MAD and CURV). After acquiring their maximal percentage motility and progressive velocity in the cauda epididymis and vas deferens, a slight decline in motility and vigour occurred in ejaculated spermatozoa, and was possibly associated with the ageing of stored spermatozoa. The results from this investigation have revealed clear trends in the maturation of the motility of vervet monkey spermatozoa during their transit through the epididymis and vas deferens and final emergence in the ejaculate, and have provided crucial baseline information on the reproductive physiology of this potentially valuable biomedical model to serve as a reference for future studies in reproductive toxicology.

Animals↗

PubMed1997

Bacterial infection of biomaterials. Experimental protocol for in vitro adhesion studies.

Some of the more common reactor systems and novel diagnostic tools employed in the study of bacterial cell adhesion and biofilm formation have been described. Sampling and experimental requirements are shown to greatly influence the design and construction of a biofilm reactor. As analytical techniques evolve, the capability to non-invasively follow the development of biofilms and to assess the attached cell reactivity has increased. Both non-invasive and invasive diagnostic methods affect the type and design of biofilm flow reactor with both types of analyses providing complementary information on biofilm processes. To correctly interpret the contribution of a specific rate process to the net accumulation of cells at a substratum, one requires a reactor system devoid of any mass transfer limitations and a process analysis approach to allow for the correct collection and analysis of data.

Animals↗

PubMed1997

The relationship between schizophrenia and irritable bowel syndrome (IBS).

Irritable bowel syndrome (IBS) has been reported in 10-22% of adults. Amongst patients seeking medical attention for IBS 70-90% may have psychiatric co-morbidity, most commonly major depression. In contrast, few studies have looked at the prevalence of IBS in psychiatric patients. To our knowledge, there are no studies assessing the prevalence of IBS in patients with schizophrenia. Using a semistructured clinical interview to study the prevalence of IBS, we compared 47 patients with schizophrenia to an age-matched control group (n = 40) of patients who were seeking treatment in a primary care physicians office for other medical illnesses. IBS was diagnosed according to the criteria of Drossman et al. Nineteen percent (n = 9) of the patients with schizophrenia met criteria for IBS in contrast to 2.5% (n = 1) of the control group (p = 0.012). Schizophrenic patients seldom complain of gastrointestinal symptoms until specifically asked. Therefore, it may be important to inquire about gastrointestinal symptoms prior to initiating pharmacotherapy in order to differentiate side effects from a prior existing condition. Prospective studies should address the question whether remission of psychosis leads to improvement or resolution of IBS.

Adult↗

PubMed1996

Fatal occupational falls in the U.S. construction industry, 1980-1989.

Death certificate analyses were conducted on all fatal occupational falls occurring between 1980 and 1989 in the United States' construction industry using the National Traumatic Occupational Fatalities surveillance system at the National Institute for Occupational Safety and Health, Division of Safety Research. Fatality rates were calculated by geographic location (region and state), and year of injury. From 1980 to 1989, there were 2798 deaths due to occupational falls in construction, representing 49.6% of all fatal occupational falls across all industries. Most of these incidents occurred among young white males. By geographical location, the highest fatality rates were observed within the subregions of the Southern states in the United States. In observing the time between the date of injury and the date of death, 66% of the fall victims died on the same day as the injury, whereas 5.7% lived more than 90 days before dying. Further research needs to be targeted at what occupations are at highest risk for a fall injury, what circumstances are attributable to these falls, and prevention strategies to reduce fall injuries and fatalities. Research is also needed to explain why there are geographic differences in occupational falls in the construction industry.

Accidental Falls↗

PubMed1996

Nonfatal occupational fall injuries in the West Virginia construction industry.

Descriptive analyses were conducted using the West Virginia workers' compensation and supplemental injury records to assess nonfatal occupational falls from elevated work surfaces in the construction industry. These analyses are based on the 182 fall injuries reported to the State workers' compensation during fiscal year 1991 for which there were complete supplemental injury data. County-specific injury rates were calculated for counties with six or more fall injuries. Most of these incidents occurred among young white males who were employed as either craftsmen and kindred workers (48%) or laborers (33%) on non-union jobs in the general construction category (SIC-15). The counties with the highest injury rates that exceed the State rate of 5.9 per 1000 construction workers were located around or near the major industrial areas of Kanawha and Monongalia counties. Of the 182 claimants in the study population, one-third had been employed in their occupation for 2 years or less. For 60% of the claimants, the length of employment with the company for which they were employed at the time of the fall injury was two years or less; 26% had been employed for six months or less. Approximately, 63% of the 182 claimants had received some type of fall protection training. Ladders and scaffolds were involved in 50% of all falls. Fall protection devices were not commonly used by the 182 construction workers who worked from elevated surfaces. Fifty percent of the claimants were using tools or handling materials when the fall occurred. Fifty-nine percent of the falls occurred from elevated work surfaces which were relatively low heights (< or = 10 feet) where few safety regulations apply even though the potential for a serious injury still exists.

Accidental Falls↗

PubMed1996

Relapse in schizophrenia: is there a relationship to substance abuse?

This retrospective study evaluated relapse in 22 patients with schizophrenia, comparing substance abusers with nonabusers. Medication compliance was ensured as all subjects were treated with decanoate neuroleptics. Substance abuse was documented by multiple urine drug screens. Substance abusers had a significantly higher readmission rate to the hospital compared to nonabusers. These data suggest that in the presence of documented medication compliance substance abuse remains a major factor contributing towards relapse.

Adult↗

PubMed1995

Reevaluation of the effectiveness of environmental designs to reduce robbery risk in Florida convenience stores.

Prevention of intentional injuries to convenience store workers has focused on prevention of robbery. Data from a cross-sectional study of the effectiveness of environmental designs to deter robbery in Florida convenience stores were reanalyzed in order to determine the effect of confounding from local crime risk factors and other environmental designs on robbery rate. Results of this reanalysis were applied to a review of the literature. Of 14 store design factors and 5 local crime risk factors considered, concealed access/escape routes, cash register located at the back or the side of the store, high county crime rate, and high county population size were significantly associated with increased robbery rate. Poor cash handling policy was significantly related to a decreased robbery rate. Results also indicated that local crime factors and some environmental designs confound the relationship between other environmental designs and robbery rate. Conclusions from this reanalysis indicated that studies of the effectiveness of environmental designs to deter robbery must adjust for confounding. Although environmental design tends to be an effective robbery deterrent strategy, results from studies have been inconsistent as to the effectiveness of specific design factors. This inconsistency is partially explained by lack of adjustment for confounding from local crime risk factors and multiple environmental design factors. Areas for further research are discussed.

Crime↗

PubMed1993

Attitudes toward and beliefs about smoking in grade school children.

A questionnaire was developed to study attitudes toward and beliefs about the health consequences and social value of smoking. After initial evaluation of the instrument's reliability, it was administered to approximately 400 children, ranging in age from 7 to 15 years. Significant age effects for some items were demonstrated, but no significant sex effects or sex by age interactions were revealed. Children as young as 7 years were found to be well aware of the health hazards of smoking and likely to express negative attitudes concerning it. We conclude that if smoking prevention programs are to have more than minimal success with youth, they must offer something more than mere information about the health hazards of smoking.

Attitude to Health↗

PubMed1992

Effect of orthostatic stress on umbilical Doppler waveforms in normal and hypertensive pregnancies.

OBJECTIVE: Our study examined the effects of orthostatic stress and maternal hemodynamics on umbilical systolic/diastolic ratios in normal and hypertensive pregnancies. STUDY DESIGN: Eighteen normal and 20 hypertensive third-trimester pregnancies were examined in the left lateral recumbent, sitting, and standing positions. Measurements included umbilical systolic/diastolic ratio, maternal blood pressure, maternal cardiac output, and maternal total peripheral resistance. RESULTS: All patients demonstrated a fall in cardiac output and a rise in total peripheral resistance with standing. No change in systolic/diastolic ratio occurred with change to the upright position in patients with normotension. Patients with hypertension exhibited a significant increase in umbilical systolic/diastolic ratio with postural change. The increase was more marked in women who had hypertension with elevated peripheral resistance. CONCLUSION: Patients with hypertension are at increased risk of elevation of systolic/diastolic ratio with postural change; women with high-resistance hypertension may be at highest risk.

Diastole↗

PubMed1992

Maternal and fetal hemodynamic effects of autologous blood donation during pregnancy.

OBJECTIVES: Our objectives were to describe the maternal and fetal hemodynamic impact of a 1 U acute blood loss during pregnancy and to compare the hemodynamic responses of pregnant women with those of nonpregnant controls. STUDY DESIGN: With Doppler techniques cardiac output and total peripheral vascular resistance were determined in 16 pregnant women in the third trimester and in 16 nonpregnant volunteers before and during orthostatic stress, before and after donation of 450 ml of whole blood. In pregnant women the fetal umbilical artery systolic/diastolic ratio was also determined. Data were subjected to multiple logistic regression analysis. RESULTS: In both groups orthostasis provoked significant decreases in cardiac output and increases in total peripheral vascular resistance. The hemodynamic effects of blood loss were less pronounced and did not significantly change the hemodynamic response to orthostasis in either group. Neither orthostasis nor blood loss caused significant changes in the umbilical systolic/diastolic ratio. CONCLUSION: These data support the hemodynamic safety of uncomplicated autologous blood donation during late pregnancy.

Blood Donors↗

PubMed1991

Yohimbine and naloxone: effects on male rat sexual behavior.

We evaluated the effects of yohimbine (2 mg/kg) and naloxone (5 mg/kg), separately and in combination, on copulatory behavior in male rats. In Experiment 1, yohimbine evinced decrements in intromission frequency, ejaculation latency, and copulatory efficiency, whereas naloxone administration was followed by an increased ejaculation latency, and the combination of yohimbine plus naloxone was without effect. In Experiment 2, yohimbine evinced decreases in intromission frequency, ejaculation latency, copulatory efficiency in the first, but not subsequent, copulatory series, as well as a decreased latency to sexual exhaustion. Further, treatment with yohimbine alone, naloxone alone, or yohimbine plus naloxone was followed by a reduction in the number of ejaculation prior to sexual exhaustion. Thus, at the doses tested, no synergistic effects were observed for the combination of yohimbine plus naloxone.

Animals↗

PubMed1982

Characterization of immunoreactive somatostatin released from rat nervous system in vitro.

There is considerable evidence that somatostatin is released from nerve terminals throughout the central nervous system in response to presynaptic stimulation, thus suggesting a neuromodulator role for the peptide. We here report the partial characterization of immunoreactive somatostatin released from rat nervous system in vitro (hypothalamus, spinal cord and hypothalamic, cortical, thalamic and striatal synaptosomes). Serial dilutions of released somatostatin immunoreactivity showed parallelism with dilutions of synthetic somatostatin standard. Somatostatin immunoreactivity released from all tissue areas coeluted with synthetic tetradecapeptide on Sephadex G-25 (fine grade) gel chromatography; more than 85% of this immunoreactivity bound to Sepharose-anti-somatostatin-serum immunoaffinity columns. In addition, immunoreactive material released from hypothalamus, spinal cord and hypothalamic and cortical synaptosomes inhibited somatotropin (growth hormone, 'STH', 'GH') release from perifused anterior pituitary in a dose-related manner, indicating biological similarity to synthetic somatostatin.

Animals↗

PubMed1981

Plasma prolactin and progesterone responses to mating are altered in ages rats.

The effects of varying amounts of copulatory stimulation on patterns of plasma concentrations of prolactin and progesterone were evaluated in 3- and 12-month-old female rats. The 12-month-old group included rats which still exhibited oestrous cycles and rats in persistent vaginal oestrus (PVO). The extent of copulatory stimulation was defined by the number of intromissions received during mating: less than or equal to 5, 15 or greater than 50. Blood samples were drawn over the 8 days after mating through a cannula inserted into the right external jugular vein. Plasma from the samples was assayed for prolactin and progesterone. In aged but still cyclic rats, pregnancy rates were positively correlated with the number of intromissions received during mating. Only one rat in PVO became pregnant. All animals which became pregnant and rats in PVO which, after mating, exhibited a disruption of the pattern of PVO, showed the nocturnal surge of plasma prolactin characteristic of pregnant and pseudopregnant rats. While these surges persisted until day 8 after mating in pregnant animals, they were absent by this time in the rats in PVO. Prolactin surges were present in some but not all of the aged rats which did not become pregnant. Progesterone concentrations were raised in all pregnant animals except the one pregnant rat in PVO and, while not related to the number of intromissions, concentrations were higher 8 days after mating in young compared with those in aged pregnant rats. Plasma progesterone was low in rats in PVO regardless of disruption of the pattern of PVO. We have concluded that the failure of limited copulatory stimulation to induce pregnancy in older rats results, at least in part, from its failure to initiate nocturnal prolactin surges. Nevertheless, our data suggest that matings which are not experimentally limited should provide ample stimulation to establish such surges. Although reduced plasma concentrations of prolactin and progesterone at pro-oestrus and reduced plasma progesterone through part of gestation may contribute to decreasing fertility in aged rats, other unidentified factors appear to be involved in mediating the capacity of extensive copulatory stimulation to induce pregnancy in these animals.

Aging↗

PubMed1979

Erythropoiesis in sickle cell anaemia during acute infection and crisis.

Erythropoiesis was evaluated in 37 patients with sickle cell anaemia, 26 of them children under 12 years of age. Mean haemoglobin, haematocrit, reticulocyte, and erythropoietin levels were similar for 11 who were asymptomatic, 11 with infections, and 12 in vaso-occlusive crisis. Mean haemoglobin, haematocrit, and reticulocyte values were significantly lower and the mean erythropoietin level significantly higher for three patients in aplastic crisis. Reticulocyte counts reflected erythropoietic activity during the asymptomatic state but were variable during infection and crisis. No erythropoietic inhibitory activity was found in any of the four clinical states. It has been suggested that erythropoietin production decreases during infection. Patients in this study responded appropriately to stress, showing no decrease in erythropoietic activity during acute infection or crisis.

Adolescent↗