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Biomedical subjects

J K Robinson

Publications and source records attributed to J K Robinson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Luminol/H2O2 chemiluminescence detector for the analysis of nitric oxide in exhaled breath.

A new instrument for the detection of nitric oxide has been developed and applied to the analysis of exhaled breath. The instrument is based on conversion of NO to NO2, using the oxidant chromium trioxide, followed by detection of chemiluminescence in the reaction of NO2 with an alkaline luminol/H2O2 solution. The presence of H2O2 is found to enhance the sensitivity of NO2 detection by a factor of approximately 20. A bundle of porous polypropylene hollow fiber membranes is used to bring the gaseous sample into contact with the luminol solution. Chemiluminescence occurring within the translucent hollow fibers is detected using a miniature photomultiplier tube. The limit of detection for NO is 0.3 ppbv for S/N = 3, and the 1/e response time is 2 s. A large interference resulting from the 4-6% CO2 concentration in exhaled breath is removed by use of an ascarite scrubber in the air stream. Breath measurements of NO were made using a sampling technique developed by Sensor Medics (Yorba Linda, CA) with simultaneous detection using the luminol/H2O2 and NO + O3 chemiluminescence techniques. The two instruments were found to be in excellent agreement. Nitric oxide levels were in the range 6.0-22.0 ppbv for healthy individuals and 40.0-80.0 ppbv for individuals with asthma or a respiratory infection. This new detector offers the advantages of compact size, low cost, and a simple configuration compared to NO detectors based on NO + O3 chemiluminescence.

Breath Tests↗
PubMed1999

Derivatization of thymine and thymine photodimers with 4-bromomethyl-7-methoxycoumarin for fluorescence detection in high-performance liquid chromatography.

Exposure of DNA to utraviolet radiation results in the formation of a number of photoproducts, including thymine photodimers. A sensitive and selective analytical method based on high-performance liquid chromatography (HPLC) and fluorescent labeling with 4-bromomethyl-7-methoxycoumarin has been developed to quantify both thymine and thymine photodimers. The identity of the thymine and thymine dimer derivatives were determined by HPLC-electrospray ionization mass spectrometry. The derivatization reaction yield was maximized by optimizing several reaction variables. The limit of detection for HPLC method was 1.0 pmol thymine and 0.4 pmol thymine dimer for S/N = 3.

Calibration↗
PubMed1999

Spatial signal detection in rats is differentially disrupted by delta-9-tetrahydrocannabinol, scopolamine, and MK-801.

Cannabinoid receptors have been implicated as having important roles in human cognitive processes, especially memory and attention. While some work has studied the effects of the active ingredient in marijuana, delta-9-tetrahydrocannabinol (THC), on short-term memory, no work has examined the involvement of these receptors in mediating attention. Therefore, the present study compared the effects of THC on the performance by rats of an operant spatial signal detection task with those of cholinergic muscarinic antagonist scopolamine and glutamatergic NMDA antagonist MK-801, both compounds known to influence attention and other cognitive processes in rats. These experiments were conducted in a two lever operant chamber in which a cue lamp was mounted over each lever. The rats were pretrained to respond rapidly on the corresponding lever following a rapid presentation of the cue lamp above it. The stimulus was presented in a random order of three durations (100, 300 or 1000 ms) to measure detectability of the stimulus under saline, THC (1.0 or 2.0 mg/kg i.p.), scopolamine (0.06-0.25 mg/kg i.p.), or MK-801 (0.06-0.25 mg/kg i.p.). THC significantly and selectively disrupted stimulus detection accuracy at the 100 ms stimulus duration, but did not influence response bias or the rate of responding. Scopolamine and MK-801 both produced alteration in errors of omission and position bias. These data suggest that THC produces an impairment in visual attention and that the nature of this impairment is qualitatively different from that produced by muscarinic-receptor or NMDA-receptor antagonism.

Animals↗
PubMed1999

Gonadectomy in adult life increases tyrosine hydroxylase immunoreactivity in the prefrontal cortex and decreases open field activity in male rats.

The prefrontal cortices in rats participate in a range of cognitive, emotional, and locomotor functions that are dependent on its rich catecholamine innervation. Sex differences identified in many of these functions suggest that the prefrontal cortex is also influenced by gonadal hormones. Previous studies have shown that prefrontal catecholamines can be modified by changes in the hormone environment in developing animals. The present analyses, carried out in male rats gonadectomized as adults, with and without supplementation with testosterone proprionate, and examined at intervals from two days to 10 weeks after surgery, revealed that both the anatomical organization of prefrontal catecholamine afferents, and a behavioral measure sensitive to their selective lesioning remain highly responsive to changes in testicular hormones in adulthood. Thus, gonadectomy in adult male rats rapidly led to a large but transient decrease in the density of tyrosine hydroxylase immunoreactivity in all layers of the dorsal anterior cingulate cortex. This was followed by a sustained period in which immunoreactivity in the supragranular layers returned to levels that were just below normal (between 72 and 79% of normal), and labeling in deep laminae stabilized at considerably elevated innervation densities (approximately 150% of normal). Neither the acute decrease nor the chronic over-innervation characteristic of gonadectomized animals was observed in rats that were gonadectomized and supplemented with testosterone proprionate. Open field activity assessed along a corresponding 10 week timeline showed that gonadectomized animals were significantly less active than hormonally intact controls, a behavioral pattern opposite to the hyperactivity which persists following prefrontal dopamine lesions. Gonadectomized animals supplemented with testosterone proprionate, on the other hand, had open field scores that were not significantly different from controls. Taken together, these findings indicate that the adult hormone environment provides a significant, and seemingly functionally significant influence over the catecholamine innervation of the rat prefrontal cortex. Such lifelong responsiveness of the prefrontal cortical catecholamines to circulating hormones suggests that gonadal steroids are an active component of the biology of normal adult cognition, and may also have relevance for cortical dysfunction in disorders such as schizophrenia which are not only strongly tied to the catecholamines, but exhibit considerable biases among men and women as well.

Age Factors↗
PubMed1999

Suspension sutures aid facial reconstruction.

BACKGROUND: Suspension, pexing or tacking sutures, which have a long history of use in facial cosmetic surgery, have only recently begun use in reconstruction. OBJECTIVE: In this study, the suspension suture was used to fix the closure line at the junction of cosmetic units, to prevent distortion of free margins secondary to wound contraction, eg, ectropion or eclabium, to prevent tenting across concavities, and to prevent scar spreading of wounds closed under tension. The acute complications and long-term effectiveness of this suturing technique in achieving the 4 desired results were evaluated. METHODS: During a 10-year period, 136 cases of surgical defects of the face created by the removal of nonmelanoma skin cancer by Mohs micrographic surgery were repaired using absorbable suspension sutures. The wounds were evaluated initially for acute complications of hemorrhage, infection, dehiscence, and necrosis; and later over 3 years for chronic sequela of hypertrophic scar, spread scar, contraction deformities such as distortion of free margins, and pigmentary changes. RESULTS: Suspension sutures were used in 60 cases of primary layered closure and 76 flaps of the face. Suspension sutures allowed primary closure of defects that would have required flaps in 72% of the cases and prevented distortion of free margins. There were more acute and long-term complications related to excess tension with primary closure than with flaps. Suspension sutures fixed the closure line at the junction of cosmetic units, prevented tenting across concavities, and both features were maintained over the duration of the study. CONCLUSION: Suspension sutures aided in obtaining linear closures, prevented distortion of free margins, prevented tenting across concavities, and fixed the closure line at the junction of cosmetic units; however, they did not prevent spread scars.

Face↗
PubMed1998

Galanin inhibits performance on rodent memory tasks.

Central administration of galanin produces performance deficits on a variety of rodent learning and memory tasks. Galanin impairs acquisition and/or retention of the Morris water task, delayed nonmatching to position, T-maze delayed alternation, starburst radial maze, and passive avoidance in normal rats. A primary site of action is the ventral hippocampus, with an additional modulatory site in the medial septum-diagonal band. The behavioral actions of galanin at rat septohippocampal sites mediating cognitive processes are consistent with previous reports of inhibitory actions of galanin on acetylcholine release and cholinergically activated transduction at the M1 muscarinic receptor in rat hippocampus. The peptidergic galanin receptor antagonist M40 blocks the inhibitory actions of galanin on memory tasks. Treatment combinations of M40 with an M1 agonist, TZTP, improves performance on delayed nonmatching to position, in rats with 192IgG-saporin-induced cholinergic lesions of basal forebrain neurons. Nonpeptide, bioavailable, subtype-selective galanin receptor antagonists may provide tools to test the hypothesis that antagonism of endogenous galanin, which is overexpressed in the basal forebrain in Alzheimer's patients, can contribute to the alleviation of the cognitive deficits associated with Alzheimer's disease.

Animals↗
PubMed1998

Microinjection of GABA-A agonist muscimol into the dorsal but not the ventral hippocampus impairs non-mnemonic measures of delayed non-matching-to-position performance in rats.

Anatomical studies of afferent and efferent connections suggest that the hippocampus may have more than one information processing role that varies along the septo-hippocampal axis. The present study was conducted to test whether a distinct functional specialization for the dorsal versus ventral extents of the hippocampus could be detected. The effects of a GABA-A receptor agonist, muscimol, microinjected into either the dorsal or ventral hippocampus on an operant, spatial delayed non-matching-to-position (DNMTP) task were measured. A decrease in the number of trials completed per session and disruption of several DNMTP discrimination parameters were produced by muscimol microinjection into the dorsal hippocampus but not into the ventral hippocampus. Muscimol injected into either site did not impair the measure of working memory, delayed choice accuracy. These results are consistent with the view that hippocampal function varies along the septo-temporal axis, and that the dorsal hippocampus is relatively more critical to visual discrimination performance than the ventral hippocampus.

Animals↗
PubMed1998

Sun protection by families at the beach.

BACKGROUND: During the last decade, results of surveys of adults showed an increase in sun protection knowledge, a slight decline in the attitude that having a tan was healthy, widespread sunscreen use as the principal method of solar protection, and an increase in sunburning. METHODS: During the summer of 1996, observers recorded the sun protection activities of 352 family groups as they arrived at the beach and did concurrent interviews. RESULTS: Ninety-eight percent of families using sunscreen applied it after arrival at the beach and it was the dominant form of sun protection used. Usually, the adult woman provided the sunscreen and applied it to a child before applying it to herself. The median delay in application from arrival at the beach to application to the last family member was 51 minutes. Wearing either a hat, shirt, or sunscreen by 1 adult was associated with wearing the same item by at least 1 child in the family group (hat, P<.001; shirt, P<.001; sunscreen, P<.001). Children's sunscreen use was associated with having fair skin and a parent who used it. CONCLUSIONS: Because those with fair skin type are more likely to use sunscreen and to burn after short periods of exposure, delay in sunscreen application may cause sunburns. While solar protection has become part of routine beach behaviors for most families, there is room for improvement with better application of sunscreen; more use of clothing, especially hats; and seeking shade.

Adult↗
PubMed1998

Delta-9-tetrahydrocannabinol (THC) fails to stimulate consumption of a highly palatable food in the rat.

THC is the active chemical component in marijuana. In humans, it is known to cause acute sedation, alterations of cognition, and to stimulate appetite. The goal of this study was to determine if THC would produce acute stimulation of the consumption of a highly-palatable food item in the rat. Separate groups of rats were administered THC (1.0 or 2.0 mg/kg) either 30, 60, or 120 min or saline 30 min prior to being placed in the presence of a highly palatable food (Nilla Wafers soaked in water). Spontaneous exploration decreased at the 2.0 mg/kg dose of THC at the 60 min time point. The amount of food eaten was not significantly changed at either dose. These results do not support the hypothesis that THC causes acute appetite stimulation in the rat. However, some other non-specific effect of THC that indirectly reduced food consumption without directly acting upon appetite is a possible explanation that cannot be presently excluded, and that will need to be assessed in future studies.

Animals↗
PubMed1998

What promotes skin self-examination?

The American Academy of Dermatology's national program of Melanoma/Skin Cancer Detection and Prevention, developed in response to the rising incidence of invasive melanoma in the United States, has annually produced extensive print, radio, and television coverage about performing skin self-examination (SSE). This study was conducted to determine factors that motivate people to perform SSE. A 1996 telephone survey evaluated performance of SSE for skin cancer and used questions to identify self-perceived. The performance of SSE was directly correlated with the self-perceived risk of the development of melanoma or skin cancer and discussions with physicians or nurses. People were motivated to perform SSE based on their perceived risk and discussions with doctors. Because patients most easily have access to primary care physicians, these physicians must be educated to identify those who are at risk for the development of melanoma. Primary care physicians and nurses should be encouraged to counsel patients about risk levels, the utility of SSE in limiting their risk, and how to perform SSE. To facilitate this process, risk levels for the development of melanoma (defined on the basis of simple and readily ascertained characteristics that help to educate physicians, nurses, and patients) are provided.

Adolescent↗
PubMed1997

Differential effects on delayed non-matching-to-position in rats of microinjections of muscarinic receptor antagonist scopolamine or NMDA receptor antagonist MK-801 into the dorsal or ventral extent of the hippocampus.

Glutamatergic NMDA and cholinergic muscarinic receptors are thought to contribute to cognitive processes mediated by the hippocampus. Evidence from lesion studies suggests that, despite cytoarchitectural uniformity within the hippocampus, information processing may not be uniform along the septo-temporal axis. The present study examined whether blockade of NMDA or muscarinic receptors in hippocampal subregions produced regional dissociations in the disruption of performance on an operant, spatial delayed non-matching-to-position (DNMTP) paradigm that also assessed vigilance. Rats were extensively pretrained on DNMTP, then bilaterally cannulated into either the dorsal or ventral hippocampus. Following retraining, scopolamine or MK-801 were administered prior to sessions. MK-801 administered into dorsal hippocampus produced delay-independent deficits in DNMTP delayed choice. Neither scopolamine administered into the dorsal or ventral hippocampus, nor MK-801 administered into the ventral hippocampus, produced significant disruption of DNMTP delayed choice. However, some dissociations were evident in other measures of vigilance. Scopolamine into the dorsal and ventral hippocampus increased errors of omission, scopolamine into the ventral hippocampus decreased sample response accuracy, and MK-801 into the dorsal hippocampus decreased sample response accuracy and increased response bias. These results are consistent with the suggestion that subregions of the hippocampus may be involved in different aspects of information processing and also suggest that the cholinergic inputs to the hippocampus may be functionally independent of NMDA receptor-mediated neurotransmission.

Animals↗
PubMed1997

Trends in sun exposure knowledge, attitudes, and behaviors: 1986 to 1996.

BACKGROUND: The American Academy of Dermatology's national program Melanoma/Skin Cancer Detection and Prevention, developed in response to the rising incidence of invasive melanoma in the United States, has annually during the past decade produced extensive print, radio, and television coverage about the dangers of sun exposure and benefits of sun protection. OBJECTIVE: We measured the progress achieved in increasing the awareness and knowledge of skin cancer and changing the attitudes, beliefs, and behaviors that affect skin cancer risk. We also describe current sun-related behavior including sunburning, assess the likelihood of practicing sun protection strategies, and provide a baseline against which future changes in sun protection behavior may be evaluated. METHODS: A 1996 telephone survey repeated questions used in 1986 to evaluate change and used classifying questions to better define attitudes and behaviors. RESULTS: From 1986 to 1996, the knowledge of the perceived harmful effects of the sun significantly broadened, but the UV exposure behavior as measured by sunburning (30% to 39%) and regular use of a tanning booth (2% to 6%) also increased. There was a decline in the attitude that having a tan was healthy; however, in 1996 having a tan was still considered to enhance appearance, particularly by men. Sunscreen use increased (35% to 53%). Women, younger persons, persons residing in areas with fewer sunny days, and whites were more likely to tan intentionally, but men who lived in the South were more likely to sunburn. CONCLUSION: During the past decade, the early process of change involving cognitive and emotional activities began. With this study, high-risk population subsets performing specific adverse behavior were identified. In the future, they can be targeted with messages that promote attitudinal and behavioral change.

Adolescent↗
PubMed1997

Placement of the tension-bearing suture in repairing the alar facial junction.

BACKGROUND: The cheek advancement flap was used to repair defects of the concave junctional zone of the nasal base, the medial aspect of the cheek, and the upper lip. Prior description of the sequence of suture placement depended on the concept of the initial suture or key suture. Splitting the functions of the initial suture into its functions of tension bearing or aligning aided the surgeon in determining the sequence and location of suture placement. OBJECTIVE: The purpose of the terminology change was to improve teaching concepts of tissue movement. METHODS: A series of 40 cases explored the use of a tension-bearing suture at the base of the cheek advancement flap, which was anchored to the fascia and periosteum at the nasal notch of the maxilla. In placement of this suture, the pyramid of the nose was elevated and the flap slid under the nose. RESULTS: Two complications occurred: one case of flap tip necrosis and one infection. There were no cases of bridging of the nasal cheek junction (sulcus) occurred. In all cases, the procedure restored the contours of the area. CONCLUSION: This redefinition of the key suture into tension-bearing and aligning suture helped the novice to place the tension-bearing suture first. In the example of the cheek advancement flap, careful placement of the tension-bearing suture promoted the restoration of the nasolabial fold.

Cheek↗