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Biomedical subjects

J Walton

Publications and source records attributed to J Walton.

At least 19 recordsLinked to original sources
PubMed1999

Auditory brainstem response forward-masking recovery functions in older humans with normal hearing.

We investigated the auditory brainstem response (ABR) recovery from forward masking using toneburst maskers and probes. Two subject groups matched for hearing thresholds were evaluated: normal-hearing young adults (21-40 years) and older subjects (63-77 years) with normal audiometric thresholds. Stimuli consisted of 1, 4 and 8 kHz tonebursts, with 2-4 cycle rise/fall time and no plateau. Forward maskers were tonebursts of the same frequency, with a 5 ms rise/fall time and a 20 ms plateau time. Probes were presented at 40 dB above threshold, and the forward masker was adjusted to a level that just eliminated the ABR to the 40 dB sensation level toneburst when the probe onset occurred at masker offset. Forward-masker intervals varied from 2 to 64 ms. ABR wave V latencies were similar for the young and old age groups regardless of toneburst frequency. Under forward-masking conditions, wave V latency was prolonged for the shorter intervals, and recovered to baseline latency by 64 ms. The forward-masker recovery functions were nearly identical for the two age groups for the 1 kHz toneburst. In contrast, there were clear differences in the recovery functions for the two age groups for the 4 and 8 kHz tonebursts. Specifically, the mean latency shift was greater for the aged group for forward-masker intervals of 16 ms or less. The two age groups showed identical latency shifts for longer forward-masker intervals. These data demonstrate prolonged recovery from forward masking in older human subjects. As these subjects had audiometric thresholds within normal limits, one plausible interpretation of this finding is that the prolonged recovery time is a manifestation of an aging effect on the central auditory nervous system rather than the periphery.

Acoustic Stimulation↗
PubMed1997

Handwriting changes due to aging and Parkinson's syndrome.

Wills signed by elderly people are often contested on the grounds the the signature is different from their earlier specimen signatures. Neurological disease, which can affect handwriting, is very common and progressive amongst elderly people. Handwriting change due to old age and neurological disease is poorly understood. To better understand this subject, we carried out a large methodical study based on almost 200 handwriting specimens of Parkinson patients and age-matched controls. Interestingly, our findings indicate that some of the handwriting changes which occur in these populations tend to resemble forgery indicia although upon close inspection they are distinguishable from them. Thus, document examiners are urged to exercise caution in assessing purported forgeries on wills and other documents signed of written during older age or a writer suffering from neurological disease.

Adult↗
PubMed1997

What is the long-term outcome for patients with very small abdominal aortic aneurysms?

OBJECTIVE: To determine the long-term outcome for patients with abdominal aortic aneurysms (AAA) less than 4 cm in AP diameter (very small AAA). DESIGN: Population-based screening study. MATERIALS AND METHODS: One hundred and forty-two patients who had AAA less than 4 cm at presentation were assessed by ultrasound at intervals of 6-12 months. The records of these patients were reviewed. RESULTS: During the period of follow-up the median annual growth rate for aneurysms while under 3.0 cm was 1 mm, rising to 2 mm when between 3.0 and 3.9 cm, and 3 mm when between 4.0 and 4.9 cm in diameter. Elective aneurysm repair was undertaken when aneurysms exceeded the threshold value, which itself increased from 4 cm to 5.5 cm in the 9 years of follow-up. More patients died with their aneurysm (n = 35) then underwent surgery (n = 23). There was one perioperative death, and three unrelated late deaths after resection. One aneurysm ruptured in a patient who had refused follow-up 5 years previously. CONCLUSIONS: This study suggests that aneurysms less than 4.0 cm diameter are relatively benign, and questions the appropriateness of early intervention.

Adult↗
PubMed1996

Spiritual relationships: a concept analysis.

Spiritual relationships are connections to self or soul, to others, to a higher power, or to nature. All relationships have the potential to be spiritual. The depth or intimacy of the relationship is directly related to human being's individual personal knowledge of self or soul-searching. Grounded theory and phenomenological research studies validate that spiritual relationships play an important role in one's spirituality. Theoretical and operational definitions, attributes, and several cases (e.g., model, related, contrary, and metaphorical) of spiritual relationships are discussed. Attributes and consequences are identified.

Holistic Nursing↗
PubMed1996

The expression of insulin-like growth factor (IGF) and IGF-binding protein (IGFBP) genes in the human placenta and membranes: evidence for IGF-IGFBP interactions at the feto-maternal interface.

The placenta synthesizes insulin-like growth factors (IGFs) and their binding proteins (IGFBPs), which are believed to regulate its growth and development in an autocrine/paracrine manner. To delineate the cellular sites of expression of IGP and IGFBP messenger ribonucleic acids (mRNAs) in human placenta throughout pregnancy, we used in situ hybridization histochemistry with 35S-labeled IGF and IGFBP complementary RNA probes on human placentas and fetal membranes of gestational ages 6 weeks to term (40 weeks). In placental regions where trophoblasts (fetal) or decidua (maternal) coexist (e.g. basal plate), the identity was delineated by their cytokeratin or vimentin immunoreactivity, respectively. Except for IGF-II, mRNAs encoding peptides of the IGF system were expressed in a similar spatial pattern and relative abundance throughout gestation. Both IGF mRNAs showed similar tissue distribution, but the IGF-II mRNA was more abundant than IGF-I mRNA at all gestational ages. IGF-II mRNA was expressed in the chorionic mesoderm of placental villi and chorionic plate in moderate abundance, and it decreased with gestation. It was also expressed in the trophoblasts of the cytotrophoblastic shell and Langhan's layer of placental villi only in the first trimester, suggesting an autocrine role for IGF-II in early cytotrophoblastic proliferation and/or differentiation. IGF-II mRNA was expressed most abundantly in the columns of intermediate trophoblasts in the anchoring villi and chorionic and basal plates. A gradient of IGF-II mRNA abundance was observed in the trophoblasts of the cytotrophoblastic column, with greater IGF-II mRNA levels in those at the invading front, suggesting a role for IGF-II in trophoblastic invasion. In the fetal membranes, IGF-II mRNA was identified in the amnion and chorion laeve. IGF-I receptor mRNA was expressed in low abundance in all cell types of the placenta. All six IGFBP mRNAs were identified in variable abundance in the decidualized stromal cells of the maternal decidua basalis and parietalis, with IGFBP-1 mRNA being expressed in the greatest abundance. The spatial pattern of expression of each IGFBP mRNA also differed among decidual cells, with IGFBP-1, IGFBP-2, IGFBP-4, and IGFBP-6 mRNAs being expressed in most cells, whereas IGFBP-3 and IGFBP-5 mRNAs were expressed in only some cells. IGFBP-1 mRNA was expressed initially in the epithelium of endometrial glands and in a population of decidualized stromal cells in early gestation, and subsequently in the majority of decidualized stromal cells. IGFBP-3 mRNA was expressed in both the decidua and certain intermediate trophoblasts of the basal plate and anchoring villi of placenta and in amnion and chorion laeve of fetal membranes. IGFBP-4 and IGFBP-5 mRNA were expressed additionally in low abundance in the chorionic mesoderm. IGFBP-6 was expressed in greater abundance in the decidua parietalis than in decidua basalis, although the general level of expression was low. The spatial pattern and relative abundance of expression of IGFBP mRNAs suggest IGFBP-1 to be the predominant IGFBP synthesized by the maternal decidual cells, interacting with the IGF-II that synthesizes fetal intermediate trophoblasts. Presumably, IGF-II and IGFBPs are used for cell to cell communication between fetal trophoblasts and maternal decidual cells at the feto-maternal interface for placental development and/or function.

Extraembryonic Membranes↗
PubMed1996

Stunned myocardium: theoretical mechanisms of injury.

Stunned myocardium may occur after an episode of prolonged or transient ischemia. This phenomenon can occur in a variety of patient groups including medical, surgical, neurologic, and cardiac patients. In the stunned myocardium, myocardial contractility is temporarily depressed, causing symptoms similar to those of cardiogenic shock. When critical care nurses are familiar with the clinical characteristics and risk factors of stunned myocardium, they can start the appropriate interventions and left ventricular function returns to normal within days with no residual hypokinesis. Critical care nurses play a key role in assisting surgeons and other noncardiac physicians in the diagnosis and care of the patient with stunned myocardium.

Adult↗
PubMed1995

Carotid duplex scanning: patterns of referral and outcome.

OBJECTIVE: Review of the results of carotid Duplex scanning. DESIGN: Retrospective review of new referrals for carotid Duplex scanning to a regional vascular laboratory. MATERIALS: 1041 referrals made over an 18 month period. METHODS: Referrals were reviewed for scan quality, diagnostic category and outcome of scanning. RESULTS: The overall detection rate of ipsilateral stenoses > 70% and occlusions was 13.5%; the detection rate of surgically significant carotid lesions (70-99%) was only 8%. Analysis by diagnostic category revealed a significantly greater detection rate for carotid lesions > 70% in patients presenting with amaurosis fugax (24%) in comparison to those with TIAs (9.5%, p = 0.0005) or following a stroke (13%, p = 0.01). Patients referred with asymptomatic bruits or prior to cardiac surgery showed a positive scan rate of 30%. Sixty-seven carotid endarterectomies have resulted from scans performed in this period. CONCLUSION: The overall rate of detection for surgically relevant lesions is low, but in comparison to a similar audit conducted in 1992, the absolute number of carotid lesions > 70% has risen by 60%. An 8% detection rate for surgically relevant lesions may be valuable in projecting the need for carotid endarterectomy arising from a given number of Duplex scans.

Adolescent↗
PubMed1995

Uptake of trace amounts of aluminum into the brain from drinking water.

Throughout the world, alum (aluminum sulfate) is used in municipal water treatment plants to clarify water. Alum treatment usually removes aluminosilicate particles from drinking water but can substantially increase its soluble aluminum content (Zhang et al., 1994; Tran et al., 1993; Kopp, 1970). Soluble aluminum is the more bioavailable and potentially toxic form. We gavaged simulated tap water, containing a low level of radioactive soluble aluminum (26Al), into the stomachs of rats. Measurements with accelerator mass spectrometry showed that trace amounts of 26Al from this single exposure directly entered their brain tissue. Uptake of a comparable level of aluminum into the human brain, from alum-treated drinking water over a prolonged period of time, may contribute to long-term health consequences for some people.

Aluminum↗
PubMed1994

Visualization of sphere packs using a dataflow toolkit.

We describe the construction of a simple application for the visualization of sphere packs, with applications to molecular graphics. Our development environment is IRIS Explorer, one of the new generation of so-called dataflow toolkits. We emphasize particularly the way in which working in such an environment facilitates the design and construction process, paying special attention to tools which aid the importing of data into the application, the design of the user interface, and the extension or modification of existing tools. Some examples of the use of the application in the field of molecular modeling are presented.

Computer Graphics↗
PubMed1994

ACID-BASE REGULATION, BRANCHIAL TRANSFERS AND RENAL OUTPUT IN A MARINE TELEOST FISH (THE LONG-HORNED SCULPIN MYOXOCEPHALUS OCTODECIMSPINOSUS) DURING EXPOSURE TO LOW SALINITIES

A number of studies have implied a linkage between acid­base and ion exchanges in both freshwater and seawater fish, although little is known about the branchial and renal acid­base transfers involved as the animals move between different salinities. To investigate the role of these transfers in a marine teleost fish as it is exposed to a dilute environment, we measured plasma acid­base values and net movements from fish to water of NH4+, HCO3- and H+ in long-horned sculpin (Myoxocephalus octodecimspinosus) placed in 100 %, 20 %, 8 % or 4 % sea water for 24­48 h. Renal excretion of H+ was also monitored in fish exposed to 4 % sea water. Sculpin proved to be somewhat euryhaline for they were able to maintain plasma ion and acid­base transfers in hypo-osmotic (20 %) sea water, but could not tolerate greater dilutions for more than several days. Plasma pH and carbon dioxide concentration (CCO2) increased in the 20 % and 8 % dilution groups, with CCO2 nearly doubling (control, 4.56 mmol l-1; 8 % group, 8.56 mmol l-1) as a result of a combined increase in the partial pressure of plasma CO2 (PCO2) and [HCO3-]. During a 44­46 h exposure, HCO3- transfers increased progressively in the most dilute water, with animals in the 8 % and 4 % groups exhibiting a net H+ loss that was smaller than that of seawater fish (control, 5.1 mmol kg-1; 8 %, 0.9 mmol kg-1; 4 %, -2.9 mmol kg-1). Animals exposed to 4 % sea water for 24 h and then returned to normal sea water had a variable plasma pH, an elevated CCO2 and a net efflux of H+ that effectively stopped (control, 0.10 mmol kg-1 h-1; 4 %, 0.02 mmol kg-1 h-1; seawater recovery, 0.20 mmol kg-1 h-1) during the low-salinity period. Renal acid excretion remained relatively constant throughout the experiment but only made up a significant portion (approximately 40 %) of the total acid transfers during the 4 % dilution period (control rate approximately 3 µmol kg-1 h-1: 3 % of branchial rate). We postulate that the increase in plasma CCO2 during exposure to low salinity may be due to mobilization of base from the intracellular bone compartment. The decrease in external salinity could induce base loss by alteration of gill ion exchanges (Na+/H+, Cl-/HCO3-) and/or changes in branchial HCO3- permeability. For the first time, we have shown that the effects of a dilute environment on acid­base transfers may be an important limitation to the survival of a euryhaline species in brackish or fresh water.

Journal Article↗
PubMed1994

Working together to meet the needs of multiple-birth families.

Health visitors have an important role in providing postnatal support to multiple-birth parents, write Jill Walton et al. Here they describe how a series of joint parent/professional seminars helped raise awareness among health visitors of the special needs of multiple-birth parents for services and support, and the importance of developing closer links with voluntary and self-help groups at local and national level.

Community Health Nursing↗