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Biomedical subjects

A Smith

Publications and source records attributed to A Smith.

At least 811 records · Page 45Linked to original sources
PubMed1992

Atrial natriuretic peptide, cyclic guanosine monophosphate and sodium excretion during postnatal adaptation in male infants below 34 weeks gestation with severe respiratory distress syndrome.

The role of atrial natriuretic peptide (ANP), in the perinatal period, is at present unclear. In adults urinary cyclic guanosine monophosphate (cGMP) is considered an index of the biological activity of plasma ANP. The aim of this study was to determine the relationship between plasma ANP, cGMP excretion (cGMPex) and sodium excretion (Naex) in preterm infants in the first days after birth. Sequential, 4 hourly, measurements of plasma ANP, cGMPex and Naex were made in 12 male neonates of median gestational age 27 weeks (range 25-33) and median birth weight 0.981 kg (range 0.635-2.029) over a median period of 5.2 days (range 2.3-10). The ratios of cGMPex to ANP and of Naex to cGMPex were each plotted against postnatal age. The ratio of cGMPex to ANP increased ten fold in the first 3-4 days after birth but then remained relatively constant; the ratio of Naex to cGMPex showed a steady increase from birth. We conclude that, in extremely immature infants, renal sodium loss in response to cGMP increases rapidly during the first 10 days after birth. In addition, after 3-4 days from birth, plasma ANP ia associated with a constant proportionate rate of cGMP excretion though, as the plateau ratio of cGMPex to ANP varied widely between babies, cGMPex cannot be used to predict plasma ANP in cross sectional studies. These changes may reflect postnatal adaptation and/or maturation of both ANP receptors and cGMP mediated cascades. In the immediate postnatal period, plasma ANP may also have a non-renal role.

Age Factors↗
PubMed1992

Effects of vocal task and respiratory phase on prephonatory chest wall movements.

A vocal reaction time paradigm was used to explore prephonatory respiratory kinematics. Movements of the rib cage and abdomen were recorded prior to production of utterances differing in length and intensity, and vocal responses were elicited in different phases and volumes of the quiet breathing cycle. A velocity threshold was used to distinguish prephonatory adjustments from the cyclical movements of the chest wall that are characteristic of quiet breathing. The results suggest that a variety of prephonatory kinematic events can occur prior to initiation of vocalization in response to a stimulus. Further, prephonatory movements appear to be adaptive in that they are influenced by the length of the utterance to be spoken and the respiratory volume at the time of voice initiation.

Adult↗
PubMed1992

Gradations in a pattern of neuromuscular activity associated with stuttering.

EMGs were recorded from muscles of the lip, jaw, and neck during conversational speech of 17 stuttering subjects. Averaged power spectra and coherence between pairs of EMGs were computed. Results indicate that tremorlike oscillations in the range of 5-15 Hz and high amplitudes of EMGs occupy a common continuum of motor patterns that may occur in stuttering. In subjects whose results fell at the strong end of this continuum, stuttered speech was distinguished by widely distributed, high-amplitude oscillations and relatively high coherence at the frequency of oscillation. At the other extreme, neither oscillatory activity nor amplitude was greater for stuttered speech; in fact stuttered and fluent speech were often associated with approximately equal EMG amplitude. These results suggest that there is not a single set of physiological events that uniformly characterize stuttering in all individuals; rather, events such as the occurrence of high-amplitude oscillations occur at different strengths in different individuals.

Adult↗
PubMed1992

Mode of Action Studies on a Chiral Diphenyl Ether Peroxidizing Herbicide: Correlation between Differential Inhibition of Protoporphyrinogen IX Oxidase Activity and Induction of Tetrapyrrole Accumulation by the Enantiomers.

The nitrodiphenyl ether herbicide 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitroacetophenone oxime-O-(acetic acid, methyl ester) (DPEI) induced an abnormal accumulation of protoporphyrin IX in darkness in the green alga Chlamydomonas reinhardtii, as determined by high-performance liquid chromatography and spectrofluorimetry. It also inhibited the increase in cell density of the alga in light-grown cultures with an I(50) (concentration required to decrease cell density increase to 50% of the noninhibited control value) of 0.16 mum. The relative ability of four peroxidizing diphenyl ether herbicides to cause tetrapyrrole accumulation in C. reinhardtii correlated qualitatively with their ability to inhibit the increase in cell density in light-grown cultures. The purified S(-) enantiomer of the optically active phthalide DPE 5-[2-chloro-4-(trifluoromethyl)phenoxy]-3-methylphthalide (DPEIII), which has greater herbicidal activity than the R(+) isomer, induces a 4- to 5-fold greater tetrapyrrole accumulation than the R(+) isomer. The I(50) for inhibition of increase in cell density in light-grown cultures of C. reinhardtii by the S(-) isomer (0.019 mum) is less than 25% of that for the R(+) isomer. DPEIII inhibits protoporphyrinogen IX oxidase activity in pea (Pisum sativum) etioplast lysates, with the S(-) enantiomer showing considerably greater potency than the R(+) isomer and the racemic mixture showing a potency intermediate between the two. The results indicate that the site at which DPEs inhibit protoporphyrinogen IX oxidase shows chiral discrimination and provide further evidence for the link between inhibition of this enzyme, protoporphyrin IX accumulation, and the phytotoxicity of DPE herbicides.

Journal Article↗
PubMed1992

Chromosome fragility in the Lennox-Gastaut epilepsy syndrome.

Chromosome fragility was sought in a well-defined cohort of patients with Lennox-Gastaut epilepsy syndrome. Twenty-five patients plus 25 age- and sex-matched normal controls had cytogenetic studies performed. All patients were taking sodium valproate, and four were also on hydantoin. Blood cultures from both patients and controls were set up simultaneously in an appropriate medium designed to elicit fragile-sites. Harvesting took place after 96 h by standard techniques. In addition to routine banded analysis, at least 50 cells were scored for chromosome breaks and gaps from each patient and control. Results showed no difference between the patients and the control group in the overall occurrence of fragility or the type of aberration detected. No fragile-X syndrome was detected. This study found no effect due to sodium valproate on the occurrence of chromosome aberrations.

Adolescent↗
PubMed1992

HLA antigens in Tlingit Indians with rheumatoid arthritis.

HLA-DR4 has been described in association with rheumatoid arthritis (RA) in multiple populations. We have studied HLA antigens in Alaskan Tlingit Indians. HLA-DR4 was decreased in the RA group (n = 32) compared with controls (n = 62) (6% vs 21% p = 0.07). The predominant DR4 allele observed was DRB1*0403 (Dw13.1). The most striking observation in these studies was a marked predominance of the DRB1*1402 allele encoding Dw16 (DRw14). This allele was present in 91% of RA cases, but was also highly prevalent in controls (80%, OR = 2.4 p = 0.20). DRB1*1402 only was observed in 47% of cases and 31% of controls. The DRB3*0101 (DRw52), and the DQA*0501 and DQB*0301 alleles encoding a subset of DQw3 were associated with DRB1*1402 in cases and in controls. HLA-Bw62 was increased in RA cases (28%) compared with controls (8%) (OR = 4.5, p = 0.01, corrected p = ns).

Adult↗
PubMed1992

Identification of a short nuclear lamin protein selectively expressed during meiotic stages of rat spermatogenesis.

The nuclear lamina is a karyoskeletal structure located at the nuclear periphery and intimately associated with the inner nuclear membrane. It is composed of a multigene family of proteins, the lamins, which show a conspicuous cell type-specific expression pattern. The functional role of lamins has not been definitively established but available information indicates that they are involved in the organization of nuclear envelope and interphase chromatin. Spermatogenesis is characterized, among other features, by stage-specific changes in chromatin organization and function. These changes are accompanied by modifications in the organization and composition of the nuclear lamina. In previous experiments we have determined that rat spermatogenic cells express a lamin closely related, if not identical, to lamin B1 of somatic cells; whereas rat somatic lamins A, C, D and E were not detected. Considering that chromatin reorganizations during spermatogenesis may be directly or indirectly related to changes of the nuclear lamina we have decided to further investigate lamin expression during this process. Here we report on the identification of a 52 kDa protein of the rat which, according to immunocytochemical and biochemical data, appears to be a novel nuclear lamin. Using meiotic stage-specific markers, we have also demonstrated that this short lamin is selectively expressed during meiotic stages of spermatogenesis.

Animals↗
PubMed1992

Reciprocal neurological developments of twins discordant for hydrocephalus.

Studies of 10 sets of twins discordant for hydrocephalus in early life revealed striking differences in degree and nature of development of verbal vs. non-verbal cognitive functions, birth order, and hand and eye preference. Despite similar (four dizygotic pairs) or identical (six monozygotic pairs) genetic endowment and grossly similar intra- and extra-uterine environmental and socio-economic influences, the consistency of the differences between the hydrocephalic children and their seemingly normal twins indicate systematic differences in pre-, peri- and/or early postnatal organization and development of hemispheric function. Follow-up studies also documented development of above-average intelligence, despite drastically reduced cerebral mantle size in hydrocephalus of early onset. The atypical patterns of development of the non-hydrocephalic twins also confirm previously described qualifications reported in studies of the significance of genetic vs. environmental factors in twins.

Adolescent↗
PubMed1992

Cutaneous oral-motor reflexes of children with normal and disordered speech.

Cutaneous reflex responses in the human jaw-closing system to low-threshold, mechanical stimulation were investigated in 30 four- to six-year-old children with normal speech and in seven children with disordered speech. Responses of these children were smaller and less frequently observed than those of a seven- to eight-year-old group in an earlier study, suggesting that cutaneous oral-motor reflexes may develop with the acquisition of speech motor skills. Preliminary observations in a very small sample of speech-impaired children suggest that future work should explore the hypothesis that development of cutaneous oral reflexes is delayed in this group. The results of this and other studies suggest that human oral-motor reflexes undergo a pattern of continuous change throughout the lifespan.

Articulation Disorders↗
PubMed1992

Atrial natriuretic peptide in the diagnosis of patent ductus arteriosus.

The aim of this study was to measure plasma atrial natriuretic peptide in preterm infants with a patent ductus arteriosus before and after closure with indomethacin. Atrial natriuretic peptide was measured in 28 preterm infants with clinical and echocardiographic evidence of a patent ductus arteriosus and in eight preterm infants who did not develop clinical evidence of a patent ductus arteriosus. Plasma concentration of atrial natriuretic peptide was measured by radioimmunoassay. In 18 infants the patent ductus arteriosus closed after one course of indomethacin; atrial natriuretic peptide levels decreased from median 1240 pg/ml (range 201-5483 pg/ml) to 266 pg/ml (range 62-1108 pg/ml). In four infants the patent ductus arteriosus closed after two courses of indomethacin and two infants had surgical ligation after indomethacin treatment failed. The patent ductus arteriosus closed spontaneously in four infants (atrial natriuretic peptide median level 152 pg/ml, range 61-495 pg/ml). In the eight infants without patent ductus arteriosus, atrial natriuretic peptide level was median 224 pg/ml (range 38-876 pg/ml). Measurement of plasma atrial natriuretic peptide concentration has a role in predicting when indomethacin treatment is indicated.

Atrial Natriuretic Factor↗
PubMed1992

Development of monoclonal antibodies that identify Vibrio species commonly isolated from infections of humans, fish, and shellfish.

Monoclonal antibodies (MAbs) against Vibrio species that infect humans, fish, and shellfish were developed for application in rapid identifications. The pathogens included Vibrio alginolyticus, V. anguillarum, V. carchariae, V. cholerae, V. damsela, V. furnissii, V. harveyi, V. ordalii, V. parahaemolyticus, and V. vulnificus. Three types of MAbs were selected. The first important group included MAbs that reacted with only a single species. A second group comprised a number of MAbs that reacted with two, taxonomically closely related Vibrio species. For example, of 22 MAbs raised against V. alginolyticus, 6 recognized a 52-kDa flagellar H antigen common to both V. alginolyticus and V. parahaemolyticus; V. anguillarum and V. ordalii also shared antigens. A third group included three genus-specific MAbs that reacted with almost all Vibrio species but did not react with other members of the family Vibrionaceae (e.g., members of the Aeromonas, Photobacterium, and Plesiomonas genera) or a wide range of gram-negative bacteria representing many genera. This last group indicated the possible existence of an antigenic determinant common to Vibrio species. Two of these three genus-specific MAbs reacted with heat-stable antigenic determinants of Vibrio species as well as lipopolysaccharide extracted from Vibrio species. The use of the MAbs in blind tests and diagnosis of clinical isolates indicated that three different types of bacteria, viz., live, formalin-fixed, and sodium azide-killed bacteria, were detected consistently. Overall, it was found that the genus-specific MAbs were very useful for rapidly identifying vibrios in the screening of acute infections, while the species-specific MAbs and others were useful for completing the diagnosis.

Animals↗
PubMed1992

Influence of cardiopulmonary bypass on water balance hormones in children.

OBJECTIVE: To determine the changes in the endocrine mechanisms of fluid balance after cardiopulmonary bypass in children. DESIGN: Prospective study; analysis of numbered plasma samples performed blind with respect to clinical data. SETTING: Regional paediatric cardiothoracic unit. PATIENTS: Nine patients, median age 4, range 2 to 9 years, five males. Patients under the age of 1 year were excluded because of the frequent blood sampling involved. MAIN OUTCOME MEASURES: Plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin, plasma renin activity, aldosterone, noradrenaline and adrenaline, and urinary concentrations of cyclic guanosine monophosphate (cGMP) as measured by radioimmunoassay. RESULTS: After 30 minutes of cardiopulmonary bypass plasma atrial natriuretic peptide (ANP) decreased from (mean (SEM)) 151 (71) pg/ml to 52 (44) pg/ml (NS), and urinary production of its second messenger cyclic guanosine monophosphate (cGMP) decreased from 1286 (600) pmol/ml to 151 (414) pmol (p < 0.05). Other plasma concentrations of hormones studied did not change significantly although arginine vasopressin, adrenaline, and noradrenaline increased whereas aldosterone and plasma renin activity decreased. After cardiopulmonary bypass stopped there was an immediate and significant rise in plasma ANP, but within the next 24 hours plasma ANP declined significantly (p < 0.05), decreasing from 294 (49) pg/ml to 64 (29) pg/ml at 22 hours. In the postoperative period there was a significant correlation between plasma ANP and both mean fluid balance (r = 0.96, p < 0.001) and mean urine output (r = 0.97, p < 0.001). Plasma aldosterone peaked (p < 0.05) at 22 hours after operation, and argine vasopressin peaked (p < 0.05) at two hours and then declined (p < 0.05) to a trough at 24 hours. Plasma renin activity, adrenaline, noradrenaline, and urinary cGMP concentrations, and mean central venous pressure did not change significantly in the postoperative period. CONCLUSION: The changes documented show the differing pattern of release of water balance hormones invoked by cardiopulmonary bypass. The central role of ANP is shown by its strong correlation with urinary output and its similarly strong relation to fluid balance.

Aldosterone↗
PubMed1992

Association of atrophy of the medial temporal lobe with reduced blood flow in the posterior parietotemporal cortex in patients with a clinical and pathological diagnosis of Alzheimer's disease.

A combination of medial temporal lobe atrophy, shown by computed tomography, and reduced blood flow in the parietotemporal cortex, shown by single photon emission tomography, was found in 86% (44/51) of patients with a clinical diagnosis of senile dementia of the Alzheimer type (SDAT). The same combination of changes was found in four out of 10 patients with other clinical types of dementia and in two out of 18 with no evidence of cognitive deficit. Of the 12 patients who died, 10 fulfilled histopathological criteria for Alzheimer's disease, nine of them having a clinical diagnosis of SDAT, and one a clinical diagnosis of multi-infarct dementia. All 10 patients with histopathologically diagnosed Alzheimer's disease had shown a combination of hippocampal atrophy and reduced parietotemporal blood flow in life. In 10 patients (nine with SDAT) out of 12 in whom the hippocampal atrophy was more noticeable on one side of the brain than on the other the parietotemporal perfusion deficit was also asymmetrical, being greater on the side showing more hippocampal atrophy. These results suggest that the combination of atrophy of the hippocampal formation and reduced blood flow in the parietotemporal region is a feature of dementia of the Alzheimer type and that the functional change in the parietotemporal region might be related to the loss of the projection neurons in the parahippocampal gyrus that innervate this region of the neocortex.

Aged↗
PubMed1992

The control of orofacial movements in speech.

Rapid, complex movements of orofacial structures are essential to produce the sounds of speech. A central problem in speech production research is to discover the neural sources that generate the control signals supplied to motoneurons during speaking. Speech movement production appears to share organizational principles with other motor behaviors; thus speech movements probably arise from an interaction of centrally generated command signals with sensory information. That speech movements are ultimately linked to the perception of language, however, has led many investigators to suggest that speech movement control involves unique features, features that may be linked to abstract linguistic units.

Brain↗