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Biomedical subjects

M A Thomson

Publications and source records attributed to M A Thomson.

At least 55 records · Page 3Linked to original sources
PubMed1989

Representation of vibrissae inputs through the climbing fiber pathway in lobule VII of the adult rat cerebellar vermis.

The present study gives a detailed description of the functional characteristics and of the topographic distribution of Purkinje cell (PC) responses, mediated through the climbing fiber pathway and elicited by mechanical stimulation of two different rows (A and C) of vibrissae in a circumscribed region of the posterior vermis of the rat cerebellum. Experiments were carried out on normal adult rats under barbiturate anesthesia. PCs were recorded in an area extending 1500 microns laterally to the midline in the vermal part of lobule VII contralateral to the stimulation. Using micromapping techniques and computer analysis, we located the cells on the map of the unfolded PC layer. Taking into account the mean latency of the responses and the probability of discharge of PCs, restricted areas of projection were found. For each row, these areas formed two longitudinal patches located between midline and plane 1100 microns and separated by a non-responsive plane at 500 microns. Cells having the best characteristics of responses to the stimulation of row C were located mainly in plane 200 microns. Cells giving the best responses to the stimulation of row A were located mainly in the posterior part of plane 200 microns which was therefore a zone of convergence for both rows.

Action Potentials↗
PubMed1988

Effects of unilateral cerebral ischemia on the hippocampal theta depth profile in the ether-anesthetized Mongolian gerbil.

In gerbils (Meriones unguiculatus) unilateral cerebral ischemia of 5 to 15 min resulted in selective destruction of the ipsilateral hippocampal CA1 stratum pyramidale. It also produced an obvious amplitude reduction in both superficial and deep theta rhythms recorded from damaged hippocampal formation. The presence of normal theta in the left normoxic hemisphere showed that the septohippocampal projections, integrity of which is essential for theta appearance, were spared by ischemia. These data have implications in relation to the two generators hypothesis of theta.

Anesthesia↗
PubMed1988

The value of serum human placental lactogen and Schwangerschaftsprotein 1 to determine gestation in an ante-natal population.

Single assays of Schwangerschaftsprotein 1 (SP1) and serum human placental lactogen (HPL) were performed in 500 consecutive patients attending a routine ante-natal clinic for their first visit. All samples were taken before 112 days gestation. Of these 500 patients, 233 had a regular menstrual cycle, were certain of last menstrual period (LMP) and delivered a normal infant after spontaneous labour. Regression equations were calculated from these results to assess their value for correcting gestation. Regression equations from previous publications were also applied to our data. The gestation and estimated date of delivery were calculated using SP1 and HPL and were compared with the actual gestation and date of delivery. The correlation was poor and did not indicate that SP1 or HPL could be used to calculate these values in the normal ante-natal population.

Adult↗
PubMed1988

Human placenta--an antibody sponge?

Maternal IgG antibodies in sera and placenta eluates were studied by a cellular enzyme-linked immunosorbent assay (CELISA) method. Antibodies were not detectable in any of the serum samples obtained before or after delivery from nine normal primigravid women. Antibody activity was, however, present in five of nine placental eluates and two of nine neonatal sera tested in CELISA. Lymphocytotoxic antibodies were not detected in any of the samples tested. These results support the concept that the absence of antibody activity in maternal sera may be caused by the immunosorbent effect of the placenta.

Birth Weight↗
PubMed1987

Two year study of cryptosporidium infection.

During a two year period 48 children admitted to hospitals in the Blackburn district were found to have cryptosporidium in stool samples. Cryptosporidium accounted for 6% of the 742 cases of childhood gastroenteritis, being as common as campylobacter. Altogether, 89% of children with cryptosporidiosis had diarrhoea, which was usually offensive and watery, and 80% vomited, the mean duration of both symptoms being six days. A substantial proportion were moderately ill with dehydration and persistent vomiting. Over half of all cases were aged 2 years or more and 37% were over 5 years. Most of the ill children were over 2 years, in contrast with other cases of gastroenteritis. Eight children were less than the 3rd centile for weight and three of these were investigated for failure to thrive. Only 6% of cases occurred in Asian children, but Asians accounted for 32% of all admissions with gastroenteritis and 59% of admissions with shigella. This unexpected ethnic difference may be due to limited contact with animals among Asians or to differences in diet.

Asia↗
PubMed1986

Temporal changes in hippocampal theta activity following twenty minutes of forebrain ischemia in the chronic rat.

The present study was designed to examine the temporal changes in the theta (theta) rhythm recorded from the dorsal hippocampal formation of the chronic rat following 20 min of cerebral ischemia. Recordings were made during both wakefulness and paradoxical sleep. The experimental results show that ischemia resulted in a drastic amplitude reduction in both superficial and deep theta. Amplitude reduction occurred between days 1 and 4 postischemia and was maintained across the subsequent survival period. This EEG alteration was associated with an excessive loss of pyramidal cells in the hippocampal CA1 area, as observed by light microscopy. The above data strongly support our previous conclusions that neural components of the CA1 area may be of fundamental importance for the appearance and the maintenance of not only superficial theta but also deep theta. Moreover, they suggest that the preparation used in the present study may be a useful model for investigations on the neuroanatomophysiological effects of transient cerebral ischemia.

Animals↗
PubMed1986

Spatial distribution of hippocampal-dentate theta rhythm following colchicine injection into the hippocampal formation of the rat.

This investigation confronts the basic question of dentate granule cell participation in the generation of superficial and/or deep theta recorded from the dorsal hippocampal formation in the ether-anesthetized rat. Granular cells were destroyed unilaterally by local injection of 2 micrograms of colchicine (COL) dissolved in 0.2 microliter of distilled water. Hippocampal EEG was recorded 8 days after the neurotoxin injection. The COL injection which destroyed most dentate granular cells but left nearby pyramidal cells of the hippocampal CA1 area virtually unaffected, failed to disrupt significantly either superficial or deep theta. In contrast, the COL injection which destroyed most dentate granular cells and, also, caused some damage to the nearby pyramidal cells of the CA1 area, resulted in a sharp alteration of both theta. These data strongly suggest that granular cells of the dentate gyrus may not be critically involved in theta production, at least in the ether-anesthetized rat. They also confirm a previous conclusion that the neuroanatomical integrity of the CA1 area of the dorsal hippocampus is necessary for the normal appearance and maintenance of both superficial and deep theta. These data are discussed in the context of the generally accepted notion that superficial and deep theta are produced by the rhythmic activity of CA1 pyramidal cells and dentate granular neurons respectively.

Animals↗
PubMed1985

Hippocampal-dentate theta disturbance after selective CA1 pyramidal cell damage in the rat.

The contribution of the CA1 area of the dorsal hippocampus to both superficial and deep theta recorded from the dorsal hippocampal formation was assessed in rats anesthetized with ether. CA1 area cells were destroyed unilaterally by local injection of 2 micrograms of ibotenic acid dissolved in 0.1 microliters of phosphate buffer. Limited destruction of CA1 resulted in partial suppression of both superficial and deep theta, whereas extensive destruction resulted in almost total suppression of both theta's. A good correlation was found between the extent of the lesion and the theta disruption. Control preparations involving destructions by means of this neurotoxin of the hippocampal CA3 area or lower blade of the dentate gyrus failed to alter either superficial or deep theta. These data suggest that neuroanatomical integrity of the CA1 area of the dorsal hippocampus is a necessary condition for the normal appearance and maintenance of both superficial and deep theta as recorded from the dorsal hippocampal formation of the ether-anesthetized rat.

Animals↗
PubMed1984

Noncytotoxic antibodies to paternal antigens in maternal sera and placental eluates.

Noncytotoxic antibodies were detected in sera from 6 of 7 primigravid women during the first trimester of pregnancy. Such antibodies directed to antigens expressed on paternal B lymphocytes were detectable within the first 4-5 weeks of gestation. Antibody activity toward paternal B lymphocytes was also detected in 6 of 10 placental eluates, and in 3 of 10 predelivery and 2 of 10 postdelivery maternal serum samples. When B lymphocytes from umbilical cord blood were used as target cells, antibodies were detected in 5 of 7 placental eluates, and in 3 of 7 predelivery and 2 of 7 postdelivery serum samples. These antibodies also reacted with selected members of a normal B lymphocyte panel. The concept of an immunological enhancing mechanism in normal pregnancy is supported by these data.

B-Lymphocytes↗
PubMed1983

Topographic organization of septal cells innervating the dorsal hippocampal formation of the rat: special reference to both the CA1 and dentate theta generators.

We determined the topographic organization of septal cells innervating monosynaptically the two generators of theta rhythm of the rostral hippocampal formation of the rat. Under ether anesthesia, horseradish peroxidase (HRP) was injected into the dorsal CA 1 region close to the corpus callosum, the ventral part of CA 1 region close to the hippocampal fissure, and the dentate hilus. The HRP micropipet tip was positioned in these hippocampal-dentate sites by recording the hippocampal EEG through the micropipet itself before HRP injection. The major findings were: (i) Injection of HRP in the superficial part of the dorsal CA 1 region (i.e., the septal pole) resulted in labeling of neurons situated mainly in the diagonal band of Broca, ipsilateral to the injection site. (ii) Injection of HRP in the deep part of the dorsal CA 1 region resulted in the labeling of a few cells scattered in the septal region ipsilateral to the injection site. (iii) After injection of HRP in the dentate hilus, labeled cells were selectively detected in the rostral half of the medial septal nucleus mainly ipsilateral to the injection site. A high degree of organization was revealed in the connections between the septal region and the rostral hippocampal formation of the rat, two cerebral regions critically involved in theta production. The results are relevant to the two-generator hypothesis of theta.

Animals↗
PubMed1983

[Spatio-temporal study of the electrical activities of the olfactory bulb of the trout Salmo gairdneri].

The electrical stimulation of the olfactory nerve allows to record steady field potentials in the olfactory bulb of the trout Salmo gairdneri. 200 microns separate recording points which are localised on a tridimensional network. At 18, 24, 30 and 38 ms the amplitudes are measured and plotted in a calculator which determines the isopotentials in any vertical, horizontal and sagittal planes. With this method, we have an instantaneous and global vision of bulbar activity and we observe striking anatomo-functional correlations in the olfactory bulb of Salmo gairdneri.

Animals↗
PubMed1983

The relationship between diabetic control and retinopathy in a group of diabetic teenagers.

Twenty insulin-dependent diabetic teenagers from the Oxford pediatric diabetic clinic were recruited to study the relationship between diabetic control and retinal microvascular disease. Two patients (10%) had evidence of minimal background diabetic retinopathy on careful ophthalmoscopy. Retinal color photography and fluorescein angiography each revealed retinopathy in 5 patients (25%) and together revealed retinopathy in 7 patients (35%). Color photography demonstrated retinopathy which had not been discovered on ophthalmoscopy. The presence of retinopathy was related to the duration of diabetes (p less than 0.02) and the glycosylated hemoglobin level (p less than 0.01). It is concluded that multiple field color photography is a useful method of assessing patients with minimal or no ophthalmoscopic retinopathy.

Adolescent↗
PubMed1980

Utilization of within-hospital services. A study of the effects of two forms of group practice.

This study examined the effect of group affiliation on the use of technical (length of stay, lab tests, etc.) and clinical (rendering and requesting consultations) resources by physicians practicing within a large acute care hospital. Comparisons in use were made between physicians in 1) a prepaid group practice (Colorado Permanente Medical Group [Kaiser]); 2) a fee-for-service group practice; and 3) "unaffiliated" physicians. Patient data were adjusted whenever possible for patient diagnosis and severity. In comparison to other physicians in the hospital, the prepaid group physicians utilized somewhat fewer technical resources, though the results were not statistically significant. Differences in the use of clinical resources were statistically significant, with the fee-for-service group physicians using consulting services the most and prepaid group physicians using them the least. The results indicate that 1) fee-for-service group structures may reinforce the incentives to share in consultation revenues; 2) prepaid group physicians may experience difficulty becoming integrated into the informal structures of physician practice patterns; and 3) the control of groups over the use of technical hospital resources may be substantially weakened when groups do not own or control the hospitals to which they admit their patients.

Analysis of Variance↗
PubMed1980

In vitro autohaemolysis during pregnancy.

In vitro autohaemolysis with and without the addition of glucose was performed on normal pregnant women chosen at random and on non-pregnant women of comparable age. Autohaemolysis was significantly greater in the pregnant than the nonpregnant. The relationship between the stage of gestation and in vitro autohaemolysis in normal pregnancy may be fitted by a quadratic curve.

Erythrocytes↗