The visual cortical association field: a Gestalt concept or a psychophysiological entity?

The receptive field of a visual neurone is classically defined as the region of space (or retina) where a visual stimulus evokes a change in its firing activity. Intracellular recordings in cat area 17 show that the visually evoked synaptic integration field extends over a much larger area than that established on the basis of spike activity. Synaptic depolarizing (dominant excitation) responses decrease in strength for stimuli that are flashed at increasing distances away from the centre of the discharge field, while their onset latency increases. A detailed spatio-temporal analysis of these electrophysiological data shows that subthreshold synaptic responses observed in the 'silent' surround of cortical receptive fields result from the intracortical spread of activation waves carried by slowly conducting horizontal axons within primary visual cortex. They also predict that a perceptual facilitation may occur when feedforward activation produced by the motion signal in the retina travels in phase in the primary visual cortex with the visually induced spread of horizontal activation. A psychophysical correlate has been obtained in humans, showing that apparent motion produced by a sequence of co-linear Gabor patches, known to preferentially activate V1 orientation selective cells, are perceived by human observers as much faster than non co-linear sequences of the same physical speed.

FAK+ and PYK2/CAKbeta, two related tyrosine kinases highly expressed in the central nervous system: similarities and differences in the expression pattern.

Focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2/cell adhesion kinase beta (PYK2/CAKbeta) are related, non-receptor, cytoplasmic tyrosine kinases, highly expressed in the central nervous system (CNS). In addition, FAK+ is a splice isoform of FAK containing a 3-amino acid insertion in the carboxy-terminal region. In rat hippocampal slices, FAK+ and PYK2/CAKbeta are differentially regulated by neurotransmitters and depolarization. We have studied the regional and cellular distribution of these kinases in adult rat brain and during development. Whereas PYK2/CAKbeta expression increased with postnatal age and was maximal in the adult, FAK+ levels were stable. PYK2/CAKbeta mRNAs, detected by in situ hybridization, were expressed at low levels in the embryonic brain, and became very abundant in the adult forebrain. Immunocytochemistry of the adult brain showed a widespread neuronal distribution of FAK+ and PYK2/CAKbeta immunoreactivities (ir). PYK2/CAKbeta appeared to be particularly abundant in the hippocampus. In hippocampal neurons in culture at early stages of development, FAK+ and PYK2/CAKbeta were enriched in the perikarya and growth cones. FAK+ extended to the periphery of the growth cones tips, whereas PYK2/CAKbeta appeared to be excluded from the lamellipodia. During the establishment of polarity, a proximal-distal gradient of increasing PYK2/CAKbeta-ir could be observed in the growing axon. In most older neurons, FAK+-ir was confined to the cell bodies, whereas PYK2/CAKbeta-ir was also present in the processes. In vitro and in vivo, a subpopulation of neurons displayed neurites with intense FAK+-ir. Thus, FAK+ and PYK2/CAKbeta are differentially regulated during development yet they are both abundantly expressed in the adult brain, with distinctive but overlapping distributions.

Determinants of contraceptive use in Morocco: stopping behaviour in traditional populations.

The determinants of modern contraceptive use in traditional populations are analysed in married women aged 30-44 living in the province of Marrakech (Morocco). Women who have never used contraception have smaller family sizes than those who do: the number of live children (or live births) is the variable with maximum predictive power on contraceptive use, while child mortality is the main inhibiting factor. The probability of contraceptive use increases with female age at marriage and decreases with the woman's age, indicating a generational change in reproductive behaviour. The socioeconomic variables education, employment and residence, have no significant independent predictive character on contraceptive use, although the interaction between education and residence does. The paper evaluates the hypothesis that traditional populations in the initial phase of their demographic transition resort to modern contraception in order to stop childbearing, when they have reached a desired number of children, rather than to space births or reduce their fertility.

PIP: The authors conclude that the determinants of contraceptive use among the rural population in Marrakech province, Morocco, were multiple and interrelated in complex ways. Birth control was a consequence of changes at both the individual and social levels. Findings indicate that women who had never used contraception had smaller family sizes than those women who used contraception. Contraceptive users had a significantly higher number of live births and living children. Child mortality was significantly greater among noncontracepting women. Contraceptive users had a significantly longer reproductive period than nonusers, which was attributed to a longer delay in the last live birth. Logistic models show that significant independent predictors of contraceptive use were the number of live births, the number of children who died before the age of 5, the age of the mother, the type of marriage, and the age at first marriage. The probability of access to contraceptives decreased with under-5 mortality, female age, marriage age, and increases in polygynous unions. This model explained 63.9% of the variance. Although residence and educational level did not significantly increase the fit of the model, the probability of contraceptive use did increase in relation to urban residence and a basic educational level. The number of live children was a predictor of contraceptive use but the best predictor of contraceptive use was family size (65.8%). The probability of contraceptive use increased among women with three or more children. Female education had no independent predictive impact on contraceptive use. Contraceptive use increased among women in polygynous unions, regardless of residence or schooling.

[New surgical procedure for the protection of the small intestine before postoperative pelvic irradiation]. / Nouveau procédé chirurgical de protection du grêle avant irradiation pelvienne post-opératoire.

A prosthesis was designed to protect the intestinal loop from external beam radiation therapy when post-operative radiation is indicated. It is a silicone inflatable balloon, which, when implanted displaces the intestinal loops out of the pelvic irradiation field. The prosthesis can be deflated between each course of irradiation, without surgery. The device has been used in 8 patients: 6 patients with recurrent pelvic tumor (2 rectal cancers, 1 anal cancer, 1 cancer of the endometrium, 1 cervical carcinoma, 1 ovarian carcinoma), 2 patients with primary tumor (1 malignant paraganglioma, 1 cervical carcinoma). Radiotherapy was administered by means of high power appliances. After radiotherapy, the prosthesis was deflated, then removed through a 3 cm incision under local or peridural anesthesia. The tolerance of the small intestine to the radiation therapy has been satisfactory in each case with no bowel injury due to radiation. Therefore, this simple device might be useful to prevent bowel injury during postoperative radiation in the treatment of abdominal and retroperitoneal tumor masses.

[New material for needle jejunostomy: technique and preliminary results]. / Nouveau matériel pour jéjunostomie à l'aiguille: technique et résultats préliminaires.

New material for needle jejunostomy was evaluated. They have the following advantages: rapidity and ease of use in jejunostomy, the possibility of a high daily calorie intake, a cutaneous fixation system allowing cleaning of the feeding tube stoma. The material is presented and the insertion technique is described. The preliminary results in 30 patients showed no mortality or morbidity related to the jejunostomy. The authors stress the importance of performing needle jejunostomy whenever long-term high calorie intake is required after the operation.

Some recent trends in infant mortality in the province of Marrakech, Morocco: a demographic transition in process.

PIP: 2 studies designed to appraise fecundity and mortality were carried out in Morocco in 1983 and 1984, on samples of 3,000 and 5,000 women respectively, in the city and in the province of Marrakech. Infant mortality was studied using the biometric method of J. Bourgeois-Pichat. The 1st results presented in this article highlight the absence of excess exogenous mortality among women under 30 years of age living in a provincial urban environment and among women from the city of Marrakech whose husbands were employed in service activities. 1st, this points to a link between the level of exogenous mortality and the standard of living of the population. In the city, exogenous mortality varies according to the occupation of the head of the family, an important factor in estimating its economic level. In the province one can assume that the standard of living of women from urban areas is higher than in the country. Moreover, small urban centers benefit from a larger infrastructure with easier access to medical care. 2nd, mortality has declined among young women. This result is certainly closely linked to the improvement of living conditions in Morocco over the last 2 decades. It is therefore reasonable to consider that a demographic transition is taking place, one which impacts on the level and structure of infant mortality.^ieng

Identification and quantitative determination of LSD by fluorescence: new data.

Tests for the detection of lysergic acid diethylamide (LSD) are not always specific; to cope with this problem the authors have developed a fluorimetric apparatus and technique for the detection and identification of LSD in samples seized from illicit traffic in drugs. The fluorimeter is not electronic and is simple to make and use, inexpensive, easy to handle and suitable for field analyses. With the new, highly sensitive and selective method of synchronous excitation spectrofluorimetry, a toxicological analytical laboratory can confirm measurements made in the field and make an immediate determination of the quantity of LSD in the samples seized. The agreement between results obtained using differential fluorimetry or synchronous spectrofluorimetry and chromatographic techniques was found to be excellent. Quantitative analysis is very useful because the amount of LSD per "dose" can vary, from one batch to another, from a few tenths of a microgram to several hundred micrograms.

Spontaneous long-term acceptance of RT-1-incompatible liver allografts in inbred rats. Analysis of the immune status.

In several combinations of inbred rats, liver allografts are spontaneously tolerated, and after a few weeks liver tolerant rats are in a state of donor-specific transplantation tolerance. In vivo and in vitro experiments were conducted to analyze the immunological status of LEW or BN rats with spontaneously tolerated (LEW X BN) F1 liver allografts several months after transplantation. Acute rejection of secondary donor-specific heart allografts retransplanted from liver-tolerant rats to normal syngeneic hosts suggests that the state of tolerance in liver-tolerant rats is related to an active modification of the immune system of the rat and not to a reduced immunogenicity of the graft. No cytotoxic antibodies or cells were found in liver-tolerant rats. Reactivity in mixed lymphocyte culture was normal or slightly reduced. Arguments for the presence of splenic suppressor cells were found in LEW tolerant rats using a local graft-versus-host assay, but these could not be found in BN rats, or when attempting to transfer or to break the tolerance state. A nonspecific humoral blocking factor was found in vitro in liver-tolerant rats but transfer of serum from liver-tolerant rats to normal syngeneic hosts did not permit a significant prolongation of donor-specific heart allografts. These results suggest that more than one mechanism may be involved at the maintenance phase of liver allograft tolerance.

A low-cost differential fluorimeter for the detection and determination of LSD in illicit preparations.

The construction and use of a differential fluorimeter for rapid detection of LSD in confiscated material under field conditions is described. The apparatus is robust, electronics-free, compact and inexpensive. Adequate sensitivity is ensured by the high quantum yield of LSD fluorescence and a large degree of specificity is obtained by carrying-out two separate measurements: one in water and one in 1 M NaOH.

Perineal wound healing after proctectomy for carcinoma and inflammatory disease.

The rate of wound healing after proctectomy was assessed in a series of 105 patients. Early healing was dependent principally on the primary diagnosis, to a lesser extent on faecal contamination and was not related to steroid administration. Early healing (with 3 months) occurred in 72 per cent of patients undergoing operation for cancer and 45 per cent of these operated on for ulcerative or Crohn's colitis.

Application of synchronous excitation spectrofluorimetry to drug analysis.

Among the analytical techniques available for the determination of toxic products, fluorimetry is, at present, one of the most frequently employed. But in many cases, measurements at low concentrations are interfered with by Rayleigh and Raman scattering. We propose to eliminate, in great part, this interference and hence increase the sensitivity of the method, by using the new synchronous excitation spectrofluorimetry. Application of this technique to the identification and determination of drugs during recent forensic investigations demonstrates its advantages over classical spectrofluorimetry.

[Identification of toxic metals after extraction and thin-layer chromatograpy of their dithizonates. Toxicological applications (author's transl)]. / Identification de métaux toxiques après extraction et chromatographie sur couches minces de leurs dithizonates. Applications toxicologiques

The technique consists in employing successively an extraction method using the dithizone-carbon tetrachloride system, at 4 different pH values, then thin-layer chromatography on silica gel, to identify and separate Ag, Cd, Co, Cu, Hg, Ni, Pb, and Zn in the form of their dithizonates. Sensitivity is of the order of 10(-7) g ion/l. This method is directly applicable in hydrology; after destruction of organic matter in the case of biological samples (blood, urine, excrement). We have applied it in toxicological analysis together with other methods for the detection of copper, lead, mercury and zinc in cases of poisoning.

Application of pulse polarography with anodic stripping voltammetry to biological and toxicological analyses for lead and cadmium.

The development of polarographic techniques within the last thirty years has made possible exceptional increases in sensitivity ; thus the order of concentration studied has passed from 10-3 g ion/1. to 10-10 g ion/1. Pulse polarography with anodic stripping voltammetry is, therefore, particularly suitable for the determination of a large number of the so-called " biologically essential " and " highly toxic " metals, more often than not present in extremely low concentrations in biological samples which may be of limited volume (blood, for example). Our principal concern has been to describe and apply a method for the determination of lead and cadmium, sufficiently sensitive, precise, practical and rapid for everyday use by biologists and toxicologists. A fortiori this method is applicable in hydrology to the determination of traces of these metals in water.