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Biomedical subjects

M A Lynch

Publications and source records attributed to M A Lynch.

At least 19 recordsLinked to original sources
PubMed1992

Domain-specific and cell type-specific localization of two types of cell wall matrix polysaccharides in the clover root tip.

Using immunocytochemical techniques and antibodies that specifically recognize xyloglucan (anti-XG), polygalacturonic acid/rhamnogalacturonan I (anti-PGA/RG-I), and methylesterified pectins (JIM 7), we have shown that these polysaccharides are differentially synthesized and localized during cell development and differentiation in the clover root tip. In cortical cells XG epitopes are present at a threefold greater density in the newly formed cross walls than in the older longitudinal walls, and PGA/RG-I epitopes are detected solely in the expanded middle lamella of cortical cell corners, even after pretreatment of sections with pectinmethylesterase to uncover masked epitopes. These results suggest that in cortical cells XG and PGA/RG-I are differentially localized not only to particular wall domains, but also to particular cell walls. In contrast to their nonoverlapping distribution in cortical cells, XG epitopes and PGA/RG-I epitopes largely colocalize in the epidermal cell walls. The results also demonstrate that the middle lamella of the longitudinal walls shared by epidermal cells and by epidermal and cortical cells constitutes a barrier to the diffusion of cell wall and mucilage molecules. Synthesis of XG and PGA/RG-I epitope-containing polysaccharides also varies during cellular differentiation in the root cap. The differentiation of gravitropic columella cells into mucilage-secreting peripheral cells is marked by a dramatic increase in the synthesis and secretion of molecules containing XG and PGA/RG-I epitopes. In contrast, JIM 7 epitopes are present at abundant levels in columella cell walls, but are not detectable in peripheral cell walls or in secreted mucilage. There were also changes in the cisternal labeling of the Golgi stacks during cellular differentiation in the root tip. Whereas PGA/RG-I epitopes are detected primarily in cis- and medial Golgi cisternae in cortical cells (Moore, P. J., K. M. M. Swords, M. A. Lynch, and L. A. Staehelin. 1991. J. Cell Biol. 112:589-602), they are localized predominantly in the trans-Golgi cisternae and the trans-Golgi network in epidermal and peripheral root cap cells. These observations suggest that during cellular differentiation the plant Golgi apparatus can be both structurally and functionally reorganized.

Antibodies, Monoclonal↗
PubMed1991

Increase in arachidonic acid concentration in a postsynaptic membrane fraction following the induction of long-term potentiation in the dentate gyrus.

We have determined the concentration of free fatty acids in membranes of slices prepared from the dentate gyrus following the induction of long-term potentiation in the anaesthetized rat. Compared to unpotentiated tissue, there was a significant increase in the concentration of free arachidonic acid 2.5 min, 45 min and 3 h after induction of long-term potentiation. There was no corresponding increase in oleic, stearic or palmitic acids. To account for the increase in free arachidonate, the activities of phospholipase A2, phospholipase A1 and phospholipase C were determined at the same three time intervals in control and potentiated tissue. Two-and-a-half minutes after the induction of long-term potentiation, activity of phospholipase A2 was enhanced, while at 45 min, and at 3 h phospholipase C activity was increased. These results suggest that the liberation of free arachidonate is due initially to phospholipase A2 activity, but that at later stages of long-term potentiation, control switches to phospholipase C. Subcellular fractionation experiments revealed an increase in free arachidonate in the postsynaptic density fraction 45 min after induction of long-term potentiation, without significant changes in synaptosomal- or glial-enriched fractions. These results are consistent with the hypothesis that arachidonic acid, released from a postsynaptic site, acts as a trophic retrograde synaptic signal in long-term potentiation in the dentate gyrus.

Animals↗
PubMed1979

Lost to follow up: a study of nonattendance at a general paediatric outpatient clinic.

50 children defined as persistent outpatient nonattenders were compared with 50 children who regularly attended the same clinics. Several factors were often found in the group of nonattenders: (a) initial referral via casualty without a letter from the family doctor, (b) hospital admission before the first outpatient appointment, (c) recognition of multiple medical problems, and (d) evidence of diffuse social problems affecting the family. 34 of the nonattenders had at least 2 of these factors, compared with only 9 children in the other group. Many of these problems can be identified at the initial consultation, and perhaps other methods of continuing health care should be provided for these children.

Adolescent↗
PubMed1979

Recognizing a child at increased risk of abuse.

Data from two studies are presented. Both highlight characteristics which help identify children at increased risk of child abuse. The first study demonstrates that the abused child when compared with unharmed children in the same family is more likely to have been the product of an abnormal pregnancy, labor, delivery and neonatal period. He is more likely to have been separated from his mother and to have been ill in the first year of life. His mother too is more likely to have been sick during that year. The second study shows that it is possible to identify 'at risk' families around the time the baby is born. When compared with controls, five factors are more common: mother aged under 20 at birth of first child, evidence of emotional disturbance, referral to the social worker, admission of baby to special care nursery, and early concern over mothering.

Child↗
PubMed1977

Predicting child abuse: signs of bonding failure in the maternity hospital.

Fifty children referred to the Park Hospital because of actual or threatened abuse were compared with 50 controls born at the same maternity hospital. Five factors were significantly more common in the abused group than among their controls: (a) mother aged under 20 at birth of first child, (b) evidence of emotional disturbance, (c) referral of family to hospital social worker, (d) baby's admission to special care baby unit, (e) recorded concern over the mother's ability to care for child. Thirty-five of the abused group had two or more of these factors compared with only five of the control group. As these data were collected from information recorded routinely at the maternity hospital, it is possible to identify most abusing families when the child is born. Such identification must lead to a comprehensive assessment of each case followed by constructive preventive action.

Adolescent↗
PubMed1976

General practice observed. Child abuse and general practice.

In a general practice of 9250 patients with 1841 children under 10 there were 12 cases of actual abuse during 1973-6. In March 1976 30 children were at risk. A preventive scheme was set up and the short-term outcome was good. There were no cases of serious abuse among the children at risk.

Child Abuse↗
PubMed1975

Ill-health and child abuse.

Intensive therapeutic work with families, in which child abuse had occurred, suggested that bonding failure related in part to the pregnancy, perinatal experience, and early ill-health of the abused proband and parents. 25 consecutive unequivocally abused children who had 1 or more siblings were selected from our referrals. Six factors emerged as highly significantly over-represented in the proband biography as compared with the control sibling group: abnormal pregnancy, abnormal labour or delivery, neonatal separation, other separation in the first six months, illnesses in the first year of life, and illness in the mother in first year of life. These data suggest that treatment of parents during pregnancy the perinatal period, and early infancy may well be fruitful in the prevention of child abuse.

Adolescent↗