The application of fluctuation analysis to studies of synaptic function in the neocortex is discussed. Analysis of failures of transmission has been valuable in indicating whether a presynaptic or a postsynaptic site is responsible for a change in synaptic efficacy. When combined with detailed ultrastructural verification of all synapses involved in an individual cell to cell connection, a reasonable estimate of quantal size and release probability under conditions of low frequency activity can be obtained. However, both the number of available release sites in functional terms and the probability that an action potential (AP) will release transmitter from any given site can vary from AP to AP at higher frequencies. A variety of presynaptic mechanisms that modulate release are now apparent. For example, one mechanism dominates release patterns at one class of connection which is insensitive to absolute firing frequency, but responsive to changes in frequency. At another class of connection, a different mechanism dominates, resulting in high sensitivity to frequency.

Animals↗

PubMedDate not supplied

An N-methylaspartate receptor-mediated synapse in rat cerebral cortex: a site of action of ketamine?

It has been proposed that three major receptor subtypes subserve the putative transmitter role of glutamate and aspartate in the mammalian central nervous system. One subtype is classified by the specific agonist N-methylaspartate (NMA) and the specific antagonist 4-amino-2-phosphonovaleric acid. It has been shown recently that excitation of neurones by NMA is also selectively reduced by dissociative anaesthetics such as ketamine and phencyclidine and by sigma opiates, drugs of abuse with common psychotomimetic properties. Responses to NMA have an unusual voltage relation which may result from a voltage-dependent block of the activated channel by physiological concentrations of magnesium. No synaptic potential with properties similar to those of responses to NMA, however, has yet been reported. We describe here an excitatory postsynaptic potential (e.p.s.p.) evoked by electrical stimulation of the white matter and recorded intracellularly from pyramidal cells in slices of rat somatosensory cortex. This e.p.s.p. has the appropriate voltage relation and sensitivity to Mg2+ and ketamine to be an NMA receptor-mediated synapse and a potential central site for the psychotomimetic actions of ketamine.

Animals↗

PubMedDate not supplied

Post-menarcheal menstrual cycle in British (Newcastle upon Tyne) girls.

Data for the first 36 menstrual intervals immediately following menarche were analysed for 298 girls studied in Newcastle upon Tyne. The mean cycle length decreased from 49 . 5 days for the first cycle in 29.5 days for cycles 31-36. There was no clear seasonal pattern in cycle length. The standard deviation within subjects in the length of menstrual interval fell sharply from 23 . 3 days for cycles 1-6 to 10-7 days for cycles 7-12 and more slowly thereafter, reaching 5 . 5 days for cycles 31-36, and was not related to age at menarche. The proportion of short cycles (17 days or less) was relatively stable, but that of long cycles (57 days or more) decreased with cycle number from 27.4% for the first cycle to about 1% for cycles 31-36. The average length of menstrual flow was 5 . 5 days irrespective of age at menarche, cycle number of season. The standard deviation of menstrual flow within subjects fell from 1 . 5 days for cycles 1-6 to 0 . 8 days for cycles 25-36.

England↗

PubMedDate not supplied

Pubertal changes in boys and girls in Newcastle upon Tyne.

669 boys and 753 girls born in 1962 and living at home were observed at approximately half-yearly intervals from 9 to 17 years of age. Mean ages of reaching various developmental stages were calculated for voice change and facial hair in boys, menarche and breast development in girls, and for axillary hair in both sexes. Peak height velocity and age at which it occurred were also calculated for both sexes. Means were generally in good agreement with those found about 15 years previously in the Harpenden Growth Study. Most pubertal changes in the present study showed gradients by social class; in boys, development was later in those with fathers in unskilled manual occupations, whereas in girls the greatest differences, where found, were between those with fathers in non-manual occupations and the remainder.

Adolescent↗

PubMedDate not supplied

Weight-for-height in adolescence.

Weight-for-height in adolescence was investigated on the basis of observations on 669 boys and 753 girls. It was found: (a) that given the age, the expected weight of individuals of the same height changes considerably with pubertal status; (b) that the change in weight for a given change in height also depends on pubertal status, and (c) that these relations vary with age so that chronological age should be taken into account when constructing weight-for-height standards. Interpretation of weight-for-height standards is briefly discussed.

Adolescent↗

PubMedDate not supplied

A longitudinal study of growth in Newcastle upon Tyne adolescents.

White Newcastle upon Tyne schoolchildren born in 1962 were examined at approximately half-yearly intervals from 9 to 17 years of age. During the last year of compulsory education losses to follow-up became selective with respect to socio-economic background, and the results reported here are restricted to 564 boys and 669 girls seen regularly between the ages of 10 and 15 years at least. Newcastle adolescents were slightly shorter and lighter than the London children on whom Tanner's British Standards were based. The longitudinal pattern of skinfold changes in boys was different from that observed in girls. Differences in height attained between occupational groups were well established by the age of five years, and the same was true of differences between family-size groups for children with fathers in manual occupations. It is inferred that differences in height between occupational and family-size groups resulted more from differences in leg than in trunk length. At age 15, the correlations of height attained with maternal height were 0.42 and 0.43, and with birthweight 0.25 and 0.28, for boys and girls respectively. Adjustment, by regression, of heights attained for birthweight, age at peak height velocity and maternal height diminished differences between occupational and family-size groups. After such adjustment, heights significantly lower than average were found only among subjects with fathers in unskilled manual occupations and with large families. Among subjects with fathers in manual occupations, subscapular and triceps skinfolds and arm circumference decreased significantly with increasing family size.

Adolescent↗

PubMedDate not supplied

Menarche in Newcastle upon Tyne girls.

Age at menarche was recorded for 699 white Newcastle upon Tyne girls taking part in a longitudinal study of growth and development during puberty. Girls from large (5+) families started menstruation about five months later than girls from small families. This effect was observed only among girls with fathers in manual occupations. The occurrence of menarche had a peak in January and a possible secondary peak about August. Height and to some extent weight increased with the age at menarche, while arm circumference and skinfolds tended to decrease. The correlation of age at menarche with weight at given height was -0.13 and that of age at menarche with height at given weight was 0.38. The correlation of age at menarche with skinfolds and arm circumference for given weight were of the order of -0.3 and for given height of the order of -0.2. The time lapse between the age at peak height velocity (PHV) and the age at menarche decreased with increasing subscapular skinfold at PHV.

Adolescent↗