Initial sequencing and analysis of the human genome

The human genome holds an extraordinary trove of information about human development, physiology, medicine and evolution. Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence.

Inhibition of angiogenesis by recombinant human platelet factor-4 and related peptides

Recombinant human platelet factor-4 (rhPF4), purified from Escherichia coli, inhibited blood vessel proliferation in the chicken chorioallantoic membrane in a dose-dependent manner. Treatment of several cell types with rhPF4 in vitro suggested that the angiostatic effect was due to specific inhibition of growth factor-stimulated endothelial cell proliferation. The inhibitory activities were associated with the carboxyl-terminal, heparin-binding region of the molecule and could be abrogated by including heparin in the test samples, an indication that sulfated polysaccharides might modulate the angiostatic activity of platelet factor-4 in vivo. Understanding of the mechanisms of control of angiogenesis by endogenous proteins should facilitate the development of effective treatments for diseases of pathogenic neovascularization such as Kaposi's sarcoma, diabetic retinopathy, and malignant tumor growth.

The force exerted by a single kinesin molecule against a viscous load

Kinesin is a motor protein that uses the energy derived from the hydrolysis of ATP to power the transport of organelles along microtubules. To probe the mechanism of this chemical-to-mechanical energy transduction reaction, the movement of microtubules across glass surfaces coated with kinesin was perturbed by raising the viscosity of the buffer solution. When the viscosity of the solution used in the low density motility assay was increased approximately 100-fold through addition of polysaccharides and polypeptides, the longer microtubules, which experienced a larger drag force from the fluid, moved more slowly than the shorter ones. The speed of movement of a microtubule depended linearly on the drag force loading the motor. At the lowest kinesin density, where dilution experiments indicated that the movement was caused by a single kinesin molecule, extrapolation of the linear relationship yielded a maximum time-averaged drag force of 4.2 +/- 0.5 pN per motor (mean +/- experimental SE). The magnitude of the force argues against one type of "ratchet" model in which the motor is hypothesized to rectify the diffusion of the microtubule; at high viscosity, diffusion is too slow to account for the observed speeds. On the other hand, our data are consistent with models in which force is a consequence of strain developed in an elastic element within the motor; these models include a different "ratchet" model (of the type proposed by A. F. Huxley in 1957) as well as "power-stroke" models.

Patterning of functional antibodies and other proteins by photolithography of silane monolayers

We have demonstrated the assembly of two-dimensional patterns of functional antibodies on a surface. In particular, we have selectively adsorbed micrometer-scale regions of biotinylated immunoglobulin that exhibit specific antigen binding after adsorption. The advantage of this technique is its potential adaptability to adsorbing arbitrary proteins in tightly packed monolayers while retaining functionality. The procedure begins with the formation of a self-assembled monolayer of n-octadecyltrimethoxysilane (OTMS) on a silicon dioxide surface. This monolayer can then be selectively removed by UV photolithography. Under appropriate solution conditions, the OTMS regions will adsorb a monolayer of bovine serum albumin (BSA), while the silicon dioxide regions where the OTMS has been removed by UV light will adsorb less than 2% of a monolayer, thus creating high contrast patterned adsorption of BSA. The attachment of the molecule biotin to the BSA allows the pattern to be replicated in a layer of streptavidin, which bonds to the biotinylated BSA and in turn will bond an additional layer of an arbitrary biotinylated protein. In our test case, functionality of the biotinylated goat antibodies raised against mouse immunoglobulin was demonstrated by the specific binding of fluorescently labeled mouse IgG.

Activation of the MKK/ERK pathway during somatic cell mitosis: direct interactions of active ERK with kinetochores and regulation of the mitotic 3F3/2 phosphoantigen

The mitogen-activated protein (MAP) kinase pathway, which includes extracellular signal-regulated protein kinases 1 and 2 (ERK1, ERK2) and MAP kinase kinases 1 and 2 (MKK1, MKK2), is well-known to be required for cell cycle progression from G1 to S phase, but its role in somatic cell mitosis has not been clearly established. We have examined the regulation of ERK and MKK in mammalian cells during mitosis using antibodies selective for active phosphorylated forms of these enzymes. In NIH 3T3 cells, both ERK and MKK are activated within the nucleus during early prophase; they localize to spindle poles between prophase and anaphase, and to the midbody during cytokinesis. During metaphase, active ERK is localized in the chromosome periphery, in contrast to active MKK, which shows clear chromosome exclusion. Prophase activation and spindle pole localization of active ERK and MKK are also observed in PtK1 cells. Discrete localization of active ERK at kinetochores is apparent by early prophase and during prometaphase with decreased staining on chromosomes aligned at the metaphase plate. The kinetochores of chromosomes displaced from the metaphase plate, or in microtubule-disrupted cells, still react strongly with the active ERK antibody. This pattern resembles that reported for the 3F3/2 monoclonal antibody, which recognizes a phosphoepitope that disappears with kinetochore attachment to the spindles, and has been implicated in the mitotic checkpoint for anaphase onset (Gorbsky and Ricketts, 1993. J. Cell Biol. 122:1311-1321). The 3F3/2 reactivity of kinetochores on isolated chromosomes decreases after dephosphorylation with protein phosphatase, and then increases after subsequent phosphorylation by purified active ERK or active MKK. These results suggest that the MAP kinase pathway has multiple functions during mitosis, helping to promote mitotic entry as well as targeting proteins that mediate mitotic progression in response to kinetochore attachment.

Psychiatric disorder among children with tuberous sclerosis

The psychiatric status of 90 children with tuberous sclerosis was investigated. Over 50 per cent of the sample showed psychotic behaviour, 59 per cent were hyperkinetic and 13 per cent severely aggressive. 57 per cent of the children who had infantile spasms were autistic, as opposed to 13 per cent in a Finnish study of children who had infantile spasms from all causes. The very high incidence of psychiatric disturbance has implications for the advice doctors should give on the management of children diagnosed to have tuberous sclerosis and for the special educational methods that may be needed.

The activities in different neural cell types of certain enzymes associated with the metabolic compartmentation glutamate

The cellular distribution of certain enzymes associated with the metabolic compartmentation of glutamate was estimated in ultrastructurally preserved and metabolically competent perikarya fractions that were enriched in astrocytes, granule cells and Purkinje cells and derived from 8-day-old rat cerebellum, and in monolayer cultures (14 days in vitro) composed principally of interneurones or astrocytes. The neuronal activities of glutamine synthetase and glutamate dehydrogenase were respectively about 4- to 8-fold and 2- to 5-fold lower than in astrocytes, depending upon the class of neurone and the type of preparation used for comparison. By contrast glutaminase activity was about 3- to 12-fold higher in neuronal than in astroglial preparations. Estimations of the specific activity of succinate dehydrogenase differed less between cell types, indicating that the differences in glutamate dehydrogenase and glutaminase were not simply related to variations in the concentration of mitochondria relative to the other cellular constituents. The findings presented provide direct evidence in support of our model assigning the 'small' glutamate compartment, where most of the labelled glutamine is synthesized, to glial cells, and the 'large' compartment to neurones, and also underline the metabolic interaction between these two cell types in the brain.

Exposure to N-methyl-D-aspartate increases release of arachidonic acid in primary cultures of rat hippocampal neurons and not in astrocytes

The release of [3H]arachidonic acid (ARA) was investigated from prelabelled primary cultures of hippocampal neurons and astroglial cells. The activation of N-methyl-D-aspartate (NMDA) subtype of glutamate receptors resulted in a dose-dependent stimulation of [3H]ARA release. The half maximal effect was obtained at about 15 microM NMDA, whereas the maximum concentration (50 microM NMDA) produced about a 2-fold increase in 7-day-old cultures. This elevation in [3H]ARA release was blocked in a dose-related manner by the NMDA receptor antagonist, 2-amino-5-phosphonovaleric acid (APV), and by Mg2+ which blocks NMDA receptor-linked Ca2+ ion channels. The removal of external Ca2+ inhibited NMDA-induced release, whereas treatment with calcimycin (A 23187, a Ca2+ ionophore) greatly increased the [3H]ARA release. The inhibitors of phospholipase A2, nordihydroguaiaretic acid and mepacrine, decreased the NMDA-dependent [3H]ARA release in a dose-related manner, maximum inhibition reaching to about 90% at high doses. Entry of Ca2+ brought about by opening the voltage-sensitive channels by high K+ had no effect on the release of [3H]ARA, indicating that NMDA gated channels are situated in a part of the neuron where Ca2+ entry through this route is more efficiently coupled to the activation of phospholipase A2. Treatment with NMDA had no significant effect on [3H]ARA release in hippocampal astroglial cells as opposed to neurons. This was not due to inability of astrocytes to release ARA, for ATP still evoked [3H]ARA release, and this was markedly inhibited by mepacrine. It is suggested that ARA act as both intracellular and intercellular messengers in the functioning of NMDA receptors in synaptic transmission and plasticity in the hippocampus.

IL-10-mediated suppression of TNF-alpha production is independent of its ability to inhibit NF kappa B activity

IL-10 has a well-characterized anti-inflammatory role that includes the suppression of inflammatory cytokine (e.g. TNF-alpha) production by monocytic/macrophage cells. Both transcriptional and post-transcriptional/translational mechanisms have been proposed to explain this process. In this study we observed that IL-10 inhibited nuclear NF kappa B DNA binding activity without affecting I kappa B degradation or translocation of NF kappa B subunits to the nucleus. While the suppression of NF kappa B in 70Z/3 pre-B cells correlated with suppression of NF kappa B transcriptional activity and expression of surface IgM, it did not correlate with the production of TNF-alpha mRNA or protein in RAW 264.7 macrophages. Similar observations in the macrophages were made with a second anti-inflammatory cytokine, IL-4. Therefore we conclude that although IL-10 or IL-4 can suppress NF kappa B activity, this appears to have little effect on the expression of the TNF-alpha gene and is unlikely to be the basis of the anti-inflammatory effects of these cytokines.

Topographical distribution of neurochemical changes in Alzheimer's disease

Biochemical indices of cortical nerve cells affected in Alzheimer's disease have been proposed (excitatory dicarboxylic amino acid, EDAA, sodium-dependent carrier; phosphate-activated glutaminase activity; serotonin type 2 recognition site; somatostatin-like immunoreactivity). These and the content of EDAAs and two related amino acids, and choline acetyltransferase (ChAT) activity have been measured in up to 13 areas of cerebral cortex and the cerebellar cortex from 16 patients with Alzheimer's disease and 17 controls. Reduction of the index of the serotonin recognition site, somatostatin content and another biochemical index of interneurones coincide and indicate a rather unexpected focal loss of such neurones from the parietal lobe. No unequivocal measure of the integrity of pyramidal neurones could be established as the content of no amino acid was reduced, the index of the EDAA carrier showed evidence of change in few brain regions and glutaminase activity was subject to unexplained variability. ChAT activity alone closely paralleled a previous report of the distribution of morphological degeneration. The results are discussed in relation to therapy and positron emission tomography.

A prevalence study of autism in tuberous sclerosis

An estimate of the prevalence of autism in tuberous sclerosis (TSC) was made by interviewing the parents of 21 children between ages 3 and 11 ascertained during a previous population study of the condition in the West of Scotland. Five of the children (24%) were rated autistic and a further four (19%), all of whom were girls, had socially impaired behavior categorized as pervasive developmental disorder, without fulfilling all the DSM-III-R criteria for autism. One further boy had disruptive attention-seeking behavior that had excluded him from his normal school. The estimated prevalence from this study of autism in TSC is 1 in 4 children in general, and 1 in 2 of those with mental retardation. Tuberous sclerosis could be a significant cause of autism and pervasive developmental disorders, particularly in girls.

Adaptive Radiotherapy Enabled by MRI Guidance

Adaptive radiotherapy (ART) strategies systematically monitor variations in target and neighbouring structures to inform treatment-plan modification during radiotherapy. This is necessary because a single plan designed before treatment is insufficient to capture the actual dose delivered to the target and adjacent critical structures during the course of radiotherapy. Magnetic resonance imaging (MRI) provides superior soft-tissue image contrast over current standard X-ray-based technologies without additional radiation exposure. With integrated MRI and radiotherapy platforms permitting motion monitoring during treatment delivery, it is possible that adaption can be informed by real-time anatomical imaging. This allows greater treatment accuracy in terms of dose delivered to target with smaller, individualised treatment margins. The use of functional MRI sequences would permit ART to be informed by imaging biomarkers, so allowing both personalised geometric and biological adaption. In this review, we discuss ART solutions enabled by MRI guidance and its potential gains for our patients across tumour types.

Kinesin swivels to permit microtubule movement in any direction

Kinesin is a motor protein that uses the energy derived from ATP hydrolysis to transport organelles along microtubules. By analyzing the thermal fluctuation of microtubules tethered to glass surfaces by single molecules of kinesin, we have measured the torsional flexibility of the motor protein. The torsional stiffness of kinesin, (117 +/- 19) x 10(-24) N.m.rad-1 (mean +/- SEM), is so low that one kT of energy (approximately 4.1 x 10(-21) J at room temperature) is sufficient to twist a kinesin molecule through more than 360 degrees from its resting orientation. Consistent with this flexibility, motility assays show that one or more kinesin molecules can move a microtubule equally well in any direction. These results explain how a motor on the surface of an organelle can rapidly bind to and capture a microtubule irrespective of the organelle's orientation. Furthermore, the flexibility ensures that several motors can efficiently work together even though they are randomly oriented on the surface of an organelle rather than being in precise arrays like the motors of muscle and cilia.

Digital photography: a new method for estimating food intake in cafeteria settings

OBJECTIVE

The primary objective of this study was to test the comparability of digital photography and visual estimation procedures for estimating food intake.

RESEARCH METHODS AND PROCEDURES

The study sample included 71 breakfast meals and 59 lunch meals eaten in a university cafeteria during a single day. A total of 66 different foods were employed as test foods that could be selected by the students. Food selections and plate waste, as estimated by digital photography and visual estimation, were compared. For digital photography, three observers independently estimated portion sizes of each food item based upon digital photographs. One observer estimated portion sizes in the cafeteria setting, using visual estimation, a method that has been validated in other studies.

RESULTS

To test the accuracy of the two procedures for measuring food intake, the estimates of food weights derived from both procedures were compared using Bland-Altman regression. In comparison to visual estimation, the digital photography method yielded comparable estimates of food selections, plate waste, and total food intake for seven of nine comparisons. The two methods of estimating food portions yielded comparable results for most (78%) types of foods. The two methods also yielded similar variability.

DISCUSSION

These findings suggest that the digital photography method is an alternative to the traditional method of estimating food intake via direct observation.

Speech dysfunction in early Parkinson's disease

The purpose of this study is to determine if subjects in the early stages of untreated Parkinson's disease (PD) or PD treated with deprenyl alone suffer from motor speech abnormalities. Speech defects are common in advanced PD, including disturbances of respiration, phonation, and articulation. We studied 12 subjects with early PD (Hoehn and Yahr stage < or = 2, mean duration disease 3.2 years) who were not taking symptomatic therapy and tested them under two conditions: on and off deprenyl. None of the subjects was depressed or demented (Mini Mental Status mean 29.9/30; Hamilton Depression Rating mean 2.7/52). All functioned independently (Schwab and England Activities of Daily Living mean 93.1/100). Acoustic and speech productions were assessed using the DSP Sona-Graph 5500 and an evaluation of dysarthria. All 12 had at least two characteristics of dysarthria on examination, although 8 were not aware of it. Vocal tremor was identified on narrow band spectrogram for four subjects. Deprenyl did not have a consistent effect on speech. Ten subjects had no detectable change in speech on deprenyl, one was worse, and one was improved.

Tuberous sclerosis: a new estimate of prevalence within the Oxford region

Within the counties administered by the Oxford Regional Health Authority (population 2 328 100) the prevalence of tuberous sclerosis was estimated as 1 in 29 900 for persons under 65 years of age. For the population below 30 years of age the prevalence was 1 in 21 500 and for children under 5 years 1 in 15 400. Cases were ascertained through the records of the Department of Medical Genetics at Oxford and the Tuberous Sclerosis Association of Great Britain and also by a questionnaire sent to selected consultants within the region. A previous estimate of prevalence within the region was 1 in 100 000. This study suggests that the prevalence at birth might be even higher than 1 in 15 000.

No connection between alcohol use and unsafe sex among gay and bisexual men

OBJECTIVE

To investigate the relationship between alcohol use and unsafe sexual behaviour.

METHODS

The paper discusses data collected from 461 gay and bisexual men interviewed in England and Wales by Project SIGMA during 1991-1992. These data were collected during face-to-face interviews using retrospective weekly diary techniques and include details of all sexual sessions and alcohol use. The 819 reported sexual sessions with other men are divided into those that involved alcohol use (30.6%) and those that did not.

RESULTS

Differences in the incidence of HIV risk behaviours between sexual sessions that involved alcohol use and those that did not are small, and none are statistically significant. Furthermore, for those men who engaged in sexual behaviour whilst under the influence of alcohol, the quantity of alcohol consumed had no effect on sexual behaviour.

CONCLUSIONS

Among gay and bisexual men, sex under the influence of alcohol is no more likely to be unsafe than sex among men who have not consumed alcohol.

Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at square root of s = 7 TeV

Charged-hadron transverse-momentum and pseudorapidity distributions in proton-proton collisions at square root of s = 7  TeV are measured with the inner tracking system of the CMS detector at the LHC. The charged-hadron yield is obtained by counting the number of reconstructed hits, hit pairs, and fully reconstructed charged-particle tracks. The combination of the three methods gives a charged-particle multiplicity per unit of pseudorapidity dN(ch)/dη|(|η|<0.5) = 5.78 ± 0.01(stat) ± 0.23(syst) for non-single-diffractive events, higher than predicted by commonly used models. The relative increase in charged-particle multiplicity from square root of s = 0.9 to 7 TeV is [66.1 ± 1.0(stat) ± 4.2(syst)]%. The mean transverse momentum is measured to be 0.545 ± 0.005(stat) ± 0.015(syst)  GeV/c. The results are compared with similar measurements at lower energies.

Population pharmacokinetics of oral morphine and its glucuronides in children receiving morphine as immediate-release liquid or sustained-release tablets for cancer pain

OBJECTIVES

(1) To determine the pharmacokinetics of morphine, morphine-6-glucuronide (M6G), and morphine-3-glucuronide (M3G) in children with cancer receiving morphine as immediate-release morphine liquid or sustained-release tablets. (2) To determine differences with age within the group and from adults. (3) To explore relationships between plasma concentration and pain measurements.

STUDY DESIGN

Blood samples were collected and plasma analyzed by high-performance liquid chromatography with electrochemical and fluorescence detection. Population pharmacokinetic parameters were derived with the program P-PHARM.

RESULTS

Forty children with a median age of 11.4 years (range 1.7 to 18.7 years) received a median dose of 1.4 mg/kg/d (range 0.4 to 24.6 mg/kg/d). A median of 4 blood samples per child was collected. Plasma clearance of morphine was 23.1 mL/min per kg body weight. The volume of distribution was 5.2 L/kg. Molar ratios of M3G/morphine, M6G/morphine, and M3G/M6G were 21.1, 4.7, and 4.2, respectively. Children <11 years had significantly higher clearance and larger volume of distribution for morphine and its glucuronides than older children and adults. Regression analysis indicated average plasma morphine concentration equal to dose (mg/kg/d) x 8.6 (95% confidence interval 7.4 to 9.9). Significant pain was present in 30% of the children. Higher pain scores were recorded in children with average morphine concentrations <12 ng/mL (P <.01 MW).

CONCLUSION

Age differences in morphine pharmacokinetics exist within children and compared with adults. The study supports a starting dose of 1.5 to 2. 0 mg/kg/d to provide plasma morphine concentrations >12 ng/mL in children with cancer pain unrelieved by mild to moderate strength analgesia.

Role of thyroid hormone and nerve growth factor in the development of choline acetyltransferase and other cell-specific marker enzymes in the basal forebrain of the rat

The effects of treatment with L-thyroxine (subcutaneously 0.3 microgram/g body weight daily from birth, i.e., day 1) and 2.5S nerve growth factor (NGF; intraventricularly 2 micrograms on 1, 3, 5, 7, and 9 postnatal days), separately and together, were studied on the biochemical development of different cell types in the basal forebrain of 10-day-old rats. The development of cholinergic, gamma-aminobutyric acid-ergic (GABAergic), and glutamatergic neurons was monitored respectively in terms of choline acetyltransferase (ChAT), glutamate decarboxylase (GAD), and glutaminase activities, whereas glutamine synthetase (GS) and 2',3'-cyclic nucleotide-3'-phosphohydrolase (CNPase) activities were used to judge the maturation of astroglial and oligodendroglial cells. Treatment with either thyroid hormone or NGF from birth significantly increased the expression of ChAT activity in the basal forebrain of neonatal rats. When both agents were administered to the same animal, in agreement with our earlier in vitro findings, the stimulation in ChAT activity was much greater than the sum of the individual effects. In hypothyroid rats, significant effects of NGF at the low doses used were not detectable, although the increase of ChAT activity induced by thyroxine was potentiated by NGF in these animals. Under the present experimental conditions neither thyroxine nor NGF treatment had an appreciable effect on the activities of glutaminase, GS, and lactate dehydrogenase. However, the administration of thyroxine markedly increased CNPase activity in normal rats, whereas in hypothyroid rats the effect on both CNPase and GAD was also significant. Similar elevations in CNPase and GAD activities were not observed after NGF treatment, suggesting that the effect of NGF was specific to the cholinergic cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional kinematics of the rearfoot during the stance phase of walking in normal young adult males

Three-dimensional video analysis was used to quantify three-dimensional motion of the rearfoot in 14 normal young adult males during the stance phase of walking. A stringent calibration procedure enabled standardization of the neutral position of the rearfoot. Surface markers were placed on the calcaneus and lower tibia, and a joint coordinate system was used to determine the relative displacement between the calcaneus and lower leg as representative of rearfoot motion. Confirmation was made of the assumption of a mechanical coupling between the rearfoot displacements of abduction/adduction and eversion/inversion. However, there were several findings which contrasted with commonly held assumptions. For example, the rearfoot was found to evert gradually, rather than rapidly, from heel contact to just prior to heel rise. Also the conventional descriptions of the composite movements of pronation and supination were not applicable to rearfoot movement in this study, and it was therefore concluded that pronation and supination are not valid descriptors of three-dimensional rearfoot motion during the stance phase of walking.

Sleep disorder and epilepsy in children with tuberous sclerosis: a questionnaire-based study

Sleep disorders were investigated in 40 children with tuberous sclerosis (TS) and compared with those found in non-disabled children and those reported in a mixed group with learning disabilities. Significantly higher levels of sleep disturbance were found in the TS group compared with both other groups. Within the TS group, current epilepsy and a high level of daytime behavioural disturbance were significantly associated with sleep disturbance, but pervasive developmental delay and high parental stress levels were not. Detailed study of the relationship between seizure activity and sleep disturbance in tuberous sclerosis is needed.

Distribution of glutamine synthetase and glial fibrillary acidic protein and correlation of glutamine synthetase with glutamate decarboxylase in different regions of the rat central nervous system

The concentration of soluble glial fibrillary acidic (GFA) protein and the specific activity of glutamine synthetase (GS) were estimated in 11 central nervous system (CNS) regions of the 90-day-old rat. Marked differences were observed in the regional distribution of these astrocyte marker proteins. The striatum and spinal cord contained the lowest concentration (per g wet weight) of GFA protein and GS activity, respectively, while the olfactory bulbs had the highest level of both astrocytic proteins. Differences between the lowest and the highest values were 3-fold for GS and 4-fold for GFA protein. More significant was the marked variation in the ratio of GS to GFA protein in different CNS regions; the highest and lowest values were in the striatum and the spinal cord respectively, and the difference between the highest and the lowest value was about 5-fold. The spinal cord contained low GS and high GFA protein; on the other hand, the colliculi had high GS and relatively low GFA protein. Immunochemical detection of GS and GFA proteins in whole homogenates of different regions showed that the variation of the specific activities of GS and the concentration of soluble GFA protein were due to the differences in their absolute protein concentrations. In different regions of the brain the activity of GS was significantly correlated with that of glutamate decarboxylase, but not with that of choline acetyltransferase. These observations provide further evidence for differing biochemical properties of astrocytes from various CNS regions and for the involvement of GS in processes associated with amino acid neurotransmission.

Effects of thyroid state on brain development: muscarinic acetylcholine and GABA receptors

A study was made of the effects of age, neonatal hypothyroidism and hyperthyroidism on the development in rat brain of muscarinic cholinergic and GABA receptors. The former receptors were estimated by the binding of [3H]quinuclidinylbenzilate and the latter by binding of [3H]muscimol to crude membrane preparations from the forebrain and the cerebellum. In the normal forebrain, the density of muscarinic cholinergic receptors (in terms of unit membrane proteins) doubled during the period 6-35 days after birth. Thyroid state had relatively little effect on this development. In contrast, in the normal cerebellum the peak of the density of the receptors was attained in the early neonatal period followed by a progressive decline reaching about half of the maximum at day 35. Furthermore, in the cerebellum this development was significantly influenced by thyroid disorders: the rate of decrease in receptor density was accelerated by hyperthyroidism and retarded in thyroid deficiency. In comparison with euthyroid rats, the density of muscarinic receptors in the cerebellum was 30% lower in the hyperthyroidism (at day 21) and 40% higher in thyroid deficiency (at day 35). The increase in the density of GABA receptors with age was very small in the normal forebrain relative to the marked rise in the cerebellum. In the forebrain, thyroid state had no significant effect on this development. In contrast, in the cerebellum the ontogenesis of GABA receptors was advanced by thyroid hormone treatment and retarded in thyroid deficiency. However, by day 35 receptor density was normal in both conditions. Thyroid state had no significant influence on the affinity of either [3H]muscimol or the [3H]quinuclidinylbenzilate binding. The results suggest that thyroid hormone disorders during early life may lead to distortions rather than synchronized shifts in the relative development of several central transmitter systems.