An efficient motion estimator with application to medical image registration

Image registration is a very important problem in computer vision and medical image processing. Numerous algorithms for registering single and multi-modal image data have been reported in these areas. Robustness as well as computational efficiency are prime factors of importance in image data registration. In this paper, a robust/reliable and efficient algorithm for estimating the transformation between two image data sets of a patient taken from the same modality over time is presented. Estimating the registration between two image data sets is formulated as a motion-estimation problem. We use a hierarchical optical flow motion model which allows for both global as well as local motion between the data sets. In this hierarchical motion model, we represent the flow field with a B-spline basis which implicitly incorporates smoothness constraints on the field. In computing the motion, we minimize the expectation of the squared differences energy function numerically via a modified Newton iteration scheme. The main idea in the modified Newton method is that we precompute the Hessian of the energy function at the optimum without explicitly knowing the optimum. This idea is used for both global and local motion estimation in the hierarchical motion model. We present examples of motion estimation on synthetic and real data (from a patient acquired during pre- and post-operative stages) and compare the performance of our algorithm with that of competing ones.

Brain morphology in children with specific language impairment

The planum temporale and pars triangularis have been found to be larger in the left hemisphere than the right in individuals with normal language skills. Brain morphology studies of individuals with developmental language disorders report reversed asymmetry or symmetry of the planum, although the bulk of this research has been completed on adults with dyslexia. Pars triangularis has not been studied in the developmental language impaired population. In this study, magnetic resonance imaging (MRI) was used for quantitative comparisons of the planum temporale (Wernicke's area) and pars triangularis (Broca's area) in children with specific language impairment (SLI) and children with normal language skills. The subjects were 11 children with SLI and 19 age- and sex-matched controls between 5.6 and 13.0 years old. Each subject received a neurolinguistic battery of tests and a high resolution volumetric MRI scan. Major results were that (a) pars triangularis was significantly smaller in the left hemisphere of children with SLI, and (b) children with SLI were more likely to have rightward asymmetry of language structures. Furthermore, anomalous morphology in these language areas correlated with depressed language ability. These findings support the hypothesis that language impairment is a consequence of an underlying neurobiological defect in areas of the brain known to subserve language.

Fast numerical algorithms for fitting multiresolution hybrid shape models to brain MRI

In this paper, we present new and fast numerical algorithms for shape recovery from brain MRI using multiresolution hybrid shape models. In this modeling framework, shapes are represented by a core rigid shape characterized by a superquadric function and a superimposed displacement function which is characterized by a membrane spline discretized using the finite-element method. Fitting the model to brain MRI data is cast as an energy minimization problem which is solved numerically. We present three new computational methods for model fitting to data. These methods involve novel mathematical derivations that lead to efficient numerical solutions of the model fitting problem. The first method involves using the nonlinear conjugate gradient technique with a diagonal Hessian preconditioner. The second method involves the nonlinear conjugate gradient in the outer loop for solving global parameters of the model and a preconditioned conjugate gradient scheme for solving the local parameters of the model. The third method involves the nonlinear conjugate gradient in the outer loop for solving the global parameters and a combination of the Schur complement formula and the alternating direction-implicit method for solving the local parameters of the model. We demonstrate the efficiency of our model fitting methods via experiments on several MR brain scans.

Deficits in auditory temporal and spectral resolution in language-impaired children

Between 3 and 6 per cent of children who are otherwise unimpaired have extreme difficulties producing and understanding spoken language. This disorder is typically labelled specific language impairment. Children diagnosed with specific language impairment often have accompanying reading difficulties (dyslexia), but not all children with reading difficulties have specific language impairment. Some researchers claim that language impairment arises from failures specific to language or cognitive processing. Others hold that language impairment results from a more elemental problem that makes affected children unable to hear the acoustic distinctions among successive brief sounds in speech. Here we report the results of psychophysical tests employing simple tones and noises showing that children with specific language impairment have severe auditory perceptual deficits for brief but not long tones in particular sound contexts. Our data support the view that language difficulties result from problems in auditory perception, and provide further information about the nature of these perceptual problems that should contribute to improving the diagnosis and treatment of language impairment and related disorders.

Atrophy of the hippocampus, parietal cortex, and insula in Alzheimer's disease: a volumetric magnetic resonance imaging study

The hippocampus, parietal cortex, and insula were measured on volumetric magnetic resonance imaging to determine whether patients with early Alzheimer's disease had significantly more atrophy than healthy controls. To determine whether the atrophy is limited to certain cortical regions, the striate cortex was measured because this area is not usually neuropathologically involved early in Alzheimer's disease. Eight mildly to moderately impaired patients who met National Institute of Neurological Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for probable Alzheimer's disease and eight controls who matched for age, gender, and educational level were studied. Atrophy was quantified in the following regions: hippocampus, parietal cortex, insular cortex, and striate cortex. The authors found significantly more atrophy of the hippocampus (p < 0.0001), parietal cortex (p < 0.025), and insula (p < 0.003) in the Alzheimer's patients. Measures of the striate cortex did not differ between the groups. There were no significant left-right differences in any of the regions measured. Their findings show that mildly to moderately impaired Alzheimer's patients have significantly more atrophy of the hippocampus, parietal cortex, and insula than healthy age-matched controls. Furthermore, this atrophy is probably discrete because the groups did not differ on measures of the striate cortex. Selective atrophy of the parietal and insular cortices has not previously been reported using the authors' methodology on volumetric magnetic resonance imaging. Their data suggest that the insula may be involved early in Alzheimer's disease and that atrophy of the insular cortex may contribute to the cognitive deficits typical of early Alzheimer's disease.

Quantified volumes of temporal lobe structures in patients with epilepsy

The T1-weighted volumetric magnetic resonance images of 31 patients with intractable temporal lobe epilepsy, and 13 control subjects matched for age and sex, were subjected to semiautomated threshold analysis. The method used proved to be relatively fast and reliable. An index of temporal lobe interhemispheric asymmetry was extracted by thresholding high-signal (white matter) pixels. Patients had significantly more asymmetrical indices for white matter and hippocampal volumes that did control subjects, and the two indices were significantly correlated, providing evidence for the validity of the white matter index. Differences in both indices were consistent with decreased tissue on the side of the focus. In classification analyses a combination of these two indices correctly predicted the side of focus at a greater rate than did either used alone. Findings provide support for the hypothesis that seizure activity is associated with atrophy in both mesial and lateral temporal lobe structures.

Pars triangularis asymmetry and language dominance

The pars triangular is a portion of Broca's area. The convolutions that form the inferior and caudal extent of the pars triangularis include the anterior horizontal and anterior ascending rami of the sylvian fissure, respectively. To learn if there are anatomic asymmetries of the pars triangularis, these convolutions were measured on volumetric magnetic resonance imaging scans of 11 patients who had undergone selective hemispheric anesthesia (Wada testing) to determine hemispheric speech and language lateralization. Of the 10 patients with language lateralized to the left hemisphere, 9 had a leftward asymmetry of the pars triangularis. The 1 patient with language lateralized to the right hemisphere had a significant rightward asymmetry of the pars triangularis. Our data suggest that asymmetries of the pars triangularis may be related to speech-language lateralization.

Magnetic resonance imaging of cerebral anomalies in subjects with resistance to thyroid hormone

OBJECTIVE

Resistance to thyroid hormone (RTH) is an autosomal dominant disease caused by mutations in the human thyroid receptor beta gene on chromosome 3. Individuals with RTH have an increased incidence of attention deficit hyperactivity disorder (ADHD). The purpose of this study was to search for developmental brain malformations associated with RTH.

METHOD

Forty-three subjects (20 affected males [AM], 23 affected females [AF]) with resistance to thyroid hormone and 32 unaffected first degree relatives (18 unaffected males [UM], 14 unaffected females [UF]) underwent MRI brain scans with a volumetric acquisition that provided 90 contiguous 2 mm thick sagittal images. Films of six contiguous images beginning at a standard sagittal position lateral to the insula were analyzed by an investigator who was blind with respect to subject characteristics. The presence of extra or missing gyri in the parietal bank of the Sylvian fissure (multimodal association cortex) and multiple Heschl's transverse gyri (primary auditory cortex) were noted.

RESULTS

There was a significantly increased frequency of anomalous Sylvian fissures in the left hemisphere in males with RTH (AM: 70%; AF: 30%; UM: 28% UF: 28%). Also, there was an increased frequency of anomalous Sylvian fissures on the left combined with multiple Heschl's gyri in either hemisphere in males with RTH (AM: 50%; AF: 9%; UM: 6%; UF: 0%). However, RTH subjects with anomalies did not have an increased frequency of ADHD as compared with RTH subjects with no anomalies.

CONCLUSIONS

Abnormal thyroid hormone action in the male fetus early during brain development may be associated with grossly observable cerebral anomalies of the left hemisphere. The effects of mutations in the thyroid receptor beta gene provide a model system for studying the complex interaction of genetic and nongenetic factors on brain and behavioral development.

Morphologic cerebral asymmetries and handedness. The pars triangularis and planum temporale

OBJECTIVE

To explore the relationship between morphologic cerebral asymmetries of the pars triangularis (PTr) and the planum temporale (PT) measured on three-dimensional, gradient-echo, magnetic resonance imaging scans of healthy right- and left-handed subjects.

DESIGN

(Blinded) comparison of healthy right- and left-handed subjects who underwent magnetic resonance imaging.

SETTING

The Seimens 1-T Magnetom (Seimens, Iselin, NH) at the University of Florida Health Science Center, Gainesville.

SUBJECTS

Healthy right-handed (n = 8) and left-handed (n = 8) subjects matched for age, sex, and educational level.

MAIN OUTCOME MEASURES

(1) Average length of the PTr (anterior ascending and anterior descending rami), (2) average length of the PT, (3) asymmetry quotients ([left-right]/[(left+right) (0.5)]) of the PTr and PT, and (4) combined asymmetry quotients of the PTr and PT.

RESULTS

There was a significant leftward asymmetry of the PTr and PT in the right-handed subjects, but there was no significant asymmetry in the left-handed subjects. When the combined asymmetry quotient of the PTr and PT was calculated, the right-handed subjects had a leftward asymmetry (87.5% [n = 7]) or left was equal to right (12.5% [n = 1]), and the left-handed subjects had a leftward asymmetry (62.5% [n = 5]), left was equal to right (12.5% [n = 1]), or a rightward asymmetry (25% [n = 2]). In the left-handed subjects, writing posture seemed to predict these combined asymmetry quotients, ie, left-handed subjects using an inverted writing posture had a leftward asymmetry and left-handed subjects using a non-inverted writing posture had a rightward asymmetry of the perisylvian speech-language regions.

CONCLUSIONS

On three-dimensional, gradient-echo, magnetic resonance imaging scans, we found a significant leftward asymmetry of the PTr and PT. When the groups were divided into right- and left-handed subjects, the former had a significant leftward asymmetry of the PTr and PT, while the latter did not. Measurements of the PTr and PT appear to be important indexes of the known functional asymmetries of the perisylvian speech-language regions.

Planum temporale asymmetry and language dominance

Language is lateralized to the left hemisphere in most individuals, and leftward asymmetry of the planum temporale has been reported in postmortem and imaging studies. In this study we measured the planum temporale on magnetic resonance imaging (MR) scans of patients (11 right-handers, 1 non-right-hander) who had selective hemispheric anesthesia or Wada testing performed for language lateralization. All subjects who had language lateralized to the left hemisphere (11 right-handers) had a leftward asymmetry of the planum temporale. One subject who had language lateralized to the right hemisphere (non-right-hander) had a strong rightward asymmetry of the planum temporale. These data suggest that planum temporale asymmetries determined by MR are associated with language dominance and may predict language laterality.

Activation of a heparin-degrading enzyme by a 'protein matrix' effect

An unusual activating effect of protein on Flavobacterium heparinase is described. The phenomenon is nonselective with respect to protein species, but does not occur with other biomolecules such as nucleic acids, polysaccharides, or free amino acids. We show that protein activates heparinase over broad ranges of temperature and ionic strength, and stabilizes the enzyme against both reversible and irreversible structural changes. The nonselective activation of an inducible enzyme by protein may be an important regulatory mechanism in microenvironments in which the concentration of organic material may vary.

Neuronal responses in the ventral striatum of the behaving macaque

To analyse the functioning of the ventral striatum, the responses of more than 1,000 single neurons were recorded in a region which included the nucleus accumbens and olfactory tubercle in 5 macaque monkeys. While the monkeys performed visual discrimination and related feeding tasks, the different populations of neurons found included neurons which responded to novel visual stimuli; to reinforcement-related visual stimuli such as (for different neurons) food-related stimuli, aversive stimuli, or faces; to other visual stimuli; in relation to somatosensory stimulation and movement; or to cues which signalled the start of a task. The neurons with responses to reinforcing or novel visual stimuli may reflect the inputs to the ventral striatum from the amygdala and hippocampus, and are consistent with the hypothesis that the ventral striatum provides a route for learned reinforcing and novel visual stimuli to influence behaviour.

Anomalous cerebral structure in dyslexia revealed with magnetic resonance imaging

OBJECTIVE

To develop quantitative methods for identifying cerebral anomalies on magnetic resonance images of subjects with language disorders and other learning disabilities.

DESIGN

Partially blinded comparison of subjects with dyslexia, unaffected relatives, and a control group balanced for age and socioeconomic status. Criterion standard: clinical diagnosis of dyslexia by physician or learning disabilities specialist on the basis of clinical assessment and family history.

SETTINGS

Hospital pediatric neurology clinic and private reading clinic.

PATIENTS AND OTHER PARTICIPANTS

VOLUNTEERS

individuals with dyslexia (seven male and two female, aged 15 to 65 years) from professional families; unaffected first- and second-degree relatives (four male and six female, aged 6 to 63 years) available in the geographical area; and controls (five male and seven female, aged 14 to 52 years).

INTERVENTIONS

Gradient echo three-dimensional scan in Seimens 1-Tesla Magnetom; 128 1.25-mm consecutive sagittal images.

MAIN OUTCOME MEASURES

(1) Average length of the temporal (T) and parietal (P) banks of the planum temporale; (2) interhemispheric coefficients of asymmetry for T and P banks: Left-Right interhemispheric coefficients of asymmetry = (L-R)/[(L+R)/2]; (3) intrahemispheric coefficients of asymmetry = (T-P)/[(T+P)/2]; and (4) qualitative assessment of gyral variants in the parietotemporal operculum.

RESULTS

All groups had left-sided asymmetry for the temporal bank and right-sided asymmetry for the parietal bank. The group with dyslexia had exaggerated asymmetries, owing to a significant shift of right planar tissue from the temporal to parietal bank. They also had a higher incidence of cerebral anomalies bilaterally (subjects with dyslexia, six of nine; relatives, two of 10; and controls, zero of 12).

CONCLUSIONS

Quantitative assessment of high-resolution magnetic resonance images can reveal functionally relevant variations and anomalies in cerebral structure. Further refinement of these measurement techniques should improve the diagnosis, classification, and treatment of language disorders and other learning disabilities.

Angelman and Prader-Willi syndrome: a magnetic resonance imaging study of differences in cerebral structure

Recent improvements in magnetic resonance imaging techniques now allow the developing brain to be visualized in sufficient detail to perform "in vivo neuropathology." In this study we compared the cortical morphology in six children with Angelman and four with Prader-Willi syndrome. These two syndromes are of special interest because, although they are both caused by deletions in the same region of chromosome 15, Angelman children are far more severely affected, and do not speak. We measured the length of the banks of the Sylvian fissure in a gapless series of thin sagittal images. Angelman children had a significantly larger proportion (75%) of anomalous fissures than the Prader-Willi children (12%). Anomalous cortical growth could result from mistimed expression and recognition of macromolecules involved in axonal guidance, target recognition, and pruning. We hypothesize that misrouting of long projection axons may be related to the Sylvian fissure anomalies and the language disorder in Angelman syndrome.

Altered precision grasping in stumptail macaques after fasciculus cuneatus lesions

Patterns of precision grasp are described in stumptail macaques (Macaca arctoides) before and after lesions of the fasciculus cuneatus (FC). Three monkeys were videotaped while reaching for and grasping small food items. From these videotapes, records were made of the style and outcome of each grasp. Kinematic measurements were also made to describe grip formation and terminal grasp. During grip formation, grip aperture was measured as the distance between the tips of the index finger and the thumb. For terminal grasp, the joint angles of the index finger were measured. The majority of grasps by normal monkeys were of the precision type, in which the item was carried between the tips of the index finger and thumb. Each normal monkey approached objects with a highly consistent grip formation; that is, the fingertips formed a small grip aperture during the approach, and the aperture varied little on repeated grasps. To grasp an item, the forefinger moved in a multiarticular pattern, in which the proximal joint flexed and the distal joint extended. As a result of this combination of movements, the forefinger pad was placed directly onto the object. Following FC transection, the monkeys were studied for 10 months, beginning 1 month after the lesion, to allow for recovery from the acute effects of surgery. The monkeys could grasp the food items, but they rarely opposed the fingertips in precision grasp. Grip formation was altered and was characterized either by excessive grip aperture or by little to no finger opening. All of the monkeys used the table surface to help grasp items. Combined multiarticular patterns of flexion and extension were never observed postoperatively; they were replaced by flexion at all joints of the fingers. These results suggest that the FCs are more important for precision grasping than for other, less refined grasp forms (e.g., power grasps; Napier, 1956). The FCs provide critical proprioceptive feedback to cerebral areas involved in the planning and/or the execution of these movements.

Alterations of natural hand movements after interruption of fasciculus cuneatus in the macaque

As part of a series of investigations on the control of fine finger movements in the macaque, spontaneous use of the hand in grooming, scratching, and manipulation was observed before and after interruption of fasciculus cuneatus (FC). Videotaped observations were made of four stumptail macaques (Macaca arctoides) living outdoors in social groups. The monkeys were followed for 1 to 3 years postoperatively. For the first 2 weeks following surgery, all monkeys neglected the affected hand and did not use it for support, locomotion, climbing, scratching, foraging, or grooming. Recovery of gross arm and hand movements occurred over a 1- to 3-month period. All the monkeys eventually used the hand for support, climbing, and object manipulation, but fine control of the fingers did not recover. Also, there was an apparent hypotonia of the fingers, imparting a "floppy" appearance to the hand. The animals coped with the loss of fine control by decreasing the frequency of some behaviors, eliminating others, and developing alternative strategies. Exploratory movements that were utilized for investigating the anogenital area or foraging for small food items were eliminated by FC interruption. There were obvious deficits in grip formation and grasp of small food objects (see Glendinning et al., this issue), but effects on similar movements during grooming only became obvious after repeated inspection of videotaped records. Self-scratching and sweeps of the hand in grooming were preserved but altered in form and frequency. The component movements in these behaviors were relatively uncoordinated, and the fingers were splayed (abducted). Often the hand was formed in a rigid posture throughout the sweeping motion, and the fingers did not stroke the skin individually. Frame-by-frame analysis of videotapes revealed that the morphology of the precision grip during grooming, in movements termed "plucks," was permanently altered. Preoperatively, the monkeys kept the index finger and thumb closely apposed and routinely made contact on the distal surfaces of the digits, as has been described for precision grip in humans. Postoperatively, this relationship was altered. The index finger frequently missed the thumb tip and made contact on the proximal part of the phalanx, or missed the thumb altogether. Thus, the dorsal column input is important for proprioceptive guidance of movements that achieve "tactile foveation," when objects or surfaces are actively contacted by the receptive areas of keenest sensitivity (on the fingertips).

Role of transforming growth factor-beta in chondrogenic pattern formation in the embryonic limb: stimulation of mesenchymal condensation and fibronectin gene expression by exogenenous TGF-beta and evidence for endogenous TGF-beta-like activity

The possible role of TGF-beta-like molecules in skeletal pattern formation in the embryonic vertebrate limb was studied by analyzing the mechanism of enhancement of chondrogenesis in chick wing bud mesenchyme in vitro and testing for the presence and distribution of endogenous TGF-beta-like activity in this tissue. Transient exposure (3-6 hr) to TGF-beta 1 (1-2 ng/ml) on the day after plating resulted in a 1.5- to 2-fold enhancement of accumulation of Alcian blue (pH 1.0)-stainable extracellular matrix 5 days later. The enhancement of differentiation was preceded by an acceleration and an increase in the extent of precartilage condensation formation, visualized by Hoffman Modulation Contrast microscopy a day after TGF-beta treatment. In contrast, neither condensation nor subsequent chondrogenesis was stimulated by transient treatment with TGF-beta 1 on the day of plating. The effectiveness of a TGF-beta treatment regimen in enhancing chondrogenesis was correlated with its effectiveness in stimulating condensation formation. Exposures to the factor for 3-6 hr on the day after plating, which most consistently stimulated both condensation formation and chondrogenesis, also corresponded to a peak in the enhancement of the steady-state level of fibronectin mRNA (fourfold to eightfold over control levels) measured at the end of the treatment period. The elevation in fibronectin mRNA levels brought about by this treatment persisted throughout the period of condensation. Endogenous TGF-beta-like activity was detected in limb mesenchyme: extracts of freshly isolated and cultured limb tissues contained 6-25 pg TGF-beta-like activity per 1 x 10(6) cells by the Mv1Lu cell proliferation inhibition assay, and indirect immunofluorescence using a polyclonal antibody directed against a TGF-beta-related peptide indicated a patchy distribution of endogenous TGF-beta-like reactivity within a day after culture. These findings are discussed in relation to the "fibronectin prepattern" hypothesis for limb pattern formation.

Comparative neuroanatomy of the sexually dimorphic hypothalamus in monogamous and polygamous voles

In the present work we evaluated the degree of sexual dimorphism in two cell groups of the medial preoptic-anterior hypothalamus (MPOA-AH) in monogamous and polygamous voles. Quantitative determinations were made of volume, cell number, and cell density for the anteroventral-periventricular nucleus (AVPV) and the sexually dimorphic nucleus of the preoptic area (SDN-POA). Polygamous montane voles (Microtus montanus) had a greater degree of sexual dimorphism in both cell groups than did monogamous prairie voles (M. ochrogaster). Most notable was the complete absence of the AVPV in male montane voles; male montane voles also had a significantly larger SDN-POA volume than did females. The only sexual dimorphism in prairie voles was a greater cell density in the female AVPV. In addition, prairie voles had larger relative brain size than did montane voles. Comparative behavioral studies have revealed a correlation between the degree of sexual dimorphism in external morphology and mating system, i.e., polygamous species display greater levels of dimorphism than do monogamous species. The present results indicate that the effects of sexual selection can also be seen in those brain regions, like the hypothalamus, that underlie social and reproductive behavior. Moreover, these results support the hypothesis that neuroanatomic dimorphisms in the MPOA-AH may be related to sex differences in behavior.

Abnormal ambient glucose levels inhibit proteoglycan core protein gene expression and reduce proteoglycan accumulation during chondrogenesis: possible mechanism for teratogenic effects of maternal diabetes

Using a tissue culture system based on a nearly pure population of avian precartilage mesenchymal cells, we have found that ambient glucose levels as little as 50% lower, or 100% higher, than normally present in embryonic sera are deleterious to cartilage development, as measured by the accumulation of highly sulfated proteoglycan and the corresponding cartilage-specific chondroitin sulfate core protein mRNA. Abnormal glucose concentrations in the ranges studied did not selectively influence cell replication, and the effects on chondrogenesis were not due to differences in overall protein synthesis or glucose utilization in the treatment groups. Core protein gene expression was more severely affected than accumulation of extracellular product, suggesting the existence of posttranscriptional compensatory mechanisms. The sensitivity to ambient glucose levels of both expression of the cartilage-specific chondroitin sulfate core protein gene and the accumulation of the corresponding extracellular matrix macromolecules during chondrogenesis suggest a molecular mechanism for the well-known adverse effect of maternal diabetes on embryonic skeletogenesis. The results further suggest that hypoglycemia resulting from stringent control of diabetes may also be deleterious to skeletal development.

Developmental regulation of constitutive and inducible expression of hepatocyte-specific genes in the mouse

Deletions in chromosome 7 of the mouse have been shown to cause failure of expression of certain liver-specific enzymes in newborn deletion homozygotes. Among these enzymes are L-tyrosine:2-oxoglutarate aminotransferase (EC 2.6.1.5) and phosphoenolpyruvate carboxykinase (GTP) [GTP:oxaloacetate carboxy-lase (transphosphorylating); EC 4.1.1.32]. The studies reported here show that in fetal stages constitutive expression of the relevant genes on the level of steady-state mRNA is identical in the livers of homozygous deletion mutants and normal littermates. Furthermore, prenatally these enzymes are expressed also in cell types other than hepatocytes. Thus, the putative trans-acting regulatory factors encoded in the deleted region of chromosome 7 of the mouse appear to be concerned specifically with the regulation of cell type-specific inducible expression of various hepatocyte-specific genes, whereas constitutive expression of the same genes is not affected.

Metallothionein mRNA expression in mice homozygous for chromosomal deletions around the albino locus

Deletions in chromosome 7 of the mouse affect the expression of the metallothionein gene Mt-1, which maps on chromosome 8, and steady-state levels of Mt-1 mRNA are reduced to 15-40% of normal in livers of newborn mice homozygous for either the c3H or c14CoS deletion. Glucocorticoids fail to induce hepatic Mt-1 mRNA levels in deletion homozygotes in contrast to normal littermates. However, zinc chloride is effective in inducing Mt-1 mRNA levels in livers of deletion homozygotes as well as of their normal littermates. Other tissues (e.g., kidney and intestine) of deletion homozygotes express basal levels of Mt-1 mRNA higher than those of normal littermates. In the intestine these are furthermore inducible by both hormonal and metal agents. Thus, loss of inducibility of the Mt-1 gene in deletion homozygotes concerns glucocorticoids only and is furthermore restricted to specific cell types (i.e., hepatocytes). The trans-acting factor(s) normally encoded in the deleted region of chromosome 7 appears to be instrumental in conferring on the metallothionein gene in hepatocytes the essential competence to respond to hormonal inducing signals.

Terminal nerve damage impairs the mating behavior of the male hamster

We examined the effects of bilateral terminal nerve (TN) transections (TNx) on the sexual behavior of male hamsters. These lesions produced a decrease in mating frequency and/or an increase in the number of intromissions required to reach ejaculation. Damage to the olfactory bulbs or rostral forebrain did not account for these effects. No amelioration of the behavioral impairments occurred over the mating sessions. Basal testosterone levels in the blood of male hamsters were not altered by TN damage. Hamsters with TNx retained their ability to detect odors, but demonstrated reduced attraction to vaginal odors as compared with unoperated animals. The reduced attraction to vaginal odors was most pronounced in sporadically mating TNx animals. These data suggest that the TN may facilitate odor-induced sexual excitation in the male hamster.

Nuclear events during early chondrogenesis: phosphorylation of the precartilage 35.5-kDa domain-specific chromatin protein and its regulation by cyclic AMP

During chondrogenesis in vivo and in vitro, a family of nonhistone proteins (Mr 35,500), designated PCP 35.5, is lost from the nuclei of precartilage mesenchyme cells. A basic subcomponent of this family, designated PCP 35.5b, is phosphorylated during the first few hours of chondrogenesis in vitro by a phosphorylating system whose activity is enhanced 12- to 15-fold by exposure of differentiating precartilage cells to dibutyryl cyclic AMP. This phosphorylating system is present in isolated precartilage cell nuclei, where it retains its dependence on cyclic AMP and its specificity for PCP 35.5b. Assays for nuclear cyclic AMP inhibitable protein phosphatase activity capable of dephosphorylating PCP 35.5b were negative, indicating that the system responsible for phosphorylating this protein is a cyclic AMP-dependent protein kinase. Chromatin fractionation studies indicate that PCP 35.5b is localized at sites previously shown to be closely associated with DNase I-sensitive domains of precartilage cell chromatin. These studies define PCP 35.5b as a strategically located component of precartilage cell chromatin which is the major or sole chromatin target of cyclic AMP-dependent phosphorylation during chondrogenesis. This chromatin modification occurs prior to overt cartilage differentiation and may therefore play a regulatory role in the acquisition of the cartilage cell phenotype.