The beta-globin gene family is organized into two distinct chromatin domains which are digested at significantly different rates by DNase I. We have investigated the possibility that this differential DNase I sensitivity is based upon differences in the higher order structure of chromatin. When nuclei are digested under low ionic strength conditions known to unfold higher order chromatin structures, the differential sensitivity is lost. That is, the relatively DNase I resistant domain, containing the transcriptionally inactive embryonic and beta-homologous globin genes, becomes sensitive. When chromatin is recondensed with either MgCl2 or NaCl, thus indicating the higher order coiling of the chromatin fiber, the differential sensitivity is restored. Furthermore, the removal of histone H1, known to be essential for stabilization of higher order chromatin structures, results in the loss of differential DNase I sensitivity. In contrast to the DNase I resistant domain, the transcriptionally active adult beta-globin genes show no increase in the rate of digestion when chromatin is unfolded, indicating that this domain may exist as an unfolded nucleosomal chain. The data further suggest that this sensitive domain may be depleted of histone H1.

Animals↗

PubMed1984

Induction of spinal seizures by natural stimulation in cats.

Transection of the spinal cord of the cat at a thoracic or lumbar level results, after as short a period as 12 days, in a preparation with such altered excitability that repeated natural stimulation of the dermatome just caudal to the transection site will induce, in as short a time as 3 days, seizure discharges. The trigger zone for the seizure spreads to caudal dermatomes when these caudal regions are repeatedly stimulated. The 'typical' T4-T7 seizure is a scratch reflex followed by the tonic-clonic seizure lasting for 20-30 s and ending with a scratch afterdischarge lasting for several minutes. Lower thoracic and upper lumbar seizures consist of tonic-clonic co-contractions of the muscles of the hindlegs, followed by rhythmical stepping movements lasting less than 1 min. Partial dorsal rhizotomy or local Cobalt application to the spinal cord may reduce the threshold for induction of seizure by natural stimulation and local Penicillin application to spinal cord induces seizure discharges similar to those induced by natural stimulation. Retransection of the spinal cord caudally, with elimination of the primary trigger zone, does not abolish the secondarily acquired triggers. The findings suggest that spinal circuits possess the ability to acquire new neuronal patterns of discharge and to transfer them to other more caudal segments.

Animals↗

PubMed1984

Alterations in globin gene chromatin conformation during murine erythroleukemia cell differentiation.

Adult beta-globin gene chromatin in murine erythroleukemia (MEL) cells acquired increased sensitivity to both micrococcal nuclease and DNase I during hexamethylenebisacetamide-induced erythoid differentiation. The DNase I hypersensitivity of the globin genes accompanied their actual transcription and was strongly correlated with commitment events. On the other hand, the rate of micrococcal nuclease digestion was closely related to the rate of globin gene transcription. Two distinct DNase I hypersensitive sites were found on the 5' side of the beta-major globin gene in HMBA-induced cells. One site was located near the 5' side of the beta-major globin gene and the second site was located approximately 3 kilobases upstream of the beta-major cap site. Following the commitment of MEL cells to differentiate, DNase I sensitivity was stably inherited in the absence of inducer. In contrast to HMBA, another inducer, hemin, known to cause the accumulation of globin-specific mRNA in MEL cells by a post-transcriptional mechanism, did not elicit alterations of beta-globin gene chromatin. The addition of dexamethasone, a hormone known to inhibit MEL cell commitment, blocked the formation of general and site-specific nuclease sensitivity of beta-globin gene chromatin prior to but not after cell commitment.

Animals↗

PubMed1984

Chromatin structure of the beta-globin gene family in murine erythroleukemia cells.

We have analyzed the chromatin structure of the beta-major globin gene and other related beta-globin genes in induced and uninduced murine erythroleukemia (MEL) cell nuclei. Nuclei were digested with either DNase I or micrococcal nuclease, and the purified DNA was hybridized to a set of cloned genomic DNA fragments covering the beta-globin gene region. This region consisted of two distinct domains as characterized by sensitivity to DNase I digestion. One domain was relatively sensitive and contained the potentially active or actively transcribed beta-major and beta-minor globin genes. The other, relatively insensitive domain contained the nontranscribed embryonic and beta-globin homologous genes. The sensitivity of these domains was not altered during erythroid differentiation. In nonerythroid cells, the entire globin gene family, including the adult and embryonic globin genes, was contained in a single relatively resistant domain. Micrococcal nuclease (MNase) also defined two general domains of nuclease sensitivity that coincided with those of DNase I. However, the relatively sensitive MNase domain containing the beta-major and beta-minor genes became more sensitive upon chemically stimulated erythroid differentiation. A detailed examination of the beta-major globin gene revealed that the actual coding region became increasingly sensitive to micrococcal nuclease after differentiation while the 5'-flanking DNA did not. Thus, micrococcal nuclease was able to accurately define the primary transcription unit of the beta-major gene.

Animals↗

PubMed1984

Reorganization of cerebral control of tactile placing after interrupting a spinal ascending system in cats with pyramid section.

Interruption of a spinal ascending system by hemisection of the spinal cord at mid-thoracic level restores the tactile placing (TP) which is lost after bulbar pyramid section in cats. To determine the location of the ascending system in the spinal cord, partial lesions involving various dorsal, lateral, or ventral tracts were made at mid-thoracic level in cats with pyramid section. To determine the supraspinal control of the recovered TP after pyramid section and spinal cord hemisection, lesions were made in other cortical and subcortical structures essential to TP and also in cortical areas which are not normally involved in TP in cats with recovered TP. The findings demonstrate that the spinal ascending system is located in the ventral part of the lateral funiculus and that the cerebral association cortex takes over the function of motor cortex in the reorganized control of TP. A slow course of TP recovery along with no recovery of impaired distal forelimb movements resulting from pyramidotomy were also observed.

Afferent Pathways↗

PubMed1984

Dihydropteridine reductase deficiency: non-response to oral tetrahydrobiopterin load test.

In a child with dihydropteridine reductase deficiency (McKusick 26163) none of four separate oral tetrahydrobiopterin loading tests resulted in a decrease of the serum phenylalanine concentration. This test cannot be recommended for screening hyperphenylalaninaemic patients for dihydropteridine reductase deficiency.

Biopterins↗

PubMed1984

A method for analyzing transcription using permeabilized cells.

Brief exposure of Friend cells to a buffered hypotonic solution containing 1% Tween 80 caused permeabilization and allowed incorporation of [3H]UTP into RNA. The incorporation was inhibited 85-97% by 20 micrograms/ml actinomycin D and the reaction product was completely hydrolyzed by 0.1 M KOH. UMP incorporation was nearly linear for 60 min at 23 degrees C; however, at 37 degrees C it ceased after 15-20 min of rapid incorporation. The inhibition of UMP incorporation by 2 micrograms/ml alpha-amanitin was much greater at 23 degrees C than at 37 degrees C. The molecular weight of the RNA synthesized in permeabilized cells is broadly distributed with about 83% larger than 18 S. In vitro transcription of the mouse beta-major globin gene was studied by hybridizing 32P-labeled nascent RNA to filter-bound DNA sequences representing this gene and its flanking regions. After induction by hexamethylene-bisacetamide, Friend cells exhibited more than fivefold increases in the rate of transcription for the beta-major globin gene as compared to the uninduced control cells. Induction also caused an increase in the transcription rate of the 3'-flanking region located downstream from the poly(A) addition site. Thus, the primary transcription unit of beta-major globin gene is essentially the same in permeabilized cells as that previously reported for nuclei isolated from the same cell line. In addition, permeabilized cells actively initiate RNA synthesis as determined by the incorporation of a thiol group at the 5' initiating nucleotide, when synthesis was in the presence of [gamma-S]-labeled nucleoside triphosphates. Permeabilized cells are about 7-11 times more active than isolated nuclei in the synthesis of both in vitro-initiated and total RNA.

Animals↗

PubMed1984

A generalized learning deficit in albino rats with early median raphe or pontine reticular formation lesions.

Recent studies suggest that lesions of the median raphe or pontine reticular formation in adult rats are associated with a nonspecific (generalized) learning impairment. The present study showed that lesions in the region of the median raphe or pontine reticular formation in 21 day old rats likewise produced a nonspecific learning impairment, as evidence by significant deficits on a visual discrimination, nonvisual incline plane discrimination, 3-cul maze, and three simple spatial problems. The finding that relatively large lateral pontomesencephalic lesions did not lead to deficient learning of any of these tasks indicates that lesion locus rather than lesion size is responsible for the production of the learning deficits observed in this study.

Animals↗

PubMed1984

Cortical mechanisms underlying acquisition of latch-box problems in the white rat.

Adult rats, previously subjected to bilateral frontal, parietal, occipital, frontocingulate or posterior cingulate ablations, were required to learn two discrete latch-box tasks (sliding a barrel-bolt to the right and elevating a hook). Those groups showing significant learning impairments had lesions to either the frontal cortex or frontocingulate cortex. The data suggest that the neocortical focus for latch-box deficits lies rostral to Level 8 on the Lashley brain diagram, while the frontocingulate focus for latch-box deficits lies within the prelimbic area.

Animals↗

PubMed1984

Maternal hyperphenylalaninemia fetal effects.

Thirty-four children of 11 mothers with untreated hyperphenylalaninemia had a pattern of malformation consisting of prenatal and postnatal growth retardation, microcephaly and central nervous system dysfunction, increased incidence of malformations, and a peculiar facial appearance. Maternal hyperphenylalaninemia appears to be teratogenic, with a variability related to the blood phenylalanine concentration.

Adolescent↗

PubMed1984

Chemotherapy of small-cell carcinoma of lung: a randomized comparison of alternating and sequential combination chemotherapy programs.

One hundred forty-seven eligible patients with small-cell carcinoma of the lung (SCCL) have been randomized to receive alternating (A) or sequential (S) combination chemotherapy. Initial treatment was with three cycles of VAM (A) or two cycles of POCC (S). VAM consists of VP16-213 200 mg/m2 intravenously (IV) day 1, Adriamycin (Adria Laboratories, Columbus, Ohio) 50 mg/m2 IV day 1, and methotrexate 30 mg/m2 IV day 1 repeated at 21-day intervals. POCC consists of cyclophosphamide 600 mg/m2 IV days 1 and 8, vincristine 1.5 mg/m2 (maximum, 2 mg) IV days 1 and 8, CCNU 60 mg/m2 po day 1, and procarbazine 100 mg/m2 po days 2 through 15. After initial treatment, all patients received whole brain radiation therapy (3,000 rad/10 fractions/2 wk). Patients with limited disease in addition received irradiation encompassing the tumor, hilar, mediastinal, and supraclavicular regions (5,000 rad/25 fractions/5 wk). After radiation, patients on arm A received POCC alternating with VAM; patients on arm S received POCC until progression when they were to be treated with VAM. The alternating arm was superior with respect to rate of complete remission (CR), median disease-free survival (MDFS), and median survival (MS). The advantage of alternating therapy was not as clearly demonstrated in the limited disease groups when interposition of involved field radiation delayed the initiation of the alternating schedule. In limited disease alone, comparing arm A with arm S, no statistically significant differences were noted. The CR rate was 42% v 54%, MDFS was 14 v 10 months, and MS was 16 v 10 months. In extensive disease, the CR rate was 44% v 20% (P = .03), MDFS was 6 v 4 months (P = .003), and MS was 10 v 7 months (P = .001). Improved treatment outcome in SCCL is achieved when combination chemotherapy regimens of similar effectiveness are administered in an alternating rather than sequential schedule.

Adult↗

PubMed1984

Thalamic mechanisms underlying acquisition of latch-box problems in the white rat.

Acquisition of a bolt latch and/or hook latch was impaired in rats with mediodorsal, ventromedial, lateral, ventrolateral, midline or parafascicular thalamic lesions, but not in rats with anterior or ventrobasal thalamic lesions. The results suggest that the motor thalamus may extend to territories beyond the ventrolateral nucleus.

Animals↗

PubMed1984

Conditioned tactile placing in cats with unilateral neodecortication or spinal cord hemisection.

The conditioned tactile placing of the forelimbs was abolished contralaterally after unilateral neodecortication or ipsilaterally after hemisection of spinal cord at high cervical level in cats. However, the conditioned response can be regained with training. The results suggest that training activates additional pathways for the conditioned response.

Animals↗

PubMed1983

Recovery of locomotor function in cats after localized cerebellar lesions.

Cats were trained to walk on a motorized treadmill, at speeds up to a brisk walk, for food reward. A cerebellar lesion was placed in each animal, either unilateral removal of paravermal cortex, or unilateral coagulation of n. interpositus, or bilateral coagulation of the fastigial nuclei. The effects of these lesions upon locomotor activity were measured by conventional kinematic methods, and were found to be generally in agreement with prior observations. Also in agreement with prior work was the fact that these initial deficits disappeared in a relatively short time. The kinematic data suggest that this recovery of function was genuine in the sense that compensatory alterations in limb motion could not be demonstrated. In disagreement with prior studies, we failed to elicit decompensation (e.g. reinstatement of the original deficits) by subsequent pyramidal tract sections, or ablation of the 'motor' cortex. We conclude that the corticospinal system is probably not essential to the recovery observed, and also that perhaps there are substantial differences in the mechanisms of recovery of 'spontaneous' overground locomotion, compared to walking on a treadmill as a conditioned instrumental response.

Adaptation, Physiological↗