Fernando García-Hernández

Fetal suprachiasmatic nucleus transplants: diurnal rhythm recovery of lesioned rats

The diurnal rhythm organization of drinking behavior was determined prior to and after suprachiasmatic nucleus (SCN) lesions. Five weeks after SCN lesions which produced total loss of the diurnal rhythm, the anterior hypothalamus including the SCN of fetal rats was transplanted into the floor of the 3rd ventricle of the lesioned rats. Eight weeks after the graft, rats recovered their rhythm. The results show that grafts allow animals to recover lost functional properties due to lesions, and further support the notion that the SCN is a pacemaker for certain behaviors.

A new motor test sensitive to aging and dopaminergic function

Neurodegenerative disorders which involve motor impairment is characteristic of old age. Although there are a few tests which attempt to assess motor incapacities, many have utilized scales which have either a great deal of subjective evaluations or are subject to learning-performance complexities. This study describes a method able to measure motor impairment of aging rats which is subject to dopaminergic influences and has negligible practice effects. The test is designed so that rats have to traverse 2 meter beams of 15 degrees inclination whose widths 3, 6, 12, 18 and 24 mm are changed on each test session using a table of random numbers. The time ceiling allowed for traversing the 2 m beams was established at 120 sec. 3-month-old rats (n = 20) and aged rats (n = 20) with a mean age of 26.5 +/- 3.8 months ranging from 23 to 34 months were utilized in this study. All young rats traversed the beams, independently of beam width, while virtually none of the old rats traversed the 3 and 6 mm beams. However, as the beam width increased more and more aged rats ascended the beam. Nevertheless, there were always a few old rats who were unable to cross even on the widest beam. When young rats were fitted with a lead belt which increased their body weight by approximately 40%, they still traversed all beam widths. On the other hand, haloperidol (0.1 and 0.2 mg/kg) severely impaired the performance of young rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Suprachiasmatic nucleus transplants function as an endogenous oscillator only in constant darkness

Rats which sustained lesions of the suprachiasmatic nucleus (SCN) were transplanted with fetal hypothalamic tissue which included the SCN. After the graft, animals were kept under a 12:12 light-dark (LD) cycle during 6 weeks at which time half the animals were placed in constant light (LL) and half in constant darkness (DD). The results showed that all grafted rats recovered the photoperiod under LD, but under constant conditions rats began to free-run only in DD. The results suggest that the grafted tissue functions as a self-sustained oscillator only in darkness.

Dibutyryl cAMP stimulates analgesia in rats bearing a ventricular adrenal medulla transplant

In the present study, a significant increase in pain threshold (current to elicit vocalization to tail shock) was found 15 and 60 min after injection of dibutyryl cyclic AMP (db cAMP) (30 micrograms) into the lateral ventricle in rats bearing a transplant of fetal adrenal medulla (AM). By contrast, no effect on pain threshold was observed in rats bearing an AM transplant but receiving no db cAMP, or in rats receiving db cAMP but not bearing an AM transplant. In primary cultures of rat fetal chromaffin cells, db cAMP increased the number of neuron-like cells that showed both vasoactive intestinal polypeptide (VIP)- and tyrosine hydroxylase (TH)-like immunoreactivity. These findings indicate that db cAMP exerts a pharmacological modulation of the functional activity (i.e. elevation in pain thresholds) of fetal adrenal AM transplants, and induces phenotypic changes in cultured chromaffin cells with expression of a peptide that elevates pain threshold.

Transplantation of the fetal occipital cortex to the third ventricle of SCN-lesioned rats induces a diurnal rhythm in drinking behavior

Fetal hypothalamic transplants which include the suprachiasmatic nuclei (SCN), were shown previously to be capable of restoring circadian rhythmicity as manifested by both diurnal and free-running rhythms in drinking behavior in rats rendered arrhythmic by SCN lesions. The question arises as to whether the transplant must be homologous tissue or whether any other fetal brain tissue can produce similar effects. In this study rats with a lesion of the SCN and with clear loss of drinking rhythms received grafts of fetal occipital cortex placed into the third ventricle. Following the graft, animals were placed in LD conditions for 8 weeks and then in DD for another 8 weeks. The results indicate that the cortical graft induced recovery of a drinking rhythm under LD lighting conditions but that under DD the rhythm was lost again. These results suggest that non-hypothalamic tissue can mediate recovery of a diurnal rhythm but that hypothalamic tissue including the SCN is required to restore circadian function with maintenance of free-running rhythms.

Reduction of motor impairment by adrenal medulla transplants in aged rats

Recently we have reported that drugs that enhance dopaminergic transmission, such as L-dopa and D-amphetamine, substantially improve the age-related deterioration of extrapyramidal motor functions, as assessed by the narrow uphill beam test. Here we report the effect of fetal adrenal medullary transplants upon the motor performance of aged rats in such a test. Rats were grafted with 300,000 cultured adrenal medullary cells, placed into the head of either the left caudate nucleus, or into both caudates. A third group was grafted with one freshly dissected adrenal medulla placed as a block of tissue into the lateral ventricle, whereas the control group sustained sham grafting. Evaluation of the motor performance of cultured and sham-grafted rats showed no improvement along the testing phase. Only adrenal block-grafted rats exhibited a significant recovery of motor coordination. Histologically, cultured cell grafts had a deteriorated appearance with poor survival rates, while block grafts exhibited chromaffin cells with round and neuron-like shapes. The results suggest that cultured adrenal grafts may not induce motor improvement due to their extremely low survival and poor integration, at least in the aged host brain, while fresh adrenal transplants may improve motor coordination for as long as 84 days.

REM sleep enhancement induced by sensory stimulation is prevented by kainic acid lesion of the pontine reticular formation

It has been shown that auditory or somatic stimulation during rapid eye movement (REM) sleep is capable of producing a significant increase in ponto-geniculo-occipital (PGO) spike density as well as in REM sleep duration. The purpose of this study was to determine the role of the medial pontine reticular formation (PRF) in mediating such increase of REM sleep duration. After a baseline recording whereby on the same recording day the control and the stimulus (auditory or somatic) alternated with each REM, a group of cats was lesioned with kainic acid in the PRF. The sleep-wake cycle was recorded again on days 15, 30 and 45 post-lesion, following the same procedure. The results showed no changes in REM sleep duration and PGO spike density in the lesioned animals. However, when sensory stimulation was applied it was ineffective in producing REM sleep enhancement, although it was able to increase PGO spike density. These findings suggest that the effects of sensory stimulation on REM sleep duration are accomplished through the PRF, probably by inducing an increase in the excitability levels of such neurons, and further suggests that PGO spike density and REM duration are independent of each other.

Chapter 58 Possible mechanisms of action of adrenal transplants in Parkinson's disease

Publisher Summary This chapter examines the possible mechanisms of action of adrenal transplants in Parkinsons disease. The contralateral grafts of fetal adrenal medulla or substantia nigra can ameliorate apomorphine-induced rotational behavior for extended periods of time in rats with unilateral 6-hydroxydopamine (6-OHDA) denervation of the nigrostriatal pathway. As adrenal medulla grafts do not increase dopamine levels in cerebrospinal fluid (CSF), but blood levels of dopamine are increased after such transplants, dopamine may gain access to the striatum via the systemic circulation. Adrenal medulla transplants in the aged rats not only induce a recovery of motor deficits but seem to reactivate dopaminergic transmission in the naturally degenerated nigro-striatal pathway, as shown by tyrosine hydroxylase (TH)-immunocytochemical staining. Similar observations of an enhanced morphological and functional recovery of nigro-striatal dopaminergic fibers by adrenal medulla grafts are described in the chapter. The role of trophic factors may be critical for this reactivation, because nerve growth factor plus noncatecholaminergic grafts reduces motor disfunctions in aged rats. The additional fact that adrenal transplants increase pain thresholds in the presence of dibutyryl cyclic adenosine monophosphate (cAMP), suggesting that chromaffin cells may have multiple biochemical actions, which in turn produce multiple effects when transplanted into the brain.

Effects of graft placement site on the survival of adrenal medulla transplants into the brain and its relation with the recovery of motor function.

BACKGROUND Because of their lack of long-term viability, adrenal tissue transplants have shown limited success in alleviating the motor disturbances associated with experimental and pathologic striatal dopamine denervation. In this study, we examined how the graft placement site influences adrenal medulla transplant survival and its relation with the reduction of motor deficits in rats bearing unilateral 6-OHDA lesion. METHODS One or 5 microL of fetal adrenal medullar tissue was grafted either inside the striatal parenchyma or into the lateral ventricle in contact with the dopamine-denervated striatum. Motor disturbances, as assessed by apomorphine-induced rotation, were correlated to the graft morphologic survival features. RESULTS Apomorphine-induced rotation showed a marginal reduction of 11% in all groups independently of graft survival features or placement site. Intrastriatal transplants showed limited viability characterized by a substantial loss of graft initial volume as well as fewer and smaller chromaffin cells compared to ventricular grafts, which had a reduced loss of graft initial volume and more and larger chromaffin cells. CONCLUSIONS Although the lateral ventricle may favor adrenal medulla transplant viability, their induced motor outcome is comparable to that induced by less viable intrastriatal grafts, suggesting that the implanted dopamine-producing cells may interact and influence striatal neurons better when placed in close proximity.

Fermentation of a waste-product from the industrial processing of the lime (Citrus aurantifolia swingle) for vitamin B12 production

SummaryThe purpose of this study was to investigate the possibility of utilizing the distillation residue, produced in the industrial processing of the lime, as a substrate for the production of vitamin B12 by Propionibacterium freudenreichii and Propionibacterium shermanii. Both microorganisms were found capable of fermenting the distillation residue with no significant differences in the production of this vitamin. However, P. shermanii was selected for the study since it presented fewer problems in the extraction and analysis of the vitamin.After NaOH, Ca(OH)2, and NH4OH were used to adjust the pH of the medium for optimal growth of the propionibacteria strains, deficiencies in the media were corrected. NaOH was selected since it provided good yield without removing fermentation sources. Under anaerobic conditions, 5,6-dimethylbenzimidazole had a positive effect on the synthesis of vitamin B12; under anaerobic-aerobic conditions, a negative effect.