Immunocytochemical and electrophysiological differentiation of rat cerebellar granule cells in explant cultures

We have used a combination of immunocytochemical and electrophysiological measurements to monitor the differentiation of cerebellar granule cells in vitro. We present immunocytochemical evidence showing that several characteristic features of developing rat cerebellar tissue were retained in postnatal explant cultures. Most notably the cultures expressed radiating GFAP-positive (Bergmann) glia processes, proliferating NSE-negative neuroblasts, and migrating NSE-positive granule cells. The latter were subdivided into 3 developmental stages--i.e., immature, intermediate, and mature granule cells, based upon cell differences in location from the explant, intensity of NSE staining, excitability, and the amplitude of voltage-dependent conductances. Immature cells were identifiable during the first week in culture and were located up to 140 micron from the explant. These cells stained lightly for NSE and displayed conductances of insufficient magnitude to generate action potentials. Intermediate cells were present after 1-2 weeks in culture and were located up to 500 micron from the explant. These cells were also NSE positive and were characterized by the presence of soma action potentials. Intermediate cells displayed 3 large voltage-dependent conductances: a transient, TTX-sensitive inward current; a delayed, TEA-sensitive outward current; and a transient, 4AP-sensitive outward current. Mature cells were present after 1 month in culture and, like intermediate cells, were no more than 500 micron from the explant. However, mature cells stained more intensely for NSE, and the somata of these cells were devoid of voltage-dependent conductances (although axonal currents were usually present). These results indicate that granule cells undergo a stereotypic sequence of differentiation in postnatal explant cultures. These stages may correspond to developmental changes in granule cells during migration into the (internal) granular cell layer in vivo.     

Rurality, remoteness and the change process: evidence from a study of maternity services in the north of Scotland.

There is a wealth of material on 'how to do' change plus empirical work revealing change process complexity. In health care, the relevance of context is highlighted, but studies of rural health-care change have focused on community impacts. There is little to inform health-care managers of how remoteness and rurality impact upon change processes. This study considered Scottish maternity units and aimed to identify issues in the change process associated with rurality and remoteness. Six units were purposively selected and 131 interviews were conducted with managers, staff and community members over 15 months. Analysis induced themes pertinent to remoteness and rurality. These included: perceived 'distance' between senior managers imposing change and the wider community of staff and residents; perceptions of community vulnerability; and tensions arising from working in small teams and living in small communities. The study provides useful insights for rural managers at a time of considerable service reconfiguration.     

Repair of DNA lesion O 6-methylguanine in hepatocellular carcinogenesis

Evidence from both experimental carcinogenesis and studies in human cirrhotic liver suggest that defective repair of the promutagenic DNA base lesion, O ⁶-methylguanine, is a factor in the multistep process of hepatocellular carcinogenesis. Ubiquitous environmental alkylating agents such as N-nitroso compounds can produce O ⁶-methylguanine in cellular DNA. Unrepaired, O ⁶-methylguanine can lead to the formation of G ? A transition mutations, a known mechanism of human oncogene activation and tumour suppressor gene inactivation. Combined treatment of rodents with an agent producing O ⁶-methylguanine in DNA, and an agent promoting cell proliferation, leads to development of hepatic nodules and hepatocellular carcinoma (HCC), cell division, hence DNA replication, being required for the propagation of tumorigenic mutation(s) in hepatocyte DNA. The paramount importance of O ⁶-methylguanine in hepatocellular carcinogenesis is indicated by the observation that transgenic mice engineered to have increased hepatic levels of repair enzyme O ⁶-methylguanine-DNA methyltransferase (MGMT) are significantly less prone to hepatocellular carcinogenesis following alkylating agent treatment. Cirrhosis is a universal risk factor for development of human HCC, and a condition that is characterized by increased hepatocyte proliferation as a result of tissue regeneration. Levels of the human repairing enzyme for O ⁶-methylguanine were found to be significantly lower in cirrhotic liver than in normal tissue. In accord with findings from animal models, this suggested a mechanism in which persistence of O ⁶-methylguanine due to defective DNA repair by MGMT, together with increased hepatocyte proliferation, might lead to specific gene mutation(s) and hepatocellular carcinogenesis. Screening for the presence and persistence of O ⁶-methylguanine in human DNA presently involves formidable technical difficulty. Indications are that such limitations might be overcome by the use of an ultrasensitive method such as immuno-polymerase chain reaction (PCR). This approach should allow parallel measurement of DNA adduct and repair enzyme in routine liver biopsy samples. It might also enable investigation of O ⁶-methylguanine in human genes specifically associated with hepatocellular carcinogenesis. Given the wide variation in human MGMT levels observed between individuals, tissues, and cells, this technology should be adapted to permit the ultrasensitive localisation and measurement of adducts and repairing enzyme in liver biopsy tissue sections. Ability to ultrasensitively measure O ⁶-methylguanine, and its repair enzyme, should prove valuable in the risk assessment of cirrhotic patients for developing hepatocellular carcinoma. Received for publication on July 6, 1998; accepted on Aug. 12, 1998     

Angiotensin-converting enzyme (ACE) gene polymorphism in type II diabetic patients with increased albumin excretion rate

Approximately one in three patients with diabetes is at risk of developing kidney disease, despite current methods of treatment. It has long been suspected that diabetic kidney disease has a genetic basis, but this has been difficult to prove. Polymorphisms of the angiotensin-converting enzyme (ACE) gene have been shown to be related to the occurrence of nephropathy in type I diabetic patients. This study showed that there was no association in the ACE genotype frequency and increased albumin excretion rate in type II diabetic patients.     

Spouse Concordance for Alcohol Dependence and Heavy Drinking: Evidence from a Community Sample

Using data from a community sample of 586 married couples, levels of spouse concordance for lifetime and current alcohol dependence and heavy drinking were estimated. In addition, marital quality ratings in concordant and discordant couples were compared. Spouse concordance was significant for lifetime alcohol dependence and for both lifetime and current heavy drinking. Marital quality varied as a function of current heavy drinking and alcohol dependence such that members of couples in which neither spouse drank heavily reported better marital quality than other couples. Furthermore, although marital quality did not differ significantly between concordant and discordant couples, couples concordant for current heavy drinking consistently reported poorer marital quality than other couples.     

Serotonergic modulation of spinal ascending activity and sacral reflex activity evoked by pelvic nerve stimulation in cats

Serotonin (5-HT) may be inhibitory to micturition at a spinal level. A potential mechanism of action for serotonergic inhibition of bladder function is a depression of the ascending limb of the supraspinal reflex mediating micturition. Ascending activity evoked by pelvic nerve stimulation was recorded in the thoracic spinal cord of anesthetized cats. For comparison, spinal reflex activity evoked by pelvic nerve stimulation was recorded on the pudendal nerve. The effects of intrathecal administration of serotonergic agents were examined to determine whether spinal and supraspinal responses to bladder afferent activation were modulated by 5-HT. Methysergide (60 nmol), a non-selective serotonergic antagonist, increased ascending activity by 61±7% and depressed spinal reflex activity by 38±6%. Zatosetron (10 nmol), a 5-HT₃ antagonist had a similar effect on both activities (increased by 93±24% and decreased by 77±7%, respectively). The effect on ascending activity of blocking 5-HT₃ receptors was also confirmed with ICS 205930 and MDL 72222. 2-Methyl-5-HT (800 nmol), a 5-HT₃ agonist, depressed ascending activity to 46±9% of control, but enhanced spinal reflex activity by 73±92%. These results demonstrate that stimulation of 5-HT₃ and methysergide-sensitive 5-HT receptors can inhibit ascending activity and facilitate spinal reflex activity elicited by activation of bladder afferents. It is suggested that descending serotonergic pathways may participate in the spinal coordination of urinary continence.     

Two levels of alliance formation among male bottlenose dolphins (Tursiops sp.)

In Shark Bay, Western Australia, male bottlenose dolphins (Tursiops sp.) cooperate in pairs and triplets to sequester and control the movements of females. We refer to this behavior as "herding" and to the male pairs and triplets as alliances. During a 25-month study (1987-1989) on the social relationships of males, we documented herding in 10 alliances. Males preferentially herded nonpregnant females likely to be in estrus. Alliance members associated with one another consistently when not herding females. Each alliance associated preferentially with one or two other alliances. Occasionally, two alliances combined and took females from another alliance or defended females against such efforts. This study documents multiple-level male alliances within a social group outside of humans.     

Head injury mortality in two centers with different emergency medical services and intensive care

The authors report data collected prospectively on 551 cases of head injury in New Delhi, India, and 822 cases in Charlottesville, Virginia. The mortality rate, adjusted for initial severity of injury, was 11.0% in New Delhi versus 7.2% in Charlottesville (p less than 0.02). There was a striking similarity in mortality rates at both centers when comparing patients with the least severe head injuries and those with the most severe injuries according to the motor score of the Glasgow Coma Scale (GCS M). However, in the group with an abnormal but purposeful motor response (GCS M = 5), the mortality rate was 12.5% in New Delhi versus 4.8% in Charlottesville (p less than 0.01). The relative absence of prehospital emergency care and the delay in admission after head injury in New Delhi are cited as two possible causes for the differences in mortality rates in this subgroup of patients with "moderate" head injuries.