Computed tomography colonography (virtual colonoscopy): review

Computed tomography examination of the colon performed after bowel cleansing and distension of the lumen with gas goes by several different names--CT colonography (CTC) and CT colography perhaps being the most common. Strictly, the term 'virtual colonoscopy' (VC), should be reserved for the process of examining 3-D, simulated endoluminal images with a capability to navigate through the bowel using appropriate software. Computed tomography colonography appears to be the name that has gained favour among radiologists, although it is suspected that 'virtual colonoscopy' will persist as a generic term due to its attractive 'high-tech' connotations for non-radiological medical and lay persons. Whatever the name, the technique has been made possible through the advent of fast helical CT scanners which allow acquisition of a volume of data, and of proprietary software which enables multiplanar reformatting and 3-D endoluminal reconstructions. It is evident that if CTC/VC can be shown to be acceptable to patients, safe, affordable and accurate, it has enormous potential as a diagnostic and screening tool for colorectal neoplasia.     

The sleep-inducing effect of ethanol microinjection into the medial preoptic area is blocked by flumazenil

Previous studies have shown that a wide range of sedative/hypnotic agents, including ethanol, induce sleep when microinjected into the medial preoptic area (MPA) of the anterior hypothalamus. The mechanism by which ethanol acts at this site to induce sleep has not been clear, though possibilities include alterations of chloride channel function in the GABA(A)-benzodiazepine receptor complex, or increases in neuronal membrane fluidity. In order to explore the former possibility, we have microinjected into the MPA ethanol 0.24 and 0.47 microM, alone and in combination with the benzodiazepine receptor antagonist flumazenil, which has no effects on membrane fluidity or voltage-dependent calcium channel function. Ethanol microinjections significantly reduced sleep latency, and tended (P<0.06) to increase total sleep time. Flumazenil given by itself had no significant effects on sleep, but when given in combination with both doses of ethanol, blocked its hypnotic effects. These data suggest that the sleep-inducing action of ethanol microinjections into the MPA is mediated by ethanol-induced alteration of GABA(A)-benzodiazepine receptor function.     

Alcohol self-administration by female macaque monkeys: a model for study of alcohol dependence, hyperprolactinemia and amenorrhea

Chronic alcohol dependence produces persistent amenorrhea in alcoholic women and female Macaque monkeys but the mechanism is unknown. In one amenorrheic alcohol-dependent monkey, prolactin levels increased from 16.5 to 63 ng/ml during chronic, high-dose alcohol self-administration (3.4 g/kg/day) and immunocytochemical examination of the anterior pituitary showed apparent hyperplasia of the lactotrophs. These data suggested that hyperprolactinemia might contribute to alcohol-induced amenorrhea. Four amenorrheic cycles (85-194 days) from two other alcoholic female monkeys that self-administered an average of 2.97 to 4.4 g/kg/day of alcohol were also studied. Each monkey became amenorrheic during the first menstrual cycle that alcohol was available. One monkey developed galactorrhea during a 97-day amenorrheic cycle when alcohol self-administration averaged 3.35 g/kg/day. Although prolactin levels were intermittently elevated above 20 ng/ml, average levels during these amenorrheic cycles (14.7 +/- 1.8 to 19.6 +/- 1.5 ng/ml) did not differ significantly from prolactin levels during normal ovulatory menstrual cycles when no alcohol was available (19.7 +/- 0.36 ng/ml). There was a negative correlation between daily alcohol dose and prolactin levels (p less than .01). High-dose alcohol self-administration was often associated with low normal prolactin levels, but a relative fall in alcohol dose was usually associated with elevated prolactin levels. These data suggest that both alcohol intoxication and relative alcohol withdrawal may alter basal prolactin levels. LH levels were significantly lower during amenorrheic cycles (16.9 +/- 1.2 to 24 +/- 1.4 ng/ml) than during nonalcohol control cycles (28 +/- 1.2 to 30 +/- 2.2 ng/ml) (p less than .001). These data are consistent with clinical data that suggest that hypothalamic amenorrhea is associated with suppression of gonadotropin secretory activity.     

Growth hormone neurosecretory dysfunction. A treatable cause of short stature

Pulsatile growth hormone (GH) secretion was assessed in a subgroup of short children to determine whether they had GH secretory abnormalities, and these results were compared with those of normal and GH-deficient children. This subgroup of children was defined as having GH neurosecretory dysfunction and met the following criteria: height, less than first percentile; growth velocity, 4 cm/yr or less; bone age, two or more years behind chronological age, normal findings from provocative GH tests (peak, greater than or equal to 10 ng/mL), low somatomedin-C level, and abnormal 24-hour GH secretory patterns. When compared with controls, both children with GH neurosecretory dysfunction and GH-deficient patients had a significant decrease in parameters relating to the total GH secretion during the 24-hour period. As with GH-deficient children, the group with GH neurosecretory dysfunction more than doubled their growth velocity after replacement therapy with exogenous human GH during the first year of treatment. As a result of these detailed studies on pulsatile GH secretion, we suggest that there is a spectrum of GH secretory abnormalities from absolute deficiency to an intermittent irregularity in GH secretion.