K opioid receptors (K receptors) have been characterized in homogenates of guinea pig and rat brain under in vitro binding conditions. K receptors were labeled by using the tritiated prototypic K opioid ethylketocyclazocine under conditions in which ,u and 8 opioid binding was suppressed. In the case of guinea pig brain membranes, a single population of high-affinity K opioid receptor sites (K sites; Kd = 0.66 nM, BMMX = 80 fmol/mg of protein) was observed. In contrast, in the case ofrat brain, two populations of K sites were observedhigh-affinity sites at low density (Kd = 1.0 nM, Bm. = 16 fmol/mg of protein) and low-affinity sites at high density (Kd = 13 nM, Bin" = 111 fmol/mg of protein). To test the hypothesis that the high-and low-affinity K sites represent two distinct K receptor subtypes, a series of opioids were tested for their abilities to compete for binding to the two sites. U-69,593 and Cambridge 20 selectively displaced the high-affinity K site in both guinea pig and rat tissue, but were inactive at the rat-brain low-affinity site. Other K opioid drugs, including U-50,488, ethylketocyclazocine, bremazocine, cyclazocine, and dynorphin (1-17), competed for binding to both sites, but with different rank orders of potency. Quantitative light microscopy in vitro autoradiography was used to visualize the neuroanatomical pattern of K receptors in rat and guinea pig brain. The distribution patterns of the two K receptor subtypes of rat brain were clearly different. The pattern of rat high-affmiity K sites paralleled that of guinea pig in the caudate-putamen, midbrain, central gray substance of cerebrum, and substantia nigra; interspecies differences were apparent throughout most of the rest of the brain. Collectively, these data provide direct evidence for the presence of two K receptor subtypes; the U-69,593-sensitive, high-affinity K, site predominates in guinea pig brain, and the U-69,593-insensitive, low-affinity K2 site predominates in rat brain. Pharmacological studies have established that ketocyclazocine-like opioids produce their antinociceptive and unique sedative actions through an interaction with K receptors (2). These drugs effect a more pronounced sedation than do other opioids and have been evaluated as anesthetic agents. K opioid drugs neither suppress morphine abstinence nor induce abstinence in morphine-dependent monkeys (3). The endogenous opioid peptide dynorphin also interacts with high selectivity at K receptors.Evidence for a separate K receptor distinct from the morphine (A) and enkephalin (Enk; 8) receptors has been provided by pharmacological (2, 4), electrophysiological (5, 6), binding (4,7,8), and solubilization and purification (9)(10)(11) studies. In vitro autoradiography was used to visualize K receptors in rat (12) and guinea pig brain (13)

The empty follicle syndrome (EFS) is a frustrating condition in which no oocytes are retrieved in an IVF cycle. Although this is an infrequent event in IVF patients, the economic consequences as well as the emotional frustration of a cancelled cycle due to the inability to obtain oocytes are enormous. The mechanisms responsible for EFS remain obscure, though many hypotheses have been put forward ranging from dysfunctional folliculogenesis to a drug-related problem. We found that the EFS is a rare event (1.8% of oocyte retrievals) but with profound implications for counselling the couple about their future reproductive performance. The chances of recurrence of EFS increase with the age of the patient (24% recurrence rate for the 35-39 year age group, and 57% for those over 40 years). We postulate that ovarian ageing, through altered folliculogenesis, may be implicated in the aetiology of EFS and its recurrence.

This study compared the use of fetal growth curves with the Rossavik mathematical model in predicting third trimester fetal growth in 27 Hispanic patients. The parameters tested were BPD, HC, AC, and FL. The growth curve method of predicting third trimester fetal growth was significantly more accurate than the mathematical model for three of the four fetal parameters tested: BPD, HC, and FL. We conclude that the mathematical model method offered no advantage over the more commonly used growth curve method for predicting third trimester fetal growth. In addition, growth curves do not require complex calculations and are conceptually simpler and easier to use.

Dilation of the uterine cervix may provide options for treatment in selected patients with infertility. The effect of dilation on patients with other sequelae of cervical obstruction such as endometriosis remains uncertain.

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