Nematic structuring of transparent and multifunctional nanocellulose papers.

The nematic structuring of cellulose nanofibers (CNFs) is proposed as a nanostructural engineering tool for exploiting the potential of CNFs in conceptually new "transparent papers". The nematic-structured CNF papers exhibit superior mechanical properties, optical transparency, gas-barrier properties, heat transfer properties and electrical resistivity, compared with conventional randomly-structured CNF papers.

Cellulose nanocrystals/polyurethane nanocomposites. Study from the viewpoint of microphase separated structure.

Cellulose nanocrystals (CNC) successfully obtained from microcrystalline cellulose (MCC) were dispersed in a thermoplastic polyurethane as matrix. Nanocomposites containing 1.5, 5, 10 and 30 wt% CNC were prepared by solvent casting procedure and properties of the resulting films were evaluated from the viewpoint of polyurethane microphase separated structure, soft and hard domains. CNC were effectively dispersed in the segmented thermoplastic elastomeric polyurethane (STPUE) matrix due to the favorable matrix-nanocrystals interactions through hydrogen bonding. Cellulose nanocrystals interacted with both soft and hard segments, enhancing stiffness and stability versus temperature of the nanocomposites. Thermal and mechanical properties of STPUE/CNC nanocomposites have been associated to the generated morphologies investigated by AFM images.

Making flexible magnetic aerogels and stiff magnetic nanopaper using cellulose nanofibrils as templates.

Nanostructured biological materials inspire the creation of materials with tunable mechanical properties. Strong cellulose nanofibrils derived from bacteria or wood can form ductile or tough networks that are suitable as functional materials. Here, we show that freeze-dried bacterial cellulose nanofibril aerogels can be used as templates for making lightweight porous magnetic aerogels, which can be compacted into a stiff magnetic nanopaper. The 20-70-nm-thick cellulose nanofibrils act as templates for the non-agglomerated growth of ferromagnetic cobalt ferrite nanoparticles (diameter, 40-120 nm). Unlike solvent-swollen gels and ferrogels, our magnetic aerogel is dry, lightweight, porous (98%), flexible, and can be actuated by a small household magnet. Moreover, it can absorb water and release it upon compression. Owing to their flexibility, high porosity and surface area, these aerogels are expected to be useful in microfluidics devices and as electronic actuators.

Effects of chronic stimulation or antagonism of opiate receptors on GH secretion in male and female rats.

The present study was undertaken to assess the role of endogenous opioid systems in the sexually dimorphic pattern of growth hormone (GH) secretion. To this end, male rats were treated chronically (6 to 12 h) with morphine and estrogen-exposed, ovariectomized female rats with morphine or naloxone. Chronic morphine exposure of male rats caused a 12-fold increase in basal GH levels and a modest rise in GH pulse frequency. These two changes resulted in a 3-fold increase in both mean GH concentration and total GH secretion over 6 h. In female rats, chronic morphine reduced GH pulse amplitudes but did not significantly affect other parameters of GH secretion. By contrast, chronic naloxone treatment of female rats reduced basal GH levels by 64% without affecting GH pulse amplitudes or pulse frequency. These data suggest that endogenous opioid systems are involved in the regulation of the basal GH secretion in both male and female rats.

Photoperiod modulates pubertal shifts in behavioral responsiveness to testosterone.

This study examined the effect of photoperiod on pubertal maturation of steroid-dependent reproductive behaviors in male European ferrets (Mustela putorius furo). In the first experiment, levels of neck gripping, mounting, and pelvic thrusting in gonadally intact prepubertal (PRE) ferrets were compared with those of adults that had undergone puberty either while housed in short days (8 hr light/16 hr darkness per day; SD), or after transfer from SD to long days (18 hr light/6 hr darkness per day; LD) at 12 weeks of age. Both LD and SD adults demonstrated significantly greater amounts of neck gripping and mounting than PRE males. In addition, a significantly greater proportion of adults in both SD and LD displayed at least one incidence of the three behaviors compared to PRE ferrets. There were no statistically significant differences in behavior of the gonadally intact LD and SD adults. In the second experiment, dose-response curves for behavioral responses to subcutaneous injections of 0, 0.5, 1.25, 2.5, 5, and 10 mg/kg testosterone propionate (TP) in oil were generated in castrated PRE, SD, and LD males. The lowest dose of TP elicited significantly greater amounts of all three behaviors in LD adults than in PRE ferrets. In addition, levels of mounting and thrusting elicited by the lowest dose of TP were significantly greater in LD adults than in SD adults. These data indicate that pubertal activation of male sexual behavior in male ferrets is accompanied by a pubertal increase in responsiveness to the behavioral effects of testosterone. Furthermore, the degree of behavioral responsiveness of adult ferrets to testosterone is modulated by environmental photoperiod experienced during reproductive maturation.

Luteinizing Hormone-Releasing Hormone Neurons which are R-etrogradely Labeled After Peripheral Fluoro-Gold Administration in the Male Ferret.

This study identified luteinizing hormone-releasing hormone (LHRH)-producing neurons which have access to fenestrated capillaries in prepubertal male European ferrets. Fluoro-Gold was injected intraperitoneally to retrogradely label neurons with terminals outside the blood-brain barrier. LHRH neurons were identified by immunofluorescence using a secondary antibody tagged with tetramethylrhodamine isothiocyanate. Cell bodies which demonstrated both tetramethylrhodamine isothiocyanate and Fluoro-Gold fluorescence were defined as LHRH-producing neurons with axon terminals in regions containing fenestrated capillaries. The total number and neuroanatomical distribution of immunopositive (LHRH +) cells concurred with previous studies in the ferret in which cell bodies were diffusely distributed from rostral forebrain through caudal diencephalon, with approximately 70% of the LHRH + cell bodies located in retrochiasmatic hypothalamus. In the present study, an average of 59.8% of all LHRH+ neuronal perikarya also contained Fluoro-Gold. The majority of Fluoro-Gold filled LHRH+ neurons demonstrated only faint to moderate amounts of Fluoro-Gold when compared to other Fluoro-Gold filled neurosecretory neurons. This limited uptake of Fluoro-Gold may be due to a relative inactivity of LHRH neurons projecting outside the blood-brain barrier. Double-labeled LHRH + neurons were dispersed throughout the entire population of LHRH+ cell bodies and no apparent nuclear groups of double-labeled neurons were found. This observation suggests that the LHRH+ neurons responsible for neurosecretion into the median eminence coexist with the LHRH+ neurons responsible for intracerebral neurotransmission or neuromodulation. One distinguishable population of LHRH + neurons was consistently observed in all the brains. Only 26% of total LHRH+ perikarya within the caudal arcuate nucleus contained Fluoro-Gold, while at least 50% of LHRH+ neurons in other structures, including the rostral arcuate nucleus, contained Fluoro-Gold. Thus, in the prepubertal male ferret, the majority of LHRH cell bodies located in the caudal arcuate nucleus may be differentially regulated and/or involved in non-neuroendocrine functions.

Luteinizing hormone-releasing hormone alters the hypothalamic effects of morphine in the rat.

Female rats exhibit a generalized refractoriness to opiate stimulation during periods of steroid-induced LH secretion. In the present study we evaluated that role of LHRH in this steroid-induced effect on opiate-responsiveness. Central administration to ovariectomized rats of native LHRH or the LHRH agonist [Des-Gly10]LHRH ethylamide causes a dose-dependent refractoriness to the hypothermic effects of morphine. The potency relationship of these two LHRH agonists in antagonizing morphine's effect was consistent with their potency in inducing LH release. Treatment of ovariectomized rats with estradiol benzoate and progesterone in a regimen which induces a preovulatory-like LH surge, antagonized morphine-induced hypothermia, and the LHRH antagonist [D-Phe2, Pro3, D-Phe6] LHRH, reversed the effects of the gonadal steroids. These results indicate that the LHRH secretory dynamics associated with the preovulatory surge of LH may serve to modulate opiate responsiveness and thereby could serve to couple behavioral, sensory, and autonomic events with this neuroendocrine response to gonadal steroids.

Opiate-thyroid hormone interactions in the regulation of thyrotropin secretion in the rat.

Studies were performed to determine the role of thyroid hormone in the suppression of thyrotropin (TSH) by opiates. Serum samples were collected by decapitation 1, 3, 6, 12, 24, or 48 h after rats were implanted with 1 sustained-release morphine (75 mg) or placebo pellet. Morphine decreased TSH by 44% at 1 h and by 83% at 3 h, and TSH remained significantly depressed by 38% through 48 h. Thyroxine (T4) levels were significantly reduced from 12 to 24 h after morphine, but triiodothyronine (T3) levels were not affected. When control or thyroidectomized (THX) rats were implanted with morphine or placebo 24 h before serum collection, morphine significantly decreased TSH, T3 and T4 in controls but had no effect on TSH in THX rats. Thus, it appears that the morphine-induced suppression of TSH release requires circulating thyroid hormone. When THX rats were chronically treated with morphine or placebo, then injected subcutaneously with saline or 1, 10 or 100 micrograms T4/kg body weight 24 h prior to serum collection, morphine treatment alone did not affect TSH in THX rats. T4 replacement caused a dose-dependent decrease in serum TSH in both morphine and placebo rats; however, TSH was suppressed significantly more in morphine than in placebo rats. Thus, while chronic morphine treatment is ineffective in suppressing in TSH in THX rats, morphine interacts with thyroid hormone to reduce TSH release. These data suggest that morphine may exert its inhibitory effect on TSH secretion by increasing the negative feedback sensitivity to thyroid hormones.

Pituitary responsiveness to luteinizing hormone-releasing hormone in prepubertal and postpubertal male ferrets.

The pituitary response to three different doses of exogenously administered LHRH was examined in prepubertal (9-wk-old) and postpubertal (32-wk-old) male ferrets. The doses of 5, 10, and 15 ng LHRH/kg body weight tested in this study produced dose-related increases in circulating LH concentrations in both pre- and postpubertal groups. In addition, a significant effect of age on LH response was observed, with the prepubertal animals demonstrating significantly greater serum LH values in response to the two higher doses than the postpubertal males. Prepubertal ferrets also exhibited a significant increase in endogenous LH pulse amplitude in sampling periods following exogenous administration of LHRH compared to baseline pulse amplitudes in periods prior to the LHRH infusions. These results suggest that the low frequency of endogenous LH pulses previously observed in prepubertal ferrets is not due to unresponsiveness of the pituitary gland to LHRH. Thus, suppression of the hypothalamo-hypophyseal axis observed in the prepubertal ferret is probably mediated at the level of the hypothalamus.

Gonadal steroid and chronic morphine treatment do not change the posttranslational processing of beta-endorphin in the rat brain.

The present study examines whether two treatments known to induce refractoriness to exogenous morphine produce this desensitization through a change in the posttranslational processing of brain beta-endorphin (beta-End). The first experiment examined whether an ovarian steroid regimen which produces a transient desensitization of brain opiate receptor mechanisms alters beta-End processing in the preoptic area (POA), medial basal hypothalamus (MBH), and brainstem (BS). The second experiment monitored the effects of morphine pellet treatment, known to produce morphine dependency, on immunoreactive beta-End forms in the hypothalamus and periaquaductal gray area of the midbrain (PAG). The individual molecular forms of beta-End were separated using ion exchange chromatography and collection fractions were quantitated for beta-End immunoreactivity by RIA. The results show that regional differences occur in the posttranslational processing of beta-End. In the hypothalamus, MBH and POA, beta-End-(1-31) and its non-acetylated C-terminal cleavage products, beta-End-(1-27) and beta-End-(1-16) were the predominant forms of beta-End. The PAG pools produced a beta-End peptide elution profile similar to the hypothalamus, although small amounts of N-acetyl-beta-End-(1-31) were also identified. The BS exhibited the least posttranslational processing of beta-End; beta-End-(1-31) was the primary product with smaller amounts of beta-End-(1-27) and beta-End-(1-26) observed. However, neither ovarian steroid treatment nor chronic morphine produced any changes in posttranslational processing of beta-End or in total beta-End concentration in any of the brain regions examined in these experiments. These data indicate that the refractoriness or tolerance to exogenous morphine associated with steroid or chronic morphine treatment cannot be explained by alterations in the biological activity of beta-End resulting from the differential regulation of its posttranslational processing products.

Alterations in brain opiate receptor mechanisms on proestrous afternoon.

We have previously observed that gonadal steroid treatments, which stimulate a proestrous-like LH surge is ovariectomized rats, cause a marked reduction in the responsiveness to opiates of a variety of CNS processes. The present study was undertaken to determine if a similar decline in opiate responses is associated with the endogenous steroid-induced LH surge on the afternoon of proestrous. Rats were evaluated for thermic, nociceptive, behavioral and LH secretory responses to morphine sulfate on diestrous I afternoon (DiPM) and proestrous morning (ProAM), times at which LH secretion is low, as well as on proestrous afternoon (ProPM) during the preovulatory LH surge. While on DiPM and ProAM, morphine caused a 33-45% reduction in serum LH levels at doses as low as 5 mg/kg b.w., in ProPM rats doses as high as 10 mg/kg did not affect LH secretion. Similarly, ProAM rats showed a prompt and sustained analgesic response to morphine, but ProPM rats showed a delayed response of shorter duration. DiPM rats showed an acute response intermediate to that of ProAM and ProPM animals. While DiPM and proAM rats exhibited the expected hypothermic response to a high dose of morphine (15 mg/kg), ProPM rats showed no decline in core body temperature, but exhibited a delayed hyperthermic response to the opiate. DiPM and ProAM rats showed a dose-dependent decline in locomotor behavior in response to morphine. In contrast, ProPM rats, which exhibited a significantly elevated basal locomotor activity, failed to show a reduction in locomotion after morphine treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Desensitization of brain opiate receptor mechanisms by gonadal steroid treatments that stimulate luteinizing hormone secretion.

We studied the effects of two ovarian steroid treatments that induce proestrous-like surges in LH secretion on responsiveness to morphine sulfate (MS), as measured by induced hypothermic, antinociceptive, behavioral, and LH secretory changes. Ovariectomized rats received no steroids (OVX), 7.5 micrograms estradiol benzoate 2 days before the experiment (EB), or EB and then 5 mg progesterone 48 h later (EBP). MS administration coincided with the steroid-induced LH hypersecretion that occurs in the EB and EBP rats at 1530-1630 h. Serum LH concentrations were determined 30 min after administration of MS. In OVX and EB rats, MS caused a dose-dependent decrease in serum LH, but even 20 mg/kg MS did not alter serum LH during the EBP-induced LH surge. Brain-mediated morphine-induced analgesia was evaluated in the three steroid treatment groups from measurement of latency to pawlick on a hot plate. EB and EBP rats were less responsive than OVX rats to MS-induced antinociception. EB and EBP rats were also less responsive than OVX animals to the spinal cord-mediated analgesia due to MS, as calculated by tail-flick latency. MS-induced hypothermia revealed a responsiveness order of OVX greater than EB greater than EBP. Whereas MS caused a dose-dependent reduction in locomotor activity in OVX and EB rats, EBP rats showed marked hyperactivity at low MS doses and were less responsive to the suppression of locomotor activity at higher doses. These marked steroid-induced changes in MS responsiveness could not be explained by altered pharmacokinetic disposition of morphine. These data indicate that treatment with EBP, which stimulates a preovulatory-like LH surge, decreases the ability of MS to induce hypothermic, antinociceptive, and behavioral responses and abolishes its capacity to suppress LH release. These effects of gonadal steroids were not observed before the LH surge, which suggests that this surge is linked to the decline in MS sensitivity. Further, the diminished response to MS appears to be a function of the magnitude of the LH surge.

Chronic morphine treatment enhances the negative and positive feedback effects of estradiol on gonadotropin secretion in ovariectomized rats.

Studies were undertaken to evaluate the effects of chronic morphine exposure on the negative and positive feedback effects of estradiol (E2) on LH and FSH secretion in ovariectomized rats. Two days of E2 exposure reduced at 1000 h and stimulated at 1600 h the serum LH concentration at each dose tested. Chronic exposure (4 days) to morphine enhanced both the inhibitory effects of E2 on LH secretion at 1000 h and E2 induction of the midafternoon surge in LH. A detailed time course of the afternoon LH response to E2 revealed that chronic morphine exposure advanced its time of onset and increased its magnitude. The response of FSH to E2 and the interaction between E2 and morphine on FSH secretion were similar to those observed for LH, albeit lower in magnitude. With extension of the E2 exposure period from 2 to 4 days, the synergistic interaction between E2 and morphine persisted for the negative, but not the positive, feedback action on LH. Chronic morphine exposure in ovariectomized rats, without E2 replacement, was ineffective in altering the LH levels at 1000 h, but had a slight stimulatory effect on LH at 1600 h, indicating an E2 requirement for the observed suppression and stimulation of LH in the morning and afternoon, respectively. The response of the anterior pituitary to exogenously administered LHRH in the morning (1000 h) and during the midafternoon hypersecretion of LH (1800 h) was markedly enhanced in animals exposed chronically to morphine. Thus, the chronic stimulation of opiate receptors with morphine enhances the inhibition and subsequent hypersecretion of LH in E2-exposed rats, advances the time of onset and enhances the magnitude of the E2-induced LH surge, and augments the response to LHRH when LH levels are low in the morning and during the E2-induced hypersecretion of LH. These data support an important role for opioid neuronal systems in the mechanism that switches the E2 signal for gonadotropin secretion from inhibitory to stimulatory and, hence, in the series of neuronal events that leads to phasic secretion of gonadotropins.

The influence of chronic morphine treatment on the negative feedback regulation of gonadotropin secretion by gonadal steroids.

The influence of continuous stimulation of opiate receptors with morphine (M) on the negative feedback effects of testosterone (T), 5 alpha-dihydrotestosterone (DHT), and 17 beta-estradiol (E2) on LH and FSH secretion was studied in rats that had been castrated 2 weeks previously. In the absence of gonadal steroids, 4 days of continuous M exposure did not alter LH or FSH levels. Similarly, Silastic capsules containing crystalline T (5 mm) or E2 [5 mm long (75 micrograms E2/ml) to 7.5 mm long (300 micrograms E2/ml)] alone had little effect on LH or FSH release. However, in M-exposed rats, T reduced serum LH by greater than 90%, and E2 reduced LH by more than 75%. Among the doses of DHT evaluated, only the highest dose (7.5-mm Silastic capsules packed with crystalline DHT) reduced LH secretion, and M exposure only slightly enhanced this suppression. M or gonadal steroids alone produced little change in FSH levels in castrated rats. However, the combination of M plus E2 or DHT further reduced FSH levels. Evaluation of pituitary responses to LHRH revealed that when administered alone, T did not alter, DHT reduced, and E2 enhanced the LH response to the decapeptide. Neither M treatment alone nor M plus T or DHT altered the pituitary LH response to LHRH. On the other hand, M appeared to enhance the stimulatory effects of E2 on pituitary responsiveness to LHRH. These findings suggest that the interaction of M and gonadal steroids at the level of the pituitary could not explain the observed marked suppression of gonadotropin secretion by suboptimal T or E2 during opiate receptor stimulation with M. Collectively, these observations are in accord with the view that endogenous opioid peptides may play a role in modulating the sensitivity of the hypothalamus to the negative feedback effects of gonadal steroids.

Regional skin temperature changes in a rat model for the menopausal hot flush.

Administration of naloxone to morphine-dependent male and female rats produced a significant rise in both tail skin temperature and foot temperature with a subsequent fall in colonic temperature. The magnitudes of the skin temperature surges were similar in the two regions, with the elevation in foot temperature preceding the rise in tail skin temperature. These regional skin temperature surges were similar in magnitude, duration and temporal pattern in both the male and female rat, and are similar to those exhibited in men and women undergoing flushing episodes. Castration of males did not alter these temperature responses. The only difference in response between male and female rats was the more pronounced fall in colonic temperature observed in morphine-dependent female rats following administration of naloxone. Neither the administration of naloxone to placebo-treated animals nor that of saline to morphine-dependent animals produced any changes in skin or colonic temperature in either male or female rats. These results suggest that the pattern of skin temperature alterations associated with morphine withdrawal in both the male and female rat is similar to the pattern of skin temperature surges associated with the hot flush in men and women, which provides additional evidence for the morphine-dependent rat as a model for women who exhibit flushing episodes. Additionally, this is the first report of a potential model for men who exhibit flushing episodes.

A decline in endogenous opioid influence during the steroid-induced hypersecretion of luteinizing hormone in the rat.

Studies were undertaken to evaluate the influence of endogenous opioid peptides (EOP) on the LH hypersecretion induced in ovariectomized rats by estradiol benzoate (EB) or EB plus progesterone (EBP). Naloxone (0.1-15.0 mg/kg) was injected before (1200 h) and during (1400 and 1530 h) the LH surge induced by EBP treatment and during the LH surge after EB treatment (1600 h). The opiate antagonist readily stimulated LH secretion before the LH surge in EBP-treated rats at 1200 h and during the LH surge in EB-treated rats at 1600 h, but was much less effective during the LH hypersecretion induced by EBP treatment at 1400 and 1530 h. This decline in the LH secretory response to naloxone during the EBP-induced LH surge was not due to changes in the response of pituitary to LHRH. These studies indicate that during the period of LH hypersecretion induced by the sequential administration of EB plus P, the influence of EOP neuronal systems on LH secretion is diminished. Thus, EOP neurons may play a role in the timing and magnitude of the LH surge in EBP-treated rats.

Melatonin rhythms in Pony mares and foals.

Melatonin concentrations in intact (N = 3) and sham-operated (N = 3) mares during March were greater (P less than 0 . 05) during the night than during the day, but this pattern was not seen in 3 mares from which the superior cervical ganglia had been removed bilaterally. When 4 Pony mares were exposed to a photoperiod of 10L:14D for 3 weeks and then to continuous darkness (0L:24D) for another 3 weeks, melatonin levels were greater (P less than 0 . 05) at the end of the 0L:24D period than during the earlier period and still displayed rhythmic fluctuations but were no longer co-ordinated with equivalent day/night rhythms or among mares. When melatonin rhythms were monitored in 3 mares and their foals housed in open pens exposed to natural lighting, significant time trends in melatonin concentrations were observed in mares when the foals were aged 1-3, 4-6 and 7-11 weeks, but foals did not display significant times trends in melatonin until they were 7-11 weeks old.

Effects of pinealectomy in Pony mares.

When mares were pinealectomized in summer or in winter there was no difference in the annual ovulation date of these animals and of pineal-intact controls during the first post-operative breeding season but in the second season the ovulation date of the winter pinealectomized mares was significantly delayed, suggesting a long-term but clear pineal involvement in seasonal reproductive patterns. Exposure of pinealectomized mares to a stimulatory photoperiod failed to advance the average date of first annual ovulation and was similar to that of intact mares receiving no stimulatory lighting. The results indicate that pinealectomy blocks the ability to respond to photostimulation. In intact mares plasma melatonin concentrations were significantly increased during darkness (P less than 0 . 003) but pinealectomized mares demonstrated no significant time trends.

Effect of pregnancy and collection technique on prostaglandin F in the uterine lumen of Pony mares.

Uterine flushings were obtained through the cervix (Method A) and through the wall of the uterus after hysterectomy (Method B) of ovariectomized Pony mares after s.c. injection of oestrogen for 1 week and progesterone for 2 weeks (Exp. 1). Non-pregnant and pregnant mares were flushed by Method A on Day 14 after ovulation and the flushings compared with those of non-pregnant mares injected i.v. with flunixen meglumine, a prostaglandin synthetase inhibitor, shortly before flushing (Exp. 3). Uterine flushings were also collected by Methods A and B from non-pregnant and pregnant Pony mares on Day 14. Endometrial and embryonic tissues from these mares were incubated with and without flunixen meglumine (Exp. 3). In all experiments, pregnancy had a significant effect on PGF content of uterine flushings or incubation media. Flushings from pregnant mares had reduced levels of PGF and were not influenced by collection technique (Exps 1 & 3). Non-pregnant Pony mares treated with progesterone responded to cervical stimulation (Method A) with an increase in intrauterine PGF over levels measured after hysterectomy (Method B) (Exps 1, 2 & 3). There was no effect on endometrial production of PGF in vitro by any tissue combination in a 2 h incubation in Krebs-Ringer-bicarbonate buffer but after 12 h incubation in Minimum Essential Medium endometrial PGF production was significantly higher when the endometria were from pregnant mares than from non-pregnant mares. PGF production in vitro was significantly suppressed by flunixen meglumine, by yolk sac membranes, and yolk sac and trophoblast, but not by trophoblast alone. The low intrauterine PGF levels in pregnant mares and the low in-vitro PGF production in the presence of the conceptus membranes may reflect inhibition of PGF synthesis and/or release by the embryo.

Effects of pituitary stalk transection on endocrine function in Pony mares.

The pituitary stalk was transected in 10 Pony mares by a surgical approach that involved dorsal reflection of the brain and micro-dissection from the ventro-lateral aspect of the pituitary. Diabetes insipidus was the most immediate and marked result, requiring extensive electrolyte and antidiuretic therapy for approximately 48 h after operation. Fluid stasis then developed and no further supportive measures were necessary. Endocrine challenge tests with GnRH and TRH before and after stalk transection indicated a loss of responsiveness (GnRH) or suppressed responsiveness (TRH) after the operation. This technique permits isolation of the pituitary from its hypothalmic releasing and/or inhibiting hormones and therefore permits more refined study of the hypothalamic-pituitary axis.