6-Hydroxydopamine lesions of the prefrontal cortex in monkeys enhance performance on an analog of the Wisconsin Card Sort Test: possible interactions with subcortical dopamine

The effects of 6-hydroxydopamine lesions of the prefrontal cortex in monkeys were investigated on two cognitive tests of prefrontal function, spatial delayed response, and attentional set shifting. The latter test provided a componential analysis of the Wisconsin Card Sort Test, a commonly used clinical test of frontal lobe function in man. Acquisition of a visual compound discrimination requiring a shift of attention from one dimension to another (extradimensional shift), for example, shapes to lines, was significantly improved. This enhancement was behaviorally specific in that there were no effects on acquisition of a discrimination that required the continued maintenance of an attentional set toward one particular dimension (intradimensional shift), nor any effects on a series of visual or spatial discrimination reversals that involved the repeated shifting of responding between two exemplars from the same dimension. In contrast, spatial delayed response performance was impaired, in agreement with previous results. Neurochemical measures showed a marked depletion of dopamine limited to the prefrontal cortex and a smaller loss of prefrontal noradrenaline. This was accompanied by a long-term adaptive change in the striatum such that extracellular dopamine in the caudate nucleus, as measured by in vivo microdialysis, was elevated in response to potassium stimulation as long as 18 months postsurgery. It is proposed that attentional set shifting is mediated by a balanced interaction between prefrontal and striatal dopamine, and that elevated dopamine contributes to the improvement in attentional set-shifting ability. This interpretation is consistent with the impairment in attentional set-shifting ability observed in patients with Parkinson's disease or with damage to the frontal lobes using the same test as used here for infrahuman primates.

Overdilation of the Wallstent to optimize portal decompression during transjugular intrahepatic portosystemic shunt placement

PURPOSE

To optimize shunt size with overdilation of the Wallstent during creation of a transjugular intrahepatic portosystemic shunt (TIPS).

MATERIALS AND METHODS

A TIPS was created in 25 patients with variceal bleeding (n = 22) or intractable ascites (n = 3). All shunts were created with one or more Wallstents that were dilated with an 8- or 10-mm balloon. In 11 patients with inadequate portal decompression or persistent filling of varices, shunts were overdilated with a 12-mm balloon.

RESULTS

Mean portosystemic pressure gradient fell from 18.0 mm Hg +/- 6.4 (standard deviation) to 6.8 mm Hg +/- 2.8 after shunt placement. In 11 patients in which shunts were overdilated, the mean gradient fell from 12.7 mm Hg +/- 5.6 after 10-mm dilation to 6.9 mm Hg +/- 2.8 (P = .01) after 12-mm dilation. In six, variceal filling occurred after 10-mm dilation but diminished or ceased after overdilation. Stent disruption did not occur. New or worsened encephalopathy occurred in four of 14 patients with 10-mm and six of 11 patients with 12-mm shunt dilation and responded to medical therapy in all but two.

CONCLUSION

Overdilation of the Wallstent during TIPS placement is effective and safe in patients with inadequate portal decompression after 10-mm shunt dilation.

Beta-adrenergic blockade does not prevent the lactate response to exercise after acclimatization to high altitude

We examined the extent to which epinephrine influences blood lactate adjustments to exercise during both acute (AC) and chronic (CH) high-altitude exposure. Eleven male sea level residents were divided into a control group (n = 5) receiving a placebo or a drug group (n = 6) receiving 240 mg/day of propranolol. All subjects were studied at rest and during 45 min of submaximal exercise (approximately 50% of sea level maximal O2 uptake) at sea level (SL) and within 4 h of exposure to and after 3 wk residence at 4,300 m (summit of Pikes Peak). Blood samples were collected from the femoral artery for epinephrine and lactate concentration. Exercising blood lactate concentration was significantly different across all altitude conditions such that AC > CH > SL (P < 0.05). For a given arterial O2 saturation, mean exercising blood lactates were lower for the beta-blocked group compared with controls; however, both groups demonstrated similar patterns across all conditions. Epinephrine levels during exercise followed a similar pattern to that of lactate, averaging 0.67, 0.43, and 0.29 ng/ml for AC, CH, and SL, respectively. The correlation between lactate and epinephrine was 0.93 and 0.84 for control and beta-blocked subjects, respectively. Whereas during exercise epinephrine was consistently higher for the beta-blocked group than controls, this difference was only significant during CH exposure. The epinephrine response was related to the extent of hypoxia in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Overtraining affects male reproductive status

OBJECTIVE

To substantiate the hypothesis that strenuous exercise disrupts the hypothalamic-pituitary-gonadal axis in men.

DESIGN

Longitudinal study.

SETTING

Normal human volunteers in an academic research environment.

PATIENTS

Five endurance-trained men (maximum oxygen consumption 65.4 +/- 3.6 mL/kg per minute [means +/- SEM]) with normal spermatogenic and hormonal profiles.

INTERVENTIONS

Semen and blood samples were collected bimonthly before, immediately after, and 3 months after overtraining, which was defined as twice the previous average weekly training volume with unchanged intensity.

MAIN OUTCOME MEASURE

Testosterone, cortisol, and sperm concentration.

RESULTS

Basal T levels decreased to 5.37 +/- 67 ng/mL from 8.68 +/- 93 ng/mL (conversion factor to SI unit, 3.47) immediately after overtraining and basal cortisol levels increased to 215.3 +/- 31 ng/mL from 145.7 +/- 27 ng/mL (conversion factor to SI unit, 2.76). This inverse relationship was highly correlated (r = -0.92). Both cortisol and T levels returned to pretraining values 3 months after resumption of previous training volume. Sperm count (91 +/- 23.3 x 10(6)) decreased significantly by 43% immediately after overtraining (52 +/- 6.8 x 10(6)) and by 52% 3 months after overtraining (44.5 +/- 20 x 10(6)). However, all values remained within normal range and would not be expected to affect fertility.

CONCLUSIONS

Our results indicate that overtraining reduces T levels, which is highly correlated with an increase in levels of cortisol and possibly a subsequent decrease in sperm concentration 74 days later.

Contrasting mechanisms of impaired attentional set-shifting in patients with frontal lobe damage or Parkinson's disease

Tests which assess the ability to shift cognitive set modelled after the Wisconsin Card Sorting Test are particularly sensitive to impairments in patients with Parkinson's disease as well as in patients with frontal lobe damage. However, the underlying mechanisms responsible for the similar deficits observed in the two patient groups are not well understood and may not be identical. For example, an apparent deficit in set-shifting ability may reflect either an impairment in the ability to shift from a perceptual dimension which has previously commanded attention (i.e. 'perseveration'), or in the ability to shift to an alternative perceptual dimension which has previously been irrelevant (i.e. 'learned irrelevance'). In this study, the performance of both medicated and non-medicated patients with Parkinson's disease were compared with a group of neurosurgical patients with localized excisions of the frontal lobes on a novel task designed to assess the relative contribution of 'perseveration' and 'learned irrelevance' to impaired set-shifting ability. Patients with frontal lobe damage were worse than controls in their ability to shift attention from a previously relevant stimulus dimension. Medicated patients with Parkinson's disease were worse at shifting to a previously irrelevant dimension. In contrast to both groups, nonmedicated patients with Parkinson's disease were impaired in both conditions. These results suggest that the gross set-shifting deficits reported in both frontal lobe patients and patients with Parkinson's disease may involve fundamentally different, though related, cognitive processes, and that these may be differentially affected by medication. Specifically, L-dopa therapy may protect Parkinson's disease patients from preservation of attention to a formerly relevant stimulus dimension.

Transcatheter manipulation of asymmetrically opened titanium Greenfield filters

PURPOSE

The problem of asymmetric opening of the modified hook titanium Greenfield inferior vena cava filter necessitating transcatheter manipulation was evaluated in a retrospective study.

PATIENTS AND METHODS

Titanium Greenfield filters were placed in 166 patients over a 36-month period. The radiographic reports of all patients were reviewed to identify cases in which the filter failed to open symmetrically after deployment and catheter or wire manipulation of the filter was performed. The reports and angiograms from these patients were reviewed with respect to the circumstances surrounding filter placement and methods to achieve more symmetric opening.

RESULTS

Transcatheter manipulation of asymmetrically opened filters was performed in 15 of 166 cases (9%). In 12 of these patients, acceptable and uneventful opening of the filter was achieved with a guide wire, pigtail catheter, or occlusion balloon catheter. In one case manipulation only partly improved orientation of the limbs, while in another case successful manipulation was complicated by distal migration. In the final case, the asymmetric filter covered only part of the lumen of the vena cava despite manipulations and a second filter was placed for optimal caval interruption. No specific cause for incomplete expansion was identified in any case.

CONCLUSION

Marked asymmetry in opening of the modified hook titanium Greenfield filter that warrants manipulation occurs infrequently, but recognition and proper management may be important to ensure optimal caval interruption.

Pulse-spray pharmacomechanical thrombolysis for treatment of thrombosed dialysis access grafts

The results of pulse-spray pharmacomechanical thrombolysis (PSPMT) of 209 thrombosed hemodialysis grafts were reviewed. In PSPMT, concentrated urokinase is injected forcefully through catheters with multiple tiny sideholes or sideslits. Catheters placed in a crisscross fashion cover the entire clot simultaneously. This therapy was successful in treating patients with thrombosed grafts. Of the 200 grafts with complete therapy, 197 grafts (99%) were patent at the end of the procedure. Mean time for pulsed-spray lysis was 40 minutes. Etiologies for graft thrombosis were anastomotic venous outflow stenosis, stenosis of the venous outflow away from the anastomosis, arterial stenosis, intragraft stenosis, pseudoaneurysms, and no identifiable cause in a small percentage. There were 16 complications, 8 of which required additional therapy or potentially compromised the graft. These results suggest that pharmacomechanical thrombolysis and angioplasty provide rapid, consistent, and safe recanalization of thrombosed hemodialysis grafts and represent an additional therapeutic approach to graft management.

Occluded peripheral arteries and bypass grafts: lytic stagnation as an end point for pulse-spray pharmacomechanical thrombolysis

Angiographic demonstration of luminal narrowing during pulse-spray pharmacomechanical thrombolysis (PSPMT) may reflect residual lysable clot, organized thrombus, platelet-rich clot, atherosclerosis, neointimal hyperplasia, or functional narrowing. The authors evaluated the efficacy and safety of lytic stagnation (initial rapid lysis followed by insubstantial further lysis with additional treatment) as an end point for PSPMT. Lytic stagnation was evaluated with serial angiography in 16 arterial and five bypass graft occlusions. Substantial lysis occurred after administration of mean doses of 512,000 units +/- 182,000 of urokinase or 5.3 mg +/- 2.0 of tissue-type plasminogen activator. Additional treatment with either of those agents produced minimal or no further change in the appearance of residual disease. Recanalization was successful in all patients after angioplasty. Distal emboli were noted in four cases, in three of which angioplasty of large intraluminal filling defects had been performed. The authors conclude that lytic stagnation is a reliable and safe end point for PSPMT in the absence of large intraluminal filling defects.

Selective management of iatrogenic femoral artery injuries

Increased femoral artery catheterization for therapy and diagnosis has resulted in a concomitant increase in iatrogenic femoral artery injuries. A 33-month experience at two affiliated institutions was reviewed to evaluate the results of a selective approach to management of these complications. During this period, 9576 femoral artery catheterizations were performed. Eighty-nine femoral artery injuries were treated surgically or by ultrasound-guided compression therapy. Cardiac catheterization procedures predominated and 61% of patients were anticoagulated. Thirty-eight cases were treated surgically: 14 pseudoaneurysms, 16 hematomas, 6 arteriovenous fistulas, 2 thromboses. Local anesthesia was used in 28 cases (74%). Arterial repair was required in 34 cases, with control being achieved below the inguinal ligament in 33 cases (97%). Punctures were found in the superficial femoral or profunda femoral rather than the common femoral artery in 17 of 38 cases (44%, P < 0.001 compared with the ultrasound group). There were two deaths (5.3%), six wound infections (16%), and no limb loss. Ultrasound-guided compression was preferentially used for stable or slowly expanding pseudoaneurysms. Cases with large hematomas causing skin ischemia were treated surgically. The pseudoaneurysms ranged from 2 to 7 cm in diameter. This technique was effective in 46 of 51 cases (90%). A single thromboembolic complication was treated by thrombolysis. There were no late recurrences. We conclude that (1) iatrogenic femoral artery injuries are associated with postcatheterization anticoagulation and punctures not located in the common femoral artery; (2) injuries requiring surgery can usually be treated under local anesthesia with infrainguinal arterial control; (3) ultrasound-guided compression is an effective method for treating iatrogenic pseudoaneurysms not associated with large hematomas.

Venous imaging and inferior vena cava filters

Thromboembolic disease is a major complication in many hospitalized patients. Imaging of deep venous thrombosis is important for making the diagnosis. After establishing the diagnosis, a decision must be made regarding anticoagulation. If the patient can not be anticoagulated, placement of an inferior vena cava filter is indicated. This paper discusses some of the latest information available on a variety of filters. However, a long-term multicenter study is needed to determine the effectiveness and safety of the available filters. A new approach to percutaneous insertion of central venous catheters is also discussed.

A specific form of cognitive rigidity following excitotoxic lesions of the basal forebrain in marmosets

The effects of N-methyl-D-aspartate-induced lesions of the basal forebrain were studied on performance of a series of visual discrimination tests that examined a range of cognitive functions in the marmoset. These included the ability to attend to the various dimensional properties of stimuli and to use just one of these properties in order to solve a discrimination (intra-dimensional shift); to switch attention from one dimension to another (extra-dimensional shift); to learn the reinforcement value of specific exemplars within a dimension (new learning); and to relearn their reinforcement value following reversal of the reward contingencies (serial reversals). Lesions of the basal forebrain did not impair the ability either to attend selectively to the dimensional properties of the stimuli or to switch attention from one dimension to the other. However, the lesion did affect various aspects of associative learning including a transient impairment of new learning and a marked disruption of serial reversal learning. The reversal deficit could be characterised as a tendency to perseverate on the previously correct stimulus and as a failure to to show the formation of a reversal learning set. In addition, the lesion prevented disruption of performance of a well-learned discrimination when novel exemplars from the irrelevant dimension were introduced (probe test). It is suggested that the functional effects of the basal forebrain lesion reflect impaired learning of stimulus-reward associations and behavioural rigidity. The finding, however, that there was no effect of the lesion on attentional set-shifting suggests that any loss of inhibitory control was specific to the level of stimulus-response or stimulus-reward associations, inhibitory control at the level of attentional selection remaining intact. The similarity of the effects of damage to the basal forebrain to those seen following damage to the orbitofrontal cortex and the amygdala are discussed in the context of the close anatomical and functional relationships that exist among these three structures.

Postangiographic femoral artery injuries: nonsurgical repair with US-guided compression

Ultrasound-guided compression repair (UGCR) of catheterization-related femoral artery injuries was evaluated as a possible new imaging-guided interventional procedure. Thirty-nine femoral artery injuries (35 pseudoaneurysms, four arteriovenous fistulas) were detected with color Doppler flow imaging in patients with enlarging groin hematomas and/or groin bruits 6 hours to 14 days after catheterization procedures. UGCR was not performed in 10 patients due to spontaneous thrombosis (n = 4), infection (n = 1) or skin ischemia (n = 1), unsuitable anatomy (n = 3), or excessive discomfort (n = 1). The remaining 29 patients underwent a full trial of compression therapy, and the lesion was eliminated in 27. Follow-up color flow scans were obtained after 24-72 hours in all 27 successful cases and at 1-15 months in 19; no recurrences or complications occurred. UGCR for acute injuries is safe and technically simple and is promising as a cost-effective, first-line treatment for uncomplicated catheterization-related femoral artery injuries. UGCR is probably not appropriate for long-standing injuries.

Pulsed-spray thrombolysis of arterial and bypass graft occlusions

Pulsed-spray thrombolysis is accomplished through forceful injection of a spray of highly concentrated urokinase into clot by using catheters with multiple side holes. We previously reported the immediate technical efficacy of the method in eight arterial and 10 bypass graft occlusions. We now describe the clinical efficacy of the method in a second, larger series of 23 native artery occlusions and 25 bypass graft occlusions. Transluminal angioplasty was performed after thrombolysis in 21 of the arteries and 24 of the bypass grafts. Initial thrombolysis was observed in all artery occlusions and all but one bypass graft occlusion with an average time for pulsed-spray lysis of 65 +/- 28 min in native arteries and 93 +/- 38 min in bypass grafts. Recanalization with improvement in symptoms or distal pulses after thrombolysis and angioplasty was achieved in 74% of treated arterial occlusions and 92% of treated graft occlusions. Of the 15 arteries that were recanalized and did not require adjunctive surgery, seven remained patent at 3-28 months follow-up. Nine of 23 recanalized bypass grafts required early adjunctive surgery. Of the nine synthetic and five saphenous vein grafts successfully recanalized and not requiring surgical revision, the mean patency was 4.3 +/- 3.1 months and 3.0 +/- 2.2 months, respectively. Minor complications were seen in 23% of cases. The two major complications (4%) involved one groin hematoma requiring surgery and one episode of gastrointestinal hemorrhage. We conclude that combined pulsed-spray thrombolysis and angioplasty achieve rapid and consistent arterial and graft recanalization with minimal risk. The method offers a favorable alternative to standard thrombolytic therapy of arterial occlusions. In occluded synthetic and vein bypass grafts, the technique is sometimes beneficial, either alone or combined with surgical revision.

Pharmacomechanical thrombolysis and angioplasty in the management of clotted hemodialysis grafts: early and late clinical results

The results of pharmacomechanical thrombolysis and angioplasty of 121 thrombosed hemodialysis grafts were reviewed. The initial pharmacomechanical method (used in 65 cases) employed clot maceration with hook-shaped catheters and clot lacing with highly concentrated urokinase. The current technique (used in 56 cases) consisted of pulsed-spray injection of urokinase into the clot. All fully treated grafts (117 cases) underwent complete or near-complete thrombolysis, and 93% remained patent after 1 day. Mean time for pulsed-spray lysis was 46 minutes +/- 21. One patient (less than 1%) had gastrointestinal bleeding and received a transfusion; minor complications occurred in 3% of patients. Primary and secondary graft patency rates for both methods at 1 year were 26% and 51%, respectively. While graft age and results of angioplasty did not influence future graft patency, shorter intervals between graft thromboses was predictive of earlier subsequent graft failure. Results suggest that pharmacomechanical thrombolysis and angioplasty provide rapid, consistent, and safe recanalization of clotted hemodialysis grafts and represent a promising additional therapeutic approach to long-term graft management.

Extra-dimensional versus intra-dimensional set shifting performance following frontal lobe excisions, temporal lobe excisions or amygdalo-hippocampectomy in man

Attentional "set" shifting was assessed in a group of 20 neurosurgical patients with localized excisions of the frontal lobes, a group of 20 patients with unilateral temporal lobe lesions and a group of 11 patients who had undergone amygdalo-hippocampus removal. These three patient groups were compared with groups of both young (age-matched) and elderly normal control volunteers on a computerized test of visual discrimination learning involving both an intra- and an extra-dimensional shift. The frontal lobe group were selectively impaired in their ability to shift response set to a previously irrelevant dimension but not to shift attention to new exemplars of a previously relevant dimension. A similar pattern was observed in the elderly group of normal control volunteers. By comparison, both the temporal lobe patients and the amygdalo-hippocampectomy patients were unimpaired in their ability to perform either shift, although both groups had significantly prolonged selection latencies at the extra-dimensional shift stage of the task. These data are compared to previous findings from patients with idiopathic Parkinson's disease and are discussed in terms of a specific attentional set shifting deficit following frontal lobe damage.

Analysis of the transition to percutaneous placement of Greenfield filters

To establish whether a transition from surgical to percutaneous placement of Greenfield filters was justified, a review of the safety, efficacy, and cost-effectiveness of the two approaches was conducted. Between 1984 and 1989, 168 filters were placed in 169 patients, 48 surgically and 120 percutaneously. Placement was successful in 45 (94%) of the 48 surgical patients and 120 (99%) of the 121 percutaneous patients. Filter misplacement occurred in three (6%) surgical patients and no percutaneous patients. Clinically evident femoral vein thrombosis occurred in only four (5%) of the percutaneous patients, while inferior vena cava thrombosis occurred in three (3%) of the percutaneous patients. One pulmonary embolus occurred after percutaneous filter placement and resulted in death. The cost of percutaneous placement was 58% that of surgical placement. A retrospective review of the experience in our patient population indicates that safety, cost, and ease of insertion make the percutaneous approach the procedure of choice for Greenfield filter placement.

Bronchial artery embolization therapy

Bronchial artery embolization, which was first described in 1973, has now become an accepted method of therapy for massive hemoptysis. Successful use of this technique requires a knowledge of the bronchial anatomy, an understanding of the patient population for whom this technique is best suited, a familiarity with the technical aspects of the procedure, and an awareness of the complications associated with this technique. Angiographic evaluation and bronchial artery embolization may be used to stabilize the patient prior to surgical therapy or may represent definitive therapy.

Sparing of attentional relative to mnemonic function in a subgroup of patients with dementia of the Alzheimer type

Patients with dementia of the Alzheimer type (DAT) received two tests of visual selective attention, together with tests of spatial and visual recognition memory and visuospatial conditional learning previously used to show deficits early in the course of DAT. One set of attentional tests compared visual discrimination learning along intra- and extra-dimensional shifts, using a "total change" design. In the 12 DAT patients capable of attempting the extra-dimensional shift (subgroup 1), performance was equivalent to that of controls. This subgroup was also unimpaired at simple and compound discrimination learning and reversal and an intra-dimensional shift. They were as accurate as controls on a visual search task requiring matching of stimuli on two dimensions with variable numbers of alternatives, but were significantly impaired in the tests of recognition memory and learning. By contrast, the other 13 patients showed marked impairments in the attentional tasks. This subgroup was also significantly worse than subgroup 1 in performance on the visual recognition and conditional learning tasks, and showed greater severity on most of the clinical ratings of dementia. The sparing of attentional shifting in patients early in the course of DAT is contrasted with the impairments previously described in patients with Parkinson's disease with only mild or absent memory loss. The implications of this double dissociation of deficits for understanding the neural bases of the cognitive deficits in these two neurodegenerative diseases are discussed and their significance for the staging of DAT is considered.

The effects of excitotoxic lesions of the basal forebrain on the acquisition, retention and serial reversal of visual discriminations in marmosets

The effects of N-methyl-D-aspartate-induced lesions of the basal forebrain (which included the cholinergic cells of the nucleus basalis of Meynert) were studied on three aspects of visual discrimination; learning, retention and reversal performance, in the marmoset. Neurobiological investigations revealed that the lesion produced large reductions in choline acetyltransferase activity within anterior regions of cortex, particularly prefrontal. In Experiment 1 lesioned animals showed impaired retention, one week after surgery, of a visual discrimination learned immediately prior to surgery and subsequently showed impaired performance over a series of reversals. The reversal deficit could be characterized as a tendency to perseverate on the previously correct stimulus on the first reversal and as a failure to show serial reversal learning on subsequent reversals. Acquisition of a novel discrimination was not impaired five weeks after surgery. As time of testing may have been a confounding factor, in Experiment 2 the effects of the same lesion on new learning were examined immediately following surgery and the effects on retention a month later. The lesion was found to disrupt new learning but did not affect retention. From the two experiments it is clear that, whereas disruption of retention and new learning was relatively transient, the impairments in reversal performance were more long lasting. In addition, lesioned animals exhibited behavioural hyperactivity and elevations in consummatory and schedule-controlled licking. The disinhibitory and preservative effects observed following lesions of the basal forebrain in this study are similar to those following lesions of the orbitofrontal cortex while the disruption of serial reversal learning is commonly seen following damage to the amygdala. Therefore, these results are consistent with the hypothesis that the range of behavioural effects of the lesion result from damage to the cholinergic afferents to orbitofrontal cortex and to the amygdala, two structures intimately connected to one another.

Impaired extra-dimensional shift performance in medicated and unmedicated Parkinson's disease: evidence for a specific attentional dysfunction

Groups of patients with Parkinson's disease, either medicated, or unmedicated and early in the course, together with age- and IQ-matched control subjects were tested in two paradigms measuring different aspects of selective attention. The first set of tests compared visual discrimination learning following intra- and extra-dimensional shifts, using a "total change" design in which each shift was made in the presence of novel exemplars of the compound stimuli used as discriminanda. The second test consisted of a visual search task in which the number of alternatives was varied. The results of the first experiment showed a selective deficit in both groups of Parkinsonian subjects in their ability to perform an extra-dimensional shift. In the visual search task, the patients were less accurate, but responded with equivalent choice reaction times to those of controls. The results are discussed in terms of the nature of the attentional dysfunction that occurs in Parkinson's disease.

Custom-made nipple-areola prostheses in breast reconstruction

The nipple-areola prosthesis is a useful temporary or permanent adjunct to breast reconstruction. The commercially available prostheses, however, are unable to reflect the remarkable normal variation in this anatomical feature. We describe the production and use of custom-made prostheses using the remaining nipple-areola complex as a template. Their success in 72 patients has led us to adopt such prostheses as routine in breast reconstruction.

Distribution and some projections of cholinergic neurons in the brain of the common marmoset, Callithrix jacchus

The distribution of choline acetyltransferase-immunoreactive (ChAT-IR) neurons was studied in the brain of the common marmoset by using immunohistochemistry. ChAT-IR neurons were found in the medial septal nucleus, vertical and horizontal limb nuclei of the diagonal band, the nucleus basalis of Meynert, pedunculopontine nucleus and laterodorsal tegmental nucleus, and also in the striatum, habenula, and brainstem cranial nerve motor nuclei. The organization of ChAT-IR neurons in the basal forebrain, midbrain, and pons is consistent with the Ch1-Ch6 nomenclature introduced by Mesulam et al. ('83). The combination of the retrograde transport of HRP-WGA with ChAT immunohistochemistry revealed the distribution of neurons in the Ch4 cell group projecting to the dorsolateral prefrontal cortex. The activity of ChAT was highest in limbic cortical structures, such as the hippocampus, and lowest in association areas of the neocortex. Lesions at various loci in the basal forebrain resulted in differential patterns of ChAT loss in the cortex, which suggests some degree of topographical organization of Ch4 projections to the cortical mantle.

Intra-hypothalamic melatonin blocks photoperiodic responsiveness in the male Syrian hamster

Exposure of male Syrian hamsters to a short daylength of 8L:16D leads to gonadal regression. This effect of photoperiod was prevented by pinealectomy or chronic exposure of the brain to exogenous melatonin delivered from in-dwelling cannulae. However, the effect of melatonin was dependent on the neural site of application. Melatonin delivered into the mid-brain, lateral hypothalamus or amygdala was ineffective. In contrast, bilateral administration of melatonin to the medial or amygdala was ineffective. In contrast, bilateral administration of melatonin to the medial hypothalamus prevented testicular regression and maintained high circulating levels of luteinizing hormone and prolactin. These findings suggest that the medial hypothalamus contains target sites for melatonin involved in pineal-mediated photoperiodic responses.

The effects of castration, testosterone replacement and photoperiod upon hypothalamic beta-endorphin levels in the male Syrian hamster

Syrian hamsters kept in long day-lengths have active gonads and high circulating levels of gonadal steroids. Under the influence of the pineal gland, animals exposed to short photoperiods undergo testicular regression, have low circulating levels of testosterone and gonadotrophins and elevated levels of beta-endorphin within the hypothalamus. This paper describes the interaction between testosterone and photoperiod in the regulation of beta-endorphin levels in three regions of the hypothalamus. Hypothalamic beta-endorphin levels were measured by a combination of high-performance liquid chromatography and radioimmunoassay techniques that allows separation of the beta-endorphin (1-31) peptide from its metabolites and precursors. All of the beta-endorphin-like immunoreactivity in the hypothalamus of the male hamster, in both photoinhibited and photostimulated conditions, was found to represent the 31-amino-acid peptide. In photostimulated hamsters, chronic castration was associated with a significant increase of beta-endorphin levels in the anterior hypothalamus and mediobasal hypothalamus, which was reversed by treatment with exogenous testosterone. Castration prevented the ability of naloxone, an opiate receptor antagonist, to release luteinizing hormone, and this effect was also reversed by exogenous steroid. In photoinhibited hamsters, however, castration had no effect upon beta-endorphin levels in the preoptic area or mediobasal hypothalamus, and there was only a small increment in the anterior hypothalamus. Significantly, beta-endorphin levels in all areas of the hypothalamus of photoinhibited castrates were not decreased by testosterone treatment. In addition, administration of exogenous testosterone did not restore sensitivity to naloxone in these animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Annual reproductive rhythms in mammals: mechanisms of light synchronization

Animals restrict the time of birth of offspring to the most advantageous time of year, usually spring or summer. This is achieved by controlling the preceding period of fertility and, in some cases, by delaying implantation of the zygote. Seasonal changes in daylength, the principal, though not the only cue, regulate pulsatile release of hypothalamic releasing factors that in turn activates the pituitary-gonadal axis. The role of the neuroendocrine system is therefore to translate the photoperiodic stimulus into an endocrine signal (Figure 12). The measurement of day length is a function of the circadian system, environmental light being sampled on a 24-hour basis. Experimental manipulations of the photoperiodic response have revealed the existence of a rhythm of sensitivity to the presence of light that is entrained by the prevailing photoperiod. Light falling within the period of maximal sensitivity results in an LD type response. It is important to note that although different species measure day length in a similar manner, the gonadal response to a given photoperiod will vary between species depending upon the nature of their seasonal reproductive strategy. Photic information is conveyed from the retina to the pineal gland by way of the suprachiasmatic nuclei of the hypothalamus and the cervical sympathetic trunk. The central connections between these structures are poorly understood. The pineal is an essential mediator of the photoperiodic response. The effects of pinealectomy vary between species, but in all cases the responses to changes in day length are blocked. The gland is neither anti- nor progonadotrophic; it merely provides a signal. This signal is probably the nocturnal release of melatonin. Studies on in vivo melatonin production and the responses of photoperiodic species to timed administration of exogenous melatonin have suggested that the duration of nocturnal melatonin production by the pineal is read by the CNS as an indicator of the length of darkness. This model for PTM provides a physiological basis to the observed rhythm of sensitivity to light. This period of sensitivity is probably a parallel to the nocturnal rhythm of melatonin production. Light falling in this phase blocks melatonin production, truncates the pineal signal, and hence produces an LD response by the CNS. The site of the signal detector is not known, although the anterior hypothalamus may be involved. How the pineal signal triggers changes in the hypothalamic LHRH pulse generator is not known. The endogenous opioids, however, especially beta-END may have a major role in exercising photoperiodic control over pituitary action.

Naloxone-induced secretion of LH in the male Syrian hamster: modulation by photoperiod and gonadal steroids

The role of endogenous opiates in the regulation of photoperiodically induced testicular regression was studied in the male Syrian hamster. In reproductively active hamsters exposed to a long photoperiod (LD; 16 h light: 8 h darkness) or to short days (SD; 8 h light: 16 h darkness) for 20 weeks or to SD after pinealectomy, administration of naloxone, a competitive opiate receptor antagonist, at doses of 2.5-20 mg/kg, significantly increased serum LH concentrations. In marked contrast, these doses of naloxone did not produce any change in LH levels in reproductively quiescent hamsters exposed to SD for 8 weeks. The influence of gonadal steroids on the LH response to naloxone was studied in hamsters castrated or castrated and implanted s.c with a capsule containing testosterone. Naloxone did not induce LH release in castrated hamsters maintained in LD or in SD, but this response was restored in LD but not SD when serum testosterone concentrations were maintained at levels similar to those observed in intact reproductively active hamsters. These results show that inhibition of reproduction by the photoperiod prevents naloxone-induced LH release in the male hamster. This lack of response to naloxone is not due, however, to the lower testosterone titres present in these animals compared with reproductively active animals. Responsiveness to naloxone can be restored when the animal is rendered insensitive to the inhibitory photoperiod either by removal of the pineal gland or by induction of photorefractoriness by extended exposure to SD.

Changes in photoperiod alter the daily rhythms of pineal melatonin content and hypothalamic beta-endorphin content and the luteinizing hormone response to naloxone in the male Syrian hamster

This study examines the possible involvement of beta-endorphin in the photoperiodic control of reproduction in the Syrian hamster. beta-Endorphin and LHRH concentrations in the medial basal hypothalamus (MBH), anterior hypothalamus (AHA), and the preoptic area (POA) as well as pineal melatonin content were determined by RIA in male Syrian hamsters exposed to either a long day [(LD) 16-h light; 8-h dark; lights on 0700-2300] or short day [(SD) 8-h light, 16-h dark; lights on 0700-1500] for 8 weeks. Groups of eight animals from each photoperiod were killed by decapitation at 4-h intervals over 24 h. Twenty minutes before death half the animals from each photoperiod were given naloxone (5 mg/kg, sc), the other half saline. Exposure to a long photoperiod maintained testicular activity while a short photoperiod induced testicular regression. Pineal melatonin content in both photoperiods was maximal at 0500 h, i.e. 2 h before the onset of light (SD, 435.58 +/- 82.7 pg/pineal; LD, 276.78 +/- 56.8 pg/pineal). However, the duration of the nighttime rise in pineal melatonin content was increased in SD animals with elevated melatonin levels at 2100 h (157.10 +/- 41.8 pg/pineal) and 0100 h (199.11 +/- 58.9 pg/pineal). In contrast pineal melatonin content in LD animals was only higher than daytime values at 0500 h. A daily rhythm of beta-endorphin content within both the AHA and MBH of animals exposed to a short photoperiod coincided with this prolonged nighttime rise in pineal melatonin content, although a causal relationship between the two was not established. Peak levels of beta-endorphin occurred at 2100 h (AHA, 6.569 +/- 1.2 pmol/mg protein; MBH, 4.877 +/- 0.45 pmol/mg protein) and at 0100 h (AHA, 6.107 +/- 0.66 pmol/mg protein; MBH, 4.49 +/- 00.79 pmol/mg protein) which was 6 h and 10 h into the dark phase, respectively, with lowest levels in the middle of the light phase (AHA, 3.561 +/- 0.56 pmol/mg protein; MBH, 2.688 +/- 0.3 pmol/mg protein). This rhythm was absent in animals exposed to a long photoperiod. There was no effect of photoperiod or time of day on the content of beta-endorphin in the POA. LHRH levels were not altered by changes in photoperiod in all three brain regions studied. In the AHA and MBH, concentrations of LHRH were similar at all times of day whereas, in the POA, LHRH levels varied with time in both photoperiods. Peak levels occurred in the middle of the dark phase at 0100 h (LD, 2.774 +/- 0.24 pmol LHRH/mg protein; SD, 3.206 +/- 0.48 pmol LHRH/mg protein) with lowest levels during the light phase (LD, 1.664 pmol LHRH/mg protein; SD, 1.775 pmol LHRH/mg protein).(ABSTRACT TRUNCATED AT 400 WORDS)

Neurotoxic lesions of the anterior hypothalamus disrupt the photoperiodic but not the circadian system of the Syrian hamster

This paper presents evidence which demonstrates that a site within the anterior hypothalamus of the Syrian hamster is essential for the expression of a photoperiodic response but not for the expression of oestrous or circadian activity rhythms. Selective lesions of the anterior hypothalamic nucleus (AHN) were produced by localized infusions of n-methyl aspartic acid (NMA). Histological analysis revealed that the suprachiasmatic and paraventricular nuclei were resistant to the toxin. Circadian locomotor activity rhythms and oestrous cyclicity were unaffected by these lesions but the photoperiodic response of the gonads to short day length (8L:16D) was completely prevented. In marked contrast to control animals, lesioned animals maintained large testes or ovulatory ovaries, even after 10 weeks of exposure to the inhibitory photoperiod. These data suggest that neurones within the AHN form an essential component of the photoperiod time-measuring apparatus which is independent of that controlling circadian rhythmicity.