Post-COVID-19 rash: An atypical manifestation of guttate psoriasis

Many complications are emerging from Coronavirus Disease 2019 (COVID-19), likely secondary to immune dysfunction and autoimmunity. While dermatologic changes have been reported, de novo guttate psoriasis, typically associated with streptococcal and other viral infections, secondary to COVID-19 infection has been minimally described. The authors report a case of a 34-year-old man who developed a diffuse rash 3 weeks following a COVID-19 infection found to have new onset guttate psoriasis who was responsive to topical corticosteroids and a vitamin D analog.

High risk and low prevalence diseases: Infected urolithiasis

INTRODUCTION

Infected urolithiasis is a serious condition that carries with it a high rate of morbidity and mortality.

OBJECTIVE

This review highlights the pearls and pitfalls of infected urolithiasis, including presentation, diagnosis, and management in the emergency department based on current evidence.

DISCUSSION

Although urolithiasis is common and the vast majority can be treated conservatively, the presence of a concomitant urinary tract infection significantly increases the risk of morbidity, to include sepsis and mortality. Identification of infected urolithiasis can be challenging as patients may have symptoms similar to uncomplicated urolithiasis and/or pyelonephritis. However, clinicians should consider infected urolithiasis in toxic-appearing patients with fever, chills, dysuria, and costovertebral angle tenderness, especially in those with a history of recurrent urinary tract infections. Positive urine leukocyte esterase, nitrites, and pyuria in conjunction with an elevated white blood cell count may be helpful to identify infected urolithiasis. Patients should be resuscitated with fluids and broad-spectrum antibiotics. Additionally, computed tomography and early urology consultation are recommended to facilitate definitive care.

CONCLUSIONS

An understanding of infected urolithiasis can assist emergency clinicians in diagnosing and managing this potentially deadly disease.

Comparing survival and mortality in patients with late-onset and young-onset vascular dementia

OBJECTIVES

Vascular dementia (VD) is one of the more common types of dementia. Much is known about VD in older adults in terms of survival and associated risk factors, but comparatively less is known about VD in a younger population. This study aimed to investigate survival in people with young-onset VD (YO-VD) compared to those with late-onset VD (LO-VD) and to investigate predictors of mortality.

DESIGN

Retrospective file review from 1992 to 2014.

SETTING

The inpatient unit of a tertiary neuropsychiatry service in Victoria, Australia.

PARTICIPANTS

Inpatients with a diagnosis of VD.

MEASUREMENTS AND METHODS

Mortality information was obtained from the Australian Institute of Health and Welfare. Clinical variables included age of onset, sex, vascular risk factors, structural neuroimaging, and Hachinksi scores. Statistical analyses used were Kaplan-Meier curves for median survival and Cox regression for predictors of mortality.

RESULTS

Eighty-four participants were included with few clinical differences between the LO-VD and YO-VD groups. Sixty-eight (81%) had died. Median survival was 9.9 years (95% confidence interval 7.9, 11.7), with those with LO-VD having significantly shorter survival compared to those with YO-VD (6.1 years and 12.8 years, respectively) and proportionally more with LO-VD had died (94.6%) compared to those with YO-VD (67.5%), χ2(1) = 9.16, p = 0.002. The only significant predictor of mortality was increasing age (p = 0.001).

CONCLUSION

While there were few clinical differences, and older age was the only factor associated with survival, further research into the effects of managing cardiovascular risk factors and their impact on survival are recommended.

Facilitated Intubation: Time to Re-examine an Old Technique With Its Associated Risks Mitigated by New Technology

BACKGROUND

Facilitated intubation (FI) refers to intubation performed using a sedative or anesthetic drug as an induction agent, without the use of a paralytic (neuromuscular blocking agent). In comparison, rapid sequence intubation (RSI) employs both an induction agent and a paralytic drug. RSI has been seen to outperform FI in terms of first-pass success when performing direct laryngoscopy and was quickly adopted as the gold standard in all situations. Recently, ketamine-only intubation has been used in situations where there is distorted anatomy or apnea intolerance (physically and physiologically difficult airways) resulting in an increased risk of a can't intubate/can't oxygenate scenario or significant hypoxemia. Frequent and recurring national ketamine shortages have resulted in renewed interest in whether or not other forms of FI are feasible in an era where other factors that mitigate complictions in achieving first-pass success (video laryngoscopy, bougie use, semi-Fowler positioning) are commonly used. We present a case series with outcomes for profoundly hypoxic patients with coronavirus disease 2019 (COVID-19) (physiologically difficult airways) undergoing FI during a time of national ketamine shortage, using modern techniques and technology to maximize first-pass success and minimize peri-intubation complication.

METHODS

We included patients with COVID-19 pneumonia with pre-intubation oxygen saturations of less than 80% (significant hypoxemia) requiring intubation who presented to a tertiary care center in southern United States between August 25, 2021, and October 22, 2021. In this specific cohort, patients underwent endotracheal intubation with midazolam for induction without the use of paralytic agents. We used video-assisted laryngoscopy to increase the success of the first-pass attempt as well as placing the patients in a semi-Fowler position (head of bed elevation 30-45°) and bilevel positive pressure pre-oxygenation to minimize peri-intubation complications.

RESULTS

Our case series included 29 consecutive patients that met the inclusion criteria. The mean ± standard deviation (SD) age of the patients was 49.5±15.0 years. The mean±SD pre-intubation oxygenation of our cohort was 73.1±5.9%. All 29 intubations were successful on the first-pass attempt. Only one patient (3.4%) required a rescue paralytic to facilitate oral opening. Of note, 27/29 (93%) of the patients did not receive any immunizations (including partial) for COVID-19. There were no incidents of peri-intubation arrest (cardiac arrest within 30 minutes of induction) or aspiration.

CONCLUSIONS

In 29 physiologically difficult patients with acute respiratory failure, in whom the physician determined that RSI posed a higher than normal risk, FI assisted by VL, semi-Fowler positioning, and bilevel positive pressure pre-oxygenation resulted in excellent successful first-pass intubation rates without any incidences of peri-intubation arrest or aspiration. While this cohort was small, our study reveals that FI with midazolam does not likely pose a higher risk than ketamine-only intubation and warrants further study.

A Review of Acute Kidney Injury

Acute kidney injury (AKI) is a serious, often silent, medical condition with diverse etiologies and complex pathophysiology. We discuss the case of a patient injured in a single vehicle rollover. Included is a discussion of prevention and supportive care, with a focus on electrolyte repletion, fluid correction, minimization of nephrotoxic exposures, and identification and treatment of the root cause.

Approach to nephrostomy tubes in the emergency department

BACKGROUND

Nephrostomy tubes are commonly placed for urinary obstruction, urinary diversion, or future endourologic procedures. While the technical success of nephrostomy tube placement is high, nephrostomy tube complications may occur.

OBJECTIVE OF REVIEW

Limited literature exists regarding the complication of nephrostomy tubes and their approach in the emergency department. This review summarizes the existing literature and provides a framework for emergency providers regarding the evaluation and management of nephrostomy tube complications.

DISCUSSION

Nephrostomy tube failure, caused by kinking, dislodgment, or migration can manifest with obstructive signs and symptoms. In well appearing patients, asymptomatic bacteriuria is common and should not be treated. However, in the presence of infectious symptoms, patients should be treated similarly to complicated cystitis or pyelonephritis. While gross hematuria is common following catheter placement, prolonged hematuria, or the return of hematuria after previous resolution should trigger investigation for hematoma formation or a delayed presentation of an intraoperative vascular injury. Finally, clinicians should obtain laboratory testing, advanced imaging, and specialty consultation if serious complications are suspected.

CONCLUSION

This narrative review highlights general nephrostomy tube care, minor complications, and troubleshooting in the emergency department. The majority of these minor complications can be managed at the bedside without specialty consultation. However, in patients with more serious complications including dislodgement, obstruction, infection, bleeding, and pleural injury, laboratory assessment and advanced imaging to include ultrasound and computed tomography with specialty consultation are essential in the patient's evaluation and management, particularly in cases of immune compromise and worsening renal function.

Small Bowel in Vagina: A Case for Pelvic Exams

Vaginal cuff dehiscence with small bowel evisceration is a serious but uncommon postoperative complication of total laparoscopic hysterectomies. The severity of surgical site dehiscence can range from small, partial to full-thickness wound dehiscence, manifesting with acute abdominal pain, vaginal bleeding, or discharge, and is often precipitated by sexual intercourse. While imaging, including a pelvic ultrasound and computed tomography (CT), may help in undifferentiated acute abdominal pain, vaginal cuff dehiscence remains a clinical diagnosis found on physical exam. Because vaginal cuff dehiscence is a clinical diagnosis, sparse data exist regarding radiographic sensitivities and specificities in the identification of vaginal cuff dehiscence. Despite the increasing literature suggesting that pelvic exams are invasive with often limited utility, the authors argue that pelvic exams remain essential in identifying complications of hysterectomies. The authors present a case of a 40-year-old woman with acute abdominal pain found to have loops of small bowel in the vaginal vault, discovered only on physical exam after negative CT and ultrasound imaging.

Interrater Agreement and Reliability of Burn Size Estimations Between Emergency Physicians and Burn Unit

The initial approach to burn injuries has remained relatively unchanged over the past several decades and revolves around trauma assessment and fluid resuscitation, frequently initiated in the emergency department (ED). While previous research suggests that emergency physicians (EP) are poor estimators at total body surface area (TBSA) affected, we believe that estimation differences are improving, specifically at academic centers with co-located burn units that emphasize burn injury education. This study investigated the interrater agreement and reliability of burn size estimations at an academic ED and its co-located burn unit. This single-center, retrospective study was conducted at a large academic ED with a co-located burn unit. The study included adult patients admitted to the burn unit after receiving paired burn size estimations from EPs and the burn unit. The primary endpoint was the interrater agreement, measured by the kappa coefficient, κ, of 10% TBSA estimation intervals. The secondary endpoint was the intraclass correlation coefficient (ICC), evaluating the reliability of exact, nonranged, and TBSA estimations. A chart review was performed for patients evaluated from November 1, 2016 to July 31, 2019. One thousand one hundred and eighty-four patients were admitted to the burn unit, 1176 of which met inclusion criteria for the primary endpoint. The κ of TBSA between EPs and the burn unit was 0.586, while the weighted κ was 0.775. These values correlate with moderate and substantial agreements, respectively. Additionally, 971 patients had exact TBSA estimations from paired EPs and the burn unit which were used for the secondary endpoint. The ICC between EPs and the burn unit was 0.966, demonstrating an excellent reliability. Further sub-analysis was performed, revealing mean over- and underestimation differences of exact TBSA estimations of 3.93 and 2.93, respectively. EPs at academic institutions with co-located burn units are accurate estimators of TBSA in the assessment of burn injuries. We believe that burn education, to include core rotations within the burn unit, plays a major role in improved burn size estimations.

Seizure-Associated Takotsubo Cardiomyopathy

Takotsubo cardiomyopathy (TCOM) is a syndrome characterized by acute systolic dysfunction that can mimic acute coronary syndrome (ACS), usually incited by physical or emotional stress. However, acute neurological dysfunction, including seizures, has been recently described as an additional risk factor for the development of TCOM. This specific case report reviews the pathophysiology of TCOM and its management. We emphasize that providers should maintain a high index of suspicion for TCOM after acute neurologic dysfunction in patients with chest pain or hemodynamic instability, while also initiating proper investigation for ACS. Although classically thought of as a transient process, recent data show that both in-hospital and post-hospital morbidity and mortality related to this condition remain concerning.

Acute coronary syndrome in Dextrocardia

Situs inversus with dextrocardia is both a clinical and diagnostic challenge for emergency physicians to properly identify acute coronary syndrome. While dextrocardia itself does not independently increase the risk of coronary artery disease, mirrored symptoms, including right-sided and rightward radiating chest pain in any patient with cardiac risk factors should raise suspicion for acute coronary syndrome. In patients with a reversed cardiac silhouette on a chest radiograph, a reversed electrocardiogram, to include both the precordial and limb leads, is necessary to evaluate for cardiac ischemia in presumed dextrocardia. The authors present a case of a 66-year-old man with dextrocardia who presented with shortness of breath and hypotension. Rapid application of a reversed electrocardiogram resulted in the timely diagnosis of ST-segment elevation myocardial infarction and activation of the cardiac catheterization laboratory resulting in the preservation of this patient's life.

Subdural Empyema in an Immunocompetent Active Duty Soldier: A Case Report

Intracranial subdural empyema is a rare clinical entity with incidence estimates of 0.1 per 100,000 people. The condition is most often the sequela of a primary infection elsewhere and carries a high morbidity and mortality. The authors present the case of a 22-year-old active duty soldier on mission on the southern border of the United States. The patient had been complaining of headaches that became progressively worse over 2 weeks and presented to a civilian hospital where he was diagnosed with intracranial abscess versus sinus thrombosis on radiographic imaging. The patient was promptly transferred to a military tertiary care center where further workup including pivotal imaging confirmed subdural empyema and right transverse sinus thrombosis. Given the rapid patient deterioration associated with subdural empyema, the emergent intravenous antibiotics, neurosurgical consultation, and subsequent collection evacuation performed are likely to credit for saving this soldier’s life. This case highlighted an atypical and time-sensitive etiology for a common complaint in the active duty population, which underscores the requirement for evacuation to higher roles of care in those soldiers with a similar diagnosis.

ST-Segment Elevation in the Setting of Diabetic Ketoacidosis: Is It Acute Coronary Syndrome?

Diabetic ketoacidosis (DKA) with resulting hyperkalemia can lead to ST-segment elevations on electrocardiogram (ECG). Previous publications theorize that significant improvements in patient potassium levels lead to the resolution of this rare phenomenon, also known as "pseudo-infarct" pattern. The authors provide a unique case along with a literature review of DKA-associated ST-segment elevations. This specific case distinctively demonstrates the resolution of the pseudo-infarct pattern in the setting of minor improvements in serum potassium and continued acidosis.

Chest Pain From Supplement Use in an Active Duty Soldier: A Case Report

In the active duty population, over-the-counter performance enhancing supplements are readily available and consumed, primarily in an unsupervised manner. While some of the active ingredients, such as caffeine and creatine, have been well studied, other sympathomimetic and vasoactive components in these products have minimal data regarding their safety profile. Further potentiating the associated risks of consumption, the quantities and purities of the reported ingredients are often unverified and can vary from serving to serving. We present a case of the deleterious side effect profiles of these lesser studied components in overconsumption in an active duty soldier. Although improvements are being made regarding product safety, the paucity of ingredient regulation and quality assurance can result in warfighter morbidity and mortality, especially when these supplements are abused or combined with other products.

Mango Dermatitis After Urushiol Sensitization

Prior exposure to poison ivy and poison oak, which are plants in the Anacardiacea family and contain high levels of urushiol, appear to be a risk factor for delayed hypersensitivity reactions to mango fruits. Cross-sensitization between these plants and mangos is believed to be secondary to an overlap in the urushiol antigen and 5-resorcinol, found predominately in mango peels. This unique combination of sensitization and reaction constitutes a type IV hypersensitivity response, mediated and driven by T cells reacting to similar antigens. We present a case of an otherwise healthy man, with a remote history of poison ivy exposure, who presented with a delayed but significant reaction to mango fruit. Obtaining the patient’s history of prior plant exposures and reactions was key to isolating the likely underlying causation of his presentation.

Adult Small Bowel Intussusception and Resolution Captured on Pelvic Ultrasound

While abdominal pain is one of the leading causes for ED visits, intestinal intussusception is an infrequent etiology in adults. We present the case of a 22-year-old woman with five days of left lower quadrant abdominal pain with initial workup investigating for a genitourinary source utilizing pelvic ultrasound which revealed small bowel-small bowel intussusception. During the study, resolution of the intussusception correlated temporally with the patient's symptoms. Transient small bowel intussusception in adults has been previously described; however, direct visualization of both the intussusception and its resolution on pelvic ultrasound has not been previously published.

Pulsatile Mass: Ruptured Common Femoral Artery Pseudoaneurysm with Active Extravasation

Delayed rupture of a pseudoaneurysm represents an extremely rare and life-threatening complication of endovascular, radiographic, and cardiac procedures. We discuss a case of a 69-year-old man with delayed rupture of a known left common femoral artery pseudoaneurysm, highlighting the importance of rapid recognition, to include the use of point of care ultrasound, if available. Computed tomographic angiography allows for better anatomic characterization and aids in operative planning, which is the mainstay of treatment. However, surgical repair in ruptured pseudoaneurysms remains a high-risk procedure.

Pleural Effusion with Mediastinal and Hemidiaphragm Mass Effect: A Case Report

Pulmonary metastases are a rare but aggressive and life-threatening complication of leiomyosarcoma. We discuss a case of a 48-year-old woman with stage 4b leiomyosarcoma who presented with dyspnea and hemodynamic instability secondary to a large lung metastasis with massive pleural effusion. This particular subset of patients is vulnerable to re-expansion pulmonary edema in a disease with poor survival rates.

More Than a Lymph Node in the Neck: A Rare Synovial Cell Sarcoma with Carotid Artery Mass Effect

The authors discuss a case of a previously healthy 33-year-old man who presented with a subacute neck mass, found to be a rare synovial cell sarcoma with mass effect on the carotid vessels. This report demonstrates the utility of point of care ultrasound and computed tomography (CT) in the workup of the patient’s neck mass. Additionally, we synthesize findings from previous studies that recommend approaching neck masses in adults with a high index of suspicion for malignancy.

Naturally draining ostium of an agger nasi cell: a case report

We describe the case of a 61-year-old woman who underwent functional endoscopic sinus surgery for chronic hyperplastic rhinosinusitis. During surgery, we were able to visualize the natural ostium of her left agger nasi cell. To our knowledge, such a finding has not been previously documented in the literature.

Naturally Draining Ostium of an Agger Nasi Cell: A Case Report

We describe the case of a 61-year-old woman who underwent functional endoscopic sinus surgery for chronic hyperplastic rhinosinusitis. During surgery, we were able to visualize the natural ostium of her left agger nasi cell. To our knowledge, such a finding has not been previously documented in the literature.

Lymphosarcoma in a sea otter (Enhydra lutris)

Lymphoblastic lymphosarcoma involving the mesenteric lymph node and thymus was discovered in a 4 yr old male sea otter (Enhydra lutris). Diagnosis was based on gross and light microscopic studies. The cause of this neoplasm was not determined. This is the first case of lymphosarcoma reported in sea otters.

Castration rapidly decreases hypothalamic gamma-aminobutyric acidergic neuronal activity in both male and female rats

The postcastration LH response is greater and somewhat more rapid in male than female rats. We have previously demonstrated that hypothalamic gamma-aminobutyric acid (GABA)ergic neuronal activity decreases following gonadectomy in male rats. To investigate whether these same hypothalamic GABA neurons decrease their activity postcastration in female rats, and whether more rapid and or greater postcastration decreases occur in male rats, we determined the timing and magnitude of the postcastration decreases in GABA turnover which are associated with the sexually dimorphic postcastration LH response. Adult male and 4-day cycling female rats were castrated between 0800 and 1000 h (females ovariectomized on diestrus day 1). Serum LH levels increased significantly by 12 h postcastration in both males and females with the magnitude of the increases being 6.2-fold in males and 2.8-fold in females. GABA turnover was determined in 16 microdissected brain structures by the GABA transaminase inhibition method at 0 h (sham-operated controls), 6 h, 12 h and 1, 2, 4 and 6 days postcastration. In male rats, in the diagonal band of Broca at the level of the organum vasculosum of the lamina terminalis [DBB(ovlt)], the rate of GABA turnover decreased significantly already by 6 h postcastration compared with the 0 h controls, and remained suppressed through 6 days. This rapid down regulation of DBB(ovlt) GABAergic neurons also occurred in female rats, however, the duration of the decrease was not as prolonged as in male rats. Similar changes occurred in the tuberoinfundibular GABAergic (TIGA) neurons projecting to the median eminence in both males and females. Down regulation of these GABAergic neurons precedes or is coincident with increased postcastration LH secretion in both sexes, and the duration of the decreases is consistent with the less robust postcastration LH response in female rats. In addition, the rate of GABA turnover decreased after castration in the interstitial (bed) nucleus of the stria terminalis, ventral aspect (INSTv), the medial preoptic nucleus, dorsomedial aspect (MPNdm) and the ventromedial nucleus, ventrolateral aspect (VMNvl) in male rats, and in the INSTv and VMNvl of female rats, while there was no effect of castration in other hypothalamic regions or control structures. The result in the female VMNvl is consistent with reports that GABA facilitates lordosis behavior in this hypothalamic structure. These findings are consistent with the hypothesis that discrete hypothalamic populations of sex steroid-sensitive GABAergic neurons mediate the postcastration LH responses in both male and female rats, and may underlie other sexually dimorphic adult phenotypes such as sex behavior.

Sex differences in GABA turnover and glutamic acid decarboxylase (GAD(65) and GAD(67)) mRNA in the rat hypothalamus

GABAergic neurons are estimated to make up more than half of the neuronal population of the hypothalamus and they likely account for some of the structural and functional sexual dimorphisms observed in the mammalian brain. We previously reported sex differences in the rate of GABA turnover in discrete hypothalamic structures of adult rats. In the present study, we extended our search for sex differences in GABA turnover to additional structures, and further determined whether these differences were associated with differences in GAD(65) and or GAD(67) mRNA levels. Utilizing the GABA transaminase inhibition method, we determined GABA turnover in 14 microdissected brain regions. The rate of GABA turnover was about 2-fold greater in male than in diestrous day one (D(1)) female rats in the diagonal band of Broca at the level of the organum vasculosum of the lamina terminalis [DBB(ovlt)], anteroventral periventricular nucleus (AVPv), median eminence (ME), and dorsomedial portion of the ventromedial nucleus (VMNdm). A sex difference also was noted in the DBB(ovlt) for GAD(65) mRNA determined by microlysate RNase protection assay. Here, GAD(65) levels were almost 2-fold greater in male rats, which suggests that differences in the activity of this GAD enzyme isoform contributes to the difference in turnover in this area. Additionally, in the dorsomedial nucleus (DMN), the GAD(65) mRNA level was significantly higher in female rats, and in the medial amygdaloid nucleus (Am), GAD(67) mRNA was higher in male rats. These data reveal striking sexual dimorphisms in the rate of GABA turnover and in GAD mRNA levels in specific populations of hypothalamic GABAergic neurons. The functional relationships between these GABAergic neurons and sexually dimorphic phenotypes associated with these structures, such as gonadotropin secretion, reproductive behaviors, seizure threshold and others, warrant further investigation.

Reconstituted basement membrane reduces proliferation and increases prolactin expression of GH3 cells

This study investigated the effects of reconstituted basement membrane Matrigel on the proliferation and prolactin expression of GH3 cells in culture for 6 days. When cells were cultured on Matrigel, the initial attachment was increased but the cell number was not changed with time whereas rapid increase in cell number was observed in cultures on plastic. Bromodeoxyuridine (BrdU)-labeling showed that BrdU incorporation ratio of GH3 cells cultured on Matrigel was about one half of that observed with cells cultured on plastic (9.7+/-0.7% vs. 18.7+/-1.2%). Immunocytochemistry revealed that the ratio of the prolactin-immunoreactive GH3 cells was about 3.6 times (58.4+/-2.9% on Matrigel vs. 16.2+/-1.4% on plastic), which was compatible with the results of Western blot analysis. In situ hybridization demonstrated that prolactin mRNA-positive cells were identified more frequently when cells were cultured on Matrigel compared to cultures on plastic. These findings indicate that Matrigel is a proper culture substrate for the long-term culture of GH3 pituitary cells due to the inhibition of overgrowth and promotion of prolactin expression.

Scanning Single-Electron Transistor Microscopy: Imaging Individual Charges

A single-electron transistor scanning electrometer (SETSE)-a scanned probe microscope capable of mapping static electric fields and charges with 100-nanometer spatial resolution and a charge sensitivity of a small fraction of an electron-has been developed. The active sensing element of the SETSE, a single-electron transistor fabricated at the end of a sharp glass tip, is scanned in close proximity across the sample surface. Images of the surface electric fields of a GaAs/AlxGa1-xAs heterostructure sample show individual photo-ionized charge sites and fluctuations in the dopant and surface-charge distribution on a length scale of 100 nanometers. The SETSE has been used to image and measure depleted regions, local capacitance, band bending, and contact potentials at submicrometer length scales on the surface of this semiconductor sample.

Tumor necrosis factor-alpha mediates endotoxin induced suppression of gonadotropin-releasing hormone pulse generator activity in the rat

Bacterial endotoxin lipopolysaccharide (LPS) is known to suppress gonadotropin secretion and this effect is assumed to be mediated by cytokines. In the present study, we examined whether LPS affected hypothalamic electrical activity associated with LH pulses, and whether tumor necrosis factor-alpha (TNF-alpha), a major cytokine induced by LPS, was involved in this process. Ovariectomized rats were fitted with chronically implanted electrode arrays in the mediobasal hypothalamus, and multiunit activity (MUA) was recorded under conscious, unrestrained conditions. Blood samples were withdrawn every 6 min through an indwelling atrial catheter or determining serum LH concentrations. Intravenous (i.v.) injection of LPS (1 microgram) suppressed characteristic increases (volleys) in MUA associated with LH pulses throughout the experimental period up to 5 h. This suppressive effect of LPS on MUA volleys was significantly attenuated by simultaneous intracerebroventricular (icv) injection of the antibody (50 ng) to TNF-alpha through an indwelling cannula in the lateral ventricle. These changes in MUA were faithfully reflected in the LH secretory pattern. Further, either i.v. (0.4-2 micrograms) or i.c.v. (20-250 ng) injection of TNF-alpha suppressed the frequency of MUA volleys and associated LH pulses in a dose-dependent manner. These results suggest that LPS leads to the suppression of gonadotropin-releasing hormone pulse generator activity through a mechanism involving TNF-alpha.