Responses of rostral fastigial nucleus neurons of conscious cats to rotations in vertical planes.

The rostral fastigial nucleus (RFN) of the cerebellum is thought to play an important role in postural control, and recent studies in conscious nonhuman primates suggest that this region also participates in the sensory processing required to compute body motion in space. The goal of the present study was to examine the dynamic and spatial responses to sinusoidal rotations in vertical planes of RFN neurons in conscious cats, and determine if they are similar to responses reported for monkeys. Approximately half of the RFN neurons examined were classified as graviceptive, since their firing was synchronized with stimulus position and the gain of their responses was relatively unaffected by the frequency of the tilts. The large majority (80%) of graviceptive RFN neurons were activated by pitch rotations. Most of the remaining RFN units exhibited responses to vertical oscillations that encoded stimulus velocity, and approximately 50% of these velocity units had a response vector orientation aligned near the plane of a single vertical semicircular canal. Unlike in primates, few feline RFN neurons had responses to vertical rotations that suggested integration of graviceptive (otolith) and velocity (vertical semicircular canal) signals. These data indicate that the physiological role of the RFN may differ between primates and lower mammals. The RFN in rats and cats in known to be involved in adjusting blood pressure and breathing during postural alterations in the transverse (pitch) plane. The relatively simple responses of many RFN neurons in cats are appropriate for triggering such compensatory autonomic responses.

Responses of caudal vestibular nucleus neurons of conscious cats to rotations in vertical planes, before and after a bilateral vestibular neurectomy.

Although many previous experiments have considered the responses of vestibular nucleus neurons to rotations and translations of the head, little data are available regarding cells in the caudalmost portions of the vestibular nuclei (CVN), which mediate vestibulo-autonomic responses among other functions. This study examined the responses of CVN neurons of conscious cats to rotations in vertical planes, both before and after a bilateral vestibular neurectomy. None of the units included in the data sample had eye movement-related activity. In labyrinth-intact animals, some CVN neurons (22%) exhibited graviceptive responses consistent with inputs from otolith organs, but most (55%) had dynamic responses with phases synchronized with stimulus velocity. Furthermore, the large majority of CVN neurons had response vector orientations that were aligned either near the roll or vertical canal planes, and only 18% of cells were preferentially activated by pitch rotations. Sustained head-up rotations of the body provide challenges to the cardiovascular system and breathing, and thus the response dynamics of the large majority of CVN neurons were dissimilar to those of posturally-related autonomic reflexes. These data suggest that vestibular influences on autonomic control mediated by the CVN are more complex than previously envisioned, and likely involve considerable processing and integration of signals by brainstem regions involved in cardiovascular and respiratory regulation. Following a bilateral vestibular neurectomy, CVN neurons regained spontaneous activity within 24 h, and a very few neurons (<10%) responded to vertical tilts <15 degrees in amplitude. These findings indicate that nonlabyrinthine inputs are likely important in sustaining the activity of CVN neurons; thus, these inputs may play a role in functional recovery following peripheral vestibular lesions.

Risk of house staff tuberculin skin test conversion in an area with a high incidence of tuberculosis.

We prospectively evaluated rates of tuberculin skin test (TST) conversion from July 1992 to June 1997 among house staff in the Emory University Affiliated Hospitals Training Program following implementation of expanded infection control measures for tuberculosis at Grady Memorial Hospital (Atlanta), which cares for approximately 200 patients with tuberculosis per year. Over 5 years, documented TST conversions occurred for 52 (2.4%) of 2,144 house staff. Conversion rates decreased after the first 6 months from 5.98 to 1.09 per 100 person-years worked over the next 4.5 years (P < .001). Multivariate analysis revealed that risk factors for TST conversion included graduation from a foreign medical school and being part of the house staff in the Department of Medicine; race or ethnicity, gender, and age were not risk factors. Over the last 4.5 years, the TST conversion rate among U.S. medical school graduate house staff (n = 1,928) was 0.72 per 100 person-years worked, and there was no significant difference in conversion rates between house staff in the Department of Medicine and house staff in other departments. In summary, TST seroconversion rates decreased significantly following full implementation of expanded infection control measures for tuberculosis and were low (< 1% per year) among U.S. medical school graduates despite their caring for large numbers of patients with tuberculosis at an inner-city public hospital.

Idiopathic CD4+ T-lymphocytopenia--an analysis of five patients with unexplained opportunistic infections.

BACKGROUND: Although patients with idiopathic CD4+ T-lymphocytopenia and serious opportunistic infections have been described previously, the clinical and immunologic features of this condition have not been well defined. METHODS: We studied in detail five patients with idiopathic CD4+ T-lymphocytopenia. The studies included serologic testing, culture, and polymerase chain reaction for the human immunodeficiency virus (HIV) types 1 and 2, serologic testing for the human T-cell lymphotropic virus (HTLV) types I and II, lymphocyte phenotyping, immunoglobulin quantitation, and lymphocyte-transformation assays, as well as attempts to isolate a retroviral agent. The results were compared with those in HIV-infected persons matched for CD4+ T-cell counts and with those in normal controls. We also studied the spouses of patients and the blood donors for one patient. RESULTS: In these five patients, there was no evidence of either HIV or HTLV infection. All the patients had both low percentages and low counts of CD4+ T cells, with relative increases in percentages, but not counts, of CD8+ cells. Numbers of B cells and natural killer cells were generally normal. As compared with HIV-infected persons, our patients had lower percentages and counts of CD8+ cells and more lymphopenia. CD4+ counts were relatively stable over time. Instead of the high immunoglobulin levels seen in HIV infection, these patients had normal or slightly low levels of immunoglobulins. The lymphocyte-transformation response to mitogens and antigens was depressed. Results in spouses and blood donors were normal. CONCLUSIONS: Idiopathic CD4+ T-lymphocytopenia differs from HIV infection in its immunologic characteristics and in its apparent lack of progression over time. Nothing about the immunologic or viral-culture studies performed in these patients or about their family members or blood donors suggests that a transmissible agent causes this condition.

Community-acquired bloodstream infection caused by Pseudomonas paucimobilis: case report and review of the literature.

Various sources of Pseudomonas paucimobilis bacterial infections have been documented. We report the third human case of bloodstream infection due to P. paucimobilis and review the literature in English regarding community-acquired and nosocomial infection due to this bacterium. Biochemical and genetic characteristics supporting the pathogenic potential of P. paucimobilis are presented, and the antibiotic susceptibility profile of the organism is summarized.

Hepatocellular carcinoma simulating amebic liver abscess: report of a case and analysis of current diagnostic methods.

Radiological and serological tests are valuable tools commonly used in diagnosing amebic liver abscess. The limitations in sensitivity and specificity of the various imaging procedures should be recognized in order to avoid misinterpretation of test results. Serodiagnostic methods present potential pitfalls primarily because of their frequent inability to differentiate previous disease from active infection, and must therefore be interpreted carefully.

Gonococcal tenosynovitis-dermatitis and septic arthritis. Intravenous penicillin vs oral erythromycin.

Twenty-three patients with disseminated gonococcal infections--15 with acute tenosynovitis, six with septic monoarticular arthritis, and two with both--were randomly given five days of erythromycin stearate or estolate, 500 mg orally every six hours (13 patients), or crystalline aqueous penicillin G potassium, 1 million units intravenously every three hours for three days (ten patients). There were no treatment failures. Cultures taken one and seven days and two and four weeks after completion of therapy were uniformly negative. Clinical resolution was rapid in both groups, as judged by response of fever, joint tenderness, and disappearance of joint effusion. Orally administered erythromycin is a useful alternative to penicillin in the treatment of disseminated gonococcal infections, particularly in penicillin-allergic pregnant women.

The microbiology and therapy of acute pelvic inflammatory disease in hospitalized patients.

We examined microbial isolates from the endocervical and peritoneal cavity of 30 women hospitalized with acute PID. Patients were randomly assigned to one of two antibiotic regimens: amoxicillin, 6 gm by mouth every 24 hours, or aqueous penicillin G, 30 million units and gentamicin, 180 to 240 mg intravenously every 24 hours. We measured response by quantifying physical examination findings. Neisseria gonorrhoeae was isolated from the cervix of 24 patients (80%) and from the peritoneal cavity of 10 (33%). Other peritoneal isolates included Enterobacteriaceae in five patients, Ureaplasma urealyticum in five, Mycoplasma hominis in six, and Chlamydia trachomatis in three. Bacteroides melaninogenicus, the most frequent anaerobe, was isolated in 11 cases. Bacteroides fragillis was not isolated from any specimen. The cure rates were the same for both regimens: three patients failed on each. Four women required total abdominal hysterectomy and unilateral or bilateral salpingo-oophorectomy.

Auxotypes and antibiotic susceptibility patterns of Neisseria gonorrhoeae from disseminated and local infections.

The arginine-hypoxanthine-uracil auxotype has been linked with the propensity of gonococci to cause disseminated infections. Gonococci recovered from 25 patients with disseminated gonococcal infections were compared with gonococci recovered from matched controls, patients with uncomplicated gonorrhea selected during the same month. Minimal inhibitory concentrations of penicillin, tetracycline, erythromycin, and ampicillin, and the nutritional requirements (auxotypes) for proline alone, arginine alone, arginine, hypoxanthine and uracil together, serine alone and cysteine-cystine (wild type) were analyzed by discriminant analysis. Significant susceptibility to penicillin characterized strains causing disseminated infection, and a proline requirement was the most common auxotype (48%) among strains isolated in Atlanta. Together the minimal inhibitory concentration of penicillin and the proline auxotype best separated the strains causing gonorrhea. The arginine-hypoxanthine-uracil auxotype was was found in only 24% of strains causing disseminated infections. A trait other than auxotype must determine the capacity of the organisms to disseminate.

Spinal epidural abscess.

This paper describes problems in the diagnosis and management of six patients with spinal epidural abscess. Since the clinical findings in this disease process are frequently misinterpreted, one must be careful to exclude this diagnosis in any patient with fever, leukocytosis, back pain and recent infection or back trauma. Alcoholic patients, in particular, seem at high risk for missed diagnosis since the clinical findings are frequently misinterpreted to be complications of alcoholism. Suspicion of spinal epidural abscess should lead to immediate lumbar puncture with manometrics as well as myelography. Once the diagnosis is established surgery should be immediate. Gram stains and cultures taken at the time of lumbar puncture or at operation will dictate appropriate antibiotic therapy. The cause of infection can be fairly well determined by the location of the abscess and a knowledge of the pathogenesis. Prognosis seems directly dependent on the preoperative neurologic status of the patient.

Immunization for the internist.

The emphasis of immunization programs and schedules has traditionally been directed to infants and children, since most of the vaccine-preventable diseases are seen predominantly in these age groups. Immunization procedures in adults are less well defined but still of importance. Diseases for which immunizations are given before disease exposure include tetanus, diphtheria, influenza, rubella, and mumps; travelers to foreign countries may need immunizations against typhoid, cholera, yellow fever, typhus, poliomyelitis, plague, and viral hepatitis; other vaccines are available before disease exposure in unusual epidemiologic situations. After exposure to disease but before onset of symptoms, immunizations are available for rabies, viral hepatitis, and measles. After the onset of clinical illness, passive immunization should be given for tetanus, diphtheria, and botulism. This paper summarizes current practices for active and passive immunization against these diseases in adults.

Recent survey of infectious meningitis in adults: review of laboratory findings in bacterial, tuberculous, and aseptic meningitis.

Infectious meningitis in adults was reviewed to establish the frequency of meningitis due to each causative agent and to reexamine the laboratory parameters that help to distinguish aseptic, bacterial, and mycobacterial meningitis. Aseptic meningitis occurred 2.2 times more often than bacterial and mycobacterial meningitis combined. The most common nonviral causative agent was the pneumococcus (23 cases) followed by the tubercle bacillus (11 cases) and the meningococcus (5 cases). Cerebrospinal fluid (CSF) Gram stain was the most useful study to rule in a bacterial cause: 89% of cases of bacterial meningitis had a positive initial Gram stain. Hyponatremia occurred in 73% of cases of tuberculous meningitis; hyponatremia combined with a negative Gram stain was highly suggestive of a tuberculous cause. One third of all patients with tuberculous and aseptic meningitis had a predominance of neutrophils in the CSF. No patient with aseptic meningitis had a CSF while count higher than 2,800 cells/cu mm or a CSF protein value higher than 250 mg/100 ml. Other reviews confirm this if cases due to lymphocytic choriomeningitis (LCM) are excluded. One patient with tuberculous meningitis in this series, and none of those cases reviewed, had a CSF white count higher than 1,200 cells/cu mm. Only 3.7% of the patients with aseptic meningitis had hypoglycorrhachia. Series reporting exclusively disease due to mumps and LCM have a higher frequency of hypoglycorrhachia.

Detection of pneumococcal polysaccharide in the sputum of patients with pneumococcal pneumonia by counterimmunoelectrophoresis.

Each of 41 patients with bacterial pneumonia was placed into 1 of 4 categories based on the relative clinical certainty of the diagnosis of pneumococcal pneumonia. The frequency of pneumococcal polysaccharide in the sputum by counterimmunoelectrophoresis (CIE) was then noted for each diagnostic category of patients. Detection of pneumococcal polysaccharide in sputum correlated with the diagnostic certainty of pneumococcal pneumonia, while results of culture of sputum were less indicative of pneumococcal infection. Saliva of 83 normal individuals failed to give positive tests for pneumococcal polysaccharide despite the presence of alpha-hemolytic streptococci on culture. Furthermore, the mere presence of pneumococci in cultures did not predict a positive test for polysaccharide by CIE nor did the absence of pneumococci mean that polysaccharide would not be detected. This study suggests that detection of pneumococcal polysaccharide appears more rapid, more sensitive, and more specific than sputum cultures in diagnosing pneumococcal infection of the lung.

Factors associated with mortality in brain abscess.

Coma on admission, multiple, deep, or ruptured abscess, inaccurate diagnosis, and inability to prove the diagnosis were factors contributing to mortality. In survivors, abscess generally followed cranial injury, surgery, or contiguous infection; in most fatal cases, brain abscess was secondary to a more remote primary infection. Ruptured or multiple abscesses or positive spinal fluid cultures were not found in survivors, and coma was present in only one. Fatal cases in patients admitted in coma usually did not exhibit focal signs, seizures, or symptoms of meningitis early in the illness; none of these patients had prior cranial injury or surgery. Absence of these delayed their seeking care and accurate diagnosis. Ruptured abscess was frequent in these patients. Most patients not in coma on admission had focal signs, seizures, symptoms or meningitis, or had prior cranial injury or surgery.

In-use contamination of intravenous infusion fluid.

During the 1970 to 1971 nationwide epidemic of septicemias caused by Enterobacter cloacae and Enterobacter agglomerans traced to intrinsic contamination of Abbott intravenous infusion products, 94 infusion systems manufactured by Baxter Laboratories were studied microbiologically and epidemiologically during hospital use. Intravenous fluid from 10 systems (11%) contained microorganisms, usually Staphylococcus or Bacillus species; one infusion was heavily contaminated with Klebsiella pneumoniae. No national epidemic organisms, E. cloacae or E. agglomerans (formerly Erwinia), were recovered, suggesting that during this period frequent contamination with these organisms was unique to Abbott's infusion products. Contamination in this study appeared to be extrinsic in origin (introduced during clinical use) and related to the duration of continuous intravenous therapy. Nine of 61 systems (15%) that had been used longer than 48 h were contaminated, whereas only 1 of 33 used less than 48 h (3%) contained microorganisms. This study and the recent national outbreak indicate that contamination of infusion fluid, both from intrinsic and extrinsic sources, must be recognized as an additional risk of intravenous therapy; however, a once-daily replacement of the delivery apparatus can significantly diminish this hazard.