Decreases in endogenous opioid peptides in the rat medullo-coerulear pathway after chronic morphine treatment.

Several biochemical changes have been described in noradrenergic neurons of the locus coeruleus (LC) after chronic morphine treatment. Changes in neurochemical expression in opioid afferent projections to the LC may be equally important in modulating noradrenergic neurons during chronic opiate exposure. To test the hypothesis that opioid peptides in LC afferents are altered after chronic opiate administration, we exposed adult male rats to either morphine or placebo pellets for 5 d. Tissue sections through the LC were processed for peroxidase or gold-silver labeling of methionine(5)-enkephalin (met-ENK) and analyzed using light or electron microscopy, respectively. Light level densitometry and ultrastructural analysis showed that there was a significant decrease in immunolabeling for ENK in LC-afferent terminals of morphine-treated rats. Western immunoblot analysis confirmed that protein levels for both leucine(5)- and methionine(5)-ENK were significantly decreased in tissue samples containing the LC after chronic morphine treatment. To test whether decreases in ENK protein expression were mirrored by decreases in gene expression, Northern blot analysis of preproenkephalin (PPE) mRNA was conducted in tissue samples obtained through the medulla, a brainstem area that contains the major opioid afferents to the LC. PPE mRNA was reduced in samples obtained from morphine-treated rats. Finally, in situ hybridization experiments confirmed significant decreases in PPE mRNA expression in the nucleus paragigantocellularis, a region known to provide a robust opioid input to the LC. These data suggest that there is a decrease in the synthesis of the opioid peptide mRNA and protein in the medullo-coerulear pathway after chronic exposure to morphine. Such alterations in opioid peptide levels during opiate dependence may contribute to the observed hyperactivity of LC neurons during opiate withdrawal.

A.E. Bennett Research Award. Anatomic basis for differential regulation of the rostrolateral peri-locus coeruleus region by limbic afferents.

BACKGROUND: Neurochemical and electrophysiological studies indicate that the locus coeruleus (LC)-norepinephrine system is activated by physiological and external stressors. This activation is mediated in part by corticotropin-releasing factor (CRF), the hypothalamic neurohormone that initiates the endocrine response to stress. We have previously shown that the central nucleus of the amygdala (CNA) provides CRF afferents to noradrenergic processes in the peri-LC area that may serve to integrate emotional and cognitive responses to stress. The bed nucleus of the stria terminalis (BNST) shares many anatomical and neurochemical characteristics with the CNA, including a high density of CRF-immunoreactive cells and fibers; however, recent studies have suggested that the CNA and the BNST may differentially regulate responses to conditioned and unconditioned fear, respectively, suggesting divergent neuroanatomical circuits underlying these processes. METHODS: In the present study, neuroanatomical substrates subserving regulation of the LC by the BNST were examined. Anterograde tract-tracing was combined with immunoelectron microscopy to test the hypotheses that BNST efferents target noradrenergic neurons of the LC and that these efferents exhibit immunolabeling for CRF. RESULTS: Ultrastructural analysis of sections that were dually labeled for the anterograde tracer biotinylated dextran amine (BDA) injected into the BNST and tyrosine hydroxylase (TH)-immunoreactivity demonstrated that BDA-labeled axon terminals formed synaptic specializations (primarily inhibitory) with TH-labeled dendrites and dendrites that lacked TH immunoreactivity. In contrast to CNA efferents that exhibited substantial immunolabeling for CRF, far fewer BDA-labeled terminals from the BNST in the rostrolateral peri-LC contained CRF. CONCLUSIONS: The present results indicate that the BNST may provide distinct neurochemical regulation of the peri-LC as compared to other limbic afferents such as the CNA. These data are interesting in light of behavioral studies showing that the CNA and BNST may be differentially involved in fear versus anxiety, respectively.

Efferent projections of the nucleus of the solitary tract to peri-locus coeruleus dendrites in rat brain: evidence for a monosynaptic pathway.

Locus coeruleus (LC) neurons respond to autonomic influences, are activated by physiological stressors, and discharge in parallel with peripheral sympathetic nerves. The circuitry underlying modulation of LC activity by physiological manipulations (i.e., hemodynamic stress, hypovolumia) remains unclear. Specifically, monosynaptic projections from primary baroreceptor centers to the LC have been suggested by electrophysiological studies but have not been unequivocally established. Light microscopic anterograde tract-tracing studies have previously shown that neurons originating in the nucleus of the solitary tract (NTS) project to a region of the rostrodorsal pontine tegmentum, which contains noradrenergic dendrites of the LC; however, it is not known whether these NTS efferents specifically target LC dendrites. Therefore, we combined peroxidase labeling of biotinylated dextran amine (BDA) or Phaseolus vulgaris-leucoagglutinin (PHA-L) from the NTS with gold-silver labeling for tyrosine hydroxylase (TH) in the rostrolateral peri-LC region. Injections placed into neighboring nuclei (nucleus gracilis, hypoglossal nucleus) served as controls. Only injections centered in the NTS produced anterograde labeling in peri-LC regions containing TH processes. By electron microscopy, BDA- or PHA-L-labeled axon terminals originating from the NTS contained small, clear, and some large dense-core vesicles and formed heterogeneous synaptic contacts characteristic of both excitatory- and inhibitory-type transmitters. Approximately 19% of the BDA and PHA-L axon terminals examined originating from the commissural portion of the NTS formed synaptic specializations with dendrites exhibiting TH immunoreactivity in the peri-LC. These results demonstrate that neurons projecting from the cardiovascular-related portion of the NTS target noradrenergic dendrites, indicating that barosensitive NTS neurons may directly modulate the activity of LC neurons and may serve to integrate autonomic responses in brain by influencing the widespread noradrenergic projections of the LC. In addition, these findings demonstrate that extranuclear dendrites are an important termination site for afferents to the LC.

Cellular interactions between axon terminals containing endogenous opioid peptides or corticotropin-releasing factor in the rat locus coeruleus and surrounding dorsal pontine tegmentum.

Recent evidence suggests that certain stressors release both endogenous opioids and corticotropin-releasing factor (CRF) to modulate activity of the locus coeruleus (LC)-norepinephrine (NE) system. In ultrastructural studies, axon terminals containing methionine(5)-enkephalin (ENK) or CRF have been shown to target LC dendrites. These findings suggested the hypothesis that both neuropeptides may coexist in common axon terminals that are positioned to have an impact on the LC. This possibility was examined by using immunofluorescence and immunoelectron microscopic analysis of the rat LC and neighboring dorsal pontine tegmentum. Ultrastructural analysis indicated that CRF- and ENK-containing axon terminals were abundant in similar portions of the neuropil and that approximately 16% of the axon terminals containing ENK were also immunoreactive for CRF. Dually labeled terminals were more frequently encountered in the "core" of the LC vs. its extranuclear dendritic zone, which included the medial parabrachial nucleus (mPB). Triple labeling for ENK, CRF, and tyrosine hydroxylase (TH) showed convergence of opioid and CRF axon terminals with noradrenergic dendrites as well as evidence for inputs to TH-labeled dendrites from dually labeled opioid/CRF axon terminals. One potential source of ENK and CRF in the dorsal pons is the central nucleus of the amygdala (CNA). To determine the relative contribution of ENK and CRF terminals from the CNA, the CNA was electrolytically lesioned. Light-level densitometry revealed robust decreases in CRF immunoreactivity in the LC and mPB on the side ipsilateral to the lesion but little or no change in ENK immunoreactivity, confirming previous studies of the mPB. Degenerating terminals from the CNA in lesioned rats were found to be in direct contact with TH-labeled dendrites. Together, these data indicate that ENK and CRF may be colocalized to a subset of individual axon terminals in the LC "core." The finding that the CNA provides, to dendrites in the area examined, a robust CRF innervation, but little or no opioid innervation, suggests that ENK and CRF axon terminals impacting LC neurons originate from distinct sources and that terminals that colocalize ENK and CRF are not from the CNA.

Evidence for coexistence of enkephalin and glutamate in axon terminals and cellular sites for functional interactions of their receptors in the rat locus coeruleus.

The authors previously showed that a subset of axon terminals in the locus coeruleus (LC) contains methionine5-enkephalin (ENK) and gamma-aminobutyric acid (GABA) immunoreactivities. However, numerous ENK-labeled terminals lacked GABA and exhibited synaptic specializations that were characteristic of excitatory-type transmitters. To determine whether ENK coexists with glutamate in the LC, preembedding immunoperoxidase detection of ENK or immunogold-silver was combined with postembedding identification of glutamate using a gold marker. Indeed, 28% of the ENK-labeled axon terminals examined (n = 250 axon terminals) also contained glutamate. To define further sites for functional interactions between opiate ligands and excitatory amino acid receptors, the ultrastructural localization of the mu-opioid receptor (MOR) was examined with respect to either the kainate receptor (KAR) or the R1 subunit of the N-methyl-D-aspartate (NR1)-type glutamate receptor in the LC. Gold-silver labeling for MOR and peroxidase labeling for either KAR or NR1 indicated that the MOR often was localized to the plasma membrane of dendrites that also exhibited immunolabeling for either glutamate receptor subtype. In contrast to the KAR, which was identified primarily in somata and dendrites, NR1 immunoreactivity also was found frequently in axon terminals as well as in glial processes. Glial processes containing NR1 occasionally exhibited immunolabeling for MOR and sometimes were directly apposed to MOR-containing dendrites in the LC. Furthermore, NR1-labeled receptors in axon terminals sometimes were presynaptic to MOR-labeled dendrites. The authors concluded that ENK and glutamate may be cotransmitters in LC afferents. Moreover, ligands at the KAR may modulate directly MOR-containing neurons in the LC, whereas actions at NR1 receptors may affect opioid-sensitive neurons through multiple cellular mechanisms, i.e., through presynaptic, postsynaptic, or glial actions.

Preoperative predictors of postoperative pain.

This study attempted to predict postoperative pain from preoperative level of anxiety and the amount of information patients possessed regarding their surgery. Pain was assessed via the McGill Pain Questionnaire (MPQ) and a measure of pain complaints--number of analgesics taken. High levels of state anxiety and a high degree of information predicted the Present Pain Intensity measured of the MPQ, but did not predict the Pain Rating Index portion of the MPQ. The number of analgesics taken was predicted from the amount of information but not the level of presurgical anxiety. Biographical variables were unrelated to postoperative pain. The results were discussed in terms of State-Trait Anxiety theory, Janis' curvilinear prediction model and a contextual perspective of information imparting.

A sandwich type acridinium-linked immunosorbent assay (ALISA) detects soluble ErbB1 (sErbB1) in normal human sera.

The epidermal growth factor receptor (ErbB1) is overexpressed in various human tumor-derived cell lines and neoplasms, where it is believed that receptor dysregulation plays a role in oncogenic transformation and tumor progression. In addition to the ErbB1 holoreceptor, numerous studies demonstrate that cells synthesize soluble or secreted forms of ErbB1, i.e., sErbB1. Overexpression of ErbB1 in a variety of tumors has led us to hypothesize that sErbB levels also may be altered during oncogenesis, tumor progression, and/or metastasis; and that these molecules may be useful tumor biomarkers. To address this hypothesis we have developed an acridinium-linked immunosorbent assay (ALISA) specific for the extracellular domain of ErbB1 that can be used to quantify the levels of sErbB1 molecules in body fluids and conditioned culture media. This assay can also detect full-length ErbB1 in cell and tissue extracts. Our ALISA is characterized by high sensitivity (intra-assay LLD < 1 fmol/ml), a broad linear range (approximately 1 to 4000 fmol/ml), and good reproducibility (CVs < 10%). Specificity experiments show that this ALISA detects p170 ErbB1 and soluble forms of ErbB1 that embody extracellular subdomains I through IV, but not forms of sErbB1 lacking subdomain IV. Our ALISA does not detect full-length ErbB2, ErbB3, or ErbB4; or p105 soluble ErbB2. We report that serum sErbB1 levels of healthy women (median = 3716 fmol/ml), ranging in age from 43 to 76 years, differ significantly from those of healthy men (median = 24,512 fmol/ml), ranging in age from 25 to 79 years. Additional analyses do not indicate that serum sErbB1 levels change with age in either healthy men or women. Immunoprecipitation experiments show that monoclonal antibodies specific for extracellular epitopes of ErbB1 completely neutralize the detection of sErbB1 in normal human sera by ALISA. Finally, we show by immunoprecipitation and Western immunoblot analyses with monoclonal antibodies specific for the extracellular domain of ErbB1 that normal human female and male sera contain a approximately 110-kDa protein. We conclude that our ALISA is measuring the relative levels of this p110 sErbB1 analog in normal human sera. Our ALISA, therefore, should be useful for measuring the levels of ErbB1 and sErbB1 molecules in tumor biopsy specimens and body fluids, respectively, and for determining whether sErbB1, like ErbB1, is a useful tumor biomarker.

A major cis activator of the IRBP gene contains CRX-binding and Ret-1/PCE-I elements.

PURPOSE: Interphotoreceptor retinoid binding protein (IRBP) is expressed exclusively and to high levels in photoreceptive cells. This study was an attempt to delineate the minimal regulated control region of the murine IRBP promoter involved in this expression pattern. METHODS: Fragments of the mouse IRBP 5' flanking region were tested for promoter activity in transient transfections of embryonic chick retina cells in primary culture. Electrophoretic mobility shift assays were used to identify specific cis-acting DNA elements within these fragments. RESULTS: Nested deletion analysis of a 1783 bp fragment of the murine IRBP 5' flanking region shows that high promoter activity is maintained with truncated fragments as short as 70 bp 5' to transcription start, but is lost with truncation to 45 bases. The 1783 bp promoter is active in cultures of retina cells but not brain cells or fibroblasts. The 70 bp fragment is active in retina and brain cells but not fibroblasts. Within retina cell cultures, the 1783 bp fragment is active in photoreceptor-like and amorphous or unidentifiable cells whereas the 70 bp is additionally active in multipolar neuron-like cells. The -70 to -45 interval contains Ret-1/PCE-I (AATTAG in the IRBP gene), a proposed retina-specific consensus sequence cis element, and a same-strand reversed copy of this sequence, GATTAA, the consensus binding element of the photoreceptor-specific trans-acting factor CRX. Mutation of either element suppresses promoter activity. Paralleling promoter tissue-specificity, the -70 to -45 fragment binds a sequence-specific protein complex found in retina and brain extracts but not fibroblasts. Mutation of both or either element inhibits this binding. CONCLUSIONS: These data suggest that a trans-acting complex binds a cis-element in the -70 to -45 sequence. This binding fully activates transcription but confers only partial tissue-specificity to IRBP gene expression.

The role of pH in altering serum ionized calcium concentration.

Although parathormone primarily determines normal ionized serum calcium concentration [Ca++] over the long term, it has little impact in the acute situation. Nonhormonal changes in [Ca++] have been related to acute changes in serum pH, but these have been believed small. With use of an experimental model of acute pancreatitis, we measured changes in [Ca++] and related them to changes in other serum constituents known to affect it. All 18 animals studied experienced a decrease in total serum calcium concentration [CaT]. Changes in [CaT] correlated only with changes in protein-bound calcium concentration [CaP] (r = 0.98, p less than or equal to 0.0005). They did not correlate independently with changes in albumin, globulin, or total protein concentration. [CaP] varied as a function of albumin, globulin, and phosphate concentration and pH according to the equation: [CaP] = 17.9 +/- 0.89 [albumin] = 0.68 [globulin] - 2.5 pH + 0.12 [phosphate]. Calculated values for [CaP], when this equation was used, correlated strongly with observed values for [CaP] (r = 0.81, p less than or equal to 0.0005). Measured [Ca++] increased in the animals early during pancreatitis and then returned to baseline levels. A few animals experienced ionized hypocalcemia. [Ca++] correlated only with changes in pH (r = 0.87, p less than or equal to 0.02). The calculated response slope was delta [Ca++]/delta pH = -2.9. It is concluded that pH has a greater effect on [Ca++] than previously recognized. The major determinant of [CaT] during periods of rapid physiologic change appears to be [CaP] while that for [Ca++] is pH.

Candida and perforated peptic ulcers.

Patients with perforated peptic ulcers who have Candida isolated from peritoneal culture have been noted to have a poor prognosis. Therefore treatment of such patients with systemic antifungal agents has been considered. Because of the toxicity and expense of such therapy, a review of the association was performed. During 1980 to 1985, 48 patients were operated on for benign perforated ulcer. The mean age of the patient group was 66 years. Intraoperative cultures were obtained in 38 patients. Microorganisms were isolated in 28 (74%) patients. Candida was isolated in 16 (57%) of the positive cultures. The overall mortality rate was 16.7%. The mortality rate for patients 65 years of age or older was 25% compared with 0% for those younger than 65 years old. The mortality rate for patients with Candida in their peritoneal fluid was 18.8%. No patient was treated with systemic antifungal agents. No patient developed candidiasis. Of the 16 patients in whom Candida was isolated, it was the only organism in 10 patients and was found in mixed culture with bacteria in six. The mortality rate for patients with Candida alone was 0%. The mortality rate for patients with mixed cultures was 50%. The presence of mixed cultures correlated strongly with both advanced patient age and shock. These factors have previously been correlated with death. It is concluded that the association between peritoneal Candida and excessive death from perforation is linked by an intervening association to advanced age and shock. In this setting, Candida does not appear to be normally pathogenic and does not require systemic antifungal therapy.

A study of the on-duty hours of surgical residents.

A time study was done to ascertain the number of hours spent in the hospital and the types of duties performed by residents enrolled in a multiple-institution, university-sponsored surgical training program. On the average, residents in the Wright State University program spent 90.1 +/- 27.1 hours in the hospital per week. Direct patient care activities required 62.7 +/- 18.8 hours (69.6%) of the average workweek. Purely educational endeavors accounted for 10.0 +/- 6.1 hours (11.1%) of the workweek. Ancillary tasks consumed an average of 8.5 +/- 8.5 hours (9.4%) of the surgical residents' time on duty per week. House officers did obtain a mean of 9.1 +/- 11.0 hours of sleep in those working hours (10.1% of the total time spent in the hospital). Although much variation existed among hospitals in the program, on-duty hours were greater in the private hospitals compared to the federal hospitals; the principal difference was the amount of time spent doing ancillary tasks (10.0 +/- 9.4 hours vs 5.6 +/- 5.6 hours; p less than 0.01). Hours worked by residents on private surgical services were longer than those of residents assigned to staff services (96.4 +/- 22.1 hours vs 86.0 +/- 29.3 hours; p less than 0.04). Again, the major difference was the greater amount of ancillary tasks performed by residents on private services (12.0 +/- 9.5 hours vs 6.2 +/- 7.0 hours; p less than 0.001). This finding could not be attributed to differences in patient census or turnover rates. Longer hours were noted on the general/thoracic surgery services compared to other surgical subspecialties (94.1 +/- 27.3 hours vs 81.5 +/- 24.8 hours; p less than 0.02). More time was spent in direct patient care on general/thoracic surgery (66.3 +/- 19.3 hours vs 54.9 +/- 15.1 hours; p less than 0.002). Despite the shorter workweek, residents on subspecialty rotations spent more time doing ancillary tasks (11.3 +/- 9.7 hours vs 7.3 +/- 7.6 hours; p less than 0.02). More than 60% of the residents' working hours in this program exceeded the arbitrary 80-hour limit, emphasizing the challenge of complying with the imposition of maximum work hours. We recommend that each program closely monitor the activities and hours of its residents to best respond to the pressures for regulation.

Incidental Meckel's diverticulectomy in adults.

BACKGROUND: Incidental Meckel's diverticulectomy has been advocated by some surgeons because of the lower associated morbidity and mortality in this setting than when resection is indicated. Others have argued that the low risk of complication occurrence does not justify prophylactic removal. The issue remains controversial. METHODS: Medical records of all adults undergoing Meckel's diverticulectomy at four acute care hospitals during the 5-year period 1989 through 1993 were retrospectively reviewed. Decision analysis was used to determine relative risks for incidental resection compared to indicated resection for a complication. RESULTS: Ninety patients underwent incidental diverticulectomy. Morbidity was 2% and mortality 0%. Four patients underwent resection for a complication of their diverticulum. Morbidity and mortality were each 0%. Combining these results with previously reported results and using decision analysis, the conditional probabilities of producing surgical morbidity or mortality in the adult population at risk by only resecting symptomatic diverticula are 0.2% and 0.04%, respectively. The comparable risks for resecting all incidentally discovered diverticula are 4.6% and 0.2%. CONCLUSIONS: Incidental diverticulectomy in adults should be abandoned.

Reduced use of resources by early tracheostomy in ventilator-dependent patients with blunt trauma.

BACKGROUND: Early tracheostomy has been advocated for ventilator-dependent patients with blunt trauma, but its advantages have not been examined critically. METHODS: We retrospectively reviewed our experience with all patients with blunt trauma undergoing tracheostomy during the 6-year period from 1990 to 1995. Patients undergoing tracheostomy within the first 6 days of hospitalization were designated as early recipients (ET) and those undergoing the procedure at 7 or more days were defined as late recipients (LT). RESULTS: The entire study group consisted of 157 patients. The ET group contained 62 patients and the LT group contained 95 patients. No statistical differences were noted between the 2 groups with respect to sex distribution, injury severity scores, probability of survival scores, or mortality rates. The mean stay in the intensive care unit for the ET group was 15 days compared with 29 days for the LT group (P < or = .001). The mean total hospital stay for the ET group was 33 days compared with 68 days for the LT group (P < or = .001). The mean estimated per-patient hospital charges for only room and ventilator care were $36,609 for the ET group compared with $73,714 for the LT group. CONCLUSIONS: ET in this patient group resulted in significantly lowered use of resources with no adverse effect on outcome.

Determination of brain death with use of color duplex scanning in the intensive care unit setting.

OBJECTIVE: To determine if color flow duplex scanning (CFDS) can be used for rapid confirmation of presumed brain death. DESIGN: Pilot cohort study comparison of CFDS with radionuclide cerebral scanning (RCS) as the criterion standard. SETTING: Community-based level I trauma center intensive care unit. PATIENTS: Twenty-four patients who satisfied criteria for presumed brain death. MAIN OUTCOME MEASURE: Confirmation of presumed brain death. RESULTS: CFDS correctly identified 16 of 24 patients as brain dead, confirmed by RCS. Eight patients with brain flow on RCS were also correctly identified by CFDS. Only two of 24 patients survived their severe injuries. CONCLUSIONS: CFDS provides a uniform, cost-effective diagnostic tool for rapid confirmation of clinical brain death with 100% accuracy. Its use should complement RCS, given its rapid interpretation, portability, and economical assessment of presumed brain death.

Surgical aspects of Clostridium septicum septicemia.

Clostridium septicum is a virulent cause of gas gangrene and sepsis. Although thought to be rare, a survey of our affiliated hospitals for a recent five-year period disclosed eight cases. Seven of the eight had an occult malignant neoplasm. The eighth patient was thought to be preleukemic. All seven malignant neoplasms involved the gastrointestinal tract. Four patients were admitted with gangrene of an extremity, three with abdominal pain, and one with both. In four patients, C septicum septicemia appeared in an extremity before the underlying gastrointestinal malignant neoplasm was recognized. Four patients had surgical therapy and two survived; four received medical therapy and one survived. Patients who have C septicum septicemia should be assumed to harbor an underlying malignant neoplasm until proved otherwise.

Opioid circuits originating from the nucleus paragigantocellularis and their potential role in opiate withdrawal.

Neurons in the rat nucleus paragigantocellularis (PGi), located in the ventrolateral medulla, send collateral projections to the locus coeruleus (LC) and to the nucleus of the solitary tract (NTS). The present study examined whether neurons in the PGi that project to both the LC and NTS contain leucine(5)-enkephalin (ENK), and also whether opioid-containing neurons in the PGi are activated following withdrawal from opiates. Retrograde transport of Fluoro-Gold (FG) from the LC and transport of a protein-gold tracer from the NTS was combined with detection of an antibody directed against ENK in the PGi. Using fluorescence and brightfield microscopy, it was established that more than half of the neurons containing both FG and the protein-gold tracer, also exhibited immunolabeling for ENK. The most frequent location of triply labeled neurons was the retrofacial portion of the PGi. In a separate series, rats were chronically implanted with morphine or placebo pellets and, on the fifth day, were subjected to an intraperitoneal injection of naltrexone. Two hours following initiation of withdrawal, rat brains were obtained and processed for detection of c-fos and in situ hybridization labeling of preproenkephalin (PPE) mRNA. Naltrexone injections into morphine-dependent rats caused a dramatic increase in c-fos as compared to control rats. Approximately 66% of the c-fos-labeled neurons exhibited labeling for PPE mRNA. These were also enriched in the retrofacial portion of the PGi. Taken together, the present data indicate that withdrawal from opiates engages opioid neurons in the PGi, some of which may coordinate activity of neurons in both the NTS and the LC.

Combined use of topical and systemic antibiotics.

An animal wound model was used to compare the effectiveness of topical and systemic antibiotics and to examine the validity of using a combined regimen of both routes of antibiotic delivery. Gross infection rates and wound bacterial concentrations were determined after contamination with Staphylococcus aureus or Escherichia coli. Both moderate (10(8) colony-forming units [CFU]) and heavy (10(12) CFU) contamination were studied for each organism. Following moderate contamination, topical and systemic antibiotics were equally effective in reducing both wound bacterial content and infection rate, but there was no benefit from the combined use of both modes of antibiotic delivery. An additive effect of the combined regimen was noted only when the level of wound contamination was heavy.

Prevention of hypocalcemia by administration of homologous plasma during experimental hemorrhagic pancreatitis in the pig.

Pancreatitis was induced in fifteen immature pigs while five additional pigs underwent sham laparotomy. Animals with pancreatitis were separated into three groups of five each with respect to fluids administered after pancreatitis was induced. Each pig in group A and the control group received normal saline, 300 ml/hour for 8 hours. Pigs in group B received pig plasma at 150 ml/hour plus normal saline at 150 ml/hour for 8 hours. Pigs in group C received pig plasma at 50 ml/hour plus normal saline at 50 ml/hour for 24 hours. Values for serum hematocrit total protein, and total calcium, were measured preoperatively and 4, 8, and 24 hours postoperatively. Control animals and group B animals experienced no change in any parameter. Group A, animals sustained transient severe hemoconcentration, permanent severe hypoproteinemia, and hypocalcemia. Group C animals displayed a transient moderate hemoconcentration and a moderate but sustained decrease in calcium concentration. It is concuded that the hypocalcemia occurring during experimental hemorrhagic pancreatitis is directly related to the early hypovolemia and can be prevented by preventing the hypovolemia.