Counted cycles method to measure the block inception time of kiloHertz frequency mammalian motor nerve block.

BACKGROUND: Kilohertz frequency alternating currents (KHFAC) produce rapid nerve conduction block of mammalian peripheral nerves and have potential clinical applications in reducing nerve hyperactivity. However, there are no experimental measurements of the block inception time (BIT) for the complete block of mammalian motor axons, i.e. the time from the start of delivery of the KHFAC to the axons reaching a fully blocked state. NEW METHOD: A "counted cycles" method (CCM) was designed to exploit characteristics of the onset response, which is typical of KHFAC block, to measure the BIT with a millisecond time resolution. Randomized and repeated experiments were conducted in an in-vivo rodent model, using trains of KHFAC over a range of complete cycle counts at three frequencies (10, 20, and 40 kHz). RESULTS: Complete motor nerve conduction block was obtained in the rat sciatic nerve (N = 4) with an average BIT range of 5 ms-10 ms. The fastest BIT measured was 2.5 ms-5 ms. There was no statistical difference between the block inception times for the three frequencies tested. COMPARISON WITH EXISTING METHODS: There are no comparable methods to measure the KHFAC BIT. CONCLUSION: The KHFAC BIT is faster than previously estimated. KHFAC motor nerve block is established in milliseconds. These results may assist in the design of methods to eliminate the onset response produced by KHFAC nerve block.

Reduction of the onset response in kilohertz frequency alternating current nerve block with amplitude ramps from non-zero amplitudes.

BACKGROUND: Kilohertz frequency alternating current (KHFAC) waveforms reversibly block conduction in mammalian peripheral nerves. The initiation of the KHFAC produces nerve activation, called the onset response, before complete block occurs. An amplitude ramp, starting from zero amplitude, is ineffective in eliminating this onset activity. We postulated that initiating the ramp from a non-zero amplitude would produce a different effect on the onset. METHODS: Experiments were conducted in an in vivo rat model. KHFAC was applied at supra block threshold amplitudes and then reduced to a lower sub block amplitude (25, 50, 75 and 90% of the block threshold amplitude). The amplitude was then increased again to the original supra block threshold amplitude with an amplitude ramp. This ramp time was varied for each of the amplitude levels tested. RESULTS: The amplitude ramp was successful in eliminating a second onset. This was always possible for the ramps up from 75 and 90% block threshold amplitude, usually from 50% but never from 25% of the block threshold amplitude. CONCLUSIONS: This maneuver can potentially be used to initiate complete nerve block, transition to partial block and then resume complete block without producing further onset responses.

Expression of luteinizing hormone/human chorionic gonadotropin receptor gene in benign prostatic hyperplasia and in prostate carcinoma in humans.

The findings that normal rat prostates express functional LH/hCG receptors led us to test the hypothesis that benign prostatic hyperplasia (BPH) and prostate carcinomas may also express this receptor gene. The data revealed the presence of LH/hCG receptor transcripts and receptor protein in normal and hyperplastic but not in atrophic glands present in BPH tissue. Smooth muscle and blood vessels in stroma of BPH tissue also contained receptors. Prostate carcinomas contain lower and more heterogeneous receptor levels than BPH tissue. Two human prostate cancer cell lines (LNCaP and DU 145) that were investigated showed the presence of a major 4.5-kilobase transcript and several minor transcripts and also the protein of LH/hCG receptors. However, androgen-sensitive LNCaP cells contained more receptors than androgen-insensitive DU 145 cells. In summary, we demonstrate for the first time that BPH and prostate cancer tissues and cell lines express LH/hCG receptor gene. These findings suggest that higher LH levels in aged men may play a role in BPH and/or prostate carcinomas.

Harvey ras (H-ras) point mutations are induced by 4-nitroquinoline-1-oxide in murine oral squamous epithelia, while squamous cell carcinomas and loss of heterozygosity occur without additional exposure.

Tumorigenesis is a multistep genetic process requiring several somatic mutations for neoplastic transformation. These mutations appear to be sequential, random, and independent events. However, we find linked, nonrandom ras mutations occurring during 4-nitroquinoline-1-oxide-induced tumorigenesis months after exposure to the carcinogen had ceased. The carcinogen had been topically applied to the oral cavity of CBA mice for 4 to 16 weeks. Dysplasia developed after 24 weeks, and carcinoma in situ and squamous cell carcinoma developed after 28 weeks. H-ras mutations were detected in 13 of 25 tissue specimens (10 of 14 invasive carcinomas and 2 of 4 carcinoma in situ, 1 of 5 dysplastic tissue, and 0 of 2 normal tissues). Approximately one-half of the tumors had G to A point mutations at codon 12 of the cellular H-ras proto-oncogene on mouse chromosome 7. None had codon 11, 13, or 61 mutations. Loss of heterozygosity occurred in 5 of 14 invasive cancers. Larger invasive squamous cell carcinomas consistently lost the wild-type allele, whereas preneoplastic lesions and small tumors were heterozygous for ras. This suggests a causal relationship between carcinogen treatment, H-ras activation, and initiation of tumorigenesis. The wild-type allele in mouse chromosome 7 is lost with the progression of tumorigenesis long after exposure to the carcinogen. Thus, loss of heterozygosity of the ras gene appears to occur without multiple carcinogen-induced mutations, i.e., as a result of a cascade of events induced by an earlier ras mutation.

4NQO carcinogenesis: a mouse model of oral cavity squamous cell carcinoma.

BACKGROUND: A murine model of oral cavity carcinogenesis is needed to study the molecular aspects of malignant transformation. 4-Nitroquinoline-1-oxide (4NQO), a water-soluble carcinogen, produces squamous cell carcinoma in rodents. Protocols were designed to investigate the temporal aspects of neoplastic transformation. METHODS: 4NQO was applied topically to mouse palates for up to 16 weeks. Mice were observed and killed from 24 to 49 weeks. RESULTS: A spectrum of lesions ranging from atypia to moderately differentiated invasive squamous cell carcinoma (SCC) was produced. The severity of the lesions corresponded to the duration of treatment and the length of observation. There was no gross or microscopic evidence of an inflammatory reaction to 4NQO. The lesions were focal and normal mucosa predominated in the treated mice. CONCLUSION: 4NQO reliably produced preneoplastic and malignant oral cavity lesions, which morphologically and histologically mimic human head and neck cancer. Lesions develop long after 4NQO exposure and without an inflammatory response. Thus, the model should be useful for molecular analysis of neoplastic transformation.

Increased expression of human chorionic gonadotropin/human luteinizing hormone receptors in adenomyosis.

Adenomyosis is a benign disease in women in which myometrium is invaded by endometrial glands and stroma. Our laboratory recently demonstrated that normal human endometrial glands and stroma express the hCG/LH receptor gene. This prompted us to investigate whether invading glands and stroma in adenomyosis also express this receptor gene. Fifteen hysterectomy specimens with confirmed histological diagnosis of adenomyosis were examined for hCG/LH receptors by in situ hybridization and immunocytochemistry. The results showed that invading glands contained more receptor mRNA and receptor protein than noninvading glands in the same endometrium. However, the degree of difference between invading and noninvading glands varied among the patients. The higher receptor expression in invading glands is specific because the invading and noninvading stroma showed similar receptor expression, invading and noninvading glands showed similar expression of cadherin, a cell adhesion receptor, and ectopic and eutopic endometrial glands from endometriosis showed similar hCG/LH receptor expression. In summary, the present results demonstrate that invading endometrial glands in adenomyosis selectively express more hCG/LH receptor mRNA and immunoreactive receptor protein than noninvading glands. Whether this increased receptor expression is the cause or a consequence of myometrial invasion of glands in unknown.

Short-term dietary copper deficiency does not inhibit angiogenesis in tumours implanted in striated muscle.

The effect of dietary copper deficiency on tumour growth, neovascularisation and microvascular integrity was studied in the rat cremaster muscle. Male, weanling Sprague-Dawley rats were fed purified diets which were copper deficient (< 0.5 micrograms g-1 of diet) or copper adequate (5 micrograms g-1 of diet). Seven days after initiation of diets, a chondrosarcoma was implanted in the cremaster muscle of each rat. Five, 10 or 20 days after tumour implantation, rats were anesthetised and their cremasters prepared for observation by intravital microscopy. Intraarterial injection of fluorescein isothiocyanate-conjugated albumin and subsequent observation of fluorescence in the perivascular space indicated no difference in microvascular albumin leakage between the tumour vasculature of copper deficient and copper adequate rats. Neither tumour growth (assessed by wet weight), vascular density (assessed by light microscopy), nor any ultrastructural characteristics of the tumour or its vasculature (assessed by electron microscopy) were affected by copper deficiency. In view of findings by others which indicate changes in tumour characteristics with copper deficiency, we conclude that the copper dependency of tumour growth and vascularisation is a function of the type of tumour, the host tissue, or the conditions of copper depletion.

Progressive microcirculatory changes caused by hypercholesterolemia in rats.

The progressive microcirculatory changes caused by hypercholesterolemia were studied in the rat cremaster model by use of intravital microscopy. Male Sprague-Dawley rats were fed either a normal chow diet or a chow diet supplemented with 1% cholesterol and 0.5% cholic acid for 1, 3, or 5 wk before experimentation. After 3 wk on the diet, hypercholesterolemia produced a significantly decreased vasoconstrictor response to norepinephrine in both arterioles and venules. After 5 wk, there was also significantly reduced macromolecular leakage induced by exogenous histamine and compound 48/80 in the high-cholesterol group. However, there was no change in the degree of base-line macromolecular leakage. Platelet thrombi formation induced by light activation of intravascular fluorescein isothiocyanate tagged to bovine serum albumin was slightly increased by hypercholesterolemia. Despite these microcirculatory changes there was no microscopic evidence of atheromatous pathology after 5 wk on the cholesterol diet. These results suggest a progressive nonspecific receptor desensitization and decreased inflammatory response shortly after the initiation of elevated serum cholesterol but before any histological evidence of atherosclerosis.

Postinfarction rupture of the left ventricular free wall: clinicopathologic correlates in 100 consecutive autopsy cases.

Among 100 consecutive autopsied cases of postinfarction rupture of the left ventricular free wall, 51% of the deaths were in-hospital and 49% were out of hospital. There were 51 men (mean age, 72 years) and 49 women (mean age, 76 years); 81% had multivessel disease. All had severe obstruction of at least one major epicardial coronary artery (98 atherosclerotic, one thrombotic, and one embolic). Acute coronary thrombosis was present in 73 cases and occurred on an atherosclerotic plaque in 72, 49 (68%) of which had associated plaque rupture. In 83 cases, the ruptured infarction represented the subject's first myocardial infarction. Despite a history of hypertension in 55 cases, appreciable left ventricular hypertrophy was observed in only 19 cases. By histopathologic age of infarction, 13 ruptures occurred during the first day, 45 between days 2 and 5, and 22 on days 6 and 7; thus, 58% occurred within 5 days and 80% within 7 days. The mid-ventricle was the most frequent site of rupture (66%). Ruptures most frequently involved the lateral aspect of the left ventricular free wall (44%). In 66 cases, the rupture tract occurred along the interface between viable and necrotic myocardium. Our findings support the observations of others that the risk factors for postinfarction left ventricular free wall rupture include age greater than 60 years, female gender, preexisting hypertension, absence of left ventricular hypertrophy, first myocardial infarction, and midventricular or lateral wall transmural infarctions.

Microvascular responses in copper-deficient rats.

In this study on copper deficiency, the rat crewmaster microcirculation was used as a model for endogenous histamine release and platelet thrombi formation. Male Sprague-Dawley rats were fed either a copper-supplemented diet (CuS, 5 ppm) or a copper-deficient diet (CuD, 0 ppm) for 5 wk before experimentation. The crewmasters of anesthetized rats were spread in a Krebs-filed tissue bath. In venules of CuS animals, photoactivation of intravascular fluorescein isothiocyanate tagged to bovine serum albumin caused significant platelet aggregation and reduction of red blood cell column diameter (RBCCD) by 40 min and stasis of flow by 60 min. In CuD animals there was only minor platelet aggregation and no reduction in RBCCD. Platelet aggregometry studies did not demonstrate reduced platelet aggregation in the CuD group, suggesting that copper deficiency alters the endothelium to inhibit adhesion. Compound 48/80 (1.0 and 10.0 microgram/ml) induced macromolecular leakage in both CuS and CuD groups, with the response in the CuD animals being significantly greater. The results demonstrate that copper deficiency results in alterations of the regulatory mechanisms governing inflammation and thrombosis.

Aortoenteric fistulas. A study of 28 autopsied cases spanning 25 years.

Among 28 autopsied patients with aortoenteric fistulas, the mean age was 67 years (range, 19 to 91 years) and 23 (82%) were men. The most common causes were aortobifemoral bypass grafts (16 cases [57%]) and gastrointestinal carcinomas (6 cases [21%]). Fistulas developed at proximal anastomosis sites in 15 of 16 patients with grafts and were associated with radiation injury in 3 of 6 patients with carcinomas. Aortoenteric fistulas involved the duodenum in 16 (57%), esophagus in 9 (32%), and other gastrointestinal sites in 3 patients (11%). They involved the abdominal aorta in 20 cases (71%) and descending thoracic aorta in 8 cases (29%). Exsanguination from aortoenteric fistulas was the cause of death in 23 cases (82%). Major risk factors for aortoenteric fistulas are aortic bypass grafts and gastrointestinal carcinomas.

The response of the rat urinary bladder microcirculation to photodynamic therapy.

Light activation of dihematoporphyrin ether (photofrin II) has been used in the treatment of bladder tumors, yet the effects of this treatment on the normal urinary bladder microcirculation have not been determined. This study involved the use of in vivo television microscopy to observe the effects of light activation (530 to 560 nm., 175 mW/cm.) on the urinary bladder microcirculation of female Sprague-Dawley rats. Animals pretreated with dihematoporphyrin ether 30 minutes prior to light activation had high serum and low tissue concentrations of the photosensitizer and activation resulted in a statistically significant reduction of red blood cell column diameter in both arterioles and venules. The reduction was primarily due to mural thrombus formation with the occlusion remaining 60 minutes after activation. Animals pretreated 48 hours before activation had low serum and high tissue concentrations of dihematoporphyrin ether and activation had no microcirculatory effects apart from occasional platelet aggregation. These results suggest that the photodynamic effect on normal (non-neoplastic) tissue treated more than 48 hours after administration of dihematoporphyrin ether is probably due to a direct effect of light and the sensitizer on the smooth muscle of the bladder rather than an effect on the microcirculation.

Surgical pathology of the tricuspid valve: a study of 363 cases spanning 25 years.

Surgical pathologic features of the tricuspid valve were reviewed in 363 patients who had undergone tricuspid valve replacement at our institution during the period 1963 through 1987. Valves were purely regurgitant in 74%, stenotic and regurgitant in 23%, and purely stenotic in 2%; two valves were neither stenotic nor regurgitant. Among 269 purely insufficient tricuspid valves, the four most common causes were postinflammatory disease (41%), congenital disorder (32%), pulmonary venous hypertension (21%), and infective endocarditis (4%). Of 92 cases of tricuspid stenosis, with or without regurgitation, postinflammatory disease was observed in 92%. Female patients accounted for 66% of the 363 cases, including 84% of those with postinflammatory disease and 64% of those with pulmonary venous hypertension. In contrast, male patients accounted for 73% of cases with endocarditis and 61% with congenital heart disease. Although postinflammatory disease accounted for 53% of the 363 cases, its relative frequency diminished from 79% during 1963 through 1967 to only 24% during 1983 through 1987. This trend may reflect the decreasing incidence of acute rheumatic fever reported in Western countries. During the same time interval, the relative frequency of congenital heart disease as a cause of tricuspid dysfunction increased from 7% to 53%, and it is currently the most common cause in our surgical population. This finding apparently reflects changes in patient referral practices and the development of new operative procedures.

Identification of atrial natriuretic factor within ventricular tissue in hamsters and humans with congestive heart failure.

In normal mammals, atrial natriuretic factor (ANF) is present within atrial myocardial cells but is absent from ventricular myocardium. In primitive organisms ANF is present within both atria and ventricle, suggesting that the ventricle may participate both in the synthesis and release of the hormone. The current study was designed to test the hypothesis that ventricular ANF develops as a homeostatic response to intravascular volume overload. Studies were performed on cardiac tissue obtained from (i) normal and cardiomyopathic hamsters, (ii) autopsied humans with and without cardiac disease, and (iii) living humans with congestive heart failure (CHF) undergoing diagnostic right ventricular endomyocardial biopsy. The myocardium was examined for the presence of immunoreactive ANF using a two-stage immunohistochemical technique, with nonimmune rabbit sera used as a negative control. There was unequivocal evidence of focal subendocardial deposits of immunoreactive ANF present in both of the ventricles of all six cardiomyopathic hamsters, four of five autopsied human subjects with CHF, and five of seven biopsied humans. No immunoreactive ANF was observed within the ventricular myocardium of control hamsters or normal humans. Utilizing crude tissue homogenates and radioimmunoassay techniques, the quantity of ANF was determined in cardiac atria, ventricles, and noncardiac skeletal muscle. Heart failure is characterized by a reduction in atrial ANF and an increase in ventricular ANF. This study demonstrates immunoreactive ANF is present within the ventricular myocardium in cardiomyopathic hamsters and humans with CHF, and suggests that the ventricle may be capable of responding to chronic volume overload by producing ANF.

Malignant neoplastic emboli to the coronary arteries: report of two cases and review of the literature.

Two patients were seen with malignant neoplastic emboli to the coronary arteries. One, a 61-year-old woman with a malignant fibrous histiocytoma of the thigh and a solitary pulmonary metastatic lesion, died of an acute myocardial infarction due to a neoplastic coronary embolus after lobectomy. The other, a 51-year-old woman with bronchogenic adenocarcinoma, died of extensive cerebral metastases. At autopsy, she also was found to have had an acute myocardial infarction associated with a neoplastic coronary embolus.

Sudden death as the initial manifestation of primary pulmonary hypertension. Report of four cases.

Four autopsy cases are presented in which sudden death was the initial manifestation of primary pulmonary hypertension. The arteriopathy was plexogenic in two cases (a 3-year-old girl and a 16-year-old boy) and was thrombotic in two other cases (55- and 59-year-old women). The diagnosis of primary pulmonary hypertension, particularly in forensic cases, requires that the pathologist be especially aware of the possibility and that a careful evaluation of multiple sections of lung be performed. Determination of the histopathologic type also is important because some forms of the disease may be familial and may be treatable in other family members if they are detected early.

Traumatic rupture of Ionescu-Shiley aortic valve after the Heimlich maneuver.

A 74-year-old woman who had undergone aortic valve replacement with an Ionescu-Shiley bioprosthesis was evaluated and treated because aortic insufficiency developed after the application of the Heimlich maneuver. Pathologic examination of the explanted valve disclosed a cuspid perforation and an adjacent tear of a second cusp at its insertion into the valve strut. Patients with unexplained acute prosthetic insufficiency should be questioned as to whether the Heimlich maneuver has been previously performed.

Temporal changes in the causes of aortic stenosis: a surgical pathologic study of 646 cases.

Among 646 patients with pure aortic stenosis who underwent valve replacement at our institution between 1981 and 1985, the three most frequent causes were calcification of congenitally bicuspid aortic valves (38%), degenerative (senile) calcification of tricuspid aortic valves (33%), and postinflammatory (presumably rheumatic) calcification and fibrosis (24%). Among the 324 patients younger than 70 years of age, calcified bicuspid valves were observed in 50%. In contrast, among 322 patients 70 years of age or older, degenerative calcification accounted for 48% of the stenotic aortic valves. During the 5 years of the study, the relative frequency of postinflammatory disease decreased from 30% to 18%, and that of bicuspid valves decreased from 37% to 33%. In contrast, the relative frequency of degenerative calcification increased from 30% to 46%. Consequently, degenerative (senile) calcification is currently the most common cause of aortic stenosis among patients undergoing valve replacement at our institution. This finding may be related to changes in life expectancy in the general population, alterations in patient referral practices, and an increased willingness of surgeons to operate on older patients. Regardless of cause, the observed temporal changes in etiologic factors for aortic stenosis may indicate a potential source of increasing health-care costs among the elderly population.