Integrative physiology of splanchnic glutamine and ammonium metabolism

The substrates for hepatic ureagenesis are equimolar amounts of ammonium and aspartate. The study design mimics conditions in which the liver receives more NH(+)(4) than aspartate precursors (very low-protein diet). Fasted dogs, fitted acutely with transhepatic catheters, were infused with a tracer amount of (15)NH(4)Cl. From arteriovenous differences, the major NH(+)(4) precursor for hepatic ureagenesis was via deamidation of glutamine in the portal drainage system (rather than in the liver), because there was a 1:1 stoichiometry between glutamine disappearance and NH(+)(4) appearance, and the amide (but not the amine) nitrogen of glutamine supplied the (15)N added to the portal venous NH(+)(4) pool. The liver extracted all this NH(+)(4) from glutamine deamidation plus an additional amount in a single pass, suggesting that there was an activator of hepatic ureagenesis. The other major source of nitrogen extracted by the liver was [(14)N]alanine. Because alanine was not produced in the portal venous system, we speculate that it was derived ultimately from proteins in peripheral tissues.

A role for Id-1 in the aggressive phenotype and steroid hormone response of human breast cancer cells

The helix-loop-helix protein Id-1 inhibits the activity of basic helix-loop-helix transcription factors, and is an important regulator of cell growth and tissue-specific differentiation. We have shown (P. Y. Desprez et al., Mol. Cell. Biol., 18: 4577-4588, 1998) that ectopic expression of Id-1 inhibits differentiation and stimulates the proliferation and invasiveness of mouse mammary epithelial cells, and that there is a correlation between the levels of Id-1 protein and the aggressiveness of several human breast cancer cell lines. Here, we show that aggressive and metastatic breast cancer cells express high levels of Id-1 mRNA because of a loss of serum-dependent regulation that is mediated by a 2.2-kb region of the human Id-1 promoter. Three lines of evidence suggest that unregulated Id-1 expression may be an important regulator of the aggressive phenotype of a subset of human breast cancer cells: (a) a constitutively expressed Id-1 cDNA, when introduced into a nonaggressive breast cancer cell line (T47D), conferred a more aggressive phenotype, as measured by growth and invasiveness; (b) Id-1 was an important mediator of the effects of sex steroid hormones on T47D cell proliferation. Estrogen stimulated proliferation and induced Id-1 expression, whereas progesterone inhibited proliferation and repressed Id-1 expression. Progesterone repressed Id-1 expression, at least in part by repressing transcription. Most importantly, an antisense oligonucleotide that reduced Id-1 protein levels reduced the ability of estrogen to stimulate cell proliferation, whereas constitutive Id-1 expression rendered cells refractory to growth inhibition by progesterone; and (c) using a limited number of breast cancer biopsies, we showed that Id-1 was more frequently expressed in infiltrating carcinomas compared with ductal carcinomas in situ. Our results suggest that Id-1 can control the malignant progression of breast cancer cells, particularly that mediated by sex steroid hormones. Moreover, Id-1 has the potential to serve as a marker for aggressive breast tumors.

Differential modulation of nociceptive responses to mu and kappa opioid receptor directed drugs by blood glucose in experimentally induced diabetes rats

The study has evaluated the effect of diabetes associated hyperglycaemia on nociception and antinociception induced by morphine, buprenorphine and pentazocine in female albino rats. Rats were allocated into 3 groups of 20 each--group I consisted of control having normal blood glucose levels (BGLs), group II consisted of streptozotocin-induced diabetics (STZ-D) having hyperglycaemia and group III consisted of diabetic rats controlled with insulin treatment. Immediately before and 15, 30 min, 1, 2 and 3 hr after injection with test drugs, rats were subjected to a thermal noxious stimulus using tail withdrawal from hot water and tail-flick latencies (TFL) so generated were recorded. Similarly, before and 30, 45 min and 1 hr after injection with drugs rats were subjected to abdominal writhing with hypertonic saline and number of writhes were counted per 90 sec. In STZ-D animals (BGLs 317.95 +/- 3.8 mg/dl) a decreased TFL with an increase in the number of writhes compared to control and diabetes controlled with insulin treatment was observed. Percent maximum possible effect of morphine (5 mg/kg, s.c.) and buprenorphine (2 mg/kg, s.c.) was significantly lower when compared to control as well as STZ-D controlled with insulin treatment groups. Similarly percent protection from writhing of morphine (0.05 mg/kg, s.c.) and buprenorphine (0.01 mg/kg, s.c.) was significantly less in comparison to control and STZ-D controlled with insulin treatment group. However, percent maximum possible effect of pentazocine (20 mg/kg, s.c.) and percent protection from writhing of pentazocine (1 mg/kg, s.c.) was significantly high in STZ-D rats when compared to control and STZ-D rats controlled with insulin treatment groups. The results suggest that both mu and kappa--opioid receptors may be modulated by blood glucose levels possibly involving cellular energetics mediated change in potassium (KATP) channels in females rats, albeit differentially.

Community studies on prevalence of HBsAg in two urban populations of southern India

OBJECTIVE

To find out prevalence of HBsAg in general population, especially in under-five children.

SETTING

Bangalore and Rajahmundry towns in southern India.

METHODS

Localities were chosen as the sampling units in each town. About 10-20 households were randomly selected from each locality. Only the youngest but apparently healthy person present in the household was interviewed for age, sex and history of jaundice any time in life. Mothers were interviewed to collect data for children below 15 years of age. Blood samples were collected from these persons on filter paper strips (18-mm diameter disc, Whatman filter paper No. 3) by finger prick method. The samples were tested for HBsAg by Micro ELISA (Ortho-Clinical Diagnostics).

RESULTS

Overall, 3.3% (95% CI, 2.0-4.5) of 737 persons in Rajahmundry and 4.2% (95% CI, 2.8-5.5) of 816 persons in Bangalore were found carriers of HBsAg. Age-specific or sex specific carrier rates were similar in Rajahmundry as well as in Bangalore. Most of the carriers (96%) denied having jaundice ever in life.

CONCLUSIONS

The results from this community based study are in agreement with the historical data from hospital based studies that about 3-5% of persons may be carriers of HBsAg and that the pool of chronic carriers of hepatitis B virus in India is built up in childhood and is then maintained in older children and adults. The results highlight the need of completing hepatitis B immunization during the infancy.

A RIA combined with SPE for the determination of a dual D2-receptor and beta2-adrenoceptor agonist, AR-C68397XX, in human plasma

A radioimmunoassay has been developed for the determination of AR-C68397XX, a dual D2-receptor and beta2-adrenoceptor agonist, in human plasma. The method incorporates solid phase sample extraction and is suitable for the determination of the analyte at pg ml(-1) concentrations. The antiserum was raised in Suffolk cross sheep following primary and booster immunisations with an immunogen prepared by conjugating a carboxyphenylmethyl derivative of AR-C68397XX, to bovine serum albumin. The radioligand was prepared by the 125I-labelled iodination of a derivative of AR-C68397XX. The solid phase extraction procedure, using octadecyl sorbent, was introduced to remove matrix interferences in the plasma and to enhance method sensitivity. The calibration range is 20-500 pg ml(-1), using 0.5 ml of undiluted human plasma sample.

Characterization of a panel of insertion mutants in human cytomegalovirus glycoprotein B

Glycoprotein B (gB; gpUL55) of human cytomegalovirus (HCMV) plays a critical role in virus entry and cell-to-cell spread of infection. To define the structure-function relationships in gB, a panel of linker-insertion mutations was generated throughout the coding region. This strategy yielded a panel of 22 mutants with four amino acid insertions and 3 large truncation mutants. Assessment of the mutant proteins' biosynthetic properties and folding patterns analyzed in context with predicted secondary features revealed novel insights into gB's structure and trafficking properties. All of the insertion mutants were able to assemble into oligomers, suggesting that oligomerization is tolerant of small insertions and/or that multiple regions of the protein may be involved. Computer algorithm predictions of gB's secondary structure indicate that the furin-recognized cleavage site falls within an exposed loop. This loop may be particularly sensitive to structural alterations, since insertions upstream and downstream of the cleavage site rendered the mutant proteins cleavage defective. In addition, a strong correlation existed between terminal folding and cleavage of gB. Interestingly, terminal folding was not correlated with delivery to the cell surface but may influence the rate of transport to the cell surface. Nine mutants, containing insertions in both the extracellular and intracellular portions of gB, retained wild-type structural properties. This panel of characterized gB mutants, the first of this type for an HCMV protein, will be a useful tool in dissecting the role of gB during HCMV infection.

Effect of dephostatin on intracellular free calcium concentration and amylase secretion in isolated rat pancreatic acinar cells

This study investigates the effects of dephostatin, a new tyrosine phosphatase inhibitor, on intracellular free calcium concentration ([Ca2+]i) and amylase secretion in collagenase dispersed rat pancreatic acinar cells. Dephostatin evoked a sustained elevation in [Ca2+]i by mobilizing calcium from intracellular calcium stores in either the absence of extracellular calcium or the presence of lanthanium chloride (LaCl3). Pretreatment of acinar cells with dephostatin prevented cholecystokinin-octapeptide (CCK-8)-induced signal of [Ca2+]i and inhibited the oscillatory pattern initiated by aluminium fluoride (AlF4), whereas co-incubation with CCK-8 enhances the plateau phase of calcium response to CCK-8 without modifying the transient calcium spike. The effects of dephostatin on calcium mobilization were reversed by the presence of the sulfhydryl reducing agent, dithiothreitol. Stimulation of acinar cells with thapsigargin in the absence of extracellular Ca2+ resulted in a transient rise in [Ca2+]i. Application of dephostatin in the continuous presence of thapsigargin caused a small but sustained elevation in [Ca2+]i. These results suggest that dephostatin can mobilize Ca2+ from both a thapsigargin-sensitive and thapsigargin-insensitive intracellular stores in pancreatic acinar cells. In addition, dephostatin can stimulate the release of amylase from pancreatic acinar cells and moreover, reduce the secretory response to CCK-8. The results indicate that dephostatin can release calcium from intracellular calcium pools and consequently induces amylase secretion in pancreatic acinar cells. These effects are likely due to the oxidizing effects of this compound.

Elimination of the interferences by keto-opiates in the GC-MS analysis of 6-monoacetylmorphine

A simple procedure to eliminate the interference from keto-opiates in the analysis of 6-monoacetylmorphine (6-MAM) by gas chromatography-mass spectrometry is described. The pretreatment of urine samples with sodium bisulfite followed by solid-phase extraction results in the elimination of the bisulfite addition products formed from the reaction of the bisulfite ions with the carbonyl carbon of the keto-opiates. This simple procedure results in the accurate quantitation of 6-MAM at a concentration of 4 ng/mL in the presence of keto-opiates up to 10,000 ng/mL.

Histomorphometry of dominant and subordinate bovine ovarian follicles

The study was designed to quantitatively characterize the histomorphological attributes of dominant and subordinate follicles in relation to follicular wave dynamics. Heifers (n = 27) were examined daily using ultrasonography to record the growth of individual follicles from 2 days before ovulation until the day of ovariectomy to obtain growing (n = 7), early static (n = 6), late static (n = 6) and regressing (n = 5) phase anovulatory dominant follicles of Wave 1, as well as preovulatory (n = 6) and subordinate (n = 42) follicles. The wall thickness of Wave 1 dominant follicles decreased dramatically (P < 0.01) during the late-static (60.2 +/- 4. 3 microm) and regressing (41.8 +/- 4.3 microm) phases compared to earlier phases. Cells of the granulosa layer of the dominant follicle of Wave 1 became loose during the late-static phase, with an increase (P < 0.001) in number of degenerating cells. Dominant follicles of Wave 1 were lined by fibroblast-like flattened cells during the regressing phase. One day after wave emergence (i.e., before selection), the three largest follicles of the wave were histomorphologically indistinguishable. The wall of the preovulatory follicle close to the medulla of the ovary was thicker (P < 0.01) than the wall facing the ovarian surface. The wall of subordinate follicles was thinner (P < 0.01) and had a lower mitotic index (P < 0.01) than that of their dominant counterparts 3 days and 6 days after wave emergence. In summary, follicular status, ascribed by ultrasonography, was associated with quantitatively distinct histomorphological characteristics. Morphometric changes in the dominant follicle during immature, mature, and post-mature phases were similar to, but occurred later than, those of subordinate follicle. The dominant follicles of Wave 1 entered histological atresia at the time of emergence of Wave 2.

Effect of Azadirachta indica (Neem) leaf aqueous extract on paracetamol-induced liver damage in rats

The effect of aqueous leaf extract of Azadirachta indica (A. indica) was evaluated in paracetamol induced hepatotoxicity in rats. Liver necrosis was produced by administering single dose of paracetamol (2 g/kg, p.o.). The liver damage was evidenced by elevated levels of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyl transpeptidase (gamma-GT) and by histopathological observations of liver sections. Aqueous A. indica leaf extract (500 mg/kg, p.o.) significantly (P < 0.01) reduced these elevated levels of AST, ALT and gamma-GT. Paracetamol induced liver necrosis was also found to be reduced as observed macroscopically and histologically.

Successful treatment of Candida glabrata endophthalmitis with amphotericin B lipid complex (ABLC)

We report a case of Candida (Torulopsis) glabrata endophthalmitis which occurred 2 months following urological surgery. The patient was treated successfully with intravenous amphotericin B lipid complex (ABLC) and flucytosine. Diagnosis and management of this condition are discussed.

A study of hypoglycaemic effects of Azadirachta indica (Neem) in normaland alloxan diabetic rabbits

Hypoglycaemic effect was observed with Azadirachta indica when given as a leaf extract and seed oil, in normal as well as diabetic rabbits. The effect, however, was more pronounced in diabetic animals in which administration for 4 weeks after alloxan induced diabetes, significantly reduced blood glucose levels. Hypoglycaemic effect was comparable to that of glibenclamide. Pretreatment with A. indica leaf extract or seed oil administration, started 2 weeks prior to alloxan, partially prevented the rise in blood glucose levels as compared to control diabetic animals. The data suggests that A. indica could be of benefit in diabetes mellitus in controlling the blood sugar or may also be helpful in preventing or delaying the onset of the disease.

Structure-activity relationship of piperine and its synthetic analogues for their inhibitory potentials of rat hepatic microsomal constitutive and inducible cytochrome P450 activities

Inhibitors of drug metabolism have important implications in pharmaco-toxicology and agriculture. We have reported earlier that piperine, a major alkaloid of black and long peppers inhibits both constitutive and inducible cytochrome P450 (CYP)-dependent drug metabolising enzymes. In the present study, an attempt has been made to prepare several novel synthetic analogues so as to relate various modifications in the parent molecule to the inhibition of CYP activities. Two types of mono-oxygenase reactions arylhydrocarbon hydroxylase (AHH) and 7-methoxycoumarin-O-demethylase (MOCD) have been studied. Inhibition studies were investigated in rat microsomal fraction prepared from untreated, 3MC- and PB- treated rat liver in vitro. Modifications were introduced into the piperine molecule: (i) in the phenyl nucleus, (ii) in the side chain and (iii) in the basic moiety. Thus, 38 compounds have been subjected to such studies, and simultaneously an attempt has also been made to arrive at the structure-activity relationship of synthetic analogues. In general, most of the inhibitory potential of the parent molecule is lost with modification in either of the three components of piperine. Saturation of the side chain resulted in significantly enhanced inhibition of CYP while modifications in the phenyl and basic moieties in few analogues offered maximal selectivity in inhibiting either constitutive or inducible CYP activities. Thus few novel analogues as CYP inactivators have been synthesized which may have important consequences in pharmacokinetics and bioavailability of drugs.

Internalization of carcinogenic lead chromate particles by cultured normal human lung epithelial cells: formation of intracellular lead-inclusion bodies and induction of apoptosis

Occupational exposure to certain particulate hexavalent chromium [Cr(VI)] compounds, such as lead chromate, has been associated with lung cancer and respiratory tract toxicity. We have previously shown that apoptosis is a major mode of death in cultured rodent cells treated with soluble sodium chromate and particulate lead chromate. Here we report the cellular and molecular effects of lead chromate and sodium chromate in normal human lung small airway epithelial (HSAE) cells, which may be one of the targets for Cr(VI)-induced lung cancer and respiratory tract toxicity. Phagocytosed lead chromate particles and intracellular lead-inclusion bodies (LIB) were observed by transmission electron microscopy and confirmed by X-ray analysis. HSAE cells exposed to lead chromate and sodium chromate underwent dose-dependent apoptosis. The cellular uptake and genomic interactions of both Cr and lead (Pb) were examined by inductively coupled plasma mass spectrometry (ICPMS) coupled with a novel, direct-injection high-efficiency nebulizer (DIHEN). Using this approach, we have quantitated a dose-dependent formation of Cr-DNA adducts and DNA-associated Pb in lead chromate-treated HSAE cells. The formation of LIB in normal human lung cells exposed to lead chromate indicates that ionic Pb is released from the particles and thus might contribute to the cell toxicity caused by lead chromate. Internalization and dissolution of lead chromate particles and the interaction of ionic Cr and Pb with DNA, may be components of the mechanism of lead chromate carcinogenesis. Lead chromate-induced apoptosis may be a mechanism to eliminate cells with chromium- and/or lead-damaged DNA.

In vitro percutaneous absorption enhancement of propranolol hydrochloride through porcine epidermis by terpenes/ethanol

The purpose of this study was to investigate the mechanism(s) of percutaneous absorption enhancement of propranolol hydrochloride (PHCL) across porcine epidermis by terpenes (e.g. menthone and limonene) in combination with ethanol. The in vitro percutaneous absorption experiments were performed using Franz diffusion cells. The solubility of PHCL in control and enhancer solutions was determined through high-performance liquid chromatography. Partitioning of PHCL to powdered SC from control or enhancer solutions was also determined in order to investigate the binding of PHCL to the SC from the SC/enhancer system. Fourier transform infrared spectroscopy (FT-IR) was employed to study the biophysical changes in stratum corneum (SC) lipids. The in vitro macroscopic barrier properties were investigated by measuring transepidermal water loss (TEWL) using Tewameter. Five percent menthone or limonene in combination with ethanol (EtOH) (menthone/EtOH or limonene/EtOH) significantly increased (P<0.05) the flux of PHCL through porcine epidermis in comparison to the control (EtOH). The partitioning of PHCL to the SC from the SC/enhancer system was also significantly greater than the SC/control system. The above enhancers showed a decrease in the peak heights and areas for both asymmetric and symmetric C-H stretching absorbances in comparison with the untreated SC, indicating the SC lipids extraction. Menthone/EtOH and limonene/EtOH enhanced (P<0.05) the in vitro TEWL through the epidermis in comparison to the control. Thus, an enhancement in the flux of PHCL by menthone/EtOH and limonene/EtOH is due to SC lipid extraction, macroscopic barrier perturbation, and improvement in the partitioning of the drug to the SC.

Low dose ct in chronic sinusitis

Role of low dose CT was assessed in 50 patients of chronic sinusitis. CT easily picks up the disease and predisposing anatomic variants, which were observed, in 78% of cases. The commonest anatomical variants was deviated nasal septum (38%),other variants found were concha bullosa in (28%) and Helle cell in 28% cases. The commonest disease pattern was osteomeatal unit pattern in 36% case. Infundibular pattern was seen in 23%, sphenoethmoidal recess pattern in 12% and sino-nasal polypopsis pattern was present in 16% of the cases. Low dose CT is preferred as it gives as good results as standard CT There is very little chances of irradiation hazard even when it has to be employed repeatedly.

Epidemiological characteristics of poliomyelitis in Delhi, 1997

OBJECTIVE

To describe the epidemiological characteristics of poliomyelitis in Delhi in 1997 after four consecutive statewide immunization campaigns with oral polio vaccine (OPV).

METHODS

Stool samples were collected from 158 cases of acute flaccid paralysis (AFP) along with their age, sex, residential address, immunization history and dates of onset of paralysis, reporting and investigation. The samples were processed for isolation of polioviruses. In addition, historical data on vaccination coverage surveys and OPV testing were reviewed. These data were analyzed to understand the epidemiological patterns of poliomyelitis in Delhi.

RESULTS

Of 158 cases of AFP, about 23% were investigated within 2 days of onset of paralysis. Two samples each were collected from 97 (61%) cases, and one each from the remaining cases. Detection of 158 cases of AFP gave an incidence of 1.34 per 100,000 population. About 36% (57/158) of AFP cases excreted poliovirus, mostly (53/158) wild poliovirus. Of the wild poliovirus isolates, 72% (38/53) and 25% (13/53) were serotypes P1 and P3 respectively; 2 isolates were P2. Almost 95% (146/154) of AFP cases and all the laboratory confirmed cases (excreting wild poliovirus) occurred in children below 5 years of age. Only one-third of AFP (55/158) or laboratory confirmed cases (18/53) had received 3 or more doses of OPV before onset of paralysis. About one-fourth of cases in both the categories were totally unvaccinated. AFP cases occurred round the year but peaked in November-December. Peaks were always observed during July-August in the past. The cases were widely scattered without any obvious clustering in any locality.

CONCLUSIONS

Poliomyelitis has declined substantially in Delhi. The study underscores the need for further efforts to improve vaccine coverage levels, AFP surveillance, and cold chain maintenance to achieve the complete interruption of transmission.

Of bugs and drugs. A guide through the labyrinth of antimicrobial therapy for respiratory tract infections

Choosing appropriate antimicrobial therapy is no longer a simple process. Even for the common problems of respiratory tract disease in children and adults, selection is complicated by both increasing microbial resistance and the daunting number of extended-spectrum antibiotics now on the market. In this article, Drs Singh and Arrieta look at the problem from all aspects and give their specific recommendations.

A new spectrophotometric method for the determination of dithianon in commercial formulations and its residues in foodstuffs

A new, simple, and rapid spectrophotometric method for the microdetermination of dithianon, on the basis of its reaction with a dithiocarbamate, is described. The red color, which develops instantaneously when mixing the fungicide with the reagent in acetonitrile, is stable for at least 1 h and is measured at 520 nm. Beer's law is applicable up to 12 micrograms/mL dithianon concentration. The method has been successfully adapted to the analysis of the fungicide in commercial formulations and its residues on grains and apple (fruit and leaves). A photometric titration method for formulation analysis of the fungicide has also been developed.

Diphtheria is declining but continues to kill many children: analysis of data from a sentinel centre in Delhi, 1997

Although diphtheria is declining in Delhi, case fatality rates (CFRs) are rising. In 1997, of 143 clinically suspected cases admitted to the Infectious Diseases Hospital 45 (32%) died. We examined their records to understand the epidemiology and reasons for high CFRs. About 53% of cases were from Delhi; they were not limited to any particular area. All the deaths and 92% (131/143) of cases occurred in children below 10 years of age. Only 12% of cases had received one or more doses of DPT. Muslims contributed significantly more cases than Hindus. CFRs were significantly higher in young (P = 0.03) and unvaccinated (P = 0.01) children and in those who received antitoxin on the third day of illness or later (P = 0.03). The study highlights the importance of improved vaccine coverage and early diagnosis and prompt administration of antitoxin in reducing CFRs for diphtheria in Delhi.

Quantitative analysis of dose- and time-dependent promotion of four phenotypes of altered hepatic foci by 2,3,7,8-tetrachlorodibenzo-p-dioxin in female Sprague-Dawley rats

Determining both the mechanism by which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) acts as a tumor promoter and the shape of the dose-response curve at low doses remains an important goal of risk-assessment-directed research. In this report, we extend previous mechanistic and descriptive work done on the effect of TCDD on promotion in the two-stage model of hepatocarcinogenesis, to include lower, more clinically relevant doses. After initiation [PH + 10 mg diethylnitrosamine (DEN)/kg], groups of female Sprague-Dawley rats were administered TCDD in one of four doses: 0.01, 0.1, 1.0, or 10 ng/kg/day for 1, 3, or 6 months. Early increases in liver weight (19-69%) due to hepatocyte hypertrophy were resolved after 3- or 6-months exposures to TCDD, and were not associated with the effects of TCDD on promotion. Non-focal cell proliferation in DEN-treated groups was significantly reduced after 1 or 3 months of exposure to 0.1 ng/kg/day TCDD, leading to U-shaped dose-response curves. TCDD effects on non-focal cell proliferation were not associated with effects on promotion. GSTP-positive AHF represented approximately 97% of the total AHF. Significant increases in both the volume fraction and the number of altered hepatic foci (AHF) were observed at the highest dose (10 ng/kg/day) for GSTP-positive AHF in DEN-treated groups. Increases in the number of G6Pase- and ATPase-deficient AHF/cm3 were observed at TCDD doses as low as 0.01 ng/kg/day. This is the lowest tumor-promoting dose of TCDD reported to date. This study represents an unusually complete data set for further dose-response analysis and simulation or mathematical modeling of TCDD-mediated promotion in the rat liver.

Corneal epithelial toxic effects and inflammatory response to perfluorocarbon liquid

We report an unusual case of corneal epithelial toxic effects associated with perfluorocarbon liquids (PFCLs). The clinical and histopathologic findings are described. An elderly man underwent vitreoretinal surgery for a complicated retinal detachment. Perfluorodecalin was used to repair the retina. It was left in situ for 8 weeks and removed via the pars plana. One month after removal of heavy liquids the patient developed a nonhealing corneal epithelial defect associated with limbitis. Perfluorodecalin was found under the superior conjunctiva. A conjunctival biopsy revealed the presence of vacuoles in the conjunctival stroma surrounded by an inflammatory response that consisted of lymphocytes, macrophages, and giant cells. On surgical removal of the PFCL from the subconjunctival space, the epithelial defect healed. The histopathologic and clinical evidence suggest that the inflammatory response and corneal epithelial ulceration were caused by the prolonged presence of PFCL in the subconjunctival space. To the best of our knowledge, PFCLs have not previously been reported to cause corneal epithelial defects or incite an inflammatory response in the human eye.

Spermatogenesis without gonadotropins: maintenance has a lower testosterone threshold than initiation

We showed previously that testosterone (T) alone could induce spermatogenesis and produce normally fertile spermatozoa in the absence of circulating gonadotropins. These studies used the hpg mouse, which is characterized by a congenital gonadotrophin deficiency due to a major deletion in the GnRH gene. Administering T by a subdermal implant of a SILASTIC brand tube impregnated with crystalline T showed that the androgenic requirement for full induction of spermatogenesis was a 1-cm length implant. Using this unique model of spermatogenesis without gonadotropins, we have now investigated the quantitative requirement for androgens to maintain spermatogenesis by testing the hypothesis that the androgenic threshold required for induction and maintenance of spermatogenesis are the same. Spermatogenesis was induced in homozygous hpg mice by T administration for 6 weeks. The first experiment determined the time-course of the regression of spermatogenesis after removal of the T-impregnated SILASTIC brand implant. Elongated spermatids were absent by 3 weeks and testicular weight regression was maximal by 4 weeks after androgen withdrawal. The second experiment examined the effects on maintenance of spermatogenesis of reducing the T dose. After full induction of spermatogenesis in homozygous hpg mice, the T implants were replaced with a range of smaller size T-impregnated SILASTIC brand implants for a further 4 weeks. All androgen-sensitive end-points (testis weight, tubular, and luminal diameters, round spermatids) were fully maintained with T implants of 0.06 cm and elongated spermatids with T implants of 0.25 cm. A further experiment showed that at very low T doses (0.06, 0.125 cm) the T effects observed at 4 weeks were maintained at 6 and 11 weeks duration. We conclude that the androgenic threshold to maintain spermatogenesis in the mouse is an order of magnitude lower than the threshold required for inducing spermatogenesis. This distinction suggests that the mechanism of action of testosterone in inducing spermatogenesis may involve regulation of a genetic switch to complete meiosis, whereas the maintenance involves a different locus of action. These findings suggest that further studies of androgen-dependent meiotic genes may be central to understanding the regulation and molecular basis of androgen-driven induction and maintenance of spermatogenesis.