Luteal contraception

The impact of oral administration of RU 486 on the ongoing functional activity of the hypothalamic-gonadotropin-corpus luteum-endometrial (H-P-CL-E) axis was assessed during the mid-luteal (MLP) and the late-luteal phase (LLP) with and without hCG-induced pseudopregnancy. Longitudinal studies with daily dosing and frequent blood sampling were conducted during three consecutive cycles (control/treatment/recovery). During MLP, uterine bleeding occurred in all subjects within 36-72 h of the first dose of RU 486, but no histological changes were discernible on endometrial biopsy taken 12-24 h before bleeding. There was a significant decrease in LH secretion, pulse amplitude but not frequency. Response to GnRH on the last day of treatment was impaired. This was followed 3 days later by a rebound LH secretion lasting for 5 days. These events were accompanied by an initial decline of estradiol, but not progesterone, and a second peak of 5 days' duration for both estradiol and progesterone. Hence corpus luteum function was prolonged by 5 days, and second bleeding ensued following the spontaneous luteolysis. Recovery cycles were normal. During LLP, a single dose of RU 486 induced uterine bleeding in all cases. This was associated with a decreased LH pulse amplitude and frequency, and a faster decline of both estradiol and progesterone as compared to control cycles. Rescue of corpus luteum function by the administration of incremental doses of hCG failed to prevent the uterine bleeding after a single dose of RU 486. Recovery cycles were normal. While the antiprogesterone effect of RU 486 at the endometrial level was predictably expressed, its effects at the H-P-CL-E axis were also demonstrated. These findings provide important clues for the design of once-monthly contraceptive methods.

[Effect of sodium selenite on the chromosomal aberration of V 79 cells induced in vitro by MNNG and MNU]

Effect of sodium selenite on chromosomal aberration of V 79 cells induced by MNNG and MNU was studied. Na2SeO3 alone, at the concentration of 10(-7)-10(-4) M, increased the incidence of chromosomal aberration. However, Na2SeO3 at 10(-7)-10(-5) M, having been preincubated with the cells for 4 hours, could reduce the number of cells with chromosomal aberration induced by MNNG. Na2SeO3 at 10(-7)-10(-4) M inhibited mutagenic activity of chromosomal aberration induced by MNU. The same inhibition was observed even sodium selenite was added to the medium simultaneously with this carcinogen. The results indicate that sodium selenite alone, at the concentration range used in this experiment, is an aberration-inducing agent. But when combined with the carcinogen, anti-cancer effect is obtained.

[Sister chromatid exchanges (SCE), chromosomal aberrations and micronuclei of cultured peripheral lymphocytes in patients with lung cancer, miners and non-mining workers of the tin mine in Yunnan]

Determination of SCE frequency, chromosomal aberration and micronucleus rate of cultured peripheral lymphocytes in 32 patients with lung cancer, 33 miners and 40 non-mining workers in Yunnan Tin Mine was carried out. The results showed that the cancer patients had higher SCE incidence, chromosomal aberration and micronucleus rate, the non-mining workers had the least and miners on an intermediate level. There was a significant difference of SCE, chromosomal aberrations and micronucleus rate between patients and non-mining workers (P less than 0.05-0.01). We also found that miners had a significant higher SCE and chromosomal aberration rate but not micronucleus rate as compared with the non-mining workers. We proposed that some carcinogens present in the Yunnan Tin Mine be responsible for the genetic damages in the miners. Chemical drugs may be considered to contribute to the genetic damage in cancer patients who had a tendency toward an increased SCE, chromosomal aberration and micronucleus rate as compared to the miners, though without reaching a statistical significance. We suggested that combination assay of SCE with chromosomal aberration or micronucleus be an useful index for screening of the high risk population and monitoring the chemical drug prevention of lung cancers in Yunnan Tin Mine.

Nucleotide sequences of Cyanophora paradoxa cellular and cyanelle-associated 5S ribosomal RNAs: the cyanelle as a potential intermediate in plastid evolution

The 5S ribosomal RNAs from the cell cytoplasm and cyanelle (photosynthetic organelle) of Cyanophora paradoxa have been isolated and sequenced. The cellular and cyanelle 5S rRNAs were 119 and 118 nucleotides in length, respectively. Both RNAs exhibited typical 5S secondary structure, but the primary sequence of the cellular species was clearly eukaryotic in nature, while that of the organellar species was prokaryotelike. The primary sequence of the cyanellar 5S rRNA was most homologous to cyanobacterial 5S sequences, yet possessed secondary-structural features characteristic of higher-plant chloroplast 5S rRNAs. Both sequence comparison and structural analysis indicated an evolutionary position for cyanelle 5S rRNA intermediate between blue-green alga and chloroplast 5S rRNAs.

[Ultrastructure of primary clear cell carcinoma of the liver]

Surgical specimens of 175 cases of primary hepatocellular carcinoma were prepared by routine paraffin section and HE stain. The clear cell cancer specimens were stained with PAS. All the specimens were observed by light microscope. Ultrathin sections were made for 50 samples and studied by electron microscope. Under the light microscope, 79 (45.1%) showed varying amounts of clear cells. According to the proportion and distribution of these cells, clear cell carcinoma of the liver was divided into three types: scattered type (16 cases, 20.3%), localized (43, 54.4%) and diffuse types (20, 25.3%). The clear cancer cells could be found in hepatoma with various degrees of differentiation. Of these 79 cases, 4 (5.1%) were grade I, 53 (67%) and 22 (27.9%) were grades II and III. Positive PAS stain gives an evidence of glycogen in the clear cell cytoplasm. 7 diffuse type clear cell hepatomas were observed with electron microscope. The cytoplasm had only fewer organelles, leading to a void appearance. The amount of the rough endoplasmic reticulum, free ribosome and polyribosome was markedly decreased. So was mitochondria, usually showing swelling and abnormality. The residual rough endoplasmic reticulum and mitochondria were out of normal arrangement. They often aggregated on one side of the nucleus or near the cell membrane. Glycogen particles were increased in some cell cytoplasms. Some particles were even and fine, some were aggregated into masses or scattered. Nuclei showed abnormalities mild to moderate. The nature of the clear cells in liver cancer is the variance of glycogen or lipid in the cytoplasm.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of antiandrogen and/or antiestrogen blockade on human prostate epithelial and stromal cell protein synthesis

To evaluate the role of small amounts of DHT in prostate tissue as a stimulus to epithelial cell growth (protein synthesis) we studied tissue from patients given various androgen-blocking drugs prior to transurethral resection of the prostate (TURP) and measured epithelial protein synthesis and DHT in the tissue specimens. We also studied the effects on stromal cell protein synthesis of an antiestrogen, tamoxifen. Test drugs prior to TURP included Megace 160 mg per day, Megace 160 mg per day plus Tamoxifen 40 mg per day, Megace 160 mg a day plus ketoconazole 1200 mg per day and tamoxifen 40 mg/day. The tissue was processed immediately and epithelial and stromal cells separated by digestion of tissue with 0.5% collagenase. After separation, epithelial cells were labeled with either [3H]leucine or L-[35S]methionine. Stromal cells were labelled with [3H]proline. DHT was measured in whole prostate tissue. Megace alone and Megace plus tamoxifen significantly decreased both [3H]leucine incorporation into protein and tissue concentration of DHT; Megace plus ketoconazole significantly decreased L-[35S]methionine incorporation into protein and DHT. Tamoxifen significantly decreased stromal protein synthesis. When the data correlating DHT with epithelial protein synthesis using both labeling techniques were combined, the curves were parallel and a strong correlation was noted between DHT and protein synthesis over a wide range of values (P less than 0.001). These results suggest that in hormone-dependent prostate cancer even small amounts of prostate DHT such as may occur from adrenal androgens following castration may significantly stimulate growth of the tumor epithelial cells. Since tamoxifen decreased stromal protein synthesis, estrogen is likely a significant growth stimulus to the increased stromal mass characteristic of benign prostatic hypertrophy.

Does positive hepatobiliary scan in cholecystitis stay positive, and for how long?

A prospective study of 11 patients who had undergone two sequential hepatobiliary scans prior to surgery demonstrated that initially positive scans could be due to acute cholecystitis, or chronic cholecystitis with exacerbation. A second hepatobiliary scan performed four to five days later differentiated acute from chronic cholecystitis. All five patients with surgery-proven acute cholecystitis remained hepatobiliary-positive, while patients with surgery-proven chronic cholecystitis reverted back to negative hepatobiliary scans if the second hepatobiliary scan was done properly.

Gas Chromatographic Determination of Propachlor in Pesticide Formulations: Collaborative Study

An isothermal gas chromatographic (GC) method for measuring propachlor in formulations was tested by 12 collaborators. Samples are prepared in acetone and determined using a GC column of 10% SP-2250 on 100-200 mesh Supelcoport, and diisobutyl phthalate as internal standard. Collaborators made single determinations on each of 2 similar materials (matched pairs) on 2 days for 3 pairs of samples. The study generated 62 matched pairs which were used in Youden’s matched pair calculations. The coefficients of variation (CV,) for flowable formulations were 0.84 and 1.48%; the CV, for the granular formulation was 1.28%. The method was simple to use and did not reveal any interferences in the samples tested. The method has been adopted official first action as an AOAC-CIPAC method.

Gas Chromatographic Determination of Butachlor in Formulations: Collaborative Study

An isothermal gas chromatographic (GC) method for measuring butachlor in formulations was tested by 15 laboratories. Samples were prepared in acetone and determined using a GC column of 10% SP-2250 on 100-120 mesh Supelcoport, and triphenyl phosphate as internal standard. Collaborators made single determinations on each of 2 similar materials (matched pairs) on 2 days for 2 pairs of samples. The study generated 56 matched pairs which were used in Youden’s matched pair calculations. Coefficients of variation (CV,) for liquid formulations were 1.06 and 0.98%. The method was simple to use and did not reveal any interferences in the samples tested. The method has been adopted official first action as an AOAC-CIPAC method.

Intraocular 9-([2-hydroxy-1-(hydroxymethyl) ethoxy] methyl) guanine levels after intravitreal and subconjunctival administration

Clearance studies in rabbits following intravitreal injection of 400 micrograms of 9-([2-Hydroxy-1-(hydroxymethyl)ethoxy]methyl) guanine demonstrated levels of the antiviral at 60 hours above the in vitro ID50 for several strains of human cytomegalovirus. Intravitreal administration of this new antiviral may have therapeutic application in the treatment of acute retinal necrosis and cytomegalovirus retinitis complicating acquired immune deficiency syndrome (AIDS).

Isolation and sequence analysis of the gene (cpdB) encoding periplasmic 2',3'-cyclic phosphodiesterase

The cpdB gene encodes a periplasmic 2',3'-cyclic phosphodiesterase (3'-nucleotidase). This enzyme has been purified previously and the gene is located at 96 min on the Escherichia coli chromosome. In this study the cpdB gene was cloned from ClaI-cleaved DNA, and the gene product was identified. DNA blotting experiments showed that the recombinant plasmid contains a deletion with respect to the expected genomic fragment of approximately 4 kilobases, which extends into the vector. Furthermore, the gene was absent from three other recombinant libraries. Together, these findings suggest the presence in the genome of an adjacent gene whose product is lethal when it is present on a multicopy plasmid. The nucleotide sequence of the cpdB gene was also determined. The 5' and 3' untranslated sequences contain characteristic sequences that are involved in the initiation and termination of transcription, including two possible promoters, one of which may contain two overlapping -10 sequences. A strong Shine-Dalgarno sequence is followed by an open reading frame which corresponds to a protein having a molecular weight of 70,954. The first 19 amino acid residues have the characteristics of a signal peptide. The 3' untranslated sequence contains two putative rho-independent transcription terminators having low thermodynamic stability.

Effects of androgen blockade with ketoconazole and megestrol acetate on human prostatic protein patterns

We studied the effects of megestrol acetate (MA) and ketoconazole (KC) on protein synthesis of epithelial and stromal cells of human prostate. Patients with benign prostatic hypertrophy (BPH) were treated with MA (160 mg/day) plus KC (1,200 mg/day) for 7 days. Prostate tissues obtained from transurethral resection (TURP) were separated into epithelial and stromal cells with 0.5% collagenase. The separated cells were incubated with L-35S-methionine in methionine-free MEM at 37 degrees C for 3 hr. The protein synthesis in both epithelial and stromal cells was significantly inhibited in the group treated with MA and KC when compared to a control group (p less than 0.05). The proteins incorporated with L-35S-methionine were analyzed by SDS-PAGE and autoradiography. The molecular weights of the epithelial and stromal proteins inhibited ranged between 35-55K.

A comparative study of the effects of tetrodotoxin and the removal of external Na+ on the resting potential: evidence of separate pathways for the resting and excitable Na currents in squid axon

To investigate whether the Na permeability of the resting membrane is determined predominantly by the excitable Na channel, we examined the effects of tetrodotoxin (TTX) and the complete removal of external Na+ on the resting potential. In the intact squid axon bathed in K-free artificial seawater, both TTX and the removal of Na+ produced small hyperpolarizations. The effect of Na removal, however, was larger than that of TTX. In the perfused squid axon, the hyperpolarization produced by the removal of external Na+ was greatly enhanced when the internal K concentration ([K+]i) was reduced. The effect of TTX, on the other hand, was not sensitive to the [K+]i or to the membrane potential. For [K+]i = 50 mM and [K+]o = 0, the average hyperpolarization produced by TTX was 1.2 mV, while the hyperpolarization produced by Na removal was approximately 21 mV. The difference between these two effects suggests that the majority of the resting Na current passes through pathways other than the excitable Na channel.

Effect of allopurinol on the utilization of purine degradation pathway intermediates by tobacco cell cultures

Suspension cultured Nicotiana tabacum (tobacco) cells grow slowly on intermediates of the purine degradation pathway (hypoxanthine, xanthine, uric acid, allantoin, and urea) as their sole nitrogen source indicating that this degradation pathway is operative in these cells. The hypoxanthine analog, allopurinol inhibited tobacco cell growth on hypoxanthine but not uric acid. This helps confirm that the site of action of allopurinol is the conversion of hypoxanthine to uric acid by xanthine oxidase. Attempts to select cells which could grow in the presence of allopurinol with hypoxanthine as the nitrogen source were not successful.

Bioavailability of selenium to residents in a low-selenium area of China

For 8 wk 5 groups of 10 men each were given 0.5 g/day DL-methionine, 150 micrograms Se/day as sodium selenite with or without methionine or 150 micrograms Se/day as selenomethionine with or without methionine. Twenty subjects received placebo as controls. Initially plasma Se rose more rapidly than RBC Se. Increases in Se levels were significantly greater with selenomethionine than with the selenite supplement. In the placebo and methionine supplemented groups neither plasma nor RBC Se varied significantly over the course of the study. Supplementation with selenium resulted in marked increases in plasma and RBC GSH-Px within 2 and 4 wk, respectively. Plasma and RBC GSH-Px activity did not differ significantly between Se-supplemented groups. These studies suggest that selenomethionine-Se was more effective in raising plasma and RBC Se than was selenite-Se. Methionine supplements may increase the bioavailability of selenium in severely deficient subjects.

Selenium intake and metabolic balance of 10 men from a low selenium area of China

Selenium intake and urinary and fecal Se excretion of 10 healthy men from a low Se area in China were determined for three consecutive days, in summer, fall, and winter of 1983, and the spring of 1984 while self-selected diets were being consumed. Mean daily Se intake was 8.8 micrograms/day with a range of 2.3-35.5 micrograms/day, and was far below the recommended range of safe and adequate Se intake of 50-200 micrograms Se/day (National Academy of Sciences/National Research Council). Mean urinary and fecal Se outputs were 3.7 and 3.4 micrograms Se/day, respectively. Mean Se balance during this time was +1.8 micrograms Se/day. Apparent absorption of Se approximated 57%. The low Se intake in this area is a cause for concern since the residents of Molimo may be at risk for Se deficiency diseases.

Acute effects of testicular and adrenal cortical blockade on protein synthesis and dihydrotestosterone content of human prostate tissue

To examine the relationship between whole prostatic dihydrotestosterone (DHT) concentrations and epithelial and stromal protein synthesis, patients awaiting surgery for benign prostatic hypertrophy were given medication to reduce circulating and tissue androgen levels for comparison to levels in untreated patients. The medications, either megestrol acetate, a progestational antiandrogen, or megestrol acetate plus dexamethasone, were given for 1 week before surgery. Aliquots of prostate tissue obtained at surgery were assayed for DHT. The remainder of the tissue was separated into stromal and epithelial cells using enzymatic separation; the incorporation of both [3H] proline into stromal protein and [3H]leucine into epithelial cell protein was then measured. Over a wide range of tissue DHT concentrations, DHT correlated significantly with [3H]proline incorporation into stromal protein (r = 0.58). Likewise, epithelial cell incorporation of [3H]leucine into protein correlated significantly with tissue DHT concentrations, with a r value of 0.79. In the case of stromal cells, no additional effects of dexamethasone given with megestrol acetate were found on stromal protein synthesis. Epithelial cell [3H]leucine incorporation into protein was paradoxically enhanced by dexamethasone plus megestrol acetate compared to the latter alone, despite the fact that tissue DHT and circulating adrenal androgens, dehydroepiandrosterone sulfate and delta 4-androstenedione, were not significantly different from values obtained after treatment with megestrol acetate alone. These studies support the conclusion that there is a dominant role of DHT in regulating protein synthesis in both prostatic epithelial and stromal cells. Dexamethasone appears to have a growth-stimulating effect on prostatic epithelial cells.

Presence of oxytocin and arginine vasopressin in human ovary, oviduct, and follicular fluid

Oxytocin and arginine vasopressin (AVP) immunoreactivity in human ovary, oviduct, and follicular fluid were measured and found to coelute with the authentic peptides using both gel filtration column chromatography and reverse phase thin layer chromatography. In ovarian tissue, mean oxytocin and AVP concentrations were 0.48 and 0.24 ng/mg protein, respectively. These values are approximately 4000-fold higher than peripheral plasma levels. The concentration of oxytocin in the corpus luteum was approximately 6-fold greater (3.12 ng/mg protein) than that in ovarian tissue with no corpus luteum. In contrast, no significant difference in the concentration of AVP was found between corpus luteal and the remaining ovarian tissues. Follicular fluid contained 299 and 131 pg/ml oxytocin and AVP, respectively. These levels were 30-fold greater than the serum level of either peptide, suggesting ovarian synthesis of the neurohypophyseal hormones. In addition, immunoreactive oxytocin and AVP were detected in the oviducts (1.01 and 0.24 ng/mg protein, respectively); however, neither peptide was detectable in myometrial tissue (less than 0.02 ng/mg protein). Our results demonstrate the presence of high concentrations of oxytocin and AVP in human ovarian and oviductal tissues as well as follicular fluid and suggest that neurohypophyseal peptides have a paracrine role in the regulation of ovarian or oviductal functions.

Effect of tamoxifen on stromal protein synthesis in the human prostate

To test the hypothesis that estrogen may have significant biological effects on the human prostate, we studied the effects of in vivo administration of tamoxifen, an antiestrogen, on human prostatic stromal protein synthesis in vitro. This was done by measuring [3H]proline incorporation in vitro in stromal cells separated enzymatically with 0.5% collagenase and trypsin from hypertrophic prostatic tissue removed at surgery. A mechanical method for separation of epithelium and stroma was attempted, but cell damage resulted in very low incorporation of [3H]proline into protein. Twelve patients were given 20 mg tamoxifen twice daily for 10 days before surgery. The serum levels of tamoxifen at the time of surgery ranged from 200-500 pmol/ml. Control tissues (14) were obtained from untreated patients. Tamoxifen decreased stromal protein synthesis, as measured by counts per min/mg protein, to approximately one third of that found in control patients (control mean, 102,428; tamoxifen-treated mean, 34,111; P less than 0.01). These results support the concept that estrogen has a significant role in the regulation of stromal protein synthesis and the pathophysiology of benign prostatic hypertrophy.

Accommodative disfacility presenting as intermittent exotropia

Accommodative disfacility and intermittent exotropia are two common clinically-observed ocular abnormalities. However, records of individual system dynamics are rare and mechanisms for possible interactive effects between the accommodation and the vergence system remain obscure in cases of system dysfunction. We present objective, quantitative, static and dynamic records of accommodation, vergence and related system responses in a symptomatic patient having accommodation disfacility and intermittent exotropia and propose that these two conditions worked in a pathogenic symbiotic manner.

Role of magnesium binding to myosin in controlling the state of cross-bridges in skeletal rabbit muscle

The effect of Mg2+ on the disposition of myosin cross-bridges was studied on myofibrils and synthetic myosin and rod filaments by employing chymotryptic digestion and chemical cross-linking methods. In the presence of low Mg2+ concentrations (0.1 mM), the proteolytic susceptibility at the heavy meromyosin/light meromyosin (HMM/LMM) junction in these three systems sharply increases over the pH range from 7.0 to 8.2. Such a change has been previously associated with the release of myosin cross-bridges from the filament surface [Ueno, H., & Harrington, W.F. (1981) J. Mol. Biol. 149, 619-640]. Millimolar concentrations of Mg2+ block or reverse this charge-dependent transition. Rod filaments show the same behavior as myosin filaments, indicating that the low-affinity binding sites for Mg2+ are located on the rod portion of myosin. The interpretation of these results in terms of Mg2+-mediated binding of cross-bridges to the filament backbone is supported by cross-linking experiments. The normalized rate of S-2 cross-linking in rod filaments at pH 8.0, kS-2/kLMM, increases upon addition of Mg2+ from 0.30 to 0.65 and approaches the cross-linking rate measured at pH 7.0 (0.75), when the cross-bridges are close to the filament surface. In rod filaments prepared from oxidized rod particles, chymotryptic digestion proceeds both at the S-2/LMM junction and at a new cleavage site located in the N-terminal portion of the molecule. Kinetic analysis of digestion rates at these two sites reveals that binding of Mg2+ to oxidized myosin rods has a similar effect at both sites over the pH range from 7.0 to 8.0.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuroendocrine control of the postpartum period

This postpartum period is characterized by stimulation of lactation and suppression of ovulation. During pregnancy a number of hormonal changes prepare the breasts for lactation following delivery. The process of lactation is functionally related to the suppression of ovulation. These two physiologic changes observed in the puerperium are considered in detail in this review.

An analysis of the direct effects of gossypol on human spermatozoa

The direct effects of gossypol and its acetic acid adduct, on the movement and functional competence of human spermatozoa were investigated employing exposure times of 1, 5 or 15 min and concentrations of 50 microM, 500 microM and 1000 microM. These compounds markedly reduced the motility, velocity, frequency of sperm head rotation and linearity of sperm progression, the most significant effects being observed with gossypol acetic acid on populations of 'capacitated' spermatozoa. Significant direct effects of gossypol on the ability of human spermatozoa to penetrate both cervical mucus and zona-free hamster ova were also observed, which were independent of any effects on motility. These results reinforce the notion that gossypol may serve a contraceptive role in the female as a 'spermicidal' agent, and suggest that this compound may also be of scientific value as a probe for identifying and isolating functionally important components of the human spermatozoon.

The influence of medium composition, osmolarity and albumin content on the acrosome reaction and fertilizing capacity of human spermatozoa: development of an improved zona-free hamster egg penetration test

The influence of medium composition, osmolarity and albumin concentration on the ability of human spermatozoa to undergo the acrosome reaction and penetrate zona-free hamster ova has been investigated. Raising the osmolarity but not the albumin concentration of the media was found to significantly increase the proportion of spermatozoa exhibiting an acrosome reaction and penetrating hamster ova, without influencing motility. There was, however, no correlation between the size of the acrosome reacted population and penetration rates between samples, suggesting that the zona-free hamster egg penetration test is more than just a measure of the availability of acrosome reacted cells. As a result of this study, a revised protocol for the hamster egg assay is described which is shorter and considerably more sensitive than conventional procedures.

Premonitory symptoms of stroke in evolution to the locked-in state

Three patients, who subsequently developed the locked-in state characterised by quadriplegia and mutism with an alert sensorium, initially had mild dysarthria and uncrossed hemisensory or hemimotor deficits involving the face and ipsilateral extremities. Case one initially mimicked a left cerebral lesion with right hemisensory deficits, a mild right facial paresis and a right homonymous field deficit. Case two initially developed both left hemimotor and hemisensory deficits and later developed a paresis of right conjugate gaze. Case three presented with left hemimotor deficit, and mild paresis of conjugate gaze to the right. All three patients died. Rostral brainstem infarctions were found at necropsy in cases one and two. Case three had a radiolucent area of the brainstem demonstrated by CT Scan. Hemisensory and hemimotor deficits also have been noted to precede reported cases of pontine infarction with the locked-in state. Acute onset of uncrossed hemisensory and hemimotor deficits with dysarthria may be caused by infarction of the pons which may predispose to the locked-in state.